CA1163569A - Rubber sheet for turntable - Google Patents
Rubber sheet for turntableInfo
- Publication number
- CA1163569A CA1163569A CA000377415A CA377415A CA1163569A CA 1163569 A CA1163569 A CA 1163569A CA 000377415 A CA000377415 A CA 000377415A CA 377415 A CA377415 A CA 377415A CA 1163569 A CA1163569 A CA 1163569A
- Authority
- CA
- Canada
- Prior art keywords
- rubber
- rubber sheet
- projections
- sheet
- hardness
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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- Compositions Of Macromolecular Compounds (AREA)
- Manufacture Of Macromolecular Shaped Articles (AREA)
- Laminated Bodies (AREA)
- Holding Or Fastening Of Disk On Rotational Shaft (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A rubber sheet for turntable is featured by a cured rubber molding having a hardness between 30°
as measured with an A-type rubber hardness tester and 15°
as measured with an F-type rubber hardness tester and an impact resilience of not less than 40 %. This rubber sheet effectively prevents the tone quality of reproduced sounds from deteriorating due to howling or external vibrations and permits reproducing source sounds faithfully.
A rubber sheet for turntable is featured by a cured rubber molding having a hardness between 30°
as measured with an A-type rubber hardness tester and 15°
as measured with an F-type rubber hardness tester and an impact resilience of not less than 40 %. This rubber sheet effectively prevents the tone quality of reproduced sounds from deteriorating due to howling or external vibrations and permits reproducing source sounds faithfully.
Description
~ 3 ~i35B9 SPEC IF ICATION
RUBBER ~SIIEET FOR T~JRNTABLE
TECHNICAI. FIELD
This invention relates to a rubber sheet for record player turntable.
BACK(~RnlJND ART
The function of such a rubber sheet is to isolate a disk record from acoustic outpu~s from a speaker, vibrations o a record player itself, etc.
and prevent howling and deterioration o SN ratio due to vibra~ions of the disk record during reproduc~ion. The howling is a sort of oscillation due to an acoustic feedback of outputs from a loud speaker to the pickup assembly and occurs mainly due to the vibrations of the speaker which are transmitted to the record player via the floor or rack where the record player is mo~lnted, or - 20 due to the direct vibrations of the record player caused by a sound pressure from the speaker. Of course, the normal condition of playback of the disk record cannot be expected when the hol~ling occurs. Even where no howling takes ~lace, the frequency response of the pickup assembly would be altered and the local resonance would be caused by such external vibrations, and the increase Of cross-modulation distortion9 the deterioration of transient phenomena, etc. would affect adversely the tone qualitv of reproduced sounds. As stated above, howling takes place mostly due to external vibrations from the floor or rack where the record player is mounted. The majority of such external vibrations is of the order less than l~0 Hz and particularly includes a superlow frequency component of approximately 5 to lQ Hz. To provide for an effective inhibition of howling, a rubber sheet for turntable which exhibits excellent vibration-damping pro~erties in such superlow frequency region is desirable.
., . '3~.
~ :~ 635~
RUBBER ~SIIEET FOR T~JRNTABLE
TECHNICAI. FIELD
This invention relates to a rubber sheet for record player turntable.
BACK(~RnlJND ART
The function of such a rubber sheet is to isolate a disk record from acoustic outpu~s from a speaker, vibrations o a record player itself, etc.
and prevent howling and deterioration o SN ratio due to vibra~ions of the disk record during reproduc~ion. The howling is a sort of oscillation due to an acoustic feedback of outputs from a loud speaker to the pickup assembly and occurs mainly due to the vibrations of the speaker which are transmitted to the record player via the floor or rack where the record player is mo~lnted, or - 20 due to the direct vibrations of the record player caused by a sound pressure from the speaker. Of course, the normal condition of playback of the disk record cannot be expected when the hol~ling occurs. Even where no howling takes ~lace, the frequency response of the pickup assembly would be altered and the local resonance would be caused by such external vibrations, and the increase Of cross-modulation distortion9 the deterioration of transient phenomena, etc. would affect adversely the tone qualitv of reproduced sounds. As stated above, howling takes place mostly due to external vibrations from the floor or rack where the record player is mounted. The majority of such external vibrations is of the order less than l~0 Hz and particularly includes a superlow frequency component of approximately 5 to lQ Hz. To provide for an effective inhibition of howling, a rubber sheet for turntable which exhibits excellent vibration-damping pro~erties in such superlow frequency region is desirable.
., . '3~.
~ :~ 635~
- 2 The conventional rubber sheets ~or turntable which typically com~rise natural rubber, isoprene rubher, chloroprene rubber, butyl ruhber, styrene-butadiene rubber, butadiene rubber, silicone rubber or urethane rubher alone or in combination, however, are inferior in vibration-damping properties especially in the superlow frequency range, and are unahle to protect effectively the tone ~uality of reproduced sounds from deteriorating due to howling or ex~ernal vibrations.
DISCLOSURE OF INVENTION
The inventor has devoted extensive and thorough efforts to the development of a new rubber sheet for turntable which effectively inhibits the tone quality of reproduced sounds from deteriorating due to howling or external vibrations and permits reproducing source sounds (for example, human voices themselves) as faithfully as possible. As a result, it has been found that the above described object can be achieved by a sheet~ e cured rubber molding having a hardness between 30 as measured with an A-type rubber hardness tester and 15 as measured with an F-type rubber hardness tester and an impac~ resilience of not less than 40 ~.
In the foregoing, the term "A-type rubber hardness ~ester" is used to mean a ruhber hardness - tester which conforms to JIS K 6301-1969. Further, the F-type rubber hardness tester implies Asker-F type rubber hardness tester bv Kobunshi Keiki Mfg. Co., Ltd.
which is o~ten used for measurements of hardness of foam rubber, urethane foam or the li~e.
Although being solid rubber, some of the cured ruhber used in accordance with the present inven~ion is too low in hardness to measure by means of ~he A-type rubber hardness tester which is of use in measuring hardness of conventional solid rubbers. To this end, the lower limit of hardness of the cured rubber used in accordance with the present invention is defined by one as measured with the P-type rubber hardness tester.
~ ~ 6~9
DISCLOSURE OF INVENTION
The inventor has devoted extensive and thorough efforts to the development of a new rubber sheet for turntable which effectively inhibits the tone quality of reproduced sounds from deteriorating due to howling or external vibrations and permits reproducing source sounds (for example, human voices themselves) as faithfully as possible. As a result, it has been found that the above described object can be achieved by a sheet~ e cured rubber molding having a hardness between 30 as measured with an A-type rubber hardness tester and 15 as measured with an F-type rubber hardness tester and an impac~ resilience of not less than 40 ~.
In the foregoing, the term "A-type rubber hardness ~ester" is used to mean a ruhber hardness - tester which conforms to JIS K 6301-1969. Further, the F-type rubber hardness tester implies Asker-F type rubber hardness tester bv Kobunshi Keiki Mfg. Co., Ltd.
which is o~ten used for measurements of hardness of foam rubber, urethane foam or the li~e.
Although being solid rubber, some of the cured ruhber used in accordance with the present inven~ion is too low in hardness to measure by means of ~he A-type rubber hardness tester which is of use in measuring hardness of conventional solid rubbers. To this end, the lower limit of hardness of the cured rubber used in accordance with the present invention is defined by one as measured with the P-type rubber hardness tester.
~ ~ 6~9
- 3 An intermediate hardness range between the measuring range of the A-type rubher hardness tester and that of the F-type rubber hardness tester may be measured with a C-type rubber hardness tester. The term "C-type rubber hardness tester" as used herein means one ~hich meets the Society of Rubber Industry Japan Standard SRIS-0101 and is widely used to measure such intermediate hardnesses between the measuring ranges of the A-type and F-type rubber hardness testers. The C-type tester is mostly used to measure the hardness of sponge7 soft rubber or the like. As the C-type rubber hardness tester, Asker-C type rubber hardness tester by Kobunshi Keiki Mfg. Co., Ltd. is used in the present invention.
If the situation permits, any of these A type, C-type and F-type rubber hardness testers may be used to determine the hardness of cured rubbers for the purpose of the present invention. However, if hardness is less than 1 when the A-type rubber hardness tester is in use 9 it is preferable to measure hardness with either the C-type ruhber hardness tester or the F-type rubber hardness tester because measurements with the A-type hardness tester accompany încreased errors. Similarly, if hardness is less than 1 for the C-type hardness tester, it is more desirable to use the F-type hardness tester in connection with hardness measurements.
Furthermore, in the case ~hat hardness is more ~han 99 for the C-type hardness tester, it is preferable to use the A-type rubber hardness tester. In the case that hardness is more than 99 for the F-type hardness tester, it is also preferable to use the C-type hardness tester or the 4-type hardness tester. Hardness values measured with the A-type, C-type and F-type rubber hardness testers will hereinafter be referred to as "A hardness", "C hardness" and "F hardness", respectively.
The cured rubber employed in accordance with the present invention bears a hardness of not more than 3n, preferably not more than 20 in A hardness to no~
less than 15, preferably not less than 30 in _ .~ ~ ;1 83569
If the situation permits, any of these A type, C-type and F-type rubber hardness testers may be used to determine the hardness of cured rubbers for the purpose of the present invention. However, if hardness is less than 1 when the A-type rubber hardness tester is in use 9 it is preferable to measure hardness with either the C-type ruhber hardness tester or the F-type rubber hardness tester because measurements with the A-type hardness tester accompany încreased errors. Similarly, if hardness is less than 1 for the C-type hardness tester, it is more desirable to use the F-type hardness tester in connection with hardness measurements.
Furthermore, in the case ~hat hardness is more ~han 99 for the C-type hardness tester, it is preferable to use the A-type rubber hardness tester. In the case that hardness is more than 99 for the F-type hardness tester, it is also preferable to use the C-type hardness tester or the 4-type hardness tester. Hardness values measured with the A-type, C-type and F-type rubber hardness testers will hereinafter be referred to as "A hardness", "C hardness" and "F hardness", respectively.
The cured rubber employed in accordance with the present invention bears a hardness of not more than 3n, preferably not more than 20 in A hardness to no~
less than 15, preferably not less than 30 in _ .~ ~ ;1 83569
- 4 hardness and exhibits an impact resilience of not less than 40 ~7 ~ preferably not less than 50 %, most preferahly from 60 to 9S ~. Such a cured rubber is a new rubber material which has not been known in the art. In other words, cured rubbers with an A hardness of not more than about 30 is known but they show an impact resilience of less than about 40 %, and those with an impact resilience of more than about ~0 ~ have an A hardness of more than about 3n. It is common knowledge that impact resilience of cured rubber declines with a decrease in its hardness.
The physical properties of the cured rubber of the present invention, i.e. an A hardness of not more than 30, preferablv not more than 20, and an impact resilience of not less than 40 %, preferably not less than 5n ~ ~ most preferably from 60 to 95 %, are definitely outside of the prior common concept.
In accordance with the present invention, the rubber sheet for turntable comprising the above described new and unique cured rubber has the remarkable advantages of sho~-ing excellent vibration-damping properties especially in superlow frequency range and pre~enting the tone quality of reproduced sounds from deteriora~ing due to howling or external vibrations.
This rubber sheet effectively absorbs and shields off vibrations of superlow frequency9 typically those less than 10 Hz, and isolates a disk record from these vibrations, thus inhi~iting howling with no likelihood of pickup outputs being modulated with these vihrations. As a result, listeners can enjoy excellent reproduced sounds over the broad range from ~reble sounds such as the soprano of female vocal sounds to bass sounds with enriched im~ressions of presence when they play back disk records.
For the cured rubber of ~he present invention, it is necessary that the hardness ranges from an A
hardness of not more than 30, preferably not more than 2n to an F hardness of not less than 15, preferably not less than 30 and the impact resilience is not less ,.
The physical properties of the cured rubber of the present invention, i.e. an A hardness of not more than 30, preferablv not more than 20, and an impact resilience of not less than 40 %, preferably not less than 5n ~ ~ most preferably from 60 to 95 %, are definitely outside of the prior common concept.
In accordance with the present invention, the rubber sheet for turntable comprising the above described new and unique cured rubber has the remarkable advantages of sho~-ing excellent vibration-damping properties especially in superlow frequency range and pre~enting the tone quality of reproduced sounds from deteriora~ing due to howling or external vibrations.
This rubber sheet effectively absorbs and shields off vibrations of superlow frequency9 typically those less than 10 Hz, and isolates a disk record from these vibrations, thus inhi~iting howling with no likelihood of pickup outputs being modulated with these vihrations. As a result, listeners can enjoy excellent reproduced sounds over the broad range from ~reble sounds such as the soprano of female vocal sounds to bass sounds with enriched im~ressions of presence when they play back disk records.
For the cured rubber of ~he present invention, it is necessary that the hardness ranges from an A
hardness of not more than 30, preferably not more than 2n to an F hardness of not less than 15, preferably not less than 30 and the impact resilience is not less ,.
- 5 than 4~ ~, preferably not less than 50 ~ most preferably from 60 to 95 ~. The cured ruhber can exhibit excellen~
vibration-damping properties especially in ~he su~rlow frequency range and prevent the tone qu~lity of reproduced sounds ~rom deteriorating due to howling or external vibrations with maintaining the general properties as a rubber shee~ for turntable, when the hardness and impact resilience fall within the above defined ranges. If the hardness is higher than the above definition and the impact resilience is lower than the above defini~ion, the vibration-damping properties become poor especially in the superlow frequency range and the soft and elastic characteristics of the cured rubber like baby s~in which is one of the significant features of the present invention, become lost.
Furthermore, the rubber sheet does not come closely in contact to nor stick to the disk record or turntable, nor does it ensure a desirable breathing phenomenon thereabove and below (this will be discussed later~.
If both hardness and impact resilience are below the above specified ranges, the rubber sheet has only a scarce self-supporting property and can not undergo the weights of a disk record, a cartridge and a pickup arm, resulting in exhibiting substantially no elasticity.
~lore particularly, the projections which are preferably provided on the rubber sheet as described later become deformed and flat, resulting in increase in the contact surface area between the rubber sheet and a disk record or turntable. As a result, the reproduced sounds tend to become heavy and it is difficult to reproduce clear and steady source sounds in a range including both treble and bass regions.
The rubber sheet of the present invention can be classified into the following three categories, depending on its physical proPerties, mainly on the basis of differences in hardness:
Category (I!: Hardness is from more than 15 to not more than 3n in A hardness and impact resilience ~ 3 6355~
~ fi is not less than 50~, particularly from 65 to 95%. The rubber sheet of ~his category peTmitS especially sounding sounds to be reproduced. Consequently, for example, sounds of a pipe organ or soprano of female vocal sounds can be reproduced as faithfully as possibl~.
Ca~egory (II): Hardness is from 1 to 15, preferably from 2 to 7 in A hardness and impact resilience is from 40 to 95 ~, more preferably fTOm 50 to 9S ~, most preferably from 60 to 95 %. The rubber sheet of the category (II~ enjoys the advantages of bo~h of the rubber sheets belonging to the category (I) and category ~ discussed below.
Category (III): Hardness is from less than 1 in A hardness to not less than 15, preferably not less than 3~ in F hardness, and impact Tesilience is not less than 4~ ~, more particularly 5~ to 95 %. The rubbeT
sheet of ~his category effectively inhibits howling and permits reproducing excellent sounds of superlow frequencies.
It is further desirable that, in addition to the above defined physical properties, the cured rubbeT
. in accordance with the present invention bears a tensile - strength of 0.1 to 100 kg./cm2, more preferably 1 to 50 kg./cm29 an elongation of 50 to 1,000 ~, more preferably 200 to 1,000 ~ and a specific gravity of 0.8 to 1.3, ` more preferably 0.89 to 1.05. If the tensile strength is less ~han the above definition, the rubber sheet shows a scarce self-supporting property and becomes fragile and easily broken upon application of small tensile foTce. ContraTily, if i~ is greater than the above difinition, the rubber sheet becomés less flexible and fails to come closely in contact ~o or stick to the disk record or the turntable. The breathing as stated above is difficult when the elongation is .smaller than the above range and the rubber sheet becomes rather extended to the maximum and sagged when it is greater than the specific range. When the specific gravity is greater than the above range, an excess load is applied 3 ~ 6~9 to a driving motor for the turntable, provided that the average thickness of the rubber sheet is greater than 2 mm., thus amplifying vibration sounds from the motor.
On the other hand~ when the specific gravity îs less than the above range, it b~comes impossible to add fillers to ~he rubber composition, with the result that the rubber sheet will have only a scarce self-supporting property.
Preferred physical constants for rubber sheets of the above-defined categories (I), (II) and (III! are as follows:
Category (I) Tensile strength: 1 to 100 kg./cm.2, particularly 5 to 50 kg./cm.
Elongation: 100 to 1,000 %, particularly 200 to 1, 000 ~
Specific gravity: 0.89 to 1.05 Category (II~
Tensile strength: 1 to 50 kg./cm.2, particularly 3 to 50 kg./cm.2 Elongation: 100 to 1,000 ~, more preferably 120 to 1,Q00 ~, and most preferably 200 to 1,000 %
Specific gravity: 0.89 to 1.05, particularly 0.93 to l.Q5 Category (III) Tensile strength: 0.1 to 50 kg /cm.2, particularly 0.1 ~o 20 kg./cm.
Elongation: ln0 to 1,0n0 %, particularly 200 to 1,000 ~
Specific gravity: 0.8~ to 1.05 The cured rubber having the above specific physical constants is obtainable by curing a rubber composition which comprises (Al 100 par~s (parts by weight, the same hereinafter) o~ a rubber component, (B!
1 to 2,00n parts of factice (preferably 5 to 2,000 parts and most preferably 100 ~o lyS00 parts) and ~C? 20 to 2,000 parts of a softening agent (preferably 5q to 2,000 -p~rts and most preferably 200 to 1,5~ parts~. The rubber composition containing such large a~ounts of a factice and a softening agent is a new rubber composition from which a particular cured rubber having a hardness of not more than 3~, particularly not more than 20 in A hardness and an impact resilience of no~ less than 40 %, preferably not less than 50 %, most preferably from 60 to 9S % is available by cuTing.
The rubber component (A~ may include, without limiting thereto, one or mOTe components such as polynorbornene, natural rubber, isoprene rubber, chlo~oprene ruhber, styrene-butadiene rubber) butadiene rubber, butvl rubber, ethylene-propylene rubber 9 ethylene-propylene-diene rubber, nitrile rubber, acryl rubber, urethane rubber, chlorinated polyethylene, chlorosulfonated polyethylene, epichlorohydrin rubber, polysulfide rubber, silicone rubber and the like as a - predominant componen~. These components may include regenerated rubber (for example, rubber powder OT the like) thereof. Furthermore, these rubber components may be either in the form of solid (powder, pellet, block, sheet, etc.~ or in the form of liquid (liquid rubber, latex, etc.l. Out of these components~ a Tubber component composed of polynorbornene as a predominant component is most favorable for the purpose of the present invention. In that case it is desirable tha~
polynorbornene accounts for 50 ~ or more (percen~ by weightg the same hereinafter) of the total weight of the rubber component and more preferably 65 % or more.
Preferably, polynorbornene used herein has an average molecular weight of about 106 to about 5 X 106 and more preferably about 2 X 106 to abou~ 3 X 106.
The f~ctice as the component (B3 may include any of various kinds of factices such as white factice, dark bro~ factice~ amber factice and blue factice which are available by vulcani~ing a variety of vegetable 3ils including L~eed oil, rapeseed oil, soybean oil, sesame oil, tung oil and castor oil with use of sulfur or 1 .~ 63569 ~, sulfur chloride. Those factices may be used alone or in ad~ixture. The factice prepared by vulcanizing rapeseed oil is mos~ favorable.
The softening agent as the component (C~ may be oils, plasticizers or other agents having a softening activity. The oi~ used herein include aromatic oils, naphthenic oils, paraffinic oils, ~egetable oils and animal oils which are commonly used as a filling oil (softening oil, process oil, e~c.l in rubbers. The vegetable oils and animal oils mentioned abo~e include castor oil, rapeseed oil, linseed oil, whale oil, fish oil and the like. Out of plasticizers widely used fOT the manufacture of rubbers9 those having a high softening performance, e.g., dibutyl phthalate, dioctyl phthalate and dioctyl sebacate may be used for the purpose of the presen~ invention. Other softening agent includes liquid rubbers. Of course, these softening agents may be used alone or as a mixture. As a rule, oil alone or in mixture with such a plasticizer is recommended.
~loreover, those widely used rubber ingredients including fillerc such as carbon black and zinc oxide, colorants, lubricants such as stearic acid and ~ antioxidants may be properly added to the rubber ;~ composition to the ex~ent that they do not impair the above-discussed physical properties, in addi~ion to the components ~A! to ~C~.
Preferred rubber compositions for the rubber sheets of the categories ~I~ to (III! are as follows:
Category (I~
Component (A1 100 parts Component (B~ 1 to 1,500 parts, preferably 5 to l,OOn parts and mos~ preferably lOQ to l,nOO
parts Component (C~ 20 to 1,50Q parts, more particularly zon to 1~000 parts Category (II !
Component ~A~ 100 parts Component (B~ 5 to 1,500 parts, preferably 20 to 19 500 ``1~
~ ~ 63~g .
parts and m~st preferably 1~0 to 1,000 parts Com~onent (Cl sn to 19500 parts, more particularly 200 to 1,000 parts 5 categOry (III~
CoJnpo n en t ~A ~ l O û parts Component (B) 20 to 2,0~0 parts, preferably 50 to 1,500 parts and most preferably 100 to 1, S00 parts : 10 Component (C) 50 to 2,000 parts, preferably Z0~ to 1, 500 parts The above rubber composition can be cured by any one of conven~ional curing methods including sulfur curing and sulfurless curing. Curing can be ca~ried out under normal conditi~ns without any specific limitations.
A typical example of the rubber composition, in the case of sulfur curing, is as follows:
(Component ! (Parts) Rubber lOn Factice 1~0 to l7~no Sotening agent 2~0 to l~son Filler 1 to 200 Antioxidant 07 5 to 6 Sulfur 0.5 to 10 - 2~ Curing accelerator 1 to 20 As ano~her significant feature of the ~ubbeT
sheet for turntable in accordance with the present invention, there is no need for after-treatments, e.g.
halogenation and coating as -experienced with the prior art rubber sheet for turntable, with the ormer ensuring increased surface hardness to make the rubber sheet not susceptible to scratches and the latter preventing deposit of dust. l~ile being very low in hardness as set forth above, the rubber sheet for turntable in accordance with the present invention is high in impact resilience, resulting in less or no scratch or dust thereon. Even where the rubber sheet is scratched or dust is attached on the Tubber sheet, it is very .
1 ~ ~35~
convenient to re~ove such scratch or du.st, if the rubber sheet is swung or crumpled with ease like cloth since it is very soft and flexible. Unlike the prior art rubber sheets, the ruhber sheet of the present invention has another surnrising advantage that washing in water is suitable for cleaning and the rubber sheet can be cleaned by washing with crumpling.
The rubber sheet for turntable in accordance with the present in~ention is subjected to no particular limitations as to configuration and may be, in principle, of any well-known configuration. Nevertheless, the following c`onfigurations, combined with the above discussed physical properties, ensure a further improvement in vibration-dam~ing properties and tone quality.
In other words, a preferable configuration of the rubber sheet for use with turntable in accordance with the present invention includes a large number of projections on a major surface of its disk-shaped sheet body.
Since a turntable or a disk record contacts the turntable rubber sheet only atop the projections, the contact area is only a minimum and external vibrations are hardly transmitted to ~he disk record.
Furthermore, the turntable rubber sheet with the above configuration provides a unique advantage as follows:
~ t is generally known that ~he substance with the smallest velocitv of sound is rubber and that with second smallest velocity of sound is air. When the rubber sheet with the above specific configuration is in contact with the turntable, a thin layer of air is ;~ confined between the rubber sheet and the turntable due to the projections so that air in this layer moves inwardly and outwardly through respective ones of the ~rojection-to-~rojection s~aces during the revolution of the turntable, as if the human being breathes.
Consequently, the rubber sheet and the disk record thereon can be regarded as resting on air. This i ~ ~35~9 insures complete isolation of the external vihrations and an improvement in tone quality~ Similarly, in the case where the rubber sheet with the specific configuration is in contact with the disk record, the foregoing situation is envisaged between the rubber sheet and the disk record. As is obvious from the foregoing, the above con-figuration effectively shields off vibrations of a superlow frequency of the order less than 10 Hz and prevents these vibrations from being transmitted to the disk record, thus inhihiting howling with no likelihood that pickup outputs would be modulated with these vibrations.
While the projections in the above specific configùration of the rubber sheet may be of various shapes without any particular limita~ions, it is preferable in order to minimi~e the contact area with the turntable or the disk record that the area of each head of the projections be as small as possible. To this end at least the head of each of the projections is ridge-shaped to make substantially a line contact with the turntable or the disk record. For example, the projections may be roof-shaped, semicircular in section or particularly knife edge-shaped. Another desirable projection has at least such a pointed head as to make substantially a point contact with the turntable or the disk record. The latter shape may include a pyramid (including a polvgonal pyramid, e.g. a triangular pyramid, a quadrangular pyramid and so on, the same hereinafter~, a cone (including an elliptical cone, the 3~ same hereinafter~, a dome (including a near sphere, a hemisphere, a column with a rounded upper portion and the like, the same hereinafter~ and the like. Preferably, each of the latter projections has such a sharp head as a needle. For each of the projections with the two different kinds of shape, it is necessary that at least the head thereof be ridge-shaped or pointed with no particular requirements as to the root thereo~. For example, it may comprise a root of a head-free pyramid ~ 1 ~3~6~
a head-free cone, etc. and a head having a roof shape, semicircular shape, a pyramid, a cone, a dome, etc.
Furthermore, other shapes (e.g. head-free pyrmaidal, pillar-shaped or column-shaped projections~ are available S as long as the contact area with the turntable or the disk record is held as small as possible. It is also obvious that these projections may be provided at its top with small recesses to ensure line contact or point contact.
It is preferable ~hat the contact area between the projection-bearing surface and the turntable or the disk record be 0.01 to 10 % of the entire area of a major surface of the rubber sheet (i.e. the area of a circle having the same diameter as that of the rubber sheet, the same hereinafter~ and more particl~larly 0.01 to 1 ~.
Preferably, the height of the projections is ~.1 to 5 mm. and more particularly 0.3 to 1.8 mm~
Failure to meet this criterion results in difficulty for the air-breathing behavior as mentioned above.
The projections may be formed on the body of the ruhber sheet regularly or at random. Regular alignments may be concentric, spiral, radial, etc. The individual projections may be either spaced at an appropriate interval or closely aligned in contact with one another. When these projections are closely aligned, the adjacent projections may be connected integrally with each other at their roots (as ribs are concentrically aligned on the body of tlle rubber sheet together with closely spaced recesses in the case where the projections are closely aligned in concentric arrays~. Pre~erably, the projections are closely aligned in concentric arravs or the like so that alignments o~ the projections hold air in a space between the rubber sheet and the turntable or the disk record. With this arrangement, the air involved therein passes through the gaps between the closely aligned projections, thus providing better breathing behavior and further improvements ln vibration-~ 1 ~35~9 .
damping properties and tone quality of reproduced sounds.
The projections may be formed integrally with the rubber sheet, or formed separately from the rubber sheet and affixed thereto by a conventional technique such as bonding.
Although the rubher sheet of the above specific configuration has the projections on the one major surface, the other major surface of the rubber sheet is free of particular limitaitons as to configuration. For example, the other major surface may be completely flat or bear the same projec*ions as set forth above or bear concentric, spiral or radial grooves or ribs. Large recesses or projec~ions each having a circular shape, a polygonal shape in plan view may be aligned regularly (e.g., concentrically, spirally or radially) or at random.
Preferred configurations of the rubber sheet for turntable in accordance with the present invention will now be discussed by reference to the drawings.
BRIEF DESCRI~TI~N OF nRAWIN(lS
Figs. 1 and 2 are partial plan views of two major surfaces of a rubber sheet for use with turntable in accordance with an embodiment of the present invention.
Fig. 3 is a vertical cross-sectional view ta~en on the line (V~-tV~ in Figs. 1 and 2.
Fig. 4 is an enlarged cross-sectional view taken on the line (W~-(W) in Fig. 1.
Fig. 5 is a vertical cross-sectional view showing an example of the shape of the edge portion of the rubber sheet for use with a turntable in accordance with the presen~ invention (that is, a vertical cross-sectional view taken on ~he line (X~-(X) in Fig. 1).
Fig. 6 is a partial perspective view o-f an example of an array of projections.
Figs. 7 and 8 are vertical cross-sectional views showing an example of a projection with small i :~ 3 ~3~
recesses.
Fig. 9 is a partial perspective view of an example of an array where projections o different shapes are used in combination.
Fig. 10 is a partial, vertical cross-s~c~ional view of the rubber sheet in accordance with the present invention when being mounted on a turntable as well as a disk record mounted on the ruhber sheet.
Figs. 11 to 13 are plan views of the rubber sheet for turntable in accordance with the present invention, wherein a plurali~y of insular arrays of projections are provided.
Figs. 14 and 15 are plan views of two major surfaces of the rubber sheet for turntable in accordance with another embodiment of the present invention.
Fig. 16 is a vertical cross-sectional view taken on the line (Y~-(Y~ in Figs. 14 and lS.
Figs. 17 and 18 are plan views of two major surfaces of the rubber sheet in accordance with further another embodiment of the present invention.
Fig. 19 is a vertical cross-sectional view taken on the line (Z!-(z~ in Figs. 17 and 18.
Figs. 20a and 2~bJ 21a and 21b, 22a and 22b and 23a and 23b are top views and cross-sectional views of the conventional rubber sheets for turntable, respectively.
Referring first to Figs. 1 through 4, the body of a rubber sheet is generally designated as ~l) and a center shaft hole is designated as ~2). A major surface of the body (1! is provided with closely spaced-apart projections (3~ in a plurality of concentric arrays (cf.
Figs. 1, 3, 4, this arrangement of projections is called "Embodiment A"~. In the following, such a concentric array of closely spaced-apart projections (3~ ~ill be referred to as "array (4~ of projections". The number of the arrays (4~ of projections is optional as long as the body (1~ of the rubber sheet is held substantially hori~on~ally on the turntable and may be typically 3 to ~ ~ ~35 ]~. The arrays (4! of projections may be equally spaced along the radial direction of the body (1~ of the rubher sheet or as indicated in Figs. 1 and 3, a plurality of blocks each comprising two or more close arrays (4) may be provided rfor example, the two arrays (4b~ and (4c), (4d~ ~nd (4e~,and (4f~ and (4g)]. It is to be understood that the arrays t4! o projections may be disposed on concentrically aligned ribs (5) as seen from Fig. 3.
Although in Embodiment A respective ones of the projections (3~ in the arrays (4~ are usually flush at their tops, they should not be limited thereto. For example, when the major surface bearing the projections (~ is to be in contact with the disk record, the projections (3) are highest in the most inner array (4a) (the nearest array with respect to the label section of the disk record~ and lower gradually in the order of the arrays (4b!, (4c!, (4d~, (4e), (4) and (4g~ so that the disk record is substantially held by means of the most inner array (4a! of projections and in no direct contact with the remaining arrays (4b), (4c!~ (4d~, (4e), (4f~ and (4g~ of projections other than the array (4a~.
In this embodiment, the disk record is maintained under non-contacting relationship with the rubber sheet on its periphery when the disk record is stationary. ~lowever, when a pickup cartridge is in operating position for playback of the disk record, the disk record comes into contact with the rubber sheet due to the weight of the cartridge w;th a minimum of contact area. This insures an improvement in vibration inhibition.
The most outer array (4g~ is usually disposed on an edge portion of the body (1) of the rubber sheet.
It is preferable that, as illustrated in a vertical cross-section~l view of Fig. 5 (that is, an enlarged cross-sectional view taken on the line (x!-(X! in Fig. 1~, the edge portion of the body (1) is outwardly inclined and the most outer array (4g~ of projections are disposed on this inclined edge portion. According to this embodiment, the edge portion of the body (l! of a `~ ~B3~
relatively thin thickness offsets tension resistance of the ruhber sheet and helps the close contact of the rubber sheet with the turntable.
The projections (3) may take the various shapes S as suggested previously in Embodiment A. F'referably, the projections (3~ are ridge-shaped at least at the head thereof. Fig. 4 depicts a typical example of the projections (3~ which are of mountain profile with a downwardly expanding skirt. For the projections (3) with the ridge-shaped heads, it is also preferable that ridges (3a~ extend along the radial direction of the body (1) of the rubber sheet as seen from Fig 1. While the projections (3~ in a particular array [e.g., (4d)] may overlap with those in the adjacent array (4e~ along the radial direction of the body (1~ of the rubber sheet, it ~ is desirable that the ridges (3a~ of the projections (3) ; in the particular array (4d~ be located in agreeement with valleys ~6) bett~een the two adjacent projections (3) in the other array (4e~ to avoid such overlapping relationship as seen from Fig. 4. This alignment provides better breathing behavior in a layer of air confined between the rubber sheet and the turntable or the disk record, thus completely shielding off the external vibrations.
Another preferred shape of the projections (3) in Embodiment A includes a pointed head. A partial perspective view of Fig~ ~ [wherein the concentric array (4~ of projections is re-aligned in a straight line]
depicts an example of such a shape of the projections -30 (3~, typically a quadrangular pyramid. In a manner :~ similar to the projections (3~ including the ridge-; shaped heads, while the projections (3~ with the pointed heads in the particular array re.g., (4d~] may overlap with those in the adjacent array re.g., (4e~ along the radial direction of the body (1~ o~ the rubber sheet, it is also desirable that the pointed heads (3b) of the projections (3! in the particular array (4d~ are located in agreement with the valleys (6) between the ~t~o ' ,;
~ ~ ~3569 adjacent projections (3! along the radial direc~ion of the body (1) of the rubber sheet to avoid such overlapping relationship. Each of ~he foregoing projections (3) has a single summi~ (3b) but may have two or more summits (3a') which may be formed by providing the ridge of the above-mentioned projection (3) having the r;dge-shaped head with small recesses as shown in Eigs. 7 and 8. Fig.
7 is a vertical cross-sectional view showing one of the projections (3~ with the ridge-shaped head having two or more .summits (3a') along the radial direction of the body (1~ of the rubber sheet and Fig. 8 is the equivalent along the circumferential direction.
Furthermore, it is obvious that in Embodiment A, the projections (3) with the ridge-shaped heads may be aligned in combination with those with the pointed heads or other different heads in the particular array (4).
An example of such combination is illustrated in a perspective view of Fig. 9 r that is, a perspective view wherein the concentric array (4) of projections is re-aligned in a straight line]. In Fig. 9, the projections(3) with the pointed heads and those with the ridge-: shaped heads [the latter is different from that in Fig. 4 in that the ridges (3a) are aligned along the circumferential direction of the body (1~ of the rubber sheet] are aligned alternatively with each other.
Preferably, as illustrated in Figs. 2 and 3,there are formed concentric grooves (7) in position to correspond to the respective arrays (4) of projections, on the opposite major surface of the rubber sheet having the above illustrated projections (3! in accordance ~ith Embodiment A, so that the rubber sheet is uniform in thickness as a whole. Each of the groo~es (7) may be formed in correspondence with one of the individual arrays (4) of ~he projections or a given number of adjacent arrays (4) of projections as seen from Fig. 3 rfor example, one of the grooves (7) for each of the ribs (5)]. With such an arrangement, the rubher sheet becomes light in weight and the layer of air is also confined in -1 1 ~3~69 the grooves (7~, thus providing an improvement in vibration absorption and tone quality. With the rubber sheet having the arrays (4) of projections on the one surface and the grooves (71 on the opposite surface, the ~one quality of reproduced sounds differs slightly depending on which surface of the rubber sheet is to be in contact with the turntable (or the disk record~.
Proper deter~ination as to which surface of the rubber sheet is to be in contact with the turntable (or the disk record~ results in providing agreeable reproduced sounds.
The turntable is usually provided with openings in the intermediate portion between the center shaft and the periphery thereof. It is thus favorable that, when the surface having the grooves (7) formed therein is to be in contact with the turntable, the most inner groove (7) be kept away from the openings and a layer of air be confined between at least the most inner groove (7) and the turnta~le.
In the case where the one major surface with the arrays (4l of projections is in contact with the disk record and the other major surface with the grooves (7~ in contact with the turntable in accordance with the present invention, the preferred rubber sheet is that wherein the projections (3~ are highest in the most inner : 25 array (4a~ and lower gradually along the arrays (4b), (4c!, (4dl, (4e~, (4f~ and (~g! and at least the most inner groove (7) is kept away from the opening of the turntable. Fig. 10 depicts the operating condition where such a rubber sheet is mounted on the turntable with the disk record resting on the rubber sheet. In Fig. 1OJ the turntable is designated (8), the center shaEt is designated (9!~ the openings of the turntable are designated (10) and the dis~ record is designated (11~. In the situation sho~n in Fig. 10, the rubber sheet is in tight contact at its central portion (corresponding to the lahel region of the disk record~
with the turntable (8~. ~ver the central portion of the rubber sheet which is in tight contact with the turntable, , ~ ~ ~35~9 - 2n -there is involved the layer of air (l2) between the disk record (ll! and the most inner array (4a) of the projections on the rubber sheetO The air in the layer (121 passes through the ga~s between the adjacen~
5 pToj ections in the array (4a) to thereby peTform the breathing as stated abo~e during rep~oduction of the disk record. On ~he other hand~ the most inner groove (7a~ in ~he rubber sheet is s~aced from the opening (lO~
of the turntable (8) so ~hat a layer o air is hermetically sealed within the groo~e ~7aj. ~ s combination of the central portion of the Tubber sheet ~hich is in tight contact with the turntable, the layer ~12) of the moving air and the laye~ of the heTmetically sealed air in the groove (7) p~ovides a further improvement in ~ibration^damping prl~perties and tone quality.
l~ile in the foregoin~ the concentric arTays (4! of the closely aligned projeetions are adapted to confine air with respect to the disk Teco~d or the turntable, other arrangements of the projections effecti~e to confine air appeaT available. For example~
as illustrated in plan views of Figs. 11 to 13, a plurality of circular (including elliptic) arrays of closely aligned projections (3), a plurality of ~5 polygonal (including a triangle and a quadrangle and so on! arrays of closely aligned projections (3), a plurality of fan-shaped arrays of closely aligned projec~ions (3!, etc. (those will be referred to as "insular arrays (13) or projections" hereinafter) may be disposed outside the label section of the disk record.
In that case, air is conined by means of the individual insular arrays ll3~ of projeotions ~o provide b~eath ng beha~ior. In addition, the insular arrays (13) of projections may be of the same dimension but a smaller one (l3) may be interposed between two adj acent greater ones (l3~ as seen from Fig. ll. Moreover, the differently shaped insular arrays (13! of projections may be used together as sho~ in Fig. 13. In ~his emb~diment, the ~ ~ ~35~9 concentric array (4~ of projections may be disposed at the central portion or peripheral portion of the body (1) of the rubber sheet together with the insular arrays (13~ as seen from Eigs. 11 and 12.
Fig. 14 is a plan view of a major sur~ace of the rubber sheet for turntable in accordance wi~h another embodiment of the present invention, Fig. 15 is a plan view of the other major surface of the rubber sheet of Fig. 14 and Fig. 16 is a vertical cross-sectional view taken on the line (Y)-(Y) in Pigs. 14 and 15. On the one major surface there are provided closely aligned projections (3) in a spiral array, as seen from Fig. 14 (this arrangement of projections is referred to as "Embodiment B" hereinafter). In the following, such a spiral array of the projections (3~ will be simply named "array (14) of projections".
In Embodiment B, respective ones of the projections (3~ in the array (14) may be all flush at their tops or lower gradually in a direction toward the periphery of the rubber sheet as in Embodiment A. Though the projections (3! may take the various shapes as discussed above, it is preferable that each of the projections includes the ridge-shaped head or the pointed head in the same manner as in Embodiment A. For the former, it is preferable that the ridges be aligned substantially in the radial direction of the body (1) of the rubber sheet as viewed from Fig. 14. The projections with the ridge-shaped head may be provided with small recesses to form two or more summits as shown in Figs. 7 and 8. It is also apparent that the projections with the ridge-shaped head may be used in combination with the projections with the pointed head or the like as shown in Fig. 9. In Embodiment B, preferably the edge portion of the body (1~ of the rubber slleet is outwardly inclined in a way similar to Embodiment A.
With regard to the other major surface of the rubber sheet provided with the projections (3~ in Embodiment B, it is also desirable that a portion ' ;
~ ~ ~3~
thereof corresponding to the array (1~) of proj~ctionsis made concave as depicted in Figs. 15 and lh ~as a result, a convex rib (15~ is formed in the remaining portion] to thereby make the thickness of the rubber S sheet uniform as a whole. The edge portion of the other major surface is usually provided with a flange portion (16~ to confine air.
Fig. 17 is a plan view of a major surface of the rubber shee~ for turntable in accordance with further another embodiment of the present invention, Fig. 18 is a plan view of the other major surface of the rubber sheet of Fig. 17 and Fig. 19 is a vertical cross-sectional view on the line (Z!-(z~ in Figs. 17 and 18.
Radial arrays of the projections ~re aligned on the one major surface of the body ~1~ of the rubber sheet, as seen from Fig. 17 (this arrangement of the projections is referred to as "Fmbodiment C" hereinafter~. In the following, the radial arrays of the closely aligned projections will be simply named "array (17) of projections".
In Embodiment C, respective ones of the projections (3) in the arrays (17) may be all flush at their tops or lower gradually in a direction to~rard the periphery of the rubber sheet as in Embodiment A.
Though the projections (3) may take the various shapes as discussed above, it is preferable that each of the projections (3) includes the ridge-shaped head or the pointed head in the same manner as in Embodiment A. The projections with the ridge-shaped head may be provided with small recesses to form two or more summits as sho~
from Figs. 7 and 8. It is also apparent that the projections with the ridge-shaped head may be used in combination with the projections with the pointed head or the like as shown in Fig. 9. In Embodimen-t C, preferably the edge portion of the body (l) of the rubber sheet is outwardly inclined as in ~mbodiment A.-With regard to the other.major sur~ace of therubber sheet provided with the projections (3~ in I 3 ~;3~9 Embodiment C, it is also desirable that portions thereof corresponding to ~he arrays (17~ of projections as shown in Figs. 18 and 19 are made radially concave to form radial concave parts ~18) in order to make the thickness of the rubber sheet uniform as a whole.
Obviously, it is not necessarily re~uired to align the projections (3) closely as in Embodiments A to C. They may be aligned at any appropriate interval.
The rubber sheet for turntable in accordance wi~h the present invention is free of any limitation as to thickness. However, the rubber sheet usually has a ma~imum thickness in the order of 2 to 8 mm. a minimum thickness in ~he order of 0.1 to 3 mm. and ari average thickness in the order of 0.1 to 6 mm. and more particularly 0.5 to 2 mm.
The rubber sheet of the present inven~ion may be made in a conventional manner. For example, the above specified rubber composition is directly press-cured within a mold of a given configuration. As an alternative, a non-cured composition in the form of sheet is prepared by calender molding or extrusion molding and then subjected to press curing. Injection molding is also available. It is also recommended that all of the projections (3! be formed in the mold at one ~ime or shaped by cutting after curing. Furthermore, the projections (3~ may be made independently of the body (1) of the rubber sheet and bonded to the body (l~ of the rubber sheet with an appropriate adhesive or the like.
BEST MQDE FOR CARRYING OUT THE INVENTION
The rubber sheet for turntable in accordance with the present inven~ion will now be described in further detail by referring to Examples and Comparative Examples.
Examples 1 to 4 Using the rubber compositions as enumerated in Table 1, several rubber sheets for turntable ~ere ~ ~ 63~6~
manufactured.
Table l Rubber Composition (in part) _ .
Examples Norsorex 150 NA (*1~ 250 250 250 250 ~hite factice S (~2~ 225 20 26n 120 ~ Sunthene 255 (*3~410 200 690 280 10 Dioctyl phthalate45 10 - -FEF carbon 50 50 25 50 Zinc oxide 5 5 5 5 Stearic acid Sumilizer MDP (*4) 2 2 2 2 15 Sulfur 2.5 2 ~ 2 2 Sunceller C~ (~5)10 8 12 9 *1: Polynorbornene ~Norsorex (resistered trademark~, average molecular weight of not less than 2 x 106) extended with 150 parts of naphthenic oil on the basis of 100 paTts of polynorbornene, sold by Nippon Zeon Co., Ltd.
: *2: White factice made by Temma Sabu Kako Kabushiki ~Kaisha *3: fflad~nark for Naphthenic oil made ~y Japan Sun~il Co.~ Ltd.
*4 Tradernark for 2,2'-Methylen~bis(4~ 1-6-tert.-butylphenol) m~de by SumitomD Chemical Co., Ltd.
*5: Trademark for N-cyclohexy1-2-benzothiazyl sulfenamide made by Sanshin Kagaku Kabushiki Kaisha.~
The rubber component was first scoured a~ about : 60C. and kneaded with additional components through the : :~ use of a Banbury mixer and a roller and shee~ed out to giYe a sheet of about 2 to 3 mm. thick. The sheet was : ~ . cut into a disk and cured by a press machine with a given mold under a pressure of 150 kg./cm2 and at a temperature of 155C. fbr-20 min.
The resultant rubber-sheets for turnt~ble application were: con-Eiguration was one as sho~n in '~
' ,: :
.
. ~
5 6 ~
Figs. 1 to 4 and 1~; diameter was 292 mm; maximum thickness was 3.7 mm; minimum thickness was 1.9 mm;
height o~ the projections (3) in the most inner array (4a~ was 0.5 mm. ~the height (Hl~ in Fig. 3] or 1.5 mm.
[the height (H2~ in Fig. 3]; length of the ridges of the projections (3) was about 3 to 6.5 mm; depth of the grooves (7) was 1 mm; and width of the grooves (7) (in the radial directionl was about 30 mm. The individual projections (3! were lower in height gradually toward the periphery of the rubber sheet.
Various physical properties of the resultant rubber sheets were measured with the results shown in Table 2. r~easurements of impact resilience, tensile strength and elongation were conducted according to JIS
K fi301-1969.
Table 2 .
Examples Physical constants --------- - --20 A hardness (degree~ 4 5 7 9 Impact resilience (~ 68 60 72 74 Tensile strength (kg./cm.) ~ 21 19 10 Elongation (~ 398 575 367 281 Specific gravity 0.977 0.98Z 1.0~30.987 Total area of the ridges of the projections (3~ (S52 in total number) in each rubber sheet of Exam~les 1 to 4 occupied about 1.45 ~ of the entire area oE the one major surface of the rubber sheet (assuming the width of the ridges was 0.25 mm.~. When a glass sheet having the same ~imension as that o-E the rubber sheet and a thickness oE 2 mm. (weight: about 300 g.) was mounted on the one major surface of the rubber sheet bearing the projections (3~, the rubber sheet was substantially in contact with the glass sheet only at the ridges of the projections (3) in the most inner array (4a). In that case, the ratio of the contact area to the entire area of the one major surface of the rubber sheet 1 ~ 6 ~
- 2h -was ahout 0.1 ~. The preferred form of the rubber sheet for turntable in accordance with the present invention features minimizing the contact area in such a way.
The following tests were carried out on the rubber sheets of Exam~les 1 to 4. For comparison, the same tests were also carried out on four sorts of rubber sheets affixed to players commercially available on the market. The rubber sheets used herein were summarized in Table 3.
rable 3 v Comparative Exam~les 1 2 3 4 Butyl SBR/NR Styrene- Butyl ~aterial rubber (*l~ butadiene rubber rubber (*2) A hardness (degree) 24 5n 57 36 Impact resilience (~ 19 - 33 Specific gravity 1~223 1.356 1.431 1.642 Halogenation No Yes Yes Yes * Fig.20aFig.21a Fig.22a Fig.23a Sha~e ( 3! Fig.20bFig.21b Fig.22b Fig.23b *1: ~lixture of st~rene-butadiene rubber and natural rubber *2: Sheet body of butyl rubber covered with a mixture of natural rubber and styrene-butadiene rubber *3: Figs. 20a and 20b, 21a and 21b, 22a and 22b and 23a and 23b are top and cross-sectional views of the rubber sheets o Comparative Examples 1 to 4, respectively. In these drawings thicknesses (hl~, ( 2!~ (h3~, (h4~, (hs)~ (h6~, (h7) and (h8~ of the rubber sheets were as follows:
~hll: 4.2 mm.
(h2): 3.5mm.
(h3~: 5 mm.
(h4!: 4 mm.
(h5!: 3.5 mm.
(h6~: 2.5 mm.
(h7!: 5 mm.
- (h8l: 4.5 ~I.
3 :i 63~9 .
Configurations were as follo~s:
Comparativ~ ~xample 1 Top surface: a circular recess of 0. 7 lTun . deep at its center ; S Bottom surface: flat COmpaTa t iY e Example 2 Top surface: a circular recess of 1.0 mm. deep at its center and a concen~crically - circular groove of 1. O mm. deep Bottom surface: flat Comparative Example 3 Top surface: a circular recess of 1.0 n~n. deep a~
its center Bottom surface: flat 1~ Comparative Example 4 Top surface: three COnCentTically circular grooves of 0. 5 mm. deep Bottom surface: flat It is noted tha t: the bottom surfaces of the ru~ber sheets of Comparative Examples 1 to 4 were all flat and in contac't wi~h the turntable. In carrying out the following tests, the rubber sheets of Comparative Exampl es 1 to 4 were mounted with their flat bottom suTface in contact with the turntable.
2s (1! Tone quali~y cest (i! Plav^back equipmen~t Pre-main amplifier: AU-D307 (Sansui Electric Co., Ltd. ) Player: DP-40F (Nippon Columbia Co., Lt~. ) Cartridge: V-15 type 3 (Shure Brothers, Inc. ) 401 (made by Mitsubishi Electric Corporation) (ii) Listening roc~n P~om of 66 m. in area (equipped with an air conditioner and a ventilator) Floor: Polyvinyl chloride-tiled (with mortared underlying layer) C~iling: Fla~ noninfla~nable material (no sound~absorEJtion opening) Inner walls: Ply~l ~.
3~B9 - 2~ -(iii~ Test method A panel of 4 trai~ed listeners A, B, C and D
was instructed to hear the following records and score them on the following parameters. The s rubber sheets of Examples 1 to 4 were set on the turntable with the surface illustrated in Fig. 1 ~one having the projections (3)] being in contact with the record.
(~) Female vocal Title of record: Valses, Canciones Y Tangos ~; (Nippon Phonogram Co., Ltd.) Singer: ~inamaria Hidalgo Accompaniment: ~lugo Videla (guitar) and others Program: Te Pido Que Lo Pienses Parameters:
(a~ if reproduced sounds are near human sounds (b) if the treble region of soprano is not distorted (c) if accompanying guitar sounds are not stronger than vocal sounds (d~ if the impressions of presence are rich (~) Concerto Title of record: "Le Quattro Stagioni" ~8 by Vivaldi (Nippon Phonogram Co., Ltd.) Performer: Roberto ~lichelucci (violin) and I Musici Program: Concerto No. 1, E ~lajor RV 269 "Spring"
Parameters:
(a) if sounds of chords are vivid (b) if the treble region is not distorted (c) if the bass region is well-reproduced ~; 35 (d) i the impressions of presence are rich (~) Flamenco gui~ar Title of record: Manolo Sanl~car in Japan (RVC Corporation) 35~9 - 2~ -Performer: ~lanolo Sanl~car (guitar~, Isidro (guitar~ and Jos~ 2~iguel (piano) rrogram: Callej6n del Carmen Parameters:
(a~if sounds of chords are we:Ll reproduced .
(b! if ~he treble region is not distorted (c~ if beats of a guitar are well reproduced (d~ if ~he impressions of presence are rich The scores as to the above parameters were 10 determined according to the following fiv2-poin~ system.
5 polnts: Exceptionally good 4 points: Very good 3 points: Good 2 points: Ordinary 1 point : Poor The sum of points as to each of the parameters evaluated by each of the listeners multiplied by five was regarded as overall evaluation by each of the listeners ~if all of the parameters are evaluated as 5 points, overall evaluation would be full mar~s (lnO
points). Also, ~he average value of overall evaluations by the four lis~eners was computed. Tables 4 to 9 indicate the results thereof.
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1 1 S3!j~9 - 3f. -( 2 ) Hohl ing test Like~ise the tone quali1:y t~st, the listenersA, B, C and D were instructed to hear the three sorts of records mentioned above and determine the presence or S absence of ho~l ing on the basis of the follvwing definition The pre-main amplifier was employed with both treble and bass being located at "flat", while volume pointed toward 11 o'clock.
Defini~ion of howling: Howling means all that the tone quality of Teproduced sounds is - deteriorated due to external vibrations and repToduction of source sounds ~for example, ~uman sounds of vocal~ is adversely affected.
lS Howling was evaluated according to the 1~-point system, wherein 10 points implied that no howling ~as observed and source sounds were reproduced as they were. Decrease in points ;ndicated increase in howling and 1 point indicated that howling was most severe and reproduced sounds were most deteriorated. The results are depicted in Table lO wherein "obverse" ~nd "reverse"
of the rubber shee~s of Examples 1 to 4 bear the following mean;ngs.
Obverse: The surface as illustrated in Fig. 1 ri.e., one having ~he projections (3) thereon] is regarded as a top surface - (i.e., one in contact with the disk record).
Re~erse: The surface as illustrated in Fig. 2 r i.e., one having the grooves (7! therein]
is regarded as a top surface.
Points in Table 10 show average values evaluated by the four listeners (frac~ions were rounded off~.
~ .
:
-` `` J ~356~
C~ ~
~ ~ , .
~ ~ ~
o ~C
' .
~ o X ~ ~ ~
:
~ ~ ,/ ~
o X
E~ ~ O` co co X o~ o O C~ ~ OD
~ C~ CO
~o ~~
`~ i ~ ' : ~ ~ ~ o ` .. . ::
, ` ' .
' ~, .
vibration-damping properties especially in ~he su~rlow frequency range and prevent the tone qu~lity of reproduced sounds ~rom deteriorating due to howling or external vibrations with maintaining the general properties as a rubber shee~ for turntable, when the hardness and impact resilience fall within the above defined ranges. If the hardness is higher than the above definition and the impact resilience is lower than the above defini~ion, the vibration-damping properties become poor especially in the superlow frequency range and the soft and elastic characteristics of the cured rubber like baby s~in which is one of the significant features of the present invention, become lost.
Furthermore, the rubber sheet does not come closely in contact to nor stick to the disk record or turntable, nor does it ensure a desirable breathing phenomenon thereabove and below (this will be discussed later~.
If both hardness and impact resilience are below the above specified ranges, the rubber sheet has only a scarce self-supporting property and can not undergo the weights of a disk record, a cartridge and a pickup arm, resulting in exhibiting substantially no elasticity.
~lore particularly, the projections which are preferably provided on the rubber sheet as described later become deformed and flat, resulting in increase in the contact surface area between the rubber sheet and a disk record or turntable. As a result, the reproduced sounds tend to become heavy and it is difficult to reproduce clear and steady source sounds in a range including both treble and bass regions.
The rubber sheet of the present invention can be classified into the following three categories, depending on its physical proPerties, mainly on the basis of differences in hardness:
Category (I!: Hardness is from more than 15 to not more than 3n in A hardness and impact resilience ~ 3 6355~
~ fi is not less than 50~, particularly from 65 to 95%. The rubber sheet of ~his category peTmitS especially sounding sounds to be reproduced. Consequently, for example, sounds of a pipe organ or soprano of female vocal sounds can be reproduced as faithfully as possibl~.
Ca~egory (II): Hardness is from 1 to 15, preferably from 2 to 7 in A hardness and impact resilience is from 40 to 95 ~, more preferably fTOm 50 to 9S ~, most preferably from 60 to 95 %. The rubber sheet of the category (II~ enjoys the advantages of bo~h of the rubber sheets belonging to the category (I) and category ~ discussed below.
Category (III): Hardness is from less than 1 in A hardness to not less than 15, preferably not less than 3~ in F hardness, and impact Tesilience is not less than 4~ ~, more particularly 5~ to 95 %. The rubbeT
sheet of ~his category effectively inhibits howling and permits reproducing excellent sounds of superlow frequencies.
It is further desirable that, in addition to the above defined physical properties, the cured rubbeT
. in accordance with the present invention bears a tensile - strength of 0.1 to 100 kg./cm2, more preferably 1 to 50 kg./cm29 an elongation of 50 to 1,000 ~, more preferably 200 to 1,000 ~ and a specific gravity of 0.8 to 1.3, ` more preferably 0.89 to 1.05. If the tensile strength is less ~han the above definition, the rubber sheet shows a scarce self-supporting property and becomes fragile and easily broken upon application of small tensile foTce. ContraTily, if i~ is greater than the above difinition, the rubber sheet becomés less flexible and fails to come closely in contact ~o or stick to the disk record or the turntable. The breathing as stated above is difficult when the elongation is .smaller than the above range and the rubber sheet becomes rather extended to the maximum and sagged when it is greater than the specific range. When the specific gravity is greater than the above range, an excess load is applied 3 ~ 6~9 to a driving motor for the turntable, provided that the average thickness of the rubber sheet is greater than 2 mm., thus amplifying vibration sounds from the motor.
On the other hand~ when the specific gravity îs less than the above range, it b~comes impossible to add fillers to ~he rubber composition, with the result that the rubber sheet will have only a scarce self-supporting property.
Preferred physical constants for rubber sheets of the above-defined categories (I), (II) and (III! are as follows:
Category (I) Tensile strength: 1 to 100 kg./cm.2, particularly 5 to 50 kg./cm.
Elongation: 100 to 1,000 %, particularly 200 to 1, 000 ~
Specific gravity: 0.89 to 1.05 Category (II~
Tensile strength: 1 to 50 kg./cm.2, particularly 3 to 50 kg./cm.2 Elongation: 100 to 1,000 ~, more preferably 120 to 1,Q00 ~, and most preferably 200 to 1,000 %
Specific gravity: 0.89 to 1.05, particularly 0.93 to l.Q5 Category (III) Tensile strength: 0.1 to 50 kg /cm.2, particularly 0.1 ~o 20 kg./cm.
Elongation: ln0 to 1,0n0 %, particularly 200 to 1,000 ~
Specific gravity: 0.8~ to 1.05 The cured rubber having the above specific physical constants is obtainable by curing a rubber composition which comprises (Al 100 par~s (parts by weight, the same hereinafter) o~ a rubber component, (B!
1 to 2,00n parts of factice (preferably 5 to 2,000 parts and most preferably 100 ~o lyS00 parts) and ~C? 20 to 2,000 parts of a softening agent (preferably 5q to 2,000 -p~rts and most preferably 200 to 1,5~ parts~. The rubber composition containing such large a~ounts of a factice and a softening agent is a new rubber composition from which a particular cured rubber having a hardness of not more than 3~, particularly not more than 20 in A hardness and an impact resilience of no~ less than 40 %, preferably not less than 50 %, most preferably from 60 to 9S % is available by cuTing.
The rubber component (A~ may include, without limiting thereto, one or mOTe components such as polynorbornene, natural rubber, isoprene rubber, chlo~oprene ruhber, styrene-butadiene rubber) butadiene rubber, butvl rubber, ethylene-propylene rubber 9 ethylene-propylene-diene rubber, nitrile rubber, acryl rubber, urethane rubber, chlorinated polyethylene, chlorosulfonated polyethylene, epichlorohydrin rubber, polysulfide rubber, silicone rubber and the like as a - predominant componen~. These components may include regenerated rubber (for example, rubber powder OT the like) thereof. Furthermore, these rubber components may be either in the form of solid (powder, pellet, block, sheet, etc.~ or in the form of liquid (liquid rubber, latex, etc.l. Out of these components~ a Tubber component composed of polynorbornene as a predominant component is most favorable for the purpose of the present invention. In that case it is desirable tha~
polynorbornene accounts for 50 ~ or more (percen~ by weightg the same hereinafter) of the total weight of the rubber component and more preferably 65 % or more.
Preferably, polynorbornene used herein has an average molecular weight of about 106 to about 5 X 106 and more preferably about 2 X 106 to abou~ 3 X 106.
The f~ctice as the component (B3 may include any of various kinds of factices such as white factice, dark bro~ factice~ amber factice and blue factice which are available by vulcani~ing a variety of vegetable 3ils including L~eed oil, rapeseed oil, soybean oil, sesame oil, tung oil and castor oil with use of sulfur or 1 .~ 63569 ~, sulfur chloride. Those factices may be used alone or in ad~ixture. The factice prepared by vulcanizing rapeseed oil is mos~ favorable.
The softening agent as the component (C~ may be oils, plasticizers or other agents having a softening activity. The oi~ used herein include aromatic oils, naphthenic oils, paraffinic oils, ~egetable oils and animal oils which are commonly used as a filling oil (softening oil, process oil, e~c.l in rubbers. The vegetable oils and animal oils mentioned abo~e include castor oil, rapeseed oil, linseed oil, whale oil, fish oil and the like. Out of plasticizers widely used fOT the manufacture of rubbers9 those having a high softening performance, e.g., dibutyl phthalate, dioctyl phthalate and dioctyl sebacate may be used for the purpose of the presen~ invention. Other softening agent includes liquid rubbers. Of course, these softening agents may be used alone or as a mixture. As a rule, oil alone or in mixture with such a plasticizer is recommended.
~loreover, those widely used rubber ingredients including fillerc such as carbon black and zinc oxide, colorants, lubricants such as stearic acid and ~ antioxidants may be properly added to the rubber ;~ composition to the ex~ent that they do not impair the above-discussed physical properties, in addi~ion to the components ~A! to ~C~.
Preferred rubber compositions for the rubber sheets of the categories ~I~ to (III! are as follows:
Category (I~
Component (A1 100 parts Component (B~ 1 to 1,500 parts, preferably 5 to l,OOn parts and mos~ preferably lOQ to l,nOO
parts Component (C~ 20 to 1,50Q parts, more particularly zon to 1~000 parts Category (II !
Component ~A~ 100 parts Component (B~ 5 to 1,500 parts, preferably 20 to 19 500 ``1~
~ ~ 63~g .
parts and m~st preferably 1~0 to 1,000 parts Com~onent (Cl sn to 19500 parts, more particularly 200 to 1,000 parts 5 categOry (III~
CoJnpo n en t ~A ~ l O û parts Component (B) 20 to 2,0~0 parts, preferably 50 to 1,500 parts and most preferably 100 to 1, S00 parts : 10 Component (C) 50 to 2,000 parts, preferably Z0~ to 1, 500 parts The above rubber composition can be cured by any one of conven~ional curing methods including sulfur curing and sulfurless curing. Curing can be ca~ried out under normal conditi~ns without any specific limitations.
A typical example of the rubber composition, in the case of sulfur curing, is as follows:
(Component ! (Parts) Rubber lOn Factice 1~0 to l7~no Sotening agent 2~0 to l~son Filler 1 to 200 Antioxidant 07 5 to 6 Sulfur 0.5 to 10 - 2~ Curing accelerator 1 to 20 As ano~her significant feature of the ~ubbeT
sheet for turntable in accordance with the present invention, there is no need for after-treatments, e.g.
halogenation and coating as -experienced with the prior art rubber sheet for turntable, with the ormer ensuring increased surface hardness to make the rubber sheet not susceptible to scratches and the latter preventing deposit of dust. l~ile being very low in hardness as set forth above, the rubber sheet for turntable in accordance with the present invention is high in impact resilience, resulting in less or no scratch or dust thereon. Even where the rubber sheet is scratched or dust is attached on the Tubber sheet, it is very .
1 ~ ~35~
convenient to re~ove such scratch or du.st, if the rubber sheet is swung or crumpled with ease like cloth since it is very soft and flexible. Unlike the prior art rubber sheets, the ruhber sheet of the present invention has another surnrising advantage that washing in water is suitable for cleaning and the rubber sheet can be cleaned by washing with crumpling.
The rubber sheet for turntable in accordance with the present in~ention is subjected to no particular limitations as to configuration and may be, in principle, of any well-known configuration. Nevertheless, the following c`onfigurations, combined with the above discussed physical properties, ensure a further improvement in vibration-dam~ing properties and tone quality.
In other words, a preferable configuration of the rubber sheet for use with turntable in accordance with the present invention includes a large number of projections on a major surface of its disk-shaped sheet body.
Since a turntable or a disk record contacts the turntable rubber sheet only atop the projections, the contact area is only a minimum and external vibrations are hardly transmitted to ~he disk record.
Furthermore, the turntable rubber sheet with the above configuration provides a unique advantage as follows:
~ t is generally known that ~he substance with the smallest velocitv of sound is rubber and that with second smallest velocity of sound is air. When the rubber sheet with the above specific configuration is in contact with the turntable, a thin layer of air is ;~ confined between the rubber sheet and the turntable due to the projections so that air in this layer moves inwardly and outwardly through respective ones of the ~rojection-to-~rojection s~aces during the revolution of the turntable, as if the human being breathes.
Consequently, the rubber sheet and the disk record thereon can be regarded as resting on air. This i ~ ~35~9 insures complete isolation of the external vihrations and an improvement in tone quality~ Similarly, in the case where the rubber sheet with the specific configuration is in contact with the disk record, the foregoing situation is envisaged between the rubber sheet and the disk record. As is obvious from the foregoing, the above con-figuration effectively shields off vibrations of a superlow frequency of the order less than 10 Hz and prevents these vibrations from being transmitted to the disk record, thus inhihiting howling with no likelihood that pickup outputs would be modulated with these vibrations.
While the projections in the above specific configùration of the rubber sheet may be of various shapes without any particular limita~ions, it is preferable in order to minimi~e the contact area with the turntable or the disk record that the area of each head of the projections be as small as possible. To this end at least the head of each of the projections is ridge-shaped to make substantially a line contact with the turntable or the disk record. For example, the projections may be roof-shaped, semicircular in section or particularly knife edge-shaped. Another desirable projection has at least such a pointed head as to make substantially a point contact with the turntable or the disk record. The latter shape may include a pyramid (including a polvgonal pyramid, e.g. a triangular pyramid, a quadrangular pyramid and so on, the same hereinafter~, a cone (including an elliptical cone, the 3~ same hereinafter~, a dome (including a near sphere, a hemisphere, a column with a rounded upper portion and the like, the same hereinafter~ and the like. Preferably, each of the latter projections has such a sharp head as a needle. For each of the projections with the two different kinds of shape, it is necessary that at least the head thereof be ridge-shaped or pointed with no particular requirements as to the root thereo~. For example, it may comprise a root of a head-free pyramid ~ 1 ~3~6~
a head-free cone, etc. and a head having a roof shape, semicircular shape, a pyramid, a cone, a dome, etc.
Furthermore, other shapes (e.g. head-free pyrmaidal, pillar-shaped or column-shaped projections~ are available S as long as the contact area with the turntable or the disk record is held as small as possible. It is also obvious that these projections may be provided at its top with small recesses to ensure line contact or point contact.
It is preferable ~hat the contact area between the projection-bearing surface and the turntable or the disk record be 0.01 to 10 % of the entire area of a major surface of the rubber sheet (i.e. the area of a circle having the same diameter as that of the rubber sheet, the same hereinafter~ and more particl~larly 0.01 to 1 ~.
Preferably, the height of the projections is ~.1 to 5 mm. and more particularly 0.3 to 1.8 mm~
Failure to meet this criterion results in difficulty for the air-breathing behavior as mentioned above.
The projections may be formed on the body of the ruhber sheet regularly or at random. Regular alignments may be concentric, spiral, radial, etc. The individual projections may be either spaced at an appropriate interval or closely aligned in contact with one another. When these projections are closely aligned, the adjacent projections may be connected integrally with each other at their roots (as ribs are concentrically aligned on the body of tlle rubber sheet together with closely spaced recesses in the case where the projections are closely aligned in concentric arrays~. Pre~erably, the projections are closely aligned in concentric arravs or the like so that alignments o~ the projections hold air in a space between the rubber sheet and the turntable or the disk record. With this arrangement, the air involved therein passes through the gaps between the closely aligned projections, thus providing better breathing behavior and further improvements ln vibration-~ 1 ~35~9 .
damping properties and tone quality of reproduced sounds.
The projections may be formed integrally with the rubber sheet, or formed separately from the rubber sheet and affixed thereto by a conventional technique such as bonding.
Although the rubher sheet of the above specific configuration has the projections on the one major surface, the other major surface of the rubber sheet is free of particular limitaitons as to configuration. For example, the other major surface may be completely flat or bear the same projec*ions as set forth above or bear concentric, spiral or radial grooves or ribs. Large recesses or projec~ions each having a circular shape, a polygonal shape in plan view may be aligned regularly (e.g., concentrically, spirally or radially) or at random.
Preferred configurations of the rubber sheet for turntable in accordance with the present invention will now be discussed by reference to the drawings.
BRIEF DESCRI~TI~N OF nRAWIN(lS
Figs. 1 and 2 are partial plan views of two major surfaces of a rubber sheet for use with turntable in accordance with an embodiment of the present invention.
Fig. 3 is a vertical cross-sectional view ta~en on the line (V~-tV~ in Figs. 1 and 2.
Fig. 4 is an enlarged cross-sectional view taken on the line (W~-(W) in Fig. 1.
Fig. 5 is a vertical cross-sectional view showing an example of the shape of the edge portion of the rubber sheet for use with a turntable in accordance with the presen~ invention (that is, a vertical cross-sectional view taken on ~he line (X~-(X) in Fig. 1).
Fig. 6 is a partial perspective view o-f an example of an array of projections.
Figs. 7 and 8 are vertical cross-sectional views showing an example of a projection with small i :~ 3 ~3~
recesses.
Fig. 9 is a partial perspective view of an example of an array where projections o different shapes are used in combination.
Fig. 10 is a partial, vertical cross-s~c~ional view of the rubber sheet in accordance with the present invention when being mounted on a turntable as well as a disk record mounted on the ruhber sheet.
Figs. 11 to 13 are plan views of the rubber sheet for turntable in accordance with the present invention, wherein a plurali~y of insular arrays of projections are provided.
Figs. 14 and 15 are plan views of two major surfaces of the rubber sheet for turntable in accordance with another embodiment of the present invention.
Fig. 16 is a vertical cross-sectional view taken on the line (Y~-(Y~ in Figs. 14 and lS.
Figs. 17 and 18 are plan views of two major surfaces of the rubber sheet in accordance with further another embodiment of the present invention.
Fig. 19 is a vertical cross-sectional view taken on the line (Z!-(z~ in Figs. 17 and 18.
Figs. 20a and 2~bJ 21a and 21b, 22a and 22b and 23a and 23b are top views and cross-sectional views of the conventional rubber sheets for turntable, respectively.
Referring first to Figs. 1 through 4, the body of a rubber sheet is generally designated as ~l) and a center shaft hole is designated as ~2). A major surface of the body (1! is provided with closely spaced-apart projections (3~ in a plurality of concentric arrays (cf.
Figs. 1, 3, 4, this arrangement of projections is called "Embodiment A"~. In the following, such a concentric array of closely spaced-apart projections (3~ ~ill be referred to as "array (4~ of projections". The number of the arrays (4~ of projections is optional as long as the body (1~ of the rubber sheet is held substantially hori~on~ally on the turntable and may be typically 3 to ~ ~ ~35 ]~. The arrays (4! of projections may be equally spaced along the radial direction of the body (1~ of the rubher sheet or as indicated in Figs. 1 and 3, a plurality of blocks each comprising two or more close arrays (4) may be provided rfor example, the two arrays (4b~ and (4c), (4d~ ~nd (4e~,and (4f~ and (4g)]. It is to be understood that the arrays t4! o projections may be disposed on concentrically aligned ribs (5) as seen from Fig. 3.
Although in Embodiment A respective ones of the projections (3~ in the arrays (4~ are usually flush at their tops, they should not be limited thereto. For example, when the major surface bearing the projections (~ is to be in contact with the disk record, the projections (3) are highest in the most inner array (4a) (the nearest array with respect to the label section of the disk record~ and lower gradually in the order of the arrays (4b!, (4c!, (4d~, (4e), (4) and (4g~ so that the disk record is substantially held by means of the most inner array (4a! of projections and in no direct contact with the remaining arrays (4b), (4c!~ (4d~, (4e), (4f~ and (4g~ of projections other than the array (4a~.
In this embodiment, the disk record is maintained under non-contacting relationship with the rubber sheet on its periphery when the disk record is stationary. ~lowever, when a pickup cartridge is in operating position for playback of the disk record, the disk record comes into contact with the rubber sheet due to the weight of the cartridge w;th a minimum of contact area. This insures an improvement in vibration inhibition.
The most outer array (4g~ is usually disposed on an edge portion of the body (1) of the rubber sheet.
It is preferable that, as illustrated in a vertical cross-section~l view of Fig. 5 (that is, an enlarged cross-sectional view taken on the line (x!-(X! in Fig. 1~, the edge portion of the body (1) is outwardly inclined and the most outer array (4g~ of projections are disposed on this inclined edge portion. According to this embodiment, the edge portion of the body (l! of a `~ ~B3~
relatively thin thickness offsets tension resistance of the ruhber sheet and helps the close contact of the rubber sheet with the turntable.
The projections (3) may take the various shapes S as suggested previously in Embodiment A. F'referably, the projections (3~ are ridge-shaped at least at the head thereof. Fig. 4 depicts a typical example of the projections (3~ which are of mountain profile with a downwardly expanding skirt. For the projections (3) with the ridge-shaped heads, it is also preferable that ridges (3a~ extend along the radial direction of the body (1) of the rubber sheet as seen from Fig 1. While the projections (3~ in a particular array [e.g., (4d)] may overlap with those in the adjacent array (4e~ along the radial direction of the body (1~ of the rubber sheet, it ~ is desirable that the ridges (3a~ of the projections (3) ; in the particular array (4d~ be located in agreeement with valleys ~6) bett~een the two adjacent projections (3) in the other array (4e~ to avoid such overlapping relationship as seen from Fig. 4. This alignment provides better breathing behavior in a layer of air confined between the rubber sheet and the turntable or the disk record, thus completely shielding off the external vibrations.
Another preferred shape of the projections (3) in Embodiment A includes a pointed head. A partial perspective view of Fig~ ~ [wherein the concentric array (4~ of projections is re-aligned in a straight line]
depicts an example of such a shape of the projections -30 (3~, typically a quadrangular pyramid. In a manner :~ similar to the projections (3~ including the ridge-; shaped heads, while the projections (3~ with the pointed heads in the particular array re.g., (4d~] may overlap with those in the adjacent array re.g., (4e~ along the radial direction of the body (1~ o~ the rubber sheet, it is also desirable that the pointed heads (3b) of the projections (3! in the particular array (4d~ are located in agreement with the valleys (6) between the ~t~o ' ,;
~ ~ ~3569 adjacent projections (3! along the radial direc~ion of the body (1) of the rubber sheet to avoid such overlapping relationship. Each of ~he foregoing projections (3) has a single summi~ (3b) but may have two or more summits (3a') which may be formed by providing the ridge of the above-mentioned projection (3) having the r;dge-shaped head with small recesses as shown in Eigs. 7 and 8. Fig.
7 is a vertical cross-sectional view showing one of the projections (3~ with the ridge-shaped head having two or more .summits (3a') along the radial direction of the body (1~ of the rubber sheet and Fig. 8 is the equivalent along the circumferential direction.
Furthermore, it is obvious that in Embodiment A, the projections (3) with the ridge-shaped heads may be aligned in combination with those with the pointed heads or other different heads in the particular array (4).
An example of such combination is illustrated in a perspective view of Fig. 9 r that is, a perspective view wherein the concentric array (4) of projections is re-aligned in a straight line]. In Fig. 9, the projections(3) with the pointed heads and those with the ridge-: shaped heads [the latter is different from that in Fig. 4 in that the ridges (3a) are aligned along the circumferential direction of the body (1~ of the rubber sheet] are aligned alternatively with each other.
Preferably, as illustrated in Figs. 2 and 3,there are formed concentric grooves (7) in position to correspond to the respective arrays (4) of projections, on the opposite major surface of the rubber sheet having the above illustrated projections (3! in accordance ~ith Embodiment A, so that the rubber sheet is uniform in thickness as a whole. Each of the groo~es (7) may be formed in correspondence with one of the individual arrays (4) of ~he projections or a given number of adjacent arrays (4) of projections as seen from Fig. 3 rfor example, one of the grooves (7) for each of the ribs (5)]. With such an arrangement, the rubher sheet becomes light in weight and the layer of air is also confined in -1 1 ~3~69 the grooves (7~, thus providing an improvement in vibration absorption and tone quality. With the rubber sheet having the arrays (4) of projections on the one surface and the grooves (71 on the opposite surface, the ~one quality of reproduced sounds differs slightly depending on which surface of the rubber sheet is to be in contact with the turntable (or the disk record~.
Proper deter~ination as to which surface of the rubber sheet is to be in contact with the turntable (or the disk record~ results in providing agreeable reproduced sounds.
The turntable is usually provided with openings in the intermediate portion between the center shaft and the periphery thereof. It is thus favorable that, when the surface having the grooves (7) formed therein is to be in contact with the turntable, the most inner groove (7) be kept away from the openings and a layer of air be confined between at least the most inner groove (7) and the turnta~le.
In the case where the one major surface with the arrays (4l of projections is in contact with the disk record and the other major surface with the grooves (7~ in contact with the turntable in accordance with the present invention, the preferred rubber sheet is that wherein the projections (3~ are highest in the most inner : 25 array (4a~ and lower gradually along the arrays (4b), (4c!, (4dl, (4e~, (4f~ and (~g! and at least the most inner groove (7) is kept away from the opening of the turntable. Fig. 10 depicts the operating condition where such a rubber sheet is mounted on the turntable with the disk record resting on the rubber sheet. In Fig. 1OJ the turntable is designated (8), the center shaEt is designated (9!~ the openings of the turntable are designated (10) and the dis~ record is designated (11~. In the situation sho~n in Fig. 10, the rubber sheet is in tight contact at its central portion (corresponding to the lahel region of the disk record~
with the turntable (8~. ~ver the central portion of the rubber sheet which is in tight contact with the turntable, , ~ ~ ~35~9 - 2n -there is involved the layer of air (l2) between the disk record (ll! and the most inner array (4a) of the projections on the rubber sheetO The air in the layer (121 passes through the ga~s between the adjacen~
5 pToj ections in the array (4a) to thereby peTform the breathing as stated abo~e during rep~oduction of the disk record. On ~he other hand~ the most inner groove (7a~ in ~he rubber sheet is s~aced from the opening (lO~
of the turntable (8) so ~hat a layer o air is hermetically sealed within the groo~e ~7aj. ~ s combination of the central portion of the Tubber sheet ~hich is in tight contact with the turntable, the layer ~12) of the moving air and the laye~ of the heTmetically sealed air in the groove (7) p~ovides a further improvement in ~ibration^damping prl~perties and tone quality.
l~ile in the foregoin~ the concentric arTays (4! of the closely aligned projeetions are adapted to confine air with respect to the disk Teco~d or the turntable, other arrangements of the projections effecti~e to confine air appeaT available. For example~
as illustrated in plan views of Figs. 11 to 13, a plurality of circular (including elliptic) arrays of closely aligned projections (3), a plurality of ~5 polygonal (including a triangle and a quadrangle and so on! arrays of closely aligned projections (3), a plurality of fan-shaped arrays of closely aligned projec~ions (3!, etc. (those will be referred to as "insular arrays (13) or projections" hereinafter) may be disposed outside the label section of the disk record.
In that case, air is conined by means of the individual insular arrays ll3~ of projeotions ~o provide b~eath ng beha~ior. In addition, the insular arrays (13) of projections may be of the same dimension but a smaller one (l3) may be interposed between two adj acent greater ones (l3~ as seen from Fig. ll. Moreover, the differently shaped insular arrays (13! of projections may be used together as sho~ in Fig. 13. In ~his emb~diment, the ~ ~ ~35~9 concentric array (4~ of projections may be disposed at the central portion or peripheral portion of the body (1) of the rubber sheet together with the insular arrays (13~ as seen from Eigs. 11 and 12.
Fig. 14 is a plan view of a major sur~ace of the rubber sheet for turntable in accordance wi~h another embodiment of the present invention, Fig. 15 is a plan view of the other major surface of the rubber sheet of Fig. 14 and Fig. 16 is a vertical cross-sectional view taken on the line (Y)-(Y) in Pigs. 14 and 15. On the one major surface there are provided closely aligned projections (3) in a spiral array, as seen from Fig. 14 (this arrangement of projections is referred to as "Embodiment B" hereinafter). In the following, such a spiral array of the projections (3~ will be simply named "array (14) of projections".
In Embodiment B, respective ones of the projections (3~ in the array (14) may be all flush at their tops or lower gradually in a direction toward the periphery of the rubber sheet as in Embodiment A. Though the projections (3! may take the various shapes as discussed above, it is preferable that each of the projections includes the ridge-shaped head or the pointed head in the same manner as in Embodiment A. For the former, it is preferable that the ridges be aligned substantially in the radial direction of the body (1) of the rubber sheet as viewed from Fig. 14. The projections with the ridge-shaped head may be provided with small recesses to form two or more summits as shown in Figs. 7 and 8. It is also apparent that the projections with the ridge-shaped head may be used in combination with the projections with the pointed head or the like as shown in Fig. 9. In Embodiment B, preferably the edge portion of the body (1~ of the rubber slleet is outwardly inclined in a way similar to Embodiment A.
With regard to the other major surface of the rubber sheet provided with the projections (3~ in Embodiment B, it is also desirable that a portion ' ;
~ ~ ~3~
thereof corresponding to the array (1~) of proj~ctionsis made concave as depicted in Figs. 15 and lh ~as a result, a convex rib (15~ is formed in the remaining portion] to thereby make the thickness of the rubber S sheet uniform as a whole. The edge portion of the other major surface is usually provided with a flange portion (16~ to confine air.
Fig. 17 is a plan view of a major surface of the rubber shee~ for turntable in accordance with further another embodiment of the present invention, Fig. 18 is a plan view of the other major surface of the rubber sheet of Fig. 17 and Fig. 19 is a vertical cross-sectional view on the line (Z!-(z~ in Figs. 17 and 18.
Radial arrays of the projections ~re aligned on the one major surface of the body ~1~ of the rubber sheet, as seen from Fig. 17 (this arrangement of the projections is referred to as "Fmbodiment C" hereinafter~. In the following, the radial arrays of the closely aligned projections will be simply named "array (17) of projections".
In Embodiment C, respective ones of the projections (3) in the arrays (17) may be all flush at their tops or lower gradually in a direction to~rard the periphery of the rubber sheet as in Embodiment A.
Though the projections (3) may take the various shapes as discussed above, it is preferable that each of the projections (3) includes the ridge-shaped head or the pointed head in the same manner as in Embodiment A. The projections with the ridge-shaped head may be provided with small recesses to form two or more summits as sho~
from Figs. 7 and 8. It is also apparent that the projections with the ridge-shaped head may be used in combination with the projections with the pointed head or the like as shown in Fig. 9. In Embodimen-t C, preferably the edge portion of the body (l) of the rubber sheet is outwardly inclined as in ~mbodiment A.-With regard to the other.major sur~ace of therubber sheet provided with the projections (3~ in I 3 ~;3~9 Embodiment C, it is also desirable that portions thereof corresponding to ~he arrays (17~ of projections as shown in Figs. 18 and 19 are made radially concave to form radial concave parts ~18) in order to make the thickness of the rubber sheet uniform as a whole.
Obviously, it is not necessarily re~uired to align the projections (3) closely as in Embodiments A to C. They may be aligned at any appropriate interval.
The rubber sheet for turntable in accordance wi~h the present invention is free of any limitation as to thickness. However, the rubber sheet usually has a ma~imum thickness in the order of 2 to 8 mm. a minimum thickness in ~he order of 0.1 to 3 mm. and ari average thickness in the order of 0.1 to 6 mm. and more particularly 0.5 to 2 mm.
The rubber sheet of the present inven~ion may be made in a conventional manner. For example, the above specified rubber composition is directly press-cured within a mold of a given configuration. As an alternative, a non-cured composition in the form of sheet is prepared by calender molding or extrusion molding and then subjected to press curing. Injection molding is also available. It is also recommended that all of the projections (3! be formed in the mold at one ~ime or shaped by cutting after curing. Furthermore, the projections (3~ may be made independently of the body (1) of the rubber sheet and bonded to the body (l~ of the rubber sheet with an appropriate adhesive or the like.
BEST MQDE FOR CARRYING OUT THE INVENTION
The rubber sheet for turntable in accordance with the present inven~ion will now be described in further detail by referring to Examples and Comparative Examples.
Examples 1 to 4 Using the rubber compositions as enumerated in Table 1, several rubber sheets for turntable ~ere ~ ~ 63~6~
manufactured.
Table l Rubber Composition (in part) _ .
Examples Norsorex 150 NA (*1~ 250 250 250 250 ~hite factice S (~2~ 225 20 26n 120 ~ Sunthene 255 (*3~410 200 690 280 10 Dioctyl phthalate45 10 - -FEF carbon 50 50 25 50 Zinc oxide 5 5 5 5 Stearic acid Sumilizer MDP (*4) 2 2 2 2 15 Sulfur 2.5 2 ~ 2 2 Sunceller C~ (~5)10 8 12 9 *1: Polynorbornene ~Norsorex (resistered trademark~, average molecular weight of not less than 2 x 106) extended with 150 parts of naphthenic oil on the basis of 100 paTts of polynorbornene, sold by Nippon Zeon Co., Ltd.
: *2: White factice made by Temma Sabu Kako Kabushiki ~Kaisha *3: fflad~nark for Naphthenic oil made ~y Japan Sun~il Co.~ Ltd.
*4 Tradernark for 2,2'-Methylen~bis(4~ 1-6-tert.-butylphenol) m~de by SumitomD Chemical Co., Ltd.
*5: Trademark for N-cyclohexy1-2-benzothiazyl sulfenamide made by Sanshin Kagaku Kabushiki Kaisha.~
The rubber component was first scoured a~ about : 60C. and kneaded with additional components through the : :~ use of a Banbury mixer and a roller and shee~ed out to giYe a sheet of about 2 to 3 mm. thick. The sheet was : ~ . cut into a disk and cured by a press machine with a given mold under a pressure of 150 kg./cm2 and at a temperature of 155C. fbr-20 min.
The resultant rubber-sheets for turnt~ble application were: con-Eiguration was one as sho~n in '~
' ,: :
.
. ~
5 6 ~
Figs. 1 to 4 and 1~; diameter was 292 mm; maximum thickness was 3.7 mm; minimum thickness was 1.9 mm;
height o~ the projections (3) in the most inner array (4a~ was 0.5 mm. ~the height (Hl~ in Fig. 3] or 1.5 mm.
[the height (H2~ in Fig. 3]; length of the ridges of the projections (3) was about 3 to 6.5 mm; depth of the grooves (7) was 1 mm; and width of the grooves (7) (in the radial directionl was about 30 mm. The individual projections (3! were lower in height gradually toward the periphery of the rubber sheet.
Various physical properties of the resultant rubber sheets were measured with the results shown in Table 2. r~easurements of impact resilience, tensile strength and elongation were conducted according to JIS
K fi301-1969.
Table 2 .
Examples Physical constants --------- - --20 A hardness (degree~ 4 5 7 9 Impact resilience (~ 68 60 72 74 Tensile strength (kg./cm.) ~ 21 19 10 Elongation (~ 398 575 367 281 Specific gravity 0.977 0.98Z 1.0~30.987 Total area of the ridges of the projections (3~ (S52 in total number) in each rubber sheet of Exam~les 1 to 4 occupied about 1.45 ~ of the entire area oE the one major surface of the rubber sheet (assuming the width of the ridges was 0.25 mm.~. When a glass sheet having the same ~imension as that o-E the rubber sheet and a thickness oE 2 mm. (weight: about 300 g.) was mounted on the one major surface of the rubber sheet bearing the projections (3~, the rubber sheet was substantially in contact with the glass sheet only at the ridges of the projections (3) in the most inner array (4a). In that case, the ratio of the contact area to the entire area of the one major surface of the rubber sheet 1 ~ 6 ~
- 2h -was ahout 0.1 ~. The preferred form of the rubber sheet for turntable in accordance with the present invention features minimizing the contact area in such a way.
The following tests were carried out on the rubber sheets of Exam~les 1 to 4. For comparison, the same tests were also carried out on four sorts of rubber sheets affixed to players commercially available on the market. The rubber sheets used herein were summarized in Table 3.
rable 3 v Comparative Exam~les 1 2 3 4 Butyl SBR/NR Styrene- Butyl ~aterial rubber (*l~ butadiene rubber rubber (*2) A hardness (degree) 24 5n 57 36 Impact resilience (~ 19 - 33 Specific gravity 1~223 1.356 1.431 1.642 Halogenation No Yes Yes Yes * Fig.20aFig.21a Fig.22a Fig.23a Sha~e ( 3! Fig.20bFig.21b Fig.22b Fig.23b *1: ~lixture of st~rene-butadiene rubber and natural rubber *2: Sheet body of butyl rubber covered with a mixture of natural rubber and styrene-butadiene rubber *3: Figs. 20a and 20b, 21a and 21b, 22a and 22b and 23a and 23b are top and cross-sectional views of the rubber sheets o Comparative Examples 1 to 4, respectively. In these drawings thicknesses (hl~, ( 2!~ (h3~, (h4~, (hs)~ (h6~, (h7) and (h8~ of the rubber sheets were as follows:
~hll: 4.2 mm.
(h2): 3.5mm.
(h3~: 5 mm.
(h4!: 4 mm.
(h5!: 3.5 mm.
(h6~: 2.5 mm.
(h7!: 5 mm.
- (h8l: 4.5 ~I.
3 :i 63~9 .
Configurations were as follo~s:
Comparativ~ ~xample 1 Top surface: a circular recess of 0. 7 lTun . deep at its center ; S Bottom surface: flat COmpaTa t iY e Example 2 Top surface: a circular recess of 1.0 mm. deep at its center and a concen~crically - circular groove of 1. O mm. deep Bottom surface: flat Comparative Example 3 Top surface: a circular recess of 1.0 n~n. deep a~
its center Bottom surface: flat 1~ Comparative Example 4 Top surface: three COnCentTically circular grooves of 0. 5 mm. deep Bottom surface: flat It is noted tha t: the bottom surfaces of the ru~ber sheets of Comparative Examples 1 to 4 were all flat and in contac't wi~h the turntable. In carrying out the following tests, the rubber sheets of Comparative Exampl es 1 to 4 were mounted with their flat bottom suTface in contact with the turntable.
2s (1! Tone quali~y cest (i! Plav^back equipmen~t Pre-main amplifier: AU-D307 (Sansui Electric Co., Ltd. ) Player: DP-40F (Nippon Columbia Co., Lt~. ) Cartridge: V-15 type 3 (Shure Brothers, Inc. ) 401 (made by Mitsubishi Electric Corporation) (ii) Listening roc~n P~om of 66 m. in area (equipped with an air conditioner and a ventilator) Floor: Polyvinyl chloride-tiled (with mortared underlying layer) C~iling: Fla~ noninfla~nable material (no sound~absorEJtion opening) Inner walls: Ply~l ~.
3~B9 - 2~ -(iii~ Test method A panel of 4 trai~ed listeners A, B, C and D
was instructed to hear the following records and score them on the following parameters. The s rubber sheets of Examples 1 to 4 were set on the turntable with the surface illustrated in Fig. 1 ~one having the projections (3)] being in contact with the record.
(~) Female vocal Title of record: Valses, Canciones Y Tangos ~; (Nippon Phonogram Co., Ltd.) Singer: ~inamaria Hidalgo Accompaniment: ~lugo Videla (guitar) and others Program: Te Pido Que Lo Pienses Parameters:
(a~ if reproduced sounds are near human sounds (b) if the treble region of soprano is not distorted (c) if accompanying guitar sounds are not stronger than vocal sounds (d~ if the impressions of presence are rich (~) Concerto Title of record: "Le Quattro Stagioni" ~8 by Vivaldi (Nippon Phonogram Co., Ltd.) Performer: Roberto ~lichelucci (violin) and I Musici Program: Concerto No. 1, E ~lajor RV 269 "Spring"
Parameters:
(a) if sounds of chords are vivid (b) if the treble region is not distorted (c) if the bass region is well-reproduced ~; 35 (d) i the impressions of presence are rich (~) Flamenco gui~ar Title of record: Manolo Sanl~car in Japan (RVC Corporation) 35~9 - 2~ -Performer: ~lanolo Sanl~car (guitar~, Isidro (guitar~ and Jos~ 2~iguel (piano) rrogram: Callej6n del Carmen Parameters:
(a~if sounds of chords are we:Ll reproduced .
(b! if ~he treble region is not distorted (c~ if beats of a guitar are well reproduced (d~ if ~he impressions of presence are rich The scores as to the above parameters were 10 determined according to the following fiv2-poin~ system.
5 polnts: Exceptionally good 4 points: Very good 3 points: Good 2 points: Ordinary 1 point : Poor The sum of points as to each of the parameters evaluated by each of the listeners multiplied by five was regarded as overall evaluation by each of the listeners ~if all of the parameters are evaluated as 5 points, overall evaluation would be full mar~s (lnO
points). Also, ~he average value of overall evaluations by the four lis~eners was computed. Tables 4 to 9 indicate the results thereof.
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1 1 S3!j~9 - 3f. -( 2 ) Hohl ing test Like~ise the tone quali1:y t~st, the listenersA, B, C and D were instructed to hear the three sorts of records mentioned above and determine the presence or S absence of ho~l ing on the basis of the follvwing definition The pre-main amplifier was employed with both treble and bass being located at "flat", while volume pointed toward 11 o'clock.
Defini~ion of howling: Howling means all that the tone quality of Teproduced sounds is - deteriorated due to external vibrations and repToduction of source sounds ~for example, ~uman sounds of vocal~ is adversely affected.
lS Howling was evaluated according to the 1~-point system, wherein 10 points implied that no howling ~as observed and source sounds were reproduced as they were. Decrease in points ;ndicated increase in howling and 1 point indicated that howling was most severe and reproduced sounds were most deteriorated. The results are depicted in Table lO wherein "obverse" ~nd "reverse"
of the rubber shee~s of Examples 1 to 4 bear the following mean;ngs.
Obverse: The surface as illustrated in Fig. 1 ri.e., one having ~he projections (3) thereon] is regarded as a top surface - (i.e., one in contact with the disk record).
Re~erse: The surface as illustrated in Fig. 2 r i.e., one having the grooves (7! therein]
is regarded as a top surface.
Points in Table 10 show average values evaluated by the four listeners (frac~ions were rounded off~.
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6 9 The results of the above detailed tone quality test and howling test reveal that the rubber sheets of the present invention (Examples 1 to 4~ were superior to the conventional ruhber sheets (Cornparative Examples 1 to 4~. It is believed that the specific physical properties and the specific configurations of the rubber sheet of the present invention contributed to such superiority. In other words, the rubber sheet of the present invention is featured by very low hardness and high impact resilience, i.e., a hardness of from not more than 309 preferably not more than 20 in A hardness to not less than 15, preferably not less than ~0 in F
hardness and an impact resilience of not less than 40 %, preferably not less than 50 %. The rubber sheet of the present invention offers the distinguished advantages of closely sticking to the disk record or the turntable and preventing a slip or resonance, as will be more clearly understood from the results of slip tests and hoist tests discussed below, and further insuring a minimum of contact area by use of the projections with the specific shapes and providing better breathing. As a result of the combination of those characteristics, the rubber sheet effectively prevents the tone quality of reproduced sounds from deteriorating due to howling or external vibrations and permits reproducing source sounds as faithfully as they are. On the other hand, in the case of the conventional rubber shee~s 9 the rubber sheet of Comparative Example 1 was low in hardness, i.e. 24 in A hardness but low in impact resilience, i.e. 19 %, and the rubber sheets of Comparative Examples 2 to 4 were high in hardness. The conventional rubber sheets, therefore, neither met the criteria of ~he present invention as to hardness and impact resilience nor did they prevent the tone quality of reproduced sounds from deteriorating due to howling or external vibrations.
(3! Slip test AEter the rubber sheet was set on the ~urntable oE a plaver (PL-380 made by Pioneer Electronic ~ ~3~
- 3g -Corporation) together with a disk -record and was rotated at a rate of ~3 1/3 r.p.m. with a stylus on the disk record~ the disk record was urged to stop, by gripping lightly the opposed radial edges of the disk record ~y both hands, to therehy allow the operator to observe the stopping movement of the turntable. The rubber sheet was "qualified" when the turntable came to a stop immediately after or within 1 second from interruption of rotating the record and was "disqualified'l when it took more than 2 seconds for the turntable to come to a stop after interruption of rotating the record. Table 11 shows the results of this test.
Table 11 Rubber sheet Evaluation - _ Example 1 Reverse "
.. ...
Example 3 Obverse Obverse '' Example 4 Reverse "
.. .. .. ~ .
Comparative Example 1 Disqualified .. ~ ,.
" 3 "
" 4 ~e In this test, the rubber sheets of Exa~ples 1 to 4 in accordance with the present invention were all qualified, whereas even the sheet of Comparative Example 1 (non-halogenated conventional product~ which apparently had the highest frictional resistance of all Comparative - Examples 1 to 4 was disqualified.
(4! Lift ~est This test was conducted to evaluate the sticking properties of rubber shee~s.
The rubber sheet (of Comparative Example 3, weight 340 g.~ to be lifted was placed on a de~k, with :
3~9 its center shaft opening sealed with a cellophane tape, and a rubber sheet to be tested was superimposed thereon with the center shaft holes aligned. Then, with the test rubber sheet gripped by thumb and index finger at its center shat opening so as to stop up the opening, the sheets as a unit were slid across the desk top beyond the edge of the desk into suspension to see whether the rubber sheet underlying the test rubber sheet would fall off. Since the top surface of the rubber sheet of Comparative Example 3 to be lifted was already halogenated, the above test was carried out to study the influence of halogenation, both in the case that the rubber sheet in question was attached to the top surface of the rubber sheet of Comparative Example 3, and in the case that the same was attached to the bottom surface, i.e~ non-halogenated surface, of the rubber sheet of Comparative Example 3. The rubber sheet of Example 1 and the rubber sheet of Comparative Example 1 ~which was deemed as bearing the best sticking properties out of Comparative Examples 1 to 4! were used as a rubber sheet in question. The surface of the rubber sheet of Example 1 as shown in Fig. 2 was held in contact with the rubber sheet to be lifted and the flat surface (i.e. bottom surface! of the rubber sheet of Comparative Example 1 in contact with the rubber sheet to be lifted.
The results of lift test indicated that, while the rubber sheet of Example 1 attracted tightlv the rubber sheet to be lifted as a suc~er and lifted up it and thus the rubber sheet did not fall, the rubher sheet of Comparative Example l failed to a~tract or lift up the rubber sheet to be lifted.
The above test made clear that the rubber sheet of Example 1 was capable of lifting up the rubber sheet of Comparative Example 3 with 3~0 g. weight. A further test was carried out to determine what weight in gm. the rubber sheet was capable of lifting up.
In other words, a plurality of the rubber sheet of Comparative Example 3 were stacked with one on the 3~g ^ 41 -other and adhered by use of a cellophane tape. Then, the rubber sheet of Example 1 was mounted thereon and subjected to the above procedure or liting.
As a result, it was revealed t~at the rubber sheet of Example 1 was able to lift up up to ln sheets of Comparative Example 3 (weight: 3.4 kg.~ en an attempt was made to lift up 10 sheets of Comparative Example 3, a break was developed at a portion of the rubber sheet of Example 1 where was held by the operator and therefore the test could be conducted no longer.
The foregoing slip and lift tests unveiled that the rubber sheet in accordance with the present invention exhibited a high friction resistance and excellent sticking properties and served as a stabilizer, thus eliminating the need for such stabilizer.
(5) Scratch test This test was conducted on the rubber sheet of Example 1 and the rubber sheet of Comparative Example 3 (which was subjected to halogenation treatment).
A cartridge portion of a player (SF-135 made by Matsushita Electric Industrial Co., Ltd.) was provided with a wèight and covered with a kraft paper so that a load of about 3~ g. was applied to the rubber sheet on the turntable with a contact area of about 2 cm. The cartridge with the weight was located about 5 cm. inside the periphery of the rubber sheet and the turntable was rotated at a rate of ~5 r.p.m. The turntable was braked to stop every 1 min. to find if any scratch was formed.
The above scratch test produced faint scratch marks on the rubber sheet of Example 1 after about 30 minutes but those marks could be easily rubbed off wi~h a finger. This was in contrast ~ith the rubber sheet of Comparative Example 3, where the test produced in a short time of 3 minu~es a large number of fine scratch marks, though no~ very conspicuous, which could not be obliterated with a finger.
The conventional rubber sheets are usually halogenated to enhance surface hardness and reduce the ~ 3 ~3569 possibility of flaws developin~ on the sheet surface as the rubber sheet of Comparative Example 3. As is evident from the foregoing results, nevertheless no halogenation treatmen~, the rubber sheet of the present invention is 5 less flawed than the conventional halogenated rubber sheets. In addition~ fine flaws can be easily cleared by finger as far as ~he rubber sheet of the present invention is concerned.
~6) Dust attachment test Ashes on the burned tip of 10 mm. long of a cigarett were dropped on a sheet of pape~, crushed by a finger and put on the test rubber sheet 2 cm. away from its center. The rubber sheet was held up at a level by both hands and then, one of the hands is left off so that the rubbeT sheet hung down. Vsing the index fingeT, the sheet was given 3 taps with a constant pressure from the re~erse side of the sheet.
The ashes could be almost completely tapped off in the case of the rubber sheets of Examples l to 4.
In the case of the rubber sheets of Compara~ive Examples 1 to 4, however 9 the ashes remained in the shape of a fan with the original position of ashes as its apex. Mo~e particula~ly, a substantial amount of the ashes remaired on the non-halogenated rubber sheet of Comparati~e Example 1.
It is appaTent from the foregoing tha~ a less amount of dust was attached on the rubber sheet of ~he present invention than that on the conventional rubber sheets tComparative Examples 2 to 4~ which were subjected to halogena~ion in order to lessen the possibility of attachment of dust.
Examples 5 to 8 The same procedures as in Examples 1 to 4 except that the rubber compositions were changed to those shown in Table 12 were repeated to produce rubber sheets for turntable.
The phvsical constants of the resultant rubber ;
1 ~ 63~69 sheet~ r~ r: easured in the s;~me ~anner a~ in Example~ 1 to 4. The result~ are also dcpicted in Tabl~ 12.
Tabl e 12 Ex. 5Ex. 6Ex~ 7Ex. 8 .
Rubber Composition (in pa~ts~
Norsorex 80 7S 80 100 ~ipol SBR 1712 (~1~ 20 - - -Espl en e sn 5 ( * 2 1 - 2 5 ~ipol IR 22tln (~3) - - 20 White factice S 420 3~n 320 210 Sunthene 55 56Q 450 440 320 Sunpar 110 (~ 4 ~ ~ ~ ~ 30 Sundex 790 (~5~ - ~ ~ 40 Dioc tvl phthalate - 80 - 50 FEF carbon 40 80 - 40 HAF carbon - - 40 ~T carbon - - - 20 7inc oxide 5 5 5 5 Stearic acid Sumilizer ~IDP
SulfuT 2.5 2.5 2.5 2 . ~
Sunceller C~ 10 10 10 9 Physical constants A hardness (degree ! 5 7 5 8 Impact Tesilie~ce (~! 67 55 59 54 Tensile strength (kg.lcm2~ 2 5 9 8 Elongation (q~! lGl 155 257 402 Specific gravity 0.945 0.979 ~n.s5s 1.015 *l: Trademark for Styrene-butadiene ruhber made by NipFon Zeon Co., Ltd.
*2: Trademar~ for Ethylene-propylene-diene rubber made by Sumitomo Chemical Co., Ltd.
~3 Trademark for Isoprene rubber made by Nippon Zeon Co., Ltd.
~4 Trademark for Paraff~nic oil made by Japan Sunoil Co., Ltd.
*5 Trademark for Aramatic oil made by Japan Sunoil Co,, Ltd.
The rub~er ~heetc of E~;aml-les 5 to 8 ~ermitte~
.
~ :~ 63~69 reproducing exc~llent tone quality sounds likewise the rubber sheets of Examples 1 to 4.
Examples 9 to 10 The same procedures as in Examples l ~o 4 except that the rubber compositions were changed to those shown in Table 13 were repea~ed to produce rubber sheets for turntable. The physical constants of the resulting rubber shee~s were measured in the same manner as in Examples 1 to 4 and presented in Table 13.
Table 13 ~x. ~ Ex. lD
Rubber Composition (in parts) Norsorex 150 NA 250 250 D.O.G. factice F lD (*1~ 240 300 Sunthene 255 130 120 Dioctyl ph~halate 10 SRF carbon 40 MT carbon - 3~
~inc oxide 5 5 SteaTic acid Ant;oxidant DDA (~2) Suntig~t S (*3) Sulfur 2 2 Sunceller CZ 8 6 Physical cons~ants A hardness (degree! 18 23 Impact Tesilience (~ 71 73 Tensile strength (kg./cm. ! 21 16 Elongation (~) 283 293 Specific gravity 0.997 0.999 ~1: Semitranslucen~ sulfur fac~ice made by D.O.G.
Deutsc~e Oelfabrick Ges. f. Chem. Erz. mbh ~ Co.
*7 Diphenylamine antioxidant made by Bayer A.G.
*3: Trad~E~k for Microcrystal~ne wax made by Seiko Xa~aku Kabush~i Kaisha ,~, ,.
`J ~ ~356~
. .
In the case that a glass sheet of about 300 g.
weight was mounted on the respective rubber sheets of Examples 9 to ln, contact area occupied about 0.01 ~ of the entire area of a major surface of the ru.bber sheet.
~he following tests were conducted on the rubber sheets of Examples 9 and 10.
(1~ Tone quality test This test was conducted in the same manner as in Examples l to 4 excep~ that the test record and parameters were changed as follows: The results are depicted in Tables 14 and 15 together with the results obtained with the rubber sheets of Example 4 and Comparative Examples 1 to 4.
Test record Title of record: Bach: toccata and fugue? l?ower Biggs at the Thomas Church (CBS Sony Inc.) Performer: Power Biggs (organ) Program: Toccata and fugue in D minor Parameters (a~ if peculiar sounds of a pipe organ were reproduced (b~ if treble was clear (c) if bass was solemn (d~ if a melody was definitely separate from an accompaniment 1 ~ 63S~9 ~ ~ Ln U~
L~
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. ~ ~ O ~C ~ N ) N 1~ ~ Ll ) E ~ ~ ~ ~ ~ a ~ 1 835~9 (2~ Howling test The test was conducted in the same manner as in Examples 1 to 4 except that the test record used in the above ~one quality test was employed and the test was carried out only in the case tha~ the rubber sheet was mounted with its one major surface shown in Pig. 1 [provided with the projections (3~] in contact with the record. The results are presented in Table lfi along with the results obtained with the rubber sheets of Example 4 and Comparative Examples 1 to 4.
Table 16 Fxample Howllng , Comparative Example 1 3 " 2 2 " 3 3 " 4 2 . The tone quality and howling tests as illustrated above revealed that the rubber sheets of the present inven~ion (Examples 9 and 10~ showed remarkable advantages over the conventional rubber sheets (Comparative Examples 1 to 4).
The rubber sheets of Examples 9 and 10 with A
hardnesses of 18 and 23, respectively, helped reproduce well-sounded sounds as compared with the rubber sheet of Example 4 with a lower hardness of 9 in A hardness.
(3) Slip test This test was carried out in the same manner as in Examples l to 4. The result was that the rubber sheets of Examples 9 and 10 were both qualified.
(4) Lift test This test was carried out on the rubber sheet of Example 9 in ~he same manner as in Fxamples 1 to 4.
The result was that the rubber sheet of Example 9 was 3~69 able to lift up up to 10 sheets (weight: 3.4 kg.) of the rubber sheet of Comparative Example 3.
(5) Scratch test This test was also carried out on the rubber sheet of Example 9 in the same manner as iYI Examples 1 to 4. The result was that a faint scratch was developed after 30 min. but could be easily removed with once rubbing by finger.
(6) ~ust attachment test The same procedure as in Examples 1 to 4 was effected. The result was ~hat less or no ashes remained on the rubber sheets of Examples 9 and 10.
., Examples 11 and 12 The same procedures as in Examples 1 to 4 except that the rubber compositions were changed to those shown in Table 17 were repeated to produce rubber sheets for turntable.
The physical constants of the resulting rubber sheets were measured in the same manner as in Examples 1 to 4. The results are presented in Table 18.
~ ;J B,3569 Table 17 Rubber composition (in parts~
Example Components - --Norsorex 150 NA 250 250 D.n.~. ~actice F ln 230 200 Sunthene 255 400 Sundex 790 - 1, noo Rapeseed oil - 15 Dioctyl phthalateS0 35 FEF carbon 50 MT carbon - S0 , Zinc oxide 5 5 : Stearic acid , : Antioxidant DDA 2 2 Suntight S
: Sulfur 2.5 2.5 Sance11er CZ 8 10 : ~ :
:
~ ~ ~3~69 U~ o~, V~ ~o ~--I~ O
o ,~
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~ ~ ~ o CO ~ ~o o ~ U~
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3~9 The following tests were effected on the rubber sheets of Fxamples 11 and 12.
(1) Tone quali~y test The test was carried out in the same manner as in Examples l to 4 except that the test reccrd and parameters were changed as follows: The results are depicted in Tables 19 and 20 together with the results obtained with the rubber sheets of Example 2 and Comparative Examples 1 to 4.
Test record Title of record: "1812 Overture" by Tchaikovsky (Telarc Records1 Performer: The Cincinnati Symphony Orchestra Conductor: Erich Kunzel Parameters (a~ if sounds of a cannon were well reproduced (b) if treble was not distorted (c1 if bass was well reproduced (d~ if the impresslons of presence were sufficient :
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~2~ Howling test The test was conducted in the same manner as Examples 1 to 4 except that the test record used in the above tone quality test was employed and the test was carried out only in the case that the rubber sheet was moun~ed with its one major surface shown in Fig, 1 rprovided with the projections (3~ in contact with the record. The results are shown in Table 21 along with the results obtained with the rubber sheets of Example 2 and Comparative Examples 1 to 4.
Table 21 Example Howling -Comparative Example 1 4 " 2 3 " 3 3 " 4 2 ~ _ ,. .
The tone quality and howling tests as illustrated above revealed that the rubber sheets of the present invention (Examples 11 and 12) showed remarkable advantages over the conventional rubber sheets (Comparative Examples 1 to 4~.
The rubber sheets of Examples 11 and 12 with C
hardness of 11 (F hardness of 73~ and F hardness of 31, respectively, further prevented howling and helped reproduce sounds of superlow requencies as compared with the rubber sheet of Example 2 with a higher hardness of 5 in A hardness.
(3~ Slip test This was carried out in the same manner as in Examples 1 to 4. The result was that the rubber sheets of Examples 11 and 12 were both qualified.
(4! Scratch test This was carriecl out on the rubber sheet of I ~ ~356~
- 5~ -Example 11 in the same manner as in Examples 1 to 4.
The result was that a faint scratch was developed after 30 min. but could be easily removed with once rubbing by finger.
(5) Dust attachment test The same procedure as in Examples 1 ~o 4 was effected. The result was that less or no ashes remained on the rubber sheets of Examples 11 and 12.
Examples 13 to lS
The same procedures as in Examples 1 to 4 except that the rubber compositions were changed to those shown in Table 22 were repeated to produce rubber sheets for turntable.
The physical constants of the resulting rubber sheets were measured in the same manner as in Examples 1 to 4. The results are presented in Table 23.
1 ~1 635~9 j, Table 22 Rubber composition (in parts) Example Components - -13 ~.4 15 - Nipol SBR 1712 13705 - -~ Natural rubber - 100 :- Baypren-112 ~ - 100 D.O.G. ~actice F 10 200 250 D.O.G. factice NP 17 [~2~ - - 240 Sunthene 255 200 110 200 MT carbon 20 50 45 Zinc oxide 5 5 . 15 Magnesia ~ ~ 4 Stearic acid Antioxidant DDA 2 Suntight S
: Sulfur 2 2 2 Sunceller CZ 4 Nocceler D~ 3~ - 2.7 " D (~4) - 0.7 ~ " TT (*5~ _ 0.4 :~ " DT (*6~ - - 1.1 ;~ 25 " TS (17~ _ _ lol . .
*l Trademark for Chloropylene rubber m~de by Bayer A.G.
. *2: Semitranslucent sulfur factice made by D.O.G.
Deutsche ~elfabrick Ges. f. Chem. Erz. mbh ~
C o . .
*3:~ralem:rk for Curing accelerator made by Ouchi Chemical Industry Co., Ltd.
*4: Trademark for Curing accelerator made by Ouchi Chemical Industry Co., Ltd.
*5 Trademark for Curing ac oelerator made by Ouchi Chemical Industry Co. J Ltd.
*6 Trademark for Curing accelerator made by Ouchi Chemical Industry Co., Ltd.
~.
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s ~ g - 5~ -*7: Curing accelerator made by OUChi Chemical - Industry Co., Ltd.
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. .
` ~3~3~69 The following tests were effected on the rubber sheets of Examples 13 to 15.
(1) Tone quality test This tes~ was carried out in the same manner as S in Examples l to 4. The results ara presented in Tables 24 to 26.
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1 ~ 835B9 (2) Howling test The test was conducted in the same manner as in Examples 1 to 4 excep~ that the test was carri~d out only in the case that the rubber sheet was mounted with - S its one major surface shown Fig. 1 tprovided with the projections (3~] in contact with the record. The results thereof are presented in Table 27.
Table 27 Example Record --Female vocal 8 8 8 Concerto 9 8 8 Flamenco guitar 9 8 8 The tone quality and howling tests as illustrated above revealed that the rubber sheets of the present invention (Examples 13 to 15) showed remarkable advantages over the conventional rubber sheets ~0 (Comparative Examples 1 to 4, see Tables 5, 7, 9 and 10).
(3~ Slip test This test was carried out in the same manner as in Examples 1 to 4. The result was that all of the rubber sheets of Examples 13 to 15 were qualified.
(4~ Lift test This test was carried out on the rubber sheet of Example 13 in the same manner as in Examples 1 to 4. The result was tha~ the rubber sheet of Example 13 was able to lift up to 6 sheets (weight: 2.0 kg.) of the rubber sheet of Comparative Example 3.
(5~ Scratch test This was also carried out on the rubber sheet of Example 13 in the same manner as in Examples 1 to 4.
The result was that a faint scratch was developed after 30 min, but could be easily removed with once rubbing by finger.
(~) Dust attachment test The same procedure as in Examples 1 to 4 was ., ~ 1 ~3~
effected. The result was that less or no ashes remained on the rubber sheets of Examples 13 to 15.
Examples 16 to 19 The same procedures as in Examples 1 to 4 except that the rubber compositions were changed to those shown in Table 28 were repeated to produce rubber sheets for turn~able.
The physical constants of the resulting rubber sheets were measured in the same manner as in Examples l to ~. The results are presented in Table 29.
~ ~ ~35~g 1able 2B
Rubber composition (in parts) Example Components - . _ - lfi 17 18 l9 Nipol SBR 1712 137. 5 - - -Nipol IR 2200 - 100 Nordel 1040 (*1~ - - 100 Millathane 76 (*2~ lû0 D.O.G. factice F 10 230 200 250 D.O.G~ factice NP 17 - - - 200 . D.O.G. faccice DS SOFT (~3) - 15 - -. Sunthene 255 200 15 20û 250 Sunp ar 110 - 7 Q
Thiokol TP-95 (*4) - - - 10 SRF carbon - 5 MT carbon 60 - 50 Light calcium carbonate - - - 10 2Q Zinc oxide 5 5 5 - Zinc stearate - - - 0. 5 Stearic acid Antioxidant DI)A 2 ' Suntigrht S
Sulfur 2 2.2 2.5 1.5 v I Sunceller CZ 4 2 Nocceler D~ - - - 3 ~, " TT - - 1. 2 M (*5) - - 2 2 " TRA (*6) _ 102 ~: Thioko.l ZC 4 56 ( * 7 ~ - - - 1 *1: Tr=~em3rk for Eth~lene-proF~lene-diene c~polym~r made by E. I.
Du Pont de Nemours & Co.
*2 Trademark for Urethane rubber made by Technical Sales &
Engineering Inc.
~3: Soft semitranslucent sulfur factice made b)r D.Q.G. Deutsche Oelfabrick Ges. f. Chem. Er~.
,~
1 1 63~9 -: mbh ~ Co.
~4: Trademark for Plasticizer made by Thiokol Corp.
: ~5: Curing accelerator made by Ouchi Chemical Industry Co.g L~d.
~6: Curing accelera~or made by Ouchi Chemical Industry Co., Ltd.
*7: Curing accellerator made by Thiokol Corp.
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~ ;1 63569 Likewise the rubber sheets of Examples 13 to 15, the rubber sheets of Examples 16 to 19 permitted reproducing excellent tone quality sounds.
hardness and an impact resilience of not less than 40 %, preferably not less than 50 %. The rubber sheet of the present invention offers the distinguished advantages of closely sticking to the disk record or the turntable and preventing a slip or resonance, as will be more clearly understood from the results of slip tests and hoist tests discussed below, and further insuring a minimum of contact area by use of the projections with the specific shapes and providing better breathing. As a result of the combination of those characteristics, the rubber sheet effectively prevents the tone quality of reproduced sounds from deteriorating due to howling or external vibrations and permits reproducing source sounds as faithfully as they are. On the other hand, in the case of the conventional rubber shee~s 9 the rubber sheet of Comparative Example 1 was low in hardness, i.e. 24 in A hardness but low in impact resilience, i.e. 19 %, and the rubber sheets of Comparative Examples 2 to 4 were high in hardness. The conventional rubber sheets, therefore, neither met the criteria of ~he present invention as to hardness and impact resilience nor did they prevent the tone quality of reproduced sounds from deteriorating due to howling or external vibrations.
(3! Slip test AEter the rubber sheet was set on the ~urntable oE a plaver (PL-380 made by Pioneer Electronic ~ ~3~
- 3g -Corporation) together with a disk -record and was rotated at a rate of ~3 1/3 r.p.m. with a stylus on the disk record~ the disk record was urged to stop, by gripping lightly the opposed radial edges of the disk record ~y both hands, to therehy allow the operator to observe the stopping movement of the turntable. The rubber sheet was "qualified" when the turntable came to a stop immediately after or within 1 second from interruption of rotating the record and was "disqualified'l when it took more than 2 seconds for the turntable to come to a stop after interruption of rotating the record. Table 11 shows the results of this test.
Table 11 Rubber sheet Evaluation - _ Example 1 Reverse "
.. ...
Example 3 Obverse Obverse '' Example 4 Reverse "
.. .. .. ~ .
Comparative Example 1 Disqualified .. ~ ,.
" 3 "
" 4 ~e In this test, the rubber sheets of Exa~ples 1 to 4 in accordance with the present invention were all qualified, whereas even the sheet of Comparative Example 1 (non-halogenated conventional product~ which apparently had the highest frictional resistance of all Comparative - Examples 1 to 4 was disqualified.
(4! Lift ~est This test was conducted to evaluate the sticking properties of rubber shee~s.
The rubber sheet (of Comparative Example 3, weight 340 g.~ to be lifted was placed on a de~k, with :
3~9 its center shaft opening sealed with a cellophane tape, and a rubber sheet to be tested was superimposed thereon with the center shaft holes aligned. Then, with the test rubber sheet gripped by thumb and index finger at its center shat opening so as to stop up the opening, the sheets as a unit were slid across the desk top beyond the edge of the desk into suspension to see whether the rubber sheet underlying the test rubber sheet would fall off. Since the top surface of the rubber sheet of Comparative Example 3 to be lifted was already halogenated, the above test was carried out to study the influence of halogenation, both in the case that the rubber sheet in question was attached to the top surface of the rubber sheet of Comparative Example 3, and in the case that the same was attached to the bottom surface, i.e~ non-halogenated surface, of the rubber sheet of Comparative Example 3. The rubber sheet of Example 1 and the rubber sheet of Comparative Example 1 ~which was deemed as bearing the best sticking properties out of Comparative Examples 1 to 4! were used as a rubber sheet in question. The surface of the rubber sheet of Example 1 as shown in Fig. 2 was held in contact with the rubber sheet to be lifted and the flat surface (i.e. bottom surface! of the rubber sheet of Comparative Example 1 in contact with the rubber sheet to be lifted.
The results of lift test indicated that, while the rubber sheet of Example 1 attracted tightlv the rubber sheet to be lifted as a suc~er and lifted up it and thus the rubber sheet did not fall, the rubher sheet of Comparative Example l failed to a~tract or lift up the rubber sheet to be lifted.
The above test made clear that the rubber sheet of Example 1 was capable of lifting up the rubber sheet of Comparative Example 3 with 3~0 g. weight. A further test was carried out to determine what weight in gm. the rubber sheet was capable of lifting up.
In other words, a plurality of the rubber sheet of Comparative Example 3 were stacked with one on the 3~g ^ 41 -other and adhered by use of a cellophane tape. Then, the rubber sheet of Example 1 was mounted thereon and subjected to the above procedure or liting.
As a result, it was revealed t~at the rubber sheet of Example 1 was able to lift up up to ln sheets of Comparative Example 3 (weight: 3.4 kg.~ en an attempt was made to lift up 10 sheets of Comparative Example 3, a break was developed at a portion of the rubber sheet of Example 1 where was held by the operator and therefore the test could be conducted no longer.
The foregoing slip and lift tests unveiled that the rubber sheet in accordance with the present invention exhibited a high friction resistance and excellent sticking properties and served as a stabilizer, thus eliminating the need for such stabilizer.
(5) Scratch test This test was conducted on the rubber sheet of Example 1 and the rubber sheet of Comparative Example 3 (which was subjected to halogenation treatment).
A cartridge portion of a player (SF-135 made by Matsushita Electric Industrial Co., Ltd.) was provided with a wèight and covered with a kraft paper so that a load of about 3~ g. was applied to the rubber sheet on the turntable with a contact area of about 2 cm. The cartridge with the weight was located about 5 cm. inside the periphery of the rubber sheet and the turntable was rotated at a rate of ~5 r.p.m. The turntable was braked to stop every 1 min. to find if any scratch was formed.
The above scratch test produced faint scratch marks on the rubber sheet of Example 1 after about 30 minutes but those marks could be easily rubbed off wi~h a finger. This was in contrast ~ith the rubber sheet of Comparative Example 3, where the test produced in a short time of 3 minu~es a large number of fine scratch marks, though no~ very conspicuous, which could not be obliterated with a finger.
The conventional rubber sheets are usually halogenated to enhance surface hardness and reduce the ~ 3 ~3569 possibility of flaws developin~ on the sheet surface as the rubber sheet of Comparative Example 3. As is evident from the foregoing results, nevertheless no halogenation treatmen~, the rubber sheet of the present invention is 5 less flawed than the conventional halogenated rubber sheets. In addition~ fine flaws can be easily cleared by finger as far as ~he rubber sheet of the present invention is concerned.
~6) Dust attachment test Ashes on the burned tip of 10 mm. long of a cigarett were dropped on a sheet of pape~, crushed by a finger and put on the test rubber sheet 2 cm. away from its center. The rubber sheet was held up at a level by both hands and then, one of the hands is left off so that the rubbeT sheet hung down. Vsing the index fingeT, the sheet was given 3 taps with a constant pressure from the re~erse side of the sheet.
The ashes could be almost completely tapped off in the case of the rubber sheets of Examples l to 4.
In the case of the rubber sheets of Compara~ive Examples 1 to 4, however 9 the ashes remained in the shape of a fan with the original position of ashes as its apex. Mo~e particula~ly, a substantial amount of the ashes remaired on the non-halogenated rubber sheet of Comparati~e Example 1.
It is appaTent from the foregoing tha~ a less amount of dust was attached on the rubber sheet of ~he present invention than that on the conventional rubber sheets tComparative Examples 2 to 4~ which were subjected to halogena~ion in order to lessen the possibility of attachment of dust.
Examples 5 to 8 The same procedures as in Examples 1 to 4 except that the rubber compositions were changed to those shown in Table 12 were repeated to produce rubber sheets for turntable.
The phvsical constants of the resultant rubber ;
1 ~ 63~69 sheet~ r~ r: easured in the s;~me ~anner a~ in Example~ 1 to 4. The result~ are also dcpicted in Tabl~ 12.
Tabl e 12 Ex. 5Ex. 6Ex~ 7Ex. 8 .
Rubber Composition (in pa~ts~
Norsorex 80 7S 80 100 ~ipol SBR 1712 (~1~ 20 - - -Espl en e sn 5 ( * 2 1 - 2 5 ~ipol IR 22tln (~3) - - 20 White factice S 420 3~n 320 210 Sunthene 55 56Q 450 440 320 Sunpar 110 (~ 4 ~ ~ ~ ~ 30 Sundex 790 (~5~ - ~ ~ 40 Dioc tvl phthalate - 80 - 50 FEF carbon 40 80 - 40 HAF carbon - - 40 ~T carbon - - - 20 7inc oxide 5 5 5 5 Stearic acid Sumilizer ~IDP
SulfuT 2.5 2.5 2.5 2 . ~
Sunceller C~ 10 10 10 9 Physical constants A hardness (degree ! 5 7 5 8 Impact Tesilie~ce (~! 67 55 59 54 Tensile strength (kg.lcm2~ 2 5 9 8 Elongation (q~! lGl 155 257 402 Specific gravity 0.945 0.979 ~n.s5s 1.015 *l: Trademark for Styrene-butadiene ruhber made by NipFon Zeon Co., Ltd.
*2: Trademar~ for Ethylene-propylene-diene rubber made by Sumitomo Chemical Co., Ltd.
~3 Trademark for Isoprene rubber made by Nippon Zeon Co., Ltd.
~4 Trademark for Paraff~nic oil made by Japan Sunoil Co., Ltd.
*5 Trademark for Aramatic oil made by Japan Sunoil Co,, Ltd.
The rub~er ~heetc of E~;aml-les 5 to 8 ~ermitte~
.
~ :~ 63~69 reproducing exc~llent tone quality sounds likewise the rubber sheets of Examples 1 to 4.
Examples 9 to 10 The same procedures as in Examples l ~o 4 except that the rubber compositions were changed to those shown in Table 13 were repea~ed to produce rubber sheets for turntable. The physical constants of the resulting rubber shee~s were measured in the same manner as in Examples 1 to 4 and presented in Table 13.
Table 13 ~x. ~ Ex. lD
Rubber Composition (in parts) Norsorex 150 NA 250 250 D.O.G. factice F lD (*1~ 240 300 Sunthene 255 130 120 Dioctyl ph~halate 10 SRF carbon 40 MT carbon - 3~
~inc oxide 5 5 SteaTic acid Ant;oxidant DDA (~2) Suntig~t S (*3) Sulfur 2 2 Sunceller CZ 8 6 Physical cons~ants A hardness (degree! 18 23 Impact Tesilience (~ 71 73 Tensile strength (kg./cm. ! 21 16 Elongation (~) 283 293 Specific gravity 0.997 0.999 ~1: Semitranslucen~ sulfur fac~ice made by D.O.G.
Deutsc~e Oelfabrick Ges. f. Chem. Erz. mbh ~ Co.
*7 Diphenylamine antioxidant made by Bayer A.G.
*3: Trad~E~k for Microcrystal~ne wax made by Seiko Xa~aku Kabush~i Kaisha ,~, ,.
`J ~ ~356~
. .
In the case that a glass sheet of about 300 g.
weight was mounted on the respective rubber sheets of Examples 9 to ln, contact area occupied about 0.01 ~ of the entire area of a major surface of the ru.bber sheet.
~he following tests were conducted on the rubber sheets of Examples 9 and 10.
(1~ Tone quality test This test was conducted in the same manner as in Examples l to 4 excep~ that the test record and parameters were changed as follows: The results are depicted in Tables 14 and 15 together with the results obtained with the rubber sheets of Example 4 and Comparative Examples 1 to 4.
Test record Title of record: Bach: toccata and fugue? l?ower Biggs at the Thomas Church (CBS Sony Inc.) Performer: Power Biggs (organ) Program: Toccata and fugue in D minor Parameters (a~ if peculiar sounds of a pipe organ were reproduced (b~ if treble was clear (c) if bass was solemn (d~ if a melody was definitely separate from an accompaniment 1 ~ 63S~9 ~ ~ Ln U~
L~
~1 O
r) LO o ,; ¢ ~ o ~ u~ Lr) o :: ~ ~
C t~ ~ ~ In Lr) o o~
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E; O
h ~ .--1 .~ ~ ~ O U ~ ~ C
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v~ O
~ ~ 63~9 a N ` -- N
~_ N ~ -- N
N N N ,~ ¦
N ~ ~ N ~
.~r-l ~ ~ O `O
. ~ ~ O ~C ~ N ) N 1~ ~ Ll ) E ~ ~ ~ ~ ~ a ~ 1 835~9 (2~ Howling test The test was conducted in the same manner as in Examples 1 to 4 except that the test record used in the above ~one quality test was employed and the test was carried out only in the case tha~ the rubber sheet was mounted with its one major surface shown in Pig. 1 [provided with the projections (3~] in contact with the record. The results are presented in Table lfi along with the results obtained with the rubber sheets of Example 4 and Comparative Examples 1 to 4.
Table 16 Fxample Howllng , Comparative Example 1 3 " 2 2 " 3 3 " 4 2 . The tone quality and howling tests as illustrated above revealed that the rubber sheets of the present inven~ion (Examples 9 and 10~ showed remarkable advantages over the conventional rubber sheets (Comparative Examples 1 to 4).
The rubber sheets of Examples 9 and 10 with A
hardnesses of 18 and 23, respectively, helped reproduce well-sounded sounds as compared with the rubber sheet of Example 4 with a lower hardness of 9 in A hardness.
(3) Slip test This test was carried out in the same manner as in Examples l to 4. The result was that the rubber sheets of Examples 9 and 10 were both qualified.
(4) Lift test This test was carried out on the rubber sheet of Example 9 in ~he same manner as in Fxamples 1 to 4.
The result was that the rubber sheet of Example 9 was 3~69 able to lift up up to 10 sheets (weight: 3.4 kg.) of the rubber sheet of Comparative Example 3.
(5) Scratch test This test was also carried out on the rubber sheet of Example 9 in the same manner as iYI Examples 1 to 4. The result was that a faint scratch was developed after 30 min. but could be easily removed with once rubbing by finger.
(6) ~ust attachment test The same procedure as in Examples 1 to 4 was effected. The result was ~hat less or no ashes remained on the rubber sheets of Examples 9 and 10.
., Examples 11 and 12 The same procedures as in Examples 1 to 4 except that the rubber compositions were changed to those shown in Table 17 were repeated to produce rubber sheets for turntable.
The physical constants of the resulting rubber sheets were measured in the same manner as in Examples 1 to 4. The results are presented in Table 18.
~ ;J B,3569 Table 17 Rubber composition (in parts~
Example Components - --Norsorex 150 NA 250 250 D.n.~. ~actice F ln 230 200 Sunthene 255 400 Sundex 790 - 1, noo Rapeseed oil - 15 Dioctyl phthalateS0 35 FEF carbon 50 MT carbon - S0 , Zinc oxide 5 5 : Stearic acid , : Antioxidant DDA 2 2 Suntight S
: Sulfur 2.5 2.5 Sance11er CZ 8 10 : ~ :
:
~ ~ ~3~69 U~ o~, V~ ~o ~--I~ O
o ,~
,, ~4 ~, ~ ~
~ ~ ~ o CO ~ ~o o ~ U~
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3~9 The following tests were effected on the rubber sheets of Fxamples 11 and 12.
(1) Tone quali~y test The test was carried out in the same manner as in Examples l to 4 except that the test reccrd and parameters were changed as follows: The results are depicted in Tables 19 and 20 together with the results obtained with the rubber sheets of Example 2 and Comparative Examples 1 to 4.
Test record Title of record: "1812 Overture" by Tchaikovsky (Telarc Records1 Performer: The Cincinnati Symphony Orchestra Conductor: Erich Kunzel Parameters (a~ if sounds of a cannon were well reproduced (b) if treble was not distorted (c1 if bass was well reproduced (d~ if the impresslons of presence were sufficient :
~ ~ n o a~ c~ ~ ) Lr) o ~ m ~t ~ u, ~ ~
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h v~ O .~ ,1 ::~ h P~ ~ ~ o ~ ~ 0 5~ 0 ~d ~ ~ cc ~ ~ ~3~
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t~ v~ O h h ~ ~ ~ h 1-~ ~ 1:: 0 ~ ~V t~ a) 1~ h ~ :~
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~2~ Howling test The test was conducted in the same manner as Examples 1 to 4 except that the test record used in the above tone quality test was employed and the test was carried out only in the case that the rubber sheet was moun~ed with its one major surface shown in Fig, 1 rprovided with the projections (3~ in contact with the record. The results are shown in Table 21 along with the results obtained with the rubber sheets of Example 2 and Comparative Examples 1 to 4.
Table 21 Example Howling -Comparative Example 1 4 " 2 3 " 3 3 " 4 2 ~ _ ,. .
The tone quality and howling tests as illustrated above revealed that the rubber sheets of the present invention (Examples 11 and 12) showed remarkable advantages over the conventional rubber sheets (Comparative Examples 1 to 4~.
The rubber sheets of Examples 11 and 12 with C
hardness of 11 (F hardness of 73~ and F hardness of 31, respectively, further prevented howling and helped reproduce sounds of superlow requencies as compared with the rubber sheet of Example 2 with a higher hardness of 5 in A hardness.
(3~ Slip test This was carried out in the same manner as in Examples 1 to 4. The result was that the rubber sheets of Examples 11 and 12 were both qualified.
(4! Scratch test This was carriecl out on the rubber sheet of I ~ ~356~
- 5~ -Example 11 in the same manner as in Examples 1 to 4.
The result was that a faint scratch was developed after 30 min. but could be easily removed with once rubbing by finger.
(5) Dust attachment test The same procedure as in Examples 1 ~o 4 was effected. The result was that less or no ashes remained on the rubber sheets of Examples 11 and 12.
Examples 13 to lS
The same procedures as in Examples 1 to 4 except that the rubber compositions were changed to those shown in Table 22 were repeated to produce rubber sheets for turntable.
The physical constants of the resulting rubber sheets were measured in the same manner as in Examples 1 to 4. The results are presented in Table 23.
1 ~1 635~9 j, Table 22 Rubber composition (in parts) Example Components - -13 ~.4 15 - Nipol SBR 1712 13705 - -~ Natural rubber - 100 :- Baypren-112 ~ - 100 D.O.G. ~actice F 10 200 250 D.O.G. factice NP 17 [~2~ - - 240 Sunthene 255 200 110 200 MT carbon 20 50 45 Zinc oxide 5 5 . 15 Magnesia ~ ~ 4 Stearic acid Antioxidant DDA 2 Suntight S
: Sulfur 2 2 2 Sunceller CZ 4 Nocceler D~ 3~ - 2.7 " D (~4) - 0.7 ~ " TT (*5~ _ 0.4 :~ " DT (*6~ - - 1.1 ;~ 25 " TS (17~ _ _ lol . .
*l Trademark for Chloropylene rubber m~de by Bayer A.G.
. *2: Semitranslucent sulfur factice made by D.O.G.
Deutsche ~elfabrick Ges. f. Chem. Erz. mbh ~
C o . .
*3:~ralem:rk for Curing accelerator made by Ouchi Chemical Industry Co., Ltd.
*4: Trademark for Curing accelerator made by Ouchi Chemical Industry Co., Ltd.
*5 Trademark for Curing ac oelerator made by Ouchi Chemical Industry Co. J Ltd.
*6 Trademark for Curing accelerator made by Ouchi Chemical Industry Co., Ltd.
~.
`.
s ~ g - 5~ -*7: Curing accelerator made by OUChi Chemical - Industry Co., Ltd.
`:
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0,0 C`~
.
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Q~
~--C~
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.,1 ~a~ I I o~
a~ ~
h h O ~ O
V) ~ ~ _ . ~ C~V) O~N~I
. .
` ~3~3~69 The following tests were effected on the rubber sheets of Examples 13 to 15.
(1) Tone quality test This tes~ was carried out in the same manner as S in Examples l to 4. The results ara presented in Tables 24 to 26.
~ J ~3~9 n Ln U~
O N~
E~ a: LO ~ ~ Lr) Ln '~: ~ o a ~ ~ L~ u) D ~ 11~ ~ Lf) ~-~ ¢ ~ o ~ ~ cl~
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¢ Ln LO U~ Lr) ~
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U') ~ X ~ O
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1 ~ 835B9 (2) Howling test The test was conducted in the same manner as in Examples 1 to 4 excep~ that the test was carri~d out only in the case that the rubber sheet was mounted with - S its one major surface shown Fig. 1 tprovided with the projections (3~] in contact with the record. The results thereof are presented in Table 27.
Table 27 Example Record --Female vocal 8 8 8 Concerto 9 8 8 Flamenco guitar 9 8 8 The tone quality and howling tests as illustrated above revealed that the rubber sheets of the present invention (Examples 13 to 15) showed remarkable advantages over the conventional rubber sheets ~0 (Comparative Examples 1 to 4, see Tables 5, 7, 9 and 10).
(3~ Slip test This test was carried out in the same manner as in Examples 1 to 4. The result was that all of the rubber sheets of Examples 13 to 15 were qualified.
(4~ Lift test This test was carried out on the rubber sheet of Example 13 in the same manner as in Examples 1 to 4. The result was tha~ the rubber sheet of Example 13 was able to lift up to 6 sheets (weight: 2.0 kg.) of the rubber sheet of Comparative Example 3.
(5~ Scratch test This was also carried out on the rubber sheet of Example 13 in the same manner as in Examples 1 to 4.
The result was that a faint scratch was developed after 30 min, but could be easily removed with once rubbing by finger.
(~) Dust attachment test The same procedure as in Examples 1 to 4 was ., ~ 1 ~3~
effected. The result was that less or no ashes remained on the rubber sheets of Examples 13 to 15.
Examples 16 to 19 The same procedures as in Examples 1 to 4 except that the rubber compositions were changed to those shown in Table 28 were repeated to produce rubber sheets for turn~able.
The physical constants of the resulting rubber sheets were measured in the same manner as in Examples l to ~. The results are presented in Table 29.
~ ~ ~35~g 1able 2B
Rubber composition (in parts) Example Components - . _ - lfi 17 18 l9 Nipol SBR 1712 137. 5 - - -Nipol IR 2200 - 100 Nordel 1040 (*1~ - - 100 Millathane 76 (*2~ lû0 D.O.G. factice F 10 230 200 250 D.O.G~ factice NP 17 - - - 200 . D.O.G. faccice DS SOFT (~3) - 15 - -. Sunthene 255 200 15 20û 250 Sunp ar 110 - 7 Q
Thiokol TP-95 (*4) - - - 10 SRF carbon - 5 MT carbon 60 - 50 Light calcium carbonate - - - 10 2Q Zinc oxide 5 5 5 - Zinc stearate - - - 0. 5 Stearic acid Antioxidant DI)A 2 ' Suntigrht S
Sulfur 2 2.2 2.5 1.5 v I Sunceller CZ 4 2 Nocceler D~ - - - 3 ~, " TT - - 1. 2 M (*5) - - 2 2 " TRA (*6) _ 102 ~: Thioko.l ZC 4 56 ( * 7 ~ - - - 1 *1: Tr=~em3rk for Eth~lene-proF~lene-diene c~polym~r made by E. I.
Du Pont de Nemours & Co.
*2 Trademark for Urethane rubber made by Technical Sales &
Engineering Inc.
~3: Soft semitranslucent sulfur factice made b)r D.Q.G. Deutsche Oelfabrick Ges. f. Chem. Er~.
,~
1 1 63~9 -: mbh ~ Co.
~4: Trademark for Plasticizer made by Thiokol Corp.
: ~5: Curing accelerator made by Ouchi Chemical Industry Co.g L~d.
~6: Curing accelera~or made by Ouchi Chemical Industry Co., Ltd.
*7: Curing accellerator made by Thiokol Corp.
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h ~ 0 0 `O ';t : ~ c cl , ~ ~ ~ 1~ 0 C~
., ~Ll ~
~ ;1 63569 Likewise the rubber sheets of Examples 13 to 15, the rubber sheets of Examples 16 to 19 permitted reproducing excellent tone quality sounds.
Claims (24)
1. A rubber sheet for turntable comprising a cured rubber molding having a hardness within the range from 30° as measured with an A-type rubber hardness tester to 15° as measured with an F-type rubber hardness tester and an impact resilience of not less than 40 %.
2. The rubber sheet of Claim 1, wherein the hardness is not more than 20° as measured with the A-type rubber hardness tester and not less than 30° as measured with the F-type rubber hardness tester and the impact resilience is not less than 50 %.
3. The rubber sheet of Claim 1, wherein the hardness is more than 15° as measured with the A-type rubber hardness tester and not more than 30° as measured with the A-type rubber hardness tester and the impact resilience is not less than 50 %.
4. The rubber sheet of Claim 1, wherein the hardness is from 1° to 15° as measured with the A-type rubber hardness tester.
5. The rubber sheet of Claim 1, wherein the hardness is less than 1° as measured with the A-type rubber hardness tester and not less than 15° as measured with the F-type rubber hardness tester.
6. The rubber sheet of Claim 1, wherein the cured rubber molding is a cured rubber molding of a rubber composition comprising polynorbornene as a predominant rubber component.
7. The rubber sheet of Claim 1, wherein the cured rubber molding is a cured rubber molding of a rubber composition comprising as a predominant rubber component at least one member selected from the group consisting of natural rubber, isoprene rubber, chloroprene rubber, styrene-butadiene rubber, butadiene rubber, butyl rubber, ethylene-propylene rubber, ethylene-propylene-diene rubber, nitrile rubber, acryl rubber, urethane rubber, chlorinated polyethylene, chlorosulfonated polyethylene, epichlorohydrin rubber, polysulfide rubber and silicone rubber.
8. The rubber sheet of Claim 1, wherein the cured rubber molding is a cured rubber molding of a rubber composition comprising (A) 100 parts by weight of a rubber component, (B) 1 to 2,000 parts by weight of a factice and (C) 20 to 2,000 parts by weight of a softening agent.
9. The rubber sheet of Claim 8, wherein the amount of the component (B) is from 5 to 2,000 parts by weight and the amount of the component (C) is from 50 to 2,000 parts by weight.
10. The rubber sheet of Claim 9, wherein the amount of the component (B) is from 100 to 1,500 parts by weight and the amount of the component (C) is from 200 to 1,500 parts by weight.
11. The rubber sheet of any of Claims 8, 9 and 10, wherein the component (A) comprises polynorbornene as a predominant component.
12. The rubber sheet of any of Claims 8, 9 and 10, wherein the component (A) comprises as a predominant component at least one member selected from the group consisting of natural rubber, isoprene rubber, chloroprene rubber, styrene-butadiene rubber, butadiene rubber, butyl rubber, ethylene-propylene rubber, ethylene-propylene-diene rubber, nitrile rubber, acryl rubber, urethane rubber, chlorinated polyethylene, chlorosulfonated polyethylene, epichlorohydrin rubber, polysulfide rubber and silicone rubber.
13. The rubber sheet of Claim 1, wherein a major surface of the body of the rubber sheet is provided with a large number of projections.
14. The rubber sheet of Claim 13, wherein at least the head of each of the projections is ridge-shaped to make substantially a line contact with a turntable or a disk record.
15. The rubber sheet of Claim 13, wherein at least the head of each of the projections is pointed to make substantially a point contact with a turntable or a disk record.
16. The rubber sheet of any of Claims 13, 14 and 15, wherein the height of the projections is 0.1 to 5 mm.
17. The rubber sheet of anyone of claims 13, 14 and 15, wherein the height of the projections is 0.3 to 1.8 mm.
18. The rubber sheet of Claim 13, wherein the projections are closely aligned in a plurality of concentrically circular arrays.
19. The rubber sheet of Claim 18, wherein at least the head of each of the projections is ridge-shaped to make substantially a line contact with a turntable or a disk record.
20. The rubber sheet of Claim 19, wherein the ridges of the projections are aligned along the radial direction of the body of the rubber sheet.
21. The rubber sheet of Claim 18, wherein at least the head of each of the projections is pointed to make substantially a point contact with a turntable or a disk record.
22. The rubber sheet of Claim 18, wherein the heads of the projections in one of a plurality of concentrically circular arrays are disposed in correspondence with the valleys between the two adjacent projections in the adjacent array in the radial direction of the body of the rubber sheet.
23. The rubber sheet of Claim 22, wherein, when being mounted with its one major surface provided with the projections in contact with a disk record and its other major surface in contact with a turntable, the projections are highest in the most inner concentrically circular array and lower gradually in the direction toward the periphery of the rubber sheet and air is confined within a space, over the central portion of the body of the rubber sheet, defined by the most inner array of the projections and the disk record.
24. The rubber sheet of Claim 23, wherein the other major surface to be in contact with the turntable is provided with a plurality of concentrically circular grooves in correspondence with the plurality of the concentrically circular arrays of the projections and air is confined at least in the most inner groove.
Applications Claiming Priority (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP14341780A JPS5766508A (en) | 1980-10-13 | 1980-10-13 | Rubber sheet for turntable |
| JP143418/1980 | 1980-10-13 | ||
| JP14341880A JPS5766509A (en) | 1980-10-13 | 1980-10-13 | Rubber sheet for turntable |
| JP143417/1980 | 1980-10-13 | ||
| JP14499880A JPS5769505A (en) | 1980-10-15 | 1980-10-15 | Rubber sheet for turntable |
| JP144998/1980 | 1980-10-15 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1163569A true CA1163569A (en) | 1984-03-13 |
Family
ID=27318637
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000377415A Expired CA1163569A (en) | 1980-10-13 | 1981-05-12 | Rubber sheet for turntable |
Country Status (3)
| Country | Link |
|---|---|
| KR (1) | KR830001562B1 (en) |
| CA (1) | CA1163569A (en) |
| IT (1) | IT1135835B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR20000015001A (en) * | 1998-08-26 | 2000-03-15 | 윤종용 | Method for coating a turntable rubber of a disk player and turntable thereof |
-
1980
- 1980-12-17 KR KR1019800004812A patent/KR830001562B1/en active IP Right Grant
-
1981
- 1981-05-12 CA CA000377415A patent/CA1163569A/en not_active Expired
- 1981-05-18 IT IT21767/81A patent/IT1135835B/en active
Also Published As
| Publication number | Publication date |
|---|---|
| KR830004091A (en) | 1983-07-06 |
| IT1135835B (en) | 1986-08-27 |
| KR830001562B1 (en) | 1983-08-12 |
| IT8121767A0 (en) | 1981-05-18 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry | ||
| MKEX | Expiry |
Effective date: 20010313 |