WO1991001558A1

WO1991001558A1 - Stratiform, inelastic, deformable, statically stable structure, for deadening undesirable natural and imposed vibrations, comprising at least a layer comprised by a particle solid phase and by a massive consistency phase, particularly for provision of tripodal supports

Info

Publication number: WO1991001558A1
Application number: PCT/EP1990/001203
Authority: WO
Inventors: Paolo Russo
Original assignee: Paolo Russo
Priority date: 1989-07-20
Filing date: 1990-07-20
Publication date: 1991-02-07
Also published as: IT1234733B; IT8916908A0

Abstract

The structure, adapted to provide mono or multisupport (1), particularly tripodal of dissipation of vibrations, comprises a particle solid phase (7), comprised by microparticles of particle grade not exceeding 40 microns. Particularly adapted are aerated powder mediums, including talc. Said microparticle phase (7) is contained by a soft enveloping phase (3), and joined to a massive consistency phase (2), which is comprised by a C-convex calotte having main outer surfaces (20, 20') substantially concentric with a camber ranging between 15 % and 60 % of its chord (C). Said surfaces (20, 20') are characterized by the following formula: R = Constant, i.e. in the form of hollow spheroidal C-convex calotte; such massive phase (2) being made of metallic material having a high specific gravity: lead being preferably and arranged with concavity (20) upwards, i.e. engaging the base of a microparticle phase member (7) and/or an enveloping phase member (3).

Description

Stratiform, inelastic, deformable, statically stable structure, for deadening undesirable natural and imposed vibrations, comprising at least a layer comprised by a particle solid phase and by a massive consistency phase, particularly for provision of tripodal supports.

The present invention relates to a stratiform, inelastic, deformable, statically stable, structure, for deadening undesirable natural and imposed vibrations, including at least a layer comprised by a particle solid phase and a massive consistency phase, wherein such massive consistency phase is comprised by a C- convex calotte with substantially parallel walls having a camber ranging between 15% and 60% of their chord. Such structure is provided with a high insulating capacity from vibration transmitted from the base as well as of rejecting vibrations imposed by aerial medium.

At present state of the art, in the modern research or applications laboratory, often it is highly desirable, if not imperative, to carry out experiments or measurements in a vibration-free environment. Optical systems with multiple components, which must be individually mounted and aligned in a precise and rigid fashion, are particularly vulnerable to vibrationally induced performance degradation. For example, any application involving interference effects obviously must be maintained as vibrationally isolated as possible. Since visible light has a wavelength of approximately half a micron, interferometry based experiments (including holography) may be impossible to perform in the presence of vibrations of even submicron amplitude. Many laser applications involve focusing the laser beam to a waist of only a few microns radios. If the position of this spot is critical to system performance, such as in the case of an ion laser pumping a jet stream dye laser, then vibrations with amplitudes in the micron range can ruin an experiment. Optical and/or mechanical machining or probing of semiconductor wafers requires similar stability. In addition, many experiments involve mechanical elements which move or vibrate and therefore must be vibrationally isolated from all critically aligned optical elements.

In short, the surface on which an optical system is mounted must satisfy several basic requirements. It must provide a rigid base on which optics can be reliably mounted and aligned, with both long term stability and no inherent vibrational resonances. It must successfully damp any vibrations caused by motorized or moving parts in the experiment, thus preventing these vibrations from influencing critical optical elements. It must isolate the experiment as a whole from ambient background laboratory vibrations. If these criteria are not met, several undesirable scenarios could result. An individual component, of the system as a whole, may not function properly. Consequently, valuable data may be buried in random noise of vibrational origin, or data may be totally misunderstood and wrongly evaluated due to vibrationally induced artifacts. In the latter case, incorrect data can lead to enormous and unnecessary wastes of time and resources, particularly if the system is a laboratory prototype of a production assembly.

To answer these needs, commercial optical tables of various designs have been developed over many years. The same basic tenets underlie all of these designs. The table top is designed to maintain a rigid and flat upper surface without being overly massive. The table is then seismically mounted, usually on air spring, to inhibit the coupling of ambient background vibration. Table tops have been constructed from granite, concrete, wood, steel and many elaborate composite structures in attempts to improve performance while controlling weight to a realistic level. Each of these has advantages and disadvantages, but without doubt the best overall performance by far can be achieved with composite construction.

Of course arrangements of this fashion are expensive and specialistic, thus justifiable only for applications of the aforesaid fashion, i.e. having an important economic or productive concern. Whereas applications even at an at least professional level consuming which could take advantage from a suitable vibration insulating are really a lot including turntable and compact disc players. On the other side despite their speciality, cost, complicacy, laborsomeness the means are scarcely effective since vibration propagation is permitted. In fact such table tops provide a "living" structure and is very complicate and difficult to control both during manufacturing and operation. However the manufacturers of these known devices do not consider as disturbing vibrations with frequency higher than 100 Hz, trusting on filtering capability of elastic suspension. The invention as claimed is intended to remedy these drawbacks and obtaining various advantages. The inventor, starting from consideration that an ideal vibration insulating system is characterized by having the lowest frequency of oscillatory motion, the minimum dumping of oscillatory motion and by being comprised by a single mass of material having a high capability of dissipating the energy for the most ample frequency spectrum; and that a vibration insulating system differs from the ideal design of the single elastically suspended as much as it may be split in elastically connected parts; the vibratory behaviour of each part is characterized by number and frequencies of its vibrating mode and by proper dumping of material: the more numerous and less dumped are the vibrating modes by elastic deformation, the lowest is the insulating effectiveness, since each vibrating mode provides a vibration transmission path of the highest energetic efficiency. Thus, the inventor has conceived a vibration insulating structure to provide insulation from outer vibrations, wherein single elastically independent masses, are individually shaped whereby the prevailing deadening function is provided by a material having an inelastic behaviour in the form of very thinly ground material enclosed by an envelope whose Sessional stiffness is negligible as well as characterized by maximum difference of acoustic impedance between the massive solid phase members and the insulating microparticle phase members. Thus between such phases exchanges of horizontal forces, operating in the insulating material (without any resistance to tensile strength and to shearing stress) occur in virtue of the shape of spheroidal C- convex calotte provided that the enveloping walls of microparticle phase,as foreseen, are not stressed. Moreover the inventor has conceived a system representing an optimal application of subject structure in tripodal support form, whereby stability against horizontal forces is obtained with contribution of top and bottom shelves bonding the massive solid members to parallelism; variously interspacing the same increases the effectiveness of multiple riflession between the, facing each other, surfaces of rigid members, resulting in an extension of such effectiveness to much more adjacent frequency bands, in order to cover the most ample frequency spectrum, in audio band; moreover, elastically camberless suspension means provides the suspended mass with a very low frequency of oscillatory motion (tipically 1 HZ) and with a minimum motion dumping.

Thus such structure provides a valuable means suitable for any use, involving integral dissipation of vibrations with any amplitude and on any level they occur. A system comprising such structure is of relatively low cost and reasonably such to be born by any professional and even by less poor amateur users.

A way of carrying out the invention is described in detail below with reference to drawings which illustrate one specific embodiment, in which:

Figure 1 is a perspective front view of an insulating system, according to the present invention supporting a possible user in the form of turntable player shown in phantom lines.

Figure 2 is a detailed front view, partially broken of one of the three cylindrical supporting columns, shown in a slightly enlarged scale.

Figure 3 is a detailed perspective view of a few bottom members of column of figure 2 shown in a still enlarged scale and wherein the bottom member is shown with its core plate symbolically broken in two halves, one of which placed at the highest adjustable level and the other at the lowest adjustable level.

Referring to fig. 1 of the drawings a conventional vibration insulating system, comprises substantially three components: a top shelf 11, one or more supports 1 and an air compressed spring 9 between the base of each support 1 and the floor 0. Conventionally, in accordance with a first prevailing configuration, the trend was to improve the table top structure 11, providing it as a stratiform, metallic, cellular (particularly honeycomb) and relatively cumbersome, as well as to air compressed springs 9; whereas scarce importance was given to improve the supports. Thus quite often the interfacing support 9 was set between the supports 1 and the top 11. In accordance with another conventional and more experimental and specific configuration the table or shelf top 11 was conceived as a member of maximum static and dynamic stiffness such as a marble, concrete, granite, wooden slab or the like, while as, generally monocolumn, support flat stratification of massive materials such as those just now mentioned, interspaced by layers of particle material such as loose very thin loose sand or the like, of cross section and thickness limited by the slab perimeter that necessarily must be at least partially open to break off vibration propagation.

The stratiform, inelastic, deformable, statically stable structure, for deadening of undesirable natural and imposed vibrations, adapted to provide mono or multisupport 1, particularly tripodal for vibration dissipation, comprising at least a layer comprised by a particle solid phase and a massive consistency phase; in accordance with the present invention, as shown in figures 1 to 3, it includes a particle solid phase 7, comprised by microparticles of particle grades not exceeding 40 microns. Particularly suitable materials are aerated powder mediums, including firstly talc. In accordance with an important feature of the present invention each microparticle phase member 7

SUBSTITUTE SHEET is contained by an enveloping soft phase member 3, such as a fabric i.e. of thickness and stiffness not exceeding that of a thin unstressed silk fabric.

In accordance with another essential feature of the present invention each massive consistency phase member 2, is comprised by a C. -convex calotte having outer surfaces 20, 20', substantially concentric, having a camber ranging between 15% and 60% of calotte chord. To support the walls of microparticle phase 7 or dynamic stiffness of structure, the C- convex calotte has C- convex surfaces 20, 20' characterized by the following formula: R=Constant, i.e. in the form of hollow spheroidal C- convex calotte; wherein R is comprised between 0,8 and 1,2 times diameter C of C- convex calotte (2). In accordance with a preferred embodiment of the present invention, the massive consistency phase 2, is made of metallic material having a high specific gravity, such as lead, being preferable. Again, in accordance with the present invention, is very important in order to provide a good stability of column 1 of members that concavity 20 of C- convex calotte member faces upwards, i.e. engages the bottom of a microparticle phase member 7 i.e. of an enveloping phase member 3.

Again, in accordance with the present invention, it is very important that the thickness ratio between microparticle solid phase 7 or enveloping phase 3 from one side and the massive consistency phase 2 from the other side is comprised between 1 and 18 times the thickness of same. As shown in figure 2, column 1 comprises five microparticle members, lb, lc, Id, le which are of different height. More precisely their height or thickness is increasing from the bottom to the top with a multiple factor which is the thickness of massive consistency phase 2, which on the contrary has constant thickness for all the calottes of the column; preferably such factor is comprised between 2 and 12. On the other side it should be considered that the minimum thickness of massive consistency solid phase member 2 is not less than 0,5 cm., while the microparticle solid phase 7 or the enveloping phase 3 should not have a

UBSTITUTE SHEET thickness less than 1 cm. Regarding the qualitative choice of material comprising the solid phases 2, 7 a combination is chosen maximizing th difference of specific acoustic resistance, which in case of talc 7/lead combination is about 55.000 Kgm/dm sec. In view of what previously set forth, a system in accordance with preferred embodiment of the present invention, includes a tripodal suppor (figure 1) comprising: three column supports 1 substantially cylindrical, bottom shelf 10, a top shelf 11 and three elastic members 9 contacting the floo 0. The bottom shelf 10 is in the form of an equilateral triangle with widel radiused corners; it is made of lead alloy, to provide it with a high rejectio capacity of vibration forced by the air; such lead alloy in addition to a hig specific acoustic resistance provides a high intrinsic vibration dumping suitable to control the amplitude and duration of vibrations in correspondenc of its vibrating mode . Top shelf 11, is shown as a square but in general will b made in a suitable form matching the needs of user device 12 and ma therefore be missing, e.g. when a user device, not shown, may be place directly on top members of column supports 1. However, shelves 10 and 1 provide a planar bond for the massive members 2 of columns 1 and therefor contribute stability to the whole system. Each support 1 is comprised by fiv massive rigid members 2 (2a, 2b, 2c, 2d, 2e) each included in a small sack 3, filled in thereunder with dumping material 7, tied with strings 5 and 6.

The rigid members 2 of lead, in addition of having a high specific acoustic resistance and intrinsic dumping high too, contribute to determining of total weigh of insulating system since it is convenient that it is much heavier than the user device 12. In fact, normally happens, that this apparatus is provided with elastic proper suspending means. Their shape, as hollow spheroidal C- convex calotte rigid members 2 and the inherent curvature, provide them with a high flexional stiffness capable to limit the elastic deformations: the axial symmetry of C- convex calotte, keeps at the minimum the number of their

SUBSTITUTE SHEET vibrating mode. The shape as spheroidal C- convex calotte provides a transfer to the bottom shelf 10 of horizontal forces applied to the top shelf 11 simply through the very compressive stress transmittable by microparticle phase 7. In other words the curvature of spheroidal C- convex calotte 2 provides a horizontal reaction which stabilizes the system and avoid straining of enveloping wall 3. Such wall 3 can be made of material having a negligible flexional. The inherent lack of strain do not permit wall 3 to provide a vibration by-pass. Such members 2 are advantageously assembled with their concavities upwards; the curvature of bottom surface of member 2 increases the limit angle, of total reflection, which of course is reached for an emission solid angle smaller than that obtained from even facing surfaces; the energy transmitted by refraction is thus reduced in favour of that reflected. Wall 3 may be made of cotton fabric having a thickness of a few tenth of millimetre.

As aforesaid, the dumping material 7 is formed by very thinly ground talc. The enveloping wall 3 comprises a cylindrical,small sack 3, including a bottom 3' and a side wall 3" joined thereto by a sewing 3'". The upper part of small sack is open for filling in the dumping material 7. Such upper part of small sack 3, includes a string 6, and is then fastened, about C- convex calotte 2, by same string 6 as well as by string 5. String 6 provides stretching of enveloping wall 3 including talc 7, in order to suitably compact the powder 7. String 5 fastens the wall 3 with C- convex calotte 2, providing thereby a filled in sealed container 3; on loading it with other members,with top shelf member 11 as well as with user device 12 to be insulated, powder 7 is increasingly compacted and the sack side wall 3 becomes relaxed as necessary. In this embodiment the height of small sack 3 is variable, tipically from 4 to 8 cm.; a number of them are arranged, preferably, in increasing order of height from the bottom shelf 10 whereby to provide a higher stability resulting column 1. Elastic members 9 substantially comprise a body 14, an elastic membrane 16 and a disc 17. Membrane 16, is engaged by ring 15 to body 14 to provide a closed volume 13,

SUBSTITUTE SHEET which is filled in with a compressed gas, whereby the bottom shelf 10, through disc 17, is elastically supported. The spring body 14 is connected, through a pipe 120, to a tank (not shown) whose volume determines the elastic constant of spring 9 and thus its oscillation frequency. Springs 9 are in contact with floor 0 by means of three lead balls 19. Plates

17 are engaged by bottom shelf 10, through three rubber discs 18.

La power that each spring 9 can provide on bottom shelf 10 may be changed, by changing the pressure within volume 13, to balance any load 12 applied with any eccentricity on the top shelf 11. Yielding of each aerial spring 9 may be advantageously different, to increase the global stability of system under the action of occasional horizontal forces. Dumping of fundamental oscillation of whole system can be changed by interposing a dissipation member on the gas line connecting volume 13 to the tankj.the dissipation member, not shown, is substantially a valve providing a throttling along pipe 120.

Members 8, each comprised by a small sack filled in with powder is placed as a member providing an inelastic joining between the top shelf 11 and each massive consistency phase top member 2; members 8 provide a main levelling of top shelf 11, since their thicknesses may be changed to reduce height differences between columns 1, due to constructive differences or due to different compacting undergone by dumping material 7. The final levelling of top shelf 11 is provided adjusting the pressure within springs 9. The final level of each of plates 17 is easily and precisely obtainable through air emission from volume 13 obtained by adjusting the inflating valve 9' of spring 9.

SUBSTITUTE SHEET

Claims

C L A I M S

1. Stratiform, inelastic, deformable, statically stable, structure, for deadening of undesirable natural and imposed vibrations, comprising at least a layer comprised by a particle solid phase and by a massive consistency phase, characterized in that particle solid phase (7) is comprised by microparticles of particle grade not exceeding 40 microns and is contained by a soft enveloping phase (3), i.e. not exceeding that of a thin unstressed silk fabric.

2. Stratiform, inelastic, deformable, statically stable, structure, for deadening of undesirable natural and imposed vibrations, as claimed in claim 1, characterized in that each massive consistency phase member (2) is comprised by a C- convex calotte having substantially parallel outer surfaces (20, 20') having a camber ranging between 15% and 60% of the chord.

3. Stratiform, inelastic, deformable, statically stable, structure, for deadening of undesirable natural and imposed vibrations, as claimed in claim 2, characterized in that in order to support the phase microparticle walls or dynamic stiffness of the resulting structure composed system, a C- convex calotte is provided whose main surface (20) is characterized by the following formula: R=Constant; wherein R is comprised between 0,8 and 1,2 times the diameter of C- convex calotte (2).

4. Stratiform, inelastic, deformable, statically stable, structure, for deadening of undesirable natural and imposed vibrations, as claimed in claim 1, characterized in that massive consistency phase members (2) are made of metallic material having a high specific gravity.

5. Stratiform, inelastic, deformable, statically stable, structure, for deadening of undesirable natural and imposed vibrations, as claimed in claim

4, characterized in that the metallic material having a high specific gravity, comprising phase members (2), is lead.

6. Stratiform, inelastic, deformable, statically stable, structure, for deadening of undesirable natural and imposed vibrations, as claimed in claim

SUBSTITUTE SHEET 1, characterized in that particle solid phase (7) is comprised by an aerated powder medium (7).

7. Stratiform, inelastic, deformable, statically stable, structure, for deadening of undesirable natural and imposed vibrations, as claimed in claim 6, characterized in that the aerated medium (7) is talc (7).

8. Stratiform, inelastic, deformable, statically stable, structure, for deadening of undesirable natural and imposed vibrations, as claimed in claims 6 and 7, characterized in that particle solid phase (7) is provided with a specific acoustic resistance Re = g V wherein g = 0,8 ÷ 1 and V = 500 ÷ 600 m/sec.

9. Stratiform, inelastic, deformable, statically stable, structure, for deadening of undesirable natural and imposed vibrations, as claimed in claim 8, characterized in that particle solid phase members (7) are provided with an optimal specific acoustic resistance of 500 Kgm/dm sec.

10. Stratiform, inelastic, deformable, statically stable, structure, for deadening of undesirable natural and imposed vibrations, as claimed in claim 1, characterized in that the thickness ratios between microparticle solid phase members (7) and/or enveloping phase members (3), from one side and massive consistency phase members (2) from the other, are comprised between 1 and 18 times the thickness of lead calotte.

11. Stratiform, inelastic, deformable, statically stable, structure, for deadening of undesirable natural and imposed vibrations, as claimed in claim 1, characterized in that the volume ratio between microparticle solid phase members (7) and/or enveloping phase members(3), from one side and massive consistency phase members (2) from the other, is increasing from 2 to 12.

12. Stratiform, inelastic, deformable, statically stable, structure, for deadening of undesirable natural and imposed vibrations, as claimed in claim 1, characterized in that thickness of microparticle solid phase members(7) increase starting from the bottom to the top according to a ratio comprised between 1,2 ÷ 1,5 times.

13. Stratiform, inelastic, deformable, statically stable, structure, for deadening of undesirable natural and imposed vibrations, as claimed in claim 1, characterized in that massive consistency phase members (2) have a minimum thickness of 0,5 cm.

14. Stratiform, inelastic, deformable, statically stable, structure, for deadening of undesirable natural and imposed vibrations, as claimed in claim 1, characterized in that microparticle solid phase (7) and/or enveloping phase (3), from one side and massive consistency phase (2) have a minimum thickness of 1 cm.

15. Stratiform, inelastic, deformable, statically stable, structure, for deadening of undesirable natural and imposed vibrations, as claimed in claim 1, characterized in that in matching materials providing solid phases (2, 7) a combination thereof is chosen maximizing the difference of specific acoustic resistance, which for talc (7) lead (2) combination amounts to about 55.000 gm/dm³/sec.

16. A system made of structures as claimed in one or more of claims from 1 to 15, characterized in that it is in the form of a tripodal support, comprising three columns supports (1) substantially cylindrical, and including a bottom shelf (10), a top shelf (11) and supporting elastic members (9), as well as levelling members (8).

17. A system as claimed in claim 16, characterized in that base shelf (10) is in the form of an equilateral triangle with widely rounded corners; it is made of lead alloy, to provide it with a high rejection capacity of vibrations imposed by aerial medium.

18. A system as claimed in claim 16, comprising at least an elastic member (9), substantially including a body (14), an elastic membrane (16) and by a disc (17), wherein membrane (16), being urged by ring (15) to engage the body (14) provides a closed volume (13), wherein a gas is pressed, in order to

SUBSTITUTE SHEET suspend the base shelf (10), through the action of the disc (17) whereby the body (14) of spring (9) is connected, through pipe (120), with a tank whose volume settles the elastic constant of springs (9) and thus the oscillation frequency o the suspended spring, characterized in that its resting on the floor (0) is provided by means of three lead balls (19).

19. A system as claimed in claim 18, characterized in that said membrane (16) has a maximum thickness of 1 mm.

20. A system as claimed in claim 18, characterized in that member (8), is comprised by an envelope filled in with powder operating as inelastic coupling member between the top shelf (11) and massive consistency phase members (2), whereby member (8) provides a main levelling of top shelf (11).

21. A process for providing a system as claimed in^" claims from 16 to 20 with structures as claimed in claims from 1 to 15, characterized in that the provi¬ sion of each elementary member includes: a) the provision of a cylindrical, sack (3), made of thin fabric, with a bottom (3¹) and a side wall (3") joined the¬ reto by a sewing (3'"), such bottom wall (3') having the same shape and size than the plane cross section of member (2), providing its cover, the upper part of said sack (3) being open for filling in with dumping material (7), such upper part having a mouth provided with a string (6), loosely placed therein with emerging knotable end lengths; b) provision of a spare loose string 5 similar to said string (6); c) the filling in of cylindrical, sack (3) with said material (7) formed with very thinly ground talc, leaving at the top of the sack (3) a suffi¬ cient space to receive a C- convex calotte (2) shortly under the sack mouth and said string (6); d) fastening of string (6), in order to provide a substantially soft saturation of container (2, 3) with powder (7), by seizing the sack mouth to pro¬ vide a collar; e) fastening of loose string (5) in order to consolidate the soft satu¬ ration of container (2, 3); and f loading the composed member (3, 7, 2) to pro¬ vide a centripetal hard compacting of powder (7) and corresponding release of centrifugal powder and thus of side walls (3") of sack (3).