CA1091876A

CA1091876A - Process of manufacture of a circular friction facing

Info

Publication number: CA1091876A
Application number: CA281,025A
Authority: CA
Inventors: Ernest H. Mccombie
Original assignee: Automotive Products PLC
Current assignee: Automotive Products PLC
Priority date: 1976-07-22
Filing date: 1977-06-21
Publication date: 1980-12-23
Also published as: FR2359323B1; GB1545081A; IN145693B; JPS5313048A; ES460967A1; IT1083664B; ATA503577A; BR7704721A; DE2731813A1; FR2359323A1; AT373371B

Abstract

ABSTRACT OF THE DISCLOSURE
A method of manufacture of a circular friction facing, suitable for use in a clutch or brake, the friction facing being re-inforced by a fibrous filler which comprises discrete lengths of fibre strand. The friction facing is produced from a dough of compounded uncured friction material that is extruded so as to orientate the fibrous filler along the longitudinal axis of the extrudate. The extrudate is then spirally wound into a circular disc-like preform such that the axes of the bits of fibrous filler are tangential to a radius of the preform and then moulding and curing the preform to produce a friction facing.

Description

~ 7 6 This invention relates to a method for the manufacture of friction facings for use as clutch facings or for disc brakes, in particular the invention relates to circular faclngs comprising spiral coils of an orientated fibrous filler, such as asbestos.

It is known for annular or disc friction elements such as clutch facings to be formed by spirally winding spun asbestos yarn, normally impregnated with an organic resin friction composition, convolutely about itself. Some difficulty may be experienced in ensuring that the resin has impregnated . to the centre of the asbestos yarn. Furthermore, the resin content of this type of construction has to be constantly monltored because the yarn is passed alternatively through resin bath~ and drying ovens until the required resln content has been picked up on the yarn.
, Also the asbestos fibre length has to be sufficient to facilitate the production of asbestos yarn, whilst in contrast it is commercially desirable to utilise shorter fibres, which are cheaper than the longer length fibres required for making ,, .
yarn.
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The ob~ect of the present invention is to produce a method of manufacture of a circular friction facing in which " ' :' the majority of the fibres of the fibrous filler are circum-ferentially aligned and in which the problems of impregnation of the fibrous filler by the resin are severely reduced.
According to this invention there is provided a method of manufacture for a circular friction facing suitable for use in a clutch or brake, and the method includes the steps of, forming a dough which includes a substantial proportion of fibrous filler ; comprising discrete lengths of fibre strand mixed into a cure-able liquid cement, extruding the dough forming an uncured ~ 10 circular preform, and moulding and curing the preform to produce a circular friction facing, characterised in that the dough con-tains fibres which generally do not exceed 1/2 inch in length (1.27 cms.) and the dough is extruded through a die of such a ; size that the majority of the fibres are orientated to lie sub-stantially parallel to the axis of the extrudate, and spirally winding the extrudate to form a disc-like preform in which the fibres are circumferentially aligned.
Sl For the purpose of this invention, the fibrous filler , . . .
` as utilised in this invention, comprises large numbers of discrete fibre strands, a substantial proportion of which , .
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~ 7 6 have sufficient length to impart some re-lnforcement to the circular facings whilst being short enough to be consistent with the process disclosed in the invention~ The flnal length of the fibre being determined by the process itself, the starting length of the fibres, and the required properties of the circular facings.

Preferably the liquid cement is a phenol formaldehyde resin, of the Resole or Novolak type, and furthermore the resin may be dissolved in a suitable solvent to facilitate the mixing of the dough, the preforms of the friction linings may be allowed to stand for sufficient time to enable the solvent to ,, -evaporate from the extruded dough.

Alternatively, modified phenol formaldehyde resins ; may be used as a binder, or melamine formaldehyde resin may also act as a binder.

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It is preferably for the fibres to be asbestos fibres (1.27 cms.) of up to approximately ~"/long and of the types known as . .
Canadian Classifications 7D, 6D or SR.

, Alternatively, other fibrous filler may be used as well as or instead of asbestos fibres, alternatives include glass fibres, rock wool, crude cotton, steel wool, sisal, carbon fibres, and non-ferrous metal fibres.

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1o~ 7 6 Also it is preferable for the dough to include 50me amorphous mineral filler, examples of suitable mineral flllers are Ferric and Ferrous Oxide, Barium Sulphate, Zinc Sulphide, Ferric Sulphide, Lead Sulphide, Ch~na Clay and Mica.

Also the dough may contain organic fillers and re-inforcements such as Carbon Black, Resin-polymerised a~shew Nut Oil, Rubber Styrene-Butadiene Copolymer Crumb and Nitrile ~ubber Crumb.

It i8 preferable for the dough to have the following ,.
composition by weight:-. A~bestos Fibre 6D Classification 40 - 60%
; Phenol Formaldehyde Resole Resin 20 - 30%
; Solvent 10 - 2070 Rubber Styrene-Butadiene Copolymer O - 10%
Brass Swarf or Copper Wire .. ~ (chopped) O - 10%
, : Carbon Black O - 2%
- Mineral Filler O - 20%. j. .
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, . , Alternatively the dough may have the following composition by welght:-Phenol Formaldehyde Novolak Resin 20 - 30%
Polymerised Cashew Nut Oil 5 - 10%
Asbestos F~bre 6D Class~ficati,on 4~ - 6Q%
Industrial Methylated Sp~rit 15 - 2Q%
Rubber Styrene-Butad~ene Copolymer Q - lQ%
; Brass Swarf 0 - 10%
Mineral Filler ~ - 2Q%
The dough ~ill preerably be extruded at a constant speed and also the cross-section of the extrudate may be foxmed to provide some ~nterlocking between the sepaxate coils of the spirally wound extrudate.
According to this invention there is p~ovided a method of manu~acture for a ci.rcular frîction facing suitable . for use in a clutch'or brak.e, and the' ~ethod i.ncludes the steps of, formi,ng a dough, which'includes a su~stanti.al propor-tion of fibrous filler comprising di.screte lengths of fibre strand mi.xed into a cuxable li.quid cement, extruding the dough, 2Q subsequentl~ forming the extrudate into an uncured cixcular prefoxm, and moulding and curing th~ preform to pxoduce a circular friction facing, chaxacterised in that the dough ~,' contains fibres wh~,c~. generally do not exceed 1~2 inch in - length (1.27 cms.~ and the dough. is extruded through a die of `: s.uch. a si.ze that the ma~ority of the fi~res axe orientated to '~: lie substantially parallel to the axi.s of the extrudate, and spirally winding the 'extrudate to form a disc-like prefoxm in . .

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105~876 which the fibres are circumfexentially aligned.
: According to another aspect of the invention there is provided a circular friction facing suita~.le for use in a clutch or ~rake, manu~actured from a fri.cti.on material having a substantial proportion of fi~rous filler, and the said filler comprises discrete lengths of fi~re strand which. generally does . not exceed 1~2 inch. U.27 cm~-l in length, and the majority of the fi~res are oxi.entated to lie in circumf~rential alignment in the facing.
~ccording to this inventi.on th.exe is also provided a circular frîction facing manu~actur.ed ~ the method defined above.
Also accord~ng to this invention there ia provided a circular friction facing formed as descxi~ed h.erein and which is moulded directly, i.n s~:tu, upon an annular plate .. member of a clutch driven plate.
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~ 7 6 Also according to this invention there is provided a circular friction facing suitable for use in a clutch or a brake, and which includes in its material make-up a substantial proportion of fibrous filler, wherein the said : 5 fibrous filler comprises dlscrete lengths of fibre strand wherein the longitundial axes of the maJority of the fibres are orientated in a circumferential array within the circular : facing.

- Preferred embodiments of the invention will now be described making reference to the accompanying drawing in . which:-, ' .

~i ~ig. 1 shows a pre-mould of a friction facing;
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. ~- Fig. 2 also shows ~ typical pre-mould;

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Fig. 3 shows alternative cross-sections of the extrudate and also illustrates the interlocking type extrudate 3 (ii) and 3 (iv), which fit together as illustrated as in Fig. 3 (v);
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Fig. 4 shows a fr~ction facing according to this ., invention moulded in situ; and Fig. 5 is a cross-section of Fig. 4 on the line `
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, , "' ,~.,` ~ . '' -1 0 ~ 1 ~,7 6 - The method of manufacsure of a clrcular frictlon faclng, according to this invention is mainly concerned with the orientation of the reinforcing fibrous filler. Durlng this process the fibres are orientated by the production process so that the longitudinal axes of the ma~ority of the fibres lie in a circumferential array around the circular clutch facing. Such a friction facing has a very high burst strength.

The fibres are made up lnto a dough of resin and fibrous filler which is extruded so that the extrusion process - orientates the fibres along the longitudinal axis of the extrudate. Le~gths of extrudate are ~pirally wound to form flat convoluted discs of cross-sectlon similar to Fig. 1 . - , and Fig. 2. This spiral of extrudate will cause the longitudinal axis of the fibres to be orientated such that the majority of the fibres lle at a tangent to a radius of the flat convoluted disc which has been formed.
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-, The flat convoluted disc will be referred to as a r~ preformed clutch friction facing or a preform. When the " 20 preform is compression moulded the separate layers of the extrudate are cured together under pressure and heat. The . . .
moulding process causes the resin to flow to fill up spaces between the extrudate and also to weldt~e layersof extrudate ~ into a single entity.
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:. . , The dough of a friction materlal is made up from a resin with a fibrous filler, and any of a number of other components that are necessary to develop the properties requlred by the particular friction material. The components of a friction material dough c~n be:-. (1) A resinous material such as one or more of thR following types:-(a) A Phenol Formsldehyde Resin of the ; Resole or Novolak type . 10 (b) An Unvulcanised Rubber (c) An Epoxy Resin (d) A Polyester Resin (e) Melamine Formaldehyde Resin

(2) A fibrous filler such as one or re of the following types:-., ','J:
;~ (a) Asbestos Fibre (Canadian Classification . 6D, 7D or 5R) .
(b) Rock Wool (c) Steel Wool -; ~-.
. 20 (d) Sisal . (e) Cotton :
,~ (f) Glass Flbre (g) Non-Ferrous Metal Fibres ^- (h) Carbon Fibres . , . .

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10~876 - (3) Organic extenders and fillers of the following types:-(a) Carbon Black (b) Resin Polymerised Cashew Nut Oil (c) Rubber Whole Tyre Crumb of the Styrene-Butadiene Copolymer type, or alternatively Nitrile Rubber Crumb.

(4) Inorganic mineral fillers of the following types:-t~'''' (a) Chalk or Whiting (b) Mineral Oxides such as:-. . .
;~ (i) Ferrous/Ferric Oxide ~ (ii) Litharge i~
~ (iii) Chromic Oxide :( 15 (iv) Lithopone .., ~ (c~ Barytes i:
(d) Mineral Sulphides such as Ferric Sulphide - 20 (e) Refractory fillers e.g. Ghina Clay, .:
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~ - (5) Metals of the following kind:-.iI
-~ (a) Copper - present as wire,chippings, ) swar~ or powder :".
(b) Brass - present as wire,chippings, swarf, or powder (c) Zinc - present as wire,chippings, swarf,or powder , A, ., 1 0 ""
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10~76 (6) Possible solvents for the resinous material, for example:-(a) Industrial Methylated Spirits (b) Isopropyl Alcohol (c) Methanol - (d) Acetone (7) Any catalysts necessary for curing the resinous material, for example:-(a) Hexamine for Novolak Resins (b) Benzoyl Peroxide for Polyester Resins (c) Sulphur for uncured natural rubber A typical composition for a dough is:-Asbestos Fibre Canadian Classification 6D 180 gms Phenol Formaldehyde Resole Resin (dry) 100 gms .~ 15 Isopropyl Alcohol 62 gms ,.~
Whole Tyre Crumb 15 gms Chopped Copper Wire 15 gms Carbon Black 2 gms . , :

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A second typical composition for a dough is:-Asbestos Fibre Candadian Classiflcation 420 gms Phenol Formeldehyde Novolak Resin 210 gms Hexamine 16 gms Polymerised Cashew Nut Oil 70 gms - Industrial Mehtylated Spirit 150 gms ' ;'',' This a basic mixture to which other materials can be added to achieve the properties required for a particular friction material.
'-' The dough is thoroughly mixed by a proprietary mixing and blending machine e.g. a~Banbury mlxer?until it reaches a smooth consistency. The dough is then placed into an extruder. Several types of extruders may be used, for example a screw type continuous extruder, a ram extruder, or a roller type extruder or callender whère the material is fed through two rollers. The type of extruder used will depend upon the consistency of the dough. For the two typical compositions -- , ` of a dough given above,it will be most convenient to use a ram extruder. The length of the fibres in the asbestos will be ~ (0.3. cms.) (1.27 cms.).
- 20 substantially scattered between ~"/and ~"/ Therefore in order to orientate the fibres in the longitudinal axis of the - extrudate, the dough is pushed through a circular die of smailer diameter than the length of the fibres. Also the ;~
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: ~ -~ , ' flow through the die should be of the lamina type flo~. A
(0.4 cms.) convenient diameter die has been found to be 5/32"/diameter, and a suitable extrusion rate between ~ ft/sec - 3 ft/sec (15 cms./sec to 1 metre/sec).
As the extrudate is taken off the extruder, it is wound in~oaflat annular convoluted coil as in Fig. 1 to form an uncured preform of the clutch friction facing.

The preform may be a single depth coil as shown in Fig. 1 or may be a plurality of layers of coils as shown in the sketch Fig. 2.

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; 10 When the desired size of preform has been reached the extrudate is cut and the preform removed. The extrudate is then fed into another annular convolution and so on.

The preform is allowed to stand at temperature of 20 - 25 C. in a conditioning room to allow most of solvent to slowly evaporate from the dough. The conditioning period required is approximately 24 hours. Alternatively the preform may be passed through ovens to speed up the removal of the solvent.

.
- When the preform has been conditioned, the preform of the clutch friction facing is then moulded by compression ' '' ' , ,: . " '~' ' ~ .' 10~76 moulding techniques at a temperature range 140 - 200 C., a pressure up to one ton/per square inch for a period of 10 -12 minutes. ~uring the moulding cycle the pressure on the moulded material is partially relieved two or three times to allow the mould to breath. This allows any solvent remaining in the dough, which will now be vapourised, to escape from the mould, together with any volatile reaction products from the final curing reactions of the resin.

After approximately 12 minutes the now formed clutch facing is removed from the mould and allowed to cool. The facing ls then trimmed and made ready for attachment to a clutch driven plate.
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The cross-section of the extrudate need not necessarily be circular. Alternative cross-sections are ~5 illustrated in Fig. 3. The cross-sections Fig. 3 (ii) and Fig. 3 (iv) have the advantage that they provide some interlock between the separate layers of extrudate and that on curing the orientated fibres of one layer ~extrudate will be inseperably mixed with the orientated fibres of another layer of extrudate.

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lO~ll~76 With reference to Fig. 4 and Fig. 5, the preform obtained after extrusion process may ~e utilised in an in situ moulding process, in ~hich the fricti.on facing 11 is moulded dtrectly onto an annular plate member 12 which is in turn directly attached to a hub member 13.
Apertures 14 are provided in that portion of the annular plate member 12 wh~ch is embedded ln the friction material 11. These apertures 14 help to provide a mechanical lock for anchoring the friction material to the annular plate . 10 member 12, and these apertures extend i.n a direction substantial-ly circumferential to a circle struck from the centre of the driven plate.
When a clutch. driven plate is manufactured by moulding a preform on both. sides of the annular plate member 12, the preform ~eing prepared as previousl~ disclosed in this specification, the compression of the friction material in the mould causes flo~ along th.e orientation of the extrudate.
This circumferential ~lo~ under compress.ion will flow material .. into the tangenti.ally orientated apertures 14.
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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of manufacture for a circular friction facing suitable for use in a clutch or brake, and the method includes the steps of, forming a dough which includes a substantial pro-portion of fibrous filler comprising discrete lengths of fibre strand mixed into a curable liquid cement, extruding the dough, subsequently forming the extrudate into an uncured circular preform, and moulding and curing the preform to produce a circular friction facing, characterised in that the dough contains fibres which generally do not exceed 1/2 inch in length (1.27 cms.) and the dough is extruded through a die of such a size that the majority of the fibres are orientated to lie substantially parallel to the axis of the extrudate, and spirally winding the extrudate to form a disc-like preform in which the fibres are circumferentially aligned.

2. A method as clammed in claim 1, wherein the filler is asbestos fibre of the type known as Canadian Classification 6D.

3. A method as claimed in claim 1, wherein the filler is asbestos fibre of the type known as Canadian Classification 7D.

4. A method as claimed in claim 1, wherein the filler is asbestos fibre of the type known as Canadian Classification 5R.

5. A method as claimed in claim 1, wherein the fibrous filler is a mixture of different fibrous materials.

6. A method as claimed in claim 2, wherein the dough has the following composition by weight:-Asbestos Fibre Canadian Classification 6D 40 - 60%
Phenol Formaldehyde Resole Resin 20 - 30%
Solvent - Industrial Methylated Spirit 10 - 20%
Rubber-Styrene Butadiene Crumb 0 - 10%
Brass Swarf 0 - 10%
Carbon Black 0 - 2%
Mineral Fillers 0 - 20%.
7. A method as claimed in claim 3, wherein the dough has the following composition by weight:-Asbestos Fibre Canadian Classification 7D 40 - 60%
Phenol Formaldehyde Novolak Resin 20 - 30%
Resin Polymerised Cashew Nut Oil 5 - 10%
Solvent-Industrial Methylated Spirit 15 - 20%
Brass Swarf 0 - 10%
Rubber-Styrene Butadiene Crumb 0 - 10%
Mineral Fillers 0 - 10%.
8. A method as claimed in claim 1, wherein the extrudate is formed so as to provide some interlock between adjacent coils of the spirally wound extrudate.
9. A circular friction facing suitable for use in a clutch or brake, manufactured from a friction material having a substantial proportion of fibrous filler, and the said filler comprises discrete lengths of fibre strand which generally does not exceed 1/2 inch (1.27 cms) in length, and the majority of the fibres are orientated to lie in circumferential alignment in the facing.

10. A clutch driven plate incorporating a friction facing as claimed in claim 9, wherein the friction facing is moulded in situ directly onto an annular member of the driven plate.

12. A clutch driven plate as claimed in claim 10, wherein the annular member is of plate form and has a plurality of circumferentially extended apertures defined therein which help lock the friction material to said member.