Document wDZdbw2DMMELMj4LgV3xNbpNE

FILE NAME Allied Signal Bendix ASB DATE 1960 July 19 DOC ASB204 DOCUMENT DESCRIPTION US Patent - Frictional Material - 292 United States Patent Office 2,945,292 Patented July 19 1960 1 Fited Nov. 28 1958 Ser No. 776,978 18 C. Cl 19 182.5 This invention relates to friction materials and ^ par- tacularly concerned with ferrous friction members for , ase as clutches brakes and the like This application usa usa cominuation of application S.N. 684,954 filed September 19 1957 now aban- doned An object of the invention w to provide a ferrous frice tion facing consisting essentially of iron graphite and a metallic lubr ant consisting of bismuth or alloys of bismuth with metals that are substantially insoluble in iron In carrying out the above object it is a further ob ject of the movention to form the fricuon member from a sintered mixture of iron powder with graphite which member also contains a lubricant metal in the form of bismuth bismuth alloys and cadmium al- Joys and wherein sraphite makes up a substantial por tion of the member will further object of the invention is to provide a farrous friction member which consish essentially of graphite ranging between 20 and 30 by weight and lubricating metal such as bismuth or bismuth alloys wherein the alloy has a mehm point not greater that the melung point of blsmult and wherein the other metals in the alloy are substantially insoluble in iron In carrying out the above object at is o further ob ject where bismuth or a bismuth alloy is used as a lubricating metal to include small quantities of an addr tional metal substantially nonalloyable with the lubricati ing metal one of such metals being coppei It a further object in some cases to utilize small quantities of sulfur not over % in combination with the iron either as an added ingredient or as an impurity in the iron used and or a cerami lite in quantitres of less than 1 Another object of the invention matemal such is to provide as multhe fer- rous friction element as heretofore disclosed with a strong metal supporting member for facilitating the mounting of the friction element said member taking the form of a sintered ferrous material of different composition and greater strength than the friction element and bonded coextensively thereto More specifically it is an object of the invention to provide a sintered ferrous friction element consisting ementially of graphne 30 to 45 parts by weight copper 0 to 15 parts by weight bismuth or insoluble alloys thereof 6 to 10 parts by weight and iron 100 parts by weight In carrying to opuonally out the include above object it is a sulfur and mullite further in the object above formulation _ Another object of the invention is to provide a fer- rous friction member containing substantial quantities of graphie together with a lubricating metal which is substantially insoluble in the metals making up the ferrous friction member said lubricating metal having a melting poim within the range of temperatures encountered during subsequent use of the friction elemem whereby the metallic lubricant melts and exudes to the surface of the element during use to stabilize the frictional char acteristics of the element Further objects and advantages of the present invention will be apparent from the following description referaman heing had to the accompanying drawings wherein preferred embodiments of the present invention are clearly shown In the drawings 20 Figure 1 is a perspective view of a typical brake band including the ferrous friction element thereon Figure 2 is a view in perspective of a conventional clutch disc utilizing the ferrous friction facing therean Figure 3 is a chart of a family of curves for ferrous 15 friction materials including different metal lubricants and showing coefficient of friction plotted against time and temperature Figure 4 is a perspective view similar to Figure 1 showing another means of attaching the friction lining to the shoe Figure 5 is a view of one segment of the fricton ma- terial and its support In modern automotive development extreme operating conditions are encountered at friction surfaces used 25 for b.akes clutches and the like These extreme condi tion make convenuonal nonmetallic clutch facings and brake linings costly to use since these materials musi operate below certain limiting temperatures if their eff^ ciency is 10 be maintained which requires cooling medis 30 and other devices to limit the temperatures 11 is there fore desirable to provide facing materials for cluiches brakes and the like which can withstand considerably higher temperatures than the usual nonmetallic materiali and which maintain substadually constant frictional char 35 acteristics throughout their operating temperature range Metallic facing matenals made from sintered metals such as sintered bronze sintered iron and the like have been used sparingly in the past and while the wear char- 40 acteristics acteristics on these elements are considerably better than nonmetallic elements it has been found difficult to control the coefficients of friction thereof through the wide range of temperatures that are encountered in normal operation whereby the build in friction during successive stops makes them erratic in their operation and therefore generally undesirable Recently improved friction facings have been pro- posed of the metallic type wherein substantial quantities of graphite have been incorporated therein to smooth out the coefficient of friction to some extent over a wide range of temperature These facings provide consider ably better operating characteristics and are frequently entirely sausfactory under normal operating conditions However when heavy duty service is encountered such as for example with taxicabs busses or stops from high speeds these friction materials do not always maintain their stability within the range desired The present invention is directed to a friction material which has a stabilized coeficient of friction and there fore is extremely useful in any application such as a clutch or brake wherein stabilized friction characteristics are desired over a wide range of temperatures whether or not the application falls in the category of a heavy duty application We believe that this stabilization of friction characteristics is accomplished through the use of a metallic lubricant which is transitory in character at the surface of the element that is to say the lub.cating metal is held in the solid state within the pores of the friction element at temperatures below its melting point and when these temperatures are exceeded this 70 metal due to its insolubility with the other components of the element and due to its expansion will exude amo Tr cee vege nie 6 Ea Pegg er = ew rayne mee ay e ge 8,046,303 . 3 the surface of the element and provide a fluid lubricant which stabilizes the frictional characterisues of the cle meat while maintaining the desired frictional character-charcter- istics thereof as provided by other components of the ele- ment It is understood that in the description to follow the ferrous frictioa element may be used in connection with brake bands or clutch discs or brake discs as the case may be For example in Figure 1. a conventional brake band is shown at 20 which includes a plurality of pads of friction material 22 attached thereto In Figure 2 a clutch disc or brake disc is shown at 30 which includes a steel disc 32 having a friction layer 34 attached thereto Specifically we have found that in a ferrous friction element wherein the major component is iron large quantities of graphite are highly desirable to supply the de- sired frictional characteristics to the element = In this connection graphite ranging from 20 to 30 by weight of the element is incorporated in the elemen~fl together with a lubricating metal such as bismuth or alloys of bismuth with metals which are insoluble in iron and wherein the melting point of the alloy does not exceed the melting point of bismuth for example bismuth alloys and cadmium alloys The low melting metal may be bismuth alone which melts at about 520 F. or it may be an alloy of bismuth and lead which melts or below the melting point of bismuth = In this con section an alloy of 889 lead and 120 bismuth has substantially the same melting point of bismuth whereas the eutectic alloy of lead and bismuth which contains 55 bismuth and 44's lead melts at about 255 F Thus bismuth alloys where the minimum bismuth percentage is 129 may be used as a substitute for pure bismuth according to use since any allos having this compositon will melt at or below the melting point of bismuth = In this connection the brake should be taken the service requirements of into consideration Heavy duty applications are best served by the higher melting point alloys whereas light duty applications may make use of the lower melting point alloys In all cases It is desirable that the melting point of the lubricating metal is in the range of temperature attained during nor mal use of the friction clement and thex condibois condibois therefore govern to a large degree the choice of material Similarly alloys of bismuth and other metals may be used wherein the other metal in the alloy is substan- tially insoluble in iron for example cadmium is in soluble in iron and alloys with bismuth to form low melt- ing point alloy In this connection an alloy of 257 bismuth and 75 cadmium has substantially the same melting point of pure bismuth whereas the eutectic alloy of 607 bismuth and 40 Ladmium melts at shout 292 F Stated broadly therefore alloys of bismuth with metals insoluble in iron wherein the alloy has a melting point not in excess of the melting point of bismuth are useful as the lubricaung metal Tbus it will be seen that we have chosen a lubrisal ing metal which is insoluble in the iron and which melts within a range of temperature generally reached by the friction element during use Other insoulble metals could possibly be used but in these cases the melting porni is sufficiently high that the liquidus state of the metal is not reached upon operation of the friction element whereby erratic results occur due to the fact that the called lubricating metal may be liquid in one case and solid in another Therefore in each instance the low melting point metal which acts as a lubricating metal melts at tem peratures within the normal operating temperature range of the friction element and in each instance where com- binations of these low melting point metals are used the eutectic mixtures thereof meh at relatively lower temperatures to quickly stabilize the frictional characteristics of the element by presenting a liquid phase at the interface between the element and the other rubbing surface etc. Some examples of suitable mixtures all proportions being in parts by weight brake drum or are us follows t { I ' EE EE Kk Ex 4. Ex Ex.6 | | | Sponge or Hidured Oxide Iron with or without 17 Cou . hined pulfor graphite . 2 |. ree ee -- ee a Ve] OO tr] 4 To] w Copper CCoppoer pp. er wens ae 6 e . Woche} Mullite oe ee ee .7 eves TJ te, oY) ad ***** ***** ***** 15 These ingredients in finely divided form for example capable of passing through a 100 mesh screen are intimately mixed and are briquetted into the desired shape under briquetting pressures ranging from 60,000 to 80,000 pounds per square inch and are then sintered under nonoxidizing conditions for from 30 to 40 min utes at temperatuers ranging from 1800 F. to 2000 F. In each case a sintered friction element is formed which will exude bismuth bismuth etc. as the case may be at the surface thereof More specific examples comprise Example 7 67 paris -250 mesh sponge iron powder combined sulfur up to % by weight 30 20 parts artificial graphite density 1.85 grams per cc - 325 mesb 8 parts 130 mesh copper powder 5 parts 100 mesh bismuth powder These ingredients are intimately mixed and are briquetted at 60,000 pounds per square inch and are then sintered for 40 minutes in a nonoxidizing atmosphere at 1800 F The resulting friction facing has a fiber strength in the order of 3720 pounds per square inch Example & 67 parts -250 mesh sponge iron powder with % com- bined sulfur . 15 parts powdered artificial graphite density 1.85 grams per cc -325 mesh 45 15 parts coarse flake natural graphite density about 2.1 grams per cc 20 to 30 mesh 5 parts 150 mesh copper powder 10 parts 100 mesh bismuth 50-50 mixture with or without pari 60 mesh synthetic mullite 50 These ingredients are intimately mixed and briquetted at 70,000 pounds per square inch and sintered for about 40 minutes in a nonoxidizing atmosphere at a tempera- ture of about 1800 F. The resulting friction element 55 has a fiber strength in the order of 3045 pounds per square inch It is understood that the lubricating metal such as bismuth alloy may be introduced by impregnation if desired although the usual technique as described here- tofore are preferred Furthermore due to the sintering step it is usually not necessary to alloy the bismuth alloying with any other metal to be used therewith since will occur in situ during the sintering All of the above friction elements made by any of the aforementioned examples are preferably bonded to a more dense and stronger material during the sintering to enable them to be riveted or welded to ^ steel shoe or plate This particular step forms no part of the present invention and is fully disclosed in copending Smiley application S.N 596.266 filed July 6 2956 as signed to the assignee of the present invention Specifi cally a backing material that is particularly useful with the present formulations since it bas similar physical change characteristics during briquetting and sintering 75 comprises a mixture of about 95 parts 100 mesh sponge 2,041,908 iron powder 5 parts low density powdered graphite 1.68 grams per cc -325 mesh and three molybdenum dimaphide powder 250 mash gredients are intimataly mixed and the mixture is in a die in desired quantity Any of the aforementioned two layers are simultaneously briquetted at presmares of from 60,000 to 80,000 pounds per square ach The briquette is sintered under conditions times and temperatures noted in any of the examples A coextensively 10 bonded material is formed having a strong backing layer and a friction facing of the desired characteristics A mentioned before the application S.N 596.266 gives a detailed disclosure of the method of making these com posite friction elements and the present invention is directed solely to the friction layer and its characteristics In place of the composite material described the fric tion layer may be supported by and bonded to a retaining device or member made of stamped or cast metal Such retuner is shown at 40 in Figures 4 and 5 The re- 20 tainer 40 is preferably made of stamped steel and is made in the form of a shallow cup or tray which carries a friction material layer 41 therein The retainer 40 may include fastening means 42 welded or otherwise attached thereto as shown in the right side of Figure 5 Or 25 the ret ser may be riveted by means of rivets 43 or dis rectly welded to the band 20 In the case of rivets 43 being used the friction layer 41 is counterbored so that the heads of the rivets bear against the container -- -- 30 all cases the friction layer 41 is sintered and bonded in situ to the container 40 by briquetting the powdered material directly in the retainer Prior to the briquetting operation the retainer surface is preferaby flash copper plated as well known in the art to facilitate the bond 35 It will be observed that when the graphite content of the friction material exceeds 25 different manufactur ing techniques are required in order to form an element having sufficient strength for the intended purpose and to this end different types of graphite are used to over 40 come probletns which arse when using either type of graphite alone These manufacturing techniques form no part of this invention and are fully disclosed in copending applicauon SN 684.853 Docket No 2712 filed September 19 1957 wherein the full disclosure of the reasons for mixing the different types of graphite are set forth In this connecuon so far as the finished fricuon element is concerned there is no substantial dif- ference in the operational characteristics of the different types of graphite but the strength of the finished clement is markedly enhanced by mixing two types of 60 Graphite While the friction element utihzing graphite in the order of 20 have good frictional characteristics and under normal operating conditions function well there is some tendency toward noisy operation under certain 5s specific conditions As the graphite content is increased this noise condition decreases to a point where the ele- ment is comparable with conventional nonmetallic ele menu at 25 of graphite and above In other words as the graphite increases the tendency toward noise de creases under all conditions The new friction facings described herein function well with conventional mating surfaces such as steel or cast iron which is normally used as clutch disc and brake drum material It will also function in combination with 65 other metals providing the lubricant metal does not alloy therewith at operating temperatures For this reason the metal of the mating surfaces should be chosco from metals and alloys that do not form intermetallic compounds with the low melting point metals such as lead bismuth 70 or cadmium used in the friction material The curves shown in Figure 3 are for two different friction linings Curve # is for the material disclosed in Example 8 Curve # is the material using % bis allom y inu steat d ofh the bismuth alloy In each 76 lustrative only and that clays silica magnesium oxide mica or any of the other refractory ceramic materials may be used with varying useful results While the embodiments of the present invention as berein disclosed constitute preferred forms it is to be understood that other forms might be adopted What is claimed is as follows 1. A friction material for use as a friction facing element consisting essentially of a sintered ferrous base having dispersed therethrough graphite in quantities of from 20 to 30 by weight together with at least one metal taken from the class consisting of bismuth bismuth and cadmium alloys wherein the melting point of the alloys does not exceed the melting point of bismuth said mentioned metal being pres ent in quantities of from % to 10 by weight 2. A friction material for use as a friction facing ele- ment consisting essentially of a sintered ferrous base having dispersed therethrough graphite in quantities of from 20 to 30 by weight together with bismuth in quantities of from % to 10 by weight 3. A friction material for use as a friction facing element consisting essentially of a sintered ferrous base having dispersed therethrough graphite in quantities of from 20 to 30 by weight together with a bismuth lead allow having a melting point not exceeding the melting point of bismuth in quantities of from % to 10 hy weight 3 A friction material for use ment consisting essentially of as a friction facing elea sintered ferrous hase having dispersed therethrough graphite in quantities of from 20 to 30 by weight together with a metal taken from the class of bismuth and bismuth alloys with metals insoluble in iron wherein said alloys have a melting point not in excess of the melting point of bismuth in quantities of from % to 10 by weight & A sintered friction material for use as a frid facing element consisting essentially of iron including sulfur up to % by weight thereof 100 paris graphite 30 to 45 parts copper up to 15 parts and a met taken from the class consisting of bismuth and bismuth alloy with metals insoluble in iron wherein said alloys have melting points not in excess of the melting point of his muth 6 to 10 parts said proportions being expressed as parts by weight 6 A sintered friction material for use as a friction facing element consisting essenually of iron including sulfur up to 1"by weight thereof 100 puits graplinte 30 to 45 parts copper up to 15 parts mullite up to 12 by weight and a mictul taken from the clas~ consisting of bismuth and lismuth alloys with metal insoluble in iron wherein said alloys have melting points not in excess of the melting point of bismuth 6 to 10 parts said proportions being expressed as parts by weight 7. A sintered friction material for use as a friction facing element consisting essentially of iron 100 parts graphite 30 to 45 parts copper up to 15 parts and bismuth 6 to 10 parts said proportions being expressed as parts by weight 8. A sintered friction material for use as a friction facing element consisting essentially of iron 100 parts graphite 30 to 45 parts copper up to 15 parts together with sulfur and mullite in quantities not in excess of % and bismuth 6 to 10 parts said proportions being expressed as parts by weight 9. A sintered friction material for use as a fricuon fac- ing clement consisting essentially of iroa 100 parts 2,946,298 7 graphite 30 to 45 parts copper up to 15 parts and a bismuth alloy 6 10 10 parts said proportions being ex- ment being coextensively attached at one surface thereof to a strong metal supporting member pressed as parts by weight 10. A heavy duty brake comprising a friction element consisting essentially of iron 67 parts graphite 20 30 parts a bismuth alloy wherein the bismuth and lead are in aqual proportions 5 1p0arts copper 8 parts all proportions being expressed in parts by weight said ele- in this References Cited in the file of this patebi UNITED STATES PATENTS 2.072,070 2,416,830 2.863.211 Fisher ............----- Heuberger ._...-...---. Wellman ._....-.------ Feb 23 Mar. 4 Dec. 9 1937 1947 1958 July 19 1960 Piled Nov. 28. 1958 W. A. LUTHER JR AL FRICTION MATERIAL 2,945,292 2 Sheet 1 40 aa ha 42 Fig 5 INVENTORS William A Luther Jr Roland P Koehring BY -- ------ ---- -- ----, --,, --,--,, 7 Their Attorney  Y & - - ' - ad = g oO = oe 2 oz 3 Fd a3 2 2 > x rz > O@enxr sf 222 > 32s 2} 2.6 ; Time in Minutes - }~--- s a 4 < 8 ad ae a | f @ Yat 2 TT ie = } Ye ' < | Fe oO e = o> ---4 a . G Pa = . :-~ 3 . * Fig. 3 im Maree so dletv ene se - ee tone i William A. Luther Koehring om,