Document DdX4w89L4zBQyg4agQb2Yrpo4

FILE NAME: Allied Signal Bendix (ASB) DATE: 1974 Sept 10 DOC#: ASB202 DOCUMENT DESCRIPTION: US Patent - Sponge Iron Friction Material United States Patent hvj Rhee et al. in] 3,835,118 145) Sept. 10, 1974 5-i) SPONGL IRON FRICTION MATERIAL |"o] Imen'.o'' Seong Kwan Rhet. Southfield. NKh . John I*. kwolek, Trov. N Y 73) Assignee The Bendix Corporation, South Bend, lnd i 721 Filed Maj 14. 1973 Appi So 360,255 c .jV Cl. ' III! . Cl. ; s 3 if I<! of Search 260 38.51 .'29.*. 106'36. -or. :u( . > " D R . 39 CD Sr 51 OK ' On : .o D I(- 3y. :<.o.3s ` \tx\ .1 hV.4N" References Cited l M i l D S I A l l s P A 'll.N 1s ' ' i-nip.a 2 . ' sjvkc ... x ,, [us tn .M34.9VK 3.492.262 ; w>u.l20 3/1969 1/19^0 5/1972 A l d r ic h ................. I0 6 'H Griffith ......................... 260/38 C la rk ........................... 106. jf I'rimary Examiner--Allan Lieberman Asuxtant Examiner--P R. Mich! Attorney, Agent, or Firm--Leo H. McCormick. J r ; William \ Antonis 1571 ABSTRACT A semi-metallic friction material for use in a vehicle hr.ike as a 'notion lining or pad The semi-meta!^ diction material unices the abrasive surface produced in coarse sponge iron to provide a high coefficient of diction and good wear resistance up to 250F to com phnu-nt the coefficient of friction and wear resistance s.ipahie ot being produeeJ by the interaction of mctal- >. an., ceramic powders, steel fibers, rubber particles md gr;>phltc .ihove 25f>T 7 Claims. 2 Drawing Figures PATENTED s e n O m 3,835,118 FIG. 2 3.835.118 1 2 SPONGE IRON FRICTION MATERIAL BACKGROUND OF THF INVENTION a high coefficient of friction upon initial engagement with a corresponding brake member These and other objects will become apparent from Friition materials consisting of graphite, metallic, ce reading this specification and viewing the drawings ramic and rubber powders held together by a thermo- ' setting resin have been used as brake pads in braking BRIEF DESCRIPTION OF THE DRAWINGS sv'ierr.' to provide a uniform coefficient of friction FIG 1 is a perspective view of a friction pad for use without excessive fade Such a brake lining material is in a brake assembly. fulls described in L S Pat No .'.4.14.998 incorporated FIG 2 is an enlarged view taken along line 2--2 of herein by reference 10 FIG 1 illustrating the relationship of the compositional The Department of T runsportalion of the l S. Gov ingredients in the friction pad. ernment has proposed that acceptable safe braking dis tance' be reduced It has been determined that if an organu friction material, such as that disclosed in I S application Ser No .V>9.'.'!!. incorporated herein by reference, could be mtvdificd to piovidc a high civfficient of frictian immediately upon engagement of the wear pads with a mating brake surface, the proposed standards could be met. Frictional modifiers havine' highci cocfTicicnt i'f friction were tried, however, un desirable side effects such as noise, poor wear. fade. grvHiving in the mating surfaces and reduced structural strength resulted SUMMARY OF THE IN\ ENTION DF:T AILED DESt RJPTION OF THE PREFERRED COMPOSITION Throughout this specification the terms metallic powder and ceramic powder arc used to denote a mate rial having a nominal size which will pass through a No Ko mesh screen and consist of at least 85 percent of a base material with the balance being mainly oxides of ^(1 * the base material. Similarly the term " sponge iron" de notes a materia! having a nominal size. 85 percent of which will pass through a No 20 mesh screen, yet will be retained on an 80 mesh screen, and consul of at least 90 percent metallic iron 25 The brake pad 12 for a shoe 14 shown ir. FIG I is \\ c have discovered a composition for a scmimelallic friction materia! wherein coarse sponge iron constructed of a semi-mctallic material whose principal ingredients are sponge iron, graphite and modifie's particle' are utilized av a `oction.il modifier The abra- held together by a thermosetting phenolic resin which 'iv e surface of the sponge iron will provide a brake lin is then cured under heat and pressure to form a ing with a high coefficient of fnenon upon inttiJ cn- blended rigid mass 16. as illustrated m FIG 2. While gagement with a corrc'nonJing b: .iking surface Be disc brake pud - are rot illustrate d. test result' indicate cause- the sponge iron part-Jc- are unanncalcd .me, the same advantages car he found when this material .a'se initaf burnish low vr.pvTcturc wcai 1on tin ts u- ed on disc hMkcs Inctv'i: pad will be 'cdiKcJ The nregular surface ot ,s The sponge iron particles 18 are irregular in shape tin- course sponge :ro:-. wliich includes minute pm wrh a surface having pin hole void' therein The noics wh! compliment the noise attenuating compo sponge iron i' produced by a method known as the nent m the semi-metallic friction materia! to essentially Sicurin proces' Ir this process, powdered magnetite el m.nate seju-.-.d associated during a frictional engage- iron ore. c.irhor. eol.e and lime arc charged in layer' men' Since the sponge iron paMielO' have a nominal 40 into covercv! cruvibk-s These ingredients are heated in ore of between To to SO mc.h whuh tone' to rupture kil"' unui reduction is complete After cvK'hng. the under transverse loads, steel fibers in a proportioned iron produced which o removed will have a physical vl.-'-nnship with the sp-'iie-. io n r.irtiele' tire added to appeara-ice of a round porous cake abou- 10 inches in the s.-r.-'-PK-tallie friction material lo provide structural diameter and 2-2'*2 inches thick The reduced sponge an.ty for the brake lining -if cakes are then crushed and disintegrated into particle' It ;s. therefore, an ohieci of this invention to provide Hoeganac' Sponge Iron Corporation. Riverton. N.J .! 'e m met.ill.. base material with a friction modifier produce' sponge iron partielc' that are unannealed, consisting of coarse sponge iron particles to in vea'c di'ignatcd M 20/8'>. having a nominal size which can cold friction and reduce wej' when used as a brake vary from 20 mesh to ko mesh have proven satisfactory pad JO for brake pads These sponge iron particles have an It is another object of this invention to provide a abrasive surface sufficient to provide a high coefficient semi-mc-ialiic base material for a brake pad having of friction upon initial engagement of the pad 12 with coarse sponge iron particle- as the principle compo a corresponding braking surface, yet are large enough nent to compliment noise reducing ingredients therein to resist abrasive wear at low operating temperatures, in attenuating sounds created upon the brake pad en- thereby reducing low temperature wear. gaging a corresponding brake member A typical composition for the scmi-metaJlic brake It is still a further object of this invention to provide pad 12 is as follows a semi-metallic material having coarse sponge iron par- tides uniformly distributed therein to provide a high coefficient of friction at low temperatures and steel fi \ olume Percent V o lum e Percent bers therein to provide structural unity when the serni- metallic material is used as a brake pad It is still a further object of thi' invention to prvvduce j senu-nietallic friction material consisting of a mixture ^ of metallic and ceramic powders, coarse sponge iron. ' graphite, rubber particle-- and steel fibers rigidly posi tioned in .i resin matrix foi use in a brake pad h.ving M eta llic (copper Ir*** \ /. Sponge Iron Pj m ic Ic * ( e ro m c P u * d e rx mII'ht.j n r r rmilli?. magnesium i*\ide * .rrjfv m i^.i i aluminum .**, - % . v n \ j. mm -xidr S le d f iSrr R h Mv p-t'i - ipl ; (1 ir ' 0 2* 1C U 4` : i is <> : :< J u . 'a |W '9 3 -Continued Volume Percent 3,835,1 18 4 metallics (compared to organics) when operating at Volume Percent temperatures below 325T. Average driving seldom re sults in temperatures above 325T and is generally con Phenolic retm hinder 23 13 to 41 sidered to generate brake temperatures of around 5 250T. Thus, the wear rate of any potentially commer cial friction material must be equivalent to organic ma terials at these lower operating temperatures The use The ingredients are mixed together and formed into of coarse sponge iron panicles has shown a significant a desired shape Then the mixture is placed in an oven reduction in both the 250*F and 325*F wear levels, where the resin is cured to hold the other ingredients 10 thereby improving the chances for commercial accep in a fixed position with respect to each other. After cur tance ing the resin the material is shaped into a finished prod As previously discussed, the proposed Department of uct such as the brake pad 12. The relationship of the Transportation reduction in acceptable safe brake various ingredients are illustrated in FIG 2 as follows, stopping distances requires that the brake systems re sponge iron particles 18. graphite particles 20. rubber 15 main balanced throughout the test. This requires a fric particles 22, ceramic powders 24, steel fibers 26, iron tion materia) which will exhibit the same friction levels powder 28 and resin 30. throughout the test. While conventional semi-metallic Brake pads manufactured according to a formula as materials exhibit better friction stability than most or represented above were compared with brake pads of ganics throughout the test, one problem was found with a conventional semi-metallic friction composition 20 conventional semi-melallic materials, that was low ini wherein the metallic powder constituted about 2001 by tial (pre-burnished) friction As a result, conventional volume of the total mixture with the following results semi-mctallic materials were unable to meet the pre- Si :. K- V : M i Svrtf M t i . r i 'i Sp>ni Iron C ocfiiocnt of Fnchon n o *: 0 u 0 o ': n u '6 0 0 \fce.*r fin > 10 lot 'K> Slop* 4: 5^ ?< < io 10 k io Thv importance of providing an initially high cocffi- burmshed stopping distances proposed by the Depart cien' for the brake pads can readily be realized from ment of 1 ransportation The use of coarse sponge iron the follow ing formula through which the effective brak 5 particles in semi-metallics have demonstrated signifi ing distance on a level roodwav may be approximated cant improvement in initial (pre-bumished) friction, which will be required if semi-metallic materials are to be considered for commercial usage where r. - braking distance in feel 1 = initial speed, miles per hour Further, upon investigating the semi-metallic mate 40 rial. it was determined that the sponge iror. will compli ment the rubber particles therein to attenuate noise or ; = coefficient of friction between friction members squeal caused upon engagement of the brake pad with such as brake pad and drum a corresponding member. Assuming that the coefficient of friction will remain It is assumed that the voids in the sponge iron parti substantial!) uniform the period of time required to 45 cles act as acoustical absorbers by breaking up the path bring a vehicle to a stop will be proportional/) reduced through which sounds may travel. The over-all transverse structural unit) of the brake As an example, assume identical vehicles wherein pads mav be varied by the amount of steel fiber 26 used one has brake pads constructed of a standard semi in the mixture However, due to the disparit) in price metallic material and the other of a semi-metallic mate 50 between steel fiber and sponge iron (about 6 times). for rial with sponge iron particles and both are traveling at mass production a volumetric change in steel fiber con 60 miles per hour, the effective braking distance will be tent will usuallv be adjusted by a proportional change as follows in the quantity of sponge iron panicles d =60'V(30 x 0.32) = 3600/9.6 - 375' Thus, we have developed a semi-metallic composi 55 tion wherein the structural characteristics are en d/sponge iron = 60~*/( 30 X0.38) * 3600/11.4 306' hanced by the use of sponge iron particles when used Thus the vehicle with the brake pads having a semi as a friction pad in a braking system. metallic material with sponge iron particles therein ex We claim choibniftosrma sthootrhteer perfofpecotsievde sbtorapkpiinngg ddiissttaannccee wofhtihche Dwiell 60 bra1k. eAassema if-rmicetitoanlliclinbiansge, smaiadtemriaaltefroiar lucseonisnisatinvgehoicflea partment of Transportation mixture of. The wear resistance of conventional semi-metallics metallic powder selected from a group consisting of are equivalent to organic materials between 350* and iron, copper, zinc and mixtures thereof from 0 to 450F and are superior to organics at temperatures 65 30 percent of the total mixture; above 450*F However, one of the major obstacles to sponge iron particles from 10 to 40 percent by vol the accpetance of semi-metallics as a friction material ume of the total mixture, said particles having a has been the poorer w'ear resistance of the semi- nominal size which can vary from 20 to 80 mesh.