US2908056A - Manufacture of bearings - Google Patents

Description

Oct 13 1959 L. J. scHMID v 2,908,056 f MANUFACTURE oF BEARINGS Filed Deo. 19, 1955 INVENTOR Mae@ ATTORNEY United States Patent MANUFACTURE OF BEARINGS Leonard J. Schmid, Brownsburg, Ind., assignor to General Motors Corporation, Detroit, Mich., a corporation Vof Delaware Application December 19, 1955, Serial No. 553,839

` z claims. (Cl. 22-123) This invention relates to the manufacture of bearings and is more particularly concernedkwith an apparatus and method of forming composite bearings comprising a reinforcing back of strong metal to which is strongly bonded a softer bearing material.

One methodI which has been used prior to this invention for making composite bearings is to weld to the reinforcing back a metallic member to form a space between the member and reinforcing back or shell within which bearing metalcan be cast. *The composite mold structure` comprising the reinforcing back and member welded thereto then has a protective cover placed thereon having a pouring basin and passages leading to the mold cavity. The entire assembly is heated, preferably in a nonoxidizing or reducing atmosphere to insure that the mold surfaces of the back and member Welded thereto will be free of oxides during the step of casting the bearing metal. vAfter the composite mold structure and protective cover have been heated to a suitable temperature, they are removed from the furnace" andimoltenbearing Y metal is cast into the mold cavity. One form of protective cover that has been used is one of molded graphite or molded clay-graphite.` The cover has a pouring basin which provides a molten head of metal inthe upper portion of the'casting to feed' bearing metal to take care of shrinkage which occurs during solidication. Where a protective atmosphere is used in the preheat furnace the cover also serves to maintain the controlled atmosphere of the furnace within the cavities after removal from the furnace. Protective covers formed of graphite or mixtures of clay and graphite deteriorate rapidly due to abrasion resulting from the handling of the covers necessitated by their reuse. Particles abraded from the undersurfaces of the cover fall into the mold cavity and become entrapped in the solidified bearing metal thereby resulting in a defective bearing. The primary object of the present invention is to eliminate disadvantages resulting from protective covers heretofore employed in making composite bearings and like articles.

Other objects and advantages of the invention will become more apparent as the description proceeds.

Reference is herewith made to the accompanying drawings in which: p

Figure l is a sectional view on line 1-1 of Figure 2 illustrating a composite protective cover in accordance with one embodiment of the present invention in position for casting molten bearing metal into contact with a reinforcing back.

Figure 2 is a top plan view with parts broken away of the protective cover of Figure 1.

Figure 3 is a fragmentary sectional view on line 3-3 of Figure l.

In Figure 1 of the drawing there is shown an annular reinforcing back or shell having Within it a.s1eeve 12 having an outwardly extending flange 14 welded at 16 to the reinforcing back at the lower end thereof to form an annular space 17 for reception of cast bearing metal. The weld 16 is continuous and forms an air-tight joint between the ange and reinforcingback. The welded assembly consisting of shell 10 and llanged sleeve 12 may be regarded as a composite mold assembly. Above the composite mold assembly is a composite protective cover. The protective cover comprises `a portion 20 formed of molded silicon carbide. portion is of generally circular configuration. The lower face of the silicon carbide portion of the protective cover has an annular groove 22 for reception of the upper end of the composite mold. The silicon carbide 'f member also has passages'24 leading from the annular groove 22 to the upper face thereof. On the upper face of the silicon carbide'member 20 there is an upwardly extending flange 26 forming anlelongatel pocket or nest for reception of 'a member .27, of molded graphite .or

molded"claygraphite. VMember 27 has a hollowportion 28 forming a pouring basin and, as seen in Figure 1, a. plurality of generally similar passages 30 leading outwardly to the right and a plurality of generally similar passages 32 leading to the left. The passages 30 and 32 Y are connected with transversely extending passages 34 and 36, respectively, which lead to the openings 24 in the silicon carbide member. 27 of the cover, the graphite or clay-graphite mixture is ing passages 30 and 32 are formedvbydrilling from the outer surface of the graphite or clay-graphite to the pouring basin and the portions of these passages' outwardly from the transverse passages 34 and 36 are stopped o by plugs 38 and 40, respectively, which may be formed of graphite, clay-graphite or other suitable refractory material. A suitable refractory cement such as Silmanite may be used to cement the plugs in place.

The composite cover has an extremely hard, refractoryv portion of molded silicon carbide which resists abrasion A from contact with the upper end of the bearing Shellfor mold, and at the same time a softer lrefractory portion of graphite or clay-graphite which can be readily drilled to form the necessary passages to conduct molten bearing metal from the pouring basin to the mold. The graphite or clay-graphite portion also provides carbon which can react with any traces of oxygen which may be present to form CO and/or CO2, thereby insuring that there will be no significant traces of oxygen to react with the shell backing and bearing metal being cast. The composite cover is one having extremely long life. The rejection rate of bearings produced by use of the composite cover is greatly lowered.

The method and apparatus of the present invention are particularly advantageous in the formation of composite bearings comprising a steel backing member and a cast bronze or cast leaded-bronze metallurgically bonded thereto. It will be understood, of course, that the principles of the invention are applicable to other backing materials and bearing metals.

It will be understood that the entire assembly including the protective cover is heated in a furnace having a nonoxidizing or reducing atmosphere therein prior to casting the molten bearing metal. A typical example of a highly satisfactory nonoxidizing atmosphere s one composed as follows:

Dew pointy-45 F.

The silicon carbide In making the upper portion.'

Thej heating is such that the molten bearing metal being cast is not chilled below its melting point`when it'v comes into contact with the-reinforcing back or shell.

Generally therefore ,themroldwand cover are heated inthe, Y

furnacegto; at temperature l sOInevvlLlat,` above: the;V 'melting4 Point-of, thebearg metal;` In the, caseiota. bronze r leaded bronzebearingmaterial atemperature on theor-v bearing; irietalJ,being':'ernployed;` reducing gastinsures, clean surfaCeS oir-,theA bearmg, back,V

so, Ythe beating;v nietal' will" become' Strongly bonded' theretqr, UnderVV some1, conditions` it; is "contemplated, '112,112

a may be.usedithiatlis4 solidfundfer atmospheric conditions,.but` which flidlor molten` attlie temperature tor'whieh'thelnoldl'fand-bearing baclcvare heatedf 4After removalli' yfr'olml the! f'rnaceilfthe' noltn bearir'ig metal is ponte man; Y

Atertlie cast bearingpmetal has 4soldviedjthe protective. cover. may, vbe removed.' Thereafter theA slevelzfis re,-Y moyed, byf 'machining and' the, backing andjcastbearing metal'ae maehinedtofnalditensins.. The result is" a ,composite bearing, comprising l a`v reinforcing backing,- ternir-lich is', stronglybondjeda cast bearir'igimetal;4

It' ,l will: understood' that the composite protective ai, s frcmi the s101111 'consisting 0f graphite @delay-graphite practice. Itivvill be understood, of course,tha,t the -ltem-l pexature ,will vary: the, melting;pointiofthepartidlllal'-i nonoxidizingl or intofthle,pollring-basinwlere, it flows into the4 s 20 n members forming'4 an lupper .wall 'for saidfcavity,` ,ndicover member formed.' of'the, material taken de rgo 2,000", v"; lia-s', proven. espeeiallyatisfctory in.,

2,908,055 v y i.

supported by said lrst cover member, a centrally located pouring basin in said's'econd'cover member, a plurality of vertically disposed apertures` in said rst cover member laterally disposed from said pouring basin, a plurality of passages in said second cover member extending substantially horizontally from said basin to each of said apertures, said passages andsaidfapertures presenting to said cavity ai'cont-inuous'-ven0l9sedwconduit-operative to inhibit passage of gases atmosphere:` n v Y h11 combinatic'mr a metallic reinforcing"rrrerrrber and a metallic sleeve member spaced fomonean'- other to, fornr: .am annular-gT kcavity tllerebet;weem.5r ayrst cover member formed of molded silicon canbide and having an annular-groove in-thee-lwerJ face thereof forthe reception of the upper ends of the said metallic mem-VV bers forming an upper Wall for said cavity, a second cover A member formed. of-.the, material.- takenfromthefglpupY consistiruttczfv graphite and,elawgraphifesupnotedfbv Said rst cover member: a, centrally; located `rplr'rulrirrg''-.basixrsinfr saidl'seoond; 4never` member, at, leastione.vertically,disposed.,V

aperture inthe `groove of said irst coverrnerr-11`2er laterally y disposed from saidpowing basi-u,..arn1;uralty0f passeses in said second,- .coyer member. extending substaniillyi h 0ri`: zontally from the' outerperipheryfofsaid'basin ltsaidw aperture, said passages, and said. aperture p-resentingtm: said,A cavityl the continuons. enclosed conduit operativeI to inhibit passageofygasesbetweensaid YCavity andEtheat-e References Citedimthele othis Apatentl UNrrEofrsrA-TES PATENTS; Y

between said cayity and the

Images