US2746142A - Method of making a brake shoe - Google Patents

Description

22, 1956 J. A. MAXWELL 2,746,142

METHOD OF MAKING A BRAKE SHOE Filed Oct. 28, 1950 INVENTOR.

FIG 6 Jog A. Maxwefl United States Patent *9 METHODOF MAKING ABRAKE SHOE .John A. Maxwell, Grosse Pointe, Mich. Application October 28, 1950,'Serial No. 192,759

3 Claims. (Cl.f29'522) This invention relates to a method of making brake 'shoesfornn internal expanding automo'bilebrake.

The shoe is built upofsa curved .outer band carrying the-brake lining, which is reinforced-preferably by a single stiffening member or web with. projectionsthereon passing through 'slots inthe band and rivetedor'welded thereto.

Brake :shoes .of this general 'naturehave been built for 'many years, ,oneform of which is ashownin Patent No. 1,818,090, granted August 11, l93l,-to -J. W.:'Peterson. A .diificulty in this type of construction .is-toform the :band;and webin true right angle relationship and maintain'lthe :perfect circular arc of the .band. When 'the band .iS .pressed as shown :in the Peterson patent there is always a certain amount of spring backnwhich differs with slight differencesin the steel used. .As the band is placed on the web to be welded thereto, it is necessary to re -form the band slightly by thepressure of 'the'welding machine, and this often forms high spots or ridges which result in uneven surface on :the brake band, in addition to that caused from slight "misalignment'from'the true right angle relationship as .explained above. :These imperfections have been so 'dilficult to controlithat many companiesh'ave gone into the more expensive process of 'formingnby rolling thebrake. shoes from T-irons and then restrilcing'them .nntil *theyiform a perfect are. This has been found to be a prime requirementz in :the bonded Jbrakes used today, since the bonding material, while producing a perfect bond, has no tensile strength of its own and therefore has to be rkeptas thin as. possible. Thus, it is desirable tokeep the maximum thicknessof the bondingmaterialrat-a007 inch. To do this it is necessary tokeep the band-within a tolerance of -002" both in its circular formationand .in-its angularity with the web.

'I prefer to blank out the band flat and simultaneously punch therein a series of spaced rectangular slots. The web is formed with rounded projectionswhieh, when the band is bent around to circular shape, snugly fitjinto fthese slots, but are of sufiicientlength-rto project .above the surface of the hand. To accommodate the=excess1of metal the slots in the band are coined out on each side to form a frusto'conical depression or chamber for a part of their. depth. In the forming die for the band provision is made for firmly clamping the web in position. The fiat band is located relative to the web by means of a centrally located rectangular projection or tongue on the web and a centrally located slot in the band, the length of said tongue being substantially the same as the thickness of the band. As the press ram descends the band is firmly clamped to the stationary die by a yielding piston or pressure pad carried by the movable die and contacting the locating means above mentioned. By further movement of the die the band is formed around the web and finally the projections are deformed so as to fill out the coined depressions so that the band is firmly cold riveted to the web and no springback results on the upstroke of the press releasing the 2,746,142 Patented May 22 1956 pressure .011 the band. The projections are then subjected to a weldingoperation of the general type'of spot .Welding. However, due to the previous cold riveting process, whereby the projections on the web are brought into intimate and firm contact with the slots in the-band, there is-not much flow ofmelted metal. Instead, the heat and pressure of the spot welding has the effect of changing the previously described cold riveting to a-hot riveting process, whereby the projection conforms to all the-intimate details of the slot, and on cooling down shrinks,

thus forming a very tight and close joint with theband. The above and other objects and features.of-thednvention will be apparent from the following description of one illustrative embodiment shown in the accompanying drawings, in which:

Fig. l -is a side view of the .Web. Fig. 2 -is-a plan view ofthe band. V -Fig. 3 isa sectional view along lines 3-'3.ofrEig, 2. Fig. 4 is a sectional view along lines H'iofzFig- --Fig.:5 showsa side view of the completed brake shoe. Fig. 6-is aiview partly in sectionshow-ing mechanism for forming the band and securing it to the web. It is to be understood that the invention-is not,liniited in its-application to the details of construction ,andarrangementof partsilustrated in the accompanying drawings, since the invention is capable of other embodi- -ments and of being practiced or carried out in various ways. Also it is to be understood that the phraseology or terminology employed herein is fonthe pupposeof ,descriptionand'not of limitation. a

The completed shoe, shown in Fig. 5 consists-principally of an arcuate band 10 to which thelining-llIis bonded. Web 12 is riveted to the inner face of.t.he,b.and 10 bythe method hereinafter outlined and not,;only,re-

.inforces the band, but has holes-formed therein for ,the

connection of the various actuating members ofthe brake. Since the number and spacing of ,these holes varies-With different makes of cars and form no partof thisinvention, they are not further described herein.

In-the manufacture of the present brake shoe, the band 10is blanked out to sizeand simultaneouslyaseries of rectangular slots 14 are formedqtherein. .Asshown inFig. 3, the upper portion of each -.of-the se-:hQles -is coinedout during the punching operation to-form ,-a chamfer 15 which is preferably extended all theway around theslot, although if desired it maybe ,confined to the two ends. In the center-ofthe band ,is punched out a rectangular slot 16, shown in Figs. 2 a;r1d.4, .the purpose of which will be outlined later.

The-web 12 is blanked out as shown, in.:Fig. 1,-With rounded rectangular projections 17 spaced v {around @the circular periphery so as to enter slots 14 whenband .10 is formed therearound. Centrally located;on ..web 12:is a tongue 18, which snuglyfits into slot;16.,in thegbami.

-.It'-will be noted -in-Figs. .3 and. 4 that ,the projections 17 are of sufficient length to project above the upper surface of the band 10 when they enter holes 14, but that the upper edge of tongue 18 is substantially flush with the upper surface thereof.

An important feature of this process is the simultaneous bending of band 10 to the form shown in Fig. 5 and the cold pressing of the extending portions of projections 17 until they tightly fill the slots 14 and the chamfers 15. In order to accomplish this, the apparatus shown in Fig. 6 is used, which comprises a base 20 supporting an abutment 22 fixed thereto, and a slida'ble abutment 24 designed to be moved toward and away from the fixed abutment by any suitable means such as an air cylinder 26, the piston of which is connected to abutment 24 by piston rod 26. By this arrangement, the web 12 may be retained fixedly in position while the band 10 is applied thereto. The upper surfaces of abut- 'trode contacts the upset projection.

ments 22 and 24 are convex so as to constitute the stationary die member of the die set.

The fiat band is placed on the stationary die member with tongue 18 of the web extending into slot 16 of the band. 'The upper, movable, die member 26 is then lowered so as to form the band and rivet the projections 17; Die member 26 is provided with a concave working surface 28, from which projects a plunger or pressure pad'30-which is urged downwardly by a compression spring 32. Pad 30 contacts the surface of band 10 beforethe start of the forming operation and clamps the band centrally over tongue 18 and slot 16 to firmly hold it in place'during the operation. Obviously other locating means 'knownto the art, such as a fixture, could 'be use'd, but this tongue and slot arrangement is far simpler and more efficient.

' Asthe upper die member 26 comes down, the pressure pad 30 firmly clamps the band in position on tongue 18, and further downward movement wraps the band around the lower die member and the web, causing projections 17 to enter slots 14. The final movement of theupper diemember flattens out the projections 17, cold riveting the band firmly to the web.

It be seen that by this method the band (assuming that the dies are accurately made) is formed to a truly cylindrical form, and is held to truly right-angle relation to the 'web, and while so formed and held is permanently secured to the WEb'iIl such manner as to prevent spring-back or other defofination due to variations in the properties of the metal, or to other causes.

The shoe is then removed from'the press and each rivet or cold-upset projection is heated to at least red heat and pressure applied thereto to cause the upset portion of the metal to soften and to fill its nest more intimately. This operation may be successfully performed in a spot welding machine in which the shoe is grounded and the elec- It will be understood/that in spite of being performed in a spot welding machine this operation is in fact a hot-upsetting operation. The metal of the cold-upset projection is heated and softened and therefore a relatively light pressure exerted thereon by the electrode is sufficient to cause sufiicient plastic deformation thereof to cause the metal to fill the nest very intimately. Heating of the shoe in the process of such an operation is limited to the upset portion of the projection, and such heating does notaifect the curvature of the band member as is the case in conventional methods where heating of the band may be such as to affect its curvature. It will be also understood that heating of the cold-upset portions of the projections relieves the internal stress produced therein by the cold-upsetting and improves the metallurgical structure of the metal.

If desired, rectangular hardened steel inserts may be placed in the upper die member, ofthe same size and "shape as the slots 14 at the top. These inserts may be spring pressed so as to contact the projections 17 prior to the mating of the dies, and may be arranged to bottom in the slots when their faces are almost flush with the upper diemember, to coin the rivet projections into the 'slots at a level equal to or even very slightly below the level of the outer band surface.

By the process and apparatus above described, applicant has produced a fabricated brake shoe of two parts, namely the web and the band, which meets the exacting requirements of modern bonded brake lining.

While a particular brake shoe, and the particular stepsin its manufacture, have been described in detail, it is not my intention to limit the scope of the invention other than by the terms of the appended claims.

I claim:

1. A method of manufacturing a brake shoe having T cross section, said method comprisingstamping out a flat arcuate piece to provide the web member with a plurality of projections on its outer periphery, providing a flat strip of metal for the band member, said strip being provided with a corresponding plurality of openings adapted to receive said projections when the strip is bent, holding the Web member, placing the band member on said web member perpendicularly thereto, bending the band member to arcua'te form between two die members, and cold, riveting the projections in said openings while the band member is so held between said die sections in its arcuate shape into which it is finally brought by said sections for bending.

2. The method defined in claim 1, with the pro ections having length greater than the thickness .of the band member material and the openings provided in the band member being chambered on the outer side thereof.

3. A method of manufacturing a brake shoe having T cross section, said method comprising stamping outan arcuate piece to provide the web member with a plurality of projections on its outer periphery, providing a flat strip of metal for the band member, said strip being provided with a corresponding plurality of openings adapted to receive said projections when the strip is bent, holding the web member, placing the band member on said web member perpendicularly thereto, bending theb'and member to arcuate form between two die members, and cold riveting the projections in said openings While the band member is so held in its arcuate shape and heating the riveted projections to at least red heat and exerting pressure thereon to spread them in their respective nests provided by the openings in the band member.

References Cited in the file of this patent UNITED STATES PATENTS

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