US1546656A - Process of making steel brake drums - Google Patents

Description

July 21,1925. 1,546,656

F. D. HANSEN ET AL I PROCESS OF MAKING STEEL BRAKE DRUMS File Apr l 1924 3 Sheets-Sheet 1 id AQM'M M 4 July 21, 1925. 1,546,656

F. D. HANSEN ET AL PROCESS OF MAKING STEEL BRAKE DRUMS Filed April 7, 1924 3 Shets-Sheet 2 f Law July 21, 1925. 6 1,546,656

- F. D. HANSEN ET AL PROCESS OF MAKING STEEL BRAKE DRUMS File April 1924 3 Sheets-Sheet 3 Patented July 21 1925.

n. HANSEN AND HERBERT w. TINKER, or MILWAUKEE, wrsoonsnt.

ASSIGNORS TO FEDERAL PRESSED STEEL COMPANY, OF MILWAUKEE, WISCONSIN,

A CORPORATION OF WISCONSIN.

PROCESS OF MAKING STEEIJ BRAKE DRUMS.

Application filed April 7, 1924. 'Seria1 No 704,766.

To all whom it may concern:

Be it known that we, FREDERICK D. HANSEN and HERBERT W. TINKER, both citizens of the United States, and residing at Milwaukee, county of Milwaukee, and State of Wisconsin, have invented certain new and useful Improvements in the Process of Mak ing Steel Brake Drums, of which the following is a specification.

In the manufacture of brake drums, which are attached to road wheels andother parts of autom'obiles and the fike, discs are cut or punched froma sheet or strip of steel of the required thickness. The discs are placed in a very powerful compression die, which cups the peripheral portion of each disc over to form the annular flange of the drum with which the frictional material of the brake is adapted to contact to effect the proper braking'action of the vehicle. VVhenthe drums are taken from the die their webs are bowed slightly outwardly, because in the pressing ope-ration the bottoms are not pressed flat, althoughthe bottom face of the punch may beperfectly flat. We attribute this bowing action to the fact that the edge of the inner die member engages the fillet or corner radius at the juncture of the webs and their flanges and as this fillet or radius is not sharply defined the bottom face of this die member does not.press as firmly against the web as it does against the radius. The bottoms also tend to spring outwardly due to some resiliency in the steel. The drums are next placed inanother die in which the opposed faces of the die members are formed for the purpose of making the web perfectly flat or giving it a slight concavity, that is pressing the web slightly inwardly past the center of the plate in which the web would lie were it flat. In many cases, it is necessary to subject the drums to the action of the second die several times in orderto give them' the proper concavity orflatness,.as the case maybe, within the small'limits required or specified by automobile companies or others. It is recognized by those skilled in the art, that it is diflicult, and in many instances nnpossible, to form the brakev drums so that the brake flanges are concentric, that is circular within the required limits, and so that the web is symmetrical throughout and free from defective or distortive swells or bulges. The

web ofthe drum, when applied, seats firmly against the wheel-hub or s okes of the wheel,

and it is desirable that t is engagement be perfect and that the flange of the drum be truly concentric so that the flange will be trulv in alignment with the friction shoe or band of the brake in order that the maximum braking effort is accomplished and eq rally distributed throughout the flange of the brake drum. It frequently happens in the manufacture of brake drums, as formerly practiced, that the flanges of'some drums are so eccentric and the webs have such large bulges or swells causing the eccentricity,

that it is necessary to hammer the bulges with a very heavy hammer, to bring the flanges within the acceptable limits of eccentricity. In some instances this cannot be done and then the brake drums are scrapped. We believe that the difficulty in securing drums which have their flanges concentric and their webs symmetrical is due to the fact that during the pressing or forming operation of the discs to cup themlto their shape unequal strains and stresses are set up in the steel and the excess material in the webs. giving the webs their convex or bowed form, exerts a radial force outwardly tending to distort or throw the flange of the drum out of concentricity. We find that usually these strains are greatest and cause the maximum distortion in the direction in which the steel has been rolled, that is in the direction of the grain of the steel, so that the diameter'of the drum is slightly greater in this direction'than it is in the transverse direction, thereby tending to give the flange a slight oval or egg-shape form. The distortiv'e swells or bulges in the web also seem to be along this greater diameter. The subsequent operation giving the webs their proper concavity or flatness explained above, in some cases tends to bring the flange toward on'centricity, but this cannot always be accomplished and usually not within close limits. The degree of eecentricity depends upon certain characteristics of or conditions in the steel, but,-as is well known by expertswersed in steel making,\though not frilly understood by them, these characteristics or conditions can not be accurately controlled or uniformly regu' lated or obviated. It has, therefore, been necessary in the past to test or measure the eccentricity of the flange and unevenness of the bearing zone of the web of each and every drum by precision instruments to determine if they are within the prescribed limits and then correct, if possible, the defects in these respects if the limits are exceeded. The testing and thorough inspection of the drums, the correcting of defects and scrapping of drums which are badly defective materially increase the cost of the drums.

The principal object of our invention is to rovide anovel process of making brake drums with substantially truly concentric brake flanges and substantially truly sym- -mertical webs and .to this .end we press ridges or ribs, preferably radiating'ones, in thewebs of the drums.

Other advantages of our invention are that the drums are strengthened, and care- .ful tests and inspection are not necessary,

thus reducing the cost of manufacture. Still further advantages of our invention will be pointed out hereinafter.

Referring to the drawings, Fig. 1 is a ver tical section through the die member and punch of a. drum-forming compression die, showing a steel disc, from which the drum is formed, between the members; Fi' 2 illustrates the brake drum after it as been cupped or formed in and removed from the compression die; Fig. 3 is ayertical section through the die member and punch of the die or tool bumping the webs ofthe drums and forming the ribs therein, the view being taken on the line 33 of Fig. 4; Fig. 4 is a top plan view taken on the line 4-4 of Fig. 3 wlth the brake drum omitted; Fig. 5 is a sectional view taken; through a drum formed by our process, the section being takenv as on the line 5-5 of Fig. 6; Fig. 6 is an inside elevation of a brake drum formed by our process; and Fig. 7 is a view similar to Fig. 6 but shows a modified form of brake drum made by our process. I

In practicing our process a steel disc 10 is pressed or formed in a suitable forming compression die, such as is conventionally illustrated in part in Fig. l in which 11 is the die member and 12 is the punch. The punch 12 is forced downwardly udder great pressure givin the disc its brake-.drum formation, as in icated by dotted lines 10 in this view. 11' indicates the stripper plates for stripping the drums from the punch. In Fig. 2 we have shown in sections a brake drum after it has been formed by the forming compression die, but we have somewhat exaggerated the convexity of the web 13 of the drum in order to illustrate more clearly its general contour. We next punch the hub opening 6 and the bolt holes 7 in the web, such as shown in Figs. 5, 6 and 7. We then place the drum over the member 13 of an-' other die or tool as shown in Fig. 3. In this figure we have shown the punch 14 in its lowest position. The die member 13 comprises a cylindrical base 13 mounted on any suitable platform 15. Mounted on top of the base 13" is a disc 16 which is fastened to the base 13 by means of screws 17'projecting through the base 13" and screwed at their upper ends into the threaded openings in the disc 16. r The disc 16 is provided with radiating grooves 18 in which are seated and secured by screws 19 hardened pieces of steel 20 provided with grooves 21 in their top faces. The upper die member or plunger 14 is secured to a power slide 23 by a screw 24. Secured to the lower face of the cylindrical. base 14 of the punch 14 is a disc 25 secured to the base 14' by screws 26. The lower face of the plate'25 is provided with grooves 27 in which are seated hardened pieces of steel 28 provided with ribs 29 on their bottom faces in alignment with the grooves 21. The mechanism for operating the punch 14 is so designed that the punch imparts a quick and powerful blow to the web of the brake drum and at the same time the ribs 29 force the metal under them into the grooves 21,

thereby forming radiating ribs 30 in the web of the brake drum. It will be observed that the bottom face of the disc 25 is slightly convex and the upper faceof the disc 16 is correspondingly concaved in order to impart a concave contour to the web of the brake drum. It will also be observed from Fig. 3 that the ribs 29 are of tapering depth, being deepest at their inner ends so that the ribs 30 formed in the web of the brake drum are of tapering depth, being deepest at their in ner ends.

We have shown in Figs. 5, 6 and 7, illustrative forms of drums made by practicing our process. We preferably form the ribs 30, as shown in these views, by depressing the metal inwardly, that is on the inside of the web so that they do not interfere with or engage the spokes or hub flange of the wheel when the drum is attached to the wheel. It is evident that as the ribs 30 are of tapering depth and are of greatest depth at their inner ends, the ribs take up the maximum amount of metal adjacent the hub opening and progressively less outwardly. l/Vhile We prefer that the ribs shall be straight as shown in Figs. 5 and (3, yet they may be curved, as, for example, illustrated in Fig.7, or they may be of any other desired and feasibleform or shape, the grooves 21 of the die and the ribs 29 of the punch being correspondingly formed or shaped. It will be observed that in Fig. 7 the outer circle of bolt holes are radially out of alignment with, that is radially between, the bolt holes of the inner circle, and this is made practical by deflecting the outer portions of the ribs.

We find that in drums made by our improved process, the unequal strains and stresses, referred to above, are either equally distributed, neutralized ,or eliminated. The ribs take up the surplus or excess metal in the web (which excess gave the web of the drum its initial bowed out contour or conr existent in the drum before the ribs are formed in its Web. This equalization or elimination of the deforming or distorting' strains by the formation of the ribs brings the brake drum flan e to its proper true concentricity and at t e same time the web is made perfectly symmetrical throughout. We have found by actual demonstration that it is only necessary to bump drums by our process once and that the flanges are much more concentric and the webs much more symmetrical than unribbed drums made from exactly the same sheet or strip of steel. It is not necessary to test drums made by our process for concentricity or symmetry or subject them to rigid inspection as the product is uniform and substantially perfect. Thus considerable saving'in the cost of manufacture is effected. Furthermore, we have discovered that the ribs, either due to the equal distribution of the strains and stresses or for some other reason, increase the strength of the flanges so that they more readily resist distortion or bending, and this is highly important as they are subjected to considerable force when the braking eflort is applied to them, and also to rough handling and use in transportation and by workmen in the factories where the drums are assembled on the automobiles. It will also be obvious that the ribs strengthen the webs of the drums radially and axially and that the ribs increase the width of the bearing surface or edge of the hub opening 6 on the barrel of the wheel hub, as the ends of the ribs form projections 31 as viewed in Fig. 5. In securing the brake drum to a wheel, the web of the brake drum is drawn up tightly against the flange of the hub by means of bolts extending through the openings 7 between the ribs, and as the segments between the ribs are comparatively narrow adjacent the holes, and separated by the grooves formed "by the rib the web of the drum is drawn more easi y and equally against the wheel and the ribs prevent the web from springing out past its center plane, (after the fashion of the bottom of a tin dish pan) as is the case in some instances with unribbed brake drums.

While we have illustrated in the drawings and described in the specification a preferred form of embodiment of the mechanisms for carrying out our process, yet it will be understood that the apparatuses are illustrative only as various changes and modifications may made therein as desired. \Ve also wish it to be understood that while we have illustrated ,our process as adapted for forming brake drums with concave webs and radiating ribs pressed inwardl and of tapering formation, it isad-a te in its broader aspect, for the manufac ure of brake drums having perfectly'flat webs throughout,

or convex webs,'and that the ribs m extend other than radially or be pressed -outwardly or may be of uniform depth. from one end to the other. 1

\Ve claim: a, 1

1. The process of making steelflhrake drums which consists in pressin discs to form drums with peripheral bra e'fianges and convex webs and then bumping the webs and forming ribs in the webs to take up the surplus metal therein and tend to make the flanges substantially truly concentric.

2. The process of making steel brake A ribs of tapering depth in the web's to take up the surplus metal and tend to make the flanges substantially truly concentric.

3. The process of making brake drums with substantially truly concentric peripheral flanges and symmetrical webs which consists in imparting a sharp blow to the webs and pressing ribs in the webs to eliminate or equalize the distortive strains and stresses.

4. The process of making brake drums with substantially truly concentric flanges and symmetrical webs, which consists in simulta-neousl' imparting a sharp blow to the webs an ressingradiating ribs of tapering depth m the webs to give the webs the desired concavity or flatness and to eliminate or equalize the distortive strains and stresses.

FREDERICK D.- HANSEN. HERBERT W. -TINKER.

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