US2118003A - Method and apparatus for finishing brake shoes - Google Patents

Description

May 17, 1938. H. K. BIGELOW METHOD AND APPARATUS FOR FINISHING BRAKE SHOES Filed March 20, 1956 5 Sheets-Sheet l INVEN TOR. fiar/y A. Bye/0n! kw ATTORVEY Ma 17, 1938. ow 2,118,003

METHOD AND APPARATUS FOR FINISHING BRAKE SHOES 4 4 FM .9 C /8 32 L7 5@ ,JD 2 1 \P INVENIOR. 7 (iffy/f. Bye/0141 4 B I [11-9 8 w? ATTORNEYS;

May 17, 1938. H. K, BIGELOW METHOD AND APPARATUS FOR FINISHING BRAKE SHOES Filed March 20, 1956 3 Sheets-Sheet 5 INVEN TQR.

Harry Kfi/ge/om ATTORNEYS.

Patented May 17, 1938 METHOD AND APPARATUS FOR FINISHING BRAKE SHOES Harry K. Bigelow, Columbus, Ohio, assignor to Benjamin S. Lurie, Columbus, Ohio Application March 20, 1936, Serial No. 69,760

2 Claims.

My invention relates to method and apparatus for finishing brake shoes. It has to do, more particularly, with a method and apparatus for abrading the surface of a brake band or brake 6 lining after it has been applied to the metal shoe.

It is well known that with the brake shoes now commonly in use, the most wear on the lining or band is intermediate the ends of the shoe. The

middle portion of the band or lining will wear out completely before the end portions thereof wear to any considerable extent. This is because the middle portion of the shoe in normal circumstances is the first part of the shoe to contact with the brake drum and is subjected to friction for greater periods of time and more often than the end portions of the shoe. It is customary to make the brake band or lining of substantially the same thickness throughout the entire length of the shoe. Thus, the middle portion of the lining or band will wear away quickly without Wearing away the end portions to the same extent. When this occurs, the proper braking action will not be obtained and there is danger of the drum being scored. It is important that the entire surface of the brake band or lining contact with the brake drum, when the brakes are fully applied, in order to obtain the proper braking action. It also sometimes happens that the metal brake shoe is made so that it is not accurately curved or, even though it is made accurately, sometimes it gets out of shape due to constant use. In these instances, if a brake lining or band of uniform thickness throughout its length is used, the proper braking action will not be obtained because the entire surface of the band or lining will not contact with the drum.

One of the objects of my invention is to provide a method and apparatus for finishing the surface of a brake band or lining after it has been-applied to the shoe in such a manner as to insure proper contact of the entire surface of the lining or band with the brake drum in order to obtain the proper braking action.

Another object of my invention is to provide a simple method and apparatus for finishing that surface of a brake shoe which is adapted to contact with the surface of the brake drum.

Another object of my invention is to provide a method and apparatus for finishing the brake band or lining after it has been applied to a brake shoe in such a manner that the band or lining will not be of uniform thickness throughout its length but will be of greater thickness at the point 1 where the greatest wear occurs.

Another object of my invention is to provide method and apparatus for finishing the band or lining of a brake shoe in such a manner as to compensate for inaccuracies in the shape of the brake shoe.

In its preferred form my invention contemplates the provision of a machine upon which the brake shoe with the lining or band already applied thereto is adapted to be mounted. This machine is provided with an abrasive wheel for 10 abrading the face of the band or lining and is provided with a carriage for supporting the shoe. The carriage is preferably so mounted on the machine that the brake shoe may be swung in an are against the face of the abrasive wheel. I provide means on the carriage for feeding the shoe forwardly against the face of the abrasive wheel in order to maintain contact of the shoe with the wheel as the band or lining is being abraded and so that the proper amount of material may be 20 removed from the band or lining.

In abrading the lining. or band, I preferably swing the segmental shoe about a center diiierent from the center of curvature of the shoe. This causes the lining or band to be ground away to 25 diiferent extents at diiferent points throughout its length. Consequently, the band or lining on the shoe will not be of the same thickness throughout its length. In most casesI prefer to abrade. the lining or band in such a manner that it will be 30 thickest at a point intermediate its ends and gradually decrease in thickness towards its ends. However, in some other cases it may be desirable to abrade it differently.

The preferred embodiment of my invention is 35 illustrated in the accompanying drawings wherein similar characters of reference designate corresponding parts and wherein:

Figure 1 is a perspective View of my preferred type of abrading machine. 0

Figure 2 is a longitudinal section of the machine illustrated in Figure 1.

Figure 3 is a plan view of the main portion of the machine illustrated in Figure 1.

Figure 4 is a transverse section taken substan- 45 tially on line 4-4 of Figure 3.

Figure 5 is a transverse section taken substantially on line 5-5 of Figure 3.

Figure 6 is a section taken through a portion of the abrading wheel substantially on line 56 50 of Figure 1.

Figure '7 is a diagrammatic plan view illustrating how the machine is set for the grinding or abrading operation.

Figure 8 is a view similar to Figure 7. 55

Figure 14 illustrates a brake shoehaving a.

lining or band of substantially the same thickness throughout its length which result may be produced with my machine.

Figure 15 is a similar view illustrating a brake shoe having the lining or band thicker at its ends than in the middle, which result may also be produced with my machine and method.

With reference to the drawings and particularly to Figures 1 to 6, my machine is shown as.

comprising a base I having an upstanding standard 2 at its rear end. This standard 2 has a rearwardly projecting support 3 and an electric motor 4 is preferably secured to the lower surface thereof. This motor 4 by means of pulley and belt connections 5 drives a vertically disposed abrading wheel 5. This wheel 5 is mounted for rotation on the standard 2 in the position indicated and is partially covered by a guard or housing I. The motor 4, by means of a belt and pulley connection 5a, also drives a suction fan disposed in a housing 8 connected by means of a conduit 9 to the housing I.

On the base I I provide a carriage which is.

adapted to support the brake shoe. This carriage comprises a flat base plate III which is mounted for sliding movement along the upper surface of the base I by means of guldeways I2 formed in member III and guides I2a in the base I. A pivot pin II passes through an opening formed in plate I 0. This pivot pin II has its lower end integrally formed with a threaded sleeve I3 through which passes a screw I5 that is mounted for rotation on the base. This screw I5 may be rotated by means of a hand wheel I6 at the forward end ofthe machine in order to move pivot pin II and, consequently, base plate III to different positions longitudinally of the machine. The screw I5 is also mounted in such a manner that it may slide longitudinally. A spring I5a normally maintains the screw I5 in its forwardmost position. However, a pivoted hand lever I5a is provided for sliding screw I5 rearwardly against the force of spring I5a. Withthis mechanism the pivot pin II maybe moved quickly close to wheel 6.

On top of the base plate III a member I! is disposed. This member is slidably mounted on the base plate I 0 in such a manner that it may be adjusted rearwardly and forwardly relative thereto and is also mounted for rotation or oscillation about pivot pin II. Thus it is free to rotate relative to the base plate. This member I I is provided with a slot I8 through which the upstanding pivot pin II extends. A sleeve I9 is disposed in loosely surrounding relation to pin II and has a collar 20 disposed thereabove which is threaded on the pin. The lower end of this sleeve I9 contacts with the upper surface of the base 'plate 1.. Loosely mounted in surrounding relation to sleeve I9 is a sleeve 2| and another sleeve 22 is threaded on sleeve 2|. These Sleeves 'As illustrated in Figure 4, a block 21 is provided for engaging the threaded portion of the screw 25. The surface of the block 21 which engages the screw 23 is provided with threads that cooperate with the threads of the screw. This block is disposed on the inner end of a pin 28 which is rotatably connected thereto. A spring 23 surrounds the pin and normally presses the block against the screw 23. Pin 28 is provided with a knurled head 30 having an inwardly projecting lug 3I which normally extends into a socket provided therefor. However, the head 30 may be pulled outwardly and rotated so that the lug 3| will be out of its socket and will maintain the pin in its outermost position and, consequently, maintain the block 21 out of contact with the screw 23.

The forward end of the member II has a handie 32 by means of which the member I! may be swung about the pivot pin II and relative to base plate III. The inner end of the member H has an arcuate shaped brake shoe supporting member 33 removably mounted thereon. This member 33 has a pair of threaded dowel pins 34 which are threaded therethrough and are adapted to be threaded into sockets 35 in member I'I. These dowel pins extend upwardly above the upper surface of member 33. A third pin 34a projects upwardly from the surface of member 33. These pins are adapted to extend into correspondingly disposed openings of a brake shoe. The dowel pins 34 are adapted to be disposed in any of a plurality of openings 35a formed in member 33 which align with sockets 35. Thus, one of the' members 33 may be used for mounting several different types of brake shoes. However, the members 33 are removable so that they'may be replaced with similar members of different sizes in order to provide means for mounting a wide variety of brake shoes on the machine. A spring 36 has one end connected to member I! and its other end is adapted to be connected to the brake shoe in order to hold it down in position on member 33.

It will be apparent that by rotating the hand wheel I6, the pivot pin II may be moved forwardly or rearwardly relative to the base of the machine. By rotating collar 20 the sleeve I3 will tend to be drawn upwardly which will lock the pivot pin II in the adjusted position. The member I! may be adjusted rearwardly or forwardlyv relative to base plate III. This may be accomplished quickly by moving pin 28 to its outermost position and then by grasping handle32 move the member I! relative to the base plate, the screw 23 merely sliding through the opening 25. Of course, during this adjustment the sleeves 2I and 22 must be so adjusted as not to grip member II. To obtain final and accurate positioning of 'the member I! relative to base plate III, the pin 23 ispermitted 'to move inwardly until the block 21 again contacts with screw 23. Then by rotating screw 23, the member I! will be moved slightly relative to the base plate III and final accurate adjustment may be obtained.

The forward surface of the abrading wheel 5 is adapted to have a 's'tutable abrasive material such as sandpaper applied thereto as indicated in Figure 6. The face of this wheel 6 has a spiral groove 31 of V-shaped cross-section formed therein. This spiral groove serves to bring about a cushioning effect between the abrading wheel and the brake shoe during the abrading operation.

In using this machine, the brake shoe is mounted on the member 33. Then the pivot pin II is so adjusted that the member l1 and the brake shoe holder carried thereby will move or swing about the proper center. The sleeves 2| and 22 are so adjusted as to permit the member I! to be moved relative to the base plate Hi forwardly or rearwardly depending upon the amount of material to be removed from the lining or band on the brake shoe. The screw 23 may be used for gradually feeding the member ll towards the wheel 6 in order to keep the surface of the shoe in contact with the wheel 6 and to gradually grind away the material to be removed. During this gradual feeding action, the sleeves -2l and 22 must be spaced apart sufficiently to permit member ll tobe adjusted relative to the base plate Ill. Calibrations 38 are provided for indicating the position of base plate In on base I. These calibrations preferably indicate the radius of the are through which the carriage swings. Calibrations 39 are provided on base plate III for indicating the position of the member IT on the base plate l0. These calibrations preferably indicate the amount of material removed from the surface of the brake shoe.

The brake shoes now commonly in use are in the form of segments which are adapted to be disposed within a brake drum. They are so shaped and so mounted that when the brakes are applied, the middle portion of each shoe is the first portion to contact with the brake drum and then the entire surface thereof is gradually brought into contact with the brake drum. These shoes are usually so shaped that it is necessary to spring or bow the shoe before the ends will contact with the brake drum. This causes the ends to quickly spring away from the brake drum when the brakes are released and thereby lessens the amount of friction and consequent heat. The middle portion of the shoe usually wears away before the end portions. Consequently, I preferably grind or finish the surface of the brake band or lining, previously applied to the shoe, in such a manner that it is thickest at the middle and gradually decreases in thickness towards the ends of the shoe.

In Figure 11 I illustrate a brake shoe l which carries a brake lining oFband ll on its outer surface. This brake band or lining Al is thicker than it ,should be after the shoe is placed in the brake drum 42 illustrated diagrammatically in Figure 10. In order for the brake shoe 4D to properly fit in the brake drum it is necessary to remove throughout the entire length thereof a portion of the lining or band material, at least the amount indicated at 43 in Figure 11. At the present time it is the common practice to re- 7 move the same amount of material throughout the length of the shoe so that the band or lining is of uniform thickness throughout its length. However, I preferably grind the band or lining in such a manner that the lining or band is thickest at its middle and gradually decreases in thickness towards its ends.

To accomplish this, the complete brake shoe, illustrated in Figure 11, is properly placed on the machine. The machine is then so adjusted that the pivot pin II will be located the proper distance from the face of the wheel ii. This distance should be equal to the radius R illustrated in Figure 10. This radius R, is the radius of the drum 42 minus the small clearance space necessary at the point on the brake shoe closest to the surface of the drum, which is the point exactly midway between the ends of the shoe. The center of the drum is indicated at C in Figure 10 and since the carriage swings about the pivot H, which is located from the grinding wheel a distance equal to the radius R, the brake shoe swings about a center point corresponding to the center C of the brake drum. It will be noted from Figure 10, that the shoe 40-, however, is not concentric with the drum 42. The center of the arc of curvature of the metal shoe 4!! is indicated in Figure 10- and other figures by the letter C. The radius of the outer surface of the metal shoe 40 is indicated by the letter R. The radius of the outer surface of the shoe with the brake band or lining applied thereto, before being ground, is the radius R. plus the radius R as indicated in Figure 9.

It will be apparent from Figures '7, l2 and 13' that the center C about which the entire shoe swings during the grinding operation will be closer to the front surface of the wheel 6 than the actual center C of the brake shoe. The radius of the outer surface of the brake shoe, before being ground, which is R plus B, is greater than the radius R. Consequently, when the carriage swings the brake shoe across the face of the grinding wheel, as indicated in the drawings, the ends of the brake band will be ground away to a greater extent than the middle portions thereof. In initially starting the grinding operation, the brake shoe will be positioned so that its outer surface will contact with the face of the wheel 6 at a point midway between the ends thereof and, as previously stated, the

distance from the pivot point I l to the face of the wheel will be equal to the radius R. When the carriage is then swung about the pivot point H, more material will be ground off the end portions of the brake hand than the intermediate portions thereof. However, in order to also grind the intermediate portions of the brake band to the desired extent, the portion I! of the carriage of the machine may be gradually fed, relative to the portion ll] of the carriage and the pivot pin H, towards the wheel 6 soas to gradually remove material from the outer surface of the lining or brake band throughout its length and until it becomes the proper thickness at its thickest point which is midway between its ends.

It should be understood that after the pivot pin l l is once positioned the proper distance from the face of the grinding wheel, its position is maintained throughout the grinding operation. As the carriage ll is fed forwardly during the grinding operation. the center C will move closer to the center C as indicated in Figures 9 and 12 where the center C is shown in two different positions. However, the center C will never coincide with the center C. The movement of the shoe during the grinding operation is illustrated by the dotted lines in Figures 9 and 12.

The shoe completed in this manner is illustrated in Figure 13 and a pair of these shoes are shown positioned in the drum 42 in Figure 10. It will be noted that the shoe is thickest at its middle and. gradually decreases in thickness towards its ends. The center of curvature C of the finished outer surface of the band of the shoe is spaced from the center of curvature C of the body portion of the shoe. This shoe is so shaped that the middle portion will first contact with the drum and then as the shoe is sprung, during the application of the brakes, the entire surface will gradually move into contact with the drum. When the brakes are released, the ends will quickly swing away from the drum. Furthermore, since the middle portion, which is the portion subjected to most wear, is thicker than the end portions, the shoe will wear for a much longer time.

It will be apparent that if a shoe is finished in this way, it will be possible to use a lining or band on the shoe thicker than that for which the -shoe and cooperating drum are designed. The

middle portion may be made thicker than the band or lining for which the shoe and drum are designed as long as there is a very slight clearance space remaining at this point. Because the shoe becomes thinner towards the ends, even though the middle portion is thicker than the band-r lining for which the shoe and drum were designed, this will not bring about undesirable heating of the drum, since the clearance space gradually increases in width away from the middleportion of the shoe.

Although I preferably finish the shoe in such a manner that the middle portion is of greater thickness than the end portions, it is possible to finish the shoe in the manner illustrated in Figure wherein the end portions are shown as being thicker thanthe middle portions. This may be desirable in extreme cases. In finishing a shoe in this way, the center of the shoe will be located closer to the face of the grinding wheel than the center about which the shoe swings during the grinding operation. Sometimes when it is desirable to apply a thinner band or lining than the shoe and drum are designed for, it is desirable to finish the shoe in this way. Also, sometimes after the shoe has been used for a length of time and has become sprung permanently out of its original shape, it is desirable to finish the shoe in this manner.

With'my method and machine it is possible to finish the band or lining of the shoe in any way to take care of inaccuracies of the shoe. Also, it is possible to so finish it that the band or lining of the shoe will be thicker at the points where wear will occur to the greatest extent.

In some cases it may even be desirable to use my machine for finishing a shoe inthe manner illustrated in Figure l4 wherein the band is of I the same thickness throughout its length. My

machine may be used in doing this, it being necessary merely to set the machine so that the carriage will swing about a center coinciding with the center of the shoe. However, I prefer to finish the shoe in such a manner that at diflerent points. throughout its length it varies in thickness, as described above.

In some instances it may be desirable to skive or sharply bevel the extreme ends of the shoe in the manner indicated at 44. .This is desirable because the rivets that hold thebrake band on the shoe are spaced slightly from the ends of the band. This eliminates any danger of chatter at the ends of the band. To skive the ends of the band, it is merely necessary to move the pivot pin ll forwardly a considerable extent by means of lever Ma and then swing the end of the band in contact with the wheel 6. An adjustable stop may be provided for limiting sliding movement of screw IS in order to limit the amount of material skived off the band in this manner.

In the specification and claims where I refer to abrading the band or lining, I also intend to cover cutting or similar operations.

Having thus described my invention, what I claim is: I

1. A machine for finishing segmental brake shoes having brake bands applied thereto comprising a body portion, an abrasive wheel mounted on said body portion for rotation in a vertical plane, a. carriage for carrying a brake shoe, said carriage comprising a base member, a shoe-carrying member mounted for swinging movement, a pivot pin axially fixed with the base member providing a bearing upon which the shoe-carrying member may swing relative to said abrasive wheel in a horizontal plane substantially at right angles to the abrasive wheel, a rotatable screw longitudinally fixed in said body portion for adjusting said pivot pin towards and away from said abrasive wheel, and clamping means on the pivot pin for said shoe-carrying member at adjusted positions with the base member of said carriage towards and away from said abrasive wheel.

2. A machine for finishing segmental brake shoes having brake bands applied thereto comprising a body portion, an abrasive wheel mounted on said body portion for rotation in a vertical plane, a carriage for carrying a brake shoe, said carriage comprising a base'member, a shoecarrying member mounted for swinging movement about a pivot pin relative to said abrasive wheel in a horizontal plane substantially at right angles to the abrasive wheel, a screw for adjusting said pivot pin towards and away from said abrasive wheel, means independent of the rota tion of the screw for reciprocating it longitudinally, and a screw for adjusting said shoe-carrying member on the base member of said carriage towards and away from said abrasive wheel.

HARRY K. BIGELOW.

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