BRAKE BLOCK HOLDER

Abstract: A brake block holder and brake block assembly for holding brake blocks for a railway wheel. The holder is characterised by the fact that it is not bifurcated having a single flange portion (54) which is frictionally restrained against rotation on a bolt (62) by means of a friction disc (58) and a compression spring (60). The arrangement is such that the spring (60) and disc (58) maintain the correct position of the holder with respect to the railway wheel thereby avoiding problems in conventional holders which are prone to disalignment and to clatter.

Description: BRAEB BLOCK: HOLDER. This invention relates to a brake block holder. The holders are sometimes known as brake heads. It is common practice for railway wheels to have a pair of brake block holders on either side of the wheel, the holders having mounted thereon brake blocks which are directly engagable with the tread of the wheel. The holders are pivotally mounted on levers which are interconnected together so that by operation of a pull rod or push rod connected to the levers the brake blocks are forced simultaneously to engage the tread of the wheel to thereby apply braking forces to the wheel. The holders are normally pivoted to the levers and a problem which occurs with known arrangements is that the pivotal interconnection tends to become sloppy permitting lateral movement of the holder about the pivot pin. This problem is exacerbated by the taper on the wheel tread which tends to rotate the block and holder about an axis which is perpendicular to the pivot pin. A serious problem which can occur when the block and holder have been rotated is that the block will engage the corner of the tread i.e. the side of the tread which is remote from the flange of the wheel. This causes localised heating which can cause failure of the wheel by radial cracking. A second problem with a sloppy pivotal connection of the head to the lever is that the brakes become very noisy because the holders vibrate or clatter on the levers. Another problem with holders of the conventional type is that special provision must be made for preventing the brake blocks from engaging the wheel tread when the brakes are not in use. The known arrangements for preventing this engagement have been troublesome owing to their cost or ineffectiveness. The object of the present invention is to provide a new form of holder which at least partially alleviates some of the problems noted above. According to the present invention there is provided a holder for a brake block for a railway wheel, said holder comprising a body having a mounting portion for mounting the holder on an operating member of a brake system for the wheel and a block mounting portion for mounting the brake block, characterised in that the mounting portion is not bifurcated and comprises a plate member which is, in use, located on an outboard side of the operating member. The invention also provides a brake holder assembly for a brake block of a railway wheel comprising a holder as defined above said assembly including a compression spring, mounting shaft friction member and fixing member, the arrangement being such that, in use, the shaft interconnects the operating member and plate member of the holder, said friction member being resiliently clamped by said spring between the plate member of the holder and the operating member, and the fixing member serves to maintain the spring, friction member and holder in their operative positions relative to the shaft. The arrangement defined above has the advantage that the flange portion of the holder is located in a plane which is located towards the outer portion of the tread of the wheel whereby the lateral force exerted by virtue of the taper of the tread of the wheel is countered by the oppositely directed force arising by virtue of the off-set mounting of the flange of the holder relative to the operating lever. The invention will now be further described with reference to the accompanying drawings, in which: FIGURE 1 is a schematic view of a railway wheel and brakes, FIGURE 2 is a side view of a known form of holder, FIGURE 3 is a cross sectional view taken along the line 3-3, FIGURE 4 is a cross sectional view taken along the line 4-4, FIGURE 5 is a fragmentary cross sectional view through the known form of holder and wheel, FIGURE 6 is a side view of the holder of the invention, FIGURE 7 is a cross sectional view along the line 7-7, FIGURE 8 shows an exploded view of a holder assembly of the invention, FIGURES 9 and 10 show the assembly of the invention in its operative position, FIGURE 11 is a schematic plan view of a railway bogey having truss bars in the brake system, and FIGURE 12 shows an adaption of one end of the truss bar for utilizing the assembly of the invention. The arrangement illustrated in Figure 1 shows a railway wheel 2 having a hub 4 and tread 6. The brake mechanism includes brake blocks 8 held by a pair of holders 10 located on opposite sides of the wheel. The holders are pivotally connected at 12 to operating levers 14 and 16. The operating lever 16 is pivotally mounted at 18 to the frame 20 of a railway vehicle. The other end of the lever 16 is pivotally connected to a connecting strap 22 which in turn is pivotally connected to the lower end of the lever 14. The upper end of the lever 14 is pivotally connected to a pull rod 24 which is moved in the direction of arrow 26 when the brakes of the vehicle are to be applied. A pair of hangers 28 extends from a pivotal connection 30 of the frame 20 to the pivot point 12 of the holder 10 and lever 14. In operation, the pull rod 24 is moved in the direction of the arrow 26 whereby the interconnection of the levers 14 and 16 cause the heads to move inwardly towards the wheel whereby the blocks 8 engage the tread of the wheel and apply the necessary braking force thereby. Figures 3 to 5 illustrate a typical known form of holder 10. It will be noted that the holder is generally bifurcated having a pair of flanges 32 and 34 which are located in use on either side of the lever 16, as shown in Figure 5. The flanges are provided with hardened bushes 35 the arrangement being such that a pin or bolt can pass through the bushes and through a bore 36 provided in the lever 16. The flanges are interconnected by a web portion 38 which has mounting formations 40 which cooperate with complementary formations provided on the rear face of a brake block 42. The other side of the block 42 has a face 44 which conforms to the shape of the tread 6 of the wheel. As can be appreciated from Figure 5, when the lever 16 moves the block 42 towards the wheel, the taper on the tread 6 will cause the block 42 to rotate in the direction of arrow 46. As the holder becomes worn, the rotation in direction of arrow 46 becomes more pronounced because of wearing at the points 48 and 50. This in turn causes severe heating at the outboard corner 52 of the tread and the heating may cause radial cracking of the wheel. Figures 6 and 7 show a holder constructed in accordance with the invention. The main characterising feature of the holder is that it has a single flange 54 which is somewhat thicker than the flanges 32 and 34 of known arrangements. The web portion 38 and mounting formations 40 are of conventional shape. A bush 56 is provided in the normal manner. Figure 8 shows the components of a holder assembly of the invention. The assembly comprises the holder 10, a friction disc 58, a compression spring 60 a bolt 62 and a castellated nut 64. The disc 58 is preferably made from Nylon and is about 5 mm thick. Figure 9 shows the assembly in its operative position. The stem of the bolt 62 passes through the spring 60 through the bore 36 provided in the lever 16 through an opening in the friction disc 58 and through the bush 56 provided in the flange 54. The nut 64 is threaded onto the free end of the bolt and a split pin is passed through the castellations and through a hole 66 provided in the end of the bolt 62. The spring exerts a maximum axial force of about 625 lbs. The nut 64 is tightened so that the spring 60 is fully compressed on the stem of the bolt 62. The friction disc 58 prevents any rotational movement of the holder about axes which are transversed to the bolt 62. Further, if the disc 58 becomes worn, the spring 60 will take any slack which will develop and thereby continue to prevent transverse rotational movements of the holder relative to the bolt. The holder and the block 42 are therefore maintained in their correct position relative to the tread 6. Further, the disc 58 will restrain rotation of the holder about the bolt when the brakes are disengaged, thereby obviating the need for special mechanisms provided in the prior art for that purpose. It will be further appreciated from Figure 9 that because of the offset of the central plane of t e flange 54 relative to the central plane of the tread 6 lateral forces will be transmitted to the block 42 by the operating lever 16 to counter the oppositely directed lateral forces produced as a consequence of the taper on the tread 6. In other words, the offset mounting of the flange 54 relative to the central plane of the tread compensates for the lateral forces normally applied to the block 42 by virtue of the taper 6. Figure 10 shows the assembly of the invention on the opposite side of the wheel and, in particular, shows the pivotal connection with the hangers 28. It will be seen that a spacer sleeve 68 is interposed between the inner side of the lever 14 and the inner hanger 28. Figures 11 and 12 show the assemblies of the invention adapted for use with railway vehicles which have truss bars 70 in their braking systems. The use of truss bars is more prevalent in goods carriages than in passenger carriages. Figure 11 shows a schematic plan view of a pair of wheels 6 connected by an axle 7. The truss bars 70 extend generally parallel to the axle 7 and terminate generally at diametrically opposite points of the wheels. The ends of the truss bars are provided with assemblies of the invention as will hereinafter be described. In use of the braking system, the truss bars are caused to move inwardly towards one another by a linkage system or the like (not shown) which is for instance connected to the bars by means of clevises 72 located near the centres of the bars 70. Movement of the bars 70 towards one another causes the brake blocks (not shown in Figure 11) carried by the holders 10 to engage the treads 6 of the wheels 2 so as to apply braking forces thereto. Figure 12 illustrates the preferred manner in which the ends of the bars 70 are modified so as to accommodate the assemblies of the invention. In this arrangement the bolt 62 is replaced by a threaded stud 74 the inner end of which is welded to the end of the truss bar 70. An annular flange 76 is also welded to the end of the truss bar 70 and/or the shaft 74. The flange 76 is preferably of a similar diameter to the friction disc 58 which bears against its face which is remote from the bar 70. The holder 10 is located on the stud 74 so that the inner face of the flange 54 bears against the friction disc 58. The castellated nut 64 is mounted on the free end of the stud 74 and the compression spring 60 acts between the inner face of the nut and the outer face of the flange 54. The action of the spring 60 resiliently clamps the friction disc 58 between the flange 54 of the holder and the flange 76 mounted on the end of the bar 70. The assembly functions analogously to that illustrated in Figures 9 and 10. Many modifications will be apparent to those skilled in the art without departing from the spirit and scope of the invention. For instance, one modification would be for the bolt 62 or stud 74 to be formed integrally with the flange 54 of the holder.

Claims: CLAIMS 1. A holder for a brake block for a railway wheel, said holder comprising a body having a mounting portion for mounting the holder on em operating member of a brake system for the wheel and a block mounting portion for mounting the brake block, characterised in that the mounting portion is not bifurcated and comprises a plate member which is, in use, located on an outboard side of the operating member. 2. A brake block holder assembly comprising a holder as defined in Claim 1 said assembly including a compression spring, mounting shaft, friction member and fixing member, the arrangement being such that, in use, the shaft interconnects the operating member and plate member of the holder, said friction member being resiliently clamped by said spring between the plate member of the holder and the operating member, and the fixing member serves to maintain the spring, friction member and holder in their operative positions relative to the shaft. 3. An assembly as claimed in Claim 2 wherein said plate member has a bore therethrough and said shaft extends through the bore whereby the holder is rotably mounted on the shaft but is frictionally restrained by said friction member. 4. An assembly as claimed in Claim 3 wherein said friction member comprises an annular disc of synthetic _ C? ι?I _ ^ iPO ,Λ» faVAT10≤P' plastics material and said shaft extends through the opening in said disc. 5. An assembly as claimed in Claim 4 wherein said disc is about 5mm thick. 6. An assembly as claimed in claim 3, 4 or 5 wherein said shaft comprises the shank of headed bolt and wherein the spring acts between the head thereof and said operating member and wherein the fixing member comprises a lock nut mounted on the free end of the bolt said lock nut bearing against the plate member of the holder. 7. An assembly as claimed in Claim 6 wherein the operating member comprises a lever pivotally mounted relative to a railway vehicle and in use is rotated by the brake system. 8. An assembly as claimed in Claims 3, 4 or 5 wherein the shaft comprises a stud projecting from the end of a truss bar of the brake system of a railway vehicle, the free end portion of the stud being threaded and wherein the fixing member comprises lock nut mounted on the stud and wherein said spring acts between the nut and the plate member of the holder, said truss bar having mounted thereon a flange adjacent to the stud whereby the spring resiliently clamps the friction member between said flange and said plate member. 9. A railway vehicle comprising a chassis, at least one axle with wheels mounted thereon, and a brake system, said brake system including brake blocks, a brake block assembly as claimed in any one of claims 2 to 8 for each brake block, and operating members for causing the brake blocks to engage the wheels, and wherein said wheels have tread surfaces which are frusto-conical, said brake blocks including engagement surfaces which are complementary to said tread surfaces, and wherein said shafts of the assemblies are parallel to said axle and said holders are rotatable in planes which are perpendicular to said axle and wherein said plate members of the holders are located outboard of central planes which pass through the centres of the tread surfaces and which are perpendicular to the axle. 10. A brake system for a railway wheel said wheel having a frusto-conical tread surface, said system including a brake block having a braking surface which is of complementary shape to said tread surface, a brake block holder which carries said brake block, a mounting shaft upon which a mounting portion of the holder is mounted for rotation about an axis which is substantially parallel to the axis of said frusto-conical surface, a biasing means for resiliently urging said holder into engagement with a friction member so as to frictionally restrain rotation of the holder on the mounting shaft and to constrain the mounting portion of the holder to rotation in a plane or planes perpendicular to the axis of the mounting shaft, said plane or planes being located closer to the smaller circumference of the tread surface than the larger circumference of the tread surface.

Inventors: SMITH SYDNEY EDWIN ALLAN, SMITH, SYDNEY, EDWIN, ALLAN
Applicants: SMITH SYDNEY EDWIN ALLAN, SMITH, SYDNEY, EDWIN, ALLAN
Application year: 1984
Main classification: B61H1
IPC codes: B61H1