Patent GB-694189-A (GB)
Title: Grinding machine
IPC: B24B19/28
Filed: 1950-10-05
Abstract: 694,189. Grinding brake shoes. BENDIX AVIATION CORPORATION. Oct. 5, 1950 [Oct. 13, 1949], No. 24363/50. Class 60. [Also in Group XXX] A brake shoe grinding machine has a rotatable brake shoe clamping drum provided with a fluid actuated clamping member to clamp a brake shoe against a brake shoe locating member on the drum. The machine comprises three main parts, namely, a conveyer 30, a shoe loading device at the delivering end of the conveyer and a rotatable clamping drum 34 which receives the brake shoe from the loading device, clamps it in a predetermined position and carries it into the grinding wheel. The conveyer 30 comprises a chain 48 carried by sprockets 44, 46 and lying beneath and between two sets of conveyer rails 52, 54, each set of conveyer rails being contituted by a pair of spaced parallel rails, having hardened and ground upper surfaces. Pusher assemblies 50 are fastened to chain 48 by attachments 56, each pusher assembly comprising a pusher member 58 having a hardened transverse flange 60 moving on the upper surfaces of the inner slide rails 62, 64 of the two sets of conveyer rails 52, 54. The pusher 58 is pivoted to attachment 56 and is pivotally connected to a link 68 preloaded by a spring 70 forcing the flange 60 toward the chain 48. Riser members 76 secured to the outer slide rails 78, 80 of the conveyer sets 52, 54 are inclined in the direction of transport; as the brake shoe is conducted along the slide rails one end of the brake shoe rim will ride upon the riser members whereas the other end, which is provided with longitudinal notches, will not. If a brake shoe is incorrectly placed on the slide rails by the operator so that the flange 60 engages the unnotched end of the shoe, this engagement will be lost when the end of the rim rides over the riser member. A similar riser member 77 is used in conjunction with a switch 82 which is engaged, to stop the machine, by a brake shoe placed on the slide rails in reversed attitude but is not engaged by a correctly positioned shoe. The conveyer 30 simultaneously conducts shoes of different widths, one channel being for narrow shoes and the other channel for wider shoes. For stopping the machine if a narrow shoe is placed in the wide channel, a safety mechanism 88, Fig. 20, is provided and comprises a leaf spring 89, which is deflected by a shoe of correct width to actuate a micro-switch 91; an overhead micro-switch 93 is briefly actuated by engagement with the top of the rim of every brake shoe which passes. Thus a shoe of correct size actuates both switches substantially simultaneously, while an undersize shoe actuates only one switch, this causing the machine to stop. On the delivering end of conveyer 30 is adjustably mounted a pair of depending inclined slides 90. The loading device which is mounted in line with the delivering end of the conveyer comprises a pair of chambers 92, 94 in, alignment with the channels and constituted by spaced guide members 98, 100 and a partition 96. A pair of gates or support members 102, 104 on the outer sides of guide members 98, 100 are pivotally supported along their upper edges by anti-friction bearings 106. The bottom edges of the gates have inwardly projecting ledges 108 and in the forward end of each ledge is a notch 110 to receive one corner of the wide end of a brake shoe rim, the other end resting on the upper portion of end slide 90. The brake shoe is positively seated in this position by a roller 114 on an arm 112 pivoted at 116 and urged towards the shoe by a spring 118. The outward swinging movement of each gate is limited by a stop or latch 122 comprising a support 124 to the outwardly bent end 126 of which is pivoted a V-shaped piece 128. It it is desired to fully open the gate, the piece 128 is pivoted to inoperative position. Each gate carries a fluid pressure power cylinder 132, the plunger 134 of which projects through the gate and engages the guide member 98 or 100. Actuation of a cylinder causes the gate to swing outwardly against its stop; that end of the brake shoe which has been resting on the ledge 108 then drops on stop plate 180 on the drum 34 under the pressure of follower arm 112. Continuing rotation of the drum will draw the brake shoe on to the clamping drum 34, this discharge motion of the brake shoe being guided by the engagement of its right end with the end slide 90. Boxes 133 partially filled with lead shot 135 are secured to the gates 102, 104 to prevent bouncing upon closure. The grinding wheel 136 is journaled on a horizontal axis to lie in a plane perpendicular to the long dimension of the chambers and parallel to the axis of rotation of the drum 34 ; the axes of the grinding wheel 136 and drum 34 are located approximately in the same horizontal plane, with the outer peripheral margin of the grinding wheel disposed adjacent the clamping stations of the drum 34. The clamping drum 34 comprises a cylindrical member 138 reduced in its axial central portion to provide a pair of annular recesses 140; the diameter of the portion intermediate the recesses is formed slightly larger than the diameter of the bottoms of the recesses, and an annular key 142 is concentrically carried by this larger portion intermediate its edges. Cavities 144, 146 are formed in the ends of member 138, and are provided with closure plates to facilitate access for maintenance purposes. A pair of identical circumferentially arranged semi-circular locating members 148, 150 are snugly fitted to the annular key 142; the members 148, 150 serve as the supporting elements for the brake shoe locating points serving to position the brake shoe axially of the drum, each set of locating points being generally indicated by a reference numeral 152. Three sets of locating points 152 are provided on each locating member 148, 150 and are circumferentially spaced to be engaged by the lateral end and centre portions of a brake shoe rim. Each set of points 152 comprises a pair of small blocks 154 having rectangular bosses, the blocks 154 being received in axially spaced sockets 158 in the locating members 148, 150. The blocks 154 are held in position by set screws 160 threaded in the members 148, 150 and adjustment axially of the drum is permitted by elongated holes receiving the heads of the set screws 160; an adjusting screw 164 engages an abutment 166. Each recess 140 receives a pair of semi-circular clamping jaws 170, each jaw being axially movable and capable of limited wobbling movement about a universal fitting 172. Spacer studs secured to the inner peripheries of the jaws locate them with respect to the bottom of the respective recess. The brake shoe is located circumferentially of the drum by pins 178 carried in each end of the segments 148, 150 and projecting laterally therefrom only far enough to be engaged by an end of a brake shoe web; the pins are eccentrically ground or have small flats for adjustment. Plate members 180 secured between the adjacent ends of the locating segments 148, 150 and projecting slightly beyond their outer peripheries serve as an initial catch or stop for the end of the brake shoe dropped from the notch 110 of the locating device. Reciprocably mounted plungers 186, 188 have spherical ends 185 loosely fitting sockets 187 in the jaws, this constituting the universal fitting 172; a rubber boot 189 is provided. Plungers 186, 188 are connected to toggles 190, 192 the hinges of the toggles being connected by a link 196 so that one toggle is straightened when the other is collapsed, causing opposite movements of the plungers 186, 188. A rod 200 is connected to bellcrank 191 of toggle 190 and to an equalizer member 202. The drum is rotatably supported by hubs 204, 206; the outer end of hub 206 carries a double acting pneumatic actuator comprising a cylinder 213 and a piston 214 connected to piston rod 210 connected by link 209 to the equalizer 202. A stationary shaft 218 contains air passages 219, 221. To prevent damage to the grinding wheel a safety mechanism 270 is positioned adjacent the drum 34 and comprises a gib 272 pivoted at 273 on a stationary support; a part 274 movable vertically on the gib 272 carries a depending trip bar 276. A microswitch 284 mounted on the top of the gib 272 has its plunger extending downwardly in registry with an actuating rod 286. A protruding tooth member 294 secured to partition 96 of the loading device is engaged by a detent 296 on post 274. If a brake shoe is not properly seated on the rotating drum it will project radially outwardly enough to engage the trip bar 276 thus disengaging detent 296 from both 294, permitting part 274 to move upwardly under the influence of springs 280 to actuate switch 284 to stop the machine. The safety switch is connected into a dynamic braking circuit to prevent the momentum of the revolving drum from carrying the brake shoe into the grinding wheel. Another safety mechanism 298 stops the grinding machine if a shoe should fail to drop out of drum 34 at the discharge point. This mechanism comprises a pair of trip fingers 300 supported on a pivot shaft 302; the shaft 302 carries a lever 304 pivotally connected to a link 306 guided in a flange member 308 to engage one end of a pivoted lever 310 arranged to actuate a micro-switch 312. If a brake shoe fails to fall from the drum 34 when the jaws 170 open, the shoe is carried around by the drum and engages the respective trip finger 300 moving it to actuate switch 312 to shut down the machine. The hub 204 of drum 34 is journaled in a transmission casing 314 containing a worm and wheel gear assembly for rotating the drum and a train of spur gears for rotating the sprocket 46 of the conveyer, the travel of the conveyer chain 48 being synchronised with the rotation of drum 34. A shaft projecting from the transmission carries cams operating fluid valves which control the actuation of the gates 102, 104