Patent GB-714872-A (GB)
Title: Grinder
IPC: B24B19/02
Filed: 1952-02-20
Abstract: 714,872. Grinding. NATIONAL BROACH & MACHINE CO. Feb. 20, 1952 [April 23, 1951], No. 4481/52. Class 60 A grinder comprises a base, a grinding wheel supported in a stationary position on the base, a rotary work support slidable in relation to the base in a direction substantially parallel to the rotational axis of the work support in order to effect relative reciprocation between the grinding wheel and a work piece mounted in the work support, a splined lead bar or screw and a co-operating lead nut, constituting lead control means for controlling the rotational position of the work support during the relative reciprocation, index mechanism intermediate the lead control means and the work support, and indexing means operated automatically by the relative reciprocation to index the work support following each relative reciprocation. A grinding machine comprises a grinding wheel 14 angularly and vertically adjustable on a column 12 mounted on a base 10; a carriage longitudinally reciprocable on the base 10 carries a tailstock 16 and an indexing headstock 18; a lead nut 20 co-operates with a lead screw 22 to impart rotation to the work as a consequence of the reciprocation. The indexing headstock 18 comprises a housing 24 having a jib construction 26 cooperating with supporting ways on the longitudinally movable carriage. A centre 46 mounted in bearings 48, 50 in the housing is provided at its forward end with a pointed element 52 and with a plate 54 having ears carrying clamp screws to engage a part secured to the work piece. The reduced end 64 of the centre 46 is mounted in bearings 66 in a bearing sleeve 42 connected by screws to a cap 40 rigidly connected to a carrier 32; the carrier 32 is transversely slotted at 34 and at its outer end is radially slotted at 36, the end of the lead bar 22 being secured in the slotted end of the carrier by clamping screws 38. An index plate 70 is. bolted to a brake ring 72 keyed to the centre 46 and co-operating with a friction brake 80 secured to the housing 24; the brake is circumferentially slotted to dissipate heat. The carrier 32 has a recess 86 across the inner end of which are ways 90 on which a slide 92 is movable radially of the axis of the headstock, a compression spring 93 urging the slide 92 radially outward. The slide 92 carries an element 94, preferably adjustable thereon, having an index finger 96. The slide 92 also carries a roller 100 co-operating unit a lune shaped cam portion 108 on a camming member 106 rotatably mounted in a sleeve 88 projecting from the carrier 32. The cam member 106 is biased, in a direction tending to force the roller 100 radially inwardly to force the finger 96 into a notch 110 of the index plate 70, by a tension spring 114 keyed at one end at 116 to the sleeve 88 and connected at the other end to a pin 118 connected to a lever 120 keyed to a shaft 122 carrying the camming member 106. The. lever 120 carries a roller 140 co-operating with the end 142 of a lever 124. The lever 124 is pivoted at 126 to a transverse support element 128 of the housing 24 and is biased by a torsion spring 130 one end of which is supported on the element 128 and the other end of which carries a pin 132 received in an opening 134 in the lever 124; the lever 124 carries a hand knob 136. Rotation of the lever 124 in a counter-clockwise direction is prevented by a stop 138 on the housing 24. During clockwise rotation of the carrier 32, the roller 140 contacts the end 142 of lever 124 and turns the latter in a counter-clockwise direction until further turning is prevented by the stop 138; further clockwise rotation of the carrier 32 then results in counter-clockwise rotation of the lever 120 thus moving the camming member 106 and carrier portion 108 to release the slide 92 which is then forced outwardly by the spring 93 to withdraw the finger 96 from the notch 110 of the index plate 70. The index plate is brought to rest by the friction brake. Further clockwise rotation of the carrier 32 takes the roller 140 past the end 142 of lever 124, and the lever 120 is rotated clockwise by the spring 114, moving the cam 108 to return the slide 92 so that the index finger 96 engages the next notch 110 of the index plate 70. Safety means to stop operation of the machine if automatic indexing does not take place comprises a switch 150 actuation of which interrupts the automatic cycle of the machine. A plunger 156, supported on the housing 24 by a guide 154, carries at its lower end a roller 160 which, upon initiation of the first stroke of reciprocation, rides up over a cam 152 carried by the frame of the machine. A lever 162 is pivotally connected at 164 to the upper end of the plunger 156, a roller 166 being carried by the upper end of the lever 162. A light tension spring 176 is connected at one end to the housing 24 and at the other end to the axle 180 of the roller 166; the spring biases the lever 162 counter-clockwise about its pivot 164, such motion being prevented by engagement of the lever 162 with a web portion 182 of the plunger 156, and also urges the lever 162 and plunger 156 downwardly to ensure contact between the roller 160 and cam 152. The index element 94 is provided with a pointed projection 184 located adjacent the path of upward movement of the roller 166; if the index finger 96 has failed to seat fully within a notch 110 of the index plate 70, the projection 184 lies in the path of upward movement of the roller 166 and swings the lever 162 clockwise; an adjustable abutment 168 on the lever 162 acts on a roller 170 on the plunger of the switch 150. The automatic cycle of the machine is terminated after the work piece has been rotated through 360 degrees; a finger 186 carried by the brake ring 72 is adapted, when in the proper rotational position, to engage the roller 166. The beginning and end of the automatic cycle takes place with the finger 186 in the position shown in Fig. 5, and the starting circuit is arranged so that while the starting button is depressed the switch 150 is ineffective to prevent automatic operation and. accordingly indexing takes place which moves the finger 186 out of the path of the roller 166; after the machine has started the finger 186 is indexed around step by step until it again reaches a position to engage the roller 166 whereupon the automatic cycle is terminated. In a modification, Fig. 10, a brake disc 202 is acted on by braking mechanism including springs 204; the lead bar 206, working in a lead nut 208, is connected to a carrier 210 carrying an index plunger 212 having an index finger 214 which co-operates with notches 216 in an index plate 218. A compression spring 220 acts on the index plunger 212 to hold the finger 214 in the notch 216. A projection 226 on the index plunger 212 co-operates with a pivoted camming element 228 in one direction of rotation so as positively to cam the index finger 214 out of the notch; reverse rotation of the carrier 210 causes the projection 226 to move the pivoted element 228 away from a stop 230. In a further modification, Fig. 11, the lead bar 248, working in a lead strut 250, is connected to a carrier 252 on which is slidablv mounted an index plunger 254 having an index finger 256 co-operating with notches 258 on an index plate 244. A compression spring 260 biases 'the plunger 254 radially outwardly; a roller 268 on the plunger 254 co-operates with a cam 266 carried by a lever 262 pivoted at 264 to the carrier 252, the lever 262 being biased by a tension spring 269 in a direction to force the plunger 254 radially inwardly. A roller 270 on the lever 262 co-operates with a pivoted element 272. In another modification, Fig. 12, the lead nut 318 and lead bar 292 have straight splines, so that there is no rotation of the work during the grinding stroke. The lead nut 318 is rotatably mounted in a support 320 and is normally held against rotation by a bolt 322 urged by a spring 324 to engage a flange 328 at one end of the nut 318. The outer end of the lead bar 292 has a recess 330 with internal helical splines engaging a helically splined shaft 334 carried by an actuating device 331 having a circular head 332. The shaft 334 is hollow and provided with an abutment 336 at its inner end through which extends a headed bolt 338 secured to the lead bar; a compression spring 342 is situated between the abutment 336 and the head of the bolt 338. An opening 344 in the head 332 of the actuating device 331 co-operates with a fixed pin 346. When the head 332 approaches the support 320 the pin 346 locks the actuating device 331 against rotation; at the same time the head 332 engages a plunger 348 which presses the bolt 322 inwardly to free the lead nut 318 for rotation. Further motion to the right results in relative motion between the lead bar 292 and the actuating device 331 which, due to the helical splines in the recess 330 in the lead bar and the shaft 334 results in rotation of the lead bar and hence of the carrier 294.