Patent GB-643260-A (GB)
Title: Improvement in grinding machines
IPC: B24B47/04
Filed: 1943-08-31
Abstract: 643,260. Stop-mechanism. BRYANT CHUCKING GRINDER CO. Aug. 31, 1943, No. 14222. Convention date, Aug. 22, 1942. [Class 83 (iii)] [Also in Group XXIII] In a grinding or other metal cutting machine having relative traverse and relative feed between the work and the tool, the amount of feed is limited by a pair of stops which are independently adjustable, automatic means being provided whereby one stop is operative to limit the feed during rough grinding and the other stop is opera. tive to limit the feed during finish grinding. The machine shown is for internal grinding and comprises a bed 1, Fig. 1, having thereon a transversely movable work carriage 2 carrying a head 3 adjustable angularly on curved ways 4 and supporting a motor-driven work chuck 5. The bed is also fitted with a carriage 15 which carries the grinding-wheel 18 and is fixed to a tubular member 20, Fig. 3, rockably and axially movable on bearings 21a; the member 20 has a central partition 21, Fig. 11, forming aligned cylinders receiving tubes 22 through which fluid is supplied or discharged by pipes 23, 24 to reciprocate the carriage axially. Feed mechanism.-The work carriage has secured thereon a bracket 25 carrying a shaft 28 screwed at 30 to engage a nut 31 rotatably mounted in the bed 1; the screw is rotatable by a hand wheel 29 having a hub 290 carrying a worm gear 34 which is rotatable by a worm 37 to give slow motion to the screw for setting up the machine. The worm is carried by a shaft 38 rotatable by a knob 39, Fig. 4, in an eccentric sleeve 40 which may be turned to engage or disengage the worm with the gear 38 by a handle 42. Power feed is produced by rotation of the nut 31, which has secured thereto a gear 45 engaging a gear 48 formed integral with a worm 56 carried by a stud 51 and engaged by threads on a quill 58 forming the piston of a fluid pressure cylinder 60, Fig. 5, in which is slidable an enlarged part 61 of the quill. The quill may have both axial and rotary motion, the axial motion causing the quill to act as a rack to rotate the gear 56 for feed, and the rotary motion effecting compensation for wear and truing of the grinding-wheel. The rotation is produced by a splined shaft 65 engaging within the quill and driven through a one-way clutch 70, 71; the shaft 65 may be locked against rotation by a bolt 75 which engages serrations in the clutch member 70 and is slidable in a cylinder 77, a spring 78 normally holding the bolt in locking engagement with the clutch. The bolt may be retracted by fluid pressure from a pipe 81, retraction of the bolt opening a port to a pipe 82 leading to means for rotating the shaft 65. This comprises a pinion 85, Fig. 7, on the shaft 72 engaged by rack teeth on a plunger 86 mounted in a cylinder 87 and pressed in one direction by a spring 93 up to a stop 89 and movable in the opposite direction by fluid supplied by the pipe 82; when the fluid unlocks the bolt 75 it passes also to the cylinder 87. Feed motion of the work carriage is produced by movement of the quill 58 to the left, Fig. 5, the movement being limited by two stops 100, 101, the stop 100 being for the finishing cut and the stop 101 for rough grinding. The stops are carried by a plunger 102 slidable in guides 103, 104 and pressed in one direction by a spring 107 and movable in the opposite direction by fluid supplied by a pipe 118 to the guide 104 which is closed to act as a cylinder; movement of the plunger brings one of the stops opposite to a plug 120 in the end of the quill 58 for engagement thereby. Each stop comprises a screw 125, Fig. 9, threaded into a sleeve 127 slidably keyed in a bore through the plunger and pressed axially by a spring 135 to the extent allowed by an adjustable collar 135; the extent to which the feed may proceed is determined by the extent to which the screws 125 project beyond the sleeves. When the stops are moved by the plug 120, the collar on the stop in operation engages one arm of a lever plate pivoted at 148, Fig. 8, so that the other arm thereof closes two push-button switches 145, 146. Traverse mechanism.-Movable with the wheel carriage is a support 200 having therein grooves to receive adjustable stops 201-203, of which the stop 201 is longer than the stop 203, and the stop 203 longer than the stop 202; the stop 201 limits the stroke of the carriage inwardly, the stop 202 determines the outer limit for normal grinding, and the stop 203 the limit of outward travel for wheel dressing, the stop in operation being determined by the axial position of a control member 204. This member is movable axially by fluid pressure and is also turnable, the turning motion being effected when an eccentric post 205 is struck by the stops 202, 203, whilst contact of the stop 201 with the post or a collar 206 turns the member 204 in the opposite direction. The member 204 is rotatable in, and axially movable with, a yoke 208 having a central plunger 214 projecting into a casing 215 in which is slidable a cup member 216 with a shank 217 having therein a port 218 connected to a pipe 219; a pipe 220 passes through the casing below the cup 216, and by admission of fluid to these pipes the axial position of the member 204 is determined. The rotary movement of the member 204 is used to effect reversal of the carriage, a portion of the member 204 having thereon gear teeth engaging a rack bar 225 connected to a pilot valve 226, to which pressure fluid is supplied from a reservoir 230 by a pump 231 and pipe 232. The pipe 232 leads to a reversing valve 235 having connections to the pipes 23, 24 and to the pilot valve such that movements of the pilot valve cause the reversing valve to be moved by fluid pressure, thus reversing the flow and exhaust to and from the cylinder 20, with a slowing down of the valve at the ends of its strokes and a swell in the motion of the wheel slide; the speed of movement of the slide is determined by throttle members 253, 2530 in the outlet from a valve 250, which moves with the yoke 208 and through which the exhaust from the cylinder is led by a pipe 248 from the pilot valve. Cycle control mechanism.-The yoke 208 carries also another valve 280 forming part of the mechanism controlling the feed motion, which is operated from a pressure fluid circuit independent of that operating the wheel traverse. The axial position of the member 204 is determined by the circuit operating the traverse through electrically controlled valves A, B, and the wheel feed and retraction by valves C, D, whilst the positioning of the rough grinding and finish grinding stops is controlled by valves E, F; these valves are held normally in one axial position, but may be moved to the other position by the energization of coils A<SP>1</SP>-F<SP>1</SP>, which are controlled by the switches 145, 146, three relays 300-302, and two motoractuated switches 303, 304. The latter comprise a motor allowed to make one rotation only by means of a latch member operated by a solenoid, and each relay 300-302 is operated by two solenoids 326, 327; 336, 337; and 344, 345 respectively to take either of two positions, in which various sets of switch arms 322-325, 332-335, 342, 343 are moved simultaneously to make and break appropriate circuits. The sequence of operations starting from the positions shown in Fig. 11 during an intermediate portion of rough grinding comprises repeated traverses of the wheel at low speed and feed of the work also at low speed until switches 145, 146 are closed, when the work is retracted rapidly, the wheel is returned rapidly to an intermediate position and slowly traversed past a truing diamond 396 carried by a bellcrank lever moved to operative position by fluid pressure; the shaft 65 also is turned to give the small feed to the work to compensate for truing and wear. When the wheel returns from its extended truing traverse a switch 401 is closed momentarily by a dog 400 on the wheel carriage; this operates the relays and starts a quick feed to bring the work and wheel together, after which the feed rate is slowed down for finishing whilst the finish stop 100 is moved opposite the quill 58, so that feed continues with repeated traverses of the wheel until the plug 120 contacts the stop 100 and closes the switches 145, 146, when the work is withdrawn and the wheel makes an outward traverse to a position of rest where it remains for work removal and replacement.