Patent GB-518914-A (GB)
Title: Improvements in multiple spindle grinding or abrading machines
IPC: B24B5/01
Filed: 1938-06-10
Abstract: 518,914. Grinding - machines. BRYANT CHUCKING GRINDER CO. June 10, 1938, No. 17312. Convention date, July 8, 1937. [Class 60] [Also in Group XXXV] A multiple spindle machine tool, described as a grinding machine has means for indexing the work head or turret, means for feeding the turret axially up to and from the grinding position, means for reciprocating the grinding wheels axially and for feeding them radially and means for trueing the wheels and adjusting them to compensate for wear. Work holders and mountings therefor.-The machine comprises a 'base 1 having thereon a pair of standards 2, 3 carrying bearings 4, 5 in which is mounted for reciprocation and rotation a shaft 6, to which is secured the hub 7 of a work holder carrying spider or turret 8. On the spider are four platforms 10 each having pivotally mounted thereon at 12, between the end faces of the work, a work head 11 which has bearing ribs riding on the platform 10 and the head being adjusted by a screw 23 ; tapered or parallel work pieces thus may be ground. In the casing of each head is a work spindle 30 having thereon spiral ribs 32 serving to force out foreign matter, and on the spindle is mounted a bevel closing chuck operated through a hollow plunger 37 actuated, to hold the work by a spring 40, and to release the work by a piston 41 in a fluid pressure cylinder 43 ; a brake ring 42, Fig. 38, on the piston is adapted to engage a head 38 to brake rotation of the plunger 37 in the work releasing position. The work is rotated by a pulley 45, each pulley being driven by a separate belt 50 from a pulley 51 driven by a flexible shaft 52 from a pulley 53, the pulleys 53 being driven by a motor 56 by a belt 54 held taut by pivoting the motor bracket 64 at 60 and acting on the bracket by a spring 62. A safety bar 65 passes through a hole 66 in the bracket to prevent excessive movement thereof in the event of belt failure. The spider 8 is moved axially by movement of the shaft 6, which has thereon a piston 71, Fig. 4a, in a hydraulic cylinder 72. Cooling fluid is supplied to the work and pressure fluid is supplied to the chucks by a central pipe 75 and four pipes 76, respectively, mounted in a bore in the shaft 6 the cooling fluid being supplied by a rotary packing gland 77, and led to the chucks by flexible pipes 81. The pressure fluid passes through a rotary coupling 85, a distributing head 86 and flexible pipes 89. The work holders may each be driven by a separate motor. Indexing mechanism.-The spider is indexed by rotation of the shaft 6 by means of a Geneva wheel 100 having slots 101 in which engages a roller 103 on an arm 102 pivoted at 104 and moved by a gear segment 105 operated by a rack 106 moved by a piston in a cylinder 107; during indexing, the spider is in position with the work pieces retracted from the grinding position, and at the completion of each indexing movement, the arm 102 operates a valve to admit fluid to the cylinder 72 to move the shaft 6 and the spider to the grinding position. The spider is locked in indexed position by means of four projections 115 on the spider, which have thereon wear plates 116 engaged by a stop 119 and a plunger 126 actuated by a fluid pressure cylinder 133. Grinding-wheel mounting and traversing mechanism.-The standard 3 is extended to form a housing 150 carrying the grinding wheel driving &c. mechanism, there being three grinding wheels' only, since one indexed position of the work spindles is a loading and unloading station. Each grinding unit comprises two aligned sleeves 155, 156 connected by a casing 157 and journalled in split adjustable tapered bearings 158, 159 mounted in sleeves .160, 161 in the housing 150, the sleeves 155, 156 being slidable axially and rockable in their bearings, and in each sleeve 156 is a spindle 170 carrying a pulley 171 driven by a belt from a motor, and on the spindle also is a pulley 175 driving belt 176, held tight by a spring jockey pulley, which drives a pulley 178 on the shaft 179 of the grinding-wheel 180 mounted in a housing 181. Each wheel is traversed axially by a circular rack 186 on the sleeve 156, the rack being moved by a gear sector 187 oscillated through linkage and a variable throw crank pin 194 by a rack formed on a double acting piston 199 in a cylinder 200. Each wheel is fed to the work by pivoting the unit about the sleeves 155, 156, and for this purpose each casing 157 has thereon a bracket 230 in which is mounted a bar 228 to which is pivoted at 227, an arm 221 carrying an adjustable shoe 215, which rides on a sleeve 210 adjustably mounted on the shaft 6, the feed being produced by a movement of the arm 221 by an eccentric 238, Fig. 18, rotated by a rack 241 on the rod of a piston 243 mounted in a cylinder 244 and pressed by a spring 245. Wear of the wheel is compensated for by axial movement of the rod 228 by a screwed part 250 therein engaged by a nut 252 worm driven by adjustable ratchet gearing 257 brought into operation by a finger 280 actuated by a lug 281 carried by a spider portion 283 rockably mounted at 284 in the sleeve 210; the finger 280 is actuated during the last 15‹ of the indexing of the spider 8. A pleated dust guard 291, Fig. 5, is connected to the part 284 and to a plate 292 on the housing 150. Wheet trueing mechanism.-The wheel trueing mechanism is carried by the spider 283 which is formed with an extension 300, Fig. 15, adjacent each wheel 180, a diamond 303 being mounted in an adjustable part 320 of the extension. The spider is held normally in inoperative angular position by a spring 305 attached to a forked part 307 in which is a tripping lever 309 projecting through the spider to engage a stud 312, Fig. 17, on the housing 9 of the spider 8, so that the spider 283 is then turned with the housing 9, during indexing, through the last 15‹ to bring the diamonds into line with the wheels 180. As the shaft 6 moves into operative position the wheels are trued and the spider is then released from the housing 9 by tripping of the lever 309 by its contact with a stud 316 on the plate 292. Work spindle loading and unloading mechanism.-The loading and unloading station is the upper side position of the work spindle, the pulley 53 thereof not being driven at that position. The work pieces are placed in a shoot 376 and are removed singly by spring fingers 369 on an arm 364 carried by a shaft 363 driven by a rack 360 operated, through links 358, and a crank by a rack 353 on a piston movable in a cylinder 351. The arm 364 swings anti-clockwise, Fig. 40, from the full line position, carrying a finished work piece on the fingers 369 into the dotted line position, where the work piece w is removed by spring catches, and falls into a shoot. An unground work piece is then allowed to move down the shoot by operation of retaining pegs actuated by the arm 364, and upon reverse movement of the arm, this work piece is carried round to the chuck 35 on the work spindle. Hydraulic drive and control mechanism.-The operations of the machine are controlled by hydraulic valves actuated in timed relation by cams adjustably carried by a shaft 480, Fig. 2, driven through a hydraulically operated clutch and planetary and change speed gearing by an electric motor 450. The cams operate valves 515- 519 (not shown) of which the valve 515 controls the wheel feeds, 516 the reciprocation of shaft 6, 517 the locking of the work holders in indexed position, 518 the transverse movements of the wheels, and 519 the work loading mechanism. The valves are similar in construction to that 515 shown in Fig. 30 and are movable against springs, as 570 in a casing 571 provided with inlet ports 560-562 and outlet ports 563-565, the casings are mounted on a header 520 having therein a supply passage 522 from a pump 525, and outlet passages 523, 524. The valve 515 is moved down by an arm actuated by a bell crank lever 552 operated by the rim of the geneva wheel when the shaft 6 moves to the indexing position, and the valve is raised to highest position by its spring when the shaft 6 moves to the operative position ; an intermediate position wherein all the ports are closed, is controlled by a cam. The valve 516 is operated partly by a cam and partly by a lever moved through a flexible cable by the arm 102. The valves 517-519 are controlled entirely by cams which actuate the valves through levers pivoted at one end and engaging the valves at the other end. Operation.-Starting with the shaft 6 in operative position, valve 517 is first operated to lock the work spider, then valve 518 is operated to admit fluid through reversing valves to the . pistons for traverse of the grinding wheels, the speed of traverse being adjusted by a throttle valve. The wheel feed is started by movement of valve 515 to the position with all the ports closed, the feeding continuing to the required limit and then allowing a "sparking out" period. During the grinding, the loading arm is being actuated by action of the valve 519, movement of the pivot 357, Fig. 40, of link 358 actuating a valve to brake the spindle at the loading station and to release the work, which is then removed after which the valve 519 is reversed, so that a new work piece is moved to loading position in the chuck, and the loading arm moved to a position out of contact with the work. When the work is finished, the grinding wheels are retracted from the work pieces by movement of the valves 515 and 518. The work spider is then unlocked by movement of the valve 517, and the shaft 6 is moved to the left to inoperative position by operation of the valve 516, and the cam shaft is unclutched. As the movement to the left continues, the geneva wheel operates the valve 515 giving a rapid feed of the grinding wheels to the limit of feed for trueing of the wheels. The final movement of the Geneva wheel also actuates a valve causing the arm 102 to be rocked to index the spider, when the arm 102 is about to complete the indexing m