Patent GB-938905-A (GB)
Title: Improvements relating to index mechanisms
IPC: B23F23/08
Filed: 1961-10-03
Abstract: 938,905. Machine tool details. GLEASON WORKS. Oct. 3, 1961 [Oct. 18, 1960], No. 35664/61. Class 83 (3). [Also in Group XXIII] An index mechanism comprises a housing and a notched index plate rotatable therein, a locking pawl supported by the housing for engagement with the notches of the plate to hold the latter against rotation relative to the housing in both directions, an indexing pawl also engageable with said notches and a carrier for said indexing pawl mounted in the housing for indexing and return motions, said indexing pawl when engaged holding the plate against rotation relative to the carrier in both directions, a fluidpressure actuated piston for effecting said indexing and return motions of the carrier, means for actuating said pawls to cause each one to relax as the other engages, said pawl actuating means being arranged to operate in such timed relation with said piston that the index pawl is engaged throughout the indexing motion and the locking pawl throughout the return motion, abutment means to stop the indexing motion when the carrier is in a definite position wherein a notch of the plate is aligned with the locking pawl, and adjustable stop means to limit the return motion of the carrier.  A cutter sharpening machine has a spindle 10, journalled in anti-friction bearings in a housing 12, on which the cutter C to be sharpened is mounted. An index plate 14 detachably secured to the spindle has notches 15 round its periphery, the plate being interchangeable with others of the same diameter but having different numbers of notches. A locking pawl 16 is pivoted at 18 to the housing 12, and has a tooth 17 urged into notch-engaging position by a spring 19. An indexing pawl 21 is pivoted at 23 to an arm 24 carried by a segmental pinion 25 rotatably supported by the spindle, and has a tooth 22 urged into notch-engaging position by a spring backed plunger 26 carried by the arm 24. For effecting alternate engagement of pawls 16, 21 with the plate a lever 27 is pivoted at 28 to the housing. Pivoted to the lever 27 at 29 is a block 31 slidable in a slot in the pawl 16 and pivoted to the lever 27 at 33 is a block 34 slidable in a slot in a pawl lifter 32. The latter is pivoted at 36 to the housing and has a flange 35 received in a slot in the tail of the pawl 21. The pawl tooth 22 enters a notch before the pawl tooth 17 fully withdraws from a notch and vice-versa. The lever 27 is pivotally connected at 41 to the rod of a piston 38 movable in a cylinder in a block 39 secured in the housing 12. Movable in another cylinder in the block 39 is a piston 42 rigidly connected to a rack 40 meshing with the segmental pinion 25. Downward travel of piston 42 is limited by an abutment 43 on the arm 24 engaging an abutment 44 on the block 39 such that, at the end of an indexing movement, the notch 15 engaged by pawl tooth 22 is directly below pawl tooth 17. Return travel of the piston 42 is limited by its abutment with a stop member 45 slidable in, but keyed against rotation with respect to, a bushing 46 fixed to the housing 12. The stop 45 is threaded to a screw 47, to which a calibrated dial 48 is secured, and also to a tubular screw 49 which is rotatable but held against axial movement. A pin 52 carried by the screw 47 extends through axially elongated slots in the screw 49, connectiong the screws for rotation together but permitting them limited relative axial motion. By turning the screw 47 the stop 45 is adjusted axially to vary the stroke of the piston 42 and a clamp nut 53 threaded on the outer end of screw 47 is then tightened to move the screw 47 upwardly relatively to the tubular screw 49 thereby taking up backlash and clamping the stop in adjusted position. In each index operation valve means first direct hydraulic fluid under pressure through port 54 to move piston 38 downwardly to release pawl 16 and engage pawl 21. As its downward limit position is approached, the piston uncovers port 56 applying pressure fluid to move piston 42 downwardly to cause indexing movement of pawl 21. Exhaust from below the piston 42 is through passage 59 and spring- closed check valve 61 into the chamber beneath piston 38 and thence through exhaust port 63. The last part of the indexing stroke is slowed by piston 42 covering port 64 of passage 59 so that final exhaust from below the piston 42 is through a bleed opening in a spring-closed check valve 65. On conclusion of the indexing stroke, pressure and exhaust connections to ports 54, 63 are reversed. Pressure fluid moves piston 38 upwardly to engage pawl 16 and disengage pawl 21. In its uppermost position the piston 38 abuts the adjacent cylinder head so that, due to a slight clearance between block 31 and its slot in lever 27, upwardly-acting hydraulic pressure does not act on the pawl 16 while it is engaged. At the conclusion of its upstroke piston 38 uncovers port 66 so that pressure fluid passes through passage 59 and check valve 65 so that piston 42 is raised, effecting return of pawl 21. Exhaust from above the piston 42 is past spring-loaded check valve 67 and through port 54.  Specification 938,904 is referred to.