Patent GB-881059-A (GB)
Title: Improvements in or relating to grinding machines for elongate work-pieces
Inventor: PLUMMER HENRY JAMES
IPC: B24B17/02
Filed: 1959-05-01
Abstract: 881,059. Copy grinding or polishing. BRISTOL SIDDELEY ENGINES Ltd. July 25, 1960 [May 1, 1959], No. 14885/59. Class 60. A machine for grinding or polishing elongate workpieces having curved surfaces, e.g. compressor or turbine blades, of the kind in which there is provision for relative reciprocation between a workpiece and a former on the one hand and a grinding head and a follower on the other hand in the longitudinal direction of the workpiece and the former and also for relative incremental feeding between the workpiece and the former on the one hand and the grinding head and the follower on the other hand in a direction transversely of the workpiece and the former, includes means for turning the workpiece and the former in unison about their longitudinal axes in predetermined angular increments when an increment of cross-feed is applied. A machine similar to that in Specification 838,887 has a table 1, on which a workpiece and a former are carried, reciprocatable longitudinally of the workpiece and the former. An upright member 12, mounted in a guideway 17 for vertical movement, passes through a central aperture 2 in the table. The member 12 carries at,its upper end arms 15, 13, the arm 15 carrying a grinding head 16 including a continuous abrasive belt 27 engageable with the workpiece and the arm 13 carrying a follower 14 engageable with the former. The parts 12, 17, 16, 14 are movable bodily in increments transversely of the workpiece and former. The table 1 has an upstanding peripheral wall 36 and a longitudinal intermediate wall 37 separating the part of the table in the vicinity of the workpiece from the remainder of the table. Instead of being clamped to the upper face of the table the workpiece and the former are mounted for angular movement about longitudinal parallel axes, opposite ends of the wall 36 having bearing mountings 50, 51 for stub shafts 52, 53 having frusto-conical sockets into which corresponding ends of pivots on the workpiece and the former, or on carriers therefor, can be fitted. A carrier comprises a base plate 54 to which the workpiece or former is clamped and end portions 56, 57 having frusto-conical projections 58 engageable with the stub shafts 52, 53. The projections and the stub shafts have dog connections. At least one of the end portions 56, 57 is detachable from the base plate 54, locating means being provided between the base plate 54 and the detachable end portion or portions. Instead of using a carrier, the workpiece or former may have integral frusto-conical ends, those on the workpiece being removed after the workpiece has been ground and polished. The stub shaft 53 for the left-hand end of the former is angularly movable by a selectively operable driving mechanism including a hydraulic cylinder 60 interconnected with the cross-feed actuating cylinder (41 in Specification 838,887) so that the cross-feed and the incremental angular movement occur simultaneously. The stub shaft 53 for the right-hand end of the former, is coupled to the adjacent stub shaft 52, to which the workpiece is attached by steel tapes 61, 62 each anchored at its ends to drums 63, 64 rotatably fast with the stub shafts 52, 53. The ends of the tapes 61, 62 are wrapped in opposite directions around each drum, and each tape comprises two lengths connected by a turnbuckle 65. The driving mechanism for the left-hand stub shaft 53 comprises a two-part worm wheel 66 on the shaft 53 arranged to be driven by a worm 67 on a shaft 68. The shaft 68 is supported in an arm 71 pivotably mounted on the wall 36 by a screw 72. A block 81 carried loosely on the worm shaft 68 is swung about the shaft axis by the rod 82 of the hydraulic cylinder 60 which is carried on the arm 71. The block 81 carries a mounting 83 for a pawl-like plunger 84 urged by a spring 85 into engagement with a ratchet wheel 86 keyed to the shaft 68. A pin 87 in the plunger 84 engages a slot in the mounting 83, so as normally to prevent rotation of the plunger. The direction of rotation of the ratchet wheel 86 can be changed by withdrawing the plunger 84 against the spring bias and turning it through 180 degrees. The stroke of the rod 82 can be varied. A friction brake 88 prevents rotation of the shaft 68 when the plunger 84 is over-riding the ratchet wheel 86. Pivoting of the arm 71 is effected by a hydraulic cylinder 75 on the arm having a plunger 74 arranged to push or pull a toggle comprising pivotably-connected links 76A, 76B, the link 76A being pivotably mounted on the wall 36 by a pin 77 passing through an elongated slot in the arm 71 and the link 76B being pivotably connected to the arm 71 by a pin 78. Pivoting of the arm 71, which is limited by a screw 79 passing through a slot 80 in the arm, moves the worm 67 into and out of mesh with the worm wheel 66. The hydraulic cylinder 75 is controlled by an electric circuit including a trip switch 90 operated by a single-lobe cam 91 mounted on the right-hand stub shaft 53. The cam is set in such angular position that when the former has turned through a predetermined angle from the datum position, the switch 90 is operated causing the cylinder 75 to swing the arm 71 to disengage the worm 67 from the worm wheel 66, so interrupting the drive to the former and workpiece, which remain in the same angular positions for the remainder of the grinding or polishing operation. A toothed quadrant 94 pivotally mounted on the bearing mounting 51 meshes with a pinion 95 keyed to the left-hand stub shaft 53. The plunger of a hydraulic cylinder 96 is operable to move the quadrant 94 to rotate the pinion 95 and thus the worm wheel 66, when the worm 67 has been disengaged from it, to return the former and workpiece to their datum positions. The cylinder 96 is interconnected with a hydraulic cylinder (43 in Specification 838,887) which raises the member 12, the grinding head and the follower at the conclusion of an operating cycle. The cam 91 may be so set that the rotary drive mechanism is disengaged by the trip switch 90 at the initial position of the workpiece and former. Specification 793,366 also is referred to.