GB1278398A - Machine tools - Google Patents

Abstract

1278398 Grinding LITTON INDUSTRIES Inc 19 April 1971 [25 March 1970] 24460/71 Heading B3D A machine tool for operating on a workpiece, such as a machine for grinding crank-pins 21, 30, comprises a pair of crank-heads 19, a pair of spindles 24 rotatably mounted by respective one of the crank-heads, and a pair of fixtures 26 secured to respective one of the spindles, each fixture having an assembly including a clamping arm 12 which is pivotally mounted to its fixture for holding a workpiece 16, and a latching arrangement 10 which, in a first position, blocks the clamping arms against movement to a workpiece-removal position and releases the fixtures for rotation with respect to the crankheads, and which, in a second position, releases the clamping arms for pivoting motion with respect to the fixtures to a workpiece removal position and blocks the fixtures against rotation with respect to the crank-heads. The crankheads are of similar construction and mounted on a carriage 71 for longitudinal movement to position the crank-pins for grinding by a wheel 22. Each outer bearing pin 16 of the crank-shaft is held in a block 27 on a fixture 26 by movement of the arm 12 about a pivot 94 by fluid pressure supplied to a cylinder 13 moving a piston 89 connected to the arm against a spring 93. An adjustable stop 28 is mounted in the arm and, with a latching element 11 in a forward position permits only slight releasing movement of the arm 12 so that the pin 16 is unclamped and the crank-shaft can be indexed but will not permit the crank-shaft to be unloaded. The latching element is formed on a piston 33 which is movable by fluid pressure in a cylinder 32 against one or more springs 37, 38 to an unlatched position to allow the arm 12 to move to an unloading position. However, such movement is only possible when the fixtures are in the correct angular position which is determined by a reduced end 44 of a plunger 42 connected by a pin 51 to the piston 33 for movement therewith engaging a bore 61 in the crank-head 19. A member 63 is movable by the end 44 of the plunger when it enters the bore to operate a switch 5LS which produces a signal indicating that the fixture is held against rotation. The arm 12 is then moved by spring 93 to its inoperable position by blocking fluid pressure supplied to cylinder 13 to permit automatic loading and unloading of the workpiece. When the new workpiece is loaded, the machine is automatically operated, grinding being effected under the control of a size gauge at a rapid, slow and fine feed rate.