GB1397775A - Cut-off device for a rotary fluid-pressure-operated machine - Google Patents

Abstract

1397775 Valves BLACK & DECKER MFG CO 8 Aug 1972 [16 Aug 1971] 36896/72 Heading G3B [Also in Divisions Fl and F2] A cut-off device for a rotary fluid-pressureoperated machine such as an air-operated grinder comprises a valve 23, Fig.2, for controlling the delivery of pressurized fluid from an inlet 37 to an outlet 39 leading to a vane-type motor 17, a spring 83 for moving the valve into its closed position, latch means for isolating the spring and control means for effecting disengagement of the latch only when the speed of rotation of the machine exceeds a predetermined value. The latch comprises a trigger 77 extending from a rotatable holder 59. The holder is restrained from axial movement, under the action of spring 83, by arcuate projections 64 on a stationary housing 61 underlying similar projections on the holder. The control means, in one example, comprises a pair of pivoted weights 87 and 89, Fig.5, which rotate with the machine and move outwardly under centrifugal force to strike the trigger 77. The holder 59 is thereby rotated, whereupon it is freed for axial movement and snaps the valve into its closed position. The speed at which the weights strike the trigger is pre-set by a screw 98. In other examples, the control means comprises a single pivoted weight (89'), Fig.10 (not shown), or a radially slidable weight (101), Fig.9 (not shown). In the normal course of events, the speed of the motor is automatically regulated by a pair of fly-weights 71, Fig.2, which act on a lever 63 to adjust the position of the valve with respect to its seat 35. If this mechanism fails, and the speed of the motor rises, the cut-off device comes into operation.