GB885126A - Improvements in or relating to the control of the grit feed of grit laying apparatus - Google Patents

Abstract

885,126. -Grit distributer. AVIATION, MINISTER OF. Feb. 5, 1959 [Nov. 5, 1957], No. 34471/57. Class 6(1). [Also in Group XXIX] The rate of feed of grit from a hopper mounted on a grit laying vehicle is controlled by a gate the opening and closing of which is effected by a servomotor controlled by the speed of the vehicle. In one embodiment, the grit 2 in a hopper 1 passes on to a conveyer belt 5 driven by the vehicle at a rate determined by the setting of a gate 4 pivoted at 7 and actuated by a doubleacting hydraulic motor 38 controlled by a pilot valve 20 which is actuated by a solenoid 30. The solenoid is controlled by a switch 13 consisting of a pair of contacts 15, 16 mounted on a sector 14 and movable about the pivot 7 by an arm 12 carrying a roller 11 which coacts with a cam 10 movable by a centrifugal governor 9 driven by the vehicle. The arrangement is such that an increase or decrease of speed of the vehicle causes movement of the sector 14 to bring either of the contacts 15, 16 into engagement with a contact 18 to complete an electrical circuit to the solenoid to move the pilot valve 20 in the direction for increasing or decreasing the opening provided by the gate 4, the movement of the latter also moving the contact 18 to an insulating portion 17 of the sector 14 so that the valve 20 is returned to its neutral position and the gate 4 brought to rest at a position corresponding to the changed speed of the vehicle. A number of cams 10 may be provided, each having a different contour for controlling the opening of the gate in accordance with the nature and size of the grit being fed from the hopper. These cams may be mounted or formed upon a plate arranged transversely of the vehicle and manually operated to bring the required cam into engagement with the roller 11. In a modification, four cams and follower rollers 11 together with the switch gear 15, 16, 18 &c. are provided and a manually operable switch is employed for selecting any one cam for control of the solenoid operated valve 20. In a further modification, a hydraulic pump driven at a speed proportional to that of the vehicle and delivering fluid to a spring- loaded piston is employed instead of the centrifugal governor. The spring-loaded piston operating through a rack and pinion gear actuates a rotary cam having a follower which operates the pilot valve controlling the gate motor. Movement of the gate causes movement of the housing of the pilot valve to bring the gate motor to rest at a position corresponding to the speed of the vehicle. A number of differently contoured cams may be provided arranged to be brought selectively into engagement with the rack. Specification 706,035 is referred to.