GB621118A - Improvements in or relating to hydraulic load-packing and load-discharging apparatusfor refuse vehicle bodies and similar load-containers - Google Patents

Abstract

621,118. Hydraulic machines. BURGESS, A. F. (Duis, G. A.). Aug. 23, 1945, No. 21596. [Class 69 (ii)] [Also in Group XXX] A hydraulic piston and cylinder 31, 30, Fig. 2, for reciprocating a load packing and discharging arm along the length of a vehicle body (see Group XXX) is controlled by a reciprocating valve member under the influence of two magnetic fields which are normally controllable to initiate the reciprocation and are also responsive to pressure in the hydraulic system to initiate the reverse arm movement. The valve is a solenoid controlled combined inter-connected inlet and outlet valve for selectively supplying hydraulic fluid from a gear pump 46, 47 to either side of the piston 31 and comprises a housing 52 with high and low-pressure passages 53, 54, a valve stem 59 having lateral projections 60, 61 by which fluid is directed along passages 56, or 57 to the piston or along a return byepass 58 to a reservoir 50 according to the position of the valve stem. Fixed to a longitudinal projection 66 on the valve stem is an armature 67 which when the valve stem is in the neutral position is spring-biassed to assume a position mid-way between a " working solenoid 71 and a " return " solenoid 72 on separate circuits. The "working" solenoid circuit comprises a battery 83, Fig. 5, a normally closed pressure actuated switch 75 which is opened only at the end of the working piston stroke when the pressure rises to a sufficiently high value, a limit switch 76 in parallel with a manuallyoperated push-switch 90, and safety switches 96, 98. The " return " solenoid circuit comprises the battery 83 and safety switches 96, 98 and a limit switch 77. Both limit switches are simultaneously operated by a member 80 on the piston rod 33 and remain closed except for a short time at the beginning and end of the working and return piston strokes respectively. To operate the piston from its stationary position at the beginning of the working stroke and with the valve in the neutral position and limit switches 76, 77 open and the pressure switch and safety switches closed, the manual switch 90 is closed to energize the working solenoid which actuates the valve to allow access of pressure fluid to the working face of the piston. The limit switches become closed shortly after the beginning of the working stroke and both solenoids become energized, but as they are of equal power and as the armature is already within the solenoid 71 no further movement occurs. At the end of the working stroke, pressure in the cylinder 30 rises sufficiently to open the switch 75 and so cause a break in the working solenoid circuit and so put the armature under the influence of the " return " solenoid whereon the valve is actuated to reverse the flow of pressure fluid. On commencement of the return stroke, pressure at the switch 75 falls causing the switch to close and at the end of the cycle both limit switches 76, 77 are opened and both solenoid circuits are broken so that the valve then assumes its neutral position and the piston cannot be restarted until the switch 90 is reoperated. Specification 601,176 is referred to.