Patent GB-1434663-A (GB)
Title: Load balancers
IPC: B66C23/00
Filed: 1974-03-01
Abstract: 1434663 Load balancing apparatus CONCO Inc 1 March 1974 [4 June 1973] 9437/74 Heading B8B A load balancer for supporting a load for manual movement while maintaining the load in balance, comprises a fluid piston and cylinder 30 operatively connected to a parallelogram linkage load support structure 10, 16, 17, 18, the piston and cylinder being controlled by a fluid circuit including a selected pressure regulating valve 52, 53 or 54 to main a substantially constant pressure in the cylinder in all positions of the load to balance the load, and balance over-ride means 85 for by-passing the pressure regulating valve and temporarily modifying the pressure in the cylinder 30 to raise a load on the balancer. The parallelogram linkage is pivoted at 26 to rigid structure 25 which pivotally supports the piston and cylinder 30, the pistonrod 32 of which is pivoted to plate structure 33 having a slot for vertical guiding engagement with rollers 34 on the structure 25, a horizontal slot 35 in the structure 33 being engageable with rollers 20 for applying the balancing forces to the parallelogram structure. Pressurized air is supplied along line 43 through a pressure regulator 42 and three position control valve 44 to one side of the piston in the cylinder 30 and the cylinder on the other side of the piston is exhaustable through a velocity responsive valve 49. The valve 44 has a central balance position blocking the cylinder supply line 45, a position in which the supply line 43 is communicated with the line 45 to supply air to the cylinder 30 in the load raising direction, and a position in which the cylinder is placed in communication with a line 46 which exhausts through a velocity responsive valve 50 facilitating load lowering. The position of the valve 44 is controlled by pilot lines 61 and 60, the pressure in line 61 being the prevailing pressure in the cylinder 30 whereas the pressure in line 60 is a pressure preselected in accordance with the load to be balanced. The pressure for line 60 is set by pressure regulation valves 52, 53 and 54 one of which is manually selected through valves 70, 71 at any one time, depending on the range of loads being handled. The balance over-ride means 85 is situated in circuit between the output line 64 from the pressure regulator valves 52, 53 and 54 and the control valve 44, and normally permits the regulated pressure to pass through valves 66, 67 in the means 85, to the valve 44. Upon manual actuation of the valves 66 or 67, the said output line 64 is isclated from the valve 44 and either a bias regulator 86 is communicated with the valve 44 when the valve 66 is selected or the valve 44 is exhausted when the valve 67 is selected, to respectively power raise or exhaust lower the load, the balance condition being re-established as soon as the valve 66 or 67 is released. The pressure supplied by the bias regulator 86 is controlled through a pilot line 88 which receives the prevailing balance pressure in line 64 plus an adjustable spring pressure 90. The velocity responsive valves 49 and 50 prevent rapid discharge of air from either side of the piston in cylinder 30 to control the rate of descent or ascent of the load.