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Abstract

A flow control system which is capable of selectively operating at least one pneumatic cylinder between high and low pressures. The flow control system allows the cylinder to engage a workpiece while under the influence of the lower pressure so as to minimize the impact on the workpiece, and thereafter subjects the cylinder to the higher pressure so as to increase the clamping load on the workpiece. Flow control is achieved by controlling the flow of high pressure air from a suitable source with a pilot-operated five ported four-way two-position control valve, a pressure regulator and a unidirectional flow control valve having an adjustable orifice. The pressure regulator is connected to one outlet port of the control valve such that the cylinder is initially supplied with air at the lower pressure when the control valve is in its normal operating position. Once the cylinder engages the workpiece, air pressure to the pilot sufficiently increases to spool the control valve to an actuated position, in which the higher air pressure provided by the supply source is delivered through the control valve to the cylinder. As a result, the clamping load of the cylinder on the workpiece is increased. The flow control system is particularly suitable for operating pneumatic cylinders which are used to actuate the electrodes of a welding gun.

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First Claim