Lock valve flow control arrangement

In combination, an operating table having a top for supporting a patient, means for adjusting the top for variably positioning the patient including at least one double-acting hydraulic cylinder, a reservoir for hydraulic fluid, a foot pedal operated hydraulic pump having an inlet receiving fluid from the reservoir and an outlet for delivery of fluid under pressure on operation of the pedal, a control valve having an inlet receiving fluid from the pump outlet, an outlet for returning fluid to the reservoir, and first and second transfer ports, said control valve being adapted to be set in a closed position blocking the transfer ports, a first open position for delivery of fluid under pressure through said first port and venting of the second port to the reservoir and in a second open position for delivery of fluid under pressure through said second port and venting of said first port to the reservoir, and flow control means in the system between said control valve and said cylinder comprising means providing a first passage interconnecting said first port and one end of said cylinder and a second passage interconnecting said second port and the other end of the cylinder, a first check valve in the first passage arranged to open in response to setting of the control valve in its said first open position and operation of the pump for delivery of fluid under pressure to said one end of the cylinder, a second check valve in the second passage arranged to open in response to setting of the control valve in its second position and operation of the pump for delivery of fluid under pressure to said other end of the cylinder, means responsive to delivery of fluid under pressure to the first check valve to open the second check valve and responsive to delivery of fluid under pressure to the second check valve to open the first check valve, first pressure responsive flow regulating means in said first passage between the first check valve and said one end of the cylinder responsive solely to pressure from said one end of the cylinder to effect flow regulation for effecting relatively smooth flow of fluid from said one end of the cylinder to the reservoir when said control valve is set in its second position, and second pressure responsive flow regulating means in said second passage between the second check valve and said other end of the cylinder responsive solely to pressure from said other end of the cylinder of effect flow regulation for effecting relatively smooth flow of fluid from said other end of the cylinder to the reservoir when said control valve is set in its first position.