Apparatus and method for pre-filling a hydraulic motor

Hydraulic press apparatus comprised of:

• a hydraulic motor having a piston operable from a retracted position through a closure stroke to a work position and beyond that through a compression stroke to a fully closed position and back again to the retracted positon;
• means for operating the piston from its retracted position through its closure stroke to its work position and from its fully closed position to its retracted position;
• means including a hydraulic power unit with a hydraulic fluid tank for supplying hydraulic fluid at sufficient presssure to drive the piston through its compression stroke;
• a reservoir for holding a supply of hydraulic fluid for use in pre-filling the hydraulic motor, said reservoir having a gas inlet for connection to a compressed gas source, a pre-fill fluid port connected to the power input side of the hydraulic motor and a hydraulic fluid drain outlet for discharging excess pre-fill fluid;
• and
• control means connected in the gas inlet, the hydraulic fluid drain outlet and the pre-fill port and to the motor for causing hydraulic fluid to be transmitted from the reservoir to the hydraulic motor under pressur from the compressed gas source as the piston is operated through its closure stroke and for allowing hydraulic fluid to be discharged from the motor to the reservoir as the piston is retracted with any excess fluid being discharged from the reservoir under compressed gas pressure through the hydraulic fluid drain outlet.

A method for operating a hydraulic motor of the type having a piston which is advanceable from a retracted position through a closure stroke to a work position and beyond that through a compression stroke to a fully closed position and back through a retraction stroke to its retracted position comprising the steps of:

• advancing the piston through its closure stroke;
• supplying from a reservoir a predetermined volume of pre-fill hydraulic fluid under reatively low pressure from a compressed gas source to the power input side of the motor as the closure stroke is executed;
• driving the piston with relatively high pressure hydraulic fluid through its compression stroke;
• retracting the piston through its retracting stroke;
• discharging into the reservoir hydraulic fluid displaced from the motor as the piston executes its retraction stroke;
• reserving from the displaced hydraulic fluid substantially the same volume as that which was supplied to the motor during the closure stroke;
• and
• expelling from the reservoir under pressure created by compressed gas any excess volume hydraulic fluid.

In combination with a hydraulic motor of the type haivng a hydraulic power unit with a hydraulic fluid tank and a piston advanceable from a retracted position through a closure stroke to a work position and beyond that through a compression stroke to a fully closed position and back through a retraction stroke to its retracted position comprising:

• a reservoir for holding a supply of hydraulic fluid for use in pre-filling the motor during its closure stroke and collecting hydraulic fluid displaced by the motor during its retraction stroke, said reservoir having a pfe-fill fluid port connected to the power input side of the motor and a hydraulic fluid drain output for discharging excess volume hydraulic fluid;
• means for controllably pressurizing and de-pressurizing the internal space of the reservoir;
• and
• control means connected in the hydraulic fluid drain outlet and the pre-fill fluid port and connected to the motor and the pressurizing and de-pressurizing means for causing hydraulic fluid to be transmitted to the motor under pressure as the piston executes its closure stroke and for causing hydraulic fluid displaced by the motor during its retraction stroke to be transmitted to the reservoir with any excess volume hydraulic fluid being expeIled under pressure through the hydraulic fluid drain outlet.