Hydraulic actuating system for hydraulically operated bending machine

Claim 2

In combination, a hydraulic motor of the reciprocating type which includes a vertically extending cylinder divided interiorly by a movable piston into a drive chamber and a discharge chamber, means for controlling the operation of said motor comprising: a tank adapted to contain a supply of hydraulic fluid; a feed conduit connecting the drive chamber to a pump, the latter being operative to pump hydraulic fluid from said tank through said feed conduit into the drive chamber to cause relative movement of the piston in one direction relative to the cylinder; a bleed conduit leading from the discharge chamber to said tank; check valve means in said bleed conduit for preventing the flow of hydraulic fluid in one direction from the discharge chamber to said tank while permitting flow of hydraulic fluid in the opposite direction through said bleed conduit; self-acting control valve means connected by means of intermediate conduits to said bleed conduit, feed conduit and said tank, said selfacting control valve means being movable in response to fluid pressure in said feed conduit between a a first position establishing a connection between the discharge chamber and said feed conduit and drive chamber, and a second position establishing a connection between the discharge chamber and said tank; and, operating valve means for interrupting the flow of hydraulic fluid from said pump to the drive chamber and for connecting the drive chamber to said tank, thereby permitting the piston to move under the influence of gravity in the opposite direction relative to said cylinder, which movement in the opposite direction will in turn create a negative pressure in the discharge chamber causing fluid to be drawn from said tank through said bleed conduit past said check valve means into the discharge chamber.

Claim 3

In combination, a hydraulic motor which includes a vertically extending cylinder divided by means of a piston into drive and discharge chambers, a piston rod extending from the piston through the discharge chamber and the cylinder end wall, means for controlling the operation of said motor comprising: a tank for containing a supply of hydraulic fluid; a pump for pumping hydraulic fluid from said tank through a feed conduit to the drive chamber; a bleed conduit leading from the discharge chamber to said tank; a check valve in said bleed conduit for preventing fluid flow from the discharge chamber back through said bleed conduit to said tank; an operating valve in said feed conduit; a by-pass conduit connected at one end to said operating valve and having its other end iN communication with said tank, said operating valve being adjustable between a feed position permitting flow of fluid from said pump through said feed conduit to the drive chamber, and a by-pass position permitting flow of fluid from said pump through said by-pass conduit back to said tank while simultaneously permitting flow of fluid from the drive chamber back through said feed conduit to said tank; self-acting control valve means having a valve housing with an interior valve chamber; first, second and third ports extending through said housing in communication with said valve chamber; a first intermediate conduit connected at one end to said bleed conduit between the discharge chamber and said check valve and at the other end to said first port; a second intermediate conduit connected at one end to said second port and having its other end in communication with said tank; a third intermediate conduit connected at one end to said third port and at the other end to said feed conduit between said drive chamber and said operating valve; spool means reciprocally contained within the interior valve chamber of said control valve means; spring means for urging said spool means into a first position at which said spool means cooperates with said housing to establish a connection via said valve chamber between said first and third ports while closing off said second port, whereby when said operating valve is in said feed position, the hydraulic fluid pumped from said tank by said pump will flow through said feed conduit to the drive chamber, thereby causing movement of said piston relative to said cylinder in one direction, with the fluid exiting from the discharge chamber being caused to also flow into the drive chamber until such time as the pressure in said feed conduit is sufficient to act on said spool means to overcome the force of said spring means, at which time said spool means will be moved to a second position closing said third port and establishing a connection via said valve chamber between said first and second ports; and, whereby upon adjustment of said operating valve to said by-pass position, said piston will be caused to move under the influence of gravity in the opposite direction relative to said cylinder, thus forcing fluid from the drive chamber back through said feed conduit to said tank while simultaneously creating a negative pressure in the discharge chamber to draw fluid from said tank through said check valve and bleed conduit into the discharge chamber.

Claim 4

In combination, a hydraulic motor which includes a vertically extending cylinder divided by means of a piston into drive and discharge chambers, a piston rod extending from the piston through the discharge chamber and the cylinder end wall, means for controlling the operation of said motor comprising: a tank for containing a supply of hydraulic fluid; a pump for pumping hydraulic fluid from said tank through a feed conduit to the drive chamber; a bleed conduit leading from the discharge chamber to said tank; a check valve in said bleed conduit for preventing fluid flow from the discharge chamber back through said bleed conduit to said tank; an operating valve in said feed conduit; a by-pass conduit connected at one end to said operating valve and having its other end iN communication with said tank, said operating valve being adjustable between a feed position permitting flow of fluid from said pump through said feed conduit to the drive chamber, and a by-pass position permitting flow of fluid from said pump through said by-pass conduit back to said tank while simultaneously permitting flow of fluid from the drive chamber back through said feed conduit to said tank; self-acting control valve means having a valve housing with an interior valve chamber; first, second and third ports extending through said housing in communication with said valve chamber; a first intermediate conduit connected at one end to said bleed conduit between the discharge chamber and said check valve and at the other end to said first port; a second intermediate conduit connected at one end to said second port and having its other end in communication with said tank; a third intermediate conduit connected at one end to said third port and at the other end to said feed conduit between said drive chamber and said operating valve; spool means reciprocally contained within the interior valve chamber of said control valve means; spring means for urging said spool means into a first position at which said spool means cooperates with said housing to establish a connection via said valve chamber between said first and third ports while closing off said second port, whereby when said operating valve is in said feed position, the hydraulic fluid pumped from said tank by said pump will flow through said feed conduit to the drive chamber, thereby causing movement of said piston relative to said cylinder in one direction, with the fluid exiting from the discharge chamber being caused to also flow into the drive chamber until such time as the pressure in said feed conduit is sufficient to act on said spool means to overcome the force of said spring means, at which time said spool means will be moved to a second position closing said third port and establishing a connection via said valve chamber between said first and second ports; and, whereby upon adjustment of said operating valve to said by-pass position, said piston will be caused to move under the influence of gravity in the opposite direction relative to said cylinder, thus forcing fluid from the drive chamber back through said feed conduit to said tank while simultaneously creating a negative pressure in the discharge chamber to draw fluid from said tank through said check valve and bleed conduit into the discharge chamber.