Fluid makeup system

Claim 2

In a closed-loop fluid-control circuit of the type which includes a double-acting cylinder having a piston and a piston rod extending therefrom operable from a reversible fluid supply source which alternately conveys fluid under pressure to a back side of the piston and then to the rod side of the piston to effect extension and retraction movement of said rod, the improved makeup system comprising, a source of makeup fluid under pressure, a flow-control valve having an inlet passage and a pair of selectable outlet passages and having a directional flow valve member therein movable from a central flow-blocking position to a pair of flow-permitting positions selectably connecting said inlet passage with one of said outlet passages, means connecting said valve in the fluid circuit across said cylinder with said movable member being responsive to fluid pressures applied to said cylinder, and means connecting said makeup fluid source to said inlet passage so that during extension of the rod the valve member will move in one of said directions and apply makeup fluid from said source through one of said outlet passages to the rod side of said circuit and during retraction of the rod the valve member will move in the other direction and drain makeup fluid from the back side of said circuit through the other outlet passage.

Claim 3

In a closed-loop fluid-control circuit of the type which includes a double-acting cylinder having a piston with a single-actuating rod and a reversible fluid supply source which alternately conveys fluid to a back side of said cylinder and then to the rod side of said cylinder to effect extension and retraction movement of said rod, the improved makeup system comprising, a source of makeup fluid remote from said circuit, a makeup pump remote from said circuit for conveying fluid from said source to said circuit, a directional flow valve having an inlet passage and selectable first and second outlet passages, said passages being interrupted by a cylindrical bore, means at the ends of said bore connecting said valve in the circuit across said cylinder, a spool in said bore responsive to pressures acting at opposite ends thereof to move from a central flow-blocking position to a first position when said rod is extended to communicate said inlet passage with said first outlet passage and receive makeup fluid and replenish the circuit and then to move to a second position when said rod is retracted to communicate said inlet passage with said second outlet passage to drain makeup fluid from the circuit.

Claim 4

In a closed-loop fluid-control circuit of the type which includes a double-acting cylinder having a piston with a single-actuating rod and a reversible fluid supply source which alternately conveys fluid to a back side of said cylinder and then to the rod side of said cylinder to effect extension and retraction movement of said rod, the improved makeup system comprising, a source of makeup fluid remote from said circuit, a makeup pump remote from said circuit for conveying fluid from said source to said circuit, a directional flow valve having an inlet passage and selectable first and second outlet passages, said passages being interrupted by a cylindrical bore, means at the ends of said bore connecting said valve in the circuit across said cylinder, a spool in said bore responsive to pressures acting at opposite ends thereof to move from a central flow-blocking position to a first position when said rod is extended to communicate said inlet passage with said first outlet passage and receive makeup fluid and replenish the circuit and then to move to a second position when said rod is retracted to communicate said inlet passage with said second outlet passage to drain makeup fluid from the circuit.

Claim 5

The makeup system of claim 2 including a relief valve connected between said makeup pump and the flow-control valve for allowing makeup fluid drained from the circuit to be expelled to said source for recirculation through said makeup pump.

Claim 6

The makeup system of claim 2 wherein said makeup pump operates continuously and the makeup fluid conveyed thereby is blocked by the flow-control valve when fluid is delivered to the rod side of the cylinder by the reversible fluid-supply source.

Claim 7

The makeup system of Claim 2 wherein said directional flow valve is remote from said closed circuit.

Claim 8

In a closed-loop fluid circuit of the type which includes a double acting cylinder having a piston with a single actuating rod and a reversible fluid supply source for alternately conveying fluid to a back side of the cylinder and then to the rod side of the cylinder to effect extension and retraction movement of said rod, the improved makeup system which comprises, a source of makeup fluid remote from said circuit, a continuous makeup pump remote from said circuit for conveying fluid from said source to said circuit, a shuttle valve having an inlet passage connected to said makeup pump, a first outlet passage connected to the rod side of the cylinder, and a second outlet passage connected to the back side of the cylinder, means connecting said shuttle valve in the circuit across said cylinder, said shuttle valve having a cylindrical bore interrupting said passages and having a movable spool therein responsive to fluid pressures applied to said cylinder to selectively register said inlet passage alternately with the first and then the second outlet passage to first add makeup fluid to the circuit and then block makeup fluid and dump fluid from the circuit, and a relief valve connected between said makeup pump and said inlet passage and adapted to return makeup fluid blocked by the shuttle valve and fluid drained from the circuit to the source for recirculation through the makeup pump.

Claim 9

In a closed-loop fluid circuit of the type which includes a double acting cylinder having a piston with a single actuating rod and a reversible fluid supply source for alternately conveying fluid to a back side of the cylinder and then to the rod side of the cylinder to effect extension and retraction movement of said rod, the improved makeup system which comprises, a source of makeup fluid remote from said circuit, a continuous makeup pump remote from said circuit for conveying fluid from said source to said circuit, a shuttle valve having an inlet passage connected to said makeup pump, a first outlet passage connected to the rod side of the cylinder, and a second outlet passage connected to the back side of the cylinder, means connecting said shuttle valve in the circuit across said cylinder, said shuttle valve having a cylindrical bore interrupting said passages and having a movable spool therein responsive to fluid pressures applied to said cylinder to selectively register said inlet passage alternately with the first and then the second outlet passage to first add makeup fluid to the circuit and then block makeup fluid and dump fluid from the circuit, and a relief valve connected between said makeup pump and said inlet passage and adapted to return makeup fluid blocked by the shuttle valve and fluid drained from the circuit to the source for recirculation through the makeup pump.