Manual disconnect and feathering control for a hydrostatic transmission

Claim 2

In a hydrostatic transmission system having a pump and motor hydraulically interconnected to form a closed circuit unit for transmitting power therethrough, and a reservoir source of fluid at charge pressure, the combination comprising: a first high pressure pilot-operated relief valve communicatively connected across said closed circuit and normally closed to fluid flow between opposite sides of said closed circuit; pilot passage means through said relief valve; high pressure pilot valve means having an inlet and outlet, said outlet being adapted to discharge to the reservoir; pilot control conduit means directly and exclusively connecting said pilot passage means with said inlet to said high pressure pilot valve means; and manually operable means directly connected to said high pressure pilot valve means for incrementally controlling the opening and closing of the latter, said relief valve movable to permit controllable short circuiting fluid pressure in the closed circuit to control power flow through the transmission in response to establishing fluid flow to the reservoir through the pilot passage means.

Claim 3

In a hydrostatic transmission system having a pump and motor hydraUlically interconnected to form a closed circuit unit for transmitting power therethrough and a reservoir source of fluid at charge pressure, the combination comprising: a pair of high pressure pilot-operated relief valves communicatively connected across said closed circuit and normally closed to fluid flow between opposite sides of said closed circuit; each of said relief valves having pilot passage means; high pressure pilot valve means having an inlet and outlet, said outlet being adapted to discharge to the reservoir; pilot control conduit means directly and exclusively connecting said pilot passage means of at least one of said relief valves to said inlet of the high pressure pilot valve means; and manually operable means directly connected to said high pressure pilot valve means for incrementally controlling the opening and closing of the latter; at least one of said relief valves being movable to permit short circuiting fluid pressure in the closed circuit to infinitely vary power flow through the transmission in response to establishing fluid flow to the reservoir through the pilot passage means.

Claim 4

In a hydrostatic transmission system having a pump and motor hydraUlically interconnected to form a closed circuit unit for transmitting power therethrough and a reservoir source of fluid at charge pressure, the combination comprising: a pair of high pressure pilot-operated relief valves communicatively connected across said closed circuit and normally closed to fluid flow between opposite sides of said closed circuit; each of said relief valves having pilot passage means; high pressure pilot valve means having an inlet and outlet, said outlet being adapted to discharge to the reservoir; pilot control conduit means directly and exclusively connecting said pilot passage means of at least one of said relief valves to said inlet of the high pressure pilot valve means; and manually operable means directly connected to said high pressure pilot valve means for incrementally controlling the opening and closing of the latter; at least one of said relief valves being movable to permit short circuiting fluid pressure in the closed circuit to infinitely vary power flow through the transmission in response to establishing fluid flow to the reservoir through the pilot passage means.

Claim 5

In a hydrostatic transmission system according to claim 2, wherein: said high pressure pilot valve means includes first and second valves; and said pilot control conduit means includes first and second conduits, said first and second conduits being connected to provide fluid communication between each of said pilot passage means and the first and second valves respectively.

Claim 6

In a hydrostatic transmission system according to claim 3 wherein: actuating block means interconnects said first and second valves, and said manually operable means is connected to said block means to control the opening and closing of both of said first and second valves.

Claim 7

In a hydrostatic transmission system having a variable displacement pump and a motor hydraulically interconnected to form a closed circuit unit for transmitting power therethrough, and a reservoir source of fluid at charge pressure, the combination comprising: a pair of high pressure pilot-operated relief valves communicatively connected across said closed circuit and normally closed to fluid flow between opposite sides of said closed circuit; each of said relief valves having pilot passage means; high pressure pilot valve means having an inlet and outlet, said outlet being adapted to discharge to the reservoir; pilot control conduit means directly connecting both of said pilot passage means to said inlet; check valve means associated with each of said relief valves for permitting hydraulic fluid flow from said relief valves into said conduit means only; and manually operable means associated with said high pressure pilot valve means for selectively controlling the opening and closing of the latter; said relief valves being movable to permit short circuiting fluid pressure in the closed circuit to incrementally vary power flow through the transmission in response to establishing fluid flow to the reservoir through the pilot passage means.

Claim 8

In a hydrostatic transmission system having a variable displacement pump and a motor hydraulically interconnected to form a closed circuit unit for transmitting power therethrough, and a reservoir source of fluid at charge pressure, the combination comprising: a pair of high pressure pilot-operated relief valves communicatively connected across said closed circuit and normally closed to fluid flow between opposite sides of said closed circuit; each of said relief valves having pilot passage means; high pressure pilot valve means having an inlet and outlet, said outlet being adapted to discharge to the reservoir; pilot control conduit means directly connecting both of said pilot passage means to said inlet; check valve means associated with each of said relief valves for permitting hydraulic fluid flow from said relief valves into said conduit means only; and manually operable means associated with said high pressure pilot valve means for selectively controlling the opening and closing of the latter; said relief valves being movable to permit short circuiting fluid pressure in the closed circuit to incrementally vary power flow through the transmission in response to establishing fluid flow to the reservoir through the pilot passage means.

Claim 9

In a hydrostatic transmission system having a pump and motor hydraulically interconnected to form a closed circuit unit for transmitting power therethrough, at least one of said pump and motor having a variable displacement, and a reservoir source of fluid at charge pressure, the combination comprising: a first high pressure pilot-operated relief valve communicatively connected across said closed circuit and normally closed to fluid flow between opposite sides of said closed circuit; pilot passage means associated with said relief valve; high pressure pilot valve means having an inlet and outlet, said outlet being adapted to discharge to the reservoir; pilot control conduit means directly and exclusively connecting said pilot passage means with said inlet to said high pressure pilot valve means; and manually operable means directly connected to said high pressure pilot vAlve means for selectively controlling the opening and closing of the latter, said relief valve movable to permit incremental short circuiting fluid pressure in the closed circuit to vary power flow through the transmission in response to establishing fluid flow to the reservoir through the pilot passage means.

Claim 10

In a hydrostatic transmission system having a pump and motor hydraulically interconnected to form a closed circuit unit for transmitting power therethrough, at least one of said pump and motor having a variable displacement, and a reservoir source of fluid at charge pressure, the combination comprising: a first high pressure pilot-operated relief valve communicatively connected across said closed circuit and normally closed to fluid flow between opposite sides of said closed circuit; pilot passage means associated with said relief valve; high pressure pilot valve means having an inlet and outlet, said outlet being adapted to discharge to the reservoir; pilot control conduit means directly and exclusively connecting said pilot passage means with said inlet to said high pressure pilot valve means; and manually operable means directly connected to said high pressure pilot vAlve means for selectively controlling the opening and closing of the latter, said relief valve movable to permit incremental short circuiting fluid pressure in the closed circuit to vary power flow through the transmission in response to establishing fluid flow to the reservoir through the pilot passage means.

Claim 11

In a hydrostatic transmission system having a pump and motor hydraulically interconnected to form a closed circuit unit for transmitting power therethrough, at least one of said pump and motor having a variable displacement, and a reservoir source of fluid at charge pressure, the combination comprising: a pair of high pressure pilot-operated relief valves communicatively connected across said closed circuit and normally closed to fluid flow between opposite sides of said closed circuit; each of said relief valves having pilot passage means; high pressure pilot valve means having an inlet and outlet, said outlet being adapted to discharge to the reservoir; pilot control conduit means directly and exclusively connecting said pilot passage means of at least one of said relief valves to said inlet of the high pressure pilot valve means; and manually operable means directly connected to said high pressure pilot valve means for incrementally controlling the opening of the latter; at least one of said relief valves being movable to permit short circuiting fluid pressure in the closed circuit to vary control power flow through the transmission in response to establishing fluid flow to the reservoir through the pilot passage means.

Claim 12

In a hydrostatic transmission system having a pump and motor hydraulically interconnected to form a closed circuit unit for transmitting power therethrough, at least one of said pump and motor having a variable displacement, and a reservoir source of fluid at charge pressure, the combination comprising: a pair of high pressure pilot-operated relief valves communicatively connected across said closed circuit and normally closed to fluid flow between opposite sides of said closed circuit; each of said relief valves having pilot passage means; high pressure pilot valve means having an inlet and outlet, said outlet being adapted to discharge to the reservoir; pilot control conduit means directly and exclusively connecting said pilot passage means of at least one of said relief valves to said inlet of the high pressure pilot valve means; and manually operable means directly connected to said high pressure pilot valve means for incrementally controlling the opening of the latter; at least one of said relief valves being movable to permit short circuiting fluid pressure in the closed circuit to vary control power flow through the transmission in response to establishing fluid flow to the reservoir through the pilot passage means.

Claim 13

In a hydrostatic transmission system according to claim 7, wherein: said high pressure pilot valve means includes first and second valves; and said pilot control conduit means includes first and second conduits, said first and second conduits being connected to provide fluid communication between each of said pilot passage means and the first and second valves respectively.

Claim 14

In a hydrostatic transmission system according to claim 8 wherein: actuating block means interconnects said first and second valves, and said manually operable means is connected to said block means to control the opening and closing of both of said first and second valves.

Claim 15

In a hydrostatic transmission system having a pump and motor hydraulically interconnected to form a closed circuit unit for transmitting power therethrough, at least one of said pump and motor having a variable displacement, and a reservoir source of fluid at charge pressure, the combination comprising: a pair of high pressure pilot-operated relief valves communicatively connected across said closed circuit and normally closed to fluid flow between opposite sides of said closed circuit; each of said relief valves having pilot passage means; high pressure pilot valve means having an inlet and outlet, said outlet being adapted to discharge to the reservoir; pilot control conduit means directly connecting both of said pilot passage means to said inlet; check valve means associated with each of said relief valves for permitting hydraulic fluid flow from said relief valves into said conduit means only; and manually operable means associated with said high pressure pilot valve means for selectively controlling the opening and closing of the latter; said relief valves being movable to permit variable power flow from the pump to the motor in response to establishing fluid flow to the reservoir through the pilot passage means.

Claim 16

In a hydrostatic transmission system having a pump and motor hydraulically interconnected to form a closed circuit unit for transmitting power therethrough, at least one of said pump and motor having a variable displacement, and a reservoir source of fluid at charge pressure, the combination comprising: a pair of high pressure pilot-operated relief valves communicatively connected across said closed circuit and normally closed to fluid flow between opposite sides of said closed circuit; each of said relief valves having pilot passage means; high pressure pilot valve means having an inlet and outlet, said outlet being adapted to discharge to the reservoir; pilot control conduit means directly connecting both of said pilot passage means to said inlet; check valve means associated with each of said relief valves for permitting hydraulic fluid flow from said relief valves into said conduit means only; and manually operable means associated with said high pressure pilot valve means for selectively controlling the opening and closing of the latter; said relief valves being movable to permit variable power flow from the pump to the motor in response to establishing fluid flow to the reservoir through the pilot passage means.