US4579044A — Two-speed shift valve

Claim 1

Independent Claim 278 words

A selector valve and motor system for a multiple-speed hoist of the type having a drum capable of carrying a load, said drum being powered by at least two fluid motors coupled to a common shaft, comprising: a valve body having a spool bore and at least first, second and third axially spaced fluid cores communicating with said spool bore; said second core communicating with a fluid supply and with a first of said fluid motors; a spool slidable axially within said spool bore, said spool having a recess for coupling any two adjacent fluid cores and sealing surfaces for blocking flow between said adjacent cores; the first core being located between the second and third cores and communicating with a second of said motors; the third core communicating with a loop bypass line for providing a loop flow path through the second motor to remove the second motor from the power input to the drum and enabling the first motor to be operated at an increased speed; said spool having a check valve communicating with the second and first cores when the spool position is such as to otherwise isolate these cores from each other, and operable upon increased pressure from the output of the second motor when driven as a pump in a hoisting condition to open a restricted flow path through the spool from the first to the second core, but blocking flow between the second and first cores when in a lowering condition, said check valve having a first surface adapted to be contacted by fluid in the first core and a second surface adapted to be contacted by fluid in the third core.

Claim 2

Dependent Claim 278 words

A selector valve and motor system for a multiple-speed hoist of the type having a drum capable of carrying a load, said drum being powered by at least two fluid motors coupled to a common shaft, comprising: a valve body having a spool bore and at least first, second and third axially spaced fluid cores communicating with said spool bore; said second core communicating with a fluid supply and with a first of said fluid motors; a spool slidable axially within said spool bore, said spool having a recess for coupling any two adjacent fluid cores and sealing surfaces for blocking flow between said adjacent cores; the first core being located between the second and third cores and communicating with a second of said motors; the third core communicating with a loop bypass line for providing a loop flow path through the second motor to remove the second motor from the power input to the drum and enabling the first motor to be operated at an increased speed; said spool having a check valve communicating with the second and first cores when the spool position is such as to otherwise isolate these cores from each other, and operable upon increased pressure from the output of the second motor when driven as a pump in a hoisting condition to open a restricted flow path through the spool from the first to the second core, but blocking flow between the second and first cores when in a lowering condition, said check valve having a first surface adapted to be contacted by fluid in the first core and a second surface adapted to be contacted by fluid in the third core.

Claim 3

Dependent Claim 44 words

The valve and motor system of claim 1, including a brake valve between the fluid supply and the motors wherein the system, when lowering a load, causes a pressure buildup between the motors and the brake valve to restrict downward movement of the load.

Claim 4

Dependent Claim 48 words

The system of claim 1, said spool having a pilot pressure passage communicating with the second surface of the check valve to maintain the valve in the closed position when lowering a load and when the opposite end of the pilot pressure passage communicates with the third core.

Claim 5

Dependent Claim 142 words

A selector valve comprising a valve body having an axial spool bore, first, second and third fluid cores spaced axially along the core and communicating therewith, said first fluid core being positioned between said second and third fluid cores, a spool slidably positioned in said spool bore, a fluid-pressure activated check valve in said spool and operable to communicate between the first and second cores, fluid passage means also operable to connect the third core with the check valve to exert a pressure on the check valve to close the check valve, wherein the check valve will restrict flow between the first and second cores until the fluid pressure in the first core exceeds the fluid pressure in the third core, at which time the check valve will be operable to vent the flow from the first core to the second core.

Claim 6

Dependent Claim 142 words

A selector valve comprising a valve body having an axial spool bore, first, second and third fluid cores spaced axially along the core and communicating therewith, said first fluid core being positioned between said second and third fluid cores, a spool slidably positioned in said spool bore, a fluid-pressure activated check valve in said spool and operable to communicate between the first and second cores, fluid passage means also operable to connect the third core with the check valve to exert a pressure on the check valve to close the check valve, wherein the check valve will restrict flow between the first and second cores until the fluid pressure in the first core exceeds the fluid pressure in the third core, at which time the check valve will be operable to vent the flow from the first core to the second core.

Claim 7

Dependent Claim 75 words

The valve of claim 4 wherein the check valve has a first surface contacted by fluid in the first core and an opposite second surface, wherein said valve spool includes an axial pilot passage which communicates with the third core and with the opposite second surface of the check valve, and wherein the fluid pressure transmitted through the axial pilot passage bypasses across the first core, which is located intermediate said second and third cores.

Claim 8

Dependent Claim 23 words

The valve of claim 4, said spool containing all of the fluid passages necessary to activate the check valve without additional external porting.

Claim 9

Dependent Claim 45 words

The valve of claim 4 wherein the spool has sealing surfaces, the cores have adjacent lands engaged by the spool-sealing surfaces for providing restriction of flow between the lands and sealing surfaces, and wherein any fluid leakage between cores during steady-state flow conditions is negligible.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1989-03-31	1989-09-30	1990-04-01	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1993-03-31	1993-09-30	1994-04-01	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1997-03-31	1997-09-30	1998-04-01	$7700.00	Window Closed / Lapsed

Two-speed shift valve

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