Low deadband marine hydraulic steering system

Abstract

A lock valve for marine hydraulic steering systems includes a valve body with a spool valve reciprocatingly received in a bore therein. A first port and a second port of the valve are connected to a manual pump. A third port and fourth port are connected to a double acting hydraulic cylinder connected to a rudder or steerable motor. There are valves within the lock valve which normally prevent fluid flowing between the ports so the steering system remains in a fixed position when the helm is released. Fluid can flow from the first port to the third port when the first port is pressurized. A return flow of fluid from the fourth port to the second port is permitted only when the first port is pressurized. When the second port is pressurized, fluid can flow the second port to the fourth port. A return flow of fluid from the third port to the first port is permitted only when the second port is pressurized. The return flow of fluid on at least one side of the valve is controlled by passageways normally blocked by the valve spool which are uncovered when the valve spool is deflected by pressurized fluid at the first port or second port.

What is claimed: .[.1. A lock valve apparatus, comprising lock valve body (19, 19.1, 19.2) having a bore (30, 30.1, 30.2) therein, a first port (21, 21.1, 21.2), a second port (22, 22.1, 22.2), a third port (23, 23.1, 23.2) and a fourth port (24, 24.1, 24.2); 
     
        between..].4. A hydraulic system, comprising: a reversible, manual pump (11) having two pump ports (15, 17); and   a lock valve (18, 18.1, 18.2) having a body (19, 19.1, 19.2) with a bore (30, 30.1, 30.2) having a valve spool (60, 60.1, 60.2) reciprocatingly received therein, a first port (21, 21.1, 21.2, hydraulically connected to one said pump port (15), a second port (22, 22.1, 22.2) connected to another said pump port (17), a third port (23, 23.1, 23.2), a fourth port (24, 24.1, 24.2), first means (40, 40.1, 40.2) for permitting a fluid flow from the first port to the third port when the first port is pressurized, second means (84, 84.1, 84.2, 94, 94.1, 72, 72.1, 90, 90.1, 74.2, 40.2, 52.2) for permitting a fluid flow from the third port to the first port only when the second port is pressurized, the second means including a fourth passageway having a first portion (94, 94.1) extending from the third port to the bore and a second portion (90, 90.1) extending from the bore to the first port, the spool normally blocking fluid flow between the two portions of the fourth passageway, the spool having a passageway which interconnects the two portions of the fourth passageway when the spool is shifted in a direction opposite said one direction, and a fifth passageway (84, 84.1) extending from the second port to the bore adjacent a second end of the spool (64, 64.1) to shift the spool in said opposite direction when the second port is pressurized, third means (84, 84.1, 84.2. 54, 54.1, 56, 56.1, 38.2, 92.2, 96.2) for permitting a fluid flow from the second port to the fourth port when the second port is pressurized, the third means including a sixth passageway (84, 84.1, 56, 56.1) between the second port and the fourth port with a one way valve (54, 54.1) therein, fourth means (82, 82.1, 82.2, 60 60.1, 60.2, 96, 96.1, 96.2, 72, 72.1, 72.2, 92, 92.1, 92.2, 84.2, for permitting a fluid flow from the fourth, port to the second port only when the first port is pressurized, the first means including a first passageway (52, 52.1, 52.2) between the first port and the third port and a one way valve (40, 40.1, 40.2) in the first passageway, the fourth means including a second passageway having a first portion (96, 96.1, 96.2) extending from the fourth port to the bore and a second portion (92, 92.1, 92.2) extending from the bore to the second port, the spool normally blocking fluid flow between the two portions, the spool having a passageway which interconnects the two portions of the second passageway when the spool is shifted in one direction, the fourth means further including a third passageway (82, 82.1, 82.2) extending from the first port to the bore adjacent a first end of the spool (62, 62.1, 62.2) to shift the spool in said one direction when the first port is pressurized; the one way valves being resiliently biased check valves, each said check valve being adjacent one said end of the spool, the spool having end portions &4, 80) configured to open each said check valve when   
     
     
        the spool is shifted towards said each check valve. 5. A hydraulic system as claimed in claim 4, wherein the check valve (40) in the first passageway is positioned to be opened by the spool when the spool is shifted in said opposite direction and the check valve (54) in the sixth passageway is positioned to be opened by the spool when the spool is 
     
     
        shifted in said one direction. 6. A hydraulic system as claimed in claim 5, including means to open the fourth passageway before the check valve in the first passageway is forced open by one said end portion of the spool. 
     
     
         . A system as claimed in claim 5, including means to open the second passageway before the check valve in the fifth passageway is forced open 
     
     
        by another said end portion of the spool. 8. A lock valve, comprising: a valve body (19);   a spool valve (59) in the body including a bore (30) with a valve spool (60) reciprocatingly received therein, the valve spool having first and second ends (62, 64) and first and second end portions (66, 68) adjacent the first and second ends respectively which sealingly engage the bore and a narrow center portion (70), providing a space (72) between the bore and the spool;   a first chamber (36) adjacent the first end of the spool;   a second chamber (38) adjacent the second end of the spool;   a first port (21);   a first passageway (82) extending between the first port and the first chamber;   a second passageway (90) extending between the first port and the bore;   a second port (22);   a third passageway (84) extending between the second port and the second chamber;   a fourth passageway (92) extending between the second port and the bore; a third port (23);   a fourth port (24);   a fifth passageway (52) extending from the first chamber to the third port;   one wall valve (40) in the fifth passageway having a valve element (42) biased towards the first chamber;   a sixth passageway (56) extending from the second chamber to the fourth port;   a one way valve (54) in the sixth passageway having a valve element (55) biased towards the second chamber;   a seventh passageway (94) between the bore and the third port, the first end portion of the spool being between the second passageway and the seventh passageway when the spool is centered, the seventh passageway communicating with the second passageway through the center portion of the spool and the bore when the spool shifts towards the first chamber; and   an eighth passageway (96) extending between the bore and the fourth port, the second end portion of the spool being between the fourth passageway and the eighth passageway when the spool is centered, the eighth passageway communicating with the fourth passageway through the center portion of the spool and the bore when the spool shifts towards the second   
     
     
        chamber. 9. A lock valve as claimed in claim 8, wherein the spool has a projection (74, 80) at each end thereof, the projections being aligned with the one way valves, whereby the fifth passageway is opened when the spool shifts towards the first chamber and the sixth passageway is opened 
     
     
        when the spool shifts towards the second chamber. 10. A valve as claimed in claim 9, wherein the one way valves are ball valves having a valve seat (44), a ball (42, 55) and a coil spring (48) resiliently biasing the ball 
     
     
        adjacent the seat. 11. A valve as claimed in claim 9, wherein the second and seventh passageways are connected together via the space (72) between the narrow center portion (70) of the spool and the bore (30) .[.primer.]. .Iadd.prior .Iaddend.to one said projection (74) opening the fifth 
     
     
        passageway. 12. A valve as claimed in claim 9, wherein the fourth and eighth passageways are connected via the space (72) between the center portion (70) of the spool and the bore (30) prior to one said projection 
     
     
        (80) opening the sixth passageway. .Iadd.13.  A lock valve apparatus comprising: a lock valve body (19) having a bore (30) therein;   a spool (60) having first (62) and second (64) ends and reciprocatingly received in said bore (30);   a spool passageway (72) between said spool (60) and said bore (30);   a first port (21);   a second port (22);   a third port (23);   a fourth port (24);   a first passageway (82) extending from said first port (21) to said first end (62) of said spool (60) for shifting said spool (60) in a first direction when said first port (21) is pressurized;   a second passageway (84) extending from said second port (22) to said second end (64) of said spool (60) for shifting said spool (60) in a second direction when said second port (22) is pressurized;   a first one way valve (40) for permitting fluid flow from said first port (21) to said third port (23) when said first port (21) is pressurized;   a second one way valve (54) for permitting fluid flow from said second port (22) to said fourth port (24) when said second port (22) is pressurized;   a first return passage (96, 92) for returning fluid from said fourth port (24) through said bore (30) to said second port (22) through a port opened by the spool (60) independently from said second one way valve (54) and through said spool passageway (72) when said spool (60) is shifted sufficiently in said first direction to allow the fluid flow through said spool passageway (72);   a second return passage (94, 90) for returning fluid from said third port (23) through said bore (30) to said first port (21) through a port opened by the spool (60) independently from said first one way valve (40) and through said spool passageway (72) when said spool (60) is shifted sufficiently in said second direction to allow the fluid flow through said spool passageway (72); and   a first unseating means (74) on said spool (60) for unseating said first one way valve (40) in response to shifting of said spool (60) in said second direction and second unseating means (80) on said spool (60) for unseating said second one way valve (54) in response to shifting of said spool (60) in said first direction. .Iaddend..Iadd.14. A lock valve apparatus as set forth in claim 13 wherein said first return passage (96, 92) includes a first return passageway (96) extending through lock valve body (19) from said fourth port (24) to said bore (30) and a second return passageway (92) extending through said lock valve body (19) from said bore (30) to said second port (22) and wherein said second return passage (94, 90) includes a third return passageway (94) extending through said lock valve body (19) from said third port (23) to said bore (30) and a fourth return passageway (90) extending through said lock valve body (19) from said bore (30) to said first port (21) thereby bypassing said one way valves (40, 54). .Iaddend..Iadd.15. A lock valve apparatus as set forth in claim 13 wherein said spool (60) includes a first end portion (66) and a second end portion (68) said first (66) and second (68) end portions reciprocatingly received in said bore (30) and connected by a center portion (70) of lesser diameter than said first (66) and second (68) end portions thereby creating said spool passageway (72) between said center portion (70) and said bore (30). .Iaddend..Iadd.16. A lock valve apparatus as set forth in claim 13 wherein said unseating means includes projections (74, 80) on said first (62) and second (64) ends of said spool (60) which are spaced apart from said one-way valves (40, 54) when the spool is centered therebetween. .Iaddend..Iadd.17. A lock valve apparatus as set forth in claim 13 including an orifice restricted flow path (100, 104) for connecting one of said return passages to a reservoir when said spool is shifted in one of said directions. .Iaddend..Iadd.18. A lock valve apparatus as set forth in claim 13 wherein said first one way valve (40) permits fluid flow from said first port (21) to said third port (23) when said first port (21) is pressurized and permits return fluid flow from said third port (23) to said first port (21) when said first unseating means (74) unseats said first one way valve (40) in response to shifting of said spool (60) in said second direction; and wherein said second one way valve (54) permits fluid flow from said second port (22) to said fourth port (24) when said second port (22) is pressurized and permits return fluid flow from said fourth port (24) to said second port (22) when said second unseating means (80) unseats said second one way valve (54) in response to shifting of said spool (60) in said first direction. .Iaddend..Iadd.19. A lock valve apparatus comprising:     a lock valve body (19) having a bore (30) therein;   a spool (60) having first (62) and second (64) ends and reciprocatingly received in said bore (30);   a spool passageway (72) between said spool (60) and said bore (30);   a first chamber (36) adjacent said first end (62);   a second chamber (38) adjacent said second end (64);   a first port (21);   a second port (22);   a third port (23);   a fourth port (24);   a first passageway (82) extending from said first port (21) to said first chamber (36) for subjecting said first end (62) of said spool (60) to fluid pressure for shifting said spool (60) in a first direction when said first port (21) is pressurized,   a second passageway (84) extending from said second port (22) to said second chamber (38) for subjecting said second end (64) of said spool (60) to fluid pressure for shifting said spool (60) in a second direction when said second port (22) is pressurized,   a first one way valve (40) for permitting fluid flow from said first port (21) to said third port (23) when said first port (21) is pressurized;   a second one way valve (54) for permitting fluid flow from said second port (22) to said fourth port (24) when said second port (22) is pressurized;   a first return passage (96, 92) including a first return passageway (96) extending through said lock valve body (19) from said fourth port (24) to said bore (30), through said spool passageway (72), and through a second return passageway (92) extending through said lock valve body (19) from said bore (30) to said second port (22) for returning fluid from said fourth port (24) to said second port (22); said first return passage (96, 92) becoming operative when said spool (60) is shifted sufficiently in said first direction to allow the fluid flow from said first return passageway (96) to communicate with said second return passageway (92) through said spool passageway (72) thereby initially bypassing said second one way valve (54) before said second one way valve (54) opens to allow full open return; and   a second return passage (94, 90) including a third return passageway (94) extending through said lock valve body (19) from said third port (23) to said bore (30), through said spool passageway (72), and through a fourth return passageway (90) extending through said lock valve body (19) from said bore (30) to said first port (21) for returning fluid from said third port (23) to said first port (21); said second return passage (94, 90) becoming operative when said spool (60) is shifted sufficiently in said second direction to allow the fluid flow from said third return passageway (94) to communicate with said fourth return passageway (90) through said pool passageway (72) thereby initially bypassing said first one way valve (40) before said first one way valve (40) opens to allow full open return.   
     
     
        .Iaddend..Iadd.20.  A lock valve apparatus as set forth in claim 19 including a first unseating means (74) on said spool (60) for unseating said first one way valve (40) in response to shifting of said spool (60) in said second direction and second unseating means (80) on said spool (60) for unseating said second one way valve (54) in response to shifting of said spool (60) in said first direction. .Iaddend..Iadd.21. A lock valve apparatus as set forth in claim 20 wherein said unseating means includes projections (74, 80) on said first (62) and second (64) ends of said spool (60) which are spaced apart from said one-way valves (40, 54) when the spool is centered therebetween. .Iaddend..Iadd.22. A lock valve apparatus as set forth in claim 19 wherein a third return passage (56, 84) includes a fifth return passageway (56) extending through said lock valve body (19) from said fourth port (24) to said second chamber (38), through said second chamber (38), and through a sixth return passage way (84) extending through said lock valve body (19) from said second chamber (38) to said second port (22) for returning fluid from said fourth port (24) to said second port (22); said third return passage (56, 84) becoming operative when said second unseating means (80) on said spool (60) unseats said second one way valve (54) in response to shifting of said spool (60) in said first direction to allow the fluid flow from said fifth return passageway (56) to communicate with said sixth return passageway (84) through said second chamber (38) subsequent to fluid flow from said fourth port (24) to said second port (22) via said first return passage (96, 92); and a fourth return passage (52, 82) includes a seventh return passageway (52) extending through said lock valve body (19) from said third port (23) to said first chamber (36), through said first chamber (36), and through an eighth return passageway (82) extending through said lock valve body (19) from said first chamber (36) to said first port (21) for returning fluid from said third port (23) to said first port (21); said fourth return passage (52, 82) becoming operative when said first unseating means (74) on said spool (60) unseats said first one way valve (40) in response to shifting of said spool (60) in said second direction to allow the fluid flow from said seventh return passageway (52) to communicate with said eighth return passageway (82) through said first chamber (36) subsequent to fluid flow from said third port (23) to said first port (21) via said second return passage (94, 90). .Iaddend..Iadd.23. A lock valve apparatus as set forth in claim 19 wherein said spool (60) includes a first end portion (66) and a second end portion (68) said first (66) and second (68) end portions reciprocatingly received in said bore (30) and connected by a center portion (70) of lesser diameter than said first (66) and second (68) end portions thereby creating said spool passageway (72) between said center portion (70) and said bore (30). .Iaddend..Iadd.24. A lock valve apparatus as set forth in claim 19 including an orifice restricted flow path (100, 104) for connecting one of said return passages to a reservoir when said spool is shifted in one of said directions. .Iaddend..Iadd.25. A lock valve apparatus as set forth in claim 19 wherein said first one way valve (40) permits fluid flow from said first port (21) to said third port (23) when said first port (21) is pressurized and permits return fluid flow from said third port (23) to said first port (21) when said first unseating means (74) unseats said first one way valve (40) in response to shifting of said spool (60) in said second direction; and wherein said second one way valve (54) permits fluid flow from said second port (22) to said fourth port (24) when said second port (22) is pressurized and permits return fluid flow from said fourth port (24) to said second port (22) when said second unseating means (80) unseats said second one way valve (54) in response to shifting of said spool (60) in     
     
     
        said first direction. .Iaddend..Iadd.26.  A hydraulic system, comprising: a reversible pump having a first pump port and a second pump port each said pump port either delivering fluid from the pump or receiving returning fluid to the pump;   a lock valve body having a bore therein;   a vent passageway communicating with said bore;   a first port hydraulically connected to said first pump port;   a second port hydraulically connected to said second pump port;   a third port hydraulically connected to a load cylinder;   a fourth port hydraulically connected to said load cylinder;   a spool reciprocatingly received in said bore, said spool having a first end and a second end and said spool having a first end portion and a second end portion wherein said second end portion moves in a first direction when pressurized fluid from said first port acts upon said first end and said first end portion moves in a second direction when pressurized fluid from said second port acts upon said second end;   a spool passageway between said spool and said bore;   a first one wall valve, resiliently biased for permitting fluid flow from said first port to said third port when said first port is pressurized;   a second one way valve resiliently biased for permitting fluid flow from said second port to said fourth port when said second port is pressurized;   a first passageway extending from said first port to said first end of said spool for shifting said spool in said first direction when said first port is pressurized,   a second passageway extending from said second port to said second end of said spool for shifting said spool in said second direction when said second port is pressurized,   a first return passage said first return passage opening to allow fluid flow from said fourth port through said bore to said second port through a port opened by the spool and through said spool passageway when said second end portion is shifted sufficiently in said first direction to allow the fluid flow through said spool passageway wherein said first return passage includes a first return passageway extending through lock valve body from said fourth port to said bore and a second return passageway extending through said lock valve body from said bore to said second port said first return passage being blocked by said second end portion when said second end portion is shifted in said second direction,   a second return passage, said second return passage being open to allow fluid flow from said third port through said bore to said first port through a port opened by the spool and through said spool passageway when said first end portion is shifted sufficiently in said second direction to allow the fluid flow through said spool passageway wherein said second return passage includes a third return passageway extending through said lock valve body from said third port to said bore and a fourth return passageway extending through said lock valve body from said bore to said first port said second return passage being blocked by said first end portion when said first end portion is shifted in said first direction;   wherein fluid returning through said first return passage is prevented from communicating with said vent passageway and fluid returning through said second return passage is prevented from communicating with said vent passageway. .Iaddend..Iadd.27. A hydraulic system as set forth in claim 26 wherein said vent passageway (102) is in said lock valve body. .Iaddend..Iadd.28. A hydraulic system as set forth in claim 27 wherein said vent passageway (102) communicates with said bore through an orifice (104). .Iaddend..Iadd.29. A lock valve apparatus comprising;   a lock valve body having a bore therein;   a spool having first and second ends and reciprocatingly received in said bore;   a spool passageway between said spool and said bore;   a vent passageway (100, 102) communicating with said bore;   a first chamber adjacent said first end;   a second chamber adjacent said second end;   at least one pump port;   at least one cylinder port;   at least one passageway extending from said pump port to said first chamber for subjecting said first end of said spool to fluid pressure for shifting said spool when said pump port is pressurized,   at least one one way valve for permitting fluid flow from said pump port to said cylinder port when said pump port is pressurized;   at least one return passage including a first return passageway extending through said lock valve body from said cylinder port to said bore, through said spool passageway, and through a second return passageway extending through said lock valve body from said bore to said pump port for returning fluid from said cylinder port to said pump port; said return passage becoming operative when said spool is shifted sufficiently to allow the fluid flow from said first return passageway to communicate with said second return passageway through said spool passageway thereby initially bypassing said one way valve   wherein fluid returning through said return passage is prevented from flowing through said vent passageway (100, 102) when said spool has shifted sufficiently to preclude communication between said return passage and said vent passageway. .Iaddend.