Hydraulic control system with locking valve to prevent accidental or unauthorized lowering of a tractor implement

Claim 2

A hydraulic system comprising: a source of fluid pressure including an assocIated reservoir, a reversible hydraulic motor having a pair of alternate inlets and operatively connected to an elevatable load, a control valve means operatively connected to said source of fluid pressure and to said fluid reservoir and having a pair of delivery ports, a locking valve having a bore, a receiving port opening into said bore, a motor port opening into said bore, and a shiftable flow control element having a first control position in which fluid is permitted to flow between said receiving port and said motor port and having a second control position in which fluid is prevented from flowing between said supply and motor ports, a first passage means interconnecting one of said alternate inlets and said motor port, said first passage means being subject to pressurization of fluid in said motor by the weight of said load when the latter is elevated, a second passage means interconnecting one of said delivery ports with said receiving port, a third passage means interconnecting the other of said alternate inlets and the other of said delivery ports, first hydraulic actuator means operatively associated with said flow control element and connected in fluid communication with said first passage means, said first hydraulic actuator being operable to move said flow control element to its second control position when said second and third passage means are not pressurized by delivery of fluid from said source and the weight of said load on said motor pressurizes the fluid in said first passage means, second hydraulic actuator means operatively associated with said flow control element and in fluid communication with said second passage means, said second actuator being operable to shift said flow control element from its second control position to its first control position when the fluid pressure in said second passage means has a predetermined relationship to the pressure in said first actuator means, and third hydraulic actuator means operatively associated with said flow control element and in fluid communication with said third passage means, said third actuator being operable to shift said flow control element from its second control position to its first control position when the fluid pressure in said third passage means has a predetermined relationship to the pressure in said first actuator means.

Claim 3

The invention of claim 1 wherein said control valve has float, lower, hold, and raise positions and wherein said locking valve includes resilient biasing means urging said control element toward its first control position.

Claim 4

A hydraulic system comprising: a source of fluid pressure including an associated reservoir, a reversible hydraulic motor operatively connected to an elevatable load and having a pair of alternate inlets, a control valve means operatively connected to said source of fluid pressure and to said fluid reservoir and having a pair of delivery ports, a locking valve having a bore, a pair of receiving ports in said bore, a pair of motor ports in said bore, and a shiftable flow control element having a first control position in which fluid is permitted to flow between one of said receiving ports and one of said motor ports and between the other of said receiving ports and the other of said motor ports and having a second control position in which fluid is prevented from flowing between said supply and motor ports, a first passage means interconnecting one of said alternate inlets and one of said motor ports, said first passage means being subject to pressurization of fluid in said motor by the weight of said load when the latter is elevated by said motor, a second passage means interconnecting the other of said alternate inlets and the other of said motor ports, third and fourth passage means interconnecting said delivery ports with said receiving ports, respectively, first hydraulic actuator means operatively associated with said Flow control element and in fluid communication with said first passage means, said first actuator means being operable to shift said flow control element to its second control position when said third and fourth passage means are not supplied pressurized fluid by said source and the weight of said load is imposed on said motor thereby pressurizing the fluid in said first passage means, second hydraulic actuator means operatively associated with said flow control element and in fluid communication with said third passage means, said second actuator means being operable to shift said flow control element from its second control position to its first control position when the fluid pressure in said third passage means has a predetermined relationship to the fluid pressure in said first actuator means, and third hydraulic actuator means operatively associated with said flow control element and connected in fluid communication with said fourth passage means, said third hydraulic actuator means being operable to move said flow control element to its first control position when the fluid pressure in said fourth passage means has a predetermined relationship to the fluid pressure in said first actuator means.

Claim 5

A hydraulic system comprising: a source of fluid pressure including an associated reservoir, a reversible hydraulic motor operatively connected to an elevatable load and having a pair of alternate inlets, a control valve means operatively connected to said source of fluid pressure and to said fluid reservoir and having a pair of delivery ports, a locking valve having a bore, a pair of receiving ports in said bore, a pair of motor ports in said bore, and a shiftable flow control element having a first control position in which fluid is permitted to flow between one of said receiving ports and one of said motor ports and between the other of said receiving ports and the other of said motor ports and having a second control position in which fluid is prevented from flowing between said supply and motor ports, a first passage means interconnecting one of said alternate inlets and one of said motor ports, said first passage means being subject to pressurization of fluid in said motor by the weight of said load when the latter is elevated by said motor, a second passage means interconnecting the other of said alternate inlets and the other of said motor ports, third and fourth passage means interconnecting said delivery ports with said receiving ports, respectively, first hydraulic actuator means operatively associated with said Flow control element and in fluid communication with said first passage means, said first actuator means being operable to shift said flow control element to its second control position when said third and fourth passage means are not supplied pressurized fluid by said source and the weight of said load is imposed on said motor thereby pressurizing the fluid in said first passage means, second hydraulic actuator means operatively associated with said flow control element and in fluid communication with said third passage means, said second actuator means being operable to shift said flow control element from its second control position to its first control position when the fluid pressure in said third passage means has a predetermined relationship to the fluid pressure in said first actuator means, and third hydraulic actuator means operatively associated with said flow control element and connected in fluid communication with said fourth passage means, said third hydraulic actuator means being operable to move said flow control element to its first control position when the fluid pressure in said fourth passage means has a predetermined relationship to the fluid pressure in said first actuator means.

Claim 6

The invention of claim 3 wherein said shiftable flow control element is a valve spool having a large diameter portion and a small diameter portion with an axially facing annular shoulder at the junction of said portions, wherein the axially outer end of said large diameter portion is the piston component of said first hydraulic actuator means, wherein said shoulder is a piston component of said second hydraulic actuator means and wherein the axially outer end of said reduced diameter portion is a piston component of said third hydraulic actuator means.

Claim 7

The invention of claim 3 wherein said control valve has float, lower, hold and raise positions and said locking valve includes resilient biasing means urging said flow control element toward its first control position.

Claim 8

A hydraulic system comprising: a source of fluid pressure including an associated reservoir, a reversible hydraulic motor having a pair of alternate inlets and operatively connected to a load to elevate the latter, a control valve means operatively connected to said source of fluid pressure and to said fluid reservoir and having a pair of delivery ports, and a shiftable flow control member with float, lower, hold and raise positions, a locking valve having a receiving port, a motor port, a shiftable flow control element having a first control position in which fluid is permitted to flow between said receiving and motor ports and having a second control position in which fluid is prevented from flowing between said receiving and motor ports, and resilient biasing means urging said flow control element toward its first control position, a first passage means interconnecting one of said alternate inlets and said motor port, said first passage means being subject to pressurization of fluid in said motor by the weight of said load when the latter is elevated by said motor, a second passage means interconnecting one of said delivery ports with said receiving port, a third passage means interconnecting the other of said alternate inlets and the other of said delivery ports, first hydraulic actuator means operatively associated with said flow control element and connected in fluid communication with said first passage means, said first hydraulic actuator being operable to move said flow control element to its second control position when the weight of said load on said motor pressurizes the fluid in said first passage means and said second and third passage means are not pressurized by delivery of fluid from said source, and second hydraulic actuator means operatively associated with said flow control element and with said second and third passage means, said second hydraulic actuator means being operable to shift said fLow control element from its second control position to its first control position when the fluid pressure in either of said second and third passage means has a predetermined relationship to the pressure in said first hydraulic actuator means.

Claim 9

A hydraulic system comprising: a source of fluid pressure including an associated reservoir, a reversible hydraulic motor having a pair of alternate inlets and operatively connected to a load to elevate the latter, a control valve means operatively connected to said source of fluid pressure and to said fluid reservoir and having a pair of delivery ports, and a shiftable flow control member with float, lower, hold and raise positions, a locking valve having a receiving port, a motor port, a shiftable flow control element having a first control position in which fluid is permitted to flow between said receiving and motor ports and having a second control position in which fluid is prevented from flowing between said receiving and motor ports, and resilient biasing means urging said flow control element toward its first control position, a first passage means interconnecting one of said alternate inlets and said motor port, said first passage means being subject to pressurization of fluid in said motor by the weight of said load when the latter is elevated by said motor, a second passage means interconnecting one of said delivery ports with said receiving port, a third passage means interconnecting the other of said alternate inlets and the other of said delivery ports, first hydraulic actuator means operatively associated with said flow control element and connected in fluid communication with said first passage means, said first hydraulic actuator being operable to move said flow control element to its second control position when the weight of said load on said motor pressurizes the fluid in said first passage means and said second and third passage means are not pressurized by delivery of fluid from said source, and second hydraulic actuator means operatively associated with said flow control element and with said second and third passage means, said second hydraulic actuator means being operable to shift said fLow control element from its second control position to its first control position when the fluid pressure in either of said second and third passage means has a predetermined relationship to the pressure in said first hydraulic actuator means.

Claim 10

The invention of claim 6 and further comprising flow control means operatively associated with said second passage means preventing delivery of pressurized fluid through said second passage means to said motor when said flow control element is in its second control position.

Claim 11

The invention of claim 7 wherein said second hydraulic actuator means comprises a pair of hydraulic actuators operatively associated with said flow control element and in fluid communication with said second passage means and said other delivery port, respectively.

Claim 12

The invention of claim 8 wherein said flow control element is a valve spool having a large diameter portion and a small diameter portion with an axially facing shoulder at the junction of said portions, wherein the axially outer end of said large diameter portion comprises a component of said first hydraulic actuator means, wherein said shoulder comprises a component of said hydraulic actuator in fluid communication with said second passage means, and wherein the axially outer end of said small diameter portion comprises a component of said hydraulic actuator in fluid communication with said other delivery port.

Claim 13

Locking valve means comprising: a valve housing having a stepped diameter bore including a large diameter section and a small diameter section, a pair of receiving ports adapted for connection to the delivery ports of a control valve and opening into said bore at spaced points thereof, and a pair of motor ports adapted for connection to opposite sides of a hydraulic lift motor and opening into said bore at spaced points thereof, a flow control spool having a large diameter portion in said large diameter section, a small diameter portion in said small diameter section and an axially facing shoulder at the junction of said portions, wall means including said large diameter section of said bore defining a first pressure chamber, said first pressure chamber and the axially outer end of said large diameter portion of said spool comprising a first hydraulic actuator, passage means connecting said first hydraulic actuator in fluid communication with one of said motor ports, wall means including said small diameter section of said bore defining a second pressure chamber, said second pressure chamber and the axially outer end of said small diameter portion of said spool comprising a second hydraulic actuator, wall means including the axially inner end of said large diameter section of said bore defining a third pressure chamber, said third pressure chamber and said shoulder comprising a third hydraulic actuator, one of said motor ports being in fluid communication with said first hydraulic actuator and said receiving ports being in fluid communication with said second and third hydraulic actuators respectively, and said flow control spool being axially shiftable from a locking position wherein flow between said receiving and motor ports is prevented to an open position wherein flow between said receiving and motor ports is permitted.

Claim 14

Locking valve means comprising: a valve housing having a stepped diameter bore including a large diameter section and a small diameter section, a pair of receiving ports adapted for connection to the delivery ports of a control valve and opening into said bore at spaced points thereof, and a pair of motor ports adapted for connection to opposite sides of a hydraulic lift motor and opening into said bore at spaced points thereof, a flow control spool having a large diameter portion in said large diameter section, a small diameter portion in said small diameter section and an axially facing shoulder at the junction of said portions, wall means including said large diameter section of said bore defining a first pressure chamber, said first pressure chamber and the axially outer end of said large diameter portion of said spool comprising a first hydraulic actuator, passage means connecting said first hydraulic actuator in fluid communication with one of said motor ports, wall means including said small diameter section of said bore defining a second pressure chamber, said second pressure chamber and the axially outer end of said small diameter portion of said spool comprising a second hydraulic actuator, wall means including the axially inner end of said large diameter section of said bore defining a third pressure chamber, said third pressure chamber and said shoulder comprising a third hydraulic actuator, one of said motor ports being in fluid communication with said first hydraulic actuator and said receiving ports being in fluid communication with said second and third hydraulic actuators respectively, and said flow control spool being axially shiftable from a locking position wherein flow between said receiving and motor ports is prevented to an open position wherein flow between said receiving and motor ports is permitted.

Claim 15

The invention of claim 10 and further comprising resilient biasing means urging said flow control spool toward its open position.

Claim 16

The invention of claim 10 and further comprising an annular recess in said small diameter portion of said spool in fluid communication with said one motor port and an axially extending passage in said spool placing said first hydraulic actuator and said recess in fluid communication.

Claim 17

The invention of claim 12 and further comprising resilient biasing means urging said flow control spool toward its open position.

Claim 18

A hydraulic system comprising: a source of fluid pressure including an associated reservoir, a reversible hydraulic motor having A pair of alternate inlets and operatively connected to an elevatable load, a control valve means operatively connected to said source of fluid pressure and to said fluid reservoir and having a pair of delivery ports, said control valve means having float lower, hold and raise positions of adjustment, a locking valve having a housing with a bore, a pair of receiving ports opening into axially spaced points of said bore, and a pair of motor ports opening into axially spaced points of said bore, and an axially shiftable flow control spool in said bore having an open position in which fluid is permitted to flow between said receiving ports and said motor ports and having a closed position in which fluid is prevented from flowing between said receiving and motor ports, a first passage means interconnecting one of said alternate inlets and said one of said motor ports, said first passage means being subject to pressurization of fluid in said motor by the weight of said load when the latter is elevated, a second passage means interconnecting the other of said alternate inlets and the other of said motor ports, third and fourth passage means interconnecting said delivery ports with said receiving ports, respectively, and fluid pressure actuating means operatively associated with said spool and with said first, third and fourth passage means, said fluid pressure actuating means being operative to shift said spool to its open position when either of said third and fourth passage means is pressurized and to shift said spool to its closed position when said first passage means is pressurized by the weight of said load on said motor and said third and fourth passage means are not pressured.

Claim 19

A hydraulic system comprising: a source of fluid pressure including an associated reservoir, a reversible hydraulic motor having A pair of alternate inlets and operatively connected to an elevatable load, a control valve means operatively connected to said source of fluid pressure and to said fluid reservoir and having a pair of delivery ports, said control valve means having float lower, hold and raise positions of adjustment, a locking valve having a housing with a bore, a pair of receiving ports opening into axially spaced points of said bore, and a pair of motor ports opening into axially spaced points of said bore, and an axially shiftable flow control spool in said bore having an open position in which fluid is permitted to flow between said receiving ports and said motor ports and having a closed position in which fluid is prevented from flowing between said receiving and motor ports, a first passage means interconnecting one of said alternate inlets and said one of said motor ports, said first passage means being subject to pressurization of fluid in said motor by the weight of said load when the latter is elevated, a second passage means interconnecting the other of said alternate inlets and the other of said motor ports, third and fourth passage means interconnecting said delivery ports with said receiving ports, respectively, and fluid pressure actuating means operatively associated with said spool and with said first, third and fourth passage means, said fluid pressure actuating means being operative to shift said spool to its open position when either of said third and fourth passage means is pressurized and to shift said spool to its closed position when said first passage means is pressurized by the weight of said load on said motor and said third and fourth passage means are not pressured.

Claim 20

The invention of claim 14 wherein said locking valve includes resilient biasing means urging said spool toward its open position.