Hydraulic control system for a backhoe

Claim 2

A hydraulic system for a backhoe including a vehicle, a boom pivoted to said vehicle, a stick pivoted to said boom, a bucket pivoted to said stick, a boom cylinder for pivoting said boom relative to said vehicle, a stick cylinder for pivoting said stick relative to said boom, and a bucket cylinder for pivoting said bucket relative to said stick; said system comprising a first hydraulic fluid delivery means for supplying hydraulic fluid under pressure, a second hydraulic fluid delivery means for supplying hydraulic fluid under pressure, means for selectively directing the hydraulic fluid from both said first delivery means and said second fluid delivery means to said stick cylinder to cause said stick to move in a digging direction when the fluid pressure in said stick cylinder is below a predetermined amount and for directing the hydraulic fluid from said first delivery means to said stick cylinder and the hydraulic fluid from said second delivery means to said bucket cylinder to cause said bucket to move in a curling direction when the fluid pressure in said stick cylinder is above a predetermined amount, and means for directing a portion of the hydraulic fluid from said second delivery means to said lift cylinder to cause said boom to lift when the fluid pressure in said bucket cylinder is above a predetermined amount.

Claim 3

A hydraulic system for a backhoe including a vehicle, a boom pivoted to said vehicle, a stick pivoted to said boom, a bucket pivoted to said stick, a boom cylinder for pivoting said boom upwardly and downwardly, a stick cylinder for pivoting said stick selectively in inwardly digging motions ad outwardly retracting motions, a bucket cylinder for selectively pivoting said bucket relative to said stick in inwardly curling motions and outwardly retracting motions; said system comprising a first hydraulic fluid delivery means for supplying hydraulic fluid under pressure, and a second hydraulic fluid delivery means for supplying hydraulic fluid under pressure; a first thRee-way control valve means selectively for blocking hydraulic fluid flow when in a first position, for directing the fluid to one end of said stick cylinder to cause pivot of said stick cylinder in said digging motions when in a second position, or for directing the fluid to the opposite end of said stick cylinder to cause pivot of said stick in said retracting motions when in a third position; a second three-way control valve means selectively for blocking the fluid flow when in a first position, for directing the fluid to one end of said bucket cylinder to cause inwardly pivot in curling motions when in a second position, or for directing the fluid to the opposite end of said bucket cylinder to cause pivot of said bucket in said retracting motions when in a third position; first means for selectively directing the hydraulic fluid from both said first delivery means and said second delivery means to said first control valve means to said first control valve means to cause said stick to move in a digging motion when said first control valve means is in said second position and when the fluid pressure in said stick cylinder is below a predetermined amount during said digging motions and for directing hydraulic fluid from said first delivery means to said first control valve means and the hydraulic fluid from said second delivery means to said bucket cylinder to cause said bucket to move in a curling motion when said first control valve is in said second position and when the fluid pressure in said stick cylinder is above a predetermined amount during said digging motion, and additional means for directing a portion of the hydraulic fluid from said second delivery means to said boom cylinder to cause said boom to lift when the fluid pressure in said bucket cylinder is above a predetermined amount during said curling motion.

Claim 4

A hydraulic system for a backhoe including a vehicle, a boom pivoted to said vehicle, a stick pivoted to said boom, a bucket pivoted to said stick, a boom cylinder for pivoting said boom upwardly and downwardly, a stick cylinder for pivoting said stick selectively in inwardly digging motions ad outwardly retracting motions, a bucket cylinder for selectively pivoting said bucket relative to said stick in inwardly curling motions and outwardly retracting motions; said system comprising a first hydraulic fluid delivery means for supplying hydraulic fluid under pressure, and a second hydraulic fluid delivery means for supplying hydraulic fluid under pressure; a first thRee-way control valve means selectively for blocking hydraulic fluid flow when in a first position, for directing the fluid to one end of said stick cylinder to cause pivot of said stick cylinder in said digging motions when in a second position, or for directing the fluid to the opposite end of said stick cylinder to cause pivot of said stick in said retracting motions when in a third position; a second three-way control valve means selectively for blocking the fluid flow when in a first position, for directing the fluid to one end of said bucket cylinder to cause inwardly pivot in curling motions when in a second position, or for directing the fluid to the opposite end of said bucket cylinder to cause pivot of said bucket in said retracting motions when in a third position; first means for selectively directing the hydraulic fluid from both said first delivery means and said second delivery means to said first control valve means to said first control valve means to cause said stick to move in a digging motion when said first control valve means is in said second position and when the fluid pressure in said stick cylinder is below a predetermined amount during said digging motions and for directing hydraulic fluid from said first delivery means to said first control valve means and the hydraulic fluid from said second delivery means to said bucket cylinder to cause said bucket to move in a curling motion when said first control valve is in said second position and when the fluid pressure in said stick cylinder is above a predetermined amount during said digging motion, and additional means for directing a portion of the hydraulic fluid from said second delivery means to said boom cylinder to cause said boom to lift when the fluid pressure in said bucket cylinder is above a predetermined amount during said curling motion.

Claim 5

The hydraulic control system of claim 2 which includes a third hydraulic fluid delivery means for supplying hydraulic fluid under pressure; a third three-way control valve means selectively for blocking the fluid flow from said third fluid delivery means to said boom cylinder when in a first position, for directing the fluid flow from said third fluid delivery means to one end of said boom cylinder to cause pivot of said boom upwardly when in a second position, or for directing the fluid flow from said third fluid delivery means to the opposite end of said boom cylinder to cause pivot of said boom downwardly when in a third position.

Claim 6

A hydraulic system for a backhoe including a vehicle, a boom pivoted adjacent one end of said vehicle, a stick pivoted adjacent one end of said boom adjacent the end thereof remote from said vehicle, a bucket pivoted to said stick adjacent the end thereof remote from said boom, a boom cylinder for pivoting said boom upwardly and downwardly relative to said vehicle, a stick cylinder for pivoting said stick selectively in inwardly digging motions and outwardly retracting motions, a bucket cylinder for selectively pivoting said bucket relative to said stick in inwardly curling motions and outwardly retracting motions, and first control valve means for directing fluid to said stick cylinder for movement of said stick in digging motions; said system comprising a hydraulic fluid source, a first pump means and a first conduit means for supplying fluid from said source to said first control valve means, first pilot operated valve means shiftable between a first condition responsive to the hydraulic pressure in said first conduit being below a predetermined amount when the digging motion of said stick is normal and a second condition responsive to hydraulic pressure in said first conduit being above a predetermined amount due to digging resistance above a predetermined amount being felt in said stick cylinder, a second pilot operated valve means, a second conduit leading from said first pilot operated valve means and having branches leading to said bucket cylinder and to said second pilot operated valve means, a second pump means for delivering fluid under pressure from said source to said first conduit when said first pilot operated valve means is in said first condition and for delivering fluid under pressure to said second conduit for the curling of said bucket when said first pilot operated valve means is in said second condition, said second pilot operated valve means being shiftable between a first condition responsive to the hydraulic pressure in branch of said second conduit leading to said bucket cylinder being below a predetermined amount when the digging motion of said stick and bucket is normal and to a second condition responsive to the hydraulic pressure in said branch of said second conduit leading to said bucket cylinder being above a predetermined amount when the digging motion of said stick and bucket is abnormal due to resistance in digging, a third conduit leading from said second pilot operated valve means to said boom cylinder for delivering fluid to said boom cylinder from said second conduit to lift said boom when said second pilot operated valve means is in said second condition.

Claim 7

A hydraulic system for a backhoe including a vehicle, a boom pivoted adjacent one end of said vehicle, a stick pivoted adjacent one end of said boom adjacent the end thereof remote from said vehicle, a bucket pivoted to said stick adjacent the end thereof remote from said boom, a boom cylinder for pivoting said boom upwardly and downwardly relative to said vehicle, a stick cylinder for pivoting said stick selectively in inwardly digging motions and outwardly retracting motions, a bucket cylinder for selectively pivoting said bucket relative to said stick in inwardly curling motions and outwardly retracting motions, and first control valve means for directing fluid to said stick cylinder for movement of said stick in digging motions; said system comprising a hydraulic fluid source, a first pump means and a first conduit means for supplying fluid from said source to said first control valve means, first pilot operated valve means shiftable between a first condition responsive to the hydraulic pressure in said first conduit being below a predetermined amount when the digging motion of said stick is normal and a second condition responsive to hydraulic pressure in said first conduit being above a predetermined amount due to digging resistance above a predetermined amount being felt in said stick cylinder, a second pilot operated valve means, a second conduit leading from said first pilot operated valve means and having branches leading to said bucket cylinder and to said second pilot operated valve means, a second pump means for delivering fluid under pressure from said source to said first conduit when said first pilot operated valve means is in said first condition and for delivering fluid under pressure to said second conduit for the curling of said bucket when said first pilot operated valve means is in said second condition, said second pilot operated valve means being shiftable between a first condition responsive to the hydraulic pressure in branch of said second conduit leading to said bucket cylinder being below a predetermined amount when the digging motion of said stick and bucket is normal and to a second condition responsive to the hydraulic pressure in said branch of said second conduit leading to said bucket cylinder being above a predetermined amount when the digging motion of said stick and bucket is abnormal due to resistance in digging, a third conduit leading from said second pilot operated valve means to said boom cylinder for delivering fluid to said boom cylinder from said second conduit to lift said boom when said second pilot operated valve means is in said second condition.

Claim 8

The hydraulic system of claim 4 in which is included shuttle valve means for locking said first pilot operated valve in said first condition during retracting motions of said bucket or said stick to prevent chattering.

Claim 9

The hydraulic system of claim 4 in which is included means for selectively locking and unlocking said first pilot operated valve and said second pilot operated valve.

Claim 10

A hydraulic system for backhoe including a vehicle, a boom pivoted to said vehicle, a stick pivoted to said boom, a bucket pivoted to said stick, a boom cylinder for pivoting said boom relative to said vehicle, a stick cylinder for pivoting said stick relative to said boom, and a bucket cylinder for pivoting said bucket relative to said stick; said system comprising hydraulic fluid delivery means for supplying hydraulic fluid under pressure, means selectively operable in a first mode or a second mode of operation for directing the fluid from said fluid delivery means only to said stick cylinder to cause said stick to move in a digging motion when the fluid pressure in said stick cylinder is below a predetermined amount, for directing at least a portion of said fluid from said fluid delivery means to said bucket cylinder to cause said bucket to move in a curling direction when the fluid pressure in said stick cylinder is above a predetermined amount and when said selectively operable means is in a first mode of operation, and for directing at least a portion of said fluid from said fluid delivery means to said bucket cylinder to cause said bucket to move in a curling direction when the fluid pressure in said stick cylinder is above a predetermined amount and when said selectively operable means is in a first mode of operation, and for directing at least a portion of said fluid from said fluid delivery means to said boom cylinder to cause said boom to lift without curling said bucket and while said stick cylinder is moving in a digging motion to level the bottom of the ditch being dug when said selectively operable means is in a second mode of operation.

Claim 11

A hydraulic system for backhoe including a vehicle, a boom pivoted to said vehicle, a stick pivoted to said boom, a bucket pivoted to said stick, a boom cylinder for pivoting said boom relative to said vehicle, a stick cylinder for pivoting said stick relative to said boom, and a bucket cylinder for pivoting said bucket relative to said stick; said system comprising hydraulic fluid delivery means for supplying hydraulic fluid under pressure, means selectively operable in a first mode or a second mode of operation for directing the fluid from said fluid delivery means only to said stick cylinder to cause said stick to move in a digging motion when the fluid pressure in said stick cylinder is below a predetermined amount, for directing at least a portion of said fluid from said fluid delivery means to said bucket cylinder to cause said bucket to move in a curling direction when the fluid pressure in said stick cylinder is above a predetermined amount and when said selectively operable means is in a first mode of operation, and for directing at least a portion of said fluid from said fluid delivery means to said bucket cylinder to cause said bucket to move in a curling direction when the fluid pressure in said stick cylinder is above a predetermined amount and when said selectively operable means is in a first mode of operation, and for directing at least a portion of said fluid from said fluid delivery means to said boom cylinder to cause said boom to lift without curling said bucket and while said stick cylinder is moving in a digging motion to level the bottom of the ditch being dug when said selectively operable means is in a second mode of operation.

Claim 12

The hydraulic system of claim 7 in which said fluid delivery means includes a single pump means.

Claim 13

The hydraulic system of claim 7 in which said fluid delivery means includes a pair of pump means.

Claim 14

A hydraulic system for a backhoe including a tractor, a boom pivoted to said tractor, a stick pivoted to said boom, a bucket pivoted to said stick, a boom cylinder for pivoting said boom upwardly and downwardly relative to said tractor, a stick cylinder for pivoting said stick selectively in inwardly digging motions and outwardly retracting motions, and a bucket cylinder for selectively pivoting said bucket relative to said stick in inwardly curling motions and outwardly retracting motions and first control valve means for directing fluid to said stick cylinder for movement of said stick in digging motions, said system comprising hydraulic fluid delivery for supplying hydraulic fluid under pressure, first pilot operated valve means receiving fluid delivery means, a first conduit leading from said first pilot operated valve means to said first control valve means, said first pilot operated valve means being shiftable to a first condition responsive to the hydraulic pressure in said first conduit being below a predetermined amount when the digging motion of said stick is normal and being shiftable to a second condition responsive to hydraulic pressure in said first conduit being above a predetermined amount due to digging resistance above a predetermined amount being felt in said stick cylinder, a second pilot operated valve means, a second conduit leading from said first pilot operated valve means and having branches leading to said bucket cylinder and to said second pilot operated valve means, when said first pilot operated valve is in said first condition the fluid from said fluid delivery means being directed only to said stick cylinder to cause said stick to move in a digging motion, and when said first pilot operated valve is in said second condition, the fluid from said fluid delivery means being directed, at least in part, to said second conduit, a third conduit leading from said second pilot operated valve to said boom cylinder, said second pilot operated valve means being shiftable between a first position in which fluid flow is blocked through said second pilot operated valve means and a second position communicating said second conduit with said third conduit to cause lifting of said boom, means selectively operable in a first condition for shifting said second pilot operated valve means into said second position responsive to a first predetermined pressure in the branch of said second conduit leading to said bucket cylinder which is greater than the pressure required to move said bucket in a curling disposition and operable in a second condition for shifting said second pilot operated valve means into said second position responsive to a second predetermined pressure in the branch of said second conduit leading to said bucket cylinder which is less than said first predetermined pressure and less than the pressure required to move said bucket in a curling disposition.

Claim 15

A hydraulic system for a backhoe including a tractor, a boom pivoted to said tractor, a stick pivoted to said boom, a bucket pivoted to said stick, a boom cylinder for pivoting said boom upwardly and downwardly relative to said tractor, a stick cylinder for pivoting said stick selectively in inwardly digging motions and outwardly retracting motions, and a bucket cylinder for selectively pivoting said bucket relative to said stick in inwardly curling motions and outwardly retracting motions and first control valve means for directing fluid to said stick cylinder for movement of said stick in digging motions, said system comprising hydraulic fluid delivery for supplying hydraulic fluid under pressure, first pilot operated valve means receiving fluid delivery means, a first conduit leading from said first pilot operated valve means to said first control valve means, said first pilot operated valve means being shiftable to a first condition responsive to the hydraulic pressure in said first conduit being below a predetermined amount when the digging motion of said stick is normal and being shiftable to a second condition responsive to hydraulic pressure in said first conduit being above a predetermined amount due to digging resistance above a predetermined amount being felt in said stick cylinder, a second pilot operated valve means, a second conduit leading from said first pilot operated valve means and having branches leading to said bucket cylinder and to said second pilot operated valve means, when said first pilot operated valve is in said first condition the fluid from said fluid delivery means being directed only to said stick cylinder to cause said stick to move in a digging motion, and when said first pilot operated valve is in said second condition, the fluid from said fluid delivery means being directed, at least in part, to said second conduit, a third conduit leading from said second pilot operated valve to said boom cylinder, said second pilot operated valve means being shiftable between a first position in which fluid flow is blocked through said second pilot operated valve means and a second position communicating said second conduit with said third conduit to cause lifting of said boom, means selectively operable in a first condition for shifting said second pilot operated valve means into said second position responsive to a first predetermined pressure in the branch of said second conduit leading to said bucket cylinder which is greater than the pressure required to move said bucket in a curling disposition and operable in a second condition for shifting said second pilot operated valve means into said second position responsive to a second predetermined pressure in the branch of said second conduit leading to said bucket cylinder which is less than said first predetermined pressure and less than the pressure required to move said bucket in a curling disposition.