Seat switch activated pump

[0002] 1. Field of the Invention

[0003] The present invention is directed to a work vehicle having an operator's seat with two working positions for controlling two work implements, wherein the position of the operator's seat controls the application of a hydraulic pump to the second work implement.

[0004] 2. Description of the Prior Art

[0005] Backhoe loaders are a common type of work vehicle for performing two work operations. The backhoe loader is provided with a front mounted loader and a rear mounted backhoe. The operator's cab is provided with a reversible seat which faces forward for transport and loading operations and to the rear for backhoe operations.

[0006] The backhoe functions of the backhoe has a higher fluid demand than the loader functions of the loader. To provide sufficient fluid, a second fluid gear pump has been provided supplying additional pressurized hydraulic fluid to the backhoe control valves. In current production machines, a first hydraulic gear pump supplies pressurized hydraulic fluid to the loader control valves, the stabilizer control valves and the backhoe control valves in series through a first supply line. A second supply line directs pressurized hydraulic fluid from the second hydraulic gear pump to the first supply line upstream from the backhoe control valves and downstream from the stabilizer control valves.

[0007] Other backhoe loader manufacturers have used manually operated switches to decouple one of the pumps from the hydraulic circuit.

[0008] It is an object of the present invention to provide a simple and automatic mechanism for coupling and decoupling a second hydraulic pump to the operation of a second work implement.

[0009] A backhoe loader is provided with a front mounted loader and a rear mounted backhoe. The operator's cab of the backhoe loader is provided with a reversible operator's seat having a first working position facing the loader and a second working position facing the backhoe. A first hydraulic pump directs pressurized hydraulic fluid through a first supply line to backhoe control valves, stabilizer control valves and loader control valves that are mounted in series. A second hydraulic pump directs pressurized hydraulic fluid through a second supply line to the first supply line upstream from the loader control valves. The second supply line is provided with a two-position solenoid valve. In its first position the valve directs the pressurized hydraulic fluid from the second hydraulic pump to sump. In its second position the valve directs pressurized hydraulic fluid from the second hydraulic pump to the first supply line. The solenoid of the two-position solenoid valve is in electrical communication with a detector. The detector sends a first signal if the operator's seat is in its first working position and a second signal if the operator's seat is in its second working position. The detector is a conventional seat switch currently used on production backhoe loaders for different applications.

[0010] FIG. 1 is a side view of a backhoe loader work vehicle.

[0011] FIG. 2 is an electrical and hydraulic schematic of the present invention.

[0012] The work vehicle 10 illustrated in FIG. 1 is a backhoe loader. The work vehicle 10 is provided with a supporting structure 12 and ground engaging means 14 comprising wheels, which support and propel the supporting structure 12. Although the ground engaging means 14 of the illustrated embodiment are wheels, the present invention could also be used on tracked work vehicles having steel or rubber tracks. The supporting structure 12 has a front 16 and a back 18. A first work implement 20 comprising a loader is mounted to the front 16 of the supporting structure 12. A second work implement 22 comprising a backhoe is mounted to the back 18 of the supporting structure 12.

[0013] The operation of the work vehicle 10 and the operation of the first and second work implements 20 and 22 are controlled from operator's cab 24. The operator's cab 24 is provided with a two-position operator's seat 26. In its first position, the operator's seat 26 faces forwardly towards the front 16 of the work vehicle 10. In this first position, the operator can drive the vehicle and operate the loader 20. In its second position, illustrated in FIG. 1, the operator's seat 26 faces rearwardly towards the back 18 of the work vehicle 10. In this second position the operator controls the operation of the backhoe 22.

[0014] The loader 20 is mounted to the front 16 of the supporting structure 12 by a mast 27 and comprises lift arms 28 and a bucket 30. The lift arms 28 are provided with lift arm hydraulic cylinders 32 for lifting the arms 28 relative to the supporting structure 12. The bucket 30 is pivotally mounted to the end of the lift arms 28. Bucket 30 is provided with a bucket-tilt hydraulic cylinder 34 for tilting the bucket 30 relative to the lift arms 28.

[0015] The backhoe 22 is mounted to the back 18 of the supporting structure 12 and comprises a boom 36, a dipperstick 38 and a bucket 40. The boom 36 is pivotally coupled to a swing frame 42 about a vertical pivot and is raised and lowered relative to the swing frame 42 by a boom hydraulic cylinder 46. The dipperstick 38 is pivotally mounted to the boom about a horizontal axis and is pivoted relative to the boom 36 by dipperstick hydraulic cylinder 48. The bucket 40 is curled and uncurled relative to the dipperstick 38 by bucket hydraulic cylinder 50. The operation of the backhoe 22 is controlled by an operator manipulating control levers 52 located in the operator's cab 24.

[0016] In the illustrated embodiment the swing frame 42 is pivotally coupled to the support structure 12. The swing frame 42 is pivoted relative to the supporting structure by swing frame hydraulic cylinders, not shown. The swing frame 42 could also be mounted to a side shift structure located between the swing frame 42 and the supporting structure for laterally shifting the swing frame relative to the supporting structure 12. The backhoe would normally be provided with stabilizers, not shown.

[0017] As illustrated in FIG. 2, a first hydraulic gear pump 54 directs pressurized hydraulic fluid through a first supply line 56 to the backhoe 22 through backhoe control valves 58, to the stabilizers through the stabilizer control valves 60 and to the loader 20 through loader control valves 62. These control valves 58, 60 and 62 are mounted in series along the first supply line 56 one after the other. The exhausted fluid is returned to sump through hydraulic return line 64. A second hydraulic gear pump 66 directs pressurized hydraulic fluid through a second supply line 68 to the first supply line 56 upstream from the backhoe control valves 58. The flow of pressurized hydraulic fluid through the second supply line 68 is controlled by a two-position solenoid valve 70. The first and second hydraulic pumps 54 and 66 receive hydraulic fluid from the sump through hydraulic line 71.

[0018] The two-position solenoid valve 70 has a first position 72 wherein pressurized hydraulic fluid from the second hydraulic pump 66 is directed to sump through return line 73. The two-position solenoid valve has a second position 74 wherein pressurized hydraulic fluid from the second hydraulic pump 66 is directed to the first supply line 56. The valve 70 is normally biased into its second position 74 by spring 76. The valve 70 is driven into its first position 72 by energizing solenoid 78.

[0019] The energization of the solenoid 78 is controlled by a detector 80 comprising a seat switch used to detect if the seat is in its first working position facing to the front towards the loader, or is in its second working position facing rearwardly towards the backhoe. When the operator's seat 26 is in its first working position facing the loader 20, the seat switch is opened closing relay 84 and providing a first signal to solenoid 78. When the seat switch is opened, the solenoid 78 is energized shifting the two-position valve 78 into its first position 72. In its first position 72, the valve 70 directs pressurized hydraulic fluid from the second hydraulic pump 66 directly to sump. When the operator's seat 26 is rotated approximately 15 degrees from its first working position towards its second working position, the seat switch is closed opening relay 84 and providing a second signal to solenoid 78. When the seat switch is closed the solenoid is deenergized and the spring 76 biases the valve 78 into its second position 74. In its second position 74, valve 70 directs pressurized hydraulic fluid from the second hydraulic pump 66 to the first supply line 56. The seat switch is in electrical communication with the relay 84 and the solenoid 78 by electrical line 82.

[0020] The invention should not be limited by the above described embodiments, but should be limited solely by the claims that follow.