Patent Application
20080011155
The main system 201 also includes a first directional control valve 208 that hydraulically couples both the source of pressurized fluid 202 and the reservoir of fluid 204 to a head end 120 and a rod end 122 of the bucket actuator 118. The levers 132 drive a spool 210 within the directional control valve 208 to one of three positions: a first position 212 routing fluid from the source of pressurized fluid 202 to the head end 120, while allowing excess fluid from the bucket actuator 118 to flow from the rod end 122 to the reservoir of fluid 204; a second position 214 routing fluid from the source of pressurized fluid 202 to the rod end 122, while allowing excess fluid from the bucket actuator 118 to flow from the head end 120; and a third position 216 shutting off all flow through the directional control valve 208. Relief valves 217 may be placed between the directional control valve 208 and the bucket actuator 118.
Similarly, the main system 201 also includes a second directional control valve 218 that hydraulically couples both the source of pressurized fluid 202 and the reservoir of fluid 204 to a head end 126 and a rod end 128 of the thumb actuator 124. A first hydraulic line 246 hydraulically couples the directional control valve 218 to the head end 126, while a second hydraulic line 248 hydraulically couples the directional control valve 218 to the rod end 128. The levers 132 drive a spool 220 within the directional control valve 218 to one of three positions: a first position 222 routing fluid from the source of pressurized fluid 202 to the head end 126, while allowing excess fluid from the thumb actuator 124 to flow from the rod end 128 to the reservoir of fluid 204; a second position 224 routing fluid from the source of pressurized fluid 202 to the rod end 128, while allowing excess fluid from the thumb actuator 124 to flow from the head end 126; and a third position 226 shutting off all flow through the directional control valve 218. Relief valves 227 may be placed between the directional control valve 218 and the thumb actuator 124. The spools 210, 220 may be a closed-center, spring, centered, operated control valve, but alternately could be a solenoid type, pressure compensated valve, or any like valve.
The auxiliary valve block 250 may be mounted on the linkage assembly 104, external to the machine 100, although other the auxiliary valve block 250 may also be mounted in other locations, such as integral with the main system 200 or internal to the machine 100. The valve block 250 includes an input 251 and outputs 253, 255. The input 251 is hydraulically coupled to the head end 126 of the thumb actuator 124, while the outputs 253, 255 are hydraulically coupled to the rod end 128 of the thumb actuator 124 and the rod end 122 of the bucket actuator 118. The valve block 250 also includes a relief valve 252 and a first and a second check valve 254, 256 downstream of the relief valve 252.
In operation, an operator may use levers 132 to move the boom 106, stick 108, bucket 110, and thumb 112. For example, by moving the levers 132 to shift the spools 210, 220 within the first and second directional control valves 208, 218 to the first position 212, 222, both the bucket actuator 118 and the thumb actuator 124 extend, rotating the bucket 110 and the thumb 112 towards one another. By moving the levers 132 to shift the spools 210, 220 to the second position 214, 224, the bucket actuator 118 and the thumb actuator 124 retract, rotating the bucket 110 and the thumb 112 away from one another.
After an operator has rotated the bucket 110 and the thumb 112 towards one another, closing the bucket 110 and the thumb 112, the auxiliary valve block 250 allows for a coordinated linkage motion. Rather than blow a relief valve 217, 227 in the first or second hydraulic lines 246, 248, the relief valve 252 in the auxiliary valve block 250 is blown, allowing the bucket actuator 118 to overpower the thumb actuator 124. The excess hydraulic oil from the head end 126 of the thumb actuator 124 is sent through the first check valve 254 to the rod end 128 of the thumb actuator 124 as make-up fluid. Because the oil discharging from the relief 252 may be greater than the volume that can be taken up by the rod end 128 of the thumb actuator 124 due to cylinder ratios, the excess oil from the head end 126 of the thumb actuator 124 is also sent through the second check valve 256 to the rod end 122 of the bucket actuator 118 to the reservoir of fluid 204.
Several advantages over the prior art may be associated with the hydraulic system 200 of the machine 100. For example, the configuration of the auxiliary valve block 250 allows for a compact, space efficient design, requiring only a single pair of hydraulic lines 246, 248 to extend to the thumb actuator 124. In addition, the design also allows for a modular setup. An operator does not need to adjust the relief setting when another hydraulic implement is used. By disconnecting the hydraulic lines 246, 248 from the thumb actuator 124 and connecting the lines 246, 248 to a different hydraulic implement, the relief valves 217, 227 within the main system 201 are used, and not the relief valve 252 of the auxiliary valve block 250, which may be set to a much lower setting than that in the main system 201.
Other aspects, objects and advantages of this invention can be obtained from a study of the drawings, the disclosure, and the appended claims.
