Fluid control system for power shovel
First Claim
1. A fluid control system for a power shovel comprising two main pumps, two control valve groups each having a running control valve at the upstream side thereof and working device control valves arranged downstream from the respective running control valve, one of said working device control valves having a need to compensate for the amount of flow of the fluid thereinto, said fluid control system further comprising a flow-dividing selector valve mechanisms respectively connected to the main pumps via main channels and being selectively operable to a first position wherein the main channels individually communicate with upstream sides of the respective running control valves and to a second position wherein one of the main channels is allowed to communicate with both of the running control valves and another of the main channels is allowed to communicate downstream from the two running control valves and upstream of the working device control valves, confluent selector valve mechanisms each connected to an intermediate portion of a channel extending from a downstream side of the running control valve of one control valve group to an upstream side of a working device control valve of the other control valve group, each of said confluent selector valve mechanisms being selectively opened to permit fluid passage by a signal for operating the working device control valve of the other control valve group to selectively perform a confluence function or blocking function, a reservoir, and shutoff valve mechanisms each connected to an intermediate portion of a fluid return channel extending from a downstream side of a downstream one of the working device control valves in each group to the reservoir, whereby the confluent selector valve mechanism of the group having a working device control valve which has a need to compensate for the amount of flow of the fluid thereinto receives a signal for closing the fluid passage working device control valve.
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Accused Products
Abstract
A control system having a flow-dividing selector valve mechanism (52) for changing the channels for causing a pressure fluid to flow from two main pumps (40), (50) into two control valve groups (60), (70) therethrough, and confluent selector valve mechanisms (80), (90) for causing the pressure fluid flowing into each group to flow into a working device control valve of the other group. The confluent selector valve mechanism (80) of the group wherein the working device control valve (62) has a need to compensate for the flow of fluid thereinto cancels the confluence function. The system has a mechanism for restricting the stroke of the spool of a working device control valve (160) to be subjected to varying loads to cause the fluid discharged from the actuator connected thereto to flow into the actuator again when the load is small. A sequence valve (170) operates the spool stroke restricting mechanism (190) by a pilot primary pressure.
78 Citations
24 Claims
- 1. A fluid control system for a power shovel comprising two main pumps, two control valve groups each having a running control valve at the upstream side thereof and working device control valves arranged downstream from the respective running control valve, one of said working device control valves having a need to compensate for the amount of flow of the fluid thereinto, said fluid control system further comprising a flow-dividing selector valve mechanisms respectively connected to the main pumps via main channels and being selectively operable to a first position wherein the main channels individually communicate with upstream sides of the respective running control valves and to a second position wherein one of the main channels is allowed to communicate with both of the running control valves and another of the main channels is allowed to communicate downstream from the two running control valves and upstream of the working device control valves, confluent selector valve mechanisms each connected to an intermediate portion of a channel extending from a downstream side of the running control valve of one control valve group to an upstream side of a working device control valve of the other control valve group, each of said confluent selector valve mechanisms being selectively opened to permit fluid passage by a signal for operating the working device control valve of the other control valve group to selectively perform a confluence function or blocking function, a reservoir, and shutoff valve mechanisms each connected to an intermediate portion of a fluid return channel extending from a downstream side of a downstream one of the working device control valves in each group to the reservoir, whereby the confluent selector valve mechanism of the group having a working device control valve which has a need to compensate for the amount of flow of the fluid thereinto receives a signal for closing the fluid passage working device control valve.
Specification