Patent ID: 7146809

Claim:
A valve block, comprising: a first port passage extending from a first side of the valve block to a second side of the valve block; a second port passage oriented substantially parallel to the first port passage and extending from the first side of the valve block to the second side of the valve block; a third port passage in hydraulic communication with both the first and second port passages, the third port passage extending from a third side of the valve block and intersecting the first and second port passages; a fourth port passage in hydraulic communication with both the first and second port passages, the fourth port passage extending from a fourth side of the valve block and intersecting both the first and second port passages but not the third port passage; a first valve mounted in the third port passage; and a second valve mounted in the fourth port passage, wherein either the first valve or the second valve opens in response to a hydraulic pressure rise rate that exceeds a predetermined level in one of the first port passage or the second port passage to allow hydraulic fluid to enter into the other of the first port passage or the second port passage.