Tool with hydraulic system for regenerative extension and two-speed operation
Embodiments of the invention provide a hydraulic tool including a hydraulic actuator cylinder, a piston, a fluid reservoir, a pump, a regeneration check valve, and a pilot-operated valve. The regeneration check valve is disposed in a regenerative extension fluid path that fluidly couples a first and second chamber of the hydraulic actuator cylinder. The pilot-operated valve is disposed in a power extension fluid path that fluidly couples the second chamber to a fluid reservoir.
1 . A pilot-operated valve for a hydraulic tool used to operate on a work piece, the hydraulic tool including a cylinder with a first chamber separated from a second chamber by a piston, a fluid reservoir, and a pump, the pilot-operated valve comprising:
a first port fluidly coupled to the second chamber;
a second port fluidly coupled to the fluid reservoir;
a pilot port fluidly coupled via a pilot line to a hydraulic supply line between the pump and the first chamber;
a valve cavity fluidly coupled to the pilot port;
a valve piston and valve rod positioned in the valve cavity;
a check valve coupled to the valve rod,
the check valve being closed in an unactuated first state when a pressure in the pilot line is below a threshold pressure value, thereby blocking a powered extension fluid path between the second chamber and the fluid reservoir in order to allow the piston to extend at a first speed as fluid fills the first chamber from the fluid reservoir;
the check valve being open in an actuated second state when the pressure in the pilot line exceeds the threshold pressure value, thereby opening the powered extension fluid path to direct fluid from the second chamber to the fluid reservoir and allow the piston to extend at a second speed less than the first speed.
2 . The pilot-operated valve of claim 1 , wherein the first port is directly fluidly coupled to the second chamber.
3 . The pilot-operated valve of claim 1 , wherein the second port is directly fluidly coupled to the fluid reservoir.
4 . The pilot-operated valve of claim 1 , wherein the valve cavity includes a valve seat and the check valve is a check ball, the check ball being seated against the valve seat in the unactuated first state, the check ball being unseated from the valve seat in the actuated second state.
5 . The pilot-operated valve of claim 1 , wherein the piston moves in a distal direction toward the work piece when the pressure in the first chamber exceeds a first threshold pressure value.
6 . The pilot-operated valve of claim 5 , wherein the first threshold pressure value is about 500 pounds per square inch.
7 . The pilot-operated valve of claim 5 , further comprising a valve spring in the valve cavity, the valve spring having a first spring rate.
8 . The pilot-operated valve of claim 7 , wherein the first spring rate is about 500 pounds per square inch.
9 . The pilot-operated valve of claim 8 , further comprising a return spring in the second chamber to return the piston in a proximal direction away from the work piece.
10 . The pilot-operated valve of claim 9 , wherein a second spring rate of the return spring is about 150 pounds per square inch.
11 . The pilot-operated valve of claim 5 , wherein the pilot-operated valve operates in the unactuated first state as the pressure of fluid provided to the pilot port via the pilot line remains below the first threshold pressure value.
12 . The pilot-operated valve of claim 11 , wherein as the pressure of fluid remains below the first threshold pressure value, fluid is provided from the second chamber via a regenerative extension fluid path between the second chamber and the first chamber through a regeneration check valve causing the piston to move at the first speed.
13 . The pilot-operated valve of claim 11 , wherein as the pressure in the first chamber and the pilot port exceeds the first threshold pressure value, the pilot-operated valve switches to operating in the actuated second state in which fluid flow from the second chamber is diverted away from a regenerative extension fluid path to the powered extension fluid path to the fluid reservoir to cause the piston to move at a second speed that is less than the first speed.
14 . The pilot-operated valve of claim 13 , wherein in the actuated second state, the piston slows down to a controlled speed to provide more precise cutting or crimping.
15 . The pilot-operated valve of claim 13 , wherein fluid flow through the regenerative extension fluid path produces a first force on the piston and fluid flow through the powered extension fluid path produces a second force that is greater than the first force.
16 . The pilot-operated valve of claim 15 , wherein the work piece is a cable and the hydraulic tool is a crimper cutter including jaws, and wherein the pressure in the first chamber increases due to increased resistance as the jaws clamp onto the cable, and wherein the pressure in the first chamber continues to increase until the second force is sufficiently large in magnitude to crimp or cut the cable.
17 . The pilot-operated valve of claim 16 , wherein once the cable is crimped or cut, the piston reaches an end of stroke, the pressure in the first chamber continues to increase until reaching a second threshold pressure value, and the pump is shut off.
18 . The pilot-operated valve of claim 17 , wherein the second threshold pressure value is about 8500 pounds per square inch.
19 . The pilot-operated valve of claim 1 , wherein the hydraulic tool includes a dump valve fluidly coupled to the first chamber; wherein when the dump valve is actuated, a fluid path is opened from the first chamber to the fluid reservoir; wherein a return spring in the second chamber causes the piston to retract in a proximal direction away from the work piece.
20 . The pilot-operated valve of claim 19 , wherein the dump value is actuated electronically.