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| Illustration 1 | g01880640 |
The hydraulic cylinder that operates the jaw is equipped with speed control valve (1). The speed control valve is used to adjust the cylinder for use with maximum power or for use in high speed. The resistance that acts against the cylinder will determine the proper mode of operation. Speed control valve (1) is mounted directly to the head end of the cylinder.
Closing the Jaw (High Speed Operation)
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| Illustration 2 | g02126903 |
(2) Auxiliary control valve (3) Check valve (4) Main valve (5) Pilot valve | |
When the hydraulic cylinder closes the jaw under little resistance, the speed control valve will shift the cylinder into high speed.
When the operator closes the jaws, auxiliary control valve (2) directs oil flow from the host machine to the speed control valve and to the head end of the cylinder. The pressure on the piston causes the cylinder to extend and the jaws close. Simultaneously, oil flows to check valve (3), main valve (4), and pilot valve (5). Spring force keeps the check valve closed when the pressure is below 18000 ± 1000 kPa (2610 ± 150 psi). When the check valve is closed, oil flow to top of pilot valve (5) is blocked. Spring force keeps the pilot valve shifted to the bottom. When the valve is shifted to the bottom, oil flows to the left end of main valve (4). The pressure at the left side of the valve causes the valve to shift to the right. When the main valve is shifted to the right, oil flows to the head end of the cylinder. High-pressure oil is at both sides of the piston, but the extra surface area at the head end causes the piston to move to the right. The extra flow that is supplied to the head end causes an increase in speed. The increase in speed results in a decrease in closing time.
Closing the Jaw (Maximum Power)
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| Illustration 3 | g02127036 |
(2) Auxiliary control valve (3) Check valve (4) Main valve (5) Pilot valve | |
When the hydraulic cylinder closes the jaw under high resistance, the speed control valve will shift the cylinder into maximum power.
When the operator closes the jaw, auxiliary control valve (2) shifts to the left. When auxiliary control valve (2) is shifted to the left, the valve directs oil flow from the host machine to the speed control valve and to the head end of the cylinder. The pressure on the piston causes the cylinder to extend and the jaws close. Simultaneously, oil flows to pilot valve (5), main valve (4), and check valve (3). Spring force keeps the check valve closed when the pressure is below 18000 ± 1000 kPa (2610 ± 150 psi). When the work tool crushes material, the resistance that is sensed in the speed control valve may increase. When the pressure exceeds the amount that is specified in the above text, the check valve opens. Oil flows to the top side of pilot valve (5) and the valve shifts to the bottom against the spring. Oil is directed from the pilot valve to the right end of main valve (4). The main valve moves to the left and oil is directed from the rod end of the cylinder back to the hydraulic tank. The direction of the oil flow to the tank causes the speed of the jaws to decrease and the power of the jaws to increase.
Retraction of the Jaw
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| Illustration 4 | g02127135 |
(2) Auxiliary control valve (3) Check valve (4) Main valve (5) Pilot valve | |
When the operator opens the jaw, auxiliary control valve (2) shifts to the right. The auxiliary valve directs oil flow from the host machine to the speed control valve.
The oil flows to the bottom of pilot valve (5). The pressure on the bottom side of the valve in conjunction with the spring holds the valve to the bottom. Oil then flows through the valve to the right side of main valve (4). This causes the valve to shift to the left. This creates a path for oil to flow through the valve to the rod side of the cylinder. The oil pressure that acts on the rod side of the piston retracts the cylinder, and the jaw opens. Oil from the head end of the cylinder returns to the hydraulic tank.