| 摘要 |
<p>1,139,763. Hydraulic presses. WERNER & PFLEIDERER. 18 Feb., 1966 [21 April, 1965], No. 7333/66. Heading B5F. [Also in Division F1] An hydraulic system for supplying pressure liquid to a line 7 leading to e.g. a press cylinder comprises a low-pressure pump 1 and a highpressure pump 11 each connected to the line 7 through respective chambers 4, 14 in a housing 5, and a spool 9 automatically reciprocable within the housing 5 so that initially both pumps feed the line 7, then the low-pressure pump 1 is by-passed through a line 2a and finally the supply from the high-pressure pump is also by-passed through a series of throttle passages 20<SP>1</SP>, 21<SP>1</SP>, 221 and a line 12a to collapse the pressure in the line 7. The spool 9 is continuously urged to the left by a force P and to the right by the pressure of fluid in a chamber 17. The chamber 17 receives fluid from the highpressure pump 11 through a line 15 having a non-return valve 16 and from the chamber 14 through a slot 19 in the spool 9. As the pressure in the line 7 builds up the pressure in the chamber 17 also increases to displace the spool to the right. When the edge 10 of the spool 9 clears the line 2a the low-pressure pump 1 is bypassed and a non-return valve 6 prevents the escape of pressure from the line 7. The pump 11 continues to increase the pressure in the line 7 until further displacement of the spool 9 causes lands 20, 21, 22 on the spool 9 to open the throttled high-pressure by-pass passage 20<SP>1</SP>, 21<SP>1</SP>, 22<SP>1</SP>. Opening of the passage 20<SP>1</SP>, 21<SP>1</SP>, 22<SP>1</SP> collapses the pressure in the line 7 and the force P returns the piston to its original position.</p> |
