Patent GB-647236-A (GB)
Title: Improvements relating to pressure-controlling or cushioning appliances
IPC: B21D24/02
Filed: 1948-07-08
Abstract: 647,236. Stamping. CARTER, A., and SLADE, G. July 8, 1948, No. 18344. [Class 83 (iv)] [Also in Group XXXII] Pressure controlling or cushioning appliances of the kind in which a hydraulic fluid is acted upon by a main ram or plunger in a primary cylinder and is forced through a resistance opening or passage in order to act upon and depress a piston in a secondary cylinder against a return-spring, is applicable to presses for drawing or cupping sheet-metal articles from blanks. The resistance opening or passage is controlled by a spring-loaded valve subjected to the full pressure of the fluid prevailing in the primary cylinder and opening to an extent depending upon the applied pressure to allow flow from the primary cylinder to the secondary cylinder, the valve being normally engaged with a seating to close the opening or passage, and a one-way valve being provided in a byepass to provide for the quick return of fluid from the secondary to the primary cylinder. The draw-ring (not shown) of a press rests upon a pressure plate 1, Fig. 1, which is rigid with the hollow rod 2 of a primary piston 3. The corresponding primary cylinder 4 is rigid with the bed ring 6 of the press and is bolted to a secondary cylinder 8 having a corresponding piston 9. A nipple 14 threaded into the lower wall of the cylinder 4 has a passage 15 which connects the cylinders 4, 8 and is formed with a seat for a valve 20 forming the upper end of a rod 16. The lower end of the rod 16 bears on a spring 17 which is in abutment with the end of a casing 18 adjustably threaded in the bottom wall of the cylinder 8. The rod 16 is slidable within a head 19 formed on the hollow pistonrod 12 of the piston 9. The rod 12 is slidable within a cylinder 23 integral with the cylinder 8, and is formed with axial grooves 25. The head 19 has a ball-valve 28 which opens upwardly into the interior of the rod 12, and a ball-valve 30 which opens to permit flow from a port 30a leading to the outer surface of the rod 12. An annular channel 31 formed in the inner wall of the cylinder 23, is connected by ports 32 with the space between the cylinders 8, 23. In operation, before pressure is applied to the plate 1 the cylinder 4 is full of liquid and the piston 3 is maintained in the position shown by a spring 7. On downward displacement of the plate 1, liquid is forced by the piston 3 through the passage 15 and opens the valve 20 against the resistance of the spring 17. This liquid displaces the secondary piston 9 against the resistance of a spring 10. When the pressure on the plate 1 is relieved, the spring 10 raises the piston 9 which returns liquid to the cylinder 4 through non-return ball-valves 22. Liquid which escapes to the lower side of the piston 9 passes through ports 32, channel 31 and valve 30 into the space below the head 19 and on downward movement of the piston 9 is pumped back through the valve 28. In the construction shown in Fig. 2, the cylinders 4, 8 are connected by pipes 33, 34 and a valve assembly 35. The latter includes a one-way valve 38 which normally permits flow from the cylinder 8 to the cylinder 4 only. The valve 38 is byepassed by a passage 39, flow through which from the cylinder 4 is controlled by a valve 41 similar to the valve 20 of Fig. 1 and which bears against a spring 43, the loading of which is adjustable at 44. The valve 30 of Fig. 1 is replaced by. a similar valve 30a disposed in the bottom wall of the cylinder 23. The plate 1 may be lowered under the action of its own weight by opening a cock 47 connecting the pipe 34 with the underside of the piston, and raising the valve 38 by means of a screwed rod 46. Also partial raising of the valve 38 during normal working of the apparatus may provide a byepass of the valve 41 and so provide a lower pressure. According to the Provisional Specification the passage 15 in the construction of Fig. 1 is in the form of converging passages in a shank depending from the lower end-wall of the cylinder 4. The passages open into the cylinder 3 at their upper end, and at their lower end into a single central passage, in a lower enlargement of which is seated the valve 16. Ports in the wall of the enlargement below the valve connect with the space outside the shank and within the pistonrod 12. The head 19 and cylinder 23 are dispensed with and their functions are fulfilled respectively by a head formed on the lower end of the shank and the hollow bore of the pistonrod 12 in which the shank head is slidable. Upwardly-opening ball-valves are formed in the shank head and ports are formed in the lower portion of the piston-rod 12. One-way ballvalves may also be provided in the bottom end wall of the piston-rod 12 to allow liquid flow from the space beneath the piston 9 to the space within the piston-rod 12. Also the valves 22 may be spring-loaded. The means described above for pumping liquid back past the piston 9, forms the subject-matter of Specification 647,237, (Group XXXII].