# US 9,038,431 B2 · Hydraulic cylinder for a hydraulic drawing cushion > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,038,431 B2 - Document ID: US9038431B2 - Status: Granted - Kind: B2 - Application number: 13/068,054 - Filed: 2011-04-29 - Published: 2011-11-03 - Granted: 2015-05-26 - Earliest claimed: 2010-05-03 - Assignees: Schuler Pressen GmbH - Applicants: Michael Micklisch; Markus Müller - Inventors: Michael Micklisch; Markus Müller - Web page: https://patentgrep.com/patent/US9038431B2 ## CPC - B21D 24/14: pneumatically or hydraulically - B21D 24/02: Die-cushions - B21D 24/10: Devices controlling or operating blank holders independently, or in conjunction with dies - F15B 11/036: by means of servomotors having a plurality of working chambers - F15B 2211/6336: representing a state of the output member, e.g. position, speed or acceleration - F15B 2211/6651: Control of the prime mover, e.g. control of the output torque or rotational speed - F15B 2211/6653: Pressure control - F15B 2211/7055: having more than two chambers - F15B 2211/76: Control of force or torque of the output member - F15B 2211/765: Control of position or angle of the output member - F15B 2211/775: Combined control, e.g. control of speed and force for providing a high speed approach stroke with low force followed by a low speed working stroke with high force, e.g. for a hydraulic press - B21D: WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL (working or processing of wire B21F) - F15B: SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR ## Abstract The invention resides in a hydraulic cylinder (23) for a hydraulic drawing cushion (20) of a drawing press (10). The hydraulic cylinder (23) includes a first operating chamber (47), a second operating chamber (48), and a third operating chamber (53). An annular piston (45) with a first piston surface area (49) and a second piston surface area (50) separates the first operating chamber (47) from the second operating chamber (48). The first and the second piston surfaces (49, 50) have the same size. A front surface of the piston rod (33) forms a third piston surface (54) which is larger than the first and second piston surfaces. The third piston surface (54) delimits the third operating chamber (53) of the hydraulic cylinder (23). The first and the second operating chambers (47, 48) are provided for controlling the position and/or the movement of the piston rod (33). The third operating chamber (53) serves to control the metal sheet clamping force of the drawing press via the piston rod (33). ## Claims ### Claim 1 Hydraulic drawing cushion (20) of a drawing press (10), the drawing press (10) including an upper tool part (14) and a lower tool part (15), the hydraulic drawing cushion (20) for exerting a clamping force on a sheet metal part (B) for forming a formed metal part, comprising: a cylinder arrangement (22) including a hydraulic cylinder (23) including a cylinder housing (30) having an internal cylinder space (31) including a first hydraulic operating chamber (47), a second hydraulic operating chamber (48), and a third hydraulic operating chamber (53), a piston rod (33) slidably supported in a cylinder opening (32) of the internal cylinder space (31), the piston rod (33) for connection with a metal sheet support ring (25) of the drawing press (10), between the first hydraulic operating chamber (47) and the second hydraulic operating chamber (48), an annular piston (45) is arranged which extends annularly around and attached to the piston rod (33), the annular piston (45) having a first piston surface (49) adjacent first hydraulic operating chamber (47) and having a second piston surface (50) adjacent the second hydraulic operating chamber (48), the first piston surface (49) and the second piston surface (50) are of essentially a same surface area and movable simultaneously together with the piston (33), the piston rod (33) having a front face which is an integral part thereof and housed within the cylinder opening (32) delimiting a third piston surface (54) having a surface area larger than either the first and the second piston surface (49, 50) and which defines an upper border of the third hydraulic operating chamber (53), a first hydraulic circuit (55) in hydraulic circuit connection with the first hydraulic operating chamber (47) and the second hydraulic operating chamber (48), a second hydraulic circuit (56) in hydraulic circuit connection with the third hydraulic operating chamber (53), the first hydraulic circuit (55) controls a position and/or movement of the piston rod (33) before the upper tool part (14) abuts the sheet metal part (B), the second hydraulic circuit (56) controls a sheet metal part (B) clamping force upon the upper tool part (14) abutting the metal sheet part (B), the hydraulic drawing cushion (20) is operated by a position and/or movement control before the upper tool part (14) abuts the metal sheet part (B), the hydraulic drawing cushion (20) is operated by a sheet metal part (B) clamping force control as soon as the upper tool part (14) abuts the sheet metal part (B), and, an electrically controllable control valve (61) connected in hydraulic circuit arrangement with the first hydraulic circuit (55) and the second hydraulic circuit (56), the electrically controllable control valve (61) in a first position (I) enables the position and/or movement control of the hydraulic drawing cushion (20) and the electrically controllable control valve (61) switches over to a second position (II) to enable the sheet metal part (B) clamping force control of the hydraulic drawing cushion (20) upon the upper tool part (14) abutting the metal sheet part (B). ### Claim 2 (depends on 1) Hydraulic drawing cushion (20) according to claim 1, wherein the surface area of the third piston surface (54) is larger than the surface area of either the first and the second piston surface (49, 50) by a factor of 3 to 10. ### Claim 3 (depends on 1) Hydraulic drawing cushion (20) according to claim 1, wherein the internal cylinder space (31) includes a first cylindrical section (40) having a first diameter (D1) and a second cylindrical section (41) having a second diameter (D2). ### Claim 4 (depends on 3) Hydraulic drawing cushion (20) according to claim 3, wherein the first and second hydraulic operating chambers (47, 48) are arranged in the first cylindrical section (40) and the third hydraulic operating chamber (53) is arranged in the second cylindrical section (41). ### Claim 5 (depends on 1) Hydraulic drawing cushion (20) according to claim 1, wherein the third hydraulic operating chamber (53) is hydraulically connected to an electrically controllable pressure control arrangement (67) for controlling the sheet metal part (B) clamping force. ### Claim 6 (depends on 1) Hydraulic drawing cushion (20) according to claim 1, wherein the third hydraulic operating chamber (53) is hydraulically connected to a suction check valve (66). ### Claim 7 (depends on 6) Hydraulic drawing cushion (20) according to claim 6, wherein the inlet suction check valve (66) is hydraulically connected to a hydraulic reservoir (65) which is under a pressure of from about 5 bar to about 15 bar. ### Claim 8 (depends on 5) Hydraulic drawing cushion (20) according to claim 5, wherein the electrically controllable control valve (61) having three switching positions including the first position (I) for the position/movement control of the hydraulic cushion (20), the second position (II) for the sheet metal part (B) clamping force control of the drawing cushion (20), and a third position (III) for providing an ejection movement of the drawing cushion (20) for ejecting the formed metal part. ### Claim 9 (depends on 8) Hydraulic drawing cushion (20) according to claim 8, further comprising an electrical control unit (70) for controlling the switching of electrically controllable control valve (61) and for controlling the electrically controllable pressure control arrangement (67) for obtaining a desired pressure in the operating chamber (53). ### Claim 10 (depends on 5) Hydraulic drawing cushion (20) according to claim 5, wherein the second hydraulic circuit (56) further includes a motor-pump unit (72) in hydraulic connection between the third operating chamber (53) and a hydraulic reservoir (65) and a storage container (69) and means for controlling a hydraulic fluid flow through the motor-pump unit (72) such that in one flow direction the motor-pump unit (72) acts as a motor and in the opposite flow direction the motor-pump unit (72) acts as generator for producing electricity. ### Claim 11 (depends on 1) Hydraulic drawing cushion (20) according to claim 1, wherein the cylinder arrangement (22) includes several hydraulic cylinders (23) each controllable independently from one another. ### Claim 12 (depends on 1) Hydraulic cushion (20) according to claim 1, wherein the first hydraulic circuit (55) includes a hydraulic fluid storage container (57) in hydraulic connection to a first motor-pump unit (58), the first motor-pump unit (58) having an outlet in operative connection with a pressure line (59), a first hydraulic line (26) is in hydraulic operative connection between the first hydraulic operating chamber (47) and the electronic control valve (61), a second hydraulic line (27, 27a) is in hydraulic operative connection between the second hydraulic operating chamber (48) and the electronic control valve (61), whereby the pressure line (59) can be selectively hydraulically connected to the first hydraulic operating chamber (47) or the second hydraulic operating chamber (48). ### Claim 13 (depends on 12) Hydraulic cushion (20) according to claim 12, wherein the first hydraulic circuit (55) further includes a pressure control valve (63) in hydraulic connection with the second hydraulic line (27, 27a) and the storage container (57), whereby when the pressure in the second operating chamber (48) exceeds a predetermined threshold value, the pressure control valve (63) opens thereby permitting hydraulic medium to flow from the second operating chamber (48) to the storage container (57).