Claims
- 1. A press assembly operable from an open condition to a closed condition to deform a workpiece, said press assembly comprising first and second members for engaging opposite sides of the workpiece during operation of said press assembly between the open condition and the closed condition, a cushion assembly operable from an extended condition to a retracted condition to absorb force transmitted from at least one of said members during operation of said press assembly between the open and the closed conditions, a pump assembly connected in fluid communication with said cushion assembly and operable from an extended condition to a retracted condition to pump fluid to said cushion assembly during operation of said press assembly from the open condition to the closed condition, a fluid reservoir, and a modulating valve connected in fluid communication with said cushion assembly, said pump assembly and said fluid reservoir, said modulating valve being operable to modulate fluid flow from said pump assembly to said fluid reservoir and to said cushion assembly during operation of said press assembly from the open condition to the closed condition to modulate transmission of force between said one of said members and said cushion assembly during operation of said press assembly between the open and closed conditions, said modulating valve being operable to a closed condition to block fluid flow from said cushion assembly to said fluid reservoir to maintain said cushion assembly in the retracted condition of said cushion assembly during a first portion of operation of said press assembly from the closed condition to the open condition, said pump assembly being operable from the retracted condition of said pump assembly toward the extended condition of said pump assembly during the first portion of operation of said press assembly from the closed condition to the open condition while said cushion assembly is in the retracted condition of said cushion assembly, said fluid reservoir being effective to supply fluid to said pump assembly during operation of said pump assembly from the retracted condition of said pump assembly toward the extended condition of said pump assembly while said cushion assembly is in the retracted condition of said cushion assembly.
- 2. A press assembly as set forth in claim 1 wherein said modulating valve is operable from the closed condition to an open condition to enable fluid to flow from said cushion assembly to said fluid reservoir and to enable said cushion assembly to operate from the retracted condition of said cushion assembly while said pump assembly remains in the extended condition of said pump assembly during a second portion of operation of said press assembly form the closed condition to the open condition.
- 3. A press assembly as set forth in claim 1 further including a check valve connected in fluid communication with said pump assembly and said cushion assembly to block fluid flow from said cushion assembly to said pump assembly during operation of said pump assembly from the retracted condition of said pump assembly toward the extended condition of said pump assembly with said cushion assembly in the retracted condition of said cushion assembly.
- 4. A press assembly as set forth in claim 1 further including a check valve connected in fluid communication with said fluid reservoir and said pump assembly to block fluid flow from said pump assembly to reservoir along a fluid flow path which is spaced apart from said modulating valve during operation of said pump assembly from the extended condition of said pump assembly to the retracted condition of said pump assembly during operation of said press assembly from the open condition to the closed condition, said check valve being effective to enable fluid to flow from said reservoir to said pump assembly during operation of said pump assembly from the retracted condition of said pump assembly toward the extended condition of said pump assembly while said cushion assembly is in the retracted condition of said cushion assembly.
- 5. A press assembly as set forth in claim 1 wherein said cushion assembly holds a volume of fluid at a first pressure when said cushion assembly is in the retracted condition of said cushion assembly, said fluid reservoir supplies fluid to said pump assembly at a second pressure which is less than said first pressure to effect operation of said pump assembly from the retracted condition of said pump assembly toward the extended condition of said pump assembly.
- 6. A press assembly operable from an open condition to a closed condition to deform a workpiece, said press assembly comprising first and second members for engaging opposite sides of a workpiece during operation of said press assembly between an open condition and a closed condition, a cushion assembly operable from an extended condition to a retracted condition to absorb force transmitted from at least one of said members during operation of said press assembly from the open condition to the closed condition, said cushion assembly including a cylinder and a piston which divides said cylinder into first and second variable volume chambers, a high pressure fluid reservoir connected in fluid communication with said first variable volume chamber in said cushion assembly, said piston being movable against the influence of fluid pressure in said first variable chamber to contract said first variable volume chamber and expand said second variable volume chamber during operation of said press assembly from the open condition to the closed condition, said piston being movable under the influence of fluid pressure in said first variable volume chamber to contract said second variable volume chamber and expand said first variable volume chamber during operation of said press assembly from the closed condition to the open condition, a pump assembly connected in fluid communication with said second variable volume chamber in said cushion assembly through a cushion assembly supply conduit, said pump assembly being operable to discharge fluid to said cushion assembly supply conduit during operation of said press assembly from the open condition to the closed condition, a first check valve connected with said cushion assembly supply conduit to block fluid flow from said cushion assembly to said pump assembly through said cushion assembly supply conduit during operation of said press assembly from the closed condition to the open condition, a low pressure fluid reservoir connected in fluid communication with said second variable volume chamber in said cushion assembly, said low pressure fluid reservoir containing fluid at a pressure which is lower than a pressure at which fluid is contained in said high pressure fluid reservoir to enable fluid discharged from said second variable volume chamber in said cushion assembly during contraction of said second variable volume chamber in said cushion assembly to flow to said low pressure fluid reservoir, a control valve connected in fluid communication with said low pressure fluid reservoir and said second variable volume chamber in said cushion assembly, said control valve being operable to a closed condition to block fluid flow from said second variable volume chamber in said cushion assembly during a first portion of the operation of said press assembly from the closed condition to the open condition to maintain said cushion assembly in the retracted condition during the first portion of the operation of said press assembly from the closed condition to the open condition, said control valve being operable to an open condition to enable fluid to flow from said second variable volume chamber in said cushion assembly to said low pressure fluid reservoir during a second portion of the operation of said press assembly from the closed condition to the open condition to enable said cushion assembly to operate from the retracted condition to the extended condition during the second portion of the operation of said press assembly from the closed condition to the open condition, a pump assembly supply conduit connected in fluid communication with said low pressure fluid reservoir and said pump assembly, and a second check valve connected with said pump assembly supply conduit to enable fluid to flow from said low pressure fluid reservoir to said pump assembly and to block fluid flow from said pump assembly to said low pressure reservoir through said pump assembly supply conduit.
- 7. A press assembly as set forth in claim 6 wherein said control valve is operable to modulate fluid flow from said second variable volume chamber of said cushion assembly to said low pressure fluid reservoir during operation of said press assembly from the open condition to the closed condition to modulate transmission of force between said one of said members and said cushion assembly during operation of said press assembly between the open and closed conditions.
- 8. A press assembly as set forth in claim 6 wherein said pump assembly includes a cylinder and a piston which are relatively movable during operation of said press assembly from the open condition to the closed condition to discharge fluid at a pressure which is greater than a pressure of fluid in said low pressure fluid reservoir.
Parent Case Info
This application claims the benefit of U.S. Provisional Application No. 60/067,007 filed Dec. 1, 1997. The benefit of the earlier filing date of the aforementioned Provisional Application Serial No. 60/067,007 under 35 U.S.C. 119(e) is claimed.
US Referenced Citations (9)
Foreign Referenced Citations (1)
Number |
Date |
Country |
3835470 |
Jun 1989 |
DEX |
Non-Patent Literature Citations (3)
Entry |
Article entitled "Advances and Trends in Sheet Metal Forming Processes",#970436, Klaus Siegert, University of Stuttgart, Copyright 1997 Society of Automotive Engineers, Inc., pp. 23 through 38. |
Article entitled "Force-Stroke-Curve of Gas Springs",#970982, K. Siegert and J. Hohnhaus, University of Stuttgart, Copyright 1997 Society of Automotive Engineers, Inc., pp. 195 through 201. |
Article entitled "The Die-Draulic Basic Unit", published prior to May 1, 1998. |