A hydraulic drawing cushion (17) for a drawing press (10) includes at least one hydraulic cylinder (21) comprising a piston rod (27) that causes a total force (G) to act on the metal sheet holding ring (20). The hydraulic cylinder (21) comprises a hydraulic work circuit (37) to generate a hydraulic work force (A) in a work direction (Z) to act on a ring part (28) to which a force can be applied on both sides. Independently, a spring force (F) acts on the piston (26). The spring force (F) is neither controlled nor adjusted, but is preset. Preferably, the spring force (F) is exclusively a function of the position or location of the piston (26) relative to the cylinder housing (25). The total force (G) acting on the piston (26) results from the addition of the vectors of the work force (A) and the spring force (F).

In a method and an apparatus for reducing the cutting impact in a hydraulically-driven precision blanking press, the force necessary to reduce the cutting impact as a counterforce is generated directly in the pressure chamber of the drive piston such that the counterforce acts directly on the cutting punch and so that the design of the press can be simplified, costs can be reduced, no additional external hydraulic-mechanical means for reducing the cutting impact are needed, and so that the loads on the press and the die can be reduced.

In a method and an apparatus for reducing the cutting impact in a hydraulically-driven precision blanking press, the force necessary to reduce the cutting impact as a counterforce is generated directly in the pressure chamber of the drive piston such that the counterforce acts directly on the cutting punch and so that the design of the press can be simplified, costs can be reduced, no additional external hydraulic-mechanical means for reducing the cutting impact are needed, and so that the loads on the press and the die can be reduced.

A linear actuator is disclosed. The linear actuator comprises a cylinder portion and a base portion. The cylinder portion comprises a housing defining internally a compression chamber for containing a fluid and comprising a piston assembly that can reciprocate within the compression chamber. The housing further defines a cylinder port in fluid communication with said compression chamber. The base portion defines a first base port and a second base port and a passage extending therebetween fluidly communicating the first base port with the second base port, and comprises valve means operable to control the flow of fluid through the second base port, in which the valve means is actuatable between an open condition in which the flow of fluid through the second base port is permitted, and a closed condition in which the flow of fluid through the second base port is substantially prevented. The cylinder portion is releasably engageable with the base portion such that the cylinder portion and the base portion may be arranged in an engaged condition in which engaged condition the cylinder port and the second base port are in fluid communication.

A double-blank detecting apparatus for a press machine that is provided with a die cushion apparatus and is configured to form blanks one by one automatically and repeatedly. The double-blank detecting apparatus includes: a position signal acquiring unit configured to acquire a slide position signal indicating a position of a slide of the press machine; a load signal acquiring unit configured to acquire a die cushion load signal indicating a die cushion load generated on a cushion pad of the die cushion apparatus; and a double-blank detector configured to detect a state in which a plurality of blanks are stacked as a double blank based on the slide position signal acquired by the position signal acquiring unit and the die cushion load signal acquired by the load signal acquiring unit.

A double-blank detecting apparatus for a press machine that is provided with a die cushion apparatus and is configured to form blanks one by one automatically and repeatedly. The double-blank detecting apparatus includes: a position signal acquiring unit configured to acquire a slide position signal indicating a position of a slide of the press machine; a load signal acquiring unit configured to acquire a die cushion load signal indicating a die cushion load generated on a cushion pad of the die cushion apparatus; and a double-blank detector configured to detect a state in which a plurality of blanks are stacked as a double blank based on the slide position signal acquired by the position signal acquiring unit and the die cushion load signal acquired by the load signal acquiring unit.

A cushion pin pressure equalizing device that can absorb a variation in height of a plurality of cushion pins and control a die cushion load highly accurately, a die cushion device, and a cushion pin pressure equalizing method are provided. An initial pressure in ascending-side pressurizing chambers of a pressure equalizing hydraulic cylinder group for absorbing a variation in height of cushion pins is controlled so as to be an appropriate pressure. The variation in height of the plurality of cushion pins can be absorbed within a shortest stroke of a slide after the slide comes into collision with a cushion pad so as to equalize die cushion loads that are applied individually to the cushion pins and a target die cushion load can be generated within the shortest stroke of the slide, whereby a response to application of the die cushion load can be stabilized without excessive delay.

A cushion pin pressure equalizing device that can absorb a variation in height of a plurality of cushion pins and control a die cushion load highly accurately, a die cushion device, and a cushion pin pressure equalizing method are provided. An initial pressure in ascending-side pressurizing chambers of a pressure equalizing hydraulic cylinder group for absorbing a variation in height of cushion pins is controlled so as to be an appropriate pressure. The variation in height of the plurality of cushion pins can be absorbed within a shortest stroke of a slide after the slide comes into collision with a cushion pad so as to equalize die cushion loads that are applied individually to the cushion pins and a target die cushion load can be generated within the shortest stroke of the slide, whereby a response to application of the die cushion load can be stabilized without excessive delay.

A press system providing excellent energy efficiency for a whole press system and capable of achieving low prices is provided. A die cushion apparatus constituting a press system supports a cushion pad, includes a hydraulic cylinder which generates a die cushion load on the cushion pad when a slide of a press machine descends, the press machine includes a hydraulic cylinder which generates part of a press load on the slide when the slide descends. The pressure generation chamber of the hydraulic cylinder for generating a die cushion load and the pressure generation chamber of the hydraulic cylinder for generating part of the press load can communicate with each other via pipes and a first logic valve for a period during which the die cushion load acts.

A press system providing excellent energy efficiency for a whole press system and capable of achieving low prices is provided. A die cushion apparatus constituting a press system supports a cushion pad, includes a hydraulic cylinder which generates a die cushion load on the cushion pad when a slide of a press machine descends, the press machine includes a hydraulic cylinder which generates part of a press load on the slide when the slide descends. The pressure generation chamber of the hydraulic cylinder for generating a die cushion load and the pressure generation chamber of the hydraulic cylinder for generating part of the press load can communicate with each other via pipes and a first logic valve for a period during which the die cushion load acts.