Abstract: The invention relates to a tool for piercing nuts, comprising a die part and a punch part and a piercing nut feeder incorporated into the punch part. The piercing nut feeder is adapted to feed piercing nuts into a piercing nut holder in the punch part so that these nuts, when the punch part is pressed against the die part by a press, are to punch holes in and be fastened to a metal sheet inserted between the punch part and the die part. A gas spring (3) is arranged between the press and the punch part, which gas spring (3) has at least one cylinder (5-7) and a piston (8-10) which is movably arranged in the cylinder (5-7) and which is aligned with the press, the pressure in the cylinder (5-7) being settable for adjusting the pressure exerted upon the piercing nut by the punch part.

Abstract: A method and an arrangement in an energy-accumulating piston-cylinder arrangement (A) has a piston/piston rod part (2), guide/end (3) and tubular casing (1). The casing (1) is provided with a fracture or sprain mark (7) in order to initiate a controlled deformation of the casing in the event of a load that produces a stress in excess of a sprain or fracture limit, or of repeated cyclical stressing that gives rise to material fatigue, so that an excess pressure in the arrangement (A) is discharged past the deformed casing.

Abstract: The invention relates to an arrangement for performing a secondary operation in a pressing tool for sheet metal forming comprising a primary cylinder/piston unit (1) arranged to pressurise an operating fluid upon closing of said pressing tool for performing a primary forming operation on a work piece. A secondary cylinder/piston unit (7) is mounted within said pressing tool, carrying tooling for conducting said secondary operation mounted on its piston rod (7c). The arrangement further comprises means (2, 20, 21) for storing said pressurised operating fluid and means for selectively allowing a first volume flow of operating fluid of a first pressure to the secondary cylinder/piston unit (7), for advancing its piston rod (7c) until the tooling encounters the work piece.

Abstract: The invention relates to an arrangement for a gas spring. The arrangement comprises a cylinder (1). At its one end, this is delimited by a fixed end wall (2), and at its other end there is a first guide (3) sealed against the inner wall of the cylinder (1) and against a piston rod (4) capable of axial movement within the cylinder (1). The piston rod (4) has a second guide (8) mounted in such a way as to be capable of sliding against the inner wall. An annular piston (9) sealed against the inner wall and against the piston rod (4) is mounted on the piston rod (4) between the guides (3; 8) in such a way that it is free to slide. This divides the inner space of the cylinder (1) into a first and a second part space (12; 13). In an initial position, in which the gas spring is unaffected, there is present in the first part space (12) a pressure which is greater than the pressure present in the second part space (13).

Abstract: Arrangement in a pressing tool for sheet metal forming in order to shut off or retard an oil flow in a hydraulic system at an arbitrarily chosen time in coordination with the closing and opening movements of the said tool. When the tool closes, a non-return valve (6) permits a flow in one direction from a primary hydraulic cylinder/piston unit (7), which is thereby compressed, to an accumulator (8). A first valve (9) selectively permits a flow between the accumulator (8) and a secondary hydraulic cylinder/piston unit (10) which, in the event of such a flow, passes from a compressed basic position to an expanded position.

Abstract: The invention relates to a degressive gas spring. This has two cylinder-piston units (1, 2), one of which is selected as a working spring (1) and the other as a slave spring (2), the cylinders (1a; 2b) and the ends of the piston rods (1b; 2b) of which are mutually operatively connected so that compression of the working spring (1) also brings about simultaneous compression of the slave spring (2). The piston rod (1b; 2b) of each spring unit (1; 2) is mounted in an end wall (1c; 2c) in such a way as to be capable of sliding and supports a piston (1h; 2h). The axial position of this in the cylinder (1a; 2a) determines the volume of an enclosed, gas-filled space (1i; 2i) inside the unit. The piston (1h; 2h) in each spring unit (1; 2) is sealed against the cylinder wall (1a; 2a). The piston (1h; 2h) and/or the end wall (1c; 2c) has a recess which forms an annual chamber (1j; 2j). The piston rod (2b) in the slave spring unit (2) has a smaller diameter than that in the working spring unit (1).