GB1181941A - Presses - Google Patents

Abstract

1,181,941. Presses. NORTON TOOL CO. Ltd. 3 Feb., 1969 [8 Feb., 1968]. No. 6269/68. Heading B5F. A press having a C-frame is provided with means for counteracting the bending force on the press frame comprising at least one tie-rod 27 connected across the gap of the frame and tensioning means adapted to apply to the tie-rod a tensile force substantially proportional to the pressing force. In the hydraulic press in Fig. 1 the tie-rod 27 carries a piston 30 in a cylinder 29 connected to the cylinder of the press piston 18. By making the areas of the piston 30 and 18 in the inverse ratio A/B, where A and B are the distances of the axes of the two pistons 18 arid 30 from the centre of bending 24, the bending effect of the hydraulic ram is neutralized by the tension in the tie-rod. In a modification (Figs. 2, 3, not shown) the tensioning means comprises an annular hydraulic cylinder (41) and piston (42), one end of the tie-rod (37) passing through this annular arrangement and having a collar (44) and flange (45) bearing against the piston (42). The other end of the tie-rod (37) is attached to the press frame in a quickly detachable manner. In Fig. 5 (not shown), the hydraulic tensioning means (60) acts upon the rear end of a lever (65) the front end of which is pivoted to the press frame, one end of the tie-rod (68) being connected to an intermediate point (69) of the lever (65) and the other end being connected to the press frame. Fig. 6 shows a mechanical press having a rotary crank 71 connected by a connecting-rod 73 to a slide member 74. Between the rod 73 and slide 74 is a load sensing device comprising a cylinder 78 and piston 79. The space above the piston 79 contains hydraulic fluid which is put under pressure on the working stroke of the press. This space is connected to the tensioning means 28. In a modification the crank press may utilize an electrical strain gauge controlling a pressure valve of an hydraulic tensioning system.