SEALING ARRANGEMENT IN HYDRAULIC PRESS

Abstract: The invention relates to a press comprising a hydraulic cylinder unit with a cylinder barrel and a piston, a seal housing (6) being provided at the hydraulic pressure side of the piston (8) in such a manner that the hydraulic pressure will force the seal housing (6) against the internal surface of the cylinder barrel (4). The seal housing (6) is designed like a rectangular ring and is made of a relatively flexible or soft material, so as to be able to adapt to the deflection of the cylinder barrel. A preferred material is bronze, but other materials are also conceivable, e.g. plastics.

Description: TITLE OF INVENTION: SEALING ARRANGEMENT IN HYDRAULIC PRESS FIELD OF INVENTION The present invention relates to a hydraulic press, and more specifically a hydraulic press provided with a preferably rectangular hydraulic cylinder unit. The rectangular hydraulic cylinder is suitable for pressing rectangular objects. The hydraulic press according to the invention also comprises a flexible frame consisting of parallel, flat pillars. A frame of this kind is known from our co- pending Swedish Patent Application No. 9602349-4, filed on June 14, 1996. The invention relates particularly to an advantageous sealing arrangement, solving the problem of leakage in rectangular hydraulic cylinders. STATE OF THE ART Rectangular cylinder units are known, as such, in various contexts, e.g. for presses and combustion engines. It is not previously known, however, to utilise rectangular hydraulic cylinders in hydraulic presses comprising a frame constructed from pillar modules. The pillars support the hydraulic cylinder from two opposite sides. SUMMARY OF THE INVENTION The present invention thus provides a press comprising a hydraulic cylinder unit with a cylinder barrel and a piston. The unit has a cross-section shape adapted to the product to be pressed. According to the invention, the press comprises a frame having parallel, flat pillars, surrounding the hydraulic cylinder unit on two opposite sides. A seal housing is arranged on the hydraulically pressurised side of the piston, in such a manner as to press the seal housing against the internal surface of the cylinder barrel, to provide adequate sealing. The invention is specified in detail by the accompanying claims. BRIEF DESCRIPTION OF THE DRAWINGS The invention is described in detail below, with reference to the accompanying drawings, in which: Fig. 1 is a front view of an embodiment of the hydraulic press according to the present invention; Fig. 2 is a side view of the hydraulic press of Fig. 1 ; Fig. 3 is a section view according to the line III-III in Fig. 2; Fig. 4 is a section view according to the line IV-IV in Fig. 1 ; Fig. 5 is a section view according to the line V- V in Fig. 1 ; DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT The invention thus relates to a hydraulic press having a hydraulic cylinder unit with a cylinder barrel and a piston, the cross-sections of which are adapted to the product to be pressed in the hydraulic press. The invention will be described with reference to a rectangular shape, as this shape is at present the most useful one. The advantage of having a rectangular cross-section of the hydraulic cylinder unit for a rectangular product, is that the pressing force will be evenly distributed across the surface to be pressed. Bending torque on the press tables outside the products are avoided. With e.g. circular hydraulic cylinder units and rectangular products, thick press tables are required to distribute the pressing force evenly across the product. Other advantages are that an adapted pressure may be used, and that the dimensions and the weight of the hydraulic press may be generally reduced in a favourable way. The hydraulic cylinder unit according to the invention is arranged in a frame as will be described in the following. A patent on the frame has been separately applied for in our Swedish Patent Application No. 9602349-4. This frame has many advantages regarding manufacture, transport and assembly, etc., as is described in more detail in said application. With reference to the drawings, a frame suitable for a hydraulic press is illustrated, together with part of the machinery equipment for the hydraulic press. Pressing dies and other conventional equipment are not shown in the drawings, for increased clarity in illustrating the idea of the invention. The frame generally comprises vertical and parallel plates or pillars 2. In the embodiment shown, the number of pillars is five. In the pillars 2, a number of holes are provided. Through these holes run threaded rods 14. The number of vertical pillars 2 and the number of threaded rods 14 may of course be varied as necessary. The pillars 2 are held at correct distances from each other by means of nuts 15, which are placed on both sides of each plate 2, and which are tightened to fix the pillars in position. The distance between the pillars can be easily adjusted by loosening the nuts and screwing them in one direction or the other to displace the pillar located between them. In this manner, the distance between the pillars 2 may be set completely arbitrarily. In order to further stabilise the frame, and to fasten items of machinery, a horizontal top plate, here called roof 1, is preferably attached to the upper side of the frame. The roof 1 may conveniently be fastened by screws, as shown in the drawings. The frame is also preferably equipped with a bottom plate or mounting 13, fastened by screws and angle irons 16. The hydraulic press frame further comprises an upper press table 3 and a lower press table 12 for fixing the hydraulic press, the press table 3 being provided with entrance holes for the hydraulic and other connectors of the hydraulic press. The press tables are fastened to the different plates by their respective screws, see e.g. at 11. Referring now particularly to Fig. 3, the design of the hydraulic cylinder unit is illustrated. The hydraulic cylinder unit comprises a cylinder barrel 4 having an approximately rectangular cross-section (see Figs. 4 and 5). The cylinder barrel 4 is fastened to the upper press table 3 by means of screws. The barrel has a hydraulic pressure inlet 5 for hydraulic fluid. The hydraulic fluid acts upon the top side of a piston 8, having a corresponding cross-section. The piston 8 is attached to a moving press table 10. An object to be pressed is placed between the moving press table 10 and the lower press table 12. When the hydraulic fluid is pressurised inside the barrel, the latter is subjected to a certain deflection, which is somewhat waved, due to the barrel only being supported at the pillars 2, see in particular the section views of Figs. 4 and 5. The piston 8, however, is only subjected to an axial pressure and does not deflect sideways. If the piston 8 had been equipped with conventional seals between the piston 8 and the cylinder barrel 4, a wave-shaped clearance would have been created here, which had been difficult to seal off. The present invention, however, includes a new sealing arrangement allow- ing an efficient seal between piston and barrel. A seal housing 6 is provided on the pressure side of the piston 8. As is best seen in Figs. 4 and 5, the seal housing is shaped like a rectangular ring. Consequently, the hydraulic pressure acts on the inside of the seal housing, pressing it against the inner surface of the barrel 4. The seal housing 6 is made of a relatively flexible or soft material, so as to be able to adapt to the deflection of the barrel. A preferred material is bronze, but other materials are also conceivable, e.g. plastics. The seal housing is fixed to the piston by fastening means extending, with a clearance (not visible), in holes in the seal housing. The clearances are large enough for the seal housing to be able to follow the deflection of the cylinder barrel 4 without causing any stressing of the piston 8. In order to further improve the seal, hydraulic seals 7A, 7B are provided in grooves in the seal housing 6. Preferably, there is a lateral seal 7A between the seal housing 6 and the barrel 4, as can be seen in the section view of Fig. 4, and an axial sealing device 7B between the seal housing 6 and the piston 8, as can be seen in the section view of Fig. 5. The sealing devices are compressed to so called zero play for an efficient sealing function. The present invention thus provides a hydraulic press having the above described advantages. As has been mentioned above, and as is evident for a person skilled in the art, many modifications and variations are conceivable, without deviating from the scope of the invention as defined by the following claims.

Claims: CLAIMS 1. A press comprising a hydraulic cylinder unit with a cylinder barrel and a piston, characterised by a seal housing (6) being arranged on the hydraulic pressure side of the piston (8) in such a manner that the hydraulic pressure will force the seal housing (6) against the internal wall of the cylinder barrel (4). 2. A press according to claim 1, characterised by the seal housing (6) being attached to the piston (8) in a radially displaceable manner. 3. A press according to claim 2, characterised by the seal housing (6) being attached to the piston (8) by means of fastening means extending, with a clearance, through holes in the seal housing (6). 4. A press according to any one of claims 1, 2 or 3, characterised by the seal housing (6) being made of a flexible material. 5. A press according to claim 4, characterised by the seal housing (6) being made of bronze or plastics. 6. A press according to any one of claims 1 to 5, characterised in that at least one sealing device (7 A, 7B) is provided in a groove in the seal housing (6). 7. A press according to claim 6, characterised in that one sealing device (7 A) is arranged in a lateral groove and in contact with the internal surface of the cylinder barrel (4), and in that one sealing device (7B) is arranged in an axial groove and in contact with the surface of the piston (8). 8. A press according to any one of claims 6 or 7, characterised in that the sealing device (7 A, 7B) is compressed to zero clearance. 9. A press according to any one of the preceding claims, characterised in that the cross-section shape of the cylinder unit is rectangular.

Inventors: PERSSON LARS, PERSSON, LARS
Applicants: LARS PERSSON I SKAANE AB, PERSSON LARS, PERSSON, LARS
Application year: 1997
Main classification: B30B1
IPC codes: B30B1, B30B15