Presses – Reciprocating press construction – Box and piston type
Patent
1995-09-19
1997-04-22
Gerrity, Stephen F.
Presses
Reciprocating press construction
Box and piston type
10026905, 10026908, 10026918, 425 77, 425DIG26, B30B 132, B30B 1528
Patent
active
056221053
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a high-pressure press, more specifically a high-pressure press; comprising a first cylinder element, at least one second cylinder element pressed into the first cylinder element, and a pair of end elements which together with the second cylinder element delimit a high-pressure chamber and of which one end element exhibits a cylinder bore, opening out into the high-pressure chamber, for a high-pressure piston and has parts which are movable to a limited extent in the axial direction and are adapted to form supports for the second cylinder element and a sealing device inserted between the second cylinder element and the high-pressure piston, the axially movable parts being loaded by hydraulic pressure in a direction towards the second cylinder element and the sealing device.
BACKGROUND OF THE INVENTION
High-pressure presses dimensioned for a pressure of up to 14,000 bar in the high-pressure chamber comprise, in a known embodiment, a thick-walled main cylinder of high-tensile steel, which is prestressed by means of several layers of prestressed steel wire wound around the cylinder, and a liner, which may be divided into an outer liner and an inner liner, pressed into the cylinder. In presses operating with such high pressures, very great demands are placed on the quality of the steel wall in the inner liner. The liner must be made with a view to preventing cracks in the inner wall surface. However, it is impossible to avoid that cracks pass which are so small that they cannot be detected with conventional crack detecting methods, but which in the long run, under the influence of the pressure variations during a number of work cycles, unavoidably extend to such an extent that the liner is finally split open and breaks into two parts.
When a pressure of the order of magnitude of 14,000 bar is allowed to act against the surfaces of fracture of the liner parts, the parts are subjected to enormous forces when, in principle, they are transformed into annular pistons. The force on one liner part can be taken up directly by the end member fixed against the liner by the press frame. As far as the other part is concerned, however, the conditions are different. In a known embodiment, the second end member, which serves as sealing or packing holder, is connected to a number of piston elements which are provided in evenly distributed axial cylinder bores in the low-pressure piston which generates the press force of the high-pressure piston. In the cylinder bores a cylinder pressure prevails, under the influence of which the packing holder end member balances the pressure on the packing exerted by the pressure in the high-pressure chamber. Since this end member also forms a support for one end of the liner, the liner fracture results in the force on the end member suddenly being multiplied. This force is transmitted via the piston elements to the low-pressure piston. The result is that heavy equipment, up to the order of magnitude of 5 tons, is moved approximately half a metre in one-thousandth of a second, which creates a powerful pressure shock in the whole hydraulic system and leads to the whole press being moved, whereby anchor bolts and connected hydraulic lines are torn off.
To avoid the dramatic consequences and the heavy costs which are connected with a liner fracture, the inner liner is regularly changed in good time before the expiry of the expected service life. Such preventive liner exchanges are costly and still do not completely solve the problems of liner fracture, since it has proved that about 10% of the liners are subjected to fracture within the expected safety margin as regards the number of work cycles.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a high-pressure press of the kind stated in the introductory part of the description, which is so designed that the above-mentioned problems and costs which are connected with liner fractures can be eliminated and reduced, respectively.
This is achieved according to t
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Asea Brown Boveri AB
Gerrity Stephen F.
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