Hydraulic press with pressure cell with a tray whic consists of prestressed lamellas

Abstract

The present invention relates to a press of pressure cell type and a tray for use in a press of pressure cell type. The tray which defines a space for arranging a forming tool and/or a workpiece has prestressing means arranged on the external surface of the tray. The prestressing means induce a compressing prestress which acts in planes parallel to the plane of the tray.

1 . A press ( 10 ) of pressure cell type, which comprises a force-absorbing press body ( 12 ,  68 ) which encloses a press chamber, in which press chamber a tray ( 20 ,  60 ,  60   a ,  60   b ,  60   c ,  60   d ,  82 ) is arranged, which defines a space ( 26 ) for arranging a forming tool and/or a workpiece, characterised in that the tray comprises an annular configuration having an internal surface which defines said space, and an external surface ( 22 ), wherein prestressing means ( 24 ) which induce a compressing prestress which acts in planes parallel to the plane of the tray are arranged on the external surface.  
     
     
         2 . A press of pressure cell type as claimed in  claim 1 , wherein said prestressing means comprises at least one prestressing element which is wound round the external surface.  
     
     
         3 . A press of pressure cell type as claimed in  claim 2 , wherein said annular configuration comprises at least one plate-shaped, annular lamellar means ( 20 ,  60 ,  60   a ,  60   b ,  60   c ,  60   d ,  82 ) which has a central hole, a workpiece being adapted to be machined in the space which is formed by the central hole.  
     
     
         4 . A press of pressure cell type as claimed in any one of claims  1 - 3 , wherein the tray comprises a number of concentric, plate-shaped, annular lamellar means which abut against one another, each have a central through hole and are located in planes that are parallel to the plane of the tray, a workpiece being adapted to be machined in the space which is mutually formed by the holes of the concentric lamellar means.  
     
     
         5 . A press of pressure cell type as claimed in any one of claims  3 - 4  combined with  claim 2 , wherein the prestressing element is band-shaped and has essentially the same width as the thickness of a lamellar means, each lamellar means being provided with a prestressing element.  
     
     
         6 . A press of pressure cell type as claimed in  claim 4  or  5  combined with  claim 4 , wherein the lamellar means are detachable from one another.  
     
     
         7 . A press of pressure cell type as claimed in any one of claims  3 - 6 , wherein the lowest lamellar means ( 20 ,  60 ,  60   b ,  60   d ) is detachably arranged on a bottom plate ( 16 ,  64 ) in the press chamber.  
     
     
         8 . A press of pressure cell type as claimed in any one of claims  3 - 7 , wherein a diaphragm support ( 18 ,  62 ) for holding a diaphragm ( 28 ) is arranged above and, when pressing the workpiece, in abutment against the uppermost lamellar means ( 20 ,  60 ,  60   a ) in such a manner that the diaphragm together with a press plate ( 14 ,  66 ) which is arranged in the upper portion of the press chamber forms a pressure cell, the diaphragm in connection with the supply of pressure medium to the pressure cell being adapted to exert a forming pressure on the workpiece arranged below.  
     
     
         9 . A press of pressure cell type as claimed in  claim 8 , which is designed with such dimensions that at least the diaphragm support, and optionally one or more lamellar means, is liftable with the purpose of uncovering the underlying lamellar means inside the press chamber, one or more of said underlying lamellar means being removable from the press chamber while the diaphragm support and any remaining lamellar means are left inside the press chamber.  
     
     
         10 . A press of pressure cell type as claimed in  claim 9 , wherein the remaining lamellar means are removable from the press chamber when the press chamber is free from said underlying lamellar means.  
     
     
         11 . A press of pressure cell type as claimed in any one of claims  3 - 10 , which comprises at least one force-transmitting means ( 52 ,  80 ), such as hydraulic pistons, which is adapted to actively apply to one or more of the lamellar means, and preferably the diaphragm support, one or more prestressing and/or predeforming forces in the plate-plane of the lamellar means so that tensile stress and compressive stress which arise in connection with pressing are counteracted.  
     
     
         12 . A press of pressure cell type as claimed in any one of the preceding claims, wherein the tray is made of hot-rolled steel plate.  
     
     
         13 . A tray ( 20 ,  60 ,  60   a ,  60   b ,  60   c ,  60   d ,  82 ) for use in a press of pressure cell type ( 10 ), which tray defines a space ( 26 ) with the purpose of arranging a forming tool and/or a workpiece, characterised in that the tray comprises an annular configuration having an internal surface which defines said space, and an external surface ( 22 ), wherein prestressing means ( 24 ) which induce a compressing prestress which acts in planes parallel to the plane of the tray are arranged on the external surface.  
     
     
         14 . A tray as claimed in  claim 13 , wherein said prestressing means comprises at least one prestressing element which is wound round the external surface.  
     
     
         15 . A tray as claimed in  claim 14 , wherein said annular configuration comprises at least one plate-shaped, annular lamellar means ( 20 ,  60 ,  60   a ,  60   b ,  60   c ,  60   d ,  82 ) which has a central hole, a workpiece being adapted to be machined in the space which is formed by the central hole.  
     
     
         16 . A tray as claimed in any one of claims  13 - 15 , which comprises a number of concentric, plate-shaped, annular lamellar means which abut against one another, each have a central through hole and are located in planes that are parallel to the plane of the tray, a workpiece being adapted to be machined in the space which is mutually formed by the holes of the concentric lamellar means.  
     
     
         17 . A tray as claimed in any one of claims  15 - 16  combined with  claim 14 , the prestressing element being band-shaped and having essentially the same width as the thickness of a lamellar means, each lamellar means being provided with a prestressing element.  
     
     
         18 . A tray as claimed in any one of claims  13 - 17 , preferably for use in a press of pressure cell type as claimed in any one of claims  1 - 12 , wherein said space has a rectangular or square cross-section in planes which are parallel to the plane of the tray.  
     
     
         19 . A tray as claimed in  claim 18 , wherein said rectangular or square cross-section is provided by means of filling elements ( 34 ,  54 ) which are arranged on the inside of the tray, which inside has an essentially oval shape, preferably defined by two parallel straight sides which are connected to one another at the ends by means of semi-circular portions.  
     
     
         20 . A tray as claimed in  claim 16 , wherein two lamellar means which abut against one another are formed in such a manner that a workpiece, such as a metal sheet, which extends transversely to said space, is kept in position when these two lamellar means have been joined.  
     
     
         21 . A tray as claimed in any one of claims  13 - 20 , wherein the tray is made of hot-rolled steel plate.  
     
     
         22 . A method for manufacturing a tray for use in a press of pressure cell type, comprising the steps of 
 forming the tray of steel plate, and    inducing a remaining compressing prestress in the tray, the prestress acting in planes parallel to the plane of the tray.    
     
     
         23 . A method as claimed in  claim 22 , wherein the step of forming the tray comprises forming plate-shaped lamellar means of steel plate, preferably hot-rolled steel-plate, and providing each of them with a through hole, and arranging each lamellar means with the plane of the plate oriented parallel to the plane of the plate of a concentrically abutting lamellar means, a workpiece being adapted to be machined in the space which is mutually formed by the holes of the concentric lamellar means.  
     
     
         24 . A method as claimed in  claim 23 , wherein prestressing elements are wound round the external edge surface of the lamellar means with the purpose of providing said prestressing.  
     
     
         25 . A method as claimed in  claim 24 , wherein a prestressing element is used, which is band-shaped and has essentially the same width as the thickness of a lamellar means.  
     
     
         26 . A method as claimed in any one of claims  23 - 25 , which comprises giving the lamellar means the desired shape by milling or cutting, such as water cutting, plasma cutting, flame cutting, etc.  
     
     
         27 . A method as claimed in any one of claims  23 - 26 , which comprises making the lamellar means of steel plate having a thickness of 80-200 mm, preferably 100-150 mm, especially 100-120 mm.