HYDRAULIC PRESS WITH A PRESSURE CELL AND A METHOD AND USE FOR IT, WHOSE PRESS BODY CONSISTS OF PRESTRESSED LAMELLAS

Abstract: The present invention relates to a press of pressure cell type and a method for manufacturing a press body part. The press body part comprises a number of plate-shaped lamellar means having the planes of the plates oriented parallel to the planes of the plates of the adjacent lamellar means. Each lamellar means has a through hole which has the same centre axis as the hole of the adjacent lamellar means. Prestressing means which induce a compressing prestress acting in the planes of the plates are arranged on an external edge surface of the main part of the lamellar means. The invention also relates to a lamellar means of a press body part.

Description: Hydraulic press with a pressure cell and a method and use for it, whose press body consists ofprestressed lamellas Field of the Invention The present invention relates to a press of pressure cell type, which comprises a press chamber being enclosed by a force-absorbing press body. The invention also re- lates to a method for manuf cturing a press body part . Background Art A press of pressure cell type generally comprises a force-absorbing press body which defines a press chamber. In the upper part of the press chamber, a press plate and a diaphragm of rubber or another resilient material are arranged, which together form a pressure cell. The pressure cell communicates with a source of pressure and expands when a pressure medium is supplied. In the lower part of the press chamber, a structural support or a tray- is arranged, which comprises a bottom plate having a tray frame. The tray supports a forming tool, a workpiece, a mat of rubber or another resilient material, covering the forming tool and the workpiece. Presses of pressure cell type are used, among other things, when forming sheet-shaped blanks, for example sheets of steel or aluminium, to short series products within the aircraft industry and the motor industry. The sheet is placed in the press in such a manner that one of its sides faces a forming tool. The resilient diaphragm is arranged on the other side of the shee . A closed space between the diaphragm and the press plate located above the diaphragm constitutes the pressure cell and this space is filled during the forming process with a pressure medium. By pumping additional pressure medium into the pressure cell, the pressure is increased in the pressure cell and the resilient diaphragm is pressed during stretching against the sheet which, in its turn, is formed round or in the forming tool . When the sheet com- pletely fits to the forming tool, the pressure in the pressure cell is released and the diaphragm is removed, after which the formed component can be taken out of the press . Another field in which presses of pressure cell type are used is wood compaction when a workpiece of wood is exposed to high pressure, either in a forming tool or on its own. Reasons for compacting wood are, for example, that it is desirable to increase the hardness of the wood, decrease the moisture content or to obtain a phase in pressure impregnation. A press of pressure cell type according to that mentioned above is known through SE 452 436. Said patent specification discloses a press plant having a forged, cylindrical press body which requires large, heavy filling blocks to provide a press chamber of an essentially rectangular cross-section. In order to handle the large forces to which the press body is exposed in connection with pressing, the body is wound with steel wire. A press of this type has to be ordered before being manufactured and the complicated work of forging and winding the press body requires several months. It usually takes 15-18 months from order to delivery. The delivery itself is very complicated since, on the one hand, the size of a large press makes road or railway transport difficult and, on the other, the weight amounts to tens of tonnes. Attempts have been made to manufacture lighter presses having less material in relation to the size than conventional presses have. However, technical problems relating to both manufacturing technique and strength have resulted in these presses only managing a limited working pressure that has been too low with respect to the high pressure which is required in a modern press plant, typically up to 1200 bar. Summary of the Invention The object of the present invention is to provide a press of pressure cell type which in comparison with prior-art technique is cheaper and faster to manufacture, as well as easier to handle and transport. Another object of the invention is to provide a method for manufacturing a press of pressure cell type, which method is quick and easy. These and other objects which will be evident from the following description are achieved by a press of pressure cell type and a method, which have the features indicated in the appended claims. According to one aspect of the invention, a press of pressure cell type is provided, which comprises a press chamber which is enclosed by a force-absorbing press body. The press body comprises a number of plate-shaped lamellar means with the planes of the plates oriented parallel to the planes of the plates of adjacent lamellar means . Each lamellar means has a through hole which has the same centre axis as the hole, said centre axis coinciding with the direction of the main axis of the press chamber being enclosed by the holes. Each lamellar means has an internal edge surface which defines the hole and an external edge surface, prestressing means which induce a compressing prestressing acting in the planes of the plates being arranged on the external edge surface of the main part of the lamellar means. Each prestressing means comprises a prestressing element which is wound round a respective lamellar means and is band-shaped and has es- sentially the same width as the thickness of a lamellar means . According to another aspect of the invention, a method is provided for manufacturing a force-absorbing press body part . The method comprises the steps of forming plate-shaped lamellar means and providing each of them with a through hole, inducing a lasting compressing prestress which acts in the planes of the plates in at least the majority of the lamellar means by winding a band-shaped prestressing element, which has essentially the same width as the thickness of a lamellar means, round the external edge surface of the lamellar means with the purpose of causing said prestress, and arranging each formed lamellar means having the plane of the plate oriented parallel to the plane of the plate of an adjacent lamellar means so that the through holes obtains a common centre axis and so that the lamellar means constitute a force-absorbing press chamber- enclosing press body part. In the present application, terms describing posi- tion and direction, such as "vertical" and "horizontal", are used. In this application, these terms are defined with respect to the arrangement of the press-body-forming lamellar means. Thus, each lamellar means extends essentially vertically, whereas the direction of the main axis of the press chamber enclosed by the lamellar means is horizontal. In the application, it should also be understood that "over/upwards/above" and "under/downwards/below" are defined with respect to the essential direction of the pressing, i.e. so that a press plate is located above a diaphragm which, in its turn, is located above a bottom plate, which means that vertically is defined as perpendicular to the press plate and horizontally as parallel to the press plate. The above- mentioned definitions have been indicated for sake of clarity since the press of pressure cell type can be inclined in different manners, and due to this fact the relative directions can vary. The present invention is thus based on the understanding that considerable improvements regarding han- dling and time expenditure can be provided by means of a press body which is divided into vertical plates and has essentially maintained force-absorbing capability due to applied prestressing means. Consequently, the invention allows deviation from the traditional manufacturing process of forming an es- sentially homogeneous press body of two cylinder halves. On the contrary, it is possible to provide a press body which is inhomogeneous by the plate-shaped lamellar means being arranged at a distance from one another. It has been found that an excellent force-absorbing capability is obtained also by means of such a hollow construction which has several operational advantages that will be described below. A prestressing means which is arranged on the external edge surface of a lamellar means preferably comprises a prestressing element that is wound round the lamellar means, such as metal wire or metal band. According to one advantageous embodiment, the prestressing element is band-shaped and has essentially the same width as the thickness of the lamellar means. If the main part of the lamellar means is prestressed by a band, the width of which (about 80- 200 mm, typically 100-200 mm) essentially equals the thickness of the lamellar means, being wound round the external edge surface of these lamellar means, several advantages will be obtained. For example, there is no essential stress concentration, but a mainly even stress distribution is obtained in the lamellar means. The shape of the lamellar means can be selected in such a manner that optimal stress distribution is achieved, also with relatively few turns of the band. A suitable band is made of spring steel having a thickness of some tens of a millimetre, typically about 0.2 mm. Due to the winding, the lamellar means obtain a considerable length of service, which means that inspections of the press can be per- formed at reasonable intervals. Conveniently, each lamellar means is provided with a number of apertures, such as two apertures symmetrically arranged on each side of the hole. In an assembled position, the lamellar means are arranged in such a manner that the apertures in the respective lamellar means have the same centre axis as the corresponding apertures in the other lamellar means. Preferably, a type of coupling means, such as a steel rod, for coupling lamellar means is adapted to run through a respective one of said series of apertures. Thus, these coupling means have a longitudinal extension which is parallel to the direction of the main axis of the press chamber. The relative distance between two lamellar means is adjustable with the aid of distance means which are arranged on the coupling means. The thickness of the distance means essentially corresponds to the desired rela- tive distance between two neighbouring lamellar means. The distance can be adapted to the stress to which the press body will be subjected when in operation. Preferably, the distance between neighbouring lamellar means, does not vary in the press body, but is similar as re- gards all lamellar means that are adjacent to one another. The distance means are made of a relatively rigid material and their inner diameter is larger than that of the coupling means at the same time as their outer dimensions are considerably larger than the apertures formed in the lamellar means. It has been found to be especially advantageous to make the thickness of the distance means essentially the same as the thickness of the lamellar means, which means that they can be made of a similar sheet-metal blank. The coupling means are tightened with the aid of suitable means to a predetermined prestressing condition so as to avoid play and motion in the construction. At the same time the coupling means promotes the structural stability of the construction regarding flexural rigid- ity, torsional rigidity and resistance to extension in all dimensions. Between the lamellar means of the press body and the press chamber which is enclosed in the lamellar means, stress distributing elements can be arranged and extend over the press chamber. Conveniently, the stress- distributing elements cooperate with the internal edge surface of each lamellar means and distribute stress or thrust, which arise in connection with pressing in the press chamber along the series of lamellar means. The stress-distributing elements can constitute parts of the wall of the press chamber. The shape of a preferably central hole which is formed in the lamellar means is made with respect to stress concentration that can arise in critical areas and that should be avoided. The stress-distributing elements are essentially quadrangular in cross-section and cooperate with plane contact surfaces of the lamellar means. The plane contact surfaces define the hole in an essentially quadrangular configuration, the end of a predetermined contact surface connecting to a contact surface which is perpendicular to said predetermined contact surface by means of a concave bending in the wall of the lamellar means. The radius of the concave bending is made relatively large with the purpose of minimising stress concentration which arises in the areas of the corners of the hole. As regards the shape, an advantageous design of the internal hole can also be described as two ovals which are parallel to one another as regards their long sides and which are separated by a quadrangular space. Preferably, also the shape of the lamellar means is considered with respect to the operating conditions . Therefore, each lamellar means is suitably given such a shape that its extension in different directions is essentially proportional to the expected thrust in the cor- responding directions. For example, the extension of the lamellar means in the vertical direction can be larger than in the horizontal direction, if the expected thrust is larger in the vertical direction. This may be the case if the direction of the pressing is essentially vertical. The number of winding turns which is arranged on the lamellar means is suitably adapted to the shape of the la- mellar means in such a manner that sufficient prestress is obtained. As mentioned above, the invention also relates to a method for manufacturing a press body part . There are a large number of advantages of the manufacturing technique according to the present invention, which will be evident in the following. The lamellar means can be given the desired shape by milling or cutting. Different types of cutting are possible, a few examples being water cutting, plasma cutting and flame cutting. Those skilled in the art will realise that this is a considerably simpler process than the forming of the traditional compact press body by forging. Preferably, the lamellar means are made of hot-rolled steel sheet which subsequently is easily given the de- sired shape. In the present invention, it has turned out to be suitable to use a sheet thickness of 80-200 mm, preferably 100-150 mm, especially 100-120 mm. Due to the fact that the lamellar means are separate units which, by degrees, together are to form a press body, manufacture can be accelerated considerably. Thus, various lamellar means blanks can be machined in the respective stations at the same time. A first lamellar means blank can be machined in a certain station and when this lamellar means blank has been moved on to a subse- quent station for further machining, a second lamellar means blank can be machined at the same time in said certain station. This parallel managing of different manufacturing steps thus turns out to be very beneficial . It is also distinctly easier to move a relatively thin la- mellar means in comparison with a large traditional press body. Preferably, some stations can process several lamellar means blanks simultaneously. The lamellar means are easily transported to the location where the press of pressure cell type is intended to be used and assembled in situ. Conveniently, a lamellar means is made in one piece. Alternatively, it can be made in several pieces and be suitably assembled to a lamellar means . Such an assembled lamellar means is firmly held together by means of bands which are wound round the external edge surface of the assembled lamellar means and/or with the aid of other locking means. Due to the ease with which the lamellar means can be handled, unlike prior-art technique it is possible to move the press of pressure cell type relatively easily from one location to another by simple disassembling and reassembling of the lamellar means. If a separate lamellar means is to be removed or replaced due to maintenance, this can easily be made in the following way. The parts of the press of pressure cell type which are enclosed by the press body are suitably removed first from the press body, after which the lamellar means which is to be removed is released. The actual releasing can be carried out by displacing a first set of coupling means, which runs through the apertures formed in the lamellar means, along the direction of the main axis of the press out of a first end of the press, i.e. a lamellar means which defines one end of the press body. Almost at the same time, a second set of coupling means is inserted along the direction of the main axis into a second end of the press body, i.e. a lamellar means which defines the other end of the press body. The displacement of the first set and the insertion of the second set of coupling means are carried out in such a manner that the lamellar means which is to be released is contactless between said first and second set. Subsequently, the lamellar means is removed from the press. If it is desirable to replace a removed lamellar means with a new lamellar means at the corresponding lo- cation, essentially the opposite is carried out compared to the method described above. First of all, a first set of coupling means is thus arranged through the apertures in the lamellar means which are positioned on one side of the location where the new lamellar means is to be incorporated, and then a second set of coupling means is arranged through the apertures in the lamellar means which are positioned on the other side of said location. Consequently, the coupling means should not protrude towards the centre more than to provide space for placing the new lamellar means. When the new lamellar means has been positioned in the press, the first set of coupling means is displaced through this lamellar means and the other lamellar means into which the second set of coupling means is inserted, at the same time as this second set is taken out of the press. Finally, only the first set of coupling means will thus run through all the lamellar means which constitute the press body. Alternatively, a lamellar means can be released and replaced by pushing out a number of the coupling means, for example half the quantity, in one direction until they are detached from the lamellar means at issue, and pushing out the remaining coupling means in the opposite direction until they are detached from the lamellar means at issue. Thus, some coupling means will still be positioned in a group of lamellar means, whereas the remaining coupling means will be positioned in another group of lamellar means, no supplementary coupling means being required for the releasing process. When the replacement has been carried out, the coupling means are simply pushed back to their initial position. When releasing and replacing a lamellar means, it is also conceivable to use an external stabilising beam which supports the other lamellar means with the purpose of increasing the stability in the construction. A great advantage of the present invention is the accessibility to the internal portion of the press body. Preferably, the internal lamellar means are integrated with limiting means for essentially permanently limiting the expansion of these lamellar means. Said limiting means conveniently comprise bands which are wound round the external edge surface of the lamellar means in a way corresponding to that of the lamellar means which form the press body. Thus, no external force-absorbing device is required on the short sides of the press chamber. The press construction can therefore be made rela- tively open by the short sides of the press chamber wall, i.e. the external sides of the internal lamellar means, being accessible to allow insertion and removal of the internal lamellar means. In the assembled press, preferably some of the internal lamellar means will at the ends of the press protrude from the actual press body. Advantageously, the internal lamellar means are loosely arranged on the bottom plate and on one another. However, a sort of control element is arranged in order to ensure correct positioning. Due to the fact that the internal structure comprises lamellar means which are loosely arranged on one another, it is possible to remove them easily one by one or several of them at the same time . Particularly great advantages are obtained by means of the above-described embodiment having internal lamellar means which are arranged on one another, especially as regards manufacturing, handling, freight and transport. In addition, these internal lamellar means are preferably made of the same kind of sheet-metal blank as the lamellar means which form the press body. Thus, each internal lamellar means, as well as the press-body- forming lamellar means, can be made in one piece or in several pieces . Also other parts included in the press are suitable to be manufactured from a similar sheet-metal blank, for example press plate, bottom plate, distance means and stress-distributing element. This means that the manufac- ture of the parts included in the press essentially can be made at one location and the parts are, for example, delivered unassembled to the location where the press is to be used, after which the press is assembled in situ. Preferably, the press of pressure cell type is assembled in situ on a suitable type of foundation which keeps the construction in position. Brief Summary of the Drawings Fig. 1 is a side view of a lamellar means which is included in a press of pressure cell type shown according to one embodiment of the invention. Fig. 2 is a perspective view in cross-section of the lamellar means in Fig. 1. Fig. 2B illustrates one example of a device for locking a band. Fig. 3 is a top view of a press of pressure cell type according to one embodiment of the invention. Fig. 4 is an end view of the press of pressure cell type in Fig. 3. Fig. 5 is a side view, partly in cross-section, of a press of pressure cell type according to one embodiment of the present invention. Fig. 6A shows the press of pressure cell type in cross-section along the line B-B in Fig. 5. Fig. 6B is a top view of a detail in Fig. 6A. Figs 7A-7E schematically illustrate different variants of lamellar means. Detailed Description of the Drawings Fig. 1 is a side view of one embodiment of a lamellar means 10 which is included in a press of pressure cell type according to the invention. Fig. 2 is a perspective view in cross-section of the lamellar means 10 in Fig. 1. The cross-section is made along the line A-A in Fig. 1. These figures show that the lamellar means 10 is plate-shaped and thus has two side surfaces or main surfaces 12. The circumference of the lamellar means 10 is defined by a relatively narrow, circumferential, external edge surface 14. The lamellar means 10 is provided with a central through hole 16 which is defined by an in- ternal edge surface 18. The hole 16 is essentially quadrangular, but without actual corners. The "corner regions" are instead rounded and bend inwards into the wall so that a larger hole area is obtained. The radii of these inward bends are made relatively large with the aim of minimising the stress concentration that arises in the corner regions . The lamellar means 10 is essentially quadrangular and has rounded corners. The shape of the lamellar means is adapted to the expected thrust which arises in connec- tion with the pressing. Thus, the material quantity or the distance between the internal and the external edge surface is larger vertically than horizontally since the main direction of pressing is vertical. A plurality of turns of a band 20 of spring steel are wound round the external edge surface 14 of the lamellar means 10, the band 20 having a width which essentially corresponds to the thickness (about 120 mm) of the lamellar means 10. The height of the layer of band is about 100 mm and the layer can consist of one single long band or several joined bands. When the lamellar means 10 is being manufactured, the band 20 is wound round the same during resistance so that a compressive prestress is permanently induced in the lamellar means 10. As shown in Fig. 2 (not in Fig. 1) , the lamellar means 10 can be pro- vided with a type of control element 22 adjacent to the external edge surface 14 of the lamellar means 10 with a view to facilitating the winding of the band. This control element 22, which is shown more clearly in Fig. 2B, also operates as a device for locking the winding of the band. 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SD φ rt 0 Φ μ- CQ Ω 0 SD μ- 03 μ- Φ cr φ tr SD 0 μ- P ø μ- Φ Ω Φ 0 ii 03 ø O li O CQ SD 0 ø 3 rt ø Pi 0 SD 0 1 ø 1 03 μ- Ω P O 0 ι-3 i I- 1 SD ø 0 μ- CQ φ h- 1 Φ <! 0 03 03 CQ Φ SD Pi 1 Φ Hi IQ - tr SD ct 0 • ϋ rt SD μ- Φ rt φ CQ Φ 0 Pi ii φ 1 to Φ ϋ tr 1 Φ ■ ! • O 0 ø H 0 IQ 1 03 • Φ Hi 03 IQ Φ with the centre axis of the central holes. Fig. 3 shows an upper press chamber wall 46 and two side walls 48 which are perpendicular thereto. Fig. 4 is an end view of the press 40 of pressure cell type in Fig. 3. From the side it is thus possible to see the main surface of an end lamellar means 42' having the central hole 52. This lamellar means 42' contains in the hole 52 together with the holes of the other lamellar means 42 a press chamber in which, for example, a work- piece of sheet-metal or wood is intended to be machined. In the upper portion of the holes, a press plate 54 is arranged in contact with the internal edge surface of the lamellar means 42. Thus, the press plate 54 can constitute the upper press chamber wall 46 shown in Fig. 3. Furthermore, Fig. 4 shows that a bottom plate 56 is arranged in contact with the internal edge surface of the lamellar means 42 in the lower portion of the holes. Between these plates 54, 56, a number of plate-shaped internal lamellar means 58 which abut against one another are arranged. The main surfaces or the plate planes of these internal lamellar means 58 have an extension which is parallel to the direction of main axis of the press chamber. Fig. 4 also shows that the longitudinal side walls 48 of the press chamber shown in Fig. 3 have a height which essentially corresponds to the distance between the upper press plate 54 and the bottom plate 56. The internal lamellar means 58 are during pressing exposed to an internal overpressure, and because of this fact the lamellar means aim at expanding, whereby high tensile stress in the internal periphery of the internal lamellar means 58 is generated. For this reason, a generator 60 of horizontal force is arranged adjacent to the left side wall in the figure. This generator 60 prede- forms and prestresses the deformation zones in the inter- nal lamellar means. Fig. 5 is a side view, partly in cross-section, of a press 70 of pressure cell type according to one embodi- ment of the present invention. A central portion of the press 70 of pressure cell type is cut out of the Figure, to the left of the central portion an ordinary side view of the press being shown and to the right of the central portion a side view in cross-section of the press being shown. Thus, to the left in the Figure the external edge surface 74 of the lamellar means 72 which are comprised in the press is shown. An upper press plate 76 and a bottom plate 78 run through the central holes of the lamel- lar means 72. Between these plates, two internal lamellar means 80a, 80b which abut against one another are arranged. Through circular apertures which were described in connection with Fig. 1 and Fig. 2, in all lamellar means included in the press body, run coupling means 82 (two of which are shown) , for example a steel rod having threaded ends. The lamellar means 72 are kept at a distance from one another by the fact that round each coupling means 82, between the lamellar means 72, there are distance means 84 having a thickness that is as large as the desired distance between the lamellar means. The distance means 84 are made of a relatively rigid material and their inner diameter is larger than that of the coupling means 82 at the same time as their external measures are essentially larger than the apertures arranged in the lamellar means 72. At the two external ends of the coupling means 82, outside the respective external lamellar means which are included in the press body, there are stop devices 86 of which at least one has a fixing and clamping mechanism which is complementary to the coupling means. In the case when the coupling means 82 comprises a rod being threaded at its ends, the attaching and stressing mechanism can comprise a washer and a nut, the washer having external measures which are essentially larger than the coupling apertures of the external lamellar means. The four coupling means 82 are thus tightened to a predetermined prestress condition. This eliminates play and motion in the construction and at the same time con- tributes to the structural stability of the construction as regards flexural rigidity, torsional rigidity and resistance to extension in all dimensions. As already mentioned, the right part of Fig. 5 is a side view in cross-section of the press 70 of pressure cell type. The cross-section is made at the centre of the press, i.e. along the main axis of the press chamber. Fig. 5 shows that the lamellar means 72 which constitute the press body are wound with a band 88 on the respective external edge surfaces. Moreover, the Figure shows that also the internal horizontal lamellar means which abut against one another are wound with a band. This winding 88 of the internal lamellar means 80a, 80b with a band is intended to essentially permanently limit expansion of the internal lamellar means, i.e. they must be able to withstand the forces which are formed in the press chamber. The internal lamellar means 80a, 80b are annular, which thus means that they define an internal, open space which is comprised in the press chamber. In addition, Fig. 5 shows an upper internal lamellar means 80a and a subjacent lower internal lamellar means 80b. A diaphragm 90 is arranged in the open space of the upper internal lamellar means 80a. The diaphragm 90 has a seal 92 against the press plate 76 and forms a pressure cell therewith. During operation, a pressure medium is supplied to the pressure cell in such a manner that the diaphragm 90 expands. The open space 94 of the lower internal lamellar means 80b is intended to contain a tool. A metal sheet which is to be pressed against the tool is suitably arranged above the tool, the diaphragm 90, when being pressurised, expanding and being formed on the tool, which means that the metal sheet that is located therebetween is also formed on the tool. Besides, the Figure shows that a mat 96 is arranged just below the diaphragm. The carpet 96 takes part in the forming of the plate and at the same time protects the diaphragm against wear. Adjacent to the internal wall of the lower internal ω to t 1 H U " l o ( Jl o ( l O Π t J ^ φ ϋ μ- ii 0 LQ 0 rt • SD Φ μ * Ω σι rt — μ * μ- SD ø SD 3 IQ φ 03 SD 0 ø SD P tr ϋ SD TJ <! 3 ii φ Φ O SD I- 1 SD 0 0 03 0 J IQ ii r μ- 0 ■ <. ø rt IQ Φ P Ω μ- rt rt 03 tr μ- rt φ 0 ii tQ μ- 03 cr Φ Hi ø ii ø rt <! 0 μ- μ- Ω ø Ω rt tQ φ μ- 0 Hi ø O φ ii ø μ- Ω LQ ø Φ rt 03 " rt tr s: 0 Φ ø- Hi μ- 03 Ω rt φ tr tr ø φ 03 SD Φ ii μ- Φ ø 0 1 Hi generated during pressing operations. Since the internal lamellar means 80a, 80b are prestressed by the turns of the band 88, no external limiting means are required and therefore, for example, the semi-circular portions can protrude from the ends of the press body as shown in Fig. 3 and Fig. 5. Since the internal lamellar means 80a, 80b protrude, they are relatively easily accessible, which is time-saving when metal sheets are removed, tools are replaced, diaphragms are replaced etc. Figs 7A-7E schematically illustrate different variants of lamellar means. As these Figures show, lamellar means can be made in different sizes and have different shapes. The lamellar means shown in Fig. 7A essentially has the shape of a square having rounded edges and is suitably used for a press body which gives a load space of 100 X 200 X 2500 mm 3 . The working pressure in such a space is typically 1200 bar. Fig. 7B illustrates another possible shape which together with identical lamellar means forms a press body which gives a load space having the dimensions 125 X 500 X 1500 mm 3 and a typical working pressure of 700 bar. Fig. 7C illustrates a lamellar means which is composed of several parts and thus, unlike the previously shown lamellar means, is not made in one piece. In this case, two central parts 120, 122 together form the central hole. Two external parts 124, 126 are arranged at the external edge of the respective central parts in such a manner that a lamellar means of a suitable shape is provided. The four parts included in the lamellar means are held together by the turns of the band (not shown) . This lamellar means is somewhat smaller than, but has essentially the same shape as, the lamellar means in Fig. 7E, which, however, is made in one piece and provides a load space having the dimensions 200 X 1100 X 200 mm 3 . Fig. 7D shows another variant of a lamellar means which is made of several parts. In this case, there are four essentially uniform parts which together form a lamellar means. Consequently, an upper left part 130, a lower left part 132, an upper right part 134 and a lower right part 136 are shown. These are held together by means of the previously described turns of the band (not shown) . As a possible alternative, a lamellar means corresponding to that shown in Fig. 7D could be made of two halves only, such as a left half and a right half, instead of four parts. The lamellar means in Fig. 7D provides with other corresponding lamellar means a load space having the dimensions 400 X 1600 X 4000 mm 3 . Those skilled in the art will thus understand from the examples illustrated above that the lamellar means can be made in one or more pieces, be given different shapes and be made in different sizes as regards both external and internal dimensions. Although some preferred embodiments have been described above, the invention is not limited thereto. It is thus possible to use variants of the internal structure other than those described. The design of the individual lamellar means can also be varied in accordance with the current needs. It should thus be understood that a plurality of modifications and variations can be provided without deviating from the scope of the present invention which is defined in the appended claims.

Claims: CLAIMS 1. A press (40, 70) of pressure cell type, which press comprises a press chamber being enclosed by a force-absorbing press body which comprises a number of plate-shaped lamellar means (10, 42, 42', 72) with the planes of the plates oriented parallel to the planes of the plates of adjacent lamellar means, each lamellar means having a through hole (16, 52) which has the same centre axis as the hole of the adjacent lamellar means, said centre axis coinciding with the direction of main axis (X) of the press chamber being enclosed by the holes and each lamellar means having an internal edge surface (18) which defines the hole and an external edge surface (14, 74) , c h a r a c t e r i s e d in that prestressing means (20, 22, 24, 26, 28, 88) which induce a compressing prestress acting in the planes of the plates are arranged on the external edge surface of the main part of the lamellar means, each prestressing means comprising a prestressing element (20, 88) which is wound round a respective lamellar means, is band-shaped and has essentially the same width as the thickness of a lamellar means . 2. A press of pressure cell type as claimed in claim 1, wherein the lamellar means are arranged at a distance from one another, preferably at a distance that corresponds to the thickness of the lamellar means. 3. A press of pressure cell type as claimed in claim 1 or 2, wherein each lamellar means is provided with a number of apertures (30) which are aligned with the corresponding apertures of the other lamellar means so that a number of series of apertures are formed, which are parallel to the direction of the main axis of the press chamber, a coupling means (82) for coupling lamellar means being adapted to run through a respective one of said series of apertures . ω ω t to μ> μ * LΠ o LΠ o (Jl o ( Jl 11. A press of pressure cell type as claimed in any one of claims 1-10, wherein an internal structure is arranged in the press chamber, which structure is made up of concentric lamellar means (58, 80a, 80b) abutting against one another and having through holes (94) and being located in planes which are parallel to the direction of the main axis of the press chamber, a workpiece being intended to be machined in the space (94) which is formed of the holes of the concentric lamellar means. 12. A press of pressure cell type as claimed in claim 11, wherein the lamellar means in the internal structure round the external edge surfaces are wound with a band (88) of essentially the same width as the thickness of the lamellar means for prestressing thereof . 13. A press of pressure cell type as claimed in claim 11 or 12, wherein the lamellar means in both the internal structure and in the press body are made of the same material and have the same thickness. 14. A press of pressure cell type as claimed in any one of claims 1-13, wherein at least one, preferably each, lamellar means is made in one piece. 15. A press of pressure cell type as claimed in claims 1-14, wherein at least one lamellar means is made in several pieces (120, 122, 124, 126, 130, 132, 134, 136) . 16. A press of pressure cell type as claimed in any one of claims 1-15, wherein the lamellar means are made of sheet steel . 17. A method for manufacturing a force-absorbing press body part intended to enclose a press chamber, c h a r a c t e r i s e d by the steps of forming plate-shaped lamellar means (10, 42, 42', 72) and providing each of them with a through hole (16, 52) , inducing a lasting compressing prestress which acts in the planes of the plates in at least the majority of the lamellar means by winding a band-shaped prestressing element (20, 88), which has essentially the same width as the thickness of a lamellar means, round the external edge surface of the lamellar means with the purpose of causing said prestress, and arranging each formed lamellar means having the plane of the plate oriented parallel to the plane of the plate of an adjacent lamellar means so that the through holes obtain a common centre axis and so that the lamellar means constitute a force-absorbing, press-chamber- enclosing press body part. 18. A method as claimed in claim 17, wherein the lamellar means are arranged at a distance from one another, preferably at a distance that corresponds to the thickness of the lamellar means. 19. A method as claimed in claim 17 or 18, which comprises the step of giving the lamellar means the desired shape by milling. 20. A method as claimed in claim 17 or 18, which comprises the step of giving the lamellar means the de- sired shape by cutting, such as water cutting, plasma cutting, flame cutting etc. 21. A method as claimed in any one of claims 17-20, which comprises the step of making the lamellar means of hot-rolled sheet steel. 22. A method as claimed in any one of claims 17-21, which comprises the step of making the lamellar means of sheet steel having a thickness of 80-200 mm, preferably 100-150 mm, in particular 100-120 mm. 23. A method as claimed in any one of claims 17-22, which comprises making the lamellar means in sequence in a number of stations according to the steps of machining a first lamellar means blank in an appropriate station, conveying said first lamellar means blank to a sub- sequent station for further machining, and machining a second lamellar means blank in said appropriate station at the same time as said first lamellar means blank is being machined in said subsequent station. 24. A method as claimed in claim 23, in which one of said stations comprises parallel machining of a plurality of lamellar means blanks. 25. A method as claimed in any one of claims 17-24, which comprises the step pf assembling the lamellar means to a press body at the location where a press (40, 70) of pressure cell type is to be used, the coupling means (82) being arranged in the lamellar means in such a manner that they are held together as a unit . 26. A method as claimed in any one of claims 17-25, which comprises the step of making the lamellar means in one piece. 27. A method as claimed in claims 17-26, which comprises the step of making the lamellar means in several pieces (120, 122, 124, 126, 130, 132, 134, 136) . 28. A lamellar means (10, 42, 42', 72) of a press body part, which is plate-shaped and has a through hole (16, 52) , the lamellar means having an internal edge surface (18) which defines the hole, c h a r a c t e r i s e d in that the lamellar means has an external edge surface (14, 74) on which a prestressing means (20, 22, 24, 26, 28, 88) is arranged, which induces a compressing prestress acting in the plane of the plates of the lamellar means, the prestressing means comprising a prestressing element (20, 88) which is wound round the lamellar means and is band-shaped and has essentially the same width as the thickness of a lamellar means. 29. A lamellar means as claimed in claim 28, wherein the lamellar means is made of sheet steel .

Inventors: HELLGREN KEIJO, HELLGREN, KEIJO
Applicants: FLOW HOLDINGS SAGL, HELLGREN KEIJO, HELLGREN, KEIJO
Application year: 2001
Main classification: B21D22
IPC codes: B30B5, B30B15