IMPROVEMENTS IN AND RELATING TO OPEN-SIDED PRESSES

Abstract: The invention relates to an open-sided press of the kind which includes a press-frame and top and bottom, essentially horizontal press-beams (1; 2) carried by a main frame-part. The top press-beam (1) is pivotally suspended on the main frame-part at a location between the ends of the beam and the rear ends of the top and bottom beams (1; 2) are mutually connected by means of a yoke (8) which functions to take-up compression forces. This arrangement avoids weld joints which are subjected to high stress concentrations, and consequently allows the press-frame to be dimensioned for very large press forces.

Description: Improvements in and relating to open-sided presses The present invention relates to an improvement in open-sided presses of the kind comprising a frame, and top and bottom, substantially horizontal press-beams which are carried by a main frame-part. The straightening of, for instance, heavy sheet-metal workpieces, large and heavy beams and flat steels requires the use of presses which are capable of exert¬ ing powerful press-forces and also of enabling large workpieces to be pressed. These requirements are dif¬ ficult to achieve with one and the same press. Earlier used portal presses can be constructed to generate powerful press-forces, but the ability of these presses to handle large workpieces is limited by the presence of the two side-frames conventional with such presses. To overcome this, it is necessary to construct a very large press, which greatly adds to the expense of such presses. Furthermore, the press then becomes extremely heavy and very difficult to move, meaning that the press must be left permanently in one position, i.e. remain static. In order to enable large workpieces to be brought readily into the press and worked easily therein, it is often desirable for the press to have a C-εhaped frame, i.e. for the press to have one side fully open, through which large workpieces can be brought into the press. A press provided with such a frame is referred to herein¬ after and in the claims as an open-sided press. One serious problem with conventional open-sided pres- ses is the difficulty experienced in constructing the press to the mechanical strength required to withstand the powerful forces which must, of necessity, be gener¬ ated by such presses. When the press is required to work at pressures of up to 90-100 tonnes, a conven¬ tionally welded open-sided press would need to be given such large dimensions as to render the press highly unattractive from the aspect of cost and size. In the case of welded press-frames, the forces occurring with repeated press operations tend to cause fatigue in the weakest and most heavily loaded parts of the weld, resulting in fracture of this weld part, whereafter the forces which resulted in said fracture become con¬ centrated at another part of the weld, until fracture occurs in this weld part. This gradual deterioration of the weld continues until the whole of the weld is destroyed. The invention is based on the perception that open- presses which are capable of working with powerful press-forces can be provided with relatively small and light frames by avoiding welds which are subjected to tensile forces. Accordingly, the main object of the present invention is to provide a frame for a powerful open-sided press in which the forces generated therein are not transmitted between mutually welded frame parts in the form of tensile forces. This object is achieved in accordance with the inven- tion with a press-frame structure in which the press forces are taken up primarily in the form of compres¬ sion forces, by a frame element which is dimensioned particularly for this purpose. Accordingly, the invention consists in an open-sided press of the kind which comprises a press-frame, and top and bottom, generally horizontal press-beams which are carried by a main frame-part, said press being characterized in that the top beam is pivotally mounted on the main frame-part at a location between the ends of said beam, and in that the rear ends of respective top and bottom beams are mutually connected by a yoke which is operative to take-up compressive forces gener- ated by the press in operation. As a result of this arrangement, the forces generated by the press will not be transmitted between mutually welded frame components in the form of tensile forces, but are instead transmitted in the form of compression forces to an element which is mounted rigidly between the beams. This element can be readily dimensioned to take-up the forces generated by the press in action. The bottom beam or beams is/are preferably supported on support means carried by said main frame-part. In this case the frame will suitably include two bottom beams, each being supported for free movement at a location between the respective ends of said beams. The press forces will therewith be transmitted in the form of compression forces, from the top and bottom beams to the aforesaid yoke connecting the rear ends of said beams, these compression forces essentially balancing out one another. Each of the two bottom beams is preferably located on a mutually different side of a column-like part of the main-part and is arranged for lateral movement in relation to the other beam, so that the spacing between said beams can be adapted to conform to the type of workpiece and working operation concerned. In the case of one preferred embodiment, the yoke which takes-up said forces will include a plate which is attached to the rear part of the top beam and which defines -a right angle with the two bottom beams and which widens in width down towards said bottom beams, such that the width of the plate at a lower edge there- of coacting with the bottom beams will correspond at least to the maximum desired distance, or spacing, between said beams. In this case, the rear ends of the bottom beams are suitably configured to enable said beams to be detacheably suspended at desired locations along the lower edge of said plate. In order to enable the bottom beams to move parallel to one another and bring said beams to their mutual maximum-spacing positions, the main-frame part is preferably provided with a bar or rail which functions • to support the bottom beams and which extends per¬ pendicularly to said beams and has a length cor¬ responding to said beam-spacing. In order to enable work to be carried out at selected positions along the length of the top beam, said beam has mounted thereon for movement along the length of said beam a hydraulic press-head which is carried by the bottom peripheral edge-surfaces of said top beam. The press-head is fitted with a tool appropriated for the work to be carried out. In this case, the terminal position of the press-head nearest the main frame-part is preferably located substantially above the bar which supports the bottom beams. The main frame-part is preferably mounted on wheels, which as a result of the relatively small dimensions and relatively light weight of the frame, will provide a mobile press which can be moved readily between dif- ferent working sites. The invention will now be described in more detail with reference to preferred embodiments thereof illustrated in the accompanying drawings, in which Figure 1 is a perspective view of an open-sided press which is provided with a press-frame constructed in accordance with the invention; Figure 2 is a rear view of part of the frame; and Figure 3 is a side view of the press and frame con- struction incorporating the improvement afforded by the invention. The illustrated open-sided press includes a C-frame, a top beam 1 and two bottom beams 2, said beams being substantially horizontal. The lower peripheral edge of the top beam 1 is provided with a flange 3 on which a press-head 4 is mounted for reciprocating movement along said beam. The press-head 4 is intended to be fitted with a tool 5 appropriate to the work to be carried out. The head 4 includes a hydraulic piston which functions to press the tool 5 against a workpiece placed on the bottom beams 2. The illustrated press is intended for press forces of up to 90 tonnes. In order to be able to work with such high press- forces, even at the extremities of the press beams, it is necessary, inter alia, to take steps to avoid such fatigue points as those which are likely to occur when the top press-beam is welded to the column-like part 6. of the main-frame part in a conventional manner. For the purpose of avoiding weld joints which exhibit high stress concentrations, the beam 1 is pivotally mounted on the column-like part 6 with the aid of a journal axle 7 which extends through the beam 1 and is attached-to the side plates of the column. The frame structure also includes a yoke 8 which connects the rear end of the top beam 1 to the rear ends of the bottom beams 2 and to which the forces generated during a press operation are transmitted in the form of com¬ pression forces. The bottom beams 2 are placed freely on support pads 9, which are mounted for lateral movement on a rail 10 located on said main-frame part and extend perpendicul¬ arly to the beams. As shown clearly in Figure 2, the rear ends of the beams 2 are suspended by hook-like devices 11 from a channel part 12 which extends perpen- dicularly to the beams 2 along the bottom edge-surface of a plate which forms said yoke 8. The yoke plate 8 is attached to the rear end of the top press-beam 1 and increases in width in a direction towards the bottom beams 2. This enables the beams 2 to be displaced laterally relative to one another, such that the mutual distance between the beams can be adjusted in accor¬ dance with the size of the workpiece concerned and the type of working operation to be carried out. This lateral displacement of the beams can be carried out readily, by moving the support pads 9 along the rail 10, with the hook-like devices 11 sliding in the chan¬ nel 12 along the bottom edge of the yoke 8 at the same time. The beams can be locked temporarily in their set positions, with the aid of locking means coacting with the channel 12. With the intention of stiffening the yoke plate 8, the plate is connected to further plates 13 which extend perpendicularly to the yoke plate 8 and which extend in- between the side-plates of the column-like frame part 6 (see Figure 3). The reference 14 identifies a number of bolts, which function solely to hold the press-beams and the yoke-plate 8 in position relative to the main fram-part. These bults are not intended to take-up any appreciable loads. During a working; operation, in which the hydraulic press-head 4 urges the tool 5 against a workpiece positioned on the bottom beams 2, the forces taken up by the press-beams 1 and 2, respectively, when the press-head is located outside the support rail 10, will be transmitted via the beams to the yoke 8 in the form of pressure forces which balance-out one another in the yoke 8. The illustrated frame will thus balance-out the force flow in a highly favorable manner, therewith enabling large press-forces to be used even when the press-head 4 is located far out along the beam 1. This provides a considerable advantage, since it is normally easier to carry out working operations at a given distance from the main frame-part. Furthermore, the working zone obtained by virtue of the inventive im¬ provement is available from three different directions, without limitations. When using very high press-forces, at least the upper press-beam will bend to some extent, said beam having a long free length, and the bottom beams will possibly also bend. Bending of the beams, however, will not result in punctiform loading of a weld joint or the like, since solely compression forces are transmitted to the yoke. The connecting devices attached to the bottom beams solely function to hold the ends of the beams in contact with the yoke for the transmission of compression forces thereto. Neither are the weld joints formed between the top press-beam 1 and the plates 13 critical, for the same reason, since the only forces transmitted are compression forces. Since the forces generated by the press are balanced- out in the press-frame, as described above, no net press-forces, among other things, will act on the support devices by means of which the press-frame is supported on the floor or like foundation surface. Consequently, the press, which as a result of its con¬ struction can be made relatively small and given a low weight, can be supported on wheels 15 so as to form a mobile unit which can be moved readily between dif- ferent work sites. The working height of the press-beams 2, and therewith the size of the gape, can be readily adapted to suit requirements, by using support pads 9 of mutually different heights, combined with adjustment to the positions in which the hook-like devices 11 are at¬ tached to the rear ends of the beams. The support pads can even be removed from the press. Although the invention has been described in the afore¬ going with reference to an exemplifying embodiment thereof illustrated in the drawings, it will be under¬ stood that modifications can be made within the scope of the inventive concept. For example, the position of the pivotal attachment of the top-beam can be varied both in the longitudinal and vertical direction. The locations at which the bottom beams are supported can also be displaced and the rear ends of the beams can be attached to the yoke with the aid of devices different to those illustrated and described.

Claims: 10 C MMS 1. An improvement in open-sided presses of the kind which comprise a frame and top and bottom, essentially horizontal press-beams (1; 2) which are carried by a main frame-part, the improvement being characterized in that the_top press-beam (1) is pivotally suspended on said main frame-part at a location between the ends of said beam; in that the bottom beam or beams (2) are freely supported at a location between their respective ends; and in that the rear ends of the top and bottom press-beams (1; 2) are mutually connected by means of a yoke (8) which is operative to take-up compression forces. 2. The improvement of claim 1, characterized in that the bottom press-beam or beams (2) is, or are, sup¬ ported by support devices (9) carried by said main frame-part. 3. The improvement of claim 2, characterized in that the press includes two bottom press-beams (2) each of which is located on a respective side of a column-like part (6) of said main frame-part; and in that the beams are mounted for lateral movement relative to one an¬ other. 4. The improvement of claim 3, characterized in that the yoke (8) includes a plate which is attached to the rear part of the top beam (1) and which defines essen¬ tially a right angle with the two bottom beams (2) and the width of which plate increases in a direction towards said bottom beams, such that the width of said 11 plate at a lower edge thereof coacting with the bottom beams will at least correspond to the maximum desired spacing between said beams. 5. The improvement of claim 4, characterized in that the rear ends of the bottom beams (2) are suspended detachable at desired locations along the lower edge of the yoke plate (8). 6. The improvement of any one of claims 2-5, charac¬ terized in that the main frame-part includes a rail (10) which functions to support the bottom beams (2) and which extends perpendicularly to said beams and has a length which at least corresponds to the maximum desired spacing between said beams. 7. The improvement of any one of claims 1-6, charac¬ terized in that the bottom edge of the top beam (1) is configured to support a hydraulic press-head (4) such as to allow said press-head to be moved along said beam, said press-head being fitted with an appropriate tool (5). 8. The improvement of claim 7, characterized in that the terminal or end position of the press-head (4) nearest said main frame-part is located essentially above the rail (10) supporting the bottom beams (2). 9. The improvement of any one of claims 1-8, charac- terized in that the main frame-part is supported on wheels (15) so as to provide a mobile press.

Inventors: SVENSSON HANS, SVENSSON, HANS
Applicants: HOVA SVETS AB
Application year: 1989
Main classification: B30B15
IPC codes: B30B15