A PRESS AND AN AUTOMATIC CURVE-FORMING DEVICE THEREFOR

Abstract: The invention relates to a press such as a folding press and a deep-draw press comprising a press frame with a lower yoke and an upper yoke which are mutually reciprocally movable with reciprocating means, wherein the lower yoke and the upper yoke are each provided with co-acting tools and wherein between a yoke and its tool are arranged curve-­ forming means (11) which comprise a series of curve-forming wedge pairs (12) which lie distributed over the length of the yoke bet­ ween the yoke and the tool, wherein each curve-forming wedge pair (12) is provided with energizable adjusting means for adjusting the mutual position of the curve-forming wedges (13, 14) of a curve-forming wedge pair (12).

Description: The present invention relates to a press, such as a folding press or a deep-draw press, which comprises a press frame with a lower yoke and an upper yoke which are mutually reciprocally movable with reciprocating means, wherein the lower yoke and the upper yoke are each provided with co-acting tools and wherein between a yoke and its tool are arranged curve-forming means which comprise at least one pair of curve-forming wedges. Such a press is known and is provided with curve-forming devices for the purpose of compensating during pressing or bending for deformations occurring in the diverse components of the press as well as in the materials for shaping. EP-A-67.766 describes a press wherein the curve-forming means are formed by one pair of curve-forming wedges extending over the whole length of the press. The top wedge is provided along its length with a number of bolts which via a toothed wheel are all connected mutually and to an adjusting motor by means of a chain. A variation in the sideways movement of the top wedge 7 along its length is possible due to a difference in mutual pitch of the bolts or a differing number of teeth of a toothed wheel for a bolt. EP-A-330.258 describes a press wherein the curve-forming wedges of a pair are mutually slidable in lengthwise direction of the press. In order to reduce the total height of a curve-forming wedge pair each curve-forming wedge can be embodied as two mutually connected wedge portions, the wedge surfaces of which connect to one another discontinuously. Variations can be of diverse origin: a) during pressing or bending the press sags as a consequence of the applied load. This sag line can be calculated but varies depending on the case of loading. When the load is short and concentrated the sag line has a shape other than with a load which runs the support points of the reciprocating means, for example the hydraulic cylinders. Extreme variations occur if the load extends laterally beyond the support points or if the press is loaded eccentrically; b) the lower yoke and the upper yoke and the tools have linearity deviations, the consequences of which are recognizable in the pressed or bent products; c) the tools used generally have dimensional variations which can only be reduced at increasingly excessive cost; d) as a result of wear, location-dependent dimensional variations occur in the tools used; and e) the material used that is to be worked is not completely homogeneous (grain size distribution), has no constant material thickness and has unevenly distributed stresses, as a result among other things of rolling, so that location-dependent varying deformation properties occur. A number of these variations are predictable, a number of other variations vary or manifest themselves during prolonged use of the press or in the case of use of different materials for working. There therefore exists a need for curve-forming means that are adjustable optimally and as accurately as possible. This adjustment has preferably to be possible independently from place to place along the length of the yoke. It is moreover desirable that the curve-forming means have the simplest possible form and construction. The invention has for its object to satisfy the above described requirements and provides a press characterized in that it comprises a press frame with a lower yoke and an upper yoke which are mutually reciprocally movable with reciprocating means, wherein the lower yoke and the upper yoke are each provided with co-acting tools, wherein between a yoke and its tool are arranged curve-forming means which comprise a series of curve-forming wedge pairs, which pairs are located along the length of the yoke distributed between the yoke and the tool, wherein each curve-forming wedge pair is provided with energizable adjusting means for adjusting the mutual position of the curve-forming wedges of a curve-forming wedge pair. The press according to the invention comprises different types of press for two- or three-dimensional shaping of plate-like material, such as a folding press and a deep-draw press. If in preference relieving means for relieving a stop for a curve-forming wedge driven by the adjusting means relieve the adjusting means, in the case the adjusting means are energized prior to adjusting of the mutual position of the curve-forming wedges, each pair of curve-forming wedges can be provided with its own adjusting means, for instance an adjusting motor which can be of low power, because after relieving during adjusting (i.e. curve-forming) the lowest possible load is applied to the curve-forming wedges. In a first preferred embodiment the relieving means consist of lifting means with which a cover plate resting on the pair of curve-forming wedges is liftable therefrom. In this way only a load is in principle exerted on the adjusting motor during adjusting which is dependent on the upper, slidable curve-forming wedge. According to a second preferred embodiment the relieving means comprise a relieving strip with which a curve-forming wedge resting against the stop is releasable therefrom. In this case the adjusting motor needs only to displace its stop because using the relieving disc the slidable curve-forming wedge is taken out of contact with the stop and, after adjusting using the adjusting means, the wedge is re-placed and strikes against the stop. Resetting of the slidable curve-forming wedge is preferably realized with spring means acting counter to the spring bias of the relieving strip and releasing the curve-forming wedge therefrom prior to adjusting. It will be apparent that the use of relieving means can be omitted if the adjusting means possess a sufficient power or the curve-forming means possess sufficient power or the curve-forming means are located between the upper yoke and the tool suspended therefrom. An optimal construction for the pair of curve-forming wedges and the adjusting means is obtained if the stop is arranged on a spindle of the adjusting means which extends substantially in the sloping contact surface of the pair of curve-forming wedges. In this case the spindle is optimally guided and the mutually exerted forces are minimal. A very compact pair of curve-forming wedges is obtained if more preferably the adjusting means comprising the adjusting motor are enclosed by the pair of curve-forming wedges, for instance if in the wedge surfaces of the curve-forming wedges an adjusting motor cavity is present. In order to enable a greater angle of slope for the wedge surfaces making mutual contact, without the self-braking effect being lost, the wedge surfaces of the pair of curve-forming wedges are preferably provided with ribs making mutual fitting contact. In this way the co-acting curve-forming wedges make mutually fitting contact because the rib edges rest against each other, thereby resulting in a larger angle of friction. In the case of use of a large number of pairs of curve-forming wedge pairs in line orientation (for example in a folding press) as well as in a plane orientation (for example in a deep-draw press), it is recommended that the adjusting means, namely the adjusting motors, of each curve-forming wedge pair are connected to a central processing/operating unit so that each pair of curve-forming wedges is selectively adjustable in order to compensate optimally for the variations occurring during pressing. It is moreover possible to embody the curve-forming wedges in cheaper materials, for example fibre-reinforced plastics, because the curve-forming characteristic of each curve-forming wedge pair is known in advance and variations that may occur later can be easily measured and compensated using the central processing/operating unit. Mentioned and other features of the press and curve-forming means according to the invention will be further elucidated hereinafter on the basis of a number of embodiments which are given only by way of example and with reference to the annexed drawings. In the drawing, figure 1 and 2 each show a perspective view of a folding press and a deep-draw press. Figure 3 shows on a larger scale a partly broken away perspective view of detail III from figure 1; Figure 4 is a view of a lengthwise section of a second embodiment of the curve-forming means according to the invention; Figure 5 is a section along the line V-V from figure 4; and Figure 6 is a variant of detail VI from figure 3. Figure 1 shows a folding press 1 according to the invention with a press frame 2 bearing a lower yoke 3 and on which is suspended an upper yoke 4. The upper yoke 4 is reciprocally movable relative to lower yoke 3 using hydraulic cylinders 5 and 6. The upper yoke 4 is provided with a bending tool 7 which is fixed to the upper yoke 4 in conventional manner. The lower yoke 3 is provided with a trough-like table 8 closed off with a cover plate 9 on which lies, as bending tool, a bending beam 10. The curve-forming means 11 according to the invention are arranged in the trough-like table 8. The curve-forming means comprise a series of (for instance twenty) curve-forming wedge pairs 12 which comprise curve-forming wedges 13 and 14 which in this embodiment are separated in lengthwise direction of the table 8 by relieving means 15 according to the invention. Figure 2 shows a deep-draw press 16 according to the invention wherein construction components corresponding with those of the folding press 1 according to the invention of figure 1 are designated with the same reference numerals. In this case the table 8 is provided with curve-forming means 11 comprising curve-forming wedge pairs 12 which extend distributed over the surface in one or two directions. Each curve-forming wedge pair 12 is adjustable independently of the other curve-forming wedge pairs 12. Figure 3 shows in more detail the curve-forming means 11 according to the invention. The curve-forming means comprise curve-forming wedge pairs 12 comprising curve-forming wedges 13 and 14 which make mutual contact with a sloping wedge surface 17 and form a contact surface 18. The bottom curve-forming wedge 13 is stationary and the top curve-forming wedge 14 is adjustable in the direction of the slope of the contact surface 18 relative to the curve-forming wedge 13 by means of the adjusting means comprising an adjusting motor 19, for instance a stepping motor or DC motor, which can drive a screwed spindle 20 onto which is screwed a nut 21 with studs 22. The wedge pair 12 encloses the stepping motor 19 because both curve-forming wedges 13 and 14 are provided with a cavity 23 the form whereof is adapted to the stepping motor 19, the screwed spindle 20 and the nut 21 with studs 22. The stepping motor 19 can be a very simple, low-power stepping motor (for example four-phase motor, electronically controlled, 1.75 Watts), since prior to adjustment the relieving means 24 are energized. These relieving means 24 comprise lifting members 25 which raise the cover plate 9, whereby the curve-forming wedge 14 rests substantially with its own weight on the contact surface 18. With an adjusting height of 10 mm per 150 mm of length and an adjusting path of 50 mm, at a screwed spindle pitch of 2 mm the adjusting time can remain short, for example 2-3 seconds. Signals for energizing the separate stepping motors 19 and the relieving means 24 are fed via wires 26 which pass through grooves 27 in the bottom 28 of the lower curve-forming wedge 13 and are fed to the central processing and operating unit 29. It is thus possible to adjust each wedge pair independently in any desired sense to obtain a determined adjusting height. In the embodiment of figure 4 the curve-forming means 11 comprise a relieving strip 31 provided with stops 30 which is reciprocally slidable with a motor 32. Using the stops 30 the top curve-forming wedges 14 can be released counter to the spring bias of spring means 33 from the nuts 21 acting as stop 21 which are screwed onto the screwed spindles 20 of each stepping motor 19. In this way the nut 21 can be adjusted with a very small load to any desired position in the nut path 34, whereafter by sliding the relieving strip 31 to the left the top curve-forming wedges 14 displace under spring force over the contact surface 18 until they strike against the stop 21 which is set at a predetermined and required position. In the same way the information for the position and energizing of each stepping motor 19 is coupled via information wires 26 to the central processing and operating unit 29. It is remarked that the contact surface 18 has an inclination such that the co-acting curve-forming wedges 13 and 14 are self-braking. A greater inclination for the contact surface 18 for a greater adjusting height is possible by providing the wedge surfaces 17 as according to figure 6 with ribs 34 and 35 running in the direction of the inclination which rest in each other's edges, thus markedly increasing the contact surface. Through the use of the relieving means 24 according to the invention it is for instance possible to use a glass fibre-reinforced plastic for the curve-forming wedges 13 and 14. The plastic DF-1008 is for instance suitable because this plastic can withstand a pressure strength of for example 165 MPa, which corresponds to approximately 60 tons per pair of curve-forming wedges. In the case of the relieving means 15 it is possible to use as lifting elements mechanical (resilient) or pneumatically, hydraulically or electrically driven lifting means. In the case of the central processing and operating unit 29 the relieving means are first energized thereby prior to adjusting wedge pairs independently and in any desired direction with the stepping motors 19. The press 1 or 16 according to the invention can be provided with sensors (lasers) with which the result of the pressing operation can be observed. For instance in the case of the folding press 1 the torsion of the shaped object can be determined with an axial sensor 36 and a detector 37 and the arranged angle of fold with a number of transverse sensors 38 with detectors 39 arranged over the length of press 1. Observed variations can thus be detected and after processing in the processing unit 29 the curve-forming can be adjusted through adjustment of one or more curve-forming wedge pairs in order to compensate for these observed variations.

Claims: A press such as a folding press and a deep-draw press comprising a press frame (2) with a lower yoke (3) and an upper yoke (4) which are mutually reciprocally movable with reciprocating means (5,6), wherein the lower yoke (3) and the upper yoke (4) are each provided with co-acting tools (7,10) and wherein between a yoke (3,4) and its tool (7,10) are arranged curve-forming means (11) which comprise at least one curve-forming wedge pair (12), characterized in that the curve-forming means (11) comprise a series of curve-forming wedge pairs (12) which lie distributed over the length of the yoke (3,4) between the yoke (3,4) and the tool, (7,10) wherein each curve-forming wedge pair (12) is provided with energizable adjusting means (19,20,21,22) for adjusting the mutual position of the curve-forming wedges (13,14) of a curve-forming wedge pair (12). A press as claimed in claim 1, characterized in that relieving means (24) for relieving a stop for a curve-forming wedge (13,14) driven by the adjusting means (19,20,21,22) relieve the adjusting means (19,20,21,22), if the adjusting means (19,20,21,22) are energized prior to adjusting of the mutual position of the curve-forming wedges (13,14). A press as claimed in claim 2, wherein the relieving means (24) comprise lifting means (25) with which a cover plate (9) resting on the pair of curve-forming wedges (12) is liftable therefrom. A press as claimed in claim 2 or 3, wherein the relieving means (24) comprise a relieving strip (31) with which a curve-forming wedge (13,14) resting against the stop (30) is releasable therefrom. A press as claimed in claim 4, wherein the relieving strip (31) releases the curve-forming wedge (13,14) from the stop counter (30) to spring bias of spring means (33). A press as claimed in claims 1-5, wherein the stop (30) is arranged on a spindle (20) of the adjusting means (19,20,21,22) which extends substantially in the sloping contact surface of the pair of curve-forming wedges (12). A press as claimed in claims 1-6, wherein the adjusting means (19,20,21,22) comprise an adjusting motor (19), which motor is enclosed by the pair of curve-forming wedges (12). A press as claimed in claim 7, wherein in the wedge surfaces of the curve-forming wedges (13,14) an adjusting motor cavity (23) is present. A press as claimed in claims 1-8, wherein the wedge surfaces of the pair of curve-forming wedges (12) are provided with ribs making mutual fitting contact. A press as claimed in claims 1-9, wherein the adjusting means (19,20,21,22) are connected to a central processing/operating unit. A press as claimed in claim 10, wherein the curve-forming wedge pairs (12) are connected for independent adjustment to the central processing/operating unit. A press as claimed in claim 10 or 11, wherein sensor means (36) are connected to the processing/operating unit with which the result of the pressing operation on a worked product is recorded.

Inventors: VAN MERKSTEIJN, JACOBUS LAMBERTUS
Applicants: MACHINEFABRIEK WILA B.V.
Application year: 1990
Main classification: B21D5
IPC codes: B21D5, B30B15