IL30366A - Hydraulic machine for deforming sheet metal - Google Patents

Description

nana *ns n» i»m*n njirjo Hydraulic machine for deforming sheet metal PRO!ffiCAM SISSON-LEHMAMH C. 28635 The present invention relates to hydraulic machines for deforming or working sheet metal, such as shears, presses in general, and in particular folding presses comprising a fixed bolster and a moving bolster.

To ensure in such machines a regular movement of the moving bolster towards the fixed bolster, various hydraulic thrust and synchronizing devices are known in which jacks perform these two functions separately orotherwise.

For maintaining the moving bolster parallel to the fixed bolster, devices are known comprising two correcting jacks located on each side of the longitudinal axis of the machine, these jacks, of the double-rod type and having two equal chambers, are interconnected by two crossed conduits so that they are self fed for movements in the same direction and of the same amplitude. Devices of this type are also known in which the two crossed conduits are also fed in such manner that a predetermined inclination of the moving bolster relative to the fixed bolster can be maintained during the stroke and that possible leakages or reduction in the volume of oil due to compression can be compensated. Several control means are known for these corrections and in particular that employing, as an indicator of angular deviations between the two bolsters, a flexible element such as a ribbon one end of which is connected to the fixed frame of the machine whereas the other end acts on a distributor feeding the two crossed conduits, whereby any angular deviation results in an action of equal value but of opposite direction of the correcting jacks.

However, these corrections are insufficient to maintain with precision the two bolsters parallel or at a predetermined angle therebetween since the adopted devices do not compensate the elastic bending of certain resisting under stress parts of the frames/and, above all, do not compensate the opening or spreading apart of the side walls of"swan neck" or C-shape which bend in different ways when the loads are eccentric, that is, offset relative to the vertical median plane of the machine, and produce angular deviations which remain uncorrected and consequently have an adverse effect on the precision of the work carried out.

The object of the invention is to remedy the aforementioned defects and insufficiencies. The invention provides a machine for deforming sheet metal, such as shears, presses presses, folding/and the like, comprising a fixed bolster and a moving bolster actuated by ono o mo»o jacks and equipped with a synchronizing system comprising two hydraulic compensating devices which are fed by the action of an indicator indicating angular deviations between the two bolsters which acts on a distributor valve which is so inserted in the hydraulic circuit that any angular deviation between the bolsters results in a corresponding movement but of opposite direction of the hydraulic compensators. In this machine, the indicator, in addition to its usual functions of maintaining the parallelism and the predetermined angles between the bolsters, receives impulses which are proportional to deviations due to the opening of the "swan-neck" side walls, that is, to differences in the elastic deformation of said side walls under stress, from a hydraulic corrector comprising a part fixed to the frame of the machine and a movable part connected to said distributor, whereby said impulses produce an additional correction of the position of the moving bolster relative to the fixed bolster and nullify the consequences of the deviations due to the opening of the side walls.

This machine also comprises a safety device which cuts off the supply of the motor of the machine as soon as the difference in the elastic deformations of the side walls reaches a predetermined limit value. Thus, the arrangement according to the invention affords an automatic correction of all undesirable variations in the relative angular position of the tv/o bolsters of the machine while affording an essential protection against abnormal overloads. In a general way, the invention results in an improvement in the quality of the work produced and ensures safety in operation.

Further features and advantages of the invention will be apparent from the ensuing description with reference to the accompanying drawings.

In the drawings : Fig. 1 is a front elevational view of the assembly of a typical machine showing the position of the main parts; Fig. 2 is a side elevational view of the assembly of the machine; Fig. 3 is a hydraulic diagram showing the indicator indicating angular deviations and the system correcting the deviations; Fig. 4 is a view of another version of the hydraulic correcting device, and Fig. 5 is a corresponding electric circuit diagram.

As can be seen in Figs. 1 and 2, the fixed frame 1 of the presently-described machine comprises two transverse side walls lc, Id to which is secured a fixed bolster 2, and two longitudinal walls la and lb between which is movable a moving bolster 3 whose stroke or travel towards the fixed bolster 2 results from the action of thrust jacks or rams 4 which bear against the walls la and lb through journals 4a, 4b.

It will be clear that in order to achieve this movement of the moving bolster, the thrust irams. must be fed with oil under pressure. However, the driving source and the hydraulic circuit elements required for achieving a rapid approach, the working stroke, the return stroke and the various stoppages, are not part of the present invention and are well known in various forms. Consequently, they have not been shown or described. Similarly, the electric diagram of the machine has been shown only partially in Fig. 5.

In the described machine, the moving bolster 3 is made parallel to, or placed at any other given angle relative to the fixed bolster 2, by the action of two auxiliary jacks 5 which operate in opposite directions as shown in Fig. 3 and constitute compensating devices. The auxiliary jacks 5 are connected by two crossed conduits or lines 22a and 23a in such manner that the chamber 20 of one communicates with the chamber 21 of the other and vice versa.

These two conduits are connected by conduits 22b, 23b and 23c to two outlet ports of a distributor slide valve 7 the whose body is integral with /fixed frame 1. One of two inlet ports of this valve is connected by the conduit 25 to the general tank of the machine and the other is connected by the conduit 24 to the common supply conduit of the thrust rams 4 so that, if the auxiliary jacks 5 must be fed, they are fed under a pressure which is proportional to that prevailing in these rams.

One end of the slide of the valve 7, which is part of a device or indicator 6 indicating angular deviations (Fig. 3) , is connected to the fixed frame 1 through a tension spring 9 and the other end is connected to a flexible element 10 which can be ,for example,a wire, cable, chain or ribbon preferably of steel.

In a first part of its path of movement, this flexible element 10 travels round two rollers 11 and 12, the spindles of which are carried by the fixed frame 1, and, between these rollers,- round a roller 13 whose spindle is carried by a yoke 14 controlled by a screwthreaded rod 15 screwthreadedly engaged in a nut 17 which is integral with the frame 1. The rod is provided with a handwheel 16 for varying the position of the roller 13 on the axis of symmetry between the two rollers 11 and 12 and consequently the length of the flexible element 10 in this part of its path.

In a second part of its path, the flexible element 10 travels round two rollers 18 and 19 whose spindles are carried by the moving bolster 3 and located on a line which is substantially perpendicular to the direction of the movement of the moving bolster towards the fixed bolster 2.

In a third part of its path, the other end of the element 10 is connected to the hydraulic correcting device, described hereinafter , which modifies the action of the element 10 on the valve 7 as a function of the pressures admitted into the conduits 22c or 23c.

In the embodiment shown in Fig. 3, this hydraulic correcting device is a double-rod jack 26 whose cylinder 27 is integral with the fixed frame 1 and divided into two chambers 29 and 30 by a piston 28 having double rods, these chambers being 28 is biased to a mid-way position in its travel by two opposed compression springs 31 and 32 bearing against the cylinder 27. The action of the spring 31 opposes those of the springs 9 and 32 and the piston 28 is therefore in static equilibrium while the flexible element 10 is under permanent tension.

The assembly is adjusted in such manner that, in this situation, the position of the two rollers 18 and 19 corresponds to a correct parallelism between the fixed and moving bolsters 2 and 3 and that the slide of the valve 7 is exactly in the mid-way position of its travel.

A block 33 integral with the piston 28 is adapted to actuate microswitches 34 and 35 of conventional break type integral with the frame 1 (Fig. 5) . These microswitches cut off the current of the maintaining coil 36 of the main switch 44 of the motor M and stop the v/hole of the machine as soon as a given amplitude of the travel of the piston 28 is reached .

In a modification shown in Fig. A, this hydraulic correcting device consists of three pins 37a, 3*fb and 3fc which are integral with the fixed frame l and on which are pivotable respectively a jack 38a, a straight lever 39 and a cranked lever 40. The other end of the jack 38a is connected to the end of the straight lever 39 by a pin 39a and a second jack 38b is connected to the other end of the lever 39 by a pin 39b and ,moreover, to the cranked lever 40 by a pin 40a.

Hooked onto the lever 40 is one end of the flexible element 10. The whole of this arrangement is put under tension by the spring 9.

The jack 38a is fed by way of the conduit 23c and the jack 38b by way of the conduit 22c. These two jacks comprise 42b respectively by two rods 43a ana 43b which become elast-ically extended as a function of the pressures prevailing in each jack and pivot the cranked lever 40 in one direction or the other on its pin 37c. In these movements, the lever 40 actuates the microswitches 34 and 35 as soon as a predetermined amplitude of movement has been reached and these switches stop the whole of the machine as explained with reference to Fig. 3.

In the general assembly arranged in this manner, only the thrust rams 4 are fed during the approach travel of the movine bolster 3, the auxiliary jacks 5 feeding themselves mutually by way of the conduits 23a and 22a for equal travels, since their sections are equal. However, as soon as any cause of disequilibrium appears and modifies the relative angular position of the two bolsters, such as an eccentric load, dissymetrical friction, leakages of oil in the auxiliary jacks 5 } the imaginary line intersecting the axes of the rollers 18 and 19 tends to become inclined vrith the moving bolster 3 in the direction of the heaviest load and, in accordance with this inclination, acts on the valve 7 through the element 10. For example, for an inclination of the moving bolster 3 in the counterclockwise direction, the slide of the valve 7 descends so that the conduit 23c is connected to the discharge while the conduit 22c is fed. The two auxiliary jacks 5, which have opposite directions of action, then produce a couple in the clockwise direction, that is, in the direction opposed to that of the inclination of the aforementioned imaginary line , this couple being maintained so long as the disequilibrium lasts and so long as the spindles of the rollers 18 and 19 have not resumed their initial position.

The loading of the machine and the correction of the parallelism defined hereinbefore have thus put the conduits 22a, 22b, 22c under pressure and connected the conduits 23a7 23b, 23c to the discharge. Consequently, in respect of Fig. 3, the chambers 30 and 29 of the jack 26 are respectively under pressure and connected to the discharge and this jack 26 acts on the flexible element 10 in the same direction as that of the cause of this disequilibrium and this produces an additional correcting effect. Similarly, in the embodiment shown in Fig. 4, the extension of the rod 43b produces the same action on the flexible element 10.

It should also be mentioned that this action is also proportional to the machine loading pressure which is defined by the pressure prevailing in the supply conduit 24 and is consequently proportional to the elastic deformations or openings of the branches of the vertical uprights lc and Id of the machine. These openings are of extent DC and DC (Fig. 2) and have no effect on the parallelism of the two bolsters in that they are of the same value at both ends of the bolsters and are not corrected in this case,hit only in this case. However s in the case of unequal deformations, affecting the parallelism of the bolsters, they are compensated by this additional correction of the feed to the auxiliary jacks 5 in the suitable direction owing to the action of the jack 26 shown in Fig. 3, or of one of the jacks 38a or 38b shown in Fig. 4, through the flexible element 10 on the position of the slide of the valve 7, since the elastic openings or deformations of the vertical side walls of the fixed frame are proportional to the differences between the supported forces and therefore to the pressure differential prevailing in the auxiliary jacks.

It will be observed that owing to the action of the microswitches 34 and 35 and the associated elements, such as 33 (Fig. 3) or lever 40 (Fig„ 4) , operation of the machine is stopped as soon as the difference in the deformations of the side walls lc and Id reaches a predetermined safety limit.

It is possible , while remaining within the scope of the invention, to replace the hydraulic correcting devices described hereinbefore by any other hydraulic device having the same supply and the same effects on the flexible element 10 as those described. It could be desired to produce purposely an angular setting , such as 0 1 and 6^2 (Fig. 1), between the fixed bolster 2 and the moving bolster 3 in order to satisfy particular requirements in the use of the machine. For this purpose, the hand wheel 16 modifies the extent to which the flexible element 10 is engaged between the rollers 11, 12 and 13 so as to increase or reduce this length and thus acts on the position of the slide of the valve 7 and modifies the position, of the moving bolster 3 by the described action of the jacks . This adjustment retains all the advantages concerning the already-described correction and maintenance of this relative position of the moving bolster 3 and fixed bolster 2.

The machine according to the present invention consequently achieves a degree of operational precision in practice which is of particular interest for the user while affording a remarkable protection of the main parts.

Although specific embodiments of the invention have been describeds many modifications and changes may be made therein without departing from the scope of the invention as defined in the appended claims.

Claims (1)

1. , A hydraulic machine for deforming sheet metal comprising: a fixed bolster, a movable bolster supported on a fixed frame having swan-neck lateral walls, a motor-pump unit for supplying oil under pressure from a tank to a hydraulic circuit which feeds at least two thrust rams for moving the movable bolster, a hydraulic synchronizing device including a hydraulic distributor valve for controlling mpvement of the movable bolster and maintain- ing the bolsters in a predetermined relative position, means for operating the distributor valve in response to angular deviation of one of the bolsters relative to the other bolster, and a correcting device including means for modifying the effect of the means for operating the distributor valve in proportion to the hydraulic pressure differential in the hydraulic circuit whereby the correcting device modifies the action of the synchronizing device so as to compensate differences in the elastic deformations of the lateral walls under load and thus maintain the relative position of the bolsters, 2» A machine according to Claim 1, wherein said hydraulic synchronizing device comprises two jacks having four chambers and two crossed conduits putting said chambers in communication with each other, said correcting device comprising two chambers which communicate with the respective conduits of said jacks of said synchronizing device and are defined by at least one piston, said distributor valve having a slide valving element, said operating means including a flexible element having one end connected to said piston and another end connected to said slide of said valve, whereby the differences in the pressures in the conduits act through said valve on said synchronizing device so as to compensate the differences between the elastic deformations of said lateral walls due to differences in load. 30366/2 " said correcting devices are defined in a hydraulic jack having a double rod and having equal sections, said hydraulic jack having a cylinder integral with said fixed frame and the piston being subjected to the combined action of the traction exerted by said flexible element and the action of a spring bearing against said cylinder and the opposed action of a second spring aleo bearing against said cylinder. 4. A machine according to claim 2, comprising a lever having two arms and mounted on a pin integral with said frame, a crank lever having two branches and pivotally mounted on a pin integral with said frame, said two chambers of said correcting devic being defined in two hydraulic jacks the first jack of which has a cylinder connected to a pin integral with said fixed frame and a piston connected to one of said arms of said lever, whereas the second of said hydraulic jacks has a cylinder connected to the othe arm of said lever and a piston is connected to one of said branches of said cranked lever, the other of said branches being connected to said flexible element of said operating means. 5· A machine according to claim 4, wherein in each jack of ¾*. d correcting device the cylinder is rendered integral with the corresponding piston by a centre rod which is capable of elastic extension in proportion to the pressure prevailing in the cylinder of the corresponding jack, 6e A machine according to claim 1, wherein said machine includes a drive motor and said hydraulic correcting device comprises two microswitches adapted to stop said motor when a maximum permissible difference between the deformation of said lateral walls is reached, said correcting device having a movable actuating element in position to actuate said switches. 7· A machine according to claim 6, wherein said actuating ele 30366/2 ^ jack of said correcting device. 8· A machine according to claim 6, wherein said actuating element includes one of the branches of said cranked lever. 9· A hydraulic machine substantially as described above by way of example and with reference to the accompanying drawings. For the Applicants DR R ERS