US3020828A - Parallel control gear for hydraulic presses, shears, or the like, having several press cylinders - Google Patents

Description

Feb. 13, 1962 J. NIEDERREITHER 0,3 8

PARALLEL CONTROL GEAR FOR HYDRAULIC PRESSES, SHEARS, OR THE LIKE, HAVING SEVERAL PRESS CYLINDERS Filed 001:. 11, 1956 2 Sheets-Sheet l FIG.| FIG. 30

I! [III INVENTOR JOHANN NIEDERREITHER ATTORNEY:

United States Patent 3,020,828 PARALLEL CONTROL GEAR FOR HYDRAULIC PRESSES, SHEARS, OR THE LIKE, HAVING SEVERAL PRESS CYLINDERS Johann Niederreither, Munich, Germany, assignor to Karl Mengele & Siihne, Gunzhurg (Danube), Germany, a firm of Germany Filed Oct. 11, 1956, Ser. No. 615,302 2 Claims. (Cl. 100-46) With the conventional types of hydraulic presses, shears and the like, having several press cylinders, it is not possible to hold the beam-type slide block-hereinafter referred to briefly as beam-actually parallel to the press table when it is partially Or wholly subjected to stress on one side.

Because the beam lies obliquely and not actually parallel to the table, shearing-01f and similar work becomes inaccurate whilst the stamping of fine sheet metal work (1 m. and below) can hardly be carried out at all.

Experiments and tests have shown that there are various factors causing the beam to sag, such as, for instance, inaccuracies in the control mechanism, faulty valves or similar trouble. In Portal presses and presses of the C type of construction, the chief trouble is to be found in the flexing-up and/ or elongation of the press frame which cause the beam to sag on one side.

This elongation and/or upwards straining of the press frame can reach dimensions amounting to from a fraction of a millimeter to a whole millimeter or even more, and the housings of the parallel control valves, which are secured to the stand heads or other points in the press frame, also become involved in the displacement which takes place. Not only do they participate in this movement but the position of the control rods concerned is also altered correspondingly and consequently the position which the piston slides bear to the housings or their oil passage crevices.

The drawbacks enumerated above are eliminated by the present invention, which, moreover, lends itself equally well not only to dual stand presses but also to presses of the multiple stand variety.

It is a primary object of this invention to eliminate any sagging of the beam caused by elongation of, and/ or upwards buckling of the press frame which is prevented by compensating the shifting of valve housings which such elongation and/or buckling causes; in other words, by effecting corresponding changes such as, for instance, in the length or angle of suitable control rods.

If dependence on pressure be chosen as the means for altering length or angle, then, according to the terms of the invention, the pressure exerted in the pressure chambers of the press cylinder, or chambers and piping connected thereto, is brought to bear on, in or against the control mechanism or in one of the hydraulic pressure devices incorporated in its members, the pistons of which, being under such pressure, move back and forth in cylinders under a counter pressure exerted by, say, springs or similar means. and. in so doing alter the length of the control rod concerned.

3,020,828 Patented Feb. 13, 1962 The pressure or stroke-dependent member which is used for altering the angle, can be designed along the lines of the corresponding member which changes length, making use of rotary piston slides or other suitable regulating devices. Y

If the pressure dependent member is used for adjusting the angle, its variable member may, for example, be fitted between two lever arms standing at an angle to each other, in which case a hydraulic pressure device will alter either directly-or, if stroke-dependent adjustment is used-indirectly, the angle which the two lever arms form with each other. In the first instance, it can be fitted between the two lever arms, at their extremities if necessary.

If a press is subjected to a one-sided pressure for a protracted period of time, an oblique positioning of the beam can also be brought about by the slide valves which are predominantly used not making a perfect seal. For complete tightness the slide rings should overlap the valve apertures by a certain length of stroke, which, depending on the diameter of the aperture, might run into some fraction of a millimeter or even more.

The longitudinal or angular alteration of the control mechanism may, according to the terms of the invention, also be utilized to reduce that portion of the beams sag which results from the parallel control valves being leaky, if it does not eliminate it completely.

Assuming the stands deflection is say, 1 mm. at 200 atmospheres pressure and the amount of overlap of the control valve, (on the non-stressed side) required to give sufficient tightness is 0.5 mm., then the variable member or control mechanism of each control valve will be lengthened by 1.5 mm. upon pressure rising from zero to 200 atmospheres. This is conditional upon a 0.5 mm. overlap of the closed control valve being achieved by extending the control device belonging to the cylinder which is under pressure. Slow sagging cannot occur because the closed control valve is perfectly tight with an overlap of 0.5 mm.

It may also be of advantage, at the rise in pressure quoted, to limit the elongation to 1.25 mm. and to allow only 0.25 mm. overlap in the control valve on the side which is not under stress. If it stays tight with this amount of overlap, parallelity will be retained. If however, it is only leakproof at an overlap of 0.5 mm., then the beam will gradually assume a slightly oblique position with relation to the table, an amount. of deflection corresponding in fact to the non-compensated 0.25 mm. of the overlap.

The advantage of this procedure becomes obvious however if the more heavily stressed end of the beam, under the pressure exerted, should move still further towards the table. The other beam end will in fact only follow suit if the beam takes up a similar sag but in the opposite direction. As soon as the more heavily stressed beam end comes to a halt however, the sag will reoccur in the old direction though it will not exceed an amount corresponding to the non-compensated 0.25 mm. of the overlap.

In the other instance however, by way of contrast, if the variation in length is 1.5 mm., the beam will stay horizontal upon coming to a halt. If however, after reaching this position, the more heavily stressed beam end should move further downwards, the other beam end will lag behind by an amount corresponding to the 0.5 mm. overlap. Using this variation in length, double the amount of sag will occur if the stressed beam end should move downwards still further due to full pressure being applied.

Therefore, depending upon whether, during operation, the stressed beam end under pressure halts at the same place or whether it moves further downwards, a larger or a smaller overlap will have to be selected and consequently, a greater or lesser elongation of the control rods or members thereof.

An overlap of the non-stressed control valve can however also be etfected by shortening its own control rods providing this is done in the direction of closure.

To this end the control rod or one member thereof is fitted with a device for shortening its length, operated by variations in either pressure or stroke. If pressure operated, the no-load lift pressures or pressures somewhat higher can be used. In the latter instance, the underlying thought is that the device for shortening at pressures which are necessary for executing empty strokes up and downwards, and which could for example lie between 30 and 70 atmospheres, will not show an immediate response, though it will be sufiicient if a response is obtained at a pressure a few atmospheres or so higher, i.e. in terms of the idle stroke pressures mentioned, at about 31 to 40 and 71 to 80 atmospheres.

An increase in pressure can be obtained by dripping-in additional oil which should penetrate inside the pressure chambers and cause the previously quoted pressure of 30 to 70 atmospheres to rise. This rise in pressure is then made use of for operating the device by, for instance, applying it to one piston which, because it is subjected to a counter-pressure spring force, can only respond when there is a rise in pressure by shortening the member or the actual control rod itself.

If pressure in the chambers drops, because more oil is being drained off than can be added by dripping-in, the reduction in pressure thus set up can be utilized to shorten the control rods.

If the pressure increase method is used, the extra pressure required can be taken from the stroke chamber of the lesser or non-loaded stand. The stroke chambers are usually separated from the control valves by springloaded return valves, and pressure can be taken off either in front of or behind these valves. The pressure exerted in the system between the control valve and the return valve will rise rapidly if the control valve leaks owing to the fact that the latter only has little space for oil, and apart from that, it is under slight pressure when initially closed. A quick overlap can be achieved by raising pressure rapidly. As can be seen the scope of the invention allows of several methods towards obtaining an overlap by varying the pressure and consequently the tightness of the control slide valves. With some of them, the device for lengthening or shortening each control rod responds to certain pressures in the pressure chambers, with others, to certain pressures in the stroke chambers of the press cylinders.

FIGS. 1 and 2 show a parallel control mechanism for presses, shears, and so on. With the aid of these illustrations and FIG. 3, it is proposed to describe examples of how the subject of the invention can be put into practical application.

In FIG. 1 there is illustrated a front view of the invention, and in FIG. 2, the side view of a hydraulic press,

whereas FIG. 3 shows variable members of control rods including devices in FIGS. a, b and c for altering the length of the control rod by application of pressure.

In FIGS. 1 and 2 the parallel control valves 1 and 2 are secured to the stand heads, which also hold the press cylinders 3 and 4. The piston or control rods 5 and 6 of the parallel control valves are fitted with variable members 7 and 8, these in turn being fitted with firmly adjustable settings 9 and 10 carrying toothed rods 11 and 12, their job being to set the piston rods to their normal length.

The toothed rods 11 and 12 engage in pinions 13 and 14 fitted to the camshaft 19 common to both control rods. The camshaft bearings 17 and 18 are fitted on the beam 20.

A set of counter rollers and 16 guide the toothed .rods 11 and 12 in their pinions 13 and 14. Two feed pipes 21 and 22 lead from the parallel control valves to the pressure chambers of the cylinders 3 and 4. These opposing the hydraulic pressure.

pipes are connected to flexible steel tubing 23 and 24 through which the oil pressure exerted in the pressure chambers of the cylinders 3 and 4 is transmitted to the variable members 7 and 8.

As an illustration of a one-sided stress between the beam and table in the left hand side, a block 25 is shown as being inserted, whereas there is no object taking the pressure of the right-hand side of the beam.

As soon as the descending beam 20 strikes the block 25, its movement is arrested, the pressure in one of the cylinders 3 increases to full force, its stand flexes up by a corresponding amount, and this takes the parallel control valve 1 upwards. At the same time however, pressure rises in the pressure device of the member 7, whose length thus increases by an amount corresponding to the upwards flexing of the stand. The control rods on this side thus stay at rest and the camshaft 19 is not rotated and the control rods on the right-hand side holding the parallel control valve closed, are not moved.

Due to this increasing pressure leak oil may gradually leak through the parallel control valve 2 into the chamber of cylinder 4. This causes its piston to move slowly downwards and the beam 20 assumes an oblique position. This obliqueness can be achieved by making the valve tighter and this in turn, by providing a greater overlap, and it is for this reason that provision is made for a correspondingly larger elongation of the pressure-dependent variable members.

Therefore, the member 7 is made to extend by more than is necessary to compensate for the flexing upwards of the stand. The toothed rod 11 then sets the camshaft 19 in rotation by an amount corresponding to the excess elongation, and this sets up, via the pinion 1-4, a

similar-sensed movement in the right-hand piston rods,

so that the parallel control valve 2 is closed still further, it forms a better seal, and no, or practically no drip oil can get into the cylinder 4. The beam 20 then stays parallel to the table.

FIGS. 3a, b, and c show some of the numerous possibilities for a practical application of a pressure-governed screw bolt 35 secured to the base 31.

The upper portion 30 carries a stroke limiter nut 36 with an annular lug 37 against which the collar 38 of the piston 34 is arrested after completing its stroke. Both the limiter nut 36 and its locknut 39 are secured by catch washers 40. The limiter nut 36 has an external thread for a pre-tensioning screw 41 whose job is to tension the springs around the piston 34 with a compressive force For this, two concave springs 44 are fitted between the collar 42 of the piston 34 and the ring. The pre-tensioning screw 41 and its locknut 45 are secured by notched washers 46.

A flexible steel tube (not shown) is fitted into the tapped drilling 47 provided and secured by a union joint; the other end'of this flexible steel tube, or other form of energy conductor, is connected to the pressure chamber of its cylinder or to a feeder leading to the latter.

Under the effect of the oil pressure exerted, the piston 34 which is provided with flutes, is pressed in the downward direction, as shown in FIG. 3a, contrary to the pressure exerted by the springs 44, until its collar 38 encounters the annular lug 37. The length of this stroke is the amount by which the members length-'-made up of the lengths of upper and baseis extended. The pistons surface area and the type of springs required are selected to produce at full force, a stroke corresponding partial overlap of the slide valve. Finally, there is an outlet connection 59 for draining off the drip oil escaping from the pressure chamber 33.

FIG. 3b shows a press device for shortening the member, and in which, for the sake of simplicity, the oil is fed in through an inlet connection 47 and a hole 49 drilled through the piston.

Attached to a screw bolt 35 is a piston 48 for shortening the variable members 30, 31.

Pressure is fed in through an inlet connection 47 and passed, via the drilled hole 49 and channels 50, to the pressure chamber 51, causing the piston 48 to move down-' wardly and so reduce the gap between upper and base. The extent of this reduction is the same as that by which the length of the variable member is also reduced.

As a counter force acting on the shortening piston 48, there are two concave springs 53 which are pressed on to the piston '48 by means of a projection 54 in the base. The pressure of the duly pre-tensioned concave springs is taken up in the pressure chamber 51 by a distance ring 55. The job of the projection 54 in the base is to provide the pre-tension required. It is held secure by a locknut 56 and notched screws 57.

The task of limiting the stroke for the shortening operation is taken care of by the upper component 30, which, after completion of the stroke governed by the gap 52, runs up against the shoulder 58 in the base 31. The stroke, i.e. the gap 52 referred to, is set with the aid of the distance ring 55.

If the member is to be fitted with both press devices provision will have to be made, as far as the shortening device is concerned, for a separate pressure oil connections 61 into the chamber 51 from the side as indicated, and the hole 49 drilled through the piston is then dispensed with, as shown in FIG. 3c.

An outlet connection 59 is provided to drain oif drip oil escaping from the pressure chambers 33 and 51.

The upper portion 30 has a hole 60 drilled down its centre, which, when the upper is joined to the piston rod of the slide valve, connects up with the drilling in the piston rod, so that pressure from the press cylinders pressure chambers can pass directly from the pressure chambers of the parallel control valve into the pressure chamber. If the drilled hole 60 method is used to transmit the pressure, then this inlet connection 47 will have to be sealed oflr and neutralized.

The remaining numbers shown in FIG. 30 refer to the same components as those indicated by these numbers in FIGS. 3a and 3b.

Various changes and modifications may be made without departing from the spirit and scope of the present invention and it is intended that such obvious changes and modifications be embraced by the annexed claims.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent, is:

1. Control mechanism for hydraulic presses, shears and similar machines having a frame and a plurality of spaced press cylinders mounted on said frame with cylinders having pistons and a press beam actuatable by said pistons; comprising self-acting parallel guidance means for said beam including a control valve mounted on said frame adjacent each of said cylinders, said valves being provided with operating piston rods, said guidance means further including toothed rods, variable means operatively connecting said toothed rods to said piston rods for automatically adjusting the relative positions thereof, and a camshaft mounted on said beam, said camshaft having spaced pinions thereon, said toothed rods meshing with said pinions to actuate said valves to thereby compensate for variations emanating from flexing of said beam during pressing operation, and hydraulic means connecting said cylinders to the respective variable means for adjusting the length of said variable means.

2. Control mechanism for hydraulic presses, shears and similar machines having a frame and a plurality of spaced press cylinders mounted on said frame with cylinders having pistons and a press beam actuatable by said pistons; comprising self-acting parallel guidance means for said beam including a plurality of control valves mounted in said frame adjacent each of said cylinders, each of said control valves being provided with operating piston rods, said guidance means further including toothed rods, variable means operatively connecting said toothed rods to said piston rods for automatically adjusting the relative position thereof, and a camshaft mounted on said beam, said camshaft having spaced pinions thereon, said toothed rods meshing with said pinions to actuate said valves to thereby compensate for variations emanating from flexing of said beam during pressing operation, and hydraulic means connecting said cylinders to the respective variable means for adjusting the length of saidvariable means, said variable means'including an upper portion connected to each of said piston rods and a base connected to each of said toothed rods, said upper portion being received in said base, an adjusting piston disposed in and extending between said upper portion and said base, spring means disposed in said base yieldingly engaging said adjusting piston for biasing the same further into said upper portion, said hydraulic means being connected to said upper portion for urging said adjusting piston outwardly of said upper portion.

References Cited in the file of this patent UNITED STATES PATENTS 2,309,944 Flowers Feb. 2, 1943 2,328,258 Cannon Aug. 31, 1943 2,510,285 Heyerman June 6,, 1950 FOREIGN PATENTS 6,814 Germany Oct. 18, 1956 306,449 Switzerland June 16, 1955

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