ITMI20061723A1 - DRIVE DEVICE - Google Patents

Description

IT2041 / 06 / BR JAUMANN PATENT STUDY

by Jaumann P. & C. Sas,

Via San Giovanni sul Muro, 13

20121 MILAN

MI 2006 A or 0 1 7 23

Company: BOSCH REXROTH AG

Headquarters: STUTTGART (Germany)

DESCRIPTION

The invention relates to an actuation device for a movable component, especially for an upper tool of a press brake, according to the introductory definition of claim 1.

Drive devices for presses, punches and guillotine shears, as well as locking units for injection molding molds are often equipped with a hydraulic force multiplication device in order to exert a high force even with a dimensioned drive motor relatively weakly. However, a high transmission ratio leads to a slow positioning movement of the driven component and a large stroke that an input element of the force multiplication device must cover for this purpose - for example a hydraulic piston. The force multiplication devices are therefore often equipped with a so-called rapid traverse which enables fast execution of positioning movements, IT2041 / 06 / BR

on the occasion of which they must be applied

only small forces.

Document EP 1301 330 B1 describes for example a locking unit for an injection molding machine. An electromotive drive unit comprises an electromotor and a screw drive. The screw transmission is coupled, with the interposition of a hydraulic multiplication of forces, with a translatable part of the mold for injection molding. The multiplication of the force is substantially constituted by a hydraulic working cylinder, in correspondence with the hydraulic piston of which the part of the mold is applied, and by two hydraulic cylinders which - from the point of view of the multiplication of the force - are arranged on the driving side and whose pistons are coupled with the screw transmission. A first piston having a small active surface is in this connection rigidly coupled to the screw transmission. The second piston having a larger active surface can be dragged, in the direction of traction of the screw transmission, by means of a stop, by geometric constraint, by the first piston and in the direction IT2041 / 06 / BR

thrust, by means of an elastic coupling or an unlockable magnetic coupling, it can only be dragged up to a certain counter-pressure. The pressure chamber, from which the first piston releases pressurized liquid in the thrust direction, is directly connected to a chamber of the hydraulic working cylinder. The corresponding pressure chamber of the second piston is connected to this chamber of the working hydraulic cylinder via a switching valve. A rapid positioning movement in the closing direction of the injection mold, i.e. a rapid stroke, is achieved when the switching valve is open. In this regard, the pressurized fluid flows out of the pressure chambers, which in the thrust direction of the screw transmission become smaller, of both hydraulic cylinders arranged on the driving side, reaching the chamber of the working hydraulic cylinder. If the switching valve is closed, the pressure chamber of the second piston is inhibited with respect to a further reduction. The force that on the driving side, through the elastic coupling or the magnetic coupling, IT2041 / 06 / BR

acts on the second piston is supported by the pressure created in the intercepted pressure chamber, so that the second piston remains stationary. The first piston, after the release of the magnetic coupling, respectively in the context of the elastic coupling compliance, can be further displaced in the thrust direction and with its relatively small active surface, it can push liquid under pressure out of the pressure chamber with it bordering. As a result, a higher pressure and thus a high multiplication of the force are achieved in the chamber of the hydraulic working cylinder.

In the case of this conventional multiplication of the force, in which a hydraulic cylinder is put at rest as a force acting on it on the driving side is supported by an intercepted pressure chamber, there is necessarily a separation of the chambers in pressure that from different pistons are invested with the force applied on the driving side in the direction of a displacement of liquid under pressure. This interferes with the objectives aimed at IT2041 / 06 / BR

a further simplification of the force multiplication device, respectively of the actuation device.

The aim of the present invention is therefore to indicate an actuation device contemplating an alternative constructive form of a force multiplication device which makes possible in particular actuation devices constructed in a simpler and more efficient manner.

This task is solved by effect of an actuation device having the characteristics of claim 1.

The drive device according to the invention is equipped with an electromotorized drive device which has a rectilinearly displaceable output element. A hydraulic force multiplying device transmits the force applied by the output element to a moving component. The force multiplication device comprises three hydraulic pistons. The first hydraulic piston defines a first pressure chamber with a first active surface, the second hydraulic piston defines an IT2041 / 06 / BR with a second active surface

second pressure chamber and the third hydraulic piston delimits a third pressure chamber with a third active surface and a fourth pressure chamber with a fourth active surface. The second active surface is substantially smaller than the first and third active surfaces. The second hydraulic piston is rigidly coupled with the output member. The first and second pressure chambers are permanently connected hydraulically. By means of a one-sided mechanical stop, the third hydraulic piston can be dragged by the second hydraulic piston in the direction of an enlargement of the third pressure chamber. In this sense, therefore, the movement of the two pistons is coupled by geometric constraint. In the other direction, the third hydraulic piston follows the second hydraulic piston up to a certain pressure in the third pressure chamber. With a changeover valve, one of the pressure chambers bordering the third hydraulic piston can be intercepted.

The particularity of the present invention consists in the fact that also the third pressure chamber is permanently connected with the IT2041 / 06 / BR

first chamber under pressure and that the fourth chamber under pressure can be intercepted by means of the changeover valve.

Contrary to the conventional solution, a displacement of liquid under pressure from the third pressure chamber into the first pressure chamber is not prevented by the switching valve. The third hydraulic piston is also not supported with respect to a force acting on it on the driving side. The place of this, according to the invention, through the interception of the fourth pressure chamber the third hydraulic piston is supported relative to a pressure which acts on it starting from the third pressure chamber. In the first, second and third pressure chambers it is therefore possible to create a higher pressure when the second hydraulic piston, smaller than the third and first hydraulic piston, is displaced in the direction of a reduction in the volume of the second pressure chamber.

This amazingly simple solution allows not only to permanently connect the second and third chambers IT2041 / 06 / BR

under pressure, but also to hydraulically connect the third pressure chamber directly to the first pressure chamber, starting from which the first hydraulic piston receives pressurized liquid during the rapid stroke. This opens the way to new possibilities regarding a simplification of the drive device. The actuation of the switching valve can otherwise take place in the same way as in the case of conventional force multiplication - open during rapid travel, closed for transmission of higher forces - so that a device can be used. command possibly already available.

With the definitions "first pressure chamber", "second pressure chamber" and "third pressure chamber" we mean not only single pressure chambers clearly delimited relative to each other. The numbering only wants to simplify the understanding of the claim. Especially embodiments such as those shown in Figures 1 and 2, in which two or three of these pressure chambers are combined to form IT2041 / 06 / BR

a single pressure chamber, are to be contemplated by the content of this claim. Other advantageous configurations are indicated in the subordinate claims.

Thus, according to claim 2, at least two of the three permanently hydraulically connected pressure chambers, i.e. the first, second and third pressure chambers, can be combined to form a single pressure chamber. As a result, the third pressure chamber in particular can also be integrated into a body in common with the first or second pressure chamber, thus saving on costly connection pipes. The amount of sealing points can be kept low and the likelihood of leakage is reduced.

A particularly preferred configuration provides that the second and third hydraulic pistons are arranged in a cylindrical body in common. As a result, it is possible to achieve a compact form of construction of the two hydraulic pistons coupled to the electromotorized drive unit directly, respectively through the mechanical stop. The subdivision, often opportune, in a cylinder-piston unit IT2041 / 06 / BR

drive-side, comprising the second and third hydraulic pistons, and in a tool-side cylinder-piston unit, contemplating the first hydraulic piston, it becomes simpler.

Additional advantages are achieved when the second hydraulic piston is made in the form of a plunger and the third annular-shaped hydraulic piston is fitted onto the second hydraulic piston and is guided on this so that it can move axially. This gives rise to a particularly simple and economical construction method of a cylinder-piston unit which comprises the second and third hydraulic pistons and which in particular has only a modest number of sealing points.

The mechanical stop is preferably obtained by means of a shoulder on one end of the second hydraulic piston which extends into the cylinder body. Such a stop is achievable in a simple and inexpensive way. The number of sealing points is further reduced, as the third hydraulic piston does not require any crossing on the outside of the cylinder body. The structuring of IT2041 / 06 / BR is therefore further simplified

drive device.

Another advantageous configuration provides for a hydraulic accumulator to be present and for the switching valve to manage a connection between the fourth pressure chamber and the hydraulic accumulator. The hydraulic accumulator can perform the function of a hydromechanical locking device, which causes the third hydraulic piston to follow the second hydraulic piston, leaning against the stop. The hydraulic accumulator can additionally equalize the pressure liquid balance in the hydraulic force multiplication device, so that this can be realized in the form of a closed system. The first hydraulic piston preferably defines with a fifth active surface, directed in the opposite direction with respect to the first active surface, a fifth chamber under pressure so that a backward movement of the component can also be achieved.

A cost-effective force multiplication device, comprising a fast stroke mode of operation, a closed hydraulic system and a reverse motion function, is achieved when an IT2041 / 06 / BR

The hydraulic connection between the fifth pressure chamber and the fourth pressure chamber is managed by the changeover valve.

The fifth pressure chamber is preferably connected to a second accumulator. As a result, a connecting pipe between the fifth and fourth pressure chambers can be spared.

According to a particularly preferred development, the switching valve is in the form of a poppet valve. The hydraulic force multiplication device is consequently substantially free from leakage.

The present invention and its advantages are learned in more detail with reference to the exemplary embodiment and its variants represented in the figures.

Here they show:

Fig. 1 a circuit diagram of an actuation device comprising a hydraulic force multiplication device, Fig. 2 a circuit diagram of the hydraulic force multiplication device represented in Fig. 1 fit IT2041 / 06 / BR

slightly modified, in which, among other things, the pressure chambers are merged to form a single cylinder body,

Fig. 3 a circuit diagram representing a further modification of a force multiplication device with completely separate pressure chambers, and

Fig. 4 a circuit diagram representing a modification of a force multiplication device, in which, among other things, a return line is replaced by a hydraulic accumulator. In order to illustrate a concrete example, the following description refers to an actuation device for an upper tool of a press brake. However, the described drive device is suitable without limitation for many other fields of use, be it punching machines, guillotine shears, or closing devices for injection molding machines, etc. According to Figure 1, a drive unit 1 of a press brake is equipped with an IT2041 / 06 / BR

electric motor 10, with a screw drive 12, for example a ball screw or roller drive, and with a hydraulic force multiplication device 20. A tool carrier 16 with the upper tool mounted thereon is shown in simplified way in the form of a massive block.

The hydraulic force multiplication device 20 is formed by three different hydraulic pistons 24, 28 and 36. The hydraulic piston 24 in the form of a plunger piston extends into a cylinder body 22. The hydraulic piston 24 is mechanically coupled rigidly with a staple 14 of the screw transmission 12. In correspondence with the end, protruding inside the cylinder body 22, of the hydraulic piston 24 there is a shoulder 26. The hydraulic piston 24 is guided movably the hydraulic piston 28 formed in the form of an annular piston. This divides the cylinder body 22 into a cylinder chamber 30 and an annular chamber 31.

The hydraulic piston 36 is arranged in another cylinder body 34. The hydraulic piston 36 IT2041 / 06 / BR

it divides the cylinder body 34 into a cylinder chamber 38 and an annular chamber 39. Together with the cylinder body 34 it therefore forms a double-acting differential hydraulic cylinder. The tool holder 16 is mounted in correspondence with the rod 37 of the hydraulic piston 36.

It should also be noted that a press brake is often equipped with several compression cylinders. The actuation device 1 is integrated in this case due to further differential cylinders which are placed in parallel with the differential cylinder formed by the piston 36 and the body 34.

A hydraulic pipe 40 connects the cylinder chamber 30 permanently with the cylinder chamber 38. Another hydraulic pipe 41, 42 leads from the annular chamber 31, delimited by the annular piston 28, passing through a switching valve 44, to the annular chamber 39 delimited by the hydraulic piston 36. A hydraulic accumulator 46 is also connected to the segment 41 of the pipeline. The switching valve 44 is made in the form of a poppet valve. It manages a hydraulic connection between the IT2041 / 06 / BR chamber

annular 31 and accumulator 46, respectively to annular chamber 39.

The active surface, with which the piston 36 delimits the cylinder chamber 38, corresponds in the case of this embodiment to the surface with which the annular piston 38 adjoins the cylinder chamber 30, with the addition of the cross-sectional area plunger rod 24. The surface with which the piston 36 delimits the annular chamber 39 is slightly smaller than the surface of the piston 28 which delimits the annular chamber 31. This is due to the fact that the rod 37 of the piston is sized in such a way as to absorb the high compressive stresses usual during the operation of the press, while piston 24 and threaded rod 14 are dimensioned in a weaker way. The cross-sectional area of the plunger rod 24 amounts to 1/5 of the circular area of the piston 36, so that a multiplication of the force by approximately the factor of 5 can be achieved.

Hereinafter, the reworking manner of the drive shown in FIG. 1 is illustrated.

IT2041 / 06 / BR

In order to bring the actuating device into a rest position in an upper stop position of the tool carrier 16, the switching valve 44 is brought into a closed position of the valve, as shown in Figure 1. The hydraulic accumulator 46 it is preloaded on a certain pressure, for example 20 bar. This pressure generates an upward force on the annular surface of the piston 36, which more or less corresponds to double the weight force of the tool holder 16 together with the upper tool. Excess force is compensated for by a pressure that is created in the plenum chambers 38 and 30. This pressure is lower than the preload pressure of the hydraulic accumulator 46. the pressure in the plenum chambers 38, 30 is sustained at of the annular surface, facing the pressure chamber 30, of the annular piston 28. in the annular chamber 31 there is a pressure which at least corresponds to the pressure in the chambers 30 and 38. This pressure is sustained at the closed switching valve 44. The annular piston 28 must be in contact with IT2041 / 06 / BR in this regard

on the stop formed by the shoulder 26, or it must be displaced as a maximum within the compressibility of the liquid under pressure, in the annular chamber 31, in the direction of a reduction thereof. A force exerted on the hydraulic piston 24 by the pressure in the cylinder chamber 30 can certainly be supported by the drive motor 10, or it can possibly be supported at an end stop (not shown) of the threaded rod 14.

To terminate the rest state, the switching valve 44 is brought into the open position. The preload pressure of the hydraulic accumulator 46 is now also present in the pressure chamber 31. The pressure in the chambers 38 and 30 is lower than the preload pressure of the hydraulic accumulator 46, as it continues to be caused by excess force on piston 36 in an ascending direction. At the annular piston 28 there is a dynamic pin in the direction of the shoulder 26, on which it now rests. A traction force therefore acts on the threaded rod 14. The force needed to stop the auction IT2041 / 06 / BR

threaded is constituted by the weight force of the tool holder 16, of the tool and of the piston 36, together, and by an additional force. This additional force is based on the difference between the forces caused by the preload pressure of the accumulator 36 on the one hand on the annular surface of the piston 36 and on the other hand on the annular surface of the piston 28. The larger the annular surface of the piston 28 with respect to the annular surface of the piston 36 the greater is the additional force to be exerted on the threaded rod.

If the electric motor 10 is now activated so that the piston 24, fixed to the threaded rod 14, is moved towards the inside of the cylinder 22, the annular piston 28 follows this due to the pressures acting on it. The liquid under pressure, pushed out of the chamber 30, flows into the chamber 38 of the cylinder and the cylinder 36 is lowered. The liquid under pressure, pushed out of the annular chamber 39, is conveyed to the annular chamber 31 passing through the pipes 41 and 42 and through the open switching valve 44. In addition, starting from the accumulator 46 a quantity of liquid in IT2041 / 06 / BR

compensation pressure flows into the annular chamber 31.

The surface of the piston 36, facing the chamber of the cylinder 38, corresponds to the sum of the surfaces of the pistons 28 and 24 which act on the chamber of the cylinder 30. The distance traveled by the piston 36 is therefore as large as the distance traveled by the staple 14. The multiplication of the stroke amounts to 1/1 if for once the modest compressibility of the liquid under pressure is not taken into account. Such a long multiplication is also called rapid stroke and allows a quick lowering of the hydraulic piston 36. Since, corresponding to the multiplication of the stroke, the multiplication of the force amounts to 1/1 and since the annular piston 28 still follows the heavy piston 24 only as long as the pressure in the chambers of the cylinders 38 and 30 does not rise above the pressure of the accumulator, this type of operation is especially suitable for rapid positioning movements, in which no large force is to be applied.

To obtain a multiplication of the stroke plus IT2041 / 06 / BR

short, which allows higher compression forces to be applied via the hydraulic post 36, the switching valve 44 is brought into the closed position. The annular chamber 31 is subsequently intercepted. A pressure existing therein is sustained at the closed switching valve 46. As the inward displacement of the piston 24 continues, the annular piston 28 initially follows this again, until the pressure in the cylinder chamber 30 rises above the pressure in the annular chamber 31. The annular piston 28 it then remains stationary and only still does the piston 24 move in the direction of a reduction in the volume of the cylinder chamber 30. The pressurized liquid pushed out of this moves into the chamber 38 and causes a further downward movement of the piston 36. The liquid in pressure pushed out of the annular chamber 39 is received by the accumulator 46. the multiplication of the stroke, respectively of the force, is the result of the dimensioned ratio between the circular surface, bordering the pressure chamber 38, of the piston 36 and the area of the cross section of the piston rod IT2041 / 06 / BR

24. In this example there is a 5/1 ratio between the surfaces. The result is a ratio of 1/5 between the strokes, that is to say that the piston 24 covers a distance five times longer than the piston 36, and a multiplication of the force of 5/1. This means that a compression force five times greater than a force applied by the electromotor drive device to the threaded rod 14 can be applied to the piston 36.

In order to raise the piston 36 again, once the descending movement has taken place, that is to say in order to perform a return movement, the plunger 24 must first be made to come out of the cylinder 22, with the valve 44 closed, until the shoulder 26 of this again rests on the annular piston 28. If it is assumed that there is no leakage, the stroke by which the piston 24 has moved inside with valve 44 closed is then equal to the stroke by which piston 24 must again be moved outwards with valve 44 closed. As soon as, as a consequence of the outward movement of the piston 24, a pressure created in the chambers in IT2041 / 06 / BR

pressure 38, 30 and 31 due to the effect of the introduction movement previously occurred, again and decreased to a pressure which on the piston 36 balances the preload pressure of the accumulator and the weight force of the tool holder 16, of the upper tool and of the piston 36, as the outward movement of the piston 24 continues, the piston 36 then moves upwards, under the influence of the preload pressure of the accumulator 46 present in the annular chamber 39. The quantity of liquid previously drawn it is now released again by the accumulator 46 in the annular chamber 39. the multiplication of the stroke amounts to 1/5. In the ascending direction, in correspondence with the piston 36, no great force is produced, since this is limited to the equivalent of the preload pressure of the accumulator.

If valve 44 were opened while a higher pressure still reigns in the pressure chambers 38, 30 and 31 than the accumulator preload pressure, the piston 28 would retract until the pressure has dropped to the accumulator preload pressure. . If, on the other hand, the piston 36 is loaded in the direction of IT2041 / 06 / BR

output of the piston rod 37, the annular piston 28 would slide to the abutment 26 and the piston 36 and the tool holder 16 would fall correspondingly abruptly.

As soon as the plunger 24 has moved out of the cylinder 22 to such an extent that its shoulder 26 rests on the annular piston 28, the valve 44 can be opened. With the further outward movement the piston 24 drags the annular piston 28 with it, by geometrical constraint, due to the support on the cantilever 26. The pressurized liquid pushed out of the annular chamber 31 is conveyed to the annular chamber 39 and to the accumulator 46. Under the action of the preload pressure of the accumulator 46, the piston 36 moves upward. The volume existing in the cylinder chamber 30 is filled by the pressurized liquid from the chamber 38. The stroke ratio amounts to 1/1. The force applicable by the piston 36 is again limited by the preload pressure of the accumulator, respectively by the permissible operating pressure of the latter.

The described working cycle of the piston 36 therefore consists of a long, first movement IT2041 / 06 / BR

multiplied descending, which is executable in the form of a rapid positioning movement, in a short, second multiplied descending movement, at which time a large compressive force is available, in a short, first multiplied return movement and in a long, second return movement multiplied, and therefore executable more quickly. Correspondingly, the electric motor 10 carries out, through the screw transmission 12, in succession two movements towards the inside of the piston 24 and subsequently two movements towards the outside of the piston 24. A stop of the electric motor between the two phases of movement towards the inside or the outside is not necessary. On the contrary, the movement phases can be differentiated by switching the valve 44.

Figure 2 shows a hydraulic force multiplying device 50 which is slightly modified with respect to the force multiplying device 20 shown in Figure 1. The component markings of the force multiplication device 50 have been preserved which correspond to those of IT2041 / 06 / BR

hole multiplying device 20. The difference between the force multiplying device 50 and the force multiplying device 20 consists in the fact that in the force multiplying device 50 the pressure chambers 30 and 38 are merged to form a chamber in pressure 54 in common. Correspondingly, the hydraulic pistons 24, 28 and 36 can all be arranged in a single body 52 of the cylinder. The connection line 40 is superfluous. In this way, a more compact, simpler structuring of the force multiplication device is achievable. The burden for piping and sealing is reduced compared to the force multiplication device 20.

Apart from the aforementioned difference, the remaining structure and mode of operation of the force multiplying device 50 correspond to the force multiplying device 20.

Figure 3 shows another force multiplying device 60, which is likewise a modification of the force multiplying device 20. There are three IT2041 / 06 / BR

hydraulic pistons 64, 72 and 36. The hydraulic piston 36, with the cylinder body 34 and the piston rod 37, correspond to the respective components of the force multiplication device 20. The hydraulic piston 64 forms, together with the body 62 of the cylinder and rod 67 of the piston, a double-acting differential hydraulic cylinder. The internal chamber of the cylinder body 62 is divided by the piston 64 into an annular chamber 66 and into a chamber of the cylinder 65. The piston rod 67 is rigidly coupled to the threaded rod of the electro-motorized actuation device. The hydraulic piston 72 likewise forms with its cylinder body 70 and the piston rod 75 a differential hydraulic cylinder. A cylinder chamber 73 and an annular chamber 74 are formed in the internal chamber of the cylinder body 70.

The chambers of the cylinders 65 and 73 are permanently connected to the chamber of the cylinder 38 by means of hydraulic pipes 80 and 81. From the annular chamber 39 a hydraulic pipe 82 leads to the annular chamber 66. A further hydraulic pipe 83 leads to the annular chamber 74 with interposition of the valve of IT2041 / 06 / BR

switching 44.

Between the piston rod 67 and the piston rod 75 there is a coupling element which, in the direction of exit of the piston rod 67, allows a dragging of the piston rod 75 by geometrical constraint. A coupling cross member 77 is formed here which is fixed to the piston rod 67. The piston rod 75 is passed through a housing hole in the coupling cross member 77. A stop 78, formed on the piston rod 75 , necessarily produces a dragging of the piston rod 75 in the exit direction. Apart from this, the coupling crosspiece 77 is guided in a translatable manner on the piston rod 75.

The pistons 64 and 72 are sized so that the ratio between the circular area, which delimits the respective cylinder chamber 65, 73, respectively, and the annular area that delimits the respective annular chamber 66, respectively 74, corresponds to the ratio between the 'circular area, facing the cylinder chamber 38, and the annular area, facing the annular chamber 39, on the piston 36. This also applies to the sum of the circular areas, IT2041 / 06 / BR

delimiting chambers of cylinders 65 and 73, of pistons 64 and 72 in relation to the sum of the annular areas delimiting annular chambers 66 and 74.

The sum of the circular areas, delimiting the chambers of the cylinders 65 and 73, of the pistons 64 and 72 corresponds to the circular area of the piston 36 which delimits the chamber of the cylinder 38. The circular area, facing the chamber of the cylinder 65, of the piston 64 amounts to 1/5 of the area with which the piston 36 delimits the chamber 38. Because of these ratios between the areas there is a multiplication of the stroke equal to 1/1 when the movement of the pistons 64 is coupled and 72. If only the piston 64 is moved, while the piston 72 is stationary, there is a multiplication of the stroke equal to 1/5 and therefore to a multiplication of the force equal to 5/1.

If the switching valve 44 is open, the piston 72 follows the piston 64 in the case of a movement in the direction of a reduction of the chambers of the cylinders 65 and 73, due to a weight force of the tool holder 16, of the tool, etc., which acts on the piston 36 and is directed towards the annular chamber 39. The pressure IT2041 / 06 / BR

»Generated by the weight force in the annular chamber 39 it propagates to the annular chamber 66 and, passing through the open switching valve 44, also to the annular chamber 74 and therefore ensures that the piston 72 follows the piston 64, going to rest on the stop 78 This makes it possible to lower the piston 36 with a long multiplication of the stroke equal to 1/1. In the event of an outward movement of the piston rod 67, the piston 64 drags the piston 72 with it by means of the stop 78. The pressurized liquid, pushed out of the annular chambers 66 and 74, is conveyed to the annular chamber 39. This leads to an upward movement of the piston 76.

When the switching valve 44 is closed the annular chamber 74 is shut off. A pressure acting on it starting from the cylinder chamber 73 is sustained by the intercepted cylinder chamber 74. Upon an inward movement of the piston rod 67 and piston 64, the piston 72 remains stationary. The coupling crosspiece 77 rises from the stop 78. Pressurized liquid pushed out of the cylinder chamber 65 is conveyed into the chamber of the IT2041 / 06 / BR

- »

cylinder 38. Pressurized liquid is correspondingly pushed from annular chamber 39 into annular chamber 66. Piston 66 is lowered. The multiplication of the force is defined, as indicated above, by the ratio between the active surfaces of the piston 64 and of the piston 36. To raise the piston 36 again, first of all the piston 64 is moved in the direction of the annular chamber 66 until the crosspiece the coupling rests on the stop 78. The valve 44 can then be part and, by pushing liquid under pressure out of the two chambers 66 and 74, a further lifting of the piston 36 can take place. The described operating mode of the force multiplication device 60 it differs only negligibly from the mode of operation of the force multiplication device 20. Due to the fact that the piston 64 is arranged in a differential hydraulic cylinder it is also possible to carry out an upward movement of the piston 36 by exerting higher forces. The obtained multiplication of the force corresponds, when the valve 44 is closed, to the ratio between the surfaces of the pistons 36 and 64. By choosing an equal IT2041 / 06 / BR

ratio between the circular areas and the annular areas in the pistons 36, 64 and 72 an accumulator can be omitted. However, it is convenient to choose the ratio between the circular and annular areas of the pistons 64 or 72 in a different way with respect to the ratio between the circular and annular areas of the piston 36, an accumulator connected to the annular chamber 39 through the hydraulic pipe 83 can thus compensate the quantities difference. As already described in connection with the force multiplying device 20, such an accumulator can additionally generate a preload force of the piston 72 in the direction of a reduction of the cylinder chamber 73, so that the piston 72 reliably follows the piston 64 also in the absence of a traction force acting on the piston rod 37. In addition, as also in the force multiplication device 20, the piston 36 is hit by an ascending preload force due to the effect of such an accumulator. The tool holder 16 is therefore prevented, when the valve 44 is closed, from suddenly lowering without the piston rod 67 having to be hit by a traction force. A driving force IT2041 / 06 / BR

* on the piston rod 67 it may possibly be supported by an end stop.

A modification of the force multiplication device 60 shown in FIG. 3 is shown in FIG. 4. The components of the force multiplication device 90, which correspond to the components of the force multiplication device 60, are provided with the same markings and are not more specifically illustrated. The following description highlights the differences between the stroke multiplication device 90 and the stroke multiplication device 60.

The piston 64, with the body 62 and the piston rod 67, is replaced by the plunger 93 which is guided into the body 92. A plunger rod 94 is attached to the plunger 93. On this piston rod 94 the coupling cross member 77 is fixed. The chamber 91 bounded by the hydraulic piston 93 is connected with the cylinder chamber 38 through the hydraulic line 80. The cylinder chamber 73 is permanently connected with the cylinder chamber 91 and therefore also with the cylinder chamber 38. The annular chamber 39, delimited by IT2041 / 06 / BR

♦ hydraulic piston 36, is connected to a hydraulic accumulator 96. The annular chamber 74, delimited by the hydraulic piston 72, can be connected, via the changeover valve, to an additional hydraulic accumulator 98. A return pipe between the chamber is unnecessary. annular 39 and annular chamber 74.

The mode of operation of the force multiplying device 90 substantially corresponds to that of the force multiplying device 20 shown in FIG. 1. From the chambers of the cylinders 91 and 73, pressurized liquid can be made to arrive in the chamber of the cylinder 38. the switching valve 44 is open the cylinder 72 follows the cylinder 93 in the direction of a reduction of the pressure chambers 91 and 73, under the action of the preload pressure which reigns in the accumulator 98. In the other direction the piston 72 is dragged by the stop 78. The accumulator 98, depending on the direction of movement, either releases the required quantity of liquid under pressure in this regard, or takes it up.

If valve 44 is closed the annular chamber 74 IT2041 / 06 / BR

• is intercepted and the cylinder 92 is blocked with respect to a reduction of the annular chamber 74. The piston 93 can now move in the direction of a reduction of the chamber 91 without dragging the piston 72 with it. with the plunger 91, it is possible to generate a raised pressure in the plenum chambers 91 and 38 by applying a modest force on the piston rod 94. A downward movement of the piston 36 is thus achievable generating a high compressive force on the rod of the piston 37. To raise the piston 36 again, with the valve 44 closed, the piston 93 is first brought back out of the body 92 until the coupling crosspiece 77 rests on the stop 787. The valve 44 is then opened and a further backward movement with the participation of both pistons 93 and 12.

The pressurized liquid pushed out of the annular chamber 389 upon the downward movement of the piston 36 is received by the hydraulic accumulator 96. When the pistons 93 and 72 move outward, the pressure in the pressure chamber 38 is lowered. effect of IT2041 / 06 / BR

£

With the preload pressure in the hydraulic accumulator 96, the piston 36 is then raised. The previously displaced liquid under pressure is returned from the hydraulic accumulator 96 to the annular chamber 39.

The preload pressure of the hydraulic accumulator 96 must be selected, in relation to the preload pressure of the hydraulic accumulator 98 and taking into account the annular areas of the pistons 36 and 72, so that, when the switching valve 44 is open, it is guaranteed that the piston 72 follows a direct inward movement of the piston rod 94. If, for example, the annular areas of the pistons 36 and 72 are the same, the preload pressure of the accumulator 96 must be below the pressure of accumulator preload 98.

In the described embodiment and its modifications, the multiplication ratio of the force for the downward movement of the piston 36 with the switch 44 closed has been indicated with 5/1. However, the specialist can certainly also opt for another multiplication ratio that will seem appropriate to him. For this purpose, they must be sized according to the IT2041 / 06 / BR ratio

only the surface of the piston 36 is desired, which

it adjoins the cylinder chamber 38, and the surface, which acts relative to this pressure chamber, of the piston 24, 64 or 93 which is directly coupled to the threaded rod.

LEGEND

1 Drive device

10 Electric motor

12 screw transmission

14 Threaded rod

16 Tool holder

20 Hydraulic force multiplication device

22 Cylinder body

24 Hydraulic piston

26 Shoulder

28 Hydraulic piston

30 Cylinder chamber

31 Annular chamber

34 Cylinder body

36 Hydraulic piston

37 Piston rod

38 Cylinder chamber

39 Annular chamber

IT2041 / 06 / BR

40 Hydraulic piping

41 Hydraulic piping

42 Hydraulic piping

44 Switching valve

46 Hydraulic accumulator

50 Hydraulic force multiplication device

52 Cylinder body

54 Cylinder chamber

60 Hydraulic force multiplication device

62 Cylinder body

64 Hydraulic piston

65 Cylinder chamber

66 Annular chamber

67 Piston rod

70 Cylinder body

72 Hydraulic piston

73 Cylinder chamber

74 Annular chamber

75 Piston rod

77 Coupling beam

78 Bar

80 Hydraulic pipeline

81 Hydraulic piping

IT2041 / 06 / BR

82 Hydraulic piping

83 Hydraulic piping

90 Hydraulic force multiplication device

91 Cylinder chamber

92 Cylinder body

93 Plunger

94 Plunger rod

96 Hydraulic accumulator

98 Hydraulic accumulator

Claims (10)

IT2041 / 06 / BR f »CLAIMS 1. Drive device for a moving component (16), especially for an upper tool of a press brake, comprising an electromotive drive unit which has an electromotor (10) and an output element (14) which can be moved rectilinearly, and comprising a hydraulic force multiplication device (20), which is arranged in a dynamic chain between the output element (14) and the displaceable component (16) and which comprises: a first hydraulic piston (36) which with a first active surface adjoins a first pressure chamber (38) filled with liquid under pressure, a second hydraulic piston (24) which is rigidly coupled with the outlet element (14) and with a second active surface adjoins a second pressure chamber (30) which is permanently connected, hydraulically, with the first pressure chamber ( 38), a third hydraulic piston (28) which with an IT2041 / 06 / BR third active surface adjoins a third pressure chamber (30) and which, with a fourth active surface oriented in the opposite direction to the third active surface, adjoins a fourth pressure chamber (31), where the second active surface is substantially smaller than the first active surface and the third active surface, a unilateral mechanical stop (26), by effect of which the third hydraulic piston (28) can be dragged by the second hydraulic piston (24) in the direction of an increase in the third pressure chamber (30), where the third hydraulic piston (28) follows the second hydraulic piston (24), in the direction of a reduction of the third pressure chamber (30), up to a certain pressure in the third pressure chamber (30), and a changeover valve (44), through which, in a first changeover position, a pressure chamber which adjoins the third hydraulic piston (28) can be intercepted, and through which, in a second changeover position, liquid in pressure can be IT2041 / 06 / BR ί * fed into this pressurized chamber, respectively pressurized liquid can be pushed out of this pressurized chamber, characterized in that the third pressure chamber (30) is also permanently connected, hydraulically, with the first pressure chamber (38), and the fourth pressure chamber (31) can be shut off with the changeover valve (44). 2. Actuation device according to claim 1, characterized in that at least two of the three pressure chambers permanently connected hydraulically are grouped together so as to form a single pressure chamber (30; 54). Drive device according to claim 2, characterized in that the second hydraulic piston (24) and the third hydraulic piston (28) are arranged in a common cylinder body (22; 52). Drive device according to claim 3, characterized in that the second hydraulic piston (24) is made in the form of a plunger and in fact IT2041 / 06 / BR And • that the third hydraulic piston (28) has the shape of a ring, is fitted onto the second hydraulic piston (24) and is guided on this in an axially movable way. 5. Actuation device according to claim 4, characterized in that the mechanical stop is formed by a shoulder (26) at one end of the second hydraulic piston (24) which extends into the cylinder body (22, 52) . Drive device according to one of claims 1 to 5, characterized in that it has a hydraulic accumulator (46; 98) and in that the switching valve (44) operates a connection between the fourth pressure chamber (31 ; 74) and the hydraulic accumulator (46; 98). Drive device according to one of claims 1 to 6, characterized in that the first hydraulic piston (36) defines a fifth pressure chamber (39) with a fifth active surface directed in the opposite direction to the first active surface. IT2041 / 06 / BR r 8. Actuation device according to claim 7, characterized in that the switching valve (44) manages a hydraulic connection between the fifth pressure chamber (39) and the fourth pressure chamber (31; 74). Drive device according to claim 7, characterized in that the fifth pressure chamber (39) is connected to a second accumulator (96). Drive device according to one of claims 1 to 9, characterized in that the switching valve (44) is designed in the form of a poppet valve. The Agent (Paolo Jaumann) delio