ES2164810T5 - SUITABLE DEVICE FOR USE WITH A PRESSURE DEVICE. - Google Patents

Abstract

THE INVENTION REFERS TO A DEVICE THAT IS SUITABLE FOR USE WITH A PRESSURE APPLIANCE, INCLUDING: A BASE IRON (10) FOR SUPPORTING A PRESSING FORCE UNLOADED ON A LOWER MOLD (11); A SHOCK IRON (16) THAT IS PROVIDED ABOVE THE BASE IRON (10), TO SUPPORT A LOWER PAD (13) OF THE LOWER MOLD (11); PUSHING PISTONS (18) TO ELEVATE THE SHOCK PLATE (16).

Description

Device suitable for use with a pressing apparatus.

The present invention relates to a device of pressing for use in a pressing apparatus for pressing in Dry granular or powder material. Molded objects can be, for example, tiles, plates, refractory bricks, etc. He invention relates to a press device that includes the device.

A pressing apparatus that includes the device according to the invention it has, in particular: a structure main to contain the pressing force, which is generally cancel; actuator devices for pressing under of the descent of an upper mold; charging devices to charge the material to be molded in a lower mold; and devices of leveling to level the top surface of the loaded material in the lower mold. The loading and leveling devices they are generally made up of a single device, called a car, which includes a grid that can slide over the mold to load and a front end that performs leveling during the return run. For a more detailed description of the device Pressing refers to PCT patent application No. WO 89/11969, on behalf of the same Applicant.

The device according to the invention is in Particular of the type that includes: a support plate or sufridera to withstand a pressing force that is discharged onto a bottom mold; a base plate that is arranged above the support plate to support the lower mold template; a percussion plate that is arranged above the plate of base so that it supports a lower mobile core of the mold lower; pusher pistons to raise the percussion plate; pusher cylinders for pusher pistons, which they are rigidly connected to the support plate; a divisor of flow to distribute the same flow to each of the cylinders of pusher, so that the percussion plate can be moved vertically, parallel to itself, under the steps of flow through the flow divider.

The name "support plate" makes commonly referring to a body that is sufficiently thick enough to absorb the pressing force without deformation permanent The support plate is normally installed under all molding devices, in direct contact with the pressing apparatus and, in particular, with the structure to contain pressing forces.

The name "motherboard" makes reference to a plate that remains attached to the support plate during all pressing cycles and it is only removed When the mold is changed. Supporting the template and the plate percussion, the base plate allows to remove in a single operation the whole set of lower molds without substantially modifying the relative positions of the various components.

The name "percussion plate" makes current reference to a plate that can move vertically and that supports the lower mobile nuclei, of so that the mobile cores can be moved to effect the loading and extraction operations of the mold. During pressing, the percussion plate remains motionless in the lower position of its vertical stroke, so that the pressing force absorbed by the percussion plate can be unloaded on the plate support.

To remove the molded part, the percussion plate rises until the upper part of the lower mobile core reaches the level of the template, so that the carriage can push the molded part forward. Once the mold extraction is finished, the percussion plate does not descend to the bottom of its stroke, but stops at a certain intermediate level, so that it is possible to load the lower mold with a previously established amount of material , according to the position in which the percussion plate has stopped. Obviously, the accuracy of placing the percussion plate in position is decisive in determining the amount of dust that is loaded in the various parts of the mold and, therefore, in order to ensure a satisfactory final result. For a more detailed description of the loading and extraction operations of the mold, reference is made to the European patent application
0 547 305 in the name of the same Applicant.

The piston and cylinder pusher units to raise the percussion plate with respect to the support plate they are generally four, and are arranged in the four corners of the percussion plate. These allow you to control effectively the parallelism between the percussion plate and the support plate, since they are all fed by identical flows, generated by A flow divider. For a more detailed description of these units, reference is made to European patent application No. 0 547 305, on behalf of the same Applicant.

The denomination "flow divider" is refers to a device that is capable of generating multiple flows They are all identical to each other. However, it is clear that a equivalent provision but rather less practical could be the of using a flow divider that engendered flows mutually different and piston and cylinder units that had sections proportionally different cross-sections. Preferably, it provides a flow divider so that it receives only one flow of liquid as feed, and divide that flow into a plurality of outflows that are all identical to each other. A flow divider is generally represented schematically in virtue of a plurality of positive displacement pumps, or volumetric, whose axes are all connected to each other mechanically, so that all pumps have to turn to it speed.

It is also evident that a equivalent flow divider providing a valve different proportional and a different encoder to control the movements of the means of action mandated by each flow of so that all flows are the same because each valve proportional can be adjusted so that all encoders Move synchronously. In other words, you can adjust the proportional valves so that all provide substantially the same flow, regardless of the effort that occurs for each of the means of action, that is, with independent of the pressure of each flow.

A preferred embodiment of a divider of the flow includes a separate feeder plunger for each of the piston and cylinder pusher units. The feeder pistons They are mechanically and rigidly connected to each other. and each one is contained in a separate feeder cylinder. Cylinders feeders are mechanically and rigidly connected to each other. Plus preferably, the feeder pistons are hollow, so that the feeder pistons are fed under the cavities For a more detailed description of a divisor of the flow, reference is made to European patent application No. 0 547 305 on behalf of the same Applicant, and in particular the Figure fifteen.

The foregoing is, in summary, the main field of industrial use of the invention, but this field does not imply any limitation on the scope of the invention, since the device and the apparatus according to the invention, in particular as described and claimed herein in the following, may be advantageously used in any other equivalent field, such as claimed in the accompanying claims.

Devices of this type are known and are have described, for example, in European patent application No. 0 547 305 in the name of the same Applicant, and in the patent application Italian nº MI94A001082, which was presented previously but published after the priority date of this request, also in the name of the same Applicant. However, it have observed that these known devices have some inconvenience In particular, under certain conditions, with the device according to the aforementioned European patent application, seizures of the pusher units of piston and cylinder, with deformation of the seats, after which hydraulic tightness is compromised. Also with neither of the two devices mentioned above is possible install usual molds in the way they are already very used, but it is necessary to modify them, and in particular using Only the lower mobile nuclei. However, of this so the molds are no longer perfectly interchangeable with presses of the usual type, in which no dividers of the flow. In addition, in the two aforementioned devices the air bubbles that are accidentally present in the oil they are removed by a vent that removes air and oil together. However, it has been observed that this system does not allow remove all the air present in the circuit, especially in the initial phase of operation. In addition, it has checked that during transport, assembly and maintenance, pusher pistons tend to get out of their cylinders With a pressure in the tank of approximately 3 bar, Enough for the extraction of the pistons. In addition, all operations to replace joints, replace scratched pistons, etc., they must be carried out on the ground, and this leads to various problems: the first of all is that the production unit remains inactive for a very long period of time, with a financial damage that is always very high, because it is it is necessary to stop the entire downstream line, ovens, etc .; In addition, maintenance work is carried out in a department which, since it deals with powder pressing, is in general dusty and is therefore unsuitable for machining with machines In addition, the mechanical equipment required for this type of Intervention is not generally available on site.

In presses of the usual type two are used long rods that are mechanically connected to each other from below, that they are made to act from below, and that they support in form cantilever the vertical movement of the percussion plate and the lower mobile nuclei both during ascent and during decline. Since the movement of the lower mobile nuclei it may get stuck due to friction or seizures between lower mobile cores and the template, a consequence of this is that in these cases the rods are subjected to great efforts, so that the rod guide bushings wear out and after a short period of time the resulting slacks produce considerable inaccuracies in the dust load in the bottom mold. In order to move the rods from below, it is it is necessary to have a so-called "pit", that is, a recess in the soil that allows access to the devices that move the rods The movement of the rods is of two kinds: one vertically, so that the percussion plate moves vertically, and a swivel, so that the rods are rotated around of its own axes, in order to unapply the percussion plate during the change of molds. The application and de-application of the percussion plate generally take place with a coupling in dovetail or T-shape, which tends to wear out with the use, especially for the corners. The fact that devices for the movement of the rods are located in the pit involves obvious problems for all the work of Tuning and maintenance It is not possible to verify the operation but by disassembling the entire unit from below.

Presses of the usual type described in what In addition to the long-term problems related to inaccuracies in dust loading, have difficulties in as for the change of the molds, due to problems of centering and placement in position. It is also necessary to provide plungers additional, simply to be able to raise the base plate and change the molds like this,

The aim of the present invention is therefore to overcome the aforementioned problems with a device pressing according to claim 1. This objective is achieved by means of the features of Claim 1. The structural and functional characteristics of the invention and its advantages over the known technique will be apparent to the view of the following description of the invention, with reference to the accompanying drawings, in which:

Figure 1 is a front view partially in cutting of the device according to the invention;

Figure 2 is a plan view of the device according to the invention;

Figure 3 is a side view partially in cutting of the device according to the invention;

Figure 4 is a front sectional view of a detail of Figure 1;

Figure 5 is a front sectional view of a second embodiment of a detail of Figure 1;

Figure 6 is a schematic view of the device and hydraulic circuit;

Figure 7 is a front sectional view of a detail of the device of Figure 1;

Figure 8 is a plan view of a detail of the device of Figure 7; Y

Figure 9 is a plan view of the detail of Figure 8 in a second separation operation.

With reference to Figures 1 to 9, the device according to the invention includes a support plate 10 to withstand a pressing force that is discharged onto a lower mold 11. In particular, lower mold 11 is formed laterally by the template 12 and at the bottom by the lower moving cores 13. A base plate 14 is arranged above the support plate 10 and supports the template 12 in under the pistons 15. The base plate 14 is removable, of so that by removing the base plate 14 it is also possible to remove the parts that are located above and in particular the plate of percussion 16 and the lower mold 11. The base plate 14 can be fixed to the support plate by means of screws 17, so that the base plate 14 remains fixed to the support plate 10 during each pressing cycle, but that can be removed for Change the mold.

The percussion plate 16 supports the cores lower movable 13 of the lower mold 11. In general, the cores lower mobiles 13 are rigidly coupled to the plate magnetically percussion.

The pusher pistons 18 are entrusted with the task of raising the percussion plate 16. Plungers 18 are contained in cylinders 19, which are rigidly connected to the support plate 10. In particular, the cylinders 19 are contained in holes 20 that are formed in the plate support 10.

The percussion plate 16 is supported by the pusher pistons 18 under a simple coupling of support 21. In this way, it is possible to allow free movement accidentally of the percussion plate 16 in a direction other than parallel to that of the support plate 10. This may occur, by example, as a result of a traffic jam that blocks the slip mutual of the lower mobile nuclei and of the template, or due to the presence of air bubbles in the oil, etc.

The length of the pusher pistons 18 is such which allows lowering the upper part 22 of the pistons 18 to a level that is not higher than that of the upper surface 23 of the support plate 10. In other words, plungers 18 can be completely removed inside the support plate 10.

The support coupling 21 is provided under an extension 24 of the percussion plate 16 through of the base plate 14. For this purpose, the base plate 14 has openings 25 to allow the passage of extensions 24. Each extension 24 is fixed in a seat 26 which is provided in the percussion plate 16. The coupling between extension 24 and the seat 26 has a certain slack, so that it allows a certain horizontal free movement between extension 24 and seat 26 before tightening bolt 9 from above. The rotation of the extension 24 is prevented by pin 8. In this way, it is possible to automatically adjust the horizontal position of the extensions 24. Bolts 9 are in fact tightened after leaving resting the percussion plate on the pusher pistons 18, of so that extensions 24 are automatically arranged in the correct position.

The support coupling 21 is of the type of self centered, and this feature has been provided under of the coupling of a concave profile 27 with a convex profile 22. In particular, preferably, the concave profile is coupled rigidly to the percussion plate 16 and the convex profile 22 is rigidly attaches to the top of the pistons 18. More preferably, the convex profile 22 is spherical and the profile Concave 27 is conical or spherical. The concave profile 27 and / or the profile convex 22 are formed with an insert made of a hard material that is rigidly coupled to the percussion plate 16 and / or the piston 18, by virtue of a forced coupling. With particular reference to Figure 4, the insert is insert plunger 18; with particular reference to the Figure 5, the insert is externally coupled on the top of the plunger 18. In all cases, the coupling Forced can be provided by hot keyed.

Each cylinder and piston unit has a upper chamber 28 and a lower chamber 29. The lower chamber 29 of each unit is fed by the flow divider 30, which in The schematic illustration of Figure 6 is actuated by the piston 31 and produces four identical flows under the four pistons 32.

A suction device 33 can be connected to each upper chamber 28 of the cylinder and piston units, of so that gas from the lower chamber 29 is aspirated, through the gasket 34. Suction device 33 is preferably a Venturi device The suction device 33 is connected to the upper chambers 28 of the pusher cylinders 19 in under a valve 35 that is able to cut the device from suction 33 and sending pressurized air to the upper chambers 28. Preferably, the suction device 33 is connected to the upper chambers 28 under the settling device 36, to decant the vestiges of the oil sucked from the chambers superior.

The encoder 6 detects a position of the flow divider 30 and therefore detects a position of the percussion plate 16. It is thus possible to adjust a valve proportional 7 according to the position signal detected by the encoder 6.

Each of the cylinders 19 is accommodated in the support plate 10 under a hole 20 that is formed on the support plate 10. Each cylinder 19 has a butt support upper 37 which is arranged so that each of the pistons 18 can pass through a hole 38 of the butt support 37.

The coupling between the cylinders 19 and the holes 20 of the support plate 10 is made under supports butt complements: each cylinder 19 has a butt support external 39 that is suitable to apply to a butt support complementary that is formed in the support plate 10. In In particular, the external buttress 39 is a wider region of the upper part of cylinder 19 while butt support complementary is a wider region of an upper part of the hole 20 in the support plate 10.

With particular reference to the realization of Figure 5, the cylinder 19 is fixed to the support plate 10, inside hole 20, by virtue of a first threaded part 40 that gear in the widest region 39 formed at the top of the cylinders 19. The butt support 27 is formed by a flange removable 41. The thickness of the cylinder 19 is in this case the enough to allow fixing the flange 41 on the cylinder 19 under a second threaded part 42 that passes through the tab 41 and which is screwed into a thread that is formed in the cylinder 19.

With reference to Figures 1 to 9, the upper surface 43 of the butt support and / or bolts 42 is at a level that is not higher than that of the upper surface 23 of the support plate 10.

The cylinders 19 are provided with the support to stop 37, which has already been fixed, and are inserted into the plate support 10 from above. The unit formed by cylinder 19 and by the piston 18 is of the double action type, so that it acts in under the upper chamber 28 and the lower chamber 29. Of this way, each unit 18 and 19 can be assembled and tested in workshop, prior to installation. Consequently, at installing is enough to insert the unit into the support plate 10.

The side wall of the cylinder 19 has a first substantially vertical hole 44 combined with a hole substantially horizontal 45, in order to feed the upper chamber 28 from below, preferably with a gas, in general air. The bottom wall of cylinder 19 has a second hole 46 substantially vertical to feed the lower chamber 29 a liquid, in general oil, from below.

A traction cylinder 47 is connected rigidly to the support plate 10 under the screws 48. A traction piston 49 is inserted in the traction cylinder 47 and has traction devices 50 to be applied to the plate traction percussion 16 and disengage from it when so What. The traction devices 50 preferably include a rotating part 51 with an enlarged upper part, so that a first rotation angle of the rotating part 51 allows to apply the percussion plate 16, as illustrated with reference in particular to Figure 8, and so that a second angle of rotation allows to unapply the percussion plate 16, as has been illustrated with particular reference to Figure 9. In particular, the first angle of rotation and the second angle of rotation are displaced in 90º each one with respect to the other. The extreme enlarged 51 has a hemispherical shape that is truncated in two opposite sides 52 and 53. The rotating part 51 includes a rod 54 which is of square cross section and that passes through the traction piston body 49. Rod 54 is operated from below, by virtue of an actuator device 55 which is an actuator Rotating hydraulic, with limited rotation.

The cylinder and piston traction unit is of the double action type and has a superior chamber 56 to which feeds a liquid, and a lower chamber 57 to which it feeds a fluid at a lower pressure, preferably constituted by air.

Preferably, the cover 58 is formed of so that it is monolithic with the percussion plate 16 and the seat of the traction devices 50 is machined on the plate percussion 16 from below. In this way, the capacity of the plate of percussion 16 to support the lower mobile nuclei is higher.

The method to replace the molds is the next:

During step a), the traction devices 50 are disengaged. The traction piston 49 rises, by virtue of the injection of air into the lower chamber 57, the enlarged end 50 of the traction devices rotates by virtue of the rotation of the rotating hydraulic actuator 55 and of the rod 54, and the traction piston 49 descends until it is completely collected inside the support plate 10, by
the oil supply to the upper chamber 56.

During step b), the pusher pistons 18 They are elevated. Locking the locking screws 17 that connect the base plate 14 to the support plate 10, and a spacer (not shown), between the percussion plate 16 and the template 12, so that the elevation of template 12 entails also automatically lifting the base plate 14. Then it will load the liquid into the lower chambers 29 of the pistons pushers 18 and air is discharged from the upper chambers 28.

During step c), the lower mold 12, 13, 14, 15 and 16, is replaced by another. Devices are inserted transfer between support plate 10 and base plate 14. The transfer devices may be constituted by example, for the forks 59 of a forklift lift

During step d), the pistons are lowered pushers 18. Liquid is discharged from the lower chambers 29 of the pusher pistons 18, and the chambers are loaded with air upper 28.

During step e), the traction devices 50 are applied to the percussion plate 16 and the traction piston 49 it is lowered, so that it generates a pulling force towards down on the percussion plate 16.

The traction piston 49 is raised by the introduction of air in the lower chamber 57 and the discharge of oil from upper chamber 56. A rotation of the part swivel 51 and rod 54 in a 90 ° travel allows place the traction devices 50 in a rotated position, suitable for application to the percussion plate 16. The descent of the traction piston 49 allows the percussion plate 16 to be applied. This descent is made by feeding pressurized oil to the upper chamber 56, and discharging air from lower chamber 57 of the traction piston 49.

The invention allows to achieve at least following advantages:

Traction devices for application to the traction percussion plate and for de-applying it in order of command they allow to automate the operations of mold replacement, radically increase the speed of operation, particularly for molds of the usual type that require the removal of all parts arranged above the support plate, from the base plate up.

The provision of traction devices in virtue of a rotating part ensures operation particularly reliable, since the movable structure is very simple and monolithic and, therefore, not very exposed to breakage. Even in the case of mold seizure, this embodiment ensures that it is possible to apply enough force to open the mold without problems.

The traction piston can be picked up inside of the support plate, so that the operations of mold change

The cylinder and piston pusher units they can be checked before installing them on the support plate; in particular, it is possible to check the hydraulic tightness, the movement, etc. The insertion of the support plate is also particularly simple

Worn units can be easily replaced, without having to work on the plate support.

The units can be fed simply from below, by means of pipes, avoiding the need for produce long horizontal holes in the support plate.

Butt support arranged above the cylinder prevents accidental escape of the pistons during transport.

The presence of the double action and the camera upper allows you to remove the pistons more easily inside the support plate

You can eliminate any air bubbles present in the oil by suction through the joints. The removal of air bubbles is very important, since the operating accuracy is based on the incompressibility of the oil and therefore in the parallel movement of the four pusher plungers

A Venturi suction device allows provide an appreciable degree of vacuum in a way simple.

A settling device allows to separate the air oil, sending only air to the device suction.

Operation is reliable, even though it happens that the percussion plate, due to accidental reasons, is find in a position where you are far from parallelism with with respect to the support plate. In this case, it is indeed sufficient with eliminating the accidental reason, without causing damage permanent to the device.

The fact that pusher pistons can be picked up completely inside the support plate allows remove without difficulty all the parts that are arranged by on top of the support plate. This allows to use the large number of molds of the usual existing type.

In addition, the simple support coupling between the pusher pistons and the percussion plate allows a particularly rapid removal of the mold.

The presence of car seats centered on the simple support coupling between the pusher pistons and the percussion plate allows very fast installation of the new mold, since the delicate step of placing in position is carried out Automatically through auto-centered seats.

The extension of the percussion plate through of the base plate allows the pusher pistons to reach the percussion plate even with a reduced length of the pistons pushers, which can therefore be collected more Easily completely inside the support plate. Plate base can also be easily removed, together with the parts superimposed, to change the mold.

Claims (18)

1. Pressing device for use in a Pressing apparatus for dry pressing of granular material or powder, which comprises:

a plate of support (10) to withstand a pressing force that is unloaded on a lower mold (11);

a plate of percussion (16) which is arranged above said plate of support (10), in order to support a lower mobile core (13) of said lower mold (11);

means of elevation to raise said percussion plate (16) consisting of pusher pistons (18), wherein said percussion plate (16) is supported by said pusher pistons (18) by virtue of a simple coupling for rest, so as to allow free accidental movement of said percussion plate (16) other than parallel to said support plate (10); Y

a plate of base (14) that is disposed on top of said support plate (10) and under said percussion plate (16), supporting said plate of base (14) a template of said lower mold (11) and being removable, so that removing said base plate (14) is it is also possible to remove said percussion plate (16) and said mold bottom (11), said base plate (14) being capable of being fixed to said support plate (10), so that it remains fixed during a pressing cycle.

2. Device according to the Claim 1, comprising: pusher cylinders (19) which are provided for said pusher pistons (18), which are preferably formed within said support plate (10) 3. Device according to at least one of the preceding claims, comprising devices of tension (50) for application to said percussion plate (16) by traction, and for de-application of it by command; said traction devices (50) preferably comprising a cylinder (47) connected to said support plate (10) and which has a traction piston (49) that is inserted in said traction cylinder (47). 4. Device according to at least one of the preceding claims, comprising a flow divider (30) to distribute the same flow to each of said cylinders of pusher (19), so that said percussion plate (16) can be moved vertically, parallel to itself. 5. Device according to at least one of the preceding claims, wherein said devices of traction (50) comprises a rotating part (51) with a part enlarged upper, so that a first angle of said part rotating (51) allows it to be applied to said percussion plate (16) and so that a second angle of rotation allows you to de-apply it from said percussion plate (16); preferably said first angle of rotation and said second rotation angle are displaced 90º. 6. Device according to the Claim 5, wherein said enlarged upper part has a hemispherical shape that is truncated on two opposite sides. 7. Device according to at least one of Claims 5 to 6, wherein said rotating part (51, 54) passes through a body of said traction plunger and is operated from below under an actuator (55), which is preferably a rotating hydraulic actuator of limited rotation 8. Device according to at least one of the preceding claims, wherein said traction unit Cylinder and piston (47, 49) is double acting type and has an upper chamber (56) to which a liquid is fed, and a lower chamber (57) to which a fluid is fed at a pressure lower, which is preferably constituted by air. 9. Device according to at least one of the preceding claims, comprising a hole (20) in said support plate to accommodate each of said cylinders of pusher (19), an upper butt support (37) for each of said pusher cylinders (19), so that each of said pusher plungers (18) can pass through a hole said butt support (37); preferably a top surface (43) of said butt support (37) is at a level that is not higher that of the upper surface of said support plate (10); preferably said pusher cylinders (19), provided with said butt support (37), which is already fixed, are introduced in said support plate (10) from above. 10. Device according to at least one of the preceding claims, wherein a unit formed by said cylinder (19) and by said pusher piston (18) is of the type of double action and has an upper chamber (28) and a lower chamber (29); said upper chamber being preferably fed (28) With a gas 11. Device according to the Claim 10, wherein a wall of said cylinder of pusher has a first substantially vertical hole (44) that is preferably combined with a hole substantially horizontal (45) to feed said upper chamber (28) from below; preferably said cylinder (19) has a second hole substantially vertical (46) to feed said lower chamber With a liquid from below. 12. Device according to at least one of the preceding claims, wherein a length of said pusher pistons (18) is such that it allows the descent of the part upper (22) of said plungers (18) to a level that is no more high than that of the upper surface of said support plate (10) 13. Device according to at least one of the preceding claims, wherein said coupling of support comprises an extension (24) of said percussion plate (16) through said base plate (14). 14. Device according to at least one of the preceding claims, wherein said coupling of support is self-centered and preferably comprises the coupling of a concave profile (27) to a convex profile (22). 15. Device in accordance with the Claim 14, wherein said concave profile (27) is coupled rigidly to said percussion plate (16), and said convex profile (22) is rigidly coupled to said upper part of said plungers (18). 16. Device according to at least one of Claims 10 to 15, comprising a device of suction (33) that can be connected to each upper chamber (28) of said cylinder and piston pusher units, so that it sucks gas from said lower chamber (29) through a gasket (34); preferably said suction device is a device of Venturi and is connected to said upper chambers (28) under of a valve (35) that is capable of cutting said device from suction (33) and sending pressurized air to said upper chambers (28). 17. Device according to at least one of the preceding claims comprising at least one valve proportional (7) to adjust a flow line connected to said plungers (18); at least one encoder (6) to detect a position of said percussion plate (16) and adjust said valve proportional (7) accordingly. 18. Pressing device that has a device pressing according to at least one of the claims precedents