GB2348620A

GB2348620A - Device for controlling the tractive force of a riveting tool

Info

Publication number: GB2348620A
Application number: GB0002838A
Authority: GB
Inventors: Martin Kovar
Original assignee: Ms Naradi S R O
Current assignee: Ms Naradi S R O
Priority date: 1999-02-05
Filing date: 2000-02-04
Publication date: 2000-10-11
Anticipated expiration: 2020-02-04
Also published as: GB0002351D0; CZ8410U1; GB0002838D0; FR2789336B1; DE10005060A1; GB2348620B; FR2789336A1; DE10005060B4

Abstract

A device for regulating the tractive force of a riveting tool for nut and screw rivets, which is produced by the pull of a hydraulic piston controlled by the stroke of a double-acting pneumatic piston (8), wherein the space (9) under the pneumatic piston (8) is closeably connected with a source of pressurised air. Between this closeable connection and the space (9) under the pneumatic piston (8) there is a switching valve (7) with a closing element (11) (figure 2) having a pressure element whose controllable pressure counteracts the pressure of the air in the space (9) under the pneumatic piston (8).

Description

Device for controlling the tractive force of a riveting tool Field of the invention The invention concerns a device for controlling the tractive force of a puetumatic hydraulic riveting tool for mit and screw rivets.

Detipt ol8se prar aat To rivet nut and screw rivets it is currently necessary to adjust the stuke of the tool's hydramlic piston, so that application of excessive force on the rivet does not result in defomkation of the thread of the rivet, or tearing ot the thread from the body of the rivet. This adjustment varies for individual sizes of nvets and is carried out by adjusting the lower outer position of the poeumatic piston of the tool. In t practice this means that the strcke of the hydranlic piston always has to be adjusted for a specific size of rivet, for its length for example, and also for the thickness of the material to be joined. Became there exists a specific production to lerance for rivets, as for joining materials, low-grade joints can result during riveting without the tool operator noticing this. It can happen that the rivet is destroyed and a further operation is necded to remove it. Problems oocur also in cases where the operator is riveting various thicknesses of materisls in successive operal;tions. In that case the riveting tool must be changed or a greater variety of rivets must be used. The risk of a low-grade joint is thus inereased, expenses are increased and work productivity reduced. Constant checking of the adjustment of the riveting tool is required. A further disadvantage is the fact that, for riveting a certaim type of rivet, it is always necessary to fill the whole space under the poematic piston with pressuised air, which is mecomomlc. kSummary of the invention The prescnt disadvantage@ are in large measure elimlnkated by the new arrangement of the device for regulating the tractive force of the pnetumatic hydraulic riveting tool for mit and acrewrivets according to this mvention. The tractive force is produced by the pull of a hydraulic piston, cootrolled by the strokc of a double-acting poeumatic piston. where the space under the poeumkatic piston is okoesmy connected with a source of pressurised air. The basis of the invention lies in the fact that between this closeable connection and the space under the poeumatic piston there is a switching valve with a closing element, having a pressure element whose controllable pressure counteracts the pressure of the air in the space under the pueunatic piston.

An advamse is that the pneumnatic pistom moves from its lower outer position to be position where the switching valve closes. That means that for riveting only an effective amotmt of pres@@ised air is used and it is not p[eccssary to fill the whole space under the poekumatic pistom. The result is increased work productivity with a corresponding reduction in the necessary assortment of rivets. An important advantage is the reduced risk of low-grade riveted joints where various thicknesses of material are riveted in successive operations During low puessures in the space under the pneumatic piston, the pressure on the upper sealing element of the closing element of the switching valve is generally, however, very low, in the order of Newion units. When the aire pressure reaches around 0.7 MPa the zwitching valve opens, but leakage can oecur to a presure of around 0.2 to 0.3 MPa, so that its operation is not beecssarily totally reliable. These disadvantages are climinated by the solution according to this invention. The swig vafie coma'isa a body in the hollow of which there is alidcably positioned a closing element, whose stroke in the axial direction is limited by stops, arranged in the bollow of the body.

The closing element has a lower part, sealably guided in the hollow of the body and reaching the lower stop dring the closing of the switching valve, and an upper part which is stepped to a diameter zmaller than the diameter of the lower part of the closing element, and also sumaller than that of the upper stop protruding into the hollow of the body, and which an provided in its end area with a sealing element, radially protruding and axially secured in its position. This upper part is axially arramged in such a way that in the closed position of the switching valve, the sealing element bears against the upper stop forming the sest, and in the open position of the switching valve towards the space under the pnesmatic piston, the operating lower surface of the upper stop bears against the front surface of the lower, wider part of the closing element. The sealed surface of the closing element at the upoper stop is smaller than the sealed surface of its lower part. The closing element has an open exterior reoezs along part of its Iength, running along both its narrower and wider parts. This exterior tecess forms. together with the wall of the hollow of the body and with the adjacent walls of the upper stop, a chamber connected, depending upon the position of the switching valve and of the sealed valve rod of the riveting tool. with the pressurises air intake, with the space under the pneumatic piston or with the outu e=L The advage of this arrangement is that the switching valve closes reliably even at low pressures, for example 0.01 MPa which occur during riveting of small diameter rivets, for example M3. At the same time tbcr is an increase in the margin of pressure in the space under the pneumztic piston in which the switching valve works reliably. That means that with a single riveting ltool it is possible to rivet in a range of rivets with diameters, for example, from Me up to M12.

Toc body ofthe swag vaive is preferably cylindrical in shape, m the form of a chalice, with a twostepped shoulder rurming through the hollow, where the front sorface of the first shoulder forms the lower stop and where in the second upper shoulder there is fixed xn L-shaped sealed ring, whose arm, protruding unto the hollow of the body, forms the upper stop. Its upper edge is arranged as seat for the sealing element of the closing element, the sealing clement consisting of the fut O-ring, partly inserted in a peripheral groove of the closing element. Transverse chamels, connected with the pressurised air inmke, pass through the wall of the body, at least one of which leads into the chamber and is situated at such a height that, throughout the stroke of the closing element, it is always above the level of the second sealing O-ring, whereby sealed guidance of the lower, wider part of the closing element is formed. The sealed surface of the closing element at the upper stop corresponds to the surface given by the diameter defined by the distance between the contact points of the first O-ring in the xat of the upper stop, and the sealed ice of the lower part of the closing element corresponds to the surface given by the diameter defined by the distance between the contact points of the secoi 0-ring in the lower part of the body. This concrete modification is an avantage from a technical point of view.

Channels are connected with a distributing space leading at the same time into the space under the pneumaic piston on the intake from the source of pressurised air and to the outer envianment, where mis distributing space is arranged along the valve rod, and individual connections are formed during the movement of the valve rod by means of sealing O-rings situated on it, one above the office, engaging with their sealing seats. By a fairly simple modification of the existing conventional arrangement of the sealed valverod of riveting tools their operating properties are markedly improved The sealing element preferably consists of a spring one end of which is inserted in an axial recels in the closing element, having pre-stress controlled by a nut screwed to me hollow of the body of the valve. A radial distributing chancel is arranged in the body along its outer perimeter, in the transition betweeeen the distributing space and the chamels, enabling a fast and uniform passage of prcsued air to me switching valve.

Brief description of the drawings For a clearer explanation, the attached drawings illustrate an example of one of the embodiments af the invention, described in more detail in me w that follows. Figure la is a cross section diagram showing the arrangement of the pneumatic hydraulic riveting tool for nut and serew rivets. Figure 1b shows the lower part in which is arranged the device according to this invention. Figures 2 and 3 show a cross-sectional overview of the switching valve ; m figure 2 it is in the closed operating position and in figure 3 in the open opetanng position. Figure 4 is an enlargement of the configuration of the switching valve and of the distributing space of the sealed valve rod of the riveting pool.

Examples of prefcrred embodiments Pressurised air is led through a tube (not illustrated) to the lower part 2 of the pneumatic hydraulic riveting tool 1 for nut and screw rivets. Through the system of chanels in the lower part 2 it is led to the space 3 under the lower sealing O-ring 26 of the sealed valve rod 4. The space 3 is closed from below by a closing nut 5. By squeezing a trigger 6, the sealed valve rod 4 is shifted downwards, its lower O-ring 26 stops sealing, the middle and upper O-rings 27, 28 start to seal and pressurised air can go across this closeable connection from the space 3 through the switching valve 7to the space 9 under the double-acting pneumatic piston 8. The pneumatic piston 8 controls by its stroloe the pull of the hydraulic piston arranged over it, which exerts the tractive force of the riveting tool 1.

The switching valve 7 is arranged as follows. The switching valve 7 comprises a cylindrical body 10 in the form of a calice, in whose through stepped hollow there is a closing element 11 (sealed piston) which shifts under pressure. The pressure element consists of a spring 13, one end of which is inserted in an axial recess in the opening element 11, having pr-stress controlled by a nut (14) screwed to the hollow of thc body 10 of the valve 7. The stroke of the closing element 1 I is limited in the axial direction by two stops, upper and lower, which are arranged in the hollow of the body 10. The spring 13 continually presses the closing element 11 in the direction of its upper stop.

The closing element 11 has a lower part sealably guide (by means of a second 0qu in the hollow of the body 10 and reaching the lower stop during the closing of the switching valve 7, and an upper part which is stepped to a diameter smaller than the diameter of the lower part of the closing element 11, and also smaller than that of the upper stop protruding into the hollow of the body d which is provided in its end area with a sealing clement, radially protruding and axiajly secured m its position.

The through hollow of the body 10 has a two-stepped shoulder. The front surface of the Srst shotder 22 forms the lower stop. In the second upper shoulder there is fixed an L-shaped sealcd ring 12, whose arum, protruding into the hollow of the body 10,forms the upper stop. The upper edge of this upper stop is arranged as a seat 21 for the sealing element of the closing element 11, consisting of the first 0-ring 20, partly inserted in the peripheral groove of the closing element 11.

The upper part of the closing dememt 11 is axially arranged in such a way that in the closed position of the switching valve 7, the first O-ring 20 bears against the upper stop forming the seat 21. and in the open position of the switching valve 7 towards the space 9 under the pneumatic piston 8 the operating lower surface of the upper stop (the L-shaped sealed ring 11) bauds against the front surface of the lower, wider part of the closing clement I1.

The closing elcmeat 11 has an open exterior recess along part of its length, running through its narrower and wider parts. This exterior recess fornns, together with the wall of the hollow of the body 10 and with the adjacent walls of the upper stop, a chamber 23 connected, depending upon the position of the switching valve 7 and of the sealed valve rod 4, with the pressurrised air intalke, with the space 9 md the pnetmatic piston 8 or with the outer environment. The exterior recess facilitates the flow of airacmss the chamber 23, reg : nrdless of the specific shap of th rame In the open position of the switching valve 7, resulting from the pre-stressing of the spring 13 and in the initial position of the sealed valve rod 4, when the trigger 6 of the riveting mol is not activated, the chambrer 23 is cormeeted with the spaoc 9 under the pnesunatic piston 8 and further, by means of transtrsc channels 17, the radial distributing channel 24 and of the distributing space along the valve rod 4, with the exhaust chaunel and the surrounding enviroument. At the same time the space 9under the pncumatic piston 8 is connected across the distributing space with the exhaust channel and the outside environment < The above-mentioned transverse chanmels 17, which pass through the wall of the body 10 and are connected with the pressurised air intake and lead into the chamber 23, are situated at such a beight in the body 10 that, throughout the stroke of the oing element 11 they are always above the level of the second sealing O-ring 19. whereby sealed guidance of the lower. wider part of the closing element 11 is fmmcd.

As mentioned, the transverse channels 17 are connected with the distributing space leading at the same time into the space 9 under the poeumatic iston 8 on the intake from the source of pressurised air and to the outer cnvironment, where this distributing space is arramged along the valve rod 4, and mdividual conneotions are formed during the movement of the valve rod 4 by means of sealing O*gs 26,27,28 sha: d aa it, one above the other, zig with eir sealing seats. The entry space of the transverse chamels 17 is sealed by exterior sealing O-rings 18 so that undesirable leakage of pressurised air does not occur. The body 10 of the valve 7. on the outer perimeter between its exterior sealing O-rings 18, at the transition between the distributing space along the valve rod 4 kand the transverse chanpels 17, is provided with a radial distributing clrammel 24, to which is limked a system of transverse connecting channels 17. All the above mentioned sealing rings are positioned in ]recessed groves. its exterior sealing O-rings 18, at the transition between the distributing space along the valve rod 4 and the transverse champels 17, is prvided with a radial distributing clamel 24 to which is limked a system of transverse connecting channels 17. All the above mentioned sealing rings are positioned in recessed groves.

The body 10 of the switching valve 7 has an outer step 16 to secure its position against shifting from the lower part 2 of the riveting tool as a resnlt of pressurised air in the space 9 under the poeumatic peton ! above the switchiag valve 7.

On squczing the trigger 6 of the riveting tool 1 (when the lower sealing O-ring 26 of the valve rod 4 stops sealing and its middle and upper o-rings 27,28 start to seal) pressurised air flows in the d space along the valve rod 4 to the radial distributing channel 24 and in the transverse channels 17 to the chamber 23 betweent the first and second sealing O-rings 19,20 of the closing element 11 (see Fig. 2). In this upper. open operating position of the closing element 11 the chamber 23 is connected with the space 9 raki the pnmumtdc piston 8 That means that pressurised air flows under the pneumatic piston 8. As pressurised air is transferred in a system of charnels of small cross section to a space 9. whcih by comparison has a relatively large capacity, this space 9 first fills and then there is am merease in pressure and a movement of the double-acting pnenmatic piston 8 in the upward direction. The tractive force of the bydraulic piston arranged over it gradually increases in the upper part of the riveting tool 1 and the rivet begins to deform. The air pressure under the pueurmatic piston 8bassically provides resistance against the movement of the hydranlic piston, in other words performing the deformation work necessary for riveting. As soon as the whole rivet is defonmen, resistance agate the movement of the hydraulic piston increases and as a result of the the air presmure increases in the space 9 under the poeumatic piston 8. After the air pressure is attained, corresponding to the set for of the compression spring 13, the valve 7 switches.

The primary force, which opens the valve 7, depends upon the size of the sealed surface of the closing dt 1 i at the upper stop, corresponding to the surface given by the dismeter D2, defined by tue distance between the contact points of the first O-ring 20 in the seat 21 of the upper stop. It is set by the compression spring 13. As soon as the upper, first sealing O-ring 20 begins at least partly to seal (it begms to descccd onto its scat 21) the air pressure immediately increases between the first and second sealing rings 20, 19 to the level of pressure of the entry air pressure into the riveting tool (around 0.5 to 0.7 MPa). By the effect of the diSetence m the size of the sealed surfaces at the Orings 20,19 in the chamber 23 (the seated surface of the lower part of the closing element 11 at the second O-ring 19, whcih corresponds to the surface given by the diarneter D1, defined by the distance b the contact points of the second O-ring 19 in the lower part of the body 10, is larger than the sealed surface of the closing element 11 at the upper stop, corresponding to the surface given by the diameter D2, defined by the distance between the coutact points of the first O-ring 20 in the seat 21 of the upper stop) eomplete closing of the valve 7 occurs. During low pressures in the space 9 under the pmeumatic pistom 8 this secondary compression force, which results from the difference in the abovementioned sealed surfaces and which presses the first O-ring 20 to the seat 21 is several times greater than the primary force produced by the spring 13. For this reason it is them necessary to remove the pressurisesd air from the chamber 23, otherwise subsequent opening of the valve 7 ould sot oocur.

This removal of pressurised air is assured by the comnection of the chamber 23 with the surrounding environment by meus of the transverse chamnels 17, the radial distributing chamnel 24 and the distributme spic along th valve rod 4, when after releasing the trgger 6 of the riveting tool 1 the lower O-ring 26 starts to seal and the middle and upper O-rings 27,28 of the valve rod 4 stop sealing (the pressurised air from the chamber 23 is taken to the surrounding environment through the middle O-ring 27 of the valve rod 4). At the same time the space 9 under the poeumatic pistom 8 is also thus connected with the surrounding environment (pressurised air is expelled from here around the upper O-ring 28 of the valve rod 4, an exhaust opening from the distributing space along the valve rod 4 being arranged between the middle and the upper O-ring 27,28 of the valve rod 4).

By setting the sprint 13 it is possible to regulate the maximum amount of tractive force in the riveting tool. 1 applied to the rivct. Thereby it is possible, by a simple means, to prevent undesirable deformation of the rivet, or even its destruction. Through regulation by means of the spring 13, exact sctting of the force applied to rivet is possible, so that riveting takes places as carly as possible and at the same time Lhc zbovc-mjeationed undesirable deformation is prevented. The switching valve 7 opens riahly evm at low pressures (for example 0. 01 MPa), which occtrr during riveting with small rivets (for example M3). At the sanie time the margin of pressure in the space 9 under the pneumatic piston 8 in which the switching valve 7 works reliably increases. With a single riveting tool it is thus ou The pueumatic piston 8 moves from the lower outer position to the position where the switching valve 7 closes. This means that only an effective amount of pressurised air is used in riveting and it is not necessary to fill the whole space under the pneumatic piston 8. There is thereby a marked saving of pressurised air and economic operation of the riveting tool.

An air pressure in dicator eam be placed in the passage opening leading to the space 9 under the natic piston 8. The dial cam be ganged according to the units of tractive force of the hydraulic piston. Altauntiveiy, a similar indicator can be placed in the hydranlic ares of the riveting tool 1. al use The device according to this invention is intended for regulation of the tractive force of poemmatic hydnulic riveting tools for nut and screw rivets.

Claims

PATENT CLAIMS 1. A device for regulatin the tractive force of a riveting tool for nut and screw rivets, which is produced by the pull of a hydraulic piston, controlled by the stroke of a double -acting poeumatic piston (8), where the space (9) under the pneurnatic piston (8) is closeably connected with a source of pressurised air, characterised in that between this closcable comnection and the space (9) under the pneumatic piston (8) there is a switching valve (7) with a closing element (11) having a tc dément whose contmllable ! cues the preamm oftWe air in the space (9) under the pneumatic piston (8).
2 A device according to claim 1, characterised in that the switching valve (7) comprises a body (10) in the hollow of which there is shdcably positioned a ctosmg element (11), whose stroke in 5 the eaxial direction is limited by stops macged m the hollow of the body (10), where the closing du (11) has a lower part, sealably guided in the bollow of the body (10) and reaching the lower stop during the closing of the switching valve (7), and an upper part which is stepped to a diameter smaller than the diameter of the lower part of the closing element (11), and also smaller rhaa that of the upper stop protruding into the hollow of the body (10), and which is provided in its end acra with a sealing clement, radially protruding and axially secured in its position, where this upper part is axially arranged in such a way that in the closed position of the switching valve (7), the sealing element bears against the upper stop forming the seat, and in the opem position of the stop valve (7) towards the space (9) under the pueumatic piston (8), the operating lower surface of the upper stop bears agamst the front surface of the lower, wider part of the closing element (11), where the scaled surface of the closing element (11) at the upper stop is smaller than the ! surface of its lower part, while the closing element (11) has an open exterior recess long part of its length, running through both its narrower and wider parts, where this exterior onns, forms, together with the wall of the bollow of the body (10) and with the adjacent walls of the upper stop, a chamber (23), connected, depending upon the position of the swetching valve (7) and of the sealed valve rod (4) of the riveting tool. with the pressuzised air mtake, with the space (9) under the pocumatic piston (8) or with the outer environment.
3. A device according to claims 1 or 2, characterised im that the body (10) of the switching valve (7) is cylindrical in shape, in the form of a chalice, with a two-stepped aboulder rumming through the bollow, where the front surface of the first shoulder (22) forms the lower stop and where in the second upper sboulder thane is fixed an L-shaped scaled ring (12), whose arm, protruding into the hollow of the body (10), forms the upper stop whose upper edge is arranged as a sest (21) for the s E element of the closing element (11), the sealing element consisting of the firs.

O-ring (20), partly inserted m the peripheral grove of the cloging element (11), winle transverse s ! 7) coontected with the pressurised air mtake, pass through the wall of the body (10), at kast one of which leads mto the cner (23) and is situated at such a height that, throughout the stroke of the closing elemcnt (11). it is ahnro above the level of the second sealing O-ring (19), whizuby sealed guidance of the lower, wider part of th closing element (11) is formed.
4. A device according to claims 2 or 3, characterised in that the scaled surface of the closing elan (11) at the upper stop corresponds to the surface given by the diameter D2, defined by the distance between the contact points of the first O-ring (20) in the seat (21) of the upper stop, and the scaled surface of the lower part of the closing element (11) corresponds to the surface given by the diameter D1, defined by the distance between the contact points of the second O-ring (19) in the loyer pu of the body (10).
5. A device according to claims 3 or 4, characterised in that channels (17) are connected with a distributing space leiding at the same time into the space (9) under the poeumatic pistom (8) on the intabe frn the source of pressurised air and to the outer envirooment, where this distributing space is arranged along the valve rod (4), and individnal connections are foomed during the mouvement of the valve rod (4) by means of scaling 0-riap situated on it, one above the other, engaging with their sealing seats.
6. A device according to any of the preceding claims 1 to 4, characterised in that a radial distributing channel (24) is arranged in the body (10) along its outer pcrimeter, at the transition between the distributing space and the channes (17).

6. A device according to any of the preceding claims 1 to 5, characterised im that the pressure element consists of a spring (13), one end of which is inserted in the axial receas in the closing element (11), having pre-strcss controlled by a nut (14) screwed to the hollow of the body (10) of tbe valve (7).

7. A device according to claim 5, characterised in that a radial distributing channel (24) is arranged m the body (10) along its outer perimeter, at the transition between the distributing space and the channes (17).

Amendments to the claims have been filed as follows PATENT CLAIMS

1. A device for regulating the tractive force of a riveting tool for nut and screw rivets, which is produced by the pull of a hydraulic piston, controlled by the stroke of a double-acting pneumatic piston (8), where the space (9) under the pneumatic piston (8) is closeably connected with a source of pressurised air, and where between this closeable connection and the space (9) under the pneumatic piston (8) there is a switching valve (7) with a closing element (11) having a pressure element whose controllable pressure counteracts the pressure of the air in the space (9) under the pneumatic piston (8), characterised in that the switching valve (7) comprises a body (10) in the hollow of which there is slideably positioned a closing element (11), whose stroke in the axial direction is limited by stops arranged in the hollow of the body (10), where the closing element (11) has a lower part, sealably guided in the hollow of the body (10) and reaching the lower stop during the closing of the switching valve (7), and an upper part which is stepped to a diameter smaller than the diameter of the lower part of the closing element (11), and also smaller than that of the upper stop protruding into the hollow of the body (10), and which is provided in its cnd area with a sealing element, radially protruding and axially secured in its position, where this upper part is axially arranged in such a way that in the closed position of the switching valve (7), the sealing element bears against the upper stop forming the seat, and in the open position of the switching valve (7) towards the space (9) under the pneumatic piston (8), the operating lower surface of the upper stop bears against the front surface of the lower, wider part of the closing element (11), where the sealed surface of the closing element (11) at the upper stop is smaller than the sealed surface of its lower part, while the closing element (11) has an open exterior rccess along part of its length, nmning through both its narrower and widcr parts, where this exterior recess forms, together with the wall of the hollow of the body (10) and with the adjacent walls of the upper stop, a chamber (23), connected, depending upon the position of the switching valve (7) and of the sealed valve rod (4) of the riveting tool, with the pressurised air intake, with the space (9) under the pneumatic piston (8) or with the outcr environment.

2. A device according to claim 1, characterised in that the body (10) of the switching valve (7) is cylindrical in shape, in the forum of a chalice, with a two-stepped shoulder nnming through the hollow, where the front surface of the first shoulder (22) forms the lower stop and where in the second upper shoulder there is fixed an L-shaped sealed ring (12), whose arm, protruding into the hollow of the body (10), forms the upper stop whose upper edge is arranged as a scat (21) for the sealing element of the closing element (11), the sealing element consisting of the first 0-ring (20), partly inserted in the peripheral groove of the closing element (11), while transverse channels (17) connected with the pressurised air intake, pass through the wall of the body (10), at least one of which leads into the chamber (23) and is situated at such a height that, throughout the stroke of the closing element (11), it is always above the level of the second sealing O-ring (19), whereby sealed guidance of the lower, wider part of the closing element (11) is formed.

3. A device according to claims 1 or 2, characterised in that the sealed surface of the closing element (I 1) at the upper stop corresponds to the surface given by the diameter D2, defined by the distance between the contact points of the first 0-ring (20) in the seat (21) ofthe upper stop, and the sealed surface of the lower part of the closing element (11) corresponds to the surface given by the diameter Di, defined by the distance between the contact points of the second 0-ring (19) in the lower part of the body (10).

4. A device according to claims 2 or 3, characterised in that channels (17) are connected with a distnbuting space leading at the same time into the space (9) under the pneumatic piston (8) on the intake from the source of pressurised air and to the outcr environnent, where this distributing space is arranged along the valve rod (4), and individual connections are formed during the movement of the valve rod (4) by means of sealing O-rings situated on it, one above the other, engaging with their sealing seats.

5. A device according to any of the preceding claims I to 3, characterised in that the pressure element consists of a spring (13), one end of which is inserted in the axial recess in the closing element (11), having pre-stress controlled by a nut (14) screwed to the hollow of the body (10) of the valve (7).