Abstract:
A device for riveting and a hydropneumatic device for pressure transmission, including a working piston and a transmitter piston in the form of a double-acting cylinder for transmitting pressure to the working piston, wherein a working stroke of the working piston in a working direction includes a first stroke and a subsequent second stroke, wherein the first stroke is controlled by means of pneumatic pressure acting on the working piston and the second stroke is controlled by means of pneumatic pressure acting on the transmitter piston, and wherein hydraulic fluid is displaced by the transmitter piston and the displaced hydraulic fluid effects the second stroke of the working piston. Regulation means having an actuating device are provided for regulating the pneumatic pressure on both sides of the double-acting cylinder of the transmitter piston such that the second stroke of the working piston is predefined by way of the regulation.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation of International Application No. PCT/EP2013/001089 filed Apr. 13, 2013, which designated the United States, and claims the benefit under 35 USC §119(a)-(d) of German Application No. 10 2012 008 902.3 filed May 8, 2012, the entireties of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a hydropneumatic device for pressure transmission and riveting device. 
       BACKGROUND OF THE INVENTION 
       [0003]    Hydropneumatic devices for pressure transmission, used for example for riveting devices, are already known in a wide variety of embodiments. 
         [0004]    Such devices have a working piston and a transmitter piston for transmitting pressure to the working piston, wherein, for the provision of a working force by the working piston, the transmitter piston, which is subjected to pneumatic action, dips into a hydraulic fluid and displaces hydraulic fluid in accordance with the positive displacement principle, and wherein the working piston, in a force stroke, is moved in a working direction by the displaced hydraulic fluid with a force transmission ratio corresponding to the effective piston surface areas. 
         [0005]    Also provided is an accumulator piston which, before the force stroke, assists a rapid traverse movement of the working piston during a first stroke and, during a rapid-traverse stroke, assists the replenishment flow of hydraulic fluid. 
         [0006]    Furthermore, between the transmitter piston and the accumulator piston, a pneumatic pressure may be realized which effects a pneumatic return movement of the transmitter piston when the operating pressure no longer acts on the transmitter piston. Furthermore, the accumulator piston is also permanently subjected to the action of a pneumatic initial pressure such that the hydraulic fluid volume present in the accumulator piston in an accumulator chamber is subjected to the corresponding pressure, or a preload. 
         [0007]    For the return movement of the transmitter piston, a pneumatic pressure which is reduced in relation to the operating pressure is predefined on a return stroke side of the transmitter piston, such that the pneumatic return movement of the transmitter piston is effected by means of the pressure between the accumulator piston and the transmitter piston, this also being referred to as an air spring. 
         [0008]    The air spring pressure acts permanently on the transmitter piston and accumulator piston and is always constant regardless of the state of movement of the pistons subjected thereto, and is, for example, approximately 0.6 bar. 
         [0009]    In the case of a mechanical spring that may alternatively be provided, which spring acts under a preload between the transmitter piston and the accumulator piston, different pressures or forces always act as a result of the different operating states, in contrast to the situation with the air spring. 
       SUMMARY OF THE INVENTION 
       [0010]    It is an object of the present invention to improve hydropneumatic devices for pressure transmission, or corresponding riveting devices, in particular in order to achieve optimum positioning, which is adapted to changed force stroke requirements, of a working piston. 
         [0011]    The present invention is based initially on a hydropneumatic device for pressure transmission, having a working piston and having a transmitter piston, which is in the form of a double-acting cylinder, for transmitting pressure to the working piston, wherein a working stroke of the working piston in a working direction comprises a first stroke and a subsequent second stroke, wherein the first stroke can be controlled by means of the pneumatic action of pressure on the working piston and the second stroke can be controlled by means of the pneumatic action of pressure on the transmitter piston, and wherein hydraulic fluid is displaced by the transmitter piston and the displaced hydraulic fluid effects the second stroke of the working piston. The first stroke of the working piston in the working direction may, in particular, be regarded as a rapid-traverse stroke, which is followed by the second stroke in the same direction, the second stroke corresponding to a force stroke. The working stroke or the force stroke is followed by a pneumatic return movement of the working piston, wherein the hydraulic fluid thus displaced acts on the transmitter piston such that a return movement of the latter is also effected. 
         [0012]    The essence of the present invention lies in the fact that regulation means having an actuating device are provided for regulating the pneumatic pressure on both sides of the double-acting cylinder of the transmitter piston such that the second stroke of the working piston can be predefined by way of the regulation. It is advantageously thus possible to realize the precise positioning of the working piston in the high-pressure state or in the second stroke by means of pneumatically regulated, in particular servo-pneumatically regulated, positioning of the transmitter piston. The transmitter piston advantageously performs the generation of force during the force stroke. By means of regulated positioning, the force stroke and the positioning and movement of the working piston can be adapted optimally to force stroke requirements that may be changed during the course of the force stroke. 
         [0013]    The working piston can, for example, be stopped in an extremely short time in the force stroke, and the working piston can be moved into a precisely predefinable position, for example, with a desired movement profile. 
         [0014]    The working piston is in the form of a double-acting cylinder, wherein both sides of the double-acting cylinder can be subjected to pneumatic action. Furthermore, a side of the working piston that faces toward the accumulator piston dips into the hydraulic fluid or the hydraulic fluid volume. 
         [0015]    The regulation means can, for example, advantageously be provided retroactively on a known hydropneumatic pressure transmission device without significant conversion measures, wherein the regulation means can be integrated without any problems into the existing systems. If appropriate, it is possible in this way to dispense with components that have hitherto been necessary, such that overall, with the aid of the present invention, the hydropneumatic pressure transmission device can either have fewer components or be of a more compact construction in comparison with previous pressure transmission devices. 
         [0016]    In particular, an accumulator piston is provided that is movable in a control chamber and is in the form of a double-acting cylinder, so that the accumulator piston, in the first stroke, assists a displacement of hydraulic fluid. The assistance is realized by way of the movement of the accumulator piston. The other side of the accumulator piston is subjected to a pneumatic action, for example, by a pressure regulator and a shuttle valve provided in the respective pneumatic line for rapid-traverse stroke assistance. 
         [0017]    It is advantageously possible in this way for the rapid-traverse stroke of the working piston to be achieved by the working piston being moved relatively rapidly from a main position to a desired working position. In the process, the accumulator piston displaces a relatively large amount of hydraulic fluid, whereby the hydraulic fluid moves the working piston forward. 
         [0018]    It is also advantageous for a chamber that accommodates the transmitter piston to be separated from a chamber that accommodates an accumulator piston. In this way, it is advantageously possible for the two sides of the transmitter piston to be subjected to pneumatic action in a regulated fashion. The pneumatic action of pressure on the accumulator piston remains unaffected by the pneumatic regulation of the transmitter piston. The air spring that acts on the accumulator piston can thus be set up independently without any problems. Also, with the separation of the chamber that accommodates the transmitter piston from the chamber that accommodates the accumulator piston, a mechanical spring may readily be realized as an alternative to the air spring. The separation may be realized, for example, by means of a fixed partition or an intermediate ring on the housing of the hydropneumatic device. 
         [0019]    The actuating device of the regulation means advantageously comprises a multi-directional valve. It is possible in this way to realize desired different switching states and regulation stages. In particular, a compressed-air supply, which is connected to the multi-directional valve via a pneumatic line, can advantageously subject the two sides of the transmitter piston to the action of the compressed air or to pneumatic action. Here, each side of the double-acting cylinder of the transmitter piston is connected by way of a dedicated line to the multi-directional valve. 
         [0020]    It is particularly advantageous for the actuating device of the regulation means to comprise precisely one multi-directional proportional valve, in particular a 5/3 directional proportional valve. It is thus advantageously possible for the transmitter piston to be advantageously regulated independent of the working piston. 
         [0021]    By means of the hydraulic fluid that is displaced in accordance with the positive displacement principle and the effective surface areas of different size that are subject to hydraulic action, a relatively large force is exerted on the working piston. Owing to the proportional regulation of the transmitter piston by means of the 5/3 directional proportional valve, wherein the transmitter piston dips into the hydraulic fluid, and a movement of the working piston to a very precise position in the high-pressure chamber is now possible. This, by means of the transmission ratio, permits indirect, highly precise regulation of the working piston to a set value or target value. 
         [0022]    It may alternatively be advantageous for the actuating device of the regulation means to comprise multiple interacting multi-directional valves, in particular two 3/2 directional proportional valves. This is advantageous, in particular, for relatively large nominal diameters of the hydropneumatic device for pressure transmission, for example for nominal diameters of ¾ inch and greater. 
         [0023]    It is also advantageous for sensor means to be provided which have a sensor arrangement or sensors by means of which a value or a physical variable can be detected and provided to the regulator or to a unit superordinate to the regulator. The unit superordinate to the regulator is, for example, one of a control unit, computer and processing unit by means of which the regulation is realized. 
         [0024]    Sensor means are advantageously provided which have a travel sensor arrangement by means of which a travel can be detected, wherein the travel is a regulating variable of the regulation means. It is thus advantageously possible to realize a travel-dependent regulation of the working piston. The travel is advantageously a stroke travel of the working piston, in particular, during the force stroke. 
         [0025]    It is also advantageous for sensor means to be provided which have a force sensor arrangement by means of which a force can be detected, wherein the force is a regulating variable of the regulation means. The force that can be detected is advantageously a force detected at the working piston or a force situated in an area in which the force imparted by the working piston acts, for example, at elements that are adjacent to the working piston during the working stroke, in particular in the vicinity of a front end of the working piston. 
         [0026]    In one advantageous modification of the present invention, sensor means are provided which have a pressure sensor arrangement by means of which a pressure can be detected, wherein the pressure is a regulating variable of the regulation means. The pressure sensor arrangement is advantageously designed to detect a liquid pressure in the hydraulic fluid and provide this detected pressure to the regulator. The liquid or hydraulic pressure in one of the high-pressure phase and during the force stroke is taken into consideration for the regulation. 
         [0027]    In one advantageous variant of the present invention, the side of the accumulator piston, which is in the form of a double-acting cylinder, is subjected to pneumatic action that can be regulated. In this way, it is possible to set up an advantageous air spring, for example, by means of regulation with a pressure regulator and a shuttle valve for the rapid-traverse stroke assistance. 
         [0028]    It may also be advantageous if the side of the accumulator piston, which is in the form of a double-acting cylinder, is subjected to pneumatic action that can be regulated by way of precisely those actuating means which effect the regulation of the pneumatic pressure on both sides of the double-acting cylinder of the transmitter piston. Accordingly, the air spring between the partition and the accumulator piston is also jointly regulated by one of the actuating means and the respective multi-directional valve. This is advantageous with regard to reduced usage of components in the arrangement, because it is possible, if appropriate, to dispense with parts such as, for example, a separate pressure regulator for the air spring. In particular, a 5/3 directional proportional valve can perform both the regulation of both sides of the transmitter piston and also the pressure regulation of the pneumatic chamber on the transmitter piston, if appropriate, with the integration of a shuttle valve for the rapid-traverse stroke assistance. 
         [0029]    In one advantageous arrangement according to the present invention, the working piston is accommodated in a movable fashion in a working piston housing of a first structural unit which is separate from a second structural unit, which has an auxiliary piston housing in which the transmitter piston and the accumulator piston are accommodated, wherein the first and the second structural units communicate hydraulically with one another via a connecting section. Via the connecting section, a hydraulic chamber that exerts a load on the accumulator piston is connected to a hydraulic chamber that exerts a load on the working piston. It is thus possible for the two structural units, if these are provided in different configurations or designs, to be combined with one another in virtually any desired manner. Also, the two structural units can be better adapted to the external conditions, for example, individually positioned or also correspondingly spaced apart from one another, and, if appropriate, spaced apart further from one another. The connecting section or the hydraulic connection of the two structural units may be realized by means of a flexible connection, such as one or more of a high-pressure hose, and by means of a fixed or tubular hydraulic line, for example. 
         [0030]    The present invention also relates to a device for one of clinching and riveting, having a driveable working piston for establishing one of a clinched arrangement and a riveted arrangement with a rivet element, where one of the hydropneumatic devices according to the present invention described above is provided. It is possible in this way to realize a clinching or riveting device that has the above-mentioned advantages. The present invention relates, in particular, to one of a clinching device and a riveting device for connecting two or more component layers, wherein the riveting device is designed, in particular, for riveting with a semi-tubular rivet or solid punch rivet. 
         [0031]    During the riveting process, a punch element is, by means of the hydropneumatic device for pressure transmission, moved linearly in the direction of the component layers to be connected to one another, and a rivet element is introduced into the component layers to be connected to one another, with one of a shaping and a punching process taking place. 
         [0032]    The present invention also encompasses a device for at least one of pressing, pressing-in, embossing, compacting, stamping, calking, clinching, punching and perforating, having a driveable working piston, wherein the device comprises a hydropneumatic device according to one of the embodiments mentioned above. In this way, with one of the aforementioned devices, which may be designed, for example, as a pressing, punching or clinching tool, it is possible to achieve the advantages of the present invention explained above. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0033]    Further features and advantages of the invention will be explained in more detail on the basis of the exemplary embodiments according to the invention illustrated in the figures. 
           [0034]      FIG. 1  shows a hydropneumatic device according to the invention for pressure transmission in section; 
           [0035]      FIGS. 2 to 6  show different variants of a hydropneumatic device according to the invention for pressure transmission, illustrated in highly schematized form and with a circuit diagram; and 
           [0036]      FIG. 7  is a schematic diagrammatic illustration with a regulation loop for a hydropneumatic device according to the invention for pressure transmission. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0037]    In the figures, corresponding parts of different exemplary embodiments are denoted, in part, by the same reference numbers. 
         [0038]      FIG. 1  shows, in section, a hydropneumatic device  1  according to the present invention for pressure transmission, also referred to hereinafter as pressure transmitter  1 . The pressure transmitter  1  has a housing  2  in which a working piston  3  is arranged in a displaceable and radially sealed manner. The working piston  3 , which in  FIG. 1  is situated in an initial position, comprises a front section with a piston rod  4  projecting outward through the housing  2  and a further section with a part piston  5  which is formed integrally with the piston rod  4 , is likewise radially sealed in the housing  2 , and is movable jointly with the piston rod  4 . The part piston  5  has a disk-shaped region of relatively large diameter and has a rear, rod-shaped region, piston section  5   a , which adjoins the disk-shaped region and which is of a smaller diameter than the latter. 
         [0039]    The part piston  5 , or the disk-shaped region, separates two pneumatic chambers  6  and  7  from one another. When a corresponding pressure prevails in the rear pneumatic chamber  6 , the working piston  3  is pushed downward in the direction of the arrow P 1 , or in the working direction. 
         [0040]    The working piston  3  delimits, in a radially sealed manner, a working chamber  8  which is hydraulically connected via a constriction to an accumulator chamber  9  situated above. The accumulator chamber  9 , which is filled with hydraulic fluid, is subjected to a load by an accumulator piston  10  that is capable of performing a displacement movement. The accumulator piston  10  is radially sealed off, and axially displaceable, with respect to a casing tube  11 , wherein the casing tube  11  circumferentially surrounds a control chamber  12  situated above the accumulator piston  10 . The control chamber  12  can be subjected to the action of pneumatic pressure. To optimize gas-liquid separation between the control chamber  12  and the accumulator chamber  9 , an annular groove  10   a  is provided on the shell surface of the accumulator piston  10 , and a further annular groove  10   b  is provided which is connected to the former annular groove, the annular grooves being connected to one another via a transverse bore. The inner annular groove  10   b  is formed on an inner wall of an inner bore that runs centrally through the accumulator piston  10 . 
         [0041]    The casing tube  11  is closed off, in the region of the accumulator chamber  9 , by a housing part  13  of the housing  2  and, in the region of the control chamber  12 , by a partition  14 . The positionally fixed partition  14  is positioned between the control chamber  12  and a further pneumatic chamber  15  which is surrounded by a further casing tube  16 , and a movable plunger piston  18  of a drive piston or transmitter piston  17  is led in a radially sealed manner through the partition  14 . The plunger piston  18  is fixedly arranged centrally on the transmitter piston  17  and extends from the latter, at one side, downward, wherein the plunger piston  18  has a considerably smaller outer diameter than the transmitter piston  17 . The plunger piston  18  is displaceable counter to the hydraulic pressure in the working chamber  8 . 
         [0042]    The plunger piston  18  extends through the partition  14  and the accumulator piston  10  and, in the initial position shown in  FIG. 1 , projects by way of its free end into the accumulator chamber  9 . The transmitter piston  17 , and the plunger piston  18 , can be moved in the pneumatically driven fashion by pressurization, via an advance stroke line  28 , of a drive chamber  19  that adjoins the transmitter piston  17 . The transmitter piston  17  adjoins, at the space opposite the drive chamber  19 , the transmitter piston return stroke chamber or further pneumatic chamber  15  which can be charged with pneumatic pressure via a return stroke line  29 . 
         [0043]    During a second stroke of the working piston or a high-pressure working movement, the drive chamber  19  can be pressurized such that the plunger piston  18 , performing a stroke movement, protrudes into one of a constriction section and a connecting bore  20  that leads from the accumulator chamber  9  to the working chamber  8 . By virtue of the front section of the plunger piston  18  protruding into the connecting bore  20 , the connection between the accumulator chamber  9  and the working chamber  8  is blocked by means of a radial seal  13   a . During the further stroke movement of the plunger piston  18  in the direction of the arrow P 1 , the plunger piston  18  protrudes further into the working chamber  8 , whereby, owing to the relatively small plunger piston diameter, a relatively high working pressure is generated in the working chamber  8 . The pressure corresponds, based on the pneumatic pressure acting on the transmitter piston  17 , to the transmission ratio of the working surface areas of the transmitter piston  17  with respect to the plunger piston  18 . In this way, a high force can be exerted on the piston rod  4  by means of the working piston  3 . 
         [0044]    For the return stroke of the plunger piston  18 , a relatively depleted pneumatic pressure in the drive chamber  19  is required. In this way, the transmitter piston with the plunger piston  18  can be moved back into the initial position illustrated in  FIG. 1 . Here, hydraulic fluid is displaced from the working chamber  8  into the accumulator chamber  9  owing to the return movement of the working piston  3 . Here, the working piston  3  is likewise moved into the initial position shown in  FIG. 1 , likewise driven by the part piston  5  and a suitable prevailing pneumatic pressure in the pneumatic chamber  7 . 
         [0045]    The arrangement according to the present invention may basically be implemented in a hydropneumatic device for pressure transmission with structurally connected working and transmitter parts, as shown in  FIG. 1 , and also in systems in which the two functions are structurally separate or are connected to one another by high-pressure lines. 
         [0046]    For the return movement of the transmitter piston  17 , the required force can be realized by means of a pneumatic pressure introduced into the transmitter piston return stroke chamber or pneumatic chamber  15 . For this purpose, the pressure transmitter is provided with an air spring. Since not the full pneumatic operating pressure is required for the return movement of the transmitter piston  17 , the pneumatic pressure in the pneumatic chamber  15 , or a so-called air spring pressure, is reduced. 
         [0047]    In principle, the same pneumatic pressure or air spring pressure as that in the transmitter piston return stroke chamber or pneumatic chamber  15  can also act on the accumulator piston  10 , whereby a hydraulic accumulator or the hydraulic fluid accommodated in the accumulator chamber  9  is kept in a state with reduced preload. Alternatively, the accumulator piston  10  may also be charged with the full operating pressure and thus kept in a state with increased preload. 
         [0048]    Also schematically illustrated in  FIG. 1  are further lines or connections which comprise an advance stroke line  23  that connects to the pneumatic chamber  6 , a return stroke line  24  that connects to the pneumatic chamber  7 , a line  31   a  that connects to the control chamber  12 , and a hydraulic line  33  that hydraulically connects to the working chamber. The functions of these will be explained in more detail below in the description relating to  FIGS. 2 to 5 . 
         [0049]      FIGS. 2 to 6  each show, for different embodiments of the present invention, a circuit diagram for an associated hydropneumatic device according to the invention for pressure transmission, the hydropneumatic device being in each case of the same basic construction as the pressure transmitter  1  from  FIG. 1 . 
         [0050]    In  FIGS. 2 to 6 , the same reference numbers as in  FIG. 1  have been used for corresponding components of the pressure transmitters according to the present invention, except for the pressure transmitter which is denoted, in  FIGS. 2 to 6 , by the reference number  21 . 
         [0051]    In  FIGS. 2 to 6 , the pressure transmitter  21  is depicted in highly schematized form, where the displaceable piston sections, or radially outer regions of at least one of the part piston  5 , a piston section  5   a , the accumulator piston  10  and the transmitter piston  17 , are illustrated in one of a simplified form and as not extending as far as the inner walls of a housing of the pressure transmitter  21 . 
         [0052]    The pressure transmitter  21  has a working piston  3  in the form of a double-acting cylinder with the piston section  5   a  of the part piston  5 , which piston section  5   a  extends into the working chamber  8  filled with hydraulic fluid and is thus subjected to hydraulic action. 
         [0053]    In the case of the pressure transmitter  21  according to the present invention, the transmitter piston  17  performs the generation of force during the force stroke. By means of regulated positioning of the working piston  3  by regulation of the transmitter piston  17  on its two pneumatically charged sides, that is to say by the pressure in the pneumatic chamber  15  and the drive chamber  19 , the working piston  3  can be optimally adapted to its force stroke requirements. 
         [0054]    At the start of a working stroke of the working piston  3 , the rapid-traverse stroke of the working piston  3  is performed. The working piston  3  is connected, by way of its pneumatic chambers  6  and  7  provided on both sides of the part piston  5 , to a 5/2 directional valve  22 , wherein the pneumatic chamber  6  can be fed with compressed air, for example, via the advance stroke line  23  and the pneumatic chamber  7  can be fed with compressed air, for example, via the return stroke line  24 . Here, the 5/2 directional valve  22  forms an actuating device for the rapid-traverse stroke control. 
         [0055]    In the advance stroke line  23  and in the return stroke line  24 , between the pressure transmitter  21  and the 5/2 directional valve  22 , there is provided in each case one throttling check valve  25  and  26 , respectively, for setting the speed of the working piston  3 . 
         [0056]    The transmitter piston  17  is internally separated, by the partition  14 , from the accumulator piston  10 . The transmitter piston  17 , as a double-acting pneumatic cylinder, is regulated on both sides, via the pneumatic chamber  15  and the drive chamber  19 , by means of a 5/3 directional proportional valve  27 , independently of the working piston  3 . 
         [0057]    Here, an advance stroke line  28  connects the 5/3 directional proportional valve  27  to the drive chamber  19 , and a return stroke line  29  connects the 5/3 directional proportional valve  27  to the pneumatic chamber  15 . The advance stroke line  28  and the return stroke line  29  are in this case connected to the 5/3 directional proportional valve  27  via separate ports. Furthermore, the 5/3 directional proportional valve  27  is connected via a further port to a pneumatic line  38  for the supply of pressure. 
         [0058]    An air spring is realized in the control chamber  12 , wherein the control chamber  12  is connected via the pneumatic line or line  31   a  to a shuttle valve  31 , and the latter is connected to a rapid-venting means  30 , or a rapid-venting valve  30 , and to the advance stroke line  23 . Alternatively (not illustrated), a mechanical spring may be used instead of the air spring. 
         [0059]    The control and monitoring of an oil pressure or hydraulic fluid pressure in the working chamber  8 , which is filled with hydraulic fluid, can be performed by means of an oil pressure switch  32  which is connected via the hydraulic line  33  to the working chamber  8 . 
         [0060]    For measurement of a travel as a regulating variable for the pneumatic regulation of the two sides of the transmitter piston  17 , or for example of an overall stroke of the working piston  3 , a travel measurement system  34 , which is illustrated merely in highly schematic form, may be positioned or mounted one of in the working piston  3  and externally. 
         [0061]    For detection or measurement of a force as a regulating variable, it is, for example, possible for a force sensor  35  to be one of mounted or externally positioned and provided on the working piston  3 , for example. Alternatively or in addition, a hydraulic fluid pressure or oil pressure, if the hydraulic fluid is an oil, may be measured or detected by means of the oil pressure switch  32  and processed further as a regulating variable. 
         [0062]    Furthermore, for the pneumatic side in the pressure transmitter  21 , a pneumatic arrangement is in this case, for example, in the form of a compressed-air supply  36 . The compressed-air supply  36  or the compressed air that is provided leads or is conducted into a supply or pneumatic line  38  via a supply pressure setting means  37  for the compressed air that is provided. Furthermore, for safety reasons, a safety valve  39  is provided in the pneumatic line  38 . 
         [0063]    The setting by way of the supply pressure setting means  37  ensures, for example, a minimum pressure of approximately 3 bar, which is the minimum required for the switching of the respective valves. Depending on at least one of the configuration and the dimensioning of the pressure transmitter  21 , a maximum supply pressure of one of, for example, at most approximately 6 bar, and at most approximately 10 bar, is set by way of the supply pressure setting means  37 . 
         [0064]    The safety valve  39  is triggered, for example, in the presence of a maximum admissible pneumatic pressure in the pneumatic line  38  of approximately 7 bar to approximately 11 bar. 
         [0065]    The mode of operation of the pressure transmitter  21  is as follows: 
         [0066]    The initiation or activation of the rapid-traverse stroke of the pressure transmitter  21  is performed pneumatically by means of the 5/2 directional valve  22 . 
         [0067]    After the rapid-traverse stroke, the regulation to the force stroke is performed by means of the transmitter piston  10 . This always takes place after the rapid-traverse stroke of the working piston  3  of the pressure transmitter  21  has come to an end, that is to say, for example, when the front end of the working piston or a rivet element propelled by the front end impacts against a resistance, for example a component layer. For the activation of the force stroke, the transmitter piston  17  is, by means of the 5/3 directional proportional valve  27 , regulated pneumatically independently of the working piston  3 . On the basis of the positive displacement principle, a relatively large force is exerted on the working piston  3 , as explained above with regard to  FIG. 1 . 
         [0068]    Owing to the proportional pneumatic regulation of the transmitter piston  17  on, for example, one of a travel-dependent, a force-dependent and a fluid-pressure-dependent basis, it is possible to realize highly precise positioning in the high-pressure chamber for the working piston  3 . The working piston  3  can, in the force stroke, move to a predefinable position in a highly accurate manner. Here, it is advantageously furthermore possible for the transmission ratio that is realized in the pressure transmitter  21  to be regulated for indirect and very precise regulation of the working piston  3 , for example, to one of a predefinable or set oil pressure, a predefinable force, a predefinable position and a predefinable travel of the working piston  3 . 
         [0069]    The region of the pressure transmitter  21  indicated by dashed lines in  FIGS. 2 to 6  shows the region illustrated by way of example for the embodiment of the present invention shown in  FIG. 1 . 
         [0070]    In  FIGS. 3 to 6 , the main elements are designed correspondingly to the arrangement shown in  FIG. 2 , such that substantially only the differences between the exemplary embodiments shown in  FIGS. 3 to 6  and the exemplary embodiment shown in  FIG. 2  will be discussed below. 
         [0071]    Accordingly, the embodiment according to the present invention shown in  FIG. 3  concerns a pressure transmitter  21  in which, by contrast to the arrangement shown in  FIG. 2 , for the regulation of the transmitter piston  17 , the regulation is set up for relatively large nominal diameters, for example nominal diameters greater than inch. Here, the 5/3 directional proportional valve  27  provided for the regulation in  FIG. 2  has advantageously been replaced by two mutually corresponding 3/2 directional proportional valves  40  and  41 . 
         [0072]    Here, the 3/2 directional proportional valve  40  is provided on the advance stroke line  28 , and the 3/2 directional proportional valve  41  is provided on the return stroke line  29 . 
         [0073]    The arrangement shown in  FIG. 3  otherwise corresponds to the arrangement shown in  FIG. 2  in terms of construction and also in terms of mode of operation. 
         [0074]    The pressure transmitter  21  according to the present invention shown in  FIG. 4  differs from the arrangement shown in  FIG. 2  in that the transmitter piston  17  together with accumulator piston  10 , with the housing or the casing tube  11  together with housing part  13 , are provided separately from the working piston  3  together with housing  2 , that is to say a transmitter component  44  that can be provided separately and a working component  45  that can be provided separately, which transmitter component and working component are connected to one another in flexible and/or rigid fashion by means of a corresponding hydraulic connection  42 . 
         [0075]    A further advantageous variant of the present invention or of a pressure transmitter  21  according to the present invention is shown in  FIG. 5 . Here, the accumulator piston  10  is moved pneumatically by means of a 5/3 directional proportional valve  43 . Here, the 5/3 directional proportional valve  43  performs not only the regulation of the transmitter piston  17 , as described with regard to  FIG. 2 , but also the pneumatic feed to the control chamber  12 . Accordingly, the rapid-venting valve  30  provided in  FIG. 2  is dispensed with. The shuttle valve  31  is correspondingly connected to the pneumatic chamber  15  and permits a selective connection to the return stroke line  29  and to the advance stroke line  23 . 
         [0076]    The pressure transmitter  21  according to the invention shown in  FIG. 6 , which shows a further separate solution with a transmitter component  44  and a working component  45 , differs from the pressure transmitter  21  as per  FIG. 4  merely in that a hydraulic cylinder  46  in the form of a double-acting cylinder is accommodated in displaceable fashion in the housing  2  of the working component  45 . The hydraulic cylinder  46  is, on one side, subjected to hydraulic action only by means of the hydraulic fluid that is also dipped into by the accumulator piston  10 . Accordingly, one side of the hydraulic cylinder  46  communicates with the accumulator piston  10 , wherein the other side of the hydraulic cylinder  46  is subjected to pneumatic action via the return stroke line  24 , as in the case of the pressure transmitter  21  shown in  FIG. 4 . 
         [0077]    Accordingly, the rapid-traverse stroke is effected exclusively by the accumulator piston  10  moving in the direction P 1 . The return stroke is, as in the other variants shown in  FIGS. 1 to 5 , effected pneumatically, wherein hydraulic fluid is displaced in the direction of the accumulator piston  10  and the latter is likewise subjected to a return movement. 
         [0078]      FIG. 7  shows, in a diagrammatic illustration, a regulation loop for a hydropneumatic device according to the present invention for pressure transmission, or a pressure transmitter  21 , which is controlled by means of a regulating device  47  indicated by a dashed border, for example, by means of a multi-directional valve  48 . During operation in practice, disturbance variables  49  such as, for example, mechanical variables can act on the pressure transmitter  21 . The disturbance variables may arise for example as a result of bending or compression of material, owing to seals or owing to air in the hydraulic fluid. 
         [0079]    By way of sensor means comprising, for example, one of a travel sensor, a force sensor and an oil pressure sensor, or by way of a sensor arrangement  50 , a regulating variable such as, for example, a stroke travel of the working piston is detected in analog form and, in this case, is converted by means of an analog-digital converter  51 . From the regulating variable r provided in digital form and a predefinable guide variable w, a regulating deviation e is formed. The regulating deviation e is processed by means of the regulating device  47 , which in this case comprises, by way of example, a proportional part  52  and an integral part  53 , and the regulating deviation is converted by means of a digital-analog converter  54  of the regulating device  47  into an analog actuation variable y. The actuation variable y acts on the multi-directional valve  48 , by means of which the regulation of the pressure transmitter  21  is performed. 
       LIST OF REFERENCE SIGNS 
       [0000]    
       
           1  Pressure transmitter 
           2  Housing 
           3  Working piston 
           4  Piston rod 
           5  Part piston 
           5   a  Piston section 
           6  Pneumatic chamber 
           7  Pneumatic chamber 
           8  Working chamber 
           9  Accumulator chamber 
           10  Accumulator piston 
           10   a  Annular groove 
           10   b  Annular groove 
           11  Casing tube 
           12  Control chamber 
           13  Housing part 
           13   a  Radial seal 
           14  Partition 
           15  Pneumatic chamber 
           16  Casing tube 
           17  Transmitter piston 
           18  Plunger piston 
           19  Drive chamber 
           20  Connecting bore 
           21  Pressure transmitter 
           22  5/2 directional valve 
           23  Advance stroke line 
           24  Return stroke line 
           25  Throttling check valve 
           26  Throttling check valve 
           27  5/3 directional proportional valve 
           28  Advance stroke line 
           29  Return stroke line 
           30  Rapid-venting means 
           31  Shuttle valve 
           31   a  Line 
           32  Oil pressure switch 
           33  Hydraulic line 
           34  Travel measurement system 
           35  Force sensor 
           36  Compressed-air supply 
           37  Supply pressure setting means 
           38  Pneumatic line 
           39  Safety valve 
           40  3/2 directional proportional valve 
           41  3/2 directional proportional valve 
           42  Hydraulic Connection 
           43  5/3 directional proportional valve 
           44  Transmitter component 
           45  Working component 
           46  Hydraulic cylinder 
           47  Regulating device 
           48  Multi-directional valve 
           49  Disturbance variable 
           50  Sensor arrangement 
           51  Analog-digital converter 
           52  Proportional part 
           53  Integral part 
           54  Digital-analog converter