Abstract:
A valve for controlling a hydropneumatic device for pressure intensifying having a working plunger and an intensifier plunger for pressure intensifying, the intensifier plunger being designed to move the working plunger hydraulically with a comparatively high transmission ratio on account of a pneumatic actuation, the valve having a differential plunger arrangement with a first plunger with a first active plunger face in a first pressure space and a second plunger with a second active plunger face in a second pressure space, the first plunger being coupled to the second plunger, the first pressure space being equipped with a first connector for, for example, a pneumatic return stroke space of the working plunger, and the second pressure space being equipped with a second connector for a pneumatic pressure source which differs from the return stroke space.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of International Application No. PCT/EP2012/002830 filed Jul. 5, 2012, which designated the United States, and claims the benefit under 35 USC §119(a)-(d) of German Application No. 10 2011 107 452.3 filed Jul. 7, 2011, the entireties of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a valve for controlling a hydropneumatic device for pressure intensifying and to a hydropneumatic device for pressure intensifying having a valve. 
       BACKGROUND OF THE INVENTION 
       [0003]    Hydropneumatic devices for pressure intensifying are used for the force-loaded movement of a die for various applications, in particular for joining by shearing and upsetting. Devices of this type have a working plunger which is moved hydraulically in a state by an intensifier plunger which is actuated pneumatically. 
         [0004]    Up to the point, at which the intensifier plunger becomes active, the working plunger is moved pneumatically with a small force. In order to position the switchover point between a non-intensified and intensified movement of the working plunger at the location, at which a great force is required at the working plunger, a valve is used which applies a working pressure to the intensifier plunger in a manner which is dependent on a pressure in a pneumatic return stroke space of the working plunger for the pneumatic return of the working plunger counter to a working stroke direction. The valve operates according to the back pressure process in relation to a differential plunger. The differential plunger has two plungers which are connected to one another and of which one has a greater plunger diameter than the other. That side with the greater plunger diameter of the differential plunger is connected to a return stroke space of the working plunger. The side with the smaller plunger diameter is connected structurally to a pressure source which provides the working pressure and is regularly used to actuate the intensifier plunger when the valve switches through. A waste air throttle with a non-return function is provided in a connecting line between the return stroke space of the working plunger and the valve, by way of which waste air throttle the waste air speed and therefore the switchover time of the valve can be set. 
         [0005]    In a basic position, the return stroke space is loaded with pressure, as a result of which the valve is situated in a position, in which the intensifier plunger is pressureless. In the case of a switchover to a working stroke, the working plunger is loaded with a pneumatic working pressure (fast stroke), with the result that the working plunger moves in a working stroke direction. 
         [0006]    If the movement of the working plunger is decelerated by an increased counterforce or comes to a standstill, the pressure drops in the return stroke space, it being possible for the speed of the pressure drop on the larger side of the valve slide to be set by adjustment of the waste air throttle. If the pressure drops in front of the greater plunger diameter, this leads to the pressure at the smaller plunger diameter displacing the differential plunger and the valve switching. During this operation, a working pressure is switched through to a pressure space of the intensifier plunger, with the result that a movement of the working plunger then takes place with a great force in accordance with the transmission ratio of the intensifier plunger (power stroke). By way of the valve, it therefore always becomes possible, when the working plunger meets a counterforce and decelerates or sets its movement, to switch over to power stroke, in order to continue and to complete a desired working stroke with a considerably higher force. 
         [0007]    The switching on and off of the air pressure can also be effected via externally actuated switching valves. 
       SUMMARY OF THE INVENTION 
       [0008]    The invention is based on the object of improving a hydropneumatic device for pressure intensifying with a valve for controlling the device in such a way that a broadened field of use is made possible for the hydropneumatic device for pressure intensifying. 
         [0009]    The invention proceeds from a valve for controlling a hydropneumatic device for pressure intensifying, which hydropneumatic device has a working plunger and an intensifier plunger for pressure intensifying. The intensifier plunger is designed to move the working plunger hydraulically with a comparatively high transmission ratio on account of pneumatic actuation, the valve having a differential plunger arrangement with a first plunger with a first active plunger face in a first pressure space and a second plunger with a second active plunger face with a second pressure space. The first plunger is coupled to the second plunger. The first active plunger face is preferably larger than the second active plunger face. The first pressure space is equipped with a first connector for a pneumatic control pressure, in particular return stroke space of the working plunger or an external switching connector, and the second pressure space is equipped with a second connector for a pneumatic pressure source which differs from the control pressure. In the case of a predefined pressure difference, the valve switches during a working stroke of the working plunger and the intensifier plunger is loaded with a working pressure. 
         [0010]    The core of the invention then lies in the fact that a third plunger with a third active plunger face is provided, which third plunger is coupled to the second plunger and has a third pressure space which can be loaded via a third connector with a pneumatic pressure source, and that the valve is such that the valve switches in the case of a predefined pressure difference between the first and third pressure space and supplies any intensifier plunger which is connected with the pressure in the second pressure space. 
         [0011]    The intensifier plunger is therefore moved by way of the pressure in the second pressure space and initiates the power stroke. 
         [0012]    The construction according to the invention has first of all the advantage that the switching of the valve by the third pressure space can take place independently of a pressure in the second pressure space. It is therefore possible to supply substantially any desired pressures to the second pressure space which is switched through to the intensifier plunger, without influencing the switching behavior of the valve. In this way, the force of the intensifier plunger can be set in a broad range by way of different pressures. In contrast, the switching behavior of the valve is defined by the differential pressure between the first and third pressure space. The pressure in the third pressure space can be set, in relation to the second pressure space, to a level which makes a desired switching behavior possible; for example, to a maximum available supply pressure. In a corresponding way, it is necessary only once to set a waste air throttle between the first pressure space and the return stroke space in such a way that a back pressure during the movement of the working plunger in the return stroke space behaves, in relation to a pressure in the third pressure space, in such a way that the valve always switches at the same desired point and supplies the intensifier plunger with the provided working pressure. 
         [0013]    If the pressure in the second pressure space to the intensifier plunger is changed, this therefore has no effect on the switching behavior, as would be the case in the prior art when a pressure regulation is made discernible immediately by a changed pressure in the second pressure space which is responsible for the switching behavior in the prior art. In this case, the waste air throttle between the first pressure space and the return stroke space would have to be adapted, in order to make the valve switch through at the same point in the case, for example, of a reduced pressure which is switched through to the intensifier plunger. 
         [0014]    According to the invention, without influencing the switching behavior, a pressure regulator can be provided in the supply line to the second connector for the second pressure space, by way of which pressure regulator the power stroke can be set as stipulated via the intensifier plunger. 
         [0015]    A pressure regulator of this type can be accommodated in the power stroke valve or at any other desired point, for example, in a switch cabinet. 
         [0016]    A proportional valve, for example, can be used as pressure regulator, which proportional valve is arranged in a line between the second pressure space and a pressure space for the intensifier plunger. However, other pressure regulating units are also conceivable. 
         [0017]    In a further particularly preferred refinement of the invention, a connecting line is provided between the second and the third pressure space, which connecting line can be closed. This affords the advantage that the valve according to the invention is likewise available for a conventionally known use, by the connecting line between the second and third pressure space remaining open, but the connector of the third pressure space to the outside being closed. If, in contrast, work is to be carried out with a reduced working pressure for the intensifier plunger with a constant, for example maximum, supplying pressure for the switching behavior, the connecting line is closed, whereby a high switching pressure can be applied at the third connector and the second connector is supplied with a reduced pressure, for example by a pressure regulator. It is likewise possible to also connect a pneumatic continuous pressure supply to the second connector in safety-relevant controllers, and to switch the continuous pressure supply through via a switched inlet to the intensifier plunger. 
         [0018]    In a further preferred embodiment, the connecting line between the second and third pressure space can be closed by a screw element, for example, by it being screwed into the connecting line between the lines of the second and third connector. 
         [0019]    In order to realize a simple coupling between the second and third plunger, it is preferred if the third plunger is configured such that it can be clipped into the second plunger. As a result, it is possible that the second plunger can also be used in systems, in which a third plunger is not provided. A provided latching possibility for the third plunger does not disrupt the function of the second plunger. However, it is also conceivable that the third plunger is configured in one piece with the further plunger, optionally with all plungers. 
         [0020]    A further essential aspect of the invention lies in the fact that a third connector is provided which can be loaded with a pressure source, and that the valve is such that the valve switches in the case of a predefined pressure difference between the first and second pressure space, and a connected intensifier plunger is supplied with the pressure of the pressure source which lies at the third connector. 
         [0021]    In this embodiment, a third switchable passage is provided in an unchanged differential plunger arrangement, which third switchable passage can be used for variable pressures at the intensifier plunger. The switching behavior of the valve is therefore likewise kept independent of the pressure which is set at the intensifier plunger. This is because the second pressure space can be loaded with the full supply pressure. In a corresponding way, as in the case of the first embodiment of the invention, a pressure-regulated line can be connected, for example, to the third connector, with the result that the pressure at the intensifier plunger, if its pressure space is connected, can be set freely in a broad range in accordance with a pressure regulation of this type. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    A plurality of exemplary embodiments of the invention are shown in the drawings and will be explained in greater detail in the following text with the specification of further advantages and details. 
           [0023]      FIG. 1  shows a diagrammatic longitudinal section of a power stroke valve according to the invention; 
           [0024]      FIG. 2  shows a section along the longitudinal axis through a hydropneumatic pressure intensifier with a convoluted stroke travel; 
           [0025]      FIG. 3  shows a section through a valve which is known from the prior art for controlling the power stroke (power stroke valve); and 
           [0026]      FIG. 4  shows a basic circuit of a hydropneumatic pressure intensifier with a valve for controlling the power stroke. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0027]      FIG. 2  shows a hydropneumatic pressure intensifier which is known from the prior art and has a convoluted travel of plunger elements only by way of example. 
         [0028]    The following text with respect to  FIG. 2  also applies in principle, however, to a pressure intensifier with a non-convoluted travel. 
         [0029]    The pressure intensifier  1  comprises a pneumatically moved intensifier plunger  2  (called plunger in the following text), with a sealed plunger section  3  which is arranged displaceably in a pneumatic space ( 8   a ) (power stroke space) of a housing section  8  of the pressure intensifier  1 .  FIG. 2  shows the completely retracted position of the plunger  2 , in which position pressure intensifying to a working plunger  4  has already taken place. The working plunger  4  is accommodated displaceably in a housing section  5  which is arranged in parallel. 
         [0030]    In the stage which is shown, a plunger rod  2   a  of the plunger  2  is dipped into a high pressure hydraulic space  7  which is sealed by the plunger rod  2   a  via a seal (not shown). The high pressure hydraulic space  7  extends via a connecting line  7   a  into a hydraulic space section  7   b  in the housing section  5 . The plunger is moved by pressure loading of the power stroke space  8   a.    
         [0031]    The power stroke space  8   a  is sealed via a wall  9  and seals (not shown) to the plunger rod  2   a  of the plunger  2  with respect to a further pneumatic space  12 . 
         [0032]    The pneumatic space  12  is defined firstly by the wall  9  and secondly by an accumulator plunger  13 . The accumulator plunger  13  has sealing elements (not shown) which firstly seal the accumulator plunger  13  toward the plunger rod  2   a  of the plunger which runs through the accumulator plunger  13 , and secondly ensure separation of the pneumatic space  12  from a low pressure hydraulic space  18 . 
         [0033]    In the completely retracted state of the plunger  2 , hydraulic liquid can be pressed out of the low pressure hydraulic space  18  into the high pressure hydraulic space  7  by way of a pneumatic movement of the accumulator plunger  13 , since the plunger rod  2   a  is then pulled out of the high pressure hydraulic space  7  to such an extent that an opening  6   a  through the seal is exposed. 
         [0034]    By way of hydraulic liquid flowing into the high pressure hydraulic space  7 , the working plunger  4  is displaced in the working direction  5  (see arrow  19 ). 
         [0035]    The supply can take place at a comparatively high speed and is called fast stroke. 
         [0036]    The working plunger  4  has a plunger section  4   a  which is sealed with respect to the high pressure space  7  or  7   b  and a plunger section  4   b  which lies opposite the former in the working direction (arrow  19 ). A hydraulic liquid volume is enclosed in a hydraulic space  20  between the plunger sections  4   a  and  4   b.    
         [0037]    The hydraulic space  20  is divided into a first region  21  and a second region  22  by a sealing section with respect to a plunger section  4   c.  A movement of the working plunger  4  can therefore take place only when the hydraulic fluid can flow over from the first region  21  and the second region  22  and vice versa. To this end, a regulating block (not shown) can be provided. 
         [0038]    A movement sequence can be as follows: In a starting situation, the plunger  2  is retracted completely in  FIG. 2  to the left-hand edge wall  8   b  of the power stroke space  8   a.  Via the accumulator plunger  13  which can be actuated pneumatically by compressed air loading of the pneumatic space  12 , first of all hydraulic liquid is displaced from the low pressure hydraulic space  18  into the high pressure hydraulic space  7 . As a result, a comparatively rapid stroke of the working plunger  4  can be brought about (fast stroke) by hydraulic fluid flowing over via the connecting line  7   a  into the hydraulic space section  7   b.    
         [0039]    To this end, the hydraulic block (not shown) permits, for example, a corresponding rapid equalization of hydraulic liquid from the second region  22  into the first region  21 . 
         [0040]    In this phase, the working plunger  4  is under low pressure. 
         [0041]    From a predefined displacement travel of the working plunger  4 , the latter is to be loaded with high pressure. To this end, the plunger rod  2   a  of the plunger  2  enters into the high pressure hydraulic space  7  through the opening  6   a  by way of pneumatic loading of the power stroke space  8   a.  This operation is initiated (see below) by a valve for controlling the power stroke (power stroke valve). As a result of the ratio of the active cross sections of the plunger section  3  with respect to the plunger rod  2   a,  an enormous pressure intensification takes place into the hydraulic liquid in the high-pressure hydraulic space  7 , with the result that the working plunger can be extended further with great force by way of the hydraulic liquid which is under high pressure, depending on how far the plunger dips into the high pressure hydraulic space  7  (power stroke). 
         [0042]    It is also necessary in this movement that hydraulic liquid can flow over from the second region  22  into the first region  21  of the hydraulic space  20 . 
         [0043]    For a return movement of the working plunger  4 , the regulating block (not shown) can be configured in such a way that a largely free flow of hydraulic liquid from the first region  21  into the second region  22  is possible. For the return movement, a pneumatic space  25  (return stroke space) is loaded with compressed air and, in the same way, the plunger  2  is moved back pneumatically over the pneumatic space  8 , with the result that hydraulic liquid from the high pressure hydraulic space  7  can flow back into the low pressure hydraulic space  18  as a result of pressure loading in the pneumatic space  25 . 
         [0044]    As a result, the accumulator plunger  13  is also moved in the direction of the wall  9 . 
         [0045]      FIG. 3  shows a valve  26  which is known from the prior art for controlling the power stroke (power stroke valve) with a displaceably mounted differential plunger  27  with a plunger  28  with a large plunger face  29  and a plunger  30  with a small plunger face  31 . 
         [0046]    The plunger  28  moves in a pressure space  32  and the plunger  30  moves in a pressure space  33 .  FIG. 3  shows the position of the differential plunger  27 , in which it is displaced as far as possible to the right. 
         [0047]    In this position, there is a connection of an outlet  34 , to which the power stroke space is connected, through the power stroke valve  26  to an outlet  35 , via which air can escape via a baffle  36 . The pressure space  33  is connected via an inlet  37  to a power stroke line (not shown). The function of the power stroke valve will be explained in the following text with reference to  FIG. 4 . Here, the connection to a pressure intensifier is shown in a very diagrammatic manner, for example to a pressure intensifier according to  FIG. 2 . 
         [0048]    A changeover from fast stroke to power stroke takes place automatically when, during the fast stroke, the working plunger  4  encounters resistance at any desired point of the stroke and comes to a standstill. The side of the differential plunger  27  with the plunger  28  with a larger plunger face is connected via a pneumatic connection  39  at the connector  38  and a waste air throttle  40  to the return stroke space  25  of the pressure intensifier  1 . The side of the differential plunger with the plunger  30  with the smaller plunger face  31  is connected via the connector  37  to a fast stroke line  41  of the pressure intensifier  1 . 
         [0049]    In the basic position of the pressure intensifier, the working plunger  4  and the plunger  2  and the accumulator plunger  13  are situated in a return stroke position, in which a return stroke pressure prevails in the return stroke space  25  via a return stroke line  42 , which return stroke pressure loads the large plunger face  29  with pressure via the connection  39 , the waste air throttle  40 , the inlet  38  and the pressure space  32  and displaces the differential plunger  27  in the opposite direction to the pressure space  32 . 
         [0050]    In the case of a switchover into a fast stroke, the fast stroke pressure prevails at the small plunger face  31  of the plunger  30  via the fast stroke line  41 , the inlet  37  and the pressure space  33 . The working plunger then moves in the direction of the arrow  19  (see also  FIG. 4 ). 
         [0051]    The air which is enclosed in the return stroke space  25  cannot escape quickly enough via the return stroke line  42 , with the result that there is a correspondingly high pressure in the pressure space  32  via the pneumatic connection  39  and the inlet  38 , as a result of which the differential plunger  27  remains in the position which is shown in  FIG. 3  despite a pressure in the pressure space  33 , in which position the power stroke space  8   a  is still pressureless. If, however, the working plunger  4  encounters resistance and comes to a standstill, the pressure in the pressure space  32  drops via the waste air throttle  40 , with the result that the power stroke valve  26  switches, by the differential plunger  27  moving into the pressure space  32  to such an extent that a connection of the inlet  37  to the outlet  34  takes place, as a result of which the power stroke space  8   a  is loaded with the fast stroke pressure or working pressure. The power stroke begins at this moment. The switchover time can be regulated via the waste air throttle  40 , depending on how fast the enclosed air in the pressure space  32  can escape. If the pressure intensifier  1  is switched into the return stroke, the air escapes immediately from the fast stroke side of the power stroke valve  26  and the air which flows in onto the larger plunger face  29  brings about a switchover of the power stroke valve  26  substantially without delay back into the basic position. 
         [0052]    The waste air throttle can also be replaced by a pneumatic switching valve for any desired switching through of the power stroke. 
         [0053]      FIG. 1  shows a power stroke valve  43  according to the invention. Identical elements as in the power stroke valve  26  are provided with identical designations. 
         [0054]    The central element of the power stroke valve is the differential plunger  27 . The differential plunger  27  has a small plunger  30  with a small plunger face  31  and a large plunger  28  with a large plunger face  29 . The plunger is mounted displaceably, as a result of which the plunger  28  moves in a pressure space  32  and the plunger  30  moves in a pressure space  33 .  FIG. 1  shows the position of the differential plunger  27 , in which it is moved as far as possible to the left. In the connected state, the pressure space  32  is connected to the return stroke space  25  by the inlet  38 . 
         [0055]    Furthermore, as in the power stroke valve  26 , an outlet  35  to a baffle (not shown) and an outlet  34  to the power stroke space are provided. Moreover, an inlet  37  exists which is supplied with a working pressure which is then applied to the power stroke space  25  via the outlet  34 , in the case of a corresponding switching position of the power stroke valve  43 . To this extent, the power stroke valve  43  has the same functional components as the power stroke valve  26 . 
         [0056]    In contrast to the power stroke valve  26 , the plunger  30  with the small plunger face  31  is coupled to a further plunger  44  which preferably has the same plunger face as the plunger  30  and moves in a pressure space  45 .  FIG. 1  shows the position as far as possible to the left. 
         [0057]    The pressure space  45  can be loaded with control air via an inlet  46 . There is a connection  47  between the inlet  37  and the inlet  46 . 
         [0058]    For the case where the inlet  46  is closed by way of a closure plug and the connection  47  between the inlet  37  and the inlet  46  is opened, the power stroke valve  43  operates exactly in the same way as the power stroke valve  26 , the plunger  44  moving in parallel with the differential plunger  27  or the smaller plunger  30 . 
         [0059]    However, the additional plunger  44  results in an additional functionality. 
         [0060]    If the connection  47  between the inlet  46  and the inlet  37  is closed, for example by way of a screw element, there is the possibility to use the inlet  46  as a separate inlet for control. 
         [0061]    The additional inlet  46  can advantageously be used when, in the case of feeding to the inlet  37  for loading the power stroke space  25  with compressed air, a pressure regulator is used, in order for it therefore to be possible to set the power during the power stroke as desired. 
         [0062]    In this case, a supply pressure without pressure reduction is applied to the inlet  46  as control inlet, whereas a pressure-regulated supply takes place via a pressure regulator at the inlet  37 . The influence of a regulated pressure for the power stroke space  25  is therefore independent of the switching behavior of the power stroke valve  43 . This is because the switching behavior is determined by the control pressure at the inlet  46  which regularly lies above the regulated pressure at the inlet  37 . The pressure which is provided for the power stroke space  25  can therefore be selected as desired in principle, in particular can lie considerably below pressure values, for which the conventional power stroke valve would no longer function reliably. Moreover, a change in the power stroke space supply pressure has no effects with regard to setting of the waste area throttle  40 . The pressure regulator for supplying the power stroke space can therefore be positioned at any desired point, for example, in a remote switch cabinet or at another point which is favorable for the user. 
         [0063]    Setting of a pressure for the power stroke space can therefore be provided in a broad range elegantly without sacrificing conventional functionality, without a switching behavior of the switching point between fast stroke and power stroke being impaired. 
         [0064]    Furthermore, it is possible to connect a pneumatic continuous pressure supply to the connector  37  and to switch it via an externally connected valve at the connector  46  when the connecting line  47  is closed. 
       LIST OF DESIGNATIONS 
       [0000]    
       
           1  Hydropneumatic pressure intensifier 
           2  Intensifier plunger (plunger) 
           2   a  Plunger rod 
           3  Plunger section 
           4  Working plunger 
           4   a  Plunger section 
           4   b  Plunger section 
           4   c  Plunger section 
           5  Housing section 
           6   a  Opening 
           7  High pressure hydraulic space 
           7   a  Connecting line 
           7   b  Hydraulic space section 
           8  Housing section 
           8   a  Pneumatic space (power stroke space) 
           8   b  Edge wall 
           9  Wall 
           12  Pneumatic space 
           13  Accumulator plunger 
           18  Low pressure hydraulic space 
           19  Arrow 
           20  Hydraulic space 
           21  First region 
           22  Second region 
           25  Pneumatic space (return stroke space) 
           26  Power stroke valve 
           27  Differential plunger 
           28  Plunger 
           29  Plunger face 
           30  Plunger 
           31  Plunger face 
           32  Pressure space 
           33  Pressure space 
           34  Outlet 
           35  Outlet 
           36  Baffle 
           37  Inlet 
           38  Inlet 
           39  Pneumatic connection 
           40  Waste air throttle 
           41  Fast stroke line 
           42  Return stroke line 
           43  Power stroke valve 
           44  Plunger 
           45  Pressure space 
           46  Inlet 
           47  Connection