Abstract:
An expulsion device expels objects or liquid materials from a reservoir using a drive piston which is subjected to the action of a pressure medium. The expulsion device includes a pressure medium container that is exchangeable and connected to a device body. An actuation device enables the pressure medium to act on the drive piston which is thus displaced in a forward and a backward direction.

Description:
FIELD OF INVENTION 
   The present invention relates to an expulsion device actuated by a pressure medium for expelling objects or liquid materials from a reservoir by means of a drive piston, subjected to the action of a pressure medium, comprising a pressure medium container, which is exchangeable and connected to a device body enabling the pressure medium to act on the drive piston. 
   BACKGROUND OF THE INVENTION 
   A device of the type set out above embodied as an driving device for driving in mechanical fastening means, such as, for example, staples, is known from EP 0 191 186 A2. In the known device a device body is fitted with a pressure medium container, which, when actuated by means of a valve system, serves to exert pressure on a piston, which is connected to an impact ram. In the known expulsion device the pressure medium container is in the form of a CO 2  cartridge, the filling pressure of which acts on the piston connected to the impact ram when an actuating device is operated, thereby bringing about a forward movement of the impact ram. In order to implement a return movement of the piston, so as to move the impact ram back into its initial position for repeating the expulsion procedure, the piston is returned to its initial position by means of a mechanical carrier device. 
   As a result of the mechanically brought about return of the piston into the initial position, only relatively low expulsion frequencies are possible with the known expulsion device. Furthermore, returning the piston into the initial position assumes the application of a corresponding manual force. Overall in this way only a relative low stapling output is possible. 
   The aim of the present invention is therefore to permit an increase in the expulsion frequency with an expulsion device which is fitted with an exchangeable pressure medium container and can therefore be operated independently of the mains. 
   SUMMARY OF THE INVENTION 
   In the expulsion device according to the invention the action of the pressure medium serves both to implement a forward movement and to implement a backward movement of the drive piston, so that in contrast to manually actuated return, a much faster backward movement is achieved. This results in considerably shortened cycle times for the return of the piston, so that overall a clear increase in the expulsion frequency is made possible. 
   A further increase in the efficiency of the expulsion device can be achieved if the device body of the expulsion device has pressure chamber, separated from the pressure medium container by means of a pressure-reducing device, for subjecting the drive piston to the action of a pressure medium with an operating pressure that is lower than the filling pressure of the pressure medium container. Through the intermediate arrangement of the pressure-reducing device the filling pressure in the pressure medium container can be increased to many times the operating pressure so that a considerably increase in the operating time of the expulsion device is achieved before it becomes necessary to exchange the pressure medium container. 
   If, in order to initiate the action of the pressure medium on the drive piston an actuating device is provided, which at the same time serves to operate a ventilation valve arrangement for ventilating a drive cylinder accommodating the drive piston, a synchronization between the pressure medium action and control of the ventilation valve arrangement is achieved in a simple manner. A particularly direct form of mechanical implementation of this synchronisation, and thereby also particularly short operating cycles of the expulsion device, become possible if the ventilation valve is connected to the actuating device by means of a ram device. 
   In a particularly preferred form of embodiment of the expulsion device the ventilation valve arrangement is designed as a piston valve with a valve axis intersecting the piston cylinder axis. On the one hand, by embodying the valve arrangement as a piston valve very high hysteresis figures can be achieved for the valve arrangement. On the other hand with the valve arrangement intersecting the drive cylinder axis particularly effective and thus rapid ventilation of the drive cylinder over the cylinder base is permitted. 
   If the drive piston simultaneously serves as a control piston for carrying out the pressure-actuated backward movement of the drive piston in the piston cylinder, the structural implementation of pressure medium-actuated drive piston return is made possible with particularly few mechanical components because of the functionally integrated effect of the drive piston. In terms of further simplified structural assembly, it also proved to be advantageous if the expulsion end of the drive cylinder is surrounded by a ring chamber with an inflow system, arranged at a distance from the end cross-section of the piston displacement of the drive cylinder, and an outflow system arranged in the area of the end-cross-section and merging into the piston displacement area, whereby the distance between the inflow system and the outflow system corresponds at least to the axial extent of the drive piston. 
   A further increase in the efficiency of use of the pressure potential provided by the pressure medium container is possible if the drive cylinder has, at its expulsion end, a cylinder base with a ram opening for a drive ram connected to the drive piston, with a radial sealing device arranged in the ram opening. This allows largely pressure medium-tight sealing of the annular gap between the drive ram and the drive opening necessary for the relative movement of the drive ram, so that leakage through the annular gap can be largely prevented. If, in addition, the sealing device is arranged in the cylinder base, any embodiment of the sealing seat is possible, irrespective of an influence of the drive ram cross-section. 
   Depending on the type and design of the container provided for combination with the expulsion device, it is possible to use the expulsion device according to the invention for expelling objects, i.e. solid bodies, or also fluid materials. 
   If, in accordance with a particularly advantageous form of embodiment of the expulsion device the container is designed as a magazine device for holding mechanical fastening means, and the drive ram serves to strike an individual fastening means arranged in a feeder channel arranged on the magazine device, the expulsion device can particularly advantageously be used as a nailing device. 
   In a further advantageous form of embodiment of the expulsion device the container is designed as a liquid reservoir, and the drive ram exerts a pressure on quantity of liquid in a dispensing system arranged on the liquid reservoir. This quantity of liquid can, for example, be a liquid paint, which is expelled in dosed quantities to produce coloured dots for instance. It is also possible to dispense quantities of adhesive, for producing adhesive dots for example. 
   An advantageous from of embodiment of the expulsion device will be described below with the aid of the drawings, in which: 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a lateral view of the expulsion device with a drive piston/cylinder unit in partial cross-section. 
       FIG. 2  shows an enlargement of the control valve arrangement which interacts with the drive piston/cylinder unit 
       FIG. 3  shows the drive piston/cylinder unit with the drive piston at a relative distance to the expulsion side piston base. 
       FIG. 4  shows the drive piston/cylinder unit shown in  FIG. 3  with the drive piston at a distance relative to the expulsion-side piston base. 
   

   DETAILED DESCRIPTION 
     FIG. 1  shows a lateral view of an overall drawing of an expulsion device  10 . The expulsion device  10  comprises a device body  13 , with a grip section  12  and a drive piston/cylinder unit  13 , whereby a pressure medium container  14  for storing compressed gas is connected to the grip section  12  and a container designed here as a magazine device  15  is connected to the drive piston/cylinder unit  13 . 
   At its end turned away from the drive piston/cylinder unit  13 , the grip section  12  is connected in a detachable manner to the pressure medium container  14  via a coupling device  16 , which can, for example, be in the form of a screw-in thread. To set an operating pressure for the drive piston/cylinder unit  13 , which is independent of a filling pressure in the pressure medium container  14 , a separate pressure chamber  18  is provided in the grip section  12  separated from the pressure medium container  14  by means of a pressure reducing device  17 . 
   Between the pressure chamber  18  and the drive piston/cylinder unit  13  there is arranged a tilling valve device  19  for subjecting a drive piston  20  of the drive piston/cylinder unit  13  to the operating pressure by way of operating the filling valve device  19  with an actuating device  21 . The filling valve device  19  has a sealing element  67 , pretensioned by a valve spring  66  in the direction of the valve opening, which is pressed against a valve opening  54  for the purpose of sealing by a valve ram  24  subject to the action of a closing spring  71 . As can be seen in  FIG. 1  a starting lever  22  of the actuating device  21  is mechanically connected via a ram rod  25  running perpendicularly to a valve axis  23  of the filling valve device  19  and a pivoting lever  26  in the grip section  12  to valve piston  27  of a ventilating valve arrangement  28 . 
   As can be seen particularly from the enlargement in accordance with  FIG. 2 , there is a ventilation valve arrangement  28  for the release and/or closing of a ventilation opening.  29  in a first cylinder base  30  of a drive cylinder  31  of the drive piston/cylinder unit  13  arranged adjacent to the ventilation valve arrangement  28 . The ventilation valve arrangement  28  comprises a valve body  32 , which is arranged between the ventilation opening  29  in the cylinder base  30  and a casing ventilation opening  33  in such a way that a valve axis  64  of the ventilation valve arrangement  28  intersects a drive cylinder axis  65  of the drive cylinder  31 . Ventilation takes place via valve opening  34  ( FIG. 2 ) of the ventilation valve arrangement  28  provided in the ventilation path, whereby the valve opening  34  simultaneously services to accommodate the valve piston  27 . Through-flow of the outgoing air from the drive cylinder  31  through the valve opening  34  is permitted or blocked via a sealing device  35  arranged in a radial manner, in this case in the form of an O-ring, on the valve piston  27 , in that the sealing device  35  is moved into and out of a valve opening  62  of the ventilation valve device  28  coaxial to the valve piston  27  by way of an appropriate axial movement. In this case, on the valve spigot  36  of the valve piston  27  there is a radial sealing device  37 , also in the form of an O-ring, which in interaction with the first sealing device  35  forms a sealing space  38  in the form of an annular gap, which is fluid-technically connected via radial ring channel device  39  to the ventilation opening  29  of the drive cylinder  31 . 
   As can be seen in  FIGS. 3 and 4 , in which the drive piston/cylinder unit  13  is shown with two different axial positions of the drive piston  20 , the drive piston/cylinder unit  13  has the drive cylinder  31  set into a casing  40 , as well as the drive piston  20  which is axially moveable within the drive cylinder  31 . As a result of the coaxial arrangement of the drive cylinder  31  in the casing  40 , a ring chamber  42  is formed in the area of an expulsion end  41  of the drive piston/cylinder unit  13 , which is connected via a first ring channel device  43  provided as an inflow device and a second ring channel device  44  designed as an outflow device to a displacement or lumen  45  of the drive cylinder  31 . To bring about a ring channel sealing  68  which is dependent on the pressure direction, the ring channel device  43  on the outer wall of the drive cylinder  31  is provided with an annular groove  69 , in which an O-ring seal  70  is arranged in an elastically pre-tensioned manner. The axial distance between the ring channel devices  43  and  44  is selected so that it is at least slightly greater than the axial dimension of the drive piston  20 . 
   In this case the drive piston  20  is designed as a sleeve into which a drive ram  46  is screwed in with a screw-in end  47 . 
   A securing pin  48  serves to prevent twisting between the screw-in end  47  of the drive ram  46  and the drive piston  20 . 
   At the expulsion end of the drive cylinder  31  a second cylinder base  49  is arranged which is provided with a ram opening  50 , into which the drive ram  46  engages with a sealing collar  51  when the drive piston  20  is positioned in the area of the expulsion end  41 . To seal the ram opening  50  a radial sealing device  63 , in this case in the form of an O-ring, is provided in the ram opening  50  and is in contacts with the drive ram  46  forming a seal in the axial positions of the drive piston shown in  FIGS. 3 and 4 . To dampen an impact of the drive piston  20  on the cylinder bases  30  ( FIGS. 1 and 2 ) and  49  during the operation of the expulsion device  10 , the cylinder bases  30  and  49  are made of an elastomer material in the present case. 
   Described below is an operating cycle of the expulsion device  10 , covering an axial forward movement of the drive piston  20  up to contact with the cylinder base  49  arranged at the expulsion end  41  and a backward movement of the drive piston  20  up to contact with the cylinder base  30  ( FIG. 1 ) arranged on the outgoing air side adjacent to the ventilation opening  29  of the drive cylinder  31 . 
   To operate the expulsion device  10  with an axial forward movement of the drive piston  20 , the starting lever  22  is moved so that the ram rod  25  is moved against the pivoting lever  26 . The lever  26  then acts on a ram end  55  of the valve piston  27  of the ventilation valve arrangement  28  and, counteracting the effect of a readjusting spring  56  (FIG.  2 ), axially moves the valve piston  27  forward to seal the ventilation opening  29 . With increasing deflection of the starting lever  22 , a carrier catch  52  arranged in an articulated manner on the starting lever  22  contacts an annular beading  53  of the valve ram  24  and the valve opening  54  ( FIG. 1 ) at the lower end of the pressure chamber  18  is released, so that with a sealed ventilation opening  29  of the drive cylinder is filled with the gas at operating pressure via a pressure pipeline  58 , extending from the valve opening  54  of the pressure chamber  18  to the ventilation end  57  of the drive cylinder  31 , which merges in a radial manner into the displacement  45  of the drive cylinder  31 . 
   As a result of the pressure filling of the drive cylinder  31 , the drive piston along with the drive ram  46  arranged on it is axially accelerated until it comes into contact against the cylinder base  49  arranged at the expulsion end  41  (FIGS.  4  and  5 ). As the carrier contact between the carrier catch  52  and the annular beading  53  on the valve ram  24  of the filling valve arrangement  19  is designed in such a way that there is a roll-off contact between the carrier catch  52  and the annular beading  53  when the starting lever  22  is operated, after a predetermined movement path of the starting lever  22  the annular beading engaged by the carrier catch  52  is released again and the valve opening  54  of the pressure chamber  18  is closed again by the closing spring-actuated valve ram  24 . 
   The drive ram  46  exerts an impact on a steel pin  58  arranged in a feeder channel  59  at the lower end of the magazine device  15  which pushes the individual steel pin  58  in the feeder channel  59  out of the feeder channel  59  and into a material arranged in front of the feeder channel. 
   When the drive piston  20  is in its impact position on the expulsion side, as shown in  FIG. 3 , the ring channel device  43  acting as the inflow device is released so that the gas can, with the ring channel seal  68  open, flow under pressure out of the displacement  45  of the drive cylinder  31  into the ring chamber  42 , and from here through the ring channel device  44  designed as an outflow device into an annular gap  60  in the drive cylinder between the drive piston  20  and the cylinder base  49  on resetting the starting lever  22  though the action of the readjustment spring  34 , the ventilation opening  29  is released again so that the pressure acting in the annular gap  60  can bring about the backward movement of the drive piston  20  in the direction of the cylinder base  30  at the ventilation end  57  ( FIGS. 1 and 2 ) of the drive cylinder  31 . When the starting lever  22  is returned to its initial position the articulated carrier catch  52  is pivoted away from contact with the annular beading  53 . 
   As can be seen from  FIGS. 3 and 4 , the sealing device  63  in the ram opening  50  largely prevents leakage from the annular gap  60  when pressure is exerted on the drive piston  20  in order to bring about a backward movement. In order, as shown in  FIG. 4 , to ensure that the drive piston  20  is returned even in the event of the drive piston  20  not coming into contact with the cylinder base  49 , the distance between the ring channel device  43  acting as an inflow device and the cylinder base  49  is greater than the axial dimension of the drive piston  20 . The drive piston  20  may not strike the cylinder base  49  as a result of too great a material resistance when driving a steel pin  58  arranged in the feeder channel  59  into a material, for example a knot area in a board being nailed. 
   
     
       
             
           
             
             
           
         
             
                 
             
             
               REFERENCE LIST 
             
             
                 
             
           
           
             
                 
             
           
        
         
             
                 
               10. Expulsion device 
             
             
                 
               11. Device body 
             
             
                 
               12. Grip section 
             
             
                 
               13. Drive piston/cylinder unit 
             
             
                 
               14. Pressure medium container 
             
             
                 
               15. Magazine device 
             
             
                 
               16. Coupling device 
             
             
                 
               17. Pressure reducing device 
             
             
                 
               18. Pressure chamber 
             
             
                 
               19. Filling valve device 
             
             
                 
               20. Drive piston 
             
             
                 
               21. Actuating device 
             
             
                 
               22. Starting lever 
             
             
                 
               23. Valve axis 
             
             
                 
               24. Valve ram 
             
             
                 
               25. Ram rod 
             
             
                 
               26. Pivoting lever 
             
             
                 
               27. Valve piston 
             
             
                 
               28. Ventilation valve arrangement 
             
             
                 
               29. Ventilation opening 
             
             
                 
               30. Cylinder base 
             
             
                 
               31. Drive cylinder 
             
             
                 
               32. Valve body 
             
             
                 
               33. Casing ventilation opening 
             
             
                 
               34. Valve opening 
             
             
                 
               35. Sealing device 
             
             
                 
               36. Sealing spigot 
             
             
                 
               37. Sealing device 
             
             
                 
               38. Sealing space 
             
             
                 
               39. Ring channel device 
             
             
                 
               40. Casing 
             
             
                 
               41. Expulsion end 
             
             
                 
               42. Ring chamber 
             
             
                 
               43. Ring channel device 
             
             
                 
               44. Ring channel device 
             
             
                 
               45. Displacement 
             
             
                 
               46. Drive ram 
             
             
                 
               47. Screw-in end 
             
             
                 
               48. Securing pin 
             
             
                 
               49. Cylinder base 
             
             
                 
               50. Ram opening 
             
             
                 
               51. Seal collar 
             
             
                 
               52. Carrier catch 
             
             
                 
               53. Annular beading 
             
             
                 
               54. Valve opening 
             
             
                 
               55. Ram end 
             
             
                 
               56. Readjustment spring 
             
             
                 
               57. Ventilation end 
             
             
                 
               58. Steel pin 
             
             
                 
               59. Feeder channel 
             
             
                 
               60. Annular gap 
             
             
                 
               61. Readjustment spring 
             
             
                 
               62. Valve opening 
             
             
                 
               63. Sealing device 
             
             
                 
               64. Valve axis 
             
             
                 
               65. Drive cylinder axis 
             
             
                 
               66. Valve spring 
             
             
                 
               67. Sealing element 
             
             
                 
               68. Ring channel seal 
             
             
                 
               69. Radial groove 
             
             
                 
               70. O-ring seal 
             
             
                 
               71. Closing spring