Abstract:
A portable, combustion-engined tool including a collapsible combustion chamber ( 1 ) having a movable separation plate ( 18 ) for dividing the combustion chamber ( 1 ), in an expanded position of the combustion chamber, in a forechamber section ( 21 ) and at least one further chamber section ( 22 ), a movable combustion chamber wall ( 14 ) arranged parallel to the separation plate ( 18 ) for limiting, together with the separation plate ( 18 ), the forechamber section, an ignition device ( 52 ) located in the forechamber section ( 21 ), and a collapse control device ( 19, 20, 33 ) for controlling movement of the separation plate ( 18 ) and the movable wall ( 14 ) after the combustion of the gas mixture in the combustion chamber.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a portable, combustion-engined tool, in particular, a setting tool including a collapsible combustion chamber divided by a separation plate in a forechamber section having an ignition device and at least one further chamber section, with the forechamber section being limited by a movable combustion chamber wall arranged parallel to the separation plate, and with the separation plate having a plurality of openings which communicates the forechamber section with the at least one further chamber section.  
           [0003]    2. Description of the Prior Art  
           [0004]    A portable, combustion-engined tool described above is disclosed in the German Publication No. 199 50 352.  
           [0005]    After the ignition process has been initiated in order to combust a fuel gas mixture, which fills the combustion chamber, the locking of the movable combustion chamber wall is lifted, a spring force provides for movement of the movable wall in a direction toward the piston, which adjoins the combustion chamber, whereby the combustion chamber is freed from waste gases. With this, the separation plate also moves in the direction toward the piston and, after a while, the movable wall lies on the separation plate, with the separation plate lying practically on the piston. As a result, the volume of the combustion chamber becomes practically reduced to zero. During the movement of the movable wall and the separation plate toward the piston, the forechamber section is deaerated only through the openings in the separation plate. To this end, at least one of the through-openings of the separation plate should be aligned with an exhaust valve located opposite the separation plate. If this is not the case, and the movable wall and the separation plate start to move toward each other only after the volume of the main or further chamber section has been reduced to zero, deaeration or the reduction of volume of the forechamber section takes place very slowly. This requires that at least one of the throughopenings of the separation is exactly aligned with the opposite exhaust valve in order to insure a more rapid deaeration of the forechamber section. Insuring such an alignment is a very tedious job.  
           [0006]    Accordingly, an object of the present invention is to provide means which would insure a rapid deaeration of the forechamber section in a tool of the above-described type under any circumstances.  
         SUMMARY OF THE INVENTION  
         [0007]    This and other objects of the present invention, which will become apparent hereinafter, are achieved by providing, in the combustion chamber, collapse control means for controlling the movement of the movable wall and the separation plate, after the combustion of the gas mixture in the combustion chamber, so that the forechamber section collapses first and only then, the further chamber section collapses. When the combustion chamber has only two chamber sections, the further chamber section is called a main chamber section.  
           [0008]    With the collapse control means according to the present invention, even if for some reasons, the exhaust valve is not aligned with the associated opening, a complete collapse of the combustion chamber can still be effected as, initially, only the movable wall is displaced toward the separation plate to reduce the volume of the forechamber section With the displacement of the movable wall, the waste gas filling the forechamber section is expelled from the forechamber section through the openings in the separation plate into the further or main chamber section. Only after the volume of the forechamber section has been reduced to zero, the movable wall and the separation plate are displaced together in the direction toward the piston in order to reduce the volume of the main chamber section also to zero. With such controlled displacement, a complete deaeration and/or reduction of the volume of the entire combustion chamber is insured under all circumstances.  
           [0009]    The collapse control means can be formed in different ways. Thus, the collapse control means can so preload the movable wall and the separation plate relative to each other that they first would be displaced toward each other and only then would be displaced together in a direction toward the piston. To this end, e.g., the central projection or lug of the separation plate can project through the movable wall, with a compression spring being arranged between the free end of the lug and the movable wall. The spring retains the separation plate in its position at the beginning of movement of the movable wall in a direction toward the piston. As a result, first, the volume of the forechamber section is reduced to zero and it is deaerated before the reduction of volume of the main chamber section begins.  
           [0010]    The collapse control means for controlling the movement of the movable wall and the separation plate can also determine the friction between the movable wall and the combustion chamber, on one hand, and between the separation plate and the combustion chamber on the other hand. When, e.g., the movable wall, for reducing the volume of the forechamber section, is driven by outer adjusting means, high friction between the separation plate and the combustion chamber, e.g., can insure that the separation plate remains stationary until the movable wall abuts it. In this way likewise, first, the forechamber section collapses, and the collapse of the main chamber section follows the collapse of the forechamber section.  
           [0011]    Further, the collapse control means can be formed as means for a pneumatic control of the movement of the movable wall and the separation plate. In this case, the movement control of the displacement of the movable wall and the separation plate can be programmed.  
           [0012]    According to further advantageous embodiment of the present invention, the through-openings of the separation plate can be formed as check valves which provide for gas flow only from the forechamber section into the further or main chamber section.  
           [0013]    For obtaining a high piston energy, the combustion, e.g., in the main chamber section, should take place as rapidly as possible. A return flow from the main chamber section into the forechamber section results in an early expansion which, in turn, leads to the cooling down of the flame formed in the main chamber section. The pressure in the main chamber, dependent on the size of the forechamber section, becomes reduced or increases very slowly. In addition, a portion of the fuel gas mixture is forced back into the forechamber section and burns there. This portion of the combustion takes place in a time-delayed manner and contributes little to the piston energy. Providing check valves in the separation plate in collapsible systems permits to increase the energy yield.  
           [0014]    Providing check valves in the separation plate insures flow only in one direction, namely, from the forechamber section into the main chamber section. This means narrowing in the flow direction and feeding of the fresh air into the forechamber section. In this case also, the collapse of the chamber sections should be so controlled that the forechamber section collapses first. If this is not the case, and the main chamber section collapses first, the check valves would not be open any more after the collapse, and the deaeration of the forechamber would practically stop.  
           [0015]    Further, the movable wall can also be provided with at least one check valve which enables flow only into the forechamber section. Through this check valve, the forechamber section can be filled with fresh air when the movable wall moves away from the separation wall and the chamber sections expand. Upon expansion of the main chamber section, the fresh air enters it through the check valves in the separation plate, with the fresh air thus filling the entire combustion chamber.  
           [0016]    The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiments, when read with reference to the accompanying drawings.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    [0017]FIG. 1 shows an axial cross-sectional view of a combustion-engined tool according to the present invention with a completely collapsed combustion chamber;  
         [0018]    [0018]FIG. 2 shows a cross-sectional view of the tool shown in FIG. 1 with expander forechamber and main chamber sections; and  
         [0019]    [0019]FIG. 3 shows a cross-sectional view of the tool shown in FIG. 2 after completion of the ignition process and a complete collapse of the forechamber section.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0020]    [0020]FIG. 1 shows a cross-sectional view of the combustion-engined tool according to the present invention in the region of its combustion chamber. As shown in FIG. 1, a combustion chamber  1  of an inventive combustion-engined tool, in particular, of a setting tool, which is shown in FIG. 1, has a cylindrical shape and includes a cylindrical wall  2  and a ring-shaped bottom  3  adjoining the cylindrical wall  2 . In the center of the bottom  3 , there is provided an opening  4 . A guide cylinder  5 , which has a cylindrical wall  6  and a bottom  7 , adjoins the opening  4  in the bottom  3  of the combustion chamber  1 . A piston  8  is slidably displaceably arranged in the guide cylinder  5  for displacement in the longitudinal direction of the guide cylinder  5 . The piston  8  consists of a piston plate  9  facing the combustion chamber  1  and a piston rod  10  extending from the center of the piston plate  9 . The piston rod  10  projects through an opening  11  formed in the bottom  7  of the guide cylinder  5 .  
         [0021]    [0021]FIG. 1 shows a non-operational position of the setting tool in which the piston  8  is in its rearward off-position. The side of the piston plate  9  adjacent to the bottom  3  of the combustion chamber  1  is located closely adjacent to the bottom  3 , with the piston rod  10  projecting only slightly beyond the bottom  7  of the guide cylinder  5 . Sealing rings  12 ,  13 , which can be provided on opposite sides of the piston plate  9  to seal the chambers on the opposite sides of the piston plate  9  from each other.  
         [0022]    Inside of the combustion chamber  1 , there is provided a cylindrical plate  14  further to be called a movable combustion chamber wall or movable wall. The plane of the plate  14  extends transverse to the longitudinal direction of the tool. The movable wall  14  is displaceable in the longitudinal direction of the combustion chamber  1 . For separating the chambers on opposite sides of the movable wall  14 , an annular sealing is provided on the circumference of the movable wall. The movable wall  14  has a central opening  16 , with an annular seal provided in the wall forming the opening  16 .  
         [0023]    Between the movable wall  14  and the annular bottom  3  of the combustion chamber  1 , there is provided a separation plate  18 . The separation plate  18  likewise has a circular shape and an outer diameter corresponding to the inner diameter of the combustion chamber  1 . The side of the separation plate  18  adjacent to the movable wall  14  is provided with a cylindrical lug  19  that projects through the central opening  16  in the movable wall  14  and the length of which exceeds the thickness of the movable wall  14  in several times. The seal provided in the opening  16  engages the outer circumference of the cylindrical lug  19 . At its free end, the cylindrical lug  19  is provided with a shoulder  20  the outer diameter of which exceeds the inner diameter of the opening  16  in the movable wall  14 .  
         [0024]    Between the movable wall  14  and the annular shoulder  20 , there is further provided a compression spring  33  which is supported, at its opposite ends, against the movable wall  14  and the shoulder  20  and which biases the separation plate  18  and the movable wall  14  toward each other. The compression spring  33  preloads the separation plate  18  and the movable wall  14  with respect to each other. The cylindrical lug  19  or, actually, the annular shoulder  20 , in an end position in which the cylindrical lug  19  is spaced from the bottom  3  by a largest distance, abuts the end wall  34  of the housing of the combustion chamber  1 .  
         [0025]    When the movable wall  14  moves away from the bottom  3 , it entrails, via the compression spring  33  and the shoulder  20 , the separation plate  18 . The movement of the separation plate  18  stops when the shoulder  20  abuts the wall  34 . With the movable wall  14  moving further, the spring  33  is compressed. At the end of movement of both the movable wall  14  and the separation plate  18 , a forechamber section  21  and a main chamber section  22  are formed between the separation plate  18  and the bottom  3 .  
         [0026]    For displacing the movable wall  14 , there are provided several, e.g., three drive rods  23  uniformly distributed along the circumference of the movable wall  14  and fixedly connected therewith. Only one of the drive rods  23  is shown in FIG. 1. The drive rods  23  extend parallel to the axis of the combustion chamber  1  and outside of the cylindrical wall  6  of the guide cylinder  5 . The drive rods  23  extend through openings  24 , respectively, formed in the separation plate  18  and through corresponding openings  25  formed in the bottom  3  of the combustion chamber  1 . Each of the openings  25  is provided win a circumferential seal located in the surface defining the opening  25  for sealing the combustion chamber  1  from outside. The movable wall  14  is connected with drive rods  23  by, e.g., screws  27  which extend through the movable wall  14  and are screwed into the drive rods  23 . The free ends of the drive rods  23  are connected with each other by a drive ring  28  which is arranged concentrically with the combustion chamber axis and which circumscribes the guide cylinder  5 . The drive ring  28  is connected with the drive rods  23  by screws which extend through the drive ring  28  and are screwed into the drive rods  23  through end surfaces of the free ends of respective drive rods  23 . Each of the drive rods  23  supports a compression spring  30  extending between the bottom  3  of the combustion chamber  1  and the drive ring  28 . The compression springs  30  are designed to always bias the movable wall  14  toward the bottom  3 .  
         [0027]    In the region of the bottom  3 , there is provided a check valve  31  which provides for flow only out from the combustion chamber  1 . In order to close the check valve  31 , i.e., to prevent gas flow from the combustion chamber  1  out, an actuation member  32  is provided on the drive ring  28 . The actuation member  32  is arranged opposite the check valve  31 . Upon displacement of the drive rods  23  in a direction in which the distance between the movable wall  14  and the bottom  3  increases, the actuation member  23  moves toward the check valve  31  and, in the position of the movable wall  14  in which the movable wall  14  is spaced from the bottom  3  by a largest possible distance, the actuation member  32  engages the check valve  31 , preventing its opening.  
         [0028]    The separation plate  18  has, along a concentric circle, a plurality of openings provided with check valves  38  arranged angularly equidistantly relative to each other. Because the check valves  38  are arranged along a concentric circle, they are also equidistantly spaced from the cylindrical axis of the combustion chamber  1 . As it has already been discussed, the medium can flow through the check valves  31  only from the forechamber section  21  into the main chamber section  22 . A flow in opposite direction is not possible.  
         [0029]    At least one check valve  36  is provided in the movable wall  3 . The check valve  36  provides for flow of air from outside into the forechamber section  21  but prevents flow in opposite direction.  
         [0030]    Also, at the lower end of the guide cylinder  5 , there is provided a plurality of outlet openings  39  for flow of air or waste gases out of the guide cylinder  5  when the piston  8  moves in a direction toward the bottom  7 . At the lower end of the guide cylinder  5 , there is provided damping means  40  for damping the movement of the piston  8 . As soon as the piston  8  passes the openings  39 , the waste gas can flow out through the openings  39 .  
         [0031]    The cylindrical wall  2  of the combustion chamber  1  has axially spaced from each other, radial openings,  41 ,  42 . The openings  41 ,  42  communicates via feed channels  43 ,  44  with a metering head  45  provided with metering valves, not shown. A liquefied gas is delivered to the metering head  45  from a flask  46 . The liquefied gas flows from the metering head  45  through the feed channels  43 ,  44  into the openings  41 ,  42  when the metering head  45  is pressed toward the cylindrical wall  2  of the combustion chamber  1 , with the channels  43 ,  44  moving inward, opening respective valves. The cross-section of the radial openings  41 ,  42  is reduced in a direction toward the combustion chamber  1 , with the respective transitional surfaces serving as stops for the feed channels  43 ,  44 . The pressing of the metering head  45  toward the cylindrical wall  2  is effected with a stirrup  47  which is pivotally supported on the cylindrical wall  2  at a pivot point  48 . The end  49  of the stirrup  47  is engaged by the movable wall  14  which lifts the end  49 , pivoting the stirrup  47  in the counterclockwise direction about the pivot point  48 . Upon pivotal movement of the stirrup  47 , the other end  50  thereof presses the metering head  45  toward the cylindrical wall  2 . This process starts shortly before the movable wall  14  reaches its end position when the forechamber  21  is completely expanded. The metering head  45  and the flask  46  form a unitary assembly and are permanently connected with each other. The system metering head  45 -flask  46  can, e.g., be titled about an axle provided in the bottom region of the flask  46 .  
         [0032]    [0032]FIG. 2 shows the tool in a position in which the forechamber section  21  and the main chamber section  22  are completely expanded. The respective end positions of the movable wall  14  and the separation plate  18 , which correspond to a completely expanded condition of the forechamber section  21  and the main chamber section  22 , are determined by respective stops. Thus, the check valve  31  can serve as a stop for the drive ring  28  the position of which determines the position of the movable wall  14 . The check valve  31 , as discussed above, is closed by the actuation member  32  mounted on the drive ring  28  and, when closed, the check valve  31  blocks further movement of the drive ring  28 . The position of the separation plate  18 , i.e., its distance from the movable wall  14  is determined, on one hand, by degree of compression of the spring  33 , which pulls the separation wall  18  toward the movable wall  14  and, on the other hand, by engagement of the shoulder  20  of the lug  19  with the end wall  34 . As shown in FIG. 2, the distance between the movable wall  14  and the separation plate  18 , in the completely expanded condition of the forechamber section  21  and the main chamber section  22 , is somewhat smaller than the length of the cylindrical lug  19 .  
         [0033]    In this position of the movable wall  14  and the separation plate  18 , the radial openings  41 ,  42  open into the forechamber section  21  and the main chamber section  22 , respectively.  
         [0034]    At the end of the cylindrical lug  19  adjacent to the separation plate  18 , there is provided a cage  51  in which an ignition device  52  is received. The ignition device  52  generates an electrical spark for igniting the fuel gas mixture in the forechamber section  21 . The ignition device  52  is located in the central region of the cage  51  the circumference of which is provided with a plurality of openings  53  through which a laminar flame front exit from the cage  51  into the forechamber section  21 .  
         [0035]    The operation of the setting tool will now be described in detail with reference to FIGS. 1, 2 and  3 .  
         [0036]    [0036]FIG. 1 shows the condition of the combustion chamber  1  in the off position of the setting tool. The combustion chamber  1  is completely collapsed, with the separation plate  18  lying on the bottom  3  of the combustion chamber  1  and the movable wall  14  lying on the separation plate  18 . In order to distinguish the movable wall  14  from the separation plate  18 , for the clarity sake, they are shown slightly separated. The piston  8  is in its rearward off-position, so that practically no space remains between the piston  8  and the separation plate  18  if one would disregard a small clearance therebetween. The position, in which the movable wall  14  lies on the separation plate  18 , results from the compressing spring  30  biasing the drive ring  28  away from the bottom  3 , with the ring  28  pulling the movable wall  14  via the drive rods  23 , toward the separation plate  18 . The movable wall  14  pushes the separation plate  18  toward the bottom  3  so that all of the movable wall  14 , the separation plate  18 , and the bottom  3  lie on each other. In this position, the actuation member  32  is spaced from the check valve  31  which, however, remains closed.  
         [0037]    The check valve  31  can actually remain open in the operating (setting) direction of the tool, however, no overpressure is generated in the combustion chamber  1 . The check valves  36 ,  38  also remain closed. The system metering head  45 -flasc  46  is spaced from the combustion chamber  1 , with the channels  43 ,  44  occupying their rearward position so that respective metering valves remain closed also.  
         [0038]    When in this condition, the setting tool is pressed with its front point against an object, the fastening element should be driven in, a mechanism, not shown, applies pressure to the drive ring  28  displacing it in the direction of the bottom  3  of the combustion chamber  1 . This takes place simultaneously with the setting tool being pressed against the object. Upon displacement of the drive ring  28  toward the bottom  3 , the movable wall  14  is lifted of the separation plate  18 , in effect, dependent on the strength of the compression spring  33 . After a while, the movable wall  14  entrains, via the spring  33 , the separation plate  18 . Finally, the cylindrical lug  19  abuts the end wall  34 , and the separation plate  18  occupies its end position. The main chamber section  22  becomes completely expanded. The movable wall  14  continues to move further, compressing the spring  33 , with the forechamber  21  being completely expanded when the spring  33  becomes completely compressed.  
         [0039]    During the expansion of the forechamber section  21  and the main chamber section  22 , the air penetrates into the chamber sections  21 ,  22  through check valves  36 ,  38 , respectively, which open upon the movable wall  14  and the separation plate  18  moving in the direction toward the end wall  34 .  
         [0040]    With the tool being further pressed against the object, the drive ring  28  moves further in a direction toward the bottom  3 . In a short while, the upper surface of the movable plate  14  engages the end  49  of the stirrup  47 , pivoting the stirrup  47  counterclockwise about the pivot point  48 . The other end  50  of the stirrup  47  pushes the metering head  45  in the direction toward the cylindrical wall  2 , with the feed channels  43 ,  44  being pressed inward of the metering head  45  and opening, thereby, the respective metering valves. A metered amount of the liquefied fuel gas is injected into the forechamber section  21  and the main chamber section  22 . It is possible to further lift the movable wall  14  somewhat until it reaches its position in which the forechamber is completely expanded, and the spring  33  is completely compressed.  
         [0041]    The further pivotal movement of the stirrup  47  is compensated by a further movement of the feed channels  43 ,  44  into the metering head  45 .  
         [0042]    In the last stage of movement of the movable wall  14  toward the end wall  34 , the check valve  31  is engaged by the actuation member  32  which prevents the check valve  31  from opening.  
         [0043]    In the completely expanded position of the forechamber and main chamber sections  21 ,  22  which is shown in FIG. 2, the movable wall  14  and the separation plate  18  are locked. This is effected by actuating a respective lever or trigger which, e.g., locks the drive ring  28 . Shortly thereafter, an ignition spark is generated by the ignition device  52 . A fuel mixture, which was previously formed in the chamber sections  21 ,  22 , e.g., an air-fuel gas mixture, starts to burn laminary in the forechamber section  21 , with a flame front propagating radially, with a comparatively slow speed, in a direction toward the check valves  38 . The flame front displaces the unconsumed air-fuel gas mixture ahead of it. The mixture enters through the check valves  38  into the main chamber section, creating there turbulence and pre-compression. The mixture cannot exit the forechamber section  21  through the check valve  36 .  
         [0044]    As the flame front reaches the check valves  38 , the flame penetrates therethrough, due to the small cross-section of the check valves  38 , in a form of flame jets into the main chamber section  22 , creating there a further turbulence. The thoroughly intermixed air-fuel gas mixture in the main chamber section  22  ignites over the entire surface of the flame jets. The mixture burns with a high speed which substantially increases the effect of combustion.  
         [0045]    The combustible mixture in the main chamber section impacts the piston  8 , which moves with a high speed toward the bottom  7  of the guide cylinder  5 , forcing the air from the guide cylinder  5  out through the openings  39 . Upon the piston plate  9  passing the openings  39 , the exhaust gas is discharged tberethrough. The piston rod  10  effects setting of a fastening element.  
         [0046]    After setting or following the combustion of the air-fuel mixture, the piston  8  is brought to its initial position, which is shown in FIG. 2, as a result of thermal feedback produced by cooling of the fuel gases which remain in the combustion chamber  1  and the guide cylinder  5 . As a result of cooling of the fuel gases, an underpressure is created behind the piston  8  which provides for return of the piston  8  to its initial position. The combustion chamber  1  should remain sealed until piston  8  reaches its initial position. In its initial position, the piston  8  can be retained, e.g., with magnetic means or the like.  
         [0047]    After it is insured that the piston  8  reached its initial position, which is shown in FIG. 1, again, the movable wall  14  and/or the drive ring  28  is (are) unlocked. The compression springs  30  bias the drive ring  28  in a direction away from the bottom  3  of the combustion chamber  1 . The actuation member  32 , which is mounted on the drive ring  28 , releases the check valve  31 . Upon displacement of the drive ring  28  away from the bottom  3  under the action of springs  30 , the drive rods  23  pull the movable wall  14  in the direction toward the bottom  3 , as shown in FIG. 3. At this movement of the movable wall  14 , the separation plate  18  remains stationary as the compression spring  33 , which is supported on the movable wall  14 , biases the separation plate  18  toward the end wall  34  (via the shoulder  20  of the lug  19  connected with the separation plate  14 ). This results in that the movable wall  14  moves toward the still stationary separation plate  18 , whereby the forechamber section  21  collapses, with the main chamber section  22 , remaining in the expanded condition. The exhaust or waste gases can leave the forechamber section  21  through the check valve  38  and enter the main chamber section  22  and therefrom outside through the open check valve  31 . Finally, the movable wall  14  lies on the separation plate  18 . After the movable wall  14  lies on the separation plate  18 , both move toward the bottom  3 , with the exhaust gases exiting from the main chamber section  22  out through the check valve  31 . The movement of the movable wall  14  and the separation plate  18  continues until the position shown in FIG. 1 is reached. The combustion chamber  1  is completely collapsed, and an aeration process can begin anew upon a next setting of the fastening element.  
         [0048]    Though the present invention was shown and described with references to the preferred embodiments, such are merely illustrative of the present invention and are not to be construed as a limitation thereof and various modifications of the present invention will be apparent to those skilled in the art. It is therefore not intended that the present invention be limited to the disclosed embodiments or details thereof, and the present invention includes all variations and/or alternative embodiments within the spirit and scope of the present invention as defined by the appended claims.