Abstract:
A method of controlling operation of a portable, combustion-engined tool including a combustion chamber ( 1 ) an inlet/outlet valve ( 26 ) of which is closed or is opened dependent on an operational phase of the tool, with the method including igniting a fuel gas mixture filling the combustion chamber ( 1 ) for build-up of gas pressure therein and closing or opening the inlet/outlet valves ( 26 ) dependent on the gas pressure developed in the combustion chamber ( 1 ), and a tool in which the method is implemented.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a portable, combustion-engined tool, in particular a setting tool for driving in fastening elements and including a combustion chamber an inlet/outlet valve of which is closed or opened dependent on an operational phase of the tool, and to a method of controlling the operation of such a tool. 
     2. Description of the Prior Art 
     In the tool described above, a drive energy is obtained by combustion of a fuel gas mixture and is transmitted by a piston to a fastening element. By pressing the tool against an object in which the fastening element is to be driven in, an ignition of the fuel gas mixture in the combustion chamber is initiated. The initiation of the ignition takes place upon actuation of an ignition device by a trigger which is actuated upon the tool being pressed against the object. The ignition device produces an electrical spark that ignites the fuel gas mixture, starting a combustion process. The increased pressure, which is produced by the combustion of the fuel gas mixture, acts on the piston which adjoins the combustion chamber, driving the same in the setting direction. At the end of its displacement in the setting direction, the piston passes past outlet openings which are formed in a guide cylinder, in which the piston is located, and through which opening exhaust or waste gases can be at least partially removed. The piston then returns to its initial position as a result of an underpressure created in the combustion chamber as a result of cooling down of residual gases still remaining in the combustion chamber. During the time the piston returns to its initial position, the combustion chamber should remain sealed from the surrounding environment. The inlet/outlet valve, through which fresh air enters the combustion chamber, should open only after the return movement of the piston has been completed. Generally, the time necessary for return of the piston to its initial position, increases with an increase of the tool temperature. In addition, a high-energy tool requires that a large expansion volume be available, which also increases the time of the return movement of the piston. 
     In conventional tools, the inlet/outlet valve can be closed with an appropriate latch fixedly connected with a trigger by a toggle lever. The inlet/outlet valve becomes open as soon as the trigger, which is associated with the piston, returns to its initial position. 
     The locking of the inlet/outlet valve with a trigger means that the shift point of the trigger cannot any more be arbitrary selected. The ignition switch can only then be actuated when the closing of the inlet/outlet valve has been completed, i.e., much later after the trigger movement. However, a prolonged trigger movement adversely affects or influences the customer acceptance of such tools. Further, with a hot tool, the return movement of the piston, as it has already been discussed above, takes more time. In this case, the user has to hold the trigger in its pulled position much longer in order to prevent the piston from occupying an erroneous position. 
     Naturally, in order to increase the time during which the piston returns to its initial position, the movement of the trigger can be damped. However, damping of the trigger movement adversely affects the trigger characteristics as the triggering force is increased, and the trigger itself does not return to its initial position sufficiently rapidly. Users view dampening of a trigger very unfavorably as it reduces the output and increases actuation forces that need be applied by a user. 
     A further non-insignificant problem consists in that not in each case, return of the piston to its exact initial position is insured. 
     Accordingly, an object of the present is a tool of the above-described type and a method of controlling its operation which would insure a complete return of the piston to its initial position before the inlet/outlet valve opens, without any manipulation of the trigger by a user. 
     SUMMARY OF THE INVENTION 
     This and other objects of the present invention, which will become apparent hereinafter, are achieved by providing a tool having blocking means providing for closing and opening of the inlet/outlet valve, and means for controlling the operation of the blocking means in accordance with the pressure in the combustion chamber; and by providing a method according to which the closing and opening of the inlet/outlet valve is effected dependent on the gas pressure in the combustion chamber. 
     In this way, the closing of the inlet/outlet valve is automatized and, in addition, ignition of the gas mixture in the combustion chamber takes place independent of the displacement position of the trigger. In this way, it is insured that the piston always returns to its initial position before opening of the inlet/outlet valve. The operation is effected completely automatically, without intervention of the user, in particular, because opening of the inlet/outlet valve is not any more controlled by the trigger movement. 
     As soon as an overpressure is produced in the combustion chamber after ignition of the fuel gas mixture therein, at least one inlet/outlet valve can be closed (if the combustion chamber has several inlet/outlet valves). This can in principle take place at any overpressure as closing of the inlet/outlet valve(s) alone is not absolutely necessary for displacement of the piston. However, closing should take place in each case after the overpressure in the combustion chamber has been created and the piston has been displaced, as now retaining of the underpressure, which is necessary for return of the piston to its initial position as a result of cooling of the residual gases, should be insured. The combustion chamber, in this case, should not be aerated, and the inlet/outlet valve should remain closed, which requires locking the valve in its closed position. Otherwise, a complete return of the piston to its initial position would not have been possible. To unsure this, closing already starts after the gas pressure have reached a predetermined, relatively small value. 
     Opening of the inlet/outlet valve takes place after expiration of a predetermined time period after overpressure in the combustion chamber has been produced. The predetermined time period can, e.g., be determined based on previous empirically determined data. At that, the time, necessary for return of the piston to its initial position, should lie within the predetermined time period. It proved advantageous to count the predetermined time period starting from the point the maximum gas pressure in the combustion chamber has been reached, as a maximum gas pressure can be easily achieved in the combustion chamber. 
     According to the present invention, as soon as the gas overpressure has been detected, somewhat shortly after the beginning of the ignition process, the closing takes place. Then, the time-delay element, which provides for automatic opening after a predetermined time period, is actuated. This time period, as it has already been discussed above, is so selected that opening starts after the piston has been completely returned to its initial position. The return of the piston to its initial position can take place independent of the actuation of the trigger which insures a reliable operation of the tool. 
     The blocking device can be formed in any arbitrary manner. It only should be insured that it reacts to the inner pressure of the combustion chamber. When the blocking device is formed as an electro-mechanical or purely electrical device, for determining the inner pressure in the combustion chamber, a pressure/voltage transformer can be used. According to the invention, the blocking device can include a pneumatic device, in which case, its operation is initiated directly by the pressure in the combustion chamber. 
     According to preferred embodiment of the present invention, the blocking device includes a check valve connected with the combustion chamber, and a pneumatic cylinder located downstream of the check valve, with the conduit connecting the check valve with the pneumatic cylinder communicating with the surrounding environment via a throttle. The check valve only permits gas flow from the combustion chamber to the pneumatic cylinder for actuating a piston having a piston rod and displaceable in the pneumatic cylinder. After the over pressure in the combustion chamber reaches its maximum and is them reduced, the check valve closes automatically as the pressure in the conduit, which connects the check valve with the pneumatic cylinder, is greater than in the combustion chamber. The conduit, together with the throttle, forms the time-delay element as the pressure in the conduit is gradually reduced by the throttle. As the pressure in the conduit is reduced, the piston is biased to its initial position by a compression spring located in the cylinder, releasing the blocking member which results in opening of the inlet/outlet valve. The speed of the movement of the piston in the cylinder and the release of the inlet/outlet valve can be selected by adjusting the throttle, whereby the predetermined time period, which is determined by the time necessary for return of the piston into its initial position can be matched to corresponding environmental conditions and/or constructive features of the tool. 
     The piston rod of the piston of the pneumatic cylinder can, e.g., pivot the blocking member into the displacement path of a drive ring, which is arranged outside of the combustion chamber, for blocking the movement of the drive ring or releasing the drive ring which actuates the inlet/outlet valve. Due to the use of the pivotal blocking member, the dimensions of the entire construction are only slightly increased. 
     The present invention can be used in tools having a single-volume combustion chamber. However, the invention can also be used in tools having a multi-sectional combustion chamber the chamber sections of which are separated by one or several separation wall(s) or plate(s) provided with a plurality of through-openings. In the later case, the pressure in the chamber section adjoining the piston controls the closing and opening of the inlet/outlet valve or valves. The present invention can also be used with tools having collapsible combustion chambers which include a plurality of chamber sections separated by movable walls which are pushed onto each other during deaeration of the combustion chamber, which results in collapse of the combustion chamber. As long as the aeration/deaeration valve(s) remains closed, and as long as the piston has not yet returned to its initial position, the collapse of the combustion chamber should be prevented, so that the same pressure conditions, which control closing/opening of the inlet/outlet or aeration/deaeration valve, control the locking or release of the movable walls of the combustion chamber. 
     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 objets 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 
     In the Drawings: 
     FIG. 1 shows an axial cross-sectional view of a combustion-engined tool according to the present invention in the region of the tool combustion chamber, with completely expanded chamber sections but with the movable walls not yet locked in their positions; 
     FIG. 2 shows a cross-sectional view of the tool shown in FIG. 1 in a condition after ignition, with the movable walls being locked in their positions and the piston being displaced; 
     FIG. 3 show a view similar to that of FIG. 2 but with the piston on its way to its initial position; 
     FIG. 4 shows a view similar to that of FIG. 1 with unlocked movable walls; and 
     FIG. 5 shows a cross-sectional view of the tool in the region of its combustion chamber, with the piston in its initial position and the chambers sections in their collapsed condition. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A combustion chamber  1  of the 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 as 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 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 . 
     FIG. 1 shows a non-operational position of the setting tool in which the piston  8  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 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. 
     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 sealing provided in the wall of the opening  16 . 
     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  has a circular shape and an outer diameter corresponding to the inner diameter of the combustion chamber. The side of the separation plate  18  adjacent to the movable wall  14  is provided with a cylindrical lug  19  that projects through he central opening  16  in the movable wall  14 . The length of the lug  19  exceeds the thickness of the movable wall  14  in several times. The annular sealing sealingly 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 outer diameter of the lug  19  and the inner diameter of the opening  16  of the movable wall  14 . At the edge of the opening  16 , there is provided a hollow cylindrical projection  17  connected with the movable wall  14 . The hollow projection  17  surrounds the lug  19 . The free end of the projection  17  is located below the shoulder  20 . 
     In the idle position of the tool, the separation plate  18  lies on the bottom  3 , and the movable wall  14  lies on the separation plate  18 . The combustion chamber  1  is in its completely collapsed condition. Upon the tool being pressed against an object into which a fastening element is to be driven in, as it would be explained later, the movable wall  14  is lifted and becomes separated from the separation plate  18 , moving away therefrom. After a while, the projection  17  engages the shoulder  20  of the lug  19  of the separation plate  18 . At that, the movable wall  14  and the separation plate  18  are spaced by a predetermined distance determined by the position of the shoulder  20 . The movable wall  14  and the separation plate  18  form together a forechamber  21  which, in effect, is a section of the combustion chamber  1  and which further below will be referred to as a forechamber section  21 . Upon further displacement of the movable wall  14 , the movable wall  14  and the separation plate  18  move together, so that a further chamber section, which further will be referred to as a main chamber section is formed between the separation plate  18  and the bottom  3  of the piston plate  9 . The main chamber section is designated with a reference numeral  22 . FIG. 1 shows both chamber sections  21 ,  22  in their completely expanded condition. 
     For displacing the movable wail  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 . The openings  25  are formed as ventilation openings and have a conical shape. The movable wall  14  is connected with drive rods  23  by, e.g., screws 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 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 extending between the bottom  3  of the combustion chamber  1  and the drive ring  28 . The compression springs  30  are designed for pulling the movable wall  14  toward the bottom  3 . 
     As it has already mentioned above, the openings  25  in the bottom  3  of the combustion chamber  1 , which also serve as ventilation openings, are conically widened outwardly. A valve tappet  32  sealingly extends into each opening  25 . The valve tapped  32  is located, with the opening  25  being open, outside of the combustion chamber  1  or beneath the bottom  3  and is retained there by a shoulder  33  provided on the drive rode  23 . When the drive rods  23  are pushed in the direction toward the bottom  3 , the shoulders  33  push the valve tappets  32  into the openings  25 , closing the valves  26  formed by the walls of the openings  25  and the valve tappets  32 . The valve  26  is formed as an inlet/outlet valve. It is to be pointed out that the separation plate  18  has a plurality of opening  38  equidistantly spaced from the axis of the combustion chamber  1 . Further, a plurality of openings  39  are provided at the lower end of the guide cylinder  5  for letting air out of the guide cylinder  5  upon movement of the piston  8  toward the guide cylinder bottom  7 . At the lower end of the guide cylinder  5 , there is also provided damping means  40  for damping the movement of the piston  8 . As soon as the piston  8  passes the openings  39 , the waste gases are expelled from the guide cylinder  5  through the openings  39 . 
     Two radial through-openings  41 ,  42  are provided in the cylindrical wall  2  of the combustion chamber  1 . Two conduits (not shown), which extend from outside into the through-openings  41 ,  42 , communicate the combustion chamber  1  with a metering valve and provide for injection of, e.g., liquefied fuel gas into respective combustion chamber sections  21 ,  22  which are formed when the movable wall  14  and the separation wall  18  are displace to their operational end positions. 
     As it has already been mentioned above, FIG. 1 shows the tool with the chamber sections in their expanded condition, i.e., with the-forechamber section  21  and the main chamber section  22  being expanded. The displacement positions of the movable wall  14  and the separation plate  18  are defined by a stop which is formed by the valve tappets  32 . The valve tappets  32 , upon being inserted, into the openings  25  form stops for arresting the displacement of the drive rods  23  which are arrested as a result of the shoulders  33  engaging the valve tappets  32 . The stoppage of the drive rods  23  results in the stoppage of the movable wall  14 . The position of the separation plate  18  is determined by the position of the shoulder  20  which, in turn, is determined by the length of the hollow projection  17  of the movable wall  14 . 
     The lug  19  forms, in its region adjacent to the separation plate  18 , an ignition cage  51  for receiving an ignition element  52 . The ignition element  52  serves for generating an electrical spark for the ignition of the air-fuel gas mixture in the forechamber section  21 . As it will be described in more detail below, the ignition device  52  is located in the central region of the cage  51  having openings  53  formed in the cage circumference. Through this openings  53 , a laminar flame front exits from the ignition cage  51  into the forechamber section  21 . 
     As shown in FIG. 1, sidewise of the guide cylinder  5 , there is located a blocking device  54 . 
     The blocking device  54  has a check valve  55 , a pneumatic cylinder  56 , a throttle  57 , and a pivotal blocking hook  58 . The check valve  55  is a one-way valve and is connected with fluid conduit  59  extending through the bottom  3  and opening into the combustion chamber  1 . The check valve  55  provides for gas flow only from the combustion chamber  1  and includes a ball  60  for blocking the conduit  59 . The ball  60  is biased into its blocking position by a spring  61 . The outlet side of the check valve  55  is connected by a channel  62  with an inlet of the pneumatic cylinder  56 . The channel  62  is connected with a branch channel in which the throttle  57 , which is adjustable, is provided. Inside the pneumatic cylinder  56 , there is located a piston  64 . The piston  64  is connected with a piston rod  65  projecting out of the pneumatic cylinder  56 . A compression spring  66  surrounds the piston rod  65  inside the cylinder  56  and is supported, at its opposite ends, against a rear surface of the piston  64  and the bottom of the cylinder  56 , respectively. The free end of the piston  65 , which is located outside of the cylinder  56 , is connected with the pivotable blocking hook  58 . The blocking hook  58  has an angular shape and pivots about an axle  67 . The axle  67  extends transverse to the longitudinal extent of the piston rod  65 . At its end opposite the end connected with the piston rod  65 , the blocking hook  58  has a nose  68  facing the guide cylinder  5 . The nose  68  is displaced into the path of the movement of the drive ring  28  when the blocking hook  58  pivots about the axle  67  in the clockwise direction. When the nose  68  is located in the path of the movement of the drive ring  28 , the compression springs supported on the drive rods  23  cannot push the drive ring  28  away from the bottom  3 . As a result, the inlet/outlet valves  26  remain closed. 
     The closing takes place after the ignition of the fuel gas mixture which increases the pressure in the combustion chamber  1 . The increased pressure is communicated, via the check valve  55 , to the cylinder  56 . This results in the displacement of the piston  64  against the biasing force of the spring  66 . Upon the displacement of the piston  64 , the piston rod  65  pivots the blocking hook  58  about the axle  67  in the clockwise direction, and the nose  68  engages the drive ring  28  from beneath. With a further increase of the pressure in the combustion chamber  1 , an increased pressure is applied to the piston  64 , retaining it in the position in which the nose  68  blocks the drive ring  28 . When the pressure in the combustion chamber  1  reaches its maximum and then diminishes, the check valve  55  remains closed as the pressure in the conduit  59  is smaller than in the channel  62 . At that, the blocking device  54  acts as an accumulator, and the blocking of the drive ring  28  is maintained, resulting in maintaining of the locking of the valves  26  and the movable wall  14 . The pressure in the channel  62  is reduced, via the throttle  57 , gradually or over a predetermined time period determined by the adjusted cross-section of the throttle  57 . When the pressure in the channel  62  is reduced below a certain value, the spring  66  biases the piston  64  in a direction toward the check valve  55 , pulling the piston rod  65  with it. Upon the piston rod  64  being pulled toward the check valve  55 , the blocking hook  58  would pivot in the counterclockwise direction about the axle  67 , withdrawing the nose  68  from the displacement path of the drive ring  28 . The drive ring  68  can now displace away from the bottom  3 , which results in the opening of the valves  26  and the displacement of the movable wall  14 , together with the separation plate  18 , toward the bottom  3 , with the waste gases being expelled from the chamber sections  21 ,  22  through the openings  38  in the separation plate and the inlet/outlet valves  26 , respectively. 
     Below, the operation of the tool according to the present invention will be discussed in detail with reference to FIGS. 2-5. In FIGS. 2-5, the same element as those in FIG. 1 are designated with the same reference numerals. 
     FIG. 2 practically corresponds to FIG. 1, only in FIG. 2, the ignition device  52  has already been actuated by a trigger or a lever (not shown). Upon actuation of the ignition device  52 , a spark is generated in the cage  51 . After the ignition, an air-fuel gas mixture starts to bum laminary in the forechamber section  21 . Upon ignition of the mixture, a flame front starts to propagate radially with a relatively small velocity. The flame front pushes the unconsumed air-fuel gas mixture ahead of itself, and the unconsumed air-fuel gas mixture penetrates through the through-openings  38  in the separation plate  18  into the main combustion chamber section  22 , creating there turbulence and pre-compression. 
     As the flame front reaches the through-openings  38 , flame penetrates therethrough, due to the small cross-section of the openings  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 ignites over the entire surface of the flame jets. The mixture bums with a high speed which leads to a sharp increase of the pressure in the main chamber section  22 . 
     The high pressure, which is generated in the main chamber section  22 , is transmitted, on one hand, to the piston  8  and, on the other hand, via the check valve  55 , to the piston  64  of the pneumatic cylinder  56 . The piston  64 , together with the piston rod  65 , is displaced away from the check valve  55 , compressing the spring  66 . The free end of the piston rod  65  pivots the blocking hook  58  about the axle  67  in the clockwise direction, whereby the nose  68  is displaced into the displacement path of the drive ring  28 . Thereby, a locking condition is obtained. 
     Simultaneously with the increase of pressure in the main chamber section  22 , the piston  8  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 therethrough. The piston rod  10  effects setting of a fastening element, being displaced in the direction shown by arrow. As in the course of movement of the piston  8 , the pressure in the main chamber section  22  decreases, resulting in the decrease of pressure in the conduit  59 . Because a maximum pressure has been stored in the channel  62 , the check valve  55  remains closed. The throttle  57  provides only for a very slow reduction of pressure in the channel  62 , and the locking condition is still maintained. 
     After setting or following the combustion of the air-fuel gas mixture, the piston  8  is brought to its initial position, as is shown in FIG. 3, as a result of thermal feedback produced by cooling of the flue gases which remain in the combustion chamber  1  and the guide cylinder  5 . As a result of cooling of the flue 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 the piston  8  reaches its initial position shown in FIG.  1 . This means that the locking condition should remain, which is insured in a manner described above with reference to FIG.  2 . The locking condition in FIG. 3 has not changed in comparison with that in FIG.  2 . 
     FIG. 4 shows a condition at which the piston  8  is brought to its initial position as a result of thermal feedback. The operation of the throttle  57  is so adjusted that only after the piston  8  is brought into is initial position, the pressure in the channel  62  is reduced to an extent at which the spring  66  is able to displace the piston  64  in a direction toward the check valve  55 . With the piston rod  65  movable together with the piston  64 , the blocking hook  58  pivots about the axle  67  in the counterclockwise direction, with the nose  68  being displaced out of the displacement path of the drive ring  28 . 
     Upon removal of the blocking hook  58  out of the displacement path of the drive ring  28 , the compression springs supported on the drive rods  23  displace the drive ring  28  away from the bottom  3  of the combustion chamber  1 , opening the inlet/outlet valves  26 . Simultaneously, the movable wall  14  is displaced toward the bottom  3 , entraining therewith the separation plate  18 , with the waste gases being discharged from the forechamber section  21  and the main chamber section  22  through the openings  38  in the separation plate  18  and the valves  26 , respectively. Upon subsequent expansion of the forechamber section  21  and the main chamber section  22 , as a result of the movement of the drive ring  28  in opposite direction, the air is aspirated into the main chamber section  22  and the forechamber section  21  through the inlet/outlet valves  26  and the through-openings  28  in the separation plate  18 , respectively. 
     Although 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 spirits and scope of the present invention as defined by the appended claims.