Abstract:
A tool for securing a connector on a conductor using an explosive charge includes a first tool member and a second tool member movably mounted on the first tool member. A breech chamber is defined in at least one of the first and second tool members. The breech chamber is adapted to receive the explosive charge. A breech opening is defined in at least one of the first and second tool members and communicates with the breech chamber. A drive member is provided. The tool is adapted to forcibly move the drive member responsive to an explosion of the explosive charge in the breech chamber. The second tool member is movable between a closed position, wherein the breech opening is closed, and an open position, wherein the breech opening is open to allow loading and unloading of the explosive charge into and from the breech chamber, by sliding the second tool member relative to the first tool member along a slide axis and additionally pivoting the second tool member relative to the first tool member about a pivot axis transverse to the slide axis.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to tools and methods for using tools and, more particularly, to tools and methods for securing or terminating connectors.  
       BACKGROUND OF THE INVENTION  
       [0002]     Electrical cables often must be terminated or joined (spliced) in various environments, such as underground or overhead. Such cables may be, for example, high voltage electrical distribution or transmission lines. In order to form such connections, a connector may be employed. To install such connectors, it may be necessary to force two members into engagement, typically such that one or both of the members are deformed. Exemplary connectors include a C-shaped sleeve and wedge combination as disclosed in U.S. Pat. No. 4,722,189 to Center. In order to install such connectors, it is typically necessary to apply a relatively great force between the wedge and the sleeve. However, the amount of force should not be excessive as this may compromise the formation or integrity of the connection. Because the connections are often formed in dangerous locations (e.g., high above the ground) and with high voltage lines, it is desirable to provide the necessary force in a manner that is convenient and safe under such circumstances.  
         [0003]     To provide the application force as discussed above, explosive charge-actuated tools (sometimes referred to as “powder-actuated tools”) are commonly used. According to some designs, explosive charge-actuated tools include a tool body, a tool head secured to the tool body, and a ram slidably mounted in the tool body. In use, the connector components are placed between the ram and the tool head. An explosive charge, typically provided in a cartridge, is exploded in the tool body such that the ram is forced against the connector to thereby force the connector components into secure engagement. The explosion of the charge may generate pressurized gas in the tool body. If not first controllably released, the pressurized gas may harm the user when the user attempts to open the tool body to remove the expended explosive charge cartridge. Thus, tools of this type may provide a mechanism for pre-releasing pressurized gas from the tool body, for example, from a breech chamber that holds the cartridge. Exemplary tools of this type include the AMPACT tool available from Tyco Electronics, Inc. and the tools disclosed in U.S. Pat. No. 4,722,189 to Center and in U.S. Pat. No. 4,905,603 to McBain. However, such tools may be difficult to operate under some circumstances or may require substantial and frequent maintenance to ensure safe and effective operation.  
       SUMMARY OF THE INVENTION  
       [0004]     According to embodiments of the present invention, a tool for securing a connector on a conductor using an explosive charge includes a first tool member and a second tool member movably mounted on the first tool member. A breech chamber is defined in at least one of the first and second tool members. The breech chamber is adapted to receive the explosive charge. A breech opening is defined in at least one of the first and second tool members and communicates with the breech chamber. A drive member is provided. The tool is adapted to forcibly move the drive member responsive to an explosion of the explosive charge in the breech chamber. The second tool member is movable between a closed position, wherein the breech opening is closed, and an open position, wherein the breech opening is open to allow loading and unloading of the explosive charge into and from the breech chamber, by sliding the second tool member relative to the first tool member along a slide axis and additionally pivoting the second tool member relative to the first tool member about a pivot axis transverse to the slide axis.  
         [0005]     According to method embodiments of the present invention, a method for using a tool for securing a connector on a conductor using an explosive charge is provided. The tool includes: a first tool member; a second tool member movably mounted on the first tool member; a breech chamber defined in at least one of the first and second tool members, the breech chamber being adapted to receive the explosive charge; a breech opening defined in at least one of the first and second tool members, the breech opening communicating with the breech chamber; and a drive member. The tool is adapted to forcibly move the drive member responsive to an explosion of the explosive charge in the breech chamber. The method includes sliding the second tool member relative to the first tool member along a slide axis. The second tool member is pivoted relative to the first tool member about a pivot axis transverse to the slide axis such that the second tool member is moved from a closed position, wherein the breech opening is closed, to an open position, wherein the breech opening is open to allow loading and unloading of the explosive charge into and from the breech chamber.  
         [0006]     Objects of the present invention will be appreciated by those of ordinary skill in the art from a reading of the figures and the detailed description of the preferred embodiments which follow, such description being merely illustrative of the present invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain principles of the invention.  
         [0008]      FIG. 1  is a perspective view illustrating the formation of a connection using a tool assembly and methods according to embodiments of the present invention;  
         [0009]      FIG. 2  is a perspective view of a drive assembly forming a part of the tool assembly of the  FIG. 1 ;  
         [0010]      FIG. 3  is a front, perspective, exploded view of the drive assembly of  FIG. 2 ;  
         [0011]      FIG. 4  is a rear, perspective, exploded view of the drive assembly of  FIG. 2 ;  
         [0012]      FIGS. 5A and 5B  are perspective views of a breech forming a part of the drive assembly of  FIG. 2  as viewed from opposed sides thereof;  
         [0013]      FIG. 6  is a side elevational view of the tool assembly of  FIG. 1  and a cartridge for use therewith, wherein the drive assembly is in an open position;  
         [0014]      FIG. 7  is a side elevational view of the tool assembly of  FIG. 1  wherein the drive assembly is in a further position;  
         [0015]      FIG. 8  is a side elevation view of the tool assembly of  FIG. 1  wherein the drive assembly is in a further position;  
         [0016]      FIG. 9  is a further perspective view of the drive assembly of  FIG. 2 ;  
         [0017]      FIG. 10  is a cross-sectional view of the drive assembly of  FIG. 2 ;  
         [0018]      FIG. 11  is a cross-sectional view of the drive assembly of  FIG. 2  taken along the same line as  FIG. 10  and wherein the drive assembly is in a further position; and  
         [0019]      FIG. 12  is a cross-sectional view of the drive assembly of  FIG. 2  taken along the same line as  FIG. 10  and wherein the drive assembly in a further position. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0020]     The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.  
         [0021]     With reference to  FIG. 1 , a tool assembly  40  according to embodiments of the present invention is shown therein. The tool assembly  40  may be used to form a connection  5  as shown in  FIG. 1 , for example. The connection  5  includes a pair of conductors  7 ,  9  securely and electrically coupled by a connector  20 . The connector  20  includes a C-shaped sleeve  22  and a wedge  24 . Connectors of this type are well-known to those of skill in the art and will not be described in further detail herein except as needed to describe embodiments of the present invention. Generally, and as described in more detail below, the tool assembly  40  may be used to force or impel the wedge  24  and the sleeve  22  into engagement using an explosive charge  32  (e.g., as provided in a cartridge  30 ; see  FIG. 11 ).  
         [0022]     With reference to  FIG. 1 , the tool assembly  40  includes an explosively actuated industrial tool  45  and an anvil or tool head  80 . The tool  45  includes a barrel or coupling  50 , a coupling nut  60 , a drive assembly  100  joined to the coupling  50  by the coupling nut  60 , and a ram  70  slidably mounted in the coupling  50 . With reference to  FIG. 6 , the drive assembly  100  includes a breech  102 , an ejector sleeve  130 , and a breech cap assembly  150 . Each of these components will be described in more detail below. The coupling  50 , the coupling nut  60  and the ram  70  are omitted from  FIGS. 11 and 12  for clarity.  
         [0023]     The coupling  50  includes threads  52  ( FIG. 10 ) on its outer surface. A bore or barrel passage  54  extends through the coupling  50  and communicates with opposed end openings  56  ( FIGS. 1 and 10 ).  
         [0024]     The breech  102  has opposed front and rear ends  104 A and  104 B. A breech chamber  106  ( FIG. 11 ) is defined in the breech  102 , which is generally tubular. The breech chamber  106  communicates with a front breech opening  108 A ( FIG. 3 ) and a rear breech opening  108 B ( FIG. 4 ). A coupling thread  110  ( FIG. 5A ) is formed on the outer surface of the breech  102  on the front end  104 A thereof. A radially extending coupling set screw bore  112  ( FIG. 3 ) is also formed on the front end  104 A for securing the breech  102  to the coupling nut  60 . A pair of opposed, axially extending guide channels  114 A,  114 B ( FIGS. 5A and 5B ) are defined in the outer surface of the breech  102  on opposed sides thereof. A pair of circumferentially extending guide channels  116 A and  116 B ( FIGS. 5A and 5B ) are also defined in the outer surface of the breech  102  on opposed sides thereof and intersect the axially extending channels  114 A and  114 B, respectively, adjacent the front end  104 A. A pair of opposed, radially extending screw holes  118  ( FIG. 4 ) are formed in the rear end  104 B. A recessed end portion  120  and an end flange  122  are also provided on the rear end  104 B ( FIG. 4 ).  
         [0025]     The ejector sleeve  130  is mounted on the recessed end portion  120 . The ejector sleeve defines a front opening  134 A ( FIG. 3 ), a rear opening  134 B ( FIG. 4 ) and a bore  132  ( FIG. 3 ) communicating with each of the openings  134 A,  134 B. The rear opening  134 B is defined by a radially inwardly extending, circumferential flange  136  ( FIG. 4 ). The bore  132  receives the recessed end portion  120  such that the flange  136  surrounds the end flange  122 . Opposed guide screws  140  ( FIGS. 3 and 10 ) extend from the screw holes  118  in the recessed end portion  120  and are slidably received in opposed axially extending slots  138  ( FIG. 3 ) defined in the ejector sleeve  130 . Grip ribs  146  ( FIG. 6 ) are provided on opposed sides of the ejector sleeve  130 . The ejector sleeve  130  further includes a lock pin recess  142  and a support recess  144  ( FIG. 4 ).  
         [0026]     The coupling nut  60  includes a threaded bore  62  ( FIG. 10 ). The threaded bore  62  is configured to threadedly engage the coupling threads  110  of the breech  102 . The coupling nut  60  serves to secure the coupling  50  to the drive assembly  100 . The coupling  50  is slidable in the coupling nut  60  so as to allow a small gap  78  (see  FIG. 10 ).  
         [0027]     The ram  70  is a generally cylindrical rod having a strike end  72  ( FIG. 10 ) and an opposed driven end  74  ( FIG. 1 ). A firing pin  76  ( FIG. 10 ) projects from the driven end. The ram  70  is slidable in the coupling  50  and the breech  102 .  
         [0028]     The breech cap assembly  150  includes a breech cap sleeve  152 , a pin guide housing  170 , a pin guide  180 , a retaining spring  181 , a gas release member or knob  190 , a piercer pin  184 , a stop screw  199 , and a lock pin  179 . The breech cap assembly  150  is movable between a closed position ( FIGS. 2 and 12 ) and an open position ( FIG. 6 ) as described in more detail below.  
         [0029]     The breech cap sleeve  152  is generally tubular and defines an axially extending passage  154  that, in the closed position, surrounds the breech  102  and the ejector  130 . A front opening  154 A ( FIG. 3 ) and a rear opening  154 B ( FIG. 4 ) communicate with the passage  154  on either end. Internal threads  156  ( FIG. 4 ) are formed adjacent the rear opening  154 B. A lock pin guide slot  158  extends axially through the threads  156 . Knurling may be formed on the outer surface of the breech cap sleeve  152  to facilitate gripping. Opposed slots  162 ,  164  ( FIG. 3 ) are defined in the breech cap sleeve  152  adjacent and in communication with the front opening  154 A. The slot  164  is longer than the slot  162 . The slots  162 ,  164  define opposed, axially extending arms  166 . Opposed guide projections or tabs  167  extend radially inwardly from respective ones of the arms  166  and into respective ones of the channels  116 A,  116 B when the breech cap assembly  150  is in the closed position. An end groove  168  formed in the breech cap sleeve  152  adjacent the rear end  154 B and is adapted to receive the retaining spring  181 .  
         [0030]     With reference to  FIGS. 3 and 4 , the pin guide housing  170  defines a front opening  174 A, a rear opening  174 B, and a bore  172  communicating with each of the openings  174 A,  174 B. Internal threads  175  are provided in the bore  172 . A knurled flange  176  is provided for manipulating the pin guide housing  170 . A tab  177  extends axially rearwardly from the flange  176 . External threads  178  are formed adjacent the front opening  174 A and are configured to mate with the threads  156  of the breech cap sleeve  152 . Slots are formed in the groove  168  of the breech cap sleeve  152  to allow the retaining spring  181  to extend therethrough and engage the threads  178 , thereby preventing full withdrawal of the pin guide housing  170  from the breech cap sleeve  152 .  
         [0031]     As best seen in  FIGS. 3 and 10 , the lock pin  179  is mounted on the threads  178  of the pin guide housing  170  such that the threads  178  are received in an intermediate cutout  179 A of the lock pin. A front portion of the lock pin  179  is slidably received in the lock pin guide slot  158  of the breech cap sleeve  152  and, when the breech cap assembly  150  is in the closed position, into the lock pin recess  142  of the ejector sleeve  130 . A rear portion of the lock pin  179  extends rearwardly from the breech cap sleeve  130  and abuts the flange  176  of the pin guide housing  170 .  
         [0032]     The pin guide  180  is disposed in the bore  172  of the pin guide housing  170 . External threads on the outer surface of the pin guide  180  mate with the internal threads  175 . An axially extending passage  182  ( FIG. 12 ) is defined in the pin guide  180 . The piercer pin  184  is slidably received in the passage  182 . According to some embodiments, the pin guide  180  and the pin guide housing  170  may be unitarily formed.  
         [0033]     The gas release knob  190  includes an end wall  191 . A flange  193  (which may be knurled) surrounds the end wall  191  for manipulating the gas release knob  190 . The piercer pin  184  is fixed within a pin bore  194  formed in the end wall  191 . A pair of gas release passages  196  formed in the end wall  191  provide fluid communication between the breech chamber  106  and the environment. External threads  197  are formed on the front end of the gas release knob  190  and mate with the threads  178  of the pin guide housing  170 . A threaded stop screw hole  198  extends axially through the flange  193 . The stop screw  199  is mounted in the stop screw hole  198  with a portion  199 A ( FIG. 10 ) of the stop screw  199  extending axially forward from the flange  193  such that the portion  199 A engages the tab  177  of the pin guide housing  170  upon rotation of the knob  190 . That is, the portion  199 A and the tab  177 , or respective portions thereof, are located at the same positions along the axis S-S and the same radial distance from the axis S-S.  
         [0034]     According to some embodiments, the piercer pin guide  184  and the gas release knob  190  may be unitarily formed. According to some embodiments, the pin guide housing  170  may be omitted. In this case, the piercer pin guide  180  may be secured to or formed as a part of the breech cap sleeve  152  and the lock pin  179  may be mounted directly on and operatively engaged by the threads  197  in a manner corresponding to that described above and illustrated for the pin guide housing  170 .  
         [0035]     With reference to  FIG. 11 , the cartridge  30  may be a cartridge of any suitable design and construction. Suitable cartridges are available from Tyco Electronics, Inc. The cartridge  30  as illustrated includes a shell  34  having a side wall  34 A, an end wall  34 B, and a radially outwardly extending flange  34 C, and defining a shell cavity  34 D. A quantity of primer  36  and the main charge  32  are disposed in the shell cavity  34 D. The primer  36  may be, for example, a quantity of nitroglycerin packaged in a cap or the like. The charge  32  may be, for example, a quantity of gun powder or other suitable propellant. The charge  32  is separated from the primer by a gas check  39 . The gas check has upstanding prongs  39 A. The cartridge may be formed of a polymeric material such as polyethylene, for example.  
         [0036]     With reference to  FIG. 1 , the tool head  80  includes an abutment  82 , a driver mount portion  84 , and a cradle  88  defined therebetween. A threaded coupling bore  86  is formed in the driver mount portion  84 . The tool head  80  is exemplary, and any suitable tool head may be employed.  
         [0037]     The foregoing components may be formed of any suitable materials. According to some embodiments, with the exception of the cartridge  30 , all of the components are preferably formed of metal and, more preferably, steel of appropriate strength and hardness.  
         [0038]     The tool assembly  40  may be used to form the connection  5  in the following manner. For the purposes of explanation, the procedure will be described starting with an initially open configuration wherein no cartridge  30  is installed in the drive assembly  100  and the drive assembly is in the open position. It will be appreciated from the description herein that certain of the steps discussed below can be revised in order.  
         [0039]     The connection  5  may be temporarily formed by installing the sleeve  22  on and about the conductors  7 ,  9 , and forcing the wedge  24  into the sleeve  22  by hand or using a hammer.  
         [0040]     When the drive assembly  100  is in the open position as shown in  FIG. 6 , the breech cap assembly  150  is located such that it does not cover the breech opening  108 B. The pin guide housing  170  and the gas release knob  190  are each unscrewed or backed out to respective open positions as shown in  FIG. 10 . Accordingly, the piercer pin  184  is retracted with respect to the pin guide  180 .  
         [0041]     According to some embodiments, it is preferable to load the tool  45  with the tool vertically oriented such that the coupling points upwardly. In order to maintain the breech cap assembly  150  in the open position, an edge of the breech cap sleeve  152  may be inserted into the support recess  144  whereby the breech cap assembly  150  is supported. Such a configuration, which is shown in  FIG. 6 , allows the user to use one hand to hold the tool  45  and the other hand to hold the cartridge  30  while the breech cap assembly  150  remains properly positioned.  
         [0042]     The cartridge  30  is inserted into the breech chamber  106  through the breech opening  108 B. In doing so, the ram  70  is inserted into the forward portion of the shell cavity  38  such that the driven end  74  of the ram is positioned above the primer  36  but separated therefrom by the prongs  39 A. According to some embodiments, the shell  34  is sized such that it will be temporarily retained in the opening  134 B by a moderate friction fit. The shell  34  may include compressible ribs on its outer surface for this purpose.  
         [0043]     With the cartridge  30  in place, the breech cap assembly  150  is lifted from the support recess  144  and slid downwardly parallel to a slide axis S-S a short distance to assume the position illustrated in  FIG. 7 . The breech cap assembly  150  is then pivoted about the tabs  167  about a pivot axis P-P in a direction B. The breech cap assembly  150  is pivoted into a position as shown in  FIG. 8 , wherein the breech cap assembly  150  is substantially coaxial with the breech  102 . It will be appreciated that the pivoting path may not be restricted to pivoting about a single point, but may instead by somewhat accurate, for example.  
         [0044]     The breech cap sleeve  152  is then pushed forward on the breech  102  along the slide axis S-S in a direction D. The slide axis S-S is transverse (and, according to some preferred embodiments, perpendicular) to the pivot axis P-P. The tabs  167  slide within the axially extending channels  114 A,  114 B to thereby guide the breech cap sleeve  152  with respect to the breech  102 . The breech cap sleeve  152  is slid onto the breech  102  until the breech cap assembly  150  reaches the position as shown in  FIG. 9 . This movement will serve to push the cartridge  30  fully into the breech  106  until the flange  34 C abuts the flange  136  of the ejector sleeve  130  if the cartridge  30  is not already so positioned.  
         [0045]     The breech cap sleeve  152  is then rotated relative to the breech  102  about the slide axis S-S in a rotational direction E ( FIG. 9 ). The tabs  167  slide within the circumferentially extending channels  116 A,  116 B to thereby guide the breech cap sleeve  152  with respect to the breech  102 . The breech cap sleeve  152  is rotated in this manner on the breech  102  until the breech cap sleeve  152  reaches the position as shown in  FIGS. 2 and 10 . In this position, the tabs  167  and the circumferentially extending channels  116 A,  116 B cooperate to prevent relative movement between the breech cap sleeve  152  and the breech  102  along the axis S-S.  
         [0046]     The pin guide housing  170  may then be rotated in a direction F ( FIG. 9 ) about the axis S-S to screw the pin guide housing  170  into the breech cap sleeve  152  and closer to the breech  102 . The threads  178  slide within the cutout  179 A of the lock pin  179  so that the lock pin  179  does not rotate but is driven forwardly through the slot  158  into the lock pin recess  142 . The pin guide housing  170  is screwed into the breech cap sleeve  152  until the forward end of the pin guide housing  170  engages the ejector sleeve  130  and forces the ejector sleeve forwardly against the breech  102 . The resulting position is shown in  FIG. 11 . In this position, the breech cap sleeve  152  is prevented from rotating relative to the breech  102  by the engagement between the lock pin  179  and the ejector sleeve  130 . Additionally, according to some embodiments the cartridge  30  is driven forward by the housing  170  such that the prongs  39 A are crushed by the ram  70 .  
         [0047]     The gas release knob  190  is then rotated in a direction G ( FIG. 9 ) about the axis S-S to screw the gas release knob  190  into the pin guide housing  170  and closer to the breech  102  until the gas release knob  190  reaches a sealing position as shown in  FIG. 12 . In this manner, the piercer pin  184  is forced forwardly such that it pierces and the end wall  34 B of the cartridge  30 . The piercer pin  184  remains in the end wall  34 B to seal the hole in the end wall  34 B thus formed.  
         [0048]     Using an alternative sequence, the housing  170  may not be screwed into the breech cap sleeve  152  as described above prior to rotating the gas release knob  190 . Instead, the gas release knob  190  is first rotated in the direction G. The rotation of the gas release knob  190  will also rotate the housing  170  into the proper position after the gas release knob  190  has reached the proper position in relation to the housing  170 . More particularly, at this time, the stop screw  199  will engage the tab  177 , thereby causing the housing  170  to rotate with the gas release knob  190 . The gas release knob  190  and the housing  170  will continue to turn together until the forward end of the housing  170  engages the ejector sleeve  130 . With the lock pin  179  and the ejector sleeve  130  interlocked in this manner, the breech cap sleeve  152  cannot be rotated relative to the breech  102  about the slide axis S-S. This procedure for rotating the housing  170  and the knob  190  may be more convenient for execution by the operator.  
         [0049]     The breech cap assembly  150  is now in the closed position as shown in  FIGS. 2 and 12 . In this position, the rear breech opening  108 B is covered by the breech cap assembly  150  and thereby effectively sealed. The front end opening  108 A is substantially sealed by the ram  70 . The ram  70  is positioned such that its forward end is substantially flush with the forward opening of the coupling  50 . According to some embodiments, the prongs  39 A may be partially crushed by the rear end of the ram  70 ; however, the strike pin  76  is spaced apart from the primer  36 . A small gap  78  ( FIG. 10 ) is defined between the coupling  50  and the breech  102  in the coupling nut  60 . The tool  45  is now prepared for firing.  
         [0050]     Prior to or following loading of the cartridge  30  as described above, the coupling  50  of the tool assembly  40  is screwed into the coupling bore  86  of the tool head  80  such that sufficient spacing between the front end of the coupling  50  and the abutment  86  remains for inserting the sleeve  7  and the wedge  9 . The tool assembly  40  thus formed is then installed about the sleeve  7  and the wedge  9  as shown in  FIG. 1  such that the components  7 ,  9  are received in the cradle  88 . The coupling is screwed into the bore  86  until the sleeve  22  abuts the abutment  82  and the forward end of the coupling  50  abuts the wedge  24 .  
         [0051]     With the tool assembly  40  prepared and positioned as described above, the user next strikes the end wall  191  of the gas release knob  190 . The gas release knob  190  may be struck using a hammer  15  ( FIG. 1 ), for example. The strike force may be directed generally along the axis S-S. By striking in this manner, the user forces the coupling  50  against the wedge  24 , which in turn slides the coupling  50  rearward in the coupling nut  60  to close the gap  78  ( FIG. 10 ). The ram  70  is also thereby driven back into the cartridge  30  and the breech  102  such that the firing pin  76  is thereby driven into contact with the primer  36  to ignite the primer  36 . The primer  36  in turn ignites the main charge  32 . The explosion of the main charge  32  is contained by the closed breech  102  so that the ram  70  is driven forwardly by the explosion and forces the wedge  24  into the sleeve  22 , thereby forming the connection  5 .  
         [0052]     The fired cartridge  30  can be removed and the tool  40  reloaded with a fresh cartridge using the following procedure. Typically, following the firing of the cartridge  30 , a pressurized gas from the exploded charge  32  will remain in the breech chamber  106 . Immediately removing the breech cap sleeve  152  from the breech  102  may cause the gas to be released in a manner potentially harmful to the user, bystanders, or the tool itself Thus, it is desirable to first pre-release the gas in a controlled fashion. To accomplish this, the gas release knob  190  is rotated in a direction H ( FIG. 9 ) about the axis S-S to unscrew the gas release knob  190  from the pin guide housing  170  to the gas release position as shown in  FIG. 11 . In this manner, the piercer pin  184  is pulled rearwardly such that it is withdrawn from the end wall  34 B of the cartridge  30 . The pressurized gas trapped in the breech chamber  106  and the cartridge  30  is allowed to escape through the hole in the end wall  34 B, the bore  182  in the pin guide  180 , and the gas release passage  196  in the gas release knob  190 .  
         [0053]     The user then continues to rotate the gas release knob  190  in the direction H such that the stop screw  199  engages the tab  177  and causes the pin guide housing  170  to rotate in the direction H with the gas release knob  190 . The rotation of the housing  170  causes the housing  170  to translate rearwardly along the axis S-S, thereby withdrawing the locking pin  179  from the locking pin recess  142 , and placing the drive assembly  100  in the position shown in  FIG. 10 . According to some embodiments, the stop screw  199  will engage and begin rotating the housing  170  after the gas release knob  190  has been rotated less than 360 degrees.  
         [0054]     The breech cap sleeve  152  is thereafter rotated relative to the breech  102  in a direction I ( FIG. 9 ) about the axis S-S to align the tabs  167  with the axially extending channels  114 A,  114 B, as shown in  FIG. 9 .  
         [0055]     The breech cap sleeve  152  is then slid (e.g., pulled) relative to the breech  102  in a direction J ( FIG. 8 ) along the axis S-S with the axially extending channels  114 A,  114 B serving to guide the breech cap sleeve  152 . The breech cap sleeve  152  is slid such that the tabs  167  engage the ejector sleeve  130  and force the ejector sleeve  130  rearwardly relative to the breech  102 . In this manner, the cartridge  30  may be dislodged from the breech  102 . The user may grasp and pull the ejector sleeve  130  using the ribs  146  to facilitate removal of the cartridge.  
         [0056]     The breech cap assembly  150  is next pivoted about the axis P-P in a direction K ( FIG. 8 ). In this manner, the breech cap assembly  150  is returned to the open position as shown in  FIG. 7 . The breech cap assembly  150  may be further lifted to the supported position of  FIG. 6 . The spent cartridge  30  is now partially exposed and dislodged and can be easily removed and discarded. After the cartridge  30  has been removed, a new cartridge can be inserted into the drive assembly  100  and the tool  45  again prepared and fired in the manner described above.  
         [0057]     The tool assembly  40  according to the present invention may provide a number of advantages. Because the drive assembly  100  is one integral or interconnected unit, it can be conveniently loaded and unloaded. In particular, it is not necessary to remove the breech cap assembly  150  or any portion thereof to access the breech chamber  102 . Nonetheless, when the breech cap assembly  152  is in the open position, the breech opening  108 B can be fully exposed to allow easy and effective insertion or removal of the cartridge. The drive assembly  100  may provide an effective, durable and reliable mechanism for safely releasing pressurized gas from the breech chamber  106  prior to opening the breech cap assembly  150 . Moreover, according to some embodiments including those illustrated in the figures, the drive assembly  100  requires that the gas release knob  190  be axially withdrawn relative to the breech  102  in order to withdraw the locking pin  179  before the breech cap sleeve  152  can be rotated relative to the breech  102 . This required sequence ensures that the piercer pin  184  will first be withdrawn from the cartridge, thereby ensuring that any pressurized gas will be released before the breech cap sleeve  152  is removed from its interlock with the circumferentially extending channels  116 A,  116 B.  
         [0058]     While the drive assembly  100  includes the rotatable housing  170  and the separately rotatable gas release knob  190 , in accordance with other embodiments of the invention the housing and the gas release knob may be integrally formed or assembled. However, the separately rotatable housing and gas release knob of the drive assembly  100  may provide enhanced safety and convenience. For example, the drive assembly  100  allows for release of pressurized gas by retracting the gas release knob  190  while still maintaining the breech cap sleeve  152  and the cartridge  30  in a secure arrangement by means of the housing  170 .  
         [0059]     As will be appreciated by those of skill in the art upon reading the description herein, the drive assembly  100  and other drive assemblies in accordance with the present invention may be used with explosive charge-actuated tools of other designs.  
         [0060]     The foregoing is illustrative of the present invention and is not to be construed as limiting thereof. Although a few exemplary embodiments of this invention have been described, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the claims. Therefore, it is to be understood that the foregoing is illustrative of the present invention and is not to be construed as limited to the specific embodiments disclosed, and that modifications to the disclosed embodiments, as well as other embodiments, are intended to be included within the scope of the appended claims. The invention is defined by the following claims, with equivalents of the claims to be included therein.