Abstract:
An explosively actuated tool for driving a fastener into a substrate is of the type in which the tool is mounted to the end of a pole-like handle to permit manipulation and actuation of the tool from a remote position wherein actuation of the tool occurs by pushing the forward end of a barrel of the tool against the substrate using the handle and then pushing on the handle which loads and then releases the firing mechanism of the tool. A lock device is incorporated to prevent “air firing” of the tool by pushing the handle without the forward end of the barrel being pressed against the substrate. The lock device has a lock member which cooperates with the firing pin or firing pin spring support of the firing mechanism to lock one or other of those components unless the lock member is released by a prior displacement caused by retraction of the barrel when its forward end is pressed against the substrate.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an explosively actuated tool for driving a fastener, such as a pin, into a substrate, for example of concrete or steel. 
   2. Description of the Prior Art 
   Explosively actuated tools for driving a fastener, such as a pin, into a hard substrate, such as of concrete or steel, are in common use and operate by detonation of an explosive charge. In most prior tools of this type, detonation of the charge drives a piston within a barrel of the tool and the piston, in turn, drives the fastener which is positioned within the forward end of the barrel prior to firing. Tools of this general type will typically have a pistol grip and the tool is actuated by operation of a trigger associated with the grip. 
   A version of the tool has been developed for driving fasteners into substrates remote from the operator, for example for driving a fastener into a ceiling while the operator is still standing on the floor beneath the ceiling or for driving a fastener into a remote wall. This version of the tool is designed to be mounted at one end of a long handle or pole held by the operator. This version of the tool is termed a “pole tool”. Pole tools are disclosed in U.S. Pat. No. 5,465,893 and European patent application 1 197 301 (AU 6997/01). In these previously proposed pole tools, the barrel, which contains the fastener driving piston, is slidably mounted within the housing of the tool. The barrel is biased to a forwards position and when the forward end of the barrel is pressed against the substrate the barrel is caused to retract into the housing so that a charge chamber formed at the rear end of the barrel moves over and encloses the explosive charge. This occurs by the operator manipulating the pole so as to press the forward end of the barrel against the substrate. The pole itself is mounted to a firing pin mechanism of the tool and further pressing movement applied to the tool via the pole loads the firing pin mechanism which, when a predetermined loading is reached, releases the firing pin to detonate the charge. 
   With these previously proposed pole tools it is possible to fire the tool by holding the housing of the tool with one hand and pressing the pole inwardly with the other hand in order to load and then release the firing mechanism, so-called “air firing” of the tool. Although the consequences of this are unlikely to be particularly serious as, if the tool is operated in this mode, the barrel will not have been displaced rearwardly so that its charge chamber encloses the charge and as a result the power output of the tool will be greatly diminished, nevertheless the fact that the tool is able to be fired in this mode does give rise to concern. 
   SUMMARY OF THE INVENTION 
   According to the present invention there is provided an explosively actuated tool for driving a fastener into a substrate, said tool having a barrel from which the fastener is fired, the barrel being mounted within a housing to project from the forward end of the housing and the barrel being displaceable rearwardly relative to the housing when the forward end of the barrel is pressed against the substrate, a firing mechanism actuable by forwards displacement of a pole-like handle attachable to the rear end of the tool to permit manipulation and actuation of the tool from a remote position, and a lock device for preventing actuation of the firing mechanism to fire an explosive charge absent displacement of the barrel into a predetermined rearwards position within the housing consequent on pressing the forward end of the barrel against the substrate. 
   In the preferred embodiment of the invention, the firing mechanism includes a firing pin and a firing pin spring which is loaded by forwards movement of structure displaced by moving the handle forwardly relative to the housing. 
   In one form, the lock device has a lock member which prevents forwards movement of said structure sufficient to effect firing, the lock member being released in response to displacement of the barrel rearwardly into said predetermined rearwards position. 
   Advantageously the predetermined rearwards position of the barrel in which release of the lock member is effected is a rearmost position in which a charge chamber at the rear end of the barrel encloses the explosive charge. The lock member is normally held in its locking position and is displaced into its released position in response to movement of the barrel into its rearmost position. 
   In one practical form of the embodiment this displacement is achieved by engagement of the lock member with a rear end part of the barrel as the barrel moves into its rearmost position. 
   Preferably the lock member is a lock lever pivotal between its locking and released positions and spring biased into its locking position. Advantageously the locking lever is displaced to its released position by a camming action when the rear end part of the barrel engages a forward end of the lever as the barrel moves into its rearmost position. The camming action can be provided by a cam surface on the lever co-operating with a cam surface within the tool housing. 
   In another form, the lock device has a lock member operative to lock the firing pin against release in the event of forwards movement of said structure absent displacement of the barrel into said predetermined rearwards position, the locking effect of the lock member being disabled in response to displacement of the barrel into said predetermined rearwards position. 
   Advantageously, the predetermined rearwards position of the barrel in which action of the lock member is disabled is a rearmost position in which a charge chamber at the rear end of the barrel encloses the explosive charge. The lock member is normally held in a position in which a locking part thereof is in alignment with, or within, a locking recess in the firing pin and is displaced into its disabled position in response to movement of the barrel into its rearmost position. 
   In one practical form this displacement is achieved by engagement of the lock member with a rear end part of the barrel as the barrel moves into its rearmost position. 
   Preferably the lock member is a lock lever pivotal between its locking and disabled positions and spring biased into its locking position. In one practical form, co-operation between the said structure and the lock lever enables displacement of the locking lever into its locking position absent the required movement of the barrel into its rearmost position. Preferably, the lock lever co-operates directly with a firing pin support forming part of said structure, a part of the firing pin support normally closing the locking recess in the firing pin and then exposing the recess to permit engagement by the lock lever when the firing pin support displaces forwardly absent the required barrel movement. 
   Further according to the present invention, there is provided an explosively actuated tool for driving a fastener into a substrate, the tool being of the type in which the tool is mounted to the end of a pole-like handle to permit manipulation and actuation of the tool from a remote position wherein actuation of the tool occurs by pushing the forward end of a barrel of the tool against the substrate using the handle and then pushing on the handle which loads and then releases a firing mechanism of the tool, the firing mechanism including a firing pin, a firing pin spring, and a firing pin spring support by which the firing pin spring is loaded, wherein the tool has a lock device to prevent air firing of the tool by pushing the handle without the forward end of the barrel being pressed against the substrate, the lock device including a lock member which cooperates with the firing pin or firing pin spring support to lock one or other of those components unless the lock member is released by a prior displacement caused by retraction of the barrel when its forward end is pressed against the substrate. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     An embodiment of the invention will now be described by way of example only with reference to the accompanying drawings in which: 
       FIG. 1  shows diagrammatically part of a pole tool in accordance with one embodiment of the invention, in an at rest condition prior to firing; 
       FIG. 1A  shows an enlarged detail of  FIG. 1 . 
       FIG. 2  shows the tool when the barrel has been displaced into a rearmost position by pressing the forward end of the barrel against a substrate; 
       FIG. 3  shows the tool during loading of the firing pin mechanism shortly before firing; 
       FIG. 3A  is an enlarged detail of  FIG. 3 ; 
       FIG. 4  shows the condition of the tool when firing has occurred; and 
       FIG. 5  shows operation of a lock mechanism if the firing mechanism is attempted to be loaded to fire the tool without the barrel being pressed against the substrate; 
       FIG. 6  shows a pole tool with an alternative embodiment of lock mechanism, the tool being shown in at rest position prior to firing; 
       FIG. 6A  shows an enlarged detail of  FIG. 6 ; 
       FIGS. 7 and 8  show successive stages in operation of the lock mechanism if the firing mechanism is loaded without the barrel being pressed against the substrate; 
       FIG. 9  shows the tool during loading of the firing mechanism shortly before firing during correct operation of the tool; 
       FIG. 9A  shows an enlarged detail of  FIG. 9 ; 
       FIG. 10  shows the condition of the tool when firing has occurred. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   A pole in accordance with the preferred embodiment of the invention is of the type disclosed in U.S. Pat. No. 5,465,893 and EP 1 197 301 discussed above and only those parts of the tool which relate to the improvement provided by the present invention will be described in detail.  FIG. 1  shows schematically the tool housing  2  and the barrel  4  slidably mounted within the forward end of the housing  2 . The barrel contains a fastener driving piston (not shown) and the charge chamber at the rear end of the barrel  4  is shown at  6 . A compression spring  8  is mounted within the housing  2  to bias the barrel  4  into a forwards position. A receiver body  10  for receiving an explosive charge carried by a charge strip in the manner illustrated in the aforesaid patent specifications is mounted in the housing  2  rearwardly of the rear end of the barrel  4  when in its forward position. The receiver body  10  mounts a firing pin  12  which is held in a retracted READY position (as shown in  FIG. 1 ) by a retractable spring loaded pawl  14  mounted within the firing pin  12  and releasably engageable with the rear end of the receiver body  10 . The firing pin  12  is associated with a return spring  16  which operates to return the firing pin  12  to the READY position after firing. A firing pin spring  18  is housed within a tubular support  20  which is mounted within the tool housing  2  for sliding movement over the firing pin  12 . At its rear end the support  20  carries an outer coupling  22  to which the pole-like handle  24  can be releasably attached. The coupling  22  is itself guided for sliding movement within a retaining collar  26  at the rear end of the housing  2 , and the collar  26  also provides sliding support for the firing pin spring support  20 . 
   In operation, when the forward end of the barrel  4  is placed against the substrate by manipulating the pole  24 , and axial force is applied via the pole  24 , the barrel  4  is displaced inwardly from the position shown in  FIG. 1  to the position shown in  FIG. 2  in which its charge chamber  6  moves over and encloses the explosive charge held in the operative position in the receiver body  10 . This is the position as shown in  FIG. 2 , although for clarity of illustration the charge itself is not actually shown in that figure. At this point further axial force applied by the pole  24  displaces the firing pin spring support  20  forwardly along the firing pin  12  thereby loading the firing pin spring  18  (see  FIG. 3 ), the firing pin  12  being held in its retracted READY position by the spring loaded pawl  14 . When the loading in the firing pin spring  18  becomes sufficient to overcome the force of the spring which biases the pawl  14  outwardly to its engaged position with the receiver body, the pawl  14  is caused to retract thereby releasing the firing pin  12  for rapid movement forwardly within the receiver body in order to detonate the explosive charge as shown in  FIG. 4 . After the tool has been fired and released from the substrate, the barrel  4  is returned forwardly to its original position by the barrel return spring  8 , and the firing pin support  20  is moved rearwardly to its original position by the firing pin return spring  16 . The firing pin  12  itself is entrained by the support  20  during this movement and is thereby returned to its retracted READY position with the spring loaded pawl  14  projecting outwardly into engagement with the rear edge of the receiver body  10 . 
   In accordance with the invention, the tool has a lock mechanism which prevents the forwards movement of the firing pin spring support  20  and thereby the loading of the firing pin spring  18  if the barrel  4  has not been displaced into its rear position (the position shown in  FIG. 2 ) by pressing the forward end of the barrel  4  against the substrate. Thus the tool cannot be “air fired” merely by applying a forwards force to the pole  24  while the body  2  of the tool is held. 
   The lock mechanism is provided by a lock lever  26  mounted to the receiver body  10  for pivotal movement and also for axial movement. For this purpose a pivot pin  28  (see  FIG. 1A ) carried by the receiver body  10  is located within an axial slot in a forward end of the lock lever  26 . A compression spring  30  mounted within the slot bears against the pivot pin  28  to apply an axial bias to the lock lever  26  to displace the lever into a forwards position in which its forwards end lies in the path of movement of the rear end of the barrel  4  as it approaches its rear limit position shown in  FIG. 2  when the forward end of the barrel has been pressed against the substrate. The lock lever  26  is also subject to a pivotal bias provided by a leaf spring  32  so that the rear end of the lock lever  26  is biased into a radially inner position in which a stop  34  on the lever  26  lies forwardly of a shoulder or other abutment  36  on the firing pin spring support  20 . This is best seen in  FIG. 1A . The rear end of the lock lever  26  is ramped at  26   a  and co-operates with a ramp surface  40  within the tool body. When the barrel  4  is displaced rearwardly into the position shown in  FIG. 2  which occurs when the forward end of the barrel  4  is pressed against the substrate (this represents the correct and intended mode of operation), as the barrel  4  approaches its rearmost position its rear end will engage the forward end of the lock lever  26  and displace the lever  26  rearwardly against the bias of the spring  30 . As a result of the co-operation between the ramped rear end  26   a  of the lever and the fixed ramp surface  40 , the rear end of the lever and thereby the stop  34  will be pivoted radially outwardly against the bias of the leaf spring  32 . This outwards displacement takes the stop  34  outside of the path of movement of the shoulder  36  on the firing pin spring support  20  so that the firing pin spring support  20  can be displaced forwardly and the firing pin spring  18  loaded in the manner previously described to fire the tool. This “released” position of the lock lever  26  is shown in  FIGS. 2 ,  3 , and  3 A. However, if the firing pin spring support  20  is moved forwardly in an attempt to “air fire” the tool without the forward end of the barrel  4  having been pressed against the substrate to displace the barrel  4  rearwardly, the lock lever  26  will remain in a position (its locking position) in which its stop  34  will lie forwardly of the shoulder  36  on the firing pin spring support  20  and will act to limit the forwards movement of the support  20  to an extent sufficient to prevent firing of the tool. This is the condition shown in  FIG. 5 . 
   The ramped surface  26   a  at the rear end of the lock lever  26  and the co-operating fixed ramp surface  40  provide a camming effect which causes displacement of the stop  34  on the lock lever out of the path of movement of the shoulder  36  consequent on axial displacement of the lock lever  26  as the barrel moves into its rear position. It will be appreciated that other camming arrangements can be used to achieve that effect. Likewise, other forms of spring and mounting arrangement can be used for the lock lever. Although as described the lock lever acts against the firing spring support, in alternative arrangements it can act against other components displaced by pressing the handle to fire the tool, for example coupling  22  and in that case the lever may be replaced by a suitable linkage. 
   After firing of the tool and release of the forward end of the barrel  4  from the substrate whereby the barrel  4  is returned to its forward position and the firing pin spring support  20  is returned to its rearward position, the spring  30  will return the lock lever  26  to its forward position in which its stop  34  lies forwardly of and in the path of movement of the shoulder  30  on the firing pin support  20  as shown in  FIG. 1A . 
   In the event that the tool is accidentally dropped from a substantial height and the end of the pole impacts upon the ground, the lock mechanism will take the full impact load. Although the lock mechanism described above can be designed with sufficient robustness to withstand such an impact load to comply with relevant standards (Australian Standard AS1873 requires that an explosively actuated tool will not be subject to charge indentation by the firing pin if dropped from a height of 3 meters), nevertheless due to restrictions in the space available within the interior of the tool, there are limits as to the extent to which the durability of the components can be improved by increasing their size. 
   In the embodiment shown in  FIGS. 6 to 10 , the lock lever  26  locks onto the firing pin  12  rather than the firing pin spring support  20 . Accordingly, the lock lever  26  will not be directly subject to an impact load imparted from the pole end of the tool if the tool is dropped. Rather, the impact load will be absorbed by the forwards displacement of the firing pin spring support  20  which is still able to be moved forwardly and will be cushioned by compression of the firing pin spring  18  and the firing pin return spring  16 , but due to the lock imposed on the firing pin itself by the lock lever  26 , the firing pin is held against release under the force of the firing pin spring. The lock mechanism of this embodiment will now be described in detail. 
   In comparison with the previous embodiment and with initial reference to  FIGS. 6 and 6A , the lock lever  26  has a locking rear end portion  26   b  which inclines inwardly towards the firing pin  12 . The firing pin  12  is formed with a locking recess  12   a  which is aligned with the locking end  26   b  of the lock lever  26  when the firing pin  12  is in its retracted READY position and when the lock lever  26  itself is in its forward position which it assumes prior to its rearwards displacement when the barrel has not been displaced into its rear position by pressing its forward end against the substrate. However in this mode, the locking recess  12   a  in the firing pin  12  is covered by a forward part  20   a  of the firing pin spring support  20  and the locking end portion  26   b  of the lock lever is biased radially inwardly against the outer surface of that part by the leaf spring  32 . 
   In the event that the firing pin spring support  20  is displaced forwardly without first pressing the forward end of the barrel against the substrate, as may arise either if an operator attempts to “air fire” the tool or drops the tool onto its pole end, the initial forwards displacement of the firing pin spring support  20  relative to the firing pin  12  causes the forward part  20   a  to displace forwardly away from the locking end  26   b  of the lock lever  26 , and an elongate slot  20   b  in the firing pin spring support  20  immediately behind that forward portion exposes the locking recess  12   a  in the firing pin  12  whereby the locking end  26   b  of the lock lever  26  displaces inwardly under the bias of leaf spring  32  to engage into the locking recess  12   a  and thereby lock the firing pin. This is shown in  FIG. 7 . There is some play between the locking end  26   a  of the lock lever  26  and the locking recess  12   a  and as further force is applied to the pole some further forwards movement of the firing pin  12  will occur under the compression force of the firing pin spring  18 , and the firing pin spring support  20  may displace forwardly to an extent sufficient to cause release of the firing pin pawl  14 , but engagement of the locking end  26   b  in the locking recess  12   a  will define a forward stop position for the firing pin  12  and past which the firing pin  12  cannot travel to fire the charge. This is shown in  FIG. 8 . Removal of the force applied to the pole allows the firing pin spring support  20  to retract and as the forward end  20   a  of the firing pin spring support retracts over the locking recess  12   a  in the firing pin  12  its rear edge engages the ramped forward surface  26   c  of the locking end portion  26   b  of the lock lever  26  and causes it to return to its radially outer position and also the firing pin returns to its original position (this is the configuration shown in  FIG. 6 ). 
   Under correct operation of the tool when the forward end of the barrel  4  is pressed against the substrate, as the barrel  4  approaches its rearmost position its rear end will engage the forward end of the lock lever  26  and displace the lever rearwardly so that its locking end  26   b  displaces rearwardly into the slot  20   b  in the firing pin spring support  20  behind the locking recess  12   a  to engage the outer surface of the firing pin  12 . This is shown in  FIGS. 9 and 9A . The firing pin  12  is thus able to be released when the firing pin spring support  20  has advanced sufficiently to release the firing pin by engagement of its forward end of the pawl  14 .  FIG. 10  illustrates the configuration after release of the firing pin. 
   It is to be noted that when the locking end  26   b  of the lock lever  26  has engaged into the locking recess  12   a  consequent on an attempt to “air fire” the tool, subsequent displacement of the barrel into the housing will not then enable firing. Firing can only be enabled by the correct sequence of operation described in the preceding paragraph. 
   In the form of embodiment as shown the locking end of the lock lever is in alignment with the locking recess in the firing pin in the at rest position but the recess is closed by the presence of the forward end portion of the firing pin spring support and against which the locking end rests. In a modified form of this embodiment, the locking end of the lock lever may actually engage within the locking recess in the at rest position and upon correct actuation of the tool the rearwards displacement of the lock lever which occurs upon the rearwards displacement of the barrel also causes the locking end of the lever to be moved out of the locking recess; this movement can be induced by a camming action. The firing pin is thereby in a condition to be released to fire the charge when the firing pin spring support has moved forward sufficiently to cause release of the firing pin pawl. 
   The configurations of the lock lever particularly described are particularly advantageous as they are able to be incorporated within existing designs of pole tool without extensive modification. 
   The embodiments have been described by way of example only and modifications are possible within the scope of the invention. 
   Throughout this specification and claims which follow, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers or steps but not the exclusion of any other integer or group of integers.