Abstract:
An explosively actuated tool for driving a fastener into a substrate is mountable to the end of a pole-like handle to permit manipulation and actuation of the tool from a remote position. 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 forwardly the handle which loads and then releases a tiring mechanism of the tool to fire the charge. The tool has a safety lock device for inhibiting loading of the firing mechanism sufficiently to initiate firing unless the tool is orientated upwardly into a vertical or near vertical orientation.

Description:
RELATED APPLICATIONS 
   The present application is based on, and claims priority from, Australian Application Serial Number 2003903682, filed Jul. 16, 2003, the disclosure of which is hereby incorporated by reference herein in its entirety. 
   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”. Such a pole tool is disclosed in U.S. Pat. No. 5,465,893. In this previously proposed pole tool, 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. 
   The pole tool disclosed in U.S. Pat. No. 5,465,893 features a ball lock safety device which prevents the tool from being fired when the tool is orientated downwardly. Although the safety device is able to properly function to prevent firing in that orientation it is not designed to function to prevent the tool from being fired when in a substantially horizontal orientation or even in an orientation just below the horizontal. 
   The present applicants have determined that it is desirable for a lock device of this type to be effective over a range of orientations of the tool and particularly when the tool is orientated approximately horizontally which is the most likely orientation at which accidental or unintentional actuation is likely to arise. 
   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 a fastener is fired by firing of an explosive charge, a firing mechanism actuable by forwards displacement of a pole-like handle attached to a rear end of the tool to permit manipulation and actuation of the tool from a remote position, and a safety lock device for inhibiting actuation of the firing mechanism when the tool is orientated substantially horizontally or downwardly from the horizontal, said lock device comprising a locking ball moveable under gravity in response to the orientation of the tool, into a position in which it inhibits operation of the firing mechanism. 
   In a 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 tool housing, and the ball of the lock device inhibits firing by movement into a position in which it prevents forwards movement of said structure sufficient to effect firing when the tool is orientated substantially horizontally or downwardly from the horizontal. 
   In a practical embodiment of the invention, the said structure includes a coupling to which the pole-like handle is attached and the coupling is slidably mounted within an enclosure at the rear end of the tool housing, with the ball being located in a space defined between the coupling and a rear face of the enclosure such that in a firing-inhibiting position of the ball, the ball will lie against said rear face to prevent forwards displacement of the coupling to a position adjacent said rear face at which firing would otherwise be enabled, a forward face of the coupling providing a chamber into which the ball can move at predetermined orientations of the tool to thereby permit the coupling to move into the position adjacent said rear face and at which firing is enabled. 
   Particularly advantageously, a forward end face of the coupling is configured to provide a surface leading into the chamber and along which the ball will roll into the chamber when the tool is orientated vertically upwardly or within a predetermined angle to the vertical, and the chamber is defined by a circumferential surface along which the ball will roll out of the chamber when the tool is subsequently lowered to a substantially horizontal inclination. 
   In a practical form of the invention the circumferential surface defining the chamber is of conical form with the axis of the surface lying longitudinally of the tool. The chamber itself is of annular form extending around a firing pin spring support forming part of said structure and to which the coupling is connected. In this practical form of the invention, forwards displacement of the coupling and thereby the firing pin spring support to a position at which firing is enabled corresponds to movement of the firing pin spring support into a forwards position at which a firing pin pawl is caused to displace thereby releasing the firing pin itself. 
   Further according to the invention, there is provided an explosively actuated tool for driving a fastener into a substrate by firing of an explosive charge, the tool being of the type in which the tool is mountable 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 forwardly the handle which loads and then releases a firing mechanism of the tool to fire the charge, wherein the tool has a safety lock device for inhibiting loading of the firing mechanism sufficiently to initiate firing unless the tool is orientated upwardly into a vertical or near vertical orientation, the lock device comprising a locking ball which, when the tool is moved upwardly into a vertical or near vertical orientation, will roll by gravity into a position in which it is unable to inhibit loading and release of the firing mechanism and when the tool is lowered out of the vertical or near vertical orientation to a horizontal orientation the ball will roll out of said position into a position in which it will block forwards movement of the handle to an extent sufficient to prevent firing. 
   It is to be understood that tools in accordance with the invention might also have one or more further safety lock devices to inhibit or prevent firing in the event that other operational requirements are not fulfilled, for example if the front end of the barrel is not displaced into a rearwards position by pressing against the substrate. It is to be understood that if such other safety lock devices are incorporated, although the safety lock device of the invention may be in a condition to enable firing when the tool is held in the required orientation, actually to permit firing to take place the firing inhibiting or locking actions provided by such other safety lock devices must also be overcome. In other words it is not only necessary to ensure that the tool is held in the required orientation to permit operation but also other actions on which the or each other safety device is dependent must also be undertaken. 

   
     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 schematically the rear part of a pole tool incorporating a ball lock safety device in accordance with a preferred embodiment of the invention; 
       FIG. 2  shows schematically the configuration of a ball of the lock device when the tool is orientated vertically upwardly; 
       FIG. 3  shows the rear part of the tool and illustrates the configuration of the ball when in a position to inhibit firing when the tool is orientated approximately horizontally; 
       FIG. 4  is a view similar to  FIG. 2  but showing the position of the ball when the tool has not been moved into an upright position within a predetermined angle of the vertical; and 
       FIG. 5  is a view similar to  FIGS. 2 and 4  and showing the position of the ball when the tool is orientated approximately horizontally. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   A pole tool in accordance with the preferred embodiment of the invention is of the type disclosed in U.S. Pat. No. 5,465,893 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 rear part of the tool housing  2 . A barrel (not shown) slidably mounted in the forward part of the housing contains a fastener driving piston and a charge chamber is formed at the rear end of the barrel. The barrel is biased into a forwards position by a compression spring mounted within the housing. A receiver body  4  for receiving an explosive charge carried by a charge strip in the manner illustrated in U.S. Pat. No. 5,465,893 and also in EP 1197301 is mounted in the housing  2  rearwardly of the rear end of the barrel when in a forwards position. 
   The receiver body  4  mounts a firing pin  6  which is held in a retracted READY position (as shown in  FIG. 1 ) by a retractable spring loaded pawl  8  mounted within the firing pin  6  and releasably engageable with the rear end of the receiver body  4 . The firing pin  6  is associated with a return spring  10  which operates to return the firing pin  6  to the READY position after firing. A firing pin spring  12  is housed within a tubular support  14  which is mounted within the tool housing  2  for sliding movement over the firing pin  6 . At its rear end the support  14  carries an outer coupling  16  to which the pole-like handle  18  can be releasably attached. The coupling  16  is itself guided for sliding movement within a retaining collar  20  defining an enclosure at the rear end of the housing  2 , and the collar  20  also provides sliding support for the firing pin spring support  14 . 
   In operation, when the forward end of the barrel is placed against the substrate by manipulating the pole  18 , and axial force is applied via the pole  18 , the barrel is displaced inwardly in which its charge chamber moves over and encloses the explosive charge held in the operative position in the receiver body  4 . At this point further axial force applied by the pole  18  displaces the firing pin spring support  14  forwardly along the firing pin  6  thereby loading the firing pin spring  12 , the firing pin  6  being held in its retracted READY position by the spring loaded pawl  8 . When the forward end of the firing pin spring support  14  meets the pawl  8 , the pawl  8  is caused to retract thereby releasing the firing pin  6  for rapid movement forwardly within the receiver body  4  in order to detonate the explosive charge. After the tool has been fired and released from the substrate, the barrel is returned forwardly to its original position by the barrel return spring, and the firing pin spring support  14  is moved rearwardly to its original position by the firing pin return spring  10 . The firing pin  6  itself is entrained by the support  14  during this movement and is thereby returned to its retracted READY position with the spring loaded pawl  8  projecting outwardly into engagement with the rear edge of the receiver body  4 . 
   In accordance with the invention the tool has a ball lock safety device which is effective to prevent forwards movement of the firing pin spring support  14  by an extent sufficient to cause release of the firing pin pawl  8  except when the tool is orientated vertically or at an inclination above the horizontal. The lock device comprises a ball  22  housed within an annular chamber  26  defined between the coupling  16  and the retaining collar  20  within which the coupling  16  is mounted for sliding movement. As shown in  FIG. 1 , the ball  22  lies between a rear face  20   a  of the collar  20  and the forward end portion of the coupling  16 . The coupling  16  is shaped to provide an annular chamber  28  lying rearwardly of the front face  16   a  of the coupling and in which the ball  22  is held captive at certain orientations of the tool as will be subsequently described; this is shown in  FIG. 2 . With the ball  22  held captive within the chamber  28 , the coupling  16  is able to move forwardly to a position in which its front face  16   a  will lie in abutting engagement with, or closely adjacent, to the rear face  20   a  of the collar  20  and when in that position the firing pin spring support  14  attached to the coupling  16  will have moved sufficiently far forwardly to have caused release of the firing pin pawl  8 . At other orientations of the tool as will be subsequently explained, the ball  22  will assume a position in which it is trapped between the front face  16   a  of the coupling  16  and the rear face  20   a  of the collar  20  thereby inhibiting movement of the coupling  16  and thereby the firing pin spring support  14  by a distance sufficient to cause release of the firing pin pawl  8 ; this is shown in  FIG. 3 . It is to be noted that the rear face  20   a  of the collar  20  is profiled to ensure that when the ball  22  is pushed against the rear face by the forwards movement of the coupling  16 , the ball will be held captive in the outer peripheral part of the rear face  20   a  and can not thereby displace radially inwardly which would have the effect of releasing the locking effect which would otherwise be provided thereby. 
   As will be described, the design of the chamber  28  and in particular the outer wall  28   a  of the chamber  28  and which is of a conical shape is critical to the operation of the lock device. Likewise, the design of the front face  16   a  of the coupling  16  and the inclination of that front face leading into the outer wall  28   a  of the chamber  28  is important. 
   To enable the tool to be fired, the tool must first be moved to an orientation in which the ball  22  is caused by gravity to roll into the chamber  28 . With the configuration shown, this means that the tool must be held upwards vertically or close to the vertical. In that condition the front face  16   a  of the coupling will incline downwardly towards the chamber  28  so that the ball will roll along the face  16   a  into the chamber  28 . The maximum angle at which the tool can be held from the vertical while still enabling the ball  22  to roll into the chamber  28  will depend on the angle of inclination α of the front face. That angle should be as small as possible consistent with ensuring that the ball  22  will always roll into the chamber  28  when the tool is orientated upwards either vertically or close to the vertical. In practice that angle will be around 10° and an angle of that general order will ensure consistent and reliable operation.  FIG. 4  shows that when α is 10° and the tool is held at an inclination of 15° to the vertical the ball  22  will not roll into the chamber  28  until the tool is inclined closer to the vertical. When the ball  22  has rolled into the chamber  28 , the tool is able to be fired as long as the ball  22  remains in the chamber  28 . However if the tool is then lowered from the vertical orientation towards a more horizontal orientation, the outer wall  28   a  of the chamber  28  will incline closer to the horizontal until it reaches a point at which the lower part of the wall  28   a  on which the ball  22  will rest will be inclined downwardly to the horizontal whereby the ball  22  will roll out of the chamber  28 .  FIG. 5  illustrates the tool when orientated horizontally and it will be seen that the wall  28   a  has a significant downwards inclination at that orientation. It will therefore clearly be understood that when the tool is lowered from the vertical a situation will be reached that the downwards inclination of the wall  28   a  will be sufficient to cause the ball  22  to roll out of the chamber  28  before the tool actually reaches the horizontal. The inclination of the  tool above the horizontal at which the ball  22  will roll out of the chamber  28  is determined by the angle β, the inclination of the wall  28   a  relative to the axis of the tool. While that angle should be as large as possible to ensure that the ball  22  will roll out of the chamber  28  while the tool is still at a substantial inclination above the horizontal, nevertheless in practice the inherent size limitations of the tool and associated structure do impose a practical limit on the size of that angle. It is also to be noted that the size of the angle β will affect the radial depth of the front face  16   a . As it is this face which will push the ball  22  against the rear face  20   a  of collar  20 , the face  16   a  must be of a sufficient depth relative to the diameter of the ball to ensure reliable operation and this will impose constraints on the inclination of the wall  28   a . However even with these constraints, the inclination can be configured to ensure that the ball will not remain within the chamber when the tool is inclined upwardly to the horizontal by an angle of less than approximately 10°. 
   Accordingly, in the tool thus described, to permit firing the tool must be orientated upwardly either vertically or close to the vertical to permit the ball to roll into the chamber and normally this would occur as part of the proper sequence of use of the tool whereby the operator orientates the tool substantially vertically towards a ceiling by manipulating the pole, and then applies the forward end of the barrel against the ceiling and pushes the pole upwardly to cause the barrel to displace inwardly to enclose the explosive charge and to drive the firing pin support forwardly to load the firing pin spring and cause release of the firing pin pawl. 
   In the event that the operator orientates the tool substantially vertically upwards to cause movement of the ball into the chamber but decides not to perform the further actions needed to actuate the tool, the tool will be disabled from subsequent actuation as soon as it is lowered to the horizontal to an extent sufficient to enable the ball to roll out of the chamber which in the practical example given is approximately 10° above the horizontal although depending on the design parameters could, and desirably should, occur at a greater angle to the horizontal. Nevertheless the major risk of inadvertent operation is likely to occur with the tool inclined by less than about 10° to the horizontal and operation in those circumstances will thereby be inhibited. 
   The ball lock safety device particularly described can readily be incorporated into some existing pole tool designs and all that is necessary to achieve this is to re-configure the collar which is attached to the rear end of the tool housing and to re-configure the pole coupling in the manner that has been described. However, other configurations of the ball lock safety device could be provided. For example, the ball could act in the manner described between the firing pin spring support and an appropriately shaped abutment surface within the interior of the tool housing. 
   The embodiment has 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.