Fastener driving tool

1. An explosively actuated fastener driving tool comprising a barrel mounted to a receiver of the tool, a driving piston within the barrel for driving a fastener at the forward end of the barrel upon firing of the tool, and a retractor pawl assembly for resetting the piston into a rear end of the barrel by forward movement of the barrel relative to the receiver following firing, wherein the retractor pawl assembly comprises a retractor pawl having a head including a shoulder adjacent thereto, wherein said head is extendible through a slot in the barrel to engage and retain the piston during forward movement of the barrel, the pawl being mounted in a housing fixed relative to the receiver and being spring biased to move radially into and out of the interior of the barrel by movement of the barrel relative to the receiver, and a release member operable to fully withdraw the pawl from the barrel to permit removal of the barrel from the receiver, the release member being mounted to the housing in such a manner that in a normal condition of the tool it cannot be moved to a position at which the pawl assembly is detached from the receiver, and

a roll pin configured to engage said shoulder for retaining the pawl within the housing.

2. A tool according to claim 1 , wherein the release member is accessible externally from the tool and is mounted to the housing for movement between a first position for normal operation of the tool and a second position in which the pawl is fully withdrawn from the barrel when removal of the barrel from the receiver is required.

3. A tool according to claim 2 , wherein the second position is radially outwardly of the first position.

4. A tool according to claim 2 , wherein the release member remains mounted to the housing when in its second position.

5. A tool according to claim 2 , wherein the movement of the release member between its first and second positions includes a rotary component of movement.

6. A tool according to claim 5 , wherein the release member is threadedly mounted to the housing for movement between its first and second positions.

7. A tool according to claim 1 , wherein the release member is a cap accessible externally from the tool and rotatably mounted to the housing.

8. A tool according to claim 7 , wherein the cap is threadedly mounted to the housing and the pawl is linked to the cap such that the pawl is withdrawn from the barrel slot when the cap is unscrewed relative to the housing, the cap remaining attached to the housing in the withdrawn condition of the pawl with the pawl remaining linked to the cap.

9. A tool according to claim 8 , wherein the stop is removable using a tool, wherein the roll pin once removed from the retractor pawl assembly allows the cap with pawl linked thereto to be detached from the housing and removed.

10. A tool according to claim 8 , wherein the pawl includes an abutment which engages the roll pin when the pawl is in its withdrawn position from the barrel.

11. A tool according to claim 8 , wherein said pawl comprises a flattened face, and wherein the roll pin is engageable against said flattened face of the pawl to angularly locate the pawl relative to the barrel slot.

12. A tool according to claim 7 , wherein a compression spring for providing the spring bias to the pawl is mounted within the interior of the cap to act between the cap and the pawl.

13. A tool according to claim 1 , wherein in a ready-to-fire condition of the tool prior to cocking the tool, the pawl engages a detent in the barrel under its spring bias in order to retain the barrel against inadvertent forwards movement from the receiver.

14. An explosively actuated fastener driving tool of the type having a driving piston for driving a fastener at the forward end of a barrel upon firing of the tool, and a retractor pawl having a head including a shoulder adjacent thereto, wherein said head is extendible into the barrel for resetting the piston into a rear end of the barrel by forward movement of the barrel relative to the receiver following firing, wherein the pawl assembly is so constructed that the pawl can be withdrawn from the barrel to permit removal of the barrel for cleaning and maintenance while the pawl assembly remains attached to the tool to prevent components of the pawl assembly from being misplaced, wherein the pawl is mounted in a housing, and a roll pin configured to engage said shoulder for retaining the pawl within the housing.