The present invention relates to a power actuated fastening tool for driving a fastener, such as a nail, into a substrate, such as a concrete beam.

Power actuated tools for driving a fastener into a substrate conventionally comprise a barrel from which the fastener is expelled by means of a piston driven by detonation of an explosive charge. The barrel is mounted for axial movement within a receiver assembly or body of the tool and after firing can be moved forwardly of the receiver assembly in order to reset the piston into the rear end of the barrel, the barrel with the piston then being retracted back into the receiver assembly in preparation for the next detonation.

In one previously proposed tool of this type, the barrel comprises separate front and rear sections, the rear section being telescopically mounted within the front section to permit limited axial movement between the two sections. The construction of the barrel in two separate sections facilitates manufacture of the barrel and the

provision for limited axial movement between the front and rear sections enables recoil on firing of the tool to be absorbed by relative axial movement between the two sections to an extended configuration. In this previously proposed tool, the two sections of the barrel are held in assembled relationship by means of a spring clip which fits over the front barrel section and lies behind, an abutment face at the forward end of the rear barrel section. The clip acts to limit forward movement of the front barrel section relative to the rear section. When the barrel is drawn by the operator forwardly of the receiver assembly to reset the piston, the clip, upon engaging the abutment face at the forward end of the rear barrel section, causes the rear barrel section to be drawn forwardly with the front section. The spring clip is normally formed out of relatively thin sheet metal and is subjected to a hammer-like action each time the barrel is drawn forwardly of the receiver assembly to reset the piston and tends to distort, which can cause fouling between the two sections of the barrel and also between the barrel and the receiver assembly when the barrel is retracted back into the receiver assembly.

According to the present invention there is provided a power actuated tool comprising a barrel having a piston for driving a fastener into a substrate upon firing of an explosive charge, the barrel being mounted for axial movement within a body of the tool whereby to permit resetting of the piston in the rear of the barrel after firing by withdrawing the barrel forwardly of the body, wherein the barrel comprises front and rear sections mounted for limited

telescopic movement one relative to the other to an extent sufficient to absorb recoil on firing of the tool, and a plurality of separate retainer elements interposed between a forwardly-facing abutment surface of the front barrel section and a rearwardly-facing abutment surface of the rear barrel section to cause entrainment of the rear barrel section with the front barrel section when the latter is drawn forwardly of the body in order to reset the piston, said retainer elements being held by means of a removable clip carried by the front barrel section.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:-

Figure 1 is a side view, partially in section, of a barrel assembly of a power actuated tool in accordance with the invention, the barrel assembly being shown with telescopic front and rear barrel sections in a contracted condition;

Figure 1A shows, to an enlarged scale, a detail of Figure 1.

Figure 2 is a section similar to Figure 1 but showing the telescopic sections in an extended condition during resetting of the piston; and

Figure 3 is an exploded perspective view showing the front and rear barrel sections prior to assembly.

As shown in the accompanying drawings, a

barrel assembly of a power actuated tool in accordance with the invention comprises rear and front barrel sections 2,4 which house a piston 6. A charge chamber 8 formed at a rear end of the barrel acts to receive an explosive charge which, on detonation, propels the piston 6 forwardly within the barrel in order to discharge a fastener at front end of the barrel into a work surface. The front barrel section 4 is mounted telescopically over the rear section 2 and the sections are movable between a fully contracted condition on firing the tool, in which a forward end face 2a of the rear barrel section 2 is engaged by an abutment face 5a on a fastener guide 5 rigidly mounted in the front barrel section 4 (see Figure 1), and an extended condition shown in Figure 2 in which the front barrel section 4 entrains the rear section 2 to enable both sections to be withdrawn from the receiver assembly or body (not shown) of the tool in order to reset the piston 6 into the rear end of the barrel.

As will now be described, the two barrel sections 2,4 are held in their assembled relationship by removable, barrel retainers which are, in turn, held by a retainer clip. In this construction, the retainers are solid and act to carry the hammer forces between the two barrel sections upon withdrawal of the barrel, the retainers serving also the prevent rotation of the forward barrel section relative to the rear section; the clip simply acts to releasably hold the retainers and does not carry any of the hammer forces generated during withdrawal of the barrel.

The forward end of the rear barrel section 2 is formed with diametrically opposed, longitudinally- extending, flats 10 (only one of which is shown in Figures 1 and 3) which terminate short of the forward end so that they are bounded at their forward end by a rearwardly facing abutment surface 12. The front barrel section 4 comprises at its rear end diametrically opposed slots 14 which are positioned to communicate with the respective flats on the rear barrel section. Each slot 14 receives a retainer segment 16 of a rigid or resilient material such as solid metal, ceramic, plastics or rubber, or a combination of such materials in a sandwich-like construction. Each retainer segment 16 comprises a part-cylindrical outer surface 18 which conforms to the cylindrical outer surface of the front barrel section and a plain inner surface 20 which is adapted to slide against the surface of the corresponding flat 10 on the rear barrel section 2. Each retainer segment 16 is stepped at its forward and rear ends to provide forward and rear lips 16a, 16b. The rear lip 16b is adapted to engage beneath the rear edge of the slot 14 as shown in Figures 1, 1A and 2 and the forward lip 16a is flush with the internal surface of an annular groove 24 formed in the front barrel section 4 immediately forwardly of the two slots 14. The annular groove 24 serves to house a C-shaped spring clip 26 which lies flush with the cylindrical external surface of the front barrel section 4.

In order to assemble the barrel, the front barrel section 4 is slid over the rear barrel section 2 until the slots 14 are facing the flats 10, with the slots 14 being located behind the abutment

surface 12 at the front end of the flats 10. The retainer segments 16 are then inserted into the slots 14, with their rear lips 16b being engaged beneath the rear edge of the slots 14. The retainer clip 26 is then inserted into the groove 24, with rearwardly extending flange-like portions 28 of the clip 26 engaging over the forward lips 16a of the two segments 16. In this manner, each retainer segment 16 is retained firmly, and non-movably, within the slot 14 by means of its two lips 16b, 16a which engage beneath the rear edge of the slot and the spring clip, respectively. When the front barrel section is moved forwardly during resetting of the piston 6, the forward face of each retainer segment 16 will strike against the abutment surface 12 at the front end of the corresponding flat 10 on the rear barrel section 2 in order to entrain the rear barrel section 2 and draw this forwardly of the receiver assembly. It'will be appreciated that the whole of the withdrawal force will be taken by the solid retainer segments 16 acting between the rear edges of the slots 14 in the front barrel section 4 and the abutment surface 12 on the rear barrel section 2 and that the spring clip 26 does not carry any of this force. Accordingly, the clip 26 is not subjected to forces tending to distort the clip and to thereby cause fouling or jamming as discussed in relation to the previously proposed construction.

Recoil on firing of the tool causes the main body of the tool to move rearwardly. Thus the rear barrel section 2 moves rearwardly relative the front section 4 and accordingly the two barrel sections move towards their expanded configuration on recoil.

It is to be noted that the maximum possible extent of the relative axial movement between the two barrel sections is sufficient to fully absorb the recoil before the retainer segments 16 engage the forward abutment surface 12. Typically a maximum permitted axial movement of about 45mm between the two barrel sections has been found sufficient to fully absorb the recoil.

The embodiment has been described by way of example only and modifications are possible within the scope of the invention.