Pneumatic ground-piercing tool

Реферат: A self-propelled impact boring tool which has a simplified tail assembly so that the tool can be readily assembled and dissembled to allow replacement of worn parts. Such a tail assembly includes a nut and an end cap which can be secured together by a series of conventional bolts which extend into threaded holes in the nut. The nut, which is screwed into the rear end of the tool body, can be clamped in position with the screws with far less torque than would otherwise be required with a conventional, unitary tailpiece. A striker having a simplified, tubular construction is provided. Such a striker has an annular impact surface and radial ports at both ends of the striker which communicate with frontwardly and rearwardly opening recesses in the striker, respectively. Identical, readily replaceable bearing seals are provided near opposite ends of the striker. The striker may also have an internal cavity in which a vibration dampen-ing material may be disposed. An improved stepped air inlet valve is threadedly coupled to the tail nut to provide a reversing function. A flexible tubular hose enters the rear of the tool and preferably extends all the way to the rearwardly opening recess in the striker, in which it is secured to the inside of a tubular bushing which engages the inner surface of the recess to provide the stepped end of the air inlet. An adjuster sleeve having exterior threads couples the hose to the threaded central hole of the tail nut. The adjuster sleeve and nut may be coupled by a large pitch, double-helix thread-ing, so that the tool can be switched to reverse mode with fewer turns of the hose, and with less likelihood of becoming jammed. The tool body is formed by swaging a steel tube to form the tapered nose of the tool. This process results in less wasted steel as compared to con-ventional machining of a solid steel bar to form the body, which is the largest single part of the tool.