Power actuated tools with power adjustment means

Details Power actuated tools with power adjustment means Power actuated tools with power adjustment means

1998-12-23

2000-03-07

Vo, Peter

Elongated-member-driving apparatus

Explosive-type driving means

With plunger

227 9, B25C 114

Patent

active

060328460

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The present invention relates to power actuated tools for driving fasteners into a substrate, and more particularly to such tools which operate by detonation of an explosive charge.
Power actuated tools for driving fasteners such as nails or pins, into a substrate such as a concrete or steel beam, conventionally comprise a barrel from which the fastener is expelled by means of a piston driven by detonation of an explosive charge.
In power actuated tools of this general type, the power output of the tool can be controlled by utilising explosive charges of different power. Alternatively a variable power adjustment system may be incorporated into the tool itself. Such power adjustment systems may operate by altering the volume of the firing chamber defined in the barrel of the tool rearwardly of the piston, or by controlled venting of combustion gases from the portion of the barrel rearwardly of the piston. The present invention relates to an improved power adjustment system which operates by providing a controlled venting of the combustion gases.


SUMMARY OF THE INVENTION

According to the present invention there is provided an explosively-actuated tool for use in setting fasteners into a substrate, comprising a barrel, a driving piston mounted within the barrel for driving the fastener into a substrate upon detonation of an explosive charge positioned at or adjacent the rear of the barrel, a firing chamber defined in the barrel rearwardly of the piston, and means for controlling the power of the tool by controlled venting of combustion gases from the firing chamber, said power control means comprising an exhaust port arrangement leading from the firing chamber through the wall of the barrel and a control member for controlling the effective open area of the exhaust port arrangement.
Advantageously, the exhaust port arrangement comprises one or more radial bores extending through the wall of the barrel. When there are two or more such bores, the bores are in axially-spaced arrangement relative to the barrel.
Advantageously, the exhaust port arrangement opens into an axial bore or other passage within the wall of the barrel, with the control member being defined by a control rod which extends into the passage by an adjustable distance.
Preferably, the control rod extends into the passage from the real end of the passage with the front end of the passage being open for discharge of the gases from the firing chamber via the exhaust port arrangement. Advantageously, the position of the control rod within the passage is controlled by a mechanism operative to cause infinite or stepwise movement of the control rod within the passage. Such a mechanism may be a screw mechanism.
Particularly advantageously, the end of the control rod is provided with a concave arcuate control edge which provides a relatively uniform relationship between displacement of the control rod and the degree of opening of the exhaust port arrangement. Such a control edge can be formed by a simple chamfer at the end of a cylindrical control rod with the passage also being cylindrical.


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 is a schematic sectional view showing the rear end portion of the barrel of a power actuated tool in accordance with the preferred embodiment of the invention and illustrating in particular a control mechanism for providing controlled venting of combustion gases from the firing chamber;
FIG. 2 is an enlarged view similar to FIG. 1 and illustrating in greater detail a control rod of the control mechanism and its relationship with the exhaust port leading from the firing chamber; and
FIGS. 3A to 3C illustrate schematically the progress of the control edge of the control rod across the array of holes forming the exhaust port.


DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows part of the barrel 2 of a power actuated tool, the barrel 2 being mounted within a main

REFERENCES:
patent: 2765464 (1956-10-01), Weichold
patent: 3204400 (1965-09-01), Kvalve
patent: 4119257 (1978-10-01), Combette et al.
patent: 4134527 (1979-01-01), Termet
patent: 4153192 (1979-05-01), Jochum
patent: 4196834 (1980-04-01), Beton
patent: 4374567 (1983-02-01), Combette et al.
patent: 4382533 (1983-05-01), Buechel et al.
patent: 4577793 (1986-03-01), Jochum
patent: 4595134 (1986-06-01), Jochum
patent: 4883212 (1989-11-01), Philipp
patent: 5657919 (1997-08-01), Berry et al.

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