Elongated-member-driving apparatus – With interlock means
Patent
1980-10-28
1983-05-24
Bell, Paul A.
Elongated-member-driving apparatus
With interlock means
173169, B25C
Patent
active
043846688
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
TECHNICAL FIELD
The present invention relates to a pneumatic type impact tool in which an impact piston-cylinder mechanism is driven by compressed air, while a part of the compressed air is used for a controlling purpose, such that a rod-shaped or blade-shaped driver rigidly connected to the impact piston drives fasteners such as nails, staple or the like one from a magazine by one from a nose. More particularly, the invention is concerned with a safety system for pneumatic impact tool of the type described, capable of avoiding injury to the personal body by mis-shooting of the fastener.
BACKGROUND ART
There have been proposed various types of pneumatic nail drivers as a kind of pneumatic impact tool driven and controlled by compressed air containing lubricating oil. One of the known nail driver has a grip formed as a part of the housing, for an easier handling and transportation by the operator. The housing contains a piston-cylinder mechanism, head valve for starting or stopping the supply of compressed air to the impact piston-cylinder mechanism, and a manually operable trigger valve for controlling the head valve. More specifically, the trigger valve is switched by a manual operation of a trigger lever, so that the head valve is switched to the position for supplying the compressed air. In consequence, the upper chamber of the impact cylinder formed at the top dead center of the impact piston is communicated with a compressed air source through an air hose, so that the compressed air is instantaneously supplied from a compressed air chamber into the upper chamber in the impact cylinder, so that the pressure of the compressed air acts on the impact piston to instantaneously drive the impact piston to the bottom dead center of the impact piston thereby to drive the nail into an object.
Another type of known pneumatic nail driver has a rod-shaped driver adapted to reciprocatingly move in a nose. A trigger safety arm mechanically connected to the trigger lever is movable reciprocatingly in the longitudinal direction of the nose. As the trigger lever is manually actuated while pressing the contact surface of the trigger safety arm against the object surface, the impact piston is moved to drive the nail into the object surface.
Each of such known pneumatic nail drivers incorporates a head valve piston adapted to move between the top dead center and the bottom dead center by the difference of the total pressure of air acting on the upper and lower surfaces, and a valve spring adapted for assisting the resetting movement of the head valve piston. The valve spring usually keeps the head valve piston stationary at the bottom dead center, so as to disconnect the upper chamber of the impact cylinder from the compressed air storage chamber. Therefore, when there is no time lag of the application of compressed air on the upper surface of the head valve piston in relation to the application of compressed air to the lower surface of the same, the compressed air is not allowed to flow into the upper chamber of the impact cylinder even at the instant at which the compressed air is supplied to the compressed air storage chamber, so that the accidental discharge of the impact piston (referred to as initial discharge of the impact piston, hereinunder) is avoided. However, in the pneumatic nail driver to which the invention pertains, a part of the lower surface of the head valve piston is directly exposed to the compressed air storage chamber, while, the compressed air supplied from the compressed air storage chamber via a control air passage including a trigger valve generating a throttling effect is applied to the upper surface of the head valve piston. As a result of this arrangement, at the instant of supply of the compressed air to the compressed air storage chamber, the compressed air acts on the lower side of the head valve piston earlier than on the upper side of the same. In consequence, the force of the compressed air acting on the lower side of the head valve piston drives the latter toward the
REFERENCES:
patent: 4106750 (1978-08-01), Karden
patent: 4165676 (1979-08-01), Siegmann
patent: 4194664 (1980-03-01), Siegmann
Hitoshi Matsumoto
Mitsuhiro Takatsuru
Tutomu Sato
Bell Paul A.
Max Co. Ltd.
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