Tools – Wrench – screwdriver – or driver therefor – Responsive to torque on work
Patent
1982-09-30
1984-07-31
Jones, Jr., James L.
Tools
Wrench, screwdriver, or driver therefor
Responsive to torque on work
B25B 2314
Patent
active
044622856
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a power tool and an associated mechanism for marking threaded fasteners such as bolts that have been torqued into a compatibly threaded hole by the power tool.
BACKGROUND ART
Conventional power tools, such as those used in the assembly of motor vehicles, generally comprise a pneumatic motor connected to a drive shaft that is adapted to carry a tool, such as a hexagonal drive socket for engaging a threaded fastener. Some known power tools incorporate marking means for visibly marking the fastener when the fastener has been tightened to a required torque. This visible indication can then be used for quality control purposes. In one such tool, the marking means comprises a spray device which delivers a quantity of liquid marking material sprayed from a jet onto the workpiece in the region of the fastener when the desired torque has been applied to the fastener. The use of a spray suffers from the disadvantages that the amount of liquid marking medium applied to the workpiece and the position at which the medium is applied are difficult to control. Thus, the tool itself can easily become contaminated with the marking medium, and, if the jet is not aligned correctly with the workpiece, the presence of the marking medium can be difficult to detect.
DISCLOSURE OF INVENTION
The present invention provides a power tool comprising a motor for rotating a drive shaft. The drive shaft is adapted to carry a tool at its torque head for engaging a threaded fastener and to carry a marking means for marking the fastener. The marking means comprises a marking stylus mounted for reciprocating movement along the torque axis into and out of contact with the fastener engaged in the tool carried by the torque head. Means are also included within the marking means for supplying a predetermined quantity of liquid marking medium to the marking stylus, for discharged therefrom onto the fastener, with each cycle of reciprocating movement of the marking stylus.
By arranging the marking stylus to reciprocate into and out of contact with the fastener and supplying predetermined quantities of marking medium to the stylus during each cycle of reciprocating movement, a controlled amount of marking medium can be deposited accurately onto the workpiece, thereby producing an accurate and reliable visible indication on the workpiece.
In the preferred embodiment of the invention, the marking stylus comprises a first piston mounted for reciprocal movement within a bore in the marking means. A marking head is carried by the first piston and the first piston contains a central conduit for conducting marking fluid from one end of the first piston to the marking head at the other end. The supply means includes a second piston mounted for reciprocal movement in the bore in line with the first piston so as to define a chamber between the first and second pistons. The second piston contains a conduit, for conducting marking fluid from a reservoir at one end of the second piston to the defined chamber, and valve means for controlling the flow of marking fluid through the chamber. The relative reciprocation of the first and second pistons thereby pumps marking fluid from the reservoir, through the chamber and into the marking head.
In order to prevent the marking medium from dripping from the chamber, the marking stylus preferably includes a pressure operated valve that controls the amount of marking fluid that flows along the conduit from the chamber to a marking head. Additionally, the marking head may preferably include a porous pad that in use, becomes impregnated with the marking medium.
The pistons may be reciprocated in the marking means by any suitable means, e.g., electrically, hydraulically or pneumatically. Preferably, however, the pistons are reciprocated pneumatically by fluid pressure.
The pistons are preferably reciprocally moved together between two end positions of the pistons by the application of fluid pressure to the pistons remote from the chamber. One of the pistons is additionally move
REFERENCES:
patent: Re29444 (1977-10-01), Alexander
patent: 3523471 (1970-08-01), Lance
patent: 3719111 (1973-03-01), Study
patent: 3774479 (1973-11-01), Lesner
Desitech Limited
Ford Motor Company
Godwin Jr. Paul K.
Jones Jr. James L.
Sanborn Robert D.
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