Tools – Including tool driving by impact delivering component or... – Structurally constrained to arcuate movement
Reexamination Certificate
2001-02-22
2002-02-12
Meislin, D. S. (Department: 3723)
Tools
Including tool driving by impact delivering component or...
Structurally constrained to arcuate movement
C081S062000, C081S177200
Reexamination Certificate
active
06345559
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a ratchet wrench having a labor saving structure, and more particularly to ratchet wrench having a labor saving structure, wherein, the drive head of the ratchet wrench is mounted in the toothed circular hole of the drive arm, the toothed circular hole has one side or two sides each defining an elongated arcuate hole, a rivet extending through the elongated arcuate slot of the drive arm and secured in the rivet hole of the fixed plate, whereby when the drive shank is driven to rotate, each of the rivets can push the drive arm along the elongated arcuate slot so that the drive arm produces a deflective effect to the drive head, thereby achieving a labor saving purpose by the principle of leverage.
2. Description of the Related Prior Art
In general, a conventional ratchet wrench in accordance with the prior art is not provided with a labor saving structure. Thus, the operator may have to exert a large force to drive the handle, thereby achieving the purpose of releasing or locking the workpiece. In such a manner, the operator has to exert a large force for driving the handle, thereby wasting the operator's energy and easily causing inconvenience to the operator.
SUMMARY OF THE INVENTION
The primary objective of the present invention is to provide a ratchet wrench that can achieve a labor saving purpose by the principle of leverage.
In accordance with the present invention, there is provided a ratchet wrench having a labor saving structure, comprising:
a drive shank having a front end provided with a fixed plate, the fixed plate having a center defining a first circular hole and having two sides each defining a rivet hole located beside the first circular hole;
a drive arm pivotally mounted on the fixed plate and having a center defining a second circular hole and having two sides each defining an elongated arcuate hole located beside the second circular hole and aligning with the rivet hole of the fixed plate;
a drive head mounted in the first circular hole of the fixed plate and the second circular hole of the drive arm;
two rivets each extending through the elongated arcuate slot of the drive arm and each secured in the rivet hole of the fixed plate; and
two C-shaped snap rings each respectively mounted on the drive head for snapping and securing the fixed plate, the drive arm and the drive head together;
wherein, when the drive shank is driven to rotate, each of the rivets can push the drive arm along the elongated arcuate slot, thereby forming a deflective leverage labor saving effect.
In accordance with the present invention, the fixed plate is located at a position lower than that of the drive shank.
In accordance with the present invention, the fixed plate and the drive arm are in parallel with the drive shank or in perpendicular with the drive shank.
In accordance with another embodiment of the present invention, the drive shank has two sides each provided with a positioning plate, and the ratchet wrench further comprises two lever arms each having a first end pivotally connected with the drive arm and the fixed plate, and a second end pivotally connected with the positioning plate of the drive shank.
Further benefits and advantages of the present invention will become apparent after a careful reading of the detailed description with appropriate reference to the accompanying drawings.
REFERENCES:
patent: 1675729 (1928-07-01), Reynolds
patent: 4819523 (1989-04-01), Souza
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