Tools – Wrench – screwdriver – or driver therefor – Handle clutched to head
Reexamination Certificate
2000-09-01
2002-01-29
Morgan, Eileen P. (Department: 3723)
Tools
Wrench, screwdriver, or driver therefor
Handle clutched to head
Reexamination Certificate
active
06341543
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a pushbar-type ratchet wrench, and more particularly to a push bar-type ratchet wrench in which the detent section of the push bar is engaged with the ratchet at a higher position for increasing the torque strength and operation sensitivity thereof.
FIG. 1
shows a conventional push bar-type ratchet wrench
10
including an elongated stem
11
, a ratchet
14
rotatably received in a through hole of the head section
12
of the stem
11
for fitting with a nut and a push bar
16
which is a solid bar with circular cross-section. Each of two ends of the push bar
16
is formed with a detent section
17
. The push bar
16
is slidably fitted in a slide way
13
of the head section
12
and pressed by a resilient member
18
, whereby the push bar
16
can be located at two positions where the detent section
17
on right side or left side is engaged with the ratchet
14
to provide one-way ratchet effect in different directions.
The conventional push bar-type ratchet wrench can hardly bear high torque and has some shortcomings in operation as follows:
As shown in
FIG. 1
, when counterclockwise wrenching the stem
11
, the ratchet
1
is engaged with the detent section
17
of the push bar for driving the ratchet to rotate in the same direction. At this time, at the contact position A, the detent section
17
will exert a tangential application force F onto the teeth of the ratchet
14
. The longitudinal component of the force Fy is directed to the ratchet at a position near the center thereof. The ratchet is a hollow structure and has relatively poor structural strength. Therefore, once the application force F reaches a certain value which makes the longitudinal component of the force Fy greater than the bending strength of the ratchet, the ratchet will be deformed and damaged and unable to be further used.
In addition, referring to
FIG. 2
, in the operation of
FIG. 1
, the ratchet
14
will exert a reaction force F′ onto the push bar
16
. The push bar
16
is a solid structure so that it is able to bear the longitudinal component of the force Fy′. However, in the case of excessively great transverse component of the force Fx′, the push bar will clog in the slide way
13
and make it impossible to further use the ratchet wrench.
Furthermore, when clockwise wrenching the wrench as shown in
FIG. 3
, the push bar
16
will be pushed rightward by the ratchet
14
and disengaged from the ratchet to provide a ratchet effect. The contact position A and the axis of the stem contain a relatively small angle &thgr;. Therefore, when the slope face s of the tooth
141
of the ratchet pushes the detent section
17
, as shown in
FIG. 4
, the perpendicular component n
2
of the application force N is applied to the push bar
16
to press the push bar
16
against the inner wall of the slide way
13
. Therefore, a larger frictional coefficient between the push bar and the inner wall is produced and the ratchet must exert a greater force onto the push bar for transversely pushing the same. As a result, the ratchet effect is insensitive.
In the other types of ratchet wrenches
19
as shown in
FIGS. 5 and 6
, the ratchets
191
and the detents
192
also have the same shortcomings.
Another conventional ratchet wrench
15
as show in
FIGS. 7 and 8
, including a push bar
153
slidably fitted in a slide way
152
of a stem
151
. Said push bar has a rectangular cross-section and has a detent section
154
formed at one end of which, said detent section
154
is engaged with a ratchet
155
. The engagement position B and the axis of the stem
151
contain a small angle &thgr;, so that the wrench
15
also have the same shortcomings.
SUMMARY OF THE INVENTION
It is therefore a primary object of the present invention to provide a push bar-type ratchet wrench with high torque strength, which is able to bear higher torque.
It is a further object of the present invention to provide the above push bar-type ratchet wrench in which the ratchet can be more sensitively operated.
REFERENCES:
patent: 2701977 (1955-02-01), Stone
patent: 5231903 (1993-08-01), Bockman, Jr.
patent: 6216563 (2001-04-01), Hsieh
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