Tools – Wrench – screwdriver – or driver therefor – Responsive to torque on work
Reexamination Certificate
2002-05-06
2003-12-30
Meislin, D. S. (Department: 3723)
Tools
Wrench, screwdriver, or driver therefor
Responsive to torque on work
C081S467000
Reexamination Certificate
active
06668690
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a screwdriver (mainly such as a power screwdriver) for use in tightening a screw into, e.g., a piece of plasterboard that is used such as on a ceiling and a wall.
2. Description of the Related Art
A screwdriver such as a power screwdriver is primarily intended for use on a fastened material such as a piece of plasterboard. The screwdriver includes an axially movable and adjustable stopper disposed on part of a unit body because a screw must be driven into the fastened material at a certain depth during screw tightening. The screwdriver further includes a screw-tightened depth adjuster for releasing a clutch when the unit body is moved to a position where the stopper abuts the fastened member during the screw tightening. The screwdriver yet further includes a mechanism for transmitting power through a one-way clutch when a motor is reversely revolved in order to back off the screw.
One such example of a prior art screwdriver as disclosed in Japanese Patent Application Laid-Out No.
8-267367
will now be described with reference to FIG.
1
.
In
FIG. 1
, a threadingly engaged stopper sleeve
3
is shown mounted on a housing
2
at a distal end thereof. The stopper sleeve
3
is relatively rotated with respect to the housing
2
, thereby adjusting a relative distance therebetween. The adjusted relative distance provides an adjusted screw-fed distance (or adjusted screw-driven depth).
In the housing
2
, a pinion
19
on an output shaft of a motor (not shown) is engaged with a gear
5
that is circumferentially mounted on a driving shaft member
4
. The driving shaft member
4
and the gear
5
are rotated as a one-piece component in a rotational direction of the driving shaft member
4
, and motor rotation is transmitted to the driving shaft member
4
through the gear
5
.
Referring to
FIG. 2
, a compression spring or a clutch spring
6
including axially extending upper and lower ends is shown coiled in a counterclockwise direction.
An output shaft member
7
includes engagement balls
18
that allow the output shaft member
7
to receive a screw-driving bit
10
in a jointly rotatable manner. A metal section
8
supports the output shaft member
7
in a pivotable and axially movable manner, but limits movement of the output shaft member
7
toward the screw-driving bit
10
. Part of the output shaft member
7
is positioned within a one-way clutch
16
. The one-way clutch
16
is retained within a driving shaft sleeve
4
a
of the driving shaft member
4
. The output shaft member
7
is axially movable within the one-way clutch
16
, while the one-way clutch
16
permits the output shaft member
7
to be pivoted in a single direction (in a direction in which a screw is tightened) with reference to the one-way clutch
16
.
A non-rotatable, but axially movable locking member
12
is positioned against the stopper sleeve
3
at an end thereof toward the driving shaft member
4
. The locking member
12
is always urged toward the stopper sleeve
3
by means of a compression spring
11
. The stopper sleeve
3
and the locking member
12
includes convex and concave claws, respectively, which claws are in constant mesh with one another at a position where the locking member
12
abuts the stopper sleeve
3
. When the claw of the stopper sleeve
3
is held in mesh with that of the locking member
12
, then the stopper sleeve
3
is locked against rotation with respect to the housing
2
, and is further immovable in an axial direction of the stopper sleeve
3
. The screw-tightened depth can be adjusted by the stopper sleeve
3
being relatively rotated in relation to the housing
2
when an operator disengages the claw of the stopper sleeve
3
from that of the locking member
12
by manually sliding the locking member
12
toward the driving shaft member
4
against the spring force of the compression spring
11
.
In the driving shaft member
4
, an axially movable umbrella-like member
13
is positioned against the output shaft member
7
at an end thereof in a direction opposite to the screw-driving bit
10
. A radially movable ball
9
within a through-hole
4
b
of the driving shaft sleeve
4
a
is seated against the umbrella-like member
13
along the outer circumference thereof or rather a tapered portion
13
a
. A spring
15
constantly urges the umbrella-like member
13
toward the output shaft member
7
.
In
FIG. 1
, the pressing force of the spring
15
causes the output shaft member
7
having the screw-driving bit
10
disposed thereon to be moved in a downward direction of FIG.
1
through the umbrella-like member
13
, and a distal end of the bit
10
remains projecting beyond that of the stopper sleeve
3
.
When driving the screw is started in such a state, then output shaft member
7
with the screw-driving bit
10
thereon is axially moved in an upward direction of FIG.
1
through the umbrella-like member
13
against the pressing force of the spring
15
.
The tapered portion
13
a
is slanted at an angle that permits an outer diameter thereof to decrease with an increase in distance between the tapered portion
13
a
and the output shaft member
7
. Such a construction allows ball
9
on the tapered portion
13
a
to protrude beyond the driving shaft sleeve
4
a
along the outer circumference thereof in response to the axial movement of the output shaft member
7
with the screw-driving bit
10
.
An output shaft sleeve
7
a
having the same outer diameter as that of the driving shaft sleeve
4
a
is disposed on the output shaft member
7
. The output shaft sleeve
7
a
includes a fixing portion
14
a
and a protruding portion
14
b
. The fixing portion
14
a
secures an end of the clutch spring
6
that extends about the output shaft sleeve
7
a
and driving shaft sleeve
4
a
along the respective outer circumferences thereof. The protruding portion
14
b
extends beyond the output shaft sleeve
7
a
along the outer circumference thereof, and abuts an end surface of the clutch spring
6
, thereby restricting the clutch spring
6
in axial position thereof. As illustrated in
FIGS. 2 and 3
, the clutch spring
6
has the bent end secured by the fixing portion
14
a
, and is thereby disposed in an axially immovable fashion.
The opposite end
6
a
of the clutch spring
6
toward the driving shaft member
4
is a free end, and the clutch spring end
6
a
is axially moved in union with the axially moved output shaft member
7
having the bit
10
carried thereon.
When the output shaft member
7
with the screw-driving bit
10
is axially moved against the spring force of the spring
15
during screw tightening, then the clutch spring end
6
a
is axially moved in union with the output shaft member
7
, and is then positioned on the ball
9
along the circumference thereof. The umbrella-like member
13
is axially moved in response to the movement of the output shaft member
7
with the screw-driving bit
10
, and the tapered portion
13
a
causes the ball
9
to protrude beyond the driving shaft sleeve
4
a
along the outer circumference thereof. As a result, the clutch spring end
6
a
can be brought into contact with the ball
9
in a rotational direction of the driving shaft member
4
, and a motor rotational force is transmitted to the clutch spring
6
through the gear
5
, driving shaft member
4
, and ball
9
.
When a motor is normally revolved, then the clutch spring
6
is deformed in a direction in which an outer diameter of the clutch spring
6
is reduced, and is thereby wound around the driving shaft sleeve
7
a
as well as the output shaft sleeve
4
a
along the respective outer circumferences thereof, thereby rotating the output shaft sleeve
4
a
jointly with the driving shaft sleeve
7
a
. As a result, the revolving force of the driving shaft member
4
is transmitted to the output shaft member
7
through the clutch spring
6
in order to revolve the screw-driving bit
10
, thereby tightening the screw.
When the screw is further driven, then an end surface of the stopper
Kikuchi Hajime
Kikuchi Noriaki
Niyada Masateru
Hitachi Koki Co,. Ltd.
Meislin D. S.
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