192 clutches and power-stop control – Clutches – Torque responsive
Reexamination Certificate
2002-12-18
2004-06-08
Lorence, Richard M. (Department: 3681)
192 clutches and power-stop control
Clutches
Torque responsive
C192S095000, C192S11000B, C173S178000
Reexamination Certificate
active
06745883
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electric power tool in which a fastening torque is adjustable, such as a driver or a driver drill.
2. Description of the Related Art
In a conventional electric power tool of this kind, a clutch ring which is a part for adjusting the fastening torque is rotatably disposed on the body of the electric power tool, so that the fastening torque can be adjusted by rotating the clutch ring.
Such a clutch ring is requested to have a mechanical strength against an external force. Therefore, a conventional clutch ring is made of a hard synthetic resin such as polyamide (PA), polycarbonate (PC), or a material in which glass fibers are added to such a resin. A plurality of convex or concave portions are disposed in the circumferential direction on the outer peripheral face for the principal purpose of enhancing the antislipping function. Furthermore, characters or icons which indicate the adjustment state of the fastening torque of the electric power tool are printed on the outer peripheral face. In order to prevent the characters or icons from being defaced as result of use, recently, the character or icon portion is sometimes formed by two-color molding with using a hard synthetic resin of the same kind as that of the clutch ring.
A torque adjusting mechanism of an electric power tool having a clutch ring of this kind will be described with reference to
FIG. 8. A
pinion
10
which is fixed to a motor shaft
9
to be driven thereby meshes with planet gears A
12
which are supported by support shafts
11
b
of a carrier A
11
, and which mesh with an internal gear A
14
fixed to a gear case A
13
. In the carrier A
11
, a sun gear A
11
a
is formed as the next stage. The sun gear A
11
a
meshes with planet gears B
17
which are supported by support shafts
15
b
of a carrier C
15
, and which mesh with an internal gear B
16
. The power of the motor shaft
9
is reducingly transmitted in a sequential manner to a sun gear C
15
a
which is formed in the carrier C
15
serving as the final stage. The sun gear C
15
a
meshes with planet gears C
20
which are supported by support shafts
19
a
of a carrier
19
that transmits a torque to an output shaft
18
, and which mesh with an internal gear C
21
. The internal gear C
21
is rotatably housed in a gear case B
23
, and shaped so as to have a plurality of claws
21
a
which extend in the axial direction from an end face on the side of the output shaft
18
. In the gear case B
23
, a plurality of through holes
23
b
which elongate in the axial direction of the gear case B
23
and in places which can correspond to the claws
21
a
of the internal gear C
21
. A ball
22
which is engageable with the claws
21
a,
and a cylindrical roller
24
which is positioned between the ball
22
and a clutch plate
25
are housed in each of the through holes
23
b
so as to be movable in the axial direction of the gear case B
23
.
The clutch plate
25
is always urged toward the internal gear C
21
by the urging force of a clutch spring
26
which will be described later. The balls
22
are always urged toward the internal gear C
21
via the clutch plate
25
and the rollers
24
to attain a state where the balls
22
are engaged with the claws
21
a
by the urging force.
The gear case B
23
has a cylindrical shape having at least two portions of different outer diameters. In the outer-diameter portion, the carrier
19
, the internal gear C
21
, and the like are housed, and the through holes
23
b
which accommodate the balls
22
and the rollers
24
are formed. In the smaller-diameter portion, the output shaft
18
is rotatably supported, and a male thread
23
a
is formed on the outer periphery.
A clutch member
27
having a female thread
27
a
which is to be screwed with the male thread
23
a
is disposed on the outer periphery of the smaller-diameter portion of the gear case B
23
. The clutch member
27
is turned in conjunction with turning of a clutch ring
1
which is turned by an external operation. The clutch member
27
is moved in the axial direction of the gear case B
23
with being turned by means of the screw coupling of the male thread
23
a
and the female thread
27
a.
The clutch member
27
receives one end of the clutch spring
26
which is interposed between the member and the clutch plate
25
, and is moved in the axial direction of the gear case B
23
while changing the axial dimension of the clutch spring
26
. The outer wall portion of the clutch member
27
is shaped so as to guide the inner diameter portion of the coil spring
26
.
As described above, when the clutch ring
1
is turned, the clutch member
27
is moved in the axial direction of the gear case B
23
to change the axial dimension of the clutch spring
26
. Namely, the tool is structured so that the axial urging force by which the clutch spring
26
urges the clutch plate
25
can be adjusted.
When the electric power tool is to be used, the urging force of the coil spring
26
is adjusted to appropriately select the sliding torque. When a load which is larger than the selected sliding torque is applied to the output shaft
18
, the claws
21
a
of the internal gear C
21
axially move the balls
22
against the urging force of the coil spring
26
and the internal gear C
21
begins to rotate, and hence the power transmission to the output shaft
18
is interrupted. Namely, the torque transmitted to the output shaft
18
can be controlled by adjusting the compression amount of the coil spring
26
as described above. The transmission of a large torque to the output shaft
18
can be attained by shortening the axial dimension of the clutch spring
26
, i.e., by compressingly turning the clutch ring
1
, and that of a small torque to the output shaft
18
can be attained by turning the clutch ring
1
so as to lengthen the axial dimension of the clutch spring
26
.
In the case of a driver drill, it is required to obtain a state where the sliding torque is not set, i.e., the state of a drill mode. This state can be attained by a configuration in which the balls
22
are caused not to be axially moved, by means such as that of fully compressing the clutch spring
26
, or that of butting a part of the clutch member
27
against the clutch plate
25
, whereby the engagement between the claws
21
a
and the balls
22
is maintained to block the rotation of the internal gear C
21
.
A plate spring
28
on which protrusions to be engaged with recesses of the clutch ring
1
are disposed is interposed between the clutch ring
1
and the gear case B
23
in order to allow the clutch ring
1
to be turned by an external force but inhibit the clutch ring
1
from being freely turned. In this way, restraint is imposed on the rotation direction in order to prevent the clutch ring
1
from being accidentally turned by the urging of the coil spring
26
.
As described above, restraint is imposed on the rotation direction of the clutch ring
1
, and, in an operation of selecting the fastening torque, the clutch ring
1
must be turned against the restraint, and hence an operation force of a certain degree is required. In a selecting operation in the case where the fastening torque is to be increased, the coil spring
26
is compressed, and therefore it is requested to exert an operation force of a larger degree. In order to enable the clutch ring
1
to be surely gripped, conventionally, a convex or concave shape for antislipping is formed in the circumferential direction on the outer peripheral face of the ring. In the case where the antislipping function is to be sufficiently exerted, the antislipping shape strongly acts on the palm because the shape is configured by the same hard synthetic resin as that of the base member, thereby producing a problem in that it is impossible to comfortably grip the ring.
SUMMARY OF THE INVENTION
The invention has been conducted in view of the above-mentioned circumstances. It is an object of the invention to provide an electric power
Adachi Yoshiaki
Eto Yasuo
Kurosawa Hideki
Takaada Kenichi
Hitachi Koki Co,. Ltd.
Lorence Richard M.
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