Tools – Wrench – screwdriver – or driver therefor – Handle clutched to head
Reexamination Certificate
1999-10-08
2001-02-13
Meislin, D. S. (Department: 3723)
Tools
Wrench, screwdriver, or driver therefor
Handle clutched to head
C192S043200
Reexamination Certificate
active
06186031
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a ratchet screwdriver, more particularly to a ratchet assembly of a ratchet screwdriver which has a relatively simple structure and which permits operation and replacement of tool bits mounted on two opposite ends of a drive shaft.
2. Description of the Related Art
FIG. 1
illustrates a first conventional ratchet screwdriver which has a hollow handle
10
formed with an axial receiving chamber
11
with open front and rear ends. An inner coupling sleeve
12
is received in the axial receiving chamber
11
adjacent to the rear end, while an outer coupling sleeve
13
is extended into the axial receiving chamber
11
and is disposed at the front end. The inner coupling sleeve
12
has a first section confining a rectangular hole portion
122
with a rectangular cross-section, and a second section confining a hexagonal hole portion
121
which has a hexagonal cross-section and which is connected to the rectangular hole portion
122
. The outer coupling sleeve
13
confines an axial hole
131
. A ratchet assembly
15
is mounted on the rear end of the handle
10
, and has one end provided with a drive projection
151
which has a rectangular cross-section and which engages the rectangular hole portion
122
, and the other end provided with a turning wheel
152
which extends out of the handle
10
. A drive shaft
16
is extended through the axial hole
131
and into the axial receiving chamber
11
of the handle
10
, and is retained in the axial hole
131
by an annular spring
132
provided on an inner surface of the outer coupling sleeve
13
. The drive shaft
16
has two opposite ends, each of which engages a tool bit
161
that has a shank portion with a hexagonal cross-section. The shank portion of one of the tool bits
161
extends into the hexagonal hole portion
121
in the inner coupling sleeve
12
, and engages non-rotatably the inner coupling sleeve
12
. When the handle
10
is rotated in a certain direction, since the drive projection
151
engages the inner coupling sleeve
12
, the inner coupling sleeve
12
engages one of the tool bits
161
, and said one of the tool bits
161
engages the drive shaft
16
, the drive shaft
16
is rotated axially to cause rotation of another one of the tool bits
161
in order to operate a workpiece, such as a screw. However, when the screwdriver applies a forward driving force along the drive shaft
16
during operation, it is likely that the drive shaft
16
pushes the inner coupling sleeve
12
rearwardly so as to push the ratchet assembly
15
outwardly of the handle
10
. In this situation, the inner coupling sleeve
12
and one of the tool bits
161
might be undesirably exposed to injure the user.
Referring to
FIGS. 2 and 3
, another conventional ratchet screwdriver is shown to include a handle
20
having a head portion
21
which is formed with an axial hole
217
with an open end, and a slot
211
. An actuator
221
and a pair of pawl plates
222
are disposed in the slot
211
. A tubular housing
23
is sleeved around the headportion
21
, and is formed with a circumferentially extending slot
231
to permit extension of an operating protrusion
223
of the actuator
221
therethrough. A drive shaft
24
is extended into the axial hole
217
in the head portion
21
. The drive shaft
24
has two opposite ends formed with an axial blind hole
243
for engaging tool bits
25
, and an intermediate portion formed as a ratchet wheel
241
. A pair of annular retaining grooves
242
are formed on opposite sides of the ratchet wheel
241
for engaging ball members
215
which are mounted on the head portion
21
and which are biased radially and inwardly by means of springs
216
to engage the annular groove
242
, thereby retaining the drive shaft
24
on the head portion
21
. As shown, the actuator
221
is operable to move in a direction transverse to an axis of the drive shaft
24
to engage a selected one of the pawl plates
222
with the ratchet wheel
241
such that the drive shaft
24
can be driven by rotating the handle
20
in a certain direction.
However, this kind of ratchet screwdriver suffers from the following drawback: When the drive shaft
24
is inserted into the axial hole
217
of the handle
20
, the pawl plates
222
will be pushed by an end wall of the drive shaft
24
. In the case the drive shaft
24
is frequently inserted into and removed from the handle
20
for replacement of the tool bits
25
, the pawl plates
222
are susceptible to deformation and displacement, thereby affecting adversely the engagement between the pawl plates
222
and the ratchet wheel
241
.
SUMMARY OF THE INVENTION
Therefore, the object of the present invention is to provide a ratchet assembly for a hand tool which can solve the aforementioned problems.
Accordingly, the ratchet assembly according to the present invention includes a tubular housing, a cylindrical ratchet body, an actuator and a biasing member. The tubular housing is adapted to be mounted on a handle of the hand tool so as to be co-rotatable axially with the handle. The housing has a surrounding wall that has an actuator confining portion which extends axially and projects radially and which confines an actuator receiving space. The actuator confining portion is formed with an axially extending slot for access to the actuator receiving space. The ratchet body is disposed rotatably in the housing, and has an annular outer surface which is provided with a first ratchet wheel and a second ratchet wheel that is axially displaced from the first ratchet wheel so as to define a slide portion on the outer surface between the first and second ratchet wheels. The actuator is disposed in the actuator receiving space, and is slidable along the ratchet body. The actuator includes a curved plate having an arc length and a central line which extends through a central point of the arc length and along a direction parallel to an axis of the ratchet body. The actuator further includes first and second pawl members which project radially from the curved plate toward the outer surface of the ratchet body and which are disposed on opposite sides of the central line. The curved plate further has an operating protrusion extending through the slot in the housing. The operating protrusion is operable to slide along the slot so as to cause the actuator to slide along the ratchet body between a first uni-directional driving position, in which the first pawl member is slid into engagement with the first ratchet wheel and the second pawl member is slid out of engagement from the second ratchet wheel, and a second uni-directional driving position, in which the first pawl member is slid out of engagement from the first ratchet wheel and the second pawl member is slid into engagement with the second ratchet wheel. The biasing member is mounted in the housing for biasing the actuator to move in a radial inward direction toward the outer surface of the ratchet body. When the actuator is in the first uni-directional driving position, the first pawl member is pushed toward the first ratchet wheel when the housing is rotated axially in a first direction to permit co-rotation of the ratchet body and the housing in the first direction. The actuator is pushed radially and outwardly to disengage the first pawl member from the first ratchet wheel when the housing is rotated axially in a second direction opposite to the first direction, thereby preventing the ratchet body from rotating with the housing in the second direction. When the actuator is in the second uni-directional driving position, the second pawl member is pushed toward the second ratchet wheel when the housing is rotated axially in the second direction to permit co-rotation of the ratchet body and the housing in the second direction. The actuator is pushed radially and outwardly to disengage the second pawl member from the second ratchet wheel when the housing is rotated axially in the first direction, thereby preventing the ratchet body from rotating with
Foley & Lardner
Meislin D. S.
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