Information
-
Patent Grant
-
6176321
-
Patent Number
6,176,321
-
Date Filed
Tuesday, September 14, 199925 years ago
-
Date Issued
Tuesday, January 23, 200123 years ago
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Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 173 48
- 173 47
- 173 29
- 173 201
- 173 104
- 173 109
- 173 117
- 074 22 R
- 074 22 A
- 200 5 B
- 200 5 C
- 200 5032
-
International Classifications
-
Abstract
A power-driven hammer drill 1 includes a rotary lever 8 for transmitting and disabling the transmission of the rotation of a motor 5 to a tool bit 4 and a slide lever 9 for transmitting and disabling the transmission of hammer blows to the tool bit 4. The rotary lever 8 is formed with a chamfer 52, whereas the slide lever 9 is formed with a straight portion 54 and a cut-out 53 which conforms to the circular edge of the rotary lever 8. When the slide lever 9 is in the lowermost position with the rotary lever 8 fitted in the cut-out 53, the rotary lever 8 is in the position to disconnect the rotation of the motor 5 to the tool bit 4, and while in this position, the slide lever 9 cannot be slid to its uppermost position, in which hammer blows cannot be transmitted to the tool bit 4. When the slide lever 9 is located in the uppermost position and the chamfer 52 of the rotary lever 8 is in the rearmost position, in which hammer blows cannot be transmitted to the tool bit 4 but rotation can be transmitted to the tool bit 4, the straight portion 54 opposes the chamfer 52 across a narrow gap so that the rotary lever 8 cannot be rotated to the rotation disabling position.
Description
This application claims priority on Japanese Patent Application No. 10-261891 filed on Sept. 16, 1998, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a hammer drill. More particularly, the present invention relates to a hammer drill having a rotation transmission mechanism which is provided between a motor and a tool bit attached to the top of a drill housing and which rotates the bit, and having a impact transmission mechanism provided also between the motor and the tool bit for transmitting hammer blows to the tool bit.
2. Description of the Related Art
It is a common practice in the art to which the present invention pertains to provide a change-over device for the rotation transmission mechanism and for the impact transmission mechanism for switching between transmission and disconnection of drive power from the motor, thus changing the operation mode of the hammer drill. The Applicant disclosed in Japan Published Unexamined Patent Application No. 9-57650 a large hammer drill which incorporates a crank mechanism, the contents of which are incorporated herein by reference. The hammer drill includes a sleeve which functions as a first change-over device for selectively transmitting rotation from the motor to the tool bit when slid to one position and disconnecting the motor rotation when slid to another position. The hammer drill additionally includes a link which functions as a second change-over device for selectively transmitting reciprocating motion of the piston to the tool bit when slid to one position and disconnecting the reciprocating motion when slid to another position. Moreover, a rotary selector knob is provided in this tool for allowing the operator to simultaneously select a combination of the slide positions of the two change-over devices, i.e., one of the three possible operation modes of the hammer drill. When a rotation-plus-hammer mode is selected, both rotation and hammer blows are transmitted to the tool holder. In a hammer-only mode, only hammer blows are transmitted to the tool holder. In a neutral mode, the tool bit is manually freely rotatable in either direction, thus allowing the operator to change the rotational angle of the tool bit.
From a viewpoint of convenience, it would be preferable to have such a large hammer drill with a crank mechanism as described above be able to operate in a rotation-only mode in addition to a rotation-plus-hammer mode and a hammer-only mode. The structure of the selector knob renders implementation of a rotation-only mode in the hammer drill very difficult. Significant changes in the design and thus increase in the manufacturing cost would be inevitable if these three modes are to be realized without altering the basic structures of the impact transmission mechanism and the rotation transmission mechanism. One possible means to achieve this goal is to provide two separate operating members for independently operating a sleeve provided for transmission of rotation separate and a link provided for transmission of hammer blows. One drawback of this configuration is that since each operating member has a position in which rotation or hammer blows are disconnected (an “off” state), the operator may unintentionally and inconveniently place the hammer drill in an off-off state, in which neither rotation nor hammer blows are transmitted to the tool bit, thus rendering the tool inoperative.
SUMMARY OF THE INVENTION
In view of the above-identified problems, an important object of the present invention is to provide a hammer drill with improved operability that allows change-over between three operating modes with two switching devices, such as levers, without inducing an “off-off” operational state.
The above object and other related objects are realized by the invention, which provides a hammer drill, comprising: a tool bit attached to a front end of the hammer drill; a motor for providing drive power for the tool bit; a rotation transmission mechanism provided between the tool bit and the motor for transmitting rotation of the motor to the tool bit; an impact transmission mechanism provided between the tool bit and the motor for transmitting hammer blows generated by the motor to the tool bit; a first change-over member associated with the rotation transmission mechanism for selectively enabling and disabling the rotation transmission mechanism to transmit the rotation of the motor to the tool bit; a second change-over member associated with the impact transmission mechanism for selectively enabling and disabling the impact transmission mechanism to transmit the hammer blows generated by the motor to the tool bit; a manually operable first operating member movable between operative and inoperative positions, wherein the first operating member, when in the operative position, operates the first change-over member so as to enable the rotation transmission mechanism and, when in the inoperative position, operates the first change-over member to disable the rotation transmission mechanism; a manually operable second operating member movable between operative and inoperative positions, wherein the second operating member, when in the operative position, operates the second change-over member so as to enable the impact transmission mechanism and, when in the inoperative position, operates the second change-over member to disable the impact transmission mechanism; and a lock means for, when one of the first and second operating members is in its inoperative position, coordinating with the other operating member so as to prohibit the other operating member from moving to its inoperative position, thus avoiding induction of an operating state of the hammer drill in which neither rotation nor hammer blows of the tool bit are available.
According to one aspect of the present invention, one of the first and second operating members is a circular rotary lever and the other operating member is a slide lever slidable tangentially to the rotary lever. Additionally, the lock means includes a cut-out formed in an edge of the slide lever for fitting the circumferential edge of the rotary lever so as to prevent the slide lever to slide when the slide lever is in its operative position, and a chamfer formed on a portion of the circumferential edge of the rotary lever such that when the rotary lever is rotated to the operative position, the chamfer is positioned adjacent the slide lever so as to allow the slide lever to slide, and when the rotary lever is rotated to the operative position and the slide lever is in its inoperative position, the chamfer closely opposes an edge of the slide lever so as to prohibit rotation of the rotary lever.
According to another aspect of the present invention, the first operating member is the rotary lever and the second operating member is the slide lever. Moreover, the rotary lever and the slide lever are disposed on a line parallel to a longitudinal axis of the tool bit, with the rotary lever interposed between the tool bit and the slide lever.
According to still another aspect of the present invention, the slide lever has a generally rectangular shape and is slidable on the rotary lever and perpendicularly to the parallel line between its operative and inoperative positions.
According to yet another aspect of the present invention, the rotary lever is rotated 180 degrees around a second axis from its inoperative position to its operative position, the second axis intersecting and oriented perpendicularly to the parallel line.
In accordance with another aspect of the present invention, the cut-out is formed in a portion of the long side of the slide lever which is adjacent to the rotary lever, leaving a portion of the long side intact where the cut-out is not formed. The intact side edge closely opposes the chamfer of the rotary lever when the rotary lever is in its operative position and the slide lever is in the inoperative position such that the rotary lever cannot be rotated back to its inoperative position unless the slide lever is slid back to its operative position.
In accordance with another aspect of the present invention, the first change-over member is a sleeve member which is rotatably disposed within a housing of the hammer drill about the longitudinal axis and slid along the longitudinal axis between an operative position, in which the rotation transmission mechanism is enabled, and an inoperative position, in which the rotation transmission mechanism is disabled. The sleeve member is interlocked with the rotation transmission mechanism so as to be rotated by the motor when in the operative position and is disengaged from the rotation transmission mechanism and secured to the housing so as to be prevented from rotating when in the inoperative position.
In one aspect, when the rotary lever is rotated approximately 90 degrees from either of the operative and inoperative positions to an intermediate position, the sleeve member is neither secured to the housing nor interlocked with the rotation transmission mechanism, thus permitting manual adjustment of the rotary angle of the sleeve member.
In another aspect, the rotary lever bears a mark adjacent to the chamfer for indicating the location of the first change-over member between its operative and inoperative positions.
To carry out the invention in one preferred mode, the impact transmission mechanism comprises a crank mechanism connected to the rotor for converting the rotation of the motor into reciprocation motion as the hammer blows. The second change-over member interlocks the motor to the crank mechanism when the slide lever is in the operative position, thus enabling the crank mechanism, whereas the second change-over member disengages the crank mechanism from the motor when the slide lever is in the inoperative position, thus disabling the crank mechanism.
Other general and more specific objects of the invention will in part be obvious and will in part be evident from the drawings and descriptions which follow.
BRIEF DESCRIPTION OF THE ATTACHED DRAWINGS
For a fuller understanding of the nature and objects of the present invention, reference should be made to the following detailed description and the accompanying drawings, in which:
FIG. 1
is a side elevation of a power-driven hammer drill according to the present invention;
FIG. 2
is a partial cross section of essential internal mechanisms of the power-driven hammer drill of
FIG. 1
;
FIG. 3
is a partial cross section of the hammer drill of
FIG. 1
, showing rotary and slide levers in cross section when the hammer drill is placed in a hammer-only mode;
FIG. 4
is a cross section of a crank mechanism of the hammer drill of
FIG. 1
when the mechanism is placed in condition for converting the rotation of a motor to reciprocating motion so as to transmit hammer blows to a tool bit attached to the drill;
FIG. 5
is a cross section of a crank mechanism of
FIG. 4
when the mechanism is disabled from converting the rotation of a motor to reciprocating motion;
FIG. 6A
shows the positions of the rotary and slide levers when the hammer drill of
FIG. 1
is placed in a hammer-only mode;
FIG. 6B
shows the positions of the rotary and slide levers when the hammer drill of
FIG. 1
is placed in a hammer plus rotation mode;
FIG. 6C
shows the positions of the rotary and slide levers when the hammer drill of
FIG. 1
is placed in a rotation-only mode;
FIG. 7
is a cross section of the internal mechanisms of the hammer drill of
FIG. 1
when the drill is in the hammer plus rotation mode;
FIG. 8
is a partial cross section of the hammer drill, showing the rotary and slide levers in cross section when the hammer drill is placed in the hammer plus rotation mode;
FIG. 9
is a cross section of the internal mechanisms of the hammer drill of
FIG. 1
when the drill is placed in the rotation-only mode;
FIG. 10
is a cross section of the internal mechanisms of the hammer drill of
FIG. 1
in a neutral state in which the tool bit can be manually rotated to a desired rotary angle; and
FIG. 11
is a partial cross section of the hammer drill, showing the rotary and slide levers in cross section when the hammer drill is placed in the neutral state.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A preferred embodiment according to the present invention will be described hereinafter with reference to the attached drawings.
FIG. 1
is a side elevation of a power-driven hammer drill
1
according to the present invention, whereas
FIG. 2
is a partial cross section of essential internal mechanisms of the power-driven hammer drill
1
. The inverted L-shaped hammer drill
1
includes a main housing
2
and a chuck
3
for releasably attaching to a tool holder (described in detail below) a tool bit
4
which protrudes from the top of the drill
1
when attached. Connected to the lower rear portion of the main housing
2
is a motor housing
6
which vertically contains a motor
5
. The hammer drill I further includes a handle housing
7
which provides a grip handle, a rotary lever
8
(a first operating member) for changing the operating mode of the hammer drill, and a slide lever
9
(a second operating member), also for operating mode change. The two levers
8
and
9
are provided on one side of the main housing
2
as shown in
FIGS. 1 and 2
. The slide lever
9
can be slid vertically and tangentially relative to the rotary lever
8
.
Referring to
FIG. 2
, the motor
5
includes a motor shaft
10
which meshes with gears
15
and
16
of an intermediate shaft
13
and a crank shaft
14
, respectively. The intermediate shaft
13
and the crank shaft
14
are oriented parallel to the motor shaft
10
and both are supported between a gear housing
11
and a gear housing
12
. The intermediate shaft
13
in turn meshes with a bevel gear
18
slidably and rotatably slipped over an also rotatable cylinder
17
which is disposed coaxially with the main housing
2
. Provided in front of the bevel gear
18
is a lock sleeve
19
which functions as a first means of changing the operating mode of the hammer drill
1
. The lock sleeve
19
is spline-connected to the cylinder
17
so as to be integrally rotatable with the cylinder and axially slidable relative to the cylinder. Additionally, the lock sleeve
19
is urged rearwards by a coil spring
24
interposed between the sleeve
19
and a stopper ring
23
slidably and rotatably fit over the cylinder
17
. Furthermore, the lock sleeve
19
is formed with engaging teeth
20
at its rear end that can mesh with coupling teeth
18
a
formed on an inner peripheral surface of the bevel gear
18
. The lock sleeve
19
is additionally formed with a flange
21
which is formed with engaging teeth
22
on its front outer peripheral surface.
Still referring to
FIG. 2
, an intermediate sleeve
25
and the tool holder
26
are slipped over the front end of the cylinder
17
. A plurality of balls
27
are fitted in the cylinder
17
, the intermediate sleeve
25
, and the tool holder
26
so as to connect these three elements
17
,
25
, and
26
, thus allowing their integral rotation. The intermediate sleeve
25
defines the front limit of the stopper ring
23
, whereas the tool holder
26
urges via another coil spring
30
a lock ring
28
which is spline-connected to the crank housing
12
on its outer surface and thus can only slide relative to the cylinder
17
. Formed at the rear end of the lock ring
28
are lock teeth
29
that can mesh with engaging teeth
22
formed at the front end of the lock sleeve
19
.
Referring now to
FIG. 3
, the rotary lever
8
is rotatably attached to a cylindrical portion
12
a
so as to protrude from a side portion of the crank housing
12
. A change pin
31
is eccentrically implanted in the inner surface of the rotary lever
8
toward the cylinder
17
through the opening of the cylindrical portion
12
a
and comes into abutment with the rear surface of the flange
21
of the lock sleeve
19
so as to limit the rearward movement of the lock sleeve
19
. In this embodiment, as shown in
FIG. 3
, when the change pin
31
is located in the forwardmost position, the lock sleeve
19
is also in its forwardmost position, bringing the engaging teeth
22
into mesh with the lock teeth
29
of the lock ring
28
. When the rotary lever
8
is manually rotated 90 degrees, the change pin
31
moves rearward by the distance corresponding to its eccentricity from the center of the rotary lever
8
, permitting the rearward movement of the lock sleeve
19
and thus disengaging the engaging teeth
22
from the lock teeth
29
. This does not bring the engaging teeth
20
at the rear of the lock sleeve
19
into mesh or engagement with the coupling teeth
18
a
of the bevel gear
18
. When the rotary lever
8
is manually rotated an additional 90 degrees so as to move the change pin
31
to its rearmost position, the lock sleeve
19
is also located in its rearmost position, in which the engaging teeth
20
is in engagement with the coupling teeth
18
a
of the bevel gear
18
.
Still referring to
FIG. 3
, a vertically oriented eccentric pin
32
projects out of the upper surface of the crank shaft
14
and is coupled via a connecting rod
33
to a piston
34
which is inserted into the cylinder
17
. This arrangement constitutes a crank mechanism for converting the rotation of the crank shaft
14
into the reciprocating motion of the piston
34
. As shown in
FIGS. 2 and 3
, a striking element
36
and an intermediate element
37
which abuts the tool bit
4
are slidably disposed in front of piston
34
and within the cylinder
17
, with an air chamber
35
defined between the striking element
36
and the piston
34
. When the piston
34
reciprocates, the striking element
36
also reciprocates as it is pneumatically interlocked with the piston
34
by the air spring effect. This causes the striking element
36
to repeatedly ram the intermediate element
37
, thus transmitting hammer blows to the tool bit
4
.
With reference to
FIG. 4
, a pair of vertical pins
38
projects upward out of the upper surface of a gear
16
of the crank shaft
14
. The gear
16
is slipped around the crank shaft
14
so as to selectively rotate integrally with the crank shaft
14
when hammer blows are to be transmitted to the tool bit
4
(see FIG.
4
). The gear
16
is not interlocked with the crank shaft
14
when hammer blows are not to be transmitted to the tool bit
4
(see FIG.
5
). The crank shaft
14
is formed with a pair of axial key grooves
39
in which a pair of keys
40
are fitted. The keys
40
are connected with a connection sleeve
41
which functions as a second means of changing the operating mode of the hammer drill
1
. As illustrated, the connection sleeve
41
is fitted around the crank shaft
14
so as to be integrally rotatable with the crank shaft
14
and axially slidable with respect to the shaft
14
. In addition, the connection sleeve
41
is urged toward the gear
16
by a coil spring
44
. The connection sleeve
41
is formed with a pair of connection holes
42
on its underside for accommodating the pins
38
of the gear
16
.
Still referring to
FIG. 4
, the slide position of the connection sleeve
41
is determined by the position of a pin
46
abutting a flange formed around the upper edge of the connection sleeve
41
. The pin
46
is eccentrically formed on a rotatable plate
45
supported by the crank housing
12
. A circular protrusion
47
is also eccentrically provided on the opposite side of the rotatable plate
45
(see
FIGS. 2
,
7
,
9
, and
10
). The protrusion
47
is fitted in a slot
49
formed the lower end of an L-shaped change-over lever
48
which is accommodated between the main housing
2
and the rotatable plate
45
. The other end of the change-over lever
48
penetrates a vertical slot
2
a
formed in the main housing
2
and is secured to the slide lever
9
at the penetration by means of a screw
50
. Therefore, when the slide lever
9
is pushed to its lowermost position, it rotates the rotatable plate
45
in the counterclockwise direction via the protrusion
47
, as seen in FIG.
2
. This also rotates and lowers the pin
46
on the opposite side of the rotatable plate
45
in the counterclockwise direction. This allows the connection sleeve
41
to be pushed down by the coil spring
44
so as to fit the connection holes
42
over the pins
38
, thus connecting the sleeve
41
to the gear
16
. When this occurs, the rotation of the gear
16
is transmitted to the crank shaft
14
via the connection sleeve
41
so as to impart reciprocating motion to the piston
34
. As shown in
FIG. 5
, conversely, when the slide lever
9
is raised to its uppermost position, it rotates the rotatable plate
45
in the clockwise direction as seen in
FIG. 2
via the protrusion
47
. This also rotates and raises the pin
46
on the opposite side of the lever
48
also in the clockwise direction, thus removing the connection holes
42
from the pins
38
. When this occurs, the gear
16
rotates idly without transmitting the rotation of the motor shaft
10
to the crank shaft
14
.
The protrusion
47
is displaced clockwise from the pin
46
on the rotatable plate
45
as seen in
FIGS. 2
,
7
,
9
, and
10
such that when the connection sleeve
41
is slid to the upper limit, the pin
46
rotates upward beyond the center of the rotatable plate
45
to the right half of the plate
45
as seen in FIG.
9
. The reason for this configuration is that the pin
46
, once shifted to this position, is biased downward by the connection sleeve
41
, which is in constant abutment with the pin
46
. This downward biasing force of the connection sleeve
41
urges the rotatable plate
45
clockwise, thus preventing unintentional counterclockwise return of the pin
46
to the position shown, for example, in FIG.
2
. This means that the slide lever
9
is also prevented from accidental return to the lowermost position, thereby maintaining the operating mode selected by the operator.
As shown, for example, in
FIGS. 2 and 6A
to
6
C, the rotary lever
8
is marked with an arrow
51
on the eccentric side thereof, where the change pin
31
is located, in order to indicate the rotational position of the lever
8
. In addition, the rotary lever
8
is formed with a chamfer
52
on the part of its circumferential edge at which the arrow
51
points. The slide lever
9
includes at its upper left side a circular cut-out
53
that matches the circumference of the rotary lever
8
and a straight portion
54
that is located below the cut-out
53
and extends toward the rotary lever
8
. Combined together, the cut-out
53
, the chamfer
52
, and the straight portion
54
constitute means to lock the movement of the two levers
8
and
9
. More particularly, as shown in
FIG. 6A
, when the slide lever
9
is located in the lowermost position, that is, in which the circular edge of the rotary lever
8
fits in the cut-out
53
, the slide lever
9
is locked in the position. In other words, the slide lever
9
cannot be slid upward to its uppermost position. The lever
9
cannot be slid upward unless the chamfer
52
of the rotary lever
8
is rotated to its rearward position as shown in FIG.
6
B. As shown in
FIG. 6C
, when the slide lever
9
is in its uppermost position, the straight portion
54
closely opposes the chamfer
52
across a narrow gap so that the rotary lever
8
is locked in the position, thus preventing the lever
8
from being rotated. In order to rotate the lever
8
as shown in
FIG. 6B
, the slide lever
9
is pulled down to its lowermost position, in which the cut-out
53
opposes the chamfer
52
.
In the operation of the hammer drill
1
, when the rotary lever
8
is rotated to the position shown in
FIG. 2
,
3
, and
6
A, in which the change pin
31
is located in the forwardmost position, with the slide lever
9
located in its lowermost position, the lock sleeve
19
is disengaged from the bevel gear
18
so as to engage and prohibit movement of the lock ring
28
. Therefore, rotation of the lock sleeve
19
is prohibited, thus preventing rotation of the cylinder
17
and the tool holder
26
. As shown in
FIG. 4
, since the slide lever
9
is located in its lowermost position, the connection sleeve
41
is located in its lowermost position, linking the crank shaft
14
to the gear
16
and thus allowing the rotation of the crank shaft
14
. The operating mode currently selected is referred to as a hammer-only mode, in which the rotation of the bevel gear
18
is not transmitted to the tool bit
4
, but hammer blows caused by the reciprocating motion of the piston
34
are transmitted to the bit
4
. In its lowermost position with the circumferential edge of the rotary lever
8
fitted in the cut-out
53
, the slide lever
9
is prevented from shifting to the uppermost position (the “off” position).
When the rotary lever
8
is rotated
180
degrees to the position shown in
FIGS. 6B
,
7
, and
8
, the change pin
31
moves rearward so that the lock sleeve
19
disengages itself from the lock ring
28
and engages the bevel gear
18
. This results in transmission of the rotation of the intermediate shaft
13
to the lock sleeve
19
via the bevel gear
18
, thus rotating the cylinder
17
and the tool holder
26
as they can rotate integrally with the lock sleeve
19
. Subsequently, therefore, the tool bit
4
is rotated to operate on a workpiece. The operating mode currently selected is referred to as a rotation-plus-hammer mode, in which both the rotation of the bevel gear
18
and the hammer blows caused by the reciprocating motion of the piston
34
are transmitted to the tool bit
4
.
By sliding the slide lever
9
upward to the uppermost position as shown in
FIGS. 6C and 9
when the hammer drill
1
is placed in the rotation-plus-hammer mode, the change-over lever
48
is raised so as to rotate the rotatable plate
45
in the clockwise direction. This causes the pin
46
to raise the connection sleeve
41
, thus decoupling the crank shaft
14
from the gear
16
. Therefore, the crank shaft
14
no longer rotates to impart reciprocating motion to the piston
34
. The operating mode currently selected is referred to as a rotation-only mode, in which the rotation of the motor
5
is transmitted to the tool bit
4
via the intermediate shaft
13
, the bevel gear
18
, the lock sleeve
19
, the cylinder
17
, and the tool holder
26
, but no hammer blow is transmitted to the bit
4
. In this mode, as the chamfer
52
of the rotary lever
8
closely opposes the straight portion
54
of the slide lever
9
across a narrow gap, the rotary lever
8
cannot be rotated to the forward most position (the “off” position) due to the interference with the straight portion
54
. As described above, the rotary lever
8
cannot be rotated to the forward most position unless the slide lever
9
is pulled down to its lowermost position.
If the rotary lever
8
is rotated downward 90 degrees from the position shown in
FIG. 2
or
7
to the middle position as shown in
FIGS. 10 and 11
so as to direct the arrow
51
vertically downward, the lock sleeve
19
moves to a neutral position in which it engages neither the lock ring
28
nor the bevel gear
18
. Therefore, the cylinder
17
and the tool holder
26
can be freely rotated by manual operation. When the motor
5
is turned off, the operator can rotate the tool holder
26
and thus the tool bit
4
to a desired rotary angle. By rotating the change pin
31
ninety degrees to the forwardmost position, the operator can place the hammer drill
1
in the hammer-only mode (see FIG.
2
), in which the tool holder
26
and the tool bit
4
are locked at the selected rotary position due to the reestablished engagement between the lock ring
28
and the lock sleeve
19
. This arrangement is convenient for use with a chisel or other tool bit whose rotary angle often needs to be selected.
Even in the neutral position, the circular edge of the rotary lever
8
remains fitted in the cut-out
53
of the slide lever
9
to maintain the lever
9
in the lowermost position. Therefore, the crank shaft
14
remains interlocked with the gear
16
, still imparting reciprocating motion to the piston
34
. In this way, an off/off state, in which the tool bit cannot provide rotation or hammer blows, can be avoided.
According to the embodiment, one of three operating modes (the hammer-only mode, the hammer plus rotation mode, and the rotation-only mode) can be selected by the operation of the rotary lever
8
and the slide lever
9
. Moreover, the lock means (the combination of the chamfer
52
, the cut-out
53
, and the straight portion
54
) prevents one lever from moving to its “off” position as long as the other lever is in the “off” position. In other words, the off/off state, in which the tool bit can neither provide rotation nor hammer blows, can be avoided so as to realize a highly operable hammer drill which allows easy and reliable mode selection.
As the slide lever
9
slides tangentially to the rotary lever
8
only when the straight portion
54
opposes the chamfer
52
, and the rotary lever
8
can be rotated only when its circular edge is fitted in the cut-out
53
, the lock means easily and selectively locks either lever in a manner that logically suggests the purpose of the lever (that is, the rotary lever is rotated to enable or disable the rotation of the tool bit, whereas the slide lever is moved linearly, i.e., slid, to enable or disable the reciprocating motion of the tool bit).
According to the foregoing embodiment, a first switch device (the rotary lever) is rotated in order to enable or disable the rotation of the tool bit, whereas a second switch device (the slide lever) is slid to enable or disable the reciprocating motion of the tool bit, as described above. However, the opposite arrangement may be adopted without departing from the scope of the invention (i.e., the rotary lever is operated in order to enable or disable the reciprocating motion of the tool bit, whereas the slide lever is operated to enable or disable the rotation motion of the tool bit). Alternatively, both levers may be operated by either slide or rotary motion. Furthermore, the mechanisms to transmit rotation and hammer blows that are enabled or disabled by the two levers need not be structured according to the foregoing embodiment; they may be changed, altered, or modified to suit specific applications.
According to the present invention, first and second operating members enable mode switching among three operating modes of an electric power drill. Furthermore, although two operating members are used, a lock means coordinates the two operating members to prohibit the two operating members from moving to their respective “off” positions at the same time, thus preventing the tool from entering an “off-off” state. In other words, while one operating member is in the position in which the operation of the motor is not transmitted to the tool bit, movement of the other operating member to the position in which the operation of the motor is not transmitted to the tool bit is prohibited. This ensures easy and accurate selection of a desired operating mode, thus providing an electric power tool with an improved operability.
Moreover, the lock means can be realized in simple and logical construction by the particular configurations of the operating members, a cut-out, and a chamfer formed on the operating members.
Equivalents
It will thus be seen that the present invention efficiently attains the objects set forth above, among those made apparent from the preceding description. As other elements may be modified, altered, and changed without departing from the scope or spirit of the essential characteristics of the present invention, it is to be understood that the above embodiments are only an illustration and not restrictive in any sense. The scope or spirit of the present invention is limited only by the terms of the appended claims.
Claims
- 1. A hammer drill, comprising:a chuck mounted on a front end of the hammer drill; a motor for providing drive power for the chuck; a rotation transmission mechanism provided between the chuck and the motor for transmitting rotation of the motor to the chuck; an impact transmission mechanism provided between the chuck and the motor for transmitting hammer blows generated by the motor to the chuck; a first change-over member associated with the rotation transmission mechanism for selectively enabling and disabling the rotation transmission mechanism to transmit the rotation of the motor to the chuck; a second change-over member associated with the impact transmission mechanism for selectively enabling and disabling the impact transmission mechanism to transmit the hammer blows generated by the motor to the chuck; a manually operable first operating member movable between operative and inoperative positions, wherein the first operating member, when in the operative position, operates the first change-over member so as to enable the rotation transmission mechanism and, when in the inoperative position, operates the first change-over member to disable the rotation transmission mechanism; a manually operable second operating member movable between operative and inoperative positions, wherein the second operating member, when in the operative position, operates the second change-over member so as to enable the impact transmission mechanism and, when in the inoperative position, operates the second change-over member to disable the impact transmission mechanism; and a lock means for, when one of the first and second operating members is in its inoperative position, coordinating with the other operating member so as to prohibit the other operating member from moving to its inoperative position.
- 2. A hammer drill in accordance with claim 1, wherein one of the first and second operating members is a circular rotary lever and the other operating member is a slide lever slidable tangentially to the rotary lever, and further wherein the lock means comprises a cut-out formed in an edge of the slide lever for fitting the circumferential edge of the rotary lever so as to prevent the slide lever to slide when the slide lever is in its operative position, and a chamfer formed on a portion of the circumferential edge of the rotary lever such that when the rotary lever is rotated to the operative position, the chamfer is positioned adjacent the slide lever so as to allow the slide lever to slide, and when the rotary lever is rotated to the operative position and the slide lever is in its inoperative position, the chamfer closely opposes an edge of the slide lever so as to prohibit rotation of the rotary lever.
- 3. A hammer drill in accordance with claim 2, wherein the first operating member is the rotary lever and the second operating member is the slide lever, and further wherein the rotary lever and the slide lever are disposed on a line parallel to a longitudinal axis of the chuck, with the rotary lever interposed between the chuck and the slide lever.
- 4. A hammer drill in accordance with claim 3, wherein the slide lever has a generally rectangular shape, being slidable on the rotary lever and perpendicularly to the parallel line between its operative and inoperative positions.
- 5. A hammer drill in accordance with claim 4, wherein the rotary lever is rotated 180 degrees around a second axis from its inoperative position to its operative position, the second axis intersecting and oriented perpendicularly to the parallel line.
- 6. A hammer drill in accordance with claim 5, wherein the cut-out is formed in a portion of the long side of the slide lever which is adjacent to the rotary lever, leaving a portion of the long side intact where the cut-out is not formed, the intact side edge closely opposing the chamfer of the rotary lever when the rotary lever is in its operative position and the slide lever is in the inoperative position such that the rotary lever cannot be rotated back to its inoperative position unless the slide lever is slid back to its operative position.
- 7. A hammer drill in accordance with claim 6, wherein the first change-over member is a sleeve member which is rotatably disposed within a housing of the hammer drill about the longitudinal axis and slid along the longitudinal axis between an operative position, in which the rotation transmission mechanism is enabled, and an inoperative position, in which the rotation transmission mechanism is disabled, and further wherein the sleeve member is interlocked with the rotation transmission mechanism so as to be rotated by the motor when in the operative position and is disengaged from the rotation transmission mechanism and secured to the housing so as to be prevented from rotating when in the inoperative position.
- 8. A hammer drill in accordance with claim 7, wherein, when the rotary lever is rotated approximately 90 degrees from either of the operative and inoperative positions to an intermediate position, the sleeve member is neither secured to the housing nor interlocked with the rotation transmission mechanism, thus permitting manual adjustment of the rotary angle of the sleeve member.
- 9. A hammer drill in accordance with claim 8, wherein the rotary lever bears a mark adjacent to the chamfer for indicating the location of the first change-over member between its operative and inoperative positions.
- 10. A hammer drill in accordance with claim 9, wherein the impact transmission mechanism comprises a crank mechanism connected to the rotor for converting the rotation of the motor into reciprocation motion as the hammer blows, and further wherein the second change-over member interlocks the motor to the crank mechanism when the slide lever is in the operative position, thus enabling the crank mechanism, and the second change-over member disengages the crank mechanism from the motor when the slide lever is in the inoperative position, thus disabling the crank mechanism.
Priority Claims (1)
Number |
Date |
Country |
Kind |
10-261891 |
Sep 1998 |
JP |
|
US Referenced Citations (11)
Foreign Referenced Citations (1)
Number |
Date |
Country |
9-57650 |
Sep 1997 |
JP |