Power-driven hammer drill having an improved operating mode switch-over mechanism

Information

  • Patent Grant
  • 6176321
  • Patent Number
    6,176,321
  • Date Filed
    Tuesday, September 14, 1999
    25 years ago
  • Date Issued
    Tuesday, January 23, 2001
    23 years ago
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)
Number Name Date Kind
3680642 Kirn et al. Aug 1972
3834468 Hettich et al. Sep 1974
3908108 Hults Sep 1975
4158313 Smith Jun 1979
4236588 Moldan et al. Dec 1980
4428438 Holzer Jan 1984
4506743 Grossman Mar 1985
4732218 Neumaier et al. Mar 1988
5111889 Neumaier May 1992
5664634 McCracken Sep 1997
5842527 Arakawa et al. Dec 1998
Foreign Referenced Citations (1)
Number Date Country
9-57650 Sep 1997 JP