Power tool

An improved power tool is provided which can alert a user of any halfway selection of a driving mode of a tool bit. A representative power tool is provided which is capable of switching among driving modes different in driving state of a tool bit. The power tool has a mode switching member that switches among the driving modes, a detecting part that detects a drive prohibited state in which any of the driving modes of the tool bit is not selected, and indicating parts that indicate a result detected by the detecting part.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a power tool switchable among driving modes different in driving state of a tool bit.

2. Description of the Related Art

Japanese non-examined laid-open Patent Publication No. 2006-957 discloses a hammer drill which is capable of switching a driving mode of a tool bit in the form of a hammer bit between a hammer drill mode in which the hammer bit is caused to perform linear movement in its axial direction and rotation around its axis and a hammer mode in which the hammer bit is caused to perform linear movement in its axial direction. The known hammer drill has an operating mechanism that converts the rotating output of the motor into linear motion and then causes the hammer bit to linearly move via a striker, and a power transmitting mechanism that transmits the rotating output of the motor at reduced speed and causes the hammer bit to rotate. The power transmitting mechanism is provided with a mechanical claw clutch for switching the driving mode of the hammer bit. In order to switch the driving mode of the hammer bit between hammer drill mode and hammer mode, a mode switching member is operated to switch the claw clutch between a power transmission state and a power transmission interrupted state.

In the known claw clutch, when the driving mode of the hammer bit is switched from hammer mode to hammer drill mode by operating the mode switching member, driving-side clutch teeth and driven-side clutch teeth are engaged with each other, so that the clutch is shifted to the power transmission state.

Therefore, when the mode switching member is not switched to a normal hammer drill mode position and selection of the driving mode of the hammer bit is in a halfway state, the clutch teeth are also in halfway engagement. Driving of the hammer drill in such a halfway clutch engagement may cause acceleration of wear and decrease of durability.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the invention to provide an improved power tool which can alert a user of any halfway selection of a driving mode of a tool bit.

In order to solve the above-described problem, according to a preferred embodiment of this invention, a power tool is provided which is capable of switching among driving modes different in driving state of a tool bit. The power tool includes a mode switching member that switches among the driving modes, a detecting part that detects a drive prohibited state in which any of the driving modes of the tool bit is not selected, and an indicating part that indicates a result detected by the detecting part. The “drive prohibited state” in this invention refers to a state in which the power tool must not be driven or driving the power tool is undesirable.

According to this invention, when selection of the driving mode of the tool bit is in the drive prohibited state in which any of the driving modes is not selected, or specifically when the mode switching member is not placed in any normal driving mode position, this state is detected by the detecting part and indicated by the indicating part. By this indication, the user is prompted to operate the mode switching member again to select the driving mode. As a result, the tool bit can be avoided from being driven in the drive prohibited state. Further, in this invention, with the construction in which the indicating part indicates that the mode switching member is placed outside of any normal driving mode position (in a halfway position), in contrast to a construction in which indication is made for each of the driving mode positions, it requires only a single indication.

According to a further embodiment of this invention, the power tool has a motor for driving the tool bit. When the detecting part detects the drive prohibited state, the indicating part controls driving of the motor and indicates by the controlled state of the motor that selection of the driving mode of the tool bit is in the drive prohibited state. The “drive control of the motor” in this invention typically represents the manner of stopping the motor or driving the motor at very slow speed so as to preclude operation of the tool bit.

According to this embodiment, when the user operates to drive the motor, the user can be made aware of any selection of the driving mode of the tool bit which is in the drive prohibited state, by visually checking the driving state of the tool bit.

According to a further embodiment of the power tool of this invention, the drive control of the motor is made by stopping the motor. The manner of “stopping the motor” here typically represents the manner of turning off the motor.

According to this embodiment, when selection of the driving mode of the tool bit is in the drive prohibited state, even if the user operates to drive the motor, the motor is not driven and thus the tool bit is not driven, so that the user can be alerted or made aware of this state.

According to a further embodiment of the power tool of this invention, the mode switching member is formed by a dial that is manually turned, and the detecting part for detecting the drive prohibited state is formed by a cam mechanism that is operated in conjunction with turning movement of the dial.

According to this embodiment, the cam mechanism can be compactly arranged in a concentrated manner in the vicinity of the dial.

According to a further embodiment of the power tool of this invention, the cam mechanism has a cam plate that rotates together with the dial, a swinging lever that swings according to a cam lift of the cam plate and a switch that is turned on and off by components of linear motion in the swinging movement of the swinging lever.

According to this embodiment, with the construction in which the switch is turned on and off by components of linear motion in the swinging movement of the swinging lever, the force of the swinging lever can be avoided from being applied to the switch in a direction other than the direction of movement, so that stable movement and failure prevention of the switch can be realized.

According to a further embodiment of the power tool of this invention, in addition to drive control of the motor, the indicating part includes an illuminating means that indicates at least one of a drive allowed state in which any one of the driving modes is selected and the drive prohibited state.

According to this embodiment, at least one of the drive allowed state and the drive prohibited state of the tool bit is indicated by the illuminating means in addition to drive control of the motor. Therefore, if the detecting part is formed only by drive control of the motor, the user may mistake the drive prohibited state for motor failure. According to this embodiment, however, the user's mistake can be avoided by using the illuminating means in combination with the motor drive control.

According to a further embodiment of the power tool of this invention, the power tool is provided and constructed as a hammer drill having at least one of hammer mode in which the tool bit is caused to perform only linear movement in its axial direction and drill mode in which the tool bit is caused to perform only rotation around its axis, and having hammer drill mode in which the tool bit is caused to perform both linear movement in its axial direction and rotation around its axis, as the driving modes of the tool bit.

According to this embodiment, in the hammer drill, when any of the hammer mode or the drill mode and the hammer drill mode is not selected, the detecting part detects this state and the indicating part indicates this state and thereby prompts the user to operate the mode switching member again to select the driving mode. As a result, the tool bit can be avoided from being driven in the drive prohibited state.

According to this invention, an improved power tool is provided which can alert a user of any halfway selection of a driving mode of a tool bit. Other objects, features and advantages of the present invention will be readily understood after reading the following detailed description together with the accompanying drawings and the claims.

DETAILED DESCRIPTION OF THE INVENTION

Each of the additional features and method steps disclosed above and below may be utilized separately or in conjunction with other features and method steps to provide and manufacture improved power tools and method for using such power tools and devices utilized therein. Representative examples of the present invention, which examples utilized many of these additional features and method steps in conjunction, will now be described in detail with reference to the drawings. This detailed description is merely intended to teach a person skilled in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention. Only the claims define the scope of the claimed invention. Therefore, combinations of features and steps disclosed within the following detailed description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe some representative examples of the invention, which detailed description will now be given with reference to the accompanying drawings.

An electric hammer drill is now explained as a representative embodiment of the power tool according to this invention with reference toFIGS. 1 to 7. As shown inFIG. 1, the hammer drill101of this embodiment mainly includes a power tool body in the form of a body103that forms an outer shell of the hammer drill101, a hammer bit119detachably coupled to a front end region (left end as viewed inFIG. 1) of the body103via a tool holder137, and a handgrip109that is connected to the body103on the side opposite to the hammer bit119and designed to be held by a user. The hammer bit119is held by a tool holding member in the form of a hollow tool holder137such that it is allowed to linearly move in its axial direction with respect to the tool holder137. The hammer bit119is a feature that corresponds to the “tool bit” according to this invention. Further, for the sake of convenience of explanation, the side of the hammer bit119is taken as the front and the side of the handgrip109as the rear.

The body103includes a motor housing105that houses a driving motor111, an inner housing in the form of a gear housing107that houses a motion converting mechanism113, a striking mechanism115and a power transmitting mechanism117, and an outer housing104that covers the gear housing107.

The driving motor is disposed such that its rotation axis runs vertically in a direction (vertical direction as viewed inFIG. 1) generally perpendicular to the longitudinal direction of the body103(the axial direction of the hammer bit119). A rotating power of the driving motor111is converted into linear motion by the motion converting mechanism113and then transmitted to the striking mechanism115. As a result, an impact force is generated in the axial direction (horizontal direction as viewed inFIG. 1) of the hammer bit119via the striking mechanism115. The motion converting mechanism113and the striking mechanism115form a striking drive mechanism.

Further, the rotation speed of the driving motor111is reduced by the power transmitting mechanism117and then the rotating output of the driving motor111is transmitted to the hammer bit119via the tool holder137. As a result, the hammer bit119is caused to rotate in a circumferential direction. The driving motor111is driven when a trigger109aon the handgrip109is depressed. The power transmitting mechanism117forms a rotational drive mechanism.

FIG. 2shows an essential part of the hammer drill101. As shown inFIG. 2, the motion converting mechanism113mainly includes a driving gear121that is formed on a motor shaft111aof the driving motor111and rotationally driven in a horizontal plane, a driven gear123that engages with the driving gear121, a crank shaft125that rotates together with the driven gear123, a crank pin126that is eccentrically disposed on the crank shaft125, a crank arm127that is loosely connected to the crank pin126, and a driving element in the form of a piston129that is mounted to the crank arm127via a connecting shaft128. The motor shaft111aand the crank shaft125are disposed parallel to each other and side by side in the longitudinal direction of the body. The crank shaft125, the crank pin126, the crank arm127and the piston129form a crank mechanism. The piston129is slidably disposed within the cylinder141and linearly moves in the axial direction of the hammer bit along the cylinder141when the driving motor111is driven.

The striking mechanism115mainly includes a striking element in the form of a striker143that is slidably disposed within the bore of the cylinder141, and an intermediate element in the form of an impact bolt145that is slidably disposed within the tool holder137and transmits the kinetic energy of the striker143to the hammer bit119. The cylinder141has an air chamber141adefined by the piston129and the striker143. The striker143is driven via pressure fluctuations (air spring) of the air chamber141awhich is caused by sliding movement of the piston129. The striker143then collides with (strikes) the impact bolt145that is slidably disposed within the tool holder137, and transmits the striking force to the hammer bit119via the impact bolt145.

The tool holder137is disposed coaxially with the cylinder141such that it can rotate, and rotated via the power transmitting mechanism117by the driving motor111. A clutch mechanism151is disposed in a region of the power transmitting mechanism117and serves to allow transmission of rotation of the driving motor111to the tool holder137or to interrupt such transmission.

In the power transmitting mechanism117, rotation of the intermediate gear131which engages with the driving gear121driven by the driving motor111is transmitted to the intermediate shaft132via the clutch mechanism151. The rotation of the intermediate shaft132is then transmitted from a small bevel gear133to the tool holder137via a large bevel gear134which engages with the small bevel gear133. The small bevel gear133is integrally formed on an axial end (upper end as viewed inFIG. 2) of the intermediate shaft132. The large bevel gear134which engages with the small bevel gear133is disposed coaxially with the cylinder141and rotates together with the tool holder137. The intermediate shaft132is disposed in parallel to the motor shaft111aof the driving motor111and perpendicularly to the axial direction of the hammer bit.

The clutch mechanism151is provided as a mode switching claw clutch for switching a driving mode of the hammer bit119. Further, the clutch mechanism151mainly includes a driving-side clutch member153which is loosely fitted onto the intermediate shaft132and a driven-side clutch member155which is spline-fitted onto the intermediate shaft132such that it can slide in the axial direction and rotate together with the intermediate shaft132in a circumferential direction. The driving-side clutch member153is connected to the intermediate gear131via a torque limiter135, and when the driving motor111is driven and the rotational load on the hammer bit119is within the range of critical value set at the torque limiter135, the driving-side clutch member153is caused to rotate together with the intermediate gear131.

The driving-side clutch member153and the driven-side clutch member155are opposed to each other in a direction (vertical direction) transverse to the axial direction of the hammer bit and have clutch teeth153a,155a, respectively, on their opposed surfaces. The driven-side clutch member155is constantly biased toward the driving-side clutch member153by a biasing force of a biasing member in the form of a clutch spring157. When the clutch teeth155aof the driven-side clutch member155is engaged with the clutch teeth153aof the driving-side clutch member153, rotation of the driven-side clutch member155is transmitted to the intermediate shaft132(seeFIG. 1). Further, when the driven-side clutch member155is separated from the driving-side clutch member153against the clutch spring157, the clutch teeth153a,155aare disengaged from each other, so that the transmission of rotation to the intermediate shaft132is interrupted (seeFIG. 2).

The electric hammer drill101has a mode switching mechanism161for switching the driving mode of the hammer bit119. In this embodiment, the mode switching mechanism161can be switched between a hammer mode for causing the hammer bit119to perform only striking movement in the axial direction and a hammer drill mode for causing the hammer bit119to perform striking movement in the axial direction and rotation in the circumferential direction. The hammer mode and the hammer drill mode are features that correspond to the “driving modes different in driving state” according to this invention.

The mode switching mechanism161is now explained with reference toFIGS. 2 to 4. The mode switching mechanism161mainly includes a mode switching dial163which can be switched between hammer mode and hammer drill mode, and is connected to the clutch mechanism151via a clutch switching mechanism171. When the mode switching dial163is placed in a hammer mode position (the hammer mode is selected), the clutch mechanism151is brought into a power transmission interrupted state. Further, when the mode switching dial163is placed in a hammer drill mode position (the hammer drill mode is selected), the clutch mechanism151is turned into a power transmission state. The mode switching dial163is disposed externally (on the upper side as viewed inFIG. 2) on the upper surface of the outer housing104and can be operated from outside by the user. The mode switching dial163is a feature that corresponds to the “mode switching member” and the “dial” according to this invention.

The mode switching dial163includes a disc163awith an operating grip163band disposed on the outer housing104such that it can be turned in a horizontal plane. The operating grip163bis mounted on the top of the disc163asuch that it extends diametrically. Further, one end of the operating grip163bin its extending direction is tapered and serves as a switching position indicating part. Further, a mark164indicating the hammer mode position and a mark165indicating the hammer drill mode position are put on the outer housing104with predetermined spacing in the circumferential direction.

A cam plate183has a circular boss part184on its underside and is fixedly fastened to the underside of the disc163aby a screw182. The boss part184is rotatably supported in an opening107aformed in the gear housing107. Specifically, the underside of the mode switching dial163disposed on the upper surface of the outer housing104faces the internal space of the gear housing107through the outer housing104and the gear housing107and is rotatably supported by the opening107aof the gear housing107. Further, an operating pin163dis mounted on the underside of the cam plate183in a position displaced from a center of rotation of the mode switching dial163and rotates together with the mode switching dial163. The operating pin163doperates in conjunction with the clutch switching mechanism171disposed within the gear housing107. Further, the cam plate183is provided as one of components forming a detecting mechanism181for detecting that the mode switching dial163is placed in a position other than normal driving mode positions, which will be described below.

The clutch switching mechanism171is provided as a switching movement transmitting member for transmitting turning movement of the mode switching dial163to the clutch mechanism151when the mode switching dial163is turned in the circumferential direction to switch the driving mode, and disposed within the gear housing107. As shown inFIG. 2, the clutch switching mechanism171mainly includes a frame member173that is rectilinearly moved in the axial direction of the hammer bit by eccentric rotation of the operating pin163dwhen the mode switching dial163is turned in a horizontal plane, a ring member175that is fitted on an outer periphery of the tool holder137and can move in the axial direction of the hammer bit, a connecting member176that transmits rectilinear movement of the frame member173to the ring member175, and a cam member177that is provided on the ring member175and controls engagement of the clutch mechanism151. Further, the frame member173is engaged with the operating pin163dvia a slot173aextending in a horizontal direction transverse to the axial direction of the hammer bit, and the frame member173is caused to rectilinearly move in the longitudinal direction of the cylinder141by components of linear motion of the eccentrically rotating pin163din the longitudinal direction of the cylinder.

The cam member177is provided on the underside of the ring member175, and an underside of the cam member177is stepped in the vertical direction transverse to the axial direction of the hammer bit and has an upper cam face177a, a lower cam face177band an inclined surface177cwhich connects the cam faces177a,177b. The cam member177serves to switch the operating state of the clutch mechanism151via a cam follower in the form of a clutch-switching actuation member159by horizontally moving in the longitudinal direction of the cylinder together with the ring member175.

As shown inFIG. 2, the clutch-switching actuation member159is provided as a member having an L-shaped section which can move rectilinearly in the vertical direction transverse to the axial direction of the hammer bit. The clutch-switching actuation member159has an upper end held in contact with the underside (cam face) of the cam member177and a lower end held in contact with an upper surface of the driven-side clutch member155in the clutch mechanism151.

In the hammer drill101constructed as described above, when the user turns the mode switching dial163to the hammer mode position (seeFIG. 3), the frame member173of the clutch switching mechanism171is moved rearward (toward the right end as viewed inFIG. 2or “toward the handgrip109”) and then the ring member175and the cam member177are also moved in the same direction. By this movement, the clutch-switching actuation member159is pushed downward by the inclined surface177cof the cam member177and moved downward in the direction of the axis of the intermediate shaft132. The clutch-switching actuation member159then comes in contact with the lower cam face177band is held in this position. By the downward movement of the clutch-switching actuation member159, the driven-side clutch member155is separated from the driving-side clutch member153against the clutch spring157, so that the clutch teeth155aof the driven-side clutch member155are disengaged from the clutch teeth153aof the driving-side clutch member153. This state is shown inFIG. 2.

In this state, when the user depresses the trigger109aon the handgrip109and the driving motor111is driven, rotation of the driving motor111is converted into linear motion by the motion converting mechanism113and then transmitted to the hammer bit119as linear motion via the striker143and the impact bolt145which form the striking mechanism115. At this time, as described above, the clutch mechanism151of the power transmitting mechanism117is in disengagement, and thus, the hammer bit119does not rotate. Therefore, when the hammer mode is selected, a predetermined hammering operation is performed solely by striking movement (hammering movement) of the hammer bit119.

When the user turns the mode switching dial163to the hammer drill mode position (seeFIG. 4), the frame member173of the clutch switching mechanism171is moved forward (toward the left end as viewed inFIG. 2or “toward the hammer bit119”). Thus, the ring member175and the cam member177are also moved in the same direction, and the upper end of the clutch-switching actuation member159slides on the inclined surface177cof the cam member177and comes in contact with the upper cam face177a. Therefore, the driven-side clutch member155is moved toward the driving-side clutch member153by the biasing force of the clutch spring157, so that the clutch teeth155aof the driven-side clutch member155are engaged with the clutch teeth153aof the driving-side clutch member153. This state is shown inFIG. 1.

In this state, when the driving motor111is driven, in addition to the striking movement of the hammer bit119in the axial direction which is caused by the motion converting mechanism113and the striking mechanism115, the rotating output of the driving motor111is transmitted as rotation to the tool holder137and the hammer bit119held by the tool holder137via the power transmitting mechanism117. Specifically, when the hammer drill mode is selected, the hammer bit119is driven by striking movement (hammering movement) and rotation (drilling movement), so that a predetermined hammer drill operation can be performed on a workpiece.

As described above, however, in the construction in which the mode switching dial163is operated to switch the claw clutch mechanism151between the power transmission state and the power transmission interrupted state by controlling engagement between the clutch teeth153aand155aof the claw clutch mechanism151in order to switch the driving mode of the hammer bit119between the hammer mode and the hammer drill mode, it may possibly happen that neither the normal hammer mode nor the hammer drill mode is selected as the driving mode of the hammer bit119. Specifically, in mode switching operation, the mode switching dial163may be placed halfway to a proper mode position. In such a case, a switching stroke of the driven-side clutch member155is inadequate, so that the clutch teeth155a,153aof the clutch mechanism151are inadequately engaged with each other. When the hammer drill101is driven in such an inadequately engaged state, in the case of switching from hammer drill mode to hammer mode, the hammer bit119continues to rotate, so that the user notices that the mode switching dial163is not turned to the normal hammer mode position. In the case of switching from hammer mode to hammer drill mode, however, the user performs the hammer drill operation without noticing such a state. As a result, wear of the clutch teeth153a,155ais accelerated and durability of the clutch mechanism151is impaired.

In this embodiment, therefore, it is constructed to alert the user that the mode selection is in a drive prohibited state in which driving of the hammer bit119is to be prohibited when neither the hammer mode nor the hammer drill mode is selected as the driving mode of the hammer bit119with the mode switching dial163. For this purpose, in this embodiment, a detecting mechanism181for detecting the drive prohibited state and an indicating mechanism for indicating the drive prohibited state according to this detection are provided. The detecting mechanism181and the indicating mechanism are now explained with reference toFIGS. 2 and 5to7.

The detecting mechanism181for detecting the drive prohibited state mainly includes a cam mechanism that operates in conjunction with the mode switching movement of the mode switching dial163, and is a feature that corresponds to the “detecting part” according to this invention. The cam mechanism mainly includes the disc-like cam plate183that rotates together with the mode switching dial163, a swinging lever185that swings according to the cam lift of the cam plate183(a difference between a radius from the center of the cam plate183to a circumferential surface183aand a radius from the center of the cam plate183to bottoms of recesses183b,183cwhich are described below) and a microswitch187that is turned on and off by components of linear motion in the swinging movement of the swinging lever185.

The cam plate183is fixedly fastened to the underside of the disc163aof the mode switching dial163by a screw182and has the circular boss part184on its underside. The boss part184is held in the opening107aof the gear housing107such that it can rotate in the horizontal plane. The cam plate183has a circumferential surface183aprovided as a region for detecting the drive prohibited state, and two generally V-shaped recesses183b,183cthat are formed in the circumferential surface183aand provided as a region for detecting the driving mode. One of the recesses183bis for use in detecting hammer mode and the other recess183cis for use in detecting hammer drill mode. Both of the recesses183b,183care formed in the circumferential surface183ain the circumferential direction with a spacing corresponding to the distance between the hammer mode position mark164and the hammer drill mode position mark165which are put on the outer housing104. As should be appreciated, the recesses183b.183care an example of regions for detecting the operating modes and the circumferential surface of the cam plate183between the recesses183b,183cis an example of regions for detecting the drive prohibited state.

The swinging lever185is disposed in front of the cam plate183and extends horizontally in a lateral direction transverse to the axial direction of the hammer bit. The swinging lever185is a feature that corresponds to the “swinging lever” according to this invention. One end of the swinging lever185in the extending direction is mounted to the gear housing107such that it can swing on a mounting shaft185ain the front-back direction (the axial direction of the hammer bit). The other end of the swinging lever185in the extending direction is designed as a pressing part185bwhich faces an actuating element187aof the microswitch187. Further, the swinging lever185is constantly biased by a spring (not shown) in such a manner as to swing toward the circumferential surface of the cam plate183.

A protrusion185cis formed on the swinging lever185at a midpoint position in the extending direction at which the swinging lever185can come in contact with the circumferential surface183aof the cam plate183. The protrusion185chas a generally V-shaped form corresponding to the shape of the recess183bfor hammer mode and the recess183cfor hammer drill mode. When the mode switching dial163is placed in (selects) the normal hammer mode position or hammer drill mode position, the swinging lever185is caused to swing rearward by the biasing force of the spring and the protrusion185cis engaged with the recess183bfor hammer mode or the recess183cfor hammer drill mode. In this engaged state, the pressing part185bis separated from the actuating element187aof the microswitch187and the microswitch187is turned off. This state is shown inFIGS. 5 and 6.

When the mode switching dial163is turned to a position other than the normal hammer mode position or hammer drill mode position, the protrusion185cis pushed out of the recess183bor183cby an inclined surface of the recess183bfor hammer mode or the recess183cfor hammer drill mode and abuts against the circumferential surface183a. Thus, the swinging lever185swings forward against the biasing force of the spring, and the pressing part185bpresses the actuating element187aof the microswitch187so that the microswitch187is turned on. This state is shown inFIG. 7. Specifically, when neither the hammer mode nor the hammer drill mode is selected as the driving mode of the hammer bit119, the microswitch187is turned on.

The pressing part185bof the swinging lever185has a flat surface and the actuating element187aof the microswitch187has a spherical surface. With such a construction, the pressing part185bof the swinging lever185pushes the actuating element187aof the microswitch187in sliding contact therewith. Therefore, on-off control of the microswitch187is made only by components of linear motion of the swinging lever185in the swinging direction (front-back direction).

The on/off state of the microswitch187is inputted as an on/off signal into a motor control device in the form of a controller189for controlling the driving motor111via a lead190. When the off signal is inputted into the controller189from the microswitch187, the controller189turns on the driving motor111. Further, when the on signal is inputted into the controller189from the microswitch187, the controller189turns off the driving motor111. When the power is on, the driving motor111can be driven by depressing the trigger109a. When the power is off, however, even if the trigger109ais depressed, the driving motor111is kept in the stopped state in which the driving motor111cannot be driven. Specifically, when the mode switching dial163is placed in a position other than the normal hammer mode position or hammer drill mode position, the controller189turns off the power and does not enable the driving motor111to be driven by depressing the trigger109a, and thereby alerts the user that the mode selection is in a drive prohibited state. In other words, unless the mode switching dial163is reliably placed in the hammer mode position or the hammer drill mode position, the driving motor111is not turned on. A drive control of the driving motor111by the controller189forms a first indicating mechanism for indicating a drive prohibited state. Further, the on signal of the microswitch187is designed and provided as a signal for detecting that the mode switching dial163is placed in a position other than the normal hammer mode position or hammer drill mode position.

Further, in this embodiment, in addition to the “first indicating mechanism” formed by the drive control of the driving motor111, a second indicating mechanism which mainly includes a lamp unit191is provided. The lamp unit191mainly includes a plurality of lamps (LED)193a,193band a lamp holding part195for holding the lamps193a,193b, and is fixedly mounted on the outside of the gear housing107. The lamps193a,193bemit light to the outside through illumination holes107b(seeFIG. 2) formed in the outer housing104. The lamps (LED)193a,193bare features that correspond to the “illuminating means” according to this invention.

One of the lamps193ais defined as a lamp for indicating a drive prohibited state and the other lamp193bas a lamp for indicating a drive allowed state. When the above-described microswitch187is in the on state, the lamp193ais turned on and the lamp193bis turned off. When the microswitch187is in the off state, the lamp193ais turned off and the lamp193bis turned on. The lamps193a,193bare designed to emit light of different colors. For example, it is designed such that the lamp193aemits red light and the lamp193bemits blue light. The first indicating mechanism and the second indicating mechanism are features that correspond to the “indicating part” according to this invention.

According to this embodiment constructed as described above, when the mode switching dial163is placed in a halfway position between the hammer mode position and the hammer drill mode position, the swinging lever185is swung forward by the cam plate183of the detecting mechanism181formed by the cam mechanism, so that the microswitch187is turned on. Thus, the mode selection is detected as being in the drive prohibited state. In response to this detected signal, the controller189turns off the driving motor111and does not enable the driving motor111to be driven. Therefore, even if the user depresses the trigger109a, the driving motor111is not driven and thus the hammer bit119is not driven. From this state, the user can be alerted or made aware of any selection of the driving mode of the hammer bit119which is in the drive prohibited state.

In a construction in which the drive prohibited state is indicated by stopping the driving motor111via the controller189, the user may mistake the drive prohibited state for motor failure. According to this embodiment, however, with the construction in which the lamp193ailluminates to indicate the drive prohibited state when the microswitch187is turned on, the mistake as described above can be eliminated. In this manner, according to this embodiment, halfway mode selection with the mode switching dial163is indicated so that the user is prompted to turn the mode switching dial163to the normal driving mode position. Thus, wear can be prevented from being accelerated by halfway engagement between the clutch teeth153a,155aof the clutch mechanism151due to a halfway mode selection.

When the mode switching dial163is placed in the normal hammer mode position or hammer drill mode position, the other lamp193billuminates and indicates that the driving mode of the hammer bit119is properly selected. At the same time, the driving motor111is turned on by the controller189and can be driven by operating the trigger109a.

According to this embodiment, with the construction in which the detecting mechanism181for detecting the drive prohibited state is formed by the cam mechanism operated in conjunction with turning movement of the mode switching dial163, the cam mechanism can be compactly arranged in a concentrated manner in the vicinity of the mode switching dial163. Further, with the construction in which the cam mechanism is disposed by utilizing a space between the gear housing107and the outer housing covering the gear housing107, rational placement is realized without increase of the size of the body103.

In this embodiment, the swinging lever185is disposed between the cam plate183and the microswitch187, and the microswitch187is turned on and off by components of linear motion of the swinging lever185in the swinging direction. Therefore, the swinging lever185can be avoided from applying a force to the microswitch187in a direction transverse to the direction of its movement, so that this construction is effective in stable movement and failure prevention of the microswitch187.

According to this embodiment, the hammer drill101has a plurality of indicating mechanisms or the “first indicating mechanism” including the drive control of the driving motor111by the controller189and the second indicating mechanism including the lamp unit191. Therefore, the drive prohibited state can be more reliably detected.

In the above-described embodiment, in the drive control of the driving motor111by the controller189, the driving motor111is described as being turned off and stopped, but it may be constructed such that the driving motor111is held in the on state and driven at a speed too slow to perform an operation by the hammer bit119.

In this embodiment, the hammer drill is explained which is capable of switching the driving mode of the hammer bit119between hammer mode and hammer drill mode, but this invention can also be applied to a hammer drill which provides a drill mode in which the hammer bit119is caused only to rotate in the circumferential direction, or a neutral mode in which the user holds the hammer bit119and can arbitrarily rotate it, in addition to the above-described two driving modes. In this case, in this embodiment, with the construction in which the circumferential surface183aof the disc-like cam plate183is provided as the region for detecting the drive prohibited state, such an additional driving mode can be easily provided by forming a recess for use in the additional mode in the circumferential surface183a. Therefore, no additional element or component is needed, so that cost increase can be prevented. As should be appreciate the hammer mode, the hammer drill mode, the drill mode and the neutral mode are each an example of an operating mode because they are each a predetermined mode in which the hammer drill can operate.

In this embodiment, the drive prohibited state is indicated by drive control of the motor via the controller189. In place of drive control of the motor, however, it may be constructed such that the drive prohibited state is indicated by locking (fixing) the operating member (the trigger109a) for driving the driving motor111such that it cannot be operated.

In this embodiment, the two different kinds of lamps, i.e. the lamp193afor indicating the drive prohibited state of the driving mode of the hammer bit119and the lamp193bfor indicating the drive allowed state, are provided and the lamps indicate the respective states. As an alternative to this construction, however, only one kind of the lamp may be provided to indicate either the drive prohibited state or the drive allowed state. Specifically, it may be constructed such that the lamp illuminates in the drive prohibited state, or such that the lamp illuminates in the drive allowed state.

In the above-described embodiment, the hammer drill101is explained as a representative example of the power tool according to this invention, but this invention can also be applied to any other power tool which is capable of switching among driving modes different in the driving state of the tool bit.

In view of the above-described, following features is also provided according to the invention.

“A power tool, which is capable of switching among driving modes different in driving state of a tool bit, comprising:a mode switching member that switches among the driving modes,a detecting part that detects a drive prohibited state in which any of the driving modes of the tool bit is not selected, andan indicating part that indicates a result detected by the detecting part, wherein:when the detecting part detects the drive prohibited state, the indicating part indicates said state and thereby prompts the user to operate the mode switching member again to select the driving mode.”

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