Patent Publication Number: US-10780564-B2

Title: Power tool

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority to Japanese patent application serial number 2016-198984 filed on Oct. 7, 2016, the contents of which are incorporated fully herein by reference. 
     TECHNICAL FIELD 
     The present invention generally relates to a power tool configured to linearly drive a tool accessory in a prescribed impact-axis direction. 
     BACKGROUND ART 
     Some power tools are configured to perform processing work on a workpiece by linearly driving (reciprocally driving) a tool accessory in a prescribed impact-axis (hammering) direction. In such power tools, a particularly large vibration is generated in the impact-axis direction. Various vibration-isolating housing structures have been proposed to deal with this vibration, i.e. to reduce the transmission of the vibration to the user. For example, in a hammer drill disclosed in Japanese Laid-open Patent Publication 2014-124698, a main-body housing, which comprises a handle that is grasped by a user, is elastically coupled to, and is capable of relative movement with respect to, an interior housing, which houses a drive mechanism, and a motor housing, which is fixed to the interior housing. 
     SUMMARY 
     In the above-mentioned known hammer drill, a lower end surface of an outer-circumferential wall of the main-body housing is designed to be in sliding contact with an upper-end surface of an outer-circumferential wall of the motor housing slidable in an effort to stabilize the sliding between the main-body housing and the motor housing. Nevertheless, in vibration-isolating housing structures of power tools, there is a demand for a much more significant improvement in the stability of the sliding of one housing relative to another housing. 
     It is therefore an object of the present teachings to disclose a vibration-isolating housing structure of a power tool, in which the stability of sliding of a first housing (or first housing part) relative to a second housing (or second housing part) is improved. 
     For example, the present teachings preferably may be applied to a power tool configured to linearly drive (reciprocally drive) a tool accessory in a prescribed impact-axis direction, i.e. along an impact axis. In one aspect of the present teachings, such a power tool may comprise a motor, a drive mechanism, a first housing (or first housing part), and a second housing (or second housing part). 
     The motor comprises a motor-main-body part and a motor shaft. The motor-main-body part comprises a stator and a rotor. The motor shaft extends from the rotor. The drive mechanism is preferably configured to drive, and/or includes components capable of driving, the tool accessory by using the motive power of the motor. The first housing houses the motor and the drive mechanism. The second housing is disposed such that it covers at least one portion of the first housing and it is coupled to, and is capable of relative movement with respect to, the first housing via at least one elastic element. With regard to the location of the motor, the motor-main-body part is spaced apart from the impact axis, and the motor shaft is disposed extending in a direction that intersects the impact axis. 
     The second housing preferably comprises a grasp part (handle), a first portion, and a second portion. The grasp part is configured to be graspable (held) by a user and extends in a rotational-axis direction of the motor shaft (i.e. extends in parallel, or substantially in parallel, with the rotational axis of the motor shaft). The grasp part has a first end part and a second end part at opposite ends thereof in the extension direction of the grasp part. The first portion of the second housing is connected to (e.g., extends perpendicularly or substantially perpendicularly from) the first end part of the grasp part, and covers the above-noted at least one portion of the first housing. The second portion of the second housing is connected to (e.g., extends perpendicularly or substantially perpendicularly from) the second end part of the grasp part. 
     The first housing comprises a first sliding part and a second sliding part. The first sliding part is configured to be capable of sliding relative to the first portion of the second housing. The second sliding part is configured to be capable of sliding relative to the second portion of the second housing and is provided on the side opposite the first sliding part with respect to the motor-main-body part in the rotational-axis direction of the motor shaft. 
     In such a power tool, the second housing, which comprises the grasp part that is grasped by the user, is coupled to, and is capable of sliding movement relative to, the first housing via the at least one elastic member. As was noted above, the first housing houses the motor and the drive mechanism constituting the sources of vibration. Therefore, the at least one elastic element that is interposed between the first and second housings makes it possible to reduce the transmission of vibration from the first housing to the second housing (particularly, to the grasp part). In addition, the two sliding parts (i.e., the first sliding part and the second sliding part), which are respectively slidable relative to the first portion and the second portion of the second housing, are provided on the first housing and are disposed on both sides of the motor-main-body part in the rotational axis direction of the motor shaft. Due to this arrangement, the sliding of the first housing relative to the second housing when the first housing and the second housing move relative to one another during operation (due to vibration generated in the first housing) can be made more stable than in embodiments in which a single sliding part is provided on only one side of the motor-main-body part. 
     According to another aspect of the present teachings, the second sliding part may be a sliding surface that extends parallel to the impact axis and may be configured to be capable of sliding in the impact-axis direction, relative to the sliding surface formed on the second portion, with the sliding surfaces of the second sliding part and the second portion of the second housing in contact with one another. In such an embodiment, because the sliding surface formed on the second portion contacts the sliding surface, which is disposed parallel to the impact axis and serves as the second sliding part, the sliding of the first housing relative the second housing can be guided thereby, and consequently the stability of sliding can be further increased. In addition, because the sliding direction is the impact axis direction, the largest and dominant vibration of the vibrations arising in the power tool (namely, the vibration in the impact axis direction) can be more effectively prevented from being transmitted to the grasp part owing to the fact that the first housing can (reciprocally) slide relative to the second housing (which includes the grasp part) due to the elastic connection of the first and second housings via the at least one elastic element. 
     According to another aspect of the present teachings, the power tool may further comprise a plate member. The plate member may be fixed to the first housing such that the plate member opposes the end part on the second portion side of the first housing in the rotational-axis direction of the motor shaft. In addition, the second portion of the second housing may comprise an interposed part (e.g., a plain linear bearing or linear motion guide). The interposed part may be configured such that at least a portion of the interposed part is disposed in a gap between the end part on the second portion side of the first housing and the plate member and is capable of sliding relative to the first housing in the impact-axis direction. The second sliding part may be formed on the end part on the second portion side of the first housing and may be configured to be capable of sliding relative to the sliding surface formed on the interposed part. Thus, by disposing the interposed part, which is capable of sliding in the impact-axis direction, between the end part on the second portion side of the first housing and the plate member, it is possible to reliably implement, with a simple configuration, a sliding-guide structure in the impact axis direction. 
     According to another aspect of the present teachings, at least the second sliding part of the first housing may be formed of a material that differs from the material of the second housing. In other words, within the first housing, the second sliding part (sliding surface) formed on the end part on the second portion side and the sliding surface formed on the interposed part of the second housing may be formed of different materials from each other. In such an embodiment, the second sliding part (sliding surface) and the sliding surface of the interposed part can be prevented from welding (fusing) to one another owing to frictional heat generated when the second sliding part is reciprocally sliding relative to the interposed part during operation of the power tool. 
     According to another aspect of the present teachings, the plate member may comprise a stop part that prohibits relative movement of the second portion with respect to the first housing beyond a prescribed (sliding) range in the impact-axis direction. In such an embodiment, it is possible to prevent the second housing from sliding relative to the first housing in the impact-axis direction more than is necessary to achieve the vibration isolating effect of the present teachings. 
     According to another aspect of the present teachings, the first housing and the second housing may be coupled via a plurality of elastic elements disposed between the first portion and the first housing and between the second portion and the first housing. Preferably, one or more of the plurality of elastic elements may be biasing springs that bias the first housing away from the second housing such that the grasp part (handle) spaces apart (is urged away) from the first housing. In such an embodiment, because the first housing and the second housing are coupled via biasing springs located on both ends of the grasp part, the transmission of vibration from the first housing to the grasp part (handle) can be more effectively reduced. 
     According to another aspect of the present teachings, the second portion may comprise a battery-mounting part, which is formed on an end part on a side that is spaced apart farther from the first portion in the rotational-axis direction of the motor shaft, and may be configured such that a battery (battery pack or battery cartridge) can be mounted thereto and dismounted therefrom. The power tool optionally may further comprise the battery (battery pack or battery cartridge), which is mounted (mountable) on the battery-mounting part. Thus, by providing the battery-mounting part on the second portion of the second housing, which is coupled, via elastic elements, to the first housing (which houses the motor and the drive mechanism), it is possible to prevent chattering (contact bounce) when the battery is mounted on the battery-mounting part and the tool is being operated (i.e. vibrations are being generated in the first housing). In addition, the mounting of the battery increases the mass of the second housing, and thereby a further reduction in vibration of the second housing can be achieved. Two or battery-mounting parts may be formed on the bottom surface of the second housing, such that two or more batteries (battery packs or battery cartridges) may be mounted on the second housing of the power tool. 
     According to another aspect of the present teachings, the second portion may comprise an illumination apparatus (light) configured to radiate (shine) light toward the location at which work is performed by the tool accessory. In this case, during processing work in which the power tool is used, it can be made easy to confirm the state of the tool accessory, the workpiece, and the like disposed at the work location. In addition, by providing the illumination apparatus on the second portion of the second housing, which is coupled via the elastic elements to the first housing, it is possible to protect the illumination apparatus from vibration (i.e. reduce the amount of vibration reaching the illumination apparatus, such that the light shining on the workpiece or work area shakes less during operation of the power tool). 
     Other objects, features, embodiments, functions, and effects of the present teachings will be readily apparent to persons of ordinary skill in the art upon reading the following detailed description of preferred embodiments of the present teachings, the claims, and the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an oblique view that shows the external appearance of a hammer drill according to the present teachings. 
         FIG. 2  is a longitudinal cross-sectional view of the hammer drill in an initial state. 
         FIG. 3  is an enlarged view of a motor-housing part, and the peripheral portion thereof, shown in  FIG. 2 . 
         FIG. 4  is an explanatory diagram that shows a rear view of the internal structure of the hammer drill in the state in which part of the housing has been removed. 
         FIG. 5  is a bottom view of the motor-housing part. 
         FIG. 6  is a cross-sectional view taken along line VI-VI in  FIG. 3 . 
         FIG. 7  is a longitudinal cross section of the hammer drill in the state in which a second housing has been moved frontward with respect to a first housing. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Embodiments of the present teachings are explained below, with reference to the drawings. It is noted that the embodiments below illustrate by example an electrically-driven hammer drill  1  (or rotary hammer), which serves as a representative, non-limiting example of a power tool (electrically-driven processing machine) according to the present teachings. The hammer drill  1  of the present embodiment is configured to perform both an operation (a hammering operation) in which a tool accessory  18 , which is mounted on (in) a tool holder  34 , is linearly driven (reciprocally driven) along a prescribed impact axis A 1  as well as an operation (a drill operation) in which the tool accessory  18  is rotationally driven around the impact axis A 1 . 
     First, a schematic configuration of the hammer drill  1  will be explained, with reference to  FIGS. 1 and 2 . The contour (outer periphery) of the hammer drill  1  is formed principally by a housing  10 . The housing  10  of the present embodiment is configured as a so-called vibration-isolating housing and comprises a first housing part  11  and a second housing part  13 , which is elastically coupled to, and is capable of moving (e.g., sliding in an oscillating or reciprocating manner) relative to, the first housing part  11 . 
     As shown in  FIG. 2 , the first housing part  11  comprises: a motor-housing part  111  that houses a motor  2 ; and a drive-mechanism housing part  117  that houses a drive mechanism  3 , which is configured to drive the tool accessory  18  by using the motive power of the motor  2 . The first housing part  11  is formed in substantially an L shape as a whole. The drive-mechanism housing part  117  has (is formed into) an elongate shape extending in the impact axis A 1  direction. The tool holder  34 , which is configured such that the tool accessory  18  can be mounted thereon (therein) and dismounted (removed) therefrom, is provided at one longitudinal (axial) end of the drive-mechanism housing part  117  in the impact axis A 1  direction. At the other longitudinal (axial) end of the drive-mechanism housing part  117  in the impact axis A 1  direction, the motor-housing part  111  is coupled and fixed to, and is incapable of relative movement with respect to, the drive-mechanism housing part  117  and is disposed such that it intersects the impact axis A 1  and projects in a direction leading away from the impact axis A 1 . Inside the motor-housing part  111 , the motor  2  is disposed such that a rotational axis A 2  of a motor shaft  25  extends in a direction orthogonal to the impact axis A 1 . 
     It is noted that, for the sake of convenience in the explanation below, (i) the impact axis A 1  direction of the hammer drill  1  is defined as the front-rear direction of the hammer drill  1 , (ii) the side on which the tool holder  34  is provided is defined as the “front side” (also called the “tip area side”) of the hammer drill  1 , and (iii) the opposite side thereof is defined as the “rear side” of the hammer drill  1 . In addition, (i) the direction in which the rotational axis A 2  of the motor shaft  25  extends is defined as the up-down direction of the hammer drill  1 , (ii) the direction in which the motor-housing part  111  protrudes from (projects below) the drive-mechanism housing part  117  is defined as the downward direction, and (iii) the opposite direction thereof is defined as the upward direction. 
     Referring again to  FIG. 1 , the second housing part  13  comprises a grasp part (handle)  131 , an upper-side (first) portion  133 , and a lower-side (second) portion  135 . The second housing part  13  has (is formed in) substantially a U shape as a whole. The grasp part  131  is configured to be graspable (held) by a user and is a portion that is disposed extending in (extends parallel to) the rotational axis A 2  direction (i.e., the up-down direction) of the motor shaft  25 . More specifically, the grasp part  131  is spaced apart rearward from the first housing part  11  and extends in the up-down direction. The upper-side portion  133  is connected to an upper-end part of the grasp part  131 . In the present embodiment, the upper-side portion  133  extends frontward from the upper-end part of the grasp part  131  and is configured to cover most of the drive-mechanism housing part  117  of the first housing part  11 . The lower-side portion  135  is connected to a lower-end part of the grasp part  131 . In the present embodiment, the lower-side portion  135  extends frontward from the lower-end part of the grasp part  131  and is disposed on a lower side of the motor-housing part  111 . 
     According to the above-described configuration, in the hammer drill  1  as shown in  FIG. 1 , the motor-housing part  111  of the first housing part  11  and the second housing part  13  are exposed externally and together form the outer (external) surface of the hammer drill  1 . The motor-housing part  111  of the first housing part  11  is sandwiched from above and below by the upper-side portion  133  and the lower-side portion  135 , respectively, of the second housing part  13 . In addition, the second housing part  13  is coupled to the first housing part  11  via elastic elements, as will be discussed below. Furthermore, the upper-side portion  133  and the lower-side portion  135  are configured to be slidable relative to (in sliding contact with) the upper-end part and the lower-end part, respectively, of the motor-housing part  111 . This configuration enables the housing  10  to function as a vibration-isolating housing as will be discussed in more detail below. 
     Two battery-mounting parts  15 , which are configured such that two rechargeable batteries (battery packs or battery cartridges)  19  can be respectively mounted thereon and dismounted (removed) therefrom, are provided on the lower-end side of the lower-side portion  135 . In the present embodiment, the two battery-mounting parts  15  are aligned in the front-rear direction. Furthermore, the hammer drill  1  operates by using the electric power (current) supplied from the two batteries  19  mounted on the battery-mounting parts  15 . 
     The detailed configuration of each portion of the hammer drill  1  is explained below, with reference to  FIG. 1  to  FIG. 6 . 
     First, the internal structure of the motor-housing part  111  will be explained, with reference to  FIG. 3 . The motor-housing part  111  has (is formed into) a generally rectangular-tube shape with a closed lower side (bottom) and an open upper side. As shown in  FIG. 3 , the drive-mechanism housing part  117  is coupled and fixed to, and is incapable of relative movement with respect to, the motor-housing part  111  with a lower-end portion of a rear-side portion of the drive-mechanism housing part  117  disposed inside the upper-end portion of the motor-housing part  111 . In the present embodiment, a compact, high-power brushless motor serves as the motor  2  and is housed in the motor-housing part  111 . The motor  2  comprises: a motor-main-body part  20 , which comprises a stator  21  and a rotor  22 , and a motor shaft  25  that extends from and rotates together with the rotor  22 . In the present embodiment, the motor-main-body part  20  is disposed spaced apart from the impact axis A 1  in the lower-end portion of the motor-housing part  111 . It is noted that, in the present embodiment, the ratio of the stack thickness T (in the up-down direction) of the stator  21  to the outer diameter D s  of the stator  21  (in the front-rear direction) is set to the fraction ⅕ (T/D s ) or less (e.g., ⅙ or less, 1/7 or less or ⅛ or less; as an upper limit the ratio may be 1/10 or greater or 1/9 or greater; that is, the outer diameter of the stator  21  in the front-rear direction is preferably 5 times or greater, and preferably 10 times or less, than the stack thickness of the stator  21  in the up-down direction), and the diameter D r  of the rotor  22  (in the front-rear direction) is greater than the stack thickness T of the stator  21 . That is, the motor  2  is configured as a motor in which the thickness in the rotational axis A 2  direction (up-down direction) is much smaller (less) than the diameter (i.e., a so-called flat or pancake motor). By using such a brushless flat motor, the length of the motor-housing part  111  in the rotational axis A 2  direction (up-down direction) can be reduced. Alternatively, additional components can be included in the motor-housing part  111  without increasing the length of the motor-housing part  111  in the up-down direction. Thus, according to such a configuration, even though the lower-side portion  135  is disposed on the lower side of the motor-housing part  111  and, in turn, the batteries  19  are mounted downward of the lower-side portion  135 , it is possible to prevent an increase in the size (overall height) of the hammer drill  1 . 
     The motor shaft  25 , which extends in the up-down direction, is rotatably supported by a first bearing  26 , which is held by (in) the lower-end part of the drive-mechanism housing part  117 , and by a second bearing  27 , which is held by (in) the lower-end part of the motor-housing part  111 . A fan  28  is provided for cooling the motor  2  and a (below-described) controller  5  and the fan  28  is fixed to the motor shaft  25  adjacent to the upper side of the motor-main-body part  20 . The fan  28  is configured such that, by driving the motor  2 , it rotates integrally with the motor shaft  25 , and thereby causes a cooling draft (air) to flow into the housing  10  via vents  139  (refer to  FIG. 2 ), which are discussed below; this cooling draft passes (flows around) the periphery of the controller  5 , and then passes (flows around) the periphery of the motor  2 . It is noted that after this cooling draft flows past the periphery of the motor  2 , it flows out to the outside of the housing  10  via vents  134  (refer to  FIG. 1 ) provided as air-exhaust ports in side surfaces of the upper-side portion  133 . The upper-end part of the motor shaft  25  projects into the drive-mechanism housing part  117 , and a drive gear  29  is formed at the terminal end of the motor shaft  25 . 
     Next, the internal structure of the drive-mechanism housing part  117  will be explained, with reference to  FIG. 2 . As discussed above, the drive mechanism  3  is housed in the drive-mechanism housing part  117 . As shown in  FIG. 2 , the drive mechanism  3  of the present embodiment comprises a motion-converting mechanism  30 , a hammer element  36 , and a rotation-transmitting mechanism  38 . 
     The motion-converting mechanism  30  is configured to convert the rotary motion of the motor  2  into linear motion and to transmit such linear motion to the hammer element  36 . The motion-converting mechanism  30  of the present embodiment is configured as a crank mechanism and comprises a crankshaft  31 , a connecting rod  32 , a piston  33 , and a cylinder  35 . The crankshaft  31  is disposed, parallel to the motor shaft  25 , on a rear-end portion of the drive-mechanism housing part  117 . The crankshaft  31  has a driven gear  311 , which meshes with the drive gear  29 , at a lower end thereof and has a crank pin  312  at an upper end thereof. One end of the connecting rod  32  is rotatably coupled to the crank pin  312 , and the other end of the connecting rod  32  is attached to the piston  33  via a pin. The piston  33  is slidably disposed inside the circular-cylindrical cylinder  35 . The cylinder  35  is coaxially coupled and fixed to a rear part of the tool holder  34 , which is disposed inside the tip area of the drive-mechanism housing part  117 . When the motor  2  is driven, the piston  33  moves reciprocatively in the impact axis A 1  direction inside the cylinder  35 . 
     The hammer element  36  comprises a striker  361  and an impact bolt  363 . The striker  361  is disposed inside the cylinder  35  so as to be slidable in (along) the impact axis A 1  direction. An air chamber  365  is formed between the striker  361  and the piston  33  and is provided for linearly moving the striker  361 , which serves as a striking element, by using air-pressure fluctuations generated by the reciprocating motion of the piston  33 . The impact bolt  363  is configured as an intermediate element, which transmits the kinetic energy of the striker  361  to the tool accessory  18 , and is disposed inside the tool holder  34  so as to be slidable in the impact axis A 1  direction. 
     When the motor  2  is driven and the piston  33  moves frontward, the air in the air chamber  365  becomes compressed, and thereby the internal pressure rises. Consequently, the striker  361  is pushed frontward at a high velocity and strikes the impact bolt  363 , and thereby the kinetic energy is transmitted to the tool accessory  18 . As a result, the tool accessory  18  is driven linearly along the impact axis A 1  and strikes (impacts) the workpiece. On the other hand, when the piston  33  moves rearward, the air in the air chamber  365  expands and the internal pressure falls, and thereby the striker  361  is pulled rearward. The hammer drill  1  performs the hammering operation by repetitively performing such operations on (using) the motion-converting mechanism  30  and the hammer element  36  such that the tool accessory  18  is linearly driven in an oscillating manner. 
     The rotation-transmitting mechanism  38  is configured to transmit the rotational motive power of the motor shaft  25  to the tool holder  34 . In the present embodiment, the rotation-transmitting mechanism  38  is configured as a gear-speed-reducing mechanism comprising a plurality of gears; the rotational motive power of the motor  2  is transmitted to the tool holder  34  after the rotational speed has been suitably reduced. It is noted that meshing-type clutches  39  are disposed along the motive-power-transmission pathway of the rotation-transmitting mechanism  38 . When the clutches  39  are put into an engaged state, the rotational motive power of the motor shaft  25  is transmitted to the tool holder  34  by the rotation-transmitting mechanism  38 , and thereby the tool accessory  18 , which is mounted in the tool holder  34 , is rotationally driven around the impact axis A 1 . On the other hand, when the engaged state of the clutches  39  is released ( FIG. 2  shows the engagement-released state), the transmission of motive power by the rotation-transmitting mechanism  38  to the tool holder  34  is cut off and the tool accessory  18  is no longer rotationally driven. 
     The hammer drill  1  of the present embodiment is configured such that one of two modes (i.e., a hammer-drill mode and a hammer mode) is selectable by manipulating (manually turning) a mode-switching dial  391 , which is provided on an upper side of the drive-mechanism housing part  117 . In the hammer-drill mode, the clutches  39  are put into the engaged state and the motion-converting mechanism  30  and the rotation-transmitting mechanism  38  are driven, and thereby the hammering operation and the drill operation are both performed simultaneously on the tool accessory  18 . In the hammer mode, the clutches  39  are put in the engagement-released state (i.e. the disengaged state) and only the motion-converting mechanism  30  is driven such that only the hammering operation is performed. Because configurations for such mode switching are well known, a detailed explanation thereof is omitted herein. 
     The internal structure of the second housing part  13  is explained below, with reference to  FIGS. 1, 2, and 4 . First, the upper-side portion  133  will be explained. As shown in  FIGS. 1 and 2 , the rear-side portion of the upper-side portion  133  has (is formed into) substantially a rectangular-box shape, in which the lower side is open, and the rear-side portion covers a rear-side portion of the drive-mechanism housing part  117  (more specifically, the portion in which the motion-converting mechanism  30  and the rotation-transmitting mechanism  38  are housed) from above. In addition, a front-side portion of the upper-side portion  133  has (is formed into) a circular-cylindrical shape and covers the outer circumference of a front-side portion of the drive-mechanism housing part  117  (more specifically, the portion in which the tool holder  34  is housed). 
     The grasp part (handle)  131  will now be explained. As shown in  FIG. 2 , a trigger  14  that can be pressed (squeezed) by the user is provided on a front side of the grasp part  131 . A switch unit  140 , which is switchable to an ON state or to an OFF state in accordance with the manipulation (pressing) of the trigger  14 , is provided in the interior of the grasp part  131 , which has (is formed into) a tubular shape. Although the details are not illustrated because it is a well-known configuration, the switch unit  140  includes: a plunger, which moves in a linked manner with the pressing of the trigger  14 ; a motor switch; and an illumination switch. 
     Each switch comprises a fixed contact and a movable contact. In an initial state in which the trigger  14  is not being pressed, each switch is maintained in the OFF (open) state. On the other hand, when the trigger  14  is pressed, the plunger is caused to move, thereby causing the movable contact to be brought into contact with the fixed contact, whereby the switch transitions to the ON (closed) state. It is noted that, in the present embodiment, while the trigger  14  is being pressed (squeezed) from its released (un-pressed) position to its maximum depressed position, the movable contact of the illumination switch makes contact with the fixed contact of the illumination switch before the trigger  14  reaches its maximum depressed position, such that an illumination unit  6  (described below) is lit. On the other hand, only when the trigger  14  reaches its maximum depressed position, the movable contact of the motor switch first makes contact with the fixed contact of the motor switch. Thus, contact actuation times for each switch are set via the plunger. 
     The switch unit  140  is electrically connected to the controller  5 , which is discussed below, by wiring (not shown). The ON-OFF states of the motor switch and the illumination switch are used by the controller  5  to control the start and stop of the supply of electric current to the motor  2  and to control the turning ON and OFF of the illumination unit  6 . 
     The lower-side portion  135  will now be explained. As shown in  FIG. 1  and  FIG. 2 , the lower-side portion  135  has (is formed into) a rectangular-box shape, the upper side of which is partially open, and is disposed on the lower side of the motor-housing part  111 . As discussed above, the two battery-mounting parts  15 , which are aligned in the front-rear direction, are provided on the lower-end side of the lower-side portion  135  of the second housing part  13 . The batteries  19  are mounted on the lower side of the battery-mounting parts  15 . 
     The configuration of the batteries  19 , which are capable of being mounted onto and dismounted (removed) from the battery-mounting parts  15 , will now be explained briefly. As shown in  FIGS. 1, 2, and 4 , each battery (battery pack or battery cartridge)  19  has (is formed into) substantially a rectangular-parallelepiped shape and comprises a hook  193 , terminals (not shown), and a pair of guide grooves  191 . It is noted that, for the sake of convenience in the explanation, the direction of each battery  19  is defined as the up-down direction in the state in which the battery  19  is mounted on the hammer drill  1 . A plurality of battery cells (not shown) are housed within a hard resin case and the battery cells are electrically connected to battery terminals disposed on the upper surface of the battery  19  between the guide grooves  191  in well-known manner. One or more communication terminals for communicating with a controller (e.g., microprocessor) and/or other electrical elements (e.g., temperature sensor) located within the battery  19  may also be provided between the guide grooves  191  in well-known manner. 
     The hook  193  and the terminals are provided on the upper side of each battery  19 , and the upper side opposes the corresponding battery-mounting part  15 . The hook  193  is configured such that one-end part in the longitudinal direction of the battery  19  (i.e., the left-right direction in  FIG. 2 , and the direction orthogonal to the paper surface in  FIG. 4 ) is biased by a spring (not shown) such that the one-end part normally protrudes upward from the upper surface of the battery  19  and such that the hook  193  is pulled in downward from the upper surface by pressing a button  195 . The terminals are provided on the upper side of the battery  19  adjacent the hook  193 . The two guide grooves  191  are formed as grooves, extending linearly in the longitudinal direction, on the upper parts of two side surfaces disposed along the longitudinal direction of the battery  19 . 
     In the present embodiment, the two battery-mounting parts  15  are a front-side, battery-mounting part  15  that is provided on the front-side portion of the lower-side portion  135 , and a rear-side, battery-mounting part  15  that is provided on the rear-side portion of the lower-side portion  135 . It is noted that the front-side battery-mounting part  15  is disposed downward of the motor  2  and is intersected by the rotational axis A 2 . As shown in  FIGS. 2 and 4 , each of the battery-mounting parts  15  is provided with guide rails  151 , a hook-engaging part  153 , and battery-connection terminals  155 . 
     The guide rails  151  protrude inward from left and right wall surfaces along a lower end of the lower-side portion  135  and are formed as projections extending linearly in the front-rear direction (i.e., the impact axis A 1  direction). The guide rails  151  are configured such that they can engage, by sliding, with the guide grooves  191  of the battery  19 . The hook-engaging part  153  is a recessed part that is recessed upward and is configured such that the hook  193  of the battery  19  can engage therewith. The battery-connection terminals  155  are configured such that they respectively electrically connect with the terminals of the battery  19  attendant with the battery  19  being fixed to the battery-mounting part  15  by the hook  193  engaging with the hook-engaging part  153 . 
     In the present embodiment, the front-side, battery-mounting part  15  and the rear-side, battery-mounting part  15  have identical configurations but differ in the direction in which the batteries  19  are mounted and dismounted. Specifically, the front-side, battery-mounting part  15  is configured such that the battery  19  engages therewith by sliding from the front toward the rear in the state in which the hook  193  is disposed at the front-upper-end part and the guide rails  151  are engaged with the guide grooves  191 . Consequently, it is configured such that the hook-engaging part  153  is disposed on the front-end part of the battery-mounting part  15 , and the battery-connection terminals  155  connect, from (at) the rear, to the terminals of the battery  19 . On the other hand, the rear-side, battery-mounting part  15  is configured such that the battery  19  engages therewith by sliding from the rear toward the front in the state in which the hook  193  is disposed at the rear-upper-end part and the guide rails  151  are engaged with the guide grooves  191 . Consequently, it is configured such that the hook-engaging part  153  is disposed at the rear-end part of the battery-mounting part  15 , and the battery-connection terminals  155  connect, from (at) the front, to the terminals of the battery  19 . 
     Thus, the front-side, battery-mounting part  15  is configured such that the battery  19  is mounted by sliding it from the front toward the rear, and the rear-side, battery-mounting part  15  is configured such that the battery  19  is mounted by sliding it from the rear toward the front. Therefore, the (e.g., front) battery  19  mounted on one of the battery-mounting parts  15  does not interfere with the (e.g., rear) battery  19  mounted on the other battery-mounting part  15  during mounting or dismounting of either of the batteries  19 . Thereby, ease of operation can be satisfactorily maintained during mounting or dismounting (removal) of the two batteries  19 . 
     It is noted that the respective guide rails  151  of the front-side, battery-mounting part  15  and the rear-side, battery-mounting part  15  are disposed along the same two virtual straight lines extending horizontally in the front-rear direction. That is, the two battery-mounting parts  15  are aligned in one row in the front-rear direction at the same position in the up-down direction. 
     As shown in  FIG. 2 , because the two battery-mounting parts  15  are configured in this manner and are provided on the lower-end part of the lower-side portion  135  such that they are aligned in the front-rear direction, a space  150  is formed in the front-rear direction between the two sets of battery-connection terminals  155 . In the area of the lower-side portion  135  covering the space  150  (more specifically, a circumferential-wall part  136  of the lower-side portion  135 ), vents  139  are formed and enable the interior and exterior of the lower-side portion  135  to communicate with each other. In the present embodiment, three of the vents  139  are provided in both the left and right wall parts covering the space  150 . In addition, the vents  139  function as inflow ports for the cooling draft. 
     As shown in  FIGS. 1 and 2 , the illumination unit  6  is provided on the front-end part (side) of the lower-side portion  135 . The illumination unit  6  of the present embodiment principally comprises one or more light-emitting diodes (LED), which serve(s) as a light source, and a case, which is made of a translucent material (e.g., a transparent resin, glass, or the like) and houses the LED(s). In the illumination unit  6 , the illumination direction of the light emitted by the LED(s) is set so that the location at which the tool accessory  18  performs work (i.e. the portion of the workpiece to be processed and/or the tip portion of the tool accessory  18 ) is illuminated. 
     Furthermore, as shown in  FIG. 2 , the controller  5  for controlling the operation of the hammer drill  1  is housed in the lower-side portion  135 . In the present embodiment, the controller  5  is configured as a control apparatus of the motor  2 , which is a brushless motor. More specifically, the controller  5  is configured as a circuit board having a control circuit (e.g., a microcomputer comprising a CPU, memory, and the like), an inverter circuit, and the like mounted thereon. It is noted that, in the present embodiment, the controller  5  also functions as the control apparatus of the illumination unit  6 . 
     The controller  5  is disposed adjacent the space  150  formed between the two sets of battery-connection terminals  155  and such that at least part(s) of the controller  5  overlap(s) the two battery-mounting parts  15  in the front-rear direction. More specifically, the controller  5  is disposed upward of the space  150  and is disposed such that, when viewed from above (or below), a center part of the controller  5  overlaps the space  150 . Furthermore, the front-end part and rear-end part of the controller  5  partially overlap the front-side, battery-mounting part  15  and the rear-side, battery-mounting part  15 , respectively. In addition, the controller  5  comprises wiring terminals  51 , to which wiring (not shown) is connected for electrically connecting the controller  5  to the motor  2 , the illumination unit  6 , the switch unit  140 , etc. The controller  5  is disposed such that the wiring terminals  51  project toward the space  150  below. 
     In the present embodiment, when the trigger  14  is pressed and the illumination switch of the switch unit  140  changes from the normal OFF state to the ON state, the controller  5  turns the LED(s) of the illumination unit  6  ON in response to an ON signal output from the illumination switch. When the trigger  14  is further pressed to its maximum depressed position such that the motor switch changes to the ON state, the controller  5  supplies electric current to drive the motor  2  in response to the outputted ON signal. It is noted that, as discussed above, the contact actuation times of the illumination switch and the motor switch differ, and therefore the illumination unit  6  turns ON before the drive of the motor  2  starts and turns OFF after the drive of the motor  2  stops. 
     Further details concerning the vibration-isolating housing structure of the housing  10  are explained below, with reference to  FIGS. 2 to 6 . As discussed above, in the housing  10 , the second housing part  13  that includes the grasp part  131  is elastically coupled to the first housing part  11  that houses the motor  2  and the drive mechanism  3 , and thereby the transmission of vibration from the first housing part  11  to the second housing part  13  (specifically, to the grasp part  131 ) is reduced because the first housing part  11  can oscillate relative to the second housing part  13  in response to vibration generated in the first housing part  11  during operation of the hammer drill  1 . 
     More specifically, as shown in  FIG. 2 , a pair of left and right first springs  71  is disposed between the drive-mechanism housing part  117  of the first housing part  11  and the upper-side portion  133  of the second housing part  13 . It is noted that, in  FIG. 2 , only the right-side first spring  71  is shown, but the configuration of the left-side first spring  71  is the same as the right-side one. Furthermore, a second spring  75  is disposed between the motor-housing part  111  of the first housing part  11  and the lower-side portion  135  of the second housing part  13 . That is, the first housing part  11  and the second housing part  13  are elastically coupled, via the first springs  71  and the second spring  75 , at both the upper-end-part side and the lower-end-part side of the grasp part  131 , respectively. In addition to these springs, an O-ring  79 , which is formed as an elastic member, is disposed such that it is interposed between the front-end part of the drive-mechanism housing part  117  and the circular-cylindrical front-side portion of the upper-side portion  133 . 
     Further details concerning the arrangement of the first springs  71  will now be explained. As shown in  FIGS. 2 and 4 , a plate member  72  is fixed by screws to the rear-end part of the drive-mechanism housing part  117 . A pair of left and right spring-seat parts  73  is provided on an upper-end part of a rear surface of the plate member  72 . The spring-seat parts  73  each have a circular-column part that protrudes rearward. In addition, a pair of left and right spring-seat parts  74  is provided on the rear-end part of the upper-side portion  133 ; the rear-end part is disposed rearward of the spring-seat parts  73 . The spring-seat parts  74  each have a circular-column part that protrudes frontward. 
     In the present embodiment, compression coil springs are used as the first springs  71 . The first springs  71  are resiliently (elastically) disposed between the spring-seat parts  74 ,  73 , in the state in which opposite end parts of the first springs  71  are externally mounted on (are mounted around the exterior sides of) the circular-column parts of the spring-seat parts  74 ,  73 , such that the central axes (longitudinal extensions) of the first springs  71  extend in parallel to the impact axis A 1  (i.e., in the front-rear direction). The first springs  71  bias (urge) the first housing part  11  (the drive-mechanism housing part  117 ) away from the second housing part  13  (the upper-side portion  133 ), i.e., such that the grasp part  131  spaces apart from the first housing part  11 . In other words, the first springs  71  bias (urge) the first housing part  11  frontward in the front-rear direction, which is the impact axis A 1  direction, and bias (urge) the second housing part  13 , which includes the grasp part  131 , rearward. 
     Further details concerning the arrangement of the second spring  75  will now be explained. As shown in  FIGS. 2 and 5 , a spring-seat part  76  protrudes downward from a center part of a front-lower-end part of the motor-housing part  111 . The spring-seat part  76  includes a front-wall part and left and right sidewall parts; a rear side of the spring-seat part  76  is open. In addition, a spring-seat part  77  is provided on the lower-side portion  135  and is formed as a recessed part whose front side is open; the spring-seat part  77  is disposed rearward of the spring-seat part  76 . In the present embodiment, the second spring  75  likewise is a compression coil spring. The second spring  75  is resiliently (elastically) disposed between the spring-seat parts  76 ,  77 , such that one end part of the second spring  75  contacts the rear surface of the spring-seat part  76  and the other (opposite) end part of the second spring  75  contacts the front surface of the spring-seat part  77 , and such that the central axis (longitudinal extension) of the second spring  75  extends in parallel to the impact axis A 1  (i.e., in the front-rear direction). The second spring  75  biases (urges) the first housing part  11  (the motor-housing part  111 ) away from the second housing part  13  (the lower-side portion  135 ), i.e., such that the grasp part  131  spaces apart from the first housing part  11 . That is, similar to the first springs  71 , the second spring  75  likewise biases the first housing part  11  frontward and biases the second housing part  13  rearward. 
     Furthermore, sliding-guide structures are provided in (on) the housing  10  to support and guide oscillating sliding movement of the first housing part  11  relative to the second housing part  13  during operation (i.e. when vibration is being generated in the first housing part  11 ). In the present embodiment, an upper-side guide part  8  and a lower-side guide part  9  are provided as the sliding-guide structures at two locations, that is, on the upper side and on the lower side of the motor-main-body part  20 . 
     First, the configuration of the upper-side guide part  8  will be explained in more detail, with reference to  FIGS. 3 and 4 . As shown in  FIG. 3 , the motor-housing part  111  has a bottomed, rectangular tube shape, and comprises: a circumferential-wall part  112 , which circumferentially surrounds the motor  2 ; and a bottom part  113 , which is connected to a lower end of the circumferential-wall part  112  and forms the lower-end part of the motor-housing part  111 . It is noted that a step part  114  is formed at an outer-edge part of the bottom part  113  and the step part  114  forms a recess that extends upward of the center part of the bottom part  113 . An upper-side sliding part  81  is formed as a structural member (discrete piece) that is separate from the circumferential-wall part  112  and has substantially a rectangular-frame (box) shape. The upper-side sliding part  81  is mounted on (around) the outer circumference of the upper-end portion of the circumferential-wall part  112 . That is, the upper-side sliding part  81  extends in a loop-shape or closed-curve shape continuously around the upper portion of the circumferential-wall part  112 . The upper surface of the upper-side sliding part  81  is a flat surface parallel to the impact axis A 1  (i.e., a flat surface whose normal line is orthogonal to the impact axis A 1 ) and constitutes a first upper-side sliding surface  811 . It is noted that, in the present embodiment, the first upper-side sliding surface  811  is a flat surface extending in the horizontal direction (i.e., a flat surface having a normal line that is orthogonal to the impact axis A 1  and that is parallel to the rotational axis A 2  of the motor shaft  25 ). 
     Opposite thereto, a lower surface of an opening (a lower-end part) of the upper-side portion  133  likewise is a flat surface parallel to the impact axis A 1  (i.e., a flat surface whose normal line is orthogonal to the impact axis A 1 ) and constitutes a second upper-side sliding surface  821 . In the present embodiment, the second upper-side sliding surface  821  likewise is a flat surface extending in the horizontal direction, and the first upper-side sliding surface  811  is slidable relative to the second upper-side sliding surface  821  in the state in which those surfaces  811 ,  821  abut and contact one another (i.e. the first upper-side sliding surface  811  is in sliding contact with the second upper-side sliding surface  821 ). The first upper-side sliding surface  811  and the second upper-side sliding surface  821  constitute the upper-side guide part  8 . 
     The upper-side sliding part  81 , which has the first upper-side sliding surface  811 , is preferably formed of a material that differs from at least the material of the upper-side portion  133 , which has the second upper-side sliding surface  821 . In the present embodiment, the second housing part  13  (the grasp part  131 , the upper-side portion  133 , and the lower-side portion  135 ) and the circumferential-wall part  112  and the bottom part  113  of the motor-housing part  111  are all formed of a polyamide-based resin, e.g., containing glass fibers (e.g., 20-35 weight percent) and other additives typically utilized in power tool housings; a polyamide-based resin preferably contains at least 50% weight percent of polyamide, e.g., PA66, of its total weight (i.e. 100 weight percent). The upper-side sliding part  81 , on the other hand, is formed of a polycarbonate-based resin, e.g., containing glass fibers (e.g., 20-35 weight percent) and other additives typically utilized in power tool housings; a polycarbonate-based resin preferably contains at least 50% weight percent of polycarbonate of its total weight (i.e. 100 weight percent). 
     It is noted that, as shown in  FIG. 4 , the portions of the circumferential-wall part  112  constituting the left and right wall parts respectively each comprise a guide part  115  that projects upward more than the upper-side sliding part  81 , which is mounted on (around) the outer circumference of the circumferential-wall part  112 . The guide parts  115  of the circumferential-wall part  112  are disposed inward of the lower-end part of the upper-side portion  133 . Therefore, when the first upper-side sliding surface  811  slides back and forth relative to the second upper-side sliding surface  821  because the upper-side portion  133  is moving (oscillating) relative to the motor-housing part  111  as a result of vibrations generated in the motor-housing part  111  during operation, the guide parts  115  prohibit (block) the upper-side portion  133  from moving in the left-right direction relative to the motor-housing part  111  and guide the upper-side portion  133  such that it moves (slides) back and forth only in the impact axis A 1  direction. Consequently, in the present embodiment, the first upper-side sliding surface  811  and the second upper-side sliding surface  821  slide relative to each other in (along) the impact axis A 1  direction (the front-rear direction) in the state in which they are in contact with one another. 
     The configuration of the lower-side guide part  9  will now be explained, with reference to  FIG. 2  to  FIG. 6 . The same as in the upper-side guide part  8 , the lower-side guide part  9  comprises a first lower-side sliding surface  911 , which is formed on a lower-side sliding part  91  of the motor-housing part  111 , and a second lower-side sliding surface  921 , which is formed on the lower-side portion  135 . 
     As shown in  FIGS. 3 and 6 , the lower-side sliding part  91  is mounted on (around) the outer circumference of the lower-end part of the circumferential-wall part  112  of the motor-housing part  111 . The lower-side sliding part  91  comprises an outer-circumferential part  912 , an outer-edge part  913 , and a protruding part  914 . The outer-circumferential part  912  has (is formed into) a rectangular-frame shape (loop shape or closed shape) and is mounted on (around) the outer circumference of the circumferential-wall part  112 . The outer-edge part  913  protrudes inward from the outer-circumferential part  912  along (and follows) the step part  114 , which is formed on the outer-edge part of the bottom part  113 . The protruding part  914  protrudes downward from an inner-side end of the outer-edge part  913  to substantially the same position as the center part of the bottom part  113 . The lower surface of the outer-edge part  913  is a flat surface parallel to the impact axis A 1  (i.e., a flat surface whose normal line is orthogonal to the impact axis A 1 ) and constitutes the first lower-side sliding surface  911 . It is noted that, in the present embodiment, the first lower-side sliding surface  911  is a flat surface extending in the horizontal direction. 
     In addition, the lower-side sliding part  91  is formed of a material that differs from at least the material of the lower-side portion  135 . In the present embodiment, the lower-side sliding part  91  is preferably formed of a polycarbonate-based resin, e.g., the same as in the upper-side sliding part  81 . 
     As shown in  FIGS. 3, 5, and 6 , a plate member  917  is fixed to the bottom part  113  such that the plate member  917  opposes the outer-edge part  913  of the lower-side sliding part  91 . In the present embodiment, the plate member  917  is configured as a substantially U-shaped metal plate whose rear side is open, and the plate member  917  is fixed by screws to the bottom part  113  from below such that the plate member  917  opposes the outer-edge part  913 . A gap is formed in the up-down direction between the first lower-side sliding surface  911 , which is the lower surface of the outer-edge part  913 , and the upper surface of the plate member  917 . 
     In addition, as shown in  FIGS. 3 and 5 , a pair of left and right forward-stop parts  918  and a pair of left and right rearward-stop parts  919  are provided on the plate member  917 . The forward-stop parts  918  and the rearward-stop parts  919  are each formed by bending a part of the plate member  917  downward. The forward-stop parts  918  and the rearward-stop parts  919  cooperate with front-contact parts  137  and rear-contact parts  138 , which are discussed below, and are configured to prohibit (block) the sliding movement of the lower-side portion  135  relative to the motor-housing part  111  beyond a prescribed range in the impact axis A 1  direction (i.e., the front-rear direction). 
     As shown in  FIGS. 3, 5, and 6 , an interposed part (plain linear bearing or linear motion guide)  922  protrudes from the circumferential-wall part  136  of the lower-side portion  135  toward the interior (toward the rotational axis A 2  of the motor  2 ), and is formed at (along) the opening (the upper-end part) of the lower-side portion  135 . It is noted that  FIG. 5  is a bottom view of the motor-housing part  111 ; however, for the sake of convenience in the explanation, an inner surface of the circumferential-wall part  136  of the lower-side portion  135  is indicated by a broken line and the interior-most edge (protruding edge) of the interposed part  922  is indicated by a chain double-dashed line. 
     At least one portion of the interposed part  922  (more specifically, at least one portion other than a rear part of the lower-side portion  135 ) is disposed in the gap between the first lower-side sliding surface  911  and the upper surface of the plate member  917  and is configured to be slidable relative to the motor-housing part  111 . The thickness of the interposed part  922  in the up-down direction is substantially the same as the distance (gap) between the first lower-side sliding surface  911  and the upper surface of the plate member  917 . 
     More preferably, the thickness of the interposed part  922  is set to be slightly less than the vertical height of the gap so that the interposed part  922  may freely slide relative to the first lower-side sliding surface  911  and the upper surface of the plate member  917  (i.e. such that the interposed part  922  is not press-fit into the gap). On the other hand, the thickness of the interposed part  922  is also preferably set to be sufficiently wide (high) so that movement of the interposed part  922  relative to the first lower-side sliding surface  911  and the upper surface of the plate member  917  in the vertical direction (in the direction of the rotational axis A 2 ) is at least substantially blocked, thereby constraining the sliding movement of the first lower-side sliding surface  911  relative to the second lower-side sliding surface  921  to only a direction perpendicular to the rotational axis A 2 . By setting the thickness of the interposed part  922  in the vertical direction in this manner, the interposed part  922  acts or functions as a linear motion guide or plain linear bearing to permit movement of the first lower-side sliding surface  911  relative to the second lower-side sliding surface  921  only in a direction perpendicular to the rotational axis A 2 . While the interposed part  922  preferably is smooth to minimize friction, it need not function as a friction-reducing element. 
     The upper surface of the interposed part  922  is a flat surface parallel to the impact axis A 1  (i.e., a flat surface whose normal line is orthogonal to the impact axis A 1 ) and constitutes the second lower-side sliding surface  921 . It is noted that, in the present embodiment, the second lower-side sliding surface  921  likewise is a flat surface extending in the horizontal direction. The first lower-side sliding surface  911  and the second lower-side sliding surface  921  are slidable in the state in which they abut and are in contact with one another. 
     When the first lower-side sliding surface  911  slides back and forth relative to the second lower-side sliding surface  921  because the lower-side portion  135  is moving (oscillating) relative to the motor-housing part  111  as a result of vibrations generated in the motor-housing part  111  during operation, a left-side portion and a right-side portion make contact with the interposed part  922  and thereby the protruding part  914  of the lower-side sliding part  91  prohibits (blocks) movement of the lower-side portion  135  in the left-right (lateral) direction with respect to the motor-housing part  111  and guides the lower-side portion  135  such that it moves in (only along) the impact axis A 1  direction i.e. movement of the first lower-side sliding surface  911  relative to the second lower-side sliding surface  921  is constrained to being substantially one-dimensional movement in parallel to the impact axis A 1 . Consequently, in the present embodiment, the first lower-side sliding surface  911  slides back and forth relative to the second lower-side sliding surface  921  substantially only in the impact axis A 1  direction (the front-rear direction) in the state in which they are in contact with one another, such that the interposed part  922  functions or acts as a plain linear bearing or linear motion guide in this respect as well. 
     It is noted that, in the present embodiment, the interposed part  922  extends continuously around three sides (front, left and right) of the motor housing  112 , e.g., in a substantially U-shape, C-shape, oval shape or horseshoe shape. However, the shape of the interposed part  922  may be modified in various ways while still satisfying the requirements of blocking or preventing movement of the first lower-side sliding surface  911  relative to the second lower-side sliding surface  921  in the vertical (up-down) direction and/or in the lateral (left-right) direction of the power tool  1 . For example, the interposed part  922  may have breaks or interruptions along its curved extension and/or one or more portions of the interior-most edge of the interposed part  922  may be straight. In addition or in the alternative, the interposed part  922  may be provided only at the longitudinal front portion of the second portion  135  of the second housing  13 , such that it only blocks or prohibits movement of the first lower-side sliding surface  911  relative to the second lower-side sliding surface  921  in the vertical direction. Another structure optionally may be provided to block movement of the first lower-side sliding surface  911  relative to the second lower-side sliding surface  921  in the lateral direction, if desired. Moreover, the interposed part  922  may be provided only along the left and right side portions of the second portion  135  of the second housing  13  (i.e. no interposed part  922  is provided at the longitudinal front portion of the second portion  135 ), such that the pair of left, right interposed parts  922  still blocks movement of the first lower-side sliding surface  911  relative to the second lower-side sliding surface  921  in both the vertical and horizontal directions, or in only one of these directions. Various other modifications are possible as long as a linear motion guiding function is provided such that movement of the first lower-side sliding surface  911  relative to the second lower-side sliding surface  921  is blocked/prohibited in the vertical direction and/or movement of the first lower-side sliding surface  911  relative to the second lower-side sliding surface is blocked/prohibited  921  in the lateral direction. 
     As shown in  FIGS. 3 and 5 , the left and right front-contact parts  137 , which protrude rearward, are provided on the front-upper-end part of the circumferential-wall part  136  of the lower-side portion  135 . In addition, the left and right rear-contact parts  138 , which protrude toward the interior of the lower-side portion  135 , are provided on the rear-upper-end part of the circumferential-wall part  136  of the lower-side portion  135 . The front-contact parts  137  are configured such that they are capable of making contact with the front surfaces of the forward-stop parts  918 . The rear-contact parts  138  are configured such that they are capable of making contact with the rear surfaces of the rearward-stop parts  919 . The front-contact parts  137  and the rear-contact parts  138  cooperate with the forward-stop parts  918  and the rearward-stop parts  919  and are configured to prohibit (block) the sliding movement of the lower-side portion  135  relative to the motor-housing part  111  beyond a prescribed range in the impact axis A 1  direction (i.e., the front-rear direction). This prescribed range or upper limit of sliding movement may be, e.g., at least 2 mm, more preferably at least 3 mm, and even more preferably at least 3.5 mm, and may be, e.g., 6 mm or less, preferably 5 mm or less, and even more preferably 4.5 mm or less. The prescribed range may be determined, e.g., as follows. When the power tool  1  is not in use, the first and second springs  71 ,  75  urge (push) the first housing part  11  away from the second housing part  13  such that the forward-stop parts  918  contact the front-contact parts  137 . At this time, the rear-contact parts  138  will be spaced apart from the rear surfaces of the rearward-stop parts  919  such that a gap is present between the rear-contact parts  138  and the rearward-stop parts  919 , as shown in  FIGS. 3 and 5 . This gap corresponds to the above-mentioned prescribed range (sliding range) of the sliding movement of the first housing part  11  relative to the second housing part  13 , because it is the maximum distance that the front housing part  11  can move (slide) relative to the second housing part  13  before the rear-contact parts  138  contact the rearward-stop parts  919  and block further relative movement (relative sliding movement). However, the prescribed sliding range of the front housing part  11  relative to the second housing part  13  may be determined in other ways, as long as the front housing part  11  is slidable relative to the second housing part by the above-mentioned distances (lengths). 
     The functions and effects of the hammer drill  1  configured as described above will now be explained. As discussed above, the first housing part  11  and the second housing part  13  are biased frontward and rearward away from each other by the first springs  71  and the second spring  75 . Thereby, as shown in  FIGS. 2 and 3 , the forward-stop parts  918  of the plate member  917  are in contact with the rear surfaces of the front-contact parts  137  in the initial state prior to the start of processing work. That is, by virtue of the front-contact parts  137  making contact with the forward-stop parts  918 , the initial arrangement (relative positional relationship) of the lower-side portion  135  relative to the motor-housing part  111  is defined. As shown in  FIGS. 2 and 4 , when the hammer drill  1  is in the (its) initial state, the first upper-side sliding surface  811  contacts the second upper-side sliding surface  821  around the entire circumference of the motor-housing part  111 . 
     When the user presses the trigger  14  to its motor-actuation position, the drive of the motor  2  starts. Vibration arises in the hammer drill  1  (more particularly, in the first housing part  11 ) owing to the drive of the motor  2  and the drive mechanism  3 . In the present embodiment, the second housing part  13  (comprising the grasp part  131  that is grasped by the user) is coupled to, and is capable of relative movement with respect to, the first housing part  11  (housing the motor  2  and the drive mechanism  3  that constitute the sources of the vibration) via the first springs  71  and the second spring  75 . Thereby, the oscillating sliding movement of the first housing part  11  relative to the second housing part  13 , which is effected by the springs  71 ,  75 , makes it is possible to reduce the transmission of vibration from the first housing part  11  to the second housing part  13  (specifically, the grasp part  131 ). 
     In particular, in the present embodiment, the first springs  71  and the second spring  75  are composed of compression coil springs that bias the first housing part  11  away from the second housing part  13  such that the grasp part  131  is spaced apart from the first housing part  11 . Furthermore, the first housing part  11  and the second housing part  13  are coupled, via the first springs  71  and second spring  75 , at both ends of the grasp part  131 . Thereby, the transmission of vibration from the first housing part  11  to the grasp part  131  can be more effectively reduced. 
     In addition, the upper-side sliding part  81  and the lower-side sliding part  91 , which are configured to be slidable relative to the upper-side portion  133  and the lower-side portion  135  of the second housing part  13 , respectively, are provided at two locations of the first housing part  11 . More specifically, the upper-side sliding part  81  and the lower-side sliding part  91  are disposed on both (opposite) sides of the motor-main-body part  20  in the rotational axis A 2  direction of the motor shaft  25 . Thereby, the stability of the oscillating sliding of the first housing part  11  relative to the second housing part  13  when the first housing part  11  moves (slides) relative to the second housing part  13  can be increased more than in embodiments in which a sliding-guide structure is provided at only one location, such as on only one side of the motor-main-body part  20 . 
     The lower-side sliding part  91  has the first lower-side sliding surface  911 , which is a flat surface parallel to the impact axis A 1 . The first lower-side sliding surface  911  is slidable in the impact axis A 1  direction (the front-rear direction) in the state in which the first lower-side sliding surface  911  is in contact with the second lower-side sliding surface  921  formed on the lower-side portion  135 . In such an embodiment, because the first lower-side sliding surface  911  and the second lower-side sliding surface  921  abut and are in contact with one another, the first housing part  11  and the second housing part  13  can be guided during the sliding movement, and consequently the stability of the sliding can be further increased. In addition, because the sliding direction is the impact axis A 1  direction, the largest and dominant vibration of the vibrations arising in the hammer drill  1 , namely, the vibration in the impact axis A 1  direction, can be effectively inhibited (blocked) from being transmitted to the grasp part  131 . 
     It is noted that, as shown in  FIG. 7 , when the second housing part  13  has moved forward relative to the first housing part  11  against the biasing forces of the first springs  71  and the second spring  75  during processing work, the rear-contact parts  138  make contact with the rear surfaces of the rearward-stop parts  919 , thereby prohibiting (blocking) further movement of the lower-side portion  135  forward with respect to the motor-housing part  111 . At this time, the rear-side portion of the first upper-side sliding surface  811  of the upper-side sliding part  81 , which is provided around the entire circumference of the motor-housing part  111 , is disposed rearward of the second upper-side sliding surface  821  of the upper-side portion  133 ; however, because the upper surface of the circumferential-wall part  112  of the motor-housing part  111  remains in contact with the second upper-side sliding surface  821 , a gap does not arise between the upper-side portion  133  and the motor-housing part  111 . Thereby, it is possible to prevent dust or the like from entering the interior of the housing  10  while the first housing part  11  is sliding relative to the second housing part  13  during operation of the hammer drill  1 . 
     In the present embodiment, as shown in  FIG. 3 , the interposed part  922 , which is provided on the upper-end part of the lower-side portion  135 , is disposed in the gap between the lower-end part of the motor-housing part  111  (more specifically, the lower surface of the outer-edge part  913  of the lower-side sliding part  91 ) and the plate member  917 , which is fixed to the lower-end part of the motor-housing part  111 . Furthermore, the first lower-side sliding surface  911  is formed on the lower surface of the outer-edge part  913 , and the second lower-side sliding surface  921  is formed on the upper surface of the interposed part  922 . Providing the interposed part  922  in this manner makes it possible to reliably implement, with a simple configuration, a sliding-guide structure in the impact axis A 1  direction. Furthermore, because the plate member  917  of the present embodiment is made of metal, even if, for example, the hammer drill  1  receives a severe impact by being dropped to the floor, the plate member  917  bends without breaking, thereby making it possible to prevent damage to the plate member  917  itself, the interposed part  922 , and the like that could impair the operability of the hammer drill  1 . 
     In the present embodiment, within the first housing part  11 , the lower-side sliding part  91 , which has the first lower-side sliding surface  911 , is preferably formed of a material that differs from the material of the second housing part  13 , which has the second lower-side sliding surface  921 . Thereby, it is possible to prevent the first lower-side sliding surface  911  and the second lower-side sliding surface  921  from becoming welded (fused) together owing to frictional heat generated by sliding friction. Furthermore, in the present embodiment, the upper-side sliding part  81 , which slides relative to the upper-side portion  133 , likewise is preferably formed of a material that differs from the material of the second housing part  13 . Thereby, the first upper-side sliding surface  811  and the second upper-side sliding surface  821  can likewise be prevented from becoming welded (fused) to one another owing to frictional heat generated by sliding friction. 
     In the present embodiment, the lower-side portion  135  comprises the battery-mounting parts  15 , which are configured such that the batteries  19  can be mounted thereon and dismounted therefrom, on the end part on the side more spaced apart from the upper-side portion  133  in the rotational axis A 2  direction (the up-down direction), that is, on the lower-end part. Because the lower-side portion  135  of the second housing part  13  is elastically coupled to the first housing part  11  such that the transmission of vibration generated in the first housing part  11  to the second housing part  13  is reduced, it is possible to inhibit or reduce chattering (contact bounce) caused by the terminals of the battery  19  rattling (bouncing) against (repeatedly separating from and then striking) the battery-connection terminals  155  of the lower-side portion  135  due to vibration when the batteries  19  are mounted on the battery-mounting parts  15  and the hammer drill  1  is being operated (i.e. vibrations are being generated by the motor  2  and the drive mechanism  3  in the first housing part  11 ). In addition, by mounting the batteries  19  on the battery-mounting parts  15 , the mass of the second housing part  13  is increased (i.e. the mass of the batteries  19  is fixed to the second housing part  13  instead of the first housing part  11  where the vibration is generated during operation), and thereby a further reduction in vibration of the second housing part  13  can be achieved. 
     In another aspect of the present teachings, the two battery-mounting parts  15  of the present teachings are provided aligned in the impact axis A 1  direction (the front-rear direction). Furthermore, the lower-side portion  135  has the vents  139 , which are formed in the area covering the space  150  formed between the two sets of battery-connection terminals  155 . The controller  5 , which controls the operation of the hammer drill  1 , is disposed adjacent the space  150  such that at least forward and rearward parts of the controller  5  overlap the two battery-mounting parts  15  in the front-rear direction. When multiple battery-mounting parts  15  are aligned, the space  150  between the battery-connection terminals  155  could become a dead (unused) space. However, by arranging the controller  5  and the plurality of battery-mounting parts  15  according to the present embodiment, the area that could be a dead space is effectively utilized as the area in which the vents  139  are provided, thereby making it possible to realize an increased efficiency in the cooling of the controller  5 . In addition, the battery-mounting parts  15  and the controller  5  are each disposed on the lower-side portion  135 , and therefore wiring between the battery-mounting parts  15  and the controller  5  can be simplified. 
     In addition, because the wiring terminals  51  of the controller  5  project toward the space  150  between the two sets of battery-connection terminals  155  of the battery-mounting parts  15 , the wiring terminals  51  and the wiring can be effectively cooled by the cooling draft that flows in from the vents  139  formed in the area covering the space  150 . 
     In addition, in the present embodiment, the fan  28  generates the flow of cooling draft that flows in from the vents  139 , passes the periphery of the controller  5 , and then passes the periphery of the motor  2 ; consequently, the controller  5  and the motor  2 , which require cooling, can be efficiently cooled. In particular, in the present embodiment, a brushless motor is used as the motor  2 . Because the control circuit, the inverter circuit, and the like are installed on the controller  5 , which serves as the control apparatus of the brushless motor, the requirement for cooling is high. In response to this requirement, in the hammer drill  1 , the control apparatus of the brushless motor can be effectively cooled. 
     A power tool such as the hammer drill  1  is configured to linearly drive the tool accessory  18  in the impact axis A 1  direction; consequently, in general, it is often the case that the dimension in the impact axis A 1  direction is set longer than in other directions. Thereby, as in the present embodiment, by aligning the plurality of battery-mounting parts  15  in the direction parallel to the impact axis A 1 , a compact arrangement becomes possible without increasing the dimensions in other directions. In addition, if multiple batteries  19  having the same shape are mounted on the battery-mounting parts  15 , which are thus aligned, then, as shown in  FIG. 2 , the bottom surfaces of the batteries  19  are disposed in a substantially coplanar manner. Consequently, the hammer drill  1  can be placed on a flat surface, such as the floor or a workbench, with a stable attitude by setting the bottom surfaces of the batteries  19  downward facing. 
     In the present embodiment, the illumination unit  6 , which is configured to radiate light toward the location at which work is performed by the tool accessory  18 , is provided on the lower-side portion  135  of the second housing part  13 , which is elastically coupled to the first housing part  11 . Thereby, during processing work in which the hammer drill  1  is used, the user can easily confirm the state (positions) of the tool accessory  18 , the workpiece, and the like disposed at the work location. In addition, by providing the illumination unit  6  on the lower-side portion  135 , it is possible to protect (isolate) the illumination unit  6  from vibration. 
     Furthermore, the illumination unit  6  is configured to turn ON, linked to the manipulation of the trigger  14  pressed by the user in order to energize and drive the motor  2 , prior to the motor  2  being energized and driven. Thereby, the user can turn the illumination unit  6  ON merely by manipulating (e.g., pressing) the trigger  14  in order to energize and drive the motor  2 . Furthermore, the user can easily confirm the location at which work is performed by the tool accessory  18  even before the start of the actual work. Furthermore, in the present embodiment, the illumination unit  6  is configured such that it turns OFF after the drive of the motor  2  stops, which makes it possible to also confirm the processing location of the workpiece for a period of time after the processing work (hammering, drilling, hammer-drilling, etc.) has ended. 
     The correspondence between the structural elements of the present embodiment and the structural elements of the present teachings are described below. The hammer drill  1  is an exemplary structure that corresponds to the “power tool” of the present teachings. The motor  2 , the motor-main-body part  20 , and the motor shaft  25  are exemplary structures that correspond to a “motor,” a “motor-main-body part,” and a “motor shaft,” respectively, of the present teachings. The drive mechanism  3  is an exemplary structure that corresponds to a “drive mechanism” of the present teachings. The first housing part  11  and the second housing part  13  are exemplary structures that correspond to a “first housing” and a “second housing,” respectively, of the present teachings. The grasp part  131 , the upper-side portion  133 , and the lower-side portion  135  are exemplary structures that correspond to a “grasp part,” a “first portion,” and a “second portion,” respectively, of the present teachings. The upper-side sliding part  81  and the lower-side sliding part  91  are exemplary structures that correspond to a “first sliding part” and a “second sliding part,” respectively, of the present teachings. The first springs  71 , the second spring  75 , and the O-ring  79  are exemplary structures that correspond to the “elastic element(s)” of the present teachings. 
     The plate member  917  is an exemplary structure that corresponds to a “plate member” of the present teachings. The interposed part  922  is an exemplary structure that corresponds to an “interposed part” of the present teachings. The forward-stop parts  918  and the rearward-stop parts  919  are exemplary structures that correspond to “stop parts” of the present teachings. The battery-mounting parts  15  and the batteries  19  are exemplary structures that correspond to a “battery-mounting part” and a “battery,” respectively, of the present teachings. The illumination unit  6  is an exemplary structure that corresponds to an “illumination apparatus” of the present teachings. 
     The above-described embodiment is merely an illustrative example, and power tools according to the present teachings are not limited to the configuration of the hammer drill  1  that has been described above in an exemplary manner. For example, the modifications described by example below also can be utilized to develop additional embodiments of the present teachings. It is noted that any one of these modifications can be effected alone or a plurality thereof can be used in combination with the hammer drill  1  described in the embodiments or in each of the claims. 
     For example, in the above-mentioned embodiment, the hammer drill  1 , which is capable of a hammering operation as well as a drill operation, is given as one example of a power tool. However, the power tool could be a power hammer that is capable of only a hammering operation (that is, the drive mechanism  3  would not comprise the rotation-transmitting mechanism  38 ). In addition, the motor  2  is not limited to a brushless DC motor that is driven by the batteries  19  as the power supply. For example, an AC motor having brushes may be used. In such an embodiment, the hammer drill  1  would be configured (designed) without the battery-mounting parts  15 . 
     In addition, if the battery-mounting parts  15  are provided, their number is not limited to two and may be one or three or more. The direction in which the battery-mounting parts  15  are aligned is not limited to the direction parallel to the impact axis A 1  and may be a direction that intersects the impact axis A 1 . The direction in which the batteries  19  are mounted on or dismounted from the battery-mounting parts  15  is not limited to the example described in the above-mentioned embodiment. For example, if the two battery-mounting parts  15  are provided aligned in the front-rear direction, then the mounting-dismounting direction may be set to the left-right direction. It is noted that, from the viewpoint of preventing vibration, the battery-mounting parts  15  are preferably provided on the second housing part  13 . 
     The number, position, and the like of the elastic elements for coupling the first housing part  11  and the second housing part  13  such that they are capable of relative movement with respect to one another is not limited to the example described in the above-mentioned embodiment and can be modified where appropriate. For example, there may be one or three or more of the first springs  71 . Two or more of the second springs  75  may be disposed. Regarding the location at which the first spring(s)  71  and the second spring(s)  75  are disposed such that they are interposed, in the above-mentioned embodiment, the first spring(s)  71  is (are) disposed inside the rear-end part of the upper-side portion  133 , and the second spring(s)  75  is (are) disposed inside the front-end part of the lower-side portion  135 . However, for example, the second spring(s)  75  likewise may be disposed inside the rear-end part of the lower-side portion  135 . In addition, from the viewpoint of preventing vibration with respect to the grasp part  131 , as in the above-mentioned embodiment, the first spring(s)  71  and the second spring(s)  75  are preferably disposed between the upper-side portion  133 , which is connected to the upper-end part of the grasp part  131 , and the first housing part  11  and between the lower-side portion  135 , which is connected to the lower-end part, and the first housing part  11 , respectively, although other arrangements are not excluded. In addition, the first housing part  11  and the second housing part  13  may be directly coupled by one or more elastic elements or may be coupled via some other member in addition to the elastic element(s). 
     As discussed above, to prevent the first lower-side sliding surface  911  and the second lower-side sliding surface  921  from becoming welded (fused) to one another, at least the lower-side sliding part  91  is preferably formed of a material that differs from the material of the second housing part  13 . However, this does not preclude these being formed of the same material. If the lower-side sliding part  91  and the second housing part  13  are formed of different materials, then not only the lower-side sliding part  91  but the entire motor-housing part  111  may be formed of the material that differs from that of the second housing part  13 . In such a case, there is no need to mount the lower-side sliding part  91 , as a separate member, on the motor-housing part  111 , and the first lower-side sliding surface  911  should be formed on the lower-end part of the motor-housing part  111 . 
     The above-described embodiment serves as an example in which the lower-side sliding part  91  is formed of a polycarbonate-based resin and the second housing part  13  is formed of a polyamide-based resin. However, the materials that can be used are not limited to these examples. Conversely, the lower-side sliding part  91  may be formed of a polyamide-based resin and the second housing part  13  may be formed of a polycarbonate-based resin. If the second housing part  13  is formed of a polyamide-based resin as in the above-mentioned embodiment, then, instead of a polycarbonate-based resin, for example, a polyacetal-based resin, iron, magnesium, aluminum, or stainless steel can be used as the material of the lower-side sliding part  91 . It is noted that a material having a melting point (or glass transition temperature) higher than that of polyamide resin is preferably used as the material of the lower-side sliding part  91 . Furthermore, the same modifications of the lower-side sliding part  91  can be effected also on the upper-side sliding part  81 . 
     In the above-mentioned embodiment, the interposed part  922  is disposed in the gap between the lower-end part of the motor-housing part  111  (more specifically, the lower surface of the lower-side sliding part  91  (the outer-edge part  913 )) and the plate member  917 , and the upper surface of the interposed part  922  is configured as the second lower-side sliding surface  921 . In this case, because the interposed part  922  is interposed between the lower-end part of the motor-housing part  111  and the plate member  917 , sliding is further stabilized. Nevertheless, the lower-side guide part  9  may be configured without using the interposed part  922 . For example, the same as in the upper-side guide part  8 , the lower surface of the lower-side sliding part  91  may be configured as the first lower-side sliding surface  911 , and the upper surface of the circumferential-wall part  136  of the lower-side portion  135  may be configured as the second lower-side sliding surface  921 . The upper-side guide part  8  may be modified to have the same configuration as that of the lower-side guide part  9 . 
     In the above-mentioned embodiment, all sliding surfaces constituting the upper-side guide part  8  and the lower-side guide part  9  are formed as flat surfaces that extend in the horizontal direction, but the sliding surfaces may have some other shape. However, in a power tool in which the largest dominant vibration arises in the impact axis A 1  direction, the sliding surfaces are preferably disposed parallel to the impact axis A 1  direction to deal with (isolate) vibration in the dominant vibration direction. In this case, the sliding surfaces may be formed as surfaces whose normal lines are orthogonal to the impact axis A 1 , but the sliding surfaces are not limited to flat surfaces and may be nonflat surfaces such as curved surfaces. 
     Furthermore, the aspects below are constructed considering the gist of the present teachings and the above-mentioned embodiment. The aspects below may be used in combination with the hammer drill  1  described in the embodiment, the above-mentioned modified examples, and/or the claims. 
     [First Aspect] 
     The first housing comprises:
         a drive-mechanism housing part extending in the impact-axis direction and housing the drive mechanism; and   a motor-housing part coupled and fixed to the drive-mechanism housing part so as to extend in the rotational-axis direction and housing the motor;       

     wherein:
         the first portion is disposed such that it covers at least part of the drive-mechanism housing part; and   the first sliding part and the second sliding part may be respectively provided on a first end part, which is on the drive-mechanism housing part side of the motor-housing part in the rotational-axis direction, and on a second end part, which on the side opposite the drive-mechanism housing part.
 
[Second Aspect]
       

     In the first aspect,
         the first sliding part and the second sliding part may be provided on a circumferential-wall part that constitutes the motor-housing part.
 
[Third Aspect]
       

     The power tool comprises:
         a plurality of the battery-mounting parts;       

     wherein:
         the plurality of the battery-mounting parts may be provided on the second portion aligned in a prescribed direction.       

     In another embodiment of the present teachings, a power tool, such as a rotary hammer or hammer drill, includes a first housing that contains a motor and a drive mechanism for linearly reciprocally driving a tool accessory along an impact axis, and a second housing that includes a handle, a first portion and a second portion. At least one elastic element connects the first and second housings such that the handle is biased away from the first housing. A first set of sliding contact surfaces is defined on or connected to the first housing and the first portion of the second housing. A second set of sliding contact surfaces is defined on or connected to the first housing and the second portion of the second housing. The first and second sets of sliding contact surfaces are located on opposite sides of the motor such that the rotational axis of the motor intersects the impact axis and the first and second sets of sliding contact surfaces. 
     Representative, non-limiting examples of the present invention were described above in detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention. Furthermore, each of the additional features and teachings disclosed above may be utilized separately or in conjunction with other features and teachings to provide improved power tools, such as but not limited to hammer drills, rotary hammers, hybrid impact-hammer-drills, etc. The present teachings are generally applicable, without limitation, to any kind of power tool, in which it may be desirable to block or reduce transmission of vibration generated within the tool body to a handle held by the user. 
     Moreover, combinations of features and steps disclosed in the above detailed description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe representative examples of the invention. Furthermore, various features of the above-described representative examples, as well as the various independent and dependent claims below, may be combined in ways that are not specifically and explicitly enumerated in order to provide additional useful embodiments of the present teachings. 
     All features disclosed in the description and/or the claims are intended to be disclosed separately and independently from each other for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter, independent of the compositions of the features in the embodiments and/or the claims. In addition, all value ranges or indications of groups of entities are intended to disclose every possible intermediate value or intermediate entity for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter. 
     EXPLANATION OF THE REFERENCE NUMBERS 
       1  Hammer drill (rotary hammer) 
       10  Housing 
       11  First housing part (first housing) 
       111  Motor-housing part (motor housing) 
       112  Circumferential-wall part (circumferential wall) 
       113  Bottom part (bottom or base) 
       114  Step part (step) 
       115  Guide part (guide) 
       117  Drive-mechanism housing part (drive mechanism housing) 
       13  Second housing part (second housing) 
       131  Grasp part (grip or handle) 
       133  Upper-side portion 
       134 ,  139  Vents 
       135  Lower-side portion 
       136  Circumferential-wall part 
       137  Front-contact part (front contact) 
       138  Rear-contact part (rear contact) 
       14  Trigger 
       140  Switch unit 
       15  Battery-mounting part 
       150  Space 
       151  Guide rail 
       153  Hook-engaging part 
       155  Battery-connection terminal 
       2  Motor 
       20  Motor-main-body part (main body of motor) 
       21  Stator 
       22  Rotor 
       25  Motor shaft 
       26 ,  27  Bearings 
       28  Fan 
       29  Drive gear 
       3  Drive mechanism 
       30  Motion-converting mechanism 
       31  Crankshaft 
       311  Driven gear 
       312  Crank pin 
       32  Connecting rod 
       33  Piston 
       34  Tool holder 
       35  Cylinder 
       36  Hammer element 
       361  Striker 
       363  Impact bolt 
       365  Air chamber 
       38  Rotation-transmitting mechanism 
       39  Clutch 
       391  Mode-switching dial 
       5  Controller 
       51  Wiring terminal 
       6  Illumination unit 
       71  First spring 
       72  Plate member (plate) 
       73  Spring-seat part (spring seat) 
       74  Spring-seat part (spring seat) 
       75  Second spring 
       76  Spring-seat part (spring seat) 
       77  Spring-seat part (spring seat) 
       79  O-ring 
       8  Upper-side guide part (upper-side guide) 
       81  Upper-side sliding part 
       811  First upper-side sliding surface 
       821  Second upper-side sliding surface 
       9  Lower-side guide part (lower-side guide) 
       91  Lower-side sliding part 
       911  First lower-side sliding surface 
       912  Outer-circumferential part 
       913  Outer-edge part 
       914  Protruding part (protrusion) 
       917  Plate member (plate) 
       918  Forward-stop part (forward stop) 
       919  Rearward-stop part (rearward stop) 
       921  Second lower-side sliding surface 
       922  Interposed part (plain linear bearing or linear motion guide) 
       18  Tool accessory (e.g., a tool bit) 
       19  Battery 
       191  Guide groove 
       193  Hook 
       195  Button