Patent Description:
Document <NUM> (<CIT>) discloses a belt sander as an example of an electric tool equipped with an electric motor. The belt sander described in Document <NUM> is equipped with a handle, an electric motor, a driving roller, an arm, a driven roller and a sanding belt. The handle allows a user to hold. The electric motor is provided at a front end part of the handle. The electric motor has a motor shaft perpendicular to a lengthwise direction of the handle. The driving roller is fixed to the motor shaft of the electric motor. The handle is provided with the arm protruding forward from the driving roller. The driven roller is provided at a front end part of the arm so that it is allowed to rotate with the driven roller being apart from the driving roller. The sanding belt is looped around the driving roller and the driven roller.

With the belt sander, the electric motor rotates the driving roller, thereby causing the sanding belt to circulate around the driving roller and the driven roller. The sanding belt circulating in this way is made contact with a target object, thereby sanding the target object.

In the belt sander, the motor shaft of the electric motor is elongated in a direction perpendicular to the lengthwise direction of the handle. The electric motor generates vibration mainly along radial directions perpendicular to the motor shaft. Therefore, when the belt sander is activated, the vibration of the electric motor causes the handle to vibrate mainly along the lengthwise direction of the handle. That is, the handle causes user's hand holding the handle to vibrate in a direction parallel with the palm thereof. It is consequently difficult to suppress such vibration of the handle with hand holding the handle.

Moreover, with the belt sander, since the motor shaft of the electric motor is perpendicular to the lengthwise direction of the handle, the electric motor protrudes in a widthwise (or transverse) direction of the handle. This makes it difficult to use the belt sander in a narrow space such as the inside of pipes in plumbing (e.g., electricity conduits or water pipes) because the electric motor becomes an obstacle.

Furthermore, the belt sander may be used outdoor such a site where the system of pipes such as electricity conduits and/or water pipes is installed. In this case, the belt sander is preferably provided with, as a power supply thereof, not an AC power supply but a buttery. <CIT> describes a one-handed abrasive device for the chain of a chain saw and cleaving tools. The device comprises an integrated battery/accumulator-operated electric motor that moves an abrasive ring via a drive roller and a deviating roller in a conventional robust housing. The battery/accumulator unit supplies an electronic unit that selectively controls the speed and direction of the electric motor. <CIT> describes a battery-powered tool according to the preamble of claim <NUM>. The battery-powered tool generally comprises a motor having a positive terminal and a negative terminal extending therefrom for continuous engagement to a rotatable actuator. Actuator has a plurality of conductive arms extending therefrom for contact with a battery assembly such that the actuator can be selectively rotated to engage the motor in both high speed and low speed operations. <CIT> relates to a power sander particularly useful in the trade of painting, specifically designed when painting louvered doors having parallel slats at an angle therein. When painting unpainted louvered doors, a primer must first be applied. To enhance the smoothness and attractiveness of the same, the primer must be sanded and up to this date it could only be done by hand because no appropriate tools where available. The tool of this invention solves the above noted problem. It is a handheld and light weight tool having an elongated blade extending from its forward end. The blade in its lateral extent is somewhat tapered but the thickness remains the same and it conforms to the space between adjacent slats. The mechanism inside the housing of the tool drives the blade in an orbital manner to simulate hand sanding. The blade has abrasive grit thereon and will sand the surfaces of two confronting slats at the same time.

The present disclosure has been achieved in view of the above circumstances, and an object thereof is to provide an electric tool that enables a user to easily suppress vibration of a motor with user's hand and that is usable even in narrow spaces and outdoors.

An electric tool according to the invention includes the features of claim <NUM>.

The electric tool according to the present disclosure enables a user to easily suppress vibration of an electric motor with user's hand, and is usable even in narrow spaces and outdoors.

An embodiment of the present disclosure will hereinafter be explained. The embodiment below is merely an example of various embodiments of the present disclosure. Various modifications in the embodiment below are possible in light of general arrangement and the like within the scope of the appended claims. For convenience of explanation, forward (F), backward (B), leftward (L), rightward (R), upward (U) and downward (D) directions in the explanation below are used. It is however not intended to define the usage directions of an electric tool according to the embodiment.

An electric tool (or power tool) <NUM> according to the present embodiment will be explained with reference to <FIG>.

As shown in <FIG>, the electric tool <NUM> is composed as, for example a handheld belt sander. Such a belt sander is a tool for sanding a target object by a polishing surface of an endless belt rotated in a circulatory manner at a high speed. The electric tool <NUM> enables a user to easily suppress vibration of an electric motor <NUM> with user's hand holding the electric tool <NUM>, and has a rod or bar shape as a whole, thereby improving usability in narrow spaces and being usable even in outdoors.

The electric tool <NUM> includes an electric tool body <NUM>, a sanding mechanism <NUM> and a battery pack <NUM>.

The electric tool body <NUM> is configured to receive electric power supplied from the battery pack <NUM> to perform drive control of the sanding mechanism <NUM>. The electric tool body <NUM> also has a rod or bar shape with a thickness or cross section that allows a user to hold in hand, and also functions as a handle <NUM> to be held in a user's hand. The electric tool body <NUM> includes a housing <NUM> that houses components for driving the sanding mechanism <NUM>.

The housing <NUM> is in the shape of a cylinder. For example, the housing <NUM> may be shaped like a circular cylinder with a thickness or cross section that allows a user to hold in hand. The housing <NUM> may be long narrow and have an appropriate length. As a specific example, the housing <NUM> is shaped like a circular cylinder that is <NUM> to <NUM> millimeters (mm) in diameter and <NUM> to <NUM> in length.

An approximately center part of a peripheral face of the housing <NUM> in a lengthwise direction thereof (i.e., a fore-aft direction) functions as the handle <NUM>. The sanding mechanism <NUM> is provided at a front end part of the housing <NUM> in the lengthwise direction. The battery pack <NUM> is detachably attached to or inserted into a back end part of the housing <NUM> in the lengthwise direction. The handle <NUM> is therefore disposed between the sanding mechanism <NUM> and the battery pack <NUM> (i.e., near sanding mechanism <NUM>). Thus, the handle <NUM> is disposed near the sanding mechanism <NUM>, thereby enabling an improvement in sanding mechanism's (<NUM>) operational performance.

The housing <NUM> is provided with an attached part <NUM> in the back end part of the housing <NUM> in the lengthwise direction. The attached part <NUM> allows the battery pack <NUM> to be detachably attached to or inserted into.

Intake holes <NUM> and exhaust holes <NUM> are provided in the peripheral face of the housing <NUM>. The intake holes <NUM> allow outside (or ambient) air to enter the electric tool body <NUM> therethrough. The ambient air serves as cooling air for the electric motor <NUM>. Two or more (e.g., five) intake holes <NUM> are provided in each region on both left and right sides of the peripheral face of the electric tool body <NUM> with the intake holes <NUM> being near a back end of the electric motor <NUM> (e.g., each of side faces of the handle <NUM>). The exhaust holes <NUM> allow inside air of the electric tool body <NUM> to exit therethrough. Two or more (e.g., five) exhaust holes <NUM> are provided in each region on both left and right sides of the peripheral face of the electric tool body <NUM> with the exhaust holes <NUM> being near a front end of the electric motor <NUM> (e.g., around a front part of the handle <NUM>).

A power switch <NUM> is provided on the peripheral face of the housing <NUM>. The power switch <NUM> is configured to turn on and off a power supply of the electric tool <NUM>. For example, the power switch <NUM> is a slide switch with a slider to be slid from side to side in the fore-aft direction. The power switch <NUM> is provided in front of the handle <NUM> on an upper region of the peripheral face of the housing <NUM> (e.g., at a location within the reach of the thumb of a hand holding the handle <NUM>).

The sanding mechanism <NUM> is of an endless belt type and includes a part for sanding a target object. In an example, the sanding mechanism <NUM> is provided at the front end part of the housing <NUM>, and includes a rod or bar shape protruding forward from the housing <NUM> in a horizontal posture. The sanding mechanism <NUM> includes a driven shaft <NUM>, a driven side bevel gear <NUM>, a driving pulley <NUM>, a driven pulley <NUM>, an arm <NUM> and a sanding belt <NUM>.

The driven shaft <NUM> is a rotary shaft to which the driven side bevel gear <NUM> and the driving pulley <NUM> are fixed. The driven shaft <NUM> is housed inside a front part of the housing <NUM>. The driven shaft <NUM> is elongated in a left-right direction of the housing <NUM> and both end parts thereof are supported by the housing <NUM> so that the driven shaft <NUM> is allowed to rotate. A right end of the driven shaft <NUM> protrudes outward from a right side face of the housing <NUM>, and the driving pulley <NUM> is fixed to a right end part of the driven shaft <NUM> as described later.

The driven side bevel gear <NUM> is a gear to be driven to rotate by the electric motor <NUM>. The driven side bevel gear <NUM> is housed inside the front part of the housing <NUM>. The driven side bevel gear <NUM> is fixed to the driven shaft <NUM> in a concentric manner. The driven side bevel gear <NUM> is therefore to rotate integrally with the driven shaft <NUM>. The driven side bevel gear <NUM> is engaged with a driving side bevel gear <NUM> fixed to a rotary shaft <NUM> of the electric motor <NUM>. Here, the driving side bevel gear <NUM> will be described later.

The driving pulley <NUM> and the driven pulley <NUM> support the sanding belt <NUM> so as to allow the sanding belt <NUM> to circularly rotate. The driving pulley <NUM> is fixed to the right end part of the driven shaft <NUM> in a concentric manner. The driving pulley <NUM> is disposed on the outer right side face of the housing <NUM>. The driving pulley <NUM> is to rotate integrally with the driven side bevel gear <NUM> via the driven shaft <NUM>.

The driven pulley <NUM> is supported by the arm <NUM> so that it is allowed to rotate. The arm <NUM> is elongated in the fore-aft direction of the housing <NUM>. A back end part of the arm <NUM> is attached to the front end part of the housing <NUM>, and a front end part of the arm <NUM> protrudes forward from the housing <NUM>.

Specifically, a front half of the arm <NUM> is shaped like a rod or bar elongated in the fore-aft direction. A back half of the arm <NUM> is shaped like a crank. The back half is bent leftward and further bent backward. A connection hole 35a is provided in a back end part of the back half of the arm <NUM>. The connection hole 35a is a hole for connection with the housing <NUM>. The connection hole 35a is cylindrical and pierced in the left-right direction. A coupling member 21a is provided on the left side face of the front part of the housing <NUM>. The coupling member 21a is a cylindrical protrusion protruding leftward from the housing <NUM> and linked with the connection hole 35a of the arm <NUM> so that it is allowed to rotate.

The coupling member 21a of the housing <NUM> is engaged with (i.e., linked with) the connection hole 35a of the arm <NUM> so that it is allowed to rotate. The arm <NUM> is accordingly linked with the housing <NUM> so that it is allowed to rotate in a predetermined angle range relative thereto in an up-down direction. That is, this enables an adjustment for the angle about the back part of the arm <NUM> relative to the housing <NUM> in the up-down direction.

The back half of the arm <NUM> (i.e., the crank-shaped part) is disposed adjacent to a front end face and a left side face of the front part of the housing <NUM>. The front half of the arm <NUM> protrudes forward with the front half shifted to the right side of the housing <NUM>. The driven pulley <NUM> is provided at the front end part of the arm <NUM> so that it is allowed to rotate. A rotary shaft of the driven pulley <NUM> is disposed in the left-right direction of the housing <NUM>. The driven pulley <NUM> is disposed in front of the driving pulley <NUM>.

The sanding belt <NUM> is formed as the endless belt. An outside surface of the sanding belt <NUM> is a sandpaper. The sanding belt <NUM> is looped around the driving pulley <NUM> and the driven pulley <NUM>.

With the sanding mechanism <NUM>, the driving pulley <NUM> rotates according to the rotation of the driven side bevel gear <NUM>. In this case, the sanding belt <NUM> rotates to circulate around the driving pulley <NUM> and the driven pulley <NUM>. Thus, the sanding mechanism <NUM> is driven to rotate.

The battery pack <NUM> is a direct-current (DC) power supply configured to supply electric power to the electric motor <NUM> inside the housing <NUM>. The battery pack <NUM> has a substantially columnar shape (e.g., rectangular columnar shape) and is the same as or slightly narrower than the housing <NUM> in thickness. A front end part 4a of the battery pack <NUM> (i.e., one end thereof) is detachably attached to (i.e., linked with) the attached part <NUM> of the housing <NUM> (i.e., the back end part of the housing <NUM>). Examples of configuration of the battery pack <NUM> include a configuration in which a storage battery such as lithium-ion battery is housed in a case, and the like.

A remaining part 4b of the battery pack <NUM> other than the front end part 4a protrudes straight backward from the back end part of the housing <NUM>. Such protrusion enables the battery pack <NUM> to function as a supplementary handle of the electric tool <NUM>. That is, it is possible for a user to employ a portion from the handle <NUM> to the battery pack <NUM> as a handle.

Internal structure of the electric tool body <NUM> and structure of the battery pack <NUM> will hereinafter be described in detail with reference to <FIG>.

The housing <NUM> possesses therein an interior space S1. The interior space S1 is formed along the lengthwise direction of the housing <NUM> (fore-aft direction). A part of the sanding mechanism <NUM> (driven shaft <NUM> and driven side bevel gear <NUM>), the electric motor <NUM> and a control circuit <NUM> are housed in the interior space S1 of the housing <NUM>.

The part of the sanding mechanism <NUM> (i.e., driven shaft <NUM> and driven side bevel gear <NUM>) is housed in a front part of the interior space S1 of the housing <NUM>. The control circuit <NUM> is housed in a back part of the interior space S1 of the housing <NUM>. The electric motor <NUM> is housed in a center part of the housing <NUM> in the lengthwise direction (i.e., next to sanding mechanism <NUM>).

Specifically, the driven shaft <NUM> is in the front part of the interior space S1 of the housing <NUM>, and is elongated in the left-right direction of the housing <NUM>-i.e., a direction perpendicular to the rotary shaft <NUM> to be described later of the electric motor <NUM>. The driven shaft <NUM> is supported by the housing <NUM> so that it is allowed to rotate. The driven side bevel gear <NUM> is fixed to the driven shaft <NUM> in a concentric manner in the front part of the interior space S1 of the housing <NUM>.

The electric motor <NUM> is configured to receive electric power supplied from the battery pack <NUM> to drive the sanding mechanism <NUM>. The electric motor <NUM> includes a motor body <NUM>, the rotary shaft <NUM>, the driving side bevel gear <NUM> and a cooling fan <NUM>.

The motor body <NUM> is composed of a rotor and a stator, and configured to convert the electric power from the battery pack <NUM> into rotary drive power. The rotary shaft <NUM> passes through an inside of the motor body <NUM> and protrudes from both front and back sides of the motor body <NUM>, and is configured to provide an outside with the rotary drive power converted by the motor body <NUM>. The electric motor <NUM> is housed in the interior space S1 of the housing <NUM> so that the rotary shaft <NUM> is parallel to the lengthwise direction of the housing <NUM>. Front and back parts of the rotary shaft <NUM> are supported by the housing <NUM> so that the rotary shaft <NUM> is allowed to rotate.

As stated above, the rotary shaft <NUM> is parallel to the lengthwise direction of the housing <NUM>. As described below, the rotary shaft <NUM> is elongated along a direction in which the sanding mechanism <NUM> in the horizontal posture (hereinafter simply referred to as the "sanding mechanism <NUM>"), the electric motor <NUM> inside the handle <NUM>, and the battery pack <NUM> are arranged side by side.

The driving side bevel gear <NUM> is fixed to a front end part of the rotary shaft <NUM> in a concentric manner, and engaged with the driven side bevel gear <NUM>. The cooling fan <NUM> is configured to generate cooling air for cooling the motor body <NUM>. The cooling fan <NUM> is disposed in front of the motor body <NUM>, and fixed to the front part of the rotary shaft <NUM> in a concentric manner. Thus, the cooling fan <NUM> is to rotate according to the rotation of the rotary shaft <NUM> to generate cooling air toward the motor body <NUM>, thereby cooling the motor body <NUM>.

Note that the driven shaft <NUM>, the driven side bevel gear <NUM> and the driving side bevel gear <NUM> constitute a transmission mechanism configured to transmit rotary drive power by the electric motor <NUM> to remaining components (mainly sanding belt <NUM>) of the sanding mechanism <NUM>. That is, when the electric motor <NUM> is activated, rotary drive power by the electric motor <NUM> is transmitted in order of the rotary shaft <NUM>, the driving side bevel gear <NUM> and the driven side bevel gear <NUM> (i.e., sanding mechanism <NUM>). In the transmission mechanism, the driven shaft <NUM> is disposed in a direction perpendicular to the rotary shaft <NUM>. A transmission direction of the rotary drive power by the electric motor <NUM> is therefore converted into the direction perpendicular to the rotary shaft <NUM>.

The control circuit <NUM> is configured to perform drive control of the electric motor <NUM>. The circuit <NUM> is composed of a printed circuit board and various electrical components mounted on the printed circuit board. The control circuit <NUM> is configured to receive electric power supplied from the battery pack <NUM> and ON or OFF information from the power switch <NUM>. The control circuit <NUM> is also configured to supply electric power to the electric motor <NUM> or stop the supply of the electric power to the electric motor <NUM> according to an ON or OFF state of the power switch <NUM>, respectively.

Note that an output level of the electric motor <NUM> may be adjusted according to a position of the slider of the power switch <NUM>. In this case, the control circuit <NUM> is configured to acquire information on the position of the slider (or slide amount) from the power switch <NUM> to adjust the electric power to be supplied to the electric motor <NUM> based on the acquired information. When the electric motor <NUM> is a DC motor, the control circuit <NUM> may supply DC power from the battery pack <NUM> to the electric motor <NUM>. When the electric motor <NUM> is an alternating-current (AC) motor, the control circuit <NUM> may convert DC power from the battery pack <NUM> into AC power to be supplied to the electric motor <NUM>.

The attached part <NUM> of the housing <NUM> includes an engagement recess 211a provided in a back end face of the housing <NUM>, and power input terminals 211b.

The engagement recess 211a allows a front part of the battery pack <NUM> to be detachably fitted in (i.e., to be connected to). The engagement recess 211a is lower than a peripheral edge of the back end face of the housing <NUM> along the lengthwise direction. Thus, in a state where the front part of the battery pack <NUM> is fitted in the engagement recess 211a, a remaining part of the battery pack <NUM> other than the front part protrudes straight backward from the back end part of the housing <NUM>.

Engagement hollows 211c are provided in an inner peripheral face of the engagement recess 211a. Two engagement hollows 211c are provided on both upper and lower sides in the engagement recess 211a. Note that the number of the engagement hollows 211c may be one or more. Note that when two or more engagement hollows 211c are provided, the engagement hollows 211c are preferably arranged at regular intervals in the inner peripheral face of the engagement recess 211a along a peripheral direction thereof.

The power input terminals 211b allows power output terminals to be described later of the battery pack <NUM> to be electrically connected to. The power input terminals 211b allows electric power from the battery pack <NUM> to pass therethrough to be provided to the control circuit <NUM>. The power input terminals 211b includes a positive input terminal and a negative input terminal. The power input terminals 211b are provided on a bottom of the engagement recess 211a. Respective tip parts of the power input terminals 211b are inside the engagement recess 211a, and protrude vertically from the bottom of the engagement recess 211a (i.e., along the fore-aft direction). Respective base parts of the power input terminals 211b are electrically connected to the control circuit <NUM>.

The battery pack <NUM> is provided with the power output terminals <NUM> and engagement projections <NUM>.

The power output terminals <NUM> allow the power input terminals 211b of the attached part <NUM> to be electrically connected with. The power output terminals <NUM> also allow electric power stored in the battery pack <NUM> to pass therethrough to be provided to the power input terminals 211b. For example, two power output terminals <NUM> (positive and negative output terminals) are provided. Note that the positive and negative output terminals are to be connected to the positive and negative input terminals, respectively. Two terminal insertion holes <NUM> are provided in a front face of the battery pack <NUM>. The power output terminals <NUM> are to be disposed in the terminal insertion holes <NUM>.

The engagement projections <NUM> are allowed to be engaged with (or fit in) the engagement hollows 211c of the attached part <NUM>. Each of the engagement projections <NUM> has, for example a trapezoid or trapezium shape whose front and back side faces are inclined as seen from the side. For example, two engagement projections <NUM> whose number is the same as that of the engagement hollows 211c are provided on an outer peripheral face of the front part of the battery pack <NUM> with respective positions thereof corresponding to those of the engagement hollows 211c. Thus, the two engagement projections <NUM> correspond to the two engagement hollows 211c.

In the present embodiment, the attached part <NUM> is formed with the engagement hollows 211c, while the battery pack <NUM> is formed with the engagement projections <NUM>. However, the attached part <NUM> may be formed with engagement projections, while the battery pack <NUM> may be formed with engagement hollows.

When the battery pack <NUM> is attached to the attached part <NUM> of the electric tool body <NUM>, the front part of the battery pack <NUM> is inserted into the engagement recess 211a of the attached part <NUM>. As a result, the front part of the battery pack <NUM> is engaged with the engagement recess 211a. In this engagement state, the power input terminals 211b of the attached part <NUM> are inserted into the terminal insertion holes <NUM> to be electrically connected to the power output terminals <NUM>. This enables the supply of electric power stored in the battery pack <NUM> to the electric tool body <NUM> via the power output terminals <NUM> and the power input terminals 211b.

In the engagement state, the engagement projections <NUM> are engaged with the engagement hollows 211c. This prevents the battery pack <NUM> from falling off from the attached part <NUM> unless the battery pack <NUM> is pulled with prescribed force or more. In other words, detaching the battery pack <NUM> from the attached part <NUM> requires pulling the battery pack <NUM> from the attached part <NUM> with prescribed force or more. In this case, the engagement projections <NUM> are disengaged from the engagement hollows 211c and the battery pack <NUM> is detached from the attached part <NUM>.

In a state where the battery pack <NUM> is attached to the attached part <NUM> of the electric tool body <NUM>, the battery pack <NUM> protrudes from the back end part of the housing <NUM> along the lengthwise direction of the housing <NUM>.

As can be seen from the internal structure of the electric tool body <NUM>, a part of the sanding mechanism <NUM> (driven shaft <NUM> and driven side bevel gear <NUM>), the electric motor <NUM> and the control circuit <NUM> are arranged side by side in one direction (i.e., fore-aft direction). Specifically, a part of the sanding mechanism <NUM> except the driven shaft <NUM> and the driven side bevel gear <NUM> is rotated around the driven shaft <NUM>. It is accordingly possible to arrange the housing <NUM> in a line relative to the housing <NUM>. Therefore, it can be considered that not only the part of the sanding mechanism <NUM> but also all the sanding mechanism <NUM> are arranged in one direction along with the electric motor <NUM> and the control circuit <NUM>.

The handle <NUM> is disposed so as to overlap the electric motor <NUM> and the control circuit <NUM> as seen from, for example the side of the electric tool <NUM>. However, considering all of the handle <NUM>, the sanding mechanism <NUM>, the electric motor <NUM> and the control circuit <NUM>, the sanding mechanism <NUM> in the horizontal posture and both of the electric motor <NUM> and the control circuit <NUM> inside the handle <NUM> are arranged in a straight line. Therefore, in the present embodiment, the handle <NUM> is regarded as being arranged in one direction along with the sanding mechanism <NUM>, the electric motor <NUM> and the control circuit <NUM>. That is, in the present embodiment, even if some components overlap or do not overlap, all of components in question are regarded as being arranged in one direction as long as all of the components in question are arranged like a straight line. Hence, the handle <NUM> is arranged in one direction along with the sanding mechanism <NUM>, the electric motor <NUM> and the control circuit <NUM>. Therefore, even if the handle <NUM> is added to a group of the sanding mechanism <NUM>, the electric motor <NUM> and the control circuit <NUM>, these components (i.e., sanding mechanism <NUM>, electric motor <NUM>, control circuit <NUM> and handle <NUM>) are arranged in one direction.

In a state where the battery pack <NUM> is attached to the attached part <NUM>, the battery pack <NUM> is also arranged in one direction along with the sanding mechanism <NUM>, the electric motor <NUM>, the control circuit <NUM> and the handle <NUM>. Even except for the control circuit <NUM>, the sanding mechanism <NUM>, the electric motor <NUM>, the battery pack <NUM> and the handle <NUM> are arranged in one direction. The arrangement of the sanding mechanism <NUM>, the handle <NUM>, the electric motor <NUM> and the battery pack <NUM> in one direction enables the electric tool <NUM> to have a rod or bar shape. Note that the control circuit <NUM> may be disposed in any space inside the housing <NUM>, and therefore the arrangement of the control circuit <NUM> hardly affects an overall shape of the electric tool <NUM>. Of the sanding mechanism <NUM>, the electric motor <NUM>, the battery pack <NUM> and the handle <NUM>, the battery pack <NUM> is disposed at the very end in one direction. Thus, the relatively heavy battery pack <NUM> is disposed at a back end part in the arrangement. That is, a heavy component such as the battery pack <NUM> is not at a center but an outside of the electric tool <NUM>. This enables an improvement in stability of the electric tool <NUM> with respect to vibration of the electric motor <NUM>.

The rotary shaft <NUM> of the electric motor <NUM> is elongated along one direction-i.e., an arrangement direction of the sanding mechanism <NUM>, the electric motor <NUM>, the battery pack <NUM> and the handle <NUM>. The electric motor <NUM> is disposed next to the driven side bevel gear <NUM>-i.e., next to the sanding mechanism <NUM>. This renders an interval between the electric motor <NUM> and the sanding mechanism <NUM> short and enables efficient transmission of rotary drive power by the electric motor <NUM> to the sanding mechanism <NUM> with a transmission loss suppressed.

In the abovementioned embodiment, the sanding mechanism <NUM> includes the endless belt, but the present disclosure is not limited to this. For example, in the present modified example, the sanding mechanism <NUM> may include a disc-shaped sanding part. With this disc-shaped sanding part, the sanding mechanism <NUM> includes a disc in place of the driving pulley <NUM>, the driven pulley <NUM>, the arm <NUM> and the sanding belt <NUM>. The disc is fixed to a driven shaft <NUM> in a concentric manner. An outer surface as a main side of the disc is a sandpaper. The disc is to be rotated by an electric motor <NUM>, and the main side of the rotating disc (sandpaper) is brought into contact with a target object, thereby sanding the target object.

In the abovementioned embodiment, the electric motor <NUM> is disposed next to the sanding mechanism <NUM>-i.e., at or near a center part of the housing <NUM> in the lengthwise direction. In the present modified example, an electric motor <NUM> may be disposed at an arbitrary position in an interior space S1 of a housing <NUM>. For example, the electric motor <NUM> may be disposed behind a sanding mechanism <NUM>-i.e., at the very back in the interior space S1 of the housing <NUM>. In this case, a rotary shaft <NUM> is elongated to a front part of the housing <NUM>. A driving side bevel gear <NUM> is fixed to a front end part of the rotary shaft <NUM> and engaged with a driven side bevel gear <NUM>. Thus, the electric motor <NUM> is disposed behind the sanding mechanism <NUM>, thereby making it possible to narrow a handle <NUM> because the electric motor <NUM> is not disposed inside a central part of the housing <NUM>, namely the handle <NUM>. Note that in this case, a control circuit <NUM> may be disposed in a free space between the driven side bevel gear <NUM>, namely the sanding mechanism <NUM> and the electric motor <NUM>.

In the abovementioned embodiment, the battery pack <NUM> is configured to be inserted into the attached part <NUM> of the housing <NUM>. In the present modified example, a battery pack <NUM> may be configured to be inserted into an attached part <NUM> of a housing <NUM> and then rotated in a peripheral direction thereof. In this case, the battery pack <NUM> is circular cylindrical, and an engagement recess 211a of the attached part <NUM> is a hollow that is circular cylindrical as well.

Each of engagement hollows 211c is shaped like an L composed of a longitudinal hollow and a lateral hollow. The longitudinal hollow is formed in an inner peripheral face of the attached part <NUM> from an opening to a bottom side of the attached part <NUM> along a lengthwise direction (fore-aft direction) of the housing <NUM>. The lateral hollow is curved in a peripheral direction of the attached part <NUM> from an end of the longitudinal hollow on the bottom side. That is, the battery pack <NUM> is inserted into the attached part <NUM> and thereby each of the engagement projections <NUM> is guided to the bottom of a corresponding longitudinal hollow. The battery pack <NUM> is then rotated and thereby each of the engagement projections <NUM> is guided in a corresponding lateral hollow. The engagement projections <NUM> are engaged with respective lateral hollows, thereby preventing the battery pack <NUM> from falling off from the attached part <NUM> even if the battery pack <NUM> is pulled behind the housing <NUM>.

In this case, each opening of terminal insertion holes <NUM> of the battery pack <NUM> is a circular arc in shape. When the battery pack <NUM> is inserted into the engagement recess 211a and then rotated, power input terminals 211b are moved in a circular arc direction of respective openings of the terminal insertion holes <NUM> with the power input terminals 211b inserted into the terminal insertion holes <NUM>. As a result, the power input terminals 211b are electrically connected to respective power output terminals <NUM>.

As can be seen from the embodiment and the modified examples described above, an electric tool <NUM> according to a first aspect includes a sanding mechanism <NUM>, a motor <NUM>, a battery pack <NUM> and a housing <NUM>. The sanding mechanism <NUM> is configured to sand a target object. The motor <NUM> is configured to drive the sanding mechanism <NUM>. The battery pack <NUM> is configured to supply the motor <NUM> with electric power. The sanding mechanism <NUM>, the motor <NUM> and the battery pack <NUM> are fixed to the housing <NUM>. The motor <NUM> possesses a rotary shaft <NUM>. The rotary shaft <NUM> is configured to transmit rotary drive power to the sanding mechanism <NUM>. The housing <NUM> possesses a handle <NUM> that allows a user to hold. The sanding mechanism <NUM>, the motor <NUM>, the battery pack <NUM> and the handle <NUM> are arranged in one direction. The rotary shaft <NUM> of the motor <NUM> is elongated in the one direction.

This configuration enables the user to easily suppress vibration of the motor <NUM> with hand. It is moreover possible to render the motor <NUM> usable or available in narrow spaces and outdoors.

Specifically, the rotary shaft <NUM> of the motor <NUM> is elongated along the one direction, and therefore parallel to a lengthwise direction of the handle <NUM>. The vibration of the motor <NUM> in operation mainly contains vibration components in a direction perpendicular to the rotary shaft <NUM> in particular. The vibration of the motor <NUM> in operation therefore mainly contains vibration components in a direction perpendicular to the lengthwise direction of the handle <NUM>. This consequently enables the user to receive the vibration with the palm of user's hand holding the handle <NUM>, thereby easily suppressing the vibration with hand.

In addition, the sanding mechanism <NUM>, the motor <NUM>, the battery pack <NUM> and the handle <NUM> are arranged in the one direction, and it is therefore possible to form an overall shape of the electric tool <NUM> into a rod or bar shape. This consequently enables the user to insert the electric tool <NUM> to be used into a narrow space such the inside of pipes in plumbing (e.g., water pipes or electricity conduits).

The electric tool <NUM> includes the battery pack <NUM>, thereby enabling outdoor use of the electric tool <NUM>.

In an electric tool <NUM> according to a second aspect turning on the first aspect, the motor <NUM> is disposed next to the sanding mechanism <NUM>.

This configuration makes it possible to shorten an interval between the motor <NUM> and the sanding mechanism <NUM>. It is consequently possible to miniaturize or simplify a transmission mechanism configured to transmit the rotary drive power by the motor <NUM> to the sanding mechanism <NUM>, thereby rendering the electric tool <NUM> small or less costly.

In an electric tool <NUM> according to a third aspect turning on a first or second aspect, of the sanding mechanism <NUM>, the motor <NUM>, the battery pack <NUM> and the handle <NUM>, the battery pack <NUM> is disposed at a farthest end in the one direction.

This configuration enables an improvement in stability of the electric tool <NUM> with respect to the vibration of the motor <NUM>. It is consequently possible to suppress the vibration of the motor <NUM> in operation.

In an electric tool <NUM> according to a fourth aspect turning on any one of the first to third aspects, the handle <NUM> is disposed between the sanding mechanism <NUM> and the battery pack <NUM>.

This configuration enables the handle <NUM> to be disposed near the sanding mechanism <NUM>. It is consequently possible to improve operational performance with respect to the sanding mechanism <NUM>-e.g., adjustment precision of increase or decrease in force to be added to the sanding mechanism <NUM> and adjustment precision of increase or decrease in movement length when the sanding mechanism <NUM> is moved.

In an electric tool <NUM> according to the invention, the battery pack <NUM> possesses a first end part 4a and a remaining part 4b other than the first end part 4a. When the battery pack <NUM> is attached to the housing <NUM>, the first end part 4a of the battery pack <NUM> is linked with the housing <NUM>. When the battery pack <NUM> is attached to the housing <NUM>, the remaining part 4b of the battery pack <NUM> protrudes from the housing <NUM>.

Claim 1:
An electric tool (<NUM>), comprising
a sanding mechanism (<NUM>) configured to sand a target object,
a motor (<NUM>) configured to drive the sanding mechanism (<NUM>),
a battery pack (<NUM>) configured to supply the motor (<NUM>) with electric power, and
a housing (<NUM>) to which the sanding mechanism (<NUM>), the motor (<NUM>) and the battery pack (<NUM>) are fixed, wherein
the motor (<NUM>) includes a rotary shaft (<NUM>) configured to transmit rotary drive power to the sanding mechanism (<NUM>),
the housing (<NUM>) includes a handle (<NUM>) that allows a user to hold,
the sanding mechanism (<NUM>), the motor (<NUM>), the battery pack (<NUM>) and the handle (<NUM>) are arranged in one direction, and
the battery pack (<NUM>) has a columnar shape or rectangular columnar shape and is the same as or narrower than the housing (<NUM>) in thickness,
the rotary shaft (<NUM>) of the motor (<NUM>) is elongated in the one direction,
the housing (<NUM>) has a back end face in a lengthwise direction of the housing (<NUM>), the back end face being provided with an engagement recess (211a) in which one end part (4a) of the battery pack (<NUM>) is to be detachably fitted,
the battery pack (<NUM>) includes the one end part (4a) and a remaining part (4b) other than the one end part (4a),
the lengthwise direction of the housing (<NUM>) is a fore-aft direction of the housing (<NUM>),
in a state where the one end part (4a) of the battery pack (<NUM>) is fitted in the engagement recess (211a), the remaining part (4b) of the battery pack (<NUM>) protrudes straight backward from the housing (<NUM>),
in a state where the one end part (4a) of the battery pack (<NUM>) is inserted into the engagement recess (211a), engagement projections (<NUM>) are engaged with engagement hollows (211c),
characterised in that
one of the engagement hollows (211c) and the engagement projections (<NUM>) are provided in an inner peripheral face of the engagement recess (211a), the other of the engagement hollows (211c) and the engagement projections (<NUM>) are provided in a front part of an outer peripheral face of the battery pack (<NUM>),
the back end face of the housing (<NUM>) is inclined relative to the lengthwise direction of the housing (<NUM>).