Patent Description:
A work machine such as a hydraulic excavator includes a crawler type of lower traveling body, an upper slewing body mounted on the lower traveling body capably of slewing, a work attachment attached to the upper slewing body to make a working motion, and a driving source mounted on the upper slewing body. As such a work machine, an electric work machine is known including an electric motor as the driving source.

An electric work machine is powered through a power supply cable. The power supply cable has a power-supply side end to be connected to an external power supply, and a machine side end to be connected to the upper slewing body on the opposite side to the power-supply side. The upper slewing body is provided with, for example, a slip ring as described in <CIT>. The slip ring constitutes a power receiving device of the upper slewing body, enabling the power supply cable to be connected to the upper slewing body with no entanglement with the electric work machine due to the slewing of the upper slewing body.

The electric work machine described in <CIT> includes a connection unit where a power feed cable and the slip ring is connected to each other, the connection unit located on the top of the power receiving device. This causes the connection between the slip ring and the power feed cable to require drawing the power feed cable into the power receiving device of the upper slewing body and performing a connection work inside the power receiving device. The connection unit, located at a position difficult for a worker to access, causes the connection work to include many man-hours and to be extremely complicated.

<CIT> discloses an electric work machine with the features of the preamble of claim <NUM>, including a power receiving device to be supplied with power through a power supply cable. The power receiving device includes a plurality of slip rings and a plurality of sliding brushes that keep contact with respective outer peripheral surfaces of the slip rings. The brushes are mounted on a brush mounting plate, and the brush mounting plate is connected to a power feed cable extending from the power receiving device.

<CIT> discloses another example of an electric work machine capable of being powered through a power supply cable.

An object of the present invention is to provide an electric work machine including a machine body and a power receiving device and allowing connection work for interconnecting the power receiving device and a power feed cable that enables the machine body to be fed with power through the power feed cable to be efficiently performed.

Provided is an electric work machine as specified in claim <NUM>.

Below will be described embodiments of the present invention with reference to the drawings. The following description about the preferred embodiments is just illustrative with no intention to limit the present invention, the application thereof or the use thereof.

<FIG> shows an electric hydraulic excavator <NUM>. The hydraulic excavator <NUM> is an example of the electric work machine according to the present invention.

The hydraulic excavator <NUM> includes a crawler type of lower traveling body <NUM>, an upper slewing body <NUM> mounted on the lower traveling body <NUM> capably of slewing, a power receiving device <NUM>, a plurality of connection wires <NUM>, a power feed cable <NUM>, and a connection box <NUM>. The upper slewing body <NUM> corresponds to the machine body according to the present invention. The machine body according to the present invention may be either the lower traveling body <NUM>.

The machine body, namely, the upper slewing body <NUM> according to the present embodiment, is connectable to an external power supply <NUM> through a power supply cable <NUM>, and the electric hydraulic excavator <NUM> can be actuated by supply of power from the external power supply <NUM> to the upper slewing body <NUM> through the power supply cable <NUM>. The power supply cable <NUM> has a power-supply side end to be connected to the external power supply <NUM> and a machine side end opposite to the power-supply side end, the machine side end being connectable to the machine body, which is the upper slewing body <NUM> in the present embodiment.

The upper slewing body <NUM> includes a slewing frame <NUM>, a counterweight <NUM>, a machine room <NUM>, a cab <NUM>, a work device <NUM>, a machine room cover, an electric motor <NUM>, and a hydraulic pump <NUM>.

The slewing frame <NUM> is connected to the lower traveling body <NUM> capably of slewing about a vertical axis relatively to the lower traveling body <NUM>. The counterweight <NUM> is disposed on the slewing frame <NUM> and located in the rear of the upper slewing body <NUM>. The machine room <NUM> is disposed on the slewing frame <NUM> and located on the front side of the counterweight <NUM>. The cab <NUM> is disposed on the slewing frame <NUM> and located frontward of the machine room <NUM>.

The work device <NUM> is adjacent to the cab <NUM> laterally of the upper slewing body <NUM>, configured to perform a predetermined working motion, that is, an excavation motion and the like in this embodiment. The work device <NUM> includes a boom <NUM>, an arm <NUM> and a work attachment <NUM>. The boom <NUM> has a proximal end and a distal end opposite to the proximal end, the proximal end being mounted on the front end of the slewing frame <NUM> capably of vertically swinging to the slewing frame <NUM>. The arm <NUM> has a proximal end and a distal end opposite thereto, the proximal end being connected to the distal end of the boom <NUM> capably of vertically rotational movement. The work attachment <NUM> is attached to the distal end of the arm <NUM>.

The machine room cover includes an electric motor cover <NUM> and a hydraulic pump cover <NUM> shown in <FIG>, covering the machine room <NUM> from above. The machine room <NUM> accommodates the electric motor <NUM> and the hydraulic pump <NUM>. The electric motor <NUM> is the driving source of the electric hydraulic excavator <NUM>, being powered to drive the hydraulic pump <NUM>. The hydraulic pump <NUM> is aligned laterally with the electric motor <NUM> and configured to be driven by the electric motor <NUM> to thereby discharge hydraulic fluid. The electric motor cover <NUM> is disposed so as to cover the electric motor <NUM> from above and capably of opening and closing. Specifically, the electric motor cover <NUM> has a front end and a rear end, the front end being capable of vertically rotational movement about the rear end to allow the electric motor cover <NUM> to be moved between a closing position and an opening position. The electric motor cover <NUM> can be pulled up from the closing position to the opening position, thereby opening the electric motor <NUM> and peripheral devices thereof accommodated in the machine room <NUM> to allow the maintenance thereof to be performed.

The hydraulic pump cover <NUM> is disposed so as to cover the hydraulic pump <NUM> from above and capably of opening and closing. Specifically, the hydraulic pump cover <NUM> is capable of rotational movement between a closing position and an opening position, configured to open the hydraulic pump cover <NUM> upward as shown in <FIG> in the opening position to thereby allow the maintenance of the hydraulic pump <NUM> and peripheral devices accommodated in the machine room <NUM> to be performed. This state involves exposure of the electric motor <NUM>, the power feed cable <NUM> for powering a not-graphically-shown control panel, the hydraulic pump <NUM> and a part of the connection box <NUM>.

The power feed cable <NUM> is connected to the machine body to allow the machine body to be fed with power through the power feed cable <NUM>. Specifically, the power feed cable <NUM> is connected to the electric motor <NUM> in the machine room <NUM> and drawn from the electric motor <NUM> upward of the position between the electric motor <NUM> and the hydraulic pump <NUM>.

In the machine room <NUM> are provided a fire plate <NUM> and a beam member <NUM> shown in <FIG>. The fire plate <NUM> is formed in a flat plate shape, located over the hydraulic pump <NUM> inside the machine room <NUM> and constructed longitudinally of the upper slewing body <NUM> to shield the hydraulic pump <NUM> from the high-temperature part of the electric motor <NUM>. The beam member <NUM> is located above the hydraulic pump <NUM> which is closer to the electric motor <NUM> than the fire plate <NUM>, having a rod shape extending longitudinally of the upper slewing body <NUM>.

The power feed cable <NUM> includes a plurality of electric wires 40a which are bundled with each other, being wired rearward from the front of the upper slewing body <NUM> along the beam member <NUM>. The plurality of electric wires 40a are separated from each other at the rear of the power feed cable <NUM> and drawn into the connection box <NUM> independently of each other.

As shown in <FIG>, the power receiving device <NUM> can be connected to the machine side end of the power supply cable <NUM> to be supplied with power by the external power supply <NUM> through the power supply cable <NUM>. The plurality of connection wires <NUM> are wirable so as to extend from the power receiving device <NUM> toward the connection box <NUM>, that is, downward in this embodiment.

The connection box <NUM> accommodates a connection unit <NUM>. The connection unit <NUM> is a unit for interconnecting the connection wires <NUM> extending from the power receiving device <NUM> and the power feed cable <NUM> extending from the upper slewing body <NUM> (specifically, from the electric motor <NUM> in this embodiment). The connection unit <NUM> is, thus, disposed outside the power receiving device <NUM>. The connection box <NUM> extends longitudinally of the upper slewing body <NUM> as shown in <FIG> and encloses an inner space, in which the connection unit <NUM> is disposed.

The connection box <NUM> has a rear part and a front part. The rear part is fixed to the upper part of the counterweight <NUM>, specifically, the upper surface of the counterweight <NUM>. The front part extends from the rear part forward toward the hydraulic pump cover <NUM> beyond the front surface of the counterweight <NUM>. The end of the front part, namely, the front end of the connection box <NUM>, is located under the hydraulic pump cover <NUM> and at rear side of the hydraulic pump <NUM>, thereby enabling the interior of the connection box <NUM> to be protected with no reduction in the maintainability of the hydraulic pump <NUM>.

The connection box <NUM> includes a bottom wall 50a, a peripheral wall 50b, and a top wall 50c, which walls constitute a box body. The bottom wall 50a has a substantially rectangular shape in plan view in this embodiment, disposed along the upper surface of the counterweight <NUM>. The bottom wall 50a is fixed to the upper surface of the counterweight <NUM> through the fixing member 12a. The fixing member 12a has a shape of substantially rectangular flat plate, being screwed to the lower surface of the bottom wall 50a while fixed to the upper surface of the counterweight <NUM>. The connection unit <NUM> is fixed to the upper surface of the front part, that is, the right part in <FIG>, of the bottom wall 50a. The peripheral wall 50b stands up from the periphery of the bottom wall 50a to enclose the inner space. The top wall 50c is disposed so as to cover the inner space on the upper side of the inner space and joined with the upper end of the peripheral wall 50b.

The top wall 50c is formed with a wiring opening <NUM> and a connection opening <NUM>, which are spaced longitudinally of the upper slewing body <NUM>.

The wiring opening <NUM> is formed at a position on the rear side of the connection opening <NUM> to allow the plurality of connection wires <NUM> to be drawn from the power receiving device <NUM> located above the connection box <NUM> into the connection box <NUM> through the wiring opening <NUM>. The power receiving device <NUM> is connected to the top wall 50c of the connection box <NUM> through a cylindrical connection member <NUM> shown in <FIG>. The connection member <NUM> includes an upper end to be connected to the power receiving device <NUM> and a lower end to be connected to the top wall 50c, the lower end being fixed to the rear part of the top wall 50c, in detail, the peripheral part of the wiring opening <NUM>, by screws or the like. The connection member <NUM> allows the plurality of connection wires <NUM> to be drawn into the connection box <NUM> from the power receiving device <NUM> through the connection member <NUM> and the wiring opening <NUM> to be connected to the connection unit <NUM>.

The connection of the power receiving device <NUM> to the upper surface of the rear part of the connection box <NUM> causes the hydraulic pump cover <NUM>, the connection unit <NUM> in the connection box <NUM> and the power receiving device <NUM> to be arranged in this order. This arrangement allows the connection wires <NUM> drawn into the interior of the connection box <NUM> from the power receiving device <NUM> and the power feed cable <NUM> drawn from the connection box <NUM> into the hydraulic pump cover <NUM> to be arranged so as to extend longitudinally of the upper slewing body <NUM> to thereby allow the arrangement to be easily performed.

The connection opening <NUM> is formed at a position on the front side of the wiring opening <NUM>, more preferably, formed at a position on the front side of the power receiving device <NUM> so as not to overlap vertically with the power receiving device <NUM>. The connection opening <NUM> is opened upward so as to allow the connection unit <NUM> to be opened upward of the connection box <NUM> through the connection opening <NUM>. The top wall 50c has an intermediate part longitudinally thereof, the intermediate part being given a step, which renders the front part formed with the connection opening <NUM> lower than the rear part formed with the wiring opening <NUM>, out of the top wall 50c.

The connection box <NUM> further includes a lid part <NUM> in addition to the box body. The lid part <NUM> is detachably attached to the top wall 50c to close the connection opening <NUM>. The lid part <NUM>, when removed from the top wall 50c, opens the connection opening <NUM> to thereby allow the connection unit <NUM> to be exposed upward through the connection opening <NUM>, thereby enabling the connection work of connecting the power feed cable <NUM> and the plurality of connection wires <NUM> in the connection unit <NUM> to each other through the connection opening <NUM> to be easily performed. Furthermore, the arrangement of the connection opening <NUM> to overlap at least a part of, preferably a whole of, the connection opening <NUM> with the connection unit <NUM> renders the connection work easier. On the other hand, when the connection work is not performed, the lid part <NUM> is attached to the top wall 50c to close the connection opening <NUM>, thereby protecting the connection unit <NUM> effectively.

The connection box <NUM> is formed with a plurality of power-feed-cable lead-in ports <NUM>, which are formed in a part of the peripheral wall 50b, the part forming the front end of the connection box <NUM>. The plurality of power-feed-cable lead-in ports <NUM>, in this embodiment, are aligned horizontally, each being opened frontward. The plurality of power-feed-cable lead-in ports <NUM> allow the plurality of electric wires 40a included in the power feed cable <NUM> to be drawn into the connection box <NUM> through the plurality of power-feed-cable lead-in ports <NUM>, respectively. It is desirable that at least the power-feed-cable lead-in port <NUM> out of the connection box <NUM> is covered with the hydraulic pump cover <NUM> from above.

The connection box <NUM>, disposed on the rear side of the hydraulic pump cover <NUM> as shown in <FIG>, prevents the connection box <NUM> and the power receiving device <NUM> connected to the connection box <NUM> from overlapping the electric motor cover <NUM> longitudinally of the upper slewing body <NUM>. On the other hand, in the connection box <NUM> according to the present embodiment, the region from the front end where the power-feed-cable lead-in ports <NUM> are provided to the connection opening <NUM> is covered with the hydraulic pump cover <NUM>.

As shown in <FIG>, the power receiving device <NUM> includes a support shaft <NUM>, a plurality of conductive rings <NUM>, a plurality of brushes <NUM>, and a case <NUM>.

The support shaft <NUM> has a lower end fixed to the upper end of the connection member <NUM>, formed in a hollow cylindrical shape extending upward from the lower end. The plurality of conductive rings <NUM> are spaced axially of the support shaft <NUM> (vertically in <FIG>) and fixed to the outer peripheral surface of the support shaft <NUM>. The plurality of brushes <NUM> are attached to the conductive rings <NUM> capably of sliding circumferentially of the conductive rings <NUM> while keeping contact with respective outer peripheral surfaces of the plurality of conductive rings <NUM>, respectively. On the other hand, the machine side end of the power supply cable <NUM> branches into a plurality of electric wires 100a, whose ends are connected to the plurality of brushes <NUM>, respectively.

The plurality of connection wires <NUM> are connected to the plurality of conductive rings <NUM>, respectively. Specifically, each of the plurality of connection wires <NUM> has a power-receiving side end connected to the corresponding one of the plurality of conductive rings <NUM> and a connection-side end which is the opposite end to the connection-side end and connected to the connection unit <NUM>. The plurality of connection wires <NUM> are drawn into the connection box <NUM> from the plurality of conductive rings <NUM>, respectively, through the inside of the support shaft <NUM> and the inside of the connection member <NUM>.

The case <NUM> is supported on the connection member <NUM> capably of relative rotation to the support shaft <NUM> about the center axis of the support shaft <NUM> while accommodating the support shaft <NUM>, the plurality of conductive rings <NUM> and the plurality of brushes <NUM>. Specifically, the case <NUM> includes a bottom wall 63a, a peripheral wall 63b and a top wall 63c. The bottom wall 63a is formed in an annular shape enclosing the upper end of the connection member <NUM> and mounted on the connection member <NUM> so as to be rotatable along the outer peripheral surface of the upper end. The peripheral wall 63b stands up on the bottom wall 63a, having a cylindrical shape enclosing the support shaft <NUM>, the plurality of conductive rings <NUM>, and the plurality of brushes <NUM> on the radially outer side thereof. The top wall 63c is joined with the upper end of the peripheral wall 63b so as to cover the support shaft <NUM>, the plurality of conductive rings <NUM> and the plurality of brushes <NUM> at the position on the upper side thereof. The plurality of electric wires 100a are drawn into the case <NUM> with vertical penetration through the top wall 63c.

The electric current output from the external power supply <NUM> flows to the plurality of brushes <NUM> through the plurality of electric wires 100a of the power supply cable <NUM>, flowing from the plurality of brushes <NUM> to the plurality of connection wires <NUM> through the plurality of conductive rings <NUM>, flowing from the plurality of connection wires <NUM> to the power feed cable <NUM> through the connection unit <NUM> in the connection box <NUM>, and finally flowing from the power feed cable <NUM> to the electric motor <NUM> installed inside the upper slewing body <NUM> and a not-graphically-shown control board. Thus powered are the electric motor <NUM> and the like from the external power supply <NUM>.

As described above, in the electric hydraulic excavator <NUM> which is an electric work machine according to the present embodiment, the connection unit <NUM> for connecting the power feed cable <NUM> extending from the plurality of connection wires <NUM> and the upper slewing body <NUM> extending from the power receiving device <NUM> to each other is accommodated in the connection box <NUM> provided in the top part of the counterweight <NUM>, thereby being located at the position outside the power receiving device <NUM>, specifically, the position away from the power receiving device <NUM> to allow a worker to easily access the connection unit <NUM>. This frees a worker from the necessity of performing complicated connection work in the power receiving device <NUM>, thus enabling the connection work to be performed more efficiently. Besides, the power receiving device <NUM> and the connection box <NUM> are allowed to be located not to hinder the work for maintenance of either of the electric motor <NUM>, the hydraulic pump <NUM> and peripheral devices thereof. Furthermore, the hydraulic pump cover <NUM> covering a part of the connection box <NUM> enables the interior of the connection box <NUM> to be protected with a simple configuration.

<FIG> shows the rear of a machine body of an electric work machine according to another embodiment of the present invention. The embodiment includes a power receiving device 60A and a connection box 50A similarly to the aforementioned embodiment shown in <FIG>; however, the power receiving device 60A and the connection box 50A are aligned not longitudinally of the upper slewing body <NUM> but laterally thereof. The connection box 50A extends laterally of the upper slewing body <NUM> and is fixed to the upper part of the counterweight <NUM> so that the entire connection box 50A is laid on the counterweight <NUM>. The power receiving device 60A is connected to the upper part of the connection box 50A so as to be laterally aligned with the connection box 50A. It is also possible that the power receiving device 60A is fixed to not the upper part of the connection box 50A but the upper part of the counterweight <NUM> and connected to the connection box 50A laterally.

Also in such other embodiment, the connection unit <NUM> interconnecting the plurality of connection wires extending from the power receiving device 60A and the power feed cable extending from the machine body can be located at a position in the connection box 50A, the position being away from the power receiving device 60A and allowing a worker to access the position, thereby allowing the wiring work to be rendered efficient. Besides, unlike the above embodiment shown in <FIG>, the connection box 50A extends laterally to be entirely laid on the counterweight <NUM>, thus being prevented from protruding rearward beyond the rear surface of the upper slewing body <NUM> while prevented from interfering with the hydraulic pump cover <NUM> and the electric motor cover <NUM> that are on the front side of the connection box 50A. The connection box 50A can be disposed so as to allow the lid part <NUM> to be exposed upward of the counterweight <NUM> without being covered with the hydraulic pump cover <NUM>, thereby allowing the connection unit <NUM> to be easier to access and enabling the workability to be improved with a simple configuration.

Although the hydraulic excavator <NUM> according to the embodiment is a large-size hydraulic excavator, the electric work machine according to the present invention is not limited thereto but allowed to be applied to, for example, a small turn type electric work machine. The power receiving device and the connection box can be disposed also on an arc-shaped counterweight that is included in a small swing type of electric work machine so as to cover the outer periphery of a machine room. The present invention, thus, can be applied regardless of the shape of counterweight.

Respective positions of the power receiving device and the connection unit according to the present invention are not limited on the counterweight. At least one of the power receiving device and the connection unit may be disposed, for example, on a part other than the counterweight in the machine body. Furthermore, the connection unit does not absolutely have to be accommodated in the connection box but only have to be disposed outside of the power receiving device. This allows the connection work to be easy.

As described above, there is provided an electric work machine including a machine body and a power receiving device and allowing connection work for interconnecting the power receiving device and a power feed cable that enables the machine body to be fed with power through the power feed cable to be efficiently performed.

The electric work machine is powerable through a power supply cable having a power-supply side end to be connected to an external power supply and a machine side end opposite to the power-supply side end. The electric work machine includes a machine body, a power receiving device, connection wires, a power feed cable, and a connection unit. The machine body includes an electric motor. The power receiving device is connected to the machine side end of the power supply cable to be supplied with power by the external power supply through the power supply cable to power the electric motor. The power receiving device includes a plurality of conductive rings and a plurality of brushes that are attached to the conductive rings so that they are capable of sliding in a circumferential direction of the conductive rings while keeping contact with respective outer peripheral surfaces of the conductive rings. The connection wires are connected to the power receiving device to extend from the power receiving device toward the connection unit. The power feed cable is connected to the machine body to allow the machine body to be fed with power through the power feed cable. The connection unit is disposed outside the power receiving device and connects the connection wires extending from the power receiving device and the power feed cable extending from the machine body to each other.

In the electric work machine, the connection unit for interconnecting the machine body extending from the connection wires and the power feed cable extending from the power receiving device is disposed outside of the power receiving device, which allows a worker to access the connection unit easily and frees the worker from complicated connection work in the power receiving device. This enables the connecting work in the connection unit to be performed efficiently.

The electric work machine further comprises a connection box that accommodates the connection unit, the connection box having an opening capable of being selectively opened and closed outside the power receiving device to allow the connection unit to be exposed to the outside of the connection box through the opening. The connection box, while accommodating the connection unit to protect it, enables a worker to easily view the connection unit from the outside of the connection box through the opening, thereby allowing the connection work for interconnecting the power feed cable and the connection wires to be efficiently performed. On the other hand, with closing the openable and closable opening, the connection unit can be protected more reliably.

In the case where the machine body includes a counterweight located in a rear part of the machine body, it is preferable that the connection box is located outside the counterweight and fixed to an upper part of the counterweight. The thus disposed connection box allows a worker to more easily access the connection unit through the opening of the connection box.

Preferably, the machine body further includes an electric motor cover that covers the electric motor capably of opening and closing the electric motor in the upper side of the electric motor, the power receiving device and the connection box located not to overlap the electric motor cover longitudinally of the machine body. This prevents the power receiving device and the connection box from hindering the electric motor cover from being opened and closed, thereby enabling an operation of opening the electric motor cover for the maintenance of the electric motor and the peripheral equipment thereof to be smoothly performed.

It is preferable that the machine body further includes a hydraulic pump aligned with the electric motor laterally of the machine body on a front side of the counterweight, and a hydraulic pump cover that covers the hydraulic pump at an upper side of the hydraulic pump, the hydraulic pump cover, the connection box and the power receiving device being aligned in this order longitudinally of the machine body. This arrangement enables both the connection wires that are drawn from the power receiving device into the connection box and the power feed cable drawn from the connection box to the inside of the hydraulic pump cover to be easily disposed.

It is preferable: the connection box extends from the counterweight toward the hydraulic pump cover; the connection box is provided with a power-feed-cable lead-in port, which is formed so as to allow the power feed cable to be drawn into the connection box through the power-feed-cable lead-in port; and the hydraulic pump cover covers at least the power-feed-cable lead-in port out of the connection box on an upper side of the power-feed-cable lead-in port. The connection box, disposed so as to extend toward the hydraulic pump cover located on the front side of the connection box, can be restrained from projecting rearward of the machine body. Besides, the connection box, which extends toward the hydraulic pump cover to allow at least the power-feed-cable lead-in port of the connection box to be covered with the hydraulic pump cover, reduces the necessity of applying fine waterproofing to the power feed cable, for example, allowing the power feed cable to be waterproofed only by the seal of the connection box. This enables the power feed cable to be protected with a simple configuration, thereby allowing both the waterproof and assembly performances to be enhanced.

Preferably, the connection box has a front end formed with the power-feed-cable lead-in port, the front end being located under the hydraulic pump cover and on a rear side of the hydraulic pump. This prevents the connection box from hindering the maintenance operation of the hydraulic pump, while restraining water from entering the connection box.

Claim 1:
An electric work machine (<NUM>) capable of being powered through a power supply cable (<NUM>) having a power-supply side end to be connected to an external power supply (<NUM>) and a machine side end opposite to the power-supply side end, the electric work machine (<NUM>) comprising:
a machine body (<NUM>) including an electric motor (<NUM>);
a power receiving device (<NUM>) connectable to the machine side end of the power supply cable (<NUM>) to be supplied with power by the external power supply (<NUM>) through the power supply cable (<NUM>), the power receiving device (<NUM>) including a plurality of conductive rings (<NUM>) and a plurality of brushes (<NUM>) that are attached to the conductive rings (<NUM>) so that they are capable of sliding in a circumferential direction of the conductive rings (<NUM>) while keeping contact with respective outer peripheral surfaces of the conductive rings (<NUM>); and
connection wires (<NUM>) connected to the power receiving device (<NUM>) to extend from the power receiving device (<NUM>), and
a power feed cable (<NUM>) connected to the machine body (<NUM>) to allow the machine body (<NUM>) to be fed with power through the power feed cable (<NUM>);
a connection unit (<NUM>) that connects the connection wires (<NUM>) extending from the power receiving device (<NUM>) and the power feed cable (<NUM>) extending from the machine body (<NUM>) to each other, the connection unit (<NUM>) being disposed outside the power receiving device (<NUM>); characterized by
a connection box (<NUM>) that accommodates the connection unit (<NUM>), the connection box (<NUM>) having an opening (<NUM>) capable of being selectively opened and closed outside the power receiving device (<NUM>) to allow the connection unit (<NUM>) to be exposed to the outside of the connection box (<NUM>) through the opening (<NUM>).