Patent Publication Number: US-2023158630-A1

Title: Tool

Description:
TECHNICAL FIELD 
     The present invention relates to a tool including a prime mover. 
     BACKGROUND 
     Various kinds of accessories may be detachably attached to tools including a prime mover. For example, in the case of a grinder including a tool accessory configured to be rotationally driven, examples of detachably attachable accessories prepared therefor include a cover used to cover a part of the tool accessory (also referred to as a wheel cover, a disk cover, a blade case, or the like), and a side handle to be held by the other hand of a user when the user holds a handle of the grinder with one of his/her hands. 
     For such a grinder, there is a demand for preventing the grinder from being used in a state that the accessory is not attached. For example, the following patent literature, PTL 1 discloses a grinder including a sensor that detects whether or not a cover is attached and a controller that prohibits a rotation of a tool accessory when the cover is not attached. Further, the following patent literature, PTL 2 discloses a grinder including a sensor that detects whether or not a cover is attached and a sensor that detects whether or not a side handle is attached. 
     CITATION LIST 
     
         
         [PTL 1] International Publication No. 2017-051893 
         [PTL 2] US Patent Application Publication No. 2018/272494 
       
    
     SUMMARY 
     Technical Problem 
     However, the techniques discussed in PTLs 1 and 2 may be unable to detect the attachment of the cover or the side handle when a failure has occurred in the sensor or when the sensitivity of the sensor reduces due to deposition of dust. Further, the configuration that prohibits the rotation of the tool accessory unless both the cover and the side handle are attached raises the necessity of providing a sensor individually separately for each of the cover and the side handle, thereby leading to a cost increase. Such problems are not limited to the grinder, and lie in common for any tool including a prime mover and configured to allow two types of accessories to be detachably attached thereto. Under these circumstances, a configuration that allows the prime mover to be driven only when the two types of accessories are attached is desired to be realized without using a sensor for the tool. 
     Solution to Problem 
     The present specification discloses a tool. This tool may include a prime mover, a switch for driving the prime mover, an operation member configured to be displaceable between an OFF position of bringing the switch into an OFF state and an ON position of bringing the switch into an ON state, a first accessory, a second accessory, a first attachment portion configured to allow the first accessory to be detachably attached thereto, a second attachment portion configured to allow the second accessory to be detachably attached thereto, a first intermediate member configured to be displaced by the attachment of the first accessory to the first attachment portion, a second intermediate member configured to be displaced by the attachment of the second accessory to the second attachment portion, and a third intermediate member configured to be displaced along a displacement route between an OFF corresponding position corresponding to the OFF position and an ON corresponding position corresponding to the ON position in conjunction with the displacement of the operation member. The first intermediate member may be located at a first blocking position of blocking the displacement route of the third intermediate member in a state that the first accessory is not attached to the first attachment portion, and be located at a first non-blocking position of not blocking the displacement route of the third intermediate member in a state that the first accessory is attached to the first attachment portion. The second intermediate member may be located at a second blocking position of blocking the displacement route of the third intermediate member in a state that the second accessory is not attached to the second attachment portion, and be located at a second non-blocking position of not blocking the displacement route of the third intermediate member in a state that the second accessory is attached to the second attachment portion. When the first intermediate member is located at the first non-blocking position and the second intermediate member is located at the second non-blocking position, the third intermediate member may be permitted to be displaced from the OFF corresponding position to the ON corresponding position so that the operation member is permitted to be displaced from the OFF position to the ON position. When at least the first intermediate member is located at the first blocking position or at least the second intermediate member is located at the second blocking position, the third intermediate member may be prohibited from being displaced from the OFF corresponding position to the ON corresponding position by at least one of the first intermediate member and the second intermediate member so that the operation member is prohibited from being displaced from the OFF position to the ON position. 
     According to this tool, in the state that at least one of the first accessory and the second accessory is not attached, at least one of the first intermediate member and the second intermediate member blocks the displacement route of the third intermediate member, by which the operation member is prohibited from being displaced from the OFF position to the ON position. On the other hand, in the state that the first accessory is attached to the first attachment portion and the second accessory is attached to the second attachment portion, the first intermediate member and the second intermediate member are displaced to the positions of not blocking the displacement route of the third intermediate member, by which the operation member is permitted to be displaced from the OFF position to the ON position. Therefore, a configuration that allows the prime mover to be driven only when both the first accessory and the second accessory are attached can be realized using only a mechanical structure without using a sensor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a vertical cross-sectional view of a grinder according to a first embodiment of the present invention, and illustrates a state that a side grip and a wheel cover are attached thereto and an operation member is located at an ON position. 
         FIG.  2    is a vertical cross-sectional view of the grinder, and illustrates a state that the side grip and the wheel cover are detached therefrom and the operation member is located at an OFF position. 
         FIG.  3    is a partial enlarged view of the grinder illustrated in  FIG.  1   . 
         FIG.  4    is a partial enlarged view of the grinder illustrated in  FIG.  2   . 
         FIG.  5    is a partial enlarged view of the grinder illustrated in  FIG.  1   . 
         FIG.  6    is a partial enlarged view of the grinder illustrated in  FIG.  2   . 
         FIG.  7    is a perspective view of a first intermediate member. 
         FIG.  8    is a perspective view of a second intermediate member. 
         FIG.  9    is a perspective view of a holding member that holds the first intermediate member and the second intermediate member. 
         FIG.  10    is a perspective view of a third intermediate member. 
         FIG.  11    is a perspective view illustrating a component of a conversion mechanism. 
         FIG.  12    is a perspective view illustrating a component of the conversion mechanism. 
         FIG.  13    is a perspective view illustrating the components of the conversion mechanism. 
         FIG.  14    illustrates the internal structure of the grinder and illustrates the state that the side grip and the wheel cover are detached therefrom. 
         FIG.  15    illustrates the internal structure of the grinder and illustrates a state that the side grip is attached thereto and the wheel cover is detached therefrom. 
         FIG.  16    illustrates the internal structure of the grinder and illustrates the state that the side grip and the wheel cover are attached thereto. 
         FIG.  17    is a vertical cross-sectional view of a grinder according to a second embodiment of the present invention, and illustrates a state that a side grip is not attached thereto and an operation member is located at a lock-off position. 
         FIG.  18    is a vertical cross-sectional view of the grinder according to the second embodiment, and illustrates a state that the side grip is attached thereto and the operation member is located at a lock-off released position and an OFF position 
         FIG.  19    is a vertical cross-sectional view of the grinder according to the second embodiment, and illustrates a state that the side grip is attached thereto and the operation member is located at the lock-off released position and an ON position 
         FIG.  20    is a partial enlarged view of the grinder illustrated in  FIG.  17   . 
         FIG.  21    is a partial enlarged view of the grinder illustrated in  FIG.  18   . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     In one or more embodiment(s), a tool may include a prime mover, a switch for driving the prime mover, an operation member configured to be displaceable between an OFF position of bringing the switch into an OFF state and an ON position of bringing the switch into an ON state, a first accessory, a second accessory, a first attachment portion configured to allow the first accessory to be detachably attached thereto, a second attachment portion configured to allow the second accessory to be detachably attached thereto, a first intermediate member configured to be displaced by the attachment of the first accessory to the first attachment portion, a second intermediate member configured to be displaced by the attachment of the second accessory to the second attachment portion, and a third intermediate member configured to be displaced along a displacement route between an OFF corresponding position corresponding to the OFF position and an ON corresponding position corresponding to the ON position in conjunction with the displacement of the operation member. The first intermediate member may be located at a first blocking position of blocking the displacement route of the third intermediate member in a state that the first accessory is not attached to the first attachment portion, and be located at a first non-blocking position of not blocking the displacement route of the third intermediate member in a state that the first accessory is attached to the first attachment portion. The second intermediate member may be located at a second blocking position of blocking the displacement route of the third intermediate member in a state that the second accessory is not attached to the second attachment portion, and be located at a second non-blocking position of not blocking the displacement route of the third intermediate member in a state that the second accessory is attached to the second attachment portion. When the first intermediate member is located at the first non-blocking position and the second intermediate member is located at the second non-blocking position, the third intermediate member may be permitted to be displaced from the OFF corresponding position to the ON corresponding position so that the operation member is permitted to be displaced from the OFF position to the ON position. When at least the first intermediate member is located at the first blocking position or at least the second intermediate member is located at the second blocking position, the third intermediate member may be prohibited from being displaced from the OFF corresponding position to the ON corresponding position by at least one of the first intermediate member and the second intermediate member so that the operation member is prohibited from being displaced from the OFF position to the ON position. 
     According to this tool, in the state that at least one of the first accessory and the second accessory is not attached, at least one of the first intermediate member and the second intermediate member blocks the displacement route of the third intermediate member, by which the operation member is prohibited from being displaced from the OFF position to the ON position. On the other hand, in the state that the first accessory is attached to the first attachment portion and the second accessory is attached to the second attachment portion, the first intermediate member and the second intermediate member are displaced to the positions of not blocking the displacement route of the third intermediate member, by which the operation member is permitted to be displaced from the OFF position to the ON position. Therefore, a configuration that allows the prime mover to be driven only when both the first accessory and the second accessory are attached can be realized using only a mechanical structure without using a sensor. 
     In one or more embodiment(s), the prime mover may be an electric motor. The tool may be a grinder including a tool accessory configured to be rotated by the electric motor. The first accessory may be a side grip. The second accessory may be a cover that partially covers the tool accessory. According to this configuration, the grinder that allows the electric motor to be driven only when both the side grip and the cover are attached can be realized without using a sensor. 
     In one or more embodiment(s), the first attachment portion may include at least two side grip attachment portions for selectively attaching the side grip. The first intermediate member may be a single member provided in common for the at least two side grip attachment portions. The first intermediate member may include at least one pressed portion configured to, when the side grip is attached to one side grip attachment portion arbitrarily selected from the at least two side grip attachment portions, be directly or indirectly pressed by the side grip, and the first intermediate member may be configured to be displaced when the at least one pressed portion is pressed. According to this configuration, the single first intermediate member is used in common for the at least two side grip attachment portions, and therefore the number of components can be reduced. 
     In one or more embodiment(s), the first intermediate member may include a first intermediate member main body having an annular shape or a partially annular shape. The at least two side grip attachment portions may be located at positions spaced apart from each other in a circumferential direction of the annular shape or the partially annular shape, respectively. According to this configuration, the first intermediate member is shaped to correspond to the layout of the at least two side grip attachment portions, and therefore the single first intermediate member can be used in common for the at least two side grip attachment portions with a simple structure. 
     In one or more embodiment(s), the first intermediate member may be configured to be rotated about a rotational axis when the at least one pressed portion is pressed. According to this configuration, in the case where the at least two side grip attachment portions are located at the positions spaced apart from each other in the circumferential direction of the annular shape or the partially annular shape, respectively, the first intermediate member can be easily displaced regardless of which is selected from the at least to side grip attachment portions to attach the first accessory. Further, this configuration eliminates the necessity of securing a space for the displacement of the first intermediate member in a direction in which the rotational axis extends, thereby allowing the tool to have a compact size in the direction in which the rotational axis extends. 
     In one or more embodiment(s), the at least one pressed portion may protrude radially outward from the first intermediate member main body. The at least one pressed portion may be provided at at least two positions respectively corresponding to positions of the at least two side grip attachment portions, respectively. According to this configuration, the first intermediate member can be easily rotated. 
     In one or more embodiment(s), the first intermediate member may include a blocking portion that blocks the displacement route of the third intermediate member when the first intermediate member is located at the first blocking position. The blocking portion may protrude radially outward from the first intermediate member main body. According to this configuration, the third intermediate member can be disposed near the outer edge of the tool to avoid the positions where main components of the tool are arranged. 
     In one or more embodiment(s), the first intermediate member main body may include a first through-hole having a circular-arc shape centered at the rotational axis. The first intermediate member may be attached rotatably along the circular-arc shape using a screw via the first through-hole. According to this configuration, the first intermediate member can be held rotatably with a simple structure. 
     In one or more embodiment(s), the at least one pressed portion may include a pressed surface angled with respect to a longitudinal direction of the side grip in such a manner that the first intermediate member is displaced in a direction different from the longitudinal direction of this side grip. The longitudinal direction of the side grip is a longitudinal direction of the side grip when the side grip is attached to the one side grip attachment portion. According to this configuration, the first intermediate member can be easily rotated. 
     In one or more embodiment(s), the second intermediate member may be configured to be linearly moved by being directly or indirectly pressed by the cover when the cover is attached to the second attachment portion. According to this configuration, the tool does not have to include a direction conversion mechanism by being designed in such a manner that the attachment direction of the cover matches a linear motion direction of the second intermediate member, thereby allowing the second intermediate member to be displaced with a simple structure. 
     In one or more embodiment(s), the second intermediate member may include a second through-hole in the form of an elongated hole having a longitudinal direction extending along a direction in which the second intermediate member is linearly moved. The second intermediate member may be attached linearly movably along the elongated hole using a screw via the second through-hole. According to this configuration, the second intermediate member can be held linearly movably with a simple structure. 
     In one or more embodiment(s), a rotational axis of the electric motor and a rotational axis of the tool accessory may intersect with each other. 
     In one or more embodiment(s), the first attachment portion and the second attachment portion may be disposed on a first side in a longitudinal direction of the tool. The operation member may be disposed on a second side opposite from the first side. The third intermediate member may be an elongate member extending in the longitudinal direction. According to this configuration, even in the case where the first attachment portion and the second attachment portion, and the operation member are arranged at positions relatively distant from each other, the above-described various embodiments of the present invention can be easily realized. 
     In one or more embodiment(s), the tool may further include a single holding member that holds the first intermediate member and the second intermediate member. According to this configuration, mounting each of the first intermediate member and the second intermediate member to the holding member automatically determines the relative positions of the first intermediate member and the second intermediate member. In other words, the relative positions of the first intermediate member and the second intermediate member do not have to be adjusted when the tool is assembled. 
     In one or more embodiment(s), a first displacement direction, which is a displacement direction of the operation member, and a second displacement direction, which is a displacement direction of the third intermediate member, may be different from each other. The tool may include a conversion mechanism configured to convert a motion of the operation member in the first displacement direction into a motion of the third intermediate member in the second displacement direction. According to this configuration, the displacement direction of the operation member is free of design constraints, and thus an optimum type of operation member can be employed according to the specifications of the tool. 
     In one or more embodiment(s), the tool may be a grinder. The grinder may include a handle housing configured to be held by a user, and a motor housing containing the electric motor therein. The handle housing may be located on an opposite side of the motor housing from the tool accessory in a direction in which the rotational axis of the electric motor extends. The above-described various embodiments can be easily applied to such a grinder. 
     In one or more embodiment(s), a tool may include a switch for driving a prime mover, an operation member configured to be displaceable in a first direction between an OFF position of bringing the switch into an OFF state and an ON position of bringing the switch into an ON state, an attachment portion configured to allow an accessory to be detachably attached thereto, a lock-off portion configured to switch a status of the operation member between a lock-off state, in which the operation member is prohibited from being displaced from the OFF position to the ON position, and a lock-off released state, in which the operation member is permitted to be displaced from the OFF position to the ON position, according to a change in an engagement state with the operation member, and a first intermediate member configured to be displaced by being directly or indirectly pressed by the accessory when the accessory is attached to the attachment portion. The first intermediate member may be located at a prohibition position of prohibiting a release operation for switching the lock-off state to the lock-off released state with the aid of abutment between members in a state that the accessory is not attached to the attachment portion, and be located at a permission position of permitting the release operation due to absence of the abutment between members in a state that the accessory is attached to the attachment portion. 
     According to this tool, the configuration that allows the prime mover to be driven only when the accessory is attached can be realized using only a mechanical structure without using a sensor. Further, normally, the operation of releasing the lock-off is accompanied by a displacement of a component easily recognizable to a user. Therefore, when the prime mover cannot be driven despite the fact that the user performs the operation of displacing the operation member from the OFF position to the ON position, the user can easily notice that the reason therefor is not a failure in the switch but because the accessory is not attached. 
     In one or more embodiment(s), the lock-off portion may be a fixed engagement structure. The operation member may be configured to be displaceable in a second direction different from the first direction from a lock-off position corresponding to the lock-off state to a lock-off released position corresponding to the lock-off released state. The release operation may include displacing the operation member from the lock-off position to the lock-off released position. 
     In one or more embodiment(s), the tool may further include a second intermediate member configured to be moved in conjunction with the displacement of the operation member in the second direction between a first corresponding position corresponding to the lock-off position of the operation member and a second corresponding position corresponding to the lock-off released position of the operation member. The first intermediate member may be configured to be displaced so as to block a displacement route of the second intermediate member from the first corresponding position to the second corresponding position when being located at the prohibition position, and so as not to block the displacement route of the second intermediate member from the first corresponding position to the second corresponding position when being located at the permission position. According to this configuration, the first intermediate member and the operation member may be disposed separately, and therefore the design flexibility of the tool is improved. 
     In the following description, embodiments of the present invention will be described in further detail with reference to the drawings. In the embodiments that will be described below, a handheld-type electric disk grinder (hereinafter simply referred to as a grinder)  10  will be cited as an example of a tool including a prime mover. 
     As illustrated in  FIGS.  1  and  2   , the grinder  10  is configured to rotationally drive a generally disk-like tool accessory  28  mounted around a spindle  25 . The spindle  25  is rotated by a rotational driving force provided from an electric motor  31  as the prime mover. A grinding stone, a rubber pad, a brush, a blade, and the like are prepared as the tool accessory  28  mountable to the grinder  10 . A user selects the appropriate tool accessory  28  according to desired processing work and mounts it to the grinder  10 . According to the grinder  10 , processing work such as grinding, polishing, and cutting can be performed on a processing target material according to the type of the tool accessory  28 . 
     In the following description, a direction in which a rotational axis AX 1  of the electric motor  31  (i.e., a motor shaft  32 ) extends is defined to be a front-rear direction of the grinder  10 . One side in the front-rear direction on which the tool accessory  28  is located is defined to be a front side, and the opposite side therefrom is defined to be a rear side. Further, a direction in which a rotational axis AX 2  of the spindle  25  (i.e., a rotational axis of the tool accessory  28 ) extends is defined to be a vertical direction of the grinder  10 . One side in the vertical direction on which the tool accessory  28  is located is defined to be a lower side, and the opposite side therefrom is defined to be an upper side. Further, a direction perpendicular to the vertical direction and the front-rear direction is defined to be a left-right direction of the grinder  10 . A right side in the left-right direction when the front side is viewed from the rear side is defined to be a right side of the grinder  10 , and the opposite side therefrom is defined to be a left side of the grinder  10 . 
     As illustrated in  FIGS.  1  and  2   , the grinder  10  includes a gear housing  20 , a motor housing  30 , and a handle housing  40 . The electric motor  31  is contained in the motor housing  30 , which is located between the gear housing  20  and the handle housing  40  in the front-rear direction, i.e., the longitudinal direction of the grinder  10 . The electric motor  31  is configured to be driven by electric power supplied from outside (alternating-current power in the present embodiment, but may be direct-current power). 
     A mechanism for transmitting the rotational driving force of the electric motor  31  to the tool accessory  28  is contained in the gear housing  20 . More specifically, a small bevel gear  23 , a large bevel gear  24 , and the spindle  25  are contained in the gear housing  20 . The small bevel gear  23  is fixed around the motor shaft  32  at the front end portion of the motor shaft  32  of the electric motor  31 . The spindle  25  is supported rotatably about the rotational axis AX 2  by bearings disposed so as to be vertically spaced apart from each other. The rotational axis AX 2  intersects with (more specifically, intersects perpendicularly to) the rotational axis AX 1  of the electric motor  31 . The large bevel gear  24  is fixed around the spindle  25  on the upper side of the spindle  25 , and is meshed with the small bevel gear  23 . The gear housing  20  includes a second attachment portion  22  at the lower edge portion thereof. The second attachment portion  22  is used to detachably attach a cover  300 . The second attachment portion  22  has a vertically extending hollow circular cylindrical shape. The spindle  25  extends vertically in the gear housing  20 , and extends out of the gear housing  20  (more specifically, the second attachment portion  22 ) on the lower side. 
     An inner flange  26  is attached around the spindle  25  at the lower end portion of the spindle  25  extending out of the gear housing  20 . A male screw portion is formed on a lower portion of the spindle  25  with respect to the inner flange  26 , and a lock nut  27  is attached to this male screw portion. The position of the tool accessory  28  relative to the spindle  25  is fixed by interposing the tool accessory  28  between the inner flange  26  and the lock nut  27  and tightening the lock nut  27 . 
     The handle housing  40  is a portion to be held by the user with one of his/her hands when the grinder  10  is in use. The handle housing  40  has a hollow circular cylindrical shape extending generally in the front-rear direction. A switch  41  for driving the electric motor  31  is contained inside the handle housing  40 . An operation member  50  is provided under the handle housing  40 . The operation member  50  is configured to be displaceable between an OFF position of bringing the switch  41  into an OFF state (refer to  FIG.  2   ) and an ON position of bringing the switch  41  into an ON state (refer to  FIG.  1   ). 
     When the electric motor  31  is driven by the user operating the operation member  50  from the OFF position to the ON position, the rotation of the motor shaft  32  is transmitted to the spindle  25  while being slowed down via the small bevel gear  23  and the large bevel gear  24 . At this time, the direction of the rotational motion is converted from the direction around the motor shaft  32  into the direction around the rotational axis AX 2  of the spindle  25 . According to this mechanism, the spindle  25  is rotated about the rotational axis AX 2  in response to the rotation of the motor shaft  32 , and the tool accessory  28  fixed by the inner flange  26  and the lock nut  27  is rotated together with the spindle  25  as a result thereof. 
     As illustrated in  FIG.  1   , the grinder  10  further includes a side handle  200  and the cover  300  as accessories thereof. The side handle  200  is prepared to be held by the user with the opposite hand from his/her hand holding the handle housing  40 . The user can further stably hold the grinder  10  by using the side handle  200 . The side handle  200  includes a grip portion  210  to be held by the user, and an attachment portion  220  to be attached to the gear housing  20 . The attachment portion  220  has a circular columnar shape extending in the longitudinal direction of the side handle  200 , and extends out of one end of the grip portion  210  in the longitudinal direction of the side handle  200 . A male screw is formed on the outer peripheral surface of the attachment portion  220 . 
     As illustrated in  FIG.  14   , the gear housing  20  includes three first attachment portions  29   a  to  29   c  for detachably attaching the side handle  200 . The first attachment portions  29   a  to  29   c  are disposed at positions spaced apart from each other in the circumferential direction around the rotational axis AX 1 . More specifically, the first attachment portion  29   a  is formed on the left surface of the gear housing  20 , the first attachment portion  29   b  is formed on the upper surface of the gear housing  20 , and the first attachment portion  29   c  is formed on the right surface of the gear housing  20 . The three first attachment portions  29   a  to  29   c  are provided at positions rotational symmetric with respect to the rotational axis AX 1 , respectively. Each of the first attachment portions  29   a  to  29   c  is in the form of a through-hole that establishes communication between the inside and the outside of the gear housing  20 . A female screw threadedly engageable with the male screw of the attachment portion  220  is formed on the inner surface forming this through-hole. 
     The side handle  200  can be attached to the gear housing  20  by screwing the attachment portion  220  of the side handle  200  into selected one from the three first attachment portions  29   a  to  29   c . The user can arbitrarily select the attachment portion of the side handle  200  from the first attachment portions  29   a  to  29   c  according to the type of the work intended to perform using the grinder  10  or according to whether the user is right-handed or left-handed. The three first attachment portions  29   a  to  29   c  are provided in the present embodiment, but the number of first attachment portions is not especially limited and may be any number equal to or greater than 1. For example, the grinder  10  may include only two first attachment portions  29   a  and  29   c.    
     As illustrated in  FIG.  1   , the cover  300  includes a cover main body  310  to cover a part of the tool accessory  28  therewith, and an attachment portion  320  to be attached to the second attachment portion  22 . The cover main body  310  covers an approximately rear half portion of the tool accessory  28 . The cover main body  310  covers the upper surface, the lower surface, and the circumferential surface between the upper surface and the lower surface of the tool accessory  28  in the present embodiment, but may cover only the upper surface and the circumferential surface depending on the type of the tool accessory  28  in use. The attachment portion  320  has a generally annular shape with an opening, and extends upward from the upper surface of the cover main body  310 . The attachment portion  320  includes opposing two flanges at two distal ends in the circumferential direction, although they are not illustrated because the structure of the attachment portion  320  is well known. A bolt is inserted into a screw hole formed at each of the flanges and is tightened in a state that the attachment portion  320  is disposed so as to surround the second attachment portion  22  of the gear housing  20 , by which the radius of the annular shape of the attachment portion  320  reduces and the attachment portion  320  is fixed to the second attachment portion  22 . 
     The above-described grinder  10  has a mechanical configuration that permits the operation member  50  to be displaced from the OFF position to the ON position only in a state that the side handle  200  is attached to any of the first attachment portions  29   a  to  29   c  of the gear housing  20  and the cover  300  is attached to the second attachment portion  22  of the gear housing  20 , and prohibits the operation member  50  from being displaced from the OFF position to the ON position in a state that least one of the side handle  200  and the cover  300  is not attached. In the following description, this mechanical configuration will be described in detail with reference to the drawings. 
     As illustrated in  FIG.  4   , the operation member  50  is provided under the handle housing  40 . The operation member  50  is a paddle-type member in the present embodiment, but may be embodied in any other form. The operation member  50  extends throughout almost the entire range of the handle housing  40  in the front-rear direction. 
     The operation member  50  includes a support shaft  51 , a protrusion  52 , a spring seat  53 , a spring  54 , and an actuation end portion  55 . The support shaft  51  is provided near the rear end of the operation member  50 . The support shaft  51  has a circular columnar shape extending in the left-right direction, and is rotatably supported by the handle housing  40 . The protrusion  52  extends in an L-shaped manner toward the upper side and the front side at an approximately central position of the operation member  50  in the front-rear direction. The distal end of the protrusion  52  is engaged with an input member  42  of the switch  41 . One end of the spring  54  is seated on the spring seat  53 . The other end of the spring  54  is seated on the handle housing  40 . The spring  54  biases the operation member  50  toward the OFF position. The actuation end portion  55  is the front end of the operation member  50  in the front-rear direction. A second horizontally extending portion  123  of a second link member  120 , which will be described below, is placed on the actuation end portion  55 . 
     When the user holds the handle housing  40  and the operation member  50  (i.e., the user presses the operation member  50  upward) in a state that the operation member  50  is located at the OFF position (refer to  FIG.  4   ), the operation member  50  is rotated, against the biasing force of the spring  54 , to the ON position (refer to  FIG.  3   ) in a direction toward the handle housing  40  with the support shaft  51  serving as a support point therefor. When the operation member  50  is displaced from the OFF position to the ON position, the protrusion  52  of the operation member  50  is displaced upward and the input member  42  engaged with the protrusion  52  is also displaced upward according thereto. When the operation member  50  reaches the ON position, the input member  42  is pressed into the switch  41 . The switch  41  detects that the input member  42  is pressed in, and transmits a signal for driving the electric motor  31  to a controller (not illustrated). When receiving this signal, the controller supplies power to the electric motor  31 . 
     Then, when the user releases his/her finger from the operation member  50 , the operation member  50  is returned from the ON position to the OFF position under the biasing force of the spring  54 . According thereto, the protrusion  52  and thus the input member  42  are also returned to their original positions. The switch  41  detects that the input member  42  is retracted, and transmits a signal for stopping the electric motor  31  to the controller. When receiving this signal, the controller stops the power supply to the electric motor  31 . A lock-off switch  57  is provided near the front end of the operation member  50  in the front-rear direction. The lock-off switch  57  is used to engage the operation member  50  at the OFF position, thereby prohibiting the displacement thereof to the ON position. 
     As illustrated in  FIGS.  1  and  2   , the grinder  10  further includes a first intermediate member  60 , a second intermediate member  70 , a holding member  140 , a third intermediate member  80 , and a conversion mechanism  100 . First, the first intermediate member  60 , the second intermediate member  70 , the holding member  140 , the third intermediate member  80 , and the conversion mechanism  100  will be described in outline. 
     The first intermediate member  60  is configured to be pressed and displaced by the attachment portion  220  of the side handle  200  by the attachment of the side handle  200  to any of the first attachment portions  29   a  to  29   c . The first intermediate member  60  is rotated by a predetermined angle about the rotational axis AX 1  as such a displacement operation in the present embodiment. The first intermediate member  60  is a generally annular member, and is disposed inside the gear housing  20  so as to surround the motor shaft  32  on the front side with respect to the electric motor  31 . 
     The second intermediate member  70  is configured to be pressed and displaced by the attachment portion  320  of the cover  300  by the attachment of the cover  300  to the second attachment portion  22 . The second intermediate member  70  is linearly moved upward as such a displacement operation in the present embodiment. The second intermediate member  70  is disposed between the motor shaft  32  and the tool accessory  28  on the front side with respect to the first intermediate member  60 . The holding member  140  is disposed on the front side with respect to the first intermediate member  60 , and holds the first intermediate member  60  and the second intermediate member  70  together. 
     The third intermediate member  80  is disposed so as to extend in the font-rear direction at the bottom portions of the gear housing  20  and the motor housing  30 . The third intermediate member  80  is configured to be displaced in the front-rear direction between an OFF corresponding position (refer to  FIG.  6   ) corresponding to the OFF position of the operation member  50  and an ON corresponding position (refer to  FIG.  5   ) corresponding to the ON position of the operation member  50  in conjunction with the displacement of the operation member  50 . The conversion mechanism  100  is configured to change the rotational motion of the operation member  50  generally in the vertical direction into the linear motion of the third intermediate member  80  in the front-rear direction. 
     The first intermediate member  60  is located at a first blocking position (refer to  FIGS.  6  and  14   ) of blocking a displacement route for displacing the third intermediate member  80  from the OFF corresponding position to the ON corresponding position in a state that the side handle  200  is attached to none of the first attachment portions  29   a  to  29   c  of the gear housing  20 , and is located at a first non-blocking position (refer to  FIGS.  5 ,  15 , and  16   ) of not blocking the displacement route of the third intermediate member  80  in a state that the side handle  200  is attached to any of the first attachment portions  29   a  to  29   c.    
     The second intermediate member  70  is located at a second blocking position (refer to  FIGS.  6 ,  14 , and  15   ) of blocking the displacement route of the third intermediate member  80  in a state that the cover  300  is not attached to the second attachment portion  22  of the gear housing  20 , and is located at a second non-blocking position (refer to  FIGS.  5  and  16   ) of not blocking the displacement route of the third intermediate member  80  in a state that the cover  300  is attached to the second attachment portion  22 . 
     In the following description, the first intermediate member  60 , the second intermediate member  70 , the holding member  140 , the third intermediate member  80 , and the conversion mechanism  100  will be described in detail. First, the first intermediate member  60  will be described. As illustrated in  FIG.  7   , the first intermediate member  60  is a single member, and is provided in common for the first attachment portions  29   a  to  29   c . The first intermediate member  60  includes a first intermediate member main body  61 . The first intermediate member main body  61  has an annular shape centered at the rotational axis AX 1  of the electric motor  31  in the present embodiment. However, the first intermediate member  60  may have a partially annular shape (i.e., an unclosed annular shape). A through-hole is formed at the central portion of the first intermediate member main body  61 . The motor shaft  32  extends through this through-hole. 
     The first intermediate member  60  further includes three pressed portions  62   a  to  62   c  and a blocking portion  64 . The three pressed portions  62   a  to  62   c  are disposed so as to be circumferentially spaced apart from each other. The pressed portion  62   a  is a portion pressed by the side handle  200  (more specifically, the distal end of the attachment portion  220 ) when the side handle  200  is attached to the first attachment portion  29   a  of the gear housing  20 . Similarly, the pressed portion  62   b  is a portion pressed by the side handle  200  when the side handle  200  is attached to the first attachment portion  29   b , and the pressed portion  62   c  is a portion pressed by the side handle  200  when the side handle  200  is attached to the first attachment portion  29   c . Therefore, the pressed portions  62   a  to  62   c  are disposed at angular positions corresponding to the angular positions of the first attachment portions  29   a  to  29   c , respectively (refer to  FIG.  14   ). Each of the pressed portions  62   a  to  62   c  protrudes radially outward from the first intermediate member main body  61 . 
     As described above, the first intermediate member  60  is configured to be rotated about the rotational axis AX 1  when any of the pressed portions  62   a  to  62   c  is pressed by the side handle  200 . A comparison between  FIG.  14    and  FIG.  15    makes it understandable that, due to the attachment of the side handle  200  to the first attachment portion  29   c , the pressed portion  62   c  is pressed by the side handle  200 , and the first intermediate member  60  is rotated in the counterclockwise direction from the position illustrated in  FIG.  14    to the position illustrated in  FIG.  15   . 
     As illustrated in  FIGS.  7  and  14   , the pressed portion  62   a  includes a pressed surface  63   a  angled with respect to the longitudinal direction of the side handle  200  when the side handle  200  is attached to the first attachment portion  29   a  (i.e., the attachment direction of the side handle  200 ). Similarly, the pressed portion  62   b  includes a pressed surface  63   b  angled with respect to the longitudinal direction of the side handle  200  when the side handle  200  is attached to the first attachment portion  29   b . Similarly, the pressed portion  62   c  includes a pressed surface  63   c  angled with respect to the longitudinal direction of the side handle  200  when the side handle  200  is attached to the first attachment portion  29   c . The pressed surfaces  63   a  to  63   c  are angled at approximately 45 degrees with respect to the corresponding longitudinal direction of the side handle  200  (refer to  FIG.  14   ). This angle can be set to any angle so as to allow the first intermediate member  60  to be displaced in a direction different from the longitudinal direction of the side handle  200 . In an alternative embodiment, this angle may be set within a range of 30 degrees or larger and 60 degrees or smaller. According to the pressed surfaces  63   a  to  63   c  angled in this manner, the first intermediate member  60  can be easily rotated. 
     The blocking portion  64  is a portion that blocks the displacement route of the third intermediate member  80  when the side handle  200  is attached to none of the first attachment portions  29   a  to  29   c . The blocking portion  64  protrudes radially outward from the first intermediate member main body  61 . The blocking portion  64  is located at the lowermost portion of the first intermediate member  60  when the side handle  200  is attached to none of the first attachment portions  29   a  to  29   c  (refer to  FIG.  14   ). On the other hand, the blocking portion  64  is retracted to the upper side and the right side with respect to the lowermost portion due to the rotation of the first intermediate member  60  when the side handle  200  is attached to any of the first attachment portions  29   a  to  29   c  (refer to  FIG.  15   ). 
     As illustrated in  FIG.  7   , the first intermediate member main body  61  includes first through-holes  65  and  66 . Each of the first through-holes  65  and  66  has a circular-arc shape centered at the rotational axis AX 1 . The first through-holes  65  and  66  are disposed at positions rotational symmetric by 180 degrees with respect to the rotational axis AX 1 . The first intermediate member  60  is attached to the holding member  140  using screws via these first through-holes  65  and  66 . More specifically, bolts  91  are inserted in the first through-holes  65  and  66  as illustrated in  FIGS.  14  to  16   . These bolts  91  are threadedly engaged with screw holes  143   a  and  144   a  of the holding member  140 , which will be described below. Due to predetermined clearances secured between the heads of the bolts  91  and the first intermediate member  60 , the first intermediate member  60  is held by the holding member  140  rotatably along the circular-arc shapes of the first through-holes  65  and  66 . According to this configuration, the first intermediate member  60  can be held with a simple structure. 
     The first intermediate member  60  further includes a protrusion  67 . The protrusion  67  extends forward from the front surface of the first intermediate member main body  61 . This protrusion  67  is used to bias the first intermediate member  60  toward the first blocking position (refer to  FIGS.  6  and  14   ) by a spring  68  (refer to  FIG.  9   ), which will be described below. 
     Next, the second intermediate member  70  will be described. As illustrated in  FIG.  8   , the second intermediate member  70  includes a base  71 , a pressed portion  72 , a blocking portion  73 , support portions  74  and  75 , and a spring seat  78 . The base  71  is a portion shaped like a flat plate having a longitudinal direction extending along the front-rear direction and lying perpendicularly to the vertical direction. The pressed portion  72  is a portion pressed upward by the attachment portion  320  of the cover  300  when the cover  300  is attached to the second attachment portion  22 , and is located at the front edge of the second intermediate member  70 . The pressed portion  72  is shaped like a flat plate lying in parallel with the base  71 . A stepped portion is formed between the base  71  and the pressed portion  72 . The displacement amount of the second intermediate member  70  when the cover  300  is attached can be reduced due to this stepped portion. More specifically, when the cover  300  is attached, the second intermediate member  70  is not displaced since the attachment portion  320  of the cover  300  is in a state of being raised to the same position as the base  71  until the attachment portion  320  is brought into a state of abutting against the pressed portion  72 , and therefore the displacement amount of the second intermediate member  70  is reduced by an amount corresponding the step compared to a configuration in which the pressed portion  72  is located at the same vertical position as the base  71 . This can lead to a reduction in a space for the displacement of the second intermediate member  70 . In other words, this can cut down an increase in the vertical size of the grinder  10 . 
     The blocking portion  73  is a portion that blocks the displacement route of the third intermediate member  80  when the cover  300  is not attached to the second attachment portion  22 . The blocking portion  73  is located at the rear edge of the second intermediate member  70 , and extends upward from the rear edge of the base  71 . The blocking portion  73  is shaped like a flat plate extending perpendicularly to the front-rear direction. When the cover  300  is not attached to the second attachment portion  22 , the blocking portion  73  is located at a position overlapping the blocking portion  64  of the first intermediate member  60  when the side handle  200  is not attached as viewed in the front-rear direction, as illustrated in  FIG.  14   . 
     The support portions  74  and  75  are disposed opposite from each other in the left-right direction on the front side with respect to the blocking portion  73  near the blocking portion  73 . The support portions  74  and  75  have generally L-like shapes extending from the base  71  in directions away from each other in the left-right direction, and then bent and extending upward after that. Second through-holes  76  and  77  are formed on the support portions  74  and  75 , respectively. The second through-holes  76  and  77  extend through the support portions  74  and  75  in the front-rear direction, respectively. The second through-holes  76  and  77  are each in the form of an elongated hole having a longitudinal direction extending along the vertical direction (i.e., a direction in which the second intermediate member  70  is linearly moved when being pressed by the cover  300 ). The second intermediate member  70  is attached to the holding member  140  using screws via these second through-holes  76  and  77 . More specifically, bolts  92  are inserted in the second through-holes  76  and  77  as illustrated in  FIGS.  14  to  16   . These bolts  92  are threadedly engaged with screw holes  145   a  and  146   a  of the holding member  140 , which will be described below. Due to predetermined clearances respectively secured between the heads of the bolts  92  and the support portions  74  and  75 , the second intermediate member  70  is held by the holding member  140  linearly movably along the second through-holes  76  and  77 . According to this configuration, the second intermediate member  70  can be held with a simple structure. 
     The spring seat  78  is provided so as to protrude upward from the base  71 . A spring  79  (refer to  FIG.  6   ) is held between the spring seat  78  and a spring seat  148  of the holding member  140  (refer to  FIG.  9   ). The spring  79  biases the second intermediate member  70  toward the second blocking position (refer to  FIGS.  6 ,  14 , and  15   ). 
     Next, the holding member  140  will be described. As illustrated in  FIG.  9   , the holding member  140  includes an annular portion  141 , a hollow circular cylindrical portion  142 , protrusion portions  143  and  144 , protrusion portions  145  and  146 , the spring seat  148 , and a spring housing portion  149 . The annular portion  141  has a disk-like shape centered at the rotational axis AX 1  of the electric motor  31 , and a through-hole is formed at the center thereof. A cutout  147  is formed on the lower side of the annular portion  141  to secure the space for the displacement of the second intermediate member  70 . 
     The hollow circular cylindrical portion  142  has a hollow circular cylindrical shape extending rearward from the annular portion  141 . The diameter of the hollow circular cylindrical portion  142  is smaller than the diameter of the annular portion  141 . The spring housing portion  149  is formed at the upper side of the hollow circular cylindrical portion  142  adjacently to the hollow circular cylindrical portion  142 . The spring housing portion  149  is formed to have a circular-arc shape centered at the rotational axis AX 1 . The spring  68  is housed in the spring housing portion  149 . The spring  68  is extensible and compressible along the circular-arc shape of the spring housing portion  149 . The rear side of the spring housing portion  149  is opened, and the protrusion  67  of the first intermediate member  60  is inserted in the spring housing portion  149  via this opening. One end of the spring  68  is supported on the inner surface of the spring housing portion  149  (a flat surface located at one end portion of the circular-arc shape), and the other end of the spring  68  is engaged with the protrusion  67 . Due to this configuration, the first intermediate member  60  is biased in the clockwise direction (i.e., toward the first blocking position). 
     The protrusion portions  143  and  144  are disposed so as to be spaced apart from each other in the left-right direction. The protrusion portions  143  and  144  extend rearward from the annular portion  141  at an approximately vertically central position of the annular portion  141 . The protrusion portions  143  and  144  include screw holes  143   a  and  144   a  including female screws formed thereon, respectively. The screw holes  143   a  and  144   a  extend forward from the rear end surfaces of the protrusion portions  143  and  144 , respectively. The bolts  91  are threadedly engaged with the screw holes  143   a  and  144   a  to mount the first intermediate member  60  to the holding member  140  in the above-described manner (refer to  FIG.  14   ). 
     The protrusion portions  145  and  146  are disposed so as to be spaced apart from each other in the left-right direction on the lower side with respect to the protrusion portions  143  and  144 . The protrusion portions  145  and  146  include screw holes  145   a  and  146   a  including female screws formed thereon, respectively. The screw holes  145   a  and  146   a  extend forward from the rear end surfaces of the protrusion portions  145  and  146 , respectively. The bolts  92  are threadedly engaged with the screw holes  145   a  and  146   a  to mount the second intermediate member  70  to the holding member  140  in the above-described manner (refer to  FIG.  14   ). The lengths of the protrusion portions  145  and  146  in the front-rear direction are shorter than the lengths of the protrusion portions  143  and  144  in the front-rear direction to allow the second intermediate member  70  to be held on the front side with respect to the first intermediate member  60 . 
     The above-described spring seat  148  is formed at the lower edge of the hollow circular cylindrical portion  142 . This holding member  140  is fitted in the gear housing  20  so as to bring the outer periphery of the annular portion  141  and the inner periphery of the hollow circular cylindrical portion  142  into abutment with the gear housing  20  in a state that the first intermediate member  60  and the second intermediate member  70  are mounted thereto. As a result, the holding member  140  is fixed to the gear housing  20 . Mounting the first intermediate member  60  and the second intermediate member  70  to the single holding member  140  automatically determines the relative positions of the first intermediate member  60  and the second intermediate member  70 , and therefore the relative positions of the first intermediate member  60  and the second intermediate member  70  do not have to be adjusted when the grinder  10  is assembled. 
     Next, the third intermediate member  80  and the conversion mechanism  100  will be described. As illustrated in  FIG.  10   , the third intermediate member  80  includes a vertically extending portion  81  and a horizontally extending portion  82 . The vertically extending portion  81  extends vertically. The horizontally extending portion  82  is shaped like an elongate rod extending forward from the lower end of the vertically extending portion  81 . The horizontally extending portion  82  includes a front end  83 . 
     As illustrated in  FIG.  1   , the conversion mechanism  100  includes a first link member  110 , a second link member  120 , and a holding member  130 . As illustrated in  FIG.  11   , the first link member  110  includes a pressing portion  111 , engagement portions  112  and  113 , and a through-hole  114 . The pressing portion  111  is located on the front side and the upper side of the first link member  110 . The pressing portion  111  includes a circular-arc curved surface facing forward. The engagement portion  112  is a portion extending in a U-shaped manner rearward at the left edge of the first link member  110 . The engagement portion  112  includes a groove  112   a  opened on the rear side thereof. The engagement portion  113  is a portion extending in a U-shaped manner rearward at the right edge of the first link member  110 . The engagement portion  113  includes a groove  113   a  opened on the rear side thereof. The engagement portions  112  and  113  are formed at positions completely overlapping each other as viewed from the left-right direction. The through-hole  114  is located on the front side and the lower side of the first link member  110 , and extends through the first link member  110  in the left-right direction. 
     As illustrated in  FIG.  12   , the second link member  120  includes a vertically extending portion  121 , a first horizontally extending portion  122 , and a second horizontally extending portion  123 . The vertically extending portion  121  extends vertically. The first horizontally extending portion  122  extends forward from the lower end of the vertically extending portion  121 . The second horizontally extending portion  123  extends rearward from the upper end of the vertically extending portion  121 . A support shaft  124  is formed at the front edge of the first horizontally extending portion  122 . The support shaft  124  extends in the left-right direction in a circular columnar manner. 
     As illustrated in  FIG.  13   , the holding member  130  is shaped like a generally cubic box. A spring seat  131  is formed on the front inner surface of the holding member  130 . A spring  132  is fixed to the spring seat  131  extensibly and compressibly in the front-rear direction in the holding member  130 . The holding member  130  is opened on the rear side and the lower side thereof, and an opening  134  and an opening  135  are formed on the rear side and the lower side, respectively. The holding member  130  includes a through-hole  133  extending through the left surface and the right surface of the holding member  130  in the left-right direction. 
     As illustrated in  FIG.  4   , due to a pin inserted so as to extend through the through-hole  114  of the first link member  110  and the through-hole  133  of the holding member  130 , the first link member  110  is supported by the holding member  130  rotatably about this pin. The third intermediate member  80  is disposed in such a manner that the vertically extending portion  81  is located between the spring  132  and the pressing portion  111  of the first link member  110 . Due to this configuration, the third intermediate member  80  is biased rearward by the spring  132 . The second link member  120  is disposed in such a manner that the support shaft  124  is inserted in the groove  112   a  of the engagement portion  112  and the groove  113   a  of the engagement portion  113 , and that the rear edge portion of the second horizontally extending portion  123  is placed on the actuation end portion  55  of the operation member  50 . The grinder  10  can be easily assembled by installing the holding member  130  on the grinder  10  after mounting the first link member  110  to the holding member  130 , compared to directly installing the first link member  110  on, for example, the housing of the grinder  10 . 
     According to this conversion mechanism  100 , the rotational motion of the operation member  50  generally in the vertical direction can be changed to the linear motion of the third intermediate member  80  in the front-rear direction. More specifically, when the operation member  50  is displaced from the OFF position illustrated in  FIG.  4    to the ON position illustrated in  FIG.  3   , the actuation end portion  55  of the operation member  50  is displaced upward. At this time, as illustrated in  FIG.  3   , the second horizontally extending portion  123  of the second link member  120  is pressed upward by the actuation end portion  55  of the operation member  50 . According thereto, the entire second link member  120  is linearly moved upward. At this time, since the support shaft  124  of the second link member  120  is inserted in the grooves  112   a  and  113   a  of the first link member  110 , the engagement portions  112  and  113  engaged with the support shaft  124  receive an upward force. According thereto, the first link member  110  is rotated about the pin inserted in the through-hole  114 . At this time, the pressing portion  111  of the first link member  110  applies a forward force to the vertically extending portion  81  while being slidably moving on the vertically extending portion  81  of the third intermediate member  80 . As a result, the third intermediate member  80  is linearly moved forward against the biasing force of the spring  132 . On the other hand, when the operation member  50  is returned from the ON position to the OFF position, the third intermediate member  80  is returned to the position illustrated in  FIG.  6    under the biasing force of the horizontally extending portion  82 . At this time, the first link member  110  is rotated and returned to the original position by being pressed rearward by the third intermediate member  80 , and the second link member  120  engaged with the engagement portions  112  and  113  is also returned to the original position by being pulled downward. 
     According to this conversion mechanism  100 , the operation member  50  and the third intermediate member  80  can be moved in conjunction with each other even with the operation member  50  and the third intermediate member  80  displaced in different directions. Therefore, the displacement direction of the operation member  50  is free of design constraints, and thus an optimum type of operation member  50  can be employed according to the specifications of the grinder  10 . 
     According to the above-described grinder  10 , the first intermediate member  60  is located at the first blocking position illustrated in  FIGS.  6  and  14    (i.e., the position of blocking the route of the displacement of the third intermediate member  80  in the front-rear direction) in the state that the side handle  200  is not attached. In this state, when the user tries to operate the operation member  50  from the OFF position to the ON position, the front end  83  of the third intermediate member  80  moved in conjunction with the operation member  50  abuts against the blocking portion  64  of the first intermediate member  60 , and therefore the third intermediate member  80  cannot be displaced forward more than that as clearly seen from  FIG.  6   . Therefore, the operation member  50  can neither be displaced to the ON position. 
     Further, the second intermediate member  70  is located at the second blocking position illustrated in  FIGS.  6  and  15    (i.e., the position of blocking the route of the displacement of the third intermediate member  80  in the front-rear direction) in the state that the cover  300  is not attached. In this state, when the user tries to operate the operation member  50  from the OFF position to the ON position, the front end  83  of the third intermediate member  80  moved in conjunction with the operation member  50  abuts against the blocking portion  73  of the second intermediate member  70 , and therefore the third intermediate member  80  cannot be displaced forward more than that as clearly seen from  FIG.  6   , even when the first intermediate member  60  is located at the first non-blocking position illustrated in  FIG.  14    (i.e., the position of not blocking the route of the displacement of the third intermediate member  80  in the front-rear direction). Therefore, the operation member  50  can neither be displaced to the ON position. 
     On the other hand, when the side handle  200  is attached, the first intermediate member  60  is rotated against the biasing force of the spring  68  by being pressed by the side handle  200 , and the blocking portion  64  of the first intermediate member  60  is displaced to a position of not blocking the route of the displacement of the third intermediate member  80  in the front-rear direction. Further, when the cover  300  is attached, the second intermediate member  70  is linearly moved against the biasing force of the spring  79  by being pressed by the cover  300 , and the blocking portion  73  of the second intermediate member  70  is displaced to a position of not blocking the route of the displacement of the third intermediate member  80  in the front-rear direction. At this time, the third intermediate member  80  can be displaced forward without abutting against the first intermediate member  60  and the second intermediate member  70  as clearly seen from  FIG.  5   . Therefore, the operation member  50  can be displaced to the ON position. Therefore, the configuration that allows the electric motor  31  to be driven only when both the side handle  200  and the cover  300  are attached can be realized using only a mechanical structure without using a sensor. 
     Further, the first intermediate member  60  is configured to be rotated about the rotational axis AX 1  when any of the pressed portions  62   a  to  62   c  is pressed by the side handle  200 . This eliminates the necessity of securing a space for the displacement of the first intermediate member  60  in the front-rear direction, thereby allowing the grinder  10  to have a compact size in the front-rear direction. 
     Further, the second intermediate member  70  is pressed by the cover  300  (more specifically, the attachment portion  320 ) and is linearly moved in the attachment direction of the cover  300  (i.e., upward) when the cover  300  is attached. This eliminates the necessity of a direction conversion mechanism, thereby contributing to the simplification of the apparatus configuration. 
     In the following description, a second embodiment of the present invention will be described with reference to  FIGS.  17  to  21   . In the following description, the second embodiment will be described focusing only on differences from the first embodiment. As illustrated in  FIG.  17   , a grinder  400  according to the second embodiment includes an operation member  450 , a lock-off portion  443 , a first intermediate member  460 , and a second intermediate member  480 . 
     As illustrated in  FIG.  17   , the operation member  450  is an elongated member extending in the front-rear direction, and is disposed under a motor housing  430  and a handle housing  440 . The operation member  450  includes an actuation end portion  451 , an engagement portion  452 , a protrusion  453 , and a protrusion  454 . The actuation end portion  451  is the front end portion of the operation member  450 , and has a thinner thickness (a vertical width) than the other portions. The actuation end portion  451  extends through a through-hole  431  formed on the motor housing  430  (refer to  FIG.  20   ) and reaches the inside of the motor housing  430 . The engagement portion  452  is a portion to be engaged with the lock-off portion  443 , which will be described below, and is in the form of a protrusion protruding rearward at the rear end portion of the operation member  450 . The protrusion  453  protrudes upward at the upper portion of the operation member  450 . The protrusion  453  is disposed on the rear side of the operation member  450  in the front-rear direction. The protrusion  454  protrudes downward at the lower portion of the operation member  450 . The protrusion  454  is disposed at an approximately central position of the operation member  450  in the front-rear direction. 
     This operation member  450  is vertically pivotal with a supporting point therefor placed at a portion of the actuation end portion  451  that is located within the through-hole  431 . When the operation member  450  is displaced upward from an OFF position illustrated in  FIG.  17   , which is the initial position, to an ON position illustrated in  FIG.  19   , a switch  441  is switched from an OFF state to an ON state via a pivotal member  455 . 
     More specifically, the pivotal member  455  is disposed above the protrusion  453  of the operation member  450 . The pivotal member  455  is configured pivotally about a pin  458  supported on a boss of the handle housing  440 , and includes a first portion  456  and a second portion  457  extending outward in the radial direction with respect to a pivotal axis thereof. The first portion  456  is disposed immediately above the protrusion  453 , and the second portion  457  is disposed on the upper side with respect to the first portion  456 . The pivotal member  455  is biased in the counterclockwise direction so as to bring the first portion  456  into abutment with the protrusion  453  of the operation member  450  by a biasing member (for example, a torsion spring), although this is not illustrated. 
     When the user performs an operation of pressing the operation member  450  upward in a lock-off released state, which will be described below, the operation member  450  is pivotally moved upward. According thereto, the protrusion  453  displaces the first portion  456  of the pivotal member  455  upward against the biasing force of the biasing member, and the pivotal member  455  is pivotally moved in the clockwise direction. As a result, the second portion  457  is also integrally pivotally moved in the clockwise direction. Then, when the operation member  450  is pivotally moved to the ON position illustrated in  FIG.  19   , an input member  442  of the switch  441  is pressed by the second portion  457  and is pressed into the switch  441 . As a result, the switch  441  is switched from the OFF state to the ON state. When the user releases the upward pressing operation on the operation member  450 , the operation member  450  is pivotally moved downward under the biasing force of the biasing member biasing the pivotal member  455  and is returned to the OFF position illustrated in  FIG.  17   . At this time, the pivotal member  455  is also returned to the position illustrated in  FIG.  17    under the biasing force of the biasing member, and the input member  442  is also retracted from the switch  441 . As a result, the switch  441  is returned from the ON state to the OFF state. 
     The lock-off portion  443  has a similar function to the lock-off switch  57  according to the first embodiment. More specifically, the lock-off portion  443  is configured to switch the status of the operation member  450  between a lock-off state, in which the operation member  450  is prohibited from being displaced from the OFF position to the ON position, and the lock-off released state, in which the operation member  450  is permitted to be displaced from the OFF position to the ON position, according to a change in the engagement state with the operation member  450 . The lock-off portion  443  is a fixed (i.e., non-displaceable) engagement structure in contrast to the lock-off switch  57  according to the first embodiment, in which the lock-off switch  57  itself is displaced. In the present embodiment, the lock-off portion  443  is formed on the rear side with respect to the operation member  450  as a part of the handle housing  440  (more specifically, a rear and lower part). 
     As illustrated in  FIG.  17   , the lock-off portion  443  includes a base portion  444 , an engagement portion  445 , and a support portion  446 . The base portion  444  is a portion protruding downward from the lower portion of the handle housing  440 . The engagement portion  445  and the support portion  446  protrude forward from the base portion  444 . The engagement portion  445  is located on the upper side with respect to the support portion  446 , and a recessed portion opened on the front side thereof is formed between the engagement portion  445  and the support portion  446 . The support portion  446  extends to the front side more than the engagement portion  445 . 
     As illustrated in  FIG.  17   , the operation member  450  is held displaceably in the front-rear direction and the vertical direction in a retained state due to the insertion of the actuation end portion  451  in the through-hole  431  and the placement of the engagement portion  452  on the support portion  446 . The operation member  450  is displaced in the front-rear direction and the vertical direction by the user&#39;s manual operation. The user can easily displace the operation member  450  in the front-rear direction by placing his/her finger on the protrusion  454 . 
     As illustrated in  FIG.  17   , the first intermediate member  460  is disposed on the front side with respect to the operation member  450 . The first intermediate member  460  is configured identically or similarly to the first intermediate member  60  according to the first embodiment, and is configured to be displaced by being directly or indirectly pressed by a side handle when the side handle as the accessory (not illustrated) is attached to an attachment portion (not illustrated). 
     As illustrated in  FIGS.  17  and  20   , the second intermediate member  480  is disposed, displaceably in the front-rear direction, between the first intermediate member  460  and the operation member  450  in the front-rear direction. As illustrated in  FIG.  20   , the second intermediate member  480  is a rod-like member extending in the front-rear direction in the present embodiment. An increased diameter portion  481 , which is larger in diameter than the other portions, is formed at the rear end of the second intermediate member  480 . The “diameter” here is intended to mean a length around the front-rear direction, and the cross-sectional shape of the second intermediate member  480  and/or the increased diameter portion  481  in a direction perpendicular to the front-rear direction is not limited to a circular shape. 
     As illustrated in  FIG.  20   , a coil spring  485  as a biasing member is disposed around the second intermediate member  480 . The coil spring  485  is held in a compressed state between a baffle plate  432  fitted in the motor housing  430  and the increased diameter portion  481 . The second intermediate member  480  is constantly biased by the coil spring  485  rearward, i.e., toward the side where the operation member  450  is located. Therefore, the increased diameter portion  481  is constantly in abutment with the actuation end portion  451  of the operation member  450  in the front-rear direction regardless of the position of the second intermediate member  480  in the front-rear direction. When the user displaces the operation member  450  forward, the second intermediate member  480  is pressed forward against the biasing force of the coil spring  485  by the operation member  450  and is displaced forward together with the operation member  450 . On the other hand, when the user releases the force displacing the operation member  450  forward, the operation member  450  and the second intermediate member  480  are returned to their original positions under the biasing force of the coil spring  485 . In this manner, the second intermediate member  480  is configured to be moved in conjunction with the displacement of the operation member  450  in the front-rear direction. 
     The functions of the grinder  400  configured in this manner will be described now. First, as illustrated in  FIG.  17   , when the operation member  450  is in the lock-off state at the OFF position, the engagement portion  452  of the operation member  450  is contained in the recessed portion between the engagement portion  445  and the support portion  446  of the lock-off portion  443 . The position of the operation member  450  at this time will be referred to as a lock-off position. When the operation member  450  is located at the lock-off position, the engagement portion  445  is located right above the engagement portion  452 , and therefore the upward displacement of the operation member  450  is restricted due to the abutment of the engagement portion  452  with the engagement portion  445  even if the user tries to perform the operation of pressing the operation member  450  upward. Therefore, the operation member  450  is prohibited from being displaced from the OFF position (refer to  FIG.  17   ) to the ON position (refer to  FIG.  19   ). When the operation member  450  is in the lock-off state at the OFF position, the second intermediate member  480  is located at a position illustrated in  FIG.  20    without being pressed forward by the operation member  450 . The position of the second intermediate member  480  at this time will be referred to as a first corresponding position. 
     The user should displace the operation member  450  forward to bring the operation member  450  kept in the lock-off state into the lock-off released state. However, as illustrated in  FIG.  20   , the first intermediate member  460  is located in front of the second intermediate member  480  in the state that the side handle is not attached to the attachment portion. Therefore, when the user tries to displace the operation member  450  forward, the distal end  482  of the second intermediate member  480  moved in conjunction with the operation member  450  abuts against the first intermediate member  460 , and therefore the forward displacement of the second intermediate member  480  (and thus the operation member  450 ) is restricted. In this manner, the first intermediate member  460  prohibits the status of the operation member  450  from being switched from the lock-off position state to the lock-off released state with the aid of abutment between members (the abutment between the first intermediate member  460  and the distal end  482  of the second intermediate member  480  in the present example). In other words, the first intermediate member  460  blocks the displacement route for displacing the second intermediate member  480  forward from the first corresponding position. 
     On the other hand, as illustrated in  FIG.  21   , in the state that the side handle is attached to the attachment portion, the first intermediate member  460  is displaced and is brought into a state of not blocking the displacement route for displacing the second intermediate member  480  forward from the first corresponding position (the first intermediate member  460  is displaced to a not-illustrated position in the cross section illustrated in  FIG.  21   ) similarly to the first embodiment. In other words, the above-described abutment between members does not occur, and the forward displacements of the operation member  450  and the second intermediate member  480  are permitted. Therefore, the user can displace the operation member  450  and the second intermediate member  480  forward to the position illustrated in  FIGS.  18  and  21    against the biasing force of the coil spring  485 . At this time, as illustrated in  FIG.  18   , the engagement portion  452  of the operation member  450  is supported on the support portion  446  of the lock-off portion  443  but the engagement portion  445  is absent right above the engagement portion  452 . Therefore, the operation member  450  is in an upward displaceable state (i.e., the lock-off released state). The position of the operation member  50  at this time will be referred to as a lock-off released position, and the position of the second intermediate member  480  at this time will be referred to as a second corresponding position. 
     When the user displaces the operation member  450  upward after the operation member  450  is brought into the lock-off released state at the OFF position in this manner, the switch  441  is switched to the ON state via the pivotal member  455  in the above-described manner as illustrated in  FIG.  19   . On the other hand, when stopping the driving of the grinder  400 , the user releases the operation of displacing the operation member  450  upward, according to which the operation member  450  is returned from the ON position (refer to  FIG.  19   ) to the OFF position (refer to  FIG.  18   ) as described above. At this time, the operation member  450  is returned from the lock-off released position (refer to  FIG.  18   ) to the lock-off position (refer to  FIG.  17   ) under the biasing force of the coil spring  485 , and the second intermediate member  480  is returned from the second corresponding position to the first corresponding position. 
     According to the above-described grinder  400 , the configuration that allows the electric motor to be driven only when the side handle is attached can be realized using only a mechanical structure without using a sensor. Further, the displacement of the operation member  450  accompanying the above-described operation of releasing the lock-off is easily recognizable to the user. Therefore, when the electric motor cannot be driven despite the fact that the user performs the operation of displacing the operation member  450  from the OFF position to the ON position, the user can easily notice that the reason therefor is not a failure in the switch  441  but because the operation of the releasing the lock-off cannot be performed due to no attachment of the side handle. 
     Further, according to the grinder  400 , the second intermediate member  480 , which is moved in conjunction with the operation member  450 , is disposed between the first intermediate member  460  and the operation member  450 . This allows the grinder  400  to have even such a layout that the first intermediate member  460  and the operation member  450  are separated, thereby improving the design flexibility of the grinder  400 . However, the second intermediate member  480  may be omitted. In this case, the actuation end portion  451  of the operation member  450  may extend to the position of the first intermediate member  460  in the front-rear direction, and the first intermediate member  460  may block the displacement route of the actuation end portion  451  only when the side handle is not attached. 
     In an alternative embodiment, the grinder  400  may be configured to allow the operation member  450  to be switched from the lock-off state to the lock-off released state only when both the side handle and the cover are attached, similarly to the first embodiment. Alternatively, the grinder  400  may be configured to allow the operation member  450  to be switched from the lock-off state to the lock-off released state only when the cover is attached. 
     In a further alternative embodiment, a displaceably configured lock-off member may be provided as a lock-off portion instead of the lock-off portion  443  having the fixed engagement structure. In this case, a second intermediate member that prohibits the lock-off member from being displaced from the lock-off position to the lock-off released position only when the side handle is not attached may be provided between the first intermediate member  460  and the lock-off member. 
     Having described the embodiments of the present invention, the above-described embodiments are intended to only facilitate the understanding of the present invention, and are not intended to limit the present invention thereto. The present invention can be modified or improved without departing from the spirit thereof, and includes equivalents thereof. Further, each of the elements described in the claims and the specification can be combined in any manner or omitted in any manner within a range that allows it to remain capable of achieving at least a part of the above-described objects or bringing about at least a part of the above-described advantageous effects. 
     For example, the shapes and the forms of the components of the above-described grinder  10  are merely examples, and can be changed in any manner as long as the functions of these components can be maintained. For example, the pressed portions  62   a  to  62   c  of the first intermediate member  60  may protrude forward or rearward instead of protruding radially outward. Alternatively, the blocking portion  64  may be omitted, and be replaced with a through-hole formed on the first intermediate member main body  61  in such a manner that the third intermediate member  80  can penetrate therethrough when the first intermediate member  60  is located at the first non-blocking position. This case means the first intermediate member main body  61  fulfills the function of blocking the displacement route of the third intermediate member  80  when the first intermediate member  60  is located at the first non-blocking position. Alternatively, at least a part of the third intermediate member  80  (for example, the horizontally extending portion  82 ) may be a wire. 
     Further, the first intermediate member  60  may be indirectly pressed by the side handle  200  when the side handle  200  is attached. More specifically, an additional member that is displaced by being pressed by the side handle  200  may be provided, and the first intermediate member  60  may be displaced by this additional member. Similarly, the second intermediate member  70  may be indirectly pressed by the cover  300  when the cover  300  is attached. 
     Further, the first intermediate member  60  may be configured to be tilted by being pressed by the side handle  200  when the side handle  200  is attached instead of being configured to be rotated when the side handle  200  is attached. For example, the first intermediate member  60  may include a support shaft on the upper side of the first intermediate member  60  and be tilted about this support shaft in such a manner that the lower edge of the first intermediate member  60  approaches the front side when the side handle  200  is attached. 
     Further, the above-described embodiments can be applied to not only the grinder  10  but also any tool including a prime mover and configured to allow two types of accessories to be detachably attached thereto. 
     DESCRIPTION OF NUMERALS 
     
         
           10 ,  400  grinder 
           20  gear housing 
           22  second attachment portion 
           23  small bevel gear 
           24  large bevel gear 
           25  spindle 
           26  inner flange 
           27  lock nut 
           28  tool accessory 
           29   a ,  29   b ,  29   c  first attachment portion 
           30 ,  430  motor housing 
           31  electric motor 
           32  motor shaft 
           40 ,  440  handle housing 
           41 ,  441  switch 
           42 ,  442  input member 
           50 ,  450  operation member 
           51  support shaft 
           52  protrusion 
           53  spring seat 
           54  spring 
           55  actuation end portion 
           57  lock-off switch 
           60  first intermediate member 
           61  first intermediate member main body 
           62   a ,  62   b ,  62   c  pressed portion 
           63   a ,  63   b ,  63   c  pressed surface 
           64  blocking portion 
           65  first though-hole 
           67  protrusion 
           68  spring 
           70  second intermediate member 
           71  base 
           72  pressed portion 
           73  blocking portion 
           74  support portion 
           76  second through-hole 
           78  spring seat 
           79  spring 
           80  third intermediate member 
           81  vertically extending portion 
           82  horizontally extending portion 
           83  front end 
           91 ,  92  bolt 
           100  conversion mechanism 
           110  first link member 
           111  pressing portion 
           112 ,  113  engagement portion 
           112   a ,  113   a  groove 
           114  through-hole 
           120  second link member 
           121  vertically extending portion 
           122  first horizontally extending portion 
           123  second horizontally extending portion 
           124  support shaft 
           130  holding member 
           131  spring seat 
           132  spring 
           133  through-hole 
           134 ,  135  opening 
           140  holding member 
           141  annular portion 
           142  hollow circular cylindrical portion 
           143 ,  144 ,  145 ,  146  protrusion portion 
           143   a ,  144   a ,  145   a ,  146   a  screw hole 
           147  cutout 
           148  spring seat 
           149  spring housing portion 
           200  side handle 
           210  grip portion 
           220  attachment portion 
           300  cover 
           310  cover main body 
           320  attachment portion 
           431  through-hole 
           432  baffle plate 
           443  lock-off portion 
           444  base portion 
           445  engagement portion 
           446  support portion 
           451  actuation end portion 
           452  engagement portion 
           453 ,  454  protrusion 
           455  pivotal member 
           456  first portion 
           457  second portion 
           458  pin 
           460  first intermediate member 
           480  second intermediate member 
           481  increased diameter portion 
           482  distal end 
           485  coil spring 
         AX 1 , AX 2  rotational axis