Patent Publication Number: US-8985424-B2

Title: Driving tool

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a driving tool having an idle driving prevention mechanism that prevents idle driving of fasteners such as nails. 
     2. Description of the Related Art 
     Japanese non-examined laid-open Patent Publication No. 2010-5714 discloses a driving tool having an idle driving prevention mechanism. In the known art, a remaining-number detecting switch for detecting the number of remaining fasteners is provided in a magazine which feeds fasteners in the form of nails onto a working axis of a driving member in the form of a driver. When the number of remaining fasteners is reduced to below a predetermined number, the remaining-number detecting switch is actuated to stop power supply to a motor. 
     According to the known driving tool, when a nail feeding member for feeding the nails from the magazine onto the working axis of the driving member reaches a predetermined position, the remaining-number detecting switch is actuated via a lever which is designed to be interlocked with the nail feeding member. Therefore, when smaller-diameter nails are used in this driving tool, a feed pitch of the nail feeding member accordingly gets shorter. As a result, the timing of switching the remaining-number detecting switch is susceptible to disturbance. 
     Specifically, after the remaining-amount detecting switch is once switched to a detecting state to output a detecting signal, it may be switched again to a non-detecting state not to output a detecting signal. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the invention to provide an improved driving tool which can prevent malfunction in detection of the number of fasteners remaining in a magazine. 
     Above-described object can be achieved by the claimed invention. According to the invention, a representative driving tool has a driving member which moves rectilinearly and drives a fastener into a workpiece, and a magazine which stores a plurality of fasteners and feeds the fasteners one by one onto a working axis of the driving member. Further, the “driving tool” in the present invention typically represents a nailing machine or a tacker. The “fastener” may include a sharp-pointed straight rod-like fastener with or without a cap on its head, and other fasteners such as a U-shaped staple. 
     According to the invention, the driving tool has a driving tool actuation control member and a retaining member. The driving tool actuation control member can be switched between an actuating position to allow actuation of the driving tool and a deactuating position to prevent actuation of the driving tool and is constantly biased toward the deactuating position from the actuating position. The retaining member can be engaged with the driving tool actuation control member and switched between a retaining position to retain the driving tool actuation control member in the actuating position by engagement with the driving tool actuation control member and a releasing position to release the driving tool actuation control member by disengagement from the driving tool actuation control member. The retaining member is switched from the retaining position to the releasing position according to the number of remaining fasteners in the magazine, and the driving tool actuation control member is switched from the actuating position to the deactuating position when the retaining member is switched to the releasing position. Further, the manner of being “biased” in the present invention represents the manner in which the biasing force is applied to the driving tool actuation control member such that the driving tool actuation control member is switched to the deactuating position, and an elastic member such as a spring or rubber is typically used as a means of applying the biasing force. The timing “according to the number of remaining fasteners” typically represents the time at which the number of remaining fasteners reaches a predetermined number including zero. 
     According to the present invention, the retaining member is switched between a retaining position and a releasing position according to the number of fasteners remaining in the magazine, and when the retaining member is switched to the releasing position, the driving tool actuation control member is released from the retaining member. Therefore, when the driving tool actuation control member is released from the retaining member, the driving tool actuation control member which is constantly biased toward the deactuating position is switched to the deactuating position and held in this position. Specifically, according to the present invention, when the number of remaining fasteners reaches a predetermined number, the driving member is prevented from being actuated. Further, once switched to the deactuating state, this state can be maintained. Therefore, malfunction is not caused. 
     According to a further embodiment of the present invention, the driving tool has a cam member which can be moved to return the driving tool actuation control member from the deactuating position to the actuating position, and the driving tool actuation control member is returned to the actuating position by movement of the cam member. Further, the manner in which “the cam member is moved” in this invention suitably includes the manner in which the cam member is moved by user&#39;s manual operation of a cam operating member, and the manner in which the cam member is moved in relation to an operation for loading (refilling) fasteners into the magazine. 
     According to the present invention, the driving tool actuation control member is returned to the initial position or actuating position by movement of the cam member, so that the driving tool is allowed to be actuated. 
     According to a further embodiment of the present invention, the movement of the cam member for returning the driving tool actuation control member from the deactuating position to the actuating position is interlocked with refilling the fasteners into the magazine. Further, the act of “refilling the fasteners into the magazine” in the present invention typically represents the act of opening the slide door with respect to the magazine body in order to refill the fasteners into the magazine. 
     According to the present invention, return of the driving tool actuation control member from the deactuating position to the actuating position can be interlocked with refilling of the fasteners. Therefore, it is rational in that the user does not have to perform an additional returning operation. 
     According to the present invention, an improved driving tool is provided which can prevent malfunction in detection of the number of fasteners remaining in a magazine. Other objects, features and advantages of the present invention will be readily understood after reading the following detailed description together with the accompanying drawings and the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a right side view showing an entire construction of a nailing machine according to this embodiment. 
         FIG. 2  is a left side view of the nailing machine. 
         FIG. 3  is a perspective view of the nailing machine. 
         FIG. 4  is a partial view of an idle driving prevention mechanism. 
         FIG. 5  is an enlarged view of part A in  FIG. 3 . 
         FIG. 6  is an enlarged view of part B in  FIG. 3 . 
         FIG. 7  is an enlarged view of part C in  FIG. 4 . 
         FIG. 8  is a view for illustrating the operation of the idle driving prevention mechanism, showing a state in which nails are remaining in a magazine, in which  FIG. 8(A)  shows the entire idle driving prevention mechanism,  FIG. 8(B)  is an enlarged partial view thereof, and  FIG. 8(C)  is an extracted view showing each of its components. 
         FIG. 9  is a view for illustrating the operation of the idle driving prevention mechanism, showing a state in which nails have run so low that a pusher has contacted a slide plate, in which  FIG. 9(A)  shows the entire idle driving prevention mechanism,  FIG. 9(B)  is an enlarged partial view thereof, and  FIG. 9(C)  is an extracted view showing each of its components. 
         FIG. 10  is a view for illustrating the operation of the idle driving prevention mechanism, showing a state in which the number of remaining nails has reached a predetermined number (idle driving prevention has started), in which  FIG. 10(A)  shows the entire idle driving prevention mechanism,  FIG. 10(B)  is an enlarged partial view thereof, and  FIG. 10(C)  is an extracted view showing each of its components. 
         FIG. 11  is a view for illustrating the operation of the idle driving prevention mechanism, showing a state of completion of idle driving prevention, in which  FIG. 11(A)  shows the entire idle driving prevention mechanism,  FIG. 11(B)  is an enlarged partial view thereof, and  FIG. 11(C)  is an extracted view showing each of its components. 
         FIG. 12  is a view for illustrating the operation of the idle driving prevention mechanism, showing a state at the beginning of return to the initial position (when a return plate starts to move), in which  FIG. 12(A)  shows the entire idle driving prevention mechanism,  FIG. 12(B)  is an enlarged partial view thereof, and  FIG. 12(C)  is an extracted view showing each of its components. 
         FIG. 13  is a view for illustrating the operation of the idle driving prevention mechanism, showing a state of completion of the movement of the return plate, in which  FIG. 13(A)  shows the entire idle driving prevention mechanism,  FIG. 13(B)  is an enlarged partial view thereof, and  FIG. 13(C)  is an extracted view showing each of its components. 
         FIG. 14  is a view for illustrating the operation of the idle driving prevention mechanism, showing a state of completion of return to the initial position, in which  FIG. 14(A)  shows the entire idle driving prevention mechanism,  FIG. 14(B)  is an enlarged partial view thereof, and  FIG. 14(C)  is an extracted view showing each of its components. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Each of the additional features and method steps disclosed above and below may be utilized separately or in conjunction with other features and method steps to provide and manufacture improved driving tools and method for using such driving tools and devices utilized therein. Representative examples of the present invention, which examples utilized many of these additional features and method steps in conjunction, will now be described in detail with reference to the drawings. This detailed description is merely intended to teach a person skilled in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention. Only the claims define the scope of the claimed invention. Therefore, combinations of features and steps disclosed within the following detailed description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe some representative examples of the invention, which detailed description will now be given with reference to the accompanying drawings. 
     An representative embodiment of the invention is described with reference to  FIGS. 1 to 14 . In this embodiment, a battery-powered nailing machine  100  is explained as a representative example of a driving tool according to the invention. As shown in  FIGS. 1 to 3 , the nailing machine  100  mainly includes a tool body in the form of a body  101  that forms an outer shell of the nailing machine  100 , a generally rod-shaped grip  103  designed to be held by a user, and a magazine  105  that stores (is loaded with) fasteners in the form of nails N to be driven into a workpiece. The grip  103  is integrally formed with the body  101  and extends from the side of the body  101  in a direction (downward as viewed in  FIG. 1 ) transverse to a longitudinal direction of the body  101  (a horizontal direction as viewed in  FIG. 1 ). A rechargeable battery pack  110  is mounted on an extending end (a lower end as viewed in  FIG. 1 ) of the grip  103 , and a driving motor  108  is powered from the rechargeable battery pack  110 . 
       FIG. 1  shows the nailing machine  100  pointed to the right or with a front end of the body  101  pointed toward a workpiece (not shown) on the right side. Therefore, in  FIG. 1 , a rightward direction is a nail driving (injecting) direction (the longitudinal direction) in which a nail is driven by a driver  116 . The driver  116  comprises an elongate rod-like member and serves as a nail driving member which moves rectilinearly in the longitudinal direction of the body  101  and moves forward within a nail driving channel of a driver guide  115  and drives the nail. The driver  116  is a feature that corresponds to the “driving member” according to the present invention. Further, for the sake of convenience of explanation, the side of the front end of the body  101  in the longitudinal direction (the right end as viewed in  FIG. 1 ) is taken as the front and its opposite side as the rear. In a state shown in  FIG. 1  in which an axis of the body  101  extends generally horizontally, the extending direction of the grip  103  is taken as the downward direction and its opposite direction as the upward direction. 
     A driver guide  115  is provided on the front end (the right end as viewed in  FIG. 1 ) of the body  101  and forms an injection port for the nails N on a working axis of the driver. The magazine  105  is mounted to the front end region of the body  101  and extends generally parallel to the grip  103 . Further, a nail feeding member in the form of a pusher  125  is provided within the magazine  105  and serves to push the nails N in a feeding direction (upward as viewed in  FIG. 1 ). The pusher  125  feeds a nail N in every nail driving operation of the driver. With such a construction, the nails are fed one by one toward the nail injection hole of the driver guide  115  in an upward direction transverse to the driving direction. 
     The body  101  is generally L-shaped as viewed from the side and mainly includes a generally cylindrical body housing  107  extending in a longitudinal direction and a motor housing  109  which extends downward from a front end region of the body housing  107  and houses the driving motor. The motor housing  109  is disposed adjacent to the magazine  105  in a front end region of the body housing  107  and connected to the body housing  107 . A driver driving mechanism (not shown) for driving the driver is housed within the body  101 . The driver is caused to move rectilinearly by the driver driving mechanism which is driven by the driving motor. At this time, the driver strikes the nail N held standby in the nail driving channel of the driver guide  115 , so that the nail N is driven into the workpiece. When a contact arm (not shown) provided adjacent to the driver guide  115  is pressed against the workpiece and then in this state, a trigger  103   a  disposed on the grip  103  is depressed once, or when the trigger  103   a  is depressed and then in this state, the contact arm is pressed against the workpiece, the driving motor is driven and one operation of driving in the nail N by the driver is performed. The driver driving mechanism for driving the driver is a known technique and not directly related to the present invention, and therefore its description is omitted. 
     The magazine  105  mainly includes a generally box-like magazine body  121  that stores a plurality of nails N joined together, for example, by an adhesive, a slide door  123  (see  FIG. 2 ) and the pusher  125  that serves to feed the nails N one by one from the magazine body  121  into the nail driving channel of the driver guide  115 . The slide door  123  is slidably mounted to the magazine body  121  in the feeding direction (the vertical direction perpendicular to the nail driving direction) of the nails N. Further, the slide door  123  is slid between an open position (to which the slide door  123  is moved downward with respect to the magazine body  121 ) in which the magazine body  121  is opened for nail loading and a closed position (to which the slide door  123  is moved upward with respect to the magazine body  121 ) in which the magazine body  121  is closed. In the closed position, the slide door  123  is locked to the magazine body  121  by a door lock  127 . 
     An idle driving prevention mechanism  130  is now explained with reference to  FIGS. 4 to 7 . The idle driving prevention mechanism  130  serves to prevent the nailing machine  100  from performing a nail driving operation by de-energizing (cutting or interrupting power to) the driving motor when the number of nails N remaining in the magazine  105  reaches a predetermined number. The idle driving prevention mechanism  130  mainly includes a slide plate  131  which can move in the same direction (upward) as the direction of movement of the pusher  125 , a switch block  135  which can move in a direction perpendicular to the direction of movement of the slide plate  131  or in the longitudinal direction of the body  101 , an electric switch  139  which is turned on and off by the switch block  135 , and a return plate  141  by which the electric switch  139  is returned from the off state to the on state. As for the above-described components of the idle driving prevention mechanism, the slide plate  131 , the switch block  135  and the return plate  141  are mounted to the magazine body  121 , and the electric switch  139  is mounted to the motor housing  109 . 
     The slide plate  131  is provided as a detecting member for detecting that the number of remaining nails N have reached the predetermined number. The slide plate  131  is an elongate member extending in the vertical direction, and a vertically extending straight slot  132  (see  FIGS. 4 and 7 ) having an open lower end is formed in one (lower) end of the slide plate  131  in the extending direction and a passive part  131   a  protruding in a direction transverse to the extending direction is formed on the other (upper) end of the slide plate  131  in the extending direction. The slide plate  131  is constantly biased downward by a biasing member in the form of a first spring  133 . When the slide plate  131  is placed in a downward position by a biasing force of the first spring  133 , the slot  132  of the slide plate  131  engages with (restrains) a pin-like engagement element  135   a  on the switch block  135 , from above, so that the switch block  135  is held away from the electric switch  139  or in a position to turn off the electric switch  139 . The state in which the engagement element  135   a  of the switch block  135  is engaged with the slot  132  of the slide plate  131  and the electric switch  139  is turned off is defined as an initial state. Further, the engagement element  135   a  protrudes substantially horizontally in a lateral direction from the side surface of the switch block  135 . The first spring  133  is a coil spring which is elastically disposed between a top inner wall surface of the magazine body  121  and an upper end surface of the slide plate  131  and applies a downward biasing force to the slide plate  131 . 
     When the number of remaining nails N becomes fewer, the passive part  131   a  comes in contact with an actuating protrusion  125   a  formed on the pusher  125 . Thereafter, when the pusher  125  is moved upward to feed the nails, the slide plate  131  is pushed up by the actuating protrusion  125   a . The actuating protrusion  125   a  protrudes in a direction transverse to the nail feeding direction and opposed to the passive part  131   a  in the vertical direction. When the number of remaining nails N reaches the predetermined number, the slide plate  131  reaches a predetermined upper end position. At this time, the engagement element  135   a  is disengaged from the slot  132 . The slide plate  131  is a feature that corresponds to the “retaining member” according to this invention. The downward position or initial position in which the slot  132  of the slide plate  131  is engaged with the engagement element  135   a  of the switch block  135  is a feature that corresponds to the “retaining position” according to this invention. An upper end position in which the engagement element  135   a  is disengaged from the slot  132 , is a feature that corresponds to the “releasing position” according to this invention. 
     The switch block  135  is provided as a control member for controlling driving of the driving motor when the number of remaining nails N reaches the predetermined number. Until the number of remaining nails N reaches the predetermined number, the engagement element  135   a  is held engaged with the slot  132  of the slide plate  131 , so that the switch block  135  which can move in the longitudinal direction of the tool body is held in a forward position to be placed away from the electric switch  139 . The switch block  135  is constantly biased toward the electric switch  139  (rearward) by a biasing member in the form of a second spring  137 . Therefore, when the slide plate  131  is moved upward and the engagement element  135   a  is disengaged from the slot  132  of the slide plate  131  (separated from a rear wall  132   a  of the slot  132 ), the switch block  135  is moved rearward by the biasing force of the second spring  137  and turns the electric switch  139  from the off state to the on state by pressing an actuating element  139   a  of the electric switch  139 . Further, as shown in  FIG. 7 , the slot  132  is designed such that the rear wall  132   a  has a length shorter than the front wall  132   b  in the vertical direction. The switch block  135  is a feature that corresponds to the “driving tool actuation control member” according to this invention. The forward position or initial position in which the switch block  135  is placed away from the electric switch  139  and turns off the electric switch, is a feature that corresponds to the “actuating position to allow actuation of the driving tool” according to this invention. The rearward position in which the switch block  135  is placed close to the electric switch  139  and turns on the electric switch, is a feature that corresponds to the “deactuating position to prevent actuation of the driving tool” according to this invention. The second spring  137  is a coil spring which is elastically disposed between the magazine body  121  and the switch block  135  and applies a rearward biasing force to the switch block  135 . 
     The electric switch  139  can be switched between a power supply position in which power is supplied to the driving motor and a power shutoff position in which the power supply is shut off. In this embodiment, the off position of the electric switch  139  is defined as the power supply position and the on position as the power shutoff position. When the electric switch  139  is switched to the on state, a switching signal of the electric switch  139  is inputted to a controller (not shown) for controlling the driving motor. When the switching signal of the electric switch  139  is inputted, even if the contact arm is pressed against the workpiece and the trigger  103   a  is depressed, the controller prevents energization of the driving motor, so that idle driving of the nails N can be prevented. 
     A return plate  141  is provided as a reset member and causes the driving motor to return from the energization prevented state or idle driving prevented state to the energization allowed state (initial state). The return plate  141  is a vertically extending cam plate and has a side surface region overlapping a side surface of the switch block  135  in the lateral direction. As shown in  FIG. 7 , a generally right-angled triangular engagement hole  143  through which the engagement element  135   a  is inserted is formed in the side surface region of the return plate  141 . Specifically, the engagement hole  143  of the return plate  141  has a rear surface  143   a  extending straight in the vertical direction, a bottom surface  143   b  extending horizontally in the longitudinal direction and an inclined surface  143   c  extending straight between an upper end of the rear surface  143   a  and a rear end of the bottom surface  143   b.    
     The return plate  141  is constantly biased downward by a biasing member in the form of a third spring  145 , and a lower surface of the return plate  141  is held in contact with a top of a stopper  147  provided on the slide door  123  of the magazine  105  so that the return plate  141  is prevented from moving downward. In the initial state in which the engagement element  135   a  of the switch block  135  is engaged with the slot  132  of the slide plate  131 , the return plate  141  is placed in a position to be prevented from moving downward by the stopper  147 , and the engagement element  135   a  is placed in a region of intersection (a lower right corner as viewed in  FIG. 7 ) of the rear surface  143   a  and the bottom surface  143   b  of the engagement hole  143 . The third spring  145  is a coil spring which is elastically disposed between the magazine body  121  and the upper end surface of the return plate  141  and applies a downward biasing force to the return plate  141 . 
     When the electric switch  139  is turned on by rearward movement of the switch block  135  and idle driving is prevented, the engagement element  135   a  of the switch block  135  is opposed to both the inclined surface  143   c  of the engagement hole  143  and the lower surface of the rear wall  132   a  of the slot  132  of the slide plate  131  with respective predetermined spaces. In this state, when the slide door  123  is opened (slid downward) and the stopper  147  is disengaged from the return plate  141 , the return plate  141  acted upon by the biasing force of the third spring  145  is moved downward. Thus, the inclined surface  143   c  of the engagement hole  143  pushes the engagement element  135   a  and returns the switch block  135  to the forward initial position. Specifically, the inclined surface  143   c  of the engagement hole  143  serves as a cam face and pushes a cam follower in the form of the engagement element  135   a . The return plate  141  is a feature that corresponds to the “cam member” according to this invention. 
     The slide plate  131 , the switch block  135  and the return plate  141  of components of the idle driving prevention mechanism  130  are housed in the magazine body  121  and covered by a covering member  149  (see  FIG. 4 ). The covering member  149  is detachably fastened to the magazine body  121  by a plurality of screws  150 . Further, a rear end part of the switch block  135  protrudes outside the magazine body  121  and the protruding rear end surface faces the actuating element  139   a  of the electric switch  139 . An engagement part  149   a  for engagement with a hook  127   a  of the door lock  127  on the slide door  123  is provided on the covering member  149 . 
     The nailing machine  100  having the idle driving prevention mechanism  130  according to this embodiment is constructed as described above and the operation of the idle driving prevention mechanism  130  is shown step by step in  FIGS. 8 to 14 .  FIG. 8  shows an initial state in which a predetermined number of nails N remain in the magazine  105 . In this case, the slide plate  131  acted upon by the downward biasing force of the first spring  133  is placed in the downward position and the engagement element  135   a  of the switch block  135  is engaged with the slot  132 . The switch block  135  is held in the forward position and the electric switch  139  is in the off state, so that the nail driving operation of the nailing machine  100  is allowed. 
     When the nail driving operation is performed by the nailing machine  100 , the pusher  125  moves straight upward in order to feed the nails N to the driver guide  115 . When the number of nails N remaining in the magazine body  121  becomes fewer, the actuating protrusion  125   a  of the pusher  125  comes in contact with the passive part  131   a  of the slide plate  131 . When the number of remaining nails N decreases even further, the pusher  125  begins to pull the slide plate  131  straight upward. This state is shown in  FIG. 9 . 
     When the number of remaining nails N reaches the predetermined number, the slide plate  131  is further moved upward until the engagement element  135   a  of the switch block  135  is separated from the rear wall  132  of the slot  132  of the slide plate  131 , so that the engagement element  135   a  is disengaged from the slot  132 . This state is shown in  FIG. 10 . 
     When the engagement element  135   a  is disengaged from the slot  132 , the switch block  135  is moved straight rearward by the biasing force of the second spring  137 . By this movement, the rear end of the switch block  135  pushes the actuating element  139   a  of the electric switch  139  so that the electric switch  139  is switched from the off state to the on state. At this time, the engagement element  135   a  of the switch block  135  is opposed to both the inclined surface  143   c  of the engagement hole  143  of the return plate  141  and the lower surface of the rear wall  132   a  of the slot  132  of the slide plate  131  and spaced a predetermined distance from each of them. This state is shown in  FIG. 11 . 
     When the electric switch  139  is switched to the on state, the switching signal of the electric switch  139  is inputted to the controller for controlling the driving motor. When the switching signal of the electric switch  139  switched to the on state is inputted to the controller, the controller prevents energization of the driving motor. Therefore, even if the contact arm is pressed against the workpiece and the trigger  103   a  is depressed, the driving motor is not energized, so that the idle driving of the nails N is prevented. 
     When the number of remaining nails N in the magazine body  121  reaches the predetermined number, the user loads the nails N into the magazine body  12 . For this purpose, the user opens the magazine body  121  by releasing the door lock  127  and pulling out the slide door  123  downward. At this time, the stopper  147  is moved downward together with the slide door  123 , so that the return plate  141  is disengaged from the stopper  147 . Therefore, the return plate  141  is moved downward by the biasing force of the third spring  145  and the engagement element  135   a  of the switch block  135  is pushed by the inclined surface  143   c  of the engagement hole  143 . The switch block  135  with the engagement element  135   a  pushed by the inclined surface  143   c  is moved straight forward against the biasing force of the second spring  137 . At this time, although the biasing force of the first spring  133  is applied to the slide plate  131  to move it downward, the slide plate  131  is prevented from moving downward by the engagement element  135   a  which is held in contact with the lower surface of the rear wall  132   a  of the slot  132  during movement of the switch block  135 . This state is shown in  FIG. 12 . 
     The engagement element  135   a  of the switch block  135  is pushed by the inclined surface  143   c  of the engagement hole  143  until completion of the downward movement of the return plate  141 , so that the switch block  135  is returned to the initial forward position. At this time, the engagement element  135   a  passes the lower surface of the rear wall  132   a  of the slot  132  of the slide plate  131  and at the same time, it comes in contact with the front wall  132   b . This state is shown in  FIG. 13 . 
     Then the slide plate  131  no longer interferes with the engagement element  135   a  so that the slide plate  131  is pushed downward by the biasing force of the first spring  133 . As a result, the engagement element  135   a  is held engaged in the slot  132 . This state is shown in  FIG. 14 . 
     Thereafter, when the user loads nails N into the magazine body  121  and then pushes up and closes the slide door  123 , the return plate  141  is pushed up against the biasing force of the third spring  145  by the stopper  147  and returned to the initial position shown in  FIG. 8 . 
     As described above, in the idle driving prevention mechanism  130  of this embodiment, when the number of remaining nails N reach the predetermined number, the switch block  135  is no longer held by the slide plate  131 , so that the switch block  135  is moved rearward by the biasing force of the second spring  137  and the electric switch  139  is actuated (turned on). Therefore, after moved rearward, the switch block  135  is held in the rearward position by the second spring  137 , so that the occurrence of a malfunction of the switch block  135  is avoided. Thus, according to this embodiment, accuracy of the idle driving prevention mechanism  130  can be increased. 
     Further, according to this embodiment, the inclined surface  143   c  forming the cam face of the return plate  141  is utilized to return the switch block  135  from the rearward position or deactuating position in which the nails N are prevented from being driven, to the forward position or actuating position in which the nails N are allowed to be driven. With this construction, the returning movement of the switch block  135  from the rearward position to the forward position can be smoothly and rationally performed. 
     Further, according to this embodiment, the return plate  141  for returning the switch block  135  from the rearward position to the forward position is actuated in conjunction with the operation of loading (refilling) nails N into the magazine  105 . Specifically, when the slide door  123  is opened (pulled downward) in order to load nails N into the magazine body  121 , the return plate  141  is actuated in conjunction with opening of the slide door  123 . Therefore, advantageously and rationally, the idle driving prevention mechanism  130  can be held in the idle driving prevented state unless nails N are loaded, and it is not necessary to perform an additional operation for returning the switch block  135 . 
     Further, in this embodiment, the return plate  141  for returning the switch block  135  to the initial position or the actuating position is actuated in conjunction with the operation of opening the slide door  123 . As an alternative to this construction, a lever member which can be turned from outside, for example, by a manual operation may be formed on the magazine  105  and the lever member may be mechanically connected to the return plate  141  such that the return plate  141  can be actuated by turning the lever member. 
     Further, in this embodiment, the nailing machine  100  is explained as a representative example of the driving tool according to the present invention, but the present invention may be applied to other driving tools such as a tacker and a stapler. 
     In view of the above-described aspects of the invention, the following features may be provided. 
     (1) 
     “The driving tool, including a driving member which moves rectilinearly and drives a fastener into a workpiece, and a magazine which stores a number of fasteners and feeds the fasteners one by one onto a working axis of the driving member, comprising: 
     a driving tool actuation control member that can be switched between an actuating position to allow actuation of the driving tool and a deactuating position to prevent actuation of the driving tool, and is constantly biased toward the deactuating position from the actuating position side, and 
     a retaining member that can be engaged with the driving tool actuation control member and switched between a retaining position to retain the driving tool actuation control member in the actuating position by engagement with the driving tool actuation control member and a releasing position to release the driving tool actuation control member by disengagement from the driving tool actuation control member, wherein: 
     the retaining member is switched from the retaining position to the releasing position according to the number of remaining fasteners in the magazine, and when the retaining member is switched to the releasing position, the driving tool actuation control member is switched from the actuating position to the deactuating position, so that the driving tool can be held in a deactuated state.” 
     (2) 
     “The driving tool as defined in any one of claims  1  to  3 , comprising a motor for driving the driving member and an electric switch that can be switched between a power supply position in which power is supplied to the motor and a power shutoff position in which the power supply is shut off, wherein, when the driving tool actuation control member is placed in the deactuating position, the electric switch is switched to the power shutoff position.” 
     (3) 
     “The driving tool as defined in any one of claims  1  to  3 , wherein the driving tool actuation control member and the retaining member are housed in the magazine and a covering member is detachably mounted to the magazine and covers the driving tool actuation control member and the retaining member which are housed in the magazine.” 
     (4) 
     “The driving tool as defined in any one of claims  1  to  3 , wherein the switching movement of the driving tool actuation control member between the actuating position and the deactuating position is a rectilinear movement.” 
     (5) 
     “The driving tool as defined in (4), wherein the switching movement of the retaining member between the retaining position and the releasing position is a rectilinear movement, and directions of the switching movements of the retaining member and the driving tool actuation control member intersect with each other.” 
     DESCRIPTION OF NUMERALS 
     
         
           100  nailing machine (driving tool) 
           101  body 
           103  grip 
           103   a  trigger 
           105  magazine 
           107  body housing 
           109  motor housing 
           110  battery pack 
           115  driver guide 
           121  magazine body 
           123  slide door 
           125  pusher 
           125   a  actuating protrusion 
           127  door lock 
           127   a  hook 
           130  idle driving prevention mechanism 
           131  slide plate (retaining member) 
           131   a  passive part 
           132  slot 
           132   a  rear wall 
           132   b  front wall 
           133  first spring (biasing member) 
           135  switch block (driving tool actuation control member) 
           135   a  engagement element 
           137  second spring (biasing member) 
           139  electric switch 
           139   a  actuating element 
           141  return plate (cam) 
           143  engagement hole 
           143   a  rear surface 
           143   b  bottom surface 
           143   c  inclined surface (cam face) 
           145  third spring (biasing member) 
           147  stopper 
           149  covering member 
           149   a  engagement part 
           150  screw