Abstract:
The present application relates to a driving machine. The driving machine has a driver blade for striking a fastener and a nose portion having formed therein an injection passage which slidably guides the driver blade, and into which the fastener is fed to be injected therefrom. An injection hole from which the fastener is injected is specified at a leading end in an injecting direction of the injection passage. The injection hole is defined by a first guide portion and a second guide portion which is movable relative to the first guide portion so as to change a cross section, perpendicular to the injecting direction, of the injection hole. A positioning apparatus is provided to dispose the second guide portion at a plurality of positions relative to the first guide portion.

Description:
This application is a Continuation of U.S. application Ser. No. 12/209,394 filed on Sep. 12, 2008, now U.S. Pat. No. 8,123,096, which is based upon and claims a priority from prior Japanese Patent Application No. 2007-238020 filed on Sep. 13, 2007 and from prior Japanese Patent Application No. 2008-109287 filed on Apr. 18, 2008, the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a driving machine. 
     2. Description of the Related Art 
     Conventionally, a driving machine is known in which a fastener such as a nail is struck by a driver blade to drive the nail into lumber or the like. In this driving machine, the diver blade is driven by using compressed air, a fuel such as a gas, a motor, or the like as its power. In this driving machine, a fastener is supplied into an injection passage in which the driver blade slides, and the fastener in this injection passage is struck by the driver blade to drive out the fastener from an injection hole at a leading end of the injection passage. 
     In the driving machine which is adapted to drive out the nail in the injection hole by this driver blade, counteraction in the operation of the driver blade is produced in a main body portion of the driving machine, so that a phenomenon occurs in which the driving machine is operated in an opposite direction to the driving direction of the fastener. Due to this counteraction, torque in which a leading end portion of a nose portion forming the injection hole is moved forward is produced at the same time as the fastener is driven out from the injection hole. The nail in the injection passage can tilt due to this torque, in which case the nail is disadvantageously driven in this tilted state, resulting in faulty nailing finish. Particularly in the case of a nail having a small head diameter and a short shank length, since the angle of inclination of the nail in the injection hole becomes large, the tendency of the nail being driven in the tilted state becomes large. 
     To prevent this, as shown in JP-2004-330372-A, a structure is disclosed in which a guide member having an inside diameter conforming to the size of the fastener used is attached to a leading end of the nose portion, and the guide member is replaced depending on an application. In addition, as shown in JP-2004-330366-A, a structure is disclosed in which a rotatable guide member having an inclined surface defined thereon for guiding the leading end portion of the fastener to the center of the injection hole is disposed at a portion where the nose portion injection hole is formed. 
     With the structure in accordance with JP-2004-330372-A, the fastener can be suitably held so as to be capable of being driven in, and yet there have been problems in that the guide member is removed during the operation, and that the removed guide member can be lost. With the structure in accordance with JP-2004-330366-A, since the guide member is located on the sliding path of the driver blade, each time the fastener is driven in, the guide member is subjected to an impact force by the driver blade, so that it has been difficult to ensure the durability of the guide member. 
     SUMMARY OF THE INVENTION 
     Accordingly, an object of the invention is to provide a driving machine in which the fastener can be suitably held so as to be capable of being driven in, and in which the durability is improved. 
     To overcome the above-described problems, in accordance with the invention there is provided a driving machine including: a driver blade for striking a fastener; and a nose portion having formed therein an injection passage which slidably guides the driver blade, and into which the fastener is fed to be injected therefrom, wherein an injection hole from which the fastener is injected is specified at a leading end in an injecting direction of the injection passage, wherein the injection hole being defined by a first guide portion and a second guide portion which is movable relative to the first guide portion so as to change a cross section, perpendicular to the injecting direction, of the injection hole, and wherein a disposing means is provided to dispose the second guide portion at a plurality of positions relative to the first guide portion. In this driving machine, the disposing means preferably disposes the second guide portion at a position where the second guide portion does not interfere with the driver blade. 
     According to the above-described construction, it is possible to form the injection hole which is adapted to the size of the fastener to be driven in by changing the cross section of the injection hole. At this time, it is possible to prevent the abutment of the driver blade against the second guide portion. 
     In addition, preferably, a magazine incorporating a plurality of fasteners and adapted to supply the fasteners into the injection passage is connected to the nose portion, and the disposing means is constructed to reciprocatably move the second guide portion in a direction from the magazine toward the injection passage, and is constructed so as to make an area of the cross section small when the second guide portion has moved in the direction from the magazine toward the injection passage. 
     According to the above-described construction, the direction in which the fastener moves from the magazine into the injection passage and the moving direction of the second guide portion can be made to substantially coincide with each other. Accordingly, it is possible to make the area of the cross section small with a simple construction. 
     In addition, the second guide portion may be mounted rotatably about an axis which is perpendicular to the injecting direction and the direction from the magazine toward the injection passage, and the disposing means may be constructed by including a spring for rotatably urging the second guide portion so as to move the second guide portion in a direction in which the second guide portion is brought into close proximity with the first guide portion and to make the area of the cross section small and a restricting portion which abuts against the second guide portion to restrict a distance provided between the second guide portion and the first guide portion by the spring. 
     In addition, the second guide portion may have a held portion which extends in the direction from the magazine toward the injection passage, and the disposing means may be constructed by including a holding portion which is provided on one of the nose portion and the magazine and which is adapted to hold the held portion slidably in the direction from the magazine toward the injection passage and is capable of fixing the held portion at an arbitrary position. 
     According to each of the above-described constructions, it is possible to fix the second guide portion at a plurality of positions relative to the first guide portion. 
     According to the driving machine in accordance with the invention, the fastener can be suitably held so as to be capable of being driven in, and the durability improves. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention will be described in detail based on the following figures, wherein: 
         FIG. 1  is a cross-sectional view of a driving machine in accordance with a first embodiment of the invention; 
         FIG. 2  is a detailed cross-sectional view of a nose portion and its vicinities when a small nail is driven in by the driving machine in accordance with the first embodiment of the invention; 
         FIG. 3  is a cross-sectional view, taken in a direction perpendicular to an injecting direction, of the first guide portion and the second guide portion when the small nail is driven in by the driving machine in accordance with the first embodiment of the invention; 
         FIG. 4  is a detailed cross-sectional view of the nose portion and its vicinities when a large nail is driven in by the driving machine in accordance with the first embodiment of the invention; 
         FIG. 5  is a cross-sectional view, taken in the direction perpendicular to the injecting direction, of the first guide portion and the second guide portion when the large nail is driven in by the driving machine in accordance with the first embodiment of the invention; 
         FIGS. 6A to 6D  are diagrams in accordance with a modification of a cam of the driving machine in accordance with the first embodiment of the invention; 
         FIGS. 7A and 7B  are diagrams in accordance with a first modification using a change lever instead of the cam of the driving machine in accordance with the first embodiment of the invention; 
         FIGS. 8A and 8B  are diagrams in accordance with a second modification using a change lever instead of the cam of the driving machine in accordance with the first embodiment of the invention; 
         FIG. 9  is a cross-sectional view of the driving machine in accordance with a second embodiment of the invention; and 
         FIG. 10  is a detailed cross-sectional view of the nose portion and its vicinities of the driving machine in accordance with the second embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to  FIGS. 1 to 5 , a description will be given of a driving machine in accordance with an embodiment of the invention. A nailing machine  1  which is shown in  FIG. 1  and is a driving machine is a machine for driving in a nail  10  ( FIGS. 2 and 4 ) which is a fastener and uses compressed air as its power. 
     In the nailing machine  1 , a frame  2 , a handle  2 A located on one side of the frame  2 , and a nose portion located on a lower end of the frame  2  are provided integrally. To accumulate compressed air from an unillustrated compressor, an accumulation chamber  2   a  is formed in the handle  2 A and the frame  2  of the nailing machine  1 . The accumulation chamber  2   a  is connected to the compressor through an unillustrated air hose. 
     A cylinder  5  having a hollow cylindrical shape is provided within the frame  2 , a piston  4 A is provided in the cylinder  5  so as to be vertically slidable, and a driver blade  4 B is formed integrally with the piston  4 A. The direction in which this driver blade  4 B moves together with the piston  4 A is defined as an injecting direction. 
     A return air chamber  5   a  for accumulating compressed air for returning the driver blade  4 B to a top dead center is formed in an outer periphery of a lower end of the cylinder  5 . A check valve  5 A is provided in an axially central portion of the cylinder  5 , and an air passage  5   b  for circulating the air in only one direction from inside the cylinder  5  to the return air chamber  5   a  outside the cylinder  5 . In addition, an air passage  5   c  which is always open to the return air chamber  5   a  is formed below the cylinder  5 . In addition, a piston valve  6  for absorbing surplus energy of the piston  4 A after the driving in of the nail  10  is provided at a lower end of the cylinder  5 . 
     The following are provided, among others, in a proximal portion of the handle  2 A: a trigger  12  which is operated by an operator; an arm plate  13  which is rotatably fitted to the trigger  12 ; a push lever  14  which protrudes from a lower end of the nose portion  3 , extends to a vicinity of the arm plate  13 , and is movable along the nose portion  3  by being urged from the frame  2  toward the nose portion  3  side; a trigger valve portion  15  which is a changeover valve communicating with a below-described main valve  42  and adapted to supply and exhaust the compressed air; and a plunger  16  for transmitting the operation of the arm plate  13  to the trigger valve portion  15 . 
     As is well known, when the pulling operation of the trigger  12  and the pushing operation of the push lever  14  against a nailed member are carried out, the plunger  16  of the trigger valve portion  15  is arranged to be pushed upward by a link mechanism of the arm plate  13  and the trigger  12 . 
     The following are provided, among others, on an outer periphery of the upper side of the cylinder  5 : the main valve  42 ; a main valve chamber  43  for accommodating the main valve  42 , a main valve spring  44  for urging the main valve  42  toward a lower dead point side; and an exhaust rubber  46  which is disposed on an upper side of the cylinder  5  and shuts off an air passage  45  for exhausting the compressed air in an upper chamber of the piston  4 A of the cylinder  5  by its abutment against the main valve  42 . In addition, the air passage  45  communicates with the atmosphere through an unillustrated exhaust port provided in an upper portion of the frame  2 . 
     As shown in  FIG. 2 , the nose portion  3  is constructed by including a first guide portion  31  which is located at a lower end of the frame  2  and extends in a parallel direction to the sliding direction of the driver blade  4 B. A magazine unit  21  which incorporates a bundle of nails  10  which are bundled and coupled together is provided on a side (right side in  FIG. 3 ) corresponding to an opening of a substantially U-shaped cross-sectional portion of a below-described injection passage  31   a  of the nose portion  3 . 
     The first guide portion  31  is fixed to the frame  2  by an unillustrated bolt, and the injection passage  31  which serves as a portion where the driver blade  4 B slides and is a portion into which the nail  10  is fed from a below-described magazine  22 . As shown in  FIG. 3 , this injection passage  31   a  is constructed such that its cross section perpendicular to the injecting direction of the driver blade  4 B is substantially U-shaped, and this substantially U-shaped opening portion is oriented from the first guide portion  31  toward the below-described magazine  22  side ( FIG. 2 ). In addition, at a leading end position in the injecting direction of the first guide portion  31 , a pair of abutting surfaces  31 A, which are adapted to be abutted against a below-described second guide portion  32 , are respectively specified at positions corresponding to end faces of leg portions of the substantially U-shaped portion, as shown in  FIG. 3 . Further, an injection hole  31   b , through which the nail  10  is injected, is specified at a position corresponding to an endmost portion of the injection passage  31   a , as shown in  FIG. 2 . 
     The second guide portion  32 , which is pivotally supported by a rotating shaft portion  33 , is provided at the leading end position of the first guide portion  31 , i.e., at a portion corresponding to the opening-side position of the substantially U-shaped portion. The rotating shaft portion  33  which pivotally supports this second guide portion  32  is provided in the magazine  22 , and its rotating shaft extends in a direction substantially perpendicular to the injecting direction and the direction in which the substantially U-shaped portion is open (direction oriented from the first guide portion  31  toward the below-described magazine  22 ). 
     The second guide portion  32  is constructed in a substantially L-shape by a guide portion  32 A defining the injection hole  31   b  in cooperation with the first guide portion  31  as well as an abutment portion  32 B abutting against a cam  34  and a spring  35  which will be described later, and is pivotally supported by the rotating shaft portion  33  at a connecting portion of this L-shape. 
     As shown in  FIG. 3 , a guide surface  32 C, which defines the injection hole  31   b  ( FIG. 2 ) and the injection passage  31   a  in cooperation with an inner surface of the first guide portion  31 , is formed in the guide portion  32 A. As shown in  FIG. 3 , the guide surface  32 C in its cross section perpendicular to the injecting direction is constructed in a curved shape in the same way as the curved portion of the substantially U-shape of the first guide portion  31 . In addition, a pair of surfaces  32 D to be abutted against, against which the abutting surfaces  31 A are abutted, are provided at a position located in close proximity to the guide surface  32 C, i.e., at positions opposing the respective abutting surfaces  31 A. As shown in  FIG. 3 , the guide surface  32 C and the surfaces  32 D to be abutted against are constructed such that when the abutting surfaces  31 A are abutted against the surfaces  32 D to be abutted against, the injection hole  31   b  defined by the guide surface  32 C and the inner peripheral surface of the first guide portion  31  does not interfere with the driver blade  43 . By virtue of this construction, when the driver blade  4 B is driven, the driver blade  4 B and the second guide portion  32  are prevented from abutting against each other, thereby making it possible to increase the durability of the nailing machine  1 . 
     The abutment portion  32 B is urged downward by the spring  35 . Accordingly, the second guide portion  32  is urged clockwise in the plane of the drawing in  FIG. 2 , i.e., such that the guide surface  32 C enters the substantially U-shaped interior of the first guide portion  31 , and the abutting surfaces  31 A abut against the surfaces  32 D to be abutted against. In addition, the cam  34  is provided at a position opposite to the spring  35  with the abutment portion  32 B located therebetween. The cam  34  is constructed such that its outer periphery is formed in a semicircular shape by a circular arc-shaped cam surface  34 A and a planar cutoff surface  34 B, and the cam  34  abuts against an opposite surface of the abutment portion  32 B to its surface against which the spring  35  abuts. Since the distance from the rotating shaft portion  33  to the cam  34  is greater than the distance from the rotating shaft portion  33  to the spring  35 , the spring  35  can be easily compressed on the basis of the principle of the lever by rotating the cam  34  to move the abutment portion  32 B upward. In addition, the distance from the rotating shaft portion  33  to the guide portion  32 A is substantially equal to the distance from the rotating shaft portion  33  to the spring  35 . A disposing means for disposing the second guide portion  32  at a plurality of positions with respect to the first guide portion  31  is formed by the cam  34 , the spring  35 , and the abutting surfaces  31 A. 
     As the cam  34  is rotated from the state shown in  FIG. 2 , the cam surface  34 A abuts against the abutment portion  32 B, so that the abutment portion  32 B moves counterclockwise in the plane of the drawing against the urging force of the spring  35 , as shown in  FIG. 4 . In conjunction with this movement of the abutment portion  32 B, the guide portion  32 A moves so as to be spaced apart from the first guide portion  31 , and the area of the cross section of the injection hole  31   b  becomes large. In addition, a contact member  14 A, which is formed continuously from the push lever  14  and is capable of abutting against the nailed member, is provided at a leading end in the injecting direction of the nose portion  3 , i.e., at a peripheral position of the first guide portion  31  and the guide portion  32 A. 
     The magazine unit  21  is provided with the magazine for loading the nails  10  therein and a nail feeder  23  for consecutively feeding into the injection passage  31   a  the nails  10  loaded in the magazine  22 . According to such a construction, the direction in which the nail  10  moves from the magazine  22  into the injection passage  31   a  and the direction of movement of the guide portion  32 A in the second guide portion  32  can be made to substantially coincide with each other. Hence, it is possible to change the area of the injection hole  31   b  by a simple construction. 
     In the case where the nail  10  is struck by the nailing machine  1  having the above-described construction, counteraction in the operation of the driver blade  43  is produced in the nailing machine  1 , so that a phenomenon occurs in which the nailing machine  1  is operated in an opposite direction to the injection direction. Due to this counteraction, torque in which the leading end portion of the nose portion  3  is moved forward (in the direction oriented from the magazine unit  21  toward the nose portion  3 ) is produced at the same time as the nail  10  is driven out from the injection hole  31   b . The head of the nail  10  can tilt due to this torque, coupled with the forward movement of the leading end portion of the nose portion  3 . Accordingly, in the case where the nail  10  is a small nail, the cam  34  is rotates to a position at which the cutoff surface  34 B opposes the abutment portion  32 B to set the cam surface  34 A in a state of non-abutment with the abutment portion  32 B, as shown in  FIG. 2 , and the abutting surfaces  31 A are abutted against the surfaces  32 D to be abutted against, as shown in  FIG. 3 , to thereby bring the guide surface  32 C into close vicinity of the inner surface of the first guide portion  31  and reduce the cross-sectional area of the injection hole  31   b . By adopting such a shape, it is possible to reduce the angle of inclination of the nail  10  in the vicinity of the leading end of the injection passage  31   a  at the time of driving in the nail  10  having a small head and a short shank length, so that the nail  10  is prevented from being driven in with its head tilted forward, thereby making it possible to prevent faulty finish. 
     On the other hand, in a case where a large nail  10  is driven in, if the cross-sectional area of the injection hole  31   b  remains small, the nail head can strike against the guide surface  32 C during the injection of the nail  10 , possibly causing damage to the surface of the guide surface  32 C. If damage is caused to the guide surface  32 C, when the nail  10  is guided to the injection hole  21   b  by being slid on the guide surface  32 C, the leading end portion of the nail  10  can possibly be caught at the damaged portion of the guide surface  32 C. Accordingly, as shown in  FIG. 4 , the cam  34  is operated to rotate so that the cam surface  34 A abuts against the abutment portion  32 B to move the abutment portion  32 B against the urging force of the spring  35 , thereby enlarging the cross-sectional area of the injection passage  31   a  and widening the injection hole  31   b , as shown in  FIG. 5 . In this state, the center (the center of the driver blade  4 B in  FIG. 5 ) of the cross section of the driver blade  4 B perpendicular to its sliding direction is set in a state of being offset from the center of the widened injection hole  31   b . Consequently, in a case where a large nail  10  is used, the occurrence of damage due to the abutment of the nail head against the guide surface  32 C is suppressed, thereby making it possible to maintain a stable supply of nails. 
     In the first embodiment, in the cam  34 , the position of the guide portion  32 A of the second guide portion  32  is specified to two locations including a position located in close proximity to the first guide portion  31  and a position spaced apart therefrom. However, the invention is not limited to the same, and the position of the guide portion  32 A of the second guide portion  32  may be specified to a plurality of locations by using a cam  134  such as the one shown in  FIG. 6A . Specifically, the cam  134  is provided with, in addition to a cam surface  134 D, a first cutoff surface  134 A, a second cutoff surface  134 B, and a third cutoff surface  1340  which are three surfaces whose distances from a center axis G of rotation are different. As shown in  FIGS. 6A to 6D , the position of the guide portion  32 A can be restricted to four locations by changing over the top face (the portion abutting against the abutment portion  32 B) served by each of these three surfaces  134 A to  134 C and the cam surface  134 D. 
     In addition, as shown in  FIGS. 7A and 7B , the positional specification of the abutment portion  32 B may be effected by using a change lever  234  instead of the cam. Specifically, in the magazine  22 , a pin  234 A is disposed at a position located in close proximity to the abutment portion  32 B, the pin  234 A being movable in a direction substantially perpendicular to each of the injecting direction and the direction in which the substantially U-shaped portion is open (direction oriented from the first guide portion  31  toward the below-described magazine  22 ). A notch  234   a  is formed in an outer peripheral portion of the pin  234 A, and an inclined surface  234 B continuing from the outer periphery of the pin  234 A is provided on the inner surface of the notch  234   a.    
     When the notch  234   a  of the change lever  234  is located at an engaging position ( FIG. 7A ), the abutment portion  32 B enters the notch  234   a  by being urged by the spring  35 , and in this state the guide portion  32 A is in close proximity to the first guide portion  31 . If the change lever  234  is moved from this state, the inclined surface  234 B abuts against an inclined surface formed at a corner of the abutment portion  32 B, and the abutment portion  32 B moves from inside the notch  234   a  to an outer peripheral portion of the pin  234 A in opposition to the urging force of the spring  35  ( FIG. 7B ). In this state, the guide portion  32 A is in a state of being spaced apart from the first guide portion  31 . 
     In addition, as shown in  FIGS. 8A and 8B , it is possible to adopt a construction in which a change lever  334  is adapted to slide in the urging direction of the spring  35 . This change lever  334  consists of a pin  334 A abutting against the abutment portion  32 B as well as a pair of arm portions  334 B respectively provided at both end portions of the pin  334 A and grasping portions of the magazine  22 . A ball  334 C which is urged toward the magazine  22  and a spring  334 D for urging the ball  334 C are provided in this arm portion  334 B. The arrangement provided is such that as this ball  334 C is fitted in one of a plurality of recessed portions  22   a  formed in the magazine  22 , the position of the abutment portion  32 B can be restricted. 
     Although in the first embodiment the shape of the injection passage is changed by rotating the second guide portion, the invention is not limited to the same. For example, it is possible to adopt a construction in which the second guide portion is moved so as to be brought into close proximity with or to be spaced apart from the first guide portion. Specifically, the second guide portion is provided with a held portion which extends in the direction from the magazine toward the injection passage. Meanwhile, the nose portion or the magazine is provided with a holding portion which is adapted to hold the held portion slidably in the direction from the magazine toward the injection passage and is capable of fixing the held portion at an arbitrary position. By adopting such a construction, the second guide portion becomes capable of moving in the direction from the magazine toward the injection passage, so that the second guide member can be brought into close proximity with or spaced apart from the first guide portion and can be fixed at a predetermined position. 
     Next, referring to  FIGS. 9 and 10 , a description will be given of the driving machine in accordance with a second embodiment of the invention. A nailing machine  401  shown in  FIG. 10  is constructed in substantially the same way as the nailing machine  1  of the first embodiment except for a nose portion  403 . Therefore, as for the construction except for the nose portion  403 ,  400  will be added to the reference numerals of the nailing machine  1 , and a description thereof will be omitted. 
     The nose portion  403  is constructed by including a first guide portion  431  which is located at a lower end of a frame  402  and extends in a parallel direction to the sliding direction of a driver blade  404 B. The first guide portion  431  is constructed by including a main trunk portion  432  and an auxiliary trunk portion  433 . 
     The main trunk portion  432  is fixed to the frame  402  by an unillustrated bolt, and a main injection passage  432   a , which is a portion where the driver blade  404 B slides and a portion to which the nails are fed from a magazine  422 , is formed therein. In the same way as the injection passage  31  of the first embodiment, this main injection passage  432   a  is formed at the position where its cross section perpendicular to the injecting direction of the driver blade  404 B is substantially U-shaped. 
     The auxiliary trunk portion  433  is disposed on the leading end side of the main trunk portion  432 , i.e., at a distal endmost position of the nailing machine  401 , and is constructed to be movable in a parallel direction to the sliding direction of the driver blade  404 B with respect to the main trunk portion  432 . Further, the auxiliary trunk portion  433  is connected to a push lever  414 . Accordingly, as the auxiliary trunk portion  433  is moved (moved upward in the plane of the drawing of  FIG. 9 ) so as to be brought into close proximity with the main trunk portion  432 , the push lever  414  is pushed upward, so that a plunger  416  can be operated on the basis of the operation of this push lever  414 . 
     The auxiliary trunk portion  433  is constructed with a substantially U-shaped cross section in the same way as the main trunk portion  432 , and an auxiliary injection passage  433   a  communicating with the main injection passage  432   a  is formed at this substantially U-shaped portion. An injection hole  433   b  from which the nail is injected is specified at the position corresponding to the endmost portion of the auxiliary injection passage  433   a . Accordingly, the nail fed into the main injection passage  432   a  is struck by the driver blade  404 B, passes through the main injection passage  432   a  and the auxiliary injection passage  433   a , and is injected from the injection hole  433   b . As for the portion of the auxiliary trunk portion  433  in proximity to the injection hole  433   b , a structure is adopted which is substantially equivalent to the structure (structure of the abutting surfaces  31 A and the like) in proximity to the injection hole  31   a  of the first guide portion  31  in the first embodiment. 
     The endmost portion which defines the injection hole  433   b  in the auxiliary trunk portion  433  serves as the portion which abuts against a nailed member. Accordingly, as the nailing machine  401  is pressed by applying the endmost portion of the auxiliary trunk portion  433  to the nailed member, the plunger  416  is pushed upward, making it possible to effect nailing. Since the leading end portion of the auxiliary trunk portion  433  only defines the injection hole  433   b , the leading end portion of the auxiliary trunk portion  433  is constructed more slenderly than the leading end portion of the nailing machine  1  in accordance with the first embodiment. Hence, as compared with the nailing machine  1  in accordance with the first embodiment, the leading end of the nailing machine  401  can be suitably applied even to a narrower portion of the nailed member, so that the operation can be suitably performed. 
     In addition, the auxiliary trunk portion  433  is provided with a plate  434  which extends in a direction from the auxiliary trunk portion  433  toward the main trunk portion  432  and in a direction from the auxiliary trunk portion  433  toward the magazine  22  and is disposed in parallel to the injecting direction. A second guide portion  435 , which is pivotally supported by a rotating shaft portion  436 , is provided at a portion corresponding to the opening-side position of the substantially U-shaped portion of the plate  434 . The rotational axis of the rotating shaft portion  436  which pivotally supports this second guide portion  435  extends in a direction which is substantially perpendicular to each of the injecting direction and the direction in which the substantially U-shaped portion is open. 
     The second guide portion  435  is constructed by a guide portion  435 A defining the injection hole  433   b  in cooperation with the auxiliary trunk portion  433  as well as an abutment portion  435 B abutting against a cam  437  and a spring  438  which will be described later, and is pivotally supported by the rotating shaft portion  436  at its substantially intermediate portion between the guide portion  435 A and the abutment portion  435 B. 
     In the guide portion  435 A, a construction (the guide surface  32 C, the surfaces  32 D to be abutted against, etc.) which is similar to that of the guide portion  32 A of the first embodiment is adopted. Accordingly, the construction provided is such that the injection hole  433   b  defined by the second guide portion  435  and the auxiliary trunk portion  433  does not interfere with the driver blade  404 B. By virtue of this construction, when the driver blade  404 B is driven, the driver blade  404 B and the second guide portion  435  are prevented from abutting against each other, thereby making it possible to increase the durability of the nailing machine  401 . 
     As the abutment portion  435 B is urged by the spring  438 , the second guide portion  435  is urged clockwise in the plane of the drawing in the same way as the second guide portion  32  of the first embodiment. In addition, the cam  437  is provided at a position opposite to the spring  438  with the abutment portion  435 B located therebetween. The cam  437  is provided with a cam surface  437 A and a planar cutoff surface  437 B, and a construction equivalent to that of the cam  34  in accordance with the first embodiment is adopted. Accordingly, by rotating the cam  437 , the spring  438  can be easily compressed to rotate the second guide portion  435  counterclockwise, such that the guide portion  435 A moves so as to be spaced apart from the auxiliary trunk portion  433 , thereby making it possible to enlarge the area of the cross section of the injection hole  433   b . Hence, in the same way as the nailing machine  1  in accordance with the invention, the size of the injection hole  433   b  can be changed in correspondence with the size of the nail to be driven in, thereby making it possible to maintain a stable supply of nails. 
     It should be noted that it goes without saying that, also in the above-described nailing machine  401  in accordance with the second embodiment, it is possible to adopt modifications of the cam which are similar to those of the first embodiment. 
     The driving machine in accordance with the invention is not limited to the foregoing embodiments, and various modifications and changes are possible within the range defined by the claims of the invention. For example, although in the above-described embodiments reference have been given to the pneumatic nailing machine, the invention is also applicable to such as a combustion-type driving machine using fuel and an electrically operated driving machine using a motor or the like.