WO2008032861A1

WO2008032861A1 - Fastener driving machine

Info

Publication number: WO2008032861A1
Application number: PCT/JP2007/068220
Authority: WO
Inventors: Masashi Nishida; Yoshinori Ishizawa
Original assignee: Hitachi Koki Co., Ltd.
Priority date: 2006-09-12
Filing date: 2007-09-12
Publication date: 2008-03-20
Also published as: TW200902255A; JP4761257B2; JP2008068329A; TWI379745B

Abstract

In a fastener driving machine (1) including a fastener blank striking preventive mechanism, the middle portion (52c) of a lock arm (52) held by a nose portion (3) or by a magazine portion (5) is supported so as to be rotatable with respect to a support shaft (53) which is provided in the nose portion (3) or magazine portion (5), and the middle portion (52c) is supported such that it can also rotate in the direction of a nose injection hole (3a) while it is spaced from the support shaft (53).

Description

DESCRIPTION

FASTENER DRIVING MACHINE

Technical Field

The present invention relates to a faster driving machine which strikes a fastener such as a nail, a rivet and a staple into a work and, specifically, the invention relates to a fastener driving machine which includes a fastener blank striking preventive mechanism.

Background Art

Generally, in a drive mechanism which is provided in a main body of a driving machine of a pneumatic type or a combustion type and is used to apply a reciprocating movement to a driver blade for striking a fastener such as a nail, rivet or a staple into a work, there is used a piston which can be reciprocated within a cylinder; and, on the end portion of the cylinder, there is provided a impact easing bumper which is used to absorb the excess energy of the driver blade after the fastener is struck. Similarly, in the main body of a driving machine of an electric type in which the rotation drive force of a flywheel to be driven by an electric motor is converted to a linear drive force and is transmitted a driver blade, in the end portion of the reciprocating passage of a driver, there is provided an impact easing bumper.

These fastener driving machines are respectively structured such that a magazine with a large number of connected fasteners loaded therein is engaged with a nose portion mounted on the main body of the driving machine, fasteners are sequentially supplied to the nose portion, and they are sequentially struck into the work using the reciprocatingmotion of the driver blade . Also, the drive mechanism of the driving machine main body for applying the striking reciprocating movement is structured such that the drive mechanism of the driver blade can be activated by the operation of a mechanical link mechanism based on an interlinking operation including the pressing operation of a push lever and the pulling operation of a trigger lever, orbythe operationof an AND gate electric circuit based on the operation of these two levers. Therefore, when, in a state where the fasteners are not loaded in the nose portion, by pressing the push lever or the like, the driver blade is driven for blank striking, an excessively large impact is applied to the impact easing bumper and the like disposed within the cylinder or the like to thereby lower the durability of the driving machine main body or damage the driving machine main body or the nose portion. It is disclosed by, for example JP-A-8-141933 , that a driving machine includes a blank striking preventive mechanism. This type of blank striking preventive mechanism is structured such that, when the amount of fasteners loaded in a connected state into the magazine reduced down to a given amount or less and a feeder provided within the magazine is moved forward to a given position, a lock arm to be moved by a feeder engaging portion provided in the feeder prevents the movement of the push lever to thereby stop the activation of the drive mechanism of the driver blade.

Disclosure of Invention

However, while examining the blank striking mechanism of the conventional fastener driving machine, the present inventors have found the following problems .

That is, in the normal operation, when the remaining amount of the connected fasteners loaded into the magazine becomes a given amount (a set remaining amount) and the feeder is thereby moved up to a given position within the magazine, the feeder engaging portion formed in the feeder is pressed against one end portion of the lock arm, and the other end of the lock arm is engaged with the engaging portion of the push lever to thereby prevent the pressing movement of the push lever. This prevents the driver blade from activating its striking operation. That is, when the remaining amount of the connected fasteners (for example, nails) loaded into the magazine is reduced down to a given amount (for example, four) , since the other end portion of the lock arm is engaged with the engaging portion of the push lever as a stopper to stop the movement of the push lever, the pushing operation of the push lever is impossible, thereby preventing the driver blade from activating its striking operation.

However, although not enforced as the operation method of the driving machine generally, when enforcing a so called push lever pressed-type striking operation in which, while the push lever is pressed against the work carelessly, only the trigger lever is pulled successively to carry out the driver blade striking operations successively, a given amount of remaining fasteners or less cannot be pressed longer to the correct positions of the nose injection hole by the feeder. As a result of this, a given amount of remaining fasteners or less are present at unstable positions between the feeder and nose injection hole within the magazine and, when the driver blade is struck against the nose injection hole in this state, the nose portion can be clogged with the fasteners such as nails, or the fasteners can damage the nose portion.

Also, the engagement between the other end portion of the lock arm and push lever just after the remaining fasteners within the magazine are reduced down to the above given amount (set amount) is attained in a thin or weak state. When the push lever is pressed against a next work in this state, the weak engagement between the lock arm and push lever can be removed due to an impact or the like which is generated when the push lever is pressed against the work. When, in this state, the trigger lever is pulled and the driver blade is struck against the nose injection hole, similarly to the above-mentioned push lever pressed-type striking operation, the nails or the like can clog the nose portion, or the fasteners can damage the nose portion.

Thus, it is an object of the invention to provide a fastener driving machine including a fastener blank striking mechanism which can prevent the nose portion from being clogged with a given amount of remaining fasteners or less and can prevent such fasteners from damaging the nose portion.

It is another object of the invention to provide a fastener driving machine in which a blank striking preventive mechanism is enhanced in reliability and durability. In attaining the above objects, according to the present patent application, there are disclosed several aspects of the invention; and, the summaries of the representative ones of these aspects are as follows . Specifically, according to one aspect of the invention, there is provided a fastener driving machine which comprises : a driving machine main body including a driver blade for striking a fastener and a drive mechanism for applying a reciprocating movement to the driver blade; a nose portion including a nose injection hole into which the fastener is supplied; a magazine portion engaged with the nose portion and extending in a direction intersecting the extending direction of the nose injection hole, including a feeder pressing a plurality of connected fasteners into the nose injection hole; a push lever movable parallel to the extending direction of the nose injection hole between a forward position and a backward position; a trigger lever operable in cooperative with a pressing operation of the push lever to the backward position, for controlling an activation of the drive mechanism of the driving machine main body; Characterized in that the fastener driving machine has a blank striking preventive mechanism comprising; a lock arm extending from one end portion to the other end portion and including a middle portion interposed between the two end portions, the middle portion ratably supported by a shaft provided on the nose portion or on the magazine portion in such a manner that it can be spaced from the support shaft and can be moved in the nose injection hole direction, a feeder engaging portion formed in the feeder such that, when the amount of remaining fasteners loaded into the magazine portion is reduced down to a given amount or less, the feeder engaging portion presses the one end portion of the lock arm; and, a push lever engaging portion formed in the push lever such that, when the one end portion of the lock arm is pressed, the push lever engages with the other end portion of the lock arm.

According to another aspect of the invention, in the above fastener driving machine, the middle portion of the lock arm includes a rotation hole portion or a rotation slit portion larger in size than the diameter of the support shaft, and is supported by the support shaft in the rotation hole portion or the rotation slit portion . According to still another aspect of the invention, in the forward position of the push lever, the amount of remaining fasteners is reduced down to the given amount and the feeder engaging portion presses the one end portion of the lock arm, by rotating the lock arm with the support shaft as a fulcrum, the other end portion of the lock arm is engaged with the push lever engaging portion to thereby stop the movement of the push lever from the forward position to the backward position, and wherein, when, in the backward position of the push lever, the amount of remaining fasteners loaded into the magazine portion is reduced down to the given amount and the feeder engaging portion presses the one end portion of the lock arm, by allowing the push lever engaging portion to function as a support portion for supporting the other end portion of the lock arm, the middle portion of the lock arm is spaced from the support shaft and is moved in the nose injection hole direction.

According to the blank striking preventive mechanism of the invention, since the middle portion of the lock arm held by the nose portion or by the magazine portion is supported not only in such a manner that it can be rotated with respect to a support shaft provided in the nose portion or in the magazine portion but also in such a manner that it can be spaced from the support shaft and can be moved in the direction of the nose injection hole, when the push lever engaging portion is allowed to function as a support portion for supporting the other end portion of the lock arm, one end portion of the lock arm can separate the middle portion of the lock arm from the support shaft and move it in the nose injection hole direction. Owing to this, even when the amount of fasteners remaining in the magazine is reduced down to a given amount or less, the feeding portion of the feeder is able to press the fasteners. Accordingly, a given amount of remaining fasteners or less are not present at unstable positions in a space between the feeder and nose injection hole within the magazine, but they are always pressed to proper positions within the nose injection hole; and, in this state, when the driver blade is struck against the nose injection hole, there can be avoided the problem that the nose portion can be clogged with the fasteners such as nails and the fasteners can damage the nose portion. Therefore, the blank striking preventive mechanism can be enhanced in reliability and durability.

The above-mentioned and other objects of the invention as well as the above-mentioned and other aspects of the invention can be understood more obviously from the following description of the present specification as well as from the accompanying drawings.

Brief Description of the Drawings

Fig. 1 is a front view of the whole of a fastener driving machine according to an embodiment of the invention. Fig. 2 is a back view of the whole of the fastener driving machine shown in Fig. 1.

Fig. 3 is a side view of the main portions of the fastener driving machine shown in Fig. 1 (in the initial state thereof), when viewed from the A-A line shown in Fig. 1.

Figs . 4A and 4B are front views of a lock arm member used in the fastener driving machine shown in Fig. 1.

Fig. 5 is a back view of the whole of the fastener driving machine shown in Fig. 1, showing its normal striking state.

Fig. 6 is a back view of the whole of the fastener driving machine shown in Fig. 1 before a push lever is pressed . Fig. 7 is a back view of the whole of the fastener driving machine shown in Fig. 1 after the push lever is pressed .

Fig. 8 is a side view of the main portions of the fastener driving machine shown in Fig. 1 (when the amount of remaining nails is 0) , when viewed from the A-A line shown in Fig . 1.

Fig. 9 is a side view of the main portions of the fastener driving machine shown in Fig. 1 (when the amount of remaining nails is 5) , when viewed from the A-A line shown in Fig. 1. Fig. 10 is a side view of the main portions of the fastener driving machine shown in Fig. 1 (when the amount of remaining nails is 4) , when viewed from the A-A line shown in Fig . 1. Fig. 11 is a side view of the main portions of the fastener driving machine shown in Fig. 1 (in the case of a pressed-type striking operation with the amount of remaining nails being 4) , when viewed from the A-A line shown in Fig . 1. Fig. 12 is a side view of the main portions of the fastener driving machine shown in Fig. 1 (in the case of a pressed-type striking operation with the amount of remaining nails being 4 ~ 0), when viewed from the A-A line shown in Fig. 1.

Best Mode for Carrying Out the Invention

Now, description will be given below of an embodiment in which the invention is applied to a nail driving machine of a compressed air type, with reference to the accompanying drawings. In all figures used to explain the embodiment, parts having the same function are given the same designations and the repeated description thereof will be omitted. Also, in the following description relating to the nail driving machine according to the invention, in a state where a direction for a fastener such as a nail to be struck by the nail driving machine is set in the horizontal direction, for convenience's sake, the direction where the fastener is struck is expressed as "a left direction or a right direction", but it is not limited to a specific embodiment or a specific intention. When the direction where the fastener is struck is set in the vertical direction, the direction can be explained as "downward or lower portion", and, its opposite direction can be explained as "upward or upper portion". Such way of expression does not limit the subject matter of the invention at all.

Fig. 1 is a front view (including sections in part) of the whole of a nail driving machine according to the present embodiment of the invention. Fig. 2 is a whole back view (external view) of a nail driving machine according to the embodiment shown in Fig. 1 and, in Fig. 2, the nail striking direction is shown as the direction (the right direction) which goes from the left side to the right side of Fig. 2, oppositely to the direction (left direction) shown in Fig. 1 which goes from the right side to the left side.

[Whole Structure of Nail Driving machine] The nail driving machine 1 includes a nail driving machine main body 2 and a nose assembly part 4 composed of a nose portion 3 and a magazine portion 5. The nail driving machine main body 2 is enclosed by a housing 9; and, the housing 9 is composed of a portion for enclosing the drive mechanism of a driver blade 11 including a cylinder 6, a piston 7 and the like, and a portion not only for constituting a handle portion 8 for gripping the nail driving machine 1 but also for constituting a portion of a pressure storage chamber 14.

On one end portion (lower end portion) of the handle portion 8, there is disposed an air plug 10 and, on the air plug 10, there is placed a dust cap 12 for prevention of entrance of dust. When operating the nail driving machine main body 2, the dust cap 12 is removed and an air hose from a compressor (not shown) is connected to the air plug 10 to thereby supply compressed air. Also, the nose portion 3 of the nose assembly part 4 is disposed on one end portion of the nail driving machine main body 2, while one end of the magazine portion of the nose assembly part 4 is mounted on the handle portion 8 of the nail driving machine main body 2 by a fastening member (bolt and nut) 13.

The compressed air, which is used as the drive source of the piston 7, is stored through the air plug 10 into the pressure storage chamber 14 formed within the nail driving machine main body 2. Within the nail driving machine main body 2, there is disposed the cylinder 6 and, within the cylinder 6, there is disposed the piston 7 which can be reciprocated in the right and left directions. The piston 7 includes the driver blade 11 mounted on the left surface (nose portion 3 side) thereof integrally with the piston 7. The leading end of the driver blade 11 is used to strike sequentially the heads of connected nails (fasteners) 15 that are loaded from the magazine portion 5 into the nose portion 3.

As shown in Fig .1, in the left portion of the cylinder 6, there is formed a nose injection hole 3a which is used to guide the driver blade 11 when the driver blade 11 is moved in the axially left direction (bottom dead center side) together with the piston 7; and, from the nose injection hole 3a, there is struck out a nail 15 to a work (not shown) such as a timber . On the outer peripheral portion of the piston 7, in order to seal the piston 7, there is mounted a well-known O ring 7a which is made of flexible material such as rubber.

On the right side (top dead center side) of the cylinder 6, there is stored a head valve (main valve) 16 made of flexible material in such a manner that it is disposed on the inner wall surface of the separation portion 9a of the housing 9 and can be slided in the right and left directions (vertical direction) . Theheadvalve 16 is energized toward its left dead center side (bottom dead center side) not only by the pressing force of a head valve. spring 16a but also by the pressing force of compressed air having flown into a head valve control passage (not shown) communicating with a trigger valve 17.

An operation part, which is to be operated by an operator, includes a trigger lever 18, an arm plate 19 rotatably mounted on the trigger lever 18, and a push lever 20 projecting from the leading end of the nose injection hole 3a and extending up to the vicinity of the arm plate 19 in such a manner that it can be engaged with the arm plate 19; and, in linking with the pressing operation of the push lever 20, the trigger lever 18 can be operated. That is, the opening and closing of the trigger valve 17 is controlled through the operation of the trigger lever 18 which can be operated together with the pressing operation of the push lever 20 to its backward position, thereby activating the reciprocating motion of the piston 7. As shown in Fig. 2, the push lever 20 includes a leading end portion 20a projecting from the leading end of the nose portion 3 (nose injection hole 3a) and a trailing end portion 20b engageable with the arm plate 19; and, the push lever 20 is disposed on the back surface side of the nose portion 3 while extending from the leading end portion 20a to the trailing endportion 20b inparallel to the extending direction of the nose injection hole 3a. On the push lever 20, there is mounted an adjuster part 21 which is used to adjust the length of the whole of the push lever 20; and, the whole of the push lever 20 is energized to a position in front of the nose portion 3 by an energizing spring (not shown) provided within the adjuster part 21. When the leading end portion 20a of the push lever 20 is pressed against a work in a normal state, the leading end portion 20a is moved back to a backward position in the vicinity of the leading end of the nose portion 3 (nose injection hole 3a) . As shown in Fig. 1, with the movement of the leading end portion 20a, the whole of the push lever 20 is moved toward the trigger lever 18, and the push lever trailing endportion 20b is engaged with the arm plate 19, thereby allowing the activating operation which can be executed by the trigger lever 18.

In Fig.1, a control passage (not shown) for pressing the head valve 16 is connected to the trigger valve portion

17 and thus, as the plunger 17a of the trigger valve portion

17 is opened and closed in the right and left directions

(opened and closed in the vertical direction) , the control passage is put into communication with the atmospheric air of the nail driving machine main body 2 or the compressed air stored in the pressure storage chamber 14. More specifically/ the plunger 17a cooperates together with a valve piston provided within the trigger valve portion 17 and thus, as the plunger 17a moves right and left (moves vertically) , the plunger 17a puts the head valve control passage into communication with the atmospheric air or into communication with the pressure storage chamber 14 which is filled with the compressed air. That is, as shown in Fig. 1, when the plunger 17a is present in the leftward state (downward state), in other words, when the plunger 17a is energized to the leftward position (downward position) by the coil spring provided within the trigger valve portion 17, the head valve control passage is allowed to communicate with the pressure storage chamber 14, whereby the compressed air is supplied. On the other hand, when the plunger 17a is pulled up in the right direction (in the upward direction) by the arm plate 19 and trigger lever 18, the control passage for pressing the head valve 16 is allowed to communicate through the trigger valve portion 17 with the external atmospheric air that exists in the neighborhood thereof. Describing specifically of the above in relation to the nailing operation, in a state where the push lever 20 is pressed against the work and the push lever 20 is moved back in the backward direction to thereby push up the arm plate 19, when the trigger lever 18 is further pulled in the direction of the trigger valve portion 17 (in the upward direction) , as described above, the plunger 17a is pushed in the left direction (in the upward direction) , whereby the head valve control passage is allowed to communicate through the trigger valve portion 17 with the atmospheric air. As a result of this, the head valve 16 is moved toward its top dead center side in the X direction to thereby allow a piston upper chamber 27, which is defined by the piston 7 and head valve 16, to communicate with the pressure storage chamber 14, and the compressed air is supplied from the pressure storage chamber 14 to the piston upper chamber 27 of the piston 7 to move the piston 7 in the left direction (in the downward direction) , thereby applying a striking force to the driver blade 11 which is mounted on the piston 7 integrally therewith.

On the left end portion (lower end portion) of the cylinder 6, there is disposed an impact easing bumper 25 which is used to absorb the excess energy of the piston 7 after the nail 15 is struck. The impact easing bumper 25 is structured such that, in order to prevent it from moving toward the top dead center side of the cylinder 6, a portion thereof has a diameter larger than the inside diameter of the cylinder 6. In the outer periphery of the left end (lower end) of the cylinder 6, there is formed a return air chamber 22 which is used to return the piston 7 from the bottom dead center thereof to the top dead center thereof; in the middle of the reciprocating passage of the piston 7 , there is formed an air passage 23 including a non-return valve 23a which is allowed to communicate only in the direction of the return air chamber 22 from the cylinder 6; and, in the outer periphery of the lower end of the cylinder 6, there is formed an air passage 24 which allows the cylinder 6 and return air chamber 22 to communicate with each other. Here, an air duster 26 is a device which includes a button 6a and is used to spray the compressed air from its air outlet to blow off dust such as wooden chips produced in the nail striking operation.

[Structure of Blank Striking Preventive Mechanism]

Next, description will be given below of a blank striking preventive mechanism according to the invention with reference to Fig. 1, which is a front view of the fastener driving machine, and Fig. 3 which is a side view of the fastener driving machine (a side view taken along the A-A direction shown in Fig. 1) .

The magazine portion 5 has one end portion 5a engaged with the nose portion 3, while the other end portion 5b thereof extends in a direction which intersects the extending direction of the nose inj ection hole 3a. Within the magazine portion 5, there is mounted a feeder 51 which is used not only to press two or more connected-type nails

(connected fasteners) 15 loaded in the magazine 5 into the nose injection hole 3a from the other end portion

5b side and but also to move forward the remaining nails

(fasteners) 15 into the nose injection hole 3a after the nails (fasteners) 15 in the nose injection portion 3a are struck. The feeder 51 is energized in the direction of one end portion 5a of the magazine portion 5 by a spring (not shown), whereby the feeder 51 is always energizing the connected nails (fasteners) 15 in the direction of the nose injection direction 3a through the feed portion 51a thereof. Thanks to this structure, when the connected nails (fasteners) 15 loaded are sequentially struck and consumed, the feeder 51 moves forward the remaining nails (fasteners) 15 toward the nose injection hole 3a and thus always pushes and loads the remaining nails (fasteners) 15 into the nose injectionhole 3a. The feeder 51 further includes a feeder engaging portion 51b and also, when the amount of the remaining nails (fasteners) 15 provides a given amount (for example, four nails) or less, the feeder 51 presses against a lock arm 52 (which will be discussed later) in a direction going to the nose inj ection hole 3a. The lock arm 52, as shown in Fig. 3, extends from one end portion 52a to the other end portion 52b, while the middle portion 52c of the lock arm 52 interposed between the two end portions thereof is held by the nose portion 3 or by the magazine portion 5. To hold the middle portion 52c, there are used a support shaft 53, a hold portion 4a disposed in the nose portion 3 or magazine portion 5, and an energizing spring 52d which energizes one end portion 52a of the lock arm 52 in the direction of the other end portion 5b of the magazine portion 5 (in the downward direction) . The lock arm 52 is supported in the following manner: that is, the middle portion 52c of the lock arm 52 can be rotated with respect to the support shaft 53 provided in the nose portion 3 or magazine portion 5 and also, as shown in Fig.12, the middle portion 52c can be moved in the nose injection hole direction so as to be spaced from the support shaft 53 by a distance dl . Especially, in order to be able to move the lock arm 52 from the support shaft 53 in a state where it is spaced from the support shaft 53, in the middle portion 5c of the lock arm 52, there is formed such a rotation slit portion 52f as shown in Fig. 4A or such a rotation hole portion 52f as shown in Fig. 4B. Each of them has an elliptic inner peripheral shape at least on the nose injection hole direction side thereof so that one end portion 52a of the lock arm 52 can be moved in the nose injection hole direction with the other end portion 52b as the center of rotation. Owing to this structure, the middle portion 52c of the lock arm 52, as shown in Fig. 12, can be moved from a first position Pl, where it is supported by the support shaft 53, to a second position P2 where it is spaced from the support shaft 53 by the distance dl .

In the push lever 20, there is formed a push lever engaging portion 20c in connection with the lock arm 52. In one case, as shown in Fig. 7 which will be discussed later, the plane surface portion of the lock arm 52 is engaged with the side surface portion of the push lever engaging portion 20c; and, in the other case, as shown in Fig. 12 which will be discussed later, the lower side surface portion of the lock arm 52 is engaged with the plane surface portion of the push lever engaging portion 20c.

[Operation of Blank Striking Preventive Mechanism] Next, description will be given below of the operation of a blank striking preventive mechanism with reference to Figs. 8 ~ 12 which are respectively side views of such mechanism taken from the line A-A shown in Fig . 1. 1. State where nails are not loaded As shown in Fig. 8, in a state where nails are not loaded in the magazine portion 5, the feeder engaging portion 51b, which is energized by a spring (not shown) , presses against one end portion 52a of the lock arm 52 in the N direction approaching the nose injection hole 3a to thereby rotate the other end portion 52b of the lock arm 52 with the support shaft 53 as the fulcrum thereof in the S direction receding from the nose injection hole 3a. Owing to this, the push lever engaging portion 20c is completely superimposed on top of the other endportion 52b of the lock arm 52, whereby the push lever engaging portion 20c is rotated into a state where it is completely engaged with the other end portion 52b of the lock arm 52. In this state, even when the push lever 20 is pushed in the trigger lever direction, that is, even when the push lever 20 is pressed against a work (not shown) , the push lever 20 is prevented from moving in the backward position direction because the other end portion 52b of the lock arm 52 exists in the moving path of the push lever 20. Therefore, the other end portion 20b of the push lever 20 is prevented from being engaged with the arm plate 19, whereby the trigger valve portion 17 cannot be activated. That is, the nail striking operation by the driver blade 11 is caused to stop. When there arises such state as shown in Fig. 8, if the feeder 51 (see Fig. 1) is made to retreat and fasteners (nails) are supplied into the magazine 5, as shown in Fig. 3, the feeder engaging portion 51b removes its pressure against the lock arm one end portion 52a, whereby the lock arm other end portion 52b retreats from the moving path of the push lever 20 and returns back to a state shown in Fig. 3, which makes it possible to resume the operation.

2. State where amount of remaining nails is equal to or more than a set amount

As shown in Fig. 9, in a state where nails are loaded into the magazine portion 5 and the remaining amount of such nails is larger than the set remaining amount (for example, five) , although the feeder engaging portion 51b is pressed against the lock arm one end portion 52, the lock arm other end portion 52b with the support shaft 53 as the fulcrum thereof is not rotated up onto the locus of the push lever engaging portion 20c. This eliminates the possibility that the push lever engaging portion 20c can be engaged with the lock arm other end portion 52b. In this state, when the push lever 20 is pushed in the trigger lever direction, as shown in Fig. 5 which is a back view of the fastener driving machine, the other end portion 52b of the lock arm 52 is moved in the direction of the backward position of the push lever 20 and the push lever other end portion 20b is engaged with the lock arm 19, which makes it possible to activate the trigger valve 17. That is, the nail striking operation by the driver blade 11 can be carried out. 3. State where amount of remaining nails is equal to a set amount

As shown in Figs. 10 and 7 which is a back view of the fastener driving machine, in a state where the remaining amount of nails loaded in the magazine portion 5 is reduced down to a set amount (for example, the remaining amount of nails is four) , the feeder engaging portion 51b, which is energized, is pressed against the lock arm one end portion 52a in the N direction approaching the nose injection hole 3a to thereby rotate the lock arm other end portion 52b with the support shaft 53 as the fulcrum thereof in the S direction receding from the nose injection hole 3a. As a result of this, the push lever engaging portion 20c is superimposed on top of the other end portion 52b of the lock arm 52 and is rotated into a state where it is engaged with the lock arm other end portion 52b. As shown in Fig. 7 which is a back view of the fastener driving machine, in this state, even when the push lever 20 is pushed in the trigger lever direction, the lock arm other end portion 52b prevents the push lever 20frommovinginthe backward position direction thereof. This makes it impossible for the push lever other end portion 20b to be engaged with the trigger lever 18. Therefore, the trigger valve portion 17 cannot be activated, thereby causing the nail striking operation by the driver blade 11 to stop.

In this state, because the nail remaining amount is a set amount (for example, 4) , the push lever engaging portion 20c is thinly or weakly engaged with the other end portion 52b of the lock arm 52. Thus, when the push lever 20 is pressed against a work or the like without being conscious that the nail remaining amount is a set amount, owing to an impact or the like generated in such pressing operation, in some cases, the engagement of the lock arm other end portion 52b can be removed. In such engagement removed state, when the trigger lever 18 is pulled to thereby activate the trigger valve portion 17, a nail striking operation by the driver blade 11 is possible .

However, in this case, in the conventional nail driving machine, there is found a problem that, when the push lever 20 is pressed against a work or the like in a state where the engagement of the lock arm other end portion 52b is removed, the plane surface portion of the push lever engaging portion 20c functions as an engaging portion (a fulcrum) with respect to the lock arm other end portion 52b, thereby preventing the lock arm one end portion 52a from rotating in the N direction. In other words, in the conventional nail driving machine, it is impossible for the feeder feeding portion 51a to press a remaining amount of nails equal to or less than a set amount of (four or less) nails in the nose injection hole 3a direction (in the N direction) . Thus, a remaining amount of nails 15, which is equal to or less than a set amount, cannot be pressed by the feeder 51 to the correct position of the nose injection hole 3a, whereby the nails are present at unstable positions in a space between the feeder feeding portion 51a and nose injection hole 3a within the magazine portion 5. When the driver blade 11 is struck against the nose injection hole 3a in a state where the nails are unstably set, the nose injection hole 3a or the like can be clogged with the nails, or the nails can damage the nose portion 3. According to the invention, there can be avoided the above-mentioned problems for the following reasons. 4. Pressed-type Striking

Fig. 11 shows an engaged state where, while maintaining the pressed state of the push lever 20, that is, while maintaining the pressed state of the push lever 20 against a work, the trigger lever 18 ispulledto execute the striking operations successively, whereby the amount of remaining nails 15 is reduced down to a set amount

(four) . In other words, Fig. 11 shows a state where, when, while maintaining the pressed state of the push lever 20 against a work, apressed-type striking operation is executed, the amount of remaining nails 15 is reduced down to a set amount (four) . In this state, the plane surface portion of the pressed push lever engaging portion

20c functions as an engaging portion (a fulcrum) with respect to the lock arm other end portion 52b. In this case, since the inner peripheral portion of the rotation hole portion 52f is formed in an elliptic shape, the movement of the lock arm middle portion 52c in the N direction cannot be restricted by the support shaft 53.

Fig. 12 shows a case where a pressed-type striking operation is enforced similarly to the case shown in Fig. 11 and, especially, an engaged state where the amount of remaining nails 15 is reduced down to a set amount or less (4 ~ 0) . As described above, since the plane surface portion of the pressed push lever engaging portion 20c functions as an engaging portion (a fulcrum) with respect to the lock arm other end portion 52b, and also since the lock arm middle portion 52c is not restricted by the support shaft 53 due to the elliptic-shaped rotation hole portion 52f but can be held such that it can be moved in the N direction, the feeder feeding portion 51a can always press the remaining nails 15 in the nose injection hole 3a direction (in the N direction) . In other words, since the fulcrum of the lock arm 52 is shifted from the support shaft 53 to the push lever engaging portion 20c, the center of rotation of the lock arm 52 can be shifted from the middle portion 52c to the other end portion 52b; and, therefore, one end portion 52a of the lock arm 52 can be moved further in the N direction than the original set position of the feeder engaging portion 51b. Accordingly, even when the remaining nails 15 are reduced in number down to or less than a set amount (four) , the remaining nails 15 can be always pressed in the nose injection hole 3a direction (in the N direction) by the feeder feeding portion 51a, and the remaining nails 15 can be always set correctly within the nose injection hole 3a. Thus, even when the driver blade 11 is struck against the nose injection hole 3a in a state where the remaining nails 15 are reduced in number down to a set amount (four), the nose inj ection hole 3a can be prevented from being clogged with the nails, or the nose portion 3 can be prevented against damage which could be otherwise caused by the nails.

Also, the engagement between the lock arm other end portion 52b and push lever engaging portion 20c just after the amount of nails 15 remaining within the magazine portion 5 is reduced down to the above-mentioned set amount is attained in a thin or weak state. When the push lever is pressed against a next work in this state, the weak engagement between the lock arm other end portion 52b and push lever engaging portion 20c may be removed due to an impact or the like which is generated when the push lever is pressed against the work. However, even in this case, similarly to the above-mentioned pressed-type striking operation, even if the amount of remaining nails 15 is reduced down to a set amount (four), as described above, since the remaining nails 15 can be always pressed in the nose injection hole 3a direction (in the N direction) by the feeder feeding portion 51a, the nose injection hole 3a or the like can be prevented from being clogged with the nails, or the damage of the nose portion 3 by the nails can be prevented. Therefore, the reliability and durability of a nail driving machine including the present blank striking preventive mechanism can be enhanced. In the above-mentioned embodiment , description has been given of a case in which a nail is used as the fastener of a driving machine. However, the invention can also apply to a fastener driving machine which strikes other fasteners than the nails such as staples (U-shaped nails) and screws. Also, even when the invention is applied to other driving machines of a combustion type or an electric type than the driving machine of a compressed air type, there can be provided similar effects to the above-mentioned driving machine of a compressed air type . Although the invention made by the present inventors has been described heretofore specifically based on the above-mentioned embodiment, the present invention is not limited to the above embodiment but other various changes are also possible without departing from the scope of the subject matter of the invention.

Claims

1. A fastener driving machine, comprising: a driving machine main body including a driver blade for striking a fastener and a drive mechanism for applying a reciprocating movement to the driver blade; a nose portion including a nose injection hole into which the fastener is supplied; a magazine portion engaged with the nose portion and extending in a direction intersecting the extending direction of the nose inj ection hole, including a feeder pressing a plurality of connected fasteners into the nose injection hole; a push lever movable parallel to the extending direction of the nose injection hole between a forward position and a backward position; a trigger lever operable in cooperative with a pressing operation of the push lever to the backward position, for controlling an activation of the drive mechanism of the driving machine main body;

Characterized in that the fastener driving machine has a blank striking preventive mechanism comprising; a lock arm extending from one end portion to the other end portion and including a middle portion interposed between the two end portions , the middle portion ratably supported by a shaft provided on the nose portion or on the magazine portion in such a manner that it can be spaced from the support shaft and can be moved in the nose injection hole direction, a feeder engaging portion formed in the feeder such that, when the amount of remaining fasteners loaded into the magazine portion is reduced down to a given amount or less, the feeder engaging portion presses the one end portion of the lock arm; and, a push lever engaging portion formed in the push lever such that, when the one end portion of the lock arm is pressed, the push lever engages with the other end portion of the lock arm.

2. A fastener driving machine according to Claim 1, wherein, thes middle portion of the lock arm includes a rotation hole portion or a rotation slit portion larger in size than the diameter of the support shaft, and is supported by the support shaft in the rotation hole portion or the rotation slit portion.

3. A fastener driving machine according to Claim 1, wherein, when, in the forward position of the push lever, the amount of remaining fasteners is reduced down to the given amount and the feeder engaging portion presses the one end portion of the lock arm, by rotating the lock arm with the support shaft as a fulcrum, the other end portion of the lock arm is engaged with the push lever engaging portion to thereby stop the movement of the push lever from the forward position to the backward position, and wherein, when, in the backward position of the push lever, the amount of remaining fasteners loaded into the magazine portion is reduced down to the given amount and the feeder engaging portion presses the one end portion of the lock arm, by allowing the push lever engaging portion to function as a support portion for supporting the other end portion of the lock arm, the middle portion of the lock arm is spaced from the support shaft and is moved in the nose injection hole direction.