Driving tool

A driving tool includes a housing, a magazine, a cylinder head, a push lever, a cylinder, a combustion chamber frame, a piston, an injection part, and a fastener feeding unit. The housing has one end portion and another end portion. The magazine is connected to the housing and accommodating a fastener. The cylinder head is disposed at the one end portion. The push lever is movable relative to the housing upon pressure contacting a workpiece in a moving direction. The cylinder is fixed to the housing. The combustion chamber frame is movable in the housing in accordance with the push lever and selectively defining a combustion chamber in cooperation with the cylinder. The piston is slidably reciprocally movable relative to the cylinder and displaced upon expansion of air/fuel mixture in the combustion chamber. The injection part is connected to the another end portion of the housing and having an injection passage in communication with the magazine. The fastener feeding unit feeding the fastener to the injection passage in accordance with the movement of the push lever. The push lever includes a first guiding part configured to be slidably engaged with the fastener feeding unit. The fastener feeding unit is movable between an initial position and a feed position positioned downstream of the initial position in a feeding direction in which the fastener is fed. The fastener feeding unit slidably moves from the initial position to the feeding position with respect to the first guiding part for feeding the fastener downstream in the feeding direction in accordance with the movement of the push lever upon pressing the workpiece.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority from Japanese Patent Application No. 2010-080375 filed Mar. 31, 2010. The entire content of the priority application is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a combustion type driving tool driving a fastener into a workpiece by using combustion and expansion of gas as a drive source.

BACKGROUND

A conventional driving tool drives a fastener such as a screw into a workpiece. For example, a driving tool disclosed in Japanese Patent Application Publication No. 2007-167986 drives a piston disposed in a cylinder by using a compressed air as a driving source. By the movement of the piston, a screw is driven into a workpiece. At the same time, a part of the compressed air is used as a driving source of a feed piston for feeding the fastener.

SUMMARY

However, if the above-described conventional structure using the part of driving source in order to feed the fastener is applied to a combustion type driving tool using the combustion and expansion of gas as the driving source for driving the fastener in the workpiece, a sufficient driving force to be applied to the feed piston for feeding the fastener can not be acquired because a temperature of the combustion gas decreases rapidly.

In view of the foregoing, it is an object of the present invention to provide a combustion type driving tool capable of stabilizingly feeding the fastener in conjunction with a movement of a push lever.

In order to attain the above and other objects, the invention provides a driving tool including a housing, a magazine, a cylinder head, a push lever, a cylinder, a combustion chamber frame, a piston, an injection part, and a fastener feeding unit. The housing has one end portion and another end portion. The magazine is connected to the housing and accommodating a fastener. The cylinder head is disposed at the one end portion. The push lever is movable relative to the housing upon pressure contacting a workpiece in a moving direction. The cylinder is fixed to the housing. The combustion chamber frame is movable in the housing in accordance with the push lever and selectively defining a combustion chamber in cooperation with the cylinder. The piston is slidably reciprocally movable relative to the cylinder and displaced upon expansion of air/fuel mixture in the combustion chamber. The injection part is connected to the another end portion of the housing and having an injection passage in communication with the magazine. The fastener feeding unit feeding the fastener to the injection passage in accordance with the movement of the push lever. The push lever includes a first guiding part configured to be slidably engaged with the fastener feeding unit. The fastener feeding unit is movable between an initial position and a feed position positioned downstream of the initial position in a feeding direction in which the fastener is fed. The fastener feeding unit slidably moves from the initial position to the feeding position with respect to the first guiding part for feeding the fastener downstream in the feeding direction in accordance with the movement of the push lever upon pressing the workpiece.

DETAILED DESCRIPTION

A combustion type driving tool according to a first embodiment of the present invention will be described with reference toFIGS. 1 through 14. A driving tool1includes a housing2, a handle3, a nose part4(injection part), a magazine5, and a motion conversion mechanism6. Throughout the specification, a direction from the housing2to the nose part4will be referred to as a “downward direction”, and its opposite direction will be referred to as an “upward direction”. Further, a direction from the magazine5to the nose part4will be referred to as “leftward”, and its opposite direction will be referred to as “rightward”.

The housing2includes a main housing21, a canister retaining portion22, and a head cover23. Within the main housing21, a cylinder7, a combustion chamber frame8, and a cylinder head9are provided.

The cylinder7has a substantially cylindrical shape and defines a first cylinder chamber7aand second cylinder chamber7btherein. Each of first and second cylinder chamber7aand7bhas a columnar shape. An upper outer peripheral portion of the cylinder7is provided with a seal portion7A in intimate contact with an inner peripheral surface8A of the combustion chamber frame8. A spring (not shown) is provided at a lower portion of the cylinder7to bias the combustion chamber frame8downward (toward a bottom dead center). Each of the first cylinder chamber7aand the second cylinder chamber7bhas an axis extending in a direction parallel to the upward/downward direction. The first cylinder chamber7ahas a volume larger than that of the second cylinder chamber7b. The cylinder7has a first bottom part defining the first cylinder chamber7a. The first bottom part has a bottom end portion formed with a bore7c. An interior of the first cylinder chamber7ais communicated with an exterior of the first cylinder chamber7avia the bore7cwhich allows a bit72(described later) to pass therethrough. The cylinder7has a second bottom part defining the second cylinder chamber7b. The second bottom part has a bottom end portion formed with a bore7d. An interior of the second cylinder chamber7bis communicated with and an exterior of the second cylinder chamber7bvia the bore7dwhich allows a rod76(described later) to pass therethrough.

A first piston71, the bit72, a supporting member73, and a first bumper74are provided in the first cylinder chamber7a. The first piston71is movable to a top dead center in which an upper surface of the first piston71is substantially flush with an upper end face of the cylinder7. The first piston71has a generally circular disk shape and is in hermetic sliding contact with an inner peripheral surface of the cylinder7through a plurality of seal members, so that the first piston71divides the first cylinder chamber7ainto an upper chamber and a lower chamber.

The bit72has a rod shape having a regular hexagonal cross-section and extends in the downward direction. The bit72has a tip end portion (bottom end portion) portion shaped to be engageable with a head of screw. The tip end portion extends to an outside of the cylinder7through the bore7c. The bit72has a base end portion (top end portion) connected to a lower end portion of the first piston71through the supporting member73. The bit72is rotatable about its axis and is supported to the first piston71by the supporting member73.

The first bumper74made from an elastic material such as rubber is disposed at an inside of the first cylinder chamber7aand lower end portion of the first cylinder7. Accordingly, direct abutment of the first piston71against a wall (first bottom part) of the cylinder7around the bore7ccan be prevented by the first bumper74. Further, the first bumper74is adapted to absorb impact force of the first piston71when the first piston71drives a screw1A described later. The abutment position between the first piston71and the first bumper74is a bottom dead center of the first piston71.

In the lower portion of the first cylinder chamber7a, the cylinder7is formed with a vent hole7ecommunicating with an exhaust port (not shown) formed in the main housing21and penetrating from inside of the first cylinder chamber7ato outside thereof. A check valve (not shown) is provided at the vent hole7eto exclusively allow combustion gas to flow from an interior of the first chamber7ato an exterior thereof. Further, an exhaust cover (not shown) is provided for covering the vent hole7e.

A second piston75, the rod76, and a second bumper77are provided in the second cylinder chamber7b. The second piston75is movable to a top dead center in which an upper surface of the second piston75is substantially flush with an upper end face of the cylinder7. The upper surface of the second piston75has an area smaller than that of the first piston71. By adjusting this area ratio, a ratio of a force for driving the screw1A downward to a force for rotating the screw1A can be suitably set. In this embodiment, the larger force for driving the screw1A downward can be acquired by setting the area of the upper surface of the first piston71larger than that of the second piston75. The second piston75has a substantial circular disk shape and is in hermetic sliding contact with an inner peripheral surface of the cylinder7through a plurality of seal members, so that the second piston75divides the second cylinder chamber7binto an upper chamber and a lower chamber.

The rod76has a bottom end portion formed with a rack76A having a predetermined length. The rack76A is in meshing engagement with the motion conversion mechanism6. The rod76extends to an outside of the second cylinder chamber7bthrough the bore7d. The rod76has an upper end portion fixed to a lower surface of the second piston75.

The second bumper77made from an elastic material such as rubber is disposed in a lower portion of the second cylinder chamber7b. Accordingly, direct abutment of the second piston75against a wall (second bottom part) of the cylinder7around the bore7dcan be prevented by the second bumper77when the second piston75moves downward. Further, the second bumper77is adapted to absorb impact force of the second piston75when the first piston71drives the screw1A. The abutment position between the second piston75and the second bumper77is a bottom dead center of the second piston75.

In the lower portion of the second cylinder chamber7b, the cylinder7is formed with a vent hole (not shown) communicating with an exhaust port (not shown) formed in the main housing21and penetrating from inside of the second cylinder chamber7bto outside thereof. A check valve (not shown) is provided at the vent hole (not shown) to exclusively allow the combustion gas to flow from an interior of the second chamber7bto an exterior thereof. Further, an exhaust cover (not shown) is provided for covering the vent hole (not shown).

The combustion chamber frame8has a hollow cylindrical shape having open ends, and is disposed over the cylinder7. The combustion chamber frame8is vertically reciprocally movable relative to the cylinder7. The combustion chamber frame8has a lower end portion integrally provided with a link member (not shown) that is connected to the push lever41. The combustion chamber frame8and the link member (not shown) are biased downward by a spring member (not shown) relative to the cylinder7. The combustion chamber frame8has the inner peripheral surface8A. The inner peripheral surface8A is in hermetic contact with the seal portion7A when the combustion chamber frame8is elevated against the biasing force of the spring (not shown). The inner peripheral surface8A and seal portion7A are adapted to maintain fluid-tightness between the combustion chamber frame8and the cylinder7when the combustion chamber frame8is elevated.

The cylinder head9is positioned at the upper side of the combustion chamber frame8and is fixed to the main housing21. The cylinder head9has a lower portion provided with a seal portion9A with which an upper inner peripheral surface portion of the combustion chamber frame8is in contact. Upon intimate contact with the seal portion9A with the upper inner peripheral surface portion, a combustion chamber1ais defined. More specifically, by the upward movement of the combustion chamber frame8, the upper inner peripheral surface portion of the combustion chamber frame8is brought into intimate contact with the seal portion9A, whereupon the combustion chamber1ais defined by an upper surface of the first piston71, the upper surface of the cylinder7, the combustion chamber frame8, and a lower surface of the cylinder head9. The combustion chamber1acan be fluid-tightly maintained because of the intimate contact between the seal portion9A and the upper inner peripheral surface portion of the combustion chamber frame8, and between the seal portion7A and the inner peripheral surface of the combustion chamber frame8.

The motion conversion mechanism6is positioned below the cylinder7and includes a first bevel gear61and a second bevel gear62. The first bevel gear61has a shaft61A rotatably supported to the main housing2. A pinion61B is provided on the shaft61A and is meshingly engaged with the rack76A of the rod76. Movement of the rod76provides rotation of the pinion61B meshed with the rack76A to convert the linear movement of the rod76into rotational movement of the first bevel gear61.

The second bevel gear62is disposed at the right side of the first bevel gear61and is rotatably supported in the nose part4. The second bevel gear62is meshingly engaged with the first bevel gear61. The rotation of the first bevel gear61is transmitted to the second bevel gear62. The second bevel gear62has a rotation center formed with a hexagonal insertion hole62athrough which the bit72extends. The hexagonal insertion hole62ahas substantially the same shape as the outer shape of bit72. Therefore, the bit72and the second bevel gear62are rotatable together coaxially with each other.

Upon movement of the rod76in the upward/downward direction, the pinion61B meshed with the rack76A is rotated. Rotation of the first bevel gear61is transmitted to the second bevel gear62meshed with the first bevel gear61so that the second bevel gear62rotates. Accordingly, the rotation of the second bevel gear62is transmitted to the bit72extending through the insertion hole62aformed in the center of the second bevel gear62.

The cylinder head9is formed with a fuel passage9afor introducing combustible gas from a gas canister1B into the combustion chamber1a. A fan motor91and an ignition plug92are provided in the cylinder head9. The fan motor91has a rotation shaft extending in a direction parallel to the upward/downward direction and protruding into the combustion chamber1a. A head switch (not shown) is provided in the main housing21to detect an upper stroke end position of the combustion chamber frame8as a result of pushing the push lever41against the workpiece (not shown). The head switch (not shown) is rendered ON when the push lever41is elevated to a predetermined position whereupon rotation of the fan motor91will be started.

The fan93is mounted on a lower portion of the rotation shaft of the fan motor91, and is exposed to the combustion chamber1a. In a state where the combustion chamber frame8is in contact with the cylinder head9, the rotation of the fan93promotes agitation between air and combustible gas, generates turbulent combustion upon ignition for promoting combustion, and discharges exhaust gas after combustion of the combustible gas out of the combustion chamber1a.

The ignition plug92is disposed at the upper region of the combustion chamber1afor igniting combustible gas supplied thereinto.

The head cover23is positioned at the upper portion of the main housing21and above the cylinder head9. The head cover23is formed with a plurality of air intake ports23a. A fresh air can be introduced into the combustion chamber1athrough the intake ports23aby the rotation of the fan93.

The gas canister retaining portion22is positioned on one side of the main housing21and extends in the upward/downward direction for retaining therein the gas canister1B. The gas canister1B accommodates therein the combustible gas and is configured to eject the combustible gas by a predetermined amount. The gas canister1B is tiltable toward the cylinder head9in accordance with the movement of the push lever41, and has a gas ejecting portion (not shown) in fluid communication with the fuel passage9a. Accordingly, the combustible gas can be ejected into the combustion chamber1avia the fuel passage9awhen the gas canister1B is urged toward the main housing21.

The handle3extends from the gas canister retaining portion22in a direction away from the main housing21, and has a trigger31and a battery accommodating section32. A battery (not shown) is detachably mounted on the battery accommodating section32. The trigger31is adapted to supply electrical current to the ignition plug92provided at the cylinder head9, upon pulling the trigger31to ignite the air/fuel mixture in the combustion chamber1ato obtain the combustion and expansion of the air/fuel mixture.

The magazine5is positioned below the handle3and is generally aligned with the main housing21in the leftward/rightward direction. A plurality of screws1A (fasteners) are arrayed inside the magazine5and are banded by a banding member1C. The magazine5has an internal portion in communication with an injection passage4aof the nose part4.

The push lever41is disposed below the main housing21and is connected to the combustion chamber frame8via the link member (not shown). The push lever41includes a contact part41A for contacting the workpiece (not shown), a connecting part41B connected to the lower end portion of the combustion chamber frame8, and a guiding part41C connecting together the contact part41A and the connecting part41B.

The contact part41A is adapted to contact the workpiece and is disposed to confront an injection passage4a(FIG. 1). An upper end of the connecting part41B is bent and connected to the combustion chamber frame8via a spring (not shown). The push lever41is biased downward by the biasing force of the spring (not shown). The guiding part41C is a plate member extending in the upward/downward direction. The guiding part41C includes a first guiding part41D and a second guiding part41E. The first guiding part41D is formed with a first penetrating hole41a. The second guiding part41E is formed with a second penetrating hole41b. The first penetrating hole41aextends in a direction diagonally to the upward/downward direction such that a length in the upward/downward direction is equal to a stroke length of the push lever41and that a length in the leftward/rightward direction is equal to one pitch length of the screws1A banded and arranged in the rightward/leftward direction. The first guiding part41D includes a first regulating surface41F and a second regulating surface41G. The first regulating surface41F defines a top edge of the first penetrating hole41a. The second regulating surface41G defines a bottom edge of the first penetrating hole41a. A top edge of the second penetrating hole41bis connected to the top edge of the first penetrating hole41a. The second penetrating hole41bhas a length longer than or equal to the stroke length of the push lever41in the upward/downward direction. A fixing piece41H for fixing a second spring described later (FIG. 3) is provided on a lower part of the guiding part41C. The fixing piece41H protrudes from the guiding part41C toward a feeder43(FIG. 3) described later and is bent such that a distal end extends upward.

As shown inFIGS. 3 through 5, the push lever41is provided with a fastener feed mechanism42as a fastener feeding unit. The fastener feed mechanism42includes the feeder43, an arm44sliding along the guiding part41C together with the feeder43, a first spring45A (FIG. 5), the second spring45B, and a guiding member46(FIGS. 3 and 4).

The feeder43has a base portion43A and two click portions43B protruding from the base portion43A in a direction away from the push lever41. The base portion43A is a plate member having a longitudinal direction parallel to the upward/downward direction and a widthwise direction parallel to the leftward/rightward direction. The base portion43A is formed with a penetrating hole (not shown) penetrating in the upward/downward direction at one end portion thereof. The two click portions43B are provided on another end portion of the base portion43A and are arrayed in the upward/downward direction.

The arm44has a main portion44A and a spring fixing portion44B protruding from the main portion44A in the leftward/rightward direction. The main portion44A has a substantially cylindrical shape. The feeder43is supported to one end portion of the main portion44A and is pivotably movable about a pin44C when the pin44C is inserted into the penetrating hole (not shown) formed in the one end portion of the feeder43. Another end portion of the aim44is positioned in the first penetrating hole41aand/or the second penetrating hole41band is engaged with the guiding part41C of the push lever41.

In an inactive state where the push lever41is not pushed onto the workpiece, as shown inFIGS. 3 through 5, the main portion44A is in contact with the first regulating surface41F (FIG. 2). In the inactive state, the click portion43B is located on the right side of the injection passage4asuch that a distance between the click portion43B and the injection passage4ais equal to one pitch length of the screws1A that are banded in the leftward/rightward direction.

As shown inFIG. 5, the first spring45A has one end connected to the spring fixing portion44B and another end connected to the base portion43A of the feeder43. Accordingly, the first spring45A biases the feeder43from the spring fixing portion44B in a direction away from the push lever41.

As shown inFIG. 7, the guiding member46has a substantially rectangular triangle plate shape. A part of the guiding member46is located in the second penetrating hole41b(FIG. 2) formed on the push lever41so that the guiding member46is movable along the second guiding part41E. A lower end portion of the guiding member46is connected to the second spring45B. The second spring45B has an upper end connected to the guiding member46and a lower end connected to the fixing piece41H. The second spring45B biases the guiding member46upward. In the inactive state where the push lever41is not pushed onto the workpiece, as shown inFIG. 3, an oblique surface of the guiding member46defines a part of the first penetrating hole41awhen the oblique surface blocks an entrance of the second penetrating hole41bat a position where the first penetrating hole41aand the second penetrating hole41bare connected. In this state, the oblique surface supports the arm44such that the arm44is engaged with the first regulating surface41F (FIG. 2). When the push lever41is elevated, the guiding member46guides the arm44toward the second regulating surface41G in the first penetrating hole41a

The nose part4extends from a lower end of the main housing2. As shown inFIG. 6, the nose part4includes a guiding side wall47and a supporting side wall48. The guiding side wall47guides the banded screws1A in the leftward/rightward direction. The supporting side wall48supports the feeder43. The guiding side wall47and supporting side wall48define an accommodating space4bfor accommodating the banded screws1A. Further, the guiding side wall47is provided with a projection (not shown) preventing the screw1A from moving rightward.

The supporting side wall48has an upper surface48A and a lower surface48B that prevent the banded screws1A from moving in the upward/downward direction. The supporting side wall48further has a first supporting surface48C and a second supporting surface48D that prevent the feeder43from moving in the upward/downward direction with respect to the main housing21. A distance between the first supporting surface48C and the second supporting surface48D is substantially equal to a length of the feeder43in the upward/downward direction. The first supporting surface48C and second supporting surface48D support the feeder43to slidably move between an initial position (FIG. 5) and a feed position (FIG. 9). The feed position is a position shifted from the initial position in the leftward direction (downstream of feeding the screw1A) for one pitch of the banded screws1A. Further, as shown inFIG. 1, the nose part4is formed with a passage4cat a left end portion thereof. A part of the band member1C corresponding to the screw1A that has been driven into the workpiece is discharged outside of the nose part4via the passage4c.

Operation of the driving tool1will next be described. In a non-operational phase as shown inFIGS. 1 through 5, since the combustion chamber frame8is connected to the push lever41via the link member (not shown), the upper end of the combustion chamber frame8is separated from the cylinder head9. Accordingly, the first vent hole (not shown) is defined between the upper end of the combustion chamber frame8and the cylinder head9. The first piston71and the second piston75are positioned at their top dead center. Further, the second vent hole (not shown) is defined between the seal portion7A and the combustion chamber frame8. The push lever41is biased downward by the biasing force of the spring (not shown), so that the tip end of the push lever41is positioned downward of the nose part4. The feeder43and the arm44is positioned at the initial position shown inFIGS. 3 through 5by the guiding part41C, the guiding member46, and the second spring45B. The click portions43B contacts to a right side of the leading screw1A.

When a user grips the handle3and pushes the push lever41against the workpiece in the this state, the push lever41is moved upward against the biasing force of the spring (not shown) and the combustion chamber frame8is moved upward via the link member (not shown). By the upward movement, the upper end of the combustion chamber frame8is brought into abutment with the cylinder head9so as to hermetically provide the combustion chamber1a.

Further, in accordance with movement of the push lever41, the gas canister1B is tilted toward the cylinder head9, so that combustible gas accumulated in the gas canister1B will be ejected once into the combustion chamber1athrough the fuel passage9a.

When the combustion chamber frame8reaches its stroke end in accordance with the movement of the push lever41, the fan switch (not shown) is turned ON to start electrical power supply to the fan motor91, thereby starting rotation of the fan93. Accordingly, combustible gas introduced into the combustion chamber1acan be agitatingly mixed with fresh air.

In this state, in accordance with the movement of the push lever41upward, the arm44relatively moves downward and leftward with respect to the push lever41in the first penetrating hole41a. Specifically, when the screw1A has not been disposed in the injection passage4a, the feeder43and arm44are guided by the guiding member46, engaged with the first guiding part41D, and move from the first regulating surface41F to the second regulating surface41G. Since the first supporting surface48C and the second supporting surface48D (FIG. 6) prevent the feeder43from moving in the upward/downward direction, the feeder43moves rightward for one pitch of the banded screws1A and does not move in the upward/downward direction with respect to the main housing21. By moving the feeder43from the initial position to the feed position, the click portions43B press and feed the leading screw1A to the injection passage4a(FIG. 5).

Then, when the trigger31is turned ON, the ignition plug92in the combustion chamber1ais ignited, thereby igniting, combusting, and exploding the air/fuel mixture. Because of the combustion and explosion, the first piston71and the bit72are moved downward until the first piston71abuts against the first bumper74. Further, the second piston75and the rod76are moved downward until the second piston75abuts against the second bumper77. After elapsing a predetermined time period, the rack76A starts to engage with the pinion61B because the rod76is formed with the rack76A upward for a prescribed distance from a point where the rack76A and the second pinion61B are engaged with each other as shown inFIG. 1. More specifically, the rack76A is formed in a position so that the rack76A and the pinion61B are engaged with each other after the screw1A contacts the workpiece. Accordingly, the rotational force is transmitted to the bit72via the motion conversion mechanism6after the screw1A contacted to the workpiece. Therefore, the screw1A is rotationally driven into the workpiece.

The combustion gas remaining in the cylinder7and the combustion chamber1ahas high temperature, and therefore, the combustion heat will be absorbed thereinto through the inner surfaces of the cylinder7and the combustion chamber frame8. Thus, temperature of the cylinder7and the combustion chamber frame8will be increased. The heat is then released to the atmosphere through the outer surfaces of the cylinder7and the combustion chamber frame8.

Because of the heat absorption into the cylinder7, the combustion gas is promptly cooled to decrease a volume thereof. Accordingly, pressure in the upper chamber of the first cylinder chamber7awill be decreased to become a pressure not more than the atmospheric pressure to cause a thermal vacuum. As a result, the first piston71can be returned to its initial top dead center position. The same is true with respect to the second cylinder chamber7b, so that the second piston75is returned to its top dead center position because of the thermal vacuum.

Then the trigger31is rendered OFF, and the user lifts the driving tool201in its entirety to separate the push lever41from the surface of the workpiece. As a result, the push lever41and the combustion chamber frame8are returned to its position shown inFIG. 1because of the biasing force of the spring (not shown). In accordance with downward movement of the push lever41, the feeder43and the arm44are guided by the first guiding part41D and move in the first penetrating hole41afrom the second regulating surface41G (FIG. 2) to the first regulating surface41F as shown inFIGS. 10 and 11. Since the first supporting surface48C and the second supporting surface48D (FIG. 6) prevent the feeder43from moving in the upward/downward direction, the feeder43and the arm44move from the feed position to the initial position in the leftward/rightward direction with respect to the main housing21. The projection (not shown) of the guiding side wall47prevents the banded screws1A from moving rightward. Therefore, when the arm44moves from the feed position to the initial position, the feed43pivots about the pin44C against the biasing force of the first spring45A such that the click portions43B contacts an outer surface of the screw1A to be driven subsequently. Accordingly, the feeder43is positioned on the right side of next screw1A (upstream side in a direction for conveying the screws), that is, the feeder43is disposed at the initial position so as to feed the next screw1A.

Then, the head switch is rendered OFF at a timing elapsing from a prescribed time period. However, the fan93continues rotation for a predetermined period of time. Because of the rotation of the fan93, air flow can be generated. That is, fresh air is introduced from the air intake ports23ainto the combustion chamber1athrough the vent hole (not shown), and the air and the residual combustion gas can be discharged through the exhaust port (not shown) of the main housing21. Accordingly, scavenging can be performed with respect to the combustion chamber1a. Then, rotation of the fan93is stopped to provide an initial stationary phase. Then, the above-described operation will be repeatedly performed for successively driving the screw1A into the workpiece. When the next screw1A to be driven subsequently is fed, the part of the band member1C corresponding to the screw1A that has been driven into the workpiece is discharged outside of the nose part4via the passage4c(FIG. 1).

Further, when the push lever41moves upward in a state where the screw1A has been disposed in the injection passage4a, as shown inFIGS. 12 through 14, the screw1A prevents the feeder43and the arm44from moving in the leftward/rightward direction. Accordingly, the arm44moves in the second penetrating hole41bagainst the biasing force of the second spring45B while pressing the guiding member46downward. That is, the arm44is guided by the second guiding part41E and moves downward with respect to the push lever41. Since the first supporting surface48C and the second supporting surface48D (FIG. 6) prevents the feeder43in the upward/downward direction, the feeder43remains at the initial position and does not feed the screw1A.

When the push lever41moves downward after the driving operation is completed, the arm44is biased by the second spring45B, and is guided by the second guiding part41E, and moves in the second penetrating hole41btoward the first regulating surface41F. Then, the arm44is disposed at the initial position and contacts the first regulating surface41F as shown inFIGS. 3 through 5.

In the driving tool1described above, the screw1A is fed to the injection passage4aof the nose part4in accordance with the movement of the push lever41in the upward/downward direction. Accordingly, the driving tool1can feed the screw1A in the injection passage4aat a timing at which the combustion chamber1ais defined. Therefore, the screw1A is stabilizingly fed and positioned in the injection passage4awhen the driving tool1starts a driving operation. Further, simple driving tool for feeding the screw1A can be provided without a separate mechanism for supplying compressed air.

Further, when the screw1A has been disposed in the injection passage4a, the feeder43does not move downstream in the conveying direction of the screw1A (leftward) in accordance with the movement of the push lever41in the upward/downward direction. With this structure, it is possible to prevent two screws from choking at the injection passage4a. Therefore, the breakage of the bit72can be prevented. Further, breakages of the nose part4, the fastener feed mechanism42, the push lever41, and the like due to forcible feeding of the screw1A can be prevented.

While the invention has been described in detail with reference to the embodiment thereof, it would be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention. For example, the feeder43of the fastener feed mechanism42may be supported to the magazine5. Further, the magazine may be a roll-type magazine.