The present invention relates to a combustion-type power tool, and more particularly, to such power tool capable of driving a fastener of driving such as a nail, an anchor, and a staple into a workpiece by igniting a mixture of air and gaseous fuel, which in turn causes a linear momentum of a piston.
Conventional combustion-type power tools are described in U.S. Pat. No. 5,194,646 and U.S. Pat. No. 4,522,162. A conventional combustion-type power tool according will be described with reference to
A handle 5 extends from a side of the canister housing 2B. The handle 5 has a trigger switch 6. A magazine 7 and a tail cover 8 are disposed below the housing 2. The magazine 7 is adapted for containing therein nails (not shown), and the tail cover 8 is adapted for feeding the nail in the magazine 7 and setting the nail to a predetermined position. A push lever 9 is movably provided at a lower end of the main housing 2A. The push lever 9 has a tip end adapted to be pressed against a workpiece 40, and has an upper end portion associated with a link member 11 fixed to a combustion chamber frame 10 described later. A compression coil spring 30 is interposed between the link member 11 and a cylinder 20 (described later) for normally urging the push lever 9 in a protruding direction away from the head cover 3.
When the housing 2 is pressed toward the workpiece 40 while the push lever 9 is in abutment with the workpiece 40 against a biasing force of the compression coil spring 30, an upper portion of the push lever 9 is retractable into the main housing 2A.
A cylinder head 12 is secured to the top of the main housing 2A for closing the open top end of the main housing 2A. The cylinder head 12 supports a motor 13 at a position opposite to a combustion chamber 23 described later. Further, an ignition plug 14 is also supported to the cylinder head 12 at a position adjacent to the motor 13. The ignition plug 14 has an ignition spot exposed to the combustion chamber 23. The cylinder head 12 has a gas canister side in which is formed a fuel injection passage 12a which allows a combustible gas to pass therethrough. One end of the fuel injection passage 12a serves as an injection port that opens at the lower surface of the cylinder head 12. Another end of the fuel injection passage 12a constitutes a gas canister connecting portion which is fluidly connected to the injection rod 4C.
As shown in
The ignition plug 14 is ignitable upon manipulation to the trigger switch 6 and upon movement of the combustion chamber frame 10 to its predetermined position because of the pressing of the push lever 9 against the workpiece 40. The motor 13 has a fan shaft 13A, and a fan 15 positioned in the combustion chamber 23 is fixed to a tip end of the fan shaft 13A.
A head switch (not shown) is provided in the main housing 2A for detecting an uppermost stroke end position of the combustion chamber frame 10 when the combustion-type power tool 1 is pressed against the workpiece 40. The head switch can be turned ON when the push lever 9 is elevated to a predetermined position for starting rotation of the motor 13.
The combustion chamber frame 10 is provided in the main housing 2A and is movable in the lengthwise direction thereof. The combustion chamber frame 10 is moved interlockingly in accordance with the movement of the push lever 9, since the lower end portion of the combustion chamber frame 10 is connected to the link member 11. The cylinder 20 is fixed to the main housing 2A. The combustion chamber frame 10 has an inner surface in sliding contact with the cylinder 20. Thus, the cylinder 20 guides movement of the combustion chamber frame 10. The cylinder 20 has an axially intermediate portion formed with an exhaust hole 20a. An exhaust-gas check valve (not shown) is provided to selectively close the exhaust hole 20a.
A piston 21 is slidably and reciprocally provided in the cylinder 20. The piston 21 divides an inner space of the cylinder 20 into an upper space above the piston 21 and a lower space below the piston 21. Further, a bumper 22 is provided on the bottom of the cylinder 20. The bumper 22 is made from a resilient material. When the piston 21 moves to its bottom dead center, the piston 21 is abuttable on the bumper 22.
As shown in
As shown in
A plurality of ribs 10A protrudes radially inwardly from the portion of the combustion chamber frame 10, the portion defining the combustion chamber 23. Each rib 10A extends in the axial direction of the combustion chamber frame 10. The ribs 10A promote stirring and mixing of the air and the combustible gas in the combustion chamber 23 in cooperation with the fan 15.
Rotation of the fan 15 performs the following three functions. First, the fan 15 stirs and mixes the air with the combustible gas as long as the combustion chamber frame 10 remains in abutment with the cylinder head 12. Second, after the mixed gas has been ignited, the fan 15 causes turbulent combustion of the air-fuel mixture, thus promoting the combustion of the air-fuel mixture in the combustion chamber 23. Third, the fan 15 performs scavenging such that the exhaust gas in the combustion chamber 23 can be scavenged therefrom and also performs cooling to the combustion chamber frame 10 and the cylinder 20 when the combustion chamber frame 10 moves away from the cylinder head 12 and when the first and second flow passages 24, 25 are provided.
A driver blade 26 extends downwards from a side of the piston 21, the side being at the cylinder space below the piston 21, toward the lower end of the main housing 2A. The driver blade 26 is positioned coaxially with the nail set in the tail cover 8, so that the driver blade 26 can strike against the nail during movement of the piston 21 toward its bottom dead center. When the piston 21 moves to its bottom dead center, the tip end of the driver blade 26 strikes against the nail, and the piston 21 abuts on the bumper 22 and stops. In this case, the bumper 22 absorbs a surplus energy of the piston 21.
Next, operation of the combustion-type power tool 1 will be described. In the non-operational state of the combustion-type power tool 1, the push lever 9 is biased away from the cylinder head 12 as shown in
With this state, if the push lever 9 is pushed onto the workpiece 40 while holding the handle 5 by a user as shown in
In accordance with the movement of the push lever 9, the gas canister 4 is tiltingly moved toward the cylinder head 12 by way of a cam mechanism (not shown). Thus, the injection rod 4C of the gas canister 4 is pressed against the gas canister connecting portion of the cylinder head 12, so that the combustible liquidized gas in the gas canister 4 is injected into the combustion chamber 23 through the gauging section 4A and the fuel injection passage 12a.
Further, in accordance with the movement of the push lever 9, the combustion chamber frame 10 reaches its uppermost stroke end whereupon the head switch is turned ON to energize the motor 13 for starting rotation of the fan 15. Rotation of the fan 15 stirs and mixes the combustible gas with air in the combustion chamber 23 in cooperation with the plurality of ribs 10A.
In this state, when the trigger switch 6 provided at the handle 5 is turned ON, spark is generated between the end of the ignition plug 14 and the ignition ground 34 to ignite the combustible gas. The combusted and expanded gas pushes the piston 21 to its bottom dead center. Therefore, a nail in the tail cover 8 is driven into the workpiece 40 by the driver blade 26 until the piston 21 abuts on the bumper 22.
After the nail driving, the piston 21 strikes against the bumper 22, the cylinder space above the piston 21 becomes communicated with the exhaust hole 20a. Thus, the high pressure and high temperature combustion gas is discharged out of the cylinder 20 through the exhaust hole 20a of the cylinder 20 and through the check valve (not shown) provided at the exhaust hole 20a to the atmosphere to lower the pressure in the combustion chamber 23. When the inner space of the cylinder 20 and the combustion chamber 23 becomes the atmospheric pressure, the check valve is closed. Combustion gas still remaining in the cylinder 20 and the combustion chamber 23 has a high temperature at a phase immediately after the combustion. However, the high temperature can be absorbed into the walls of the cylinder 20 and the combustion chamber frame 10. Absorption of the heat into the cylinder 20 etc. causes rapid cooling to the combustion gas. Thus, the pressure in the sealed space in the cylinder 20 above the piston 21 further drops to less than the atmospheric pressure creating a so-called “thermal vacuum”. Accordingly, the piston 21 can be moved back to the initial top dead center position.
Then, the trigger switch 6 is turned OFF, and the user lifts the combustion-type power tool 1 from the workpiece 40 for separating the push lever 9 from the workpiece 40. As a result, the push lever 9 and the combustion chamber frame 10 move away from the cylinder head 12 because of the biasing force of the compression coil spring 30 to restore a state shown in
In the conventional combustion-type power tool 1, the spark generated between the end of the ignition plug 14 and the ignition ground 34 must not be blown out by a flow of air-fuel mixture provided by the rotation of the fan 15. To this effect, conventionally, rotation number of the fan 15 or a configuration of blades of the fan 15 are configured to avoid accidental blow-out. However, air-fuel agitation performance, combustion energy and gas blowing performance may be lowered.
It is therefore, an object of the present invention to provide a combustion type power tool provided with an arrangement that improves ignitability capable of maintaining a spark at the ignition plug against the fan flow of air-fuel mixture without lowering the performance of the fan.
This and other object of the present invention will be attained by a combustion-type power tool including a housing, a cylinder, a piston, a combustion chamber frame, a fan, an ignition unit, and a protecting member.
The housing has one end. The cylinder head is disposed at the one end and formed with a fuel injection passage. The cylinder is disposed in and fixed to the housing. The cylinder defines an axial direction. The piston is slidably disposed in the cylinder and reciprocally movable in the axial direction. The combustion chamber frame is disposed in the housing and movable in the axial direction. The combustion chamber frame is abuttable on the cylinder head to provide a combustion chamber in cooperation with the cylinder head and the piston. The fan is rotatably disposed in the combustion chamber for agitating and mixing an air with a combustible gas injected into the combustion chamber through the fuel injection passage. The ignition unit includes an ignition plug exposed to the combustion chamber, and an ignition ground. The ignition unit generates a spark between the ignition plug and the ignition ground to ignite a mixture of air and the combustible gas, to thus provide a fire. The protecting member protects the fire against a flow of the mixture of air and the combustible gas. The flow is provided by the rotation of the fan.
In another aspect of the invention, there is provided an ignition arrangement in a combustion type power tool in which a fan is provided in a combustion chamber defined by a cylinder head, a movable combustion chamber frame, a cylinder and a piston, a motive power of the piston being generated upon combustion of a mixture of air and a combustible gas in the combustion chamber. The ignition arrangement includes an ignition plug, an ignition ground, and a protecting member. The ignition plug is exposed to the combustion chamber. The ignition ground is disposed in the combustion chamber and generates a spark between the ignition plug and the ignition ground to ignite the mixture to thus provide a fire. The protecting member is disposed in the combustion chamber that protects the fire against a flow of the mixture provided by the rotation of the fan.
In another aspect of the invention, there is provided a combustion-type power tool including a housing, a combustion chamber, a fan, an ignition unit, and a flow speed decreasing member.
The housing defines an outer frame. The combustion chamber is provided in the housing. The fan is provided in the combustion chamber and mixes an air with a combustible gas injected into the combustion chamber. The ignition unit includes an ignition plug and an ignition ground. The ignition unit is provided in the combustion chamber. The flow speed decreasing member decreases a flow speed of a mixture of the air and the combustion gas running through a area between the ignition plug and the ignition ground.
In the drawings;
A combustion type power tool according to a first embodiment of the present invention will be described with reference to
The second shelter wall 35B extends in a circumferential direction and protrudes from the annular surface 12C in the axial direction. The second shelter wall 35B is joined to a radially outer end of the ignition ground holding portion 33 so that these are integral with each other. Since the first and second shelter walls 35A and 35B are adapted to mostly surround the area between the ignition plug 14 and the ignition ground 34, a speed of air-fuel mixture running through the area can be reduced. This can prevent a fire generated by the spark from being blown off by the fan flow of air-fuel mixture. Accordingly, stabilized ignitability is attainable, and stable combustion can result.
An essential portion of a combustion-type power tool according to a second embodiment is shown in
The single shelter wall 35C surrounds the area between the ignition plug 14 and the ignition ground 34. An inverted U-shaped notched portion 35d is formed at a circumferentially extending portion of the shelter wall 35C, and another inverted U-shaped notched portion 35d is formed at a boundary between the shelter wall 35C and the ignition ground holding portion 133. The lower surface of the notched portion 35d is positioned at the lower side than the end face 31. The notched portions 35d is functionally equivalent to the gaps 36 of the first embodiment for facilitating cleaning to the ignition plug 14 and the ignition ground 34 and to a region ambient thereto.
An essential portion of a combustion type power tool according to a third embodiment is shown in
An essential portion of a combustion type power tool according to a fourth embodiment is shown in
An essential portion of a combustion type power tool according to a fifth embodiment is shown in
An essential portion of a combustion type power tool according to a sixth embodiment is shown in
An essential portion of a combustion type power tool according to a seventh embodiment is shown in
Another shelter wall 41 protrudes from the upper horizontal surface portion 10B of the combustion chamber frame 10 in the axial direction of the fan shaft 13A. The other shelter wall 41 extends in the circumferential direction of the fan and has one end positioned close to the ignition ground holding portion 633 when the combustion chamber frame 10 is positioned to provide a sealed combustion chamber 23.
With this arrangement, blow-off of a fire generated by the spark by the fan flow of air-fuel mixture can be restrained thereby providing a stabilized ignitability, yet maintaining sufficient performance of the fan to provide high agitation performance, high combustion energy and high gas flowing performance.
The foregoing embodiments would provide advantage over the conventional arrangement shown in
While the invention has been described in detail with reference to specific embodiments thereof, it would be apparent to those skilled in the art that many modifications and variations may be made therein without departing from the spirit of the invention, the scope of which is defined by the attached claims.
For example, as shown in
Number | Date | Country | Kind |
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P2005-043276 | Feb 2005 | JP | national |