The present invention relates to a combustion-type power tool, and more particularly, to a combustion-type fastener driving tool in which combustible gas is ejected from a gas canister into a combustion chamber, mixed with air and ignited to drive a piston, thus generating power to drive nails or the like.
The combustible gas is ejected into the combustion chamber 111 from the gas canister assembled in the housing 102. In the combustion chamber 111, the combustible gas and air are stirred and mixed together by the fan 113. The ignition plug body 116 ignites the resultant mixture gas. The mixture gas explodes to drive piston 109 for driving the driver blade, which in turn drives nails into a workpiece such as a wood block. Such conventional power tool is disclosed in U.S. Pat. No. 5,197,646 and Japanese Patent Publication No. Hei 3-25307.
The combustion-type driving tools disclosed in these publications provide a head cap 104 having a structure as shown in FIG. 4. In the combustion-type driving tool of
The electrode 116A of the ignition plug body 116 and an opposing electrode section 156 oppose to each other. The electrode section 156 has a protruding section protruding around the axis 113a and in a circumferential direction of the fan 113. By virtue of this positional relation between the electrode 116A and the opposing electrode section 156, a main stream A and a sub-stream B develop in the combustion chamber 111 as shown in
A cover may be provided to cover both the electrode 116A and the opposing electrode section 156 to improve ignitability of the gas-fuel mixture. However, this not only increases the number of components of the combustion-type driving tool to increase production cost, but also makes it troublesome to clean the interior of the combustion chamber. Thus, maintenance to the combustion chamber becomes degraded.
It is an object of the present invention to provide a combustion-type power tool capable of preventing the sub-stream from passing through the gap between the electrode and the opposing electrode section, and yet capable of providing a desirable ignition without lowering the maintenance efficiency of the tool.
This and other objects of the present invention will be attained by a combustion-type power tool including a housing, a head section, a combustion chamber frame, a cylinder, a piston, a motor, a fan, an ignition plug body, and an opposing electrode section. The head section closes the one end of the housing and is formed with a gas passage having one end functioning as a gas injection port for ejecting combustible gas and another end in communication with a gas canister. The combustion-chamber frame is provided in the housing and movable in a lengthwise direction of the housing. The combustion-chamber frame has one end abuttable on the head section. The cylinder is secured to the housing and is in communication with an interior of the combustion-chamber frame. The cylinder guides the movement of the combustion-chamber frame. The piston is reciprocally movable with respect to the cylinder. A combination of the piston, the head section, the combustion-chamber frame and a head section side of the cylinder defines a combustion chamber when the one end of the combustion-chamber frame abuts on the head section. The motor is supported on the head section. The fan is secured to the motor and is positioned in the combustion chamber. The fan is rotatable about a rotation axis. The ignition plug body is supported by the head section and has an electrode positioned in the combustion chamber for igniting a mixture of air and the combustible gas. The opposing electrode section is provided in the combustion chamber and is located closer to the head section than the fan to the head section. The opposing electrode section opposes to the electrode for generating a spark therebetween. The opposing electrode section is supported by the head section at a supporting position positioned closer to the axis of the fan than the electrode to the axis of the fan, and the opposing electrode section protrudes outwardly from the supporting position in a radial direction of the rotation axis.
By the rotation of the fan, a mixture of air and combustible gas is circularly moved in the combustion chamber as a main stream. Further, a sub-stream is generated upon generation of the main stream. The sub-stream can flow along the bottom surface of the opposing electrode section, and cannot be entered into the ignition space defined between the electrode and the opposing electrode section. Thus, the sub-stream does not flow across the ignited flame generated between the electrode and the opposing electrode section. Consequently, desirable ignition can result. Further, because the opposing electrode section can serve as a shielding member, maintenance to the ignition area can be facilitated without increase in numbers of components.
Preferably, the head section has a combustion chamber defining surface which at least includes a first part surrounding the rotation axis of the fan, a second part supporting the ignition plug body, and a third part located radially outer side of the second part in the radial direction of the rotation axis of the fan. The electrode of the ignition plug body is located at the second part. Further, the second part is located farther from the piston than the first and third parts to the piston for providing a protruding ignition space. Further, the opposing electrode section has an opposing surface in opposition to the piston, the opposing surface being flush with the third part in the radial direction of the fan. With this arrangement, the opposing electrode section can efficiently shield the ignition space without disturbing the flow of sub-stream. Thus, desirable ignition can be obtained.
Alternatively, the opposing electrode section has an opposing surface in opposition to the piston, the opposing surface being positioned farther from the piston than the third part to the piston in the radial direction of the fan. This structure can further prevent or restrain the main stream flowing along the third part toward the rotation axis of the fan from entering into the ignition space.
In the drawings;
A combustion-type power tool according to one embodiment of the present invention will be described with reference to
A head cover 10 is mounted on the top of the main housing 2A. The head cover 10 has a motor-supporting section 10A. A storage cover 18 is hingedly mounted on the top of the canister housing 2B through a pin 60 and selectively opens or closes the top of the canister housing 2B. A handle 26 having a trigger switch 25 extends from the canister housing 2B. A magazine 27 and a tail cover 28 are provided on the bottoms of the main housing 2A and canister housing 2B. The magazine 27 contains nails (not shown), and the tail cover 28 is adapted to guide each nail to a predetermined position.
A push lever 5 is movably provided at the lower end of the main housing 2A and is positioned in conformance with a nail setting position defined by the tail cover 28. The push lever 5 is coupled to a coupling member 57 that is secured to a combustion-chamber frame 6 which will be described later. When the entire housing 2 is pressed toward a workpiece while the push lever 5 is in abutment with the workpiece, an upper portion of the push lever 5 is retractable into the main housing 2A.
A head cap 4 is secured to the top of the main housing 2A and closes the open top end of the main housing 2A. The head cap 4 supports a motor 12 having a motor shaft 12A. A fan 13 is coaxially fixed to the motor shaft 12A. The head cap 4 also supports an ignition plug body 16. The motor 12 is driven when the push lever 5 moves upward to a predetermined position. The head cap 4 has a canister housing side in which is formed an ejection passage 34 which allows a combustible gas to pass therethrough. One end of the ejection passage 34 serves as an ejection port 15 that opens at the lower surface of the head cap 4. Another end 32 of the ejection passage 34 is communicated with a gas canister 14 which will be described later. The head cap 4 has a seal 52 for providing a seal between the head cap 4 and an upper end of the combustion-chamber frame 6 when the upper end of the combustion-chamber frame 6 abuts on the head cap 4.
The combustion-chamber frame 6 is provided in the main housing 2A and is movable in the lengthwise direction of the main housing 2A. The uppermost end of the combustion-chamber frame 6 is abuttable on the lower surface of the head cap 4. The coupling member 57 described above is secured to the lower end of the combustion-chamber frame 6 and is connected to the push lever 5. A cylinder 3 is fixed to the main housing 2A. The inner circumference of the combustion-chamber frame 6A is in sliding contact with an outer peripheral surface of the cylinder 3 for guiding the movement of the combustion-chamber frame 6. A compression coil spring 7 is interposed between the lower end of the cylinder 3 and the lower end of the coupling member 57 for biasing the combustion-chamber frame 6 in a direction away from the head cap 4. The cylinder 3 has a lower portion formed with an exhaust hole 50 in fluid communication with the above-mentioned exhaust port 55. An exhaust-gas check valve (not shown) is provided to selectively close the exhaust hole 50. A bumper 51 is provided on the bottom of the cylinder 3. A seal 53 is provided on the top of the cylinder 3 to provide a seal between the inner circumference of the lower part of the combustion-chamber frame 6 and the outer circumference of the upper part of the cylinder 3 when the combustion-chamber frame 6 abuts on the head cap 4.
A piston 9 is slidably and reciprocally provided in the cylinder 3. When the upper end of the combustion-chamber frame 6 abuts on the head cap 4, the head cap 4, the combustion-chamber frame 6, the upper portion of the cylinder 3, the piston 9 and the seals 52 and 53 define in combustion a combustion chamber 11. A plurality of ribs 3A are provided on the inner peripheral portion of the combustion-chamber frame 6 which defines the combustion chamber 11. The ribs 3A extend in the lengthwise direction of the main housing 2A and project radially inwardly toward the axis of the main housing 2A. The ribs 3A cooperate with the fan 13 to promote the stirring and mixing of air with the combustible gas in the combustion chamber 11. The above-mentioned intake port (not shown) is adapted to supply air into the combustion chamber 11, and the exhaust hole 50 and the exhaust port 55 are adapted to exhaust the combusted gas from the combustion chamber 11.
A driver blade 8 extends downwards from a side of the piston 9, the side being opposite to the combustion chamber 11 to the lower end of the main housing 2A. The driver blade 8 is positioned coaxially with the nail setting position in the tail cover 28, so that the driver blade 8 can strike aginst the nail. When the piston 9 moves downward, the piston 9 abuts on the bumper 51 and stops.
The fan 13 is provided in the combustion chamber 11, and the ignition plug body 16 and the ejection port 15 are respectively exposed and open to the combustion chamber 11. Rotation of the fan 13 performs the following three functions. First, the fan 13 stirs and mixes the air with the combustible gas as long as the combustion-chamber frame 6 remains in abutment with the head cap 4. Second, after the mixed gas has been ignited, the fan 13 causes turbulence of the air-fuel mixture, thus promoting the combustion speed of the air-fuel mixture in the combustion chamber 11. Third, the fan 13 performs scavenging such that the exhaust gas in the combustion-chamber 11 can be scavenged therefrom when the combustion-chamber frame 6 moves away from the head cap 4.
As
An opposing electrode section (for example, a cathode) 56 is provided on the head cap 4 at a position in confrontation with the electrode 16A of the ignition plug body 16 for generating a spark in cooperation with the electrode 16A. The opposing electrode section 56 is positioned closer to the head cap 4 than the fan 13 to the head cap. The opposing electrode section 56 is supported by the head cap 4 at a position closer to the axis 13a of the fan 13 than the electrode 16A to the axis 13a. The opposing electrode section 56 protrudes from the head cap 4 outwardly in the radial direction of the fan 13. The opposing electrode section 56 has a surface in confrontation with the piston 9, and the surface lies flush with the third part 4C of the head cap 4 in the radial direction of the fan 13.
The canister housing 2B has a bottom wall 35. The canister housing 2B and the storage cover 18 define a gas canister chamber 17 in which the gas canister 14 is accommodatable. The canister housing 2B has the lower inner peripheral surface portion provided with a stepped section 24. A compression spring 23 is seated on the stepped section 24. A leaf spring 20 is secured to the storage cover 18 so as to push the gas canister 14 from above.
The gas canister 14 contains liquidized combustible gas. The gas canister 14 has a cap 19 at its top. The cap 19 has a rod 31 for ejecting a predetermined amount of the liquidized gas. An annular member 22 is secured to the outer circumference of the gas canister 14 at a position near the top of the gas canister 14. The above-mentioned compression spring 23 is interposed between the annular member 22 and the stepped section 24 for biasing the gas canister 14 upwards. When the storage cover 18 is closed, the gas canister 14 is pushed down against the biasing force of the compression spring 23 and is positioned in alignment with the ejection passage 34. A cam (not shown) is provided in the housing 2. The cam is angularly rotatable in synchronism with the movement of the push lever 5 by a predetermined moving stroke. Upon rotation of the cam, the gas canister 17 moves, so that the rod 31 is pushed against the open end 32 of the head cap 4. Thus, the liquidized gas in the gas canister 14 can be ejected into the ejection passage 34 through the rod 31.
With this structure, in the non-operational state of the combustion type nail driver 1, the push lever 5 is biased downward by the biasing force of the compression coil spring 7, so that the push lever 5 protrudes from the lower end of the tail cover 28. Thus, the uppermost end of the combustion-chamber frame 6 is spaced away from the head cap 4 because the coupling member 57 couples the combustion-chamber frame 6 to the push lever 5. Further, a part of the combustion-chamber frame 6 which part defines the combustion chamber 11 is also spaced from the top portion of the cylinder 3. Hence, a gap is provided between the head cap 4 and the combustion chamber frame 6, and a gap is also provided between the top of the cylinder 3 and the frame 6. In this condition, the piston 9 stays at the top dead center in the cylinder 3.
With this state, if the push lever 5 is pushed onto the workpiece such as a wood block while holding the handle 26 by a user, the push lever 5 is moved upward against the biasing force of the compression coil spring 7. At the same time, the combustion-chamber frame 6 which is coupled to the push lever 5, is also moved upward, closing the above-described gaps between the head cap 4 and the combustion-chamber fame 6 and between the cylinder 3 and the frame 6. Thus, the sealed combustion chamber 11 is provided by the seals 52 and 53. Upon elapse of a predetermined time period after the push lever 5 is pushed onto the workpiece, the gas canister 14 is pushed and the combustible gas is ejected into the combustion chamber 11 through the ejection port 15. Further, the motor 12 is turned on at the same time, rotating the fan 13. The fan 13 and the ribs 3A protruding into the combustion chamber 11 cooperate, stirring and mixing the combustible gas with air in the combustion chamber 11.
As shown in
The sub-stream B is also developed when the main stream A is generated. The sub-stream B is directed upwardly along the vertical wall that connects the fist part 4A to the second part 4B of the head cap 4. As described above, the opposing electrode section 56 is supported by the head cap 4 at a position closer to the axis 13a of the fan 13 than the electrode 16A to the axis 13a, and, the opposing electrode section 56 protrudes outward in the radial direction of the fan 13. Hence, the sub-stream flows along the bottom surface of the opposing electrode section 56 and cannot flow into the protruding ignition space 4a. In other words, the sub-stream B cannot flow across the ignited flame generated in the gap between the electrode 16A and the opposing electrode section 56. Further, since the bottom surface of the opposing electrode section 56 opposing to the piston 9 lies flush with the third part 4C of the head cap 4, the sub-steam B can flow smoothly along the bottom surface and the third part 4C without any turbulence. In other words, the bottom surface of the opposing electrode section 56 can effectively prevent the sub-stream B from being disturbed, which ensures desirable ignition of the gas mixture.
Then, when the user turns on the trigger switch 25 at the handle 26, the ignition plug body 16 generates a spark, which ignites the gas mixture. At this time, the fan 13 keeps rotating, promoting the turbulent combustion of the gas mixture. This enhances the output of the power tool. The combusted and expanded gas pushes the piston 9 downward. Therefore, a nail in the tail cover 28 is driven into the workpiece through the driver blade 8 until the piston 9 abuts on the bumper 7.
As the piston 9 passes by the exhaust hole 50, the check valve (not shown) opens the exhaust hole 50 because of the application of the combustion gas pressure to the check valve. Therefore the combustion gas is discharged from the cylinder 3 through the exhaust hole 50 and then discharged outside through the filter 54 and exhaust port 55. The check valve is closed when the pressure in the cylinder 3 and combustion chamber 11 is restored to the atmospheric pressure as a result of the discharge. Combustion gas still remaining in the cylinder 3 and the combustion chamber 11 has a high temperature at a phase immediately after the combustion. However, the high temperature can be absorbed into the walls of the cylinder 3 and the combustion-chamber frame 6 to rapidly cool the combustion gas. Thus, the pressure in the sealed space in the cylinder 3 further drops to less than the atmospheric pressure (creating a so-called “thermal vacuum”). Accordingly, the piston 9 is moved back to the initial top dead center in the cylinder 3 by virtue of the pressure difference between the internal pressure in the combustion chamber 11 and the pressure in the lower part of the cylinder 3 lower than the piston 9.
Then, the user turns off the trigger switch 25 and lifts the combustion type nail driver 1 from the workpiece and the push lever 5 is separated from the workpiece. As a result, the push lever 5 and the combustion-chamber frame 6 move downward due to the biasing force of the compression coil spring 7. The above-mentioned gaps are provided again. The fan 13 keeps rotating for a predetermined time period after the trigger switch 25 is turned off. Thus, fresh air flows into the combustion chamber 11 through the intake port and through the gaps, expelling the residual gas through the exhaust port 55. Thus, the combustion chamber 11 is scavenged. Then, the fan 13 stops rotating, and the combustion type nail driver 1 restores the initial state.
The combustion-type power tool according to the present invention is not limited to the above-described embodiment, but various changes and modifications can be made within the scope of the invention, which is defined by the claims. For example, in the above-described embodiment, the bottom surface of the opposing electrode section 56 opposing to the piston 9 is flush with the third part 4C in the radial direction of the fan 13. However, the bottom surface of the opposing electrode section 56 opposing to the piston 9 can be positioned farther from the piston 9 than the third part 4C to the piston 9. This structure can further reduce a probability of entering the main stream flowing along the third part 4C into the protruding ignition space 4a.
Moreover, in the above-described embodiment, the combustion-chamber frame 6 is connected to the push lever 5 through the separate coupling member 57. However, the combustion-chamber frame 6 and the coupling member 57 can be formed integrally with each other as a single unit, and this unit can be coupled to the push lever 5.
Number | Date | Country | Kind |
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P2003-044863 | Feb 2003 | JP | national |
Number | Name | Date | Kind |
---|---|---|---|
4256071 | Casull | Mar 1981 | A |
5197646 | Nikolich | Mar 1993 | A |
6584945 | Porth | Jul 2003 | B2 |
20010006046 | Thieleke et al. | Jul 2001 | A1 |
Number | Date | Country |
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1 053 834 | Nov 2000 | EP |
3-25307 | Apr 1991 | JP |
Number | Date | Country | |
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20040164117 A1 | Aug 2004 | US |