1. Field of the Invention
The present invention relates to a gas canister holder for holding a gas canister filled with a liquefied gas in a compact engine using liquefied gas as a fuel.
2. Description of Background Art
In a compact gas engine using liquefied gas mainly containing a butane gas charged in the gas canister as a fuel, a gas canister holder is provided for detachably attaching the gas canister so as to connect a carburetor chamber in the engine.
A compact gas engine is shown in FIG. 7 as an embodiment of the conventional compact gas engine. In FIG. 7, 1 denotes a compact gas engine and this compact gas engine 1 is constituted by parts mentioned below. A crank case 2, includes a cylinder 3 fixed to an upper portion of the crank case 2 and having an air intake port 4 and an exhaust port 5. A muffler 6 communicates with the exhaust port 5. A mixer 7 includes an air passage 8 and an amount adjusting chamber 9 communicating with an air passage 10. An air cleaner 11 provides outside air and feeds to the mixer 7. A muffler cover 12 communicates with the muffler 6.
A crank shaft 13 is supported by the crank case 2. A crank arm 14 is provided in the crank shaft 13. A connecting rod 15 is provided for connecting a crank pin 16 and a piston pin 17. A piston 18 and an ignition cap 19 are provided in a top portion of the cylinder 3.
Further, a gas canister holder 21 is provided for holding a cassette type gas canister A filled with a liquefied petroleum gas, and the gas canister holder has a cylindrical case 22 fixedly attached to a lower portion of the crank case 2. An end portion of the case 22 is provided with a gas canister outlet and inlet port 22a for taking in and out the gas canister A. A cap 23 is inserted and fitted into an inner portion of the gas canister outlet and inlet port 22a in the case 22 so as to be held thereby, and a compression coil spring 24 is provided for pushing the gas canister A.
A carburetor chamber case 31 is provided on the other end portion of the case 22, and the carburetor chamber case has an injection port 32 to which a nozzle-shaped discharge port B provided in a front end portion of the gas canister B is inserted. Further, a pressure adjusting device 33 is provided adjacent to a fuel passage connecting between the carburetor chamber case 31 and the pressure adjusting device 33. A fuel passage 35 connects the pressure adjusting device 33 and the amount adjusting chamber 9 of the mixer 7.
A structure for holding and fixing the cap 23 to the case 22 in the gas canister holder 21 will be described below with reference to FIG. 8. FIG. 8 is a drawing as seen from a Z direction in FIG. 7. An engaging groove 25 is formed on a peripheral wall surrounding the gas canister outlet and inlet port in the case 22 at regular intervals in a circumferential direction, and an engaging hook 26 engaging with and disengaging from the engaging groove 25 is formed on a peripheral wall of the cap 23. Accordingly, the engaging groove 25 substantially has an L shape and comprises an insert and non-insert portion extending along an axial direction of the case 22 and an engaging portion having a portion continuing the insert and non-insured portion so as to extend along a peripheral direction and a portion continuing the peripheral portion so as to extend along the axial direction. The engaging hook 26 is inserted into the insert and non-insert portion of the engaging groove 25 so as to move along the peripheral portion of the engaging and disengaging portion and is again returned along the axial portion so as to be engaged. As mentioned above, the cap 23 is inserted into the outlet and inlet port 22a of the case 22 and rotated to the peripheral direction so as to be mounted in a bayonet manner. In the case of removing the cap 23 from the case 22, the inverted operation to the operation mentioned above is performed.
When the gas canister A is fitted to the inner portion 4 of the case 22 and the cap 23 is fitted and fixed to the case 22, an end surface portion of the outlet and inlet port 22a side of the gas canister A is pressed by the compression coil spring 24 provided in the cap 23. Accordingly, the discharge port B provided in the opposite end portion is brought into contact with the injection port 32 of the carburetor chamber case 31 so as to be kept in an air tight state, and as it is pressed inward the gas canister discharge valve of the canister A is opened. Accordingly, the gas fuel corresponding to the liquid charged in the gas canister A enters into the carburetor chamber case 31 and is gasified. The gas fuel gasified within the carburetor chamber case 31 successively passes through the passage 34, the pressure adjusting device 33, the passage 35, the amount adjusting chamber 9 in the mixer 7 and the passage 10 so as to enter into the air passage 8 in the mixer 7 and is mixed with the air so as to be fed to the inner portion of the cylinder 3 through the air intake port 4.
In the gas canister holder in the compact gas engine in accordance with the conventional art, the following problems exist.
In the case where the gas canister A is fitted to the inner portion of the case 22 so as to fit and hold the cap 23 to the case 22, the case 23 receives a force toward the inner portion of the cap (rightward in FIG. 7) through the compression coil spring 24 from the base end portion of the gas canister A, and the engaging hook 26 of the cap 23 receives a force toward the opposite direction to the case of the cap 23 (leftward in FIG. 7) from the portion along the peripheral direction in the engaging groove 25 of the case 22. Therefore, the cap 23 fitted to the case 22 is held by two pressing forces opposite to each other mentioned above. On the contrary, in the case where the cap 23 is fitted to the case 22 at a time when the gas canister A does not exist in the inner portion of the case 22, the spring 24 does not work and the forces mentioned above do not respectively act, so that the cap 23 is free with respect to the case 22. Therefore, there is a risk that the engaging hook 26 of the cap 23 freely moves within the engaging groove 25 of the case 22 during transit of the engine 1 so that the cap 23 gets out of place from the case 22 and further the removed cap 23 is lost.
The cap 23 fitted to the conventional case 22 is formed by pressing the metal plate. However, in the case where the compact gas engine 1 is used for a machine operating outdoors for a long time, in summer season, the metal cap 23 becomes hot if exposed to direct sunshine, so that there is a risk that the operator is burned when the operator holds the engine with unprotected hands. On the contrary, in the case where the compact gas engine 1 is used for a machine operating outdoors for a long time, the gas canister A is replaced relatively frequently. In the case of replacing the gas canister A, the operator holds the cap 23 and attaches the cap to and detaches the cap from the case 22. In this case, as mentioned above, in the summer season, since the temperature of the cap 23 is high, there is a risk that the cap 23 may burn the operator's unprotected hands.