Combustion-type power tool having cooling arrangement

1. A combustion-type power tool comprising:

a housing;

a cylinder disposed in the housing, the cylinder defining an axial direction;

a cylinder head disposed at an end of the housing;

a combustion chamber frame disposed in the housing and movable between a first position and a second position, the combustion chamber frame including a base section, a head section abuttable on the cylinder head to provide a combustion chamber when the combustion chamber frame is at the first position, and a connection portion for connecting the head section with the base section; and

a fan rotatably disposed in the combustion chamber;

wherein the fan includes fan blades which define a widthwise center line and having widthwise edge portions of the fan blades which define a widthwise edge line at a side of the cylinder head; and

wherein the widthwise center line is offset from the connection portion toward another end of the housing, and the widthwise edge line is offset from the connection portion toward the cylinder head when the combustion chamber frame is at the second position.

2. The combustion-type power tool as defined in claim 1 , wherein the base section extends along the cylinder and is connected to a push lever, the push lever being movable in the axial direction against a workpiece; and

wherein the head section extends in the axial direction toward the cylinder head.

3. The combustion-type power tool as defined in claim 1 , wherein the connection portion is extended perpendicular to the axial direction and connects between the base section and the head section.

4. The combustion-type power tool as defined in claim 1 , wherein the combustion chamber is formed by the cylinder head, the combustion chamber frame and an upper surface of a piston slidably disposed in the cylinder, when the combustion chamber frame is at the first position.

5. The combustion-type power tool as defined in claim 1 , wherein an air flow passage is formed between the cylinder head and the head section of the combustion chamber frame, when the combustion chamber is at the second position.

6. The combustion-type power tool as defined in claim 1 , further comprising a head switch disposed in the housing to detect a position of the combustion chamber frame relative to the housing.

7. The combustion-type power tool as defined in claim 6 , wherein the fan is rotated for a period of not more than 7 seconds when the head switch detects that the combustion chamber frame is at a predetermined position.