Vehicle-carrying purpose wrench
BACKGROUND OF THE INVENTION 
     This invention relates to a wrench and in particular to one which is easily carried and can take the vehicle electric power as its power source thereby it facilitates the replacement of the wasted tire of a vehicle in any event. 
     The prior wrenches for replacing the wasted tire generally can be classified into two categories, namely manual type and pneumatic type. The former has to use the man power to loosen the wasted tire from the vehicle or to tighten the new tire to the vehicle. Therefore it is unpractical for use, especially for female driver. The latter, usually being seen in the vehicle maintenance station, utilizes a compressor as the power source to drive a pneumatic wrench for tightening or loosening the screws. However, such equipment is too cumbersome to be carried along with the vehicle thereby it still can not meet the practical requirement for the drivers. 
     It is, therefore, an object of the present invention to obviate and mitigate the above-mentioned drawbacks. 
     SUMMARY OF THE INVENTION 
     It is the primary object of the present invention to provide vehicle-carrying purpose wrench which has a compact form and hence can be carried along with a vehicle for replacing the wasted tire at all events. 
     It is another object of the present invention to provide a vehicle-carrying purpose wrench which can take the cigarette ligter socket in a vehicle as its electrical power source without the necessity of other power generators. 
     It is a further object of the present invention to provide a vehicle-carrying purpose wrench which is economical to use. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partial cross-sectional view of a preferred embodiment of the present invention; 
     FIG. 2 is a fragmental perspective view of a tool assembly of the present invention; 
     FIG. 3 is a cross-sectional view taken along the line 3--3 of the FIG. 1; 
     FIG. 4 is a partial cross-sectional view thereof showing the prosent invention being in a operation status; 
     FIG. 5 is a cross-sectional view taken along the line 5--5 of the FIG. 4; 
     FIG. 6 is a local perspective view illustrating the relative position between a drive member and a transmission member when an elastic member being in a pressed setuation; and 
     FIG. 7 is a local perspective view illustration the relative position between a drive member and a transmission member when the elastic member being in an unpressed situation. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings and more particularly to FIG. 1, a preferred embodiment of the present invention mainly comprises a housing assembly (1), a tool assembly (2) and a trigger assembly (3). The housing assembly (1) consists of a a motor casing (10, a tool casing (11), a cover (12) and a handle (13). In the interior of the motor casing (10) is disposed a roversible motor (M) which can be driven to rotate both in forward and reverse directions by the electric power supplied from the cigarette lighter socket of a vehicle. A tool casing (11) connected with the motor casing (10) comprises in its interior a tool assembly (2) which is used to replace the wasted tire of a vehicle. The cover (12) is fixed to one side of the tool casing (11) by means of screws. The handle (13) is disposed below the motor casing (10) and the tool casing (11) for easily grasping the present invention. Further, the handle is formed at its upper portion with a space to receive the trigger assembly (3). 
     Referring to FIG. 2, the tool assembly (2) mainly comprises a main body (20), a drive member (21), a transmission member (22), an elastic member (23), a drive shaft (24), a follower shaft (25) a follower member (26). The main body (20) has two parallel side walls (201) and (202) and a recess (203) formed therebetween. The first side wall (201) is provided at the center with an aperture (201a) through which the shaft of the motor can engage with the drive shaft (24). Around the central axis of the aperture (201a) are furnished with three equally spaced pin holes (201b) in which three pins (204) can be respectively located. At the upper portions of the side walls (201) and (202) are properly provided two pin holes (201c) and (202c) in alignment, the inner diameters of which are somewhat larger than the outer diameter of a fixing pin (205). The drive member (21) is rotatably mounted in the recess (203) of the main body (20) by passing the fixing pin (205) through the aperture (210) of the drive member (21) and pin holes (201c) and (202c) of the side walls (201) and (202). 
     The drive member (21) further comprises two wings (211) extending dawnward and an extension (212). Referring to FIG. 3 or 4, the inner surfaces of the wings (211) form an arcuate surface of which the radius of curvature is arranged to correspond to that of the first circumferential section (220) of the transmission member (22). In other words, when the transmission member (22) has been located in the recess (203) of the main body (20), the first circumferential section (220) thereof can slightly contact the inner arcuate surface of the wings (211) of the drive member (21). The transmission member (22) further is provided with a second circumferential section (221) in which a notched slot (222) is formed to correspond to the extention (212) of the drive member (as shown in FIG. 6 or 7). The transmission member (22) is furnished with a central hole (223) having a rectangular key (224) formed thereon so that after the drive shaft (24) having passed through the central hole (223) of the transmission member (22) with the rectangular key slot (240) engaging with the rectangular key (224), the drive shaft (24) together with the transmission member (22) can rotate synchronously. One end of the drive shaft (24) passes through the elastic member (23), the transmission member (22) and the side walls (201) and (202) of the main body (20) to join with the shaft of the motor (M) so as to be capable of being driven to rotate thereby. The other end of the drive shaft (24) having a stop ring (241) to prevent the elastic member (23) from being dropped out thereof can receive the connection end (250) of the follower shaft (25). A follower member (26) which is fixed to the follower shafts (25) is a ring-shaped body having teeth on the circumference thereof to correspond to the wings (211) of the drive mtmber (21). The other end of the follower shaft (25) is a rectangular-shaped body (251) to cooperate with a sleeve for tightening or loosening the screws as replacing wasted tires. 
     As the elements described hereinbefore are received within the main body (20) by inserting the cover (27) sealingly into the aperture (202a) of the side wall (202) thereof. 
     Referring to FIG. 1, after those above-mentioned elements have been assembled, a Y-shaped press plate (30) of the trigger assembly (3) is arranged to lean against a stop (31) which in turn tightly contact with the first side wall (201) of the main body (20) to make the pins (204) project inwardly so that the first circucumferential section (220) of the transmission member (22) can slightly contact with the inner arcuate surface of the drive member (21) (FIG. 6) to compress the elastic member (23) as well as to prevent the wings (211) of the drive member (21) from engaging with the teeth (260) of the follower member (26) as shown in FIG. 3. Under such circumstance, even the drive member (21) can be driven to rotate by the motor (M), the follower member (26) still will not be rotated accordingly. 
     However, as shown in FIG. 4, when the trigger (32) of the trigger assembly (3) is pressed along the arrow F, the upper portion (320) of the trigger (32) will push the lower end (301) of the Y-shaped press plate (30) from its original posetion shown in FIG. 1. Therefore, the compressed elastic member (23) will push the transmission member (22) toward the first side wall (201) of the main body (20) so that, as shown in FIG. 7, the first circumferential section (220) will disengage from the inner arcuate surface of the drive member (21) to make the drive member (21) rotatable about the fixing pin (205) to some extent. 
     Referring to FIG. 5, when the motor (M) drives the drive shaft (24) together with the transmission member (22) and the main body (20) to rotate synchronously, the drive member (21), owing to the disengagement from the first corcumferential section (220) of the transmission member (22) as well as the effect of the centrifugal force, will rotate in such a manner that one of the two wings (211) of the drive member (21) can engage with one of the teeth (260) of the follower member (26) to drive the follower shaft (25) to rotate accordingly. Then, a sleeve (not shown) connected with the rectangular-shaped body (251) of the follower shaft (25) can be rotated thereby to assemble/disassemble the screws which are used to fix the tire to a vehicle. 
     Conclusively, the present invention utilizes the vehicle cigarette lighter socket as an electric power source to make a reversible motor combined with a tool assembly in such a manner that the transmission of the rotation force produced by the motor can be controlled by a trigger assembly which can adjust the engagement/disengagement relationship between the wings of the drive member and the teeth of the follower member. Therefore, it indeed has not only the novelty and inventiveness but also the practicability.