Socket wrench device for rotating a spark plug

A socket wrench device for rotating a spark plug, said spark plug having a hexagonal intermediate portion and an externally threaded portion, said device comprising:

• a socket member, having a first end surface and a second end surface, including a hexagonal hole formed in said first end surface thereof, an endless series of ratchet teeth provided on an intermediate portion of said second end surface of said socket member, and an externally threaded portion positioned near said ratchet teeth, said hexagonal hole being shaped in conformity with said hexagonal intermediate portion of said spark plug;
• a driving member including an endless series of ratchet teeth provided on an end surface thereof engaging with said ratchet teeth of said socket member, an outward flange extending from said driving member, and a hole formed in said driving member;
• an annular spring element sleeved on said driving member;
• and
• a retaining sleeve having a large-inner-diameter portion located at an end thereof, a small-inner-diameter portion located at the other end of said sleeve, a middle-inner-diameter portion interposed between said small-inner-diameter portion and said large-inner-diameter portion, a large-diameter shoulder defined between inner surfaces of said large-inner-diameter portion and said middle-inner-diameter portion, and a small-diameter shoulder defined between inner surfaces of said middle-inner-diameter portion and said small-inner-diameter portion, said large-inner-diameter portion having a threaded inner surface engaged threadably with said externally threaded portion of said socket member so as to retain both said driving member and said spring element on said socket member, said spring element being brought into contact with said small-diameter shoulder of said sleeve at one end surface thereof and with said flange of said driving member at the other end surface thereof so as to bias said ratchet teeth of both said socket member and said driving member to join together, a circumference of said second end surface of said socket member being brought into contact with said large-diameter shoulder of said sleeve, both said socket member and said retainer being capable of rotating with said driving member when said driving member is initially rotated to screw said spark plug into a threaded hole of a cylinder of an internal combustion engine;
• whereby, when subsequent continuous rotation of said wrench device tightens said spark plug against said cylinder to a predetermined extent, an external torque which is applied to said wrench device compresses said spring element, so that said ratchet teeth of said driving member are disengaged from said ratchet teeth of said driving member, thereby stopping rotation of said spark plug relative to said cylinder.