Pneumatic driven ratchet wrench

A pneumatic driven ratchet wrench comprising:

• a wrench housing having a handgrip section, a head section, and a middle section disposed between and interconnecting said head section and said handgrip section;
• a pneumatic motor mounted rotatably in said middle section and rotatable relative to said wrench housing about a central axis;
• a ratchet wheel unit mounted rotatably in said head section;
• first and second gear members mounted in said wrench housing and disposed adjacent to said ratchet wheel unit;
• an urging member disposed in said wrench housing for biasing said first and second gear members to engage said ratchet wheel unit;
• a transmission unit mounted in said middle section, driven by said pneumatic motor, and including a swingable driving link that is swingable about a first axis perpendicular to said central axis, said first and second gear members being pivoted to said swingable driving link so that said first and second gear members can be simultaneously and alternately moved to and fro when said swingable driving link is driven by said pneumatic motor to swing about said first axis;
• and
• a gear-selecting unit including an operating knob, a swingable switching member that is mounted to said wrench housing, and first and second pushing members mounted slidably in said wrench housing, said operating knob being mounted movably on an exterior of said wrench housing and being disposed distal from said head section, each of said first and second pushing members being connected to said swingable switching member, said swingable switching member being driven to swing about a second axis by said operating knob so as to drive sliding movement of one of said first and second pushing members from a releasing position to a pushing position and simultaneous sliding movement of the other one of said first and second pushing members from the pushing position to the releasing position, said second axis being perpendicular to said central axis;
• wherein each of said first and second pushing members pushes a respective one of said first and second gear members to move away and disengage from said ratchet wheel unit when moved from the releasing position to the pushing position;
• and
• wherein each of said first and second gear members is released from the respective one of said first and second pushing members to move toward and engage said ratchet wheel unit by the biasing action of said urging member when the respective one of said first and second pushing members is moved from the pushing position to the releasing position.