Patent ID: 7181988

Claim:
An actuator comprising: a frame; a driving source provided at one end of said frame; a driving force-transmitting mechanism comprising a driving pulley connected to and rotatably supported by a drive shaft of said driving source, a driven pulley rotatably supported at the other end of said frame, and a belt member which runs over said driving pulley and said driven pulley; a slider to which a driving force is transmitted by said driving force-transmitting mechanism under a driving action of said driving source, said slider being displaced reciprocally in an axial direction of said frame; a guide mechanism including a pair of first guide rails installed in said axial direction to inner wall surfaces of said frame, a pair of second guide rails installed in said axial direction to side surfaces of said slider opposed to said frame, and a plurality of balls which roll along ball-rolling grooves formed in said first and second guide rails respectively, for guiding said slider when said slider is displaced along said frame; and a tension-adjusting mechanism for adjusting a tension of said belt member, said tension-adjusting mechanism comprising a pulley holder which rotatably retains said driven pulley, said pulley holder comprising a plate member, which extends in a widthwise dimension of said frame and opposes said first guide rails, and wherein respective ends of said plate member engage with ball-rolling grooves formed in said first guide rails, wherein said first and second guide rails are formed of a hardened metal material subjected to a hardening treatment separately from said frame and said slider and thereafter said first and second guide rails are installed in said frame and said slider, and wherein said frame and said slider are formed of a non-hardened light metal material or a resin material having a weight lighter than that of said hardened metal material.