Electric hair trimmer

A hair trimmer comprising:

• a casing having a longitudinal axis and also having an actuating device;
• a cutter head disposed at one end of the casing and including a generally elongated fixed blade and a movable blade adapted to be driven by the actuating device so as to reciprocate relative to the fixed blade in a direction parallel to a lengthwise direction of the fixed blade to trim the hairs;
• a hair restraint means for regulating the distance between the cutter head and the scalp, configured to permit the hairs to extend across a space between the cutter head and the hair restraint means in a substantially bundled form of a thickness equal to the distance between the scalp and the cutter head, said hair restraint means having a contact portion adapted to be held in contact with a scalp with a plane of relative sliding movement of the fixed and movable blades held generally perpendicular to the scalp, said contact portion being, relative to an imaginary plane extending orthogonal to the cutter head and touching tips of cutting teeth of the movable blade, spaced from the scalp a first distance which is relevant for the thickness of the hairs to be trimmed;
• a retainer edge arranged at a rearward position relative to the imaginary plane so as to regulate the quantity of the hairs to be trimmed during one working step to an amount corresponding to a second distance between the imaginary plane and the retainer edge;
• and
• an attachment having the contacting portion and adapted to be removably mounted on the casing, wherein the attachment has a knob moving in a direction parallel to a lengthwise direction of the cutter head and a direction changing portion operable to make the contacting portion move in a direction perpendicular to the lengthwise direction of the cutter head in response to a movement of the knob.