Electric hand-held hair cutting appliances come in a number of different types depending on the intended use of the appliance, such as for trimming facial or body hair, clipping the hair on one's head or on a pet, or for shaving facial or body hair. Such hair cutting appliances typically have at least one stationary blade and at least one reciprocating blade. Each of the blades includes a plurality of shearing teeth defining a cutting edge margin. The shearing teeth of the reciprocating blade overlie, in face-to-face contact with, the shearing teeth of the stationary blade. The reciprocating blade is operatively connected to an eccentric drive assembly such that rotation of the drive assembly linearly reciprocates the reciprocating blade relative to the stationary blade so that the shearing teeth of the reciprocating blade reciprocate across the shearing teeth of the stationary blade, thereby producing shearing action between the reciprocating blade teeth and the stationary blade teeth.
It is common for the reciprocating blade to be held in sliding engagement with the stationary blade by a blade mounting device that typically includes a spring member that biases the blades together. Known conventional blade mounting devices, however, have several disadvantages. For example, one known blade mounting device includes a double torsion spring for such a purpose. The spring has a pair of arms that hold the reciprocating blade against the stationary blade. The coil portions of the spring are fixed relative to the stationary blade, so during reciprocating movement of the reciprocating blade, the spring arms cause the reciprocating blade to move along an arcuate path, rather than a desired linear path, relative to the stationary blade.
In another known example, the blade mounting device includes a double torsion spring pressing a linear guide component against the reciprocating blade for guiding the reciprocating blade along a linear path across the stationary blade. The linear guide component is connected to a base of the blade mounting device by a pair of resiliently flexible (i.e., elastic) arms. The arms are constructed to have a low modulus of elasticity so that a large majority of the force exerted by the spring is applied to the linear guide component, as opposed to the arms. However, because the arms have such a low modulus of elasticity, the arms tend to buckle during heavy loading, leading to the reciprocating blade moving rearward on the stationary blade. This rearward movement displaces the shearing teeth of the reciprocating blade relative to the shearing teeth of the stationary blade, which can negatively affect the quality of the cut by the hair cutting appliance.
USPTO Backgrounds
USPTO Backgrounds