Knife for cutting in sliding contact with ruler edge

Claim 1

A knife comprising in combination: a hollow blade holder of tubular form provided with a longitudinal slit therealong; an elongated knife blade slidably mounted in said blade holder and having a longitudinal cutting edge with a forward tip part and a sliding flank face provided near said tip part for sliding along a ruler edge thereby to enable the tip part to advance in a controlled path in cutting a material lying under the ruler edge, said knife blade being of a break-off type and having longitudinally equally spaced grooves disposed at a specific angle relative to the cutting edge of the blade and dividing the blade into a plurality of successively disposable blade units, said knife blade being provided with engagement holes disposed at intervals along the length of the blade; a guide member rigidly secured to said blade holder at a position spaced apart from and in front of said tip part in said path of cutting advance; a manually operable slider engaging in said slit in the blade holder for guided sliding movement along the slit, said slider being connected to said knife blade, whereby the blade can be adjustably moved longitudinally by manually moving the slider; and knife bladle locking means for preventing said blade from moving longitudinally relative to said blade holder, said locking means comprising a tongue-like member extending from said blade holder longitudinally and forwardly and having an elastically deflectable property, a locking projection on the forward end of said tongue-like member for disengageably engaging any one of said engagement holes, a lever member integrally connected to said forward end of the tongue-like member and extending rearwardly along the same, and a projection on said lever member midway between the ends thereof and engaging with said blade holder to function as a fulcrum for said lever member, whereby when the free end of the lever member is manually depressed, the forward end of the tongue-like member is raised to disengage said locking projection from the hole with which it has been in engagement, thus allowing longitudinal movement of the knife blade.