An adjustable safety utility knife includes an elongated ergonomically shaped
handle formed of two elongate shell members each having a
peripheral edge and an outer generally convex surface and an inner generally
concave surface. The shell members are fastened at the
peripheral edges along a vertical parting plane to form an elongated
internal cavity. The
handle defines a front end, a back end and an intermediate portion suitable for being gripped by a user and also defining top and bottom surfaces extending along opposite sides of the shell members along the
peripheral edges. The
handle has a slot-like aperture at the front end substantially aligned with the parting plane and dimensioned for passage of a flat
cutting blade therethrough. A guide element within the elongated cavity guides the
cutting blade between a first position for safely storing the blade fully inside the cavity and a second position for selectively extending the blade beyond the aperture to
expose at least a portion thereof. A manually operated button is arranged on the top surface and coupled to the guide element for selectively moving the blade between the first and second positions. The guide element includes a
carriage within the elongated
internal cavity for supporting a flat
cutting blade and guide elements on at least one of the inner generally concave surfaces for guiding the
carriage and cutting blade carried thereby between the first and second positions. The
carriage includes a locking element for normally locking a cutting blade mounted thereon to substantially fix the cutting blade against relative longitudinal movements between the cutting blade and carriage. The locking element includes an unlocking element the actuation of which releases the cutting blade to permit relative longitudinal movements between the cutting blade and the carriage. A blade release element on one of the shell members actuates the unlocking element when manual force is applied thereto, whereby application of a force on the release element releases the cutting blade and enables it to be withdrawn through the front end aperture.