US 3,999,290 A · Safety knife

Abstract

A safety knife adapted for cutting corrugated cardboard boxes and the like which is characterized by having a cutting blade which is continuously biased toward a retracted position within the knife's handle. The blade is held within a carriage that is slidable along a groove within the handle. A tension spring attached to the carriage urges the carriage toward its retracted position at all times. A dragging means is provided for pulling the carriage out of the handle and bringing the blade into contact with a structure to be cut. In one embodiment, this dragging means includes a cantilevered wire firmly attached to the slidable carriage, with the distal end of said wire having a hook which is adapted to drag along the structure to be cut. When the blade is cutting, the wire flexes backward into a position alongside the blade where it does not interfere with the cutting action. If the blade is ever withdrawn from the cardboard being cut, the tension spring immediately pulls the blade safely back into the handle. Depending upon whether the hook normally rests in a protruding position, or whether it normally rests in a sheltered position where it is at least partially shielded by the handle, the knife can be designed to begin cutting anywhere along a planar surface or a cut may be initiated only at the edge of a surface. In another embodiment, the dragging means includes a cantilevered arm made of a material like nylon or acetal resin; a serrated tip is typically provided at the end of such an arm so that the tip may be engaged with the structure to be cut. After engaging the tip, pulling the handle along the surface to be cut automatically pulls the carriage out of the handle and brings the blade into a cutting position. The handle is designed to be firmly gripped in a convenient manner, with all fingers being held in a natural position. No special "finger control" is necessary to keep the blade extended, and the knife may even be easily used by a person wearing bulky gloves.

Claims14

Dependent claims

A safety knife, comprising:

a. a handle having a cavity therein, with a portion of the cavity being elongated to define a groove;
b. a carriage slidable along the groove in the handle, and said carriage being adapted to hold a blade, with said carriage having a retracted position within the handle at which the blade does not protrude outside of the handle, and said carriage also having an extended position at which the blade partially lies beyond the boundary of the handle such that a portion of the blade is exposed for cutting;
c. spring means for biasing said carriage toward its retracted position at all times;
and
d. means for pulling the blade into contact with a structure to be cut, with said means including an element for dragging along said structure and for pulling the carriage in opposition to the spring means from its retracted position toward its extended position as the handle is moved across the surface of the structure to be cut.

2 more elements

A safety knife, comprising:

a. a handle having an exterior configuration adapted to be easily grasped by a person's hand, and the handle having a thin and elongated cavity therein, with a portion of the cavity defining a groove which extends in a direction generally parallel to the longitudinal axis of the handle;
b. an U-shaped carriage slidable along the groove in said handle, and said carriage being adapted to hold a cutting blade, with said carriage having a first position wherein it is fully retracted within the handle and the cutting blade is similarly retracted completely within the handle, and said carriage having a second position in which it is partially extended out of the front of said handle, with the cutting blade having a cutting edge exposed outside of the handle when the carriage is in its second position;
c. mechanical stops for limiting travel of the carriage so that it is restricted to excursions between the first and second carriage positions;
d. a tension spring for biasing the carriage toward its first, retracted position at all times;
e. a cantilevered wire attached at its proximate end to the side of the carriage, and said wire being extended in a forwardly direction such that it lies alongside the carriage and protrudes for a short distance outside of the handle at all times;
and
f. a hook provided at the distal end of said wire, with the hook having an inclination which is generally perpendicular to the longitudinal axis of the handle, whereby said hook may be engaged with a structure to be cut so that it will resist movement of the carriage in a direction generally parallel to the longitudinal axis of the handle as the handle is pulled backward.

4 more elements

Dependencies are inferred from the claim text.

Safety knife

Life of this patent

Safety knife

Life of this patent

Abstract

Claims14