Safety utility knife

• US 4,091,537 A
• Filed: 04/26/1977
• Issued: 05/30/1978
• Est. Priority Date: 04/26/1977
• Status: Expired due to Term

• Current Assignee: Stevenson Machine Shop
• Original Assignee: Stevenson Machine Shop
• Inventors: Stevenson, Wayne E. Jr.
• Primary Examiner(s): Jones, Jr., James L.
• Assistant Examiner(s): Zatarga, J. T.
• Application Number:
  US05/790,960
• Time in Patent Office: 399 Days
• Field of Search: 30/286, 30/289, 30/294, 30/293, 30/151
• US Class Current: 30/286
• CPC Class Codes: B26B 29/02 Guards or sheaths for knives

Abstract

A hand-held safety utility knife having an elongated shaped handle within which a replaceable cutting blade is securely retained, wherein the knife assembly is also provided with a compression-extension spiral spring loaded retractable blade guard that is mechanically cooperative with the cutting blade of the knife and manually activated for retraction by depressing a compression-extension spiral spring loaded trigger thereby enabling cutting utility of the blade in use application, and upon manual trigger release after use application provides non-use safety locking of the guard with respect to the utility knife cutting blade.

Claims

1. A safety utility knife comprised of a separable elongated shaped two-piece handle adapted to positionally secure and retain therein a replaceable cutting blade having a cutting edge said two-piece handle also being further provided with a spare cutting blade storage recess therein, which is old, characterized by:

(a). an elongated geometrically configured spiral spring activated retractable blade guard cutting edge rod member provided with an insertably assembled first compression-extension spiral spring to movably communicate compressive and extensive coaction therewith, said rod member in the extended position being adjacently, downwardly disposed with respect to and in the same general plane as said cutting edge, said rod member having an inner end within the handle with a shoulder adjacent said inner end,

(b). a mechanically cooperative geometrically configured spiral spring activated blade guard cutting edge rod member release and lock trigger provided with an insertably assembled second compression-extension spiral spring to movably communicate compressive and extensive coaction therewith, and

(c). a manually initiated mechanically cooperative alignment coaction between said elongated geometrically configured spiral spring activated retractable blade guard cutting edge rod member and said geometrically configured spiral spring activated blade guard cutting edge rod member release and lock trigger to enable retraction of said blade guard cutting edge rod member through an opening in said blade guard cutting edge rod member release and lock trigger into a longitudinally disposed axially aligned first spiral spring tubular opening within said handle against the coactive compressive force of said first spiral spring retained therein to thereby expose the cutting edge of said cutting blade for severing service upon a manually imparted finger-force depression of said blade guard cutting edge rod member release and lock trigger against the coactive compressive force of said second spiral spring when said knife is employed in combination with a concurrent manually imparted use application pressure directed by way of said handle towards a surface to be severed, wherein, following which, upon release of said manually imparted use application pressure to said handle, said manually initiated mechanically cooperative alignment coaction being coactively cooperative reversely thereby enables automatic extension of said blade guard cutting edge rod member outwardly of said longitudinally disposed axially aligned first spiral spring tubular opening through said opening in said blade guard cutting edge rod member release and lock trigger under the coactive extensive force of said first spiral spring to position said blade guard cutting edge rod member in protective cover of the cutting edge of said cutting blade, and upon a subsequent release of said manually imparted finger-force depression upon said blade guard cutting edge rod member release and lock trigger thereby also enables said blade guard cutting edge rod member release and lock trigger to automatically extend under the coactive extensive force of said second spiral spring and thereupon cause a positive mechanical engagement locking of said blade guard cutting edge rod member by means of said trigger opening engaging said shoulder on said rod member in a close proximity downwardly disposed longitudinally extended position relative to and guardably protective of said cutting edge of said cutting blade.

2. The safety utility knife according to claim 1 in which said blade guard cutting edge rod member has a longitudinally disposed outward terminal end provided with a serrated tip.

3. The safety utility knife according to claim 2 in which said serrated tip is positioned at an angle relative to the longitudinal axis of said blade guard cutting edge rod member.

4. The safety utility knife according to claim 3 in which said angle is between 0 and 90°

.

5. The safety utility knife according to claim 4 in which said angle is 45°

.

6. The safety utility knife according to claim 1 in which said elongated geometrically configured spiral spring activated retractable blade guard cutting edge rod member is comprised of a plurality of integrally communicating longitudinally disposed cylindrical rod sections of different but respectively uniform cross-sectional diameter dimension throughout.

7. The safety utility knife according to claim 6 in which said plurality of integrally communicating longitudinally disposed cylindrical rod sections are in turn respectively of different longitudinal dimension.

8. The safety utility knife according to claim 6 in which a first longitudinal section, being a blade guard per se, has a first cross-sectional diameter;

a second longitudinal section, being a trigger catch adjacent said shoulder has a second cross-sectional diameter which is less than but at least half of that of said first cross-sectional diameter;

a third longitudinal section, being a first compression-extension spiral spring retaining collar, has a third cross-sectional diameter which is greater than but less than twice of that of said first cross-sectional diameter; and

a fourth longitudinal section, being a first compression-extension spiral spring guide, has a fourth cross-sectional diameter which is less than said first cross-sectional diameter but greater than said second cross-sectional diameter.

9. The safety utility knife according to claim 8 in which said blade guard per se has a first longitudinal dimension which is greater than twice that of said trigger catch the same comprising a second longitudinal dimension, wherein a third longitudinal dimension, being that of said first compression-extension spiral spring retaining collar, is more than twice that of said trigger catch but less than half that of said blade guard per se, and a fourth longitudinal dimension, being that of said first compression-extension spiral spring guide, being the same as that of said first compression-extension spiral spring retaining collar.

10. The safety utility knife according to claim 1 in which said blade guard cutting edge rod member release and lock trigger opening is circular having a diameter which is greater than that of the cross-sectional diameter of said blade guard per se thereby coactively enabling said blade guard per se to retractively and extensively communicate therethrough upon alignment coaction therewith, but less than that of the cross-sectional diameter of said first compression-extension spiral spring retaining collar thereby coactively restricting communication thereof therethrough.