Knife

Information

  • Patent Grant
  • 6510612
  • Patent Number
    6,510,612
  • Date Filed
    Wednesday, July 11, 2001
    23 years ago
  • Date Issued
    Tuesday, January 28, 2003
    21 years ago
  • Inventors
  • Examiners
    • Payer; Hwei-Siu
    Agents
    • Dimock Stratton Clarizio LLP
    • Eisen; Mark B.
Abstract
A utility knife having a quick release feature, whereby a resilient blade engaging member biased to the locked position engages an opening in the blade, and when the blade engaging member is pushed against the end of a guide slot it automatically releases from the blade allowing the blade to be removed from the knife handle. The knife handle structure reinforces the throat of the knife, by providing a double channel configuration comprising an outer channel with a blade retaining surface and an inner channel inverted relative to the outer channel and providing a blade supporting surface. The outer channel is tapered toward the inner channel about the throat of the knife, to reinforce the throat and prevent deformation under the stresses imparted by the knife blade when in use.
Description




FIELD OF THE INVENTION




This invention relates to knives. In particular, this invention relates to a retractable utility knife with improved blade support and blade replacement features.




BACKGROUND OF THE INVENTION




Utility knives are used in a variety of commercial and domestic applications, including construction, household repairs, arts and crafts and many others. Utility knives provide the advantage of being extremely sharp, and are typically loaded with a blade which is scored into segments, so that as the tip of the blade becomes dull the end segment can be broken off and the user can continue using the knife by exposing the next successive segment, which is still sharp.




However, utility knives present a number of disadvantages, particularly in heavy duty applications such as construction. Eventually, when the last segment has been broken off of the blade, the blade must be replaced. Conventionally, this requires removing the sliding body which retains the blade in the knife handle, attaching a new blade, and replacing the sliding body into the knife handle. This can be a difficult operation to perform without a surface to rest the knife on (for example while on a ladder), and increases opportunities for injury because of the manipulation required in order to hold the blade on the sliding body while inserting it into the knife handle.




Moreover, in heavy duty applications there is a considerable amount of force experienced by the blade, for example when cutting wallboard and other surfacing materials, which tends to deflect the blade laterally. The primary resistance to deflection of the blade within the handle is provided by the throat of the handle, which conventionally provides a single layer of supporting surface (generally metallic) on each side of the blade. Accordingly, over time the cutting force on the blade tends to widen the throat of the knife handle, which in turn allows the blade to deflect more when in use. This results in inaccurate cuts and the blade segments breaking off prematurely.




It would accordingly be advantageous to provide a utility knife with a quick release feature which allows the blade to be changed without removing the sliding body from the knife handle and with minimal manipulation. It would further be advantageous to provide a knife structure which reinforces the throat of the knife, thereby reducing deflection of the blade during use and thus minimizing opportunities for inaccurate cuts and premature breakage of the blade.




SUMMARY OF THE INVENTION




The present invention provides a utility knife having a quick release feature, whereby forcing the sliding body toward the throat of the knife handle releases the blade, so that a new blade can be inserted easily and without removing the sliding body from the knife handle.




The invention accomplishes this by providing a resilient blade engaging member, biased to the locked position, which engages an opening in the blade in normal use. When the blade engaging member is pushed against the end of the guide slot in which the sliding body travels, it automatically releases from the blade allowing the blade to be removed from the knife handle and a new blade positioned and engaged therein.




The present invention further provides a knife handle structure which reinforces the throat of the knife, to better restrain the knife blade against deflection and thus to prolong the life of the knife blade and facilitate the accuracy of cutting with the knife.




The invention accomplishes this by providing a knife handle having a double channel configuration, comprising an outer channel providing a blade retaining surface and an inner channel inverted relative to the outer channel and providing a supporting surface for the blade. In the preferred embodiment the outer channel is tapered toward the inner channel about the throat of the knife, to reinforce the throat and prevent deformation under the stresses imparted by the knife blade when in use.




The present invention thus provides a knife, comprising a handle, comprising an outer channel having a back surface, side surfaces and retaining flanges depending inwardly from the side surfaces, an inner channel comprising blade supporting surface and sides, the sides abutting the side surfaces of the outer channel and the blade supporting surface being spaced from the retaining flanges for slidably receiving a blade therebetween, and a sliding body for engaging the blade trapped between the retaining flanges and the blade supporting surface, the sliding body having a locking member for locking a position of the sliding body within the handle.




In further aspects of the invention, the inner channel is disposed in inverted relation to the outer channel; a portion of the back surface of the outer channel tapers toward the blade supporting surface and abuts the blade supporting surface at a throat of the knife; the locking member comprises a locking bolt extending through the sliding body and through a guide slot in the blade supporting surface and into a nut trapped between the sides of the inner channel; the blade engaging member comprises a blade engaging member for engaging the blade to the sliding body, the blade engaging member comprising a body portion and a resilient blade engaging arm projecting from the body portion, the blade engaging arm having a blade engaging projection for extending through an opening in the blade, and a cam finger extending through the guide slot disposed between the blade engaging projection and an end of the guide slot adjacent to a throat of the knife, whereby when the sliding body is moved so that the blade engaging finger is pressed against the end of the guide slot the blade engaging projection recedes from the opening in the blade to disengage the blade from the sliding body; the back surface of the outer channel comprises an opening through which the cam finger extends when the blade engaging projection recedes from the opening in the blade; and/or a pocket clip is affixed to an opening in the blade supporting surface and covers an end of the handle opposite the throat of the knife.




The present invention in a further embodiment provides a knife, comprising a handle, comprising an outer channel having a back surface, side surfaces and retaining flanges depending inwardly from the side surfaces, a blade supporting surface having a guide slot, spaced from the retaining flanges for slidably receiving a blade therebetween, and a sliding body trapped between the retaining flanges and the blade supporting surface, the sliding body having a locking member disposed through the guide slot for locking a position of the sliding body within the handle, and comprising a blade engaging member for engaging the blade to the sliding body, the blade engaging member comprising a body portion, and a resilient blade engaging arm projecting from the body portion, the blade engaging arm having a blade engaging projection for extending through an opening in the blade, and a cam finger extending through. The guide slot, disposed between the blade engaging projection and an end of the guide slot adjacent to a throat of the knife, whereby when the sliding body is moved so that the blade engaging finger is pressed against the end of the guide slot, the blade engaging projection recedes from the opening in the blade to disengage the blade from the sliding body.




In further aspects of the further embodiment of the invention, a portion of the back surface of the outer channel tapers toward the blade supporting surface and abuts the blade supporting surface at a throat of the knife; the back surface of the outer channel comprises an opening through which the cam finger extends when the blade engaging projection recedes from the opening in the blade; the blade supporting surface is part of an inner channel is disposed in the outer channel; the inner channel is disposed in inverted relation to the outer channel; the locking member comprises a locking bolt extending through the sliding body and through a guide slot in the blade supporting surface and into a nut trapped between the sides of the inner channel; and/or a pocket clip is affixed to an opening in the blade supporting surface and covers an end of the handle opposite the throat of the knife.











BRIEF DESCRIPTION OF THE DRAWINGS




In drawings which illustrate by way of example only a preferred embodiment of the invention,





FIG. 1

is a perspective view showing the utility knife according to the invention in a partially opened condition;





FIG. 2

is a front elevational view of the utility knife of

FIG. 1

;





FIG. 3

is a rear elevation of the handle in the utility knife of

FIG. 1

;





FIG. 4

is a cross sectional side elevation of the utility knife of

FIG. 1

;





FIG. 5

is an enlarged partial cross section of the utility knife of

FIG. 1

showing the sliding body position for release of the blade;





FIG. 6

is an enlarged partial cross section of the utility knife of

FIG. 1

showing the blade engaging member in a release position;





FIG. 7

is a plan view of the blade engaging member; and





FIG. 8

is an elevational view of the blade engaging member.











DETAILED DESCRIPTION OF THE INVENTION





FIG. 1

illustrates a preferred embodiment of the utility knife


10


according to the invention. The utility knife comprises a handle


20


, a blade support


30


, a sliding body


40


for retaining the blade


2


and locking the blade


2


at a desired position within the handle


20


, and a locking element


50


which engages the blade


2


to the sliding body


40


.




In the preferred embodiment, the handle


20


comprises an outer channel


22


having a back face


24


, side faces


26


and inwardly depending flanges


28


which retain the blade


2


in the handle


20


and conceal the cutting edge


2




a


and spine


2




b


of the blade


2


when the blade


2


is retracted into the handle


20


.




Disposed within the outer channel


22


is a blade support surface


30


, spaced from the retaining flanges


28


with sufficient clearance to allow the blade


2


and blade engaging member


50


(described below) to slide freely within the space defined between the retaining flanges


28


and the blade support surface


30


, while providing substantial support for the blade


2


against lateral shimmying and deflection while in use. In the preferred embodiment the blade support surface


30


is formed by an inner channel


32


having a front face


34


and sides


36


which can be welded, soldered or otherwise suitably affixed to the outer channel


22


. The blade supporting surface


30


further comprises a guide slot


38


defining a path of travel for the sliding body


40


, and optionally an opening


39


for receiving a pocket clip


70


(omitted from

FIG. 1

for clarity, shown in FIG.


4


).




The sliding body


40


comprises a blade engaging member


50


, described below, and a locking member comprising a locking bolt


42


having a rotary knob


42




a


and stem


42




b


(seen in

FIGS. 4

to


6


) extending through the guide slot


38


into a nut


44


trapped within the sides


36


of the inner channel


32


or otherwise suitably trapped within the outer channel


22


to prevent rotation of the nut


44


. The stem


42




b


of the locking bolt


42


extends through the body


52


of the blade engaging member


50


, through the guide slot


38


and into the nut


44


, to restrict movement of the sliding body


40


to within the limits of the guide slot


38


.




The blade


2


is engaged to the sliding body


40


by the blade engaging member


50


, illustrated in

FIGS. 7 and 8

. A body portion


52


is provided with an opening


54


through which the stem


42




b


of the locking bolt


42


extends. Preferably spring flanges


56


are provided on either side of the opening


54


, splayed slightly away from the body


52


so as to push against a hub


42




c


of the rotary knob


42




a


and thus force the body portion


52


against the blade supporting surface


30


, to prevent the sliding body


40


from shimmying within the handle


20


. The body portion


52


is formed wide enough to be trapped between the flanges


28


and the blade supporting surface


30


, and is preferably approximately the same thickness as the blade


2


.




A locking arm


60


which fits through the slot


38


extends forwardly of the body portion


52


, and provides an engaging projection


62


, for example in the form of a loop. The engaging projection


62


projects in the direction of the blade


2


, and projects beyond the body portion


52


to bias the blade engaging member


50


to the locked position in which the engaging portion


62


extends through an opening


4


in the blade


2


, The engaging projection


62


also preferably extends from the arm


60


in a direction away from the throat


80


of the knife


10


, so as to resist a longitudinal force pulling the blade


2


out of the handle


20


. The engaging portion


62


terminates in a cam finger


64


, for releasing the blade


2


in the manner described below. Preferably the entire blade engaging member


50


is stamped as an integral piece from spring steel, or another suitable resilient material




The throat


80


of the utility knife


10


, best seen in

FIG. 2

, comprises the inwardly depending blade retaining flanges


28


of the outer channel


22


, the blade supporting surface


30


and a tapered portion


24




a


of the rear surface


24


of the outer channel


22


, which tapers toward the throat


80


and abuts the blade supporting surface


30


. This provides additional reinforcement to the front face


34


of the inner channel


32


along the portion which experiences the most lateral stress when the knife


10


is in use, and thus resists widening of the throat


80


(i.e. deformation of the blade supporting surface


30


which increases its spacing from the blade retaining flanges


28


), which tends to lower the useful life of the blade


2


by causing premature breakage, and reduces the accuracy of cutting. The tapered portion


24




a


of the outer channel provides an opening


24




b


through which the locking arm


60


and cam surface


64


project when the blade engaging member


50


is in the unlocked position shown in

FIG. 6

, as described below. The front face


34


of the inner channel


32


may extend beyond the throat


80


to provide additional support against deflection of the blade


2


, and to provide an edge which facilitates breaking off of dull the blade segments.




In a storage condition, the sliding body


40


is locked at a position where the blade


2


is retracted into the handle


20


. To use the utility knife


10


the user grasps the rotary knob


42




a


and turns it to loosen the bolt


42


and release the sliding body


40


, and slides the sliding body


40


toward the throat


80


. Edge


58


of the blade engaging member


50


pushes against the concealed end of the blade


2


, to force the blade


2


out of the handle


20


and expose the end segment of the blade


2


. The user rotates the rotary knob


42




a


in the other direction to tighten the bolt


42


and lock the sliding body


40


, and can then use the knife


10


with the blade


2


locked in position. The reinforcing strength provided by the tapered portion


24




a


of the outer channel


22


against the blade supporting surface


30


at the throat


80


of the knife


10


helps to maintain the blade


2


secure against shimmying and lateral deflection while the knife


10


is in use.




As the outer segment of blade


2


dulls, the user can break off the dull segment, unlock the sliding body


40


and further extend the blade


2


to expose the next segment of blade


2


, which has been protected by the handle


20


and is thus still sharp. When the last segment of the blade is dull, the user must replace the blade


2


. The user rotates the rotary knob


42




a


to loosen the bolt


42


and forces the sliding body


40


toward the throat


80


. As can be seen in

FIG. 5

, as the sliding body


40


approaches the end of the slot


38


, the cam finger


64


engages the end of the slot


38


. As the sliding body


40


is moved closer to the throat


80


, cam finger


64


draws locking arm


60


inwardly until engaging projection


62


has receded from the hole


4


in the blade


2


, as shown in FIG.


6


. At this point, the blade


2


is disengaged from the sliding body


40


and can be removed from the handle


20


. A new blade


2


is inserted in its place, lining up the opening


4


over the engaging projection


62


. By pushing the blade


2


into the handle


20


, the sliding body


40


is forced away from the throat


80


and as the cam finger


64


slides up the end of the slot


38


the resilient locking arm


60


returns to the engaging position in which the projection


62


extends through the opening


4


of the blade


2


. At the point shown in

FIG. 5

, the new blade


2


is locked to the sliding body


40


and can be retracted into the handle


20


for use or storage.




Advantageously, the engaging projection


62


is angled away from the throat


80


(i.e. toward the sliding body


40


), so that a longitudinal force pulling the blade


2


away out of the knife


10


actually draws the engaging projection


62


further through the hole


4


, as the blade is pulled into the inflection portion


63


, to prevent dislodgement of the blade


2


.




Various embodiments of the present invention having been thus described in detail by way of example, it will be apparent to those skilled in the art that variations and modifications may be made without departing from the invention. The invention includes all such variations and modifications as fall within the scope of the appended claims.



Claims
  • 1. A knife, comprisinga handle, comprising an outer channel having a back surface, side surfaces and retaining flanges depending inwardly from the side surfaces, a blade supporting surface having a guide slot, spaced from the retaining flanges for slidably receiving a blade therebetween, and a sliding body trapped between the retaining flanges and the blade supporting surface, the sliding body having a locking member disposed through the guide slot for locking a position of the sliding body within the handle, and comprising a blade engaging member for engaging the blade to the sliding body, the blade engaging member comprising a body portion, and a resilient blade engaging arm projecting from the body portion, the blade engaging arm having a blade engaging projection for extending through an opening in the blade, and a cam finger extending through the guide slot, disposed between the blade engaging projection and an end of the guide slot adjacent to a throat of the knife, whereby when the sliding body is moved so that the cam finger is pressed against the end of the guide slot, the blade engaging projection recedes from the opening in the blade to disengage the blade from the sliding body.
  • 2. The knife of claim 1 in which a portion of the back surface of the outer channel tapers toward the blade supporting surface and abuts the blade supporting surface at a throat of the knife.
  • 3. The knife of claim 2 in which the back surface of the outer channel comprises an opening through which the cam finger extends when the blade engaging projection recedes from the opening in the blade.
  • 4. The knife of claim 2 in which a pocket clip is affixed to an opening in the blade supporting surface and covers an end of the handle opposite the throat of the knife.
  • 5. The knife of claim 1 in which the blade supporting surface is part of an inner channel is disposed in the outer channel.
  • 6. The knife of claim 5 in which the inner channel is disposed in inverted relation to the outer channel.
  • 7. The knife of claim 5 in which the locking member comprises a locking bolt extending through the sliding body and through the guide slot in the blade supporting surface and into a nut trapped between the sides of the inner channel.
  • 8. A knife, comprisinga handle, comprising an outer channel having a back surface, side surfaces and retaining flanges depending inwardly from the side surfaces, an inner channel comprising blade supporting surface and sides, the sides abutting the side surfaces of the outer channel and the blade supporting surface being spaced from the retaining flanges for slidably receiving a blade therebetween, and a sliding body for engaging the blade trapped between the retaining flanges and the blade supporting surface, the sliding body having a locking member for locking a position of the sliding body within the handle.
  • 9. The knife of claim 1 in which the inner channel is disposed in inverted relation to the outer channel.
  • 10. The knife of claim 9 in which a portion of the back surface of the outer channel tapers toward the blade supporting surface and abuts the blade supporting surface at a throat of the knife.
  • 11. The knife of claim 10 in which a pocket clip is affixed to an opening in the blade supporting surface and covers an end of the handle opposite the throat of the knife.
  • 12. The knife of claim 9 in which the locking member comprises a locking bolt extending through the sliding body and through a guide slot in the blade supporting surface and into a nut trapped between the sides of the inner channel.
  • 13. The knife of claim 4 in which the locking member comprises a blade engaging member for engaging the blade to the sliding body, the blade engaging member comprising a body portion and a resilient blade engaging arm projecting from the body portion, the blade engaging arm having a blade engaging projection for extending through an opening in the blade, and a cam finger extending through the guide slot disposed between the blade engaging projection and an end of the guide slot adjacent to a throat of the knife, whereby when the sliding body is moved so that the cam finger is pressed against the end of the guide slot, the blade engaging projection recedes from the opening in the blade to disengage the blade from the sliding body.
  • 14. The knife of claim 13 in which the back surface of the outer channel comprises an opening through which the cam finger extends when the blade engaging projection recedes from the opening in the blade.
US Referenced Citations (12)
Number Name Date Kind
3448518 Sklar Jun 1969 A
4170062 Machida Oct 1979 A
4196515 Sugiyama Apr 1980 A
D324475 Staubitz et al. Mar 1992 S
5269063 Okada Dec 1993 A
D347563 Okada Jun 1994 S
D386959 Okada Dec 1997 S
D392173 Okada Mar 1998 S
D398829 Okada Sep 1998 S
D399114 Okada Oct 1998 S
D431170 Okada Sep 2000 S
6226873 Okumura May 2001 B1
Foreign Referenced Citations (1)
Number Date Country
1522454 Aug 1978 GB