GB2063140A - Knife with interchangeable blade - Google Patents

Abstract

A knife 10 comprises an interchangeable blade 11 with a cutting edge 12 and a shank 13, a handle 14 having a threaded bore 23, a sleeve 28 mounted on the handle, and a chuck 34 having a head 35 and a threaded shank 36. The chuck head is formed with a plurality of radially flexible jaws 40, to receive the blade therebetween, the chuck shank being insertable through the sleeve for threaded engagement with the threaded bore 23 to retract the jaws into engagement with the sleeve member and thereby clamp the blade in the chuck. <IMAGE>

Description

SPECIFICATION Knife with interchangeable blade The present invention relates in general to a knife having an interchangeable blade held by a chuck member in a clamping engagement, and more specifically relates to such a knife having means for facilitating release of the knife blade from the chuck member.

Knives having interchangeable blades mounted in a chuck member are well known in the art. The standard construction for such knives includes an elongate handle portion with an axial bore at one end, a sleeve member, and a chuck member having a head portion divided into jaws for receiving the shank of a blade and a shank section threadable into the bore of the handle. The shank section of the chuck member is insertable through the sleeve member so that as it is threaded into the handle, the chuck member head portion is moved into retractive, frictional engagement with the sleeve to force the jaw members of the head portion toward one another securely clamping the knife blade therebetween.

Although knives having the above construction provide a secure mounting of the blade in a releasable fashion, the tight frictional engagement between the sleeve member and the chuck member head portion is often difficult to break, especially under conditions where the knife blade has remained in the head portion for a considerable period whereby there may even be corrosion between the sleeve member and the head portion. In such case, considerable force must be applied on the sleeve member to loosen its engagement with the head portion, and often such separation is impossible to achieve without causing damage to the sleeve member or head portion. Also, applying such force is hazardous because one must necessarily work closely to the knife blade and may be accidently cut unless extreme care is taken.

The object of the present invention is to overcome the foregoing problems.

Accordingly, the present invention provides a knife having an interchangeable blade with a cutting edge portion and a shank portion, said knife comprising an elongate handle means having a longitudinally extended bore; a sleeve member mounted at one end of said handle means, said sleeve member projecting outwardly from said one end in coaxial alignment with the axis of said bore; chuck means having a head portion and a threaded shank section, said head portion being formed with a plurality of longitudinally extended radially flexible fingers, with certain of said fingers spaced a distance apart to receive said blade therebetween; coacting portions on said sleeve member and on said head portion for moving said fingers radially inwardly into clamping engagement with said knife blade in response to a retractive movement of the head portion within said sleeve member; and threaded means within said handle means for threaded engagement with said shank section for moving said fingers into and out of clamping engagement with said knife blade in response to relative rotational movement between said threaded means and said sleeve member.

The present invention provides an improved knife construction that provides for automatic release of the engagement between the sleeve and the chuck head portion. Also, the handle of the knife is specifically adapted to facilitate use of the knife in cutting operations and to prevent rolling of the knife when not in use.

In the drawings: Figure 1 is a side view in elevation of a first preferred embodiment of the knife of the present invention; Figure 2 is an enlarged detail view of the blade end of the knife of Figure 1 with certain portions thereof broken away and shown in section to expose interior construction; Figure 3 is a side view in elevation of a sleeve member forming part of the knife of Figure 1 with portions broken away to expose interior construction; Figure 4 is an exploded perspective view of the knife end shown in Figure 2; Figure 5 is a side view in elevation of a second preferred embodiment of the knife of the present invention;; Figure 6 is an enlarged foreshortened view of the knife of Figure 5 with certain portions thereof broken away and shown in section to expose interior construction, and Figure 7 is an enlarged exploded perspective view of the blade end of the knife of Figure 5.

With reference to the drawings, a first preferred embodiment of the invention is shown at 10 in Figure 1, having a thin pointed blade 11 with a cutting edge 12 and a shank portion 13. The cutting edge portion 12 is of a razor blade construction and when new, also has a razor blade sharpness. The knife 10 is adapted to permit ready replacement of the blade 11 with ease and safety from injury to the user.

To provide a convenient hand hold, the knife 10 has a rod shaped elongate handle 14 preferably formed from plastic or other such material having a low coefficient of friction. The handle 14 has an elongate body 20 that is tapered on a slight incline to the rear and includes a polygonally shaped front portion 21 with a plurality of flat sides 22 to prevent rolling of the knife 10 when not in use. A front end portion 15 of the body 20 is formed with a relatively steep inwardly inclined section 16 that serves as a shoulder against which one can apply a rearwardly directed pressure on to pull the knife during a cutting operation. As best shown in Figure 4, a terminal nipple or sleeve section 17 protrudes forwardly of the inclined section 16 and has a reduced cross sectional diameter relative to the remainder of the handle 14.The nipple section 17 has an annular flange 18 spaced from the tapered portion 16 to define a shallow annular groove 19. An internally threaded axial bore 23 extends through the sections 16 and 17 that the sidewall of the nipple section 17 is relatively thin.

Diametrically arranged slots 24, only one of which is shown, are formed in such sidewall to divide the section 17 into two halves 25 and 26 that are resiliently deformable towards one another during insertion of the section 17 into one end 27 of a sleeve member 28, as indicated in Figure 2. The sleeve member 28 has a knurled exterior 29 and an axial bore 30 formed with an inwardly tapered end section 31 (Figure 3) to provide an inclined inner wall portion 32. The opposite end 27 of the bore 30 is of a reduced opening formed by an internal flange 33.

During insertion of the nipple section 17 into the sleeve end 27, the nipple halves 25 and 26 are pressed towards one another by contraction of the nipple flange 18 by the sleeve flange 33 for seating of the flange 33 in the annular groove 19 of the nipple section 17. With the flange 33 seated, the nipple halves 25 and 26 spring apart so that the flanges 18 and 33 are in abutting engagement and serve as coacting members for retaining the sleeve 28 coupled on the nipple section 17 in a manner that permits axial rotation of the sleeve 28 with respect to the handle 14.

A chuck member 34 (Figure 4) preferably formed from a yieldable metal or high strength plastic, is employed for holding the blade 11 and has a head portion 35 at one end and a threaded shank section 36 on an opposite end. The head portion 35 has a cylindrical shaped rear or inner section 37 intermediate the shank section 36, and a front or outer longitudinal section 38 having a reversely tapered exterior or peripheral surface having an annular ridge 39 of maximum diameter so that the forward end of the head portion 35 is of a frusto-conical shape. The head portion 35 is divided into four similar jaw portions 40 by a pair of intersecting slots 41 and 42 that are orthogonal to one another and extend substantially the length of the head portion 35.Thus, the jaw portions 40 are separated from each other by the slots 41 and 42 to provide, in effect, a plurality of longitudinally extended radially flexible fingers spaced a distance apart to receive the blade shank portion 13 therebetween.

The chuck ember 34 is longer than the sleeve member 28 and is insertable therethrough for threadable engagement of the handle threaded bore 23 with the chuck member shank section 36. Once this threaded engagement is initiated, clockwise rotation of the handle 14 relative to the chuck member 34 will further thread the shank section 36 into the bore 23. As the shank section 36 is threaded into the bore 23, the chuck head portion 35 is contracted within the bore 30 of the sleeve member 28 whereby the inclined surface 32 of the sleeve member 28 and the chuck head portion 35 are moved into frictional engagement. To induce threading of the chuck member shank section 36 into the bore 23, an O-ring 43 is disposed on the shank section 36 adjacent the rear section 37 of the chuck member head portion 35.The O-ring 43 acts to engage the periphery of the sleeve member bore 30 for preventing rotation of the chuck member 34 with the handle 14 and thereby insuring relative movement therebetween as the handle 14 is rotated.

The maximum diameter of the tapered chuck head portion 35 is larger than the diameter of the sleeve bore 30 whereby on a continued retraction of the chuck head portion 35 into the sleeve member 28, the jaw members 40 of the head portion 35 are forced together to securely clamp the blade shank portion 13 therebetween. Concurrently the sleeve member 28 tightly grips the chuck head portion 35 to hold the chuck member 34 against rotation in the sleeve member 28. Thus, if the sleeve member 28 was not rotatably coupled to the handle 14, clockwise rotation of the sleeve member 28 relative to the handle 14would loosen the chuck member 34 and sleeve member 28 as a unit from the handle 14.

However, such loosening is highly undesirable because it would be difficult, as well as hazardous because of the blade 11, to disengage the chuck member 34 from the sleeve member 28.

The present invention is adapted to avoid such unitary loosening or unthreading of the chuck member 34 and sleeve member 28 relative to the handle 14 by the rotatable coupling of the sleeve member 28 to the handle 14. Consequently, clockwise rotation of the sleeve member 28 with respect to the handle 14 serves not only to unthread the chuck member 34 from the handle 14 but also breaks the tight frictional engagement between the chuck member 34 and the sleeve member 28, thereby substantially facilitating removal of the blade 11 from the chuck member 34 and significantly reducing the possibility of one being accidently cut by the blade 11.

As is apparent from the above description, a considerable amount of rotation occurs between the sleeve member 28 and the handle 14 and much of this rotation occurs while the member 28 and handle 14 frictionally engage one another. In prior art knives, such rotation has caused galling of the frictionally engaged portions of the member 28 and handle 14to such an extent that the chuck member cannot be sufficiently tig htened about the blade 11.

However, the present invention in addition to providing automatic release of the blade 11, also eliminates the problem of galling by employing the low coeffi cientoffriction plastic handle 14 that does not deteriorate significantly through the frequent rotational frictional engagement with the sleeve member 28.

Referring now to Figure 5, a second preferred embodiment of the invention is shown generally at 50. The knife 50 has a generally cylindrically shaped hollow handle 51 that resembles that of the knife 10 in that it has an inclined front end section 52 and a polygonally shaped portion 49 extending rearwardly therefrom. However, the end section 52 is the terminal end of the handle 51 and an axial bore 53 (Figures 6 and 7) extends therefrom the entire length of the handle 51 to a rear end 54 thereof.

The handle rear end 54 has an internal flange 55 in the bore 53 to serve as a retainer for a threaded member 56 that includes a body portion 57 with a knurled knob portion 58 at one end. The body portion 57 has a diameter slightly smaller than that of the handle bore 53, and the threaded member 56 is rotatably received in the bore 53 through the front end thereof. Axially extended from the other end of the body portion 57 is an extension section 59 with an internally threaded axial bore 60 extended rearwardly from the free end of the section 59.The diameters of the knob portion 58 and the extension section 59 are less than that of the body portion to provide, respectively, an abutment shoulder 61 on the rear of the body portion 57 in abutting engagement with the internal flange 55 of the handle end 54 to prevent the threaded member56from passing through the rear end 54 of the handle 51, and an abutment shoulder 62 at the front of the body portion 57 for a purpose to be described below.

Fixed on the inclined front end portion 52 of the handle 51 is a sleeve member 63 having a front portion 64 and a rear portion 64a that is disposed in the handle bore 53 in a tight press fit. The rear portion 64a may extend into the bore 53 sufficiently so as to receive the threaded member extension section 59 and abut against the threaded member abutment shoulder 62 to hold the threaded member 56 in position adjacent the handle flange 55. However, it is preferable to employ a plastic washer 65 seated between the threaded member shoulder 62 and the sleeve portion 64a to reduce frictional wearing therebetween. The periphery of the front portion 64 of the sleeve member 63 is substantially flush with the terminal end 52 of the handle 51 and extends axially outwardly therefrom.The sleeve member 63 has a through bore 66 concentric with the handle bore 53 and includes a front end 67 that is outwardly tapered at 68.

A chuck member 69 is similar to the chuck member 34 has a shank section 70 insertable through the sleeve member 63 to threadably engage the bore 60 of the threaded member 56 so that clockwise rotation of the chuck member 69 retracts such member further into the sleeve member 63 until a head portion 71 of the member 69 engages the tapered sidewall 68 of the sleeve bore 66 in the same contractive, locking arrangement for a blade 72 as previously described for the knife 10. However, in the knife 50 once the chuck member shank section 68 is initially threadably engaged with the threaded member 56, the threaded member 56 can be rotated by the knob 58 to retract the chuck member 69 into the sleeve member 63. This reduces to a minimum, handling of the chuck member 69 with its associated blade 72.An O-ring 73, similar to the O-ring 43 of the knife 10, is disposed on the shank section 68 to retard rotational movement of the chuck member 69 relative to the threaded member 56 as also previously described.

To remove the blade 72 from the knife 50 simply requires counterclockwise rotation of the threaded member 56 via the knob 58 whereupon the chuck member head portion 71 will be forced axially outwardly from engagement with the sleeve member 63. The knife 50 thereby provides a blade removal operation similar to that of the knife 10.

Thus, both embodiments 10 and 50 of the present invention provide means for breaking the tight frictional engagement between a chuck member in which a knife blade is secured and an encircling sleeve through the force of the chuck member as it is unthreaded from an associated handle portion. It should be noted that in the embodiment 10, the sleeve member 28 is rotatably coupled to the handle 14 whereas in the embodiment 50 the sleeve member 63 is fixed to the handle 51 in a tight press fit.

Consequently, rotation of the sleeve member relative to an associated handle is not essential to provide the desired blade removal operation of the present invention, but there must be relative movement between the sleeve member and the handle threaded portion.

Claims (11)

1. A knife having an interchangeable blade with a cutting edge portion and a shank portion, said knife comprising an elongate handle means having a longitudinally extended bore; a sleeve member mounted at one end of said handle means, said sleeve member projecting outwardly from said one end in coaxial alignment with the axis of said bore; chuck means having a head portion and a threaded shank section, said head portion being formed with a plurality of longitudinally extended radially flexible fingers, with certain of said fingers spaced a distance apart to receive said blade therebetween; coacting portions on said sleeve member and on said head portion for moving said fingers radially inwardly into clamping engagement with said knife blade in response to a retractive movement of the head portion within said sleeve member; and threaded means within said handle means for threaded engagement with said shank section for moving said fingers into and out of clamping engagement with said knife blade in response to relative rotational movement between said threaded means and said sleeve member.

2. A knife according to claim 1 wherein said threaded means is formed by threads in said longitudinally extended bore of said handle means; and there are provided coacting abutment members on an end of said handle means and one end of said sleeve member to rotatably couple said sleeve member on said handle means in an axial relation for relative rotational movement between said sleeve member and said threaded means.

3. A knife according to claim 1 wherein said handle means comprises a generally cylindrically shaped major portion; and a yieldable end portion reduced in diameter relative to said major portion and having flange means thereon for insertion into one end of said sleeve member; and internal flange means located on said one end of said sleeve member for engaging said flange means of said handle portion in an abutting engagement to rotatable couple said sleeve member and said handle means in an axial relation.

4. A knife according to claim 1, 2 or 3, wherein means are disposed on the threaded shank section of said chuck means for engaging said sleeve member to prevent rotation of the chuck means with said handle means.

5. A knife according to claim 1, wherein said sleeve member is fixed on said end of said handle means; said bore of said handle means is extended from said one end of said handle means to the opposite end thereof, and said threaded means is formed of a member rotatably disposed in said bore of said handle means and having a portion extended from said opposite end of said handle means for rotation of said threaded means relative to said sleeve member.

6. A knife according to claim 5, wherein coacting abutting portions are located on said threaded means and said handle means to retain said threaded means in the bore of said handle means.

7. A knife according to claim 5 or 6, wherein said member of said threaded means has an axially extended threaded bore in threaded engagement with said shank section of said chuck means.

8. A knife according to any of claims 1 to 7, wherein said one end of said handle means includes a shoulder portion against which pressure can be applied to pull the knife during a cutting operation.

9. A knife according to any of claims 1 to 8, wherein said handle means includes a polygonally shaped portion to retard rolling movement of said knife when not in use.

10. A knife according to any of claims 1 to 9, wherein said handle means is formed from a material having a low coefficient of friction.

11. A knife constructed and adapted to operate substantially as herein described with reference to ; the embodiment of Figures 1 to 4 or the embodiment of Figures 5 to 7.