CA1262206A - Knife - Google Patents

Abstract

ABSTRACT

There is provided a knife having a blade and handle. The knife incorporates acceleration detection means adapted to cause automatic retraction of the blade into the handle upon detection of violent movement of the knife at least with the cutting edge of the blade in a leading attitude.

Description

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IMPROVED KNIFE

BACKGROUND TO THE INVENTION

This invention concerns a knife of the kind (hereinafter termed 'of the kind referred to') comprising a blade and handle.

In industry many accidents are caused by hand ~nives. Tne most serious injuries occur when the blade, forcibly applied to the work-piece, slips and strlkes the lim~s or body of the user. In textile mills such accidents happen most frequen~ly where residual thread is being stripped Erom bobblns or where entangled threads are being cut away from rollers on spinning ' machines.

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In such accidents the worker may be applying a force of such magnitude ~c 150 N) that the knife, at the moment of slipping, can move with an acceleration l0 times that of gravity.

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It is an object of the present invention ~o j provide a knife of the kind referred to which prevents `, 25 or al least reduces the incidence of the kinds of , accident men~ioned above.

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' ~6;~C)6 SUMMARY OF TI~E INVENTLON

~ ccordlng to the present invention there is provided a knife of the kind referred to incorporating accelera~ion detection means adapted ~o cause automatic retraction of the blade into the handle upon detection of violent movement of she knife at least with the cutting edge of the blade in a leading at~itude.

BRIEF DESCRIPTION OF THE ORAWINS~S

The inven~ion will be further apparent from the following description, with reference to the flgures of ~' ~he accompanying drawing, which show, by way of example ', 15 only, ~o forms of knife of the kind referred to and embodying the invention.
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~ Of the drawings:-:;
Figures 1 and 2 are longi~udinal cross-sections through the first form of knife with ~he blade thereof in its extended and retracted positions respectively.

Figure 3 is a longitudinal cross-section through the second form of ;~ , :

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knife with the blade thereof in an extended operative position;

- and Figure 4 is an end view of the knife seen in the direction of arrow IV on Figure 3.

DETAIL~.D DESCRIPTION OF T~E PREFERRED EMBODIMENTS

Referring first tO Figures 1 and 2 it will be seen that the first form of knife comprises a handle 10 of hollo~ box-llke construction and a ~lade 11 on the forward end of a tang 12. The blade 11 and tang 12 are slidable axially within the handle 10 to enable the blade 11 tO be moved from an operative position wherein its cu~ting edge lla extends out~ardly from the forward . end of ~he handle (Figure 1) to an inoperative or safe position ~herein the ~lade 11 is fully retracted into he handle 10 (Figure 2).

A tension spring 13 has its opposite ends '~ anchored to the blade 11 and the rear of the handle 10 ~e~ respec~ively and acts to urge the blade 10 in~o its j inoperative or safe posltion.

~,, The blade 11 may ~e slid into its operative position by pushing on the end of the tang 12 which :
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~, pro]ec~s rear~ardly from the handle 10 and there locked in posi~ion by engagemen~ of a latch 14 projecting from ~he tang 12 ~l~h a detent 15 ln a heavy arm 16 pivotally connected with the handle 10 at 17 and extending generally parallel with the tang 12.

In use if the body of the knife accelerates violently in the plane of movemen~ of the arm 16 with the cutting edge of the blade in a leading attitude, the arm, o~ing to its inertia, moves relative to the tang 12 thus releasing the lalch and retracting the blade.
~qually cne latch may be released tO retract the blade 11 for safe storage simply by a sharp rap on the handle 10 of the knlfe.
; Tne sensitiv1ty of the system may ~e engineered ~y appropriate geomecry but day to day adjustments may made ~y adjusting the force exerted on the arm 16 by a compression spring 18 ~y means of a grub screw 19.
~0 Referring now to Figures 3 and 4, it will be seen that the second form of knife comprises a handle 110 formed from two shell-like halves 111 and 112 which can ~e joined by screws at 113 and 114 on a longltudinal 25 central plane of the handle 110 to form a box-like enclosure which houses the working par~s of the knife.

The knife includes a blade 115, which is a replaceable item, and which is clamped bet~een support plates 116 by means of a screw 1.17. To gain access tO
screw 117 for blade replacement purposes it is necessary ~o separate the handle halves 111 and 112 One of the support plates 116 is connected to or integrally formed wi~h a rearwardly projecting tang-like member 118 ~hich has a longltudinally extending lateral recess 119 which houses a tension spring 120 ~hose forward end is anchored tO tne member 118 adjacent the I plates 116 and whose rearward end is anchored tO a s transverse pin 121 extending between the halves 111 and . 15 112 and through a longitudinally extending slot 122 in ~ the mem~er 118.

i The assembly including mernber 118 is slidable between a forward positi.on wherein the blacle 115 pro~rudes operatively from ~he handle 110 and a rearward position wherein the blade 115 is retracted to lie within ~he body of the handle 110. The spring 120 acts - to urge the assembly including member 118 into the rearward position.
'~ A cranked lever 125 is pivotally mounted at the rear oi the handle such that one of its arms 126 is 'J

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accessl~le from wltnout tne handle foL movement (in the dlrectlon of arLo~ X) agalnst the action o a return torslon spring 127 tO move the other of its arms 128 in~o engagement with an abutment surface at the rear end of member .L18 tO slide the assem~ly including member 118 forwardly to lock blade 115 protruding outwardly from handle 110 by a desired extent by engagement of one of a series of longitudinally spaced teeth 130 alony the upper face of member 118 with a tooth 131 on the underside of a pivotally mounted weighted arm 132 mounted ~ith1n tne nandle 110 above member 118. A
spring 133 urges arm 132 towards member 118 and its Strength lS selected to ensure retrac~ion of the assembly lncluding member 118 and hence blade 115 when tne handle 110 of the knife accelerates in the plane of movemen~ of arm 132 wi~h the cuttlng edge oE the blade ~ in a leading at~itude at or above a predetermined rate because of relative movement between arm 132 and member 118 to dlsenyage the tooth 131 from ~he tooth 130 ; 20 Again the blade 115 may be moved to its retracted position by delivery of a sharp rap to the handle 110.

I~ will be appreciated that it is not intended to limi~ the lnvention to the above example only, many variations, such as might readily occur to one skilled in the art, belng possible, wi~hout departing from the scope thereof as defined by the appended claimsO
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For example, a longitudlnal thumb slide protruding from t~e underside of ~he Kinfe nandle may be provided for movement of the blade carrylng assembly to i~s forward or operaclve position.

Other means for detectlng acceleration tnan that descri~ed may ~e used such as electronic transducer means, but a simple mechanical system is preferred on the grounds of reliability and cos~.

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Claims (11)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows.

1. A knife comprising a blade and a handle incorporating acceleration detection means and blade retraction means adapted to cause automatic retraction of the blade into the handle upon detection of violent movement of the knife at least with the cutting edge of the blade in a leading attitude.

2. A knife according to Claim 1 wherein the blade is arranged for sliding movement between a forward or operative position wherein it extends outwardly from the handle and a rearward or retracted position wherein the blade is located wholly within the handle, the blade being carried by a rearwardly extending tang-like member extending longitudinally of the handle.

3. A knife according to Claim 2 wherein spring means is provided between said tang-like member and the handle and serves to urge the blade to its rearward or retracted position.

4. A knife according to Claim 3 wherein a pivotted lever is located within the handle to extend generally parallel with said tang-like member and has a tooth formation on its face adjacent said tang-like member adapted to engage a cooperating tooth formation on the tang-like member to latch same to hold the blade in its forward or operative position against the action of said spring means, the arrangement being such that said violent movement causes relative movement between the lever and tang-like member to break the engagement between the cooperating teeth.

5. A knife according to Claim 4 wherein there is a plurality of longitudinally spaced teeth on the tang-like member enabling the blade to be latched with a desired extent of protrusion.

6. A knife according to Claim 4 wherein said lever is urged towards the tang-like member by resilient means which may be adjustable.

7. A knife according to Claim 3 wherein said spring means comprises a tension spring connected between said tang-like member adjacent the forward end thereof and a rearward part of the handle.

8. A knife according to Claim 2 including manually operable means for sliding the tang-like member and hence blade from its rearward or retracted position to its forward or operative position.

9. A knife according to Claim 8 wherein said manually operable means comprises a cranked lever which may be pivotted to bring one of its arms to bear against the end of the tang like member to push it forwardly.

10. A knife according to Claim 9 wherein the cranked lever may be operated against the action of return spring means therefor.

11. A knife according to Claim 1 wherein the handle is comprised by two separate halves which form a box-like enclosure for the working parts of the knife.