Retractable blade knife

Claim 2

A retractable blade knife comprising a casing having a slot in one side thereof, a blade, a slidable blade carrier mounting the blade and engaging at least one edge thereof, an operating button projecting through said side slot and a leaf spring associated with the operating button for biasing the button into selective locking engagement with the casing and for removably holding the blade on the blade carrier, said casing comprises a body having a slot in one end through which the blade can be extended and retracted and a cover detachably attachable to the body to enclose the blade carrier and spring, wherein the cover has two curled opposite end portions which respectively hook over two corresponding end portions of the body, firstly one end portion of the cover being hooked over one end portion of the body and then the cover being pivotable thereabout until the other end portion of the cover hooks over the other end portion of the body, whereby the cover can snap into place when attached to the body.

Claim 3

A retractable blade knife as claimed in claim 1 wherein the slot through which the operating button projects is in the cover.

Claim 4

A retractable blade knife as claimed in claim 1 wherein the body is of molded plastics material and the cover is of sheet metal.

Claim 5

A retractable blade knife as claimed in claim 1 wherein two sides of the body have rebates for the cover to nest therein.

Claim 6

A retractable blade knife as claimed in claim 1 wherein the spring is an arched cantilever spring which is permanently attached to the blade carrier.

Claim 7

A retractable blade knife as claimed in claim 1 wherein the operating button is biased by the leaf spring into engagement with detents in the casing to lock the blade selectively not only in the extended and retracted positions but also in an intermediate position.

Claim 8

A retractable blade knife as claimed in claim 1 wherein no part of the knife is screw-threaded.

Claim 9

A retractable blade knife as claimed in claim 1 wherein the casing is formed with a facility in the form of a hole to allow for hanging the knife on a hook, connection of the knife to a key ring, attachment of the knife to a string anchorage, or the like.

Claim 10

A retractable blade knife as claimed in claim 1 wherein the slot through which the operating button projects is in the cover; wherein said cavity is large enough to provide additional blade storage space; wherein the body is of molded plastics material and the cover is of sheet metal; wherein two sides of the body have rebates for the cover to nest therein; wherein the spring is an archEd cantilever spring which is permanently attached to the blade carrier; wherein the operating button is biased by the leaf spring into engagement with the detents in the casing to lock the blade selectively not only in the extended and retracted positions but also in an intermediate position; wherein a plurality of edges of the blade are engaged by the blade carrier to locate the blade in a given position relative to the blade carrier; wherein a tang of the blade is abuttingly engaged by a rearward pair of lugs and a forward pair of lugs, said pairs of lugs forming part of the blade carrier; the rear end of the tang is abuttingly engaged by a forwardly directed lug of the blade carrier; and the rear end of a keyhole slot in the tang is abuttingly engaged by a rearwardly directed lug of the blade carrier; the leaf spring pressing the blade against a base of the blade carrier; said lugs all upstanding from the base of the blade carrier; wherein, for releasably locking the blade and blade carrier as a unit releasably in different positions, including at least the extended position and the retracted position, relative to the casing, the button is formed with a flange which can seat in between any one of three pairs of detent-forming notches which are formed in two inwardly drawn skirts of the cover, the skirts extending along the sides of the slot through which the button projects; wherein the button is attached to an arched portion of the spring intermediate positions at which the spring respectively is attached to the blade carrier and engages the blade, so that the flange can be unseated by depression of the button for extension or retraction of the blade; wherein no part of the knife is screw-threaded; and wherein the casing is formed with a facility in the form of a hole to allow for hanging the knife on a hook, connection of the knife to a key ring, attachment of the knife to a string anchorage, or the like.

Claim 11

A retractable blade knife as claimed in claim 1 wherein a plurality of edges of the blade are engaged by the blade carrier to locate the blade in a given position relative to the blade carrier.

Claim 12

A retractable blade knife as claimed in claim 10 wherein a tang of the blade is abuttingly engaged by a rearward pair of lugs and a forward pair of lugs, said pairs of lugs forming part of the blade carrier; the rear end of the tang is abuttingly engaged by a forwardly directed lug of the blade carrier; and the rear end of a keyhole slot in the tang is abuttingly engaged by a rearwardly directed lug of the blade carrier; the leaf spring pressing the blade against a base of the blade carrier; said lugs all upstanding from the base of the blade carrier.

Claim 13

A retractable blade knife as claimed in claim 1 wherein, for releasably locking the blade and blade carrier as a unit releasably in different positions, including at least the extended position and the retracted position, relative to the casing, the button is formed with a flange which can seat in between any one of three pairs of detent-forming notches which are formed in two inwardly drawn skirts of the cover, the skirts extending along the sides of the slot through which the button projects.

Claim 14

A retractable blade knife as claimed in claim 12 wherein the button is attached to an arched portion of the spring intermediate positions at which the spring respectively is attached to the blade carrier and engages the blade, so that the flange can be unseated by depression of the button for extension or retraction of the blade.