A REPLACEABLE BLADE KNIFE

Abstract: A replaceable blade knife (1) comprises two elongate handle portions (3, 4) and a blade carrier (5) assembled together; the blade (6) protruding, or being arranged to protrude, from a front end (8) of the handle (2), between respective front ends (9, 10) of the two handle portions (3, 4). The upper handle portion (3) has a thumb-nail-sized aperture (26) through a rear end part thereof. When the knife (1) is assembled, the two handle portions (3, 4) are slid relatively longitudinally of one another, the upper handle portion (3) moving forwardly of the lower handle portion (4), until a latch part (31) near the rear end of the lower handle portion (4) clicks into latching engagement with the front edge (36) of the aperture (26) in the upper handle portion (3). The upper handle portion (3) is formed near its front end (9) with two downwardly projecting flank portions (14, 15), each said flank portion having an integral, forewardly projecting piece (16, 17) at the bottom of the flank portion. The front (10) of the lower handle portion (4) is formed with upwardly projecting flank portions (20, 21), each said flank portion having an integral, rearwardly projecting piece (22, 23) at the top of the flank portion, to overlie and hence interlock with a forwardly projecting piece (16, 17) at the bottom of the corresponding flank portion (14, 15) of the upper handle portion (3). At the rear edge of the aperture (26), the upper handle portion (3) is formed, at the bottom thereof, with a forwardly directed projection (27) which engages in a recess (28) at a rear wall (29) of the lower handle portion (4) to interlock the two handle portions (3, 4) together at the rear end of the handle (2).

Description: This invention relates to a replaceable blade knife comprising an elongate handle, formed by two elongate handle portions, and a blade carrier assembled together; the blade protruding, or being arranged to protrude, from a front end of the handle, between respective front ends of the two handle portions. The blade may or may not be extendable and retractable and may or may not be a snap-off blade, adapted for used bits of the blade to be snapped-off and discarded from time to time. US-A-4 240 202, on which the preamble of claim 1 is based, discloses a replaceable blade knife comprising an elongate handle, formed by two elongate handle portions, and a blade carrier assembled together; the blade protruding, or being arranged to protrude, from a front end of the handle, between respective front ends of the two handle portions; the two handle portions interlocking together with each other at or near the front end of the handle to resist splaying apart thereof in the event of side loading of the blade; the two handle portions interlocking with each other also at or near the rear end of the handle, to prevent the two handle portions from being parted at the rear end of the handle; a first one of said two handle portions having an aperture through a rear end part thereof; said two handle portions being longitudinally displaceable relative to one another to disengage the interlocking together of the two handle portions and thereby allow separation of the two handle portions; the knife comprising selectively releasable means in the aperture for preventing, except when released, the longitudinal displacement of the two handle portions. The invention provides a replaceable blade knife as claimed in each of the claims, to which reference is directed. The invention will be described by way of example with reference to the drawings, wherein:- FIG. 1 is a front elevational view of a replaceable blade knife embodying the invention; FIG. 2 is a rear elevational view of the replaceable blade knife embodying the invention of Fig. 1; FIG. 3 is a section on III-III of Fig. 1; FIG. 4 is a top view of the knife of Figs. 1 to 3; FIG. 5 is an exploded underneath view of the knife of Figs. 1 to 4; FIG. 6 is a view of the insides of the two handle portions and the blade carrier with blade of the knife of Figs. 1 to 5; and FIGS. 7, 8 and 9 are respectively a front view, a side view and an end view of the blade carrier of the knife of Figs. 1 to 6. The illustrated replaceable blade knife 1 comprises an elongate handle 2 formed by two elongate handle portions 3, 4 of plastics material, namely, an upper handle portion 3 and a lower handle portion 4, and a blade carrier 5, assembled together. A blade 6 is mounted on the blade carrier 5, which is housed within the handle 2 and is adapted and arranged to slide along guides 7 within the handle 2 towards and away from the front end 8 of the handle 2, to extend and retract the blade 6. When extended, the blade 6 protrudes from the front end 8 of the handle 2 between respective front ends 9, 10 of the two handle portions 3, 4. The blade carrier 5 is provided with a resiliently biased button 11 which protrudes through an elongate slot 12 in the upper handle portion 3 for extending and retracting the blade 6, the button 11 being biased into releaseable engagement with internal detent formations 13 on the upper handle portion 3, at each side of the slot 12. The upper handle portion 3 is formed near its front end 9 with two downwardly projecting flank portions 14, 15 at the top and bottom sides of the upper handle portion 3 respectively, spaced rearwardly a little from the very front end 9 of the upper handle portion 3. Each said flank portion 14, 15 of the upper handle portion 3 has an integral, forwardly projecting piece 16, 17 at the bottom of the flank portion, to interlock with the lower handle portion 4 in a manner to be described. As shown in Fig. 6, the upper handle portion 3 is cut away at 18 and 19 to receive upwardly projecting flank portions 20, 21 of the lower handle portion 4, in a manner to be described. The lower handle portion 4 is formed at the very front thereof with the above-mentioned upwardly projecting flank portions 20, 21. Each said flank portion 20, 21 of the lower handle portion 4 has an integral, rearwardly projecting piece 22, 23 at the top of the flank portion, to overlie and hence interlock with the forwardly projecting piece 16, 17 at the bottom of the corresponding flank portion 14, 15 of the upper handle portion 3. As shown in Fig 6, the lower handle portion 4 is formed with two recesses 24, 25 behind its two flank portions 20, 21, to receive the two flank portions 14, 15 of the upper handle portion 3, for interlocking the two handle portions 3, 4 together at the front end 8 of the handle 2. The upper handle portion 3 has a thumb-nail-sized aperture 26 through a rear end part of the upper handle portion. At the rear edge of the aperture 26, the upper handle portion 3 is formed, at the bottom thereof, with a forwardly directed projection 27 which engages in a recess 28 at a rear wall 29 of the lower handle 4 portion to interlock the two handle portions 3, 4 together at the rear end of the handle 2, to prevent the two handle portions 3, 4 being parted at the rear end of the handle 2. The lower handle portion 4 has a resiliently deflectable, integrally formed latch part 31 which occupies the aperture 26 when the two handle portions 3, 4 are assembled together. The latch part 31 is in the form of a cantilever extending generally forwardly and at an angle to the plane of the blade 6, to protrude into the aperture 26, from its attachment point at 32 to the rear end of a main body part 33 of the lower handle portion 4. A front end 34 of the latch part 31 is of stepped formation, to provide a narrow, forwardly projecting, ledge 35. This front end 34 of the latch part 31 latchingly engages a front edge 36 of the aperture 26 when the two handle portions 3, 4 are assembled together. The front edge 36 of the aperture 26 in the upper handle portion 3 presses down upon the ledge 35 of the latch part 31, giving the latch part 31 a slight resilient deflection to maintain latching engagement. An internal, integral, resiliently flexible spring leaf 37 of the upper handle portion 3 projects downwardly from a top wall 38 of the upper handle portion, and longitudinally engages the rear of an internal rib 39 of the lower handle portion 4, so as to tend to push the lower handle portion 4 forwardly of the upper handle portion 3 and thereby bias the front end 34 of the latch part 31 longitudinally of the handle 2 into its latching engagement with the front edge 36 of the aperture 26. When the two handle portions 3, 4 are assembled together, the flank portions 14, 15 at the front end of the upper handle portion fit generally behind the flank portions 20, 21 at the front end of the lower handle portion 4, interlocked by the lower handle portion flank portion pieces 22, 23 overlying the upper handle portion flank portion pieces 16, 17 as described above. The external or upper surface 40 of the latch part 31 follows the contour of the external or upper surface 41 of the upper handle portion 3 around the edge of the aperture 26, sloping relative to the plane of the blade 6. The latch part 31 is resiliently deflectable out of the latching engagement with the front edge 36 of the aperture 26 by a manual pressure applied to the upper surface 40 of the latch part 31 within the aperture 26. The disengagement of latch part 31 necessitates - due to the angle of the latch part 31 to the plane of the blade 6 - a very slight rearward movement of the lower handle portion 4 against the resilient bias of the spring leaf 32 of the upper handle portion 3. The two handle portions 3, 4 are thereupon longitudinally displaceable in the opposite direction relative to one another, the upper handle portion 3 moving rearwardly of the lower handle portion 4, to disengage the interlocking both at the front end and at the rear end of the handle 2 and thereby allow separation of the two handle portions 3, 4, for replacing the blade 6. When the knife 1 is reassembled, the two handle portions 3, 4 are slid relatively longitudinally of one another, the upper handle portion 3 moving forwardly of the lower handle portion 4, until the latch part 31 clicks into latching engagement with the front edge 36 of the aperture 26 in the upper handle portion 3. As shown in Figs. 7 to 9, the blade carrier 5 is of conventional construction, comprising a pressed metal piece 42 and the above-mentioned button 11, which is a plastic button which is assembled onto an upwardly bent cantilever spring portion 43 of the metal piece 42. The plastic button 11 has side projections 44 to engage the detents 13 of the upper handle portion 3. The metal piece 42 is formed with the usual projection 45 to engage in a recess 46 in the non-cutting edge of the blade 6, to interlock the blade 6 with the blade carrier 5 in the usual way.

Claims: A replaceable blade knife comprising an elongate handle (2), formed by two elongate handle portions (3, 4), and a blade carrier (5) assembled together; the blade (6) protruding, or being arranged to protrude, from a front end (8) of the handle (2), between respective front ends (9, 10) of the two handle portions (3, 4); the two handle portions (3, 4) interlocking together with each other at or near the front end (8) of the handle (2) to resist splaying apart thereof in the event of side loading of the blade (6); the two handle portions (3, 4) interlocking with each other also at or near the rear end of the handle (2), to prevent the two handle portions from being parted at the rear end of the handle (2); a first one (3) of said two handle portions (3, 4) having an aperture (26) through a rear end part thereof; said two handle portions (3,4) being longitudinally displaceable relative to one another to disengage the interlocking together of the two handle portions (3, 4) and thereby allow separation of the two handle portions (3, 4); the knife comprising selectively releasable means (31, 36) in the aperture (26) for preventing, except when released, the longitudinal displacement of the two handle portions (3, 4); characterised in that said selectively releasable means (31, 36) comprises a resiliently deflectable, integrally formed latch part (31) which is attached to a main body part (33) of said second handle portion (4) and which occupies said aperture (26) when the two handle portions (3, 4) are assembled together; said latch part (31) is in the form of a cantilever extending generally forwardly and at an angle to the plane of the blade (6), to protrude into said aperture (26), from its attachment point (32) to the main body part (33) of said second handle portion (4); a front end (34) of said latch part (31) latchingly engages a front edge (36) of said aperture (26) and is biased longitudinally of the handle (2) into said latching engagement due to longitudinal engagement of a resiliently flexible part (37) of one handle portion (3) with the other handle portion (4); and said latch part (31) is resiliently deflectable out of said latching engagement by manual pressure applied through said aperture (26). A knife as claimed in claim 1, wherein the latch part (31) and the front edge (36) of the aperture (26) have a stepped formation (35) on at least one thereof, where they interengage, to maintain the latching engagement thereof. A knife as claimed in claim 2, wherein the stepped formation (35) is on the latch part (31). A knife as claimed in any preceding claim wherein said resiliently flexible part (37) of one handle portion (3) is an internal downwardly extending projection from a top wall (38). A knife as claimed in any preceding claim wherein each said handle portion (3, 4) includes, at the front end of the handle (2), at least one integral longitudinally projecting piece (16, 17, 22, 23) to interlock with the other handle portion (4, 3).

Inventors: GILBERT, RICHARD
Applicants: THE STANLEY WORKS LIMITED
Application year: 1990
Main classification: B26B5
IPC codes: B26B5, B26B1