GB2472154A

GB2472154A - Chisel with removable blade element

Info

Publication number: GB2472154A
Application number: GB1015222A
Authority: GB
Inventors: Simon Hackett
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-09-13
Filing date: 2010-09-13
Publication date: 2011-01-26
Also published as: GB201015222D0

Abstract

The chisel 10 includes a handle (12, Figure 2b), a shaft 14 and a removable blade element 16 having a cutting edge 18. A releasable non-screw-threaded engagement means 42, 66 is for releasably engaging the blade element 16 with the shaft 14 without the use of a screw-threaded fastener. The chisel may also include a releasable screw-threaded fastening means for further releasably fastening the blade element to the shaft with the use of a screw-threaded fastener. The releasable non-screw-threaded engagement means may include a Morse taper. The removable blade element may be disposable.

Description

Chisel The present invention relates to a chisel having a removable blade element which is preferably disposable.

A chisel is a well known carpentry tool and comes in various widths and specifications for different kinds of jobs. However, it is always an issue keeping the, typically bevelled, cutting edge at the end of the blade of the chisel sharp and ready for use. A dull cutting edge will result in a poorly finished work piece. The cutting edge may be dull due to the user forgetting to check the keenness of the edge prior to beginning work, or may be dulled or damaged during work for example when striking a knot or a hidden nail or screw. This all therefore takes time away from the job in hand when having to resharpen the cutting edge. Oilstones are still typically used for resharpening a cutting edge of a chisel, but this relies on having one to hand and also having the time, typically being ten minutes or more, to grind and hone the edge.

The present invention seeks to provide a solution to these problems.

According to the invention, there is provided a chisel comprising a handle, a shaft, a removable blade element having a cutting edge, and releasable non-screw-threaded engagement means for releasably engaging the blade element with the shaft without the use of a screw-threaded fastener.

Preferable and/or optional features of the invention are set forth in claims 2 to 18, inclusive.

The invention will now be more particularly described, by way of example only, with reference to the accompanying drawings, in which Figure 1 shows a shaft with a removable blade element having a cutting edge of a first embodiment of a chisel, in accordance with the invention; Figures 2a and 2b show diagrammatic elevational side views of a second embodiment of the chisel, in accordance with the invention; and Figures 3a to 3c show diagrammatic views of a third embodiment of a chisel having a removable blade element, in accordance with the invention.

Refening firstly to Figure 1 of the drawings, a chisel 10 comprises a handle 12, a shaft 14 and a removable blade element 16 having a cutting edge 18. The handle 12 is shown in the second embodiment of Figure 2b, but typically includes a profiled grip 20 for a user's hand, a closed proximal end 22 which may be reinforced for striking with a hammer or other implement, and an open distal end 24 for receiving a tang at the proximal end 26 of the shaft 14. The tang of the shaft 14 may be permanently held within the handle 12, or may be removable.

Alternatively, a female connector part may be provided on the shaft 14 with the distal end 24 of the handle 12 having a complementarily shaped male connector part receivable therein.

The shaft 14 itself is preferably formed from metal, such as hardened or tempered steel.

However, as the blade element 16 having the cutting edge 18 is removable, other suitable support materials could be considered for the shaft 14, since the shaft 14 no longer has to be suitable for incorporation of an integral one-piece cutting edge 18.

The shaft 14 includes a back 28 which is planar along at least a majority of its longitudinal extent, a preferably longitudinally faceted face 30 which is generally slightly shorter than the back 28, and a blade element mounting portion 32 at a distal end 34 of the shaft 14. The blade element mounting portion 32, in this embodiment, includes a bevel portion 36 which extends from the face 30, opposing secondary bevels 38 which are between distal edges 40 of the bevel portion 36 and the back 28, and a mounting slot 42 which is between the two opposing secondary bevels 38.

The slot 42 tapers inwardly to form a channel across the lateral extent of the shaft 14 having a bottom surface 44 which has a smaller lateral extent than that of the opening 46 to the channel. In this embodiment, the slot 42 has open ends 48. However, this is optional and it may be beneficial to have closed ends to prevent or limit lateral displacement of the removable blade element 16 during use.

A release opening 50 is provided in the bevel portion 36 of the shaft 14. In this case, the release opening 50 is an aperture which extends through the shaft 14 to the back 28.

However, the release opening 50 may be bottomed. In any event, the release opening 50 breaks at least partially into the bottom of the slot 42. Although cylindrical in this s embodiment, the release opening 50 may be other shapes, such as frusto-conical. The release opening 50 may also extend normally to the back 28 of the shaft 14, or it may be angled to extend in a handle to cutting edge direction of the chisel 10.

The removable blade element 16 of this embodiment comprises a blade body 52 which tapers to the sharp cutting edge 18 at its leading proximal end 54, a trailing distal end 56 having acute opposing faces 58 so as to be complementarily shaped to match the opposing secondary bevels 38 of the shaft 14, and a laterally broad projecting element which extends outwardly between the acute opposing faces 58. The in use removable blade element 16 will endure substantial force, and is therefore formed of hard resilient material, such as tempered steel.

The blade body 52 preferably has a planar or substantially planar back 62 so as to be coplanar with the back 28 of the shaft 14. The face 64 of the blade body 52 may be coplanar with the bevel portion 36 of the shaft 14, or may be shaped to provide a secondary differently angled bevel portion for the cutting edge 18. The face 64 of the blade body 52 may also include two differently angled bevels in a longitudinal direction of the chisel 10, as necessity dictates.

The projecting element 60 forms a broad rigid tongue 66 which tapers slightly in the cutting edge to handle direction of the chisel 10. The taper of the tongue 66 is complimentary with the taper of the slot 42 of the shaft 14 so that a Morse taper fit is formed when the two are engaged. With the removable blade element 16 engaged with the shaft 14, a free distal edge 68 of the tongue 66 which is spaced from the acute opposing faces 58 extends slightly into the release opening 50. The blade element 16 is held laterally stable by the acute opposing faces 58 engaging with the opposing secondary bevels 38.

When the cutting edge 18 becomes dull, a non-specific thin elongate hard implement, such as a nail, screw, centre-punch or screwdriver shaft, is urged into the release opening 50 and against the free distal edge 68 of the tongue 66 of the blade body 52.

This releases the Morse taper engagement between the tongue 66 and the slot 42, allowing simple finger-tip removal of the blade element 16. The blade element 16 can then either be saved for resharpening or disposed of. In any event, a replacement blade element having a pre-sharpened cutting edge is immediately reattached to the shaft 14 and the job at hand can be continued.

This first embodiment utilises a releasable non-screw-threaded engagement means by way of the Morse taper fit. This in itself is typically sufficient to securely and releasably i0 hold the blade element 16 to the shaft 14 and is particularly beneficial in that a dedicated release tool is not required as this can often be mislaid in a busy working environment. However, it is possible to additionally provide screw-threaded fastening means to secondarily engage blade element 16 with the shaft 14. For example, a screw threaded opening may be provided through the bevel portion 36 of the shaft 14 and which intersects the slot 42. With the tongue 66 of the blade element 16 taper fit engaged within the slot 42, a grub screw or other screw-threaded fastener can be wound down onto the upper flat of the tongue 66 or through an opening in the tongue 66.

Conveniently, the release opening 50 may include a screw-threaded bore by which a screw-threaded fastener can be tightened down onto the tongue 66 to aid in retaining the blade element 16 on the shaft 14. Removal of the screw-threaded fastener allows access to the free distal edge 68 of the tongue 66, whereby release from the Morse taper engagement can be affected.

Additionally or alternatively, it would be feasible to include a cam element in the release opening 50. With the tongue 66 engaged in the slot 42, the cam element would be axially turned to engage and urge the tongue 66 out of engagement with the walls of the slot 42, thereby allowing simple removal. The cam element may be a key which is rotatable by a user's fingers, or have a slotted head which is rotatable by a screwdriver,

for example.

Referring to Figures 2a and 2b, a second embodiment of a chisel 10 is diagrammatically shown in elevation. Like references refer to like parts, and further detailed description is therefore omitted.

The chisel 10 of this embodiment still comprises the handle 12, shaft 14 and removable blade element 16 having the cutting edge 18 as described above. However, the tongue and Morse taper fit are dispensed with. The blade body 52 is a cap for fitment on the bevel portion 36 of the shaft 14. The base of the shaft 14 includes an undercut 70 adjacent to the distal end 34 for engaging and retaining a lower edge 72 of the blade body 52, and one or more teeth 74 are provided on the bevel portion 36 for engagement with openings in an undersurface 76 of the face 64 of the blade body 52. The cap-like i0 blade body 52 is then removed by prising the face 64 of the blade body 52 away from engagement with the teeth 74 and lifting clear.

As with the first embodiment, although releasable non-screw-threaded engagement means is utilised, a further releasable screw-threaded fastening means as previously described can be used for secondary engagement, if needs be.

is Refening finally to Figures 3a to 3c, a third embodiment of a chisel 10 is diagrammatically shown. Like references again refer to like parts, and further detailed

description is therefore omitted.

The chisel 10 of this third embodiment comprises the handle 12, shaft 14 and removable blade element 16 having a cutting edge 18 as previously described. The shaft 14 in this case includes a male dovetail portion 78 which extends from adjacent to the distal end 34 of the shaft 14 and partway along the longitudinal extent of the shaft 14. The male dovetail portion 78 includes longitudinal inwardly angled surfaces along edges 80 of the back 28 of the shaft 14.

The blade element 16, as shown in plan in Figure 3c, is generally T-shaped. The stem 82 of the blade element 16 includes a complementarily shaped female dovetail portion 84 at each side edge, as shown in lateral cross-section in Figure 3b.

The sliding dovetail engagement between the back 28 of the shaft 14 and the stem 82 of the blade element 16 prevents the blade element 16 from dropping away from the shaft 14 when in use.

A tooth or pin 86 is preferably utilised on the back 28 of the shaft 14 to engage with an opening 88 in the stem 82 of the blade body 52 or vice versa. This holds the engaged blade element 16 longitudinally when in use. To replace the blade element 16, the stem 82 is simply prised away from the tooth or pin 86 and slid longitudinally out of the female dovetail portion 84.

Although a sliding dovetail connection is suggested, the releasable non-screw-threaded engagement means could be a key and keyway.

Rather than tooth or pin engagement with an opening, the dovetail connection or key / keyway could taper to provide a taper fit as with the first embodiment.

Additionally or alternatively, as with the first embodiment, screw-threaded fastening means could be considered for secondary engagement of the blade element with the shaft.

It is thus possible to provide a chisel having a removable blade element, thereby is allowing quick and simple blade interchanging without requiring resharpening. It is also possible to provide a chisel whereby the removable blade element is held to the shaft by releasable non-screw-threaded engagement means thus enabling release and removal without a dedicated release tool.

The embodiments described above are provided by way of examples only, and various other modifications will be apparent to persons skilled in the field without departing from the scope of the invention as defined in the appended claims.

Claims

Claims 1. A chisel comprising a handle, a shaft, a removable blade element having a cutting edge, and releasable non-screw-threaded engagement means for releasably engaging the blade element with the shaft without the use of a screw-threaded fastener.
2. A chisel as claimed in claim 1, further comprising releasable screw-threaded fastening means for further releasably fastening the blade element to the shaft with the use of a screw-threaded fastener.
3. A chisel as claimed in claim 2, wherein the screw-threaded fastening means is included as part of the non-screw-threaded engagement means.
4. A chisel as claimed in any one of claims 1 to 3, wherein the releasable non-screw-threaded engagement means includes a release opening in the shaft for accessing a proximal end of the fitted removable blade element.
5. A chisel as claimed in claim 4, wherein the release opening is an aperture which passes through the shaft.
6. A chisel as claimed in claim 5 or claim 6, wherein the release opening has a longitudinal extent which extends at a non-perpendicular angle to the longitudinal extent of the shaft.
7. A chisel as claimed in any one of claims 4 to 6, wherein the release opening has an elongate lateral cross-section.
8. A chisel as claimed in any one of the preceding claims, wherein the releasable non-screw-threaded engagement means comprises a Morse taper, wherein a distal end of the shaft includes a tapering opening, and a proximal end of the removable blade element includes a complimentarily shaped tapering projecting element.
9. A chisel as claimed in claim 8, wherein the tapering opening is a slot which extends the lateral extent of the shaft.
10. A chisel as claimed in claim 8 or claim 9, wherein the tapering opening is formed in a distal end wall of the shaft.
11. A chisel as claimed in any one of the claims 8 to 10, wherein the tapering projecting element is a broad arm having a lateral extent which matches or substantially matches that of a cutting edge of the removable blade element.
12. A chisel as claimed in any one of the preceding claims, wherein the removable blade element includes upper and lower distal end walls having which a non-coplanar with each other and which have upper and lower free edges, respectively, which in use meet flush or substantially flush with corresponding upper and lower longitudinal surfaces of the shaft.
13. A chisel as claimed in any one of claims 1 to 7, wherein the removable blade element includes a key or keyway and the shaft includes the other of the key or keyway, the key and keyway extending longitudinally of the chisel.
14. A chisel as claimed in claim 13, wherein the key and keyway laterally define a dovetail.
15. A chisel as claimed in claim 13 or claim 14, wherein the removable blade element is T-shaped.
16. A chisel as claimed in any one of the preceding claims, wherein the releasable non-screw-threaded engagement means includes a notch on one of the removable blade element and the shaft and a retaining protrusion on the other of the removable blade element and the shaft, the notch and retaining protrusion being releasably interengagable to hold the blade element to the shaft.
17. A chisel as claimed in claim 16 wherein the notch and retaining protrusion prevents or limits the in use blade element moving laterally relative to the shaft.
18. A chisel as claimed in any one of the preceding claims, wherein the removable blade element is disposable.
19. A chisel substantially as hereinbefore described with reference to Figures 1, Figures 2a and 2b, or Figures 3a to 3c of the accompanying drawings.