REPLACEABLE BLADES AND TOOLS UTILISING SAME

Abstract: A replaceable blade (13) is held in place by the interengagement of a locking nodule (21) on a leg (18) of the replaceable blade (13) with a locking notch (31) on a blade holder (11) of a tool without the need for a separate fastener. A hand tool (10) has a blade holder (11) with the replaceable blade (13) arranged to seat in a recess (14) in the blade holder (11).

Description: REPLACEABLE BLADES AND TOOLS UTILISING SAME FIELD OF INVENTION The present invention relates to replaceable blades as well as tools such as hand planes, gasket scrapers, and chisels utilising such replaceable blades. BACKGROUND ART For the sake of convenience, the invention will be described in relation to wood chisels but it is to be understood that the invention is not limited thereto as it may be applied to other hand tools such as gasket scrapers and hand planes. Wood chisels are primarily designed for tasks associated with wood and usually consist of a shank having a handle at one end and a sharpened cutting edge or tip at the other end. In the normal course of events, wood chisels can come into contact with many materials that will damage the tip of the chisel. Such chisel damage may result from working on timber having obscured nails or adjacent to concrete or masonry surfaces. Also, a wood chisel may be misused by chipping at putty, concrete, slag or mortar, by scraping paint, by opening tins or removing ceramic or vinyl tiles. Maintenance and repair to a chisel tip is essential in order to retain an effective cutting edge. Sharpening the blunted cutting edge requires a considerable amount of skill that the average handyman or tradesman may not possess. If the cutting edge cannot be resharpened, the chisel must be replaced. Similar comments apply in respect of hand planes which are primarily designed for tasks associated with wood and usually consist of a main body having a handle at each end and which carries a sharpened blade that may be adjusted with respect to a rectangular opening in the sole plate of the main body of the plane. In the normal course of events, the cutting tip of the blade can easily be damaged and thus there is a need for an improved hand plane having a replaceable blade. SUMMARY OF THE INVENTION According to one aspect of the invention there is provided a replaceable blade for a tool comprising a body portion, a cutting edge at one end of the body portion and at least one leg at the other end of the body portion, the or each leg having locking means adapted to engage a complementary-shaped locking recess on the tool to secure the blade to the tool without a separate fastener. According to another aspect of the invention there is provided a hand tool comprising a blade holder having a recess and a replaceable blade having locking means adapted to engage the recess of the shank for releasably connecting the blade to the blade holder. In a preferred form of the invention, the connection means includes one or more legs on the blade adapted to engage with the recess formed in the blade holder. BRIEF DESCRIPTION OF THE DRAWINGS Fig 1 is a perspective view from above of a hand tool in the form of a chisel according to one embodiment of the invention, Fig 2 is a perspective view from below of the chisel shown in Fig. 1 , Fig 3 is a partially cutaway view similar to Fig. 2 showing the replaceable blade piece separated from the stem of the chisel, Fig 4 is an underneath plan view of the chisel shown in Fig. 3, Fig 5 is a view similar to Fig. 4 showing the replaceable blade piece connected to the stem of the chisel, Fig 6 is a view taken along lines VI-VI of Fig. 5, Fig 7 is a view taken along lines VII-VII of Fig. 5, Fig 8 is a partially cutaway underneath view of a chisel according to a second embodiment of the invention, Fig 9 is a partially cutaway underneath view of a chisel according to a third embodiment of the invention, Fig 1 0 is a partially cutaway underneath view of a chisel according to a fourth embodiment of the invention, Fig 1 1 is a view similar to Fig 1 0 of a fifth embodiment of the invention, Fig 1 2 is a plan view of a hand tool according to a sixth embodiment of the invention, Fig 1 3 is a side view taken along lines A-A of Fig. 1 2, Fig 1 4 is an underside view of the blade and blade holder taken in the direction C-C of Fig. 1 3, Fig 1 5 is a plan view taken in the direction of lines B-B of Fig. 1 3, Fig 1 6 is a sectional view taken along lines D-D of Fig. 1 5, and Fig 1 7 is a view similar to Fig. 1 3 of a seventh embodiment of the invention. MODES FOR CARRYING OUT THE INVENTION The hand tool 1 0 shown in Fig. 1 is, in this instance, a chisel which has a shank 1 1 , a handle 1 2 and a replaceable blade piece 1 3 locked into a recess 1 4 on the bottom face 1 5 of the shank 1 1 . The blade piece 1 3 has a body portion 1 6, a cutting edge 1 7 at one end of the body portion 1 6 and a pair of spaced apart legs 1 8 and 1 9 at the other end of the body portion 1 6. The blade piece 1 3 may, of course, be connected to any tool. In this instance, each leg 1 8 and 1 9 is inwardly tapered towards its free end and the space between the legs 1 8 and 1 9 defines a locating recess 20. At the free end of each leg 1 8 and 1 9 there is an outwardly extending locking nodule 21 of generally semi-circular form. At each side of the blade piece 1 3 there is a first edge 22 adjacent the cutting edge 1 7, a second inwardly directed bevelled edge 23 and a third bevelled edge 24 at the body portion 1 6. An aperture 25 is provided in the body portion 1 6 for receiving the end of a punch or similarly pointed instrument when the blade piece 1 3 is to be removed from the shank 1 1 . The recess 14 is of a shape that is complimentary to that of the blade piece 1 3 and on each side is a first inwardly bevelled edge 26 at its open end and a second longitudinally extending bevelled edge 27 terminating at leg-receiving passageways 28 and 29 dimensioned to receive the legs 1 8 and 1 9 respectively. In between the passageways 28 and 29 there is a guide piece 30 adapted to mate in the locating recess 20 of the blade piece 1 3. At the end of each passageway 28 and 29 there is an outwardly directed notch 31 of generally semi-circular form adapted to mate with the locking module 21 of each leg 1 8 and 1 9. In order to connect the blade piece 1 3 to the recess 1 4, the blade piece 1 3 is partially placed into the recess 1 4 by manually holding both the blade piece 1 5 and the shank 1 1 together and then resting the cutting edge 1 7 on a piece of wood or similar non-damaging material with the blade piece 1 3 and the shank 1 1 in a vertical position. Pressure is then exerted by placing the other hand on the handle 1 2 and manually pushing downwards to complete the location of the legs 1 8 and 1 9 in the passageways 28 and 29. As can be seen in Figs. 4, 5 and 6, the legs 1 8 and 1 9 are slightly narrower than the passageways 28 and 29 to provide a clearance 32 when the legs 1 8 and 1 9 are fully located in the passageways 28 and 29. The clearance 32 allows the legs 1 8 and 1 9 to spring inwards towards the guide piece 30 during a push fit. The locking nodules 21 initially make contact with the tapered edge 33 of each passageway 28 and 29 and deflect the legs 1 8 and 1 9 inwardly until the legs 1 8 and 1 9 are fully located in the passageways 28 and 29 when the locking nodules spring outwardly to achieve a tight fit in the locking notches 31 . Preferably, the shank 1 1 is fabricated from a high grade quality carbon steel giving the shank some flexibility as well as hardness and durability. The blade piece 1 3 is also fabricated from high grade quality carbon steel so treated to allow flexing of the legs 1 8 and 1 9. The blade piece 1 3 is strongly connected and locked into the recess 14 as the legs return to their original or free position after being deformed as they move into the passageways 28 and 29. Thus, the blade piece 1 3 is locked into the recess 1 4 of the shank 1 1 without any additional mechanical fixing component. The blade piece 1 3 may be removed by applying a force via a punch or similarly pointed instrument at the aperture 25 as mentioned above. The action of removing a blade piece 1 3 and inserting a new blade piece 1 3 can be completed in a matter of seconds. A range of sizes of cutting edges 1 7, 1 7a and 1 7b of the blade piece 1 3 may be accommodated by the same shank as indicated in Fig. 4. As can be seen in fig. 7, the outwardly bevelled edges 24 of the body portion 1 6 of the blade piece 1 3 are a push fit in the longitudinally extending bevelled edges 27 of the recess 1 4. This configuration of blade connection disperses any fragments of waste timber thus preventing such waste from entering and lodging in the space between the blade piece 1 3 and the recess 1 4. In the embodiment of the invention shown if Fig. 8, the blade piece 1 3 has only one lug 1 8 and the recess 1 4 of the shank 1 1 has only one leg-receiving passageway 28. The locking nodule 21 seats in the locking notch 31 as with the other embodiment of the invention. In the embodiment shown in Fig. 9, the locking arrangement of the nodules 21 and the notches 31 is replaced by a stud or dowel 35 upstanding from the base of the recess 1 4 which, when the blade piece is fully in place, engages in notches 40 and 41 in the legs 1 8 and 1 9. As the blade piece 1 3 is being pushed into the recess 14, the dowel 35 forces the legs 1 8 and 1 9 apart in much the same way as the legs 1 8 and 1 9 of the first embodiment are pushed together by the incline face 33 of the leg receiving passageways 28 and 29 of the first embodiment. In the embodiment of Fig. 1 0, the dowel 40 is so located in the recess 41 that it seats at the body end of the legs 1 8 and 1 9. In the embodiment of Fig. 1 1 , a tab 42 at the end of the blade piece 1 3 is bent downwards by a pointed instrument and seats in a recess 43 formed in the shank 1 1 . The invention may by applied to other hand tools such as gasket scrapers which have a blade or scraper working portion like that of a chisel. For example, the hand plane 1 1 0 shown in Figs. 1 2 to 1 7 includes a main body 1 1 1 having a sole plate 1 1 2, an upwardly directed boss 1 1 3, side walls 114 and transverse walls 115. At the front end of the hand plane 110 there is a front hand grip 116 secured to the main body 111 by screw 117 and at the rear end of the hand plane 110 there is a rear hand grip 118 secured to the main body by screw 119. The boss 113 which is located between the side walls 114 has a first inclined face 120 and a second inclined face 121 over which seats a cover 122 that is secured to the boss 113 by screw 123. Forward of the boss 113 there is a transverse rectangular opening 124 through which projects a disposable blade 125 that is connected to the underside of a blade holder 126 by legs 127 that locate in recesses 128 in the blade holder 126. The legs 127 have outwardly directed locking lugs 129 which engage in similarly shaped locking recesses 130 in the recesses 128. When the disposable blade is being placed on the holder 126, the legs are forced together and when fully home the locking lugs 129 engage the locking recesses 130 as can be seen in Fig. 14. In order to connect the disposable blade 125 to the holder 126, the holder 126 is removed from the plane 110 and the legs 127 partially placed into the recesses 128 by manually holding both the disposable blade 125 and the blade holder 126. The cutting edge of the disposable blade 125 is then placed on a piece of wood or similar non-damaging material with the disposable blade 125 and the blade holder 126 in a vertical position. Pressure is then exerted by manually pushing downwards on the blade holder 126 to complete the location of the legs 127 in the recesses. In this instance, the disposable blade 125 has an elongated slot 131 in which is located a pivot dowel 132. A finger hole 133 is provided in the upper end of the blade holder 126 to assist in the adjustment of the blade 1 25 as will be described below. In another embodiment of the invention, the disposable blade 1 25 may be secured to the blade holder 1 26 by a screw 1 32a as shown in Fig. 1 7. A support plate 1 34 is secured to the main body 1 1 1 by screws 1 35 as can be seen in Fig. 1 5. The support plate 1 34 carries an adjustment screw 1 36 having a knob 1 37 and which is threaded through nut 1 38 on the underside of the support plate 1 34. At the inner end of the adjustment screw 1 37 there is a pivot washer 1 39 and a pivot cap 140. In order to square up the edge of the replaceable blade 1 25 in the rectangular opening 1 24, the blade holder 1 26 is moved to the left or right by a finger inserted in the hole 1 33. The replaceable blade will pivot on either the screw head or the dowel so once the blade edge protrudes from the sole of the plane to the required cutting depth and is square with respect to the rectangular opening 1 24, the blade holder 1 26 is tightened down by rotating the knob 1 37. In a preferred form of the invention the main body 1 1 1 and the front and rear hand grips 1 1 6 and 1 1 8 are made of a suitable plastics material. The disposable blade is made from hardened and tempered carbon steel and the blade holder 1 26, support plate 1 34 and adjustment screw 1 36 are made of mild steel.

Claims: CLAIMS 1 . A replaceable blade for a tool comprising a body portion, a cutting edge at one end of the body portion and at least one leg at the other end of the body portion, the or each leg having locking means adapted to engage a complementary-shaped locking recess on the tool to secure the blade to the tool without a separate fastener. 2. A blade according to claim 1 and including a pair of spaced apart legs, each of which has a locking means. 3. A hand tool comprising a blade holder having a recess and a replaceable blade having locking means adapted to engage the recess to releasably connect the blade to the blade holder without the use of a separate fastening device. 4. A hand tool according to claim 3 wherein the replaceable blade has a body portion, a cutting edge at one end of the body portion and a leg at the other end of the body portion; said leg having the locking means. 5. A hand tool according to claim 4 wherein the locking means comprises a locking nodule which extends outwardly from the leg and which engages a similarly shaped notch formed in the recess of the blade holder. 6. A hand tool according to claim 3 wherein the replaceable blade has a body portion, a cutting edge at one end of the body portion and a pair of spaced apart legs at the other end of the body portion, each of said legs having the locking means. 7. A hand tool according to claim 6 wherein the recess in the blade holder has a pair of spaced apart passageways adapted to receive the spaced apart legs of the replaceable blade. 8. A hand tool according to claim 7 wherein the locking means comprises a locking nodule extending outwardly from the end of each leg and a similarly shaped notch at the end of each passageway. 9. A hand tool according to claim 6 wherein the sides of the body portion are bevelled and the recess has similarly bevelled side edges. 10. A hand tool according to claim 6 wherein the blade holder has an upstanding stud in the recess and the legs are adapted to pass either side of the stud and wherein the locking means comprises a recess formed in each leg adapted to receive the stud. 1 1 . A hand tool according to claim 1 0 wherein the recesses are at the body portion end of the legs. 1 2. A hand tool according to claim 1 0 wherein the recesses are spaced from the body portion. 1 3. A hand tool according to claim 3 wherein the locking means comprises a tab on the blade piece which is adapted to engage a recess formed in the shank. 1 4. A hand tool according to claim 3 which is a chisel and wherein the blade holder is the shank of the chisel. 1 5. A hand tool according to claim 3 which is a gasket scraper and wherein the blade holder is the shank of the gasket scraper. 1 6. A hand tool according to claim 3 which is a hand plane which includes a body having a sole plate and an aperture in the sole plate and wherein the blade holder is carried by the plane.

Inventors: BATCHELOR PAUL, BATCHELOR, PAUL
Applicants: BATCHELOR PAUL, FIRST AUSTRALIA DESIGN TECHNOL, BATCHELOR, PAUL, FIRST AUSTRALIA DESIGN TECHNOLOGY
Application year: 1997
Main classification: B25D3
IPC codes: B25D3, B25G3, B27G17