WO1991004140A1

WO1991004140A1 - Rotary chisel blade

Info

Publication number: WO1991004140A1
Application number: PCT/AU1990/000411
Authority: WO
Inventors: Allan Noel Porter
Original assignee: Allan Noel Porter
Priority date: 1989-09-12
Filing date: 1990-09-11
Publication date: 1991-04-04
Also published as: GB9204112D0; GB2251577B; GB2251577A

Abstract

A rotary chisel blade (2) for connection with a hand held rotary power tool. The chisel blade (2) includes a resilient disc (4) having a plurality of gullets (6) for removing waste formed in the periphery (8) of the disc (4). A tooth (10) having a cutting edge (12) is fixed to each gullet (6). An arcuate portion (14) of the cutting edge (12) is formed on a corner of the each tooth. Each tooth (10) is provided with a first flat face (16) which is perpendicular to the plane of rotation of the blade (2) and is inclined forward of a radius (R) of the disc (4) in the direction of rotation. A second flat face (18) is contiguous with and extends from the first flat face (16) in a direction away from the periphery (8). The cutting edge (12) extends along the edge of the first and second flat faces (16, 18).

Description

ROTARY CHISEL BLADE

FIELD OF THE INVENTION

The present invention relates to a rotary chisel blade for chiselling, carving, shaping and cutting solid materials such as wood, plastic, aluminium and other non- ferrous metals, and soft stone.

DISCUSSION OF THE PRIOR ART

Many different tools exist for carving and shaping material however, in practice, it has been found that these tools are limited in respect of the material for which they may be used, the inability to both remove waste -quickly and leave a high quality surface finish, their inconvenience for use, and the safety precautions required for use.

A wood-working tool of the type disclosed in US Patent No. 4850407 (Inkster K.R. and Lewis D.J.) is useful for quickly shaping and wasting wood. The tool essentially comprises a disk with chainsaw-like teeth disposed about the periphery. Due to the nature of the teeth, the wood-working tool may produce a "kick-back" action, which can pull the rotary tool out of the hands of the operator thereby creating a danger for the user. While this problem is alleviated to an extent by the provision of depth control projections, it remains an operational and practical difficulty of use of the wood-working tool. Moreover, it has been found that the "kick¬ back" is inconsistent and unpredictable in nature resulting in a lack of confidence by the user when working with the tool. In addition, the Inkster tool is both costly and complex to sharpen as it requires a specifically manufactured small round stone, which is also currently of limited availability.

SUMMARY OF THE INVENTION The present invention was developed with a view to providing a rotary chisel blade for use with a hand power tool for quickly and conveniently chiselling, carving, shaping, and cutting solid material. According to the invention there is provided a rotary chisel blade adapted for connection to a rotary power tool, said blade comprising: a resilient disc; at least one gullet formed in the periphery of said disc for removal of waste; a cutting means disposed in said gullet, said cutting means being provided with a cutting edge including an arcuate portion; whereby, in use, said chisel blade can cut material in a plane parallel to the plane of rotation.

Preferably the cutting means includes a first flat face lying in a plane substantially perpendicular to the plane of rotation, the arcuate portion of the cutting edge being formed on a corner of the first flat face of the cutting means.

Preferably the corner of the first flat face provided with the arcuate portion of the cutting edge extends radially beyond the periphery of the disc, whereby the chisel blade can cut material in a plane substantially perpendicular to the plane of rotation.

Preferably the first flat face is inclined at a first angle forward of a radius of the disc relative to the direction of rotation.

Preferably the cutting means further comprises a second flat face lying in a plane substantially perpendicular to the plane of the disc, the second flat face extending away from the periphery of the disc and inclined at a second angle forward of the radius of the disc relative to the direction of rotation, the second angle being greater than the first angle, wherein the cutting edge extends along an edge of the first and second flat faces of the cutting means.

According to another aspect of the present invention there is provided a rotary chisel blade adapted for connection to a rotary power tool, said blade comprising: a resilient disc; a plurality of gullets formed in the periphery of said disc for removal of waste, the gullets being equally spaced around the disc; a plurality of cutting means disposed in respective ones of said gullets, each one of said cutting means being provided with a cutting edge including an arcuate portion, whereby in use said chisel blade can cut material in a plane parallel to the plane of rotation.

Preferably the chisel blade further comprises a guard member disposed between the rotary tool and the chisel blade, the guard member extending radially beyond the cutting edges of the disc.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings in which:

Figure 1 is a front view of the rotary chisel blade provided with three gullets and corresponding cutting means;

Figure 2 is a top view of a portion of the chisel blade illustrated in Figure 1;

Figure 3 is a side view of the cutting means of the blade; Figure 4 is an enlarged side view of the cutting means and gullet; and

Figure 5 is a cross-sectional view of the blade and a guard member connected with a rotary power tool.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Referring to the drawings, it can be seen that the chisel blade 2 comprises a resilient disc 4 with three gullets 6 formed in the periphery 8 thereof. The gullets 6 are equally spaced around the disc 4. Disposed in and fixed to each gullet 6 is a cutting means 10 in the form of a tungsten carbide tooth. Each tooth 10 is provided with a cutting edge 12 which includes an arcuate portion 14, (refer Figure 3) . The cutting edge 12 is arranged so that the chisel blade 2 can cut material in a plane parallel to the plane of rotation of the blade 2. The plane of rotation corresponds with the plane containing the disc 4. In figure 1, the direction of rotation is assumed to be anti-clockwise. Each tooth 10 is provided with a first flat face 16 which lies in a plane perpendicular to the plane of rotation of the disc 4 and extends beyond the periphery 8. The first flat face 16 is inclined at an angle A forward of a radius R of the disc relative to the direction of rotation of the blade 2. The arcuate portion 14 of the cutting edge 12 forms a first corner 15 of the first flat face 16, (refer Figure 3) . The flat face 16 also has a second corner 17 extending radially beyond the periphery of the disc 4 which is arcuate in form. However in an alternative embodiment, the corner 17 may be square.

Each tooth 10 further comprises a second flat face 18 which lies in a plane substantially perpendicular to the plane of the disc 4. The second flat face 18 is contiguous with and extends from the first flat face 16 in a direction away from the periphery 8. The second flat face 18 is inclined at an angle B forward of the radius R of the disc 4 relative to the direction of rotation. The angle B being greater than the first angle A. A portion of the cutting edge 12 extends along side edges of the first and second flat faces 16, 18. As seen in Figure 4, this portion of the cutting edge 12 is in the shape of a dog leg.

As with essentially all teeth on cutting devices such as saws and chain saws, the teeth 10 are relieved rearward of the cutting edge 12. The angle of relief C of the teeth 10 is typically set at 10°. However, this can be varied to suit particular applications by sharpening the teeth 10 accordingly. The teeth 10 are also slightly skewed (refer Figure 2) so that the cutting edge 12 forms a leading edge of the teeth 10 in the direction of rotation of the disc 4. The angle of skew S may typically vary between 2° and 5°. In one form of the invention, the teeth 10 have a height H of 10mm, a width W of 5mm, and a thickness T of 3mm. A rear face 22 of the tooth 10 extends radially beyond the periphery 8 by a distance in the order of 1.5mm.

The teeth 10 may be arranged to be either alternately offset with respect of the plane of the blade 2, or all offset to one side in a mutually aligned manner. Due to the manner in which the blade 2 operates, it is not necessary for adjacent teeth 10 to be alternately offset as is the case with typical saws and chain saws.

The gullets 6 assist in removing waste, that is, the fragments or pieces of material cut from a bulk material being chiselled, carved or shaped, during use. The gullets 6 are formed by removing substantially triangular shaped portions from the periphery 8 of the disc 4. The amount of waste removed by the blade 2 is, in part, dependant on the size and geometry of the gullet 6. In general terms, as the distance between the first face 16 and a forward edge 24 of the gullet 6 increases, so does the maximum amount of material that can be removed per revolution of the blade 2. The gullets 6 are formed with a radial surface 26 which is inclined forward of the radius of the disc in the direction of rotation. The angle of inclination of the radial surface 26 is A degrees, being the same as the angle of inclination of the first flat face 16. The teeth 10 are welded to the radial face 26 of each gullet 6. The disc 4 is made of spring steel or saw steel. A hole is formed in the centre of the disc 4 to allow connection to a driven spindle of a hand held rotary power tool 20 such as an angle grinder. The diameter of the disc 4 is arranged to be marginally smaller than a recommended grinding disc size for a particular grinder. In order to suit a standard 100mm angle grinder, the disc 4 is made to a diameter of 95mm.

For increased safety, the blade 2 is also provided with a guard member 28 in the form of a clear flexible plastic disc. As most clearly illustrated in Figure 5, the guard member 28 is formed with a diameter greater than that of the disc 4 so as to extend radially beyond the cutting edges of the disc 4. The guard member 28 overlies the disc 4 and is located between the rotary tool 20 and the disc 4. The guard member 28 acts to prevent the user from accidently coming into contact with the cutting means 10 during use. It further functions as a deflector to avoid waste being thrown in the direction of the user. As the guard is clear, it also allows the user to see the cutting edges 12, thereby permitting accurate manipulation of the blade 2.

The blade 2 and guard 28 are connected to the spindle 30 of the rotary power tool 20 by a conventional washer/locking nut system 32. The blade 2 can be used in a plane varying from being parallel to, to perpendicular to, the material being worked. Furthermore, the blade 2 can be used in any direction, ie., towards the user away from the user or at any angle to the user. When the blade 2 is used in a manner so that the rotary tool 20 is pulled towards the user it will not "kick-back" .

Due to the arcuate portion 14 of the cutting teeth 10 it has been found that the blade 2 leaves a relatively smooth finish, similar to that provided by course sand paper. Accordingly, if a smoother finish is required, only minimal additional sanding is necessary with a fine sand paper. As a result of the resilience of the blade 2 the disc 4 tends to follow the work piece rather than dig in, providing minimal strain on the user. When the blade 2 is not parallel with the work material, the resilience of the disc 4 also tends to increase the effective work area (i.e., the length of the cutting edge in contact with the material) . The resilience of the disc 4 further allows the blade 2 assists in reducing the likelihood of damage to the blade during use and handling.

The blade 2 is particularly useful in cutting and shaping aluminium. Presently such operation is performed by an abrasive disc. However, due to the malleable characteristic of aluminium the pores of the abrasive disc tend to fill and clog with the wasted aluminium. The result is that the abrasive disc "skids" over the aluminium significantly reducing the efficiency thereof. Accordingly, the user must apply enormous pressure on the disc which cause the aluminium to heat up significantly. The pressure placed on an abrasive disc to cut aluminium also places considerable load on the bearings of the rotary tool driving the disc. In addition, the abrasive disc leaves a burr which must be subsequently removed from the work piece. Finally, due to the nature of abrasive discs they wear significantly during use and must be frequently replaced.

A blade 2 in accordance with an embodiment of the invention does not suffer from any of the above described disadvantage. Due to the gullets 6 the blade 2 does not clog up. Very little pressure is required to effect cutting or shaping of aluminium and as the blade 2 is made of steal it does not wear away, and requires only occasional shapening of the teeth 10. The blade 2 also leaves a smooth finish requiring no further surface finishing.

When the blade 2 is used for cutting, shaping or grinding of non-ferrous metals it is advantageous for the first flat face 16 to be inclined rearward of the radius R of the disc 4 in the direction of rotation.

Sharpening of the teeth 10 can be performed easily and quickly by conventional methods. In addition, it will be apparent that a rotary chisel blade in accordance with the embodiment of the present invention is both relatively simple and cheap to manufacture. No complex moulding or machining is necessary.

Now that a preferred embodiment of the chisel blade 2 has been described in detail, it will be apparent to those skilled in the mechanical arts that numerous modifications may be made to the blade 2 without departing from the basic inventive concepts. For example, in the illustrated embodiment, three gullets 6 are shown. However, the number of gullets 6 may be increased or decreased. Furthermore, the gullets 6 may be formed in shapes other than the substantially triangular shape illustrated in the drawings. In particular, the gullets 6 may for example, be formed in a substantially U- shaped manner. All such variations and modifications are to be considered within the scope of the invention, the nature of which is to be determined from the foregoing description and the appended claims.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A rotary chisel blade adapted for connection to a rotary power tool, said blade comprising: a resilient disc; at least one gullet formed in the periphery of said disc for removal of waste; a cutting means disposed in said gullet, said cutting means being provided with a cutting edge including an arcuate portion; whereby, in use, said chisel blade can cut material in a plane parallel to the plane of rotation.

2. A chisel blade according to claim 1, wherein said cutting means includes a first flat face lying in a plane substantially parallel to the plane of the disc, and wherein said arcuate portion of the cutting edge is formed on a corner of the first flat face.

3. A chisel blade according to claim 2, wherein the corner of the first flat face provided with the arcuate portion of the cutting edge, extends radially beyond the periphery of the disc, whereby in use the chisel blade can cut material in a plane substantially perpendicular to the plane of rotation.

4. A chisel blade according to claim 3, wherein the flat face is inclined at a first angle forward of a radius of the disc relative to the direction of rotation.

5. A chisel blade according to claim 4, wherein the cutting means further comprises a second flat face lying in a plane substantially perpendicular to the plane of the disc, said second flat face extending away from the periphery of the disc and inclined at a second angle forward of the radius of the disc relative to the direction of rotation, the second angle being greater than the first angle, wherein the cutting edge extends along an edge of the first and second flat faces of the cutting means.

6. A rotary chisel blade adapted for connection to a rotary power tool, said blade comprising: a resilient disc; a plurality of gullets formed in the periphery of said disc for removal of waste, the gullets being equally spaced around said disc; a plurality of cutting means disposed in respective ones of said gullets, each one of said cutting means being provided with a cutting edge including an arcuate portion, whereby in use, said chisel blade can cut material in a plane parallel to the plane of rotation.

7. A chisel blade according to claim 6, wherein each cutting means includes a first flat face lying in a plane substantially perpendicular to the plane of rotation, wherein the arcuate portion of the cutting edge is formed on a corner of the first flat face.

8. A chisel blade according to claim 7, wherein the corner of the first flat face provided with the arcuate portion of the cutting edge, extends radially beyond the periphery of the disc, whereby the chisel blade can cut'material in a plane substantially perpendicular to the plane of rotation.

9. A chisel blade according to claim 8, wherein the flat face is inclined at a first angle forward of a radius of the disc relative to the direction of rotation.

10. A chisel blade according to claim 9, wherein the cutting means further comprises a second flat face lying in a plane substantially perpendicular to the plane of the disc, said second flat face extending away from the periphery of the disc and inclined at a second angle forward of the radius of the disc relative to the direction of rotation, the second angle being greater than the first angle, wherein the cutting edge extends along an edge of the first and second flat faces of the cutting means.

11. A chisel blade according to claim 7, wherein the corner of the first flat face provided with the arcuate portion of the cutting edge extends radially beyond the periphery of the disc, whereby the chisel blade can cut material in a plane substantially perpendicular to the plane of rotation.

12. A chisel blade according to claim 6, wherein each of the cutting means are offset to the same side of the disc in a mutually aligned manner.

13. A chisel blade according to any one of the preceding claims, further comprising a guard member disposed between the rotary tool and said chisel blade, the guard member extending radially beyond the cutting edge about the disc.

14. A chisel blade according to claim 3 or claim 8 wherein the flat face is inclined at an angle rearward of a radius of the disc relative to the direction of rotation.

SUBSTITUTE H