NZ570471A - A side of a polygonal aperture to be cut has two saw blades of different cutting plates in close proximity - Google Patents

Abstract

Disclosed is a cutting device for cutting through a work substrate. The cutting device comprises a plurality of cutting plates (101a, 101b, 102a, 102b), at least one of the plates having at least one linear saw blade (110a, 110b,) with a cutting edge (111) for cutting through the substrate. The cutting plates at least partially overlie each other, with their saw blades directed forward to be presented against the substrate. The plates are arranged such that the saw blades define the outline of an aperture that is to be cut. The plates are capable of a reciprocating linear movement so that their cutting edges cut the substrate, the movement being effected by an eccentric cam arrangement (120, 121) associated with a rotating drive shaft (100). A side of the aperture to be cut has two saw blades in close proximity, each blade associated with a different plate.

Description

1 DEVICE FOR FORMING NON-CIRCULAR APERTURES FIELD OF INVENTION The present invention applies to apparatus for the powered cutting of rectangular and polygonal apertures, particularly in materials such as wallboards.

BACKGROUND DESCRIPTION The present invention was developed as an improved method of cutting rectangular holes, for service access and faceplates, in wallboards. However it is envisaged that the present invention has broader applications and need not be restricted merely to the cutting of holes which are rectangular in shape, nor merely to the cutting of wallboards. 10 However, for simplicity of description, the specification herein will focus primarily on rectangular cutting unless otherwise stated. The reader should appreciate that the principles may be applied to a wider range of applications.

In modern dwellings and buildings it is common for a large number of services to be present, particularly electrical and communication. A large number of these terminate 15 on the visible face of walls, and occasionally floors or ceilings. Particular examples include electrical sockets and switches, though it is becoming increasingly common in both commercial and residential premises for there to be additional outlets for telecommunications lines, computer and data networks, audio and video routing systems, aerial connections, etc. As technology develops, the number of wiring 20 networks appears to increase, along with the number of connection sockets present in a wall. Manufacturers of electrical outlets and fittings have catered to this demand by also providing faceplates with appropriate inserts for the wiring system. These, depending on local or individual practice, typically screw or otherwise attach to a flush-box mounted behind the wallboard.

Access to a flush box, for the connection and fitting of a faceplate, requires an aperture to be cut or formed into the wallboard to allow access to the wiring within the flush box. Tradition has dictated that these apertures be rectangular, and most fittings require a rectangular aperture of commensurate size to the flush-box to be present in the 2 wallboard if the faceplate is to be fitted and mounted. When the aperture is properly cut, the faceplate covers the aperture.

A problem which arises, however, is that not all flush box apertures in walls are accurately cut. Mainly the apertures are manually cut by a small handsaw, or with a 5 retractable hand-held knife, depending on the nature of the wallboard. It is common for one or more edges of the rectangle to be over-cut, resulting in an aperture which extends past an edge of the face plate and becomes visible. Sometimes apertures are cut too large, particularly if cut before the wallboard is fixed to the wall, or if the contractor has not taken the time to mark and position the outline of the aperture accurately. Again 10 there is a problem, this being that the faceplate cannot mask the formed aperture.

Hand cutting apertures is also quite slow. While this might have been acceptable when the average room had one power outlet and one light switch, most contemporary rooms have double, or more, numbers of fittings. Attempting to speed the cutting process often results in sloppy work, necessitating subsequent patching - which is not always 15 totally successful - apart from the additional work and expense it creates.

These problems also extend to other fittings in a building, such as for ventilation and lighting. While a majority of these require circular apertures, which are covered by face plates, there is also occasional need for non-circular apertures. It is envisaged that the present invention can also address these types of applications, and others, which may 20 require non-circular apertures.

It is interesting to note that as the average number of recessed light-fittings and ventilation vents have increased in buildings, hole cutting saws for attachment to battery and power drills have become quite prevalent. Available in a wide range of diameters, their use has almost completely replaced the former hand cutting of circular apertures 25 for lights and ventilation holes - except for very large diameters. This has significantly improved not only the accuracy of circular aperture cutting (and problems with faceplates not covering irregularly shaped or sized holes), but the speed with which the tradesperson can complete their work - mark the centre, then drill. It highlights that it is easier for trades people to accurately mark the centre of an aperture than its outline -30 hence having a cutting tool, which merely required a single mark at the centre of the aperture to be formed, would aid both speed and accuracy. It is envisaged that these 3 benefits would apply for the cutting of a wide range of apertures, including flush-box and rectangular apertures, if only there was a viable product available.

Accordingly there is a need for a powered tool, or accessory attachable to a powered tool, which would enable the rapid and accurate cutting of rectangular, polygonal, or 5 non-circular apertures.

The prior art has not, to the knowledge of the inventor, provided any viable solutions to the problems of forming rectangular apertures. As previously mentioned, the common method of cutting rectangular apertures is by use of a hand saw or cutting device. A powered alternative is known which comprises a template which is held against the wall to help guide a high-speed cutting bit on a drill which the user moves around the template. However, this can raise quite a bit of dust, and has the potential to damage the flush box or wiring if depth control for the cutting bit is not provided when cutting a wallboard already in place.

Another solution has been to use what can be likened to two rectangular cookie cutters, one placed either side of the wallboard, and which are then clamped together to cut an aperture. Unfortunately this technique may not lend itself to some types of wallboards (e.g. non-plaster wallboards, or newer fibre reinforced plaster wallboards), and can only be performed on wall-boards not yet affixed to the wall - a serious limitation.

It is therefore one object of the present invention to address these issues.

It is a further object of the present invention to provide a means for the fast and accurate cutting of rectangular or polygonal apertures.

At the very least it is an object of the present invention to provide the public with a useful alternative choice.

Aspects of the present invention will be described by way of example only and with reference to the ensuing description.

GENERAL DESCRIPTION OF THE INVENTION According to one aspect of the present invention there is provided a cutting device for cutting through a work substrate, said cutting device comprising a plurality of cutting 4 plates, a said cutting plate comprising at least one linear saw blade with a cutting edge for cutting through said work substrate; the cutting plates arranged to at least partially overlie each other and oriented such that their linear saw blades are directed forwardly to be presented against an intended work 5 substrate; there being sufficient cutting plates arranged such that their associated saw blades substantially define the outline of the aperture that the cutting device is intended to cut in said work substrate; a plurality of said cutting plates capable of a reciprocating linear movement such that 10 their associated cutting edges perform a cutting action on a said work substrate; the reciprocating action of said reciprocating cutting plates being effected by an eccentric cam arrangement associated with a rotating drive shaft.

According to another aspect of the present invention there is provided a cutting device, substantially as described above, in which a said cutting plate comprises a support plate 15 from which extends a said linear saw blade.

According to another aspect of the present invention there is provided a cutting device, substantially as described above, in which said support plate is integrally formed with a said linear saw blade.

According to another aspect of the present invention there is provided a cutting device, 20 substantially as described above, in which a said linear saw blade is manufactured separately to said support plate, and subsequently affixed thereto.

According to another aspect of the present invention there is provided a cutting device, substantially as described above, in which said support plate is of a plastics material.

According to another aspect of the present invention there is provided a cutting device, 25 substantially as described above, in which a plurality of support plates overlie each other substantially coextensively and are able to move relative to each other.

According to another aspect of the present invention there is provided a cutting device, substantially as described above, in which a said linear saw blade is made of a metal.

According to another aspect of the present invention there is provided a cutting device, substantially as described above, in which a cutting edge comprises one or more of: an abrasive edge, a serrated edge, a toothed edge, a sharpened knife edge, an edge comprising diamond material, an edge comprising a tungsten carbide material, an edge 5 comprising an aluminium oxide material, an edge comprising a material whose Mohs hardness is greater than crystalline aluminium oxide.

According to another aspect of the present invention there is provided a cutting device, substantially as described above, in which, a cutting plate comprises two distanced and parallel linear saw blades.

According to another aspect of the present invention there is provided a cutting device, substantially as described above, in which for a side of the aperture intended to be created in said work substrate, there are two linear saw blades in close proximity associated therewith, and each associated with different cutting plates.

According to another aspect of the present invention there is provided a cutting device, 15 substantially as described above, in which the two associated linear saw blades are configured such that their linear reciprocating movements are such that their cutting . edges are travelling in opposing directions for at least part of the time during a cutting action.

According to another aspect of the present invention there is provided a cutting device, 20 substantially as described above, in which said rotating drive shaft passes through said cutting plates.

According to another aspect of the present invention there is provided a cutting device, substantially as described above, in which there is associated with the rotating drive shaft one or more cam portions which interact with the cutting plates to effect a linear 25 reciprocating movement.

According to another aspect of the present invention there is provided a cutting device, substantially as described above, in which a said cam interacts with an aperture on said cutting plate to effect a linear reciprocating movement. 6 According to another aspect of the present invention there is provided a cutting device, substantially as described above, in which a forward end of the rotating drive shaft, being the end closest to the work substrate when the cutting device is in operation, is capable of drilling into the work substrate.

According to another aspect of the present invention there is provided a cutting device, substantially as described above, in which the forward end of the rotational drive shaft allows for a drill bit to be removably attached.

According to another aspect of the present invention there is provided a cutting device, substantially as described above, in which the rear end of the rotating drive shaft, being 10 the end farthest from the work substrate when the cutting device is in operation, is either attached to a motor or attachable to a device with a motor can capable of rotationally driving the rotating drive shaft.

According to another aspect of the present invention there is provided a cutting device, substantially as described above, in which a said device with a motor comprises a power 15 drill, angle grinder, drill press, or a power wrench/driver tool.

According to another aspect of the present invention there is provided a cutting device, substantially as described above, which includes a fan assembly capable of either of forcing air onto, or drawings air away from, the work substrate in the vicinity of the aperture being formed during use of the cutting device.

According to another aspect of the present invention there is provided a cutting device, substantially as described above, in which the fan assembly comprises a fan blade assembly attached to the rotating drive shaft.

According to another aspect of the present invention there is provided a cutting device, substantially as described above, which includes a handle for a user to steady the cutting 25 device.

According to another aspect of the present invention there is provided a cutting device, substantially as described above, adapted for cutting through work substrates comprising plaster based wall and ceiling products. 7 According to another aspect of the present invention there is provided a cutting device, substantially as described above, adapted for cutting through work substrates comprising composite wood boards.

According to another aspect of the present invention there is provided a cutting device, 5 substantially as described above, adapted for cutting rectangular apertures.

According to another aspect of the present invention there is provided a cutting device, substantially as described above, characterised comprising at least one pair of cutting plates; each cutting plate comprising a support plate with a pair of distanced, parallel linear saw 10 blades extending substantially perpendicularly to the general plane of the support plate; one cutting plate of the pair dimensioned to nest inside the other, such that their support plates are substantially adjacent and parallel to each other, and either i) such that their linear saw blades are arranged in substantially coextensive pairs, each pair comprising one saw blade from each cutting plate of the pair, or 15 ii) such that the planes of the linear saw blades are arranged into pairs, each pair comprising one saw blade from each cutting plate of the pair, and when the planes of each saw blade of the pair are substantially parallel and adjacent each other; each support plate of the pair of cutting plates including an eccentric aperture which 20 interacts with a cam, the shape of the eccentric aperture being such to drive a said cutting plate in a linear reciprocating motion, and wherein the apertures of each cutting plate differ so as to provide a parallel linear reciprocating motion but a substantially different direction to its partner.

According to another aspect of the present invention there is provided a cutting device, 25 substantially as described above, when used to create apertures in a work substrate.

According to another aspect of the present invention there is provided a cutting device having at least one cutting plate, each cutting plate comprising a support plate which a substantially linear saw blade rising therefrom; optionally one cutting plate having a pair of distanced parallel linear saw blades rising 30 therefrom; 8 there being at least one cutting plate for each side or pair of parallel sides of an aperture to be formed; within the support plate of each cutting plate there being positioned an aperture which interacts with a cam such that, upon rotation of the cam each cutting plate is driven in a 5 linear reciprocating motion parallel to the linear axis of an attached linear saw blade.

According to one aspect of the present invention there is provided a cutting device having at least one pair of cutting plates, each cutting plate comprising a support plate which a substantially linear saw blade rising therefrom; each cutting plate of a said pair arranged such that the linear saw blades are 10 substantially coextensive with each other, and their support plates substantially parallel to each other; there being positioned, within the support plate of each cutting plate of the pair, an aperture which interacts with a cam such that, upon rotation of the cam each cutting plate is driven in a linear reciprocating motion parallel to the linear axis of an attached 15 linear saw blade.

According to another aspect of the present invention there is provided a cutting device, substantially as described above, in which said aperture is eccentric in nature.

According to another aspect of the present invention there is provided a cutting device, substantially as described above, in which said aperture is offset.

According to another aspect of the present invention there is provided a cutting device, substantially as described above, in which each cutting plate possesses two linear saw blades, each being substantially parallel to, and distanced from, each other.

According to another aspect of the present invention there is provided a cutting device, substantially as described above, in which there are two pairs of cutting plates, each pair 25 being arranged such that the linear axes of the linear saw blades of a pair are substantially perpendicular to those of the other.

According to another aspect of the present invention there is provided a cutting device, substantially as described above, in which there are three or more pairs of cutting plates, each pair being arranged such that their linear saw blades cuts a side of the aperture. 9 According to another aspect of the present invention there is provided a cutting device, substantially as described above, in which the cam is present on a rotatable shaft which is attachable to means for powering its rotation.

According to another aspect of the present invention there is provided a cutting device, 5 substantially as described above, in which the means for powering rotation of the shaft comprises at least one of: a battery powered drill, a mains powered drill, an electric motor.

According to another aspect of the present invention there is provided a cutting device, substantially as described above, in which a said electric motor is mounted on the body 10 of the cutting device.

According to another aspect of the present invention there is provided a cutting device, substantially as described above, in which one end of the rotatable shaft is tapered.

According to another aspect of the present invention there is provided a cutting device, substantially as described above, in which one end of the rotatable shaft includes a 15 drilling bit, or provision for the attachment of same.

According to another aspect of the present invention there is provided a cutting device, substantially as described above, in which the rotatable shaft is mounted within guide bearings.

According to another aspect of the present invention there is provided a cutting device, 20 substantially as described above, in which there is provided a handle.

According to another aspect of the present invention there is provided a cutting device, substantially as described above, in which the body is formed substantially of a plastics material.

According to another aspect of the present invention there is provided a cutting device, 25 substantially as described above, in which at least the support plate of a cutting plate is formed of a plastics material.

According to another aspect of the present invention there is provided a cutting device, substantially as described above, in which the teeth of a linear saw blade comprise at least one of: tungsten carbide teeth, a tungsten carbide abrasive face, a diamond abrasive face, boron nitride teeth, ceramic teeth.

According to another aspect of the present invention there is provided a cutting device, substantially as described above, in which there is present one or more pairs of cutting plates, where each cutting plate of the pair has only a single linear cutting blade, and there is also present one or more pairs of cutting plates where each cutting plate of the pair has a pair of linear cutting blades.

According to another aspect of the present invention there is provided a cutting device, substantially as described above, in which all the pairs of cutting plates are such that each cutting plate of a pair has only a single linear cutting blade.

According to another aspect of the present invention there is provided a cutting device, substantially as described above, in which all the pairs of cutting plates are such that 15 each cutting plate of a pair has only a pair of linear cutting blades.

According to another aspect of the present invention there is provided a cutting device, substantially as described above, in which the cutting plates are configured to cut a rectangle.

According to another aspect of the present invention there is provided a cutting device, 20 substantially as described above, in which the cutting plates are dimensioned to cut an aperture whose size is commensurate for a flush box or faceplate fitting.

According to another aspect of the present invention there is provided a cutting device, substantially as described above, in which the cutting plates are configured to cut a rhombus.

According to another aspect of the present invention there is provided a cutting device, substantially as described above, in which the cutting plates are configured to cut a regular polygon. 11 According to another aspect of the present invention there is provided a cutting device, substantially as described above, in which the cutting plates are configured to cut a non-regular polygon.

According to a further aspect of the present invention there is provided a cutting device 5 comprising at least one pair of cutting plates; each cutting plate comprising a support plate with a pair of distanced, parallel linear saw blades extending substantially perpendicularly to the general plane of the support plate; one cutting plate of the pair dimensioned to nest inside the other, such that their support plates are substantially adjacent and parallel to each other, and either 10 i) such that their linear saw blades are arranged in substantially coextensive pairs, each pair comprising one saw blade from each cutting plate of the pair, or ii) such that the planes of the linear saw blades are arranged into pairs, each pair comprising one saw blade from each cutting plate of the pair, and when the planes of each saw blade of the pair are substantially parallel and adjacent each other; each support plate of the pair of cutting plates including an eccentric aperture which interacts with a cam, the shape of the eccentric aperture being such to drive a said cutting plate in a linear reciprocating motion, and wherein the apertures of each cutting plate differ so as to provide a parallel linear reciprocating motion but a substantially different direction to its partner.

According to a further aspect of the present invention there is provided a cutting plate, suitable for use in a cutting device such as described above, comprising a support plate containing an aperture interacting with a cam, and at least one linear saw blade rising substantially perpendicularly therefrom.

According to another aspect of the present invention there is provided a cutting device, 25 substantially as described above, in which the aperture is eccentric in nature.

The present invention may be seen to focus on particular arrangements of cutting plates, which are responsible for the cutting of the sides of the aperture to be formed. Ancillary to this is the rotatable drive shaft, and a body upon which the components may be mounted; these being described in more detail later. 12 A cutting plate according to the present invention may take a number of forms. In its simplest form it comprises a support plate, which is preferably planar and relatively thin. It may be rectangular in shape, though may adopt other shapes in order to save weight and materials.

It may be formed of metal, though a variety of plastics and other materials are readily available which possess preferred qualities of rigidity and strength. Plastics fabrication methods may offer advantages over metal fabrication techniques, depending on manufacturing considerations. A preferred embodiment uses a plastics support plate, which has some thickness (compared to a metal equivalent) for rigidity, and removed 10 portions to reduce weight plus the amount of materials used.

The support plate, in effect, supports at least one cutting blade. A cutting blade is generally a linear blade as it cuts in a linear fashion. As it typically undergoes a linear reciprocating sawing effect, it is referred herein as the linear saw blade.

The linear saw blade generally rises from the support plate at a substantially 15 perpendicular angle, though other angles may be used in specialised embodiments of the invention. It generally has a length such that the length, combined withjits distance of travel, equates to the length of the aperture side that it is intended to cut.

The linear saw blade may be formed of metal, typically with a cutting edge comprising hardened or toughened teeth. However, the blade may be formed of other materials, including plastics, if the option of tips or coatings are to be applied to the teeth, or an abrasive cutting edge is used. Such tips and coatings may be materials used for cutting hard materials, or specialist materials. Some examples include, but are not restricted to: tungsten carbide teeth, a tungsten carbide abrasive coating, a diamond abrasive coating, boron nitride teeth, ceramic teeth. Blades of composite materials may also be considered. Abrasive cutting edges may also be used, as are commonly used on saw blades for cutting hard materials. Again, examples include: an edge comprising a diamond material, an edge comprising a tungsten carbide material, an edge comprising an aluminium oxide material, an edge comprising a material whose Mohs hardness is greater than crystalline aluminium oxide. 13 The linear saw blade may be integrally formed with the support plate, though this is a matter of manufacturing preference and design. The linear saw blade is typically positioned near an edge of the support plate, though can vary in different possible embodiments.

In preferred embodiments for cutting rectangular apertures for electrical faceplates, each cutting plate has two linear saw blades. These are preferably parallel to each other, though distanced apart. As each saw blade will act on an opposite edge of the aperture to be formed, the distance of separation of the linear saw blades will be commensurate to the appropriate dimensions of the aperture.

While simple embodiments of the present invention may have only one saw blade cutting each side of the aperture to be formed, preferred embodiments utilise a pair of adjacent and parallel saw blades for each side of the aperture. Preferentially these will move, during operation, in substantially opposite directions. The use of blade pairs has the potential to accelerate the cutting process. Different cutting edges may be provided 15 on different members of the adjacent blade pairs.

The cutting plates, whether they be single plates or pairs (for dual cutting action on each side of the aperture to be formed), are generally disposed to be oriented according to the shape of the aperture. For rectangular apertures this typically means orienting the cutting plates such that there are linear saw blades arranged in substantially 20 perpendicular directions - defining the approximate shape of the rectangular aperture to be formed. For a hexagon, for instance, there may be three (or six) cutting blade sets. For a triangle there is typically three. Variations exist according to whether there is a dual cutting action (from a pair of blades) along each side of the aperture to be formed, and whether each cutting plate has one or two associated linear saw blades. For 25 triangular apertures, each cutting plate can have only one linear saw blade. As can be appreciated, there is potential for being able to cut a range of specialised polygonal shapes, both regular and irregular, according to need and preference.

In the majority of examples the support plate portions of the cutting plates are substantially one on top of the other - i.e. they appear coextensive when viewed along 30 the axis of the rotating drive shaft. This is mainly to reduce the vertical profile of the .14 device. Each support plate portion has an aperture through which a drive shaft passes. There is at least one cam present on this rotatable shaft where it interacts with cutting plates. While there may be multiple cams which act on different cutting plates, or groups of cutting plates, one preferred embodiment has only one cam portion for 5 simplicity. This cam may be formed directly on the shaft, or present on an element attached to the shaft.

A cam may comprise a bearing, to reduce wear and friction. In one preferred embodiment a cam is created by using a bearing through which the rotating drive shaft passes, but where the aperture in the bearing through which the shaft passes (and is 10 fixed to the centre of the bearing) is off-centre.

Collars or features on the shaft help maintain the plates vertically (i.e. in the direction of the longitudinal axis of the shaft) in position. Eccentric apertures in the support plates, through which the shaft passes, interact with the cam in the preferred embodiment to result in a linear reciprocating motion for the cutting plates. Their motion will be in 15 some form of synchronisation, with the shape of the cam an aperture determining aspects such as distance of travel and timing. These may be optimised for different embodiments of the present invention, and may take into account factors such as: rate of cutting, optimal speed of blade travel, the material or range of materials to be cut, the nature of the blade teeth, and the speed of the device or motor driving the shaft, etc. It 20 is envisaged that some experimentation may be required to optimise a specific embodiment, though it is considered that this will be well within the ability of the average skilled worker given the description herein.

The bottom end of the shaft, being the end at the cutting edge of the saw blades, may extend past the teeth of the saw blades. In this respect the shaft can act as a locating or 25 positioning guide for the device. To facilitate this the bottom end of the shaft may be modified to be tapered to a point, be of slim diameter, comprise a drilling bit, or have provision for the connection of a drilling bit. The drill bit may be replaceable to allow for different materials which may be encountered, and for wear.

The top end of the shaft is typically maintained in position by bearings, and other 30 features restricting longitudinal movement of the various elements. The top end, in an accessory embodiment, is typically exposed and allows for the attachment of a battery or mains powered drill. Other devices may be attachable for specialised embodiments, though battery drills are one of the most common power tools used on modern construction sites.

In alternative embodiments an integral motor may be provided. This may be either 5 battery or mains powered. In specialised embodiments the device may be provided on, or attachable to, a drill press. This would be especially useful for cutting non-circular apertures in sheet metals, etc.

The body in non-powered (accessory) embodiments may be formed of a variety of materials. This may be metal, though again many suitable plastics materials exist. A 10 handle is typically provided to steady the device. Soft feet, which may be partially retractable, may be provided to avoid damage to the wall or surface surrounding the aperture.

Possible modifications envisaged include the inclusion of a gearbox to reduce or alter rotational speed of the shaft (driving the reciprocating movement of the cutting plates) 15 relative to powering device. One or more ratios may be able to be selected.

The cutting plates may be readily detachable for replacement. This allows the user to replace teeth to compensate for wear, or to substitute cutting plates with different blade or teeth types.

As can be appreciated there are many variations to the present invention, and ways by 20 which it may be implemented. A specific embodiment will be described, by way of example, next.

DESCRIPTION OF DRAWINGS Figure 1 is a perspective diagrammatic exploded view of one preferred embodiment of a rectangular cutting device according to the present invention, and Figure 2 is a perspective diagrammatic exploded view of another preferred embodiment of a rectangular cutting device according to the present invention. 16 DESCRIPTION OF PREFERRED EMBODIMENT With reference to the drawings, and by way of example only, there is provided a rectangular cutting device, shown in exploded view in figure 1.

In this embodiment there is a first pair of cutting plates (la,b) and a second pair of 5 cutting plates (2a,b). Each cutting plate (1,2) has a central planar support plate (3) - for simplicity this is identified only on cutting plate (2b) - with an oval aperture (4) positioned therein. The width of the oval (4) at its narrowest point is comparable to the effective width of the cam (6) and is elongated perpendicularly to the longitudinal axis of the saw blades (7a,b) associated with the support plate (3).

The saw blades (7a,b) extend substantially perpendicularly from the support plate (3) -this is the same for all the cutting plates (1,2). In this example the cutting plates (1,2) are formed from metal in their entirety, with the teeth of the saw blades (7a,b) being of toughened steel. However, the cutting plates may be formed at least partly of plastics materials, with the teeth of the saw blades (7a,b) being tipped or coated with suitable 15 cutting materials, or the saw blades (7a,b). The inside of the aperture (4) may be lined with a different material to reduce wear.

The apertures (4) of each pair (la,b; 2a,b) are also offset to produce an alternating reciprocal movement - i.e. one cutting plate of a pair moves in one direction, while the other moves in the opposite direction. The fit between pairs of cutting plates may also 20 be sloppy, as the dust resulting from a cutting operation can clog and bind arrangements where tolerances are too tight.

The shaft (10) passes through the apertures (4) and is secured in the body (11) by an arrangement of collars and bearings (generally indicated by numeral 12). A lower flange (14) maintains the cutting plates (1, 2) in place, and also acts as a cam in 25 conjunction with upwardly directed boss (15). This boss (15) may be a bearing. A comparable flange (16) with boss is also provided above the cutting plates (1,2).

A handle (17) is provided for holding the device. The lower tip (18) of the shaft (10) is tapered to act as a locating guide for the device. 17 In practice a battery drill (not shown) is attached to the upper protruding end of the shaft (10). The tip (18) of the shaft (10) is located against the centre of the aperture and, in the case of plasterboard, the apparatus pushed against the wall (or surface) until the shaft's tip (18) penetrates and the cutting plates (1, 2) engage. Powering the drill rotates 5 the shaft (10), driving the cutting plates (1, 2) in a linear reciprocating action, and effecting cutting of the wall or surface. Where the surface is of a harder material than soft plasterboards, a drill bit may be provided at the tip (18) of the shaft (10).

Figure 2 illustrates an alternative embodiment of the present invention, and which utilises plastics materials for some components. As for the other illustrated 10 embodiment, there is provided a rotating drive shaft (100) able to be connected to a motor or power drill (not shown). Most of the remaining components are fixed or maintained in position relative to the shaft (100).

A plurality of cutting plates are provided, arranged into pairs (101a, 101b) (102a, 102b). Each member of a pair travels in a substantially opposite linear reciprocating motion to 15 its partner as the drive shaft (100) rotates - as per the previously described embodiment.

Each cutting plate (101 - 102) comprises a support plate (103) of a plastics material, dimensioned and fashioned to be stiff with respect to deformation out of the plane of the plate. An elongated circular central aperture (104) is provided which interacts with cam assemblies on the shaft (100) to impart a linear reciprocating movement to the cutting 20 plate (101 - 102) as the shaft (100) rotates. On opposing edges of the support plate (103) are parallel linear saw blades (110a, 110b), each with a cutting edge (111) comprising teeth. Screws (114) or other fastening means attach the linear saw blades (110) to the support plate (103). The arrangement is such that each nested cutting plate (101 - 102) can undergo a reciprocating linear motion without interfering with the 25 others.

The cams interacting with the plate apertures (104) comprise bearing assemblies (120, 121). Each assembly comprises two bearings (125a, 125b) fixed to a central connector (126). The central connector (126) has a central off-centre aperture through which the shaft (100) passes, and to which it is fixed. As a consequence, as the connector (126) is 30 mounted off-centre relative to the shaft (100), so too are the associated bearings (125). 18 The result is a cam able to interact with the apertures (104) of the plates (101 -102). Figure 2 shows the relative off-centre positions which are achieved by each cam assembly (120, 121). The interaction of the cam assemblies (120, 121) are substantially as for the previously described embodiment of figure 1.

Also provided are end collars (130, 131) to maintain components on the shaft (100). A body (135) is provided to help retain (and constrain the direction of movement) of the cutting plates (101 - 102). A handle (136) is also provided. Operation and use are as for the embodiment of figure 1.

Aspects of the present invention have been described by way of example only and it 10 should be appreciated that modifications and additions may be made thereto without departing from the spirit or scope of the present invention as defined in the appended claims.

It should also be understood that the term "comprise" where used herein is not to be considered to be used in a limiting sense. Accordingly, 'comprise' does not represent 15 nor define an exclusive set of items, but includes the possibility of other components and items being added to the list.

This specification is also based on the understanding of the inventor regarding the prior art. The prior art description should not be regarded as being authoritative disclosure on the true state of the prior art but rather as referencing considerations brought to the mind 20 and attention of the inventor when developing this invention.

Claims (26)

RECEIVED at IPONZ on 14 June 2011 -19 - THE CLAIMS DEFINING THE INVENTION ARE:

1. A cutting device for cutting through a work substrate, said cutting device comprising a plurality of cutting plates, a said cutting plate comprising at least one linear saw blade with a cutting edge for cutting through said work substrate; the cutting plates arranged to at least partially overlie each other and oriented such that their linear saw blades are directed forwardly to be presented against an intended work substrate; there being sufficient cutting plates arranged such that their associated saw blades substantially define the outline of the aperture that the cutting device is intended to cut in said work substrate; the aforesaid plurality of said cutting plates capable of a reciprocating linear movement such that their associated cutting edges perform a cutting action on a said work substrate; the reciprocating action of said reciprocating cutting plates being effected by an eccentric cam arrangement associated with a rotating drive shaft; the cutting device further characterised such that for a side of the aperture intended to be created in said work substrate, there are two linear saw blades in close proximity associated therewith, and each associated with different cutting plates.

2. A cutting device as claimed in claim 1 in which the two associated linear saw blades are configured such that their linear reciprocating movements are such that their cutting edges are travelling in opposing directions for at least part of the time during a cutting action.

3. A cutting device as claimed in either claim 1 or claim 2 in which a said cutting plate comprises a support plate from which extends a said linear saw blade.

4. A cutting device as claimed in claim 3 in which said support plate is integrally formed with a said linear saw blade.

5. A cutting device as claimed in claim 3 in which a said linear saw blade is manufactured separately to said support plate, and subsequently affixed thereto. RECEIVED at IPONZ on 14 June 2011 -20-

6. A cutting device as claimed in either claim 3 or claim 5 in which said support plate is of a plastics material.

7. A cutting device as claimed in any one of claims 2 through 5 in which a plurality of support plates overlie each other substantially coextensively and are able to move relative to each other.

8. A cutting device as claimed in any one of the preceding claims in which a said linear saw blade is made of a metal.

9. A cutting device as claimed in any one of the preceding claims in which a cutting edge comprises one or more of: an abrasive edge, a serrated edge, a toothed edge, a sharpened knife edge, an edge comprising diamond material, an edge comprising a tungsten carbide material, an edge comprising an aluminium oxide material, an edge comprising a material whose Mohs hardness is greater than crystalline aluminium oxide.

10. A cutting device as claimed in any one of the preceding claims in which, a cutting plate comprises two distanced and parallel linear saw blades.

11. A cutting device as claimed in any one of the preceding claims in which said rotating drive shaft passes through said cutting plates.

12. A cutting device as claimed in claim 11 in which there is associated with the rotating drive shaft one or more cam portions which interact with the cutting plates to effect a linear reciprocating movement.

13. A cutting device as claimed in claim 12 in which a said cam interacts with an aperture on said cutting plate to effect a linear reciprocating movement.

14. A cutting device as claimed in any one of the preceding claims in which a forward end of the rotating drive shaft, being the end closest to the work substrate when the cutting device is in operation, is capable of drilling into the work substrate.

15. A cutting device as claimed in claim 14 in which the forward end of the rotational drive shaft allows for a drill bit to be removably attached. RECEIVED at IPONZ on 14 June 2011 -21 -

16. A cutting device as claimed in any one of the preceding claims in which the rear end of the rotating drive shaft, being the end farthest from the work substrate when the cutting device is in operation, is either attached to a motor or attachable to a device with a motor can capable of rotationally driving the rotating drive shaft.

17. A cutting device as claimed in claim 16 in which a said device with a motor comprises a power drill, angle grinder, drill press, or a power wrench/driver tool.

18. A cutting device as claimed in any one of the preceding claims which includes a fan assembly capable of either of forcing air onto, or drawings air away from, the work substrate in the vicinity of the aperture being formed during use of the cutting device.

19. A cutting device as claimed is claimed in claim 18 in which the fan assembly comprises a fan blade assembly attached to the rotating drive shaft.

20. A cutting device as claimed in any one of the preceding claims which includes a handle for a user to steady the cutting device.

21. A cutting device as claimed in any one of the preceding claims adapted for cutting through work substrates comprising plaster based wall and ceiling products.

22. A cutting device as claimed in any one of the preceding claims adapted for cutting through work substrates comprising composite wood boards.

23. A cutting device as claimed in any one of the preceding claims adapted for cutting rectangular apertures.

24. A cutting device according to claim 1 and characterised comprising at least one pair of cutting plates; each cutting plate comprising a support plate with a pair of distanced, parallel linear saw blades extending substantially perpendicularly to the general plane of the support plate; RECEIVED at IPONZ on 14 June 2011 -22 - one cutting plate of the pair dimensioned to nest inside the other, such that their support plates are substantially adjacent and parallel to each other, and either i) such that their linear saw blades are arranged in substantially coextensive pairs, each pair comprising one saw blade from each cutting plate of the pair, or ii) such that the planes of the linear saw blades are arranged into pairs, each pair comprising one saw blade from each cutting plate of the pair, and when the planes of each saw blade of the pair are substantially parallel and adjacent each other; each support plate of the pair of cutting plates including an eccentric aperture which interacts with a cam, the shape of the eccentric aperture being such to drive a said cutting plate in a linear reciprocating motion, and wherein the apertures of each cutting plate differ so as to provide a parallel linear reciprocating motion but a substantially different direction to its partner.

25. A cutting device as claimed in any one of the preceding claims, when used to create apertures in a work substrate.

26. A cutting device, substantially as described herein with reference to the accompanying drawings.