NZ720247A - Improved cutting device - Google Patents

Abstract

device for cutting an aperture in a surface including a body adapted for attachment to a power tool, a cutting head for attachment to said body, said cutting head having blade means for cutting said aperture, wherein the cutting head has motion imparted thereto based on eccentric rotary movement.

Description

IMPROVED HOLE CUTTING DEVICE Field of the Invention This invention relates to a hole cutting device, and more particularly to a device that cuts differently shaped holes in a surface and is able to be attached to a power tool.

Background of the Invention Traditionally in order to cut a rectangular hole in a surface, such as plaster-board, to enable an electrical socket plate to abut against the plaster wall and connect wires at the back thereof, skilled tradespeople have used a blade with serrated teeth and roughly cut out the required shape manually. This can be an extremely tedious job to do numerous times for one ng where there are many electrical socket outlets. It also takes a long time to cut out each socket hole and therefore delays or prevents the people from undertaking other jobs.

The present invention seeks to overcome the above disadvantages by providing a device that can cut holes in a e, ularly plaster walls, that saves time and turns a relatively tedious task into a simple and more efficient task.

Summary_of the Invention ing to a first aspect of the invention there is provided a device for cutting an aperture in a surface including: a body d for attachment to a power tool; a cutting head for attachment to said body, said cutting head having blade means for cutting said aperture; wherein the g head has motion imparted thereto based on ric rotary movement.

The device may further include means for providing said eccentric rotary movement, said means having a bush with at least one eccentric aperture such that rotation of the bush through the power tool provides motion to the cutting head that enables the blade means of the cutting head to cut the surface.

The device can further include gear means to provide an output onal speed of an output shaft that differs from the input rotational speed on an input shaft, said output shaft connected to the providing means and the input shaft connected to the power tool.

The means for providing said eccentric rotary movement can be a bush having said at least one eccentric aperture. The device may further include a mounting for mounting the head to the body, said mounting adapted to engage with said bush. The mounting can have a recess in which said bush is affixed to said mounting. The head is preferably gular and has four upstanding panels and a base or rear panel, said base panel connected to each of the upstanding panels such that an opening is defined by the head. Each of the four ding panels K‘”\r preferably has an outer serrated edge for g against the surface.

The head may further include one or more slots to enable removal of any loose particles from the surface being cut. The aperture is preferably used to fit an electrical socket plate to said surface.

Brief Description of the Drawings A red embodiment of the invention will hereinafter be described, by way of example only, with reference to the drawings in which: Figure 1 is a perspective View from above and the rear of a device used to cut an re in a surface; Figure 2 is a perspective View from above and the front of the device of Figure l ; Figure 3 is a front view of the device of Figure l ; Figure 4 is a side view of the device of Figure 1; .

Figure 5 is a front perspective View of a head or attachment to a part of the device of Figure 1; Figure 6 is a part sectional front view of the device of Figure l ; Figure 7 is a part nal side View g the internal ents of the device of Figure 1; Figure 8 is a part sectional perspective View of the device shown in Figure 7; Figure 9A is a front perspective View from above of a mounting for the head or ment of Figure 5; Figure 9B is a rear perspective view from above of the mounting of Figure 9A; Figure 10A is a front perspective View from above of a bush adapted to fit or connect to a recess in the mounting of s 9A and 9B; Figure 10B is a front sectional view of the bush of Figures 10A and 10B showing eccentric apertures protruding therethrough; and Figure 10C is a rear perspective view from above of the bush of Figure 10A.

Detailed Descrimion of the Preferred Embodiment Referring to Figures 1 and 2 there is shown a device 2 used to create an aperture in a surface, such as a wall, and in particular a plaster wall by cutting through the plaster which conforms to the shape of the g head 4. It is particularly, but not exclusively, suited to cutting apertures to enable a switch panel/plate to fit against the plaster wall. The cutting head 4 is attached to body 6 which has an input shaft 8 protruding from a first end 10. The shaft 8 is able to be fitted to a standard chuck of a drill or similar rotational power device. Second end 12 is opposite first end 10 and is where the head 4 is attaChed to the body 6.

Referring also to Figures 3 and 4, the head 4 is rectangularly—shaped and can be any other suitable shape depending on the purpose that the device 2 is used. The sides and ends of the rectangular head 4 are generally plate-like with two opposed long side plates 14 and 16 While the two end plates 18 and 20 are shorter and opposed to one another. Each of the outer edges of the plates 14, 16, 18 and 20 has blade means in the form of a serrated cutting blade. This is depicted respectively at edges 22, 24, 26 and 28. A pair of tion points 30 and 32 enable the head 4 to be secured or connected to second end 12 of body 6 and more particularly to a mounting (block or bracket) 33 shown in Figure 8. Generally screws are used to mount the head 4 to the block 33. Recess 34 which can extend on one or both sides of the body, that is either on side 39 as is shown in Figure 4 or side 41 or both sides. The recess 34 has a lip 36 formed around the recess 34 and this provides a gripping surface for the user when using the device 2.

Referring to Figure 5 there is shown a more detailed diagram of head 4. As previously mentioned the outer edges 22, 24, 26 and 28 of the panels 14, 16, 18 and 20 have a serrated edge which cuts against the surface when agitated. Each of the panels 14, 16, 18 and 20 share a fold line with, and are formed substantially perpendicularly, to a rear side or panel 38 of the head 4.

The head 4 therefore defines an opening or open area to enable the teeth in the serrated edges in each of the panels to out against the surface. Any residual dust or powder can exit through apertures 46 and 48 located respectively in panels 18 and 20. A gap therefore exists between each adjacent panel 14, 16, 18 and 20. Apertures 40 and 42 are used for ng means to protrude therethrough in order to secure the head 4 to the body 6 or to the mounting 33 through the apertures 41 and 43 on mounting 33 (see Figure 9A). Larger aperture 44 enables a guide pin ”M: 50 to protrude hrough. The guide pin 50 is used to locate the head 4 against the surface to be cut and provides a point of reference for the user of the device 2.

Referring to Figure 6 there is shown a sectional front View of the device 2. Bush 64 has a pair of eccentric apertures 67, 68 co-aligned h their centres, that is the apertures 67, 68 are offset from the origin 47 of bush 64 (as seen in Figure 10b). Alternatively, one eccentric aperture can be used such that it extends through the bush 64. Referring also to Figures 7 to 10C, bush 64 fits to the interior wall 63 of recess 66 of mounting 33. The rear side 75 of the bush 64 may abut against the side 73 of a further bush 71 in ng 33 to fit snuggle in recess 66. Thus side 73 represents a circular step n the interior surface of recess 66 and the aperture 78 through bush 71. Bush 64 has a further internal bush 77 having re 68, so that side 79 of bush 77 represents a step between aperture 68 and aperture 67 or recess 81 of bush 64 and bush 77. The pin 50 extends through the aperture 67, 68 of bush 64 and through the open recess 66 and aperture 78 of bush 71. s 7 and 8 show a gearing or converter mechanism, enclosed within body 6, which provides rotational speeds of output shaft 62 at about 14 times the speed of input shaft 8. Input shaft 8 drives first gear 52 which is in contact with and meshes with a smaller gear 54 ted to intermediate shaft 58. This in turn drives gear 56 in the same direction and same speed as gear 54. Gear 56 meshes with and is engaged with a further gear 60 which is connected to the output shaft 62 and the output shaft 62 is connected to guide pin 50. The rotational gear 60 is in the same onal direction as gear 52 and input shaft 8. In this embodiment, each of gears 52 and 56 have 46 teeth while each of gears 54 and 60 have 12 teeth. Thus, due to the gear teeth ‘ 5 ratio of gears 52 and 54, shaft 58 generally rotates at a speed of 3.83 times faster than the input shaft 8. Gear 56 rotates at the same speed as shaft 58. Due to the gear teeth ratio of gears 56 and 60 being 3.83 to 1.0, output shaft 62 generally rotates at about 14.70 times faster than the input shaft 8.

The effect of the eccentric res 68, 67 of bush 64, which fits within recess 66 of block 33, is that the rotational shaft 62 imparts a movement in the head 4. Bush 64 is ly connected to the recess 66 of the mounting 33 and shaft 62 is firmly connected to bush 64.

Rotation therefore of the eccentric apertures 68, 67 results in rotational nt of the head 4.

Generally the maximum nt of the serrated edges 22, 24, 26 and 28 of the head 4 is plus or minus 1 mm. Other tolerances or offsets of movement of the edges 22, 24, 26 and 28 of head 4 include up to +/- 2mm, but preferably at +/— 1mm, +/- 0.75mm and +/- 0.5mm. In a first half turn of the shaft 62, edges 22 and 24 will move in one direction by up to a millimetre while edges 26 and 28 will also move in a direction perpendicular to edges 22 and 24. In the second half revolution of shaft 62 the parallel edges 22 and 24 will move in the opposite direction to their movement in the first half turn, an extension of up to 1 millimetre from the mean, while the opposing edges 26 and 28 move in the opposite direction to their movement in the first half turn of the shaft 62, by up to a millimetre from the mean. The overall effect is a cutting action where edges 22 and 24 move rd and forward in a generally horizontal motion while edges 26 and 28 move generally upwards and downwards in their cutting action. The result is that eventually, with pressure applied to the body 6 and ore to the head 4, and with the centre or guiding pin 50 located on the e, a section of the plaster or the surface is cut out leaving a ntially rectangular hole, in accordance with the rectangular—shaped head 4. Pin 50 does not rotate but is sprung firmly and is able to be recessed into a central bore of output shaft 62, when such pressure is applied.

Figures 9A and 9B shows mounting 33 with recess 66 and an internal bush 71 with its own aperture 78. The bush 64 depicted in Figure 10a fits snugly in and is secured to the recess 66 of mounting 33. The bush 64 has an internal bush 77 with an eccentric aperture 68 and recess 81 of which aperture 67 is also eccentrically positioned. The eccentricity of apertures 67, 68 is also shown in Figure 10b. An aperture 37 in flange 35 is used to accommodate a fastener and 3O , the fastener being in the form of a shoulder bolt, to secure the mounting 33 to the body 6 in a recess at the front or second end 12 of the body 6. This keeps the ng 33 level and therefore the head 4 and corresponding blades 22, 24 are kept level. The head of the shoulder bolt compresses the spring against the back side of flange 35 (as seen in Figure 9A).

In use, a user affixes the head 4 (from a number of possible configurations/shapes) to the body 6 of the device 2. The body 6 may or may not already be attached to the rotational power device, such as a drill, h input shaft 8. The user marks out or determines where to make the cut in the plaster surface. Guide pin 50 can be used to stabilise or guide the head 4 While ng the head 4 with the surface and during the use of device 2. The user then activates the rotary device to which the device 2 is attached and the cutting action of head 4 commences with the respective blades moving in two alternating directions to cut through the plaster, based on the eccentric movement of bush 64 and the connected mounting 33.

Claims (10)

The claims defining the invention are as follows:

1. A device for cutting an aperture in a surface ing: a body adapted for attachment to a power tool; a cutting} head for attachment to said body, said cutting head having blade means for cutting said aperture; wherein the cutting head has motion imparted thereto based on eccentric rotary movement.

2. A device according to claim 1 r ing means for ing said eccentric rotary 10 movement, said means having a bush with at least one eccentric aperture such that rotation of the , bush through the power tool provides motion to the cutting head that enables the blade means of the cutting head to cut the e.

3. A device according to claim 2 further including gear means to provide an output 15 rotational speed of an output shaft that differs from the input rotational speed on an input shaft, said output shaft connected to the providing means and the input shaft connected to the power tool.

4. A device ing to claim 3 wherein the means for providing said eccentric rotary 20 movement is a bush having said at least one eccentric aperture.

5. A device according to claim 4 further including a mounting for mounting the head to the body, said mounting adapted to engage with said bush. 25

6. A device according to claim 5 wherein said mounting has a recess in which said bush is affixed to said mounting.

7. A device ing to any one of the previous claims wherein said head is rectangular and has four upstanding panels and a base or rear panel, said base panel connected to each of the upstanding panels such that an opening is defined by the head.

8. A device according to claim 7 wherein each of the four upstanding panels has an outer serrated edge for cutting against the surface.

9. A device according to claim 8 wherein the head r includes one or more slots to enable removal of any loose particles from the surface being cut. 10 ”A“

10. A device according to any one of the previous claims such that the aperture is used to fit an electrical socket plate to said surface.