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Title:
CIRCULAR SAWING DEVICE AND METHOD FOR ARRANGING RING SHAPED RECESS OR A HOLE HAVING A RABBETED EDGE IN A PIECE OF WORK, IN PARTICULAR IN PLASTERBOARD
Document Type and Number:
WIPO Patent Application WO/2017/146569
Kind Code:
A1
Abstract:
The present invention relates to a circular sawing device, in particular a circular sawing device for arranging a circular cut in a piece of work, in particular in plasterboard. The circular sawing device according to the invention comprises a pair of saw blades arranged in concentric spaced relationship for producing concentric cuts in a piece of work, and material removing members arranged between said blades for removing material of the piece of work between the cuts produced by said saw blades. The present invention further relates to a method for arranging ring shaped recess or a hole having a rabbeted edge in a piece of work, in particular in plasterboard. The method according to the invention comprises producing concentric cuts in a piece of work by means of a pair of saw blades arranged in concentric spaced relationship, and removing material of the work between the cuts produced by said blades by means of material removing members arranged between said blades.

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Inventors:
BOSKE RICHARD ALEXANDER (NL)
SINNAEVE FRANK (BE)
GUNST STEPHAN (BE)
Application Number:
PCT/NL2017/050105
Publication Date:
August 31, 2017
Filing Date:
February 22, 2017
Export Citation:
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Assignee:
BOORWERK B V (NL)
FRANK SINNAEVE INTERIEUR ARCH BVBA (BE)
STEPHAN GUNST COMM V (BE)
International Classes:
B23B51/04; B23B51/10
Domestic Patent References:
WO2007049012A12007-05-03
Foreign References:
US3672785A1972-06-27
JPH08187721A1996-07-23
FR1047779A1953-12-16
EP1002606A12000-05-24
Other References:
None
Attorney, Agent or Firm:
LOUWAARD, Jan-Willem Paul (NL)
Download PDF:
Claims:
Claims

1. Circular sawing device comprising:

- a pair of saw blades arranged in concentric spaced relationship for producing concentric cuts in a piece of work;

- material removing members arranged between said blades for removing material of the piece of work between the cuts produced by said saw blades.

2. Circular sawing device according to claim 1 , wherein at least the outer saw blade, preferably both the inner and the outer saw blade, has a saw edge with unset cutting teeth having a negative rake.

3. Circular sawing device according to claim 1 or 2, wherein the material removing members are embodied for removing material by scraping.

4. Circular sawing device according to claim 3, wherein the material removing members comprise pens having a pointed end for scraping, wherein preferably the tip of the pointed end is flattened. 5. Circular sawing device according to claim 4, wherein the pointed ends of the pens are moved along circular paths when the device is rotated about the central axis of the concentric blades, wherein a plurality of said circular paths have a different radius, and wherein said circular paths of different radius are distributed, preferably evenly distributed, over the radial distance between the pair of saw blades.

6. Circular sawing device according to claim 4 or 5, wherein adjacent pens are mutually offset in radial direction and circular direction relative to the central axis of the concentric saw blades. 7. Circular sawing device according to any of claims 1 to 6, wherein the device comprises a cleaning body that extends between said pair of saw blades and that is provided with apertures, preferably one for each material removing member, through which apertures the material removing members extend with the cleaning body in a first position, wherein said cleaning body is movable relative to the material moving members along the central axis of the pair of saw blades and along the material removing members towards a free end of said material removing members into a second position, wherein preferably in said second position the material removing members do not extend through said apertures.

8. Circular sawing device according to claim 7, wherein the apertures closely fit around the material removing members.

9. Circular sawing device according to claim 7 or 8, wherein the cleaning body comprises a ring shaped body that in said first position closely fits between the pair of saw blades in a concentric relationship with said saw blades.

10. Circular sawing device according to claim 9, wherein the device comprises a first rotary body on which the inner saw blade is arranged and a second rotary body on which the outer saw blade is arranged, wherein the first rotary body and the second rotary body are movable relative to each other along the central axis of the concentric inner saw blade and outer saw blade, wherein the material removing members are arranged on the second rotary body, and wherein the ring shaped body is arranged on or is an extension of the first rotary body.

11. Circular sawing device according to claim 9, wherein the device comprises a rotary body on which the pair of saw blades and the material removing members are arranged and from which the pair of saw blades and the material removing members extend in axial direction relative to the central axis of said pair of blades, and wherein the ring shaped body is movable relative to said rotary body between said first position and said second position, preferably by means of at least one ring shaped body moving member that extends through an aperture in said rotary body. 12. Circular sawing device according to claim 11, wherein the cleaning body further comprises a circular or second ring shaped body that extends within the inner saw blade in concentric relationship therewith and that is connected to said first ring shaped body through at least one opening in the inner saw blade that allows for moving the cleaning body relative to inner saw blade.

13. Circular sawing device according to claim 9, wherein the cleaning body is a first rotary body having arranged thereon the inner saw blade and the outer saw blade, and wherein the device comprises a second rotary body having arranged thereon the material removing members, wherein the first rotary body and the second rotary body are movable relative to each other along the central axis of the concentric inner saw blade and outer saw blade.

14. Circular sawing device according to any of claims 1 to 13, wherein the device further comprises a drill arbor, that is preferably configured at one end thereof to be arranged in a drill chuck, wherein the pair of saw blades are arranged concentric with the central longitudinal axis of said arbor.

15. Circular sawing device according to claim 14 and any of claims 7 to 13, wherein at least one of the cleaning body and the material removing members is arranged for sliding along the central longitudinal axis of the arbor in order to move the cleaning body and the material removing members relative to each other, wherein the device comprises a coupling arrangement for releasable coupling the at least one of the cleaning body and the material removing members to the arbor, wherein the coupling arrangement preferably provides at least one of axial and rotational locking of said at least one of the cleaning body and the material removing members relative to the arbor. 16. Circular sawing device according to any of claims 1 to 15,

further comprising:

- at least one stop configured for limiting the distance over which the pair of saw blades cut into the work.

17. Circular sawing device according to claim 16,

wherein

- the device comprises a plurality of stops, preferably three, distributed, preferably evenly distributed about the central axis of the pair of saw blades.

18. Circular sawing device according to claim 17 or 18,

wherein

- the stop comprises a wheel, preferably a wheel having an axis of rotation that intersects the central axis of the pair of saw blades.

19. Circular sawing device according to any of claims 1 to 18, wherein the saw edge of the inner saw blade extends beyond the saw edge of the outer saw blade.

20. Circular sawing device according to any of claims 1 to 19, wherein the saw edge of the outer saw blade is at substantially the same level along the central axis of the pair of saw blades or extends beyond the removing edge of the material removing members.

21. Method for arranging a ring shaped recess or a hole having a rabbeted edge in a piece of work, in particular in a piece of plasterboard, comprising:

- producing concentric cuts in a piece of work by means of a pair of saw blades arranged in concentric spaced relationship; and

- removing material of the piece of work between the cuts produced by said blades by means of material removing members arranged between said blades.

22. Method according to claim 21, wherein removing material of the work between the cuts produced by said blades is by scraping.

23. Method according to claim 22, wherein removing material of the work between the cuts produced by said blades is by means of pens having a pointed end for scraping.

24. Method according to any of claims 21 to 23, wherein

- before producing concentric cuts in a piece of work a cleaning body provided with apertures is arranged between said pair of saw blades such that the material removing members extend through said apertures, wherein preferably each material removing member extends through a respective aperture,

and wherein

- after removing material of the work the cleaning body is moved towards the saw edge of the saw blades, preferably at least until the material removing members no longer extend through the apertures, such that after moving the cleaning body the removed material is removable from the cleaning body.

Description:
Circular sawing device and method for arranging ring shaped recess or a hole having a rabbeted edge in a piece of work, in particular in plasterboard

The present invention relates to a circular sawing device, in particular a circular sawing device for arranging a circular cut in a piece of work. The present invention also relates to a method for arranging a circular cut in a piece of work.

Circular sawing devices for arranging a circular cut in a piece of work are commonly known as hole saws. Hole saws generally comprise a saw blade that is mounted on a drill arbor in concentric spaced relationship to the central longitudinal axis of the drill arbor for producing a circular cut in a piece of work. By producing a circular cut a circular hole may be obtained in the piece of work.

The present invention has for its object to provide a circular sawing device for arranging in a piece of work a ring shaped recess, and more in particular for arranging in a piece of work a hole with a rebated edge.

The circular sawing device according to the invention comprises a pair of saw blades arranged in concentric spaced relationship for producing concentric cuts in a piece of work, and material removing members arranged between said blades for removing material of the piece of work between the cuts produced by said saw blades.

In the circular sawing device according to the invention the material removing members provide a ring shaped recess in a piece of work, while that pair of saw blades, in particular concentric tubular saw blades, provide a well defined inner edge and outer edge of the recess. In a preferred embodiment the saw edge of the inner one of pair of saw blades extends beyond the saw edge of the outer one of the pair of saw blades, in particular such that the inner saw blade cuts deeper into the piece of work than the outer saw blade. This allows for arranging in the piece of work a hole having a rebated edge.

In advantageous embodiments of the circular sawing device according to the invention, the device according to the invention is configured for or at least particularly advantageous for arranging a ring shaped recess, in particular a hole having a rebated edge, in plasterboard.

Plasterboard generally has a core layer of gypsum sandwiched between two outer layers of lining paper including various additives in the gypsum core layer. Plasterboard is widely used as a covering element for walls and ceilings. Arranging a ring shaped recess or a hole having a rebated edge in plasterboard allows for instance for arranging objects in walls and ceilings having a plasterboard cover.

In an advantageous embodiment of the circular sawing device according to the invention at least the outer saw blade, preferably both the inner and the outer saw blade, has a saw edge with unset cutting teeth having a negative rake. The unset cutting teeth having a negative rake provide a clean cut in the lining paper and the gypsum core layer, such that the remaining edge of the plasterboard around the recess arranged by means of the device is well defined. In particular the unset cutting teeth prevent fraying and tearing of the lining paper along the edge of the recess and crumbling of the gypsum core layer along said edge. Furthermore, the unset cutting teeth are less prone to get filled with the cut away lining paper and in particular the cut away gypsum material that as a result of additives is extremely sticky. At least the outer saw blade has a saw edge with unset cutting teeth having a negative rake. In applications where the accuracy and neatness of the inner edge of the ring shaped recess or the hole with rebated edge is less important, for instance in case the inner edge will be covered after installing an object in the ring shaped recess or the hole with rebated edge, other saw edges than a saw edge with unset cutting teeth having a negative rake may be applied for the inner saw blade. It would even be possible that the inner saw blade lacks a saw edge. An inner saw blade having no saw edge may be used as a guide when providing an existing hole in a piece of work with a rebated edge by means of the circular sawing device according to the invention.

In a further advantageous embodiment the material removing members are embodied for removing material by scraping. In particular for removing the gypsum from the gypsum core layer of plasterboard, scraping is particularly effective. In a preferred embodiment thereof the material removing members comprise discrete pens having a pointed end for scraping. Preferably, the pointed end is conical. By providing discrete pens having a pointed end as material removing members, it is prevented that material that is removed by means of the material removing members builds up against the material removing members to the extent that the removed material hinders operation of the material removing members. Build-up material may hinder operation by diminishing the scraping action of the material removing member or by increasing the scraping action of the material removing member. Both may result in a less accurate depth of the recess. In particular the discrete pens having a pointed end prevent the build up of sticky gypsum material that is scraped from the gypsum core layer against the material removing members. In a preferred embodiment, the tips of the scraper pens are flattened, in particular such that the end surfaces of the pens extend in the same plane that is perpendicular to the central longitudinal axis of the concentric saw blades. This allows for a particular accurate depth of the recess produced by the scraper pens. The flattened tip of the scraper pins is preferably provided by a free end that is frustoconical. Advantageously, the pens are oriented parallel to the central axis of the concentric pair of saw blades. Furthermore, the pens preferably have a cross-section with rounded edges, more preferably have a circular cross-section. In a preferred embodiment the diameter of the cross- section of the scraper pens is in the range of 1mm to 5mm, preferably in the range of 2mm to 4mm, more preferably substantially 3mm. In a preferred embodiment the diameter of the cross-section at the tip of the pointed end of the scraper pens is in the range of 0, 1 mm to 0,5 mm; more preferably in the range of 0,2 mm to 0,4 mm; most preferably substantially 0,3 mm.

In an advantageous embodiment of the device according to the invention having discrete pointed pens, the central longitudinal axes of the pointed ends of the pens are moved along circular paths when the device is rotated about the central axis of the concentric blades, wherein a plurality of said circular paths have a different radius, and wherein said circular paths of different radius are distributed, preferably evenly distributed, over the radial distance between the pair of saw blades. In a preferred embodiment thereof, the radial distance between adjacent circular paths is about twice the diameter of the pointed end of the scraper pens.

In a further advantageous embodiment of the device according to the invention having discrete pointed pens, adjacent pens are mutually offset in radial direction and circular direction relative to the central axis of the concentric saw blades. This additional feature effectively prevents build up of gypsum material against the material removing members. In a preferred embodiment, the angular distance between adjacent pens is substantially the same. Preferably, adjacent scraper pens do not have adjacent circular paths.

In a further advantageous embodiment of the circular sawing device according to the invention the device comprises a cleaning body that extends between said pair of saw blades and that is provided with apertures, preferably one for each material removing member, through which apertures the material removing members extend with the cleaning body in a first position, wherein said cleaning body is movable relative to the material moving members along the central axis of the pair of saw blades and along the material removing members towards a free end of said material removing members into a second position, wherein preferably in said second position the material removing members do not extend through said apertures. This additional feature of a movable cleaning body facilitates the cleaning of the space between the pair of concentric saw blades. In particular the cleaning body allows for moving the removed material that is collected in the space between the pair of concentric saw blades toward the open end of said space. This is in particular advantageous in case the removed material is sticky, such as gypsum material that is removed from the gypsum core layer of plasterboard, and tends to stick to and build up against the surfaces enclosing the space between the concentric pair of saw blades. In a preferred embodiment thereof, the apertures closely fit around the material removing members. Although it is preferred that the cleaning body is provided with one respective aperture for each material removing member, it would be possible to have one aperture for a group of two or more material removing members that are arranged so close that substantially no removed material collects between the material removing members of such group. Although it is preferred that in the second position of the cleaning body the material removing members do not extend through the apertures of the cleaning body, it would be possible that in the second position of the cleaning body a substantial portion of material removing members no longer extends through the apertures while a small portion of the material removing members still extends through the apertures. Even if a small portion of the material removing members still extends through the apertures in the second position of the cleaning member, bringing the removed material closer to the free ends of the material removing members makes cleaning of the space between the pair of concentric saw blades easier than cleaning of the space between the pair of concentric saw blades with the cleaning body in the first position wherein the removed material is further away from the free ends of the material removing members and thus harder to reach.

In an advantageous embodiment of the device according to the invention wherein the device comprises a cleaning body, the cleaning body comprises a ring shaped body that in said first position closely fits between the pair of saw blades in a concentric relationship with said saw blades.

In a preferred embodiment thereof, the device comprises a first rotary body on which the inner saw blade is arranged and a second rotary body on which the outer saw blade is arranged, wherein the first rotary body and the second rotary body are movable relative to each other along the central axis of the concentric inner saw blade and outer saw blade, wherein the material removing members are arranged on the second rotary body, and wherein the ring shaped body is arranged on or is an extension of the first rotary body.

In a first advantageous alternative embodiment the device comprises a rotary body on which the pair of saw blades and the material removing members are arranged and from which the pair of saw blades and the material removing members extend in axial direction relative to the central axis of said pair of blades, and wherein the ring shaped body is movable relative to said rotary body between said first position and said second position, preferably by means of at least one ring shaped body moving member that extends through an aperture in said rotary body. In an advantageous embodiment thereof the cleaning body further comprises a circular or second ring shaped body that extends within the inner saw blade in concentric relationship therewith and that is connected to said first ring shaped body through at least one opening in the inner saw blade that allows for moving the cleaning body relative to inner saw blade. This advantageous embodiment allows for pushing the plug of material, that is cut out by means of the inner saw blade of the pair of saw blades, out of the inner saw blade when the cleaning body is moved relative to said rotary body between said first position and said second position. In this embodiment the cleaning body thus facilitates easy cleaning of the space between the pair of saw blades as well as the space within the inner saw blade.

In a second advantageous alternative embodiment the cleaning body is a first rotary body having arranged thereon the inner saw blade and the outer saw blade, and wherein the device comprises a second rotary body having arranged thereon the material removing members, wherein the first rotary body and the second rotary body are movable relative to each other along the central axis of the concentric inner saw blade and outer saw blade.

In a further advantageous embodiment of the circular sawing device according to the invention, the device further comprises a drill arbor, that is preferably configured at one end thereof to be arranged in a drill chuck, wherein the pair of saw blades are arranged concentric with the central longitudinal axis of said arbor. In a preferred embodiment thereof including a cleaning body as described herein above, at least one of the cleaning body and the material removing members is arranged for sliding along the central longitudinal axis of the arbor in order to move the cleaning body and the material removing members relative to each other, wherein the device comprises a coupling arrangement for releasable coupling the at least one of the cleaning body and the material removing members to the arbor, wherein the coupling arrangement preferably provides at least one of axial and rotational movement blocking of said at least one of the cleaning body and the material removing members relative to the arbor. In a preferred embodiment thereof the coupling arrangement comprises a notch and a spring loaded latch, preferably a manually operated latch, that releasably engages the notch for releasably coupling at least one of the cleaning body and the material removing members to the arbor.

In a further advantageous embodiment of the circular sawing device according to the invention, the device further comprises at least one stop configured for limiting the distance over which the pair of saw blades cut into the work. This feature allows for providing a ring shaped recess or a rebated edge with an accurate depth. In an advantageous embodiment thereof the device comprises a plurality of stops, preferably three, distributed, preferably evenly distributed about the central axis of the pair of saw blades. This feature advantageously provides that the depth of the ring shaped recess or the rebated edge is substantially the same along the circumference of the ring shaped recess or rebated edge.

In a preferred embodiment of the circular sawing device according to the invention provided with at least one stop, the stop comprises a wheel, preferably a wheel having an axis of rotation that intersects the central axis of the pair of saw blades. The wheel will rotate about its axis of rotation when the wheel is brought into contact with the surface of the piece of work. The rotation of the wheel prevents damage of the surface and possible build up of gypsum material against the stop that may result in inaccurate depth.

In a further advantageous embodiment of the circular sawing device according to the invention, the saw edge of the inner saw blade extends beyond the saw edge of the outer saw blade. This allows for arranging in a piece of work a hole with a rebated edge. Alternatively the saw edge of the inner saw blade are at substantially the same level along the central axis of the pair of saw blades. This allows for arranging in a piece of work a ring shaped recess. In a further advantageous embodiment of the circular sawing device according to the invention the saw edge of the outer saw blade is at substantially the same level along the central axis of the pair of saw blades or extends beyond the removing edge of the material removing members.

The present invention further relates to a method for arranging ring shaped recess or a hole having a rabbeted edge in a piece of work, in particular in plasterboard. The method according to the invention comprises producing concentric cuts in a piece of work by means of a pair of saw blades arranged in concentric spaced relationship, and removing material of the work between the cuts produced by said blades by means of material removing members arranged between said blades.

In a preferred embodiment of the method according to the invention removing material of the work between the cuts produced by said blades is by scraping. In an advantageous embodiment thereof removing material of the work between the cuts produced by said blades is by means of pens having a pointed end for scraping.

In an advantageous embodiment of the method according to the invention before producing concentric cuts in a piece of work a cleaning body provided with apertures is arranged between said pair of saw blades such that the material removing members extend through said apertures, wherein preferably each material removing member extends through a respective aperture, and after removing material of the work the cleaning body is moved towards the saw edge of the saw blades, preferably at least until the material removing members no longer extend through the apertures, such that after moving the cleaning body the removed material is removable from the cleaning body.

The accompanying drawings are used to illustrate non-limitative preferred exemplary embodiments of the present invention. The above stated and other advantages, features and objectives of the invention will become more apparent, and the invention better understood, from the following detailed description when read in combination with the accompanying drawings, in which:

- Figures 1 to 5 show a preferred embodiment of a circular sawing device according to the invention in different views;

- Figures 6 to 11 show in longitudinal section the circular sawing device of figures 1 to 5 while being used for performing a method according to the invention for arranging a hole having a rebated edge in a piece of plasterboard;

- Figures 12 and 13 show a first alternative embodiment of a circular sawing device of figures 1 to 5 in different views;

- Figures 14 and 15 show a second alternative embodiment of a circular sawing device of figures 1 to 5 in different views; - Figures 16 and 17 show a third alternative embodiment of a circular sawing device of figures 1 to 5 in different views;

- Figures 18 to 20 show a fourth alternative embodiment of a circular sawing device of figures 1 to 5 in different views;

- Figures 21 and 22 show an alternative embodiment of the circular sawing device of figures 18 to 20 in different views.

In figures 1 to 5 a circular sawing device 1 is shown. The circular sawing device has a pair of saw blades, i.e. an inner saw blade 3 and an outer saw blade 5. The saw blades 3, 5 are arranged in concentric spaced relationship, having a common central axis A. Central axis A is defined by the central longitudinal axis of an elongate drill arbor 7 on which the saw blades 3, 5 are mounted.

The drill arbor 7 is configured at a first end 7a to be received in a drill chuck of a drill. In the shown exemplary embodiment the drill arbor 7 has for this purpose at the first end 7a thereof a first end part 9 with a cross-sectional shape that corresponds to a hexagon. A drill arbor as shown in figures 1 to 3 having at a first end thereof a cross-sectional shape that corresponds to a hexagon is commonly referred to as a HEX shank. Alternatively, the first end part 9 of the drill arbor 7 has a different cross-sectional shape, preferably such that the drill arbor is configured as a TRIANGLE, SDS, SDS-PLUS, or STRAIGHT shank. A pilot drill 11 is arranged at second end 7b of drill arbor 7.

The outer saw blade 5 is arranged on and extends from a fist rotary body 13. The rotary body 13 is provided with an adapter 15 has an adapter body 17 with a longitudinal bore 19 therein. Longitudinal bore 19 of adapter 15 has a central longitudinal axis B and has a hexagonal cross- sectional shape. In the shown exemplary embodiment adapter 15 is mounted on the rotary body 13 by means of bolts 21, 23. The adapter 15 is alternatively integrated into the rotary body 13 or provided with other per se known measures for mounting the adapter 15 to the rotary body 13. The outer saw blade 5 is coaxial with the central longitudinal axis B and extends parallel to the central longitudinal axis B. The outer saw blade 5 is at the free end 5a thereof away from the first rotary body 13 provided with a sawing edge 27 having an tooth pattern consisting of unset cutting teeth 29 having a negative rake. Material removing members embodied by discrete scraper pens 25 are arranged on and extend from the fist rotary body 13. The scraper pens 25 extend parallel to the central longitudinal axis B. The scraper pens 25 are arranged radially inside the outer saw blade 5. The scraper pens 25 have a circular cross-section. The scraper pens 25 are each at the free end 25a thereof provided with a pointed tip 31. In particular the scraper pens 25 are conical at the free end 25a. Stops for limiting the distance over which the pair of saw blades 3, 5 cut into a piece of work embodied as wheels 33 are arranged on the first rotary body 13. The wheels 33 have an axis of rotation D that intersects the central longitudinal axis B. The wheels 33 are arranged radially outside the outer saw blade 5. The inner saw blade 3 is arranged on and extends from a second rotary body 35. The rotary body 35 is provided with an adapter 37 that has an adapter body 39 with a longitudinal bore 41 therein. Longitudinal bore 41 of adapter 37 has a central longitudinal axis C and has a hexagonal cross-sectional shape. In the shown exemplary embodiment adapter 37 is mounted on the rotary body 35 by means of bolts 43, 45. The adapter 37 is alternatively integrated into the rotary body 35 or provided with other per se known measures for mounting the adapter 37 to the rotary body 35. The inner saw blade 3 is coaxial with the central longitudinal axis C and extends parallel to the central longitudinal axis C. The inner saw blade 3 is at the free end 3a thereof away from the second rotary body 35 provided with a sawing edge 47 having an tooth pattern consisting of unset cutting teeth 49 having a negative rake. The second rotary body 35 is provided with a ring shaped cleaning body 51 that extends radially outside the inner saw blade 3 in radial direction. The cleaning body 51 is for each scraper pen 25 provided with an aperture in the form of a circular through hole 53.

Both adapter 15 of the first rotary body 13 and the adapter 37 of the second rotary body 35 are configured to mount the respective rotary body 13, 35 on the drill arbor 7. The drill arbor 7 is provided at the second end 7b thereof with a second end part 55 with a cross-sectional shape that corresponds to a hexagon. The longitudinal bores 19, 41 of the adaptor bodies 17, 39 of adapters 15, 37 are through bores an have a hexagonal cross-sectional shape that allows the second end 7b of the drill arbor 7 to be received in the longitudinal bores 19, 41 of the adaptor bodies 17, 39, such that the central longitudinal axis B, C of the respective longitudinal bores 19, 41 and the central longitudinal axis A of the drill arbor 7 coincide. The cross-sectional shape of the longitudinal bores 19, 41 and the cross-sectional shape of the second end part 55 of the drill arbor 7 are adapted to each other such that the inner surface of the longitudinal bores 19, 41 is in contact with and can slide over the surface of the second end part 55 of the drill arbor 7 along the central longitudinal axis A of the drill arbor 7. Because the cross-sectional shapes of second end part 55 of drill arbor 7 and the longitudinal bores 19, 41 of the adapters 15, 37 are other than round, once the second end part 55 of the drill arbor 7 is received in the longitudinal bores 19, 41 the adapters 15, 37 and the drill arbor 7 are coupled in rotation directions E and F around the respective central longitudinal axes A, B, C. As a result, a rotation of adapters 15, 37 and drill arbor 7 relative to each other in these rotation directions E and F is blocked. Although the hexagon shape is preferred for the cross- sectional shape of the second end part 55 of the drill arbor 7 and for the longitudinal through holes 19 and 41, other cross-sectional shapes which are other than round can likewise be applied.

The second end part 55 of the drill arbor is provided with two notches, in particular notches transverse to the central longitudinal axis A of the drill arbor 7, embodied here as circumferential grooves 57, 59, that are spaced apart along the central longitudinal axis A of the drill arbor 7. Each adapter 15, 37 is provided with a latch, in particular a latch that operates transverse to the central longitudinal axis B, C, of the longitudinal bore 19, 41 of the adapter 15, 37. In the detailed view to figure 4 is shown that the latch of adapter 15 is embodied here as a spring loaded latch plate 61 that is slidably received in the adaptor body 17. The latch plate 61 has an aperture 63 though which the drill arbor 7 can extend when the drill arbor 7 is received in the longitudinal bore 19 of the adaptor body 17. As shown in the detail to figure 4, when the latch plate 61 is aligned with one of the circumferential grooves 57, 59, of the drill arbor 7, the latch plate 61 is pushed by means of a spring 65 in direction of arrow F a first position (shown in said detailed view) wherein the latch plate 61 extends in the longitudinal bore and in the groove 57 such that movement of the adaptor 15 along the drill arbor 7 in direction parallel to the central longitudinal axis A of the drill arbor 7 is blocked. In the situation shown in the detailed view to figure 4, the adapter 15 is blocked for both axial movement and rotational movement relative to the central longitudinal axis A of the drill arbor 7. The latch plate 61 extends outside the adapter body 17, such that it can be pushed by an operator in the direction of arrow G against the force exerted by the spring 65 on the latch plate 61 in a second position wherein the latch plate 61 no longer extends in the longitudinal bore 19 and the groove 59. In said second position of the latch plate 61, axial movement of the adapter 15 along the drill arbor 7 in direction parallel to the central longitudinal axis A of the drill arbor 7 is no longer blocked. With adapter 15 can be moved along the drill arbor 7 in direction parallel to the central longitudinal axis A of the drill arbor 7. Adapter 37 of the second rotary body 35 is provided with a latch of the same type, such that adapter 37 can be arranged on the drill arbor 7 such that axial movement of the adapter 37 along the drill arbor 7 in direction parallel to the central longitudinal axis A of the drill arbor 7 is blocked, by aligning the spring loaded latch plate 61 with one of the grooves 57, 59 and allowing the latch plate to extend in said groove. Although the embodiment of a latch plate is preferred, other embodiments of a latch such as latch balls and the like may likewise be applied. Still further, in stead of the notches being provided on the drill arbor 7, the notches may be provided on inner surface of the through holes of the adapters while latches are provided on the drill abor 7. Although, the coupling arrangement for releasably coupling the adapters 15, 37 to the drill arbor 7 that includes a notch and a spring loaded latch is preferred, other releasable coupling arrangements based on form-fit or coupling arrangements based on friction-fit such as with clamps that clamp onto the drill arbor 7 or with screws that are forced against the drill arbor 7, or with other friction-fitting coupling elements may likewise be applied.

In figures 1 and 2 is shown that the second end 55 of the drill arbor 7 is received in the longitudinal bore 19 of the adaptor body 17 of adaptor 15 of rotary body 13 and is received in the longitudinal bore 41 of the adaptor body 39 of adaptor 37 of rotary body 35. As a result both adapters 15, 17 and the rotary bodies 13, 35 provided therewith are coupled to the drill arbor 7, such that rotational movement of the adapters 15, 17 and the rotary bodies 13, 35 relative to the drill arbor 7 around the central longitudinal axis A is blocked. The central longitudinal axes A, B, and C coincide, such that the inner saw blade 3 and the outer saw blade 5 are concentric relative to said central longitudinal axes.

In figure 1, the first rotary body 13 and the second rotary body 35 are in a first position relative to each other wherein the latch plate 61 of the adapter 17 of the first rotary body 13 is aligned with and extends in the lower groove 57 of the drill arbor 7 and the latch plate of the adapter 37 of the second rotary body 35 is aligned with and extends in the upper groove 57 of the drill arbor 7. In this position, each of the scraping pens 25 that is arranged on the first rotary body 13 extends through a hole 53 in the cleaning body 51 that is arranged on the second rotary body 35. In this position the scraper pens 25 are arranged between the concentric saw blades 3 and 5. The saw blades 3 and 5 form the side walls and the cleaning body the bottom wall of a space S in which the scraper pens 25 are arranged and that is open ended opposite to the bottom wall. In the shown position, the saw edge 3a of the inner saw blade 3 extends beyond the saw edge 5a of the outer saw blade 5 as seen in the direction from the first end 7a of the drill arbor 7 to the second end 7b of the drill arbor 7 indicated by arrow H. The tip of the pilot drill 11 extends beyond the saw edge 3a of the inner saw blade 3 as seen in the direction from the first end 7a of the drill arbor 7 to the second end 7b of the drill arbor 7 indicated by arrow H.

In figure 5 the circular sawing device 1 as shown in figure 1 is shown from above. As shown in figure 5, the inner saw blade 3 and the outer saw blade 5 are concentric relative to central longitudinal axis A of the drill arbor 7. When the device 1 is rotated about the central longitudinal axis A of the drill arbor 7 and the saw edges 3a, 5a of the saw blades 3, 5 are brought into contact with a piece of work, the saw blades 3, 5 will produce concentric cuts. In case the circular cut produced by means of the inner saw blade 3 cuts through the piece of material, a circular hole in the piece of material results and a cut out plug of material is left in the space T within the inner saw blade 3. The scraper pens 25 are arranged between the inner saw blade 3 and the outer saw blade 5. Adjacent scraper pens 25 are mutually offset in radial direction and circular direction relative to the central axis of the concentric saw blades 3, 5 defined by the central longitudinal axis A of the drill arbor 7. The pointed ends of the scraper pens 25 are moved along circular paths when the device 1 is rotated about the central longitudinal axis A of the drill arbor 7.

As shown in figure 5, the scraper pens 25 are distributed between the inner saw blade 3 and outer saw blade 5. The circular paths 26a, 26b, 26c of the central longitudinal axis of 31a of the scraper pens 25a, 25b, and 25c are shown in figure 5. The circular paths of the other scraper pens are not shown. Scraper pens 25a, 25b, and 25c have adjacent circular paths but are not adjacent scraper pens. The same applies to the other scraper pens 25. In this preferred embodiment the diameter of the pins is about 3mm, the radial distance rj between adjacent circular paths is about 0,6 mm, while the radius r 2 of the pointed end 31 of the scraper pens 25 is about 0,15 mm. Although these values have been proven to effective, other values of the diameter of the pens, ΐ and r 2 may be effective for specific composition of the material that is to be scraped away. The scraper pens 25 are distributed such that circular paths of different radius are evenly distributed over the radial distance R between the pair of saw blades 3, 5. When the device 1 is rotated about the central longitudinal axis A of the drill arbor 7 and the pointed ends of the scraper pens 25 are brought into contact with a piece of work, the pointed ends of the scraper pens 25 will remove material by scraping away material between the concentric cuts produced by means of the saw blades 3, 5. The material that is scraped away will collect in the space S defined between the inner saw blade 3, the outer saw blade 5 and the cleaning body 51 through which the scraper pens 25 extend. As shown in figure 5, the holes 53 in the cleaning body 51 through which the scraper pens 25 extend closely fit around the scraper pens 25. As shown in figure 5, in the shown first position, the ring shaped cleaning body 51 closely fits between the pair of saw blades 3, 5 in a concentric relationship with said saw blades 3, 5.

As shown in figure 5, three wheels 33 are evenly distributed about the central longitudinal axis A of the drill arbor 7.

In case from the situation shown in figure 1 the axial blocking of the adapter 15 of the first rotary body 13 is released by pushing the latch plate 61 in the direction of arrow G, the first rotary body 13 can be axially moved along the second end part 55 of the drill arbor 7 in the direction from the second end 7b of the drill arbor 7 to the first end 7a of the drill arbor 7 indicated by arrow I, such that the first rotary body 13 and the second rotary body 35 are brought in a second position relative to each other as shown in figure 2. By moving the first rotary body 13 and the second rotary body 35 relative to each other, the cleaning body 51 is moved relative to the scraper pens 25 in the direction of arrow H from a first position, shown in figure 1 , wherein the scraper pens 25 extend through the holes 53 in the cleaning body 51 to a second position, shown in figure 2, wherein the scraper pens 25 no longer extend through the holes 53 in the cleaning body 51. In the second position shown in figure 2, the one side wall of the space S of figure 1 formed by the outer saw blade 5 is removed and the scraper pens 25 are removed from said space S, while the other side wall formed by the inner saw blade 3 and the bottom wall formed by the cleaning body 51 remain in place. This allows for easy cleaning of the space S, i.e. removing the material scraped away by means of the scraper pens 25, after use of the circular sawing device 1, as will be explained in more detail herein below under reference to figure 10.

In case from the situation shown in figure 2, the axial blocking of the adapter 37 of the second rotary body 35 is released by pushing the latch plate 61 (that is accessible from underneath the second rotary body 35 via aperture 67) in the direction against the force of the spring such that the latch plate no longer extends in the longitudinal hole 41 of the adapter 37 and in the upper groove 57, the second rotary body 35 can be axially moved along the second end part 55 of the drill arbor 7 in the direction from the second end 7b of the drill arbor 7 to the first end 7a of the drill arbor 7 indicated by arrow I. As a result the second end 7b of drill arbor 11 is moved relative to the second rotary body 35 and the inner saw blade 3 in the direction from the first end 7a of the drill arbor 7 to the second end 7b of the drill arbor 7 indicated by arrow H. Since the second end 7b of drill arbor 11 has a greater diameter than the pilot drill 11 , this allows to push a plug of material that after use of the circular sawing device 1 is arranged within the inner saw blade 3 out of the saw blade 3 as will be explained in more detail herein below under reference to figure 11.

As shown in figure 4, the first rotary body 13 does not provide access to the aperture 67 and latch plate 61 of the adapter 37 of the second rotary body 35 from underneath the first rotary body 13. Alternatively, the first rotary body 13 may be provided with an aperture therein that does provide access to the aperture 67 and latch plate 61 of the adapter 37 of the second rotary body 35 from underneath the first rotary body 13, thereby allowing more easy access to the latch plate 61 of the adapter 37 of the second rotary body 35.

Although it is preferred that the second rotary body 35 is releasably mounted on the drill arbor 7, the second rotary body 35 may alternatively be fixed to the drill arbor 7. Furthermore, although it is preferred that the latch plate 61 of the adapter 37 of the second rotary body 35 can be accessed from underneath via an aperture 67 in the second rotary body 35, alternatively the latch plate 61 of the adapter 37 of the second rotary body 35 may not be accessible from underneath. The latter may result in the function of pushing out of the plug of material no longer being available. In order to alternatively facilitate pushing a plug of material out of the inner saw blade, both the first rotary body and the second rotary body may be provided with an aperture through which a tool such as a screw driver or the like may be put in order to push out a plug of material out of the inner saw blade from underneath.

In figures 6 to 11 a method for arranging a hole with a rebated edge in plasterboard by means of the circular sawing device as shown in figures 1 to 5 is illustrated. The plasterboard 69 piece of work has a core layer 71 of gypsum sandwiched between two outer layers 73, 75 of lining paper. For using the circular sawing device as shown in figures 1 to 5, the first end 7a of the drill arbor 7 is mounted in a drill chuck of a drill (not shown) and is rotated by means of the drill about the central longitudinal axis A of the drill arbor 7.

As shown in figure 6, for arranging the hole, the pilot drill 11 is brought into contact with and into the surface of the plasterboard 69, thereby forming a guide for further drilling.

Subsequently, the saw edge of the inner saw blade 3 is brought into contact with the outer layer 73 of lining paper. The unset cutting teeth 49 of the saw edge 3a of the inner saw blade 3 then cut through the lining paper of outer layer 73, into the gypsum core layer 71, and eventually through the lining paper of outer layer 73. As a result, as shown in figure 7, a plug 77 of plasterboard is cut out by means of the inner saw blade 3 leaving a circular hole in the plasterboard 69. As soon as the inner saw blade 3 has cut out the plug 77 of plasterboard, the inner saw blade 3 serves a guide for further drilling.

By bringing the saw edge of the outer saw blade 5 into contact with the outer layer 73 of lining paper, during or after cutting the plasterboard 69 with the inner blade 3, the unset cutting teeth 49 of the saw edge 5a of the outer saw blade 5 then cut through the lining paper of outer layer 73, into the gypsum core layer 71 so as to produce a second circular cut concentric with the circular cut produced by means of the inner saw blade 3. While producing the second circular cut by means of the outer saw blade 5, the pointed ends 31 of the scraper pens 25 are brought into contact with the outer layer 73 of lining paper and scrape away the lining paper of the outer layer 73 and gypsum material of the core layer 73 in between the saw blades 3 and 5. The gypsum material 79 that is scraped away by means of the scraper pens 25 collects in the space S defined between the saw blades 3, 5 and the cleaning body 51.

The outer saw blade 5 cut into and the scraper pens 25 scraped away the material of the plasterboard 69 until, as shown in figure 8, the wheels 33 come into contact with the surface of the plasterboard 69.

As shown in figure 9, after subsequently taking the circular sawing device 1 out of the plasterboard 69, a hole 81 with a rebated edge 81a remains in the plasterboard 69. Furthermore, a plug of material 77 cut away from the plasterboard 69 remains within the inner saw blade 3 and material scraped away by means of the scraper pens 25 remains in the space S defined between the saw blades 3, 5 and the cleaning body 51.

By subsequently moving the first rotary body 13 with the outer saw blade 5 and the scraper pens 25 arranged thereof in the direction of arrow I away from the second rotary body 35 having the inner blade 3 and the cleaning body 51 arranged thereon, as described herein above under reference to figures 1 and 2, the position of the first rotary body 13 and the second rotary body 35 as shown in figure 10 results. As shown the material that was scraped away by means of the scraper pens 25 and remained in space S, is now easily accessible and can be scraped of the surface of cleaning body 51 unhindered by the scraper pens 25 and the outer saw blade 5. Since the holes in the cleaning body 51 closely fit the scraper pens 25 that extend through the holes during scraping, by moving the scraper pens 25 out of the holes 53, any material that despite the circular cross-section of the scraper pens 25 sticks to the scraper pens 25, is scraped of the scraper pens 25 when moving the first rotary body 13 with the outer saw blade 5 and the scraper pens 25 arranged thereof in the direction of arrow I away from the second rotary body 35.

By subsequently moving the second rotary body 35 with the outer saw blade 3 arranged thereon in the direction of arrow I relative to the drill arbor 7, as described herein above under reference to figure 2, the position of the first rotary body 13 and the second rotary body 35 as shown in figure 11 results wherein the plug of material 77 that was arranged within the inner saw blade 3 was pushed out of the inner blade 3 by means of the second end 7b of the drill arbor 7.

Although the provision of a cleaning body is preferred, in an alternative embodiment of the circular sawing device as shown in figures 1 to 5, the device is not provided with a cleaning body. In a preferred embodiment thereof, the inner saw blade 3, the outer saw blade 5, and the scraper pens 25 are all arranged on the first rotary body 13, while the second rotary body and the cleaning body of the embodiment shown in figures 1 to 5 are then dispensed with. In this embodiment it would still be possible to push a plug of material out of the inner saw blade 3. As a further alternative it would be possible that the first rotary body 13 is fixed to the drill arbor 7.

Although the provision of the wheels 33 as a stop is preferred, in an alternative embodiment of the circular sawing device as shown in figures 1 to 5, the device is not provided with wheels 33 as a stop for limiting the depth that the outer blade 5 and the scraper pens 25 reach into the piece of material, or with a different embodiment of a stop, such as a protrusion arranged on the first rotary body that is stationary relative to the first rotary body.

In figures 12 to 22 further alternative embodiments of the circular sawing device as shown in figures 1 to 5 are shown.

In figures 12 and 13 a circular sawing device 101 is shown that differs from the circular sawing device as shown in figure 1 in that in stead of scraper pens 25 material removing members are arranged between the saw blades 3 and 5 that are embodied as additional saw blades 125 spirally arranged between the pair of concentric saw blades 3, 5. Each of the saw blades 3, 5 and 125 has a saw edge having a teeth pattern consisting of unset cutting teeth having a negative rake. In this embodiment the inner saw blade 3 and the outer saw blade 5 are arranged on the first rotary body 13. The second rotary body, the cleaning body, and the wheels of the embodiment of figures 1 to 5 are dispensed with. When the first rotary body 13 is mounted on the drill arbor 7 with the adapter 15 as in the embodiment shown in figures 1 to 5, the plug of material 77 cut out by means of the inner saw blade 3 can be pushed out by moving the first rotary body 13 in the direction of arrow I relative to the drill arbor 7, wherein the plug of material 77 is pushed out by the second end 7b of the drill arbor 7. Alternatively, the first rotary body 13 may be fixed to the drill arbor 7.

In figures 14 and 15 a circular sawing device 201 is shown that differs from the circular sawing device as shown in figure 1 in that in stead of scraper pens 25 material removing members are arranged between the saw blades 3 and 5 that are embodied as scraping chisels 225. Three pairs of chisels 225 are arranged between the saw blades 3, 5, wherein each pair of chisels 225 is arranged adjacent one of the wheels 33. As shown in figure 15 the for each pair of chisels 225, the chisels 225 may be arranged on different radial locations between the saw blades 3, 5, such that despite each pair of chisels 225 not covering the total radial distance between the saw blades 3, 5, all of the material of the work between the cuts produced by means of the saw blades 3, 5 is effectively removed. In this embodiment the inner saw blade 3 and the outer saw blade 5 are arranged on the first rotary body 13. The second rotary body and the cleaning body of the embodiment of figures 1 to 5 are dispensed with. When the first rotary body 13 is mounted on the drill arbor 7 with the adapter 15 as in the embodiment shown in figures 1 to 5, the plug of material 77 cut out by means of the inner saw blade 3 can be pushed out by moving the first rotary body 13 in the direction of arrow I relative to the drill arbor 7, wherein the plug of material 77 is pushed out by the second end 7b of the drill arbor 7. Alternatively, the first rotary body 13 may be fixed to the drill arbor 7.

In figures 16 and 17 a circular sawing device 301 is shown that differs from the circular sawing device 1 as shown in figure 1 in that the inner saw blade 3, the outer saw blade 5, and the wheels 33 are arranged on the second rotary body 35, while the scraper pens 25 are arranged on the first rotary body 13. The cleaning body 51 is an integral part of the second rotary body 35. In the first position shown in figure 16, the scraper pens 25 extend through holes in the cleaning body 51. In the second position shown in figure 17, wherein the first rotary body 13 having the scraper pens 25 arranged thereon has been moved along the central longitudinal axis A of the drill arbor 7 relative to the second rotary body 35 in the direction of arrow I, the scraper pens 25 no longer extend through the holes 53. As a result cleaning of the space S between the sawing blades 3 and 5 is no longer hindered by the scraper pens 25. Furthermore, by moving the scraper pens 25 out of the holes 53, any material that despite the circular cross-section of the scraper pens 25 sticks to the scraper pens 25, is scraped of the scraper pens 25 when moving the first rotary body 13 with the scraper pens 25 arranged thereon in the direction of arrow I away from the second rotary body 35. When the second rotary body 35 is mounted on the drill arbor 7 with the adapter 37 as in the embodiment shown in figures 1 to 5, the plug of material 77 cut out by means of the inner saw blade 3 can be pushed out by moving the second rotary body 37 in the direction of arrow I relative to the drill arbor 7, wherein the plug of material 77 is pushed out by the second end 7b of the drill arbor 7. Alternatively, the second rotary body 35 may be fixed to the drill arbor 7.

In figure 18 to 20 a circular sawing device 401 is shown that differs from the circular sawing device as shown in figure 1 in that the inner saw blade 3, the outer saw blade 5, and the scraper pens 25 are arranged on the first rotary body 13. The second rotary body of the embodiment of figures 1 to 5 is dispensed with. The ring shaped cleaning body 51 extends between the inner saw blade 3 and the outer saw blade 5 and is movable relative to the first rotary body 13 between a first position (shown in figure 18) wherein the scraper pens 25 extend through the holes 53 in the cleaning body 51, and a second position (shown in figure 20) wherein the scraper pens 25 do not extend through said holes 53. The cleaning body 51 is movable relative to the scraper pens 25 along the central longitudinal axis A of the drill arbor 7 and along the scraper pens 25 towards and beyond the pointed ends of the scraper pens by means of ring shaped body moving members 83 that extends through an aperture 85 in said first rotary body 13. When the first rotary body 13 is mounted on the drill arbor 7 with the adapter 15 as in the embodiment shown in figures 1 to 5, the plug of material 77 cut out by means of the inner saw blade 3 can be pushed out by moving the first rotary body 13 in the direction of arrow I relative to the drill arbor 7, wherein the plug of material 77 is pushed out by the second end 7b of the drill arbor 7. Alternatively, the first rotary body 13 may be fixed to the drill arbor 7. According to a further alternative of the embodiment shown in figures 18 to 20, the cleaning body further comprises a circular or second ring shaped body that extends within the inner saw blade in concentric relationship therewith and that is connected to the ring shaped body that extends between the saw blades 3, 5, through at least one opening in the inner saw blade 3 that allows for moving the cleaning body relative to inner saw blade. In this alternative embodiment the plug of material 77 that is cut out by means of the inner blade 3 is pushed out of the inner blade 3 by means of the circular or second ring shaped body that extends within the inner saw blade 3 while at the same time the scraped away material is moved out of the space between the inner saw blade 3 and the outer saw blade 5. In this alternative embodiment the circular or second ring shaped body that extends within the inner saw blade 3 may be fixed to the drill arbor 7, such that when moving the first rotary body 13 in the direction of arrow I relative to the drill arbor 7, the cleaning body that is fixed to the drill arbor 7 is moved relative to the first rotary body 13 having arranged thereon the saw blades 3, 5 and the scraper pens 25. Such an embodiment is shown in figures 21 and 22. In this embodiment, the cleaning body 51 of the circular sawing device 501 further comprises a circular body 51b that extends within the inner saw blade 3 in concentric relationship therewith and that is connected to the ring shaped body 51a that extends between the saw blades 3, 5, through three openings 87 in the inner saw blade 3 that allows for moving the cleaning body 51 relative to inner saw blade 3. The cleaning body 51 is fixed to the drill arbor 7. Starting from the situation shown in figure 21, the first rotary body 13 may be moved in the direction of arrow I relative to the drill arbor 7, such that the cleaning body 51 that is fixed to the drill arbor 7 is moved relative to the first rotary body 13 having arranged thereon the saw blades 3, 5 and the scraper pens 25 into a position as shown in figure 22.

Although the principles of the invention have been set forth above with reference to specific embodiments, it must be understood that this description is given solely by way of example and not as limitation to the scope of protection, which is defined by the appended claims.