Core drill for a cementitious building material

Abstract

The present invention relates to a core drill for drilling in cementitious building materials. The core drill is for deep hole drilling, holes being at least 300 mm deep. The core drill is cylindrical and has a front end provided with a plurality of abrasive segments and a rear end, opposite to the front end, having orifices for extracting dust, formed during drilling, from the hole being drilled and into a hollow interior of the core drill. A cylindrical surface between the front end and the rear end has at least two holes provided along each of at least two axial linear or non-linear extensions along the cylindrical surface. The core drill is capable of extracting dust through the holes and through orifices in the rear end of the core drill, from even deep holes, both when drilling horizontally, vertically and in any direction askew.

Description

[0001] HILTI Aktiengesellschaft in Schaan

[0002] Furstentum Liechtenstein

[0003] Core drill for a cementitious building material

[0004] Field of the invention

[0005] The present invention relates to a core drill for drilling in cementitious building material. The core drill is cylindrical and has a front end provided with a plurality of abrasive segments and a rear end, opposite to the front end, having a fastening mechanism for fastening the core drill to a drilling machine. The core drill has a cylindrical surface extending along an axial extension between the front end and the rear end. The cylindrical surface defines a hollow interior of the core drill between the front end and the rear end of the core drill.

[0006] Core drills are commonly known and used for drilling in cementitious building material when having to make relatively larger holes where a non-core drill will be too difficult to use when drilling in cementitious building material. During drilling, abrasive elements of the core drill advance into the material, leaving a cementitious core inside the hollow interior of the core drill.

[0007] During drilling, dust is formed. The dust is hazardous to the person performing drilling and possibly other persons in vicinity of a drilling site, and the dust must be removed. Often water is used during drilling to cool the abrasive elements, but possibly also for collecting the dust before being formed before being emitted into surroundings of the drilling site. Use of water necessitates access to water and special equipment for providing the water.

[0008] DE 202 01 300 U1 discloses a drill bit with two or more drilling debris removal grooves extending around the drill crown body on its outer mantle surface. Each groove extends from the crown base to the edge of the crown at the opposite end, in between two cutting tools. The drill crown has a round cylindrical pot-shaped body with a base at one end containing a shaft holder and its opposite end open. Cutting tools are distributed around the crown periphery at the open end. The drilling debris removal grooves follow a spiral path from the open end of the drill crown to its base. Drilling debris removal holes are optionally provided in the base. The drilling debris removal holes are recessed along the drilling debris 30 removal grooves, recessed from the outer mantle surface of the crown drill crown body. US 2005 / 0016775 A1 discloses a plurality of chip evacuating grooves in a vertical direction in parallel with a rotational axis of a core main body, and formed at an outer peripheral face of the core main body in a circumferential direction from a lower end portion to an upper 35 end portion of the core main body in a cylindrical shape, The core drill is provided with a drilling blade at a lower end edge thereof. Further, a sectional area of the chip evacuating groove is formed to gradually increase from a lower end to an upper end of the core main body. Further, a number of projections are formed at the outer peripheral face of the core main body between the chip evacuating grooves. Thus, the chip evacuating grooves are embedded beneath the outer peripheral face of the core drill, as viewed in a radial direction from a rotational axis of the core drill, and the projections form the outer peripheral face.

[0009] When the holes are recessed from the outer mantle surface or the outer peripheral surface, dust and debris, formed during drilling, may collect in the grooves and clog the holes.

[0010] A so-called suction housing may be used with a core drill. The suction housing is attached to a rear end of the core drill. The suction housing has an exhaust pipe intended for being connected to a vacuum source. The rear end of the core drill has holes. Dust formed during drilling is sucked out of the hollow interior of the core drill, through the holes in the rear end 15 of the core drill, into the suction housing and out through the exhaust pipe by means of the vacuum source. However, not all dust formed during drilling can and will be sucked from the drilling site.

[0011] EP 0 558 817 A2 discloses a hood-like collecting device arranged downstream of apertures of 20 an abrasive bit in such a way that its bottom area overlaps the top of the abrasive bit all round. A conical center part with a large receiving space for the drilling dust adjoins the fastening area of the collecting device. The peripheral surface of this conical center part is interrupted at one point for creating an inlet for a connection piece. The end part of the hood-like collecting device has a lower region that extends over the cover of the drill. The lower region of the collecting device has a diameter being the same as the cover of the drill.

[0012] One object of the invention may be to provide a core drill where the amount of dust formed during drilling is extracted from the drilling site in a more efficient and safer manner

[0013] Another object of the invention may also be to provide a core drill assembly, where the one and same suction housing is capable of being attached to core drills with various diameters.

[0014] Still another object of the invention may be to provide a core drill both having better and safer dust extraction and also having other improved properties to known core drills.

[0015] Summary of the invention One, or more, or all objects of the invention may be obtained by one, or more or all embodiments of a core drill according to the invention as disclosed in the claims, or of a core drill assembly according to the invention as disclosed in the claims.

[0016] Brief Description of the drawings

[0017] One, or more, or all objects of the invention may be obtained by one, or more or all embodiments of a core drill according to the invention as disclosed in the claims, or of a core drill assembly according to the invention as disclosed in the claims.

[0018] The aspects of the invention are described or explained in more detail below, purely by way of example, with reference to working examples shown schematically in the drawing. Identical elements are labelled with the same reference numerals in the figures. The described embodiments are generally not shown true in scale, and they are also not to be interpreted as limiting the invention. Specifically,

[0019] Fig. 1 is a photo showing a drill hole drilled by a core drill according to state of the art,

[0020] Fig. 2 is a drawing of a core drill assembly with a suction housing, according to state of the 10 art,

[0021] Fig. 3 is a sketch drawing of a core drill assembly according to the invention with a suction housing attached, during drilling in a cementitious building material,

[0022] Fig. 4 is a drawing of a core drill rear end, seen from inside the core drill, with a selected plurality of holes and a selected shape of the holes for dust extraction to a suction housing, 15

[0023] Figs. 5A, B are drawings of a preferred embodiment of a core drill with a rear end and such rear end, both the core drill and the rear end according to the invention,

[0024] Fig. 6 is a drawing of an embodiment of a core drill according to the invention,

[0025] Figs. 7A-C are drawings of a possible embodiments of a core drill with vacuum-increasing insert plate inside the interior of the core drill,

[0026] Fig. 8 is a drawing of a possible embodiments of a core drill with improved heat dissipation from the abrasive segments to the cylindrical extension,

[0027] Figs. 9A, B are drawings of a possible embodiments of a core drill with notch-preventing layout of a lowermost circumference of the core drill, Fig. 10 is a sketch of one alternative embodiment of a core drill with heat conductive backing and notch-preventing layout of a foremost circumference of the core drill,

[0028] Fig. 11 is a sketch of another alternative embodiment of a core drill with heat conductive backing and notch-preventing layout of a foremost circumference of the core drill,

[0029] Figs. 12A, B are drawings of a suction housing according to the invention for a core drill according to the invention and / or according to state of the art,

[0030] Fig. 13A, B are drawings showing an insert ring for a suction housing according to the invention for a core drill according to the invention and / or according to state of the art,

[0031] Figs. 14A, B are drawings of a possible embodiment of suction housing according to the invention for a core drill according to the invention and / or according to state of the art,

[0032] Fig. 15 is a drawing of core drill with a small diameter, said core drill intended for being used with a suction housing as shown in one of Fig. 12A, B, Fig. 13, Fig. 14,

[0033] Fig. 16 is a drawing of drill hole extender with a small diameter, said extender intended for being used with a suction housing as shown in one of Fig. 12A, B, Fig. 13, Fig. 14,

[0034] Fig. 17 is a drawing showing a possible first alternative embodiment of a suction outlet of a suction housing according to the invention,

[0035] Fig. 18 is a drawing showing a possible second alternative embodiment of a suction outlet of a suction housing according to the invention,

[0036] Fig. 19A-C are drawings showing a possible first embodiment of an extension for a core drill when drilling deep holes, and

[0037] Fig. 20A-C are drawings showing a possible second embodiment of an extension for a core drill when drilling deep holes.

[0038] Detailed Description

[0039] Reference will now be made in detail to the present preferred embodiment, an example of which is illustrated in the accompanying drawings. It is to be understood that the technology disclosed herein is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The technology disclosed herein is capable of other embodiments and of being practiced or of being carried out in various ways.

[0040] Fig. 1 is a photo showing a drill hole 1 drilled into a cementitious building material by a core drill (not shown). The core drill generates a drill hole 1 having sidewalls, a drill gap, and a core 2, which is not visible, because drilling dust has accumulated on top of the core 2. The drilling dust must be removed manually or by a vacuum source from the drill hole 1. However, the drilling dust, if accidentally inhaled, is hazardous to the person having to remove the dust. Therefore, there is a need for the drilling dust to be removed in other ways than manually by a person and in a way ensuring that as little dust as possible is expelled to the surroundings of the drill hole 1.

[0041] Fig. 2 is a drawing showing a core drill assembly DA, that is, a core drill 3 and a suction housing 8. The core drill 3 has a front end 4 and a rear end 5. At the front end 4 of the core drill 3, a plurality of abrasive segments 6 are provided. The abrasive segments 6 have an abrasive material such as carborundum or diamond deposited. The core drill 3 is circular cylindrical apart from circumferential grooves 7, which are arranged at regular intervals along the core drill 3.

[0042] The core drill 3 exhibits an outer surface, a major part of which outer surface extending linearly, parallel to a rotational axis A of the core drill 3 and extending circularly around the rotational axis of the core drill, where the rotational axis A of the core drill 3 is defined by an axis of rotation of a drive shaft of a drilling machine, to which the core drill is connected for drilling. The outer surface has an outermost cylindrical surface extension, defined by part of the cylindrical surface extending the most outwards, as seen radially from the rotational axis A of the core drill. The outermost cylindrical surface is interrupted by the circumferential grooves 7. The circumferential grooves 7 constitute part of the outer surface but does not constitute part of the outermost cylindrical surface of the core drill 3.

[0043] The suction housing 8 is placed on the rear end 5 of the core drill 3. The suction housing 8 is attached to the rear end 5 of the core drill 3 by means of an attachment mechanism (not shown) provided inside the suction housing 8. The attachment mechanism is intended for attaching the suction housing 8 to the rear end 5 of the core drill 3 and the attachment mechanism also functions as means for attaching a drilling machine (not shown) to the core drill 3. The suction housing 8 has an exhaust pipe 9 extending radially from a side surface of the suction housing 8. The exhaust pipe 9 is intended for connecting a hose of a vacuum 10 source for extracting dust, formed during drilling, through holes (see Fig. 5) in the rear end 5 of the core drill 3 to the suction housing 8 and through the exhaust pipe 9. Fig. 3 is a sketch of a core drill assembly DA according to the present invention, the core drill assembly DA configured for extracting drilling dust during drilling so that the dust does not have to be removed by a person after the drill hole has been drilled.

[0044] The core drill assembly DA comprises a core drill 3 and a suction housing 8. A front end 4 of the core drill 3 has abrasive segments 6 coated with a hard material such as carborundum or diamond. During drilling, the core drill 3 rotates with a certain rotational speed about a rotational axis A of the core drill 3, whereby the front end 4 of the core drill 3 with the abrasive segments 6 propagates into the cementitious building material, leaving a drill hole 1 with a core 2 and a drill gap between the core and the drill hole.

[0045] A distance of the drill gap between the core and the drill hole is defined by a radial extension of the abrasive segments 6 in a plane perpendicular to the rotational axis A of the core drill 3. The abrasive segments 6 have a larger radial extension from the rotational axis A of the core drill 3 than the cylindrical surface constituting another part than the abrasive segments 6 of the core drill 3, that is, part of the core drill 3 extending above the abrasive segments 6, as viewed in the figure.

[0046] One spacing is present between an inner surface 12 of the cylindrical part of the core drill 3 and the outer circumference 10 of the core 2 of the drill hole 1. Another spacing is present between an outer surface 13 of cylindrical part of the core drill 3 and the inner circumference 11 of the drill hole 1. Each of the spacings on each side of the cylindrical part of the core drill 3 may be between 1 mm and 3 mm in radial direction from the rotational axis A of the core drill 3, depending on the on the radial extension of the abrasive segments 6. The radial extension of the abrasive segments 6 defines the outer surface of the core and the inner surface of the drill hole 1.

[0047] The core drill 3 has a rear end 5 with orifices 14 (see also Fig. 5). The orifices 14 in the rear end 5 of the core drill 3 are intended for extracting dust, formed during drilling, from the interior of the core drill 3 and to the suction housing 8 attached to the rear end 5 of the core drill 3. The suction housing 8 is preferably made from a plastic material such as polyoxymethylene (POM). Inside the suction housing 8, a fastening mechanism is provided.

[0048] An attachment mechanism 15 is rotationally attached to the suction housing 8 along a roller bearing. The attachment mechanism is for attaching the core drill 3 to a drilling machine (not shown). The attachment mechanism 15 is often a nut extending from the rear end 5 and being an integrated part of the rear end 5, see as example Fig. 6B. The drilling machine will be attached oppositely to the core drill 3 in relation to the suction housing 8. The suction housing 8 has an exhaust pipe 9 extending laterally. The exhaust pipe 9 is intended for a tube of a vacuum apparatus to be connected to the suction housing 8.

[0049] The core drill 3 according to the present invention has a plurality of holes 16A, 16B, 16C, 16D and 16E along selected generatrixes of the core drill 3. The holes 16A-16E are provided along the length of the core drill 3. In the embodiment of the core drill 3 shown, five holes 16A-16E are provided along two generatrixes, where a first of the two and a second of the two generatrixes are placed diametrically opposite to each other. A most forward hole 16A (foremost hole 16A) along each of the generatrixes is placed close to the front end 4 of the core drill 3 and close to the abrasive elements 6. A most rearward hole 16E (rearmost hole 16E) along each of the generatrixes is placed close to the rear end 5 of the core drill 3. The remaining three holes 16B, 16C and 16D along each of the generatrixes, that is, the holes from and between the most forward hole 16A and toward the most rearward hole 16E, are placed so that there is an equidistant distance between centers of the holes 16A-16E along each of the generatrixes.

[0050] In other embodiments of a core drill according to the invention, more than four holes, or only two holes, may be placed along each of the generatrixes selected, and / or holes may be placed along only one generatrix or along more than two generatrixes of the core drill, and / or holes may be placed along a helix configuration or along another geometrical configuration along the core drill, as opposed to being placed in a linear configuration, as shown in the figure.

[0051] A cross-sectional area of the holes along the core drill 3 is selected depending on a cross- sectional area of the spacing between the outer surface of the core drill and the inner surface of the drill hole. Alternatively, or additionally a cross-sectional area of the holes along the core drill 3 is selected depending on a cross-sectional area of the spacing between the inside surface of the core drill 3 and the outer surface of the core.

[0052] The cross-sectional area of each of the holes are selected so that the cumulative cross-10 sectional area of all the holes along all generatrixes is between 80% and 120%, possibly between 90% and 110%, of the cross-sectional area of the spacing between the outer surface of the core drill and the inner surface of the drill hole, and / or of the cross-sectional area of the spacing between the inside surface of the core drill and the outer surface of the core of the drill hole.

[0053] Fig. 4 is a drawing showing the rear end 5 of one core drill 3. Circular orifices 14A and 14B are provided in the rear end 5. In the embodiment shown, the number of orifices in the rear end 5 are six larger circular orifices 14A and six smaller circular orifices 14B. Centers of each larger circular orifice 14A extend along part of a smaller circular circumference of the rear end 5. Centers of each of the smaller circular orifices 14B extend along a larger circular 20 circumference of the rear end 5, respectively. As mentioned, the orifices in the rear end 5 are for extracting dust, during drilling, from the interior of the core drill to the suction housing 8 (see fig. 3) intended for being attached on the rear end 5 of the core drill.

[0054] The figure also shows additional holes 17 along the cylindrical extension of the core drill 3, at the very top of the cylindrical surface, in immediate vicinity to the rear end 5 of the core drill 3. The holes 17 provide access for secondary air to enter at the rearmost part of the hollow interior of the core drill 3. Secondary air entering at the rearmost part of the hollow interior provides a kind of injector effect to dust at the rearmost part of the hollow interior.

[0055] The injector effect assists in all dust in the hollow interior being sucked out of the hollow interior through the openings 14A, 14B in the rear part 5 of the core drill 3, eliminating dust collecting along the inner surface of the circular extension in a space between the inner surface and the position of the holes in the rear part, especially when drilling non-vertically.

[0056] In the embodiment shown, two injector holes 17 are shown, situated diametrically opposite to each other. Depending on the diameter of the core drill, the length of the core drill and the position, shape and size of the holes in the rear part of the core drill, another number of injector holes may be provided, possibly four or more injector holes for core drills with relatively larger diameters and / or with fewer holes in the rear part of the core drill.

[0057] Fig. 5A and 5B are drawings showing an embodiment of a rear end 5 for a core drill and showing an embodiment of a core drill with such rear end, the rear end having dual functions.

[0058] The rear end 5 has a plurality of openings 14C, 14D for extracting dust from an interior of the core drill. The openings are provided circumferentially along the rear end surface. A plurality of first openings 14C are provided along a first circumference along the rear end 5. A plurality of second openings 14D are provided along a second circumference along the rear end 5, the first circumference extending at a first distance from a center of the core drill. The first distance is larger than a second distance along which the second circumference is extending.

[0059] Along an intermediate circumference between the first circumference along which the plurality of first openings extends and the second circumference along which the plurality of second openings extends, a number of collars 18 is provided. The collars 18 are bent towards the interior of the core drill, and the collars 18 extend a distance into a top of the interior of the core drill. The collars 18 thereby extend a distance between a plane surface of the rear end 5 facing the interior of the core drill and into the interior of the core drill. The collars 18 are intended for providing a stop between the interior of the core drill and the plane surface of the rear end 5, facing the interior of the core drill. During drilling, an initial part of the core of the cementitious building material being drilled may be displaced towards the rear end of the core drill due to the suction provided through the openings in the rear end 5, however, before the entire core to be drilled has been drilled. This may happen if the initial part of the core being drilled breaks off from the rest of the core to be drilled. The collars 18 prevent any initial part being broken off the rest of the core from blocking the openings 14A.14B, resulting in dust extraction in such situation being maintained.

[0060] The figure also shows a nut 15 extending from the rear 5 of the core drill. The nut 15 is intended for attaching the core drill to a drive shaft of a drilling machine or to a drive shaft extending in prolongation of a drilling machine and being driven by the drilling machine. A size of nut is M41 , requiring a relatively large wrench to tighten and loosen the nut.

[0061] Fig. 6 is a drawing of an embodiment of a core drill 3 according to the invention. The core drill 3 has abrasive segments 6 at a front end 4 of the core drill 3. Four holes 16A, 16B, 16C, 16D are provided along a first generatrix of the core drill 3. Other four holes (not shown) are provided along a second generatrix of the core drill 3, the second generatrix being diametrically opposite to the first generatrix shown in the photo. The entire axial length of the core drill 3, excluding an axial extension of the abrasive segments 6, is approximately 325 mm. The holes 16A-16D have an opening, at least part of which holes has a cross-section extending from an outermost cylindrical surface 19 of the core drill , through a wall of the core drill 3 and to a hollow interior of the core drill 3, see also Fig. 3.

[0062] A most forward hole 16A, closest to the abrasive elements 6, is provided about 20 mm from the front end 4 of the core drill 3, excluding the axial extension of the abrasive elements. A most rearward hole 16D, closest to the rear end 5 of the core drill 3, is provided about 315 mm from the front end 4 of the core drill 3, excluding the axial extension of the abrasive segments. A hole 16B next to the most forward hole 16A is provided about 120 mm from the front end 4 of the core drill 3. A hole 16C next to the most rearward hole 16D is provided about 220 mm from the front end 4 of the core drill 3. The other holes mentioned, however not shown, along the other diametrically opposite generatrix, are provided at same distances along the other generatrix.

[0063] In the embodiment shown, the core drill 3 is provided with circumferential grooves 7 extending circumferentially along the outer surface of the core drill 3. In the embodiment shown, the circumferential grooves 7 are provided for reducing frictional forces between the outermost surface 19 of the core drill 3 and the inner surface 11 (see Fig. 3) of the cementitious building material being drilled into. In other embodiments, the core drill is not provided with any grooves, or the core drill is provided with fewer grooves than the number of grooves shown in the figure. In general, holes are provided non-dependent of the position of any grooves. Each of the holes is provided at a certain distance from the front end and the rear end, respectively, of the core drill.

[0064] The core drill exhibits an outer surface 19, a major part of which outer surface extending linearly, parallel to a rotational axis of the core drill, and extending circularly around the rotational axis of the core drill. The outer surface has an outermost cylindrical surface 19, defined by part of the cylindrical surface extending the most outwards, as seen radially from the rotational axis of the core drill. The outermost cylindrical surface 19 is interrupted by the circumferential grooves 7. The circumferential grooves 7 extend along circles in planes perpendicular to the rotational axis A of the core drill. The circumferential grooves 7 constitute part of the outer surface but does not constitute part of the outermost cylindrical surface of the core drill.

[0065] In general, preferred embodiments of a core drill have a foremost hole along each of the axial extensions having a cross-sectional area being larger than a cross-sectional area of the rearmost hole, and where the cross-sectional area of the foremost hole and the cross-sectional area of the rearmost hole having a value depending on one of the following factors: a mutual axial distance between the foremost hole and the rearmost hole, a distance between the front end and the foremost hole in comparison with a distance between the foremost end and the rearmost hole.

[0066] Also, in general, preferred embodiment has at least one intermediate hole, the intermediate hole having a cross-sectional area smaller than the cross-sectional area of the foremost hole and being larger than the cross-sectional area of the rearmost hole, and where the cross- sectional area of the at least one intermediate hole having a value depending on one of the 20 following factors: a mutual axial distance between the foremost hole and the intermediate hole, a distance between the front end and the foremost hole in comparison with a distance between the foremost end and the intermediate hole.

[0067] Fig. 7A, 7B, 7C are drawings showing an embodiment of a core drill 3 with an insert plate 20 inserted into the interior of the core drill 3, close to the rear end 5 of the core drill 3. The insert plate 20 is inserted at a selected distance from the rear end 5 of the core drill 3. The insert plate 20 has a cross-sectional area being smaller than a cross-sectional area of the interior of the core drill 3 at the rear end 5 of the core drill 3. The insert plate 20 has six extensions 21 providing an intersection between the main part of the insert plate 20 and the interior circumference of the core drill 3, thereby holding the insert plate 20 in position laterally and longitudinally in relation to the interior circumference and the longitudinal extension of the core drill 3. The insert plate 20 having a cross-sectional area smaller than a cross-sectional area of the interior of the core drill provides an annular orifice 22 along the inner circumference of the interior of the core drill. When suction is provided at the rear end 5 of the core drill 1 , through the openings shown, suction of dust must pass the annular orifice 22. Thus, close to the rear end 5 of the core drill 3, suction of dust pass along the interior surface of the core drill 3 before dust enters the openings, closer to the axis of the core drill 3.

[0068] During drilling of some cementitious building material, like clay bricks, debris formed may comprise larger and heavier particles, apart from dust, than during drilling, e.g., concrete. During drilling of horizontal holes, the larger particles tend to collect along a lowermost part of the interior circumference of the core drill, due to gravity. The insert plate forces the vacuum towards the inner surface of the core drill, ensuring that not only dust, but also the larger and heavier particles collecting along the inner surface of the core drill 3, during drilling of a horizontal hole, are sucked from the interior of the core drill 3 through the annular orifice 22.

[0069] Along two generatrixes individually displaced 180 degrees in relation to each other, holes 16A-16K are provided along a linear extension. In Fig. 7A, six holes 16A, 16B, 16, 16D, 16E, 16F are arranged along the first generatrix of the two generatrixes. In Fig. 7B, five holes 16G, 16H, 161, 16J, 16K are arranged along the second generatrix of the two generatrixes. A foremost hole 16A, 16G is placed closest to the front end 4 of the core drill 3. A rearmost hole 16F.16K is placed closest to the rear end 5 of the core drill 3. Four holes 16B-16E and three other holes 16H-16J, respectively, are placed equidistant between the foremost hole 16A.16G and the rearmost hole 16F.16K.

[0070] In the embodiment shown, the holes along each of the two generatrixes are placed equidistant. However, the holes are placed with the foremost hole along the first generatrix relatively closer to the front end 4 of the core drill 3 compared to the foremost hole of the second generatrix placed relatively distant from the front end 4 of the core drill 3. In the embodiment shown, a cross-sectional area of the foremost hole along the one generatrix shown in Fig. 7A is larger than a cross-sectional area of the foremost hole along the second generatrix shown in Fig.7B. The cross-sectional area of each of the holes is selected depending on the distance between the hole in question and the front end 4 of the core drill 3.

[0071] In the embodiment shown, each of the holes along the two generatrixes have different cross- sectional areas. In other embodiments, all holes, or some of the holes along each genetrix have the same cross-sectional area. In the embodiment shown, the holes along each generatrix have a circular cross-section. In other embodiments, all the holes, or some of the holes, may have another cross-section than circular, as example, laterally oblong. In the embodiment shown, the rearmost hole 16F along the first generatrix shown in Fig. 7A has a diameter of 2.5 mm, and the foremost hole 16A along the first generatrix shown in Fig. 7A has a diameter of 5.0 mm. The four holes 16B, 16C, 16D, 16E placed along the first generatrix shown in Fig. 7A, between the rearmost hole 16F and the foremost hole 16A, have diameters of 3.0 mm, 3.5mm, 4.0 mm and 4.5 mm, as viewed along the first generatrix, and as viewed from the rearmost hole 16F.

[0072] In the embodiment shown, the rearmost hole 16K along the second generatrix shown in Fig. 7B has a diameter of 3.0 mm, and the foremost hole 16G along the second generatrix shown in Fig. 7B has a diameter of 5.0 mm. The three holes 16H, 161, 16J placed along the second generatrix shown in Fig. 7B, between the rearmost hole 16K and the foremost hole 16G, have diameters of 3.5mm, 4.0 mm and 4.5 mm, as viewed along the second generatrix, and as viewed from the rearmost hole 16K.

[0073] In other embodiments, the number of holes along each of the generatrixes may be another number than six and five, as example, less than six or five holes or more than six and five holes, possibly depending on the length of the core drill. In other embodiments, the six or five, or more or fewer, holes may be placed in other, non-equidistant distances between each other. In other embodiments, the holes may be placed along a helix or along another geometrically shaped line, as opposed to being placed along a linear line as shown in Fig. 7A and Fig. 7B.

[0074] In other embodiments, the holes may have other cross-sectional shapes than circular, as example oblong, either in an axial direction or in a circumferential direction. In other embodiments, each of the holes may have other cross-sectional areas depending on the shape of the holes and / or depending on the size of the holes. In other embodiments, some of the holes may have one shape, as example, circular, and other holes may have another shape, as example, oblong, and still other holes may have still other geometrical shapes.

[0075] A core drill 3 with a plurality of holes, and where the cross-sectional area of the holes decreases from the foremost hole and towards the rearmost hole, is because the holes are closer to the front end of the core drill where the dust is formed during drilling.

[0076] Fig. 8 is a drawing showing an embodiment of a core drill 3 with improved cooling of the abrasive segments 6 by increasing heat dissipation, during drilling, due to friction between the abrasive segments and the cementitious building material, the heat dissipation taking place from the abrasive segments 6 to the front end 4 of the cylindrical surface and further along the cylindrical surface of the core drill 3. In the embodiment shown, the entire cylindrical extension of the core drill is made as a layered structure made of a first material layer 3A with a first material at an external part of the cylindrical extension, a second material layer 3B with a second material at an intermediate part of the cylindrical extension and a third material layer 3C with a third material at an inner part of the cylindrical extension.

[0077] An outer diameter of the core drill 3 may, as example be any of between 50 mm and 400 mm. A material layer thickness of the first material layer 3A of the first material, as viewed in a radial extension, that is, sideways in the figure, may be 0.7 mm. A material layer thickness of the second material layer 3B of the second material, as viewed in the radial extension, that is, sideways in the figure, may be 0.7 mm. A material layer thickness of the third material layer 3C of the third material, as viewed in the radial extension, that is, sideways in the figure, may be 0.7 mm. Thus, the material layer thickness of the cylindrical extension of the core drill 3, as viewed in the radial extension, that is, sideways in the figure, is 2.1 mm.

[0078] Other material layer thicknesses of any of the first material layer, the second material layer and the third material layer, and thus the material layer thickness of the cylindrical extension, may be different to 0.7 mm and 2.1 mm, respectively. Also, the material layer thickness of the first material layer, the second material layer and the third material layer need not be the same, depending on a need for resistance towards wear and a need for thermal conductivity of the core drill.

[0079] The first material is a ferrous material, preferably a steel alloy, having a high resistance towards wear, however, possibly having a limited thermal conductivity compared to, as example, a copper alloy. The second material is a copper alloy, possibly copper itself, having an increased thermal conductivity, however, possibly having a low resistance towards wear compared to, as example, a steel alloy. The third material is also a ferrous material, preferably a steel alloy, having a high resistance towards wear, however, possibly also having a limited thermal conductivity compared to, as example, a copper alloy.

[0080] The first material layer 3A and the third material layer 3C, during drilling, are facing the inner surface of the drill hole and the core and / or dust and debris generated during drilling, respectively. Therefore, the first material layer 3A and the third material layer 3C are preferably made from materials with a high resistance toward wear. The second material layer 3B is layered between the first material layer 3A and the third material layer 3C and is neither in contact with the inner surface of the drill hole, nor in contact with the core and / or dust and debris generated during drilling. Therefore, the second material need not have a high resistance towards wear. The second material may then be chosen for other characteristics such as increased thermal conductivity such as a copper alloy or copper itself. The abrasive segments 6 of the core drill 3 are attached to an outer periphery of the cylindrical extension of the core drill 3. The abrasive segments 6 are in contact with all three material layers, that is, the first material layer 3A, the second material layer 3B and the third material layer 3C. During drilling, the abrasive segments 6 get heated due to friction between the abrasive segments 6 and the drill hole. Because the abrasive segments 6 are in contact with also the second material layer 3B having an increased thermal conductivity, a large amount of the heat generated in the abrasive segments 6 during drilling, is transferred to the second material layer 3B and dissipates from the outer periphery of the cylindrical extension further along the cylindrical extension. Most of the heat generated is dissipated to the second material layer 3B, and only a minor part of the heat generated is dissipated to the first material layer 3A and the third material layer 3C.

[0081] Because of the increased heat dissipation from the abrasive segments 6 to the cylindrical extension of the core drill 3, the abrasive segments 6 are less heated during drilling. The result is that the working lifetime of the abrasive segments 6 is increased, and that a risk of the abrasive segment 6 being damaged by heat generated during drilling is decreased.

[0082] In the embodiment shown, the core drill 3 is made of an external first material layer 3A with high resistance toward wear, an intermediate second material layer 3B with an increased thermal conductivity and an internal third material layer 3C, also with a high resistance towards wear. In an alternative embodiment, at least part of, or the entire, cylindrical extension of the core drill is made only by two material layers, an external first material layer 3A with high resistance toward wear, and an internal second material layer 3B with increased thermal conductivity.

[0083] Fig. 9A and Fig. 9B are drawings showing embodiments of core drills 3 preventing cracks being build up at a circumference at the front end 4 of the cylindrical extension of the core drill 3, due to dynamic forces during drilling, where the abrasive segments 6 are attached to the circumference. Crack prevention is obtained by eliminating geometrical discontinuities between the abrasive segments 6 and the circumference at which the abrasive segments 6 are attached to the front end 4 of the cylindrical extension of the core drill 3, along a circumferential direction along the cylindrical surface of the core drill 3.

[0084] In Fig. 9A, an interface between the abrasive segments 6, at positions where the abrasive segments 6 are attached to the cylindrical part of the core drill 3, is shaped with a curvature 23, the curvature 23 may be any shape as long as at least a transition between the abrasive segments 6 and the circumference of the cylindrical part of the core drill 3 does not exhibit a geometrical discontinuity, that is, does not exhibit an abrupt transition such as a 90 degrees transition between a lateral surface of the abrasive segments 6 and a circumferential extension.

[0085] In Fig. 9B, a transition between a lateral surface of the abrasive segments 6 and a circumferential extension is provided with a recess 24 positioned where, otherwise, a 90 degrees transition between a lateral surface of the abrasive segments 6 and an extension of the lowermost circumference. In the embodiment shown, the recess 24 has the shape of part of a circle with a selected radius. In alternative embodiments, the shape of the recess may be, e.g., an oval or other shapes exhibiting a curvature.

[0086] Fig. 10 is a sketch of one alternative embodiment of a configuration of segments of a core drill. The sketch shows, unfolded along a linear extension for the purpose of illustration, part of the circumference of a lower end 40 of the core drill. The figure shows five segments 6.

[0087] Each of the segments 6 are bonded to the lower end 40 of the cylindrical part of the core drill through a backing material 41 . The backing material 41 is made from a material with a higher heat conduction coefficient than a heat conduction coefficient of the material which the lower end 40 of the cylindrical part of the core drill is made of. The backing material 41 is preferably made of a sintered compound comprising steel and copper. Other compounds may be used, having a higher heat conduction coefficient than a heat conduction coefficient 30 of the material which the lower end 40 of the cylindrical part of the core drill is made of.

[0088] Each of the segments 6 has a laterally linear shape at a tip where each of the segments 6 engages the cementitious building material during drilling, and a rounded shape where each of the segments 6 engages the backing material 41. The rounded shape reduces, or possibly eliminates, a risk of cracking occurring in a transition between the segments 6 and the backing material 41. Crack prevention is generally obtained by eliminating geometrical discontinuities between the segments 6 and the backing material 41.

[0089] Also, a lateral extension along which the segments 6 engage the backing material 41 is longer than the extension of the segments at the tip of the segments, thereby providing a larger extension of engagement between the segments 6 and the lower end 40 of the cylindrical part of the core drill, via the backing material 41 . The larger extension provided results in a larger heat conduction surface between the segments 6 and the lower end 40 of the cylindrical part of the core drill, compared to if the segments 6 extended the same lateral extension in the figure as that of the tip of the segments 6.

[0090] The backing material made from a material with a higher heat conduction coefficient than a heat conduction coefficient of the material which the lower end of the cylindrical part of the core drill is made of has further advantages than the ones mentioned above. If part of the cylindrical extension is made partly from at least two materials, a first material having a first thermal conductivity, and a second material constituting at least part of an internal part of the cylindrical extension of the core drill, and having a second thermal conductivity, where the second thermal conductivity being higher than the first thermal conductivity, an improved heat conduction is obtained, initially from the segments to the cylindrical part of the core drill and subsequently from the cylindrical part of the core drill.

[0091] A backing material with a higher heat conduction coefficient than a heat conduction coefficient of the material which the lower end of the cylindrical part of the core drill is made of also has the further advantage of enabling attaching the segments to the lower end of the cylindrical part of the core drill by other methods than brazing as used in prior art core drills, possibly by laser welding or other methods not possible with prior art core drills. The abrasive segments of the core drill shown in Fig. 10 are preferably attached by laser welding.

[0092] Fig. 11 is a sketch of another alternative embodiment of a configuration of segments of a core drill. The sketch shows, unfolded along a linear extension for the purpose of illustration, part of the circumference of a lower end 40 of the core drill. The figure shows four segments 6 and shows intermediate parts 42, between the segments 6.

[0093] Each of the segments 6 has a rectangular shape and is supported along three edges, along a lateral extension and along each of the vertically extending side edges. Each segment 6 is positioned in a cavity at the lower end 40 of the core drill, with only the tip of the segments 6 not being supported by the cavity. Support is provided by part of the intermediate parts 42 extending as far as to the tip of the segments 6, and the lower end 40 of the core drill exhibiting the cavity providing support for three edges of the segments 6. Between the three supported edges of the segments 6 and the cavity of the core drill, a backing material 43 is provided, bonding the segments 6 to the lower 40 end of the core drill.

[0094] The backing material 43 is made from a material with a higher heat conduction coefficient than a heat conduction coefficient of the material which the lower end of the cylindrical part of the core drill is made of. The backing material 43 is preferably made of a sintered compound comprising steel and copper. Other compounds may be used, having a higher heat conduction coefficient than a heat conduction coefficient of the material which the lower end 40 and the intermediate parts 42 is made of.

[0095] Corners 44 of the cavities at the lower end 40 of the core drill are rounded. Rounded corners 44 reduce, or possibly eliminate, a risk of cracking occurring in a transition between the segments 6, the backing material 43 and the corners 44 of the cavities. Crack prevention is generally obtained by eliminating geometrical discontinuities between the laterally extending part of the cavities and the axially extending sides of the cavities.

[0096] Also, the extension along which the segments 6 engage the backing material 43 is longer than the extension of the segments only along a lateral extension, thereby providing a larger surface for heat exchange between the segments 6 and the lower end 40 of the core drill, via the backing material 43. The larger extension results in a larger heat conduction surface between the segments 6 and the lower end 40 of the cylindrical part of the core drill, compared to if the segments were bonded to the lower end 40 of the cylindrical part of the core drill, via the backing material 43, but only along a lateral extension of the segments 6.

[0097] Support of the segments 6 along the vertically extending side edges of the segments 6 also reduces vibrations possibly occurring during drilling. Each of the intermediate parts 42 has a recess 45. The recess 45 reduces the amount of material of the intermediate part 42 extending as far as to the tip of the segments 6. Each of the recess 45 in the intermediate part 43 reduces the amount of material of the intermediate parts 42 having to be worn away during drilling, apart from material of the segments 6 and apart from the part of the intermediate section 42 supporting vertically extending side edges of the segments 6. Also, each of the recesses 45 in the intermediate part 43 assists in dust formed during drilling being sucked from the front end 4, through the recesses 45 and into the interior of the core drill 3.

[0098] During drilling, the material of the intermediate part 42 supporting side edges of the segments 6 at the lower end 40 of the core drill will be worn down at the same pace as, or possibly at a faster pace than, the tip of the segments 6. An outermost cutting edge at the tip of the segments 6 will thereby always be exposed to the cementitious building material during drilling, because of part of the intermediate part 42 supporting the side edges of the segments 6 is worn at least as fast as, or faster than, the segments 6.

[0099] The backing material made from a material with a higher heat conduction coefficient than a heat conduction coefficient of the material which the lower end of the cylindrical part of the core drill is made of has further advantages than the ones mentioned above.

[0100] If part of the cylindrical extension is made partly from at least two materials, a first material 20 having a first thermal conductivity, and a second material constituting at least part of an internal part of the cylindrical extension of the core drill, and having a second thermal conductivity, where the second thermal conductivity being higher than the first thermal conductivity, an improved heat conduction is obtained, initially from the segments to the cylindrical part of the core drill and subsequently from the cylindrical part of the core drill. A backing material with a higher heat conduction coefficient than a heat conduction coefficient of the material which the lower end of the cylindrical part of the core drill is made of also has the further advantage of enabling attaching the segments to the lower end of the cylindrical part of the core drill by other methods than brazing as used in prior art core drills, possibly by laser welding or other methods not possible with prior art core drills. The abrasive segments of the core drill shown in Fig. 11 are preferably attached by brazing.

[0101] Fig. 12A and Fig. 12B are drawings showing an embodiment of a suction housing 8. The suction housing 8 has similarities to the suction housing 8 shown in Fig. 3. The suction housing 8 is preferably made of POM. Inside the suction housing 8, a drill fastening mechanism 15 is provided, being attached to the suction housing 8 along a roller bearing 25. The attachment mechanism 15 is for attaching a core drill to a drilling machine via the suction housing 8. The drilling machine will extend oppositely to the core drill (see Fig. 3) in relation to the suction housing 8.

[0102] The suction housing 8 has an exhaust pipe 9 extending laterally. The dust exhaust pipe 9 is intended for a pipe of a vacuum source to be connected to the suction housing 8. In the embodiment shown, the exhaust pipe 9 is placed tangentially to in the suction housing 8. Dust in the suction housing 8, having been extracted by a core drill, preferably by a core drill of the invention, but not necessarily by a core drill of the invention, through the orifices in the rear end of the core drill, is forced along a vortex inside the suction housing 8. Placing the exhaust pipe 9 tangentially provides a better flow of dust from the inside of the suction housing 8 to an inlet of the exhaust pipe and to the pipe of the vacuum source.

[0103] Fig. 13A and Fig. 13B are drawings showing a possible embodiment of a suction housing 8 for a core drill, either for a core drill according to the present invention or for a prior art core drill.

[0104] The suction housing 8 is divided into a first part 8A and a second part 8B. The first part 8A, constituting a main housing of the suction housing 8, has a rear end intended for being attached to a drilling machine and a front end intended for being attached to the second part 8B of the suction housing 8, and with a suction outlet 9 for attaching a vacuum source to the suction housing 8. The second part 8B has a rear end releasably attached to the front end of the first part 8A and a front end for being attached to a rear end of a core drill (see Fig. 11A and 11 B), alternatively for being attached to a rear end of a drill hole extender (see Fig. 14).

[0105] The first part 8A, at the rear end facing upwards in the drawings, is provided with a transition ring 30 intended for abutting an end face of an interface between the rear end of the suction housing 8 and a drilling machine so that the transition is substantially airtight. The transition ring 30 is fixed to the rear end of the first part 8B by a plurality of screws 31 . The transition ring 30 may be exchanged with another transition ring with another extension depending on the size and the shape of the interface toward the drilling machine.

[0106] The first part 8A is provided with the suction outlet 9. In the embodiment, the suction outlet 9 constitutes a separate part with a flange abutting a dust outlet opening of the first part 8A. The suction outlet 9 is attached to the first part 8A of the suction housing 8 in a releasable manner by a pair of snap-lugs 33 of the suction outlet 9. Only one snap-lug 33 is shown, the other snap-lug is placed oppositely to the one snap-lug. The snap-lugs 33 engage part of a circumference of a dust outlet opening in the first part 8A, and into which the suction outlet 9 is inserted. The dust outlet opening is not visible because of the suction outlet 9 being inserted.

[0107] When pressing the snap-lugs 33, the suction outlet 9 can be released from the first part 8A of the suction housing 8. When the suction outlet 9 is released from the first part 8A of the suction housing 8, the dust outlet opening in the housing is accessible. In the embodiment shown, the dust outlet opening is oblong, with a widest part of the dust outlet opening extending laterally along a lateral extension L. When the dust outlet opening is accessible, and because the widest part of the dust outlet opening extends laterally, even a relatively large head of wrench may be inserted through the dust outlet opening.

[0108] The wrench is used in a known manner when fastening or releasing the core drill (not shown) from the drilling machine, or when fastening or releasing a drive shaft for the core drill from the drilling machine. Because the suction outlet 9 is releasable from the housing of the first part 8A of the suction housing 8, and because the widest part of the dust outlet opening extends laterally, the head of a wrench may be inserted through the dust outlet opening without having to dissemble the suction housing 8 from the drilling machine.

[0109] The second part 8B of the suction housing 8, at the rear end facing upwards in the drawing, is provided with a plurality of snap-lugs 34 engaging a rim 35 of the front end of the first part 8A, thereby attaching the second part 8B to the first part 8A. The second part 8B, at the front end, is provided with a groove 36 with a selected shape of an inner circumference of the groove 36, preferably a circular shape, and with a selected inner extension of the groove 36. The inner circumference of the groove 36 is selected depending on a shape and extension of an outer circumference of a rear end of a core drill which the suction housing 8 is to be attached to.

[0110] The transition ring 30 of the first part 8A is capable of being exchanged with another transition ring depending on the shape and extension of an end face of the drilling machine used for drilling. The second part 8B with snap-lugs 34 makes the second part 8B capable of being exchanged with another second part depending on the shape and extension of a rear end of the core drill used for drilling. The possibility of exchanging the transition ring 30, and the possibility of exchanging the second part 8B, provides a possibility of using the first part 8A of the suction housing with any drilling machine together with any core drill, and not being limited to a suction housing only capable of being used with one or a limited number of drilling machine brands and being used with one or a limited number of core drills.

[0111] In one alternative embodiment, only the transition ring is capable of being exchanged for the suction housing being capable of being used with a large variety of drilling machines. In another alternative embodiment, only the second part is capable of being exchanged for the suction housing being capable of being used with a large variety of core drills.

[0112] Fig. 14A and Fig. 14B are drawings showing an embodiment of a core drill 3 with a relatively small cross-sectional area of 7850 mm2or smaller, which are core drills with an outer diameter of 100 mm or less for core drills having a circular outer circumference.

[0113] Circumferential openings 37 are provided at a part of the cylindrical circumference of the core drill 3 in close vicinity to the rear end 5 of the core drill 1. Size and shape of the circumferential openings 37 may be selected empirically, depending on the cross-sectional area of the core drill 3 and / or depending on the length of the cylindrical part of the core drill 3.

[0114] The circumferential openings 37 are provided as a substitution for openings in the rear end of the core drill, when the cross-sectional area of the drill is relatively small, so that there is no space at the rear end for providing openings because of a needed size of the fastening nut 15 for attaching the core drill to the drilling machine or to a shaft between the core drill and the drilling machine, the fastening nut 15 thus taking up most of the space at the rear end of the core drill, leaving no space for dust extraction openings in the rear end.

[0115] However, suction of dust, formed during drilling, through the circumferential openings 37 along the circumference of the core drill, instead of through openings in the rear end of the core drill, necessitates a suction housing capable of providing suction laterally to the outer circumference of the cylindrical part of the core drill, in close vicinity to the rear end.

[0116] The suction housing 8 shown in Fig. 13A and 13B is capable and suitable for providing suction laterally to the outer circumference of the cylindrical part of the core drill, in close vicinity to the rear end. A second part may be selected, possibly among various second part of the suction housing 8, with an internal shape end extension a little larger than the shape and extension of the rear end of the core drill which the suction housing 8 is to be used together with. Using the suction housing shown in Fig. 13A and 13B is accomplished by inserting a resilient sealing ring along an inside circumference of the second part 8B of the suction housing, and along a part of the inner circumference of the second part 8B close to the front end of the second part. The sealing ring has an inner circumference with an extension similar to, or a little smaller, than an extension of the outer circumference of the cylindrical part of the core drill, depending on the resilient properties of the sealing ring of the suction housing.

[0117] The front end of the second part of the suction housing is placed over the rear end 5 of the core drill 3 and is displaced a short distance forwards, towards the front end of the core drill, so that the inner circumference of the sealing ring abuts the outer circumference of the core drill, and so that the sealing ring abuts the outer circumference along part of the cylindrical part of the core drill past the circumference along which the openings are provided.

[0118] When a suction housing 8 as shown in Fig. 13A and 13B is attached to a core drill 3 as shown in Fig. 14A and 14B, the circumferential openings 37 are placed within the second part 8B of the suction housing 8. When suction is applied to the suction housing 8, dust formed during drilling is extracted through the circumferential openings 37 from the interior of the core drill 3 to the inside of the second part 8B of the suction housing 8, from the second part 8B into the first part 8A of the suction housing 8 and out through the suction outlet 9.

[0119] Along four generatrixes individually displaced 90 degrees in relation to each other, five holes are provided along a linear extension. In Fig. 14A, five holes 16A, 16B, 16C, 16D, 16E along a first of the four generatrixes are shown, and in Fig. 14B another five holes 16F, 16G, 16H, 161, 16J along a second of the four generatrixes are shown. A foremost hole 16A, 16F of the five holes is placed closest to the front end 4 of the core drill 3. A rearmost hole 16E, 16J of the five holes is placed closest to the rear end 5 of the core drill 3. Three other holes of the five holes are placed equidistant between the foremost hole and the rearmost hole.

[0120] In the embodiment shown, the five holes along each of the four genetrices are placed equidistant. However, the holes are placed with the foremost hole 16A along the first generatrix relatively closer to the front end 4 of the core drill 3 compared to the foremost hole 16F of the second generatrix placed relatively distant from the front end 4 of the core drill 3. In the embodiment shown, a cross-sectional area of the foremost hole 16A along the first generatrix shown in Fig. 14A is larger than a cross-sectional area of the foremost hole 16F along the second generatrix shown in Fig. 14B. The cross-sectional area of each of the holes is selected depending on the distance between the hole in question and the front end 4 of the core drill 3. In the embodiment shown, each of the holes along the four generatrixes, two of which are shown, have different cross-sectional areas. In other embodiments, all holes, or some of the holes along each genetrix have the same cross-sectional area. In the embodiment shown, the holes along each generatrix have a circular cross-section. In other embodiments, all the holes, or some of the holes, may have another cross-section than circular, as example, laterally oblong.

[0121] In the embodiment shown, the rearmost hole 16E along the first generatrix shown in FIG. 14A has a diameter of 3.0 mm, and the foremost hole 16A along the first generatrix shown in Fig. 14A has a diameter of 5.0 mm. The three holes 16B, 16C, 16D placed along the first generatrix shown in Fig. 14A, between the rearmost hole 16E and the foremost hole 16A, have diameters of 3.5 mm, 4.0 mm and 4.5 mm, as viewed along the generatrixes, and as viewed from the rearmost hole 16E.

[0122] In other embodiments, the number of holes along each of the generatrixes may be another number than five, as example, less than five holes or more than five holes, possibly depending on the length of the core drill. In other embodiments, the five, or more or fewer, holes may be placed in other, non-equidistant distances between each other. In other embodiments, the holes may be placed along a helix or along another geometrically shaped line, as opposed to being placed along a linear line as shown in Fig. 14A and Fig. 14B.

[0123] In other embodiments, the holes may have other cross-sectional areas than circular, as example oblong, either in an axial direction or in a circumferential direction. In other embodiments, each of the holes may have other cross-sectional areas depending on the shape of the holes and / or depending on the size of the holes. In other embodiments, some of the holes may have one shape, as example, circular, and other holes may have another shape, as example, oblong, and other holes may have still other geometrical shapes.

[0124] A core drill 3 with a plurality of holes, and where the cross-sectional areas of the holes decreases from the foremost hole towards the rearmost hole, is used because the holes with larger cross-sectional area are closer to the front end 4 of the core drill 3, where the dust is formed during drilling.

[0125] Fig. 15 is a drawing showing an embodiment of a drill hole extender 38 used when drilling very deep holes, where the longitudinal extension of the core drill itself is not long enough to reach all the way through the extension of the hole to be drilled. The drill hole extender 38 is intended for providing an extension between a suction housing, as example, the suction housing as shown in the figure, and a core drill being operated by a drilling machine along a drive shaft extending through the suction housing and through the drill hole extender 38 to the core drill 3.

[0126] In the embodiment shown, the drill hole extender 38 has a front end intended for abutting the rear end of a core drill and a rear end attached to a suction housing. In the embodiment shown, the suction housing is of the type shown in Fig. 11A and 11 B. However, the rear end of the drill hole extender 38 may be attached to other suction housing than the one shown in Fig. 11A and 11 B as example, attached to a suction housing as shown in Fig. 15 or attached to prior art suction housing.

[0127] Attachment of the rear end of the drill hole extender 38 is provided in a similar manner as the core drill shown in Fig. 11 A and 11 B is attached to the second part of the suction housing, that is, the front end of the second part of the suction housing is placed over the rear end of the drill hole extender 38 and is displaced a short distance forwards, towards the front end of the drill hole extender 38 so that an inner circumference of the second part of the suction housing abuts an outer circumference along the rear end of the drill hole extender 38.

[0128] When suction is applied to the suction housing, the dust formed during drilling is extracted firstly through the interior of the core drill itself (not shown), through openings in the rear end of the core drill and into the drill hole extender 38, through the drill hole extender 38 from the openings in the rear end of the core drill and to the inside of the second part of the suction housing, into the first part of the suction housing and out through the suction outlet 9.

[0129] Fig. 16 is a drawing of an alternative embodiment of a suction outlet 9 of a suction housing 8. A second part of the suction housing is not attached to the first part of the suction housing.

[0130] In the embodiment, the suction outlet 9 is attached to the first part 8A of the suction housing 8 in a releasable manner by snap-lugs of the suction outlet 9. The snap-lugs engage part of a circumference of a dust outlet opening in the housing of the first part 8A, into which the suction outlet 9 is inserted. The dust outlet opening is not visible because of the suction outlet 9 being inserted.

[0131] By manually pulling the snap-lug, the suction outlet 9 can be released from the first part 8A of the suction housing 8. When the suction outlet 9 is released from the first part 8A, the dust extraction opening in the housing is accessible. In the embodiment shown, the dust extraction opening is oblong, with a widest part of the dust extraction opening extending laterally. When the dust extraction opening is accessible, and because the widest part of the dust extraction opening extends laterally, a head of wrench may be inserted through the dust extraction opening. The wrench is used in a known manner when fastening or releasing the core drill (not shown) from the drilling machine, or when fastening or releasing a drive shaft for the core drill from the drilling machine. Because the outlet is releasable from the housing of the first part 8A of the suction housing 8, and because the widest part of the dust extraction opening extends laterally, the head of a wrench may be inserted through the dust extraction opening without having to dissemble the suction housing 8 from the drilling machine.

[0132] Fig. 17 is a drawing of yet an alternative embodiment of a suction outlet 9 of a suction housing 8. The suction housing 8 is divided into a first part 8A and a second part 8B and the second part is attached to the first part 8A of the suction housing 8.

[0133] In the embodiment, the suction outlet 9 is an integrate part of the first part of the suction housing 8, that is, the suction outlet 9 is not releasable from the first part of the suction housing 8.

[0134] The suction outlet 9 has a cross-sectional area which may, and often will, be larger than a cross-sectional area of a suction hose of a vacuum source. If that is the case, an adapter may be inserted between the suction outlet 9 and the suction hose of the vacuum source.

[0135] In the embodiment shown, at one end in the interface between the first part 8A of the suction housing 8 and the suction outlet 9, the suction outlet 9 is oblong, alternatively circular, and at another end, where a vacuum hose of a vacuum source, alternatively an adapter, is to be fitted, the suction outlet is circular. Because a widest part of the suction outlet 9, at the interface between the suction outlet 9 and the first part 8A of the suction housing, is oblong and extends laterally, a head of wrench may be inserted through the suction outlet 9, from the other end and through the one end.

[0136] The wrench is used in a known manner when fastening or releasing the core drill (not shown) from the drilling machine, or when fastening or releasing a drive shaft for the core drill from the drilling machine. Because the suction outlet 9 is releasable from the first part 8A of the suction housing 8, and because the widest part of the dust extraction opening extends laterally, the head of a wrench may be inserted through the dust extraction opening without having to dissemble the suction housing 8 from the drilling machine.

[0137] Fig. 18 is a drawing showing an embodiment of a suction housing 8 for a large diameter core drill, that is, a core drill having a diameter of more than 400 mm. The suction housing 8 has a main part covering the rear end of the core drill, when the suction housing 8 is abutting the rear end of the core drill. Ribs 39 are provided for increasing rigidity and structural integrity of a large size the suction housing. The suction housing 8 has a suction outlet 9 for the dust and possible small size debris sucked out the openings in the rear end of the core drill. Fig. 19A, Fig. 19B and Fig. 19C show a first embodiment for an elongated extension 38 (drill hole extender) when drilling deep holes, deeper than a length of the core drill 3 itself (see also Fig. 15). The elongated extension 38 extends between the suction housing 8 and the rear end 5 of the core drill 3. At the front end 4 of the core drill 3, the abrasive segments 6 are provided.

[0138] The figures show a suction housing 8 with a suction outlet 9. Fig. 19B, a cross-sectional view, shows a drive shaft 46 for the core drill 3. The drive shaft 46 for the core drill 3 has a drive shaft extension 47 extending from the suction housing 8 to the rear end 5 of the core drill 3. Between the drive shaft extension 47 and the rear end 5 of the core drill 3, a connector 48 is provided, enabling driving of the core drill 3 in an extended position in relation to the suction housing 8. In the embodiment shown, a first diameter D1 of the core drill 3 is larger than a second diameter D2 of the drive shaft extension 47. The second diameter D2 of the drive shaft extension 47 may be between 100 mm and 110 mm, suitable for most drilling machines for core drilling. In the embodiment shown, the drive shaft extension 47 is a pipelike configuration.

[0139] A cylindrical extension sleeve 38 is provided between the suction housing 8 and the rear end 5 of the core drill 3, the extension sleeve 38 encapsulating the drive shaft extension 47. The extension sleeve 38 has a flange 49 towards a bottom circumference of the suction housing 8. Dust formed during drilling may be extracted from the interior of the core drill 3, through holes 14 in the rear end 5 of the core drill 3, along a spacing S between an outer surface of the drive shaft extension 47 and an inner surface of the extension sleeve 38 and into the interior of the suction housing 8 and out through the suction outlet 9 of the suction housing 8.

[0140] In the embodiment shown, the first diameter D1 of the core drill 3 is also larger than a third diameter D3 of the extension sleeve 38. The holes 14 in the rear end 5 of the core drill 3 are positioned in the rear end 5 of the core drill 3 so that the holes 14, seen along a diameter of the core drill 3, in the plane of Fig. 19B, and in an axial direction of the core drill 3, extend between the interior of the core drill 3 and into the spacing S between the drive shaft extension 47 and the extension sleeve 38. Dust formed during drilling may then be extracted from the interior of the core drill 3 into the spacing S between the drive shaft extension 47 and the extension sleeve 38, through holes (not shown) in the flange 49, to the interior of the suction housing 8 and to the suction outlet 9 of the suction housing 8.

[0141] Between a bottom circumference of the suction housing 8 and the flange 49 between the bottom circumference of the suction housing 8 and the extension sleeve 38, a first ring-shaped seal 51 is provided, providing a dust-proof seal between the bottom circumference of the suction housing 8, not rotating during drilling, and the flange 49, rotating during drilling, because of the flange 49 being attached to extension sleeve 38 and the extension sleeve 38 being attached to the rear end 5 of the core drill 3. The first ring-shaped seal 51 provides a vacuum-proof seal between the bottom circumference of the suction housing 8 and the flange 49, when vacuum is present inside the suction housing 8.

[0142] In the embodiment shown, between the suction housing 8 and the drive shaft 46 a roller bearing 52 is provided. Between the roller bearing 52 and the interior of the suction housing 8, a second ring-shaped seal 53 is provided. During drilling, the second ring-shaped seal 53 prevents dust inside the interior of the suction housing 8 from accessing the roller bearing 52. However, if no precautions are made, a lifetime of the second ring-shaped seal 53 is limited due to abrasive action on the second ring-shaped seal 53 of dust formed during drilling, sucked from the interior of the core drill 3 and into the interior of the suction housing 8.

[0143] To possibly avoid dust formed during drilling and sucked into the interior of the suction housing 8 from limiting the lifetime of the second ring-shaped seal 53, the drive shaft 46 is provided with an air-channel 54, preferably one circumferential channel extending circumferentially in the drive shaft 46, between an inner surface of the drive shaft 46, where a drive shaft of a drilling machine is to be connected to the drive shaft 46, and an outer surface of the drive shaft, along which outer surface an inner ring of the roller bearing 52 is attached.

[0144] The air-channel 54 extends from a top of the drive shaft 46, from an inlet 54A of the air-channel, the inlet 54A having access to the surroundings of the drive shaft 46 and of the suction housing 8. The air-channel 54 extends from the inlet 54A along and inside the drive shaft 46. When the air-channel reaches a plane P corresponding to a lower surface of the second ringshaped seal 53, the lower surface having access to the interior of the suction housing 8, the air-channel 54 diverts to an extension along the plane P towards an outlet 54B of the airchannel 54, the outlet 54B having access to the interior of the suction housing 8. The outlet 54B of the air-channel 54 is positioned where the lower surface of the second ring-shaped seal 53 extends along the plane P inside of the suction housing 8 is positioned.

[0145] The inlet 54A of the air-channel 54 allows air from the surroundings to enter the air-channel 54, by the suction force applied in the interior of the suction housing 8, and the air-channel 54 allows the air from the surroundings to enter the interior of the suction housing 8 through the outlet 54B of the air-channel 54. Because the air from the surroundings is let out in a direction along the plane P, where the lower surface of the second ring-shaped seal 53 is positioned, the second ring-shaped seal 53 will always, when a suction force is applied to the interior of the suction housing 8, be subjected to air from the surroundings. The air from the surroundings does not have any dust from the drilling. Therefore, the air from the surroundings, when let out along the plane P of the lower surface of the second ring-shaped seal 53, will blow away dust from the second ring-shaped seal 53, dust which is present in the interior of the suction housing 8 during drilling. The lifetime of the second ringshaped seal 53 is significantly increased compared to if the air-channel 54 is not provided.

[0146] Fig. 20A, Fig. 20B and Fig. 20C show a first embodiment for an elongated extension when drilling deep holes, deeper than a length of the core drill 3 itself. The figures show a suction housing 8 with a suction outlet 9 extending sideways. A drive shaft 46 of the core drill 3 has an extension 47 extending from the suction housing 8 to the rear end 5 of the core drill 3.

[0147] Between the drive shaft extension 47 and the rear end 5 of the core drill 3, a connector 48 is provided, enabling driving of the core drill 3 in an extended position in relation to the suction housing 8. In the embodiment shown, a first diameter D1 of the core drill 3 is larger than a second diameter D2 of the drive shaft extension 47. The second diameter D2 of the drive shaft extension 47 may be between 100 mm and 110 mm, which is suitable for most drilling machines for core drilling. In the embodiment shown, the drive shaft extension 47 is a pipelike configuration.

[0148] In the embodiment shown, an extension sleeve (see Fig. 19A-19C) is not provided between the suction housing 8 and the rear end 5 of the core drill 3. Instead of an extension sleeve, a dust extraction insert 55 is provided, forming a transition between a rear end of the drive shaft extension 47 and the interior of the suction housing 8. The dust extraction insert 55 is provided with holes 56. Dust formed during drilling may be extracted from the interior of the core drill 3 through the interior of the drive shaft extension 47, through the holes 56 in the dust extraction insert 55 and into the suction housing 8 and out through the outlet 9.

[0149] In the embodiment shown, the first diameter D1 of the core drill 3 is the same as, or smaller than, a second diameter D2 of the drive shaft extension 47. Therefore, no holes are provided in the rear end 5 of the core drill 3 as such holes would have no connection to the interior of the suction housing 8. As mentioned, dust formed during drilling is therefore extracted through the interior of the core drill 3, through the drive shaft extension 47 into the interior of the suction housing 8 and to the suction outlet 9 via the holes 56 in the dust extraction insert 55.

[0150] Between a bottom circumference of the suction housing 8 and a top flange 49 of the extension sleeve 38, a first ring-shaped seal 51 is provided, providing a dust-proof seal between the bottom circumference of the suction housing 8, not rotating during drilling, and the top flange 51 of the drive shaft extension 47, rotating during drilling because of the drive shaft extension 47 being attached to the rear end 5 of the core drill 3. The first ring-shaped seal 51 provides a vacuum-proof seal between the bottom circumference of the suction housing 8 and the flange 49, when vacuum is present inside the suction housing 8.

[0151] In the embodiment shown, between the suction housing 8 and the drive shaft 46 a roller bearing 52 is provided. Between the roller bearing 52 and the interior of the suction housing 8, a second ring-shaped seal 53 is provided. During drilling, the second ring-shaped seal 53 prevents dust inside the interior of the suction housing 8 from accessing the roller bearing 52.

[0152] However, if no precautions are made, a lifetime of the second ring-shaped seal 53 is limited due to abrasive action on the second ring-shaped seal 53 of dust formed during drilling, sucked from the interior of the core drill 3 and into the interior of the suction housing 8.

[0153] To possibly avoid dust formed during drilling and sucked into the interior of the suction housing 8 from limiting the lifetime of the second ring-shaped seal 53, the drive shaft 46 is provided with an air-channel 54, preferably one circumferential channel extending circumferentially in the drive shaft 46, between an inner surface of the drive shaft 46 where a drive shaft of a drilling machine is to be connected to the drive shaft 46, and an outer surface of the drive shaft 46, along which outer surface an inner ring of the roller bearing 52 is attached.

[0154] The air-channel 54 extends from a top of the drive shaft 46, from an inlet 54A of the air-channel, the inlet 54A having access to the surroundings of the drive shaft 46 and of the suction housing 8. The air-channel 54 extends from the inlet 54A along and inside the drive shaft 46. When the air-channel 54 reaches a plane P corresponding to a lower surface of the second ring-shaped seal 53, the lower surface having access to the interior of the suction housing, the air-channel 54 diverts to an extension along the plane P towards an outlet 54B of the airchannel 54, the outlet 54B having access to the interior of the suction housing 8. The outlet 54B of the air-channel 54 is positioned where the lower surface of the second ring-shaped seal 53 extends along the plane P inside of the suction housing 8 is positioned.

[0155] The inlet 54A of the air-channel 54 allows air from the surroundings to enter the air-channel 54, by the suction force applied in the interior of the suction housing 8, and the air-channel 54 allows the air from the surroundings to enter the interior of the suction housing 8 through the outlet 54B of the air-channel 54. Because the air from the surroundings is let out in a direction along the plane P, where the lower surface of the second ring-shaped seal 53 is positioned, the second ring-shaped seal 53 will always, when a suction force is applied to the interior of the suction housing 8, be subjected to air from the surroundings.

[0156] The air from the surroundings does not have any dust from the drilling. Therefore, the air from the surroundings, when let out along the plane P of the lower surface of the second ring-shaped seal 53, will blow away dust from the second ring-shaped seal 53, dust which is present in the interior of the suction housing 8 during drilling. The lifetime of the second ringshaped seal 53 is significantly increased compared to if the air-channel 54 is not provided.

Claims

Claims1. Core drill (3) for drilling in cementitious building material, the core drill (3) being cylindrical with an outer diameter between 50 mm and 1.250 mm and a length of an outermost cylindrical extension being at least 300 mm parallel to a rotational axis (A) of the core drill (3), the outermost cylindrical extension defining an outermost cylindrical surface of the core drill (3),■ the core drill (3) having a front end (4) provided with a plurality of abrasive segments (6) and a rear end (5), opposite to the front end (4), having a fastening mechanism (15) for fastening the core drill (3) to a drilling machine, the outermost cylindrical extension extending between the front end (4) and the rear end (5) of the core drill (3), the outermost cylindrical extension having one radius from the rotational axis (A) of the core drill (3),■ the core drill (3) possibly having a plurality of grooves, each groove extending along a plane perpendicular to the rotational axis (A) of the core drill (3), each of the grooves extending along a cylindrical extension having a radius from the rotational axis of the core drill being smaller than the radius of the cylindrical extension of the outermost cylindrical surface,■ the rear end (5) of the core drill (3) having a plurality of orifices (14), and the cylindrical extension having a plurality of holes (16A-16K) placed along the outer cylindrical extension along at least one axial extensions along the cylindrical part of the core drill (3), the at least one axial extension being one of a linear extension parallel to the axial extension and a non-linear extension oblique to the axial extension, and■ the plurality of holes comprising at least two holes placed along the at least one axial extension along the cylindrical part of the core drill (3), the at least two holes along being a foremost hole placed more towards the front end (4) of the core drill (3) than a rearmost hole, and a rearmost hole placed more towards the rear end (5) of the core drill (3) than the foremost hole, and■ the plurality of holes along the cylindrical surface having an opening in the cylindrical extension, each opening of the holes having a cross-sectional area, at least part of the cross-sectional area of each of the holes extending along one of the outermost cylindrical surface and a groove, with the proviso of the core drill having at least one groove.

2. Core drill according to claim 1 , where the plurality of holes comprises at least three holes provided along each of the at least two axial extensions along the cylindrical extension of the core drill (3), the at least three holes being a foremost hole towards the front end (4)of the core drill (3) and a rearmost hole towards the rear end of the core drill (3) and at least one intermediate hole between the foremost hole and the rearmost hole,■ each of the at least three holes along the cylindrical extension having an opening facing the outer cylindrical extension, and each opening of the holes along the cylindrical extension having a cross-sectional area, at least part of the cross-sectional area of each of the holes extending along one of the outermost cylindrical surface and a groove, with the proviso of the core drill having at least one groove.

3. Core drill according to any of the preceding claims, where the plurality of holes extend along an axial extension between 10 mm from the front end (4) and 10 mm from the rear end (5), and with the proviso of at least one intermediate hole being provided, the at least one intermediate hole being placed so that substantially a same distance is established between neighboring holes along the axial extension, from the foremost hole and the subsequent holes along the cylindrical extension and up to the rearmost hole.

4. Core drill according to any of the preceding claims, where a plurality of injector holes is provided along the outermost cylindrical surface, the injector holes (17) provided at a position along the outermost cylindrical surface so that an opening of the injector holes (17) face a hollow interior of the core drill, and that the opening of the injector holes (17) is between 0 mm and 10 mm from the rear end (5) of the core drill (3).

5. Core drill according to any of the preceding claims, where holes extend along the cylindrical extension along at least two axial extensions, where along one axial extension one plurality of holes extend, and where along another axial extension another plurality of holes extend, where the other plurality of holes count the same number of holes, or count another number of holes, than the one plurality of holes, and where the one axial extension is either linear or non-linear, and where the other axial extension is either linear or non-linear.

6. Core drill according to any of the preceding claims, where the plurality of holes placed along the cylindrical extension are between 2 holes and 10 holes along one axial extension, and between 2 holes and 10 holes along another axial extension, and where a foremost of the holes have a center between 5 mm and 50 mm from the front end (4), where a rearmost hole of the holes have a center between 5 mm and 50 mm from the rear end (5), and where intermediate holes along each of the axial extension are positioned substantially equidistant between the foremost hole and the rearmost hole with a mutual distance between the intermediate holes being between 30 mm and 100 mm.

7. Core drill assembly (DA) according to any of the preceding claims, a cumulative cross- sectional area of the holes along the axial cylindrical extension is between 70% and 130%, possibly between 80% and 120%, possibly between 90% and 110%, of a cross- sectional area of a spacing between an outside cylindrical extension of the core drill (3) and an inside cylindrical extension of a drill hole being drilled by the core drill.

8. Core drill according to any of the preceding claims, the rear end (5) of the core drill (3) having a plurality of fins extending from one end of the fins proximate to the rear end (5) and a another end of the fins distant from the rear end (5) of the core drill, the fins extending into a hollow interior of the core drill, the extension of the fins into the hollow interior of the core drill being between 3 mm and 30 mm, depending on a length of the cylindrical extension of the core drill (3) and / or depending on a cross-sectional area of the cylindrical extension of the core drill (3).

9. Core drill according to any of the previous claims, where an insert plate is provided inside the hollow interior of the core drill (3), the insert plate having a main extension and having lateral extensions extending from the main extension, the lateral extensions extending between the main extension of the insert plate and an inner circumference of the hollow interior of the core drill, and where annular orifices are provided between the main extension and the inner circumference of the core drill, the annular orifices provided between the main extension and the lateral extensions, the annular orifices providing access between one part of the hollow interior facing towards the foremost end of the core drill, and another part of the inner hollow facing the rearmost end of the core drill.

10. Core drill for drilling in cementitious building material, the core drill (3) being cylindrical with an outer diameter between 50 mm and 1.250 mm and a length of an outermost cylindrical extension being at least 300 mm parallel to a rotational axis of the core drill, the outermost cylindrical extension defining an outermost cylindrical surface of the core drill (3),■ the core drill (3) having a front end (4) provided with a plurality of abrasive segments (6) and a rear end (5), opposite to the front end (4), having a fastening mechanism for fastening the core drill (3) to a drilling machine,■ the outermost surface having a major axial and circumferential extension and having an outer cylindrical surface extending between the front end (4) and the rear end (5), the outer cylindrical surface, along a major surface area of the outer cylindrical surface, having one and the same axial and circumferential extension,■ where at least a foremost part, preferably all part, of the cylindrical extension of the core drill comprises a first material constituting at least part of an external part of the cylindrical extension of the core drill, and having a first thermal conductivity, and■ where at least the foremost part, preferably all part, of the cylindrical extension of the core drill comprises a second material constituting at least part of an internal part of the cylindrical extension of the core drill, and having a second thermal conductivity,■ the second thermal conductivity being higher than the first thermal conductivity, preferably the second thermal conductivity being at least two times higher than the first thermal conductivity, preferably being at least three times higher than the first thermal conductivity, possibly being at least five times higher than the first thermal conductivity.11 . Core drill according to claim 10, the first material being a steel alloy and the second material being a non-steel alloy, possibly being an aluminum alloy, or possibly being a copper alloy, or possibly being a non-metal material.

12. Core drill according to claim 10 or 11 , where■ at least the foremost part, preferably all part, of the cylindrical extension of core drill comprises the second material constituting at least part of an internal part of the cylindrical extension of the core drill, and having a second scratch hardness,■ at least the foremost part, preferably all part, of the cylindrical extension of core drill comprises a third material constituting at least part of an innermost part of the cylindrical extension of the core drill, and having a third scratch hardness,■ the third scratch hardness being higher than the second scratch hardness, preferably the third scratch hardness being at least two times higher than the second scratch hardness.

13. Core drill according to claim 12, the third material being a steel alloy and the second material being a non-steel alloy, possibly being an aluminum alloy, or possibly being a copper alloy, or possibly being a non-metal material.

14. Core drill according to any of claims 10-13, where the abrasive segments are provided along a periphery at the foremost end of the cylindrical extension of the core drill, and where an intersection between each of the abrasive segments and the periphery of the cylindrical extension of the core drill is void of an intermediate material between a diamond-holding part of the abrasive segments and the material of the periphery of the cylindrical extension of the core drill.

15. Core drill according to any of the preceding claims, the core drill (3) having an outer surface with a major axial and circumferential extension having an outer cylindrical surface extending between the front end (4) and the rear end (5),■ the outer cylindrical surface, along a major surface area of the outer cylindrical surface, having one and the same axial and circumferential extension, and the abrasive segments provided along a periphery at the foremost end of the cylindrical extension of the core drill, and■ an intersection between each of the abrasive segments and the periphery of the cylindrical extension of the core drill made from a material having a thermal conductivity larger than a thermal conductivity of the material of the periphery of the cylindrical extension of the core drill.

16. Core drill according to any of the preceding claims, the core drill (3) having an outer surface with a major axial and circumferential extension having an outer cylindrical surface extending between the front end (4) and the rear end (5),■ the outer cylindrical surface, along a major surface area of the outer cylindrical surface, having one and the same axial and circumferential extension, and the abrasive segments provided along a periphery at the foremost end of the cylindrical extension of the core drill, and■ an intersection between each of the abrasive segments and the periphery of the cylindrical extension of the core drill being void of a geometric discontinuity, the intersection exhibiting part of at least one of the following shapes: an oval or a circle, with a smallest radius of at least 1 mm.

17. Core drill for drilling in cementitious building material, the core drill (3) being cylindrical with an outer diameter between 50 mm and 1.250 mm and a length of an outermost cylindrical extension being at least 300 mm, the outermost cylindrical extension defining an outermost cylindrical surface of the core drill (3),■ the core drill (3) having a front end (4) provided with a plurality of abrasive segments (6) and a rear end (5), opposite to the front end (4), having a fastening mechanism for fastening the core drill (3) to a drilling machine,■ the core drill (3) having an outer surface with a major axial and circumferential extension having an outer cylindrical surface extending between the front end (4) and the rear end (5), the outer cylindrical surface, along a major surface area of the outer cylindrical surface, having one and the same axial and circumferential extension, wherethe abrasive segments provided along a periphery at the foremost end of the cylindrical extension of the core drill, and■ an intersection between each of the abrasive segments and the periphery of the cylindrical extension of the core drill being void of a geometric discontinuity, the intersection exhibiting part of at least one of the following shapes: an oval with a smallest radius of at least 1 mm.

18. Core drill according to any of the preceding claims, where the abrasive segments are positioned along the circumference of the foremost end of the cylindrical extension of the core drill, and where a distance between a center position of neighboring abrasive segments, as viewed in a circumferential direction along the circumference of the foremost end, has a value being an integer, when the distance is divided by a number approximately being 3.14, or at least when divided by a number between 3.0 and 3.3.

19. Core drill assembly having a core drill (3) according to any of claims 1-18 and having a suction housing (8) connected to the rear end (5) of the core drill (3),■ the suction housing (8) having an exhaust pipe (9) extending laterally in relation to the rotational axis of the core drill (3), when the suction housing (8) is connected to the rear end (5) of the core drill (3), and the exhaust pipe (9) configured for connecting a vacuum source to the suction housing (8),■ an insert ring (17) inserted inside an internal circumference (18) of a part of the suction housing (8) at a position where part of the suction housing (8) is to be connected to the rear end (5) of the core drill,■ the insert ring (17) having an outer circumference (19) with an extension corresponding to an extension of the inner circumference of the suction housing, and■ the insert ring (17) having an inner circumference (20) with an extension corresponding to an extension of an outer circumference of the rear end (5) of the core drill (3).

20. Core drill assembly having a core drill (3) according to any of claims 1-18 and having a suction housing (8) connected to the rear end (5) of the core drill (3),■ the suction housing (8) having an exhaust pipe (9) extending laterally in relation to the rotational axis of the core drill (3), when the suction housing (8) is connected to the rear end (5) of the core drill (3), and the exhaust pipe (9) configured for connecting a vacuum source to the suction housing (8),■ the suction housing (8) comprising a first part (8A) and a second part (8B) attached to the first part of the suction housing (8), the second part constituting an interfacebetween the first part (8A) of the suction housing (8) the rear end (5) of the core drill (3), the second part (8B) having an inner circumference with an extension corresponding to an extension of a circumference of the first part (8A) of the suction housing, and the second part (8B) having an inner circumference with an extension corresponding to an extension of an outer circumference of the rear end (5) of the core drill (3).

21. Core drill assembly having a core drill (3) according to any of claims 1-18 and having a suction housing (8) connected to the rear end (5) of the core drill (3),■ the suction housing (8) having an exhaust pipe (9) extending laterally in relation to the rotational axis of the core drill (3), when the suction housing (8) is connected to the rear end (5) of the core drill (3), and the exhaust pipe (9) configured for connecting a vacuum source to the suction housing (8), and■ the exhaust pipe (9) attached to a circumference of the suction housing (8) at a position between where the suction housing (8) is to be facing the rear end (5) of the core drill (3) and a rear end of the suction housing (8),■ the exhaust pipe (9) having a lateral dimension along an inside opening of the exhaust pipe (9), seen along a plane perpendicular to the rotational axis of the core drill, when the core drill is connected to the suction housing, the lateral extension of the exhaust pipe being at least 50 mm.

22. Core drill assembly having a core drill (3) according to any of claims 1-18 and having a suction housing (8) attached to the rear end (5) of the core drill (3),■ the core drill assembly comprising a drive shaft extension (47) extending between a drive shaft (46) and a rear end of the core drill (3), the drive shaft (46) at least partly extending inside the suction housing (8),■ the drive shaft extension extending between a flange abutting an outer circumference of the suction housing and a rear end of the core drill (3), the outer circumference extending toward the rear end of the core drill (3),■ the drive shaft extension having a hollow interior extending from a distant end of the drive shaft (46) towards the rear end of the core drill to a proximate end of the drive shaft extension (47) towards the suction housing,■ the drive shaft extension having at least one hole at the proximate end of the drive shaft extension, the at least one hole providing passage between the interior of the drive shaft extension and the interior of the suction housing,the drive shaft extension capable of allowing dust from an interior of the core drill to pass from holes in the rear end of the core drill, along the interior of the drive shaft, through the at least one hole and to the interior of the suction housing.

23. Core drill assembly having a core drill (3) according to any of claims 1-18 and having a suction housing (8) attached to the rear end (5) of the core drill (3),■ the core drill assembly comprising a drive shaft extension (47) extending between a drive shaft (46) and a rear end of the core drill (3), the drive shaft (46) at least partly extending inside the suction housing (8),■ the core drill assembly comprising an extension sleeve extending between an outer circumference of the suction housing and a rear end of the core drill (3), the extension sleeve surrounding the drive shaft extension (47),■ the extension sleeve extending between a flange abutting an outer circumference of the suction housing (8) and a rear end of the core drill (3), the outer circumference extending towards the rear end (5) of the core drill (3),■ the extension sleeve having a hollow interior extending from a distant end towards the rear end (5) of the core drill (3) to a proximate end of the drive shaft extension (47) towards the suction housing (8),■ the extension sleeve having at least one hole at the proximate end of the drive shaft extension (47), the at least one hole providing passage between an interior of the extension sleeve and the interior of the suction housing (8),■ the extension sleeve capable of allowing dust from an interior of the core drill to pass from holes in the rear end of the core drill, along the interior of the extension sleeve, through the at least one hole and to the interior of the suction housing.

24. Core drill assembly having a core drill (3) according to any of claims 1-18 and having a suction housing (8) attached to the rear end (5) of the core drill (3),■ the core drill assembly comprising a drive shaft (46) the drive shaft (46) at least partly extending inside the suction housing (8),■ the core drill assembly having a bearing extending between the drive shaft (46) and the suction housing, and the core drill assembly having a ring-shaped seal extending between the bearing and the interior of the suction housing (8),■ the drive shaft extension (47) having an air channel extending between an inlet of the air channel to an outlet of the air channels, the inlet provided at one end of the drive shaft (46) to an opposite end of the drive shaft,■ the inlet having access to surroundings of the suction housing, and the outlet opening into the interior of the suction housing, in a plane P extending along a surface of the ring-shaped seal facing the interior of the suction housing.

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