Core drill

A plurality of chip evacuating grooves (16, 26, 36, 46a, 46b) in a vertical direction in parallel with a rotational axis of a core main body (14) are formed at an outer peripheral face of the core main body (14) in a circumferential direction from a lower end portion to an upper end portion of the core main body (14) in a cylindrical shape provided with a drilling blade (15) at a lower end edge thereof. Further, a sectional area of the chip evacuating groove (16) is formed to gradually increase from a lower end to an upper end of the core main body (14). Further, a number of projections (52, 62, 70, 72) are formed at the outer peripheral face of the core main body (14) between the chip evacuating grooves.

TECHNICAL FIELD

The present invention relates to a core drill for concrete for boring a comparatively large through hole for piping to concrete, a stone material or the like constituting a wall or a foundation of a building or the like.

BACKGROUND ART

A core drill has conventionally been used for boring a comparatively large hole for passing a water pipe, a gas pipe or a pipe for an air conditioner to a wall, a floor, a foundation or the like constituted by concrete, a stone material or the like in constructing or adding or reforming a building. A core drill is attached with drilling blades formed by sintering diamond abrasive grains by a metal bond at a lower end edge of a core main body formed in a cylindrical shape circumferentially at intervals and by pressing the drilling blades to a concrete face and rotating the core main body, a groove in a shape of a circular ring is cut to form at concrete or the like and by cutting the groove gradually deeply, a hole penetrating concrete or the like is bored. The core drills are used in tools of a wet type cutting the hole by supplying a fluid for cooling to the drilling blades and a dry type which does not supply the cooling fluid.

In drilling operation by the core drill, when the drilling blades formed at a front end thereof cut concrete, a stone material or the like, a large amount of chips of concrete or the like is produced. When the chips are clogged between the core main body and an inner wall face of the bored hole, a resistance against rotating the core drill is increased to thereby reduce a drilling efficiency. Although when the core drill is used in the wet-type tool, the chips are evacuated comparatively efficiently by operation of making the cooling fluid flow, in operation by the dry type tool, the chips may not be evacuated sufficiently to thereby prolong an operational time period of boring.

Therefore, according to a core drill of a background art, an outer peripheral face of a core main body is formed with a chip evacuating groove in a spiral shape and chips produced by drilling blades at a front end thereof are evacuated to an upper side of the core main body via the groove by rotating the core drill (refer to, for example, JP-B-06-092083). Further, there is known a core drill improving evacuation of chips by forming an abrasive grain layer at a surface of a projected streak portion formed at an outer peripheral face of a core main body formed with a groove for evacuating chips and further finely grinding chips produced at drilling blades at a front end thereof by the abrasive grain layer (refer to, for example, JP-A-2000-309013)

According to the core drill of the background art, the chip evacuating groove for evacuating chips is formed in the spiral shape at the outer peripheral face of the core main body and therefore, there poses a problem that production cost is increased by requiring a number of steps in working by, for example, a lathe in producing the core main body. Further, according to the core drill of the background art, the groove for evacuating chips is formed by the same sectional area from a front end side to an upper end of the core drill and therefore, there poses a problem that operation of evacuating chips is not sufficiently carried out, chips formed at the front end portion is compressed to clog at inside of the groove, and the chips are brought into close contact with a wall face of the cut hole of concrete to thereby hamper the drilling efficiency.

Further, according to a hand-held tool for carrying out drilling operation by grabbing the tool by the hand, the outer peripheral face of the core main body is brought into contact with an inner wall face of a concrete hole in a wide area by swinging an axis line of the core drill and therefore, there also poses a problem that a drilling function is reduced by reducing a rotational speed of the core drill by increasing a friction resistance. In order to rotate the core drill at high speed against the friction resistance, a large-sized tool having a larger driving force needs to use.

DISCLOSURE OF THE INVENTION

It is a problem of the invention to resolve the above-described problem of the background arts and provide a core drill facilitating production and capable of reducing cost. Further, other problem of the invention is to provide a core drill capable of evacuating chips produced by a drilling blade efficiently to an upper side even when a dry type tool a is used and capable of promoting a drilling function by reducing a friction resistance between the core drill and an inner peripheral face of a concrete hole.

In order to resolve the former problem, the invention is characterized in a core drill including a shank connected to a rotating tool at an upper end thereof and constituted by a core main body in a cylindrical shape provided with a drilling blade at a lower end edge thereof, wherein a plurality of streaks of chip evacuating grooves in parallel with a rotational axis of a core main body are formed at an outer peripheral face of the core main body at intervals in a peripheral direction from a lower end portion to an upper end portion of the core main body in the cylindrical shape.

Further, the core drill according to the invention is characterized in that the chip evacuating groove is formed such that a sectional area thereof is gradually increased from the lower end portion to the upper end portion.

Further, the core drill according to the invention is characterized in that an opening for communicating inside and outside of the core main body is formed at a bottom of the chip evacuating groove.

Further, in order to achieve the latter problem, the invention is characterized in a core drill including a shank connected to a rotating tool at an upper end thereof, constituted by a core main body in a cylindrical shape provided with a drilling blade at a lower end edge thereof and formed with a chip evacuating groove at an outer peripheral face of the core main body from a lower end portion to an upper end portion of the core main body in the cylindrical shape, wherein 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, the core drill according to the invention is characterized in that the chip evacuating groove is formed in a spiral shape at the outer peripheral face of the core main body.

Further, the core drill according to the invention is characterized in that an opening for communicating inside and outside of the core main body is formed at a bottom of the chip evacuating groove.

Further, the core drill according to the invention is characterized in that a slender groove is formed at the outer peripheral face of the core main body between contiguous ones of the chip evacuating grooves and from the lower end portion to the upper end portion of the core main body.

Further, the core drill according to the invention is characterized in that a lateral groove is formed at the outer peripheral face of the core main body between contiguous ones of the chip evacuating grooves and in a circumferential direction of the core main body.

Further, a core drill according to the invention is characterized in a core drill including a shank connected to a rotating tool at an upper end thereof and constituted by a core main body in a cylindrical shape provided with a drilling blade at a lower end edge thereof, wherein a plurality of streaks of chip evacuating grooves extended from a lower end portion to an upper end portion of the core main body in the cylindrical shape are formed at an outer peripheral face of the core main body along a circumferential direction and a number of projections projected from the outer peripheral face of the core main body in a radial direction are formed at the outer peripheral face of the core in the cylindrical shape between contiguous ones of the chip evacuating grooves.

BEST MODE FOR CARRYING OUT THE INVENTION

An explanation will be given of a mode for carrying out the invention based on embodiments shown in the drawings as follows.FIG. 1shows the core drill10according to a first embodiment of the invention which is constituted by the shank11coupled to a rotating tool and transmitted with a rotating force similar to the background art, and the drill main body12coupled to a lower end portion of the shank11. The drill main body12is constituted by the core main body14in a cylindrical shape the upper end portion13of which is closed, and a plurality of drilling blades15attached to a lower end edge of the core main body14at intervals in a circumferential direction. The drilling blade15is molded in a tip-like shape by sintering a metal bond mixed with diamond abrasive grains and the drilling blades15are bonded to the lower end edge of the core main body14by welding at equal intervals in a peripheral direction.

A plurality of the chip evacuating grooves16extended in a vertical direction in parallel with a rotational axis of the core drill are formed at an outer peripheral face of the core main body14at predetermined intervals in the peripheral direction. By forming the chip evacuating groove16in parallel with the shaft of the core main body14in this way, in comparison with the groove in the spiral shape of the background art, working by a lathe or the like is not needed, fabricating steps are simplified and fabrication cost or the like can be reduced.

Further, according to the embodiment, as shown byFIG. 2, the chip evacuating groove16is cut to gradually change a depth thereof such that a depth L2of the chip evacuating groove at the upper end portion13is larger than a depth L1of the chip evacuating groove at the lower end portion proximate to the drilling blades15to thereby form the chip evacuating groove16such that a sectional area thereof is increased to an upper side. Therefore, in pushing up chips at inside of the chip evacuating groove16to the upper side by chips produced by the drilling blades15at the lower end portion of the core main body14, chips are prevented from being clogged at inside of the chip evacuating groove16at the widened upper portion.

Further, the groove bottom portion17of the chip evacuating groove16is formed with the opening18for communicating inside and outside of the cylinder of the core main body14and air compressed on an inner side of the core main body14by progressing drilling by the core drill10is exhausted to an outer side of the core main body14. At this occasion, compressed air to be exhausted is exhausted into the chip evacuating groove16and therefore, compressed air is not hampered from being exhausted and operation of evacuating chips at inside of the chip evacuating groove16to the upper side is promoted by a flow of compressed air to be exhausted.

FIG. 3shows a state in the midst of drilling operation by the core drill10in the above-described embodiment. By rotating the core drill10, a surface of concrete C is cut by the drilling blades15to thereby form a groove in a ring-like shape. Further, at an initial stage of the drilling operation, a rotational center of the drilling blades15is positioned by mounting a center pin at a center of the core drill10. Chips P produced by cutting by the drilling blades15are moved into the chip evacuating groove16, pushed up to the upper side gradually by the chips P successively produced by the drilling blades15and evacuated to the surface of the concrete. Although air on the inner side of the core main body14is compressed in accordance with progress of drilling, air is exhausted to the outer side of the core main body14via the opening18and the drilling efficiency is not hampered by compressed air. Further, when drilling is further progressed and the core main body14is immerged in the concrete C to a portion of the opening18, by the flow of exhausting compressed air, chips at inside of the chip evacuating groove16are helped to evacuate to the upper side and therefore, chips are evacuated excellently. Further, concrete powder dust remaining at a space on the inner side of the core main body14is exhausted to outside from the opening18and therefore, a resistance against rotation which is brought about by storing the powder dust at the inner side space is nullified, loss in rotating the core main body14is reduced and drilling can be carried out efficiently.

FIG. 4shows the core drill20according to other embodiment of the invention and although the embodiment is the same as the above-described embodiment in that the outer peripheral face of the core main body14is formed with a plurality of the chip evacuating grooves26in parallel with a rotational axis line of the core drill20, the chip evacuating groove26of the embodiment is cut to form such that a depth of the groove is formed to be the same from a lower end to an upper end thereof and a groove width of the chip evacuating groove is gradually increased such that a groove width W2at an upper end portion thereof is wider than a groove width W1at a lower end portion of the core main body14to thereby form the chip evacuating groove such that a sectional area of the chip evacuating groove26is gradually increased from the lower end to the upper end. Therefore, chips produced by the drilling blades15are pushed up to the upper side of the chip evacuating groove26having a large sectional area and therefore, chips are not clogged at inside of the chip evacuating groove26and evacuation is carried out excellently.

FIG. 5shows the core drill30according to still other embodiment of the invention which is formed such that the chip evacuating groove36formed at the outer peripheral face of the core main body14is formed such that a sectional area thereof is gradually increased from a lower end side to an upper end thereof to thereby prevent chips from being clogged at inside of the chip evacuating groove36. According to the embodiment, the chip evacuating groove36is formed by cutting in a spiral shape along the outer peripheral face of the core main body14such that a depth of the chip evacuating groove36is gradually deepened from a lower end to an upper end thereof. According to the chip evacuating groove36of the embodiment, different from the chip evacuating groove in the spiral shape according to the background art, a plurality of streaks of the chip evacuating grooves36in the spiral shape increasing the spiral pitch are arranged in the circumferential direction at equal intervals along the outer peripheral face of the core main body14to thereby facilitate to evacuate chips produced by the drilling blades15to the upper side.

FIG. 6shows the core drill40according to still other embodiment, similar to the above-described embodiment shown inFIG. 1, the chip evacuating grooves46ain the vertical direction in parallel with the rotational axis line are formed at the outer peripheral face of the core main body14at equal intervals in the peripheral direction and a plurality of streaks of the chip evacuating grooves46bin the spiral shape similar to those of the embodiment shown inFIG. 5are formed to intersect with the chip evacuating grooves46ain the vertical direction. By forming the chip evacuating grooves46a,46bin this way, evacuation of chips to the upper side is further improved by operation of rotating the portion of the core main body14.

In any of the above-described embodiments, by forming diamond abrasive grain layers on an outer surface of the core main body14formed to arrange among the chip evacuating grooves16,26,36,46a,46b, bringing the abrasive grain layers into contact with chips produced by the drilling blades15to further finely polish chips to further make evacuation of chips effective and bringing the diamond abrasive grain layers into contact with an object to be cut of concrete or the like, the resistance against rotation can be reduced and further excellent cutting operation can be carried out.

FIG. 7shows an example of forming a slender groove36afrom the lower end portion to the upper end portion of the core main body14on the outer peripheral face between the contiguous chip evacuating grooves36. A plurality of the slender groove36amay be provided. According thereto, a contact area between the outer peripheral face of the core main body14and concrete is reduced and therefore, the resistance against rotation is reduced, the rotational speed can be maintained and the high drilling function can be ensured.

Further, the similar slender groove36acan be formed at the outer peripheral face between the contiguous chip evacuating grooves16or26also in the examples of FIG.1and FIG.4.

Further,FIG. 8shows an example of forming a lateral groove36bin the circumferential direction of the core main body14to the outer peripheral face between the contiguous chip evacuating grooves36. The lateral groove36bis formed along the rotational direction, the contact area between the outer peripheral face of the core main body14and concrete is reduced and therefore, also in this case, the resistance against rotation is reduced, the rotational speed can be maintained and the high drilling function can be ensured.

Further, the similar lateral groove36bcan be formed at the outer peripheral face between the contiguous chip evacuating grooves16or26also in examples of FIG.1and FIG.4.

Next, still other embodiment of the invention will be explained. As shown byFIG. 9, similar to the above-described embodiment, the core drill50according to the embodiment is constituted by the shank11coupled to a rotating tool, and the drill main body12attached to the lower end portion of the shank11and the drill main body12is constituted by the core main body14in the cylindrical shape the upper end portion13of which is closed and the drilling blade15attached to the lower end edge of the core main body14. The outer peripheral face of the core main body14is formed with a plurality of the chip evacuating grooves51extended in the vertical direction in parallel with the rotational axis of the core drill50at predetermined intervals in the peripheral direction. Further, the chip evacuating groove51is cut such that the depth of the upper end portion13becomes gradually larger than that of the lower end portion proximate to the drilling blades15and formed such that a sectional area of the chip evacuating grooves51is gradually increased to the upper side. Thereby, chips produced by the drilling blades15are prevented from being clogged at inside of the chip evacuating groove51. A bottom of the chip evacuating groove51is formed with the opening18for communicating inside and outside of the cylinder of the core main body14. Also the effect by the opening18is as described above.

Further, a number of the projections52are formed at the outer peripheral face of the core main body14between the contiguous chip evacuating grooves51of the core main body14of the core drill50according to the embodiment from the lower end portion to the upper end portion of the core main body14. As shown by FIGS.10(a),10(b) and10(c), the projection52is formed in a shape of a triangular pyramid and the top portion53is projected in a radial direction of the core main body14and the top portion53of the projection52is brought into contact with an inner peripheral face of a concrete hole bored by the drilling blades15. The projection52can be formed at the outer peripheral face of the core main body14by means of welding or the like. By bringing the top portion53of the projection52into contact with the inner peripheral face of the concrete hole bored by the drilling blade15, a total of the outer peripheral face of the core main body14is not brought into contact with the inner peripheral face of the concrete hole. Therefore, the friction resistance in rotating the core drill50is reduced and the rotational speed of the core drill can be prevented from being reduced.

FIG. 11shows the core drill60according to still other embodiment and according to the embodiment, a plurality of streaks of the chip evacuating grooves61in the spiral shape are formed at the outer peripheral face of the core main body14along the outer peripheral face of the core main body14at equal intervals in the circumferential direction and the chip evacuating grooves61are formed such that a sectional area of the chip evacuating groove61is gradually increased from a lower end side to an upper end thereof to thereby prevent chips from being clogged at inside of the chip evacuating groove61.

A number of the projections62are formed at the outer peripheral face of the core main body14between the contiguous chip evacuating grooves61of the core drill60from the lower end portion to the upper end portion of the core main body14. As shown by FIGS.12(a),12(b) and FIG.(c), the projection62is formed in a shape of a pyramid a bottom face of which is formed in a rectangular shape or a rhombic shape and formed to project the top portion63of the projection62from the outer peripheral face of the core main body14in the radial direction. By bringing the top portion63of the projection62into contact with the inner peripheral face of the concrete hole bored by the drilling blades15, a total of the outer peripheral face of the core main body14is not brought into contact with the inner peripheral face of the concrete hole to thereby reduce the friction resistance in rotating the core drill60.

Although in the above-described embodiments, an explanation has been given by the embodiments in which the chip evacuating grooves51,61formed at the outer peripheral face of the core main body14are formed in parallel with the center axis line of the core drill or in the spiral shape, the shape and the structure of the chip evacuating groove may be constituted by any of the embodiments, further, a groove in the vertical direction and a groove in the spiral shape may be integrated to form as in the embodiment shown in, for example, FIG.6. Further, the shape of the projection is not limited to the shape of the triangular pyramid and the shape of the pyramid but as shown by FIGS.13(a),13(b) and13(c), the shape may be formed by the projection70in a shape of a circular cone projecting the top portion71thereof in the radial direction, or, as shown by FIGS.14(a),14(b) and14(c), the shape may be formed by the projection72in a semispherical shape bulging the top portion73in a spherical shape in the radial direction. Further, two or more of shapes in the shape of the triangular pyramid, the shape of the pyramid, the shape of the circular cone and the semispherical shape may be combined.

Further, the invention is not limited to the above-described embodiments but can variously be modified within the technical range of the invention and the invention naturally covers the modifications.

The application is based on Japanese Patent Application Japanese Patent Application No. 2002-010740) filed on Jan. 18, 2002, Japanese Patent Application (Japanese Patent Application No. 2002-306664) filed on Oct. 22, 2002 and Japanese Patent Application (Japanese Patent Application No. 2003-003646) filed on Jan. 9, 2003 and contents thereof are incorporated here by reference.

INDUSTRIAL APPLICABILITY

According to the core drill of the invention, by forming the chip evacuating groove in parallel with the shaft of the core main body, in comparison with the groove formed in the spiral shape of the background art, fabricating steps are simplified and fabrication cost or the like can be reduced.

Further, by forming the core drill according to the invention such that the sectional area of the chip evacuating groove is gradually increased from the lower end to the upper end, in pushing up chips at inside of the chip evacuating groove to the upper side by chips produced by the drilling blades, chips are pushed up in a direction of widening the sectional area of the groove and therefore, chips are not clogged at inside of the chip evacuating groove, chips are evacuated excellently and chips can be prevented from constituting the resistance against rotation of the core drill. Therefore, the drilling efficiency can be promoted.

Further, according to the core drill of the invention, by forming the opening for communicating inside and outside of the core main body at the bottom of the chip evacuating groove, the concrete powder dust remaining at the inner side space of the core main body14is evacuated to outside from the opening18and therefore, the resistance against rotation produced by storing the powder dust in the inner side space is eliminated, loss in rotating the core main body14is reduced and drilling can be carried out efficiently.

Further, by forming the chip evacuating groove in the spiral shape at the outer peripheral face of the core main body, chips produced in drilling can be facilitated to evacuate to the upper side.

Further, by forming the slender groove or the lateral groove at the outer peripheral face between the contiguous chip evacuating grooves in the core drill according to the invention, the contact area between the outer peripheral face of the core main body14and concrete is reduced and therefore, the resistance against rotation is reduced, the rotational speed can be maintained and the high drilling function can be ensured.

Further, in the core drill of the invention, by forming a number of the projections projected from the outer peripheral face of the core main body in the radial direction at the outer peripheral face of the core main body between the chip evacuating grooves formed at the core main body, the top portions of the projections projected in the radial direction are brought into contact with the inner peripheral face of the concrete hole bored by the drilling blades, the friction resistance by bringing the total face of the core main body into contact with the inner peripheral face of the concrete hole can be prevented from being increased and the drilling function by reducing the rotational speed of the core drill can be prevented from being reduced.