DRILL RETAINER FOR PERCUSSIVE AND ROTARY DRILLING MACHINES

Abstract: A combination of a drill holder and a drill in which the drill holder has a bushing (19) for receiving a shank of either a hammer drill or a rotational drill and having a conical frustum (24) for transferring the boring pressure to a corresponding conical frustum (18) on the drill shank (12) of a rotational drill and for simultaneously centering the shank (12) in the bushing (19). A locking member (22) engages a locking recess (16) to prevent inadvertent removal of the shank (12). The length of the shank (12) is such that its free end (15) is outside the range of influence or operation of a percussion member (25). Rotative forces are transmitted by cooperating carrier ribs of the bushing and carrier grooves of the shank.

Description: DRILL RETAINER FOR PERCUSSIVE AND ROTARY DRILLING MACHINES The present invention relates to a new combination of a drill holder and a drill. Thus, the present invention provides a combination comprising a drill holder having a substantially cylindrical passage for axially receiving the free end of a corresponding drill shank inserted into the passage from an outer end thereof towards an inner end thereof and provided with at least one releasable, radially displaceable locking member for limiting the axial movement of the drill shank in the passage towards said outer end thereof, the interior surface of said passage having at least two axially extending and inwardly projecting carrier ribs for transmitting rotative forces from the drill holder to the drill shank, and a drill having a substantially cylindrical shank for being received in said passage, the outer peripheral surface of said shank having at least one axially delimited recess for receiving said locking member and at least two axially extending carrier grooves extending from the free end of the shank and each having a cross sec- tion and circumferential location on said shank surface corresponding to receiving one of said carrier ribs, the periphery of the outer end of said passage defining a first frustum corresponding to a cone or a pyramid with four or more triangular sides, said first frustum having its apex located inside the passage and substantially on the axis of rotation of the drill shank. The drill holder may comprise an axially reciprocative per¬ cussion member with a field of operation adjacent the inner end of said passage. The drill may be a non-percussive rotation type drill for drilling in metal, wood and the like, and the drill shank adjacent the end opposite the free end thereof may be pro¬ vided with a shoulder defining a second frustum corresponding to and for abutting against said first frustum and having its apex located substantially on the axis of rotation of the drill shank at a point between said shoulder and said free end. Hereby a novel retention and rotation of such a drill is obtained with the frustums taking up the boring pressure and at the same time centering the drill in the passage. The distance from the shoulder of the shank to the free end thereof may be such that said free end lies outside said field of operation when said first frustum and second frustum abut one another. In this way, a non-percussive type drill may be employed in a percussion type boring apparatus without having to replace the drill holder and stop the action of the percussion member. This is a major advantage for persons employing both percussive and non-percussive drills in that the same equipment easily and handily can be utilized for both types of drills. Preferably, the at least one recess for receiving the at least one locking member has an axial extent for allowing axial displacement of the shank in response to the percussive influence thereon by the percussion member from a position wherein the end of the shank is in said field of operation to a position outside the field of operation, the at least one locking member being constituted by a spherical or cylindri¬ cal body displaceable through an aperture in the passage from a first, outer position in which the shank may freely be removed from the passage and a second, inner position in which the shank is prevented from removal from the passage by abutment of the at least one locking member with the axial delimitation of said at least one recess. Advantageously, said at least two carrier grooves comprise two grooves arranged diametrically opposite each other in relation to the rotational axis of the shank, said grooves having a generally U-shaped cross section with a carrier flank for transmitting the rotational forces and a generally opposed inactive flank, said carrier flank penetrating deeper into the shank than said inactive flank. Hereby it is obtained that the area of the carrier flank is increased while removing less of the core material of the shank thereby weakening the shank less with regard to fatigue stress and torsional stress. Preferably, said carrier flank is substantially planar, the direction of said carrier flank at right angles to the axial direction of same substantially intersecting the axis of rotation of the shank. Hereby the frictional resistance and wear is reduced in relation to the cooperation with the respective carrier ribs in transmitting rotational forces to the shank. In a preferred embodiment of the combination according to the invention, the outer peripheral surface of the shank is circular cylindrical in relation to the axis of rotation of said shank and, furthermore, the interior surface of said passage is circular cylindrical in relation to the axis of rotation of said shank. As the tendency is to employ larger diameter drills with the same drill holder and drill shank dimensions, the rotative forces to be transmitted to the shank are increased, and therefore it is advantageous that said outer peripheral surface of the shank has one or more pairs of additional axially extending carrier grooves having a carrier flank and an inactive flank, each of said additional grooves of a pair arranged substantially diametrically opposite one another in relation to the axis of rotation of the shank. Furthermore, the wear on the carrier ribs and the carrier flanks is hereby reduced by distributing the rotative forces on a larger carrier flank area. So as to distribute the rotative forces as evenly as possible across the circumference of the shank and thereby reduce stress concentrations, the additional carrier grooves subdi¬ vide the circumferential distance between said two U-shaped groves into substantially equal portions. To obtain a larger total carrier flank area with as slight reduction of the shank cross sectional area as possible, the additional grooves have a generally V-shaped cross section, and at least one of the additional grooves at least partially overlies one axially delimited recess. So as to further increase the total carrier flank area and transmit part of the rotative forces closer to the operative regions of the drill so as to reduce the oscillating torque stresses in the shank and thereby reduce fatigue stresses, at least two of the axially extending carrier grooves may have an axial extent from the free end of the shank substantially longer than the axial extent of said at least one axial recess from said free end. In a preferred embodiment, the diameter of the shank is substantially equal to 10 ram and the axial extent of all the carrier grooves from the free end of the shank is at least 2 mm longer than the axial extent of said at least one axial recess from said free end, while in the currently most pre¬ ferred embodiment the axial extent of all the carrier grooves from the free end of the shank is the same and in the range of 5 to 9 mm longer than the axial extent of said at least one axial recess from said free end. The rotative forces transmitted to the shank by portions of the carrier flanks near the free end of the shank give rise to greater oscillating torque stresses than those transmitted by portions remote from the free end, and therefore it is advantageous that the carrier ribs are such that only a partial extent substantially less than the entire length of the carrier flank of the carrier grooves is utilized for transmitting the rotational forces, said utilized partial extent extending from the innermost limit of the groove towards the free end of the shank, and preferably the length of each rib is substantially equal to said utilized partial extent of the respective carrier flank, and preferably the utilized partial extent of each of the carrier flanks is less than half the entire length thereof. For the sake of simplicity and inexpensiveness, preferably the at least one axially delimited recess of the shank of said non-percussive type drill has an axial length only slightly larger than the axial extent of the corresponding at least one locking member. Advantageously, the shank of the non-percussive type drill is manufactured separately from the rest or fluted portion of the drill and is provided with attachment means for cooperat¬ ing with corresponding attachment means at the inactive end of the fluted portion of the drill for fixedly interconnect¬ ing said shank and said fluted portion to constitute the final drill, the shank advantageously being manufactured from a metal powder component or from a suitable plastic material such as for instance polyamide. The attachment means may comprise an axial recess in the end of the shank opposite the free end thereof for receiving a corresponding axial end portion of the fluted portion, said end portion being fixed in the recess by means of adhesive or solder, or the attachment means for the metal powder compo¬ nent shank may comprise a circular, planar, radial surface at the free end of the shank and at the inactive end of the fluted portion, said surfaces having substantially equal dimensions and being fixedly attached to each other by means of friction welding, resistance welding or ultrasonic weld¬ ing. The invention further relates to a drill holder for use in a combination according to the invention and to a drill for use in a combination according to the invention. The invention will now be further described with reference to the drawings, wherein Fig. 1 is a lateral view of the shank of an embodiment of a hammer drill according to the invention, Fig. 2 is a lateral view of the hammer drill shank of Fig. 1 rotated 90 o in relation to Fig. 1, Fig. 3 is a sectional view along line III-III in Fig. 1, Fig. 4 is a lateral view of the shank of a non-percussive drill according to the invention, Fig. 5 is a partially sectional fragmentary side view of a drill holder according to the invention with the shank of a non-percussive drill according to invention received therein, Fig. 6 is an enlarged sectional view along line VI-VI in Fig. 5 of a drill holder passage according to the invention with a shank of a non-percussive drill according to the invention received and locked therein, Fig. 7 is a fragmentary side view of a first embodiment of the attachment between a shank of a non-percussive drill according to the invention to the fluted portion of same, and Fig 8. is a fragmentary side view of a second embodiment of the attachment between a shank of a non-percussive drill according to the invention to the fluted portion of same. Referring to Fig. 1-3 a circular cylindrical hammer drill shank 1 having a free end 2 is provided with axially extend¬ ing carrier grooves 3 being open towards the free end 2 and having a generally U-shaped cross section and each having a carrier flank 4 and an inactive flank 5, both said flanks 4 and 5 extending radially with respect to the axis of rotation 6 of the shank 1. The radial extension of the carrier flank 4 is longer than the radial extension of the inactive flank 5. The shank 1 is furthermore provided with two axially extend¬ ing locking recesses 7 with a semi-circular cross section and being closed towards the free end 2 by an axial delimitation 8a and towards the opposite end by an axial delimitation 8b. The shank 1 is further provided with three pairs of addi¬ tional axially extending carrier grooves 9 that are open towards the free end 2 and have a generally V-shaped cross section, each groove 9 having a carrier flank 10 and an inactive flank 11, the carrier flanks 10 extending radially with respect to the axis of rotation 6. The additional grooves 9 are arranged in pairs diametrically opposed each other in relation to the axis 6 and such that they are substantially evenly distributed over the circumfer¬ ence between the grooves 3. Each of the additional grooves 9 to a certain extent overlaps one of the locking recesses 7. Referring to Fig. 4, a circular cylindrical drill shank 12 for a non-percussive rotational drill is provided with car¬ rier grooves 13 and 14 corresponding to the carrier grooves 3 and 9, respectively, of the shank 1 in Fig. 1-3. The shank 12 has a free end 15 and two locking recesses 16. The shank 12 is further provided with a radially expanded portion 17 forming an intermediate shoulder 18 with the shank 12, said shoulder 18 constituting a conical boring pressure receiving and shank centering frustum. Referring now to Fig. 5, the shank 12 shown in Fig. 4 is inserted in a drill holder comprising a bushing 19 defining a passage 20 enclosing the shank 12. The bushing has a two opposed channels 21 (only one of which is shown) in each of which a spherical locking member 22 is displaceably arranged and pressed into engagement with the respective locking recess 16 by means of a locking ring 23. At its outer end the bushing 19 is radially outwardly tapered defining a conical boring pressure delivering and shank centering frustum 24 corresponding to the frustum defined by the shoulder 18 of the shank 12. The drill holder further comprises a reciprocative percussion member 25 having a percussion end surface 26. The length of the shank 12 is such that the end 15 thereof is spaced from the end surface 26 and thus is located outside the range of influence or operation of the percussion member 25. Referring now to Fig. 6, the bushing 19 encloses the shank 12. The bushing 19 has inwardly projecting, axially extending carrier elements or ribs 22 and 23 substantially correspon¬ ding to the carrier grooves 13 and 14, respectively, of the shank 12. The ribs 22 and 23 have active flanks 24 and 25, respectively, for transmitting rotative forces in the direc¬ tion of the arrow R to active flanks 26 and 27, respectively, of the carrier grooves 13 and 14, respectively. In operation, the drill shank 12 is inserted into the bushing 19 until the shoulder 18 abuts the frustum 24 and the locking members 22 enter into engagement with the locking recesses 16. The shank is caused to rotate in the direction of the arrow R in Fig. 6 by the rotating bushing 19 by means of the abutting interaction between the active flanks 24, 25 and the active flanks 26, 27, respectively. The abutment of the shoulder 18 against the frustum 24 transmits the necessary boring pressure from the drill holder to the drill for boring a hole in for instance wood or metal. Said abutment further automatically centers the shank 12 in the bushing 19 and prevents wobbling and tilting of said shank. No rotative forces of importance are transmitted to the shank 12 by said abutment. When removing the drill from the hole being bored, the axial locking interaction of the locking members 22 with the inner- most edges of the locking recesses 16 prevents the shank 12 from inadvertently being pulled out of the bushing 19 because of friction between the drill and the bored hole. The spacing between the free end 15 of the shank 12 and the percussion surface 26 of the percussion member 25 prevent percussive forces from being transmitted to the drill shank 12 which otherwise would damage the drill. If it thereafter is necessary to drill in for instance con¬ crete or stone utilizing a percussive hammer drill having a shank l as shown in Fig. 1-3, the locking members 22 are displaced radially outwards in the respective channels 21, thereby allowing the shank 12 to be pulled out of the bushing 19 to be replaced by the shank 1. The shank l is inserted into the bushing 19 until the free end 2 thereof abuts the percussion surface 26 in which position the locking members 22 may be displaced radially inwards into engagement with the respective locking recesses 7. In this position of the shank 1, a sectional view correspond¬ ing to the sectional view of Fig. 6 would be identical to the view of Fig. 6. The operation of the hammer drill is there- after very similar to the operation of hammer drills well known in the art. Referring now to Fig. 7, the radially expanded portion 17 of the shank l has a projection 30 with smaller diameter and having a planar end surface 31. The shank 1 with its expanded portion 17 may be made of a metal powder component. A fluted portion 32 of the drill has a planar end surface 33 with the same diameter as the end surface 31. The surfaces are welded together so as to form the final drill by means of any suit¬ able welding process such as for instance friction welding, resistance welding or ultrasonic welding. Referring now to Fig. 8, the radially expanded portion 17 of the shank 1 has an axial recess 34 for receiving an axial end portion of the fluted portion of the 32 of the drill. The end portion of the fluted portion 32 is fixed in the recess by means of soldering or a suitable adhesive. The shank l in this instance may be made of a metal powder component or any suitable plastic material such as for instance polyamide. The configuration of the carrier grooves 3, 9 and 13, 14 in the shanks 1 and 12, respectively, is the same except for the slightly shorter length of the grooves 13 and 14 compared to the grooves 3 and 9 owing to the necessary spacing between the free end 15 of the shaft 12 and the percussion end 26 of the percussion member 25. This allows the interchanging of the corresponding drills in the drill holder. A very common diameter for shanks for hammer drills is 10 mm, and if this diameter is chosen for the shanks 1 and 12, the effective length of the grooves 3, 9 and 13, 14 is approximately 7 mm longer than the axial extension of the recesses 7 away from the free end 2 of the shank 1. It may be longer or shorter, but should be at least 2 mm. Besides affording a larger interaction area between the carrier flanks of the carrier grooves and the carrier ribs, thereby reducing the wear and deformation of said flanks, this extra length transfers part of the transmitted forces to the region of the shaft 1 not weakened by the recesses 7 and also reduces the torsional stresses in the shank 1 resulting from said transmission of forces. The configuration of the carrier grooves 3 is chosen to allow utilization of the hammer drills according to the invention in many conventional drill holders having carrier ribs fit¬ ting into the grooves 3. If this compatibility feature is omitted, each of the grooves 3 could be replaced by one or more carrier grooves having a configuration like the carrier grooves 9 and disposed around the periphery of the shank such that the maximum stresses in the shank l resulting from the transmission of rotative forces are reduced. To avoid high notch sensibility in the apex of the V-shaped cross section of the carrier grooves 9, said apex may be rounded in accordance with computerized calculations based on computerized simulations of the stresses resulting from the complex interaction of forces in the shank 1 during drilling operations. The drill holder according to the invention may also be used for receiving and rotating screw driver bits of the type well known in the art and having a shank similar to the shank 12. The angle of inclination relative to the axis 6 of the frustum 24 and the shoulder 18 is chosen larger than the wedge locking angle of the said frustum and shoulder so that the shank 12 may be removed easily from the bushing 19. The principle according to the invention of combining co¬ operating frustums on the shank and the bushing with a lock¬ ing member cooperating with a locking recess may be applied to a drill holder solely intended for rotational drills and screw driver bits, i.e. the drill holder having no percussive member.

Claims: CLAIMS 1. A combination comprising a drill holder having a substantially cylindrical passage for axially receiving the free end of a corresponding drill shank inserted into the passage from an outer end thereof towards an inner end thereof and provided with at least one releasable, radially displaceable locking member for limiting the axial movement of the drill shank in the passage towards said outer end thereof, the interior surface of said passage having at least two axially extending and inwardly projecting carrier ribs for transmitting rotative forces from the drill holder to the drill shank, and a drill having a substantially cylindrical shank for being received in said passage, the outer peripheral surface of said shank having at least one axially delimited recess for receiving said locking member and at least two axially extending carrier grooves extending from the free end of the shank and each having a cross section and circumferential location on said shank surface corresponding to receiving one of said carrier ribs, the periphery of the outer end of said passage defining a first frustum corresponding to a cone or to a pyramid with four or more triangular sides, said first frustum having its apex located inside the passage and substantially on the axis of rotation of the drill shank. 2. A combination according to claim 1, wherein the drill holder comprises an axially reciprocative percussion member with a field of operation adjacent the inner end of said passage. 3. A combination according to claim 1 or 2, wherein the drill is a non-percussive type drill for drilling in metal, wood and the like and the drill shank adjacent the end opposite the free end thereof is provided with a shoulder defining a second frustum corresponding to and for abutting against said first frustum and having its apex located substantially on the axis of rotation of the drill shank at a point between said shoulder and said free end. 4. A combination according to claim 2 and 3, wherein the distance from the shoulder of the shank to the free end thereof is such that said free end lies outside said field of operation when said first frustum and second frustum abut one another. 5. A combination according to claim 1 or 2, wherein the drill is a percussive type drill for drilling in concrete, stone and the like. 6. A combination according to claim 2 and 5, wherein the at least one recess for receiving the at least one locking member has an axial extent for allowing axial displacement of the shank in response to the percussive influence thereon by the percussion member from a position wherein the end of the shank is in said field of operation to a position outside the field of operation, the at least one locking member being constituted by a spherical or cylindrical body displaceable through an aperture in the passage from a first, outer posi¬ tion in which the shank may freely be removed from the pass¬ age and a second, inner position in which the shank is pre¬ vented from removal from the passage by abutment of the at least one locking member with the axial delimitation of said at least one recess. 7. A combination according to any of the preceding claims, wherein said at least two carrier grooves comprise two grooves arranged diametrically opposite each other in rela¬ tion to the rotational axis of the shank, said grooves having a generally U-shaped cross section with a carrier flank for transmitting the rotational forces and a generally opposed inactive flank, said carrier flank penetrating deeper into the shank than said inactive flank. 8. A combination according to any of the preceding claims, wherein said carrier flank is substantially planar, the di¬ rection of said carrier flank at right angles to the axial direction of same substantially intersecting the axis of rotation of the shank. 9. A combination according to any of the preceding claims, wherein the outer peripheral surface of the shank is circular cylindrical in relation to the axis of rotation of said shank. 10. A combination according to any of the preceding claims, wherein the interior surface of said passage is circular cylindrical in relation to the axis of rotation of said shank. 11. A combination according to any of the claims 7-10, where¬ in said outer peripheral surface of the shank has one or more pairs of additional axially extending carrier grooves having a carrier flank and an inactive flank, each of said addi¬ tional grooves of a pair arranged substantially diametrically opposite one another in relation to the axis of rotation of the shank. 12. A combination according to claim 11, wherein the addi¬ tional carrier grooves subdivide the circumferential distance between said two U-shaped groves into substantially equal portions. 13. A combination according to claim 11 or 12, wherein said additional grooves have a generally V-shaped cross section. 14. A combination according any of the claims 11-13, wherein at least one of the additional grooves at least partially overlies one axially delimited recess. 15. A combination according to any of the claims 7-14, where- in at least two of the axially extending carrier grooves have an axial extent from the free end of the shank substantially longer than the axial extent of said at least one axial recess from said free end. 16. A combination according to any of the claims 9-15, where- in the diameter of the shank is substantially equal to 10 mm. 17. A combination according to claim 15 and 16, wherein the axial extent of all the carrier grooves from the free end of the shank is at least 2 mm longer than the axial extent of said at least one axial recess from said free end. 18. A combination according to claim 15 and 16, wherein the axial extent of all the carrier grooves from the free end of the shank is the same and in the range of 4 to 9 mm longer than the axial extent of said at least one axial recess from said, free end. 19. A combination according to any of the preceding claims, wherein the carrier ribs are such that only a partial extent substantially less than the entire length of the carrier flanks of the carrier grooves are utilized for transmitting the rotational forces, said utilized partial extent extending from the innermost limit of the grooves towards the free end of the shank. 20. A combination according to any of the claims 19, wherein the length of each rib is substantially equal to said uti¬ lized partial extent of the respective carrier flank. 21. A combination according to claim 19 or 20, wherein said utilized partial extent of each of the carrier flanks is less than half the entire length thereof. 22. A combination according to any of the claims 3, 4 or 6- 21, wherein the at least one axially delimited recess of the shank of said non-percussive type drill has an axial length only slightly larger than the axial extent of the correspond¬ ing at least one locking member. 23. A combination according to any of the claims 3, 4 or 6- 22, wherein the shank of the non-percussive type drill is manufactured separately from the rest or fluted portion of the drill and is provided with attachment means for cooperat¬ ing with corresponding attachment means at the inactive end of the fluted portion of the drill for fixedly interconnect¬ ing said shank and said fluted portion to constitute the final drill. 24. A combination according to claim 23, wherein the shank is manufactured from a metal powder component. 25. A combination according to claim 23, wherein the shank is manufactured from a suitable plastic material such as for instance polyamide. 26. A combination according to any of the claims 23-25, wherein the attachment means comprise an axial recess in the end of the shank opposite the free end thereof for receiving a corresponding axial end portion of the fluted portion, said end portion being fixed in the recess by means of adhesive or solder. 27. A combination according to claim 24, wherein the attach¬ ment means comprise a circular, planar, radial surface at the free end of the shank and at the inactive end of the fluted portion, said surfaces having substantially equal dimensions and being fixedly attached to each other by means of friction welding, resistance welding or ultrasonic welding. 28. A combination according to any of the preceding claims, wherein the drill holder is adapted for being mounted on a portable or hand-held drilling machine. 29. A drill holder for use in a combination according to any of the preceding claims. 30. A drill for use in a combination according to any of the claims 1-28. 31. A drill holder comprising the features of a drill holder according to any of the claims 1-28. 32. A drill comprising the features of a drill according to any of the claims 1-28.

Inventors: NIELSEN MOGENS BJARNE, NIELSEN, MOGENS, BJARNE
Applicants: AMERICAN TOOL COMP INC, NIELSEN MOGENS BJARNE, AMERICAN TOOL COMPANIES, INC., NIELSEN, MOGENS, BJARNE
Application year: 1995
Main classification: B25D17
IPC codes: B23B31, B23B45, B25D17