A DRILL FOR ROCK AND CONCRETE

Abstract: With drilling in rock and concrete there is used a drill rod provided at its forward end with a cutting means and intended for rotation. The rod comprises a thin-walled tube (11) the central cavity (20) of which is formed such that openings (22 and 23) are formed adjacent the forwardly situated cutting bit (12) on either side of the bit. The central cavity (20) communicates in its rear portion with one or more openings (28) in a part (13) attached to a shank, and in turn the part (13) coacts with a surrounding sleeve means (26) such as to form a suction coupling for sucking out rock dust from the drill hole.

Description: A DRILL FOR ROCK AND CONCRETE Drills for making holes in rock and concrete and intended for use with electrical hand drilling machines are generally made with carbide tips, which are fastened by brazing to a steel shank. Drilling is generally done dry, and the drilling machines generally provide torque and axial blows. During drilling the rock is crushed and pulverized due to the percus¬ sive and rotating contact with the carbide tip. For conveying the rock dust thus formed out of the hole, traditional drills are provided with at least two helical shaped grooves which extend from close to the tip along the shank of the drill. Drilling in a downward direction is more difficult to perform than in other directions for two reasons, both depending on difficulties with conveying the rock dust. The rock dust easily compacts in the grooves, and also it is not lifted up from the bottom of the hole to the beginning of the grooves and packs around the drill tips to prevent blows being trans¬ ferred to the rock. When drilling in a downward direction it is therefore necessary to lift the drill out after a short drilling length and clean the whole by blowing. This is particularly applicable with drilling in moist rock or con¬ crete. The result will be that the straightness of the hole and its roundness deteriorate, as well as the bore tip becoming worn more rapidly. When drilling in mines and the like, and when large hole dia¬ meter holes are made in concrete, the rock is generally removed by blowing in air, or pumping in water or water mixed with air at an excess pressure through the drill rod, which is made hollow for this purpose and without helical grooves. The rock dust is here conveyed out from the hole in the space between the outside of the drill rod and the wall of the hole. A disadvantage with all the mentioned methods is, however, that the rock dust collects at the drill hole openings where it can be difficult to handle. This is particularly a great disadvantage with drilling indoors. In drilling upwards, or horizontally, the rock dust is also a problem, e.g. it can fall into the drilling machine chuck, which will then be rapidly worn. Other structures for avoiding the problems with the rock dust include bellows which are pressed against the rock around the opening of the hole, which does not facilitate conveyance up out of the hole when drilling downwards. It has also been proposed, for hollow drills which are provided with a large number of cutting edges round the end face of the drill and which leave a core during drilling, to use a combination of liquid supply on the outside of the drill and suction on the inside of the drill partly to cool the cutting edges and partly to retain the core when the drill breaks through a floor structure or a wall. The present invention relates to a drill with a carbide cutting bit extending over the entire diameter of the hole, and adpated for drilling holes in rock or concrete without the supply of liquid, the dry rock dust being removed by suction in one or more ducts in the interior of the drill rod. To avoid the ducts being blocked by rock dust, their openings at the bit are made with a less area than the rest of the duct and with a sharp edge. The drill rod is made with a smooth cylindrical exterior of a less diameter than the length of the bit. Since carbide is relatively brittle, and can crack for unevenly distributed percussion, the carbide bit should be brazed into a holder part which supports the major part of the bit length, and in turn receives the precus- sion effect from the entire cross sectional area of the drill rod. Immediately under the upper end of the drill shank the duct or ducts are connected via a rotary coupling of a known type to a dust suction means. The upper end of the drill rod is formed in a manner known per se for transmission of percussion and torque from the drilling machine. The invention will now be described in more detail and in connection with the accompanying drawing figures, where Figure 1 is side view of one embodiment of the invention, Figure 2 illustrates the embodiment in Figure 1 with a means mounted on it for connection to a suction means, Figure 3 illustrates an alterantive embodiment. Figure 4 is a side view of the cutting bit and holder part separated from the drill rod in Figure 1, Figure 5 is a side view of the cutting bit and holder part in Figure 4, Figure 6 is a front view of the cutting bit and holder part in Figures 4-5, and Figure 7 illustrates the shank and a connection part, Figure 8 illustrates an alternative embodiment. The drill 10 illustrated on the drawings comprises a tube 11, provided at its forward end with a cutting bit 12 made from carbide or other like hardwearing material. The rear part of the tubular drill rod 11 comprises a cylindrical connection part 13 and axially rearward thereof a shank 14 adapted for transmission of percussion and torque. The tubular drill rod 11 is connected to the part 13 by brazing, preferably with a silver or copper based metal, and percussion from a drill machine 15 is also transferred via a shoulder 16 formed on the part 13, this shoulder extending round the entire circum¬ ference of the tube 11. The part 13 and shank 14 are preferably integral. To provide centering and a large joint surface for the brazed joint, the part 13 is made, for large drill dia¬ meters, with an axially projecting tubular spigot 17, which is thrust into the tube 11. For small drill diameters the cavity 27 is formed in the part 13 with a stepped bore so that the shoulder 16 will be situated inside the bore. At its lower end the drill rod 11 is joined by brazing to a steel holder part 18, and percussion is also transmitted through a radially formed annular shoulder 19 on the holder part 18, against which shoulder the tube 11 is intended to rest. For providing centering and larger joint surface, the holder part 18 is formed with an axially projecting spigot 20, the diameter of which is adjusted so that the spigot can be inserted in the central cavity 21 of the tube 11. At its forward end the holder part 18 is provided with a central U- shaped slot 22 for accommodating the cutting bit 12, which is inserted and brazed in the slot. The bit 12 has greater length than the slot so that it determines the diameter of the drillng hole. By having the bit 12 fastened in a separate holder part 18, of more ductile material it has been possible to reduce the stresses on the cutting bit 12 made from carbide or similar material. In addition, the holder part 18 is provided with two recesses 22 and 24 extending axially and in diametrically opposite positions, along the entire length of the spigot 20. At its lower end, the tube 11 can be cut off square, according to Figure 1. Another advantageous embodiment is where according to Figure 2, the tube 11 is provided with tongues 32 on the portions of circumference not resting against the shoulder 19, such that these tongues cover the major por¬ tion of the recesses 23 and 24. Each recess 23, 24 is formed with a lesser cross section than that of the central cavity 21 of the tube 11. It is thus intended that air and dust caused by the drilling are sucked in through the recesses 23 and 24 and further into the central bore 21 in the drill rod 11. There is a cylindrical tubular sleeve 25 round the part 13 and implemented such as to form a swivel coupling, which in turn is provided with a tubular side connection 26. The part 13 is hollow and provided with an axially central cavity 27, as well as one or more holes 28, which are intended to lie at the same level and have approximately the sa t section as the bore 29 in the side connection 26. The tubular sleeve 25 is rotatably mounted round the part 13 and rests against an annular shoulder 30 on the part 13. Both the cavity 27 and holes 28 have a greater cross section than the recesses 23 and 24. It is thus ensured that the particles coming in via the recesses 23, 24 into the hollow drill 10 are not caught up in it. The annular shoulder 30 can be supplemented by an exterior flange or support ring 31. The side connection 26 is intended for connecting to a separate suction means, such as an industrial vaccutn cleaner (not shown). The part 13 and tubular sleeve 25 form a swivel coupling, whereby the sleeve 25 is thus not intended to be rotated during drilling, but is fixed by the tubular side connection 26 to the drilling machine. The parts 13 and 25 of the swivel coupling can thus be given dimensions which are independent of the drill diameter, as will be seen from Figures 1 and 3 where the drill rod 11 and cutting bit 12 in Figure 3 are considerably less than in Figure 1, but otherwise with unaltered dimensions for the part 13. In an alternative embodiment of the invention, and for short drills, the holder part 18 can also be made integral with or in contact with the part 13 and shank 14. The recesses 23 and 24 then reach the whole way up from the forward tip of the holder part 18 to the lower edge of the part 13 there they are connected by axially made ducts 29 with the holes 28. Since in this case the holder part 18 extends backwards to the part 13 where the axial percussion is transmitted, there is no need of the engagement surface 19 and the tube 11 can therefore have the form of a thin walled tube, which promotes increased suction capacity in the inner cavity 21 of the tube 11.

Claims: AMENDED CLAIMS [received by the International Bureau on 18 December 1989 (18.12.89) original claims 1-8 replaced by amended claims 1-7 (2 pages)] 1. Drill (10) for making holes in rock and concrete with the aid of a hammering and rotating electrical hand drilling machine, including a drill rod in the forward end of which there is arranged a cutting bit (12) which determines the cutting diameter and which is made from carbide or similar hardwaring material, said drill rod having the form of a smooth cylindrical tube (11), the outer diameter of which is less than the cutting bit (12) and said central cavity (20) of the tube (11) being formed such that adjacent the cutting bit (12) there are formed two openings (22) and (23), one on either side of the bit (12), characterized in that the cutting bit (12) is provided in a holder part (18) which is attached to the forward end of the drill rod (11), in that the holder part (18) is generally flat and is provided with a wedge shaped point, in that the outside of the holder part (18), on either side of the cutting bit (12), is provided with axially extend¬ ing through-like recesses (23, 24) forming the lower openings to the inner cavity of the tube and which to a major extent project into the tube (11), and in that the tube (11) at its rear end portion facing away from the cutting bit (12) is connected to a cylindrical part (13) with one or more openings (28), which are arranged for co-action with a sleeve means (26) surrounding said part and provided with a side connection, such as to form a suction coupling of the swivel type for connecting to a suction means. 2. Drill as claimed in claim 1, characterized in that the lower openings (23, 24) have a lesser cross section than the interior cavity (21) of the tube. 3. Drill as claimed in claim 1 or 2, characterized in that the lower openings (23, 24) have a lesser cross section than each of the upper openings (28) . 4. Drill as claimed in any one of claims 1-3, characterized in that with the major part of its rear edge and its flat sides the cutting bit is fixed in a U-shaped slot (22) on the steel holder part (18) which is projecting inwards a distance into the tube (11), the tube thus engaging axially against a radial engagement surface (19) on the holder part (18). 5. Drill as claimed in any one of claims 1-4, characterized in that the shank (14) and part (13) attached to the shank are integral and that a tubular part (17) extends from the part (13) and is formed with a diameter such that it is easily insertable into the tube (11). 6. Drill as claimed in claim 4, characterized in that the holder part (18) extends axially into union with the part (13), the recesses (23, 24) being formed axially along the entire holder part (18) to the part (13) where they are connected with the holes (28) via axially extending ducts (29) in the inner wall of the part (13). 7. Drill as claimed in any one of claims 1-6, characterized in that the lower part of the tube (11) is provided with tongues (32) axially projecting from the rest of the tube and in diametrically opposing positions for being partially inserted into and covering the major part of the recesses (23, 24) on the holder part (18).

Inventors: SCHAGERSTROEM TONIE, SCHAGERSTROEM, TONIE
Applicants: SCHAGERSTROEM TONIE, SCHAGERSTROEM, TONIE
Application year: 1988
Main classification: E21C7
IPC codes: E21B10, E21B17, E21B21