WO1999034085A1

WO1999034085A1 - Combined rotation drill

Info

Publication number: WO1999034085A1
Application number: PCT/IT1998/000282
Authority: WO
Inventors: Stefano Tongiani
Original assignee: Stefano Tongiani
Priority date: 1997-12-29
Filing date: 1998-10-15
Publication date: 1999-07-08
Also published as: ITMS970012A0; AU9644598A; IT1297925B1; ITMS970012A1

Abstract

A drill comprising a substantially tubular, cylindrical stem (1) connectable to a drive device to receive therefrom a rotational movement around its own axis. Stem (1) pivotally supports at its inside a coaxial shaft (15), connectable to the drive device to receive therefrom a rotational movement at a different speed from that of stem (1). Stem (1) pivotally supports also disk-shaped cutting means (31), placed in correspondence to its free end and rotatable with respect to the stem on a diametrical plane thereof, and gear means (24), meshing with shaft (15) and cutting disks (31), to operate disks (31) as a consequence of the speed difference between shaft (15) and stem (1).

Description

TITLE COMBINED ROTATION DRILL DESCRIPTION Field of the Invention The present invention relates to the field of drilling tools, and in particular concerns a drill for use in the drilling field in general, for instance the mining, oil or building ones, in that of stone manufacturing, as well as in all the similar fields. Description of the Prior Art

At present, in the drilling field widia bit drills are used in a substantially exclusive way. Three kinds of drills are essentially known, corresponding to three different drilling systems. In a first system the drill is simply made of a metal stem, to an end of which cutting bits, radially extending, are connected. The drill is rotationally operated around its own axis and fed with a constant speed along the same axis . In a second kind of drill, a cutting action on the material substantially similar to the previous one is enhanced by a crumbling action provided by a pneumatic hammer, slidable within a bore axially formed in the drill to exert a percussion on the bottom thereof, placed in correspondence to the end of the drill and then adjacent to the bits.

Finally, a third kind of drill comprises a rotating stem, axially operated with a constant feeding speed, from the end of which a number of cutting tools axially extend, freely rotatable around their own axis, radially spaced and convergent with respect to that of the stem itself. Gear means prevent the independent rotation of the tools, angularly equally spaced around the stem axis. With this system, it is the friction between the material to be removed, induced by the rotation of the stem and by its feeding, as well as by the interaction among the tools, to rotate the cutting tools, allowing them to exert a substantially crumbling^' action on the material itself.

It has to be pointed out that in the drills of the first two kinds the cutting edges operate with a cutting speed which decreases radially to zero in correspondence of the rotation axis. As for the drills of the third kind, it is not possible to establish a direct relation between the parameters which can be controlled from the external and the cutting speed with which the single tools work on the material, since the rotation thereof around their own axis is driven by the interaction between tool and material and between tool and tool. As a consequence, the local speeds in the cutting edges, beside being unpredictable, are extremely variable, and the probability to have in some points very low, or even null, cutting speeds is very high. In general, it has to be stressed how a locally null cutting speed is a serious drawback. In fact, in the areas where the cutting speed is low, the action on the material is prevalently a crumbling one. This does not allow the use of tools made of a too hard, and consequently brittle, steel and on the contrary it compels to use tools made of tough steel. However, the latter wear very quickly, and the continuous dressing operations, required during the drilling, cause important losses in productivity.

More specifically, the second of the above mentioned systems, known in the field also as "bore-bottom hammer system", for the high drilling speed which can be achieved, is the one having the higher productivity. However, for a correct operation, the drill requires excellent sharpening conditions of its cutting edges and so, for the above described reasons, the dressing must be particularly frequent. It will be easily appreciated how this can be severe for what concerns time wastes, namely in case of deep boreholes. Its use is then limited to low-depth boreholes, i.e. not deeper than some tens of metres.

For deep boreholes, e.g. those for oil wells, which can reach even some kilometres depths, the third system is generally chosen. The relative simpleness of the drilling head makes it very reliable, and the losses in productivity due to breakdowns are then modest. Besides, the substantially crumbling action of the drill is not too much affected by the progressive wearing of the cutting edges, whereby it is not necessary to provide to very frequent dressings thereof. This also because generally in such drillings the material to be worked is not too hard, whereby even an almost completely crumbling action of the head actually assures a high feeding speed. But a problem concerned with the dressing even in this case arises, because the considerable depth makes even rare breaks extremely long and then troublesome. Nevertheless, these breaks are now and then necessary, because in the subsoil strata of very hard material, e.g. quartz, can be found, the drilling of which requires a cutting action of the tool.

The low or null cutting speeds does not allow also the use of diamond bits, having the highest hardness, because when operated with a low cutting speed the diamond has substantially no cutting capability, and the drill would break the material with a purely compressive action, with consequent too high stresses, wears and intolerably low drilling speeds.

Other drawbacks specifically concern the bore-bottom hammer drill, drastically limiting the possibilities of use of this system, which as said is at least in theory more productive than the others. In fact this drill, exploiting the percussion of a pneumatic hammer, causes very high noise emissions. Besides, the considerable air flow rate required for operating the hammer is ejected from the drilled hole carrying to the outside a large amount of dust, which hardly can be kept inside the drilling yard. These two aspects prevent, or however strongly limit, the use of the drill in urban environments and in general where the environmental impact of the drilling operations has to be kept as restrained as possible. Finally, this drill doesn't allow the accomplishment of large boreholes, for which hugely powered pneumatic hammers, requiring then an air flow rate impossible to feed in the drilling conditions, would be necessary. Summary of the Invention The main object of the present invention is to provide a drill whi^'ch, keeping the external operating parameters constant, works with a substantially constant and determined speed in all the points of the cutting front.

A particular object of the present invention is to provide a drill of the above mentioned kind which, allowing the accomplishment of high operating speeds in all the points of the cutting front, can assure an actual cutting action on the material to be worked, permitting then the use of high hardness materials for the construction of the tool, with consequently reduced losses of productivity due to dressing operations.

A further object of the present invention is to - D -

provide a drill of the above mentioned kind, the operation of which involves relatively low noise emission and substantially no dust ones, so that the drill can be used even in urban environments. These objects have been achieved with the drill according to the present invention, characterised in what stated in the enclosed claim 1.

Brief description of the drawings

Other features and advantages of the drill according to the present invention will be apparent from the following description of one of its embodiments, to be intended only as an example and not a limitation, with reference to the attached drawings in which:

- figure 1 is a side view of the drill according to the invention;

- figure 2 is an axial cross sectional view of the drill of figure 1 taken along line II-II;

- figure 3 is a transversal cross sectional view of the drill of figure 1 taken along line III-III; - figures 4 and 5 are transversal cross sectional views of the drill respectively taken along lines IV- IV and V-V of figure 2;

- figure 6 is an axial cross sectional view of an example of a drive device of the drill according to the invention;

- figure 7 is an axial cross sectional view of an extension member to be put between the drill according to the invention and the drive device of figure 6.

Description of the preferred embodiment With reference to the figures from 1 to 5 , the drill according to the invention comprises a cylindrical tubular stem, generally indicated at 1, made by a coupling section 2 and a front section 3, coaxially engaged with each other by means of a screwed connection (figure 2) , sealed by a couple of 0-rings 35. Coupling section 2 has at its free end a sleeve 5, engageable with a drive device, described below, for carrying into rotation the whole stem 1 around its own axis. Front section 3, the free end of which is shaped according to an hemispherical dome 6, comprises two halves 3a, 3b, mutually fixed along a diametrical plan of stem 1 by means of screws 50 and with the assistance of locating pegs 51.

Stem 1 internally defines a recess 7, having a composite shape, in which the following parts, starting from sleeve 5 and communicating each other, can be identified: a substantially cylindrical bore 8, axially extending along coupling section 2 and part of front section 3; a first chamber 9, substantially cylindrical, formed in front section 3 with an axis incident and orthogonal to that of stem 1; and a second chamber 10, substantially cylindrical as well, formed in front section 3 in correspondence to hemispherical dome 6, with an axis parallel to ^'that of first chamber 9.

In correspondence to first chamber 9 and second chamber 10, respective couples of through seatings 11 and 12 are formed in front section 3, each couple being coaxial to the respective chamber. Namely, the axis of each seating 12 lies on the base plane of hemispherical dome 6, i. e. that from which dome 6 extends. A disk-shaped cut is also diametrically formed in dome 6, coaxially to second chamber 10. Cut 13 opens chamber 10 on the outside across dome 6, reaching first chamber 9.

A shaft 15 pivotally engages within bore 8 of recess 7 via a couple of bearings 14. A coupling element 16, placed within bore 8 as well, is keyed to the end of shaft 15 adjacent to coupling section 2 of stem 1, by means of a key 19.

Going into further details, the inner rings of bearings 14 are axially blocked between a shoulder 15a of shaft 15 and a shoulder face 16a of coupling element 16, a spacer 20 being placed between the rings. Outer rings of bearings 14 abut against a shoulder surface 3c of front section 3 and a retainer cap 21 engaging via screws 22 with front section 3 itself, externally to coupling element 16. In correspondence to sleeve 5 coupling element 16 has also an axial protrusion 17, comprising an axial fork 17a and a stop ring 17b, allowing its engagement with the above mentioned drive device. Rings 37 for sealing the lubricant are placed near bearings 14, according to an obvious arrangement for an expert in the field.

The end of shaft 15 placed adjacent to front section 3 of stem 1 supports a bevel gear 23 within first chamber 9, within which two wheels 24 are also placed. Wheels 24 are pivotally supported via bearings 25 by a first axle 26, integrally extending between the two seatings 11 of front section 3, each wheel 24 being substantially adjacent to a respective seating 11.

Each wheel 24 has two gears, i. e. a bevel gear 24a, meshing with bevel gear 23 of wheel 15, and a spur gear 24b, which on one side is placed externally to the same bevel gear 23 and on the diametrically opposed one extends within second chamber 10, to mesh with a spur gear 27a of a respective wheel 27. More precisely, wheels 27 are turnably supported within second chamber 10 by a second axle 28, extending between seatings 12 of front section 3, via a couple of bearings 29. These are axially blocked between a - o -

shoulder 28a of second axle 28 and a spacer 52 retained by a cap 30, engaging by means of an axial screw 53 with second axle 28 itself.

Each wheel 27 supports near the respective gear 27a a couple of disks 31, housed within cut 13, axially spaced by a gap 34. A respective crown of radial diamond bits 32 is connected to the outer profile of disks 31. Bits 32, angularly equally spaced, extend out of hemispherical dome 6, along the whole opening of cut 13 thereon. To prevent the interference, when disks 31 rotate, between bits 32, extending within first chamber 9, and first axle 26, a radial cut 26a is centrally formed in axle 26 itself.

Along the whole shaft 15 an axial duct 33 is formed, communicating through a diametrical seating 54, centrally formed in first axle 26, with cut 13, to permit the flow therein of a fluid for refrigerating cutting bits 32. The fluid is fed from the external to axial duct 33 in a known way through a hole 36 centrally formed in coupling element 16. The drill according to the invention works in the following way. Stem 1 and shaft 15 are rotated, respectively via sleeve 5 of coupling section 2 and protrusion 17 of coupling element 16, with different speeds. This makes bevel gears 24a of wheels 24, keyed on first axle 26 rotating integrally to front section 3 of stem 1, mesh with bevel gear 23 of shaft 15. Wheels 24 then, besides being revolved around shaft 15 by first axle 26, rotate around the same axle 26, in opposite directions from each other. The engagement between spur gears 24b of wheels 24 and those 27a of wheels 27, also revolved integrally to stem 1 by second axle 28, causes their rotation around second axle 28 itself. Disks 31, integral to wheels 27, are consequently counter-rotating with respect to each other. Bits 32 then have a cutting action on the material which comes from the combination of a rotation around second axle 28 and a rotation around the axis of stem 1. It will be easily appreciated that, thanks to this, there is no significant reduction of the cutting speed in the area surrounding the rotation axis of the drill.

The drill according to the invention can be operated in a way which is substantially obvious to an expert in the field. Nevertheless, figure 6 shows an example of drive device, to be connected to the drill for the operation thereof. Though this device does not directly fall within the scope of the invention, a brief description of it, limited to its functionally relevant parts, will be provided hereinafter. The device comprises a fixed frame 38, pivotally supporting a cup 40, engageable with sleeve 5 of coupling section 2 of stem 1 and which can be operated in a known way by an engine, not shown. Frame 38 pivotally supports also a shaft 39, internally coaxial to cup 40 and fit to the^' connection with protrusion 17 of coupling element 16 to rotate shaft 15.

Respective gears 41 and 42 are keyed on shaft 39, axially hollow to permit the flow of the refrigerating fluid, and on cup 40. Furthermore, frame 38 houses a train of gears, generally indicated at 43, by means of which the transmission of the rotation from gear 42 of cup 40 to gear 41 of shaft 39 is allowed.

By varying the design parameters of train 43, the transmission ratio between cup 40 and shaft 39 can be controlled within a wide range, whereby it is possible to accomplish different operating speeds for stem 1 and shaft 15, possibly even in opposite directions, and as a consequence to establish the speed of disks 31 carrying cutting bits 32.

Only seldom the connection between the drill according to the invention and a drive device like that above described occurs directly. As a matter of fact, when the depth of the borehole increases it is necessary to make use of one or more consecutive extension members, like that shown in figure 7, to be put between the device and the drill. It substantially comprises two tubular elements, an external one 44 and an internal one 45, coaxial and rotatable with respect to each other.

Corresponding ends of elements 44, 45 have respective coupling members 46 and 47 substantially identical to sleeve 5 and protrusion 17 of the drill, and so fit to the connection respectively with cup 40 and shaft 39 of the drive device. The other ends of elements 44, 45 likewise provide coupling members 48 and 49 substantially corresponding to cup 40 and shaft 39 and so engageable both directly with the drill and with another extension member.

The important advantages that the drill according to the invention achieves when compared to prior art solutions are first of all concerned with the accomplishment of a substantially constant cutting speed all over the cutting front . Tests lead with different operating parameters and for different materials to be worked have shown in various points of the cutting ^■ front speed variations not higher than 0.5%. As a consequence, increasing the cutting speed of bits 32, it is possible to ensure an actual cutting action on the material to be worked, and so to allow the use of hard steel bits, needing infrequent dressings and consequently allowing a high productivity. Though the possibility of operating with a very low, even null, cutting speed is not precluded, the combination of the two rotations of the bits permits to reach very high speeds, superior to those suggested considering the types of materials to be worked in the drilling area. Namely, the drill can easily operate within the rim speed ranges suggested for diamond disks, comprised between 10 and 70 m/sec. Diamond disks, besides offering the highest hardness, reduce the problem of the dressing to a negligible extent. As a matter of fact, the cutting edge with a diamond lining is continuously renewed in use because when the diamond chips, each representing an infinitesimal cutting edge, progressively wear, exert a higher and higher stress on the supporting binder until they are pulled off and uncover a virgin chip, until that moment unused and so perfectly cutting.

Thanks to the possibility of precisely checking from the external the speed of the cutting front, the characteristic parameters of the tool can be chosen (in particular the granulometry of the diamond lining) for best fitting each specific speed.

Moreover, the drill according to the invention operates with pretty reduced noise emissions, and in any case definitely lower than those of the drills of the bore- bottom system. There is no limitation to the maximum diameter of the boreholes which can be made and the produced dust comes up to the surface and out of the hole together with the refrigerating fluid. This makes the drill perfectly fit to the use even n urban environments, and in any case wherever the drilling demands the observance of the surrounding environmental conditions. It will be appreciated then how all the objects of the invention can be considered as fully achieved.

In the depicted embodiment a couple of counter- rotating wheels 24 is provided, each made through the connection of two parts respectively associated to bevel gear 24a and spur gear 24b. Wheels 24, housed within second chamber 10, can operate, via a respective wheel 27, a couple of disks 31, counter-rotating as well. This solution proves itself advantageous for a balanced operation of the drill, but it is obvious that a single wheel 24 is sufficient to assure the operation of a single wheel 27, and so of one or more disk(s) 31, rotating in the same direction. Anyway, the shown and described drill gearing is generally to be intended only as an example, since an expert in the field may adopt structurally different solutions, provided they can accomplish an equivalent transmission between shaft 15 and disks 31.

To avoid that, in very deep boreholes, the progressive wearing of the cutting disks 31 may cause the carrying out of slightly but perceptibly conical holes, one or more further axles, supporting respective cutting disks 31, can be placed in a parallel way along stem 1. In this way the supplementary disks perform a grinding action on the walls of the hole, which then remains constantly cylindrical with the increasing depth. Other variations and/or modifications that can be brought to the combined rotation drill according to the invention fall within the scope of the invention itself as stated in the appended claims .

Claims

1. A drill comprising a cylindrical stem ( 1 ) connectable to a drive device to receive therefrom a rotational operation around its own axis, characterised in that said stem (1) is substantially tubular and pivotally supports at its inside a coaxial shaft (15) , connectable to said drive device to receive therefrom a rotational operation at a different speed from that of said stem (1) , said stem (1) pivotally supporting also disk-shaped cutting means (31) , placed in correspondence to its free end and rotatable with respect to said stem on a substantially diametrical plane thereof, and transmission means (24) cooperating with said shaft (15) and said cutting means (31) to operate said cutting means (31) as a consequence of the speed difference between said shaft (15) and said stem (1) .

2. The drill according to claim 1, wherein said transmission means (24) comprise gear means (24) pivotally supported by a first axle (26) integrally extending within said stem (1) orthogonally to said diametrical plane and engaging with gears (23, 27a) respectively integral to said shaft (15) and said cutting means (31) .

3. The drill according to claim 1, wherein said free end of said stem (1) has substantially the shape of a dome

(6), said cutting means (31) comprising at least one cutting edge disk (31) pivotally supported by a second axle (28) , integral to said stem (1) and lying on the base plane of said dome (6) , said at least one disk (31) being housed within a diametrical cut (13) formed in said dome (6) and extending therefrom with its cutting rim.

4. The drill according to claim 3, wherein said gear means (24) comprise at least one double gear wheel (24) , comprising a bevel gear (24a) , engaging with a bevel gear (23) integral to said shaft (15) , and a spur gear (24b) engaging with at least one spur geared wheel (27) integral to said at least one cutting disk (31) .

5. The drill according to claim 4, wherein said tubular stem (1) internally defines a first chamber (9) , within which said first axle (26) is placed to support said at least one double gear wheel (24) , said shaft (15) protruding into said first chamber (9) , and a second chamber (10) within which said second axle (28) is placed to support said at least one spur geared wheel (27) and said at least one cutting disk (31) .

6. The drill according to claim 5, wherein said first axle (26) supports at its ends a couple of said double gear wheels (24) , each engaging with a respective of said spur geared wheels (27) , mounted on said second axle (28) .

7. The drill according to claim 6, wherein two cutting disks (31) are mounted spaced on said second axle (28) , each integral to a respective of said spur geared wheels

(27) and supporting a respective crown of radial cutting bits (32) angularly equally spaced.

8. The drill according to claim 7, wherein said cutting disks (31) are counter-rotating.

9. The drill according to claim 2, wherein an axial duct (33) is formed along said shaft (15), permitting in co-operation with a diametrical seating (54) formed in said first axle (26) , the feeding of a refrigerating fluid of said cutting means (31) within said second chamber (10) .

10. The drill according to claim 1, wherein said cutting means (31) are diamond disks.

11. The drill according to claim 3, comprising a number of said cutting edge disks (31) , placed in series along said stem (1) .