The invention relates to a down-the-hole drilling devi ^¬ ce according to the preamble of the independent claim directed thereto.

A way to carry out earth drilling in a developed manner with respect to traditional technique is known e.g. from Finnish Patent No. 95618. A drilling head in a drilling unit of the drilling apparatus that exists inside a casing part or in other words a so called earth pipe or casing pipe presented in this patent is formed of a first frame part and an annular second frame part, the drilling surfaces of which being provi- ded with drilling organs, such as drill bits or like, of the first and second drilling means or in other words of a center drill or a pilot and a reaming drill or a reamer. In this solution the first frame part forming the pilot, is being released from the second frame part forming the reamer, in order to pull the same alone off from a drilled hole after the drilling situation .

The solution in question is provided with an arrange- ment, which locks the said drilling means together for a drilling situation unrotatively in respect with each other and in both directions longitudinally, in which context as an advantageous embodiment a bayonet coup ^¬ ling has been used.

After many years of experience, the drilling device according to the above mentioned patent has proved very efficient in practise and also very easy to be adjusted for different kinds of drilling purposes. E.g. regar- ding a drilling device of this type, there has, howe ^¬ ver, been found possibilities for making its func ^¬ tioning more efficient particularly in drilling of different kinds of soils. In this context modifications of the first drilling means i.e. the pilot have been developed and tested, wherein e.g. a feed channel of the flushing flow arrangement has been used, which at least partly ends up on the drilling surface at a flushing channel that exists in the longitudinal direc ^¬ tion of the drilling device essentially lower than the lowest part of the drilling surface of the pilot. Furt ^¬ hermore the flushing channel on the drilling surface of the pilot has been arranged to widen in its longitu- dinal direction towards the outer periphery of the pilot in order to make flushing on the drilling surface more efficient.

Despite the above modifications, an adequate result has not been achieved under all circumstances particularly due to clogging of the drilling surface e.g. particu ^¬ larly in drilling clayey soil or soil comprising soft sand . It is an aim of the down-the-hole drilling device ac ^¬ cording to the present invention to bring about a de ^¬ cisive improvement particularly in the problems descri ^¬ bed above in drilling different types of soil and thus to raise essentially the level of prior art. In order to carry out this aim, the down-the-hole drilling devi ^¬ ce according to the invention is mainly characterized by what has been presented in the characterizing part of the independent claim directed thereto. As the most important advantages of the down-the-hole drilling device according to the invention may be mentioned simplicity of constructions and operating prin ^¬ ciple enabled by the same. The above are first of all thanks to the fact that the applicability of the dril- ling device, being found profitable in practice as such, can be further improved by making possible drilling with the same drilling device construction having an efficiently operating drilling face for a wide va- riety of soil types. Thanks to the invention, by virtue of the supplementary flushing groove on the bottom of the flushing channel, more space is left for the soil and drilling waste facing the drilling surface of the drilling device. In this context as an advantageous embodiment, a supplementary flushing groove having a constant width from an opening of the feed channel to the outer periphery of the pilot can be exploited. The drilling efficiency can be further enhanced by exploi- ting a supplementary flushing groove having a cross section that at least partly gets larger in its longi ^¬ tudinal direction. In this way removing of the drilling waste through the return flow channels on the side surface of the pilot can be made furthermore even more efficient simply by a backward sloping bottom of the supplementary flushing groove. Furthermore, as an ad ^¬ vantageous embodiment of the invention, the side walls of the flushing channels and the supplementary flushing grooves are aligned with a plane parallel with the longitudinal direction of the drilling arrangement, in which case the longitudinal edges of the said side walls bring about more efficient cutting effect parti ^¬ cularly in drilling of soft material and particularly clay .

By virtue of the invention, the functioning of the drilling device may be enhanced also by eli ^¬ minating/retarding wear thus increasing the life time of the drilling arrangement. Thanks to the invention also the speed of drilling can be increased with res ^¬ pect to traditional constructions thanks to avoiding clogging of the drilling face, whereby also both air and water can be used as the flushing medium. Other advantageous embodiments of the down-the-hole drilling device according to the invention have been presented in the dependent claims directed thereto. In the following description the invention is being illustrated in detail with reference to the appended drawings, in which in figure 1

is shown a perspective view of an advanta ^¬ geous down-the-hole drilling device according to the invention with a casing shoe, in figure 2

is shown a perspective view of an alternative down-the-hole drilling device with respect to the one shown in figure 1 with a casing shoe, the pilot thereof having a drop center i.e. concave front, in figure 3

is shown a front view of the drilling device according to figure 1, in figure 4

is shown a longitudinal cross-section of the drilling device according to figure 1 toget ^¬ her with a casing shoe and a casing part, in figure 5

is shown a longitudinal cross-section corres ^¬ ponding to figure 4 of the drilling device according to figure 2, in figure 6

is shown a side view of the pilot of the drilling device shown in figure 1, in figure 7

is shown a side view of the pilot of the drilling device according to figure 2, and in figure 8

is shown a side view of an alternative pilot design particularly with respect to the one shown in figure 6.

The invention relates to a down-the-hole drilling devi ^¬ ce, being meant for drilling a hole with a casing part 2. The drilling device comprises in its drilling head I: a drilling arrangement, having first drilling means 4 for drilling a center hole and second drilling means

5 for reaming the center hole for the casing part 2 ; and a flushing flow arrangement 6 for feeding of a flushing medium onto a drilling surface P of the drilling arrangement by one or more feed channels 6a and for discharging the same from the drilling surface P together with drilling waste backwards with respect to the drilling direction. The casing part 2 is arranged to be pulled into the hole to be drilled by power in ^¬ fluence directed thereto from the drilling arrangement, such as the first and/or the second drilling means 4,

5. A feed channel 6a of the flushing flow arrangement

6 at least partly ends up on the drilling surface P at a flushing channel 6al that exists in the longitudinal direction s of the drilling device essentially behind a rearmost part PI ' of the drilling surface PI of at least of the first drilling means 4 as shown in figures 4-8. The flushing flow arrangement 6 comprises on a bottom of the flushing channel 6al a supplementary flushing groove 6a2 as seen in figures 1, 2, 4-8 that extends from the feed channel 6a towards the outer periphery of the drilling arrangement.

As an advantageous embodiment of the down-the-hole drilling device according to the invention, the dril- ling head I of the drilling device 1 consists of a first frame part 4a and a second frame part 5a. The drilling surfaces PI, P2 formed of end surfaces of the frame parts are provided with drilling organs of the first and the second drilling means 4, 5, such as an integrated drilling part, separate drilling pieces, bits or like. The essentially rotationally symmetrical first and second drilling means 4, 5 are coupled with each other on the first hand at least during a drilling situation in a power transmitting manner by means of a coupling arrangement in order to carry out co-operation thereof for a rotational motion, a feeding motion and/- or a hammering motion and on the other hand removably in order to enable removal of the first drilling means

4 from a drilled hole. The drilling arrangement is provided with a casing shoe 8 as shown e.g. in figures 4 and 5 for pulling the casing part 2 into the hole by means of a shoulder arrangement L enabling an indepen- dent rotational movement of the casing part 2 and the drilling device 1 with respect to each other and rest ^¬ ricting mutual longitudinal s movement thereof. With reference e.g. to figures 4 and 5, the flushing flow arrangement 6 comprises one or more longitudinal s return flow channels 6b on the side surface of the first drilling means 4 for removing drilling waste between the first and second drilling means 4, 5 inside the casing part 2. The flushing channel 6al on the drilling surface PI of the first drilling means 4 wi- dens in its longitudinal direction r towards the outer periphery of the first drilling means 4. The supplementary flushing groove 6a2 has a constant width from an opening 0 of the feed channel 6a in the flushing chan ^¬ nel 6al to the outer periphery of the first drilling means 4, such as the first frame part 4a.

As a furthermore advantageous embodiment of the down- the-hole drilling device according to the invention, the supplementary flushing groove 6a2 may be construc- ted to have a cross section perpendicular to its longitudinal direction r that remains constant for the whole length thereof (this kind of embodiment has not been shown in the drawings) . The drilling devices in the drawings 1, 3, 4, 6 and 8 have a pilot 4; 4a with a planar drilling surface PI, when instead the drilling devices shown in figures 2, 5 and 7 have a pilot with a drop center i.e. concave front DR.

As a furthermore advantageous embodiment of the down- the-hole drilling device 1 according to the invention, the supplementary flushing groove 6a2 has a cross sec- tion perpendicular to its longitudinal direction r that at least partly gets larger in its longitudinal direc ^¬ tion r.

Furthermore, as an advantageous embodiment of the down- the-hole drilling device according to the invention, the supplementary flushing groove 6a2 is connected to a return flow channel 6b of the flushing flow arrange ^¬ ment 6 for returning of the flushing medium together with drilling waste on the side surface of the first drilling means 4 with a part 6a2' having a backward sloping bottom as shown e.g. in figures 4 and 5.

Furthermore, as an advantageous embodiment of the down- the-hole drilling device according to the invention, the supplementary flushing groove 6a2 comprises a part

6a2" with a bottom in an essentially transverse plane with respect to the longitudinal direction s of the drilling device as shown e.g. in figures 4 and 5. Furthermore, as an advantageous embodiment of the down- the-hole drilling device according to the invention, the cross section of the supplementary flushing groove 6a2 perpendicular to its longitudinal direction r is arched as shown e.g. in figures 6 and 7.

As a furthermore advantageous embodiment of the down- the-hole drilling device according to the invention, the cross section of the supplementary flushing groove 6a2 perpendicular to its longitudinal direction r is essentially rectangular or square shaped as shown e.g. in figure 8. With reference e.g. to figures 6-8, as a furthermore advantageous embodiment of the down-the-hole drilling device according to the invention, the essentially planar bottom of the flushing channel 6al and/or the supplementary flushing groove 6a2 is connected in a rounded manner to the respective sidewalls sw thereof.

Furthermore, as an advantageous embodiment of the down- the-hole drilling device according to the invention, the sidewalls sw of the one or more flushing channels 6al and/or supplementary flushing grooves 6a2 are aligned with a plane parallel with the longitudinal direc ^¬ tion s of the drilling device, thanks to which the longitudinal edges of the said channels improve radi ^¬ cally the drilling efficiency of the drilling device in drilling of most heterogeneous soil types.

It is clear that the invention is not limited to the embodiments shown or described above, but instead it can be modified within limits of the basic idea of the present invention according to the needs at any given time. It is thus clear, that the constructions of the drilling devices being illustrated in the drawings may vary in practice very much merely when being carried out with differing diameters. Furthermore a supplemen- tary flushing groove can be exploited, the width of which increases in its longitudinal direction, or the bottom of which may be sloped backward in an arched manner. Also the one or more feed channels, the flush ^¬ ing channels and/or the supplementary flushing grooves may be arranged in more or less sloped positions than shown in the drawings. Furthermore bevellings in diffe ^¬ rent corners of the drilling device constructions shown in the drawings can be replaced by more or less rounded shapes etc. On the other hand, instead of the type of embodiments shown in the drawings, it is naturally possible to use as the drilling device also other dril ^¬ ling devices that are applicable for the same purpose, in which a casing part may be exploited in connection with the drilling that is drawn into the ground unrota- tively without or with a casing shoe. The casing part can naturally also be pulled into the hole by the first frame part i.e. the pilot, in which case the second frame part i.e. the reamer, such as a "reaming ring", may be situated further back in the longitudinal direction than the reamers presented in the drawings. It is not that significant for the down-the-hole dril ^¬ ling device according to the invention, either, how the first and second drilling means are coupled with each other, so that a wide variety of different solutions can be exploited as the power transmission assemblies between the same.