METHOD FOR INNER CLEANING OF A CORE BIT WITH REVERSED FLUID FLUSHING AND A CORE BIT HEREFOR.

Method for inner cleaning of a core_ bit with reversed fluid flushin and a core bit herefor.

TECHNICAL FIELD Making holes in structures such as floors, flooring structures, walls, bridges, roads, runways, underwater columns and foundations etc. is carried out today to a large extent with the aid of tubular drills, so-called core drills, which often use diamonds or carbide as cuttin material. Core drilling, which may typically take place in concrete, brick or composite material, is tied to a series of problems. The requirements of cooling the drill bit and removing drill cuttings mean that water at a given pressur is generally supplied through the interior of the drill, and after having passed the cutting means, and having cooled the means, this water departs through the gap on the outside of the drill, drill cuttings being taken away at the same time. This dirty water may cause large problem and must generally be sucked up as well as possible. When making holes in such as a concrete flooring structure, this is relatively uncomplicated as long as the water only flows up around the drilling equipment. However, when the drill breaks through the flooring structure, water streams out into the underlying space, while the core liberated by drilling falls down into this space. Special precaut¬ ions must thus be taken for the space in question, from the aspects of both pure safety and dirtying.

Even before the drill breaks through there can be pro lems- in connection with drilling into such as conduits for electric cables and the like. When this happens, the water can flow off through such conduits and in the most unfavourable case even reach an electrical distribution bo

Other cavities in the flooring structure also give rise to the flow of water in it, which can cause trouble- some damage. This is particularly the case in connection with so-called floating flooring. With drilling in walls etc., when in principle the -drill must be kept horizontal, the difficulties in cater¬ ing for the water streaming out with the drill cuttings willbe_^very great. With the object of alleviating the above-mentioned problems it has been proposed to work with reversed fluid or water circulation direction. This means that a fluid intended for removing drill cuttings and/or cooling the core drill is supplied on the outside of the drill and that the fluid is sucked up after it has in general passed the cutt¬ ing means of the drill and through the interior of the drill. In other words, the interior of the core drill is connected to a suction source in a suitable way. This suct¬ ion source may usually comprise a conventional suction apparatus which can also suck up liquids, which has previ¬ ously been utilized for sucking up cooling water carrying drill cuttings flowing up from a drill hole on the outside of the core drill.

A series of considerable effects can be expected by a "reversal" of the fluid flow direction. The fluid (gene¬ rally water or air), which may be easily supplied without pressure to the outside of the core drill, e.g. quite simply through a pipe opening out adjacent the drill where it goes into the floor or the like., can be given a controlle flow path in direct connection to the core drill and cannot leave this flow path and cause problems. The fluid is suck¬ ed directly in along the core drill without externally be¬ ing able to spread away from the drill hole, even if the latter is horizontal. Once down in the drill hole the fluid is sucked along the drill, and suitably via the cutting means, effectively into the interior of the drill without any fluid flowing away transversely through a pierced con¬ duit or the like. The fluid, which takes the drill cuttings with it up through the interior of the drill, keeps the outside of the drill clean and provides a polishing or grinding effect on the drill core inside the drill. The drill core will thus be extremely smooth and easily handled The absence of deposits of drill cuttings enables the drill core to be generally easily removed after completed drilling.

Two considerable effects could be utilized in conn- ection with drilling through-holes. In the first place it should be possible to prevent the flow of liquid into the other space, and in the second place it should be possible to prevent the drill core from falling down into the other space, by virtue of its being retained firmly by suction inside the core drill. This retaining suction effect ought to be able to be utilized for also lifting up in a simple and smooth way a core broken free from the bottom of^" a bottoming drill hole, particularly when it is deep.

However, in practical trials it has been found diffi- cult to achieve all the advantages accounted for above in a reliable way. The reason for this is that it is difficult to get control over the fluid flow inside the core drill and the deposits of_, drill cuttings and/or drill sludge in¬ side the drill, particularly when drilling in concrete structures or substructures. The deposits have been found to create the risk that both circulation of the fluid and the suction effect cease. This may give rise to unenvisag- ed and uncontrolled outflows of fluid, overheated cutting means, dropped drill cores etc. The effects of such can be particularly troublesome in connection with through-going drilling and in connection with taking up the core drill from a drill hole.

OBJECT OF THE^' INVENTION The object of the present invention is to provide a new method of making holes with the utilization of a core drill and an improved core drill for use in conjunction herewith, whereby the problems with deposits inside the drill and deficient control of fluid circulation and suct- ion are substantially decreased. SUMMARY OF THE INVENTION

The above-mentioned object is achieved by a method and a core drill in accordance with the invention which have the features disclosed in the accompanying claims. The method in accordance with the invention thus means essentially that as the former drill core moves in the core drill, the inner wall of the drill is cleaned in front of, preferably immediately in front of, the upper surface of the core, from deposits of drill cuttings and/ /or drill sludge, so that the core can move in the drill without the suction gap between said inner wall and drill core being blocked up by such deposits. It is advantageous here to screen off or limit the interior cross-section of the drill between the upper surface of the drill core and the cleaning location in front so that sucking out in the interior of the drill can take place through a sub¬ stantially reduced, preferably centrally situated cross- -sectional area.

According to a preferred embodiment of the method in accordance with the invention, the cleaning is provided by the core being caused to thrust in front of it a cleaning member in cleaning engagement with the inner wall of the drill, free suction passages from the suction gap to the interior of the drill above the core being maintained be- tween the core and the cleaning member. In accordance with the invention the cleaning member is suitably utilized for providing the above mentioned cross-sectional restriction.

The core drill in accordance with the invention is essentially distinguished in that it comprises.an inner wall cleaning member displaceably arranged in the drill tube, which is preferably circu ferencially in cleaning engagement with the inner wall of the tube, and arranged so that during drilling it can be displaced in the tube in front of, and by the formed core to clean the inner wall from deposits and prevent blocking of the suction gap formed between the inner wall of the tube and the core during drilling. In accordance with the invention, the cleaning member to advantage includes a tubular or sleeve- -shaped element, the outer diameter of which is adjusted to the inner diameter of the drill tube, and which has a clean ing face facing towards the interior of the drill tube, pre ferably cut slopingly backwards or bevelled, the member being adapted for co-action with the core so that suction passages are secured between the member and the core when the latter thrusts the member in front of it. As previously indicated, it is advantageous that the cleaning member, also includes screening or limiting elements extending across th cross-section of the drill tube in front of, and preferably at a small spacing from the upper part of the formed drill core, so that a preferably centrally situated suction open¬ ing is formed which is substantially reduced in relation to the cross-sectional area of the drill tube.

The invention will be further perceived from the foll owing closer description of a non-restricting embodiment an with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic side view of an apparatus for drilling holes in a floor utilizing a core drill and "rever¬ sed" fluid circulation direction. Fig. 2 is a schematic ver¬ tical sectional view with certain section parts unnecessary for understanding the invention being removed, of a core. drill in accordance with the invention.

DESCRIPTION OF EMBODIMENT _.

The apparatus illustrated in Figs 1 and 2 includes a drill stand 1 with a drilling machine 3 attached thereto for controllable raising and lowering, there being a core drill and a suction means 7 attached to the drilling machine. In¬ side the drill there is a cleaning member 6 which will be described more closely later. The apparatus is adapted for drilling a hole 9 in a concrete floor 11. The suction means 7 has its suction line 13 connected to a suction connection means 15 upwards on the drill 5. Water cleaned in the suctio means is recirculated via a line 17 to the edge of the hole 9, where the water is allowed to flow without pressure down into the hole at the side of the drill 5, as indicated by the arrow 18. The water thus flows downwards on the outside of the drill 5 in an ingoing suction gap 22 formed between the hole wall 20 and the outer wall 21 of the drill, past the core drill cutting means 19 in the spaces between the cutting means while taking with it drill cuttings and coolin the cutting means,up through an outgoing suction gap 23 between the inner wall 24 of the drill and the core 25, which is formed, through the cleaning member 6 and through the hollow shank 27 of the core drill 5 as well as the suction con¬ nection means 15 and the line 13 back to the suction means 7. This flow of water is illustrated by arrows in the Figs. 1-2.

The construction of the suction coupling means 15 will be seen from Fig. 2. In the upper end wall 28 of the cylindrical core drill 5 there- is attached an axial hollow shank 27, as mentioned, such that its lower open end 29 extends a small distance into the interior of the core drill 5. A plug 31 is fixed into the upper end of the shaft, and constitutes a connection element for connecting the core drill to the drilling machine 3, which may be of any optio¬ nal kind. The plug 31 may be threaded internally, indicated by dashed lines 33, if the connection requires threaded engagement.

The tubular shank has a cylindrical outer surface with a waisted area 35 in the middle. In this area there is a round hole 3.7. in the wall of the shank 27 leading into its interior. Round the cylindrical portion of the shank 27 there is a cylindrical tubular sleeve 39 having a lateral connection pipe stub 41 for the line 13 from the suction means 7. The pipe stub 41 is at a level with, and has appro¬ ximately the same section as the hole 37. The sleeve 39, which is rotatable relative the shank 27, rests on a cir¬ cumferential shoulder 43 downwards on the shank 27 and connects substantially sealingly to both cylinder surfaces 45,47 on either side of the waisted area 35. This area thus defines, together with the sleeve 39, an annular gap 49 in communication both with the interior of shank 27 and core drill 5 and with the pipe stub 41 independent of the rela- tive positions between the sleeve 39 and shank 27. There is thus ensured a continuous suction effect.

It will be understood that the described suction connection means is very simple and that the sleeve 39 can readily be thrust on to and removed from the shank 27. In other words, the same sleeve can be used in combination with many different core drills of different sizes and im¬ plementation, as long as these are merely provided with a tubular shank 27 provided with a hole and of uniform imple¬ mentation. The cleaning member 6 (Fig. 2) comprises a circumfe¬ rential collar or sleeve-like element 51, the outer diame¬ ter of which is only slightly less than the inner diameter of the drill tube 5. The element is freely displaceable within the core drill and has a height such that it does not have any tendency to bind. The upper face 53 of the element 51 constitutes a cleaning face and is bevelled backwards so that a sharp edge is formed which can easily pare or scrape off deposits or sediment 55 on the inner wall 24 of the drill tube 5. These deposits 55 have been found to form easily due to the rotation of the drill tube giving a centrifuging effect. The backward bevel also gives an advantageous deflection of cleaned-off material towards the center of the drill tube, where the material is rapidly entrained and sucked up towards and out through the shank 27.

The lower face 57 of the element 51 is similarly obliquely cut. or bevelled, although in the opposite direct¬ ion. This bevel is not entirely circumferential, since there are six portions 59 uniformly distributed around the circumference which entirely lack a bevel and therefore for abutments for co-action with the upper part 26 of the core 25. Contact between the abutments 59 and the core 25 is ensured by the inner diameter of the element 51 being less than the diameter of the core. In connection with drilling the element 51 will consequently be thrust into the drill tube by the core 25 formed, and thereby clean that portion of the inner wall 24 lying above the suction gap 23. In ■ other words, this gap does not risk being blocked up due to the circumferential edge of the core digging into depo¬ sits or sediment on the inner wall 24. The portions 59 en¬ sure that the opening of the suction gap 23 cannot be close off by the lower edge 57 of the element 51, and there are always free suction paths or passages in towards the inte¬ rior of the drill tube 5. It should be emphasized that the lower bevel 57 on the element 51 contributes to directing the flow from the suction gap 23 in towards the centre of the drill tube and that after drilling it facilitates the return of the element 51 towards the end of the drill provi ed with cutting means 19 if, contrary to expectations, there would be any deposits on the inner wall of the tube. In other words, a cleaning effect can also be obtained on the return of the cleaning member 6. Such a return is also facilitated by the cleaning member 6 having a certain weigh This also prevents the member from being sucked inwards in the drill tube 5 instead of being thrust in by the core 25. According to a furth'er aspect of the present invent- ion, the cleaning member 6 also includes a throttling or restricting element 61 connected to the collar or sleeve- -like element 51. This restricting element has the form of a circular disc, the circumference of which is sealingly joined to the element 51 at the lower or outer end of the latter and has a central hole 63, with a diameter which is approximately the same as the diameter of the suction hole in the shank. The hole 63 could however be even smaller if further increased fluid velocity therethrough were desirable by this means. The discelement 61 is at a small distance from the upper part 26 of the core 25, whereby the free space between the core and the cleaning member will be small. As will be seen, the cleaning member 6 has the cha¬ racter of a piston-like free insert, which is suitably place inside the drill tube 5 before the cutting means 19 are fitted. When the latter are in place they prevent the clean ing member from falling out of the drill tube.

A further essential feature is that the cleaning mem¬ ber will not be subjected to any unfavourable effect of centrifugal force,- due to its symmetrical construction and association with the inner wall of the drill. It has been found that utilizing a cleaning member in accordance with the invention results in that a continuous high suction effect can be maintained. The amount of fluid on the opening side of the cleaning member will be very small. This in combination with high suction effect through the hole 63 enables the entire avoidance of unenvisaged fluid release in connection with taking up the core drill. The suction and thereby lifing effect on a loose core will also be better.

It has also been surprisingly found that the condit- ions accounted for above mean that it is possible to operat with generally substantially less fluid flow, while retain¬ ing good cooling of the cutting means and good removal of drill cuttings, which is very advantageous.

The invention is, of course, not limited to the illu- strated and described embodiment, and alterations and modi¬ fications are possible within the scope of a wide inter¬ pretation of the following claims, while utilizing the basi inventive concept, namely an active or mechanical cleaning of the inner wall of the core drill for removing deposits thereon.