CA1213879A

CA1213879A - Drifting equipment

Info

Publication number: CA1213879A
Application number: CA000453461A
Authority: CA
Inventors: Jan-Erik Norberg; Jorgen R. Almgren
Original assignee: Trelleborg AB
Current assignee: Trelleborg AB
Priority date: 1983-05-06
Filing date: 1984-05-03
Publication date: 1986-11-12
Also published as: ZA843410B; IT1174076B; SE8302599D0; IT8420796A1; IT8420796A0; WO1984004562A1; SE8302599L; EP0142545A1

Abstract

ABSTRACT

A drilling equipment comprising a drill bit (19) and a pneumatically operated sinker drill machinery therefor comprises a non-return valve (20) which is positioned between said drill bit and said sinker drill machinery and is in the form of a dome-shaped valve member (25) formed of elastomer material and having throughflow slots (26) adapted to open when compressed air is supplied in one direction through said valve member, and to close again when the supply of compressed air is discontinued, to prevent flow in the opposite direction. The throughflow slots (26) preferable have been formed by cutting said dome-shaped valve member (25) without any appreciable removal of material.

Description

DRILLING EQUIPMENT

The present invention relates to pn~uma~ic drilling equipment of the type comprising a drill bit and a dri-~-ing device therefor having a pneumatically operated sinker drill machinery. With this type of equipment, considerable difficulties are encountered in that water, sand and clay in the drill hole may flow bacXwards up through the drill bit and into the sinker drill machiner-~, as a result of which drilling must frequently be discon-tinued and the sinker drill machinery cleaned. To coun-1~ teract such inflow of water, sand and clay, it has beentried to mount nonreturn valves in the air supply duct supplying air to and removing air from the pneumatically operated sinker drill machinery. Known conventional non-return valves for this purpose have been bulky and, from considerations of space and also for functional reasons, had to be placed in the air supply duct ahead of the air inlet to the sinker drill machinery. These known non-return valves have entailed some improvement, but have been unable completely to stop penetration of water, sand and clay into the sinker drill machinery.
Furthermore~ ln additisn to being bulky, the known non-return valves are design~d in an expensive manner.
With the present i~ven~ion, it has now been found possible to position the non return valve in the air supply duct between the sinker drill machinery and the drill bit, provided that a special non-re-turn valve is - used. Accordiny to the inven ion, the non-return valve should be in the form of a dome-shaped valve member consisting of elastomer materlal and having its convex side facing in the direction of the air flow, said valve member brid~ing the air supply duct and having through-flow slots adapted to open when compressed air is sup-plied through the sinkPr drill machinery and to close again when t~e compressed alr supply is discontinued.

The dome-shaped valve mPmber preferably is conical on its outer side and preferably also on its inner si-3e, The throughflow slots in the ~ome-shaped ~Jalve memb~r preferably have apertures which, if the dome-shape~
valve member is viewed from its convex side, ext2nd crosswise across said valve member. It was found that the best result is obtained if the intersecting through-flow slots intersect one another slightly offset in relation to the top of the dome-shaped valve member.
In this manner, the throughflow slots will ext~nd like chords across the dome-shaped valve member~ The through-flow slo s preferably are provided by cutting the dome-shaped valve member without any substantial removal of material, whereby the non-return valve will obtain high sealing capacity when it is to prevent water, sand and clay from penetrating backwards through thé air su~ply duct. ?
Swedish patent specification 7709894 5 (413,929) discloses an injector which is utilised for injecting material through drill holes or other holes in rock or other solid material. This injector is provided at its outer end with a detachable injector nozzle in the form of a non-return valve, and an expandable expander for sealing against the wall of ~he hole in which the injector is inserted. In one of its embodiments, the injector nozzle i5 formed with a dome-shaped valve por-tion consisting of elastomer material and bridging the end of the injector pipe, The injector nozzle has through-flow slots adapted to open upon injection of the seal-ing material under pressure through ~he injector pipeand to close again when the pressure of the sealing material in the injector pipe is relieved. This prior art injector is intended for the injec~ion of cement or other stabilising compounds or for static position-ing in a drill hole. It must be regarded as surprisingthat the difficulties encountered with dynamic sinker drill machineries and drill bits associated therewith can be eliminated by using the dome-shapcd non-re~u-.n valve previously known in and per s~ in con~unc~ion with the inj~ctor.
An embodiment of the drilling equipment a~cording to the invention will be described in more ~etail ~Delowl reference being had to the accompan~ing dra~Jing in r,7hich Fig. 1 illustrates an embodiment of a drilling equipment designed in accordance with the present inven-tion;
Fig. 2 illustrates~ partly in section, a drill bit comprised by the equipment;
Fig~ 3 is a vertical section through a non-return valve in the equipment according to the invention; and Fig, 4 is a plan view of the non return valve, seen from the tip endO
The drilling equipment illustrated in Fig; 1 is an example of different drilli~g e~uipments that may be designed in accordance with this invention~ The em-bodiment illustr~ted comprises a flushing head 11, a drill pipe 12~ a liner pipe 13, a winged sleeve 14, a sinker drill machinery 15, a bit pipe 16, a guide 17, a reamer 18 and a pilot bit 19. The equipment is such that the pilot bit 19 and the reamer 18 together drill a hole having the same or a slightly larger diameter than the liner pipe 13. Furthermore~ the equipment is such that all components can be pulled up through the liner pipe 13 which may remain in the drill hole. The sinker drill machinery 15 of the equipment is operated by compressed air which is supplied down to ~he sinker drill machinery through the drill pipe 17, and the air leaving the sinker drill machinery is discharged through a central hole in the pilot bit, In known drilling equip-ment of this type~ a non-re~urn valve has been mounted in the air supply duct at the transition between the sinker drill machinery 15 and the winged sleeve 14.
According to the present invention, however, a non-return valve 20 is positioned in the air supply duct 21 between the tip of the drill bit 19 and th~
sinker drill machinery 15. As will appear from Fig. 2, the non-return valve has been positioned in a r"idened portion of the air supply duct, such that the non-return valve supports itself against a shoulder 22. In ~his manner, the non-return valve will be completely enclosed by the pilot drill bit which thus can be mounted in normal manner in the rest of the drilling equipment and without necessitating further modification thereof.
In the em~odiment illustrated9 the pilot drill b_t is mounted by means of a large thread 230 In the embodiment illustrated, the non-return valve 20 has an outer metal ring 24 which is vulcanised to a conical ~lastomer body 25 extending in the manner of a dome out of the metal ring. In the embodiment il-lustrated, the elastomer body is conical, its conical outer side having a slightly ~aller top rake than its conical inner side9 whereby the thickness of the ela-stomer ~aterial will be slightly smaller at the tip end of the conical elastomer body than at the base end thereof~ adjacent the metal ring 24. By this design, functional advantages are obtained.
In the embodiment of the non-return valve illustrat-ed in Figs. 3 and 4, two intersecting cuts 26 have been made in the conical elastomer body. These cuts extend practically all the way down to the metal ring 24 and have been formed without any appreciable removal of material. In this manner, the non-return valve will obtain high sealing capacity. In the embodiment illu-strated, the intersection of the two cuts has been placedeccentrically in relation to the tip of the conical elastomer body, as indicated by two diametrical lines in Fig. 4, whereby an improved sealing capacity of the non-return valve is obtained. The four lips 27 which are formed by the ~wo cuts 26, will act as sealing lips that are moved apart under the action of th~ compressed ~"f' air flowing down from the sinker drill machinery 15 towards the tip of the drill bit 19. hs soon as the supply of compressed air ceases, the four lips 27, ~e-cause of their elasticity, will return into their seal-ing initial po~ition, as sho~m in Figs. 3 and 4. If water, sand or clay should tend to flow upwards tnrougn the air supply duct 21, after the supply of compressed air through said duct has been discontinued, the "a~er, clay or sand will press against the four lips 27 which thus will be compressed together even more, thereby increasing the sealing capacity upon an increasing back pressure in the drilling equipment.
The dome-shaped non-return valve described above may have the cuts 2~ positioned in a different manner, for example along chords of the elastomer body, if this should be desired. It is also possible to use other dome shap~s than the conical shape illustrated in the drawing. However, care must be'taken that the capacity of the non~return valve to prevent backflow or fluid, such as w~ter t sand and clay, increases upon an increase in pressure, and that the non-return valve will have good opening capasity upon supply of compressed air to and through the sinker drill machinery.

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An equipment of the type comprising a drill bit and a driving device therefor having a pneumatically operated sinker drill machinery, said drilling equipment comprising an air supply duct which serves to supply air to and remove air from the pneumatically operated sinker drill machinery and which comprises a throughflow hole extending axially through the drill bit to remove the operating air from the sinker drill machinery, and a non-return valve being mounted in said air supply duct to counteract fluid flow in the backwards direction therethrough, characterised in that said non-return valve is positioned between the drill bit and the sinker drill machinery and comprises a dome-shaped valve member of elastomer material, said valve member having its convex side facing in the air supply direction and bridging the air supply duct and having throughflow slots adapted to open when compressed air is supplied through said sinker drill machinery and to close again when the supply of compressed air is discontinued.

2. An equipment as claimed in claim 1, characterised in that the dome-shaped valve member is conical on its outer side and, preferabley, also on its inner side.

3. An equipment as claimed in claim 1 or 2, characterised in that said throughflow slots in said dome-shaped valve member have openings which, if the dome-shaped valve member is viewed from its convex side, extend crosswise thereacross.

4. An equipment as claimed in claim 1 or 2, wherein said throughflow slots in said dome-shaped valve member have openings which, if the dome-shaped valve member is viewed from its convex side, extend crosswise thereacross, characterised in that the intersecting throughflow slots have their intersection slightly offset in relation to the tip of the dome-shaped valve member.

5. An equipment as claimed in any one of claims 1 or 2, characterised in that said throughflow slots have been formed by cutting said dome-shaped valve member without any appreciable removal of material.

6. An equipment as claimed in claim 1 or 2, wherein said throughflow slots in said dome-shaped valve member have openings which, if the dome-shaped valve member is viewed from its convex side, extend crosswise thereacross characterised in that said throughflow slots have been formed by cutting said dome-shaped valve member without any appreciable removal of material.

7. An equipment as claimed in claim 1 or 2, wherein said throughflow slots in said dome-shaped valve member have openings which, if the dome-shaped valve member is viewed from its convex side, extend crosswise thereacross, characterised in that the intersecting throughflow slots have their inter-section slightly offset in relation to the tip of the dome-shaped valve member, said throughflow slots have been formed by cutting said dome-shaped valve member without any appreciable removal of material.

8. The use of a dome-shaped valve member formed of elastomer material and having throughflow slots adapted to open when compressed air is supplied in one direction through said valve member and to close again when said compressed air supply is discontinued, to prevent flow in the opposite direction, as a non-return valve positioned between the drill bit and a pneumatically operated sinker drill machinery, in an air supply duct for supplying air to and from said sinker drill machinery.