DRILLING EQUIPMENT

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 pneumatic drilling equipment of the type comprising a drill bit and a driv¬ r 9 *. ing device therefor having a pneumatically operated sinker drill machinery. With this type of equipment, 5 considerable difficulties are encountered in that water, sand and clay in the drill hole may flow backwards up through the drill bit and into the sinker drill machinery, as a result of which drilling must frequently be discon¬ tinued and the sinker drill machinery cleaned. To coun- 10 teract such inflow of water, sand and clay, it has been tried to mount non-return 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, 15 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 20 water, sand and clay into the sinker drill machinery. Furthermore, in addition to being bulky, the known non¬ return valves are designed in an expensive manner. With the present invention, it has now been found possible to position the non-return valve in the air 25 supply duct between the sinker drill machinery and the drill bit, provided that a special non-return valve is used. According to the invention, the non-return valve should be in the form of a dome-shaped valve member consisting of elastomer material and having its convex 30 side facing in the direction of the air flow, said valve member bridging the air supply duct and having through- flow slots adapted to open when compressed air is sup¬ plied through the sinker drill machinery and to close again when the compressed air supply is discontinued. OMPI « #Λs.. wIiPfOu , The dome-shaped valve member preferably is conical on its outer side and preferably also on its inner side. The throughflow slots in the dome-shaped valve member preferably have apertures which, if the dome-shaped valve member is viewed from its convex side, extend 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 extend like chords across the dome-shaped valve member. The through- flow slots 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 the air supply 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 the hole in which the injector is inserted. In one of its embodiments, the injector nozzle is 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 the injector pipe and to close again when the pressure of the sealing material in the injector pipe is relieved. This prior art injector is intended for the injection of cement or other stabilising compounds or for static position- ing in a drill hole. It must be regarded as surprising that the difficulties encountered with dynamic sinker drill machineries and drill bits associated therewith can be eliminated by using the dome-shaped non-return valve previously known in and per se in conjunction with the injector. An embodiment of the drilling equipment according 5 to the invention will be described in more detail below, reference being had to the accompanying drawing in which Fig. 1 illustrates an embodiment of a drilling equipment designed in accordance with the present inven¬ tion; 10 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, 15 seen from the tip end. The drilling equipment illustrated in Fig. 1 is an example of different drilling equipments that may be designed in accordance with this invention. The em¬ bodiment illustrated comprises a flushing head 11, a 20 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 25 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 the sinker 30 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-return valve has been mounted in the air supply duct at the transition between the -- ■ 5 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 the sinker drill machinery 15. As will appear from Fig. 2, the non-return valve has been positioned. in a widened portion of the air supply duct, such that the non-return valve supports itself against a shoulder 22. In this 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 embodiment illustrated, the pilot drill bit is mounted by means of a large thread 23. In the embodiment illustrated, the non-return valve 20 has an outer metal ring 24 which is vulcanised to a conical elastomer 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 smaller top rake than its conical inner side, whereby the thickness of the ela¬ stomer material 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 placed eccentrically 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 two cuts 26, will act as sealing lips that are moved apart under the action of the compressed air flowing down from the sinker drill machinery 15 towards the tip of the drill bit 19. As soon as the supply of compressed air ceases, the four lips 27, be¬ cause of their elasticity, will return into their seal- " ing initial position, as shown in Figs. 3 and 4. If 5 water, sand or clay should tend to flow upwards through the air supply duct 21, after the supply of compressed air through said duct has been discontinued, the water, clay or sand will press against the four lips 27 which thus will be compressed together even more, thereby 10 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 26 positioned in a different manner, for example along chords of the elastomer body, if this 15 should be desired. It is also possible to use other dome shapes 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 water, sand and clay, increases upon an increase 20 in pressure, and that the non-return valve will have good opening capacity upon supply of compressed air to and through the sinker drill machinery. Λ

Claims: CLAIMS 1. An equipment of the type comprising a drill bit (19) and a driving device therefor having a pneu¬ matically operated sinker drill machinery (15) , said drilling equipment comprising an air supply duct (21) which serves to supply air to and remove air from the pneumatically operated sinker drill machinery and which comprises a throughflow hole (21) extending axially through the drill bit to remove the operating air from the sinker drill machinery (15) , and a non-return valve (20) being mounted in said air supply duct (21) to coun¬ teract fluid flow in the backwards direction therethrough, c h a r a c t e r i s e d in that said non-return valve (20) is positioned between the drill bit (19) and the sinker drill machinery (15) and comprises a dome-shaped valve member of elastomer material, said valve member having its convex side facing in the air supply direc¬ tion and bridging the air supply duct (21) and having throughflow slots (26) 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, c h a r a c ¬ t e r i s e d in that the dome-shaped valve member (25) is conical on its outer side and, preferably, also on its inner side. 3. An equipment as claimed in claim 1 or 2, c a ¬ r a c t e r i s e d in that said throughflow slots (26) in said dome-shaped valve member (25) 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 3, c h a r a c ¬ t e r i s e d in that the intersecting throughflow slots (26) have their intersection slightly offset in relation to the tip of the dome-shaped valve member (25) . 5. An equipment as claimed in any one of claims 1-4, c h a r a c t e r i s e d in that said throughflow slots (26) have been formed by cutting said dome-shaped valve member (25) without any appreciable removal of material. 6. The use 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 said compressed air supply is discontinued, to prevent flow in the opposite direction, as a non-return valve (20) positioned between the drill bit (19) and a pneumatically operated sinker drill machi¬ nery (15) , in an air supply duct (21) for supplying air to and from said sinker drill machinery. jU EA OMPI

Inventors: ALMGREN JOERGEN RICHARD, NORBERG JAN-ERIK, ALMGREN, JOERGEN, RICHARD, NORBERG, JAN-ERIK
Applicants: TRELLEBORG AB
Application year: 1984
Main classification: E21B21
IPC codes: E21B7, E21B21