APPARATUS FOR DIRECTING AND STEERING THE FOREMOST PART OF A DRILLPIPE AT DRILLINGS

Abstract: Apparatus for directing and steering of the foremost part of a drillstring by earth drillings, formed by a connecting part formed by a lower housing part and an upper housing part, provided with a central opening for the passing of the drilling fluid and a drive shaft of the motor of the bit, or motor rotor, while one housing part is provided with an inserting part that is intended to be inserted in the other housing part, and of which the outer circumference is smaller than the inner circumference of the other housing part that is intended to receive the inserting part, while the housing parts are provided with means by which they can be detachably connected to each other.

Description: Apparatus for directing and steering the foremost part of a drillpipe at drillings. The invention relates to an apparatus for directing and steering the foremost part of a drillpipe at drillings. Such an apparatus is known. When by an embodiment of the known apparatus one has to drill further to create a side branch starting from a vertical bore, the drillstring is first retrieved from the vertical bore, whereafter a wedge shaped gui- ding piece is let down into the borehole, and subsequently the drillstring is again lowered into the borehole, where the wedge shaped guiding piece deviates the foremost part of the drillstring sidewards, so that the borehole is drilled in a more horzizontal direction, to form the required side track. With another embodiment of the known apparatus for forming of a side branch starting from the vertical bore, at the bottom end of the drillstring a bend piece is incorporated, which carries the bit and a drilling motor. To form the side branch, the bit when driven by the drilling motor and non-rotating drill string is drilling ahead sidewards forming the required side track. With again another embodiment of the known apparatus for yielding of a sideward deviation starting from the vertical borehole one or more stabilizers are applied, whereby the foremost part of the drillstring can again be deviated. With all these embodiments of the known apparatus it is always required, for the incorporation of the wedge shaped guiding piece, or of the bend piece at the bottom of the drillstring, or of the stabilizers, to retrieve the whole drillstring from the borehole, subsequently lower down the tapered shaped guiding piece in the borehole, or to incorporate the bend piece, or the stabilizers at, or nearby the bottom end of the drillstring. This repetitive retrieving of the drillstring out of the borehole to make the necessary arrangements for further sidewards drilling starting from the vertical borehole is very time consuming and costly. This has lead to developments in which the bend piece can be adjusted by hand at the drilling site by which it is possible to economize on stand-by equipment at the drilling site. From the Dutch patent application NL-A-9001883 and from EP-A-0 502 084 is known an apparatus for remote steering and directing of the foremost part of a drill pipe. As the drilling motor as disclosed in these applications comprises all of the basic devices to which the improvements relate, these will be explained with reference to this. This drilling motor comprises in short the following main features: a remote adjustable bend piece, an adjusting system, which system is made up of a piston which is surrounded by a housing part, which piston is build up of an enveloping part (or sleeve) provided with a strong spring and a coaxial piston part provided therein, which is provided with an inwardly directed collar and a soft spring, through which a shaft with local thickenings is passed, while the sleeve relative to the housing part and the coaxial part relative to the sleeve can move upwards and downwards under the influence of the mass flow and the springs, while the movements are limited by a ratchet and stop system and a locking mechanism made up of a closed groove and a plug mounted in a tangentially movable saddle. It is an object of the present invention to provide an improved apparatus. The invention can be subdivided in: - a substantially improved adjustable bend piece, which is very easy to mount and remove, so that the drawback of the application of costly equipment, such as an expensive break-out unit, is obviated. As a result this adjustable bend piece can be applied in the situation in which this is economically advan- tageous as a manual adjustable bend piece at the drilling site. To this end the bend piece is made up of two housing parts, which are rotatably connected to each other through an inner and an outer toothing and which are fixed into each other by means of a radial wedge which can be expanded by introducing from outside expansion elements. The constructive execution is particularly also suitable as a non-flexible connection for housing parts or drillpipe parts which is very simple to mount and to dismantle, which is very economical as the present connections after several times of mounting and removal of parts usually have to be replaced. - In the application of a mass flow switch between the sleeve and the coaxial piston part. The drawbacks, that the steering and directing by means of the mass flow only can take place within the margin that is available between the operational and maximum mass flow, which is often not sufficient, and the drawback that no positive locking is possible, are hereby obviated. To this end the mass flow switch is made up of a groove with loops with internal smaller groove parts with stop- and upwards inclined ends, provided at the outer side of the coaxial piston part and in which a con- necting body inserts with an internal spring loaded pin, which, depending on the position of the connecting element in the groove, inserts up to into the smaller groove parts and which connecting element is supported in a movable saddle which forms part of the sleeve and which can rotate around the axial centre line thereof. - In the application of a locking mechanism, by which the drawbacks are obviated of a groove in the inner side of the housing part which is very difficult to make, or the application of an extra casing which will limit the constructional space to much. To this end the closed groove with in- and out hook positions and provided with smaller groove parts with upwards inclined- and stop ends is accommodated in a cylindrical shaped body, which forms part of the sleeve and which can rotate relative to the axial centre line thereof, in which the connecting element with internal spring loaded pin is connected to the housing part and inserts up to within the groove, while the pin, depending on the position of the connecting element can insert in the groove up to within the smaller groove parts . - In the application of a radially gliding contraction ring in the coaxial piston part, by which the drawbacks, consisting in the substantial limitation of the magnitude of the adjusting forces to be generated and pressure difference amplitude during the switching, in the case of swinging or inclined shafts, are obviated. To this end a radially movable ring is applied of which the axial measurement can be chosen in such a way, that the radial hydraulic forces in the annular flow channel between the ring and the shaft, force the ring to centralize itself with the centre line of the shaft. The invention will be described with reference to Fig. 1 , 2 , 3 , 4 and 5. Fig. 1 shows a schematic view of an embodiment of a drill pipe, such as is connected to the end of a drill pipe 1. At the drill pipe side in front of the motor of the drill a stabilizer 2 is provided. The drill motor itself can be subdivided in the housing, in which the drive motor 3 is provided, the drive housing with a bend 4, between which the connecting shaft is located, which connects the shaft of the drive motor to the shaft of the bearing housing 5. At the end of the bearing housing the bit 6 is located. In this schematic example also the stabilizer 7 at the bearing housing is present. Fig. 2 shows a longitudinal section of an adjustable bend piece 4 according to the invention, by which: - very simple mounting and removal is made possible, - great forces and moments can be transmitted without play, - a swinging shaft can be passed internally through the bend piece, even in the case of a drill motor with a heavy and swinging and also inclined shaft, while a sufficiently large annular flow channel will remain present. The house with bend is subdivided in two parts, that is: an upper part 8 that is provided with an inserting part 10 which inserts in the lower part 9, onto which an outer toothing 11 is provided, which fits within the inner toothing 12 provided in the upper part of the lower housing part 9, which are formed in such a way, that the housing parts can rotate without play relative to each other in planes through the centre lines of the housing parts 8 and 9. The axial pressure forces are transmitted from the upper part 8 to the lower part 9 by a ring shaped shoulder 13 provided on the inserting part 10 of which the spherical shaped surface rests against the bowl shaped surface of a cylindrical ring 14, which is supported in the lower housing part 9 by means of a ring 15, which fits in a recess 26 of the housing part 9 , which or reasons of mounting is carried out in three part . The axial pulling forces are transmitted from the lower housing part 9 to the inserting part 10 by a ring shaped wedge 16 against which a ring shaped element 17 rests, of which the spherical shaped surface rests against the bowl shaped surface of the shoulder 13. The lower housing part 9 is at the upper end formed by a ring- and spherical shaped surface 19, which rests against a ring and bowl shaped surface 20 disposed on a cylindrical sealing ring 21-, which is provided around a contracted part 22 of the upper housing part 8. The toothings and spherical- and bowl shaped surfaces all have a joint centre point of rotation 23. Where it is necessary sealing rings and equalization of pressure elements are provided. Fig. 3 shows a cross section at the level of the radial wedge 16 which at the outer side is provided with shoulders 18 which fit into recesses 24 in the housing part 9. The radial wedge 16 is for mounting formed in 4 sections, whereby from the ends so much material has been removed, that the enveloping of the sections when radially inwards displaced is smaller than the inner diameter at the end of the housing part 9. By means of 4 expansion pins 25, which can be inserted from outside the sections of the radial wedge 16 expand until the shoulders 18 are fixed solidly and positively in the recesses 24 in the lower housing part 9. In the shown configuration the ring shaped element 17 is formed in two sections for mounting. This element 17 can also be formed as one whole, the shoulder 13 then has to be formed as a loose element and be fixed to the inserting part 10 by means of one or more auxiliary elements. This embodiment of the bend piece is particularly suitable for the easy mounting and removing without the necessity of the use of an expensive break-out unit or other equipment. The mounting is carried out in a very simple manner, by the mounting of the parts 15, 14 in the housing part 9, placing of the parts 21, 16 and 17 onto the inserting part 10 and the subsequent insertion of the inserting part 10 in housing part 9 and the afterwards insertion from outside of the expansion pins 25. Removal is done in a very simple manner by removing the pins 25 from outside and the subsequent pulling out of each other of the housing parts 8 and 9. According to an embodiment of the invention the bend piece is carried out as a bend piece, which is adjustable at the surface of the drilling site, in the case this is economically advantageous. To this end the inserting part 10 is provided with a further inserting cylindrical shaped adjusting organ 31 which is supported in a ring shaped element 30 which at the outer side is provided with a spherical shaped surface which rests in a cylindrical shaped ring with internal bowl shaped surface 29, which serves as second adjusting organ 32 and which is supported in the housing part 9. The centre lines of the adjusting organs 31 and 32 are orientated relative to each other such that at axial displacement or rotation of the adjusting organ 32 or adjustment of the toothings 11 and 12 relative to each other the angle between both housing parts 8 and 9 is changed. In the third case the element 30 does not have to be applied. In a further embodiment according to the invention the bend piece is carried out as a non-flexible connection of two housing parts or drill pipe parts, wherein the toothings 11 and 12 can be carried out as straight toothing and the spherical and bowl shaped surfaces can be left out and if desired it can also be carried out as straight connecting piece. In a further embodiment according to the invention the bend piece is remote controlled under the influence of the mass flow. The adjusting organ 32 to this end is connected to the sleeve 44 of the piston 43, 44 of the adjusting system, which will be explained further on. At the displacement of the adjusting organ 32 relative to the inserting organ 31 the housing part 8 hinges relative to the other housing part 9 about the centre point of rotation 23. In fig. 4 a longitudinal section of an adjusting system according to the invention is shown, which is made up of the following main parts: - a shaft 39 with thickenings 40, 41 and 42, - a thrust body in the shape of a piston part 43 with a contraction 45 that surrounds the shaft 39, - an enveloping piston part or sleeve 44 that envelops the piston part 43, and to which the adjusting organ 32 is connected. The piston part 43 is provided with a soft spring 46 working against the direction of flow, which is supported in the sleeve 44. The sleeve is provided with a strong spring 47 working against the direction of flow which is supported in the lower part of the housing part 9. In Fig. 4 it is shown, that in the piston 43 are provided a number of extending spring loaded ratchets 48, which can move over the inner surface of the sleeve 44, the recesses 49 and 50 and the intermediate surface 51 of the sleeve 44. The piston part 43 is locked against rotation relative to the sleeve 44 by pin groove connections 52. In NL-A-9001883 are provided on the outer surface of the sleeve 44 one or more closed loops 61 in- and out hook positions, provided with a connecting element, which is mounted in a two-sided spring loaded saddle, which can rotate around the axis of housing part 9 and which is axially supported in an additional sleeve or a groove provided in the inner side of housing part 9. According to a further embodiment of the invention one or more grooves 61 are now provided onto a cylindrical shaped body 68, which forms part of the sleeve 44 and which can rotate relative to the axial centre line thereof and which can be carried out in one or more axial divided parts. In the groove 61 smaller groove parts 62 with upwards inclined- 63 and stop ends 64 are provided. The connecting element 65 herein is carried out as a plug, which can be mounted in the housing part 9 and is carried out with a cylindrical end 66, which inserts up to into the groove 61. The element 66 is provided with an internal spring loaded pin 67, which, depending on the position of the connecting element 65, 66 in the groove 61, can insert up to into the smaller groove parts 62. This further embodiment has the advantage, that no additional sleeve around the piston is required which would limit the constructional space too much or that in the inner side of the housing part 9 a tangential groove with spring loaded saddle has to be provided, which is very difficult to make. According to a further embodiment according to the invention the piston part 43 is provided on the outer side with one or more grooves 54 with loops, with internal smaller groove parts 55 with stop- 56 and upwards inclined ends 57, as well as a connecting element 58 between the grooves of piston part 43 and sleeve 44, which functions as mass flow switch. The connecting element 58 here is carried out as a cylindrical shaped plug, internally provided with a spring loaded pin 59. The plug is mounted in gliding saddle 60, which forms part of the sleeve 44 and which is axially supported therein in a groove and which can rotate around the axis of sleeve 44. The connecting element 58 extends up to into the groove 54 and the pin 59 up to into the smaller groove parts depending on the position of the connecting element 58 in the groove 54. An axial groove 70 is provided in the outer side of the sleeve 44. Herein inserts a fixed pawl 69, fixed to housing part 9, for lifting the spring loaded ratchets 48. In Fig. 5 the operation of the adjusting system is explained, whereby for clarification purposes it is presumed that the mechanism operates a bend piece. The manner of operation of the adjusting system lies in a co-operation between hydraulic-, spring forces, mass flow switch and the locking mechanism under the influence of the mass flow. The position of the contraction 45 relative to the shaft 39 determines depending on the mass flow the magnitude of the downflow directed hydraulic forces exerted on the piston parts 43 and 44. The counteracting forces are provided by the soft spring 46 and the strong spring 47. The mass flow switch limits the movement of the piston part 43 relative to the sleeve 44. (See diagram I). The locking system limits the movement of the sleeve 44 relative to the housing part 9. (See diagram II). The combined movement determines the position of the contraction 45 relative to the shaft 39 and housing part 9. (See diagram III). Drilling with straight bend piece. In Fig. 5 the situation is shown in which the bend piece is in the straight and locked position. During the drilling the pumps are regularly switched on and switsched off in order to lengthen for instance the drill pipe periodically. This must not cause adjustment of the bend. During the switching on and switching off of the pumps the connecting body 58 moves from Position 1 to Position 2 and back in the first loop of the groove 54 , whereby the smaller groove parts in co-operation with the upwards inclined 57 and stop end 56 and the pin 59 see to it that the connecting body 58 cannot leave the first loop and as drawn, against the hands of the clock, moves through the loop. Position 1 is the stop end in the first loop for upflow movement of the contraction 45 of the piston part 43 relative to the sleeve, as this cannot further move upflow. Position 2 functions as downflow stop. In order to be able to move further downflow the hydraulic force should, after abutment of the connecting element 59 in Position 2 via the connecting element, move the sleeve 44 downflow. This is not possible because the hydraulic force in Position 2 is smaller than the counteracting force of the strong spring 47, which would have to conquered for further downflow movement of the sleeve 44. Unlocking in straight position of the bend. In order to get out of the locking of the first loop the mass flow is first increased in such a measure that the connecting element 58 moves from Position 1 to Position 2. Subsequently it is lowered in such a measure that the force of the spring 46 displaces the con- necting body 58 to about Position 3. The contraction 45 is then close to thickening 40. The thickening 40 on the shaft 39 thereafter increases the upflow movement of the contraction 45 by which this neutralizes the force of the soft spring 46. Thereafter the mass flow is increased again whereby the connecting body 58 will displace from Position 3 to Position 4, where the ratchet 48 abuts with stop end 34 on sleeve 44 and further movement relative to sleeve 44 is blocked. Bending of the bend. In Position 4 the contraction 45 has arrived at the height of the second thickening 41. The hydraulic force is greater than the counteracting force of the strong spring 47 by which the piston parts 43, 44 will jointly move downflow and at the same time adjusting work is conducted. In this case the bend will be adjusted. The connecting element 65 moves from Position a to Position b. Locking of the bend. Having arrived in this position b the ratchet 48 is lifted by the fixed pawl 69. The sleeve 44 then moves upflow under the influence of the strong spring 47, whereby the connecting element 66 moves from Position b to Position c, where the strong spring 47 locks displa- cement in downflow direction and the plug 65, 66 in upflow direction. Piston part 43 then is unlocked relative to the sleeve 44 and will under the influence of the hydraulic force compress the soft spring further until stop Position 5 is arrived at, where further downflow movement relative to sleeve 44 is blocked, because the hydraulic force there is smaller than the force of the strong spring 47. The bend is then in the bent and locked position. At the stopping of the pumps the connecting element 58 will displace to stop Position 6. Operation in bent position of the bend. The operation of the system in the second loop is similar to that in the first loop and is for this reason not further described. Unlocking of the bend. In order to get out of the locking in the second loop a similar procedure is followed as with the first loop and the connecting element moves from Position 7 to 8 , during which movement ratchet 48 of piston part 43 abuts with the stop end 34 of the sleeve 44. The contraction 45 is then at the height of the thickening 42 and piston part 43 and sleeve 44 move together downflow while compressing the strong spring 47, while the con- necting element 65, 66 moves from position c to d. The connecting body 65, 66 there blocks the piston 43, 44 in downflow direction relative to the housing part 9. Straight adjusting of the bend. At the subsequent switching off of the pumps piston part 43 as well as sleeve 44 move upflow under the influence of the soft 46 and strong 47 spring to the start position and the connecting element 58 moves from Position 8 to 1 and the connecting element 65, 66 from Position d to a. The system can be carried out as multiple adjusting system by extension of the groove 54 with more loops and the groove 61 more in- and out hook positions. A particular feature of the system is that the movement of the contraction 45 relative to the shaft with thickenings during the switching determines the nature of the course of the pressure difference. In the present example, when adjusting from straight to bend, a sine natured course will appear, while a jump course will appear when adjusting from locked bent position to unlocked bent position. With a multi-stage system for each switching a singular characterizing course can be created, by routing of the groove 54 and thereby adapting the displacement of the contraction 45 relative to the shaft 39 with thickenings. As a result a univocal detection at the surface is possible of the position in which the system is below ground and one is not any more dependant on detection by measuring of amplitude, which often leads to uncla- rities. A further improvement according to the invention is a radially gliding contraction ring 45 in the situation, in which the shaft swings or displaces radially. With a fixed contraction the magnitude of the hydraulic force and the pressure change is limited because the inner size of the ring 45 must fit around the enveloping of the swinging and or inclining shaft. By the application of a radially gliding contraction ring 45, axially dimensioned such that the hydraulic forces in the annular flow channel force the ring to centralize around the centre line of the shaft the inner size may be chosen smaller than the enveloping of the shaft. By this the inner size of the contraction may also in these kind of situations be further reduced, so that the generated hydraulic pressure differences and -forces can be adapted to values required for detection and adjustment. The longer the drilling hole the stron- ger the damping of the signal becomes. 1. drillstring 2. stabilizer 3. drive motor 4. connecting housing with bend 5. bearing housing 6. bit 7. stabilizer 8. upper housing part 9. lower housing part 10. inserting part 11. outer toothing 12. inner toothing 13. ring shaped shoulder 14. cylindrical ring 15. ring 16. radial wedge 17. ring shaped element 18. shoulders 19. ring- and spherical shaped surface 20. ring- and bowl shaped surface 21. cylindrical seal ring 22. contracted part 23. centre point of rotation 24. recesses 25. pins 26. recess 27. 28. 29. spherical shaped surface 30. ring shaped element 31. adjusting organ 32. adjusting organ 33. bowl shaped end 34. stop edge 35. 36. 37. 38 . 39. connecting shaft, shaft 40. thickenings 41. thickenings 42. thickenings 43. thrust body in the shape of a piston part 44. enveloping piston part (or sleeve) 45. contraction or ring 46. spring 47. strong spring 48. ratchets 49. recesses 50. recesses 51. intermediate surface 52. pin groove connections 53. cylindrical shaped plug 54. one or more grooves 55. smaller groove parts 56. stop end 57. upwards inclined end 58. connecting element 59. spring loaded pin 60. saddle 61. grooves 62. smaller groove parts 63. upwards inclined ends 64. stop ends 65. connecting element 66. cylindrical end 67. spring loaded pin 68. cylindrical shaped body 69. fixed pawl 70. axial groove

Claims: C l a i m s 1. Apparatus for directing and steering of the foremost part of a drillstring by earth drillings, formed by a connecting part formed by a lower housing part and an upper housing part, provided with a central opening for the passing of the drilling fluid and a drive shaft of the motor of the bit, or motor rotor, while one housing part is provided with an inserting part that is intended to be inserted in the other housing part, and of which the outer circumference is smaller than the inner circumference of the other housing part that is intended to receive the inserting part, characterized in that the housing parts are provided with means by which they can be detachably connected to each other . 2. Apparatus according to claim 1, characterized in that the means are formed by an element which is provided around the inserting part and which is supported thereon, of which the outer circumference is variable and which is provided with parts, which, at a certain outer circumference of the element insert in recesses which are provided in the inner circumference of the other housing part. 3. Apparatus according to claim 2, characterized in that the element is formed by a radial wedge which at its outer side is provided with shoulders which fit into the recesses in the lower housing part. 4. Apparatus according to claim 3, characterized in that the radial wedge has been carried out in two or more sections, while it co-operates with expansion parts which are to be inserted between the sections, by means of which the outer circumference of the assembly of the sections can be enlarged, such that the shoulders insert in the recesses in the lower housing part. 5. Apparatus according to claim 4, characterized in that the expansion parts can be inserted or operated from the outside. 6. Apparatus according to claim 3 or 4 , characterized in that the expansion parts are formed by expansion pins. 7. Apparatus according to one of the preceding claims, characterized in that the one housing part is provided with an inner toothing which co-operates with an outer toothing provided on the other housing part or the inserting part. 8. Apparatus according to one of the preceding claims, characterized in that the housing parts are provided with adjusting organs that co-operate with each other for the a justment of the position of both housing parts relative to each other . 9. Apparatus for directing and steering of the foremost part of a drillstring by earth drillings, having a piston [43, 44] enclosed by a housing, which piston [43, 44] under steering of the mass flow of the drilling fluid is movable between two or more end positions, and wherein the piston [43, 44] is connected with at least one adjusting organ, which co-operates with a device for the steering and directing of the end of the drill string, while the piston [43, 44] further is provided with a central opening for the passing of the drilling fluid and the drive shaft [39] of the motor of the bit, or motor rotor, while the piston [43, 44] is formed by a sleeve [44], which is movable be- tween two end positions in a housing part provided with a spring [47], which at the one side bears against the sleeve [44], and at the other side against the housing part [9], while coaxially with this sleeve [44] a piston part is slidable up and down, and co-operates wih a weaker spring, which at the one side bears against the sleeve [44], and at the other side against the piston part [43], and in which the piston part [43] is provided with an inwardly directed collar or vaulting [45], which co-operates with at least one local thickening [40, 41, 42] arranged on the shaft [39], such that by the increasing of the mass flow of the drilling fluid above the operating value, the piston part [43] with the collar [45] is moved towards the thickening [40, 41, 42] where it diminishes the flow opening for the drilling fluid, by which the thrust pressure on the piston [43, 33] is increased and whereby the piston part [43] and sleeve [44] are moved forward in the housing part against a spring force [47] to the adjusting position, for the displacement of the adjusting organ [31] connected with the sleeve [44], characterized in that the piston part [43] at the outer side is provided with at least one groove [54], which groove encloses a connecting element [58] which is mounted in the surface of the sleeve [44] enveloping the piston part [43]. 10. Apparatus according to claim 9, characterized in that the groove [54] is provided with loops with inter- nal smaller groove parts [55] and stop- [56] and upwards inclined ends [57]. 11. Apparatus according to claim 9 or 10, characterized in that the connecting element [58] is formed by a cylindrical shaped plug [58] provided with a spring loaded pin [59], which plug can insert in the groove [54] and which pin [59] can insert in the smaller groove parts [55], 12. Apparatus according to claim 9, 10 or 11, characterized in that the connecting element [58] is mounted in a gliding saddle [60] which is rotatable around the axis of the sleeve [44] and which saddle [60] is axially supported in a groove provided in the sleeve [44]. 13. Apparatus according to one of the preceding claims, characterized in that the collar or vaulting [45] on the piston part [43] consists of a contraction ring [45] which is radially movable in a ring shaped recess which is provided in the piston part [43]. 14. Apparatus according to one of the preceding claims, in which a locking mechanism is present, which is operated by the up and down movement of the piston [43, 44], with at least two end positions, which correspond to the end positions of the piston [43, 44], characterized in that the locking mechanism is made up of at least one cylindrical shaped body [68] accommodated in the outer covering of the sleeve [44], which forms a part of the sleeve [44], and which cylindrical shaped body [68] can rotate about the axial centre line of the sleeve [44], while in the outer covering of the cylin- drical shaped body [68] at least one bowl shaped channel or groove [61] is provided with the shape of a closed loop [61], while the bowl shaped channel encloses a connecting element such as a plug [65, 66, 67] which is mounted in the housing part [9] surrounding the cylindrical shaped body [68]. 15. Apparatus according to one of the preceding claims, characterized in that the plug [65, 66, 67] comprises a cylindrical end [66] with an internal spring loaded pin [67]. 16. Apparatus according to one of the preceding claims, characterized in that the bowl shaped channel [61] along parts thereof comprises smaller groove parts [62], in which the pin [67] can insert. 17. Apparatus according to one of the preceding claims, characterized in that the groove parts [62] are provided with upwards inclined ends [63] and stop ends [64].

Inventors: VAN DEN BERGH JOHANNES WILHELM, VAN DEN BERGH, JOHANNES, WILHELMUS, HENRICUS
Applicants: BERGH JOHANNES W H DEN, VAN DEN BERGH, JOHANNES, WILHELMUS, HENRICUS
Application year: 1998
Main classification: E21B7
IPC codes: E21B7, E21B17, E21B23