GB2047778A - Direct drive for deep boring cutters or similar tools operable in a bore hole - Google Patents

Abstract

A direct drive for deep boring cutters or similar tools operable in a bore hole, including a drive shaft (5), connectible between a rotor (2) and a cutter (6), and a bearing housing (8; 7, 9, 10, 12) coaxial with the drive shaft (5) and connectible to a stator (1) as well as to a locking device (18) which can lock the drive shaft to the bearing housing when the cutter (6) gets jammed. The locking device (18) comprises two sleeves (19, 20) which can be locked together upon relative axial movement between the drive shaft (5) and the bearing housing (8) in one direction. In order to prevent accidental engagement of the locking device (18) a safety device (26) is provided which resists the engagement of the sleeves (19, 20) and whose effect is only overcome by a predetermined upwards directed axial force greater than those experienced during normal boring operations. Once the locking device is engaged, the cutter is unjammed by rotation in the direction opposite to the boring direction, by rotation of the bearing housing in a known manner. Various embodiments of locking devices and safety devices are described with reference to other figures, some of the safety devices are resettable after cutter unjamming. <IMAGE>

Description

SPECIFICATION Direct drive for deep boring cutters or similar tools operable in a bore hole The invention relates to a direct drive for deep boring cutters or similar tools operable in a borehole including a drive shaft connectible between a rotor and a tool, and a bearing housing coaxial to the drive shaft and connectible to a stator as well as to a locking device which, when put into operation, can lock the drive shaft to the bearing housing.

The locking mechanism provided in a known direct drive of this kind is used in the bearing housing to stop the drive shaft, which is connected to the tool, in cases where the tool, in particular a deep boring cutter, has become stuck in the unit for any reason during a boring operation. Further turning motion of the cutter by means of the direct drive is then impossible, because its drive shaft and the rotor of the direct drive are connected with the drive shaft are stuck as well as the cutter. However, locking of the drive shaft to the bearing housing, brought about by a locking mechanism, permits transmission oftorquefrom the bearing housing to the drive shaft and thus to the jammed tool.The rotating motion of the bearing housing, which is opposite to the normal operating rotational direction of the cutter, is transmitted in a well-known manner from the cutter over a turntable installed in the bore hole over the bore tubing line and the stator of the drive into the bearing housing. The torque which must be applied in this manner to loosen the jammed tool or chisel is considerable, so that a high demand must be placed on the functionability and continuous operability of the locking mechanism. In particular, it must be guaranteed that the locking device does not cause inadvertent jamming of the drive shaft, i.e., locking it with the bearing housing, during normal boring operation.

According to the present invention there is provided a direct drive for deep boring cutters or similar tools operable in a bore hole, including a drive shaft connectible between a rotor and a tool, and a bearing housing coaxial to the drive shaft and connectible to a stator as well as to a locking device which, when put into operation, can lock the drive shaft to the bearing housing wherein the locking device includes a first locking sleeve which encircles the drive shaft and a second locking sleeve which is connected to the bearing housing, relative axial motion of the drive shaft and the bearing housing in a first direction engaging the locking device between the drive shaft and the bearing housing, and relative axial motion in the opposite direction permitting disengagement of the drive shaft and bearing housing, and wherein safety device which resists engagement of the locking sleeves is provided, which resistance to the engagement can be overcome by exerting a predetermined, upwards directed axial force on the bearing housing.

A simple and reliable method of operation of the locking mechanism is provided by the fact that with this arrangement the mutual locking engagement of the drive shaft and bearing housing is brought about by their axial relative motion, since, in case of jamming of the tool in the unit, an upward-directed axial force is introduced via the bore tubing line and the stator of the direct drive into the bearing housing. This is accomplished with the aid of a lifting device arranged over the bore hole in a well-known manner. This tensile force can, without further ado, be regulated to be large enough that secure interlock is always guaranteed, regardless of the resistances which may occur during the boring operation, e.g.

resistances occasioned by the flushing liquid or boring mud. On the other hand, the safety device guarantees that the mutual interlocking engagement of the locking sleeves is not released within the range of such upward-directed axial forces which lie within the orders of magnitude of the forces which usually occur in boring operations. Moreover, according to the invention, this locking engagement is only released after overcoming the resistance which is opposed to the engagement motion of both of the locking sleeves; and which is due to the safety device and which is accomplished by a suitable preset upward-directed force installed over the borehole. Notwithstanding this, the possibility of releasing the locking engagement again in case of need by relative motion in the opposite direction can be accomplished easily.

In one arrangement according to the invention, both of the locking sleeves can form a friction locking mechanism together. Alternatively both locking sleeves together can form a lock by means of members which can be closed by mutual engagement and for this they may be constructed particularly as gear toothed- or claw-locking devices.

The safety device can include at least one shearable member that is sheared at a predetermined axial force and which frees the locking sleeves for an engaging motion. Alternatively, the safety device may be formed by a clamping sleeve, which is located over or under the locking mechanism and above an axial bearing or between the inner ring of an axial bearing and the drive shaft and which secures these parts against relative motion by mutual clamping engagement. The clamping grip may be overcome by a predetermined axial force to free the engagement motion of both of the locking sleeves.

In contrast to a safety device operating by means of shearable links, a safety device developed in this manner is still usable even after the cutter is set free, since then only an opposing downward-directed force needs to be employed to overcome the clamping engagement of the clamping sleeve to affect the required loosening of the locking sleeves from their locking engagement.

An additional way of making the safety device permits continued use of the implement after it is loosened, as described above, consists of a sleeve, screwed to the drive shaft and secured against turning, and a cooperating elastic deformable lock sleeve. Stopping of the locking sleeves after the tool has been freed is achieved by setting the tool on the hole bottom, whereby, under the load exerted by the bore line, the drive shaft and sleeve screwed to it are pushed back to their starting positions and the lock sleeve experiences an elastic recovery.

Embodiments of the invention will now be described with reference to the accompanying drawings, in which: Figures lea, 76 and ic, taken together, show, in axial section, a direct drive for deep boring cutters, or similar tools operable in a bore hole, according to a first embodiment.Figure 1 a represents a full axial section, while Figures 1b and leach represent a half axial section and form the lower parts of the drive; Figure 2a shows an enlarged scale, the portion of the direct drive which contains a locking mechanism and a safety device of the embodiment of Figures 1 a, 1b and 1 c, the locking mechanism and the safety device being shown in their unlocked, respectively, unreleased positions; Figure 2b shows the portion of Figure 2a, but with the locking mechanism and the safety device shown in their locked, respectively released positions; Figure 2c shows a section taken along the line AA of Figure 2a;; Figures 3a and 3b show an alternative embodiment of locking mechanism and safety device, in the unlocked and locked positions, respectively, unreleased and released positions as for Figures 2a and 2b; Figure 3c shows a section taken along the line BB of Figure 3a; Figures 4a and 4b show yet another embodiment of locking mechanism and safety device in the unlocked and locked, respectively, unreleased and released positions as for Figures 2a and 2b; Figure 5shows an axial section through the region of the direct drive containing the locking device and the safety device, indicating an additional embodiment of the safety device; Figure 6 shows a cross section through the direct drive in the region of the safety device shown in FigureS; Figures 7, 8 and 9 each show a variation of the safety device shown in Figure 5 and 6;; Figure 10 shows a further embodiment of a direct drive, in an axial section, with a further modified safety device; the locking device and the safety device in the right-hand half of Figure 10 being shown in their unlocked, respectively, unreleased, positions, and in the left half of Figure 10 in their locked, respectively released positions; Figure 11 shows a perspective view of a locking sleeve assigned to a bearing housing; Figure 12 shows an elevational view of a locking sleeve which operates with the locking sleeve of Figure 11 and which is assigned to a drive shaft; Figure 13 shows a top view of the locking sleeve of Figure 12; Figures 14, 15and 16 show in a similar manner as in Figures 11, 12 and 13 an additional arrangement for the cooperating locking sleeves, Figure 15 being a perspective rather than elevational view;; Figure 17 shows the locking device of Figure 10 in half axial section, on a larger scale, and in the unreleased state, and Figure 18 shows the locking device of Figure 10 in the released state.

Referring firstly to Figures la, 1b and Ic, a direct drive for deep bore cutters or similar tools operable in a bore hole includes a stator 1 and a rotor 2 which in a well-known manner form a working space.

Flushing liquid is pumped downward as a working medium through a bore pipe line and enters into the working space at high pressure, is forced into a helical path thus rotating the rotor, whereby a portion of the pressure energy of the working medium is translated into rotational energy for the tool.

The rotor 2 is connected to a drive shaft 5 which is in the form of a hollow shaft. The connection is made by way of a universal shaft 3 with a diverting pipe 4 for flushing liquid connected to it. This, in turn, is screwed to the drive shaft 5. The drive shaft 5 carries on its lower end as a tool a cutter 6 which is represented by the cutter connecting device.

The stator 1 is connected with statortube 7 by means of a bearing housing 8, which surrounds the intermediate shaft 3, the diverting pipe 4 for the flushing liquid and the drive shaft 5, and which includes an intermediate tube 9, fastened directly to the statortube 7, a main tube 10, screwed onto the intermediate tube 9 adjacent an axial bearing 11 and a lower supporting pipe or carrier tube 12 for a lower radial bearing 13 of the drive shaft 5. An additional radial bearing 14 of the drive shaft 5 is provided in the mutual connecting region of the intermediate pipe 9 and the main pipe 10.

The thrust of the cutter 6 is transmitted from drill collars (not shown), which are arranged in a wellknown manner over the stator 1, by way of the stator tube 7 and the main tube 10 of the bearing housing 8 to the axial bearing 11, which, for its part, transmits this axial force acting as a thrust to the drive shaft 5.

In addition a sleeve 15 is provided on whose upper front face is braced the inner ring array of a threaded sleeve 17 which is screwed onto the drive shaft 5.

The radial bearing 14 has the additional duty of reducing the differential pressure between the flushing liquid forward flow to the cutter 6 and the flushing liquid backward flow in the annular space between the wall of the bore hole and the bearing housing 8. The usual pressure differences at the cutter 6 are between 50 and 80 bar.

Furthermore, a locking device, the whole designated 18, is included in the drive. This is arranged in the bearing housing 8 and serves to bring about an interlock between the bearing housing 8 and the drive shaft 5 when the cutter 6 is jammed. The locking device 18 is formed as a ratchet mechanism which includes first, a locking sleeve 20, adjoining the drive shaft 5, and second, a locking sleeve 20, adjoining the bearing housing 8; which can be moved into a mutual locking engagement by an axial relative motion of drive shaft 5 and bearing housing 8.

Both of the locking sleeves 19 and 20 form a friction lock in the embodiment of Figures 1 and 2, in that they exhibit conical contra-rotating regions of friction surfaces inclined toward each other for a mutual frictional engagement. The locking sleeve 19 is connected with the hollow shaft 5 with the help of keys 21 and fixed to the shaft 5 on the top side at 22, while it is supported on the underside by an inner sleeve 23 of the radial bearing 14 which is itself supported by the inner ring assembly 16 of the axial bearing 11. The locking sleeve 20 is supported from below on an outer sleeve 24 of the radial bearing 14, which is connected firmly with threaded projection 25 of the main tube 10 of the bearing housing 10 such as by welding.By this means the locking sleeve 20, which, moreover, is slotted longitudinally, is supported for axially displacement with respect to the locking sleeve 19 in the bearing housing 10.

A safety device, the whole designated as 26, normally prevents a mutual locking engagement of the locking sleeves 19 and 20, so that the drive shaft 5 turns unimpeded inside the bearing housing 8 in normal boring operation to rotate the cutter 6.

According to the embodiment of Figures 1 and 2, the safety device 26 includes a ring sleeve 27 with projecting cotter pins 28 at its circumference as well as a packing sleeve 29, which engages the cotter pins 28. In doing so, the packing sleeve 29 is supported at one end on the outer bearing assembly 30 of the axial bearing 11 and at the other end on the cotter pins 28 of the ring sleeve 27, which act as shear members. The under side of the ring sleeve 27 is, in turn, supported on the upper ring surface of threaded projection 31 of carrier tube 12.

The condition of the locking device 18 on the one hand and the safety device 26 on the other hand is illustrated in Figure 2a in normal boring operation, during which the drive shaft 5 turns inside the bearing housing 8 to act as rotating drive for the cutter 6 which is represented in the drawing by the cutter connecting arrangement to the drive shaft 5. If the cutter 6 jams, the drive shaft, the universal shaft 3 and the rotor 2 stop. Starting with the drill table (not shown) the stator tube 7 and with it the intermediate tube 9, the main tube 10 of the bearing housing as well as the lower supporting pipe 12 of the lower radial bearing 13 are then pulled upward over the drill tube linkage. The axial force expended herewith is increased until, at a predetermined value, the shear pins 28 located on the ring sleeve 27 are sheared off.By this action the main tube 10 of the bearing housing 8 and, with it, the supporting pipe 12 of the lower radial bearing 13 as well as the intermediate tube 9 and the stator tube 7 are pulled upward which results in the sleeve 24 driving the locking sleeve 20 upward. A mutual locking engagement of the locking sleeves 19, 20 follows from this.

This locked state of the locking device 18 is illustrated in Figure 2b. In this position, now, with the aid of the turntable, the bore tube line, which is located over the bore hole, and, with this, the stator tube 7 and the bearing housing 8 can be set into rotation; and the torque generated in this manner can be transmitted from the bearing housing 8 by way of the locking device 18, which is in the locked position, to the drive shaft 5 or the cutter 6. With the aid of a considerably greater torque than can be introduced by the direct drive in normal boring operation, the cutter 6 can be released from its jam by means of the turntable using the rotating procedure described.

The rotational motion to release the cutter is opposite to the rotational direction in normal boring operation.

While the locking device 18 is above and the safety device 26 is located below the axial bearing 11 in the embodiment of Figures 1 and 2, the arrangement is encountered in reverse in the embodiment of Figures 3a, 3b and 3c, in that the locking device 18 is located below and the safety device 26 above the axial bearing 11. In this case, the locking mechanism 18 is again formed of a friction lock. The first locking sleeve 19, which adjoins the drive shaft 5, is, in this case, formed of the threaded sleeve 17 screwed to the drive shaft 5. The threaded sleeve 17 supports the inner bearing ring assembly 16 of the axial bearing with its upper front face.The second locking sleeve 20, which adjoins the bearing housing 8, is formed of the connecting threaded projection 31 of the supporting pipe 12 for the outer element of the lower radial bearing 13, in this embodiment. To operate as friction locks both of the locking sleeves 19,20 or the threaded sleeve 17 and the threaded projection 31 exhibit contra-rotating conical friction surfaces 32 and 33 inclined toward each other. The upper front face of the threaded projection 31 supports-the outer bearing ring assembly 30 of the axial bearing 11 by way of a spacing collar 34.

In this embodiment the safety device consists of a sleeve 35 which is connected to a sleeve 37 with cotter pins 36 used as stopping links. The sleeve 37, for its part, is connected with the drive shaft 5 by an upper adapter sleeve 38 in a way not further described. Alternatively, the sleeve 37 can form the radial bearing 14with the sleeve 24.

As already explained in connection with Figure 1 and 2, when the cutter jams, the cotter pins 36 of the safety device 26 shear off when a specified upward directed axial force is reached, whereupon the bearing housing 8 and with it the stator tube 7 are moved upward until both of the locking sleeves 19 and 20 of the locking mechanism 18 attain a mutual locking engagement by frictional engagement on their friction surface regions 32 and 33. The transfer of torque to free the jammed cutter takes place by analogy with the example of Figure 1 and 2 via the stator tube 7 and the bearing housing 8, the threaded projection 31 forming the locking sleeve 20, of the supporting pipe 12, to the threaded sleeve 17 which forms the locking sleeve 19 and which is screwed to the drive shaft 5. On the one hand, the condition of the locking mechanism 18 and the safety device 26 is illustrated in Figure 3a during normal boring operation, while Figure 3b illustrates the safety device 26 in the released condition and the locking mechanism 18 during locking engagement of its locking sleeves 19 and 20.

In the embodiment of Figure 4a and 4b, as in the case of the embodiment of Figure 3, the safety device 26 is arranged above and the locking mechanism 18 is arranged below the axial bearing 11. The arrangement of the safety device 26 is not functionally different from that shown in Figure 3, and differs from this in construction only in the fact that, instead of cotter pins 36 as shearing links, a ring flange 39 is formed at the circumference of the sleeve 35, on which the bottom of packing sleeve 37 rests.

The locking arrangement 18 is not formed as a friction locking mechanism in this embodiment; both locking sleeves 19 and 20 in this case, rather, form a lock with mutually engageable, closed locking members; specifically, in the example under discussion, a gear toothed lock with axial locking outer gear 40 on which is located the locking sleeve 19 adjoining the drive shaft 5, and an axial locking inner gear 41 at which is located the locking sleeve 20 adjoining the bearing housing 8. The arrangement and formation of the safety device 18 corresponds in other respects with the embodiment described with respect to Figure 3. The locking sleeve 19 is again formed from the threaded sleeve 17, screwed to the drive shaft, and the locking sleeve 20 is formed from the threaded projection 31 of the supporting pipe 12.

Therefore, equivalent reference marks are used for equivalent parts, as has already been done in the embodiment of Figure 3. The function of the locking arrangement 18 of Figure 4 corresponds with the function of the locking arrangement 18 of Figure 3; whereby it must only be remarked that the engaged state of the locking mechanism 18 is achieved by engaging the gears of the outer gearing 40 on the threaded sleeve 17 with the inner gearing 41 of the threaded projection 31 of the supporting pipe 12, rather than by a friction engagement of friction surfaces or friction surface regions. Figures 4a and 4b correspond to Figures 3a and 3b with regard to the actual operating state.

In the ways of carrying out the construction of the safety device 26 described so far, the shearable link or links must be renewed by replacing the corresponding parts to make the safety device operable again in order to avoid an inadvertent engagement motion of locking sleeves of the locking mechanism in cases in which the upward directed axial force is greater than the longitudinal force which is transmitted over the bore linkage to the cutter and which may be the case in certain conditions of boring. The upward directed axial force is produced by the differential pressure between the drive and the bore cutter.

The construction illustrated in Figure 5 avoids such a replacement of the safety device.

The general construction of the direct drive of Figure 5 corresponds to the above described embodiments, so that the same references are again used for the same or for corresponding parts. The bearing housing 8 is again equipped with a lower radial bearing 13 and an upper radial bearing 14 and the axial bearing 11 is arranged between them. The locking mechanism 18 is formed as a gear lock according to the embodiment of Figure 4, whereby the threaded sleeve 17 screwed to the drive shaft 5, forms the locking sleeve 19 and the threaded projection 31 forms the locking sleeve 20. The outer bearing ring assembly 30 of the axial bearing 11 is fixed axially and prestressed between a ring 42 and the upper shoulder 43 of the threaded projection 31 by the interposition of an adapter sleeve 44.

In this embodiment the safety device 26 is formed from a clamping sleeve 45, which is arranged between the inner ring assembly 16 of the axial bearing 11 and the drive shaft 5. The clamping sleeve bridges the annulus between these parts and secures them against relative motion by mutual clamping engagement. While the outer ring assembly 30 of the axial pressure bearing 11 is clamped on top and bottom, the inner bearing ring assembly 16 of the axial bearing 11 is only supported on its bottom side toward the drive shaft; in particular on the upper ring surface or shoulder 46 of the threaded sleeve 17. This arrangement is illustrated in the drawing.A reversed arrangement is, however, also possible, in which the clamping sleeve 45, which is formed to bridge an annuls, is arranged between the outer bearing ring assembly 30 and the bearing housing 8 and results in affixing the inner bearing ring assembly 16 on the drive shaft 5.

The clamping sleeve 45 may have a corrugated or a toothed circumference. The corrugations or teeth of the clamping sleeve 45 may, in this case, run in axial or radial planes, or may take the form of screw threads. According to the illustration in Figure 6, the clamping sleeve 45 exhibits axial, i.e. longitudinal, rounded corrugations. According to the illustration in Figure 7, rounded corrugations 48 are provided which run transversely, i.e. in radial planes. These corrugations form the circumference of the clamping sleeve 47. A modification of this arrangement is shown in Figure 8, according to which the corrugations 48' exhibit a flattened profile. According to the example of Figure 9 teeth 49, which run in the shape of threads, are formed at the circumference of the clamping sleeve 47.

In normal boring operation the downwarddirected axial forces which exert a longitudinal force on the cutter are transmitted from the bearing housing 8 to the outer bearing ring assembly 30 of the axial bearing 11, by the balls of the axial bearing 11 to the inner bearing ring assembly 16 and by the clamping sleeve 45 to the drive shaftS. By this arrangement a uniform load distribution is achieved simultaneously on each of the individual bearings of the axial bearing 11 which are stacked over each other.

The upward-directed axial forces produced in an already described way when the cutter jams are transmitted from the bearing housing 8 to the drive shaft 5 and the cutter 6 by the axial bearing 11 and by the clamped connection between the inner bearing ring assembly 16, the clamping sleeve 45 and the drive shaft 5. This is shown in the right half of Figure 5 by a sequence of arrows. As soon as these axial forces exceed the clamping force exerted by the clamping sleeve 45, which is represented in Figure 6 by arrows 50 and 51, an upward motion of the whole axial bearing 11 in relation to the drive shaft 5 is brought about. The axial force which overcomes the clamping engagement produced by the clamping sleeve 45, can be predetermined, at least in order of magnitude, in such a way that the clamping engagement of the clamping sleeve 45 is not overcome in normal boring operation. If the clamping engage mentofthe clamping sleeve 45 is overcome, release of the engagement motion of both of the locking sleeves 19,20 of the locking mechanism 18 ensues.

The locking sleeves 19,20 of the locking mechanism 18 are shown in the left half of Figure 5 in the position in which a transferoftorque between bearing housing 8 and drive shaft 5 brings about a locking engagement.

After the jammed bore cutter is released, the locking mechanism 18, which is in a locked or blocked position, may be unlocked easily by striking the bearing housing 8 with a downward-directed axial force which is greater than the clamping force produced by means of the clamping sleeve 45 between the inner bearing ring assembly 16 and the drive shaftS. When this clamping force is exceeded, the bearing housing 8 and the axial bearing 11 slide downward until the latter sits on the upper ring surface or shoulder 46 of the threaded sleeve 17.By this means the locking mechanism 18 and the safety device 26 are returned to their starting position, shown in the right half of Figure 5; in which the locking mechanism 18 permits free rotation of the drive shaft 5 in the bearing housing 8, and in which the safety device 26 is ready to perform its safety function anew without repair work being required to achieve this.

An additional embodiment of a safety device which is reusable, i.e. reversible, after being used once is illustrated in Figures 10, 17 and 18. The general arrangement of the bearing housing shown in Figure 10 corresponds to that shown in Figures 5 and 1, so that, in as far as possible, the same references are used again for the same or for similar elements. In the embodiment of Figures 10, 17 and 18, the safety device 26 comprises a sleeve 52 which is screwed to the driveshaft 5 with a threaded connection 53 and is secured against turning by a key 54. In the illustrated example, the sleeve 52 forms a part of the upper radial bearing 14 of the drive shaft 5.

An elastically deformable locking sleeve 55 operates together with the sleeve 52. In the example presented the locking sleeve 55 is formed as a longitudinally slotted spring sleeve which forms a one piece part of the upper inner ring 56 of the inner bearing ring assembly 16 of the axial bearing 11.The shape and construction material of the locking sleeve 55 is chosen so that an elastic deformation of the locking sleeve 55 when engaging the sleeve 52 remains guaranteed even in long term operation.

The surface 57 of the sleeve 52 and the surface 58 of the locking sleeve 5, on which both sleeves normally bear, (compare Figure 17), are treated to reduce wear.

The locking mechanism 18 is formed as a gear lock in the performance example of Figure 10 corresponding to the embodiment of Figure 5. Figure 11 shows the threaded projection 31 of the supporting pipe 12 for the lower radial bearing 13 of the drive shaft 5 on a larger scale. The threaded projection 31 also forms the locking sleeve 20 with the locking inner gearing 41 in the form of axial teeth or studs 59 with bevelled front edges.

The threaded sleeve 17 of Figure 12 and 13 which forms the locking sleeve 19 operates together with the threaded projection 31 of Figure 11 which forms the locking sleeve 20. The threaded sleeve 17, for its part, has on it the locking-outer gearing 40 in the form of axial teeth or studs 60 with bevelled front edges for a locking engagement with the teeth 59 of the locking sleeve 20. As may particularly be seen in Figure 13, three studs spaced 1200 apart are distributed on the outer circumference of the threaded sleeve 17. The teeth 59 have a corresponding arrangement on the inner circumference of the threaded projection 31.This arrangement is very sturdy and provides ample play between the teeth 59, 60 which counteracts jams and guarantees reliability of operation of such a locking mechanism over a long time period; Avariation of such a lock is illustrated in Figure 14 to 16, wherein the locking sleeve 20 forms a claw lock together with the locking sleeve 19. According to this, corresponding to the description in Figure 14, an inner clamping arrangement 61 in the shape of three claws 62 separated from one another by an angular interval of 1 20" on the inner circumference of the threaded projection 31. According to Figure 15 and 16, the threaded sleeve 17, which forms the locking sleeve 19 operates together with the threaded projection 31, which forms the locking sleeve 20 according to Figure-14.The threaded sleeve 17 exhibits at its outer ci rcumference an axial outer ratchet 63 in the forum of three claws 64 separated by an average anguiar spacing of 1200 to provide a locking engagement with the claws 62 of the threaded projection 31. This arrangement is also very sturdy and provides adequate play between the claws 62 and 64 to preventjams.

In Figure 17 the safety device 26 is depicted in its normal operating condition in which it opposes the engagement motion of the locking sleeves 19 and 20 by a resistance which can be overcome only by the predetermined, upward-directed axial force. Figure 18 illustrates the safety device 26 in the operating condition in which it releases the locking sleeves 19 and 20 for a mutual engagement motion two cause stoppage of the drive shaft 5, i.e. its locking with the bearing housing 8, to release the jammed boring cutter in the manner described. For this, the predetermined upward-directed tensile force is again directed to the bearing housing 8, as illustrated by the sequence of arrows in Figure 18.When a predetermined tensile force is reached, an axial relative motion of the locking sleeves 19 and 20 takes place; whereby the sleeve 52, which is connected with the drive shaftS, slides over the lock sleeve 55 under the influence of the counter force introduced by the drive shaft 5. The lock sleeve is deformed elastically by appropriate force application. The threaded sleeve 17, which forms the locking sleeve 19, is inserted into the locking sleeve 20 formed by the threaded projection 31, by the axial relative displacement of the drive shaft 5, which slides through under the axially fixed axial bearing 11. By this means, mutual interlock of the bearing housing 8 and the drive shaft 5 is achieved. The displacement path of the sleeves in the region of the safety device 26 as well as the locking mechanism 18, at any given time, is given in Figure 10 by Y.The locked condition of locking sleeves 18 and 19 is illustrated in Figure 10.

Unlocking of the locking sleeves 18 and 19 after the cutter 6 has been released is achieved by setting the tool on the bottom of the hole. Under the load exerted by the bore line, the sleeve 52 of the safety device 26 is thus pushed back into their starting position together with the drive shaftS; while, at the same time the slotted lock sleeve experiences an elastic recovery. A renewed stoppage of the drive shaft 5 in the bearing housing 8 by locking engagement of the locking sleeve 18 and 19 can only be released by the specific upward-directed tensile force evoked by the displacement of the sleeve 52.

Because of this correspondingly large regulated tensile force, an inadvertent stoppage when the bore tube line is lifted does not occur. Consequently, the safety device 26 remains continuously serviceable over a long period of time and possesses a high degree of reliability.

Claims (24)

1. A direct drive for deep boring cutters or similar tools operable in a bore hole, including a drive shaft connectible between a rotor and a tool, and a bearing housing coaxial to the drive shaft and connectible to a stator as well as to a locking device which, when put into operation, can lock the drive shaft to the bearing housing, wherein the locking device includes a first locking sleeve which encircles the drive shaft and a second locking sleeve which is connected to the bearing housing, relative axial motion of the drive shaft and the bearing housing in a first direction engaging the locking device between the drive shaft and the bearing housing, and relative axial motion in the opposite direction permitting disengagement of drive shaft and bearing housing, and wherein safety device which resists engagement of the locking sleeves is provided, which resistance to the engagement can be overcome by exerting a predetermined, upwards directed axial force on the bearing housing.

2. A direct drive as claimed in claim 1, wherein the locking sleeves together form a friction lock.

3. A direct drive as claimed in claim 2, wherein the locking sleeves have facing contrarotatable conical friction surface regions which are engageable to produce a mutual friction interlock, the second locking sleeve being braced against the first locking sleeve and displaced from it axially in the bearing housing.

4. A direct drive as claimed in claim 2 or claim 3, wherein the second locking sleeve is slotted longitudinally.

5. A direct drive as claimed in any one of claims 2 to 4, wherein the first locking sleeve is connected to the drive shaft by means of keys.

6. A direct drive as claimed in claim 2 or claim 3 wherein the first locking sleeve is formed by a threaded casing screwed onto the drive shaft and the second locking sleeve is formed buy a part of the bearing housing.

7. A direct drive as claimed in claim 1,wherein the locking sleeves each have locking members which can be mutually engaged in a positive manner to form a catch.

8. A direct drive as claimed in claim 1 or claim 7, wherein the locking sleeves together form a ratchet.

9. A direct drive as claimed in claim 8, wherein the first locking sleeve is comprised by a threaded sleeve which is screwed to the drive shaft and which has an axial externally gear-toothed locking mechanism and wherein a part of the bearing housing comprises the second locking sleeve and has an axial internally gear-toothed locking mechanism.

10. A direct drive as claimed in claim 1 or claim 7, wherein the first and the second locking sleeves together form a claw locking mechanism.

11. A direct drive as claimed in claim 10, wherein the first locking sleeve is comprised by an axially external claw threaded sleeve screwed to the drive shaft, and wherein a part of the bearing housing forms the second locking sleeve and is axially internally-clawed.

12. A direct drive as claimed in any one of claims 6 to 11, wherein the part of the bearing housing which forms the second locking sleeve is comprised by an externally threaded connecting projection of a supporting tube of the bearing housing.

13. A direct drive as claimed in claim 12, wherein the bearing housing supporting tube which comprises the second locking sleeve also supports an outer element of a lower radial bearing of the drive shaft.

14. A direct drive as claimed in any one of the preceding claims, wherein the safety device includes at least one shearable link which shears at a predetermined axial force and releases the locking sleeves for an interlocking motion.

15. A direct drive as claimed in claim 14, wherein the shearable link is comprised by a cotter pin projecting over the outer circumference of a ring sleeve or by a flange and wherein the ring sleeve is clamped into the bearing housing by means of a packing sleeve capable of admitting a counterbalance and resting on the cutter or similar tool, the packing sleeve being engaged on the cotter pin or on the flange.

16. A direct drive as claimed in claim 14 or claim 15, wherein the safety device is arranged over or under the locking mechanism and an axial bearing is located between them.

17. A direct drive as claimed in any one of claims 1 to 13, wherein the safety device comprises a clamping sleeve located between an inner ring assembly of an axial bearing and the drive shaft and' which secures these parts against relative motion by clamping engagement, which clamping engagement can be overcome by a predetermined axial force in order to achieve release of the engagement motion of the locking sleeves.

18. A direct drive as claimed in claim 17, wherein an outer ring assembly of the axial bearing is clamped into the bearing housing on to top or on the bottom side, while the inner ring assembly is only supported with its underside toward the drive shaft, or vice versa.

19. A direct drive as claimed in claim 17 or claim 18, wherein the clamping sleeve has a corrugated or a toothed circumference.

20. A direct drive as claimed in claim 19, wherein corrugations or teeth of the clamping sleeve progress in axial or radial planes, or are in the form of threads.

21. A direct drive as claimed in any one of claims 1 to 13, wherein the safety device is comprised by a sleeve, which is screwed onto the drive shaft and secured against turning, and a lock sleeve which acts with the screwed-on sleeve and is elastically deformable.

22. A direct drive as claimed in claim 21, wherein the lock sleeve is comprised by a longitudinally slotted spring sleeve.

23. A direct drive as claimed in claim 21 or claim 22, wherein the lock sleeve is comprised by a one-piece portion of an inner ring of an axial bearing.

24. A direct drive for deep boring cutters or similar tools operable in a bore hole, substantially as herein described with reference to and as illustrated in Figures la, ib, ic, 2a, 2b and 2c, Figures 3a and 3b, Figure 4a and 4b, Figure 5 with Figure 6,7, 8 or 9, Figures 10,17 and 18, Figures 11,12 and 13, or Figures 14, 15 and 16 of the accompanying drawings.