NO20240502A1 - A tractor for propelling an apparatus inside a cylindrical body - Google Patents

Description

[0001] A TRACTOR FOR PROPELLING AN APPARATUS INSIDE A CYLINDRICAL BODY

[0002] TECHNICAL FIELD

[0004] The present disclosure relates to a tractor for propelling an apparatus inside a cylindrical body. Moreover, the present disclosure relates to an assembly comprising a tool and a tractor. Further, the present disclosure relates to a cylindrical body assembly comprising a cylindrical body and a tractor or an assembly.

[0006] BACKGROUND

[0008] Contemporary technologies employ several different mechanisms for performing operations inside a cylindrical body, such as oil and gas wells, water injection and production pipelines. One such mechanism is a pipeline tractor. Pipeline tractors employ different mechanisms for propulsion or movements of the tractors inside a cylindrical or an elongated body.

[0010] For instance, WO 2022/129328 A1 discloses an apparatus for propulsion and operations inside a cylindrical body, such as a pipeline, and comprises a central shaft, at least one motor and motor control unit, a number of wheels arranged to rotate round the shaft with a tilted angle, and a sensor module comprising sensors. However, there is still a need for improving tractors for propelling an apparatus inside a cylindrical body.

[0012] SUMMARY

[0014] In view of the above, an object of the present disclosure is to provide a tractor for propelling an apparatus inside a cylindrical body, which tractor can be controlled in an appropriate manner.

[0016] The above object is obtained by a first aspect of the present disclosure in accordance with claim 1.

[0018] As such, a first aspect of the present disclosure relates to a tractor for propelling an apparatus inside a cylindrical body. The tractor comprises an input shaft adapted to receive a torque.

[0019] The tractor further comprises a drive portion that in turn comprises a drive shaft adapted to be rotated around an axis of rotation of the drive shaft. The drive portion further comprises a set of propulsion members comprising at least one propulsion member, preferably two or more propulsion members. Each propulsion member in the set of propulsion members is rotationally fixed to the drive shaft. The tractor is adapted to assume a propulsion condition in which each propulsion member in the set of propulsion members is adapted to transfer a force from an inner surface of the cylindrical body to the drive shaft to thereby propel the tractor relative to the cylindrical body.

[0021] The tractor further comprises a torque transferring portion adapted to receive a drive shaft torque portion of the torque received by the input shaft and to transfer at least a portion of the drive shaft torque portion to the drive shaft. The drive shaft torque portion has a maximum value. The torque transferring portion is such that the torque transferrable via the torque transferring portion is limited to a predetermined threshold torque value. The predetermined threshold torque value is less than the maximum value.

[0023] The tractor of the first aspect of the present disclosure implies that the torque transferrable to the drive shaft, and consequently the torque transferrable to the propulsion member or propulsion members, may be limited to the predetermined threshold torque value. This in turn implies that the propulsion member or propulsion members will not be imparted excessive torque during use. This may in turn result in the propulsion member(s) and/or the cylindrical body may be protected from excessive wear. Moreover, the above also implies that the tractor may exhibit preferred propulsion characteristics in various operating conditions.

[0025] For instance, if the tractor is connected to a tubing, such as a coiled tubing, the tubing may impart a force on the tractor in a direction opposite to a propulsion force imparted by the propulsion member(s). As such, the tractor may be held back by the tubing. In such an operating condition, an undesirably large torque could be imparted on the propulsion member(s) and/or the cylindrical body. However, the tractor according to the first aspect of the present disclosure implies that the torque imparted on the propulsion member(s) and/or the cylindrical body may be kept appropriately low.

[0027] As another example, the tractor could be connected to a tool, such as a drill tool, adapted to perform for instance a milling operation in the cylindrical body in order to e.g. remove an undesired object in the cylindrical body. As such, the tool may constitute an example of an apparatus that the tractor is adapted to propel. Such a milling operation may result in the speed of the tractor relative to the cylindrical body being relatively low since unobstructed movement of the tractor is prevented. This could in turn result in the propulsion member(s) slipping or that the tractor applies too high a load onto the tool. By virtue of the tractor according to the present disclosure, the tractor may apply an appropriate load on the tool in order for the tool to be able to carry out its intended operation. When the tool is a drill tool, such as a drill bit, the load on the tool may also be referred to as a “weight on bit”.

[0029] Preferably, the torque transferring portion is adapted to receive the drive shaft torque portion of the torque received by the input shaft and to transfer at least 90%, preferably at least 95%, of the drive shaft torque portion to the drive shaft, as long as drive shaft torque portion is at or below the predetermined threshold torque value. As such, as long as the drive shaft torque portion is at or below the predetermined threshold torque value, the torque transferring portion is adapted to transfer at least substantially the entire drive shaft torque portion to the drive shaft. Moreover, preferably, once the predetermined threshold torque value has been reached, the torque transferred via the torque transferring portion may remain at the predetermined threshold torque value.

[0031] Optionally, the predetermined threshold torque value is less than 90%, preferably less than 80%, of the maximum value. A predetermined threshold torque value below any one of the below limits implies an appropriate operation of the tractor.

[0033] Optionally, the torque transferring portion comprises a slip clutch. The slip clutch is adapted to slip when the drive shaft torque portion exceeds the predetermined threshold torque value. Preferably the slip clutch is adjustable such that the predetermined threshold torque value can be varied. The slip clutch may be a cost-efficient means for ensuring that the torque transferring portion is such that the torque transferrable via the torque transferring portion is limited to a predetermined threshold torque value.

[0035] Optionally, the torque transferring portion comprises an input shaft side portion rotationally connected, preferably rotationally fixedly connected, to the input shaft and a drive shaft side portion rotationally fixedly connected to the drive shaft. The input shaft side portion comprises an input shaft side torque transferring surface and the drive shaft side portion comprises a drive shaft side torque transferring surface. The torque transferring portion is such that a torque up to a surface transfer threshold torque value, being dependent on the threshold torque value, can be transferred via contact between the input shaft side torque transferring surface and the drive shaft side torque transferring surface. The above implies that an appropriate transfer and limitation of the transferred torque.

[0037] Optionally, the torque transferring portion is such that for a torque difference between the input shaft side portion and the drive shaft side portion exceeding the surface transfer threshold torque value, the torque transferring portion assumes a condition in which the input shaft side torque transferring surface rotates relative to the drive shaft side torque transferring surface. The above implies an appropriate means for ensuring that the torque transferring portion is such that the torque transferrable via the torque transferring portion is limited to a predetermined threshold torque value.

[0039] Optionally, the torque transferring portion is such that when the input shaft side torque transferring surface contacts the drive shaft side torque transferring surface and rotates relative to the drive shaft side torque transferring surface in at least a predetermined direction of rotation, the input shaft side portion is displaced relative to, and away from, the drive shaft side portion in a direction parallel to the axis of rotation of the drive shaft. The above implies that the input shaft side portion and the shaft side portion may in a straightforward way arrive at a condition in which torque transfer between the surfaces is limited.

[0041] Optionally, the torque transferring portion comprises a biasing member adapted to impart a biasing force onto the input shaft side portion towards the drive shaft side portion in a direction parallel to the axis of rotation of the drive shaft. The biasing member implies that the input shaft side portion and the shaft side portion may achieve a transfer of torque up to the predetermined threshold torque value in a straightforward manner. Moreover, though purely by way of example, by modifying the biasing member, it may be possible to adjust the predetermined threshold torque value.

[0043] Optionally, the input shaft side torque transferring surface extends in a circumferential direction around the axis of rotation of the drive shaft. The input shaft side torque transferring surface comprises a first input shaft surface portion and a second input shaft surface portion. The first input shaft surface portion and the second input shaft surface portion are separated by an input shaft longitudinal distance in a direction parallel to the axis of rotation of the drive shaft. The first input shaft surface portion and the second input shaft surface portion are separated by an input shaft circumferential distance in the circumferential direction. A ratio between the input shaft longitudinal distance and the input shaft circumferential distance may be at least 5%, preferably at least 10%. A ratio at or above any one of the above limits implies an appropriate torque transfer between the surfaces.

[0045] Optionally, the drive shaft side torque transferring surface extends in a circumferential direction around the axis of rotation of the drive shaft. The drive shaft side torque transferring surface comprises a first drive shaft surface portion and a second drive shaft surface portion. The first drive shaft surface portion and the second drive shaft surface portion are separated by a drive shaft longitudinal distance in a direction parallel to the axis of rotation of the drive shaft. The first drive shaft surface portion and a second drive shaft surface portion are separated by a drive shaft circumferential distance in the circumferential direction. A ratio between the drive shaft longitudinal distance and the drive shaft circumferential distance may be at least 5%, preferably at least 10%. A ratio at or above any one of the above limits implies an appropriate torque transfer between the surfaces.

[0047] Optionally, the input shaft side torque transferring surface and the drive shaft side torque transferring surface have complementary shapes. This also implies an appropriate torque transfer between the surfaces.

[0049] Optionally, the input shaft side portion comprises an input shaft side portion surface assembly extending in a circumferential direction around the axis of rotation of the drive shaft. The input shaft side portion surface assembly comprises the input shaft side torque transferring surface. The input shaft side portion surface assembly further comprises an input shaft side slip surface extending in the circumferential direction. The drive shaft side portion comprises a drive shaft side portion surface assembly extending in a circumferential direction around the axis of rotation of the drive shaft. The drive shaft side portion surface assembly comprises the drive shaft side torque transferring surface. The drive shaft side portion surface assembly further comprises a drive shaft side slip surface extending in the circumferential direction. The torque transferring portion is such that when the input shaft side slip surface contacts the drive shaft side slip surface and rotates relative to the drive shaft side slip surface in at least a predetermined direction of rotation, the input shaft side portion remains stationary relative to the drive shaft side portion in a direction parallel to the axis of rotation of the drive shaft or is displaced towards, and relative to, the drive shaft side portion in a direction parallel to the axis of rotation of the drive shaft. The above implies that the input shaft side portion may rotate relative to the shaft side portion with an appropriately low amount of resistance when the above slip surfaces abut each other.

[0051] Optionally, the input shaft side portion is rotationally connected, preferably rotationally fixedly connected, to the input shaft, preferably via a splined joint. The above implies an appropriate possibility to rotationally connect the input shaft side portion to the input shaft.

[0053] Optionally, the torque transferring portion comprises a plurality of pairs of the input shaft side portion and the drive shaft side portion, each pair being in accordance with any one of the above options. The above implies that the transferred torque can be distributed amongst a plurality of pairs of the input shaft side portion and the shaft side portion which may reduce the loading on each pair.

[0055] Optionally, the tractor is adapted to propel an apparatus inside a cylindrical body having an elongate extension, the axis of rotation of the drive shaft being adapted to extend along the elongate extension when the tractor is in use. This implies that the tractor can be implemented in an appropriately compact manner.

[0057] Optionally, the further comprises a motor rotationally fixedly connected to the input shaft, preferably the motor is adapted to rotate the input shaft. The above implies that the input shaft can be rotated in an appropriate manner.

[0059] A second aspect of the present disclosure relates to an assembly comprising a tool and the tractor according to the first aspect of the present disclosure.

[0061] Optionally, the tool is rotationally connected to the input shaft, preferably the tool is a drill tool. This implies that the input shaft may power the tractor as well as the tool.

[0062] Optionally, the tool is rotationally connected, preferably fixedly connected, to the input shaft via a tool shaft, preferably the tool shaft extends at least partially within the drive shaft. This implies a compact tractor.

[0064] Optionally, the tool and the input shaft are located on opposite sides of the drive portion, along the axis of rotation of the drive shaft.

[0066] A third aspect of the present disclosure relates to a cylindrical body assembly comprising a cylindrical body and the tractor according to the first aspect of the present disclosure or the apparatus according to the second aspect of the present disclosure.

[0068] BRIEF DESCRIPTION OF THE DRAWINGS

[0070] In the drawings:

[0072] Fig.1 is a schematic side view of a tractor for propelling an apparatus inside a cylindrical body;

[0074] Fig. 2 illustrates a helical shape;

[0076] Fig. 3 is a schematic cross-sectional side view of a tractor;

[0078] Fig. 4 is a schematic side cross-sectional side view of an assembly;

[0080] Fig.5 is a schematic side cross-sectional view of torque transferring portion;

[0082] Fig.6 is an exploded view of a drive shaft side portion and a sleeve;

[0084] Fig.7 illustrates an implementation of an input shaft side portion and a drive shaft side portion;

[0086] Fig.8a and 8b illustrate an implementation of an input shaft side portion;

[0088] Fig.9a and 9b illustrate an implementation of an drive shaft side portion;

[0089] Fig. 10 is an exploded view of an implementation of an input shaft side portion and a drive shaft side portion, and

[0091] Fig.11 is a schematic cross-sectional side view of a tractor.

[0093] DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0095] Fig.1 illustrates a tractor 10 for propelling an apparatus inside a cylindrical body 12. Fig.1 illustrates a cross-sectional view of a cylindrical body 12. Purely by way of example, and as will be elaborated on further hereinbelow, the apparatus may be a tool. Instead of, or in addition to, a tool, the apparatus may be a sensor such as a camera (not shown).

[0097] In the following description, the term "cylindrical body" is used to describe any kind of body having an elongated extending opening, such as a pipeline, duct, channel, tube, drilled well with or without casing. Examples are flexible risers, umbilicals, oil or gas wells during or after drilling, oil or gas production pipelines, water pipes, waste pipes, process plant pipelines, geothermal wells, etc.

[0099] As illustrated in Fig.1, the tractor 10 comprises an input shaft 14 adapted to receive a torque. Purley by way of example, the torque may be produced by a torque producing unit (not shown) located outside the cylindrical body 12 and the torque may be transferred to the input shaft 14 via a torque transferring assembly 16. As a non-limiting example, the torque transferring assembly 16 may comprise a coiled tubing assembly. However, instead of, or in addition to, the above, and as will be elaborated on hereinbelow, the torque may be at least partially produced by a motor forming part of the tractor 10.

[0101] As indicated in Fig.1, the tractor 10 further comprises a drive portion 18 that in turn comprises a drive shaft 20 adapted to be rotated around an axis of rotation A of the drive shaft 20. The drive portion 18 further comprises a set of propulsion members 22 comprising at least one propulsion member 24, 26, 28, 30, preferably two or more propulsion members 24, 26, 28, 30. In Fig.1, six propulsion members are visible of which four propulsion members 24, 26, 28, 30 are numbered. However, it is envisaged that other implementations of the drive portion 18 may comprise fewer or more propulsion members.

[0102] As may be realized from Fig.1, though purely by way of example, the tractor 10 may be adapted to propel an apparatus inside a cylindrical body 12 having an elongate extension and the axis of rotation A of the drive shaft 20 may be adapted to extend along the elongate extension when the tractor 10 is in use.

[0104] Each propulsion member 24, 26, 28, 30 in the set of propulsion members 22 is rotationally fixed to the drive shaft 20. Moreover, the tractor is adapted to assume a propulsion condition in which each propulsion member 24, 26, 28, 30 in the set of propulsion members 22 is adapted to transfer a force from an inner surface 32 of the cylindrical body 12 to the drive shaft 20 to thereby propel the tractor 10 relative to the cylindrical body 12.

[0106] Here, it should also be noted that, by way of example only, each propulsion member 24, 26, 28, 30 in the set of propulsion members 22 may be such that when the drive shaft 20 rotates around the axis of rotation A and the propulsion member 24, 26, 28, 30 transfers a force from the inner surface 32 of the cylindrical body 12 to the drive shaft 20, a contact point between the propulsion member 24, 26, 28, 30 and the inner surface 32 of the cylindrical body 12 will vary as the drive shaft 20 rotates around the axis of rotation A such that a trajectory 34 of subsequent contact points will form a helical shape on the inner surface 32 of the cylindrical body 12. Such a helical shape is indicated in Fig.2. It should be noted that the helical shape indicated in Fig.2 may be obtained for a plurality of different implementations of the propulsion member 24, 26, 28, 30.

[0108] Fig.3 illustrating a cross-sectional side view of an embodiment of a tractor 10 indicates that the tractor 10 further comprises a torque transferring portion 36 adapted to receive a drive shaft torque portion T<ds >of the torque T<in >received by the input shaft 14 and to transfer at least a portion of the drive shaft torque portion to the drive shaft 20. The drive shaft torque portion T<ds >has a maximum value T<max>. The torque transferring portion 36 is such that the torque transferrable via the torque transferring portion is limited to a predetermined threshold torque value T<thres>. The predetermined threshold torque value T<thres >is less than the maximum value T<max>.

[0110] Moreover, as may be gleaned from Fig.3, the input shaft 14 may comprise a threaded portion 38 adapted to be connected to another threaded portion of a torque transferring assembly 16 (see Fig.1) or a motor (see e.g. Fig.11) adapted to produce a torque.

[0111] Irrespective of whether or not the input shaft 14 has a threaded portion 38, the input shaft 14 is adapted to receive the torque T<in>. The torque T<in >received by the input shaft 14 may be referred to as an input torque. Moreover, as indicated above and as also indicated in Fig.3, the torque transferring portion 36 is adapted to receive a drive shaft torque portion T<ds >of the torque T<in >received by the input shaft 14 and to transfer at least a portion of the drive shaft torque portion T<ds >to the drive shaft 20.

[0113] Purely by way of example, in embodiments of the tractor 10, the torque T<in >received by the input shaft 14 may fully correspond to the drive shaft torque portion T<ds >such that T<in >= T<ds>.

[0115] However, in other embodiments of the present disclosure, the drive shaft torque portion T<ds >may be less than the torque T<in >received by the input shaft 14 such that T<ds >< T<in>.

[0116] Purely by way of example, it is envisaged that in embodiments of the present disclosure, the torque T<in >received by the input shaft 14 may be split up into the drive shaft torque portion T<ds >and at least another portion that is intended to be used for another purpose.

[0118] To this end, though purely by way of example, Fig.4 illustrates a side cross-sectional view of a second aspect of the present disclosure relating to an assembly 40 comprising a tool 42 and the tractor 10 according to the first aspect of the present disclosure.

[0120] As may be gleaned from Fig.4, though purely by way of example, the tool 42 is rotationally connected to the input shaft 14. As a non-limiting example, and as exemplified in Fig.4, the tool 42 is a drill tool. Moreover, as indicated in Fig.4 by way of example only, the tool 42 is rotationally connected, preferably fixedly connected, to the input shaft 14 via a tool shaft 44. In the Fig.4 embodiment, by way of example only, the tool shaft 44 extends at least partially within the drive shaft 20. Furthermore, as indicated in Fig.4 by way of example only, the tool shaft 44 may comprise a conduit adapted to guide fluid to the tool 42. Purely by way of example, if the tractor 10 comprises a fluid motor, see e.g. Fig.11 below, such a conduit may guide fluid from an exhaust of the fluid motor to the tool 44.

[0122] As a non-limiting example, and as indicated in Fig.4, the tool 42 and the input shaft 14 may be located on opposite sides of the drive portion 18, along the axis of rotation A of the drive shaft 20.

[0123] As such, in embodiments of the tractor 10 or the assembly 40, the drive shaft torque portion T<ds >may only form a portion of the torque T<in >received by the input shaft 14. To this end, using Fig.4 as a non-limiting example, the torque T<in >received by the input shaft 14 may be split up into the drive shaft torque portion T<ds >as well as a tool torque portion T<tool >adapted to power the tool 42. Purely by way of example, and as exemplified in Fig.4, the tool torque portion T<tool >may be transferred to the tool 42 via the tool shaft 44.

[0125] Irrespective of how large a part of the torque T<in >received by the input shaft 14 the drive shaft torque portion T<ds >forms, the torque transferring portion 36 may be adapted to receive the drive shaft torque portion T<ds >of the torque T<in >received by the input shaft 14 and to transfer at least 90%, preferably at least 95%, of the drive shaft torque portion T<ds >to the drive shaft 20, as long as the drive shaft torque portion T<ds >is at or below the predetermined threshold torque value T<thres>. As such, as long as the drive shaft torque portion T<ds >is at or below the predetermined threshold torque value T<thres>, the torque transferring portion 36 is adapted to transfer at least substantially the entire drive shaft torque portion T<ds >to the drive shaft 20. Moreover, preferably, once the predetermined threshold torque value has been reached, the torque transferred via the torque transferring portion 36 may remain at the predetermined threshold torque value T<thres>.

[0127] Purely by way of example, the predetermined threshold torque value T<thres >may be less than 90%, preferably less than 80%, of the maximum value T<max>.

[0129] Fig. 5 illustrates an example implementation of the torque transferring portion 36. As may be realized from Fig.5, the torque transferring portion 36 may comprise a slip clutch 46. The slip clutch 46 is adapted to slip when the drive shaft torque portion T<ds >exceeds the predetermined threshold torque value T<thres>.

[0131] The slip clutch 46 may be implemented in a plurality of different ways. As a non-limiting example, a slip clutch 46 may comprise one or more friction plates (not shown) adapted to transfer a torque up to the predetermined threshold torque value T<thres>. For a torque above the predetermined threshold torque value T<thres>, at least one of the friction plates may slip relative to another friction plate, thereby preventing that a torque above the predetermined threshold torque value T<thres >is transferred via the slip clutch 46. As a non-limiting example, the friction plates may be planar or bowed.

[0132] Moreover, the slip clutch 46 may be adjustable such that said predetermined threshold torque value T<thres >can be varied. As a non-limiting example, a slip clutch 46 may comprise a tensioner (not shown) by which it is possible to alter the contact force between adjacent friction plates to thereby alter the friction force between plates.

[0134] It is also envisaged that other implementations of the slip clutch 46 may comprise other torque transferring members than friction plates, such as clutch discs or the like.

[0136] Fig.5 also illustrates an example implementation of the torque transferring portion 36 comprising an input shaft side portion 48 rotationally connected, preferably rotationally fixedly connected, to the input shaft 14. Moreover, the Fig.5 torque transferring portion 36 comprises drive shaft side portion 50 rotationally fixedly connected to the drive shaft 20. The input shaft side portion 48 and the drive shaft side portion 50 may be regarded as forming part of, or even constitute, the above-mentioned slip clutch 46.

[0138] Purely by way of example, and as indicated in Fig.5, the torque transferring portion 36 may comprise a plurality of pairs 52, 52’ of the input shaft side portion 48, 48’ and the drive shaft side portion 50, 50’. The Fig.5 implementation of the torque transferring portion 36 comprises two pairs 52, 52’ of the input shaft side portion 48, 48’ and the drive shaft side portion 50, 50’ but it is envisaged that other implementations may comprise only one pair 52 of input shaft side portion 48 and the drive shaft side portion 50. Moreover, it is envisaged that other implementations may comprise more than two pairs of input shaft side portion 48 and the drive shaft side portion 50.

[0140] The below presentation of the input shaft side portion 48 and the drive shaft side portion 50 is applicable any pair 52, 52’ of to the input shaft side portion 48 and the drive shaft side portion 50.

[0142] Purely by way of example, and as indicated in Fig.5, the input shaft side portion 48 may be rotationally connected, preferably rotationally fixedly connected, to the input shaft 14. Purely by way of example, and as indicated in Fig.5, the input shaft side portion 48 may be connected to input shaft 14 via a splined joint 54. As such, the input shaft side portion 48 may be rotationally fixed to the input shaft 14 but may be allowed to move relative to the input shaft in a direction being parallel to the axis of rotation A of the drive shaft 20. This possibility is indicated by double arrows in Fig.5.

[0143] Moreover, as may be gleaned from Fig.5, the drive shaft side portion 50 may be directly or indirectly connected to the input shaft 14 via a bearing assembly 56 comprising at least one bearing 58. In the Fig.5 example, the bearing assembly 56 comprising a single bearing 58 exemplified by a ball bearing. However, in other embodiments of the tractor 10, the bearing assembly 56 may comprise a plurality of bearings (not shown).

[0145] Furthermore, as indicated in Fig.5, the drive shaft side portion 50 may be rotationally fixedly connected to the drive shaft 20 via a sleeve 60 that is at least rotationally fixed to a portion of the drive shaft 20. As a non-limiting example, and as indicated in Fig.5, the sleeve 60 may enclose at least a portion of the input shaft 14 in a circumferential direction around the axis of rotation A of the drive shaft 20.

[0147] Purely by way of example, the sleeve 60 may be connected to the drive shaft by means of a bolt joint (not shown). By way of example only, the drive shaft side portion 50 may be rotationally fixedly connected to the sleeve 60. To this end, reference is made to Fig.6 illustrating an implementation of the drive shaft side portion 50 and the sleeve 60 in an exploded view. As may be realized from Fig.6, the drive shaft side portion 50 may be rotationally fixedly connected to the sleeve 60 via a sleeve connection arrangement comprising a plurality of teeth 62 arranged on an end portion of the sleeve 60 and a plurality of teeth 64 forming part of the drive shaft side portion 50. The teeth 62, 64 are adapted to engage, thereby providing a rotationally fixed connection between the drive shaft side portion 50 and the sleeve 60.

[0149] Fig.7 illustrates an implementation of a pair 52 of the input shaft side portion 48 and the drive shaft side portion 50. The pair 52 forms part of an implementation of the torque transferring portion 36.

[0151] As illustrated in Fig.7, the input shaft side portion 48 comprises an input shaft side torque transferring surface 66 and the drive shaft side portion 50 comprises a drive shaft side torque transferring surface 68. In an attempt to facilitate the presentation of the input shaft side portion 48 and the drive shaft side portion 50 illustrated in Fig.7, the surfaces 66, 68 are located at a distance from each other along the axis of rotation A of the drive shaft (not shown in Fig.7). However, as may be realized from the below presentation, the input shaft side torque transferring surface 66 and the drive shaft side torque transferring surface 68 are adapted to be in contact in at least one condition of the torque transferring portion 36.

[0153] As a non-limiting example, the input shaft side torque transferring surface 66 and the drive shaft side torque transferring surface 68 may have complementary shapes.

[0155] Purely by way of example, the torque transferring portion 36 is such that a torque up to a surface transfer threshold torque value T<surf,thres>, being dependent on the threshold torque value T<thres>, can be transferred via contact between the input shaft side torque transferring surface 66 and the drive shaft side torque transferring surface 68. As indicated by arrows in Fig.7, the torque can be transferred via contact between the input shaft side torque transferring surface 66 and the drive shaft side torque transferring surface 68 by means of normal forces as well as frictional forces between the input shaft side torque transferring surface 66 and the drive shaft side torque transferring surface 68 when the two surfaces 66, 68 are in contact.

[0157] Purely by way of example, in embodiments of the torque transferring portion 36 containing a single pair of the input shaft side portion 48 and the drive shaft side portion 50, the surface transfer threshold torque value T<surf,thres >may be equal to the threshold torque value T<thres>. Moreover, as another non-limiting example, for embodiments of the torque transferring portion 36 containing a plurality of pairs of the input shaft side portion 48 and the drive shaft side portion 50, the surface transfer threshold torque value T<surf,thres >may be a fraction of the threshold torque value T<thres>. By way of example only, for n pairs of the input shaft side portion 48 and the drive shaft side portion 50, the surface transfer threshold torque value T<surf,thres >may be 1/n times the threshold torque value T<thres >for each pair of the input shaft side portion 48 and the drive shaft side portion 50, i.e. T<surf,thres >= T<thres >/n.

[0159] Moreover, again with reference to Fig.7, the torque transferring portion 36 may be such that for a torque difference between the input shaft side portion 48 and the drive shaft side portion 50 exceeding the surface transfer threshold torque value T<surf,thres>, the torque transferring portion 36 assumes a condition in which the input shaft side torque transferring surface 66 rotates relative to the drive shaft side torque transferring surface 68. As such, by way of example only, if the input shaft side torque transferring surface 66 is in contact with the drive shaft side torque transferring surface 68, for a torque exceeding the surface transfer threshold torque value T<surf,thres>, the input shaft side torque transferring surface 66 may slip relative to the drive shaft side torque transferring surface 68.

[0161] Moreover, as also indicated in Fig.7, the torque transferring portion 36 may be such that when the input shaft side torque transferring surface 66 contacts the drive shaft side torque transferring surface 68 and rotates relative to the drive shaft side torque transferring surface 68 in at least a predetermined direction of rotation R1, the input shaft side portion 48 is displaced relative to, and away from, the drive shaft side portion 50 in a direction parallel to the axis of rotation of the drive shaft A.

[0163] As such, by way of example, when the input shaft side torque transferring surface 66 is in contact with the drive shaft side torque transferring surface 68, for a torque exceeding the surface transfer threshold torque value T<surf,thres>, the input shaft side torque transferring surface 66 may slip relative to the drive shaft side torque transferring surface 68 and the input shaft side portion 48 may be displaced relative to, and away from, the drive shaft side portion 50 in a direction parallel to the axis of rotation of the drive shaft A. This can in turn prevent a torque exceeding the surface transfer threshold torque value T<surf,thres >from being transferred via the surfaces 66, 68.

[0165] Reverting to Fig.5, as indicated therein, the torque transferring portion 36 may comprise a biasing member 70 adapted to impart a biasing force onto the input shaft side portion 48 towards the drive shaft side portion 50 in a direction parallel to the axis of rotation of the drive shaft A. Purely by way of example, the biasing member 70 may be implemented by a spring, such as a helical spring, although other implementations are also contemplated. Purely by way of example, the biasing member 70 may comprise one or more magnetic elements (not shown) adapted to impart the biasing force. As another non-limiting example, the biasing member 70 may comprise a hydraulic or pneumatic cylinder (not shown). As a non-limiting example, a portion of the biasing member 70 may be connected, preferably fixedly connected, to a portion 71 of the input shaft 14.

[0167] As may be realized from Fig.5 and Fig.7, the magnitude of the biasing force may govern the above-mentioned surface transfer threshold torque value T<surf,thres >at which the input shaft side torque transferring surface 66 rotates relative to the drive shaft side torque transferring surface 68. Thus, by an appropriate choice of the biasing member 70, such as the constitution and/or pretensioning thereof, a desired surface transfer threshold torque value T<surf,thres >may be obtained which in turn may result in a desired predetermined threshold torque value T<thres >for the torque transferring portion 36.

[0169] Fig.8a and Fig.8b illustrate an implementation of the input shaft side portion 48 in a front view and a side view, respectively. As may be realized from Fig.8a, the input shaft side torque transferring surface 66 extends in a circumferential direction C around the axis of rotation of the drive shaft A. As indicated in Fig.8a, the input shaft side torque transferring surface 66 comprises a first input shaft surface portion 72 and a second input shaft surface portion 74.

[0171] With reference to Fig.8b, the first input shaft surface portion 72 and the second input shaft surface portion 74 are separated by an input shaft longitudinal distance 76 in a direction parallel to the axis of rotation A of the drive shaft (not shown). Moreover, as indicated in Fig.8a, the first input shaft surface portion 72 and the second input shaft surface portion 74 are separated by an input shaft circumferential distance 78 in the circumferential direction C. As indicated in Fig.8a, the circumferential distance 78 may be defined as the circumference of a circle segment extending from the first input shaft surface portion 72 to the second input shaft surface portion 74. Thus, the first input shaft surface portion 72 and the second input shaft surface portion 74 may be located at the same radial distance, i.e. a distance in a direction perpendicular to the axis of rotation A, from the axis of rotation A of the drive shaft (not shown). As indicated in Fig.8a, a radius of the circle segment may be such that the circle segment is located radially within, i.e. between a radial inner limit and a radial outer limit of, the input shaft side torque transferring surface 66. Purely by way of example, and as indicated in Fig.8a, the radius of the circle segment may correspond to an average radius R<av >of the input shaft side torque transferring surface 66, i.e. an average distance in a radial direction to the axis of rotation A.

[0173] A ratio between the input shaft longitudinal distance 76 and the input shaft circumferential distance 78 may be at least 5%, preferably at least 10%. As such, and as indicated in Figs.8a and 8b, the input shaft side torque transferring surface 66 may be regarded as slanted.

[0174] In a similar manner as for Figs.8a and 8b, Fig.9a and Fig.9b illustrate an implementation of the drive shaft side portion 50 in a front view and a side view, respectively.

[0176] As may be realized from Fig.9a, the drive shaft side torque transferring surface 68 extends in a circumferential direction C around the axis of rotation A of the drive shaft 20. The drive shaft side torque transferring surface 68 comprises a first drive shaft surface portion 80 and a second drive shaft surface portion 82.

[0178] With reference to Fig.9b, the first drive shaft surface portion 80 and the second drive shaft surface portion 82 are separated by a drive shaft longitudinal distance 84 in a direction parallel to the axis of rotation A of the drive shaft 20. Moreover, as indicated in Fig.9a, the first drive shaft surface portion 80 and the second drive shaft surface portion 82 are separated by a drive shaft circumferential distance 86 in the circumferential direction. As indicated in Fig.9a, the drive shaft circumferential distance 86 may be defined as the circumference of a circle segment extending from the first drive shaft surface portion 80 to the second drive shaft surface portion 82. Thus, the first drive shaft surface portion 80 and the second drive shaft surface portion 82 may be located at the same radial distance, i.e. a distance in a direction perpendicular to the axis of rotation A, from the axis of rotation A of the drive shaft (not shown). As indicated in Fig.9a, a radius of the circle segment may be such that the circle segment is located radially within, i.e. between a radial inner limit and a radial outer limit of, the drive shaft side torque transferring surface 68. Purely by way of example, and as indicated in Fig.9a, the radius of the circle segment may correspond to an average radius R<av >of the drive shaft side torque transferring surface 68, i.e. an average distance in a radial direction to the axis of rotation A.

[0180] A ratio between the drive shaft longitudinal distance 84 and the drive shaft circumferential distance 86 may be at least 5%, preferably at least 10%. As such, and as indicated in Figs.9a and 9b, the drive shaft side torque transferring surface 68 may be regarded as slanted.

[0182] Fig.10 illustrates an implementation of an input shaft side portion 48 and a drive shaft side portion 50. As a non-limiting example, the input shaft side portion 48 and a drive shaft side portion 50 may form a pair 52.

[0183] As indicated in Fig.10, the input shaft side portion 48 may comprises an input shaft side portion surface assembly 88 extending in a circumferential direction C (see Fig.8a) around the axis of rotation A of the drive shaft 20. The input shaft side portion surface assembly 88 comprises the input shaft side torque transferring surface 66. The input shaft side portion surface assembly 88 further comprises an input shaft side slip surface 90, 92 extending in the circumferential direction C. In fact, Fig.10 illustrates two input shaft side slip surfaces 90, 92. Here, reference is also made to Fig.8a illustrating the input shaft side portion surface assembly 88 comprising the input shaft side torque transferring surface 66 and the two input shaft side slip surfaces 90, 92. As may be realized from Fig. 8a and Fig.8b, the input shaft side portion surface assembly 88 actually comprises two subsets of surfaces, each subset comprising an input shaft side torque transferring surface 66 and two input shaft side slip surfaces 90, 92.

[0185] In a similar vein, as indicated in Fig.10, the drive shaft side portion 50 may comprise a drive shaft side portion surface assembly 94 extending in a circumferential direction (see Fig.9a) around the axis of rotation A of the drive shaft 20. The drive shaft side portion surface assembly 94 comprises the drive shaft side torque transferring surface 68. The drive shaft side portion surface assembly 94 further comprises a drive shaft side slip surface 96, 98 extending in the circumferential direction C. In fact, Fig.10 illustrates two drive shaft side slip surfaces 96, 98. Here, reference is also made to Fig.9a illustrating the drive shaft side portion surface assembly 94 comprising the drive shaft side torque transferring surface 68 and the two drive shaft side slip surfaces 96, 98. As may be realized from Fig.9a and Fig.9b, the drive shaft side portion surface assembly 94 actually comprises two subsets of surfaces, each subset comprising drive shaft side torque transferring surface 68 and two drive shaft side slip surfaces 96, 98.

[0187] The torque transferring portion 36 is such that when the input shaft side slip surface 90, 92 contacts the drive shaft side slip surface 96, 98, e.g. when the input shaft side slip surface 90 contacts the drive shaft side slip surface 96 or when the when the input shaft side slip surface 92 contacts the drive shaft side slip surface 98, and rotates relative to the drive shaft side slip surface 96, 98 in at least a predetermined direction of rotation, the input shaft side portion 48 remains stationary relative to the drive shaft side portion 50 in a direction parallel to the axis of rotation A of the drive shaft (not shown in Fig.10) or is displaced towards, and relative to, the drive shaft side portion 50 in a direction parallel to the axis of rotation A of the drive shaft.

[0188] Fig.11 illustrates a further embodiment of the tractor 10 of the present disclosure. In the Fig.11 embodiment, the tractor 10 further comprises a motor 100 rotationally fixedly connected to the input shaft 14. As a non-limiting example, the motor 100 may be connected to the input shaft 14 via the threaded portion 38 thereof. In the Fig.11 embodiments, the motor 100 is adapted to rotate the input shaft 14. As a non-limiting example, the motor may be a fluid motor or an electric motor.

[0190] Fig.11 also illustrates by way of example only an example of a third aspect of the present disclosure relating to a cylindrical body assembly 102 comprising a cylindrical body 12 and the tractor 10 according to the first aspect of the present disclosure or the assembly according to the second aspect of the present disclosure.

[0192] It should be noted that the present disclosure is not limited to any one of the above examples. On the contrary, may alternative embodiments falling within the scope of the appended claims are contemplated.

Claims (20)

1. CLAIMS

1. A tractor (10) for propelling an apparatus inside a cylindrical body (12),

said tractor (10) comprising an input shaft (14) adapted to receive a torque;

said tractor (10) further comprising a drive portion (18) that in turn comprises a drive shaft (20) adapted to be rotated around an axis of rotation (A) of said drive shaft (20), said drive portion (18) further comprising a set of propulsion members (22) comprising at least one propulsion member (24, 26, 28, 30), preferably two or more propulsion members (24, 26, 28, 30), each propulsion member (24, 26, 28, 30) in said set of propulsion members (22) being rotationally fixed to said drive shaft (20), said tractor (10) being adapted to assume a propulsion condition in which each propulsion member (24, 26, 28, 30) in said set of propulsion members (22) is adapted to transfer a force from an inner surface (32) of said cylindrical body (12) to said drive shaft (20) to thereby propel said tractor (10) relative to said cylindrical body (12),

said tractor (10) further comprising a torque transferring portion (36) adapted to receive a drive shaft torque portion (T<ds>) of said torque received by said input shaft (14) and to transfer at least a portion of said drive shaft torque portion (T<ds>) to said drive shaft (20), wherein said drive shaft torque portion (T<ds>) has a maximum value (T<max>), said torque transferring portion (36) being such that said torque transferrable via said torque transferring portion (36) is limited to a predetermined threshold torque value (T<thres>), said predetermined threshold torque value (T<thres>) being less than said maximum value (T<max>).

2. The tractor (10) according to claim 1, wherein said predetermined threshold torque value (T<thres>) is less than 90%, preferably less than 80%, of said maximum value (T<max>).

3. The tractor (10) according to claim 1 or claim 2, wherein said torque transferring portion (36) comprises a slip clutch (46), said slip clutch (46) being adapted to slip when said drive shaft torque portion (T<ds>) exceeds said predetermined threshold torque value (T<thres>), preferably said slip clutch (46) is adjustable such that said predetermined threshold torque value (T<thres>) can be varied.

4. The tractor (10) according to any one of claims 1 - 3, wherein said torque transferring portion (36) comprises an input shaft side portion (48) rotationally connected, preferably rotationally fixedly connected, to said input shaft (14) and a drive shaft side portion (50) rotationally fixedly connected to said drive shaft (20), said input shaft side portion (48) comprising an input shaft side torque transferring surface (66) and said drive shaft side portion (50) comprising a drive shaft side torque transferring surface (68), said torque transferring portion (36) being such that a torque up to a surface transfer threshold torque value (T<surf,thres>), being dependent on said threshold torque value (T<thres>), can be transferred via contact between said input shaft side torque transferring surface (66) and said drive shaft side torque transferring surface (68).

5. The tractor (10) according to claim 4, wherein said torque transferring portion (36) is such that for a torque difference between said input shaft side portion (48) and said drive shaft side portion (50) exceeding said surface transfer threshold torque value (T<surf,thres>), said torque transferring portion (36) assumes a condition in which said input shaft side torque transferring surface (66) rotates relative to said drive shaft side torque transferring surface (68).

6. The tractor (10) according to claim 5, wherein said torque transferring portion (36) is such that when said input shaft side torque transferring surface (66) contacts said drive shaft side torque transferring surface (68) and rotates relative to said drive shaft side torque transferring surface (68) in at least a predetermined direction of rotation, said input shaft side portion (48) is displaced relative to, and away from, said drive shaft side portion (50) in a direction parallel to said axis of rotation (A) of said drive shaft (20).

7. The tractor (10) according to any one of claims 4 to 6, wherein said torque transferring portion (36) comprises a biasing member (70) adapted to impart a biasing force onto said input shaft side portion (48) towards said drive shaft side portion (50) in a direction parallel to said axis of rotation (A) of said drive shaft (20).

8. The tractor (10) according to any one of claims 4 to 7, wherein said input shaft side torque transferring surface (66) extends in a circumferential direction (C)

around said axis of rotation (A) of said drive shaft (20), said input shaft side torque transferring surface (66) comprising a first input shaft surface portion (72) and a second input shaft surface portion (74), said first input shaft surface portion (72) and said second input shaft surface portion (74) being separated by an input shaft longitudinal distance (76) in a direction parallel to said axis of rotation (A) of said drive shaft (20), said first input shaft surface portion (72) and said second input shaft surface portion (74) being separated by an input shaft circumferential distance (78) in said circumferential direction (C), a ratio between said input shaft longitudinal distance (76) and said input shaft circumferential distance (78) being at least 5%, preferably at least 10%.

9. The tractor (10) according to any one of claims 4 to 8, wherein said drive shaft side torque transferring surface (68) extends in a circumferential direction (C) around said axis of rotation (A) of said drive shaft (20), said drive shaft side torque transferring surface (68) comprising a first drive shaft surface portion (80) and a second drive shaft surface portion (82), said first drive shaft surface portion (80) and a second drive shaft surface portion (82) being separated by a drive shaft longitudinal distance (84) in a direction parallel to said axis of rotation (A) of said drive shaft (20), said first drive shaft surface portion (80) and said second drive shaft surface portion (82) being separated by a drive shaft circumferential distance (86) in said circumferential direction (C), a ratio between said drive shaft longitudinal distance (84) and said drive shaft circumferential distance (86) being at least 5%, preferably at least 10%.

10. The tractor (10) according to any one of claims 2 to 9, wherein said input shaft side torque transferring surface (66) and said drive shaft side torque transferring surface (68) have complementary shapes.

11. The tractor (10) according to any one of claims 6 to 10, when dependent on claim 6, wherein said input shaft side portion (48) comprises an input shaft side portion surface assembly (88) extending in a circumferential direction (C) around said axis of rotation (A) of said drive shaft (20), said input shaft side portion surface assembly (88) comprising said input shaft side torque transferring surface (66), said input shaft side portion surface assembly (88) further comprising an input shaft side slip surface (90, 92) extending in said circumferential direction (C), said drive shaft side portion (50) comprising a drive shaft side portion surface assembly

(94) extending in a circumferential direction (C) around said axis of rotation (A) of said drive shaft (20), said drive shaft side portion surface assembly (94) comprising said drive shaft side torque transferring surface (68), said drive shaft side portion surface assembly (94) further comprising a drive shaft side slip surface (96, 98) extending in said circumferential direction (C), said torque transferring portion (36) being such that when said input shaft side slip surface (90, 92) contacts said drive shaft side slip surface (96, 98) and rotates relative to said drive shaft side slip surface (96, 98) in at least a predetermined direction of rotation, said input shaft side portion (48) remains stationary relative to said drive shaft side portion (50) in a direction parallel to said axis of rotation (A) of said drive shaft (20) or is displaced towards, and relative to, said drive shaft side portion (50) in a direction parallel to said axis of rotation (A) of said drive shaft (20).

12. The tractor (10) according to any one of claims 4 to 11, wherein said input shaft side portion (48) is rotationally connected, preferably rotationally fixedly connected, to said input shaft (14), preferably via a splined joint (54).

13. The tractor (10) according to any one of claims 4 to 12, wherein said torque transferring portion (36) comprises a plurality of pairs (52, 52’) of said input shaft side portion (48) and said drive shaft side portion (50), each pair (52, 52’) being in accordance with any one of claims 4 to 12.

14. The tractor (10) according to any one of the preceding claims, wherein said tractor (10) is adapted to propel an apparatus inside a cylindrical body (12) having an elongate extension, said axis of rotation (A) of said drive shaft (20) being adapted to extend along said elongate extension when the tractor (10) is in use.

15. The tractor (10) according to any one of the preceding claims, further comprising a motor (100) rotationally fixedly connected to said input shaft (14), preferably said motor is adapted to rotate said input shaft (14).

16. An assembly (102) comprising a tool (42) and the tractor (10) according to any one of claims 1 – 15.

17. The assembly according to claim 16, wherein said tool (42) is rotationally connected to said input shaft (14), preferably said tool (42) is a drill tool.

18. The assembly according to claim 17, wherein said tool (42) is rotationally connected, preferably fixedly connected, to said input shaft (14) via a tool shaft (44), preferably said tool shaft (44) extends at least partially within said drive shaft (20).

19. The assembly according to any one of claims 16 - 18, wherein said tool (42) and said input shaft (14) are located on opposite sides of said drive portion (18), along the axis of rotation (A) of said drive shaft (20).

20. A cylindrical body assembly (102) comprising a cylindrical body (12) and the tractor (10) according to any one of claims 1 – 15 or the assembly (102) according to any one of claims 16 - 19.