WO2014193240A1

WO2014193240A1 - Torque measuring arrangement for a quill shaft

Info

Publication number: WO2014193240A1
Application number: PCT/NO2014/050085
Authority: WO
Inventors: Norvald Harald RØYSET
Original assignee: Rolls-Royce Marine As
Priority date: 2013-05-28
Filing date: 2014-05-27
Publication date: 2014-12-04
Also published as: NO20130740A1

Abstract

The present invention concerns an arrangement (20) for measuring torque in a transmission system with a quill shaft (2) coaxially inside a bore of a driveshaft (3), coaxially supported in a sleeve (6). The quill shaft is fixed to the driveshaft (3) at a first end and to the sleeve (6) at a second end, whereby a load applied to the driveshaft (3) results in torsion of the quill shaft (2) and a torsional displacement of the driveshaft (3) in the sleeve (6). The arrangement includes a measuring surface (221) extending circumferentially along a segment angle of the transmission system and the measuring surface extends with a varying distance in an axial direction along at least a part of the segment angle at one of the sleeve (6) and the driveshaft (3). A gap sensing element (21) is provided for measuring the size of a gap between the gap sensing element (21) and the measuring surface (221) at the other of the sleeve (6) and the driveshaft (3).

Description

Torque measuring arrangement for a quill shaft.

TECHNICAL FIELD

The present invention relates to a transmission system comprising a quill shaft assembly with a torque measuring arrangement, a thruster in a vessel with a transmission system including a torque measuring arrangement and a torque measuring arrangement for measuring torque in a quill shaft. The arrangement measures torque or twisting moment in a propulsion system/transmission, typically for a marine thruster in a vessel, boat or ship. The propulsion system includes a thruster with a quill shaft. The arrangement for measuring torque comprises at least one distance or proximity sensor.

BACKGROUND OF THE INVENTION

There are numerous methods for measuring torque or stresses in a shaft. Common methods include using strain gauges to measure strain directly on a shaft to monitor or test stresses a system is exposed to. Torque may also be measured by measuring the amount of torsion in a shaft, but in rotating shafts such measurements may be complicated to perform as it is necessary to compare an angular position between each side of the shaft exposed to torque, and as the shaft is rotating.

Torque measurement data can for instance be used for design purposes, to control operational parameters such as throttle settings and propeller pitch, to estimate power output, to ensure that operational parameters are within design conditions to prevent overloading, to estimate maintenance or servicing intervals and in connection with troubleshooting in the event of a transmission failure.

Propellers and in particular propellers in thrusters, may be subjected to large transient loads. Such thrusters include azimuth thrusters. When a vessel or a ship is at sea there are some known situations where transient loads occur. Such situations include ventilation of the propeller(s) and/or situations where the entire propeller leaves the water. When the propeller is unloaded, considerable torsional vibration or oscillation can occur in the entire driveline. When the propeller / thruster reenters the water, a high peak torque normally occur. This torque can be much higher than the design load of the gears / sprockets in the transmission driving the propeller. This can result in pitting, tearing damage and tooth fracture or break-offs. Thrusters are particularly exposed to the above mentioned situations and are thus particularly exposed to the mentioned problems.

Accordingly, there is a need for a propeller shaft torque or moment measuring arrangement and system for a thruster in a vessel, boat or ship.

SUMMARY OF THE INVENTION

It is a purpose with the present invention to enable measurements of the magnitude of transient loads in a resilient transmission system involving a propeller shaft and a quill shaft arrangement for reducing peak torque loads where wind-up of the quill shaft also will generate a certain relative offset between the propeller shaft and a gear wheel carrier or sleeve, indicating torsion of the quill shaft without measuring the torque directly on the quill shaft.

It is an object of the present invention to provide an arrangement and a system for measuring torque by measuring the torsion of the propeller shaft relative to a gear wheel carrier or sleeve, indicating torque in a quill shaft.

Another object of the invention is to provide a new or improved arrangement or set-up and a system for torque measurement in a thruster for a vessel, boat or ship.

Yet another object of the invention is to provide an alternative arrangement and a system for torque measurement in a thruster for a vessel.

The main features of this invention are stated in the independent claims. Additional features of the present invention are given in the dependent claims. The present invention thereby includes a transmission system comprising a quill shaft assembly between a driving unit and a driven unit, including a quill shaft coaxially inside a bore of a driveshaft, coaxially supported in a sleeve, wherein the quill shaft is fixed to the driveshaft at a first end and to the sleeve at a second end. A load applied to the driveshaft thereby results in torsion of the quill shaft. A torque measuring arrangement is configured to measure the torsional displacement of the driveshaft in relation to the sleeve and includes a measuring surface extending circumferentially along a segment angle at one of the driveshaft and the sleeve extends with a varying distance in an axial direction along at least a part of the segment angle at the one of the sleeve and the driveshaft. A gap sensing element is located to measure the size of a gap between the gap sensing element and the measuring surface at the other of the sleeve and the driveshaft.

The measuring surface extending circumferentially along a segment angle may be located on a separate measuring surface element attached to the one of the sleeve and the driveshaft.

The measuring surface element may be arch shaped and formed as a ring segment limited by two segment sides defining the segment angle.

The arch shaped measuring surface element may include three arch shaped measuring surfaces (whereof one arch shaped measuring surface is parallel to a radial axis and normal to the longitudinal axis.

The arch shaped measuring surface element may further include bolt holes for attachment to a drive shaft or a sleeve.

The transmission system may further comprise a passage for conducting signals detected by the gap sensing element to a telemetry and/or processing or device in the one of the sleeve and the driveshaft holding the gap sensing element.

The measuring surface element may be attached to a ring-shaped circumferential face on the sleeve and the gap sensing element may be attached to the driveshaft.

The measuring surface element may be attached to a ring-shaped circumferential face on the driveshaft and the gap sensing element may be attached to the sleeve.

The gap sensing element may be a mechanical sensor with a mechanical probe part biased towards the measuring surface element.

The gap sensing element may be an inductive proximity switch, an electronic proximity sensor or an optical gap sensing element. The sleeve may be a gear carrier and the driveshaft may be is a propeller shaft fixed to a propeller of a vessel.

The invention further includes a thruster in a vessel, comprising a transmission system as described above.

The thruster may be an azimuth thruster and, said propeller may be located in said azimuth thruster. The invention further includes a torque measuring arrangement for measuring torque in a quill shaft coaxially inside a bore of a driveshaft, coaxially supported in a sleeve, wherein the quill shaft is fixed to the driveshaft at a first end and to the sleeve at a second end, whereby a load applied to the driveshaft at one end and to the sleeve at the other end results in torsion of the quill shaft. A measuring surface extends circumferentially along a segment angle at one of the driveshaft and the sleeve, extending with a varying distance in an axial direction along at least a part of the segment angle at the one of the sleeve and the driveshaft, and a gap sensing element for measuring the size of a gap between the gap sensing element and the measuring surface at the other of the sleeve and the driveshaft.

The axial direction is also defined as a direction parallel to an axis of revolution or a longitudinal axis of the quill shaft assembly.

The a torque measuring arrangement described above may include all of the features related to the torque measuring arrangement of the transmission system.

Furthermore, the invention relates to a torque measuring system for a thruster in a vessel, comprising the torque measuring arrangement described above. Furthermore, the invention may relate to an arch shaped measuring surface element formed as a ring segment with two crossing radial segment sides defining a segment angle and a longitudinal axis defined as an axis perpendicular to the two crossing segment sides, and at least one arch shaped measuring surface on the arch shaped measuring surface element. The at least one arch shaped measuring surface is parallel to a radial axis and inclined in relation to the longitudinal axis. In the context of this specification, the "crossing radial segment sides" of the arch shaped measuring surface element is intended to describe that theoretical radial lines extending along each of the segment sides will cross each other at an angle defining a segment angle. The arch shaped measuring surface element may include three distict arch shaped measuring surfaces whereof one arch shaped measuring surface is parallel to a radial axis and normal to the longitudinal axis.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention are apparent from and will be further elucidated, by way of example(s), with reference to the attached drawings, wherein:

Fig. 1 shows a quill shaft assembly with a torque measuring arrangement of the present invention;

Fig. 1 b is a schematic representation of a transmission system including a quill shaft with an arrangement for measuring torsion and thus torque in a quill shaft assembly of the present invention;

Fig. 2 is a cross-sectional view showing a detail of a torque measuring arrangement of the present invention;

Fig. 2b is a cross-sectional view corresponding to fig. 2, but where a gap sensing element is omitted;

Fig. 3 illustrates a measuring surface element for a torque measuring arrangement;

Fig. 4a-4d show different positions of the drive shaft in relation to the gear wheel carrier or sleeve according to the load that is applied thereto and detectable by the torque measuring arrangement;

Fig. 5a and 5b are a front view and a top view respectively of an alternative embodiment of a measuring surface element; Fig. 6a and 6b are a front view and a top view respectively of an alternative embodiment of a measuring surface element;

Fig. 7a-7b show different positions of the drive shaft in relation to the gear wheel carrier or sleeve according to the load that is applied thereto and detectable by the torque measuring arrangement; and

Fig. 8 is a schematic representation of a vessel with an azimuth thruster including a quill shaft and a transmission system of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Figure 1 shows an overview of a quill shaft assembly 1 for a vessel such as a boat or a ship, where a quill shaft 2 is arranged within a drive shaft 3 for providing an elastic connection between a propeller and a transmission on the vessel, and where an arrangement for measuring torque 20 in the quill shaft assembly of the invention is included. A "transmission" is in the context of this specification meant to describe the mechanical connection between a

motor/engine and possibly a gearbox/reverse gear and drive line with the quill shaft assembly 1 , and a mechanical load/propeller. The quill shaft is located coaxially inside a bore of the driveshaft 3 that is coaxially supported in a sleeve 6.

The quill shaft is fixed to the driveshaft 3 at a first end and to the sleeve 6 at a second end, whereby a load applied to the driveshaft results in torsion of the quill shaft 2 and a torsional displacement of the driveshaft 3 in relation to the sleeve 6.

The quill 2 shaft is fixed to the driveshaft 3 in that the quill shaft 2 includes a splined quill shaft outboard end and a quill shaft inboard end with a quill shaft flange 9. The quill shaft inboard end is thereby adapted to be driven by the transmission of the vessel. A compliant, resilient or elastic portion of the quill shaft 2 is located between the splined quill shaft portion and the quill shaft flange 9.

The drive shaft 3 includes a longitudinal drive shaft bore, a drive shaft outboard end and a drive shaft inboard end. The outboard end of the drive shaft bore is provided with a splined portion. The quill shaft 2 is arranged in the bore of the drive shaft 3. The splined quill shaft outboard end meshes with the splined portion of the drive shaft bore for providing transfer of torque between the drive shaft 3 and the quill shaft 2 at the outboard end of the shafts.

Torsion in the compliant portion allows dislocation of the quill shaft 2 in a circumferential direction in relation to the bore of the drive shaft 3.

The sleeve 6 is shown as a gear wheel carrier with a gear wheel 7 supporting the drive shaft 3 and the gear wheel 7 to simultaneously provide support for the gear wheel 7 and axial support for the drive shaft 3 through two anti friction bearings 10. The two anti friction bearings 10, shown as roller bearings, thereby form both axial and radial support for the drive shaft/quill shaft

combination and for the sleeve 6 forming the gear wheel carrier with a gear wheel 7.

A flanged bearing housing 1 1 for attachment to for instance a thruster housing on the vessel surrounds and supports the sleeve 6.

A drive shaft flange 31 with bolt holes 32 is provided for attachment of a propeller.

The gear wheel on the carrier or sleeve 6 is schematically shown as gear arrangement 7. In a preferred embodiment the gear arrangement 7 is a bevel gear.

A plain bearing 8 is located at the inboard end of the drive shaft 3 to allow a slight rotation between the drive shaft 3 and the sleeve 6 to allow torsion of the quill shaft 2 and to prevent loads / stresses in torsion on the drive shaft 3 inboard of the splined portion. The quill shaft flange 9 located on the inboard end of the quill shaft 2, is bolted onto the sleeve 6 for transferring torque between the sleeve 6 driven by the gear arrangement 7, and the quill shaft 2.

A drive shaft bearing 10' supports the drive shaft 3 and is located on the drive shaft 3 between the inboard and outboard end of the drive shaft 3. A fixed part of the drive shaft bearing 10' will typically be carried by a portion of a thruster housing. The drive shaft bearing 10' will reduce the bending moment on the drive shaft 3 and on the two anti friction bearings 10 supporting the sleeve 6. The above described set up results in a small rotation of the drive shaft in relation to the sleeve 6 when a torque is applied to the quill shaft, and this rotation is measured with the arrangement for measuring torque 20 of the invention. Fig. 1 b is a schematic representation of a transmission system including a quill shaft with an arrangement for measuring torsion and thus torque in a quill shaft assembly of the present invention. A driving unit in the form of an

engine/motor 27 is driving a gearbox 28, and a quill shaft assembly 29 is located between the gearbox 27 and a driven unit in the form of a mechanical load / propeller 34. The quill shaft assembly 29 includes the quill shaft, the drivesaft and the torque measurement arrangement. The in some cases, the gearbox 28 may be omitted and the motor 28 may be connected directly to the quill shaft assembly 29.

Figure 2 corresponds to fig. 1 , omitting some parts for clarity, and illustrates the arrangement for measuring torsion and thus torque or torque measuring arrangement 20 that is located between the drive shaft 3 and the sleeve 6 for thereby measuring the movement of the drive shaft 3 relative to the sleeve 6. The torque measuring arrangement 20 comprises a gap sensing element 21 / sensor element with a housing and a measuring surface element 22 having an inclined profile shown in figure 3. The gap sensing element 21 with a housing is located in the drive shaft 3, and the measuring surface element 22 is located on the sleeve 6.

The gap sensing element 21 for measuring the size of a gap between the gap sensing element 21 and a measuring surface of the measuring surface element 22 can be located at the other of the sleeve 6 and the driveshaft 3, but is located in the driveshaft in fig. 2.

A groove, duct or passage 23 onto or into the drive shaft 3 is provided in order to (e.g. in a wired manner) transfer signals from the gap sensing element to a suitable CPU or processing, computing or calculating devices or appropriate telemetry devices (not shown). The passage 23 extends longitudinally inside the drive shaft 3.

A ring-shaped circumferential face 61 is located on the sleeve 6. A sensor attachment element 35 is bolted onto an external ring-shaped circumferential face 31 is located on the drive shaft 3, supporting the gap sensing element 21 . The sensor attachment element 35 includes a bore for the gap sensing element and bores for attachment bolts. The bore for the gap sensing element communicates with, and may be aligned with the passage 23. An outer end 36 of the gap sensing element 21 may include external threads, and the bore of the sensor attachment element 35 may include internal threads for attachment of the gap sensing element 21 to the sensor attachment element 35. Bolt holes 222 are provided in the measuring surface element 22 for attaching the measuring surface element 22 th the internal ring-shaped circumferential face 61 located on the sleeve 6.

Similarly, the measuring surface element 22 is mounted to the opposite facing ring-shaped circumferential face 61 of the sleeve 6.

There will be a certain gap between the circumferential face 61 and the external radial or circumferential face 38. At least a portion of the internal ring- shaped radial or circumferential face 61 will be facing another portion of the external ring-shaped radial face 38 and the gap sensing element.

The arrangement 20 for torque measurement, located between the drive shaft 3 and the gear wheel carrier or sleeve 6 is adapted for measuring the movement of the drive shaft 3 relative to the sleeve 6. The torque measuring arrangement 20 comprises the gap sensing element 21 and the measuring surface element 22, each mounted or arranged on a ring-shaped radial or circumferential face in a stepped section of one of the drive shaft 3 and the sleeve 6. The gap sensing element 21 and the measuring surface element 22 oppose or face each other. The measuring surface element 22 has an arc-shape adapted to the respective portion of the ring-shaped circumferential face, and the measuring surface includes at least one measuring surface with an axial or longitudinal gap or distance between the measuring surface element 22 and the gap sensing element 21 . The gap or may be one of: constant, increasing and decreasing, thus allowing for torque measurement of the movement of the drive shaft 3 relative to the sleeve 6 depending on the load applied to the drive shaft.

Fig. 2b is a cross-sectional view corresponding to fig. 2, but where a gap sensing element (21 in fig. 2) is omitted. In addition to the features of fig. 2, do fig. 2b show a bore 24 in the sensor attachment element. The bore 24 in the sensor attachment element forms a cavity 25 for the gap sensing element. Figure 3 shows a measuring surface element and the shape of the sensing surface 221 of the measuring surface element 22. The measuring surface element 22 is arch shaped and is adapted to the respective part or portion of the ring-shaped circumferential face or surface. The sensing surface 221 is provided with a radial measuring surface 221 b, where the gap between the measuring surface element 22 and the gap sensing element is substantially constant, and at least one measuring surface 221 a, 221 c, where the gap between the elements 21 , 22 is substantially continuously changing (or possibly stepwise in the event of a non mechanical gap sensing element) (i.e. increasing or decreasing). In the embodiment shown in figure 3, the constant measuring surface 221 b is arranged between two changing measuring surfaces 221 a, 221 c of the entire sensing surface 221 on the measuring surface element 22, such that the gap between said elements 21 , 22 for each of the two changing sensing areas 221 a, 221 c is decreasing when starting from the constant measuring surface 221 . In addition the measuring surface element 22 can include at least one fastening arrangement in the form of bolt holes 222 for appropriate attachment of the measuring surface element 22 to the respective part or portion of the ring-shaped radial face. Four bolt holes 222 allow attachment of the measuring surface element 22 to the respective part or portion of the ring-shaped circumferential face.

Figures 4A-4D show different positions of the drive shaft 3 in relation to the sleeve 6. The different positions indicate the torsion (strain) in the quill shaft and thus the load applied to the resilient transmission system, and that is detectable by the torque measuring arrangement 20 of the present invention. The torsion in the quill shaft, results in a shift or displacement of the drive shaft 3 in relation to the sleeve 6 and in an alteration in the gap between the measuring surface element 22 and the gap sensing element. Figure 4A illustrates the position of the drive shaft 3 in relation to the sleeve 6 at neutral load (approximately 0°) applied to the drive shaft 3. Figure 4B illustrates the position of the drive shaft 3 in relation to the sleeve 6 at nominal load (approximately 2,3°) applied to the drive shaft 3. Figure 4C illustrates the position of the drive shaft 3 in relation to the sleeve 6 at overload (approximately 4,6°) applied to the drive shaft 3. Finally, figure 4D illustrates the position of the drive shaft 3 in relation to the sleeve 6 at negative load (approximately -1 ,15°) applied to the drive shaft 3. The minimal distance or gap between the sensor 21 and the sensing surface can be e.g. approximately 1 mm, and the maximal distance or gap between the sensor 21 and the sensing surface can be e.g. approximately 5 mm. It is desired to have a linear response curve of the sensor 21 in that range.

A supply voltage for the sensor 21 (provided by a suitable DC power supply) can for example be limited to about 3-12V DC, and is preferably from about 6V to about 8V DC. The gap sensing element / proximity sensor can be a mechanical sensor that includes a mechanical probe part biased towards the measuring surface element 22. Alternatively may the gap sensing element or the proximity sensor be an inductive proximity switch, an electronic or an optical gap sensing element, measuring the distance without physical contact between the measuring surface element 22 and the gap sensing element. The gap will typically be between 1 and 5 mm. The output from the sensor can be analog or digital. The figures 4a-4c show two torque measuring arrangements 20 arranged 180° apart. Using two torque measuring arrangements 20 provide redundancy of the system in the event of failure of one system, and enables acquisition of an average reading to improve accuracy.

The figures 5a, 5b, 6a and 6b show a front view and a top view of two further embodiments of a measuring surface element 22 corresponding to the measuring surface element of fig. 3 but where the configuration of the sensing surfaces 221 A, 221 B are adapted to different applications. Again, the measuring surface element 22 is arch shaped and is adapted to the respective part or portion of the ring- shaped circumferential face it is to be attached to. The arch shaped measuring surface element 22 is formed as a ring segment with two crossing radial segment sides 223 defining a segment angle and a longitudinal axis 225 defined as an axis perpendicular to the two crossing segment sides 223. The at least one arch shaped measuring surface 221 on the arch shaped measuring surface element 22 is parallel to a radial axis and inclined with an angle 224 in relation to the longitudinal axis 225.

The sensing surface 221 is provided with two radial sensing areas 221 a and 221 c for sensing in both a forward a rearward rotational direction. Figs. 5a and 5b show an embodiment with a third radial sensing area 221 b located in a gap or recess provided between the two inclined radial sensing areas 221 a and 221 c. This embodiment is better suited for electronic sensors without physical contact between the measuring surface element 22 and the sensor. The third radial sensing area 221 b in the recess between the two inclined radial sensing areas 221 a and 221 c will provide a distinct reading of the sensor in a neutral position. To tell the computer system that it is the 0 position. The sensor gives 0 voltage / signal in this position. The gap between the measuring surface element 22 and the gap sensing element is substantially constant along the narrow third radial sensing area 221 b. The gap between the inclined measuring surfaces 221 a, 221 c of the measuring surface element 22 and the gap sensing element is substantially continuously reduced as the amount of torsion is increased away from the neutral direction in either direction. This sensing surface is particularly adapted for thrusters with a reversing gear and fixed propellers.

Fig. 6a and 6b show an embodiment with an apex provided between the two inclined radial sensing areas 221 a and 221 c. This embodiment is better suited for mechanical sensors with physical contact between the measuring surface element 22 and the sensor. The apex 221 B between the two inclined radial sensing areas 221 a and 221 c will provide a distinct reading of the sensor in a neutral position. The gap between the measuring surface element 22 and the gap sensing element is at its shortest at the apex. The gap between the inclined measuring surfaces 221 a, 221 c of the measuring surface element 22 and the gap sensing element is substantially continuously increased as the amount of torsion is increased away from the neutral direction in either direction. The apex has a small flat portion extending 0.1 ° to both directions from a center position and the two inclined radial sensing areas 221 a and 221 c extend 6.5° to either direction from the center position. The size of the radial sensing areas will depend of the resilience and thus the allowed torsion of the propulsion system.

The embodiments of figs. 5a, 5b, 6a and 6b are typically used for systems with a fixed propeller where the rotational direction of the driveshaft changes for reversing purposes.

Figs. 7a and 7b show different positions of the drive shaft 3 in relation to the sleeve 6 in a solution with the measuring surface element 22 shown in figs. 6a and 6b, similar to the figs. 4a-4d. Similarly, the different positions indicate the torsion (strain) in the quill shaft and thus the load applied to the resilient transmission system, and that is detectable by the torque measuring arrangement 20 of the present invention. In fig. 7a there is 0° torsion and the gap sensing element 21 measures a gap between the apex of the measuring surface element 22 and the gap sensing element 21 of 1 mm, representing the minimum distance.

In fig. 7b there is 2.3° torsion and the gap sensing element 21 measures a gap between the radial, inclined portion of the measuring surface element 22 and the gap sensing element 21 representing the magnitude of the torsion and thus the torque

Fig. 8 is a schematic representation of a vessel 40 with an azimuth thruster 37 including a quill shaft and a transmission system of the invention driving a propeller 39. The thruster may include an L-drive or a Z-drive.

Claims

1 . A transmission system comprising a quill shaft assembly (29) between a driving unit and a driven unit, including a quill shaft (2) coaxially inside a bore of a driveshaft (3), coaxially supported in a sleeve (6), wherein the quill shaft is fixed to the driveshaft (3) at a first end and to the sleeve (6) at a second end, whereby a load applied to the driveshaft (3) results in torsion of the quill shaft (2);

a torque measuring arrangement (20) configured to measure the torsional displacement of the driveshaft (3) in relation to the sleeve (6), including a measuring surface (221 ) extending circumferentially along a segment angle at one of the driveshaft (3) and the sleeve (6) extending with a varying distance in an axial direction along at least a part of the segment angle at the one of the sleeve (6) and the driveshaft (3), and a gap sensing element (21 ) for measuring the size of a gap between the gap sensing element (21 ) and the measuring surface (221 ) at the other of the sleeve (6) and the driveshaft (3).

2. The transmission system of claim 1 , wherein the measuring surface (221 ) extending circumferentially along a segment angle is located on a separate measuring surface element (22) attached to the one of the sleeve (6) and the driveshaft (3).

3. The transmission system of claim 2, wherein the measuring surface element (22) is arch shaped and formed as a ring segment limited by two segment sides (223) defining the segment angle.

4. The transmission system of claim 3, wherein the arch shaped measuring surface element (22) includes three arch shaped measuring surfaces (221 a, 221 b, 221 c) whereof one arch shaped measuring surface (221 ) is parallel to a radial axis and normal to the longitudinal axis.

5. The arrangement (20) of any of claims 2 -4, wherein the arch shaped measuring surface element (22), further includes bolt holes (222) for attachment to a drive shaft (3) or a sleeve (6).

6. The transmission system according to claim 1 , further comprising a passage (23) for conducting signals detected by the gap sensing element (21 ) to a telemetry and/or processing or device in the one of the sleeve (6) and the driveshaft (3) holding the gap sensing element (21 ).

7. The transmission system according to any of claims 2 to 6 wherein the measuring surface element (22) is attached to a ring-shaped circumferential face (61 ) on the sleeve (6) and the gap sensing element (21 ) is attached to a the driveshaft (3).

8. The transmission system according to any of claims 2 to 6 wherein the measuring surface element (22) is attached to a ring-shaped circumferential face (38) on the driveshaft (3) and the gap sensing element (21 ) is attached to the sleeve (6).

9. The transmission system according to any of claims 1 to 8, wherein the gap sensing element (21 ) is a mechanical sensor with a mechanical probe part biased towards the measuring surface element 22.

10. The transmission system according to any of claims 1 -8, wherein the gap sensing element (21 ) is an inductive proximity switch, an electronic proximity sensor or an optical gap sensing element. .

1 1 . The transmission system according to any of claims 1 -10, wherein the sleeve (3) is a gear carrier and the driveshaft (3) is a propeller shaft fixed to a propeller (39) of a vessel (40).

12. A thruster (1 ) in a vessel (40), comprising a transmission system according to claim 8.

13. A thruster (1 ) in a vessel (40) according to claim 10, wherein the thruster is an azimuth thruster (37) and, wherein said propeller (39) is located in said azimuth thruster (37).

14. A torque measuring arrangement (20) for measuring torque in a quill shaft (2) coaxially inside a bore of a driveshaft (3), coaxially supported in a sleeve (6), wherein the quill shaft (2) is fixed to the driveshaft (3) at a first end and to the sleeve (6) at a second end, whereby a load applied to the driveshaft (3) at one end and to the sleeve (6) at the other end results in torsion of the quill shaft (2), comprizing:

a measuring surface (221 ) extending circumferentially along a segment angle at one of the driveshaft (3) and the sleeve (6), extending with a varying distance in an axial direction along at least a part of the segment angle at one of the sleeve (6) and the driveshaft (3), and a gap sensing element (21 ) for measuring the size of a gap between the gap sensing element (21 ) and the measuring surface (221 ) at the other of the sleeve (6) and the driveshaft (3).