The present invention relates to a torque limiting assembly for limiting the amount of torque being transferred from a torque supplying shaft to a torque receiving appliance, and further to a method of adjusting and limiting the amount of torque being transferred from a torque supplying shaft to a torque receiving appliance by providing a torque limiting assembly.

Torque limiting assemblies are well known in the art of rotating mechanical power transmission systems as essential safety devices for preventing damages to mechanical equipment. A torque limiting assembly is used to provide an accurate torque overload protection for many different kinds of rotating mechanical power transmission systems. In particular, the torque limiting assembly is employed as a coupling between a torque supplying shaft and a torque receiving appliance.. The torque supplying shaft receives input torque from a torque generating device, such as an engine or a turbine, which in turn is powered by e.g. wind, water, steam, gas or the like. The torque receiving appliance may be e.g. an electrical generator, a tool such as a drill or any other industrial machinery requiring an input of torque for operating,

During regular non-over!oad operation of the mechanical power transmission system, the torque limiting assembly transfers substantially the full amount of torque generated by the torque supplying shaft to the torque receiving appliance, except for the minimal friction losses occurring in every mechanical power transmission systems. In case of a non-regular operation, where the torque generated by the torque supplying shaft exceeds a specific torque value, the torque limiting assembly limits the torque to the specific torque value or a lesser value. The specific torque value should correspond to the rating of the mechanical power transmission system in order to avoid damages in the mechanical power transmission systems due to torque overload . Damages due to torque overload may otherwise occur in the torque receiving appliance, in shafts and/or gears of the mechanical power transmission system and/or in the torque generating device. Such damages often result in a permanent breakdown of the system and may require be very extensive and expensive repairs.

A non-regular operation, i.e. a torque overload operation, may be caused by a jam in the shaft or gear of the mechanical power transmission system. Alternatively, the torque overload operation may be caused by a jam or a failure of torque receiving appliance, e.g. a short circuit of a generator or in an electrical power supply network. In such cases the intrinsic rotational energy of the torque generating device may cause an excessive rotational momentum to occur on the torque supply shaft. Yet alternatively, the overload operation may be caused by a failure or jam in the torque generating device, either due to an unexpectedly high input power caused by e.g. a storm in case of a wind turbine as the torque generating device, or a or a flood in case of a water turbine as the torque generating device. Occasionally, an overload operation may occur due to a jam in the torque generating device, in such cases the intrinsic rotational energy of the torque receiving appliance may cause an excessive rotational momentum to occur on the torque supply shaft, thereby causing the torque receiving device to supply torque to the torque generating device. in all of the above torque overload operations, the torque limiting assembly is employed to limit the torque transferred by the mechanical power transmission systems,. Such torque limiter assemblies typically utilize two parts, such as plates, which are in friction contact and which during regular operation rotate synchronously but which will slip or slide in relation to each other in case of a torque overload.

Such torque limiter assemblies have been manufactured by the applicant company and are described in e.g. the international patent application WO 2008/049428 of the applicant company. Similar devices are described in the German utility model DE 20 2005 000215 U1 , describing a slip clutch employing a spring washer. Further prior art documents include US 3 319 508 describing a resilient retaining ring and US 4 338 798, describing an adjustable torque limiting apparatus with frictionly coupled discs.

It is an object of the present invention to limit the torque in a mechanical system including a shaft between a torque generating device and a torque receiving appliance, without substantially extending the distance between the torque generating device and the torque receiving appliance. Typically, the torque limiting assembly must be employed in locations which are very narrow and which are having a limited amount of space. Such locations may be inside the top housing of a wind power plant. There is thus a need for the torque limiting assembly to be as compact as possible for not necessitating any enlargement of the housing. It is an advantage compared to the prior art that the torque limiting assembly according to the present invention is adjustable and very simple to install and adjust due to the convenient location of the adjustment screws and installation screws. A feature of the present invention is the improved reliability due to the employment of multiple friction surfaces.

The above object, need, advantage and feature together with numerous other objects, needs, advantages and features which will be evident from the below detailed description of preferred embodiments of the adjustable torque limiter are, according to a first aspect of the present invention obtained by a torque limiting assembly comprising:

a torque input part for coaxial connection to a rotational motion torque supplying shaft and

a torque output part for connection to a rotational motion torque receiving appliance and for coaxial mounting in relation to the torque input part, the torque output part being configured as a torque limiting first annular disc having opposite first and second sides including a first and a second specific torque defining friction surface, respectively, the torque limiting first annular disc defining a first central aperture having a diameter substantially larger than the diameter of the torque supplying shaft,

the torque input part including four components being:

a hub component defining a through-going cylindrical bore defining a tight fit clearance with the torque supplying shaft, the hub component further defining a first radial surface including a third specific friction surface for contacting the first specific torque defining friction surface of the torque limiting first annular disc, the hub component further defining a reception surface opposite the first radial surface, the hub component further defining an outer conical surface tapering away from the first radial surface and defining a first maximum diameter juxtaposed the first radial surface and a first minimum diameter opposite the first radial surface, the hub component further having an annular flange located within the first central aperture when the third specific friction surface is contacting the first specific friction surface, the annular flange defining an exposed annular end face, the hub component further including a first plurality of screw threads extending from the reception surface into the hub component and being parallel to the through-going cylindrical bore, and a second plurality of screw threads extending from the annular end face into the annular flange and being parallel to the through going cylindrical bore,

a conical locking ring defining an inner conical surface for cooperating with the outer conical surface of the hub component when the conical locking ring is mounted on the hub component, the inner conical surface defining a second minimum diameter larger than the diameter of the through-going cylindrical bore of the hub component and a second maximum diameter slightly smaller than the first maximum diameter and substantially larger than the first minimum diameter for providing a substantial contact surface between the inner conical surface and the outer conical surface when the conical locking ring is mounted on the hub component, the locking ring further comprising a first multitude of through-going holes being in registration or alignment with the first plurality of screw threads when the conical locking ring is mounted on the hub component,

a second annular disc defining a second centra! aperture having a diameter slightly larger than the diameter of the torque supplying shaft and having opposite second and third radial surfaces, the second radial surface including a fourth specific torque defining friction surface for contacting the second specific torque defining friction surface, the second annular disc further comprising a second multitude of through-going holes being in registration or alignment with the second plurality of screw threads when the second annular disc is mounted on the hub component, and

a combined annular spring washer and fixation ring defining a third central aperture having a diameter slightly larger than the diameter of the torque supplying shaft and defining an inner fixation ring and an outer spring member, the inner fixation ring comprising a third multitude of through-going holes being in registration or alignment with the second multitude of through-going holes and the second plurality of screw threads when the inner fixation ring is mounted on the hub component, the outer spring member protruding outwardly from the inner fixation ring, the outer spring member being in contact with and applying a clamping force onto the third radial surface of the second annular disc to achieve a first friction force between the first and third specific torque defining friction surfaces and a second friction force between the second and fourth specific torque defining friction surfaces,

the torque limiting assembly further comprising:

a first set of screws mounted in the first multitude of through-going holes and fixated to the first plurality of screw threads, and

a second set of screws mounted in the second and third multitudes of through going holes and fixated to the second plurality of screw threads . The above torque limiting assembly is preferably used in a mechanical system where the torque is being transferred between the torque supplying shaft and the torque receiving appliance. The torque input part is connected to the rotational motion torque supplying shaft being e.g. an engine, a wind turbine, a water turbine or the like. The torque output part is connected to a rotational motion torque receiving appliance typically being an electrical generator; however, other mechanical appliances may be contemplated as well. There between a gear may be used for changing of the rotational speed. During regular operation the torque input part and the torque output part rotate synchronously, however, during non-regular operation when the torque exceeds the specific value corresponding to the torque rating representing the safe operation of the mechanical system, the torque input part and the torque output part rotate non-synchronously and thermal energy resulting from the friction between the torque input part and the torque output part is dispersed into the specific torque defining surfaces. The use of two separate specific torque defining friction surfaces on each side of the first annular disc of the torque output part will allow for increased redundancy in case one side is

deteriorated by oil or fat from the mechanical system. By using two cooperating conical surfaces which are clamped together by axially extending screws, a very large clamping force may be established between the torque supplying shaft and the torque input part. By establishing a through-going cylindrical bore, the torque limiting assembly may be completely accommodated on the torque supplying shaft, thereby not extending the distance between the torque supplying shaft and the torque receiving appliance. When assembled, the annular flange should preferably establish a tight clearance with the first annular disc for acting as a hub around which the first annular disc may rotate in a symmetric and well balanced fashion.

The combined annular spring washer and fixation ring dispenses with the requirement of having a separate fixation ring and spring washer. The spring member should be bent towards the third radial surface and contacting the third radial surface while the fixation ring should not contact the third radial surface for allowing a certain margin for adjustment of the spring force and thereby the friction force, i.e. the torque limit.

The above object, need, advantage and feature together with numerous other objects, needs, advantages and features which will be evident from the below detailed description of preferred embodiments of the adjustable torque limiter are, according to a second aspect of the present invention obtained by a torque limiting assembly comprising:

a torque input part for coaxial connection to a rotational motion torque supplying shaft and

a torque output part for connection to a rotational motion torque receiving appliance and for coaxial mounting in relation to the torque input part, the torque output part being configured as a torque limiting first annular disc having opposite first and second sides including a first and a second specific torque defining friction surface, respectively, the torque limiting first annular disc defining a first central aperture having a diameter substantially larger than the diameter of the torque supplying shaft,

the torque input part including four components being: a hub component defining a through-going cylindrical bore defining a tight fit clearance with the torque supplying shaft, the hub component further defining a first radial surface including a third specific friction surface for contacting the first specific torque defining friction surface of the torque limiting first annular disc, the hub component further defining a reception surface opposite the first radial surface, the hub component further defining an outer conical surface tapering away from the first radial surface and defining a first maximum diameter juxtaposed the first radial surface and a first minimum diameter opposite the first radial surface, the hub component further having an annular flange located within the first central aperture when the third specific friction surface is contacting the first specific friction surface, the annular flange defining an exposed annular end face, the hub component further including a first plurality of screw threads extending from the reception surface into the hub component and being parallel to the through-going cylindrical bore, and a second plurality of screw threads extending from the annular end face into the annular flange and being parallel to the through going cylindrical bore,

a conical locking ring defining an inner conical surface for cooperating with the outer conical surface of the hub component when the conical locking ring is mounted on the hub component, the inner conical surface defining a second minimum diameter larger than the diameter of the through-going cylindrical bore of the hub component and a second maximum diameter slightly smaller than the first maximum diameter and substantially larger than the first minimum diameter for providing a substantial contact surface between the inner conical surface and the outer conical surface when the conical locking ring is mounted on the hub component, the locking ring further comprising a first multitude of through-going holes being in registration or alignment with the first plurality of screw threads when the conical locking ring is mounted on the hub component,

a second annular disc defining a second central aperture having a diameter slightly larger than the diameter of the torque supplying shaft and having opposite second and third radial surfaces, the second radial surface including a fourth specific torque defining friction surface for contacting the second specific torque defining friction surface, the second annular disc further comprising a second multitude of through-going holes being in registration or alignment with the second plurality of screw threads when the second annular disc is mounted on the hub component, and

a set of individual springs, the set defining a third central aperture having a diameter slightly larger than the diameter of the torque supplying shaft and each of the individual springs defining one of a third multitude of through-going holes being in registration or alignment with the second multitude of through-going holes and the second plurality of screw threads when each of the individual springs are mounted on the hub component, the springs being in contact with and applying a clamping force onto the third radial surface of the second annular disc to achieve the first friction force between the first and third specific torque defining friction surfaces and the second friction force between the second and fourth specific torque defining friction surfaces,

the torque limiting assembly further comprising:

a first set of screws mounted in the first multitude of through-going holes and fixated to the first plurality of screw threads, and

a second set of screws mounted in the second and third multitudes of through going holes and fixated to the second plurality of screw threads.

Individual springs will provide the additional advantage of individual adjustment by adjusting the third multitude of through going holes. According to a further embodiment, the springs are disc springs.

The above object, need, advantage and feature together with numerous other objects, needs, advantages and features which will be evident from the below detailed description of preferred embodiments of the adjustable torque limiter are, according to a third aspect of the present invention obtained by a torque limiting assembly comprising:

a torque input part for coaxial connection to a rotational motion torque supplying shaft and

a torque output part for connection to a rotational motion torque receiving appliance and for coaxial mounting in relation to the torque input part, the torque output part being configured as a torque limiting first annular disc having opposite first and second sides including a first and a second specific torque defining friction surface, respectively, the torque limiting first annular disc defining a first central aperture having a diameter substantially larger than the diameter of the torque supplying shaft,

the torque input part including four components being:

a hub component defining a through-going cylindrical bore defining a tight fit clearance with the torque supplying shaft, the hub component further defining a first radial surface including a third specific friction surface for contacting the first specific torque defining friction surface of the torque limiting first annular disc, the hub component further defining a reception surface opposite the first radial surface, the hub component further defining an outer conical surface tapering away from the first radial surface and defining a first maximum diameter juxtaposed the first radial surface and a first minimum diameter opposite the first radial surface, the hub component further having an annular flange located within the first central aperture when the third specific friction surface is contacting the first specific friction surface, the annular flange defining an exposed annular end face, the hub component further including a first plurality of screw threads extending from the reception surface into the hub component and being parallel to the through-going cylindrical bore, and a second plurality of screw threads extending from the annular end face into the annular flange and being parallel to the through going cylindrical bore,

a conical locking ring defining an inner conical surface for cooperating with the outer conical surface of the hub component when the conical locking ring is mounted on the hub component, the inner conical surface defining a second minimum diameter larger than the diameter of the through-going cylindrical bore of the hub component and a second maximum diameter slightly smaller than the first maximum diameter and substantially larger than the first minimum diameter for providing a substantial contact surface between the inner conical surface and the outer conical surface when the conical locking ring is mounted on the hub component, the locking ring further comprising a first multitude of through-going holes being in registration or alignment with the first plurality of screw threads when the conical locking ring is mounted on the hub component,

a second annular disc defining a second central aperture having a diameter slightly larger than the diameter of the torque supplying shaft and having opposite second and third radial surfaces, the second radial surface including a fourth specific torque defining friction surface for contacting the second specific torque defining friction surface, the second annular disc further comprising a second multitude of through-going holes being in registration or alignment with the second plurality of screw threads when the second annular disc is mounted on the hub component, and

a fixation device defining a third multitude of through-going holes being in registration or alignment with the second multitude of through-going holes and the second plurality of screw threads when the fixation device is mounted on the hub component, the fixation device being in contact with and applying a clamping force onto the third radial surface of the second annular disc to achieve a first friction force between the first and third specific torque defining friction surfaces and a second friction force between the second and fourth specific torque defining friction surfaces,

the torque limiting assembly further comprising:

a first set of screws mounted in the first multitude of through-going holes and fixated to the first plurality of screw threads, and

a second set of screws mounted in the second and third multitudes of through going holes and fixated to the second plurality of screw threads,

According to a further embodiment, the hub component comprises a hub component proper including the through-going cylindrical bore, and, a third angular disc including the first radial surface, the hub component and the third angular disc being fixated by the second set of screws.

In the above embodiment, the first radial surface does not form part of the hub component proper. Thus, when the first radial surface is worn out, it is not necessary to exchange the full hub component, merely the third annular disc. According to a further embodiment, the hub component proper defines the second plurality of screw threads and the third annular disc defining a fourth plurality of screw threads in registration with the second plurality of screw threads. According to an alternative embodiment, the inner and outer conical surfaces define a tapering angle in relation to the cylindrical bore of between 0.1 degrees and 30 degrees, preferably between 3 degrees and 10 degrees and more preferably between 5 degrees and 7 degrees.

According to an alternative embodiment, the torque limiting assembly is made of steel. Steel is a suitable material due to its rigidity and durability.

According to an alternative embodiment, the friction coefficient between the first and third specific torque defining friction surfaces and between the second and fourth specific torque defining friction surfaces varies by 0%-100%, preferably by 10%- 30%, more preferably by 20%-30%. When the torque limiting assembly is limiting the torque, heat is generated in the torque defining friction surfaces. Different friction coefficients may be desirable for allowing an improved temperature distribution inside the torque limiting assembly, e.g. by allowing the hub component to absorb more heat than the first and second annular discs. According to an alternative embodiment, the distance between the first maximum diameter and the second maximum diameter comprise 1-20 mm, preferably 2-10 mm and more preferably 4-5 mm, the distance between the first minimum diameter and the second minimum diameter comprises 1-20 mm, preferably 2-10 mm and more preferably 4-5 mm, the distance between the first maximum diameter and the first minimum diameter comprises 10-200 mm, preferably 20-100 mm and more preferably 40-50 mm, and/or, the distance between the second maximum diameter and the second minimum diameter comprises 10-200 mm, preferably 20-100 mm and more preferably 40-50 mm. The above numbers constitute suitable numerical values for allowing an effective clamping of the torque supplying shaft.

According to an alternative embodiment, the torque output part further comprises a number of mounting flanges with mounting holes for connecting to the rotational motion torque receiving appliance, the number being 2-20, preferably 2-10, more preferably 4. The receiving appliance is preferably mounted onto the mounting flanges. In this way the access to the second set of screws will not be obscured.

According to an alternative embodiment, the first set of screws amounts to 4-50 screws, preferably 10-30 screws, more preferably 18 screws, and, the second set of screws amounts to 4-50 screws, preferably 10-30 screws, more preferably 20 screws. The above number of screws is suitable for allowing a secure fastening and proper adjustment,. According to an alternative embodiment, further including a first friction plate located between the first and third specific torque defining friction surface and/or including a second friction plate located between the second and fourth specific torque defining friction surface. Friction plates may be used for achieving a well defined friction coefficient. When the torque limiting assembly must limit the torque, the specific torque defining friction surfaces will be worn, and it is evident that the specific torque defining friction surfaces must be replaced after some time of use. By using separate friction plates, the exchange of the specific torque defining friction surfaces will be simpler and less expensive. The torque limiting assembly may advantageously be incorporated in a water power plant or a wind power plant.

The above object, need, advantage and feature together with numerous other objects, needs, advantages and features which will be evident from the below detailed description of preferred embodiments of the adjustable torque limiter are, according to a fourth aspect of the present invention obtained by a method comprising providing a torque limiting assembly according to the first aspect and performing the two main steps of;

performing the sub-steps of: accommodating the torque supplying shaft inside of the through-going cylindrical bore of the hub component, subsequently accommodating the inner conical surface of the conical locking ring juxtaposed the outer conical surface of the hub component and subsequently tightening the first set of screws, and performing the sub-steps of: accommodating the first specific friction surface of the first annular disc juxtaposed the third specific friction surface of the hub component, subsequently accommodating the fourth specific torque defining friction surface of the second annular disc juxtaposed the second specific torque defining friction surface of the hub component, subsequently accommodating the outer spring member of the combined annular spring washer and fixation ring juxtaposed the third radial surface of the second annular disc and subsequently tightening and adjusting the second set of screws,

Brief description of the drawings

Fig, 1 is a section view of a torque limiting assembly according to the present invention.

Fig. 2 is an exploded view of a torque limiting assembly according to the present invention.

Figs. 3a and 3b are schematic views illustrating the working principle of a adjustable torque limiting assembly according to the present invention.

Fig. 4 is a perspective view of an alternative embodiment of a torque limiting assembly 10' according to the present invention.

Fig. 5a and 5b are side views of the torque limiting assembly in which the torque adjustment screws have been fastened loosely and tightly, respectively.

Fig. 6 is a perspective view of yet an alternative view of a torque limiting assembly 10' according to the present invention,,

Fig. 7 is a perspective view of yet further an alternative view of a torque limiting assembly 10' according to the present invention.

Detailed description of the drawings

Fig, 1 shows an adjustable torque limiting assembly according to a preferred embodiment of the present invention, in particular suitable for a wind power plant, and which is as a whole being designated the reference numeral 10. The torque limiting assembly 10 may be used for transferring and limiting the torque from a torque generating device such as an engine, a turbine, a wind mill or a water mill to a torque receiving device such as an electrical generator or various kinds of driving arrangements such as a ship's screw or tools such as drills.

The torque limiting assembly 10 comprises an axially symmetrical torque input part 12 designed to accommodate a cylindrical torque supplying shaft 14, The torque input part 12 comprises four main parts, where the first part being a hub component 20, The hub component 20 defines a through-going central bore 16 having a shape corresponding to the outer surface 18 of the torque supplying shaft 14 to allow the torque supplying shaft 14 to enter and be accommodated in the through-going central bore with a thigh fit. The hub component 20 extends in an axial direction and is made of steel, thereby exhibiting some flexibility. The hub 12 further comprises an outwardly extending flange 22 defining a first radial surface 18 and an opposite surface comprising a plurality of axially extending first plurality of screw threads 24 parallel to the through-going central bore 16 and an outer conical surface 32 tapering away from the outwardly extending flange 22., The hub component 20 further comprises an annular flange 23 extending in an axial direction and located between the through-going central bore 16 and the first radial surface 18. The annual flange 23 defines an end surface having a second plurality of screw threads 25 extending axially into the hub component 20 parallel to the through-going central bore 16,

The torque input part 12 further comprises an axially symmetrical Socking ring 26 to be positioned outside of the hub component 20. The locking ring 26 comprises a first multitude of through-going holes 28 corresponding in number and position to the axial threads 24 of the hub 12. The locking ring 26 further comprises an inner conical surface 34 having an area and a tapering angle corresponding to the outer conical surface 32 of the hub 12. To assemble the locking ring 26 onto the hub component 20 after the torque supplying shaft 14 has been inserted into the through-going central bore 16, the inner conical surface 34 of the locking ring 26 is slid onto the outer conical surface 32 of the hub component to position the through- going holes 28 in registration and alignment with the first plurality of screw threads 24. Thereafter, torque shaft installation screws 30 are inserted into through-going holes 28 and fastened to the first plurality of screw threads 24 for fastening the locking ring 26 in relation to the hub 12, The inner and outer conical surfaces 34 32 are being s!idably cooperating thereby allowing the hub component 20 to be bent inwardly upon tightening of the screws 30 for clamping the torque supplying shaft 14 tightly to the hub component 20.

The torque limiting assembly 10 further comprises a torque output part 35, The torque output part 35 defines a first annular disc 36 which defines a first side 40 and an opposite second side 42, The first side 40 of the first annular disc 36 comprises a first friction disc 44 and the second side 42 of the first annular disc 36 comprises a second friction disc 46. The first annular disc 36 defines a first central aperture 47 having a diameter being substantially larger than the torque supplying shaft 14 and slightly larger than the maximum diameter defined by the annular flange 23.. When the first annular disc 36 is being mounted onto the hub component 20, the first friction disc 44 of the first side 40 of the annular disc 36 is abutting the first radial surface 18 of the hub component 20 and the annular flange 23 of the hub

component 20 is extending into the first central aperture 47 by a tight clearance. The torque output part 35 is further provided with four outwardly extending flanges 38, which are provided with screw holes 40 for connection to the momentum receiving device (not shown).

The torque input part 12 further comprises a second annular disc 48 defining a second radial surface 50 and an opposite third radial surface 52. The second annular disc 48 further comprises a second central aperture 54 having a diameter being slightly larger than the diameter of the torque supplying shaft 14 and a second plurality of through-going holes 56 corresponding in number and position to the second plurality of screw threads 25 of the annular flange 23. The second radial surface 50 of the second annular disc 48 is being mounted abutting the second friction disc 46 of the second side 42 of the first annular disc and the second plurality of through-going holes 56 are positioned in registration and alignment with the second plurality of screw threads 25 of the annular flange 23,

The torque input part 12 further comprises an annular spring washer 50 constituting a combined spring washer and fixation ring. The spring washer 50 comprises an inner fixation ring 60 comprising a third plurality of through-going holes 62

corresponding in number and position to the second plurality of screw threads 25 of the annular flange 23. The spring washer 50 further comprises an outwardly and axially protruding flexible spring member 64. The spring washer 50 is positioned outside the third radial surface 52 of the second annular disc 48 and the third plurality of through-going holes 62 are positioned in registration and alignment with the second plurality of through-going holes 56. The spring member 64 thereby contacts the third radial surface 52 of the second annular disc 48, while a gap is formed between the fixation ring 60 and the third radial surface 52 of the second annular disc 48. To mount the torque limiting assembly 10 together, a plurality of torque adjustment screws 66 are inserted through the second and third plurality of through-going holes 56 and 62 and are fastened by the second plurality of screw threads 25 of the annular flange 23 of the hub component 20. The torque which can be transmitted between the torque input part 12 and the torque output part 35 is now limited by the friction force between the first radial surface 18 of the hub component 20 and the first side 40 of the first annular disc 36 or the friction force between the second radial surface 50 of the hub component 48 and the first side 40 of the first annular disc 36. By tightening the torque adjustments screws 66, the spring member 64 will apply an increasing spring force onto the second annular disc 48, thereby establishing an increasing friction force between the first radial surface 18 of the hub component 20 and the first side 40 of the first annular disc 36, and, between the second radial surface 50 of the hub component 48 and the first side 40 of the first annular disc 36, as the friction force is

proportional to the spring force. The second annular disc will distribute the spring force evenly over the second radial surface 50, The spring force, and thereby the friction force, may be decreased by loosening the torque adjustment screws 66. The friction force is also depending on the friction coefficient of the materials used, and in particular by the first and second friction discs 44 and 46, respectively, in case the torque to be transferred exceeds the amount, which can be transferred by the friction force between the first radial surface 18 of the hub component 20 and the first side 40 of the first annular disc 36, or, between the second radial surface 50 of the hub component 48 and the first side 40 of the first annular disc 36, the torque output part 35 wiil slip in relation to the hub component 12. The friction force may be calculated according to the formula be!ow:

F _f =const*F _s

Where F _f = is the friction force, const is the friction coefficient and F _s is the spring force.

Fig, 2 shows an exploded view of the torque limiting assembly 10 as shown in Fig , 1 The preferred embodiment according to the present invention may be assembled and adjusted on site in a very convenient manner. The torque limiting assembly 10 may for instance be assembled according to the below method, As a first step, the torque supplying shaft (not shown here, designated 14 in fig 1) is inserted into the through-going central bore 16. The inner surface of the central hub 20 should fit by a tight clearance around the drive shaft 18. In a second step, the locking ring 26 is applied and slipped onto the outer conical surface 32 of the hub component 20. The outer conical surface 32 of the hub component 20 forms a tapered surface. The inner conical surface 34 of the locking ring 26 forms a corresponding tapered surface. By inserting the torque shaft installation screws 30 through the first multitude of through-going holes 28 of the locking ring 26 and into the first plurality of screw threads 24 and by tightening the screws 30, the tapered surface of the inner conical surface 34 of the locking ring 26 wiil subject the hub component 20 to an inwardly directed force due to the tapered shape of the inner conical surface 34 and the corresponding tapered shape of the outer conical surface 32. By bending the hub component 20 slightly inwards, the torque supplying shaft (not shown) will be clamped into a fixated position in relation to the hub 12, and will be held in place by the friction force, which is understood to be larger than the friction force between the torque input part 12 and the torque output part 35. The screws 30 should be tightened sufficiently for preventing any unintentional slip between the torque supplying shaft (not shown) and the hub component 20. It should be noticed that the torque shaft installation screws 30 are inserted in an axial direction making them easily accessible from the outside. The torque shaft installation screws 30 will not be obscured by any other part of the torque supplying shaft 14 or the assembly 10. Thus, any assembly, adjustment or disassembly of the locking ring 26 can be performed easily at any time,

The first annular disc 36 is applied onto the hub component 20 from the opposite side of the locking ring 26 for contacting the first radial surface 18 of the hub component 20, The annular flange 23 of the hub component 20 is surrounded by the first annular disc 36 and acting as a hub in relation to the first annular disc. The diameter of the first central aperture 47 of the first annular disc should be only slightly larger than the maximum diameter of the annular flange 23 of the hub component 20 in order for the first annular disc 36 to be able to rotate relative to the hub component 20. The first and second friction discs 44 and 46 are preferably attached to the first and second surfaces 40, 42, respectively, of the first annular disc 36, for establishing juxtaposing friction surfaces between the first radial surface 18 and the first friction disc 44, and, further juxtaposing friction surfaces between the second radial surface 50 and the second friction disc 46. Alternatively, the friction discs 44 and 46 may also be separate components, thereby establishing four juxtaposed friction surfaces, i.e. between the first radial surface 18 and the first friction disc 44, between the first friction disc 44 and the first side 40, between the second side 42 and the second friction disc 46 and between the second friction disc 46 and the second radial surface. The second annular disc 48 and the spring washer 50 are positioned onto the second friction disc 46, applying the second and third plurality of through-going holes 56 62 in registration and alignment with the second plurality of screw threads 25. The torque adjustment screws 66 are inserted into the second and third plurality of through-going holes 56 62 into the second plurality of screw threads 25., By tightening the torque adjustment screws 66, the amount of friction between the first annular disc 36 and the hub component 2 is increases and thereby, the maximum amount of torque which may be transferred from the hub component 20 to the first annular disc 36 increases. Consequently, by loosening the torque adjustment screws 66, the force applied by the spring washer 50 decreases, thereby allowing less torque to be transferred from the hub component 12 to the first annular disc 36, The whole assembly 10 is preferably made of steel. For the first and second friction discs 44 and 46, different kinds of steel may be used for achieving different frictions coefficients between the first annular disc 36 and the second annular disc 48, and, between the first annular disc 36 and the hub component 20, Preferably, a material having a high thermal conductivity is used for both the friction discs 44 and 46. The benefit of using dual juxtaposed friction surfaces is that in case one of the friction discs 44, 46 have been deteriorated by e.g. lubricants such as fats and/or oils used for lubricating the drive shaft (not shown), the other friction disc may still be able to operate normally. Thereby, a longer service life of the torque limiting assembly may be achieved..

During normal operation, the hub component 20, the second annular disc 48 and the first annular disc 36 are all rotating synchronously. This is the situation during normal operation when a suitable amount of torque is being transferred from the torque input part 12 to the torque output part 35. in case of a failure, such as a short circuit generator or a drive shaft being stuck, the torque will increase dramatically. A dramatic increase of torque will in most cases cause a breakdown and severe damage to the equipment, unless a torque limiting assembly is employed. To avoid damage, the first annular disc 36 will slip in relation to the hub component 20 and the second annular disc when a specified torque value has been overrun. The first annular disc 36 will then rotate in relation to the hub component 20 and the second annular disc 48 and thereby the equipment must not be to sustain the excessive torque which would otherwise be applied. It should be noted that the hub

component 20 and the second annular disc 48 are fixed together by the torque adjustment screws 66 and therefore always rotate synchronous.

Fig. 3a shows a schematic view of the tightening of the torque shaft installation screws 30. It can be seen that the maximum diameter D1 of the inner conical surface 34 is slightly larger than the maximum diameter D2 of the outer conical surface 32, and that the minimum diameter d 1 of the inner conical surface 34 is slightly larger than the minimum diameter d2 of the outer conical surface 32. By tightening the torque shaft installation screws 30, the outer conical surface 32 will apply an inwardly directed force to the inner conical surface 34 of the hub component and constrict the through-going central bore 16 by bending the hub component 20 slightly inward. This will cause the hub component 20 to be securely fastened onto the outer surface of the torque supply shaft.. The filled lines represent the non-tightened state whereas the dashed lines represent the tightened state,. The inwardly bending of the hub component 20 preferably is in the sub mm range.

Fig. 3b shows a schematic view of the tightening of the torque adjustment screws 66 into the second plurality of screw threads 25. By tightening the torque adjustment screws 66, the fixation ring 60 of the spring washer 50 will be moved in a direction towards the third radial surface 52 of the second annular disc 48. The flexible flange 54 of the spring washer 50 will thereby apply an increasing spring force against the second annular disc 48, which will cause the first annular disc 36 to be clamped between the second annular disc 48 and the hub component 20. The friction force and thereby the transmittable torque between the torque input part 12 and the torque output part is determined by the friction coefficient of the material used for the friction discs 44 and 46 and by the force applied by the spring washer 50 onto the circular plate 48. The transmittable torque may therefore be adjusted any time by tightening or loosening the torque adjustment screws 66 and/or exchanging the first and/or second friction discs 4446. The torque adjustment screws 56 are inserted in an opposite direction in relation to the torque shaft installation screws 30 and are always easily accessible for adjustment from the outside. The torque adjustment screws 56 are as well as the torque shaft installation screws 30 accessible at any time and will never be obscured by any other parts of the torque limiting assembly 10. The filled lines represent the non-tightened state whereas the dashed lines represent the tightened state.

Fig. 4 shows a perspective view of an alternative embodiment of a torque limiting assembly 10' according to the present invention. The torque limiting assembly 10' shares all features of the previously presented torque limiting assembly 10, except that the hub component 20 of the torque input part 12 has been divided into a hub component proper 20' and a third annular disc 21. The third annular disc 21 comprises the first radial surface 18 and is located between the first friction disc 44 and the hub component proper 20'. The third annular disc 21 is located at the opposite side of the first radia! surface 18 and is fastened to the hub component proper 20' via the second plurality of screw threads 25', which penetrated the third annular disc 21 and enters the hub component proper 20' for receiving the torque adjustment screws 66', which in the present embodiment has been made slightly longer. This allows the first radial surface 18 to be removed and serviced without removing the hub component proper 20' from the shaft 14.

Further, the present embodiment includes spring members 64' between each of the heads of the torque adjustment screws 66 and the second annular disc 48, Thus, the fixation ring 60 and the adjoined spring member 64 of the previous embodiment has been omitted. The spring members 64' constitute disc springs which are individually mounted on each of the torque adjustments screws 66. This allows individual adjustment of each disc spring. Fig. 5a shows a side view of the torque limiting assembly 10' in which the torque adjustment screws 66 have been fastened loosely. This yields a high force between the friction discs 44, 46, which results in a low friction between the torque input part 12 and the torque output part 35. The low friction will cause the torque limiting assembly 10' to allow the torque input part 12 to slip in relation to output part 35 at low torque values.

Fig . 5b shows a side view of the torque limiting assembly 10', in which the torque adjustment screws 66 have been fastened tightly. This yields a high force between the friction discs 44, 46, which results in a high friction between the torque input part 12 and the torque output part 35. The high friction will cause the torque limiting assembly 10' to prevent slipping between the torque input part 12 and the torque output part 35 at low torque values, while the torque input part 12 is allowed to slip in relation to output part 35 at high torque values. Fig. 6 shows a perspective view of an alternative embodiment of a torque limiting assembly 10" according to the present invention. The torque limiting assembly 10" shares all features of the previously presented torque limiting assembly 10, including the unitary hub component 20 of fig 1. However, the torque limiting assembly 10" includes the spring members 64' between each of the heads of the torque adjustment screws 66 and the second annular disc 48 of fig 4.

Fig. 7 shows a perspective view of yet an alternative embodiment of a torque limiting assembly 10"' according to the present invention. The torque limiting assembly 10"' shares all features of the previously presented torque limiting assembly 10, except that the hub component 20 of the torque input part 12 has been divided into a hub component proper 20' and a third annular disc 21 similar to the embodiment of fig 4, However, the torque limiting assembly 10" does not include the spring members of figs 4 and 6, but instead includes the annular spring washer 50 of fig 1 constituting a combined spring washer and fixation ring.

Although the present invention has been described above with reference to a specific embodiment of the torque limiting assembly, it is of course contemplated that numerous modifications may be deduced by a person skilled in the art, and modification readily perceivable by a person having ordinary skill in the art in consequently to be construed part of the present invention as defined in the appending claims.

List of parts with reference to the figures: 10. Torque limiting assembly

12 Torque input part

14. Torque supplying shaft

16. Through-going central bore

18. First radial surface

20. Hub component

21. Third annular disc

22. Outward!y extending flange

23, Annular flange

24. First plurality of screw threads

25 Second plurality of screw threads.. 26. Locking ring

28 First multitude of through-going holes 30 Torque shaft installation screws 32, Outer conical surface

34. Inner conical surface

35. Torque output part

36. First annular disc

38 Mounting flange

40. First side

42, Second side

44. First friction disc

46 Second friction disc

47. First central aperture

48 Second annular disc

50. Second radial surface

52. Third radial surface

54. Second central aperture

56. Second plurality of through-going holes

58. Spring washer

60, Fixation ring

62. Third plurality of through-going holes 64. Spring member

66. Torque adjustment screws