SE539088C2

SE539088C2 - A universal coupling for transferring rotary movements between an input shaft and an output shaft

Info

Publication number: SE539088C2
Application number: SE1550124A
Authority: SE
Inventors: Al-Najjar Basim
Original assignee: Al-Najjar Basim
Priority date: 2015-02-05
Filing date: 2015-02-05
Publication date: 2017-04-04
Also published as: SE1550124A1; EP3253979A1; WO2016124378A1

Description

A universal coupling for transferring rotary movements between an input shaft and an output shaft Field of the invention The present invention relates to a universal coupling for transferring rotary movements from an input shaft to an output shaft. The coupling comprises an input and output joint member movably coupled to each other, and the input joint member is fixedly connected to the input shaft and the output joint member is fixedly connected to the output shaft. The present invention also relates to the use of the universal coupling.

Prior Art A universal coupling, also called a universal joint, a cardan coupling, or a cardan joint is commonly used for transmission of rotary movements between two rotating shafts of different angles. The universal coupling allows shafts not in line with each other a limited freedom of movement in any direction while transmitting rotary movements. The universal coupling allows the shafts to 'bend' in any direction. The universal coupling is used, for example, in cars, electrical machines or between two rotating machines, such as electrical motors, pumps, compressors, turbines, or generators.

A traditional universal coupling comprises, for example, of a pair of hinges fixedly connection to the shafts and located close together, oriented at 90° to each other, and connected by a cross shaft to allow the shafts to bend relative each other.

A problem with existing universal couplings is that they cannot efficiently transfer rotational forces and movements between shafts having an angle between them which is larger than 30°. Another problem with the existing universal couplings it that they only allow limited freedom of movements in any direction while transmitting rotary movements.

Object and summary of the invention It is an object of the present invention to at least partly overcome the above mentioned problems, and to provide an improved universal coupling that more efficiently transfers rotational movements and forces between the shafts. A particular object of the invention is to provide a universal coupling that efficiently transfers rotational forces and movements between shafts having an angle between them which is larger than 30°.

This object is achieved by a universal coupling as defined in claim 1.

The universal coupling comprises an input joint member and an output joint member movably coupled to each other. The input joint member is fixedly connected to the input shaft and the output joint member is fixedly connected to the output shaft. The invention ischaracterizedin that each of the input and output joint members comprises at least one annular part having a cross section and defining a central aperture, the annular part of the input joint member passes through the aperture of the annular part of the output joint member, the annular part of the output joint member passes through the aperture of the annular part of the input joint member, and the areas of the central apertures are larger than the cross section areas of the annular parts such that two spaced apart contact points are formed between the annular parts of the input and output joint members.

Due to the fact that the area of each of the apertures is larger than the cross sectional area of each of the annular parts, the annual parts are allowed to move relative each other in several degrees of freedom, i.e. linear movements along the axis of the shaft, circumferential movements, and angular movements about the axis of the shaft. Two spaced apart contact points are formed between the annular parts of the input and output joint members when the shafts are rotated. The rotational force of the input shaft is transferred to the output shaft through these contact points. The positions of the contact points are moving while the input and output shaft are rotating. The movements of the contact points are enabled due to the fact that the annual parts are allowed to move relative each other in several degrees of freedom. The coupling is effective because the movement and power are transferred through point-to-point contact between input and output annular parts.

The invention makes it possible to transfer rotational movement with high efficiency between two rotating shafts having an angle relative each other between 0 and 90°. In particular, the invention enables efficient transfer of rotational movement and forces between two rotating shaft having an angle larger than 30°. A further advantage is that the new universal coupling provides a simple construction to manufacture. The cost for production can therefore be kept low compared to existing couplings. Due to decreased wear and tear of the coupling parts, the life time of the coupling is increased, which further reduces costs, such as operation and maintenance costs.

The invention enables, with unlimited freedom in three dimensions of space, construction of a coupling for transmitting rotary movements between shafts not in line with each other. The invention also enables construction of a coupling for transmitting rotary movements between shafts not in line with each other, allowing any angel in the interval of 0 and 90° between the shafts during transmitting of the rotary movements. The angle between the shafts is not necessary static during operation, i.e. transmission of movements. The coupling allows the angle between the shafts to change during operation.

Whereas know couplings are restricted to an angle of the shafts of about 30°, the coupling of the present invention can transfer rotational movements between shafts of an angel up to about 90°. The new coupling can thus be used for an increased number of applications.

According to an embodiment of the invention, the area of each of the central apertures is at least ten times larger than the cross section area of each of the annular parts. For example, the cross section of the annular parts are circular, elliptical or rectangular. Preferably, the diameter of the central apertures is at least five times larger than a width or diameter of the cross section area of the annular parts. The ratio between the area of the central apertures and the area of the cross section area of the annular parts, is important for the establishment of the two spaced apart contact points. The ratio is further important for the rotational freedom of the shafts relative to each other. The coupling is also easy to manufacture at a larger ratio, which in turn reduces costs for manufacturing.

According to an embodiment of the invention, a periphery of the annular part of the input joint member defines a first plane, and a periphery of the annular part of the output joint member defines a second plane, and said two contact points are intersection points between the first and second planes.

According to another embodiment of the invention, the longitudinal axis of the input shaft and a periphery of the annular part of the input joint member are coplanar, and the longitudinal axis of the output shaft and a periphery of the annular part of the output joint member are coplanar. This embodiments provide for all the advantages mentioned above as well as for a simple and relatively cheap construction. For example, the annular part are ring shaped. The annular parts may for example be rings that are coupled together.

According to one embodiment of the invention, the input joint member comprises primary and a secondary input annular parts attached to each other, the primary and secondary input annular parts defining primary and secondary input central apertures, the output joint members comprises primary and secondary output annular parts attached to each other, the input and output annular parts defining primary and secondary output central apertures, the primary input annular part passes through the primary output central aperture, and the secondary input annular part passes through the secondary output central aperture, and the area of each the central apertures is larger than the cross section area of each of the input and output annular parts, and a first pair of spaced apart contact points are formed between said primary input and output annular parts, and a second pair of contact points are formed between said secondary input and output annular parts. This embodiment reduces or even eliminates backlash during transfer of rotational movements between the shafts at revers rotation of the shafts.

Each of the input and output joint member may comprise two annular parts that are connected to the shaft such that the primary annular part extends substantially perpendicular to the secondary annular part. Additional spaced apart contact points are thus formed between the input joint member and the output joint member, namely between the two primary annular parts and two secondary annular parts. The additional spaced apart contact points provided for in this embodiment improve the contact or connection between the first and the output joint member, while remaining a freedom of rotation of the shafts relative to each other in various angles and in three dimensional directions. This embodiment further improves transfer of rotation and decreases backlash problems. This construction is still relatively simple and can therefore still be manufactured at low cost. Further, interferences and vibrations during rotation are reduced.

According to one embodiment of the invention, a periphery of the annular part of the input joint member and the input shaft define a first plane, and a periphery of the annular part of the output joint member and the output shaft define a second plane, and each of the input and output annular parts comprises two displacements on opposite sides of the annular part, the displacements are configured to divide the annular part in two portions, whereby one portion of the annular part is positioned on one side of the first and second plane respectively, and the other portion of the annular part is positioned on the opposite side of the first and second plane respectively. Preferably, the distances of the portions to the plane are equal. An advantage with the displacements is to secure the interactions between the annular parts of input and output shafts and therewith transfer of movement and power.

According to an embodiment of the invention, a length of the displacement is at least twice a height of the annular part. Improved symmetry of the joint member results in improved transfer of rotation and power between the shafts. The contact points between the first and second annular part are moving overthe annular parts during rotation of the input and output shafts. If the sliding and traveling velocity of this movement is substantially the same at a constant rotation velocity of the shafts, the energy losses during the transfer are minimized. Symmetry of the joint improves the stability of the sliding and traveling velocity of the movement of the contact points overthe annular part. This velocity is preferably substantially constant.

According to a further embodiment of the invention, one of the input and output shafts are linearly movable in a direction extending along the longitudinal axis. According to another embodiment of the invention, both the input and output shafts are linearly movable in a direction extending along the longitudinal axes. The coupling of the invention can be used in an increased number of applications due to the improved flexibility of the shafts and the joint compared to existing couplings.

According to an embodiment of the invention, said annular parts are made of metal or a metal alloy. Preferably, the joint is made of strong material that can withstand tear and wear and material which is available and can be manufactured at low cost.

According to an embodiment of the invention, said annular parts are provided with means for reducing friction between the contact points between the annular parts. For example, a special arrangement of rolling elements bearing can be arranged in order to reduce the friction. Thus, general wear and tear and deterioration are decreased compared and energy losses related to the transfer are reduced.

The invention also relates to a use of the universal coupling according as defined above for transmission of rotational movement in rotating machines, such as a car or an electrical machine.

Brief description of the drawings The invention will now be explained more closely by the description of different embodiments of the invention and with reference to the appended figures.

Figs, la -c shows a universal coupling according to a first embodiment of the invention in different positions during rotation.

Fig. 2a shows one example of a joint member including one annular part seen from above.

Fig. 2b shows a side view of the joint member shown in figure 2a.

Fig. 3a shows a cross cut B - B through the annular part shown in figure 2.

Fig. 3b shows another example of a cross section of an annular part.

Fig. 4a shows a perspective view of another example of a joint member including one annular part.

Fig. 4b shows a front view of the joint member shown in figure 4b.

Fig. 5 shows a universal coupling according to a second embodiment of the invention. Fig. 6 shows a universal coupling according to a third embodiment of the invention. Fig. 7 shows a perspective view of an example of a joint member including two annular parts.

Fig. 8 shows an example of a joint member having an annular part including a special arrangement of rolling elements bearing.

Detailed description of preferred embodiments of the invention Figures la-c show a first embodiment of a universal coupling 3 for transferring rotary movements between an input shaft 1 and an output shaft 2. Each of the shafts 1, 2 are arranged to rotate about a longitudinal axis LI, resp. L2 that extends along the shaft. The coupling 3 comprises an input joint member 5, which is fixedly connected to the input shaft 1 and an output joint member 6, which is fixedly connected to the output shaft 2. The input and output joint members are movably coupled to each other. The longitudinal axis LI, L2 of the shafts extend at an angle a relative to each other. The angle a may vary between 0 and about 90° in three dimensional space. In figures la -c, the angle a is about 40°. The shafts are allowed to move relative each other. The figures la-c shows the shafts 1, 2 and the coupling 3 in different positions during rotation of the shafts 1, 2. The invention enables construction of a coupling for transmitting rotary movements between shafts not in line with each other, allowing any angel of a in the interval of 0 and 90° between the shafts during transmitting of the rotary movements. The angle a between the shafts is not necessary static during operation, i.e. during transmission of movements between the shafts. The coupling 3 allows the angle between the shafts to change during operation.

Each of the input and output joint members 5, 6 comprises one annular part 8,12 defining a central aperture 9,13. The annular part 8 of the input joint member 5, in the following named input annular part, passes through the aperture 13 of the annular part 12 of the output joint member 6, in the following named output annular art. In the same way, the output annular part 12 passes through the aperture 9 of the input annular part 8. This way, the input and output joint members are movably coupled to each other. The input and output annular parts 8, 12 contact each other by two spaced apart contact points 16, 17 during rotation of the shafts 1, 2. The positions of the contact points 16,17 changes during the rotation of the shafts 1, 2 and thus during movement of the joint members 5, 6 relative to each other, as shown in figures la-c. Rotational movements of the input shaft 1 is transferred to the output shaft 2 through the contact points 16,17. The positions of the contact points 16,17 are moving while the input and output shaft are rotating. Thus, movement and power are transferred through point-to-point contact between input and output annular parts 5, 6.

The annular parts has a cross section, and the shape of the cross-section may vary. The cross section may, for example, be rectangular, square, elliptical or circular. The aperture is suitably circular or substantially circular. However, the aperture may also be elliptical.

The area A of the central aperture 9, 13 of each of the input and output annular parts is essentially larger than the cross section area of the annular part. Preferably, the area of each of the central apertures is at least ten times larger than the cross section area of each of the annular parts. Thus, the joint members are allowed to move relative each other in at least three degrees of freedom, and the two spaced apart contact points 16, 17 are formed between the input and output annular parts 5, 6.

A first plane 14, shown in figure 4b, is defined by a periphery of the input annular part 8 and the longitudinal axis LI of the input shaft 1, and a second plane 14, as shown in figure 4b, is defined by a periphery of the output annular part 12 and the longitudinal axis L2 of the output shaft 2. In this embodiment, the two contact points 16, 17 are intersection points between the first and second planes. In the embodiment shown in figure 1 the longitudinal axis LI of the input shaft and the periphery of the input annular part 8 extend along the same first plane, i.e. are coplanar. Likewise, the longitudinal axis L2 of the output shaft 2 and the periphery of the output annular part 12 are coplanar. For example, the input and output joint members 5, 6 have substantially the same size and dimensions. However, it is not necessary that both joint members 5, 6 have the same size and dimensions. Figures 2a-b shows an example of a joint member 8' including one annular part 5' having a circular cross section attached to a shaft 1. The shaft 1 and the periphery of the annular part 8' defines a plane 4. The joint member shown in figure 2b can be an input joint member as well as an output joint member, and the shaft can be an input shaft as well as an output shaft. Thus, the plane 14 illustrates a first plane defined by the periphery of the annular part of the input joint member and the input shaft as well as a second plane defined by a periphery of the annular part of the output joint member and the output shaft. Figure 3a shows a cross cut B - B through the annular part 8'. The annular part 8' has an aperture 9'. The aperture 9' has a diameter di and an area Ai. The cross section of the annular part 5' has a diameter d2and an area A2. The diameter di of the aperture 9' is substantially larger than the diameter d2of the cross section of the annular part 5'. Thus, the area Ai of the aperture 9' is substantially larger than the area A2of the cross section of the annular part 5'. Preferably, the diameter di of the central aperture is at least five times larger than the diameter d2of the cross section area of the annular part 5'. Preferably, the diameter di of the central aperture is at least ten times larger than the diameter d2of the cross section area of the annular part. Figure 3b shows a cross cut through another example of an annular part 5 having a rectangular cross section, as shown in figure la - c. The cross section has a height h, a width w and an area A3. The area Ai of the aperture 9 is substantially larger than the area A3of the cross section of the annular part 5. Figures 4a-b shows another example of a joint member 5" including one annual part 8". Figure 4a shows the joint member in a perspective view and 4b shows the joint member in a front view. The annual part shown in figure 4b can be a primary or secondary input annual part, or a primary or secondary output annual part, and the shaft can be an input shaft as well as an output shaft. Thus, the plane 14 illustrates a first plane defined by the periphery of the input annular part and the input shaft as well as a second plane defined by a periphery of the output annular part and the output shaft.

The annular part 8" comprises two displacements lOa-b arranged on opposite sides of the annular part. The displacements lOa-b divide the annular part 8" in two portions 11a and lib. One portion 11a of the annular part is positioned on one side of a plane 14 defined by the periphery of the annual part 8" and the longitudinal axis LI of the shaft 1, and the other portion lib of the annular part is positioned on the opposite side of the plane 14. The length I of the displacements lOa-b is larger than the height h of the annular part shown in figure3b. The length is preferably at least about twice the height of the annular part. The length I may be three, four or more times larger than the height h of the annular part.

The first displacement 10a is preferably positioned at the outer end of the shaft, as shown in figure 4. The second displacement 10b is preferably positioned on the opposite side of the annular part. Preferably, but not necessary, the input joint member 5, 5" and the output joint member 6, 6" are the same or substantially the same. Figure 5 shows a second embodiment of a universal coupling 3" including input and output joint members 5" and 6", each comprising annular parts 8"and 12" provided with displacements lOa-b. Figure 6 shows third embodiment of a universal coupling 3"'. In this embodiment, each of the input and output joint members 5"', 6"' comprise two annular parts 8a-b and 12a- b. The input joint member 5"' comprises primary and a secondary input annular parts 8a, 8b attached to each other. The primary and secondary input annular parts define primary and secondary input central apertures 9a, 9b, as shown in figure 7. The output joint members 6"' comprises primary and secondary output annular parts 12a, 12b attached to each other. The input and output annular parts define primary and secondary output central apertures 13a, 13b. The primary input annular part 8a passes through the primary output central aperture 13a, and the secondary input annular part 8b passes through the secondary output central aperture 13b. The area of each of the central apertures 9a-b, 13a-b is larger than the cross section area of each of the input and output annular parts 8a-b, 12a-b. A first pair of spaced apart contact points 16,17 are formed between the primary input and output annular parts 8a, 12a, and a second pair of contact points 18, 19 are formed between the secondary input and output annular parts 8b, 12b. The primary annular parts 8a and 12a of the joint members 5"' and 6"' contact each other by two spaced apart contact points 16,17. The secondary annular parts 8b and 12b of the joint members contact each other by two spaced apart contact points 18, 19 during rotation of the shafts 1, 2. Thus, there are four contact points 16, 17, 18, 19 between the joint members 5"' and 6"' during rotation of the shafts. This embodiment reduces or even eliminates backlash during transfer of rotational movements between the shafts at revers rotation of the shafts.

Each of the annular parts 8a-b, 12a- b defines a plane 14 together with the longitudinal axis of the shafts, as shown in figure 4b. The peripheries of the primary and secondary input annular parts 8a, 12a define primary and secondary input planes respectively, and the peripheries of the primary and secondary output annular parts 8b, 12b define primary and secondary output planes. The primary and secondary input/output planes extend at an angle (3 relative each other. The angle (3 depends on the angle a, and can vary between 0°<|3 < 180°. The primary and secondary annular parts 8a, 8b and 12a, 12b of each joint member are attached to each other in two positions; one attachment position 15a located at the end of the shaft, and another attachment position 15b located at an opposite side of the joint member.

Figure 7 shows the joint member 5"' in a perspective view. The joint member 5"' includes two annular parts 8a and 8b in the following denoted primary and secondary annular parts. The primary and secondary annular parts 8a and 8b are arranged perpendicular to each other and are attached to each other at two positions 15a-b. Each of the annular parts 8a, 8b, 12a, 12b, as shown in figure 6 and 7, may comprise two displacements lOa-b on opposite sides of the annular part. In each joint member, the primary and secondary annular parts are attached to each other at the displacements as shown in figure 6 and 7. In an alternative embodiment, the annular parts are uniform and does not contain any displacements, or it may include more than two annular parts.

The coupling 3"' comprises two input annular parts in the following denoted primary and secondary input annular parts 8a-b, and two output annular parts in the following denoted primary and secondary output annular parts 12a - b. The coupling 3"' is formed by connecting the four annular parts 8a-b, 12a - b such that the primary input annular part 8a passes through a primary output aperture 13a of the primary output annular part 12a and the secondary input annular part 8b passes through a secondary output aperture 13b of the secondary output annular part 12b, as shown in figure 6. The primary annular parts may extend substantially perpendicular to the secondary annular parts.

Additional spaced apart contact points are formed between the input joint member and the output joint member, namely between the two primary annular parts and the two secondary annular parts. One pair of spaced apart contact points 16,17 are formed between the primary input part 8a and the primary output part 12a, and another pair of spaced apart contact points 18,19 are formed between the secondary input part 8b and the secondary output part 12b.

Friction may occur in the contact points between the annular parts. In an additional embodiment of the invention, the annular parts comprise an arrangement to minimize friction between the contact points. An example may be annular parts 5"" that comprise a special arrangement of rolling elements bearing 24, as shown in figure 8. Rolling elements 24 are arranged in an area where the annular parts meet during rotation of the coupling. The whole universal coupling can be enclosed by a cover to isolate it from the surroundings and to maintain the lubricant in the contact points longer time to reduce friction and prolong life length of the joint.

In any of the embodiments described above, at least one of the shafts may be movable in a direction extending along the longitudinal axis LI, L2. Advantageously, both shafts may be movable in a direction extending along the longitudinal axis LI, L2. Thus, transfer of movement and power are allowed at larger angles between the shafts, for example, angles larger than 90°.

The joint of the present invention is flexible. The longitudinal axes LI, L2 are able to extend at an angle a in an interval of 0 - 90°. The longitudinal axes can extend at an angle a in three dimensions in space.

The flexibility allows the universal coupling of the present invention to be used for numerous applications. The coupling can for example be used for transmission of rotational movement and power in a car, pumps, compressors, turbines, generators or an electrical machine.

The universal coupling, or at least the annular parts may, for example, be made of carbon fiber, reinforced plastic, metal or a metal alloy. Preferably the universal coupling is made from one and the same material. Examples of materials may be stainless steel.

The present invention is not limited to the embodiments disclosed but may be varied and modified within the scope of the following claims. For example the measures and dimensions of the joint members may vary and be adapted for the application in which the coupling is to be used. The joint members and/or the shafts may be made of other materials. The joint member may include more than two annular parts.

Image available on "Original document"

Claims

1. A universal coupling (3; 3"; 3"') for transferring rotary movements between an input shaft (1) and an output shaft (2), wherein each of the shafts are arranged to rotate about a longitudinal axis (LI, L2) of the shaft, the coupling comprising: an input joint member (5; 5';5";5"') and output joint member (6; 6"; 6"') movably coupled to each, and the input joint member is fixedly connected to the input shaft and the output joint member is fixedly connected to the output shaft, each of the input and output joint members comprises at least one annular part (8, 12; 8'; 8", 12"; 8a, 8b,12a,12b) having a cross section and defining a central aperture (9,13;9a,9b), the annular part of the input joint member passes through the aperture of the annular part of the output joint member, and the annular part of the output joint member passes through the aperture of the annular part of the input joint member such that two spaced apart contact points (16,17; 18.19) are formed between the annular parts of the input and output joint members,characterized in that the area (A; AI) of each the central apertures is at least ten times largerthan the cross section area (A2, A3) of each of the annular parts.

2. The universal coupling according to claim 1, wherein a periphery of the annular part (8, 8'; 8"; 8a, 8b) of the input joint member and the input shaft define a first plane (4; 14), and a periphery of the annular part (12; 12"; 12a, 12b) of the output joint member and the output shaft define a second plane (4; 14), and said two contact points (16,17; 18.19) are intersection points between the first and second planes.

3. The universal coupling according to any of the previous claims, wherein the input joint member (5"') comprises primary and a secondary input annular parts (8a, 8b) attached to each other, the primary and secondary input annular parts defining primary and secondary input apertures (9a, 9b), the output joint members (6"') comprises primary and secondary output annular parts (12a, 12b) attached to each other, the input and output annular parts defining primary and secondary output apertures (13a, 13b), the primary input annular part passes through the primary output aperture, and the secondary input annular part passes through the secondary output aperture, and the area of each the apertures is larger than the cross section area of each of the input and output annular parts, and a first pair of spaced apart contact points (16,17) are formed between said primary input and output annular parts, and a second pair of contact points (18,19) are formed between said secondary input and output annular parts.

4. The universal coupling according to any of the previous claims, wherein a periphery of the annular part (8"; 8a, 8b) of the input joint member and the input shaft define a first plane (14), and a periphery of the annular part (12"; 12a, 12b) of the output joint member and the output shaft define a second plane, and each of the input and output annular parts (5", 6") comprises two displacements (lOa-b) on opposite sides of the annular part, the displacements are configured to divide the annular part in two portions (11a, lib), whereby one portion of the annular part is positioned on one side of the first and second plane respectively, and the other portion of the annular part is positioned on the opposite side of the first and second plane respectively

5. The universal coupling according to claim 4, whereby a length (I) of the displacement (10) is at least twice a height (h) of the annular part (8,12).

6. The universal coupling according to any of the previous claims, wherein said annular parts are metal or a metal alloy.

7. Use of the universal coupling according to any of the claims 1 - 6 for transmission of rotational movement in rotating machines.