AU2013322276B2

AU2013322276B2 - Flexible coupling

Info

Publication number: AU2013322276B2
Application number: AU2013322276A
Authority: AU
Inventors: Christopher Thomas TOSIO
Original assignee: Individual
Current assignee: Individual
Priority date: 2012-09-25
Filing date: 2013-04-26
Publication date: 2017-01-12
Anticipated expiration: 2033-04-26
Also published as: ZA201502730B; IN2014KN01141A; AU2013322276A1; MX2015003774A; WO2014049454A1; BR112015006544A2

Abstract

The invention relates to a flexible coupling, typically for use in a sugar mill. The coupling (10, 110) has a drive side yoke (12, 112) connected to a drive shaft at a transverse orientation relative to the drive shaft and a driven side yoke (14, 114) connectable to a driven shaft at a transverse orientation relative to the driven shaft. There is also a compression strut (16, 116) located between the drive and driven shafts, also at an orientation transverse to the drive and driven shafts. Drive connection means acts between the ends of the yokes and the ends of the compression strut so that drive can be transmitted from the drive shaft to the driven shaft via the drive connection means and the compression strut. In accordance with the invention, the drive and driven yokes each have a hub (18, 118, 24, 124) mountable to the respective drive or driven shaft and a pair of tubes (20, 120, 26, 126) radiating in opposite directions from the hub.

Description

H:\tu\lli6trAOVcn\NRPortbHtJCClGWI2l72y*»_l docv£</l I/2CII6 2013322276 01 Dec 2016 - 1 -

FLEXIBLE COUPLING THIS invention relates to a flexible coupling.

In a sugar mill it is normal fora high torque, low speed drive to be supplied through a coupling from a rotary drive to a roller which acts relative to one or more counter-rollers to crush raw sugar cane fed to the mill. In practice, the required high torque, low speed drive is transmitted from a drive shaft to a driven roller shaft. Ideally, the drive and driven shafts should be in perfect axial alignment and incapable of axial movement towards or away from another. However, in sugar milling and other applications there is frequently misalignment between the drive and driven shafts, and also possible axial movement between the shafts in the event of, say, breakage or failure of the mill roller shaft. Accordingly the coupling in such applications must be sufficiently flexible to accommodate such variations.

Couplings of the general type described in the specification of South African patent ZA88/0607 have, over the years, proved themselves suitable for use in sugar mill duties as summarised above. A coupling of this kind has a first yoke which can be mounted transversely on the drive shaft and a second yoke which can be mounted transversely on the driven shaft. A compression strut, which is also arranged transversely relative to the drive and driven shafts, is located between the two yokes. Opposite ends of the first and second yokes are connected to one another by drive connectors which act on the ends of the compression strut such that rotation of the first yoke, caused by rotation of the drive shaft, is transmitted to the second yoke, and hence to the driven shaft, via the compression strut and drive connectors.

The drive connectors may be flexible and provided by belts, straps, ropes or the like. Alternatively they may be rigid elements which extend between the ends of the yokes and the ends of the compression strut. In either case, the coupling has sufficient flexibility to accommodate misalignments of the drive and driven shafts both in a radial and an axial sense.

While couplings of the known type have been found to work well, they have the disadvantage that they are expensive to manufacture. One reason for this is the fact that the known yokes are fabricated from steel plate. 2013322276 01 Dec 2016 H'.'gtt\liUcntovcn\NRPonbUDCC\GWU2172')ilM.diXv25n^20Ki -2-

According to this invention there is provided a flexible coupling comprising a drive side yoke connectable to a drive shaft at a transverse orientation relative to the drive shaft, a driven side yoke connectable to a driven shaft at a transverse orientation relative to the driven shaft, a compression strut located between the drive side yoke and the driven side yoke at an orientation transverse to the drive shaft and driven shaft, and drive connection means acting between the ends of the yokes and the ends of the compression strut, whereby drive can be transmitted from the drive shaft to the driven shaft via the yokes, drive connection means and compression strut, wherein each of the drive and driven yokes comprises a hub mountable to the respective drive or driven shaft and a pair of tubes radiating in opposite directions from the hub.

Typically the tubes of each yoke are axially aligned with one another. In the preferred embodiments, the hub and tubes of each yoke are reinforced by gusset plates fixed externally to and extending over the hub and tubes on opposite sides thereof. There may be two or more parallel gusset plates extending continuously over the hub and tubes on each side thereof.

In the preferred embodiments, the compression strut is of tubular construction with a round or rectangular cross-section. PCT/IB2013/053313 WO 2014/049454 -3- in one particularly preferred embodiment, the compression strut has a rectangular cross-section and has a flat profile in an axial direction.

Typically each yoke carries axially oriented drive connection pins towards either end thereof. These may be tubular and may extend cantilever fashion from the ends of the yokes, the drive connection pins of one yoke extending in the opposite direction to the drive connection pins of the other yoke.

In one embodiment of the invention the drive connection means comprises closed loop, flexible drive connectors which are looped around the drive connection pins carried by the yokes and which pass over or through the ends of the compression strut.

In another embodiment, the drive connection means comprises closed loop, flexible drive connectors which are connected between the drive connection pins carried by the yokes and corresponding drive connection pins carried at the ends of the compression strut.

In yet another embodiment, the drive connection means comprises rigid links connected rotatably, via bushes of Vesconite or other low friction material, between the drive connection pins and corresponding drive connection pins carried at the ends of the compression strut. In this embodiment, the bushes may seat on stainless steel sleeves of the drive connection pins. Typically, a bush of each rigid link has an elongate aperture in which a round drive connection pin is rotatably received.

In a preferred embodiment, each rigid link comprises a central steel plate with opposite ends, curved elements formed of flat steel bar fixed by welding to the opposite ends of the central plate to form an assembly and a bounding member formed of flat steel bar which surrounds and is fixed by welding to the assembly, the bounding member including curved end portions which, in combination with the curved elements, form openings in which the bushes are located. HAg\vAIiilcnvmeh\NRPonbI\DCOGWI2l72')l!l_ldOC\-29/l 1/2016 2013322276 01 Dec 2016 -4-

The invention will now be described in more detail, by way of non-limiting example only, with reference to the accompanying drawings which diagrammatically illustrate flexible couplings, suitable for use in transmitting rotary torque from a drive shaft to a driven mill or roller shaft in a sugar mill.

In the drawings:

Figure 1 shows a drive side axial view of a first embodiment of coupling; Figure 2 shows a view of the first embodiment of coupling, in the direction of the arrow 2 in Figure 1, with the drive connector straps omitted in the interests of clarity; Figure 3 shows an axial view of the drive side yoke of the first embodiment of coupling; Figure 4 shows a transverse view of the drive side yoke seen in Figures 1 to 3; Figure 5 shows a transverse view of the driven or mil! side yoke seen in Figures 1 to 3; Figure 6 shows how a drive connection pin is connected to a yoke in the first embodiment of coupling; Figure 7 shows an axial view of the compression strut of the first embodiment of coupling; Figure 8 shows a perspective detail of an end of the compression strut seen in Figure 7; Figure 9 shows a drive side axial view of a second embodiment of coupling; Figure 10 shows an axial view of the compression strut used in the coupling seen in Figure 9; Figure 11 shows a side view of the compression strut seen in Figure 10; Figure 12 shows a cross-sectional view of the compression strut seen in Figures 10 and 11; Figure 13 shows a cross-sectional side view of a yoke of the second embodiment; 2013322276 01 Dec 2016 H \gu\latcnvovcn\NRPonbl\DCOGWU2l72li;*n_l docs-25/l -5-

Figure 14 shows a perspective view of a connecting link used in the second embodiment;

Figure 15 shows an axial view of the connecting link seen in Figure 14; and

Figure 16 shows a cross-section at the line 16-16 in Figure 15.

The coupling 10 seen in Figure 1 is suitable for transmitting rotary torque from a drive shaft (not shown) to a driven shaft (not shown) in a sugar mill. It has a drive side yoke 12, a mill or driven side yoke 14 and a compression strut 16. In operation, the drive side yoke 12 is mounted transversely to the drive side shaft and the driven or mill side yoke 14 is mounted transversely to the driven or mill side shaft. PCT/IB2013/053313 WO 2014/049454 -6-

The ends of the drive and mill side yokes 12 and 14 are connected to one another by drive connection means which acts between the ends of the yokes, on the ends of the compression strut 16. More is said below about these means.

As thus far described, the coupling has the primary features of a coupling of the known type referred to previously. One feature of the illustrated coupling 10 which is not conventional is the actual construction of the drive and driven side yokes 12 and 14.

Referring to Figures 1 to 4, the drive side yoke 12 has a central hub 18 and a pair of axially aligned tubes 20 radiating from the hub in opposite directions. The hub and tubes are reinforced laterally and against transverse bending by gusset plates 22. The gusset plates 22 are provided in pairs on opposite sides of the hub 18 and tubes 20, and in the illustrated embodiment extend for the full length of the hub and tube structure. In other embodiments, the gusset plates extend for only a part of the length of the structure, in the illustrated embodiment, the gusset plates on each side are parallel to one another and are fixed to the hub and tubes by fillet welds.

In use, the drive side shaft locates in the hub 18. Typically, the shaft has a square cross-section while the internal profile of the hub is also generally square, but somewhat oversize with respect to the shaft and with rounded corners and inwardly concave sides. With such an arrangement, rotational engagement between the shaft and the hub takes place at points on the four flat sides of the shaft, near to the comers but not at the corners themselves.

As shown in Figure 5, the driven side yoke 14 has a structure which is largely the same as that of the drive side yoke. As illustrated the yoke 14 includes a central hub 24, tubes 26 and reinforcing gussets 28 arranged in pairs on opposite sides of the hub and tube structure. The cross-section of the driven shaft and the internal profile of the hub 24 may be similar to those described above for the corresponding drive side components. PCT/IB2013/053313 WO 2014/049454 -7-

The drive side yoke 12 carries a pair of drive connection pins 30, one towards either end. The pins are fixed cantilever fashion to the yoke and project axially from the yoke in one axial direction only, into the space between the two yokes. For example, as viewed in Figure 2, both pins 30 project to one side only of the yoke. Each of the pins 30 carries four flanges 32, 34, 36 and 38 which define lands 40, 42 and 44 between them. in a similar manner, the driven side yoke 14 carries axially oriented drive connection pins 41 carrying flanges corresponding to those carried by the pins 30. The pins 41 also project into the space between the two yokes, but in the opposite direction to that in which the pins 30 project.

The arrangement is such that, when the yokes 12 and 14 are spaced apart from one another by a predetermined distance, the lands 40, 42 and 44 of the pins 30 are in alignment with the corresponding lands defined by the flanges of the pins 41.

The manner in which each pin 30, 41 is fixed to its associated yoke 12, 14 is illustrated in Figure 6. As shown in this Figure, each pin 30, 41 is of tubular form and is fixed cantilever fashion in reinforcing sleeves 46, 48 fixed in diametrically aligned holes in the associated tube 20, 26.

The compression strut 16 includes an elongate tube 50 carrying end structures 52 at either end. Each end structure 52 includes spaced apart, inner and outer curved plates 54, 56. Internal plates 58 subdivide the curved space between the plates 54 and 56 into curved passages 60. The end of the tube 50 is connected to the inner curved plate 54 by spaced apart brackets 62.

The ends of the yokes 12 and 14 are connected to one another by drive connection means including drive connectors 66 (seen in Figure 1 only and omitted from the other Figures in the interests of clarity of illustration), arranged in pairs. Each drive connector 66 is provided by a closed loop strap or sling 68 of a suitable flexible material. WO 2014/049454 PCT/IB2013/053313 -8-

One strap of each pair passes around a iand 40 of a pin 30 of the drive side yoke 12 and around the corresponding iand of the pin 41 of the driven side yoke 14. Similarly, the other strap of the pair passes around the land 44 of the pin 30 and around the corresponding land of the pin 41.

Between the ends of the yokes, each connector strap passes through one of the passages 60 in an end structure 52 of the compression strut 16. In operation, tension in the connector straps places the compression strut 16 under axial compression as described below in more detail.

As in couplings of the known type, rotation of the drive yoke 12 is transmitted to the driven yoke 14 through the connector straps 68 and compression strut 16. The flexibility of the straps provides the coupling 10 with sufficient overall flexibility to accommodate fairly substantial radial misalignments between the drive and driven shafts, and also to accommodate relative axial movement between the shafts.

In practice in a sugar mill application, operational drive during the milling of sugar cane is in one rotary direction, it may however be necessary or appropriate in certain circumstances for the drive to take place in the opposite rotary direction. One such circumstance may be when the mill has “choked" and the normal drive has seized as a result.

Rigid links 64 are provided for transmission of rotary torque in the reverse direction. These links are connected between the ends of the compression strut 16 and the ends of the yokes 12, 14. Each link 64 has one end connected pivotally by a pin 70 to the brackets 62 at an end of the compression strut.

The opposite end of each link is formed with a slotted opening in which the iand 42 of a pin 30, or the corresponding iand of a pin 41, is received. With this arrangement, the relevant end of the link is connected pivotally and slidably to the end of a yoke 12, 14. PCT/IB2013/053313 WO 2014/049454 -9-

It will be understood that the [inks will be operative to transmit a reverse drive from the drive side yoke 12 to the driven or mill side yoke 14 and hence from the drive shaft to the driven shaft. The ability of the links to slide to a limited extent relative to the associated yokes will also enable the coupling to accommodate slight kick-backs which might occur, for example if the drive shaft is suddenly stopped as a result of a power failure or for any other reason.

It will be understood that the connections between the links 64 and the yokes and compression strut will be sufficiently loose to allow the coupling 10 to have the required flexibility to accommodate shaft misalignments and relative axial movements.

Many variations of the embodiment described above are possible. By way of example it would be possible for the compression stmt to carry drive connection pins at either end, possibly similar to the pins 30 and 41. Separate drive connectors, typically closed loop flexible drive connection straps or slings could then be connected between the ends of the drive and driven yokes and the ends of the compression strut.

Figures 9 to 16 illustrate a second embodiment of the invention. In these Figures, components corresponding to those illustrated in Figures 1 to 8 are designated by the same reference numerals prefixed by the numeral A major difference between the embodiments is the fact that flexible straps or slings are not used at all as the drive connectors of the drive connection means. Instead, the drive connectors are provided by rigid connecting links 200 each connected at one end to an end of a yoke 112, 114 and at the other end to an end of the compression strut 116. A typical link 200 illustrated in Figures 14 to 16. The link 200 comprise a central plate 202 formed with an oval cut-out 204 for weight reduction purposes. PCT/IB2013/053313 WO 2014/049454 -10-

Circulariy curved plates 206 are welded to curved ends of the central plate at 208. These plates are formed by bending flat steel bar of the appropriate width.

The assembly of central plate 202 and curved plates 206 is bounded by an elongate ring 210 having straight side portions 212 and circularly curved end portions 214, The long edges of the central plate 202 are welded to the side portions 212 of the ring at 216. In practice, the ring 210 is provided by a length of flat steel bar which is bent to the illustrated shape and the ends of which are connected to one another by welding at 218.

In combination, the curved plates 206 and the curved end portions 214 of the ring 210 form openings 220 and 222. The opening 220 accommodates a bush 224, of Vesconite or other low friction material, defining a circular central aperture. The opening 222 also accommodates a bush 226 of Vesconite or other low friction material, However the central aperture of this bush is not perfectly circular. Its dimension 228 is slightly greater, typically 3mm greater, than its dimension 230. The central aperture is accordingly slightly elongate in shape.

The Vesconite bushes 224, 226 are not shown in Figure 14.

Figure 13 illustrates the drive side yoke 112. As in first embodiment, the yoke has a central hub 118 and a pair of tubes 120 radiating from the hub in opposite directions. The tubes carry drive connection pins 130 towards their ends as illustrated. Each of these pins has a reduced diameter end 232 on which is mounted a round cylindrical, stainless steel sleeve 234. The driven side yoke has a similar structure to the drive side yoke.

The compression strut 116 is illustrated in Figures 10 to 12. Whereas the compression strut 16 of the first embodiment is formed by a tube of round cross-section, the tubular compression strut 116 has a rectangular cross-section. PCT/IB2013/053313 WO 2014/049454 -11-

The axial dimension 236 of the strut is substantially less than the transverse dimension 238. The compression strut accordingly has a flat profile in the axial direction, i.e. in a direction parallel to the drive and driven shafts.

The compression strut is formed by opposing steel plates 240 each bent to a tipped channel shape. The plates are connected to one another by bolts 242 passing through aligned holes in the lips or flanges 244.

The compression strut includes end structures 152 each including a pair of axially spaced plates 246 carrying connection pins 247 extending between the plates in an axial direction parallel to the axes of the drive and driven shafts. These pins are round in cross-section and are fitted externally with round cylindrical, stainless steel sleeves 248 similar to the sleeves 234.

In the assembled coupling 110, the links 200 are connected between the ends of the yokes and the ends of the compression strut, in each case with a Vesconite bush 224, 226 mounted rotatably on a stainless steel sleeve 234, 248 respectively. End caps 250 (two of which are seen in Figure 9) hold the ends of the links on the drive connection pins 130 of the yokes.

The coupling 110 operates in a manner similar to the coupling 10, with rotary drive being transmitted from a drive shaft (not shown) connected to the drive side yoke to a driven shaft (not shown) connected to the mill or driven side yoke through the connecting links 200 and the compression strut 116. During normal operation, the connecting links 200 are in tension and the compression strut is in longitudinal compression.

Misalignments which may exist between the drive and driven shafts are accommodated to a small extent by the inherent resilience of the Vesconite bushes and to a greater extent by the fact that the bushes 226 have slightly elongate shapes, thereby allowing for some transverse play between the round cylindrical stainless steel sleeves 234 and the bushes. 2013322276 01 Dec 2016 H^gw\lnicn»ovcn\NRPoni>l'DCClGtt'\i2172ysii„l .docs*25/l P2(U(> - 12-

When compared to known couplings, the couplings 10 and 110 described above have the advantage that the coupling can be made relatively inexpensively. In both cases, this is largely attributable to the fact that the yokes have basically a tubular form, with the tubes themselves typically being of a commercially available size. The second embodiment has the further advantage that the coupling, as a whole, can have a reduced axial dimension, this being attributable to the fact that the compression strut has a flat profile in the axial direction. A further advantage of the second embodiment is that the rigid connecting links 200 perform the functions of both the slings 68 and the links 64 of the first embodiment. The simple, fabricated structure of the links 200, which are formed from commercially available fiat steel bar and plate, leads to further cost reductions.

While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not by way of limitation. It will be apparent to a person skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus, the present invention should not be limited by any of the above described exemplary embodiments.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A flexible coupling comprising a drive side yoke connectable to a drive shaft at a transverse orientation relative to the drive shaft, a driven side yoke connectable to a driven shaft at a transverse orientation relative to the driven shaft, a compression strut located between the drive side yoke and the driven side yoke at an orientation transverse to the drive shaft and driven shaft, and drive connection means acting between the ends of the yokes and the ends of the compression strut, whereby drive can be transmitted from the drive shaft to the driven shaft via the yokes, drive connection means and compression strut, wherein each of the drive and driven yokes comprises a hub mountable to the respective drive or driven shaft and a pair of tubes radiating in opposite directions from the hub.
2. A flexible coupling according to claim 1, wherein the tubes of each yoke are aligned with one another.
3. A flexible coupling according to claim 1 or claim 2, wherein the hub and tubes of each yoke are reinforced by gusset plates fixed externally to and extending over the hub and tubes on opposite sides thereof.
4. A flexible coupling according to claim 3, wherein the coupling comprises two or more parallel gusset plates extending continuously over the hub and tubes on each side thereof.
5. A flexible coupling according to any one of the preceding claims wherein the compression strut is of tubular construction.
6. A flexible coupling according to claim 5, wherein the compression strut has a round or rectangular cross-section.
7. A flexible coupling according to claim 6, wherein the compression strut has a rectangular cross-section and has a flat profile in an axial direction.
8. A flexible coupling according to any one of the preceding claims wherein each yoke carries axially oriented drive connection pins towards either end thereof.
9. A flexible coupling according to claim 8, wherein the drive connection pins are tubular and extend cantilever fashion from the ends of the yokes, the drive connection pins of one yoke extending in the opposite direction to the drive connection pins of the other yoke.
10. A flexible coupling according to claim 8 or claim 9, wherein the drive connection means comprises closed loop, flexible drive connectors which are looped around the drive connection pins carried by the yokes and which pass over or through the ends of the compression strut.
11. A flexible coupling according to claim 8 or claim 9, wherein the drive connection means comprises closed loop, flexible drive connectors which are connected between the drive connection pins carried by the yokes and corresponding drive connection pins carried at the ends of the compression strut.
12. A flexible coupling according to claim 8 or claim 9, wherein the drive connection means comprises rigid links connected rotatably, via bushes of Vesconite or other low friction material, between the drive connection pins and corresponding drive connection pins carried at the ends of the compression strut.
13. A flexible coupling according to claim 12, wherein the bushes seat on stainless steel sleeves of the drive connection pins.
14. A flexible coupling according to claim 12 or claim 13, wherein a bush of each rigid link has an elongate aperture in which a round drive connection pin is rotatably received.
15. A flexible coupling according to any one of claims 12 to 14, wherein each rigid link comprises a central steel plate with opposite ends, curved elements formed of flat steel bar fixed by welding to the opposite ends of the central plate to form an assembly and a bounding member formed of flat steel bar which surrounds and is fixed by welding to the assembly, the bounding member including curved end portions which, in combination with the curved elements, form openings in which the bushes are located.