GB2181515A - A torque-transmitting coupling arrangement - Google Patents

Abstract

A torque-transmitting coupling arrangement for connecting at least approximately aligned shafts [12,18], comprises at least one diaphragm coupling assembly (22) and at least one gear coupling assembly (24), connected in series with one another and axially spaced along the transmission path whereby to accommodate axial and/or angular variations in the positions of the shafts. <IMAGE>

Description

SPECIFICATION A torque-transmitting coupling arrangement The present invention relates to a torquetransmitting coupling arrangementforcoupling shafts of different components or units of a machine, which shafts may have angular or other misalignments and the ends of which shafts, connected to the coupling arrangement may experience axial dis placements during operation,forexample,dueto thermal expansion or vibration.

In one known such coupling arrangement two coupling assemblies are provided, both formed as diaphragm coupling assemblies. This coupling is described, for example, at page 18 of a pamphlet entitled "Contoured Flexible Diaphragm Coupling", produced by The Bendix Corporation Electric and Fluid Power Division. Another known coupling arran gementforthis purpose comprises two gear coupl- ing assemblies, optionally with curved teeth. This coupling is described in a pamphlet "Curved Teeth Couplings", produced by the Tacke Com pa ny (see for example page 20).

Atorque-transmitting coupling arrangement for coupling shafts of two interconnected components of a machine unit is described in DE-05 2655178. In this coupling arrangement each ofthecomponents is connected to an intermediary connecting shaft via a pairofcouplings consisting of a diaphragm disc and a gear coupling, the gear coupling and diaphragm discofeach pair being connected in parallel with each other in thetorquetransmission path, with interposition of a torsionally resilient shaft which ensure that in each pairofcouplings part ofthetorque is transmitted by the diaphragm disc and the rest of the torque by the gearcoupling.Atthe same time, the diaphragm dise ensures, by means of the torsionally resilient shaft, that the gear coupling retains a central position without the use of limitstops.

The disadvantage of this known torquetransmitting coupling arrangement is that when working under load relative axial displacement ofthe gearcouplings may not be possible sothatany thermal expansion which arises may lead to axial overload.

The problem on which the present invention is based is that of providing a torque-transmitting coupling arrangement in which axial overloads dur ingtorquetransmissioncan be avoided.

According to the present invention, therefore, there is provided a torque-transmitting coupling arrangementforconnecting at least approximately aligned shafts, comprising at least one diaphragm coupling assembly and at least one gear coupling assembly, connected in series with one another and axially spaced along the transmission path whereby to accommodate axial andlorangularvariationsin the positions ofthe said shafts.

The coupling arrangement ofthe invention allows atolerance in the axial separation of the facing ends ofthe shafts to be coupled because of the presence of the gear coupling assembly whilst, during operation under load, axial variations in the separation ofthe facing ends ofthecoupled shafts can beac commodated by the diaphragm coupling if relative axial displacement ofthe gears of the gearcoupling is prevented due to frictional forces. Thus variations in length of one of other ofthe shafts can be com pensated by the diaphragm coupling assembly, without relative axial movement of the gears being necessary in the gear coupling assembly.Atthe sametimethe restoring forces generated upon re silient deformation ofthe diaphragm coupling assembly can be kept small by selecting appropriate dimensions ofthe diaphragm coupling assembly, so that these restoring forces do not lead to any damage to the components even under extreme conditions.

Further, it is possible that during operation, ifthe torquetransmission is interrupted forashorttime or ifthetransmittedtorquefalls in value, even temporarily,thediaphragm coupling can relax owing to the possibility of axial readjustment ofthe gear coup- ling assembly when released from the full transmitted load to allow the coupling arrangement as a wholeto adapt to the particular axial separation of the facing ends of the coupled shafts.

The significance ofthe above-described behaviour of the coupling arrangement ofthe invention becomes all the more comprehensible if it is considered that in addition to the inevitable friction, axial locking phenomena can also arise in the teeth of the gear coupling as a result of driving or hammering in.

As far as the transmission of axial vibrations is concerned, the behaviour of the arrangement of the invention is substantially determined by the diaphragm coupling assembly, which attenuates the transmission of vibrations between the coupled shafts even if the gear coupling assembly is loaded and difficultto move in the axial direction, and thereby transmitting such vibrations.

The series connection ofthegearcoupling assembly with the diaphragm coupling assembly necessarily ensures the "guiding " of the gear coupling assembly in the axial direction, i.e. no special measures such as limit stops are necessary to restrict relative axial movement of the teeth in the gear coupling assembly.

The ability ofthe coupling arrangement according to the invention to compensate axial and angular misalignments between the shafts to be coupled is based on the articulation which arises in the diaphragm coupling assembly; this ability is present two a small extent also in gearcoupling assemblies, and can be increased for example by making at least one of the cooperating sets ofteeth as curved teeth.

Compared with the prior art coupling arrangements, the arrangement ofthe present invention is distinguished by requiring only a small amount of space, and having a low weight. Assembly costs are also low in relation to prior art arrangements having two diaphragm coupling assemblies insofarasthe greater balancing cost of a diaphragm coupling assembly has to be met only in relation to one and not two such assemblies.

Diaphragm coupling assemblies having laminated link diaphragms as shown in the Bendix pamphlet may also be used in the diaphragm coupling arrangement ofthe invention.

Various embodiments of the present invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which: Figure lisa schematic axial section showing a first embodiment of the invention; Figure2 is a similar schematic axial section showing a second embodiment in which two diaphragm coupling assemblies and one gear coupling assembly are connected in series; Figure 3 is another schematic axial section show ingathirdembodimentwhich isa modificationofthe coupling arrangement of Figure 1, in which the diaphragm coupling assembly is constructed with a double diaphragm; and Figure 4 is a further schematic axial section showing afourth embodiment in which the gearcoupling assembly is constructed as a plug connection assembly.

Referring now to the drawings, in Figure 1 there is shown a compressor 10with a driveshaft 12and a drive unit 14 with an input shaft 16 connected to a drive motor (not shown) and an output shaft 18. The drive unit outputshaft 18 and the compressor input shaft 12 are connected together buy a coupling arrangement 20. The coupling arrangement20comprises a diaphragm coupling assembly 22 and a gearcoupling assembly 24.

The diaphragm coupling assembly 22 comprises a rigid coupling disc 22a having a central boss 22b with a tapered hole into which a tapered end 1 2a ofthe compressor input shaft 12 is fitted, and a flexible diaphragm disc 22cwhich is connected to a hollow shaft 26,forexample, byweldingtotheradiallyinner edge. The rigid coupling disc 22a is centred in rela tiontotheflexiblediaphragm disc 22c by interlocking centring projections (not shown) and the two discs are connected together around their perimeters by fixings such as screws schematically indicated by the broken lines 22d.

The gear coupling assembly 24 comprises an ex ternally toothed gear 1 8a on the output shaft 18 ofthe drive unit 14 and an internallytoothed ring gear24a which is connected to a flange 26a ofthe hollow shaft 26 by fixings such as screws generally indicated by the broken lines 24b. The teeth on the components 18a and 24a have been shown as straight cut eeth but may be curved teeth.

When the machine unit illustrated in Figure 1 is assembledtheaxial distancebetweenthefacing ends of the shafts 1 2a and 1 8a is not critical because compensation can be achieved by the gear coupling assembly 24. Assembly and dismantling are made easierbythefactthatthe hollow shaft 26 can be inserted during assembly between the compressor 10 andthedriveunitl4afterthese have been assembled and fixed in position and on the other hand can be removed without the compressor 10 or the drive unit 14being displaced ordismantled.

If at least one of the shafts 12,16 is subjectto a large degree ofthermal expansion,which is an especially common feature with very long shafts, then length compensation during operation is automatically effected by the diaphragm coupling assembly 22, eventhough,when underload,thegearcoupling assembly 24 moves only with difficulty in the axial direction, or may even be entirely axially locked.

Moreover, axial vibrations are not transmitted, or are transmitted only in a strongly damped manner, thanks to the flexibility of the diaphragm disc 22c.

In the embodiment of Figure 2 similarorcorresponding parts are identified with the same reference numerals as in Figure 1, but raised by 100. In this embodiment a second diaphragm coupling assembly 128 is provided between the hollow shaft 126andthe gear coupling assembly 124, this further diaphragm coupling assembly 128 including the flange 124c ofthe gear ring 1 24a to which is fitted a diaphragm dise 128a which is similartothe dia- phragm coupling assembly 22 described in connection with Figure 1. In use both the diaphragm disc 122e and the diaphragm dise 128a contribute to the transmission of torque.The embodiment of Figure 2 has, in addition to the advantages described in relation to the embodiment of Figure 1 ,thefurther advantage that greater angular play can beac- commodated, possibly even without the use of curved teeth for the gears 11 8a, 1 24a. Furthermore, this embodiment is capable of greater resilientdeformation in the axial direction, which enables itto accommodate larger degrees of thermal expansion than the embodiment of Figure 1. In the embodiment of Figure 3the same orsimilarcomponents are identified with the same reference numerals as in Figure 1, but raised by 200.The gear coupling assembly 224 of the embodiment of Figure 3 is the same as the gear coupling assembly 24 of the embodiment of Figure 1 However, the diaphragm coupling assembly 222 differs from that ofthe embodiment of Figure 1 in that the coupling disc 222a is also formed as a resilient diaphragm disc. In this way a greater axial ortorsional resilience is achieved and, as in the embodiment of Figure 2, this enables larger degrees of thermal expansion to be accommodated than in the embodiment of Figure 1.

All three embodiments shown in Figures 1 to 3 have in commonthefactthat in the gearcoupling assembly 24 or124 or 224 no special steps are neces- sary to limit relative axial displacement ofthe meshing teeth. Rather, this function is taken care of by the diaphragm coupling assembly 22 or 122 or 222.

In the embodiment of Figure 4, again corresponding parts are identified with the same reference num erals as in Figure 1, raisedthistime by300.

In this embodiment a coupling disc 322a is located on the inputshaft3l 2 and has a cylindrical hu b 322b connected for rotation with the input shaft 312 by a key 322e. The coupling disc 322a is again fixed at its perimetertothe perimeter of the diaphragm disc 322cofthediaphragm coupling assembly 322. The right-hand end ofthe hollowshaft326 is provided with internal teeth 330, which engage with external teeth 332 of a gear carried on the drive output shaft 318. The teeth 330 and 332 together form the gear coupling assembly 324. In this embodimentthere is on the one hand the possibility, owing to the use of a gearcoupling assemblywithinthehollowshaft326, of effecting a plug-type coupling with the drive unit 314, which coupling occupies minimal space in the radial direction and is light. On the other hand the use ofthe diaphragm coupling assembly 322 on the left hand side ofthetransmission allows the possibility of a conventional hub connection with the unit 310. It should be mentioned that the coupling disc 322a may alternativelybeformedasaflangeforced ontothe shaft312, or alternatively, as in the embodiment of Figure 3, may be formed as a second diaphragm disc.

Claims (11)

1. Atorque-transmitting coupling arrangement for connecting at least approximately aligned shafts, comprising at least one diaphragm coupling assembly and at least one gearcoupling assembly, connected in series with one another and axially spaced along the transmission path whereby to accommodate axial and/or angularvariations in the positions of the said shafts.

2. A coupling arrangement as claimed in Claim 1, in which the axial restoring forces exerted by the diaphragm coupling assembly upon relative axial dis placementofthetwo coupled shafts are small in rela tion to the axial frictional resistance in the gearcoupl- ing assembly when under load.

3. A coupling arrangement as claimed in Claim 1 orClaim 2, in which the diaphragm coupling assembly comprises a resilient disc secured at or adjacent its periphery to a connection flange on or carried by one ofthe shafts to be coupled and fixed radially inwardly of its periphery for rotation with a torque transmission member connected to the gear coupling arrangement.

4. Acoupling arrangement as claimed in Claim 3 in which the gear coupling arrangement comprises a first gear having radially outwardly directed teeth engaged co-axially with a second gear having radially inwardly directed teeth.

5. A coupling arrangement as claimed in any preceding Claim, in which the gears ofthe gear assembly have straight teeth.

6. Acoupling arrangement as claimed in any of Claims 1 to 4, in which the gears ofthe gearassembly have curved teeth.

7. Acoupling arrangement as claimed in any of Claims 3to 6, in which thetorquetransmission member is a hollowtubularelement.

8. A coupling arrangement as claimed in any of Claims3to 7 in which the said connection flange per ipherally secured to the said resilient disc is itself a resilient disc mountable on one ofthe said two shafts to be coupled.

9. Acoupling arrangement as claimed in any of Claims 4to 8, in which the said second gear is constituted by teeth formed on the interior of the said hollow transmission element.

10. Acoupling arrangement substantially as hereinbefore described with reference to, and as shown in, Figure 1 or Figure 2 or Figure 3 or Figure 4 ofthe accompanying drawings.

11. Any novel integerorstep, orcombination of integers or steps, hereinbefore described and/or shown in the accompanying drawings, irrespective of whether the present Claim is within the scope of, or relates to the same or a different invention from that ofthe preceding Claims.