GB1580540A

GB1580540A - Toothed rotary coupling

Info

Publication number: GB1580540A
Application number: GB26085/77A
Authority: GB
Original assignee: ZF Friedrichshafen AG
Current assignee: ZF Friedrichshafen AG
Priority date: 1976-06-23
Filing date: 1977-06-22
Publication date: 1980-12-03
Also published as: DE2628038C3; FR2356047A1; DE2628038A1; SE7707081L; IT1115864B; DE2628038B2

Description

(54) TOOTHED ROTARY COUPLING (71) We, ZAHNRADFABRIK FRIED RICHSHAFEN AKTIENGESELLSCHAFT, of Friedrichshafen - on - the - Bodensee, Federal Republic of Germany, a Joint-Stock Company organised under the laws of the Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a toothed coupling for connecting a transmission gearing, particularly a hydrodynamic torque converter, to a driving engine, particularly an internal combustion engine, such as are mainly used in motor vehicles.

As is well known, a torque converter can be connected to a driving engine, particularly aii internal combustion engine, by different kinds of couplings, for example with the aid of simple diaphragm couplings, curved toothed couplings with once-through lubrication, and rotationally fast connections with roller-shaped coupling elements between annularly superimposed driving and driven parts.

Simple diaphragm couplings consist essentially of two or more sheet metal diaphragms fastened at their inner edge to the engine flywheel, while the outer part is bolted to the torque converter. This coupling entails considerable expense for assembly, since after the parts (torque converter and engine) have been brought together the outer bolts fastening the diaphragms to the torque converter must be tightened one by one. Because of the shortage of space this is done through an axial opening on the engine side of the flywheel casing with the aid of an offset spanner. For this purpose the flywheel is turned tooth by tooth through the top dead centre window in the flywheel casing until the respective bolt comes to lie in front of the axial opening. This work requires considerable attention on the part of the fitter, in order to ensure that no bolt is omitted and that the prescribed tightening torque for the bolt is observed. The time required for assembly is also correspondingly long. Since the diaphragm coupling is situated axially between the flywheel and the torque converter, considerable space is required for it.

Furthermore, in most cases it is not possible to dispense with length adjustment on the transmission side, because the diaphragms would fracture if subjected to excessive axial deflection.

Another known diaphragm coupling is the clamp ring connection with diaphragm. This coupling also consists of a double sheet metal diaphragm which at its inner edge is bolted to the torque converter and at its outer edge has a centring ring. On its face turned towards the converter the flywheel is in turn provided with a clamp ring which comes to surround the centring ring. For assembly purposes the diaphragm is bolted to the torque converter and its centring ring is aligned accurately. It must be carefully checked whether the matching surfaces between the clamp ring and centring ring are clean and free from grease, and if necessary they must be cleaned and degreased. The engine is then moved up to the torque converter until its flywheel comes to lie with the clamp ring fastened on it exactly above the centring ring. The tangential bolt of the clamp ring is then tightened.

This entire assembly operation is very timeconsuming and moreover the coupling takes up a great deal of space.

Once-through lubricated curved tooth couplings are also known, particularly for special kind of transmissions. These are steel-on-steel couplings which in order to prevent the rapid occurrence of contact corrosion must have an adequate throughflow of lubricating oil, which necessarily entails onerous and relatively expensive delivery of oil, together with seals, and soon. Because of losses through splashing this coupling results in reduced efficiency.

Couplings are known which consist essentially of a driving plate fixed in respect of rotation and sliding to the engine shaft and having, on its peripheral edge, bowl-shaped semi-cylindrical bulges which are open inwards, i.e. towards the shaft, while the transmission gear casing cover has identical bowl-shaped semi-cylindrical bulges which are open outwards, i.e. in the opposite direction to that of the bulges of the driving plate, the superimposed bulges forming cylindrical cavities. These cylindrical cavities contain fitting plastics rollers which may be joined together by a web, thus forming a ring of rollers. For the installation of this coupling the rollers are inserted in the bulges of the casing cover and the driving plate is then pushed on, so that a rotationally fast connection is made. This connection is space-saving and at the same time comPensates for plays but it cannot transmit high torques such as occur in a motor vehicle, because the plastics material of the rollers does not withstand heavy shearing stresses.

In marine transmission gears rotationally fast connections are known (Twin Disc Bulletin No. 313.B), in which the driving element and the driven element are likewise disposed concentrically one within the other and have external and internal teeth pointing towards one another, while rubber sleeves of relatively large volume are disposed over the teeth of the inner toothed ring and serve as coupling elements. Through the high coefficient of friction and adhesion of the rubber the sleeve adheres to the flanks of the teeth and the entire relative movements which have to be compensated by the coupling are taken up in the soft rubber of large volume (buffer function). Depending on the torque to be transmitted and the size of the coupling, the hardness of the rubber mixture must vary. In order to withstand heavier torques the coupling teeth provided with rubber sleeves are arranged in two rows, which means a loss of space. Because of the restricted space available and the closed shape of the casing in motor vehicles the coupling may be subjected to heating to about 130"C because of its proximity to the torque converter and engine. However, the elastic material of the sleeves will tolerate an operating temperature of a maximum of only 120"C, so that it cannot be used in rotationally fast connections for motor vehicles having torque converter transmissions.

Unlike marine transmission gears, the motor vehicle torque converter does not have its own mounting on the engine side, but is supported by means of the coupling on the parts joined to the engine shaft. Because of their sleeve-like shape and also because of the very elastic material, known rubber coupling parts are unsuitable for this radial mounting, since they are too elastic for radial support and permit excessive radial movement.

The problem underlying the invention is that of providing a toothed coupling between a driving engine and a torque converter, particularly for vehicles, which while of spacesaving, compact construction and of a type which can be produced inexpensively, is distinguished by simple installation which can be effected as quickly as possible and by ease of servicing. Furthermore, the coupling should require no maintenance, should be silent and vibration damping, while it should permit the radial mounting of parts of the torque converter transmission or of the torque converter with a self-centring action during operation. The relative axial movements and difference in length between engine and transmission gear and also installation tolerances should be compensated.

Accordingly, the present invention consists in a toothed coupling, comprising an outer internally toothed ring connectible to a driving engine, for example to an internal combustion engine via a flywheel, an inner externally toothed ring meshing with the outer ring with a predetermined clearance between the tooth flanks of the meshing teeth and connectible to a member adapted to be driven by said engine, for example the casing of a hydrodynamic torque converter, and a cap member of plastics material (as hereinafter defined) mounted on each tooth of the outer ring and filling the gap constituted by said clearance, the plastic material being substantially non-elastic and resistant to pressure and friction and being heatresistant.

The invention also consists in a toothed coupling for connecting a gearing, particularly a torque converter transmission, to a driving engine, for example an internal combustion engine, wherein an outer ring element fastened on the engine shaft, for example the flywheel, has internal teeth which are disposed concentrically around external teeth on an inner ring on the transmission casing, and wherein over each tooth of the outer ring coupling elements are disposed which enclose the peripheral surface of the respective tooth and which fill the gap between the tooth flanks of the two meshing rings, the inner and outer profiles of each coupling element being identical to the tooth flank profile of the inner or outer toothed ring of the coupling and the coupling elements being constructed as caps which are mounted on the teeth of the outer toothed ring, the caps being made of plastic material which is substantially non-elastic and resistant to pressure and friction and is heatresistant. The cap members, in internal and external profile are identical with the tooth profile of the inner and outer rings of teeth respectively of the coupling. The cap members are mounted on the outer ring in the unfitted state, and remain firmly seated there because of special means provided or of special construction. The parts can now simply be pushed together and the coupling can be regarded as completely installed. Centrifugal force during operation increases the adhesion of the cap members on the outer ring of teeth.

The coupling of the invention provides the advantage of effecting compensation for all relative movements and differences in length between engine and transmission gear, particularly resulting from thermal expansion, shaft alignment errors, such as wobble eccentricity, fitting tolerances, and so on. The coupling of the invention effects the radial mounting of parts of the torque converter transmission or torque converter with a selfcentring action during operation, while at the same time completely transmitting the torque. The substantially non-elastic cap members of the coupling have nevertheless a noise and vibration damping action. At the same time the coupling requires no maintenance and no lubrication. The teeth of this coupling do not require heat treatment, that is to say tempering or hardening, because the relative movements take place between the tooth flanks of the inner ring of teeth and the plastics cap members, whose material is selected to withstand the heavy stressing (pressures, friction, temperature). The term "plastics material" is herein defined as a material of predominantly plastics composition which may include a filler of a metallic or mineral composition. For the cap members, the plastics material used is preferably PTFE which can be very satisfactorily used together with bronze, bronze and graphite and minerals, such as mica. Furthermore, polyamides can also be used with PTFE.

Another advantage of the invention is its small compact construction, which requires small axial space. Furthermore, the invention can be put into practice very inexpensively. The expedient formation of insertion bevels and precentring diameters on the different component parts permit rapid assembly without problems, and even assembly without visibility. This factor is very important, since, for example in a motor vehicle, very little space is available. Moreover, the time required for assembly is drastically reduced by using a coupling of the invention.

The particular construction of the cap arrangement, in which a number of cap members are connected together to form a multiple cap, can still further reduce the time required for fitting the cap members on the outer ring, thus still further reducing the total time required for assembly. By virtue of the simple construction of the coupling, mechanical fitting of the cap members on the outer ring is possible, thus enabling the assembly of the coupling to be included in automated production processes.

The toothed coupling of the invention considerably facilitates servicing, that is to say in comparison with diaphragm couplings only a single type of torque converter is now required instead of the four types needed hitherto, since with only one torque converter connection geometry it is possible to comply with the installation conditions of all engines used at the present time with torque converter transmissions. This again considerably reduces the cost of manufacture and stockkeeping.

In order that the invention may be more readily understood, reference is made to the accompanying drawings which illustrate diagrammatically and by way of example embodiments thereof, and in which: Figure 1 shows in elevation a hydrodynamic torque converter connected to a driving engine, the toothed coupling of the invention being shown in partial section; Figure 2 is an enlarged sectional view through the toothed coupling of the invention, showing a first kind of cap members used; Figures 3A and 3B are two cross-sections on the line III-III of Figure 4 of a cap member of the invention according to Figure 2, showing two kinds of opening; Figure 4 is a plan view of a cap member according to Figures 2 and 3; Figure 5 is a section through the toothed coupling of the invention, with a second kind of cap member; Figure 6 is a side view of the cap member shown in Figure 5; Figure 7 is a plan view of the cap member of Figures 5 and 6; Figure 8 is a section through the toothed coupling of the invention, with a third kind of cap; Figure 9 is a side view of the cap member of Figure 8; Figure 10 is a longitudinal section through a cap member of a fourth kind; Figure 11 is a side view of the cap member according to Figure 10; Figure 12 is a plan view of the cap member according to Figures 10 and 11; Figure 13 is a longitudinal section through a toothed coupling according to the invention, with a fifth kind of cap; Figure 14 is a side view of the cap member according to Figure 13; Figure 15 shows an enlarged view of detail A in Figure 13; Figure 16 is a longitudinal section through a toothed coupling of the invention, with a sixth kind of cap member; Figure 17 is a view from below of a cap member according to Figure 16, in a first variant; Figure 18 is a longitudinal section of a cap member according to Figures 16 and 17 with two rectangular openings; Figure 19 is a side view of a cap member according to Figures 17 and 18; Figure 20 is a view from below of a second variant of a cap member according to Figure 16; Figure 21 is a longitudinal view of a cap member according to Figures 16 and 20 with slit-shaped openings; Figure 22 is a side view of a cap member according to Figures 16, 20, 21; Figure 23 is an end view of a tooth of the toothed outer ring with recesses for mounting a cap member of a seventh kind; Figure 24 is an elevation of a tooth according to Figure 23; Figure 25 is an end view of a cap member of the seventh kind; Figure 26 is a longitudinal section through a cap member according to Figure 25; Figure 27 is an end view of a tooth of the outer toothed ring with recesses for mounting a cap member of an eighth kind; Figure 28 is an elevation of a tooth according to Figure 27, Figure 29 is an end view of a cap member of the eighth kind; Figure 30 is a longitudinal section through a cap member according to Figure 29; Figure 31 is a longitudinal section through a toothed coupling according to the invention, showing a cap member of a ninth kind; Figure 32 is a perspective view of a cap member according to Figure 31; Figure 33 is a partial radial section through a toothed coupling according to the invention with a multiple cap arrangement (tenth kind); Figure 34 is a longitudinal section through a cap member of an eleventh kind, with a tooth; Figure 35 shows a cap member in a section on the line XXXV-XXXV of Figure 34; and Figure 36 is a plan view of the cap member according to Figures 34 and 35.

A driving engine 1, for example an internal combustion engine, having a flywheel 2 is made rotationally fast by way of a toothed coupling 30 with a hydrodynamic torque converter, as can be seen in Figure 1. The coupling 30 consists of a so-called inner toothed ring which is provided with external teeth 8 and is mounted frontally or preferably peripherally on the converter 3, of an outer toothed ring 4 which is provided with internal teeth 9 and which is fastened to or is integral with the flywheel 2, and of cap members 31 or 32 (Figs. 2 to 4) for the teeth 9.

The converter component provided with the teeth 8 has a relatively large insertion bevel 5 and also a guide diameter 6 which corresponds to the smallest tip circle diameter of the caps in the toothed ring 4. The teeth 8, 9 of the two rings and the caps in turn have large insertion bevels 7 which facilitate assembly. The caps 31 to 43 may be made in a multiplicity of shapes in respect of axial and also radial fastening on the teeth 9. The teeth 9 of the toothed ring 4 are adapted correspondingly to the cap fastening.

Figures 2 to 4 show two embodiments of caps, i.e. caps 31 and 32, wherein for radial securing the cap is provided with a projection 12 while the tooth 9 has a correspondingly shaped recess. For axial securing of the cap the tooth 9 is provided with a pin 10 which engages a corresponding aperture 11 or 11' in the cap 31 or 32. This aperture may be of rectangular shape 11 or in the form of a through-slot 11 Figures 5 to 7 show another cap 33 which has a recess 33' into which a projection 14 on the tooth 9 projects for the purpose of securing the cap 33 axially, a shoulder 13 in the tooth 9 serving for radial securing of the cap 33.

The cap 34 in Figures 8 and 9 has for the purpose of radial fastening a bead 25 on each side wall which beads engage in corresponding recesses 24 in the tooth 9. For axial positioning the tooth has a recess 29 in the longitudinal direction, into which the cap fits over its length. With the same shape of tooth the cap may be shaped like the cap 35 in Figures 10,11 and 12, where the width of the side parts of the cap exceeds the bottom part, extending over the entire length of the tooth and thus enlarging the transmission area.

Moreover the tooth 9 may have a similar recess to that in Figure 8 and in addition be provided with a projection 15 which in conjunction with a recess 16 in a cap 36 ensure axial and also radial securing.

Figures 13 to 15 show a V-shaped cap 36, which for the purpose of axial positioning is inserted into a recess 29 on the tip of the tooth 9, radial securing being effected by means of a projection 15 at the outer end of the recess and an inclined recess 16 at the base of the cap.

Figures 16 to 22 show a cap 37, 38 which is mounted on a tooth 9 provided with two pins 10 of the kind shown in Figure 2. Here the cap 37 has a radial opening 11, while in the cap 38 the opening 11' is in the form of a slit.

As illustrated in Figures 23 to 26, a cap 39 is provided for securing purposes with a round hump 18 on each of its two inner flanks, each hump fitting into a recess 17 in the tooth flanks.

A cap 40 of the kind shown in Figures 27 to 30 may be provided on each of its inner flanks with a longitudinal bead 20 of any shape, which engages in a corresponding recess 19 in the flank of the tooth 9.

Another cap 41 of the type shown in Figures 31 and 32 has a front wall 23 and a web 21 projecting far into the tooth 9.

In order to facilitate assembly the caps are provided with insertion bevels 22.

A cap 43 of the kind shown in Figures 34 to 36 is provided on each of its shorter sides with a recess 27 into each of which a front bead 28 on the teeth 9 fits. A projection 26 over each of the recesses effects the radial positioning of the cap 43.

All the caps 31 to 43 may be combined to form multiple caps 42 as in Fig. 33. The multiple caps 42 consist of two or more caps which are joined together and of which all or at least one, if possible the middle one, have a fastening action.

The mounting of the caps or multiple caps on the toothed ring 4 is effected relatively simply, individually or a plurality at a time, either by hand or automatically in suitable machines.

The operation of assembling the coupling is initiated with the aid of the insertion bevel 5 and the adjoining continuous guide diameter 6, which corresponds to the smallest tip circle diameter of the caps in the toothed ring 4. The coupling parts are thereby precentred radially. This results in easy insertion into the toothing, which, like the caps, also has insertion bevels 7 and 22 respectively.

After complete assembly only the flanks of the coupling teeth will be in contact with the interposed cap flanks, taking over the radial mounting of the transmission. In practice this permits mounting without visibility, which results in a considerable saving of time and energy.

WHAT WE CLAIM IS: 1. A toothed coupling, comprising an outer internally toothed ring connectible to a driving engine, for example to an internal combustion engine via a flywheel, an inner externally toothed ring meshing with the outer ring with a predetermined clearance between the tooth flanks of the meshing teeth and connectible to a member adapted to be driven by said engine, for example the casing of a hydrodynamic torque converter, and a cap member of plastics material (as hereinbefore defined) mounted on each tooth of the outer ring and filling the gap constituted by said clearance, the plastics material being substantially non-elastic and resistant to pressure and friction and being heat resistant.

2. A toothed coupling for connecting a gearing, particularly a torque converter transmission, to a driving engine, for example an internal combustion engine, wherein an outer ring element fastened on the engine shaft, for example the flywheel, has internal teeth which are disposed concentrically around external teeth on an inner ring on the transmission casing, and wherein over each tooth of the outer ring coupling elements are disposed which enclose the peripheral surface of the respective tooth and which fill the gap between the tooth flanks of the two meshing rings, the inner and outer profiles of each coupling element being identical to the tooth flank profile of the inner or outer toothed ring of the coupling, and the coupling elements being constructed as caps which are mounted on the teeth of the outer toothed ring, the caps being made of plastics material which is substantially non-elastic and resistant to pressure and friction and is heat-resistant.

3. A toothed coupling according to claim 1 or 2, wherein for securing the cap members on the teeth of the outer ring, each cap member is provided with a projection located internally on an end wall of the cap member and engaging a recess at the root of the tooth, each of the teeth having a pin on the crest of the tooth which pin engages an aperture in the portion of the cap covering the tooth crest.

4. A toothed coupling according to claim 1 or 2, wherein for securing the cap members on the teeth of the outer ring, each of said teeth is provided with a projection which has a shoulder and which engages in an L-shaped recess provided in an end wall of the cap member.

5. A toothed coupling according to claim 1 or 2, wherein for securing cap members of substantially V-shaped cross-section on the teeth of the outer ring, each of said teeth has in its crest a recess into which the cap member fits over its entire length or by part of its base, each said cap member being provided at the upper part of its inner flanks with a bead which engages in a recess at the root of the tooth.

6. A toothed coupling according to claim 1 or 2, wherein for secunng cap members of substantially V-shaped cross-section on the teeth of the outer ring, each said tooth has in its crest a recess which is provided with a projection and in which engages the base of the cap member, which base has an inclined recess which co-operates with said projection.

7. A toothed coupling according to claim 1 or 2, wherein for securing cap members of the substantially V-shaped cross-section on the teeth of the outer ring, each said cap member has two openings into which pins on the crest of the tooth project, and wherein the openings are in the form of radial through recesses or of transverse slots.

8. A toothed coupling according to claim 1 or 2, wherein for securing cap members of substantially V-shaped cross-section on the teeth of the outer ring, each said cap member is provided on its inner flanks with one or more bulges, the tooth flanks being correspondingly provided with one or more recesses receiving said bulges.

9. A toothed coupling according to claim

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Claims

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21 projecting far into the tooth 9.

In order to facilitate assembly the caps are provided with insertion bevels 22.

A cap 43 of the kind shown in Figures 34 to 36 is provided on each of its shorter sides with a recess 27 into each of which a front bead 28 on the teeth 9 fits. A projection 26 over each of the recesses effects the radial positioning of the cap 43.

All the caps 31 to 43 may be combined to form multiple caps 42 as in Fig. 33. The multiple caps 42 consist of two or more caps which are joined together and of which all or at least one, if possible the middle one, have a fastening action.

The mounting of the caps or multiple caps on the toothed ring 4 is effected relatively simply, individually or a plurality at a time, either by hand or automatically in suitable machines.

The operation of assembling the coupling is initiated with the aid of the insertion bevel 5 and the adjoining continuous guide diameter 6, which corresponds to the smallest tip circle diameter of the caps in the toothed ring 4. The coupling parts are thereby precentred radially. This results in easy insertion into the toothing, which, like the caps, also has insertion bevels 7 and 22 respectively.

After complete assembly only the flanks of the coupling teeth will be in contact with the interposed cap flanks, taking over the radial mounting of the transmission. In practice this permits mounting without visibility, which results in a considerable saving of time and energy.

WHAT WE CLAIM IS: 1. A toothed coupling, comprising an outer internally toothed ring connectible to a driving engine, for example to an internal combustion engine via a flywheel, an inner externally toothed ring meshing with the outer ring with a predetermined clearance between the tooth flanks of the meshing teeth and connectible to a member adapted to be driven by said engine, for example the casing of a hydrodynamic torque converter, and a cap member of plastics material (as hereinbefore defined) mounted on each tooth of the outer ring and filling the gap constituted by said clearance, the plastics material being substantially non-elastic and resistant to pressure and friction and being heat resistant.
2. A toothed coupling for connecting a gearing, particularly a torque converter transmission, to a driving engine, for example an internal combustion engine, wherein an outer ring element fastened on the engine shaft, for example the flywheel, has internal teeth which are disposed concentrically around external teeth on an inner ring on the transmission casing, and wherein over each tooth of the outer ring coupling elements are disposed which enclose the peripheral surface of the respective tooth and which fill the gap between the tooth flanks of the two meshing rings, the inner and outer profiles of each coupling element being identical to the tooth flank profile of the inner or outer toothed ring of the coupling, and the coupling elements being constructed as caps which are mounted on the teeth of the outer toothed ring, the caps being made of plastics material which is substantially non-elastic and resistant to pressure and friction and is heat-resistant.
3. A toothed coupling according to claim 1 or 2, wherein for securing the cap members on the teeth of the outer ring, each cap member is provided with a projection located internally on an end wall of the cap member and engaging a recess at the root of the tooth, each of the teeth having a pin on the crest of the tooth which pin engages an aperture in the portion of the cap covering the tooth crest.
4. A toothed coupling according to claim 1 or 2, wherein for securing the cap members on the teeth of the outer ring, each of said teeth is provided with a projection which has a shoulder and which engages in an L-shaped recess provided in an end wall of the cap member.
5. A toothed coupling according to claim 1 or 2, wherein for securing cap members of substantially V-shaped cross-section on the teeth of the outer ring, each of said teeth has in its crest a recess into which the cap member fits over its entire length or by part of its base, each said cap member being provided at the upper part of its inner flanks with a bead which engages in a recess at the root of the tooth.
6. A toothed coupling according to claim 1 or 2, wherein for secunng cap members of substantially V-shaped cross-section on the teeth of the outer ring, each said tooth has in its crest a recess which is provided with a projection and in which engages the base of the cap member, which base has an inclined recess which co-operates with said projection.
7. A toothed coupling according to claim 1 or 2, wherein for securing cap members of the substantially V-shaped cross-section on the teeth of the outer ring, each said cap member has two openings into which pins on the crest of the tooth project, and wherein the openings are in the form of radial through recesses or of transverse slots.
8. A toothed coupling according to claim

1 or 2, wherein for securing cap members of substantially V-shaped cross-section on the teeth of the outer ring, each said cap member is provided on its inner flanks with one or more bulges, the tooth flanks being correspondingly provided with one or more recesses receiving said bulges.
9. A toothed coupling according to claim

1 or 2, wherein for the radial securing of the cap members of substantially V-shaped cross-section on the teeth of the outer ring, there is provided on each of the inner flanks of the cap member a longitudinal bead which engages in a respective recess extending along the tooth flanks.
10. A toothed coupling according to claim 1 or 2, wherein for the securing of the cap members on the teeth of the outer ring, each cap member is provided with a front wall and a web fitting into a radial slotshaped recess in the crest of the tooth.
11. A toothed coupling according to claim 1 or 2, wherein for the securing of the cap members on the teeth of the outer ring, the cap members are closed on all four sides, and wherein on each of the shorter sides a recess and a projection are provided which engage over respective beads on the end faces of the said teeth.
12. A toothed coupling according to claim 1 or 2, and any of claims 3 to 11, wherein two or more cap members are combined to form a multiple cap arrangement, all the partial cap members or at least one of them, preferably the centre one, in each case being a supporting cap member.
13. A toothed coupling, substantially as herein described with reference to and as shown in the accompanying drawings.