EP0483029B1 - High pressure hydraulic generator-receiver for power transmission - Google Patents

Description

The present invention refers to a hydraulic generator-receiver for power transmission.

EP 0165884 describes such an apparatus comprising two pinions 9, 10 coupled inside a stator, at least one of them being devoid of mechanical bearing, which stator also comprises at least one opening. inlet 40 and a discharge opening 40 for a pressurized liquid, while two flanges 21, 22 close the stator on either side of the two pinions 9, 10 on which they provide a lateral seal.

EP 0 262 189 has described such an apparatus, the drive pinion 9 of which alone is provided with mechanical bearings 123.

The stator comprises a flexible envelope 36 subjected externally to a centripetal pressure which enables it to ensure sealing on the tops of the teeth of the pinions 9, 10 with helical teeth located in the envelope 36. Hydrostatic compensation forces on the flanges 21, 22 and on the envelope 36 come on the one hand from the pressure of the area 34 of permanent total pressure and on the other hand from the pressure prevailing in the hydrostatic balancing compensation sectors 38 and 60 respectively of the envelope and flanges. Said sectors are supplied by channels 43 and 23. Two covers 54, 55 cover said flanges while a body 49 surrounds the envelope 36.

The internal hydraulic balancing is ensured by a hydraulic winding comprising rotor conduits in the pinions 9 and 10 and stator in the flanges 21 and 22 and the casing 36, the successive switching between the rotor and stator conduits being ensured by their scrolling ends one in front of the other on a switching circle 20. Balancing between the hollow of teeth is ensured by the permanent connection between the hollow of opposite teeth for an even number of teeth, and the hollow of opposite teeth with an offset of one demipas for an odd number of teeth via the conduits 23 of the flanges and of the channels formed in the pinions. Of course, this connection does not exist between the engagement zone 3 and those respectively 6, in which hydraulic bearings are created diametrically opposite to the engagement point 3 of the pinions 9 and 10. Thus, at during the rotation of the pinions 9 and 10, said winding relates the pairs of opposite teeth so as to obtain the same hydraulic pressure in the hollow of teeth for diametrically opposite angular positions and to create two opposite forces on the pinions in sight to cause them to mesh without play in zone 3.

In EP 262189, the rotor circuits in the pinions 9, 10 are constituted by groups of conduits 102 diametrically opposite on the switching circle 20 and parallel (or inclined to the value of the angle of the propeller) to the axis pinions 9, 10 and radial 101, joining the opposite conduits 102 of the π to form an H. The stator circuits are constituted by the grooves 23, the connections 30 and the conduits 43. The high pressure supply of the zone 34 of permanent total pressure is effected by a preferential valve system also allowing the decompression of this zone 34 when desired. Seal anti-extrusion devices are incorporated in the hydrostatic compensation sectors 38 and 60 respectively delimited by the seals 37 and 45, the zone 34 being defined outside these seals and closed on the axis of the pinions 9 and 10 by the seals 58.

The embodiment according to EP 0 262 189 entails risks of deformation of the plastic flanges 21 and 22 in the areas where they have the grooves 100 when in them the low pressure prevails, while the outside of the flanges is in permanent total high pressure from zone 34. Likewise, this embodiment has provided anti-extrusion seal devices also serving as reinforcement for plastic parts at the outlet orifices 40. These devices are not entirely satisfactory, lead to produce the outlet orifices 40 only in the flanges and covers and do not allow their production in the casing 36 and the body 49, which casing could be deformed by the action of the High Pressure.

Finally, for large displacements, the increase in the diameter of the pinions leads to an increase in the number of sectors in proportion, which gives a more costly realization as a result of the greater number of sectors and more difficult to balance due to the sectors under pressure intermediaries.

The improvements which are the subject of the present invention aim to remedy these drawbacks and to allow the production of a generator-receiver which responds particularly well to the wishes of the practice.

To this end, to avoid the risk of collapse of the flanges, provision has been made to drown in each flange a reinforcing insert, one face of which is flush with its internal wall opposite each gear 9, 10. In addition, the covers and the body have projections directed towards the interior of the device and suitable for penetrating into depressions of the flanges and of the casing respectively, said depressions being formed in the hydrostatic compensation sectors of the flanges and of the casing. In order to facilitate the adjustments of the plastic parts to one another, that is to say the flanges and the casing, the projections of the covers and of the body have sections with oblique faces with respect to which said plastic parts are forced up. The devices for supplying zone 34 and for returning leaks have been simplified. To reduce the action of the area 34 on the flanges at the grooves 100, in particular when the latter are at low pressure, this area 34 has been reduced in surface area and therefore in resulting force by a new relative arrangement of the joints. 58 and 45, 45 'and 45' '. Finally, for large displacements, the solution adopted consists in multiplying the number of satellites (pinions driven by the main pinion), each satellite always having four sectors (2 HP and 2 BP), and the main pinion a number of sectors depending on the number of satellites, the sectors always being either HP or BP and separated from each other by the zone 34 of value corresponding to the value of the "hydraulic bearings" in 6.

• Fig. 1 est une coupe longitudinale d'un appareil comportant les perfectionnements suivant l'invention.
• Fig. 2 est une vue partielle d'un flasque vu à partir de l'intérieur de l'appareil.
• Fig. 3, 4 et 5 sont des coupes suivant III-III, IV-IV et V-V (fig. 2).
• Fig. 6 est une coupe transversale de l'appareil suivant l'invention.
• Fig. 7 est une coupe suivant VII-VII (fig. 1), on y a fait figurer en I-I et VI-VI les plans de coupe de fig. 1 et 6.
• Fig. 8 est une coupe suivant VIII-VIII (fig. 7 et 11).
• Fig. 9 est une coupe développée partielle illustrant l'intérieur de l'enveloppe.
• Fig. 10 est une coupe suivant X-X (fig. 9). On y a représenté le plan de coupe de fig. 9.
• Fig. 11 est une coupe suivant XI-XI (fig. 1). On y a représenté le plan de coupe de fig. 6.
• Fig. 12 est une vue extérieure partielle de l'enveloppe qui entoure les pignons.
• Fig. 13 est une coupe suivant XIII-XIII (fig. 12).
• Fig. 14 est une coupe suivant XIV-XIV (fig. 12). On y a représenté en XIII-XIII le plan de coupe de fig. 13.
• Fig. 15 est une vue développée partielle de l'extérieur de l'enveloppe.
• Fig. 16 est une coupe partielle suivant XVI-XVI (fig. 8 et 15).
• Fig. 17 est une coupe semblable à celle de fig. 16, mais illustrant une variante de réalisation.
• Fig. 18 est une coupe partielle suivant XVIII-XVIII (fig. 20) illustrant la nouvelle disposition relative des joints 58 et 45 côté pignon mené 10.
• Fig. 19 est une coupe partielle suivant XIX-XIX (fig. 21) illustrant la nouvelle disposition relative des joints 58 et 45 côté pignon menant 9.
• Fig. 20 est une coupe suivant XX-XX (fig. 18) montrant la rainure 100 incorporée dans le secteur 60, côté pignon mené 10. On a représenté en XVIII-XVIII le plan de coupe de fig. 18.
• Fig. 21 est une coupe suivant XXI-XXI (fig. 19) montrant la rainure 100 incorporée dans le secteur 60, côté pignon menant 9. Le plan de coupe de XIX-XIX de fig. 19 est montré sur cette figure.
• Fig. 22 et 23 montrent un générateur-récepteur suivant l'invention comportant deux et trois pignons satellites et illustrés couvercle et flasque enlevés.

The appended drawing, given by way of example, will allow a better understanding of the invention, the characteristics which it presents and the advantages which it is capable of providing:

• Fig. 1 is a longitudinal section of an apparatus comprising the improvements according to the invention.
• Fig. 2 is a partial view of a flange seen from inside the apparatus.
• Fig. 3, 4 and 5 are sections along III-III, IV-IV and VV (fig. 2).
• Fig. 6 is a cross section of the apparatus according to the invention.
• Fig. 7 is a section along VII-VII (fig. 1), there are shown in II and VI-VI the section planes of fig. 1 and 6.
• Fig. 8 is a section along VIII-VIII (figs. 7 and 11).
• Fig. 9 is a partial developed section illustrating the interior of the envelope.
• Fig. 10 is a section along XX (fig. 9). There is shown the section plane of FIG. 9.
• Fig. 11 is a section along XI-XI (fig. 1). There is shown the section plane of FIG. 6.
• Fig. 12 is a partial exterior view of the envelope which surrounds the pinions.
• Fig. 13 is a section along XIII-XIII (fig. 12).
• Fig. 14 is a section along XIV-XIV (fig. 12). There is shown in XIII-XIII the section plane of FIG. 13.
• Fig. 15 is a partial developed view of the exterior of the envelope.
• Fig. 16 is a partial section along XVI-XVI (fig. 8 and 15).
• Fig. 17 is a section similar to that of FIG. 16, but illustrating an alternative embodiment.
• Fig. 18 is a partial section along XVIII-XVIII (fig. 20) illustrating the new relative arrangement of the joints 58 and 45 on the driven pinion side 10.
• Fig. 19 is a partial section along XIX-XIX (fig. 21) illustrating the new relative arrangement of the joints 58 and 45 on the driving pinion side 9.
• Fig. 20 is a section along XX-XX (FIG. 18) showing the groove 100 incorporated in the sector 60, on the driven pinion side 10. The section plane of FIG. 18.
• Fig. 21 is a section along XXI-XXI (fig. 19) showing the groove 100 incorporated in the sector 60, pinion side leading 9. The section plane of XIX-XIX of fig. 19 is shown in this figure.
• Fig. 22 and 23 show a generator-receiver according to the invention comprising two and three planet gears and illustrated cover and flange removed.

As illustrated in fig. 1 to 6, each of the flanges 21, 22 made of plastic material, comprises a reinforcement piece produced in the form of an insert 207. The plastic material of each flange is overmolded on the insert 207, the outer face of which is flush with the inner one of each flange. The insert is made of a metallic material with a high coefficient of friction since it is in sliding contact with the pinions 9, 10. The insert 207 has in profile in plan the shape of a face of glasses that is - say that it has two circular parts joined by a bi-concave junction 211 (fig. 2). The bi-concave junction 211 can be entirely inserted into the plastic for the part concerning the friction concerning the teeth at the point of engagement 3: the friction on the faces of teeth is then carried out by the plastic and makes it possible to better compensate for the differences in width H between the teeth of the driving and driven pinions, of the order of a hundredth of a millimeter.

It is observed that the insert 207 has grooves 210 (FIGS. 2 and 5) in which the plastic material constituting the flanges 21, 22 penetrates to form a bead in which is formed each cell 100 located on the switching circle 20 and connected by channel 23 to the connecting conduits 30.

Each circular part of the insert 207 has three radial tabs 209 facing outwards and arranged between the grooves 210 and corresponding to the hydraulic bearings (fig. 2).

In the hydrostatic balancing inter-sector zones and those of the hydraulic bearings, recesses 205 facilitate the cooling of the plastic after the injection operation and give greater flexibility to the flanges 21, 22 (fig. 3 and 7). ).

It is noted that grooves 215 are provided on the face of each insert 207 in contact with the pinions 9 and 10 to create fluid bearings.

To facilitate understanding, the sectors which are adjacent to the meshing zone 3 of the pinions 9 and 10 have been referenced 60 ′ and 60 ″. They roughly affect a shape with double curvature or in policeman's hat (fig. 8 ), the sector 60 '' being of shorter length than that of the sector 60 'due to the configuration of the balancing sectors of the flanges 21 and 22.

Illustrated in fig. 6, 7 and 8 the manner in which the flanges 21 and 22 are anchored with respect to the covers 54, 55. Each of them has projections 201 arranged symmetrically with respect to the engagement zone 3 of the pinions 9 and 10 (fig. 7) and extending in the balancing sectors 60 of the flanges 21, 22. A projection 201 'shaped as an inverted policeman's cap, integral with each cover 54, 55 is arranged in one of the balancing sectors 60' located partly opposite the two pinions 9 and 10. Another projection 201 '' in the sector 60 '' is provided on the covers 54, 55 opposite that 201 '. Its shape is similar to that of the latter, but it is more restricted in length due to the configuration of the balancing sectors on the flanges 21, 22.

The projections 201, 201 ', 201''forcefully engage in the recesses of the flanges 21-22 so as to ensure a tightening at the joints 45, 45' and 45 '' and a play elsewhere, this engagement and this tightening is allowed by a tilt difference of the order of 5 ° between the respective faces which cooperate. Note that the ends of the stripped faces of the projections 201, 201 ', 201''are hollowed out by pressure distribution grooves 202, 202', 202 '' respectively.

The protrusions considered of the covers constitute anti-extrusion devices for seals, which are force-fitted in the recesses of the flanges at the seals 45, 45 ', 45' '.

We have shown in fig. 6, 8, 9, 10 and 11 that, in the same way that the flanges are anchored relative to the covers, provision has been made to spare in the internal face of the body 49 of the bosses 203, 203 'extending in the balancing sectors 38 and 38' and constituting anti-extrusion devices for the joint cooperating with depressions produced in correspondence in the envelope 36. These bosses 203 and 203 'engage by force in the recesses of the envelope 36, so as to ensure a tightening at the level of the seals 37 and 37' and a play elsewhere, this engagement and this tightening being allowed by a tilting deviation of the order of 5 ° between the respective faces which cooperate. The ends of the bosses 203, 203 'are provided with pressure distribution grooves 204, 204' (see fig. 8, 9, 10, 11, 12, 13, 14). The envelope 36 comprises, in its part receiving the bosses 203 ′, a rectangular opening into which an element 49 a of the boss 203 (fig. 8) of the body 49 provided with the orifice 40 penetrates. This rectangular opening is permitted by the anchoring of the envelope 36 in the bosses 203 and 203 ′ of the body 49 of height slightly less than the width of the toothing and of width in relation to the module thereof. In this way, the orifices 40 can be produced in the body 49.

It is possible to provide recesses 206 in the envelope 36 in order to facilitate its cooling after injection and to provide it with greater flexibility (FIGS. 1, 9, 10, 12, 14).

The finish of the projections 201, 201 ', 201' 'and the bosses 203, 203' as well as the faces of the covers 54, 55 and those inside of the adjoining body 49 is such that it presents a particularly high surface finish to receive the plastic parts of the flanges 21, 22 and of the casing 36 as well as the joints of the corresponding sectors 60, 60 ', 60' 'and 38, 38'. This surface condition is obtained for example by a plastic overmolding or a coating of oven-baked epoxy paint. The anti-extrusion joint effect of the projections and bosses is reinforced by a plastic border 0.3 to 0.5 mm high around the periphery of the joint housings on the flanges 21, 22 and on the casing 36. This border also absorbs differences in ribs.

Leaks are recovered by means of conduits 218 closed by a plug 219 and by a particular conduit 213 formed through the pinion 10 and parallel to the axis thereof. The leaks recovered by these conduits are evacuated towards the low-pressure circuit by means of a piping connected in the hole 217 (fig. 1 and 8). Food of zone 34, a permanent total high pressure zone, is produced by the orifice 216 from the high pressure generated or received.

The grooves 30, linked to the grooves 100 by the conduits 23, have a greater or lesser angular value depending on the operating conditions. In the example above, they are limited to the value of the diameter of the conduit. In reality, because of their respective positions in each of the flanges 21 and 22 relative to the inclination of the teeth, their value is equivalent to twice the diameter of the duct (when one is masked by a full of teeth, the the other is always in connection with the hollow of the tooth and vice versa). These grooves 30 can be completed by a groove 212 halfway up the envelope 36, centered on the conduit 43, so that the groove 30 can always be made as short as possible, for example reduced to the diameter of the conduit 23. According to the priority direction of rotation, this groove 212 can be offset relative to the conduit 43 to promote faster pressurization on one side relative to the other side of the sector. These arrangements are illustrated in FIGS. 12, 13, 14, 15, 16, 17.

Likewise, the connecting conduit 23 can take the form referenced 214 on the generators-receivers of large displacement to favor the creation of the fluid bearings (fig. 17).

The action of the pressure in the zone 34 at the level of the grooves 100 has led to placing a metal insert, that is to say the manifold 207 in the flanges 21-22. To reduce the action of this pressure in said zone 34 between the seals 58 and 45 (and 45 ', 45''), a new arrangement of this zone consists in placing the seal 58 above the seal 45 by housing it in a throat of the covers 54 and 55. The sector 60 then includes the grooves 100 which are subjected to the same compensation pressure as the sector 60 (either HP or BP). The collector 207 can then be reduced in diameter and the grooves 100 possibly provided again in the plastic part. This arrangement requires the use of a spacer 221 on the driven pinion side, this and the bearing 123 on the driving pinion side then being inserted into the plastic of the flanges 21-22. This plastic insertion makes it possible to make the bearing-flange assembly in one piece, to angularly separate the spacer 221 and the bearing 123 from the manifold 207 and to overcome the misalignment of the bearings bores. These provisions are illustrated in fig. 18, 19, 20 and 21.

For large torques at low rotational speed, requiring large displacements, these can be obtained by providing a greater or lesser number of satellites (pinions driven). This arrangement makes it possible to obtain smaller dimensions and to be able to play on these dimensions either by producing materials of large diameter and short length, or the reverse. This construction is permitted by varying the number of teeth Z of the driving pinion and the number of teeth z of the driven satellite pinions.

Possible construction: n satellites

pour 2 N = 2n sur pignon menant.n = 1 Satellite Z = z for 2 N = 4 on the driving pinion.
n = 2 Satellites Z = z for 2 N = 4 on the driving pinion.
n = 3 Satellites Z = 1.5 z for 2 N = 6 on the driving pinion.
n = 4 Satellites Z = 2 z for 2 N = 8 on the driving pinion.
n = n Satellites Z ≧ $\frac{\text{nz}}{\text{2}}$

for 2 N = 2n on the driving pinion.

• que le nombre de secteurs sur le pignon mené est toujours égal à quatre, deux secteurs HP opposés et deux secteurs BP opposés.
• que les secteurs sur pignon menant sont quelque soit leur nombre, soit HP, soit BP, mais pas en pression intermédiaire.
• que lorsque n est impair, le pignon menant ne peut avoir de conduits d'équilibrage, les secteurs opposés étant respectivement HP et BP, ce qui ne perturbe pas l'équilibrage général, celui-ci se faisant par l'intermédiaire des secteurs de compensation hydrostatique sur les flasques.
• que la cylindrée par tour est égale à la cylindrée par tour du pignon menant multipliée par le nombre de satellites n, soit :
  
  $\text{cylindrée par tour C = KM²ZH x n x π}$
  
  
  $\text{C avec KM = hauteur de dent}$
  
  
  
  M module apparent de denture, H largeur de denture, n nombre de satellites.
• que si n est pair, les satellites opposés peuvent être court-circuités par un distributeur hydraulique permettant d'avoir $\frac{\text{n}}{\text{2}}$
  
  cylindrées possibles.

   Fig. 22 et 23 illustrent ces dispositions. Fig. 22 montre un générateur-récepteur, couvercle et flasque en levés, de construction avec deux satellites. Les pignons menés sont référencés 10' . Le pignon menant 9', comporte le même nombre de dents Z que celui z des pignons menés. L'ensemble tourillonne dans l'enveloppe 36' logée dans le corps 49' . Les orifices 40 HP-BP sont soit HP, soit BP, d'un même côté (Traits pleins à la même pression soit HP, soit BP ; Traits pointillés à la même pression, soit BP, soit HP). L'équilibrage est réalisé de la même façon que dans les constructions précédentes, le pignon menant peut être équilibré par les conduits rotoriques puisque les secteurs opposés sont au même potentiel de pression.
   Fig. 23 montre un générateur-récepteur, couvercle et flasque enlevés, comportant trois satellites dont les pignons menés sont référencés 10'' et le pignon menant 9''. Le pignon menant 9'' est pourvu d'un nombre de dents Z 1,5 fois plus important que celui z des pignons menés 10''.Note :

• that the number of sectors on the driven pinion is always equal to four, two opposite sectors HP and two opposite sectors BP.
• that the sectors on the driving pinion are whatever their number, either HP or BP, but not at intermediate pressure.
• that when n is odd, the driving pinion cannot have balancing conduits, the opposite sectors being HP and LP respectively, which does not disturb the general balancing, this being done by means of compensation sectors hydrostatic on the flanges.
• that the displacement per revolution is equal to the displacement per revolution of the driving pinion multiplied by the number of satellites n, that is:
  
  $\text{displacement per revolution C = KM²ZH xnx π}$
  
  
  $\text{C with KM = tooth height}$
  
  
  
  M apparent toothing module, H toothing width, n number of satellites.
• that if n is even, the opposite satellites can be short-circuited by a hydraulic distributor allowing to have $\frac{\text{not}}{\text{2}}$
  
  displacement possible.

Fig. 22 and 23 illustrate these provisions. Fig. 22 shows a generator-receiver, cover and flange raised, of construction with two satellites. The driven pinions are referenced 10 '. The driving pinion 9 ′ has the same number of teeth Z as that of the driven pinions. The assembly pivots in the envelope 36 'housed in the body 49'. The orifices 40 HP-BP are either HP or BP on the same side (solid lines at the same pressure or HP or BP; dotted lines at the same pressure, either BP or HP). Balancing is carried out in the same way as in the previous constructions, the driving pinion can be balanced by the rotor conduits since the opposite sectors are at the same pressure potential.
Fig. 23 shows a generator-receiver, cover and flange removed, comprising three satellites whose driven pinions are referenced 10 '' and the driving pinion 9 ''. The driving pinion 9 '' is provided with a number of teeth Z 1.5 times greater than that z of the driven pinions 10 ''.

The assembly pivots in a 36 '' envelope housed in the 49 '' body. The orifices 40 HP-BP are either HP or BP, on the same side. Balancing is carried out in the same way as in the previous constructions. However, the driving pinion cannot be balanced by the rotor conduits since the opposite sectors are not at the same pressure potential. The driving pinion is balanced by means of the hydrostatic compensation sectors provided on the flanges.

Claims (10)

1. A hydraulic generator-receiver with helicoidal pinion gearing (9 and 10), in which internal balancing is provided by a hydraulic winding system comprising rotor and stator ducts which give rise to hydraulic bearings and play-free gearing, and in which internal sealing is provided by a flexible system comprising two discs (21, 22) incorporating grooves (100) and an envelope (36) which is hydrostatically compensated by means of hydrostatic compensation sectors (60, 38), characterised in that the discs (21, 22) are moulded onto an insert (207) with a good friction coefficient whose outer surface is flush with the inner face of each disc and which comprises two circular parts connected by a bi-concave joint (211), the said insert incorporating grooves (210) in each of which the plastics material constituting the discs penetrates in order to form a bead in which each groove (100) is provided.
2. A generator-receiver according to claim 1, characterised in that the covers (54, 55) and the body (49) bear projections (201, 201', 201'') and bosses (203, 203') respectively which engage forcefully in the corresponding recesses provided in the discs (21, 22) and the envelope (36).
3. A generator-receiver according to claim 2, characterised in that the projections (201, 201', 201'') and the bosses (203, 203') incorporate lateral faces which act together through an offset of the order of 5° with the faces of the corresponding depressions so that the discs and the envelope can be force fitted with respect to the covers (54, 55) and the body (49) at the joints (45, 45', 45'') - (37, 37') respectively.
4. A generator-receiver according to claim 3, characterised in that the projections (201, 201', 201'') and the bosses (203, 203') are coated in a layer of plastics material or stove-cured epoxy paint.
5. A generator-receiver according to any one of the foregoing claims, characterised in that:

   - leaks are returned via a low pressure duct (218) connected to a connection (217) of the cover (55),

   - the total permanent feed to the high pressure zone (34) generated or received is connected to an orifice (216) in the cover (55).
6. A generator-receiver according to any one of the foregoing claims, characterised in that the hydrostatic compensation sectors can be balanced by means of a groove (212) made in the envelope (36) at the level of the duct (43) which may be eccentric with respect to that duct (43) in accordance with the priority direction of rotation, and the priority type of functioning, whether a generator or receiver.
7. A generator-receiver according to any one of the foregoing claims, characterised in that the driven pinion (10) is provided with a balancing duct (213) for the low pressure chambers located on the axis of that pinion (10).
8. A hydraulic generator-receiver according to claim 1, characterised in that the insert (207) has balancing grooves (215) on the face in contact with the surface of the pinions (9 and 10) to encourage the creation of a fluid bearing between the face of the insert (207) and the face of the pinions (9 and 10).
9. A generator-receiver according to any one of the foregoing claims, characterised in that the seal (58) is housed in the bores of the covers (54 and 55) to reduce the size of the area (34) in this vicinity by making it annular and enclosing the grooves (100) in the sectors (60) in order to subject them to the same hydrostatic compensation pressure and in that this arrangement constitutes a flexible plastics link between the spaces (221), the bearings (123) and the inserts (207) respectively, a link formed by a plastics part of the discs (21 and 22).
10. A generator-receiver according to any one of the foregoing claims, characterised in that the number of satellites n may be 1, 2, 3, ... n, and that the number of teeth Z in the principal driving pinion is linked to the number of teeth z in the satellite pinions by the relationship Z ≧ $\frac{\text{nz}}{\text{ 2}}$

    

    , except for n = 1, where Z = z, and Z and z may be odd or even.

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