FR2492022A1 - Temporary fixed connection of wheel to shaft - uses radial shaft expansion in pulley bore using conical hydraulic piston in thin-walled sleeve - Google Patents

Abstract

The rigid coupling may secure a pulley wheel (4) on a shaft (3), using the axial displacement of a conical piston (8) in a sleeve (5) of the complementary form to effect a radial expansion of the shaft once located in a pulley (4) bore. The conical interface (6) is lubricated and the displacement of the piston relative to the sleeve is brought about by hydraulic force. The piston and the sleeve are mounted in a hollowed out (2) portion of the shaft, and the former may have radial (8a) and axial (17,18,22) passages feeding fluid under pressure to circumferential grooves (15,16) and the conical interface. A circular length (7) of the sleeve bore may locate opposite a reduced circular length (9) of the piston to form a pressure chamber. The chamber may be sealed (14) and closed (11) by a composite ring which screws (12) into the sleeve.

Description

Rigid coupling device mounted under fluid pressure.

 The present invention relates to a rigid coupling device which can be assembled and disassembled by means of a pressurized fluid and making it possible to produce a force transmission connection between a cylindrical shaft and a part having a bore concentric with the shaft without requiring no special machining of any of the elements to be assembled. The part having the bore and cooperating with the shaft may for example be a pulley, a pinion etc.

The tree has at least one hollow portion which can be blind in certain embodiments.

 Mechanical assemblies are already known in which the coupling elements consist of split conical rings as described for example in French patents 2 187 049 and 2 284 794. The tightening of the two split conical rings and the relative displacement which results, is done by means of a plurality of screws.

 It can be seen that these devices have a certain number of drawbacks, the existence of the slots in the conical rings in particular resulting in increased risks of corrosion.

Furthermore, it is necessary to exert significant axial forces during assembly, which requires the use of a large number of screws, the tightening of which must be carried out in a rigorously distributed and progressive manner. Given the difficulties during assembly, there are also frequent jamming phenomena which can even make disassembly impossible.

 To overcome these drawbacks, couplings that have been force-fitted using a pressurized fluid have already been recommended. US Patent 3,531,146 describes an assembly device of this type for two ends of coaxial shafts.

In this device, a thin sleeve with a cylindrical bore and a conical outside diameter is brought into clamping contact on the shafts by means of a thick sleeve with a cylindrical outside diameter and a conical bore. The sleeve acts as a piston and is actuated by means of a pressurized fluid introduced into a pressure chamber. During assembly, the two conical surfaces of the assembly members are separated by a film of pressurized fluid which allows their relative displacement.

 It is found in practice that assembly devices of this type require special reinforcement when applied to the assembly of hollow shafts due to the pressure exerted by the coupling.

 The present invention relates to the mounting by expansion under pressure of fluid of rigid couplings of this type applied to shafts having at least one hollow portion.

 The rigid coupling device according to the invention, mounted under fluid pressure, allows the assembly of a part comprising a bore with a shaft penetrating into this bore and having at least one hollow portion. The device comprises two coupling members whose conical surfaces in contact must be separated during assembly and disassembly by a film of pressurized fluid. One of the two coupling members can then be moved by the action of a pressurized fluid. According to the invention, the coupling device comprises a thin ring which can be introduced into the hollow portion of the shaft and which has a conical internal bore inside which a piston with a conical external surface can move. coupling of the device of the invention therefore achieve by their very structure a reinforcement of the hollow portion of the shaft.

 To introduce the fluid under pressure to the conical surfaces in contact with the two coupling members, the piston, which may be solid or with thick walls, further comprises passage means capable of ending up between the conical surface of the piston and the tapered bore of the thin ring.

 In a first embodiment, the thin ring preferably has a portion of cylindrical bore defining with a reduced diameter portion of the piston a pressure chamber closed by a closure member fixed to the ring. The piston includes passage means for supplying the pressure chamber with pressurized fluid.

 A seal which can advantageously be of flat annular structure, seals the pressure chamber.

 In a preferred embodiment applied to the case where the hollow portion of the shaft is constituted by a blind recess, the conicity of the piston is such that the portion of smaller diameter is located on the side of the blind bottom of the hollow portion. The front external surfaces of the thin ring and of the piston are substantially flush with the front end of the shaft after assembly of the coupling device.

 In another embodiment also applied to the case where the hollow portion of the shaft is constituted by a blind recess, the conicity of the piston is reversed so that it is the portion of larger diameter which is on the bottom side blind of the hollow portion.

 The pressure chamber can then be defined between the blind bottom and the front end opposite the piston, kept at a certain distance. The piston includes passage means for supplying the pressure chamber with pressurized fluid. Tightness is ensured simply by tightening the parts.

 Alternatively, the front end of the piston on the side of the blind bottom of the hollow portion has a recess which acts as a pressure chamber. This chamber is delimited on the side of the blind bottom by a closure member which bears on the blind bottom and relative to which the piston can move. The piston comprises, as previously, passage means for supplying the pressure chamber with pressurized fluid.

 The pressure chamber is sealed by an appropriate seal.

 In all cases, a hole passing through the piston is preferably provided to allow the evacuation of air and fluid from the blind bottom of the hollow portion of the shaft.

 The coupling device is assembled by first supplying pressurized fluid, for example oil, to the conical surfaces in contact with the two coupling members, then by introducing a pressurized fluid which may also be of oil, in the pressure chamber, which causes the displacement of the piston inside the conical bore of the thin ring and the elastic deformation by expansion of said ring and of the wall of the shaft, thus ensuring the friction connection between the outer surface of the shaft and the bore of the member to be coupled. When the desired tightening is obtained, the fluid supply between the two conical surfaces in contact which are therefore forcibly assembled is cut off. For small diameter couplings, the supply of pressurized fluid to the pressure chamber can be use the same passages as for the conical surfaces in contact with the coupling elements. The pressurized fluid spreads first between the aforementioned conical surfaces and then gradually fills the pressure chamber, thereby causing the displacement of the piston as has just been said. On the contrary, larger diameter couplings provide a separate supply.

 To disassemble the coupling according to the invention, the fluid under pressure is introduced between the two conical surfaces in contact and a valve forming part of a plug closing the fluid supply duct of the pressure chamber is opened in a controlled manner . This controls the speed of the axial displacement of the piston which allows the coupling to be dismantled.

The invention will be better understood on studying the detailed description of some embodiments taken by way of nonlimiting examples illustrated by the appended drawings in which
fig. 1 is a sectional view of the end of a shaft provided with a coupling device according to the invention;
fig. 2 is a similar sectional view of a first variant; and
fig. 3 is a similar sectional view of a third variant.

 As shown in FIG. 1, the coupling device according to the invention referenced 1 as a whole is introduced into a blind recess 2 made at the end of a cylindrical shaft 3 in order to assemble on this shaft a part 4 which is for example a pulley and which has a cylindrical bore cooperating with the cylindrical outer surface of the shaft 3 in line with the blind recess 2.

 The coupling device 1 comprises a thin ring 5 having a cylindrical outer surface and easily introduced by a sliding adjustment in the recess 2. The cylindrical outer surface of the ring 5 preferably has a helical thread of small section, not shown on the figure, emerging outside. This net promotes the evacuation of the oil possibly covering the cylindrical surfaces in order to facilitate the introduction of the device into the recess. The thin ring 5 has a tapered bore portion 6 and a cylindrical bore portion 7 on the outside. A piston 8 of conical outer surface having substantially the same conicity as the conical bore 6 of the ring 5 is introduced inside the latter. The conicity of the piston 8 is such that its portion of smaller diameter is located side of the bottom 24 of the blind chamber 2.

 On the outside, the piston 8 has a portion 9 of reduced diameter defining with the portion 7 of the cylindrical bore of the ring 5, an annular pressure chamber 10, closed by an annular closure member 11 screwed by its thread 12 to 1 end of the cylindrical bore portion 7 of the ring 5. It will be noted that blind recesses 13 make it possible to facilitate the tightening and screwing of the closing member 11. A flat annular seal 14 is mounted inside of the pressure chamber 10 in contact with the internal face of the closure member 11 and surrounding the reduced diameter portion 9 of the piston 8 so as to seal the pressure chamber 10 by elastic deformation.

 The creation of a film of fluid such as oil between the two conical surfaces opposite the thin ring 5 and the piston 8, is made by means of two annular grooves 15 and 16 formed on the external surface of the piston 8 and communicating with each other by axial grooves 17 also made on the outer surface of the piston 8. It will be noted that it would be possible without difficulty to provide more than two annular grooves.

 The pressurized fluid is brought through the supply passage 18 disposed substantially axially inside the piston 8 in a substantially radial passage 18a formed inside the piston 8 and communicating with the circular groove 15. A fluid inlet connection 19 connected to the passage 18 is provided in the portion 9. In this way the pressurized fluid is supplied between its conical surfaces whatever the angular position of the piston 8.

 The pressure chamber 10 is supplied with pressurized fluid through the radial passage 20 formed in the reduced diameter portion 9 of the piston 8 and connects to the fluid supply connection 21.

 It will be noted that the two fluid inlet connections 19 and 21 are arranged side by side in the front face of the portion 9 which reduces the size of the device of the invention and facilitates the mounting of the inlet conduits. pressurized fluid.

 An axial bore 22 passes through the piston 8 right through so as to allow the evacuation of the air and of the fluid which may remain in the blind bottom of the recess 2 during the mounting of the coupling device of the invention. The bore 22 can be closed after assembly by a threaded plug cooperating with the thread 22a.

 It will be noted that the axial lengths of the thin ring 5 and of the conical piston 8 are determined so as to obtain the desired tightening for the friction transmission of a determined force such as a torque, an axial force or combined loads. The front faces of the piston 8 and of the ring 5 are then preferably substantially in the same plane.

When the coupling device is assembled, there remains, as can be seen in FIG. 1, a spacing between the front internal face 23 of the piston 8 and the bottom 24 of the blind recess 2. The value of this spacing is chosen so that if the piston 8 comes into contact with the bottom 24, the permissible stress depending on the nature of the material chosen for the various members of the coupling device is not exceeded.

 The depth of the recess 2 is preferably chosen so that the external front faces of the piston 8 and of the thin ring 5 are substantially flush with the front end face of the shaft 3 and of the part 4 to be assembled.

 The coupling device is assembled as follows.

 A pressurized hydraulic fluid such as oil is introduced through the passage 18 so as to completely separate the two conical surfaces facing the thin ring 5 and the piston 8. Next, a pressurized hydraulic fluid is introduced such as through the passage 20 in the pressure chamber 10 which causes an axial force on the annular front face 25 of the piston 8 delimiting the pressure chamber 10 and a displacement of the piston 8 inside the thin ring 5. This displacement is made possible by the existence of the oil film between the two conical facing surfaces. When the desired tightening is obtained, the fluid under pressure is no longer applied to the pipe 18, which causes the two opposite conical surfaces to be tightened.

 The pressure chamber 10 is then discharged.

 In the case of a coupling of smaller diameter, it would be possible to suppress the supply passage 20 of the pressure chamber 10 and to be satisfied for the assembly to supply the pressure chamber 10 with the pressurized fluid coming from circular grooves 15 and 16, spread between the two conical surfaces and then gradually filling the pressure chamber 10.

 For dismantling the coupling device of the invention. The threaded hole 21 is closed by a threaded plug, not shown in the figure, and comprising a peelable opening valve. The pressurized fluid is introduced through the supply passage 18 by gradually opening the aforementioned valve. Cn thus controls the movement of the piston 8 to the left in FIG. 1 inside the thin ring 5, since the two conical surfaces joined by force are separated by a film of pressurized fluid which eliminates friction. During disassembly, the chamber 10 is subjected to a pressure which is a function of the surface of the radial projection of the conical assembly.

 The embodiment illustrated in FIG. 2 on which the identical parts have the same references is distinguished from the previous embodiment only by the reverse taper of the piston and the resulting difference in the configuration of the pressure chamber.

 As can be seen in fact in fig. 2, the taper of the piston 26 is such that it is its portion of larger diameter which is on the side of the blind bottom 24 of the recess. The thin ring 27 of course has an internal surface of conicity equal to that of the piston 26 so as to be able to co-operate with the latter as in the previous embodiment.

 The pressure chamber 29 is here defined between the bottom 24 of the recess and the internal front surface 28 of the piston 26. In order to give the pressure chamber 29 suitable dimensions, a certain distance remains between these facing front walls.

 The pressurized fluid is supplied through passage 30.

In this embodiment, the sealing of the pressure chamber 29 is ensured only by the clamping of the parts and in particular the clamping between the outer surface of the thin ring 27 and the bore of the shaft 3. The film d oil between the piston 26 and the ring 27 is created as before thanks to the existence of the grooves 15, 16 and 17.

 In the embodiment of FIG. 3 where the identical parts have the same references, the piston 31 has the same conicity as the piston 26 of the embodiment of FIG. 2. Its portion of larger diameter is therefore on the side of the blind bottom 24 of the recess. An annular recess 32a practical in the piston 31 and opening onto its internal face 31a defines a pressure chamber 32 which is delimited on the side of the blind bottom 24 by the front face of a sealing member 33 in the form of a ring which comes bear on the bottom 24. A flat annular seal 34 disposed in the chamber 32 in contact with the closure member 33 seals the pressure chamber 32. The pressure chamber 32 is supplied with fluid under pressure through the passage 35. Under these conditions, the pressurization of the chamber 32 causes the movement to the left of FIG. 3 of the piston 31, the closure member 33 being immobilized by its support against the bottom 24 of the blind recess. The oil film between the piston 31 and the thin ring 27 is created as before thanks to the existence of the grooves 15, 16 and 17.

 Although in this embodiment the pressure chamber 32 is produced in the form of an annular recess, it will be understood that it would be perfectly possible to design a recess of cylindrical shape formed in the axis of the piston 31 and then cooperating with a closing member resembling an auxiliary piston bearing as before on the bottom 24 of the blind recess.

 Although the invention has been described with reference to examples where the tree had a blind recess, it will be understood that it can be applied without much modification in the case of a tree having an internal hollow portion. In the same way it will be understood that the part 4 may not be exactly fixed to the end of the shaft 3 but be slightly offset.

Claims (10)

 1. Rigid coupling device mounted under fluid pressure between a part (4) comprising a bore and a shaft (3) penetrating into the bore and having at least one hollow portion (2), the device comprising two members coupling whose conical surfaces in contact can be separated during assembly by a film of pressurized fluid, one of the two members being able to be displaced by the action of the pressurized fluid, characterized in that it comprises a thin ring (5) which can be introduced into the hollow portion (2) of the shaft (3) and having an internal conical bore (6) inside which a piston (8) with a conical external surface can move.  2. Coupling device according to any one of the preceding claims, characterized in that the piston (8) comprises passage means for introducing a fluid under pressure between the conical outer surface of the piston and the conical bore of the thin ring (5).  3. Coupling device according to claim 1, characterized in that the ring (5) has a cylindrical bore portion (7) defining with a portion (9) of reduced diameter of the piston (8) a pressure chamber (10) closed by a closure member (11) fixed to the ring (5), the piston (8) comprising passage means for supplying the pressure chamber with pressurized fluid.  4. Coupling device according to claim 2 characterized in that a flat annular seal (14) is mounted in the pressure chamber (10) and seals it.  5. Coupling device according to any one of the preceding claims, characterized in that the hollow portion of the shaft is blind, the conicity of the piston (8) being such that the portion of smaller diameter is located on the bottom side blind end of the hollow portion and, the front external surfaces of the thin ring and of the piston coming substantially flush with the front end of the shaft.  6. Coupling device according to claim 1 or 2, characterized in that the hollow portion of the shaft is blind and that the conicity of the piston is such that the portion of larger diameter is on the side of the blind bottom of the hollow portion.  7. Coupling device according to claim 6, characterized in that a pressure chamber (29) is defined between the blind bottom of the hollow portion and the front end facing the piston, the piston comprising passage means for supplying the pressure chamber with pressurized fluid.  8. Coupling device according to claim 6, characterized in that the front end of the piston on the side of the blind end of the hollow portion has a recess (32a) acting as a pressure chamber, delimited, on the side of the blind bottom, by a closure member (33) bearing on said blind bottom, the piston comprising passage means for supplying the recess with pressurized fluid.  9. Coupling device according to claim 8, characterized in that a seal (34) cooperates with the closure member and the recess to ensure the sealing of the pressure chamber.  10. Coupling device according to claim 5, characterized in that a bore (22) passes through the piston for the evacuation of air and fluid from the blind bottom of the hollow portion of the shaft.