Hydraulic coupling device

Abstract

A hydraulic coupling device comprises an inner sleeve 12 with a tapered outer surface 12b and an outer sleeve 14 with a tapered inner surface 14a. The tapered inner surface is mounted on the tapered o

Description

CXI 15 CXI 20 25 The present invention relates to the field of hydraulic coupling devices, notably used to create a simple connection between two shafts. Classically, a hydraulic coupling device comprises a thin inner sleeve and a thick outer sleeve. The outer surface of the inner sleeve is slightly tapered and the bore of the outer sleeve has a corresponding taper. The inner sleeve bore is somewhat larger than the diameter of the shafts to be connected, so that the inner sleeve can be passed over them with ease. The hydraulic coupling device further comprises a piston or nut screwed on the inner sleeve and delimiting together with the inner and outer sleeves a hydraulic chamber intended to be filed by oil or similar liquid. A seal is proved on the nut to avoid an oil escape from the chamber between the nut and the inner and outer sleeves. The coupling device is mounted by driving the outer sleeve up on the taper of the inner sleeve using oil pumped into the hydraulic chamber. This compresses the inner sleeve onto shafts creating an interference fit. When the outer sleeve has reached the correct drive-up position, the injection pressure is released and the oil connection is plugged. With the drive-up operation, the outer sleeve is radially expanded. This impacts the initial radial clearance between the outer diameter of the nut and the outer sleeve. There is also a risk for the seal provided on the nut to be tilted which could lead to an escape of oil. Otherwise, the outer surface of the outer sleeve may be provided with a radial flange to secure a brake disc, creating a braking function or using a drive unit. The outer surface of the radial flange may also be provided with teeth or other mechanical component. The final machining of such outer components needs to be made with the hydraulic coupling device in mounted position by using a dummy shaft. One aim of the present invention is to overcome these drawbacks. The invention relates to a hydraulic coupling device comprises an inner sleeve provided with a tapered outer surface, an outer sleeve 5 provided with a tapered inner surface mounted on the tapered outer surface of the inner sleeve, and a nut screwed on the inner sleeve. According to a general feature, the device further comprises a cylinder made separately from the outer sleeve and secured thereto, the nut being engaged at least in part into the cylinder. The inner sleeve, the 10 cylinder, the nut and the outer sleeve delimit together a chamber. According to another general feature, the cylinder is provided with a frontal face axially abutting against a frontal face of the outer sleeve. In a first embodiment, at least one of these frontal faces is 15 provided with a coating having a coefficient friction higher that of said frontal face. In a second alternative embodiment, at least one of the frontal faces of the cylinder and outer sleeve comprises at least one protrusion engaged into a complementary recess formed on the other frontal face. 20 In a third embodiment, at least one of the frontal faces of the cylinder and outer sleeve is provided with a coating having a coefficient friction higher that of said frontal face, and at least one of these frontal faces comprises at least one protrusion engaged into a complementary recess formed on the other frontal face. 25 With such a design, the cylinder is less impacted by the radial expansion of the outer sleeve during the drive-up operation. Otherwise, with the coating and / or the permanent mechanical clutch between the cylinder and the outer sleeve, the connection between these two parts enables close or equal torque transmission capacity as 30 the conventional hydraulic coupling device. If needed, the final machining of the cylinder can be made before to mount the hydraulic coupling device and therefore without using a dummy shaft. For example, the friction coefficient of said coating may be at least equal to 0,3 and preferably at least equal to 0,45. With such a design, it is also possible to foresee different materials for the cylinder and the outer sleeve, for example having 5 different material properties. Alternatively, the cylinder and the outer sleeve may be formed from the same material but exhibit different mechanical properties. For example, mechanical properties may vary depending on dimensions and heat treatment. The cylinder may protrude radially outwards with respect to the 10 outer surface of the outer sleeve, for example if the cylinder comprises outer components, such as flange or teeth. Alternatively, it could however be possible to foresee that the cylinder be radially offset inward with respect to the outer surface of the outer sleeve, or flush with this outer surface. 15 In one embodiment, the nut comprises a main portion and a nose having a reduced outer diameter and protruding axially towards the outer sleeve. Preferably, the device comprises a first seal radially interposed between the inner sleeve and the nose of the nut, and a second seal 20 radially interposed between the cylinder and the nose. Alternatively, it could be possible to have a single seal provided on the nut and having an inner edge in contact with the inner sleeve and an outer edge in contact with the cylinder. In this case, the nut may not be provided with the nose. This seal could be secured to a frontal face 25 of the nut axially facing the outer sleeve. The device may further comprise at least one seal axially provided between the outer sleeve and the cylinder. Advantageously, the chamber is radially defined between the tapered outer surface of the inner sleeve and the bore of the cylinder. 30 The chamber may be axially defined between the nut and the outer sleeve. Preferably, the outer sleeve, or the cylinder or the nut, may be provided with at least one injection conduit made into its thickness and opening into the chamber. The present invention and its advantages will be better understood by studying the detailed description of specific embodiments given by way of non-limiting examples and illustrated by the appended drawing on which: 5 - Figure 1 is a partial cross-section of a hydraulic coupling device according to a first example of the invention, and Figure 2 is a partial cross-section of a hydraulic coupling device according to a second example of the invention. The hydraulic coupling device 10 illustrated on Figure 1 10 comprises an annular inner sleeve 12, an annular outer sleeve 14 mounted on the inner sleeve, and an annular piston or nut 16 screwed on the inner sleeve. CXI 15 CXI 20 As will be described later, the device 10 further comprises an annular cylinder 18 made separately from the outer sleeve 14 and secured thereto. The inner sleeve 12 comprises a cylindrical inner surface or bore 12a and a tapered outer surface 12b which is radially opposite to the bore 12a. The inner sleeve is also provided at one axial end with an outer thread 12c extending radially outward. In the illustrated example, the outer thread 12c is radially offset inwards with regard to the tapered outer surface 12b. The outer sleeve 14 comprises a tapered inner surface matching with the tapered outer surface 12b of the inner sleeve mounted onto this tapered outer surface. The outer sleeve 14 25 14a and also comprises an outer surface 14b which is radially opposite to the tapered inner surface 14a. The outer sleeve 14 further comprises two opposite first and second frontal faces 14c, 14d which axially delimit the tapered inner surface 14a and the outer surface 14b. As previously mentioned, the cylinder 18 is made separately from the outer sleeve 14. The cylinder 18 radially surrounds the inner sleeve 12. The cylinder 18 radially surrounds the tapered outer surface 12b of the inner sleeve left free by the outer sleeve 14. The cylinder 18 also radially surrounds partly the nut 16. The cylinder 18 axially protrudes with respect to the frontal face 14c of the outer sleeve. The 10 CXI 15 CXI 20 25 cylinder 18 radially protrudes with respect to the outer surface 14b of the outer sleeve. The nut 16 is here partly engaged into the cylinder 18. Alternatively, the nut 16 may be fully engaged into the cylinder 18. A slight radial clearance is provided between the nut 16 and the cylinder 18. The cylinder 18 is mounted axially against the frontal face 14c of the outer sleeve. The cylinder 18 is secured to the outer sleeve 14. In the illustrated example, the device 10 comprises a plurality of fixing screws 20 to secure the cylinder 18 to the outer sleeve 14. The screws 20 are spaced apart in the circumferential direction, preferably regularly. The screws 20 extend axially through the cylinder 18. Each screw 20 is engaged inside a threaded hole (not shown) formed from the frontal face 14c of the outer sleeve. The cylinder 18 comprises a cylindrical inner surface or bore 18a and a outer surface 18b which is radially opposite to the bore 18a. The outer surface 18b is radially offset outwards with respect to the outer surface 14b of the outer sleeve. The cylinder 18 also comprises two opposite first and second frontal faces 18c, 18d which axially delimit the bore 18a and the outer surface 18b. The frontal face 18d axially abuts against the frontal face 14c of the outer sleeve. As will be described later, a high friction coating 23 is provided on the frontal face 18d of the cylinder. The coating 23 has a coefficient friction higher than that of the frontal face 18d. The nut 16 also comprises a cylindrical inner surface or bore 16a and a cylindrical outer surface 16b which is radially opposite to the bore 16a. The nut 16 further comprises two opposite first and second frontal faces 16c, 16d which axially delimit the bore 16a and the outer surface 16b. As previously mentioned, a slight radial clearance is provided between the nut 16 and the cylinder 18. This radial clearance is provided between the outer surface 16b of the nut and the bore 18a of the cylinder. The bore 16a of the nut is provided with an inner thread 16e engaged with the outer thread 12c of the inner sleeve. 10 25 The nut 16, the outer sleeve 14, the inner sleeve 12 and the cylinder 18 delimit together an annular hydraulic chamber 22. The chamber 22 is axially delimited by the nut 16 and the outer sleeve 14. More precisely, the chamber 22 is axially delimited by the frontal face 16d of the nut and the frontal face 14c of the outer sleeve. The chamber 22 is radially delimited by the inner sleeve 12 and the cylinder 18. More precisely, the chamber 22 is radially delimited by the bore 18a of the cylinder and the tapered outer surface 12b of the inner sleeve. The chamber 22 is intended to be filed by oil or similar liquid. To this end, an injection conduit 24 is provided into the thickness of the outer sleeve 14. A first end of the injection conduit 24 opens into the chamber 22. The injection conduit 24 opens onto the frontal face 14c of the outer sleeve. An injection hole 26 is provided on the outer surface 14b of the outer sleeve and is connected to a second end of the injection conduit 24 which is opposite to the first end. Alternatively, the injection conduit 24 and the injection hole 26 may be provided on the nut 16 or on the piston 18. The outer sleeve 14 is also provided with additional injection conduits (not shown) in order to be able to build up an oil film between the tapered outer and inner surfaces 12b, 14a of the inner and outer sleeves. In the illustrated example, the nut 16 comprises a main portion 28 and a nose 30 having a reduced outer diameter and protruding axially towards the outer sleeve 14. In the illustrated example, the main portion 28 and the nose 30 are made in one part. Alternatively, the nose 30 may be made separately from the main portion 28. The main portion 28 of the nut delimits the bore 16a, the outer surface 16b and the frontal face 16c. The nose 30 delimits the frontal face 16d. The device 10 further comprises a first annular seal 32 radially interposed between the outer surface 12b of the inner sleeve and the nose 30 of the nut, and a second seal 34 radially interposed between the bore 18a of the cylinder and the nose. The seal 32 radially comes into contact with the nut 30 and the outer surface 12b of the inner sleeve. The seal 32 may come into contact with a cylindrical or tapered portion of the outer surface 12b. The seal 34 radially comes into contact with the nut 30 and the bore 18a of the cylinder. The seals 32, 34 do not protrude with respect to the frontal face 16d of the nut. In the illustrated 5 example, the seals 32, 34 have in cross-section a circular shape. Alternatively, the seals 32, 34 may have other shapes. The device 10 further comprises an additional seal 36 axially provided between the outer sleeve 14 and the cylinder 18. The seal 36 is axially provided between the frontal face 14c of the outer sleeve and 10 the frontal face 18d of the cylinder. The seals 32 to 36 are respectively provided to avoid an oil escape from the chamber 22 between the nut 16 and the inner sleeve 12, the nut and the cylinder 18, and between the cylinder and the outer sleeve 14. 15 As previously mentioned, the coating 23 is provided on the frontal face 18d of the cylinder. The coating 23 has a coefficient friction higher than that of the frontal face 18d. The coating 23 may be sprayed on the frontal face 18d. In the illustrated example, the coating 23 covers partly the frontal face 18d. The coating 23 covers only the portion of this 20 frontal face which comes axially into contact with the frontal face 14c of the outer sleeve. The coating 23 is in axial contact with the frontal face 14c. Alternatively, the coating 23 may cover the entire frontal face 18d of the cylinder. The friction coefficient of the coating 23 is at least equal to 0,3, 25 and preferably at least equal to 0,45. For example, the friction coefficient may range between 0,3 and 0,6. The hardness of the coating 23 may be at least equal to 700 HV. For example, the surface roughness of the coating 23 ranges between 3 pm and 4 pm. The thickness of the coating 23 ranges between 0,02 mm and 0,04 mm. In one embodiment, the coating 30 23 may be a tungsten carbide coating. Alternatively, it is possible to foresee other friction increasing coatings. The coating may be applied with a plasma spraying technology. In this example, the coating 23 is provided on the frontal face 18d of the cylinder. Alternatively, the coating 23 may be provided on the frontal face 14c of the outer sleeve. The coating 23 may cover the entire frontal face 14c or may cover only the portion of this frontal face which comes axially into contact with the frontal face 18d of the cylinder. In such alternative embodiment, the coating 23 is in axial 5 contact with the frontal face 18d of the cylinder. Alternately, the coating may also be provided both on the frontal face 18d of the cylinder and on the frontal face 14c of the outer sleeve. In this case, the coatings axially come into contact each other. The example shown on Figure 2, in which identical parts are 10 given identical references, differs from the previous example in that the frontal face 18d of the cylinder comprises a plurality of protrusions 40 which protrude into recesses 42 of complementary shape formed on the frontal face 14c of the outer sleeve. 15 20 The protrusions 40 are spaced apart in the circumferential direction, preferably regularly. Each protrusion 40 extends axially. Each protrusion 40 is engaged into one of the recesses 42 of complementary shape. In the illustrated example, the protrusions 40 are made in one part with the the cylinder. The shape of each recess 42 formed on the frontal face 14c of the outer sleeve is complementary to that of the associated protrusion 40 of the cylinder. Each recess 42 extends axially inwards from the frontal face 14c. Each protrusion 40 formed on the cylinder is located inside the associated recess 42 formed on the outer sleeve. Each protrusion 40 is entirely housed inside the associated recess 42. The protrusions 40 and 25 the recesses 42 form a permanent mechanical clutch that couples the cylinder 18 and the outer sleeve 14 by interference fit. In the illustrated example, the protrusions 40 are formed on the frontal face 18d of the cylinder and the recesses 42 are formed on the frontal face 14c of the outer sleeve. Alternatively, it is possible to 30 foresee a reversed arrangement with the protrusions 40 formed on the frontal face 14c of the outer sleeve and the recesses 42 formed on the frontal face 18d of the cylinder. In another embodiment, protrusions may be formed both on the frontal face 18d and the frontal face 14c and each protrude into a recess formed on the frontal face 14c or on the frontal face 18d. In another embodiment, it could also be possible to foresee protrusions on the frontal face 18d of the cylinder and / or on the frontal 5 face 14c of the outer sleeve together with the coating as previously described covering at least one of these frontal faces. 29 01 24

Claims

1. Hydraulic coupling device comprising an inner sleeve (12) provided with a tapered outer surface (12b), an outer sleeve (14) 5 provided with a tapered inner surface (14a) mounted on the tapered outer surface (12b) of the inner sleeve, and a nut (16) screwed on the inner sleeve (12), characterized in that the device further comprises a cylinder (18) made separately from the outer sleeve (14) and secured thereto, the cylinder (18) being provided with a frontal face (18d) 10 axially abutting against a frontal face (14c) of the outer sleeve, the nut (16) being engaged at least in part into the cylinder (18), in that the inner sleeve (12), the cylinder (18), the nut (16) and the outer sleeve (14) delimit together a chamber (22), and in that at least one of the frontal faces (14c, 18d) of the cylinder and outer sleeve is provided 15 with a coating (23) having a coefficient friction higher that of said frontal face, and / or at least one of these frontal faces (14c, 18d) comprises at least one protrusion (40) engaged into a complementary recess (42) formed on the other frontal face.

2. Device according to claim 1, wherein the friction20 coefficient of said coating is at least equal to 0.3.

3. Device according to claim 1, wherein the frictioncoefficient of said coating is at least equal to 0.45.

4. Device according to any of the preceding claims, wherein the cylinder (18) is made of a material different from the material of 25 the outer sleeve (14).

5. Device according to any of the preceding claims, wherein the cylinder (18) protrudes radially outwards with respect to the outer surface (14b) of the outer sleeve6. Device according to any of the preceding claims, wherein 30 the nut (16) comprises a main portion (28) and a nose (30) having a reduced outer diameter and protruding axially towards the outer sleeve (14).

7. Device according to claim 6, further comprising a first seal (32) radially interposed between the inner sleeve (12) and the nose (30) 35 of the nut, and a second seal (34) radially interposed between the cylinder (18) and the nose.LO CXI i— i—CM8. Device according to any of the preceding claims, further comprising at least one seal (36) axially provided between the outer sleeve (14) and the cylinder (18).

9. Device according to any of the preceding claims, wherein 5 the chamber (22) is radially defined between the tapered outer surface (12b) of the inner sleeve and the bore (18a) of the cylinder.

10. Device according to any of the preceding claims, wherein the chamber (22) is axially defined between the nut (16) and the outer sleeve (14).10 11. Device according to any of the preceding claims, whereinthe outer sleeve (14) comprises at least one injection conduit (24) opening into the chamber (22) for filling the chamber (22) with oil.

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