WO2022135801A1

WO2022135801A1 - Wide-angle constant-velocity joint with optimized lubrication

Info

Publication number: WO2022135801A1
Application number: PCT/EP2021/082122
Authority: WO
Inventors: Gianni Tenca; Andrea BURATO
Original assignee: Comer Industries S.P.A.
Priority date: 2020-12-22
Filing date: 2021-11-18
Publication date: 2022-06-30

Abstract

A constant-velocity joint (1) with optimized lubrication, comprising a central body (2) which is associated with two internal forks (3) which protrude on opposite sides along a longitudinal axis (A) and is provided with an annular chamber (4) which is extended on a central plane (P) that is transverse to the longitudinal axis (A) and a guiding element (7) which is accommodated so that it can move on said central plane (P) within the annular chamber (4). Each one of the internal forks (3) is associated with a respective external fork (8) by means of the interposition of a corresponding cross (9) and each external fork (8) is provided with a respective tab (10) which is associated with the guiding element (7) by virtue of relative retention means (11) which form a first kinematic pair (12) adapted to allow at least one relative translation and a second kinematic pair (13) adapted to allow at least one relative rotation. The joint (1) furthermore comprises first sealing means (14) interposed between the walls (4a) of the annular chamber (4) and the guiding element (7), second sealing means (15) being associated with each one of the first kinematic pairs (12).

Description

WIDE-ANGLE CONSTANT- VELOCITY JOINT WITH OPTIMIZED LUBRICATION

The present invention relates to a wide-angle constant- velocity joint with optimized lubrication.

Wide-angle constant- velocity joints are known which are typically used in cardan shaft transmission systems for agricultural machines, in which the angular offset between the longitudinal axis of the cardan shaft and the longitudinal axis of the driving shaft of the power take-off (PTO) of the tractor and/or of the driven shaft of the work implement to be actuated (PIC) can reach values of several dozen degrees (up to 60°-80°).

These constant- velocity joints of the known type are constituted essentially by a central body which supports two internal forks which protrude along a longitudinal axis on opposite sides of said central body, each fork being coupled to a respective external fork by virtue of the interposition of a corresponding cross. The central body is provided internally with an annular chamber which is extended transversely to the longitudinal axis between the two internal forks and in which a guiding disk or planet gear is accommodated so that it can move by sliding and is connected to tabs which protrude from both external forks.

Such tabs are generally associated with spherical heads which are arranged in sliding contact on a cylindrical surface which forms an axial sliding seat provided in the guiding disc along the longitudinal axis. In some cases it is known to provide a bushing provided internally with a concave surface shaped like a spherical dome, which is interposed between each spherical head and the cylindrical surface in order to reduce the contact pressures involved and the wear of the components, increasing as a whole the mechanical strength of the joint.

In use, the external forks of the joint are designed to be coupled respectively to one of the two ends of the telescopic shaft and to one of the driving shaft of the PTO of the tractor and the transmission shaft of the PIC of the work implement.

A pair of guiding rings can be interposed between the internal walls of the chamber and the guiding disk and also can move by sliding transversely to the longitudinal axis. The presence of the rings makes it possible to keep the guiding disk in position during sliding, delimiting laterally the volume of the annular chamber in which the guiding disk moves with respect to the outside environment.

The lubrication of the parts in relative motion is generally obtained by leakage of lubricant introduced through the internal chamber of the central body. The lubricant leaks between the guiding disk, the rings, if any, and the internal walls of the chamber, and also between the spherical heads associated with the tabs of the external forks, the spherical sliding bearings, if any, and the axial seat of the guiding disk, and therefore must be replenished periodically.

The correct lubrication of the parts in relative motion, as well as the reduction of the consumption of lubricant and of the frequency of the required maintenance interventions, are typical critical aspects of wide- angle constant- velocity joints.

In this regard, numerous technical solutions have been developed which are aimed at ensuring good lubrication and at the same time at limiting the frequency of the maintenance and lubricant replenishment interventions.

USSN 2002/010027 Al, for example, proposes a solution which provides for the use of protective bellows arranged externally to the constant- velocity joint in order to delimit a sealed chamber which contains lubricant, avoiding its dispersion.

Although this solution makes it possible to reduce considerably the need to perform interventions on the joint, it is not free from drawbacks, since it increases considerably the complexity of its structure and construction and increases its space occupation. US 7,033,278 B2, moreover, teaches to use guiding rings shaped like Belleville washers in order to limit the escape of lubricant through the interspaces formed in the coupling between the guiding disk, the rings and the surfaces of the chamber inside the central body.

The escape of lubricant in the coupling region between tabs of the external forks and the guiding disk is in any case free, and therefore this solution solves the problem only partially.

Moreover, WO 2008/151223 Al provides for forming, inside the central body, a lubricant reserve ring directly communicating with the internal chamber in order to increase the volume of lubricant that can be accumulated inside it.

Although this solution makes it possible to reduce the frequency with which lubricant replenishment interventions are to be performed, it does not solve the problem of the consumption thereof and has increased external space requirements in a radial direction.

In an attempt to improve this solution, USSN 2020/132127 Al provides a constant- velocity joint which, in addition to the lubricant reserve ring which communicates with the internal chamber, is provided with sealing rings which are interposed between the walls of said chamber, the guiding rings and the guiding disk and a dosage system which makes it possible to adjust the flow of the lubricant from the reserve ring to the internal chamber. This dosage system consists of a series of calibrated passages for the controlled leakage of the lubricant.

Although this solution makes it possible to limit lubricant dispersion and consumption, it does not limit in any way its escape in the coupling region of the tabs of the external forks with the guiding disk. Furthermore, it has a considerable structural complexity.

The aim of the present invention is to eliminate the drawbacks noted above of the background art, by providing a constant- velocity joint with optimized lubrication which makes it possible to reduce considerably, if not eliminate completely, the consumption and dispersion of lubricant, minimizing the need to perform interventions for maintenance on the components and for replenishment of said lubricant.

Within this aim, an object of the present invention is to limit the operating costs of the joint and increase its reliability over time.

Another object of the present invention is to not entail structural and constructive complications and to not penalize the overall space occupation of the joint.

A further object of the present invention is to provide a structure which is simple, relatively easy to provide in practice, safe in use, effective in operation, and relatively low-cost.

This aim and these and other objects which will become better apparent hereinafter are all achieved by the present constant- velocity joint with optimized lubrication having the characteristics as set forth in claim 1 and optionally provided with one or more of the characteristics according to the dependent claims.

Further characteristics and advantages of the present invention will become more apparent from the detailed description of some preferred but not exclusive embodiments of a constant- velocity joint with optimized lubrication, illustrated by way of non-limiting example in the accompanying drawings, wherein:

Figure 1 is a sectional view, taken along a plane that passes through the longitudinal axis, of a first embodiment of a constant- velocity joint with optimized lubrication according to the invention;

Figure 2 is a sectional view, taken along a plane that passes through the longitudinal axis, of a variation of the first embodiment of the joint according to the invention;

Figure 3 is an enlarged-scale view of a portion of Figure 2;

Figure 4 is a sectional view of the joint of Figure 2 in the maximum angle position; Figure 5 is an enlarged-scale view of a portion of Figure 4;

Figure 6 is a sectional view, taken along a plane that passes through the longitudinal axis, of a further variation of the first embodiment of the joint according to the invention;

Figures 6a and 6b are enlarged-scale views of respective details of Figure 6;

Figure 7 is a sectional view, taken along a plane that passes through the longitudinal axis, of a second embodiment of the joint according to the invention;

Figure 8 is a sectional view, taken along a plane that passes through the longitudinal axis, of a variation of the second embodiment of the joint according to the invention;

Figure 9 is an enlarged-scale view of a portion of Figure 8;

Figure 10 is a sectional view of the joint of Figure 8 in the maximum angle position;

Figure 11 is an enlarged-scale view of a portion of Figure 10;

Figure 12 is a sectional view, taken along a longitudinal plane, of a universal joint transmission shaft in which the joint according to the invention is applied.

With reference to the figures, the reference numeral 1 generally designates a constant- velocity joint with optimized lubrication.

The joint 1 comprises a central body 2 which is associated with two internal forks 3 which protrude on opposite sides along a longitudinal axis A and is provided with an annular chamber 4 which is extended along a central plane (line P in the figures) which is transverse to the longitudinal axis A.

More precisely, the central plane P is substantially perpendicular to the longitudinal axis A.

In the present description, the term "substantially" is understood to mean excluding the conventional machining and assembly tolerances of the components.

In the first embodiment shown, the central body 2 is composed of two half-shells 2a and 2b which are mutually connected by virtue of threaded elements 6.

The central body 2 is provided with a pair of annular flanges 5 which are extended around the longitudinal axis A and are mutually parallel and spaced.

Each internal fork 3 is blended with a respective flange 5 on the opposite side of the other of said two flanges.

The annular chamber 4 is constituted by an interspace formed between the flanges 5. The mutually facing walls of the flanges 5 form the side walls 4a and the perimetric edge 4b of the chamber 4.

The walls 4a can be planar or contoured.

Lubricant is introduced in the chamber 4 and is distributed by leaking in order to reduce friction and wear phenomena among the components of the joint 1 in relative motion.

The joint 1 furthermore comprises a guiding element 7 which is accommodated so that it can move on the central plane P within the chamber 4.

Each internal fork 3 is associated with a respective external fork 8 by interposition of a corresponding cross 9. Conventional bearings, not described in detail since they are known to the person skilled in the art, are interposed between the pivots of each cross 9 and the prongs of the respective forks 3 and 8.

Each external fork 8 is provided with a respective tab 10, which is associated with the guiding element 7 by virtue of relative retention means 11 which form a first kinematic pair 12 adapted to allow at least one degree of freedom in relative translation and a second kinematic pair 13 adapted to allow at least one degree of freedom in relative rotation. The tab 10 has an elongated shape and the inclination of its axis of extension S with respect to the longitudinal axis A can vary as a function of the operating conditions of the joint 1. The joint 1 is sized to allow a transmission of motion up to a relative inclination between the axes of extension S of the tabs 10 equal to a maximum angle (designated by 2a in Figures 4-5, 10-11).

Preferably, the first kinematic pair 12 is of the cylindrical type, in order to allow a relative combined rotary and translational motion of the elements that constitute it.

Preferably, the second kinematic pair 13 is of the spherical type, so as to allow a relative rotation about the three Cartesian axes (three-dimensional rotation) of the elements that constitute it.

Moreover, the joint 1 provides for first sealing means 14 which are interposed between the walls 4a of the chamber 4 and the guiding element 7 and are adapted to prevent the leakage of lubricant between them toward the outside of said chamber.

Such first sealing means 14 can provide for one or more conventional first rings, for example made of rubber or other similar material, which are interposed between the walls 4a of the chamber 4 and the guiding element 7.

Preferably, the joint 1 provides for a pair of guiding rings 17 which are interposed between the guiding element 7 and the walls 4a of the chamber 4 on opposite sides of said element along the longitudinal axis A.

In this case, the first sealing means 14 are interposed between each wall 4a of the chamber 4 and the guiding ring 17 which faces it and between said ring and the guiding element 7.

In greater detail, the embodiments shown have a pair of guiding rings 17 shaped like annular plates. For each guiding ring 17, the first sealing means 14 comprise a first ring 14a which is interposed between the wall 4a that faces it and the guiding ring 17 and a second ring 14b which is interposed between said guiding ring and the guiding element 7.

Each first ring 14a is accommodated in an annular groove which is formed on the wall 4a proximate to the corresponding internal radial end, but it is not excluded that it might be accommodated in the corresponding guiding ring 17.

Each second ring 14b is accommodated in an annular groove which is formed on the guiding element 7 proximate to the corresponding external radial end, but it is not excluded that it might be accommodated in the corresponding guiding ring 17.

The guiding rings 17 delimit laterally, on opposite sides of the central plane P, the chamber 4 beyond the extension of the side walls 4a formed by the flanges 5.

Conveniently, the joint 1 comprises second sealing means 15 which are interposed between the elements of each one of the first kinematic pairs 12 and are adapted to prevent the leaking of lubricant between them toward the outside environment.

Such second sealing means 15 can provide for one or more conventional second rings, for example made of rubber or other similar material, interposed between the elements of each one of the first kinematic pairs 12.

The presence of the first and second sealing means 14 and 15, respectively, makes it possible to avoid the leaking of the lubricant both outside the chamber 4 and in the region of the first kinematic pairs 12, reducing its dispersion considerably.

In order to obtain a substantial elimination of the dispersion of lubricant it is possible to also provide third sealing means 16 interposed between the elements of each one of the second kinematic pairs 13 and adapted to prevent the leaking of lubricant between them toward the outside environment.

The third sealing means 16 can provide for one or more conventional second rings, for example made of rubber or other similar material, interposed between the elements of each one of the second kinematic pairs 13. The guiding element 7 comprises a disk-like element 18 which is arranged at the central plane P and is provided with at least one radial channel 19 the peripheral end of which is open at the chamber 4. Through the radial channel 19, the lubricant leaks from the chamber 4 toward the axial region of the joint 1.

Preferably there is a plurality of radial channels 19 which are angularly spaced around the longitudinal axis A.

The peripheral region of the disk-like element 18 is retained between the walls 4a or between the optional guiding rings 17 in all the angular configurations assumed by the joint 1.

In the embodiments shown there are four radial channels 19 which are spaced in pairs at 90° around the longitudinal axis A.

Furthermore, the guiding element 7 comprises a pair of coupling elements 20 which are substantially parallel to said longitudinal axis A and protrude on opposite sides of the central plane P toward a corresponding external fork 8.

For each external fork 8, the retention means 11 are interposed between the corresponding tab 10 and the corresponding coupling element 20.

In greater detail, for each external fork 8, the retention means 11 comprise a bushing 21, which is provided with an external surface 21a and with an internal surface 21b which is concave and shaped like a spherical dome, and a spherical head 22, coupled to the internal surface 21b, which are interposed between the corresponding tab 10 and the corresponding coupling element 20. The second kinematic pair 13 is formed between the bushing 21 and the spherical head 22. The bushing 21 and the corresponding spherical head 22 constitute what is called a spherical sliding bearing.

In order to ensure the correct operation of the joint 1 as the operating conditions vary, each coupling element 20 has a longitudinal extension that is at least equal to the value Lmax that corresponds to the maximum distance of the plane of arrangement of the second sealing means 15 from the central plane P in the maximum angle configuration (Figures 4-5 and 10-11), which is defined by the following equation:

£/w<xr=£0+D-(l-cos(a)) wherein:

L0 is the distance of the plane of arrangement of the second sealing means 15 from the central plane P in the configuration in which the axis of extension S of the tab 10 of the corresponding external fork 8 substantially coincides with the longitudinal axis A (Figures 3 and 9);

D is the distance between the center O of the spherical head 22 and the central plane C of the respective cross 9. The expression “central plane C of the cross 9” is understood to reference the plane that is perpendicular to the axis of extension S of the corresponding tab 10 that passes through the intersection point of the axes of the arms of said cross; a is an angle equal to half the angle defined between the axes of extension S of the tabs 10 in the maximum angle configuration.

In Figures 5 and 11, M designates the central diametrical plane of the spherical head 22, i.e., the plane that passes through the center O of said head and is perpendicular to the axis of extension S of the corresponding tab 10 in the first embodiment or to the longitudinal axis A in the second embodiment.

Furthermore, on a plane that passes through the longitudinal axis A, each one of the spherical heads 22 has an angular extension on both sides of the corresponding central diametrical plane M that is at least equal to half (angle designated by a in Figures 5 and 11) the angle of maximum inclination (designated by 2a in Figures 5 and 11) that can be obtained between the axes of extension S of the tabs 10 in the maximum angle configuration.

In a further improved variation, the joint 1 can have valve means 23 for limiting the pressure inside the chamber 4 which are associated in fluid communication with said chamber. Such valve means 23 make it possible to evacuate partially the lubricant accommodated in the chamber 4 if, during filling, an excessive quantity thereof is introduced or if, during the operation of the joint 1, internal overpressures occur which might compromise its functionality.

In a first embodiment (shown in three variations in Figures l-6b), each coupling element 20 is constituted by a sleeve 24, which is extended substantially parallel to the longitudinal axis A and is provided with a substantially cylindrical internal wall 24a, and each tab 10 is constituted by a pivot 25, which is extended along the corresponding axis of extension S.

It should be noted that the sleeves 24, in moving on the central plane P, remain substantially parallel to the longitudinal axis A as the angular configuration assumed by the joint 1 varies.

For each external fork 8, the spherical head 22 of the retention means

11 is integrally associated with a respective pivot 25 and the external surface 21a of the bushing 21 is substantially cylindrical and associated, so as to slide in a direction that is parallel to the longitudinal direction A, with the internal wall 24a of the corresponding sleeve 24. The first kinematic pair

12 is therefore formed between the internal wall 24a of the sleeve 24 and the external surface 21a of the bushing 21.

It is not excluded that, for each external fork 8, the pivot 25 and the corresponding spherical head 22 might be provided integrally monolithically.

Furthermore, the internal cavities of the sleeves 24 communicate with each other and with the radial channels 19, so that the lubricant can reach the first and second kinematic pairs 12 and 13.

In a first variation (Figure 1), the joint is provided with the first sealing means 14 and with the second sealing means 15.

In a second preferred variation (Figures 2-5), the joint 1 is also provided with the third sealing means 16.

In a third further improved variation (Figures 6-6b), the joint 1 is provided with the valve means 23 in addition to the sealing means 14, 15, 16.

In greater detail, for each of the first kinematic pairs 12 the second sealing means 15 comprise a second ring which is partially accommodated in a first annular seat 26 formed on the external surface 21a of the corresponding bushing 21. The second ring 15 protrudes from the corresponding first seat 26 so as to seal the gap formed between the bushing 21 and the sleeve 24, avoiding the leaking of lubricant toward the outside. It is not excluded that the first seat 26 might be provided in the internal wall 24a of the sleeve 24.

It should be noted that for each of the first kinematic pairs 12 the second sealing means 15 are arranged on the opposite side of the central plane P with respect to the center O of the corresponding spherical head 22. In this manner, the center O is located between the central plane P and the plane of arrangement of the second sealing means 15 for all the angular configurations assumed by the joint 1.

Even more preferably, for each of the first kinematic pairs 12, the second sealing means 15 are arranged proximately to the end of the bushing 21 that is directed toward the corresponding external fork 8.

In the second and third variations, for each of the second kinematic pairs 13, the third sealing means 16 comprise a third ring which is partially accommodated in a second annular seat 27 formed on the internal surface 21b of the corresponding bushing 21.

The third ring 16 protrudes from the corresponding second seat 27 so as to seal the gap formed between the bushing 21 and the spherical head 22, avoiding the leaking of lubricant toward the outside. It is not excluded that the second seat 27 might be provided on the spherical head 22.

It is noted that for each one of the second kinematic pairs 13 the third sealing means 16 are arranged on the opposite side of the central plane P with respect to the center O of the corresponding spherical head 22. In this manner, the center O is located between the central plane P and the plane of arrangement of the third sealing means 16 for all the angular configurations assumed by the joint 1.

Even more preferably, for each of the second kinematic pairs 13, the third sealing means 16 are arranged proximately to the end of the bushing 21 that is directed toward the corresponding external fork 8.

The second and third sealing means 15 and 16, respectively, might be arranged at the same distance from the central plane P or at different distances.

In the third variation (Figures 6, 6a, 6b), the valve means 23 comprise a first maximum pressure valve 28 which is accommodated in a through hole 29 formed in one of the flanges 5 and adapted to establish a communication between the chamber 4 and the outside environment. The first valve 28 (shown in detail in Figure 6a) can be of the type of a conventional ball valve. The first valve 28 can be constituted by a valve body 30 provided with an opening 31 for the passage the lubricant which is aligned with the through hole 29 and along which a ball-type flow control element 32 is accommodated so that it can move, being pushed toward an annular abutment seat 33 by a compression spring 34 having an appropriate elastic constant and interposed between said flow control element and an annular shoulder 35 associated with the valve body 30.

Preferably, the valve means 23 can provide for at least one second maximum pressure valve 36 which is accommodated in an axial hole 37 formed in at least one of the pivots 25 along the corresponding axis of extension S and adapted to establish a communication between the region inside the sleeves 24 and the outside environment. The second valve 36 (shown in detail in Figure 6b) can be of the type of a conventional ball valve. The second valve 36 can be shaped in a manner that is fully similar to what has been described above with reference to the first valve 28.

In a second embodiment (shown in two variations in Figures 7-11), each of the coupling elements is constituted by a pivot 38, which is extended in a direction that is substantially parallel to the longitudinal axis A and is provided with a substantially cylindrical external wall 38a, and each one of the tabs 10 comprises a hub 39, which is directed toward the central plane P and is extended along the corresponding axis of extension S.

It should be noted that the pivots 38, by moving on the central plane P, remain substantially parallel to the longitudinal axis A as the angular configuration assumed by the joint 1 varies.

For each external fork 8, the spherical head 22 of the retention means

11 is provided with an axial hole 40, which is substantially cylindrical and arranged substantially parallel to the longitudinal axis A, and associated slidingly with the respective pivot 38 and the bushing 21 integrally associated within the respective hub 39. In this case, the first kinematic pair

12 is formed between the external wall 38a of the pivot 38 and the internal wall of the axial hole 40 of the spherical head 22.

The external surface 21a of the bushing 21 is substantially cylindrical, but it is not excluded that it might have a different shape which in any case matches the shape of the internal cavity of the hub 39.

In a first variation (Figure 7), the joint 1 is provided with the first sealing means 14 and with the second sealing means 15.

In a second preferred variation (Figures 8-11), the joint 1 is also provided with the third sealing means 16.

It is not excluded that in a third variation, not shown, the joint 1 might be provided with the valve means 23 in addition to the sealing means 14, 15, 16.

In greater detail, for each of the first kinematic pairs 12, the second sealing means 15 comprise a second ring which is partially accommodated in a first annular seat 41 which is formed in the axial hole 40 of the corresponding spherical head 22.

The second ring 15 protrudes from the corresponding first seat 41 so as to seal the gap formed between the axial hole 40 and the pivot 38, avoiding the leakage of lubricant toward the outside. It is not excluded that the first seat 41 might be provided on the pivot 38.

It should be noted that for each of the first kinematic pairs 12 the second sealing means 15 are arranged on the same side of the central plane P with respect to the center O of the corresponding spherical head 22. In this manner the plane of arrangement of the second sealing means 15 is located between the center O and the central plane P for all the angular configurations assumed by the joint 1.

Even more preferably, for each one of the first kinematic pairs 12, the second sealing means 15 are arranged proximately to the end of the axial hole 40 that is directed toward the central plane P.

It should be noted that in the second variation, for each one of the second kinematic pairs 13, the third sealing means 16 comprise a third ring which is partially accommodated in a second annular seat 42 which is formed on the internal surface 21b of the corresponding bushing 21.

The third ring 16 protrudes from the corresponding second seat 42 so as to seal the gap formed between the bushing 21 and the spherical head 22, avoiding the leakage of lubricant toward the outside. It is not excluded that the second seat 42 might be provided on the spherical head 22.

It should be noted that for each of the second kinematic pairs 13, the third sealing means 16 are arranged on the same side of the central plane P with respect to the center O of the corresponding spherical head 22. In this manner, the plane of arrangement of the third sealing means 16 is located between the center O and the central plane P for all the angular configurations assumed by the joint 1.

Even more preferably, for each of the second kinematic pairs 13, the third sealing means 16 are arranged proximate to the end of the bushing 21 that is directed toward the central plane P.

The second and third sealing means 15 and 16, respectively, can be arranged at the same distance from the central plane P or at different distances.

The pivots 38 are provided with respective longitudinal channels 43 which communicate with each other and with the radial channels 19, each of which is open at the respective hub 39 so as to allow the passage of lubricant toward the respective second kinematic path 13.

Figure 12 shows a universal joint transmission system 100, which is not described in detail since it is of a known type, which comprises essentially a telescopic shaft 101 constituted by two sections which are associated in mutual longitudinal sliding with respect to each other and is provided, at the opposite ends, with respective universal joint connection assemblies designed to be associated in use respectively with a driving shaft and with a driven shaft.

Typically, for application in agricultural machines, the driving shaft is the one of the power takeoff of a tractor (PTO) and the driven shaft is the actuation shaft of a work implement (PIC).

At least one of the connecting assemblies is constituted by a joint 1 as described above.

In the embodiment shown, at one of the ends of the telescopic shaft 101 there is a joint 1 and at the opposite end there is a conventional universal joint 102.

It is not excluded that a joint 1 according to the invention might be provided at both ends of the telescopic shaft 101.

The joint 1 can be used to connect the telescopic shaft 101 both to the driving shaft and to the driven shaft.

In practice it has been found that the described invention achieves the proposed aim and objects, and in particular the fact is stressed that the joint according to the invention makes it possible to reduce, if not eliminate, the consumption and dispersion of lubricant and therefore the need to perform maintenance interventions.

At the same time, the first sealing means, the second sealing means and the optional third sealing means act as a barrier against the entry of dust or any other external contamination into the joint according to the invention, preserving its functionality.

Furthermore, the joint according to the invention is reliable and durable over time, ensuring optimum lubrication of the components in relative motion.

Moreover, the joint according to the invention does not entail structural complications or increases in space occupation such as to penalize its application.

The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims.

All the details may furthermore be replaced with other technically equivalent elements.

In practice, the materials used, as well as the contingent shapes and dimensions, may be any according to the requirements without thereby abandoning the protective scope of the claims that follow.

The disclosures in Italian Patent Application No. 102020000031793 from which this application claims priority are incorporated herein by reference.

Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims

1. A constant-velocity joint (1) with optimized lubrication, comprising a central body (2) which is associated with two internal forks (3) which protrude on opposite sides along a longitudinal axis (A) and is provided with an annular chamber (4) which is extended on a central plane (P) that is transverse to said longitudinal axis (A) and a guiding element (7) which is accommodated so that it can move on said central plane (P) within said annular chamber (4), each one of said internal forks (3) being associated with a respective external fork (8) by means of the interposition of a corresponding cross (9) and each external fork (8) being provided with a respective tab (10) which is associated with said guiding element (7) by virtue of relative retention means (11) which form a first kinematic pair (12) adapted to allow at least one relative translation and a second kinematic pair (13) adapted to allow at least one relative rotation, and first sealing means (14) being provided which are interposed between the walls (4a) of said annular chamber (4) and said guiding element (7), characterized in that it comprises second sealing means (15) associated with each one of said first kinematic pairs (12).

2. The joint (1) according to claim 1, characterized in that it comprises third sealing means (16) associated with each one of said second kinematic pairs (13).

3. The joint (1) according to claim 1, characterized in that said first kinematic pair (12) is of the cylindrical type.

4. The joint (1) according to claim 1, characterized in that said second kinematic pair (13) is of the spherical type.

5. The joint (1) according to claim 1, characterized in that it comprises a pair of guiding rings (17) which are interposed between said guiding element (7) and the walls (4a) of said annular chamber (4) on opposite sides of said element, the first sealing means (14) being interposed between the walls (4a) of the annular chamber (4) and the at least one pair of guiding rings (17) and between said rings and the guiding element (7).

6. The joint (1) according to one or more of the preceding claims, characterized in that said guiding element (7) comprises a disk-like element (18) which lies at said central plane (P) and is provided with at least one radial channel (19) the peripheral end of which is open at said annular chamber (4).

7. The joint (1) according to claim 1 or 6, characterized in that said guiding element (7) comprises a pair of coupling elements (20) which are substantially parallel to said longitudinal axis (A) and protrude on opposite sides of said central plane (P) toward a corresponding external fork (8), for each external fork (8) the retention means (11) being interposed between the corresponding tab (10) and the corresponding coupling element (20).

8. The joint (1) according to claim 7, characterized in that, for each one of said external forks (8), said retention means (11) comprise a bushing (21), provided with an external surface (21a) and with an internal surface (21b) which is concave and shaped like a spherical dome, and a spherical head (22), coupled to said internal surface (21b), which are interposed between the corresponding tab (10) and the corresponding coupling element (20), the second kinematic pair (13) being formed between the bushing (21) and the spherical head (22).

9. The joint (1) according to claim 8, characterized in that each one of said coupling elements (20) has a longitudinal extension that is at least equal to the value Lmax defined by the following equation:

£/w<xr=£0+D-(l-cos(a)) wherein:

L0 is the distance of said second sealing means (15) from said central plane (P) in the configuration in which the tab (10) of the corresponding external fork (8) is arranged substantially parallel to said longitudinal axis (A);

D is the distance between the center (O) of the corresponding spherical head (22) and the central plane (C) of the respective cross (9); a is an angle equal to half the angle defined between the axes of extension (S) of said tabs (10) in the maximum angle configuration.

10. The joint (1) according to claim 8, characterized in that on a plane that passes through said longitudinal axis (A) each one of said spherical heads (22) has an angular extent, on both sides of the corresponding central diametrical plane (M), at least equal to half the angle of maximum inclination (2a) that can be obtained between the axes of extension (S) of said tabs (10) in the maximum angle configuration.

11. The joint (1) according to one or more of the preceding claims, characterizing that it comprises valve means (23) for limiting the pressure inside said annular chamber (4), which are associated in fluid communication with said chamber.

12. The joint (1) according to claim 8, characterized in that each one of said coupling elements (20) comprises a sleeve (24) provided with a substantially cylindrical internal wall (24a), in that each one of said tabs (10) comprises a pivot (25) and in that, for each one of said external forks (8), said spherical head (22) of said retention means (11) is integrally associated with a respective pivot (25) and the external surface (21a) of said bushing (21) is substantially cylindrical and slidingly associated with the internal wall (24a) of the corresponding sleeve (24), the first kinematic pair (12) being formed between the internal wall (24a) of the sleeve (24) and the external surface (21a) of the bushing (21).

13. The joint (1) according to claim 12, characterized in that the internal cavities of said sleeves (24) communicate with each other and with said at least one radial channel (19).

14. The joint (1) according to claim 12, characterized in that for each one of said first kinematic pairs (12) said second sealing means (15) are 21 arranged on the opposite side of said central plane (P) with respect to the center (O) of the corresponding spherical head (22).

15. The joint (1) according to claim 14, characterized in that for each one of said first kinematic pairs (12) said second sealing means (15) are arranged proximate to the end of said bushing (21) that is directed toward the corresponding external fork (8).

16. The joint (1) according to claim 12, characterized in that for each one of said second kinematic pairs (13) said third sealing means (16) are arranged on the opposite side of said central plane (P) with respect to the center (O) of the corresponding spherical head (22).

17. The joint (1) according to claim 16, characterized in that for each one of said second kinematic pairs (13) said third sealing means (16) are arranged proximately to the end of said bushing (21) that is directed toward the corresponding external fork (8).

18. The joint (1) according to one or more of claims 1-11, characterized in that each one of said coupling elements (20) comprises a pivot (38) provided with a substantially cylindrical external wall (38a), in that each one of said tabs (10) comprises a hub (39) that is directed toward said central plane (P), and in that, for each external fork (8), said spherical head (22) of said retention means (11) is provided with a substantially cylindrical axial hole (40) slidingly associated with a respective pivot (38) and said bushing (21) integrally associated with the inside of the respective hub (39), the first kinematic pair (12) being formed between the external wall (38a) of the pivot (38) and the wall of the axial hole (40) of the spherical head (22).

19. The joint (1) according to claim 18, characterized in that for each one of said first kinematic pairs (12) said second sealing means (15) are arranged on the same side of said central plane (P) with respect to the center (O) of the corresponding spherical head (22).

20. The joint (1) according to claim 19, characterized in that for each 22 one of said first kinematic pairs (12) said second sealing means (15) are arranged proximately to the end of said axial hole (40) that is directed toward said central plane (P).

21. The joint (1) according to claim 19, characterized in that for each one of said second kinematic pairs (13) said third sealing means (16) are arranged on the same side of said central plane (P) with respect to the center (O) of the corresponding spherical head (22).

22. The joint (1) according to claim 21, characterized in that, for each one of said second kinematic pairs (13), said third sealing means (16) are arranged proximately to the end of said bushing (21) that is directed toward said central plane (P).

23. The joint (1) according to one or more of claims 18-22, characterized in that said pivots (38) are provided with respective longitudinal channels (43) which communicate with each other and with said at least one radial channel (19), each being open at the respective hub (39).

24. A universal joint transmission system (100) comprising a telescopic shaft (101) provided, at the opposite ends, with respective universal joint connection assemblies which can be associated in use respectively with a driving shaft and with a driven shaft, characterized in that at least one of said connecting assemblies comprises a joint (1) according to one or more of claims 1-23.