FR2890145A1 - Sealing boot for confining lubricant at e.g. tripod joint, has pressure distribution unit disposed in broad zone of sealing lug overlapping in axial view with transversal section of tulip or locking unit when lug is at rest - Google Patents

Abstract

The boot has a pressure distribution unit (38) disposed in a broad radial zone (32) of a sealing lug defining a central axis. The distribution unit is adapted for distributing, along circumferential direction around the axis, pressure between the lug and a tulip (7) of a tripod joint, where the pressure is exerted by a locking unit (22) on the lug. The distribution unit overlaps in axial view with a transversal section of the tulip or the locking unit when the lug is at rest. An independent claim is also included for an assembly comprising a complementary element and a sealing boot.

Description

The present invention relates to a bellows seal, of the type

  comprising a sealing bead having a radially thin zone and a radially enlarged zone, the aforementioned zones of the sealing bead being adapted

  for receiving a sealing member of the sealing heel on a complementary element, such as a homokinetic joint tulip.

  Such a type of sealing bellows is frequently arranged on two shafts, for example connected by a hinge or a constant velocity joint, such as a tripod joint. These bellows have concentric or helical folds and contain lubricant in which bathes the joint or seal.

  The fixing of this type of bellows is carried out, in known manner, by tightening clamping members on each of the bellows of the bellows, thus firmly gripping it against each of the shafts or against a part integral with each shaft. These clamping members may be closed rings, collars, especially ear, or any other 2C) appropriate element. Unless major deterioration of the bellows membrane, the areas most critical to the good sealing of the device are located at the close contacts between the inside of the beads and the corresponding shaft.

  In the case of known bellows, the outer surface of the heel has, in axial view, a circular section, while the inner surface, in the rest state of the heel, is complementary to the outer surface of the corresponding shaft. Once assembled, the known beads 30 lead to an unequal distribution of heel pressure against the complementary element in the circumferential direction.

  The object of the invention is to overcome the drawback mentioned above and to provide a bellows that ensures excellent sealing.

  According to the invention, this object is achieved with a sealing bellows of the aforementioned type, characterized in that it comprises, in the radially enlarged zone, at least one first pressure distribution member which is adapted to distribute according to the invention. the circumferential direction about the central axis, the pressure between the sealing bead and the complementary element which is exerted by the clamping member on the sealing bead, and which, when the sealing bead is at rest, overlaps in axial view the cross section of the complementary element or the clamping member.

  The bellows may comprise one or more of the following features, taken individually or in any technically possible combination: the radially thin zone has a radially outer surface on which the clamping member is mounted, the radially outer surface defines a distal point which is the point of this surface which is radially furthest from the central axis, and the first pressure distribution member extends radially outside this distal point; - The radially outer surface has a circular arc section, and the first pressure distribution member extends radially outside the circle defined by this arc; - The sealing bellows comprises a second pressure distribution member which is disposed on the same radially enlarged area as the first pressure distribution member, which, when the sealing heel is at rest, overlaps in axial view the section. cross section of the complementary element or the clamping member and which is circumferentially separated from the first pressure distribution member; the first pressure distribution member and the second pressure distribution member are located on the same radial side of the sealing bead; - The or each pressure distribution member is integral with the sealing heel; - The sealing bellows comprises axial retaining means of the clamping member on the sealing bead, in the unclamped state of the clamping member; the axial retaining means comprise at least one radial retaining protrusion offset axially from the or each pressure distribution member and adapted to retain the clamping member in a first axial direction; - The axial retaining means are adapted to retain the clamping member in only one axial direction; - The axial retaining means comprise at least one second radial retaining projection axially offset from the or each first radial projection and adapted to retain the clamping member, in a second axial direction opposite to the first axial direction; and the or each retaining protrusion is circumferentially offset from each radially enlarged zone.

  The invention also relates to an assembly, of the type comprising - a complementary element having a non-circular outer surface comprising partial surfaces radially close and radially distant, and - a sealing bellows comprising a sealing bead having a radially radially inner fitting adapted to be applied to the outer surface of the complementary element, characterized in that the sealing bellows is a sealing bellows as defined above, and in that the pressure distribution member is applied on a partial surface radially close together.

  According to another characteristic of the assembly, the complementary element is a tulip of a tripod joint.

  The invention will be better understood on reading the description which follows, given solely by way of example and with reference to the drawings, in which: FIG. 1 is a side view of a transmission joint comprising a bellows according to the invention, whose portion delimited by the axes in bold is shown in longitudinal section; Figure 1A is a cross-sectional view of the seal shown in Figure 1 along the line A-A; - Figure 2 is an enlarged view of detail II of Figure 1A, the clamping member being omitted; - Figure 3A is a view similar to that of Figure 2 of a bellows in the state of rest according to a second embodiment of the invention; - Figure 3B is a view similar to the view of Figure 3A of a bellows according to a third embodiment of the invention; FIG. 4 shows the circumferential shape of the pressure between the sealing bead and the tulip of a homokinetic joint for the two embodiments of FIGS. 2 and 3A and for a known bellows, and FIGS. 5 and 6 show variants of a bellows according to the invention.

  FIGS. 1 and 1A show a transmission joint 1, connecting a first shaft 4 and a second shaft 6. The two shafts 4 and 6 are connected by a mechanical transmission member, not shown in detail, which requires good lubrication. medium including grease. The confinement of this lubricant at the seal is provided by the bellows 2, which is fixed at its small end on the shaft 4, integral with the male element 5 of the seal, and which is fixed at its large end to the periphery. a female element 7 of the seal, integral with the shaft 6.

  The shaft 6 defines a central axis X-X. In what follows, the expressions circumferentially, radially, and axially will be used with respect to this axis XX The bellows 2 comprises a bellows body 10, consisting of an elastic membrane, of plastic material, with several folds of increasing diameter from 4. Each end of the bellows is in the form of a sealing bead 11, 12.

  The inner surface of each bead 11, 12 is intended to be sealed tight against the periphery of the complementary member. In FIG. 1, the heel 11 is mounted in close contact on the shaft 4 and the heel 12 on the element 7. The heel 11 therefore has a diameter which is much smaller than that of the heel 12.

  In the example shown in Figures 1 and 1A, the seal 1 is a tripod joint, the male element 5 has three roller journals 8, angularly spaced 120 from each other. The female element 7 has housings 9, each intended to receive a roller 8. In cross section, with respect to the axis XX of the shaft 6, the outer profile of the female element 7 is therefore trilobal and consists of the succession of the outer profiles of these housings 9, as shown in Figure 2. Thus, the female element 7 forms an outer surface 13 which is non-circular and which comprises radially close partial surfaces 13A and radially remote partial surfaces 13B . In order to seal the seal, the inner profile of the heel 12 has a number of excrescences directed towards the inside of the seal so that it is complementary to the outer profile of the female element 7 previously described. In the example shown, the heel 12 thus has a trilobal inner profile.

  In Fig. 2 is shown an enlarged view of detail II of Fig. 1A.

  In this view, the clamping member 22 has been omitted, but is indicated in phantom.

  The heel 12 is therefore in the rest state, unsolicited by the clamping member 22.

  The sealing heel 12 has radially thin zones 30 as well as radially enlarged zones 32. The radially thin zones 30 apply against the tulip 7 at the housing 9, whereas the radially widened zones 32 apply against the tulip 7 between the housing 9 and form the aforementioned growths.

  The sealing bead 12 also has a radially outer surface 34 for supporting the clamping member 22, as well as a radially inner surface 36, which is applied in the state mounted against the tulip 7.

  The outer surface 34 has in each radially thin zone 30 a cross section perpendicular to the axis XX, which is in the form of a circular arc with radius R. The outer surface 34 defines a distal point which is the point of this surface 34 in the thin zone 30 furthest from the axis XX. In the present case, the surface 34 of the zone 34 has a circular section so that all the points of the surface satisfy this condition. Alternatively, the surface 34 of the thin zone 30 has a non-circular section shape.

  Moreover, the sealing bead 12 comprises, in each radially enlarged zone 32, a pressure distribution member 38 which is adapted to distribute in the circumferential direction the pressure exerted by the clamping member 22 on the heel of the bead. 12, and this at the contact between the inner surface 36 of the heel 12 and the outer surface of the tulip 7.

  In this case, the pressure distribution member 38 is formed by an addition of material which overlaps, in axial view, the cross section of the clamping member 22, when the heel 12 is in the state of rest. In other words, the pressure distribution member 38 is an outgrowth which extends a distance d beyond the circle defined by the arc of the surface 34 in the radially thin zones 30.

  Preferably, the pressure distribution member 38 is integral with the sealing bead 12, which facilitates manufacture.

  In Figure 3A is shown a second embodiment of the heel 12 according to the invention.

  In what follows, only the differences with respect to the embodiment of FIG. 2 will be described. Similar elements bear the same references.

  First, it should be noted that this heel 12 is shown in the idle state. It is neither mounted on the tulip 7 nor tightened by the clamping member 22.

  In broken lines is indicated the profile of the tulip 7.

  As a difference with respect to the heel 12 of FIG. 2, the sealing heel of this bellows 2 has a radially outer surface 34 which has a circular section with a radius R, and this both in the radially thin zones 30 and in the zones radially enlarged 32.

  The pressure distribution member 38 of each enlarged zone 32 is formed by a single radial outgrowth 5 of material which overlaps the profile of the surface of the tulip 7 in the state of rest radially.

  The pressure distribution member 38 has a thickness which increases progressively from the vicinity of the thin portions 30 to the circumferential center of the enlarged zone 32. The pressure distribution member 38 has a maximum thickness d at the circumferential center of the enlarged zone 32.

  In Figure 3B is shown a third embodiment of the bellows. This embodiment differs from that of Figure 3A in what follows.

  The heel 12 comprises two pressure distribution members 38 which are arranged on one side and the other of the circumferential center of the enlarged zone 32, and this on the radially inner side.

  The two pressure distribution members 38 are circumferentially separated by a separating portion 40 of the enlarged zone 32, the separation portion 40, the axial surface of which coincides with the resting surface with the external surface of the tulip 7.

  Thus, one of the pressure distribution members 38 forms an additional pressure distribution member 38.

  Alternatively, the two pressure distribution members 38 may be located on the radially outer side.

  In FIG. 4, the shape of the pressure between the external surface of the tulip 7 and the inner surface 36 of the bead 12 is schematically shown.

  The abscissa is the circumferential angle. The positions of 0 and 60 correspond to the circumferential centers of two adjacent thin zones 30 while the position of 30 corresponds to the center of an enlarged zone 32.

  On the ordinate is indicated the pressure. The curve A in phantom represents the pressure profile of a known bead whose profile in the state of rest corresponds to the profile of the tulip 7 and the clamping member 22.

  Curve B corresponds to the heel pressure distribution of Figure 2.

  Curve C corresponds to the heel pressure distribution of Figure 3A.

  As can be seen, the pressure difference between the thin zones 30 and the enlarged zones 32 is lower for the heels according to the invention.

  In addition, the pressure in the zone 32 is greater for the heels according to the invention than for the known heel.

  Thus, the tightness of the bellows 12 is improved.

  In Figure 5 is shown a variant of the bellows of Figure 2, which differs from the bellows of Figures 1 and 2 by what follows. Similar elements bear the same references.

  This bellows 2 further comprises axial retaining means of the clamping member 22 on the sealing heel 12, when the clamping member 22 is in the untightened state.

  These axial retaining means comprise, on the one hand, a plurality of first radial projections 50 disposed on the heel 12. These radial projections 50 are axially offset from the pressure distribution members 38 and are situated axially between these members 38 and the body of the bellows 10. These projections 50 protrude radially from the pressure distribution members 38. Thus, these radial projections 50 are adapted to retain the clamping member 22 against a displacement in a direction directed towards the body of the bead 10.

  The axial retention means further comprises a plurality of second radial projections 52 which are axially offset from the pressure distribution members 38, in the direction directed towards the opening of the heel 12. Thus, these second radial projections 52 are adapted to retain the clamping member 22 against an axial displacement directed towards the opening of the heel 12.

  As is apparent from FIG. 5, the axial retaining protrusions 50, 52 are circumferentially offset from the radially widened zones 32, and are exclusively on the radially thin zones 30 of the heel 12.

  In addition, the first axial retaining protrusions 50 are circumferentially offset from the second axial retaining projections 52, so that in axial view they do not overlap. This arrangement facilitates the molding of the bellows.

  In this case, the heel 12 has three first axial retaining protrusions 50 and three second axial retaining projections 52.

  Alternatively, the heel 12 has two or four axial first projections 50 and / or two or four second axial retaining projections 52.

  In Figure 6 is shown another variant of the sealing bellows, which differs from the bellows of Figure 5 by the following.

  This bellows 2 has no second axial retaining projection 52, so that the clamping member 22 is retained axially only in the direction directed towards the body of the heel 10.

  Alternatively not shown, the bellows 2 may comprise only second retaining projections 52, but no first retaining projection 50.

Claims (13)

  Sealing bellows (2), of the type comprising a sealing bead (12) defining a central axis (XX) and having a radially thin zone (30) and a radially enlarged zone (32), the aforementioned zones ( 30,32) of the sealing bead (12) being adapted to receive a clamping member (22) of the sealing bead on a complementary element (7), such as a homokinetic joint tulip, characterized in that it comprises, in the radially enlarged zone (32), at least one first pressure distribution member (38) which is adapted to distribute in the circumferential direction about the central axis (XX), the pressure between the heel of sealing (12) and the complementary element (7) which is exerted by the clamping member (22) on the sealing bead (12) and which, when the sealing bead (12) is at rest, axially overlaps the cross section of the complementary element (7) or the clamping member (22).   2. sealing bellows (2) according to claim 1, characterized in that the radially thin zone (30) has a radially outer surface (34) to which the clamping member (22) is applied in the assembled state. ), in that the radially outer surface (34) defines a distal point (P) which is the point of this surface (34) which is radially furthest from the central axis (XX), and in that the first pressure distribution member (38) extends radially outwardly from this distal point (P).   Sealing bellows (2) according to claim 2, characterized in that the radially outer surface (34) has a circular arc section, and that the first pressure distribution member (38) is extends radially outside the circle defined by this arc.   4. sealing bellows (2) according to claim 1 to 3, characterized in that it comprises a second pressure distribution member (38) which is disposed on the same radially enlarged area (32) as the first member of pressure distribution (38), which, when the sealing bead (12) is at rest, overlaps in axial view the cross-section of the complementary element (7) or the clamping member (22) and which is circumferentially separated from the first pressure distribution member (38).   Sealing bellows according to Claim 4, characterized in that the first pressure distribution member (38) and the second pressure distribution member (38) are located on the same radial side of the sealing bead (12). .   6. Sealing bellows according to any one of claims 1 to 5, characterized in that the or each pressure distribution member (38) is integral with the sealing heel (12).   7. Sealing bellows according to any one of the preceding claims, characterized in that it comprises axial retaining means of the clamping member (22) on the sealing heel (12), in the state not tightened the clamping member (22).   8. Sealing bellows according to claim 7, characterized in that the axial retaining means comprise at least one radial retaining projection (50; 52) axially offset from the or each pressure distribution member (38) and adapted to retain the clamping member (22) in a first axial direction.   Sealing bellows according to claim 8, characterized in that the axial retaining means (50; 52) are adapted to retain the clamping member (22) in only one axial direction.   Sealing bellows according to claim 8, characterized in that the axial retaining means (50; 52) comprise at least one second radial retaining projection (50; 52) axially offset from the or each first radial projection ( 50; 52) and adapted to retain the clamping member (22) in a second axial direction opposite to the first axial direction.   11. Sealing bellows according to any one of claims 7 to 10, characterized in that the or each retaining projection (50; 52) is circumferentially offset from each radially enlarged zone (32).   12. A set of the type comprising: - a complementary element (7) having a non-circular outer surface comprising radially close (13A) and radially remote partial surfaces (13B), and - a sealing bellows (2) comprising a heel sealing member (12) having a radially inner surface (36) adapted to bear on the outer surface of the complementary member (7), characterized in that the sealing bellows is a sealing bellows according to any one of the preceding claims, and in that the pressure distribution member (38) is applied to a radially close partial surface.   13. The assembly of claim 12, characterized in that the complementary element is a tulip (7) of a tripod joint.