A seal includes a supporting ring and at least one sealing ring. The at least one sealing ring has a sheath. The at least one sealing ring and the supporting ring are interconnected. The supporting ring has an outer periphery and is, at least in part, surrounded on the outer periphery by the sheath of the at least one sealing ring in a radial direction. The at least one sealing ring has at least one dynamically loaded sealing lip, which is arranged on a side of the at least one sealing ring facing radially away from the sheath. The at least one sealing ring includes an electrically conductive polymer material. The sheath and the sealing lip transition into one another as one piece.

CROSS-REFERENCE TO PRIOR APPLICATION

Priority is claimed to German Patent Application No. DE 10 2017 004 061.3, filed on Apr. 27, 2017, the entire disclosure of which is hereby incorporated by reference herein.

FIELD

The invention relates to a seal, comprising a supporting ring and at least one sealing ring, the sealing ring and the supporting ring being interconnected, the supporting ring comprising an outer periphery and being, at least in part, surrounded on the outer periphery by a sheath of the sealing ring in the radial direction, the sealing ring comprising at least one dynamically loaded sealing lip, which is arranged on the side of the sealing ring facing radially away from the sheath.

BACKGROUND

A seal of this kind is known from DE 10 2014 010 269 A1.

The supporting ring consists of a tough and hard material, for example a metal or polymer material. The sealing ring is directly or indirectly connected to the supporting ring, the sealing ring consisting of an elastomer material.

Furthermore, the previously known seal comprises a substantially annular disk made of an electrically conductive and air-permeable material, the disk being designed as an individual part produced separately from the supporting ring and being connected to the supporting ring. The disk consists of an electrically conductive nonwoven and is designed as a preliminary seal.

The preliminary seal is associated with the sealing lip of the sealing ring adjacently thereto at an axial spacing. When used as intended, the preliminary seal is arranged on the side of sealing lip facing the surroundings.

The preliminary seal has the function of preventing impurities from the surroundings from penetrating the sealing lip. As a result, consistently effective use-related properties of the seal are achieved over a long service life.

A further seal is known from DE 103 40 802 A1. The sealing ring of said seal consists of an electrically conductive elastomer material. The seal is used to seal components comprising toothed parts, charge separations occurring when said toothed parts move. The resultant currents are discharged in part by the medium to be sealed, i.e. the used lubricant, and currents are in part transferred to the components to be sealed with respect to one another. The advantage of the electrically conductive elastomer material is that currents can be easily discharged through the sealing ring.

In one of the previously known embodiments, the dynamically loaded sealing lip is associated, on the side facing axially away from the chamber to be sealed, with a dust lip, which is formed in one piece with the sealing lip, is made of the same material as said sealing lip, and therefore also consists of an electrically conductive elastomer material.

However, it should be noted that, when used as intended, elastomer materials always have to be sufficiently lubricated in order to achieve a satisfactory service life, the medium to be sealed usually providing the lubrication. If, when the seal is used as intended, the lubrication is insufficient, the elastomer material of the sealing ring wears quickly, and the use-related properties of the seal worsen after just a short service life.

SUMMARY

In an embodiment, the present invention provides a seal, comprising: a supporting ring; and at least one sealing ring, the at least one sealing ring having a sheath, the at least one sealing ring and the supporting ring being interconnected, wherein the supporting ring comprises an outer periphery and is, at least in part, surrounded on the outer periphery by the sheath of the at least one sealing ring in a radial direction, the at least one sealing ring comprising at least one dynamically loaded sealing lip, which is arranged on a side of the at least one sealing ring facing radially away from the sheath, wherein the at least one sealing ring is comprised of an electrically conductive polymer material, and wherein the sheath and the sealing lip transition into one another as one piece.

DETAILED DESCRIPTION

In order for the object to be achieved, the sealing ring consists of an electrically conductive polymer material, and the sheath and the sealing lip are formed so as to transition into one another as one piece.

Polymers materials—in contrast with elastomer materials—are advantageous in that they have largely consistently effective use-related properties over a long service life, even if said polymer materials are only insufficiently lubricated. For this reason, the dynamically loaded sealing lip can be easily arranged on the side of a main sealing lip facing the surroundings, as a practically non-lubricated preliminary seal.

In contrast with an electrically conductive nonwoven, an electrically conductive polymer material is advantageous in that the contact pressure of the sealing lip on a surface to be sealed of a machine element to be sealed is practically constant for the whole of the service life.

Also in contrast with a sealing lip that consists of an electrically conductive nonwoven, a sealing lip made of a polymer material withstands dry running just as effectively, a polymer material does not absorb any moisture and can also, over a long service life, reliably seal machine elements which are to be sealed and are operated at high speeds, for example at more than 20,000 min−1. Furthermore, in comparison with sealing rings made of a nonwoven, sealing rings made of a polymer material are advantageous in that they can more effectively compensate for any displacement of a shaft to be sealed.

As a result of the electrically conductive polymer material of the sealing ring, an uncoupled electrical bridge forms between the machine elements to be sealed with respect to one another. Said machine elements to be sealed with respect to one another may be formed, for example, by a shaft to be sealed having a surface to be sealed, and a housing which surrounds the shaft to be sealed on the outer periphery thereof at a radial spacing, the seal being arranged in the gap formed by the spacing.

According to an advantageous embodiment, the electrically conductive polymer material may be a PTFE material. A material of this kind in particular has the above-described advantages because sealing lips consisting of said material have practically self-lubricating properties. Therefore, a sealing lip made of a material of this kind practically does not wear at all even after a long service life and therefore largely maintains the same use-related properties.

The sheath and the sealing lip are preferably formed of the same material. This is advantageous in that a seal of this kind is easy and cheap to manufacture.

If, as a result of the particular circumstances of the application, it is advantageous to produce the sheath and the sealing lip from different materials, these two different polymer materials are both electrically conductive such that it is possible to discharge electrostatic charge from the sealing arrangement comprised by the seal.

According to an advantageous embodiment, the supporting ring may be substantially L-shaped and has a radial leg and an axial leg which adjoins the radial leg externally in the radial direction.

The supporting ring may generally consist of a metal or polymer material.

The advantageous use-related properties of the seal do not require the supporting ring to be electrically conductive, because electrical voltage puncture is prevented by the sealing ring consisting, from the sealing lip to the sheath, of an electrically conductive polymer.

Radially internally with respect to the radial leg, the dynamically loaded sealing lip is usually articulated. By contrast, the sheath is radially externally supported by the axial leg.

The axial leg may be completely surrounded by the sheath on the outer periphery. In this respect, it is advantageous that the electrical conductivity of the seal functions particularly reliably as a result of the sheath being well supported by the axial leg.

The sheath extends, along the radial leg in the radial direction, so as to transition into the dynamically loaded sealing lip as one piece. As a result, a simple electrically conductive connection is established between the machine elements to be sealed with respect to one another, for example between a shaft to be sealed and a housing which surrounds the periphery of the shaft to be sealed.

The electrically conductive sealing ring brings about controlled electric potential equalization between the machine elements to be sealed with respect to one another.

This therefore eliminates mechanical damage to the machine elements as a result of electrostatic charge in one of the machine elements and subsequent voltage puncture towards the other machine element having a different electric potential.

In the sealing arrangement in which the above-described sealing ring is used, one of the machine elements to be sealed with respect to one another is earthed to a defined ground potential (for example, the body of a motor vehicle as an electrical ground potential) such that potential equalization with respect to the other machine element is achieved by the electrically conductive sealing ring.

According to a first embodiment, the dynamically loaded sealing lip may be formed as a main sealing lip for sealing a medium to be sealed in a chamber to be sealed. For this purpose, when the seal is used as intended, the dynamically loaded sealing lip is generally axially curved towards the chamber to be sealed.

On the side of the sealing lip radially facing the machine element to be sealed, said sealing lip may, for example, have a surface profiling, it being possible for the surface profiling to have lubricant pockets and/or a backflow twist, for example.

According to another embodiment, the dynamically loaded sealing lip may be formed as a preliminary sealing lip.

A preliminary sealing lip is an uncoupled electrical bridge. In this context, “uncoupled” is understood to mean that the sealing function of a used main sealing lip is uncoupled from the function of an electrical bridge formed by the preliminary sealing lip. The preliminary sealing lip is not in direct contact with the medium to be sealed. It is advantageous that the electrical resistance of the preliminary sealing lip remains substantially constant over the whole of the service life. If the preliminary sealing lip were to come into contact with the medium to be sealed, the resistance would change constantly and uncontrollably when the seal is used as intended.

If the above-claimed sealing lip is formed as a preliminary sealing lip, a further dynamically loaded sealing lip, as a main sealing lip for sealing a medium to be sealed in a chamber to be sealed, is arranged upstream of said preliminary sealing lip in the axial direction in a functional series arrangement. The material of which a further sealing lip of this kind consists may be suited to the particular use-related circumstances. It is not necessary for the further sealing lip to also be electrically conductive.

The further dynamically loaded sealing lip may consist of a polymer or elastomer material. If a polymer material is used, for example a PTFE material, it is possible to dispense with separately produced spring elements, for example annular spiral coiled springs, which press the further sealing lip against the machine element to be sealed so as to be resiliently radially prestressed.

By contrast, if an elastomer material is used, the sealing lip made of said material may be radially surrounded on the outer periphery by a spring element, for example an annular spiral coiled spring. In particular in the case of a stationary shaft to be sealed and/or only low relative overpressure in the chamber to be sealed, the spring element ensures effective sealing by the further sealing lip on the surface to be sealed of the machine element to be sealed.

The supporting ring may consist of a metal material. Supporting rings of this kind are easy and cheap to produce in many dimensions.

The sealing ring may be in direct abutting contact with the supporting ring.

According to another embodiment, the sealing ring may be in indirect abutting contact with the supporting ring by means of an elastomer track.

The elastomer track may completely surround the axial leg and/or the radial leg. This is advantageous in that the supporting ring is thus particularly well protected from external influences, for example from exposure to moisture.

Without electric potential equalization, as is brought about by the above-described seal, the machine elements to be sealed with respect to one another could be mechanically damaged as a result of voltage puncture. As a result of the potential equalization, varying amounts of electric potential in the machine elements are equalized.

Generally, the closer the machine elements having varying electric potentials are adjacently associated with one other, the greater the likelihood of voltage puncture. Voltage puncture of this kind may cause removal of material from the machine element having a relatively lower charge and an undesirable change to the microstructure of the material in the region of the voltage puncture.

The first machine element may be formed by a drive shaft of an electric motor, and the second machine element may be formed by a housing of a gearbox that is connected to the electric motor and surrounds the drive shaft.

This specific use of the above-described seal is particularly advantageous. If the electric motor and the gearbox together form a drive unit, the operation of the electric motor usually causes individual components of the drive unit to become statically charged and thus brings about differences in potential between components that are not statically charged. In general, it is possible to bring about potential equalization between components having varying potentials by means of relatively complex design measures. In the seal according to the invention, this potential equalization is achieved in a very simple manner by means of the sealing ring itself, which is made of an electrically conductive material, the seal having a simple structure and being easy and cheap to produce.

FIGS. 1 to 4each show one embodiment of a seal.

The seal comprises a supporting ring1and a sealing ring2, the sealing ring2being fixed to the supporting ring1.

The supporting ring1is L-shaped and comprises a radial leg7and an axial leg8, which is completely surrounded by the sheath5in the peripheral direction12. The sealing ring2comprises a dynamically loaded sealing lip6, which is arranged on the side of the sealing ring2facing radially away from the sheath5in radial direction4.

The sealing ring2consists of an electrically conductive polymer material (a PTFE material in the shown embodiments), the sheath5and the sealing lip6being formed so as to transition into one another as one piece. As a result, the sealing ring2is electrically conductive, from the sealing lip6to the sheath5, in order to ensure electric potential equalization between a shaft13to be sealed and a housing14, which surrounds the shaft13to be sealed on the outer periphery3at a radial spacing. As a result, electrostatic charge between the shaft13to be sealed and the housing14is prevented, as is voltage puncture, which could damage the machine elements13,14to be sealed with respect to one another.

In the shown sealing arrangement, it is particularly advantageous that the sheath5of the sealing ring not only ensures the above-described potential equalization, but is also formed so as to be statically sealing. There is therefore no requirement for a separately produced static seal for sealing with respect to the housing14.

FIG. 1shows a first embodiment, which is particularly easy and cheap to produce. The seal consists of only two parts, specifically the supporting ring1and the sealing ring2, the sealing ring2comprising the sheath5and the sealing lip6, which are formed so as to transition into one another as one piece and are formed of the same material.

In the embodiment shown here, the sealing lip6is axially curved towards a chamber15to be sealed of the sealing arrangement.

By contrast, inFIG. 2, the dynamically loaded sealing lip6is formed as a preliminary sealing lip and is axially curved towards the surroundings16of the sealing arrangement. In addition, in this embodiment, the further sealing lip9is provided, which is provided as a main sealing lip for sealing the medium to be sealed in the chamber15to be sealed. The further sealing lip9is arranged upstream of the dynamically loaded sealing lip6in the axial direction10in a functional series arrangement, as viewed from the chamber15to be sealed.

InFIGS. 1 and 2, the dynamically loaded sealing lip6is directly abuttingly fixed to the supporting ring1. The further sealing lip9inFIG. 2is also in direct abutting contact with the supporting ring1.

FIG. 3shows a third embodiment, which is similar to the embodiment fromFIG. 2, the supporting ring1being completely surrounded by the elastomer track11. The dynamically loaded sealing lip6and the further dynamically loaded sealing lip9are connected to the elastomer track11such that the sealing ring2is in indirect abutting contact with the supporting ring1by means of an elastomer track11.

An elastomer sealing lip17which, between the dynamically loaded sealing lip6and the further dynamically loaded sealing lip9in the axial direction10, sealingly surrounds the surface to be sealed of the shaft13to be sealed so as to be radially prestressed is arranged on the radial leg7on the radially inner periphery.

FIG. 4shows a fourth embodiment, which is similar to the embodiment fromFIG. 3, a further dynamically loaded sealing lip9consisting of an elastomer material being used in place of the further dynamically loaded sealing lip9consisting of a polymer material. Said further sealing lip9is in the form of a conventional radial shaft sealing ring, said lip being sealingly pressed, by means of an annular spiral coiled spring18, against the outer periphery3of the shaft13to be sealed.

Just as inFIG. 3, an elastomer sealing lip17, which forms a preliminary seal for the further sealing lip9and is arranged axially upstream of said further sealing lip towards the surroundings16, is arranged between the dynamically loaded sealing lip6and the further dynamically loaded sealing lip9in the axial direction10.

InFIGS. 3 and 4, the above-described electric potential equalization is achieved by the dynamically loaded sealing lip6, which electrically conductively connects the shaft13to be sealed to the housing.

Overall, it is a notable advantage that the dynamically loaded sealing lip6which brings about the electric potential equalization consists of a wear-resistant polymer material such that said sealing lip can be arranged not only in the chamber15to be sealed containing the medium to be sealed, as shown inFIG. 1, thereby being lubricated by the medium to be sealed. Said sealing lip may also be arranged in the surroundings16, as shown inFIGS. 2 to 4, and therefore does not come into contact with the medium to be sealed in the chamber15to be sealed. On account of the advantageous polymer material that is used, lubrication by means of the medium to be sealed is not required.