Shaft seal device

Abstract

The invention relates to a shaft seal, in particular a radial shaft seal, having at least one sealing element (5, 5a) made of a polyfluorocarbon, preferably made of polytetrafluoroethylene. The sealing element (5, 5a) is provided with a sealing lip (4, 4a) which, under the action of a radial force, bears against a surface to be sealed. The sealing element (5, 5a) is supported by at least one elastomer element which is formed by a sealing ring (7, 7a).

Description

TECHNICAL FIELD

[0001] The invention relates to a shaft seal, in particular a radial shaft seal. BACKGROUND

[0002] In shaft seals in the form of radial shaft seals, polyfluorocarbons, in particular polytetrafluoroethylene, are advantageously used as a material for the sealing element, since this material has special physical and chemical properties. The sealing element is configured as an annular sheet, the region of which radially inside is elastically bent in order to form a sealing lip. A creep phenomenon can be observed with polyfluorocarbons, in particular polytetrafluoroethylene. Furthermore, the material has a small mechanical strength. The creep of this material leads to a weakening of the sealing action. In order to counteract this creep effect, the radial pretension acting on the sealing lip is increased for this purpose. But this leads to a correspondingly more severe wear of the sealing lip. Different fillers are therefore added to the sealing element, which complicate and make more expensive the manufacture of the sealing element.

[0003] DE 10 2012 001 226 describes an alternative shaft seal, in particular a radial shaft seal, having at least one sealing element, which is provided with a sealing lip, which, under the action of a radial force, lies on the surface to be sealed, and at least one elastomer element, which loads the sealing lip in the direction of the surface to be sealed. Suitable elastomer elements can only be manufactured at high cost due to their cross section. SUMMARY

[0004] It is an object of the invention to configure a shaft seal of the type mentioned at the outset in such a way that the shaft seal can be manufactured more simply and more economically.

[0005] The object is achieved by a shaft seal according to the invention.

[0006] The shaft seal comprises an elastomer element, which supports the sealing element. According to the invention, a sealing ring is used as the elastomer element. According to the invention, the sealing ring supports the sealing element in such a way that the sealing lip, which achieves a dynamic seal relative to the shaft, is pressed in the direction of the surface to be sealed. The sealing lip is usually curved in the direction of the medium side. The sealing ring does not come into contact with the sealing lip itself, but rather with the transition region of the sealing element to the sealing lip, in which the sealing element has been curvedly extended. The sealing lip thereby contributes efficiently to preventing a weakening of the pretension due to creep and due to wear of the sealing lip. As a simple component, the sealing ring contributes to the error-free installation of the sealing ring, which reduces the error rate and the manufacturing costs of the shaft seal.

[0007] The sealing element is advantageously designed as an annular disk, the radially inner region of which is elastically bent to form a sealing lip. The annular disk requires less space and thus contributes to achieving small dimensions and economical production of the shaft seal.

[0008] According to an advantageous embodiment of the present invention, the sealing ring can be an O-ring with a circular cross-section. This gives the sealing ring a common, standard shape and can therefore be manufactured industrially, for example, by injection molding, in large quantities and thus economically. The economical and simple availability of the sealing ring eliminates the need for costly stockpiling of such rings. This reduces the manufacturing costs of the shaft seal.

[0009] According to an alternative embodiment of the present invention, the sealing ring can have an elliptical cross-section. Depending on the installed state, the elliptical cross-section can be designed with no, one, or two axes of symmetry. The elliptical cross-section of the sealing ring can be designed at least so that, even in the undeformed state, the sealing ring has the largest possible contact surface with the sealing element. To this end, the elliptical sealing ring can be designed so that its larger cross-sectional dimension extends radially in the shaft seal, while its smaller cross-sectional dimension extends axially. This distributes the supporting effect of the sealing ring over a larger surface area of ​​the sealing element and thus exerts this supporting effect further radially.

[0010] According to an alternative embodiment of the present invention, the sealing ring can be a square ring or have a bone-shaped cross-section. The bone-shaped cross-section can be achieved, for example, by compression molding. The square ring provides two contact lines with the sealing element, which are spaced as far apart as possible depending on the size of the square ring. This ensures that the support of the sealing element or the pressure acting on the sealing lip, in particular, acts as far radially inward as possible. Furthermore, tearing of the contact joint between the sealing element and its axially acting support surface can be avoided.

[0011] The shaft seal can have a support surface for the sealing ring, which is situated axially opposite the sealing element and against which the installed sealing ring rests in order to exert a supporting force on the sealing element.

[0012] According to an advantageous embodiment of the application, the support surface can have a recess which is annular. The recess can be continuous or have interruptions, for example can be configured as recesses which are arranged next to one another. The radial edges of the recess concentrate the contact forces of the support surface acting on the sealing ring resting on the support surface onto a smaller surface, whereby the load acting on the sealing ring is increased. Furthermore, the recess allows the force to be introduced onto two introduction areas on the sealing ring which extend from a force introduction surface which is narrow in the radial direction in the relaxed state. The sealing ring can thus transmit its support force over a wider area.

[0013] According to a further advantageous embodiment of the application, the surface to be sealed is a peripheral surface of a rotating shaft or a stationary shaft. A compact design can thus be achieved.

[0014] Alternatively, the surface to be sealed can be a peripheral surface of a running sleeve which is non-rotatably fitted on a rotating shaft or a stationary shaft. The sealing element is thus not in direct contact with the rotating shaft or the stationary shaft. The material of the running sleeve can instead be chosen so as to achieve an optimum interaction with the sealing element.

[0015] According to a further advantageous embodiment of the application, a plurality of sealing elements can be arranged next to one another in the axial direction, the sealing elements each resting with one side on a support element. The sealing action of the shaft seal can thus be increased and can be adapted to higher requirements, whereby the range of use of the shaft seal can be expanded.

[0016] The sealing elements can advantageously rest with their other side on the sealing ring described in detail above.

[0017] The subject matter of the present application is also derived from all the content and features disclosed in the drawings and the description. Even if these content and features are claimed as essential to the invention, they are new with respect to the prior art, both individually and in combination with one another.

[0018] Further features of the application are derived from the description and the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0019] The principles of the application will be explained in detail below with reference to several embodiments which are shown in the drawings. Among others:

[0020] Figures 1 to 4 Different embodiments of a shaft seal according to the application are each shown in an axial half-section. DETAILED DESCRIPTION

[0021] According to Figure 1The shaft seal arrangement includes a running sleeve 1, which is non-rotatably mounted on a shaft to be sealed (not shown). The running sleeve 1 is preferably fitted onto the shaft to be sealed using a press fit. At one end, the running sleeve 1 has an annular flange 2 oriented radially outward. The other end 3 of the running sleeve 1 can be flared in a funnel shape. The radial dimensions of the annular flange 2 are greater than those of the flared end. The funnel-shaped flared end of the running sleeve 1 facilitates better alignment during installation of the shaft seal and can serve as a transport fixture and for encapsulating pre-lubricant to prevent drag and contamination.

[0022] The two sealing lips 4, 4a of the two sealing elements 5, 5a rest sealingly against the cylindrical outer side of the running sleeve 1 or its circumferential surface 27 under radial preload. The sealing elements form part of the dynamic sealing structure of the shaft seal. Alternatively, only one sealing element or more than two sealing elements may be provided. The sealing elements 5, 5a are advantageously sealing discs that are elastically bent in their radially inner regions to form the sealing lips 4, 4a. The sealing lips 4, 4a are elastically bent toward the media side 6.

[0023] Each sealing element 5, 5a rests on a support disc 19, 19a on its side facing away from the media side 6. The support disc rests with its radially inner region 20 over the entire surface of the transition region from the sealing element 5, 5a to the sealing lip 4, 4a and is bent with its radially inner section toward the media side 6. Another support disc 19b is provided on the side facing the media side 6 and is equidistant from the support disc 19. As viewed in the axial direction of the shaft seal arrangement, the support disc 19b overlaps the annular collar 2 of the running sleeve 1 and is spaced axially apart from the support disc 19b.

[0024] Support fins 19, 19a, 19b extend radially as far as the cylindrical peripheral wall 10 of the housing 9. The radial outer edges of the support fins 19, 19b are advantageously fixed to the peripheral wall. Support fin 19a transitions into the peripheral wall 10 at a right angle and is advantageously formed integrally with the peripheral wall. The other end of the peripheral wall 10 transitions at a right angle into a radially outwardly oriented annular flange 13. In the installed position of the shaft seal, the housing 9 rests with this annular flange in a known manner against the side of a device having a receiving opening for the shaft seal. The housing 9 is advantageously constructed integrally and is preferably made of a metal material. Depending on the intended use of the shaft seal, the housing 9 can be made of a suitable, preferably hard plastic.

[0025] If the support plates 19, 19b are made of metal, they are advantageously welded to the peripheral wall 10. Alternatively, the support plates can also be pressed in.

[0026] On the outer side of the peripheral wall 10 of the housing 9, a sealing structure 21 is provided, which constitutes a static seal in the installed position of the shaft seal. The sealing structure 21 can be applied, for example as shown, as a sealing strip or as a planar layer and extends annularly on the periphery of the peripheral wall 10. In the installed position of the shaft seal, the sealing structure 21 is elastically deformed and thereby ensures that a reliable static seal is achieved.

[0027] On the side facing the medium side 6, each sealing element 5, 5a is partially covered by an O-ring 7, 7a as an elastomer element. The O-ring 7, 7a has a circular cross-section and on one peripheral section and thereby planarly abuts against the sealing element 5, 5a up to the transition area of the sealing element to the sealing lip 4, 4a. The O-ring is made of an elastic plastic, rubber, rubber-like material and similar materials.

[0028] The O-ring 7, 7a abuts in the axial direction on the support web 19 or 19b on its side facing the medium side 6. The O-ring is loaded between the sealing element 5, 5a and the support web 19, 19b under pretension, so that the O-ring is deformed (not shown) and thereby exerts a pressure on the sealing element 5, 5a and the transition area thereof to the sealing lip 4, 4a.

[0029] The circular cross-section of the O-ring 7, 7a makes it possible to achieve a very compact design of the shaft seal. As a standard component, the O-ring 7, 7a can be obtained economically and simply.

[0030] The support webs 19, 19a, 19b each have an annularly encircling recess 30. The recess can alternatively be configured as a plurality of recesses arranged in a ring and thereby approximately as configured with interruptions. The recess 30 increases the stiffness of the support web 19, 19a, 19b, so that the support web does not necessarily achieve its stiffness only in relation to its material thickness. Thus, at the same load capacity, the support web can be configured more slender, so that the shaft seal can be achieved more compactly and its manufacture can be more economical.

[0031] Furthermore, the recess can be arranged such that it is located in the contact face of the support web 19, 19b and the mounted O-ring 7, 7a, respectively. The recess thereby influences the pressure action of the O-ring 7, 7a, since the recess enlarges the originally concentrated, in the shown cross-section point-like contact face of the O-ring 7, 7a, when the O-ring 7, 7a is not loaded. When the O-ring 7, 7a is loaded, the load on the sides of the central region of the contact face of the O-ring 7, 7a is increased by the recess 30, although the central region is unloaded, and the load is concentrated in a smaller space by the edges of the recess 30.

[0032] The O-rings 7 , 7 a shown advantageously also rest against the inner side of the circumferential wall 10 , thereby supporting the sealing rings 7 , 7 a in the radial direction.

[0033] The sealing elements 5, 5a are arranged in the manner described above between the O-rings 7, 7a and the support discs 19, 19a, and rest against each of the O-rings and the support discs. The support discs 19, 19a, 19b secure the components 7, 7a, 5, 5a of the shaft seal. The O-rings 7, 7a are spaced sufficiently apart from the sealing lips 4, 4a so that they do not impede the mobility of the sealing lips 4, 4a.

[0034] The supporting discs 19 , 19 a , 19 b and / or the O-rings 7 , 7 a can be chemically and / or mechanically connected to the sealing element 5 , 5 a .

[0035] according to Figure 2 The embodiment differs from the previously described embodiment in that the O-rings 70 and 70a have different cross-sections. Instead of a circular cross-section, the O-rings have an elliptical cross-section, specifically a symmetrical cross-section having two opposing circular arcs and a straight section. The O-rings 70 and 70a are arranged so that their smaller width extends in the axial direction.

[0036] Because the shaft seal is wider in the radial direction due to the oval cross-section of the O-rings 70, 70a, the support discs 19, 19a, 19b are also wider in the radial direction compared to the previous embodiment. Accordingly, the sealing elements 5, 5a are also dimensioned differently, with the area where they abut against the support discs 19, 19a being wider in the radial direction compared to the previous embodiment. The groove 30 is less significant due to the oval cross-section of the O-rings 70, 70a and can therefore be omitted here, but it can of course be provided.

[0037] All other components of the shaft seal device, which are marked with the same reference numerals as in the previous embodiment, remain unchanged and also have the properties and functions described therein, and therefore will not be described again in order to avoid repetition, but will be referred to in detail. Figure 2 Public content also applies here.

[0038] In addition to the effects described above, the radially wider dimensions of the O-rings 70, 70a also offer the additional advantage of a larger radial range of action. The O-rings 70, 70a thus support their associated sealing elements 5, 5a over a greater radial extent. This is due not only to the O-rings 70, 70a having a larger contact surface with the support discs 19, 19b on the one hand and the sealing element 5, 5a on the other, but also to the continued support in the transition area between the sealing element 5, 5a and its sealing lip 4, 4a. This support not only maintains the preload of the sealing lip 4, 4a but also prevents the sealing element 5, 5a from separating from the support rings 19, 19a in a radially outward direction.

[0039] according to Figure 3 The embodiment described above Figure 2 The embodiments differ in the cross-sections of O-rings 170 and 170a. These cross-sections can be described as bone-shaped. Starting from a rectangle, this cross-section is achieved by strongly rounding the corners (viewed in axial section) with semicircular shapes. These corners, replacing the sides of the rectangle, transition streamlined into curved or concave constrictions. This results in a material distribution of O-rings 170 and 170a that concentrates a greater amount of elastic material in four areas around the circumference of O-rings 170 and 170a.

[0040] Such an O-ring can have external dimensions which correspond in principle to Figure 2 The outer dimensions of the O-rings 70, 70a in the radial and axial directions are shown. As a result, all other components of the shaft seal can in principle have the same dimensions and provide the same properties and functions as here, so in order to avoid repetition, they will not be described again, but will be described in detail. Figure 3 The disclosed content is also applicable. It is just that due to the special cross-sectional shape of the O-ring 170, 170a, the groove 30 is no longer effective and can therefore be omitted.

[0041] Although the special bone-shaped cross section of the O-ring 170, 170a has the same Figure 2 The radially identical dimensions of the O-rings 170, 170a result in a relatively better radial range of action. Since not only is the support of the O-rings 170, 170a on the respective support rings 19, 19b shifted radially into the region of the O-rings 170, 170a closer to the periphery, but the support and force action of the O-rings on the sealing elements 5, 5a also expand radially in the same manner, the O-rings act radially further inwards and thus more effectively in the transition region of the sealing elements 5, 5a and here closer to the sealing lips 4, 4a.

[0042] according to Figure 4 The embodiment is consistent with the above Figure 3 The design principle of the O-ring 170, 170a of the embodiment of the invention is different only in the radial size of the square ring 270, 270a. The cross section of the square ring 270, 270a is therefore particularly different from the embodiment of the invention. Figure 3 Compared with the embodiment of FIG. 1 , a more compact structure of the shaft sealing device is achieved.

[0043] The cross section of the square ring 270, 270a is point symmetrical and can thus be inscribed in a square. Figure 1 The cross section of the embodiment is the same as that of the shaft seal, so that all other components of the shaft seal are Figure 1 The components marked with the same reference numerals in FIG. 1 may remain unchanged with respect to this embodiment; these components have the same properties and functions as those described there and are therefore not described again to avoid repetition. Figure 4 It is also deemed to have been made public.

[0044] According to Figure 1 Unlike the embodiment of the present invention, the cross section of the square ring 270, 270a first achieves a better radial range of action than the above embodiment. Figure 3 As explained, the square ring extends in particular radially inwards at a similar distance and thus with similar effect into the transition region of the sealing elements 5, 5a and here is equally close to the sealing lips 4, 4a. In combination with its compact size, this square ring thus achieves a high-performance shaft seal.

[0045] Since the shaft sealing device described in detail above relates to some embodiments, those skilled in the art can modify these embodiments in a common manner without departing from the scope of the present invention. In particular, the housing can be designed in other forms than those described here.

Claims

1. A sealing system comprising a shaft sealing device, comprising: at least one sealing element (5, 5a) made of polyfluorocarbon, the sealing element being provided with a sealing lip (4, 4a) which bears against a surface to be sealed under radial force; and at least one elastomeric element formed by a sealing ring (7, 7a, 70, 70a, 170, 170a, 270, 270a), the elastomeric element supporting the sealing element (5, 5a), the sealing element being a sealing disc which is elastically bent in a radially inner region to form a sealing lip (4, 4a'), characterized in that The sealing ring (7, 7a, 70, 70a, 170, 170a, 270, 270a) is flatly abutted against the sealing element (5, 5a) up to the transition area between the sealing element and the sealing lip (4, 4a), so that the sealing ring (7, 7a, 70, 70a, 170, 170a, 270, 270a) is spaced sufficiently apart from the sealing lip (4, 4a) so that the sealing ring does not hinder the mobility of the sealing lip (4, 4a).

2. The sealing system according to claim 1, characterized in that The sealing ring (7, 7a) has a circular cross section.

3. The sealing system according to claim 1, wherein: The sealing ring (70, 70a) has an elliptical cross section.

4. The sealing system according to any one of claims 1 to 3, characterized in that The sealing ring (7, 7a, 70, 70a, 170, 170a, 270, 270a) rests on the supporting surface (19, 19a, 19b).

5. The sealing system according to claim 4, characterized in that At least one groove (30) is provided in the support surface (19, 19a, 19b).

6. The sealing system according to claim 1, wherein: The surface to be sealed is the circumference of a rotating or stationary shaft.

7. The sealing system according to claim 1, wherein: The surface to be sealed is the circumferential surface (27) of a running sleeve (1), which is seated in a rotationally fixed manner on a rotating shaft or a stationary shaft.

8. The sealing system according to claim 1, wherein: A plurality of sealing elements (5, 5a) are arranged side by side in the axial direction, and each of the sealing elements rests on a supporting surface (19, 19a) with one side surface.

9. The sealing system according to claim 1, wherein: The shaft sealing device is a radial shaft sealing device.

10. The sealing system according to claim 1, wherein: The sealing element (5, 5a) is made of polytetrafluoroethylene.

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