SEALING SYSTEM HAVING PRESSURE RELIEF ELEMENTS AND USE OF A SEALING SYSTEM TO PRODUCE AN INTERMEDIATE-SPACE PRESSURE CASCADE

Abstract

A sealing system is between two components, which are translatorily movable relative to each other along a motional axis for sealing off a high-pressure side from a low-pressure side. The sealing system includes pressure relief elements. The use of such a sealing system produces an intermediate-space pressure cascade.

Claims

1. A sealing system between two components, which are translatorily movable relative to each other along a motional axis, for sealing off a high-pressure side from a low-pressure side; wherein an outer component has a first annular groove, which is open to an inner component and is facing toward the low-pressure side, and two second annular grooves, which are open to the inner component and are facing toward the high-pressure side; wherein in the first annular groove is provided a sealing arrangement, the sealing arrangement comprising a first sealing ring, made of an elastically deformable material, which bears against the inner component, and a first pretensioning ring, made of an elastically deformable material, which radially tensions the first sealing ring and seals it off from the first annular groove; wherein in respectively every second annular groove is provided a pressure relief element, each pressure relief element comprising a second sealing ring , made of an elastically deformable material, which bears against the inner component, and a second pretensioning ring, made of an elastically deformable material, which radially tensions the second sealing ring and seals it off from the second annular groove; wherein the second sealing ring has a sealing edge having a high-pressure-side contact surface angle and a low-pressure-side contact surface angle; wherein to each pressure relief element is assigned at least one connecting channel via which: an intermediate space between the sealing arrangement and the first pressure relief element is connectable to the high-pressure side; or an intermediate space between two adjacent pressure relief elements is connectable to the high-pressure side; or two adjacent intermediate spaces are connectable to each other via the connecting channel; wherein each connecting channel, in a pressure situation P.sub.ZN>P.sub.H or P.sub.ZN>P.sub.ZH, is closed and, in a pressure relief situation P.sub.ZN≧P.sub.H+P.sub.crit or P.sub.ZN≧P.sub.ZH+P.sub.crit, is open; wherein P.sub.H is the hydraulic pressure on the high-pressure side, P.sub.ZN the hydraulic pressure in the low-pressure-side intermediate space, P.sub.ZH the hydraulic pressure in the high-pressure-side intermediate space, and P.sub.crit a pressure increase value at which, or in excess of which, the connecting channel is open; wherein P.sub.crit is defined by a deformation of the second pretensioning ring; wherein the connecting channel, in the pressure situation P.sub.ZN>P.sub.H or P.sub.ZN>P.sub.ZH, is closed off by the second pretensioning ring; wherein the high-pressure-side contact surface angle of the sealing edge of the second sealing ring is less than or equal to the low-pressure-side contact surface angle of the sealing edge, so that in the pressurized state, and upon a to-and-fro movement of the inner component in the outer component, there is set for the second sealing ring a specific leakage rate, via which the hydraulic pressure in the low-pressure-side intermediate space is adjusted; and wherein the second sealing ring and the second pretensioning ring of the two pressure relief elements are respectively configured in one piece with each other and consist of polyurethane, wherein P.sub.crit is defined by an at least portional deformation of the second pretensioning ring in a direction radial to the motional axis, and wherein the sealing edge of the sealing ring of each pressure relief element is rounded, and wherein the second sealing ring of the two pressure relief elements are respectively provided with a support ring, and wherein the support ring of at least one pressure relief element has a radius solely on its inner side facing toward the inner component.

2. The sealing system as claimed in claim 1, wherein the first sealing ring and the first pretensioning ring of the sealing arrangement are configured in one piece with each other and consist of polyurethane.

3. The sealing system as claimed in claim 1, wherein the second pretensioning ring of the pressure relief element has a leg, which is configured in the manner of a sealing lip and which, in the pressure situation P.sub.ZN>P.sub.H or P.sub.ZN>P.sub.ZH, bears with a sealing edge sealingly against the groove bottom of the second annular groove, and wherein the sealing-lip-like leg, in the pressure relief situation, is moved out of its sealing contact against the groove bottom.

4. The sealing system as claimed in claim 1, wherein at least one of the connecting channels comprises a through bore disposed in the pressure relief element, and/or groove portions which are configured on the pressure relief element and/or in the outer component and are open toward the second annular groove.

5. The sealing system as claimed in claim 4, wherein one of the groove portions is disposed on a low-pressure-side end face of the pressure relief element, or on an outer side, facing toward the groove bottom of the second annular groove, of the second pretensioning ring, or on an end face, facing toward the high-pressure side, of the second sealing ring of the pressure relief element.

6. The sealing system as claimed in claim 1, wherein the outer component is a cylindrical housing and the inner component is a piston rod of a piston guided in the cylindrical housing.

7. The sealing system as claimed in claim 1, wherein the second sealing ring of at least one pressure relief element is provided with a support ring, which has an inner side facing toward the inner component and having shallow cone angles or having a radius.

8. The use of a sealing system as claimed in claim 1 to produce an intermediate-space pressure cascade, wherein the hydraulic pressures in the intermediate spaces are set such that at every second sealing ring the same pressure difference is obtained.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Further advantages of the invention emerge from the description and the figures of the drawing. Below, the invention is explained on the basis of an illustrative embodiment represented in the drawing, wherein:

[0025] FIG. 1 shows a sealing system according to the invention in a base pressure situation, in a partial sectional representation; and

[0026] FIG. 2 shows the sealing system according to FIG. 1 in a pressure relief situation, in a partial sectional representation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] FIG. 1 shows a sealing system 10 according to the invention between two mutually movable components for sealing off a high-pressure side H from a low-pressure side N.

[0028] An inner component 12 is arranged in an outer component 14 such that it can perform a translatory movement axially along a motional axis 16. The outer component 14 can be configured, for instance, as a cylindrical housing, and the inner component 12 as a piston rod of a piston guided in the housing. In FIG. 1, the upper half space of the sealing system 10 is shown in a partial longitudinal section. The outer component 14 has in total three annular grooves, which are open toward the inner component 12, a first annular groove 18, which is facing toward (disposed closer to) the low-pressure side N, and two second annular grooves 20a and 20b, which are arranged on (disposed closer to) the high-pressure side H. In the first annular groove 18 is provided a sealing arrangement 22. Naturally, the annular grooves can also be formed through the inner component.

[0029] The sealing arrangement 22 comprises a first sealing ring 24, made of an elastically deformable material, which bears against the inner component 12, and a first pretensioning ring 26, made of an elastically deformable material, which radially tensions the first sealing ring 24 and seals this off from the first annular groove 18. The first pretensioning ring 26 can be realized, for instance, as an O-ring. The sealing arrangement 22 serves as a primary seal, for which reason a sealing edge 28 of the first sealing ring 24 has a steep pressure gradient. The steep pressure gradient and the associated low leakage rate depends on a high-pressure-side contact surface angle α and a low-pressure-side contact surface angle β between the first sealing ring 24 and the inner component 12, wherein the high-pressure-side contact surface angle α exceeds the low-pressure-side contact surface angle β.

[0030] In the second annular groove 20a is arranged a first pressure relief element 30a, in the further second annular groove 20b a further pressure relief element 30b. The pressure relief elements 30a and 30b respectively comprise a second sealing ring 32a, 32b and a second pretensioning ring 34a, 34b. The second sealing rings 32a, 32b are tensioned by the second pretensioning rings 34a, 34b in the radial direction against the inner component 12.

[0031] The second sealing ring 32a, 32b and the second pretensioning ring 34a, 34b of both pressure relief elements 30a, 30b are respectively configured in one piece with each other and consist of elastically deformable polyurethane.

[0032] The second sealing rings 32a, 32b bear with their sealing edges 36 in each case sealingly against the inner component 12, wherein corresponding high-pressure-side contact surface angles α.sub.a and α.sub.b are respectively smaller than a corresponding low-pressure-side contact surface angle β.sub.a or β.sub.b. The resulting shallow pressure gradient can also be attained by symmetrical, that is to say equal, contact surface angles on a sealing edge 36. In addition, the drag behavior can be influenced by a rounding of the respective sealing edge 36.

[0033] Through the arrangement of the sealing arrangement 22, the first pressure relief element 30a and the further pressure relief element 30b one behind the other, a first intermediate space Z.sub.a between the sealing arrangement 22 and the first pressure relief element 30a and a further intermediate space Z.sub.b between the first pressure relief element 30a and the further pressure relief element 30b are defined.

[0034] The pressure relief elements 30a, 30b are respectively provided with a support ring 38. The support rings 38 engage in an indentation (not detailed) of the second sealing rings 32a, 32b and can consist, for instance, of metal or a suitable viscoelastic plastic. The support rings 38 serve on the one hand to support the second sealing rings 32a, 32b in the radial direction. On the other hand, when the pressure relief elements 30a, 30b are pressurized on the high-pressure side, the support rings 38 serve to prevent or counter an unwanted extrusion of the second sealing rings 32a, 32b into the intermediate spaces Z.sub.a and Z.sub.b respectively. For the purpose of an, as far as possible, low-friction relative movement of the inner and outer component 12, 14, the two support rings 38 to the inner component 12 can respectively be arranged in a contact-free manner. One or more of the second support rings 38 can have an inner side 39 facing toward the inner component 12 and having shallow cone angles or having a radius, as is shown by way of example in FIG. 1 in respect of the second support ring 38 of the first pressure relief element 30a. Such a design of the inner side 39 of the support ring 38 is of advantage, in particular, where the support ring 38 bears against the inner component, in terms of a reduced friction of a fluid passage which may be necessary for the pressure equalization, as well as in terms of an increased life. Furthermore, the support ring 38 can also be provided with an axial through bore (or axial groove)—not represented in detail in the drawing—for the pressurized fluid, in order to enable a completely unimpeded (axial) passage of the fluid into the connecting channel.

[0035] The shallow pressure gradients at the sealing edges 36 permit respectively at the pressure relief elements 30a, 30b a (pre)determined leakage in the pressurized state and upon a translatory movement of the inner component 12 in the outer component 14. The respective leakage rate determines the hydraulic pressure in the intermediate space which on the low-pressure side borders the respective pressure relief element 30a, 30b, in the case of the first pressure relief element 30a the pressure P.sub.Za in the first intermediate space Z.sub.a, in the case of the further pressure relief element 30b the pressure P.sub.Zb in the further intermediate space Z.sub.b. The intermediate-space pressures P.sub.Za and P.sub.Zb are set such that a stepped increase from the pressure PN on the low-pressure side up to the pressure P.sub.H on the high-pressure side arises in the sealing system 10, P.sub.N<P.sub.Za<P.sub.Zb<P.sub.H.

[0036] The choice of specific intermediate-space pressures P.sub.Za and P.sub.Zb allows the production of an equal-level pressure cascade, in which the sealing arrangement 22, as well as both pressure relief elements 30a, 30b, in particular the first sealing ring 24 and both second sealing rings 32a, 32b, are loaded with the same pressure difference P.sub.Za−P.sub.N=P.sub.Zb−P.sub.Za=P.sub.H−P.sub.Zb.

[0037] In FIG. 1, the base pressure situation P.sub.N<P.sub.Za<P.sub.Zb<P.sub.H of an intermediate-space cascade is shown. The sealing arrangement 22 bears on the low-pressure side against the first annular groove 18 and thus seals off the first intermediate space Z.sub.a from the low-pressure side N.

[0038] The second pretensioning rings 34a, 34b of the first and of the second pressure relief element 30a, 30b respectively have a substantially L-shaped cross section having a first leg 40a, 40b and a second leg 42a, 42b, configured as a sealing lip. The first leg 40a, 40b is molded onto the respective second sealing ring 32a, 32b and extends from the second sealing ring 32a, 32b radially in the direction of the groove bottom 44 of the respective second annular groove 20a, 20b. The second legs 42a, 42b respectively extend axially in the direction of the high-pressure side H of the sealing system 10. In the base pressure situation, the second legs 42a, 42b of the second pretensioning rings 34a, 34b bear sealingly with their sealing edge 46, in an elastically pretensioned manner, respectively against the groove bottom 44 of the second annular groove 20a, 20b. It should be noted that the second sealing rings 32a, 32b protrude, with their end face 48 facing toward the high-pressure side H, respectively over a free end 50 of the second leg 42a, 42b of the respective second pretensioning ring 34a, 34b, axially in the direction of the high-pressure side H. In the present case, the pressure relief elements 30a, 30b are arranged in the second annular grooves 20a, 20b with an axial play, but can also be arranged in the second annular grooves 20a, 20b without any such axial play.

[0039] Serving to equalize the pressure between the first intermediate space Z.sub.a and the further intermediate space Z.sub.b, or between the second intermediate space Z.sub.b and the high-pressure side H, are connecting channels 52. In the present case, the connecting channels respectively comprise groove portions 52a, 52b, 52c in the second sealing rings 32a, 32b or the second pretensioning rings 34a, 34b of the pressure relief elements 30a, 30b.

[0040] The groove portions 52a are arranged on a (stepped) low-pressure-side end face 54 of the pressure relief elements 30a, 30b. The groove portions 52a can also partially be configured on the respective support rings 38.

[0041] The groove portions 52b are arranged on an outer side 56, facing toward the groove bottom 44, of the second pretensioning rings 34a, 34b of the pressure relief elements 30a, 30b and run axially in the direction of the sealing edge 46 assigned to the groove bottom 44. The groove portions 52c are respectively arranged on the high-pressure-side end face 48 of the second sealing rings 32a, 32b of the pressure relief elements 30a, 30b.

[0042] The groove portions 52c are arranged on the low-pressure side of the sealing edge 46 of the respective second pretensioning ring 34a, 34b. In the shown base pressure situation P.sub.Za<P.sub.Zb, the pressure relief element 30a, 30b bears on the low-pressure side against the respective second annular groove 20a, 20b. The groove portions 52a, 52b are sealed off from the groove portion 52c by the sealing edge 46, bearing against the groove bottom 44, of the second pretensioning rings 34a, 34b, i.e. the connecting channels 52 assigned to the two pressure relief elements 30a, 30b are respectively closed off in a functionally fluid-tight manner.

[0043] In FIG. 2 is represented how the position of those individual elements of the sealing system 10 according to the invention which are shown in FIG. 1 changes upon entry into a pressure relief situation P.sub.Zb≧P.sub.H+P.sub.crit.

[0044] In this pressure relief situation, the pressure P.sub.Zb in the further intermediate space Z.sub.b has risen above the pressure P.sub.H on the high-pressure side H, whereupon the further pressure relief element 30b has been displaced to the high-pressure side H and consequently bears with its high-pressure-side end face 48 against a high-pressure-side flank 58 of the second annular groove 20b.

[0045] As a result of a further rise in the intermediate-space pressure P.sub.Zb, the second pretensioning ring 34b is activated and undergoes a (portional) deformation radially in the direction of the inner component 12, as is illustrated with the arrow 60. Upon this deformation of the second pretensioning ring 34b, the sealing edge 46, in the pressure relief situation P.sub.Zb≧P.sub.H+P.sub.crit, is lifted out of its sealing contact against the groove bottom 44 and, in this way, a fluidic connection of the intermediate space Z.sub.b via the groove portions 51a and 52b to the groove portion 52c, and hence to the high-pressure side H, is opened up. The pressure medium present in the intermediate space Z.sub.b flows along the flow direction 62 (shown in dashed representation) through the connecting channel 52 and thereby makes its way onto the high-pressure side H. This relieving of pressure in the further intermediate space Z.sub.b takes place up to the point at which the low-pressure-side overpressure no longer exceeds the pressure increase value p.sub.crit, p.sub.Zb−p.sub.H>p.sub.crit, and the second pretensioning ring 34b, due to its inherent natural elasticity, again comes to bear sealingly against the groove bottom 44 and in this way closes off the connecting channel 52 in a fluid-tight manner. Both the situation of the sealing arrangement 22 and the position of the first pressure relief element 30a remain unchanged, both in the pressure situation P.sub.Zb>P.sub.H and in the pressure relief situation P.sub.Zb≧P.sub.H+P.sub.crit, since P.sub.N<P.sub.Za<P.sub.Zb continues to apply. The pressure relief of the further intermediate space Z.sub.b thus has no effects whatsoever on the sealing arrangement 22, which illustrates the effectiveness and advantageousness of a multistep pressure cascade for relieving the pressure of a primary seal.

[0046] It should be noted that the first sealing ring and the first pretensioning ring of the sealing arrangement 22 disposed in the first annular groove 18 are configured in one piece with each other in a manner corresponding to the pressure relief elements and can consist of polyurethane.

[0047] Naturally, the groove portions 52a, 52b and/or 52c can be arranged, at least partially, in that component 12, 14 which forms the second annular grooves 20a, 20b. Furthermore, the connecting channel 52 can comprise, instead of one or more of the above-described groove portions 52a, 52b, 52c, also one or more through bores, which extend through the pressure relief element 30a, 30b.