Sealing device

[0001] This non-provisional application claims benefit to German priority document Application Serial No. 10215311.6-12 filed Apr. 8, 2002, which disclosure is hereby incorporated by reference herein.

[0002] The present invention relates to a sealing device. More specifically, the present invention relates to a sealing device for sealing off a moving shaft or rod in a transition area between a high-pressure space, carrying, for example, a liquid medium, and a low-pressure area.

[0003] It is known to use seals made of thermoplastic or elastomeric materials which, on the one side, rest against the circumference of the shaft and, on the other side, against a housing or parts thereof.

[0004] As a result of high pressures, which in some systems are above 200 bar, as well as a pressure difference in comparison to the low-pressure area resulting therefrom, the rate of motion of the shaft, the temperature and type of the medium to be sealed off, a very high wear of the sealing rings will occur. That leads to a low durability and a correspondingly low service life of the system in which such a sealing device is used. On the whole, the durable reliability of the system is severely restricted.

[0005] Furthermore, operation-caused wear of the seals or sealing rings and the related frequent interruptions of the operation naturally result in high costs to which the repair costs are added, so that a sealing device of the above-mentioned type stands in the way of an optimized economic operation.

[0006] Other sealing solutions consist of providing a sealing ring which reaches around the shaft with a slight circumferential throttling gap. Along the length of this throttling gap, the pressure difference between the high-pressure space and the low-pressure area is reduced.

[0007] However, this is connected with a relatively high leakage flow which, also as a result of the flow rate, contributes to an erosion wear by which the throttling gap is enlarged. Finally, this results in unacceptable leakages which have to be eliminated by corresponding repairs.

[0008] For eliminating these problems, the throttling gap has to be kept very small which, however, because of the required precision, can be implemented only by means of very high manufacturing expenditures and correspondingly high manufacturing costs. Components of larger dimensions are therefore usually not produced.

[0009] The present invention is a sealing device for a movable shaft arranged between a high-pressure space and a low-pressure area of a pressure-resistant housing bounding the high-pressure space. The sealing device includes a deformable pressure ring, and a sealing ring that surrounds the shaft and is partially deformable by the deformable pressure ring. The pressure ring is supported under pressure at an outer circumference of the sealing ring with the sealing ring resting either against or almost against the shaft.

[0010] The sealing ring is formed as a sleeve, which preferably consists of hard metal or ceramics. It is formed in the manner of an elevation in the area of the partial deformation. The remaining area of the sealing ring encloses the shaft at a narrow gap distance.

[0011] Before a mounting, the sealing ring has a continuously smooth interior wall. After the deformable pressure ring is acted upon by a force, the partial deformation in the direction of the shaft will take place as a result of the transmitting deformation forces of the pressure ring. Depending on the applied force, a more or less extensive deformation will take place; that is, a more or less massive construction of a beaded ring occurs and it becomes precisely adjustable how closely this beaded ring rests against the shaft.

[0012] Even in the event of a wear of this closely contacting beaded ring, caused by the axial and/or rotational movement of the shaft, this wear can be compensated as a result of an adjustment and a further deformation of the pressure ring.

[0013] The pressure ring itself consists of metal or of a suitable plastic material. It is supported on the wall of the pressure-resistant housing which in this respect represents an abutment.

[0014] The force for deforming the pressure ring and thus for partially deforming the sealing ring can be transmitted by way of a thrust ring and can be generated by screws, threads or a hydraulic system. The force is applied to the low-pressure area and is greater than the counterforce resulting from the operating pressure existing in the high-pressure space, the force being freely adjustable.

[0015] The elastic transverse deformation, which results in the formation of the above-mentioned beaded ring, reduces the gap between the sealing ring and the shaft which originally existed in that area. The gap is reduced according to the desired demands with respect to the leakage amount, the manufacturing tolerances to be compensated and/or the compensation of the preceding wear. If required, leakage flows can even be reduced to zero.

[0016] Since the sealing ring or the entire sealing device operates almost without wear, these are considerable improvements particularly with respect to the operating costs. An exchange of the sealing ring is also not required after many hours of operation so that the service life of the system into which such a sealing device is installed will be significantly longer with resulting cost improvements.

[0017] Other objects or features of the present invention will become apparent from the following detailed description when considered in conjunction with the accompanying drawings.

[0018] FIG. 1 is a cross-sectional view of an embodiment of a sealing device, according to the present invention.

[0019] FIG. 2 is a cross-sectional view of another embodiment of a sealing device, according to the present invention.

[0020] FIG. 3 is a cross-sectional view of another embodiment of a sealing device, according to the present invention.

[0021] FIGS. 1-3 each show an embodiment of a sealing device 100, 200, 300 respectively, for a rod or shaft 2. The shaft 2 is movably disposed in a guide (not shown) arranged between a high-pressure space 10 and a low-pressure area 11 of a pressure-resistant housing 1 that bounds the high-pressure space 10. The shaft 2 may be movable back and forth in axial direction A-A as well as rotating or swiveling in direction R or the reverse of direction R.

[0022] Each sealing device 100, 200, 300 has a sealing ring 3 which preferably consists of hard metal or ceramics and is constructed as a sleeve that surrounds the shaft 2. The inside diameter of the sealing ring 3 is essentially slightly larger than the outside diameter of the shaft 2, so that an interior gap 7 is formed.

[0023] A pressure ring 4, forming a static seal, has one side resting against a portion of an outer jacket (not shown) of the scaling ring 3. Pressure ring 4 is deformable and may be made of metal or of a plastic material or both. On another side, pressure ring 4 is supported on a wall of the pressure-resistant housing 1, where it rests in a receiving device 22, as shown in FIGS. 1 and 3.

[0024] By way of a spacer ring 6, acting as the thrust ring, a force F originating from the low-pressure area 11 is applied in the axial direction A, so that the pressure ring 4 deforms. The pressure ring 4 is held in an expansion-resistant manner by sides of the receiving device 22, which sides are formed, on the one hand, by a wall of the housing 1 and, on the other hand, by a step-shaped projection of the sealing ring 3 (see FIGS. 1 and 3). In the housing 1 and the spacer ring 6, feeding bores 15, 16 are provided so that liquid can be entered between the spacer ring 6 and the shaft 2 for cooling and lubrication.

[0025] For the embodiment shown in FIG. 2, there is a receiving space 22 which is comparable with the receiving device 22 shown in FIGS. 1 and 3. Pressure ring 4 is placed in receiving space 22 and is bounded by sealing ring 3 and a wall of the housing 1, as well as by a front surface of a thrust piece 12 which is arranged between the sealing ring 3 and the spacer ring 6 and encloses the shaft 2 in a ring shape.

[0026] As shown in FIG. 2, when the force F is applied, deformation forces acting upon the pressure ring 4 are radially guided in the direction of the shaft 2, causing a partial deformation and forming a beaded ring 5 on an interior wall of the sealing ring 3. That partial deformation, depending on the applied force F, has the result that beaded ring 5 rests against shaft 2 or almost rests against shaft 2.

[0027] In the case of the embodiment illustrated in FIG. 1, the sealing ring 3 is axially displaced by pressure onto the spacer ring 6, in which case the sealing ring 3 experiences a pretensioning by the axial reduction of a chamber 9 adjacent to the housing 1. In this case, the force F is greater than the product of the pressure of the medium in the high-pressure space 10 and the ring surface of the sealing ring 3 acted upon by pressure in the high-pressure space 10 minus the pressure in the low-pressure area 11 multiplied by the effective ring surface of the spacer ring 6.

[0028] Depending on the adjustment of the force F by way of screws, threads or hydraulic devices (not shown), the beaded ring 5 moves more or less closer to the shaft 2. In this case, the beaded ring 5 may even exercise a certain compressive stress upon the shaft 2.

[0029] In the embodiments shown in FIGS. 1 and 3, the sealing ring 3 is disposed in an axially displaceable manner. In the embodiment shown in FIG. 2, the sealing ring 3 is fixedly positioned; that is, it is supported on a base of a shoulder 23, while it carries the pressure ring 4 on an opposite end. In the embodiment of FIG. 2, the shaping-out toward the beaded ring 5 also takes place as described above by the spacer ring 6, but it occurs indirectly, because the thrust piece 12 is arranged between the sealing ring 3 and the spacer ring 6.

[0030] An expansion of the interior gap 7 of the sealing ring 3, because of internal pressure and a resulting decrease of the sealing effect of the beaded ring 5, is prevented by an exterior gap 8. Gap 8 is formed such that the outside diameter of the sealing ring 3, in a length region essentially projecting into the high-pressure space 10, is smaller than the inside diameter of the high-pressure space 10.

[0031] The exterior gap 8 is connected with the high-pressure space 10, so that the same pressure that is in the high-pressure space 10 exists in the interior gap 7, which gap 7 is also connected with the high-pressure space 10 and the exterior gap 8.

[0032] In the embodiment illustrated in FIG. 2, the connection between the high-pressure space 10 and the exterior gap 8 may be established by radial grooves 14 which are provided in the sealing ring 3 on a front face or side, of the sealing ring 3, which is supported on the shoulder 23 of the housing 1.

[0033] In addition, as a result of the interior gap 7, a throttling and thus a partial reduction of pressure takes place so that a lower pressure exists at a sealing area formed by the beaded ring 5 than in the high-pressure space 10.

[0034] In the embodiment according to FIG. 2, the sealing ring 3 rests firmly against the shoulder 23 in the direction of the force F and the force F is applied by way of the thrust piece 12 to the pressure ring 4. That provides adjustability, particularly in the case of greater lengths of sealing devices 3. Furthermore, different materials, which may be optimal for their respective functions, can be used for the sealing ring 3 and the thrust piece 12.

[0035] In the case of the sealing device 300, shown in FIG. 3, the sealing ring 3 is relatively short in comparison with sealing device 100, shown in FIG. 1. For sealing device 300, the throttling of pressure takes place by way of a sleeve 17. The sealing ring 3 rests against one side of the sleeve 17 and the sleeve 17 has a bevel 21 on the side facing the sealing ring 3. There is a lengthening of interior gap 19, in the form of a bevel 21, which causes a related increase of the axial contact tension, which is higher than the pressure in the high-pressure space 10. A sealing effect is thereby generated which prevents a pressure compensation between an exterior gap 18, open in the direction of the high-pressure space 10, and the interior gap 19. The exterior gap 18 is shorter than interior gap 19 which extends along the entire length of the sleeve 17.

[0036] In order to generate an initial pretensioning, a pressure spring 20 is provided which, on one side, is supported on the shoulder 23 of the housing 1 and, on the other side, is supported on the front side of the sleeve 17 facing away from the sealing ring 3.

[0037] Although the present invention has been described and illustrated in detail, it is to be clearly understood that the same is by way of illustration and example only, and is not to be taken by way of limitation. The spirit and scope of the present invention are to be limited only by the terms of the appended claims.