Piston compressors, particularly single-acting ones, require sealing along the oscillating piston rod 5. The sealing typically must be carried out against the (low) ambient pressure pu being present in the crankcase. Referring to
Packing rings 6, 7 are self-actuating seals, which usually require a certain pressure difference p1-p2 (
In a combination of a radially and a tangentially cut packing ring the sealing toward the piston rod is carried out essentially only by means of the tangentially cut packing ring, the ring segments of which may slide together by means of the tangential type of cut in case of wear, thus continuing the sealing effect. The radially cut packing ring essentially serves only to seal the wear gap of the tangential packing ring in axial direction, and is therefore subject only to little wear during the initial running-in phase. The radial packing ring shows wear only up to the point at which the ring segments are positioned adjacent to each other in circumferential direction. The radially and tangentially cut packing rings therefore show varying degrees of wear. In addition to the circumstance that the tangentially cut ring always shows quicker wear due to the larger surface adjustment than the radially cut one, the tangential ring typically also has an uneven wear pattern in circumferential direction, which may be accompanied by an opening of the tangential cuts and therefore a significantly increased leakage. In this manner such a ring may lose a large degree of the sealing effect thereof, even if the same has not yet reached the wear stop thereof (as opposed to the consumables compensation gap). Furthermore, a packing ring combination made from radially and tangentially cut packing rings requires elastic deformations of the ring segments with increasing wear in order to be able to maintain the sealing effect. In this regard only those materials are suitable for such packing ring combinations, which allow respective elastic deformations.
JP 05-044850 A1 has already suggested the use of a six-part segmented seal ring, which has three sealing segments embodying a continuous sealing surface on the radial interior. The sealing segments abut wedge-shaped support segments that are arranged there between. With the wear of the sealing segments the sealing segments move radially toward the interior and glide along the support segments, which essentially remain in the same position. Such a seal ring may therefore be subjected to a very high degree of wear without losing the sealing effect thereof. For this purpose the rate of wear, apart from the pressures present, essentially only depends on the ring material or on the material combination of the ring/piston rod selected, and may therefore be very high such that the seal ring may show wear rather quickly. The seal ring must therefore be exchanged in a timely manner before the sealing segments have too much wear, thus possibly resulting in damage or even destruction due to the mechanical and/or thermal stresses. However, since the actual wear cannot be seen from the outside, the seal must be checked periodically, which is often also accompanied by a (premature) exchange of the seal rings. The life of the seal rings is therefore possibly not optimally utilized.
It is therefore one object of the present invention to remedy the problems stated above, particularly to provide a packing ring that may be subjected to a high degree of wear, which wears very slowly, and is capable of optimally utilizing the wear potential available.
The problem is solved according to the invention in that a number of first sealing segments, a number of second sealing segments, and a number of support segments are provided, wherein the support segments and the second sealing segments are arranged in an alternating successively abutting manner in the circumferential direction, and the first sealing segments are arranged in a manner axially abutting the second sealing segments and the support segments, and a nose extending axially is provided on the second sealing segments, which is arranged in the circumferential direction between two adjacent first sealing segments. Utilizing this arrangement of the segments it is achieved that the sealing segments are relieved by another segment, thus reducing the rate of wear of the packing ring. Furthermore, the material of the sealing segments available may be greatly utilized for the formation of wear in this manner.
If a gap is provided in circumferential direction between an axial nose and the adjacent first sealing segments, a beak-in phase is created, in which the first sealing segments are pressed stronger against the counter sealing surface, whereby the sealing surface of the first sealing segments may be adjusted accordingly. In this manner a high degree of sealing effect of the packing ring is achieved from the beginning.
The sealing surface of the packing ring may be reduced, if the support segments are embodied with a larger interior radius, than the second sealing segments. Utilizing this measure the frictional heat caused by the packing ring may be reduced, by means of which less cooling power is required for the seal, or by means of which the packing ring may be utilized under more complex environmental conditions (pressure, relative speeds, etc.).
The rate of wear of the packing ring may be optimally adjusted in a simple manner, if the circumferential front surfaces of the support segments and of the second sealing segments are tilted as opposed to a radial. Said angle is a freely adjustable design parameter, by means of which the packing ring may be optimally adjusted to the respective use and specification. In a particularly advantageous manner the angle is selected such that the circumferential front surfaces of the axial nose taper in a wedge shape from the radial interior to the radial exterior.
In order to enable a full-surface contact of the first and the second sealing segments the circumferential front surfaces of the first sealing segments are advantageously tilted according to the wedge shape of the axial nose as opposed to a radial.
A radial groove for a single-acting packing ring may be realized very easily, if the axial width of the axial nose is smaller than the axial width of the first sealing segments, since the nose itself forms said groove in this case. In this manner a weakening of the first sealing segments by means of such a radial groove may be omitted.
The present invention is explained in further detail based on the schematic, exemplary, non-limiting
The perspective illustrations of a segmented packing ring 20 according to the invention in accordance with
The first sealing segments 21 have a first sealing surface 27 positioned radially on the inside, which abuts an oscillating piston rod during operational use, and seals the same in axial direction. The second sealing segments 22 have a second sealing surface 28 positioned radially on the inside, which abuts an oscillating piston rod during operational use, and seals the same in axial direction. Thus a sealing surface that is closed in circumferential direction is formed by means of the first sealing surface 27 and the second sealing surface 28. The first sealing segments 21 further also overlap the joint formed between the second sealing segments 22 and the support segments 23 by means of the circumferential surfaces 25, 26, thus also sealing said joint in axial direction. In radial direction the sealing is carried out by means of the joint formed between the second sealing segments 22 and the support segments 23 by means of the circumferential surfaces 25, 26.
The circumferential front surfaces 29 of the axial noses 24 on the second sealing segments 22 may be tilted as opposed to a radial at an angle β by the center of the packing ring 20 such that the circumferential surfaces 29 taper from the radial interior toward the radial exterior in the manner of a wedge. The circumferential front surfaces 30 of the first sealing segments 21 are preferably arranged in a parallel manner such that a full-surface contact of the circumferential front surfaces 29, 30 is enabled. A gap may be provided between the circumferential front surfaces 29, 30 of the support segments and the second sealing segments 22 in circumferential direction such that the circumferential front surfaces 29, 30 do not abut each other equally.
The axial width of the axial nose 24 may also be smaller than the axial width of the first sealing segments such that the nose 24 slightly protrudes toward the interior in an axial manner as opposed to the free front surface of the first sealing segments 21. In this manner the noses 24 simultaneously also form a radially aligned groove at the front surface of the packing ring 20 for a single-acting packing ring 20. In case the nose 24 does not slightly protrude toward the interior a radial groove may also be provided on, the first sealing segment 21 on the free front surface in order to obtain a single-acting packing ring. Such a radial groove is not required for a double action packing ring.
The circumferential front surfaces 25, 26 of the second sealing segments 22 and the support segments 23 may be arranged in a tilting manner at an angle a as opposed to a radial. The support segments 23 have a circumferential surface 33 positioned radially toward the interior, which may have a greater radius than the sealing surface 27, 28 of the first and second sealing segments 21, 22 such that an annular gap is created on the support segments 23 on the radial interior. Such an annular gap decreases the sealing surface of the packing ring 20, and therefore also simultaneously the frictional heat created.
The function of the packing ring 20 according to the invention is explained as follows with reference to
If the gap h is closed due to said different rates of wear, and the first sealing segments 21 abut the axial noses 24 (as illustrated in
For this purpose the gap h may be omitted. If available, the gap h serves to provide a type of break-in phase, in which the sealing surfaces 27 of the first sealing segments 21 are pressed against the counter sealing surface in a stronger manner in order to obtain a high sealing effect from the beginning by means of an adjustment of the sealing surface 27 achieved I this manner. Furthermore, it is ensured that the sealing effect is provided on the sealing surface 27 from the beginning regardless of the manufacture-related fluctuations in the dimensions of the segments 21, 22, 23. The annular gap formed by the support segments 23 may also be omitted. However, the same also serves to enable the sealing effect on the sealing surface 28 of the second sealing segments 22 as a function of the manufacture-related fluctuations in the dimensions of the segments 21, 22, 23 from the beginning.
The sealing segments 21, 22 wear in this manner until the first sealing segments 21 abut each other in circumferential direction. Furthermore, only the second sealing segments 22 would wear further. The material of the sealing segments 21, 22 available may therefore be utilized at a high degree before the packing ring 20 has to be exchanged.
The use of a segmented packing ring 20 according to the invention described above is described based on
A segmented packing ring 20 according to the invention may also be realized using a pressure compensation in a simple manner as described below with reference to
Furthermore, the second sealing segments 22 may also be embodied in a pressure compensated manner. For this purpose pressure compensation grooves 35 extending in circumferential direction may be incorporated in the radial interior circumferential surface 28 of the second sealing segments 22, which extend in circumferential direction, but not across the entire circumferential length of the second sealing segments 22. Said pressure compensation grooves 35 are connected to the front surface 38 of the nose 24 by means of an axial groove 36. In this manner the pressure present at the free front surface 38 of the nose 24 also acts upon the pressure compensation groove 35. Instead of the axial groove 36 the pressure compensation groove 35 in the second sealing segment could also be connected to the radial exterior circumferential surface of the sealing segments via a radial bore, whereby the pressure acting there would also act upon the circumferential groove 35. However, it is of course also conceivable to embody the packing ring 20 with pressure compensation grooves 34 in the first sealing segments 21 only, or with pressure compensation grooves 35 in the second sealing segments 22 only. The acting surface pressing action between the packing ring 20 or the individual sealing segments 21, 22 of the packing ring 20 and the counter sealing surface, i.e. at the piston rod, may be reduced by means of such a pressure compensation, thus reducing the wear of the packing ring 20.
The effect of the pressure compensation grooves 34, 35 is shown based on the use of the packing ring as a seal of a piston rod 5 of a compressor with reference to
Number | Date | Country | Kind |
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A153/2009 | Jan 2009 | AT | national |