AT504864A1 - CUTTED PACK RING - Google Patents

Description

734.AT • ···························· ··································································· ····· ··

Sliced packing ring

The subject invention relates to a cut packing ring consisting of a plurality of ring segments, which are spaced to form a wear gap between adjacent ring segments in the circumferential direction and the wear gap 5 is sealed radially outwardly by a resting on the adjacent ring segments circular segment-shaped end element, and a pressure pack, a seal and a compressor with such a packing ring.

Koibenkompressoren, especially in double-acting design, require a seal of the crank-side compression chamber in the cylinder, in which the time-varying Zylin-10 derdruck prevails, along the oscillating piston rod. This seal typically has to take place against the prevailing in the crankcase ambient pressure. The sealing elements, which are used in such a seal 4, are called packing rings 6, 7 and are in a so-called pressure pack 2, consisting of a number of packing rings 6, 7, arranged as exemplified in a conventional embodiment in Fig. 1 15 , The sealing elements can follow unavoidable lateral movements of the piston rod 5 without losing their sealing effect. To increase the service life and reliability of a pressure pack 2, a plurality of such packing rings 6, 7 are connected in series in a pressure pack 2. Such pressure packs 2 are well known in various designs, e.g. from GB 928 749 A or US Pat. No. 1,008,655 A. 20 Particularly in the case of higher pressures, in the case of conventional arrangements, considerable extrusion of the packing rings 6, 7 may also occur in the gap formed between the piston rod 5 and the packing housing. To avoid this extrusion as much as possible, additional metallic support rings 8 not touching the piston rod 5 may be used between the ring on the low pressure side and the chamber disk 10, e.g. 25 in US 3,305,241.

Packing rings 6, 7 are self-activating seals which, for a sufficient sealing effect, ie a sufficiently small leakage, generally require a certain pressure difference pi-P2 to be sealed (FIG. 1c). The gas pressure in a packing chamber 3 builds up in the sealed columns of a packing ring 6, 7 from the higher level Pi to 30 the lower level p2 in the next packing chamber 3 from. FIG. 1 c schematically shows this pressure reduction in the sealing gap formed between packing ring 6, 7 and piston rod 5. This sealing gap plays an essential role with regard to the performance of the packing rings 6, 7, since the relative movement of the contact surfaces between the piston rod 5 and rings 6, 7 causes a wear of the packing rings 6, 7. -1- • · · · · · • " · · · · • · · · ··· • · · · · ·· ·· ··

734.AT • · · · · # · · · · · · · · · · · · ······

The ring wear is mainly influenced by the surface pressure between packing ring and piston rod. On the packing rings acts radially outward pressure p, usually the high pressure p-ι, thus causing a surface pressure pf the piston rod. If an uncut packing ring, the inner diameter of which exactly corresponds to the piston rod diameter in the unloaded state, is subjected to a pressure Pi on its outer circumference, this causes, according to the rigidity of the packing ring in the circumferential direction, a surface pressure Pf to the piston rod, which is smaller than Pi. The "gear ratio" p </ pi of an uncut packing ring, in addition to the excess / undersize of the inner diameter of the ring relative to the piston rod by -10 in the unloaded state, depends mainly on the ring rigidity. Conventional ring materials lead with conventional ring dimensions to such circumferential stiffnesses that uncut rings no longer sufficiently seal at their inner diameter after only a very short time or after only a small amount of wear (in combination with thermal expansions, especially after compressor standstill phases) and in the non-15 mode pass more continuously on the piston rod resting "throttle ring". This mode is characterized by high leakage. Uncut packing rings are therefore generally unsuitable for use in pressure packs.

The ring wear therefore usually requires cut ring shapes, which allow an automatic continuous readjustment of the ring during material removal at the sealing gap ring / piston-20 rod. Industry standard are axially adjacent radially and tangentially cut rings 6, 7, which are used in pairs to cover each other occurring butt joints for wear compensation, as shown schematically in Fig. 1b. Such radially / tangentially cut ring combinations are single-acting seals which are only in one direction, e.g. in the direction of the crosshead of a compressor 25 sors, while in the course of the crank-side Reexpansionsphase of the reciprocating compressor 1, the radial sections ensure that no higher pressure can be included in the pack. In the case of cut ring shapes, circumference springs 9 wound around the outer circumference are conventionally used, which press the packing rings 6, 7 into the piston rod 5 even in the unpressurised state. Such cut-off packing rings with wear stop (defined by the wear gap) abruptly change into the state of a "throttle ring" with the associated high leakage after a certain wear defined by the initial gap dimension.

For cut ring shapes, a mechanical balance also requires equality of mean pressure levels acting on the outer and inner circumference of the ring. 35 Due to the fact that the average effective gas pressure in the sealing gap ring / piston rod is smaller than that at the outer circumference, a force acts in the radial direction • · · · · · · · · · ·

· «····· ♦ · · __ • j · · ··; · · J · 734AT »§ ·· ··· ···· ·· inside, with which the tangentially cut ring is pressed against the piston rod. The size of this, the surface pressure characterizing force determined on the one hand, the gas leakage through this gap, as this gas leakage in Grenzfail vanishing surface pressure, which corresponds to a non-contact labyrinth seal, is greatly increased and 5 generally decreases with increasing surface pressure. On the other hand, both the wear and the frictional heat generated during operation increase with the contact pressure, wherein increased frictional heat generation, especially in dry running applications, a sensitive increase in the piston rod temperature can entail, which in turn is typical wear materials used in addition wear considerably increased. Depending on the proportion of the leakage through the sealing gap ring / piston rod to the total leakage of the ring, increasing the contact pressure force can thus result in an increase in the wear rate with only insignificantly reduced packing leakage. For the realization of both a low wear of the sealing elements and thus a long service life and a sufficiently low gas leakage having piston rod 15 sealing system so that the size of the contact pressure is an essential factor.

Constructive designs for the reduction of these surface pressure usually make use of the concept of "pressure compensation" in which the pressure reduction in the sealing gap ring / piston rod is influenced by grooves, slots, holes in or on the rings or the like in such a way that the middle, the Surface pressure reducing 20 gas pressure increased in this sealing gap. Although such well-known concepts typically have less wear, the leakage is usually higher and may be such that the achievable life of the package, i. the length of time that the sealing system operates within tolerable limits is reduced despite comparably low wear of the packing rings. The 25 reasons for the increased leakage pressure-balanced ring designs are not necessarily in the reduced surface pressure in the sealing gap ring / piston rod, but are typically due to a "tilting" of the rings. This effect is due to uneven wear of the rings along the contact zone with the piston rod. Namely, the local wear rate is proportional to the local surface pressure, where the local surface pressure for pressure balanced concepts deviates more from the average surface pressure than for conventional, non-pressure compensated designs. The more irregular the material removal in the axial direction in the sealing gap is distributed along the contact zone, the greater the tendency of the packing rings to tilt. When tilted, in turn, the contact geometry of the various ring cuts and bumps changes, which can usually lead to an increase in the leakage. The tendency to tilt is weaker in non-pressure balanced radial / tangential cut rings. -3- ······ ···································································· 734 ··

In addition to tilting the rings, regardless of whether they are pressure balanced or not, another effect can increase the leakage significantly. In addition to the fact that the tangentially cut ring always wears faster because of the larger surface pressure than the radially cut, namely, the tangential ring typically has a non-uniform wear in the circumferential direction, whereby an opening of the adjacent tangential sections of adjacent ring segments and thus a significant increased leakage can go along. Thus, such a tangentially cut ring, even if he has not yet reached its wear stop (given by the material removal, which reduces the Verschleißkompensationsrestspaltbreite to zero), losing its sealing effect to the largest-10 th part.

It is an object of the subject invention to provide a tangentially cut packing ring, which is subjected to low wear and thus achieves an increased life and has a low leakage.

This object is achieved in that on the packing ring, an element 15 is arranged, which rests on both adjacent ring segments and on the adjacent ring segments exerts a force apart the ring segments. Such an element thus counteracts the force exerted by the applied pressure contact force, whereby the contact pressure and thus the wear can be reduced.

If the circular segment-shaped closing element at the same time forms the element by the 20 contact surfaces between the ring segments and the circular segment-shaped closure element at an angle to each other, on the one hand tilting of the circular segment-shaped closing element in the axial direction can be prevented and on the other hand a very simple embodiment of such an element can be achieved.

If a yielding element is arranged in the wear gap, the force reducing the contact force 25 can be made dependent on the wear and the reducing force can be adjusted by appropriate design of the resilient element according to the application.

Very simply such a resilient element is formed by an acting on both ring segments spring element, wherein the spring element is advantageously designed as an elastic rubber element 30 which rests either in the longitudinal direction or in the transverse direction of the two ring segments and thus is more compressed with increasing wear.

Alternatively, as a resilient element in the wear gap, a cylindrical rigid element can be arranged, which ends with its ends in one of both ring segments. ·

• · · · · · · · ···· ·· • # · • · ·

734.AT th provided recess inserted, wherein the cylindrical rigid element advantageously at least partially has a larger cross-section than the recesses in the ring segments. Thus, the force counteracting the wear increases the deeper the rigid element penetrates into the ring material. Particularly simple is the cylindrical rigid element 5 as a double cone and the recess is tapered or stepped, wherein the smaller cross section of the recess is provided facing away from the wear gap.

Such a cut packing ring is particularly advantageously used in a pressure pack with a number of packing rings and combined with a radially cut packing ring which bears axially against the cut packing ring.

In order to prevent or reduce extrusion of the cut packing ring into the gap between the movable part and the housing part, it is advantageous to provide a support ring which rests axially on the cut packing ring. In order to ensure that the low pressure prevails in the wear gap of the packing ring, since otherwise the circular segment-shaped end elements could not be pressed against the ring segments sufficiently, which could noticeably increase the leakage, a radial groove can advantageously be arranged on the support ring on one end face. which is connected to an axial through recess in the support ring. Alternatively, a radial groove is arranged on the support ring on an end face, which is connected to an axial recess in the support ring 20, wherein the axial recess opens into a arranged on the other end face of the support ring circumferential groove.

Such a pressure pack can be used particularly advantageously in a seal between a housing part of a machine, in particular a compressor, and a part of the machine which is movable relative to the housing part, in particular an oscillating piston rod.

The subject invention will be described with reference to the exemplary, schematic, advantageous embodiments showing and not limiting Figures 1 to 9 described. It shows

1 is a seal of a piston rod of a compressor,

2 shows a radially cut and a cut according to the invention packing ring,

Fig. 3 different versions of a arranged in the wear gap, the segments apart element.

Fig. 4 is a representation of the resulting force effects, -5- • • ··· · 9 · · 9 9 9

734.AT • 9 9 9 9 9 · 9 9 9 • 9 9 · ··· 9 9 9 9 9 # 9 9 9 · 9 9 9 99 99 · # · 9999 99

FIG. 5 shows a further embodiment of a packing ring cut in accordance with the invention, FIG.

6 is a representation of the resulting force effects,

Fig. 7 and 8 each depicting a support ring and 5 Fig. 9 shows another embodiment of an inventively cut pack rings.

Fig. 2 shows a packing ring combination, e.g. in a pressure pack 2 as shown in Fig. 1 can be used. In this case, a conventional radially cut packing ring 25 is combined with a second packing ring 20 cut according to the invention, the radially cut packing ring 25 resting axially on the packing ring 20 and the packing ring 20 resting against a support ring 8, 50, 51 or on the wall of the packing chamber 3 (or another contact surface) is axially applied. The radially cut packing ring 25 comprises two ring segments 26, which are arranged spaced apart in the circumferential direction to form a wear gap 27. On the radially outer peripheral surface may still be incorporated 15 circumferential groove 28 in which in a known manner a circumferential spring 9 (Fig. 1) can be arranged.

The packing ring 20, which is actually sealed in the axial direction, is four-parted in this example and comprises two ring segments 21, the ends of which are cut off along a circular chord, thereby producing a flat, straight contact surface 24. The radially inner peripheral surfaces of the ring segments form the sealing surfaces 29. To form a wear gap 23, the ring segments 21 are again spaced from each other in the circumferential direction. On the contact surfaces 24 of the two ring segments 21 is ever a circular segment-shaped end element 22 movable. The ring segments 21 and the circular segment-shaped closing element 22 can move relative to each other along the contact surface 24. In addition, the circular segment-shaped closing element 22 seals the radial wear gap 23 in the radial direction. On the radially outer peripheral surface of the ring segments 21 and / or the circular segment-shaped end elements 22 may again be incorporated a circumferential groove 28 in which in a known manner a circumferential spring 9 (Fig. 1) can be arranged, which are the loosely adjacent parts of Packungsrin-30th ges 20, especially at a standstill, when no pressure is zusammenhäit.

Of course, the packing ring 20 may also consist of more ring segments 21 and associated circular segment-shaped end elements 22, as shown in Fig. 9 based on a six-part packing ring 20. Furthermore, the contact surface 24 between the ring segments 21 and the end segment 22 in the form of a segment of a circle does not have to be a straight line, but in principle could also be arbitrarily curved or inclined, as long as the width of the ring segment 21. ·· ·· • · β · · fl # *

734AT ···· ·· the necessary mobility of the ring segments 21 to compensate for the wear is not impaired.

In the wear gap 23, a resilient element 40 is arranged between the two adjacent ring segments 21, as shown in Fig. 3, which exerts on the ring segments 21 5 and this force apart. The resilient element 40 may be embodied as a spring element 30, e.g. As in the example shown in Fig. 3a and 3b as an elastic cylindrical member which can be upset by the wear of the ring segments 21 and the associated contraction of the ring segments 21 either in the longitudinal direction (Fig. 3a) or in the transverse direction (Fig. 3b). The spring element 30 10 can also be mounted in a recess 31 on the ring segments 21. As spring element 30, however, basically every resilient element, e.g. also a simple spiral spring, in question.

However, the resilient element 40 can also be designed as a rigid element 32, 34, 36, 38, which is inserted into a recess 33, 35, 37, 39 on the ring segments 21. For example, 15 as a double cone 32 which is inserted on both sides into a bore 33 on the ring segments 21, wherein the bore 33 has an at least partially smaller cross section than the double cone 32, as shown in Fig. 3c. Or as a cylinder 34 which is inserted on both sides in a tapered bore 35 on the ring segments 21, wherein the bore 35 tapers away from the wear gap 23 and has an at least partially smaller cross section 20 than the cylinder 34, as shown in Fig. 3d. Or as a cylinder 36 which is plugged into a stepped bore 37 on the ring segments 21 on both sides, wherein the stepped bore 37 has an at least partially smaller cross section than the cylinder 36 and the smaller cross section is provided away from the wear gap 23, as in Fig. 3e shown. Or as a needle element 38 which is inserted on both sides in a bore 39 on the Ringseg-25 elements 21, wherein the bore 39 has the same cross-section as the needle member 38 but slightly lower than the needle member 38 in the unworn state of the ring segments 21 in the bore inserted, preferably by 5-50% of the width of the wear gap 23 in the unworn state, as shown in Fig. 3c.

Thus, when the ring segments 21 contract when worn, the force F * exerted by the post member 30 acts against contraction, as shown in FIG. The contact pressure F2 is produced essentially by the pressure pt which is to be sealed radially on the outside of the packing ring 20 and which presses the ring segments 21 against the moving part, such as e.g. a piston rod 5, presses. The force exerted by an optionally present circumferential spring 9 force can be neglected on the other hand. As a result of the pressing force F2, the ring segments 21 wear on the sealing surface 29 and the ring segments 21 slide along the contact surface 24 between ring segments 21 and kreisseg- •············

734.AT ♦ ······················································································································································································································································ This movement is now counteracted by the compliant element 40, which generates a wear-dependent force F *, e.g. by the resilient element 30 or by a rigid element 32, 34, 36, 38, which penetrates deeper into the ring segment material and the penetration of a greater resistance entge-5 stands the further the element 32, 34, 36, 38 penetrates. A defined in the wear gap 23 element 40 defined compliance gives the packing ring 20 thus with increasing wear gently increasing circumferential rigidity, which, with constantly applied pressure, a continuous decrease of the contact force F2 and thus the wear with the operating time entails. 10 In the embedding phase of the packing rings 20, i. in the transient initial phase of operation during which worn ring material is attached to the surface of the moving part, e.g. the piston rod surface, anlagert and forms a so-called transfer film, the formation of which allows a low friction operation mode and small wear, thus a higher contact pressure F2 is available, which decreases in a controlled manner with the wear in 15 ongoing operation. Of importance in this context is that in the direction of the wear gaps 23 symmetrical sectional shape of the packing ring 20 - in contrast to conventional tangentially cut rings - ensures a symmetrical in the direction of wear gaps 23 wear pattern in which a defined relationship between decrease in the wear gap width and wear 20th the ring segments 21 consists. This allows a simple structural design of the relationship between the decrease of the contact force F2 and the wear.

The contact surfaces 41 between the ring segments 21 and the circular segment-shaped end element 22 may also have an angle α to each other, as shown in Fig. 5. On the one hand, such an embodiment offers the advantage that any tilting of the 25 segment-shaped closing element 22 is kinematically locked in the axial direction. On the other hand, as the angle of intersection α increases, so does the force F * which presses radially apart the two ring segments 21. which results from the pressing of the circular segment-shaped closing element 22 on the ring segments 21, as shown in Fig. 6. Thus, a similar effect of reducing the pressing force F2 as when using a resilient element 40 can be achieved. However, the decrease in the contact force F2 in this case would not depend on the wear of the ring segments 21. In addition, however, in such an arrangement in the wear gap 23, a resilient element 40 may be arranged, which would again be a dependent on wear radially pushing apart force P arise. -8- • • • • • 4 4 4 4 4 4 • • 4 • • 4 4 4 4 4 • • 4 • 44 «• 4 4 • • • • • • • 4 4 4 44 44 44 4 4444 44

734.AT

Between packing ring 20 and the wall of the packing chamber 3, a support ring 50 could also be arranged in a known manner, analogously to the support ring 8 of FIG. 1, in order to possibly extrude the packing ring 20 into the gap between the piston rod 5 and a chamber disk 10 (FIG ) to prevent or reduce. When using a, preferably metallic, support ring 50 to increase the extrusion resistance is to ensure that in the wear gap 23 of the packing ring 21, the low pressure prevails p2, otherwise the circular segment-shaped terminating elements 22 could not be sufficiently pressed against the ring segments 21, which could noticeably increase the leakage.

For this purpose, the support ring 50, as shown in FIG. 7, can have a circumferential groove 51 at the end face 55 facing the packing ring 20, which is arranged substantially at the same radial distance as the wear gaps 23 of the packing ring 20. This circumferential groove 51 is moved over axial, continuous, opening into the circumferential groove 52 recesses 52 in the support ring 50 and radial, on the side facing away from the packing ring 20 end 54 of the support ring 50 and connected to the axial recesses 52 Nu-15 th 53 with the low pressure p2 on the packing ring 20th connected away. In an alternative embodiment of the support ring 50 of FIG. 8, the support ring 50 may also have axial, continuous recesses 55, which open into the wear gaps 23 of the packing ring 20 and arranged over radial, on the side facing away from the packing ring 20 end face 54 of the support ring 50 and with the axial recesses 20 55 connected grooves 56 are connected to the low pressure p2 on the side facing the packing ring 20 abge. In such embodiments, a support ring 50, the flow cross-section, which connects the volume formed in the wear gap 23 with the volume downstream of the support ring 50, can be significantly increased. 25

Claims (19)

························································································································································································································ 734.AT 1. Cut packing ring consisting of a plurality of ring segments (21) which are arranged spaced in the circumferential direction to form a wear gap (23) between adjacent ring segments (21) and the wear gap (23) radially outwardly by a on the adjacent Ring segment (21) resting on the circular segment-shaped end element (22) is sealed, characterized in that on the packing ring (20) an element is arranged, which abuts both adjacent ring segments (21) and on the adjacent ring segments (21) one of the ring segments (21) exerting force. 2. Cut packing ring according to claim 1, characterized in that the element is at the same time the circular segment-shaped end element (22) and to the contact surfaces between the ring segments (21) and the circular segment-shaped end element (22) at an angle (a) to each other. 3. Cut packing ring according to claim 1 or 2, characterized in that in the wear gap (23) a resilient element (40) is arranged. 4. Cut packing ring according to claim 3, characterized in that a on both ring segments (21) engaging spring element (30) is arranged. 5. Cut packing ring according to claim 4, characterized in that the 20 Federeiement (30) is designed as an elastic rubber element which rests either in the longitudinal direction or in the transverse direction of the two ring segments (21). 6. Cut packing ring according to claim 3, characterized in that in the wear gap (23) a cylindrical rigid element (32, 34, 36, 38) is arranged, which is provided with its ends in each case in a at both ring segments (21) recess 25 (Fig. 33, 35, 37, 39). 7. Cut packing ring according to claim 6, characterized in that the cylindrical rigid element (32, 34, 36, 38) at least partially has a larger cross-section than the recesses (33,35,37,39) in the ring segments (21). 8. Cut packing ring according to claim 7, characterized in that the 30 cylindrical rigid element (32) is designed as a double cone. -10- 734AT «·· · · · · # + ·· ·· ·· · ···· ·· 9. A cut packing ring according to claim 7, characterized in that the recess (35, 37) is veijüngend or stepped, wherein the smaller cross section of the recess (35, 37) facing away from the wear gap (23) is provided. 10. pressure pack with a number of packing rings wherein at least one cut packing ring (20) according to one of claims 1 to 9 is provided in the pressure pack. 11. A pressure pack according to claim 6, characterized in that in the pressure pack, a radially cut packing ring is provided, which rests axially on the cut packing ring (20). 12. A pressure pack according to claim 6 or 11, characterized in that a support ring (50) is provided, which rests axially on the cut packing ring (20). 13. A pressure pack according to claim 12, characterized in that on the support ring (50) on a front side (54) a radial groove (56) is arranged, which is connected to an axial continuous recess (55) in the support ring (50). 14. A pressure pack according to claim 12, characterized in that on the support ring (50) on a front side (54) a radial groove (53) is arranged, which is connected to an axial recess (52) in the support ring (50) and the axial recess (52) in a on the other end face (55) of the support ring (50) arranged circumferential groove (51) opens. 15. sealing between a housing part (11) of a machine and a relative to the housing part (11) movable part (5) of the machine, wherein in the seal at least one pressure pack (2) according to one of claims 6 to 14 in a packing chamber (3 ) is arranged. 16. Seal according to claim 15, characterized in that the ring segments (21) rest on the movable part (5) of the machine. 17. Seal according to claim 16, characterized in that the radially cut ne packing ring of the side with the high pressure (p ^ is arranged facing. 18. Seal according to claim 16, characterized in that the support ring (50) of the side with the low pressure (p2) faces facing and the support ring (50) on a wall of the packing chamber (3) is supported. -11- • ············································································································································································································································ 19. A compressor with a seal between a housing part (11) of the compressor (1) and a piston rod (5) of the compressor (1), wherein the seal is arranged in a packing chamber (3) and is designed according to one of claims 15 to 18 , -12-