GB2113336A

GB2113336A - Axial tubular compensator

Info

Publication number: GB2113336A
Application number: GB8300943A
Authority: GB
Inventors: Peter Berger; Hanspeter Muller; Udo Erlenmayer
Original assignee: Witzenmann GmbH
Current assignee: Witzenmann GmbH
Priority date: 1982-01-14
Filing date: 1983-01-14
Publication date: 1983-08-03
Also published as: FR2519730A1; DK12583A; NL8300071A; SE8300079L; DK12583D0; FR2519730B1; FI74789B; GB2113336B; DK152622C; DK152622B; SE8300079D0; FI74789C; AT386265B; GB8300943D0; NL183903B; FI830041A0; BE895604A; SE455341B; ATA470282A; FI830041L

Abstract

An axial tubular compensator, the axial extension of which for a compression test is blocked by a radially resilient spring ring (11) acting between stop surfaces on an end sleeve 2 and a ring 6 carried by a guide tube 5. When the compensator warms up on first being used, the spring ring automatically moves from its blocking position into another radial position (shown in dotted lines in Fig. 2) and thus releases the axial displaceability of the compensator in both directions. <IMAGE>

Description

SPECIFICATION Axial tubular compensator This invention relates to an automatically guided axial tubular compensator, in particular for long-distance heating pipelines, comprising a single- or multiple-wall bellows with tubular sleeves arranged at its ends and a guide tube which surrounds the bellows and one end of which is guided displaceably on one tubular sleeve and may be secured there by means of a releasable holding element and the other end of which is connected to the other tubular sleeve, the length of stroke of the bellows being limited by stops in both directions.

An axial compensator of this type is known from the German Offenlgungsschrift No.

26 20 334. The compensator is axially longitudinally set to the fitting dimensions dependent upon the operating conditions by a plurality of axial setting screws which are connected to the guide tube on the one hand and to one tubular sleeve on the other hand. In this way the compensator may be set to the desired length and hence to the desired prestressing. As soon as the tubing is acted upon by higher temperatures after fitting the compensator, the compensator is contracted, during which the heads are broken off from the setting screws. The compensator is then freely movable axially within the limits to its stroke defined by the stops.

In numerous applications it is specified that the tubing together with the fitted compensator should be subjected to a compression test before the tubes are secured to their holding or joining points. This compression test is performed with considerable stressing from internal pressure and leads to the bellows being stretched to its maximum length. After the compression test the bellows can usually no longer draw back the attached tubings but remains rather in its position of maximum stretching or at least close to this position.

This means that the bellows has no or only very slight extension reserves with respect to a further extension of the bellows. The tubing must therefore, if extension reserves of this nature are required in operation, be pushed back mechanically, which involves considerable complication.

Taking this as a starting point, the present invention aims to provide an axial compensator of the type described which may be prestressed in any position within the operating path and may be blocked for the compression test so that the desired stroke reserve may be retained in both stroke directions. In addition, the blocking of the compensator is to be released automatically when the tubing is warmed up.

The present invention provides an axial tubular compensator, comprising a single- or multiple-wall bellows with tubular sleeves arranged at its ends and a guide tube which surrounds the bellows and one end of which is guided displaceably on one tubular sleeve and may be secured there by means of a releasable holding element and the other end of which is connected to the other tubular sleeve, the length of stroke of the bellows being limited by stops in both directions, wherein between the said one tubular sleeve and the associated displaceable end of the guide tube there is interposed a radially resilient spring ring which in one radial position bears against stop surfaces of the sleeve and of the guide tube or parts joined thereto in each case and blocks their axial displacement so as to extend the bellows and which in its other radial position permits axial displacement between the said stop surfaces, and wherein when the stop surfaces are displaced axially so as to contract the bellows the said spring ring moves automatically from the blocking position into the other radial position.

The arrangement according to the invention offers the advantage that the blocking for the compression test occurs precisely at the point determined for the correct pre-stressing and that it is automatically released when the tubing is first warmed up. The blocking therefore allows stroke reserves to be provided which are not used up during the compression test and subsequent manual release of the blocking becomes superfluous.

According to a first preferred embodiment of the invention, the spring ring occupies its blocking positon in the stressed state, a stop surface axially displaceable thereto blocking the radial release of the spring ring and this stop surface releasing the spring ring when the bellows contracts, so that it snaps out of its blocking position.

In order that the spring ring does not remain in an undefined manner in the compensator and possibly obstruct its movements when it snaps out of the blocking position, it is preferred that the spring ring should be snapped into a gripping chamber which receives it. This gripping chamber is arranged joined to the stop surface blocking the radial release of the spring ring and firmly holds the spring ring undetachably after it is snapped out.

For the spring ring acting in two radial positions it is not important which of the components displaceable relative to one another the spring ring is mounted in, i.e.

whether it moves radially outwards or radially inwards when leaving the blocking position.

In order that the spring ring should have only a a small gap if possible in the blocking position the first variant is preferred. For this purpose the spring ring is suitably mounted in a groove extending in the peripheral direction in the one tubular sleeve or a part connected thereto in the stressed state and snaps out wards into a slide ring mounted on the guide tube when released.

There are various possibilities for constructing the axially displaceable stop surface which holds the spring ring in the blocking position and releases it only during the contraction of the bellows. Annular surfaces extending in the peripheral direction and which are displaced relative to the spring ring during the contraction of the bellows are particularly suitable for this. Instead of this, however, the axially displaceable stop surface may be formed by a plurality of clasps supporting it radially over the periphery of the spring ring in the blocking position, these clasps supporting the spring ring either internally or externally depending upon the direction in which it is to snap out of the blocking position. The bent ends of the clasps advantageously bear loosely against the outside of a slide ring secured to the guide tube.This ensures that they are drawn away from the slide ring during the first contraction of the bellows without their being pushed back again and striking the spring ring during possible subsequent extension of the bellows.

According to a further embodiment of the invention, it is not the inherent stress of the spring but a positive guide which is used for transferring the spring ring from the blocking position to the other radial position. This guide advantageously comprises oblique surfaces inclined in the axial direction and which, during the contraction of the bellows, bear against the spring ring and lift it out of the carrier portion holding it axially until it engages in the oblique surfaces.

In order that the tubular sleeves may be properly guided it is preferred that one tubular sleeve should have a plurality of rails which are distributed over its periphery and extend axially and on which the associated end of the guide tube is guided axially displaceably and, where appropriate, non-rotatably. The releasable holding element may be clamped in these rails and at the same time their ends may bear the stops for limiting the length of stroke. The permissible range of stroke of the compensator and its pre-stressing are set at the place of work by positioning the rails accordingly.

If rails of this type are used for guiding the tubular sleeves, the spring ring may be guided in transverse grooves in these rails in a simple manner and the spring ring may be guided positively by oblique surfaces which are secured to a slide ring of the guide tube and arranged to move under the spring ring.

It is preferred that, instead of being in the form of the previously known setting screw to be screwed in axially, the releasable holding element should be formed as a shearing pin which may be clamped and which has a predetermined breaking point and consequently permits contraction of the bellows when the compensator is stressed in a predetermined manner. This makes securing the compensator easier and the broken off parts of the transverse pin cannot obstruct the displacement path of the compensator.

There are various possibilities for the design of the spring ring. An approximately circular cross-section is preferably used. This offers the advantageous possibility that the stop surface blocking the extension of the compensator and the release of the spring ring may be constructed in the form of a single oblique annular surface with an inclination of approximately 45 . Instead of this, however, it is also perfectly possible to use a spring ring with a rectangular cross-section which cooperates with radial and axial stop surfaces.

The invention will be further described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is an axial section through a compensator according to the present invention; Figure 2 is an enlarged view of the blocking device of the compensator shown in Fig. 1; Figure 3 is a cross-section along the line Ill-Ill in Fig. 1; Figure 4 shows a blocking device with clasps; Figure 5 is an axial view of the blocking device shown in Fig. 4; and Figure 6 shows a blocking device with a guide.

As shown in Fig. 1, an axial tubular compensator comprises bellows 1 shown contracted in the drawing and the ends of which are welded to cylindrical tubular sleeves 2 and 3. A thin protecting tube 4 is disposed inside the bellows 1 and has one of its ends secured to the sleeve 3 and the other of its ends extending some way into the sleeve 2 with a slight degree of play.

The outside of the bellows 1 is surrounded by a guide tube 5. One end of this guide tube is likewise secured to the sleeve 3, while its opposite end is guided displaceably over the sleeve 2 and may be locked thereto. For this purpose the free end of the guide tube 5 is provided with a slide ring 6 which runs with a slight degree of play over a plurality of axially arranged rails 7 distributed over the periphery of the tubular sleeve 2.

The length of the stroke of the bellows 1 is limited by stops 8 and 9 in both directions of stroke. These stops may be in the form of rings, blocks or the like welded on or radially insertable clamping pins.

The blocking of the compensator at the point determined for the desired pre-stressing and at the same time also for the compression test is described in greater detail below with reference to Fig. 2.

Fig. 2 illustrates first of all a shearing pin 10, which may be inserted into a radial bore in the slide ring 6 and a bore in the rail 7 arranged matching the latter. The shearing pin 10 has a predetermined breaking point in the gap between the slide ring 6 and the rail 7.

Its cross-section is dimensioned in such a way, while taking the total number of shearing pins used into consideration, that the shearing pin or pins shear off during the first warming up of the compensator, so that the bellows may operate freely within the stops 8 and 9 for defining the stroke.

Since the fastening of the bellows by means of the shearing pin 10 would not be equal to the stresses occurring during a compression test and the bellows would be drawn into its maximum extended position while shearing off the shearing pins 10, which has the disadvantages outlined above, an additional blocking is performed by means of a radially resilient spring ring 11. In its compressed state the spring ring 11 is disposed with its inner peripheral area in a transverse groove 12 in each of the rails 7 distributed over its periphery. The transverse groove 12 is formed in such a way that it presents axial and oblique radial abutment surfaces 1 2a and 1 2b respectively at least to the inside of the spring ring and to the side thereof facing the bellows. At its left-hand external peripheral area the spring ring 11 is supported on an oblique surface 6a of the slide ring 6.

The abutment surfaces 6a, 1 2a and 1 2b ensure that the axial tensile forces occurring during the compression test of the compensator and its adjoining tubing are absorbed by the spring ring 11 and therefore cannot stretch the bellows to its maximum length of stroke. In this connexion the sole purpose of the shearing pin 10 is to hold the oblique surfaces so as to bear against the spring ring 11 in such a way that it cannot snap radially outwards on account of its inherent stressing.

After the first compression test the compensator is immediately ready for operation without additional steps being required. During the first warming up of the compensator the attached tubes expand, i.e. the compensator is contracted and the guide tube 5 together with the slide ring 6 is moved to the left relative to the tubular sleeve 2. The shearing pins are torn off at their predetermined breaking point and the oblique surface 6a releases the spring ring 11 at its outer peripheral area.

In this way the spring ring can snap radially outwards out of the groove 12 on account of its inherent stressing and is caught by the gripping chamber in the form of an annular groove 13 adjacent to the oblique surface 6a.

The diameter of this annular groove 13 is selected to be such that the spring ring 11 lies snugly therein radially but with play axially. This ensures that the spring ring is ejected out of the groove 12 not only locally but also over its entire periphery. The blocking is thus removed automatically without additional displacement forces being required for this. The compensator is then free in both axial directions.

Fig. 3 illustrates the arrangement of the guide tube 5 with its slide ring 6 on the rails 7 distributed over the periphery of the tubular sleeve 2. In order to keep the bellows free from possible torsional stresses, it is possible to provide the slide ring 6 with inwardly extending projections which are arranged laterally on the rails 7 with a slight degree of play. In this way the slide ring 6 is mounted on the tubular sleeve 2 so as to be axially displaceable but non-rotatable.

The guide tube 5 is advantageously provided with a drainage hole 14 in its lower part.

The embodiment illustrated in Fig. 4 operates essentially on the same principle. Corresponding parts are therefore provided with the same reference numerals.

The radially resilient spring ring 11 is again used to block the compensator during the compression test. In contrast to the embodiment already described, however, in the blocking position the spring ring 11 is positioned in its radial outer position and snaps radially inwards when the compensator first warms up.

A pluraity of clasps 15, which are distributed over the periphery and which may be mounted axially on the outside of the tubular sleeve 2 so that they engage under the spring ring 11, are used to hold the spring ring 11 in its radial outer position. This position is illustrated in Figs. 4 and 5.

The clasps are advantageously formed in each case by two axial arms 1 5a and 1 5b whose front ends engaging under the spring ring 11 are provided with oblique surfaces, while their rear ends are connected together by a bent bracket 1 sic. They are guided by the rails 7 since their arms 1 5a and 1 5b extend laterally on either side of a rail 7 with a slight degree of play. The bent bracket 1 sic rests against the outside of the slide ring 6 facing the bellows without being rigidly joined to it.

The mode of operation is as follows: When the compensator first warms up, the slide ring 6 is displaced to the left relative to the tubular sleeve 2 and the rails 7 secured thereto in accordance with the contraction of the bellows. In the process, the shearing pin 10, the purpose of which is merely to hold the compensator in the desired pre-stressing, is first of all torn off. The slide ring 6 is then displaced to the left taking with it the clasps 15 bearing thereon so that the arms 1 5a and 1 5b are drawn away under the spring ring 11. The snap ring 11 then moves to its radially inner position on account of its inherent elasticity so that it no longer projects into the displacement path of the slide ring 6.If an extension of the bellows then occurs owing to a cooling of the tubing, the slide ring 6 may move unhindered to the right, while the clasps 15 remain in the outer position already reached.

The embodiment illustrated in Fig. 6 is characterized in that the displacement of the spring ring 11 between its two radial positions no longer depends upon the inherent elasticity of the spring ring but rather that this displacement is effected by a guide. For this purpose the slide rig 6 is provided with an extension which engages over the spring ring and the opposite side of which has a ramp 6b which, when the compensator first warms up and after the shearing pin 10 has been torn off, comes to bear against the spring ring 11 and lifts it out of the blocking position. In the course of this lifting movement the spring ring 11 engages in a recess 6c in the slide ring 6 so that it is held undetachably and prevented from snapping back.

In Fig. 6 the spring ring 11 is in its radially inner position in the blocking position. The ramp 6b is therefore arranged in such a way that it moves under the spring ring 11 on its radially inner side and gradually pressed it outwards.

The spring ring 11 may instead, of course, be in its radially outer position in the blocking position, so that it must be forced inwards off the radially outwardly acting ramp in order to permit the axial displaceability of the slide ring 6.

In both cases axial stops, which are not shown in greater detail and which are offset in the peripheral direction relative to the ramps 6b, ensure that the spring ring 11 cannot yield axially with respect to the ramp 6b when the compensator first warms up. Such stops may, for example, be formed by a plurality of shearing pins which are distributed over the periphery and secured to the sleeve 2 or to the rails 7 and which project so far radially outwards that they force the spring ring 11 into the recess 6c. For this purpose their outer areas may run in longitudinal grooves or the like in the slide ring 6. In order that they should not block a counter movement of the sliding ring 6, namely when the spring ring 11 held in the recess 6c strikes the axial stops, they are advantageously provided with a predetermined breaking point.

Claims

1. An axial tubular compensator, comprising a single- or multiple-wall bellows with tubular sleeves arranged at its ends and a guide tube which surrounds the bellows and one end of which is guided displaceably on one tubular sleeve and may be secured there by means of a releasably holding element and the other end of which is connected to the other tubular sleeve, the length of stroke of the bellows being limited by stops in both directions, wherein between the said one tubular sleeve and the associated displaceable end of the guide tube there is interposed a radially resilient spring ring which in one radial position bears against stop surfaces of the sleeve and of the guide tube or parts joined thereto in each case and blocks their axial displacement so as to extend the bellows and which in its other radial position permits axial displacement between the said stop surfaces, and wherein when the stop surfaces are displaced axially so as to contract the bellows the said spring ring moves automatically from the blocking position into the other radial position.

2. A tubular compensator as claimed in Claim 1, wherein the spring ring occupies its blocking position in the stressed state, a stop surface axially displaceable thereto blocking the radial release of the spring ring and the said stop surface releasing the spring ring when the bellows contracts, so that it snaps out of its blocking position.

3. A tubular compensator as claimed in Claim 2, wherein when the bellows contracts, the spring ring is arranged to snap into a gripping chamber which receives it.

4. A tubular compensator as claimed in any of Claims 1 to 3, wherein in order to block the extension of the bellows and to block the spring ring, a common stop surface is arranged in the form of an oblique annular surface with an inclination of approximately 45,.

5. A tubular compensator as claimed in any of Claims 1 to 4, wherein the spring ring is disposed in a groove extending in the peripheral direction in the said one tubular sleeve or a part connected thereto in the stressed state and snaps outwards into a slide ring mounted on the guide tube when released.

6. A tubular compensator as claimed in Claim 2, wherein the axially displaceable stop surface is formed by a plurality of clasps supporting it radially over the periphery of the spring ring.

7. A tubular compensator as claimed in Claim 6, wherein a bent connecting bracket of the clasps bears loosely against the outside of a slide ring secured to the guide tube.

8. A tubular compensator as claimed in Claim 1, wherein the spring ring is arranged to be transferred from the blocking position to the other radial position by a positive guide which comprises oblique surfaces inclined in the axial direction and which, when the bellows contracts, bear against the spring ring and lift it out of a carrier portion holding it axially until it engages in the oblique surfaces.

9. A tubular compensator as claimed in any of Claims 1 to 8, wherein the said one tubular sleeve has a plurality of rails which are distributed over its periphery and extend axially and on which the associated end of the guide tube is guided axially displaceably and, where appropriate, non-rotatably.

10. A tubular compensator as claimed in Claim 9, wherein the ends of the rails bear the stops for limiting the length of stroke of the bellows.

11. A tubular compensator as claimed in Claim 9 or 10 when appendant to Claim 8, wherein the spring ring is guided in transverse grooves in the rails and the said oblique surfaces are secured to a slide ring of the guide tube and arranged to move under the spring ring.

12. A tubular compensator as claimed in any of Claims 1 to 11, wherein the releasable holding element is in the form of a shearing pin which may be clamped.

13. A tubular compensator as claimed in any of Claims 1 to 12, wherein the spring ring has a circular cross-section.

14. An axial tubular compensator according to Claim 1, substantially as herein described with reference to, and as shown in, Figs. 1, 2 and 3, Figs. 4 and 5, or Fig. 6 of the accompanying drawings.