GB2230326A - Gland assembly for sealing a spindle - Google Patents

Description

t 1 Gland assembly for sealing a spindle The invention relates to a gland

assembly for sealing a spindle at the location at which it passes through the wall of a casing.

One form of a sealing gland assembly for sealing a spindle where it passes through a mounting opening extending through the wall of a casing, which separates regions at different pressures from each other, comprises a sealing sleeve which is disposed around the spindle and which is accommodated in an annular chamber which is arranged concentrically with respect to the mounting opening. The sealing sleeve is surrounded by spring mans which are also accommodated in the annular chamber, and is thereby pressed radially against the spindle. A gland assembly of that kind may be used for example in fittings in order to ensure that the control spindles which are required for the transmission of rotary or pivotal movements to internal shut-off members of the fittings are satisfactorily sealed off in relation to internal pressure, in the region in which the spindles pass through the casings. A gland assembly of that kind may be used more particularly in relation to the control spindle of a ball-type or globe valve.

In another form of gland assembly for a globe valve, arranged within an annular chamber in the region of a mounting opening which extends through the wall of the casing of the valve and which rotatably but axially immovably accomnodates the control spindle is a sealing sleeve which is disposed around the control spindle and which consists of polymer materials. The sealing sleeve is in turn enclosed by a spring means in the form of an 0-ring, which is pressed into the annular chamber, of rubber or another incompressible material, whereby the sealing sleeve is pressed against the spindle. It has been found that, in such a construction, wear which necessarily occurs at the sealing sleeve very rapidly results in leakage occurring through the gland assembly. That is due to the fact that, because of the inc omp ressibility of the material forming the 0-ring, the pressure with which the sealing sleeve is pressed against the spindle passing therethrough is gradually progressively reduced as a result of the wear 2 which inevitably occurs. In that respect that assembly has proven to be particularly unsuccessful when it is required to provide a sealing action in respect of very high pressures.

Another form of gland assembly for sealing a spindle as described in German patent specification No 1 908 074 provides a sealing sleeve disposed within an annular chamber and surrounding the control spindle. The sealing sleeve has an internal peripheral sealing portion which co-operates with the spindle, and an outer sealing portion which provides the sealing action in relation to the casing.

The outer sealing portion is formed by a radial flange on the sealing sleeve, which is pressed axially against a shoulder provided in the casing on the side which is remote from the side at which the gland assembly is subjected to a pressure, whereas the inner peripheral sealing portion which provides the sealing action in relation to the spindleis formed by the side, which is towards the pressurised area, of a portion of the sealing sleeve which is disposed practically without any clearance around the spindle in the region of the radial flange which is axially braced against the shoulder in the casing. It will be appreciated that in that construction, a pressure can build up in the annular gaps between the SEPindle and the sealing sleeve on the one hand and between the sealing sleeve and the annular chamber in the casing which accommodates the sealing sleeve, on the other hand, although the pressure build-up decreases with increasing distance frcrn the side of the gland assembly at which it is subjected to the pressure. A necessary condition for that assembly to provide an effective seal is that the sealing region between the shoulder in the casing and the radial flange on the sealing sleeve, which is pressed against same, is to be at a greater distance frcm the side of the gland assembly which is subjected to the increased pressure, than the inner peripheral sealing portion wh--4ch is operative to provide a seal between the dy and the sealing sleeve, for it is only in that case that the outward surface area of the sealing sleeve which is subjected to pressure predominates over the inward surface area thereof which is subjected to pressure, thereby to ensure that the sealing sleeve is pressed against the s pindle.

!L 3 However, as a result of wear which occurs in the sealing sleeve, due to use of the arrangement, it may happen that the inner peripheral sealing portion is progressively axially displaced away from the side of the gland assembly at which a high pressure obtains, with the result that the sealing effect gradually decreases and ultimately is substantially lost when the inner peripheral sealing portion moves away from the pressurised side of the gland assembly, beyond the outer sealing region.

According to the present invention there is provided a gland assembly for sealing a spindle where it passes through a mounting opening extending through a casing wall, comprising a sealing sleeve disposed around the spindle and accaated in use in an annular ch&nber which is arranged concentrically with respect to the mounting opening, and a spring means also accanTedated in the annular chamber around the sealing sleeve and operable to press the sealing sleeve radially against the spindle, the spring mans including a spring ring of expanded pure graphite which under the action of an axial force applied thereto is radially stressed between a wall portion which radially outwardly delimits the annular chamber and the sealing sleeve.

As will be seen in greater detail hereinafter in relation to specific embodiments, the gland assembly according to the present invention can ensure an effective sealing effect even after a long period of operation, being capable of maintaining a satisfactory sealing effect irrespective of wear of the components of the assembly, as a result of use thereof. Where the gland assembly is intended for sealing a spindle in relation to a casing separating considerably different pressures from each other, it is capable of withstanding elevated pressures over a sustained period of time while affording a high degree of adaptability in relation to different levels of pressure. 0 4 As will be appreciated, wear of the sealing sleeve, due to use of the assembly, necessarily results in an increase in the volume of the space within the annular chamber, which accommodates the spring ring forming the spring means. As an incompressible material is unable to adapt to a variation in volume, wear of that nature, in a gland assembly using an 0- ring which is pressed into an annular chamber, results in a progressive drop in the biasing force produced by the way in which the 0-ring is pressed into the annular chamber, with the consequence that the pressing force which was originally operative to press the sealing sleeve against the spindle gradually decreases until it has totally gone.

On the other hand, a spring ring of expanded pure graphite is compressible to such a degree that, within the limits of the possible increase in volume which may occur due to wear of the sealing sleeve, within the space in which the spring ring is accannodated, it is capable of following such "an increase in volume, and the radial stressing of the spring ring as between the sealing sleeve and the outer wall of the annular chamber, which is due to the axial biasing force applied to the spring ring, remains practically unaltered. The sealing action of the gland assembly therefore remains effective with practically no variation, irrespective of any wear which may occur.

In accordance with a preferred feature of the invention, the spring ring of expanded pure graphite may bear directly against the outer wall of the annular chamber delimited in the casing, and may thereby provide a static sealing effect at that location, while the radial pressure of the sealing sleeve against the spindle provides a static and dynamic sealing effect.

In accordance with another preferred feature of the invention, the sealing sleeve is in the form of a sealing member which is open at one end thereof and which has first and second limb portions, the spring ring of expanded pure graphite causing one of the limb portions thereof to be pressed against the spindle and the other limb portion to be pressed against the outer wall delimiting the annular chamber, thereby providing static and dynamic sealing effects in relation to the spindle and the wall of the annular chamber.

Embodiments of a gland assembly according to the present invention will be described by way of example with reference to the accompanying drawings in which:

Figure 1 is a diagrc-rffmtic view in section of half of a gland assembly comprising a sealing sleeve of generally L-shaped sectional configuration, Figure 2 is a view corresponding to that shown in Figure 1 of a modified embodiment of the 'gland assembly with a different form of sealing sleeve and spring ring.

Figure 3 is a view corresponding to that shown in Figure 1 of another Embodiment of the gland assembly having a sealing sleeve in the form of a sealing member of U-shaped cross-section, which is open at one end, and Figure 4 is a view corresponding to that shown in Figure 1 of still another embodiment of the gland assembly h aving a sealing sleeve in the form of a sealing member which is radially outwardly open.

Referring firstly to Figure 1, reference numeral 10 therein generally denotes a sealing gland assembly for use in relation to a suitable fitment such as a globe valve, while reference numeral 11 denotes a mounting opening in a valve casing 12 which is only generally indicated. A rotatably mounted control spindle 13 extends outwardly from the interior of the casing 12 through the mounting opening 11. The control spindle 12 which serves to actuate a shut-off Member in the valve, between a closure position and an open position thereof, is mounted in such a way as to be rotatable but axially immovable in the casing by suitable mans which are not illustrated and which are also 6 not relevant in the context of the present invention. The spindle 12 is non-rotatably coupled to the above-mentioned shut-off member by suitable mans.

The spindle 13 is guided in its portion which extends through the mounting opening 11 by means of a mounting sleeve or bush 14 which is only indicated in the drawing but which is suitably accdated in the mounting opening 11. On the side of the mounting sleeve 14 which is remote from the interior of the casing 12, as indicated at 15. an annular chamber 16 is provided in the casing 12, in coaxial relationship with the mounting sleeve 14, for example by being turned in the casing 12. On the side which faces towards the interior 15 of the casing 12, the annular chamber 16 is delimited by a radially extending shoulder 17.

A sealing assembly which is generally identified by reference numeral 18 is accommodated in the annular chamber 16. The sealing assembly 18 includes a sealing sleeve 20 which is disposed snugly around the spindle 13, coaxially with respect to the mounting sleeve 14. The ea sleeve 20 has a radial flange 21 which extends outwardly at the side of the sealing sleeve 20 which is rewte from the interior 15 of the casing 12 and which extends as far as the radially outward wall delimiting the annular chamber 16 in the casing 12. Outwardly of its portion which extends in the axial direction of the mounting opening 11, the sealing sleeve 20 is s = ounded by a spring ring 22 of expanded pure graphite, which is accommodated in the annular chamber 16 and which thus extends between the radial flange 21 on the sealing sleeve 20, and the shoulder which delimits the annular chamber 16 at the side thereof which is towards the interior 15 of the casing 12. Arranged on the side of the sealing sleeve 20 which is remote fran the interior 15 of the casing 12, and in coaxial relationship with 30 the sealing sleev4 20, is a pressing ring 24 which bears against and thus applies an axial biasing force to the radial flange 21 on the sealing sleeve 20, thereby axially bracing the spring ring 22 of expanded pure graphite between the radial flange and the shoulder 17 of 1 Z.

7 the annular chamber 16. The result of that axially bracing ef fect is that the sealing sleeve 20 is pressed radially against the spindle 13 by the action of the spring ring 22, thereby providing a static and dynamic sealing effect in the region of the spindle 13, as indicated at 25. As a result of the radial bracing action produced in respect of the spring ring 22 by virtue of the axial force applied therEto by the pressing ring 24, a static sealing effect is produced at the locations indicated at 26 and 27 in Figure 1, between the sealing sleeve 20 s = ounding the spindle 13 and the spring ring 22 on the one hand, and between the spring ring 22 and the radially outwardly disposed wall of the annular chamber 16, on the other hand. In the region of the mounting opening 11, a cover 30 which is only diagrammtically indicated is fitted on to the casing 12 on the outside thereof and firmly but releasably joined to the casing 12 in a 15 suitable manner, for exaTple by screwing. The cover 30 has a through bore (not referenced) which is aligned with the mounting opening 11 through the wall of the casing 12, and a recess 31 which is coaxial with respect to the annular chamber 16 in the casing 12 and which is formed therein for ex"le by turning. An outwardly extending flange 20 portion 32 of. pressing ring 24 which acts on the spring ring 22 by way of the radial flange 21 on the sealing sleeve 20 is accommodated in the recess 31, with axial play relative to a contact surface 33 of the casing 12, which is towards the cover 30. Reference will now be made to Figure 2 in which the same components as those already shown in Figure 1 are identified by the same reference numerals. In the Figure 1 construction, the sealing arrangement generally indicated at 18 in Figure 1 differs from that shown in Figure 1 insofar as the sealing sleeve 201 and, in conformity therewith the spring ring 221 of expanded pure graphite, have been modified. In the iment shown in Figure 2 therefore, disposed m the radial flange 22 at the radially outward edge thereof is an annular collar portion 34 which extends concentrically around the portion of the sealing sleeve 201 which embraces the spindle 13, and extends 8 towards the interior 15 of the casing 12, that is to say, in the axial direction of the mounting opening 11. The spring ring 221 which is accommodated in the annular chamber 16 is provided in the region of the annular c611ar portion 34 with an annular groove which extends around the edge of the spring ring 22' and which is adapted to receive the annular collar portion 34, in the manner clearly shown in Figure 2.

From a functional point of view, the embodiment shown in Figure 2 operates in an equivalent manner to the embodiment shown in Figure 1. In view of the application of an axial biasing force to the spring ring 221, the spring ring is subjected to a radial bracing effect and produces a static and dynamic sealing effect as between the sealing sleeve 20' and the spindle 13, at the location indicated at 25, while a static sealing effect is produced at the location indicated at 27 between the casing 12 and the spring ring 221 and at the location indicated at 26 between the spring ring and the sealing sleeve 201.

Referring now to Figure 3, shown therein is an embodiment of the gland assembly in which the sealing sleeve of the sealing arrangement is in the form of a sealing mr 40 of U-shaped cross-section, being open at the end towards the shoulder 17 defined by the casing 12, adjacent the open end of the sealing member 40. The spring ring 42 of expanded pure graphite is accmniodated within the U-shape configuration of the sealing member 40. As a result of the radial bracing effect caused by the spring ring 42 being subjected to an axial force, a static and dynamic sealing effect is thus produced at the locations 25 indicated at 43 and 44 in the region of the spindle 13 and the casing 12. Reference will now be made to Figure 4 showing a modified embodiment using a sealing sleeve in the form of a sealing mr 401 of U-shaped cross-section. In this embodiment however, the web portion of the U-shape, wLich closes the end thereof, is the portion of the sealing member 401 which is disposed snugly around the spindle 13, while the spring ring 421 of expanded pure graphite is accommodated t 9 between the limb portions of the U-shape, which extend radially outwardly at a spacing from each other. As in the embodirrents described above with reference to Figures 1 and 2, the application of an axial force to the spring ring 421 causes the spring ring to be radially braced between the casing 12 and the portion of the sealing sleeve member 40' which is disposed around the spindle 13, thereby producing a static sealing action as between the casing and the spring ring at the location indicated at 441 and a static and dynamic sealing action between the sealing sleeve member 401 and the spindle 13 at the location indicated at 431.

The above-described gland assemblies with a spring ring of expanded pure graphite acting as the spring mans are suitable in particular for gland assemblies which are to provide a sealing effect in situations involving high and very high pressures. In that respect, the higher the density of the pure graphite packing, the better is the gland assembly capable of providing an effective long-term seal in relation to proportionately increasing pressures.

Spring rings of the above-indicated kind can be produced by spiral winding of thin strips of expanded pure graphite on to a mandrel member which corresponds to the respective internal diameter required in respect of the spring ring, and axial pressing of the wound bodies produced in that way. The ring can be readily adapted to the respective range of pressures involved in the intended situation of use, by virtue of the degree of the axial pressing effect produced, which also involves a corresponding reduction in the initial volume of the wound bodies referred to above. In relation to spring rings of expanded pure graphite for use in relation to extremely high pressures, the wound bodies may be subjected to a pressing operation such as to reduce them to approximately half of their initial volume.

It will beappreciated that the above-described constructions have been set forth solely by way of example and illustration of the present invention and that various =difications nay be made therein without thereby departing fran the scope of the invention.

Claims (6)

1. A gland assembly for sealing a spindle where it passes through a mounting opening extending through a casing wall, comprising a sealing sleeve disposed around the spindle and accomnodated in use in an annular chamber which is arranged concentrically with respect to the mounting opening, and a spring means also accwTnodated in the annular chamber around the sealing sleeve and operable to press the sealing sleeve radially against the spindle, the spring means including a spring ring of expanded pure graphite which under the action of an axial force applied thereto is radially stressed between a wall portion which radially outwardly delimits the annular chamber and the sealing sleeve.

2. An assembly according to claim 1 wherein the spring ring bears directly against said wall portion which radially outwardly delimits the annular chamber to provide a static sealing effect at that location and the radial pressure of the sealing sleeve against the spindle provides for static and dynamic sealing thereat.

3. An assembly according to claim 1 wherein the sealing sleeve comprises a member which is open at one end and which is of a crosssection providing limb portions which bear against the spindle and the radially outward wall portion of the annular chamber under the radial force of the spring ring, thereby to produce static and dynamic sealing effects at the spindle and said wall portion.

4. A gland assembly substantially as hereinbefore described with reference to any Figure of the accompanying drawings.

5. In a valve fitting, a gland assembly according to any one of the preceding claims.

6. A valve fitting including: a casing; an opening extending through said casing between thenter:lor and the exterior thereof; a k 11 spindle movably disposed in said opening; an annular chamber provided in said casing in concentric relationship with said opening adjacent said spindle, the annular chamber including a wall portion formed by said casing and radially outwardly delimiting the annular chamber; and a gland assembly for sealing the spindle relative to the casing, ccmprising: a sealing sleeve disposed around the spindle and operable for sealing co- operation therewith; a spring ring of expanded pure graphite accmTnodated in said annular charberbet-, said wall portion and the sleeve; and weans operable to apply an axial force to said spring ring thereby to brace said spring ring radially between said wall portion and the sleeve and thereby cause said sealing sleeve to bear against the spindle.

p Pueo Holbom. london WC11R 4TP. er coples =gybe oed trom The Patant Office.