GB2028439A - High Pressure Seal - Google Patents

Abstract

Packing 33 for use in sealing high pressure installations includes a deformable seal ring 35 integral with a backup ring 37 of greater hardness and smaller diameter. The packing is placed in an annular clearance area 31 between coaxial members 11, 15 with the seal ring 35 under pressure engaging confronting surfaces of the members. The backup ring 37 prevents extrusion of the seal ring into the clearance 43 between the members and helps to maintain alignment between these members. Interlocking means can be integrally formed in the process of molding the seal backup rings to help maintain their integrity after molding. The packing can be made in long lengths from which an appropriate length can be cut and its ends joined to form a ring of the desired diameter. This also enables the packing to be introduced into the clearance area between members without requiring disassembly of those members. <IMAGE>

Description

SPECIFICATION High Pressure Seal Summary of the Invention The present invention is directed to an improved, high pressure, composite packing adapted for use particularly in large diameter, heavy weight installations, such as, for example, in submarine stern tubes, and to the method of making this assembly. The improved packing includes a deformable seal ring integrally joined or molded to a backup ring of greater hardness and is constructed so that the seal ring is deformed under pressure to fully engage the surfaces to be sealed. The backup ring functions to prevent extrusion of the seal ring at the clearance area between the mating sealed surfaces.

Advantageously, the integral packing elelement can be formed in indeterminate lengths.

When it is desired to install a seal, the appropriate length of packing is cut and positioned in the clearance area between diverse members after the ends of the packing have been joined and suitably secured as by vulcanizing. This is a decided advantage over preformed annular packing rings which often require disassembly of the parts before installation.

Furthermore, forming the packing in indeterminate lengths which can be used to form a variety of ring diameters materially reduces required inventory.

Also, an integral seal and backup ring is considerably easier to handle than some prior art assemblies employing separate O-rings and backup rings which are positioned adjacent one another at assembly. In those assemblies the relatively soft O-rings are flimsy and difficult to handle, particularly in the larger ring sizes. In the integral construction of the present invention, the harder backup ring renders the assembly firmer and easier to handle.

Still further, the relatively hard backup ring in the integral construction of this invention provides support and alignment for the parts being sealed.

Of course, the backup ring, in preventing extrusion of the softer seal into the clearance area between the sealed parts, significantly adds to the expected life of the packing which is a decided advantage in installations of this type.

The packing of the present invention finds particular use in dynamic installations, and is particularly advantageous in large diameter, heavy weight, high pressure environments as is found in submarine stern tubes. However, it should be understood that the invention is useful in both static and dynamic installations, and with small as well as large parts.

A packing utilizing a single seal and backup ring will fulfill most needs especially where the packing is exposed to high pressure on one side only. However, where high pressure can occur at either or both sides of the packing, it may be desirable to utilize a pair of backup rings integrally joined or molded to a seal ring sandwiched therebetween.

Further objects and advantages of the present invention will become more apparent from a consideration of the detailed description to follow, taken in conjunction with the drawings and annexed hereto.

Brief Description of the Drawings Fig. 1 is a cross-sectional view illustrating a typical high pressure installation in which the present invention finds use; Fig. 2 is an enlarged view of a portion of Fig. 1 showing a preferred form of the invention; Fig. 3 is a view similar to Fig. 2 showing a modified form of the invention; Fig. 4 is a view similar to Fig. 2 showing a modified construction for use in installations where high pressure can occur at both sides of the seal; Fig. 5 is a view similar to Fig. 3 showing a modified construction for use in installations where high pressure can occur at both sides of the seal; and Fig. 6 is an exploded view showing the method of assembly of the present invention.

Detailed Description Referring now more specifically to the drawings, and particularly Fig. 1, a representative high pressure installation in which the present invention finds particular use is seen to include a housing 11 having a pressure plate 13 slidably fitted therein. The housing 11 has an annular bore 1 5 and counterbore 17, the bore 1 5 slidably receiving a reduced diameter portion of the pressure plate 1 3. The housing 11 and pressure plate 13 have complementary projections and slots 21,23 which facilitate limited reciprocation between the housing and pressure plate 1 3 but prevent relative rotation therebetween. A compression spring 24 normally spaces the pressure plate 1 3 from housing 11 as shown.

An endplate 25 has an annular projection 27 pressed within the counterbore 1 7 of the housing 11 and, together with a shoulder 29 between - counterbore 1 7 and bore 15, defines a packing recess 31. An elongated shaft or tube 30, representative of a submarine stern tube, extends through the pressure plate 1 3 and endplate 25.

In accordance with the present invention, a novel composite packing ring, shown generally at 33, and a preferred form of which is in Fig. 2, is disposed within the packing recess 31. The packing ring 33 is shown to include first and second components 35, 37 joined together as an integral unit.

Packing component 35 sealingly engages surfaces 39, 41 on housing 11 and pressure plate 13 and has a generally circular configuration. Seal component 35 is constructed of a relatively resilient material having a durometer of from about 50 to about 75. Preferably, the durometer of the seal component 35 is about 60 to 65 so that it can conform to slight irregularities in surfaces 39, 41 and yet can withstand high pressure attendant in the system in performing its sealing function.

The packing component 37 forms a backup ring or heel and is constructed of a material similar to the seal component 35. However, backup component 37 is harder than and has a higher durometer than component 35, desirably in the range of from about 80 to 100, and preferably about 90 to 95. The backup component 37 is positioned on the downstream pressure side of the seal component 35 and functions to prevent extrusion of the softer seal 35 into a clearance area 43 between pressure plate 1 3 and endplate 25. However, the width of the backup component 37, measured radially of the packing ring 33, is less than the width of the seal component 35 so that the seal component 35, and not the backup component, sealingly engages surfaces 39, 41, as described above.

The higher hardness of the backup component prevents it from being deformed under the action of the high pressure in the system. Furthermore, the harder backup component 37 is also somewhat stiffer than seal component 35 and makes the composite assembly relatively easy to handle, especially in the larger sizes. This is a considerable improvement over prior art assemblies using separate O-rings and backup rings. O-rings are relatively soft and flimsy which makes them difficult to handle, particularly in the larger sizes.

The packing ring 33 of the present invention can be constructed from a variety of rubber or rubber-like materials, including resin-based, phenolicbased, and epoxy-based plastics, capable of being compounded to produce a compliable support and sealing member. For example, natural and synthetic rubbers, such as neoprene, silicone and Buna-N, are known to be suitable materials, as are polyurethane elastomers and VITON (Trademark of E. I. DuPont de Nemours and Co., Inc.) fluroelastomers. A particularly suitable material is polyetherurethane which can readily be molded to form both packing components 35, 37 and which, when cured, will bond together to form an integral assembly.

One of the inherent and important advantages of the present invention is that the packing assembly can be formed in continuous, indeterminate lengths. As seen in Fig. 6, when packing ring 33 is to be installed, the endplate 25 need only be withdrawn as shown. The appropriate length of packing material is cut and positioned around tube 30, and its ends then suitably joined together, for example, by vulcanizing. The formed packing ring 33 is then placed in the cavity 31 and the endplate 25 repositioned as shown in Fig. 1.

It will be appreciated that installation of a preformed annular ring would require removal of the tube 30 from housing 11 before installation.

It will further be appreciated that the integral nature of packing material made up of the seal and backup components 35, 37 facilitates easy handling of the packing material in that the softer and more pliant seal component 35 is rigidified and supported by the stiffer backup component 37.

In assembly, the backup component 37 or the packing ring 33 provides substantial support to help maintain alignment between the parts 11, 13 being sealed. In certain installations, such as in submarine stern tubes, these parts can weigh upwards of several hundred pounds so that this supporting function is relatively important.

Obviously, proper support and alignment helps to reduce abrasion between moving parts being sealed.

The composite packing material of this invention can be manufactured using a number of different techniques. For example, the backup or.

heel 37 can be molded and cured, and then used as a mold insert while forming and curing the seal component 35. Alternatively, the two different materials used to form components 35, 37 can be loaded, uncured, into separate mold sections and the integral packing material molded and cured in a single cycle.

Furthermore, it will be appreciated that other forming techniques can be used to form the integral packing material described, and that this invention contemplates forming the packing material in indeteminate lengths, as described, as well as directly forming annular packing rings 33 to the desired diameter.

The packing assembly 33 illustrated and described above in Figs. 1 and 2 is installed in a dynamic installation, i.e., one where the diverse members 11, 13 to be sealed can move relative to one another. However, this invention is also usable in static installations, i.e., one where the members to be sealed undergo no relative motion. A typical static installation is shown in Fig. 1 wherein a packing assembly 53 similar in all respects to packing 33 is installed in a cavity between tube 30 and collar 55. A ring 57 fixes the collar 55 and tube 30 against relative movement.

A modified form of packing in accordance with the invention is illustrated at 1 33 in Fig. 3. There, the backup component 137 is generally crescent shaped in cross-section, and partially encompasses a seal component 135. As was the case in the preferred embodiment, the comoonents 135, 137 can be molded, or otherwise formed, in a single cycle. Alternatively, one component, preferably, backup 137, can be formed first and used as an insert while molding seal component 135. If the latter technique is used, backup component 137 can be formed with a projecting anchor 145 so that when the seal component 135 is molded in place, an anchor recess 147 is formed intimately engaging anchor 145. Obviously, other configurations, including an anchor recess in the backup component 137, can be used.

The embodiments described above and shown in Figs. 1-3 are constructed for use in installations where high pressure occurs at only one side of the packing assembly. In environments where high pressure can occur at both sides, packing assemblies such as shown in Figs. 4 and 5 may be utilized. The packing assemblies of Figs. 4 and 5 are substantially the same as those described above in Figs. 2 and 3 except that opposed backup components 37', 37' and 137' 137' sandwich seal components 35', 135'.

In both "sandwich" arrangements, the seal components 35', 135' have a width, measured radially of the packing rings 33', 133', greater than the width of the backup components. Thus, in both cases, the seal components 35', 135' perform the desired sealing function against surfaces 39, 41 while the backup components 37', 37' and 137', 137' prevent extrusion of the seal components into either of clearance areas 43, 44.

The materials used in, and the method available for formation of the packing assemblies described in Figs. 4 and 5 are substantially the same as those illustrated and described above for Figs, 2 and 3.

By the foregoing there has been disclosed an improved packing asembly for use in high pressure, static, or dynamic installations calculated to fulfill the inventive objects set forth here and above, and while preferred embodiments of this invention have been illustrated and described above in detail, various additions, substitutions, modifications and omissions may be made thereto without departing from the spirit of the invention.

Claims (14)

Claims

1. A high pressure packing ring assembly including a seal component and a backup component integrally joined together, said backup component having a greater hardness than said seal component and a smaller dimension than said seal component in a direction measured radially of said packing ring.

2. A high pressure packing assembly as defined in claim 1 wherein said seal and backup components are formed from a material selected from the group consisting of resin-based, phenolic-based, and epoxy-based plastics, and natural and synthetic rubbers.

3. A high pressure packing assembly as defined in claim 1 wherein said seal component has a durometer of from about 50 to about 75, and said backup component has a durometer of from about 80 to about 100.

4. A high pressure packing assembly as defined in claim 1 wherein said seal and backup components are contiguous elements of moldable and curable material integrally joined together by curing.

5. A high pressure packing assembly as defined in claim 1 wherein at least one of said seal and backup components is moldable and is joined to the other of said components by interengagement of complimentary projection and recess means.

6. A high pressure packing assembly as defined in claim 1 wherein said seal component is sandwiched between a pair of backup components.

7. A high pressure packing assembly including a seal component and a backup component integrally joined together, said seal component having a durometer of from about 60 to about 65, and said backup component having a durometer of from about 90 to about 95.

8. A high pressure packing assembly for use in installations having relatively moveable parts and wherein confronting annular surfaces formed in said parts define an annular seal cavity, said packing assembly including an integrally joined composite seal ring and backup ring disposed in said annular seal cavity, said seal ring having opposed surfaces engaging opposed annular surfaces in said seal cavity, said backup ring being disposed on the downstream pressure side of said seal ring and partially encompassing and supporting said seal ring, said backup ring, when said seal ring is slightly compressed between said annular surfaces, being disposed to engage said opposed surfaces, said backup ring being formed of a material of greater hardness than said seal ring and functioning to prevent extrusion of said seal ring into a clearance between said sealed surfaces, said backup ring also supporting said sealed members and helping to maintain alignment therebetween.

9. A method of making a high pressure packing assembly comprising the steps of forming an elongated seal member and backup member having different hardnesses, and integrally joining said members along substantially contiguous faces to form an elongated composite assembly.

10. A method as defined in claim 9 which includes the steps of cutting said elongated composite assembly to size, and bring opposite ends of said cut assembly together in abutting relation, and joining said abutting ends to form a ring.

11. A method of making a high pressure, annular, packing assembly comprising the steps of forming first and second pliable members having different durometer ratings and being integrally joined along substantially contiguous faces to form a composite assembly, bringing opposite ends of said packing assembly together in abutting relation, and joining said abutting ends to form a ring.

12. A method of making a high pressure packing assembly comprising the steps of joining first and second moldable materials along contiguous surfaces to form an integral, elongated member having first and second portions of different hardnesses, and joining opposite ends of said elongated member to form a ring.

13. A method of making a high pressure packing assembly comprising the steps of selecting a first member, and integrally molding a second member having a different hardness than said first member to said first member to form a composite assembly.

14. A high pressure packing assembly substantially as hereinbefore described with reference to the accompanying drawings.

1 5. A method of making a high pressure packing assembly substantially as hereinbefore described with reference to the accompanying drawings.