GB2172347A

GB2172347A - Sealing rings

Info

Publication number: GB2172347A
Application number: GB08521477A
Authority: GB
Inventors: Robert S Allison
Original assignee: General Connectors Corp
Current assignee: Meggitt Simi Valley Inc
Priority date: 1985-03-12
Filing date: 1985-08-29
Publication date: 1986-09-17
Also published as: FR2578940A1; JPS61211572A; JPH0228033B2; GB2172347B; GB8521477D0; FR2578940B1; DE3532440A1

Abstract

A tubular ring is formed from a suitable rubber like material. A circumferential slit 18 is formed on the periphery of the ring which communicates with the bore in the ring. Then the sides of the slit are spread apart far enough so a garter spring 22 can be inserted through the slit into the bore of the ring. The garter spring 22 is sized so it is movably mounted in the bore of the ring so it can exert the required compressive force on the finished seal. The sides of the slit are then cemented together and a fiberglass cloth 24 is cemented to the inner surface 28 of the ring to form a work contacting surface on the seal. <IMAGE>

Description

SPECIFICATION Sealing rings This invention relates to a method of forming a ring shaped seal with a garter spring movably mounted in a centrally disposed bore in the seal.

As described more fully in U.S. Patent 4,453,723, there is a need for use in aircraft for a ring shaped rubber seal having a garter spring movably mounted in a centrally disposed bore in the seal where the bore and the garter spring are in spaced relationship to the inner work contacting surface of the seal. With this arrangement the seal will have an extended work life.

However, the method of forming the seal, as described in U.S. Patent 4,453,723, is not always satisfactory because the tolerances and physical characteristics of the resulting seals may not be sufficiently uniform.

The method required the formation of a tubular semi-cured rubber or rubber-like insert by a conventional extruding machine. This insert was cut to the required length. Next, a garter spring also cut to the desired length was inserted in the bore of the insert. The ends of the garter spring were designed so they could be secured together in a manner well known in the art to form a ring shaped insert with the garter spring movably mounted in the bore of the tubular ring.

Next, layers of silicon impregnated fiberglass cloth were inserted in a mold cavity. Then the ring shaped tubular insert was laid over the fiberglass cloth. Thereafter, a ring shaped piece of uncured rubber was inserted in the mold cavity and the mold was closed. Finally, the mold was inserted in an oven for a period sufficient to cure the rubber and form the seal.

This method was not satisfactory because in the curing process, contrary to expectation, the semicured rubber insert would contract down around the garter spring in a random fashion so that the garter spring was not always free to move in the bore in the seal. Consequently, the seals manufactured by this method did not have uniform performance characteristics.

According to the present invention there is provided a method of forming a seal, the method comprising: providing a tubular ring of "set cured" elastomeric material with a circumferential slit, the slit communicating with the bore of the ring; splaying apart the sides of the slit and inserting a garter spring into the bore of the ring, the turns of the spring being dimensioned such that the spring is free to move in the bore of the ring and is able to contract independently of the ring to exert a compressive force thereon; bonding the opposing faces of the slit together; and bonding a wear resistant material to the inner surface of the ring to form the work engaging surface of the seal.

By way of example only, a method embodying the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a perspective view of a length of rubber-like tubular material from which the seal is formed, cut to the proper length after it leaves the extruder and showing the centrally disposed bore formed in the material.

Figure 2 discloses the rubber like tube after its ends have been glued together to form an '0-ring'.

Figure 3 discloses the ring shaped seal mounted on a rotating spindle with a knife blade advancing to cut a circumferential slit in the seal communicating with the bore in the seal.

Figure 4 discloses an enlarged cross-sectional view of the seal showing the slit communicating with the bore in the seal.

Figure 5 discloses the seal shown in Figure 4 after the split sides of the seal were separated and the ring shaped garter spring was inserted in the bore.

Figure 6 is a cross-sectional view of the seal shown in Figure 5 taken on the line 6-6.

Figure 7 discloses an exploded cross-sectional view of the mold with the seal mounted on one or more layers of fiberglass cloth in the mold cavity.

Figure 8 discloses the mold shown in Figure 7, with its two parts in assembled relation and the seal in the mold cavity.

Figure 9 discloses a stack of molds mounted one on top of each other so that a number of seals can be formed simultaneously.

Figures 10 and 11 are enlarged cross-sectional views of the completed seals, wherein Figure 11 discloses a seal witha modified cross-section formed in an appropriately shaped mold.

Referring to Figure 1 of the drawing, a tubular rubber like material suitable for a seal is extruded by any conventional mechanism in a set cured condition with the tube cut to the proper length.

Then the opposed ends 12 of each length of material 10 are coated with an adhesive, and are joined together to form a tubular ring 10 having a centrally disposed bore 20 formed therein, see Figure 2.

Next, the ring is mounted on a power driven rotary spindle 14 and a knife 15 is forced against the periphery 16 of the ring 10 until it forms a circumferential slit 18 which communicates with the bore 20, see Figure 3 and 4. Thereafter, the sides of slit 18 are forced apart and a suitably shaped ring shaped garter spring 22 is forced through the separated sides of the slit 18, see Figures 5 and 6. The garter spring 22 is sized so when it is in the bore 20, the turns of the garter spring do not adhere to the walls of the bore, so that the garter spring can move independently of the body of the seal.In addition, the diameter of the garter spring is selected so when the garter spring is in the bore of the ring, the garter spring can exert the proper compressive force on the ring independent of the temperature over a wide temperature range to compensate the finished seal for the time caused decreasing resilience of the elastomeric material forming the seal.

Next, one or more layers of ring shaped silicon impregnated fiberglass cloth 24 are inserted in the mold cavity in section 30, see Figure 7. Then the ring 10 with the garter spring movably mounted in the bore 20 is mounted on the mold section 30 in such a way that the fiberglass cloth 24 faces and abuts the inner surface 28 of ring 10.

Next, the sides of the slit 18 and the inner surface 28 of the ring 10 are coated with a heat reactive adhesive. Thereafter, the fiberglass cloth is trimmed to the proper length and mold section 30 is covered by mold section 46, see Figure 7. The mold is then inserted in an oven which tightly bonds the facing sides of the slit 18 together and bonds the fiberglass cloth 24 to the inner surface 28 of the ring to form the work contacting surface of the seal, see Figure 10. With this arrangement, the garter spring 22 will not adhere to the inner walls of the bore in the seal because the garter spring has been inserted in the bore 20 after the rubber or rubber like material comprising the ring 10 was in a 'set cured' condition.

As seen in Figure 7, each mold is formed in two mating parts. The first consists of a mold section 30, having a generally cylindrical base portion 31 and a centrally disposed cylindrical portion 33 extending up from the base portion, see Figures 7 and 8. The upwardly extending cylindrical portion is smaller in diameter than the base portion 31 in this particular embodiment, although other configurations where the opposite is true are contemplated. The periphery 35 of the upwardly extending cylindrical portion 33 is generally concave, and in this embodiment serves to completely shape the inner surface of the seal which will ultimately engage a sealing surface on a duct or connector. This arrangement is important because the entire inner work contacting surface of the seal 10 is formed from surface 35 on mold section 30.This prevents the formation of 'flash' on the inner work contacting surface of the seal.

The second part of the mold consists of a ring shaped mold section 46, including a bore 47, and a counterbore 48, see Figures 7 and 9. Sections 30 and 46 in assembled relation form a complete mold for one seal, see Figure 8.

In order to assemble mold sections 30 and 46 together, mold section 30 is provided with positioning surfaces 54 and 56 which are positioned on the periphery of a circle, see Figure 7. Surface 54 in addition to functioning as a positioning surface for mold section 46 also serves as the base of the mold cavity, see Figure 7. Mold section 46 rests on mold section 30 and cooperates with it to form the mold cavity 61, see Figure 9. The counterbore 48 of mold section 46 has locating surfaces 50 and 52 which are on the diameter of a circle and bear against surfaces 54 and 56 of the mold section 30 and embrace them to hold the sections 30 and 46 together.

In stacked relationship, the lower surface 58 on mold section 30 rests on the upper surface 59 on mold section 46. This closes the mold cavity 61, so a seal can be formed when the molds are inserted in an oven, see Figure 8. The periphery 49 of the bore 47 in mold section 46 is, in this embodiment, concave, and completely defines the entire outer surface 13 of the seal, remote from the inner work contacting surface, see Figure 8. Consequently, flash cannot form on the outer work contacting surface. The elimination of the formation of flash reduces the labor required to finish the seal. In assembled relation with mold section 46 resting on mold section 30, the concave surfaces 35 and 49 face each other defining the peripheral limits of the mold cavity 61, see Figure 8.

A number of molds, each comprising a mold section 46 and a mold section 30, can be stacked on an upright support 44, see Figure 9, so a number of seals can be formed at the same time. A closure member 60 having a centrally disposed support receiving bore 62 is at the top of the stack of molds. This section has a lower surface 64 which is shaped like surface 58 on mold section 30 and closes off the top mold cavity 61 in the stack of molds.

An alternative method of forming a seal using the general principles of this invention may be more suitable for seals having tiny diameters. In this method, the mold is designed to form a tubular ring having a centrally disposed bore formed therein and having a circumferential slit formed by the mold communicating with the bore in the ring.

When the ring leaves this first mold, the tubular rubber ring is in a set cured condition. At this point a suitably shaped garter spring is inserted through the separated sides of the slit into the bore of the tubular ring 10. The garter spring 22 is sized so when it is in the bore 20 of the seal 10, the turns of the garter spring do not stick to the surface of the bore whereby the garter spring is movably mounted in the bore of the seal and can exert adequate compressive force on a seal for making a sealing engagement with a surface of an aircraft duct independent of temperature over a wide temperature range to compensate for the decreasing resilience of the elastomeric material forming the seal over a period of time.

Next, adhesive is applied to the facing surfaces of the slit in the tubular ring and to the inner surface of the ring. Then the ring is inserted in a second mold which has suitably shaped ring shaped layers of fiberglass cloth positioned in the mold so they abut the inner surface of the ring. When the mold is closed off and inserted in the oven, the heat finally bonds the facing surface of the slit together and bonds the fiberglass cloth to the inner surface of the ring to form the completed seal.

Claims

1. A method of forming a seal, the method comprising: providing a tubular ring of 'set cured' elastomeric material with a circumferential slit, the slit communicating with the bore of the ring; splaying apart the sides of the slit and inserting a garter spring into the bore of the ring, the turns of the spring being dimensioned such that the spring is free to move in the bore of the ring and is able to contract independently of the ring to exert a compressive force thereon; bonding the opposing faces of the slit together; and bonding a wear-resistant material to the inner surface of the ring to form the work engaging sur face of the seal.

2. A method according to claim 1 in which the circumferential slit is provided by slitting the outer periphery of a preformed tubular ring.

3. A method according to claim 1 in which the tubular ring with its circumferential slit is formed by a moulding process.

4. A method according to claim 1 or claim 2 in which the tubular ring is initially formed from a length of the 'set cured' elastomeric tubular material by applying adhesive to the opposed ends of the tube and then joining the opposed ends together.

5. A method according to any one of the preceding claims in which the wear-resistant material comprises a fiberglass cloth.

6. A method according to any one of the preceding claims in which an adhesive is applied to the said inner surface of the ring for bonding the wear-resistant material to the surface.

7. A method according to claim 6 in which adhesive is applied to the opposing faces of the said slit for bonding the said faces to one another.

8. A method according to claim 7 in which, after applying the adhesive, the bonding of the material to the ring and the bonding of the opposed faces of the slit to one another is achieved by inserting the ring in a mold such that one or more layers of the material abut the inner surface of the ring, closing the mold, and inserting the mold in the oven.

9. A sealing ring produced by a method according to any one of the preceding claims.

10. A method of forming a sealing ring, the method being substantially as herein described with reference to the accompanying drawings.

11. A sealing ring substantially as herein described with reference to the accompanying drawings.