GB2214996A

GB2214996A - Pressure actuated seal

Info

Publication number: GB2214996A
Application number: GB8824388A
Authority: GB
Inventors: Gordon L Corke; John Bush
Original assignee: General Connectors Corp
Current assignee: Meggitt Simi Valley Inc
Priority date: 1988-02-16
Filing date: 1988-10-18
Publication date: 1989-09-13
Also published as: FR2627250A1; DE3843088A1; FR2627250B1; GB8824388D0

Description

1 -1- PRESSURE ACTUATED O-RING SEAL ar,15 invention relates to a seal for

use in aircraft and more particularly to an 0-ring seal which relies on the pressure in the aircraft ducts and connectors to supplement the elastomeric material forming the seal to maintain the seal in sealing engagement with a duct in such a way that the pressure in the duct compensates the seal for the decreasing resilience of the elastomeric material forming the seal.

Seals used in aircraft must satisfy a number of criteria. They must, of course, make a good scaling engagement with a duct to prevent leakage. In addition, since the seals are generally formed from an elastomeric material, they need a supplement to compensate the seal for the decreasing resilience of the elastomeric material forming the seal to prevent leakage. In addition, the seals need to have a reasonable amount of mass to be able to withstand, for a reasonable period of time, high temperatures caused by fires adjacent the ducts, to prevent snol:e and flame from entering into the passenger cabin.

In the past, as shown by the patent to Newman US Patent 3,695,639, aircraft seals for use with duct connectors on aircraft had two different designs. The outer seal, as shown, in Fig. 3 in U.S. Patent 1 3,695, 639 was generally circular in 1 0 cross section and was formed from an elastomeric material. It had sufficient mass so that it could for a reasonable period of time withstand high teriperatures caused by a fire. In addition, a back up inner seal was mounted in side by side relationship to the in In the outer seal The inner seal functioned differently fiom outer seal. As shown in Fig. 4, the leg of the seal was spaced relationship to the inner surface of the connector. this way, pressure from the interior of the connector could reach the inner surface of the web portion of the seal and-exert radially inwardly directed pressure on the pipe or duct embraced by the inner seal. This radially inwardly directed pressure exerted by the seal was often supplemented by a garter spring mounted on the web portion of the inner seal.

As stated above, the outer seal disclosed in this patent was more massive than the inner seal and maintal.ned a sealing engagement with the outer surface of the duct or pipe by the resilience of the elastomeric forming the core. The more massive outer seal cooperated with the inner seal in that while the outer seal was preventing leakage and smoke from a fire from reaching the inner seal, the inner seal supplemented the function o.1 the outer seal and prevented leakage of smoke and gasses into the interior of the cabin for a reasonable peric,3 of time to give the passengers a better chance to escape.

However, as stated aove, elastomeric material tends to harden in time. particularly when it is exposed to high temperatures, and when it hardens it tends to leak. For that U a reason the outer seal shown in Fig. 3 in U.S. Patent # 3,695,639 would tend to leak after a period of time, and the redundancy provided by the inner seal would be lost because the inner seal would be solely responsible for preventing leaking in the duct.

To prevent this from happening, in U.S. Patent 11 4,453,723 a garter spring was mounted in the center of the outer seal, see Fig. 1B. This garter spring compensated the outer seal for the decreasing resilience of the elastomeric material forming the seal caused by exposure to high temperatures for a long period of time.

If in addition, the gas pressure inside the connector could be used to supplement the radially inwardly directed force on the seal provided by the garter spring the outer seal shown in U.S. Patent # 4,453,723 would last longer and it would make a better sealing engagement with a duct.

We will describe a seal which is solid and somewhat circular in cross section and which is designed to utilize the gas pressure inside the connector to exert a radially inwardly directed force on the seal to compensate the seal for the decreasing resilience of the elastomeric material forming the seal.

invention will become more apparent when better understood in the light of the accompanying drawings and specification wherein:

Fig. 1 is an clevational view of a O-ring type seal .0 constructed accor-iing to the principles of this invention but with a double layer of fiberglass. cloth on the outer and side surfaces of the seal for symmetry but with nothing covering the inner work contacting portion of the seal.

Fig. 2 is a sectional view taken on the line 2-2 of Fig. 1 and disclosing the seal mounted inside a coupling after the seal has been post cured in an oven.

Fig. 3 discloses an exploded cross sectional view of a mold with the seal mounted on one or more layers of fiberglass cloth in the mold cavity.

Fig. 4 discloses the mold shown in Fig. 3 with the various parts of the mold ansembled together with the seal in the mold cavity before the seal has been post cured in an oven.

Figs. 5 to 7 disclose other embodiments of seals in a prepost cured condition, and in particular Fig. 5 discloses another embodiment of a seal wherein the seal has a single layer of fiber glass cloth on the outer surface, and two layers of fiberglass cloth on the bottom surface of the seal and on one side of the sezal, while the opposite side of the seal has three layers of fiberglass cloth bonded to it.

Fig. 6 discloses still another embodiment of a seal somewhat like the seal shown in Fig. 5, having a single layer of -fiber glass cloth on the outer surface, but with the outer peripheral surface of the seal concave.

Fig. 7 discloses still another embodiment of a seal in a pre post cured condition showing three layers of fiberglass cloth on one side ot the seal, two layers on the inner circumfernantial diameter of the sea!, no layer of fiberglass cloth an the side of the seal opposite the side of the seal having three layers of fiberglass cloth, and with a single layer of fiberglass cloth on the outer peripheral surface of the seal.

Fig. 8 discloses another embodiment of a seal in a pro post cured condition wherein the sea! is provided with a -centrally -h a single disposed radially inwardly extending groove lined wit layer of fiberglass cloth for better transmission of the gas -ing surface of the pressure in the connector to the work contact seal.

Figs. 9, 10, and 11 disclose additional embodiments of the seal constructed according to the principles of this invention, built with different 'numbers of plys of fiberglass on the sides, and showing the concave sides of the seal caused by the post curing process, and showing a centrally disposed groove formed in the outer periphery of the seal to receive a garter spring for expanding the seal to make a good sealing contact with a conduit at low temperatures.

Fig. 12 discloses a seal like the seals shown in Figs. 9, 10, and 11, with a garter spring movably mounted in a bore disposed inside the seal in spaced relationship to all the outer surfaces of the seal to offset the decreasing resilience of the clastomoric material forning the body of the seal and with a work contacting surface which has a smaller radius of curvature then the other seals to improve its sealing characteristic,,.

i Fig.13 discloses a cross sectional view of the two ply fiberglacs cloth used to surround three sides of the sea! Fig. 14 discloses an embodiment of the seal like that shown in Fig. 2 however having radial gas passage channels or grooves formed in at least one of the side walls of the seal.

Fig. 15 discloses an enlarged portion of the seal shown in Fig. 14.

Fig. 16 discloses another embodiment of the housing or connector wherein a conduit extends from the connector to the outer portion of the seal.

Fig. 17 discloses another embodiment of the seal wherein a conduit or channel extends into the side of the seal and curves up to the outer portion of the seal to transmit the gas pressure in the housing or connector to the outer peripheral surface of the seal.

Referring now to.Fig. 1 of the drawing, a seal constructed according to the principles of this invention and indicated jenerally by the reference numeral 10 comprises a central core 12 formed from a high temperature silicone rubber which is stable up to 600 Degrees F and compounded for a life duration of about 2000 flight hours. The seal is manufactured by joserting it into a mold 14 which has a mold cavity shaped to.a proper size. The mold comprises a base portion 16, ring shaped and closure portions 18, an outwardly extending centrally disposed post 20 and a top plate 22 of the mold which is provided with an opening 24 for %eceiving the post 20.

In assembled relation the central core 12 is inserted in the mold cavity 26. In the particular embodiment shown in Figs. 3 and 4, a double layer of fiberglass cloth 30 laid in the mold cavity covering three sides of the central core 12, but leaving uncovered,the inner surface 28 of the mold which is shaped to form the work contacting surface 29 of the seal. The fiberglass cloth 30, see Fig. 13 is coated with silicone rubber on one side 301. With this arrangement, when the two plys of fiberglass cloth are pressed together and heat is applied, the heat causes the silicone rubber on sides 301of the fiberglass cloth to bond together to form the double ply fiberglass cloth, see Fig. 13. Then when the mold 14 is closed as shown in Fig. 4, and heat is applied the seal has reached its set cured condition.

In the set cured condition, the seal corring from the mold will have straight sides and an arcuate work engaging portion formed by surface 28 in the mold see Figs 5 to 8.

As described above, the set cured seals leaving the mold co uld have various shapes, as shown in Figs. 5, 6,7, and 8 to satisfy various needs of the scal housing or connector 34. However, to this point, the seal is not complete. It must be post cured. This requires the seal to be inserted in an oven which is hot enough to drive off all the volatile naterials in the seal. Otherwise, when the seal is inserted in a seal housing 34, the chemical by-products of vv.lcanizatiLon could, if the housing 34 is subjected to high tenperatures, cause what is known as a reversion so that the silicone core in effe-t melts down. Post curing is performed in a hot air circulating oven in a manner well known in the art. The effect of curing the seal is to cause the straight sides of the seal' as it comes from the mold to change to concave curves, as shown in Figs. 2 and 9.

Heretofore, as shown U.S. Patent 141 2,695,639, the sides of the core of the seal were not coveyed by any fiberglass cloth, and in particular, the outer surface of the seal was in sealing engagement with the housing. As a consequence, pressure inside the housing or connector could not be used to augment the work engaging portion of the se-al in con-tact with the duct or pipe- 17 Referring to U.S. Patent 4?f 4,453, 723, it is similarly seen that although the sides of the core of the seal are covered by two layers of silicone impregnated fiberglass the outer surface of the seal, remote from the work contacting portion of the seal has no covering of fiberglass, so that this c-urface makes a sealing engagement with the inner surface of the web portion 31 of the connector 34. As a consequence the outer and inner seals in U.S. patents 3,695,639, and 4,453,723 did not utilize the pressure inside the connector to assist the seal in making a sealing engagement with the conduit or duct 17.

As stated above, a principle object of this invention is to design the outer O-ring seal so it utilizes the pressure inside the housing or connector to assist the outer seal in making. a better sealing contact with the outer surface of the duct or conduit 17.

To do this, and referring to Fig. 2 of the drawing, it is seen that a double layer of fiberglass cloth covers three sides of the core of the seal including the outer surface 36 of the seal.' With this arrangement, the fibers in the fiberglass cloth covering 'Che three sides of the central core 12 of the seal act as air passages and permit the gas pressure inside the housing or connector 34 to permeate the sides of the seal to the outer peripheral surface 36 of the seal thereby causing the gas pressure on the outer surface of the seal 10 to exert a radially inwardly directed pressure on the seal. In addition, as stated above, the seal 10 shown in Fig. 1 has sufficient mass to withstand high temperatures which may be causcd by a fire burning for an extended period of time. Thus it will prevent gas and smoke from entering the cabin compartment enabling the passengers to escape from an inflamed aircraft.

The use of f! -erglass cloth covering three sides of the seal shown in Fig 2 is one method of perm itting the gas pressure in the housing or connector to rise to the outer surface 36 of the seal so that the pressure in the connector or housing can exert an auxiliary inwardly directed force on the work contacting surface 29 of the seal. OIL-her mpthods to accomplish the same effect are contemplated. For example, in place of the fiberglass ' cloth nay be used. Moreover, a tube cloth, other kinds of or conduit 35 could extend through the seal or be rounted along the sides of the seal extending to the outer surface. 36 of the seal where the pressure in the housing could be exerted inwardly on the scal, see Fig 17. Alternatively a tubular conduit 37 could 1 _10extend from a suitable place on the housing 34 and be connected to the outer portion of the seal, as shown in Fig. 16. or extend through the seal as shown in. Fig. 17. In addition, it is contemplated that one side of the seal could be made with a plurality of narrow gas transmitting channels on the surface of the seal leading to the outer peripheral portion of the seal, see Figs. 14 and 15. If necessary, these narrow gas transmitting channels could be reinforced by embedding suitably shaped plastic or metal liners to prevent the pressure inside the housing or connector from, compressing the channels 32 thus restricting 'Che passages.

It is apparent that seals utiliZing the gas pressure in-tide the housing or connector to reinforce the resilience of the silicone rubber composing the seal, form a better seal than those previously constructed.

In addition, if desired, a closed coil tension type garter spring 42 can be movably mounted in a bore 43 formed in the core of the seal to further to further improve the sealing characteristics of the seal. In this way, if in the course of time, the silicone rubber forming the core of the seal hardens and becomes less able to make a sealing contact with a duct, the design of the seal makes use of both the gas pressure inside the connector and the compressive force exerted by the internally inserted garter spring 42, see Fig. 12, thus compei..;ating the seal for the decreased resilience of the silicone rubber and thereby extending its service life.

- - 7-11- It is noted, as seen in Fig. 2 and Fig. 9, that the process of post curing the seal causes the upper surface 36 of the seal to assume a inwardly concave shape. This physical characteristic causes the upper surface 36 of the seal to act as a sort of lens to focus or direct the gas pressure in the connector housing through the seal toward the work contacting surface 29 thus increasing its sealing contact with the surface on the duct 17. As stated above, the process of post curing the seals causes the concave shapes shown in figs. 9, 10, and 11. In addition as the seal is used, it tends to shrink somewhat s6 that at low temperntures the work..-ontact surface 29 of the seal does not make a good sealing engagement with the surface on the duct.. When the airplane engines are operating, the seals in the duct get hot, thereby maintaining a perfect seal.

Nonetheless, it is desirable for the seals to maintain a good sealing engagementwith the surface on a duct 17 even at low temperatures. To accomplish this, a garter spring receiving groove 44 may be formed in the outer surface 36 of the seals shown in Figs. 9, 10, and 11. The purpose of these grooves is to accept a garter spring 46 of the proper size which will exert additional on the seals, thu-- ensuring a good sealing engagement with the exterior surface of the ducts 17 even when the seals are cold. The seals disclosed in Figs. 9, 10, and 11 al.1 operate 'on the sane principle, but they differ in the number of plys of fiberglass cloth covering the three sides of the seals to satisfy different technical requirements imposed by the shape of 1 the housing and the physical conditions in which the seal is used Fig. 12 which has a centrally disposed garter spring 42 mounted inside the elastomeric material forming the body of the seal and which has a spring receiving groove 44 formed on the outer peripheral surface 36 of the seal for receiving the garter spring 46 also has a differently shaped work contacting surface 291. This surface has a radius of curvature which is small is comparison to the width of the seal and smaller than the radius of curvature of the other seals disclosed herein. Under some circumstances, a seal having a smaller radius of curvature as disclosed in Fig. 12 makes a better sealing contact with the outer surface of a duct.

V

Claims

1: A seal for use in aircraft comprising a central core formed from an elastomeric- material, a gas conduit extending along the side of the seal to the outside periphery of the seal so when the seal is mounted in a connector, gas pressure in the connector is transmitted through the gas conduit to the outside periphery of the seal inside the "connector enabling the gas pressure encapsulated at the outside periphery of the connector over the seal to be transmitted to the inner periphery of the seal thus exerting an inwardly directed force on the seal causing the work contacting surface of the seal to make a better scaling engagement with a surface on a duct.

3 2: A seal for use in aircraft comprising a central core formed from an elastomeric material, gas pressure conducting means associated with the seal so that if the seal is mounted in a connector, said gas pressure conducting means transmits the gas pressure in the connector to the outer periphery of the seal inside the connector enabling the gas pressure encapsulated at the outer periphery of the seal in the connector to exerll: an inwardly directed force on the seal to cause the work engaging surface of the seal to make a scaling engagementwith a suriace on a duct.

11 I 9 3: A method of making a seal comprising forming a ring from an elastomeric material, forming a mold having a mold cav-Lty with the shape of the seal, inserting a double ply of silicone impregnated fiberglass cloth inside the mold cavity in such a way that the fiberglass cloth covers three sides of the mold cavity leaving the surface of the mold which forms the work contacting surface of the seal uncovered by the fiberglass, inserting the ring of elastomeric material inside the mold cavity so the silicone impregnated fiberglass cloth covers three sides of the ring leaving the surface of the ring bearing against the surface of the mold forming the work contacting surface of the seal uncovered, closing off the mold and applying heat to the mold to form a set cured seal, then removing the seal from the mold and inserting it in an oven to post cure the seal so that fiberglass cloth is bonded to three sides of the seal with the fibers of the fiberglass cloth forming gas pressure transmitting passagcways to the outer periphery of the seal, leaving the inside periphery of the seal which forms the work contacting surface of the seal, uncovered by the silicone impregnated fiberglass.

1 4: A method of making a seal comprising the st-eps of forming a mold having a mold cavity of the proper size, forming a ring of elastomerric material sized to fit into the mold cavity, inserting a double ply of silicone impregnated fiberglass cloth inside the mold cavity in such a way that the fiberglass cloth covers three sides of the mold cavity leaving the inner surface of the mold cavity which forms the work contacting surface of the seal uncovered, inserting the ring of elastomeric material inside the mold cavity so the silicone impregnated fiberglass cloth covers three sides of the ring of elastomeric material leaving the inner periphery of the ring bearing against the surface of the mold forming the work contacting surface of the seal uncovered, closing off the mold and applying heat to the mold to form the set cured seal, then removing the seal from the mold and heating it in an oven to post cure the seal and bond the fiberglass cloth to three sides of the seal with the fiberglass cloth fibers forming gas pressure transmitting passageways leading to the outer periphery of the seal, leaving the work contacting surface of the seal adapted to engage the cuter surface of a duct, uncovered by the fiberglass cloth.

k -175: A method of forning a seal comprising the steps of I formIng a mold having a mold cavity of the proper size, forming a ring of elastomeric material sized to fit into the mold cavity, shaping the mold so that the portion of the ring Chat fornis the outer surface of the seal is provided with a central disposed garter spring receiving cavity extending downward from the upper surface of the seal, shaping the inner surface of the mold so it forms the work contacting surface of the seal, inserting a double ply of silicone impregnated f1berglass cloth inside the mold cavity in such a way that the fiberglass cloth covers three sides the mold cavity leaving the inner surface of the ring of elastomeric material bea.7ing against the surface of the mold forming the work pontacting surface of the seal uncovered, closing off the mold and applying heat to the mold to form the set cured seal, removing the seal from the mold and inserting it into an oven to post cure the seal so the fiberglass cloth is bonded to the three sides of the elastomeric ma-trial with the fibers in the fiberglass cloth forming gas pressure transmitting passage ways to the outer surface of the seal, with the re.-..iaining side of the seal forming the work contacting surface of the seal uncovered, by the fiberglass cloth so that the gas pressure at the outer portion of the seal exerts a inwardly directed force on the seal to cause the work contacting surface of the seal to make a positive seal with the outer surface on a duct.

. 6: A method of form ing a seal comprising the steps of forming a rold of proper size, forming a ring of elastomeric material sized to fit into the mold cavity, shaping the mold so a gas pressure transmitting conduit is formed in the ring from one side of the ring to the portion of the ring serving as the outer surfare of the seal, shaping the inner surface of the mold cavity so it forms the work contacting surface oE the seal, closing off the mold cavity and applying heat to set cure the seal, then removing the set cured seal from the mold and inserting it in an oven to post cure the seal to complete the seal so that the gas pressure at the outer portion of the seal exerlts an inwardly diracted force on the seal to cause the work engaging surface of the-seal to produce a sealing engagement with a surface on a duct.

c 1 7: The method of forming a seal described in claim 5 wherein the mold is- shaped so that portion of the mold which forms the outside diameter of the seal is provided with a centrally disposed garter spring receiving cavity extending downward from the upper periphery of the seal, inserting a closed coil tension type garter spring in the cavity to expand the seal after it has been post cured enabling the seal to make a scaling engagemen t with a work contacting surface on a duct when the seal is cold.

9 8: The combination of a connector housing and a seal, said connectui: housing adapted to be connected to a conduit in an aircraft having a generally radially outwardly projecting seal receiving recess formed in the housing,. a seal mounted in the housing, said seal sized so it makes a close fit in said seal receiving recess and compritiing a central core formed from an elastomeric material, at least some of the surfaces of the seal excluding the surface that contacts the conduit covered by at least one layer of material, said material having fibers which forms gas passageways to the surface of the seal remote from the conduit, whereby gas pressure in the conduit is tr,;n--,,,-,iitted to the outer portion of the seal inside the recess where it exerts a inwardly directed force on the seal to cause the work engaging surface of the seal to make a sealing engagement with a surface on a duct.

h ill 9: The seal described in claim 8 wherein said material covering some of the surfaces of the seal comprising one or more plys of silicone impregnated fiberglass.

10: The combination of a connector housing and a seal, said connector housing adapted to be cohnected to a conduit in an aircraft and having a generally radially outwardly projecting seal receiving recess formed in the housing, a seal mounted in the housing, said seal sized so it makes a close fit in said seal receiving recess and comprising a central- core formed from an elastomeric sealing material, one of the surfaces of the duct making a sealing angagement with said conduit, a gas passageway connected from the conduit to the outer portion of the seal receiving recess whereby gas pressure in the conduit is transmitted to the outer portion of the sea! inside the recess were it exerts an inwardly directed 'force on the seal to cause the work contacting surface of the seal to produce a better sealing engagement with the surface of the conduit.

1 11: The combination of a connector housing and a seal, said connector housing adapted to be connected to a conduit in an aircraft having a generally radially outwardly projecting seal receiving recess formed in the housing, a seal mounted in the housing, said seal sized so it makes a close fit in said seal receiving recess and comprising a central core formed -from an elastomeric material, one of the surfaces of the seal making a sealing contact with a surface on the duct, three of the surfaces of the seal, excluding the surface of the seal in work e ngaging contact with the surface of a duct, covered by two plys of silicone impregnated fiberglass. said fiberglass having fibers which forms gas passageways leading to the outer periphery of the seal, whereby gas pressure in the conduit is transmitted to the outer periphery of the seal inside the recess where it exerts an inwardly directed force on the seal to cause the work engaging surface of the seal to make a sealing engagement with a surface on a duct.

12: The seal described in claim 11 wherein said seal is formed with a concentric bore in space relationship to all surfaces of the seal, a garter spring is movably mounted inside said bore in the seal to further improve the sealing characteristics of the seal so that when the elastomeric material forming the core of the seal hardens and becomes less able to make A sealing contact with the auct-, the garter spring compensates the seal for the decreased resil-ence of the elastomeric material forming the core of the seal.

i 1 1 1 13: The seal described in claim 12 wherein a garter spring receiving groove is formed.in the outer periphery of the seal for receiving an additional garter spring, said additional garter spring sized to fit into the said groove in.the outer periphery of the seal, in such a way that it expands the seal, whereby the seal maintains a sealing engagement with the surface on the conduit when the seal is cold.

14: The seal described in c:LAm 1 wherein the radius of curvature of the work ccntacting surface of the seal is small in comparison to the width of the seal.

15. A seal as claimed in claim 1 substantially as hereinbefore described with reference to the accompanying drawings.

Published 1989 at The Patent Office, State House, 66 71 High Holborn, Zn Ton WC1R 4TP. Further copies maybe obtained from The Patent Office.

Wes Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed bY Multiplex techniques ltd, St Mary Cray, Kent, Con. 1187 -1