CA1324171C

CA1324171C - Enclosure seal

Info

Publication number: CA1324171C
Application number: CA000522756A
Authority: CA
Inventors: Robert A. Duchrow
Original assignee: Robert A. Duchrow; Allen-Bradley Company Inc.
Current assignee: Allen Bradley Co LLC
Priority date: 1985-12-20
Filing date: 1986-11-12
Publication date: 1993-11-09
Anticipated expiration: 2010-11-09
Also published as: US4699293A

Abstract

Abstract of the Disclosure A seal for an enclosure of electrical equipment which is clamped between sealing surfaces on the enclosure base and the enclosure cover. The seal includes a cavity of a preferred hour-glass configuration and resiliently retains a resilient seal member of a preferred triangular configura-tion. The outer wall portions of the cavity permit expansion of the resilient seal member when the cover is forced against the base to provide a seal around the outer periphery of the enclosure.

Description

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ENCLOSURE SEAL

Background of the Invention The field of the invention is enclosures for electrical equipment, and particularly, enclosures which seal elec-trical e~uipment from the surrounding environment.
There are numerous applications where electrical devices such as switches, relays and terminal blocks must be sealed off from the surrounding environment. Such seals may, for example, exclude liquids such as water where the equipment is exposed to the weather or it may inhikit the passage of gases wh~re the equipment is exposed to volatile vapors.
Standards have been established for seals of various types and it is, of course, an objective in the art to meet these standards with any proposed structure. ~-Standards for sealed enclosures may take the orm of I specific structural requirements or they may take the form i of performance re~uirements. One such structural standard ~ -~
J reguires that the juncture between two par~s of an enclosure -, 1 . .
'~ be formed by metal against metal, with the metal having a jZ9 specified width. On the other hand, to meet certain perfor~
mance standard~ i~ has been found that rings of elastomeric ,material must be used at the junction of two enclosure ! parts-~;, Although prior enclosures are txpically designed to i25 meet a speciic standard, there are some enclosures avail- -iable which meet more than one standard. For example, there ¦is described in U.S. Paten~ 4,158,757, which is commonly -¦~ssigned, a~ enclosure ~eal which includes a metal frame Iwhich is clamped between sealing surfaces cn an enclosure ", ,,1--~32~
base and the enclosure cover. Another ty~e of such enclosure, for example, provides a metal flange at the juncture of its base and cover with a rubber 0-ring clamped between the mating flange surfaces. In seals of the latter type, it is ~, 5 common to provide grooves in each flange surface to receive the 0-ring. This is disadvantageous as two such grooves ~ must be provided. In addition, the 0-ring must be aligned .~ with the opposing grooves and this can cause both an instal-lation and sealing probl~m.

~ 10 SummarY of the Invention ;! The present invention relates to an imp~oved seal for ', an enGlosure. It include~ a cavity disposed in one of the sealing surfaces of the enclosure cover or enclosure base.
, The cavity i5 constructed and arranged for both retaining a J 15 resilient seal member therein and permitting compressive - --expansion thereof in the same cavity. The seal also includes i the resilient seal member having at least one portion for ~¦ sealing engagament with one of the sealing surfaces when a ~t eover is fastened in place over a compartment. In a prefer-i 20 red manner, the cavity has inwardly extending and divergin~
wall por~ions terminating in an end wall as well as outward-ly extending and diverging wall portions resulting in a constricting portion between the wall portions. Also prefer-I ably the resilient member is constructed and arranged to i 25 be resiliently positioned between the inwardly extending ~;l wall portion6 and to expand into the outwardly extending qi wall portions whe~ compres_ed Dy an opposing sealing surface. -~
' A general object of ~e invention is to provide a i metal-to-metal seal and ar. elastomeric seal for an enclosure 30 of electrical equipment. The elastomeric seal is provided '1 l -2-~ 3 2 '~
01 by a cavity in one of the sealing surfaces which will allow for 02 initial retention of a resilient member when placed there:in yet 03 will allow for expansion of the elastomeric seal irlto another 04 portion of the cavity wher, ~ontacted by ar, opposing sealing 05 s-lrface. The sealing surfaces are provided in the usual 06 surrounding flanges. They are determined by the applicable 07 standard and they mate with the sealing surfaces on the enclosure 08 base and cover to provide the desired metal-to-metal seal.
09 An object of the invention is to provide an elastomeric seal without increasing the cost of the enclosure. This is 11 accomplished by machining a single cavity in one of the sealing 12 surfaces of the enclosure while eliminating an opposing cavity in 13 the opposing sealing surfaces as well as orientation of the 14 elastomeric seal therewith.
Yet another object of the invention is to facilitate the 16 placement of an elastomeric seal in an enclosure with a 17 metal-to-metal seal. The cavity and the elastomeric seal are 18 c~onstructed and arranged so that a slight compression with 19 insertion of the elastomeric seal into a portion of the cavity ., .
will effect retention. This results in ease of installation and 21 at the same time obviates misplacement of the elastomeric seal 2~ when the cover and base are separated.
f~23 ,~ more specific object of the invention is to obviate the I, 24, fabrication of additional component parts such as fastening members l~25 for the elastomeric seal or the use of a retentive adhesive.
26 An embodiment of the invention is an enclosure for an , 27 electrical device, the combination comprising a base having a ,;28 bottom and one or more upright walls which define a compartment ' 29 for receiving the electrical device, a firsk sealing s,:,rface formed on the upright wall and surrounding the compartment, a ~, 31 ~ .

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~1 coveL havir,g a second sealing surface which opposes and contacts02 the first sealing surface when the cover ls positioned in place 03 over the cavity, and a seal disposed between the opposing first and 04 second sealing surfaces. The seal also includes a cavity disposed~05 in one of the base or cover, the cavity defined by an inner portion 06 and an outer portion and constructed and arranged for both 07 retaining a resilient seal member therein and permitting 08 compressive expansion thereof, the seal also including the 09 resilient seal member having at least one portion for extending from the cavity and for sealing engagement with one of the sealing ll surfaces when the cover is fastened in place over the comparkment.
~12 The seal member is constructed and arranged to be guided by the 13 outer portion and self oriented by the inner portion of the cavity.
14 Another embodiment of the invention is a seal for jlS assembly having two elements to be joined at mating surfaces with ,, ` ¦16 the mating surfaces being relatively flat, comprising a cavity 17 defined by an inner portion and an outer portion disposed in one of 18 the mating surfaces. The cavity is constructed and arranged for ~19 both retaining a resilient seal member therein and permitting compressive expansion thereof. The seal also includes the 21 resilient seal member having at least one portion for sealing i22 engagement with one of the mating surfaces when the relatively flat 323 mati~g surfaces are in contact. The seal member is of a 24 substantially solid configuration in cross section so that it is ~25 self oriented and self retained in the inner portion and ~26 compressively expanded in the outer portion of the cavity.
27 The foregoing and other objects and advantages of ~28 the invention will appear from the following description. In ~29 the description reference is made to the accompanying drawiny ~'30 which forms a part hereof, and in which there is shown 31 - 3a -. ~, ~ " .
' ~ c3 2 ~
. by way of illustration a preferred embodiment of the inven-- tion. Such embodiment does not necessarily represent l~he full scope of the invention, however, and reference is therefore made to the claims herein for interpreting the , 5 scope of the invention.

'1 , .
I Brief Descri~tion of the Drawing Fig. 1 is a top view of an enclosura with a portion , broken away to illustrate the seal of the present inve~tion;
,~ Fig. 2 is an enlarged partial view in horizontal cross 10 section of the invented seal showing the elastomeric sPal -.
being positioned in th~ se~l cavity;
Fig. 3 is a view similar to Fig. 2 showing the el,asto-m~ric seal seated in the cavity; -:
Fig. 4 is a view similar to Fig. 3 illustrating the 15 elastomeric seal compressed by an opposing sealing sur~ace; -:.
and Fig. S is a partial view in side elevation of the cavity shown in Fig~. 2, 3 and 4.

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~ Descrie~n of the Preferred Embodiment ~.
~ 20 ~eferring to Fig. 1, an enclosure for a handle controlled .
switch or the like includes a base 10 and a cover, or top 11. The ~ase 10 is of a generally rectangular configuration and i5 cast from aluminum. It includes a bottom 12 an~
upright walls such as 13 which define a compartment 14 for I 25 an electrical device. The handle controlled switch or other ; electrical device is mounted within the compartment 14 and .~ it is connected to other aevlces ~not shown in the dravings) .,~ .
~ through openings lS and 16 formed in the end wall 13. A
.~ control wiring conduit opening 17 is provided through the :1 ,. .

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bottom and a mounting flange 18 extends therefrom. Sur-rounding the compartment 14 is a peripheral flange 19.
The generally rectangular cover 11 is also cast from aluminum. It also has a peripheral flange 20 which is arranged to mate with the flange 19. The seal qenerally 21 is housed in the flange 20 for sealing engagement with the flange 19. Bolts 22 are of the quick release type. They are inserted through appropriate openings in the flange 20 ~`l .' and are threadably fastened in the flange 19 to secure the 10 top 11 to the base 10. A switch control handle 23 opera-tively extends through the cover 11 in the usual manner for connection with an enclosed electrical device. A breather device 24 i.s also provided through the wall 25 of the cover - .i 11 .
~-~ 15 Referring to Figs. 2-4, th~ seal 21 includes a cavity 25 which is substantially hour-glass in configuration. It has the opposing inwardly extending and diverging wall portions 26 and 27 terminating in an end wall 28. The - cavity 25 is also defined by the outwardly extending and diverging wall portions 29 and 30 resulting in constricting ,, .
-~l portions 31 and 32. An elastomeric and resilient seal member 33 has portio~s which are dimensioned larger than the `~ distance between the constricting portions 31 and 32 . This is bast seen in Fig. 2. The seal member i8 preferably of an eguilateral triangular configuration and when fully seated against ~he end wall 28 will also be resiliently confined between wall ~ortions 26 and 27. This is the retentive state for the seal member 33 before it is cont~cted by the i flange 19 of the base 10.
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As shown in Fig. 4, tha seal me~ber 33 is in contact with a sealing surface 3~ of the flange 19. In this state, - sealing surface 34 will force sealing member 33 into the cavity 25 and cause the otherwise conically extending section to assume i- compacted state between the outwardly extending wall portions 29 and 30. It should be further pointed out ~I that the mating sealing surface 34 on the flange 19 as ~ell as the mating sealing surface 35 on the flange 20 are highly machined surfaces. These provide a metal-to-metal s al ~-~
between the ~langes 19 and 20 and par~icularly between the seal member 33 and the inside of the compartment 14.
Fig. S illustrates the cavity 25 formed in the flange 20. The outwardly extending wall portions 29 and 30 not , only provide a cavity area for the se~l member 33 to expand ..
15 when contacted by the sealing surface 34 of the flange 19 ~ but also afford a guiding suxface ~or the iieal member 33 :I when placed initially in the cavity 25.
I The cavity 25 has a confi~rition which i5 substantially i hour-giass. It will be noted that wall portions 26 and 27 .i have a lar~er wall surface than wall portions 29 and 30.
~ How~ver, the confiquration of cavity 25 can be of various ~ geometric configurations with the provision that it a~ford a retentive cavity portion as well as a portion to accommodate the seal member when it is compres~ed.
~ .
The seal member may be formed from an elastomeric material such as neoprene rubber. The particular material ~ chosen is usually dictated by the proposed end use of the -~ enclosure. For example, use o the enclosure in the petro-chemical industry might suggest a fluorocarbon rubber, ~30 whereas a silicone rubber mi~ht be more appropriate if the `3enclosure is to be subject~d to relativeily high temperatures.

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Although various sized and shaped seal members 33 are possible, a seal member 33 ha~ing the cross-sectional config-uration of an equilateral triangle with sides measuring one-quarter inch is preferred regardless of the size of the S enclosure. Reliability of the s~al has ~een found to de-crease with seal members of smaller dimension and seal mem-bers of larger dimensions do not significantly improve performance. Alternatively the seal member 33 could take ,, an hour-glass configuration similar to cavity 25 and with portions slightly larger for sealing conkact purposes. This , I .
configuration would afford additiona] resilient material for contact with the sealing surface 34 when the sealing member is compressed.
~, It can be appreciated that the size and shape of the ;~ 15 enclosure can vary considerably from that dicclosed herein.
The invented seal 21 may th~r~fore take a co~responding num~er o~ sizes and shapes. In any case, however, the present invention provides a substantial metal-to-metal seal ;~ around the enclosure adjacent to the enclosure compartment, ~0 and it provides an elastomeric seal around the outer p~ri-i phery of the enclosure. The elastomer seal is retained in ~-~
the flange of the enclosure without adhesives or other astening devices and is expandable into a cavity formed in the sam~ flange.

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Claims

1. An enclosure for an electrical device, the combination comprising:
a base having a bottom and one or more upright walls which define a compartment for receiving the electrical device;
a first sealing surface formed on said upright wall and surrounding said compartment;
a cover having a second sealing surface which opposes and contacts said first sealing surface when said cover is positioned in place over said cavity;
a seal disposed between said opposing first and second sealing surfaces, said seal also including a cavity disposed in one of said base or cover, said cavity defined by an inner portion and an outer portion and constructed and arranged for both retaining a resilient seal member therein and permitting compressive expansion thereof, said seal also including said resilient seal member having at least one portion for extending from said cavity and for sealing engagement with one of said sealing surfaces when said cover is fastened in place over said compartment, said seal member constructed and arranged to be guided by said outer portion and self oriented by said inner portion of said cavity.

2. The enclosure as defined in claim 1 wherein said cavity has opposing inwardly extending and diverging wall portions terminating in an end wall as well as outwardly extending and diverging wall portions resulting in a constricting portion between said wall portions.

3. The enclosure as recited in claim 1 wherein said seal is disposed in said cover.

4. The enclosure as recited in claim 3 in which said sealing surfaces are flat and said seal is positioned adjacent said sealing surfaces.

5. The enclosure as recited in claim 1 in which said first and second sealing surfaces and said seal are positioned in a flanged portion surrounding said base and said cover.

6. The enclosure as recited in claim 2 wherein said cavity has a configuration which is substantially hourglass.

7. The enclosure as recited in claim 6 wherein said inwardly extending wall portions of said cavity have a larger wall surface than said outwardly extending wall portions.

8. The enclosure as recited in claim 7 wherein said resilient seal member is of a generally equilateral triangular configuration in cross-section.

9. The enclosure as recited in claim 8 wherein said base and said cover are composed of a metallic material and said resilient seal member is composed of a solid elastomeric material.

10. A seal for an assembly having two elements to be joined at mating surfaces with said mating surfaces being relatively flat comprising:
a cavity defined by an inner portion and an outer portion disposed in one of said mating surfaces, said cavity constructed and arranged for both retaining a resilient seal member therein and permitting compressive expansion thereof, said seal also including said resilient seal member having at least one portion for sealing engagement with one of said mating surfaces when said relatively flat mating surfaces are in contact, said seal member being of a substantially solid configuration in cross section so that it is self oriented and self retained in said inner portion and compressively expanded in said outer portion of said cavity.

11. The seal as recited in claim 10 wherein said cavity has opposing inwardly extending and diverging wall portions terminating in an end wall as well as outwardly extending and diverging wall portions resulting in a constricting portion between said wall portions.

12. The seal as recited in claim 10 wherein said seal is disposed in a cover member.

13. The seal as recited in claim 10 wherein said cavity has a configuration which is substantially hourglass.

14. The seal as recited in claim 13 wherein said resilient seal is of a generally equilateral triangular configuration in cross section and is composed of an elastomeric material.