US3457361A - Hermetic electric terminals - Google Patents

Description

July 22, 1969 RUCLAR'K 3,457,361

HERMETIC ELECTRIC TERMINALS Filed Jan. 2'7, 196'? Mum United States Patent US. Cl. 174-153 5 Claims ABSTRACT OF THE DISCLOSURE A hermetic terminal assembly for mounting in a hole in a panel comprises a novel tubular insulating and sealing insert member having a T-shaped longitudinal cross-sec tion and an axially positioned flanged electrode pin conductor inserted therein. Its basic novelty is inherent in its special insert composition and construction which involves a non-yielding flange-like section at one end with which is incorporated a resilient, or memory conscious type barrel section, to provide hermeticity, that protrudes axially therefrom but with both parts constituting a continuous body without any interfacial seam, weak section or inherent basic body change except that the flange section is impregnant hardened by adding thereto certain fillers. A push nut or spun-out electrode shank convolution abutting the insert barrel would be adjusted to compress the barrel member against the panel member thus effecting therewith an hermetic seal. The use of the nonyielding insert flange adds an improvement in the barrel sealing, improved dimensional stability, and also reduces size requirements for a given electrical rating of the terminal.

This invention relates to hermetic electric terminals of a type which may be used for passing electric current through a sealed container. The terminal of the present invention is of the anchored flanged type.

There is provided in accordance with the present invention a terminal which may be mounted in an aperture in a panel of varying thickness within a wide range of values. This feature constitutes a substantial advantage over prior types of terminals which required special reworking for use in panels thicker than about of an inch. Also it will be found when using the terminal of the present invention, that its heighth above the panel will remain uniform irrespective of the thickness of the panel in which it is mounted.

Other advantages attained through the use of the terminal of the present invention are quick assembly, high permissible operating temperatures, good arc-over resistance and very low electrical loss characteristics.

In its simplest form the terminal of the present invention includes a metal electrode which has been inserted axially through a hole in a partially resilient flanged insert formed with a flange portion which is relatively hard with respect to its integrated resilient, barrel portion. The insert may be formed of suitable rubber compositions or special memory-type plastic compositions so that the barrel portion of the insert will be formed of a high elongation material and the flange portion of a low elongation material. It has been found that an elongation factor of at least 200% is much to be preferred for the barrel por tion of the insert so that the compressive forces of the barrel portion, upon mounting the terminal in a panel, will provide a good hermetic seal. The use of a relatively hard flange on the insert will aid in controlling the above panel heighth of the insert.

The manner in which these new combinations of insert materials function to provide the improved hermetic terminal of the present invention will be more fully discussed hereinbelow.

It has been found by forming the flange portion of the insert of a high durometer material which is compatible with and homogeneously mouldable with the softer and more resilient material forming the barrel portion of the insert, that there is provided a terminal in which the externally exposed flange portion does not flow and thereby lose its shape under the force required to compress the barrel portion when mounting the terminal in a panel. Also the flange portion will have a high are resistance characteristic whereas the barrel portion, which is normally subsequently coated with potting compound, oil or varnish, may be permitted to sacrifice some are resistance in favour of a higher resiliency to provide better sealing.

The insert may be formed of rubber, such as for example, silicone rubber such as that sold by the General Electric Company (United States) as No. SE. 505. This silicone rubber may be compounded with the materials suggested by the manufacturer to obtain a durometer reading of about 60 to 70) on the Shore A scale. This compound would be used in moulding the barrel portion of the insert. The flange portion would be then moulded from the SE. 505 compound formulation suggested by the General Electric Company for producing a rubber having a durometer reading of about 90 (85 to 95) on the Shore A scale. By loading the flange producing cavities in the insert mould with this latter compound and the barrel producing cavities with the durometer compound, a completely integral insert having a hard flange portion and a soft barrel portion is formed. It is also possible to add to the durometer and arc resistance characteristics of the flange portion of the insert by mixing into the 90 durometer rubber composition from 3 to about 10 or more percent of very finely powdered polytetrafluoroethylene, by weight.

In the alternative the insert may be formed of a plastic material such as that sold under the trademark Teflon by the E. 'I. du Pont Company and specified as either TFE or PEP. In this instance the material for the barrel portion may be of virgin stock having a durometer of 50 to 60 on the D scale and the flange portion may be formed from the same stock mixed with glass fibers, or ceramic fibers, or short lengths of oriented synthetic plastic or resinous fibers such as those sold under the trademarks Orlon and Teflon or the polyamide-imide formed from a high temperature film of Al. polymers as supplied by Amoco Chemical Corporation of Chicago, Ill., U.S.A., and described in their bulletin H.T.l. It has also been discovered that the flange portion of the insert when formed from Teflon may be toughened by the addition to the flange material of mats of the noted amide-imide in film form with the mats being perforated to form a mesh-like material and arranged so as to form a large number of layers within the flange portion. Additionally the flange portion when formed from a plastic may be reinforced with perforated mats of a polyimide film sold as Kapton Type H and made by E. I. du Pont de Nemours & Co. of Wilmington, Del., U.S.A., and disclosed in their bulletin Hl. Also rather than utilizing perforated mats of Kapton, the film may be cut into thread-like strips having sawtooth-like edges and mixed with the plastic material forming the flange portion of the insert.

The electrode used in the terminal of the present invention consists of a rod-like shank member with an annular electrode flange mounted on it. When the electrode is inserted into the insert the electrode flange member on the electrode should be so arranged that its end surface abuts the free end surface of the insert flange and the shank passes through and projects beyond the insert,

and the projecting portion of the electrode may be provided with a wire-wrapping groove. The portion of the shank to one side of the electrode flange and on which the insert is mounted may also include one or more shank encircling convolutions or ribs. If there is more than one convolution present they may be of increasing diameter towards the electrode flange on the shank. These ribs will normally lie in a plane substantially parallel to that of the electrode flange.

It has been found that by providing convolutions on the shank of the electrode it is possible to insert the electrode into the insert and the insert into an aperture in a panel and then apply pressure at both ends of the insert so as to force the barrel portion of the insert towards the flange portion and thus expand the diameter of the barrel portion to form a seal between the panel and the electrode. Through this manipulation and if a hardened section of material is provided at the free end of the insert barrel portion, the insert will lock into position on one of the convolutions. Additionally, these convolutions may be spun 20 on the shank under compression. When the insert is dis torted during mounting in the panel there is a natural tendency for the barrel portion to endeavour to expand against the push-on nut when one is used, as a result of the memory characteristics of the material forming the barrel portion. This action is of course necessary in order to cause the teeth of the push-on nut to engage the electrode shank to an extent sufficient to provide the required locking action. This results in the required hermetic seal between the insert panel and electrode.

In some instances the plastic materials used to form the insert may not have suflicient resiliency after compression to cause the teeth of the push-on nut to bite sufliciently into the electrode shank and when such is the situation it is possible to use a tension-producing electrode flange as disclosed in US. Patent No. 3,166,634 issued to Richard U. Clark. This would, in some instances, be used where an unconvoluted electrode shank is employed. If a pushon nut is employed with a convoluted electrode shank, the nut would not require a spring-like flange but rather the nut would lock between the convolutions automatically.

In accordance with the broad aspect of this invention, there is therefore provided a hermetic electric terminal comprising: a metal electrode, an annular electrode flange located on said electrode between its ends so as to define a first electrode shank portion projecting to one side of said flange and a second electrode shank portion projecting to the other side of said flange, an insert formed from an electrically non-conducting material located on said second shank portion of said electrode so that said second shank portion passes substantially axially through said insert, said insert consisting of a flange portion which abuts said electrode flange and a barrel portion remote from said electrode flange, the material forming said flange portion being such as to render it substantially non-yielding and the material forming said barrel portion being yieldable to permit its compression when mounting said terminal in an aperture in a panel and means co-operable with said barrel portion and said electrode to maintain said barrel portion under compression when said terminal is mounted in a panel so as to provide a hermetic seal between said electrode and said panel.

Referring now to the drawings which illustrate preferred embodiments of this invention:

FIGURE 1 is a view in elevation of one form of electric terminal;

FIGURE 2 is a partially longitudinal sectioned view of the terminal of FIGURE 1; and

FIGURE 3 is a view in elevation of another form of electrode as may be used in the terminal of the present invention.

Referring to FIGURE 1, there is shown an electrical terminal provided with an electrode 1 to which is secured to an annular electrode flange 4 which is positioned above the midway point along the length of the electrode 1. A notched area 5 suitable for a wire-Wrapped connection is formed adjacent the lower end of the electrode 1. A tubular insert 6 is provided on the electrode 1 which passes axially through the insert 6. Insert 6 is provided with an insert flange portion 2 which, as disclosed hereinabove, is relatively hard as compared with the material forming the insert barrel portion constituting the re- 10 mainder of the insert 6. A push-on nut 3 is positioned on the electrode 1 in abutting relationship with the lower end of the flanged insert 6 and just above the notched area 5.

Referring to FIGURE 2, there is shown the electrode 1 as it passes axially through the flanged insert 6 and there is also shown the reinforcing material located in the insert flange portion 2 for the purpose of reinforcing and stiffening that portion of the insert constituting the flange 2 as compared with the remainderof the insert. The reinforcing material shown in FIGURE 2 consists of short fibers. However, long fibers, perforating film in mat form or even thick sponge-like washers of plastic or ceramic material may be used as alternatives. The latter will provide a stiffening framework within the plastic insert flange portion 2 and become impregnated with the plastic material formingthe flange portion.

The electrode shownin FIGURE 3 includes an integral electrode flange 4 having a radially extending wave-like configuration. Convolutions 7 are shown on the shank of the electrode 1. Also shown is a wire-wrapped notch 5 on the lower end portion of the electrode 1.

It will be obvious to those skilled in the art that various types of base stocks of rubber may be used to form the insert for the terminal, as for example certain types of the more complex fluorocarbon rubbers which, in some instances, may have better resistance to the insulating oils which may be in contact with the terminals under certain conditions. 0f course the use of such rubbers is within the scope of the present invention. It is also obvious that the electrode pin may be made with an' axial through 0 hole.

I claim:

1. In combination in an hermetic electric terminal for sealably engaging in a hole ina panel, a metal electrode, an annular flange located on said electrode between its ends so as to define a first electrode shank portion projecting from one side of said flange and a second electrode shank portion projecting from the other side of said flange, a singular tubular insert formed from electrically non-conducting material located on said second shank portion of said electrode so that said second shank portion passes axially through said insert, said insert consisting of a flange portion which abuts said electrode flange and a barrel portion remote from said electrode flange, said two insert portions forming one continuous body and the material forming said insert flange portion only being of a relatively high durometer hardness in respect to the barrel, by virtue of loading material incorporated within the confines of said flange and being such as to render it substantially non-yielding, and the material forming said barrel portion being yieldable and of a low durometer hardness which renders it capable of being herroot diameters and the aperture through said insert has a diameter smaller than said convolution root diameter so that when said insert is mounted on said electrode the barrel portion of said insert is locked under longitudinal compression by forcing said barrel along said electrode in the direction of the electrode flange until said barrel '5 clears said electrode convolutions but abuts the last convolution it clears.

3. The terminal of claim 1 wherein said insert is formed of a memory type plastic material and said flange portion is reinforced by incorporating thereinto during forming perforated mats of a polyamide-imide film material.

4. The terminal of claim 1 wherein said insert member is formed of rubber having a durometer of from 50 to 70 in the barrel portion and from 85 to 95 in the flange portion as read on the Shore A scale, and said flange is impregnated with from 3% to 10%, in respect to its weight, by finely divided polytetrafiuoroethylene.

5. The terminal of claim 1 wherein said insert flange is reinforced by moulding thereinto a porous ceramic washer impregnated with a material compatible with that forming said flange portion.

6 References Cited UNITED STATES PATENTS FOREIGN PATENTS 3/ 1959 France. 7/1960 Great Britain.

LARAMIE E. ASKIN, Primary Examiner U.S. Cl. X.R.

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