US3366730A - Shielded connector for preventing arcing and surface leakage - Google Patents

Description

Jan. 30, 1968' A. o. ADAMS SHIELDED CONNECTOR FOR PREVENTING v ARCING AND SURFACE LEAKAGE Filed Sept. 24, 1965 United States Patent SHIELDED CONNECTOR FOR PREVENTING ARCING AND SURFACE LEAKAGE Andrew 0. Adams, Inglewood, Calif., assignor to Leach Corporation, San Marino, Califi, a corporation of Delaware Filed Sept. 24, 1965, Ser. No. 489,879

9 Claims. (Cl. 174151) This invention relates in general to terminal connectors and more particularly relates to a new and improved shielded electrical terminal connector for preventing arcing at high altitude areas and other low pressure areas.

Todays modern rocketry, satellites and high altitude aircraft have produced new critical requirements for electrical terminal connectors for the circuitry utilized in these devices. When such electrical circuitry is placed in an aircraft or rocket, for example that achieves flights at altitudes in the range of 80,000 to 100,000 feet, the various electrical connections are subject to a critical alternating current leakage at that altitude, in the form of arcing from the uninsulated connections to other uninsulated conductive materials. In electrical circuits such as relays, the electrical connections are often made at terminal posts which are mounted in a sealed, airtight metal container. Adequate precaution must be taken to insure against arcing between such terminal posts and any uninsulated areas of the container which houses the electrical circuitry.

In the past, the prior art techniques for avoiding arcing have centered primarily around two different but related approaches. Each of these prior art appoaches suffer from numerous disadvantages which are avoided by the principles of this invention.

One typical prior art assembly utilizes a plurality of electrically conductive terminal posts which are insulated form a container by a glass seal or any other suitable insulating material. To avoid any possibility of leakage or arc-over between the terminal and the container it has been customary practice to insulate the entire outer surface of the container by coating it with a ceramic substance of a high dielectric constant. The enamel is baked on the container at high temperatures which tend to increase the fabricating problems for the container and is an inefficient and costly operation.

In addition, this baked enamel surface is easily chipped and damaged. For example, the enamel coating is often chipped from the container surface by assembly-line opstations, or worse yet when the electrical connections are being made at the terminal posts after the component container is mounted in the aircraft. In either event, the chipped relay container must be discarded or the entire component assembly discarded because each chipped area provides a direct exposure of material for a short circuit arcing path between the electrical terminal post and the chipped area. This chipping is particularly objectionable when it occurs during the installation of a packaged component in the aircraft or other equipment, because the entire component often is discarded and a new one installed.

Attempts have been made in the past to eliminate this objectionable enamel surface and such attempts in general have proved unsatisfactory. One attempt has been to utilize an oversized collar of porcelain or rubber material that seats over and surrounds a major portion of the terminal connector. Experience has shown that this collar must extend well above the surface of the container and it thus increases the over-all height of the container and terminal posts. Further, this type of connection is cumbersome and does not alleviate the breakage problem inasmuch as the porcelain is often cracked when the electrical connection is tightened down on the terminal post. Similarly rubber collars deteriorate and split. Such cracks or splits provide direct shorts from the post to the uninsulated metal container. Furthermore, this porcelain colla-r has in the past been soldered or otherwise fastened to the container structure and when cracked or otherwise damaged the entire container must be discarded.

The foregoing disadvantages of the prior art are eliminated by the shielded terminal connector of this invention which provides a simple, rugged inexpensive connector which eliminates any surface leakage or gap arcing throughout all pressure areas, including the critical pressure at approximately 80,000 to 100,000 feet. In accordance with the principles of this invention, a shielded connector comprises a conductive terminal post having an oversized landing that is housed in an insulating material held in an electrically conductive container. An elastic insulating washer surrounds the landing and is seated over the insulating material. A rigid disk having an aperture similar to the landing is seated over the post and in contact with the washer, said disk includes a recessed area for receiving a nut threaded to the terminal post and contacting the landing area. The periphery of the insulating disk, including a portion of the recessed area extend ing beyond the threaded nut, defines sufiicient area of insulating material for shielding any arcing tendency between the post, the nut, and the metal container. In addition, the flanged area formed by the outside periphery of the disk and the recessed area in which the nut is recessed extends outwardly from the outer edge of the nut a sufficient distance that the existing air gap between the outer edge of the nut and the nearest point on the container is greater than a critical arcing gap for the electrical potential connected to the terminals. Various alternative shapes of the insulated disk are provided as such shapes may be required for different specified voltages under different operating conditions. With the new and improved terminal connector of this invention, should any breakage occur at the insulated disk there is no requirement that the container or components be discarded, as in the prior art, because the cracked shielding disk may readily be replaced by simply removing the threaded nut and placing a new shielding disk over the terminal post. The foregoing features and principles of this invention will more readily be understood by reference to the accompanying drawing in which:

FIG. 1 is a top view of a terminal post in accordance with the principles of this invention;

FIG. 2 is a side elevation taken along line 2-2 into the paper of FIG. 1; and

FIGS. 3 through 5 depict alternative configurations for the shielding disk of this invention.

FIG. 1 depicts a top view of the terminal connector 25 of this invention, an electrical conductor 5, and one portion of a container 10. It should be understood that a plurality of such terminals may exist in a container which houses electrical components. For example, container 10 may house capacitors, relays, or numerous other electrical components requiring electrical connections as part of their operation.

The terminal 25 of this invention includes a threaded post 11 which is insulated and mounted in the container 10. A threaded nut 12 which may be circular as shown, is threaded to mate with the threads of post 11. Nut 12 is threaded onto the post 11 and is seated in an annular recess 13 of a rigid shielding disk 14. This disk 14 may be of any suitable rigid material which is a high dielectric such as molded diallylphthalate or Bakelite, or other similar insulating materials characterized by ease in forming and high impact resistance. r

The terminal connector 25 of this invention is shown in side elevation in FIG. 2 taken along the line 22 into the paper at FIG. 1. In FIG. 2 the threaded electrically conductive post 11 is shown with a cylindrical oversized landing area 15 of suflicient depth to extend through the flange extensions 16 in container 10. This landing is bonded by a ring of insulating material 17 to the flange area 16 of container 10. This insulating material 17 may be any well known insulator such as a glass seal or a ceramic material having a high dielectric constant and capable of forming an airtight seal. An elastic washer 18 which may be circular, as shown, and consisting of rubber or silicone-base material surrounds the landing area 15 of threaded post 11 and seats over the insulating seal 17. This washer 18 provides a shield blocking any are gap which otherwise would exist through the air between the portion of landing 15 that is above the insulator material 17 and the nearest metal flange area 16 of container 10. Washer 18, in addition to blocking the arc gap from areas 15 and 16, blocks any surface leakage across the insulating glass 17 when the terminal post is fully assembled and washer 18 is compressively seated between the insulating material 17 and disk 14. Washer 18 also serves as an airtight seal, when compressed, to stop any minute leaks which might be present in the glass insulating material 17 At this point it should be understood that it is general practice in component packaging, to hermetically seal the container 10 so as to form an airtight chamber within the container that is subjected to a predetermined atmospheric pressure such as the pressure at sea level. This pressure is highly resistant to arcing and surface leakage, and thus the air gap and surface leakage problem solved by this invention is present only at the exposed upper terminals. Thus there is no requirement for the terminal connector of this invention to be employed on the inside of the container 10- unless that portion is not pressurized.

Shielding disk 14 is provided with an aperture substantially the same as landing area 15 of threaded post 11. Disk 14 is seated over post 11 and rests against the upper surface of washer 18. A threaded nut 12, which in this embodiment is circular, has a downwardly extending shoulder that matches the upper part of landing 15 of post 11. This circular nut 12 threads tightly against landing area 15 as by a spanner wrench inserted in the indentations 21.

Circular nut 12 and post 11, including the oversized landing 15 are all of high electrical conductivity material such as stainless steel. A copper core 9, shown in dotted lines, may run the full length of post 11 to further enhance its conductivity characteristics, if desired. The upper threaded surface of nut 12 includes a beveled shoulder 8 which serves as a trench for solder or other material for preventing any further turning or loosening of nut 12 when it has been seated with proper torque on post 11. Conductor 5 is compressively sandwiched to nut 12 by fastening means 6 which may be another threaded nut. Other well known techniques for securing nut 12 to its fixed position are available and may be employed. It is desirable, however, that nut 12 be removable if necessary to replace insulator 14, if it should become damaged in some way.

As the side elevation of FIG. 2 shows, the diameter of the circular nut 12 is less than the inside diameter of annular recess 13 of shielding disk 14. This diameter difference is chosen to represent an area, which coupled with the remaining insulating area, is sufiicient to eliminate any surface leakage.

As mentioned hereinbefore, there are at least two possible leakage paths (shown symbolically by dashed line 22 and solid arrow 23) which must be blocked for suitable connector operation at the critical pressure mentioned hereinbefore. One of these paths is the surface area path shown by dashed lines 22. Disk 14 is shaped at its outer periphery to increase the surface area path 22 by any desired amount such that for the particular signal to be applied to terminal 25 of this invention there is sufiicient surface area of an insulated material to prohibit any surface area arcing even at critical pressures. The second arc path, consists of a direct line from any uninsulated portion of nut 12 to the nearest unshielded surface point of container 10. One such typical direct arc path which is blocked by this invention, is shown by the solid arrow 23. This pat-h 23 extends from the upper corner surface of circular nut 12 to the nearest point on the uninsulated container 10. Are path 23 is also blocked, or shielded, by disk 14 having an outwardly extending flange, or overhang, such that any possibility of arcing at path 23 is impossible.

It is obvious that the shielding disk 14 may assume any desired configuration depending upon the particular electrical requirements of the component to which electrical energy is to be supplied. Some of these many possible alternative shapes are shown in FIGS. 3 through 5. In FIGS. 3 through 5, there is a downwardly extending flange area 30 as well as an upwardly extending flange area 31. This downwardly extending flange 30 may be utilized to add further compression and confinement to the elastic was-her 18 if such confinement is necessary to avoid arcing from landing 15 to container 10. Furthermore, this compressive confinement of washer 18 further enhances the sealing capacity to guard against minute pressure leaks in the insulator material 17, and provides protection of Washer 18 from aging, splitting and deterioration.

In the disk 34 of FIG. 3 the outside edge 35 is a concave peripheral curve around the circumference of disk 34. This concave groove 35 increases the surface area available for any given diameter. In a similar manner, the periphery 55 of insulator disc 54 of FIG. 5 is convex to increase the amount of surface area for any given diameter. A rectangular peripheral circumference 45 is provided for the disk 44 of FIG. 4 as another alternative shape.

It is to be understood that the foregoing features and principles of this invention are merely descriptive, and that many departures and variations thereof are possible by those skilled in the art, without departing from the spirit and scope of this invention.

What is claimed is:

1. In a packaged electrical component, an improved electrical connector for supplying current at a high applied voltage through an aperture to the interior of a hermetically sealed container having an unshielded electrically conductive outer surface, said electrical connector being operative for preventing electrical arcing including electrical surface leakage between the connector and the containers unshielded outer surface for the applied voltage at critical high-altitude atmospheric pressures to which the component may be subjected, said connector comprising an electrically conductive post, a compression seal insulatively housing the post in an airtight seal to the aperture in the container, an elastic washer of high dielectric material surrounding said post and shielding the surrounded area from electrical arcing between the surrounded area of the post and the unshielded surface of the container; a shielding disk of rigid insulating material surrounding the post and spaced away from the unshielded surface of the container by being seated on the upper surface of the elastic washer; means for receiving an electrical conductor seated within the recess in the upper surface of the shielding disk and removably fastened into electrically conductive contact with the post; said shielding disk having a recess in the upper side forming a raised peripherally extending flange extending outwardly from the electrical conductor receiving means and overhanging the mounting aperture of the container a spaced distance therefrom for insulatively interrupting any are paths from the conductor receiving means to the container surface, and for presenting an insulating surface including said peripheral edge and the outer surface of said elastic washer, interposed between said conductor receiving means and the container of length sufiicient to insulatively interrupt any electrical surface leakage paths between the current receiving means and the container surface.

2. In a packaged electrical component, an improved electrical connector for supplying current at a high applied voltage through an aperture to the interior of a hermetically sealed container having an unshielded electrically conductive outer surface, said electrical connector being operative for preventing electrical arcing including electrical surface leakage between the connector and the containers unshielded outer surface for the applied voltage at critical high-altitude atmospheric pressures to which the component may be subjected, said connector comprising a threaded post having an oversized landing, a ring of insulating material for sealing said post in an airtight seal to the aperture of the container with the oversized landing outwardly extending above the upper surface of the container, an elastic washer of insulating material surrounding the oversized landing and seated to cover the insulating material for enhancing the airtight seal when compressed, a rigid shielding disk of insulating material having an aperture substantially equal to the oversized landing seated on said elastic washer and having an annular recess in the unseated side, a flat circular metal nut having a diameter less than the diameter of the annular recess threaded on the post and seated in said recess with a downwardly extending shoulder passing through the aperture in the disk and seated on said landing when said elastic washer is compressively loaded by said threaded nut, an electrical conductor coupled to said post at an upper surface of said circular nut, and an insulating surface area for preventing arcing and surface leakage between the circular nut and the unshielded surface of the container, said area formed by a portion of the insulating disk spaced from the container by the elastic washer and extending outwardly beyond the outermost edge of the metal nut and insulatively interposed between the outermost edge of the circular nut and the surface of the unshielded container nearest thereto.

3. In a packaged electrical component, an improved electrical connector for supplying current at a high applied volt-age through an aperture to the interior of a hermetically sealed container having an unshielded electrically conductive outer surface, said electrical connector being operative for preventing electrical arcing including electrical surface leakage between the connector and the containers unshielded outer surface for the applied voltage at critical high-altitude atmospheric pressures to which the component may be subjected, said electrical connector comprising an electrically conductive post extending through a mounting aperture in the container and having an oversized landing on the post formed by an oversized collar; a glass compression seal for insulatively housing, in an airtight seal between the post and the mounting aperture, said collar with the landing being exposed at the upper outside surface of the glass compression seal; an elastic washer of high dielectric material compressibly surrounding said post for shielding the post including said landing area from electrical arcing between the post and the nearest unshielded surface of the container, and covering the glass seal, for sealing any minute leaks in the glass compression seal; a rigid shielding disk of insulating material having an aperture larger than the post and being seatably spaced from the unshielded outer surface of the container by said elastic washer; a conductor receiving seat means removably secured to the conductive post and seated against the disk for compressing the elastic washer, said seat means including a downwardly extending portion passing through the opening in the shielding disk and engaging the oversized landing of the post to form a current-conductive path therewith; said shielding disk having a recess in the upper side forming a raised peripherally extending flange extending outwardly and separated by an airspace from the seat means and overhanging the mounting aperture of the container a spaced distance therefrom for insulatively interrupting any are paths from the conductor receiving seat means to the container surface, and for presenting an insulating surface including said peripheral edge and the outer surface of said elastic washer, interposed between said seat means and the container of length sufficient to insulatively interrupt any electrical surface leakage paths between the seat means and the container surface.

4. A connector in accordance with claim 1 wherein said conductive post is threaded and includes an oversized unthreaded portion which is insulated from the metal container by said compression seal and extends above the area of insulation between the post and the container, and wherein said elastic washer is a resilient material having an opening for receiving the upwardly extending oversized portion of the post.

5. A connector in accordance with claim 4 wherein said shielding disk has an aperture in the recessed area substantially matching that of the oversized portion of the post, and wherein said means for receiving an electrical conductor to said post includes a first threaded nut with a downwardly extending shoulder passing through the aperture of said disk and said elastic washer to join with the oversized portion when threaded on said post, said first nut of a thickness extending above the upper surface of the disk, and a second threaded nut for compressively sandwiching an electrical conductor between it and the first nut.

6. A shielded electrical connector in accordance with claim 5 wherein said first nut is circular and wherein said recess in said disk is a larger circular area for receiving said first nut with an annular air gap between the edge of the circular nut and the inner edge of the flanged area of the disk defined by the circular recessed area.

7. A shielded electrical connector in accordance with claim 6 wherein said flanged area of said disk has a round convex periphery.

8. A shielded electrical connector in accordance with claim 6 wherein said flanged area of said disk has a concave periphery.

9. A shielded electrical connector in accordance with claim 6 wherein said flanged area of said disk has a grooved periphery.

References Cited UNITED STATES PATENTS 2,346,162 4/1944 Hanopol 174-152 X 2,550,112 4/1951 Fields 174153 2,897,472 7/1959 OBrien l74153 X FOREIGN PATENTS 1,009,425 3/1952 France.

LARAMIE E. ASKIN, Primary Examiner.

Claims (1)

1. IN A PACKAGED ELECTRICAL COMPONENTS, AND IMPROVED ELECTRICAL CONNECTOR FOR SUPPLYING CURRENT AT A HIGH APPLIED VOLTAGE THROUGH AN APERTURE TO THE INTERIOR OF A HERMETICALLY SEALED CONTAINER HAVING AN UNSHIELDED ELECTRICALLY CONDUCTIVE OUTER SURFACE, SAID ELECTRICAL CONNECTOR BEING OPERATIVE FOR PREVENTING ELECTRICAL ARCING INCLUDING ELECTRICAL SURFACE LEAKAGE BETWEEN THE CONNECTOR AND THE CONTAINER''S UNSHIELDED OUTER SURFACE FOR THE APPLIED VOLTAGE AT CRITICAL HIGH-ALTITUDE ATMOSPHERIC PRESSURES TO WHICH THE COMPONENT MAY BE SUBJECTED, SAID CONNECTOR COMPRISING AN ELECTRICALLY CONDUCTIVE POST, A COMPRESSION SEAL INSULATIVELY HOUSING THE POST IN AN AIRTIGHT SEAL TO THE APERTURE IN THE CONTAINER, AN ELASTIC WASHER OF HIGH DIELECTRIC MATERIAL SURROUNDING SAID POST AND SHIELDING THE SURROUNDED AREA FROM ELECTRICAL ARCING BETWEEN THE SURROUNDED AREA OF THE POST AND THE UNSHIELDED SURFACE OF THE CONTAINER; A SHIELDING DISK OF RIGID INSULATING MATERIAL SURROUNDING THE POST AND SPACED AWAY FROM THE UNSHIELDED SURFACE OF THE CONTAINER BY BEING SEATED ON THE UPPER SURFACE OF THE ELASTIC WASHER; MEANS FOR RECEIVING AN ELECTRICAL CONDUCTOR SEATED WITHIN THE RECESS IN THE UPPER SURFACE OF THE SHIELDING DISK AND REMOVABLY FASTENED INTO ELECTRICALLY CONDUCTIVE CONTACT WITH THE POST; AND SHIELDING DISK HAVING A RECESS IN THE UPPER SIDE FORMING A RAISED PERIPHERALLY EXTENDING FLANGE EXTENDING OUTWARDLY FROM THE ELECTRICAL CONDUCTOR RECEIVING MEANS AND OVERHANGING THE MOUNTING APERTURE MEANS TO THE CONTAINER SURFACE, THEREFROM FOR INSULATIVELY INTERRUPTING ANY ARC PATHS FROM THE CONDUCTOR RECEIVING MEANS TO THE CONTAINER SURFACE, AND FOR PRESENTING AN INSULATING SURFACE INCLUDING SAID PERIPHERAL EDGE AND THE OUTER SURFACE OF SAID ELASTIC WASHER, INTERPOSED BETWEEN SAID CONDUCTOR RECEIVING MEANS AND THE CONTAINER OF LENGTH SUFFICIENT TO INSULATIVELY INTERRUPT ANY ELECTRICAL SURFACE LEAKAGE PATHS BETWEEN THE CURRENT RECEIVING MEANS AND THE CONTAINER SURFACE.

Images