High voltage electrical connector lead assembly

[57] ABSTRACT

A high-altitude, high-voltage electrical connector lead assembly having an externally threaded bushing containing a contact pin, and an external electrical lead containing a contact pin socket. Surroundingly engaging, but longitudinally movable upon the exterior surface of the electrical lead in tightly-fitting fashion is an internally threaded flexible cap. Upon assembling the connector assembly, the lead, with its flexible cap, is grasped so as to insert the end of the lead containing the contact pin socket into engagement with the bushing contact pin. When the socket and pin are thus engaged, the flexible cap is then pushed or slid along the exterior surface of the lead, the flexibility of the cap permitting its internal threads to flexurally “skip” over the external threads of the bushing. A resilient O-ring is also positioned on the external lead, the O-ring being located between the interior face of the flexible cap and the annular end of the bushing. Upon completion of the pushing operation performed upon the cap, the latter may be screw-threaded any remaining distance along the bushing, this operation serving to axially compress and radially expand the resilient O-ring, such that the latter forms a fluid-tight seal.

Claims, 5 Drawing Figures

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PATENTED Μ 311973

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HIGH VOLTAGE ELECTRICAL CONNECTOR LEAD ASSEMBLY

BACKGROUND OF THE INVENTION

The present invention relates generally to electrical 5 connectors and more particularly to an improved highaltitude, high-voltage electrical connector lead assembly for providing a fluid-tight lead-in to sealed electrical units, such as are employed in high altitude aircraft, guided missiles, and the like. 10

The deterioration of the insulation qualities of air caused by the drop in atmospheric pressure on reaching the higher altitudes now attainable has rendered inadequate high-voltage lead-in connectors as have been heretofore employed. For example, studs brought out ¹⁵through ceramic insulators are subject to arcing from stud to stud or from the stud to the metal casing, where reliance is placed in whole or in part upon the dielectric strength of air. Also commonly employed as highvoltage connectors are plug-type arrangements where ²θ the connection is provided with a surrounding insulating sleeve, the assembly being enclosed in a supporting metal jacket. The free path from connection to jacket within such connectors is subject to arcing at high alti- ₂₅tudes, and furthermore, the seal against oil seepage for hermetically sealed oil-filled units has in general been found to be unsatisfactory.

One type of high-altitude, high-voltage electrical connector lead assembly currently being employed, which solves the problems heretofore noted, is that assembly disclosed in U.S. Pat. No. 2,958,844, to Willard A. Smith et al. which is assigned to the assignee of the present application. While this assembly has been generally successfully employed, it however has not been 35 found to be entirely satisfactory in all commerical applications. One problem, for example, that has been encountered in the use of the patented assembly is that because of the threaded method of connecting the component parts together, that is, the screwing of the 40 connector cap onto the connector bushing, the external leads, which are fixed at one end to the end of the connector portion carrying the cap and at their other end to other electrical components have a great deal of torque transmitted thereto in the course of turning the 45 cap to threadably tighten it onto the bushing, and this problem becomes especially severe in the case where these leads are very short. This results in the deterioration of the connections, both between the external leads and the cap connector portion, as well as between 50 the external leads and the other electrical components to which the opposite ends of the leads are connected. In addition, because the cap must be tightly threaded onto the bushing portion to provide a suitable connection, the assembly time is quite extensive for putting to- ³³gether the component parts.

connector lead assembly which will greatly decrease assembly costs in systems manufacture.

Yet another object of the present invention is to provide an improved high-altitude, high-voltage electrical connector lead assembly which will reduce the amount of torque normally transmitted to connector leads during systems manufacture, and thereby provide for more reliable connections.

It is a further object of the present invention to provide an improved high-altitude, high-voltage electrical connector lead assembly which is quick and easy to assemble, yet is sufficiently difficult to disassemble so as to prevent the accidental or inadvertent disconnection of the various components.

A yet further object of the present invention is the provision of an improved high-altitude, high-voltage electrical connector lead assembly which will accommodate component parts of different lengths.

The foregoing objectives are achieved according to this invention through the provision of a high-altitude, high-voltage electrical connector lead assembly having a cylindrical bushing portion having a lead contact pin fixed to one end thereof and extending axially thereinto, and an external lead adapted to be received in the other end of the cylindrical bushing and having a lead contact pin receptacle for frictionally mating with the bushing lead contact pin. To additionally secure the connection, the bushing portion of the assembly is externally threaded along an end part of its length, while the external lead has an internally threaded flexible cap disposed thereon which is capable of longitudinally sliding movement upon the exterior surface of the external lead. In assembling the connector, the external lead, with its longitudinally slidable cap disposed thereon, is inserted into mating contact with the bushing lead contact pin, and at the conclusion of this step, the cap is slid longitudinally along the exterior surface of the external lead and is subsequently pushed or snapped with some force onto the bushing portion, the cap flexing and consequently permitting its internal threads to slide along or over a portion of the external threads of the bushing. An O-ring also is positioned on the external lead, being adapted to provide a fluid seal between the cap interior and the cylindrical bushing interior upon connection thereof. Thus, when the cap cannot be pushed or snapped onto the bushing any further, it may subsequently be threadingly screwed upon the remainder of the threaded portion of the bushing, this last mentioned threading action serving to axially compress and radially expand the internally located Oring between the closed end of the cap and the annular end of the cylindrical bushing and about the external lead, respectively, so that the O-ring consequently acts as a fluid-tight seal.

BRIEF DESCRIPTION OF THE DRAWINGS

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide an improved high-altitude, high-voltage ⁶⁰electrical connector lead assembly.

Another object of the present invention is to provide an improved high-altitude, high-voltage electrical connector lead assembly which will greatly reduce the as- ₆₅sembly time in systems manufacture.

Still another object of the present invention is to provide an improved high-altitude, high-voltage electrical

Various other objects, features, and attendant advantages of the present invention will be more fully appreciated as the same becomes better understood from the following detailed description when considered in connection with the accompanying drawings, in which like reference characters designate like or corresponding parts throughout the several views, and wherein:

FIG. 1 is an exploded perspective view of a highaltitude, high-voltage electrical connector lead assembly constructed according to this invention and showing its cooperative parts;

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FIG. 2 is a cross-section view of an assembled highaltitude high-voltage electrical connector lead assembly as illustrated in FIG. 1, taken along line 2—2 of FIG. 1;

FIG. 3 is an enlarged fragmentary sectional view of the threaded cap and bushing of the assembled highaltitude, high-voltage electrical connector lead assembly as illustrated in FIG. 2;

FIG. 4 is an enlarged fragmentary sectional view of another embodiment of a threaded cap and bushing which may be employed in an assembled high-altitude, high-voltage electrical connector lead assembly as illustrated in FIG. 2; and

FIG. 5 is a side view of another embodiment of an electrical lead which may be employed in the highaltitude, high-voltage electrical connector lead assembly as illustrated in FIG. 1, the lead of this embodiment having a molded O-ring thereon.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, and more particularly to FIGS. 1 and 2 thereof, there is shown a high-altitude, high-voltage electrical connector lead assembly generally indicated by the reference character 10 comprising a cylindrical bushing 12, an Ο-ring 14, a tubular cap 16, and an external lead 18. The cylindrical bushing 12 may be of a suitable dielectric material, preferably of a type which can be threaded, molded in plastic, and subjected to the wide range of temperatures encountered in high-altitude applications and bonding operations, such as for example, soldering, without cracking, such as a laminated phenolic-base resin, steatite ceramic or the like. The dielectric material selected however, will no doubt depend to some extent upon the method employed to seal the electrical unit. If for example, the unit is to be encased in a metal can for hermetic sealing, a steatite ceramic, metalized to provide a surface 20 extending circumferentially of bushing 12 and which is solderable to the sealed electrical unit casing 22 to thereby achieve a fluid-tight seal preventing seepage of oil around the bushing, may be utilized. As an alternative, a laminated phenolic suffices where the electrical unit is embedded, or potted, in plastic.

Still referring to FIGS. 1 and 2, it is seen that in order to facilitate assembly between the component parts of the present invention, which will be discussed in detail hereinafter, bushing 12 extends through casing 22 of the particular sealed electrical unit utilized, thereby defining a portion 24 which projects from the particular sealed electrical unit, and a portion 26 which is interior of the electrical unit. Projecting portion 24 contains external threads 28, which may extend almost the full length of portion 24 or approximately one-half the length of bushing 12, and an end face 30 which is apertured as at 32. The aperture 32 defines an entranceway to a recess 34 which extends substantially over the entire length of the bushing 12, the recess 34 being terminated by an end face 36 of the interior portion 26 of bushing 12.

Inserted within end face 36 and located along the longitudinal axis of bushing 12 is a plug 38, which may be rigidly maintained or secured within an aperture 40 in the end plate 36, as for example, by soldering or brazing. Plug 38 has at one end a contact pin 42 which extends axially into the recess 34 of bushing 12, and has at the other end an ear 44 which projects axially exter nally of the bushing 12 and facilitates the attachment of other electrical leads, not shown, extending from other electrical components situated internally of the sealed electrical unit.

Still referring to FIGS. 1 and 2, the external lead 18 shown therein is composed of an insulated wire conductor portion 46, and an elongate substantially rigid insulating sheath portion 48, which surroundingly encapsulates wire 46. Wire portion 46 thus enters the rigid sheath portion 48 through one end of an axial cylindrical opening 54 extending through the sheath, and the other end of the through opening defines an entranceway to a contact pin socket 60 disposed therein and being of such diameter as to form a friction fit with bushing contact pin 42. The contact pin socket 60 and the conductor of lead wire 46 are electrically connected within the through opening 54 via a solder well 62 disposed therein.

It will be noted that the rigid insulation sheath 48 may be encapsulated over the wire core 46 by any suitable method according to the type of materials employed. For example, typical insulating materials utilized for high voltage leads are silicone-rubber or natural rubber compositions which expand upon soaking in temporary liquid plasticizers, such as the aromatic liquids toluene, benzene, or their derivatives. Accordingly, after stripping the end of the wire 46 of its insulation to expose the wire conductor, the conductor is connected to the contact pin socket 60, for example, by having the latter crimped thereon, and the insulating sheath, which may be a silicone-rubber composition as described herein, is soaked in toluene, and is pulled over the connection between the conductor of wire 46 and the socket 60, extending beyond the adjacent insulative covering of wire 46 in one direction and terminating at the end of socket 60 in the other direction. Thereafter, upon evaporation of the toluene, the insulation composition shrinks to its original diameter into tight engagement with the wire conductor, the socket, and the insulative covering of the wire to provide a rigid sheath. If desired, the stripped conductor and socket may be soldered before covering with the sheath 48 to provide a solder well designated at 62.

In connection with the aforementioned, it should also be noted that to assure maximum protection against arcing, it is preferred that bushing 12 be filled as completely as possible with dielectric materials encompassing the metallic elements of the contact assembly to rid the assembly of residual air gaps. Accordingly, the inside diameter of the bushing 12, or of recess 34 is only slightly larger than the outside diameter of the rigid lead insulation sheath 48, being sufficient just to admit lead 18 internally of bushing 12 without difficulty, with the result being that substantially all of the space within the bushing 12 is occupied by dielectric material.

Finally, to secure together the component parts of the lead assembly of the present invention as will be discussed more fully hereinafter, the tubular dielectric cap 16 is provided, being internally threaded at 68 for cooperation with external threads 28 of bushing 12 and having an end wall portion defining a central aperture 70, and being composed of an appropriate phenolic resin, such as, for example, low density polyethylene, so as to be sufficiently resilient and flexible for a purpose more fully discussed hereinafter. In conjunction with cap 16, the resilient O-ring 14 is designed with a diameter so as to enable its being seated within cap 16

3,750,084 against the end wall thereof and also so as to be in tight surrounding engagement with insulation sheath 48 of lead 18. Similarly, the central aperture 70 in cap 16 is of such diameter that it too affords a tight fit between lead insulation sheath 48 and the cap. To facilitate ma- 5 nipulation of cap 16, longitudinal projecting ribs 72 are provided upon the outer peripheral surface 74 thereof.

With particular reference to FIGS. 1 and 2, the assembly of the electrical connector of the present invention will be apparent. With bushing 12 encased within 10 electrical unit wall 22 and protruding therefrom, flexible cap 16 is flexurally fitted upon external rigid lead sheath 48, and a similar operation is performed with respect to O-ring 14 and sheath 48, the O-ring 14 and cap 16 being positioned relative to the sheath 48 as shown 15 in the dotted line position of FIG. 2.

To assemble the connector, the subassembly composed of lead 18, cap 16, and O-ring 14, is grasped by means of rigid sheath 48, whereby the end of the sheath portion 48 is inserted within bushing 12, so that lead 20 contact pin socket 60 is axially aligned with bushing contact pin 42 and makes frictional contact therewith, the longitudinal insertion of lead 18 within bushing 12 in the direction of the arrow A being terminated upon the abutment of the rigid lead sheath end face with the 25 interior face of bushing end plate 36. It will be noted at this point that cap 16 and O-ring 14 are still in the dotted line positions relative to lead sheath 48.

Upon complete insertion of rigid lead sheath 48 within bushing 12, as determined by the respective ³⁰abutment of the end faces thereof, as discussed heretofore, final securement of the component parts of the assembly can now take place. In accordance with such operation, the flexible cap 16 and the O-ring 14 are slid along the exterior surface of rigid lead sheath 48 in the ³⁵direction of arrow A. With reference to FIGS. 2, 3, and 4, it will be seen that upon sliding flexible cap 16 and O-ring 14 as heretofore mentioned, the internal threads 68 of flexible cap 16 will encounter external threads 28 of bushing 12. Due to the flexibility of cap 16, and the ⁴θ particular contour or configuration of the relative threads, forcibly pushing the cap at this time will enable the flexible cap 16 to be moved along and over bushing 12, each thread 68 of cap 16 flexurally “skipping” over the corresponding threads 28 of bushing 12. It can ⁴⁵therefore be appreciated that a quick, pushing motion in the direction of arrow A will cause cap 16 to be snapped onto the bushing 12. Forward progress of the cap relative to bushing 12 will usually be halted before its limit of threaded travel is completed. Cap 16 may ⁵⁰ then be screw-threaded relative to bushing 12 for engaging the remaining threads, such action respectively axially compressing and radially expanding O-ring 14 between the inside face 76 of cap 16 and the annular end surface 30 of the bushing 12 and between the inside wall of the cap and the sheath 48. The O-ring 14 may be formed of rubber or other similar material, such that the resulting action just described upon O-ring 14 provides the assembly with a fluid-tight seal.

Referring now to FIGS. 3 and 4, two embodiments of thread configuration for the cap and bushing are illustrated. FIG. 3 discloses external threads 28 of bushing 12 being of the conventional zig-zag design, whereas the internal threads 68 of flexible cap 16 are of a truncated zig-zag design, the respective sides of which, 78 and 80, include the same angle with respect to a plane passing through the longitudinal axis of the assembly.

In FIG. 4, however, the threads of each part are seen to be of saw-tooth configuration.

Examination of FIGS. 3 and 4, in conjunction with the above disclosure, will make it apparent that, due to the specific thread configurations, and by an appreciation of the force magnitudes involved in the pushing and pulling operations, although the flexible cap 16 may be snapped partway onto bushing 12, it cannot be snapped or pulled off, but on the contrary, these respective parts can only be separated by a reverse screwthreading operation. Hence, although the connector may be quite easily and quickly assembled, it is difficult to disassemble it unintentionally. Consequently, more reliable connections result, and inadvertent and accidental disconnections cannot occur.

Referring now to FIG. 5, a second embodiment of the external lead is disclosed, this lead 18', being similar to lead 18, is composed of an insulated wire 46 and a rigid insulation sheath 48, but an additional feature of this lead however, is that an O-ring 82 is integrally molded with the insulation sheath 48. Although this particular lead embodiment can sufficiently and effectively perform its respective functions within the lead assembly of the present invention, it will be appreciated that with this embodiment, the relative lengths of the various components, i.e., of the bushing receptacle and the external lead, especially its cap portion, are fixed, due to the fact that upon ultimately assembling the lead assembly, O-ring 82 must be seated in abutting relationship to end face 30 of bushing 12 while the cap must be simultaneously able to reach the threaded periphery of the bushing 12, such that standard receptacles can be used and the lead may be plugged in or be readily repairable in the field with a replacement piece.

With the non-molded O-ring embodiment of FIGS. 1 and 2, on the other hand, a loose O-ring has the advantage of accomodating different lengths of component parts, and thus of being readily field repairable even in the absence of a standard-size piece.

Thus, it may be seen that the high-altitude, highvoltage electrical connector lead assembly of the present invention has important advantages over the known prior art structures in that the connector may be rapidly assembled, the assembly process through its provision of a snap-on cap consequently eliminating much of the threading step that heretofore results in turning the wire 46, which is connected at its other end and, thereby preventing the introduction of torque at the other lead end connections, and facilitating more rapid and more reliable connector assemblies.

Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is to be understood, therefore, that within the scope of the appended claims the present invention may be practiced otherwise than as specifically described herein. Accordingly,