CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of the earlier filing date of, U.S. Provisional Patent Application No. 62/001,208, filed on May 21 , 2014 and U.S. Patent Application No. 14/531 ,097, filed on November 3, 2014, the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

[0002] Embodiments of the invention relate to an apparatus for connecting and disconnecting electrical circuits underwater or in other harsh environments.

BACKGROUND

[0003] The first rudimentary electrical connectors that could be connected and disconnected underwater appeared in the mid-1960's, with reliable commercial products not becoming available until the mid-1980's. Prior to that time, subsea systems had to be fully connected electrically before submersion. In the intervening years many Offshore Industry applications have been developed that require electrical elements to be repeatedly connected and disconnected while immersed in seawater. There are several known devices that fulfill thai requirement. A subset of such devices comprises connectors wherein the electrical contacts consist of pins and sockets to be joined in a chamber filled with a benign substance that protects them from the external environment. The protective substance, a mobile dielectric material such as oil, grease, or gel, hereinafter referred to simply as fluid or oil, is pressure-balanced to ambient in-situ conditions by way of a compensating element which is typically a flexible wall of the chamber in which it is housed. Representative examples of the prior art can be found in US Patents 3,508, 188; 3,522,576; 3,643,207; 4,085,993; 4, 142,770: 4,373,767; 4,795,359; 4,948,377; and 5, 171, 1 58. [0004] In this subset of prior-art underwater connectors the pins generally have elongated electrically-conductive shafts that are coated with dielectric sheaths, and have exposed electrically conductive contact tips. The pins enter the contact chamber by way of penetrable end-seal passages that are intended to remain sealed from the outside environment before, during, and after mating and de-mating. Once mated, the conductive pin-tips are completely immersed within the contact chamber, leaving a portion of the electrically insulated shafts exposed to the in-situ environment. For ease of discussion, the connector unit in which pins are housed shall hereafter be referred to as the "plug," and the unit housing the sockets within the mating chamber shall be referred to as the "receptacle. ^" '

[0005] it is a challenge to keep the receptacle end-seal passages leading into the oil chamber closed before, during, and after mating and de-mating. To meet that challenge, connectors that represent this subset and are currently commercially available have evolved into complex devices having plug pins with circular cross sections, and receptacles with resilient end-seals having circular, re-sealable passages to accept the respective cylindrical pins. Currently on the market there are connectors employing one or the other of two different approaches for keeping the cylindrical, bore-like end-sea! passages sealed at all times.

[0006] in the first approach, when the connector portions are unmated the elastomeric receptacle end-seal passages are occupied by rigid, non-electrically-conductive, cylindrical stoppers housed within the mating chamber. The stoppers are biased outward by robust springs. During mating, the entering plug pins force the stoppers inward beyond the end-seals and further into the mating chamber, thereby compressing the springs. The result is that the receptacle mating-chamber end-seal passages are always occupied, either by the stoppers when unmated. or by the plug pins when mated. That keeps the circular end-seal passages always sealed from the outside environment, but it does so at the expense of a great deal of complexity. The springs must be robust to guarantee reliable return of the stoppers into the end-seal passages upon demating. That creates substantial mating forces, and requires a latching mechanism or other means to keep the connector portions from springing apart once mated. And even though the return springs are robust, failures occasionally occur when the spring-driven stoppers fail to return outward into the end-seal passages. That leaves a leak path between the chamber fluid and the in-situ environment. A representative example of this sort of connector is found in US Patent 4,948,377. [0007] The second, less reliable approach to the circular end-seal closure challenge is to pinch resilient, tubular, end-seai passages closed when the connector portions are unmated. The force required to keep the circular tubular passages pinched closed is provided either by an elastomeric sphincter surrounding the passage, or by a metal spring, or by both a spring and an elastomeric sphincter acting together. Upon mating, the pinched tube is forced open by a slender, tapered end of the circular cross-section incoming plug pin; thus remaining sealed against the plug pin's surface during mating and de-mating, and while mated. One example of this sort of connector is found in US Patent 4.373,767. The invention has no stoppers or stopper-biasing springs, and therefore is mechanically much simpler than connectors built around the concept mentioned in section [005]. it has major disadvantages however: the substantial force required to pinch a circular end-seal passage completely closed makes mating and de-mating difficult, sometimes resulting in tearing of the tubular passage, and subsequent failure. The construction has the further disadvantage of failure of the circular tubular passages to close properly after prolonged mating at cold temperature. When that happens a leak path is created between the chamber oil and the in-situ environment, for instance electrically conductive seawater. In addition, the high stress required of such end- seals is detrimental to the seal's elastomeric properties. All of these disadvantages compromise the reliability of this sort of connector.

[0008] There is third, completely different, approach which is not currently on the market. The early technology disclosed in US Patent 3,643,207 approached the connector seal-closure problem in a much less complex way. nstead of attempting to keep circular bore-shaped resilient passages closed, it employed one narrow, siitted passage through an elastomeric receptacle end-seal for each respective one blade-like plug pin. Little or no end- seai material was removed in creating the slits. A slit is much easier to keep closed than a cylindrical bore because it is closed in its natural unstressed condition. A blade-like pin causes little distortion of a properly-sized siitted opening, and only slight stress on the elastomeric seal material. Although the blade-in-slit sealing concept itself is very sound, connectors incorporating that approach lacked the necessary attributes to function reliably. For example, the only mechanism provided to close the slits was the elasticity of the resilient end-seal material through which the slits were cut. Upon demating after prolonged mating at cold temperatures the slits closed very slowly, allowing a temporary leak path between the chamber fluid and the in-situ environment. When that happened, the chamber fluid became contaminated by intruding environmental fluid such as seawater, thereby degrading its electrical properties. No positive means were included to isolate conductive elements within the chamber fluid from each other, so intruding contaminants occasionally caused electrical circuit-to-circuit internal breakdown. For those and other reasons the concept was abandoned years ago in favor of the aforementioned more complex approaches.

[0009] In addition to the fact that all of the aforementioned products have some technical shortcomings, the complexity and expense of the underwater connectors described in paragraphs [005] and [006] puts them out of reach of many, if not most, harsh environment projects. Those described in paragraph [007] never resulted in viable commercial products. What is still needed is a connector device that reduces or overcomes the shortcomings found in the known harsh environment connectors as described above, while simultaneously reducing the complexity and cost of manufacture. This invention fulfills that need.

SUMMARY

[0010] Invention embodiments described herein provide for an apparatus which includes a first connector unit hereafter called the "plug" and a second connector unit hereafter called the ''receptacle" which can be repeatedly connected and disconnected underwater or in other harsh environments without loss of electrical integrity. Although the described embodiments are intended for use subsea, is clear that they could be used in myriad applications wherein the electrical junctions, when connected, must remain sealed from each other and from the in- situ environment; and when disconnected, receptacle contacts must remain electrically isolated from each other and from the in-situ environment.

[001 3 ] In one embodiment of the invention the plug unit houses a first one or more electrical "pins" characterized by elongated, blade-like, insulated shafts with exposed electrically-conductive tips. The receptacle unit houses a respective one or more electrical "sockets" housed in a chamber filled with a mobile dielectric substance sealed from the exterior environment. When the plug and receptacle units are joined, the one or more plug pins seaiably penetrate respective one or more slitted passages into the receptacle chamber, their conductive tips thereby joining the respective one or more socket contacts within the oil- ill led receptacle chamber. Active closure means which augment the resiliency of the slitted passages are provided to urge said passages seaiably closed before, during, and after mating and demoting. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The invention is presented herein in general terms without regard to any specific application. It will be easily understood that the described apparatus can be readily adapted to a wide variety of housings, contact arrangements, sizes, materials, and exterior configurations, making it adaptable to a broad spectrum of applications.

[0013] Other features and advantages of the present invention will become more readily apparent to those of ordinary skill in the art after reviewing the following detailed description and the accompanying drawings, in which like reference numbers refer to like parts:

[0014] FIG, 1 is a partial axial cross-sectional view of old art taken from US 4,085,993;

[0015] FIG. 2 is a cross-section taken through 2 - 2 of Figure 1 ;

[0016] FIG. 3 shows a dividing element of the US 4,085,993 receptacle;

[0017 { FIGS. 4a and 4b show various seal radial cross-sections;

[0018] FIGS. 5a and 5b show various pin radial cross-sections in slitted openings;

[001 ] FIG. 6a, 6b, and 6c indicate potential cross-sections for blade-like pin contacts:

[0020] FIG. 7 is an oblique view of connector unit 1 ;

[0021] FIG. 8 is an oblique view of connector unit 2;

[0022] FIG. 9 is an oblique view of a plug electrical contact 26;

[0023] FIG. 10 is an oblique axial quarter-section view of connector unit 1 ;

[0024] FIG. I I is an oblique axial quarter-section view of resilient seal 43;

[0025] FIGS. 12a and 12b are oblique axial quarter-section views of connector unit 2;

[0026] FIG. 13 is an oblique axial half-section view of receptacle internal components including the end-seal 88, end-seal standoff 140, and leaf spring 147;

[0027] FIG. 14 is an oblique view of receptacle end-seal standoff 140; [0028] FIG. 15 is an oblique view of the receptacle leaf spring 147;

[0029] FIG. 16 is an oblique view of a receptacle electrical contact 56;

[0030] FIG. 17 is an oblique axial quarter-section view of resilient seal 73;

[0031 ] FIG. 18 is an oblique axial sectional view of receptacle shell 6;

[0032] FIGS. 19a and 19fo are partial axial quarter-section views of mated connector plug and receptacle units 1 and 2,

DETAILED DESCRIPTION

[0033] Figures 1 , 2, and 3 are examples of old art taken from US Patent 4,085,993 in which Figure 1 is a partial axial cross-section of plug connector unit 10 and receptacle connector unit 12. Plug unit 10 has blade-like pins 16 whose shafts are coated by a thin dielectric material 18. Receptacle unit 12 has respective electrical sockets 22 housed in chamber 24. Chamber 24 is filled with a dielectric fluid such as Silicone oil. Resilient disc 30 is perforated by slits 32 through which respective plug pins 16 sealably pass during mating and de-mating. Boot 40 communicates with the in-situ environment by way of a central bore in plate 36, thus equalizing the dielectric fluid pressure within chamber 24 to that exterior to receptacle connector unit 12.

[0034] The '993 construction lacks a number of essential aspects whose absence causes the connector units to be ineffective. As an example, no means other than the resiliency of disc 30 is provided to close the slitted openings upon demating. Therefore, upon

disconnection of the plug and receptacle units, the only force available to reclose slits 32 is the elasticity of the resilient materia! from which disc 30 is made. Even the most elastic- materials when deformed for long periods of time, and particularly in a cold environment, will not snap back to their original shape when urged to do so only by their inherent elasticity. They return slowly, if at all. That slow return, in the case of slitted passages 32, allows in-situ fluid such as seawater to enter fluid chamber 24 and contaminate the fluid therein; and, it allows the chamber oil to leak out. Vanes 58 with holes 60, 62 seen in Figures 2, 3 retard the electrical shorting of adjacent receptacle contacts due to such contamination, but they do not prevent it. Another problem with relying solely upon the seal material's elasticity to close the slits is that, to be even minimally effective, the seal material must be extremely elastic. But known very elastic materials such as natural rubber have little resistance to degradation by sunlight and chemicals, and so can only be used in a limited number of applications.

[0035] A further disadvantage of relying solely upon the e!astomeric properties of disc 30 to keep slits 32 sealably closed under all circumstances is that even a modest pressure differential between the fluid in chamber 24 and the exterior environment causes the slits to weep. Almost invariably in fluid-filled connector units there is at least a small quantity of air entrapped within the oil -filled mating chamber typified by '993 chamber 24 when it is initially filled with fluid. Unless the air is excessive, that is no problem; when the units are subjected to high external pressure the air collapses and eventually goes into solution. Boot 40 or its equivalent expands to compensate for the air's absence. The amount of

compensation required cannot exceed that of the volume of air that was entrapped when the oil -filled mating chamber was initially filled. In contrast, when exposed to high temperature and/or low in-situ pressure the air expands. There is a practical limit to how much air can compress, but no such limit on how much it can expand. Expanding air within the oil-filled mating chamber causes boot 40, or its equivalent to collapse to its limit, after which the expanding air within the oil chamber results in fluid leakage through slitted openings typified by 32. The now defunct '993 connector units, whose seals relied solely upon their resiliency to keep the slitted passages closed, could not be shipped by air without losing fluid. They often arrived at their destinations unfit for use.

[0036] One design goal for high-reliability fluid-filled connectors is that chambers wherein the pin-socket contacts are joined must be at least doubly sealed both from the in-situ environment, and from the mating chambers of other pin-socket pairs within the connector. Connectors with blade-like plug pins and slitted-passage receptacle seals typified by US Patents 3,643,207 and 4,085,993 do not satisfy that goal. Aside from vanes 58 which limit contamination migration, there are no means to doubly seal individual pin-socket pairs from each other or from the in-situ environment. As a result, seawater ingress into chamber 24 from one slitted passage can migrate to electrically bridge the gap between pin-socket pairs within the chamber causing electrical breakdown. In the case of a damaged passage 32, a direct conductive seawater path can exist to the outside environment, allowing electrical shorting to the seawater. The lack of redundant sealing renders all prior art connectors employing slitted-passage receptacle end-seals unacceptable for high-reliability applications. [0037] Figures 4a and 4b illustrate some problems associated with the US Patent 4,373,767 technique of sealing a circular cross-section passage 1 1 through a resilient end-seal 13 by pinching it closed. It requires considerable force to pinch the circular passage 11 of Figure 4a into the partially closed shape shown in Figure 4b. Completely closing the passage at end points 15 in Figure 4b would result in very high stress of the seal material at the ends of the pinched opening. Also, the required pinching force makes the insertion and subsequent withdrawal of a cylindrical plug pin difficult and potentially harmful to the seal. When elastomers are forcibly pressed against rigid surfaces for long periods of time they conform to irregularities on those surfaces on a microscopic scale, and no longer slide against them easily; they adhere.

[0038] Figure 5a demonstrates why it is not practical to use circular cross-section pins with slitted seal passages. Figure 5a is a radial cross-section through a portion of seal 17 with a slitted passage 23 and a round cross-section pin 19 within the passage. The passage walls do not conform well to the pin, leaving unsealed leak paths 21. Leak paths 21 could only be completely closed if seal 17 were either highly compressed onto the pin or grossly stretched around the pin, but either of those would make insertion and subsequent withdrawal of the pin very difficult due to adherence, possibly damaging the seal. In contrast, Figure 5b shows a blade-like pin 25 passing through the slitted passage 23 in seal 17. The blade is able to confonn to the passage walls, and with only minimum stretch of seal 17 leaves no leak path. Blade-like pins require relatively little force to penetrate or be w ithdrawn from the seal's slitted passage. "Biade-Iike" pins are not required to be of simple fiat-sided cross-section as shown in Figure 5b. They can be of any elongated cross-sectional shape that fills an elastomeric slitted passage without creating high stress on the seal. Some of the many examples of pin cross-sectional shapes that could be used with slitted passages are shown in Figures 6a. 6b, and 6c. For example Figure 6b and 6c show that the pins do not necessarily have to have either a constant width or parallel sides, in the case of the Figure 6c blade contact, the chamber's slitted end-seal opening to would be crescent shaped in order to sea! ably receive it. Many other functional shapes could be devised.

[0039] Figures 7, 8 and 9 illustrate respectively embodiments of plug unit 1 , receptacle unit 2, and typical plug pin 26 of the invented connector. Outer shell 46 of plug 3 has cylindrical bore 3 sized to receive forward cylindrical projection 4 of receptacle shell 6. During and after mating of the units, bore 3 in cooperation with projection 4 serve to keep the units axia!ly aligned. Plug shell vent holes 39 permit free flow of the in-situ environmental material, for instance seawater, into and out of plug bore 3 during mating, de-mating, and thereafter. Key 5 of plug shell 46 cooperates with keyway 8 of receptacle shell 6 to rotationally lock plug 1 to receptacle 2. Lateral slot 37 at the end of keyway 8 serves as a cleanout for debris that otherwise might block the free entrance of key 5 into keyway 8. Plug pins 26 comprise blade-like shafts 7 with dielectric sheaths 27, exposed conductive tips 28, cylindrical sections 29 with knurled surfaces 31 , o-ring grooves 33, rear shoulders 35, and solder cups 37. Pins 26 project outward into plug bore 3. Openings 90 in receptacle end wall 65 are positioned to receive respective plug pins 26.

[0040] Figure 10 depicts an axial quarter-section of plug 1. Pins 26 are press fit into bores 49 in plug base 45 until plug pin rear shoulders 35 seat against respective shoulders 47 of plug base 45. O-rings 41 seat in grooves 33 effectively sealing the interface between plug base 45 and plug pins 26. Plug base 45 can be made from an engineered plastic material such as glass reinforced Ultem. Knurled plug-pin surfaces 31 have an interference fit to diameters 49 of plug base 45, thereby rotationally locking plug pins 26 to base 45. Shoulders 47 in base 45 acting in cooperation with plug pin shoulders 35 limit the rearward travel of said plug pins within base 45. Once the plug pins are fully inserted into plug base 45, retainer rings 51 are put in place thereby fixing the pins axially within the plug base. Plug forward resilient seal 43 shown partially cut away in Figure 1 1 has inner bores 55 that seal to cylindrical projections 53 of plug base 45. Figure 10 shows plug alignment key 106 acting with keyway 105 in plug base 45 and with keyway 107 in plug shell 46 to rotationally lock plug base 45 to plug shell 46. Retainer ring 108 seats in groove 109 in plug shell 46 to axially limit the rearward travel of plug base 45 within plug shell 46. Shoulder 1 10 of plug shell 46 in cooperation with shoulder 1 1 1 of plug base 45 limits the forward travel of plug base 45 within plug shell 46. O-ring 1 12 seated in groove 1 13 of plug base 45 seals the interface between base 45 and bore 1 16 of plug shell 46. Forward portion 1 14 of plug forward resilient seal 43 scalable fits to bore 1 15 of plug shell 46 thus providing a backup seal for o-ring 1 12.

[0041] Receptacle unit 2 is shown in axial quarter-section in Figures 12a and 12b.

Receptacle base 70 inserts into bore 120 of receptacle shell 6. The forward movement of base 70 within shell 6 is arrested by the cooperation of shoulder 121 of base 70 with shoulder 122 of shell 6. The interface between base 70 and bore 120 of shell 6 is sealed by o-ring 123 which seats in groove 124 of base 70. High-strength barrier 125 fits in bore 120 rearward of base 70. High-strength barrier 125 serves to prevent damage to connector receptacle unit 2 that might otherwise result from high differential pressure across base 70. Barrier 125 can be made from high-strength plastic for light duty applications, or from a variety of metals for heavy duty service. Both barrier 125 and base 70 are restrained from rearward movement within shell 6 by retainer ring 126 in groove 127 of receptacle shell 6. Key 128 acting with keyways 129, 330, and 131 rotationally aligns base 70 and high-strength barrier 125 to receptacle shell 6. Key 128 is held in place axially by retainer ring 126 and by the forward end 132 of keyway 129 of shell 6.

[0042] Receptacle end-seal 88 shown in Figures 12a and 13 consists of flexible wall 82 which terminates on its posterior end with inward facing shoulder 133 and on its anterior end by wall 135. Shoulder 133 of end-seal 88 seats in groove 138 of receptacle base 70 thereby sealing the interface between base 70 and end-seal 88. The exterior surface of end-seal 88 at shoulder 133 also seals the interface between the rear portion of end-seal 88 and forward bore 339 of shell 6, thereby providing a redundant seal to o-ring 123. Segmented nibs 92 projecting radially outward from wall 135 serve to radially center wall 135 within forward bore 339 of receptacle shell 6, and serve to keep resilient wall 135 from squirming radially outward during mating.

[0043] End-seal standoff 140 shown in Figures 30, 33, and 14 has a knurled posterior end 142 that press fits into socket 141 of receptacle base 70. The knurl rotationally locks standoff 140 to base 70. Standoff 140 maintains end-seal 88 in axial position relative to receptacle shell 6. End-seal 88 shown clearly in Figures 12a and 13 has one or more inward projecting sleeves 144 each with respective s fitted passage 80. Openings 150 in end wall 351 of standoff 140 are shaped and spaced to pass respective inward-projecti g sleeves 144 through said end wall when assembled. End wall 335 of end-seal 88 is rotationally positioned within receptacle unit 2 by sleeves 144 in cooperation with openings 150 in standoff 340. Standoff 140 can be made from a high strength plastic material such as glass reinforced Ultem.

Passages 80 in end wall 335 of end-seal 88 extend inward from respective shaped seal seats 98 and thence completely through sleeves 84, thus permitting the insertion of shafts 7 of plug pins 26 through respective seal passages 80 and onward into oil chamber 79.

[0044] The invention maintains a seal between receptacle fluid chamber 79 and the in- situ operating environment at all times. It does so while exerting only a minimum amount of squeeze of receptacle resilient end-sea! 88 against the shafts 27 of plug pins 26. As described earlier, any more than a slight squeeze would cause the resilient material of s lifted passages 80 to adhere to the shafts of respective pins 26 after prolonged periods of mating. That, in turn, could damage the passages and result in unacceptably high demating forces. The invention utilizes active closure means that augment the resiliency of end-seal 88 to urge passages 80 sealably closed. In the presently described embodiment there are two such active closure means, each comprising a unique spring construction. The first-described active closure means utilizes circular spring 101. seen clearly in Figures 12b and 13, which seats in rectangular recess 146 in end wall 135 of end-seal 88. Spring 101 can be made, for instance, from a flexible plastic such as Ryton which is resistant to both a wide variety of chemicals and to seawater. Circular spring 101 is slightly distorted radially inward by flat sides 152 of recess 146 thereby exerting a light outward force on flat sides 152 that in conjunction with nibs 92 acting against bore 139 provide a means auxiliary to the resiliency of end wall 135 to urge the seaward portions of slitted passages 80 sealably closed when connector units 1 and 2 are unmated. The seaward portions of slitted passages 80 are gently urged together by spring 101.

[0045] The invention's second active closure means provided to augment the resiliency of end-seal 88 in urging slitted passages 80 sealably closed utilizes respective outward biased tines 147 of leaf spring 148 shown most clearly in Figures 13 and 15. Leaf spring 148 can be made from plastic material such as Ryton. Tines 147 do not work by pressing opposed sides of slitted passages 80 together, as circular spring 101 does. Instead, leaf-spring tines 1 8 kink respective resilient sleeves 144, which are axialiy straight in their relaxed condition, laterally outward across respective edges 148 of openings 150 of standoff 140. Kinking passages 80 closes them without putting any more than very slight compression on sleeves 144, thus allowing insertion and withdrawal of plug pins 26 with minimum force, and with minimum stress on the resilient sleeve material. When shafts 7 of plug pins 26 are inserted into respective passages 80 they straighten sleeves 84, concurrently flexing respective leaf- spring tines 147 laterally inward. Upon demating, as plug pins 26 are withdrawn from receptacle end-seal passages 80, they first pass outward of the inner projections 144 of end- seal 88. As they do, leaf-spring tines 147 flex radially outward thereby kinking passages 80 closed. The interface between the in-situ seawater and the chamber oil is sealed at that point. Further withdrawal of plug pins 26 to the point where they exit slitted openings 80, allows circular spring 101 to actuate outward closing the seaward entrances to slitted openings 80. The end result is that passages 80 are completely sealed and seawater free. The invented connector would function in the absence of either circular spring 101 or !eaf-spring tines 147, but incorporating both components results in a more reliable product with minimum total squeeze on plug pins 27 when mated, and minimum demating force.

[0046] Typical receptacle socket contacts 56 shown in Figures 12a and 16 comprise cylindrical sections 57 with partially knurled surfaces 59, and o-ring grooves 61 , rear shoulders 63, and solder cups 64. O-rings 66 seated in grooves 61 seal the interfaces between receptacle socket contacts 56 and respective bores 69 of receptacle base 70. Socket contacts 56 are press fit into bores 69 in receptacle base 70 to the point where receptacle socket contact rear shoulders 63 seat against respective shoulders 71 of receptacle base 70. Knurled receptacle socket contact surfaces 59 have an interference fit to diameters 69 of receptacle base 70, thereby rotationally locking receptacle socket contacts 56 to base 70. Shoulders 71 acting in cooperation with receptacle socket contact shoulders 63 limit the rearward travel of said receptacle socket contacts within base 70. Base 70 can be made from a high-strength plastic such as glass reinforced Ultem. Once the receptacle socket contacts are fully inserted into receptacle base 70, retainer rings 72 are put in place, thereby fixing socket contacts 56 axially within the receptacle base. Receptacle inner resilient seal body 73 shown partially cut away in Figures 12a and 17 has inner bores 74 that are sealed on their posterior ends by resilient seal body 73 acting against cylindrical portions 75 of socket contacts 56, and on their anterior ends by closed slit-like openings 76 through resilient seal body 73 thereby creating closed inner chambers 77, seen in Figure 12b, wherein respective socket contact tines 78 are housed. The one or more closed inner chambers 77 housing respective contact tines 78 are, in turn, housed within outer chamber 79. Bore 74a through seal body 73 is lightly stretch-fit to smooth portion 142a of standoff 140, thereby sealing the interface between them. Wall 82 of receptacle end-seal 80 is sealabiy pressed between shoulder 153 of inner resilient sea! body 73 and inner diameter 139 of receptacle shell 6 thereby isolating interface 154 from communication with any contaminants within the fluid of chamber 79. Such contaminants, seawater for instance, could otherwise migrate from chamber 79 into interface 154 causing degradation of the electrical isolation between adjacent receptacle contacts 56. Outer chamber 79 and one or more inner chambers 77 are all filled with oil and sealed from each other. Outer chamber 79 is sealed from the in-situ environment by one or more closed slitted passages 80. The one or more slit-like openings 76 seal respective inner chambers 77 from outer chamber 79. There is no obvious means to keep seal body 73 from moving axially forward. It is kepi in place due to the fact that interface 139 is hermetically sealed so that any

- 32 - urge to disp!ace 73 axially forward would create a vacuum at interface 139 whose tendency would be to suck 73 back into place.

[0047] Referencing Figures 12b and 17, the one or more slit-like openings 76 that seal respective inner chambers 77 have active closure means consisting of constrictive band 81 seated in groove 81 a of seal body 73 that augments the resiliency of inner seai body 73 to urge the slit-iike openings sealab!y closed. Constrictive band 81 can be an elastomeric band or a garter spring, for instance. In keeping with the earlier discussion of minimizing the squeeze against plug pins 26, the constrictive force is slight; that's all that's needed.

[0048] When plug pins 27 enter outer and inner fluid-filled chambers 79, 77 the fluid volume they displace must be accompanied by an enlargement of the chamber volumes in order to keep the internal pressure constant. By the same reasoning, when pins 27 are subsequently withdrawn from chambers 79, 77 the chamber sizes must reduce to account for the withdrawn volume. Similarly, when the in-situ environmental pressure changes, the inner chamber 77 and outer chamber 79 volumes must change in order to balance their internal pressure to that of the outside environment. Those volume changes require some element of the chambers to move, thereby altering their size. In the invention, the movable elements in both the inner and outer chambers are resilient portions of the chambers. The fluid within individual inner chambers 77 is substantially pressure balanced to the pressure within outer chamber 79 by the resiliency of inner seal 73. The pressure within outer chamber 79 is approximately balanced to the in-situ environmental pressure by way of outer chamber resilient wall 82. Space 83 between receptacle shell 6 and outer chamber resilient wall 82 is freely vented to the exterior environment by a network of channels 84 incised into the inside of end wall 65 of receptacle shell 6 as shown in Figure 18. Channels 84 are in direct communication the in-situ environment through openings 90 in end wall 65. Referencing Figures 13 and 18, channels 84 on the inside of receptacle shell end wail 65 connect to other channels 86 molded into the anterior face of receptacle end-seal 88, which channels, in turn, lead to gaps 91 in radially outward projecting nib 92 of end-seal 88. Gaps 91 communicate directly with space 83 that surrounds wall 82 of end-seal 88.

[0049] Resilient plug end-seal 43, shown in Figures 7, 10, and 11 , has a forward projecting first nipple 93 for each respective plug pin 26. First nipples 93 offer strain relief for shafts 7 of respective plug pins 26 where shafts 7 pass through respective ports 94 of wall 95 of plug shell 6. [0050] Resilient plug end-seal 43, shown in Figures 7, 10, and 1 1 , has a forward projecting second nipple 96 for each respective plug pin 26, said second nipple comprising a forward projection 96 of each respective first nipple 93. Second nipples 96 have shaped ends 97 which, when plug unit 1 and receptacle unit 2 are mated, press conformably and sealably into shaped seats 98 in resilient receptacle end-seal 88 shown in Figure 13, thus forming first respective sealing barriers for receptacle oil chamber 79 when connector units 1 and 2 are mated. These respective sealing barriers ensure that, as opposed to prior art constructions, no portions of shafts 7 of plug pins 26 are exposed to the in-situ environment when connector units 1 and 2 are mated. US Patent 3,643,207 has a similar construction; however, the corresponding sealing barriers are formed between projecting resilient nipples at the bases of the plu pins and shaped openings in the hard faceplate of the receptacle. If mated submerged, that construction traps portions of the in-situ environment within the small uncompensated volumes defined laterally by the shaped faceplate openings and axially by the space between respective resilient plug nipples and the resilient end- seal of the receptacle unit. Thus there remains, undesirably, a portion of the insulated plug-pin shafts exposed to a small amount of in-situ environmental fluid even when the connector units are mated. If the '207 units were instead mated before submersion, the small uncompensated trapped volumes would be urged to collapse by the ambient pressure, thereby possibly rendering the units difficult to dernate, or damaging them, or simply sucking fluid into them either from the oil chamber or from the external environment.

[00513 Referencing Figures 7, I I , 19a and 19b, plug forward projecting second nipples 96 pass through, but do not seal to respective openings 90 in end wall 65 of receptacle shell 6 when plug unit 1 and receptacle unit 2 are mated. Furthermore, when said units are mated a gap 100 remains between respective plug end wall 95 and receptacle end wall 65. Gap 100 com municates freely by way of vents 39 in plug shell 46 to the in-situ environment, thereby leaving a path from the outside environment to openings 90 and thence through the aforementioned described system of vanes 84, 86 and gaps 91 described in Figures 13 and 18, and finally into space 83 surrounding flexible wail 82 of receptacle end-seal 88. Thus, the in- situ pressure acts directly on flexible wall 82 substantially balancing the pressure of the oil within receptacle chambers 79 and 77 to the in-situ pressure.

[0052J One other sealing means for receptacle unit 2 when mated to plug unit 1 is provided by the slight stretch fit of each one or more shafts 7 of plug pins 26 within respective slit-shaped passages 80 in receptacle end-seal 88. Still another sealing means for receptacle unit 2 when mated to plug unit 1 is provided by the slight stretch fit of each one or more shafts 7 of plug pins 26 within respective slit-shaped passages 76 in receptacle inner chamber end-seal 73.

[0053] Figure 19a illustrates mated connector units 1 and 2. The mating sequence is as follows: Forward projection 4 of receptacle shell 6 enters bore 3 of plug shell 46 thereby axial iy aligning the two connector units. With further insertion, face 65 of receptacle shell 6 encounters key 5 of plug unit 1 , and can proceed no further until the mating units are rotated in such a way that key 5 enters keyway 8. The key and keyway rotationaliy orient the mating units. As mating continues, tips 28 of plug pin shafts 7 pass through respective openings 90 in receptacle front wall 65 and encounter respective shaped openings 98 in end wall 135 of end-seal 88 which guide them into respective s fitted passages 80 of sleeves 144. As plug shaft tips 28 proceed into slitted passages 80 they overcome a slight squeeze on the outward portion of the passages that is exerted by the outward force supplied by circular spring 101 , and they overcome a very light stretch of passages 83 around the exterior surfaces of plug pins 26. Figure 13 illustrates the end-seal sleeves and passages in the unmated condition, and Figures 1 a and 19b show them in the mated condition. As plug shafts 7 proceed further into slitted passages 80 they bend sleeves 144 radially inward from their kinked shape shown in Figure 13 into their straightened shape shown in Figures 19a and 19b, simultaneously straightening tines 147 of leaf spring 148. As shafts 7 enter and proceed through slitted passages 80 they are wiped clean of any residue from the in-situ environment. Plug shafts 7 then pass through sleeves 144 and into fluid chamber 79 where they are bathed in dielectric oil. The volume of fluid displaced by entering shafts 7 is compensated by expansion of flexible wall 82 into surrounding space 83. Further insertion of shafts 7 into the receptacle unit causes conductive shaft tips 28 to overcome a slight squeeze exerted by constrictive band 81 in order to pass onward through a second set of respective slitted openings 76 in receptacle rear seal 73 where they must also overcome a very slight stretch fit within openings 76. The amount of fluid displaced in the one or more inner chambers 77 is compensated for by- expansion of flexible wall portions of rear sea! 73. Plug pin conductive tips 28 make contact with respective receptacle contact tines 78 within respective oil-filled chambers 77. As mating completes, forward resilient shaped nipples 96 of plug front seal 43 are conformably pressed into shaped openings 98 of receptacle end-seal 88 thereby sealing every portion of shafts 7 from the external environment, and simultaneously adding an additional level of sealing for internal oil chambers 79, 77 of receptacle unit 2.

[0054] Demating of connector units 1 and 2 proceeds in the reverse order of the mating sequence just described.

[0055] It is clear from the foregoing discussion that the invention provides a very reliable connector embodying multiple levels of protection for the electrical circuits from the in-situ environment, while doing so with an uncomplicated, and economical construction, it houses the receptacle socket contacts within nested oil chambers. The chambers have simple, independent, active closure means to keep them sealed from each other, and from the outside environment. The invention is further distinguished from prior art by the fact that every electrically conductive element of the mated plug and receptacle units is at least doubly sealed from the harsh working environment. No segments of the plug pins, for instance, are exposed to the in-situ environment when the connector units are mated. The invention permits connector units to be built in a wide range of sizes and resistant materials making them suitable for both light and heavy duty applications. Compared to prior art connectors now on the market the invention's Spartan simplicity makes it particularly adaptable for miniaturization.

[0056] The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles described herein can be applied to other embodiments without departing from the spirit or scope of the invention. Thus, it is to be understood that the description and drawings presented herein represent a presently preferred embodiment of the invention and are therefore representative of the subject matter which is broadly contemplated by the present invention. It is further understood that the scope of the present invention fully encompasses other embodiments that may become obvious to those skilled in the art and that the scope of the present invention is accordingly limited by nothing other than the appended claims.