Abstract:
An electrical connector adapted for mounting to an electrical apparatus used in either high pressure or high temperature, or both high temperature and high pressure, applications. A metal body is provided for mounting to the electrical apparatus with at least one conductor for carrying electricity to or from the electrical apparatus extending therethrough and a thermoplastic jacket is applied over the conductors to the end of the metal body that is subjected to either high pressure or high temperature, or both high temperature and high pressure, for sealing around the conductor. An insulative material is interposed between the metal body and the conductor for sealing around the conductor. In addition to providing two independent internal and two independent external seals, the glass-to-metal seal limits cold-flow (creep) of thermoplastic along the pin and through the metal body. This feature effectively eliminates the catastrophic hydraulic failures possible with prior connectors utilizing a pin, metal body, and high temperature thermoplastic. Because of the redundant internal and external seals, the connector provides undistorted electrical performance in the most hostile environments of temperature and pressure.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to electrical connectors useful in many applications, but particularly intended for use in hostile environments. More specifically, the present invention relates to single and multi-pin electrical connectors for use in high-pressure, high-temperature applications which commonly occur in the oilfield, but which are also encountered in geothermal and research applications. 
   Oil wells are being drilled to deeper depths and encountering harsher conditions than in the past. Many of the electrical connectors in the oilfield are exposed to the environment of the open well bore, where at maximum depth, pressures rise to over 30,000 psig, temperatures exceed 500° F., and the natural or chemically-enhanced well bore environment is extremely corrosive. In part because of these conditions, many downhole tools are oil-filled, but regardless of whether the tools are oil- or air-filled, the high temperatures and pressures of oil wells require the use of specially-designed electrical connectors for both power and communication to such tools. Metal connectors with glass seals such as those described in U.S. Pat. No. 3,793,608 were developed for use in these hostile environments. Such connectors are available from a number of vendors, including Kemlon Products and Development Co., Ltd. (Pearland, Tex.), Hermetic Seal, and Deutch and, up until the last five years or so, have given good service. Another variety of connectors, developed by Kemlon Products in the early 1980&#39;s and in the early 1990&#39;s by Schlumberger Well Services (Houston, Tex.), and currently manufactured by Kemlon Products and by Greene, Tweed (Houston, Tex.), utilizes a thermoplastic housing constructed of very high temperature housing material such as the aromatic polyether ketones (PEEK, PEK, PAEK, and PEKK) and conductors of various metals. However, as wells have gone deeper and simultaneous temperature and pressure conditions have increased, the environment for these connectors has become increasingly hostile, and certain disadvantages and limitations of both types of connectors have come to light. 
   Existing connectors can fail in at least two ways. The more common failure mode for glass-sealed connectors is caused by the almost inevitable presence of moisture and by well bore chemicals, either of which can cause current to arc, or short, from the conductor to the metal body of the connector. Because glass-sealed connectors utilize a metal shell to house the glass-sealed pin conductors, the presence of moisture in the vicinity of the pins may cause arcing or electrical leakage between pins or from pins to ground. Although expensive because they require that the electrical apparatus be pulled from the well, most such electrical failures are repairable in that the apparatus can be repaired and the connector replaced. 
   Conditions are improved in connectors in which ceramic insulation extends the insulating distance, or arc path, but the problem is not solved by the use of such materials. Because they are such a precise assembly of different materials, glass to metal sealed connectors are particularly affected by exposure to a wide range of operating temperatures. The effect results from the different coefficients of thermal expansion between the metal and the glass, which can cause cracking of the glass as temperatures increase over a wide range of operating temperatures, i.e., −100° F. to over 500° F. Such temperature ranges are encountered, for instance, in oilfield operations in the Artic, where a tool with many connectors may be put into service at an ambient surface temperature of −100° F. and then lowered 30,000 feet into a “hot” formation deep in the earth. This differential expansion problem was recognized in the afore-mentioned U.S. Pat. No. 3,793,608, and may result in the electrical failure described above. 
   To address this problem, the ceramic material used to extend the insulation must be chosen to match the glass in thermal expansion. Otherwise, the thermal cycling could break the bond between the glass and the ceramic, presenting a possible arc path between the pin and body at the ceramic glass interface. Ceramic materials are available with thermal expansion coefficients that match the types of glass utilized in such conductors, and that also have desirable dielectric properties and high compressive strengths, but they have low tensile and flexural strengths. Because space limitations frequently require pin patterns that are closely spaced in the connector and the ceramic material is not strong in flexural strength, the extended ceramic may become cracked internally, for instance, when a pin is bent and then straightened out. The damage to the ceramic is almost impossible to detect visually and with the presence of moisture, frequently leads to arcing, electrical leakage, and direct shorts. Further, the short may be unexpected because the connector, or even the electrical apparatus having the connector installed thereon, tested normally on the surface (at room temperature and in a dry environment), but when the electrical apparatus is run downhole, the short suddenly appears. 
   Previous attempts to improve the glass-sealed, metal connector have met with varying degrees of success. For instance, ceramic materials are known to have excellent dielectric properties, to be very strong in compression (for instance, from high ambient pressure), and to be highly resistant to acid, alkali, water, and organics, and would therefore seem to present an ideal material for inclusion in such connectors. However, ceramics are brittle, and oilfield personnel are not well known for their careful handling of equipment such that connectors including ceramic materials are prone to the kind of electrical failure described above when a pin is bent, for instance. Further, in the higher temperature environments of the wells currently being drilled, even connectors comprised of ceramic materials suffer from the above-characterized problem of differential thermal expansion and the resulting electrical failure. 
   Another improved version of the glass-sealed, metal connector utilizes a wafer, or cap, comprised of a very high temperature thermoplastic material having favorable dielectric properties (such as PEEK or PEK) that is bonded, or epoxied, to the metal body of the connector to provide a longer arc path, resulting in increased insulation resistance and a more flexible and “forgiving” insulator that is less prone to damage from bending moments exerted on the pin(s). However, in adverse conditions, a problem that has arisen with some connectors having such a plastic “cap” is that it is possible for water to accumulate under the cap. When water accumulates under the cap of such connectors, the water provides an electrically conductive path between the pins and/or between the pins and the metal body that results in an undesired electrical leakage or a distortion in the electrical signal from the electrical apparatus. 
   Although the second failure node also occurs in connectors other than those that utilize thermoplastic materials, connectors that utilize thermoplastic materials are widely used in the oilfield, and therefore provide a good illustration of the problem. This second failure mode is referred to as hydraulic leakage and is the more disastrous in that it results in serious and expensive damage to the electrical apparatus and, in the case of an electrical apparatus that is a downhole tool or instrument, expensive and embarrassing lost time on the rig floor because the entire tool must be pulled from the well and rebuilt or replaced. Thermoplastic materials are molded at high temperature and pressure and have the very significant advantage of resisting moisture. Arcing distances are naturally greater for a connector of the same geometrical structure because there is no metal body for the pins to short to. Further, a pin that bends may not cause shorting problems because the thermoplastic is flexible and does not easily break or crack. A further advantage of such connectors is that because the conducting pins are sealed to the plastic during the molding process, the moisture does not leak along the pin inside the connector even when pins have been bent and then straightened. 
   However, a characteristic of thermoplastic materials is that they can be re-molded if later exposed to conditions of temperature and pressure of the type likely to be encountered, for instance, in deep oil wells. Creep, sometimes referred to as cold-flow, occurs when the conditions of temperature and pressure cause a change in the shape of an item. At the extremes found in oilfield applications, temperatures and pressures approach the molding conditions of these high temperature thermoplastics, and cold-flow becomes significant as the plastic extrudes though the spaces between the pin of the connector and the surrounding metallic oil tool housing or connector support plate. In some cases, the molded pin can move enough to cause an interruption in the electrical signal, and in others the plastic flows enough to cause a hydraulic failure. In this failure mode, either through mishandling or because the connector is subjected to conditions that exceed the capabilities of the materials or the construction of the connector, the integrity of the connector is compromised. As a result of such hydraulic failure, the connector becomes the route for the ingress of steam, water, or other fluid(s) from the well bore and into the electrical apparatus, driven by the high downhole pressure, and hence the electrical apparatus is severely damaged or destroyed. 
   This list of the disadvantages and limitations of known connectors is not intended to be exhaustive, but is intended instead to illustrate some of the difficulties caused by the construction and the materials utilized in such connectors. 
   As is apparent from this summary of known and/or presently available connectors for hostile applications, there is a need for, and it is an object of the present invention to provide, a connector that maintains favorable electrical performance properties even when utilized in high-pressure, high-temperature applications. 
   There is also a need for an electrical connector including thermoplastic materials in which the cold flow of the thermoplastic material is restricted, or even prevented, in high-temperature and/or high-pressure environments to provide a primary seal to the bulkhead of the electrical apparatus to which the connector is engaged, on the high pressure side of the connector ahead of the glass-to-metal seal, brazed ceramic seal, or glass-ceramic seal and forming an internal seal between the conductor and the external environmental fluids, and it is an object of the present invention to provide such an apparatus and method. 
   Another object of the present invention is to provide an electrical connector that provides a long arc path between the metal body of the connector and the central conductor, and maintains the length of that arc path under high-temperature and/or high-pressure conditions, so as provide favorable electrical performance in hostile applications. 
   Another object of the present invention is to provide an electrical connector that maintains its favorable electrical properties at temperatures and pressures up to and exceeding 500° F. and 30,000 psi. 
   Another object of the present invention is to provide an electrical connector that maintains its favorable electrical properties at high temperatures and pressures and that includes structure that provides strain relief from bending moments applied to the conductor(s) of the connector. 
   Yet another object of the present invention is to provide an electrical connector utilizing thermoplastic materials which are press fit, molded over, or shrink fit onto the conductor and in which, to the extent that any cold flow does occur upon exposure of the thermoplastic material to high-temperature and/or high-pressure conditions, the thermoplastic material fills every void around the conductor to improve the insulation properties of the connector. 
   Another object of the present invention is to provide an electrical connector that combines the hydraulic advantage of the glass-sealed connector with an overmolding of thermoplastic material such as an aromatic polyether ketone having a structure that resists cold flow, moisture, and arcing, and which is capable of operating properly at higher pressures and temperatures than presently known molded thermoplastic connectors. 
   Other objects, and the advantages, of the present invention will be made clear to those skilled in the art by the following description of the presently preferred embodiments thereof 
   SUMMARY OF THE INVENTION 
   These objects are achieved by providing an electrical connector adapted for mounting to or engaging an electrical apparatus used in applications in which the electrical apparatus is subjected to either high pressure or high temperature, or both high temperature and high pressure, comprising a metal body for mounting to the electrical apparatus having at least one conductor extending through the body for carrying electricity to or from the electrical apparatus. An insulative material is interposed between the metal body and the conductor extending through the metal body to seal around the conductor. A thermoplastic jacket is applied, and preferably molded, over the conductor and to the end of the metal body that is subjected to either high pressure or high temperature, or both high temperature and high pressure, for sealing around the conductor and for sealing between the conductor and between the connector and the electrical apparatus when subjected to either high pressure or high temperature, or both high temperature and high pressure. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a longitudinal sectional view of a preferred embodiment of an electrical connector constructed in accordance with the teachings of the present invention. 
       FIG. 2  is a longitudinal sectional view of the electrical connector of  FIG. 1  as engaged to an electrical apparatus, such as an oilfield tool. 
       FIG. 3  is an enlarged sectional view of the electrical connector and electrical apparatus shown in  FIG. 2  before application of heat, pressure, or heat and pressure. 
       FIG. 4  is an enlarged sectional view similar to the view shown in  FIG. 3  but after application of heat, pressure, or heat and pressure. 
       FIG. 5  a longitudinal sectional view of a second preferred embodiment of an electrical connector constructed in accordance with the teachings of the present invention. 
       FIG. 6  is a longitudinal sectional view of a third preferred embodiment of an electrical connector constructed in accordance with the teachings of the present invention. 
       FIG. 7  is a longitudinal sectional view of a fourth preferred embodiment of an electrical connector constructed in accordance with the teachings of the present invention. 
       FIG. 8  is a longitudinal sectional view of a fifth preferred embodiment of an electrical connector constructed in accordance with the teachings of the present invention. 
       FIG. 9  is a longitudinal sectional view of a sixth preferred embodiment of an electrical connector constructed in accordance with the teachings of the present invention. 
       FIG. 10  is a longitudinal sectional view of a preferred embodiment of a multiple-pin, or multi-conductor, electrical connector constructed in accordance with the teachings of the present invention. 
       FIG. 11  is an end view of a second preferred embodiment of a multiple-pin electrical connector constructed in accordance with the teachings of the present invention. 
       FIG. 12  is a longitudinal sectional view of the metal body of the multiple pin electrical connector of  FIG. 11  taken on the line  12 - 12  in  FIG. 11 . 
       FIG. 13  is a longitudinal sectional view of an electrical connector of  FIG. 11  after assembly of the metal body shown in  FIG. 12  to a thermoplastic jacket. 
       FIG. 14  is a longitudinal sectional view of a third preferred embodiment of a multi-pin connector constructed in accordance with the teachings of the present invention. 
       FIG. 15  is a longitudinal sectional view of a fourth preferred embodiment of a multi-pin connector constructed in accordance with the teachings of the present invention. 
       FIG. 16  is a longitudinal sectional view of a fifth preferred embodiment of a multi-pin connector constructed in accordance with the teachings of the present invention. 
       FIG. 17  is an end view of a sixth preferred embodiment of a multi-pin connector constructed in accordance with the teachings of the present invention. 
       FIG. 18  is a longitudinal sectional view of the multi-pin connector of  FIG. 17  taken along the line  18 - 18  in  FIG. 17 . 
       FIG. 19  is a longitudinal sectional view off a seventh preferred embodiment of a multi-pin connector constructed in accordance with the teachings of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to the figures, a first preferred embodiment of an electrical connector constructed in accordance with the teachings of the present invention is indicated generally at reference numeral  10 . The connector  10  comprises a metal body  12  that is provided with threads  14  for engaging the bulkhead (not shown) of an electrical apparatus such as a downhole tool or other oilfield equipment. In the embodiment shown in  FIG. 1 , body  12  is also provided with an annular groove  16  for receiving an O-ring  52 , but as will be shown in the description of other embodiments of the connectors constructed in accordance with the present invention set out below, the groove  16  and O-ring  52  may be omitted depending upon the particular application and/or the nature of the electrical apparatus to which the body is engaged. Those skilled in the art will also recognize that the connector  10  need not be engaged to the electrical apparatus by threaded engagement. The connector  10  can also be engaged to the electrical apparatus in other ways, for instance, by welding, tapered threads, and in other ways known in the art. A central conductor  18  extends through an elongate bore  20  in body  12 , and in the case of the connector  10  shown in  FIG. 1 , is sealed in the metal body by the glass  22  in the annulus between the outside diameter (O.D.) of conductor  18  and the inside diameter (I.D.) of the bore  20  in body  12 . In all of  FIGS. 1-5 , pressure is exerted in the direction of the arrow  24  shown in  FIG. 4 . Additionally, if the threads  14  are sufficiently long to withstand the load from the pressure against O-ring  52 , connector  10  can withstand pressure from the reverse direction, or threaded side. In this regard, the connector of the present invention can be utilized in applications requiring pressure from both directions. 
   In the connector  10  shown in  FIG. 1 , the annulus between the O.D. of conductor  18  and the I.D. of bore  20  is also filled with ceramic material  26  and  28  on both the pressure and non-pressure sides, respectively, of the glass  22 . In addition to providing the usual benefits of ceramics in a connector such as the connector  10  shown in  FIG. 1 , the ceramic material  26 ,  28  centralizes the conductor  18  and keeps the glass  22  from running out of the annulus when fired or melted. 
   A jacket  30  comprised of thermoplastic material is molded over the pressure side of conductor  18 . Jacket  30  is provided with an annular groove  32  for receiving O-ring  58  and an optional so-called dogknot  34  for “booted” (no boot is shown) applications. Just as with the metal body  12  and as shown in other embodiments described below, those skilled in the art will recognize that the groove  32  and O-ring  58  may be omitted depending upon the particular application and/or the nature of the electrical apparatus to which the connector  10  is engaged. Jacket  30  is press fit, molded over, or shrink fit over conductor  18 ; for instance, in a presently preferred embodiment, the thermoplastic material is high pressure molded at temperatures up to 900° F. over the conductor  18 . As shown at reference numeral  36 , the conductor  18  is provided with a plurality of grooves over which the thermoplastic material is molded so that the thermoplastic material fills the voids as the thermoplastic shrinks during cooling, thereby providing a seal against well bore fluids and electrical insulation between the conductor  18  and the bulkhead of the electrical apparatus. Anti-rotation grooves  38  are provided in the surface  13  of metal body  12  that is opposed to the surface  31  of thermoplastic jacket  30  to resist any tendency of jacket  30  to turn relative to body  12  when in use or during installation and removal. 
   In  FIG. 2 , a connector similar to the connector  10  shown in  FIG. 1 , but with a wider annular groove  16  on the body  12  for receiving a back-up ring  59  in addition to the O-ring  58 , is shown threadably engaged to the bulkhead  15  of an electrical apparatus. As used herein, the phrase “electrical apparatus” is intended to refer to any apparatus that operates on electrical current and/or that requires electrical input or output, for instance, from instrumentation in the apparatus. Typical examples of electrical apparatus contemplated by this phrase include downhole oilfield tools, geothermal tools, geological and other earth science research tools, and instrumentation for such tools, but this list is intended to be illustrative and is not intended to limit the type of apparatus with which the connectors of the present invention are utilized. Similarly, the reference herein to the “bulkhead” of the electrical apparatus is not intended to limit the type of tool with which the electrical connectors of the present invention may be utilized. Some other terms that might also be used to describe such structure, depending in part upon the nature of the electrical apparatus contained therein, include the terms “housing,” “casing,” “wall,” and “shell.” The O-ring  58  located in the groove  32  on jacket  30  provides the primary seal to the O.D. of the thermoplastic material and an O-ring  58  located in the annular groove  16  in body  12  provides a secondary seal, thus ensuring that the outside diameter of the connector is effectively sealed to bulkhead  15 . 
   Referring to  FIGS. 3 and 4 , which show the connector of  FIG. 2  both before ( FIG. 3 ) and after ( FIG. 4 ) application of pressure (or pressure and heat), the manner in which the connector of the present invention utilizes the above-described “re-molding” of the thermoplastic material comprising jacket  30  is illustrated. As shown in  FIG. 3 , before application of pressure, tolerances between the I.D. of the recess in bulkhead  15  and the O.D. of both metal body  12  and thermoplastic jacket  30  are close enough that the O-rings  52  or  58 , and/or the back-up ring  59 , are initially energized to seal between the I.D. of the bulkhead  15  and the O.D. of either or both of the metal body  12  or the thermoplastic jacket  30 . Upon application of pressure in the direction of arrow  24  in  FIG. 4 , the back-up ring  59  and O-ring  52  are compressed to seal between the O.D. of body  12  and the I.D. of bulkhead  15 . Similarly, O-ring  58  is compressed and seals between the O.D. of jacket  30  and the I.D. of bulkhead  15 . As pressure increases and/or heat builds, the thermoplastic material comprising jacket  30  cold flows in the direction toward the surface  13  of metal body  12 , but of course the metal body  12  is quite unyielding such that the thermoplastic material comprising jacket  30 , being effectively confined by the surface  13  of body  12  and the I.D. of bulkhead  15 , tends to expand radially outwardly into sealing contact with the I.D. of bulkhead  15  (compare  FIGS. 3 and 4 ). The grooves  36  in conductor  18  take advantage of the sealing created by the shrinkage of the thermoplastic material comprising jacket  30 , and the conductor  18  is hermetically sealed to the metal body  12  by the glass  22 . The effect of this design is to provide two different and independent internal seals between the conductor  18  and the external body  12  of connector  10 , the first being created by the seal between the thermoplastic material comprising jacket  30  and the pin/conductor  18  and the second being created by the seal between the glass  22 , pin  18 , and metal body  12 . The grooves  36  in conductor  18  take advantage of the sealing created by the shrinkage of the thermoplastic material comprising jacket  30 , and the conductor  18  is hermetically sealed to the metal body  12  by the glass  22 . Similarly, the design of the connector of the present invention provides separate external seals. The O-ring  58  located in the groove  32  on jacket  30  seals the O.D. of the thermoplastic to bulkhead  15  and O-ring  52  located in the annular groove  16  in body  12  likewise seals between body  12  and bulkhead  15 , thus ensuring that the outside of connector  10  is effectively sealed to the bulkhead  15  of the electrical apparatus. 
   Referring to  FIGS. 3 and 4 , the portion of the ceramic insulator  26  that extends out of the surface  13  of body  12  that is indicated at reference numeral  40  creates a long arc path between the conductor  18  and the metal body  12 . It will also be noted that the glass  22  in the annulus between the O.D. of conductor  18  and the I.D. of bore  20  of the body  12  seals the conductor  18  such that the internal arc path is along the surface  40 . The extended length of ceramic  26  provided by the portion  40  shown in  FIGS. 3 and 4  constitutes a longer arc path compared to the distance between conductor  18  and body  12  shown in  FIGS. 5 and 6 , for instance. 
   The particular metals utilized for the body  12  and conductor  18  are presently utilized in high-pressure, high-temperature connectors, as are the specific ceramics and glass, it being the particular construction of the connector of the present invention that confers it desirable properties. By way of illustration, several grades and alloys of stainless steel, titanium, Inconel, Monel, and others are utilized in the body  12  of connector  10 ; similarly, conductor  18  may be comprised of Inconel, Monel, Alloy 52, beryllium copper, molybdenum, stainless steel, nickel-iron bearing alloys, and other conductive materials. As known in the art, the particular glass that is utilized is a function of the material comprising the pin and body, it being important to match the coefficients of thermal expansion for the reasons described above and in the above-described U.S. Pat. No. 3,793,608. The particular glass that is utilized is preferably a glass with high volume resistivity to provide good electrical insulation. Similarly, many ceramic materials may be utilized to advantage, the particular ceramic being selected depending upon its resistance to acid, alkali, organic solvents, and/or water, and its dielectric properties. Depending upon the particular application of the connector, it may also be advantageous to utilize a higher strength ceramic material such as a zirconia. 
   The thermoplastic utilized in jacket  30  is preferably a thermoplastic with most, and preferably all, of the following characteristics: good dielectric properties, extremely high viscosity at the 500+° F. temperatures likely to be encountered in downhole environments, high volume resistivity in this same temperature range, a thermoplastic that maintains its strength in this same temperature range, has low water absorption, is resistant to acids, bases, and solvents, and is non-hydrolyzable. Thermoplastics that have been used to advantage in the jacket  30  include, but are not limited to, aromatic polyether ketones, including polyaryletherketone (PAEK), polyetheretherketone (PEEK), polyetherketone (PEK), and polyetherketoneketone (PEKK), as well as blends of such thermoplastics with other plastic materials, including modifiers and extenders, as well as other polymers. 
   Referring now to  FIG. 5 , a second embodiment of a connector constructed in accordance with the present invention is indicated generally at reference numeral  42 . Connector  42  is comprised of the same component parts as connector  10  shown in  FIG. 1  such that the same reference numerals are used to designate the common parts of both embodiments, but connector  42  is intended for use in different applications than the connector  10  shown in  FIGS. 1-4  in that the metal body  12  of connector  42  lacks a groove such as the groove  16  in the body  12  of connector  10  ( FIGS. 1-4 ) for an O-ring for effecting the above-described seal with the bulkhead (not shown) of the electrical apparatus to which the body  12  is engaged. Another difference between connector  42  and connector  10  can be seen by reference to the annulus between the O.D. of conductor  18  and the I.D. of the bore  20  through metal body  12 . Instead of rings of ceramic material on both the high and low pressure sides of the glass seal  22  such as the ceramic insulators  26  and  28  in  FIGS. 1-4 , the connector  42  shown in  FIG. 5  is provided with a single ceramic insulator  28  on the low pressure side of glass seal  22 . To reduce cost and to obtain a more secure fit of the opposed surfaces  13 ,  31  of body  12  and jacket  30 , the body  12  is provided with a nipple  46  that extends into an appropriately sized cavity (not numbered) in jacket  30 . The glass seal  22  extends around conductor  18  all the way up into nipple  46 , but those skilled in the art who have the benefit of this disclosure will recognize that the thermoplastic material comprising jacket  30  can be formed with a complimentary-shaped nipple that extends down into the bore  20  in body  12  into contact with glass  22  even if the glass  22  does not extend up into the nipple  46 . 
   A third embodiment of the connector of the present invention is shown at reference numeral  48  in  FIG. 6 . In the connector  48 , the O.D. of nipple  46  is provided with a plurality of grooves  50  such that, when jacket  30  is overmolded onto body  12 , the connection is even more secure than in the connector  42  shown in  FIG. 5 . By comparison of the connector  48  in  FIG. 6  to the connectors  10  and  42  in  FIGS. 1-5 , it can be seen that no groove is provided for an O-ring on the O.D. of jacket  30  such that the connector  48  seals only to the bulkhead (not shown) of the electrical apparatus to which the metal body  12  is threadably engaged. An O-ring  52  and back-up ring  59  are shown in the groove  16  for that purpose. It can also be seen that the connector  48  is provided with an insulating, flexible sleeve  54  on the low pressure side of the ceramic insulator  28  to provide some flexibility and/or vibration resistance to the connector  48  and to decrease the likelihood of damage to the ceramic insulator  28  from bending forces that might otherwise tend to cause the conductor  18  to move relative to body  12 . In the embodiment shown, like the jacket  30 , sleeve  54  is comprised of thermoplastic material, but those skilled in the art will recognize that other flexible insulating materials are likewise utilized for this purpose. 
   A fourth embodiment of a connector constructed in accordance with the present invention is indicated generally at reference  56  in  FIG. 7 . Both the O-ring  52  in groove  16  and the O-ring  58  in groove  32  for effecting independent primary and secondary seals are shown in  FIG. 7 . Those skilled in the art who have the benefit of this disclosure will recognize that, although not required in all applications, it may be advantageous to provide back-up rings  59  for better effecting the seal between the O.D. of connector  56  and the bulkhead of the electrical apparatus to which connector  56  is engaged. 
   By reference to the fifth embodiment of a connector constructed in accordance with the present invention shown at reference numeral  60  in  FIG. 8 , it can be seen that the connector can also be configured only with an O-ring  58  for effecting a seal between the thermoplastic jacket  30  and the bulkhead of the electrical apparatus to which the connector  60  is engaged. In this regard, connector  60  is configured in the same manner as connector  42  ( FIG. 5 ), but unlike connector  42 , connector  60  includes the flexible insulating sleeve  54  shown in the connectors  48  and  56  ( FIGS. 6 and 7 , respectively). The connector  61  shown in  FIG. 9  is likewise provided only with an O-ring  58  for sealing between the thermoplastic comprising jacket  30  and the bulkhead of the electrical apparatus, and also lacks any ceramic such as the ceramic insulators  26  and  28  shown in  FIGS. 1-4 , being only provided with a flexible sleeve  54  on the low pressure side of glass  22 . 
   The structure and function of the component parts of the connectors shown in  FIGS. 1-9  are equally useful when utilized in multi-pin connectors, and several embodiments of multi-pin connectors constructed in accordance with the present invention are shown in  FIGS. 10-19 , in which like numerals are utilized to designate the component parts shown in the connectors shown in  FIGS. 1-9 . In a first multi-pin connector constructed in accordance with the present invention, indicated generally at reference numeral  62  in  FIG. 10 , the connector  62  is provided with multiple conductors  18 , each provided with a glass seal  22  and a ceramic insulator  28  on the low pressure side of glass seal  22 . It can be seen that the body  12  is provided with a collar  64 , similar in function to the nipple  46  of the connectors shown in  FIGS. 1-6 , such that the surface  13  of body  12  that is opposed to the surface  31  of jacket  30  is, in effect, recessed. The O.D. of collar  64  is provided with a plurality of grooves  50  so that the jacket  30  is securely retained to body  12  when shrink fit to collar  64  and grooves  50  after overmolding or press-fitting over body  12  and cooling. The collar  64  enhances the joining of the thermoplastic material comprising jacket  30  to the body  12  by minimizing stresses due to differences of thermal expansion between the thermoplastic and body materials. 
   A second embodiment of a multi-conductor connector constructed in accordance with the present invention is indicated generally at reference numeral  66  in  FIGS. 11-13 . As shown in  FIG. 11 , connector  66  is provided with six conductors, or pins,  18  and as shown in  FIG. 12 , connector  66  is similar in construction to connector  10  ( FIGS. 1-4  and  6 ) in that the outside diameter of the nipple  46  of metal body  12  is provided with grooves  50  and the thermoplastic jacket  30  is molded or press-fit over body  12  and cooled to shrink fit over the O.D. of nipple  46  as shown in  FIG. 13 . 
   A third embodiment of a multiple-conductor connector constructed in accordance with the present invention is indicated generally at reference numeral  68  in  FIG. 14 . Connector  68  is provided with ceramic insulators  26 ,  28  on the high and low pressure sides, respectively, of glass seal  22  in a manner similar to the connector  10  shown in  FIGS. 1-4 . The thermoplastic jacket  30  of connector  68  is, like the jacket  30  of connector  66  ( FIGS. 11-13 ), engaged to the grooves  50  on the O.D. of nipple  46  by overmolding and/or press-fitting so as to shrink fit the jacket  30  over body  12  in the manner described above. The O-ring  58  residing in the groove  32  in the O.D. of jacket  30  effects a seal to the bulkhead (not shown) of the electrical apparatus to which connector  68  is engaged; the location of the groove  16  and O-ring  52  over the O.D. of body  12  provides a secondary seal to the bulkhead (not shown in  FIG. 14 ), sealing the body  12  and glass-to-metal internal seal, and further limits cold flow of the thermoplastic material comprising jacket  30  in hostile applications. The molded thermoplastic stand-off  69  shown in  FIGS. 14 and 15  extends the insulation and increases the arc distance between the conductors  18  and body  12  as compared to the arc distance in a connector such as the connector  66  shown in  FIG. 13 . 
   Referring now to  FIG. 15 , a fourth embodiment of a multi-conductor connector constructed in accordance with the present invention is indicated generally at reference numeral  70 . Embodiment 70 is similar in construction to the embodiment 68 shown in  FIG. 14 , but the jacket  30  of connector  70  is formed in the shape of a right cylinder and does not include the dogknot  34  (used in conjunction with an elastomeric/rubber boot (not shown)) formed in the O.D. of the jacket  30  of connector  68 . Another difference between connector  68  ( FIG. 14 ) and connector  70  ( FIG. 15 ) is that the ceramic insulating insulator  26  around conductors  18  of connector  70  does not extend out of the surface  13  of body  12  into jacket  30  in the manner shown at reference numeral  40  in  FIG. 14 . Yet another difference between connector  68  ( FIG. 14 ) and connector  70  ( FIG. 15 ) is the addition of the flexible insulator or thermoplastic sleeve  54  on the low-pressure side of metal body  12 . A fifth embodiment, connector  72  shown in  FIG. 16 , is similar in construction to the connector  70  of  FIG. 15 , but does include the portion  40  of ceramic insulator  26  extending out of the surface  13  of metal body  12  into a complimentary-shaped cavity (not numbered) in the surface  31  of jacket  30 . 
   A sixth embodiment of a multi-conductor connector constructed in accordance with the present invention is indicated generally at reference numeral  74  and  80  in  FIGS. 17 and 18 . The conductor  18  of connector  74 , instead of being insulated from body  12  and sealed with a glass seal and one or more ceramic ring(s), is insulated from body  12  by a combination seal and insulator  76  comprised of a metalized and brazed ceramic material. An O-ring  58  residing in groove  32  on jacket  30  provides the above-described seal of the connector  74  to the bulkhead and the brazed metalized ceramic provides an internal seal between the metal body  12  and conductor  18  in the same manner as described above in connection with the connectors shown in  FIGS. 1-16 . Overmolding or press-fitting the portion  78  of ceramic insulator  76  that extends from the surface  13  of body  12  with the thermoplastic jacket  30  provides durability to a material that is otherwise so brittle that the bending of a conductor  18  would result in hydraulic failure. 
   Those skilled in the art who have the benefit of this disclosure will recognize that certain changes can be made to the component parts of the apparatus of the present invention without changing the manner in which those parts function to achieve their intended result. For instance, some of the various connectors shown in  FIGS. 1-19  include two O-rings while others include only one, and it will be recognized from this disclosure by those skilled in the art that any of the various embodiments shown herein may or may not include an O-ring on the jacket  30 , an O-ring on the body  12 , O-rings on both jacket  30  and body  12 , or no O-rings at all. Seals between the metal body and the electrical apparatus to which it is engaged can also be effected by welding (electron-beam, laser, or other weld), using tapered interference threads, or an “autoclave” style metal-to-metal seal. Similarly, it will be noted by those skilled in the art that the longer the arc path between conductor  18  and body  12 , the more likely the connector will retain its desirable insulative properties such that those skilled in the art will recognize that any of the embodiments shown herein can be constructed with a glass, glass-ceramic, or ceramic insulator that provides a long arc path. In addition, those skilled in the art will recognize that where ceramic insulators are exposed as depicted in connectors  10  and  66 , for instance, an embodiment utilizing an exposed thermoplastic sleeve such as is shown at reference numeral  54  or flexible insulator comprised of other materials as known in the art can be supplied as in connectors  48 ,  56 ,  61 , and  70 . All such changes, and others which will be clear to those skilled in the art from this description of the preferred embodiments of the invention, are intended to fall within the scope of the following, non-limiting claims.