Abstract:
A releasable electrical connection and related methods use lateral compression of an electrically conductive spring to form a forced abutting solderless connection between the spring and a corresponding electrical lead, with the lead pressed between the spring and a support. The connection can be readily broken and remade for servicing related electrical equipment, such as an oxygen sensor assembly.

Description:
BACKGROUND 
       [0001]    The present invention relates to electrical connections, and more particularly to releasable electrical connections. 
         [0002]    Numerous approaches have been taken for making electrical connections. For example, some electrical connections are made by soldering wires together. However, such connections are not readily releasable. As such, numerous releasable connection approaches have been proposed, such as the USB connector found in numerous electronic devices for power and/or data transmission. However, USB and similar connections may not be suitable for some applications, such as in harsh environments. As such, there remains a need for alternative approaches to making releasable electrical connections. 
       SUMMARY 
       [0003]    A releasable electrical connection is described that relies on lateral compression of an electrically conductive spring, which may be generally cylindrical, to form a forced abutting connection between the spring and a corresponding electrical lead, with the lead pressed between the spring and a support. 
         [0004]    In one or more embodiments, a releasable electrical connector assembly includes a cap portion and a base portion. The cap portion is releasably mated to the base portion such that the cap portion and the base portion longitudinally overlap. The cap portion includes an electrically non-conductive cap outwardly laterally bounding a cavity. The cap portion also includes a first electrical conductor assembly extending through the cap and partially disposed in the cavity. The first electrical conductor assembly includes a first conductor and a spring mounted to a distal end portion of the first conductor. The spring extends along a longitudinal spring axis and has a circumference about the spring axis. The base portion includes a core extending proximally toward the cap and an electrically conductive lead disposed outward of the core. The spring is laterally compressed between the cap and the lead such that, at a first longitudinal location along the spring axis, a first portion of the circumference of the spring is non-conductively abutting the cap and a second portion of the circumference, disposed at the first longitudinal location along the spring axis, is electrically conductively abutting the lead. The lead, at the first location, directly faces the core on a side of the lead opposite the spring. 
         [0005]    The base portion may be proximally enclosed by the cap. The spring may comprise a coil having multiple layers disposed in convolute fashion about the spring axis. There are advantageously additional pairs of leads and conductor assemblies that are spaced from each other around the core axis, advantageously substantially similar to the first lead and conductor assembly. The various additional pairs may be disposed symmetrically relative to the core. The second portion of the circumference may subtend an angle of not more than about 10° about the spring axis. In some embodiments, the base portion includes an oxygen sensor electrically coupled to the lead. 
         [0006]    In one or more embodiments, a releasable electrical connector assembly includes a female cap portion releasably mated to a male base portion such that the cap portion and the base portion longitudinally overlap. The female cap portion includes an electrically non-conductive cap outwardly laterally bounding a first cavity; 
         [0007]    a first electrical conductor assembly extending through the cap and having an distal end portion disposed in the cavity; the first electrical conductor assembly including a first conductor and a first spring mounted to a distal end portion of the first conductor. The spring extends distally along a longitudinal first spring axis. The male base portion includes a nonconductive core extending proximally toward the cap along a longitudinal core axis and having an outer surface disposed about the core axis. The male portion also includes a first electrically conductive lead disposed outward of the outer surface of the core. The core and the first lead are disposed in the cap so that: 1) proximate the cavity the first lead is pressed between the outer surface of the core and the first spring; 2) the spring is laterally compressed normal to the first spring axis between the first lead and the cap; 3) an electrical path extends between the first conductor and the first lead via the first spring. In some embodiments, the electrical connector assembly may include one or more additional cavities, springs, leads disposed so as to form additional electrical connections. 
         [0008]    In one or more embodiments, a method of electrical connection includes providing a cap portion and a base portion. The cap portion includes an electrically non-conductive cap bounding a cavity. The cap portion further includes a first electrical conductor assembly extending through the cap and having an end portion disposed in the cavity. The first electrical conductor assembly includes a first conductor and a spring mounted to a distal end portion of the first conductor. The spring extends along a longitudinal spring axis and having a peripheral external surface disposed about the spring axis. The base portion includes a core extending proximally along a longitudinal base axis toward the cap, and an electrically conductive lead disposed outward of the core. The method includes moving the cap portion distally and relative to the base portion and to engagement therewith so as to releasably mate the cap portion to the base portion such that the cap portion and the base portion longitudinally overlap. The releasably mating causes lateral compression of the spring between the cap and the lead such that a first portion of the external surface of the spring non-conductively abuts the cap and a second portion of the external surface, disposed at a same longitudinal location along the spring axis as the first portion, electrically conductively abuts the lead to electrically connect the first conductor to the lead. 
         [0009]    In some embodiments, the releasably mating includes proximally enclosing the base portion with the cap portion. The method may further include crimping the spring to the end portion of the first conductor. The cap portion may further include a shell disposed outwardly from the cap, and the releasably mating may include releasably engaging the shell with the base portion. The method may include removing a first base portion from the cap portion so as to break an electrical connection between the conductor associated therewith and the first lead. Thereafter, a second base portion is releasably coupled to the cap portion such that the cap portion and the second base portion longitudinally overlap. As a result of coupling the cap portion to the second base portion, the spring is laterally compressed between the cap and the second lead of the second base portion such that a third portion of the external surface of the spring non-conductively abuts the cap and a fourth portion of the external surface, disposed at a same longitudinal location along the spring axis as the third portion, electrically conductively abuts the second lead to electrically connect the first conductor to the second lead. 
         [0010]    In one or more embodiments, a method of electrical connection includes releasably mating a female cap portion to a male base portion such that the cap portion and the base portion longitudinally overlap. The female cap portion includes an electrically non-conductive cap, having a cavity, and a first electrical conductor assembly. The first electrical conductor assembly extends through the cap and has an distal end portion disposed in the cavity. The first electrical conductor assembly includes a first conductor and a first spring mounted to a distal end portion of the first conductor, with the spring extending distally along a longitudinal first spring axis. The male base portion includes a nonconductive core extending proximally toward the cap along a longitudinal core axis, with an outer surface disposed about the core axis. A first electrically conductive lead is disposed outward of the outer surface of the core. The mating includes moving the female cap portion distally toward the male base portion such that: 1) the core enters an opening of the female cap; 2) the first lead is pressed inward between the outer surface of the core and the first spring; 3) the spring is laterally compressed normal to the first spring axis between the first lead and the cap; 4) an electrical path is formed between the first conductor and the first lead via the first spring. 
         [0011]    The various aspects discussed above may be used alone or in any combination. Further, the present invention is not limited to the above features and advantages. Indeed, those skilled in the art will recognize additional features and advantages upon reading the following detailed description, and upon viewing the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  shows an oxygen sensor assembly according to an embodiment of the present invention, with the cap portion mated to the base portion. 
           [0013]      FIG. 2  shows a vertical cross-sectional view of the assembly of  FIG. 1 . 
           [0014]      FIG. 3  shows a perspective view of the assembly of  FIG. 1 , with some elements of the cap portion omitted for clarity, including one spring omitted from the corresponding wire. 
           [0015]      FIG. 4  shows a perspective view of a core, with two of four associated leads shown. 
           [0016]      FIG. 5  shows a top view of the core of  FIG. 4 , with four associated leads shown. 
           [0017]      FIG. 6  shows a vertical cross-section of a cap portion. 
           [0018]      FIG. 7  shows a underside (distal) perspective view of a cap. 
           [0019]      FIG. 8  shows one exemplary conductor assembly, of which there are four in the assembly of  FIG. 1 , with the spring laterally uncompressed. 
           [0020]      FIG. 9  shows a top cross-sectional view taken at plane P (see  FIG. 2 ). 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    The present application is directed to a releaseable electrical connector and/or methods of making releasable electrical connections. The discussion below may generally be in the context of a releasable electrical connection for a combustion engine oxygen sensor assembly, but it should be understood that the releasable electrical connection(s) disclosed herein may be used in other applications. 
         [0022]    Referring to  FIGS. 1-2 , an exemplary oxygen sensor assembly, generally indicated at  10 , includes a distal positioning section  12  and a proximal connection section  13 . The distal positioning section  12  includes a mounting shell  14 , typically externally threaded and in the form of a hexport housing, for mounting to a suitable location of an engine (not shown). A proximal portion of the mounting shell advantageously includes an external circumferential recess  15  for accepting detents  54 , as discussed further below. A inner insulator  18  fits inside an outer insulator  16 , which in turn fits inside the mounting shell  14 . The outer insulator  16  includes an axial bore extending proximally from its distal tip. The inner insulator  18  supplies mounting support for an oxygen sensor chip  19  disposed distally from the tip of the inner insulator  18 . A suitable oxygen sensor chip  19  is disclosed in U.S. Patent Application Publication No. 20110186446, the disclosure of which is incorporated herein in its entirety. The oxygen sensor chip  19  is exposed to the ambient environment via the bore of the outer insulator  16 . The oxygen sensor chip  19  may advantageously be disposed in spaced relation to the tip of the inner insulator  18 , and supported thusly by the distal portions of a plurality of flat conductor wires (or “leads”)  40  bent as shown so as to clampingly hold the oxygen sensor chip  19 . The inner insulator  18  and the outer insulator  16  are electrically insulating, and may be formed of suitable refractory or high temperature material. Thus, the leads  40  are electrically isolated from the typically conductive mounting shell  14 . 
         [0023]    The connection section  13  is disposed proximally of the positioning section  12 , and includes the connector assembly  20 . The connector assembly  20  includes a base portion  30  and a cap portion  50  releasably mounted to the base portion  30 . The base portion  30  is advantageously affixed to the positioning section  12  and includes a base  32  and a core  34  extending proximally from the base  32  along a core axis C. For the illustrative embodiment of  FIGS. 2-3 , the proximal portion (upper end portion as illustrated) of the mounting shell  14  and outer insulator  16  acts as the base  32 . As shown in  FIGS. 4-5 , the core  34  advantageously includes a plurality of lobes  36 , with recesses  38  formed therebetween that form channels  38  extending parallel to the core axis C. The channels  38  have a depth toward the core axis C, referred to as a radial depth, of D1. The core  34  is advantageously non-conductive and may be formed of a suitable material, such as a ceramic refractory material. Each lead  40  extends from the positioning section  12  and into the corresponding channel  38 . While not required, the lead  40  may advantageously include a bent proximal section  42  that is bent inward toward the core axis C so that a portion of the lead  40  in the channel  38  extends in a direction transverse to the core axis C. The proximal end section of each channel  38  is advantageously ramped as shown at  39  to facilitate the connection process, as discussed further below. As can be appreciated, in the region of the channel  38 , one lateral side  47  of the lead  40  directly faces the core  34  and the other lateral side  48  faces outward (toward the cap  60 ). Note that lateral side  47  may advantageously also abut the portion of the core  34  forming the “floor” of the corresponding channel  38 . 
         [0024]    Referring to  FIG. 2  and  FIGS. 6-9 , the cap portion  50  includes an outer shell  52 , an insulator cap  60 , proximal conductor assemblies  80 , and an optional proximal seal  58 . The outer shell  52  helps protect the electrical connection formed by the connector assemblies  80  from the environmental contaminants. The outer shell  52  peripherally surrounds the cap  60 , and includes a distal portion with one or more inner raised areas forming detents  54  for mating with the circumferential recess  15  of the mounting shell  14  to releasably hold the cap portion  50  to the base portion  30 . The shell  52  may be conductive or non-conductive, as is desired. The insulator cap  60  resides inward of the shell  52  and helps electrically insulate the components therein from the shell  52 . The cap  60  includes a plurality of longitudinally extending and distally opening recesses  62  that are advantageously generally part-round in cross-section. See  FIG. 7 . The recesses  62  are disposed in spaced relation to each other about a central longitudinally extending opening  61  which receives the core  34  as discussed further below. The opening  61  is distally open, and may be proximally closed or open as desired. Advantageously, the number of recesses  62  in the cap  60  match the number of channels  38  in the core  34  and are correspondingly positioned. The recesses  62  have a depth of D2. The combination of a given recess  62  in the cap  60  and the corresponding channel  38  in the core  34  both bound, and advantageously jointly form, a generally peripherally enclosed cavity  70  when the core  34  is inserted into the cap  60 . Thus, the cavity  70  formed by a given recess  62  in the cap  60  and the corresponding channel  38  has a radial depth of D1+D2 in the portion thereof not including the ramped section  39  of the channel  38 . Further, the cap  60  laterally bounds the cavity  70  in the outward direction. See  FIG. 9 . The cap  60  is non-conductive. 
         [0025]    Referring to  FIG. 8 , the proximal conductor assemblies  80  each include a distal portion of a proximally extending wire  82 , and a spring  90  mounted thereto at the distal portion. The wire  82  may take any suitable form known in the art, such as a plastically insulated conductive multi-stranded or solid copper conductor. The end portion  84  of the wire&#39;s conductor has the wire&#39;s insulation (if any) removed, and the spring  90  is mounted thereto. The spring  90  may be mounted to the wire  82  by any suitable means, such as by crimping, soldering, conductive epoxy, or a combination thereof. The spring  90  is resiliently laterally (radially) compressive with at least an electrically conductive outer surface. In some embodiments, the spring  90  may be a simple post-like generally cylindrical shell of spring material, or a solid but compressible pin. However, the spring  90  advantageously takes the form of a generally cylindrical body formed by a rolled convolute coil of resilient conductive material. An example of a suitable spring  90  is a coiled spring pin available from Spirol International Corporation of Danielson, Conn. The spring  90  extends longitudinally along a longitudinal spring axis L, which is advantageously parallel to the core axis C. The spring  90  includes a peripheral surface  92 , part  94  of which is in contact with the cap  60 , and another part  96  of which faces toward the core  34  of the base portion  30  and is in contact with the corresponding lead  40 . See  FIG. 9 . The spring  90  has an uncompressed size (measured normal to the spring axis L) denoted D3. The distal tip of the spring  90  may be advantageously tapered inward toward the spring axis L, so as to have a smaller cross-sectional profile (measured normal to the spring axis L), to facilitate the mating of the cap portion  50  to the base portion  30 . 
         [0026]    The proximal seal  58  cooperates with the shell  52  so that debris, fluids, and other environmental contaminants are kept away from springs  90 . The seal  58  may also aid in keeping the proximal conductor assemblies  80  properly aligned. The seal  58  is advantageously non-conductive. 
         [0027]    As indicated above, the cap portion  50  is releasably attached to the base portion  30 . When the cap portion  50  is disconnected from the base portion  30 , the electrical connection between a given wire  82  and the corresponding lead  40 , and hence the oxygen sensor chip  19 , is opened. To make an electrical connection, the cap portion  50  is oriented relative to the base portion  30  such that the core axis C is parallel to the spring axes L, with the cap portion  50  spaced from the base portion  30 . The cap portion  50  is then moved distally toward the base portion  30 , along core axis C, so that the distal tips of the springs  90  begin to enter the corresponding recesses  38  on the core  34 . The interaction of the ramped proximal end section  39  of the channel  38  and the tapered tip of the spring  90  facilitate entry of the spring  90  into the corresponding channel  38 . The cap portion  50  is further distally advanced so that the detents  54  on the shell  52  engage the circumferential recess  15  of the mounting shell  14  to fully mate the cap portion  50  to the base portion  30 . When fully mated, the cap portion  50  and the base portion  30  longitudinally overlap a significant extent. A portion of that overlap includes an area where a given spring  90  is pressed against its corresponding lead  40  so as to make the electrical connection. The pressing force is supplied, at least in part, by the lateral compression of the spring  90 . Because the spring&#39;s uncompressed cross-sectional size D3 is larger than the lateral (radial) depth D1+D2 of the corresponding cavity  70 , the spring  90  is laterally compressed when captured in the cavity  70  by mating the cap portion  50  to the base portion  30 . This compression is facilitated by the convolute coil nature of the spring  90 . That is, the individual layers of the spring  90  material making the coil are displaced relative to each other (e.g., the coil is “wound” tighter) so that the spring  90  is laterally compressed to reduce its cross-sectional size to match the available space, advantageously without changing its longitudinal length. 
         [0028]    As can be appreciated, the spring  90  is laterally compressed between the lead  40  (backed by the core  34 ) and the cap  60  when the cap portion  50  is mated to the base portion  30 . Thus, portion  94  of the outer peripheral surface  92  of the spring  90  abuts the cap  60 , while portion  96  of the spring outer peripheral surface  92  abuts the lead  40 , thereby making the electrical connection. This may be seen with reference to  FIG. 9 , which is a distally looking cross-section of the connector assembly  20  at plane P (at IX-IX in  FIG. 2 ), which is normal the core axis C at location X along the core axis C. Location X is in the region of the spring  90 , approximately longitudinally halfway along the zone where the spring  90  abuts the lead  40 . As can be seen, peripheral surface portion  94  abutting the cap  60  is generally opposite the peripheral surface portion  96  that abuts the lead  40 . The angle β subtended by the conductor abutment portion  96  is advantageously not more than about three degrees to about ten degrees. Further, the conductor abutment portion  96  advantageously extends longitudinally for the majority of the longitudinal length of the spring  90 , so that there is abundant area over which the electrical connection is made. 
         [0029]    When the cap portion  50  is mated to the base portion  30 , the electrical connection path formed in part by the connection assembly  20  extends along the proximally disposed wire  82 , to the spring  90 , to the lead  40  (conductor), and to the oxygen sensor chip  19 , with the connection between the spring  90  and the lead  40  being releasable by unmating the cap portion  50  from the base portion  30 . Note that the electrical connection between the spring  90  and the corresponding lead  40  is both readily releaseable and solderless. 
         [0030]    As can be appreciated, the electrical connection may be readily made and released using the present approach. For example, the cap portion  50  may be releasably mated to the base portion  30 , and the completed assembly used for a period of time. If a fault is subsequently detected in the oxygen sensor chip, or some other malfunction occurs, the cap portion  50  may be removed from the base portion  30 , but remain “wired” to the engine control system. The base portion  30  may be dismounted from the engine and inspected for repair or replacement. For replacement, a different base portion  30  is then mounted to the engine and the original cap portion  50  is then mated to the new base portion  30 . Of course, the sequence of mating/unmating the base portion  30  to the engine and the cap portion  50  may be reversed when appropriate. Thus, the oxygen sensor assembly  10  may be repaired/replaced without having to disconnect the cap portion  50  from the engine&#39;s control system. 
         [0031]    The discussion above has been in the context of a connector assembly  20  making multiple parallel electrical connections. In one illustrative embodiment, there are four parallel connections, with pairs of springs  90  and leads  40  symmetrically disposed at 90° intervals around the core axis C. For such an arrangement, it may be advantageous to have opposing pairs of leads  40  form a circuit path through the oxygen sensor chip  19 , the other pair of leads  40  forming a second and separate circuit path through the oxygen sensor chip  19 . Further, for such an arrangement, a line  97  between the spring axes L of opposing springs  90  would pass through the core axis C, while a line  98  between spring axes L of adjacent springs  90  would pass through the core  34 , but not the core axis C. Such an arrangement is believed advantageous; however, there may be more or less parallel connections, as is desired. Thus, there could be two, three, six, eight, etc. connections, which may be symmetrically or asymmetrically disposed. Further, the connector assembly  20  may make only one electrical connection (e.g., one spring  90  and one lead  40 ), as is desired. Additionally, if there is more than one lead  40  in a given recess  38 , one spring  90  may make abutting electrical contact with more than one lead  40  in the base portion  30 , such as might be advantageous for connecting a common ground. 
         [0032]    The discussion above has generally assumed that the core  34  includes an appropriate number of channels  38  in which the corresponding leads  40  are partially disposed. Indeed, the illustrated core is symmetric about the core axis C. While such an arrangement is believed advantageous, such is not required. In some embodiments, the core  34  may have channels  38  that are asymmetrically disposed (with the recesses  62  advantageously being likewise asymmetrically disposed). Also, in some embodiments, the core  34  may not have channels  38 , but instead have a flat and/or smooth exterior surface. Thus, the core  34  may, for example, have a rectangular, square, triangular, hexagonal, etc., or round cross-sectional profile, either with or without channels  38 . 
         [0033]    The core  34  and cap  60  may include suitable indexing features so as to help ensure that the cap  60  is properly aligned relative to the core  34  when the core is disposed in the core  60 , so that the various leads  40  and conductors  82  are connected in a predetermined pattern, or a limited number of patterns. For example, the core  34  may have a generally rectangular cross-section, and the opening  61  in the cap  60  may have a corresponding rectangular shape, thereby allowing the core  34  to be inserted into the cap  60  in two possible orientations. Other indexing/keying features known in the art, such as key tabs/slots, may be used additional or alternatively. 
         [0034]    While the description above has included one or more seals  58 , more or less seals may be employed as appropriate to help keep environmental contaminants away from the electrical connection area. For example, the base portion  30  may include a seal  33  disposed between the core  34  and the inner insulator  18 . 
         [0035]    The discussion above has been in the context of the shell  52  of the cap portion  50  fitting over the proximal end of the base portion  30 , so that the cap portion  50  encloses the proximal portion of the base portion  30  and forms the outermost portion of the assembly  20  where the cap portion  50  and the base portion  30  overlap. While this is believed to be advantageous, in some embodiments, the base portion  30  may have an outer rim wall (not shown) that the cap portion  50  is received into such that the base portion  30  is the outermost portion of the assembly  20  in the overlap region. Regardless of the shell configuration, because the core  34  fits into the cap  60  to form the electrical connection, the base portion  30  with the core  34  is considered the male portion of the connector assembly  20 , while the cap portion  50  with the cap  60  is considered the female portion of the connector assembly  20 . 
         [0036]    In some embodiments, the spring  90  may have a notch  99  cut therethrough, generally perpendicular to the spring axis L, and advantageously oriented away from the core  34 . Further, while it is believed advantageous if the leads  40  are formed by flat wires, the leads  40  may be formed by round, obround, or other shaped conductors, as is desired. 
         [0037]    In some embodiments, a silicone-based thermoplastic or other suitable seal material can be applied to the circumferential recess  15  of mounting shell  14 , which, upon heating, will flow into the space between the base  32  and the shell  52  in order to improve the sealing of the electrical connection from environmental elements like moisture, oils, other fluids, etc. This flowable seal material may require removal and replacement in subsequent re-connections; however, there may be advantages to using such flowable seal material in particularly harsh environments. 
         [0038]    As mentioned above, the connection approach may be used for other applications than as a part of an oxygen sensor assembly  10 . For example, a similar structure may be used, with a simple replacement of oxygen sensor chip  19  with a different sensor chip, such as a dedicated ignition spark detector, or other detector. Likewise, the connection approach could advantageously be used on other, non-combustion engine applications where it is desired to allow for repair/replacement with minimal or no rewiring. 
         [0039]    The present invention may, of course, be carried out in other ways than those specifically set forth herein without departing from essential characteristics of the invention. The present embodiments are to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.