Abstract:
A seal fitting for use in connecting the lead wire from the sensor on one side of bulkhead or housing to a thermocouple (TC) or resistance temperature detector (RTD) on the other side of the sensor or housing, intended for use in applications in which the sensor is located in oil, and usually oil under pressure, such as in a turbine or compressor. The seal fitting is mounted to a port on the bulkhead/housing and includes means for clamping the lead wire from the TC or RTD sensor in electrical contact with a male conductive pin and means for clamping the lead wire from the TC or RTD in electrical contact with a female conductive pin. Both the male conductive pin and the female conductive pin are enclosed within male and female connectors that are assembled in such a way that the conductive pin passes through a ceramic to metal seal at a ceramic insulator to both seal electrically and prevent wicking of the oil along the wires.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a seal fitting for use with thermocouples, resistance temperature detectors (RTDs), and other sensors for monitoring temperature and other physical properties of lubricants and other fluids contained in a confined space, and particularly, for use with fluids that are under vacuum, pressure, and/or high flow rates such as in bearings or in turbine generators, motors, and/or compressors. 
   The difficulty in preventing the passage of a fluid from a sealed or confined space along the thermocouple or RTD leads exiting past the seals is well known. Through long experience, the manufacturers of machinery such as turbine generators, motors, and compressors have come to expect that lubricant will escape along the lead wires that output signals from a temperature sensor in the lubricant to a gauge or central processing unit (CPU) for monitoring operation of the machinery. So far as is known, no seal is available that effectively prevents the so-called oil wicking of such fluids from a confined space in which the fluid is contained along the thermocouple or RTD wires. The problem is exacerbated by the vacuum, pressure, and/or flow rate of the fluid (in the case of machinery such as turbines and compressors) and by such factors as the viscosity of the fluid, flow rate, temperature, and other physical and operating properties of the machinery and the fluid. 
   It is, therefore, an object of the present invention to provide a seal fitting that effectively resists passage of fluid from within a confined space along the leads that extend from a thermocouple, probe, RTD, or other sensor positioned on one side of the housing or bulkhead in which the fluid is contained in a confined space to a gauge or other circuitry at which physical properties of the fluid are monitored. 
   Another object of the present invention is to provide a seal fitting in which the component parts of the fitting can be changed so quickly and conveniently, and without dissassembling the fitting, that routine maintenance can be accomplished without interrupting the operation of the machinery. 
   Another object of the present invention is to provide a seal fitting that is capable of being used for connecting lead and instrument wires of various sizes (gauges) while still maintaining an effective seal against oil wicking. 
   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 a seal fitting for connecting the lead wire of a thermocouple (TC) or resistance temperature detector (RTD) sensor positioned on one side of a bulkhead or housing to the lead wire of the TC or RTD positioned on the other side of the bulkhead comprising a shell, means in the housing for clamping the lead wire from the sensor of the TC or RTD, and a ceramic disk retained in the housing in spaced relationship with the sensor wire clamp. A male conductive pin with one end in contact with the sensor wire clamping means extends through the ceramic disk with the ceramic material comprising the disk sealing against the male conductive pin. A tube that is filled with an insulating material is engaged to the shell with the ceramic disk interposed between the tube and the sensor wire clamping means and a female conductive pin extends through the insulating material in the tube into contact with the male conductive pin. The female conductive pin in the tube is also in contact with means for clamping a lead wire from the TC or RTD. Although not limited to this use, the seal fitting of the present invention is intended for use in applications in which it connects the above-described lead wire from a sensor that is positioned on one side of a bulkhead and a lead wire from an instrument that is positioned on the other side of the bulkhead. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side elevational, exploded view of a preferred embodiment of a thermocouple and RTD connector constructed in accordance with the teachings of the present invention. 
       FIG. 2  is a side elevational view of the connector of  FIG. 1  with the body fitting removed to show the assembled male-female halves of the thermocouple and RTD connector of the present invention. 
       FIG. 3  is a longitudinal sectional view of the male connector of the thermocouple and RTD connector of  FIG. 1 . 
       FIG. 4  is a detailed sectional view of a portion of  FIG. 3 . 
       FIG. 5  is a longitudinal sectional view of the female connector of the thermocouple and RTD connector of  FIG. 1 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to the figures, a preferred embodiment of a seal fitting constructed in accordance with the teachings of the present invention is indicated generally at reference numeral  10 . Seal fitting  10  comprises a body fitting  12 , preferably comprised of metal, and male and female connectors  14  and  16 , respectively. As shown in  FIG. 2 , the male and female connectors  14 ,  16  are assembled to each other with a concentric nut  18  having threads  20  thereon for mating with the internal threads (not shown) in one end of body fitting  12  for retaining body fitting  12  over the male connector  14 . An internal shoulder (not shown) on nut  18  bears against the shoulder  22  formed on male connector  14  to trap the male connector  14  between nut  18  and inside body fitting  12 . Strain reliefs  24 A,  24 B are provided at each end of the male-female connector assembly and the outside diameter (O.D.) of male connector  14  is provided with one or more (three being shown in the figures) raised headers, or annular rings,  26  having grooves  28  therebetween for receiving an O-ring (not shown in  FIGS. 1  or  2 , but shown in sectional view in  FIG. 3 ) therein for sealing against the inside diameter (I.D.) of body fitting  12  when the male connector  14  is received therein. In the preferred embodiment shown, each of the male and female connectors  14 ,  16 , as well as the nut  18  and strain reliefs  24 , are comprised of metal, preferably stainless steel, but those skilled in the art who have the benefit of this disclosure will recognize that it is not a requirement of the present invention that these parts be made of metal to function in the manner intended to accomplish their intended purpose. 
   Although not limited to this application, in one application, the seal fitting  10  is utilized to connect the lead wire(s) from the sensor of a thermocouple (TC) or resistance temperature detector (RTD) that is positioned in an oil bath of, for instance, a turbine or compressor, and the body fitting  12  screws into the port of a housing or bulkhead (not shown) in which the oil is contained on the screw threads  13  formed at the end of body fitting  12 . The lead wire from the sensor for the TC or RTD, or more usually, more than one such lead wires, extends out of the housing through the port. As set out below, provision is made in the embodiment shown for connecting four such sensor lead wires to an instrument for providing information as to the temperature of the oil in the housing, but those skilled in the art will recognize that the seal fitting of the present invention is utilized to advantage for connecting one, two, four, six, or however many TC or RTD sensor lead wires as is needed in a particular application to the lead wires from their respective TCs or RTDs. For this reason, one end of seal fitting  10  (shown at the right in  FIG. 1 ) is designated as the oil side of the connector and the other end (shown at the left in  FIG. 1 ) is the instrument side. This right/left oil/instrument orientation is maintained throughout  FIGS. 1–5 . 
   As shown in  FIG. 3 , in which the male connector  14  of  FIGS. 1 and 2  is shown in enlarged, sectional detail, male connector  14  comprises an elongate, tubular shell  30 . An adapter  32  is welded around the transition sleeve  34  at the end of shell  30  opposite the strain relief  24 B, the weld between shell  30  and adapter  32  being indicated at reference numeral  36 . The inside diameter (I.D.) of shell  30  is enlarged in the portion  38  and a spacer  40  is positioned in the enlarged I.D. portion  38  at the end proximate strain relief  24 B. As best shown by reference to  FIG. 4 , a notch  42 , or in the case of the embodiment shown, four notches spaced at approximately 90° intervals, is formed in spacer  40  and a clamp, indicated generally at reference numeral  44 , for clamping a lead wire (not shown) is positioned in notch  42 . The clamp  44  is retained within notch  42  by a spacer cap  46  that is trapped between spacer  40  and the stepdown  48  formed in the shell  30  of male connector  14 . As explained in more detail below, spacer  40  and spacer cap  46  are preferably comprised of a thermoplastic material such as PEEK or PEKK, and in a particularly preferred embodiment, the cap  46  is adhered to spacer  40  as well as being trapped between spacer  40  and stepdown  48 . 
   As best shown in  FIG. 4 , clamp  44  is comprised of a clamping tab  50  that is biased radially outwardly from the longitudinal axis of male connector  14  on two coil springs  52 , the springs  52  being maintained in the desired upright position in notch  42  by a threaded tab  54  positioned between the underside of clamping tab  50  and the inside walls of the notch  42  and spacer cap  46 . A cap screw  56  extends down through a threaded hole (not numbered) in clamping tab  50  and, when turned by a screwdriver or other implement (not shown) inserted through the hole  58  in the shell  30  of male connector  14 , cap screw  56  moves the clamping tab  50  either away from or towards (the latter being in a direction against the bias applied to clamping tab  50  by springs  52 ) the longitudinal axis of male connector  14  on the threads in threaded tab  54 . For purposes of convenience, the directions of movement of clamping tab  50  are referred to herein as being radially outwardly (with the bias applied by springs  52 ) or inwardly (against the bias applied by springs  52 ) with respect to the longitudinal axis of the substantially cylindrical male connector  14 . 
   Although not required for clamp  44  to function in the manner described, the threaded tab  54  is preferably comprised of a thermoplastic such as PEEK or PEKK and preferably adhered to spacer  40  and spacer cap  46  in the same manner in which spacer cap  46  is adhered to spacer  40 . A prong  60  is affixed to clamping tab  50  and extends radially inwardly (toward the longitudinal axis of male connector  14 ) through a hole (not numbered) in spacer  40  into a bore  62  that extends into spacer  40  in a direction substantially parallel to the longitudinal axis of male connector  14 . Bore  62  opens through a hole  64  in spacer cap  42  to form a receptacle for insertion of the above-described lead wire (not shown) from the sensor for the TC or RTD and clamping of the sensor lead wire as cap screw  56  is tightened to cause the prong  60  to engage the lead wire. 
   Referring again to  FIG. 3 , it can be seen that a portion of the bore  62  in spacer  40  is provided with a metal conductive pin  66  that extends longitudinally (in a direction substantially parallel to the longitudinal axis) in the shell  30  of male connector  14  from spacer  40  through a hole (not numbered) in an insulating disk  68  positioned in shell  30  at the end opposite strain relief  24 B. Clamping the lead wire in bore  62  by tightening cap screw  56  causes the lead wire to be pushed into electrical contact with conductive pin  66  by prong  60 . A tube  70  surrounds the conductive pin  66  as it passes through the hole in insulator  68 . Tube  70  and transition sleeve  34  are preferably both comprised of a nickel iron alloy (Chromel, for instance), and insulating disk  68  is preferably comprised of alumina or other highly insulative ceramic material. The combination of the weld  36  and insulating disk  68  provides a hermetic seal between the sensor in the oil bath or reservoir on one side of the bulkhead and the TC or RTD on the other side. 
   Referring now to  FIG. 5 , female connector  16  is shown in enlarged sectional view. Insofar as the parts of the clamp  44  in female connector  16  are identical to those of the clamp  44  shown and described above in connection with  FIGS. 3 and 4 , the same reference numerals are used in the clamp  44  in  FIG. 5 . The clamp  44  of female connector  16  clamps a lead wire from the TC or RTD in a bore  62  in spacer  40  in the same manner in which the lead wire from the sensor for the TC or RTD is clamped in the above-described male connector  14 , but the end of the longitudinally-extending female conductive pin  72  of female connector  16  terminates in a receptacle  74  for receiving the end portion  75  of the male conductive pin  66  that extends through the insulating disk  68  in male connector  14  (hence the designation of the two portions of seal fitting  10  as the male  14  and female  16  connectors). By receipt of male conductive pin  66  in the receptacle  74  of female conductive pin  72 , current can pass through seal fitting  10 , but a seal is established against the migration of any oil (or other moisture) through connector along the lead wires, hence the designation of the connector of the present invention as a non-oil wicking seal fitting. 
   Female conductive pin  72  extends longitudinally through a main spacer  75  confined within the sleeve  76  comprising a portion of female connector  16 . A main nut  78  is placed over sleeve  76  before sleeve  76  is threaded onto a backnut  80  and bears against the shoulder  82  formed on sleeve  76  when male connector  14  is assembled to female connector  16  so that the internal threads of main nut  78  engage the threads  33  on the O.D. of the adapter  32  at the end of male connector  14  opposite strain relief  24 B to draw the male and female connectors  14 ,  16  together. Sleeve  76  fits over a retaining spacer  84 , both main spacer  75  and retaining spacer  84  preferably being comprised of a plastic, or even more preferably, a thermoplastic material as described above, to provide insulation around conductor  72 . An orientation pin  86  is provided for orienting the conductors  72  during assembly of sleeve  76  to the spacer  40 , backnut  80 , and retaining spacer  84 , and a retaining pin  90  having a retaining ring  88  welded or otherwise affixed thereto on one end and a retaining collar  92  welded or otherwise affixed thereto on the other end extends through the component parts  72 ,  75 ,  76 , and  84  to hold the component parts  72 ,  75 ,  76 , and  84  to the spacer  40  of female connector  16 . 
   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. 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.