Abstract:
A two-terminal temperature sensor connects a first end of thermistor or other thermometer device to a first electrical terminal via an inner compression coil. A second electrical terminal is connected to a second end of the thermistor via an outer compression coil and a formed conductor. The inner compression coil and thermistor are positioned within the formed conductor. The inner compression coil and thermistor are prevented from contact with the formed conductor by an inner insulating tube. The first and second electrical contacts are mounted in a molded terminal assembly that insulates the electrical contacts from one another. The entire assembly is housed within a housing that is electrically isolated from the formed conductor and outer compression coil via an outer insulating tube and an insulating disk.

Description:
BACKGROUND 
       [0001]    A thermistor is a type of resistor with resistance varying according to its temperature. Temperature sensors utilizing thermistors are widely used to monitor the temperature of various components in an engine. For example, the oil, coolant, and/or engine block temperature may be monitored. In many thermistor-based temperature sensors, one side of the thermistor is connected to a positive terminal that is further connected to a wire leading to a computer. The opposite side of the thermistor is often connected to the temperature sensor casing which in turn is connected to ground. As the surrounding temperature changes, the temperature of the thermistor changes and it&#39;s resistance value changes. Using a table of resistance values for reference, the computer may use the resistance value of the temperature sensor to determine the temperature of the thermistor. 
         [0002]    In marine applications, such as boats, ships, and yachts, temperature sensors may be occasionally submerged in water or at least regularly come in contact with water. In such cases, there exists a need for a temperature sensor that does not utilize the temperature sensor casing for a return electrical path. Further, the computer may be physically mounted a long distance from the temperature sensor and may not share the same ground as the device being monitored. Additionally, the computer may be especially sensitive to electrical interference and thus must be electrically isolated from the device being monitored. In both cases, there exists a need for a temperature sensor that provides a dedicated return path to the computer for temperature monitoring. 
         [0003]    Further, there exists a need for a temperature sensor that is both robust and durable, while being accurate, compact in size, and easy for a consumer to assemble or repair if required. 
       SUMMARY 
       [0004]    A two-terminal temperature sensor utilizing a thermistor or other thermometer device is herein disclosed. A first electrical terminal may be connected to a first end of the thermistor via an inner spring. A second electrical terminal may be connected to a second end of the thermistor via an outer spring and a formed conductor. The inner compression coil and thermistor are positioned within the formed conductor. The inner spring may be prevented from contacting the formed conductor by an inner insulating tube. The first and second electrical contacts may be mounted in a molded terminal assembly that insulates the electrical contacts from one another. The entire aforementioned assembly may be mounted in a housing that is electrically isolated from the formed conductor and outer compression coil via an outer insulating tube and an insulating disk. 
         [0005]    The temperature sensor described herein is directed toward reducing the overall size of thermistor-based temperature sensors. According to one aspect of the device, thermal conductivity between the medium and the thermistor is improved, providing more accurate temperature monitoring. According to another aspect of the device, the electrical circuit is simplified reducing the size of the temperature sensor housing. This reduction in size and complexity may reduce manufacturing costs and increase longevity of the temperature sensor. The reduction in complexity may also enable an end user to assemble the temperature sensor at the point of installation rather than the manufacturer at the manufacturing facility. Further, the reduced size may enable a deep well socket to pass over the temperature sensor terminals and insulator for easier installation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is an isometric view of a two-terminal temperature sensor. 
           [0007]      FIG. 2A  is a cross-sectional view of the two-terminal temperature sensor of  FIG. 1  as indicated in  FIG. 1 . 
           [0008]      FIG. 2B  is a detail sectional view of the lower right-hand corner of  FIG. 2A . 
           [0009]      FIG. 3A  is a multi-sectional view of the two-terminal temperature sensor of  FIG. 1 . 
           [0010]      FIG. 3B  is a top plan view of the two-terminal temperature sensor of  FIG. 1 . 
           [0011]      FIG. 4  is an exploded isometric view of the two-terminal temperature sensor of  FIG. 1 . 
           [0012]      FIG. 5  is an exploded isometric view of the terminal insulator and terminals of the two-terminal temperature sensor of  FIG. 1 . 
           [0013]      FIG. 6A  is an isometric view of a terminal assembly with a Packard type connector. 
           [0014]      FIG. 6B  is a first elevation view of the terminal assembly of  FIG. 6A . 
           [0015]      FIG. 6C  is a second elevation view of the terminal assembly of  FIG. 6A . 
           [0016]      FIG. 6D  is a top plan view of the terminal assembly of  FIG. 6A . 
           [0017]      FIG. 7A  is an isometric view of a terminal assembly with threaded terminal connectors. 
           [0018]      FIG. 7B  is a first elevation view of the terminal assembly of  FIG. 7A . 
           [0019]      FIG. 7C  is a second elevation view of the terminal assembly of  FIG. 7A . 
           [0020]      FIG. 7D  is a top plan view of the terminal assembly of  FIG. 7A . 
       
    
    
     DETAILED DESCRIPTION 
       [0021]      FIG. 1  is an isometric view of one embodiment of a two-terminal temperature sensor  1 . In this embodiment, the housing  2  comprises a cylindrical body with an opening on one end and a threaded exterior  24  for screwing the temperature sensor  1  into a threaded hole in a device to be measured. Further, the housing  1  may be equipped with a hexagonal interface  25  for a wrench or socket. The hexagonal interface  25  may be used to aid in screwing the temperature sensor  1  into the threaded hole and tightening the bottom of the hexagonal interface  25  against the top of the threaded hole thereby securing the temperature sensor  1  to the device to be measured. Other ways of attaching the temperature sensor  1  to the device to be measured are contemplated, for example, welding, soldering, bolting, crimping, and press-fitting. 
         [0022]    A terminal insulator  6  may comprise an insulating material with a short terminal  4  and a long terminal  5  protruding therefrom. The short terminal  4  and the long terminal  5  may be utilized as male electrical connectors for wires with female connectors leading to a computer or any other device that may measure the resistance offered by the temperature sensor  1  and determine the temperature of the thermistor based on the resistance measured. Other terminal insulator  6  configurations and electrical connectors are contemplated as discussed in detail with reference to  FIGS. 6 and 7 . Also protruding from the terminal insulator  6  between the short terminal  4  and the long terminal  5  may be a terminal divider  15 . The terminal divider  15  acts as an insulator and ensures that the short terminal  4  and the long terminal  5 , or corresponding electrical connectors attached thereto, do not inadvertently come in contact with one another. Further, the terminal divider  15  may be a moulded part of the terminal insulator  6  or it may be separately attached to the terminal insulator  6 . As discussed in detail below with reference to  FIG. 5 , the terminal insulator  6  may be attached to the housing  2  via a crimp  16 . Other ways of attaching the terminal insulator  6  to the housing  2  are contemplated, for example, gluing, overmoulding, bolting, screwing, and press-fitting. 
         [0023]      FIGS. 2A ,  2 B, and  3 A show cross-sectional views of an embodiment of the temperature sensor  1 . The housing  2  may be a substantially cylindrical structure with a closed bottom and an open top. The side walls of the housing  2  may be thinner near the bottom for maximum heat transfer and thicker near the top for added structural strength. Further, the bottom may incorporate a pedestal  26  upon which a thermistor  10  may be mounted. The housing  2  may be equipped with threads  24  on its exterior for attachment to the device to be measured and a hexagonal interface  25  to aid in installing the temperature sensor  1 . Further, the top of the housing  2  may be crimped  16  around the terminal insulator  6 , described more fully below. 
         [0024]    Adjacent to the interior surface of the housing  2  may be an outer insulating tube  13 . The outer insulating tube  13  may be a thin, hollow, cylindrical tube with open ends comprised of a material that is not electrically conductive, for example, plastics, ceramics, wood-based products, and paper-based products. The outer insulating tube  13  may be positioned inside the housing  2 , with one end resting against the bottom of the housing  2  in an annular well  27  surrounding the pedestal  26 . In this manner, the outer insulating tube  13  extends beyond the components it encircles to ensure against electrical contact with the housing  2 . 
         [0025]    An insulating disk  14  may be positioned inside the outer insulating tube  13  with a bottom face supported by the pedestal  26  at the bottom of the housing  2 . The insulating disk  14  may be a thin, circular disk that is composed of a material that is not electrically conductive, but is thermally conductive, for example, a rubberized fabric. 
         [0026]    A formed conductor  12  may be positioned inside the outer insulating tube  13  resting against the top of the insulating disk  14 . The formed conductor  12  may be a thin, hollow, cylindrical tube with an open top, closed bottom, and openings on each side (see  FIG. 4 ). Alternatively, the formed conductor may have a solid sidewall. Further, the formed conductor  12  is comprised of a material that is electrically conductive. The outer insulating tube  13  serves to prevent the formed conductor  12  from making electrical contact with the housing  2 . 
         [0027]    Adjacent to the interior surface of the formed conductor  12  may be a inner insulating tube  11 . The inner insulating tube  11  may be a thin, hollow, cylindrical tube with open ends comprised of a material that is not electrically conductive, for example, plastics, ceramics, wood-based products, and paper-based products. The inner insulating tube  11  may be positioned inside the formed conductor  12 , with one end resting against the bottom of the formed conductor  12 . 
         [0028]    A thermistor  10  or other thermometer device (e.g., a thermocouple) may be positioned inside the inner insulating tube  11  and rest against the bottom of the formed conductor  12 . The thermistor  10  may be formed as a solid cylindrical or disk shape with resistance properties that vary according to temperature. 
         [0029]    In another embodiment, the housing  2  may be electrically non-conductive and the temperature sensor  1  may not include an outer insulating tube  13  and/or a insulating disk  14 . The housing may serve to prevent the formed conductor  12  and/or thermistor  10  from electrical contact with anything in physical contact with the exterior of the housing  2 . The housing  2  may be comprised of, for example, plastics or ceramics. 
         [0030]    An electrically conductive inner compression coil  9  may be positioned inside the inner insulating tube  11  and against the top of the thermistor  10 . The inner insulating tube  11  extends below the inner compression coil  9  and around the sidewalls of the thermistor  10  and serves to prevent the inner compression coil  9  from electrical contact with the formed conductor  12 . An electrically conductive outer compression coil  8  may be positioned against an upper edge or rim of the formed conductor  12  and inside the outer insulating tube  13 . The outer insulating tube  13  also serves to prevent the outer compression coil  8  from electrical contact with the housing  2 . 
         [0031]    The terminal assembly  3  may be comprised of a short terminal  4  and a long terminal  5  that are substantially enveloped in a terminal insulator  6  that is electrically non-conductive. As shown in  FIGS. 2A and 3B , the terminal insulator  6  is adapted to keep the short terminal  4  and the long terminal  5  from contacting one another and is adapted to be inserted into the top of the housing  2 . An electrically non-conductive washer  7  may be placed between the terminal insulator  6  and the top of the housing  2 . This washer  7  may serve to electrically isolate the terminal insulator  6  from the top of the housing  2  as well as seal the interface between the terminal insulator  6  and the top of the housing  2  against moisture and other contaminants. The terminal insulator  6  may be crimped in place. 
         [0032]    The long terminal  5  extends from the top of the terminal assembly  3  through the terminal insulator  6  to engage with and partially compress the inner compression coil  9 . Thus, the long terminal  5  is electrically connected to the top of the thermistor  10  via the inner compression coil  9 . The short terminal  5  extends from the top of the terminal assembly  3  partially through the terminal insulator  6  and against and partially compressing the outer compression coil  8 . Thus, the short terminal  5  is electrically connected to the bottom of the thermistor  10  via the outer compression coil  8  and formed conductor  12 . 
         [0033]    The compression of the inner compression coil  9  presses the thermistor  10  firmly against the bottom of the formed conductor  12  to ensure good electrical contact for completing the circuit. The thermistor  10  is also positioned very close to the bottom of the temperature sensor  1  both in close thermal proximity to the operating environment and having good thermal transfer with the pedestal  26  to provide a very accurate temperature reading. 
         [0034]      FIG. 4  illustrates embodiments of the components of the temperature sensor  1  and how they are assembled. Assembly is made simple so that it may be accomplished by the end user of the two-terminal temperature sensor. The following components may be placed sequentially in the housing  2  through the open top: the insulating disk  14  may be placed against the closed bottom of the housing  2  on the pedestal  26 ; the outer insulating tube  13  may be situated over the insulating disk  14  and adjacent the closed bottom of the housing  2  around the pedestal  26 ; the formed conductor  12  may be placed inside the outer insulating tube  13  and adjacent the insulating disk  14 ; the inner insulating tube  11  may be placed inside and adjacent the bottom of the formed conductor  12 ; the thermistor  10  may be placed inside the insulating tube  11  and adjacent the bottom of the formed conductor  12 ; the inner compression coil  9  may be placed inside the insulating tube  11  and adjacent the top of the thermistor  10 ; the outer compression coil  8  may be placed inside the outer insulating tube  13  and adjacent the top of the formed conductor  12 ; a washer  7  may be placed inside the housing  2  and adjacent the top of a shoulder inside the housing  2  just above the hexagonal interface  25 ; and the terminal assembly  3  may be compressed against the washer  7 , outer compression coil  8 , and inner compression coil  9  while crimping the top rim of the housing  2  against a groove in the outer surface of the terminal assembly  3 . 
         [0035]      FIG. 5  illustrates embodiments of the components of the terminal assembly  3  and how they are assembled. The terminal assembly  3  may comprise the short terminal  4 , long terminal  5 , terminal insulator  6 , and terminal divider  15 . The terminal insulator  6  and terminal divider  15  may be molded together from a non-conductive material. Alternatively, the terminal divider  15  may be formed separately and attached to the terminal insulator  6 . The short terminal  4  and long terminal  5  are inserted in apertures running through the terminal insulator  6  on each side of the terminal divider  15 . As a result, the short terminal  4  and long terminal  5  protrude from the bottom and the top of the terminal insulator  6 . The short terminal  4  and long terminal  5  are secured in place by any available means, for example adhesive, overmoulding of the terminal insulator  6 , bolts, screws, or press-fitting. 
         [0036]      FIGS. 6A-6D , and  7 A- 7 D illustrate various styles of terminal assemblies for use with various electrical connectors.  FIGS. 6A-6D  illustrate a terminal assembly  3  with a Packard type connector. In this embodiment, a molded female connector  19  extends from the terminal insulator  6  and has a short terminal  20  and long terminal  21  molded in the terminal assembly  3 . A boss  22  for holding a mating male clip may be molded to the side of molded female connector  19 . 
         [0037]      FIGS. 7A-7D  illustrate a terminal assembly  3  with threaded terminal connectors. In this embodiment, a short threaded terminal  17  and a long threaded terminal  18  provide a screw-type connection and are molded in terminal insulator  6  and isolated from one another by terminal divider  15 . Screws  23  thread into the short threaded terminal  17  and long threaded terminal  18  to allow for a crimp-on wire terminal, for example, to be attached. These are just a few examples of possible electrical connectors that may be used in conjunction with the two-terminal temperature sensor. Other electrical connectors are contemplated, for example, various plug and socket connectors and soldered connections. 
         [0038]    All directional references (e.g., proximal, distal, upper, lower, upward, downward, left, right, lateral, front, back, top, bottom, above, below, vertical, horizontal, clockwise, and counterclockwise) are only used for identification purposes to aid the reader&#39;s understanding of the present invention, and do not create limitations, particularly as to the position, orientation, or use of the invention. Connection references (e.g., attached, coupled, connected, and joined) are to be construed broadly and may include intermediate members between a collection of elements and relative movement between elements unless otherwise indicated. As such, connection references do not necessarily infer that two elements are directly connected and in fixed relation to each other. The exemplary drawings are for purposes of illustration only and the dimensions, positions, order and relative sizes reflected in the drawings attached hereto may vary. 
         [0039]    The above specification, examples, and data provide a complete description of the structure and use of exemplary embodiments of the invention. Although various embodiments of the invention have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the spirit or scope of this invention. Other embodiments or implementations are therefore contemplated. It is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative only of particular embodiments and not limiting. Changes in detail or structure may be made without departing from the basic elements of the invention as defined in the following claims.