Abstract:
A compact industrial process transmitter is provided having an electronics module that includes a top surface with a plurality of lead attachment points thereon. At least one of the lead attachment points disposed on the top surface of the compact temperature transmitter electronics module includes a upwardly extending external lead attachment clip. In some aspects, a plurality of upwardly extending lead attachment clips as well as lead attachment points that have a lead wire engaging surface that is substantially flush with or raised above the top surface of the compact temperature transmitter electronics module.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to process transmitters. More specifically, the present invention relates to compact process transmitters.  
       BACKGROUND OF THE INVENTION  
       [0002]     The process industry employs process variable transmitters to monitor process variables associated with substances such as solids, slurries, liquids, vapors, and gasses in chemical, pulp, petroleum, pharmaceutical, food and other processing plants. Process variables include pressure, temperature, flow, level, turbidity, density, concentration, chemical composition and other properties. A process fluid temperature transmitter provides an output related to a sensed process fluid temperature. The temperature transmitter output can be communicated over a process communication loop to a control room, or the output can be communicated to another process device such that the process can be monitored and controlled. In order to monitor a process fluid temperature, the transmitter includes a sensor, such as a resistance temperature device (RTD) or thermocouple.  
         [0003]     One specific type of temperature transmitter is known as a head-mount temperature transmitter. Such a transmitter generally includes a connection head or junction box that is ruggedized for exposure to harsh environments. The connection head can be designed in accordance with the criteria of current DIN standard 43 729 Form B. Such design is relatively smaller than other process variable transmitter enclosures. The smaller design facilitates transmitter mounting in crowded installation environments. Further, the smaller design also provides a smaller mass coupled to the sensor probe. Such mass reduction reduces the possibility of vibration damage occurring in the transmitter.  
         [0004]     The connection head, or junction box can be explosion-proof in conformance with NEC Sections 500-503, dated 1996. Typically, an electronics module is placed within the connection head and mounted with fasteners to provide a transmitter that is highly modular. Such modularity facilitates transmitter configuration changes as well as maintenance. An example of such a head-mount temperature transmitter is the Model 248 Temperature Transmitter available from Rosemount, Inc. of Eden Prairie, Minn.  
         [0005]     This connection head size limitation puts severe constraints on the types of lead connections that are available within the transmitter. Traditionally, terminal blocks have been used for connecting sensor, communication, and/or power leads to the transmitter electronics itself. Additionally, some known compact temperature transmitters also provide external lead attachment clips to facilitate the attachment of external leads by a technician to the electronics module for maintenance and/or diagnostics. These known attachments have suffered from certain drawbacks.  
         [0006]     Known external lead attachment clips have generally undesirably expanded the physical envelope of the electronics package. This is because such clips generally provided additional metallic loops which extend beyond the diameter of the electronics package. In industrial processing control environments employing compact transmitters such as those which comply with DIN standard 43 729 Form B, such expansion of the physical envelope is highly undesirable.  
         [0007]     The provision of a compact process transmitter that is able to comply with the stringent space constraints of DIN standard 43 729 Form A or Form B while facilitating lead attachments and while providing external lead attachment clips that do not undesirably expand the physical envelope of the electronics module would be desirable to the art.  
       SUMMARY OF THE INVENTION  
       [0008]     A compact industrial process transmitter is provided having an electronics module that includes a top surface with a plurality of lead attachment points thereon. At least one of the lead attachment points disposed on the top surface of the compact temperature transmitter electronics module includes an upwardly extending external lead attachment clip. In some aspects, a plurality of upwardly extending lead attachment clips are provided. Additionally, some lead attachment points can have a lead wire engaging surface that is substantially flush with or raised above the top surface of the compact transmitter electronics module. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a diagrammatic view of a compact temperature transmitter in which embodiments of the present invention are particularly useful.  
         [0010]      FIGS. 2A and 2B  are top plan and front elevation views of a compact temperature transmitter electronics module in accordance with embodiments of the present invention.  
         [0011]      FIG. 3  is a perspective view of a single lead attachment point and upwardly extending external lead attachment clip in accordance with embodiments of the present invention.  
         [0012]      FIGS. 4A and 4B  are perspective views of an upper lead engagement plate and lower lead anchor with in accordance with embodiments of the present invention.  
         [0013]      FIGS. 5A and 5B  are perspective and front elevation views of a lower lead anchor having an upwardly extending lead attachment clip in accordance with embodiments of the present invention.  
         [0014]      FIG. 6  is a side elevation cross section view of the lead attachment anchor illustrated in  FIGS. 5A and 5B  deployed on a compact temperature transmitter electronics module.  
         [0015]      FIG. 7  is a perspective view of a lower lead attachment anchor in accordance with an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]     Although the present invention will be described with reference to embodiments of a specific compact temperature transmitter, workers skilled in the art will recognize that embodiments of the present invention may be practiced with any compact industrial process measurement and/or control transmitters without departing from the spirit and scope of the invention.  
         [0017]     As used herein a “compact” transmitter is intended to mean any industrial control and/or measurement transmitter employing a transmitter electronics module that is substantially circular in shape having a diameter of approximately 1.7 inches (45 millimeters) or smaller and a height of 0.97 inches (24.5 millimeters) or less. This physical envelope will ensure that the module will fit within a transmitter head specified in DIN Standard 43 729 (1978)  
         [0018]      FIG. 1  is a diagrammatic view of compact industrial measurement and control transmitter  10  in accordance with embodiments with the present invention. Transmitter  10  usually includes a field hardened enclosure, sometimes referred to as a connection head  12 , probe portion  14  containing therein a suitable industrial sensor, such as a temperature sensor  16 , and wiring access port  18 . Transmitter  10  also includes, disposed within connection head  12 , compact transmitter electronics module  20  electrically coupled to sensor  16  via wires  21 . In operation, transmitter  10  is generally mounted within an industrial process control and measurement installation and coupled to a process control and measurement loop through access port  18 .  
         [0019]      FIGS. 2A and 2B  are top plan and front elevation views, respectfully, of compact transmitter electronics module  20  in accordance with embodiments of the present invention. As illustrated in  FIG. 2A , module  20  is preferably circular in shape and has an outer diameter that is approximately 44 millimeters or less. Additionally, compact transmitter electronic module  20  includes a number of lead attachment points  23  disposed on, or near top surface  24  of module  20 . Lead attachment points  23  as used herein are physical locations on the electronics module that couple to leadwires. Module  20  is also adapted to receive a pair of spring loaded mounting screws  26  that are used to mount module  20  within connection head  12  (shown in  FIG. 1 ). Finally, compact transmitter electronic module  20  also includes through-hole  28  which is provided to facilitate connection to sensor wiring, which sensor(s) are generally disposed below module  20 , as illustrated in  FIG. 1 .  
         [0020]      FIG. 3  is a perspective view of a lead attachment point  23  in accordance with embodiments of the present invention. Lead attachment point  23  generally includes a molded cavity  30  that is molded into or disposed upon the top surface  24  of compact transmitter electronics module  20 . Screw  32 , upper washer  34 , and anchor  36  are positioned within molded cavity  30 . Also illustrated in  FIG. 3  is upwardly extending external lead attachment clip  38 . In order to couple a lead wire to lead attachment point  23 , screw  32  is withdrawn to such an extent that a gap will form between upper plate  34  and anchor  36  that is large enough to accommodate the lead. The lead is than inserted between upper plate  34  and anchor  36  and screw  32  is rotated to bear against upper plate  34  thereby compressing and retaining the lead within and between upper plate  34  and anchor  36 . External lead attachment clip  38  can be provided on one or all of lead attachment points  23 . Moreover, as will be described in further detail later in the specification, external lead attachment clip  38  can be constructed as a part of anchor  36 , plate  34  or screw  32 .  
         [0021]      FIGS. 4A and 4B  illustrate upper plate  40  and anchor  42  that can cooperate in accordance with embodiment of the present invention. Upper plate  40  generally includes a screw engaging surface  44  and upwardly extending external lead attachment clip  46  disposed on one side of plate  40 . As illustrated in  FIG. 4A  the upwardly extending external lead attachment clip  46  may be in the form of an upwardly extending loop ( 46  as illustrated in  FIG. 4A ) or an upwardly extending hook ( 38  illustrated in  FIG. 3 ). Hooks and loops allow module  20  to be easily coupled to an external handheld field communications/diagnostic device. Moreover, hooks and clip allow the connection to be made in such a manner that the leads will not fall off, thus allowing the technician to perform other tasks without having to hold the leads in place. Plate  40  also includes through-hole  48  that is sized to pass a standard attachment screw such as screw  32  illustrated in  FIG. 3 .  
         [0022]      FIG. 4B  is a perspective view of anchor  42  with which mounting plate  40  can be used to practice an embodiment of the present invention. Anchor  42  includes electrical attachment tang  50  coupled to bottom plate region  52  which is in turn coupled to anchor tab  54 . Bottom plate region  52  also preferably includes an integral threaded sleeve  56  that is adapted to threadably receive a standard attachment screw, such as screw  32 . In operation, anchor  42  is disposed firmly within a junction block and upper plate  40  sits atop anchor  42 . A lead wire is passed between upper plate  40  and anchor  42  and is urged against anchor  42  by virtue of the lead attachment screw passing freely through clearance hole  48  and threadably securing within sleeve  56 .  
         [0023]      FIGS. 5A and 5B  are perspective and front elevation views of an alternate lead attachment anchor in accordance with an alternate embodiment of the present invention. As illustrated in  FIG. 5A  an upwardly extending external lead attachment clip  60  is coupled directly to anchor  62  which otherwise substantially resembles anchor  42  illustrated and described with respect to  FIG. 4B . The provision of clip  60  in anchor  62  allows standard upper mounting plates or even round washers to be used to connect lead wires.  
         [0024]      FIG. 6  is a cross sectional side elevation view of anchor  62  deployed within compact transmitter electronics module  20  in accordance with embodiment of the present invention. Transmitter module  20  includes upper transmitter surface  24  which is preferably, as illustrated in  FIG. 6 , substantially coplanar with upper lead engaging surface  64  of anchor  62 . Anchor  62  also includes anchor tab  54  which is cooperatively disposed within slot  66  in transmitter module  20  such that anchor  62  does not rotate when screw  32  is rotated. Beneath the head of screw  32  is a flat washer  68  that is used to bear against a lead wire (not shown) to electrically connect and physically couple the lead wire to the transmitter. Preferably, an upwardly extending external lead attachment clip  60  is included to facilitate coupling the lead to external maintenance and/or diagnostics devices. Such devices are very useful for configuring field devices; troubleshooting problems with field devices or performing any other type of maintenance as may me be appropriate.  
         [0025]      FIG. 7  is a diagrammatic view of lead anchor  70  in accordance with an alternate embodiment of the present invention. Lead anchor  70  is substantially identical to lead anchor  62  illustrated and described with respect to  FIGS. 5A and 5B  except that lead anchor  70  includes a external lead attachment clip  72  that is in the form of a hook.  
         [0026]     Although the present invention has been described with reference to specific embodiments of a head-mount type process temperature transmitters, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. While embodiments of the present invention have generally provided an external lead attachment clip connected to and integral with either a mounting plate or an anchor of a lead junction block connection, it is expressly contemplated that embodiments of the present invention can be practiced using a sufficiently adapted lead attachment screw and standard mounting plates and anchors. Specifically, a screw having a screw head that has an upwardly extending lead attachment clip region would provide benefits of the present invention as long as the screw is still adapted to receive sufficient torque such that it could be tightened by an appropriate tool.