Patent Publication Number: US-2005127895-A1

Title: Current sensor wire clamp

Description:
PRIORITY  
      This application claims priority to U.S. Provisional Patent Application 60/528,449, filed Dec. 10, 2003. 
    
    
     BACKGROUND  
      Individuals that work with electrical wiring and circuits are often interested in knowing the amount of electrical current flowing through a particular conductor. Convenient tools for measuring the current flowing through a conductor include the Hall effect current sensor, the toroidal core current sensor and split core sensors (collectively, the split core sensors and toroidal core sensors are also known as “current transformers”). Current transformers and Hall effect devices are electromagnetic sensors that measure current based upon the principle that a current carrying conductor produces a magnetic field.  
      With reference to  FIG. 6 , a typical prior art current sensor includes a housing  110  with a channel  118  formed therethrough. A current transformer (not shown) is positioned within the housing and surrounds the channel  118 . A toroidal core may be positioned around the channel  118  within the housing  110 . The current transformer is connected to leads designed to carry a current to an analyzer. Alternatively, a toroidal core current sensor may comprise a toroidal coil wound around the core.  
      When utilizing these current sensors, the technician typically threads the cable or other conductor carrying the current to be tested through the channel formed in the housing. When alternating current flows through the cable, the changing magnetic field created by the alternating current induces a current on the current transformer. This current flowing through the current transformer is related to the current flowing through the conductor. The current flowing through the current transformer may be analyzed for its relationship to the current flowing through the cable. For example, to take a correct reading using Hall effect current sensors, the current sensor needs to remain relatively stationary with respect to the cable from which current is being measured, and it is important to keep the orientation of the Hall effect sensor consistent with respect to the wire. Most prior art current sensors require the technician to hold the current sensor stable upon the cable to make sure that it remains stationary and in the proper orientation. Alternatively, the technician can place the current sensor on the ground or hang the current sensor from the cable and try to make sure that the cable remains stationary when a reading is taken. Unfortunately, this is not easily accomplished, especially if the cable will be prone to movement as the technician works on and tests the electrical circuit that comprises the cable. Therefore, it would be desirable to provide a Hall effect sensor that can maintain its position relative to the cable without assistance from a technician.  
      Additionally, a Hall effect sensor may also be permanently attached to a particular cable to continuously monitor the current passing through the cable, with the Hall effect sensor in communication with a monitoring device. Therefore, in circumstances where the Hall effect sensor is in communication with a monitoring device, a technician is not available to maintain the position of the sensor in relation to the cable. For all current transformers and Hall effect sensors, it is often desirable to take a sensor reading with the current sensor suspended upon a vertical hanging or inclined cable. If the current sensor is not retained in place upon the cable, the current sensor may slide down the cable and next to other equipment that may interfere with the reading of the current sensor, or the orientation of the sensor may not be ideal. Accordingly, it would be advantageous to provide a current sensing device that may be secured to a cable without placing undue tension on the cable. Further, it is desirable to provide a current sensing device that may be releasably secured to a cable without the need for a tool to disengage the cable, thereby allowing a technician to remove the sensor from the cable after testing is complete.  
     SUMMARY  
      The embodiments of the present invention relate to an apparatus for sensing current in a wire or cable, and specifically to an apparatus that is capable of securing itself in a proper orientation to the wire or cable it is sensing without additional support from a technician. In particular, one embodiment of the present invention relates to a current sensor for sensing current in a wire. The current sensor in this embodiment comprises a housing that has a channel through the channel being large enough so that a wire can fit through the channel; and a core inside the housing, the core positioned so that the core surrounds the channel. The sensor further comprises a jaw rotatably mounted to the housing, the jaw attached to the housing by a pivot pin. The jaw is operable to reduce the size of the channel by rotating the jaw in one direction. Additionally, the jaw has a pawl that can engage a number of notches that are on the face of the housing, the pawl and notches operable to allow movement of the jaw in one direction, but restrict movement in the opposite direction.  
      Optionally, the pawl of the current sensor may also comprise a flange operable to disengage the pawl from a notch when an upward force is applied to the flange. Further, the upward force may be applied without the aid of a tool by using, for example, a finger or other digit. Further, the jaw may operably rotate at an angle perpendicular to the axis of a wire within the channel, and the jaw may engage the wire without penetrating an insulating sheath around the wire. In at least one embodiment, the jaw may comprise a convex or concave surface.  
      In a second embodiment of the present invention, a current sensor for sensing current in a wire includes a housing having a channel therethrough of a size large enough to accommodate a wire. The channel would pass through the housing, and a core would surround the channel. Further, the current sensor would have a core surrounding the channel, and a jaw mounted to rotate about a pivot pin. The jaw would be operable to reduce the size of the channel or a channel opening as the jaw is rotated about he the pivot pin. The jaw would also have a pawl operable to engage several notches located on a face of the housing, with the pawl further comprising a flange operable to disengage the pawl from a notch when upward force is applied to the flange. Thus, when upward force is applied to the flange, the jaw is allowed to move in both directions about the pivot pin.  
      Optionally, the current sensor of the second embodiment could have a jaw that rotates at an angle perpendicular to the axis of a wire within the channel. Another option of this embodiment includes the ability for jaw to engage the wire without perforating an insulating sheath around the wire.  
      A third embodiment of the present invention is a current sensor for sensing current in a wire comprising a housing having a channel, with the channel having at least one open side that allows a wire to be inserted into the channel without breaking a complete circuit. Further, to allow the channel to have at least one open side, the sensor has a core comprising at least two portions. The two portions of the core are positioned around the closed side of the channel through its center when the at least two portioned are aligned to form a continuous loop. Additionally, the sensor includes a slidable housing cover that can operate to allow the at least two portions of the core to be moved relative to one another so that the channel is accessible from at least one side when the housing is placed in a first position, and operable to allow full contact between the first and second core portions to form a continuous loop when the housing is in a second position. Moreover, the sensor includes a jaw rotatably mounted to the housing about a pivot pin so that the jaw can reduce the size of at least one opening of the channel as the jaw is rotated about the pivot pin. Finally, the jaw includes a pawl mounted thereon and operable to engage the several notches located on a face of the housing, with the pawl further including a flange operable to disengage the pawl from the notches when upward force is applied to the flange. When upward force is applied to the flange, the jaw may be moved in both directions about the pivot pin.  
      Optionally, the flange of current sensor of this third embodiment may be manually operable to disengage the pawl without the aid of a tool. Additionally, a the jaw may rotate in a plane perpendicular to a longitudinal axis of the wire running through the channel.  
      According to a fourth embodiment of the present invention, a current sensor for sensing current in a wire may include a housing having a channel formed therethrough, with that channel having at least one open side that allows a wire to be placed within the channel without breaking a completed circuit. Further, the sensor includes a Hall effect sensor within the housing, operable to sense the current of the wire within the channel. Further, the sensor includes a jaw rotatably mounted to the housing by a pivot pin. The jaw is operable to engage a wire within the channel so that the wire is positioned against an inside wall of the channel as the jaw is rotated about the pivot pin. Further, the jaw includes a pawl mounted to the jaw and operable to engage a plurality of notches located on a face of the housing, with the pawl further comprising a flange operable to disengage the pawl from the notches when an upward force is applied to the flange, thereby allowing movement of the jaw in both directions about the pivot pin. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  shows a side plan view of one embodiment of a Current Sensor Wire Clamp;  
       FIG. 2  shows a perspective view of the Current Sensor Wire Clamp of  FIG. 1 ;  
       FIG. 3  shows an enlarged cross-sectional view of a pawl located on the Current Sensor Wire Clamp along line III-III of  FIG. 1 ;  
       FIG. 4  shows a perspective view of an alternative embodiment of the Current Sensor Wire Clamp of  FIG. 5  with the moveable bar positioned in the channel; and  
       FIG. 5  shows a top plan view of an alternative embodiment of a Current Sensor Wire Clamp with a moveable bar removed from the channel;  
       FIG. 6  shows a perspective view of a typical prior art current sensing device.  
       FIG. 7  shows a top plan view of an alternative embodiment of the Current Sensor Wire Clamp wherein the sensor employed is a Hall effect sensor.  
       FIG. 8  shows a perspective view of an alternative embodiment of the Current Sensor Wire Clamp wherein the sensor employed is a Hall effect sensor. 
    
    
     DESCRIPTION  
       FIGS. 1 and 2  show one embodiment of a current sensor wire clamp including a housing and a cam device for securing the current sensor to a cable. The current sensor housing  10  includes a front face  12  and a back surface  14  with sidewalls  16  extending therebetween. The face  12  and back surface  14  are substantially parallel. The sidewalls  16  are substantially perpendicular to the face  12  and the back surface  14 .  
      A channel  18  is formed through the housing  10  from the face  12  to the back surface  14 . The channel  18  may be substantially cylindrical in shape, and is designed to receive a cable or other conductor carrying current to be measured. The central axis of the channel defines an axis  30  where the cable is intended to be inserted. As is standard in the art, a current transformer (not shown) is positioned within the housing  10  such that the current transformer surrounds the channel  18 , yet remains encased within the housing. This current transformers may take many embodiments, such as a core and toroidal coil, a core and bobbin coil, or other current transformers used in the art.  
      A clamp  20  is positioned upon the face  12  of the housing  10 . The clamp  20  comprises a jaw  22  that is rotatably connected to the face  12  of the housing by a pivot pin  26 . The jaw  22  is rotatable around the pivot pin  26  such that the jaw  22  rotates substantially parallel to the face  12  and substantially perpendicular to the axis  30 . The jaw  22  is generally curvilinear in its shape, with a sloping cable engagement surface  32 , and jaw  22  may also take the shape of a cam, or may be convex, or concave in nature. Cable engagement surface  32  slopes to allow greater retention of the wire within the channel when jaw  22  is engaging wire coating and wedging the wire against the interior walls of channel  18 . When the jaw  22  is rotated about the pivot pin  26 , the sloping cable engagement surface  32  gradually decreases the size of the opening  34  of channel  18  as it bisects the axis  30 . The jaw  22  is slightly thicker at the cable engagement surface  32  than other portions of the jaw  22 . The jaw  22  is secured by the pivot pin point  26  which may comprise a screw, bolt, rivet or other fastening means that allows the jaw  22  to pivot freely.  
      A pawl  24  is positioned in a slot  28  formed in jaw  22 . As shown in  FIG. 3 , the pawl  24  includes a first arm  48  that extends outward from the jaw  22  within the slot  28  and a second arm  36  that extends substantially perpendicularly to first arm  48  upward from the surface of the jaw  22 . A flange  38  extends substantially perpendicularly from the second arm  36 . The pawl  24  also includes a tip  40  with a sloped surface  42  that generally forms an acute angle with respect to the arm  48 . The pawl  24  is allowed to pivot with respect to the jaw  22  as the first arm  48  flexes up and down with respect to the jaw  22 .  
      A series of notches  44  (partially obstructed) are formed on the surface of the face  12  of the housing and form a ratchet surface designed to engage the tip of the pawl. The notches  44  are spaced radially upon the face  12  of the housing concentric with the pivot pin. Each notch is separated from the adjacent notch to allow the tip  40  of the pawl  24  to enter the space between the notches. When the tip  40  of the pawl  24  engages the notches  44 , the jaw  22  may be rotated clockwise, but counterclockwise rotation is prevented. However, upward movement of the flange  38 , away from the jaw  22  will cause the tip  40  of the pawl  24  to disengage the notches  44 , and the jaw  22  may then be rotated either clockwise or counterclockwise around the pivot pin  26 . A small lip  46  is also positioned upon the jaw  22  such that it extends above the surface of the jaw  22 . The lip  46  is useful to assist with rotation of the jaw  22  around the pivot pin  26 , as it provides a larger surface that may be grasped by the user or pushed either clockwise or counterclockwise.  
      In operation, an electrical technician interested in knowing the current flowing through a cable first rotates the jaw  22  in a clockwise manner so the jaw  22  does not block the opening  34  to the channel  18 . The technician then inserts the cable through the channel  18  of the housing  10  and again rotates the jaw  22  clockwise until the cable engagement surface  32  is firmly positioned against the cable, causing an opposing pressure on the conductor by the channel wall  18 . Because of the ratchet action between the notches  44  on the face  12  of the housing  10  and the pawl  24 , the jaw  22  is prevented from moving in the counterclockwise direction and firmly clamps the current sensor to the cable. With the current sensor firmly joined to the cable, the technician is free to take current measurements, knowing that the current sensor will remain in place upon the cable.  
      An alternative embodiment is shown in  FIGS. 4 and 5 . This alternative embodiment of the invention is generally described using the same reference numerals that were used to refer to the embodiment associated with  FIGS. 1-3 . As shown in  FIG. 4 , the current sensor includes a housing  10  having a face  12  and sidewalls  16 . A channel  18  is formed through the housing. Unlike the embodiment shown in  FIGS. 1-3 , this channel  18  is not enclosed and is a U-shaped indentation in the side of the housing. A moveable bar  52  can be slid to close channel  18  once a wire is inserted. Accordingly, the coil and any core positioned within the housing surrounding the channel is U-shaped and the moveable bar  52  completes a toroidal assembly. The moveable bar  52  includes a portion of the magnetic core and when the bar  52  is moved into place in the channel  18  (as shown in  FIG. 5 ), the magnetic core of the current sensor is completed. The moveable bar  52  may take a number of different forms such as a sliding bar or hinged bar. This core configuration comprises more than one portion that may be moved in relation to one another, and thereafter moved back into position so that the two portions are brought back into physical contact with one another to allow the current sensor to operate.  
      In operation, when the U-shaped channel is accessible (as shown in  FIG. 5 ), the sensor core is open, and the current sensor is inoperable. However, having the channel accessible, the current sensor can be placed over a wire without having to cut the wire and re-establish the wire&#39;s connection to complete the circuit. Once the wire is placed within the U-shaped channel along the axis  30 , sliding bar  52  can be placed in the closed position as shown in  FIG. 4  to allow the current sensor core to surround the wire and determine the current flowing through the wire. When in the closed position, the core is complete, and the sliding bar  52  is snapped into a locked position, as squeeze locks  54  snap into corresponding reliefs (not shown) in housing  10 . Sliding bar  52  can then be released by placing opposing force on the squeeze locks  54  and pulling sliding bar away from the closed position. Therefore, the current sensor of the present embodiment can be applied to a wire without disassembling an existing circuit by simply disengaging bar  52  to expose U-shaped channel  18 , sliding the wire into the channel, and closing bar  52  as shown in  FIG. 4 .  
      Additionally, it is contemplated that this embodiment of the current invention can be stabilized upon the wire to allow for accurate current sensing without requiring the technician to hold the sensor in place. With reference to  FIGS. 4 and 5 , a clamp  20  is also located upon the housing, including a jaw  22  having a cable engagement surface  32 . This jaw  22  is generally formed as a portion of a circle, and includes a claw-like protuberance  50  that forms the cable engagement surface  32 . A pawl  24  is positioned upon an edge of the jaw  22  and includes an arm  36  with an associated flange  38 , as well as a tip (not shown) similar to tip  40  shown in  FIG. 3 , that is designed to engage notches  44  located on the face  12  of the housing. The notches on the surface of the face are dimensioned and are generally radially positioned concentric with a pivot pin  26  of the jaw  22 . The jaw  22  may be rotated upon the face  12  of the housing  10  such that the cable engagement surface  32  moves perpendicularly across the axis  30  of the channel. When a cable is located in the channel  18 , the jaw  22  may be rotated clockwise and placed snugly against the cable, causing an opposing pressure on the conductor by the wall of channel wall  18 , but counterclockwise rotation of the jaw  22  is prohibited by the ratchet effect formed between the pawl tip and the notches  44 . If the flange  38  is moved away from the face (for example by a technician pulling upward on the flange with his finger), the pawl tip is released from the notches  44 , and the jaw  22  may rotate freely, thereby allowing the cable to be released by rotating the jaw  22  in a counterclockwise rotation.  
      Referring now to  FIGS. 7 and 8 , another embodiment of the present invention contemplates the use of a Hall effect sensor with housing  10 . This alternate embodiment of the invention is generally described using the same reference numerals that were used to refer to the embodiment associated with  FIGS. 4 and 5 , and this alternate embodiment resembles the previous embodiment with the exception that there is no need for sliding bar  52  due to the fact that a Hall effect sensor, such as the Hall plate sensor supplied by Micronas Technology Group, located at Technopark Technoparkstrasse 1, CH-8005 Zurich Switzerland, does not require the use of a core that surrounds the wire to be sensed. Instead, the Hall effect sensor (not shown) within housing  10  simply should be placed in an orientation so that the Hall plate is maintained so that its flat plate surface is kept parallel to the wire to be sensed when jaw  22  is closed upon the wire.  
      With reference to  FIGS. 7 and 8 , a clamp  20  is also located upon the housing, including a jaw  22  having a cable engagement surface  32 . This jaw  22  is generally formed as a portion of a circle, and includes a claw-like protuberance  50  that forms the cable engagement surface  32 . A pawl  24  is positioned upon an edge of the jaw  22  and includes an arm  36  with an associated flange  38 , as well as a tip (not shown) similar to tip  40  shown in  FIG. 3 , that is designed to engage notches  44  located on the face  12  of the housing. The notches on the surface of the face are dimensioned and are generally radially positioned concentric with a pivot pin  26  of the jaw  22 . The jaw  22  may be rotated upon the face  12  of the housing  10  such that the cable engagement surface  32  moves perpendicularly across the axis  30  of the channel. When a cable is located in the channel  18 , the jaw  22  may be rotated clockwise and placed snugly against the cable, causing an opposing pressure on the cable by the wall of channel wall  18 , but counterclockwise rotation of the jaw  22  is prohibited by the ratchet effect formed between the pawl tip and the notches  44 . If the flange  38  is moved away from the face (for example by a technician pulling upward on the flange with his finger), the pawl tip is released from the notches  44 , and the jaw  22  may rotate freely, thereby allowing the cable to be released by rotating the jaw  22  in a counterclockwise rotation. Of course, housing  10 , channel  18 , and jaw  22  may take many forms in this embodiment, with the aim that jaw  22  places wire against the inside wall of channel  18  so that the Hall effect sensor (not shown) within housing  10  remains stationary and in proper orientation with the wire or cable being sensed. Therefore, channel  18  may take the shape of a curved wall upon which jaw  22  traps a cable against, two angled walls wherein jaw  22  traps the wire within the angle formed by the intersection of the two walls, or a flat surface against which jaw  22  engulfs the cable against, limiting movment of the cable by the engaging surface  32  of jaw  22 , or several other shapes and configurations that will be apparent to one of ordinary skill in the art.  
      Although the present invention has been described in considerable detail with reference to certain preferred versions thereof, other versions are possible. For example the clamp could include multiple jaws instead of a single jaw. In addition, the jaw  22  need not rotate about a single pivot pin  26 , but could be designed to move back and forth in a linear fashion. Therefore, the spirit and scope of the invention should not be limited to the description of the preferred versions contained herein.