Abstract:
A grounding clamp includes a safety lock-out which locks the operation of the clamp in the absence of a hot-stick. A clamping member cooperates with a frame having an arm, and is selectively biasable by a user to translate the clamping member relative to the frame to clamp a conductor between the clamping member and arm. The lock-out cooperates with the clamping member to prevent the translation of the clamping member unless in the presence of an insulating tool such as a hot-stick.

Description:
FIELD OF THE INVENTION 
       [0001]    The present disclosure is generally in the field of grounding clamps used for grounding high voltage conductors. More particularly, the present disclosure relates to grounding clamps which have locks that are actuable through the use of an insulated line tool. 
       BACKGROUND 
       [0002]    Electrical workers use grounding cables on an almost daily basis in the industry to help manage dangerous voltages and currents in de-energized power lines and electrical equipment. Grounds are designed to be installed and removed using an insulating tool, for example an insulating tool called a Grip-All stick or Shotgun, to keep the worker at a safe distance from the hazard. 
         [0003]    When installing grounds, the first connection is always made to a ground point. Workers will normally make this connection by hand instead of with the insulating tool, as there is no hazardous energy when making this connection. 
         [0004]    Any time a connection is made to a conductor or apparatus that could be at a different electrical potential from ground, this connection must be made using an insulating tool. This is especially true in a high voltage environment (for example, over 69 Kv). Due to the design of conventional ground clamps, they can be installed and removed by hand instead of being installed using an insulating tool. It is not uncommon in applicant&#39;s experience for workers to make the mistake of installing a ground clamp on a conductor, or removing one from a conductor by hand instead of with an insulating tool. This potentially exposes the worker to a voltage potential and consequently may result in electrocution of the worker. To applicant&#39;s knowledge, this has accounted for fatalities and electrocution incidents in the industry. 
         [0005]    Consequently, there is a need in the industry for a locking ground clamp that operates in combination with an insulating tool so as to prevent the worker or lineman from being able to operate the ground clamp without the use of the insulating tool. This is to inhibit workers or linemen from attempting to install the ground clamp by hand. To accomplish this a locking mechanism is described below which prevents manual operation of the ground clamp as the ground clamp can only be actuated or un-locked with or in the presence of the insulating tool. 
       SUMMARY 
       [0006]    A grounding clamp includes a safety lock-out which locks the operation of the clamp in the absence of a hot-stick. The clamp includes a frame and a first clamping member defining a capture cavity and an opening. The opening provides access into the cavity for a conductor to be captured in the cavity. The first clamping member cooperates with the frame, and is selectively biasable by a user between an unclamped position wherein the clamping member is retracted and a clamped position wherein by translation of the first clamping member relative to the frame the conductor is clamped between the first clamping member and an arm or second clamping member on the frame when the conductor is positioned in the cavity. The lock-out has first and second positions and cooperates with the first clamping member to prevent the selective biasing of the first clamping member from the unclamped position to the clamped position when the lock-out is in the first position. The lock-out is normally biased into the first position. In the second position, the selective biasing of the first clamping member to the clamped position is enabled. A hot-stick head is mountable onto, or mounted on, an end of the hot-stick or other insulating tool (collectively referred to herein as a hot-stick). The hot-stick head is adapted to couple onto the frame and to cooperate with the lock-out to bias the lock-out into the second position when the head is coupled with the frame. 
         [0007]    In an embodiment of the present disclosure, the second clamping member is in opposed facing relation to the first clamping member, and located at an opposite end of the frame from the first clamping member. The first clamping member includes a threaded bore. A correspondingly threaded shaft is rotatably journalled in the threaded bore, whereby rotation of the shaft in the bore translates the first clamping member relative to; that is away from or towards, the second clamping member. The frame includes a first couple. The hot-stick head includes a second couple couplable with the first couple on the frame whereby the head of the hot-stick is selectively and detachably coupled onto the frame. 
         [0008]    In an embodiment of the present disclosure, the lock-out includes a ferrous member resiliently biased into a first position and the hot-stick head includes a magnet cooperating with the ferrous member to magnetically bias the ferrous member, and thereby the lock-out, into the second position when the head is coupled with the frame. 
         [0009]    In an embodiment of the present disclosure, the ferrous member is resiliently biased by a resilient biasing force into a locking position when the lock-out is in the first position to thereby prevent rotation of the threaded shaft in the threaded bore, and wherein a magnetic attractive force of the magnet is greater than the resilient biasing force whereby the lock-out is magnetically biased into the second position against a return biasing of the resilient biasing force. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a partially cut away view, illustrating an embodiment of the present disclosure in a locked position; and 
           [0011]      FIG. 2  is a partially cut away view, illustrating an embodiment of the present disclosure in an unlocked position. 
           [0012]      FIG. 3  is an alternative embodiment of the grounding clamp of  FIG. 1 , in the locked position. 
           [0013]      FIG. 4  is the grounding clamp of  FIG. 3  and a hot-stick ready for mounting to the grounding clamp. 
           [0014]      FIG. 5  is the grounding clamp and hot-stick of  FIG. 4  with the grounding clamp mounted to the hot-stick and the grounding clamp in the locked position. 
           [0015]      FIG. 6  is the grounding clamp and hot-stick of  FIG. 5  with the grounding clamp unlocked by actuation of the hot-stick. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    In an embodiment of the present disclosure, a locking grounding clamp  30  comprises a frame  36  supporting a clamping member  34 . The frame includes a clamping member  32  at opposite-ends of the frame. The clamping member and frame define a capture cavity  31  therebetween having an opening  31 A. The capture cavity  31  is sized to receive conductor  20 , shown in cross section in  FIG. 2 , via opening  31 A. Advantageously capture cavity  31  conforms in shape, and so as to encircle, conductor  20 . 
         [0017]    Square shaft  42  is supported on or within the frame  36  and disposed alongside clamping member  34 . Square shaft  42  (which is square in cross section) is inserted through opening  26  at the upper end  36 A of frame  36 , through a channel or cut-out  27  running along frame  36 , and through an opening  28  located in the locking portion  37  of frame  36 . Ferrous lock-out ring  50  is mounted adjacent portion  37 . The square shaft  42  is journalled through a square opening (not shown) in the center of ring  50 . A coupling eye  44  is mounted or formed at the end of square shaft  42  adjacent ring  50 , opposite portion  37  within spring housing  46 A. The square shaft  42  is also inserted through the hollow centre of a threaded shaft  39 . Threaded shaft  39  is provided with a square shaped bore sized so as to slidably snugly couple with the square shaft  42  whereby rotating the square shaft  42  in direction C about a rotational axis a extending through the centre of the square shaft  42  results in rotating the threaded shaft  39  in the same rotational direction as rotation of shaft  42 . Square shaft  42  is free to rotate within openings  26 ,  28  and within channel  27 . For example, openings  26 ,  28  may be round. 
         [0018]    A threaded bore is formed in collar  38 . Collar  38  is coupled to clamping member  34 . The threading of the threaded bore in collar  38  rotatably mates with the threading on the external surface of the threaded shaft  39 . Thus, an insulating tool grasping the coupling eyelet  44  and rotating the coupling eyelet  44  and the square shaft  42  in direction C about the axis of rotation a results in rotation of both the square shaft  42  and the threaded shaft  39 . Rotation in a first direction about axis a, urges clamping member  34  in direction A towards clamping arm  32 . Rotating the coupling eyelet  44  in an opposite direction translates clamping member  34  in direction B, away from clamping arm  32 . 
         [0019]    As stated above, lock-out ring  50  is disposed adjacent the locking portion  37  of the frame  36 , and has a square channel through its centre. Advantageously, lock-out ring  50  is ferrous. The square channel in ring  50  is sized so as to snugly slidably receive the square shaft  42 . Ring  50  thus also rotates in direction C along with the rotation of square shaft  42  about the rotational axis a. Ring  50  includes a plurality of teeth  52 . Locking portion  37  similarly comprises a plurality of teeth  33 . The teeth  33  on locking portion  37  are in opposed facing relation so as to complement the teeth  52  on ring  50  such that when ring  50  is urged towards the locking portion  37  of frame  36 , teeth  33  releasably lock with teeth  52 . In particular, teeth  33  interleave between teeth  52 , thereby preventing rotation of ring  50  relative to locking portion  37  and frame  36 . 
         [0020]    Ring  50  and spring  46  are located in spring housing  46 A in the end  37  of frame  36  corresponding to eyelet  44 . Spring  46  is disposed between the base  46 B of spring housing  46 A and ring  50 . Spring  46  surrounds the square shaft  42 . The spring  46  resiliently biases ring  50  against the locking portion  37  of the frame  36 , causing the plurality of teeth  33  on locking portion  37  to couple with the plurality of teeth  52  on ring  50 . Thus, when ring  50  is biased against locking portion  37 , the coupling of the plurality of teeth  33  with the plurality of teeth  52  prevents rotation of ring  50  relative to the frame  36  and locking portion  37 , thereby also preventing rotation square shaft  42  about rotational axis a. This prevents linear translation of clamping member  34  relative to frame  36 . 
         [0021]    As illustrated in  FIG. 2 , hot-stick  10  includes an insulated body  12 , a head  14 , a coupling clamp  16  and a plurality of magnets  18  (shown in dotted outline). The plurality of magnets  18  and the coupling clamp hook  16 A (seen in  FIG. 4 ) are disposed within the head  14 . 
         [0022]    In operation, as illustrated in  FIG. 2 , a lineman seeking to operate the grounding clamp  30  will grasp the insulated body  12  of a hot-stick  10  and manipulate the coupling clamp  16  so as to couple the coupling clamp hook  16 A to the coupling eyelet  44 . Upon coupling the coupling clamp  16  to the coupling eyelet  44 , the plurality of magnets  18  disposed within the head  14  attract ring  50  in direction B, causing the plurality of teeth  33  on locking portion  37  to uncouple from the plurality of teeth  52  on ring  50 . Once ring  50  becomes uncoupled from the locking portion  37  of frame  36 , the square shaft  42  may be freely rotated. By rotating, using a twisting motion in direction D about the length (or longitudinal axis) of hot-stick  10 , the lineman may then rotate square shaft  42  in direction C. This results in a corresponding rotation of the threaded shaft  39 , thereby causing clamping member  34  to translate linearly in either direction A or direction B, depending on the direction of rotation of square shaft  42 . In this manner, the capture cavity  31  may only be opened to receive a conductor  20  via opening  31 A or closed to enclose a conductor  20  within cavity  31  when the coupling clamp  16  of the hot-stick  10  is coupled with the coupling eyelet  44  so as to disengage the lock-out ring. 
         [0023]    Once the grounding clamp  30  has either been engaged around or disengaged from a conductor  20 , the lineman may unhook the coupling clamp  16  from the coupling eyelet  44  and remove the hot-stick  10  from the locking ground clamp  30 . By removing the hot-stick  10  from the grounding clamp  30 , and therefore removing the magnetic field caused by the plurality magnets  18  disposed within the head  14 , the magnetic force causing the ferrous member  50  to move in direction B is removed and therefore the spring force applied in direction A by spring  46  against ring  50  will once again resiliently urge ring  50  in direction A towards locking portion  37 , whereby the plurality of teeth  33  once again engage with the plurality of teeth  52  and bring the grounding clamp  30  into the locking position, as shown in  FIG. 1 . 
         [0024]    Additional embodiments of the locking grounding clamp are seen in  FIGS. 3-6 . In  FIG. 3 , the grounding clamp is similar to the above described embodiment of  FIGS. 1 and 2  which uses magnets, but the lock-out ring  50  is connected directly to the locking mechanism so that pulling ring  50  down in direction E retracts teeth  52  from interlocking between teeth  33 . As before, shaft  42  is journalled in hollow shaft  39  and provides a movable connection, for example a telescopic coupling, to the threaded shaft  39 . The spring  46  is a very stiff spring to keep the lock-out in the locked position, and to discourage manual unlocking of the lock-out ring  50 . 
         [0025]    As seen in  FIG. 4 , the insulating hot-stick  10  may incorporate a lever  54  to overcome the very stiff spring tension and to release the lock-out mechanism by uncoupling the lock-out ring  50 , allowing the ground clamp eye  44  to be turned in direction C to rotate the shaft  42  to thereby open or close the clamp member  54  onto the conductor  20 . 
         [0026]    A bearing within bearing interface  56  may be incorporated into the end of the insulating hot-stick  10  or into the ground clamp interface with the hot-stick, for example into the base of spring housing  46 A, to allow twisting rotation of the hot-stick when under the spring tension. 
         [0027]    In another embodiment a universal joint (not shown) may be incorporated into the end of the insulating hot-stick to allow operation when the stick and ground clamp are not in alignment; that is, not aligned longitudinally. 
         [0028]    As seen in  FIG. 5  the hot-stick is mounted to the clamp  30  when the lever  54  is partially actuated in direction F to capture the clamp  30  by engaging hook  16 A on the hot-stick  10  with the eye  44 . The locking mechanism is still engaged as the lock-out ring  50  remains in its locked position. 
         [0029]    As seen in  FIG. 6 , to unlock the grounding clamp, so as to allow its use by the lineman, the lever  54  is fully actuated by pulling the lever fully down in direction F. This retracts the actuating rod  56  connected to the hook  16 A on the upper end of the hot-stick  10  along the hot-stick thereby pulling down on the eye  44  on the base of the grounding clamp. Pulling down on eye  44  also pulls down ring  50  onto the spring  46  which releases the teeth  52  on ring  50  in the locking mechanism. The bearing  56  allows the hot-stick to be twisted in direction D while under tension from the compressed spring  46 . 
         [0030]    As will be appreciated by one skilled in the art, various other mechanisms may be employed to actuate a lock-out locking mechanism disabling the grounding clamp so that the lock-out will lock the operation of the clamp unless in the presence of an insulating tool such as a hot-stick. For example, the lockout does not necessarily have to employ mating sets of teeth as other braking mechanisms, including those relying on friction or adhesion, between mating components may also work. Further, the spring and magnet arrangement in the lock-out described above may be reversed. Also the proximity or presence of the hot-stick, so as to unlock the lock-out, may be detected by the lock-out other than by the use of a magnetic field, and operate other than by a magnet field overcoming a resilient biasing of one locking component against another. For example, the mating of the hot-stick with the clamp may mechanically disengage a spring-loaded latch mechanism, wherein for example, a pushing of the hot-stick against a plunger within a coupling housing on the clamp will disengage the latch mechanism in the lock-out. 
         [0031]    As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the spirit or scope thereof. Accordingly, the scope of the invention is to be construed in accordance with the substance defined by the following claims.