Abstract:
A protective shield that may be secured to an electrical racking rod of the type used for performing electrical work on various types of energized electrical equipment. The protective shield includes a transparent plate formed of an impact resistant, fire retardant material; a clamping mechanism secured to the plate and at least one adaptor for securing the racking rod to the plate. The adaptor is engaged by the clamping mechanism to secure the racking rod to the plate. The protective shield provides physical protection to workers when removing or resetting electrical circuit breakers by acting as a barrier between the worker and the equipment while providing complete visibility to the task being performed. A plurality of adaptors may be provided to enable the plate to be utilized with any one of a plurality of different diameter racking rods.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This is a standard utility application claiming priority from U.S. Provisional Application Ser. No. 60/650,899, filed Feb. 8, 2005, the entire specification of which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Technical Field  
         [0003]     The invention relates to a protective safety shield for use in the electrical industry. More particularly, the invention relates to a safety shield that may be clamped to different diameter racking rods and can be used to protect workers from electrical arcs, flashes and fragmentation explosions which can occur while opening and closing circuit breakers.  
         [0004]     2. Background Information  
         [0005]     Tripping and resetting electrical circuit breakers can pose a serious threat of injury to electrical workers because of the potential risk of the occurrence of electrical arcs, electric flashes and fragmentation explosions. These arcs, flashes or explosions are capable of causing electrical burns, molten metal burns and flesh wounds caused by flying debris.  
         [0006]     Circuit breakers are typically mounted in a protective cabinet. In order to perform routine maintenance and repair, the worker has to open the cabinet and, using a racking rod, shift the breakers either vertically or horizontally in order to disconnect them from the power source. The breakers are then removed from the cabinet and the necessary maintenance or repair is performed. When the work is completed, the breakers are replaced in the cabinet and then, using the racking rod, are moved either vertically or horizontally back into connection with the power source. Both the tripping and resetting require the worker to be located close enough to reach the cabinet with the racking rod and this puts them at risk because the circuit is energized when it is tripped and become energized when it is being reset.  
         [0007]     Various devices have been proposed in the art to assist and protect the worker during the tripping and resetting of the breaker. These devices have included different types of hot sticks, eye protection, hard hats, flame retardant clothing and gloves. Yet other devices have included mechanized systems for moving and placing breakers in order to allow the worker to remain at a slightly safer distance from the equipment. There is, however, no way for the worker to maintain a completely safe distance when the breakers are tripped and reset.  
         [0008]     U.S. Pat. No. 5,666,253, assigned to the present assignee, discloses a shield that physically protects linemen using a hot stick as they work. The shield protects the worker from electrical arcs, electrical flashes and fragmentation explosions and from objects and debris produced during the pulling of pad-mounted switches, the insertion of fuses into overhead transformers or numerous other applications. This shield includes a plate formed of a transparent material and a clamping means for removably mounting the plate to the hot stick. However, the hot sticks used in conjunction with the device proposed by this patent are long and of a fairly large diameter. They are therefore not suitable for opening breaker circuits in more cramped quarters. Tripping and resetting breakers requires the use of racking rods and depending on the application, racking rods of different diameters may need to be utilized. All of these racking rods are significantly smaller in diameter than the hot sticks used for working on overhead lines.  
         [0009]     There is therefore a need in the art for a protective shield that can be used in conjunction with a plurality of different diameter hot sticks or racking rods for tripping and resetting differently sized circuit breakers in close quarters.  
       SUMMARY OF THE INVENTION  
       [0010]     The device of the present invention comprises a protective shield that may be secured to an electrical racking rod of the type used for performing electrical work on various types of energized electrical equipment. The protective shield comprises a transparent plate formed of an impact resistant, fire retardant material; a clamping mechanism secured to the plate and at least one adaptor engageable by the clamping mechanism for securing the racking rod to the plate. The plate includes an opening through which the racking rod is passed. The adapter has a collar which can pass through the opening and a shoulder which cannot pass through the opening. The adapter further includes an internal axial bore within which a section of the racking rod is retained. The clamping mechanism engages the collar of the adaptor and holds it in such a position that the plate is disposed between the clamping mechanism and the shoulder of the adaptor. The adaptor holds the racking rod in such a position that it lies substantially right angles to the plate. A secondary shield may be mounted to the clamping mechanism to protect that portion of the adaptor that extends through the opening. A plurality of adaptors may be provided to enable the plate to be utilized with any one of a plurality of different diameter racking rods.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     Preferred embodiments of the invention, illustrative of the best modes in which applicants have contemplated applying the principles, are set forth in the following description and are shown in the drawings and are particularly and distinctly pointed out and set forth in the appended claims.  
         [0012]      FIG. 1  is a diagrammatic plan view of a worker using the protective shield in accordance with the present invention;  
         [0013]      FIG. 2  is a partial perspective view of a safety shield in accordance with the present invention and showing an adaptor and connected racking rod being inserted through the opening in the shield;  
         [0014]      FIG. 3  is an exploded perspective view of the adaptor of the present invention being positioned around a racking rod;  
         [0015]      FIG. 3A  is a side view of the adaptor in accordance with the present invention and engaged with the racking rod;  
         [0016]      FIG. 4  is a partial perspective view of the safety shield engaged with an adaptor and its connected racking rod;  
         [0017]      FIG. 5  is a frontal fragmentary view of the protective shield of  FIG. 3  showing the clamping mechanism is an open position;  
         [0018]      FIG. 6  is a frontal fragmentary view of the protective shield of  FIG. 4  showing the clamping mechanism engaged with the adaptor; and  
         [0019]      FIG. 7  is a partial cross-sectional front view through the adaptor when engaged with the racking rod. 
     
    
       [0020]     Similar numbers refer to similar parts throughout the drawings.  
       DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0021]     Referring to  FIGS. 1-7 , there is shown a protective shield in accordance with the present invention and generally indicated at  10 . Shield  10  includes a plate  12 , preferably formed from a transparent, flame-retardant plastic material such as polycarbonate, and a clamping mechanism  20  for engaging a racking rod  16  as will be described hereafter. Plate  12  preferably is formed with a central opening  14  therein through which racking rod  16  is inserted. Clamping mechanism  20  locks racking rod  16  to shield in such a manner that a portion of the rod extends outwardly from either side of plate  12 . Opening  14  may include a slot  18  ( FIG. 2 ) that allows rod  16  to be more easily inserted through opening  14 . Clamping mechanism  20  is mounted on plate  12  by fastening bolts  28  and associated nuts  30  and washers. Clamping mechanism  20  includes a base  22  that is secured to plate  12 , a bolt arm  24  and clamp arm  26  that is pivotally mounted on base  22 . Clamp arm  26  is pivotable between an open position and a closed position. When clamp arm  26  is in the open position, racking rod  16  may be moved relative to shield  10 . When the clamp arm is in the closed position, racking rod  16  is locked within clamping mechanism  20  and is prevented from moving relative to shield  10 . Clamping mechanism  20  is designed to clamp around racking rod  16  so that rod  16  lies in a plane that is substantially perpendicular to plate  12  ( FIG. 1 ). The structure and functioning of clamping mechanism  20  is described in detail in U.S. Pat. No. 5,666,253, the entire specification of which is incorporated herein by reference.  
         [0022]     In accordance with a specific feature of the present invention, an adaptor  32  is provided to enable clamping mechanism  20  to tightly engage a racking rod  16  that has a diameter which is significantly smaller than the diameter of opening  14 . Adaptor  32  comprises a collar  44 , which has a diameter smaller than that of opening  14  and can therefore pass through opening  14 ; and a shoulder  46  that is concentric with collar  44  and extends outwardly away from collar  44 . Shoulder  46  has a greater diameter than that of opening  14  and consequently shoulder  46  of adaptor  32  cannot pass through opening  14 . Adaptor  32  is provided with an axial bore  56  ( FIG. 5 ) through which rod  16  is inserted. Bore  56  preferably is substantially equal in diameter to rod  16  so that adaptor  32  tightly engages rod  16 . Clamping mechanism  20  engages collar  44  of adaptor  32  and thereby retains rod  16  in locking engagement with shield  10 .  
         [0023]     In accordance with a preferred embodiment of the invention, and as seen in  FIG. 3 , adaptor  32  preferably is comprised of first and second clamping members  34 ,  36  that are releasably secured together. First clamping member  34  comprises a generally C-shaped collar section  44   a  with a shoulder section  46   a  extending outwardly away from collar section  44   a . Collar section  44   a  has an arcuate outer wall  60  and a substantially planar wall  62  having a semi-circular channel  56   a  formed therein. Shoulder section  46   a  extends outwardly from outer wall  60 . Second clamping member  36  comprises a generally C-shaped collar section  44   b  with a shoulder section  46   b  extending outwardly away from therefrom. Collar section  44   b  has an arcuate outer wall  52  and a substantially planar wall  54  having a semi-circular channel  56   b  formed therein. Shoulder section  46   b  extends outwardly away from outer wall  52  of collar section  44   b.    
         [0024]     When first and second clamping members  34 ,  36  are secured together, planar walls  62  and  54  are disposed in abutting contact with each other. Collar sections  44   a  and  44   b  form the adaptor&#39;s collar  44 ; the shoulder sections  46   a  and  46   b  form the adaptor&#39;s shoulder  46  and channels  56   a  and  56   b  together form the axial bore  56  of adaptor  32 . Adaptor  32  is therefore a substantially tubular member having a central axial bore  56  for receiving racking rod  16  therethrough and having a circumferential shoulder  46  radiating outwardly away from the outer wall of the collar section  44  to prevent the rod  16  and adaptor  32  from passing through opening  14  in plate  12 . The adaptor  32  has a first end  48  which constitutes an end wall of collar  44 ; and a second end  50  which constitutes an end wall of shoulder  46 .  
         [0025]     As may be seen in  FIG. 3A , adaptor  32  has a total length A-A′ of around 2⅛ inches, collar  44  is about 2 inches long and shoulder  46  has a length B-B′ of about ⅛ inch. The radius C-C′ of each of the collar sections  44   a ,  44   b  is smaller than the radius D-D′ of each of the shoulder sections  46   a ,  46   b . The diameter E-E′ of shoulder  46  is about 2 5/16 inches and the diameter F-F′ of collar  44  is about 1¼inches.  
         [0026]     First and second clamping members  34 ,  36  are adapted to be positioned around the circumferential outer wall of racking rod  16  so that rod  16  is received within the bore  56  formed by channels  56   a  and  56   b . First and second clamping members  34 ,  36  are locked together around rod  16  by a plurality of fasteners  38 . Fasteners  38  are inserted through apertures  40  in first clamping member  34  and screwed into aligned threaded screw holes  42  in second clamping member  36 . Rod  16  is thereby clamped between first and second clamping members  34 ,  36  so that it cannot slide longitudinally within bore  56 . Adaptor  32  and rod  16  therefore move as if they were a unitary member. It will be understood that any other type of suitable securing mechanism could be used on adaptor  32  to securely lock rod  16  therein.  
         [0027]     In use, adaptor  32  is used to connect shield  10  and racking rod  16  in the following manner. If racking rod  16  has a diameter of ⅝ inch for example, then an appropriately sized adaptor  32  (i.e., an adaptor having a bore  56  of slightly more than ⅝ inch) is utilized. Second clamping member  36  of adaptor  32  is positioned to receive rod  16  in channel  56   b . First clamping member  34  is placed over second clamping member  36  so that rod  16  is received in channel  56   a  and planar walls  54  and  62  abut each other. Fasteners  38  are inserted through apertures  40  in first clamping member  34  and into internally threaded holes  42  in second clamping member  36 . Fasteners  38  are screwed into holes  42  until first and second clamping members  34 ,  36  cannot be separated from each other and rod  16  is substantially prevented from sliding longitudinally through bore  56 . At this point, racking rod  16  is sufficiently securely held between first and second clamping members  34 ,  36  so that rod  16  cannot be withdrawn therefrom. A free end (not shown) of racking rod  16  is inserted through opening  14  in shield  10  and rod  16  is passed through opening  14  until collar  44  of adaptor  32  lies within opening  14  and shoulder  46  abuts plate  12  of shield  10 .  
         [0028]     Clamping mechanism  20  is then engaged to secure adaptor  32  to shield  10 . Base  22  of clamping mechanism  20  has a V-shaped configuration ( FIGS. 2, 4  and  5 ) formed by a pair of outwardly extending angled legs  22   a  and  22   b  which join together at a curved corner  22   c . A U-shaped recess  64  is formed in curved corner  22   c , and extends throughout the width of base  22 . Arcuate clamping surfaces  66  are formed on each of the base legs adjacent recess  64 . Surfaces  66  are adapted to engage with collar  44  of adaptor  32 . The outer ends of legs  22   a  and  22   b  are each formed with a central recess (not shown) through which bolts  28  are passed to secure bolt arm  24  and clamp arm  26  thereto. Arms  24 ,  26  can be pivoted between an open position ( FIG. 2 ) and closed position ( FIG. 4 ) and in a plane substantially parallel to that of plate  12 .  
         [0029]     A rocker shoe  68  is pivotally attached to clamp arm  26  by a bolt  70 . Rocker shoe  68  pivots in the same plane as clamp arm  26  with respect to plate  12 . Rocker shoe  68  has a generally triangular shape with a concave shaped outer surface  72 . When clamping mechanism  20  is moved into the closed position, clamping surfaces  66  of base  22  engage outer wall  52  of second clamping member  36  and concave surface  72  of rocker shoe  68  engage outer wall  60  of first clamping member  34 . Racking rod  16  is thereby securely engaged with shield  10 .  
         [0030]     A secondary shield  74  is preferably attached to rocker shoe  68  and is disposed between the rocker shoe and plate  12 . Secondary shield  74  is fastened to rocker shoe  68  by bolt  70 . Shield  74  preferably is formed with a U-shaped opening  76  for receiving a portion of the collar  44  of adaptor  32  therein when adaptor  32  is inserted through opening  14 . The secondary shield  74  is shaped and sized to cover portions of opening  14 , such as slot  18  and the annular area between adaptor  32  and the periphery of opening  14 . The interior surface of shoulder  46  abuts the surface of secondary shield  74  and aids in preventing adaptor  32  from being drawn through opening  14 . Secondary shield  74  is automatically positioned around a portion of adaptor  32  when clamp arm  26  is pivoted into a closed and clamped position.  
         [0031]     A yoke  80  is provided at the second end of clamp arm  26 , for engaging bolt arm  24  when clamping mechanism  20  is moved into a closed position. A fastener  82 , such as a wing nut, is adjustably mounted on a threaded portion of bolt arm  24 . When yoke  80  is engaged with bolt arm  24 , fastener  82  is rotated so as to engage yoke  80  and thereby secure arm  26  in its closed and locked position. When fastener  82  is tightened, concave surface  72  of rocker shoe  68  is pressed firmly against adaptor  32  as described above and therefore adaptor  32 , and therefore rod  16  are locked into engagement with shield  10 .  
         [0032]     It will be understood that a plurality of racking rods of different diameters can be connected to shield  10  by utilizing a plurality of different adaptors. Each of the adaptors will preferably have a collar  44  of diameter F-F′ and a shoulder  46  of diameter E-E′, but the diameter of the central axial bore  56  will differ from one adaptor to another. The different diameter bores will correspond to the various racking rod diameters so that any of the rods will be able to be securely retained within the appropriate adaptor and can therefore be secured to shield  10 . So, for example, adaptors  32  will be manufactured having an interior bore  56  with a diameter of substantially ½ inch, ⅝ inch, 1 inch etc. These adaptors are designed to respectively receive rods  16  having diameters of substantially ½ inch, ⅝ inch, 1 inch diameter etc. The worker would simply select the appropriate racking rod for the job and then select the appropriate adaptor for use with that racking rod and the shield. If a different diameter racking rod is needed, the first adaptor and racking rod are removed and a second diameter racking rod and the appropriate adaptor are engaged with the shield. For ease of use, the appropriate adaptor may be kept permanently attached to the complementary sized racking rod.  
         [0033]     In accordance with another of the features of the invention, the protective shield  10  can be removed easily from the racking rod  16  by disengaging rod from clamping mechanism  20 . Shield  10  can then be stored and carried in a protective carrying case.  
         [0034]     In summary, the protective shield of the present invention provides a relatively simple and inexpensive, yet highly efficient and effective device, which is readily mounted on and removed from various diameter racking rods to protect a worker from electrical arcs, flashes and fragmentary explosions, and in which the shield can be easily removed and placed in a convenient protective storage case and provides the user with protection without restricting his mobility while utilizing the device the invention.  
         [0035]     Although the device of the present invention is indicated as being used on a racking rod, it is readily understood to anyone skilled in the art that the device can be used on other types of rods or similar devices for actuating other types of equipment where protection is desired, such as the turning of a valve or other equipment, where injury could occur to the individual, other than with electrical equipment.  
         [0036]     In the foregoing description, certain terms have been used for brevity, clearness and understanding; but no unnecessary limitations are to be implied therefrom beyond the requirement of the prior art, because such terms are used for descriptive purposes and are intended to be broadly construed.  
         [0037]     Moreover, the description and illustration of the invention is by way of example, and the scope of the invention is not limited to the exact details shown or described.  
         [0038]     Having now described the features, discoveries and principles of the invention, the manner in which the improved security container is constructed and used, the characteristics of the construction, and the advantageous, new and useful results obtained; the new and useful structures devices, elements, arrangements, parts and combinations, are set forth in the appended claims.