Patent Publication Number: US-6987664-B2

Title: Finger guard for power distribution panel

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation of U.S. patent application Ser. No. 09/932,466, filed on Aug. 17, 2001, now issued as U.S. Pat. No. 6,870,729, on Mar. 22, 2005, the disclosure of which is incorporated herein by reference. 

   FIELD OF THE INVENTION 
   The present invention relates to power distribution units. More specifically, the present invention relates to providing finger guards for circuit breakers used with power distribution units. 
   BACKGROUND OF THE INVENTION 
   Power distribution units are used to distribute power supplied by a main electrical source to a variety of devices requiring power. The power distribution unit may include an internal power bus that powers one or more circuits. Each of these circuits may include a protective device, such as a fuse or a circuit breaker, which is accessible through one of the walls or panels of the unit. A power distribution unit may have the capacity for more circuits than are required when the unit is installed, which provides for future expansion. In such installations, one or more of the circuits may be left open, that is, without having any protective device. 
   The openings through which these omitted protective devices will extend are often covered to prevent unwanted or accidental contact with the power bus within the unit. This may be done with a flat plate or blank cover secured over the opening. When a protective device is inserted into the opening to provide an additional power circuit, this blank is then removed and discarded. A mounting plate may then be attached to the protective device and the device inserted into the power distribution unit. When a switched circuit breaker is the protective device installed, the mounting plate may incorporate a finger guard structure to protect the switch from accidental contact opening the circuit and interrupting power in the circuit. 
   Several concerns arise in the area of finger guards, including ease of use and reliability. Providing separate mounting plates and blank covers can be difficult to coordinate and manage, especially when the circuit protective devices are added later. Further developments in finger guards are desired. 
   SUMMARY OF THE INVENTION 
   The present invention relates to a finger guard for an electrical circuit breaker, the finger guard including a rear plate with an opening, a guard portion extending from the plate adjacent the opening, and a removable portion, or knock-out, positioned within the opening. 
   The present invention further relates to a finger guard for an electrical circuit breaker, the finger guard including a rear plate with an opening, a guard portion extending from the plate adjacent the opening, and opposing ramped finger grips on the outer walls of the guard portion. 
   The present invention also relates to a finger guard for an electrical circuit breaker, the finger guard including a rear plate with an opening, a guard portion extending from the plate adjacent the opening, and the plate further including a designation holder. 
   The present invention relates as well to an electrical power distribution system with a chassis having an electrical circuit including a mount for an electrical circuit breaker and an opening providing access to the mount, a finger guard mounted across the opening, the finger guard including an opening covered by a removable portion. 
   The present invention also relates to an electrical power distribution system with a chassis having an electrical circuit including a mount for an electrical circuit breaker and an opening providing access to the mount, a finger guard mounted across the opening, the finger guard including opposing ramped finger grips on the outer walls of the guard portion. 
   The present invention further relates to an electrical power distribution system with a chassis having an electrical circuit including a mount for an electrical circuit breaker and an opening providing access to the mount, a finger guard mounted across the opening, the finger guard including a designation holder. 
   The present invention relates as well to a method of removing a finger guard from an opening on an electric power distribution chassis, removing a portion covering an opening in the finger guard, mounting the finger guard to an electrical circuit breaker, and inserting the electrical circuit breaker into a circuit breaker mount in an electrical circuit within the chassis. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate several aspects of the invention and together with the description, serve to explain the principles of the invention. A brief description of the drawings is as follows: 
       FIG. 1  is a front perspective view of a portion of a power distribution unit according to the present invention. 
       FIG. 2  is a front view of the power distribution unit of  FIG. 1 . 
       FIG. 3  is a side view of the power distribution unit of  FIG. 1 . 
       FIG. 4  is a bottom view of the power distribution unit of  FIG. 1 . 
       FIG. 5  is a side view of a finger guard according to the present invention mounted to a switchable circuit breaker and a schematic electrical circuit including a circuit breaker mount for the power distribution unit of  FIG. 1 . 
       FIG. 6  is a front perspective view of a finger guard according to the present invention. 
       FIG. 7  is a front view of the finger guard of  FIG. 6 . 
       FIG. 8  is a side view of the finger guard of  FIG. 6 . 
       FIG. 9  is a rear view of the finger guard of  FIG. 6 . 
       FIG. 10  is a bottom view of the finger guard of  FIG. 6 . 
   

   DETAILED DESCRIPTION 
   Reference will now be made in detail to exemplary aspects of the present invention that are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
     FIG. 1  shows a portion of a power distribution panel  10  for use in a telecommunications installation, such as a rack, to provide power to other devices within the same installation. Panel  10  includes protective devices in the form of circuit breakers and fuses. Typically on the rear of panel  10  is a power input connection  98  where a power supply feed is connected. As shown in  FIG. 5 , an internal bus  100  distributes the current provided through power input connection  98  into a series of separate distribution circuits  102 . Each distribution circuit  102  is electrically connected with a power output connection  112  by a lead  104 . Power output connection  112  is also on the rear of panel  10 , and provides power to a device mounted elsewhere in the telecommunications installation. Distribution circuits  102  require a protective device such as circuit breaker  30  be mounted in the distribution circuit to complete the electrical path and to provide over-current protection for the distribution circuit. 
   Referring now to  FIGS. 1 through 4 , power distribution panel  10  includes a front face  12 , a side  14 , a top  16  and a bottom  18 , along with a rear face and an opposing side which are not shown, forming an enclosure for the power bus housed by panel  10 . Finger guards  20  are mounted in an access opening  22  in front face  12 . Behind each of six finger guards  20  are mounts  110  to mount the protective devices completing and providing over-current protection for each of six internal distribution circuits  102 . Power distribution units may include more or less than the six circuits  102  shown. Also located on front face  12  are power indicator lamp  24  and electrical fuse array  26 , providing additional over-current protection to electrical circuits within power distribution panel  10 . 
     FIG. 5  shows finger guard  20  mounted to the front of a protective device, in this case a switched circuit breaker  30 . Also shown is mount  110  of distribution circuit  102  for receiving such a protective device. A pair of mounting studs  32 , located at the rear of circuit breaker  30 , interface with the stud receivers  106  which are part of mount  110 . Insertion of mounting studs  32  in stud receivers  106  and placing switch  33  of switched circuit breaker  30  into a closed position will complete the electrical path for each distribution circuit  102 . Also located to the rear of circuit breaker  30 , between mounting studs  32 , are alarm leads  34 . Alarm leads  34  are received by alarm interface  108  of mount  110  to provide a connection with alarm circuits  114  within power distribution panel  10 . Alarm circuits  114  will initiate failure alarms when the current flowing through circuit breaker  30  is disrupted. Also shown in  FIG. 5  are screws  21 , which are discussed further below. 
   Referring now to  FIG. 6 , finger guard  20  includes a front face  44 , a rear face  46 , side guards  36 , a top wall  38  and a bottom wall  40  cooperating to define an enclosure  42 . A removable portion or knock-out  56  closes a portion of the rear of enclosure  42  while the front of enclosure  42  is open. A portion of the rear of the enclosure is opened by the removal of knock-out  56 , forming an opening  57 , through which a portion  31  of circuit breaker  30  extends, as shown in  FIG. 5 . Also extending from circuit breaker  30  through opening  57  into enclosure  42  is switch  33  for setting circuit breaker  30  into an open or closed position. The remainder of the rear of enclosure  42  is closed by front face  44  and rear face  46 . 
   At the bottom of finger guard  20  is located an indicia holder  48  through which is formed opening  61 . An indicia cover  52  removably mounts to the front of indicia holder  48 . Cover  52  can include indicia or it can be transparent to visible light for trapping a designation card  50  to identify the circuit protected by circuit breaker  30 . Cover  52  includes opposing edges  114  along the rear which engage lips  116  along the top and bottom of indicia holder  48  to securely and removably hold cover  52  to indicia holder  48 . 
   Located on the distal ends of the outer surfaces of top wall  38  and bottom wall  40  are opposing ramped finger grips  54 . Ramped finger grips  54  provide a positive and comfortable surface for grasping and removing circuit breaker  30  connected to mount  110  inside power distribution panel  10 , when finger guard  20  is mounted to circuit breaker  30 , as shown in  FIG. 5 . Ramped finger grips  54  may have ridges  55  formed in the ramped surface, as shown in  FIG. 8 , or may be have some alternative surface treatment to increase friction and improve grip. 
   Referring now  FIGS. 7 through 10 , mounting openings  60  extend from front face  44  to rear face  46  of finger guard  20 . Mounting openings  60  receive removable fasteners such as screws  21  for securing finger guard  20  to circuit breaker  30 . The upper mounting opening  60  is located within enclosure  42  above knock-out  56 . Openings  60  may be located in other positions along finger guard  20 . 
   Knock-out  56  is joined to finger guard  20  by perforations, webbing or thinned portions  45 , such as along the top and bottom of opening  57 . Knock-out  56  is removed from opening  57  by applying force to knock-out  56  from the rear sufficient to break thinned portions  45 . Alternatively, notches  41  in knock-out  56  provide openings for the insertion of a flat-bladed tool such as a screwdriver from the front and apply force to the rear of knock-out  56  using the leverage of the screwdriver to break thinned portions  45 . Finger guard  20  is made from molded plastic having appropriate physical properties to permit the connection between finger guard  20  and knock-out  56  to be broken along thinned portions  45  with the application of reasonable force without damaging the remainder of finger guard  20 . 
   Along the rear of finger guard  20  is a rear notch  64  in side guards  36 . Rear notch  64  is sized to receive portion  31  of circuit breaker  30  when finger guard  20  is mounted to circuit breaker  30 . Not all circuit breakers include such an extension  31 , having instead a flat front face. In addition, other protective devices may or may not have such an extension  31 . Finger guard  20  is usable with such other protective devices, with or without an extension  31 . 
   Side guards  36  include an arched portion  66  to provide additional protection to switch  33  of switched circuit breaker  30  extending into enclosure  42 . Arched portion  66  is shown coextensive with opening  57  and rear notch  64 . Side guards  36  may have alternative shapes, either curved or straight, provided that side guards  36  extend enough from front face  44  to provide the desired protection to the switch  33 . 
   Power distribution panel  10  may include one or more internal distribution circuits  102  without a protective device such as circuit breaker  30  completing the electrical pathway between the power input terminal  98  and the power output terminal  112 . In this case, opening  22  in front face  12  proximate the mounts  110  for the protective devices will be covered by a finger guard  20 , as shown in  FIG. 2 . Finger guard  20  is held to front face  12  by a tab  62  inserted into a slot  68  through front face  12  above opening  22 . Tab  62  includes a ramped portion  120  which extends through slot  68  and engages the rear of front face  12 . Opening  61  through indicia holder  48  also accepts a removable fastener such as a screw  21  which engages an opening  69  through front face  12  below opening  22  to secure finger guard  20  to front face  12 . Knock-out  56  covers opening  57  and cooperates with front face  44  of finger guard  20  when mounted to front face  12  of panel  10  to prevent accidental or unwanted contact with the electrical power components within panel  10 . 
   To complete a distribution circuit, finger guard  20  is removed from front face  12  by removing the removable fastener such as screw  21  from opening  69  and opening  61 , and withdrawing tab  62  from slot  68 . Knock-out  56  is removed from opening  57  by exerting force on the rear of knock-out  56  and breaking thinned portions  45 . Finger guard  20  in then placed on the front of a protective device such as circuit breaker  30  so that portion  31 , if present, extends into rear notch  64  and switch  33  of circuit breaker  30  extends into enclosure  42 . Removable fasteners such as screws  21  are then inserted through openings  60  to engage appropriate openings in circuit breaker  30  to mount finger guard  20  to circuit breaker  30 . Circuit breaker  30  with finger guard  20  mounted to it is then inserted through opening  22  in front face  12  of panel  10  so that mounting studs  32  engage stud receivers  106  of mount  110  in distribution circuit  102  and alarm leads  34  are received by alarm interface  108 . As the circuit breaker is fully inserted into the mount, tab  62  of finger guard  20  again engages an edge of slot  68  on front face  12  of panel  10  and rear face  46  of finger guard  20  rests against front face  12 . A removable fastener such as screw  21  is then inserted through opening  61  to engage opening  69 , securing finger guard  20  to front face  12 . 
   With regard to the foregoing description, it is to be understood that changes may be made in detail, especially in matters of the construction materials employed and the shape, size and arrangement of the parts without the scope of the present invention. It is intended that the specification and depicted aspects be considered exemplary only, with a true scope and spirit of the invention being indicated by the broad meaning of the following claims.