Patent Publication Number: US-11651921-B2

Title: Electrical connector with non-linear spring force

Description:
BACKGROUND 
     The present inventions relate generally to an electrical connector, and more particularly, to an electrical connector coupling first and second electrical components together. 
     Typically, industrial facilities are provided with one or more power supply panels  10  to distribute electrical power throughout the industrial facility. An example of a power supply panel  10  is shown in  FIGS.  1 - 2   . As shown, the panel  10  includes an electrical box  12 . Within the box  12 , mounting structures  14  are also provided to mount a power supply bus  16  and a series of circuit breakers  18 . Power is supplied to the bus  16  with one or more lugs  20  which are connected to electrical power supply cables and to the bus  16 . The circuit breakers  18  are electrically connected to the bus  16  with an electrical connector  34  described in more detail below. Electrical cables are also connected to each circuit breaker  18  to supply electrical power to various electrical circuits throughout the industrial facility. Commonly, the total electrical capability of the power supply panel (i.e., the bus  16 ) is required to be within 150 A to 1,200 A. It is understood that the box  12  may also contain a variety of other electrical accessories in addition to the power supply bus  16  and circuit breakers  18 . Although the described arrangement may be used with a single phase system, the illustrated system is a three-phase system. Thus, three lugs  20  are provided to supply power; three connecting slots  22  are provided in the bus  16 ; and each circuit breaker  18  has three output connectors  24 . A cover  26  is also typically provided to enclose the bus  16  and other electrical hardware within the box  12 . 
     SUMMARY 
     Improved electrical connectors are described for connecting a circuit breaker to a power supply bus. The power supply bus has an opening through which the connector is inserted to establish an electrical connection. The electrical connector includes first and second contact portions that contact first and second sides of the opening. A spring applies a bias force to the contact portions to press the contact portions against the sides of the opening. The spring force of the connector is non-linear so that the spring force of the connector stays within the desired spring force over a greater range of compressions. 
    
    
     
       BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
       The invention may be more fully understood by reading the following description in conjunction with the drawings, in which: 
         FIG.  1    is a perspective view of the internal portion of a power supply panel; 
         FIG.  2    is an exploded view of the power supply panel; 
         FIG.  3    is a cross-sectional view of a power supply bus of the power supply panel; 
         FIG.  4    is a front view of a circuit breaker; 
         FIG.  5    is a side view of a prior art electrical connector; 
         FIG.  6    is a chart showing the spring force of different electrical connectors; 
         FIG.  7    is a side view of an improved electrical connector; 
         FIG.  8    is a side view of another improved electrical connector; and 
         FIG.  9    is a chart showing the spring force of different angles for the spring of  FIG.  8   . 
     
    
    
     DETAILED DESCRIPTION 
     The power supply bus  16  is shown in cross-section in  FIG.  3   . As shown in  FIG.  1   , the circuit breaker  18  and bus  16  are mounted to the base  14  of the box  12 . The bus  16  is preferably a stacked arrangement with a connecting slot  22  (i.e., an opening  22 ) between two contact plates  28  for each phase. The contact plates  28  are separated from each other with a spacer  30 . In high amperage applications, it is preferred that both contact plates  28  defining a slot  22  are made of a conductive material like copper and the spacer  30  therebetween is also conductive. It is understood that other electrically conductive materials may also be used including, for example, aluminum. However, it may be possible in lower amperage applications for only one of the two plates  28  to be conductive and for the spacer  30  and the other plate  28  to be made of an insulative material. On the top and bottom of each plate  28 , an insulated plate  32  is preferably provided. The insulated plate  32  may be made of fiber reinforced plastic. As shown, the insulated plates  32  preferably include an extension portion  34  that extends outward beyond the respective plate  28  and covers a portion of the respective connector  76 ,  82 . 
     As shown, three electrical connectors  76  (or  82 ) are provided between the bus  16  and the circuit breaker  18 , since the illustrated system is a three-phase system. In a single phase system, there would only be one connector  76 ,  82  between the bus  16  and the circuit breaker  18 . The connector  76 ,  82  may be used with a variety of circuit breakers  18  having 1, 2, 3 or 4 poles. Each connector  76 ,  82  is coupled at a first end  36  to a respective connecting slot  22  of the bus  16  and at a second end  38  to the circuit breaker  18 . In use, the connectors  76 ,  82  are preferably attached to the circuit breaker  18  by the manufacturer and supplied with the circuit breaker  18 . When the circuit breaker  18  is installed into the box  12 , the first end  36  of each connector  76 ,  82  slides into the respective connecting slot  22  of the bus  16  to electrically interconnect the bus  16  and the circuit breaker  18 . 
     A prior art connector  40  is shown in  FIG.  5    that may be used with the circuit breaker  18  of  FIG.  4    (in place of the improved connectors  76 ,  82 ) to connect the circuit breaker  18  to the power supply bus  16 . As shown, the connector  40  is rigidly attached at the second end  40  to a bar  42 . Although not illustrated, the bar  42  is attached to the circuit breaker  18  with bolts, rivets or some other type of rigid connection (see holes  74  in  FIGS.  7 - 8   ). The first end  36  slides into the connection slot  22  in the power supply bus  16  in order to electrically connect the circuit breaker  18  to the bus  16 . A cantilevered spring  44  may be provided which is rigidly attached to the second end  40  and contacts the inner side of a second arm  46  with a free end  48  to apply an outward force thereto. As shown in  FIG.  6   , the connector  40  of  FIG.  5    exerts a linear spring force  50  as it is compressed. This may be a disadvantage because only a small range of compression of the connector  40  results in a spring force within the desirable range  52 . That is, there is a substantial range of initial compression that is below the desirable range  52  where the connector  40  may not exert sufficient contact force against the contact plates  28 . There is also a substantial range of compression that is above the desirable range  52  where the connector  40  may exert excessive contact force against the contact plates  28  which may make insertion and removal of the connector  40  from the bus  16  difficult. 
     As shown in  FIG.  6   , the improved electrical connectors  76 ,  82  exert a non-linear spring force  54  against the opening  22  (i.e., the contact plates  28 ) as the connectors  76 ,  82  are inserted into the bus  16 . For example, in a first stage  56  of compression, the spring rate of the connector  76 ,  82  is greater than the spring rate of the connector  76 ,  82  in a second stage  58 . In this example, the first stage  56  covers compressions of the connector  76 ,  82  that are less than the compressions in the second stage  58 . That is, when the connector  76 ,  82  is initially compressed, the spring rate is high and the exerted spring force increases quickly. However, after the initial compression, the spring rate transitions to a lower spring rate so that the spring force increases at a slower rate as the connector  76 ,  82  is further compressed. Thus, the spring force flattens out in the second stage  58  to allow the exerted spring force to stay within the desired range  52  over a greater range of compressions compared to the linear spring force  50  of the prior art connector  40 . Desirably, the first stage  56  is defined by compressions of the connector  76 ,  82  of less than 0.005 inch, while the second stage  58  is defined by compressions of the connector  76 ,  82  between 0.010 inch and 0.025 inch. 
     Turning to  FIGS.  7 - 8   , the improved electrical connectors  76 ,  82  have a first end  36  that is inserted into one of the connecting slots  22  of the bus  16  to connect a circuit breaker  18  to the bus  16 . The second end  38  of the connector  76 ,  82  is connected to the circuit breaker  18  (e.g., with a bolt or rivet through a hole  74  in the second end  38 ). The first end  36  has a bend  60  between two arms  62 ,  64  of the connector  76 ,  82 , with the first arm  62  defining the second end  38  of the connector  76 ,  82  and the second arm  64  defining a free end  48  of the connector  76 ,  82 . First and second contact portions  66 ,  68  are located between the bend  60  and the second end  38  and the free end  48 , respectively. When the connectors  76 ,  82  are inserted into the bus, the first and second contact portions  66 ,  68  are compressed against each other by the plates  28 . The first contact portion  66  may be parallel with the plates  28 , while the second contact portion  68  may be angled in the free state so that it is angled inward toward the bend  60  and outward toward the free end  48 . 
     The connectors  76 ,  82  may also have a spring  78 ,  84  that engages the second arm  64  to bias the second arm  64  outward. For instance, the spring  78 ,  84  may be located between the first and second arms  62 ,  64 . Most preferably, the spring  78 ,  84  may be a cantilevered spring  78 ,  84  with a first end  70  that is connected to the first arm  62  and a second free end  72  extending toward the second arm  64 . The first end  70  may be connected to the second end  38  of the connector  76 ,  82  with the hole  74  and a bolt or rivet therethrough. Desirably, the first and second arms  62 ,  64  of the connector  76 ,  82  are made of copper while the spring  78 ,  84  is made of steel. 
     As shown in  FIG.  7   , in one connector  76 , the spring  78  may have a hook  80  extending toward the free end  48  of the second arm  64 . The hook  80  may be spaced apart from the free end  48  of the second arm  64  in the free state before the connector  76  has been compressed. After the connector  76  has been partially compressed (i.e., the first stage). The free end  48  of the second arm  64  may engage the hook  80  of the spring  78  so that the spring  78  provides greater resistance to further compression (i.e., the second stage). Thus, the spring  78  provides a buttressing force in the second stage such that the bend  60  between the first and second arms  62 ,  64  and the spring  78  both elastically flex to produce a combined spring force that is flatter than the first stage. 
     As shown in  FIG.  8   , in another connector  82 , the spring  84  may be angled between the first and second arms  62 ,  64 . Like the connector  76  of  FIG.  7   , the first end  70  of the spring  84  may be connected to the second end  38  of the connector  82 . However, the spring  84  may follow the shape of the first arm  62  down to the inner surface of the first contact portion  66  where the spring  84  is angled upward toward the second contact portion  68 . Thus, the spring  84  may extend at an angle between the first and second contact portions  66 ,  68  to engage the inner sides of the contact portions  66 ,  68 . The second end  72  which contacts the second arm  64  may have a bend  86  contacting the inner side thereof. The combined spring force of the connector bend  60  and the spring  84  may result in a non-linear spring force as illustrated in  FIG.  9   . As shown, the spring force of the connector  82  in  FIG.  8    varies depending on the angle of the spring  84  from a vertical line. For example, the spring force of the connector  82  is more non-linear when the angle of the spring  84  is 60° from vertical than when the spring  84  is angled 25° from vertical. Preferably, the spring  84  is angled 25° or more from vertical, and more preferably, 45° or more from vertical. Preferably, the spring  84  is not angled more than 75° from vertical. 
     While preferred embodiments of the inventions have been described, it should be understood that the inventions are not so limited, and modifications may be made without departing from the inventions herein. While each embodiment described herein may refer only to certain features and may not specifically refer to every feature described with respect to other embodiments, it should be recognized that the features described herein are interchangeable unless described otherwise, even where no reference is made to a specific feature. It should also be understood that the advantages described above are not necessarily the only advantages of the inventions, and it is not necessarily expected that all of the described advantages will be achieved with every embodiment of the inventions. The scope of the inventions is defined by the appended claims, and all devices and methods that come within the meaning of the claims, either literally or by equivalence, are intended to be embraced therein.