Abstract:
A fuse employing a plurality of tuning fork terminal configurations with an improved current capacity within a smaller footprint and a housing design to provide the terminals with insert protection and strain relief.

Description:
CROSS-REFERENCE 
       [0001]    This application claims priority to U.S. Provisional Patent Application Ser. No. 61/155,969, which was filed on Feb. 27, 2009, the entirety of which is herein incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    Embodiments of the invention relate to the field of fuses. More particularly, the present invention relates to a one-piece tuning fork terminal design and a two piece housing which provides strain relief and overstress protection during insertion. 
         [0004]    2. Discussion of Related Art 
         [0005]    As is well known, a fuse (short for “fusible link”) is an overcurrent protection device used in electrical circuits. In particular, when too much current flows, a fuse link breaks or opens thereby protecting the electrical circuit from this increased current condition. A “fast acting’ fuse creates an open circuit rapidly when an excess current condition exists. A “time delay” fuse generally refers to the condition where the fuse does not open upon an instantaneous overcurrent condition. Rather, a time lag occurs from the start of the overcurrent condition which is needed in circuits used for motors which requires a current surge when the motor starts, but otherwise runs normally. 
         [0006]    The terminals of a fuse may have a tuning fork configuration where a first prong is spaced from a second prong to accommodate insertion of a male or female terminal as disclosed in U.S. Pat. No. 6,407,657 the contents of which are hereby incorporated by reference. Each of the first and second prongs have a normal force toward the space formed therebetween which acts against the male receiving terminal to define an electrical connection. As these terminals are positioned within a fuse box, this normal force may degrade over time which compromises the electrical connection between the terminal prongs and the male receiving terminal. In addition, the size, shape and composition of the terminals may limit the current capacity of the fuse. Moreover, the housing needs to be configured to limit the strain forces applied to the terminals and the fusible link during assembly, installation and operation. Thus, there is a need for an improved fuse employing tuning fork terminal configurations with an increased current capacity and a housing design to provide terminal insertion protection and strain relief. 
       SUMMARY OF THE INVENTION 
       [0007]    Exemplary embodiments of the present invention are directed to a fuse which provides improved current capacity, strain relief and insert protection. In an exemplary embodiment, the fuse includes a plurality of conducting terminal portions having first and second prongs and a gap disposed therebetween. At least one of the terminal prongs has an upper end, a lower end and an angled wall disposed between the lower and upper end. The angled wall is configured to provide increased surface area of a first of the plurality of conducting terminal portions. A fusible link is disposed between the plurality of terminal portions where the fusible link is configured to interrupt current flowing between the plurality of terminal portions upon certain high current conditions. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  illustrates a perspective view of a fuse in accordance with an embodiment of the present invention. 
           [0009]      FIG. 2  is a plan view illustrating a fusible element in accordance with an embodiment of the present invention. 
           [0010]      FIG. 2A  is a side view illustrating a fusible element in accordance with an embodiment of the present invention. 
           [0011]      FIG. 3  is a plan view of housing half  20  in accordance with an embodiment of the present invention. 
           [0012]      FIG. 3A  is a side view of the housing half shown in  FIG. 3  taken along lines A-A in accordance with an embodiment of the present invention. 
           [0013]      FIG. 4  is a plan view of housing half  25  in accordance with an embodiment of the present invention. 
           [0014]      FIG. 4A  is a bottom view of housing half  25  shown in  FIG. 4  in accordance with an embodiment of the present invention. 
           [0015]      FIG. 4B  is a side view of the housing half shown in  FIG. 4  taken along lines A-A in accordance with an embodiment of the present invention. 
           [0016]      FIG. 5  illustrates a perspective view of a fuse in accordance with an embodiment of the present invention. 
           [0017]      FIG. 6  is a plan view illustrating a fusible element in accordance with an embodiment of the present invention. 
           [0018]      FIG. 6A  is a side view illustrating a fusible element in accordance with an embodiment of the present invention. 
           [0019]      FIG. 7  is a plan view of housing half  120  in accordance with an embodiment of the present invention. 
           [0020]      FIG. 7A  is a side view of the housing half shown in  FIG. 7  taken along lines A-A in accordance with an embodiment of the present invention 
           [0021]      FIG. 8  is a plan view of housing half  125  in accordance with an embodiment of the present invention. 
           [0022]      FIG. 8A  is a bottom view of housing half  125  shown in  FIG. 8  in accordance with an embodiment of the present invention. 
           [0023]      FIG. 8B  is a side view of the housing half shown in  FIG. 8  taken along lines A-A in accordance with an embodiment of the present invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0024]    The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention, however, may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, like numbers refer to like elements throughout. 
         [0025]      FIG. 1 . is a perspective view of a fuse  10  having a fusible element  12  positioned within a housing  15 . Housing  15  has a generally rectangular or box profile which provides complete enclosure of fusible element  12 . Housing  15  comprises a first half  20  and second half  25  (shown transparently for ease of explanation) which may be thermally bonded or force fit together once fusible element  12  is positioned within the housing. Each of the first and second halves  20  and  25  have cut out or aperture portions (as described below) which are aligned such that when the two halves  20  and  25  are joined define a pair of openings  16  and  17  configured to receive terminals during installation. 
         [0026]      FIG. 2  is a plan view of fusible element  12  which includes two terminal portions  30  and  40  having length L and a fusible link portion  35 . Fusible element  12  may be made from a copper alloy and manufactured as a single piece and stamped to the desired shape. In particular, fusible link  12  may be formed from a copper alloy having, for example; approximately 97.9% Cu, 2% Sn, 0.1% Fe and 0.03% P or 99.8% Cu, 0.1% Fe and 0.03% P. First terminal portion  30  is defined by a first prong  31  and a second prong  32 . Similarly, second terminal portion is defined by a first prong  41  and second prong  42 . When an overcurrent condition occurs, fusible link  35  breaks causing an open circuit between terminals  30  and  40 . Fusible link  35  includes a bridge section  35   a  having curved portions  35   b  and a diffusion bore section  35   c  similar to the S-shaped fuse link portion  27  as disclosed in U.S. Pat. No. 5,229,739 assigned to the assignee of the present invention the contents of which are incorporated herein by reference. This diffusion bore  35   c  includes a tin pellet which lowers the temperature at which the copper alloy melts. In addition, diffusion bore  35   c  defines a pair of reduced sections  35   d  which are configured to accelerate the tin diffusion effect of the pellet at an overload current condition and lowers the voltage drop readings at the rated current. In particular, when an overcurrent condition occurs, the temperature of fusible link  35  increases to the point where the tin pellet melts and flows into the curved portions  35   b  of bridge section  35   a  and the fuse opens. 
         [0027]    As can be seen, first and second terminals  30  and  40  have a configuration similar to a tuning fork with a retaining portion  37  and  47  used to provide strain relief for the fusible element  12  as described in more detail in  FIG. 3 . A gap  33  is formed between first prong  31  and second prong  32  of first terminal portion  30  to a rounded portion  36 . Gap  43  is formed between first prong  41  and second prong  42  of second terminal portion  40  to a rounded portion  46 . Gaps  33  and  43  are configured to receive terminals from a fuse box, fuseholder or panel. First terminal portion  30  includes top and bottom ridges  31   a  on first prong  31  and ridge  32   a  on second prong  32 . Second terminal  40  includes top and bottom ridges  41   a  on first prong  41  and ridge  42   a  on second prong  42 . Each of these ridges provides electrical contact to terminals inserted in gaps  33  and  43 . 
         [0028]    Prong  31  of terminal  30  includes an angled wall section  34   a  extending from top ridge  31   a  toward rounded portion  36 . Prong  32  of terminal  30  includes angled wall section  34   b  extending from ridge  32   a  toward rounded portion  36 . Similarly, prong  41  of terminal  40  includes angled wall section  44   a  extending from top ridge  41   a  toward rounded portion  46 . Prong  42  of terminal  40  includes angled wall section  44   b  extending from ridge  42   a  toward rounded portion  46 . These angled wall sections  34   a ,  34   b ,  44   a  and  44   b  provide increased material cross sectional area of each of the terminals  30  and  40  of fusible element  12 . In addition, the thickness of the material used for the first ( 31 ,  41 ) and second prongs  32 ,  42 ) increases the cross sectional area of the fusible element  12  which likewise increases the current capacity. Turning briefly to  FIG. 2A  which is a side view of fusible element  12 , terminal  30  having a thickness T 1  and fusible link  35  having a thickness T 2 . These thicknesses may be configured according to a desired maximum current capability. Fusible element  12  may be manufactured from a single piece of copper alloy which is thinned for fusible link portion  25  and stamped to form terminal portions  30  and  40 . Tabs  30   a  and  40   a  connect adjacent fusible elements after stamping which are cut to define individual fusible elements  12  during manufacture. Typical tuning fork terminals have a 30 A current capacity. By utilizing copper alloy material, angled wall sections  34   a ,  34   b ,  44   a  and  44   b  as well as the thickness (T 1 ) to length L of terminal portions  30  and  40 , fuse  10  has a current carrying capacity of, for example, approximately 60 A. In this manner, the fuse in accordance with the present invention can replace existing fuse designs with a smaller footprint while providing a larger current carrying capacity. 
         [0029]      FIG. 3  is a plan view of housing half  20  having an upper portion  21  and lower portion  22 . Upper portion  21  is configured to house fusible link  35  and lower portion  22  is configured to house terminals  30  and  40 . Lower portion  22  includes a first chamber  23  within which first terminal  30  of fusible element  12  is positioned. Lower portion  22  also includes a second chamber  24  within which second terminal  40  of fusible element  12  is positioned. First and second chambers are separated by partition  26  which maintains electrical isolation between first terminal  30  and second terminal  40  to prevent shorting therebetween. Cut-out areas  16   a  and  17   a  form half of the openings  16  and  17  for receiving terminals. First chamber  23  includes a plurality of raised bumps  23   a  which support first terminal  30  and second chamber  24  includes a plurality of raised bumps  24   a  which support second terminal  40 . A strain relief assembly  27  is disposed between upper portion  21  and lower portion  22  and is integrally formed with partition  26 . In particular, strain relief assembly  27  includes a centrally disposed upper post  27   a  and a pair of transversely extending ridges  27   b  and  27   c . Post  27   a  is aligned with lower post  27   d  at the lower end of partition  26  each of which is used to join housing halves  20  and  25 . Ridge  27   b  is contiguous with retaining portion  37  of fusible element  12  and ridge  27   c  is contiguous with retaining portion  47  of fusible element  12  when the fusible element is positioned within housing  15 . The positioning of portions  37  and  47  of fusible element  12  against ridges  27   b  and  27   c  provides strain relief for fuse  10 . In particular, when terminals are inserted into gaps  33  and  43  (shown in  FIG. 2 ), fusible element  12  is pushed upward in housing  15  such that portions  37  and  47  are forced into ridges  27   b  and  27   c  which maintains fusible element  12  in position. Housing walls  28  and  29  in lower portion  22  prevent first prongs  31  and  41  from separating away from second prongs  32  and  42  respectively. When terminals are inserted into gaps  33  and  43 , first prongs  31  and  41  are forced outward toward walls  28  and  29 . Wall  28  provides a retention force against prong  31  in direction ‘x’ and wall  29  provides a retention force against prong  41  in direction ‘y’. In this manner, the normal force of the prongs, which is the force of first prongs  31  and  41  toward respective second prongs  32  and  42 , is maintained. This normal force provides integrity to the electrical connection between fusible element  12  and the terminals when the terminals are inserted into gaps  33  and  43 .  FIG. 3A  is a side view of housing half  20  taken along lines A-A shown in  FIG. 3 . Housing half  20  includes an extending side wall  50  and an upper wall  51 . Partition wall  26  extends a distance above bumps  23   a . Posts  27   a  and  27   d  extend above partition wall  26 . Ridge  27   b  is approximately at the same height as partition  26 , but may have alternative configurations to provide the strain relief function as described above. 
         [0030]      FIG. 4  is a plan view of housing half  25  which, when combined with housing half  20 , forms housing  15 . Housing half  25  includes an upper portion  21 ′ and lower portion  22 ′. Upper portion  21 ′ of housing half  25  in combination with upper portion  21  of housing half  20  houses fusible link  35 ; and lower portion  22 ′ of housing half  25  in combination with lower portion  22  of housing half  20 , houses terminals  30  and  40 . Lower portion  22 ′ includes a first chamber  23 ′ within which first terminal  30  is positioned. Lower portion  22 ′ also includes a second chamber  24 ′ within which second terminal  40  is positioned. First and second chambers are separated by partition  26 ′ which includes a pair of apertures  27   a ′ and  27   d ′ which receive posts  27   a  and  27   d  of housing half  20 . First chamber  23 ′ includes a plurality of raised bumps  23   a ′ which support first terminal  30  and second chamber  24 ′ includes a plurality of raised bumps  24   a ′ which support second terminal  40 .  FIG. 4A  is a bottom view of housing half  25  in which cut-out areas  16   a ′ and  17   a ′ align with cut-out areas  16   a  and  17   a  of housing half  20  to define openings  16  and  17  for receiving terminals.  FIG. 4B  is a side view of housing half  25  taken along lines A-A shown in  FIG. 4 . Housing half  25  includes upper portion  21 ′, partition wall  26 ′ which extends a distance above bumps  23   a ′. Cut-out area  16   a ′ is aligned with first chamber  23 ′ to allow a terminal to enter opening  16  and be disposed between first prong  31  and second prong  32  of terminal  30 . 
         [0031]      FIG. 5 . is a perspective view of a fuse  110  having a fusible element  112  positioned within a housing  115 . Housing  115  has a generally rectangular or box profile which provides complete enclosure of fusible element  112 . Housing  115  is depicted as being clear, but this is for illustrative purposes to show fusible element  112 . Housing  115  comprises a first half  120  and second half  125  which may be thermally bonded or force fit together once fusible element  112  is positioned within the housing. Each of the first and second halves  120  and  125  have cut out or aperture portions which are aligned such that when the two halves  120  and  125  are joined define a pair of openings  116  and  117  configured to receive terminals during installation. 
         [0032]      FIG. 6  is a plan view of fusible element  112  which includes two terminal portions  130  and  140  having length L and a fusible link portion  135 . Similar to fusible element  12  shown in  FIG. 2 , first terminal portion  130  is defined by a first prong  131  and a second prong  132 . Similarly, second terminal portion  140  is defined by a first prong  141  and second prong  142 . When an overcurrent condition occurs, fusible link  135  breaks causing an open circuit between terminals  130  and  140 . Fusible link  135  includes a bridge section  135   a  having curved portions  135   b  and a diffusion bore section  135   c . This diffusion bore  135   c  includes a tin pellet which lowers the temperature at which the copper alloy melts. Diffusion bore  135   c  defines a pair of reduced sections  135   d  which are configured to accelerate the tin diffusion effect of the pellet at an overload current condition and lowers the voltage drop readings at the rated current. When an overcurrent condition occurs, the temperature of fusible link  135  increases to the point where the tin pellet melts and flows into the curved portions  135   b  of bridge section  135   a  and the fuse opens. 
         [0033]    First and second terminals  130  and  140  have a configuration similar to a tuning fork with a retaining portion  137  and  147  used to provide strain relief for the fusible element  112 . A gap  133  is formed between first prong  131  and second prong  132  of first terminal portion  130  to a rounded portion  136 . Gap  143  is formed between first prong  141  and second prong  142  of second terminal portion  140  to a rounded portion  146 . Gaps  133  and  143  are configured to receive terminals from a fuse box, fuseholder or panel. First terminal portion  130  includes top and bottom ridges  131   a  on first prong  131  and ridge  132   a  on second prong  132 . Second terminal  140  includes top and bottom ridges  1141   a  on first prong  141  and ridge  142   a  on second prong  142 . Each of these ridges provides electrical contact to terminals inserted in gaps  133  and  143 . 
         [0034]    Prong  131  of terminal  130  includes an angled wall section  134   a  extending from top ridge  131   a  toward rounded portion  136 . Prong  132  of terminal  130  includes angled wall section  134   b  extending from ridge  132   a  toward rounded portion  136 . Similarly, prong  141  of terminal  140  includes angled wall section  144   a  extending from top ridge  141   a  toward rounded portion  146 . Prong  142  of terminal  140  includes angled wall section  144   b  extending from ridge  142   a  toward rounded portion  146 . These angled wall sections  134   a ,  134   b ,  144   a  and  144   b  provide increased material cross sectional area of each of the terminals  130  and  140  of fusible element  112 . In addition, the thickness of the material used for the first ( 131 , 141 ) and second prongs ( 132 ,  142 ) increases the cross sectional area of the fusible element  112  which likewise increases the current capacity. Prong  132  of terminal  130  includes a pair of notches toward the lower end of the prong. Similarly, prong  142  of terminal  140  includes a pair of notches toward the lower end of the prong. These notches are the result of removal of bridge material used to support terminals  130  and  140  during the manufacturing process. 
         [0035]      FIG. 6A  is a side view of fusible element  112 , terminal  130  having a thickness T 1  and fusible link  135  having a thickness T 2 . These thicknesses may be configured according to a desired maximum current capability. Fusible element  112  may be manufactured from a single piece of copper alloy which is thinned for fusible link portion  125  and stamped to form terminal portions  130  and  140 . Typical tuning fork terminals have a 30 A current capacity. As can be seen, fusible element  112  does not include tab portions ( 30   a ,  40   a ) shown in  FIG. 2 . By utilizing copper alloy material, angled wall sections  134   a ,  134   b ,  144   a  and  144   b  as well as the thickness (T 1 ) to length L of terminal portions  130  and  140 , fuse  110  has a current carrying capacity of, for example, approximately 60 A. In this manner, the fuse in accordance with the present invention can replace existing fuse designs with a smaller footprint while providing a larger current carrying capacity. 
         [0036]      FIG. 7  is a plan view of housing half  120  having an upper portion  121  and lower portion  122 . Upper portion  121  of housing half  120  is configured to house fusible link  135  and lower portion  122  is configured to house terminals  130  and  140 . Lower portion  22  includes a first chamber  23  within which first terminal  130  of fusible element  112  is positioned. Lower portion  122  also includes a second chamber  124  within which second terminal  140  of fusible element  112  is positioned. First and second chambers are separated by partition  126  which maintains electrical isolation between first terminal  130  and second terminal  140  to prevent shorting therebetween. Cut-out areas  116   a  and  117   a  form half of the openings  116  and  117  for receiving terminals. 
         [0037]    When terminals are inserted into gaps  133  and  143 , first prongs  131  and  141  are forced outward toward walls  128  and  129 . Wall  218  provides a retention force against prong  131  in direction ‘x’ and wall  129  provides a retention force against prong  141  in direction ‘y’. In this manner, the normal force of the prongs, which is the force of first prongs  131  and  141  toward respective second prongs  132  and  142 , is maintained. This normal force provides integrity to the electrical connection between fusible element  112  and the terminals when the terminals are inserted into gaps  133  and  143 . Housing half  120  is essentially the same as housing half  20  shown with referenced to  FIG. 3 . However, housing half  120  includes a fewer number of bumps  123   a ,  124   a  to maintain terminal portions  130 ,  140  respectively in position within the housing half  120 . In particular, bumps  123   a  assist in limiting the amount of contact between terminal portions  130 ,  140  and housing half  120 . In particular, prongs  131 ,  132  of terminal portion  130  and prongs  141 ,  142  of terminal portion  140  are disposed in housing half  120 . Each of the prongs  131 ,  132 ,  141  and  142  are prevented from contacting housing half  120  by bumps  123   a . This allows air to flow between the fusible element  112  and housing half  120  to provide heat dissipation by limiting the number of contact points between the fusible element  112  and the housing. A strain relief assembly  127  is disposed between upper portion  121  and lower portion  122  and is integrally formed with partition  126 . Strain relief assembly  127  is essentially the same as that shown with respect to  FIG. 3 . However, housing half  120  includes post  127   e  disposed between posts  127   a  and  127   d.    
         [0038]      FIG. 7A  is a side view of housing half  120  taken along lines A-A shown in  FIG. 7 . Housing half  120  includes an extending side wall  150  and an upper wall  151 . Partition wall  126  extends a distance above bumps  123   a . Posts  127   a ,  127   d  and  127   e  extend above partition wall  126 . Ridge  127   b  is approximately at the same height as partition  126 , but may have alternative configurations to provide the strain relief function as described above. 
         [0039]      FIG. 8  is a plan view of housing half  125  which, when combined with housing half  120 , forms housing  115 . Housing half  125  includes an upper portion  121 ′ and lower portion  122 ′. Upper portion  121 ′ of housing half  25  in combination with upper portion  121  of housing half  120  houses fusible link  135 ; and lower portion  122 ′ of housing half  125  in combination with lower portion  122  of housing half  120 , houses terminals  130  and  140 . Lower portion  122 ′ includes a first chamber  123 ′ within which first terminal  130  is positioned. Lower portion  122 ′ also includes a second chamber  124 ′ within which second terminal  140  is positioned. First and second chambers are separated by partition  126 ′ which includes apertures  127   a ′,  127   d ′ and  127   e ′ configured to receive posts  127   a ,  127   d  and  127   e  of housing half  120 . First chamber  123 ′ includes a plurality of raised bumps  123   a ′ which support first terminal  130  and second chamber  124 ′ includes a plurality of raised bumps  123   a ′which support second terminal  140 . Similar to bumps  123   a  shown in  FIG. 7 , bumps  123   a ′ assist in limiting the amount of contact between terminal portions  130 ,  140  and housing half  112 . 
         [0040]      FIG. 8A  is a bottom view of housing half  125  in which cut-out areas  116   a ′ and  117   a ′ align with cut-out areas  116   a  and  117   a  of housing half  120  to define openings  116  and  117  for receiving terminals.  FIG. 8B  is a side view of housing half  125  taken along lines A-A shown in  FIG. 8 . Housing half  125  includes upper portion  121 ′, partition wall  126 ′ which extends a distance above bumps  123   a ′. Cut-out area  116   a ′ is aligned with first chamber  123 ′ to allow a terminal to enter opening  116  and be disposed between first prong  131  and second prong  132  of terminal  130 . 
         [0041]    While the present invention has been disclosed with reference to certain embodiments, numerous modifications, alterations and changes to the described embodiments are possible without departing from the sphere and scope of the present invention, as defined in the appended claims. Accordingly, it is intended that the present invention not be limited to the described embodiments, but that it has the full scope defined by the language of the following claims, and equivalents thereof.