Patent Publication Number: US-7710236-B2

Title: Fuse systems with serviceable connections

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of U.S. Provisional Application 60/834,591 entitled FUSES WITH SERVICEABLE CONNECTIONS filed Aug. 1, 2006, the entirety of which is hereby incorporated herein by reference. 

   TECHNICAL FIELD 
   The present disclosure generally relates to fuse systems and, in particular, to an electrical fuse system having both a non-serviceable fuse and a serviceable connection facilitating use of a serviceable fuse, if needed. 
   BACKGROUND 
   Fuses are commonly-used in various products to protect electrical components and wiring from receiving unintended high levels of electrical current that could otherwise damage the protected components and wiring. In particular, fuses are positioned in electrical circuits between the power source and the component or wiring to be protected. When a fuse experiences an electrical current level that exceeds a threshold current (rated for the particular fuse), the fuse “blows,” thereby disconnecting the power source from the protected wiring or component. Thus, the protected component or wiring is protected from the unintended high current level. 
   Many electrical distribution centers, such as those used for motor vehicles, utilize loose-piece replaceable fuses to protect electrical components and wiring. These replaceable fuses come in various sizes with various current-handling capabilities and are typically chosen based on the current-carrying requirements of the circuit they are intended to protect. They are typically installed between two terminals in a system in an accessible location. If such a conventional serviceable fuse blows in the field, it is may be replaced with a similar fuse by a consumer or service person, such as, in the case of motor vehicles, a mechanic in a garage. Examples of replaceable fuses may be found in U.S. Pat. No. 5,346,411 entitled “Tap-In Blade Fuse”; U.S. Pat. No. 2,527,160 entitled “Plug Type Fuse”; and U.S. Pat. No, 3,581,262 entitled “Safety Fuse With Glass Coating On Fusible Portion.” Such replaceable fuses offer the advantage of being readily available to the consumer or the mechanic at the time that a replacement is needed. When replacement fuses are in an accessible location, they are readily removed and replaced and are therefore referred to herein as “serviceable fuses.” 
   As an alternative to the above-described serviceable fuses, some electrical distribution centers use non-replaceable or “non-serviceable fuses” to protect electrical components and wiring. Non-replaceable fuses are commonly integrated onto circuit boards during manufacture and cannot be replaced or serviced without replacing the entire circuit board. Examples of non-serviceable fuses may be found in United States Patent Application Number 2005233515 entitled “Method Of Etching A Semiconductor Device”; United States Patent Application Number 2003205777 entitled “Integrated Fuse With Regions Of Different Doping Within The Fuse Neck”; U.S. Pat. No. 5,552,757 entitled “Surface-Mounted Fuse Device”; U.S. Pat. No. 5,923,239 entitled “Printed Circuit Board Assembly Having An Integrated Fusible Link”; and German Patent Number 3,723,832 entitles “Printed Circuit With An Integrated Fuse.” Other “non-serviceable fuses within the meaning of this disclosure include fuses that would otherwise be replaceable but for their physical location in the system (i.e., fuses that are positioned in inaccessible locations). 
   While serviceable fuses are conveniently replaceable, they can represent a significant cost to the manufacturer of the original product in comparison to the use non-serviceable fuses. A serviceable fuse is more costly to manufacture than a non-serviceable fuse. Further, a serviceable fuse must be physically installed, either manually or by machine, in the terminals in the electrical distribution center assembly, thereby adding additional steps and costs to the manufacturing process. Even where the installation is accomplished automatically, various steps in the automated process, such as manual loading of the supply tubes for the automatic insertion equipment, must still be performed manually. On the other hand, non-serviceable fuses are less costly to manufacture and they do not require any special handling or fixturing. However, when such a non-serviceable fuse blows, it is not possible for a mechanic or consumer to rapidly and inexpensively replace the fuse alone. Instead, the entire device or a circuit board (on which the non-serviceable fuse resides) must be replaced when a non-serviceable fuse blows. Thus, it is significantly more costly to replace a non-serviceable fuse (i.e., replace an entire circuit board) than to replace a serviceable fuse. 
   As a result, a dilemma exists in designing fuses into electrical systems. It may be advantageous to a manufacturer to choose a non-serviceable fuse instead of a serviceable fuse at the time of manufacture to save manufacturing cost. However, it may be disadvantageous to have a non-serviceable fuse rather than a serviceable fuse at the time that a repair is needed, since the repair will be more expensive. Thus, the choice of a non-serviceable fuse may increase warranty cost and consumer dissatisfaction. Hence, in retrospect, if the fuse never blows, a non-serviceable fuse is more cost effective, but if the fuse blows during the lifetime of the electrical system, a serviceable fuse is more cost effective. 
   The embodiments disclosed herein are intended to address this dilemma. Further areas of applicability of the present invention will become apparent from the detailed description provided herein. It should be understood that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are intended for purposes of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
   SUMMARY 
   The present application discloses a fuse system having both a non-serviceable fuse and a fuse terminal system for selectively installing a serviceable fuse. The fuse terminal system has first and second terminals for selectively connecting a serviceable fuse in electrical parallel with the non-serviceable fuse. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments of the present invention will now be described by way of example in greater detail with reference to the attached figures, in which: 
       FIG. 1A  is a perspective exploded view of an exemplary fuse system wherein a printed circuit type non-serviceable fuse for protecting a component of an electrical system (not shown) is in electrical parallel with a fuse terminal system for a serviceable fuse, and illustrating a serviceable fuse; 
       FIG. 1B  is a perspective view of an alternative fuse system to that shown in  FIG. 1A  having a surface mounted non-serviceable fuse; 
       FIG. 2  is a side elevation view of the exemplary fuse system of  FIGS. 1A and 1B  illustrating frangible material on a fuse terminal; 
       FIG. 3  is a top view of the exemplary fuse system of  FIG. 1A  with a housing shown in phantom line; 
       FIG. 4  is a front elevation view of the exemplary fuse system of  FIGS. 1A and 3  with a housing shown in phantom line; 
       FIG. 5  is the front elevation view of the exemplary fuse system of  FIGS. 1A ,  3  and  4  with a serviceable fuse installed; 
       FIG. 6A  is a schematic view of an exemplary fuse system protecting a local electrical component; 
       FIG. 6B  is an alternative schematic view of an exemplary fuse system protecting a remote electrical component; 
       FIG. 6C  is an alternative schematic view of an exemplary fuse system wherein the non-serviceable fuse protects a local electrical component and the fuse terminal system is located remotely from the electrical component; 
       FIG. 7  is a schematic drawing view of an exemplary fuse system protecting multiple remote electrical components; and 
       FIG. 8  is a schematic drawing view of an exemplary fuse system with non-serviceable fuses protecting multiple electrical components locally wherein each of the non-serviceable fuses is provided with a remote fuse terminal system for a serviceable fuse at a electrical distribution location. 
   

   DETAILED DESCRIPTION 
   Disclosed herein is a fuse system having both a non-serviceable fuse and a fuse terminal system for selectively installing a serviceable fuse. The fuse terminal system has first and second terminals for selectively connecting a serviceable fuse in electrical parallel with the non-serviceable fuse. The “non-serviceable fuse” is, in most embodiments, a non-replaceable type fuse integrated onto a circuit board, but it may also be other types of fuses that are difficult to service, such as a replaceable type fuse that is particularly inaccessible to the mechanic or consumer at the time replacement is needed. The fuse terminal system is configured to be used with replaceable fuses, such as those commonly used in motor vehicle applications or in consumer electronics, referred to herein as “serviceable fuses.” 
   Refer now to the drawings wherein like numerals indicate like or corresponding parts throughout the several views and exemplary embodiments are illustrated. FIGS.  1 A and  3 - 5  illustrate an exemplary fuse system  10  protecting an electrical component (not shown), which may include an electrical device, an electrical circuit, or electrical wiring. The fuse system  10  includes both (i) a non-serviceable fuse  20  disposed between electrical contacts  22  and  24  and (ii) a terminal system comprising terminals  16  and  18  for selectively connecting a serviceable fuse  30 . Terminals  16  and  18  are in electrical communication with contacts  22  and  24 , respectively. The fuse system  10  is intended to be electrically connected at terminals  22  and  24  generally between a power source (not shown) and the protected electrical component. The fuse system  10  may be assembled on a board  12 , such as a printed circuit board. As will be described later herein, the board  12  may be used solely for the fuse system  10 , may support additional fuse assemblies or, alternatively, may support the electrical component protected by the fuse system  10 . 
   In the exemplary embodiment shown in  FIG. 1A  and  FIGS. 3-7 , the non-serviceable fuse  20  is a trace of a printed circuit board configured in such a way so that it will “blow” and open the circuit to disconnect the protected component from the power source when the current flowing through the non-serviceable fuse  20  exceeds a predetermined threshold current level. The predetermined current threshold or “rating” of fuse  20  is accomplished, for example, by adjusting the trace width and/or shape of the fuse  20 . 
     FIG. 1B  illustrates an alternative exemplary fuse system  10 ′, which is similar to the fuse system  10  of  FIG. 1A  except that the non-serviceable fuse  20 ′ in  FIG. 1B  is a low cost surface mountable fuse that is surface mounted to the board  12 ′. As will be appreciated by those skilled in the art, various other types of non-serviceable fuses can be used in place of non-serviceable fuse  20  ( FIG. 1A ) or non-serviceable fuse  20 ′ ( FIG. 1B ) to reduce the original cost of manufacturing the fuse system as compared to using a serviceable fuse. 
   The exemplary fuse terminal system (i.e., terminals  16  and  18 ) shown in  FIG. 1A  may be surface-mounted to the board  12  or may be mounted to the board  12  by inserting terminal leads  14  into the board  12 , as shown in  FIGS. 2 and 4 . The fuse terminal system is configured to receive and electrically connect a serviceable fuse  30  via fuse blades  32  and  34 . When installed, serviceable fuse  30  is electrically parallel to non-serviceable fuse  20 . 
     FIG. 2  illustrates a more detailed view of the exemplary terminals  16  and  18  as shown in  FIGS. 1A and 1B . Terminals  16  and  18  each have fingers  36  and  38  that resiliently accept and secure the blades  32  and  34  (from  FIGS. 1A and 1B ), respectively, and engage the blades to provide an electrical connection to the serviceable fuse  30 . At least one of the terminals  16  and  18  may be provided with a web  40  of frangible material extending between the fingers  36  and  38 . The web  40  is broken by the blade  32  or  34  of a serviceable fuse  30 , when it is inserted between the fingers  36  and  38 , as shown in  FIG. 5 . A broken web  40  provides a visual indication that a serviceable fuse  30  has been used in the fuse system  10 . This indication may be useful if, during or after servicing an electrical component, a consumer or a service technician cannot remember whether a replacement or serviceable fuse  30  was removed from the fuse terminal assembly of this fuse system  10  or from another fuse system. Though one particular type of fuse terminal system and serviceable fuse is shown in  FIGS. 1A-5 , various other types of known fuse terminal systems and serviceable fuses can be used in place thereof. 
   As shown in  FIGS. 3 and 4 , the fuse system  10  may include a cover  50 , which cooperates with the board  12  to form a housing or enclosure. The cover  50  may be similar to the covers for protecting terminal assemblies conventionally used with serviceable fuses  30  that are provided as original equipment by manufacturers. The cover  50  may cover multiple fuse systems  10  or  10 ′ or other components associated with the board  12 . The cover  50  is provided with slots  52  and  54  proportioned to permit the blades  32  and  34  of the serviceable fuse  30  to extend therethrough. 
   A web  56  of material, which may be formed in a molding process when the cover  50  is created, may be provided across at least one of the slots or apertures  52  or  54 . The web  56  may be broken by one of the blades  32  or  34  of a replacement or serviceable fuse  30  when a serviceable fuse is installed in the terminal assembly, as shown in  FIG. 5 . It will be appreciated that web  40  described previously and shown in  FIGS. 2 and 3 , may be used in addition to or, alternatively, instead of web  56  shown in  FIGS. 3 and 4  to provide a visual indication that a serviceable fuse  30  has at some time been used with fuse system  10 . 
   Thus, in use, the fuse system  10  or  10 ′ described above relies upon non-serviceable fuse  20  or  20 ′ to provide protection against unintended high electrical currents in the first instance. If and when the non-serviceable fuse blows, it can be easily “replaced” by installing a serviceable fuse  30  in the fuse terminal system (terminals  16  and  18 ). If the non-serviceable fuse never blows, then there is no need to ever install a serviceable fuse. In this way, the initial cost of manufacturing the electrical system is reduced as compared to having to install at the outset a serviceable fuse that may never blow, while, at the same time, the fuse terminal system provides a relatively convenient and low-cost option for “replacing” a blown non-serviceable fuse (with a serviceable fuse) without having to replace the entire circuit board. 
     FIGS. 6A ,  6 B,  6 C,  7  and  8  show schematic circuit diagrams of various ways in which fuse systems  10  and  10 ′ shown in  FIGS. 1A and 1B  can be arranged on circuit boards. As shown in  FIGS. 6A ,  6 B,  6 C,  7  and  8 , a fuse system  110  or  210  (corresponding to fuse systems  10  and  10 ′ in  FIGS. 1A and 1B ) may be used locally with the electrical component being protected by the fuse system as well as remotely therefrom. For example, as shown in each of  FIGS. 6A-6C , an electrical component  100  is protected by a fuse system  110  including non-serviceable fuse  120 , such as the non-serviceable fuses  20  and  20 ′ described above. The fuse system  10  further includes a fuse terminal system having terminals  116  and  118 , such as the terminals  16  and  18  described above. The terminals  116  and  118  are adapted to accept a serviceable fuse (not shown), such as serviceable fuse  30  described above, to be connected electrically in parallel with the non-serviceable fuse  120  in the event that the non-serviceable fuse has blown. 
   In the embodiment shown in  FIG. 6A , the component  100  may be mounted on the same board  112  as is mounted both the non-serviceable fuse  120  and the terminals  116  and  118 . In the embodiment shown in  FIG. 6B , the non-serviceable fuse  120  may be mounted on the same board  112  as the terminals  116  and  118 , but the board  112  may be remotely located relative to the component  100 . In the embodiment shown in  FIG. 6C , the non-serviceable fuse  120  may be part of an assembly  102  that includes the component  100  and is remotely located from the terminals  116  and  118 . 
   In some embodiments, as shown in  FIGS. 7 and 8 , a fuse system  210  may be used advantageously to protect multiple electrical components  100  and  200  disposed remote from a common board  212 , such as an electrical distribution center. As shown in the embodiment of  FIG. 7 , the board  212 , may be provided with a first non-serviceable fuse  120  connected in series with and protecting electrical component  100  and a second non-serviceable fuse  220  connected in electrical series with and protecting electrical component  200 . The board  212  of  FIG. 7  is further provided with a first fuse terminal system having terminals  116  and  118  connected in electrical parallel with the first non-serviceable fuse  120  and a second fuse terminal system having terminals  216  and  218  connected in electrical parallel with the second non-serviceable fuse  220  to respectively accept serviceable fuses (not shown) as needed to protect the remotely located components  100  and  200 . Alternatively, as shown in the embodiment of  FIG. 8 , a common board  212  may support the terminals  116 ,  118 ,  216  and  218  while the serviceable fuses  120  and  220  may be remotely located relative to the board  212 . In particular, the serviceable fuses  120  and  220  may be collocated with the respective components  100  and  200  which they protect. 
   It is to be understood that the above description is intended to be illustrative and not restrictive. Many alternative approaches or applications other than the examples provided would be apparent to those of skill in the art upon reading the above description. The scope of the invention should be determined, not with reference to the above description, but should instead be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. It is anticipated and intended that future developments will occur in the arts discussed herein, and that the disclosed systems and methods will be incorporated into such future examples. In sum, it should be understood that the invention is capable of modification and variation and is limited only by the following claims. 
   The present embodiments have been particularly shown and described, which are merely illustrative of the best modes. It should be understood by those skilled in the art that various alternatives to the embodiments described herein may be employed in practicing the claims without departing from the spirit and scope as defined in the following claims. It is intended that the following claims define the scope of the invention and that the method and apparatus within the scope of these claims and their equivalents be covered thereby. This description should be understood to include all novel and non-obvious combinations of elements described herein, and claims may be presented in this or a later application to any novel and non-obvious combination of these elements. Moreover, the foregoing embodiments are illustrative, and no single feature or element is essential to all possible combinations that may be claimed in this or a later application. 
   All terms used in the claims are intended to be given their broadest reasonable constructions and their ordinary meanings as understood by those skilled in the art unless an explicit indication to the contrary is made herein. In particular, use of the singular articles such as “a,” “the,” “said,” etc. should be read to recite one or more of the indicated elements unless a claim recites an explicit limitation to the contrary.