Abstract:
A fuse for a moderately hazardous environment comprising includes: (i) a fuse element; (ii) first and second terminals connected to the fuse element; and (iii) a metal enclosure placed around the fuse element, the enclosure configured to protect the environment from an opening of the fuse element, and wherein the first and second terminals extend from the metal enclosure.

Description:
BACKGROUND 
     The present disclosure relates generally to circuit protection and more particularly to fuse protection for moderately hazardous environments. 
     Forklift trucks (“forklifts”) have been used either to lift goods of relatively heavy weight up to an elevated location or to lower the goods to the ground. Forklifts also can be used to move the goods from one place to another within a limited working area. Depending on the power sources employed, the forklifts are classified into an engine-driven forklift, which may operate in an outdoor area and an electromotive forklift, which is suitable for indoor operation, due to its reduced emission of exhaust gas and noise. 
     In either case, forklifts may operate in a potentially hazardous environment, such as a potentially flammable or explosive environment. Accordingly, fuses for forklifts need to be maintained such that an opening of the fuse element, which can cause a spark, does not cause an explosion or start a fire. Fuses for forklifts and similar vehicles are therefore required to be located inside a metal casing according to Underwriters Laboratories (“UL”) standard 583. Enclosing all of the forklift fuses in the same enclosure is space consuming, relatively expensive and makes servicing the fuses difficult. 
     Accordingly, an improved fuse for a moderately hazardous environment is needed. 
     SUMMARY 
     The present disclosure provides a fuse for a moderately hazardous environment, which is classified under UL 583 as EE and ES. The fuse includes terminals that extend from a protective enclosure, which makes servicing the fuses easier than with prior fuses for moderately hazardous environment conditions, which were fully enclosed. 
     The fuse in one embodiment includes a fuse element. First and second terminals extend from or are connected to the fuse element. A metal enclosure is placed around the fuse element. The enclosure is sized and configured to protect the environment from an opening of the fuse element. The first and second terminals extend from the metal enclosure. 
     In one embodiment, the enclosure includes first and second end caps connected to a metal body of the enclosure. The first and second terminals extend through the first and second end caps, e.g., through slits in the end caps, respectively. The end caps can be plastic, e.g., a high temperature thermoset plastic or thermoform plastic or other suitable insulator, such as ceramic or rubber. The metal body of the enclosure can be aluminum, steel or stainless steel, for example. 
     The first and second end caps are attached mechanically to the metal body of the enclosure, for example, staked to the enclosure via the first and second terminals. For example, the terminals can have one or stamped stake or bump that fastens the terminals to the end caps. Alternatively or additionally, the insulating end caps are adhered to the metal body. The end caps can each have an outer portion that mates flush with an outer surface of the metal portion of the enclosure and an inner portion that fits snugly inside the metal portion. 
     The enclosure can have different cross-sectional shapes, such as an at least substantially rectangular or square shape, an at least substantially elliptical shape or an at least substantially round shape. The enclosure can have a wall thickness of at least The thickness of walls  98  in an embodiment is at least about 0.053 inch (1.35 mm), although thinner or greater thicknesses could be used alternatively, for example, based on the metal chosen or for other applications. In one embodiment, the outside surface of the enclosure (e.g., metal portion) is marked with rating information, such as voltage and current rating information, make and manufacturer. 
     The fuse element can be rated for example for up to ninety-six VDC and one-thousand amps. It is contemplated however to configure the fuse element for higher voltage and amperage ratings if the industry has such a need. The fuse element can be serpentine, thinned or otherwise non-linear. The element in one embodiment is made of a copper alloy and be formed integrally with or attached to at least one of the first and second terminals, which can be of the same or different material, such as copper alloy, zinc alloy, silver or silver plating. 
     In one embodiment, the fuse includes an insulating housing placed around the fuse element and inside of the enclosure. The insulating housing can be ceramic and fixed to the element or terminals. The insulating housing in one embodiment includes a window allowing a service person to see if the element has opened. The housing and window are in essence a leftover from the prior art which used a large metal enclosure having a removable lid and therefore may not be needed in the present application. 
     In one embodiment, the fuse includes an opened-fuse indicator positioned to inform a person that the fuse element has opened. The indicator can be a light emitting diode (“LED”) placed in parallel with the element. Normally, not enough current flows through the LED to energize it. Upon an opening of the element, energy is shunted through the LED, energizing it an causing the LED to become illuminated, informing the service person of same. The LED is placed on one of the end caps in one embodiment. 
     In an alternative embodiment, a fuse bank is provided, which includes a plurality of fuse element assemblies. The enclosure here is sized to hold the plurality of fuse element assemblies. The enclosure again includes a metal body and insulating, e.g., plastic end caps. The plastic end caps each include a plurality of slits. Each slit accepts one of the terminals extending from one of the fuse elements. The fuse elements can be attached to the end caps mechanically and individually via stakes or bends in the terminals as shown below. The end caps in one embodiment each include an outer portion that mates flush with an outer surface of the enclosure and an inner portion that fits inside the enclosure. 
     The fuses of the fuse bank can again have intermediate insulating, e.g., ceramic, housings that surround each fuse element. The terminals extend from the fuse elements and from the insulating housings. The housings are positioned inside the bank enclosure and include viewing windows that allow an operator to view whether the fuse element has opened or not. 
     The fuse bank embodiment can also employ opened-fuse indication, e.g., LED&#39;s, described above. It is contemplated to provide a separate LED for each fuse element of the fuse bank. For example, the LED&#39;s can be placed adjacent to an associated fuse terminal on one of the end caps. 
     The different fuse elements can be rated for the same voltage and amperage or different voltages and amperages. The enclosure in one embodiment is at least substantially rectangular in cross-section, aluminum, steel or stainless steel, can have a wall thickness of at least about 0.053 inch (1.35 mm) and be provided with rating information for each fuse. 
     It is accordingly an advantage of the present disclosure to provide an improved fuse for a moderately hazardous environment. 
     It is another advantage of the present disclosure to provide a fuse system for a moderately hazardous environment, which is easier to diagnose when one or more of the fuses of the system opens. 
     It is a further advantage of the present disclosure to provide a fuse for a moderately hazardous environment, which can include open-fuse indication. 
     Additional features and advantages are described herein, and will be apparent from, the following Detailed Description and the figures. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1A  is an exploded view of one embodiment of a moderately hazardous environment fuse of the present disclosure. 
         FIGS. 1B to 1D  are top, front and perspective views, respectively, of the moderately hazardous environment fuse of  FIG. 1A  as assembled. 
         FIGS. 2A to 2C  are top, front and perspective views, respectively, of an alternative moderately hazardous environment fuse of the present disclosure. 
         FIGS. 3A and 3B  are top, front and perspective views, respectively, of an alternative moderately hazardous environment fuse of the present disclosure. 
         FIG. 4  is a perspective view of a moderately hazardous environment fuse bank of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings and in particular to  FIGS. 1 to 4 , fuse  10  illustrates one embodiment of a moderately hazardous environment fuse of the present disclosure. As discussed above, one application for fuse  10  is a fork lift, which falls under UL 583 EE and ES classifications. It should be appreciated however that fuse  10  can be used in other applications, including other moderately hazardous environment applications such as with vehicles operating with flammable products. 
     Fuse  10  includes a fuse element  12 , which is sized to open at rated current and i 2 R values. For example, fuse  10  can be rated for operation anywhere up to ninety-six VDC and one-thousand amps. In any of the embodiments described herein an arc-quenching material such as sand or a larger grain material can be added to the fuse, e.g., within the protective enclosure described below, to boost the fuses ratings. Again, fuse element  12  can be made for larger voltages and amperages if needed. 
     Fuse element  12  can be thinned (e.g., in one or two dimensions relative to terminals  14  and  16 ), serpentine in shape or otherwise non-linear in shape. Element  12  in one embodiment is made of a silver, copper, copper alloy or zinc alloy and can be formed integrally with or be attached to at least one of the first and second terminals  14  and  16 . Element  12  can be fast acting (e.g., according to a CNN designation used by the eventual assignee of the present disclosure) or have a time delay before opening (e.g., according to a CNL designation used by the eventual assignee of the present disclosure). 
     Element  12  can be made of a base metal, such as copper or copper alloy, which is skived and inlaid with other desirable metals listed above. Terminals  14  and  16  may be made of one or more of copper, copper alloy, zinc or silver. Terminals  14  and  16  can be made of the same or different metal(s) as element  12  and accordingly be formed integrally with or attached to element  12 . Tin or other low melting temperature metal spot can be placed at the position on the element at which it is desired for element  12  to open. The tin melts and diffuses into element  12  increasing resistance and causing element  12  to open more quickly. 
     Element  12  in an embodiment is about 0.020 to 0.080 inch (0.51 to 2.03 mm) thick by 0.060 to 0.260 inch (1.52 to 6.6 mm) wide by about 1.00 inch (2.54 cm) long. Terminals  14  and  16  in an embodiment are sized to receive a ¼ to 5/16 inch (6 to 8 mm) diameter bolt. In addition to changing the fuse element characteristics by varying width and thickness, bridges can be formed in element  12  for example by punching or otherwise providing one or more opening in the element at the position on the element at which it is desired for element  12  to open. 
     Terminals  14  and  16  each include a connecting slot  18   a  and  18   b , which receives a mounting screw for holding fuse  12  firmly in place. In the illustrated embodiment, connecting slots  18   a  and  18   b  are oriented in different directions to enable fuse  12  to be inserted and removed readily. Alternatively, connecting slots  18   a  and  18   b  are oriented in a same direction, e.g., both opening to the sides of terminals  14  and  16  to provide for a side load/removal. 
     In the illustrated embodiment, housing restraining tabs  20   a  and  20   b  are located between terminals  14  and  16  and fuse element  12 . Tabs  20   a  and  20   b  and terminals  14  and  16  form locking grooves  22  that each lock around an end wall  32  of an insulating housing  30 . End walls  32  each define a slit  34 , which is sized to allow one of the locking grooves  22 , but not a corresponding locking tab  20   a  or  20   b , to fit through the slit  34 . In this manner, locking tabs  20   a  and  20   b  restrain fuse element  12  within insulating housing  30 . 
     Insulating housing  30  provides a first layer of protection around fuse element  12  in the event that element  12  opens. Housing  30  can be a ceramic material, plastic material or other suitable insulating material. Housing  30  supports a viewing window  36 . As mentioned above, housing  30  may not be required. 
     To operate in a moderately hazardous environment, an enclosure  40  is placed around housing  30  and fuse element  12 . It should be appreciated that while housing  30  is shown with fuse  10 , it is contemplated to provide fuse  10  without housing  30 . 
     Enclosure  40  includes a metal portion  42  and end caps  44  and  46 . Metal portion  42  in the illustrated includes walls  48 , which can form the generally rectangular shape as illustrated or form a square shape. Alternatively, metal portion  42  forms an elliptical or round shape. The thickness of walls  48  in an embodiment is at least about 0.053 inch (1.35 mm), although thinner or greater thicknesses could be used alternatively, for example, based on the metal chosen or for other applications. Metal portion  42  can for example be made of aluminum, steel or stainless steel. 
     In the illustrated embodiment, metal enclosure  42  displays indicia or information, such as rating, company name and/or brand indicia or information. The indicia is for example laser etched onto or into metal portion. Alternatively, the information is printed onto metal portion  42 . Further alternatively, a separate label is provided. Still further alternatively, space permitting, some or all of the indicia or information is provided on one or both end caps  44  and/or  46 . 
     Metal enclosure  42  in one embodiment is anodized. The anodized surface provides an aesthetic finish and adds an extra insulating barrier because the anodized surface is nonconductive. The anodized surface provides an extra insulating barrier in the unlikely event that a molten fuse element  12  bridges to the inside of metal enclosure  42 . 
     End caps  44  and  46  of housing are made of an electrically insulating material so that they can contact conductive terminals  14  and  16 , respectively, in communication with fuse element  12 . End caps  44  and  46  in one embodiment are made of a relatively high melting temperature plastic material, such as Rynite™, Ryton™ or other thermoset plastic or thermoform plastic having a melting temperature of at least about 180° C. End caps can alternatively be made of another suitable insulator, such as ceramic or rubber. 
     An open-fuse indicator system  50  illustrates one embodiment for providing open-fuse indication to an operator or service person attempting to diagnose the status of fuse  10 . Open-fuse indicating system  50  includes a low voltage bulb  52  powered via leads  54   a  and  54   b . The operation of low voltage bulb  52  is independent of polarity so the operator can replace fuse  10  in either direction. In an alternative embodiment, open-fuse indicator system  50  includes a full wave rectifier (not illustrated) allowing a light emitting diode (“LED”) to be used instead of a bulb. 
     Leads  54   a  and  54   b  are connected in parallel to opposite sides of fuse element  12 . Under normal operation, when element  12  is conducting current, resister  56  does not allow enough energy to pass through bulb to illuminate the LED. When element  12  opens and stops conducting current, enough current passes through resister  56  to illuminate bulb  52 . In this manner, the operator can see which fuse  10  has opened after removing a panel of the, e.g., fork lift, and without having to look fuse-by-fuse until finding the opened fuse. 
     In the illustrated embodiment, end cap  44  defines an aperture  62  for receiving lamp  52  of open-fuse indicating system  50 . Lamp  52  can be placed on either or both end caps  44  and  46 . Open-fuse indication is not provided. For higher voltage applications, an arc-quenching material such as sand can be filled into fuse  10  through hole  62 . Lamp  52  or a plug if no indication is used is then fitted into hole  62  to prevent loss of the sand. 
     End caps  44  and  46  each include an outer portion  64  and an inner portion  66 . Outer portion  64  includes sidewalls  68  that mate flush with walls  48  of metal portion  42  in the illustrated embodiment. Inner portion  66  includes sidewalls  72  that fit snugly within or press-fit to the inner surfaces of walls  48  of metal portion  42 . 
     End caps  44  and  46  each include a slit  74 , which extends through both outer portion  64  and inner portion of  66  of the end walls. Slits  74  are sized to let terminals  14  and  16  connected to (e.g., extending integrally from or attached to) element  12  to extend outside of end caps  44  and  46  of enclosure  40  when fuse  10  is assembled as seen in  FIGS. 2A to 2C . Slits  74  are sized to be slightly wider and thicker than terminals  14  and  16 , so that end caps  44  and  46  can be slid over the terminals without too much difficulty, but so that a minimum amount of open space resides between the edges of the slits  74  and the outer surfaces of terminals  14  and  16  to reduce the chance of a spark from an opened element  12  from leaving enclosure  40 . 
     Fuse  10  of  FIGS. 1A to 1D  shows one embodiment for holding fuse element  12  and terminals  14  and  16  firmly within enclosure  40 . Here, stakes or bumps  76  are formed in terminals  14  and  16  just outside of end caps  44  and  46 . Stakes  76  can be stamped or punched into metal terminals  14  and  16 , e.g., via a cold-staking process in one embodiment. 
     Stakes or bumps  76  prevent enclosure  40  from traversing in either direction over terminals  14  and  16 . The stakes also provide a sturdy, mechanical attachment of end caps  44  and  46  to metal body  42 , which should prevent the resulting enclosure  40  from rupturing or coming free from the terminals upon an opening of fuse element  12  if for example housing  30  is not provided. 
     Stakes or bumps  76  are shown extending downwardly in  FIGS. 1A to 1D  but could alternatively extend upwardly or in alternating directions. Two stakes per side are illustrated but more than two stakes  76  per side could be provided. Further alternatively, one or more elongated stake could be provided. 
     Referring now to  FIGS. 2A to 2C , fuse  60  illustrates an alternative moderately hazardous environment fuse of the present disclosure. Fuse  60  includes many of the same components (including alternative embodiments thereof) as shown and described for fuse  10 . Those components are numbered the same. 
     The primary difference between fuse  60  and fuse  10  is that stakes or bumps  76  of fuse  10  are replaced with bends  78  formed in terminals  14  and  16  of fuse  60 . Bends  78  in the illustrated embodiment are made on two sides of terminals  14  and  16 , adjacent to end caps  44  and  46 . Bends  78  also attach end caps  44  and  46  to body  42  to form enclosure  40  in a firm and mechanical manner. Bends  78  are shown being bent in alternating directions, providing stability, but could alternatively be bent in the same direction. 
     Referring now to  FIGS. 3A and 3B , fuse  70  illustrates a further alternative moderately hazardous environment fuse of the present disclosure. Fuse  70  includes many of the same components (including alternative embodiments thereof) as shown and described for fuse  10 . Those components are numbered the same. 
     The primary difference between fuse  70  and fuse  10  is that stakes or bumps  76  of fuse  10  are replaced with inner snap-fitting protrusions  82 , which snap-fit into mating recesses  84  formed in end caps  44  and  46 . Protrusions  82  can be rounded as illustrated. In an alternative embodiment, end cap recesses  84  are not performed but are formed instead by pressing end caps  44  and  46  into terminals  14  and  16 , respectively. Here, protrusions  82  can be pointed. 
     The attachment mechanism of fuse  70  is advantageous in one respect because the attachment of enclosure  40  to terminals  14  and  16  occurs upon the coupling of end caps  44  and  46  to body  42 , in essence saving a manufacturing step of stamping or bending discussed above with fuses  10  and  60 , respectively. The attachment mechanism of fuse  70  may, however, not be as strong mechanically as those of fuses  10  and  60 . 
     In one preferred embodiment, terminals  14  and  16  are coined or otherwise thickened just outside of end caps  44  and  46 , respectively. The thickened sections hold end caps  44  and  46  against enclosure  40  and to the extent that they run the length of slits  74 , seal the slits. 
     In any of the embodiments described herein, the end caps  44  and  46  are additionally or alternatively adhered to metal body  42 . A non-flammable adhesive or epoxy can be suitable for this application. 
     Referring now to  FIG. 4 , fuse bank  80  illustrates a further alternative moderately hazardous environment fuse arrangement of the present disclosure. Fuse bank  80  holds a plurality of fuse element/terminal/housing assemblies described above. For ease of illustration, those assemblies are not shown here. Fuses made according to any of the attachment mechanisms described above for attaching the fuse element assemblies to the enclosure  90  can be placed in fuse bank  80 . As illustrated by the rating indicia on metal body  92  of bank  80 , bank  80  can house fuses having the same or different ratings. All of the alternate embodiments discussed above for the indicia, e.g., the application of the indicia, are applicable with block  80 . 
     To operate in a moderately hazardous environment, an enclosure  90  is placed around the fuses of bank  80 . Enclosure  90  includes a metal body  92  and end caps  94  and  96 . Metal portion  92  in the illustrated includes walls  98 , which can form the generally rectangular shape as illustrated. The thickness of walls  98  in an embodiment is at least about 0.053 inch (1.35 mm), although thinner or greater thicknesses could be used alternatively, for example, based on the metal chosen or for other applications. Metal portion  92  can for example be made of any of the materials discussed above for metal portion  42 . 
     End caps  94  and  96  of housing are made of an electrically insulating material so that they can contact conductive terminals  14  and  16 , respectively, in communication with fuse element  12 . End caps  44  and  46  in one embodiment are made of any of the materials discussed above for end caps  44  and  46 . 
     End caps  94  and  96  each include an outer portion  104  and an inner portion  106 . Outer portion  104  includes sidewalls  108  that mate flush with walls  98  of metal portion  92  in the illustrated embodiment. Inner portion  106  includes sidewalls  112  that fit snugly within or press-fit to the inner surfaces of walls  98  of metal portion  92 . 
     End caps  94  and  96  each include a plurality of slits  114 , one for each fuse, which extend through both outer portion  104  and inner portion of  106  of the end caps. Slits  114  are sized to let terminals  14  and  16  connected to (e.g., extending integrally from or attached to) elements  12  to extend outside of end caps  94  and  96  of enclosure  90  when the fuses are assembled into bank  80 . Slits  114  are sized to be slightly wider and thicker than terminals  14  and  16 , so that end caps  94  and  96  can be slid over terminals  14  and  16 , respectively, without too much difficulty, but so that a minimum amount of open space resides between the edges of the slits  114  and the outer surfaces of terminals  14  and  16 . 
     It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present subject matter and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.