Abstract:
A fluxer includes a single, wide furnace enclosure that is sufficiently large and prewired to accommodate multiple fusion positions. The furnace includes at least one movable insulated partition that defines the actual insulated volume of the furnace.

Description:
STATEMENT OF RELATED CASES 
       [0001]    This case claims priority to U.S. patent application Ser. No. 62/148,229 filed Apr. 16, 2015 and incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to the preparation of inorganic samples by fusion, and more particularly to a system and methods for doing so. 
       BACKGROUND 
       [0003]    Analyzing an inorganic sample via analytical techniques such as x-ray fluorescence (XRF), inductively coupled plasma (ICP), atomic absorption (AA) requires that the sample be specially prepared before analysis. The sample must often be in the form of a homogeneous, solid, smooth-surface shape, such as that of a disk or bead. In this form, the sample does not exhibit mineralogical, grain-size, or orientation effects that might otherwise skew the analytical results. 
         [0004]    A process known as “fusion” can be used to prepare samples for XRF, ICP, and AA. During the fusion process, a powdered sample is dissolved in a solvent, typically a lithium borate flux. The flux is solid at room temperature and must therefore be liquefied, which typically occurs at high temperature (c.a. 900 to 1000° C.). 
         [0005]    As a consequence of the high temperatures required, the fusion process is performed in a heater/furnace/burner. Energy for the process is supplied either by gas (i.e., a gas burner) or electricity (i.e., an electric heater or furnace). Electrically powered furnaces can be inductive or resistive. 
         [0006]    The heater or furnace, along with other control circuitry, etc., is contained with a larger enclosure; the assemblage is typically called a “fluxer”. 
         [0007]    “Platinumware” holders, including a “crucible holder” and a “mold holder” or “mold rack” are used in conjunction with the fluxer. The moniker “platinumware” derives from the fact that the crucibles and molds are typically made of platinum.  FIG. 1  and  FIG. 2  depict respective prior-art crucible holder  100  and mold rack  200 , as used in some resistive-heated furnaces available from Katanax, Inc. of Québec, Canada. The platinumware holders are arranged to move in and out of the hot zone (i.e., furnace or burner flame) under the control of a motor/actuator. 
         [0008]    Crucible holder  100  is capable of supporting plural crucibles  112 . In the embodiment shown, crucible holder  100  is designed to accommodate five crucibles  112 . As depicted in  FIG. 1 , crucible holder  100  includes support beam  102 , spacers  104 , retaining beams  106 , brackets  108 , and end shafts  110 , arranged and interrelated as shown. Mold rack  200  is capable of supporting plural molds  224 , which is typically consistent with the number of crucibles  112  in the crucible holder. Mold rack  200  includes support beams  214 , mold retainers  216 , spacers  218 , brackets  220 , and end supports  222 , arranged and interrelated as shown. 
         [0009]    In use, crucible holder  100  is disposed above molder holder  200 . Crucible holder is supported so as to be rotatable about its longitudinal axis (i.e., an axis that aligns with the two end shafts  110 ). Crucibles  112  and molds  224  are situated to align with one another so that hot solution poured from each crucible  112  is received by a respective mold  224 . 
         [0010]    To begin the fusion process, the flux and sample are deposited into crucibles  112 , which are then moved into the furnace cavity to begin the fusion process. See, e.g., http://www.katanax.com/cgi/show.cgi?products/K2prime/K2primevideo.I=en.html. 
         [0011]    After the flux is liquefied, and after complete dissolution of the sample, the molten solution in the crucible(s) is poured into the plate-shaped platinum mold(s). Cooling results in a small, homogeneous glass-like disk or bead of sample, now suitable for analysis. 
         [0012]    The throughput required of a fluxer will of course vary from one customer/lab/site (hereinafter “site”) to another. And the requirements at a given site can change over time. In particular, with the increasing popularity of the fusion technique, it is likely that a site will see their fusion demands increase over time. Although some gas-fired fluxers are designed with a larger casing to accommodate a variable number of burners, no electrical fluxer offers this flexibility. 
         [0013]    In particular, when designing gas fluxers, it is relatively easy to provide a manifold with multiple gas outputs, each one capable of functioning as a fusion position. To reduce the number of fusion positions, one or more of the gas outputs are capped or plugged. To increase the number of fusion positions, one or more burners are coupled to the gas outputs. The burners are typically positioned quite close one to another, so there is not much cost to providing the potential for a large capacity, even if a number of the fusion positions remain unused. 
         [0014]    The issue of spare capacity is more complicated with electric fluxers. If a large furnace is built, all heating elements must be operated to provide the requisite heating, even if only a few samples are being processed such that spare capacity remains. Alternatively, a fluxer could be designed to accommodate several individual furnaces situated adjacent to one another. But since each furnace requires several inches of insulation, when positioned side-by-side, the thickness of the (insulated) side walls widens the fluxer to an unacceptable size. 
         [0015]    To satisfy increasing fusion demands, it is advantageous to conduct the fusion process as quickly as possible. This implicates the fluxer&#39;s temperature response; that is, the relative speed with which it is capable of changing temperature and stabilizing at temperature targets. Despite its many benefits, a perceived drawback of a typical electric fluxer is that its temperature cannot vary as quickly as that of a gas fluxer. 
         [0016]    As a consequence, there is a need for an electric fluxer that can accommodate an increase in the number of fusion positions (i.e., the number of simultaneous samples that can be accommodated per run). This would enable an initial modest throughput to be increased without having to purchase a new fluxer. Furthermore, there is a need for an electric fluxer with increased temperature responsivity, which will speed the fusion process thereby increasing throughput. 
       SUMMARY 
       [0017]    The present invention provides a way to address the aforementioned shortcomings of electric fluxers. The illustrative embodiment of the invention is a fluxer having a modular electric “fusion” furnace. 
         [0018]    A fluxer in accordance with the present teachings includes a single, wide furnace enclosure that is sufficiently large and prewired to accommodate multiple fusion positions. The furnace includes at least one movable insulated partition that defines the actual insulated volume of the furnace (i.e., the furnace cavity). In the illustrative embodiment, the furnace accommodates a maximum of three fusion positions and includes two movable insulated partitions. The term “insulated” and inflected forms thereof, as used in this disclosure and the appended claims, means thermally insulated. The partitions can be sited at four different positions (i.e., one position at either end of the furnace enclosure and two intermediate positions that divide the enclosure into thirds). Three heating elements are disposed across the top of the furnace spanning the middle third of the furnace enclosure (i.e., the central fusion position). 
         [0019]    Placing one movable partition at each of the two intermediate positions defines a small heated furnace cavity that covers the middle third of the furnace enclosure. This provides a single fusion position. Moving one of the partitions from the intermediate position to the nearest end of the furnace enclosure enlarges the insulated cavity to encompass two fusion positions. And moving both partitions, one each to opposite ends of the furnace enclosure enlarges the insulated volume to the full size of the furnace enclosure to accommodate three fusion positions. Thus, by virtue of the movable insulated partitions, a variable size furnace cavity is created. 
         [0020]    Each enlargement of the insulated cavity beyond a single fusion position requires additional parts. In the illustrative embodiment, for each additional fusion position, two heating elements, a crucible-holder assembly, and mold-holder assembly are added (among other parts). 
         [0021]    The use of movable insulated partitions, as disclosed herein, significantly reduces the length of furnace enclosure compared to what would be required if multiple single-position furnace cavities, each with its own insulating walls, were located adjacent to one another. 
         [0022]    The furnace disclosed herein differs from a conventional electric furnace in other ways as well. For example, in some embodiments, the furnace has a reduced wall thickness compared to conventional electric furnace designs. 
         [0023]    Reducing the thickness of the insulating walls of the furnace cavity improves temperature responsiveness, because the lower mass of the furnace enclosure enables faster heat-up and cool down. Wall thickness can be reduced to near-zero, at least theoretically, provided that the heating element(s) have enough power to maintain the crucible at required temperatures. Conversely, the more insulation, the less power is required to maintain a constant temperature. Furthermore, reducing furnace wall thickness results in a larger furnace cavity (for an enclosure having the same external size). 
         [0024]    The thickness of the insulation is ultimately a tradeoff between power requirements (i.e., how much is acceptable) and temperature responsiveness. By way of comparison, the wall thickness of a conventional electric furnace, as used in a fluxer, is typically about four inches. In the illustrative embodiment, all walls/movable partitions are less than 2 inches in thickness. For example, in some embodiments, the top wall of the furnace is 1.75 inches in thickness and all other insulated walls and movable partitions have a thickness of 1 inch. 
         [0025]    In accordance with some embodiments, certain other aspects of the fluxer are altered to reduce the impact of heat losses from the relatively thinner walls of the furnace. 
         [0026]    One alteration is to relocate the opening of the furnace to the bottom thereof; in conventional designs, the opening is located on the side of the furnace. Furthermore, the furnace is fitted with a movable door. To the extent the furnace door is open, the fact that the opening is at the bottom helps retain the heated air therein (since hot air rises). And incorporating a furnace door that is mechanically independent of the outer door/safety shield of the fluxer enables the furnace to be kept closed during crucible loading, pouring and cooling operations, thus conserving heat. 
         [0027]    In conventional fluxers, the trajectory of the crucible/mold holder as it travels from the loading point to the furnace cavity is typically horizontal or vertical. However, a furnace in accordance with the present teachings having its opening located at the bottom requires a non-standard trajectory. In particular, the crucible holder and mold holder must travel vertically to enter and exit the furnace and must travel horizontally to move from the loading position toward the furnace or vice-versa. 
         [0028]    The inventors recognized that adopting an arc-like trajectory for movement of the crucible/mold holder is an efficient way to provide the requisite vertical and horizontal motion. A direct motor drive simplifies the mechanism and is sturdier than linear motion assemblies, which can seize due, for example, to chemical attacks. 
         [0029]    In order to minimize, to the extent practical, the overall mass that is being heated in the furnace to speed heating and cooling, the structure of the crucible/mold holder has been changed from the conventional design. In particular, conventional crucible holders and mold holders accommodate multiple crucibles and molds (see, e.g.,  FIGS. 1 and 2 ). Since embodiments of the modular fusion furnace might only have one or two fusion positions operating, the extra mass of conventional crucible/molder holders would simply dull the temperature responsiveness of the fluxer. 
         [0030]    In fact, the inventive crucible holder and mold holder is significantly different than conventional designs. The crucible holder accommodates a single crucible and the mold holder accommodates a single mold. When situated in its holder, the crucible in restricted from horizontal movement by a hoop and restricted from vertical movement by an upper and lower retainer. In the illustrative embodiment, the upper retainer is not oriented vertically (it is not orthogonal to the hoop) in at least one plane. This geometry results in an opening through which a crucible can be inserted into or removed from the crucible holder. 
         [0031]    To load the crucible into the crucible holder, the crucible is tilted from a neutral position. When appropriately tilted, the crucible can slide between the upper retainer and the hoop. When the crucible is in the “cage” created by the bars and hoop, it is rotated back to a neutral position. 
         [0032]    Based on the structural arrangement of the crucible holder, when it is tilted fully to pour the contents of a crucible into an underlying mold, the crucible will not fall out of the crucible holder. This is because in this rotated position, a portion of the upper edge of the crucible (now in a partially inverted position) bears on the upper retainer. Thus, the geometry of the crucible holder enables the crucible to be secure for pouring without requiring a movable locking bar or a metallic clip (which relies on metal resilience), as in conventional designs. 
         [0033]    An illustrative embodiment of the invention is a fluxer comprising a modular electrically powered furnace having a furnace cavity characterized by a length that is variable due to the presence, within the furnace, of at least one movable insulated partition that is moved to determine the length of the furnace cavity; and a platinumware assembly, wherein the platinumware assembly comprises a rocking module and one or more instances of platinumware, each instance including a crucible holder and a mold holder, wherein the number of instances determine placement of the at least one movable insulated partition. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0034]      FIG. 1  depicts a prior-art crucible holder. 
           [0035]      FIG. 2  depicts a prior-art mold rack. 
           [0036]      FIG. 3A  depicts a cutaway view of a fluxer in accordance with the illustrative embodiment of the present invention. 
           [0037]      FIG. 3B  depicts a side view of a platinumware assembly for use in conjunction the fluxer shown in  FIG. 3A . 
           [0038]      FIG. 4A  depicts a front view of the interior of the furnace of the fluxer of  FIG. 3 , wherein the furnace is configured for a single fusion position. 
           [0039]      FIG. 4B  depicts a front view of the interior of the furnace of the fluxer of  FIG. 3 , wherein the furnace is configured for two fusion positions. 
           [0040]      FIG. 4C  depicts a front view of the interior of the furnace of the fluxer of  FIG. 3 , wherein the furnace is configured for three fusion positions. 
           [0041]      FIGS. 5A-5C  depict perspective views of the furnace configurations shown in  FIGS. 4A through 4C , respectively. 
           [0042]      FIG. 6  depicts the fluxer of  FIG. 3 , showing the movement of a crucible holder and a mold holder between a loading position and an operating position in accordance with the present teachings. 
           [0043]      FIG. 7A  depicts a perspective view of a portion of the crucible-holder for use in conjunction with the fluxer of  FIG. 3 . 
           [0044]      FIG. 7B  depicts a front view of the crucible holder of  FIG. 7A . 
           [0045]      FIG. 7C  depicts a side view of the crucible holder of  FIG. 7A . 
           [0046]      FIGS. 8A-8E  depict, via a sequence of front views, a method by which a crucible is positioned within the crucible holder of  FIG. 7A . 
       
    
    
     DETAILED DESCRIPTION 
       [0047]      FIG. 3A  depicts a side, cut-away view of fluxer  300  in accordance with the illustrative embodiment of the present invention. 
         [0048]    Fluxer  300  includes enclosure  330 , outer door/safety shield  332 , tiltable touch screen  334 , blower  336 , agitation system  338 , beaker well  340 , crucible movement motor  342 , power connection  344 , furnace  346 , furnace door  356 , heating elements  358 , and platinumware assembly  377 . 
         [0049]    Outer enclosure  330  and safety shield  332  comprise metal, such as mild steel or aluminum. The operation of safety shield  332  is mechanically independent from furnace door  356 , enabling furnace  346  to be kept closed (i.e., to retain heat) during operations in which the safety shield is raised, such as crucible loading, cooling, etc. 
         [0050]    Tiltable touch screen  334  is the user interface for the fluxer  300 . Blower  336  blows air into enclosure  330  for cooling. Agitation system  338 , which is a magnetic agitation system, agitates fluid in a beaker that is placed in beaker well  340  when preparing ICP (inductively coupled plasma) solutions for ICP analysis. Power connection  344  brings power to fluxer  300 . 
         [0051]    Referring now to  FIG. 3B  as well as  FIG. 3A , platinumware assembly  377  includes rocking module  365  and one more instances of “platinumware”  373 . Rocking module  365  includes one or more motors  366 . Each instance of platinumware  373  includes a single crucible holder  362 , shaft  364 , a single mold holder  368 , and arms  370 . As discussed later in conjunction with  FIGS. 5A through 5C , rocking module  365  includes plural coupling regions that receive, as desired, one or more instances of platinumware  373 . 
         [0052]    Crucible holder  362  is coupled, via shaft  364 , to motor  366 . During the heating process when platinumware  373  is within furnace  346 , motor  366  rocks the crucible left-to-right a few dozen degrees to provide agitation. The motor also rotates crucible holder  362  during pouring operations, wherein the contents of crucible  372  is poured into underlying mold  374 . 
         [0053]      FIG. 3A  depicts crucible  372  in crucible holder  362  and mold  374  in mold holder  368 ;  FIG. 3B  depicts crucible holder and molder holder without crucible or mold. Crucible holder  362  is described in more detail later in this disclosure in conjunction with  FIGS. 7A-7C and 8A-8E . 
         [0054]    The “heart” of fluxer  300  is furnace  346 . As will become clear from this disclosure, furnace  346  is non-conventional in its structure and, to a certain extent, in its operation as well. 
         [0055]    As depicted in  FIG. 3A , furnace  346  includes top wall  350  of insulation, front wall  352  of insulation, back wall  354  of insulation, and door  356 , which, when closed, functions as a bottom wall of insulation. A thin metal enclosure  348  surrounds the aforementioned top wall, front wall, and back wall. Enclosure  348  also extends over the sides of furnace  346 . The same thin metal that composes enclosure  348  is disposed on the outer surfaces of door  356 . 
         [0056]    Top wall  350  has the greatest thickness (of insulation). This is to address the fact that hot air rises (i.e., if all walls had the same thickness of insulation, heat loss would be greatest through the top wall). For example, in some embodiments, top wall  350  has a thickness of 1.75 inches and front wall  352 , back wall  354 , and door  356  have a thickness of 1 inch. 
         [0057]      FIGS. 4A - FIG. 4C  depict front views of furnace  346 , with front wall  352  removed for clarity. Enclosure  348  is depicted covering top wall  350 , extending down the (left and right) sides of furnace  346  to door  356 . The same thin metal as used for the enclosure covers all outside surfaces of door  356 . Back wall  354  includes three openings  480 . Fingers  357  extending from inside surface of door  356  are dimensioned and arranged to be received by openings  480 . Fingers  357  are sized so that there is a gap  481  ( FIG. 4A ) between the outer edge of finger  357  and the edge of opening  480 . This gap enables shaft  364  of crucible holder  362  and arms  370  of mold holder  368  to pass through back wall  354  and into the interior of furnace  346  (see central fusion position). 
         [0058]    In the embodiment depicted in  FIG. 4A  furnace  346  is configured with a single fusion position, which is located in the middle (left to right) of the furnace. Movable partition  482 A is positioned about one-third of the length of furnace  346  from the left side of enclosure  348  and movable partition  482 B is positioned about one-third of the length of furnace  346  from the right side. The movable partitions are insulating walls; in the illustrative embodiment, the thickness of each movable partition  482 A and  482 B is equal to the thickness of front wall  352  (not depicted in  FIG. 4A ), back wall  354 , and door  356 . 
         [0059]    As seen from  FIG. 4A , the aforementioned locations site the movable partitions on either side of the central fusion position to define furnace cavity  484 - 1 . Three heating elements  358  are disposed horizontally, side-by-side and extend front to back just below top wall  350 . In other embodiments, depending on size and element type, fewer than three heating elements or more than three heating elements may suitably be used. It is notable that there is no insulation to the left of movable partition  482 A or to the right of movable partition  482 B. Crucible  372  is disposed in crucible holder  362  and mold  374  is disposed in mold holder  368 . 
         [0060]    Chimney  486  vents corrosive gases from furnace cavity  484 - 1 . The chimney can be, for example, a ceramic tube. 
         [0061]      FIG. 5A  depicts a perspective view of furnace  346  configured for a single fusion position (like  FIG. 4A ). In this figure, door  356  is depicted “open” such that fingers  357  are not engaged with openings  480 . Rocking module  365  has three coupling regions  588  for receiving up to three crucible holders. Since the furnace is configured for a single fusion position, only one crucible holder is coupled to rocking module  365 . Mold holders couple to rocking module  365  directly below each crucible holder. Movable partitions  482 -A and  482 -B are disposed on either side of the central fusion position to define furnace cavity  484 - 1 . 
         [0062]    In some embodiments, a single motor  366  drives all crucible holders  362  that are coupled to rocking module  356 . For example, motor  366  can be installed at the central coupling region  588  while actuating a pushrod system that is able to rotate the shafts of the crucible holders that couple to the other coupling regions  588 . 
         [0063]    In the embodiment depicted in  FIG. 4B , furnace  346  is configured with two fusion positions, which include the left and central positions. To accommodate these two fusion positions, movable partition  482 A is sited all the way to the left side of enclosure  348  and movable partition  482 B is positioned, as before, about one-third of the length of furnace  346  from the right side thereof. This positions movable partition  482 A to the left of the left fusion position and movable partition  482 B to the right of the central fusion position, defining furnace cavity  484 - 2 . 
         [0064]    Adding a fusion position requires the addition of certain other elements to furnace  346 . In addition to a second crucible holder  362  and second mold holder  368 , two heating elements  358 , a power switching device (not depicted) that controls power to the heating elements (e.g., snap-in solid state relays, etc.), and a second chimney  486  and are added above the left fusion position. It will be understood that in some other embodiments, partitions  482 A and  482 B are positioned so that the furnace cavity includes the central fusion position and the right fusion position, rather than the left fusion position. 
         [0065]      FIG. 5B  depicts a perspective view of furnace  346  configured for two fusion positions (like  FIG. 4B ). Rocking module  365  receives two instances of crucible holders and mold holders at two of coupling regions  588 . Movable partition  482 -A is sited at the left end of the furnace and movable partition  482 -B is sited on the right side of the central fusion position to define furnace cavity  484 - 2 . 
         [0066]    In the embodiment depicted in  FIG. 4C , furnace  346  is configured so that all three fusion positions are operational. To accommodate three fusion positions, movable partition  482 A is positioned all the way to the left side of enclosure  348  and movable partition  482 B is positioned all the way to the right side of the enclosure. This positions movable partition  482 A to the left of the left fusion position and movable partition  482 B to the right of the right fusion position, defining furnace cavity  484 - 3 . 
         [0067]    As before, to accommodate the third fusion position, the same elements are added to furnace  346  (i.e., a third crucible holder  362 , third mold holder  368 , two heating elements  358 , a power switching device [not depicted], and a third chimney  486 ). 
         [0068]      FIG. 5C  depicts a perspective view of furnace  346  configured for three fusion positions (like  FIG. 4C ). Rocking module  365  receives three instances of crucible holders and mold holders. Movable partitions  482 A and  482 B are sited at the left and right ends of the furnace to define furnace cavity  484 - 3 . 
         [0069]    Although two heating elements are added for each additional fusion position in the illustrative embodiment, in other embodiments, a greater or lesser number of heating elements could be added as a function of element size and type, as well as furnace size. 
         [0070]    Thus, through the use of movable partitions  482 A and  482 B, a variable-size furnace cavity is created. The size of the furnace cavity is appropriately altered to accommodate a specific number of fusion positions. Since the cavity is no larger than it needs to be, and since rocking module  365  has the capability to couple to a desired number of crucible holders and mold holders (up to its maximum capability), no more mass than is necessary is being temperature cycled. This improves the temperature responsiveness of fluxer  300 . 
         [0071]    Also, because of the use of movable partitions, as opposed to the use of plural, individual, adjacent furnace cavities, only two side insulating walls, as opposed to four (to create three cavities), are required. This reduces the amount of space required for a given number of fusion positions. 
         [0072]    Although the illustrative embodiment depicts furnace  346  and rocking module  365  with a maximum of three fusion positions, it is to be understood that in other embodiments, as desired, a furnace and rocking module may have a maximum two fusion positions, or a maximum of more than three fusion positions, such as four, five, etc. It is notable that even if the furnace has a capability for accommodating more than three fusion positions, two movable partitions can still be used to create a furnace cavity of the required size. 
         [0073]    In some further embodiments, rather than using two movable partitions, a fluxer having a variable-size furnace cavity includes only a single movable partition. In such embodiments, one of the movable partitions is replaced by a fixed partition; that is, a side wall. For example, with reference to  FIG. 4B , movable partition  482 A could be a fixed wall. To create a single fusion position, movable partition  482 B is moved to a position that is about one-third of the length of enclosure  348  away from the left wall, so that the furnace cavity includes only the left fusion position. To accommodate two fusion positions, movable partition  482 B is moved to the position in which it appears in  FIG. 4B . And to accommodate three fusion positions, movable partition  482 B is moved all the way to the right. 
         [0074]    Returning again to  FIG. 3A , furnace  346  opens at the bottom thereof, rather than at the side as in conventional designs. Thus, door  356  serves as the “bottom” wall of the furnace. Door  356  is (automatically) movable; the door is shown ajar in  FIG. 3A . The door is actuated by a motor (not depicted), which drives a belt (not depicted) that rotates pulley  359 . The pulley has lever  360  attached thereto. Door  356  is pivotally coupled to lever  360  at a location close to, but not at, the end of the lever. A bearing (not depicted) extends from the back (right side of the figure) of the non-visible side of door  356  and engages slot  375 . This arrangement forces the desired (rotational) movement between lever  360  and door  356 . Rotating the pulley clockwise causes door  356  to open by dragging the door to the left to completely clear the furnace opening to provide access to the interior thereof. To close the door, the pulley is rotated counterclockwise. Pin  361  catches the edge of door  356 , forcing it upward near the end of the movement to seal the opening of furnace  346 . 
         [0075]    To the extent that door  356  is open, the fact that the opening of the furnace is located at the bottom thereof helps to retain the heated air therein. And incorporating door  356 , which is mechanically independent of the opening/closing of safety shield  332 , enables the furnace to be kept closed during crucible loading, pouring and cooling, thereby retaining heat. 
         [0076]    Referring now to  FIG. 6 , platinumware assembly  377  is shown in two positions: position “A,” which is the loading position (i.e., for loading crucibles  372  and molds  374 ) near the safety shield  332  and position “B,” which places platinumware  373  in furnace  346 . In conventional fluxers, the trajectory of the platinumware (embodied as in  FIGS. 1 and 2 ) as it travels from the loading point to the furnace cavity is typically horizontal or vertical. As a consequence of the bottom-opening furnace of the illustrative embodiment, a non-standard trajectory for platinumware assembly  377  is required. In particular, it must travel vertically to enter and exit the furnace cavity and horizontally to move from the loading position toward the furnace or vice-versa. 
         [0077]    In accordance with embodiments of the present invention, platinumware  373  exits furnace  346  in arc-like trajectory T. This non-linear trajectory combines the vertical motion needed to exit the furnace with the horizontal motion required to bring platinumware assembly  377  close to the user for loading crucibles  372  and molds  374 . In some embodiments, this non-linear movement of platinumware assembly  377  is accomplished by a mechanism that provides sufficient torque to move the platinumware assembly and keeps the platinumware  373  horizontal. In an exemplary embodiment, the mechanism includes two motors that drive a belt that rotates a pulley coupled to a lever. A double lever arrangement keeps the platinumware horizontal. Direct motor drive simplifies the mechanism while being sturdier than linear motion assemblies, which can seize due, for example, to chemical attacks. 
         [0078]    As a consequence of the design and operation of furnace  346 , platinumware  373  for use in conjunction with the illustrative embodiment must be significantly different than conventional designs, as shown in  FIGS. 1 and 2 . 
         [0079]      FIG. 7A  depicts crucible-holder  362 . Crucible holder  362  includes horizontally-oriented retainer  790 , upper retainer  792 , and lower retainer  796 . Horizontally-oriented retainer  790  restricts crucible  372  from any horizontal movement. Upper retainer  792  prevents crucible  372  from falling out of crucible holder  362  during pouring operations and lower retainer  796  supports crucible  372  against gravity during loading and heating operations. 
         [0080]    In the illustrative embodiment, horizontally-oriented retainer  790  is a hoop (hereinafter “hoop  790 ”). In a neutral position, the hoop is oriented horizontally. Upper retainer  792  includes rise portion  793  and retaining bar  794 . The rise portion is located on the hoop at its midline and supports retaining bar  794  over the hoop and substantially parallel thereto. Lower retainer  796  includes drop portion  797  and retaining bar  798 . The drop portion is located on the hoop at its midline and supports retaining bar  798  below the hoop and substantially parallel thereto. 
         [0081]      FIG. 7B , which is a front view of  FIG. 7A  (crucible  372  not shown) and  FIG. 7C , which is a side view of  FIG. 7A  (crucible  372  not shown), provide additional information about the structure of crucible holder  362 . As can be seen from  FIG. 7B , neither rise portion  793  nor drop portion  797  are orthogonal to hoop  790 . The angle, α, subtended between rise portion  793  and hoop  790 , is greater than 90 degrees. As discussed further below in conjunction with  FIGS. 8A-8F , this structural arrangement facilitates insertion and removal of crucible  372  from crucible holder  362 . Although drop portion  797  is depicted in the illustrative embodiment as being co-linear with rise portion  793 , in some other embodiments, the drop portion is orthogonal to hoop  790  (i.e., extending straight down in  FIG. 7B ). 
         [0082]    As can be seen from  FIG. 7C , hoop  790  is disposed relatively closer to retaining bar  798  than retaining bar  794 . In conjunction with obtuse angle α, this arrangement facilitates insertion and removal of crucible  372  from crucible holder  362 . 
         [0083]    Based on the arrangement of horizontally-oriented retainer  790 , upper retainer  792 , and lower retainer  796 , when crucible holder  362  tilts fully to the right (c.a. 120 to 130 degrees by rotation about axis A-A in direction P ( FIG. 7A )) for pouring the contents of crucible  372 , the crucible will not fall through the space between retaining bar  794  and hoop  790 . This is because in this fully tilted position, a portion of the upper edge of crucible  372  (which would be in a partially inverted position) bears on retaining bar  794 . Thus, in the illustrative embodiment, the geometry of the crucible holder enables the crucible to be secure for pouring without requiring a movable locking bar or a metallic clip (which relies on metal resilience) as in conventional designs. 
         [0084]    The angle α ( FIG. 7B ) is a function of crucible dimensions (height and diameter) relative to the size of hoop  790  and height of rise portion  793  of upper retainer  792 . In other words, there is nothing particularly significant about the value of angle α; it is simply the angle that results as a consequence of the sizes of the various elements noted above. There are a number of standard sizes for crucibles. Thus, in accordance with the illustrative embodiment, to the extent that a choice of crucible is available, a crucible should be selected that has a height-to-width ratio that results in a “securing geometry” when used in conjunction with the crucible holder. As used in this disclosure and the appended claims, the term “securing geometry” means that a crucible can be secured for pouring within the crucible holder without requiring a locking function (e.g., movable locking bar, metallic clip, etc.). 
         [0085]    The loading motion of crucible  372  is depicted in  FIGS. 8A through 8E  via front views of crucible holder  362 .  FIG. 8A  depicts a front view of crucible holder  362  sans crucible  372 . As depicted in  FIGS. 8B and 8C , crucible  372  is initially tilted so that it can be slid between retaining bar  794  and hoop  790 . When the crucible is in the “cage” created by the various bars and hoop, it is rotated, as depicted in  FIG. 8D , toward an un-tilted position.  FIG. 8E  depicts crucible  372  in its final, fully supported and neutral position within crucible holder  362 . 
         [0086]    It is to be understood that the disclosure teaches just one example of the illustrative embodiment and that many variations of the invention can easily be devised by those skilled in the art after reading this disclosure and that the scope of the present invention is to be determined by the following claims.