Abstract:
An apparatus is provided to automatically cover and uncover crucibles according to a predetermined procedure in a proximate analyzer. A series of crucibles mounted in a first carousel is heated in a furnace. A second carousel mounted above the first carousel holds crucible covers. A mechanism synchronizes the movements of the carousels so that the heated crucibles are automatically covered and uncovered at the appropriate times during the analysis with a corresponding cover by lowering or raising the second carousel. The movements of both carousels are automatically controlled so that at appropriate points in the testing cycle they rotate simultaneously about a common central axis and a crucible is deposited on a weighing platform by controlling the vertical motion of the entire carousel apparatus. The crucible is weighed either with or without a crucible cover depending on the stage of the analysis without the need of manual intervention.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to the automation of proximate analyzers and the like, and more particularly, to apparatus and a method for opening and closing crucibles during such analysis.  
           [0002]    Systems for proximate analysis of fossil fuels such as coal and coke through the use of heat are well known. The samples are subject to a heating and cooling cycle in a furnace chamber. The samples are in crucibles. The crucibles are in turn seated on a platter or carousel positioned within the chamber. At various times during the cycle the crucibles are covered or uncovered through the placing or removal of crucible covers. A weighing platform is positioned within the furnace chamber. The carousel continuously deposits the crucibles in a predetermined sequence on the weighing platform and the weights of the crucibles monitored to calculate the contained volatiles based on weight loss during heating.  
           [0003]    U.S. Pat. No. 4,522,788, to Sitek et al., issued on Jun. 11, 1985, is directed to such a system. In this patent, the crucibles are placed manually on a carousel and covered and uncovered manually during the analysis. The crucibles are uncovered for initial weighing and then heated in nitrogen atmosphere to remove moisture content from the samples in them, the covers are then remounted by hand and the crucibles are heated to a higher temperature also in a nitrogen atmosphere to obtain volatiles, cooled, removed by hand in the presence of nitrogen atmosphere and heated again in oxygen atmosphere to obtain ash. In order to make such analyses more efficient and safer there is a need for a proximate analysis system that can automatically cover and uncover a series of crucibles at the appropriate stages of the analysis without requiring manual intervention.  
         SUMMARY OF THE INVENTION  
         [0004]    The present invention meets the foregoing needs by use of a second upper carousel sharing a common axis with the original lower carousel. The crucibles are mounted in openings on the lower carousel and the crucible covers are mounted in openings on the upper carousel. The lower carousel is used solely for the manipulation of the crucibles and the upper carousel for the manipulation of the crucible covers. The carousels both rotate and move up and down along their central axis. The movements of both carousels are coupled so as to simultaneously move around their central axis but move independently along their common vertical axis.  
           [0005]    At appropriate points in the testing cycle, individual crucible are automatically deposited on a weighing platform through vertical motion of the entire dual carousel apparatus. The presence or absence of a crucible cover during weighing is determined by the vertical motion along the common axis of the upper carousel. Two pneumatic cylinders control the vertical movement of the carousels. The first pneumatic cylinder acts to raise and lower the dual carousel mechanism so that a crucible is deposited on the weighing platform and a second pneumatic cylinder act to raise and lower the upper carousel in relation to the lower carousel. When the vertical movement of the upper carousel is such as to bring the upper and lower carousel together, the crucible covers rest on, and seals the crucibles, during heating, or weighing. When the upper carousels are separated, the crucible is uncovered and open to the atmosphere during heating and weighing. Thus, in the cycle, the carousels will automatically act to remove the covers during heating to remove moisture, remount the covers to obtain volatiles and remove the covers to obtain ash. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]    [0006]FIG. 1 is a schematic drawing showing a prior art proximate analyzer.  
         [0007]    [0007]FIG. 2A is a schematic drawing showing the present invention with the view having a partial cut out of the furnace chamber showing the two carousels together in heating mode.  
         [0008]    [0008]FIG. 2B is a schematic drawing showing the present invention with the view having a partial cut out of the furnace chamber showing the two carousels apart in weighing mode.  
         [0009]    [0009]FIG. 2C is a schematic drawing showing the present invention with the view having a partial cut out of the furnace chamber showing the two carousels together and the covered crucible in weighing mode.  
         [0010]    [0010]FIG. 3 is a tilted front perspective view of the present invention showing its attachment to a support structure.  
         [0011]    [0011]FIG. 4 is a tilted back perspective view of the present invention showing its attachment to a support structure.  
         [0012]    [0012]FIG. 5 is a perspective view of the dual carousel mechanism without its support structure tilted on its side.  
         [0013]    [0013]FIG. 6A is a cross-sectional drawing of a segment of the dual carousel system in closed position showing a crucible containing a sample seated in a carousel covered with a crucible cover seated in the upper carousel.  
         [0014]    [0014]FIG. 6B is a cross-sectional drawing of a segment of the dual carousel system in open position showing an uncovered crucible containing a sample seated in a carousel and the crucible cover seated in the upper carousel raised up to uncover the crucible. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0015]    [0015]FIG. 1 is a schematic partial cut away view of a prior art proximate detector  100  showing the interior of the furnace chamber. As can be seen in the drawing, there is one carousel  110  which is capable of holding multiple crucibles. The carousel is capable of moving up and down to positions  110 A and  110 B to heat a crucible and place a crucible on a weigh platform  112  for weighing. At different stages in the heating process, it may be necessary to place a cover on certain crucibles. According to the prior art scheme, such placement of covers is performed manually on each crucible.  
         [0016]    [0016]FIG. 2A shows improved proximate analyzer  200  of the present invention in the same view as prior art analyzer shown in FIG. 1. The present invention differs in that there are two carousels in the furnace chamber  205 . Upper carousel  201  carries and transports crucible covers exemplified by crucible cover  204  while lower carousel  202  carries and transports crucibles exemplified by crucible  203 . When carousel  201  and carousel  202  are brought together a cover  204  is placed on a crucible  203 .  
         [0017]    [0017]FIG. 2B shows the position of carousels  201  and  202  at a point in the analytical cycle where a crucible  203  is weighed uncovered. Lower carousel  202  is in its lowered position allowing a crucible  203  to be placed on the balance platform  210  while crucible cover  204  is retained above and separated from a crucible  203  by upper carousel  201  during weighing on a balance  206 .  
         [0018]    [0018]FIG. 2C shows both the lower carousel  202  and upper carousel  201  lowered allowing a crucible  203  to have a cover  204  on it while being weighed on the balance  206 .  
         [0019]    The detailed mechanism of the present invention may be understood by reference to FIG. 3 which is a tilted front perspective top view, FIG. 4 which is a tilted back perspective top view of the present invention with both the upper carousel  201  and lower carousel  202  in the closed position and FIG. 5 which is a view of the dual carousel system without a support structure tilted on its side to show its components. The furnace chamber which forms a part of the proximate analyzer is not shown in these drawings.  
         [0020]    The mechanism is supported by a base  303  which, in the present embodiment, is comprised of two beams  303   a  and  303   b  that hold the system components including balance  206 . Arm  302  attached to base  303  and supported by a brace  306  is connected to component  407   a  of a slide joint  407 , and component  407   b  of slide joint  407  is connected to body  301  which supports the dual carousel mechanism and which moves up and down along slide joint  407 , better seen in FIG. 4, to place crucibles  203  on balance platform  210  connected to balance  206  by means of shaft  207 . The space between the two beams of base  303  allows room for the upper carousel pneumatic cylinder  304  to move up and down between the beams when both the carousels are lowered onto the balance platform  210 .  
         [0021]    The body  301  is connected to an elevation block  314  as seen in FIG. 4. The connection between the elevation block  314  and the main support arm  302  is accomplished through a slide joint  407  which allows the dual carousel system to move up and down along the main support arm  302 . The combination of body  301  which is connected to elevation block  314  which is in turn connected to elevation shaft  316  projecting from pneumatic cylinder  311  supports the weight of the entire dual carousel mechanism. Pneumatic elevation cylinder  311  mounted on base beam  303   a  raises and lowers the entire dual carousel mechanism. Although pneumatic means are preferred, any other means known in the art to raise or lower a structure such as worm gears or pulley arrangements may be used to control the vertical movement of the entire dual carousel mechanism.  
         [0022]    The carousels themselves can be made from any rigid material that can withstand elevated temperatures without substantial deterioration or distortion, preferably metallic sheet materials such as stainless steels, and any other such materials used in the art. As seen in FIG. 5 upper carousel  201  has openings  518  to accommodate crucible covers  204  and lower carousel  202  has openings  520  to accommodate crucibles  203 .  
         [0023]    As seen most clearly in FIG. 5 a retainer  514  is connected to shaft  502  which fixes the position of hollow shaft  502  between two bearings (not shown) one on each side within body  301  so that when moving upper carousel shaft  510  up for removal of crucible covers shaft  502  will not be shifted or dragged up relative to body  301  around the upper carousel shaft  510 . In addition, in the present embodiment, a screw  516  protrudes from retainer  514  that serves to activate a magnetic sensor producing a signal indicating the horizontal rotational position of the carousels thereby enabling the position of each crucible to be tracked by a computer program that monitors the analysis and calculates weight loss at each stage. As will be apparent to those skilled in the art, other means of tracking the position of the carousels may be used such as reflective tape affixed to shaft  502  which in conjunction with a light source sends a signal to an appropriate sensor.  
         [0024]    As most clearly seen in FIG. 5, the lower carousel  202  is attached to a hollow shaft  502  by means of small disk  504  which is attached to the bottom of lower carousel  202  by attaching means known in the art such as riveting welding and the like. Hollow shaft  502  is connected to a gear  506  at the end distal to small disk  504 . An opening (not shown) at the center of small disk  504  and lower carousel  202  allows passage of shaft  510  which is connected to upper carousel  201 . The lower carousel  202  is turned using a step motor  406  which has a pulley  408  connected to the drive shaft of step motor  406 . The pulley  408  is connected to the gear  506  with a belt  410 . The step motor  406  is connected to the main body  301  using a motor support  508  most clearly seen in FIG. 5. While the step motor  406  directly controls the rotation of the lower carousel  202 , there is no motor which independently turns the upper carousel  201 . Any other suitable means known in the art may be used to drive the rotation of lower carousel  202 . Movement of upper carousel  201  is achieved via a synchronization pin  414  which is screwed into the upper face of lower carousel  202  and protrudes through the upper face of upper carousel  201  via keyhole  416  thereby synchronizing the rotation of the carousels. Synchronization pin  414  is sufficiently long so that it remains within keyhole  416  when upper carousel  201  is raised during normal operation of the analyzer.  
         [0025]    Upper carousel  201  is connected to a solid shaft  510  which then passes through the hollow shaft  502  of the lower carousel  202  and is then connected to the piston shaft (unseen) from upper carousel pneumatic cylinder  304  via a rotational coupling  512  to accommodate the rotational motion imparted by gear  506 . The connection of the upper carousel  201  to the end of shaft  510  distal from pneumatic cylinder  304  is made by using a central screw  412  although other fastening means known in the art may be used. As is known in the art, a screw connects the rotational coupling  512  and the piston shaft of pneumatic cylinder  304  to allow the rotational coupling  512  to rotate freely while the screw is fixed to the pneumatic cylinder  304 . The shaft  510  for upper carousel  201  is fixed to the rotational coupling  512  thereby allowing carousel  201  to rotate while being raised or lowered by pneumatic cylinder  304 . Pneumatic cylinder  304  is connected to the main body  301  using support columns  305 .  
         [0026]    The vertical movement of upper carousel  201  is controlled by pneumatic cylinder  304  via carousel shaft  510 . Although pneumatic means are preferred, any other means known in the art to raise or lower a structure such as worm gears or pulley arrangements may be used to control the vertical movement of upper carousel  201 . By lowering carousel  201 , crucible  203  is covered with crucible cover  204  while by raising carousel  201  crucible cover  204  is removed from crucible  203 .  
         [0027]    [0027]FIG. 6A is a cross-sectional schematic drawing of a crucible  203  seated within an opening  520  of lower carousel  202  that is closed with crucible cover  204  which is seated within an opening  518  of upper carousel  201  when the carousels are in the closed position. FIG. 6B is a cross-sectional schematic drawing of a crucible  203  seated within an opening  520  of lower carousel  202  and a crucible cover  204  which is seated within an opening  518  of upper carousel  201  when the carousels are in the open position. As seen in FIG. 6A the crucible  203  has a ledge  601  around its exterior perimeter with the ledge located in the upper portion of the crucible. The maximum diameter of crucible  203  exclusive of ledge  601  relative to opening  520 , which is preferably a circular opening, is such that crucible  203  fits relatively loosely within opening  520  and ledge  601  rests on the surface of carousel  202 . To facilitate this, the lower portion of crucible  203  beneath ledge  601  may be a conical segment. Under the aforesaid circumstances with the crucible cover  204  raised, as shown in FIG. 6B and FIG. 2B, crucible  203  will be supported only by balance platform  210  when the dual carousel mechanism is lowered sufficiently via pneumatic cylinder  311  as the loose fit permits carousel  202  to drop below supporting crucible ledge  601 . Balance  206  will therefore register the actual weight of crucible  203  plus the weight of any contents.  
         [0028]    Similarly, crucible cover  204  has ledge  602  around its exterior perimeter with the ledge located at the top of the cover. As shown in FIG. 6A crucible cover  204  has a lip  603  that fit over the rim  604  of crucible  203  to cover it. Preferably, lip  603  tapers to facilitate fitting over rim  604  of crucible  203 . The maximum diameter of crucible cover  204  exclusive of ledge  602  relative to opening  518 , which is preferably a circular opening, is such that crucible cover  204  fits loosely within opening  518  and ledge  602  rests on the surface of carousel  201 . Under the aforesaid circumstances with the crucible cover  204  lowered, as shown in FIG. 6A, and FIG. 2C crucible  203  covered by crucible cover  204  will be supported only by balance platform  210  when the dual carousel mechanism is in the closed position and is lowered sufficiently via pneumatic cylinder  311 , as the loose fit permits lower carousel  202  to drop below supporting crucible ledge  601  and upper carousel  201  to drop below supporting ledge  602  so that crucible cover  204  rests only on crucible  203  which stands freely on balance platform  210 . Balance  206  will therefore register the actual weight of crucible  203  plus the weight of crucible cover  204  plus the weight of any contents.  
         [0029]    Crucible  203  and crucible cover  204  may be fabricated of any materials commonly used in the art, such as thermally stable and durable ceramic compositions and metals.  
         [0030]    The carousels of the present invention are designed to operate within a furnace as schematically depicted in FIGS. 2A, 2B and  2 C. When the mechanism is operated with the covers off or in an open position, the processes that occur to raise carrousel  201  are as follows: the piston of pneumatic cylinder  304  pushes rotational coupling  512  up, pushing shaft  510  up through hollow shaft  502 . This, in turn, pushes upper carousel  201  up, thereby separating it from lower carousel  202  and carrying crucible covers  204  away from crucibles  203 . When pneumatic cylinder  311  lowers the dual carrousel mechanism so that crucible  203  touches balance platform  210 . The distance between the carousels is adjusted so that it is great enough to keep crucible  203  out of contact with either the upper carousel  201  or crucible cover  204 .  
         [0031]    When the mechanism is operated with the covers on or in a closed position, the processes that occur to lower carrousel  201  are as follows: the piston of pneumatic cylinder  304  pulls rotational coupling  512  down pulling shaft  510  down through hollow shaft  502  and pulls upper carousel  201 , to which shaft  510  is connected, down to bring it together with lower carousel  202  so that covers  204  on carousel  201  are placed on crucibles  203  on carousel  202 . When pneumatic elevation cylinder  311  goes down, crucible  203 , covered with cover  204  will be deposited on balance platform  210 .  
         [0032]    The advantages of the improvement of the present invention may be understood by comparison with the prior art. A proximate analysis including a cycle for moisture, volatiles and ash using the prior art analyzer of U. S. Pat. No. 4,522,788 requires the following steps: obtaining the tare weight of the crucibles, introducing sample to all crucibles, reweighing to obtain sample weight, heating the furnace, reweighing to obtain moisture content, opening the furnace door and manually covering the crucibles, closing the furnace and ramping the temperature higher to obtain volatiles, cooling the furnace down, opening the furnace door half way (to avoid too much heat loss) to allow manual removal of the crucible covers with tools in order to go to the ash cycle. Removal of the covers is necessary in order to burn the coal and then determine the weight of residual ash.  
         [0033]    Normally the interior of the furnace is flushed with nitrogen during the moisture and volatiles cycles to avoid oxidation, while the ash cycle is conducted in an oxygen atmosphere to facilitate oxidation of the sample remaining in the crucible after the previous cycles.  
         [0034]    In the system of the present invention, after the tare weight of the crucibles have been obtained and the samples introduced and their weight obtained, with the upper and lower carousels in the closed position, the operator places the crucible covers on top of the crucibles, thereby covering the crucibles, and the weight of the covers is obtained by reweighing and the cycle starts by raising the covers automatically and increasing the temperature. The crucibles are reweighed to obtain moisture and the covers are automatically placed on top of the crucibles for volatile analysis and the furnace temperature is again increased and the crucibles are weighed with covers on to obtain volatiles. The covers are then removed automatically to start the ash analysis cycle.  
         [0035]    The system of the present invention provides the following advantages over the prior art: safety, no danger of an operator being burned due to manual handling of crucible covers at high temperatures; the convenience of unattended operation; and better reproducibility of the analytical results mostly volatiles because the furnace door never opens during analysis, therefore no air gets inside the furnace that may affect volatile results by oxidation.  
         [0036]    The system of the present invention may be applied to any process where the automated covering and uncovering of a series of containers is necessary or useful.  
         [0037]    It is understood that the present embodiments described above are to be considered as illustrative and not restrictive. It will be obvious to those skilled in the art to make various changes, alterations and modifications to the invention described herein. To the extent that these variations, modifications and alterations depart from the scope and spirit of the appended claims, they are intended to be encompassed therein.