Abstract:
An apparatus for moving a series of boats loaded with samples into one end of a furnace, testing each sample by heating it to the point where the gases to be analyzed are released and discarding the boat with the remaining ashes, while maintaining the sample and the gasses emitted by the sample free from atmospheric contamination in the furnace. The sample is initially positioned in the furnace by use of a pushing mechanism in the form of a rod driven by a step motor. The boat remain in position after the gasses are driven from the sample, until another sample is introduced. The boat with the new sample pushes the boat with the ashes of the previous sample towards a means for automatic extraction of the boat from the furnace.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an automatic loader used for loading and unloading samples into a resistance furnace, for moving samples for analysis into and out of a high temperature furnace while protecting the sample from contamination by ambient atmosphere. 
     A common method of analyzing the content of a sample is to place the sample in a furnace at a sufficient temperature that gases are driven from the sample. The gases are then analyzed to obtain the desired information. Any ash or other residue then remaining from the sample is discarded. Such furnaces can be used to analyze any gas which can be obtained by burning or exposing a sample in a furnace to high temperature to obtain information such as carbon or sulfur content of a sample. 
     A conventional furnace to perform such analysis may be a resistance furnace having an elongated central tube in which the sample is positioned at the tube midpoint. The interior of the tube is flooded with a gas such as oxygen to isolate the sample from the atmosphere and to standardize the interaction with the sample. The mid point is the point of highest temperature, and thus the point where the gasses are driven or burned from the sample. The gasses to be analyzed are then drawn from one end of the furnace. The sample is normally in a crucible or boat which is placed in and removed from the furnace by hand through the same opening in the furnace. A number of attempts have been made to automate the process of introducing the sample into a furnace, drawing out of the gasses for analyzes and, thereafter, removing the remaining ashes and the crucible which carried the sample. For example, U.S. Pat. No. 5,314,662 to Hemzy, et al., and U.S. Pat. No. 5,395,586 to Hemzy, et al., show systems for automatically pushing into the furnace and retrieving a sample in a crucible from the same end of the furnace. 
     SUMMARY OF THE INVENTION 
     The present invention relates to an apparatus for moving a series of boats loaded with samples into one end of a furnace, testing each sample by heating it to the point where the gases to be analyzed are released and discarding the boat with the remaining ashes, while maintaining the sample and the gasses emitted by the sample free from atmospheric contamination in the furnace. In the present invention, this is accomplished by automatically pushing the boat with the sample to the center of the furnace, allowing any gasses to be driven out of the sample and then removing the sample through the opposite end of the furnace. 
     The sample is initially positioned in the furnace by use of a pushing mechanism in the form of a rod driven by a step motor. Since the remains of the samples in the previous boat have been reduced as far as possible by the action of the furnace, in most cases their continued existence in the furnace does not affect analysis of any later introduced sample. In accordance with the present invention, under such circumstances the boats remains in position after the gasses are driven from the sample, until another sample is introduced. The boat with the new sample pushes the boat with the ashes of the previous sample towards a means for automatic extraction of the boat from the furnace. However in testing certain materials, the spent ashes, while not adding additional gasses, may absorb gasses from the sample being analyzed. In such situations, instead of keeping the spent samples and their boats in a line in the furnace to position the boats for removal, the pushing mechanism which positions the sample in the center of the furnace, may be reintroduced into the furnace and extended to a greater length after the gasses are driven out of the sample, so that the boat containing the spent ashes is removed from the far end of the furnace. 
     The length of time that the sample remains at the hottest point of the furnace is determined by the gasses emitted by the sample under test. That is, when the sensors doing the analysis no longer sense any additional gas emitted by the sample, the cycle for eventual removal of the spent sample can be activated. 
     The furnace is sealed against outside gasses by either or both the introduction of specific gasses under positive pressure and by mechanical means. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a prospective view of the front end of a resistance furnace in accordance with the first embodiment of the present invention; 
     FIG. 2 is a partial prospective view of the front end in accordance with the first embodiment of the present invention; 
     FIG. 3 is a prospective view of the rear end of a resistance furnace in accordance with the present invention; 
     FIG. 4 is a prospective view of the mechanism for removal of spent samples without its cover plate; 
     FIG. 5 is another prospective view of the mechanism for removal of spent samples without its cover plate; 
     FIG. 6 is a partial cut-away side view of the mechanism for removal of spent samples; 
     FIG. 7 is a schematic view of the furnace including a loading and unloading means in accordance with the present invention; 
     FIG. 8 is a front view of a door over the entry port of furnace in accordance with the second embodiment of the present invention; 
     FIG. 9 is a cross section view taken along plane A-B of FIG. 8, showing the sealing mechanism of the second embodiment of the present invention in an open position; 
     FIG. 10 is a cross-sectional view taken along plane C-D of FIG. 8, showing the second embodiment of the present invention; and 
     FIG. 11 is a cross section view taken along plane A-B of FIG. 8, showing the sealing mechanism of the second embodiment of the present invention in a closed position. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present mechanism may be used with any analytical furnace which generates sufficient temperature to burn or otherwise cause a sample to emit gasses. It could, for example, be a high temperature resistance furnace  1  such as seen in FIGS. 1,  3  and  7 . 
     As with any such analysis, the individual samples are weighed prior to introduction into the furnace so that the results of the testing can be calculated in terms of weight. The sample may be weighed prior to being placed in its boat or the boat may be weighed with and without the sample. The boat  17  containing the sample is introduced into the furnace through a loading mechanism  2  having a belt  3  which moves the boat  17  to an opening  16  in the furnace. The belt  3  is driven by stepping motor  4  through gears  5  and  7  and timing belt  6 . To assure against contamination and errors in measurement, the interior of the furnace is flooded by a gas under pressure introduced through conduit  18  to orifice  19  to assure that the interior of the furnace and more importantly the gasses emitted by the sample are not contaminated by the outside atmosphere. For most analyses, the carrier gas would be oxygen, but for some analysis, such as nitrogen analysis, it may be an inert gas or a combination of gasses. 
     As seen more clearly in FIG. 2, when a boat  17  is moved in position by belt  3  opposite the opening  16 , the boat  17  contacts metal strip  14 , which closes a switch  13 . The closing of the switch  13  emits a signal to a computer system guiding the entire analysis cycle. Upon activation by switch  13 , the stepping motor  4  is deactivated and thus belt  3  stops until the end of the analyzes cycle. 
     Rod  10  has teeth  11  along at least part of its outer surface to allow it to interact with gear  9  and stepping motor  8  to move the sample boat  17  into the furnace  1 . Rod  10  is mounted in sleeve  12  which has a cut away portion at gear  9  to allow interaction between the rod  10  and the motor  8 . Upon closing of switch  13 , motor  8  is activated and drives gear  9 . Rotation of gear  9  drives teeth  11  of rod  10  forward and, thus, rod  10  and boat  17  move into the furnace tube  32  which runs through the length of furnace  1 . Sensor  15  on sleeve  12  controls the extension of rod  10  and thus the position of boat  17 . The sensor  15  may be any conventional type which can sense when rod  10  has extended sufficiently to position the boat  17  in the center of furnace tube  32 , i.e, the hottest portion of the furnace. The rod  10  then retracts and the gasses are burnt or driven from the sample in boat  17 . The gasses burnt or driven from the sample are drawn from the furnace through exit box  20  and exhaust tube  25  by a suction pump (not shown) to conventional analysis apparatus (not shown). 
     Depending on whether or not the gasses driven from a sample will interact with the spent sample, the furnace has two modes of operation. If there is no interaction between the gasses emitted by the sample and the spent samples, the introduction of a new sample and boat  17  is used to push the boats  17  containing spent samples toward a mechanism to remove the them from the furnace. More specifically, as each boat  17  enters the furnace  1  and is positioned at the mid-point, it pushes the prior boats  17  toward exit box  20 . During the period when gas is being driven from a new sample, exit box  20  is hermetically sealed to assure that all emitted gasses are analyzed without loss of gasses through exit box  20 . After enough boats  17  have been analyzed in the furnace  1  so, the first spent boat  17  is pushed into the interior  31  of exit box  20 . Exit box  20  will open for removal of the spent boat  17  after the gasses have been driven from the last sample and delivered to the analysis equipment (not shown). 
     Support bar  29  holds exit box  20  in position. Support bar  29  is attached to furnace  1  at the end opposite from where boat  17  is initially placed in the furnace  1  and holds exit box  20  in position. Support bar  29  has mounted on it pneumatic cylinders  22  and springs  23  for operating the exit box  20  to allow ejection of the spent samples. Springs  23  are attached at their opposite ends to exit door  21 . During analysis, exit door  21  of exit box  20  is held tightly closed by springs  23 . Under pressure of spring  23 , O-ring  35  seals the door  21  to the sides of the exit box  20  to assure that gasses to be analyzed will not leak from the exit box  20  while being drawn into tube  25 . Upon the complete removal of the gasses for analysis, door  21  at the bottom of exit box  20  is opened by the action of pneumatic cylinders  22  which overcomes springs  23 . Since door  21  is situated at the bottom of exit box  20 , the spent sample and the boat  17  simply falls out of the exit box  20 . During the period when the door  21  is driven open by the cylinders  22 , oxygen is flushed through the exit box  20  under pressure from tube  24  to prevent air entering into the furnace  1  and, thereby contaminating the analysis. After the boat  17  falls from exit box  20 , the pneumatic cylinders  22  are released and the springs  23  acts to close door  21  and seal exit box  20 . The other sides of exit box  20  are also constructed to seal the exit box  20  during analysis of a sample. The cover plate  27  forming the end of exit box  20  is mounted with an O-ring  34  and the entire assembly is force fit by screws  33  that pulls the exit box  20  against the body of a collapsible O-ring  36 . 
     If gasses emitted from the sample will react with spent samples, the rod  10  may be automatically operated in a two-step fashion, first positioning the boat  17  in the center of the furnace and withdrawing out of the furnace, and then after all gasses are driven from the sample as measured by the analyzing equipment, re-extending rod  10  for the length of tube  32 , pushing boat  17  into the interior  31  of exit box  20 . The rod  10  is withdrawn and the mechanism of exit box  20  is then activated resulting in removal of the spent sample in boat  17  through door  21 . A fan  26  and hood  28  are used to cool the exit box  20 . 
     A second embodiment is shown in FIGS. 8-11. In this embodiment the entry way for a sample into the furnace is protected by a sliding door  105  controlled by cylinder  113  through rod  111  The sliding door is mounted in sliding door frame  100  formed from one or more pieces of metal. The sliding door frame  100  is mounted on furnace  1  so as to interconnect with entranceway  101  of tube  32  of furnace  1  by screws (not shown) which pass through opening  116  on sliding door frame  100 . The screws in holes  116  pull end plate  119  against O-rings  118  forming a seal across the furnace combustion tube  32 . Cylinder  113  is mounted on framework  114  which is attached to the sliding door frame  100 . The sliding door frame  100  forms an open box  102  within which sliding door  105  is positioned when the door  105  is closed. The box  102  has grooves  103  in which the sliding door  105  is mounted. Prior to rod  10  positioning boat  17  in furnace  1 , the pneumatic piston  113  is activated, raising rod  111  and, thereby, pulling sliding door  105  away from entry way  101  and up thereby giving access to tube  32  through an opening  110  in end plate  115 . Rod  111  is attached to door  105  through pin  109 , lever arm  107  supports and allows the rotation of shaft  106  and thereby pressing cam  108  against O-ring  110 . 
     After the boat  17  is placed in the center of furnace  1  and rod  10  is withdrawn, the piston  113  pushes rod  111  downward, letting door  105  fall to the bottom of groove  103  in cavity  112 . As piston  113  continues to push rod  111  downward, arm  107  is rotated after the sliding door  105  reaches the bottom of groove  103 , thereby forcing sliding door  105  against O-rings  110  sealing furnace entranceway  101  in tube  32 . 
     Inlet opening  117  allows insertion of gasses under pressure into entranceway  101  to prevent contamination when the sliding door  105  is open and to provide the appropriate environment for driving the gasses out of the sample. Once a sample has been analyzed and no further gasses are being emitted by the sample, a new analysis cycle begins with the piston  113  opening sliding door  105 . 
     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.