Abstract:
An automated apparatus for determining the calorific value of combustible substances employs an integrated, isothermal water reservoir to reduce the complexity of the apparatus and facilitates automation of the calorimeter by providing a convenient source of isothermal water. A moving divider is used to reconfigure the isothermal water reservoir to either provide for temperature equilibration prior to sample analysis or define a fixed volume of water during analysis in which high precision temperature measurements can be recorded. The apparatus includes mechanisms for controlling the moving divider, a sample holding combustion vessel, and loading, cleaning, and unloading the combustion vessel. This eliminates key analysis steps that had previously required manual intervention by an operator.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims priority under 35 U.S.C. § 119(e) on U.S. Provisional Application No. 60/677,988 entitled A UTOMATED  C ALORIMETER , filed on May 5, 2005, by Kevin R. Brushwyler, the entire disclosure of which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The present invention relates to a calorimeter including a combustion vessel and an integrated isothermal fluid reservoir.  
         [0003]     A somewhat complicated apparatus has been employed for the determination of the calorific value of solid and liquid substances in accordance with standard methodology (ASTM/ISO documents). The operation of such an apparatus is well understood and has been described in, for example, the American National Standard Institute ANSI/ASTM D5865.  
         [0004]     Prior calorimeters have required the use of multiple internal and external reservoirs with which to contain and manage the water required to operate the apparatus. U.S. Pat. Nos. 4,398,836 and 4,616,938 disclose calorimeters which have a tank for holding a calorimeter combustion vessel and a separate water tank coupled by conduits and valves for supplying water to the vessel. In another calorimeter disclosed in U.S. Pat. No. 4,616,938, two distinct reservoirs were employed, including an internal jacket reservoir and a permanent internal bucket reservoir. In another calorimeter disclosed in U.S. Pat. No. 5,322,360, four distinct water reservoirs are employed:  
         [0005]     1) A first internal reservoir, commonly referred to as a jacket, is employed to provide a constant isothermal environment. 
        2) A second internal reservoir is employed to provide a ballast volume of water from which to fill an external burette.     3) A third external reservoir, commonly referred to as a burette, is employed to deliver a reproducible amount of analysis water.     4) A fourth transportable reservoir, commonly referred to as a bucket, is used to receive the water delivered from the burette and to contain the combustion vessel. The bucket is installed in the analyzer and temperature measurements of the bucket are recorded during the course of the analysis.        
 
         [0009]     One disadvantage of using separate reservoirs in a calorimeter is that, during routine operation, the systems require an external source of coolant water to eliminate thermal energy generated by the combustion of the sample. Also, the use of multiple reservoirs in such prior art systems requires numerous valves and conduits with which to direct the water to and from the reservoirs.  
         [0010]     The operation of prior art isothermal calorimeters is further complicated by the requirement to maintain the temperature of the water substantially constant in all reservoirs from one analysis to the next. Additionally, upon the completion of an analysis, any heat resultant from the combustion of the sample must be removed.  
         [0011]     Furthermore, prior art designs required the use of a distinctly separate bucket reservoir in order to ensure that the volume of water contained therein be maintained substantially constant from one analysis to the next. This requirement is a result of the fact that any variation in this volume is proportionally related to imprecision in the observed results. Assuming no other source of error, a variation of 1 part in 1000 in the volume of water will limit the precision the apparatus, correspondingly, to 1 part in 1000.  
         [0012]     Various instrumental approaches have been used to reduce this source of error. Typically, these approaches employ either a sensor or an overflow port with which to limit the volume of the water. Among other factors, such approaches are dependant either upon the surface tension of the water or the sensitivity and reproducibility of the sensor. In order to eliminate heat resultant from the combustion of the sample, these approaches require that the water in the bucket be substantially drained and refilled before each analysis. In some cases, the bucket and the combustion vessel must be dried by the operator in order to ensure that the correct volume of water is present.  
         [0013]     Common practice for operating prior art instruments requires significant manual intervention by the operator and strict care to operate in a reproducible manner consistent with the desired precision and accuracy of the apparatus. Manual removal of the pressurized vessel from the apparatus constitutes a potential hazard if it is mishandled or otherwise accidentally damaged.  
         [0014]     Such handling of the combustion vessel may lead to variations in the initial thermal energy state of the calorimeter. Since the measurement of the calorific value of the sample is based upon a differential measurement of the thermal energy of the calorimeter before and after combustion, such errors in the initial energy state reduces the precision of the apparatus.  
         [0015]     As such, to reduce the error of measurement, it would be desirable that manual handling of the combustion vessel by the operator is minimized and/or in some manner automated. Also, it would be desirable to retain the combustion vessel inside the instrument where the initial temperature can be controlled by allowing the combustion vessel to be in intimate contact with the isothermal water circulated within a jacket.  
       SUMMARY OF THE INVENTION  
       [0016]     In accordance with the present invention, these desirable goals are achieved using an improved apparatus and method developed for determining the calorific value of combustible substances. The apparatus employs a moving divider, which can be used to partition a single isothermal reservoir into an outer jacket and an internal bucket for receiving the calorimeter vessel. The apparatus requires fewer plumbing components than prior art systems and is amenable to automation. This reduces operator labor and minimizes operator intervention which can result in analysis errors.  
         [0017]     In one embodiment of the invention, a calorimeter system including an isothermal reservoir includes a combustion vessel; an outer jacket having a wall, a fluid inlet and an overflow outlet located near an upper end; a system for circulating fluid from said fluid inlet to provide a constant temperature of fluid within said jacket; a thermally insulated member positioned within said jacket in spaced relationship to the wall thereof and having an internal volume therein defining a bucket for receiving a calorimeter combustion vessel, said insulating member having a height less than the height of said jacket such that fluid in said jacket fills said bucket; and a movable closure member selectively coupled to said calorimeter combustion vessel and including a seal engaging said insulated member for sealing said bucket from said jacket during combustion of a sample within said combustion vessel.  
         [0018]     In another embodiment of the invention, a fully automated calorimeter including a combustion vessel and an isothermal reservoir for receiving said combustion vessel is provided and includes a combustion vessel with an open top; a closure member for said top of said combustion vessel, wherein said combustion vessel and closure member include interlocking members; an isothermal reservoir including a bucket for receiving said combustion vessel and a surrounding water jacket having water therein controlled to a predetermined temperature; an arm coupled to said cover for said combustion vessel for lifting said combustion vessel and said cover when said combustion vessel and cover are locked together to a first position in which an upper end of said combustion vessel and said cover are withdrawn from said bucket with a lower end of said combustion vessel held in thermal contact with said water jacket; a gripper assembly including arms for engaging said combustion vessel when in said first position for holding the combustion vessel in said first position and against rotation; rotary actuator means coupled to said cover of said combustion vessel for rotating said cover while said arms of said gripper assembly hold said vessel in a stationary position to disengage the locking members between said cover and said combustion vessel; and wherein said arm is movable to subsequently raise the cover from said combustion vessel to a second position for gaining access thereto and a third lowered position sealing a portion of said isothermal reservoir surrounding said combustion vessel from the remainder of said isothermal reservoir during combustion of a sample. This embodiment contemplates the sequential steps of operation of these structural components.  
         [0019]     In yet another embodiment, a method of cleaning a combustion vessel of a calorimeter includes providing a combustion vessel having an open top; providing a source of pressurized air and cleaning fluid; providing a cover for said combustion vessel which includes an inlet check valve and a nozzle with an outlet directed downwardly in said vessel; providing an exhaust, including a mechanically defeatable check valve and a sipper tube, extending through the cover into said vessel, wherein said combustion vessel is cleaned by the admission of pressurized air and cleaning fluid subsequent to combustion, wherein the byproducts of combustion are exhausted from said combustion vessel through said check valve and the cleaning fluid is removed through said sipper tube.  
         [0020]     These and other features, objects and advantages of the present invention will become apparent upon reading the following description thereof together with reference to the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]      FIG. 1  is an exploded, vertical, partially cross-sectional, view of a calorimeter embodying the present invention, shown with the calorimeter combustion vessel opened;  
         [0022]      FIG. 2  is an exploded, vertical, partially cross-sectional view of a calorimeter embodying the present invention, shown with the calorimeter combustion vessel closed prior to immersion in the isothermal reservoir;  
         [0023]      FIG. 3  is a view of the calorimeter, partially in vertical cross section, showing the combustion vessel immersed during an analysis, and partially in phantom, showing the relationship of the combustion vessel and cover;  
         [0024]      FIG. 4  is a fragmentary perspective view of the calorimeter, shown in an open position and showing the lifting and locking mechanism for the cover and the gripping mechanism for handling the calorimeter vessel;  
         [0025]      FIG. 5  is an enlarged fragmentary perspective view of the calorimeter shown with the cover in a closed position on the vessel and showing the gripping mechanism in a gripping position for holding the calorimeter vessel when enclosed prior to immersion in the isothermal reservoir;  
         [0026]      FIG. 6  is an enlarged fragmentary perspective view of the calorimeter with the gripping mechanism shown in a releasing position for allowing the calorimeter vessel to be lowered into the isothermal reservoir;  
         [0027]      FIG. 7  is a fragmentary perspective view of the calorimeter, showing the divider forming cover assembly lowered to an analysis position for the calorimeter;  
         [0028]      FIG. 8  is a top plan view, partly broken away, of the calorimeter showing the cover locking control and the vessel gripping mechanism;  
         [0029]      FIG. 9  is an enlarged cross-sectional view of the cover assembly and combustion vessel;  
         [0030]      FIG. 10  is a schematic view of the calorimeter including a flow diagram of the fluid components of the calorimeter;  
         [0031]      FIGS. 11A-11C  are a flow diagram showing the steps in the sequence of operation of the calorimeter of the present invention; and  
         [0032]      FIG. 12  is a block electrical circuit diagram of the control system for the calorimeter. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0033]     Referring initially to  FIGS. 1-7 , there is shown a calorimeter  10  embodying the present invention. In  FIGS. 1 and 4 , the calorimeter is shown in an open position for loading a sample. In  FIGS. 2 and 5 , the calorimeter is shown in a closed, sealed position prior to immersion in an isothermal reservoir.  FIGS. 3 and 7  show the calorimeter in position during an analysis. The calorimeter includes a calorimeter combustion vessel  20 , which is made of stainless steel about 0.25 inches thick with an open top  25  and a bullet-shaped curved blunt enclosed lower end  28 . Vessel  20  includes internal bayonet threads  22  (best seen in  FIG. 9 ) near the top thereof for lockably receiving external bayonet threads  32  of cover assembly  30  ( FIGS. 1, 4 , and  9 ). Vessel  20  also includes a pair of external gripper flats  24  on opposite sides ( FIGS. 4-6  and  9 ) cooperating with the gripping mechanism  120 , as described below, to allow the vessel to be held by arms  122 ,  124  of the gripper mechanism  120 , as seen in  FIGS. 1, 2 ,  4 , and  5 , in a predetermined raised position for rotatably unlocking and locking the cover  30  thereto. The vessel further includes an annular mass reduction groove  26  for reducing the overall thermal mass of the vessel.  
         [0034]     Near the open top end  25  of the combustion vessel  20  is an O-ring receiving recess  27  ( FIG. 9 ) which cooperates with an O-ring  35  fitted within an O-ring receiving groove  34  ( FIG. 1 ) of the cover assembly  30  to sealably cover the open top  25  of the combustion vessel  20  when the cover is locked in place during an analysis. The generally cylindrical cover assembly  30  includes a high pressure check valve  321  ( FIG. 10 ) and a coaxial, centrally located nozzle  36  ( FIGS. 1, 3 , and  9 ) which is pointed downwardly toward the curved end  28  of the combustion vessel for introducing both pressurized oxygen at 420 psi for pressurizing the vessel prior to the combustion of a sample and also introducing a mixture of a cleaning fluid, such as water, and pressurized air during a cleaning cycle of the combustion vessel  20  as described below.  
         [0035]     Cover assembly  30  also includes a sipper tube  37  ( FIGS. 3, 9 , and  10 ) which extends from a mechanically defeatable, high pressure check valve in the cover  30  and a gas flow path through top assembly  40  for the exhaust of byproducts of combustion and flushing water and air during the cleaning cycle. The sipper tube  37 , as best seen in  FIG. 9 , has an open lower end which is substantially adjacent the bottom of the curved floor of the combustion vessel and is coupled to an exhaust outlet, such that substantially all water and byproducts of combustion are exhausted from the vessel through a port located in the Kynar® block  78  and exhausted through tubing routed through cover  40  during the cleaning cycle. Check valve  75  is actuated by a pneumatically actuated hammer  76  ( FIG. 9 ) movably and sealably mounted within a Kynar® block  78  secured within the lower section  42  of top assembly  40 . A pneumatic fitting  79  coupled to the upper section  45  of top assembly  40  supplies pneumatic pressure to selectively actuate valve  75  as described below.  
         [0036]     The cover assembly  30  additionally includes a fuse holder comprising a pair of electrodes  38  ( FIGS. 1, 3 , and  4 ) with an electrically heated filament  39  ( FIG. 1 ) mounted therebetween to initiate combustion of the sample via ignition of a cotton string fuse  39 ′. A sample holding cup  31  retains, for example, a one gram sample to be analyzed (typically an organic material) and is removably held by a sample cup holding ring  33  positioning cup  31  below fuse  39 ′.  
         [0037]     Cover assembly  30  is coupled to the lower section  42  of Teflon® coated aluminum top  40  by a threaded retainer ring  43  having a knurled exterior surface. Ring  43  engages an annular flange  47  on the cover  30  ( FIG. 9 ) to secure the cover to the lower section  42  of top  40 . The exterior surfaces of the aluminum top sections  42  and  45  are Teflon® coated to resist corrosion during exposure to water and byproducts of combustion. The aluminum top  40  has excellent thermal characteristics which promote fast equilibration with the water in the isothermal fluid reservoir  70  into which the combustion vessel and lower section  42  of top  40  are immersed. Mechanical contact between the upper cover  45  and the lower cover  42  is minimized to limit the transfer of heat from the bucket  50  to the surrounding isothermal reservoir  70 . The top  40  includes conduits extending therethrough, through which the nozzle  36  is supplied oxygen, air, and water and a conduit for the sipper tube  37  and electrical conductors for the heated filament  39 . The combustion vessel  20 , through its connection with cover  30  and top  40 , is raised and lowered into and out of the isothermal reservoir  70  ( FIGS. 1-7  and  10 ) by lift assembly  110  ( FIGS. 4-8 ), which also locks and unlocks the cover assembly  30  between an open position and removed from the combustion vessel  20  ( FIG. 4 ) while vessel  20  is being held by the gripping arms  120 ,  122  in a closed, lowered position ( FIG. 7 ) for analysis, as described below.  
         [0038]     Top  40  includes an upper truncated concave section  45  which is coupled to lift assembly  110  ( FIG. 4 ) by a cylindrical member  106  having an axle  108  which is coupled to a crank arm  132 , as described below, for opening and closing vessel  20 . Top  40  also includes an inwardly, downwardly tapered lower section  42  which is sealed to upper section  45  by an O-ring seal  44  ( FIG. 9 ) with sections  42  and  45  held together by suitable threaded fasteners  49 . The lower section  42  of top  40  includes an annular groove  46  ( FIG. 9 ) near its widest area for receiving a sealing O-ring  48  which, as seen in  FIG. 3 , sealably engages tapered upper annular surface  52 ′ to seal the closed combustion vessel  20  within a bucket  50  ( FIGS. 1-3 ). Bucket  50  is defined by the inside of cylindrical walls  52  of stainless steel vacuum dewar  53  having an outer wall  53 ′ and annular bottom  51  resting on a floor  54  of the bucket  50 . Although the bucket  50  is defined, in part, by the vacuum dewar  53 , other cylindrical structures using alternative thermally insulating materials may be employed.  
         [0039]     The floor  54  is configured to insulate bucket  50  from the surrounding generally cylindrical jacket  80  of isothermal reservoir  70 . For such purpose, the floor includes downwardly and outwardly extending legs  56  which are sealed by O-ring  61  to dewar  53  and O-ring  64  to a support plate  67  spaced by insulating annular pedestal  62  from the floor  82  of jacket  80 . This configuration provides an open, thermally insulating volume  58  between floor  54  of bucket  50  and the floor of jacket  80 .  
         [0040]     Floor  54  also includes a circular recess  57  for receiving an impeller  59  which extends upwardly from floor  54  and includes an embedded permanent magnet. Impeller  59  is rotated at a speed of about 700 rpm by a rotating magnetic field drive  60  positioned under floor  54  of bucket  50 . Impeller  59  is made of a nonferrous metal or a thermoplastic material.  
         [0041]     The internal volume of bucket  50  holds approximately 1.5 L (liter) of fluid, typically water, between the lower seal  61  and the upper sealing O-ring  48  which engages the tapered upper edge  52 ′ of dewar  53  when in a closed position, as illustrated in  FIGS. 3 and 7 . A baffle  65  ( FIGS. 1-3 ), having a shape substantially conforming to that of the combustion vessel  20  but having a diameter slightly greater than the vessel, concentrically surrounds the combustion vessel. Baffle  65  is mounted within bucket  50  by suitable mounting hardware (not shown) in a conventional manner. Baffle  65  has an opening  63  near the bottom thereof and a curved annular wall  66  adjacent and spaced from the impeller  59  for circulating water within the bucket  50  in a direction indicated by arrows B in  FIG. 3  during an analysis. Sealably extending through the floor  56  by suitable O-rings is a thermister  55  for measuring the temperature rise of the isothermal fluid (typically water) within the bucket  50  during an analysis sequence.  
         [0042]     As best seen in  FIGS. 1-3 , the bucket  50 , including the stainless steel dewar  53 , is submerged within a concentric, generally cylindrical jacket  80  having side walls  84  and a bottom  82  with lower outlet port  86  which communicates with a circulatory pump  88 . Communicating with the inlet of the pump  88  also is a cold water (fluid) inlet  89 . The outlet of pump  88  is coupled by conduit  90  (which integrally includes a heater  92 ) to a pair of water discharge openings  93  and  94  which introduce water into the jacket volume  85  as well as into the bucket  50  when open and around the exterior of the top section  45  of top  40  when the bucket is sealed. The fluid inlet, pump, and heater can be integrated within the jacket  80  in some embodiments, thereby eliminating the external conduit  90 .  
         [0043]     Jacket  80 , which has an internal volume of approximately 4.5 L, further includes an overflow port  87  which communicates with a drain  83 . The level of the water within jacket  80  is controlled by a level indicator  96 , which indicates when the water level has reached the level of the overflow port  87 . A water jacket temperature sensing thermister  91  is mounted within the wall  84  of jacket  80  to sense the temperature of the water within the jacket and surrounding the stainless steel dewar  53 . The water temperature prior to combustion within the jacket volume  85  and in the bucket  50  is held to 25° C.+/−0.001° C., thereby providing an isothermal environment having a volume of 6 L for the submerged combustion vessel prior to combustion. The starting temperature of 25° C. will typically rise in the bucket approximately 3.5° C. during an analysis, while the temperature of the surrounding jacket remains at 25° C. The combination of a slow rate of cold water introduced to inlet  89  through a water manifold  98  ( FIG. 10 ) during an analysis sequence, together with controlling heater  92 , assures this precise temperature management of the water within the jacket  80 . The jacket tank preferably has walls  84  made of a low thermal conductivity thermoplastic material to facilitate the control of temperature within the jacket surrounding bucket  50 .  
         [0044]     As seen with reference to  FIGS. 4-8 , the calorimeter further includes a mechanical frame  100  within a cabinet  101 . A lift assembly  110  is mounted to frame  100  and includes a lift cylinder  109  which has a cylinder rod  112  having an end coupled to a horizontally extending arm  114 , which has a generally U-shaped cross section. One end of arm  114  is mounted to a vertically extending support pedestal  116  suitably slidably mounted to frame  100 . Actuation of cylinder  109 , therefore, raises and lowers the top  40  of the combustion vessel ( FIG. 1 ) and, when locked to the combustion vessel  20  itself, also raises and lowers the vessel into and partially from within bucket  50 , as illustrated in the position of  FIGS. 3 and 7 , respectively. When fully raised, the lifting assembly  110  lifts the top  40  and components, including cover  30 , form the combustion vessel, as seen in  FIGS. 1 and 4 .  
         [0045]     The opposite end of arm  114  is coupled to the top  40  of the calorimeter  10  by a rotary coupling member  106 . The top section  45  also defines a manifold which sealably couples the various conduits through top  40  for supplying oxygen, air, water, and electricity to the combustion vessel. As seen in  FIGS. 4-8 , conduits, tubes, and hoses  97  for supplying electricity, oxygen, air, and water extend over arm  114  and are coupled through the manifold in upper section  45  of top  40  to the heating element  39 , nozzle  36 , and sipper tube  37  for the operation of the calorimeter.  
         [0046]     The lifting assembly  110  provides the additional function of rotating the top  40  and cover  30  secured thereto for removing the cover from vessel  20  ( FIGS. 1 and 4 ) and locking the cover to vessel  20  ( FIGS. 2, 3 , and  5 - 8 ) while the vessel is held by gripping assembly  120 . The combustion vessel is selectively gripped by gripping arms  122 ,  124 , as shown in a gripping position in  FIGS. 1, 2 ,  4  and  5 , where gripping arms  122  and  124  compressively engage the gripping flats  24  on the sides of combustion vessel  20 . The gripping arms are pivotally mounted by pivot axles  119  ( FIGS. 4-8 ) to the top  111  of frame  100  and are spring-loaded to an open position ( FIGS. 6 and 7 ) by tension springs  121  ( FIG. 8 ) and  123 . Tension cables  125  and  126  coupled to ends of arms  122  and  124  at an end opposite their pivot coupling to top  111  and are strung around a plurality of pulleys  127  and are coupled to the lower end  134  of control rod  128  of a cylinder  129 . Cylinder  129  and pulleys  127  are mounted to the side wall  133  of frame  100 . When actuated to extend rod  128  from cylinder  129 , the cables  125  and  126  are tensioned to selectively close the gripping arms against tension springs  121  and  123 , as shown in  FIG. 4 , to hold the vessel  20  in a partially submerged position and fixed against rotation ( FIGS. 1, 2 ,  4 , and  5 ). When in this position, the cover assembly  30  can be rotated for opening ( FIGS. 1 and 4 ) and closing ( FIGS. 2 and 5 ), while the gripping arms hold the vessel in place using the structure and operation now discussed.  
         [0047]     The lift assembly  110  includes an actuator cylinder  130  ( FIGS. 4-8 ), which is pivotally coupled at pivot coupling  131  ( FIG. 8 ) at one end to an arm  114 . Cylinder  130  includes a rod  133  which is pivotally coupled at pivot axle  135  to one end of a crank arm  132  to rotate top  40  and the integral cover assembly  30  through coupling member  106  with respect to the combustion vessel  20  when held by gripper arms  122  and  124 . The axle  108  ( FIG. 9 ) of cylindrical coupling member  106  is supported by a suitable bearing in arm  114  for allowing the cover assembly  30  and top  40  to be rotated between locked and unlocked positions by the selective actuation of cylinder  130 . When unlocked, cylinder  109  is actuated for raising the top  40  and cover  30  to a loading position, as shown in  FIGS. 1 and 4 , after an analysis has been completed or before an initial analysis.  
         [0048]     After being loaded with a sample and a fuse, cylinder  109  is actuated to lower top  40  and cover  30  until O-ring seal  35  ( FIG. 1 ) seats against the inner cylindrical wall of vessel  20 , while arms  122  and  124  hold the vessel. Cylinder  130  is then actuated to extend rod  133  and rotate the cover assembly  30  through crank arm  132  about 1/16 of a turn, such that the mating bayonet threads engage, to a locked and sealed position. Cylinder  129  is then actuated to tension cables  125  and  126 , such that arms  122  and  123  release the combustion vessel  20 . Cylinder  109  is then actuated to lower arm  114  and the vessel attached thereto into the bucket  50  until O-ring seal  48  engages and seals against surface  52 ′ of the dewar  53 , thereby fluidly isolating bucket  50  from jacket  80 . The tapered surface  44  ( FIGS. 1-3 ) of lower section  42  of top  40  gradually forces excess fluid and air out of the bucket  50  as cylinder  109  lowers the top into sealing engagement with the bucket. The tapered edge  52 ′ also serves to center the top  40  on the bucket  50 . The lower end of travel of cylinder  109  (fully retracted) serves as a dead stop to provide a reproducible closing and sealing pressure. Arm  114  has an adjustable mounting to cylinder shaft  112  ( FIG. 4 ) to select the desired sealing effect.  
         [0049]      FIG. 10  is a schematic flow diagram of the various oxygen, air and water supplies, as well as rinse materials and control valves, conductors, and conduits, which are employed for preparing and operating the calorimeter during a cycle of analysis. The structure elements shown in the previously described drawings have the same reference numbers in  FIG. 10 . Referring now to  FIGS. 10-12 , there is shown the control system for the calorimeter which is controlled by a control circuit  140  ( FIG. 12 ) which includes a microcontroller  142 , interface circuits  144 , and an Ethernet interface  146 . The microcontroller is coupled to a PC  148  through Ethernet interface  146 . The PC may be coupled to a monitor  149  and to a printer  150  for printing out the results of an analysis.  
         [0050]     A computer  148  conventionally includes a keyboard for the operator to input parameters for the operation of an analysis, including the selection of a method as indicated by block  200  in  FIG. 11A  and sample information data, such as sample type, weight and the like, as shown by blocks  202  and  206 . The operator then cleans the crucible, weighs the sample, and adds the sample to the crucible, as shown by block  204 , recording the sample information as shown by block  206 . The program then asks the operator whether or not spiking will be employed, as shown by block  208 . If so, a spiking material is added to the sample, as shown by block  210 , and the weight of the spiking material is added into the system as shown by block  212 . If no spiking is employed, the next step is block  214  in which the sample is placed in the crucible  31 , the crucible  31  is placed in the ring holder  33  ( FIGS. 1 and 4 ), and fuse  39 ′ is installed. From then on the sequence of operation of the calorimeter  10  is entirely automated, which automated sequence is initiated by an operator actuating a switch  141  ( FIG. 12 ), as indicated by block  216  in the flow diagram of  FIG. 11A .  
         [0051]     With the analyzer in the position shown in  FIG. 1 , the vessel cover  30  is first lowered by the actuation of valve  300  ( FIG. 10 ) which applies pneumatic pressure from a source  302  to cylinder  109  ( FIG. 4 ) to initially lower the top  40  into engagement with vessel  20 . Next, the cap lock valve  304  ( FIG. 10 ) is actuated, which actuates cylinder  130  ( FIG. 5 ) for locking the cap to the vessel  20 . Once cap  30  has been locked to the vessel  20 , valve  305  ( FIG. 10 ) is actuated to actuate the gripper assembly  120  by activation of cylinder  129  to release the tension on cables  125  and  126 , such that gripper arms  122  and  124  release the vessel from the grippers with the vessel and top still being coupled to the lift assembly  110  ( FIG. 6 ).  
         [0052]     Subsequently, the vessel is lowered to the position shown in  FIGS. 3 and 7  within the bucket  50  by actuation of the vessel lowering valve  306  ( FIG. 10 ), with this sequence being illustrated in  FIGS. 11A and 11B  as blocks  218  through  238 . The water level is checked by the water level sensor  96  ( FIG. 1 ), as indicated by block  242  ( FIG. 11B ), and, if the water level is acceptable, a test is made of the heating filament  39 , as indicated by block  244 . If the water level is low, water is introduced through manifold  98 , and parts  93  and  94  and the analysis sequence is restarted once the equilibrium temperature has been reached, as indicated by block  241  in  FIG. 11B . If firing element  39  for fuse  39 ′ is open, the analysis is aborted, as indicated by block  245 .  
         [0053]     The next step is the filling of the vessel with oxygen, as indicated by block  246  in  FIG. 11B , which is achieved from the supply  308  ( FIG. 10 ) of pressurized oxygen through valves  310  and  312  with a pressure regulator  314  monitoring the oxygen pressure, which is approximately 500 psi. An oxygen vent valve  316  is employed for venting oxygen through exhaust vent  315  upon completion of filling. The oxygen flows into the analyzer through conduit  318  and through a check valve  321  within top  40  to nozzle  36 .  
         [0054]     Once the oxygen pressure in the vessel has reached 420 psi as determined by pressure sensor  247  ( FIG. 12 ) which is located within vessel  20 , oxygen valve  310  is disabled. Then, the pressure sensor is monitored to determine if the vessel has any leaks, as indicated by block  248  ( FIG. 11B ). If the vessel passes the leak test as indicated by block  250 , valve  312  is closed and subsequently vent  316  is opened, as indicated by block  252 . At the same time this takes place, the equilibration time as selected by the operator has begun as indicated by block  254  in  FIG. 11B  to allow the calorimeter to reach thermal equilibrium prior to the firing of the fuse  39 ′.  
         [0055]     The next step is the firing of fuse  39 ′ by the igniter  39  (indicated by block  258 ) in which the enriched oxygen atmosphere within the combustion vessel combusts the sample, raising the temperature within the vessel  20 , which, in turn, transfers the heat to the circulated water within bucket  50 . During the entire time the vessel is submerged, the water pump  88  and heater  92 , in conjunction with jacket thermister  91  and water manifold  98  maintain the temperature within the jacket  80  at the 25° C. level. The temperature detected by bucket thermister  55  is then monitored, as indicated by block  260  and  262  to calculate, using standard ASTM methodology, the calorific value of the sample contained within vessel  20  using a conventional algorithm.  
         [0056]     Next, the vessel raising and lower cylinder  306  is actuated to control cylinder  109  to raise the vessel to the intermediate position (shown in  FIG. 5 ) where gripper assembly  120  is actuated through valve  320  to actuate cylinder  129  for gripping and holding the vessel in the position shown in  FIG. 5 , thus raising and locking the vessel in position as illustrated by block  264  and  FIG. 11C . The vessel is checked for being in the proper position, as shown by step  266 , by suitable sensors (not shown). Next, the vessel is vented, as illustrated by block  268 . This process includes the actuation of the vessel exhaust valve  75  ( FIG. 9 ) by the application of pneumatic pressure through valve  322  ( FIG. 10 ), which applies pressure from inlet  79  to pneumatic cylinder  79 ′ ( FIG. 9 ) to actuate hammer  76  which, in turn, actuates the valve  75  venting the high pressure exhaust gases from the vessel through the outlet conduit in the Kynar® block  78  through top  40  to a vent station  324 , which includes a suitable fluid and filter mechanism.  
         [0057]     The vessel is then washed by the application of a pressure through valve  326  to a proportional pump  328 , which draws cleaning fluids, such as a titration/rinse and/or water in reservoir  330  ( FIG. 10 ) and injects the washing fluid under air pressure also from the purge valve  332  and conduits  317  and  318  through valves  319  and  320  into vessel  20  through nozzle  36 . The pneumatic pressure and cleaning fluid provided by pump  328  and air from cylinder  302  substantially flushes the byproducts of combustion from the vessel and up through sipper tube  37  through valve  75  into the exhaust collector vessel  324 . This cycle is repeated as necessary, as indicated by block  270  in  FIG. 11C .  
         [0058]     Next, valve  334  in the valve manifold  350  shown in  FIG. 10  is actuated to actuate cylinder  130  to unlock the top  40  from the vessel  20  by rotating the top in a counterclockwise direction 1/16 of a turn, as indicated by block  272  in  FIG. 11C . Subsequent to rotation of top  40  to unlock the top, valve  306  is again actuated to actuate cylinder  109  to raise the top and cover  30  from the vessel to the initial position shown in  FIG. 4 . These steps are represented by block  272  in  FIG. 11C . The position of the vessel is then checked, as indicated by block  274 , and the crucible  31  is removed from the vessel cover  32  as indicated by block  276 . The program then asks whether additional samples are to be run, as indicated by block  278 . If not, the vessel is again closed, as shown by block  285  in the previously described sequence. If additional samples are to be run, the operator proceeds to step  200  in  FIG. 11A . If no additional samples are to be run, the vessel is lowered into the reservoir, as indicated by block  284 , through the sequence previously described, is position tested as indicated by block  286 , and the program ended, as indicated by block  288 .  
         [0059]     Prior and during an analysis, the water manifold  98  ( FIG. 10 ) receives fresh water from a water fill inlet  336 , which is cooler than the 25° C. water as necessary, and introduces this cooling water to the heater  92  through conduit  338  to add water as required to the jacket  80  if either the water level is low, as detected by sensor  96 , or the water temperature is too high with heater  92  turned off. Thus, the temperature can be increased or decreased with the system shown by the introduction of either tap water or water from a chiller through inlet  336  and valves  337  and  339  as desired. Valve  337  provides a quick fill or quick cool higher flow rate, while a restricter  341  limits the filling flow rate. The jacket can be emptied through a drain fitting  340 , which has a quick disconnect which seals the drain during normal operation of the calorimeter.  
         [0060]     Thus, the calorimeter system of the present invention provides a hands-off automated handling of the calorimeter vessel  20  within a isothermal reservoir  70  which has a dividing member comprising the top  40  and seal  48  which divides bucket  50  from the jacket  80  and provides a carefully controlled environment for the detection of the temperature increase within the bucket during an analysis. The jacket temperature is carefully controlled through the use of a circulatory system including a heater and cooled water inlets to maintain the jacket temperature substantially stable at 25° C. Further, the system of the present invention provides a unique automated washing system for the vessel, such that physical operator intervention is unnecessary, thereby increasing the reliability and repeatability of subsequent analyses.  
         [0061]     It will become apparent to those skilled in the art that various modifications to the preferred embodiment of the invention as described herein can be made without departing from the spirit or scope of the invention as defined by the appended claims.