Thermal analysis apparatus

A thermal analysis apparatus includes: a sample temperature control device for surrounding a sample placed on a measurement position and controlling the temperature of the sample; a balance beam for supporting the sample and capable of tilting about a pivot point; and a sample moving device that allows the balance beam to slide between a first position at which the sample is situated at the measurement position and a second position at which the sample is situated at a distant position which is a position outside the sample temperature control unit. The distant position is a position which is deviated laterally from a line trajectory extending from the measurement position to the outside of the sample temperature control device. When the sample is at the measurement position, the balance beam is allowed to linearly slide and subsequently to rotationally slide about an axial line, to thereby transport the sample from the measurement position to the distant position.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a thermal analysis apparatus for measuring thermal characteristics of a sample while controlling the temperature of the sample.

2. Description of the Related Art

There have been known various types of thermal analysis apparatuses, such as a TG (Thermogravimetory) apparatus, a DTA (Differential Thermal Analysis) apparatus, and a DSC (Differential Scanning Calorimetory) apparatus. The TG apparatus measures a weight change of a sample with respect to a temperature change or a time lapse. The DTA apparatus simultaneously heats a reference substance being stable in a thermal characteristics and a sample of interest, and then measures a temperature difference exhibited between the reference substance and the sample at the time when the sample reacts to a heat. Thus, the DTA apparatus can detect, based on the temperature difference occurred, a thermal change having been occurred in the sample. The DSC apparatus measures the amount of heat when endothermic reaction or exothermic reaction occurs in the sample while it is heated, cooled, or held at a constant temperature. In addition, there have been known apparatuses that analyze a gas generated from a substance while it is heated. Known as such apparatuses are a TG-MAS apparatus (meaning a thermo gravimetry and mass spectrometry apparatus), a TPD apparatus (meaning a temperature programmed desorption apparatus), and the like.

In the above apparatuses, a heating unit is used for heating a sample. For example, Japanese Patent Laid-Open Publication No. 4-361145 discloses, at pages 2 to 3 and in FIG. 1 thereof, a heating unit using a heater obtained by winding a heater wire around a cylindrical bobbin. In the thermal analysis apparatus using such a type of heating unit, a sample of interest has to be inserted into and removed from the inner heating region of the heating unit. For example, Japanese Patent Laid-Open Publication No. 2005-331432 discloses, at page 7 and in FIG. 2 thereof, a technique for facilitating the aforesaid inserting and removing operation for the sample. In the technique, a heating unit such as an electric furnace is moved so as to release the sample outside the heated region.

In recent years, conditions required for the thermal analysis apparatus has been diversified. More specifically, measurements under a specific environment have been required to be performed. Such a measurement may be, for example, a simultaneous measurement of the TG gas analysis and the DTA gas analysis or a measurement under a predetermined humidity atmosphere. In order to meet the diversification, many types of the heating units have been available, and a large number of accessories have been added to the heating unit. For example, tubes for carrying gas may be additionally provided to a heating unit for a gas analysis. Further, a humidity generator may be additionally provided to a heating unit for a humidity analysis. In such cases, the weight of the entire heating unit becomes large thereby to apply a large load on a mechanism for moving the heating unit. Thus, it becomes necessary to prepare a large-scaled moving mechanism capable of enduring a large load. Further, it is necessary to prepare and secure a space allowing tubes to move when the heating unit is moved. Since a conventional thermal analysis apparatus requires a large-scale moving mechanism and a space for allowing tubes or the like to move freely as mentioned above, there is a problem that the apparatus inevitably has a large-sized and a strongly-built construction.

SUMMARY OF THE INVENTION

The present invention has been made to solve the above problems, and an object thereof is to provide a thermal analysis apparatus for performing thermal analysis measurement using a temperature control unit including a heating unit, in which a mechanism for exchanging samples to be measured is easier to be made very small in structure.

A first thermal analysis apparatus according to the present invention includes: a sample temperature control unit for surrounding a sample placed on a measurement position and controlling the temperature of the sample; a sample supporting unit for supporting the sample; and a sample moving unit for allowing the sample supporting unit to slide between a first position at which the sample is situated at the measurement position and a second position at which the sample is situated at a distant position which is a position outside the sample temperature control unit.

In the above structure, the sample is placed on a predetermined position of the sample supporting unit usually in a state where it is enclosed in a vessel having a predetermined shape and capacity, although the sample can be placed by itself. The term “sample” indicates in the present specification a sample itself or a sample as encapsulated in a vessel. Therefore, “to place a sample on the sample supporting unit” denotes that a sample itself is placed on the sample supporting unit or that a vessel encapsulating a sample is placed on the sample supporting unit.

Examples of the above thermal analysis apparatus include a TG apparatus, a DTA apparatus, a DSC apparatus, a TG-DTA apparatus, and the like. In the TG apparatus, the sample supporting unit is constituted by a balance beam provided with a sample plate, on which the sample is placed. In the DTA apparatus and the DSC apparatus, the sample supporting unit is constituted by a heat transmitting structure provided with a thermosensitive plate. The sample is placed on the thermosensitive plate, and a thermocouple connected to the thermosensitive plate measures the sample temperature. In the TG-DTA apparatus, the sample supporting unit is constituted by a balance beam provided with a thermosensitive plate. The sample is placed on the thermosensitive plate, and a thermocouple connected to the thermosensitive plate measures the sample temperature.

According to the first thermal analysis apparatus having the configuration described above, when the sample is taken out of the sample temperature control unit, the sample temperature control unit is not moved but the sample supporting unit is moved. Therefore, even when the heavy sample temperature control unit including a heater unit is employed or accessories such as a tube are provided in the sample temperature control unit, a structure for performing replacement of the sample can be configured in a smaller size and in a simpler manner.

In the first thermal analysis apparatus according to the present invention, it is preferable that the distant position be a position which is deviated laterally relative to a line trajectory extending from the measurement position to the outside of the sample temperature control unit. If the distant position is present on the line trajectory extending from the sample temperature control unit, it may be difficult for the operator to perform some sort of processing for a sample section of the sample supporting unit at the distant position. Such a processing may be a replacement of the sample or maintenance of a heat-sensitive portion. On the other hand, if the distant position is set to a position deviated from the line trajectory, the operator can easily accomplish the processing. Further, even if the sample is dropped during the processing, precision devices or mechanisms within the thermal analysis apparatus are not contaminated and damaged by the sample dropped.

A second thermal analysis apparatus according to the present invention includes: a sample temperature control unit for surrounding a sample placed on a measurement position and controlling the temperature of the sample; a balance beam for supporting the sample and capable of tilting about a pivot point; and a sample moving unit for allowing the balance beam to slide between a first position at which the sample is situated at the measurement position and a second position at which the sample is situated at a distant position which is a position outside the sample temperature control unit.

The second thermal analyses apparatus is an apparatus that uses the balance beam to measure a weight change of the sample. Examples of this thermal analysis apparatus include a TG apparatus and a TG-DTA apparatus. Generally, in these apparatus, a tilt detection sensor for detecting the tilting angle of the balance beam, a beam driving mechanism for applying a rotation torque to the balance beam, and the like are additionally provided around the balance beam. In the present invention, the balance beam is moved between the first and the second positions in order to move the sample from the inside of the sample temperature control unit to the outside thereof and vice versa. At this time, various mechanisms additionally provided to the balance beam do not have to be moved together with the balance beam. However, in the case where the balance beam and mechanisms additionally provided thereto are not separable each other because of its own structural feature, the additionally provided mechanisms are moved together with the balance beam.

According to the second thermal analysis apparatus, when the sample is taken out of the sample temperature control unit, the sample temperature control unit is not moved but balance beam is moved. Therefore, even when the heavy sample temperature control unit is employed or accessories are provided in the sample temperature control unit, a structure for performing replacement of the sample can be configured in a smaller size and in a simpler manner.

In the second thermal analysis apparatus, it is preferable that the distant position be a position which is deviated laterally relative to a line trajectory extending from the measurement position to the outside of the sample temperature control unit. As a result, when an operator performs some sort of processing for the sample section at the distant position, the operator can easily accomplish the processing. Further, even if the sample is dropped during the processing, devices within the thermal analysis apparatus are not damaged by the sample dropped.

Further, it is preferable that the second thermal analysis apparatus includes a cover for surrounding the sample temperature control unit and the balance beam, and it is also preferable that the cover has an opening for taking out and putting in the sample at a portion corresponding to the distant position. The cover surrounding the sample temperature control unit and the balance beam can prevent the balance beam and the like from being exposed to air atmosphere, allowing a correct weight measurement. Further, by giving the opening to the cover corresponding to the distant position, the sample may be attached to and removed from the balance beam through the opening. This enables to exchange samples through the opening.

In the second thermal analysis apparatus, it is preferable that the sample moving unit has a liner movement unit for allowing the balance beam to linearly slide and a rotational movement unit for allowing the balance beam to rotationally slide, and it is further preferable that the distant position be a position which is deviated laterally relative to a moving path of the sample on which the sample slides linearly as driven by the linear movement unit.

In the present invention, the sample moving unit may be configured only by the linear movement unit. In this case, the distant position of the sample is defined on the line trajectory extending from the measurement position. Alternatively, the sample moving unit may be configured by a combination of the linear movement unit and the rotational movement unit. In this case, the sample supported by the balance beam may be conveyed to a position deviated from the line trajectory. Conveying the sample to such a deviated position results in the following two advantages. A first advantage is that even if the sample is dropped from the balance beam, it is possible to prevent the main mechanism of the thermal analysis apparatus from being hit and damaged by the dropped sample. The second advantage is that it is possible to move the sample near the operator, making it easy for the operator to perform replacement of the sample.

Further, in the second thermal analysis apparatus, it is preferable that the rotational movement unit includes a gear member integrated with the balance beam so as not to be rotatable relative to the balance beam and a rack immovably provided in a position at which it can engage with the gear member. By allowing the gear member and the rack to engage with each other while the balance beam slides linearly as driven by the linear movement unit, the balance beam can rotationally slide by utilizing the linearly driving force caused by the linear movement unit.

Further, in the second thermal analysis apparatus, the moving speed of the balance beam is preferably increased gradually when it starts to rotationally slide after completion of its linear slide movement and/or when it starts to linearly slide after completion of its rotational slide movement. With this configuration, a smoothly change of movement of the balance beam both from the linear slide movement to the rotational slide movement and from the rotational slide movement to the linear slide movement can be obtained, thereby to prevent the balance beam from being damaged as well as prevent the sample from being dropped from the balance beam.

Further, in the second thermal analysis apparatus, the sample moving unit preferably increases the moving speed of the balance beam gradually when the balance beam starts its sliding movement from the first position or second position and/or preferably decreases the moving speed of the balance beam gradually when the balance beam stops its sliding movement toward the first position or second position. With such a construction, the balance beam may start or stop its own sliding movement slowly and smoothly, thereby to prevent the balance beam from being damaged as well as prevent the sample from being dropped from the balance beam.

A third thermal analysis apparatus according to the present invention includes: a sample temperature control unit for surrounding a sample placed on a measurement position and controlling the temperature of the sample; a balance beam for supporting the sample and capable of tilting about a pivot point; a detection mechanism provided to the balance beam for detecting a tilt of the balance beam; a beam driving mechanism provided to the balance beam for driving the balance beam to tilt about the pivot point; a balance unit having the balance beam, the detection mechanism, and the beam driving mechanism in an integrated manner; and a sample moving unit for allowing the balance unit to slide between a first position at which the sample is situated at the measurement position and a second position at which the sample is situated at a distant position which is a position outside the sample temperature control unit.

The third thermal analysis apparatus is a thermal analysis apparatus having a structure in which a mechanism for detecting a tilt of the balance beam and a beam driving mechanism for giving a rotation moment to the balance beam are additionally provided to the balance beam. In this thermal analysis apparatus, the beam driving mechanism gives a rotation moment to the balance beam in accordance with the tilt of the balance beam detected by the tilt detection mechanism, thereby enabling a feedback control for maintaining the balance beam in a horizontal state at all times. Thus, based on the amount of an electric current applied to the beam driving mechanism during the feedback control, the tilt amount of the balance beam and hence the weight change in the sample can be calculated and obtained.

In the third thermal analysis apparatus having the configuration described above, the balance beam, the detection mechanism, and the beam driving mechanism are integrated with each other to form a balance unit, and the balance unit is allowed to slide by the sample moving unit to thereby allow the balance beam to move between the first and the second positions. According to the third thermal analysis apparatus, when the sample is taken out of the sample temperature control unit, the sample temperature control unit is not moved but the balance beam is moved. Therefore, even when a heavy sample temperature control unit is employed or accessories are provided in the sample temperature control unit, a structure for performing replacement of the sample can be configured in a small size and in a simple manner.

Also, in the third thermal analysis apparatus, the distant position is preferably a position which is deviated laterally relative to a line trajectory extending from the measurement position to the outside of the sample temperature control unit. As a result, an operator may easily perform some sort of processing for the sample section, such as a replacement of the sample or maintenance of a heat-sensitive portion, at the distant position. Further, even if the sample is dropped during the processing, precision devices or mechanisms within the thermal analysis apparatus are not contaminated or damaged by the sample dropped.

A fourth thermal analysis apparatus according to the present invention includes: a protective tube for surrounding a sample placed on a measurement position; a heat application unit provided around the protective tube for heating the inside of the protective tube; a balance beam capable of tilting about a pivot point while supporting the sample; a detection mechanism provided to the balance beam for detecting a tilt of the balance beam; a beam driving mechanism provided to the balance beam for allowing the balance beam to tilt about the pivot point; a balance unit having a housing in which the pivot point, the detection mechanism, the beam driving mechanism, and portions of the balance beam that correspond to the pivot point, the detection mechanism, the beam driving mechanism are contained; and a sample moving unit for allowing the balance unit to slide between a first position at which the sample is situated at the measurement position and a second position at which the sample is situated at a distant position which is a position outside the sample temperature control unit, wherein when the balance unit is situated at the first position, the protective tube and the housing are connected to each other in an air-tight manner.

The fourth thermal analysis apparatus is a thermal analysis apparatus including a balance unit, which containing (1) the tilt detection mechanism for the balance beam, (2) the driving mechanism for the balance beam, (3) the portion at which the balance beam is supported, and (4) portions of the balance beam that corresponds to the tilt detection mechanism and the driving mechanism. A portion of the balance beam at which the sample is supported and the vicinity thereof protrude from the housing. In the thermal analysis apparatus having the above configuration, the entire balance unit including the housing is allowed to slide by the sample moving unit to thereby allow the balance beam to move between the first and the second positions.

According to the fourth thermal analysis apparatus, when the sample is taken out of the sample temperature control unit, the sample temperature control unit is not moved but the balance beam is moved. Therefore, even when a heavy sample temperature control unit is employed or accessories are provided in the sample temperature control unit, a structure for performing replacement of the sample can be configured in a small size and in a simple manner.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A thermal analysis apparatus according to the present invention will be described based on an embodiment. It should be noted that the present invention is not limited to the following embodiment. While the present invention is described below by referring to the accompanying drawings, the components may be shown in the drawings with dimensional ratios that differ from the actual ratios for the purpose of clearly showing characteristic parts thereof.

FIG. 1Ashows the entire structure of a TG-DTA apparatus, which is an example of a thermal analysis apparatus according to the present invention. InFIG. 1A, the thermal analysis apparatus1has a main body cover2, three covers3a,3b, and3cfitted to the upper side of the main body cover2, and an operating section cover4fitted to the portion which is on the front side of the covers3ato3cand on the upper side of the main body cover2. Devices used for performing thermal analysis are stored in an inner space surrounded by the above covers2,3ato3c, and4. These covers are made of metal, synthetic resin, or the like. The coupling between these covers is realized by an arbitrary coupling technique, such as a technique with a screw clamp or an engaging technique in which a pair of engaging members are engaged with each other.

FIG. 2shows the thermal analysis apparatus1ofFIG. 1Ain a state where the upper covers3a,3b,3cand the operating section cover4have been removed therefrom.FIG. 3shows a longitudinally sectional structure of the thermal analysis apparatus1as viewed from its front side.FIG. 4shows a transversely sectional structure of the thermal analysis apparatus1as viewed from above. InFIG. 2, a balance unit6, a sample moving unit7, and a sample temperature control unit8are mounted inside the cover2.

The sample temperature control unit8has, as shown inFIGS. 3 and 4, a protective tube14, a heater12, a cooling fin9, and an air duct10. The heater12functions as a heater unit for heating a sample S and a reference substance R. The cooling fin9and the air duct10jointly function as a cooling unit for cooling the sample temperature control unit8. The cooling fin9also cools the sample S and the like. The heater12is formed by, for example, winding a heater wire around a cylindrical heater bobbin. As shown inFIG. 4, a temperature control circuit13is connected to the heater wire of the heater12. The temperature control circuit13controls an electric current to be supplied to the heater wire of the heater12according to a temperature control program stored in the circuit itself or a temperature control program stored in a host computer (not shown).

The protective tube14is made of, for example, ceramic and formed into a cylindrical shape. The protective tube14is mounted within the heater12. The main function of the protective tube14is to protect the heater12from a gas generated from the sample S. The right side portion of the protective tube14is a large-diameter cylindrical portion, and the left side thereof is a small-diameter cylindrical portion. The large-diameter portion of the protective tube14is housed in the inner heating area of the heater12. The protective tube14extends outside the heater12at its right side, and the cooling fin9is disposed around the portion of the protective tube14protruded from the heater12. The right end surface of the protective tube14is opened.

The balance unit6has a housing18constructed by fixing a plate-shaped transparent cover17to the upper surface of a box-formed base body16by means of an arbitrary position-fixing method such as screwing. The housing-base body16is made of metal or synthetic resin. The transparent cover17is made of, for example, synthetic resin having a characteristic of allowing light to pass through itself. An opening19for allowing the passage of a balance beam is formed in substantially the center of the side plate on the left side of the housing-base body16. The housing18is formed into an airtight structure, excluding the portion of the opening19. Although described in detail later, the reason for forming the top of the housing18using the transparent cover17is that replacement of the balance beam, which is performed by an operator at the portion of the opening19, is enabled without removal of the upper cover of the housing18.

FIG. 5Ashows the structure of the balance unit6as taken a plane view thereof.FIG. 6shows the structure of a balance mechanism mounted within the balance unit6as taken a side view and an electric circuit associated with the balance mechanism. Although one of two balance mechanisms located on the back side cannot actually be seen because it is arranged behind the front side balance mechanism inFIG. 6, the two balance mechanisms are arranged up and down for descriptive purposes.

InFIG. 5A, two balance mechanisms, that is, a reference-side balance mechanism21aand a sample-side balance mechanism21bare mounted inside the housing18. The balance mechanisms21aand21bhave balance beams23aand23b, respectively, which are supported by torsion wires22aand22bfor pivotal movement. The torsion wires22aand22b, hereinafter, may be referred to merely as pivot points. The balance beams23aand23bare constructed by connecting second beams25aand25bto first beams24aand24bsupported by the torsion wires22aand22b.

L-shaped socket portions26aand26bare provided at the left ends of the first beams24aand24b, respectively. Plug portions27aand27bare provided at the right ends of the second beams25aand25b, respectively. The plug portions27aand27bare inserted into the socket portions26aand26bas shown inFIGS. 5B and 5Cto allow the first beams24a,24band second beams25a,25bto be coupled to each other, thus forming the balance beams23aand23b. In the present embodiment, the sample-side balance beam23bserves as a sample supporting unit for supporting the sample S. Marks denoted by reference numerals29aand29binFIGS. 5B and 5Care confirmation marks for confirming the attachment angle of the plug portions27aand27bto the socket portions26aand26b.

InFIG. 5A, sample plates30aand30bare fixed to the leading end of the second beams25aand25b. A thermosensitive plate is generally used in the TG-DTA apparatus as a sample plate, and therefore, the sample plate may hereinafter be referred to as a thermosensitive plate. A reference substance R being stable in a thermal change is placed on the reference-side thermosensitive plate30a, and a sample S to be measured is placed on the sample-side thermosensitive plate30b. It should be noted that both the reference substance R and sample S are placed on the thermosensitive plates30aand30bwith the substance and the sample being enclosed in vessels having a predetermined shape. Although detailed illustration is omitted, a plurality of thermocouple wires forming a thermocouple are fixed to the bottom surfaces of the thermosensitive plates30aand30bby welding, and the like. The thermocouple wires extend through the inside of the second beams25aand25bto the plug portions27aand27bto form terminals for electrical connections. On the other hand, a DTA measurement circuit31is connected to the socket portions26aand26b. Input/output lines starting from the DTA measurement circuit31extend to the socket portions26aand26bto form terminals for electrical connections. The DTA measurement circuit31is, inFIG. 2, provided in an appropriate location within a space surrounded by the cover2.

The insertion of the plug portions27aand27binto the socket portions26aand26bcauses their inner terminals to electrically be connected to each other, allowing the thermocouple wires extending from the thermosensitive plates30aand30bto be connected to the input/output port of the DTA measurement circuit31. The DTA measurement circuit31detects a change of temperature difference of the sample-side thermosensitive plate30brelative to the reference-side thermosensitive plate30awith respect to a time lapse. The detected change of temperature difference gives an occurrence of a thermal change in the sample S. The structure for connecting the plug portions27a,27band the socket portions26a,26bmay be the structure disclosed in Japanese Patent Laid-Open Publication No. 8-184545.

When the plug portions27a,27bis fitted to the socket portions26a,26b, respectively, the first beams24a,24band the second beams25a,25bare connected to each other, thus forming the balance beams23a,23b. Further, removing the plug portions27a,27bfrom the socket portions26a,26b, respectively, separates the first beams24a,24band the second beams25a,25b. Separation and connection of the first beams24a,24band the second beams25a,25bare carried out mainly for exchanging the second beams25a,25b. Operators need to perform the exchange of the second beams25aand25bwhile viewing the plug and socket portions. In the present embodiment, the upper cover17of the housing18is made of a transparent member, so that operators can perform the exchange of the second beams25aand25bwhile viewing the plug and socket portions without removing the upper cover17from the housing base body16. This is very convenient.

InFIG. 6, a first electromagnetic coil33ais provided near the pivot point22aof the first beam24aof the reference-side balance beam23a. A magnet34apenetrates the first electromagnetic coil33a. A second electromagnetic coil33band a third electromagnetic coil33care provided near the pivot point22bof the first beam24bof the sample-side balance beam23b. The second electromagnetic coil33band the third electromagnetic coil33care wound separately around one side and the other side of a single coil bobbin. Alternatively, they may be wound around a single coil bobbin in an overlapped manner. A magnet34bpenetrates both the second and third electromagnetic coils33band33c. The magnets34aand34bare fixed to the housing base body16as seen fromFIG. 5A.

InFIG. 6, the first electromagnetic coil33aand the magnet34afunction together as a beam driving unit28afor tilting the balance beam23aabout the pivot point22a. Further, the second and the third electromagnetic coils33b,33c, and the magnet34bfunction together as a beam driving unit28bfor tilting the balance beam23babout the pivot point22b. The balance weights35aand35bare fixed with screws on a suitable position of the first beams24aand24bso as to be changeable in position. By appropriately controlling the position of the balance weights35aand35bon the beams, the balance beams23aand23bare set to an initial position where they keep their balance.

Tilt detection mechanisms37aand37bare provided at the right end of the first beams24aand24b, respectively. The tilt detection mechanisms37aand37bhave slits38a,38bformed at the rear ends of the first beams24a,24b, light sources39a,39bdisposed in one sides of the slits38a,38b, and light-sensitive elements40a,40bdisposed in the other sides of the slits38a,38b. The light sources39aand39bmay be, for example, a light emitting diode, respectively. The light emitting diode may be referred to as “LED” hereafter. The light-sensitive elements40aand40bmay be, for example, a photodiode, respectively.

A feedback control circuit42is provided between the tilt detection mechanisms37a,37band beam driving units28a,28b. The feedback control circuit42controls the balance beams23aand23b, respectively, to maintain a horizontal state. The third electromagnetic coil33chas terminals at an upstream side and a downstream side with respect to flow of an electric current. A TG measurement circuit43is connected to the downstream side terminal of the third electromagnetic coil33c. The TG measurement circuit43calculates a weight change occurring in the sample S based on the value of an electric current flowing through the third electromagnetic coil33c. The feedback control circuit42and the TG measurement circuit43are, inFIG. 2, provided in appropriate locations within a space surrounded by the cover2.

The feedback control circuit42and the TG measurement circuit43may employ the same structure of circuit as that disclosed in Japanese Patent Laid-Open Publication No. 8-292142. These circuits will briefly be described below. The feedback control circuit42has a reference-side control circuit44connected to the output terminal of the light-sensitive element40ain the reference-side balance mechanism21a. The reference-side control circuit44includes, for example, a proportional-integral derivative circuit, which may be referred to as “PID circuit”. The output of the reference-side control circuit44is separately taken in a parallel circuit. In one of the parallel circuit, the output of the reference-side control circuit44is transmitted to the input terminal of the first electromagnetic coil33awithin the beam driving unit28aon the side of the reference-side balance mechanism21athrough an amplifier circuit45a. In the other of the parallel circuit, the output of the reference-side control circuit44is transmitted to the input terminal of the second electromagnetic coil33bwithin the beam driving unit28bon the side of the sample-side balance mechanism21bthrough a gain setting unit46and an amplifier circuit45b.

The feedback control circuit42further has a sample-side control circuit47connected to the output terminal of the light-sensitive element40bwithin the sample-side balance mechanism21b. The sample-side control circuit47also includes, for example, a PID circuit. The output signal of the sample-side control circuit47is transmitted to the input terminal of the third electromagnetic coil33cwithin the beam driving unit28bon the side of the sample-side balance mechanism21bthrough an amplifier circuit45c. The TG measurement circuit43is connected to the output terminal of the third electromagnetic coil33c. The TG measurement circuit43calculates a weight change occurring in the sample S based on the value of an electric current flowing through the third electromagnetic coil33c.

When the balance beam23awithin the reference-side balance mechanism21atilts because of some reason, the position of the slit38ais changed to change the amount of light received by the light-sensitive element40a, resulting in change of the output signal of the light-sensitive element40a. The reference-side control circuit44generates a compensation signal based on the change of the output signal of the light-sensitive element40aand outputs it to the first electromagnetic coil33awithin the reference-side beam driving unit28athrough the amplifier circuit45a. As a result, an electric current flows through the first electromagnetic coil33a, allowing interaction between the coil33aand the magnet34ato generate a force. This force generates a rotation moment in the direction opposite to the tilt of the balance beam23ato compensate the tilt, thus maintaining the horizontal state of the reference-side balance beam23a.

The compensation signal output from the reference-side control circuit44is also supplied to the second electromagnetic coil33bwithin the sample-side beam driving unit28bthrough the gain setting unit46and the amplifier circuit45b. As a result, the same amount of compensation moment as that for the reference-side balance beam23ais given to the sample-side balance beam23b. In addition, in the sample-side balance mechanism21b, the output signal of the light-sensitive element40bchanges with the tilt of the balance beam23band, correspondingly, the sample-side control circuit47generates a compensation signal and outputs it to the third electromagnetic coil33cwithin the sample-side beam driving unit28bthrough the amplifier circuit45c. As a result, an electric current flows through the second electromagnetic coil33band the third electromagnetic coil33cboth within the sample-side beam driving unit28b, allowing interaction between the coils33b,33cand magnet34bto generate a force. This force generates a rotation moment in the direction opposite to the tilt of the balance beam23bto compensate the tilt, thus maintaining the horizontal state of the sample-side balance beam23b. A weight change occurring in the sample S is calculated by the TG measurement circuit43based on the value of an electric current which has flowed through the third electromagnetic coil33c.

In the present embodiment, a compensation signal for the tilt of the reference-side balance beam23ais fed back not only to the reference-side balance beam23aitself but to the sample-side balance beam23b. Thus, when the two balance beams are influenced by a factor other than the weight change occurring in the sample S, it is possible to prevent unnecessary noise from occurring in a transitional control state immediately after that, enabling the TG measurement with high reliability.

InFIG. 5A, portions that are the pivot points22a,22b, the tilt detection mechanisms37a,37b, and the beam driving units28a,28b, as well as portions of the balance beams23aand23bthat correspond respectively to the above portions are housed in the housing18. Note that such portions of the balance beams23aand23bthat correspond respectively to the above portions coincide substantially with the first beams24aand24b. Portions of the balance beams23aand23bother than the above mentioned portions, that are substantially equal to the second beams25aand25b, extend outside the housing18through the opening19formed in the side plate of the housing18.

In the present embodiment, the operator performs a replacement of the sample S supported by the sample-side balance mechanism21b, after the balance unit6is moved and the sample S is taken out of the protective tube14ofFIG. 4. Hereinafter, a configuration that allows such movement of the balance unit6will be described.

InFIG. 3, the sample moving unit7is provided below the housing18. The sample moving unit7has a rail51fixed to a frame50, a slider52sliding along the rail51, and a unit base plate53fixed on the slider52. The housing base body16of the housing18is provided on the unit base plate53in such a manner as to be rotationally moved about an axial line X0passing through the center of a gear member56provided at the rear side of the housing18and extending vertically. A structure for rotatably setting the housing base body16on the base plate53as described above can be arbitrarily selected. Specifically, for example, the housing base body16and the base plate53are rotatably coupled to each other through a shaft member provided on the axial line X0. Alternatively, the housing base body16is guided with an appropriate guide member so as to be rotated on the base plate53about the axial line X0.

InFIG. 3, the sample moving unit7includes an electric motor54capable of controlling the output rotational velocity. The motor may be, for example, a pulse motor or a stepping motor. The output shaft of the motor54is coupled to the slider52for transmitting a drive force. When the motor54is activated to rotate its output shaft, the slider52slides along the rail51. Such a slider mechanism may be achieved by a mechanism in which, for example, a screw shaft is fixed to the output shaft of the motor54, the slider52is equipped with a female thread capable of engaging with a male thread of the screw shaft, and the male thread and the female thread are engaged with each other. The rail51extends linearly and, accordingly, the slider52slides linearly in the horizontal direction ofFIG. 3, as denoted by arrows A-A′. When the slider52slides, the housing18fixed to the slider52also slides integrally therewith.

FIGS. 3 and 4show the housing18as being situated at the leftmost position in the A′-direction. In this state, the left side plate of the housing18is brought into contact with the right end surface of the protective tube14, and the right side opening of the protective tube14and an opening19of the left-side side plate of the housing base body16communicate with each other. As shown inFIG. 4, the reference substance R supported by the balance beam23aof the reference-side balance mechanism21aand the sample S supported by the balance beam23bof the sample-side balance mechanism21bin the housing18are situated inside the protective tube14, that is inside the heater12.

The position of the sample S situated within the heater12as described above is defined as a measurement position Ps of the sample S. Further, the position of the sample-side balance beam23bat which the sample S is situated at the measurement position Ps is defined as a first position of the sample-side balance beam23b. In the following description, the position of the reference substance R at the time when the sample S is situated at the measurement position Ps may be referred to as a measurement position of the reference substance R. Further, the position of the reference-side balance beam23aat which the reference substance R is situated at the measurement position may be referred to as a first position of the balance beam.

A pipe62is provided between the left end of the small-diameter portion of the protective tube14and the right side wall of the housing base body16. An air exhauster63is provided on the pipe62. The air exhauster63may be, for example, an air exhaust pump. When the sample-side balance mechanism21bor the like is situated in the aforesaid first position, the left-side side wall of the housing base body16and the right side opening of the protective tube14are connected to each other in an air-tight manner. By activating the air exhauster63under such an air-tight condition, the insides of the protective tube14and the housing18can be formed into a vacuum or a decompressed atmosphere. Evacuating the inside of the protective tube14and the housing18is carried out in order to enable of measuring the thermal characteristics of the sample S in a vacuum, or to enable of replacing the current atmosphere within the protective tube14and the housing18with an another intended gas atmosphere.

In the thermal analysis apparatus1according to the present embodiment, a weight change in the sample S relative to the reference substance R is measured with the balance mechanisms21aand21bbeing situated in the first positions and the inside of the protective tube14being set in a vacuum as occasion demands, while the reference substance R and the sample S are heated by the heater12to increase their temperature according to a predetermined temperature rising program.

When the sample moving unit7is activated inFIG. 3and thereby the housing18linearly slides in the direction of the arrow A (that is, the right direction), the housing18linearly slides in the direction shown by the arrow A inFIG. 7along a line trajectory L0to allow the left side plate of the housing base body16to be away from the right end surface of the protective tube14as illustrated inFIG. 7. When the housing18slides by a distance longer than the length of each of the second beams25aand25b, the reference substance R and the sample S supported by the leading ends of the beams25aand25bare taken out of the protective tube14, that is, the sample temperature control unit8.

The above-mentioned gear member56is provided at the side surface and the rear end of the bottom plate of the housing base body16. The gear member56protrudes partially from the housing base body16. The gear member56is fixed to the housing base body16so as not to be rotatable. A rack57is immovably provided at the right corner inside the cover2. The tooth surface of the rack57is situated on the linear movement path of the tooth surface of the gear member56. Accordingly, when the housing18linearly slides by a predetermined distance in the direction of the arrow A, the tooth surface of the gear member56can engage with the tooth surface of the rack57.

The gear member56is fixed to the housing base body16so as not to be rotatable relative to the housing base body16, and further, the bottom plate of the housing base body16is rotatable relative to the base plate53about the axial line X0. Therefore, when the housing18further linearly slides in the direction of the arrow A (that is, the right direction) after the gear member56and the rack57have been engaged with each other, the housing18rotationally slides relative to the unit base plate53about the axial line X0in the direction of an arrow B (that is, in the counter-clockwise direction), as shown inFIG. 8.

After the housing18has slid rotationally by a predetermined angle in the counter-clockwise direction inFIG. 8A, both the reference substance R supported by the balance beam23aof the reference-side balance mechanism21ain the housing18and the sample S supported by the balance beam23bof the sample-side balance mechanism21bin the housing18are situated outside the protective tube14, that is outside the sample temperature control unit8. More specifically, the sample S is situated at the position deviated laterally (downwardly inFIG. 7) from the line trajectory denoted by the arrow L0inFIG. 7. The position of the sample S situated outside the sample temperature control unit8as mentioned above is defined as a distant position Pr. Further, the position of the sample-side balance beam23bat which the sample S is situated at the distant position Pr is defined as a second position of the balance beam. Although the distant position Pr can be set on the line trajectory L0as the case may be, it is set in the position deviated laterally from the line trajectory L0in the present embodiment.

When the sample-side balance beam23bis situated at the second position, both the sample S supported at the distant position Pr while being supported by the sample-side balance beam23band the reference substance R supported by the reference-side balance beam23aare situated in the operating section cover4. An opening59is formed at a portion of the upper surface of the operating section cover4in facing relation the reference substance R and the sample S. Although the opening59may merely be a simple opening, the opening59according to the present embodiment is provided with an opening and closing shutter60. The opening and closing shutter60is interlocked with a sliding knob61provided on the front of the operating section cover4. When the knob61is set to a closing position on the right side, the shutter60is closed. On the other hand, when the knob61is set to an opening position on the left side shown inFIG. 8B, the shutter60is opened. When the shutter60is opened with the sample-side balance beam23bbeing situated at the second position, an operator may view the reference substance R and the sample S through the opening59. In this state, an operator can exchange samples S with an exchanging tool such as tweezers. Further, the operator can perform replacement of the reference substance R according to the need.

As is clear from the description described above, the sample moving unit7ofFIG. 3can make both the reference-side balance mechanism21aand the sample-side balance mechanism21bofFIG. 4slide from the first position shown inFIG. 4to the second position shown inFIG. 8A. Thereafter, the unit base plate53is driven to slide linearly in the direction of the arrow A′ with the sample-side balance mechanism21bor the like being situated at the second position ofFIG. 8A. At this time, the gear member56and the rack57cooperate to make the balance unit6slide rotationally in the direction of the arrow B′. Later, when the sample S reaches the position on the line trajectory L0as shown inFIG. 7, the balance unit6starts to slide linearly in the direction of the arrow A′ following the slide movement of the base plate53and, finally, reaches the first position shown inFIG. 4. In the first position of the balance unit6the TG-DTA measurement can be performed for the sample S.

InFIG. 3, a blower fan64is set in the left end area of the internal space of the cover2. The air supply port of the blower fan64is connected to the air duct10. When the blower fan64is activated, air is supplied from the air duct10to the heater12to thereby forcibly cool the heater12. The cooling fin9assists the cooling processing for the heater12. This cooling processing is not performed during the thermal analysis measurement but performed for cooling the sample temperature control unit8as soon as possible after the measurement. A guide member65provided opposite to the side surface of the housing base body16guides the linear slide movement of the housing18in the direction of arrows A and A′.

Operation of the thermal analysis apparatus1having the configuration described above will be described below.

InFIG. 8A, the balance unit6is set at the illustrated second position. In this state, the thermosensitive plate30barranged at the leading end of the sample-side balance beam23bis situated at the distant position Pr which is a position outside the sample temperature control unit8. The distant position Pr in this case is positioned below the opening59of the operating section cover4. At this time, the thermosensitive plate30aarranged at the leading end of the reference-side balance beam23ais also situated below the opening59. When the knob61is slid to open the shutter60of the opening59(seeFIG. 8B), the thermosensitive plates30aand30bcan be viewed through the opening59. Therefore, an operator can place a reference substance R and a sample S on the thermosensitive plates30aand30b, respectively, with tweezers.

Then, a start button arranged at a predetermined position is depressed after the shutter60is closed. When the start button is depressed, the motor54of the sample moving unit7ofFIG. 3is activated to allow the unit base plate53ofFIG. 8Ato linearly slide in the direction of the arrow A′. At this time, the balance unit6to rotationally slide on the base plate53in the direction of the arrow B′ because of the effect of the engagement of the gear member56and rack57, resulting in reaching the position at which the sample S is situated on the line trajectory L0, as shown inFIG. 7

Thereafter, the unit base plate53successively slides linearly in the direction of the arrow A′, and the balance unit6follow it to move in the direction of the arrow A′, too. This movement allows the reference substance R supported by the reference-side balance beam23aand sample S supported by the sample-side balance beam23bto be inserted into the protective tube14. Finally, the reference-side balance beam23aand the sample-side balance beam23bwithin the balance unit6move to their first positions shown inFIG. 4and stop there. In this state, the reference substance R and the sample S are situated at their measurement positions Ps inside the heater12of the sample temperature control unit8.

Subsequently, the temperature control circuit13allows the heater12to generate heat according to a predetermined temperature rising program to thereby heat the reference substance R and the sample S. When physical properties of the sample S change to thereby change the weight of the sample S during such a heating process, a difference in the tilt angle occurs inFIG. 6between the sample-side balance beam23bsupporting the sample S and the reference-side balance beam23asupporting the reference substance R whose physical properties do not change. The feedback control circuit42and the TG measurement circuit43measures a weight change of the sample S based on the difference of the tilt angle. At the same time, the temperature change in the sample S relative to the reference substance R is measured by the DTA measurement circuit31ofFIG. 5A. As a result, measurement data based on which a TG-DTA diagram is drawn is obtained.

After completion of measurement, the corresponding information is displayed on a display device (not shown) provided in an appropriate position in the thermal analysis apparatus1ofFIG. 1A. The operator confirms this information and operates a button (not shown) to instruct execution of processing for collecting the sample S. The motor54ofFIG. 3is correspondingly activated to allow the balance unit6to linearly slide in the direction of the arrow A. After the balance unit6has traveled a predetermined distance, the reference substance R and the sample S come out of the protective tube14as shown inFIG. 7. Thereafter, the balance unit6continues to slide linearly to make the gear member56and the rack57engage with each other. Then, the balance unit6rotationally slides in the direction of the arrow B by virtue of engagement of the gear member56and the rack57, resulting in allowing the reference-side balance beam23aand the sample-side balance beam23bto reach their second positions shown inFIG. 8A.

When the balance beams23aand23bare situated at the second positions, the reference material R and the sample S supported by the balance beams23aand23bare situated at the position (that is, the distant position Pr) below the opening59of the operating section cover4. At this time, information indicating that the sample S has been placed at the distant position Pr is displayed on a display device (not shown) provided in a predetermined position of the thermal analysis apparatus1. When the operator who has confirmed the information wants to perform take-out or replacement of the sample S, he or she slides the knob61in the direction of the arrow C to open the shutter60. Through the shutter60thus opened, the sample S is taken out or replaced by another sample S.

As shown inFIG. 1A, the pull out table (that is, a drawable table)67is provided at a lower portion of the operating section cover4. The pull out table67can be pulled outside, as shown inFIG. 1B. InFIG. 8B, operators can drop the sample S or the reference substance R by mistake when he or she takes them outside or puts them inside through the opening59with the shutter60being opened. Since the dropped sample S or the like is received by the pull out table67contained in the operating section cover4, operators easily get back the dropped sample S by pulling the pull out table67outside as shown inFIG. 1B.

As described above, according to the thermal analysis apparatus1of the present embodiment, when the sample S shown inFIG. 4needs to be taken out of the sample temperature control unit8, the sample temperature control unit8is not moved, but the housing18is allowed to slide. The slide of the housing18brings the sample-side balance beam23bsliding to thereby convey the sample S to the distant position Pr which is a position outside the sample temperature control unit8. Therefore, even when the heavy sample temperature control unit8is employed or accessories such as a gas supplying tube are provided in the sample temperature control unit8, a structure for performing replacement of the sample S, such as the sample moving unit7shown inFIG. 3, can be configured in a small size and in a simple manner.

It is preferable that the movement speed of the balance beams23aand23bbe gradually increased to a predetermined speed when they start to linearly slide in the direction of the arrow A from the first position shown inFIG. 4, or when they start to rotationally slide in the direction of the arrow B′ from the second position shown inFIG. 8A. That is, it is preferable to perform a so-called slow start. Further, it is preferable that the movement speed of the balance beams23aand23bbe gradually decreased when they are stopped at the first position (FIG. 4) or the second position (FIG. 8A). That is, it is preferable to perform a so-called slow stop. Such a speed control prevents the balance beam from being damaged or deformed and prevents the sample or the like from being dropped from the balance beam. The speed control described above can be achieved by, for example, control of the rotation speed for the output shaft of the motor.

It is preferable that the movement speed of the balance beams23aand23bbe gradually increased to a predetermined speed when they start to rotationally slide in the direction of the arrow B inFIG. 8Aafter finishing to linearly slide in the direction of the arrow A inFIG. 7. In addition, it is preferable that the movement speed of the balance beams23aand23bbe gradually increased to a predetermined speed when they start to linearly slide in the direction of the arrow A′ after finishing to rotationally slide in the direction of the arrow B′. Such a speed control prevents the balance beam from being damaged or deformed and prevents the sample or the like from being dropped from the balance beam. The speed control described above can be achieved by, for example, control of the rotation speed of the motor. Alternatively, by making a partial change in the tooth shapes of the gear member56and the rack57, the above speed control can be obtained.

As shown inFIG. 1A, all the mechanisms for carrying out thermal analysis measurement are disposed within a space surrounded by the cover2, the covers3ato3c, and the operating section cover4, so that the balance beam and the like are not exposed to air atmosphere, allowing a correct weight measurement. Further, as shown inFIG. 8A, the opening59is provided in the operating section cover4at the portion corresponding to the distant position Pr of the sample S, making it easy to take out and put in the sample S and the like through the opening59.

As shown inFIG. 8A, the distant position Pr of the sample S is defined as the position at which the sample S is deviated from the line trajectory L0in the lateral direction (that is, the downward direction ofFIG. 8A). With this configuration, even if the sample S is dropped from the balance beam23b, it is possible to prevent the main mechanism of the thermal analysis apparatus1from being hit and damaged by the dropped sample S. Further, it is possible to move the sample S near the operator, making it easy for the operator to perform replacement of the sample S.

InFIG. 5A, the second beams25aand25bconstituting the balance beams23aand23bare detachably attached to the first beams24aand24b. Detaching the second beams25aand25bfrom the first beams24aand24bis achieved by removing the plug portions27aand27bof the second beams25aand25bfrom the socket portions26aand26bof the first beams24aand24b. On the other hand, Attaching the second beams25aand25bto the first beams24aand24bis achieved by fitting the plug portions27aand27bof the second beams25aand25bto the socket portions26aand26bof the first beams24aand24b. Since the housing18is made of an opaque metal material or an opaque resin material in a conventional thermal analysis apparatus, it is necessary to remove the upper cover of the housing18for visual confirmation of the inside of the housing18in order to accomplish the attachment and detachment between the plug portion and socket portion. Removing and re-fitting of the upper cover is very troublesome. On the other hand, in the present embodiment, the upper cover17of the housing18is made of a transparent material, so that the operator can visually confirm the connection portions of the balance beams23aand23bthrough the upper cover17. Therefore, it is possible to accomplish the attachment and detachment between the first beams24a,24band the second beams25a,25bwithout removal of the upper cover17, making it easier to attach and detach the second beams25aand25b.

Another Embodiment

InFIG. 8A, the distant position Pr of the sample S is defined as the position that is deviated laterally from the line trajectory L0. Alternatively, however, it is possible to set an appropriate position on the line trajectory L0as the distant position Pr of the sample S. Also in this case, it is possible to perform replacement of a sample not by moving the sample temperature control unit8but by moving the balance beam23b, thereby achieving the object of the present invention.

InFIG. 5A, the balance mechanism21afor the reference substance R is employed in addition to the balance mechanism21bfor the sample S. However, the present invention can also be applied to a TG apparatus having a configuration in which only the balance mechanism21bfor the sample S is employed.

Although the present invention is applied to a TG-DTA apparatus in the embodiment described above, the present invention can also be applied to another type of thermal analysis apparatus, such as a TG apparatus, a DTA apparatus, and a DSC apparatus. In the case where the present invention is applied to the TG apparatus, a DTA function is unnecessary, eliminating the need to provide the DTA measurement circuit31inFIG. 5and the need to fix the thermocouple wire to the thermosensitive plates30aand30b. In the case where the present invention is applied to the DTA apparatus, the balance mechanism is unnecessary, so that a configuration that uses a long supporting bar in place of the balance beam to support a sample can be adopted. In the case where the present invention is applied to the DSC apparatus, a configuration that uses a long supporting bar to support a sample stage provided with a thermosensitive plate for DSC can be adopted.

The thermal analysis apparatus shown inFIG. 4includes the mechanism for rotationally moving the housing18about the axial line X0, and the mechanism includes the gear member56and the rack57. Alternatively, however, another mechanism may be adopted in the present invention, for example, as shown inFIGS. 9 to 11. This mechanism includes an L-shaped contact member76, a pole member77and a coil spring74. The pole member77is immovably provided at the right corner inside the cover2and extends in a direction perpendicular to the plane ofFIG. 9.

A first bracket71having a plate shape is fixed to one side of the box-formed base body16. The first bracket71has a plurality of hook portions71aat the upper portion thereof. As shown inFIG. 11, the unit base plate53is equipped with a stopper73and a second bracket72. The second bracket72has a hook portion72aat the upper portion thereof. One end of the coil spring74is hooked to any desired one of the plurality of hook portions71aof the first bracket71. The other end of the coil spring74is hooked to the hook portion72aof the second bracket72. InFIG. 9the base body16is urged by the coil spring74to rotate clockwise about the axial line X0, and is brought into contact with the stopper73.

InFIG. 9the housing18places the sample S at the measurement position Ps. If the unit base plate53is driven to slide linearly by a predetermined distance in the direction shown by the arrow A, the contact member76hit the pole member77as shown inFIG. 10. Further sliding of the unit base plate53in the direction shown by the arrow A causes a rotation moment around the axial line X0to the housing18at a contact point between the contact member76and the pole member77. Due to the rotation moment, the housing18slide rotationally counterclockwise about the axial line X0against biasing force of the coil spring74as shown inFIG. 11, to thereby convey the sample S from a position on the line trajectory L0to the distant position Pr.

Later, the unit base plate53is driven to slide linearly in the direction shown by the arrow A′. Then, the housing18rotates clockwise about the axial line X0, so that the sample S supported by the housing18through the second beam25bof the balance beam23bis conveyed back from the distant position Pr to the position on the line trajectory L0as shown inFIG. 10. Further sliding of the unit base plate53in the direction shown by the arrow A′ places the sample S at the measurement position Ps as shown inFIG. 9. Thus, the sample S is enabled to be measured for a thermal analysis.

In this embodiment of the present invention the mechanism for rotationally moving the housing18about the axial line X0includes the contact member76, the pole member77and the coil spring74. This mechanism may be simple in structure and stable in operation without malfunction.