Elemental analysis device

Abstract

Provided is an elemental analysis device that can replace an electrode tip and, at the time of replacement, can not seal air in the electrode, thereby reducing errors in elemental analysis. An elemental analysis device (100) sandwiches a crucible (MP) in which a sample is placed between a first electrode (31) and a second electrode (32), heats the sample by causing a current to flow between the first electrode (31) and the second electrode (32), and the second electrode (32) includes a second electrode body (32B) having a substantially cylindrical front end portion, a second electrode tip (32C) provided at a front end surface of the second electrode body (32B), a cover (32D) that sandwiches a portion of the second electrode tip (32C) between the second electrode body (32B) and the cover (32D) in a state in which the portion is exposed to the outside, and a second threaded connection structure (32S) that includes a male threaded portion (S1) and a female threaded portion (S2) formed between the second electrode body (32B) and the cover (32D), and the second threaded connection structure (32S) further includes an air discharge groove (321) that extends in a thread pitch direction of at least one of the male threaded portion (S1) and the female threaded portion (S2) and is formed in a manner in which a portion of the thread is cut.

Description

Technical Field

[0001] This invention relates to an elemental analysis apparatus that heats a sample and analyzes the elements contained in the sample based on the generated sample gas. Background Technology

[0002] To quantify elements such as nitrogen (N), hydrogen (H), and oxygen (O) contained in a sample, an elemental analysis apparatus is used. Such an apparatus holds a graphite crucible containing the sample within a heating furnace, with a pair of electrodes clamping it. An electric current flows directly through the crucible, heating both the crucible and the sample. The sample gas generated by heating is then extracted from the furnace and passed through an analytical mechanism consisting of an NDIR (Non-Dispersive Infrared) analyzer and a TCD (Thermal Conductivity Detector) to measure the concentration of various components.

[0003] For example, the heating furnace of the elemental analysis apparatus shown in Patent Document 1 includes: an upper electrode with a receiving recess formed therein; and a lower electrode on which a crucible is placed. By raising the lower electrode, the crucible is received in the receiving recess while being held between the upper and lower electrodes.

[0004] The lower electrode comprises: a generally two-section cylindrical lower electrode body with a crucible placed at the front end; a lower electrode tip disposed on the front end face of the lower electrode body; and a cover that fixes the lower electrode tip relative to the lower electrode body. Specifically, a threaded connection structure consisting of male and female threads is formed between the outer circumferential surface of the front end of the lower electrode body and the inner circumferential surface of the cover, allowing only the lower electrode tip to be replaced.

[0005] However, when the cap is threaded to the lower electrode body, air may be trapped in the gap between the male and female threads. If the furnace is filled with carrier gas for elemental analysis to heat the sample, there is a possibility that the trapped air may leak from the lower electrode as a component other than the sample gas. Especially when measuring trace amounts of nitrogen (N) in the sample gas, even a very small amount of air leakage can cause a significant measurement error due to the nitrogen (N) in the air. In other words, making the lower electrode tip replaceable can lead to errors in elemental analysis.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: US Patent No. 9808797 Summary of the Invention

[0009] The technical problem to be solved by the present invention

[0010] The present invention was made in view of the problems described above. The object of the present invention is to provide an elemental analysis apparatus that allows for the replacement of electrode tips and, when the furnace is filled with carrier gas to purge air at the start of elemental analysis, can quickly expel the air sealed inside the electrodes, thereby preventing measurement errors caused by air mixing in during sample gas generation.

[0011] Technical solutions for solving technical problems

[0012] That is, the elemental analysis apparatus of the present invention is characterized in that the elemental analysis apparatus holds a crucible containing a sample between a first electrode and a second electrode, and heats the sample by passing an electric current through the first electrode and the second electrode. The second electrode comprises: a second electrode body having a generally cylindrical front end; a second electrode tip disposed on the front end face of the second electrode body; a cover having the second electrode tip clamped between the cover and the second electrode body in a state where a portion of the second electrode tip is exposed to the outside; and a second threaded connection structure consisting of a male thread portion and a female thread portion formed between the second electrode body and the cover. The second threaded connection structure further comprises an venting groove, which extends in the pitch direction of at least one of the male thread portion and the female thread portion and is formed by cutting off a portion of the thread.

[0013] In such an elemental analysis apparatus, because of the venting groove, when the furnace is filled with carrier gas and the air inside the furnace is vented before sample heating during elemental analysis, the air located in the gap between the male and female threads can be discharged from the venting groove to the outside of the second electrode. Therefore, the second electrode tip can be replaced, and even if air is trapped inside the second electrode, such air can be prevented from mixing with the sample gas, thus preventing measurement errors. Furthermore, especially when measuring trace amounts of nitrogen (N) contained in the sample gas, measurement accuracy can be improved compared to the past.

[0014] In order to secure the cover with the second electrode tip in a state where the second electrode tip is correctly positioned relative to the second electrode body, it is sufficient to form a recess on the front end face of the second electrode body in which a portion of the second electrode tip is embedded.

[0015] In order to easily install the O-ring for maintaining internal sealing onto the second electrode while the second electrode is inserted into the receiving recess of the first electrode, and to fully utilize its function, it is sufficient to do so in the following manner: a stepped portion is formed on the front end side of the second electrode body, and an O-ring is provided in the annular groove formed by the stepped portion and the edge of the cover when the cover is threadedly connected to the second electrode body.

[0016] In order to fully expel the air present between the threads through the vent groove during the process of installing the cover onto the second electrode body, it is sufficient to do so in the following way: forming an vent channel that connects the inner side of the second threaded connection structure to the outer side of the second electrode, wherein the vent groove forms at least a portion of the vent channel.

[0017] In order to fully expel the air flowing in the exhaust groove toward the forward direction of the cover during the threaded connection of the cover to the second electrode body, the cover may be provided in the following manner: the cover has: a top part having: an exposed opening for exposing the second electrode tip to the outside; a pressing plate disposed around the exposed opening for pressing the second electrode tip toward the front end face of the second electrode body when the cover is threadedly connected to the second electrode body; and a side part being generally cylindrical, with the female threaded portion formed on the inner circumferential surface.

[0018] In order to ensure that the ability to expel air from the second electrode to the outside is not reduced even if the exhaust channel is deformed or dust accumulates due to repeated analysis, the cover is provided that it also has one or more vents formed on the top surface that are further outward than the exposed opening.

[0019] In order to further improve the air discharge performance by increasing the passage for air to be discharged not only from the top side of the cover but also from the end side, the cover may be provided in the following manner: the cover also has one or more gas discharge slots that extend from the inner circumference to the outer circumference on the side portion.

[0020] As one way to form the exhaust channel in order to discharge air from the vent or the gas discharge groove into the outside of the second threaded connection structure, the exhaust groove is formed in the female thread portion of the cover.

[0021] For example, even if the exhaust groove is formed in the male thread portion of the electrode body, an exhaust channel can be formed, for example, through the vent of the cover, to connect the interior of the second threaded connection structure with the outside of the second electrode, thereby discharging the air present between the threads to the outside.

[0022] In order to allow air to be discharged from the lower side through the gas discharge groove even when the vent groove is formed in the male thread portion of the electrode body, it is sufficient to include an annular recess formed near the base end of the male thread portion of the second electrode body, the annular recess communicating with the vent groove formed in the male thread portion.

[0023] To heat the crucible in a confined space and easily extract only the sample gas generated from the sample, the following approach can be adopted: the first electrode has a receiving recess that internally accommodates the crucible, and the second electrode is configured to move between a first position where the crucible is located within the receiving recess and a second position where the crucible is located a predetermined distance away from the first position and positioned outside the receiving recess.

[0024] One specific embodiment of the second electrode is as follows: the crucible is placed on the second electrode.

[0025] Invention Effects

[0026] Thus, in the elemental analysis apparatus of the present invention, the threaded connection structure formed between the second electrode body and the cover has an exhaust groove formed in a manner that extends in the pitch direction and cuts off the threads. Therefore, when installing the second electrode tip, air located in the gap can be discharged to the outside simply by threading the male thread portion and the female thread portion together. Therefore, it is possible to prevent components other than the sample gas from leaking out of the second electrode during elemental analysis, thereby preventing analytical errors. Attached Figure Description

[0027] Figure 1 This is a schematic diagram illustrating the elemental analysis apparatus according to the first embodiment of the present invention.

[0028] Figure 2 This is a schematic cross-sectional view showing the state in which the first electrode and the second electrode of the first embodiment hold the crucible.

[0029] Figure 3 This is a schematic exploded perspective view of the first electrode in the first embodiment and a schematic diagram of the end face of the flange portion.

[0030] Figure 4 This is a schematic exploded perspective view of the second electrode in the first embodiment.

[0031] Figure 5 This is a schematic cross-sectional view showing the usage state of the mounting fixture for the elemental analysis apparatus according to the second embodiment of the present invention.

[0032] Figure 6This is a schematic perspective view showing the mounting fixture of the second embodiment.

[0033] Figure 7 This is a schematic diagram illustrating an example of a first electrode tip in another embodiment of the present invention.

[0034] Figure 8 This is a schematic diagram showing the surface side of the cover of the second electrode, according to another embodiment of the present invention.

[0035] Figure 9 This is a schematic diagram showing the back side of the cover of the second electrode in another embodiment.

[0036] Figure 10 This is a schematic diagram illustrating another embodiment of the cover for the second electrode.

[0037] Figure 11 This is a schematic diagram showing the exhaust flow channel when an exhaust groove is formed on either the female thread or the male thread.

[0038] Explanation of reference numerals in the attached figures

[0039] 100··· Elemental Analysis Apparatus

[0040] 1. Supply Source

[0041] 2··· Refining device

[0042] 3. Heating Furnace

[0043] 31···First Electrode

[0044] 31B···First Electrode Body

[0045] 311···Containment recess

[0046] 312···Outflow Hole

[0047] 313···Sample insertion hole

[0048] 31C...First electrode tip

[0049] 314··· Insertion tube

[0050] 315···Flange

[0051] 316··· Through Hole

[0052] 317···Gas Discharge Tank

[0053] 31S···First threaded connection structure

[0054] 32···Second Electrode

[0055] 32B···Second Electrode Body

[0056] ST Steps

[0057] 322···Concave part

[0058] 32C...Second electrode tip

[0059] 32D···cover

[0060] 32S···Second Threaded Connection Structure

[0061] 323···Exposed mouth

[0062] 324···Pressing plate

[0063] 325··· Vent

[0064] 326···Gas Discharge Tank

[0065] 327··· Annular concave portion

[0066] 32F···Exhaust Channel

[0067] 4. Dust Filter

[0068] 5. CO Detection Department

[0069] 6. Oxidizer

[0070] 7. CO2 Detection Department

[0071] 8. H2O Detection Department

[0072] 9···Removal mechanism

[0073] 10. Mass Flow Controller

[0074] 11. N2 Testing Department (Thermal Conductivity Analysis Department) Detailed Implementation

[0075] The elemental analysis apparatus 100 of the first embodiment of the present invention will be described with reference to the figures. Figure 1 The diagram shows a schematic of the elemental analysis apparatus 100 according to the first embodiment. The elemental analysis apparatus 100 heats and melts a sample, such as a metal sample or a ceramic sample (hereinafter simply referred to as a sample), contained in a graphite crucible MP, and analyzes the sample gas generated during this process to measure the amount of elements contained in the sample. In the first embodiment, C (carbon), H (hydrogen), and N (nitrogen) contained in the sample are the elements to be measured.

[0076] like Figure 1As shown, the elemental analysis apparatus 100 includes: a heating furnace 3 for heating a sample contained in a crucible MP; an inlet channel L1 for introducing a carrier gas into the heating furnace 3; and an outlet channel L2 for exporting a mixture of the carrier gas and the sample gas from the heating furnace 3. More specifically, the elemental analysis apparatus 100 comprises a heating furnace 3, various devices installed in the inlet channel L1 or the outlet channel L2, and a control calculation unit COM that controls the devices and calculates the measured concentrations, etc. The control calculation unit COM is, for example, a computer equipped with a CPU, memory, A / D converter, D / A converter, and various input / output devices. It executes a program stored in the memory, and various devices cooperate to perform the function of the measurement value calculation unit C1, which will be described later. In addition, the control calculation unit COM also functions as a display unit (not shown) that displays the concentrations of various elements contained in the sample based on the outputs of, for example, the CO detection unit 5, the CO2 detection unit 7, the H2O detection unit 8, and the N2 detection unit 11.

[0077] Each part is described in detail.

[0078] A gas cylinder serving as a carrier gas supply source 1 is connected to the base of the inlet channel L1. In the first embodiment, He (helium) is supplied into the inlet channel L1 from the supply source 1. In addition, a purifier 2 is provided on the inlet channel L1 to remove trace amounts of hydrocarbons contained in the carrier gas, thereby improving the purity of the carrier gas.

[0079] The purifier 2 is formed of a material that physically adsorbs hydrocarbons contained in the carrier gas but does not substantially adsorb the carrier gas itself. Furthermore, the material forming the purifier 2 does not chemically react with the carrier gas or the hydrocarbons. That is, the purifier 2 can be, for example, a purifier used in a gas chromatograph, and the material forming the purifier 2 can be, for example, a zeolite-based molecular sieve. Other materials forming the purifier 2 may include silica gel, activated carbon, and caustic soda asbestos. The purifier 2 can regenerate its adsorption capacity, for example, by heating to desorb the adsorbed molecules.

[0080] The heating furnace 3 is configured such that a graphite crucible MP containing a sample is held between a pair of electrodes, and current flows directly through the crucible MP to heat both the crucible MP and the sample. When heating the sample, the pressure of the carrier gas is adjusted by a pressure regulating valve (not shown) located upstream of the heating furnace 3 to maintain a pressure of 60 kPa or less, more preferably 40 kPa or less, within the heating furnace 3. Details regarding the electrodes of the heating furnace 3 will be described later.

[0081] Next, the devices installed on the outlet flow channel L2 will be described.

[0082] On the outlet flow channel L2, starting from the upstream side, a dust filter 4, a CO detection unit 5, an oxidizer 6, a CO2 detection unit 7, an H2O detection unit 8, a removal mechanism 9, a mass flow controller 10, and an N2 detection unit 11, which serves as a thermal conductivity analyzer, are arranged in sequence.

[0083] Filter 4 filters out carbon soot and other contaminants contained in the sample gas and removes dust.

[0084] The CO detection unit 5 detects CO (carbon monoxide) contained in the mixed gas passing through the dust filter 4 and measures its concentration using an NDIR (non-dispersive infrared gas analyzer). This CO detection unit 5 operates effectively even when the oxygen concentration inside the sample is high, prioritizing measurement accuracy. Specifically, it is preferable to measure CO concentrations of 150 ppm or higher.

[0085] The oxidizer 6 oxidizes the CO and CO2 contained in the mixed gas that has passed through the CO detection unit 5, and oxidizes H2 to H2O (water) to generate water vapor. In the first embodiment, copper oxide is used as the oxidizer 6, and its temperature is maintained at a temperature below 450°C by means of a heating resistor placed around it.

[0086] The CO2 detection unit 7 is an NDIR (Normally Induced Detection and Reduction) unit that detects CO2 in the mixed gas passing through the oxidizer 6 and measures its concentration. From the viewpoint of measurement accuracy, the CO2 detection unit 7 operates effectively even when the oxygen concentration in the sample is low (e.g., less than 150 ppm).

[0087] The H2O detection unit 8 is an NDIR detector that detects H2O in the mixed gas that has passed through the CO2 detection unit 7 and measures its concentration. Furthermore, the flow path from the oxidizer 6 to the H2O detection unit 8 is configured such that the temperature of the mixed gas is maintained above 100°C, and the H2O remains in a water vapor state. This design prevents measurement errors caused by condensation from occurring in the H2O detection unit 8.

[0088] The removal mechanism 9 adsorbs and removes CO2 and H2O contained in the mixed gas. This removal mechanism 9 is composed of an adsorbent, for example, using the same configuration as the purifier 2 provided on the inlet channel L1 described above.

[0089] The mass flow controller 10 is a flow control device comprising a flow sensor M1, a control valve M2, and a flow controller M3 as a single component. This mass flow controller 10 supplies a mixed gas to the downstream N2 detection unit 11 to maintain a constant flow rate. Therefore, even if the pressure of the mixed gas fluctuates due to the removal mechanism 9, the pressure of the mixed gas in the N2 detection unit 11 can be maintained at a suitable measurement value. In the first embodiment, the mass flow controller 10 is configured to operate at pressures lower than 60 kPa, for example, even if the pressure difference before and after is 20 kPa, thereby maintaining the pressure within the heating furnace 3 at 60 kPa.

[0090] The N2 detection unit 11 is a TCD (thermal conductivity detector) that measures the concentration of N2, a predetermined component contained in the mixed gas, based on the change in the thermal conductivity of the mixed gas and the flow rate of the supplied mixed gas. That is, since the mixed gas supplied to the N2 detection unit 11 consists essentially only of carrier gas and N2, the concentration of N2 in the mixed gas corresponds to the measured change in thermal conductivity. Furthermore, in the first embodiment, no flow meter is provided downstream of the N2 detection unit 11, and the downstream side of the N2 detection unit 11 is directly connected to the exhaust port of the outlet flow channel L2.

[0091] Measurement signals indicating the concentration of each component obtained from each detection unit are input to the measurement value calculation unit C1. The measurement value calculation unit C1 calculates the concentrations of O, H, and N contained in the sample based on each measurement signal. Furthermore, when calculating the oxygen concentration contained in the sample, the measurement value calculation unit C1 uses the oxygen concentration obtained from the CO detection unit 5 as the output value if the oxygen concentration inside the sample is above a predetermined threshold (150 ppm), and uses the oxygen concentration obtained from the CO2 detection unit 7 as the output value if it is below the threshold.

[0092] Finally, the pair of electrodes set in the heating furnace 3 are described in detail.

[0093] like Figure 2 Cross-sectional view Figure 3 as well as Figure 4 As shown in the perspective view, the heating furnace 3 includes: a first electrode 31, which is an upper electrode fixed above; and a second electrode 32, which is a lower electrode disposed below, and is a lower electrode for placing the crucible MP.

[0094] like Figure 3 As shown in (a), the first electrode 31 is a generally two-section cylindrical electrode with a thin cylindrical upper side and a flat disc-shaped lower side. The first electrode 31 includes: a first electrode body 31B, as shown in (a). Figure 2As shown in the cross-sectional view, a hollow cylindrical receiving recess 311 is formed in the lower central portion to house the crucible MP; and a first electrode tip 31C is provided within the receiving recess 311 so that it can be attached to and detached from the first electrode body 31B. The first electrode tip 31C is the portion that directly contacts the upper edge of the generally cylindrical crucible MP and is consumed due to repeated elemental analysis. Furthermore, the first electrode body 31B is formed, for example, of copper, and the first electrode tip 31C is formed, for example, of a copper alloy containing tungsten. That is, the first electrode tip 31C is formed of a material with a higher hardness than the first electrode body 31B.

[0095] The first electrode body 31B has the shape of the first electrode 31, such as Figure 2 As shown in the cross-sectional view, the cylindrical receiving recess 311 is formed to extend vertically from the center of the flat disc-shaped portion. Additionally, a sample gas outlet hole 312 extending horizontally is formed with an opening on the side of the receiving recess 311. Furthermore, a sample insertion hole 313 for placing a sample into the crucible MP is formed on the upper side of the receiving recess 311. The sample insertion hole 313 is a generally thin, hollow cylindrical hole with a diameter smaller than that of the receiving recess 311, and is formed to extend vertically along the central axis of the first electrode 31.

[0096] like Figure 2 as well as Figure 3 As shown in (a), the first electrode tip 31C is generally a two-section cylindrical shape, comprising: a thin cylindrical insertion tube 314 into which a sample insertion hole 313 is inserted into the first electrode body 31B; and a flat plate-shaped flange portion 315 extending radially from the lower end side of the insertion tube 314. Furthermore, the first electrode tip 31C also comprises: a through hole 316 formed to axially penetrate the insertion tube 314 and the flange portion 315; and a gas outlet groove, in which one end of the flange portion 315 is open at least on the side of the through hole 316 and extends radially. Figure 3 As shown in the lower end view of the first electrode head 31C in (b), the gas outlet grooves are arranged at 90° intervals in a manner symmetrical about the central axis, and there are four of them. Figure 2 As shown in (b), the inner end of the gas outlet groove in the radial direction opens inside the crucible MP. Furthermore, in the first embodiment, the other end of the gas outlet groove opens on the outer circumferential surface of the flange 315. That is, sample gas generated from the sample inside the crucible MP due to heating flows out from inside the crucible MP through the gas outlet groove to the outside of the crucible MP. Thereafter, the sample gas flows out from the receiving recess 311 through the outlet hole 312 formed in the first electrode body 31B to the outlet channel L2.

[0097] A fixing structure is provided between the first electrode body 31B and the first electrode tip 31C to detachably fix the first electrode tip 31C relative to the first electrode body 31B. More specifically, a first threaded connection structure 31S, consisting of a male thread portion S1 and a female thread portion S2, is formed between the outer peripheral surface of the insertion tube 314 of the first electrode tip 31C and the inner peripheral surface of the sample insertion hole 313 of the first electrode body 31B as a fixing structure. Through this first threaded connection structure 31S, the first electrode tip 31C is configured to be detachable relative to the first electrode body 31B. In addition, there is no groove cut in the pitch direction on the thread of the first threaded connection structure 31S. Therefore, when the first threaded connection structure 31S is fully threaded connected, the flange portion 315 is tightly attached to the upper wall surface of the receiving recess 311, and the male thread portion S1 and the female thread portion S2 are tightly attached without gap. Therefore, it is possible to prevent the sample gas flowing out of the crucible MP from accumulating in the gap between the first electrode body 31B and the first electrode tip 31C or from flowing back.

[0098] Next, while referring to Figure 2 as well as Figure 4 The second electrode 32 will be described below.

[0099] The second electrode 32 is configured to be movable in the vertical direction, for example by a cylinder (not shown), and a portion thereof is inserted into the receiving recess 311 together with the placed crucible MP. Specifically, the second electrode 32 is configured to move between a first position that clamps the crucible MP located in the receiving recess 311 between the first electrode 31 and a second position that moves a predetermined distance away from the first position and the crucible MP is positioned outside the receiving recess 311.

[0100] Furthermore, the second electrode 32 includes: a second electrode body 32B, which is generally bi-cylindrical; a second electrode tip 32C, which is disposed on the front end face of the second electrode body 32B and is in the shape of a thin disc; and a cover 32D, which fixes the second electrode tip 32C relative to the second electrode body 32B and has an exposure opening for exposing the contact surface of the second electrode tip 32C that contacts the crucible MP to the outside. Additionally, the second electrode body 32B and the cover 32D are formed of an alloy containing copper, and the second electrode tip 32C is formed of an alloy containing tungsten.

[0101] Thus, the second electrode 32 is composed of three separate parts, configured so that only the second electrode tip 32C can be replaced. More specifically, a second threaded connection structure 32S, consisting of a male threaded portion S1 and a female threaded portion S2, is formed between the outer peripheral surface of the front end of the second electrode body 32B and the inner peripheral surface of the cover 32D.

[0102] The structure of the second threaded connection structure 32S differs from the structure of the first threaded connection structure 31S formed on the first electrode 31. That is, as... Figure 4 As shown, a venting groove 321 is formed on the male thread portion S1 of the second threaded connection structure 32S, extending in the thread pitch direction and formed by cutting off a portion of the thread. The venting groove 321 is configured, for example, to cut off the thread to the height of the thread bottom, but it can also be formed shallower. Furthermore, four venting grooves 321 are arranged at 90° intervals in an axisymmetric manner relative to the central axis of the second electrode 32. The number of venting grooves 321 is not limited to four; it can be fewer or more. Also, they do not necessarily have to be configured in an axisymmetric manner.

[0103] Because of the exhaust groove 321, even when the cover 32D is installed, air is trapped between the threads of the second threaded connection structure 32S. For example, when the air present in the heating furnace 3 is replaced with carrier gas, the air in the second electrode 32 can be discharged from the exhaust groove 321 to the outside of the second electrode 32.

[0104] The second electrode body 32B has a recess 322 formed on its front end face in such a way that it substantially fits into the back side of the second electrode tip 32C, and as shown in the figure Figure 2 As shown, a stepped portion ST is formed on the front end side, opposite to the edge of the cover 32D. The front end face of the second electrode 32 on the front end side, where the second electrode tip 32C is mounted, is formed with the smallest diameter, and the portion of the stepped portion ST is expanded to have an outer diameter approximately the same as the outer diameter of the mounted O-ring SL.

[0105] Specifically, by pre-embedding the second electrode tip 32C into the recess 322, alignment of the second electrode tip 32C relative to the second electrode body 32B is possible. Furthermore, with the position of the second electrode tip 32C determined, by threading the cover 32D to the second electrode body 32B, the second electrode tip 32C can be fixed while maintaining its correct position.

[0106] Furthermore, an O-ring SL is disposed in the annular groove RT formed between the stepped portion ST of the second electrode body 32B and the edge of the cover 32D. That is, before the cover 32D is installed, there is no component restricting the axial movement of the O-ring SL. In addition, the annular groove RT is formed to be slightly larger than the thickness of the O-ring SL. In order to hold the crucible MP with each electrode and carry current, during the process of inserting the second electrode 32 into the receiving recess 311 of the first electrode body 31B, the O-ring SL slides and abuts against the edge side of the cover 32D, thereby forming a seal in the receiving recess 311. Due to this configuration, it is not necessary to install it with a very large inner diameter of the O-ring SL as in the past, which simplifies the installation operation of the O-ring SL.

[0107] The cover 32D has a top portion D1 and a side portion D2. The top portion D1 has an opening 323 for exposing the second electrode tip 32C to the outside, and a pressing plate 324 disposed around the opening 323, which presses the second electrode tip 32C against the front end face of the second electrode body 32B when the cover 32D is threadedly connected to the second electrode body 32B. The side portion D2 has a female thread S1 formed on its inner circumferential surface. Furthermore, a gap is formed between the end face of the side portion D2 and the second electrode body 32B, so that even when the cover 32D and the second electrode body 32B are fully threadedly connected, air passing through the vent groove 321 will not be obstructed from venting from the lower edge of the cover 32D to the outside of the second electrode 32.

[0108] If the elemental analysis apparatus 100 is configured in this way, since the first electrode tip 31C is detachable from the first electrode body 31B via the first threaded connection structure 31S, even if the first electrode tip 31C is worn out due to repeated elemental analysis, only the first electrode tip 31C can be replaced. Therefore, it is not necessary to replace the entire first electrode 31, including the first electrode body 31B, as was done previously.

[0109] Furthermore, since the second electrode tip 32C is configured to be detachable via a second threaded connection structure 32S formed between the second electrode body 32B and the cover 32D, only this part can be replaced when the second electrode tip 32C is consumed.

[0110] Due to these features, the time, labor, and cost of replacing consumables required for continuous elemental analysis in furnace 3 can be significantly reduced compared to the past.

[0111] Furthermore, since the second threaded connection structure 32S has an exhaust groove 321 that extends through each thread in the pitch direction, by filling the heating furnace 3 with carrier gas before sample heating, air in the second electrode 32 can be discharged to the outside through the exhaust groove 321. Moreover, during sample heating, there is no air in the second electrode 32, and thermally expanded air does not leak out of the second electrode 32 when sample gas is generated, as was the case previously. That is, air containing nitrogen (N), which can cause errors, will not leak out of the second electrode 32 when sample gas is generated, thus improving the measurement accuracy of trace amounts of nitrogen (N) contained in the sample gas in the N2 detection unit 11.

[0112] Then refer to Figure 5 as well as Figure 6 The mounting fixture 200 for an elemental analysis apparatus according to the second embodiment of the present invention will be described below.

[0113] The mounting fixture 200 of the second embodiment is used to mount the first electrode tip 31C relative to the first electrode body 31B of the elemental analysis apparatus 100 described in the first embodiment. Specifically, the first electrode tip 31C, formed as an axisymmetric component, needs to be mounted to the deepest part of the receiving recess 311 of the first electrode body 31B. Since the hardness of the first electrode tip 31C is higher than that of the first electrode body 31B, if mounting is performed without the mounting fixture 200, there is a possibility that the first electrode tip 31C will cut into the first electrode body 31B and be mounted at an angle. To solve this problem, the first electrode tip 31C needs to be rotated within the receiving recess 311 of the first electrode body 31B while aligning its axial direction with that of the first electrode body 31B, and then threadedly connected.

[0114] Specifically, such as Figure 5 Cross-sectional view and Figure 6 As shown in the perspective view, the mounting fixture 200 includes: a cylindrical guide 20A that fits into the receiving recess 311; a rotating shaft 20B, which is a cylindrical rod-shaped component mounted in a manner consistent with the axial direction of the guide 20A and configured to rotate relative to the guide 20A; and a engaging component 20C, which is provided at the front end of the rotating shaft 20B and protrudes radially, and has a generally cuboid shape that engages with the gas outlet groove 317 of the first electrode tip 31C.

[0115] In the second embodiment, the guide 20A has an outer diameter that is approximately the same as the maximum diameter portion of the receiving recess 311. By embedding the guide 20A into the receiving recess 311, the axial direction of the guide 20A and the rotation shaft 20B can be substantially aligned with the axial direction of the receiving recess 311 of the first electrode body 31B and the sample insertion hole 313. In this state, rotating the rotation shaft 20B relative to the guide 20A allows the first electrode tip 31C, which engages with the gas outlet groove and the engaging member 20C, to rotate while maintaining the correct posture and to be threadedly connected to the first electrode body 31B.

[0116] Thus, according to the mounting fixture 200 of the second embodiment, it becomes easy to install the first electrode tip 31C vertically into the deepest part of the receiving recess 311, making it possible for the end face of the flange portion 315 of the first electrode tip 31C to completely abut against the edge of the crucible MP. Therefore, it is possible to prevent situations such as insufficient current flow or failure to heat the sample as intended due to insufficient contact between the flange portion 315 and the crucible MP.

[0117] Further embodiments of the present invention will be described.

[0118] like Figure 7 As shown in the figures, the shape of the gas outlet groove 317 formed on the first electrode tip 31C is not limited to the shape described in the various embodiments. For example, the gas outlet groove 317 may be open at only one end relative to the through hole 316, and the other end of the gas outlet groove 317 may not be open on the outer peripheral surface of the flange portion 315. In addition, the number of gas outlet grooves 317 is not limited to four, and may also be two or three.

[0119] Various diameters can be prepared for the through hole of the first electrode tip. For example, if the sample being inserted is rod-shaped, the diameter can be changed to an appropriate size to prevent blockage between the sample insertion hole in the first electrode body and the crucible. That is, since the diameter of the sample channel can be appropriately changed simply by replacing the first electrode tip, it is easy to replace it with a diameter suitable for the shape and properties of the sample. Furthermore, the fixing structure that detachably fixes the first electrode tip relative to the first electrode body is not limited to the first threaded connection structure. The fixing structure can also be, for example, an engaging structure or a fitting structure consisting of engaging claws and engaging grooves formed between the first electrode tip and the first electrode body.

[0120] like Figure 8 of (a), Figure 8 (b) Figure 9As shown in the figures, as a variation of the cover 32D of the second electrode 32, the cover 32D may also include: a vent 325, which opens on the top part D1, further outward than the exposure opening 323 used to expose a part of the second electrode tip 32C to the outside; an exhaust groove 321, which extends in the pitch direction of the thread and is formed in the female thread portion S2 by cutting off a part of the thread; and a gas discharge groove 326, which extends in the radial direction on the lower end face of the side part D2, which is the edge of the cover 32D.

[0121] like Figure 8 As shown in (b), the vent 325 is configured to communicate between the inside and outside of the second electrode 32 when the cover 32D is threadedly connected to the second electrode body 32B and the second electrode tip 32C is fixed. That is, in this embodiment, the vent 325 is formed as a cut extending radially from the exposed opening 323, extending to a point further outward than the outermost periphery of the thin disc-shaped second electrode tip 32C fixed by the cover 32D. In addition, four vents 325 are provided at 90° intervals in a manner symmetrical about the central axis of the second electrode 32.

[0122] like Figure 9 As shown, the exhaust groove 321 and the gas discharge groove 326 are also arranged in a manner symmetrical about the central axis at 90° intervals, and there are four of them, so as to be arranged in a manner that is approximately in phase with the vent 325. The vent 325 and the exhaust groove 321 are close to each other at their respective ends, and the exhaust groove 321 and the gas discharge groove 326 form orthogonal and uninterrupted grooves.

[0123] If a vent 325 is formed on the top surface D1 of the cover 32D in this way, air in the gap between the threads of the second threaded connection structure 32S can be more easily discharged from the top surface D1 side during the installation of the cover 32D. Furthermore, air can be easily discharged from between the edge of the cover 32D and the O-ring SL via the gas discharge groove 326. Therefore, even if repeated analysis causes thermal effects on the second electrode 32, resulting in deformation of the vent groove 321 or accumulation of dust, the gas discharge performance is unlikely to be significantly reduced.

[0124] Then in Figure 10 Another variation of the cover 32D is shown. Instead of forming the vent 325 as a cutout, it can be formed as a through hole, for example. The through hole can be formed simply by being located on the outside of the second electrode tip 32C that the cover 32D presses against. Furthermore, for Figures 8 to 10The cover 32D shown has a vent 325, an exhaust groove 321, and a gas discharge groove 326, each positioned in the same phase, but their positions can also be offset relative to the circumferential direction. Furthermore, the cover 32D may include at least one of the vent 325, exhaust groove 321, and gas discharge groove 326. For example, the cover 32D may include either the vent 325 or the gas discharge groove 326, and only the exhaust groove 321 may be formed in the second electrode body 32B. Additionally, it may be configured to reduce the overall size of the cover 32D and to make the gap between the outer side of the side portion D2 and the inner side of the first electrode 31 a predetermined value or higher, further facilitating air discharge from the gas discharge groove 326.

[0125] like Figure 11 As shown, because an exhaust channel 32F is formed that connects the inner side of the second threaded connection structure 32S to the outer side of the second electrode 32, when the cover 32D is installed relative to the second electrode body 32B, air located between the threads can be quickly discharged to the outer side of the second electrode 32. Specifically, when an exhaust groove 321 is formed in the female thread portion S2 of the cover 32D, as... Figure 11 As shown in (a), the air present between the threads can be discharged from the upper side of the cover 32D through the vent 325 via the vent groove 321, and can also be discharged from the lower side of the cover 32D via the gas discharge groove 326.

[0126] In addition, such as Figure 11 As shown in (b), even when the vent groove 321 is formed on the male threaded portion S1 of the electrode body 32B instead of the female threaded portion S2 of the cover 32D, the same vent channel 32F can still be formed. Specifically, an annular recess 327 is formed near the base end of the male threaded portion S1, and this annular recess 327 is formed to communicate with both the vent groove 321 and the gas discharge groove 326. That is, the annular recess 327 is formed by cutting the second electrode body 32B inward to the circumferential side in a manner that, for example, has a depth approximately the same as the height of the thread of the male threaded portion S1. In this way, even when the vent groove 321 is formed on the male threaded portion S1, the air present between the threads can be quickly discharged to the outside of the second electrode 32 through the vent hole 325 or the gas discharge groove 326 of the cover 32D.

[0127] The shape of the second electrode tip and cover is not limited to the shapes shown in each embodiment.

[0128] For example, to facilitate adjusting the position of the vent groove in the second threaded connection structure to a suitable location, the mark indicating the installation direction of the cover may not be circular, but rather a cut-out portion. Furthermore, the vent groove in the second threaded connection structure formed on the second electrode can be formed not only in the male thread portion but also in the female thread portion. These vent grooves can be synchronized in a manner that ensures their circumferential positions are substantially consistent when the cover and the second electrode body are fully threadedly connected. That is, the vent grooves formed on both the male and female thread portions can be aligned to increase the area through which air can pass. Alternatively, the vent groove may be formed only in the female thread portion.

[0129] The positional relationship and direction of movement of the first and second electrodes are not limited to those shown in each embodiment. For example, the second electrode can be moved horizontally relative to the fixed first electrode to accommodate the crucible in the receiving recess.

[0130] Furthermore, various modifications to the embodiments and combinations of parts of each embodiment are possible as long as they do not violate the spirit of the invention.

[0131] Industrial applicability

[0132] According to the present invention, an elemental analysis apparatus is provided that can prevent components other than the sample gas from leaking out of the second electrode during elemental analysis, thus preventing analytical errors.

Claims

1. An elemental analysis device characterized by comprising: the elemental analysis device clamping a crucible into which a sample is put between a first electrode and a second electrode, heating the sample by causing a current to flow through the first electrode and the second electrode, the second electrode having: a second electrode main body having a substantially cylindrical front end portion; a second electrode tip provided at a front end surface of the second electrode main body; a cap clamped with the second electrode tip in a state of exposing a part of the second electrode tip to the outside between the second electrode main body and the cap; and a second threaded connection structure constituted by a male threaded portion and a female threaded portion formed between the second electrode main body and the cap, the second threaded connection structure further having an exhaust groove extending in a thread pitch direction of at least one of the male threaded portion and the female threaded portion and formed in a manner of cutting a part of a thread, a step portion being formed at a front end side of the second electrode main body, an O-ring being provided in an annular groove formed by the step portion and an edge of the cap in a state where the cap is threadedly connected to the second electrode main body.

2. The elemental analysis device according to claim 1, characterized in that: a recess into which a part of the second electrode tip is fitted is formed at a front end surface of the second electrode main body.

3. The elemental analysis device according to claim 1 or 2, characterized in that: an exhaust flow passage that communicates an inner side of the second threaded connection structure with an outer side of the second electrode is formed, the exhaust groove forms at least a part of the exhaust flow passage.

4. The elemental analysis device according to claim 1 or 2, characterized in that: the cap has: a top surface portion having: an exposure port that exposes the second electrode tip to the outside; and a pressing plate provided around the exposure port and pressing the second electrode tip toward a front end surface of the second electrode main body in a state where the cap is threadedly connected to the second electrode main body; and a side surface portion that is substantially cylindrical and has the female threaded portion formed at an inner peripheral surface.

5. The elemental analysis device according to claim 4, characterized in that: the cap further has one or a plurality of gas vents formed at the top surface portion at an outer side than the exposure port.

6. The elemental analysis device according to claim 4, characterized in that: the cap further has a gas discharge groove extending from an inner peripheral side to an outer peripheral side at the side surface portion.

7. The elemental analysis device according to claim 1 or 2, characterized in that: the exhaust groove is formed at the female threaded portion of the cap.

8. The elemental analysis device according to claim 1 or 2, characterized in that: the exhaust groove is formed at the male threaded portion of the second electrode main body.

9. The elemental analysis device according to claim 8, characterized in that: the elemental analysis device further has an annular recess formed near a base end of the male threaded portion of the second electrode main body, the annular recess communicates with the exhaust groove formed at the male threaded portion.

10. The elemental analysis device according to claim 1 or 2, characterized in that: ​ The first electrode has a housing recess in which the crucible is housed, The second electrode is configured to be movable between a first position in which the crucible housed in the housing recess is held between the first electrode and the second electrode, and a second position in which the crucible is disposed outside the housing recess at a prescribed distance from the first position.

11. The elemental analysis device according to claim 1 or 2, wherein The crucible is placed on the second electrode.

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