Chromatography column connection assembly

Abstract

The utility model discloses a purpose at providing a kind of chromatographic column connecting assembly, prevent the air seal structure failure of junction.In chromatographic column connecting assembly, elastic component is set in its axial through inner cavity, can be elastically deformed along the axial direction of connecting piece, with base end and movable end, including multiple disc springs, wherein at least part adjacent disc spring outer ring is relatively arranged, and at least part adjacent disc spring inner ring is relatively arranged;Annular pressing plate outer periphery and the inner cavity inner wall of connecting piece rigid connection, limit the base end of elastic component and the activity freedom degree along the axial direction of connecting piece;Wherein, in the state that chromatographic column connecting assembly is connected to sample introduction module, elastic component is pre-compressed state because of and graphite sleeve resistance top, and movable end thus applies axial pre-tightening force to graphite sleeve.

Description

Technical Field

[0001] This utility model relates to gas chromatography analysis instruments, specifically to a sealing structure for the connection between a gas chromatography column and an injection module. Background Technology

[0002] Gas chromatographs are commonly used laboratory equipment for component separation and detection analysis. They mainly consist of a separation unit and a detection and analysis unit. The chromatographic column, as the core component of the separation unit, directly determines the stability of the carrier gas and sample gas delivery through its connection and sealing with the injection module, which in turn affects the detection accuracy and operational reliability of the instrument.

[0003] Currently, the conventional connection structure between gas chromatography columns and injection modules mainly uses a nut and a graphite ferrule for fixing and sealing. Specifically, the nut and graphite ferrule are sequentially fitted onto the end of the column. After the column is inserted into the connection port of the injection module, axial pressure is applied to the graphite ferrule by tightening the nut, causing the graphite ferrule to undergo plastic deformation and form an airtight structure, thus completing the axial fixation of the column.

[0004] However, there is a failure issue with the gas-tight structure. According to the inventors' analysis, in actual gas chromatograph operations, the chromatographic column needs to undergo programmed temperature increases according to the separation requirements of the sample. The column and the connection port repeatedly experience a heating-cooling thermal cycle. Under long-term thermal cycling conditions, the thermal expansion and contraction deformation of the threaded connection will cause a decrease in the axial preload of the connection, resulting in a drop in the pressure required for sealing. This can ultimately lead to leakage of carrier gas or sample gas, causing deviations in the detection results and reduced parallelism. Utility Model Content

[0005] The purpose of this invention is to provide a chromatography column connection assembly to prevent the failure of the gas-tight structure at the connection point.

[0006] To achieve the aforementioned objective, a chromatographic column connection assembly includes a connector having an axially penetrating inner cavity. The connector is provided with a structure for connection to a gas chromatography injection module and has an opening at one end for receiving a graphite ferrule. The chromatographic column connection assembly further includes a stop structure and an elastic component. The elastic component is disposed within the inner cavity and is elastically deformable along the axial direction of the connector. It has a base end and a movable end and includes multiple disc springs, wherein at least some of the outer rings of adjacent disc springs are arranged opposite each other, and at least some of the inner rings of adjacent disc springs are arranged opposite each other. The stop structure is an annular pressure plate, the outer periphery of which is rigidly connected to the inner wall of the inner cavity of the connector, restricting the degree of freedom of movement of the base end of the elastic component along the axial direction of the connector. When the chromatographic column connection assembly is connected to the injection module, the elastic component is in a pre-compressed state due to abutment against the graphite ferrule, and the movable end therefore applies an axial pre-tightening force to the graphite ferrule.

[0007] In one embodiment, a sleeve seat is further provided between the movable end of the elastic component and the graphite sleeve, the sleeve seat being slidable along the axial direction of the connector, and the movable end of the elastic component applying an axial preload to the graphite sleeve through the sleeve seat.

[0008] In one embodiment, the inner wall of the connector is provided with an inner shoulder, and the outer periphery of the ferrule is provided with a flange. When the chromatographic column connection assembly is not connected to the injection module, the flange abuts against and limits the inner shoulder.

[0009] In one embodiment, the sleeve holder includes a guide shaft, and the connector includes a guide hole, with the guide shaft and the guide hole being slidably engaged.

[0010] In one embodiment, the annular pressure plate is rigidly connected to the inner wall of the connector by welding.

[0011] In one embodiment, the inner cavity of the end of the connector with the opening includes a cylindrical hole for engaging with the cylindrical portion of the graphite sleeve.

[0012] In one embodiment, the opening of the connector is an outwardly flared horn-shaped opening.

[0013] In one embodiment, the structure for connecting to the gas chromatography injection module is an external thread located on the outer periphery of the connector.

[0014] When the column connector is connected to the injection module, the elastic component is pre-compressed due to its contact with the graphite ferrule, thus applying a continuous axial preload to the ferrule. During the programmed temperature cycling process of the gas chromatograph, the connection between the connector and the injection module deforms due to thermal expansion and contraction, causing the axial preload at the connection point to decrease. At this time, the pre-compressed elastic component automatically releases through its own elastic deformation, compensating for the preload shortfall and maintaining a stable clamping force on the graphite ferrule, preventing seal failure and gas leakage. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of a gas chromatograph.

[0016] Figure 2 for Figure 1 Enlarged schematic diagram of point I in the middle.

[0017] Figure 3 This is a cross-sectional view of the chromatographic column connection assembly according to an embodiment of the present invention.

[0018] Figure 4 This is a schematic diagram illustrating the application of the chromatographic column connection assembly according to an embodiment of the present invention in the connection between a gas chromatography column and an injection module.

[0019] Explanation of reference numerals in the attached figures: 1-Connector, 13-Inner shoulder, 14-Guide hole, 15-Cylindrical hole 2-Stop structure, 21-Joint, 31-Elastic component, 310-Base end, 311-Modible end 4-Sleeve holder, 41-Flange, 42-Guide shaft, 5-Graphite sleeve, 51-Cylindrical part, 6-Injection module, 61-Carrier gas line, 62-Split gas line, 63-Purge gas line. 7-chromatographic column, 8-Separation unit, 81-Carrier gas cylinder, 82-Flow meter, 84-Oven, 9-Detection and analysis unit, 91-Detector, 92-Data processing system, 93-Data recording system. Detailed Implementation

[0020] The specific embodiments of this utility model will be further described in detail below with reference to the accompanying drawings.

[0021] Figure 1The gas chromatograph shown includes a separation unit 8 and a detection and analysis unit 9. The separation unit 8 includes a carrier gas bottle 81, a flow meter 82, an injection module 6, an oven 84, and a chromatographic column 7. The detection and analysis unit 9 includes a detector 91, a data processing system 92, and a data recording system 93. A gas chromatograph is an analytical instrument that utilizes the difference in partition coefficients between the stationary and mobile phases to achieve the separation and quantitative detection of multi-component mixtures. The carrier gas (mobile phase), controlled by the flow meter 82, from the carrier gas bottle 81 carries the vaporized sample into the chromatographic column 7 (stationary phase) at the injection module 6. Due to differences in adsorption capacity, solubility, or affinity of different components in the sample on the stationary phase, the migration rates of each component in the chromatographic column 7 differ, achieving separation after passing through a certain length of the chromatographic column 7. Figure 1 The intermediate oven 84 controls the temperature and temperature change process of the chromatographic column 7, adjusting the distribution behavior of sample components between the stationary phase and the mobile phase, thereby achieving effective separation of the mixture. The separated components sequentially enter the detector 91, which converts the concentration or mass signal of the component into an electrical signal. After processing by the data processing system 92, the data is recorded by the data recording system 93, generating a chromatogram. Qualitative analysis is performed based on retention time, and quantitative analysis is performed based on peak area or peak height.

[0022] like Figure 1 and Figure 2 As shown, the injection module 6 has a vaporization chamber inside its injection port and an injection septum at the top for injecting liquid samples via syringe puncture. The injection port is connected to three gas lines. The carrier gas line 61 delivers carrier gas, which enters from the lower side wall of the injection port, flows upward into the vaporization chamber, and carries the vaporized sample downward into the chromatographic column 7. High-purity nitrogen or helium is typically used as the carrier gas, propelling the sample through the column. The split gas line 62 extends from the lower side wall of the injection port, opposite the carrier gas inlet. In split mode, most of the carrier gas and sample mixture is discharged through the split gas line, with only a small portion entering the column 7. The amount of sample entering the column 7 is controlled by adjusting the split ratio (the ratio of the split gas flow rate to the column flow rate), preventing overloading of the column 7. The purge line 63 extends from the upper side wall of the inlet and is used to purge residual sample gas below the septum to prevent the sample adsorbed by the septum from being released in subsequent analyses, causing memory effects and baseline drift.

[0023] The chromatographic column 7 is connected to the injection port of the injection module 6 via a connecting structure at the bottom of the injection module 6. The chromatographic column 7 is inserted through the connecting hole at the bottom of the injection module 6, and a graphite sleeve 5 is fitted onto the end of the chromatographic column 7. Axial pressure is applied to the graphite sleeve by tightening the connector, causing plastic deformation of the graphite sleeve 5 and simultaneously sealing the gap between the outer wall of the chromatographic column 7 and the inner wall of the connecting hole of the injection module 6, forming an airtight structure. This sealing structure is a critical component of the injection port gas system. Leakage can lead to unstable carrier gas flow, inaccurate split ratio, sample loss, and consequently, deviations in detection results, decreased parallelism, and even safety hazards due to the leakage of harmful gases. The following embodiments address improvements to this connection and sealing structure.

[0024] like Figure 3 The column connection assembly shown is used to achieve a sealed connection between the gas chromatography column 7 and the injection module 6, solving the problem of seal failure caused by the decay of preload under thermal cycling conditions.

[0025] The column connection assembly includes a connector 1. Optionally, connector 1 is integrally machined from 304 stainless steel or Hastelloy to meet the requirements of high temperature resistance, corrosion resistance, and mechanical strength, and is compatible with the wide operating temperature range of the gas chromatograph from -60°C to 350°C. Connector 1 has an axially extending cylindrical cavity to accommodate internal functional components and through which the chromatographic column 7 passes. Connector 1 is provided with a structure for connection with the gas chromatography injection module 6, and also has an opening at one end for receiving a graphite ferrule 5.

[0026] The column connection assembly also includes a stop structure 2 and an elastic component 31. The stop structure 2 is an annular pressure plate, the outer periphery of which is rigidly connected to the inner wall of the connector 1, providing a stable axial support foundation for the elastic component 31. Even within a wide operating temperature range of -60℃ to 350℃, the axial support foundation of the elastic component 31 remains unchanged. The elastic component 31 is disposed within the inner cavity of the connector 1 and can elastically deform along the axial direction of the connector 1. It has a base end 310 and a movable end 311. The elastic component 31 includes multiple disc springs, with the outer rings 312 of some adjacent disc springs facing each other, and the inner rings 313 of some adjacent disc springs facing each other. Thus, the multiple disc springs are mainly configured in series to form a sealing force control structure. The stop structure 2 restricts the degree of freedom of movement of the base end 310 of the elastic component 31 along the axial direction of the connector 1 towards the side opposite to the opening, ensuring that the elastic force of the elastic component 31 is transmitted entirely towards the opening direction.

[0027] With the column connection assembly connected to the injection module 6, the elastic component 31 is in a pre-compressed state due to its contact with the graphite ferrule 5, thus applying a continuous axial preload to the graphite ferrule 5. When the gas chromatograph undergoes a programmed temperature cycle, the connection between the connector 1 and the injection module 6 deforms due to thermal expansion and contraction, causing a decrease in the axial preload at the connection point. At this time, the base of the elastic component 31 remains in a constant position at any temperature within a wide temperature range. The pre-compressed elastic component 31 automatically releases through its own elastic deformation, compensating for the preload shortfall and maintaining a stable clamping force on the graphite ferrule 5, preventing seal failure and gas leakage. The pre-compressed elastic components 31 are configured in series to form a sealing force control structure, suitable for applying a predetermined torque using a torque wrench, thereby loading a predetermined sealing force onto the graphite ferrule 5, ensuring sealing performance while preventing overloading.

[0028] Continue to refer to Figure 3 In one embodiment, a retainer seat 4 is further provided between the movable end 311 of the elastic component 31 and the graphite retainer 5. Optionally, the retainer seat 4 is made of the same metal material as the connector 1. The retainer seat 4 can slide along the axial direction of the connector 1. The movable end 311 of the elastic component 31 applies an axial preload to the graphite retainer 5 through the retainer seat 4.

[0029] The ferrule holder 4 prevents the sharp edges of the elastic component 31 from directly contacting the brittle graphite ferrule 5, thus avoiding local stress concentration and preventing the graphite ferrule 5 from breaking. On the other hand, it can evenly distribute the concentrated elastic force of the elastic component 31 to the entire end face of the graphite ferrule 5, ensuring that the sealing surface is subjected to uniform force and avoiding leakage caused by insufficient local sealing pressure.

[0030] Continue to refer to Figure 3 In one embodiment, the inner wall of the inner cavity of the connector 1 is provided with an inner shoulder 13, which is an annular protrusion extending circumferentially along the inner cavity of the connector 1. The outer periphery of the ferrule seat 4 is provided with a flange 41, which is an annular flange extending radially along the outer periphery of the ferrule seat 4. The outer diameter of the flange 41 is larger than the inner diameter of the inner shoulder 13.

[0031] When the column connection assembly is not connected to the injection module 6, the flange 41 abuts against the inner shoulder 13 to prevent the sleeve seat 4 and the elastic component 31 from falling off from the opening end of the connector 1 during transportation and storage. No additional packaging or fixing structure is required, which improves the ease of use and assembly reliability of the product.

[0032] In one embodiment, the ferrule holder 4 includes a guide shaft 42, and the connector 1 includes a guide hole 14. The guide shaft 42 and the guide hole 14 are slidably engaged. The guide shaft 42 may optionally be a cylindrical shaft segment, coaxially arranged with the ferrule holder 4; the guide hole 14 may optionally be a cylindrical hole segment, coaxially arranged with the connector 1. The sliding engagement of the guide shaft 42 and the guide hole 14 can restrict the radial freedom of movement of the ferrule holder 4 along the connector 1, ensuring that the ferrule holder 4 is always coaxial with the connector 1 during axial sliding, avoiding radial wobble, thereby ensuring that the axial preload of the elastic component 31 can be uniformly and coaxially transmitted to the entire sealing surface of the graphite ferrule 5, preventing local sealing failure caused by uneven force.

[0033] like Figure 3 As shown, the stop structure 2 can optionally be made of the same material as the connector 1. The outer diameter of the annular pressure plate matches the inner diameter of the connector 1, and a through hole for the chromatographic column 7 to pass through is provided in its center. The annular pressure plate can uniformly bear the axial reaction force of the elastic component 31, avoiding structural deformation caused by stress concentration.

[0034] The annular pressure plate is welded to the inner wall of the inner cavity of the connector 1. In this embodiment, laser welding is used, and the welding position is located at the junction 21 between the outer periphery of the annular pressure plate and the inner wall of the inner cavity of the connector 1. Continuous welds are preferably used, resulting in small welding deformation and not affecting the dimensional accuracy of the inner cavity.

[0035] The connector 1 has an open end with an inner cavity including a cylindrical hole 15 for mating with the cylindrical portion of the graphite ferrule 5. The diameter of the cylindrical hole 15 matches the outer diameter of the cylindrical portion 51 of the graphite ferrule 5. The cylindrical hole 15 radially positions the cylindrical portion of the graphite ferrule 5, preventing radial displacement of the graphite ferrule 5 during installation and use, ensuring the coaxiality of the graphite ferrule 5 with the connection holes of the chromatographic column 7 and the injection module 6, thereby ensuring uniform stress on the sealing surface and improving sealing reliability. Figure 3 In the embodiment shown, the cylindrical hole 15 is in the extending direction of the guide hole 14.

[0036] like Figure 3 As shown, the opening of the connector 1 is an outwardly flared horn. The flared horn serves two purposes: firstly, it guides the graphite ferrule 5 into the cavity of the connector 1; secondly, the deformed graphite ferrule 5 forms a surface contact fit with the conical sealing surface of the flared horn, increasing the sealing contact area. It also provides axial guidance and radial centering for the graphite ferrule 5, forming a reliable gas-tight structure.

[0037] Preferably, the connector 1 is a structure known in the industry as a nut. That is, the structure of the connector 1 for connecting with the gas chromatography injection module 6 is an external thread on the outer periphery of the connector 1, which matches the internal thread connection hole of the injection module 6. It has good interchangeability and can directly replace the existing conventional connecting nut without any modification to the injection module.

[0038] Combination Figures 2 to 4 The stop structure 2, the elastic component 31, and the ferrule seat 4 are arranged sequentially along the axial direction of the connector 1. When the column connector assembly is not connected to the injection module 6, the flange 41 of the ferrule seat 4 abuts against the inner shoulder 13 of the connector 1, the guide shaft 42 of the ferrule seat 4 is inserted into the guide hole 14 of the connector 1, and the elastic component 31 is in a natural or slightly compressed state.

[0039] When the column connection assembly is connected to the injection module 6, the graphite ferrule 5 is placed in the opening of the connector 1, and the cylindrical part of the graphite ferrule 5 is inserted into the cylindrical hole 15. The connector 1 is tightened so that the graphite ferrule 5 is clamped between the ferrule seat 4 and the bottom of the connection hole of the injection module 6. As the connector 1 is tightened, the graphite ferrule 5 pushes the ferrule seat 4 to move, compressing the elastic component 31 to put it into a pre-compressed state, thereby applying a stable axial preload to the graphite ferrule 5.

[0040] During the operation of the gas chromatograph, when subjected to heating-cooling thermal cycles, the thermal expansion and contraction deformation of the threaded connection and the high-temperature creep of the graphite ferrule 5 cause a decrease in the axial preload at the connection point. At this time, the pre-compressed elastic component 31 releases through its own elastic deformation, pushing the ferrule seat 4 along the guide hole 14 toward the graphite ferrule 5 side, compensating for the loss of preload, maintaining a stable clamping force on the graphite ferrule 5, and preventing seal failure and gas leakage.

[0041] Combination Figures 2 to 4 The installation and use of the column connection assembly are the same as those for conventional gas chromatography column connection nuts, requiring no additional training. The specific steps are as follows: S1: Place the column connection assembly and graphite sleeve 5 onto one end of the column 7 in sequence, leaving a 3-5 mm extension length of the column 7. S2: Insert the chromatographic column 7 into the connection port of the injection module 6, and align the external thread of the connector 1 with the internal thread connection hole of the injection module 6. S3: Use a torque wrench to tighten the connector 1 to the set torque value of 0.4 Nm, so that the elastic component 31 reaches the pre-compression state. At this time, the axial pre-tightening force on the graphite sleeve 5 is about 500 N, and the connection and installation of the chromatographic column 7 are completed.

[0042] As shown in the figure, the column connection assembly integrates a stop structure 2, a pre-compression elastic component 31, and a ferrule seat 4 into a single elastic compensation structure within the connector 1. This provides continuous axial preload, effectively compensating for the preload loss generated by the graphite ferrule 5 under thermal cycling conditions. Therefore, it can significantly improve the sealing stability of the gas chromatography column connection, prevent nut loosening and gas leakage, and extend the service life of the column. At the same time, it has a compact structure and is easy to install, and can directly replace existing conventional connecting nuts.

Claims

1. A chromatographic column connection assembly, comprising a connector having an axially through-hole, the connector having a structure for connecting to a gas chromatography injection module, and having an opening at one end for receiving a graphite ferrule; Its features are, The column connection assembly also includes a stop structure and an elastic component; The elastic component is disposed in the inner cavity and can elastically deform along the axial direction of the connector. It has a base end and a movable end. The elastic component includes a plurality of disc springs, wherein at least some of the outer rings of adjacent disc springs are arranged opposite each other, and at least some of the inner rings of adjacent disc springs are arranged opposite each other. The stop structure is an annular pressure plate, the outer periphery of which is rigidly connected to the inner wall of the connecting member, thereby restricting the degree of freedom of movement of the base end of the elastic component along the axial direction of the connecting member; When the column connection assembly is connected to the injection module, the elastic component is in a pre-compressed state due to its contact with the graphite ferrule, and the movable end therefore applies an axial pre-tightening force to the graphite ferrule.

2. The chromatographic column connection assembly according to claim 1, characterized in that, A sleeve seat is provided between the movable end of the elastic component and the graphite sleeve. The sleeve seat can slide along the axial direction of the connector. The movable end of the elastic component applies an axial preload to the graphite sleeve through the sleeve seat.

3. The chromatographic column connection assembly according to claim 2, characterized in that, The inner wall of the connector is provided with an inner shoulder, and the outer periphery of the ferrule is provided with a flange. When the chromatographic column connection assembly is not connected to the injection module, the flange abuts against and limits the inner shoulder.

4. The chromatographic column connection assembly according to claim 2, characterized in that, The sleeve holder includes a guide shaft, and the connector includes a guide hole, with the guide shaft and the guide hole being slidably engaged.

5. The chromatographic column connection assembly according to claim 1, characterized in that, The annular pressure plate is rigidly connected to the inner wall of the connector by welding.

6. The chromatographic column connection assembly according to claim 1, characterized in that, The inner cavity of the end of the connector with the opening includes a cylindrical hole for engaging with the cylindrical portion of the graphite ferrule.

7. The chromatographic column connection assembly according to claim 1, characterized in that, The opening of the connector is an outward-flaring flared mouth.

8. The column connection assembly according to any one of claims 1 to 7, characterized in that, The structure for connecting to the gas chromatography injection module is an external thread located on the outer periphery of the connector.

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