A headspace gas chromatography injector

Abstract

The present invention discloses a headspace gas chromatography sample injector, comprising: a control system, a gas circuit system, a positioning system and a bottom plate; wherein the control system comprises a control panel and a single chip microcomputer, and the control panel is connected to the single chip microcomputer through a cable; the positioning system comprises a sample plate, a gear plate, a motor, a cylinder, a cylinder arm, a central axis rod, and a side axis rod; the gas circuit system comprises a three-way needle inlet valve, a three-way needle retracting valve, an air pressure stabilizing valve, a two-way air inlet valve, a current limiting filter, a six-way injection valve, a two-way air outlet valve, a three-way exhaust valve, a vacuum pump, and an injection needle. The present invention can realize automatic headspace injection of gas samples by being used in conjunction with a gas chromatograph.

Description

Technical Field

[0001] The invention relates to the technical field of gas detection, and more particularly to a headspace gas chromatography injector. Background Art

[0002] Human activities will emit various gases into the atmosphere, such as air conditioning refrigerant Freon; sulfur dioxide, hydrogen sulfide, carbon dioxide, carbon monoxide produced by steelmaking and coal burning; nitrous oxide produced by cement manufacturing or agricultural soil fertilization; methane produced by rice planting or coal mining, etc., will pollute the atmospheric environment, and air pollution prevention and control is urgent. Sampling, analyzing and monitoring the emitted polluted gases is a prerequisite for studying gas pollution and carrying out targeted prevention and control, but the concentration of many gases in the atmosphere is very low, and the sample gas needs to be sampled and sent to the laboratory for analysis by specialized instruments. Glass containers can be used as the preferred container for loading trace gas samples because of their low gas adsorption. They are also the preferred containers for automated gas sampler analysis. Gases are easily compressed, easy to diffuse or leak, and greatly affected by temperature. They are generally injected into the chromatographic injection port for analysis using a gas-tight needle. Automatic injection is also generally carried out using a mechanical arm to drive the gas-tight needle injection, but the structure is complex and the cost is also high.

[0003] Headspace injection is a convenient and fast sample injection method in gas chromatography. Its principle is to place the sample to be tested in a closed container, heat it to make the volatile components evaporate from the sample matrix, reach equilibrium in the gas-liquid (or gas-solid) phase, and directly extract the top gas for chromatographic analysis to test the composition and content of the volatile components in the sample. The use of headspace injection technology can avoid the lengthy and tedious sample pretreatment process, avoid the interference of organic solvents on the analysis, and reduce the contamination of the chromatographic column and injection port.

[0004] However, the existing samplers cannot quickly discharge the sampled material inside the sampler when sampling an object, which not only reduces the working efficiency of the sampler, but also reduces the activity of the sampled object and the protective measures are inappropriate. Moreover, traditional headspace sampling is mainly for gas-liquid or gas-solid mixed samples, and heating technology is required.

[0005] Since all components in gas samples are in gaseous state and gas is easy to compress and store, more samples can be stored in a small volume, and compression can generate the power for injection without heating. Gas is sensitive to pressure, and quantitative injection under normal pressure using an injection valve and a quantitative tube is the simplest and most efficient injection method in the field of gas analysis.

[0006] Therefore, how to provide a simple and efficient automatic sampling technology suitable for gas samples is a problem that technical personnel in this field need to solve urgently. Summary of the invention

[0007] In view of this, the present invention provides a headspace gas chromatography injector, which combines headspace injection technology, valve injection technology and single-chip computer automatic control technology, and adopts a control system, a gas path system and a positioning system to realize automatic headspace injection of gas samples.

[0008] In order to achieve the above object, the present invention adopts the following technical solution:

[0009] A headspace gas chromatography sample injector comprises a control system, a gas path system, a positioning system and a bottom plate; the positioning system is electrically connected to the control system; the positioning system is fixed on the bottom plate;

[0010] The gas circuit system includes a cylinder, a cylinder driving device, a two-way air inlet valve, a flow limiting filter, a six-way injection valve, a quantitative tube, a two-way air outlet valve, a three-way exhaust valve, a vacuum pump, and an injection device;

[0011] The three-way needle inlet valve, the three-way needle retracting valve and the air pressure stabilizing valve are connected through a three-way joint; the three-way needle inlet valve is connected to the upper air chamber of the cylinder; the three-way needle retracting valve is connected to the lower air chamber of the cylinder; the six-way injection valve is connected to the flow limiting filter; the vacuum pump, the three-way exhaust valve, the two-way outlet valve, the six-way injection valve, the flow limiting filter, the two-way intake valve and the injection device are connected in sequence;

[0012] The first interface of the six-way injection valve is connected to high-purity nitrogen, the six-way injection valve is equipped with a quantitative tube, the two ends of the quantitative tube are located at the second and fifth interfaces of the six-way injection valve, the third and fourth interfaces of the six-way injection valve are respectively connected to the two-way gas outlet valve and the flow limiting filter, and the sixth interface of the six-way injection valve is connected to a gas chromatograph;

[0013] Specifically, the three-way exhaust valve, three-way needle inlet valve and three-way needle outlet valve are all normally closed two-position three-way solenoid valves. This valve has three interfaces, namely the air inlet, air outlet and exhaust port. The exhaust port is located at the top of the valve. When the valve is in the closed state with no power on, the air inlet is sealed by a sealing gasket, and gas cannot pass through, while the air outlet and the exhaust port are connected; when the valve is energized, the air inlet and the air outlet are connected, while the exhaust port is not connected; the two-way air inlet valve and the two-way air outlet valve are normally closed two-position two-way solenoid valves, which only have an air inlet and an air outlet. When the valve is closed without power on, the air inlet and the exhaust port are not ventilated, and when the valve is energized and opened, the air inlet and the air outlet are connected.

[0014] Furthermore, the air inlet of the two-way air inlet valve is connected to the needle seat, and the air outlet is connected to the flow limiting filter; the air outlet of the two-way air outlet valve is connected to the third interface of the six-way injection valve, and the air inlet is connected to the air outlet of the three-way exhaust valve, the air inlet of the three-way exhaust valve is connected to the vacuum pump, and the exhaust port is connected to the atmosphere; the air outlet of the three-way needle inlet valve is connected to the upper air chamber of the square cylinder, the air inlet is connected to the three-way joint, and the exhaust port is connected to the atmosphere; the air outlet of the three-way needle retreat valve is connected to the lower air chamber of the square cylinder, the air inlet is connected to the other interface of the three-way joint, and the exhaust port is connected to the atmosphere.

[0015] Preferably, the flow limiting filter body is made of stainless steel, and the internal gas channel is filled with micron-sized stainless steel powder, which is sintered and fixed at high temperature. The flow limiting filter can play three roles. First, it can filter dust particles above the micron level in the gas sample. Second, this filter only occupies a dead volume of microliters, which can greatly reduce the impact of filter sample gas residue or cross-contamination. Third, it can limit the intake flow rate of the gas sample, so that the gas sample flow in the intake pipe is in a slow steady flow state, preventing the intake sample from mixing with the residual gas in the intake pipe. The new sample gas adopts a slow push replacement method to flush out the old sample gas in the original pipeline, thereby improving the injection accuracy and shortening the flushing time.

[0016] Preferably, the gas connection system provides two self-headspace injection modes, one of which is a direct self-headspace injection mode, in which the sample gas is stored in a compressed form in a headspace sample bottle. When the direct headspace injection mode is adopted, the two-way air inlet valve and the two-way air outlet valve are in an open state, and the three-way exhaust valve is in a closed state. When the injection needle is inserted into the headspace sample bottle, the compressed gas sample in the headspace bottle passes through the needle seat, the flow limiting filter, the 4th, 5th, 2nd and 3rd interfaces of the six-way injection valve in sequence under the action of its own pressure, and then passes through the two-way air outlet valve. The compressed sample gas is flushed into the air intake pipe in a slow push-displacement manner when passing through the three-way exhaust valve until its pressure is balanced with the atmospheric pressure. The gas sample to be analyzed is stored in the quantitative tube of the six-way injection valve, and the excess sample gas is discharged into the atmosphere, thereby realizing automatic loading of the gas sample. When the sample loading is completed, the six-way injection valve is opened, and the sample gas stored in the quantitative tube is brought into the chromatogram by the carrier gas for injection and analysis. Another headspace injection mode uses the vacuum pump, the two-way outlet valve and the three-way exhaust valve as auxiliary components, which can be used during the injection. Before sampling, a small amount of gas sample is used to clean the air inlet pipeline to improve the cleaning efficiency and cleanliness. Its main working mode is that after the injection needle is inserted into the head space sample bottle, the vacuum pump, the three-way exhaust valve and the two-way outlet valve are first opened, and the vacuum pump draws vacuum on the air inlet pipeline, the flow limiting filter and the quantitative tube at the rear end of the two-way air inlet valve, and then the two-way outlet valve is closed and the two-way air inlet valve is opened, so that the gas sample in the head space sample bottle can flush the corresponding air inlet pipeline and the quantitative tube under the action of the self-head space pressure, and then the two-way air inlet valve is closed and the two-way air outlet valve is opened. The two-way air outlet valve is used to draw vacuum from the quantitative ring by the vacuum pump, and then the two-way air outlet valve is closed, the two-way air inlet valve is opened, and the quantitative ring is cleaned with sample gas. This process is repeated for several times to improve the cleanliness of the air inlet pipeline and the injection accuracy. After the flushing is completed, the two-way air inlet valve and the two-way air outlet valve are kept open, and the three-way exhaust valve and the vacuum pump are closed. The excess sample gas will be discharged into the atmosphere through the exhaust port of the three-way exhaust valve, so that the sample gas to be analyzed is stored in the quantitative ring in the form of normal pressure, completing the sample loading process. Since the volume of the air inlet pipeline and the quantitative ring is very small compared to the volume of the gas sample bottle, the vacuum-assisted self-headspace injection mode can meet the volume required for automatic injection analysis even when the sample amount is very small.

[0017] The cylinder is fixed on the positioning system and connected to the cylinder driving device;

[0018] The injection device is connected to the cylinder;

[0019] The cylinder driving device, three-way needle inlet valve, three-way needle retracting valve, two-way air inlet valve, six-way injection valve, two-way air outlet valve, three-way exhaust valve, vacuum pump and gas chromatograph are electrically connected to the control system respectively.

[0020] Preferably, the cylinder driving device comprises: a three-way needle inlet valve, a three-way needle return valve and an air pressure-stabilizing valve; the three-way needle inlet valve outlet and the three-way needle return valve outlet are respectively connected to the cylinder; the three-way needle inlet valve inlet and the three-way needle return valve inlet are respectively connected to the air pressure-stabilizing valve outlet; the air pressure-stabilizing valve inlet is connected to compressed air; the three-way needle inlet valve and the three-way needle return valve are respectively electrically connected to the control system;

[0021] The cylinder comprises: a cylinder barrel, a piston, and a cylinder shaft; the piston divides the cylinder into an upper air chamber and a lower air chamber;

[0022] The upper air chamber is communicated with the air outlet of the three-way needle valve, and the lower air chamber is communicated with the air outlet of the three-way needle valve;

[0023] A needle position probe is installed on the top of the cylinder; a needle position magnet is installed on the piston; the needle position probe is electrically connected to the control system;

[0024] One end of the cylinder shaft is connected to the piston, and the other end is connected to the injection device.

[0025] The injection device comprises: a needle seat and an injection needle, one end of the needle seat is connected to the cylinder shaft, and the other end is connected to the injection needle, and the interior of the needle seat is connected to the air inlet of the two-way air inlet valve.

[0026] Among them, both ends of the needle seat are external threads, and the middle is a hexagonal prism. The upper external thread is connected to the cylinder shaft. The cylinder shaft and the piston are an integrated structure. The lower external thread is connected to the internally threaded injection needle. There is a 90-degree gas channel hole inside the needle seat that connects the inner center of the needle's external thread and the center of one of the faces of the hexagonal prism, and there is also an air intake channel on the prism surface. The injection needle is processed with threads inside, and is connected to the needle seat through this thread. A small rectangular hole is processed on the side wall of the needle tube near the needle tip to prevent the needle from piercing the rubber sealing pad. There is a conical sealing ring with a circular hole in the middle inside the needle, which fits the threaded end face of the needle seat and the conical surface inside the side hole needle to form a sealed space.

[0027] Preferably, the positioning system comprises: a sample plate, a gear plate, a cylinder arm, a central axis device, a side axis device, a sliding arm, a gear and a power device;

[0028] The sample tray and the gear tray are both fixedly mounted on the central axis device, and the sample tray is located on the upper part of the gear tray; the sample tray is provided with bottle holes arranged in an involute manner; and the gear tray surface is provided with slide grooves corresponding to the bottle holes;

[0029] The central axis device and the side axis device are both vertically mounted on the bottom plate;

[0030] The slide arm and one end of the cylinder arm are both mounted on the side axis device, and the slide arm is parallel to the cylinder arm; a guide head is fixedly arranged on the slide arm, and the guide head slides in the slide groove; the cylinder is fixed on the cylinder arm;

[0031] The gear is connected to the power device, and the gear is matched with the gear plate.

[0032] Further, the slide arm includes: an upper slide and a lower slide, the upper slide and the lower slide are fixedly mounted on the side axis device, the upper slide and the lower slide are PCB circuit boards with components welded thereon, and the guide head is arranged on the upper slide;

[0033] The upper slide and the lower slide are electrically connected to the control system via conductive wires respectively;

[0034] The starting position and the ending position of the slide slot are respectively provided with a starting magnet and a final magnet; the upper slide is provided with a starting probe and a final probe; the starting probe and the final probe are both electrically connected to the control device.

[0035] The upper slide is welded with a capacitive grid displacement sensor, the head of the capacitive grid displacement sensor is located in the guide head, and a capacitive grid circuit is pasted inside the slide groove; the capacitive grid displacement sensor is powered by the upper slide.

[0036] Furthermore, the central axis device comprises: a central axis bearing portion and a central axis rod; the lower end of the central axis rod is fitted in the central axis bearing portion; and the sample plate and the gear plate are both fixedly mounted on the central axis rod;

[0037] The paraxial device comprises: a paraxial bearing part and a paraxial rod; the lower end of the paraxial rod is fitted in the paraxial bearing part; and the upper slide plate and the lower slide plate are both fixedly sleeved on the paraxial rod;

[0038] Furthermore, the central axis bearing portion and the side axis bearing portion are both vertically mounted on the bottom plate.

[0039] Furthermore, the square cylinder fixing hole in the cylinder arm is used to fix the square cylinder, and the large round hole in the middle allows the cylinder shaft and the connected needle seat to pass smoothly. There is a cylinder arm locking hole at the right end of the cylinder arm, through which the cylinder arm can be just sleeved on the side shaft rod, and the cylinder arm can slide up and down on the side shaft rod. When sliding to a suitable height position, a long screw can be screwed into the locking threaded hole to clamp and lock the cylinder arm on the side shaft rod. There is also a locking hole notch on the other side of the corresponding locking hole, which can make the locking clamping deformation force evenly distributed and easier to clamp and tighten.

[0040] Furthermore, the injection device also includes an adjusting rod and a bottle blocking plate, the bottle blocking plate is a metal plate with a center and two side holes; the cylinder is fixed to the cylinder arm through the adjusting rod; there are at least two adjusting rods, which are symmetrically arranged, and the adjusting rod includes: a screw rod, a nut and a screw, one end of the screw rod is an external thread, the other end is a hexagonal prism on the outside and an internal thread on the inside; one end of the external thread of the screw rod passes through the cylinder arm and is connected to the cylinder and is locked with a nut; the screw passes through the side hole of the bottle blocking plate and is screwed into the internal thread of the screw rod.

[0041] Specifically, the adjusting rod is in the shape of a long rod, one end of which is an external thread, and the other end is a hexagonal prism with an internal thread on the outside; the bottle blocking piece is in the shape of a rectangular metal sheet, and there is a small round hole in the center of the sheet that allows the injection needle to pass smoothly, and this small hole also has the function of straightening the needle; there is a screw hole in the middle of the left and right ends of the bottle blocking piece, and the screw passes through the bottle blocking piece and is screwed into the internal thread of the adjusting rod. A hexagonal nut is first screwed into the external thread of the adjusting rod as a lock, and then the external thread of the adjusting rod is passed through the fixing hole on the cylinder arm and screwed into the threaded fixing hole on the square cylinder.

[0042] When it is necessary to adjust the height of the bottle blocking piece, first loosen the fixing screws and locknuts, then rotate the hexagonal prism on the adjusting rod. When rotating clockwise, the outer thread of the adjusting rod screws into the threaded hole of the cylinder, and the position of the adjusting piece increases. When rotating counterclockwise, the outer thread of the adjusting rod screws out of the threaded hole of the cylinder, and the position of the adjusting piece decreases. Adjust it until the needle tip is just hidden in the small hole of the bottle blocking piece when it is in the uppermost position, and the positions of the adjusting rods on both sides are the same height. Then tighten the locknuts and screws in sequence.

[0043] Preferably, the central axis bearing component and the side axis bearing component are the same, both comprising: a bearing seat, a bearing and a shaft cylinder; the bearing seat is open at the top, cylindrical, hollow, and has an external threaded interface at the bottom, which is screwed to the base plate through the external threaded interface; the bottom of the bearing sleeve is connected to the base plate and there is an annular depression inside; there are two bearings, which are respectively located at the upper and lower ends of the bearing seat, the shaft cylinder is a hollow cylinder, and its inner diameter is larger than the inner diameter of the bearing, it is located between the two bearings, and the two end surfaces of the shaft cylinder are in close contact with the inner ring end surfaces of the upper and lower bearings; the central axis rod and the side axis rod are located inside the bearing and the shaft cylinder.

[0044] Preferably, the sample plate and the gear plate are mounted on the central axis through a plate base, and the plate base includes: a locking hole at the center, screw holes at the four corners and a locking nail hole at one side, a locking hole notch is provided on one side of the locking hole, and a penetrating locking hole through groove is provided on the other side corresponding to the locking hole notch, and the locking nail hole is perpendicular to the locking hole through groove; screw holes consistent with the screw holes are provided on the gear plate and the sample plate.

[0045] Specifically, the bearing seats of the two shafts have the same structure, with an opening at the top, cylindrical, hollow, and an external thread interface at the bottom, which can be screwed to the bottom plate. There is an annular depression inside the bottom of the bearing sleeve connected to the bottom plate, which is convenient for the outer ring of the bearing seat to reduce the contact surface between the shaft and the bottom plate, keep the bearing seat in close contact with the bottom plate and perpendicular to the bottom plate; there are two small round holes on the side wall of the middle part of the bearing seat, which is convenient for using a rod-shaped tool (such as a screwdriver) to reach into the hole to help tighten or loosen the bearing seat thread and remove it.

[0046] The bottom of the central axis rod is matched with a bearing, a shaft tube and another bearing in sequence. The inner ring of the bearing is in close contact with the central axis rod, and the shaft tube is a hollow cylindrical shape. The two end faces of the shaft tube are in contact with the inner ring end faces of the bearing, but not with the central axis rod, supporting the upper and lower bearings, keeping the central axis rod vertical, and allowing the central axis rod, the inner ring of the bearing and the shaft tube to rotate smoothly at the same time. Then press the central axis rod with the bearing and the shaft tube into the bearing seat, so that the outer rings of the upper and lower bearings are in close contact with the inner wall of the bearing seat, so that the central axis rod can rotate smoothly in the bearing seat. The assembly method of the side axis is the same as that of the central axis.

[0047] Furthermore, there is a long rounded groove on the central axis, in which a standard rounded flat key can be placed. After the rounded flat key is placed inside, half of its height protrudes from the surface of the axis. When the disk shaft sleeve of the sample disk is put on the central axis, the protruding rounded flat key can be stuck in the notch on the disk shaft sleeve, and the hand-tightened locking pin can be screwed into the top of the disk shaft sleeve to accurately position the sample disk on the central axis.

[0048] Preferably, the sample plate comprises an upper plate, a middle plate, a lower plate, a single-way copper column, a double-way copper column and fixing screws; the middle plate is arranged between the upper plate and the lower plate, and is connected by the single-way copper column, the double-way copper column and fixing screws; the upper plate and the middle plate have the same structure, a central axis hole is arranged at the center position, and bottle position holes arranged in an involute manner are arranged on the plate surface; except that the bottle position holes are not arranged on the lower plate, the other structures are the same as those of the upper plate.

[0049] Preferably, the control system includes a control panel and a single-chip microcomputer, and the control panel is connected to the single-chip microcomputer with a wiring harness; the positioning system, three-way needle inlet valve, three-way needle retracting valve, two-way air inlet valve, six-way injection valve, two-way air outlet valve, three-way exhaust valve, vacuum pump, and cylinder drive device are respectively connected to the single-chip microcomputer with conductive wires and are controlled by a program in the single-chip microcomputer.

[0050] It can be seen from the above technical solution that compared with the prior art, the present invention has the following beneficial effects:

[0051] The present invention can achieve

[0052] 1) Fast, high-precision and accurate positioning. The involute combined with the capacitive grid circuit and the motor speed change technology makes the positioning rate reach 1 meter per second. Mobile positioning can be achieved in just a few seconds, and the displacement detection accuracy is improved to 0.02 mm. It can also be programmed to decelerate when it is about to reach the target bottle position to prevent the inertia caused by high-speed movement, making the positioning accurate and efficient.

[0053] 2) The injector can control the six-way injection valve and the gas chromatograph, and adopts the valve switching injection mode, so that the injector can be applied to gas chromatographs of various models and injection modes. It only needs to connect the sixth outlet of the six-way injection valve to the corresponding injection port of the chromatograph and control the start of the chromatograph to realize automatic injection;

[0054] 3) This injector adopts the method of self-headspace injection, which greatly saves the sample storage space and the volume occupied by the injector. The gas sample is sealed and stored in the headspace sample bottle in a compressed manner. When injecting, the pressure in the sample bottle provides the power for flushing the pipeline and injecting, realizing self-headspace injection. The compressed storage of gas requires only a small amount of gas sample to achieve injection, which is also applicable to the case of small sample volume. In addition, the injector can provide more sample positions under a certain volume, improving the efficiency of automation;

[0055] 4) The use of a flow-limiting filter ensures that the gas sample replaces the old sample in a steady and slow flow, using less gas to clean the air intake pipeline, improving the accuracy of sample injection and preventing cross contamination of samples;

[0056] 5) In addition to providing a self-headspace sampling method, a vacuum pump is also used to assist in self-headspace sampling, so that even a small amount of gas samples can be sampled from the headspace, and the efficiency and cleanliness of the pipeline cleaning can also be improved. When using a vacuum pump to assist in self-headspace sampling, first use a vacuum pump to evacuate the air intake pipeline and the quantitative tube, then use the sample gas to fill the pipeline from the headspace for cleaning, cycle several times, and finally use the self-headspace technology to fill the quantitative tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0058] Figure 1 The accompanying drawing is a schematic diagram of the overall structure of the present invention;

[0059] Figure 2 The accompanying drawing is a schematic diagram of the gas circuit system structure of the present invention, wherein the six-way injection valve is in a closed state;

[0060] Figure 3 The accompanying drawing is a schematic diagram of the six-way injection valve in an open state;

[0061] Figure 4 The accompanying drawing is a schematic diagram of the cylinder arm structure of the present invention;

[0062] Figure 5 The accompanying drawing is a schematic diagram of the gear plate structure of the present invention;

[0063] Figure 6 The accompanying drawing is a schematic diagram of the structure of the disc on the sample tray of the present invention;

[0064] Figure 7 The accompanying drawing is a schematic diagram of the disc seat structure of the present invention.

[0065] Among them, in the figure,

[0066] 1-control panel; 2-single chip microcomputer; 3-three-way needle inlet valve; 4-three-way needle outlet valve; 5-air pressure regulating valve; 6-three-way exhaust valve; 7-two-way outlet valve; 8-two-way inlet valve; 9-vacuum pump; 10-six-way injection valve; 101-quantitative tube; 11-gas chromatograph; 12-limiting filter; 13-sample plate; 131-upper plate; 132-middle plate; 133-lower plate; 134-shaft sleeve hole; 135-bottle position hole; 14-gear plate; 141-slideway; 142-starting magnet; 143-end position Magnet; 144-capacitor gate circuit; 15-cylinder; 151-piston; 152-upper air chamber; 153-lower air chamber; 16-cylinder arm; 17-middle axis rod; 18-side axis rod; 19-needle seat; 20-injection needle; 21-needle position probe; 22-slide arm; 221-upper slide; 222-lower slide; 23-guide head; 24-intake pipe; 25-bottom plate; 26-motor; 27-gear; 28-adjusting rod; 29-bottle stopper; 30-disc seat; 31-bearing seat; 32-bearing; 33-shaft cylinder. DETAILED DESCRIPTION

[0067] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0068] Example

[0069] like Figure 1-7 As shown, the main components of the device of the present invention are:

[0070] 1) Control system: mainly includes control panel 1 and single chip computer 2 (based on the design and customization of Hongjing STC12C5A); and control panel 1, motor 26 (planetary reduction motor), six-way injection valve 10, vacuum pump 9, two-way outlet valve 7, two-way inlet valve 8, three-way exhaust valve 6, gas chromatograph 11, needle position probe 21, three-way needle inlet valve 3, three-way needle retracting valve 4, upper slide 221 and lower slide 222 are respectively connected to single chip computer 2 by conductive wires and are controlled by the program in single chip computer 2. Control panel 1 is connected to single chip computer 2 by flat cable, and has LCD screen to display information and keys to input parameters or commands. The end position probe, the start position probe and the needle position probe 21 are all Hall sensors that can obtain position information through magnetic induction; the upper slide 221 and the lower slide 222 are long rectangular PCB circuit boards with components welded on them, the end position probe, the start position probe and the capacitive gate displacement sensor are welded on the upper slide 221, and are all powered by the upper slide 221, and the capacitive gate displacement sensor head is located in the guide head 23. The capacitive gate circuit 144 is attached to the slide groove 141 of the gear plate 14 with adhesive.

[0071] 2) Gas system (such as Figure 2 shown):

[0072] The three-way exhaust valve 6, the three-way inlet needle valve 3, and the three-way outlet needle valve 4 are all normally closed two-position three-way solenoid valves. This valve has three interfaces, namely the air inlet, the air outlet, and the exhaust port. The exhaust port is located at the top of the valve. When the valve is closed and not powered, the air inlet is sealed by a sealing gasket, and the gas cannot pass through, while the air outlet and the exhaust port are connected in gas path; when the valve is powered, the air inlet and the air outlet are connected, while the exhaust port is blocked; the two-way inlet valve 8 and the two-way outlet valve 7 are normally closed two-position two-way solenoid valves, which only have an air inlet and an air outlet. When the valve is closed and not powered, the air inlet and the exhaust port are not ventilated, and when the valve is powered on and opened, the air inlet and the air outlet are connected; the six-way injection valve is equipped with a quantitative tube 101, which is respectively connected to the second and fifth interfaces of the six-way injection valve 10, and the sample to be analyzed is quantitatively stored in this tube. The gas path connection is as follows Figure 2As shown, the air inlet of the two-way air inlet valve 8 is connected to the needle seat 4, and the air outlet thereof is connected to the flow limiting filter 12, and the other end of the flow limiting filter 12 is connected to the 4th interface of the six-way injection valve 10; the air outlet of the two-way air outlet valve 7 is connected to the 3rd interface of the six-way injection valve 10, and the air inlet thereof is connected to the air outlet of the three-way exhaust valve 6, and the air inlet of the three-way exhaust valve 6 is connected to the vacuum pump 9, and the exhaust port thereof is connected to the atmosphere; the air outlet of the three-way needle inlet valve 3 is connected to the upper air chamber 152 of the square cylinder 15, and the air inlet thereof is connected to the three-way joint, and the exhaust port is connected to the atmosphere; the air outlet of the three-way needle retreat valve 4 is connected to the lower air chamber 153 of the square cylinder 15, and the air inlet thereof is connected to the other interface of the three-way joint, and the exhaust port is connected to the atmosphere;

[0073] Figure 2 The structure of the needle injection device is also shown. Both ends of the needle seat 19 are external threads, and the middle is a hexagonal prism. The upper external thread is connected to the cylinder shaft, and the lower external thread is connected to the internally threaded injection needle (side hole needle). There is a 90-degree gas passage hole connecting the inner center of the needle external thread and the center of one of the faces of the hexagonal prism inside the needle seat 19, and there is also a trachea joint (inlet pipe 24) on the prism surface. The side hole needle is processed with threads inside, and is connected to the needle seat 19 through this thread. A rectangular small hole is processed on the side wall of the needle tube near the needle tip to prevent the needle from piercing the rubber sealing pad and generating foam to block the needle tube. There is a conical sealing ring with a circular hole in the middle inside the needle, which fits the threaded end face of the needle seat 19 and the conical surface inside the side hole needle to form a sealed space.

[0074] The adjusting rod 28 is in the shape of a long rod, one end of which is an external thread, and the other end is a hexagonal prism with an internal thread on the outside; the bottle blocking piece 29 is in the shape of a rectangular metal sheet, and there is a small round hole in the center of the sheet that allows the side hole needle to pass smoothly, and this small hole also has the function of straightening the needle; there is a screw hole in the middle of the left and right ends of the bottle blocking piece 29, and the screw passes through the bottle blocking piece 29 and is screwed into the internal thread of the adjusting rod 28. A hexagonal nut is first screwed into the external thread of the adjusting rod 28 as a lock, and then the external thread of the adjusting rod 28 is passed through the fixing hole on the cylinder arm 16 and screwed into the threaded fixing hole on the square cylinder 15. Figure 4 The structure of the cylinder arm 16 is shown. When the height of the bottle blocking piece 29 needs to be adjusted, first loosen the fixing screws and locknuts, then rotate the hexagonal prism on the adjusting rod 28, rotate the adjusting rod 28 clockwise to screw the external thread into the cylinder thread hole, the position of the adjusting piece is raised, rotate the adjusting rod 28 counterclockwise to screw the external thread out of the cylinder thread hole, the position of the adjusting piece is lowered, and the needle tip is adjusted to be just hidden in the small hole of the bottle blocking piece 29 when the needle is in the uppermost position, and the positions of the adjusting rods 28 on both sides are at the same height, and then tighten the locknuts and screws in sequence.

[0075] After the compressed air passes through the air pressure regulating valve 5 and the three-way joint, it supplies air to the three-way needle valve 3 and the three-way needle valve 4. Figure 2 As shown, when needle insertion is required, the three-way needle injection valve 3 is opened, and the compressed gas enters the upper air chamber 152 through the upper air inlet of the square cylinder 15, while the lower air chamber 153 is at normal pressure. The compressed gas pushes the piston 151 and the cylinder shaft inside the cylinder to move downward, and drives the needle seat 19 and the side hole needle to move downward together. The needle pierces the rubber sealing pad of the head space bottle below and extends into the head space bottle. At this time, the three-way needle injection valve 3 is closed, so that the compressed gas in the upper air chamber 152 is discharged through the exhaust port of the three-way needle injection valve 3, keeping the upper air chamber 152 at normal pressure, and completing the needle insertion action. When the needle needs to be withdrawn, the three-way needle withdrawal valve 4 is opened, and the compressed gas enters the lower air chamber 153 of the square cylinder 15, pushing the piston 151 and the cylinder shaft to move upward, and driving the needle seat 19 and the side hole needle to move upward. At this time, the side hole needle is in the headspace bottle. Due to the friction between the rubber seal in the headspace bottle cap and the needle, the headspace bottle is also driven to move upward. When the headspace bottle cap contacts the bottle stopper 29, the bottle stopper 29 prevents the headspace bottle from moving further upward, so that the side hole needle overcomes the friction resistance and pulls out from the rubber seal and hides the needle tip in the bottle stopper 29, and the headspace bottle falls back under the action of gravity. When the piston 151 rod moves to the uppermost part, the small circular magnet located at the center of the top of the piston 151 rod approaches the needle position probe 21 fixed on the top of the square cylinder, indicating that the needle has moved to the position. At this time, the system closes the three-way needle withdrawal valve 4, and the compressed gas in the lower air chamber 153 is discharged from the exhaust port of the three-way needle withdrawal valve 4, completing the needle withdrawal action.

[0076] Figure 4 The cross-sectional view of the cylinder arm 16 is shown. The square cylinder fixing hole is used to fix the square cylinder, and the large circular hole in the middle allows the cylinder shaft and the connected needle seat 19 to pass smoothly. There is a cylinder arm 16 locking hole at the left end of the cylinder arm 16, through which the cylinder arm 16 can be exactly sleeved on the side shaft rod 18, and the cylinder arm 16 can slide up and down on the side shaft rod 18. When sliding to a suitable height position, a long screw can be screwed into the locking threaded hole to clamp and lock the cylinder arm 16 on the side shaft rod 18. There is also a locking hole notch on the other side of the corresponding locking hole, which can make the locking clamping deformation force evenly distributed and easier to clamp and tighten.

[0077] 3) Positioning system

[0078] Figure 5 The structural diagram of the gear plate 14 is listed, Figure 5 The structure diagram of the disc 131 on the sample disc 13 is listed. Figure 4As shown, the gear plate 14 is in the shape of a disk, with a large circular hole in the center and four chassis fixing holes. The gear plate 14 can be locked on the disk seat 30 by screws, and the disk seat 30 is then locked on the central axis by long screws. A circle of teeth is evenly distributed on the outer ring of the gear plate 14. A slide groove 141 is processed in an involute shape on the front of the gear plate 14. A cylindrical starting magnet 142 and a final magnet 143 are buried at the starting position of the outer ring of the slide groove 141 and the end position of the inner ring of the slide groove 141, respectively, to indicate the starting position and the end position of the slide groove 141. A capacitive gate circuit 144 with adhesive backing is pasted in the middle of the inner part of the slide groove 141, which can be used to indicate the displacement of the slider in the slide groove 141.

[0079] Figure 6 1 is a structural diagram of the upper disc 131 of the sample disc 13. There is a large circle (sleeve hole 134) and four screw fixing holes in the middle of the upper disc 131. The disc can be fixed to the disc base 30 by screws, and then the disc base 30 is fixed to the sleeve by long screws. The structure of the middle disc 132 is the same as that of the upper disc 131, and the bottom disc is the same as that of the upper disc 131 except that there is no bottle position hole 135.

[0080] Figure 7 It is a schematic diagram of the cross-sectional structure of the disc seat 30. The upper disc 131 or the bottom disc 133 can be fixed to the disc seat 30 by screws, the sleeve passes through the locking hole, and the locking pin is screwed into the locking pin hole to clamp the disc seat 30 of the sample disc 13 and lock it on the sleeve.

[0081] The structure of the sample tray 13 is as follows: Figure 1 As shown, the sample plate 13 is mainly composed of an upper plate 131, a middle plate 132, a lower plate 133, a plate sleeve, a plate seat 30, a single-pass copper column, a double-pass copper column and fixing screws. Figure 5 As shown, there are four screw holes on the outer ring of the upper disk 131, and the upper part of the upper disk 131 is connected to the single-pass copper column by screws, and the upper disk 131 is clamped between the screws and the single-pass copper column, the middle disk 132 is clamped by the threaded end of the single-pass copper column and the double-pass copper column, and the bottom disk is clamped by screws and the double-pass copper column. The four single-pass copper columns and the double-pass copper columns and the locking screws connect the outer rings of the three disks, and in the center of the disk, the upper disk 131 and the lower disk 133 are fixed to the disk seat 30 with screws, and then the disk shaft sleeve is passed through the upper disk seat 30, the middle disk 132 and the lower disk seat 30, and is locked to the disk shaft seat by the screws of the upper disk seat 30 and the lower disk seat 30.

[0082] The structures of the central axis rod 17 and the side axis rod 18 are as follows: Figure 1As shown in . The components of the middle shaft include a bearing seat 31, a bearing 32, a shaft cylinder 33, a shaft seat hole, a middle shaft rod 17, a keyway and a hand-tightened locking pin. The components of the side bearing include a bearing seat 31, a bearing 32, a shaft cylinder 33, a shaft seat hole, and a side shaft rod 18; the bearing seats 31 of the two shafts have the same structure, with an opening at the top, a cylindrical shape, and a hollow center. There is an external threaded interface at the bottom, which can be screwed onto the bottom plate 25 through the external threaded interface. There is an annular depression at the bottom of the bearing sleeve connected to the inside of the bottom plate 25, which is convenient for the outer ring of the bearing seat 31 to reduce the contact area between the shaft and the bottom plate 25, keep the bearing seat 31 in close contact with the bottom plate 25 and perpendicular to the bottom plate 25; there are two small round holes on the middle side wall of the bearing seat 31, which is convenient for using a rod-shaped tool (such as a screwdriver) to reach into the hole to help tighten or loosen the bearing seat 31 thread and remove it. The assembly structure of the middle shaft and the side shaft is also shown in Figure 1 As shown, the bottom end of the central axis rod 17 is sequentially fitted with a bearing, a shaft cylinder 33 and another bearing, the inner ring of the bearing is in close contact with the central axis rod 17, and the shaft cylinder 33 is a hollow cylindrical shape, the two end faces of the shaft cylinder 33 are in contact with the inner ring end face of the bearing, but not in contact with the central axis rod 17, supporting the upper and lower bearings, keeping the central axis rod 17 vertical, and allowing the central axis rod 17, the inner ring of the bearing and the shaft cylinder 33 to rotate smoothly at the same time. Then, the central axis rod 17 with the bearing and the shaft cylinder 33 is pressed into the bearing seat 31, so that the outer rings of the upper and lower bearings are in close contact with the inner wall of the bearing seat 31, so that the central axis rod 17 can rotate smoothly in the bearing seat 31. The assembly method of the side shaft is the same as that of the central shaft. There is also a long rounded groove on the central axis 17, in which a standard rounded flat key can be placed. After the rounded flat key is placed inside, half of its height protrudes from the surface of the axis. When the disk sleeve of the sample disk 13 is placed on the central axis, the protruding rounded flat key can be stuck in the notch on the disk sleeve, and a hand-tightened locking pin can be screwed into the top of the disk sleeve to accurately position the sample disk 13 on the central axis 17.

[0083] Positioning principle: During assembly, the cylinder arm 16 and the sliding arm 22 are coaxially fixed on the side axis rod 18, the vertical position of the needle is consistent with the vertical position of the guide head 23, and the sample plate 13 and the gear plate 14 are also coaxially fixed on the central axis rod 17. When positioning is required, the single chip microcomputer 2 detects the position of the guide head 23 in the slide arm 22 based on the starting position probe on the slide arm 22. When the position does not meet the specific position, the single chip microcomputer 2 drives the planetary reduction motor 26 to rotate, and the gear 27 on the motor 26 drives the gear disk 14 to rotate, and the sample disk 13 fixed on the central axis rotates coaxially. Moreover, since the guide head 23 on the slide arm 22 is in the slide groove 141 of the gear disk 14, the slide groove 141 distributed in an involute line will push the guide head 23, and the guide head 23 pushes the slide arm 22, and the slide arm 22 pushes the side axis rod 18 to rotate. The side axis rod 18 drives the coaxially fixed cylinder arm 16 to rotate, and the cylinder arm 16 drives the needle head to move to the top of the corresponding slide groove 141. When the guide head 23 slides in the slide groove 141, the capacitive displacement sensor in the guide head 23 records its displacement distance. When the moving distance is reached, the movement stops, so that the needle position stops at the corresponding hole position on the sample disk 13, and the positioning of the needle position is completed.

[0084] Moreover, since the grooves of the gear plate 14 are involute distribution, the speed of the guide head 23 in the outer and inner circles of the slide groove 141 will be very different during gear transmission. The single-chip computer 2 system will record the position of the plate according to the involute function, adjust the speed of the motor 26, and control the moving speed of the guide head 23 in the slide groove 141. When it is far away from the target bottle position, it will run at a high speed, and when it is close to the target bottle hole position, it will reduce the speed to prevent the rotation inertia from being too large and affecting the positioning accuracy. After using the capacitive grid positioning, the maximum moving speed can reach 1.8 meters per second, and the displacement resolution can reach 0.02 millimeters, which can change the speed to quickly and accurately locate the position of the sample bottle.

[0085] 4) Main process of function realization

[0086] When the planetary gear motor 26 rotates to the corresponding sample bottle position, there are two self-headspace injection processes:

[0087] (1) Ordinary self-headspace injection process: the single-chip microcomputer 2 controls the opening of the three-way needle valve 3, and the compressed air enters the upper air chamber 152 of the square cylinder 15 to push the piston 151, and the piston drives the needle seat 9 and the injection needle 20, so that the injection needle 20 pierces the headspace bottle seal and enters the headspace bottle. At this time, the three-way needle valve 3 is closed, and the compressed gas in the upper air chamber 152 is discharged from the exhaust port of the three-way needle valve 3, and the air chamber 152 is restored to normal pressure; then the single-chip microcomputer opens the two-way air inlet valve 8 and the two-way air outlet valve 7, and the compressed sample gas in the headspace sample bottle passes through the side hole of the injection needle, the "L"-shaped channel in the needle seat 9, the two-way air inlet valve 7, the flow limiting filter, the fourth interface, the fifth interface, the quantitative tube 101, the second interface, and the third interface on the six-way injection valve 10 in sequence under the action of its own pressure, and then enters the atmosphere through the exhaust port of the two-way air outlet valve 7 and the three-way exhaust valve 6. In this process, the flow limiting filter will filter the particles in the sample and limit the gas The flow rate makes the gas in the air intake pipe in a steady flow state, pushing the gas in the original pipe to replace it into the atmosphere, and at the same time using the sample gas to flush the air intake pipe until the pressure in the headspace bottle is consistent with the external atmospheric pressure, the single chip microcomputer 2 respectively closes the two-way air inlet valve 8 and the two-way air outlet valve 7. At this time, the quantitative tube is filled with pure sample gas at normal pressure, the single chip microcomputer 2 opens the three-way needle withdrawal valve 4, and the compressed air enters the lower air chamber 153 of the square cylinder 15, pushing the piston in the cylinder to move upward, driving the needle seat 9, the injection needle and the headspace bottle to move upward, and the headspace bottle is restricted by the upper bottle blocking piece so that the injection needle is pulled out of the headspace bottle, and the headspace bottle returns to its original position under the action of gravity. When the piston reaches the top of the cylinder, the needle position probe on the square cylinder 10 detects the return of the needle, the needle withdrawal solenoid valve 4 is closed, and the compressed gas in the lower air chamber 153 is discharged from the exhaust port of the three-way needle withdrawal valve 4, and the air pressure in the lower air chamber returns to normal pressure; then the single chip microcomputer 2 controls the opening of the six-way injection valve 10 and switches to Figure 3 At the same time, the single chip microcomputer 2 controls the gas chromatograph 11 to start the analysis function. At this time, the high-purity carrier gas (such as nitrogen) flows through the first interface, the second interface, the quantitative tube 101, the fifth interface and the sixth interface on the six-way injection valve 10 in sequence, and the sample to be analyzed at normal pressure in the quantitative tube 101 is brought into the gas chromatograph 11 for injection analysis. When all the sample gases are brought into the gas chromatograph 11 within a certain period of time, the single chip microcomputer 2 closes the six-way injection valve 10 and returns to Figure 2 The gas flow path shown in the figure completes one gas injection. Then the single chip computer 2 controls the movement of the sample tray to the next bottle position, and the single chip computer 2 detects whether the gas chromatograph 11 has completed the analysis of the previous sample and is ready. When it is detected that the analysis of the previous sample is completed and ready, the single chip computer 2 automatically controls the injection again until the set number of injections is completed.

[0088] (2) Vacuum cleaning assisted self-headspace sampling process: This process uses a vacuum pump combined with self-headspace cleaning of the air intake pipe and the quantitative tube. The working steps are as follows: the single chip microcomputer 2 controls the opening of the three-way needle valve 3, and the compressed air enters the upper air chamber 152 of the square cylinder 15 to push the piston 151. The piston drives the needle seat 9 and the injection needle 20, so that the injection needle 20 pierces the sealing gasket of the headspace bottle and enters the interior of the headspace bottle. At this time, the three-way needle valve 3 is closed, and the compressed gas in the upper air chamber 152 is discharged from the exhaust port of the three-way needle valve 3, and the air chamber 152 is restored to normal pressure; then the single chip microcomputer opens the vacuum pump 9, the three-way exhaust valve 6 and the two-way outlet valve 7, and extracts the air from the two-way intake valve 8 to the vacuum pump 9 The intake pipe 24 and the quantitative tube 10 are drawn. 1 and the flow-limiting filter 12 are vacuumed, then the two-way outlet valve 7 is closed and the two-way inlet valve 8 is opened. Under the action of its own pressure, the compressed sample gas in the headspace sample bottle passes through the side hole of the injection needle, the "L"-shaped channel in the needle seat 9, the two-way inlet valve 7, the flow-limiting filter, the 4th interface, the 5th interface, the quantitative tube 101, the 2nd interface, the 3rd interface on the six-way injection valve 10 to the air inlet of the two-way outlet valve 7, so as to clean this part of the air inlet pipeline; then the above vacuuming and cleaning process can be repeated as needed, and the more cycles, the more thoroughly the air inlet pipeline 24 is flushed with the sample gas; when the cyclic cleaning is completed, keep the vacuum pump 9 and the three-way exhaust valve 6 in the closed state, and the two-way inlet valve 7 is opened. The air valve and the two-way air outlet valve are in the open state, and the residual compressed sample gas in the headspace bottle flows through the injection needle, the "L"-shaped channel in the needle seat 9, the two-way air inlet valve 7, the current limiting filter, the 4th interface, the 5th interface, the quantitative tube 101, the 2nd interface, and the 3rd interface on the six-way injection valve 10 in sequence, and then enters the atmosphere through the exhaust port of the two-way air outlet valve 7 and the three-way exhaust valve 6. In this process, the current limiting filter will filter the particles in the sample and limit the flow rate of the gas, so that the gas in the air inlet pipeline is in a steady flow state, pushing the gas in the original pipeline into the atmosphere, and at the same time using the sample gas to flush the air inlet pipeline until the pressure in the headspace bottle is consistent with the external atmospheric pressure, and the single-chip microcomputer 2 closes the two-way air inlet respectively. Valve 8 and two-way air outlet valve 7. At this time, the quantitative tube is filled with pure sample gas at normal pressure. The single-chip microcomputer 2 opens the three-way needle withdrawal valve 4, and the compressed air enters the lower air chamber 153 of the square cylinder 15, pushing the piston in the cylinder to move upward, driving the needle seat 9, the sampling needle and the head space bottle to move upward. The head space bottle is restricted by the upper bottle blocking piece so that the sampling needle is pulled out of the head space bottle, and the head space bottle returns to its original position under the action of gravity. When the piston reaches the top of the cylinder, the needle position probe on the square cylinder 10 detects that the needle has returned to its original position, and the needle withdrawal solenoid valve 4 is closed. The compressed gas in the lower air chamber 153 is discharged from the exhaust port of the three-way needle withdrawal valve 4, and the air pressure in the lower air chamber returns to normal pressure; then the single-chip microcomputer 2 controls the opening of the six-way injection valve 10 and switches to Figure 3At the same time, the single chip microcomputer 2 controls the gas chromatograph 11 to start the analysis function. At this time, the high-purity carrier gas (such as nitrogen) flows through the first interface, the second interface, the quantitative tube 101, the fifth interface and the sixth interface on the six-way injection valve 10 in sequence, and the sample to be analyzed at normal pressure in the quantitative tube 101 is brought into the gas chromatograph 11 for injection analysis. When all the sample gases are brought into the gas chromatograph 11 within a certain period of time, the single chip microcomputer 2 closes the six-way injection valve 10 and returns to Figure 2 The gas flow path shown in the figure completes one gas injection. Then the single chip 2 controls the movement of the sample tray to the next bottle position, and the single chip 2 detects whether the gas chromatograph has completed the analysis of the previous sample and is ready for injection. When it is detected that the analysis of the previous sample is completed and ready, the single chip 2 automatically controls the injection again until the set number of injections is completed.

[0089] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A headspace gas chromatography injector, characterized in that: It includes a control system, an air circuit system, a positioning system and a base plate; the positioning system is electrically connected to the control system; the positioning system is fixed on the base plate; The gas circuit system includes a cylinder, a cylinder driving device, a two-way air inlet valve, a flow limiting filter, a six-way injection valve, a quantitative tube, a two-way air outlet valve, a three-way exhaust valve, a vacuum pump, and an injection device; The cylinder driving device comprises: a three-way needle inlet valve, a three-way needle outlet valve and an air pressure stabilizing valve; The three-way needle inlet valve, the three-way needle retracting valve and the air pressure stabilizing valve are connected through a three-way joint; the three-way needle inlet valve is connected to the upper air chamber of the cylinder; the three-way needle retracting valve is connected to the lower air chamber of the cylinder; the six-way injection valve is connected to the flow limiting filter; the vacuum pump, the three-way exhaust valve, the two-way outlet valve, the six-way injection valve, the flow limiting filter, the two-way intake valve and the injection device are connected in sequence; The first interface of the six-way injection valve is connected to high-purity nitrogen, the six-way injection valve is equipped with a quantitative tube, the two ends of the quantitative tube are located at the second and fifth interfaces of the six-way injection valve, the third and fourth interfaces of the six-way injection valve are respectively connected to the two-way gas outlet valve and the flow limiting filter, and the sixth interface of the six-way injection valve is connected to a gas chromatograph; The cylinder is fixed above the positioning system and connected to the cylinder driving device; The injection device is threadedly connected to the cylinder; The cylinder driving device, the two-way air inlet valve, the six-way injection valve, the two-way air outlet valve, the three-way exhaust valve, and the vacuum pump are electrically connected to the control system respectively.

2. A headspace gas chromatography sample injector according to claim 1, characterized in that: The air outlet of the three-way needle valve and the air outlet of the three-way needle valve are respectively connected to the cylinder; the air inlet of the three-way needle valve and the air inlet of the three-way needle valve are respectively connected to the air outlet of the air pressure stabilizing valve; the air inlet of the air pressure stabilizing valve is connected to the compressed air; the three-way needle valve and the three-way needle valve are respectively electrically connected to the control system; The cylinder comprises: a cylinder barrel, a piston, and a cylinder shaft; the piston divides the cylinder into an upper air chamber and a lower air chamber; The upper air chamber is communicated with the air outlet of the three-way needle valve, and the lower air chamber is communicated with the air outlet of the three-way needle valve; One end of the cylinder shaft is connected to the piston, and the other end is connected to the injection device; A needle position probe is installed on the top of the cylinder; a needle position magnet is installed on the piston; the needle position probe is electrically connected to the control system; The injection device comprises: a needle seat and an injection needle, one end of the needle seat is threadedly connected to the cylinder shaft, and the other end is connected to the injection needle, and the interior of the needle seat is connected to the air inlet of the two-way air inlet valve.

3. A headspace gas chromatography sample injector according to claim 1, characterized in that: The positioning system comprises: a sample plate, a gear plate, a cylinder arm, a central axis device, a side axis device, a sliding arm, a gear and a power device; The sample tray and the gear tray are both fixedly mounted on the central axis device, and the sample tray is located above the gear tray; the sample tray is provided with bottle holes arranged in an involute manner; and the gear tray surface is provided with slide grooves corresponding to the bottle holes; The sample plate comprises an upper plate, a middle plate, a lower plate, a single-pass copper column, a double-pass copper column and fixing screws; the middle plate is arranged between the upper plate and the lower plate, and connected by the single-pass copper column, the double-pass copper column and the fixing screws; the upper plate and the middle plate have the same structure, a central axis hole is arranged at the center, and the plate surface is provided with bottle holes arranged in an involute manner; the lower plate has the same structure as the upper plate except that the bottle holes are not arranged; The central axis device and the side axis device are both vertically mounted on the bottom plate; The slide arm and one end of the cylinder arm are both vertically mounted on the side axis device, and the slide arm is parallel to the cylinder arm; a guide head is fixedly arranged on the slide arm, and the guide head slides in the slide groove; the cylinder is fixed on the cylinder arm; The gear is connected to the power device, and the gear is matched with the gear plate.

4. A headspace gas chromatography sample injector according to claim 3, characterized in that: The slide arm comprises: an upper slide and a lower slide, the upper slide and the lower slide are fixedly mounted on the side axis device, the upper slide and the lower slide are PCB circuit boards with components welded thereon, and the guide head is arranged on the upper slide; The upper slide and the lower slide are electrically connected to the control system via conductive wires respectively; The starting position and the ending position of the slide slot are respectively provided with a starting magnet and a final magnet; the upper slide is provided with a starting probe and a final probe; the starting probe and the final probe are both electrically connected to the control device.

5. A headspace gas chromatography sample injector according to claim 4, characterized in that: The upper slide is welded with a capacitive grid displacement sensor, the head of the capacitive grid displacement sensor is located in the guide head, and a capacitive grid circuit is pasted inside the slide groove; the capacitive grid displacement sensor is powered by the upper slide.

6. A headspace gas chromatography sample injector according to claim 4, characterized in that: The central axis device comprises: a central axis bearing part and a central axis rod; the lower end of the central axis rod is fitted in the central axis bearing part; and the sample plate and the gear plate are both fixedly sleeved on the central axis rod; The paraxial device comprises: a paraxial bearing part and a paraxial rod; the lower end of the paraxial rod is fitted in the paraxial bearing part; and the upper slide plate and the lower slide plate are both fixedly sleeved on the paraxial rod; Furthermore, the central axis bearing portion and the side axis bearing portion are both vertically mounted on the bottom plate.

7. A headspace gas chromatography sample injector according to claim 6, characterized in that: The central axis bearing component and the side axis bearing component are the same, both comprising: a bearing seat, a bearing and a shaft cylinder; the bearing seat is open at the top, cylindrical, hollow, and has an external threaded interface at the bottom, which is screwed to the base plate through the external threaded interface; the bottom of the bearing sleeve is connected to the base plate and there is an annular depression inside; there are two bearings, which are located at the upper and lower ends of the bearing seat respectively; the shaft cylinder is a hollow cylinder with an inner diameter larger than the inner diameter of the bearing, and is located between the two bearings, and the two end faces of the shaft cylinder are in close contact with the inner ring end faces of the upper and lower bearings; the central axis rod and the side axis rod pass through the inner holes of the bearing and the shaft cylinder.

8. A headspace gas chromatography sample injector according to claim 6, characterized in that: The sample plate and the gear plate are mounted on the central axis through a plate seat, and the plate seat includes: a locking hole located in the center, screw holes located in the four corners, and a locking nail hole located on one side, a locking hole notch is provided on one side of the locking hole, and a penetrating locking hole through groove is provided on the other side corresponding to the locking hole notch, and the locking nail hole is perpendicular to the locking hole through groove; screw holes consistent with the screw holes are provided on the gear plate and the sample plate.

9. A headspace gas chromatography sample injector according to any one of claims 1 to 8, characterized in that: The control system includes a control panel and a single-chip microcomputer. The control panel is connected to the single-chip microcomputer by wiring. The positioning system, three-way needle inlet valve, three-way needle retracting valve, two-way air inlet valve, six-way injection valve, two-way air outlet valve, three-way exhaust valve, and vacuum pump are respectively connected to the single-chip microcomputer by conductive wires and are controlled by a program in the single-chip microcomputer.

10. A headspace gas chromatography sample injector according to claim 9, characterized in that: The headspace gas chromatography injector includes two headspace injection modes, which are as follows: The first is a direct headspace injection mode, in which the sample gas is stored in a headspace sample bottle in a compressed form. When the direct headspace injection mode is adopted, the two-way inlet valve and the two-way outlet valve are in an open state, and the three-way exhaust valve is in a closed state. When the injection needle is inserted into the headspace sample bottle, the compressed gas sample in the headspace bottle passes through the needle seat, the limiting filter, the 4th, 5th, 2nd and 3rd interfaces of the six-way injection valve in sequence under the action of its own pressure, and then is discharged into the atmosphere through the exhaust ports of the two-way outlet valve and the three-way exhaust valve. The compressed sample gas flushes the air intake pipeline when passing through until its pressure is balanced with the atmospheric pressure. The gas sample to be analyzed is stored in the quantitative tube of the six-way injection valve, and the excess sample gas is discharged into the atmosphere, so as to realize automatic loading of the gas sample. When the sample loading is completed, the six-way injection valve is opened, and the sample gas stored in the quantitative tube is brought into the chromatogram by the carrier gas for injection and analysis; Secondly, the vacuum pump, the two-way air outlet valve and the three-way exhaust valve are used as auxiliary components, and their main working mode is that after the injection needle is inserted into the head space sample bottle, the vacuum pump, the three-way exhaust valve and the two-way air outlet valve are opened first, and the vacuum pump draws vacuum on the air inlet pipe, the flow limiting filter and the quantitative tube at the rear end of the two-way air inlet valve, and then closes the two-way air outlet valve and opens the two-way air inlet valve, so that the gas sample in the head space sample bottle flushes the corresponding air inlet pipe and the quantitative tube under the action of the self-head space pressure, and then closes the two-way air inlet valve and opens the two-way air inlet valve. The two-way air outlet valve is used to draw vacuum from the quantitative tube by the vacuum pump, and then the two-way air outlet valve is closed and the two-way air inlet valve is opened, and the quantitative tube is cleaned with sample gas. This process is repeated for several cleanings to improve the cleanliness of the air inlet pipeline and the injection accuracy. After the flushing is completed, the two-way air inlet valve and the two-way air outlet valve are kept open, and the three-way exhaust valve and the vacuum pump are closed. The excess sample gas will be discharged into the atmosphere through the exhaust port of the three-way exhaust valve, so that the sample gas to be analyzed is stored in the quantitative tube in the form of normal pressure, completing the sample loading process.

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