A measuring instrument and method for measuring gas content in packaging bags

Abstract

The present invention provides a special measuring instrument and a measuring method for measuring the gas content in a packaging bag. The measuring instrument includes an air source, a negative pressure generator, a water source, a lower tube, a measuring tube, and a water receiving tray. The measuring tube includes a transparent inner tube and an outer tube that are mutually sleeved. The upper part of the inner tube opens in the outer tube, and a scale is provided on the tube wall. The lower tube is installed at an inclined angle to the horizontal plane, the upper part of the lower tube is connected to the inner tube, and the bottom is connected to the water source. One end of the negative pressure generator is connected to the outer tube, and the other end is connected to the air source. A negative pressure gauge is provided on the pipeline connected to the negative pressure generator above the outer tube. The inner tube, the outer tube, and the lower tube are all connected to the water receiving tray through a drainage pipe. The air source, the negative pressure generator, the measuring tube, the lower tube, and the water source are connected by valves, switches, and pipelines to form a closed measuring system. The measuring instrument of the present invention has a simple and reasonable structural design and can be widely used in food packaging and food processing industries.

Description

Technical Field

[0001] The invention relates to the technical field of gas content measurement, and in particular to a measuring instrument and a measuring method for measuring the gas content in a food packaging bag. Background Art

[0002] In the food packaging material industry, a certain amount of gas is inevitably mixed in when producing large-capacity three-side sealed and four-side sealed multi-layer composite packaging bags for the food industry. Usually, the gas exists between the interlayers of each bag film, between the inner film and inside the nozzle. Too much air mixed in the packaging bag will cause problems when the packaging bag is packed, and the oxygen component mixed in the gas after the customer fills it will cause the packaging contents to oxidize and turn black, so the gas content in the bag must be controlled. To control the gas content and determine whether the total amount of gas mixed in the food packaging bag meets the relevant quality standards, the gas content must be measured first, but for the means of measuring the gas content in the packaging bag, various professional measuring instrument manufacturers lack corresponding methods and products.

[0003] The present invention utilizes Boyle's Law or Mariotte's Law: under certain conditions, the volume of a gas changes with the pressure change, develops a measurement method and manufactures a special measuring instrument, which can achieve the purpose of measuring the gas content in a food packaging bag and meet the relevant measurement requirements. Summary of the invention

[0004] In order to solve the problem in the food processing industry that the gas content in the packaging bag cannot be detected and whether the total amount of gas contained meets the relevant quality standards cannot be determined, the present invention provides a special measuring instrument and a measuring method for measuring the gas content in the packaging bag.

[0005] The specific technical solution adopted by the present invention is: a measuring instrument for measuring the gas content in a packaging bag, comprising an air source, a negative pressure generator, a water source, a lower cylinder, a measuring cylinder, and a water receiving tray.

[0006] The measuring tube comprises a transparent inner tube and an outer tube which are sleeved on each other, the upper part of the inner tube is opened in the outer tube, and a scale is provided on the tube wall;

[0007] The lower cylinder is installed at an inclined angle to the horizontal plane, the upper part of the lower cylinder is connected to the inner cylinder, the bottom is connected to the water source, and a lower cylinder cover is provided on the lower cylinder;

[0008] One end of the negative pressure generator is connected to the outer cylinder, and the other end is connected to the gas source. A negative pressure gauge is provided on the pipeline connected to the negative pressure generator above the outer cylinder;

[0009] The inner cylinder, outer cylinder and lower cylinder are all connected to the water receiving pan through drainage pipes;

[0010] The air source, the negative pressure generator, the measuring tube, the lower tube and the water source are connected by valves, switches and pipelines to form a closed measuring system.

[0011] Furthermore, a negative pressure switch is provided on the pipeline connecting the negative pressure generator and the outer cylinder, a pressure regulating valve and a water inlet valve are provided in sequence on the connecting pipeline between the water source and the lower cylinder, and a pressure reducing valve, a pressure gauge and an air valve switch are provided in sequence on the connecting pipeline between the air source and the negative pressure generator.

[0012] Furthermore, the drainage pipe connecting the lower cylinder and the water receiving pan comprises a lower cylinder drainage pipe and a lower cylinder emptying pipe, the lower cylinder drainage pipe is connected to the water inlet pipe of the lower cylinder, the lower cylinder emptying pipe is arranged at the low-position water outlet at the bottom of the lower cylinder, the lower cylinder emptying pipe is provided with a lower cylinder emptying valve, the lower cylinder drainage pipe is provided with a lower cylinder drainage valve, the drainage pipe connecting the outer cylinder and the water receiving pan is provided with an outer cylinder drainage valve, and the drainage pipe connecting the inner cylinder and the water receiving pan is provided with an inner cylinder drainage valve.

[0013] Furthermore, the scale range of the inner cylinder is 0-380 mm, the angle between the lower cylinder and the horizontal plane is 60°, and a muffler is provided on the negative pressure generator.

[0014] Furthermore, the measuring instrument also includes a calibration cylinder, the bottom of which is connected to the drainage pipe of the inner cylinder through a pipe, an exhaust valve is installed on the top, and an inlet and outlet valve is provided on the pipeline connecting the calibration cylinder and the drainage pipe of the inner cylinder. A scale is provided on the wall of the calibration cylinder, and the scale range of the calibration cylinder is 0-50ml.

[0015] The present invention also includes a method for measuring gas content using the above-mentioned measuring instrument, comprising the following steps:

[0016] S101, injecting clean water into the lower tube until the water level is lower than the lowest edge of the upper opening of the lower tube;

[0017] S102, placing the packaging bag to be tested in the lower drum;

[0018] S103, injecting water into the lower cylinder until the water level rises to the zero mark in the inner cylinder;

[0019] S104, turning on the negative pressure generator to generate negative pressure in the measuring tube, recording the height H of the water level rise in the inner tube and the negative pressure value ΔP in the measuring tube;

[0020] S105, according to the formula Calculate the gas content V1 in the packaging bag, where D is the inner cylinder diameter, unit: mm; P1 is the atmospheric pressure, unit: KPa; ΔP is in KPa; H is in mm; V1 is in ml.

[0021] Further, in step S105, when the inner cylinder diameter D is 43.6 mm, Determine whether the gas content in the packaging bag is less than 380ml. When the gas content is less than 380ml, the negative pressure gauge value ΔP is 60.65KPa and the water level in the inner tube no longer rises, V1=H, and the rising water level in the inner tube is equal to the gas content V1 in the packaging bag; when the gas content in the packaging bag is greater than 380ml, the negative pressure gauge ΔP is 40Kpa and the water level in the inner tube no longer rises, V1=2.29H, and the rising water level in the inner tube multiplied by 2.29 is equal to the gas content in the packaging bag.

[0022] The present invention also includes a method for calibrating the airtightness of the above-mentioned measuring instrument, comprising the following steps:

[0023] S201, injecting clean water into the lower cylinder until the water level in the inner cylinder rises to a level greater than the maximum scale of the calibration cylinder;

[0024] S202, flushing the water in the inner cylinder into the calibration cylinder to the maximum scale;

[0025] S203, draining the water in the inner drum to the zero mark;

[0026] S204, starting the negative pressure generator to generate negative pressure in the measuring cylinder, and when the water level in the inner cylinder stops rising, recording the water level scale A in the inner cylinder;

[0027] S205, drain the water in the calibration cylinder into the inner cylinder, record the rising water level scale B in the inner cylinder, when the difference of BA is not equal to the height corresponding to the total volume of water in the calibration cylinder, adjust the air source pressure to change the suction volume to obtain a correct water level B, when the difference of BA is equal to the height corresponding to the total volume of water in the calibration cylinder, turn off the negative pressure generator, drain the water in the inner cylinder into the calibration cylinder, the water in the calibration cylinder should return to the maximum scale, and the system calibration is completed.

[0028] Furthermore, after the system calibration is completed, the system measurement accuracy can also be reviewed. The specific methods are: a. Prepare a balloon and blow air into it; b. Prepare a measuring cup of appropriate capacity, measure the volume of the balloon using the displacement method and record it; c. Use this instrument to measure the gas volume of the balloon. The measurement result should be equal to the balloon volume measured by the displacement method. The measurement accuracy of the instrument has been reviewed and measurement can be carried out.

[0029] When the measuring instrument of the present invention measures the gas content, the specific measuring principle is as follows: the measuring instrument follows the Boyle-Mariotte law (Boyle's law or Mariotte's Law, referred to as Boyle-Mariotte law): for a fixed amount of gas in a closed container, at a constant temperature, the product of the pressure and volume of the gas is a constant (or the pressure and volume of the gas are inversely proportional). In the present invention, the lower cylinder, the measuring cylinder, and the outlet of the negative pressure generator are connected by a pipeline to form a closed container, and the measured packaging bag is immersed in the water in the lower cylinder. After the negative pressure is formed by the negative pressure generator on the upper part of the measuring cylinder, the pressure in the closed container decreases. According to the Boyle-Mariotte law, the volume of the gas in the bag expands. Due to the incompressibility of the fluid, the height of the water surface rise in the measuring cylinder can be converted into the expanded volume of the gas in the bag. The gas content in the bag can be calculated based on the expanded volume of the gas in the bag and the negative pressure value.

[0030] Derivation of measurement formula: According to the Wave-Mars law, it is derived as follows:

[0031] PV=C

[0032] P1V1=P2V2

[0033] P1V1=(P1-ΔP)(V1+ΔV)

[0034] C = constant, P1-normal pressure (i.e. one atmosphere), V1-volume of gas in the bag at normal temperature and pressure (i.e. gas content in the bag), P2-pressure in the closed measuring system after negative pressure is generated, V2-volume of gas in the bag after negative pressure is generated, ΔP-negative pressure value (i.e. negative pressure gauge reading), ΔV-volume expansion of gas in the bag after negative pressure is generated (calculated by measuring the inner diameter D of the inner tube and the height of the water surface rise).

[0035] Continue to deduce as follows:

[0036] P1V1=P1V 1+ +P1ΔV-ΔPV1-ΔPΔV

[0037] ΔPV1+ΔPΔV=P1ΔV

[0038] ΔPV1=P1ΔV-ΔPΔV

[0039]

[0040]

[0041] Substitute the inner diameter D of the inner cylinder and the height H of the water surface rising after the negative pressure of the inner cylinder, and continue to derive:

[0042]

[0043]

[0044] The units of diameter and height are unified as mm, the units of volume are unified as ml, and the units of pressure and negative pressure are unified as KPa. The results are as follows:

[0045]

[0046] The inner diameter of the inner cylinder is measured to be D = 43.6 mm, and P1 is taken as a standard atmospheric pressure (101.3 KPa), and the following results are obtained:

[0047]

[0048] When the measured negative pressure ΔP=60.65KPa,

[0049]

[0050] V1 = H, i.e. the gas content in the bag (ml) = the height of the water surface rising after measuring the negative pressure in the inner cylinder H (mm)

[0051] When the measured negative pressure ΔP = 40KPa,

[0052]

[0053] V1=2.29H, i.e. the gas content in the bag (ml) = 2.29 times the height H (mm) of the water surface rising after measuring the negative pressure of the inner cylinder.

[0054] Compared with the prior art, the present invention has the following advantages and effects:

[0055] 1. The measuring instrument for measuring the gas content in a packaging bag of the present invention has a simple and reasonable structural design, and can measure the gas content in a food packaging bag to determine whether the gas content in the bag meets the corresponding quality standards. It can be widely used in food packaging and food processing industries.

[0056] 2. The measuring method described in the present invention is based on the law that the volume of gas changes with the change of pressure under certain conditions. A negative pressure generator is used to generate negative pressure in the measuring cylinder, and the volume of the packaging bag in the lower cylinder increases. The water level in the inner cylinder is measured to rise. The gas content in the corresponding packaging bag can be calculated based on the height of the water level rise and the measured negative pressure value. The measuring method is simple and feasible, and the measuring result is accurate and reliable. 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 some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0058] Figure 1 It is a schematic diagram of the structure of the measuring instrument of the present invention.

[0059] Explanation of the reference numbers: 1. Lower cylinder; 2. Water collecting tray; 3. Inner cylinder; 4. Outer cylinder; 5. Negative pressure gauge; 6. Pressure regulating valve; 7. Pressure reducing valve and pressure gauge; 8. Air valve switch; 9. Negative pressure switch; 10. Lower cylinder drain valve; 11. Water inlet valve; 12. Lower cylinder drain valve; 13. Negative pressure generator; 14. Inner cylinder drain valve; 15. Outer cylinder drain valve; 16. Muffler; 17. Calibration cylinder; 18. Exhaust valve; 19. Inlet and outlet valves. DETAILED DESCRIPTION

[0060] The present invention is further described in detail below in conjunction with embodiments. The following embodiments are for explanation of the present invention but the present invention is not limited to the following embodiments.

[0061] Example 1: Figure 1 As shown, a measuring instrument for measuring the gas content in a packaging bag includes an air source, a negative pressure generator 13, a water source, a lower cylinder 1, a measuring cylinder, and a water receiving tray 2.

[0062] The measuring tube comprises a transparent inner tube 3 and an outer tube 4 which are sleeved with each other. The upper part of the inner tube 3 is opened in the outer tube 4, and the bottom is not connected with the outer tube 4. A scale is provided on the wall of the tube, and the scale ranges from 0 to 380 mm.

[0063] The lower tube 1 is installed at an inclined angle to the horizontal plane, the upper high-position water inlet of the lower tube 1 is connected to the inner tube 3, the bottom high-position water inlet is connected to the water source, and the lower tube 1 is provided with a lower tube cover;

[0064] One end of the negative pressure generator 13 is connected to the outer tube 4, and the other end is connected to the gas source. A negative pressure gauge 5 is provided on the pipeline connected to the negative pressure generator 13 above the outer tube 4.

[0065] The inner cylinder 3, the outer cylinder 4 and the lower cylinder 1 are all connected to the water receiving pan 2 through a drainage pipe;

[0066] The air source, negative pressure generator 13, measuring tube, lower tube 1, and water source are connected by valves, switches, and pipelines to form a closed measuring system to achieve the measuring function.

[0067] Specifically, Figure 1As shown, a negative pressure switch 9 is provided on the pipeline connecting the negative pressure generator 13 and the outer cylinder 4, a pressure regulating valve 6 and a water inlet valve 11 are provided in sequence on the connecting pipeline between the water source and the lower cylinder 1, a pressure reducing valve, a pressure gauge 7, and an air valve switch 8 are provided in sequence on the connecting pipeline between the air source and the negative pressure generator 13, the drainage pipeline connecting the lower cylinder 1 and the water receiving tray 2 includes a lower cylinder drainage pipeline and a lower cylinder emptying pipeline, the lower cylinder drainage pipeline is connected to the water inlet pipeline of the lower cylinder 1, a lower cylinder drainage valve 10 is provided on the lower cylinder drainage pipeline, the lower cylinder emptying pipeline is arranged at the low-level water outlet at the bottom of the lower cylinder 1, a lower cylinder emptying valve 12 is provided on the lower cylinder emptying pipeline, an outer cylinder drainage valve 15 is provided on the drainage pipeline connecting the outer cylinder 4 and the water receiving tray 2, and an inner cylinder drainage valve 14 is provided on the drainage pipeline connecting the inner cylinder 3 and the water receiving tray 2. Among them, the lower cylinder emptying valve 12 is used to empty the tap water of the test medium in the lower cylinder 1.

[0068] The negative pressure generator 13 is connected to a compressed air source as an energy source through an air valve switch 8, and is connected to the upper part of the outer cylinder 4 through a negative pressure switch 9, so as to generate the negative pressure required for measurement. The lower cylinder drain valve is provided to discharge the test medium in the lower cylinder 1 to a level below the lowest edge of the upper opening of the lower cylinder 1, so as to take out the measurement packaging bag.

[0069] The lower cylinder 1 is a metal cylinder installed at an angle of 60° to the horizontal plane, and the lower cylinder cover is arranged at the upper end of the lower cylinder 1. When measuring the gas content of the packaging bag, clean water is injected into the lower cylinder 1 through the pressure regulating valve 6 and the water inlet valve 11. When the water level rises to below the lowest edge of the upper opening of the lower cylinder 1, the water inlet valve 11 and the pressure regulating valve 6 are closed, and the packaging bag to be tested is placed.

[0070] As a preferred embodiment, a muffler is provided on the negative pressure generator 13 to reduce the noise generated when the negative pressure generator 13 is working.

[0071] In this embodiment 1, the functions of various valves and switches are as follows:

[0072] The pressure reducing valve and the pressure gauge 7 are used to connect to a compressed air source and adjust the air pressure so as to adjust the speed and intensity of the negative pressure generated by the negative pressure generator 13 .

[0073] The pressure regulating valve 6 is used to connect the water source, inject the test medium into the lower cylinder 1, and adjust the water supply flow and speed.

[0074] The water inlet valve 11 is used to open and close the water inlet of the lower drum 1.

[0075] The lower drum drain valve 10 is used to drain the lower drum 1 until the water level is lower than the lowest edge of the upper opening of the lower drum 1, so as to open the lid and put in or take out the bag to be tested.

[0076] The gas valve switch 8 is used to open and close the gas supply of the negative pressure generator 13.

[0077] The negative pressure switch 9 is used to open and close the negative pressure connection of the measuring cylinder, and to exhaust air when water is injected into the lower cylinder 1 using the water inlet valve 11.

[0078] The outer cylinder drain valve 15 is used to measure the drainage of the outer cylinder 4.

[0079] The inner tube drain valve 14 is used to measure the drainage of the inner tube 3.

[0080] Embodiment 2: A measuring instrument for measuring the gas content in a packaging bag. The difference from Embodiment 1 is that the measuring instrument further comprises a calibration cylinder 17. The bottom of the calibration cylinder 17 is connected to the drainage pipe of the inner cylinder 3 through a pipe. An exhaust valve 18 is installed on the top. An inlet and outlet valve 19 is provided on the pipeline connecting the calibration cylinder 17 and the drainage pipe of the inner cylinder. A scale is provided on the wall of the calibration cylinder 17, and the scale range is 0-50ml.

[0081] The calibration cylinder 17 is used to calibrate the air tightness of the measuring system when parts are repaired or pipes and joints are replaced in the measuring instrument.

[0082] The inlet and outlet valve 19 is used to check the water inlet and outlet of the cylinder 17.

[0083] The exhaust valve 18 is used to calibrate the opening and closing of the cylinder 17 with the outside.

[0084] In the measuring instrument described in Examples 1 to 2 of the present invention, after the negative pressure generator 13 forms negative pressure on the upper part of the outer tube 4 of the measuring tube, the pressure in the sealed container decreases. According to the Bo-Mars law, the volume of gas in the test packaging bag expands. Due to the incompressibility of the fluid, the height of the water surface rise in the measuring tube can be converted into the expanded volume of gas in the bag. The gas content in the bag can be calculated based on the expanded volume of gas in the bag and the negative pressure value.

[0085] When the gas content in a packaging bag is measured using the measuring instrument described in Examples 1 to 2 of the present invention, the specific measuring method includes the following steps:

[0086] S101, pre-test preparation stage: connect the tap water pipeline and compressed air, use the pressure reducing valve to adjust the air source pressure to about 4 bar, put the water tray 2 in place, and ensure that all switch valves are in the closed position;

[0087] S102, open the water inlet valve 11, control the water source flow rate through the pressure regulating valve 6, inject clean water into the lower tube 1 until the water level is lower than the lowest edge of the upper opening of the lower tube 1, and then close the water inlet valve;

[0088] S103, open the lower drum cover, roll the packaging bag to be tested into a loose cylinder from the short side direction (large-sized bags should be folded in half before rolling), put it into the lower drum 1, and then adjust the bag to be as loose as possible to avoid tight winding, and close the lower drum cover;

[0089] S104, open the water inlet valve 11 and the negative pressure switch 9, inject water into the lower cylinder 1 until the water level rises to the zero mark in the inner cylinder 3, close the water inlet valve 11, observe the water level, which should be based on the lowest point of the water surface, and adjust the valve opening to control the water flow during water injection. If the water level exceeds the zero position, open the inner cylinder drain valve 14 to lower the water level to zero;

[0090] S105, turn on the air source switch 8, turn on the negative pressure generator 13, generate negative pressure in the measuring tube, record the height H of the water level rise in the inner tube 3, and the negative pressure value ΔP on the negative pressure gauge on the measuring tube, according to the formula:

[0091] Calculate the gas content V1 in the packaging bag, where D is the inner cylinder diameter, unit: mm; P1 is the atmospheric pressure, unit: KPa; ΔP is in KPa; H is in mm; V1 is in ml.

[0092] Among them, in step S105, the inner cylinder diameter D is 43.6 mm

[0093] hour, Determine whether the gas content in the packaging bag is less than 380ml. When the gas content is less than 380ml, observe that the negative pressure gauge ΔP is 60.65KPa and the water level in the inner tube 3 no longer rises, first close the negative pressure switch 9, wait for one minute after closing the gas source switch 8, and record the water level scale H in the inner tube 3. This value is the gas content V1=H in the packaging bag; when the gas content in the packaging bag is greater than 380ml, observe that the negative pressure gauge ΔP is 40Kpa and the water level in the inner tube 3 no longer rises, first close the negative pressure switch 9, wait for one minute after closing the gas source switch 8, and record the water level scale H in the inner tube 3. The gas content in the side packaging bag V1=2.29H, that is, the rising water level in the inner tube 3 multiplied by 2.29 is equal to the gas content in the packaging bag.

[0094] S106, open the negative pressure switch 9, open the lower drum drain valve 10, drain the lower drum 1 until the water level is lower than the lowest edge of the upper opening of the lower drum 1, close the lower drum drain valve 10, open the lower drum cover, take out the tested bag, and prepare for the next test.

[0095] When the measuring instrument parts described in Embodiment 2 of the present invention are repaired or the valves are replaced to open the pipeline for reconnection, it is necessary to verify the air tightness of the measuring system. The specific verification method includes the following steps:

[0096] S201, confirm that there is no bag in the lower cylinder 1, close the lower cylinder cover, open the negative pressure switch 9 and use the water inlet valve to inject clean water into the lower cylinder 1 until the water level in the inner cylinder 1 rises to a level greater than the maximum scale of the calibration cylinder 17. During the water injection process, pay attention to adjusting the opening of the pressure regulating valve 6 and close the water inlet valve 11;

[0097] S202, open the calibration cylinder exhaust valve 18, open the calibration cylinder inlet and outlet valve 19 and control the opening, flush the water in the inner cylinder 3 into the calibration cylinder 17 to the maximum scale mark of 50 ml, and close the exhaust valve 18 and the inlet and outlet valve 19;

[0098] S203, open the inner drum drain valve 14 and control the opening to drain the water in the inner drum 3 to the zero mark, and close the inner drum drain valve 14;

[0099] S204, turn on the air source switch 8, the negative pressure generator 13 generates negative pressure in the measuring cylinder, pay attention to the water level in the measuring cylinder, when it stops rising or after 1 minute, record the water level scale A of the inner cylinder 3, and turn off the negative pressure switch 9 and the air source switch 8;

[0100] S205, open the calibration cylinder inlet and outlet valve 19, drain all 50ml of water in the calibration cylinder 17 into the inner cylinder 3, record the rising water level scale B in the inner cylinder 3, the difference of BA should be equal to 35.5mm (corresponding to 50ml volume), when the difference of BA is not equal to the height of 35.5mm corresponding to the total volume of water in the calibration cylinder 17, adjust the gas source pressure reducing valve to change the amount of air pumped, and obtain a correct water level B, when the difference of BA is equal to the height corresponding to the total volume of water in the calibration cylinder, close the negative pressure switch 9, drain the water in the inner cylinder 3 into the calibration cylinder 17, the water in the calibration cylinder should return to the maximum scale of 50ml, close the calibration cylinder inlet and outlet valve 19, at this time the measurement system (air tightness) is confirmed, and the instrument re-establishes the conditions for correctly measuring the gas content in the bag. Open the lower cylinder drain valve 10 until the water level is lower than the lowest edge of the upper opening of the lower cylinder 1, open the lower cylinder cover, and put in the test bag for measurement.

[0101] S206, after the system calibration is completed, the system measurement accuracy can also be reviewed, the specific method is as follows:

[0102] a. Prepare a balloon and blow air into it. Note that it is best not to pressurize it. Just blow it up.

[0103] b. Prepare a measuring cup of appropriate capacity, measure the volume of the balloon using the displacement method and record it;

[0104] c. Determine the gas volume of the balloon by the measurement method of the present invention, and the measurement result should be equal to the balloon volume measured by the water displacement method;

[0105] d. After the instrument measurement accuracy has been reviewed, measurement can be carried out.

[0106] In addition, it should be noted that the shapes and names of the parts and components of the specific embodiments described in this specification may be different. Any equivalent or simple changes made based on the structure, features and principles described in the patent concept of the present invention are included in the protection scope of the patent of the present invention. The technicians in the technical field of the present invention can make various modifications or supplements to the specific embodiments described or replace them in a similar manner, as long as they do not deviate from the structure of the present invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for measuring gas content using a measuring instrument for measuring gas content in a packaging bag, characterized in that: The measuring instrument comprises an air source, a negative pressure generator, a water source, a lower cylinder, a measuring cylinder, and a water receiving tray. The measuring tube comprises a transparent inner tube and an outer tube which are sleeved on each other, the upper part of the inner tube is opened in the outer tube, and a scale is provided on the tube wall; The lower cylinder is installed at an inclined angle to the horizontal plane, the upper part of the lower cylinder is connected to the inner cylinder, the bottom is connected to the water source, and a lower cylinder cover is provided on the lower cylinder; One end of the negative pressure generator is connected to the outer cylinder, and the other end is connected to the gas source. A negative pressure gauge is provided on the pipeline connected to the negative pressure generator above the outer cylinder; The inner cylinder, outer cylinder and lower cylinder are all connected to the water receiving pan through drainage pipes; The air source, negative pressure generator, measuring tube, lower tube and water source are connected by valves, switches and pipelines to form a closed measuring system; The scale range of the inner cylinder is 0-380 mm, the angle between the lower cylinder and the horizontal plane is 60°, and the negative pressure generator is provided with a muffler; The measuring instrument also includes a calibration cylinder, the bottom of the calibration cylinder is connected to the drainage pipe of the inner cylinder through a pipe, an exhaust valve is installed on the top, the pipeline connecting the calibration cylinder and the inner cylinder drainage pipe is provided with an inlet and outlet valve, and the cylinder wall of the calibration cylinder is provided with a scale, and the scale range of the calibration cylinder is 0-50ml; The method for measuring gas content by the measuring instrument comprises the following steps: S101, injecting clean water into the lower tube until the water level is lower than the lowest edge of the upper opening of the lower tube; S102, placing the packaging bag to be tested in the lower drum; S103, injecting water into the lower cylinder until the water level rises to the zero mark in the inner cylinder; S104, turning on the negative pressure generator to generate negative pressure in the measuring tube, recording the height H of the water level rise in the inner tube and the negative pressure value △P in the measuring tube; S105, according to the formula Calculate the gas content V1 in the packaging bag, where D is the inner cylinder diameter, unit: mm; P1 is the atmospheric pressure, unit: KPa; △P unit: KPa; H unit: mm; V1 unit: ml; In step S105, when the inner cylinder diameter D is 43.6 mm, ; Determine whether the gas content in the packaging bag is less than 380ml. When the gas content is less than 380ml, the negative pressure value △P is 60.65KPa and the water level in the inner tube no longer rises, V1=H, and the rising water level in the inner tube is equal to the gas content V1 in the packaging bag; when the gas content in the packaging bag is greater than 380ml, observe that the negative pressure gauge △P is 40Kpa and the water level in the inner tube no longer rises, V1=2.29H, and the rising water level in the inner tube multiplied by 2.29 is equal to the gas content in the packaging bag; When the measuring instrument parts are repaired or the valves are replaced to open the pipeline for reconnection, the air tightness of the measuring system needs to be verified. The specific verification method includes the following steps: S201, injecting clean water into the lower cylinder until the water level in the inner cylinder rises to a level greater than the maximum scale of the calibration cylinder; S202, flushing the water in the inner cylinder into the calibration cylinder to the maximum scale; S203, draining the water in the inner drum to the zero mark; S204, starting the negative pressure generator to generate negative pressure in the measuring cylinder, and when the water level in the inner cylinder stops rising, recording the water level scale A in the inner cylinder; S205, drain all the water in the calibration cylinder into the inner cylinder, record the rising water level scale B in the inner cylinder, when the difference between BA is not equal to the height corresponding to the total volume of water in the calibration cylinder, adjust the air source pressure to change the suction volume to obtain a correct water level B, when the difference between BA is equal to the height corresponding to the total volume of water in the calibration cylinder, turn off the negative pressure generator, drain the water in the inner cylinder into the calibration cylinder, the water in the calibration cylinder should return to the maximum scale, and the system calibration is completed; After the system calibration is completed, the system measurement accuracy is reviewed by the following method. The specific steps are: a. Prepare a balloon and blow air into it; b. Prepare a measuring cup of appropriate capacity, measure the volume of the balloon by the displacement method and record it; c. Use this instrument to measure the gas volume of the balloon. The measurement result should be equal to the balloon volume measured by the displacement method. The measurement accuracy of the instrument has been reviewed and measurement can be carried out.

2. A method for measuring gas content using a measuring instrument for measuring gas content in a packaging bag according to claim 1, characterized in that: A negative pressure switch is provided on the pipeline connecting the negative pressure generator and the outer cylinder, a pressure regulating valve and a water inlet valve are provided in sequence on the pipeline connecting the water source and the lower cylinder, and a pressure reducing valve, a pressure gauge and an air valve switch are provided in sequence on the pipeline connecting the air source and the negative pressure generator.

3. A method for measuring gas content using a measuring instrument for measuring gas content in a packaging bag according to claim 2, characterized in that: The drainage pipe connecting the lower cylinder and the water receiving pan comprises a lower cylinder drainage pipe and a lower cylinder emptying pipe, the lower cylinder drainage pipe is connected to the water inlet pipe of the lower cylinder, the lower cylinder emptying pipe is arranged at the low-position water outlet at the bottom of the lower cylinder, the lower cylinder emptying pipe is provided with a lower cylinder emptying valve, the lower cylinder drainage pipe is provided with a lower cylinder drainage valve, the drainage pipe connecting the outer cylinder and the water receiving pan is provided with an outer cylinder drainage valve, and the drainage pipe connecting the inner cylinder and the water receiving pan is provided with an inner cylinder drainage valve.

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