High-precision liquid chromatograph mobile phase pressure measuring device

Abstract

The invention relates to a high-precision liquid chromatograph mobile phase pressure measuring device, which effectively solves the problem of large error of the liquid chromatograph mobile phase pressure measuring device. According to the technical scheme, the liquid chromatograph comprises a step-shaped shell, a piston-like body is arranged in the shell, a sealing ring is arranged on the inner side of a step surface, the left end of the piston-like body is in contact with the sealing ring, a mobile phase of the liquid chromatograph flows through a first cavity, and a second cavity is filled with a liquid medium with constant pressure. The piston-like body is always pushed and pressed to the position in contact with the supporting bolt through large pressure in the second cavity, so that the position of the piston-like body is kept constant, the compression amount of the sealing ring is kept constant, and the sealing effect of the piston-like body is improved while the two cavities are sealed and isolated. Interference variables such as friction damping or deformation damping which are not easy to measure cannot be generated in the axial direction of the piston-like body, so that the pressure of the mobile phase can be calculated more accurately.

Description

Technical Field

[0001] The present invention relates to the field of high-end equipment manufacturing, and in particular to a high-precision liquid chromatograph mobile phase pressure measuring device. Background Art

[0002] Liquid chromatography is a commonly used device for detecting the purity of various vulcanization accelerators. Its principle is to use the mobile phase as a carrier to carry the sample to be tested through the stationary phase in the chromatographic column at a steady flow rate. Different components form a flow rate gradient due to the different strengths of their interaction with the stationary phase due to their physical and chemical properties, and flow out in sequence to achieve separation. Its separation accuracy depends on the stable delivery of the mobile phase, so the pumping pressure of the mobile phase needs to be monitored in real time.

[0003] The invention patent with application number: CN202210117574.1 discloses a pressure measuring device for a liquid chromatograph, which separates two chambers by an elastic diaphragm. The mobile phase flows through the second chamber. The pressure of the mobile phase causes the elastic diaphragm to deform and squeeze the liquid medium in the first chamber. The pressure sensor in the first chamber measures the pressure change of the liquid medium, thereby indirectly monitoring the pressure of the mobile phase. The patent isolates the pressure sensor from the mobile phase, avoiding corrosion damage to the pressure sensor by the mobile phase.

[0004] In the process of converting the pressure of the mobile phase in the second cavity of the above-mentioned patent into the pressure of the liquid medium in the first cavity through the elastic diaphragm, the elastic diaphragm undergoes elastic deformation and generates elastic potential energy. That is to say, part of the pressure of the mobile phase is converted into the elastic potential energy of the elastic diaphragm, and there is partial pressure loss. This partial pressure loss is difficult to measure, so that the pressure of the liquid medium in the first cavity is lower than the pressure of the mobile phase in the second cavity. The greater the pressure of the mobile phase, the greater the deformation of the elastic diaphragm, and the more obvious the pressure loss. The mobile phase of the liquid chromatograph is usually transported at a high pressure of tens to hundreds of bars to improve the separation efficiency. Summary of the Invention

[0005] The invention provides a high-precision mobile phase pressure measuring device for a liquid chromatograph, aiming to improve the precision of the mobile phase pressure measuring device for a liquid chromatograph from the perspective of design principle.

[0006] The technical solution includes a shell, which is a two-section stepped cylindrical structure consisting of a thin section on the left and a thick section on the right. The connection between the thin section and the thick section of the shell forms an annular step surface. A piston-like body is installed in the shell, and there is a gap between the outer wall of the piston-like body and the inner wall of the shell. A sealing ring is installed on the inner side of the step surface. The left end of the piston-like body is in contact with the sealing ring. The piston-like body divides the shell into a first chamber on the left and a second chamber on the right; a first liquid inlet pipe and a first liquid outlet pipe are installed on the first chamber, and the mobile phase of the liquid chromatograph flows into the first chamber through the first liquid inlet pipe and then flows out through the first liquid outlet pipe. The second chamber is filled with a liquid medium with constant pressure, and the liquid pressure in the second chamber is greater than the liquid pressure in the first chamber. Several support bolts are evenly distributed on the circumference of the stepped surface of the shell. The support bolts vertically penetrate the stepped surface. The head of the support bolt is equipped with a first pressure sensor. The left end of the piston-like body contacts the head of the support bolt, and the first pressure sensor measures the pressure at the contact point.

[0007] A second pressure sensor is installed on the stepped surface. The second pressure sensor contacts the left end of the sealing ring. The pressure between the sealing ring and the stepped surface can be measured by the second pressure sensor.

[0008] There are multiple second pressure sensors evenly distributed around the circumference.

[0009] The sealing ring is provided with an avoidance hole, and the right end of the supporting bolt passes through the avoidance hole and contacts the left end of the piston-like body.

[0010] The second chamber is provided with a second liquid inlet pipe, a pressure stabilizing valve is provided on the second liquid inlet pipe, and the second liquid inlet pipe is connected with a quantitative liquid pump.

[0011] The second chamber is provided with a second liquid outlet pipe, and the second liquid outlet pipe is provided with a switch valve.

[0012] The right end of the shell is equipped with a pre-compression bolt along the axis of the shell. Before the liquid in the second chamber is pressurized, the pre-compression bolt presses against the right end of the piston-like body and keeps the sealing ring in a compressed state.

[0013] The first chamber is equipped with a temperature sensor for detecting the temperature of the mobile phase.

[0014] The left end of the shell is provided with a first end cover, and the right end is provided with a second end cover, and the first end cover and the second end cover are both connected to the shell via threads.

[0015] The present invention isolates the pressure sensor from the mobile phase in the first chamber and the hydraulic oil in the second chamber through a sealing ring, thereby preventing the solution and the hydraulic oil from corroding or penetrating into the pressure sensor and causing damage.

[0016] The present invention uses the higher pressure in the second chamber to always push the piston-like body to a position in contact with the support bolt, so that the position of the piston-like body remains constant, thereby keeping the compression of the sealing ring constant. While achieving sealed isolation between the two chambers, no interference variables such as friction damping or deformation damping that are difficult to measure are generated in the axial direction of the piston-like body, thereby enabling more accurate calculation of the pressure of the mobile phase. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a left view of the present invention.

[0018] Figure 2 It is the front view of the present invention.

[0019] Figure 3 The present invention is a three-dimensional Figure 1 .

[0020] Figure 4 The present invention is a three-dimensional Figure 2 .

[0021] Figure 5 It is an assembly diagram inside the housing of the present invention.

[0022] Figure 6 It is a three-dimensional cross-sectional view of the present invention.

[0023] Figure 7 for Figure 1 AA section view in.

[0024] Figure 8 for Figure 1 BB cross-section view in.

[0025] Figure 9 A perspective view of the support bolts.

[0026] Figure 10 A half-section view of the shell.

[0027] Figure 11 for Figure 6 Magnified view of position C in the middle. DETAILED DESCRIPTION

[0028] In conjunction with the accompanying drawings, the present invention includes a shell 1, which is a two-section stepped cylindrical structure consisting of a thin section on the left and a thick section on the right. The connection between the thin section and the thick section of the shell 1 forms an annular step surface 2. A piston-like body 3 is installed in the shell 1. There is a gap between the outer wall of the piston-like body 3 and the inner wall of the shell 1, that is, there is no pressure between the outer wall of the piston-like body 3 and the inner wall of the shell 1. In addition, there is an oil film in the gap, so there is no friction resistance between the outer wall of the piston-like body 3 and the inner wall of the shell 1. A sealing ring 4 is installed on the inner side of the step surface 2. The left end of the piston-like body 3 contacts the sealing ring 4. The piston-like body 3 divides the shell 1 into a first chamber 5 on the left and a second chamber 6 on the right.

[0029] The first chamber 5 is equipped with a first liquid inlet pipe 7 and a first liquid outlet pipe 8. The mobile phase of the liquid chromatograph flows into the first chamber 5 through the first liquid inlet pipe 7 and then flows out through the first liquid outlet pipe 8. Multiple first liquid inlet pipes 7 can be set, and multiple mobile phases can be connected at the same time. The pressure of the mobile phase in the first chamber 5 acts on the left end of the piston-like body 3. The second chamber 6 is filled with a liquid medium with constant pressure. The pressure in the second chamber 6 acts on the right end of the piston-like body 3, and the liquid pressure in the second chamber 6 is greater than the liquid pressure in the first chamber 5.

[0030] The piston-like body 3 is pushed to the left by the hydraulic pressure in the second chamber 6 and pressed against the sealing ring 4, thereby achieving effective isolation between the first chamber 5 and the second chamber 6; the right end of the piston-like body 3 is subjected to the liquid pressure of the second chamber 6, and the left end is subjected to the liquid pressure of the first chamber 5, the sealing ring 4 and the reaction force at the step surface 2. The forces at both ends are balanced, so that the position of the piston-like body 3 always remains stationary.

[0031] A number of support bolts 9 are evenly distributed on the circumference of the stepped surface 2 of the shell 1. The support bolts 9 pass through the stepped surface 2 vertically. The head of the support bolt 9 is equipped with a first pressure sensor 10. The left end of the piston-like body 3 is in contact with the head of the support bolt 9, and the first pressure sensor 10 measures the pressure at the contact point; the reaction force of the support bolt 9 on the piston-like body 3 can be calculated by the first pressure sensor 10, and the compression amount of the sealing ring 4 is constant. The reaction force of the sealing ring 4 on the piston-like body 3 can be calculated by multiplying the elastic coefficient of the sealing ring 4 by the compression amount. In addition, the pressure of the second chamber 6 on the piston-like body 3 is constant and known, so the pressure of the first chamber 5 can be calculated according to the equilibrium state of the piston-like body 3.

[0032] The measurement value of each first pressure sensor 10 multiplied by the end area of the support bolt 9 and the piston-like body 3 is the supporting force of the support bolt 9 on the piston-like body 3. The sum of the supporting forces of all support bolts 9 on the piston-like body 3 is the total supporting force from the support bolts 9.

[0033] By adjusting the screw-in length of each support bolt 9, the supporting force of each adjusting bolt on the piston-like body 3 is adjusted to be the same, which can facilitate the calculation of the supporting force and improve the supporting stability of the piston-like body 3.

[0034] Since the end face of the piston-like body 3 and the stepped surface 2 are both rigid, the surface-to-surface contact cannot ensure uniform pressure everywhere, and it is not convenient to calculate the supporting force of the stepped surface 2 on the piston-like body 3. Therefore, multi-point support of the piston-like body 3 is performed by multiple supporting bolts 9 instead of surface-to-surface contact between the stepped surface 2 and the piston-like body 3, which can more accurately calculate the supporting force of the supporting bolts 9 on the piston-like body 3.

[0035] A second pressure sensor 11 is installed on the stepped surface 2. The second pressure sensor 11 is in contact with the left end of the sealing ring 4. The second pressure sensor 11 can measure the pressure between the sealing ring 4 and the stepped surface 2. Multiplying the pressure by the contact area, that is, the end face area of the sealing ring 4, can obtain the rebound force of the sealing ring 4 on the piston-like body 3. The method of measuring the reaction force of the sealing ring 4 by the second pressure sensor 11 is more accurate than the method of simply calculating by the compression amount, and can avoid the error caused by the change of the elastic coefficient due to the aging of the sealing ring 4.

[0036] There are multiple second pressure sensors 11 evenly distributed around the circumference, and the pressure average value is taken through multi-point measurement to improve accuracy.

[0037] The average value of the measurement values of all the second sensors multiplied by the end area of the sealing ring 4 is the force exerted by the step surface 2 on the sealing ring 4, that is, the reaction force of the sealing ring 4 on the piston-like body 3. Since the position of the piston-like body 3 does not change during the working process and the compression amount of the sealing ring 4 is constant, the supporting force is constant.

[0038] The sealing ring 4 is provided with an avoidance hole 12 , and the right end of the support bolt 9 passes through the avoidance hole 12 and contacts the left end of the piston-like body 3 .

[0039] The second chamber 6 is provided with a second liquid inlet pipe 13, and the second liquid inlet pipe 13 is provided with a pressure-stabilizing valve 14. The second liquid inlet pipe 13 is connected to a quantitative liquid pump. The quantitative liquid pump and the pressure-stabilizing valve 14 cooperate to maintain a constant pressure in the second chamber 6; the pressure-stabilizing valve 14 can adopt an overflow valve or a pressure reducing valve, etc. The setting of the hydraulic circuit is a conventional technology in the hydraulic field and will not be discussed in detail in this application.

[0040] The second chamber 6 is provided with a second liquid outlet pipe 15, on which a switch valve 16 is provided. The switch valve 16 is normally closed during operation. During maintenance, the hydraulic oil in the second chamber 6 can be discharged through the second liquid outlet pipe 15 when necessary.

[0041] The right end of the shell 1 is equipped with a pre-stressing bolt 17 along the axis of the shell 1. Before the liquid in the second chamber 6 is pressurized, the pre-stressing bolt 17 presses against the right end of the piston-like body 3 and keeps the sealing ring 4 in a compressed state, maintaining the sealing state between the piston-like body 3 and the stepped surface 2. After the liquid in the second chamber 6 is pressurized, the piston-like body 3 moves to the right to further compress the sealing ring 4, and the piston-like body 3 is disengaged from the pre-stressing bolt 17. The right end of the piston-like body 3 is only subjected to liquid pressure.

[0042] The first chamber 5 is provided with a temperature sensor 18 for detecting the temperature of the mobile phase.

[0043] The shell 1 is provided with a first end cover 19 at the left end and a second end cover 20 at the right end. The first end cover 19 and the second end cover 20 are both connected to the shell 1 via threads. The first end cover 19 is used to inspect the first chamber 5 when necessary; the second end cover 20 is used to assemble the piston-like body 3 into the second chamber 6 and to inspect the second chamber 6 when necessary.

[0044] The principle of the present invention is described in detail as follows: During operation, hydraulic oil is first pumped into the second chamber 6 through the second liquid inlet pipe 13. The pressure regulating valve 14 and the quantitative liquid pump maintain the liquid pressure in the second chamber 6 constant. Then the hydraulic pressure in the second chamber 6 acts on the pressure F at the right end of the piston body 3. 右 Constant, there are: F 右= P2S2; among them, P2 is the pressure in the second chamber 6; S2 is the end surface area of the piston-like body 3; At this pressure F 右 Under the action of , the piston-like body 3 is pushed to the left, and the sealing ring 4 is further compressed until the left end of the piston-like body 3 contacts the right end of the supporting bolt 9.

[0045] The mobile phase enters the first chamber 5 through the first liquid inlet pipe 7 and then flows out of the first chamber 5 through the first liquid outlet pipe 8. The liquid pressure of the mobile phase in the first chamber 5 acts on the left end of the piston-like body 3. The pressure of the mobile phase on the piston-like body 3 is: F 左1 =P1S1; where P1 is the pressure of the mobile phase; S1 is the cross-sectional area of the first chamber 5 .

[0046] At this time, fine-tune each adjusting bolt to make the readings of each first pressure sensor 10 consistent. Then the total supporting force of each supporting bolt 9 on the left end of the piston-like body 3 is: F 左2 =P3S3N, where P3 is the reading of the first pressure sensor 10; S3 is the right end surface area of the support bolt 9; N is the number of support bolts 9 .

[0047] The readings of the second pressure sensors 11 at this time are respectively P 41 , P 42 …P 4n , then the average value of the readings of the second pressure sensors 11 is P4=(P 41 +P 42 +…+P 4n ) / n, where n is the number of the second pressure sensors 11; the reaction force of the sealing ring 4 on the piston-like body 3: F 左3 =P4S4, where S4 is the end surface area of the sealing ring 4; F 左3 The essence is the rebound force of the sealing ring 4, and its size is determined only by the compression of the sealing ring 4. Since the position of the piston-like body 3 does not move, the compression of the sealing ring 4 is constant, so the reaction force F of the sealing ring 4 on the piston-like body 3 is 左3 Constant.

[0048] According to the equilibrium state of the piston-like body 3, we have: F 右 = F 左1 + F 左2 + F 左3 ; Substitute into the above formulas to calculate: P1=(F 右 -F 左3- P3S3N) / S1, In the above formula, all other variables except P1 and P3 are constants. Therefore, the relationship between the pressure P1 in the first chamber 5 and the reading P3 of the first pressure sensor 10 is unique and definite. Therefore, the pressure P1 of the mobile phase in the first chamber 5 can be obtained by the reading of the first pressure sensor 10.

[0049] It should be noted that when installing the device, the shell 1 is preferably installed in a horizontal position. At this time, the gravity of the piston-like body 3 does not affect the balance of its left and right sides, so its gravity does not need to be taken into account; the shell 1 can also be installed in a vertical position. At this time, the gravity of the piston-like body 3 needs to be taken into account when formulating the force balance equation at both ends of the piston-like body 3.

[0050] The present invention achieves sealed isolation of the two chambers without generating difficult-to-measure interference variables such as friction damping or deformation damping in the axial direction of the piston-like body 3, thereby enabling more accurate calculation of the pressure of the mobile phase.

Claims

1. A high-precision liquid chromatograph mobile phase pressure measuring device, comprising a housing (1), characterized in that: The shell (1) is a two-section stepped cylindrical structure consisting of a thin section on the left and a thick section on the right. The connection between the thin section and the thick section of the shell (1) forms an annular stepped surface (2). A piston-like body (3) is installed in the shell (1). There is a gap between the outer wall of the piston-like body (3) and the inner wall of the shell (1). A sealing ring (4) is installed on the inner side of the stepped surface (2). The left end of the piston-like body (3) contacts the sealing ring (4). The piston-like body (3) divides the shell (1) into a first chamber (5) on the left and a second chamber (6) on the right; the first chamber (5) is equipped with a first liquid inlet pipe (7) and a first liquid outlet pipe (8). The mobile phase of the liquid chromatograph flows into the first chamber (5) through the first liquid inlet pipe (7) and then flows out through the first liquid outlet pipe (8). The second chamber (6) is filled with a liquid medium with a constant pressure, and the liquid pressure in the second chamber (6) is greater than the liquid pressure in the first chamber (5); A plurality of support bolts (9) are evenly distributed on the circumference of the stepped surface (2) of the housing (1). The support bolts (9) vertically penetrate the stepped surface (2). The heads of the support bolts (9) are equipped with a first pressure sensor (10). The left end of the piston-like body (3) contacts the heads of the support bolts (9). The first pressure sensor (10) measures the pressure at the contact point.

2. A high-precision liquid chromatograph mobile phase pressure measuring device according to claim 1, characterized in that: A second pressure sensor (11) is installed on the stepped surface (2). The second pressure sensor (11) contacts the left end of the sealing ring (4). The pressure between the sealing ring (4) and the stepped surface (2) can be measured by the second pressure sensor (11).

3. A high-precision liquid chromatograph mobile phase pressure measuring device according to claim 2, characterized in that: A plurality of the second pressure sensors (11) are evenly distributed around the circumference.

4. A high-precision liquid chromatograph mobile phase pressure measuring device according to claim 1, characterized in that: The sealing ring (4) is provided with a relief hole (12), and the right end of the supporting bolt (9) passes through the relief hole (12) and contacts the left end of the piston-like body (3).

5. The high-precision liquid chromatograph mobile phase pressure measuring device according to claim 1, characterized in that: The second chamber (6) is provided with a second liquid inlet pipe (13), a pressure stabilizing valve (14) is provided on the second liquid inlet pipe (13), and the second liquid inlet pipe (13) is connected to a quantitative liquid pump.

6. A high-precision liquid chromatograph mobile phase pressure measuring device according to claim 5, characterized in that: The second chamber (6) is provided with a second liquid outlet pipe (15), and the second liquid outlet pipe (15) is provided with a switch valve (16).

7. A high-precision liquid chromatograph mobile phase pressure measuring device according to claim 1, characterized in that: The right end of the housing (1) is provided with a pre-stressing bolt (17) along the axis of the housing (1). Before the liquid in the second chamber (6) is pressurized, the pre-stressing bolt (17) presses against the right end of the piston-like body (3) and keeps the sealing ring (4) in a compressed state.

8. The high-precision liquid chromatograph mobile phase pressure measuring device according to claim 1, characterized in that: The first chamber (5) is equipped with a temperature sensor (18) for detecting the temperature of the mobile phase.

9. The high-precision liquid chromatograph mobile phase pressure measuring device according to claim 1, characterized in that: The shell (1) is provided with a first end cover (19) at the left end and a second end cover (20) at the right end. Both the first end cover (19) and the second end cover (20) are connected to the shell (1) via threads.

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