Active back pressure piston vacuum gauge

Abstract

The utility model discloses an active back pressure piston type vacuum gauge, including at least one cylinder, a piston is movably arranged in the inside of cylinder and is spaced apart with the inner wall of cylinder predetermined distance, and the piston divides the inside of cylinder into vacuum cavity and back pressure cavity, is provided with pressure spring in back pressure cavity. Back pressure vacuum pump, and the suction port of back pressure vacuum pump communicates with back pressure cavity. The vacuum chamber of measurement, and the exhaust port of back pressure vacuum pump and the vacuum cavity of cylinder communicate with the vacuum chamber of measurement respectively. When working, back pressure vacuum pump continuously pumps out the air of back pressure cavity, and the piston moves under the pressure difference of vacuum cavity and back pressure cavity and compresses pressure spring. Under the effect of back pressure vacuum pump, the pressure ratio of back pressure cavity and vacuum cavity is lower than a certain value, and back pressure vacuum pump constantly pumps away the gas that leaks from the gap, and even if the air pressure of vacuum cavity changes, still actively keep the pressure ratio lower than a certain value, so that just need to measure the displacement of piston, and the air pressure value can be obtained.

Description

Technical Field

[0001] This utility model relates to the field of vacuum gauge technology, specifically to an active back pressure piston vacuum gauge. Background Technology

[0002] A vacuum gauge is an instrument used to measure the degree of vacuum. It is an indispensable component of a vacuum system, used to monitor, control, and ensure that processes are conducted under the required vacuum environment. Based on their measurement principles, vacuum gauges can be classified into: those utilizing mechanical properties, those utilizing gas dynamics effects, and those utilizing charged particle effects.

[0003] Patent document No. 2008201693182 discloses a compensated vacuum gauge, specifically comprising a cylindrical body with a certain degree of transparency. The inner cavity of the body has two working zones of different diameters. A piston and an indicator connected to the piston are installed within each working zone. A compression spring is installed at the other end of the piston. A sealing gas plug is installed at one end of the body, and a stopper with a connection hole is installed at the other end. The body is mounted on a support, which has a scale plate. In use, the vacuum support is fixed horizontally, with its tail connected to the environment being measured. When the external air pressure decreases, the air pressure at both ends of the piston becomes unbalanced. The gas (or compression spring) inside the sealed cavity pushes the piston outward, thus visually displaying the measured vacuum level (or absolute pressure).

[0004] The aforementioned patent can measure vacuum levels, but it has the following problems: 1. The piston and the cylindrical body are in direct contact, resulting in significant friction. This makes the vacuum gauge insensitive to minute pressure changes, thus reducing accuracy and sensitivity. Furthermore, long-term use can easily cause wear on the piston and the cylindrical body. 2. To reduce friction, the piston and the cylindrical body cannot be pressed too tightly, but this can lead to poor sealing at both ends of the piston, causing gas leakage inside the cavity. This leakage directly contaminates the measurement results. Utility Model Content

[0005] In view of the problems existing in the prior art, the purpose of this utility model is to provide an active back pressure piston vacuum gauge that can achieve accurate measurement of air pressure.

[0006] To achieve the above objectives, the technical solution of this utility model is as follows: An active backpressure piston vacuum gauge includes at least one cylinder, a piston movably disposed inside the cylinder and spaced a predetermined distance from the inner wall of the cylinder, the piston dividing the interior of the cylinder into a vacuum chamber and a backpressure chamber, a compression spring disposed in the backpressure chamber, one end of the compression spring being connected to the piston and the other end being connected to the lower end face of the interior of the cylinder; a backpressure vacuum pump, the suction port of the backpressure vacuum pump being connected to the backpressure chamber; a test vacuum chamber, the exhaust port of the backpressure vacuum pump and the vacuum chamber of the cylinder being connected to the test vacuum chamber respectively; during operation, the backpressure vacuum pump continuously pumps air into the backpressure chamber, and the piston moves under the pressure difference between the vacuum chamber and the backpressure chamber and compresses the compression spring.

[0007] Furthermore, an iron core is provided at the lower end of the piston along the axial direction of the cylinder, and an inductor coil is axially provided on the lower end face of the cylinder along the axial direction of the cylinder, with the iron core cooperating with the inductor coil. Furthermore, the piston is provided with a magnetic ring, which cooperates with a magnetic induction switch disposed on the outer wall of the cylinder. Furthermore, the outer wall of the cylinder is provided with main scale graduation lines, and the outer wall of the piston is provided with vernier scale graduation lines, the main scale graduation lines and the vernier scale graduation lines are matched. Furthermore, the piston is made of aluminum alloy. Furthermore, the pressure ratio between the vacuum chamber and the back pressure chamber is greater than 100. Furthermore, there are two cylinders, and the two cylinders have different ranges. The suction port of the back pressure vacuum pump is connected to the back pressure chamber of each of the two cylinders. Furthermore, the cylinder includes an upper end cover and a lower end cover. The upper end cover is disposed in the opening at the upper end of the cylinder, and the lower end cover is disposed in the opening at the lower end of the cylinder. The two ends of the compression spring are respectively connected to the piston and the lower end cover. The beneficial effects of this utility model are as follows: 1. The compression of the spring is used to indicate the air pressure. The piston is driven by the pressure difference on both sides to overcome the spring force and produce displacement. The displacement of the piston is also the change in the compression of the spring. Multiplying it by the spring coefficient gives the spring force. Dividing the spring force by the piston area gives the air pressure of the vacuum to be measured.

[0008] Second, there is a gap between the piston and the inner wall of the cylinder, so the friction force between the piston and the cylinder can be ignored. Only the pressure difference of the air pressure and the elastic force of the compression spring affect the relative displacement of the piston. Therefore, the measurement accuracy is high. The leakage of the gap between the piston and the cylinder is removed by the back pressure vacuum pump, keeping the back pressure less than one percent of the vacuum chamber to be measured. Therefore, the influence of the back pressure can be ignored and the air pressure can be directly calculated.

[0009] Third, by adjusting the piston diameter and spring parameters, different measurement ranges can be flexibly configured to cover the range from low and medium vacuum to partial high vacuum.

[0010] Fourth, the air pressure value can be calculated by measuring the change in inductance of an inductor coil.

[0011] Fifth, by combining the scale lines of the main scale and the vernier scale, more precise displacement can be read, thereby improving measurement accuracy.

[0012] 6. By cooperating with the magnetic ring on the piston and the magnetic induction switch on the outer wall of the cylinder, a switch signal can be output to the control system when the pressure to be measured reaches the preset pressure value, so as to facilitate subsequent steps.

[0013] 7. Two cylinders with different measuring ranges can be used in combination, with back pressure provided by a back pressure vacuum pump, thereby expanding the measurement range. Attached Figure Description

[0014] Figure 1 This is a structural diagram of a preferred embodiment of the present invention; Figure 2 This is an enlarged structural schematic diagram of the present invention; Figure 3 This is a structural diagram of another preferred embodiment of the present invention.

[0015] Figure Labels 1. Cylinder; 11. Vacuum chamber; 12. Back pressure chamber; 13. Magnetic induction switch; 14. Main scale graduation line; 15. Upper end cover; 16. Lower end cover; 2. Piston; 21. Magnetic ring; 22. Vernier scale graduation line; 3. Compression spring; 4. Back pressure vacuum pump; 5. Vacuum chamber to be tested; 6. Iron core; 7. Inductor coil; 8. First cylinder; 9. Second cylinder. Detailed Implementation

[0016] In the description of this utility model, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", "top surface", "bottom surface", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the position or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0017] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features. Thus, the use of "first" and "second" to define a feature may explicitly or implicitly include one or more of that feature. In this description of the utility model, "a number" means two or more, unless otherwise explicitly specified.

[0018] In this utility model, unless otherwise explicitly specified and limited, the terms "assembly," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can also refer to a mechanical connection; they can refer to a direct connection or a connection through an intermediate medium; or they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0019] In this embodiment, "interface" refers to the boundary line or contact surface between two different materials or media.

[0020] The utility model will be further described below with reference to the accompanying drawings and specific embodiments. The following description is merely exemplary and does not limit the scope of protection of the utility model.

[0021] This utility model discloses an active back-pressure piston vacuum gauge, comprising at least one cylinder 1, a piston 2 movably disposed inside the cylinder 1 and spaced a predetermined distance from the inner wall of the cylinder 1, the piston 2 dividing the interior of the cylinder 1 into a vacuum chamber 11 and a back-pressure chamber 12, a compression spring 3 disposed in the back-pressure chamber 12, one end of the compression spring 3 being connected to the piston 2, and the other end being connected to the lower end face of the interior of the cylinder 1. A back-pressure vacuum pump 4, the suction port of the back-pressure vacuum pump 4 being connected to the back-pressure chamber 12. A vacuum chamber 5 to be measured, the exhaust port of the back-pressure vacuum pump 4 and the vacuum chamber 11 of the cylinder 1 being connected to the vacuum chamber 5 to be measured. During operation, the back-pressure vacuum pump 4 continuously pumps air into the back-pressure chamber 12, and the piston 2 moves under the pressure difference between the vacuum chamber 11 and the back-pressure chamber 12, compressing the compression spring 3.

[0022] Specifically, on the one hand, because the back pressure vacuum pump 4 actively evacuates the back pressure chamber 12 (i.e., continuously provides back pressure to the back pressure chamber 12), its pressure is much lower than that of the vacuum chamber 11. This results in a low back pressure in the back pressure chamber 12, making the pressure difference across the piston 2 approximately equal to the gas pressure in the vacuum chamber 11. This allows the displacement of the piston 2 to directly reflect the pressure to be measured. On the other hand, there is a gap between the piston 2 and the inner wall of the cylinder 1, meaning that gas will leak from the vacuum chamber 11 (high-pressure side) to the back pressure chamber 12 (low-pressure side). The vacuum chamber 11 is connected to the vacuum chamber 5 to be measured, and its gas pressure is higher (the pressure to be measured), while the back pressure chamber 12 is evacuated, resulting in a lower gas pressure. If the back pressure vacuum pump 4 were not used to evacuate the piston, the leaked gas would accumulate in the back pressure chamber 12, causing the pressure in the back pressure chamber 12 to gradually increase. This would change the pressure difference across the piston 2, making the piston 2 displacement inaccurate and thus affecting the accuracy of the gas pressure measurement. In this design, on the one hand, the suction port of the back pressure vacuum pump 4 is connected to the back pressure chamber 12, continuously removing gas leaking from the gap and actively maintaining a stable and low pressure in the back pressure chamber 12. On the other hand, there is a gap between the piston 2 and the inner wall of the cylinder 1, so there is no friction between the piston 2 and the inner wall of the cylinder 1, meaning there are no other external forces affecting the accuracy of the pressure measurement data. This ensures that the pressure difference mainly depends on the pressure in the vacuum chamber 11 (the pressure to be measured).

[0023] More specifically, piston 2 moves under the influence of the pressure difference on both sides and compresses spring 3. When piston 2 stabilizes, the force generated by the pressure difference balances the elastic force of spring 3, at which point the following formula holds: ,in The pressure to be measured is the pressure in vacuum chamber 11. Let A be the air pressure in the back pressure chamber 12, k be the effective area of ​​piston 2, k be the spring constant of compression spring 3, and X be the effective displacement of compression spring 3 (which is also equivalent to the effective displacement of piston 2). Since the back pressure vacuum pump 4 maintains the back pressure chamber 12 at a relatively stable low back pressure, the air pressure in the back pressure chamber 12 can be ignored or treated as a correction term. After simplification, we can obtain... That is, the elastic force of the compression spring 3 is obtained from the effective displacement of the piston 2, and the elastic force is divided by the effective area of ​​the piston 2 to finally obtain the air pressure of the vacuum chamber 11.

[0024] Of course, in some other embodiments, different measurement ranges can be formed by adjusting the effective area of ​​the piston 2 and the parameters of the compression spring 3 (such as the outer diameter of the compression spring 3, the wire diameter of the compression spring 3, and the effective number of coils of the compression spring 3), thereby covering the range from low and medium vacuum to partial high vacuum.

[0025] As a preferred embodiment of this utility model, it must meet the aforementioned requirements. Therefore, the back pressure of the back pressure chamber 12 is so small as to be negligible. Thus, in this embodiment, the pressure ratio between the vacuum chamber 11 and the back pressure chamber 12 is greater than 100. This means that, throughout the entire measurement range of the vacuum gauge, the back pressure... The back pressure is always less than 1% of the current pressure to be measured, thus ensuring that the theoretical error caused by ignoring the back pressure is always less than 1%, thereby meeting the requirements of precision measurement. Specifically, in this embodiment, the back pressure vacuum pump 4 is a vacuum pump suitable for medium to high vacuum, and its flow rate is greater than the leakage of the piston 2 gap.

[0026] As a preferred embodiment of this utility model, the cylinder 1 is always placed vertically during use, so that the piston 2 is not affected by lateral forces.

[0027] In a preferred embodiment of this invention, an iron core 6 is provided at the lower end of the piston 2 along the axial direction of the cylinder 1, and an inductor coil 7 is axially arranged on the lower end face of the cylinder 1 along the axial direction of the cylinder 1. The iron core 6 and the inductor coil 7 cooperate with each other. Specifically, the iron core 6 moves towards the inductor coil 7 as the piston 2 moves, and gradually overlaps with the inductor coil 7 axially. The inductance value of the inductor coil 7 varies depending on the depth of overlap between the inductor coil 7 and the iron core 6. When the impedance of the inductor coil 7 changes in the AC circuit, and the voltage remains constant, the current changes with the position of the piston 2. The current value in the circuit is converted from analog to digital and sent to a microprocessor (not shown in the figure) for processing and conversion into the air pressure of the vacuum chamber 5 to be measured, and outputs a digital air pressure signal, which becomes a digital barometer, so as to obtain a more accurate air pressure value.

[0028] In a preferred embodiment of this invention, the piston 2 is made of aluminum alloy. Firstly, using lightweight aluminum alloy for the piston 2 minimizes the influence of gravity, allowing the spring force of the compression spring 3 to be almost entirely determined by the pressure difference, simplifying calculations and calibration, and improving measurement accuracy. Secondly, aluminum alloy is a non-ferromagnetic material. The alternating magnetic field generated by the inductor coil 7 needs to penetrate the iron core 6 and change the magnetic reluctance of the magnetic circuit through the displacement of the iron core 6, thereby causing a change in inductance. If the piston 2 itself is a magnetic material (e.g., steel), it would form a bypass magnetic circuit, severely interfering with or even short-circuiting the magnetic field of the coil, making the relationship between the inductance change and the displacement of the iron core 6 non-linear, insensitive, or even completely ineffective.

[0029] In a preferred embodiment of this invention, the piston 2 is provided with a magnetic ring 21, which cooperates with a magnetic induction switch 13 disposed on the outer wall of the cylinder 1. Specifically, the magnetic induction switch 13 is installed at a specific position on the outer wall of the cylinder 1, which is equivalent to pre-setting a pressure value. When the piston 2 moves to a position at the same level as the magnetic induction switch 13, it indicates that the pressure of the vacuum chamber 5 under test has reached the aforementioned pre-set pressure value, thereby enabling the output of a switch signal to the control system (not shown in the figure) for subsequent operation.

[0030] Specifically, the side of piston 2 is coated with a friction-reducing coating to prevent displacement deviation of piston 2 after long-term use, which could cause scratches on the inner wall of cylinder 1.

[0031] In a preferred embodiment of this invention, the outer wall of the cylinder 1 is provided with a main scale graduation line 14, and the outer wall of the piston 2 is provided with a vernier scale graduation line 22. The main scale graduation line 14 and the vernier scale graduation line 22 cooperate with each other. Specifically, the vernier scale graduation line 22 has twenty divisions, and the vernier scale graduation line 22 is the length of nineteen divisions of the main scale. That is, when the vernier scale graduation line 22 is aligned with the main scale graduation line 14, the accurate value of one-twentieth of the division of the main scale graduation line 14 can be read, thereby improving the measurement accuracy.

[0032] In a preferred embodiment of this invention, the cylinder 1 is a transparent tube, which allows for direct reading of the air pressure value.

[0033] In a preferred embodiment of this utility model, the cylinder 1 includes an upper end cover 15 and a lower end cover 16. The upper end cover 15 covers the opening at the upper end of the cylinder 1, and the lower end cover 16 covers the opening at the lower end of the cylinder 1. The two ends of the compression spring 3 are connected to the piston 2 and the lower end cover 16, respectively.

[0034] In another preferred embodiment of this utility model, there are two cylinders 1 with different measurement ranges. The intake port of the back pressure vacuum pump 4 is connected to the back pressure chamber 12 of each of the two cylinders 1. Specifically, the two cylinders 1 are a first cylinder 8 and a second cylinder 9. The measurement range of the first cylinder 8 is 0-10 Pa, and the measurement range of the second cylinder 9 is 0-500 Pa. The first cylinder 8 and the second cylinder 9 share a single back pressure vacuum pump 4 to provide back pressure, thereby covering the pressure measurement range from 0.01 Pa to 500 Pa. It should be noted that the first cylinder 8 and the second cylinder 9 are no different from the cylinders 1 described above except for their measurement ranges; they are only used to better distinguish between the two cylinders 1 with different measurement ranges.

[0035] Of course, there can be more than two cylinders 1, and the ranges of these cylinders 1 are all different.

[0036] The above description is a further detailed explanation of the present utility model in conjunction with specific preferred embodiments. It should not be considered that the specific implementation of the present utility model is limited to these descriptions. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the present utility model, and all such deductions or substitutions should be considered to fall within the protection scope of the present utility model.

Claims

1. An active backpressure piston vacuum gauge, characterized in that, include: At least one cylinder, a piston is movably disposed inside the cylinder and spaced a predetermined distance from the inner wall of the cylinder, the piston divides the interior of the cylinder into a vacuum chamber and a back pressure chamber, a compression spring is disposed in the back pressure chamber, one end of the compression spring is connected to the piston and the other end is connected to the lower end face of the interior of the cylinder; A back pressure vacuum pump, wherein the suction port of the back pressure vacuum pump is connected to the back pressure chamber; The vacuum chamber to be tested is connected to the exhaust port of the back pressure vacuum pump and the vacuum chamber of the cylinder, respectively. During operation, the back pressure vacuum pump continuously pumps air into the back pressure chamber, and the piston moves under the pressure difference between the vacuum chamber and the back pressure chamber, compressing the compression spring.

2. The active back pressure piston vacuum gauge according to claim 1, characterized in that: The piston has an iron core at its lower end along the axial direction of the cylinder, and an inductor coil is provided on the lower end face of the cylinder interior along the axial direction of the cylinder. The iron core and the inductor coil cooperate with each other.

3. The active back pressure piston vacuum gauge according to claim 1, characterized in that: The piston is equipped with a magnetic ring, which cooperates with a magnetic induction switch disposed on the outer wall of the cylinder.

4. The active back pressure piston vacuum gauge according to claim 1, characterized in that: The outer wall of the cylinder is provided with main scale graduation lines, and the outer wall of the piston is provided with vernier scale graduation lines, with the main scale graduation lines cooperating with the vernier scale graduation lines.

5. The active back pressure piston vacuum gauge according to claim 1, characterized in that: The piston is made of aluminum alloy.

6. The active back pressure piston vacuum gauge according to claim 1, characterized in that: The pressure ratio between the vacuum chamber and the back pressure chamber is greater than 100.

7. The active back pressure piston vacuum gauge according to claim 1, characterized in that: The cylinder has two barrels with different ranges, and the suction port of the back pressure vacuum pump is connected to the back pressure chamber of each of the two cylinders.

8. The active back pressure piston vacuum gauge according to claim 1, characterized in that: The cylinder includes an upper end cover and a lower end cover. The upper end cover is disposed in the opening at the upper end of the cylinder, and the lower end cover is disposed in the opening at the lower end of the cylinder. The two ends of the compression spring are respectively connected to the piston and the lower end cover.

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