A device for detecting formaldehyde concentration in an indoor environment

Abstract

The application belongs to the technical field of formaldehyde detection, and in particular discloses an indoor environment formaldehyde concentration detection device, which comprises a formaldehyde detector and a holding part, a pressing plug is arranged in the holding part, a cavity in the formaldehyde detector is connected with a U-shaped structure composed of a filter pipe and a reflux pipe at the end of the cavity, a one-way valve one is arranged at the side end of the filter pipe, and a one-way valve two is arranged at the side end of the reflux pipe, so as to control the one-way circulation of the airflow. The pressing plug is driven to reciprocate along the guide rail by a transmission assembly composed of a connecting seat, a second rod and a first rod, the sliding block shields the air inlet hole when moving, so that the cavity is sealed, when the pressing plug is pushed in, the gas in the cavity is forced to enter the filter pipe through the one-way valve one to filter out formaldehyde, when the pressing plug is pulled out, the gas returns through the reflux hole, the one-way valve two and the reflux pipe, after repeated circulation, a zero formaldehyde environment is established around the sensor and the zero point reference is automatically recorded. Meanwhile, the jacking sleeve is popped up along the inserting rod under the spring thrust and protrudes from the holding part shell, so as to forcibly warn that the filter pipe has reached the replacement period in a passive mechanical way.

Description

Technical Field

[0001] This invention relates to the field of formaldehyde detection technology, specifically to a device for detecting formaldehyde concentration in indoor environments. Background Technology

[0002] Handheld formaldehyde concentration detectors are widely used for indoor air quality monitoring. These devices typically include a housing, air inlet, semiconductor gas sensor, processing circuitry, and display screen. Their working principle involves the semiconductor gas sensor converting the formaldehyde concentration signal into an electrical signal, which is then processed by the circuitry and displayed on the screen as the current formaldehyde concentration value in the environment. Because semiconductor gas sensors suffer from zero-point drift, zero-point calibration in clean air is necessary after prolonged use. One existing calibration method involves introducing clean air filtered through activated carbon or chemical filters into the sensor as zero air, and then using this clean air as the new zero-point reference for the sensor's output signal.

[0003] However, existing handheld devices have the following shortcomings when performing zero-point calibration: First, relying on a micro-pump to drive gas circulation through a filter to obtain zero gas increases the device's power consumption, size, and cost. On the other hand, passive filtration relying on natural diffusion is difficult to fully replace the gas around the sensor with clean zero gas, resulting in low calibration efficiency and unreliable reference. Second, the built-in filter gradually wears out and fails during use, but users cannot intuitively know the remaining lifespan of the filter or when to replace it. If calibration is continued after the filter fails, it will introduce an incorrect zero-point reference, leading to a systematically lower subsequent measurement value. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides an indoor formaldehyde concentration detection device, which solves the problems of existing handheld formaldehyde detection devices lacking a manual air circulation drive method that does not rely on an electric pump, and users being unable to know the remaining lifespan of the built-in filter, resulting in invalid calibration and erroneous zero-point reference even after the filter fails.

[0005] To achieve the above objectives, the present invention provides the following technical solution: an indoor formaldehyde concentration detection device, comprising a formaldehyde detector and a grip, wherein the formaldehyde detector has an air inlet and a sensor is installed inside, and a cavity is opened inside the formaldehyde detector. The gripping part is provided with a squeeze plug inside. A filter tube and a return tube are respectively provided at the end of the cavity. The filter tube and the return tube are connected in the middle to form a U-shaped structure and merge into a pipe at the middle connection. A return hole is opened at the end of the middle pipe. The filter tube is provided with a one-way valve one on its side end, and the return pipe is provided with a one-way valve two on its side end. The one-way valve one only allows gas to flow from the cavity to the filter tube, and the one-way valve two only allows gas to flow from the return pipe to the cavity. The squeeze plug is connected to a manual operating component, which drives the squeeze plug to be pushed into or pulled out of the cavity. When the squeeze plug is pushed in, it compresses the gas around the sensor into the cavity and forces the gas to enter the filter tube through one-way valve one. The filtered gas returns to the cavity where the sensor is located through the return hole. When the squeeze plug is pulled out, the gas enters the cavity through the return hole, one-way valve two, and return pipe. Through the reciprocating motion of the squeeze plug, the gas circulates and filters in a closed loop formed by the cavity, filter tube, return pipe, and return hole until a zero-formaldehyde environment is formed around the sensor. The formaldehyde detector records the output signal of the sensor at this time as the zero-point reference value.

[0006] In some embodiments, the manual operating component is a slider located on the outside of the grip portion. The slider's stroke covers the air inlet, and when the slider is pushed, it covers the air inlet, thus isolating the sensor cavity from the outside world.

[0007] In some embodiments, guide rails connected to the inner wall of the gripping part are provided at the four corners of the squeeze plug. The guide rails are embedded inside the squeeze plug and extend to the end of the squeeze plug's stroke. The squeeze plug slides along the guide rails in a directional manner.

[0008] In some embodiments, the side end of the extrusion plug is provided with a transmission assembly consisting of rod one and rod two, and the end of rod two is provided with a connecting seat. The slider is connected to the transmission assembly through the connecting seat, and the thrust of the slider is transmitted to the extrusion plug through the connecting seat, rod two, and rod one.

[0009] In some embodiments, the filter tube is a replaceable tubular filter device with two ports facing the same side, connected to the exhaust end on the cavity side and the air port on the return hole side, respectively, and the filter tube is filled with a filter material that selectively adsorbs formaldehyde.

[0010] In some embodiments, the cavity containing the sensor is a strip-shaped groove structure with the same cross-section as the squeeze plug and a partition in the middle.

[0011] In some embodiments, a filter tube life warning mechanism is also included, which includes: The insert rod is located inside the gripping part, the lifting sleeve is sleeved on the top of the insert rod and can slide upward along the insert rod, and the spring is sleeved on the outside of the insert rod and provides upward preload to the lifting sleeve. A ring groove is opened on the outside of the lifting sleeve. An intercepting pin, which is rotatable and located inside the grip, is inserted into the annular groove on one side to limit the ejection of the lifting sleeve. A positioning post is located inside the grip section. A gear is located above the positioning post. The gear's central shaft is connected to the positioning post. A ratchet is coaxially located at the lower end of the gear. A ratchet tooth is located on one side of the ratchet tooth. A connecting shaft is located at the side end of the ratchet tooth. A cam disk is located below the ratchet. The connecting shaft is inserted into the surface of the cam disk.

[0012] In some embodiments, a collar is provided on the outer side of the second rod, and a rack is provided on the side end of the collar. The rack meshes with a gear. When the second rod is pushed forward, the rack drives the gear to rotate clockwise, and the gear drives the coaxial ratchet to rotate in the same direction, while the cam disk remains stationary. When the second rod is retracted, the rack drives the gear to rotate counterclockwise, and the ratchet rotates counterclockwise synchronously and abuts against the ratchet. The ratchet drives the cam disk to rotate counterclockwise through a tooth groove angle via the connecting shaft.

[0013] In some embodiments, when the cumulative number of times the squeeze plug is withdrawn reaches a preset value, the cam disc rotates a full revolution, and its protruding end abuts against the intercepting pin, forcing the intercepting pin to deflect out of the annular groove. The lifting sleeve loses its obstruction and, under the thrust of the spring, pops up along the insertion rod and protrudes out of the gripping housing.

[0014] In some embodiments, a damping rubber ring is provided at the connection between the intercepting needle and its central axis.

[0015] Compared with the prior art, the present invention provides an indoor formaldehyde concentration detection device, which has the following beneficial effects: By manually driving the reciprocating motion of the squeeze plug, and coordinating with the airflow direction control of one-way valves one and two, a forced unidirectional circulating airflow is established between the sensor cavity, filter tube, and return tube without the need for a micro air pump. Each push-pull operation forces the gas in the cavity to repeatedly pass through the filter tube, gradually filtering out formaldehyde until its concentration approaches zero. The sensor monitors and confirms the zero-point reference in real time during the dynamic cycle, ensuring reliable calibration results unaffected by the cleanliness of the external air source.

[0016] Simultaneously, the reciprocating motion of the squeeze plug, through the cooperation of the transmission components, rack, pinion, ratchet, and ratchet teeth, synchronously drives the cam disc to accumulate rotation angles, automatically and passively recording the number of times the filter tube is used in the mechanical counting mechanism. When the accumulated number of uses reaches the preset value, the cam disc triggers the intercepting pin to deflect out of the annular groove of the lifting sleeve. The lifting sleeve pops out under the thrust of the spring and protrudes from the grip housing, providing a clear physical signal to forcibly warn the user to replace the filter tube. The entire calibration operation and life warning share the reciprocating stroke of a single manual operating component, resulting in a highly integrated structure. No additional electronic control components or manual memorization of replacement cycles are required, avoiding the risk of incorrect calibration caused by continuing to use a filter tube after it has failed. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram showing the location of the internal cavity in the disassembled state of the outer shell of the gripping part of the present invention; Figure 3 This is a schematic diagram of the internal structure of the gripping part of the present invention; Figure 4 This is a schematic diagram of the guide rail distribution direction of the present invention; Figure 5 This is a schematic diagram of the overall pathway distribution of the filter tube and return tube of the present invention; Figure 6 This is a schematic diagram showing the overall orientation of the connection positions of rod one, rod two, and the extrusion plug in this invention; Figure 7 This is a schematic diagram showing the installation positions of the gears and racks of the present invention; Figure 8 This is a schematic diagram showing the detailed structural position of the gear, coaxial ratchet, and cam disc of the present invention.

[0018] In the diagram: 1. Formaldehyde detector; 2. Handle; 3. Air inlet; 4. Sensor; 5. Cavity; 6. Return hole; 7. Filter tube; 8. Return tube; 9. One-way valve 1; 10. One-way valve 2; 11. Squeezing plug; 12. Rod 1; 13. Rod 2; 14. Connecting seat; 15. Slider; 16. Guide rail; 17. Lifting sleeve; 18. Insert rod; 19. Spring; 20. Intercepting pin; 21. Cam plate; 22. Connecting shaft; 23. Ratchet; 24. Ratchet wheel; 25. Gear; 26. Rack; 27. Collar; 28. Ring groove; 29. ​​Positioning pin. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "front end," "rear end," "both ends," "one end," and "the other end," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device 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 invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0021] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "equipped with," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0022] Please see Figure 1-8 In this embodiment: an indoor formaldehyde concentration detection device includes a formaldehyde detector 1 and a grip part 2. The formaldehyde detector 1 has an air inlet 3 for taking in the detection gas, and a sensor 4 is installed inside it. A cavity 5 is opened inside the formaldehyde detector 1, and a squeeze plug 11 is installed inside the grip part 2. A filter tube 7 and a return tube 8 are respectively installed at the end of the cavity 5. The two tubes are connected in the middle to form a U-shaped structure and merge into a single tube at the middle connection point. A return hole 6 is opened at the end of the middle tube.

[0023] As the squeeze plug 11 moves into the cavity 5, it compresses the gas surrounding the sensor 4 into the cavity 5, forcing the gas to pass through the filter tube 7 to remove formaldehyde. The filtered gas then re-enters the cavity containing the sensor 4 through the return hole 6. This ensures that residual air must pass through the filter tube 7 and be filtered to zero before reaching the sensor 4, thus establishing a zero-formaldehyde environment within the sealed small space. The formaldehyde detector 1 then automatically records the output signal of the sensor 4 as the zero-point reference value, thereby achieving calibration.

[0024] To prevent impurities from being drawn back into the filter tube 7 during the reciprocating motion of the squeeze plug 11, one-way valve 9 and one-way valve 10 are respectively installed on the side ends of the filter tube 7 and the return pipe 8. When the squeeze plug 11 is pushed into the cavity 5, gas enters the return hole 6 only through the filter tube 7; when the squeeze plug 11 is pulled out, gas is drawn into the return pipe 8 through the return hole 6 until it is pulled out. That is, when the squeeze plug 11 is pushed into the cavity 5, the gas path of the filter tube 7 is connected; when the squeeze plug 11 is pulled out, the gas path of the return pipe 8 is connected.

[0025] The filter tube 7 is a replaceable tubular filter device, filled with a filter material that selectively adsorbs formaldehyde, such as activated carbon or potassium permanganate alumina, or other chemical filter media known in the art. This invention only incorporates adaptive design in its external shape and interface layout, ensuring that its two interfaces face the same side, facilitating a compact connection within the housing with the air vent of the chamber to which sensor 4 belongs.

[0026] The formaldehyde detector 1 employs common existing technologies and typically includes a housing, display screen, buttons, circuit board, and power module. The sensor 4 uses a semiconductor gas sensor to convert the formaldehyde concentration signal into an electrical signal. After processing by the circuitry, the signal is displayed on the screen in ppm or mg / m³ as the current formaldehyde concentration value. This part is a common existing technology and will not be described in detail below.

[0027] To ensure the stable movement of the squeeze plug 11 into the cavity 5, guide rails 16 are provided at its four corners, connected to the inner wall of the gripping part 2. The guide rails 16 are embedded inside the squeeze plug 11 and extend to the end of the squeeze plug 11's stroke. The squeeze plug 11 slides along the guide rails 16 to ensure its movement stability.

[0028] The squeeze plug 11 has a transmission assembly consisting of rod 12 and rod 23 on its side. A connecting seat 14 is located at the end of rod 23, and a slider 15 is located on the outer side of the grip 2. The slider 15 is connected to the connecting seat 14 for manually driving the squeeze plug 11. The user only needs to push the slider 15 with their thumb to transmit the pushing force through the connecting seat 14 to rod 12, rod 23, and finally to the squeeze plug 11. The air inlet 3 is within the stroke range of the slider 15. When the formaldehyde detector 1 needs calibration, the operator can cover the air inlet 3 while pushing the slider 15 forward, preventing external gas from entering the internal sealed space and disrupting the calibration environment.

[0029] To ensure that the squeeze plug 11 can compress most of the gas for filtration, the cavity of sensor 4 is designed as a strip-shaped groove structure. The cross-section of the cavity is the same as that of the squeeze plug 11, and a partition is made in the middle to further improve the sealing performance.

[0030] An insert rod 18 is disposed inside the grip portion 2, and a lifting sleeve 17 is fitted onto the top of the insert rod 18. The lifting sleeve 17 is inverted and attached to the outside of the insert rod 18, and can slide upward along the insert rod 18. A spring 19 is fitted onto the outside of the insert rod 18, and the spring 19 always provides axial preload to the upper lifting sleeve 17. The lifting sleeve 17 is used to pop outward under the thrust provided by the spring 19 until it protrudes from the housing of the grip portion 2, providing a warning to the user.

[0031] To control the ejection of the lifting sleeve 17, an annular groove 28 is formed on its outer side. Inside the gripping part 2, a rotatable intercepting pin 20 supported by a single axis is installed. A damping rubber ring is provided at the connection between the intercepting pin 20 and its central axis to prevent minor vibrations from causing the intercepting pin 20 to deviate. One side of the intercepting pin 20 is inserted into the annular groove 28 to limit the ejection of the lifting sleeve 17.

[0032] The gripping part 2 has a positioning post 29 inside, which provides support for extended connection. A gear 25 is located above the positioning post 29, and the central shaft of the gear 25 is connected to the positioning post 29 as a rotational support. A ratchet 24 is coaxially arranged at the lower end of the gear 25, and a ratchet tooth 23 is provided on one side of the ratchet 24. A connecting shaft 22 is provided on the side end of the ratchet tooth 23 for support. A cam disk 21 is located below the ratchet 24, and the connecting shaft 22 is inserted into the surface of the cam disk 21.

[0033] The rotation of gear 25 can drive ratchet 24. When gear 25 rotates clockwise, ratchet 24 rotates in the same direction, and the position of cam disk 21 remains unchanged; when gear 25 rotates counterclockwise, ratchet 24 also rotates counterclockwise. At this time, ratchet 24 abuts against ratchet 23, forcing ratchet 23 to drive cam disk 21 to rotate through connecting shaft 22.

[0034] A collar 27 is provided on the outer side of lever 13, and a rack 26 is provided on the side end of collar 27. The rack 26 is used to control the rotation of gear 25, and the rotation direction of gear 25 is related to the movement direction of lever 13. When lever 13 is pushed forward, rack 26 drives gear 25 to rotate clockwise; when lever 13 is retracted, rack 26 drives gear 25 to rotate counterclockwise. Since the movement of lever 13 is related to the squeeze plug 11, when squeeze plug 11 is pulled outward once, gear 25, through the engagement of ratchet 24 and ratchet 23, causes cam disk 21 to rotate counterclockwise by one tooth groove position. After cam disk 21 rotates one revolution, its protruding end abuts against intercepting pin 20, forcing intercepting pin 20 to deflect out of annular groove 28, and lifting sleeve 17 loses its obstruction and is ejected by spring 19.

[0035] Through the above structure, the ejection cycle of the lifting sleeve 17 is related to the number of times the squeeze plug 11 is pushed and pulled, and the number of times the squeeze plug 11 is squeezed is related to the number of times the filter tube 7 has been used. Therefore, the usage cycle of the filter tube 7 can be recorded by the number of teeth on the ratchet 24. For example, if the number of teeth on the ratchet 24 is set to 100, then pulling the squeeze plug 11 out 100 times means that the filter tube 7 has filtered 100 times. At this time, the lifting sleeve 17 ejects outward to remind the user that the filter element has reached the replacement cycle.

[0036] In this embodiment, before calibrating the formaldehyde detector 1, the slider 15 on the outside of the grip 2 is pushed. The slider 15 transmits force to the squeeze plug 11 through the connecting seat 14 via rod 2 13 and rod 12. The squeeze plug 11 moves into the cavity 5 along the guide rail 16. During the movement of the slider 15, it covers the air inlet 3, isolating the cavity where the sensor 4 is located from the outside. When the squeeze plug 11 moves forward, it squeezes the gas around the sensor 4 into the cavity 5. The gas is forced to enter the filter tube 7 through the one-way valve 1 9. The clean gas after formaldehyde removal returns to the cavity where the sensor 4 is located through the return hole 6. When the squeeze plug 11 is pulled out, the one-way valve 1 9 closes and the one-way valve 2 10 opens. The gas is drawn into the cavity 5 through the return pipe 8 from the return hole 6, and then pushed into the filter tube 7 again by the next push action. After repeated cycles, a zero-formaldehyde environment is formed around the sensor 4. The formaldehyde detector 1 records the output signal of the sensor 4 at this time as the zero-point reference value. Simultaneously, the reciprocating movement of lever 13 drives the rack 26 on its outer collar 27 to move back and forth. When pushing forward, rack 26 drives gear 25 to rotate clockwise, and gear 25 drives the coaxial ratchet 24 to rotate in the same direction, while cam disc 21 remains stationary. When retracting, rack 26 drives gear 25 to rotate counterclockwise, and ratchet 24 rotates counterclockwise and abuts against ratchet 23. Racket 23 drives cam disc 21 to rotate counterclockwise through one tooth groove angle via connecting shaft 22. Each time the extraction action is completed, cam disc 21 accumulates one tooth groove angle. When the number of extractions of squeeze plug 11 reaches the preset value, cam disc 21 rotates one full revolution, and its protruding end abuts against intercepting needle 20, causing it to deflect out of the annular groove 28 on the outer side of lifting sleeve 17. Lifting sleeve 17 loses its obstruction and, under the push of spring 19, pops upward along insertion rod 18 and protrudes out of the gripping part 2 housing, indicating that filter tube 7 has reached its replacement cycle.

[0037] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An indoor formaldehyde concentration detection device, comprising a formaldehyde detector (1) and a grip (2), wherein the formaldehyde detector (1) has an air inlet (3) and a sensor (4) is disposed inside it, and a cavity (5) is formed inside the formaldehyde detector (1), characterized in that: The gripping part (2) is provided with a squeeze plug (11) inside. A filter tube (7) and a return tube (8) are respectively provided at the end of the cavity (5). The filter tube (7) and the return tube (8) are connected in the middle to form a U-shaped structure and merge into a pipe at the middle connection. A return hole (6) is opened at the end of the middle pipe. The filter tube (7) is provided with a one-way valve (9) at its side end and a one-way valve (10) is provided at its side end. The one-way valve (9) allows gas to flow from the cavity (5) to the filter tube (7) and the one-way valve (10) allows gas to flow from the return pipe (8) to the cavity (5). The squeeze plug (11) is connected to a manual operating component, which is used to drive the squeeze plug (11) to push into the cavity (5) or to pull out of the cavity (5). When the squeeze plug (11) is pushed in, it squeezes the gas around the sensor (4) into the cavity (5) and forces the gas to enter the filter tube (7) through the one-way valve (9). The filtered gas returns to the cavity where the sensor (4) is located through the return hole (6). When the squeeze plug (11) is pulled out, the gas enters the cavity (5) through the return hole (6), the one-way valve (10) and the return pipe (8). The reciprocating motion of the squeeze plug (11) causes the gas to circulate and filter in the closed loop formed by the cavity (5), the filter tube (7), the return pipe (8) and the return hole (6) until a zero formaldehyde environment is formed around the sensor (4). The formaldehyde detector (1) records the output signal of the sensor (4) at this time as the zero reference value.

2. The indoor formaldehyde concentration detection device according to claim 1, characterized in that: The manual operating component is a slider (15) located on the outside of the grip (2). The stroke of the slider (15) covers the air inlet (3). When the slider (15) is pushed, it covers the air inlet (3) and isolates the cavity where the sensor (4) is located from the outside.

3. The indoor formaldehyde concentration detection device according to claim 2, characterized in that: The four corners of the squeeze plug (11) are provided with guide rails (16) connected to the inner wall of the gripping part (2). The guide rails (16) are embedded inside the squeeze plug (11) and extend to the end of the stroke of the squeeze plug (11). The squeeze plug (11) slides along the guide rails (16).

4. The indoor formaldehyde concentration detection device according to claim 3, characterized in that: The side end of the compression plug (11) is provided with a transmission assembly consisting of rod one (12) and rod two (13). The end of rod two (13) is provided with a connecting seat (14). The slider (15) is connected to the transmission assembly through the connecting seat (14). The thrust of the slider (15) is transmitted to the compression plug (11) through the connecting seat (14), rod two (13), and rod one (12).

5. The indoor formaldehyde concentration detection device according to claim 4, characterized in that: The filter tube (7) is a replaceable tubular filter device with its two ports facing the same side, and connected to the exhaust end on the cavity (5) side and the air port on the return hole (6) side, respectively. The filter tube (7) is filled with filter material that selectively adsorbs formaldehyde.

6. The indoor formaldehyde concentration detection device according to claim 1, characterized in that: The cavity to which the sensor (4) belongs is a strip-shaped groove structure, with the same cross-section as the squeeze plug (11), and a partition is made in the middle.

7. The indoor formaldehyde concentration detection device according to claim 5, characterized in that: It also includes a filter tube life warning mechanism, which comprises: The insert rod (18) is located inside the grip (2), the lifting sleeve (17) is sleeved on the top of the insert rod (18) and can slide upward along the insert rod (18), and the spring (19) is sleeved on the outside of the insert rod (18) and provides upward preload to the lifting sleeve (17). A ring groove (28) is opened on the outside of the lifting sleeve (17). An intercepting pin (20) is installed inside the grip (2) and is rotatable. The intercepting pin (20) is inserted into the annular groove (28) on one side to limit the ejection of the lifting sleeve (17). A positioning post (29) is set inside the grip (2). A gear (25) is set above the positioning post (29). The central shaft of the gear (25) is connected to the positioning post (29). A ratchet (24) is coaxially set at the lower end of the gear (25). A ratchet tooth (23) is set on one side of the ratchet tooth (23). A connecting shaft (22) is set on the side end of the ratchet tooth (23). A cam disk (21) is set below the ratchet tooth (24). The connecting shaft (22) is inserted into the surface of the cam disk (21).

8. The indoor formaldehyde concentration detection device according to claim 7, characterized in that: A collar (27) is provided on the outer side of the second rod (13), and a rack (26) is provided on the side end of the collar (27). The rack (26) meshes with the gear (25). When the second rod (13) is pushed forward, the rack (26) drives the gear (25) to rotate clockwise. The gear (25) drives the coaxial ratchet (24) to rotate in the same direction, and the cam disk (21) remains stationary. When the second rod (13) is pulled back, the rack (26) drives the gear (25) to rotate counterclockwise. The ratchet (24) rotates counterclockwise and abuts against the ratchet (23). The ratchet (23) drives the cam disk (21) to rotate counterclockwise by one tooth groove angle via the connecting shaft (22).

9. The indoor formaldehyde concentration detection device according to claim 8, characterized in that: When the cumulative number of times the squeeze plug (11) is pulled out reaches the preset value, the cam disk (21) rotates a full revolution, and its protruding end abuts against the intercepting needle (20), forcing the intercepting needle (20) to deflect out of the annular groove (28). The lifting sleeve (17) loses its obstruction and, under the thrust of the spring (19), pops up along the insert rod (18) and protrudes out of the gripping part (2) housing.

10. The indoor formaldehyde concentration detection device according to claim 9, characterized in that: A damping rubber ring is provided at the connection between the intercepting needle (20) and its central axis.

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