Anti-backflow pipette

Abstract

The invention belongs to the technical field of pipettes, and discloses an anti-backflow pipette which comprises a pipette body shell, a first-stage elastic joint, a second-stage elastic joint and a digital display group which are arranged in the pipette body shell, and a pressing adjusting group, an adjusting rod is arranged in the digital display group on the pressing adjusting group and is used for being matched with the digital display group to carry out digital display adjustment; an air chamber is arranged between the first-stage elastic joint and the digital display set, and the adjusting rod enters a rod cavity of the air chamber to be connected with a piston in the rod cavity. According to the invention, the valve core can be conducted only in the process of liquid absorption and liquid discharge. And when not in operation, the central gas path of the guide hole of the valve core is staggered to cut off the gas path. Therefore, the piston rod is partially isolated from the liquid taking suction head. And even if the pipette is put down, oscillated, shaken and the like, the liquid does not flow back. And the whole operation process of the pipette is not changed compared with that of a traditional pipette, and the anti-backflow effect can be achieved by normal use of an operator without deliberate operation.

Description

Technical Field

[0001] This invention belongs to the field of pipette technology, specifically a backflow-proof pipette. Background Technology

[0002] A pipette is a widely used instrument in biochemistry laboratories, essentially a more precise type of dropper. Its main principle lies in its piston stroke for volume addition and its knob adjustment mechanism. Most pipettes on the market do not include anti-backflow functionality; they rely on the airtightness between the tip and the tube to restrict liquid flow through pressure. However, when there is a large amount of liquid in the tip and the pipette is tilted, backflow can easily occur. Therefore, operating procedures must prohibit operators from laying the pipette horizontally; otherwise, backflow will contaminate or even corrode the delicate internal parts of the pipette, rendering the entire pipette unusable.

[0003] CN113546704B discloses a backflow prevention dispensing gun, relating to the field of dispensing gun technology. It includes a dispensing gun body, a backflow prevention assembly, a nozzle assembly, and a reinforcement assembly. The dispensing gun body has anti-slip textured edges on one side, and a piston pusher is mounted on its upper part. The backflow prevention assembly is fixed to the lower part of the dispensing gun body and includes an inlet tube, a backflow prevention chamber, a flow channel, a mounting frame, a high-pressure air bladder, a bellows, and a lifting baffle plate. The inlet tube is connected to the lower middle part of the dispensing gun body, and a backflow prevention chamber is installed on the lower exterior of the dispensing gun body. This backflow prevention dispensing gun, through the backflow prevention assembly, ensures that the high-pressure air bladder and bellows, along with the upper lifting baffle plate, tightly adhere to the lower outer side of the inlet tube, effectively sealing the inlet tube and preventing liquid backflow. During dispensing, the inclined micro-suction cup adheres tightly to the inner wall of the container, preventing air bubbles from forming during dispensing due to hand tremors.

[0004] The backflow prevention scheme in the aforementioned literature places the backflow prevention component before the drainage component, which means that the liquid is located after the backflow prevention component when it is added to the sample. The liquid may have already flowed back before the sample is added. In addition, the component also includes a check chamber and flow channel, etc. The liquid flow path is too long, which increases the amount of liquid residue in the path and makes it difficult to ensure the accuracy of the sample addition.

[0005] This application proposes an anti-backflow solution to overcome the above-mentioned defects and bring about a better anti-backflow effect when applied to pipettes. Summary of the Invention

[0006] To address the problems mentioned in the background section, the present invention provides an anti-backflow pipette.

[0007] To achieve the above object, the present application provides the following technical scheme: A backflow prevention pipette gun, comprising a gun body shell, a first elastic joint, a second elastic joint and a digital display group arranged in the gun body shell, and a pressing adjustment group, wherein an adjusting rod is arranged in the inside of the digital display group on the pressing adjustment group for cooperating with the digital display group to perform digital display adjustment;

[0008] A gas chamber is arranged between the first elastic joint and the digital display group, and a rod cavity of the adjusting rod entering the gas chamber is connected with a piston therein;

[0009] The gas chamber can compress the first elastic joint downward after gas is discharged therefrom.

[0010] The pipette gun further comprises a liquid taking and discharging group arranged below, one side of the liquid taking and discharging group is provided with a side gas channel communicated with the gas chamber, and the inside of the liquid taking and discharging group is further provided with a valve core.

[0011] Preferably, the gas chamber comprises a gas cavity vertically movably arranged in the inside of the gun body shell, the bottom of the gas cavity is supported by the first elastic joint, the inside of the gas cavity is further provided with a piston and an elastic cap arranged below the piston, and the inner cavity of the gas cavity is connected with the side gas channel through a hose.

[0012] Preferably, the liquid taking and discharging group comprises a liquid taking and discharging pipe, the bottom end of the liquid taking and discharging pipe is detachably sleeved with a detachable connector, the detachable connector is divided into upper and lower parts, the upper part of the detachable connector is communicated with the side gas channel and is internally provided with a valve core, and the lower part of the detachable connector is used for sleeving a liquid suction head.

[0013] Preferably, the upper part of the detachable connector is obliquely provided with a valve cavity, the valve cavity is cross-connected with a vertical gas channel in the inside of the detachable connector, the valve cavity is internally slidably provided with a valve core and an elastic member abutting on the bottom of the valve core, when there is no pressure in the side gas channel, the guide hole of the valve core is dislocated from the gas channel, and when there is pressure, the guide hole of the valve core is communicated with the gas channel.

[0014] Preferably, the upper part of the detachable connector is provided with an inclined boss for opening the valve cavity and accommodating the valve core, the outside of the inclined boss is provided with an inclined surface, and a gas groove is arranged on the inclined surface.

[0015] The bottom end of the side gas channel is provided with an inclined surface capable of being parallelly attached to the inclined surface of the inclined boss, and the inclined surface of the inclined boss is provided with a layer of air-tight ring.

[0016] Preferably, a snap ring is arranged on the top end inner wall of the valve cavity to limit the valve core below.

[0017] Preferably, the side of the gun body shell is slidably mounted with a removal suction head group, which is integrally elastically supported by a spring on the framework inside the gun body shell, and further comprises a push tube and a detachable push tube;

[0018] The push tube is movably sleeved outside the liquid taking and discharging pipe and the side air channel, and the detachable push tube is sleeved outside the detachable connector.

[0019] Preferably, vertical and uniform screw joints are arranged on the push tube and the detachable push tube, and the screw joints are used for screwing screws into the push tube and the detachable push tube for fixation.

[0020] The detachable push tube is divided into an upper part and a lower part, the upper part is sleeved outside the upper part of the detachable connector, and the lower part of the detachable push tube is sleeved outside the lower part of the detachable connector.

[0021] Preferably, a stepped surface is arranged at the joint of the upper part and the lower part of the detachable connector, and a bone piece is arranged inside the detachable push tube and supports the stepped surface, so as to support the detachable connector upward and tightly fit with the side air channel.

[0022] Preferably, a hollow cavity is arranged on the outer periphery of the push tube and is used for adapting to the external boss on the detachable connector.

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] 1. In the present application, a gas chamber is arranged inside the gun body shell, and a detachable connector is arranged. The gas chamber is used as an initial pressing section, and the elastic coefficient inside the gas chamber is the smallest compared with the first and second elastic sections. Therefore, the gas chamber is firstly pressed down in the pressing process, the pressure is finally borne by the pressing adjustment group, the adjustment rod pushes the piston in the gas chamber downward, the pressure in the gas cavity is increased and is conducted to the side air channel and the detachable connector through the hose, and then the valve core is pushed to open the vertical air path formed by the liquid taking and discharging pipe and the detachable connector. Only in the process of liquid suction and discharge, the valve core is opened. When not in operation, the central air path of the valve core is dislocated to cut off the air path, so that the piston rod and the liquid taking suction head are isolated. Even if the pipette is placed upside down, vibrated or shaken, liquid backflow will not occur. The operation process of the pipette is not changed compared with the traditional pipette, and the operator can achieve the backflow prevention effect by normal use, without special operation.

[0025] 2. This invention uses a valve core to block the backflow of liquid in the lower air passage of the detachable connector, preventing it from flowing back into the drain / intake pipe and contaminating the piston rod or even deeper components. In this case, the entire detachable connector can be disassembled, cleaned, dried, and then reassembled, or the entire detachable connector can be replaced. This minimizes the risk of contamination to delicate components such as the piston rod and spring in the internal drain / intake pipe.

[0026] 3. This invention also features a two-section splicing structure at the bottom of the removal nozzle assembly, with micro-screws screwed into the screw connector for connection and fixation. The detachable push tube and detachable connector have a clearance fit, preventing the detachable push tube from being obstructed by the inclined boss when descending. Furthermore, the detachable push tube's support plate can rest against the stepped surface of the detachable connector, using its elasticity to push the detachable connector upwards when the removal nozzle assembly is not pressed, further compressing the inclined boss and side air passage, deforming the airtight ring between their inclined surfaces, thereby enhancing overall airtightness. The lower half of the detachable push tube is adapted to the lower half of the detachable connector; when the detachable push tube is compressed downwards, it can directly kick off the lower nozzle, making the operation convenient. When disassembling or replacing the detachable connector, simply disassemble the detachable push tube and then pull out the detachable connector directly. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of the present invention;

[0028] Figure 2 This is an internal sectional view of the present invention;

[0029] Figure 3 This is a structural disassembly diagram of the present invention;

[0030] Figure 4 For the present invention Figure 3 Enlarged schematic diagram of part A;

[0031] Figure 5 For the present invention Figure 3 Enlarged diagram of part B;

[0032] Figure 6 This is a cross-sectional view of the detachable mechanism and detachable push tube of the present invention;

[0033] Figure 7 This is an external schematic diagram of the detachable structure of the present invention.

[0034] In the diagram: 100, gun body shell; 101, hook; 200, gas chamber; 201, gas cavity; 202, piston; 203, elastic cap; 204, hose; 300, primary elastic joint; 400, secondary elastic joint; 500, digital display assembly; 600, suction head removal assembly; 601, spring; 602, push tube; 603, detachable push tube; 6031, bone plate; 604, screw connector; 700, pressing adjustment assembly; 701, adjusting rod; 800, liquid extraction assembly; 801, liquid extraction tube; 802, side air passage; 803, detachable connector; 8031, valve cavity; 8032, elastic element; 8033, valve core; 8034, retaining ring; 8035, airtight ring; 8036, stepped surface; 8037, sloping boss. Detailed Implementation

[0035] 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.

[0036] First embodiment, such as Figures 1-3 As shown, the present invention provides an anti-backflow pipette, including a pipette housing 100 and a primary elastic joint 300, a secondary elastic joint 400, and a digital display assembly 500 disposed inside the pipette housing 100. It also includes a press adjustment assembly 700, on which an adjustment rod 701 is disposed inside the digital display assembly 500 for digital display adjustment. An air chamber 200 is disposed between the primary elastic joint 300 and the digital display assembly 500. The adjustment rod 701 enters the rod chamber of the air chamber 200 and connects to a piston therein. After gas is discharged from the air chamber 200, it can compress the primary elastic joint 300 downwards with the press adjustment assembly 700. The pipette also includes a lower dispensing / draining assembly 800, with a side air passage 802 communicating with the air chamber 200 on one side. A valve core is also disposed inside the dispensing / draining assembly 800, and the pressure transmitted through the side air passage 802 opens the dispensing / draining tube. The air chamber 200 includes an air cavity 201 vertically and movably installed inside the gun body shell 100. The bottom of the air cavity 201 is supported by a primary elastic joint 300. The air cavity 201 also has a piston 202 and an elastic cap 203 located below the piston 202. The inner cavity of the air cavity 201 is connected to the side air passage 802 through a hose 204. The liquid intake and drainage assembly 800 includes a liquid intake and drainage pipe 801. The bottom end of the liquid intake and drainage pipe 801 is detachably fitted with a detachable connector 803. The detachable connector 803 is divided into upper and lower parts. The upper part of the detachable connector 803 is connected to the side air passage 802 and has a valve core inside. The lower part of the detachable connector 803 is used to fit a liquid suction head.

[0037] In the above embodiment, by setting the air chamber 200 inside the gun body shell 100 and setting the detachable detachable joint 803. The air chamber 200 serves as the initial pressing section, and its internal elastic coefficient is smaller than that of the first-stage elastic section 300 and the second-stage elastic section 400. Therefore, it is pressed down first during the pressing process, and the pressing adjustment group 700 is pressed to finally make the adjustment rod 701 push the piston 202 in the air chamber 200 downward, and the pressure in the air cavity 201 increases and is conducted to the side air channel 802 and the detachable joint 803 through the hose 204. In turn, the valve core is pushed, and the vertical air path formed by the liquid suction and discharge pipe 801 and the detachable joint 803 is opened. As the pressure continues to increase, the first-stage elastic section 300 is pressed down, and the piston rod in the liquid suction and discharge group 800 is lowered synchronously to start the first-stage exhaust and liquid suction stage. In this stage, the second-stage elastic section 400 is not affected because its elastic coefficient is the highest. After the first-stage exhaust and liquid suction stage ends, the pressure is released. The air chamber 200 returns to its original state, and the pressure also recovers. The valve core in the detachable joint 803 resets, which originally cuts off the air path. Therefore, the piston rod and the liquid suction and discharge head are isolated. Even if the pipette is placed upside down, shaken, or shaken, liquid backflow will not occur.

[0038] When it is necessary to discharge the liquid in the suction head to the outside, the second-stage elastic section 400 is compressed after the first-stage elastic section 300 is pressed to the position. Because the elastic coefficients of the two are quite different, the operator will feel the segmentation very obviously. Continuous pressing to the bottom will completely discharge the liquid in the suction head, and the liquid suction and discharge process is completed.

[0039] The second embodiment, as shown in Figure 6 and Figure 7 The upper part of the detachable joint 803 is inclined to form a valve cavity 8031, which is cross-connected with the vertical air path inside the detachable joint 803. The valve core 8033 and the elastic member 8032 supporting the bottom of the valve core 8033 are slidably arranged in the valve cavity 8031. When there is no pressure in the side air channel 802, the guide hole of the valve core 8033 is misaligned with the air path. When there is pressure, the guide hole of the valve core 8033 is in communication with the air path. The upper part of the detachable joint 803 is provided with an inclined boss 8037 for forming the valve cavity 8031 and accommodating the valve core 8033. The outer part of the inclined boss 8037 is provided with an inclined surface, and the inclined surface is provided with an air groove. The bottom end of the side air channel 802 is provided with an inclined surface that can be parallelly attached to the inclined surface of the inclined boss 8037. The outer periphery of the inclined surface of the inclined boss 8037 is provided with a gas-tight ring 8035. The top inner wall of the valve cavity 8031 is provided with a snap ring 8034 to limit the valve core 8033 below.

[0040] In this embodiment, the liquid intake / exhaust assembly 800 is a two-section detachable connection. The side air passage 802 and the detachable connector 803 are connected by a sleeve joint, a quick and easy connection method. After the two are tightly pressed together, the valve chamber 8031 ​​in the upper part of the detachable connector 803 will form a communication channel with the side air passage 802, allowing the pressure in the air chamber 200 to directly act on the valve core 8033 through the side air passage 802. This pushes the valve core 8033 downwards along the valve chamber 8031, compressing the elastic element 8032 to contract. Initially, the vertical guide hole of the valve core 8033 and the vertical air passage of the detachable connector 803 are misaligned; after the valve core 8033 descends, they are in a connected state. Subsequently, the primary elastic joint 300 and the secondary elastic joint 400, in conjunction with the liquid intake / exhaust assembly 800, can perform the liquid intake / exhaust operation normally.

[0041] When liquid backflow occurs in the suction head, the liquid is blocked by the valve core 8033 in the lower air passage of the detachable connector 803, preventing it from flowing back into the drain / take-out tube 801 and contaminating the piston rod or even deeper components. Therefore, the entire detachable connector 803 can be disassembled, washed, dried, and reinstalled, or the entire detachable connector 803 can be replaced. This minimizes the risk of contamination to the piston rod, spring, and other delicate components in the drain / take-out tube 801.

[0042] The third embodiment, such as Figures 3-7 As shown, the suction head assembly 600 is slidably mounted on the side of the gun body shell 100. The suction head assembly 600 includes a spring 601 that elastically supports its entire structure on the internal frame of the gun body shell 100. The suction head assembly 600 also includes a push tube 602 and a detachable push tube 603. The push tube 602 is movably sleeved outside the liquid intake / exhaust tube 801 and the side air passage 802, and the detachable push tube 603 is sleeved outside the detachable connector 803. Both the push tube 602 and the detachable push tube 603 are provided with vertically aligned and identical screw connectors 604, which are used to screw screws into them to fix the push tube 602 and the detachable push tube 603. The detachable push tube 603 is divided into upper and lower parts. The upper part is sleeved outside the upper part of the detachable connector 803, and the lower part of the detachable push tube 603 is sleeved outside the lower part of the detachable connector 803. The upper and lower parts of the detachable connector 803 are connected by a stepped surface 8036. A bony plate 6031 is provided inside the detachable push tube 603, supporting the stepped surface 8036 to push the detachable connector 803 upwards, thus ensuring a tight fit with the side airway 802. A hollow cavity is provided on the outer periphery of the push tube 602 to accommodate the external protrusion on the detachable connector 803.

[0043] In the embodiment, the bottom end part of the pipette tip set 600 is also designed in two sections. The push tube 602 and the detachable push tube 603 are connected and fixed by screwing the micro screw in the screw joint 604 after alignment. The upper part of the detachable push tube 603 is sleeved on the upper half of the detachable joint 803. The inner cavity shape of the detachable push tube 603 and the vertical projection of the outer surface shape of the detachable joint 803 are in a containing relationship, and the two are in clearance fit, so that the detachable push tube 603 will not be interfered by the inclined boss 8037 when it goes down.

[0044] And the detachable push tube 603 is also provided with a bone piece 6031, which can be supported on the stepped surface 8036 of the detachable joint 803, and use the elastic force to push the detachable joint 803 upward when the pipette tip set 600 is not pressed, further compress the inclined boss 8037 and the side air duct 802, extrude and deform the air-tight ring 8035 between the two inclined surfaces, thereby enhancing the overall air tightness. When the bone piece 6031 is not arranged, the detachable joint 803 and the liquid taking and discharging pipe 801 can only be tightly fitted by the snap ring at the joint, which is easy to loosen.

[0045] The lower half of the detachable push tube 603 is adapted to the lower half of the detachable joint 803. When the detachable push tube 603 is extruded to go down, it can directly kick off the lower pipette tip. In operation, the overall maintains the original feel and process of the pipette gun, and a well-trained operator will not feel uncomfortable.

[0046] Working principle and use process of the present application:

[0047] When the pressing adjustment group 700 is pressed down, the air chamber 200 is the initial pressing section, and its internal elastic coefficient is the smallest compared with the first elastic section 300 and the second elastic section 400. Therefore, it is pressed down first in the pressing process, and the pressing adjustment group 700 is pressed to finally make the adjustment rod 701 push the piston 202 in the air chamber 200 downward, the pressure in the air cavity 201 increases and is conducted to the side air duct 802 and the detachable joint 803 through the hose 204. Then the valve core 8033 is pushed to open the vertical air path formed by the liquid suction and discharge pipe 801 and the detachable joint 803. As the pressure continues to increase, the first elastic section 300 is pressed down, and the piston rod in the liquid suction and discharge group 800 is synchronously lowered to start the first-stage liquid discharge and suction stage. After the first-stage liquid discharge and suction stage ends, the pressure is released. The air chamber 200 returns to its original state, and the pressure also recovers, and the valve core 8033 resets to cut off the original air path. Thus, the piston rod and the liquid suction head are isolated. Even if the pipette is placed upside down, shaken or shaken, liquid backflow will not occur. When the pipette is placed upside down or shaken, the liquid will be directly intercepted by the valve core 8033 and cannot enter the liquid suction and discharge pipe 801. Then the detachable joint 803 can be directly detached and replaced.

[0048] It should be noted that the relative terms such as first and second, etc. are used herein only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "contain" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or device.

[0049] Although the embodiments of the present application have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and alterations can be made without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A backflow prevention pipette, comprising a body shell (100) and a primary elastic joint (300), a secondary elastic joint (400) and a digital display group (500) arranged inside the body shell (100), characterized in that: Further comprising a pressing adjustment group (700), which is provided with an adjusting rod (701) inside the digital display group (500) for adjusting the digital display of the digital display group (500); The gas chamber (200) is arranged between the primary elastic section (300) and the digital display group (500), and the rod cavity of the adjusting rod (701) entering the gas chamber (200) is connected with a piston therein; The gas chamber (200) can be compressed with the pressing adjustment group (700) downwards after the gas is discharged therefrom. The liquid taking and discharging group (800) further comprises a valve core, and the pressure conducted through the side gas channel (802) can guide the liquid taking and discharging pipe.

2. A backflow resistant pipette according to claim 1, characterized in that: The gas chamber (200) comprises a gas cavity (201) vertically movably arranged inside the gun body shell (100), the bottom of the gas cavity (201) is supported by the primary elastic section (300), and the gas cavity (201) further comprises a piston (202) and an elastic cap (203) arranged below the piston (202); the inner cavity of the gas cavity (201) is connected with the side gas channel (802) through a hose (204).

3. The anti -backflow pipette according to claim 1, characterized in that: The liquid taking and discharging group (800) comprises a liquid taking and discharging pipe (801), the bottom end of the liquid taking and discharging pipe (801) is detachably sleeved with a detachable connector (803), the detachable connector (803) is divided into an upper part and a lower part, the upper part of the detachable connector (803) is in communication with the side gas channel (802) and is internally provided with a valve core, and the lower part of the detachable connector (803) is used for sleeving a liquid suction head.

4. A backflow resistant pipette according to claim 3, wherein: The upper part of the detachable connector (803) is obliquely provided with a valve cavity (8031), the valve cavity (8031) is cross-connected with a vertical gas channel in the detachable connector (803), the valve cavity (8031) is slidably provided with a valve core (8033) and an elastic member (8032) supporting the bottom of the valve core (8033), when there is no pressure in the side gas channel (802), the guide hole of the valve core (8033) is dislocated from the gas channel, and when there is pressure, the guide hole of the valve core (8033) is in communication with the gas channel.

5. A backflow resistant pipette according to claim 4, wherein: The upper part of the detachable connector (803) is provided with an inclined boss (8037) for opening the valve cavity (8031) and accommodating the valve core (8033), the outer part of the inclined boss (8037) is provided with an inclined surface, and the inclined surface is provided with a gas groove; The bottom end of the side gas channel (802) is provided with an inclined surface capable of being parallelly attached to the inclined surface of the inclined boss (8037), and the outer periphery of the inclined surface of the inclined boss (8037) is provided with a gas-tight ring (8035).

6. A backflow resistant pipette according to claim 4 or 5, characterized in that: The inner wall of the top end of the valve cavity (8031) is provided with a snap ring (8034) for limiting the valve core (8033) below.

7. A backflow resistant pipette according to any one of claims 3-5, characterized in that: The side of the gun body shell (100) is slidably mounted with a removal suction head group (600), the removal suction head group (600) includes a spring (601) which elastically supports the whole on the framework inside the gun body shell (100), the removal suction head group (600) further includes a push tube (602) and a detachable push tube (603); The push tube (602) is movably sleeved outside the liquid taking and discharging pipe (801) and the side air channel (802), and the detachable push tube (603) is sleeved outside the detachable joint (803).

8. A backflow resistant pipette according to claim 7, wherein: The push tube (602) and the detachable push tube (603) are both provided with vertically aligned and consistent specification screw joints (604), the screw joints (604) are used for screwing screws into the push tube (602) and the detachable push tube (603) for fixing the push tube (602) and the detachable push tube (603); The detachable push tube (603) is divided into upper and lower two parts, the upper part is sleeved outside the upper part of the detachable joint (803), and the lower part of the detachable push tube (603) is sleeved outside the lower part of the detachable joint (803).

9. A backflow resistant pipette according to claim 8, wherein: The upper part and the lower part of the detachable joint (803) are provided with a stepped surface (8036) at the joint, the inside of the detachable push tube (603) is provided with a bone piece (6031) which is supported on the stepped surface (8036), and the detachable joint (803) is supported upward so as to be closely attached to the side air channel (802).

10. The anti -backflow pipette according to claim 7, characterized in that: The push tube (602) is provided with a hollow cavity outside the circumference for adapting to the external boss on the detachable joint (803).

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