Dental handpiece assembly capable of preventing back suction
By introducing a multi-stage check valve structure and flexible tubing into the dental handpiece assembly, the problems of contaminant retention and cross-infection caused by back suction after dental handpiece use are solved, achieving both equipment safety and convenient disinfection.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-18
- Publication Date
- 2026-03-10
AI Technical Summary
Dental handpieces are prone to backflow after use, which can lead to the retention of contaminants and pose a risk of cross-infection, especially when the contaminants contain pathogenic microorganisms, thus posing a health threat to patients and healthcare workers.
A dental handpiece assembly with anti-backflow feature was designed, employing a multi-stage check structure and flexible tubing, including primary, secondary, and tertiary check structures. Reverse flow of the medium is prevented through elastic elements and movable valve cores, and independent sealing and sterilization of each tubing are achieved by combining detachable connectors and gaskets.
It effectively prevents contaminants from lingering in pipes and equipment, reduces the risk of cross-infection, and ensures the safety of dental procedures and the removable sterilization of equipment.
Smart Images
Figure CN223979862U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of dental equipment, specifically to a dental handpiece assembly for preventing backflow. Background Technology
[0002] Dental handpieces use compressed air to drive a high-speed rotating impeller, which in turn drives a dental drill to rotate at high speed for cutting. When the air supply stops, the impeller continues to rotate briefly due to inertia. Simultaneously, due to the water hammer effect, a negative pressure is generated at the head of the dental handpiece, drawing in nearby saliva and other liquids. Contaminants retained in the dental handpiece, air / water supply pipes, air supply system, or water supply system can be carried into the mouth of the next patient, potentially causing iatrogenic cross-infection. This is especially true if these contaminants contain highly infectious pathogens, which could pose a serious health threat to the next patient. Currently, dental handpieces require disinfection after each use. However, contaminants in the backflow delivery pipes and air / water supply equipment cannot be effectively eliminated. Furthermore, current dental handpieces are only replaced after each patient's use, leaving the sealed connectors of the end pipe open. This allows pathogen-containing media from the handpiece to easily spill into the treatment room or operating room, posing a risk of pathogen contamination to the medical environment and the hands of medical staff disassembling the handpiece. In addition, under normal circumstances, the media delivery pipes, air source, and water source systems cannot be disinfected for each person at a single frequency. During the next use or dental treatment, pathogens from the handpiece, pipes, air source, water source systems, and the medical environment can easily be introduced into the next patient's mouth, posing a potential risk of cross-infection. Summary of the Invention
[0003] The purpose of this invention is to address the shortcomings of existing technologies by providing a dental handpiece assembly that prevents backflow. It has a simple and compact structure, prevents backflow from contaminating pipes and equipment, and avoids cross-infection.
[0004] The purpose of this utility model is achieved as follows: a dental handpiece assembly for preventing backflow, comprising:
[0005] The mobile phone has a first front sealing end face with N protruding insertion tubes at its tail end, where N≥2;
[0006] The first connector is detachably connected to the mobile phone. Its downstream end is provided with a first rear sealing end face. The first connector has N cavities inside. Each cavity has an insertion hole section downstream for insertion of the insertion pipe. The upstream end is sealed and connected to the outer pipe. The N or NM cavities are provided with a first-level check structure.
[0007] The first sealing gasket is sandwiched between the front sealing end face and the first rear sealing end face, and has a through hole for the insertion pipe to pass through;
[0008] The first locking cap is fitted over the first connector and is detachably connected to the tail end of the mobile phone and axially presses the first connector to make the first sealing gasket press and seal.
[0009] The flexible conduit has a second connector and a third connector at both ends. The second connector is detachably connected to the first connector. The flexible conduit includes N branch pipes, each branch pipe connecting to the corresponding cavity within the second and third connectors. A secondary check structure is installed in the cavity upstream of the primary check structure in the second connector; M is an integer and M <N。
[0010] The third connector is a detachable connector used for detachable connection with the supply equipment. A tertiary check structure is provided in the cavity of the third connector located upstream of the secondary check structure.
[0011] The check valve structure includes an elastic element, a movable valve core, and a valve orifice arranged sequentially inside the cavity. The elastic element presses against the valve core to close the valve orifice.
[0012] The downstream end of the second connector is provided with a second rear sealing end face, the downstream of the internal cavity is provided with an insertion hole section, the upstream sealing connection is provided with an external pipe, the tail end of the first connector is provided with a second front sealing surface, the second locking cap sleeved on the second connector is detachably connected to the first connector and axially presses the second connector, and a second sealing gasket is provided between the first and second connectors.
[0013] The upstream end of the third connector is provided with a third rear sealing end face and a third sealing gasket adapted to the sealing end face, which is used for sealing connection with the interface of the supply equipment. The upstream of its internal cavity is provided with an insertion hole section, and the downstream sealing connection is an external pipe. The third locking cap, which is sleeved on the outside of the third connector, is used to connect with the water tank interface and press the third sealing gasket tightly.
[0014] Each locking cap has an internal thread for connection and an internal limiting protrusion in its inner hole. An external limiting protrusion is provided on the outer periphery of the connector corresponding to each locking cap. The inner limiting protrusion and the outer limiting protrusion are positioned by axial interference.
[0015] The first and second joints have a check valve structure in the cavity, which includes a stepped hole section. The small diameter section of the stepped hole section is an insertion hole section, and the large diameter section is equipped with an elastic element and a movable valve core. The elastic element abuts against the shoulder of the stepped hole section. The large diameter section of the stepped hole is sealed to the insertion end of the outer pipe, and the inner insertion end of the outer pipe is provided with a valve hole.
[0016] The third connector has a check valve structure in the cavity, which includes a stepped hole section. The small diameter section of the stepped hole section is an insertion hole section, and the large diameter section contains an elastic element and a movable valve core. The large diameter section of the stepped hole section is sealed to the insertion end of the outer pipe, and the elastic element abuts against the outer pipe. A valve hole is provided at the shoulder of the stepped hole section.
[0017] The downstream end of the external tube is press-fitted with the corresponding lumen.
[0018] The outer pipe end is provided with a tapered joint, a pagoda joint, or a quick connector; the mobile phone and the first locking cap are connected by threads, buckles, or clamps.
[0019] The present invention has a simple and compact structure, which can prevent contamination of pipelines and water and gas source equipment, and can avoid the risk of cross-infection caused by bacteria and viruses remaining in the pipelines for driving gas, water intake and atomizing gas.
[0020] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Attached Figure Description
[0021] Figure 1 This is a schematic diagram of the structure of this utility model;
[0022] Figure 2 An exploded view of the connection structure between the mobile phone and the first connector;
[0023] Figure 3 This is a schematic diagram of the installation structure of the movable valve core;
[0024] Figure 4 This is a schematic diagram of the fourth lumen.
[0025] Figure 5 This is a schematic diagram of the cross-sectional structure of the third connector.
[0026] In the attached diagram, 100 is the mobile phone, 102 is the first rear sealing end face, 103 is the second front sealing surface, 110 is the insertion pipe, 200 is the first connector, 201 is the first front sealing end face, 202 is the inner limiting protrusion, 210 is the cavity, 211 is the insertion hole section, 212 is the outer pipe, 213 is the elastic element, 214 is the movable valve core, 215 is the valve hole, 218 is the large diameter section, 219 is the hole shoulder, and 300 is the second... A sealing gasket, 310 is a through hole, 400 is a first locking cap, 410 is an outer limiting protrusion, 500 is a flexible pipe, 510 is a branch pipe, 600 is a second connector, 602 is a second rear sealing end face, 603 is a second locking cap, 604 is a second sealing gasket, 700 is a third connector, 702 is a third rear sealing end face, 703 is a third sealing gasket, 800 is a third locking cap, and 2121 is a tapered connector. Detailed Implementation
[0027] Referring to the accompanying drawings, specific embodiments of the present invention will be described in detail.
[0028] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0029] In the description of this application, it should be understood that the terms center, upper, lower, front, back, left, right, vertical, horizontal, top, bottom, inner, and outer, indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing this application and 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, and therefore should not be construed as a limitation of this application. In the description of this application, 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 indicated technical features. Thus, features defined as first and second can be used to explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, multiple means two or more. It should be noted that in practical applications, due to limitations in equipment accuracy or installation errors, absolute parallelism or perpendicularity is difficult to achieve. The descriptions of vertical, parallel, or unidirectional in this application are not absolute limitations, but rather indicate that vertical or parallel structural settings can be achieved within a preset error range, and the corresponding preset effects can be achieved. In this way, the technical effects of the defined features can be maximized, and the corresponding technical solutions can be easily implemented, thus having high feasibility.
[0030] In the description of this specification, references to the terms "an embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.
[0031] See Figure 1-5, An embodiment of a dental handpiece 100 that prevents backflow includes: the handpiece 100, the first joint 200, the first gasket 300, and the flexible pipeline 500. The handpiece 100 has a front sealing end face with N extended insertion pipes 110 at the tail end, where N is greater than or equal to 2 and N is an integer. The handpiece 100 usually has two-hole, three-hole, four-hole, or six-hole types, and N is 2, 3, 4, or 6 respectively. For example, two holes are used for inlet drive gas and return gas; the four-hole type is used for inlet drive gas, atomizing gas, inlet water, and return gas. When there is a return gas pipeline, the outlet pipeline does not need to be provided with a valve core to seal the pipeline.
[0032] The first joint 200 is detachably connected to the handpiece 100. The detachable connection method can be threaded connection, snap connection, or hoop connection, etc. After use, the handpiece 100 can be separated for separate disinfection, which is more thorough. Its downstream end has a first rear sealing end face 102. The first joint 200 has N cavities 210 inside. Each cavity 210 has an insertion hole section 211 at the downstream for the insertion pipe 110 to be inserted, and the upstream is hermetically connected to the external connection pipe 212. The external connection pipe 212 can be a straight pipe joint. The external connection pipe 212 can also be provided with an external tapered joint 2121 or a pagoda head, which can be connected to a flexible pipeline or inserted into a conventional dental pipeline joint. And an anti-backflow structure of the first level is provided in N or N - M cavities 210;
[0033] The first gasket 300 is sandwiched between the front sealing end face and the first rear sealing end face 102 and has a through hole 310 for the insertion pipe 110 to pass through;
[0034] The first locking cap 400 is sleeved outside the first joint 200, is detachably connected to the tail end of the handpiece 100, and axially presses the first joint 200 to press and seal the first gasket 300;
[0035] The flexible pipeline 500 has a second joint 600 and a third joint 700 at both ends. The second joint 600 is detachably connected to the first joint 200. The flexible pipeline 500 includes N branch pipelines. Each branch pipeline 510 communicates with the corresponding cavity 210 in the second and third joints 700. A second-level anti-backflow structure is provided in the cavity 210 corresponding to the upstream of the first-level anti-backflow structure in the second joint 600; M is an integer and M < N. 2 Further, the third joint 700 is a detachable joint for detachably connecting to a supply device. A third-level anti-backflow structure is provided in the cavity 210 located upstream of the second-level anti-backflow structure in the third joint 700. Specifically in this embodiment, see Figures 1-3 , The handpiece 100 has a front sealing end face at its tail end and four externally extended insertion pipes 110 protruding from the front sealing end face; three of the four insertion pipes 110 can be used as channels for atomizing gas, inlet water, and inlet air respectively, and the other insertion pipe 110 can be used as an exhaust channel,
[0036] The connector can be made of plastic or metal, preferably stainless steel. Its downstream end has a rear sealing face, and multiple sealing grooves or sealing protrusions can be provided on the sealing surface to allow the sealing gasket to be embedded, thereby improving the sealing performance. The sealing gasket can be made of rubber.
[0037] It is understandable that the first front sealing surface, the first rear sealing surface, and the first sealing gasket 300 turns can achieve a sealed connection between the rear end of the handpiece 100 and the first connector 200, and make each channel independent of each other. The four lumens 210 can be used for the insertion and docking of four insertion tubes 110, which can meet the transmission of four working media of the handpiece 100 in dental operation, and can realize the needs of water inlet, air inlet, atomized gas inlet, and gas exhaust. Among them, the gas exhaust tube is located downstream of the patient, and it is necessary to prevent leakage and contamination between it and other tubes. Since the water inlet, air inlet, and atomized gas inlet tubes are prone to backflow, the three lumens 210 are arranged with A check valve structure, such as a movable valve core 214, is provided. Under the action of the elastic element 213, the movable valve core 214 forms a normally closed structure. When the pressure of the water, air, or atomized gas entering from the upstream end forces the movable valve core 214 to overcome its elastic force, the passage between the valve core and the valve hole 215 is opened, allowing continuous water, air, or atomized gas intake. When backflow occurs, and the medium needs to move in the opposite direction, the backflow pressure acts on the valve core, simultaneously superimposed with the elastic pressure of the elastic element 213, making the valve core and valve hole 215 close more tightly. This prevents the backflow working medium from entering the pipeline or the rear end of the connector, thus preventing pipeline contamination. The first locking cap 400 is detachably connected to the tail end of the handpiece 100 for easy disassembly. The handpiece 100 can be removed separately and disinfected independently from the first connector 200, ensuring thorough disinfection and simplifying the structure of the handpiece 100, avoiding difficulties in disinfection and maintenance. Meanwhile, the first connector 200 and the second connector 600 are detachably connected. After use, by first disassembling the first connector 200 and the second connector 600, the first connector 200 and the mobile phone 100 can form a sealed space, preventing liquid from flowing out of the mobile phone 100 after disassembly. At the same time, the downstream end of the flexible pipe 500 can be sealed off through a connector to prevent air contamination inside the pipe.
[0038] Since the mobile phone 100 typically requires disinfection after each single use, and the first connector 200 needs frequent disassembly, frequent disassembly can easily lead to seal failure, further increasing the risk of contamination in the pipeline and source equipment. Furthermore, the high-frequency disinfection of the mobile phone 100 and the first connector 200, coupled with their internal structures susceptible to fluctuating temperatures, can easily cause backflow and seal failure. The secondary check valve structure prevents the backflow of pathogens. The exposed end of the second connector 600 can be wiped or soaked for disinfection. By installing multiple connectors and at least two levels of check valve structures along the entire mobile phone 100 supply route, it is possible to further prevent backflow of liquid into equipment such as the compressor and water tank that are not frequently disinfected or replaced.
[0039] When a three-stage check valve structure is installed, the flexible conduit 500 can be completely sealed at both ends via connectors, preventing the risk of leakage during disassembly. The flexible conduit 500 is designed for single use, especially after use by patients carrying infectious pathogens, significantly reducing the risk of cross-infection and preventing leakage during disassembly. During disassembly, the first connector 200 and the second connector 600 are removed first. The first connector 200 and the mobile phone 100 form an independent integrated structure. Similarly, the flexible conduit 500, the second connector 600, and the third connector 700 form an independent integrated structure, preventing potential contaminants from the mobile phone 100 and the flexible conduit 500 from flowing into the external space, allowing for transfer under low-risk conditions.
[0040] The check structure can be a diaphragm check or a swing check structure. In some embodiments, the check structure includes an elastic element 213, a movable valve core 214, and a valve orifice 215 arranged sequentially within a cavity 210. The elastic element 213 presses against the valve core to close the valve orifice 215. The elastic element 213 can be a helical compression spring. The movable valve core 214 is arranged in three of the cavities 210. Under the action of the elastic element 213, the movable valve core 214 forms a normally closed structure. When the pressure of the water, air, or atomized gas at the upstream end causes the movable valve core 214 to overcome the elastic force, the passage end face of the valve core and the valve orifice 215 is open, allowing continuous water, air, or atomized gas intake. When backflow occurs and the medium needs to move in the opposite direction, the backflow pressure acts on the valve core and is superimposed with the elastic pressure of the elastic element 213, making the valve core and valve orifice 215 close more tightly, preventing the backflow working medium from entering the pipeline or the rear end of the connector in reverse, thus preventing pipeline contamination. The movable valve core 214 is spherical, and the valve orifice 215 is spherical. The spherical valve core utilizes a sealing method between the ball and the valve orifice 215, providing excellent sealing performance and effectively preventing media leakage. The spherical valve core achieves opening and closing control through ball movement, ensuring smooth operation and minimizing noise and vibration. Its simple structure makes it easy to manufacture and process, resulting in a long service life. The spherical valve core offers flexible switching, reducing the likelihood of jamming, and its low friction during use ensures stable and accurate flow. Alternatively, the movable valve core 214 can also be conical or other shapes, with the valve orifice 215 adapted to its shape.
[0041] In some embodiments, the cavities 210 with check valve structures in the first and second connectors 600 include stepped bore sections. The smaller diameter section of the stepped bore section is an insertion section 211, and the larger diameter section 218 contains an elastic element 213 and a movable valve core 214. The elastic element 213 abuts against the shoulder 219 of the stepped bore section. The larger diameter section 218 of the stepped bore seals against the insertion end of the outer connecting pipe 212, and the inner insertion end of the outer connecting pipe 212 is provided with a valve hole 215. The stepped bore structure facilitates the installation of the elastic element 213 and the movable valve core 214, resulting in lower processing costs, a simple and compact structure, and weight reduction. The fourth cavity 210 of the four cavities includes a straight bore section. The front section of the straight bore section forms the insertion section 211, and the rear section forms a rear connection hole. This cavity 210 is used for venting. The straight bore section is easy to process and can have a large flow cross-section to facilitate gas discharge.
[0042] In some embodiments, the cavity 210 of the third connector 700 with a check valve structure includes a stepped bore section. The small-diameter section of the stepped bore section is an insertion section 211, and the large-diameter section 218 contains an elastic element 213 and a movable valve core 214. The large-diameter section 218 of the stepped bore seals against the insertion end of the outer connecting pipe 212, and the elastic element 213 abuts against the outer connecting pipe 212. A valve hole 215 is provided at the shoulder 219 of the stepped bore section. The stepped bore structure facilitates the installation of the elastic element 213 and the movable valve core 214, reduces processing costs, and results in a simple, compact structure that also reduces weight.
[0043] In some embodiments, the downstream end of the outer tube 212 is interference-fitted with the corresponding cavity 210, and a valve hole 215 is provided at the front end of the outer tube 212. This structure facilitates the processing of the valve hole 215, especially when the valve hole 215 is located at the outer end of the outer tube 212, making processing convenient and reducing production costs. The downstream end of the outer tube 212 is inserted into the corresponding cavity 210 and interference-fitted with the inner wall of the cavity 210. This connection structure is simple, has good centering accuracy, can withstand torque, axial force, or a combination of both loads, and has high load-bearing capacity. It can also work reliably under impact and vibration loads. At the same time, this connection structure can achieve excellent sealing, and is particularly suitable for small-sized pipe connections, enabling the overall size and weight of the mobile phone 100 to be smaller. Of course, the outer tube 212 can also be connected by bonding or other methods; it can also be an integral structure with the main body of the first connector 200.
[0044] In some embodiments, the downstream end of the second connector 600 is provided with a second rear sealing end face 602, the downstream end of the internal cavity 210 is provided with an insertion section 211, the upstream end is sealed and connected to the outer pipe 212, the tail end of the first connector 200 is provided with a second front sealing surface 103, the second locking cap 603, which is sleeved on the second connector 600, is detachably connected to the first connector 200 and axially presses the second connector 600, and a second sealing gasket 604 is provided between the first and second connectors 600. The second connector 600 is connected to the tail end of the first connector 200 by the second locking cap 603, and after pressing, the relative independence and sealing of each pipeline are achieved simultaneously.
[0045] In some embodiments, the connection form of the third connector 700 can be the same as that of the second connector 600. The upstream end of the third connector 700 is provided with a third rear sealing end face 702 and a third sealing gasket 703 adapted to the sealing end face for sealing connection with the interface of the supply equipment. The upstream of its internal cavity 210 is provided with an insertion section 211, and the downstream sealing connection is an external pipe 212. The third locking cap 800, which is sleeved on the third connector 700, is used to mate with the water tank interface and press the third sealing gasket 703. With this structure, a detachable connection structure can be realized, while the pipelines can be relatively sealed.
[0046] In some embodiments, the inner hole of each locking cap is provided with an internal thread for connection and an inner limiting protrusion 202. An outer limiting protrusion 410 is provided on the outer periphery of the connector corresponding to each locking cap. The inner limiting protrusion 202 and the outer limiting protrusion 410 are positioned by axial interference. With this structure, each locking cap can achieve axial tightening by connecting the connector to be connected via a thread, and by axial interference positioning, axial pressure is applied to the corresponding connector, and the sealing gasket is pressed tight. This enables the independence and sealing of each flow channel, preventing air or water leakage. The outer limiting protrusion 410 can be an annular shoulder, and the inner limiting protrusion 202 can be an annular shoulder 219. The fit between the shoulder and the shoulder 219 enables limiting, pressure transmission, and tightening of the connector.
[0047] Using the above scheme, before dental treatment, the sterilized handpiece 100 can be locked into a single structure by using a locking cap to secure the first connector 200. Flexible pipes connect the first connector 200 and the water tank interface via the second connector 600 and the third connector 700, respectively. At each connector connection, a compressed sealing gasket ensures that each channel is independent, meeting the transmission requirements of the four working media of the handpiece 100 during dental procedures. This allows for water intake, air intake, atomized gas intake, and gas exhaust, achieving aseptic preparation of the entire device. After treatment, the handpiece 100 and the first connector 200 can be disassembled as a whole, and then individually disassembled for sterilization. Common sterilization methods such as high-temperature sterilization can be used. Through a multi-stage check valve structure, when backflow occurs and the media needs to move in the opposite direction, the backflow pressure acts on the valve core, simultaneously superimposed with the elastic pressure of the elastic element 213. This results in a tighter closure between the valve core and the valve orifice 215, preventing the backflow working media from entering the pipe or the rear end of the connector, thus preventing pipe contamination and avoiding the risk of cross-infection caused by bacteria and viruses remaining in the pipe.
[0048] The above description is merely a preferred embodiment of this utility model and is not intended to limit the scope of this utility model. Obviously, those skilled in the art can make various modifications and variations to this utility model without departing from its spirit and scope. Therefore, if these modifications and variations of this utility model fall within the scope of the claims of this utility model and their equivalents, this utility model also intends to include these modifications and variations.
Claims
1. A backflow resistant dental handpiece assembly, comprising: The utility model relates to a detachable connection device for flexible pipe, which comprises: a mobile phone (100) with a first front sealing end face (201) provided with N (N>=2) external plug-in pipes (110) at the tail end; a first connector (200) detachably connected with the mobile phone (100) and provided with a first rear sealing end face (102) at the downstream end, N pipe cavities (210) in the first connector (200), a plug-in hole section (211) provided at the downstream end of each pipe cavity (210) for the plug-in pipe (110) to be plugged in, and an external connecting pipe (212) sealingly connected at the upstream end, and a first check valve structure provided in N or N-M pipe cavities (210); a first sealing gasket (300) clamped between the front sealing end face and the first rear sealing end face (102) and provided with a through hole (310) for the plug-in pipe (110) to pass through; a first locking cap (400) sleeved on the outside of the first connector (200) and detachably connected with the tail end of the mobile phone (100) to axially compress the first connector (200) and make the first sealing gasket (300) tightly sealed; a flexible pipe (500) provided with a second connector (600) and a third connector (700) at both ends, the second connector (600) being detachably connected with the first connector (200), the flexible pipe (500) comprising N branch pipes, each branch pipe (510) being connected with a corresponding pipe cavity (210) in the second and third connectors (700), and a second check valve structure being provided in the pipe cavity (210) in the second connector (600) corresponding to the upstream of the first check valve structure; M is an integer and M < N.
2. The anti-backflow dental handpiece assembly of claim 1, wherein: The third connector (700) is a detachable connector used for detachable connection with a supply device, and a third check valve structure is provided in the pipe cavity (210) in the third connector (700) upstream of the second check valve structure.
3. A backflow preventing dental handpiece assembly according to claim 1 or 2, wherein: The check valve structure comprises an elastic element (213), a movable valve core (214) and a valve hole (215) provided in the pipe cavity (210) in sequence, and the elastic element (213) is pressed against the valve core to close the valve hole (215).
4. The anti-backflow dental handpiece assembly of claim 1, wherein: The downstream end of the second connector (600) is provided with a second rear sealing end face (602), the downstream end of the internal pipe cavity (210) is provided with a plug-in hole section (211), and the upstream end is sealingly connected with an external connecting pipe (212), the tail end of the first connector (200) is provided with a second front sealing face (103), a second locking cap (603) sleeved on the outside of the second connector (600) is detachably connected with the first connector (200) and axially compresses the second connector (600), and a second sealing gasket (604) is arranged between the first and second connectors (600).
5. The anti-backflow dental handpiece assembly of claim 2, wherein: The upstream end of the third connector (700) is provided with a third rear sealing end face (702) and a third sealing gasket (703) matched with the sealing end face for sealing connection with an interface of a supply device, the upstream end of the internal pipe cavity (210) is provided with a plug-in hole section (211), and the downstream end is sealingly connected with an external connecting pipe (212), and a third locking cap (800) sleeved on the outside of the third connector (700) is used for abutting against a water tank interface and compressing the third sealing gasket (703).
6. A reverse suction preventing dental handpiece assembly according to claim 4 or 5, wherein: The inner hole of each locking cap is provided with an inner thread for connection and an inner limiting protrusion (202), and the outer periphery of the joint of each locking cap is provided with an outer limiting protrusion (410), and the inner limiting protrusion (202) and the outer limiting protrusion (410) are positioned in axial interference.
7. The anti-backflow dental handpiece assembly of claims 1 or 4, wherein: The pipe cavity (210) provided with a check structure in the first and second joints (600) comprises a stepped hole section, the small-diameter section of the stepped hole section is a plug hole section (211), an elastic element (213) and a movable valve core (214) are arranged in the large-diameter section (218), the elastic element (213) abuts against a hole shoulder (219) of the stepped hole section; the large-diameter section (218) of the stepped hole is sealingly matched with the inserted end of the external pipe (212), and the inserted end of the external pipe (212) is provided with a valve hole (215).
8. The anti-backflow dental handpiece assembly of claims 1 or 5, wherein: The pipe cavity (210) provided with a check structure in the third joint (700) comprises a stepped hole section, the small-diameter section of the stepped hole section is a plug hole section (211), an elastic element (213) and a movable valve core (214) are arranged in the large-diameter section (218), the large-diameter section (218) of the stepped hole is sealingly matched with the inserted end of the external pipe (212), the elastic element (213) abuts against the external pipe (212), and the valve hole (215) is arranged at the hole shoulder (219) of the stepped hole section.
9. A reverse suction preventing dental handpiece assembly according to claim 4 or 5, wherein: The downstream end of the external pipe (212) is in interference fit with the corresponding pipe cavity (210).
10. The anti-backflow dental handpiece assembly of claim 1, wherein: The end of the external pipe (212) is provided with a taper joint (2121), a pagoda joint or a quick joint; the mobile phone (100) and the first locking cap (400) are connected through threads, buckles or hoops.