Improved m3 screw-on feedthrough filter

Abstract

The utility model discloses an improved M3 screw feedthrough filter relates to feedthrough filter structure technical field. Among them, the thread section end face of metal screw shell is bonded with the polytetrafluoroethylene gasket of the metal lead sleeve joint cooperation through the encapsulation material, the polytetrafluoroethylene conduit that can extrude elimination encapsulation material inner interstice is still inserted in the thread section inner hole of metal screw shell, and the polytetrafluoroethylene conduit is set up outside the metal lead, and the both ends of polytetrafluoroethylene conduit are in contact with the setting of the through -type filter and polytetrafluoroethylene gasket respectively. The utility model provides an improved M3 screw feedthrough filter, and its simple structure, low cost and can significantly improve the pressure level.

Description

Technical Field

[0001] This utility model relates to the field of feedthrough filter structure technology, and in particular to an improved M3 screw-mounted feedthrough filter. Background Technology

[0002] M3 screw-mounted feedthrough filters are widely used in signal transmission systems, combining isolation, shielding, and filtering functions. They are favored for their small size and light weight. The structure of a traditional M3 screw-mounted feedthrough filter is as follows: Figure 1 As shown, the device includes a screw-on metal housing with a through-hole filter internally mounted. A metal lead is coaxially mounted inside the metal housing, penetrating the through-hole filter and extending to the outside of the housing at both ends. The gap between the metal housing and the metal lead is filled with encapsulating material. Traditional M3 screw-on feedthrough filters typically have a maximum operating voltage of 200V and a withstand voltage of 2.5 times the maximum operating voltage, i.e., 500V. However, with increasing application demands, users require a withstand voltage of 1250V (corresponding to an operating voltage of 500V), a requirement that traditional structures and manufacturing processes cannot meet. Specifically, as... Figure 2 As shown: Due to structural size limitations, the gap between the inner hole of the threaded section of the existing M3 screw-on feedthrough filter and the metal lead wire is typically no more than 0.4 mm, with a depth greater than 4 mm. When using traditional potting processes, high-viscosity resin encapsulants have the following inherent defects during filling: First, the narrow cavity structure makes it difficult for the encapsulant to completely fill the bottom, easily trapping air and forming voids that cannot be expelled; second, air bubbles mixed in during stirring and potting cannot be completely eliminated, forming randomly distributed micro-gaps after curing. Since the dielectric strength of air is only 1.5 kV / mm, far lower than the 5-10 kV / mm of the encapsulant itself, when the aforementioned voids exist inside the product, the actual withstand voltage will significantly decrease to below 600V. Under a test voltage of 1.25 kV, the internal air gaps are highly susceptible to dielectric breakdown, leading to short-circuit failure of the product.

[0003] Furthermore, existing M3 screw-on feedthrough filters, due to the less than 0.5mm minimum air gap between the threaded end face of their metal screw-on housing and the lead wire, are prone to surface discharge or arcing under high-voltage testing or application conditions, further limiting the product's withstand voltage performance. To meet higher withstand voltage requirements, existing technologies typically use larger M4 or larger screw-on housings to increase the gap and improve withstand voltage. However, this sacrifices the miniaturization advantage of the M3 structure and cannot fundamentally solve the internal defects caused by the potting process.

[0004] Therefore, how to effectively improve the withstand voltage of the M3 screw-on filter to above 1.25 kV while maintaining the original structural dimensions, and avoid internal breakdown and external arcing caused by the potting process, has become a technical problem that urgently needs to be solved in this field. Utility Model Content

[0005] The purpose of this invention is to provide an improved M3 screw-mounted feedthrough filter, which has a simple structure, low cost, and significantly improved withstand voltage level.

[0006] The technical solution of this utility model to solve the above-mentioned technical problems is: an improved M3 screw-mounted feedthrough filter, including a metal screw-mounted shell, a through-hole filter, metal leads and encapsulating material, wherein a polytetrafluoroethylene gasket that is sleeved and matched with the metal leads is bonded to the threaded end face of the metal screw-mounted shell through the encapsulating material. The threaded section of the metal screw-on outer shell is also inserted with a polytetrafluoroethylene (PTFE) conduit that can squeeze out the voids in the encapsulating material. The PTFE conduit is sleeved outside the metal lead wire, and its two ends are respectively in contact with the through-hole filter and the PTFE gasket.

[0007] As a further improvement of this utility model, the inner diameter of the polytetrafluoroethylene conduit is adapted to the outer diameter of the metal lead wire, and the outer diameter of the polytetrafluoroethylene conduit is smaller than the inner diameter of the inner hole of the threaded section of the metal screw-on outer shell.

[0008] As a further improvement of this utility model, the length of the polytetrafluoroethylene conduit is not less than the depth of the inner hole of the threaded section of the metal screw-on outer shell.

[0009] As a further improvement of this utility model, the polytetrafluoroethylene gasket has a through hole in the center for the metal lead wire to pass through, and the outer diameter of the polytetrafluoroethylene gasket is larger than the inner diameter of the inner hole of the threaded section of the metal screw-on housing.

[0010] As a further improvement of this utility model, the thickness of the polytetrafluoroethylene gasket is 0.5mm to 1.5mm.

[0011] As a further improvement of this utility model, the wall thickness of the polytetrafluoroethylene conduit is not less than 0.2 mm.

[0012] As a further improvement of this utility model, the encapsulating material is epoxy resin.

[0013] Beneficial effects Compared with the prior art, the advantages of the improved M3 screw-mounted feedthrough filter of this utility model are as follows: 1. Fundamentally eliminate internal potting defects and improve body insulation strength: After the M3 screw-mounted feedthrough filter is assembled and welded, the encapsulating material is first injected into the gap between the inner hole of the threaded section of the metal screw-mounted outer shell and the metal lead wire, reaching 1 / 2 depth of the gap. Then, a polytetrafluoroethylene conduit is installed on the metal lead wire, and a second potting is performed after the polytetrafluoroethylene conduit is in place. During installation, this conduit effectively pushes and fills the encapsulant to the bottom of the cavity, completely expelling air that is easily trapped at the bottom due to the narrow structure, thus preventing the formation of voids at the bottom. Simultaneously, the conduit itself completely encapsulates the metal leads. Even if sporadic air bubbles remain during the curing process of the encapsulant, the high-insulation-strength PTFE material (breakdown voltage >5kV / mm) acts as a reliable insulation barrier, ensuring that the metal casing and leads do not break down due to air bubbles, thereby increasing the product's body insulation withstand voltage to over 1.25 kV. 2. Effectively prevents external surface discharge and arcing: By bonding a polytetrafluoroethylene gasket to the end face of the threaded section, the surface creepage distance and spatial distance between the end face of the metal threaded housing and the metal lead are significantly increased, effectively blocking the discharge and arcing path that may be generated at the port under high voltage, and solving the problem of external arcing. 3. Maintaining miniaturization advantages and extremely high cost-effectiveness: Without changing the standard dimensions and installation method of the M3 screw-mounted feedthrough filter, a leap in withstand voltage performance from less than 600V to over 1.25kV has been successfully achieved. This allows the M3 specification product to replace some M4 and larger specification products, retaining its core advantages of small size and light weight. The added cost of PTFE conduit and PTFE gasket is extremely low, less than 1% of the total product cost. No expensive equipment is required, the process is simple, and it is very suitable for mass production. 4. Excellent versatility and scalability: The design principles and structure adopted in this solution can also be applied to larger screw-mounted feedthrough filters such as M4, M5, and M6 to further improve their withstand voltage reliability and consistency, and have broad application prospects.

[0014] The present invention will become clearer from the following description and in conjunction with the accompanying drawings, which are used to explain the embodiments of the present invention. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the existing M3 screw-mounted feedthrough filter. Figure 2 A schematic diagram of the structure of an existing M3 screw-mounted feedthrough filter with gaps; Figure 3 This is a schematic diagram of the structure of this utility model.

[0017] Among them: 1-metal screw-on housing; 2-through-type filter; 3-metal lead wire; 4-encapsulation material; 5-polytetrafluoroethylene conduit; 6-polytetrafluoroethylene gasket. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this utility model, and not all of them. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0019] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; of course, they can also refer to a mechanical connection or an electrical connection; furthermore, they can refer to a direct connection, an indirect connection through an intermediate medium, or a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0020] Embodiments of the present invention will now be described with reference to the accompanying drawings.

[0021] Example: The specific embodiments of this utility model are as follows: Figure 3 As shown, an improved M3 screw-type feedthrough filter is based on the following concept: addressing the pressure resistance bottleneck caused by the small internal potting gap and external clearance of traditional M3 screw-type feedthrough filters, the filter introduces a combination structure of PTFE conduit 5 and PTFE gasket 6 to collaboratively solve the problems of internal breakdown and external arcing without changing the overall dimensions of the product, thereby achieving a leapfrog improvement in pressure resistance performance.

[0022] The improved M3 screw-mounted feedthrough filter consists of a metal screw-mounted housing 1, a through-hole filter 2, metal leads 3, encapsulating material 4, a polytetrafluoroethylene conduit 5, and a polytetrafluoroethylene gasket 6.

[0023] The metal screw-on housing 1, the through-hole filter 2, and the metal lead wire 3 are first assembled into a single structure by welding. The encapsulating material 4 is epoxy resin, which is used to fill the gaps and cure, serving both fixing and insulation purposes.

[0024] The key improvement in this implementation plan is: A polytetrafluoroethylene (PTFE) conduit 5, capable of compressing and eliminating voids within the encapsulating material 4, is inserted into the threaded section of the metal screw-on housing 1. The PTFE conduit 5 is fitted over the metal lead 3. The inner diameter of the PTFE conduit 5 is tightly fitted to the outer diameter of the metal lead 3, allowing it to be stably fitted onto the lead; its outer diameter is smaller than the inner diameter of the threaded section of the metal screw-on housing 1, ensuring sufficient space for encapsulation and smooth insertion. Furthermore, the length of the PTFE conduit 5 should not be less than the depth of the threaded section of the metal screw-on housing 1, ensuring complete coverage of high-voltage risk areas. Additionally, the wall thickness of the PTFE conduit 5 is not less than 0.2 mm; based on the breakdown voltage strength of PTFE material greater than 5 kV / mm, this 0.2 mm wall thickness alone can provide insulation protection exceeding 1 kV.

[0025] A polytetrafluoroethylene (PTFE) gasket 6 is bonded and fixed to the threaded end face of the metal screw-on housing 1 using an encapsulating material 4. The gasket has a through hole at its center for the metal lead 3 to pass through, and the outer diameter of the PTFE gasket 6 is larger than the inner diameter of the inner hole of the threaded section of the metal screw-on housing 1, thus effectively covering the port. The thickness of the PTFE gasket 6 is between 0.5 mm and 1.5 mm; this size significantly increases the creepage distance without affecting the overall structural compactness.

[0026] During assembly, one end of the PTFE conduit 5 contacts the through-hole filter 2, while the other end contacts the PTFE gasket 6, thus forming a continuous insulating barrier from the inside out.

[0027] The implementation principle and technical effects of this device are explained below: The principle behind eliminating internal potting defects: In terms of manufacturing process, this device employs a step-by-step potting method. First, approximately half the depth of the encapsulating material 4 is poured into the gap between the inner hole of the threaded section of the metal screw-on housing 1 and the metal lead 3. Then, the PTFE conduit 5 is inserted along the metal lead 3. During this process, the inserted end of the PTFE conduit 5 acts like a piston, pushing the first-poured encapsulating material 4 downwards, forcing it to fill to the bottom of the cavity, thereby completely expelling the air trapped at the bottom and eliminating the bottom void problem caused by the "narrowing effect." After the PTFE conduit 5 is installed, a second potting is performed to fill the remaining space. At this point, even if there are occasional tiny air bubbles remaining in the encapsulating material 4 during the second potting, the PTFE conduit 5 itself becomes a reliable solid insulating barrier. It physically separates the metal lead 3 and the metal screw-on housing 1, ensuring that the area of ​​the encapsulating material 4 containing the air bubbles no longer directly bears the entire high voltage differential. Because the dielectric strength of polytetrafluoroethylene is much higher than that of air and epoxy resin, the overall insulation withstand voltage (insulation strength) of the product is significantly improved to over 1.25 kV.

[0028] The principle of preventing external arcing: The PTFE gasket 6 covers the threaded end face of the metal screw-on housing 1. Its functions are twofold: first, it increases the spatial distance between the end face of the metal screw-on housing 1 and the metal lead 3, significantly increasing the original air gap of less than 0.5mm; second, it provides an insulation path with high surface resistance, greatly extending the surface creepage distance. These two factors work together to effectively increase the surface discharge voltage, blocking the path for arcing to occur at the threaded end face of the metal screw-on housing 1 under a 1.25kV test voltage.

[0029] Maintaining miniaturization and high cost-effectiveness: All improvements are made inside and on the end face of the standard M3 housing, without changing its external thread size or installation method. The added PTFE conduit 5 and PTFE gasket 6 are standardized, inexpensive industrial parts with minimal cost increase but significant effect, enabling the M3 product to replace some pressure ratings that would otherwise require larger sizes (such as M4), making it highly economical.

[0030] Versatility and scalability: The insulation enhancement concept of this "conduit + gasket" is a modular design concept that can be applied to screw-mounted filters such as M4, M5, and M6. By adapting conduits and gaskets of different sizes, the withstand voltage reliability and consistency of the entire product series can be systematically improved.

[0031] The present invention has been described above in conjunction with the preferred embodiments, but the present invention is not limited to the embodiments disclosed above, but should cover various modifications and equivalent combinations made in accordance with the essence of the present invention.

Claims

1. An improved M3 screw-mounted feedthrough filter, comprising a metal screw-mounted housing (1), a through-hole filter (2), metal leads (3), and encapsulating material (4), characterized in that, The threaded end face of the metal screw-on housing (1) is bonded with a polytetrafluoroethylene gasket (6) that is fitted with the metal lead wire (3) by an encapsulating material (4). The threaded section of the metal screw-on housing (1) is also inserted with a polytetrafluoroethylene conduit (5) that can squeeze out the voids in the encapsulating material (4). The polytetrafluoroethylene conduit (5) is sleeved on the outside of the metal lead wire (3), and the two ends of the polytetrafluoroethylene conduit (5) are respectively in contact with the through-hole filter (2) and the polytetrafluoroethylene gasket (6).

2. The improved M3 screw-mounted feedthrough filter according to claim 1, characterized in that, The inner diameter of the polytetrafluoroethylene conduit (5) is adapted to the outer diameter of the metal lead (3), and the outer diameter of the polytetrafluoroethylene conduit (5) is smaller than the inner diameter of the inner hole of the threaded section of the metal screw-on housing (1).

3. The improved M3 screw-mounted feedthrough filter according to claim 1 or 2, characterized in that, The length of the polytetrafluoroethylene conduit (5) is not less than the depth of the inner hole of the threaded section of the metal screw-on outer shell (1).

4. The improved M3 screw-mounted feedthrough filter according to claim 1, characterized in that, The polytetrafluoroethylene gasket (6) has a through hole in the center for the metal lead wire (3) to pass through, and the outer diameter of the polytetrafluoroethylene gasket (6) is larger than the inner diameter of the inner hole of the threaded section of the metal screw-on housing (1).

5. The improved M3 screw-mounted feedthrough filter according to claim 1 or 4, characterized in that, The thickness of the polytetrafluoroethylene gasket (6) is 0.5 mm to 1.5 mm.

6. The improved M3 screw-mounted feedthrough filter according to claim 1, characterized in that, The wall thickness of the polytetrafluoroethylene conduit (5) is not less than 0.2 mm.

7. The improved M3 screw-mounted feedthrough filter according to claim 1, characterized in that, The encapsulating material (4) is epoxy resin.

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