Hermetically sealed travel switch

Abstract

The application discloses airtight stroke switch; including shell, push mechanism and static contact system, the push mechanism is arranged in the shell and extends from one end of the shell, the static contact system is fixed at the other end of the shell and seals the end of the shell; by loading the spring into the bellows, the spring is connected in parallel with the bellows, compared with the existing spring and the bellows in series, the space required for compression is reduced, so that the switch volume is smaller; the contact system is designed as 3 groups of contact pairs redundant structure, so that the product has higher impact and vibration resistance; the contact system is put into the sealed cavity filled with inert gas, and the tail end of the wire part is filled with epoxy glue, so that the product can adapt to more severe natural environment.

Description

Technical Field

[0001] This invention relates to a gas-tight limit switch. Background Technology

[0002] Hermetically sealed limit switches are generally fully sealed structures, with the inside filled with inert gas to protect the internal contact structure. They can withstand harsh environments such as sand, dust, humidity, and radiation, ensuring the reliability of the switch operation. Therefore, hermetically sealed limit switches are commonly used in equipment or systems operating in harsh environments, such as those used in space stations, deep space exploration, and weapons systems operating around the clock and routinely at sea.

[0003] Currently, the mainstream airtight limit switches on the market mainly use bellows as a structure for sealing and transmitting external force. However, due to the limitation of bellows compression, the product size is relatively large.

[0004] For example, CN109192588B discloses a limit switch with multiple signals. It uses a bellows as a seal and a ring of moving contacts is evenly distributed on the outer surface of the spindle. The moving contacts and stationary contacts form a sliding contact pair. Every two moving contacts are connected to form a circuit. However, the moving contacts are directly fixed to the insulating sleeve during processing, which requires high processing precision between the insulating sleeve and the moving contacts. If the precision of the moving contacts is insufficient, it may cause unstable installation of the moving contacts. If the moving contacts are too large, it may damage the insulating sleeve during assembly. Summary of the Invention

[0005] The purpose of this invention is to address the problem that existing airtight limit switches are limited by the compression amount of the bellows, resulting in a large product size. This invention provides an airtight limit switch by installing a spring inside the bellows and connecting the spring and the bellows in parallel. Compared with the existing method of connecting the spring and the bellows in series, this reduces the space required for compression, making the switch smaller.

[0006] The technical solution of the present invention: The present invention provides an airtight limit switch, comprising a housing, a pushing mechanism and a static contact system, wherein the pushing mechanism is disposed inside the housing and extends from one end of the housing, and the static contact system is fixed to the other end of the housing and seals that end of the housing; The actuating mechanism includes a bellows assembly, a moving contact system, a stationary contact system, and a spring. The moving contact system is located in the bellows assembly, and the spring supports the moving contact system between the upper end of the moving contact system and the lower end of the bellows assembly. The stationary contact system extends into the bellows assembly and is adapted to contact / disconnect with the moving contact system to enable current flow.

[0007] The outer shell locks the pushing mechanism and the static contact system inside it through the support bushing. The connection between the outer shell and the support bushing is narrowed to form an interference fit, and laser welding is performed at the narrowed part. The housing is filled with inert gas, and the support bushing is fixed with epoxy resin, forming a fully sealed structure for the switch.

[0008] The bellows assembly is formed by laser welding of an actuator, a bellows diaphragm, and a base. Multiple bellows diaphragms are welded together to form a telescopic bellows. The two ends of the bellows are welded to the actuator and the base, respectively. The base is sealed to the static contact system, together forming the variable-volume sealed cavity. The inert gas is a 99% pure inert gas. The base is a cylindrical body, with a support plate at one end connected to the corrugated diaphragm. The support plate has a stepped hole machined from the inside out at its center. A spring bushing is installed in the stepped hole. The outer wall of the spring bushing fits with the stepped hole, and its top forms a limiting step with the stepped hole. An insulating bushing is installed inside the spring bushing. The bottom of the insulating bushing fits against the bottom of the spring bushing. The other end of the insulating bushing extends out of the base from the center hole of the spring bushing. A bushing is also installed inside the base. The bushing is threaded to the base to fix the spring bushing and the insulating bushing axially. One end of the spring is in contact with the push post, and the other end is assembled in the limiting step. An insulating bushing is provided between the spring and the moving contact to achieve insulation.

[0009] The opening of the base is fitted with the static contact system through a narrowing method to fix the static contact system inside the bellows assembly, and laser welding is performed at the narrowing point. An insulating sleeve is also installed inside the base. The insulating sleeve is fitted between the static contact system and the base, and the two bottom ends of the insulating sleeve are in contact with the static contact system and the bushing, respectively.

[0010] The static contact system includes a base, contact pieces, long leads, and short leads. There are six contact pieces in total, which are evenly distributed in a regular hexagonal shape. Three contact pieces alternately form the current input terminal, and the remaining three contact pieces alternately form the current output terminal, forming three sets of redundant contact pairs. The six contact pieces are respectively riveted to the long leads and the short leads. Three long leads and three short leads extend out of the housing and are connected by conductive pieces to form an integrated input / output terminal.

[0011] The static contact system also includes a mounting base and support plates. The mounting base is mounted on the base and the centers of the two are matched through a square shaft hole to achieve positioning. The six support plates are riveted to the long and short terminals respectively and press the contact plates together to form support on the outside of the contact plates. The mounting base is provided with a partition on the outside to separate each long and short terminal. The base is provided with a terminal fixing plate on its outer edge. The bottom of the base is closed. The terminal fixing plate is provided with through holes evenly distributed. Long terminals and short terminals are connected in the through holes by glass powder sintering.

[0012] The moving contact system includes a push column, one end of which is machined with a first-level limiting step, and the other end is machined with a thread. An inner insulating bushing and an outer insulating bushing are installed at the step. The outer walls of the adjacent ends of the inner and outer insulating bushings are joined to form six uniform arc grooves. Six moving contact pieces are respectively installed in the arc grooves. Nuts are installed on the threads at the end of the push column to adjust the distance between the inner and outer insulating bushings and lock the moving contact pieces. The other end of the push column is machined with a spring seat that contacts the spring. The diameter of the spring seat is larger than that of the push column, and a limiting head is provided at the end of the spring seat.

[0013] The beneficial effects of this invention are: 1. By inserting the spring inside the bellows and connecting the spring and the bellows in parallel, compared with the existing method of connecting the spring and the bellows in series, the space required for compression is reduced, making the switch smaller.

[0014] 2. The present invention designs the contact system as a redundant structure with 3 sets of contact pairs, which makes the product more resistant to impact and vibration.

[0015] 3. In this invention, the contact system is placed in a sealed cavity filled with inert gas, and the end wire is encapsulated with epoxy resin, enabling the product to adapt to harsher natural environments. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the switch assembly.

[0017] Figure 2 A schematic diagram of the assembly structure of the propulsion structure and the bellows assembly.

[0018] Figure 3 This is a schematic diagram of the bellows assembly structure.

[0019] Figure 4 This is a schematic diagram of a static contact system.

[0020] Figure 5 This is a schematic diagram of the moving contact system.

[0021] Figure 6 This is a schematic diagram of the base structure.

[0022] In the diagram: 1-Outer shell, 2-Support bushing, 3-Pushing mechanism, 4-Sealing ring, 5-Bellows assembly, 6-Spring, 7-Moving contact assembly, 8-Insulating sleeve, 9-Plate, 10-Bushing, 11-Insulating bushing, 12-Static contact system, 13-Conductive sheet, 14-Cable, 15-Actuator, 16-Bellows diaphragm, 17-Base, 18-Base, 19-Mounting seat, 20-Support piece, 21-Contact piece, 22-Push column, 23-Inner insulating bushing, 24-Moving contact piece, 25-Outer insulating bushing, 26-Nut, 27-Terminal pin fixing plate, 28-Long terminal pin, 29-Short terminal pin, 30-Glass powder, 31-Spring seat, 32-Limit head, 33-Mounting ear. Detailed Implementation

[0023] The technical solution of the present invention is further described below, but the scope of protection is not limited to what is described.

[0024] An airtight limit switch includes a housing 1, a pushing mechanism 3, and a static contact system 12. The pushing mechanism 3 is located inside the housing 1 and extends from one end of the housing 1. The static contact system 12 is fixed to the other end of the housing 1 and seals that end. The housing serves as an integral support and external mounting base. One end of the housing extends out to receive external driving force from the pushing mechanism, while the other end is fixed and sealed by the static contact system, achieving coaxial assembly and spatial isolation between the moving and fixed components. This ensures a straight and unbiased action transmission path, avoids lateral jamming, and forms a closed internal cavity, providing a foundation for an airtight environment.

[0025] The actuating mechanism 3 includes a bellows assembly 5, a moving contact system 7, a stationary contact system 12, and a spring 6. The moving contact system 7 is housed within the bellows assembly 5. The spring 6 is supported between the upper end of the moving contact system 7 and the lower end of the bellows assembly 5. The stationary contact system 12 extends into the bellows assembly 5 and is adapted to contact / disconnect with the moving contact system 7 to allow current flow. The spring is built into the bellows, forming a parallel structure with the bellows. Both extend and retract synchronously. The restoring force is provided by the spring, and the sealing is provided by the bellows. Compared to the traditional series layout of spring and bellows, the axial compression space is significantly reduced, and the overall product length is shortened by ≥30%, achieving miniaturization.

[0026] The outer casing 1 locks the push mechanism 3 and the static contact system 12 within it via the support bushing 2. The connection between the outer casing 1 and the support bushing 2 is narrowed to form an interference fit, and laser welding is performed at the narrowed area. The outer casing 1 is filled with inert gas, and epoxy resin is used to fix and seal the support bushing 2, creating a fully sealed structure for the switch. The narrowing creates a radial clamping force between the support bushing and the outer casing, and the laser welding forms a continuous weld seam with a metallurgical bond, eliminating capillary leakage channels. This achieves a permanent gas-tight seal, with a helium leak detection rate of 1×10⁻⁶. -9 Pa·m 3 / s, meeting the sealing requirements for aerospace and deep space exploration.

[0027] High-purity inert gas isolates oxygen, moisture, and dust, while epoxy resin potting seals the wiring lead gaps, forming a double-sealed barrier. This prevents internal contact oxidation, electrolytic corrosion, and dust accumulation, and allows it to withstand sand, high humidity, vacuum, and radiation environments, extending its lifespan to over 100,000 cycles.

[0028] The bellows assembly 5 is formed by laser welding of an actuator 15, a corrugated diaphragm 16, and a base 17. Multiple corrugated diaphragms 16 are welded to form a telescopic bellows. Both ends of the bellows are welded to the actuator 15 and the base 17, respectively. The base 17 is sealed to the static contact system 12, together forming the variable-volume sealed cavity. The inert gas is a 99% pure inert gas. Multiple corrugated diaphragms are stacked and welded to form a flexible telescopic wall. The actuator inputs external force, and the base is connected to the static contact system, forming a telescopic, leak-proof sealed cavity. The external force is transmitted flexibly without friction or dust, the telescopic stroke is stable, and the cavity volume changes smoothly with the movement.

[0029] The base 17 is a cylindrical body, with a support plate at one end connected to the corrugated diaphragm 16. A stepped hole, running from the inside out, is machined in the center of the support plate. A spring bushing 9 is installed inside the stepped hole, with its outer wall fitting into the stepped hole and its top forming a limiting step. An insulating bushing 8 is installed inside the spring bushing 9, with its bottom fitting against the bottom of the spring bushing 9. The other end of the insulating bushing 8 extends out of the base 17 from the center hole of the spring bushing 9. A bushing 10 is also installed inside the base 17, threadedly connected to the base 17, axially fixing the spring bushing 9 and the insulating bushing 8. The stepped hole positions the spring bushing, the threaded bushing provides axial clamping force, and the insulating bushing isolates conductive components, forming an integrated positioning-insulation-fixing structure. The spring coaxiality error is ≤0.05mm, ensuring no skew or jamming, while reliably blocking the conductive circuit to prevent misdirection and leakage.

[0030] One end of the spring 6 contacts the push post 22, and the other end is fitted into the limiting step. An insulating bushing 8 is provided between the spring 6 and the moving contact 24 to achieve insulation. The spring provides a stable restoring force, and the insulating bushing blocks the current path between the spring and the moving contact. The restoring force is stable, the action is consistent, the electrical insulation is reliable, and there is no risk of cross-current or leakage.

[0031] The opening of the base 17 forms an interference fit with the static contact system 12 through a narrowing method, fixing the static contact system 12 inside the bellows assembly. Laser welding is performed at the narrowing point. The combination of narrowing and laser welding achieves integrated mechanical fixation and airtight sealing between the base and the static contact system. This results in high connection strength, leak-free sealing, and resistance to vibration and impact without loosening.

[0032] like Figure 1The assembly process of the outer shell 1, the support bushing 2, and the pushing mechanism 3 is as follows: The sealing ring 4 is installed into the outer shell 1, then the pushing mechanism 3 is installed into the outer shell, and finally the support bushing 2 is installed into the outer shell. The tail end of the support bushing is first narrowed with the outer shell to make the support bushing and the outer shell interference fit, and then laser welding is performed at the narrowed part.

[0033] like Figure 2 The actuating mechanism includes a bellows assembly 5, a spring 6, a moving contact system 7, an insulating bushing 8, a spring bushing 9, a bushing 10, an insulating sleeve 11, a static contact system 12, a conductive sheet 13, and a cable 14. First, the moving contact system 7 is installed into the bellows assembly 5. Then, the spring 6, spring bushing 9, and insulating bushing 8 are installed. One end of the spring 6 contacts the actuating post 22, and the other end contacts the spring bushing 9. Next, the bushing 10 is installed. The bushing 10 is threadedly connected to the base 17. Tightening the bushing 10 secures the spring bushing 9 and insulating bushing 8. The spring bushing 9 fixes the spring 6 in place. Inside the bellows, the insulating sleeve 11 and the static contact system 12 are then sequentially installed into the bellows assembly 5. The base 18 and the base 17 in the static contact system 12 are narrowed to make the base 18 and the base 17 interference fit. Then, the narrowed part is laser welded in the equipment filled with inert gas to make the pushing structure form a variable volume sealed cavity. The conductive sheet 13 is welded to the long terminal 28 and the short terminal 29. Finally, the two wires of the cable 14 are welded to the conductive sheet 13 on the short terminal 29 and the two wires of the cable 14 are welded to the conductive sheet 13 on the long terminal 28.

[0034] As shown in Figure 3, the bellows assembly includes an actuator 15, a bellows diaphragm 16, and a base 17. Multiple bellows diaphragms 16 are laser-welded to form a bellows, and then the actuator 15 and the base 17 are welded to both ends of the bellows.

[0035] As shown in Figure 4, the static contact system includes a base 18, a mounting base 19, support plates 20, and contact plates 21. First, the mounting base 19 is installed into the base 18. The mounting base 19 and the base 18 are fitted together by a square shaft and hole to limit their movement. Then, three support plates 20 and three contact plates 21 are riveted onto the long lead 28. Next, the three support plates 20 and three contact plates 21 are riveted onto the short lead 29. The three short leads 29 are connected together through conductive plates 13 to form an input or output terminal. The three long leads 28 are connected together through conductive plates 13 to form an input or output terminal.

[0036] like Figure 5 The moving contact system includes a push post 22, an inner insulating bushing 23, a moving contact 24, an outer insulating bushing 25, and a nut 26. The inner insulating bushing 23, the moving contact 24, the outer insulating bushing 25, and the nut 26 are sequentially installed into the push post 22. The inner insulating bushing 23 and the outer insulating bushing 25 provide insulation, and the nut 26 is threadedly connected and fixed to the push post.

[0037] like Figure 6 The base 18 includes a terminal fixing plate 27, a long terminal 28, a short terminal 29, and glass powder 30. The terminal fixing plate 27 is sintered with the long terminal 28 and the short terminal 29 through the glass powder.

[0038] When the product is not subjected to external force, contact piece 21 contacts moving contact 24, and the product forms a current loop through cable 14, long lead 28, stationary contact piece 21, moving contact 24, short lead 29, and conductive piece 13, at which time the product is in the connected state. When the actuator 15 is subjected to external force, the actuator moves into the product, and the actuator 15 drives the moving contact system 6 to move. When it moves to a certain distance, contact piece 21 disconnects from moving contact 24, and contact piece 21 contacts inner insulating bushing 23, at which time the product is in the disconnected state.

Claims

1. A gas-tight limit switch, characterized in that: It includes a housing (1), a pushing mechanism (3) and a static contact system (12). The pushing mechanism (3) is located inside the housing (1) and extends from one end of the housing (1). The static contact system (12) is fixed to the other end of the housing (1) and seals that end of the housing (1). The pushing mechanism (3) includes a bellows assembly (5), a moving contact system (7), a stationary contact system (12), and a spring (6). The moving contact system (7) is placed in the bellows assembly (5), and the spring (6) is supported between the upper end of the moving contact system (7) and the lower end of the bellows assembly (5). The stationary contact system (12) extends into the bellows assembly (5) and is adapted to contact / disconnect with the moving contact system (7) to achieve current flow.

2. The gas-tight limit switch as described in claim 1, characterized in that: The outer shell (1) locks the pushing mechanism (3) and the static contact system (12) inside it through the support bushing (2). The connection between the outer shell (1) and the support bushing (2) is narrowed to form an interference fit, and laser welding is performed at the narrowed part. The outer casing (1) is filled with inert gas, and the support bushing (2) is fixedly encapsulated with epoxy resin, so that the switch forms a fully sealed structure.

3. The gas-tight limit switch as described in claim 1, characterized in that: The bellows assembly (5) is formed by laser welding of an actuator (15), a bellows diaphragm (16) and a base (17). Multiple bellows diaphragms (16) are welded to form a retractable bellows. The two ends of the bellows are welded to the actuator (15) and the base (17) respectively. The base (17) is sealed to the static contact system (12) to form the variable volume sealed cavity. The inert gas is a 99% pure inert gas. The base (17) is a cylindrical body. One end of the base (17) connected to the corrugated diaphragm (16) is provided with a support plate. The center of the support plate is machined with a stepped hole from the inside to the outside. A spring bushing (9) is installed in the stepped hole. The outer wall of the spring bushing (9) is fitted with the stepped hole and its top is fitted with the stepped hole to form a limiting step. An insulating bushing (8) is installed in the spring bushing (9). The bottom of the insulating bushing (8) is fitted with the bottom of the spring bushing (9). The other end of the insulating bushing (8) extends out of the base (17) from the center hole of the spring bushing (9). A bushing (10) is also installed inside the base (17). The bushing (10) is threadedly connected to the base (17) to fix the spring bushing (9) and the insulating bushing (8) axially. One end of the spring (6) is in contact with the push post (22), and the other end is fitted inside the limiting step. An insulating bushing (8) is provided between the spring (6) and the moving contact (24) to achieve insulation.

4. The gas-tight limit switch as described in claim 3, characterized in that: The opening of the base (17) is formed with the static contact system (12) by means of narrowing to fix the static contact system (12) in the bellows assembly, and laser welding is performed at the narrowing.

5. The gas-tight limit switch as described in claim 4, characterized in that: An insulating sleeve (11) is also installed inside the base (17). The insulating sleeve (11) is fitted between the static contact system (12) and the base (17). The bottom two ends of the insulating sleeve (11) are in contact with the static contact system (12) and the bushing (10) respectively.

6. The gas-tight limit switch as described in claim 1, characterized in that: The static contact system (12) includes a base (18), contact pieces (21), long leads (28) and short leads (29). There are six contact pieces (21) in total, which are evenly arranged in a regular hexagonal shape. Three pieces alternately form the current input terminal, and the remaining three pieces alternately form the current output terminal, forming three sets of redundant contact pairs. The six contact pieces (21) are respectively riveted to the long leads (28) and the short leads (29). Three long leads (28) and three short leads (29) extend out of the outer shell (1) and are respectively connected by conductive pieces (13) to form an overall input / output terminal.

7. The gas-tight limit switch as described in claim 6, characterized in that: The static contact system (12) also includes a mounting base (19) and support plates (20). The mounting base (19) is mounted on the base (18) and the center of the two is matched through a square shaft hole to achieve positioning. The six support plates (20) are riveted to the long terminal (28) and short terminal (29) respectively and press the contact plate (21) tightly, forming support on the outside of the contact plate (21). The mounting base (19) has a partition on the outside to separate each long terminal (28) and short terminal (29). The base (18) is provided with a terminal fixing plate (27) on its outer side. The bottom of the base (18) is closed. The terminal fixing plate (27) is provided with through holes evenly. The long terminal (28) and the short terminal (29) are sintered and connected in the through holes by glass powder (30).

8. The gas-tight limit switch as described in claim 1, characterized in that: The moving contact system (7) includes a push column (22). One end of the push column (22) is machined with a first-level limiting step, and the end is machined with a thread. An inner insulating bushing (23) and an outer insulating bushing (25) are installed at the step. The outer walls of the adjacent ends of the inner insulating bushing (23) and the outer insulating bushing (25) are joined to form six uniform arc grooves. Six moving contact pieces (24) are respectively installed in the arc grooves. A nut (26) is installed on the thread at the end of the push column (22) to adjust the distance between the inner insulating bushing (23) and the outer insulating bushing (25) to lock the moving contact pieces.

9. The gas-tight limit switch as described in claim 8, characterized in that: The other end of the push column (22) is machined with a spring seat (31) that contacts the spring (6). The diameter of the spring seat (31) is larger than that of the push column (22), and the end of the spring seat (31) is provided with a limiting head (32).

Images