Double-locking parameter design method of three-position switch transmission mechanism and transmission mechanism

Abstract

The invention discloses a double-locking parameter design method of a three-position switch transmission mechanism and the transmission mechanism. The method comprises the following steps: determining the horizontal and vertical distances between a rotation axis O1 of an output crank arm of an operating mechanism and a rotation axis O2 of an output shaft of the three-position switch; connecting O1 and O2, and establishing rectangular coordinate systems I and II; a circle is drawn with the center of the rectangular coordinate system I as the circle center and the trial length r1 of the crank as the radius, and the crank intersects with the circumference of the circle A1, B1 and C1; taking the center of the rectangular coordinate system II as a circle center, trying to take the length r2 of the rocker as a radius to draw a circle, and enabling the rocker to intersect with the circumference of the circle A2, B2 and C2; connecting A1, B1 and C1 with A2, B2 and C2 to form three sections of connecting lines, and measuring the length of the connecting lines; determining an included angle between the three-position switch and the rocker in the center line of the grounding position; and verifying that the electrical gap between the isolation fracture and the grounding fracture of the three-position switch is a set value. According to the invention, the parameters of the three-position switch transmission mechanism are determined, and the operation safety is improved.

Description

Technical Field

[0001] The invention relates to a parameter design method for double locking of a three-position switch transmission mechanism, and also relates to a three-position switch transmission mechanism obtained by using the parameter design method. Background Art

[0002] Three-position switches are crucial components in power supply systems, often used in hub stations, electrical phase splitters, and traction substation access points. They connect or disconnect circuits between power supply segments, improving power supply flexibility and enabling switching between single and double-sided power supply. In no-load conditions, the three-position switch can be controlled to disconnect or close the power supply circuit for electrical equipment. During maintenance, the three-position switch can also be safely grounded, meeting various maintenance needs.

[0003] A three-position switch has three positions: closed, isolated (open), and grounded. The closed position connects the circuit and carries current; the isolated position isolates the power supply and creates a clear break; and the grounded position releases residual charge and maintains zero-potential grounding protection. This requires that the operating mechanism of the three-position switch also has three positions: closed, isolated, and grounded. In order to meet the electrical performance requirements of the three-position switch in each position, the rational design of the three-position switch transmission mechanism is particularly important:

[0004] ⑴ When the three-position switch is in the closed position, it must not only bear the rated current, but also the rated short-time withstand current and rated peak withstand current at any time. It requires that the contact fingers and static contacts of the three-position switch have good coordination, that is: all the contact fingers of the three-position switch are in 100% contact with the conductive plane of each static contact.

[0005] ⑵ When the three-position switch is in the grounding position, the three phases need to be short-circuited to the ground. Its first function is to release the residual charge on the power lines and power equipment to the ground; the second function is to keep the power lines and power equipment at zero potential. It also requires the moving contact and the static contact of the three-position switch to have good coordination, that is: all the contact fingers of the moving contact and the conductive plane of the static contact reach 100% contact. Some places may also need to carry the rated short-time withstand current and the rated peak withstand current.

[0006] (3) When the three-position switch is in the open position, it must be reliably isolated from the power supply, forming a clear disconnection to prevent the power supply from being connected in the event of misoperation or overvoltage, thereby ensuring the safety of maintenance personnel and equipment. There must be sufficient distance and reliable insulation between the moving contact and the static contact after disconnection to ensure isolation under various conditions and prevent insulation breakdown in the event of overvoltage and phase-to-phase flashover. If the gas gap between the moving contact and the static contact is too small, it may cause voltage breakdown in the gas gap and discharge, or even cause personal safety accidents and equipment damage accidents when the power is connected.

[0007] ⑷ The dynamic thermal stability requirements from the rated short-time withstand current and the rated peak withstand current, as well as the shock / vibration and impact from nature, all require that the three-position switch have necessary protection measures in the closed position, isolation (open) position and grounding position to prevent accidents caused by false operation. Especially in the closed position and grounding position, the impact from the short-time withstand current and the rated peak withstand current is the biggest test for the safe operation of the three-position switch. Summary of the Invention

[0008] The first object of the present invention is to provide a parameter design method for double locking of a three-position switch transmission mechanism, so that the three-position switch can meet its electrical performance requirements in the closed position, the isolated position and the grounded position.

[0009] The first object of the present invention is achieved by the following technical measures: a parameter design method for a double-locking transmission mechanism of a three-position switch, characterized by comprising the following steps:

[0010] S1. Determine the relative installation position of the operating mechanism and the three-position switch according to the structural layout, and confirm the horizontal distance L and vertical distance H between the rotation axis O1 of the operating mechanism output arm and the rotation axis O2 of the three-position switch output shaft;

[0011] S2. Draw the rotation axis O1 of the operating mechanism output crank arm and the rotation axis O2 of the three-position switch output shaft on the diagram;

[0012] S3. Draw the center line of the three-position switch with the output shaft rotation axis O2 as the center of the circle;

[0013] S4. Connect the rotation axis O1 of the output crank arm of the operating mechanism and the rotation axis O2 of the output shaft of the three-position switch. The line O1-O2 is the frame of the transmission mechanism. With the hinge points at both ends of the frame as the center and the X1 axis and Y1 axis as the dividing lines, establish a rectangular coordinate system I; with the X2 axis and Y2 axis as the dividing lines, establish a rectangular coordinate system II;

[0014] S5. Draw a circle with the center of rectangular coordinate system I as the center and the length r1 of the crank as the radius. Rotate the crank clockwise twice, 90° each time, at the lower end of the third quadrant of rectangular coordinate system I, at its initial angle α. The crank intersects the circumference of the circle at intersection points A1, B1, and C1.

[0015] S6. Draw a circle with the center of rectangular coordinate system II as the center and the length r2 of the joystick as the radius. At the lower end of the third quadrant of rectangular coordinate system II, rotate the joystick clockwise twice, first 65° and then 60°, at its initial angle β. The joystick intersects the circumference of the circle at points A2, B2, and C2.

[0016] S7. Connect the intersection points A1, B1, and C1 with the intersection points A2, B2, and C2 to form three lines: A1-A2, B1-B2, and C1-C2. The lines are connecting rods. Measure the lengths of the connecting rods respectively.

[0017] If the length difference between the three connecting lines A1-A2, B1-B2, and C1-C2 is within the set range, the designed transmission mechanism is established and the process proceeds to step S8. Otherwise, another crank length r1, crank initial rotation angle α, rocker length r2, and rocker initial rotation angle β are determined, and steps S5 to S7 are repeated until the length difference between the three connecting lines A1-A2, B1-B2, and C1-C2 is within the set range, and the process proceeds to step S8.

[0018] S8. Confirm the angle between the center line of the three-position switch in the grounded position and the center line of the rocker in the grounded position;

[0019] S9. Using the confirmed parameters, verify that the electrical gap between the isolation break and the grounding break of the three-position switch is the set value. If the verification is successful, the parameters that meet the double locking of the three-position switch transmission mechanism are determined;

[0020] Otherwise, according to steps S1 to S8, the design is re-optimized until the electrical gap between the isolation break and the grounding break of the three-position switch is verified to be the set value, and the parameters that meet the double locking of the three-position switch transmission mechanism are determined.

[0021] The present invention can determine the parameters of the transmission mechanism of the three-position switch. Based on these parameters, the transmission mechanism can realize the double locking function of the three-position switch in the closed position and the grounded position, ensuring that the contacts of the three-position switch are not passively separated when the three-position switch is in the closed position and the grounded position, thereby improving the safety of operation and enabling the three-position switch to meet its electrical performance requirements in the closed position, the isolated position and the grounded position.

[0022] The setting range of the present invention is 0 to 2 mm.

[0023] The set value of the present invention is 75 mm ± 3 mm.

[0024] A second object of the present invention is to provide a three-position switch transmission mechanism calculated using the above-mentioned parameter design method for the double locking of the three-position switch transmission mechanism.

[0025] The second object of the present invention is achieved through the following technical measures: a three-position switch transmission mechanism calculated using the above-mentioned parameter design method for double locking of the three-position switch transmission mechanism, which is a hinged four-bar mechanism consisting of an operating mechanism output crank arm, a connecting rod, a three-position switch output crank arm and a frame, characterized in that when the horizontal distance O1 between the rotation axis O1 of the operating mechanism output crank arm and the rotation axis O2 of the three-position switch output shaft is 59 mm and the vertical distance is 165 mm, the length of the operating mechanism output crank arm is 81 mm, and the initial angle of its rotation is 7°; the length of the three-position switch output crank arm is 92 mm, and the initial angle of its rotation is 27°; the length of the connecting rod is 166 mm, and the angle between the center line of the three-position switch in the grounded position and the center line of the three-position switch output crank arm in the grounded position is 63°.

[0026] Compared with the prior art, the present invention has the following significant effects:

[0027] (1) The present invention can determine the parameters of the three-position switch transmission mechanism. Based on these parameters, the transmission mechanism can realize the double locking function of the three-position switch in the closed position and the grounded position, ensuring that the contacts of the three-position switch are not passively separated when they are in the closed position and the grounded position, thereby improving the safety of operation and enabling the three-position switch to meet its electrical performance requirements in the closed position, the isolated position and the grounded position.

[0028] ⑵ When the three-position switch is in the grounding position, for the example of a specific implementation method, the angle between the output crank arm of the operating mechanism and the connecting rod is 3°. At this time, as long as the output crank arm of the operating mechanism is locked and no longer rotates clockwise, the three-position switch itself will not be separated from the static contact of the moving contact of the three-position switch regardless of whether it is under the action of positive or reverse external force (here mainly refers to electric power, vibration / vibration impact force) (theoretically there is a slight displacement, but it will not affect the electrical performance of the three-position switch), ensuring that the contacts are not passively separated when the three-position isolating switch is in the grounding position, thereby improving the safety of operation; that is: the three-position switch can only be operated when the output crank arm of the operating mechanism rotates counterclockwise under human power and external force.

[0029] ⑶ When the three-position switch is in the closed position, for the example of a specific implementation method, the angle between the output crank arm of the operating mechanism and the connecting rod is 3°. Similarly, at this time, as long as the output crank arm of the operating mechanism is locked and no longer rotates counterclockwise, the three-position switch itself will not be separated from the static contact of the moving contact of the three-position switch regardless of whether it is under the action of positive or reverse external force (here mainly refers to the impact force of electric power and vibration). (Theoretically, there is a slight displacement, but it will not affect the electrical performance of the three-position switch), ensuring that the contacts are not passively separated when the three-position disconnector is in the grounded position, thereby improving the safety of operation; that is, the three-position switch can only be operated when the output crank arm of the operating mechanism rotates clockwise under human power and external force.

[0030] (4) Locking the output crank arm of the operating mechanism does not affect the operation of the operating mechanism. It has a simple structure and is easy to implement. It is also a desired design function of the operating mechanism.

[0031] ⑸ When many unknown factors such as the crank, rocker, connecting rod, crank initial angle, rocker initial angle, etc. of the hinged four-bar mechanism are uncertain, the parameter design method of the present invention can achieve satisfactory results and at the same time guide designers to improve design efficiency and design level. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] Figure 1 It is a side view of the three-position switch, transmission mechanism and operating mechanism;

[0034] Figure 2 This is a front view of the three-position switch, transmission mechanism and operating mechanism;

[0035] Figure 3 This is a schematic diagram of a three-position switch in the grounded position;

[0036] Figure 4 This is a schematic diagram of a three-position switch in the open position;

[0037] Figure 5 This is a schematic diagram of a three-position switch in the closed position;

[0038] Figure 6 It is a schematic diagram of the definition of various parameters of the transmission mechanism;

[0039] Figure 7 It is a schematic diagram of the simulated motion of the transmission mechanism parameter design;

[0040] Figure 8 This is a schematic diagram of an example of designing the grounding position parameters of a transmission mechanism;

[0041] Figure 9 This is a schematic diagram of the design example of the transmission mechanism opening position parameters;

[0042] Figure 10 This is a schematic diagram of an example of designing the closing position parameters of a transmission mechanism;

[0043] Figure 11 This is a schematic diagram of an example of locking the grounding position parameter design of a transmission mechanism;

[0044] Figure 12 This is a schematic diagram of an example of locking the transmission mechanism closing position parameter design.

[0045] In the figure: 1-three-position switch, 11-contact finger, 2-transmission mechanism, 3-operating mechanism, 4-grounding static contact, 5-closing static contact, 6-crank, 7-frame, 8-rocker, 9-connecting rod, 10-locking pin, O1-rotation axis of the output crank arm of the operating mechanism, O2-rotation axis of the output crank arm of the three-position switch, L-horizontal distance, H-vertical distance, L1-grounding break, L2-isolating break, L3-center line of the three-position switch, α-initial angle of crank rotation, β-initial angle of rocker rotation. DETAILED DESCRIPTION

[0046] The present invention provides a parameter design method for a double-locking transmission mechanism of a three-position switch. The parameters of the transmission mechanism are determined as follows:

[0047] (1) The length of the output crank arm of the operating mechanism and its initial rotation position;

[0048] (2) The length of the output arm of the three-position switch and its initial rotation position;

[0049] (3) The length of the connecting rod between the output crank arm of the three-position switch and the output crank arm of the operating mechanism;

[0050] ⑷ The angle between the center line of the three-position switch in the grounded position and the center line of the output arm of the three-position switch in the grounded position.

[0051] like Figure 3 、 Figure 4 、 Figure 5 As shown, the three-position switch 1 is in the grounding position, the opening position, and the closing position, respectively. According to the electrical clearance requirements of the three-position switch 1, it is confirmed that the electrical clearance between the grounding break L1 and the isolating break L2 of the three-position switch 1 is approximately 75 mm (i.e., 75 mm ± 3 mm, which is a maximum control value. In actual design, there are other factors that affect this electrical clearance, so the 75 mm mentioned below is not marked with a tolerance). When all the contact fingers of the three-position switch 1 reach 100% contact with the conductive planes of the static contacts, the center line L3 of the three-position switch 1 rotates from the grounding position to the isolating position with a rotation angle of 65°, and vice versa; the center line L3 of the three-position switch 1 rotates from the isolating position to the closing position with a rotation angle of 60°, and vice versa.

[0052] The rotation axis O2 of the three-position switch output shaft and the rotation axis of the three-position switch output crank arm are the same center of the circle, and rotate synchronously with the three-position switch 1, that is: the three-position switch output crank arm rotates from the grounding position to the isolation position, the rotation angle is 65°, and vice versa; the three-position switch output crank arm rotates from the isolation position to the closing position, the rotation angle is 60°, and vice versa.

[0053] It is known that the operating mechanism 3 can intermittently rotate forward and reverse twice, each time rotating 90°, and the operating sequence is the same as that required by the three-position switch.

[0054] like Figures 1 to 12 As shown, the present invention includes the following steps:

[0055] S1, see Figure 1 、 Figure 2 The figure shows a three-position switch 1, a transmission mechanism 2, and an operating mechanism 3. The relative installation positions of the three-position switch 1 and the operating mechanism 3 are determined based on the structural layout. The horizontal distance L and vertical distance H between the rotation axis O1 of the output crank arm of the operating mechanism 3 and the rotation axis O2 of the output shaft of the three-position switch 1 are determined to obtain the distance parameters. In this embodiment, the horizontal distance L is 59 mm and the vertical distance H is 165 mm.

[0056] S2, such as Figure 6 、 Figure 7 As shown, use CAD drawing software or draw on paper to draw the rotation axis O1 of the output arm of the operating mechanism 3 (which is the same center as the rotation axis of the output shaft of the operating mechanism) and the rotation axis O2 of the output shaft of the three-position switch 1;

[0057] S3. With the rotation axis O2 of the output shaft of the three-position switch 1 as the center of the circle, draw the center line L3 of the three-position switch 1. The angle between the closed position and the isolated position is 65°, and the angle between the isolated position and the grounded position is 60°. You can also draw the center line of the output arm of the three-position switch. The angle between the closed position and the isolated position is 65°, and the angle between the isolated position and the grounded position is 60°.

[0058] S4. Design the transmission mechanism (hinge four-bar mechanism) based on the positions of the three-position switch output crank arm and the operating mechanism output crank arm, and when the grounding position, isolation position, and closing position are simultaneously established;

[0059] Connect the rotation axis O1 of the output shaft of the operating mechanism 3 and the rotation axis O2 of the output shaft of the three-position switch 1. The connecting line O1-O2 is the frame 7 of the transmission mechanism. With the hinge points at both ends of the frame 7 as the center and the X1 axis and Y1 axis as the dividing lines, a rectangular coordinate system I is established; with the X2 axis and Y2 axis as the dividing lines, a rectangular coordinate system II is established;

[0060] S5. Draw a circle with the center of rectangular coordinate system I as the center and the length r1 = 81 of crank 6 (the output arm of the operating mechanism) as the radius. Rotate crank 6 clockwise twice, 90° each time, at the lower end of the third quadrant of rectangular coordinate system I, at its initial rotation angle α = 7°. The crank 6 intersects the circumference of the circle at intersection points A1, B1, and C1.

[0061] S6. Draw a circle with the center of rectangular coordinate system II as the center and the length r2 = 92 of the rocker 8 (the output arm of the three-position switch) as the radius. At the lower end of the third quadrant of rectangular coordinate system II, rotate the rocker 8 clockwise twice, first by 65° and then by 60°, at its initial rotation angle β = 27°. The rocker 8 intersects the circumference of the circle at intersection points A2, B2, and C2.

[0062] According to the position of the frame, the crank rotates 90° each time, the rocker rotates about 60-65° each time, and the length of the rocker is greater than the length of the crank; the connecting rod is a fixed length, the starting position of the crank should be at the lower end of the third quadrant of the rectangular coordinate system I, and its limit position should be the central axis Y1 of the third and fourth quadrants of the rectangular coordinate system I; similarly, the starting position of the rocker should be at the lower end of the third quadrant of the rectangular coordinate system II, and its limit position should be the central axis Y2 of the third and fourth quadrants of the rectangular coordinate system II; based on the above judgment, a crank length and an initial angle at the lower end of the third quadrant are preliminarily tried; a rocker length and an initial angle at the lower end of the third quadrant are preliminarily tried to confirm that the rocker length is greater than the crank length.

[0063] S7. Connect the intersections A1, B1, and C1 with the intersections A2, B2, and C2 to form three lines (A1-A2, B1-B2, and C1-C2) (the line connecting the output arm end of the operating mechanism and the output arm end of the three-position switch, i.e., connecting rod 9), and measure the length of connecting rod 9 respectively.

[0064] If the length difference between the three connecting lines A1-A2, B1-B2, and C1-C2 is within the set range (the set range is 0-2 mm), the designed transmission mechanism is established and the process proceeds to step S8. Otherwise, another crank length r1, crank initial rotation angle α, rocker length r2, and rocker initial rotation angle β are taken, and steps S5-S7 are repeated until the length difference between the three connecting lines A1-A2, B1-B2, and C1-C2 is within the set range (the set range is 0-2 mm), and the process proceeds to step S8.

[0065] In this embodiment, the length of the A1-A2 connecting line is 165.656 mm, the length of the B1-B2 connecting line is 165.297 mm, and the length of the C1-C2 connecting line is 165.941 mm. The lengths of the three connecting lines are approximately equal, that is, the connecting rod 9, and the designed transmission mechanism is established;

[0066] S8. Confirm that the angle between the center line of the three-position switch in the grounded position and the center line of the rocker in the grounded position is 63°;

[0067] S9. Use the confirmed parameters to verify that the electrical clearance between the isolating break L2 and the grounding break L1 of the three-position switch is 75 mm. If the verification is successful, the parameters that meet the double locking requirement of the three-position switch transmission mechanism are determined. Otherwise, re-optimize the design according to steps S1 to S8 until the electrical clearance between the isolating break and the grounding break of the three-position switch is verified to be 75 mm, and the parameters that meet the double locking requirement of the three-position switch transmission mechanism are determined.

[0068] See also Figures 8 to 10 , respectively showing the design parameters of the transmission mechanism in the grounding position, the opening position and the closing position; Figure 11 and Figure 12 , respectively showing that the transmission mechanism is locked in the grounding position and the closing position parameter design, and the output arm of the operating mechanism is locked by the locking pin 10.

[0069] In this embodiment, the confirmed parameters are used to verify that the electrical clearance between the isolation break and the grounding break of the three-position switch is 75 mm. The parameters of the transmission mechanism are designed and confirmed as follows:

[0070] (1) The length of the output arm of the operating mechanism is 81 mm, and its initial rotation angle is 7°;

[0071] (2) The length of the output arm of the three-position switch is 92mm, and its initial rotation angle is 27°;

[0072] (3) The length of the connecting rod between the output crank arm of the three-position switch and the output crank arm of the operating mechanism is 166mm;

[0073] (4) The angle between the center line of the three-position switch in the grounding position and the center line of the output arm of the three-position switch in the grounding position is 63°.

[0074] This embodiment represents one of the optimal parameter combinations for the overall structural scheme of a three-position switch. Specifically, when the horizontal and vertical distances between the operating mechanism's output crank arm's rotation axis O1 and the three-position switch's output shaft's rotation axis O2 are 59 mm and 165 mm, the primary goal is to achieve a double-locking function for the transmission mechanism under specific conditions. The present invention allows for varying these horizontal and vertical distances, resulting in a variety of optimal parameter combinations, enabling the transmission mechanism to achieve double-locking, single-locking, and unlocking functions.

[0075] The design of the four-bar mechanism of the transmission mechanism of the present invention, especially when there are conditional restrictions on three positions, makes it difficult for the connecting rod length to reach an ideal state (i.e., equal). In practical applications, the connecting rod is one. Under normal circumstances, there will be changes in the feedback angle or electrical gap, but the changes will not affect the product performance (or within the design tolerance range).

[0076] In the actual drawing of the present invention, the relevant lengths and angles can be accurate to two decimal places, and the design margin and design tolerance when the movable contact of the three-position switch reaches 100% contact with each static contact can be considered.

[0077] A three-position switch transmission mechanism calculated using the above-mentioned parameter design method for double locking of the three-position switch transmission mechanism is a hinged four-bar mechanism consisting of an operating mechanism output crank arm, a connecting rod, a three-position switch output crank arm and a frame. When the horizontal distance O1 between the operating mechanism output crank arm rotation axis and the three-position switch output shaft rotation axis O2 is 59 mm and the vertical distance is 165 mm, the length of the operating mechanism output crank arm is 81 mm, and its initial rotation angle is 7°; the length of the three-position switch output crank arm is 92 mm, and its initial rotation angle is 27°; the length of the connecting rod is 166 mm, and the angle between the center line of the three-position switch in the grounded position and the center line of the three-position switch output crank arm in the grounded position is 63°.

Claims

1. A parameter design method for double locking of a three-position switch transmission mechanism, characterized in that The following steps are involved: S1. Determine the relative installation position of the operating mechanism and the three-position switch according to the structural layout, and confirm the horizontal and vertical distances between the rotation axis O1 of the output crank arm of the operating mechanism and the rotation axis O2 of the output shaft of the three-position switch; S2. Draw the rotation axis O1 of the output crank arm of the operating mechanism and the rotation axis O2 of the output shaft of the three-position switch on the diagram; S3. Draw the center line of the three-position switch with the rotation axis O2 of the output shaft of the three-position switch as the center of the circle; S4. Connect the rotation axis O1 of the output crank arm of the operating mechanism and the rotation axis O2 of the output shaft of the three-position switch. The connecting line O1-O2 is the frame of the transmission mechanism. With the hinge points at both ends of the frame as the center and the X1 axis and Y1 axis as the dividing line, a rectangular coordinate system I is established; with the X2 axis and Y2 axis as the dividing line, a rectangular coordinate system II is established; S5. Take the center of rectangular coordinate system I as the center of the circle and the length r1 of the crank as the radius to draw a circle. Rotate the crank at the lower end of the third quadrant of rectangular coordinate system I clockwise twice at its initial rotation angle α, each time by 90°. The crank intersects the circumference of the circle at intersection points A1, B1, and C1. S6. Draw a circle with the center of rectangular coordinate system II as the center and the length r2 of the rocker as the radius. At the lower end of the third quadrant of rectangular coordinate system II, the rocker rotates clockwise twice at its initial rotation angle β, the first rotation is 65°, and the second rotation is 60°. The rocker intersects the circumference of the circle at intersection points A2, B2, and C2. S7, correspondingly connect the intersection points A1, B1, C1 and the intersection points A2, B2, C2 to form three connecting lines A1-A2, B1-B2, and C1-C2, which are connecting rods, and measure the lengths of the connecting rods respectively; If the length difference of the three connecting lines A1-A2, B1-B2, and C1-C2 is within the set range, the designed transmission mechanism is established, and the process goes to step S8; otherwise, another length r1 of the crank, an initial angle α of the crank rotation, a length r2 of the rocker, and an initial angle β of the rocker rotation are taken, and steps S5 to S7 are repeated until the length of the three connecting lines A1-A2, B1-B2, and C1-C2 is within the set range, and the process goes to step S8; S8. Confirm the angle between the center line of the three-position switch in the grounding position and the center line of the rocker in the grounding position; S9. Use the confirmed parameters to verify that the electrical gap between the isolation break and the grounding break of the three-position switch is the set value. If the verification is successful, determine the parameters that meet the double locking of the three-position switch transmission mechanism; Otherwise, according to steps S1 to S8, the design is re-optimized until the electrical gap between the isolating break and the grounding break of the three-position switch is verified to be the set value, and the parameters that meet the double locking of the three-position switch transmission mechanism are determined.

2. The parameter design method for double locking of a three-position switch transmission mechanism according to claim 1 is characterized in that: The setting range is 0 to 2 mm.

3. The parameter design method for double locking of a three-position switch transmission mechanism according to claim 1 is characterized in that: The set value is 75 mm ± 3 mm.

4. A three-position switch transmission mechanism calculated by the parameter design method for double locking of a three-position switch transmission mechanism according to any one of claims 1 to 3, which is a hinged four-bar mechanism consisting of an operating mechanism output crank arm, a connecting rod, a three-position switch output crank arm and a frame, characterized in that: When the horizontal distance between the rotation axis O1 of the operating mechanism output crank arm and the rotation axis O2 of the three-position switch output shaft is 59mm and the vertical distance is 165mm, the length of the operating mechanism output crank arm is 81mm, the length of the three-position switch output crank arm is 92mm, and the length of the connecting rod is 166mm.

5. The three-position switch transmission mechanism according to claim 4 is characterized in that: The initial rotation angle of the output crank arm of the operating mechanism is 7°.

6. The three-position switch transmission mechanism according to claim 5, characterized in that: The initial rotation angle of the output crank arm of the three-position switch is 27°.

7. The three-position switch transmission mechanism according to claim 6, characterized in that: The angle between the center line of the three-position switch at the grounding position and the center line of the output arm of the three-position switch at the grounding position is 63°.

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