CN112038801A - Radio frequency switch - Google Patents

Abstract

A radio frequency switch comprises an insulating base, an insulating upper cover, a movable terminal and a fixed terminal which are clamped between the insulating base and the insulating upper cover, and a metal shell which fixedly holds the insulating base and the insulating upper cover into a whole, the movable terminal comprises a first welding foot arranged on the longitudinal first side of the insulating base, a main cantilever extending from the first welding foot to the upper part of the surface of the insulating base, and a pair of leaf spring arms respectively extending downwards from the two transverse sides of the main cantilever along the longitudinal direction, the static terminal comprises a second welding foot arranged on the second longitudinal side of the insulating base and contact arms which respectively extend to the upper parts of the pair of leaf spring arms from the second welding foot and are contacted with the leaf spring arms, the longitudinal second side edge of the insulating base protrudes upwards to form a support wall, the support wall comprises an inclined surface facing the longitudinal first side of the insulating base, and the free ends of the pair of leaf spring arms abut against the inclined surface in an initial state. This application guarantees that the elasticity performance is more miniaturized simultaneously.

Description

Radio frequency switch

Technical Field

The invention relates to the field of electric connectors, in particular to a radio frequency switch.

Background

With the advent of the intelligent era, in the field of increasingly miniaturized electronic information, such as mobile phones, wireless local area network devices and other various devices, the radio frequency switch is used for detecting radio frequency signals of various electronic devices, and the radio frequency switch is required to be further miniaturized, however, in the process of miniaturizing the radio frequency switch, the force arm of an elastic part with the function of the radio frequency switch is reduced, so that the micro radio frequency switch fails in the processes of passing through an IR furnace and detecting plugging and unplugging, and great challenges are provided for miniaturization, and therefore, a more miniaturized and reliable radio frequency switch technical scheme is needed to be provided.

Disclosure of Invention

In view of the above, it is desirable to provide a radio frequency switch that can maintain good elastic contact performance while being miniaturized.

In order to solve the technical problem, the application provides a radio frequency switch, including insulator foot, insulating upper cover, centre gripping in insulator foot with moving terminal, quiet terminal between the insulating upper cover and will insulator foot with the metal casing as an organic whole of insulating upper cover fixing, moving terminal including locate the vertical first side of insulator foot first weld leg, from first weld leg extends to the main cantilever of insulator foot surface top and from the horizontal both sides of main cantilever respectively along the oblique downwardly extending pair of leaf spring arm that forms of longitudinal direction, quiet terminal including locate the vertical second side of insulator foot second weld leg and from the second weld leg extends to a pair of contact arm above the leaf spring arm and contact arm that contact respectively, the vertical second side edge of insulator foot upwards protrudes and is formed with the buttress wall, the buttress wall includes towards the inclined plane of the vertical first side of insulator foot, the free ends of the plate spring arms abut against the inclined surface of the supporting wall in an initial state, and when the main cantilever is pressed downwards, the plate spring arms move towards the first longitudinal side of the insulating base along the inclined surface.

Preferably, the leaf spring arm comprises a support arm formed by extending from two lateral sides of the main cantilever and a support end formed by bending upwards from a free end of the support arm, a support point supported on the inclined plane is arranged on the lower surface of the support end, and the main cantilever and the support arm are integrally straight or integrally downward sunken.

Preferably, an end of the longitudinal first side of the main boom is higher than an end of the longitudinal second side of the support arm.

Preferably, the upper surface of insulating base sets up downwards and is formed with recessed space, the surface on inclined plane with the lower surface in recessed space is connected main cantilever is when being pushed down, main cantilever and support arm whole orientation be sunken form elastic deformation in the recessed space, and the end edge of the vertical second side of support end moves towards vertical first side.

Preferably, the vertical both sides of insulator foot are equipped with the equipment respectively move the first leg of terminal with first breach and the second breach of the second leg of quiet terminal, recessed space is located insulator foot's upper surface intermediate position, insulator foot's upper surface is followed first breach orientation the groove of dodging has been seted up to the second breach direction, dodge the groove with recessed space intercommunication, the second breach with recessed space intercommunication, first leg is located the bottom of first breach, first leg is bent upwards to be followed first breach upwards extends and is formed with first vertical portion, main cantilever is certainly first vertical portion is bent along longitudinal direction and is formed, main cantilever suspension in dodge the top of groove and recessed space.

Preferably, it upwards protrudes to be formed with the accepting part to dodge the horizontal both sides in groove, the accepting part is close to the upwards protrusion in second breach one side is formed with the dog, the insulator foot surface is in the upwards protrusion in second breach one side is formed with first support column, move the terminal still include certainly main cantilever is close to the horizontal both sides extension of first breach one side is formed with support in supporting part on the accepting part, the supporting part orientation second breach one side quilt the dog is spacing.

Preferably, the stationary terminal further includes a second vertical portion bent from one end of the second fillet and extending upward along the second notch, and a fixing portion bent from the second vertical portion in a longitudinal direction and supported on the first support column, and the pair of contact arms extend obliquely upward from two lateral sides of the fixing portion.

Preferably, the insulating upper cover including be equipped with the tube-shape portion of jack, be formed in the main part of tube-shape portion bottom, be formed in on the main part bottom surface with dodge the pit that the groove corresponds, be formed in the horizontal both sides of pit and with the acceptance portion centre gripping the pressure platform of supporting part reaches certainly the briquetting that the downward protrusion of main part bottom surface formed, main cantilever suspension in dodge between groove and the recessed space and the pit, the briquetting with the common centre gripping of first support column the fixed part.

Preferably, the supporting portion includes a downward-folded portion formed by bending and extending downward from two lateral sides of the main cantilever and a supporting leg supported on the receiving portion and formed by horizontally bending the downward-folded portion, the supporting leg is limited by the stopper, and the supporting leg is clamped by the pressing table and the receiving portion.

Preferably, the insulating base upper surface is lieing in second breach position department still is equipped with the second support column, the second support column is located the vertical outside of first support column, the horizontal plane of second support column is less than the horizontal plane of first support column, the fixed part is crossed earlier after the second support column again support in first support column upper surface.

Preferably, the metal shell includes a covering cylinder portion covering the cylindrical portion, a covering plate extending outward from an outer periphery of a bottom of the covering cylinder portion, side covering side walls formed by bending and extending downward from both lateral sides of the covering plate, and a clamping wall formed by bending the bottom of the covering side walls inward relative to each other and clamped on a bottom surface of the insulating base, and the leaf spring arm does not overlap with the clamping wall in the vertical direction.

Preferably, the inner wall surface of the covering cylinder portion is provided with a protruding portion, the outer peripheral surface of the covering cylinder portion is provided with a covering groove, the insulating upper cover is integrally injection-molded in the covering cylinder portion in the metal housing, and the protruding portion is covered by the covering groove.

This application radio frequency switch is through the vertical second end of insulating base upwards protrusion forms the knee wall, and form the orientation on the knee wall the inclined plane of the vertical second end of insulating base, the free end of the leaf spring arm of moving the terminal form support in support end on the inclined plane pushes down main cantilever, when leaf spring arm elastic deformation down, the support end of leaf spring arm need not along vertical the second end of insulating base removes, but follows the inclined plane court the first end direction of insulating base removes, and from this, can not lengthen when leaf spring arm deformation to need not to provide more spaces in longitudinal direction and supply the leaf spring arm of moving the terminal removes, but makes leaf spring arm length diminishes when deformation, so, can effectively reduce the product size so that it is miniaturized.

Drawings

Fig. 1 is a perspective assembly view of the rf switch of the present application;

FIG. 2 is an exploded perspective view of the RF switch of the present application;

FIG. 3 is an exploded perspective view of an alternative embodiment of the RF switch of the present application;

FIG. 4 is a diagram illustrating the engagement of the moving terminal and the fixed terminal of the RF switch of the present application;

fig. 5 is a perspective view of the rf switch of the present application with the movable and stationary terminals mounted on the insulating base and in a non-operating state without being pressed down;

FIG. 6 is a side view of the RF switch of the present application with the moving and stationary terminals in a non-operational state;

fig. 7 is a perspective view of the rf switch of the present application with the movable and stationary terminals mounted on the insulating base and in a pressing-down operating state;

fig. 8 is a side view of the rf switch of the present application with the movable and stationary terminals in an operating state.

The meaning of the reference symbols in the drawings is:

metal shell-10; a cover plate-11; a coating barrel part-12; a convex portion-121; an introduction hole-13; a cladding sidewall-14; a clamping wall-15; an insulating upper cover-20; a main body portion-21; a cylindrical portion-22; a coating groove-221; a jack-23; a pressing platform-24; briquetting with a briquette machine-25; a pit-26; an insulating base-30; a bottom plate-31; a receiving portion-311; a stopper-312; avoidance slot-313; -a recessed space-314; a first gap-315; a second gap-316; a support table-32; first and second support posts-331, 332; a support wall-35; an edge portion-351; bevel-352; a movable terminal-40; a first leg-41; a first vertical portion-42; a main cantilever-43; a leaf spring arm-44; a support arm-441; support end-442; support point-443; a support portion-45; a fold-down portion-451; supporting feet-452; a stationary terminal-50; a second fillet-51; a second upright portion-52; a fixed part-53; contact arm-54.

Detailed Description

To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

It will be understood that when an element is referred to as being "secured to" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

In the present application, the X direction shown in fig. 1 is the left-right direction (lateral direction), the Y direction is the front-back direction (longitudinal direction), and the Z direction is the vertical direction.

Referring to fig. 1 to 4, the rf switch of the present application includes an insulating base 30, an insulating upper cover 20, a moving terminal 40 clamped between the insulating base 30 and the insulating upper cover 20, a fixed terminal 50, and a metal housing 10 holding the insulating base 30 and the insulating upper cover 20 together.

The insulating base 30 includes a bottom plate 31 and a plurality of supporting bases 32 formed to protrude upward from the outer side of the bottom plate 31. A first notch 315 and a second notch 316 for assembling the movable terminal 40 and the fixed terminal 50 are respectively opened at two longitudinal ends of the bottom plate 31. An avoiding groove 313 is formed in the middle of the bottom plate 31 on one side of the first notch 315 along the longitudinal direction, and a concave space 314 is formed in the middle of the bottom plate 31 to the second notch 316. The avoidance groove 313 is provided with receiving portions 311 on both lateral sides, the receiving portions 311 protrude upward toward the second notch 316 to form a stop 312, and the receiving portions 311 are a part of the bottom plate 31.

The bottom plate 31 is formed with a first supporting column 331 and a second supporting column 332 protruding upwards inside the second notch 316, the first supporting column 331 is located inside, the second supporting column 332 is located outside, and the horizontal plane of the first supporting column 331 is higher than the horizontal plane of the second supporting column 332. The bottom plate 31 is formed with a support wall 35 protruding upward at an end edge of the second notch 316, and the support wall 35 is formed with an edge portion 351 protruding upward and a slope 352 extending obliquely downward from the edge portion 351 toward the first notch 315. The support walls 35 are located at both lateral sides of the second notch 316.

The movable terminal 40 includes a first solder leg 41 located at the bottom of the first notch 315, a first vertical portion 42 formed by bending one end of the first solder leg 41 upward and extending upward along the first notch 315, a main cantilever 43 formed by bending the first vertical portion 42 horizontally and extending toward the second notch 316, and a pair of leaf spring arms 44 formed by branching and extending from two lateral sides of the main cantilever 43. The main cantilever 43 extends from above the avoiding groove 313 to the recessed space 314, wherein the width of the main cantilever 43 above the recessed space 314 is greater than the width of the main cantilever 43 above the avoiding groove 313. The pair of leaf spring arms 44 are formed by extending from both lateral sides of the free end of the main suspension arm 43 obliquely toward the recessed space 314, and each leaf spring arm 44 includes a support arm 441 extending from both lateral sides of the main suspension arm 43, a support end 442 bent upward from the free end of the support arm 441, and a support point 443 formed on the lower surface of the support end 442, wherein the support point 443 is supported on the inclined surface 352 of the support wall 35, and the end edge of the support end 442 does not extend beyond the support wall 35.

The movable terminal 40 further includes a support portion 45 formed by bending downward from two lateral sides of one end of the main cantilever 43 close to the first solder tail 41, and the support portion 45 is supported on the receiving portion 311 and is limited by the stopper 312. The support portion 45 includes a downward folded portion 451 formed by bending and extending obliquely downward and a support leg 452 formed by horizontally bending an end portion of the downward folded portion 451, and the support leg 452 is supported on the receiving portion 311. The support by the support portion 45 provides an elastic support force to the main suspension arm 43 to make the main suspension arm 43 more elastic. The stopper 312 limits the supporting foot 452 from moving toward the second notch 316.

The stationary terminal 50 includes a second fillet 51 located at the bottom of the second notch 316, a second vertical portion 52 bent upward from the second fillet 51 and extending upward along the second notch 316, a fixing portion 53 bent from the second vertical portion 52 and extending to the first support column 331, and a pair of contact arms 54 extending obliquely upward from the fixing portion 53 along the lateral outer side. A pair of contact arms 54 contact and make electrical connection, respectively, over a pair of leaf spring arms 44.

The insulating upper cover 20 includes a main body 21, a cylindrical portion 22 formed to protrude upward from the main body 21, and an insertion hole 23 penetrating the cylindrical portion 22 and the main body 21. A concave pit 26 is formed at the position of the main body part 21 corresponding to the avoiding groove 313, and a pressing platform 24 for pressing the supporting leg 452 on the receiving part 311 is formed at the position of the concave pit 26 corresponding to the receiving part 311 and the stopper 312 in a downward protruding manner. The main body 21 is formed with a pressing block 25 at a position corresponding to the first and second supporting posts 331, 332. A covering groove 221 is formed on the outer peripheral surface of the cylindrical portion 22 near the body portion 21, and the covering groove 221 is preferably an annular groove.

The metal shell 10 includes a covering cylinder 12 covering the periphery of the cylindrical part 22, a covering plate 11 extending outward from the periphery of the bottom of the covering cylinder 12, side covering sidewalls 14 formed by bending downward from both lateral sides of the covering plate 11, and a clamping wall 15 formed by bending inward from the bottom of the side covering sidewalls 14. The middle of the coating cylinder part 12 is provided with an introduction hole 13 concentric with the insertion hole 23. A convex part 121 is formed on the inner wall surface of the coating cylinder part 12 in a punching manner towards the direction of the center of a circle at a position corresponding to the coating groove 221, the insulating upper cover 20 and the metal shell 10 are integrally injection-molded, and the convex part 121 is coated in the coating groove 221 so that the insulating upper cover 20 and the coating cylinder part 12 are tightly combined and are not easy to separate.

The insulating upper cover 20 is integrally injection-molded in the metal housing 10, or the insulating upper cover 20 may be separately injection-molded and then assembled in the metal housing 10.

The assembly method of the radio frequency switch of the application is as follows:

the metal shell 10, the movable terminal 40 and the fixed terminal 50 are formed by punching, the clamping wall 15 of the metal shell 10 is not bent from the bottom of the cladding side wall 14, and the movable terminal 40 and the fixed terminal 50 are both independently connected with a material belt; injection moulding insulating base 30, insulating upper cover 20 (insulating upper cover 20 can be after metal casing 10 stamping forming again with metal casing 10 mould injection moulding). Mounting the movable terminal 40 on the insulating base 30, with the first leg 41 and the first vertical portion 42 located at the first notch 315, the main cantilever 43 extending from above the avoiding groove 313 to above the recessed space 314, the pair of leaf spring arms 44 extending from above the recessed space 314 obliquely downward to abut against the inclined surface 352 of the supporting wall 35, and the leaf spring arms 44 abutting against the inclined surface 352 of the supporting wall 35 through the supporting points 443; the pair of support portions 45 is supported on the receiving portion 311. The stationary terminal 50 is assembled to the insulating base 30, the second solder leg 51 and the second vertical portion 52 are located at the position of the second notch 316, the fixing portion 53 is supported on the upper surface of the first supporting column 331, and the pair of contact arms 54 are electrically connected to the inner sides of the pair of leaf spring arms 44. The insulating upper cover 20 and the metal shell 10 are then assembled downward above the insulating base 30, the supporting legs 452 of the supporting portion 45 are clamped between the receiving portion 311 and the pressing table 24, and the fixing portion 53 is clamped between the first supporting column 331 and the pressing block 25. Finally, the bottom of the cladding side wall 14 of the metal shell 10 is bent inward to form a clamping wall 15 clamped on the bottom surface of the insulating base 30 so as to hold the insulating base 30 and the insulating upper cover 20 together.

Referring to fig. 5 to 8, the operation principle of the rf switch of the present application is as follows:

when the movable terminal is initially in a non-working state (as shown in fig. 5 and 6), the main cantilever 43 of the movable terminal 40 is arched upward under the support of the pair of leaf spring arms 44 and the support portion 45, and the pair of contact arms 54 of the fixed terminal 50 are electrically contacted with the inner sides of the pair of leaf spring arms 44; at this time, the imaginary line L1 is defined as an initial position, the imaginary line L2 is defined as an operating position, and the free end of the support end 442 is at the initial position L1 in the vertical direction.

When the movable terminal is in an operating state (as shown in fig. 7 and 8), after the probe (not shown) is inserted into the insertion hole 23, the main cantilever 43 of the movable terminal 40 is pressed downward, so that the main cantilever 43 and the leaf spring arm 44 are forced to deform downward elastically, and the leaf spring arm 44 is separated from the contact arm 54, at this time, the support end 442 of the leaf spring arm 44 moves along the inclined surface of the support wall 35 toward the first notch 315, that is, the free end of the support end 442 moves from the initial position L1 toward the first notch 315 to the operating position L2, and at the same time, the stopper 312 limits the support leg 452 of the support portion 45 from moving toward the second notch 316, so as to ensure that the movable terminal 40 does not move toward the second notch 316 as a whole.

The rf switch of the present application forms the support wall 35 by protruding upward at the longitudinal second end of the insulating base 30, and a slope 352 is formed on the support wall 35 toward the second longitudinal end of the insulation base 30, the free end of the leaf spring arm 44 of the movable terminal 40 forms a support end 442 supported on the inclined surface 352, when the main suspension arm 43 is pressed down and the leaf spring arm 44 is elastically deformed downward, the supporting end 442 of the leaf spring arm 44 does not need to move along the longitudinal direction of the second end of the insulating base, but moves along the inclined surface 352 in the direction of the first end of the insulating base 30, whereby the leaf spring arm 44 is deformed without being lengthened, so that there is no need to provide more space in the longitudinal direction for the leaf spring arm 44 of the movable terminal to move, but the length of the leaf spring arm 44 is reduced during deformation, so that the size of the product can be effectively reduced to be miniaturized.

The technical features of the above embodiments can be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the above embodiments are not described, but should be considered as the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above examples only express preferred embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims (12)

1. A radio frequency switch comprises an insulating base, an insulating upper cover, a movable terminal and a fixed terminal which are clamped between the insulating base and the insulating upper cover, and a metal shell which fixes the insulating base and the insulating upper cover into a whole, wherein the movable terminal comprises a first welding foot arranged on a longitudinal first side of the insulating base, a main cantilever extending from the first welding foot to the upper part of the surface of the insulating base, and a pair of plate spring arms formed by obliquely and downwardly extending from the two transverse sides of the main cantilever along the longitudinal direction respectively, the fixed terminal comprises a second welding foot arranged on a longitudinal second side of the insulating base and a contact arm extending from the second welding foot to the upper parts of the pair of plate spring arms respectively and contacting with the second welding foot respectively, and the radio frequency switch is characterized in that a support wall is formed by upwards projecting the edge of the longitudinal second side of the insulating base and comprises an inclined plane facing the longitudinal first side of the insulating base, the free ends of the plate spring arms abut against the inclined surface of the supporting wall in an initial state, and when the main cantilever is pressed downwards, the plate spring arms move towards the first longitudinal side of the insulating base along the inclined surface.

2. The rf switch of claim 1, wherein the leaf spring arm includes a support arm extending from two lateral sides of the main cantilever, and a support end bent upward from a free end of the support arm, the support end having a support point supported on the inclined plane on a lower surface thereof, and the main cantilever and the support arm are integrally straight or integrally downward-recessed.

3. The radio frequency switch of claim 2, wherein an end of the main cantilever on a first longitudinal side is higher than an end of the support arm on a second longitudinal side.

4. The RF switch according to claim 2, wherein the upper surface of the insulating base is recessed downward to form a recessed space, the surface of the inclined surface is connected to the lower surface of the recessed space, when the main arm is pressed downward, the main arm and the supporting arm are elastically deformed in a recessed manner toward the recessed space as a whole, and the end edge of the longitudinal second side of the supporting end moves toward the longitudinal first side.

5. The RF switch according to claim 4, wherein the insulating base has a first notch and a second notch respectively formed on two longitudinal sides thereof for assembling the first leg of the movable terminal and the second leg of the fixed terminal, the recessed space is located at a middle position of the upper surface of the insulating base, an avoiding groove is formed on the upper surface of the insulating base along the direction of the first notch toward the second notch, the avoiding groove is communicated with the recessed space, the second notch is communicated with the recessed space, the first leg is located at a bottom of the first notch, the first leg is bent upward and extends upward along the first notch to form a first vertical portion, the main cantilever is formed by bending the first vertical portion in a longitudinal direction, and the main cantilever is suspended above the avoiding groove and the recessed space.

6. The RF switch according to claim 5, wherein the avoiding groove has a receiving portion formed by two lateral sides protruding upward, the receiving portion has a stopper formed by one lateral side protruding upward near the second notch, the surface of the insulating base has a first supporting pillar formed by one lateral side protruding upward near the second notch, the movable terminal further includes a supporting portion formed by extending from two lateral sides of one lateral side of the main cantilever near the first notch, and the supporting portion is retained by the stopper toward the second notch.

7. The RF switch according to claim 6, wherein the stationary terminal further includes a second vertical portion bent from one end of the second solder tail and extending upward along the second gap, and a fixing portion bent from the second vertical portion in a longitudinal direction and supported on the first support pillar, and a pair of the contact arms are formed extending obliquely upward from both lateral sides of the fixing portion.

8. The RF switch according to claim 7, wherein the insulating upper cover includes a cylindrical portion having a hole, a main portion formed at a bottom of the cylindrical portion, a recess formed on a bottom surface of the main portion corresponding to the avoiding groove, pressing pads formed on lateral sides of the recess and clamping the supporting portion with the receiving portion, and a pressing block formed to protrude downward from the bottom surface of the main portion, the main cantilever is suspended between the avoiding groove and the recess, and the pressing block and the first support pillar clamp the fixing portion together.

9. The RF switch according to claim 7, wherein the supporting portion includes a downward folded portion formed by bending downward from two lateral sides of the main cantilever and a supporting leg horizontally bent from the downward folded portion and supported on the receiving portion, the supporting leg is limited by the stopper, and the supporting leg is clamped by the pressing table and the receiving portion.

10. The RF switch according to claim 7, wherein a second supporting pillar is further disposed on the upper surface of the insulating base at the second notch, the second supporting pillar is located longitudinally outside the first supporting pillar, a horizontal plane of the second supporting pillar is lower than a horizontal plane of the first supporting pillar, and the fixing portion passes over the second supporting pillar and then is supported on the upper surface of the first supporting pillar.

11. The radio frequency switch according to claim 1, wherein the metal case includes a covering cylinder portion covering the cylindrical portion, a covering plate extending outward from an outer periphery of a bottom of the covering cylinder portion, side covering sidewalls bent downward from both lateral sides of the covering plate, and a clamping wall bent inward from a bottom of the covering sidewall and clamped on a bottom surface of the insulating base, and the leaf spring arm does not overlap with the clamping wall in an up-down direction.

12. The radio frequency switch according to claim 11, wherein a convex portion is formed to protrude from an inner wall surface of the covering cylinder portion, a covering groove is formed on an outer peripheral surface of the covering cylinder portion, the insulating upper cover is integrally injection-molded in the covering cylinder portion in the metal case, and the convex portion is covered with the covering groove.

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