KR20060046503A - Thermally actuated switch - Google Patents

Abstract

Provided is a thermal switch which prevents deformation of the cover and enables a resin mold.

A case 1 made of synthetic resin having an accommodating portion 1a having an upper surface opened, first and second fixed terminals 2 and 3 arranged in a partially exposed manner in the accommodating portion 1a, and an accommodating portion ( Inverted in 1a), having one end connected to the first fixed terminal 2 and a movable contact 7 contacting and spaced apart from the fixed contact 3a formed on the second fixed terminal 3 on the other end side. The bimetal piece 6 which is possible, and the cover 8 made of synthetic resin superposed | polymerized on the case 1 so that the accommodating part 1a may be provided, The case 1 and the cover 8 in the cover 8 are provided. The metal deformation prevention part 9 which can withstand the resin flow pressure at the time of resin molding was formed.

Description

Thermal Response Switch {THERMALLY ACTUATED SWITCH}

1 is a cross-sectional view showing a thermal switch of the present invention.

Fig. 2 is a plan view showing a state where the cover of the thermal switch of the present invention is removed.

3 is a cross-sectional view showing a cover of the thermally active switch of the present invention.

Fig. 4 is a bottom view showing the cover of the thermally active switch of the present invention.

Fig. 5 is an operation explanatory diagram showing the inversion operation of the bimetal piece of the present invention.

6 is a perspective view showing a conventional thermal switch.

7 is a cross-sectional view showing a conventional thermal switch.

<Explanation of symbols for main parts of drawing>

1: case 1a: storage

1b: concave groove 1c: boss

2: first fixing terminal 2a: contact piece

2b: projecting portion 2c: connecting terminal portion

3: second fixed terminal 3a: fixed contact

3c: connection terminal section 4: static characteristic thermistor

5: leaf spring piece 5a: spring portion

5b: opening 5c: attachment

6: bimetallic piece 6a: inversion part

7: movable contact 8: cover

8a: engagement recessed portion 8b: top plate portion

8c: inclined portion 8d: concave portion

9: heartwood (deformation prevention part) 9a: display part

9b: connection

(Patent Document 1) Japanese Unexamined Patent Publication No. 2001-52580

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermally active switch, and more particularly, to a structure of a thermally active switch that inverts a movable contact by thermal cohesion of a bimetal piece to open and close an electrical contact.

As a structure of the conventional thermally active switch, a movable contact formed on a bimetallic piece is formed by using a thermally active element (bimetal) facing a plurality of metals having different coefficients of thermal expansion, and the normally closed contact circuit together with the movable contact. The thing of the structure which consists of a fixed contact is known (for example, refer patent document 1).

Hereinafter, the structure of the conventional thermal actuation switch is demonstrated based on drawing.

6 is a perspective view showing a conventional thermal switch, Figure 7 is a cross-sectional view showing a conventional thermal switch.

In the figure, the insulating case 31 is formed in the form of a box in which the upper surface is opened by an insulating material such as synthetic resin. Each terminal is arrange | positioned at the inner bottom part of this insulating case 31, and the one end of each terminal is guided outward from the both side surface side of the insulating case 31. As shown in FIG.

 The first terminal 32 is formed of a conductive metal material, and an attachment hole 32a to which the fixed contact 33 is fixed is formed at one end side, and an insulating case 31 is formed at the other end side of the first terminal 32. The connection terminal part 32b which extends outward from the side part of the side is formed. Incidentally, the inclined portion 32d is formed in the first terminal 32, and the inclined portion 32d is embedded in the inner bottom of the insulating case 31.

The 2nd terminal 34 is formed with the electroconductive metal material, and the protrusion part 34a by which the one end part of a bimetallic piece is welded is formed in the one end side. On the other end side of the second terminal 34, a connection terminal portion 34b which is led outward from the side surface portion of the insulating case 31 is formed. Incidentally, the inclined portion 34d is formed in the second terminal 34, and the inclined portion 34d is embedded in the inner bottom of the insulating case 31.

The bimetallic piece 35 is laminated and bonded to two kinds of metal materials having different thermal expansion coefficients, for example, from a high expansion material made of a material having a high electrical resistance and a low expansion material made of a material having a low electrical resistance. Formed. One end side of the bimetal piece 35 is fixed with a movable contact 36 in contact with and spaced apart from the fixed contact 33, and the other end side is welded to the protruding portion 34a formed in the second terminal 34. have. In addition, in the center of the bimetallic piece 35, a dome-shaped inverted portion 35a which is expanded in order to promote the inversion action is formed.

The cover 37 is formed in substantially plate shape from insulating materials, such as synthetic resin, is attached to the opening part of the insulating case 31, and the 1st, 2nd terminal 32 arrange | positioned inside the insulating case 31 is carried out. , 34), the bimetallic piece 35, and the influence of dust, gas, etc. on the movable contact 36, the fixed contact 33, etc. are prevented.

Next, operation | movement is demonstrated and it is in the state which the movable contact 36 and the fixed contact 33 which are arrange | positioned facing each other contact | connect on normal temperature and normal use temperature surface. If the temperature rises for some reason from this state, the bimetallic piece 35 performs an inversion operation in response to the increase in temperature. At this time, the movable contact 36 fixed to the bimetallic piece 35 is separated from the fixed contact 33, and the contact is turned off.

Furthermore, when the temperature drops from this state and returns to the original room temperature, the bimetal piece 35 inverts and returns as the temperature decreases, and the movable contact 36 contacts the fixed contact 33 so that the contact is on. And return to the initial state.

In recent years, in order to improve the intensity | strength with respect to the drop impact of an electric device, there exists a request to resin-mold (hot melt) the circuit board in which the electronic component was mounted in the metal mold | die. However, in the above-described conventional thermal switch, since the cover is formed of a thin resin plate, there is a problem that the cover may be deformed by the pressure at the time of the resin mold.

Therefore, an object of the present invention is to solve the above-described problems, to prevent deformation of the cover, and to provide a thermodynamic switch capable of resin mold.

MEANS TO SOLVE THE PROBLEM In order to solve the said subject, in this invention, as a 1st solution means, the case made from the synthetic resin which has the accommodating part which opened the upper surface, the 1st and 2nd fixed terminal arrange | positioned in part in the accommodating part, and said number A reversible bimetal piece which is housed in a soldering section, and has one end connected to the first fixed terminal, and a movable contact fixed to and fixed to the fixed contact formed on the second fixed terminal on the other end thereof; The cover made of synthetic resin superposed | polymerized on the case was provided, and the said cover and the deformation | transformation prevention part made of metal which can withstand the resin flow pressure at the time of the resin mold of the said cover were formed in the structure.

Moreover, as a 2nd solution means, it was set as the structure which formed the said deformation prevention part with the metal core material, and this core material was integrally embedded in the said cover.

Further, as a third solution means, the core material is formed of a metal plate material, a part of the core material is exposed to the lower surface side of the cover to form an exposed portion, and at the time of inversion of the bimetal piece, the end where the movable contact is fixed and the exposed surface are exposed. It was set as the structure formed so that an addition contact was possible.

Moreover, as a 4th solution means, it was set as the structure which adhere | attached by the ultrasonic welding over the perimeter of the accommodating part of the housing | casing part of the said case, and the polymerization part of the cover.

Best Mode for Carrying Out the Invention

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of the thermal switch of this invention is shown to FIG. 1 is a cross-sectional view of a thermally active switch of the present invention, FIG. 2 is a plan view showing a state in which a cover of a thermally active switch is removed, FIG. 3 is a cross-sectional view of a cover of a thermally active switch, FIG. 4 is a bottom view of a cover of a thermally active switch, 5 is an explanatory view of the operation during the inversion operation of the bimetal piece.

In the figure, the case 1 is formed in the form of a box in which the upper surface is opened as an insulating material made of synthetic resin, and the housing portion 1a is formed. In the inner bottom part of the storage part 1a of this case 1, each fixed terminal mentioned later is integrally embedded, one part of one end side is exposed and arrange | positioned, and the other end side of each said fixed terminal is a case (1). ) Are drawn outward from both side faces. Moreover, the circular recessed groove 1b is formed in the center of the inner bottom part of the case 1. In addition, bosses 1c protruding upward are formed at two corner portions of one opening of the case 1, and engagement recesses 8a of the boss 1c and the cover 8 described later are provided. The cover 8 is positioned so that the cover 8 is positioned in the case 1.

The 1st fixed terminal 2 is formed in electroconductive metal materials, such as brass, in flat form. One end side of the first fixed terminal 2 is bent from the inside of the case 1 to the bottom surface side and extends to the center of the housing portion 1a of the case 1, and the extended tip is The contact piece 2a is formed in the inner bottom face of the said recessed groove 1b. In addition, at one end side of the housing portion 1a, a protruding portion 2b, which is knitted upwardly by a press or the like, is formed in the vicinity of the root that is in contact with the contact piece 2a, and the protruding portion 2b is a bimetal which will be described later. It is a welding part fixed to the one end of the piece 6.

Moreover, the other end side of the 1st fixed terminal 2 is bent from the inside of the said case 1 to the bottom face side, This curved front side is led out from the side part of the said case 1, etc. The connecting terminal portion 2c to be connected is formed.

Similarly, the second fixed terminal 3 is formed of a conductive metal material such as brass in a flat plate shape. One end side of the second fixed terminal 3 is exposed to the other end side of the housing portion 1a of the case 1, and a fixed contact 3a in contact with the movable contact 7 described later is formed in the center thereof. It is.

Moreover, the other end side of the 2nd fixed terminal 3 is bent from the inside of the case 1 to the bottom face side like the said 1st fixed terminal 2, and this curved front end side of the said case 1 The connection terminal part 3c which is led outward from the side part and connected to another electronic device or the like is formed.

In addition, a static thermistor 4 is held in the concave groove 1b. The static thermistor 4 is an electronic element (PTC element) that generates heat by energization, has a disk shape, and has electrodes on the upper and lower sides, and the upper and lower electrodes of the static thermistor 4 are the concave grooves 1b. Spring portion 5a of the contact piece 2a of the first fixed terminal 2 exposed on the inner bottom surface of the back plate) and the plate spring piece 5 described later fixed to one end side of the second fixed terminal 3. ) Is held between the ends of the circuit and held in an electrically connected state.

When the bimetallic piece 6 mentioned later is inverted by temperature change, this static characteristics thermistor 4 is made to generate | occur | produce heat | fever and performs the self hold operation which maintains the inverted state of the bimetallic piece 6.

The leaf spring piece 5 is formed from the electroconductive metal plate which has a spring property, and is formed in a U shape with the substantially flat plate-shaped spring part 5a and the opening part 5b between both ends of this spring part 5a. It has a pair of attachment part 5c extended. The leaf spring piece 5 has an attachment portion (a) in a state in which the spring portion 5a faces the contact piece 2a of the first fixed terminal 2 exposed on the inner bottom surface of the concave groove 1b. 5c) is fixed to one end of the second fixed terminal 3 by a method such as resistance welding.

At this time, the said leaf spring piece 5 is attached in the state which the fixed contact 3a formed in the center of the one end side of the said 2nd fixed terminal 3 was exposed in the opening part 5b of the attachment part 5c. Through this opening part 5a, the movable contact 7 formed in the bimetallic piece 6 mentioned later and the said fixed contact 3a are made to contact and space.

The leaf spring piece 5 is disposed on the upper side of the static thermistor 4 held in the concave groove 1b formed in the inner bottom center of the case 1, and on the upper side of the static thermistor 4; One end of the electrode and the spring portion 5a are connected, and the other end of the lower electrode of the static thermistor 4 is exposed to the inner bottom surface of the concave groove 1b by the elasticity of the leaf spring piece 5. The contact piece 2a is pressed against and held. As described above, since the static characteristic thermistor 4 can be elastically held by the spring property of the leaf spring piece 5, the first fixed terminal 2 and the second fixed terminal can be prevented and reliably held. Electrical connection of (3) can be ensured.

The bimetallic piece 6 laminates and joins at least two types of metal materials having different thermal expansion rates into a flat plate shape, for example, of a high expansion material made of a material having a high thermal expansion rate and a low expansion material made of a material having a low thermal expansion rate. Formed. One end side of the bimetal piece 6 is fixed to the protruding portion 2b formed on the first fixed terminal 2 by a method such as laser welding. On the other hand, on the other end side which becomes the free end of this bimetallic piece 6, the movable contact 7 which consists of silver-tin oxide etc. which contact and spaced apart from the said fixed contact 3a is fixed by methods, such as a laser welding.

In this case, the coupling point of the said 1st fixed terminal 2 and the one end side of the said bimetal piece 6 is made to be partially combined with the said projection part 2b which protruded in part on the 1st fixed terminal 2 and formed. Therefore, when the bimetallic piece 6 is inverted, it is easy to invert and the operation characteristic is not impaired.

Moreover, the dome-shaped inversion part 6a which expanded in order to promote reversal action is formed in the center part of the said bimetal piece 6, The temperature characteristic of the said bimetal piece 6 is formed by forming this inversion part 6a. That is, the inversion operation according to the temperature plane can be surely performed.

The cover 8 is formed in the box shape which opened the lower surface from the insulating material made of synthetic resin. In addition, concave engaging recesses 8a are formed in two corner portions of one of the openings of the cover 8, and the engaging recesses 8a and the boss 1c of the case 1 are formed. The case 1 and the cover 8 are positioned and polymerized. In this case, the periphery of the housing 1a of the case 1 and the periphery of the opening of the lower surface of the cover 8 are brought into close contact and polymerized.

Moreover, the core material 9 which consists of a flat metal plate is integrally embedded in the upper plate part 8b of the said cover 8 by methods, such as insert molding. This core material 9 is embedded over almost the entire surface of the upper plate portion 8b of the cover 8 to form a flat shape. Moreover, on the lower surface side of the upper plate part 8b of the said cover 8, a part of the said flat core material 9 is exposed and the display part 9a is formed, and this display part 9a and the said bimetal piece One end side to which the movable contact 7 of (6) is fixed is arranged to face each other. In addition, at the time of inversion of the said bimetal piece 6, the edge part to which the said movable contact 7 was fixed, and the said display part 9a are formed so that abutment is possible.

Further, the thickness of the cover 8 is such that the fixed side of the bimetal piece 6 is thick, and the inclined portion 8c is formed so that the free end side (movable contact 7 side) becomes thin, and the core material 9 is embedded and held. It is possible to reduce the height in the height direction while making it possible to avoid interference with the bimetal piece 6. (See Figure 3)

In addition, the core material 9 is integrally formed by being connected to the hoop material via the connection part 9b, and mass production is possible by cutting the connection part 9b in the recessed part 8d formed in the side wall of the cover 8. It is. Moreover, since the cross section of the cut part of this connection part 9b does not protrude outside than the recessed part 8d, an external appearance can be made small and a handling operation can be performed safely. (See Figure 4)

In order to assemble the thermally actuated switch of the above configuration, the static thermistor 4 is formed in the concave groove 1b of the housing portion 1a of the case 1 in which the first and second fixed terminals 2, 3 are arranged. And fixing the attachment portion 5c of the leaf spring piece 5 to the electrode on the upper side of the static characteristic thermistor 4 in a state where the spring portion 5a of the leaf spring piece 5 is connected. By fixing to one end of the terminal 3 by a method such as resistance welding, the lower electrode of the static thermistor 4 is pressed against the contact piece 2a of the first fixed contact 2 by the leaf spring piece 5. Keep it. At this time, the leaf spring piece 5 is attached from the opening part 5b of the attachment part 5c in the state which the fixed contact 3a formed in the center of the one end side of the 2nd fixed terminal 3 was exposed.

Next, the bimetal piece 6 is inserted into the housing portion 1a of the case 1 with the fixed contact 3a and the movable contact 7 facing each other, and the one end side of the bimetal piece 6 is first fixed. The protrusion 2b of the terminal 2 is fixed by laser welding or the like. At this time, the fixed contact 3a and the movable contact 7 are in the state electrically connected. In this state, a switch block is formed.

Next, the cover 8 is covered from the upper side of the switch block, and the bosses 1c formed at the two corner portions of the housing portion 1a of the case 1 and the two corner portions of the opening of the cover 8 are formed. It catches on the engagement recessed part 8a, and positions and superposes | polymerizes. And the superposition | polymerization surface of the case 1 and the cover 8 is welded by the method of ultrasonic welding, etc., the switch block and the cover 8 are integrated, and assembly is completed.

In this state, the first and second fixed terminals 2, 3 are in an electrically conducting state via the bimetal piece 6, and the static thermistor 4 is formed of the first and second fixed terminals (2). It is connected in parallel between 2 and 3).

In this case, the case 1 and the cover 8 are integrally brought into close contact with each other by ultrasonic welding while the spring portion 5a of the leaf spring piece 5 is in elastic contact with the static thermistor 4. Since the static characteristics thermistor 4 is held elastically by the leaf spring piece 5 and there is no fear of cracking or damage even if vibration is applied during ultrasonic welding, the case 1 and the cover are prevented. The sealing property of (8) can be improved and the intrusion of a liquid or gas from the exterior can be prevented. In addition, the entire circumference of the polymerization portion between the case 1 and the cover 8 can be brought into close contact by ultrasonic welding, and the sealing property in the storage portion at the time of the resin mold can be enhanced.

In addition, in the upper plate portion 8b of the cover 8, the core 9 made of a flat metal plate is integrally embedded by a method such as insert molding, and a circuit in which electronic components such as a thermal switch is mounted. Since the deformation | transformation prevention part at the time of board | substrate becomes a resin mold (hot melt) in a metal mold | die is formed, it is supposed that a metal deformation | transformation prevention part can be easily formed in the said cover 8 made of synthetic resin by insert molding.

In addition, the deformation preventing part made of metal may be formed by covering the metal frame so as to cover the cover 8 from the outside in addition to being integrated with the cover 8 by insert molding. In addition, by insert molding, it is also possible to use a linear material other than a flat metal plate. In any case, the deformation of the cover 8 can be prevented in the inverted region of the bimetal piece 6, that is, in the height direction of the housing portion 1a of the case 1.

Next, the operation of the thermal actuation switch of the above configuration will be described.

As shown in FIG. 1, in the normal temperature and normal use temperature surface, the movable contact 7 and the fixed contact 3a which are mutually arrange | positioned mutually contact each other, and the contact is ON state. At this time, although the bimetal piece 6 and the static thermistor 4 are connected in parallel between the 1st and 2nd fixed terminals 2 and 3, the bimetallic piece with respect to the internal resistance value which the static thermistor 4 has is carried out. Since the resistance value of (6) is extremely small, no current flows through the static thermistor 4, and a current applied between the first and second fixed terminals 2 and 3 flows through the bimetal piece 6.

Therefore, a substantial current does not flow to the static thermistor 4 side, and the static thermistor 4 hardly generates heat.

In this state, when temperature rises for some reason, as shown in FIG. 5, the inversion part 6a formed in the bimetallic piece 6 to which the movable contact 7 is fixed will perform inversion operation according to a rise of temperature. Conduct. At this time, the movable contact 7 fixed to the bimetallic piece 6 is driven together with the bimetallic piece 6, is separated from the fixed contact 3a, and the contact is turned off. In this case, the inverted portion 6a of the inverted bimetallic piece 6 inverts its bulge portion and projects in the positive characteristic thermistor 4 direction, that is, in the inner bottom direction of the case 1.

In addition, at this time, the one end side to which the movable contact 7 of the bimetal piece 6 is fixed is made of a metal plate exposed to the lower surface side of the upper plate portion 8b of the cover 8 by inverting the inverting portion 6a. It will be in the state which contacted the display part 9a of (9). As described above, the bimetal piece 6 is inverted due to the heat during the resin mold because the end portion where the movable contact 7 is fixed and the display portion 9a are formed to be in contact with each other when the bimetal piece 6 is inverted. Even if the end where the movable contact 7 is fixed is in contact with the upper plate portion 8b of the cover 8, the bimetal piece 6 is stuck in the cover 8 or the cover 8 is shaved. It is supposed to be preventable. In addition, the bimetallic piece 6 does not deform or the set temperature is shifted.

When the contact is turned off in this way, the voltage between the first and second fixed terminals 2, 3 is applied to the static thermistor 4 so that the static thermistor 4 operates, that is, energizes and generates heat. do. By the heat generation of such a static thermistor 4, the bimetallic piece 6 is maintained in the inverted position shown in FIG. 5, and it is maintained that the movable contact 7 and the fixed contact 3a remain off. do. That is, it becomes a self hold state.

At this time, the heat generation of the static thermistor 4 is efficiently transmitted to the bimetal piece 6 by placing the dome-shaped inverting portion 6a of the bimetal piece 6 in close proximity to the static thermistor 4. Will be.

To release the off state of the self-maintained contact, the applied voltage between the first and second fixed terminals 2, 3 may be cut off. In this way, when temperature falls from this state and returns to original normal temperature, the inversion part 6a of the bimetallic piece 6 will invert and return in response to the fall of temperature, and will be opposite to the direction of the static thermistor 4 The projecting contact 7 causes the movable contact 7 to contact the fixed contact 3a, thereby bringing the contact on, and returning to the initial state.

According to the structure of the thermally actuated switch of the present invention described above, the case 1 made of a synthetic resin having an accommodating portion 1a having an upper surface thereof, and the first part of which is partially exposed in the accommodating portion 1a. Fixed contacts housed in the first and second fixed terminals 2 and 3 and the accommodating portion 1a and connected at one end to the first fixed terminal 2 and formed at the second fixed terminal 3 at the other end. The reversible bimetal piece 6 to which the movable contact 7 which contacts and spaces the 3a is fixed, and the cover made of synthetic resin polymerized on the case 1 so as to cover the housing part 1a ( 8), the deformation prevention part is formed by holding the metal core 9 in the upper plate part 8b of the said cover 8, and when the said case 1 and the said cover 8 are resin-molded, The deformation preventing portion allows the upper plate portion 8b of the cover 8 to withstand the resin flow pressure. By forming the metal core 9 made of metal, the deformation of the cover 8 made of synthetic resin can be prevented, and the movable area of the movable contact portion in the housing portion 1a of the case 1 can be secured. Therefore, it is possible to provide a thermal switch capable of being made of a resin mold.

 In addition, although the above embodiment has been described as having a built-in static holding thermistor for self-holding, the present invention can be applied to a thermally active switch that does not have a self-holding function.

As described above, the thermally actuated switch of the present invention is housed in a case made of a synthetic resin having an accommodating portion with an open top surface, first and second fixed terminals arranged in part in the accommodating portion, and housed in the accommodating portion. A reversible bimetal piece having one end connected to the first fixed terminal and a movable contact fixed to the fixed contact formed on the second fixed terminal on the other end, and polymerized on the case to cover the housing; The cover is provided, and the cover and the deformation preventing portion made of metal which can withstand the resin flow pressure when the cover is resin-molded, thereby preventing the deformation of the cover made of synthetic resin, and the movable contact in the housing portion of the case Since the negative movable area can be reliably secured, a thermodynamic switch capable of being made of a resin mold can be provided.

Further, by forming the deformation preventing portion with a metal core material and embedding the core material integrally with the cover, the metal deformation preventing portion can be easily formed on the cover made of synthetic resin by insert molding.

In addition, the core material is formed of a metal sheet, and a part thereof is exposed on the lower surface side of the cover to form an exposed portion. When the bimetal piece is inverted, the core member is formed so that the exposed portion and the exposed portion are brought into contact with each other. Even if the bimetal piece is inverted by the heat and the movable contact portion abuts on the cover, the movable contact portion can be prevented from being stuck to the cover or the cover is cut.

In addition, by fixing the circumference of the housing portion of the case and the polymerization portion of the cover over the entire circumference by ultrasonic welding, the entire circumference of the polymerization portion between the cover and the case can be adhered by ultrasonic welding, and the number of resin molds The sealing property in a payment part can be improved.

Claims (4)

A case made of a synthetic resin having an upper surface with an open portion, a first and a second fixed terminal partially exposed and disposed in the storage portion, and one end side connected to the first fixed terminal by being accommodated in the storage portion; And a reversible bimetal piece having a movable contact fixed to and spaced apart from the fixed contact formed on the second fixed terminal on the other end thereof, and a cover made of a synthetic resin polymerized on the case so as to cover the housing. And a deformation preventing portion made of metal capable of withstanding the resin flow pressure when the case and the cover are resin molded. The method of claim 1, And the deformation preventing portion is formed of a metal core, and the core is integrally embedded in the cover. The method of claim 2, The core member was formed of a metal sheet, and a part of the core member was exposed to the lower surface side of the cover to form an exposed portion. When the bimetal piece was inverted, the core member was formed so as to contact the exposed portion and the exposed portion. Thermal switch. The method according to any one of claims 1 to 3, And a circumferential portion of the housing portion of the case and a polymerized portion of the cover by ultrasonic welding over the entire circumference.

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