Method for assembling a temperature-dependent switch

Abstract

To provide a method of assembling temperature-dependent switch, which does not damage a temperature-dependent switching mechanism arranged inside the switch.SOLUTION: The present invention relates to a method of assembling a temperature-dependent switch. The method includes the steps of: (i) providing a switch housing having a first electrode, a second electrode and a temperature-dependent switching mechanism arranged in the switch housing, the switching mechanism being configured to switch in a temperature-dependent manner between a closed state where, below a response temperature, the switching mechanism is in the closed state, in which the switching mechanism establishes an electrically conductive connection between the first electrode and the second electrode, and an open state where, above the response temperature, the switching mechanism is the open state, in which the switching mechanism disconnects the electrically conductive connection; (ii) heating the switching mechanism to a temperature equal to or higher than a response temperature to bring the switching mechanism into the open state; and (iii) attaching a first external terminal to the first electrode or to a part electrically connected with the first electrode by applying heat to form a material-locking connection, while the switching mechanism is in the open state.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a method for assembling a temperature-dependent switch.

Background Art

[0002] A number of temperature-dependent switches are generally already known. An exemplary temperature-dependent switch is disclosed in German Patent Publication No. 10 2019 110 448.

[0003] Such temperature-dependent switches are mainly used in a known manner for monitoring the temperature of a device. For this purpose, the switch is thermally contacted with the device to be protected, for example via one of its outer surfaces, so that the temperature of the device to be protected affects the temperature of the switching mechanism arranged inside the switch.

[0004] The switch is typically electrically connected in series to the supply circuit of the device to be protected via a connecting cable, so that the supply current of the device to be protected flows through the switch below the response temperature of the switching mechanism.

[0005] Such a temperature-dependent switch comprises a temperature-dependent switching mechanism, which is arranged in a switch housing and opens and closes the conductive connection between two electrodes of the switch according to its temperature. More precisely, the temperature-dependent switching mechanism is configured to switch between a closed state and an open state in a temperature-dependent manner, in the closed state the switching mechanism is assumed to be below the response temperature, the switching mechanism establishes a conductive connection between the two electrodes, and in the open state the switching mechanism is assumed to be above the response temperature, and the switching mechanism interrupts the conductive connection.

[0006] The term "electrode" should be interpreted in the most common way in this regard. This is an electrical contact that serves to connect to an electrical device to be protected by the switch, or an electrical contact that is electrically conductive with such an external terminal of the switch. These electrodes are led from the outside to the inside of the switch housing and are fixed to the switch housing or formed by a part of the switch housing itself.

[0007] To enable the above temperature-dependent switching function, the temperature-dependent switching mechanism arranged inside the switch housing usually includes a bimetal part that rapidly deforms from its low-temperature state to its high-temperature state when the response temperature is reached, thereby lifting and separating a movable contact part arranged on a movable element relative to the switch housing from a fixed contact part. The fixed contact part is connected to one of the two electrodes, while the movable contact part interacts with either the bimetal part or a spring part assigned to the bimetal part.

[0008] Also known is a structure in which the movable element of the temperature-dependent switching mechanism is configured as a contact bridge, which is carried by the bimetal part and directly establishes an electrical connection between the two electrodes. A temperature-dependent switch having a switching mechanism configured in such a way is disclosed, for example, in German Patent Publication No. 197 08 436.

[0009] In the above two configuration types, the bimetal part is preferably configured as a bimetal disk and preferably exists without being subjected to force within the switching mechanism in the low-temperature state. The spring part is preferably configured as a snap-action spring disk and is mechanically coupled to the bimetal part. The spring part is clamped within the switch housing and is connected to the switch housing by material bonding or inserted into the switch housing.

[0010] However, in principle, the spring part, especially in the case of a more cost-effective variant of such a temperature-dependent switch, can also be completely omitted. In such a case, the function of the spring part is taken over by the bimetal part. An exemplary temperature-dependent switch of this type is disclosed in German Utility Model Publication No. 20 2009 012 616.

[0011] Regardless of the configuration type of the temperature-dependent switching mechanism, such a temperature-dependent switch is typically electrically connected to a device protected via a connection part fixed to an electrical supply line or two electrodes. In principle, flexible connection strands, rigid connection lugs or connection cables are directly connected to the electrodes by a material connection. The strands, terminal lugs or cables are often soldered or welded to switches known from the prior art.

[0012] However, soldering or welding of the supply line or connection part has proven to be problematic in many respects.

[0013] Generally used soldering processes are difficult to automate and are not environmentally friendly, especially due to the additional soldering flux used with lead-containing solder. In addition, cold solder joints may occur, which must be absolutely avoided.

[0014] Therefore, an improved material locking connection for the supply line or connection part can in principle be realized via a welding connection, but these also have various drawbacks. In particular, common welding processes pollute the environment and are time-consuming and costly. Furthermore, in such a welding process, the switch can be heated considerably, and the switching operation of the temperature-dependent switching mechanism can be induced by welding, which is generally not desirable.

[0015] In tests conducted by the applicant, when terminal lugs or stranded wires were soldered or welded to the switch housing, it was shown that due to the heat generated during the process, the fixed contact parts inside the switch housing where the temperature-dependent switching mechanisms interacted could peel off from the electrodes assigned to the contact parts.

[0016] Also, due to heat generation, the fixed contact parts and the movable contact parts of the temperature-dependent switching mechanism may undesirably fuse together, or at least their geometric shapes may change, causing the pre-assembled switch to no longer switch, or at least not switch reliably.

[0017] Furthermore, the generation of heat leads to the bimetal part and / or the spring part being affected, and as a result, the necessary switching characteristics of the switching mechanism undesirably change.

[0018] In the worst case, this can potentially lead to the failure of all functions of the switch.

[0019] The heat generated inside the switch housing is particularly prominent when the switch housing is made of metal and the supply cable or connection part is directly welded or soldered to the switch housing. Due to the very good heat conduction characteristics of the metal, this results in particularly strong heat generation inside the switch housing. This is especially important because usually, after the switching mechanism has already been installed inside the housing or after the housing has been closed, that is, after the switch itself already exists as a semi-finished element, the supply line or connection part is only attached to the housing. Thus, whether the heat generated inside the switch causes damage as described above can only be checked within a limited range or at least with great effort.

[0020] To prevent this, the supply line or connection part is often pre-fixed to the switch housing, i.e., before the temperature-dependent switching mechanism is installed. However, this has various drawbacks. On the one hand, when the switching mechanism is installed within the switch housing, the supply line / connection parts are "in the way", which makes the handling of the switch during assembly more difficult. Furthermore, in order to achieve a sealed switch housing, it is easy to first insert the switching mechanism into the switch housing, seal the switch housing, and then attach the supply line or connect the connection part to the switch housing.

[0021] To enable such attachment of the supply line and the connection part to the switch housing after installation of the temperature-dependent switching mechanism and to avoid the above-mentioned problem of undesirable heat generation in the switch housing, German Patent Publication No. 10 2019 110 448 mentioned at the beginning proposes attaching the supply line or the connection part to the switch housing by ultrasonic welding. Compared with conventional welding methods, ultrasonic welding generates significantly less heat. It has been shown that in this way, most of the above-mentioned problems can be prevented. However, the use of the ultrasonic welding process is relatively expensive because very special welding tools are required.

Summary of the Invention

Problems to be Solved by the Invention

[0022] Therefore, an object of the present invention is to provide an improved method for assembling a temperature-dependent switch that overcomes the above-mentioned problems. In particular, the method of the present invention is intended to enable the safe and continuous attachment of external terminals to the switch without damaging the temperature-dependent switching mechanism arranged inside the switch.

Means for Solving the Problems

[0023] According to the present invention, this problem is solved by a method for manufacturing / assembling a temperature-dependent switch comprising the following steps. (i) A step of providing a switch housing in which a first electrode, a second electrode, and a temperature-dependent switching mechanism are disposed inside, the switching mechanism being configured to switch depending on temperature between a closed state in which a conductive connection is established between the switching mechanism and the first and second electrodes when a temperature lower than the response temperature is assumed, and an open state in which the switching mechanism disconnects the conductive connection when a temperature equal to or higher than the response temperature is assumed; (ii) A step of heating the switching mechanism to a temperature equal to or higher than the response temperature to put the switching mechanism in the open state; (iii) A step of attaching a first external terminal by applying heat to and performing a material-lock joint on the first electrode or a portion electrically connected to the first electrode while the switching mechanism is in the open state.

[0024] Thus, in the method according to the present invention, it is only proposed to first install the switching mechanism in the switch housing and then attach the first external terminal to the switch pre-manufactured as a semi-finished product by a material-lock joint with heat applied (e.g., by soldering or welding).

[0025] However, the applicant has recognized that the above-mentioned harmful effects that may occur in the switching mechanism disposed inside the switch housing due to the heat generated thereby can be unexpectedly reduced or completely avoided by additionally heating the switching mechanism to a temperature equal to or higher than the response temperature of the switching mechanism before the first external terminal is attached.

[0026] Heating of this switching mechanism leads to intentionally opening the switching mechanism in advance. This not only cuts off the conductive connection between the two electrodes but also cuts off the thermally conductive connection between the two electrodes caused by the switching mechanism. As a result, the heat generated when the first external terminal is attached by a material lock joint no longer has a damaging effect on the device of the temperature-dependent switching mechanism because, unlike in the closed state, the switching mechanism is in the open state and its components are not pressed against each other.

[0027] Therefore, before the first external terminal is attached, the movable contact provided in the normal switching mechanism has already been lifted from the fixed contact, while the movable contact is stationary in the closed state of the switching mechanism. Therefore, direct heat conduction between the fixed contact and the movable contact is eliminated. Therefore, it is also impossible for the movable contact of the switching mechanism to fuse or weld to the fixed contact or the first electrode due to the heat generated when the first external terminal is attached to the first electrode.

[0028] Furthermore, the vulnerable devices of the switching mechanism (e.g., the bimetal part and the spring part) are usually further away from the joint point of the first external terminal or, in the open state of the switching mechanism, are further away from the first electrode than in the closed state of the switching mechanism. Therefore, the vulnerable devices of the switching mechanism are effectively protected from the heat generated during the material lock joint by preheating the switching mechanism according to the present invention, during which the switching mechanism is kept in the open state.

[0029] Furthermore, the method according to the present invention has the advantage of effectively preventing the undesirable switching operation of the switching mechanism that may occur due to the generation of heat when the first external terminal is attached. This is because the switching mechanism is already in the open state at this time and also remains in this open state due to further heat input when the first external terminal is attached.

[0030] Thus, the above problems are completely solved.

[0031] In addition, the attachment of the first external terminal by material locking joint by applying heat is characterized by including a soldering process or a welding process.

[0032] During this process, the switching mechanism is already in its open state, so that, as described above, the heat introduced into the switch housing no longer affects the switching mechanism in any way. Therefore, according to the present invention, the conventional soldering and welding processes can be inserted at low cost. These material locking joint processes can be automated, leading to further cost advantages.

[0033] In a further improvement example, the switching mechanism is heated to a temperature above the response temperature by heating the switch housing and the switching mechanism arranged inside the switch housing with an external heat source.

[0034] Therefore, the switching mechanism arranged inside the switch housing is indirectly heated from the outside. This external heating leads to a regular switching operation of the switching mechanism and does not cause any damage to the switching mechanism itself. Heating by an external heat source has relatively low energy consumption, high cost-effectiveness, and an automated method is possible.

[0035] In step (ii) of the method, the temperature at which the switching mechanism is overheated is preferably higher than 100°C. The switching mechanism is particularly preferably heated to a temperature higher than 150°C in step (ii) of the method.

[0036] Thereby, it is guaranteed that the temperature-dependent switching mechanism is surely in an open state before step (iii) of the method is executed.

[0037] In a further improvement example, by passing the switch housing and the switching mechanism disposed therein through a heating section in an automated manner, it is preferable to heat the switching mechanism to a temperature equal to or higher than the response temperature.

[0038] Such a heating section is configured, for example, as a heating tunnel through which the switch housing automatically passes. In this way, the switch housing can be heated continuously and thus harmlessly. Such a heating section can be incorporated into an automated production line or assembly line without difficulty.

[0039] Also, it is preferable to automatically perform the attachment by material lock joining with heat application to the first external terminal after passing through the heating section.

[0040] In a further improvement example, the method according to the present invention further includes the step of (iv) attaching the second external terminal to the second electrode or a portion electrically connected to the second electrode by material lock joining with heat application.

[0041] This further step (iv) can be performed before step (ii), that is, before the switching mechanism is brought into its open state by external heating. This is possible especially when the heat generated during the material lock joining of the second external terminal does not have too great a damaging effect on the switching mechanism disposed inside the switch housing. This applies especially when the second external terminal is attached to a location on the switch away from the switching mechanism and / or is not in direct thermal contact with the switching mechanism.

[0042] However, this type of improvement example is particularly advantageous for a switch in which the two electrodes are disposed on opposite sides of the switch housing. In this case, the vulnerable parts of the switching mechanism are at a greater distance from the second electrode in the closed state than in the open state, while in the open state, they are often at a greater distance from the first electrode than in the closed state.

[0043] While the switching mechanism is in the closed state, the second external terminal is attached to the second electrode or an element connected to the second electrode, and after the switching mechanism is brought to its open state, if the first external terminal is attached to the first electrode or an element connected to the first electrode, the vulnerable parts of the switching mechanism are as far as possible away from the respective bonding points during both bonding processes. In this way, the heat generated during the two bonding processes has as little adverse effect as possible on the vulnerable parts of the switching mechanism.

[0044] However, depending on the structure of the switch and the structure of the switching mechanism inside it, it may also be advantageous for both bonding processes, i.e., the attachment of both external terminals, to be carried out after step (ii), i.e., when the switching mechanism is already in the open state.

[0045] In a further improvement example, the switch housing has a lower part and a cover part that closes the lower part and is electrically insulated from the lower part, and at least a part of the cover part is made of a conductive material, and the first electrode is arranged on the cover part.

[0046] In this improvement example, it is preferable that the cover part of the switch housing is made of metal. Therefore, the heat generated during the bonding process during step (ii) of the method is particularly high, and the method according to the present invention has particularly advantageous effects.

[0047] The lower part can also be made of a conductive material, for example, metal. The outer side of the cover part facing away from the inside of the switch housing and the outer side of the lower part facing the inside of the switch housing can be used as the contact connection of the external terminals of the switch. Therefore, the cover part and the lower part can themselves form the connection electrodes of the switch.

[0048] The first electrode can comprise a contact portion that extends outwardly from the inside of the switch housing through the cover portion. Thus, this contact portion can be of the type of piercing contact or through-contact, which forms the first electrode on the inside and includes a contact surface for the first external terminal on the outside. In such a case, the heat conduction that occurs between the bonding point and the first electrode during step (ii) of the method is particularly high, and in this case, it is particularly advantageous according to the present invention if the switching mechanism is already in the open state in advance.

[0049] In a further improvement, the method constituting steps (i)-(iii) is repeated for a plurality of temperature-dependent switches, and while steps (i)-(iii) are being executed, the switch housings of the plurality of temperature-dependent switches are fixed to a common conveyor belt.

[0050] This enables the automatic assembly of the switches.

[0051] Preferably, the conveyor belt comprises a plurality of receiving portions, to each of which one of the switch housings of the plurality of temperature-dependent switches is fixed, and each of the plurality of receiving portions is electrically connected to the second electrode of its respective switch housing and comprises a connecting piece to which the second external terminal is attached by a material-lock joint by applying heat.

[0052] This connecting piece enables a very simple method of attaching the second external terminal. Thus, the receiving portions provided on the conveyor belt, which are preferably ring-shaped, are used not only for transporting the switches but also for simplifying the bonding process for attaching the second external terminals to the individual switches.

[0053] In a further improvement, the temperature-dependent switching mechanism includes a bimetal part.

[0054] In the context of the present invention, the bimetal part is understood as a multilayer consisting of two, three or four inseparably connected parts with different coefficients of thermal expansion, and an active sheet-like device. The connection of the individual layers of metal or metal alloy is materially or positively locked and is achieved, for example, by rolling.

[0055] Such a bimetal part has a first geometric structure in its low-temperature state and a second geometric structure in its high-temperature state, and between the two structures, it switches hysteretically according to temperature. When the temperature changes beyond the response temperature or below its reset temperature, such a bimetal part changes so as to spring to another structure.

[0056] In a further improvement, the temperature-dependent switching mechanism comprises a spring part that interacts with the bimetal part.

[0057] The bimetal part is preferably a temperature-dependent bimetal snap-action disk. The spring part is preferably a snap-action spring disk that is independent of temperature.

[0058] Further features and advantages of the present invention will be apparent from the accompanying drawings and the following description.

[0059] It should be understood that the above features and the features described hereinafter can be used not only in the combinations shown in each case, but also in other combinations and alone, without departing from the scope of the present invention.

Brief Description of the Drawings

[0060] One embodiment of the present invention is shown in the accompanying drawings and will be described in more detail in the following description.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

DETAILED DESCRIPTION OF THE INVENTION

[0061] FIGS. 1 and 2 show an exemplary temperature-dependent switch that can be assembled by the method according to the present invention. This switch is generally represented by the reference numeral 10.

[0062] FIG. 1 shows the switch 10 in its low-temperature state. FIG. 2 shows the switch 10 in its high-temperature state.

[0063] It is understood that the switch 10 shown in FIGS. 1 and 2 is only one example of various possible temperature-dependent switches that can be assembled by the method according to the present invention. However, the manufacturing method or assembly method according to the present invention can, in principle, also be used for various other temperature-dependent switches having a configuration different from that of the switch 10 shown in FIGS. 1 and 2. However, the switch 10 shown in FIGS. 1 and 2 will be described below as an example of a possible temperature-dependent switch in order to explain the basic structure and function of such temperature-dependent switches.

[0064] The switch 10 includes a switch housing 12, inside of which a temperature-dependent switching mechanism 14 is arranged. The switch housing 12 includes a pot-shaped lower part 16 and a cover part 18, and this cover part is held by the folded or flanged upper edge 20 of the lower part 16 to the lower part 16.

[0065] In the example of switch 10 shown in FIGS. 1 and 2, both the lower part 16 and the cover part 18 are made of a conductive material, preferably metal. An insulating foil 22 is disposed between the lower part 16 and the cover part 18. The insulating foil 22 provides electrical insulation of the lower part 16 from the cover part 18. Similarly, the insulating foil 22 provides a mechanical seal that prevents liquid or contaminants from entering the interior of the switch housing 12 from the outside.

[0066] In this example, since the lower part 16 and the cover part 18 are each made of a conductive material, thermal contact to the electrical device to be protected can be made through their outer surfaces. The outer surfaces also function as electrical external terminals of the switch 10. For example, a first electrical external terminal can be attached to the switch 10 on the outer surface 24 of the cover part 18, and a second electrical external terminal can be attached to the outer surface 26 of the lower part 16.

[0067] In the example of switch 10 shown in FIGS. 1 and 2, an insulating layer 28 is further disposed outside the cover part 18.

[0068] The switching mechanism 14 is clamped between the lower part 16 and the cover part 18. The switching mechanism 14 includes a bimetal part 30, a spring part 32, and a movable contact part 34.

[0069] The bimetal part 30 includes a temperature-dependent bimetal snap-action disk with a central opening therein, and the bimetal snap-action disk slides over the movable contact part 34.

[0070] The spring part 32 includes a snap-action spring disk that is not temperature-dependent, and this spring disk is also fitted onto the movable contact part 34 having a central opening therein, but from the opposite bottom surface. In this way, the two snap-action disks 30, 32 are fitted onto the movable contact part 34 from both sides.

[0071] In the low-temperature state of the switch 10 shown in FIG. 1, the snap-action spring disk 32 supports the movable contact portion 34 from below by pressing its inner edge region 36 against the circumferential annular collar 38 of the movable contact portion 34 from below. Here, the snap-action spring disk 32 is supported by the outer circumferential edge portion 42 on the inner base 44 of the lower part 16.

[0072] In this state of the switch 10, the inner edge region 40 of the bimetal snap-action disk 30 is preferably freely placed on this collar 38 of the movable contact portion 34 from the opposite upper side. The outer peripheral edge 46 of the bimetal snap-action disk 30 hangs freely inside the housing 12. In this type of switch 10, in this way, the bimetal snap-action disk 30 is housed with little force applied without being firmly clamped inside the switch housing 12 in the low-temperature state.

[0073] In the low-temperature state of the switch 10 shown in FIG. 1, the temperature-dependent switching mechanism 14 establishes a conductive connection between the two electrodes 50, 52 of the switch 10 by pressing the movable contact portion 34 against the fixed contact portion 48 arranged on the cover portion 18. The contact pressure by which the movable contact portion 34 is pressed against the fixed contact portion 48 in the low-temperature state of the switch 10 is provided inside the switch 10 by the snap-action spring disk 32.

[0074] The part of the switch housing 12 functions here as the electrodes 50, 52, between which the temperature-dependent switching mechanism 14 establishes a conductive connection in the low-temperature state of the switch 10. More precisely, in the switch 10 shown in this specification, the fixed contact portion 48 functions as the first electrode 50, and the lower part 16 of the switch housing 12, or the inner bottom 44 of the lower part 16, functions as the second electrode 52.

[0075] Starting from the low-temperature state of the switch 10 shown in FIG. 1, the temperature of the device to be protected, and thus the temperature of the switch 10 and the bimetal snap-action disk 30 disposed within the switch, rises to, or rises beyond, the response temperature of the switching mechanism 14 corresponding to the response temperature of the bimetal snap-action disk 30, the bimetal snap-action disk 30 snaps from the convex low-temperature configuration shown in FIG. 1 to the concave high-temperature configuration shown in FIG. 2. During this snap action, the outer peripheral edge 46 of the bimetal snap-action disk 30 is supported by the bottom side 54 of the cover portion 18. At its center or its inner edge region 40, the bimetal snap-action disk 30 pushes the movable contact portion 34 downward and lifts the movable contact portion 34 from the fixed contact portion 48. As a result, the snap-action spring disk 32 bends downward simultaneously at its center, and as a result, the snap-action spring disk 32 snaps over from its first geometric configuration shown in FIG. 1 to its second geometric configuration shown in FIG. 2. The conductive connection between the two electrodes 50, 52 of the switch 10 previously established via the switching mechanism 14 is thus interrupted.

[0076] In this way, the temperature-dependent switching mechanism 14 is configured to establish and disconnect the conductive connection between the two electrodes 50, 52 in a temperature-dependent manner. Below the response temperature of the bimetal snap-action disk 30, the switching mechanism 14 is in its low-temperature state shown in FIG. 1 and establishes a conductive connection between the two electrodes 50, 52. As soon as the response temperature of the bimetal snap-action disk 30 is exceeded, the bimetal snap-action disk 30 brings the switching mechanism 14 to the high-temperature state shown in FIG. 2. In this state, the conductive connection between the two electrodes 50, 52 is interrupted.

[0077] Figure 5 schematically shows, in the form of a simplified flowchart, the process for manufacturing / assembling such a temperature-dependent switch 10 according to the present invention. In the first step S101, a switch housing 12 is provided together with a switching mechanism 14 disposed therein. This first step S101 includes inserting the switching mechanism 14 into the switch housing 12 and closing the switch housing 12 in order to generate the assembled state of the switch 10 shown in FIGS. 1 and 2.

[0078] Subsequently, in step S102, the switching mechanism 14 is intentionally heated to a temperature exceeding the response temperature of the bimetal snap-action disk 30, putting the switching mechanism 14 in the open state shown in FIG. 2. In this open state of the switching mechanism 14, in step S103, a first external terminal is fixed to the first electrode 50 of the switch 10.

[0079] FIG. 3 schematically shows the procedure of this assembly process using an example of automatic assembly, where a plurality of such temperature-dependent switches 10 are successively attached onto a movable conveyor belt 56. The step S101 of the first method of providing a switch housing 12 together with a switching mechanism 14 disposed therein is not explicitly shown in FIG. 3 because this can be realized by a conventional automatic or manual method. FIG. 3 particularly visualizes the assembly process between steps S102 and S103 of the method.

[0080] In the assembly process schematically shown in FIG. 3, in order to prevent the switches 10 from slipping or being lost, individual switches 10 each having a switch housing 12 are individually fixed to the conveyor belt 56. The switch 10 is preferably fixed to the conveyor belt 56 in a material locking manner. For this purpose, the conveyor belt 56 is provided with a plurality of receiving portions 58, as particularly seen in FIG. 4, and the conveyor belt 56 is shown in a plan view from above with no switch 10 inserted.

[0081] The receiving part 58 is an annular receiving part into which the switch 10 is inserted from above. The receiving part 58 is particularly preferably adapted to the diameter of the lower part 16 of the switch housing 12. As shown in FIGS. 1 and 2, the lower part 16 of each switch 10 has a circumferential shoulder 60 recessed on the bottom side, and the annular receiving part 58 is fitted into this shoulder and preferably soldered or welded thereto.

[0082] In addition, each of the receiving parts 58 comprises a connecting piece 62 which is essentially useful for attaching the second external terminal of each switch 10, as will be described in detail below.

[0083] During the assembly process, the conveyor belt 56 moves in the direction of arrow 64, whereby the switch 10 fixed to the conveyor belt 56 passes through the individual assembly steps described below.

[0084] First, the second external terminal 66 provided as a cable lug and a connection lug, connection cable or stranded wire are conductively connected to the second electrode 52 of the switch 10. For this purpose, the second external terminal 66 is soldered or welded to the connecting piece 62 which is fixed to the lower part 16 or the second electrode 52. This is schematically shown in FIG. 3 by the first welding gun 68.

[0085] The second external terminal 66 is attached in the low-temperature state of the switch 10. This has the advantage that the maximum possible distance is maintained between the movable contact part 34 of the switching mechanism 14 and the solder joint to which the second external terminal 66 is attached. The risk of the movable contact part 34 fusing with the fixed contact part 48 is minimized by the heat generated thereby.

[0086] Next, the switch 10 is brought to a high temperature state by external heating. At this time, each switching mechanism 14 assumes the open state shown in FIG. 2. This is done, in this case, by passing the switch 10 through a heating tunnel or a heating section 70. One or more external heat sources 72 are provided on this heating section 70, and this heat source is schematically illustrated in FIG. 3 by a heating wire. However, it will be understood that the heat source 72 may be any type of heat source, such as a warm air heat source, an infrared heat source, an induction heat source, etc.

[0087] The switch within the heating section 70 is preferably continuously heated by the heat source 72 to a temperature exceeding the response temperature of the switching mechanism. Typically, heating up to a temperature higher than 100°C is sufficient for this purpose, for example, heating up to a temperature in the range of 150°C to 270°C.

[0088] After passing through the heating section 70, the switching mechanisms 14 of all the switches 10 are accordingly in their open or high temperature states. Although the switching mechanism 14 of the switch 10 is in this open state, a first external terminal 74, also provided as a cable lug, connection strand, normal cable or connection lug, as shown at the right hand edge of FIG. 3, is welded or soldered to the upper surface of the fixed contact portion 48 that functions as the first electrode 50. This step is schematically shown in FIG. 3 by a second welding gun 76.

[0089] As particularly seen in FIG. 2, the movable contact portion 34 of the switching mechanism 14 has a maximum distance from the fixed contact portion 48 in the open state. Further, there is no direct mechanical or thermal contact between the two contact portions 34, 48. This minimizes the risk of the two contact portions 34, 48 fusing together due to the heat generated when the first external terminal 74 is attached. In this way, the fragile components 30, 32, 34 of the switching mechanism 14 are protected in the best possible way from damage that could occur due to the extremely high heat generation inside the switch housing 12.

[0090] The method according to the invention thus enables the automatic assembly / manufacture of a temperature-dependent switch, which enables a stable and sustainable attachment of the external terminals 74, 66 and at the same time protects the temperature-dependent switching mechanism 14 provided in the switch in the best possible way.

[0091] As already mentioned, the assembly method according to the invention is suitable not only for the temperature-dependent switch 10 as schematically shown in FIGS. 1 and 2, but also for various other temperature-dependent switches having similar / equivalent switching characteristics.

Claims

1. A method of assembling a temperature dependent switch (10), comprising the steps of: (i) providing a switch housing (12) having first and second electrodes (50, 52) and a temperature dependent switching mechanism (14) disposed therein, the switching mechanism (14) configured to switch in dependence on temperature between a closed state, assumed below a response temperature, in which the switching mechanism (14) establishes a conductive connection between the first and second electrodes (50, 52), and an open state, assumed above the response temperature, in which the switching mechanism (14) breaks the conductive connection; (ii) heating the switching mechanism (14) to a temperature equal to or greater than the response temperature to place the switching mechanism (14) in an open state; (iii) while the switching mechanism (14) is in an open state, attaching a first external terminal (74) to the first electrode (50) or a portion electrically connected to the first electrode (50) by applying heat to form a material-locking bond.

2. The method of claim 1 , wherein attaching the first external terminal (74) by joining and connecting the material comprises a soldering or welding process.

3. 2. The method of claim 1, wherein the switching mechanism (14) is heated to a temperature equal to or greater than the response temperature by heating the switch housing (12) and the switching mechanism (14) disposed therein with an external heat source.

4. The method of claim 1, wherein the temperature to which the switching mechanism (14) is heated is greater than 100°C.

5. 2. The method of claim 1, wherein the switch housing (12) and the switching mechanism (14) disposed therein are passed through a heating section (70) in an automated manner such that the switching mechanism (14) is heated to a temperature equal to or greater than a response temperature.

6. 6. The method of claim 5, wherein the attachment of the first external terminal (74) by material lock bonding is performed in an automated manner after passing through the heating section (70).

7. Furthermore, 2. The method of claim 1, further comprising the step of: (iv) attaching a second external terminal (66) to the second electrode (52) or to a portion electrically connected to the second electrode (52) by thermal material lock bonding.

8. The method of claim 7, wherein step (iv) is carried out before step (ii).

9. 2. The method of claim 1, wherein the switch housing (12) has a lower portion (16) and a cover portion (18) closing the lower portion (16) and electrically insulated from the lower portion (16), the cover portion (18) being at least partially made of a conductive material, and the first electrode (50) being disposed on the cover portion (18).

10. 10. The method of claim 9, wherein the first electrode (50) comprises a contact portion (48) extending from an interior of the switch housing (12) outwardly through a cover portion (18).

11. 2. The method of claim 1, wherein steps (i)-(iii) are repeated for a plurality of temperature dependent switches (10), and while steps (i)-(iii) are being performed, the switch housings (12) of the plurality of temperature dependent switches (10) are secured to a common conveyor belt (56).

12. 12. The method of claim 11, wherein the conveyor belt (56) comprises a plurality of receiving portions (58), each receiving portion having one of the switch housings (12) of the plurality of temperature dependent switches (10) fixed thereto, each of the plurality of receiving portions (58) having a connecting piece (62) electrically connected to the second electrode (52) of the respective switch housing (12), and a second external terminal (66) attached to the connecting piece by material locking bonding through the application of heat.

13. The method of claim 1 , wherein the temperature dependent switching mechanism (14) comprises a bimetallic portion (30).

14. The method of claim 13, wherein the temperature dependent switching mechanism (14) comprises a spring portion (32) interacting with a bimetal portion (30).

15. 15. The method of claim 14, wherein the bimetallic portion (30) is a temperature dependent bimetallic snap action disk and the spring portion (32) is a temperature independent snap action spring disk.

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