EP0279368A2 - Temperature limiter - Google Patents

Abstract

In a temperature limiter (1) with a rod-like temperature sensor (6), the outer tube is formed by a continuously tensile-stressed insulating tube (7) extending into a base (2). An inner rod (8), optionally articulated two or more times in the longitudinal direction, is constructed as a continuously pressure-loaded rod, characterized by temperature-dependent length expansion. The temperature limiter (1), e.g., for a glass ceramic unit, may have a circuit breaker (5) closer to the temperature sensor, and a more-remote signal switch (4). In that case, for operating the remote signal switch, a flat bar-like transfer member (9) traverses both switches through openings (54). The transfer member is coupled at the associated end and in adjustable manner with an operating member (30) for the signal switch (4), receiving the adjustment member (34). The parts are constantly held together in clearance-free manner by the tension of a restoring spring (40).

Description

The invention relates to a temperature limiter with a rod-shaped temperature sensor that actuates at least one switch.

Such temperature limiter, which can also be used generally as a temperature switch, find particular application where electrically heated devices, such as electric hot plates, radiant heaters of glass ceramic cooking units, oven muffle or the like. should be protected against overheating. From DE-OS 34 23 086 (US-PS 4 544 831) a corresponding temperature limiter for regulating or limiting the temperature of radiation or contact radiators of electric cooking appliances has become known, in which an existing pipe made of insulation material through a within the Base acting on a rod compression spring is constantly kept under pressure, since the inner rod loaded by the spring on train acts with its outer end on the outer end of the insulation tube. The Isola tion tube consists of relatively brittle and therefore slightly brittle material, which on the one hand makes it difficult to introduce the compressive forces into its ends and on the other hand also leads to strength problems between the ends because the insulation tube is subject to buckling. Therefore, with this design, a relatively large diameter of the insulation tube is to be aimed at, and end caps are provided at its ends to introduce the compressive forces as uniformly as possible, which results in a very complex design with relatively large cross sections. Since the temperature sensor, for example when arranged on radiant heaters, causes retroreflection, which also increases with increasing diameter of the temperature sensor, local overheating of the heating resistors can occur as a result of this retroreflection. The requirement for a relatively small diameter is usually met in the case of temperature sensors with a metallic outer tube, but the electrical conductivity of this outer tube is disadvantageous in many applications, which is why an insulation protection tube must then be placed on the metallic outer tube, which is a very complex design and again Increase in the diameter of the temperature sensor.

The invention has for its object a temperature limiter or the like. to create the type mentioned, which allows a very slim compact design of the temperature sensor with a simple structure and high functional reliability.

This object is achieved in a temperature limiter of the type mentioned by the design according to the invention. In a further embodiment, the inner rod of the temperature sensor only needs to be surrounded by a single tube, in spite of the electrically insulating sheathing, which in turn is made of a high-temperature-resistant material with low ther Mix expansion coefficient and high electrical insulation properties can exist, this insulation tube because of its exclusive tensile load can be formed not only with a relatively small diameter, but also with a relatively small wall thickness, so that the outer width of the temperature sensor, the outer diameter of the inner rod only by about two to Triple to surpass. In addition, the arrangement can be such that the envelope surface defined by the outer surface of the outer tube represents the outermost boundary of the temperature sensor over its entire length, over which no parts at all over the largest part of its length extending to the extreme end of the temperature sensor, like end caps or the like protrude. Furthermore, because the inner rod is only loaded under pressure and can be relatively closely surrounded by the insulation tube, there is a very exact temperature-dependent movement of the inner end of the inner rod which is decisive for the switching process or operations.

The design according to the invention is suitable for those temperature limiters which have only a single switch, but in particular also for temperature switches which have two or more switching contacts, for example for different switching functions, as is the case where one switch as the circuit breaker has the power controls the heating to be switched, while a further switch as a hot alarm or signal switch switches a signal device which indicates whether or not the heated device has a temperature which is too high for contact, for example above 60 ° C.

A particularly advantageous further development in rod sensors of any kind results from rod parts joined together by pressure force. The adjacent rod parts expediently have different coefficients of expansion, so that there is a structured inner rod, held together only under the functional pressure forces, which ensures a very reliable transmission of the different elongations of the different rod parts.

The expansion rod sensor according to the invention can also be installed very easily, can be designed in an adjustable manner and stored in such a way that it can be changed in position, for example in an articulated manner, in relation to the heating in relation to the base.

Temperature limiters with two or more switching functions are mostly used for separate switching of two circuits, namely, for example, the heating power circuit and a signal circuit for indicating the hot state of this heating or an associated device zone, but both switching processes are influenced by a single temperature sensor. This makes it relatively difficult to design the arrangement in such a way that the switching points of the two switches can be precisely adjusted individually. With numerous electrical heaters, such as electric hot plates, radiant heaters of glass ceramic cooking units, oven muffles or the like. However, such an adjustment is often desirable in such a way that it can be carried out in a simple manner even after the temperature limiter has been installed.

From DE-OS 34 23 086 (US Pat. No. 4,544,831) a temperature limiter for regulating or limiting the temperature of radiation or contact heaters of electric cooking appliances has become known, in which the actuator and the transmission member have a rotationally symmetrical, two-stage cylindrical component form, the larger section of which forms an annular actuating surface for the one switch and the slimmer section with its end surface forms a smaller actuating surface for the other switch which points in the same direction. The distance between them Both actuating surfaces determine the adjustment for the switch further away from the temperature sensor and must be fixed by grinding in before installing this component, after which a further adjustment is no longer possible. Furthermore, the arrangement is such that when the inner rod of the temperature sensor expands, the contacts of the switch located farther away are closed, the transmission member not acting directly on the snap spring of the associated snap switch, but rather on a relief spring which loads the latter into the open position, which ensures a safe operation and the exact switching function of this switch, also because its snap function is largely disabled.

From DE-OS 28 39 161 a temperature limiter has also become known, in which both switches can subsequently be easily adjusted essentially independently of one another, but here the switches lie next to one another transversely to the temperature sensor, so that a direct linear actuation of both switches by the temperature sensor is not given, but transverse transmission levers are provided.

In particular, compared to these known designs, the invention is further based on the object of creating a temperature limiter of the type mentioned, which also enables subsequent or at any time adjustment of the switching point of the switch further away from the temperature sensor.

This object is achieved with a temperature limiter of the type mentioned in that a distance change in two possible directions is provided for adjustment. Because, for example, the distance of the actuating element from the pressure rod can be adjusted with an adjusting member, the switching accuracy of the more distant switch can be very precise can be set. An adjustment member belonging to the inner rod of the temperature sensor and therefore provided for adjusting the switch closer to the temperature sensor, and the adjustment member belonging to the actuating element can be arranged in a simple manner, for example as an extension of the temperature sensor, one behind the other, for example, axially coincident with one another, a particularly advantageous embodiment being provided if the parts of these adjusting elements, which are formed, for example, by actuating heads and are used for actuation, are directed away from one another and are on opposite sides of the temperature limiter, that is to say, for example, on the outer end of the temperature sensor on the one hand and on the opposite end of the base on the other.

The adjusting members can thus be easily accessible and provided with the same axis so that all the forces to be transmitted by the temperature sensor occur as pure pressure forces and no bending forces are brought about. This applies in particular to the transmission of the forces from the transmission element to the adjusting element and from this to the separate actuating element, which is expediently arranged to be linearly movable, essentially coaxially with the transmission element. This also has a direct or direct effect of the expansion or inner rod of the temperature sensor on the switches, which significantly increases the switching accuracy.

A particularly advantageous further development, in particular in the case of temperature switches of the type described, is obtained if the transmission member or the actuating member has or have cross sections which differ from the cylindrical cross section, since on the one hand a more compact accommodation of these members is possible and on the other hand in a simple manner also one opposite the base can be secured against rotation. This anti-rotation of the Transmission member can be transferred directly to the actuator to prevent rotation, so that this does not require direct rotation-protected guidance relative to the base, which also increases the ease of movement of the system and thus the switching accuracy. Another advantage of this arrangement results from the fact that the actuator and the transmission member can be practically identical in shape or with the same cross-sections, which on the one hand significantly simplifies manufacture even when these two parts are composed of two separate, identical parts to form the common component are and on the other hand assembly easier, since both ends of this component can be arranged in the same way in both possible positions.

• Fig. 1 einen erfindungsgemäßen Temperaturbegrenzer in Ansicht bei geöffnetem Gehäuse;
• Fig. 2 einen Schnitt etwa nach der Linie II-II in Fig. 1;
• Fig. 3 einen Bauteil des Temperaturbegrenzers in einer weiteren Ausführungsform;
• Fig. 4 eine Draufsicht auf den Bauteil gemäß Fig. 3;
• Fig. 5 eine weitere Ausführungsform des Bauteiles in einer Darstellung entsprechend Fig. 4;
• Fig. 6 einen Ausschnitt der Fig. 2 in einer weiteren Ausführungsform;
• Fig. 7 eine weitere Ausführungsform eines Tempera­turbegrenzers in einer Betriebsanordnung;
• Fig. 8 eine weitere Ausführungsform eines Tempera­turfühlers im Axialschnitt.

These and further features of preferred developments of the invention are also apparent from the description and the drawings, the individual features being able to be implemented individually or in groups in the form of sub-combinations in one embodiment of the invention and in other fields. Embodiments of the invention are shown in the drawings and are explained in more detail below. The drawings show:

• 1 shows a temperature limiter according to the invention in view with the housing open;
• Figure 2 is a section approximately along the line II-II in Fig. 1.
• 3 shows a component of the temperature limiter in a further embodiment;
• FIG. 4 shows a top view of the component according to FIG. 3;
• 5 shows a further embodiment of the component in a representation corresponding to FIG. 4;
• FIG. 6 shows a detail from FIG. 2 in a further embodiment;
• 7 shows a further embodiment of a temperature limiter in an operating arrangement;
• Fig. 8 shows another embodiment of a temperature sensor in axial section.

The temperature switch shown in FIGS. 1 and 2, which should preferably be used as a temperature limiter 1, has a base 2 made of insulation material, which can be opened on its top or front side and can be closed with a plate-shaped flat cover 3. Two switches in the form of snap switches are arranged in the base immediately adjacent to one another and one behind the other, structurally or in terms of their outer dimensions. These switches can be used for any separate switching operations and are preferably provided as a circuit breaker 5 and as a signal switch 4 so that the power of the connected heating is switched off with the circuit breaker 5 above a predetermined temperature by adjustment, while with the signal switch 4 above one by adjustment predetermined, relatively low temperature of the heated device, a signaling device, for example a signal lamp, is switched on and is only switched off again when the temperature falls below this second temperature. The base 2 is designed as a substantially closed housing, which surrounds the switch protected on all sides.

A rod-shaped, rectilinear temperature sensor 6 is attached to a base narrow side lying on the periphery of the flat rectangular base 2, which is substantially longer than the longitudinal sides of the base 2 parallel to its longitudinal direction and essentially parallel to the central plane lying between the front and the rear the base 2 is. The temperature limiter 6 is closer to the front than to the rear of the base 2, which is closed parallel to the front.

The temperature sensor 6 consists essentially of an outer tube 7 which is made of a high-temperature resistant material with a very low coefficient of thermal expansion throughout its entire length and which has in particular electrical insulating properties, preferably quartz glass, ceramic or the like. consists of and an inner rod 8, which is arranged in the outer tube 7 substantially without contact and has a much larger expansion coefficient than the outer tube 7. The outer tube 7 and the inner rod 8 are each approximately cylindrical over their entire length, the outer diameter of the inner rod 8 being smaller than the inner diameter of the outer tube 7 by substantially less than half of this diameter, such that only a relatively narrow between these two parts Gap distance is given and the outer diameter of the relatively thick-walled outer tube 7 can be kept relatively small, for example in the order of the diameter of helical heating resistors, which has the heating assigned to the temperature limiter 1.

The inner end 46 of the outer tube 7, which is located at the base 2, is formed into a form-fitting member 47, which is formed in one piece with it and protrudes only radially outward, in the form of an annular flange which is thus formed in one piece with the outer tube 7. This inner end 46 of the outer tube 7, which extends into the base 2, is essentially centered in a flange plate 10 which forms the entire associated narrow-side housing wall of the base 2.

This, made of metal flange plate 10 has an outwardly projecting, penetrated by the inner end 46 of the outer tube 7 approach, the form-locking member 47, which may have the same or greater thickness than the flange plate 10, on the inside of this flange plate 10 immediately adjacent to Opening is present. The transition of the form-locking member 27 into the jacket of the outer tube 7 is concavely curved in cross-section on the outside in cross-section and lies essentially over the entire area on the correspondingly convexly curved transition area between the opening and the inside of the flange plate 10, as well as the flat, annular end face the form-locking member 47 rests essentially over the entire surface on the inside of the flange plate 10; this results in relatively low specific surface pressures. The substantially oblong-rectangular flange plate 10 is provided on its ends associated with the long sides of the base 2 with U-shaped angled edge profiles, the U-legs of which are directed away from the flange plate 10 and are directed towards one another in holding slots 44 on the long sides of the base 2 by inserting the front of which interlock positively.

The inner end 48 of the consistently constant cross-sections and thread-free and collar-free inner rod 8 is only slightly, namely only about the order of one to four times its diameter over the inner end surface of the outer tube 7 and is with a spherically curved end surface 49 in Center on the polygonal transmission surface 29 of a flat profile-shaped actuator 32 which forms a one-piece component with a transmission element 9 adjoining its other end of approximately the same cross section.

With its outer end face 50, the inner rod 8 rests against an end face of an adjusting member 12, which is approximately axially identical to it, under spring pressure, this adjusting member 12 being axially positively supported under this spring pressure only in the associated direction relative to the outer tube 7. The end face 50 is shown as a flat end face and the corresponding end face of the adjusting member 12 as a spherical end face, but both end faces of the inner rod 8 can be of the same design, so that it can be inserted in the outer tube 7 with the same effect in both possible turning positions. If these end surfaces are spherical, the two counter surfaces provided for them are expediently flat, while these counter surfaces are expediently spherical if the end surfaces of the inner rod 8 are essentially flat.

The adjusting member 12, against which the inner rod 8 rests within the outer tube 7, is guided in a sleeve-shaped intermediate member 51, which is also completely inside this outer tube 7 and has a thread, which has constant cross sections over its length and whose outer width is smaller than the inner width of the outer tube 7 , namely approximately the same as the outer width of the inner rod 8.

The outer end portion 52 of the outer tube 7 is narrowed in a truncated cone shape and thereby forms an inner, annular stop surface 53 on which the intermediate member 51 rests axially secured with its outer end surface under the spring force. These interlocking surfaces are, for example by flattening, Krallprofi, self-locking conical training or the like. designed so that they lead to an anti-rotation of the intermediate member 51 relative to the outer tube 7.

The adjusting member 12, which is designed as a stud, protrudes over both ends of the intermediate member 5, its outer end being able to protrude from the outer tube 7 for easy access. To assemble the adjusting member 12, it only needs to be thrown into the assembly as an assembly with the intermediate member 51 through the inner end of the outer tube 7, after which it lies loosely against the stop surface 53 and is secured in this position by inserting the inner rod 8.

The two switches 4, 5 each have a multi-angled strip-shaped switch carrier 13 or 14 which is designed as a stamped and bent part and which is equipped with a snap spring 15, 16 formed by a leaf spring, which carries or forms a switching contact 17 at its free end. The two identically designed, but oppositely arranged switch supports 13, 14, including their snap springs 15, 16, are arranged essentially mirror-symmetrically to a central plane perpendicular to the central axis 18 of the temperature sensor 6 or to their direction of actuation in such a way that the snap springs 15, 16 essentially on the opposite sides of the switch carrier 13, 14 are. The switching contacts are assigned to the housing-fixed counter contacts 19, 20, which are part of connecting parts (not shown) projecting beyond the outside of the base 2, for example connecting plugs, or are electrically conductively connected to such connecting parts. Corresponding connecting parts or connecting plugs, not shown in more detail, are also connected in an electrically conductive manner to the switch carriers 13, 14, these connecting parts being inserted into slots in the base 2 and thereby being able to form the fastening of the respective switch carrier. In the exemplary embodiment shown, the switch carriers 13, 14 are, however, fastened in the base 2 with angled fastening lugs 45.

The transmission member 9 or the actuating member 32, which is made of electrically non-conductive insulating material, is not guided directly on the base 2, but is completely contact-free with respect to the latter and is only guided in that the transmission member 9 penetrates openings 54 in the switch carriers 13, 14, at least one of which these openings 54 are adapted to form a sliding guide to the cross section of the transmission member 9 and the openings 54 are perpendicular to the longitudinal direction of the snap springs 15, 16.

The transmission element 9 also completely passes through the switch 4, which is further away from the temperature sensor 6, and is coupled with its free end to a separate, sleeve-shaped actuating element 30 in such a way that it takes this form-fit directly with the movements away from the temperature sensor 6, but even the associated actuating element Counter member 31 of the adjacent switch 4 is not touched in the sense of actuation. This actuating counter-element, which is essentially formed by a snap-in spring, which is partially circular in cross-section and which projects in the direction of the actuating element 30 and is penetrated by the transmission element 9 essentially without contact in the region of a symmetrical opening, becomes actuation only touched by the actuating element 30, specifically in the region of at least one longitudinal limit of the opening which is narrower than the bead width. This contact takes place laterally outside the outer surface or the outer surfaces of the transmission member 9 and laterally outside of its wider outer surfaces.

The actuating element 30 and the transmission element 9 engage in the manner of a telescopic rod, preference being given to the actuating element at least partially, ie at least over part, the transmission element on the outer circumference extends over its circumference, so that the aforementioned actuation of the switch 4 can be carried out in a very simple manner. The actuating element 30 acting on the switch 4 in the direction of switching off is rigid in itself, so that the switching function is very precise. The actuating element is applied with a return spring 40 without play against the transmission element 9, this spring 40, apart from the switch springs which only become effective when switched off, the only one on the actuating element 30, the transmission element 9, the actuating element 32, the inner rod 8 and that Adjusting member 12 is acting spring 40, which holds all these parts together in the manner of a structured pressure rod in each functional position under pressure without play.

The surface of the actuating element 30 acting on the transmission member 9 is provided on an adjusting member 34 in the form of a stud screw, which is screwed into a corresponding internal thread of the actuating element 30 so that its spherical end face facing the inner rod 8 lies in each adjusting position within the actuating element 30 and always projects over this end face a longitudinal section of the actuating element 30, in which the associated end of the transmission element 9 engages in a longitudinally guided manner and is secured against rotation in a form-fitting manner. The actuating element thus has a longitudinal extent and lies approximately parallel to it, in particular in alignment, with the transmission element 9 and / or with the adjusting element 34, so that a very compact arrangement which works very precisely even with high switching numbers results.

Furthermore, the adjustment member 34 is due to the described design with a pressure surface, namely in particular with its end face, on a transmission surface 36, namely in particular on the associated end face, of the transmission member 9 in any position of the transmission member 9 without play. This end surface 36 is suitably the same as that End surface 49 of the actuating element 32 is formed, so it may also be spherical if necessary, namely, for example, when the pressure surface of the adjusting member 34 is flat.

The fact that the actuating element 30 and the transmission element 9 are coupled to one another within the actuating element 30 also results in a position of the adjoining surfaces which determine the adjustment, namely the pressure surface and the transfer surface 36, which is protected against contamination, although the actuation element 30 could be prevented from rotating also take place with respect to the base, but there is a substantially lower-friction arrangement if the longitudinal guide between the actuating element 30 and the transmission element 9 is provided.

The actuating element 30 is guided by two measures, namely on the one hand by the suspension on the spring 40 and by guidance in a bearing plate 55, it being conceivable to provide only one of the two measures alone. The guide in the bearing plate 55 forms a sliding guide with respect to the base 2 and is preferably formed in that a cylindrical end section 56 of the adjusting member 34 protruding above the actuating element 30 and held free of thread as a sliding pin engages in a centered manner in a bearing opening 57 of the bearing plate 55. The bearing plate 55, which is at a distance from the associated end of the actuating element 30, forms the bearing opening 57 with a shoulder directed away from the actuating element 30.

Furthermore, the bearing plate 55 with lateral zones lying on both sides is inserted from the front of the base 2 into opposite slots in the associated housing inner surfaces of this base 2 and secured in the assembled position by the inside of the housing cover 3 resting against it. The bearing plate 55, the bearing opening 57 is closed by the end section 56, on the associated side of the base 2 also forms a closure plate for the housing interior or a corresponding housing wall and is expediently made of approximately the same thickness of sheet metal as the flange plate 10. Characterized in that the housing interior of the base 2 is closed on two opposite narrow sides on the one hand by the flange plate 10 and on the other hand by the bearing plate 55, there is also a very simple manufacture of the base 2 from insulating material.

A certain storage and guidance of the actuating element 30 by the return spring 40 results from the fact that the return spring 40, which is in particular approximately axially aligned with the transmission element 9, and which is designed as a truncated cone-shaped helical compression spring, has a narrowed annular end both essentially at the circumference and at abuts an outwardly projecting collar 58 of the actuating element 30, this collar 58 being provided approximately in the middle of the length of the actuating element 30. The other, expanded end of the return spring 40 is expediently on the inside of the bearing plate 55, so that a separate abutment is not required. The actuating element 30 is therefore arranged in a contact-free manner with respect to base-fixed surfaces, except via its connection to the adjusting member 34 or the return spring 40.

The outer end of the adjusting member 34, which lies within the base 2, is easily accessible from the outside of the bearing plate 55 at all times. On the side of the ring collar 58 facing the temperature sensor 6, the actuating element 30 is provided with a longitudinal slot 59 penetrating it on two diametrically opposite sides, the width of which is adapted to the profile thickness of the flat rectangular cross section of the end section 26 or of the transmission member 9, whereby the inside width of the actuator supply element 30 is smaller than and the outer width is approximately the same size as the larger profile width of the end section 26 compared to the profile thickness, so that it engages in both opposite parts of the longitudinal slot 59 guided.

The actuating element 30 and the actuating member 32 lie one behind the other due to the design described in the longitudinal direction of the transmission member 9 and have two actuating surfaces 60, 61 facing each other. The actuating surface 60 of the actuating element 30 is formed by the sleeve end face lying on both sides of the longitudinal slot 59, that is to say penetrated by the longitudinal slot 59, while the actuating surface 61 of the actuating member 32 is formed by a shoulder surface projecting radially approximately the same distance as the actuating surface 60. Since the transmission element 9 or the actuating element 32 is guided against rotation by at least one of the switch carriers 13, 14 by means of a form-fitting sliding guide, the actuating element 30 is also arranged against rotation with respect to the base.

The transmission element 9 or the actuating element 32 can also have a cross-section other than a flat, rectangular one, namely, for example, a round, square or similar cross-section, but in order to be able to be arranged essentially symmetrically to a common central axis and to have at least approximately the same or To be able to have identical cross sections, at least partially cross sections that deviate from circular cross sections, that is to say that they have radial extensions of different sizes in the circumferential direction. Therefore, projecting actuating surfaces 61 of the actuating element 32 can be created in a simple manner in that the latter and the transmission element 9 are rotated relative to one another by a certain angle about the common longitudinal axis, that is to say they are not aligned with one another with regard to their cross sections. Nevertheless, the transmission link 9 and that Actuating element 32 have approximately the same maximum radial extensions with respect to a common central axis, so that a very space-saving arrangement is possible. In the illustrated embodiment, the transmission member 9 and the actuating member 32 are oriented rotated by 90 ° relative to one another, so that the actuating surfaces 61 protrude on both sides over the flat sides of the transmission member 9, while this protrudes with its narrow sides over the flat sides of the actuating member 32 in the same way.

3 shows, the transmission element 9a and the actuating element 32a, which form a common component 62, can also be of the same length such that their transmission surfaces 36a, 29a are at equal longitudinal distances from the center of the length of this component 62, that is to say from it Transverse median plane 63. The end surfaces of the transmission element 9a and the actuating element 32a facing away from the transmission surfaces 29a, 36a are also symmetrical to the transverse central plane 63, namely in this, so that both end surfaces can optionally be used as the actuating surface 61a. The component 62 can thus be mounted as a reversible component in two arrangements with the same effect in the base 2, so that there is no need to pay attention to a special position, which makes automatic assembly much easier.

As shown in Fig. 4, the transmission member 9a and the actuator 32a are longitudinally symmetrical to each other, so that each of these two parts protrudes equally far over the other on both sides. However, it is also conceivable according to FIG. 5 that at least one of these parts, in the exemplary embodiment shown, the transmission element 9b is slightly offset from the center of the other component, namely the actuating element 32b, so that the latter further than over a flat side of the transmission element 9b whose other side protrudes. The arrangement is there Appropriately taken so that the actuator 32b is offset from the side of the base 2 on which the switch contacts 17 lie, so that it takes up less space on this side and the housing interior can be made correspondingly narrower.

Otherwise, the same reference numerals are used in FIGS. 3 to 8 for corresponding parts as in the other figures, but with different letter indices.

The configuration described creates a temperature switch in which the switch 4 is secured against excessive stress by overpressure, since the actuating element 30 is effective only in the reset path, that is to say with a decreasing sensor temperature, and otherwise, namely when the switch 4 is switched on, this switch 4 releases unencumbered.

Compared to the training according to DE-OS 34 23 086 (US Pat. No. 4,544,831), the training according to the invention has significant advantages. In the known solution, an adjustability of the mutual distance between the actuating surfaces is not provided and practically also not possible because, on the one hand, there is no constant contact of the actuating element with the associated actuating counterpart and, on the other hand, because the actuating surfaces point in the same direction, such that the actuating surface of the actuating element press the associated signal switch at too high a temperature and thus at least misalign, if not damage it.

In addition, in this known arrangement the inner rod is not connected to the outer tube as a compression rod, but as a tension rod, which entails a complex construction and the disadvantage that the switching accuracy also depends on the reliability of the inner rod under tension depends spring. Compared to a design according to DE-OS 28 39 161, there is the advantage, among other things, that the switches can be arranged one behind the other and actuated so directly that inaccuracies due to internal deformations are largely excluded, although in this known solution both switches can be adjusted directly.

The shape of the transmission element 9, on the one hand, and the actuating element 32, on the other hand, which differs from the cylindrical shape, also gives rise to significant advantages with regard to storage, the spatially advantageous accommodation, assembly and functional reliability. At the same time, it can be taken into account by the design according to the invention that it is usually more expedient for installation and electrical connection reasons if the switch 5 closer to the temperature sensor 6 is the circuit breaker, since then the switch 5 associated with it is also on the outside of the base 2 Connection parts are closer to the temperature sensor 6 and thus to the heating to be switched than the corresponding connection parts of the other switch 4, which is usually provided as a circuit breaker.

As shown in FIG. 6, the outer tube 7c, which is designed as an insulation tube, can advantageously be articulated in all directions within a narrow pivot angle about at least one axis that intersects its central axis 18a approximately at a right angle, preferably about an articulation point approximately in its central axis 18c, so that it is at Can avoid overloads and also be very precisely aligned when installing the temperature switch.

In the illustrated embodiment, the form-locking member provided at the inner end of the insulation tube 7c is designed as an annular spherical partial cap 47c, while the flange plate 10c on the inside is designed as a complementary, spherical bearing socket 64, which has the through surrounds passage opening for the inner end 46c of the insulation tube 7c. The partial cap lies under the pressure of the restoring spring in the bearing socket 64 with such great friction that the respectively set pivot position of the temperature sensor 6c is secured by self-locking. The pivot axis or the center of the ball of the bearing surfaces can expediently lie in the contact surface between the inner end 48c of the inner rod 8c and the transmission surface 29c, so that the adjustment does not change due to pivoting movements.

The passage opening in the flange plate 10c is corresponding to the maximum pivoting angle of the temperature sensor 6c larger than the outer width of the section of the insulation tube 7c lying in it. However, it is also conceivable to provide a slight pivoting mobility of the temperature sensor 6 relative to the base 2 in the case of an embodiment according to FIGS. 1 and 2.

As further shown in FIG. 6, the inner rod or the part of the temperature sensor which has the larger coefficient of expansion and is therefore expediently pressure-loaded or pressure-loading, consists of at least two sections which adjoin one another in the longitudinal direction and which, in terms of their length, their cross section and their expansion effect, affect different zones of the measurement Heating, for example, are coordinated in such a way that one or more zones practically do not or only slightly influence the temperature value sensed by the sensor, while one or more further zones mainly influence this value and therefore, despite the temperature sensor being extended over both types of zones, the representative measuring zones represent. Sections of the inner rod lying one behind the other or generally immediately adjacent to one another have expediently different expansion coefficients for this purpose or these sections consist of different materials, the thermal expansion coefficient of one type of sections can be as close as possible to the area of the expansion coefficient of the outer tube 7c. These sections thus form purely mechanical and thermally essentially inactive transmission sections between the other, thermally active sections on the one hand and for transmitting the change in length to the switch or switches on the other.

It is also conceivable to structure the outer tube in a corresponding manner, but this would only be relatively easy to carry out if the outer tube is under pressure in every functional position. This results in a particularly simple and advantageously reliably acting embodiment of any type of rod sensors if, in the case of an inner rod having at least two separate rod parts which are connected in the longitudinal direction, adjacent rod parts consist of separate individual sections which are pressurized in the longitudinal direction of the inner rod and which preferably have the same cross sections and / or have approximately the same length, so that an immediate, tensile loading of adjacent rod parts to one another - as is also conceivable - is not necessary.

As further shown in FIG. 6, three separate measuring range sections 65, 66, 67 of the inner rod 8c of the temperature sensor 6c are provided for the longitudinal section of the temperature sensor 6c intended for the arrangement in the heated area of the heating to be switched. This longitudinal section is at a distance from at least one end of the temperature sensor 6c, in particular at a distance from its base-side end, which is why a rod end section 68 is provided in the associated remaining longitudinal section of the temperature sensor 6c, which is designed as a thermally essentially inactive section and only as Transmission link serves. This End section 68 can - depending on the requirements - connect to a thermally inactive or a thermally active section 67.

The thermally inactive sections suitably consist of ceramic or a material with similar properties, while the thermally active sections suitably consist of a metallic material. The end section 68 is in one piece throughout. Adjacent sections advantageously do not abut one another in a punctiform or articulated manner, but are placed against one another in such a way that they align one another as closely as possible, which can be achieved, for example, by flat, adjoining end faces or by the fact that the intermeshing ends are complementarily conical . However, due to the inner width of the outer tube 7c, which is relatively closely matched to the outer width of the inner rod, a possibly slightly bent course of adjacent sections is not disadvantageous unless a particularly high measuring accuracy is required.

7 shows the assignment of a temperature limiter 1d according to the invention to a heater 69, this heater being a radiant heater for the hob of a stove, an oven muffle or the like. and to be arranged on the underside or outside of a heating plate 70, for example a glass ceramic plate.

The heating 69 has a shell-shaped support 71, which essentially consists of an inner insulation shell 72 made of pressed insulating material and an outer support shell 73 made of sheet metal or the like. consists. Separately switchable heating resistors 74, 75 in the form of, for example, exposed resistance wire helices are arranged on the bottom of the insulation shell 72, which form separate heating fields 76, 77. In the illustrated embodiment, one forms in a middle Field of spiral-shaped heating resistor 74, a central heating field 76, which is surrounded by the second heating field 77 in an annular manner, wherein at least one heating resistor 75 is also spirally laid here. The heating fields 74, 75 can also be delimited from one another by an annular intermediate wall which protrudes from the bottom of the insulation shell 72 approximately to the temperature sensor 6d or to the heating plate 70, consists of insulation material and surrounds the inner heating field 74.

The temperature limiter 1d is arranged such that its base 2d is located outside the heating 69 or the carrier 71 directly on its outer circumference and with its housing cover 3d close to the underside or outside of the heating plate 70. The temperature sensor 6d projects through the edge of the carrier 71 approximately diametrically into the heating and, with its end remote from the base 2d, at least partially penetrates the opposite region of the edge of the carrier 71. The temperature sensor 6d is parallel to the heating plate 70 between the latter and the heating resistors 74, 75.

The length of the central section 66d of the inner rod of the temperature sensor 6a lying in the area of the heating field 76 corresponds to the length with which the temperature sensor 6d spans this heating field 76. This section 66d is designed as a thermally active section, while the two subsequent sections 65d, 67d span the annular heating field 77 and are designed as thermally inactive sections. One end section 75d extends to the adjusting member 12d, while the other section 67d extends into the base 2d.

The circuit of the heating resistors is provided in such a way that the heating resistor (s) 75 of the outer heating field 77 can optionally be switched on to the heating resistor 74 of the central heating field 76, that is to say during the operation of the heater tongue 69, the central heating field 76 is always heated. Since only this heating field 76 thermally influences the temperature sensor 6d, the working accuracy of the temperature limiter 1d is equally good, regardless of whether the outer heating field 77 is switched on or not. Since the inner rod has a greater coefficient of expansion than the outer tube or the insulation tube at least over sections of its length, the inner rod is always loaded under pressure, while the outer tube is always loaded under tension.

As shown in FIG. 8, the outer or insulation tube 7e of the temperature sensor 6e can also be essentially closed at the outer end with an end wall 52e and thereby form a direct pressure support for the associated end of the inner rod 8e in such a way that an adjusting member is provided in this area is not provided. In this case, the adjusting member 12e lies in the region of the base-side end of the outer tube 7e, this end expediently being designed such that it engages longitudinally in the base or in the flange plate 10e. As shown in Fig. 8, e.g. this end of the outer tube 7e be provided with an external thread which engages in a corresponding internal thread of the flange plate 10e with such great friction that an inadvertent rotation of the outer tube 7e by hand during assembly or the like. is not to be feared. The arrangement is expediently such that a tool is required for the adjusting rotation of the outer tube 7e, or the like on a form-locking member, for example on key surfaces, a diametrical slot. must be rotatably attached to the outer end of the outer tube 7e.

Compared to the training according to DE-OS 33 33 645, in which the inner rod consists of several partial rods of the same expansion coefficient, the inventive design has the advantage that the temperature sensor can be designed so that any longitudinal sections as desired participate differently in the expansion behavior. Compared to the design according to EP-AO 116 861, the design according to the invention has the particular advantage that the thermally active section is arranged in the area of a heated zone and adjacent sections can only be connected to one another by placing them against one another.

Claims (10)

1. temperature limiter (1) for a heater (69), in particular a glass ceramic heating unit, with an essentially rod-shaped temperature sensor (6) which is provided for actuating at least one switch (4, 5) arranged on a base (2), characterized in that the temperature sensor (6) has an outer tube (7) and an inner rod (8) located therein with mutually different coefficients of thermal expansion. 2. Temperature limiter, in particular according to claim 1, characterized in that the inner rod (8) is directly surrounded by an insulation tube (7) which forms an abutment for the outer end of the inner rod (8) removed from the base (2) that the inner rod (8) is supported as a pressure rod on the insulation tube (7) arranged under tensile pressure, so that the base-side end (46) of the insulation tube (7) is secured against movement in the direction of the other, outer end (52) with the base (2), and that preferably the base-side end (46) of the insulation tube (7) is in one piece with this Formed form-locking member (47), in particular an enlarged ring flange, for engagement in the base (2), preferably the outer end of the inner rod (8) being formed, for example, by approximately the same external cross-section as the inner rod (8) having an internal thread sleeve Intermediate member (51) and an adjusting member (12) is supported on the insulation tube (7) and lies within the insulation tube (7) and the intermediate member (51) carrying an adjusting screw is loosely inserted into the insulating tube (7) with the adjusting screw (12) and with the inner rod (8) against an inner stop surface (53) of the insulation tube (7) is pressed assembly, preferably in such a way that the stop surface (53) through the inner shoulder of a truncated cone-shaped section of the insulation tube (7) is formed, which in particular forms its outer end section (52) or, with its narrower end, its outer end surface. 3. Temperature limiter, in particular according to claim 1 or 2, characterized in that the insulation tube (7c) is articulated within a narrow swivel angle, in particular via a spherical partial cap (47c) engaging in a bearing socket (64), and / or that the inner rod (8c) has a greater coefficient of expansion than the insulation tube (7c) at least over partial sections of its length, preferably adjacent rod parts made of in the longitudinal direction of the inner rod (8c) in the case of an inner rod (8c) which has at least two separate rod parts and adjoins in the longitudinal direction Pressurized separate at For example, the same cross-sections and / or approximately the same length individual sections (65, 66, 67, 68) consist of at least two sections (65, 66, 67, 68) adjoining in the longitudinal direction are different expansion coefficients or of different materials, of which preferably at least one essentially inactive section of the pressure-loaded part of the temperature sensor (6c), in particular at least one end section (68), has approximately the same expansion coefficient as the tensile-loaded part (7c) of the temperature sensor (6c), preferably in such a way that at least one base-side end section ( 68) of the pressure-loaded part (8c) of the temperature sensor (6c) is designed as an essentially inactive section, which is designed in particular as a one-piece transmission section up to the associated actuating element (32) and essentially up to the longitudinal part of the temperature sensor (6c ) reic ht. 4. Temperature limiter, in particular according to one of the preceding claims, characterized in that different longitudinal sections (65d, 66d, 67d) of the inner rod separate heating fields (77, 76) of a radiant heater (69) or the like. are assigned, whereby preferably a section (66d) of the one expansion coefficient is assigned to a central heating field (76) and two sections (65d, 67d) of the other expansion coefficient adjoining on both sides are assigned to an outer, annular heating field (77). 5. Temperature limiter, in particular according to one of the preceding claims, characterized in that for actuating at least one further switch (5, 4) from the base end (48) of the inner rod (8) a closer to the temperature sensor (6) actuation member (32) for a switch (5) and an actuating element (30) further away from the temperature sensor (6) for the other switch (4) is influenced via a transmission member (9) and the actuating member (32) and the actuating element (30) Act in particular with an adjusting member (34) at variable distance on actuating counter-members (37, 31) of both switches (5, 4), at least one of which at least one of the switch parts (14, 16; 13, 15) associated with openings (54) is penetrated by the transmission element (9), the actuating element (30) and the transmission element (9) preferably intermeshing in the manner of a telescopic rod, or the actuating element (30) at least partially overlaps the transmission element (9) on the outer circumference and / or the adjusting element (34) mounted on the actuating element (30) and in particular is formed by an adjusting screw engaging in an internally threaded sleeve, which is essentially within the actuation lementes (30), preferably such that the actuating element (30) has a longitudinal extent and is approximately parallel, in particular in alignment, with the transmission member (9) and / or the adjusting member (34). 6. A temperature limiter, in particular according to one of the preceding claims, characterized in that the actuating element (30) is rigid in itself and in particular with a return spring (40) tension-free relative to the one with the transmission member (9) in any position against the inner rod (8) Transmission member (9) is fixed and / or the adjusting member (34) with a pressure or end face on a transmission or. End surface (36) of the transmission member (9) rests in any position of the transmission member (9) without play, preferably the actuating element (30) and the transmission member (9) within the actuation element (30) are coupled together and in particular the pressure surface and the transmission surface (36) abut against each other within the actuating element (30). 7. Temperature limiter, in particular according to one of the preceding claims, characterized in that the actuating element (30) relative to the transmission element (9) and / or relative to the base (2) via a particularly exclusively between the actuating element (30) and the transmission element (9 ) provided or secured by the engagement of a profile end of the transmission member (9) in at least one longitudinal slot (59) formed longitudinal guide (59) that preferably the actuating element (30) over a, in particular in its longitudinal direction with it, sliding guide against the Base (2) is in particular guided in such a way that an end section (56) of the adjusting member (34) protruding above the actuating element (30) and designed as a sliding pin engages in a bearing opening (57) of a bearing plate (55) inserted into the base (2) , on the associated side a closure plate or a housing wall for a housing space of the housing-shaped sock ls (2) forms that the actuating element (30) is preferably guided in alignment with the return spring (40), for example, lying approximately coaxially with the transmission member (9), which in particular has a narrowed annular end on the circumference or on an annular collar (58 ) of the actuating element (30) or with one end against the bearing plate (55) and / or that the actuating element (30) is arranged in a contact-free manner with respect to base-fixed surfaces in addition to its connection via the adjusting member (34) or the return spring (40). 8. Temperature limiter, in particular according to one of the preceding claims, characterized in that the actuating element (30) and the actuating member (32) lie one behind the other in the longitudinal direction of the transmission member (9) and two facing each other, in particular by one laterally via the adjusting member (34) projecting sleeve face of the actuating element (30) and a radially approximately equally protruding shoulder surface of the actuating member (32), actuating surfaces (60, 61) have that preferably the transmission member (9) or the actuating member (32) relative to the base (2) , in particular by positive sliding guidance of the transmission element (9) in switch supports (13, 14), secured against rotation, and the transmission element (9) in particular snap springs (15, 16) of the switches (4, 5) in the area of bead-shaped actuating counter-elements (31 , 37) passes through without contact and / or that the transmission element (9) or the actuating member (32) has a polygonal, in particular flat, rectangular cross section, the transmission member (9) and the actuating member (32) in particular having approximately the same radial extent with respect to a common central axis (18) or having essentially identical cross sections and around a common longitudinal axis (18) are twisted against each other. 9. Temperature limiter, in particular according to one of the preceding claims, characterized in that the transmission element (9a) and the actuating element (32a) are formed by a component (62) which has approximately equal distance transmission surfaces (62) on both sides with respect to a transverse central plane (63) 29a, 36a) for the connection with the inner rod (8) and the actuating element (30) as well as oppositely pointing actuating surfaces (61a), in particular in the transverse central plane (63), for the selective engagement in the Actuating counter-member (37) of the switch (5) closer to the temperature sensor (6), the transmission member (9a) and the actuating member (32a) preferably being formed by two profile sections of the same length and in particular forming a reversible component (62). 10. Temperature limiter, in particular according to one of the preceding claims, characterized in that a switch designed as a circuit breaker (5) is closer to the temperature sensor (6) and is associated with the actuator (32) and that the further from the temperature sensor (6) is removed, in particular switches designed as signal switches (4) are assigned to the adjustably mounted actuating element (30).

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