EP0993015B1 - Switching device for an electric heating appliance - Google Patents

Abstract

The switching device has a rod-shaped temperature sensor (15) consisting of a tube (16) containing an elongate element (17) of differing thermal expansion coefficients. A switch (22) with a snap-action spring is actuated by the temperature sensor via a separate operating device which is formed integrally with the spring. The spring may be a compression spring.

Description

The invention relates to a switching device according to the preamble of Claim 1 for an electric heater.

EP-A-0225490 shows a switching device of the aforementioned type. An actuator for the switch is here with a spring element connected by spot welding.

Another switching device of the aforementioned type is, for example known from DE-OS 28 39 161. This points as an actuator a one-sided lever through which a rod-shaped Longitudinal element is guided. A fixation takes place via a coil spring supported on the base, the lever against a screw thread at the end of the Stab led mother presses. The on the screw thread of the Stabes running mother serves as an adjustment device. In the Lever two actuating pins are used, each in face the opposite direction and press two switches.

TASK AND SOLUTION

The invention has for its object a aforementioned Switching device to create the disadvantages of the stand the technology avoids, in particular reduces the assembly effort and enables reliable operation.

This problem is solved by the features of the claim 1. Advantageous embodiments of the invention are the subject of subclaims.

A one-piece embodiment of the at least an actuating part with the spring element before simplified everything assembly, but beyond that there may be others Advantages. Due to the one-piece design, at least an attachment or storage, especially for at least an actuating part can be saved. A fixed assignment or connection between the actuator and the spring element increases the mechanical reliability of the switching device, since misalignment is avoided.

An actuator can leaf spring on the Support the base, especially with both end areas Increase the spring effect. The longitudinal element can on the Attack actuator, preferably at least has an actuating part for contact with the switch.

Spring element and the at least one actuating part and / or the actuating device are made from a single piece of material. A particularly simple design can be made from a flat material worked out and shaped accordingly by bending. A Another possibility is, for example, a firm connection by gluing or welding, possibly also pressing. In particular, a One-piece covers the items in the installed state can act as a single part, the individual parts in at least a positive connection in a direction other than the assembly direction exhibit.

The spring element is preferably designed as a compression spring in order to achieve a precise To ensure work. The spring element is preferably like a leaf spring. A leaf spring is advantageous with both end areas or ends held in the base, in particular by spring force caused concern in investment areas. A leaf spring can be beneficial essentially transverse to the direction of expansion of the temperature sensor run, whereby unwanted shear forces or the like are avoided can.

The temperature sensor is particularly preferably located or grips approximately in the center on the leaf spring so that it is loaded evenly. The actuator runs advantageously in the vicinity of the temperature sensor, in particular it is arranged approximately in the middle of the leaf spring.

The actuating part advantageously has two protruding from the spring element Legs to rest on the switch, in particular it is in approximately U-shaped. The U-shaped legs are preferred rotated by approx. 90 ° to the longitudinal extension of the leaf spring. The thigh can each be led to different switches, preferably lying them at the same switch. The temperature sensor can point directly into the U-shape or walk into it.

A mechanical connection between the temperature sensor is preferred and an adjustable actuator Transmission, in particular an adjustment device. The Adjustment device advantageously engages the temperature sensor at, especially at its end. Preferably, the Adjustment device on the longitudinal element over the pipe can survive.

A preferred storage option for the adjustment device is on the actuator, in particular it is on it attached. In one execution option, it can be in the Attack or center the center of a U-shaped operating part be included. As a further advantageous possibility the spring element a receptacle for the adjusting device a, especially with a one-piece training of Spring element and actuating part.

A holder for the adjustment device can be a thread for be an adjustment screw, preferably in the direction of Longitudinal element and / or in the direction of actuation of the switch runs. By changing the pitch of the adjusting screw the adjustment accuracy can be varied.

The transmission of the actuating force can be done through the switch and / or the switching spring, in particular through a corresponding breakthrough, but not for reasons of stability should be open towards the edge. Depending on the type of installation on the one hand the longitudinal element can be carried out or on the other hand the adjustment device or an adjustment screw.

The longitudinal element is at least partially advantageous as a rod executed, especially completely as a rod. He's with you Temperature sensor, the various heating areas a heater covered, possible, each a heating area with a bar area or separate bar assign coordinated properties. The bars are then arranged one after the other in the tube so that their individual dimensions become an overall dimension can add. The longitudinal element is particularly preferred but designed as a one-piece rod. Advantageously points the longitudinal element has a lower coefficient of expansion on as the pipe, as material, e.g. Ceramics or Glass on.

According to one possible embodiment, the at least one Actuating part essentially embrace the rod, preferably rest in the end area. In doing so he educates advantageous a guide for the rod, especially for Securing the rod against unintentional movement across Operating direction. A positive connection between Actuating part in a plane transverse to the direction of actuation can cause unwanted movement of the parts against each other prevent. A guide can be at least as inflection an actuating part towards the rod. The inflection is preferably with one Outside diameter of the rod corresponding recess provided in or along which the rod runs. A Guiding through an adjusting screw can be more extensive than the rod tubular section, for example as a bore be formed in the end face of the adjusting screw.

A so-called overpressure protection of the switch can thereby be realized that the operating part in the operating direction has a certain elasticity. This can be done by achieved at least one S-shaped or Z-shaped bend are, preferably as a bend in the manner of a spring knee, which combined with a guide described above can be.

The leaf spring is preferably in the base in a receiving chamber stored, which in particular essentially opposed the direction of actuation for the Has leaf spring. The receiving chamber can the contact areas in the direction of deflection of the leaf spring expand. The leaf spring is preferably in continuous Base walls that serve as investment areas and limit enlargement. The extension in is preferred approximately symmetrical, in particular symmetrical to one along the Actuating level. An agility the leaf spring in the receiving chamber can be reached be that the receiving chamber at the point of maximum Width exceeds the length of the leaf spring. In this way the leaf spring can expand laterally when relaxing. In addition, inserting the leaf spring is easier, if the leaf spring in the unstressed state a certain Has play in the reception chamber.

The material for the base is suitable due to heat, Strength and insulation reasons especially ceramic material, for example steatite. The base can do that Form housing for the switching device and all walls and have supports, whereby it is only by a simple, essentially flat lid is to be covered.

These and other features go beyond the claims also from the description and the drawings, wherein the individual features individually or separately several in the form of sub-combinations in one embodiment of the invention and in other fields be and advantageous as well as protective designs can represent, for which protection is claimed here. The division of the application into individual sections as well Subheadings limit those made under them Statements not in their general validity.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1

eine Draufsicht auf eine erfindungsgemäße Schalteinrichtung mit einer Blattfeder, die zwei einen Schalter betätigende Schenkel als Betätigungsteil aufweist und

Fig. 2

eine Schrägansicht einer Abwandlung der Blattfeder aus Fig. 1 mit Schenkeln, die eine nach innen gezogene Einbiegung zur Führung eines Stabes des Temperaturfühlers aufweisen.

Two preferred exemplary embodiments of the invention are illustrated in the drawings and are described in more detail below. The drawings show:

Fig. 1

a plan view of a switching device according to the invention with a leaf spring which has two legs actuating a switch as an actuating part and

Fig. 2

an oblique view of a modification of the leaf spring of FIG. 1 with legs that have an inward bend to guide a rod of the temperature sensor.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Fig. 1 shows a switching device 11 according to the invention has a base 12 which contains all components or carries. The base 12 can on not shown Way, for example by means of twist tabs and Intervention cams on a tin plate edge shown in dashed lines 13 one containing a radiant heater Tin plates are attached. A stick-shaped protrudes Temperature sensor 15 at least partially in a known manner over the radiator, preferably over most of it.

The temperature sensor 15 consists of an outer tube 16 and a rod 17 running therein. In the illustrated The embodiment is the rod 17 made of ceramic material and the outer tube 16 made of a metal with much higher Expansion coefficient. The upper end of the outer tube 16 has a transversely projecting collar 18 with which it is fixed is connected and in the lateral receiving slots 19th engages to fix the tube 16. The rod 17 is in the example shown a piece over the collar 18 of the Tube 16 over. At the end of the temperature sensor, not shown 15, the tube 16 is closed, the rod 17th is either firmly clamped to the pipe end or is attached.

There is a free space above the rod end 21 a snap switch 22, which has a free end 23 on one Switch carrier 24 is attached. With one between two Spring legs 26 centrally running spring clip 27, the is supported on a bearing 28 of the switch carrier 24 the snap effect of the snap switch described below 22 scored. At its other free end it carries Snap switch 22 an upward switching contact head 30, which is opposite a mating contact head 32, which is attached to a plug connection lug 37.

The switch carrier 24 is attached both by engagement of the the free end 23 of the snap switch 22 carrying area in a suitable recess of the base 12 and through the Course of a connecting tab 31 through an implementation in the base 12. The connecting tab 31 is used together with a second connecting tab 40 and a second connected thereto Plug-in tab 43 for electrical contacting a heating, not shown, via the connecting lugs. The Switch 22 interrupts the connection between the plug connector lug 37 nd connecting strap 31, Fig. 1 shows the interrupted state.

Both the switch carrier 24 and the snap switch 22 have an overlapping breakthrough that in Extension of the rod 17 lies. On both sides of this Breakthrough has the snap switch 22 two by bending manufactured bumps 29 on.

The room in which the snap switch 22 sits is in the outside to in a receiving chamber 33 for a leaf spring 34 as Spring element over. An extension closes to the outside 35 to the receiving chamber 33 into which the leaf spring 34 is bent. The extension is approximately triangular formed, symmetrical to the longitudinal axis of the rod 17th and opens into an opening 36.

An adjusting screw 38 is in the center of the leaf spring 34 stored, preferably by a mounted in the leaf spring 34 Thread. The upper end of the adjusting screw 38 is through the opening 36 even when the base 12 is closed Adjustment of the switching device 11 accessible. The screw tip 39 abuts the rod end 21, being rounded or is spherical. Alternatively, the screw tip 39 with a tubular section as a guide Bar end 21 overlap a certain distance to slip off to avoid. A tip or a mandrel is also possible the screw tip 39, which in a recess on the front side engage the rod end 21 and the same effect demonstrate.

The leaf spring has on both sides of the adjusting screw 38 34 an outgoing, angled down leg 41 as Actuator on. The legs 41 lie with their lower edge 42 in the switching state shown on the switching heads 29 of the snap switch 22.

FUNCTION

The switching device shown in Fig. 1 works in essential as follows:

The adjusting screw is pressed by the tensioned leaf spring 34 38 the rod 17 against the end of the outer tube 16. In the cold The state of the heating is the deflection of the leaf spring 34 such that the legs 41 and the lower edge 42 a good one Piece above the snap switch 22 or the switch block 29 lie. The snap switch 22 is at its free end 23 attached to the switch carrier 24 such that the spring legs 26 above the system of the spring clip 27 on the Bearing 28 run and the switch contact head 30 on the Mating contact head 32 abuts.

If the heater is now put into operation, it develops Heat through which the outer tube 16 is much stronger expands as the rod 17. This means that the rod end 21 to move away from the leaf spring 34 on the collar 18. This allows the leaf spring 34 to relax and down the legs 41 move towards the snap switch 22. At a certain adjustable temperature with a corresponding expansion of the outer tube 16 can by Turn the adjusting screw 38 to set the point exactly be on which the leg 41 by abutment on the switch blocks 29 the spring legs 26 under the contact of the spring clip 27 pressed on the bearing 28. Since this is the Is the switching point or snap point of the snap switch 22, the spring clip 27 abruptly presses the end with the switch contact head 30 away from the mating contact head 32 downwards. The switch is therefore at an adjustable temperature been triggered. An application example is an overtemperature protection for radiant heating under a glass ceramic hob, which, for example, at a temperature of should start at approx. 650 ° C. By opening the switch the power supply to the heater is interrupted and the risk of overheating the glass ceramic avoided. By the subsequent cooling of the outer tube 16 pulls it back together, pushes the rod 17 up, which again the leaf spring 34 and thus the leg 41 after moved away from the switch holes 29 above and a new one Closing the switch 22 causes.

An embodiment variant of the legs 41 of the leaf spring 34 is shown in Fig. 2. That of the essentially elongated rectangular leaf spring 34 outgoing Legs 41 have a bend 44 in their course, which is designed like a spring knee. Behind the Bend 44 the legs 41 diverge again, but with a smaller distance from each other than before the inflection 44. Bends 44 are especially in such designs advantageous in which the rod 17 between the Leg 41 is enough.

On the inner edge 45 of the bend 44 is one in the direction of the rod arcuate recess 46 attached in which the Rod 16 runs out. In the example shown are Recesses 46 so deep that the inner edges 45 of the Bend 44 to each other to about half the rod diameter approach. This is a wrap that is considered sufficient of the rod 16 possible, the rod in the transverse direction secures against movement relative to the legs 41. The Recesses 46 can with a certain force on the Rod 17 abut, since a relative movement between the rod and Legs only occur during the adjustment process.

Another advantage of the spring-loaded bends 44 is that there is a certain spring action between the Adjusting screw 38 or rigid with it in the direction of the rod connected upper part of the legs 41 and the lower sections the leg 41 or the lower edges 42 possible is. This can overpress the snap switch 22 avoid or at least partially reduce. However, in order to The suspension should not guarantee precise switching be too soft.

Furthermore, in the middle of the leaf spring 34 is one of the Leaf spring pulled down threaded nozzle 48 with the To see receiving thread for the adjusting screw 38.

Claims (12)

1. Switching device for an electric heating device with a substantially rod-shaped temperature sensor (15), which comprises a tube (16) and a longitudinal element (17) located therein, the tube (16) and the longitudinal element (17) having different thermal expansion coefficients, and with at least one switch (22) arranged in a base (12) and operated by the temperature sensor (15) and which is provided with a switch spring (26), particularly a catch spring, the temperature sensor (15) tripping the switch (22) by means of an actuator separate from the switch spring (26) and which has at least one actuating part (41), which is loaded along the actuating direction by a spring element (34), the at least one actuating part (41) being constructed in one piece with the spring element (34), characterized in that the spring element (34) and the at least one actuating part (41) and/or the actuator are worked from a single material piece.
2. Switching device according to Claim 1, characterized by an actuator, which is supported in leaf spring-like manner on the base (12), in particular with both ends, and on which engages the longitudinal element (17), it preferably having at least one actuating part (41) for bearing on the switch (22).
3. Switching device according to Claim 1 or 2, characterized in that the spring element (34) is constructed as a compression spring.
4. Switching device according to one of the preceding Claims, characterized in that the spring element is a leaf spring (34) preferably retained with both ends in the base (12) and it in particular runs substantially transversely to the extension direction of the temperature sensor (15), which engages and/or bears roughly centrally on the spring element (34) and the at least one actuating part (41) is roughly centrally positioned on the spring element (34).
5. Switching device according to one of the preceding claims, characterized in that the at least one actuating part has two legs (41) projecting from the spring element (34) for bearing on the switch (22), the actuating part (41) being in particular U-shaped.
6. Switching device according to one of the preceding claims, characterized in that an adjusting device (38) is a mechanical connection between the temperature sensor (45) and the actuator, the adjusting device (38) preferably engaging on the temperature sensor (15), particularly the longitudinal element (17).
7. Switching device according to claim 6, characterized in that the adjusting device (38) is mounted on and in particular fixed to the actuator.
8. Switching device according to claim 6 or 7, characterized in that the spring element (34) has a receptacle for the adjusting device, in particular a thread (48) for an adjusting screw (38), the adjusting screw (38) preferably running in the direction of the longitudinal element (17) and/or in the actuating direction of the switch (22).
9. Switching device according to one of the preceding claims, characterized in that the longitudinal element is a rod (17) and in particular the at least one actuating part (41) substantially embraces the rod (17), preferably engaging on the outside of the end region of the rod (17), and forms a guide (46) for the rod (17), particularly for securing against a movement of the rod transversely to the actuating direction.
10. Switching device according to claim 9, characterized in that the guide is an inward curvature (44) of the at least one actuating part towards the rod (17), the inward curvature (44) preferably being provided with a recess (46) corresponding to the external diameter of the rod (17) and with which it engages on said rod (17).
11. Switching device according to one of the preceding claims, characterized in that the at least one actuating part (41) has elasticity in the actuating direction and in particular at least one bend, preferably in the form of an inward curvature (44) in the manner of a spring elbow.
12. Switching device according to claim 4, characterized in that the leaf spring (36) in the base (12) is mounted in a reception chamber (33) with bearing areas, which in particular point substantially in the actuating direction, and the reception chamber (33) is widened from the bearing areas in the bending direction of the leaf spring (36), the widening being in particular roughly symmetrical.

Images