EP0818796B1 - Thermal switch, in particular adjustable temperature controller - Google Patents

Description

Field of application and state of the art

The invention relates to a temperature switch according to the preamble of claim 1, in particular an adjustable temperature regulator, with a snap-action switch, which is one of an expansion element actuated switching spring, on which one of the expansion element acting relative to the switching spring movable pressure element.

In temperature controllers, especially those with a thermo / hydraulic Working extension system, enters for the shift spring Overload problem when the temperature controller is at or near his switch-off point, that is, when warm, to a lesser Temperature is reset or turned off. Here is the extended expansion box far beyond the switch-off point in Direction pressed on the switch spring, so that these overloaded and under Circumstances can be permanently damaged.

To solve this problem, many proposals have already been made. Thus, a snap spring is described in DE 44 35 303 A, the Overloads to a greater extent endures than previous snap springs.

Furthermore, a temperature switch is described in DE 20 58 511 C, in which the expansion box in a parallelogram of resilient Switch levers connected by a transmission rod is located. The actual Schnappfederbetätigung happens by the power flow second lever, which acts under its spring force on the snap-action switch while the expansion box over the remaining lever mechanism only is pressed to their relief. This system works flawlessly, However, it is very expensive to manufacture.

It is also known from DE 24 22 684 C a temperature switch become, in which a double snap spring of one in an expansion sleeve lying ceramic rod is actuated. In this case works the snap-action switch as "opener", i. at elevated temperature retracts the ceramic rod and by relieving the snap spring the contact opens. In such a system would be described Problem does not occur. It is not one adjustable temperature limiter.

From GB-A-1 378 693 it is known, via a push rod a Apply force to an actuating pin of a microswitch. From a pusher on the push rod is doing the force on a counter a spring-pressed part is exerted on the actuating pin in such a way that the pusher can retreat over another spring. So will prevents over-pressing of the microswitch.

From US-A-4,565,989 a temperature switch is known in which also via an expansion element and a power transmission a snap-action switch is triggered. The triggering of the snap-action switch takes place via a leaf spring, which to prevent can override a override of the snap switch.

Task and solution

The object of the invention is a temperature switch of the aforementioned To create kind of, with little structural and above all Spatial effort without overload risk works flawlessly.

This object is achieved by the claim 1. Thereby, that the overload protection a between expansion element and snap spring contains activated buffer element, which at a above the actuating force of the switching spring lying in the switching point Compressive force is compressible, the transfer happens on direct Ways and without any elasticity or the strain of one Foreign power and therefore absolutely free of play. Only when exceeding the maximum Actuation force occurs Zusammendrükung the buffer element a, wherein this force should be such that it is below which is a damage to the snap spring inducing force. It can also help if the snap spring after overcoming its switching point is supported on a stop, preferably immediately at their point of actuation. Although the embodiment of the invention with a squeezable buffer element the structurally cheapest, it would also be possible, acting on train buffer element use.

The buffer element may be directly in the actuator, i. the between expansion box and snap spring lying pressure piece or the like. A simple version contains one preloaded, wegbegrenzte spring, such as a compression spring. The bias is slightly greater than the actuation force of Switching spring and lower than that for mechanical stress critical force.

The buffer element is a can consisting of two against pulling apart limited, but compressible, sleeve-shaped Can parts that surround the compression spring. These two Halves of the buffer element thus engage positively in one another and are spread by the compression spring. It can one of the can parts be attached directly to an expansion box, for example soldered in place of the usual pressure piece, while the cooperating Can part made of electrically insulating Material can exist and thus the expansion system electrically from the mostly live snap spring separates. The can parts do not have to be closed Mantel exist, but it could be for example the made of sheet metal can also part of several lateral Webs exist, which in the manner of a claw the other can part take.

The invention makes it possible that the expansion element directly on the most trained as expression of snap spring Actuation point acts. This allows the smallest size. However, it is also possible to increase the snap spring sensitivity a transmission lever interpose. But this can also be directly in Pressure direction and thus without expensive storage be educated. He can, for example, unilaterally Art be supported by a cutting edge bearing and with his other side on the snap spring, while the Buffer element at a corresponding to the desired transmission ratio Positioned body of this one-armed Levers attacks.

A particularly simple embodiment is with an L-shaped Lever given, either on a spring-loaded carrier suspended and supported or in a recess this switch spring carrier is guided.

Due to the small size and the possibility without expensive Double lever etc. to work even if a translation is provided, lies the actual contact area, in the seated on the shift spring movable contact and the one or more mating contacts are so far away that they were easily enclosed by an insulating cover can be to this area against contact and pollution to protect. This also allows the reduction of Size, because it is easier than the legally required minimum distances (Clearances and creepage distances, high voltage resistance) ensured by current-carrying parts to touchable parts can be. Such a contact chamber can be made suitable plastic material as an integral part of an im be provided remaining housing made of metal. she can act as a substantially U-shaped hood in a recess of the upper housing part by clipping, guide grooves etc. are attached. It acts as one of the contacts largely surrounding "spark chamber" and separates the touchable Parts of the current-carrying.

The invention thus makes possible in an advantageous embodiment For example, the following structure:

A working with a hydraulic expansion box Temperature controller with screw thread setting points as Intermediate link between the expansion box and the snap-action switch a buffer element. This works if necessary over a L-shaped transmission lever on the actuation point of the Snap switch on.

The buffer element consists of a button-shaped, entirely closed can, consisting of two cup-shaped, each other consists of halves, between which a compression spring is biased. The buffer element transmits the Switching force of the expansion can in the force range in which the snap spring actuation takes place without any elasticity, so completely rigid, while in a beyond Overload collapses telescopically.

These and other features are excluded from the claims also from the description and the drawings, wherein the individual features in each case alone or to several in the form of subcombinations in one embodiment of the invention and realized in other fields his and advantageous as well as protectable versions represent protection for which protection is claimed.

The subdivision of the application into individual sections as well Intermediate headlines limit those made under them Statements not in their generality.

Brief description of the drawings

Fig. 1

einen Längsschnitt durch einen Temperaturregler,

Fig. 2

eine Draufsicht auf den Basisteil des Temperaturreglers (entlang Schnittlinie II in Fig. 1),

Fig. 3

eine stark vergrößerte Ansicht eines Details in Richtung des Pfeils III in Fig. 1 und

Fig. 4

einen Teilschnitt durch die Funktionskomponenten eines Temperaturreglers in einer anderen Ausführungsform

An embodiment of the invention is illustrated in the drawings and will be explained in more detail below. In the drawings show:

Fig. 1

a longitudinal section through a temperature controller,

Fig. 2

a plan view of the base part of the temperature controller (along section line II in Fig. 1),

Fig. 3

a greatly enlarged view of a detail in the direction of arrow III in Fig. 1 and

Fig. 4

a partial section through the functional components of a temperature controller in another embodiment

Description of a preferred embodiment (Figures 1 to 3)

Fig. 1 to 3 show the switching component of a temperature controller 11. To her belong only schematically indicated Temperature sensor 12, e.g. in the form of one with an expansion fluid filled tube via a capillary tube 13 is connected to an expansion box 14. The Expansion box consists of two bowl-shaped corrugated Sheet metal membranes, which are connected together at the edge. over a connection nipple 15, the capillary tube 13 is connected. At the top of the expansion box 14 is a retaining bolt 16 welded, in a hollow setting shaft 17 plugged. This has an external thread 18, with an internal thread 19 working together in one of a metal case 20 pulled sleeve 21 is provided. The adjusting shaft 17 is flattened on one side to a knob rotatably take. In it an adjusting screw 22 is provided which acts on the retaining bolt 16.

The housing 20 is made of sheet metal and has the shape a rectangular, partially open box the top fastening claws 22 for installation of the Temperature controller are formed. The bottom is from a base part 23 of temperature-resistant, form-solid and electrically insulating material, for example steatite or other ceramic material. At this the housing is defined by twist tabs 24.

The plate-shaped base part 23 carries a snap-action switch 25. This has a switching spring 26 which is connected to a Switch spring carrier 27 is attached. The switch spring carrier 27 is a relatively small solid sheet metal part that is a tabbed abutment 28 in the form of a bend. On him is a switching tongue 29 supported by an approximately U-shaped Notch separated from the rest of the switching spring is. By their deflection and bias, they are the Switch spring gives, can with their contact remote end through Rivets 30 switch spring fixed to the switch spring carrier her front, the switch contact 31 end bearing at her Snap switching point between two stable switch positions. In the closed position shown in Fig. 1 are her Contact 31 on a mating contact 32, located at a Counter contact bridge 33 is located. In the off position lies the front end of the switching spring on one of the Base part molded, an abutment-forming projection 34th on.

Create snap-action switch carrier 27 and mating contact bridge 33 by U-shaped fastening straps, on the one hand as Verdrehlaschen 35 and on the other hand as well formed by rotation flat tabs 36, 37 formed over which also the electrical connection at the bottom the plate-shaped base part takes place.

At the bottom of the expansion box 14 is a buffer element 38 trained and effective actuator appropriate. It consists of one at the bottom of the Expansion box welded in the form of a sheet metal shell formed can part 39, which by means of bent edge or tooth-like edge projections 40 under the protruding outer edge 41 of a second can part 42 engages the shape one of electrically insulating material, for example Steatite, has existing crucible. Inside the two Can parts 39, 42 is a compression spring 43 is arranged. she is clamped between the two parts of the can so that they have a Preload, which is certainly greater than that Operating force that the snap-action switch needs to over to be pushed away its switching point.

The thus formed as a closed pressure cell buffer element acts on a pronounced pressure point 44 of an L-shaped Lever 45, which turned on as a translation lever is. With his also to create unique Pressure conditions pronounced front end 46 he acts on an actuating point 47 of the switching spring, by a transverse bead is formed.

At the opposite end of the lever, which is wider than long, two are at a great distance from each other down bent support legs 48 are provided, the ends of cutting edge bearings 49 form by being on the surface of the base part 23 are supported. As can be seen from Fig. 3, is by a curved lower edge of the support leg 48 for it ensured that clear support conditions are given.

The two support legs protrude from both sides in each a recess 50 in the side edge of the snap switch carrier 27 in, so that the support legs are guided therein. Projecting lugs 51 on the inside of the support leg 48th are barb-like and care after the Lever 45 under pressure from above into the recesses 50 is pressed in, for a backup against lifting the Lever. On the switch spring carrier 27 is a stop 52 below the actuating point 47 of the snap spring provided so that he intercepts these after execution of their snap action and prevents further deflection.

Fig. 1 shows that the contact area, i. the front end the switching spring 26 with the contact 31 and the mating contact 32, from an existing insulating material cover 53rd is surrounded. It covers the top, front and the off both side surfaces. Because the bottom of the base plate 23 is formed, so one only to the switch interior open chamber formed, the risk of contamination and contact excludes. The cover 53 is snap-locked fixed to a slot 54 of the housing.

function

The assembly of the temperature controller according to the invention can be made individual components that can be prefabricated by simple plugging, bending or crimping operations made become. The filled and soldered component probe / capillary tube / expansion box 12, 14 contains the upper one Can part 39. It is then only necessary, the spring 43 to insert, squeeze, so that they have their bias receives and then the claws or teeth 40 bend so that the buffer member 38 held together as a button-shaped unit becomes.

The parts of the snap switch are on the base part 23rd by inserting into the slots 53 and twisting the tabs 36, 37 and the twisting tabs 35 set.

The lever 45 is from above the snap switch carrier pressed and locked due to a formed by the noses 51 Snap lock in there.

The adjustment is made via the adjusting screw 22.

In operation, the adjusting shaft 17 for adjusting a rotated certain temperature, so that over the thread 18, 19 the expansion box 14 and thus the buffer element 38 in a certain position along the axis 55 of the setting shaft is brought.

When heating the temperature sensor 12 expands in the Probe 12 contains expansion fluid and expands the Expansion box 14, so that the buffer member 38 after moved down, the lever 45 is pivoted clockwise and acts on the snap spring via the actuation point 47. The lever 45 is supported on its cutting bearings 49th from. Due to the shorter lever arm between the cutting bearings and the pressure point 44 on the lever opposite the Distanzbetätigungsstelle 47 to cutting bearings 49 is the switching movement translated in the ratio 2: 1.

The support of the switching spring via the switching tongue 29 is so made that in the unloaded state of the switching spring the outer end with the contact 31 abuts the mating contact, the Switch is closed. The over the flat latches 36, 37 connected circuit is via the snap spring closed and the switch is on.

If now the switching point is exceeded by that the switching spring moves down so far that it snaps and rests on the projection 34, then the Switch off. This force is from the buffer element 38 transferred without own compression. It works So as a rigid actuator.

In normal operation now no significant expansion the expansion box more done, because the controller addressed and the sensor 12 acting on heating a any electric heater or other elements thereby normally switched off. If now, however, the User by rotation of the adjusting shaft 17 by means of not shown actuator knob the controller to a low Temperature or turn it off, so he moves to allow the expansion box to continue on the switch, i. "Out" direction.

Now comes the buffer element 38 to the effect. At a clear above for the switch-off of the snap-action switch necessary force on the actuating point 47 may be the Compress spring 43 so that the two can halves 39, 42 telescopically push through the buffer element formed actuator button so gives in. The Switching spring can sit on the stopper 52, so that she is not bent unnecessarily. The forces and the deflections are in any case in the elastic range of the switching spring, so that no permanent damage occurs. When canceled overload, e.g. when cooling the regulated Device, the buffer element expands under the effect of Spring 43 back to exactly the same length as before Squeezing out.

It will be appreciated that by the invention a particularly simple method of overload protection was created. The actuation is carried out via a in the operating state absolutely pressure-resistant and yielding only in case of overload, itself but then again exactly expanding, transfer link in Shape of a sitting on the pressure cell self-actuating knob. The transmission lever can be very short and compact so that it does not affect the size. There are no spring elements necessary on the switching spring itself Act. Rather, the spring is effective in the buffer element, if the circuit is already done and serves only for overload protection.

Embodiment of Fig. 4th

Fig. 4 shows an embodiment in which in a similar manner formed buffer element 38 on a metal pressure piece 56th the expansion box is attached and immediately, i. without Translation lever 45, on the actuating point 47 of Switching spring 26 acts. This design, the preferred is, if no translation is necessary, is special easy and with direct switching action. Otherwise, the Training and function the same as described in FIGS. 1 to 3.

Claims (12)

1. Thermal switch, in particular an adjustable temperature controller, with a snap-action switch (25), which has a switching spring (26) which is actuated by an expansion element (14) and is acted on by an actuating element which can be moved by the expansion element (14) in relation to the switching spring (26), characterized by an overload preventer for the switching spring (26), the overload preventer including a buffer element (38) which is arranged between the expansion element (14) and the switching spring (26) and can change its length when there is a force at the switching point that is above the actuating force of the switching spring (26), and the buffer element (38) being a cell which comprises two sleeve-shaped cell parts (39, 42) which are restricted with respect to being pulled apart but can be compressed and enclose a compression spring (43).
2. Thermal switch according to Claim 1, characterized in that the buffer element (38) is a pressure element which can be compressed by the force that is above the actuating force of the switching spring (26).
3. Thermal switch according to Claim 1 or 2, characterized in that the buffer element (38) is contained in the actuating element.
4. Thermal switch according to one of the preceding claims, characterized in that the buffer element (38) includes a prestressed, travel-limited spring (43).
5. Thermal switch according to Claim 1, characterized in that one of the cell parts (39) is attached to an expansion cell (14) of a thermal/hydraulic expansion system (12, 13, 14) and/or in that another of the cell parts (42) consists of electrically insulating material.
6. Thermal switch according to one of the preceding claims, characterized in that the switching spring (26) has a distinctly formed actuating point (47), on which the actuating element (38, 45) acts.
7. Thermal switch according to one of the preceding claims, characterized in that, after overcoming its switching point, the switching spring (26) is supported on a stop (52), preferably directly at its actuating point (47).
8. Thermal switch according to one of the preceding claims, characterized in that its expansion element (14) acts on its switching spring (26) via a lever (45), the lever being supported on one side in the manner of a knife-edge bearing and acting with its other side (46) on the switching spring (26).
9. Thermal switch according to Claim 8, characterized in that the counterbearing of the knife-edge bearing is provided on a switching spring carrier (27) and the lever (45) is hooked on the latter.
10. Thermal switch according to Claim 8, characterized in that the lever (45) has an L shape and is guided in particular in at least one recess (50) in a switching spring carrier (27).
11. Thermal switch according to one of Claims 8 to 10, characterized in that the supporting leg (48) of the L-shaped lever (45) forming the knife-edge bearing (49) has a forked form with two bearing points (49) lying at a lateral distance from each other, the supporting legs (48) preferably engaging in lateral recesses (50) in the switching spring carrier (27) and being secured there by a snap-action securement (51).
12. Thermal switch according to one of the preceding claims, characterized in that the region of the switching contacts (31, 32) of the snap-action switch (25) is surrounded by an insulating covering (53).

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