DE102011016896C5 - Thermostatic switch - Google Patents

Abstract

Temperature protection switch having a first connection plate (1) with a fixed contact (2), a second connection plate (3) which is electrically conductively connected to a movable contact (5), an insulator body, from which the two connection plates (1, 3) protrude, a bimetal disc (7) which, when a switching temperature is exceeded, separates a conductive connection between the two terminal plates (1, 3), a housing (10) into which the insulator body (6a, 6b) is inserted, the movable contact (5) is attached to a first leg (4a) of a U-shaped bent spring (4) which contacts the second connecting plate (3) with a second leg (4b), wherein between the first leg (4a) of the spring (4) and the Bimetallscheibe (7) a plunger (8) is arranged, which presses the bimetallic disc (7) when the switching temperature against the first leg (4a) and thus lifts the movable contact (5) from the fixed contact (2), wherein the housing ( 10) e ine top and a bottom, which are connected to each other via narrow sides, and wherein the housing (10) is open at one of its narrow sides and is inserted with this side on the insulator body (6a, 6b).

Description

The invention relates to a temperature protection switch.

Such a temperature protection switch is used to protect electrical equipment, motors, transformers and the like from overheating. It should open when the temperature at its place of use exceeds a predetermined limit. This limit is hereinafter referred to as the switching temperature. The switching temperature is dictated by a bimetallic disc, which can not change its shape or curvature continuously, but only by leaps and bounds, when a minimum mechanical stress determined by the shape of the bimetallic disc and by its elastic properties has built up by temperature change in the bimetallic disc. For safety reasons, tolerance limits specified for the switching temperature must be observed.

From the DE 195 09 656 C2 as well as from the DE 196 37 706 A1 is a temperature protection switch with a cup-shaped housing known. In the known switch, the bimetallic disc carries the movable contact. When the switch is closed, the current therefore flows over the bimetallic disc. In this case, heat is generated in the bimetal disc, which depends on the current intensity and the ohmic resistance of the bimetallic disc. This is disadvantageous for some applications, because a temperature which is higher than the temperature at the location to be monitored of the electrical device can be faked by the current heat generated in the contact spring. It may therefore come to unwanted tripping of the bimetallic switch.

From the EP 1 774 555 B1 a temperature protection switch with an improved current carrying capacity is known in which the bimetallic disc carries a contact bridge which connects a fixed contact of the first terminal plate electrically conductively connected to a fixed contact of the second terminal plate with the switch closed. When the switch is closed, the current therefore no longer flows through the bimetal disc, but instead through the contact bridge, which has a much lower electrical resistance. This switch can therefore carry much higher electrical currents before ohmic heat loss leads to an opening of the switch.

A temperature protection switch for high currents is also from the DE 10 2008 048 554 B3 known. This switch has a flat insulator body, which carries a connecting plate on its top and bottom. The movable contact is electrically connected via a leaf spring with one of the two connection plates. In a recess of the insulator body is a bimetallic disc, against which a buckling of the leaf spring. When snapping the bimetallic disc lifts the leaf spring, so that the attached to the leaf spring movable contact lifts from the fixed contact. Similar to the one from the EP 1 774 555 B1 Thus, the current does not flow through the bimetal disc, so that the permissible currents are not limited by the electrical resistance of the bimetal disc.

From the DE 31 36 312 A1 a temperature protection switch is known in which the terminal plates are fastened to the outside of a cup-shaped insulator and are each connected via a rivet with a contact in the interior of the insulator. One of the two contacts is formed as a fixed contact, which is arranged on a side wall of the cup-shaped insulator. The fixed contact cooperates with a movable contact, which is connected via a U-shaped spring bent electrically connected to the rivet of the second connection plate. On the spring leg, which carries the movable contact, loads a plunger, which is passed through a block the cup-shaped insulator closing block and is moved by a bimetallic disc, which is arranged outside of the cup-shaped insulator body in a metal housing. When the sound temperature is exceeded, the bimetal disc presses the two legs of the contact spring together, so that the movable contact is lifted from the fixed contact.

To form temperature circuit breakers as current monitors, d. H. In the case of a critical current, to force a triggering of the switch, it is known to increase the electrical resistance of the switch, for example by the terminal electrodes are connected in series with a heating resistor or even have a relatively high electrical resistance, which is characterized by its length, cross section and material can be adjusted. But it is much more difficult to prevent a current-induced triggering of a thermal circuit breaker.

Object of the present invention is to show a way to realize a compact thermal circuit breaker, which shows a reliable switching behavior, which is largely unaffected by the current heat generated in the temperature protection switch.

This object is achieved by a temperature protection switch having the features specified in claim 1. Advantageous developments of the present invention are the subject of dependent claims.

In the temperature protection switch according to the invention, the current flows through a contact spring, which carries the movable contact on a first leg and contacts the second connection plate with a second leg. Between the first leg of the spring and the bimetallic disc, a plunger is arranged, which presses the bimetallic disc at the switching temperature is exceeded against the first leg and so lifts the movable contact from the fixed contact. The construction according to the invention makes possible a compact temperature protection switch which can also be used at high electrical powers, for example for currents of more than 10 A at a mains voltage of 230 V. In particular, a temperature protection switch according to the invention has the following advantages over known temperature protection switches: The current carrying capacity of a switch according to the invention is higher than the one from the DE 10 2008 048 554 B3 known switch, since the bimetallic disc is arranged at a greater distance from the contact spring. A heating of the contact spring that is unavoidable at higher currents therefore has a significantly less effect on the bimetallic disk. In other words, the bimetallic disc of a thermal circuit breaker according to the invention is even less affected by the heat loss of a current flowing through the switch. In addition, the disadvantage of the switch known from DE 10 2008 048 554 B3 can also be overcome with a temperature protection switch according to the invention in that the bimetal disc is thermally insulated from the environment inside the insulator body and the known switch therefore reacts only very slowly to changes in the ambient temperature.

A temperature protection switch according to the invention advantageously has a construction which is as flat as that of FIG DE 195 09 656 C2 known temperature protection switch. However, the current carrying capacity of a switch according to the invention is substantially greater, since heating of the bimetallic disc is avoided by ohmic heat loss.

The current carrying capacity of a switch according to the invention is as good as the current carrying capacity of the from DE 31 36 312 A1 known switch. However, a switch according to the invention has a much more compact construction and can be produced more easily. The pot-shaped housing of the known thermal circuit breaker has namely a considerable height result that makes a use for the protection of electric motors practically impossible. In addition, the known switch consists of a very large number of items that must be joined together in a large number of complex manufacturing steps. The connecting plates and the contact spring must be firmly riveted to the pot-shaped insulator and the metal plate must be secured with a plate-shaped metal housing to the cup-shaped insulator.

An advantageous development of the present invention provides that the two legs of the spring for opening the switch are bent apart from the plunger. When snapping the bimetallic disc pushes the plunger, the first leg of the spring, which carries the movable contact, ie away from the second leg. In other words, the spring of a thermal circuit breaker according to the invention is thus claimed on the opening of the switch to train, while in contrast to the legs of the contact spring in which from the DE 31 36 312 A1 known temperature protection switch to open the switch of the plunger are pressed together. The inventive measure that the two legs of the spring to open the switch are bent apart from the plunger, allows a particularly compact design of the thermal circuit breaker.

A further advantageous development of the invention provides that the spring is fastened to the second connection plate with a section which extends transversely to the longitudinal direction of the two spring legs. In this way, the spring can be arranged compactly between the two connecting plates.

A further advantageous development of the invention provides that the insulator body is composed of two sub-bodies, wherein the two connecting plates are located between the sub-bodies. In this way, the production of a thermal circuit breaker according to the invention can be considerably simplified. The connection plates can be inserted together with the spring and the two contacts in a first part body. Thereafter, a second part body made of an electrically insulating material, preferably made of plastic, placed on the contact plates on the contact plates. The two body parts can be positively connected with each other, for example, by crimping or latching, non-positively, for example, by jamming or hot stamping, or are materially connected, for example, glued or welded. However, the two partial bodies can also be held together by the deferred housing, for example. As an alternative to the use of partial bodies, it is also possible to produce the insulator body by encapsulation of the connection plates.

A further advantageous development of the invention provides that the bimetal disc is seated on the outside of the insulator body. The temperature of the bimetallic disc nourishes in this way largely to the ambient temperature of the thermal circuit breaker and remains largely unaffected by heat loss of the current flowing through the thermal circuit breaker. Preferably, the bimetallic disc sits in a recess on the outside of the insulator body. In this way, it is advantageous to facilitate the assembly of the temperature protection switch.

According to the invention it is provided that the housing has an upper side and a lower side, which are connected to each other via narrow sides. Such a housing is flat, which is an important advantage in using the thermal protector to protect motors and similar equipment. The housing is open on one of its narrow sides and attached with this side on the insulator body. Particularly preferred is the housing elongated. The extending in the longitudinal direction of the housing narrow sides then have a greater length than the transverse to the longitudinal direction extending housing opening.

A further advantageous development of the present invention provides that a portion of the insulator body protrudes from the housing, for example, the insulator body form a stop for the housing. Preferably, a portion of the spring is arranged in a protruding from the housing portion. It is particularly preferred that a bent portion of the spring, which connects the two spring legs, arranged in the protruding from the housing portion of the insulator body. This means that a cutting plane defined by the housing opening passes through the spring.

A further advantageous development of the present invention provides that the insulator body has on a front side, from which protrude the terminal plates, a protruding portion which lies between the connecting plates. Preferably lies in this section of the bent portion of the spring which connects the two spring legs

A further advantageous development of the present invention provides that the housing is made of a ferromagnetic material, for example of steel. In this way, a magnetic shield can advantageously be achieved by simple means.

A further advantageous development of the present invention provides that the plunger protrudes between the two connecting plates when the switch is open. Preferably, the plunger protrudes between the terminal plates even when the switch is closed.

The fixed contact can be formed in a temperature protection switch according to the invention of the first terminal plate. Preferably, however, the fixed contact is a separate component which is fastened on the connection plate.

Further details and advantages of the invention will be explained with reference to embodiments with reference to the accompanying drawings. Identical and corresponding components are designated therein by corresponding reference numerals. Show it:

1 an exploded view of an embodiment of a temperature protection switch according to the invention;

2 an oblique view of the thermal circuit breaker without housing;

3 a view too 2 with removed part body;

4 a sectional view of the temperature protection switch; and

5 a further embodiment of a temperature protection switch according to the invention.

The in the 1 to 4 shown temperature protection switch has a first connection plate 1 that has a solid contact 2 carries, and a second connecting plate 3 that about a spring 4 electrically conductive with a movable contact 5 connected is. The connecting plates 1 . 3 are in the 1 and 3 shown as a one-piece stamped part. After assembly, the connection plates 1 . 3 separated by a bridge connecting the connecting plates is removed.

The fixed contact 2 can on the first connection plate 1 be attached for example by welding or riveting. Likewise, the preferably U-shaped bent spring 4 with the moving contact 5 and with the second connecting plate 3 welded or riveted. The connecting plates 1 . 3 as well as the contacts 2 . 5 and the spring 4 can be preassembled to a module. The connecting plates 1 . 3 can still be designed as a common component, as in 1 is shown. In particular 3 shows is the spring 4 over a space between the two connection plates 1 . 3 arranged.

The two connecting plates 1 . 3 protrude from an insulator body, which consists of two partial bodies 6a . 6b is composed. The two part bodies 6a . 6b consist of an electrically insulating material, such as plastic. The first part body 6a makes a recording for the flashings 1 . 3 then from the second part body 6b is closed.

On the outside of the insulator body, preferably in a recess of the first part body 6a , is a bimetal disc 7 arranged, which when a switching temperature is exceeded, a conductive connection between the two connecting plates 1 . 3 separates. The bimetal disc 7 acts via a pestle 8th on the contact spring 4 one between the two connecting plates 1 . 3 protrudes through. The pestle 8th is in a channel of the first part of the body 6a arranged. If the bimetal disc 7 snaps over their sound temperature is exceeded, the plunger 8th from the bimetal disc 7 against the first leg 4a the contact spring 4 pressed the moving contact 5 wearing. This is the first leg 4a from the second leg 4b that on the second connection plate 3 abuts, bent away. In other words, the two thighs 4a . 4b the feather 4 for opening the temperature protection switch of the plunger 8th bent apart. The contact spring 4 So is a bow spring, which is bent to open the thermal circuit breaker.

The bimetal disc 7 is in the recess of an outer side of the first body part 6a from a ring 9 held. The ring 9 is preferably made of metal, since so the thermal coupling of the bimetallic disc 7 is improved to the environment of the switch. The ring 9 covers the edge of the bimetal disc 7 and may, for example, by gluing or clamping, for example by hot stamping, on the part body 6a be fastened to the insulator body. The bimetal disc 7 is in the illustrated embodiment on a bead of the insulator body. In this way, the contact surface between bimetallic disc can be 7 and insulator body thus minimize the thermal coupling of the bimetallic disc.

The insulator body 6a . 6b is after assembly in a housing 10 plugged. The housing 10 is a flat case cap. The housing 10 So has a top and a bottom, which are connected via narrow sides. On one of the narrow sides is the case 10 open so that in this end of the preferably elongated housing 10 the insulator body 6a . 6b can be inserted. Preferably, the connection plates protrude 1 . 3 with one end out of the case 10 out. In particular 4 shows, protrudes the insulator body 6a . 6b out of the case 10 out. In the out of the case 10 protruding portion of the insulator body is a section of the spring 4 arranged, namely the two spring legs 4a . 4b connecting curved section. The feather 4 So it is only partially in the case 10 arranged.

The connecting plates 1 . 3 protrude from an end face of the insulator body 6a . 6b out. At the front of the insulator body 6a . 6b a protruding section that hisses the two connecting plates. This protruding section protrudes from the housing 10 out and contains the curved section of the spring 4 , which connects the two spring legs.

The housing 10 can be made of ferromagnetic metal, such as steel, to shield the switching mechanism of the thermal circuit breaker magnetically. This is important, for example, in the use of the thermal protector for electric motors or transformers, since in such applications typically strong magnetic fields occur.

The bimetal disc 7 is preferably a circular disk, but may also have a different shape and be formed for example as an elongated strip.

5 shows an exploded view of another embodiment of a thermal circuit breaker. This embodiment differs from the embodiment described above substantially only in that a self-holding function of the switch has been added. This self-holding function causes enough heat to be produced after opening the switch to prevent the switch from automatically closing. For the self-holding function is a resistor in the illustrated embodiment 11 , Preferably, a ceramic resistor, for example a PTC resistor, provided, which the two connecting plates 1 . 3 connects electrically conductive with each other. The resistance 11 can of a leaf spring 12 against the two connecting plates 1 . 3 be pressed.

An electrical resistance for a self-holding function, for example, outside of the housing, for example, on a protruding from the housing opening end face of the insulator body 6a . 6b to be ordered. It is also possible, the insulator body 6a . 6b form as an electrical resistance for a self-holding function. In this case, the insulator body 6a . 6b or at least one of the two partial bodies 6a . 6b a bad insulator or a bad electrical conductor, so that when the switch is open, a current flows through the insulator body, which generates sufficient heat loss to cool the bimetallic disc 7 below their switching temperature.

LIST OF REFERENCE NUMBERS

1

first connecting plate

2

fixed contact

3

second connecting plate

4

contact spring

4a

first thighs

4b

second leg

5

moving contact

6a

first part body

6b

second part body

7

bimetal disc

8th

tappet

9

ring

10

casing

11

resistance

12

leaf spring

Claims (9)

Temperature protection switch with a first connecting plate ( 1 ) with a fixed contact ( 2 ), a second connecting plate ( 3 ) electrically conductive with a movable contact ( 5 ), an insulator body, from which the two connecting plates ( 1 . 3 ), a bimetal disc ( 7 ), which when a switching temperature is exceeded, a conductive connection between the two connecting plates ( 1 . 3 ) separates a housing ( 10 ) into which the insulator body ( 6a . 6b ), the movable contact ( 5 ) on a first leg ( 4a ) of a U-shaped bent spring ( 4 ), which is connected to a second leg ( 4b ) the second connecting plate ( 3 ), wherein between the first leg ( 4a ) the feather ( 4 ) and the bimetallic disc ( 7 ) a pestle ( 8th ) is arranged, the bimetallic disc ( 7 ) when the switching temperature is exceeded by the first leg ( 4a ) and so the movable contact ( 5 ) from the fixed contact ( 2 ), whereby the housing ( 10 ) has an upper side and a lower side, which are connected to each other via narrow sides, and wherein the housing ( 10 ) is open on one of its narrow sides and with this side on the insulator body ( 6a . 6b ) is plugged. Thermal circuit breaker according to claim 1, characterized in that the two limbs ( 4a . 4b ) the feather ( 4 ) for interrupting a conductive connection between the two connecting plates ( 1 . 3 ) of the plunger ( 8th ) are bent apart. Thermal circuit breaker according to one of the preceding claims, characterized in that the second leg ( 4b ) the feather ( 4 ) on the second connecting plate ( 3 ) is present. Thermal circuit breaker according to one of the preceding claims, characterized in that the insulator body consists of two part bodies ( 6a . 6b ), the two connecting plates ( 1 . 3 ) between the two partial bodies ( 6a . 6b ) lie. Thermal circuit breaker according to one of the preceding claims, characterized in that the housing ( 10 ) is made of a ferromagnetic material, preferably of steel. Thermal circuit breaker according to one of the preceding claims, characterized in that the bimetal disc ( 7 ) sits outside of the insulator body. Thermal circuit breaker according to claim 6, characterized in that the bimetal disc ( 7 ) is seated in a recess on the outside of the insulator body. Thermal circuit breaker according to one of the preceding claims, characterized in that the plunger ( 8th ) with the switch open between the two connecting plates ( 1 . 3 ) protrudes. Thermoswitch according to one of the preceding claims, characterized in that the insulator body a ring ( 9 ) carrying the edge of the bimetallic disc ( 7 ) covered.

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