EP0778598B1 - Switch with a switching mechanism actuated at an excessive temperature - Google Patents

Abstract

The switch has a switch mechanism (12) which switches on excessive temperature, to open and close a switch circuit which connects the terminals (26,38) of the switch (10). The switch mechanism (12) has an electrically conductive spring part (29). This acts against a bimetallic component (33) in dependence on the temperature of the latter. In its relaxed state, the spring part (29) is electrically connected to an external terminal (38). It also carries a movable contact (28) which is connected to a fixed contact (24) in dependence on the temperature of the bimetallic component (33). The fixed contact is electrically connected to the other terminal (26). The movable contact (28) is formed integrally with the spring part (29). The movable contact is preferably formed as a curved surface or bump on the spring part. The bimetallic part may be a bimetallic snap plate arranged over the bump (30).

Description

The present invention relates to a switch with a Overtemperature switching mechanism for opening and closing a circuit that can be connected to external connections of the switch, the rear derailleur depending on the temperature a bimetallic snap disc working against it, comprises electrically conductive spring part, which in the rest position is electrically connected to an external connection and one piece formed as a dome on the spring part movable Contact that depends on the temperature of the bimetallic snap disc is in contact with a fixed contact who is electrically connected to the other external connection.

Such a temperature-dependent switch is from US-A-5 121 095 known.

From DE-C2-29 17 482 a switch is known, which serves to monitor the temperature of a device. For this he will via its external connections in series with the one to be monitored Device switched and arranged so that the temperature of the monitoring device affects the temperature of a bimetal part. If the switching temperature is exceeded, opens the rear derailleur the connection between the two external connections, and the circuit above it is interrupted. If the temperature drops, the circuit becomes again closed, although this may not be the case bistable temperature-dependent switches are also known.

The known switch has an electrically conductive one Lower part and one that closes it electrically conductive cover part existing housing, with for insulation an insulating film between the lower part and the cover part is provided. On the cover part there is an inward protrusion Area formed as a fixed contact. The rear derailleur has a spring washer on which by a flange the movable contact is attached to that with the fixed contact comes in plant. There is a bimetallic snap disc over the spring washer put that below the switching temperature is accommodated in the housing without forces. The current flows over the conductive cover part, the contact, the spring washer and the conductive lower part, in which the spring washer supported. If the switching temperature is exceeded, then snaps the bimetallic snap disk and presses the spring washer with their contact away from the cover part.

The mechanical assembly of the known switch is special expensive because the contact over the flanged edge must be attached to the spring washer.

A comparable switch is known from DE-A1-37 10 672. This so-called temperature monitor is self-holding trained, so includes a parallel to the bimetal switchgear switched heating resistor, with the switchgear open is connected in series between the external connections and heats up so far by the current flowing through it that the bimetal switchgear is above its switching temperature holds so that it does not return to the basic state. The high-resistance parallel resistor is in the cover part integrated, either from insulating material or from one there is electrically conductive resistance material.

With this switch, the movable contact is loose in the spring washer inserted and over a protruding ring shoulder clamped between the spring washer and the bimetallic snap washer.

The disadvantage here is that during the final assembly, which in the Usually done manually by trained personnel, initially the spring washer into the lower part, then the contact part into the spring washer and finally the bimetal snap washer must be placed over the contact part. This process is very time-consuming and can only be automated to a limited extent. Furthermore, it can cause the contact part to slip during assembly, so that the committee is increased.

In order to eliminate these disadvantages, DE-A1-43 37 141 already proposed to weld the contact to the spring washer.

This does adversely affect the aforementioned drawbacks removed the final assembly of the switch, but it's like required for the switch from DE-C2-29 17 482 mentioned above, through additional measures the contact on the spring washer to fix.

In all known switches discussed so far The moving contact is a turned part that can only be used with the appropriate Material and manufacturing costs can be made so that it adds significantly to the total cost of the known switches.

FR-A-14 33 185 is another temperature-dependent Known switch, which is an annular spring element with a Has spring tongue projecting radially inwards. The spring element is between a fixed contact and a bimetallic disc arranged such that the spring tongue in the open Switching state supported on a bimetallic disc. jumps the bimetallic disc due to an increase in temperature, so she presses the spring tongue against the fixed contact of the switch on, the current flowing through the spring element.

From US-A-5 121 095 already mentioned at the beginning is a Known switch that has an approximately ring-shaped Has spring tongue, which is firmly clamped at one end and is connected to a first electrical external connection. The other movable end of the spring tongue is closed Switching status at a fixed contact with a second electrical external connection is connected. In the counter a bimetallic snap disc is inserted, which is exceeded jumps around a limit temperature and over a higher one Spring washer and an actuating base attached to it a dome-shaped at the movable end of the Spring tongue trained contact stands out from the fixed contact.

Proceeding from this, it is an object of the present invention training switch mentioned in such a way that he a simple and inexpensive construction and easy to assemble is.

According to the invention this object is achieved in that the Bimetallic snap disc is placed over the calotte.

The object on which the invention is based is achieved in this way completely solved. The inventor of the present application has namely recognized that surprisingly it is not required after all is to use a rotating part as a moving contact part, but that this moving contact is also made of the material the spring washer can be manufactured. So far was in State of the art has always been assumed that the movable Contact must be a separate contact part, which is preferably lies loosely in the spring washer, but at most retrospectively be attached to the spring washer by suitable measures can. This should ensure that the spring properties the spring washer regardless of the massive Contact part can be made. The inventor has now however recognized that this is based on a prejudice, the spring properties of the spring part, on which the contact is in one piece is fully trained for the intended applications sufficient. Furthermore, the inventor found that it too is not necessary to turn a rotating part as a moving contact use, but that the contact resistance and the current conductivity even with one made of the material of the spring part formed mobile contact are sufficient.

The new switch has a number of advantages on. The manufacturing costs are reduced by the one Reduced the number of components that can be found in the new switch are, since the new spring part, so to speak, the previous contact part as well as the previous spring part replaced. Furthermore, it is no longer required the contact part before or during the Final assembly of the switch to attach to the spring washer, see above that this manufacturing step is omitted. Overall, with that not just the component costs, the cost of stockpiling and the number of components but also the time required reduced for the final assembly, which is now also automatic can take place, whereby further committee is avoided. Another The advantage is that the number of contact resistances, the number of contact areas required the absolute minimum is reduced because of the contact resistance between the contact part used in the prior art as well the spring washer disappears. The quality of the entire contact resistance the switch is thus improved, the Problems with material selection against the background of aging be solved. Because the contact washer and spring part are now out are made of the same material, those with electrical fall Contacts between dissimilar metals occurring Problems such as corrosion gone.

It is also advantageous that when assembling the new switch no complex positioning work is required, the bimetallic snap disc is centered on the calotte, so to speak by itself.

It is preferred if the calotte closes in the contact area the bimetallic snap disc has an insulating layer.

The advantage here is that in each switching state of the new Switch is avoided that current through the bimetallic snap disk to be led. This prevents the Current flow through the switchgear warms the bimetal snap disc and thus a shift in the switching temperature leads.

It is generally preferred if the spherical cap is in the contact area has a resistance layer to the fixed contact.

The advantage here is that in the closed state of the new Switch the resistance formed by this resistance layer connected in series between the external connections of the switch is and through the operating current flowing through it of the device to be protected is heated. This warming can either be used to switch the switching temperature of the bimetal switchgear with a kind of preheating. on the other hand can have a current sensitivity via this resistor be set as this as a measure in itself from a standing start is known in the art. If that exceeds that Switching device flowing operating current of the consumer preselected value, so the heating of the resistor becomes like this large that the bimetallic snap disc switches the rear derailleur and breaks the circuit. The arrangement of this resistor now on the calotte of the spring washer has special advantages on because an expensive assembly of the heating resistor - like them is required in the prior art - can be omitted here. The spring part is, so to speak, with pre-assembled resistance delivered so that despite the property of current sensitivity no further assembly steps result. The resistance layer can e.g. B. by sputtering, in thick-film and thin-film technology or applied by other suitable methods become.

Further advantages result from the description and the attached drawing.

It is understood that the above and those below Features to be explained not only in each case specified combination, but also in other combinations or can be used alone, without the scope of leaving the above invention.

The invention is illustrated in the drawing and is in the following description explained in more detail.

The single figure shows a schematic longitudinal section through the new switch.

In the single figure, a switch is shown at 10, the one Housing 11 comprises, in which a bimetallic switching mechanism 12 is arranged is.

The housing 11 comprises an electrically conductive lower part 14 and a cover part 15 made of insulating material is supported on a shoulder 16 of the lower part 14. By a flanged edge 17 of the lower part 14 becomes the cover part 15 pressed onto the shoulder 16 so that a so-called encapsulated Switch 10 is created.

On the inside of the cover part 15 is a heating resistor 21 provided, which via an outer contact ring 22 with the Shoulder 16 is in electrical connection. About an inner Contact ring 23 is the heating resistor 21 with a fixed contact 24 connected, in the form of a rivet 25 through the cover part 15 goes through and a first outer terminal 26 of the switch 10 forms. Between the two contact rings 22, 23 is on an insulating layer 27 is provided for the heating resistor 21.

A movable contact 28 is assigned to the fixed contact 24, is the integral part of a spring washer 29 and the shape of a Dome 30 has. The made of electrically conductive material manufactured spring washer is supported with its edge 31 on the floor 32 of the lower part 14. Over the calotte 30 is a bimetallic snap disk 33 slipped, which has an edge 34.

In the contact area to the fixed contact 24, the calotte has 30 on a resistance layer 35, which is a heating resistor 36 forms. Furthermore, is in the contact area to the bimetallic snap disk 33 an insulating layer 37 is provided on the calotte 30, so that in this area there is no electrical connection between the spring washer 30 and the bimetallic snap disk 33.

Finally, it should be mentioned that a second external connection 38 of the switch 10 is formed by the lower part 14 itself.

In the switch position shown in Fig. 1 is the Bimetal snap disk 33 below its response temperature, so that the spring washer 29 for electrical contact between the lower part 14 and the fixed contact 24 and thus the external connection 26 provides. In a row between the external connections 25 and 38, the heating resistor 36 is connected, which is thus from Current of one to be connected to the external connections 26, 38 Device is flowed through. The heating resistor 21 is parallel switched to the bimetal switchgear 12 and is in the in Fig. 1 shown switching position by the series connection Bimetal switchgear and heating resistor 36 bridged. The Resistance values of the heating resistors 36 and 21 are selected so that the operating current of the device to be protected essentially flows through the heating resistor 36.

If now due to an elevated temperature of the thermally the new switch 10 related device or due to excessive current flow through the heating resistor 36 and the associated heat development the temperature of the Bimetal snap disk 33 rises above the response temperature the bimetallic snap disc suddenly snaps, supports itself with its edge 34 on the insulating layer 27 and lifts against the force of the spring washer 29, the cap 30 of the fixed Contact 24 from. The current now flows through the heating resistor 21, which develops sufficient heat to the bimetal rear derailleur to keep in the open state. Even without that Insulating layer 27 would have no current through the bimetallic snap disk 33 flow because they pass through the insulating layer 37 is isolated from the spring washer 29. The insulation layer 37 further ensures in the state shown in Fig. 1 that even in the rest position of the switching mechanism 12, no partial flow through the bimetallic snap disk 33 flows and the switching temperature changed by that.

Of course, the new switch can also be used without heating resistors 21 and / or 36 are built, the switch 10 then only serves to monitor the temperature.

Claims (4)

1. A switch with a temperature dependent switching mechanism (12) switching at excess temperature and for opening and closing a circuit connectable to external terminals (26, 38) of the switch (10), whereby the switching mechanism (12) comprises an electrically conductive spring element (29) working dependent on the temperature of a bimetallic snap disk (23) against the latter, the spring element being in its rest position electrically connected to an external terminal (38) and carrying a movable contact (28) that is integrally configured as a dome at the spring element, the movable contact resting against a fixed contact (24) depending on the temperature of the bimetallic snap disk, the fixed contact being electrically connected with the other external terminal (26), characterized in that the bimetallic snap disk (33) is slipped over the dome (30).
2. The switch of claim 1, characterized in that the dome has an insulating layer (37) in a contact region with the bimetallic snap disk (33).
3. The switch of claim 1 or claim 2, characterized in that the dome has a resistive layer (35) in a contact region with the fixed contact (24).
4. The switch of any of claims 1-3, characterized in that it comprises a housing (11) having an electrically conductive lower part (14) in which the spring element (29) is supported, and a cover part (15) which closes the lower part (14) and carries the fixed contact (24).

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