Electricity: electrothermally or thermally actuated switches – Thermally actuated switches – With bimetallic element
Reexamination Certificate
1999-04-12
2001-01-30
Picard, Leo P. (Department: 2835)
Electricity: electrothermally or thermally actuated switches
Thermally actuated switches
With bimetallic element
C337S333000, C337S343000, C337S053000, C337S077000
Reexamination Certificate
active
06181233
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is related to a temperature-dependent switch having two connection electrodes mounted on an insulating support, a switching mechanism that as a function of its temperature makes an electrically conductive connection between the two connection electrodes, and a resistance element that is connected to the two connection electrodes electrically parallel to the switching mechanism.
2. Related Prior Art
A switch of this kind is known from DE 21 13 388 A.
The known switch is a thermostat for protecting an electrical device, the switch being connected electrically in series with the device to be protected and in thermal contact with the device.
The two connection electrodes are planar metal parts of which one carries a fixed countercontact and the other a bimetallic element on whose free end sits a movable countercontact coacting with the fixed countercontact. The two metal parts are arranged one above another, and clamp between them a PTC resistor that, with interposition of a spring, is in electrical contact with both connection electrodes.
This configuration made up of insulating support, metal parts with fixed and movable countercontacts, and PTC resistor is slid into a housing, whereupon the housing opening is encapsulated with a sealing compound.
If the temperature of the device being protected exceeds the response value of the bimetallic element, the latter lifts the movable countercontact away from the fixed countercontact, thereby interrupting the supply of current to the device. A small residual current now flows through the PTC resistor arranged parallel to the switching mechanism thus constituted, developing sufficient heat to hold the switching mechanism open; this function is called “self-holding.”
A disadvantage with the known switch is that the PTC resistor is mechanically retained only when the switch is completely assembled, making assembly of this switch quite complex. Replacement of the PTC resistor is not possible.
A further self-holding temperature-dependent switch is known from DE 43 36 564 A1. This known switch comprises a bimetallic switching mechanism arranged in an encapsulated housing. The housing is arranged on a support plate on which conductor paths and resistors are provided. A PTC resistor, which is soldered parallel to the switching mechanism with external connectors, is provided outside the housing on the support.
A disadvantage of this switch is that it not only requires a relatively large number of components, but also has large dimensions.
SUMMARY OF THE INVENTION
In view of the above, it is an object of the present invention to improve the temperature-dependent switch mentioned at the outset in such a way that it can be assembled economically and easily; preferably, replacement of the resistance element is to be possible.
According to the present invention, this object is achieved in the case of the switch mentioned at the outset in that the resistance element is inserted into the insulating support perpendicular to the connection electrodes, so that it sits inside the insulating support and is retained by it.
The object underlying the invention is completely achieved in this fashion.
Specifically, the inventors of the present application have recognized that a surprisingly simple switch can be created if the resistance element is not arranged in sandwich fashion between the connection electrodes or on a separate support next to the switch, but rather is directly retained internally in the insulating support. The switch can then first be completely fabricated before the resistance element is then inserted subsequently into the insulating support. If the resistance element is dispensed with, the switch does not have the self-hold function, but in many applications this is sufficient.
If, on the other hand, the switch is to be equipped with a self-hold function, all that is necessary is to insert the resistance element. It is now possible, with one and the same basic switch, to selectably insert different resistance elements in order to adapt to different utilization conditions in terms of operating current and response temperature. The result is a great advantage in terms of production, since the switch as such can be prefabricated in large quantities so that later the various resistors merely need to be added. This possibility was also offered by the switch known from DE 43 36 564 A1 cited above, but there the subsequent installation of the resistance element was very complex. In contrast, DE 21 13 388 A, also mentioned above, does not allow this partial production of the switch; the PTC resistor, clamped between the connection electrodes in the interior of the housing, needed to be delivered in the correct configuration during production itself.
Altogether the new switch thus offers the advantage that the basic switch can be prefabricated and then later equipped, to order, with a resistor. Since it is thereby possible to manufacture the basic switch in a single production operation in much greater quantities, specifically because the specialization of the switch is not defined until later, the overall result is also a decrease in production costs, since the lot size for production of the basic switch can be much larger than in the case of the generic switch.
In an improvement, it is preferred if the two connection electrodes comprise planar metal parts which are arranged in one plane; and if the resistance element rests on the metal parts.
This feature is also advantageous in terms of assembly engineering, since the electrical connection between the resistance element and the connection electrodes is accomplished via the geometrical arrangement of the resistance element on the connection electrodes, where they are held by the insulation element.
It is further preferred if the two connection electrodes are equipped with contact ends which are arranged at a distance one behind another in the longitudinal direction of the switch; and if the resistance element spans the distance.
This feature is also advantageous in terms of assembly engineering, since it makes possible, for example, a temperature-dependent switching mechanism in which a bimetallic spring is mounted on the one contact end and carries on its other end a movable countercontact which coacts with a fixed countercontact mounted on the other contact end. The resistance element is then arranged, so to speak, geometrically and electrically in parallel with this bimetallic spring.
It is further preferred if the insulating support is equipped with projections which clamp the resistance element between them and press it onto the connection electrodes.
This feature is also advantageous in terms of assembly engineering; the resistance element needs be pressed, so to speak, only from outside between the projections, where it is then simultaneously held by their spring effect and pushed onto the connection electrodes. Later replacement of the resistance element is, however, also possible as a result; this can be advantageous under certain utilization conditions.
In general, it is also preferred if the one connection electrode carries a fixed countercontact and the other a bimetallic element on whose free end sits a movable countercontact coacting with the fixed countercontact.
The advantage with this feature is that a technically very simple switching mechanism is used, in which the operating current flows through the bimetallic element itself so that a further spring part can be dispensed with.
It is further preferred if the resistance element is a PTC block.
The advantage here in terms of assembly engineering is that an easily handled and easily contacted PTC block is used, the outer surfaces of which can be configured in known fashion as terminals.
Further advantages are evident from the description and the appended drawings. It is understood that the features mentioned above and those yet to be explained below can be used not only in the respective combinations indicated, but also in other combinations or in isolatio
Becher Michael
G{umlaut over (u)}ttinger Edwin
Hofs{umlaut over (a)}ss Marcel
Harness & Dickey & Pierce P.L.C.
Picard Leo P.
Thermik Geratebau GmbH
Vortman Anatoly
LandOfFree
Temperature-dependent switch does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Temperature-dependent switch, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Temperature-dependent switch will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2555926