Electrical transmission or interconnection systems – Switching systems – Condition responsive
Reexamination Certificate
1999-07-29
2001-04-03
Jackson, Stephen W. (Department: 2836)
Electrical transmission or interconnection systems
Switching systems
Condition responsive
C337S368000
Reexamination Certificate
active
06211582
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an electrical switching device, particularly a timing or clocking power control device, with a switching device socket and terminals. The electrical switching device has a snap-action switch with at least one catch spring, which carries at least one switching contact stud. The snap-action switch can be tripped by a thermomechanical switching member.
Such switching devices are known from DE 26 25 716. Further known are heating devices for thermomechanical switching members being made up of supports of isinglass or ceramics, carrying a heating resistor or the like. Heating resistors often are made up of thin wire which, in consequence of applying a voltage, produces heat. The problem with such supports for heating resistors is that the materials are easily breakable and difficult to produce because of their characteristics.
SUMMARY OF THE INVENTION
The purpose of the invention is to provide a switching and heating device containing a support which is easier to use, handle and produce.
This problem is solved by an electrical switching device having the features of claim
1
. The heating device has a metal support for at least one heating resistor for the thermo-influencing of the thermomechanical switching member. The metal support can be easily handled and is in no danger of breaking easily.
The thermomechanical switching member is preferably a thermobimetal and, in a particularly preferred arrangement, the coating having the higher expansion coefficient points towards the support or the heating resistor.
In an embodiment of the invention, the support comprises a flat material, and is preferably a plate with a thickness between 0.1 and 4 mm, e.g. approximately 1 mm. The plate can be rectangular.
The support advantageously has an electrically insulating layer between at least one surface and at least one heating resistor. It can be fitted in a non-detachable manner to the top of the support and essentially covers the support. An insulating layer, for example, can be applied by a thick-film process and is preferably vitreous or constituted by glass. Alternatively, insulating films or the like can be used, possibly made from synthetic materials able to withstand high temperatures. An insulating layer of glass or the like applied by a thick-film process can make it possible to apply flat and directly thereto a heating resistor, thereby forming a thick-film heating resistor. It can be connected to at least one contact or a metal contact bank, which can also be applied in a thick-film process. A contact bank can at least partially applied directly to the insulating layer and, in some areas, can overlap or coincide with the heating resistor to form an electrical contact. Preferably, a second contact bank can rest directly on the support material and contact the support. For this purpose, the insulating layer preferably only partially covers a surface of the support, so that in the free, uncovered portion the contact bank can rest directly on the support. Thus, the support is connected via the contact bank to the heating resistor or to one end thereof. It is also possible to have a third contact bank, which forms a center tap of the heating resistor. It is preferably located on the insulating layer and projects laterally under the heating resistor.
The surface of the support is preferably at least partially formed from a steel suitable for the thick-film process, namely, a so-called thick-film steel. More details can be found in EP-A 885 579. According to one embodiment, the support comprises several nondetachably interconnected layers, particularly at least one thick-film steel layer as the outside for the heating device and at least one copper containing layer. Preferably, the layer structure of the support is symmetrical to its median plane and, in a particularly preferred embodiment, has a core layer of copper and outer layers of thick-film steel. This structure has the advantage of avoiding a bimetal effect of the support because the copper core is substantially enclosed. The central copper layer should be thicker than the outer layers, preferably two to twenty times as thick and, most preferably, approximately four times as thick. Such a material can be produced, for example, in a large-area form by plating individual metal sheets or the like and then cutting out and separating the individual support plates.
The support can be secured to the switching member, for example, by contact welding. The switching member is preferably metallic and electrically conductive and can form an electrical terminal for the heating device. The support and switching member can be in flat contact in the vicinity of their connection and both are at least partially flat and planar. In one embodiment, the switching member can be spaced roughly from the central third of the support or the heating resistor thereof, and preferably has a limited, roughly identical spacing with respect thereto and in the longitudinal direction projects well beyond the support. The switching member is preferably elongated and engages the catch spring with its free end, particularly on a free end of the catch spring. The end of the switching member can be bent in a hook-like manner and advantageously has, in the hook-like bend, a recess in the longitudinal direction of the switching member.
One possibility of an adjusting device for modifying the spacing between the switching member and the catch spring can be provided in the vicinity of the free end of the switching member, for example, in the hook-like bend. An adjustment can take place through a rotary or turning movement. For this purpose, it is advantageous to provide a pin with a circumferential and constantly increasing diameter widening, which is mounted in the bend and engages with the diameter widening on the free end of the catch spring. A spacing change can be brought about by turning. If the turning axis and/or pin axis are perpendicular to the switching member movement direction, a force occurring in the axial direction during adjustment leads to no regulation or setting of the catch spring and a precise adjustment is possible. For adjustment purposes a portion of the pin preferably has tool working faces. The diameter widening preferably runs in the elongated recess. If the bend for the pin carries radially outwards the more strongly expanding layer of the switching member or thermobimetal, the bend on heating closes and fixes the adjusting pin, so that a rotation thereof can be avoided.
Alternatively, an adjusting device can act on the support, particularly on the side remote from the switching member and/or on the heating device. As a result, the position of the support and/or the catch spring can be determined relative to a mounting of the catch spring, with which the support is connected by means of the switching member engaging on said spring. According to a further development, the adjusting device is at least partially electrically conductive, preferably metallic and advantageously forms an electrical terminal for the heating resistor. One possibility is constituted by a metal screw mounted in the switching device socket and which points in the switching member movement direction and engages on a contact or contact bank of the heating resistor. The screw bearing can be connected to a terminal for the switching device and is in particular in one piece. For improved insulation, the connection can at least partially run within the switching device socket and is preferably injection molded into it during manufacture. It is thus possible to provide a tag or the like at a point different to the terminal for the heating device.
The switching member can be resiliently fixed to the switching device socket, preferably on a portion of the terminal for the switching device extending over the inside of said socket. It preferably engages under elastic tension on a regulating device or its position. With the support for the heating resistor, it can engage on a contact device for the heating means.
The catch spring is
Mannuss Siegfried
Platt Nils
Reimold Gunther
Akerman & Senterfitt
E.G.O. Elektro-Geratebau GmbH
Jackson Stephen W.
Polk Sharon
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