The present invention relates to an electrical switch, particularly of microswitch design.
Electrical switches are mass-produced products used in numerous appliances that have electrical functions. A preferred, although not limiting, field of application of the switches considered here is that of door closures for washing machines, dishwashing machines, stoves and similar electrical domestic appliances (so-termed “white goods”). Microswitches, which, for example, operate in response to the closing of the door or in response to the locking of a closing element of the door closure, and thus allow various states of the closure to be identified, are often built into such door closures.
The mass-produced character of the switches considered here normally exerts a high cost pressure in production, with not only the manufacture of the individual parts, but also their fitting, being cost factors to be taken into account.
An object of the present invention is to provide an electrical switch that can be produced with a small resource input and has a high functional reliability.
This object is achieved, according to the invention, by an electrical switch, comprising at least one pair of switching contacts, which can be moved, relative to one another, between an in-contact position and an out-of-contact position, for the purpose of making and breaking an electrical path leading via the two switching contacts, and comprising spring means, which bias the two switching contacts relative to one another in the direction of one of their two relative positions. The spring means in this case comprise a coiled spring, which is made of an electrically conductive material, is located in the electrical path in series with the switching contact pair, and has at least one turn.
Within the scope of the invention, the term coiled spring comprises both axially acting helical springs and torsionally loaded torsion springs having spring legs that project approximately in a radial plane relative to the turn axis of the torsion spring. Such torsion springs are frequently also termed leg springs. Coiled springs are normally extremely reliable and have a long functional life. In addition, they are already commercially available as a mass-produced product, which does not require any special preparation, and is therefore cost-effective.
According to one embodiment, the coiled spring can be a helical spring loaded, particularly loaded in compression, substantially in the direction of its spring axis. It can be realized to be cylindrical, it being equally possible, however, to use a non-cylindrical coiled spring, for instance a barrel-shaped coiled spring.
A first of the two switching contacts can be located at an axial front face of the helical spring. In particular, it can be constituted directly by an end turn of the helical spring, such that no additional measures need be taken to constitute this switching contact (e.g. a welded-on contact plate). The second switching contact, on the other hand, is attached, expediently, in a fixed manner; this, likewise, is clearly not a necessity.
According to another embodiment, the coiled spring can be a torsion spring loaded in torsion, and one of the spring legs of the torsion spring can constitute a first of the two switching contacts.
In the case of a preferred development, the switch has two fixed conductor elements, which are made of electrically conductive material and arranged with a mutual spacing, the coiled spring being in constant contact with one of the conductor elements and being able to be brought into and out of contact with the other of the conductor elements by means of an actuating element. In particular, in the case of the coiled spring being realized as a helical spring, the actuating element can in this case be arranged to be movable in the direction of the axis of the helical spring, and, in the case of being realized as a torsion spring, be arranged to be movable in the transverse direction, in particular perpendicularly relative to the coil axis of the torsion spring. This is advantageous, in order to make the best possible use of the spring force of the coiled spring for the purpose of biasing the actuating element.
The switch according to the invention preferably has a switch housing, comprising a receiving shaft, into which the actuating element is inserted such that it can move up and down.
For simple, manual assembly, the actuating element is realized, advantageously, with formations that allow the coiled spring and the actuating element to be joined together to constitute a preassembly unit, before the actuating element is fitted to a housing of the switch. These formations can comprise, for example, a spring insertion space, which is constituted in the actuating element and into which the coiled spring spring can be inserted under bias. The fitting of the actuating element, equipped with the coiled spring, into the switch housing is then facilitated in that an alternative space, for a respective conductor element, adjoins the spring insert space on both sides, respectively.
At least one of the conductor elements, in particular both conductor elements, can be pushed through a through-opening in the actuating element. This can be used to achieve loss-proof fastening of the actuating element on a basic housing of the switch via the conductor element alone, without the need to take additional measures to secure the actuating element.
For good-quality contact with the coiled spring, and for simple and cost-effective production, the conductor elements are preferably realized in the form of pins. Alternatively, they can be realized, for example, in the form of strips or plates.
Further, it is to be pointed out that, although the conductor elements can be of like design, this is by no means imperative. Clearly, the two conductor elements can be of designs that differ from one another.
For a structurally simple design and a simple, rapid assembly of the switch according to the invention, the conductor elements can extend transversely through the receiving shaft and be held in the walls of the receiving shaft. For this purpose, the conductor elements can be pushed, from outside the receiving shaft, through push-through slots in a first wall region of the shaft, and be advanced transversely through the receiving shaft until they go into retaining recesses in a second wall region of the receiving shaft that is opposite the first wall region.
The push-through slots can open, on the side of the first wall region that is opposite the receiving shaft, into a space that serves to receive a connector plug. The switch according to the invention thus requires nothing, as electrically conductive components, other than the two conductor elements and the coiled spring, and fulfils the requirement for a small number of structural parts. Apart from these components, the switch according to the invention requires, in addition, only the switch housing and the actuating element, such that the switch overall can be assembled from no more than five components.
The receiving shaft can have, for example, a rectangular cross-section.
A particularly cost-effective design makes provision whereby the conductor elements are made of a wire material, in particular a wire material having a rectangular cross-section.
They can then be produced simply by being cut into lengths from a roll of wire, and need not be punched out of a sheet-metal material.
According to an embodiment of the present invention, the electrical switch can operate as a normally-closed contact, i.e., as an opener. Then, in the non-operative state of the switch, the switching contacts are in their in-contact position.
Alternatively, the electrical switch can operate as a normally-open contact, i.e., as a closer. In this case, the switching contacts assume their out-of-contact position in the non-operative state of the switch. In this case, there can be provided a spring element, which is separate from the coiled spring and acts counter to the latter, and which biases the two switching contacts in the direction of their out-of-contact position.
According to another aspect, the invention further achieves the object stated at the outset by an electrical switch, particularly of microswitch design, comprising
In the case of this aspect, the spring element can be, for example, a coiled spring in the form of a helical spring or a torsion spring. Likewise conceivable is the use of a leaf spring, for instance in a V shape, one of the limbs of the V being constantly in contact with one of the conductor elements, and the other limb of the V being brought, by the actuating element, into contact and out of contact with the other conductor element.
The invention is explained further in the following with reference to the appended drawings, wherein:
In the case of the on/off microswitch represented in
In total, the switch 10 according to the exemplary embodiment shown in
In the following, the arrow direction A is also referred to as the axial direction, because it coincides with the direction in which the helical spring 40 is fitted.
In the exemplary case shown, the receiving shaft 23 has a rectangular cross-section and is delimited, correspondingly, by four shaft side-walls arranged in a rectangle. Of these four shaft side-walls, two are emphasized separately in the figures, and denoted by references 21 and 22. The two walls 21, 22 are opposite one another, and serve to retain and support the two conductor pins 50, 60 on the switch housing 20. For this purpose, the switch side-wall 21 is provided with two retaining recesses 25, 26 for the tips of the conductor pins 50, 60, which retaining recesses are arranged above one another at a distance in the arrow direction A (i.e. in the axial direction). The retaining recesses 25, 26 are shaped into the wall 21 from the inside of the shaft, and preferably extend only through a part of the thickness of the wall 21. They can thus delimit the insertion depth of the conductor pins 50, 60. In the shaft side-wall 22, on the other hand, there are two push-through slots 27, 28 for the conductor pins 50, 60, which push-through slots extend fully through the wall 22. The push-through slots 27, 28 are arranged such that they are precisely axially opposite the retaining recesses 25, 26, and allow the conductor pins 50, 60 to be pushed through from the outside of the shaft side-wall 22.
When in the fitted state, the two conductor pins 50, 60 extend transversely through the shaft 23 and reach, with their tips, into the retaining recesses 25, 26. They thereby lie parallelwise in relation to one other and axially above one another, and extend perpendicularly in relation to the axial direction A.
The length of the conductor pins 50, 60 is so selected that, when in the fitted state, they protrude slightly outwards into a housing space 24 that serves to receive a connector plug, not represented in greater detail, to which the switch 10 can be coupled. The part of the housing 20 that surrounds the space 24 constitutes, correspondingly, a plug socket for the connector plug.
For the purpose of fitting, the conductor pins 50, 60 are introduced into the housing space 24 from the open side of the plug socket, and are pushed through the push-through slots 27, 28. They are then advanced until, with their leading ends, they go into the retaining recesses 25, 26 and cannot be advanced further. It is understood that the retaining recesses 25, 26 and/or the push-through slots 27, 28 can be of sufficiently constricted size or otherwise designed to ensure that the conductor pins 50, 60 are retained in the housing 20 in a loss-proof manner.
The actuating element 30 has, corresponding to the receiving shaft 23, a rectangular contour as viewed in an axial cross-section. It has an axially elongate, slot-type opening 32, which extends transversely through the actuating element 30 from one rectangular side to the opposite rectangular side, and which is delimited downwardly and upwardly in the axial direction by the material of the actuating element 30. In a middle region, the slot 32 is widened, transversely relative to the slot plane, to constitute a spring insertion space 31 (see
The slot regions axially above and below the spring insertion space 31 constitute alternative spaces 34, 35 (see
The transition steps between the spring insertion space 31 and the alternative spaces 34, 35 that adjoin axially on both sides are denoted by the references 36, 37, 38, 39 (see, in particular,
The actuating element 30 has an actuating head 41, which projects at least slightly from the shaft 23 and which, via an external manipulation element (not represented in greater detail), can act upon the actuating element 30 for the purpose of switch actuation. Expediently, the actuating element 30 is also made of plastic.
In the fitted state, as shown, for example, in
For a full electrical contact between the helical spring 40 and the conductor pins 50, 60, it is expedient if, in the final assembled state, the axial support of the helical spring 40 is effected substantially exclusively via the conductor pins 50, 60 and, accordingly, the bearing contact of the helical spring 40 with the transition steps 36-39 is removed, at least insofar as possible. For this purpose, the axial distance between the two conductor pins 50, 60 (determined by the axial distance between the retaining recesses 25, 26 and between the push-through openings 27, 28) is somewhat less than the axial distance between respectively axially opposing steps of the transition steps 36-39. At the same time, the retaining recesses 25, 26 and the push-through openings 27, 28 are so located that, in the fitted state, both conductor pins 50, 60 project somewhat into the spring insertion space 31. Consequently, when the switch is in the non-actuated state, the helical spring 40 is held in compression between the two conductor pins 50, 60.
In the case of the switch 10, the upper conductor pin 60 and the end turn 42 of the helical spring 40 constitute a pair of switching contacts, which are movable towards one another, within the meaning of the invention. In this case, the switching contact constituted by the conductor pin 60 is fixed, while the switching contact constituted by the end turn 42 is movable.
The ends of the conductor pins 50, 60 that project from the shaft side-wall 22 into the housing space 24 serve as electrical interface elements for contacting with complementary interface elements of the connector plug.
For the purpose of operating the switch 10, the actuating element 30 is pressed down, i.e. in the direction into the shaft 23, as indicated by an arrow F in
If the actuating force is removed, the actuating element 30 moves back upwards, under the action of the relaxing helical spring 40, until the helical spring 40 comes back into bearing contact on the upper conductor pin 60. The switch 10 is then back in the closed state.
For assembling of the switch 10, the helical spring 40 is first inserted in the spring insertion space 21 of the actuating element 30. The actuating element 30, with the helical spring 40 held therein, is then introduced into the receiving shaft 23 of the switch housing 20, being so inserted to the extent that the lower conductor pin 50 can be inserted without difficulty in the housing 20 and can thereby be threaded through the lower alternative space 35. The actuating element 30 is then pressed more deeply into the shaft 23. This compresses the helical spring 40, which now comes into contact with the already fitted lower conductor pin 50. The actuating element 30 is now pressed so deeply into the shaft 23 that the upper conductor pin 60 can be inserted in the housing 20 and thereby threaded through the upper alternative space 34. The actuating element 30 can then be released; the assembling operation is complete.
The conductor pins 50, 60 are composed, for example, of a wire material having a rectangular, in particular a square, cross-section but, alternatively, they can be produced from a round wire. It can be seen in
It is pointed out that, instead of a helical form of the spring 40, another form of an electrically conductive, yet elastic element can be selected, without the simplicity of assembling being significantly impaired and the low number of switch components being increased as a result. The idea of a switch having an actuating element that can be fitted in a loss-proof manner by means of two conductor elements that can be inserted through it and are held on a housing of the switch, whereas an electrically conductive spring element that, for its part, can to be preassembled with the actuating element to constitute a unit, being located between the two conductor elements, is regarded as being independently patentable within the scope of the invention, this being irrespective of whether the spring element is coiled or is of another design.
For the following explanation of the exemplary embodiments of
The switch 10a according to the exemplary embodiment of
The conductor elements 50a, 60a and the actuating portion 80a are arranged in differing vertical planes, such that the actuating portion 80a can be moved out of the position below the conductor element 60a, as shown in
If there is no force F1 acting upon the actuating element 75a, the electrical switch is in the equilibrium position shown in
If, as shown in
The switch variants of
In the case of the variant of
Number | Date | Country | Kind |
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10 2008 037 312.5 | Aug 2008 | DE | national |