IMPROVED MULTIWAY ELECTRICAL SWITCH HAVING A TACTILE EFFECT AND A SINGLE TRIPPING MEMBER

Abstract: The invention provides a switch (10) comprising a support (12) for fixed contacts (26, 28), a contact plate (44) which comprises contact blades (50), which is placed vertically between a member for actuating the switch and the bottom (25, 34) of the housing, and an overall dome-shaped monostable tripping member (36) which is elastically deformable for the purpose of allowing the electrical connection between the fixed contacts (26) to be established via the contact plate (44), characterized in that the tripping member (36) is vertically interposed between the bottom (25) of the housing (22) and a central part (46) of the contact plate (44) so as to define a high vertical position of the contact plate corresponding to its rest state.

Description: Improved multiway electrical switch having a tactile effect and a single tripping member The present invention relates to an electrical switch having a tactile effect. The invention relates more particularly to a very small switch of the type comprising a contact-carrying support which defines a housing in the bottom of which at least two fixed electrical contacts are placed and which houses an overall dome- shaped tripping member which is elasticaUy deformable, from a stable rest state, due to the action of an actuating member, especially a pusher, which acts on the central part of the tripping member in a direction approximately perpend icular to the bottom of the housing , for the purpose of establishing electrical connection between the two fixed contacts. According to this design , when the central part of the overall dome-shaped tripping member is acted upon, the latter suddenly leaves its stable rest state in order to establish electrical connection between a fixed contact, generally a lateral contact against which the lower peripheral edge of the tripping member bears, and a central fixed contact which strikes the central part of the tripping member, which is made of a conductive material. The sudden change of state of the tripping member gives its user, who acts directly or indirectly on the actuating pusher, a tactile sensation of the change of state of the tripping member and therefore the change of the switch . According to a known design, the tripping member is, for example, made in the form of a domed disc or of an element having a rectangular outline of pyramidal overall shape. Two examples of such a design are described and shown in documents FR-A-2,734,398 and FR-A-2,735,276. The increasingly high degree of miniaturization of the components which are placed in electronic devices and are mounted , in particular, on a printed circuit board , results in the d imensions of these components being very significantly reduced , both in terms of their footprint on the printed circuit board and their vertical height above the board . Apart from the miniaturization of the components, and therefore of the switches, it is desirable also to reduce the number of electronic components associated with the switches, whether these are integrated components or discretes. These components, and especially transistors, are needed together with a switch when it is desired to have several separate switching channels associated with a single switch. For this purpose, WO-A-99/28937 has proposed an electrical switch having a tactile effect, of the type mentioned above, which has very small dimensions and allows multiway switching without the use of complementary electronic components such as transistors . In that document, the switch is of the type comprising : - a support which defines a housing in the bottom of which at least two fixed electrical contacts are placed; - a contact plate, made of a conductive material, which comprises at least two contact blades, which is placed vertically between a member for actuating the switch and the bottom of the housing and , under the action of the actuating member, can switch from a stable rest state, in which each contact blade lies vertically above an associated fixed contact, to an active contact state, in which each blade is in contact with its associated fixed contact; and - an overall dome-shaped tripping member which is elasticaUy deformable, from a stable rest state, due to the action of the actuating member which acts on the central part of the tripping member in a d irection approximately perpendicular to the bottom of the housing , for the purpose of establishing electrical connection between the fixed contacts via the contact plate. J According to the design proposed in that document, the intermediate contact plate is interposed vertically between the tripping member and the bottom of the housing , and the actuating member acts, directly or ind irectly, on the tripping member. During its sudden downward travel, the central part of the tripping member engages with the free ends of the contact blades of the contact plate in order to deform these blades elasticaUy downwards. At the end of the tripping travel, the contact blades are thus each brought almost simultaneously into electrical contact with their associated fixed contact. A simple tripping action on the single tripping member thus makes it possible to electrically connect the output terminals, almost simultaneously, so as to ensure switching of several electrical channels connected to the output terminals of the switch, for example three channels. In such a design , the central part of the monostable-type tripping member " strikes" the free ends of the contact blades, which flex elasticaUy with a relatively large deformation travel. The aim of the invention is to propose another example of a construction of an electrical switch of the above-mentioned type which makes it possible to improve its reliability and to further reduce its dimensions. For this purpose, the invention provides a switch characterized in that the tripping member is vertically interposed between the bottom of the housing and a central part of the contact plate so as to define a high vertical position of the contact plate corresponding to its rest state. By virtue of this design , the tripping member no longer participates directly in establishing the electrical connections between the contact blades and their associated fixed contacts which result from the vertical downward travel of the contact plate. The contact blades are only slightly flexed at the end of travel. According to further characteristics of the invention : - the contact plate comprises at least one pair of elasticaUy deformable opposed stabilizing branches which extend from the central part and the free ends of which bear against the bottom of the housing ; - the contact blades are elasticaUy deformable; - the contact blades lie parallel to one another ; - each contact blade lies in the plane of the contact plate ; - the stabilizing branches lie approximately parallel to the contact blades ; - the contact blades are opposed in pairs with their roots joined to the central part of the contact plate from which they extend in cantilever fashion ; - the switch has two pairs of contact blades which can engage with four associated fixed contacts ; - the contact plate has a pair of stabilizing branches which are placed transversely between the two pairs of contact blades ; - the contact plate has two pairs of stabilizing branches which are placed transversely between two adjacent pairs of contact blades ; - all the fixed contacts lie approximately in the same plane ; - one of the contact blades of the contact plate is permanently deformed so that its free end is permanently in electrical contact with an associated fixed electrical contact, independently of the state of the contact plate. Further characteristics and advantages of the invention will appear on reading the detailed description which follows, for the understand ing of which reference will be made to the appended drawings in which : - Figure 1 is an exploded perspective view which illustrates a support carrying fixed contacts, a tripping member and a contact plate belong ing to an electrical switch having a tactile effect produced in accordance with the teachings of the invention ; - Figure 2 is a top view which illustrates the various components in Figure 1 in the assembled position and in the stable rest state of the tripping member and of the contact plate, with partial cutaway of the contact plate ; - Figure 3 is a longitudinal sectional view on the line 3-3 in Fig ure 2 ; - Figure 4 is a longitudinal sectional view on the line 4-4 in Figure 2 ; - Figures 5 and 6 are views similar to those in Figures 3 and 4 in which the tripping member and the contact plate, with its contact blades, are illustrated in the position for establishing a contact between the various channels of ' the switch ; and - Figure 7 is a partial top view, similar to that in Figure 2, which illustrates an alternative embodiment. Figure 1 shows a contact-carrying support which , according to a known general design , essentially consists of a body or casing 12 which is moulded in an insulating plastic and which in this case is of rectangular parallelepipedal overall shape. The body 12 is bounded by transverse lateral faces 14 and longitudinal lateral faces 16 , by a lower face 18 and by a horizontal upper face 20 into which a housing 22 opens . The housing 22 is bounded by a peripheral wall 24 of rectangular outline and by a bottom 25 which is approximately plane and parallel to the lower 18 and upper 20 faces. The body 12 is produced by overmoulding over conducting elements which constitute, in the example illustrated in the figures, a series of four fixed electrical contacts 26. The switch also comprises actuating means and an upper closure plate of known design (not shown) . Each fixed electrica l contact 26 consists of a metal strip wh ich is bent so that its in ner end 28 , located inside the switch 1 0 , lies in the plane bottom 25 of the latter, being slig htly raised above the bottom , while its outer end 30 projects long itud inally to the outside of the casi ng 12 , beyond the transverse latera l face 16, in order to form a connection terminal which , in this design, allows the switch 10 to be mounted on a printed circuit board (not shown) , for example using the technique of surface mounting the components. The fixed contacts 26 here are four in number, which lie longitud inally parallel to one another and are associated in pairs of fixed contacts 26 aligned longitudinally two by two in the bottom 25 of the housing 22. The upper faces of the inner contact ends 28 lie in the same plane parallel to the plane at the bottom 25. According to a known design, the switch 10 includes a tripping member 36, designed to be housed in the housing 22, this member being an element made from a sheet, for example metal sheet, which has an overall dome shape in the form of a spherical cap, the circular lower outline 38 of which has a shape and d imensions which are complementary to those of a cavity 32 made in the bottom of the housing and which is bounded by a peripheral part 34 of additional thickness and by four long itud inally oriented vertical partitions 40 adjacent to the inner ends 28 of the fixed contacts 26, the free ends 42 of which partitions 40 participate in the positioning of the monostable dome 36 by engaging with its lower edge 38. The lower outline 38 of the dome defines a lower general plane for the tripping member 36 to bear in the bottom 25 of the housing 22. The general concavity of the tripping member 36 is turned towards the bottom 25 and the tripping member can be deformed , in opposition to its intrinsic elasticity, in a vertical tripping direction V and from its stable rest state illustrated in the Figures 1 , 2 and 3 to an unstable trip state illustrated in Figures 5 and 6. According to a known design, a tripping member 36 changes state suddenly, beyond a defined tripping travel, so as to impart a tactile sensation of the tripping to the user. The tripping may be carried out by means of an actuating pusher (not shown) which is a conventional pusher extending in the vertical direction V or, for example and by way of an alternative, by means of a laterally operated pusher of the type described and shown in document FR-A-2,735,276. According to the teachings of the invention, and so as to almost simultaneously make electrical contact between the various fixed contacts 26, a contact plate 44 is interposed vertically between the actuating member (not shown) and the tripping member 36. The contact plate 44 is a plate made of a conductive material which is, for example, produced by cutting it out of a thin metal sheet in order to g ive it the grid shape illustrated by way of example in the figures. In the example illustrated in the figures, in which the insulating casing 12 has four fixed contacts 26, the contact plate 44 is cut out so as to have four electrical contact blades 50, each of which is associated with a fixed contact 26 respectively. Like the fixed contacts 26, the contact blades 50 are parallel to one another and are aligned two by two in pairs. As may be seen more particularly in Figures 1 and 2, each contact blade 50 extends longitudinally in cantilever fashion from a central part 46, in the form of a transverse strip, and the length of each contact blade is such that its rounded free end 52 is located in line with the inner end 28 of an associated fixed contact 26 of the casing 12. I n the rest state of the contact plate 44, the contact blades 50 extend in the general plane of the contact plate 44. Each pair of two longitudinally aligned contact blades 50 is, in this illustrative example, placed at a transverse end of the central part 46 of the contact plate. Lying longitudinally between the two pairs of contact blades 50 and from the central portion of the central part 46 of the plate 44 are two opposed stabilizing and bearing branches 54 of the contact plate 44. In a top view, as may be seen in Figure 2, each stabilizing branch 54 flares out from its root which joins it to the central part 46 of the plate 44. Each stabilizing branch 54 is bent vertically downwards, while the central part 46 is plane and horizontal. Thus, the free end edge 56 of each stabilizing branch bears against a facing part of the bottom 25, which part is bounded transversely by the partitions 40 and longitudinally by the part 34 of additional thickness. Thus, the stabilizing branches define a high vertical rest position of the general plane of the plate 44, in which plane the contact blades 50 lie, and they position the plate, longitudinally and transversely, in the housing 22. The high rest position of the contact plate 44 is such that the lower face 47 of its central part is slightly away from the convex upper face 37 of the dome 36. By prestressing the stabilizing branches 54, the actuating member brings the lower face 47 into contact with the dome 36, 37. I n this position , there is, of course, a slight vertical clearance between each contact blade 50 and the inner end 48 of the associated fixed contact 26, as may be seen in Figure 4. The operation of the switch 10 that has just been described is as follows. Starting from the rest position illustrated in Figure 2, the user trips the device by acting , directly or indirectly, on the central part 46 of the tripping member 36 (vertically downwards) in order to act simultaneously on the dome 36 and to cause it to trip from the stable position illustrated in Figures 3 and 4, that is to say to cause the sudden deformation of the dome 36 which reaches its unstable config uration and its position illustrated in Figure 5. Because of the sudden downward travel of the dome 36, the central part 46 of the contact plate 44, which is " pinched" vertically between the actuating member and the dome 36, drops suddenly and the entire contact plate 44 thus changes state, so as to reach its low vertical position illustrated in Figures 5 and 6. This downward travel of the contact plate 44 is accomplished against the intrinsic elasticity of the stabilizing branches 54. At the end of the tripping travel, the four contact blades 50 are thus all brought almost simultaneously into electrical contact, each with the lower end 28 of the associated fixed contact 26, as may be seen in Figure 6. During the vertical downward travel of the contact plate 44, each free end 52 of a contact blade thus " lands" on the inner end 28 of the associated fixed contact and each contact blade is then flexed elasticaUy so as to guarantee the electrical contact. Simply carrying out a tripping action on the central part 46 of the contact plate 44, and therefore on the single tripping member 36, therefore makes it possible to electrically connect together the four output terminals 30 almost simultaneously so as to provide switching of several electrical channels connected to the output terminals 30 of the switch 10 , that is to say in this case three channels. Upon releasing the force applied to the actuating member, the elasticity of the monostable dome 36 causes it to return automatically to its stable rest state by acting vertically upwards on the central part 46 of the contact plate which is thus elasticaUy returned to its high rest position by the stabilizing branches 54. In order to guarantee that the switch is properly sealed , it is possible to provide a rectangular sealing film (not shown) which is, for example, adhesively bonded around its periphery to the upper face 35 of the peripheral part 34 of additional thickness. In the alternative embodiment illustrated in Figure 7, the contact plate 44 has two pairs of opposed stabilizing branches 54 which are arranged at the opposed transverse ends of the central part 46, while the two pairs of contact blades are in this case adjacent and located between the stabilizing branches 54. According to an alternative embodiment, not shown, one of the contact blades 50 is initially permanently deformed by bending it so that its free end 52 is permanently in contact with an associated fixed contact 26 of the insulating casing 12, this being so whatever the state of the tripping member 36. Thus, one of the output terminals 30 constitutes the common reference contact of the contact plate 44, this design facilitating the downstream electronic management of the signals resulting from establishing the electrical contact for the three channels, especially by making it easier to carry out an operation to electrically test the trip state of the switch. By virtue of the presence of a metal contact plate, it is possible to produce the domed tripping member from a non- conductive material. The invention is not limited to the embodiments that have just been described . In particular, it is not limited to the number of electrical channels that it is possible to establish simultaneously.

Claims: CLAIMS 1 . Electrical switch (10) having a tactile effect, of the type comprising : - a support (12) which defines a housing (22) in the bottom (25) of which at least two fixed electrical contacts (26, 28) are placed ; - a contact plate (44), made of a conductive material, which comprises at least two contact blades (50), which is placed vertically between a member for actuating the switch and the bottom (25, 34) of the housing and , under the action of the actuating member, can switch from a stable rest state, in which each contact blade (50) lies vertically above an associated fixed contact, to an active contact state, in which each blade (50) is in contact with its associated fixed contact (26, 28) ; and - an overall dome-shaped tripping member (36) which is elasticaUy deformable, from a stable rest state, due to the action of the actuating member which acts on the central part of the tripping member (36) in a d irection (V) approximately perpendicular to the bottom (25) of the housing (22) , for the purpose of establishing electrical connection between the fixed contacts (26) via the contact plate (44) ; characterized in that the tripping member (36) is vertically interposed between the bottom (25) of the housing (22) and a central part (46) of the contact plate (44) so as to define a high vertical position of the contact plate corresponding to its rest state. 2. Electrical switch according to the preceding claim, characterized in that the contact plate (44) comprises at least one pair of elasticaUy deformable opposed stabilizing branches (54) which extend from the central part (46) and the free ends (56) of which bear against the bottom (25) of the housing . 3. Electrical switch according to either of the preceding claims, characterized in that the contact blades (50) are elasticaUy deformable. 4. Electrical switch according to any one of the preceding claims , characterized in that the contact blades (50) lie longitudinally parallel to one another. 5. Electrical switch according to any one of the preceding claims, characterized in that each contact blade (50) lies in the plane of the contact plate (44). 6. Switch according to the preceding claim taken in combination with Claim 2, characterized in that the stabilizing branches (54) lie approximately parallel to the contact blades (50). 7. Electrical switch according to any one of the preceding claims , characterized in that the contact " blades (50) are opposed in pairs with their roots joined to the central part (46) of the contact plate from which they extend in cantilever fashion . 8. Switch according to the preceding claim, characterized in that it has two pairs of contact blades (50) which can engage with four associated fixed contacts (26, 28). 9. Switch according to the preceding claim, taken in combination with Claim 2, characterized in that the contact plate (44) has a pair of stabilizing branches (54) which are placed transversely between the two pairs of contact blades (50). 10. Switch according to Claim 8, taken in combination with Claim 2, characterized in that the contact plate has two pairs of stabilizing branches (54) which are placed transversely between two adjacent pairs of contact blades (50). 1 1 . Electrical switch according to any one of the preceding claims, characterized in that all the fixed contacts (26, 28) lie approximately in the same plane. 12. Electrical switch according to any one of the preceding claims , characterized in that one of the contact blades of the contact plate is permanently deformed so that its free end is permanently in electrical contact with an associated fixed electrical contact, independently of the state of the contact plate. AMENDED CLAIMS [received by the International Bureau on 12 February 2001 (12.02.01); original claim 1 amended; remaining claims unchanged (1 page)] 1. Electrical switch (10) having a tactile effect, of the type comprising : - a support (12) which defines a housing (22) in the bottom (25) of which at least two fixed electrical contacts (26, 28) are placed ; - a contact plate (44), made of a conductive material, which comprises at least two contact blades (50), which is placed vertically between a member for actuating the switch and the bottom (25, 34) of the housing and, under the action of the actuating member, can switch from a stable rest state, in which each contact blade (50) lies vertically above an associated fixed contact, to an active contact state, in which at least one blade (50) is in contact with its associated fixed contact (26, 28) ; and - an overall dome-shaped tripping member (36) which is elasticaUy deformable, from a stable rest state, due to the action of the actuating member which acts on the central part of the tripping member (36) in a direction (V) approximately perpendicular to the bottom (25) of the housing (22), for the purpose of establishing electrical connection between fixed contacts (26) via the contact plate (44) ; characterized in that the tripping member (36) is vertically interposed between the bottom (25) of the housing (22) and a central part (46) of the contact plate (44) so as to define a high vertical position of the contact plate corresponding to its rest state. 2. Electrical switch according to the preceding claim, characterized in that the contact plate (44) comprises at least one pair of elasticaUy deformable opposed stabilizing branches (54) which extend from the central part (46) and the free ends (56) of which bear against the bottom (25) of the housing. 3. Electrical switch according to either of the preceding claims, characterized in that the contact blades (50) are elasticaUy deformable.

Inventors: JANNIERE ALAIN, JANNIERE, ALAIN
Applicants: ITT MFG ENTERPRISES INC, JANNIERE ALAIN, ITT MANUFACTURING ENTERPRISES INC., JANNIERE, ALAIN
Application year: 2000
Main classification: H01H13
IPC codes: H01H13