EP0494278B1 - Electric switch - Google Patents

Abstract

In order to obtain a good sliding behaviour between a contact bridge and strip conductors punched out of a metal sheet, an electric switch has strip conductors provided with at least one protuberance that extends at least over the full range of movement of the contact bridge.

Description

The invention relates to an electrical switch in which conductor tracks are firmly connected to a base plate made of an insulating material. Such a switch is described for example in DE-A-1904616. With this switch, the conductor tracks formed by etching out are leveled by means of a pressing process, so that they may be flush with the surface of the base plate.

DE-A-37 37 907 describes a switch in which the conductor tracks are designed as flat surface sections of a sheet metal blank which are cut out of the originally full-surface sheet metal blank by punching. The conductor tracks are initially still connected to one another by connecting webs, so that the sheet metal board as a whole can be embedded in a base plate made of insulating material, during the manufacture of which it is partially extrusion-coated by plastic injection molding. The connecting webs between the conductor tracks are subsequently removed by drilling through the base plate and the connecting webs.

One or more contact bridges sit in a guiding and actuating device, by means of which they can be moved along the assigned conductor tracks. The contact bridges are in contact with the conductor tracks under the action of pressure springs.

Depending on the desired switching operations, either one or both conductor tracks of the two mutually parallel conductor tracks, which are jointly covered by a contact bridge, are interrupted at certain points, so that, strictly speaking, two or more conductor tracks of different lengths are located one behind the other. At the transition points of two such conductor tracks lying one behind the other, either the space between them is filled up to the height of the conductor tracks by the insulating material of the base plate or there is a gap between them.

The contact bridges are mostly punched out of sheet metal blanks. Sometimes they are also bent. If greater manufacturing tolerances occur on the guiding and actuating device for the contact bridge and / or on the base plate having the conductor tracks, which are generally produced as injection-molded plastic parts, for example the top of the base plate has the same height as If the top of one of the conductor tracks reaches or even protrudes slightly above it, the electrical switching properties of such a switch can be severely impaired. If the space between the conductor tracks is filled with insulating material at a transition point, it is easier to slide the contact bridge over the transition point. However, there is then a risk that the insulating material will partially get onto the conductor track when it is overmolded and that there may later be contact difficulties, for example a delayed switching contact or premature interruption of the contact. If a gap is created at the transition points between the conductor tracks by means of a corresponding shaped piece, contact difficulties due to undesired insulating material on the conductor tracks are avoided. However, there is a risk that the sliding behavior of the contact bridge will deteriorate and that a more or less strongly inhibited sequence of movements will occur at the transition points.

The invention is therefore based on a switch of the type resulting from the preamble of claim 1. The object of the invention is to develop such a switch so that its electrical switching properties can be improved with little effort. This object is achieved by the combination of features resulting from the characterizing part of claim 1. In principle, the invention consists in using a conductor track formed from sheet metal, the flat part of which is used for anchoring in the switch, while the rail-shaped elevation creates a reliable contact for the contact bridge. The conductor tracks thus each have at least one elevation which extends at least over the entire associated movement range of the contact bridge, only the transition points between two conductor tracks lying one behind the other being excluded. The contact bridge lies exclusively on this elevation of the interconnects assigned to one another. This results in a clearly defined contact surface between the contact parts interacting in pairs. This always results in consistently good switching properties, which are largely independent of any manufacturing tolerances of the metal parts and the plastic parts accommodating them.

By designing the switch according to claim 2, the elevations can be produced very easily and very inexpensively.

In an embodiment of the switch according to claim 4, the transition of the Contact bridge considerably facilitated and the contact bridge does not get caught. In one embodiment of the switch according to claim 5 it is achieved that at a transition point the contact bridge is passed from one conductor track to the one behind it without changing its altitude and thus also without mechanical interruption or disturbance of the movement sequence.

In one embodiment of the switch according to claim 8, it is achieved that during the longitudinal movement of the contact bridge on the conductor tracks assigned to it, the contact point between the contact bridge and the elevation of each of the two conductor tracks on the contact bridge constantly changes its position. This prevents the elevation of the conductor tracks from running in on the surfaces of the contact bridge resting on them. This increases the life of the contact bridge and prevents contact difficulties due to contact erosion. Advantageous further developments for different applications result from claims 9 to 12.

In a further development of the switch according to claim 13, the contact bridge receives a cylindrically shaped contact surface and contact surface without burrs, which acts as a skid in both directions of movement. This considerably improves the sliding behavior of the contact bridge on the conductor tracks and at the transition points and also further reduces the occurrence of disturbances in the movement sequence, in particular at the transition points. All of this is accomplished in a very inexpensive way. This configuration of the switch also makes it possible, in accordance with claim 14, to attach locking lugs in pairs in the area of both end faces of the contact bridge with opposite orientation. This in turn results in a symmetrical mounting of the contact bridge in the guiding and actuating device, thereby preventing the contact bridge from tilting or even tilting. Such a contact bridge is also used with advantages regardless of the features of the preceding claims.

The invention is explained in more detail below with reference to several exemplary embodiments shown in the drawings.

Fig. 1

einen Vertikalschnitt des Schalters mit Unterteil, Oberteil und Deckel;

Fig. 2

eine Draufsicht des Schalters bei abgenommenem Oberteil und Deckel;

Fig. 3

eine Draufsicht einer Blechplatine mit den Leiterbahnen für das Unterteil;

Fig. 4

einen Querschnitt einer einzelnen Leiterbahn;

Fig. 5

einen ausschnittweise dargestellten Längsschnitt des Unterteils im Bereich einer Übergangsstelle zweier Leiterbahnen;

Fig. 6

einen ausschnittweise dargestellten Längsschnitt eines abgewandelten Unterteils im Bereich einer Übergangsstelle;

Fig. 7

eine ausschnittweise dargestellten Längsschnitt des Unterteils nach Fig. 6 parallel zu dem Schnitt nach Fig. 6;

Fig. 8

eine Seitenansicht einer Kontaktbrücke des Schalters;

Fig. 9

eine Stirnansicht der Kontaktbrücke nach Fig. 8;

Fig.10

eine Draufsicht der Kontaktbrücke nach Fig. 8;

Fig.11

eine Draufsicht des Unterteils mit Leiterbahnen eines weiteren Ausführungsbeispiels des Schalters.

Show it:

Fig. 1

a vertical section of the switch with the lower part, upper part and cover;

Fig. 2

a plan view of the switch with the top and lid removed;

Fig. 3

a plan view of a sheet metal board with the conductor tracks for the lower part;

Fig. 4

a cross section of a single conductor track;

Fig. 5

a fragmentary longitudinal section of the lower part in the region of a transition point of two conductor tracks;

Fig. 6

a fragmentary longitudinal section of a modified lower part in the region of a transition point;

Fig. 7

a fragmentary longitudinal section of the lower part of Figure 6 parallel to the section of Fig. 6.

Fig. 8

a side view of a contact bridge of the switch;

Fig. 9

an end view of the contact bridge of FIG. 8;

Fig. 10

a plan view of the contact bridge of FIG. 8;

Fig. 11

a plan view of the lower part with conductor tracks of another embodiment of the switch.

The switch 20 in the embodiment shown in FIGS. 1 to 3 has a housing 21 which is formed by a lower part 22, an upper part 23 and a cover 24. An actuation button 25 is arranged on the cover 24.

The lower part 22 is made of a thermoplastic material with good electrical insulation properties in a spraying process. It has a base plate 26, in the top 27 of which two sheet metal plates 28 and 29 with different conductor tracks (FIG. 3) and the associated connecting tabs 31 and 32 (FIG. 1) are embedded. The connecting lugs 31 and 32 protrude vertically from the underside 33 of the base plate 26 and are aligned in two rows.

Five longitudinal walls 34 to 38 and two transverse walls 39 and 40 are arranged on the upper side 27 of the base plate 26. The five longitudinal walls are arranged parallel to one another at certain intervals and adjoin the transverse walls 39 and 40 at their two ends. As a result, the two outer longitudinal walls 34 and 38 together with the transverse walls 39 and 40 form a closed peripheral wall of the lower part.

The two longitudinal walls 35 and 36 and the two longitudinal walls 37 and 38 have the same clear distance from one another. Together with the associated section of the transverse walls 39 and 40, they delimit a chamber 41 and 42, respectively. A carriage 43 or 44 is accommodated therein, which is shorter than the chamber in question. The clear width of the chambers 41 and 42 and the width of the carriage 43 and 44 are matched to one another in such a way that the carriages are guided in a straight line in the chambers.

The carriages 43 and 44 are designed identically to one another. Each of them has three recesses which are aligned transversely to their direction of displacement. They are down, i. H. towards the base plate 26, open and at least partially closed towards the top. Depending on the requirements of the circuit diagram, a contact bridge is inserted in one or more of the recesses. In the carriage 43, there are the two contact bridges 45 and 46. In the carriage 44, there are the two contact bridges 47 and 48. The contact bridges are each pressed down by a helical compression spring 49, which is supported on the ceiling of the carriage.

The paired longitudinal walls 35 and 36 and 37 and 38 and the base plate 26 together form part of a guide and Actuator 50 for the carriages 43 and 44 and the contact bridges arranged thereon. The chambers of the lower part, in particular the chambers 41 and 42 for the slides 43 and 44, are covered by the upper part 23, which is provided with a base 51, the underside of which is smooth and flat, at least in the region of the chambers 41 and 42. The bottom 51 of the upper part 23 therefore forms a further part of the guiding and actuating device 50. It prevents the carriages 43 and 44 from being able to deflect upwards as a result of the reaction force of the helical compression springs 49.

In the floor 51 in the plan area of the two chambers 41 and 42 there is a longitudinal slot of a certain width. An actuating rib 52 or 53 extends through it, which is fixedly connected to the carriage 43 or 44, and is generally integrally formed thereon. The actuating ribs 52 and 53 are provided on the mutually facing sides with a rack profile 54 and 55, respectively. A pinion 56 engages therein, which is rotatably mounted by means of a vertically aligned bearing journal 57. The bearing pin 57 is integrally formed on the upper part 23. The hub 58 of the toothed pinion 56 extends through an opening 59 in the cover 24. The actuation button 25 is connected in a rotationally fixed manner to this hub 58.

The two sheet metal plates 28 and 29 (FIG. 3) firmly connected to the base plate 26 each have two plate sections 61 and 62 or 63 and 64, which are arranged next to one another with respect to the central plane of the carriages 43 and 44. Along the center line of each of the circuit board sections, the circuit board plate is provided with an elevation in the form of a bulge, as is illustrated in FIG. 4 for the circuit board section 61 by the elevation 65. In the same way, the board section 62 is provided with the elevation 66, the board section 63 with the elevation 67 and the board section 64 with the elevation 68. The contact bridges in the carriages 43 and 44 rest on these elevations, which in each case results in a precisely defined contact point.

In accordance with the requirements of the circuit diagram for the switch 20, the two mutually associated circuit board sections 61 and 62 as well as 63 and 64 are either connected to one another in sections or are separated from one another in sections by longitudinal punchings 69, 71 or 72. By Transverse cut-outs, each of which adjoins one of the longitudinal cut-outs 69, 71 or 72, the board sections 61 to 64 are divided into individual, in part different lengths, lengths. These longitudinal sections form the conductor tracks 81 to 86 in the area of the sheet metal plate 28 and the conductor tracks 87 to 90 in the area of the sheet metal plate 29.

So that the insertion of the metal plates 28 and 29 into the injection mold is easier during the manufacture of the lower part 22 and the correct arrangement and alignment of the different conductor tracks is maintained during the encapsulation, the metal plates 28 and 29 have the inner edge on which the connecting lugs 31 and 32 are arranged, the interconnects which are adjacent to one another in the longitudinal direction are initially connected to one another by a web 91. These webs 91 are subsequently removed through a bore 92, which are indicated by dash-dotted lines in FIG. 3. Similarly, webs are initially also present at other locations on the sheet metal blanks, which are subsequently removed again by means of a bore.

At the transition point between two conductor tracks lying one behind the other in the direction of displacement of the carriages 43 and 44, the material of the base plate 26 can either be at the same height as the sheet metal plate outside the elevation of the conductor tracks, as shown in FIG. 5. However, it is more expedient if the base plate 26 has a gap 93 between two conductor tracks lying one behind the other, as shown in FIG.

So that the contact bridge does not get stuck at such a transition point or its displacement movement is even disturbed, it is expedient to arrange a guide rib 94 on at least one side of the conductor track (FIG. 7). Their height is at least approximately equal to the height of the elevations adjacent to the gap 93, for example the elevation 65, of the interconnects lying at the transition point, for example the interconnects 81 and 82. Or it is at most slightly higher. Ramp sections 95 adjoin the guide rib 94 in both directions, which facilitate the sliding of the contact bridge onto the guide rib 94.

The sliding over of a contact bridge from the elevation of a conductor track to the elevation of the other conductor track or from a guide rib to the elevation of the adjacent conductor track can also be facilitated by the fact that the elevation of the conductor track does not end at the transition point with a sharp edge, as is the case in FIG 96 and its elevation 97 is shown, but that the end section of the conductor track is ramp-shaped, as shown in FIG. 5 on the right with the conductor track 98 and the end section 99 of its survey 100.

The improvement in the sliding properties of the contact bridges on the conductor tracks, but also the electrical switching properties of these parts, is additionally improved in that the contact bridges 45 to 48 are formed by a folded sheet metal blank, as can be seen from FIGS. 8-10. The folding back of such a contact bridge, such as the folding back 101 of the contact bridge 45 (FIG. 9), faces the conductor tracks. These contact bridges are first punched out in an H shape. They are folded along the center line of the web of the H-profile, so that they then have a U-shaped side view (Figure 8). In the middle of their web part they have a small elevation, which are used to guide the helical compression springs 49.

Due to their formation from a symmetrically designed sheet metal blank, a detent 107 and 108 can be formed on both legs 102 and 103 of the sheet metal blank 104 in the area of both end faces 105 and 106 of the contact bridge, which are produced by notching and simultaneous slight bending, as long as the sheet metal blank 104 is not yet folded. With the latching lugs 107 and 108, the contact bridges can be latched into one latching surface of the slide both in the longitudinal and in the transverse direction.

To reduce the mechanical wear of the elevations of the conductor tracks, it is expedient to give the elevation of a conductor track at least in sections a course which deviates within the width of a contact bridge from the movement line of a specific point of the contact bridge, so that when the contact bridge moves relative to the conductor tracks the contact point not only on the conductor tracks, but also hikes at the contact bridge. This is clear from the exemplary embodiment of a switch 110 shown in FIG. 11. With him, the contact bridges 111 and 112 are arranged on a pivoting part, not shown in detail, which is pivotably mounted on the lower part 113 by means of a circular recess 118. The contact bridges 111 and 112 move during a swiveling movement of the swiveling part in each case on an arc-shaped movement path. The conductor tracks with their elevations 114 to 117 each run in a straight line. As a result, when the pivoting part moves, a relative movement of the elevation of the conductor track relative to the folding back of the contact bridges always begins. Such a relative movement of the contact point on the contact bridges, which reduces the erosion, can also be achieved by other combinations of the course of the movement path of a contact bridge and the outline shape of the elevation of the interconnects interacting with it. When the contact bridge moves in a straight line, the outline of the elevation of the interconnects interacting with it can also be a straight line, which, however, encloses an acute angle with the line of movement of a point of the contact bridge. In the case of a curved movement path of the contact bridge, in particular in the case of a circular arc, the outline of the elevation of the conductor tracks can also be curved and also circular arc-shaped, as long as the movement line of a point of the contact bridge is not congruent with the course of the elevation. This can be achieved by aligning the curvatures in opposite directions or, in the same direction, by varying the size of the curvature, and even with the same curvature by mutually intertwining the two curvatures.

Claims (14)

1. An electric switch comprising the features:

   - a sheet metal blank (28) has metal conductors (81 ... 85) provided by punchings (69, 73 ... 76),

   - the sheet metal blank (28) is firmly connected with a base plate (26) of an insulating material by partially injection-moulding around it,

   - a bridging contact (47, 48) is movable alongside the metal conductors by means of a guiding and operating device (50),

   characterized by the features:

   - the metal conductors (81 ... 85) have at least one projection (65) each, extending at least over the entire range of motion of the bridging contact (45, 46), the bridging contact (47, 48) being in abutment on the projection.
2. An electric switch as claimed to claim 1,
   characterized by the feature:

   - the projection (65) of the metal conductors (81 ... 85) is formed as a bulge of the sheet metal blank (61).
3. An electric switch as claimed in claim 1,
   characterized by the feature:

   - the projection of the metal conductors is formed as a metal coating, preferably a silver coating.
4. An electric switch as claimed in any one of claims 1 to 3,
   characterized by the feature:

   - in the transitional place of two metal conductors (96; 98) positioned one behind the other in the direction of motion of the bridging contact (46), the end portions (99) of the projections (100) facing each other are formed in the manner of a slope.
5. An electric switch as claimed in any one of claims 1 to 4,
   characterized by the feature:

   - in the transitional place of two metal conductors (81; 82) positioned one behind the other in the path of motion of the bridging contact (46), a guide rib (94) is arranged at least on one side of the metal conductors,

   - - which is aligned at least substantially in parallel to the path of motion of the bridging contact (46), and

   - - which extends at least substantially from the end of the projection (65) of one metal conductor (81) to the beginning of the projection (65) of the metal conductor (82) positioned behind the other one.
6. An electric switch as claimed in claim 5,
   characterized by the feature:

   - the guide rib (94) has either the same height as the adjacent projections (65) or a slightly larger height than the latter.
7. An electric switch as claimed in claim 5 or 6,
   characterized by the feature:

   - the guide rib (94) has a sloped portion at the front and/or rear in the direction of motion of the bridging contact (46).
8. An electric switch as claimed in any one of claims 1 to 7,
   characterized by the feature:

   - the projection (114 ... 117) of one metal conductor has at least partially a course, which deviates from the line of motion of a point of the bridging contact (111, 112) within the width of the path of motion of the bridging contact (111, 112).
9. An electric switch as claimed in claim 8 with a straight path of motion of the bridging contact,
   characterized by the feature:

   - the projection of the metal conductor extends linearly and includes a pointed angle with a line of motion of a point of the bridging contact.
10. An electric switch as claimed in claim 8 with a straight path of motion of the bridging contact,
    characterized by the feature:

    - the projection of the metal conductor is curved.
11. An electric switch as claimed in claim 8 with an arc-shaped, in particular a circular path of motion of the bridging contact (111, 112),
    characterized by the feature:

    - the projection (114 ... 117) of the metal conductor is straight and extends alongside a chord of the line of motion of a point of the bridging contact (111, 112).
12. An electric switch as claimed in claim 8 with an arc-shaped, in particular a circular path of motion of the bridging contact,
    characterized by the features:

    - the projection of the metal conductor is curved, preferably circular,

    - the curvature of the projection extends in the same direction as the curvature of a line of motion of a bridging contact point and is either larger or smaller than the latter or is swivelled relative to it with the base,

    - and/or the curvature of the projection extends in opposite direction to the curvature of the line of motion of a bridging contact point.
13. An electric switch as claimed in any one of claims 1 to 12,
    characterized by the feature:

    - the bridging contact (45) is formed by a folded sheet metal blank, the folded back (101) of which is turned towards the metal conductors (81 ... 86).
14. An electric switch as claimed in claim 13,
    characterized by the feature:

    - in the area of both front sides (105; 106) of the bridging contact (45), a detent (107, 108) is released on at least one shank, preferably on both shanks of the folded sheet metal blank and bent towards the outside, the locking surface of the detent is turned towards the folded back (101).

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