EP0344625B1 - Electrical push button switch - Google Patents

Description

The invention relates to an electrical push button switch mentioned in the preamble of claim 1.

Pushbutton switches are switches without latching (locking) of the moving contact pieces, whereby the contact pieces return to their starting position by means of an internal retraction force when the driving force ceases (e.g. finger pressure). Pushbutton switches are preferably used for short-term closing (on button) or opening (off button) of circuits. Pushbutton switches are known as pushbuttons or rocker switches in various embodiments.

In particular for circuits with low voltages and currents, pushbutton switches have become known which trigger a single switching operation with the aid of snap springs. This principle is preferably used for computer and typewriter keyboards. The snap springs rest on outer contact feet on conductor surfaces. With the help of a fixed plunger, the snap spring is pressed in the middle. If the actuating force acting on the actuating element exceeds the restoring force of the snap spring, it springs over. Since there is a conductor track surface directly in the middle under the snap spring, a connection of the conductor tracks is made after the snap spring. Since the snap spring rests on the printed circuit board after it has flipped over, it is not possible to push it through further for the purpose of stepped connection of a further circuit. In order to create a step switch, it is necessary that at least a second one is triggered with the same actuating element after a first switching operation.

A two-stage switch has become known, which is actuated by a linearly displaceable push button and in which two snap springs are arranged one above the other, which are activated in succession by means of a rigid switching plunger acting centrally on the snap springs.

From DE-A-2931370 a tip button provided with an operating rocker is known which has two spring-loaded contact disks arranged at a distance above one another via a centrally arranged stationary contact, which initially contact one another when acted upon and the stationary contact when further acted upon in a second stage to contact.

The disadvantage here is the small number of switch positions that can be achieved. Another disadvantage is that the step switch requires its own housing, which must be completely attached to a printed circuit board and in which the contact feet led out to the outside must be connected separately. In addition, it is disadvantageous that in the case of step switches with two superimposed ones Snap springs must adhere to very fine manufacturing tolerances. The load capacity with regard to switching capacity and service life is also low due to the larger switching travel of the upper snap spring. It is therefore an object of the invention to provide an electrical key switch of the type mentioned in the preamble of claim 1 while avoiding the known disadvantages to develop a multi-pole step switch, which enables a step-by-step connection of circuits and which can be created in a flat design, as well as manufacturing advantages.

This object is achieved by the features characterized in claim 1. Appropriate refinements and developments of the subject matter of the invention are characterized in more detail in the subclaims.

The fact that, for the purpose of forming a multi-pole step switch, the known principle of a two-step push button switch is abandoned and the push button switch is designed as a rocker switch with an actuating rocker, this alone alone doubles the switching positions. In addition, the additional use of shift plungers which are variable in length depending on the actuating force compared to the prior art enables a step-by-step switching in the same direction.

Due to the planar arrangement of the snap springs on a printed circuit board, the step switch according to the invention can be produced particularly advantageously in a flat design in cooperation with the switching plungers formed on the rocker arms of the actuating rocker in parallel with one another.

Furthermore, as a result of the arrangement of the switching tappets that is axisymmetric with respect to the pivot axis of the actuating rocker, a user-friendly configuration of the subject matter of the invention is made possible because of the symmetrical force and lever ratios achieved thereby.

The preferably dome-shaped snap springs in combination with an alternating gap-setting of the snap springs result in a particularly space-saving arrangement.

Manufacturing advantages can be achieved in that the snap springs are pre-positioned by means of a positioning plate and placed over a circuit board. As a result, the electrical part (circuit board, positioning plate with snap springs) and the mechanical part (actuating rocker with molded switching plungers) are separated in terms of production technology in the step switch according to the invention. The soldering of separate contact connections can be omitted.

In a particularly preferred embodiment, the step switch according to the invention is equipped on each side of the actuating rocker with a variable-length and a constant-length switching plunger. It can thus be used as a window lifter button for the step-by-step actuation of window lifter motors in motor vehicles, resulting in a 5-position button. A rest position is defined by the horizontal position of the operating rocker. As a result of the snap spring which is arranged near the pivot axis (first switching position), which is initially caused when the actuating rocker is actuated, the window is to be opened or closed as long as the button is pressed. If the actuation rocker (second switch position) is pressed further, while the first switch position remains switched on, the window is automatically moved to the respective end position with the help of downstream electronics (eg activation of a surge relay). In this case, the button does not need to be pressed any further.

Exemplary embodiments of the invention are described and explained in more detail below with the aid of the drawings.

Figur 1:

Den erfindungsgemäßen Stufentastschalter in Schnittdarstellung gemäß der in Figur 2 eingezeichneten Schnittlinie A-B gemäß einem ersten Ausführungsbeispiel.

Figur 2:

Eine Aufsicht auf die Anordnung der vom erfindungsgemäßen Stufentastschalter zu aktivierenden Schnappfedern ohne Gehäuseoberteil und ohne Betätigungswippe gemäß einem ersten Ausführungsbeispiel,

Figur 3:

eine schematische Ansicht einer Hälfte des erfindungsgemäßen Stufentastschalters in Ausgangsposition P₀ gemäß einem weiteren Ausführungsbeispiel mit n=3 Schaltstößeln 8,9.

Show it:

Figure 1:

The step switch according to the invention in a sectional view according to the section line AB drawn in Figure 2 according to a first embodiment.

Figure 2:

A top view of the arrangement of the snap springs to be activated by the step switch according to the invention without an upper housing part and without an operating rocker according to a first exemplary embodiment,

Figure 3:

is a schematic view of half of the tap changer according to the invention in the starting position P₀ according to another embodiment with n = 3 switching plungers 8.9.

A first embodiment is described below. As can be seen in FIG. 1, the step switch according to the invention has a lower housing part 1, in which a printed circuit board 3 is arranged. On the circuit board 3 there are snap springs SF _n , SF _n ', which are positioned with the aid of a positioning plate 4 below rocker arms A, A' an actuating rocker 5.

In the upper housing part 2, the two-armed actuating rocker 5 is mounted so that it can be pivoted about a pivot axis 16 running parallel to the positioning plate 4. On each, preferably large rocker arm A, A 'of the rocker 5 are perpendicular to this two in each case in the direction of the four snap springs SF₁, SF₂ SF₁', SF₂ 'facing switching plunger 8.9. Approximately at the level of a first actuating rocker bearing (not shown) and spaced apart from the pivot axis 16 of the actuating rocker 5, there is a second switching plunger 9 and also at the level of a second actuating rocker bearing (not shown), but a first switching plunger 8 is formed at a greater distance from the pivot axis 16. The second switching plunger 9 is designed to be variable in length by means of a slidable and telescopically guided and spring-loaded slider 7 depending on an actuating force acting on the actuating rocker 5. For this purpose, the second switching plunger 9 has a molded-on sleeve 6, in the displacement 10 of which the slide 7 is held by means of molded-on locking lugs 11. The slider 7 is pressurized by a preloaded compression spring DF₁, the compression spring DF₁ being held biased on the one hand in a first blind hole 13 of the second switching plunger 9 and on the other hand in a second blind hole 14 of the slide 7. The height of the displacement 10 is dimensioned such that it depends on the maximum spring travel Δx of the snap springs SF _n , SF _n 'and on the number n (n = 1, 2, 3 ...) of the switching plungers 8 formed in each case on a rocker side , 9 (n-1) Δx. In the present exemplary embodiment with a first switching plunger 8 and a second switching plunger 9, the slider 7 can thus be displaced by Δx.

The first switching plunger 8, which is always the most distant from the pivot axis 16 switching plunger in embodiments with n switching plungers compared to the second switching plungers 9, is rigid in itself so that it cannot change its length. Its length is always (n-1) Δx shorter than the length of the second switching plunger 9 closest to the swivel axis in a rest position P₀.

Figure 2 shows a plan view of the arranged in the positioning plate 4 snap springs SF₁, SF₂, SF₁ ', SF₂'. The spherical crown K₁, K₂, K₁ ', K₂' are positioned directly below the plunger tips S₁, S₂, S₁ ', S₂'. The snap springs SF₁, SF₂, SF₁ ', SF₂' are preferably dome-shaped, three rotationally symmetrical around the respective dome apex and parallel to the dome height are performed dome sections.

The operation of the step switch according to the invention will be described below using the first embodiment. In the rest position P₀, in which the tilt angle α of the actuating rocker 5 is zero degrees, the plunger tips S₁, S₂ of the switching plunger 8, 9 lie in an alignment plane 15 forming the maximum tilting angle α with the positioning plane of the positioning plate 4. The plunger tip S1 of the second switching plunger 9 lies on the crown crown K1 of the associated snap spring SF₁. The plunger tip S2 of the first switching plunger 8 has the distance Δx in the rest position P₀ from the crown crown K2 of the snap spring SF₂ assigned to the first switching plunger 8. Since the spring constant D1 in the second Switching plunger 9 arranged compression spring DF₁ is dimensioned so that it is greater than the spring constant D₀ of the snap springs SF _n , SF _n ', is achieved by the actuating force 5 acting on the operating rocker 5 initially jumps to the second switching plunger 9 associated snap spring SF₁. Since there is a conductor track directly in the middle under the snap spring SF 1, a connection of conductor tracks is established via the snap spring SF 1. The tip S₂ of the first switching plunger 8 lies on the crown part K₂. So that a first switching position P₁ is reached. If the actuating force on the actuating rocker 5 is further increased, the compression spring DF 1 is compressed within the second switching plunger 9 by Δx, as a result of which the slide 7 is moved into the displacement 10 of the second switching plunger 9 and the rigid first switching plunger 8 has the associated snap spring SF₂ activated. So that the second switching position P₂ is triggered. The same applies to the other side of the rocker switch 5.

The mode of operation of the tap changer according to the invention will be described with reference to FIG. 3 in a further exemplary embodiment with three switching plungers 8, 9 molded onto each rocker half. The first two switching plungers counted from the pivot axis 16 in the direction of increasing distance are variable-length second switching plungers 9, while the switching plunger most distant from the pivot axis 16 is a rigid first switching plunger 8. In the rest position P₀ the plunger tip S₁ rests on the associated snap spring SF₁. The plunger tip S2 is removed from the crown crown K2 of the associated snap spring SF₂ by Δx. The plunger tip S3 of the first switching plunger 8 is removed from the crown crown K3 of the associated snap spring SF₃ by 2Δx. After activating the first switching position P₁ S2 rests on the associated snap spring SF₂, while S3 is removed by Δx from the assigned snap spring SF₃. When the second switching position P₂ is activated, the second switching plunger 9 near the swivel axis is shortened by Δx, since the spring constant D2 of the middle second switching plunger 9 is larger than the spring constant D1 of the compression spring DF₁ of the second switching plunger 9 near the pivot axis. When pressing the actuating rocker 5 further up to the maximum tilt angle α, the associated snap spring SF 3 is activated by the rigid first actuating plunger 8 and the third switching position P 3 is triggered. Here, the compression spring DF₂ arranged in the middle second switching plunger 9 has been pushed together by Δx, while the pressure spring DF₁ located in the second switching plunger 9 near the pivot axis has pushed together by 2Δx. After reaching the third working position P3, the plunger tips S1, S2, S3 are all in the positioning plane specified by the positioning plate 4. By suitable dimensioning of the spring constants D₁, D₂ of the compression springs DF₁, DF₂ arranged in the two second switching plungers 9, D2 greater than D1 greater than D0, a step switch with three working positions P₁, P₂, P₃ can be created on each side of the rocker 5.

Claims (7)

1. Electrical key switch, especially for the stepwise actuation of window lift motors in motor vehicles, having at least two snap springs and having a two-armed actuating rocker (5) which is tiltable up to a maximum tilt angle (α) about a stationary pivot axis (16) and which can be brought out of a stable starting position (P_o) into 2n (n = 1, 2, 3 ...) unstable switching positions (P_n, P_n′), characterized in that switch strikers (8, 9) n in number, which are differently spaced from the pivot axis (16), are shaped on at each rocker arm (A, A′), that one of the strikers which is disposed furthest from the pivot axis is a constant-length first switch striker (8) and the strikers nearer to the pivot axis are actuating-force-dependent variable-length second switch strikers (9), in that snap springs (SF_n, SF_n′), in each instance beneath striker tips (S_n, S_n′) centered with respect to these and to be sprung in by these, with a simultaneously increasing tilt angle by means of actuating forces increasingly attacking the actuating rocker (5), progressively stepwise away from the pivot axis (16) in each instance along a maximum spring path ΔX, of the spring constant D_o, are disposed in planar fashion in a positioning plane predetermined by a position plate (4), in that the n-1 second switch strikers (9) exhibit in each instance one sliding piece (7) which is displacable in a stroke space (10) of a sleeve (6) shaped on at the switch striker (9) by a maximum of (n-1)ΔX and which is stressed by means of a compression spring (DF_n-1, DF_n-1′) and which forms the striker tip, in which the respective compression spring (DF_n-1, DF_n-1′) is held with prestress on the one hand in a first blind hole (13) of the second switch striker (9) and on the other hand in a second blind hole (14) of the sliding piece (7), in that the respective spring constant D_n-1 of each compression spring (DF_n-1, DF_n-1′) is greater than the spring constant D₀ of the snap springs (SF_n, SF_n′) and the respective spring constant D_n-1 of the compression springs (DF_n-1, DF_n-1′) is in each instance greater than the spring constant D_n-2 of an adjacent compression spring (DF_n-2, DF_n-2′), which is disposed closer to the pivot axis (16) and is in each instance smaller than the spring constant D_n of an adjacent compression spring (DF_n, DF_n′), disposed further from the pivot axis (16), and in that in the starting position (P_o) the striker tips (S_n, S_n′) lie in an alignment plane (15) forming a maximum tilt angle (α) with the positioning plane, and after tilting of the actuating rocker (5) through the maximum tilt angle (α) all striker tips (S_n, S_n′) lie in the positioning plane.
2. Electrical key switch according to Claim 1, characterized in that the switch strikers (8, 9), which can be brought into the switching positions (P_n), of the first rocker arm (A) and the switch strikers (8, 9) which can be brought into the switching positions (P_n′) of the other rocker arm (A′) as well as the snap springs (SF_n, SF_n′) corresponding thereto are disposed in each instance axially symmetrically with respect to the pivot axis (16).
3. Electrical key switch according to Claim 1 or 2, characterized in that the snap springs (SF_n, SF_n′) are positioned by means of a positioning plate (4) on a printed circuit board (3).
4. Electrical key switch according to one of the preceding claims, characterized in that the sliding piece (7) is held and guided by means of engagement lugs (11) in the stroke space (10) of the sleeve (6).
5. Electrical key switch according to one of the preceding claims, characterized in that each rocker arm (A, A′) is designed with a wide surface.
6. Electrical key switch according to one of the preceding claims, characterized in that the snap springs (SF_n, SF_n′) are designed in the shape of spherical segments, three spherical segment portions guided rotationally symmetrically about the respective spherical segment crown (K_n, K_n′) and parallel to the spherical segment height being realized, and in that the snap springs (SF_n, SF_n′) are alternately gap-set in a space-saving fashion.
7. Electrical key switch according to one of the preceding claims, characterized in that it exhibits preferably precisely one first actuating striker (8) and precisely one second actuating striker (9) on each side of the actuating rocker (5).

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