Electric Push-Button Switch

Abstract

An electric pushbutton switch includes a guide housing, a switching element having a haptic element that produces a pressure point and a return spring that generates a restoring force, an actuator for actuating the switching element, and a resilient tolerance compensation element arranged between the guide housing and the actuator. The switching element being stationary relative to the guide housing and the actuator being movable relative to the guide housing. The actuator actuates the switching element against the restoring force when the actuator is moved relative to the guide housing in an actuating direction of the actuator towards the switching element. The resilient tolerance compensation element is arranged between the guide housing and the actuator. The resilient compensation element has a spring force directed in the actuating direction of the actuator towards the switching element and opposite the restoring force of the return spring of the switching element.

Claims

1. An electric pushbutton switch comprising: a guide housing; a switching element having a haptic element that produces a pressure point and a return spring that generates a restoring force, the switching element being stationary relative to the guide housing; an actuator for actuating the switching element, the actuator being movable relative to the guide housing, wherein the actuator actuates the switching element against the restoring force when the actuator is moved relative to the guide housing in an actuating direction of the actuator towards the switching element; and at least one resilient tolerance compensation element arranged between the guide housing and the actuator, each resilient compensation element having a spring force directed in the actuating direction of the actuator towards the switching element and opposite the restoring force of the return spring of the switching element.

2. The electric pushbutton switch of claim 1 wherein: the switching element is a microswitch.

3. The electric pushbutton switch of claim 1 wherein: the actuator includes a button.

4. The electric pushbutton switch of claim 1 further comprising: a printed circuit board; and wherein the switching element is arranged on the printed circuit board.

5. The electric pushbutton switch of claim 1 wherein: the actuator includes a support bar and a button supported thereon; and each resilient tolerance compensation element is arranged between the guide housing and respective portion of the support bar to be arranged between the guide housing and the actuator.

6. The electric pushbutton switch of claim 1 wherein: the actuator includes a button and first and second support bars in a one-piece design; the at least one resilient tolerance compensation element includes first and second resilient tolerance compensation elements; and the first resilient tolerance compensation element is arranged between the guide housing and the first support bar to be arranged between the guide housing and the actuator and the second resilient tolerance compensation element is arranged between the guide housing and the second support bar to be arranged between the guide housing and the actuator.

7. The electric pushbutton switch of claim 1 wherein: the switching element further includes a switch tappet; and wherein an underside of the actuator rests against the switch tappet.

8. The electric pushbutton switch of claim 1 wherein: the at least one resilient tolerance compensation element includes at least one coil spring.

9. The electric pushbutton switch of claim 1 wherein: the at least one resilient tolerance compensation element includes two resilient tolerance compensation elements, and each resilient tolerance compensation element is a coil spring.

10. The electric pushbutton switch of claim 9 wherein: the two coil springs are situated in parallel to one another.

11. The electric pushbutton switch of claim 1 wherein: in an unactuated state of the actuator, the spring force of each resilient tolerance compensation element is in equilibrium with the restoring force of the return spring of the switching element whereby actuation of the actuator begins and ends with being free of force.

12. The electric pushbutton switch of claim 1 wherein: the haptic element is a snap dome.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] An exemplary embodiment of an electric pushbutton switch in accordance with the present invention (“the inventive pushbutton switch”) is illustrated and explained in greater detail below with reference to the drawings, which include the following:

[0013] FIG. 1 illustrates a perspective view of the inventive pushbutton switch;

[0014] FIG. 2 illustrates a sectional view of the inventive pushbutton switch;

[0015] FIG. 3 illustrates an exploded view of the inventive pushbutton switch;

[0016] FIG. 4 illustrates a conventional pushbutton switch;

[0017] FIG. 5 illustrates a sectional view of the conventional pushbutton switch;

[0018] FIG. 6 illustrates a first force-displacement curve of the conventional pushbutton switch resulting when the conventional pushbutton switch has excessive play;

[0019] FIG. 7 illustrates a second force-displacement curve of the conventional pushbutton switch resulting when the conventional pushbutton switch has excessive pretension;

[0020] FIG. 8 illustrates an ideal force-displacement curve of the conventional pushbutton switch resulting when the conventional pushbutton switch has no excessive play and no excessive pretension;

[0021] FIG. 9 illustrates a first force-displacement curve of the inventive pushbutton switch resulting when the inventive pushbutton switch has manufacturing-related variations in dimensions of the switch components which would result in the conventional pushbutton switch having excessive play;

[0022] FIG. 10 illustrates a second force-displacement curve of the inventive pushbutton switch resulting when the inventive pushbutton switch has manufacturing-related variations in dimensions of the switch components which would result in the conventional pushbutton switch having excessive pretension;

[0023] FIG. 11 illustrates a third force-displacement curve of the inventive pushbutton switch resulting when the inventive pushbutton switch has manufacturing-related variations in dimensions of the switch components which would result in the conventional pushbutton switch having no excessive play and no excessive pretension;

[0024] FIG. 12 illustrates a schematic view of the conventional pushbutton switch; and

[0025] FIG. 13 illustrates a schematic view of the inventive pushbutton switch.

DETAILED DESCRIPTION

[0026] Detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the present invention that may be embodied in various and alternative forms. The Figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.

[0027] Referring initially to FIGS. 4 and 5, a conventional electric pushbutton switch is shown. The conventional pushbutton switch includes a guide housing 10, an actuation element (or actuator) 20, and a switching element (or switch) 30. Actuating element 20 and switching element 30 are arranged within guide housing 10.

[0028] Actuating element 20 is movable or displaceable relative to guide housing 10. Switching element 30 is stationary relative to guide housing 10. Actuating element 20 is configured to actuate switching element 30. Particularly, actuation element 20 being moved or displaced relative to guide housing 10 towards switching element 30 causes the actuation element to actuate the switching element.

[0029] Guide housing 10 is designed as an approximately cuboidal hollow body. Guide housing 10 includes an upper housing part 12. Upper housing part 12 is open on one side.

[0030] The conventional pushbutton switch further includes a printed circuit board (PCB) 16 and a base plate 18. Switching element 30 is arranged on PCB 16. PCB 16 is arranged on base plate 18. Base plate 18 closes off the open side of upper housing part 12.

[0031] Actuating element 20 includes a button 22. Button 22 protrudes into a panel recess 14 of upper housing part 12. Actuating element 20 further includes, in a lateral projection, two support bars 22 in a one-piece design. As shown in FIG. 5, in the non-actuated state of the conventional pushbutton switch, support bars 24 rest against the bottom side of upper housing part 12. In this position, support bars 24 serve as switching travel end stops.

[0032] Switching element 30 may be designed as a microswitch and includes a return spring (or restoring spring) 32, a switch tappet (or switch plunger) 34, and a haptic element 36. Haptic element 36 is, for example, a snap dome or a snap disk.

[0033] The underside of actuation element 20 rests against switch tappet 34 of switching element 30. Actuating element 20 is held in its initial position in the non-actuated state of the conventional pushbutton switch by the force of return spring 32 of switching element 30.

[0034] When button 22 of actuation element 20 is pressed, return spring 32 is initially compressed via switch tappet 34 and with its elastic force (or spring force) acts on snap dome 36. When a sufficiently large spring force is applied to snap dome 36, snap dome 36 snaps out of its stable initial position into a metastable position in which snap dome 36 closes or opens switching contacts on PCB 16.

[0035] When button 22 is released, return spring 32 relaxes. As a result, snap dome 36 snaps back into its initial position and actuation element 20 is returned to its initial position by the restoring force of return spring 32.

[0036] However, in this relatively simple design of the conventional pushbutton switch, component tolerances must be considered which make it difficult to produce optimal short-stroke haptics. This applies all the more when an arrangement of multiple pushbutton switches is provided, for which the aim is to have the most uniform switching haptics possible.

[0037] If the dimensions of the components of the conventional pushbutton switch, due to manufacturing-related dimensional deviations, are such that spaces form either (i) between upper housing part 12 of guide housing 10 and support bars 24 of actuation element 20 or (ii) between actuation element 20 and switch tappet 34 of switching element 30, then this results in a loose, “shaky” seat of actuation element 20 in guide housing 10. Consequently, this leads to a “loose” or “soft” switching feel (e.g., rattling) during actuation of switching element 30. As such, in this case, the conventional pushbutton switch has excessive play.

[0038] On the other hand, if the manufacturing-related dimensions of the components result in return spring 32 of switching element 30 being significantly pretensioned before switching element 30 is actuated, then switch tappet 34 only travels a relatively short actuating path until snap dome 36 snaps. Consequently, due to switching hysteresis, snap dome 36 subsequently remains in the actuated position. As such, in this case, the conventional pushbutton switch is excessively pretensioned.

[0039] This is illustrated in FIGS. 6, 7, and 8 which illustrate respective force-displacement curves of the conventional pushbutton switch. In each of FIGS. 6, 7, and 8, for the above-mentioned cases, the actuating force “F” of switching element 30 is plotted with respect to the actuating travel (or actuation path) “S” of actuation element 20 by way of example.

[0040] FIG. 8 qualitatively shows an ideal force-displacement curve of the conventional pushbutton switch resulting when the conventional pushbutton switch has no excessive play and no excessive pretension. The upper portion of the ideal force-displacement curve shows the increase in the actuating force F of switching element 20 over the actuating travel S of actuation element 30 due to compression of return spring 32. The drop in the middle portion of the ideal force-displacement curve at the changeover or switching point P (“peak force”) shows the snapping of snap dome 36. The end point of the ideal force-displacement curve is reached at the end stop E.

[0041] The dashed-line portion of the ideal force-displacement curve shows when actuation element 20 is returning to its initial position after button 22 is released. It is apparent that for the actuating travel S=0, the ideal force-displacement curve begins and ends with an actuating force F>0.

[0042] FIG. 6 illustrates a first force-displacement curve of the conventional pushbutton switch resulting when the conventional pushbutton switch has excessive play. The conventional pushbutton switch has excessive play when actuation element 20 has excessive play. The first force-displacement curve shows that the increase in actuating force F of actuation element 20 starts only for an actuating travel S>0 of switching element 30. With no actuating force (i.e., actuating force F=0), the actuating travel S is not clearly defined, resulting in the above-mentioned “loose” or “shaky” design (i.e., rattling).

[0043] FIG. 7 illustrates a second force-displacement curve of the conventional pushbutton switch resulting when the conventional pushbutton switch has excessive pretension. The conventional pushbutton switch has excessive pretension when return spring 32 of switching element 30 is significantly pretensioned before switching element 30 is actuated. Accordingly, actuation element 20 is excessively pretensioned by the elastic or spring force of return spring 32. The second force-displacement curve shows that after a short distance of actuating travel S of switching element 30, a one-time response of snap dome 36 occurs. Due to the switching hysteresis, snap dome 36 is no longer able to return to its initial position.

[0044] Pushbutton switches having these types of large dimensional deviations may be unusable and are typically sorted out during manufacture. However, this leads to the conclusion that, for reliable functioning of the pushbutton switch, the actuation stroke cannot be smaller than the allowed tolerance travel paths, which may add up in a disadvantageous manner. This makes it difficult to design a cost-effective pushbutton switch having a relatively short actuation stroke.

[0045] An electric pushbutton switch in accordance with embodiments of the present invention solves this problem in a simple manner.

[0046] Referring now to FIGS. 1, 2, and 3, with continual reference to FIGS. 4 and 5, an exemplary embodiment of an electric pushbutton switch in accordance with the present invention (“the inventive pushbutton switch”) is shown. FIG. 1 illustrates a perspective view of the inventive pushbutton switch; FIG. 2 illustrates a sectional view of the inventive pushbutton switch; and FIG. 3 illustrates an exploded view of the inventive pushbutton switch.

[0047] The inventive pushbutton switch solves the noted problem of the conventional pushbutton switch in a simple manner. As the design of the inventive pushbutton switch in many details is the same as the conventional pushbutton switch, a repeated description of the already explained components and their mode of operation may be dispensed with. In addition, for better comparability, identical or functionally equivalent parts of the inventive pushbutton switch have been denoted by the same reference numerals previously used for the conventional pushbutton switch. The primary intent of the following discussion is to describe the differences in design and mode of operation of the inventive pushbutton.

[0048] The inventive pushbutton switch, as shown in FIGS. 1, 2, and 3, differs from the conventional pushbutton switch shown in FIGS. 4 and 5, in that the inventive pushbutton switch includes at least one resilient tolerance compensation element 40 arranged between guide housing 10 and actuation element 20. The direction of action of the elastic or spring force of the at least one resilient tolerance compensation element 40 is oriented in the actuating direction of actuation element 20 and opposite to the restoring force of return spring 32 of switching element 30.

[0049] In this exemplary embodiment, the inventive pushbutton switch includes two resilient tolerance compensation elements 40 and each resilient tolerance compensation element 40 is a coil spring (or a helical spring).

[0050] As shown in FIGS. 2 and 3, coil springs 40 are situated in parallel to one another and are arranged between (i) the inner side of upper housing part 12 of guide housing 10 and (ii) respective support bars 24 of actuation element 20. In each case, coil springs 40 exert an elastic or spring force in the direction toward switching element 30.

[0051] When actuation element 20 is not actuated, the spring forces of coil springs 40 are in equilibrium with the elastic or spring force of return spring 32 of switching element 30. As a result, pressing on button 22 of actuation element 20 always begins free of force and the actuating force F of actuation element 20 subsequently increases approximately linearly. In this way, the same haptics are always achieved, at least from a qualitative standpoint.

[0052] Coil springs 40 also provide, in the actuating direction, play-free support of actuation element 20 within guide housing 10 and compensate for path or travel tolerances of actuation element 20 within guide housing 10.

[0053] The design of the exemplary embodiment of the inventive pushbutton switch shown in FIGS. 1, 2, and 3 is of course only an example to illustrate principles of the concept according to the present invention. Such design may be modified in many ways without departing from the principles of the inventive concept. It is a characteristic of the inventive concept that the at least one resilient tolerance compensation element 40 acts on actuation element 20 before the upper end stop of actuation element 20.

[0054] In any case, the force of the at least one resilient tolerance compensation element 40 acts in the actuating direction of button 22 of actuation element 20 and opposite the direction of the restoring force due to return spring 32 of switching element 30. One or multiple resilient tolerance compensation elements 40 may be provided, it being possible to use either tension springs or compression springs.

[0055] Referring now to FIGS. 9, 10, and 11, with continual reference to FIGS. 1, 2, and 3, first, second, and third force-displacement curves of the inventive pushbutton switch are shown. The first force-displacement curve in FIG. 9 results when the inventive pushbutton switch has manufacturing-related variations in dimensions of the switch components which would result in the conventional pushbutton switch having excessive play, such as described with respect to FIG. 6. The second force-displacement curve in FIG. 10 results when the inventive pushbutton switch has manufacturing-related variations in dimensions of the switch components which would result in the conventional pushbutton switch having excessive pretension, such as described with respect to FIG. 7. The third force-displacement curve in FIG. 11 results when the inventive pushbutton switch has manufacturing-related variations in dimensions of the switch components which would result in the conventional pushbutton switch having no excessive play and no excessive pretension, such as described with respect to FIG. 8. Accordingly, the first, second, and third force-displacement curves are different force-displacement curves for pushbutton switches having manufacturing-related variations in dimensions of the switch components, which for a pushbutton switch having a conventional design would result in shaking (FIG. 9), jamming (FIG. 10), or ideal normal functioning (FIG. 11).

[0056] Due to the design of the inventive pushbutton switch, the first, second, and third force-displacement curves of FIGS. 9, 10, and 11, respectively, have the same pattern from a qualitative standpoint. It is apparent that each of these force-displacement curves begins free of force when button 22 of actuation element 20 is actuated; i.e., they begin with zero actuating force of switching element 30 (i.e., actuating force F=0 at the beginning of the actuation), and end once again when button 22 is released with zero actuating force of switching element 30 (i.e., actuation force F=0 at the end of the actuation). In these force-displacement curves, only the particular position of the changeover point P of snap dome 36 varies slightly with regard to the actuating travel S of actuation element 20.

[0057] The beginning position and end position (actuating travel S=0) of button 22 are determined by the equilibrium position of return spring 32 of switching element 30 and of the tolerance compensation elements 40. These positions may differ slightly due to spring tolerances for various pushbutton switches, but without adversely affecting the functioning.

[0058] The reason for the different behavior of the conventional pushbutton switch compared to the inventive pushbutton switch is explained in greater detail with reference to FIGS. 12 and 13. FIG. 12 illustrates a schematic view of the conventional pushbutton switch and FIG. 13 illustrates a schematic illustration of the inventive pushbutton switch.

[0059] The position of the changeover point P of the conventional pushbutton switch illustrated in FIG. 12 depends on various dimensions of the switch components that are more or less well maintained for manufacturing reasons.

[0060] These dimensions are (i) the height A of switching tappet 34 of switching element 30 above PCB 16, (ii) the size B of actuation element 20 in the switching direction, and (iii) the height C of guide housing 10 above PCB 16. The dimensions A, B, and C of the conventional pushbutton switch together determine the switching travel tolerance S.sub.tol_1 of the conventional pushbutton switch. The position of actuation element 20 relative to switching element 30 is thus significantly influenced by the dimensional deviations of various switch components.

[0061] In contrast, for the inventive pushbutton switch illustrated in FIG. 13, the starting position of actuation element 20 is determined essentially by the equilibrium position of two spring systems. Namely, return spring 32 of switching element 30 on the one hand, and tolerance compensation elements 40 (coil springs 40) on the other hand. Tolerance compensation elements 40 to a significant extent compensate for the dimensional deviations, likewise present here, of the switch components. A switching travel tolerance S.sub.tol_2 of the inventive pushbutton switch may thus be achieved which is significantly smaller, and often only a fraction of the switching travel tolerance S.sub.tol_1 of the conventional pushbutton switch.

[0062] Thus, due to the arrangement of the inventive pushbutton switch, the influence of the tolerances of the individual components on the switching path is reduced.

[0063] The inventive pushbutton switch is advantageous in that no calibration is required, and as a result it is not necessary to provide external access for adjustment systems. The inventive pushbutton switch is also advantageous that due to the tolerance compensation elements, soft end stops are provided which reduce the noise when the end stops are reached.

[0064] A further advantage of the inventive pushbutton switch its design compensates for influences of temperature and moisture.

TABLE-US-00001 Reference numerals and symbols 10 guide housing 12 upper housing part 14 panel recess 16 printed circuit board 18 base plate 20 actuation element (actuator) 22 button 24 support bars 30 switching element (switch) (e.g., microswitch) 32 return spring (restoring spring) 34 switch tappet (switch plunger) 36 haptic element (e.g., snap dome or snap disk) 40 resilient tolerance compensation element(s) (e.g., coil spring(s)) A, B, C dimensions of switch components E end stop F actuating force P changeover or switching point (peak force) S actuating travel (actuation path) S.sub.tol_1, S.sub.tol_2 switching travel tolerances

[0065] While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the present invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the present invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the present invention.