Push button switch assembly

Push button switch assembly, in particular for insertion in a control panel of a domestic appliance, the push button switch assembly comprising at least one push button and a frame for receiving the at least one push button, wherein the push button has a push button cap, whose top wall or rather upper side is to be manipulated by a user, and an actuating element, in particular an actuating pin, for actuating a switch, especially a micro switch, of a circuit board arranged underneath the push button switch assembly upon actuation of the push button cap, wherein the push button cap is provided with spring legs resting on a frame bottom and counteracting the actuation of the push button cap, characterized in that at least two spring legs are provided, which are formed in a rotationally symmetric or in an axially symmetric arrangement at the push button cap.

The present invention relates to a push button switch assembly, in particular for insertion in a control panel of a domestic appliance, the push button assembly comprising at least one push button and a frame for receiving the at least one push button, wherein the push button has a push button cap, whose top wall or rather upper side is to be manipulated by a user, and an actuating element, in particular an actuating pin, for actuating a switch, especially a micro switch, of a circuit board arranged underneath the push button switch assembly upon actuation of the push button cap, wherein the push button cap is provided with spring legs resting on a frame bottom and counteracting the actuation of the push button cap.

Control panels of domestic appliances normally comprise a plurality of different operational controls for setting specific functions, for example push buttons or the like. Such push buttons may be arranged separately or side by side in order to define a push button panel. It is important, that the functional units are spatially adjusted to one another such that the push buttons arranged at the operating panel and the electric switching elements positioned underneath the control panel cooperate without any problems.

One known push button switch assembly is described in EP-A-1 482527. This push button switch assembly comprises several push buttons each having a push button cap and an actuating element in the form of an actuating pin, whereas the push button cap and the actuating element are formed as a one-piece component. The actuating elements extend from the assigned push button cap towards an electric switching element of the domestic appliance in order to effect a switching operation upon actuation of the push button cap. The push buttons are received and guided by a frame, which in turn is fixed to the control panel of the appliance. In order to move the push buttons back in their initial position after actuation, each actuation element cooperates with a silicone mat with carbon pill, which generates the necessary restoring force.

One drawback of the one-piece design of the push buttons of the push button switch assembly according to EP-A-1482527 is that sink marks are created on the visual surface of the push button caps during their manufacture. This is not desirable for optical reasons. Moreover, the silicone mat cannot compensate deviations in position of the push buttons due to manufacturing tolerances of the control panel and/or the push buttons and/or the frame and/or the switching. This may lead in worst case to disturbances of the appearance as well as to rattle noises.

In order to overcome the mentioned drawbacks, EP-A-1467390 proposes to provide the push button cap and the actuating element of each push button as separate components, wherein each push button cap is formed with two spring legs, which rest on the frame and create the restoring force necessary to move the push button cap back in its initial poison after actuation.

However, the two-part design of the push button as proposed in EP-A-1467390 leads to an undefined and alterable position of the actuating element between the frame and the electric switching element. Thus, an accurate and stable position of the actuating element relative to the tactile switches on the electronic board cannot be ensured. Moreover the undefined position of the actuating element can lead to an unwanted rattle. In addition, due to the asymmetric design of its two spring legs a rocking over the diagonal of the top wall of the push button cap is possible, what is not desirable in regard to haptics.

Starting from this prior art it is an object of the present invention to provide a push button assembly of the above-mentioned kind, which overcomes or reduces the described drawbacks.

This object is solved by providing a push button switch assembly, in particular for insertion in a control panel of a domestic appliance, the push button switch assembly comprising at least one push button and a frame for receiving the at least one push button, wherein the push button has a push button cap, whose top wall or rather upper side is to be manipulated by a user, and an actuating element, in particular an actuating pin, for actuating a switch, especially a micro switch, of a circuit board arranged underneath the push button switch assembly upon actuation of the push button cap, wherein the push button cap is provided with spring legs resting on a frame bottom and counteracting the actuation of the push button cap, wherein at least two spring legs are provided, which are formed in a point symmetric or in an axially symmetric arrangement at the push button cap. Thanks to this symmetric push button cap design the push button cap of the at least one push button is held in a defined position. This promotes the appearance of the push button switch assembly, in particular if the push button assembly comprises more than one push button, because the push button caps can be properly aligned with each other. Moreover, the symmetric push button design leads to a very good position stability of the push button cap, so that a rocking over the diagonal of the top wall of the push button cap is no longer possible, what is desirable in regard to haptics.

The push button cap and the actuating element are formed as a one-piece component. Thus, no or at least nearly no rattle can occur due to an undefined position of the actuating element. Moreover, the total number of components is reduced, what is advantageous in regard to the manufacture and assembly of the push button switch assembly. Furthermore, the loading of the circuit board generated by the actuating element is adjustable by means of the spring legs of the push button cap. Thus, no additional load adjusting means need to be provided. Preferably, the push button cap, the actuating element and the spring legs are formed as a one-piece component. By this, the above named aspects can be improved further.

The actuating element is advantageously formed at a position spaced apart from the top wall of the push button cap in order to prevent the formation of sink marks on the visible surface of the push button during its manufacture. Preferably, a clearance is formed between the beginning of the actuating element and the top wall of the push button cap.

The forces of the spring legs, that counteract the actuation of the push button cap, can be adjusted by material and/or geometry variation. Thus, the actuating and return forces can be set, e.g. in order to prevent an overloading of the circuit board.

Ribs are provided at the inside of the frame and/or at the push button cap for fixation or positioning of the push button cap. By means of such ribs a fine-tuning in regard to fixation and orientation of the push buttons is possible.

The ribs at the frame and the ribs at the push button cap are preferably matched with each other.

According to one aspect of the present invention, at least a second push button is provided and ribs are asymmetrically arranged at opposite sidewalls of the push button caps.

The asymmetrical arrangement of the ribs is preferably chosen in such a manner, that the push button caps can also be assembled in a state rotated by 180°. This simplifies the assembly.

Preferably, at least two push buttons are arranged in a length-wise row, wherein push button positioning means, which correspond to the ribs formed at the push buttons, are provided at the short sides at the frame.

At each of the length-wise sidewalls of the frame fixing means can be formed for a proper assembly of the push button switch assembly in an opening of a control panel of a domestic appliance.

Preferably, four or at least four spring legs are provided, which are formed in a point symmetric or in an axially symmetric arrangement at the push button cap. This enables or improves a uniform guidance of the push button cap.

Preferably, two spring legs are formed at the bottom wall on each of the opposite sides of the actuation element and/or the spring legs are arranged as at least one pair, wherein preferably the spring legs of a or each pair extend downwards in opposed directions, respectively, such that the or each pair of spring legs describes an inverted V-shape. This can ease the manufacturing of the legs, as no separate parts are necessary.

FIGS. 1 to 20show a push button switch assembly10according to an embodiment of the present invention and different views of its components. The push button switch assembly10is to be inserted in a control panel (not shown) of a domestic appliance, in particular in a control panel made of glass, metal, plastic or another material having similar characteristics. As main components the push button switch assembly10comprises five identically formed push buttons12and a frame14for receiving the five push buttons12and for guiding their movements upon actuation.

One push button12is shown in detail throughoutFIGS. 1 to 7. The push button12is formed as a one-piece component and comprises a push button cap16and an actuating element18. The push button cap16essentially has the form of a square tube and has a top wall20, a bottom wall22and two opposed sidewalls24and26. The top wall20, whose upper side is to be manipulated by a user, is dome-shaped. Each sidewall24and26is formed with a slit28, which extends between the bottom wall22and the top wall20and is open towards the bottom wall22. One of the two face surfaces of each sidewall24and26is provided with a rib30in such a manner, that the two ribs are arranged diagonally opposed. The actuation element18is connected to the center portion of the planar bottom wall22. Two spring legs32and34are formed at the bottom wall22on each of the opposite sides of the actuation element18underneath the slits28. The spring legs32and34extend downwards in opposed directions, respectively, such that each pair of spring legs32and34describes an inverted V-shape. At the other two opposite sides of the actuation element18, the bottom wall22is formed with an one-sided open clamping recess36, respectively. The actuating element18has a cruciform cross section and extends from the bottom wall22of the push button cap16at right angle.

The frame14, which is shown in detail throughoutFIGS. 8 to 14, has a longitudinal shape and is designed to receive the five push buttons12. The frame14comprises a frame bottom wall38as well as four frame sidewalls40,42,44and46, which are provided at their upper ends with a circumferential edge48, that rests—when received in an opening of a control panel—on the outer side of the control panel as shown inFIG. 20. At the lower end of the frame sidewalls40,42,44and46fixing means50in the form of snap arms are provided, which snap behind the bottom face of the control panel during the assembly of the frame14. The distance between the circumferential edge48and the fixing means50is chosen in such a manner that a clamping force is created between the frame14and the control panel in the inserted state of the frame14. In order to receive the actuating elements18of the five push buttons12, five openings52are formed in the frame bottom wall38in equal intervals and in alignment with each other. At each of two opposing sides of each opening52an upwardly extending snap arm54is provided, whereas the two snap arms54of each opening52engage the clamping recesses36of a push button cap16of an assigned push button12in the assembled state of the push button switch assembly10. Accordingly, the frame14comprises a total of ten aligned snap arms54. At the other two opposing sides of each opening52, inner ribs56are formed, which are matched with the slits28formed in the sidewalls24and26of each push button cap16and received therein in the assembled state of the push button switch assembly10. In order to achieve a good fit of the frame14within an opening of a control panel of a domestic appliance, the longish frame sidewalls40and44are provided with outer ribs58, which extend upwards from the frame bottom wall38.

During the assembly of the push button switch assembly10, the frame14is pushed into an opening60of a control panel62from above at first, such that the fixing means50of the frame14snap behind the bottom face of the control panel62and the circumferential edge48rests on the top face of the control panel62. In this state, a close fit between the frame14and the control panel62is ensured by means of the outer ribs58of the frame14. Thereafter, the actuating elements18of the push buttons12are inserted in the assigned openings52of the frame14. During this insertion movement, the snap arms54upwardly protruding from the frame bottom wall38are received in the clamping recesses36of the assigned push buttons12, until the push button caps12are snap-fittingly held at the frame14. In this state, the spring legs32,34of the push buttons12rest on the frame bottom wall38with little pretension, such that the upper sides of all five push buttons12are arranged on the same level. Moreover, the inner ribs56of the frame14are received in the slits28of the push button caps16. Furthermore, the single push buttons12are oriented with respect to each other by means of the ribs30provided on the face surfaces of the push button caps16. As shown inFIG. 20, the actuating element18of each push button12is also received and guided in a guiding structure64of a housing66, which is arranged between the control panel62and a circuit board68comprising the micro switches70to be switched by means of the actuating elements18of the push buttons12.

In order to effect a switching operation of a micro switch70, the assigned push button12needs to be pressed down against the spring forces of the spring legs32and34, until the free end of the actuation element comes into contact with the micro switch70. Upon releasing the push button12, it is automatically moved back upwardly in its initial position by means of the spring legs32and34.

Due to the fact, that the push button cap16and the actuating element17of each push button12are formed as a one-piece component, the total number of components is limited. This is very positive in terms of the manufacture, the assembly and the costs of the push button switch assembly10. Since the actuating element18is formed at a position spaced apart from top wall20of the push button cap16, sink marks at the top wall20will not be generated during the manufacture of the push button12.

Thanks to the symmetrical arrangement of the spring legs32and34, a rocking over the diagonal of the top wall20of the push button cap16is prevented during the manipulation of the push button12, what is positive in terms of haptics. Due to the restoring force of the spring legs32and34, the ribs30formed at the face side of each push button cap16and the inner ribs56of the frame and the mating slits28of each push button cap16, a very defined and accurate positioning of the push buttons12within the frame12and with respect to the micro switches70of the circuit board68is achieved. Also, the push buttons12are aligned to each another very well.

Since the ribs30of each push button12are diagonally displaced, the push buttons can be assembled in either position, i.e. turned by 180°. Push button positioning means, which correspond to the ribs30formed at the push buttons12, can be provided at the short sides at the frame14, even though not shown.

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