Rotary switch for a glass ceramic cooktop

The invention relates to a rotary switch for a glass ceramic cooktop, which rotary switch includes a rotary knob projecting above the glass ceramic plate. The rotary knob interacting with a switch unit disposed on an underside of the glass ceramic plate. The rotary knob interacts with the switch unit via a knob axis and the switch unit includes a signal generator for generating a signal on the based on an angular position of the knob axis.

BACKGROUND OF THE INVENTION

The invention relates to a rotary switch for a glass ceramic cooktop.

In household appliances, control elements which may be embodied as rotary switches, sliding switches or as electronic switches, touch-sensitive (contact) switches for example, are well-known for the purpose of activating or setting functions. The use of rotary switches is preferred owing to their good operability. In the case of household appliances which constitute a glass ceramic cooktop, which is also referred to as a glass ceramic stovetop, the use of rotary switches has, however, been possible only to a limited extent hitherto.

In DE 20 2005 019 978 U1, for example, a control device is described which can represent a rotary switch, for example. In this case, in one embodiment, one part of the rotary switch, which represents a rotary control, is provided on the top of the glass ceramic plate and interacts contactlessly with sensor elements which are disposed on the underside of the glass ceramic plate such that control signals are transmitted to a controller that is disposed underneath the plate. In a further embodiment, the rotary control disposed on the glass ceramic plate is connected via a control device axis or, as the case may be, rotational axis to a control device which represents an energy controller. In this arrangement the rotational axis projects through an opening in the plate. Also provided on the control device, in particular on the rotary control, are contact sensors via which further functions of the appliance actuated by means of the control device can be activated. For example, the contact sensors can be used for switching a hotplate on and off. In the embodiment in which the rotary control is connected to the control device via a rotational axis, the signals of the contact sensors are transmitted along the rotational axis.

A disadvantage of this known control device is that in the case of the embodiment in which no opening is provided, the signal for controlling the hotplate can only be transmitted by magnetic or optical means. As a result, a relatively complex and expensive design is required and the detection function can easily be affected by accumulated dirt or other external influences. Conversely, in the case of the embodiment in which the rotary position of the rotary knob is transmitted via a rotational axis, i.e. mechanically, the rotary position is available solely as an input for the control device. In the last-mentioned embodiment, therefore, the rotary position cannot be used for other purposes.

BRIEF SUMMARY OF THE INVENTION

The object of the present invention is therefore to provide a rotary switch for a glass ceramic cooktop which has a simple design and can be used in a variety of ways.

This object is achieved according to the invention by means of a rotary switch for a glass ceramic cooktop, said rotary switch comprising a rotary knob which projects beyond the glass ceramic plate and interacts with a switch unit that is disposed on the underside of the glass ceramic plate. The rotary switch is characterized in that the rotary knob interacts with the switch unit via a knob axis and the switch unit comprises at least one signal generation unit for generating an electrically processible information signal on the basis of the angular position of the knob axis.

As a result of the interaction of the rotary knob with the switch unit disposed on the underside of the glass ceramic plate, the rotary movement of the rotary knob is transmitted via mechanical means to the switch unit for further processing and is consequently less sensitive to accumulations of dirt and other environmental conditions such as high temperatures, for example. Since a signal generation unit is also provided on the underside of the glass ceramic plate, the current angular position, i.e. the degree of rotation of the rotary knob, can be used for control, regulating and other functions. Accordingly, a plurality of functions can be executed by way of the degree of rotation of the rotary knob. Moreover, owing to the arrangement of the signal generation unit underneath the glass ceramic plate, the generated signals can be easily forwarded, via a board for example, and also used at other points of the cooktop or stovetop.

According to a preferred embodiment, the switch unit comprises at least one switch component, in particular a power switch, which is actuated by means of the signal generation unit. The switch component can be a mechanical switch or an electrical switch. As the power switch is actuated by the signal generation unit it is possible to make control of the power output of the cooktop dependent on the angular position. As a result, for example, a separate, central power voltage circuit by means of which the operation of the hotplate can be activated, in particular a main switch relay on the electronics board of the glass ceramic cooktop, which is necessary in the case of traditional appliances, can be dispensed with. Particularly preferably the power switch is connected by means of mechanical or electrical contacts on the signal generation unit. This means that the power switch is actuated independently of the signal generated by the signal generation unit, thereby increasing the operational safety of the glass ceramic cooktop.

According to the invention, the signal generation unit and the power switch are preferably disposed adjacent to each other. In particular, the signal generation unit is arranged around the rotational axis of the rotary knob and the power switch is radially adjacent to the signal generation unit. Owing to this arrangement of the signal generation unit and the switch, the overall installation height of the switch unit is minimized. As a result of this, the installation height corresponds to the height that is available in a glass ceramic stovetop, which means that no structural modifications to the stovetop need to be provided in order to be able to use the rotary switch according to the invention. Furthermore, the rotary switch can be arranged at different positions of the stovetop or cooktop, for example in immediate proximity to the hotplate requiring to be controlled in each case.

According to one embodiment, the signal generation unit generates a signal voltage as a function of the angular position of the rotary knob. Since the signal is present as a signal voltage, it is immediately available for further processing. Thus, the signal voltage can be routed for example to a display element or to a control element and be used there directly as an input variable.

The signal generation unit preferably has a rotary disk. A rotary disk, within the meaning of the invention, designates a disk which, when the knob axis or, as the case may be, rotary shaft is rotated, is rotated through the same angle. The rotary disk is preferably removably connected to the knob axis and has a greater outer diameter than the knob axis. Owing to the greater diameter, the top and/or underside of the rotary disk can on the one hand be made available for information transfer purposes. On the other hand, switching or actuation of a switch component that is radially spaced at a distance from the knob axis is possible by means of the rotary disk.

In order to generate a voltage signal, the rotary disk can be used for example with a comb for mechanically transmitting the angular position to a board of the switch unit. In this case the rotary disk represents a contact disk. In this embodiment the signal generation unit can be for example what is termed a Gray-code unit. However, other signal generation units are also possible. For example, the signal generation unit can represent an optical unit. In this case the angular position of the rotary knob can be determined via optical elements on the rotary disk. The advantage of using a rotary disk in the signal generation unit is that the circumference of the rotary disk can be used for other purposes, in particular for switching a radially adjacent switch in the switch unit. The switch component or switch can be switched mechanically or electrically.

In a preferred embodiment, at least one switch element for switching the power switch is provided on the circumference of the rotary disk. Said switch element can represent a switch contact or a mechanical resistance. A switch of the switch unit can easily be actuated by means of said switch elements. Furthermore, mechanical resistances can be used for example to generate a latching haptic which delivers feedback on the actuation of the rotary knob to the user. A precise definition of a torque of the rotary knob can also be realized via the switch elements.

The switch unit is preferably connected to a display unit. It is particularly preferred if the output of the signal generation unit serves as an input for the display unit. This enables the signal generated on the basis of the angular position of the rotary knob to be output on a display. This can be effected for example by means of a seven-segment display by means of which the selected power stage of the cooktop can be displayed. The switch unit and in particular the signal generation unit or a board of the switch unit are preferably connected via a signal cable to the display unit, in particular to a display board on which display elements are provided.

According to a preferred embodiment, the switch unit is connected to the rotary knob via a mounting unit. In this arrangement the mounting unit is removably connected to the switch unit. As a result of providing a separate mounting unit it can be ensured, on account of the decoupling, that the switch unit is relieved of mechanical stresses, such as impact shocks, for example. Furthermore, functions such as the press-and-turn function, which is also referred to as the “push to turn” function, can also be realized owing to the decoupling of the mounting unit from the switch unit. The mounting unit is preferably embodied in two parts and has a lower and an upper part. The two parts can be joined to each other by means of a screw connection and between them accommodate the edge of an aperture in the glass ceramic plate. On the lower part of the mounting unit a recess or a projection can be provided which can engage with a corresponding projection or a corresponding recess on the glass ceramic plate and so provide an anti-twist protection for the mounting unit. Alternatively or in addition the anti-twist protection can also be created for example by affixing on the underside of the glass ceramic plate a sheet-metal strip into which the lower part of the mounting unit engages with the upper part of the mounting unit on account of the connecting force or is pressed into the latter. In addition to its pure retaining function on the glass ceramic plate, the mounting device also serves to seal the inner region of the stovetop against the exterior.

The knob axis or, or as the case may be, rotary shaft of the rotary knob is preferably integrated in the mounting unit. Said rotational axis can engage in a corresponding cutout of the switch unit and in particular with the signal generation unit.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

FIG. 1shows a perspective view of the rotary switch1according to the invention in the uninstalled state. The rotary switch1consists of a mounting unit2and a switch unit3. To make the individual components more easily recognizable, a rotary knob that is to be mounted on the mounting unit2is not shown.

The mounting unit2consists, as can be seen fromFIG. 3, of an upper part21and a lower part22. The lower part22consists of a ring which has a hexagonal exterior and a thread on the inside. By this means the ring can be screwed to the upper part21. The upper part21, which is shown in more detail inFIG. 4, has a retaining ring211, as well as a threaded part212connecting to the retaining ring211. The glass ceramic plate5of the glass ceramic cooktop is accommodated between the retaining ring211and the lower part22. An aperture51is provided in the glass ceramic plate5for that purpose. The aperture51has a diameter corresponding to the outer diameter of the threaded part212. The threaded part212is a hollow cylinder on the outside of which a thread213is incorporated. Provided on the bottom edge of the threaded part212are latching hooks214which extend downward in the axial direction of the threaded part212and beyond the latter. A knob axis or rotary shaft215runs in the inside of the threaded part212. Said rotary shaft215projects over the top of the retaining ring211and beyond the bottom edge of the threaded part212. In the embodiment shown, the end of the rotary shaft215projecting over the bottom edge of the threaded part212corresponds to the end of the latching hooks214projecting over the bottom edge of the threaded part212.

The rotary shaft215is held in a bearing216(seeFIG. 3) in the upper part21of the mounting unit2. The rotary shaft215can be rotated in the upper part21via said bearing216and preferably also displaced axially. As can be seen fromFIG. 4, the rotary shaft215is in the shape of a rod, the latter having an essentially round cross-section. The round cross-section is flat on one side, however. This shape of the rotary shaft215enables a rotary force to be exerted by means of a rotary knob onto the rotary shaft215and in addition permits the rotary force to be easily transmitted to other components.

The switch unit3also provided in the rotary switch1has an essentially box shape. The top of the switch unit3is formed by a plate-shaped cover31(seeFIG. 5). Latching cutouts311for receiving the latching hooks214of the mounting unit2are provided in the cover31. Also provided in the cover31is an opening312to allow the rotary shaft215to pass through. The opening312has a circular cross-section with a diameter that is at least equivalent to the diameter of the rotary shaft215. Thus, the opening312permits the rotary shaft215to be rotated about its axis. Running downward from the edge of the cover31are arms313via which a board32is joined to the cover31. Also provided on the cover31are spacers314which hold the board32at a predetermined distance from the cover31. Disposed in the switch unit3between the cover31and the board32are a signal generation unit33and a switch34. The signal generation unit33and the switch34are arranged adjacent to each other on the board32. In this case the signal generation unit33is provided underneath the opening312for the passage of the rotary shaft215.

Since the end of the rotary shaft215projecting beyond the underside of the threaded part212corresponds to the projecting end of the latching hooks214, when the latching hooks214are introduced into the latching cutouts311, the rotary shaft215does not protrude or protrudes only slightly into the opening312of the cover31and into the signal recording unit33disposed thereunder. Only when the rotary shaft215is pressed downward via the rotary knob, i.e. in the direction of the signal generation unit33, does the rotary shaft215come into engagement with the signal recording unit33. A lock (not shown) can be provided in the mounting unit2. This enables the so-called “push to turn” function to be realized, with which an actuation of the rotary switch1is only possible if the rotary knob is moved by at least a certain amount in the direction of the glass ceramic plate5, i.e. has been depressed. The switch unit3is also reliably protected by the separately provided mounting unit2against mechanical stresses which occur, for example, in the event of lateral impact shocks against the rotary knob.

The switch34, which represents in particular a microswitch, is disposed between the cover31and the board32in such a way that the terminals341and342are disposed facing away from the signal generation unit33and project beyond the board32. This enables the switch34to be connected in a simple manner.

Only the circular housing331of the signal generation unit33can be seen inFIG. 6. A rotary disk332, which is just discernible through the opening312inFIG. 5, is preferably provided in the housing331. Provided in the rotary disk332is an engagement opening333through which the rotary shaft215can engage with the signal generation unit33and in particular with the rotary disk332. The engagement opening333has a shape which corresponds to the shape of the cross-section of the rotary shaft215. On the side facing the switch34the housing331of the signal generation unit33has a recess334.

A possible layout of the signal generation unit33and its interaction with the switch34are indicated schematically inFIGS. 7 and 7a. The actuation side of the microswitch34, which represents a pushbutton343in the embodiment shown, faces the signal generation unit33.

With the actuation side and in particular with the pushbutton343, the switch34engages via the recess334with the housing331of the signal generation unit33. In the signal generation unit33, the rotary disk332in the embodiment shown has an essentially circular shape with a flat section3321. In the view shown, the rotary disk332is in a position in which the flat section3321faces toward the pushbutton343. In this position the switch34is consequently not activated. If the switch34represents a normally open contact, an electric circuit routed through the switch34is therefore interrupted in this position.

If the rotary knob is turned, the rotary disk332rotates correspondingly owing to the engagement of the rotary shaft215in the engagement opening333of the rotary disk332. As a result, in the embodiment shown inFIG. 7, the pushbutton343of the switch34comes into contact with the rotary disk332and the electric circuit that is routed through the switch34is closed.

Also indicated inFIG. 7is a contact comb335which is mounted on the underside of the rotary disk332and rubs against the board32. As a result of the rubbing of the contact comb335, a signal can be generated which corresponds to the respective absolute angular position of the rotary disk332. Since the rotary disk332is connected to the rotary knob via the rotary shaft215, the generated signal thus reflects the angular position of the rotary knob. The signal generated in this way can be forwarded via the board32and made available to other components for further processing.

A possible application is shown inFIGS. 8 and 9. In this arrangement the rotary switch1according to the invention is disposed on a display board4. Arranged on the display board4are display elements41which represent in particular seven-segment displays. Also provided on the display board4are terminals42via which the display board4can be contacted. In the embodiment shown, the display board4is placed on the cover31of the switch unit3and rests with its edge against the lower part22of the mounting unit2. However, the display board4can also be provided spaced at a distance from the switch unit3. In particular, a mechanical contact between the switch unit3and the display board4is not necessary. The signal generated in the signal generation unit33can be transmitted to the display element41via the board32or, given a corresponding alignment of the signal generation unit33, also via the cover31. The signals generated by the signal generation unit33in respect of the angular position of the rotary shaft215can preferably be transmitted to the display board4via a signal cable (not shown).

This illustrated arrangement can be installed in a glass ceramic stovetop. In this case the glass ceramic plate is accommodated between the upper part21and the lower part22of the mounting unit2. In this way both the switch unit3and the display board4are disposed in a protected location underneath the glass ceramic plate.

In an arrangement of this kind, if a rotary knob connected to the rotary shaft215is turned from a zero position by a user wanting to actuate the stovetop, this rotation is transmitted via the rotary shaft215to the signal generation unit33, in particular to the rotary disk332of the signal generation unit33. The edge of the rotary disk332, which in the zero position was aligned with the flat section3321toward the pushbutton343of the switch34, now stands, in the rotated position, with a part of the round circumference in contact with the pushbutton343of the switch34and actuates the switch34.

If the switch34is embodied as a normally open contact, the voltage required to operate the hotplate can be made available in this state. At the same time the rotation of the rotary disk332effected by the turning of the rotary knob is transmitted via the contact comb335to the board32in such a way that a voltage signal is recorded there which is routed to further units. Preferably the signal recording unit33represents a Gray-code switch. The signal thus generated can be transmitted to the display unit41, via which the operating stage corresponding to the current angular position of the rotary shaft215can be displayed.

Furthermore the signal generated by the signal generation unit33can also be transmitted to other units, such as, for example, a controller which regulates the heating output of the hotplate for the selected power stage.

The invention is not restricted to the embodiments shown in the figures.

Thus, for example, instead of the flat section on the rotary disk as shown, one or more other mechanical resistances can be provided via which other positions of the switch apart from the pure On and Off position can also be achieved if necessary. For example, projections can be provided at defined intervals around the circumference of the rotary disk, each of which leads to the switch component being switched to a different switch stage. The pushbutton on the switch shown in the figures is also not obligatory. Alternatively, contacts can be provided on the side of the switch facing the signal generation unit. In this case contacts are preferably also provided distributed around the circumference of the rotary disk of the signal recording unit. As soon as the contacts of the rotary disk come into contact with the contact of the switch, this can effect the desired switch position.

The embodiment of the signal recording unit with a contact comb can also be replaced according to the invention by an embodiment in which the generation of the signal can be achieved by, for example, optical, capacitive or other means.

By means of the present invention it is possible to combine a mechanical switch knob with electrical displays and/or electronic functions on glass ceramic cooktops. This is achieved in that as a result of turning the rotary knob a power switch or other switch component is simultaneously actuated and information regarding the angular position is picked up as an electrically processible signal. This has the advantage that the ease of operation of a knob-controlled stovetop, in particular owing to the size of the rotary knob and a haptic feedback, can be combined with the convenience of an electronic controller. This means that features of the stovetop, such as, for example, a timer function or other electronic functions that are controlled via the signal generation unit, are possible that are not possible using a pure knob-controlled cooktop with energy controller. Moreover, the individual rotary switches can be positioned virtually freely, thereby enabling cooktops to be equipped with up to e.g. six heating elements. By using the additional electrical switch component, in particular the power switch, it is possible to save on expensive main switch relays on the electronics board of the glass ceramic cooktop. Finally, as a result of the decoupling of the mechanical mounting unit and the switch unit, the switch components are relieved of impact shocks and other mechanical stresses. Assembly and wiring are also made easier by the decoupling of mounting unit and switch unit. Furthermore, a significant advantage of the present invention lies in the low installation height of the switch. This allows the rotary switches to be used also with glass ceramic cooktops in spite of the constricted installation situation that obtains there.