CONTROL CARTRIDGE DESIGNED AS SCALDING PROTECTION VALVE

Abstract

The invention relates to a control cartridge for single-lever mixer taps, comprising a housing in which a ceramic base disk and a rotatable and displaceable ceramic control disk resting on the base disk are situated. An inlet for the cold water and hot water, respectively, and an outlet for the mixed water are situated in the base disk, and the mixed water is diverted in the control disk and leaves the control cartridge via the outlet in the base disk. In order for automatic scalding protection to be integrated into the control cartridge, i.e., for the control cartridge to automatically close in the event of a scalding temperature of the mixed water, according to the invention at least one shape memory alloy (SMA) element is situated on the control disk, and takes on the temperature of the mixed water during operation of the control cartridge, and upon reaching a scalding temperature of the mixed water, expands and hereby automatically moves the control disk into the closed position in which no water arrives at the outlet, and the SMA element is supported on the one hand on the control disk and on the other hand on the housing.

Claims

1. A control cartridge for single-lever mixer taps, comprising a housing in which a ceramic base disk and a rotatable and displaceable ceramic control disk resting on the base disk are situated, wherein an inlet for the cold water and hot water, respectively, and an outlet for the mixed water are situated in the base disk, and the mixed water is diverted in the control disk and leaves the control cartridge via the outlet in the base disk, characterized in that at least one shape memory alloy (SMA) element is situated on the control disk, and takes on the temperature of the mixed water during operation of the control cartridge, and upon reaching a scalding temperature of the mixed water, expands and hereby automatically moves the control disk into the closed position in which no water arrives at the outlet, and the SMA element is supported on the one hand on the control disk and on the other hand on the housing.

2. The control cartridge according to claim 1, characterized in that the SMA element is situated on the side of the control disk facing away from the base disk.

3. The control cartridge according to claim 1, characterized in that the SMA element is an SMA metal sheet or an SMA wire.

4. The control cartridge according to claim 1, characterized in that only SMA elements are used which expand with a force of at least 50 N when the scalding temperature is reached.

5. The control cartridge according to claim 1, characterized in that two or more, preferably identical, SMA elements are used.

Description

[0010] The invention is explained in greater detail with reference to eight figures. All figures show an identical design of a control cartridge according to the invention in various positions.

[0011] The valve or the control cartridge having scalding protection is advantageously designed as follows:

[0012] FIG. 8 shows a control cartridge 1 according to the invention. A base disk 3 made of ceramic, which is sealed off with respect to the cylinder wall of the housing 2, is situated in a plastic cylindrical housing 2. Three boreholes, one for the cold inlet 5a, one for the hot inlet 5b, and a borehole as the outlet 6 for the mixed water, are situated in the base disk 3. The base disk 3 is secured against rotation with respect to the cylindrical housing 2. The housing 2 and the base disk 3 thus form a unit that is similar to a cylindrical cup. The two inlets 5a, 5b are connected in a water-tight manner to the water supply network via a fitting body (not shown). The mixed water borehole, i.e., the outlet 6, is connected to a fitting, for example the outlet of a shower fitting.

[0013] An additional disk made of ceramic, the control disk 4 is situated above the base disk 3. This control disk 4 may be moved translationally as well as rotationally via the pivot 8. The control disk 4 may be turned to the left and the right about the center axis 9 of the cylindrical housing 2 at an angle (pivot point 9). In addition, the control disk 4 may be translationally displaced in the direction of its axis of symmetry. In the illustrated version (see FIG. 1) this distance is 5 mm. The control disk 4 increases or decreases the cross sections of the inlets 5a, 5b and their inlet boreholes due to its translational and rotational movement. In FIG. 1 this valve is schematically illustrated in the fully open position. The hot and cold inlets 5a, 5b are opened to the greatest extent possible, so that the highest volumetric flow results at this position. FIGS. 1, 3, 4, 5, 6 each show a section perpendicular to the center axis 9 (see FIG. 8) of the control cartridge, i.e., a top view of the control disk 4.

[0014] These movements are generally known from the operation of a single-lever mixer tap in the bathroom or kitchen. The control disk is translationally moved by the up/down motion of the handle, and is rotationally moved by a rotary motion. FIG. 2 illustrates these movements on a shower fitting by way of example. The arrows 11a, 11b indicate the up and down positions, and the arrows 12a, 12b indicate cold and hot. The same applies for all other single-lever mixer taps in the kitchen or on a wash basin, for example.

[0015] According to the invention, two shape memory alloy (SMA) elements 7a, 7b are inserted into the control disk 4 in a form-fit manner (see FIG. 3). The SMA elements 7a, 7b are made of a shape memory alloy (nickel-titanium alloy), and have the property of deforming at a certain, definable temperature. In everyday operation, these SMA elements 7a, 7b have no function, and take part in the movements of the control disk 4, and mixed water flows around them when the valve is open.

[0016] In one preferred embodiment, these SMA elements 7a, 7b are metal sheets or wires.

[0017] The valve is illustrated in the closed position in FIG. 3. The inlets 5a, 5b and their inlet boreholes are now concealed by the control disk 4. In the housing 2, water (and also the SMA elements 7a, 7b) take on or have already taken on the surrounding temperature when the valve has been closed for a fairly long time.

[0018] FIG. 4 shows a valve position which may be typical for showering or hand washing. The valve is opened and turned by 20 into the hot position. The temperature of the mixed water is now a comfortable 38 C. This position and a countless number of intermediate positions take place during the product life cycle; estimates range from 4 to 6 million movements. In tests by the applicant on its endurance test stands, 500,000 load changes were tested, corresponding to approximately 4.5 million movements.

[0019] If the cold water feed is throttled or fails altogether, the mixed water temperature may increase to values that result in scalding of the user. Now (and only now) do the SMA elements 7a, 7b perform their function. Above a certain temperature of the mixed water (46 C., for example), the SMA elements 7a, 7b are designed to take on a shape as illustrated in FIG. 5. The control disk 4 is displaced in the direction of its axis of symmetry due to the deformation of the SMA elements 7a, 7b (see arrow direction in FIG. 5). The valve is now closed and prevents further feed of both cold water and hot water.

[0020] It is presumed that friction forces of approximately 80 N are to be expected between the base disk 3 and the control disk 4 and the lever mechanism, not illustrated. The SMA elements 7a, 7b must apply this force. There is a concern that a portion of the force for friction between the SMA elements 7a, 7b and the housing 2 may be lost. In addition, toward the end of the transformation, only 83% of the force is conducted in the translation direction (cos 34, see FIG. 5). At the beginning of the translation this force is virtually 100%, which certainly meets the performance of the transformation process. At the beginning of the transformation this force is quick and strong, but toward the end it is somewhat slower and weaker. When all these circumstances are taken into account, it is concluded that each of the two SMA elements 7a, 7b must apply at least 50 N.

[0021] This force is greatly dependent on the normal force of the slide pairing and/or of the ceramic/ceramic tribological system. The lever mechanism has only a minor influence, since slide pairings are selected here with an extremely low coefficient of friction. The force is generally structurally influenceable, although in the system described here this is the case only to a limited extent, since the entire system has been optimized for volumetric flow and hydraulic function, and therefore the normal force is hardly still influenceable. Further optimizations are conceivable only via the coefficient of friction. In addition, there is a concern that for comparable systems the force will increase over time due to degradation of the tribological system. This is particularly true for the present system, since it is a so-called open system in which water flows completely around the control disk 4. For this reason, appropriate reserves must be taken into account in order for the system to function even under these conditions.

[0022] The transformation process should preferably proceed quickly and without a further increase in the temperature; 1 to 2 seconds are acceptable.

[0023] The restoring of the SMA elements 7a, 7b, i.e., the SMA metal sheets, takes place mechanically via the handle of the fitting (FIG. 2). An automatic recovery of the SMA elements 7a, 7b after the water cools is advantageous.

[0024] The SMA elements 7a, 7b are shown in the normal state on the right side of FIG. 6 and in the deformed state on the left side; FIG. 7 shows an illustration of one of the SMA elements 7a, 7b, designed here as a steel sheet, in the undeformed state in two views.

[0025] FIG. 8 (also see the description above) shows a control cartridge 1 according to the invention in a cylindrical housing 2 made of plastic. A base 13 having an inlet 14b for hot water and an inlet 14a for cold water, as well as a mixed water outlet (not shown in FIG. 8) are situated in the housing 2. A base disk 3 made of ceramic is situated above the base 13. Three boreholes, one for the cold inlet 5a, one for the hot inlet 5b, and a borehole for the mixed water, are situated in the base disk 3. The base disk 3 is secured against rotation with respect to the cylindrical housing 2. The housing 2 and the base disk 3 thus form a unit that is similar to a cylindrical cup. The two inlets 5a, 5b via the inlets 14a, 14b are connected in a water-tight manner to the water supply network via a fitting body. The mixed water borehole is connected to the outlet of a fitting, for example the outlet of a shower fitting.

[0026] An additional disk made of ceramic, the control disk 4 is situated above the base disk 3. Situated on this control disk are the SMA elements 7a, 7b, which move the control disk 4 in the closing direction when they are acted on by hot water, until the control cartridge 1 is closed. The control disk is covered by a bearing disk 15 made of ceramic.