Abstract:
A thermostatic mixer wherein the apertures intended for inlet of warm water are so conditioned as to oppose to the flow a smaller resistance than the apertures intended for inlet of cold water, thus causing an asymmetric operation of the thermostatic mixer which results in a more rapid correction of accidental increases in temperature.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to improvements in or relating to thermostatic mixer devices for hydraulic systems, which devices are intended to be fed by a cold water pipe and a warm water pipe and to deliver water at a predetermined intermediate temperature regulated by a thermostat, which is fed, for exemple, to the various fixtures of a bathroom. 
     More exactly the invention relates to those types of thermostatic mixers in which a thermometric element immersed in the water of regulated temperature produces the displacement of a throttling member which cooperates with inlet apertures for the cold and the warm water respectively, by modifying in opposite directions the free passages in such a way as to compensate the temperature variations of the regulated water. 
     With these types of thermostatic mixers, in case of a feeding pressure variation occurring in only one of the inlet pipes, this variation generates a variation of the ratio of the warm water flow to the cold water flow and consequently a variation of the temperature of the delivered water, and the thermometric element has to intervene with a corrective action which, however, is substantially delayed by the thermic inertia. 
     Now, considerable temporary reductions of the pressure frequently occur in the cold water pipes, especially in consequence of sudden large diversions of water, as for instance those which are caused by actuation of flowmeter valves. These sudden drops of the pressure are not transmitted to the associated warm water pipe because of the hydraulic accumulator effect of the accumulation water heaters which are used generally. Accordingly, when the pressure in the cold water pipe decreases, there occurs for a short but not negligible period of time a delivery of excessively hot water which may produce damage, even serious damage, for instance if at that time a shower is being used. 
     The reverse phenomenon, i.e. a decrease of the pressure in the warm water pipe, occurs less frequently, because generally no fixtures of high instantaneous consumption of water are inserted in these pipes, and anyhow the consequence of such decrease would be a delivery of water having a lower temperature, which may produce a certain inconvenience, but no damage. 
     BRIEF SUMMARY OF THE INVENTION 
     In consideration of the higher frequency and seriousness of consequences of the pressure drops in the cold water pipe as compared with those which occur in the warm water pipes, the object of the present invention is to render asymmetric the operation of the throttling member controlled by a thermometric element in a thermostatic mixer, in such a manner that the throttling action exerted on the flow of the incoming warm water, as a consequence of an increase of the temperature of the regulated water, will be accomplished more rapidly than the reverse action. 
     This effect can be achieved according to the invention by giving to the inlet apertures for the warm water such a configuration that they oppose to the flow of the water therethrough a resistance which is substantially smaller than that opposed by the inlet apertures for the cold water. Under these circumstances the throttling member, normally, must throttle more the passage of the warm water than the passage of the cold water, in order to maintain the right mixing ratio, instead of assuming normally an almost symmetric position, as occurs with the known thermostatic mixers. It follows that at the moment of the action intended to compensate an increase of the temperature, it is sufficient for the throttling member to move less to reach the new position of equilibrium, and the corrective action can be accomplished in a considerably shorter period of time. 
     The different resistance opposed to the flow by the apertures for the warm water and the cold water respectively, can be obtained by sizing differently said apertures, or by providing a partial throttling of the same, or also by means of other arrangements capable of enhancing or respectively hindering the flow. 
     In particular, in the types of mixers having a tubular member for separating the warm water from the cold water, which tubular member is provided with end recesses forming a castellation-like denticulation and defining the apertures for the passage of the water into the interior of the tubular member, wherein the throttling member or distributing valve is slidably mounted, the different resistances may advantageously be obtained by giving different characteristics to the castellation-like denticulations, such as a different width of the recesses or passages between the denticulation projections, the presence of a throttling ring, and so on. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The invention will appear more clearly from the following description of illustrative and non limitative embodiments shown diagrammatically in the accompanying drawing, wherein: 
     FIG. 1 is an axial cross-sectional view of a thermostatic mixer device, of the type with a tubular separation member having castellation-like denticulations; 
     FIG. 2 is a side elevational view, cross-sectional in its right-hand half, of the tubular member configurated in such a manner as to realize the concept of the invention in a first embodiment; 
     FIG. 3 is a plan view showing the same tubular member, in the upper half of the Figure, as it appears when looking at it from the top and, in the lower half of the Figure, as it appears when looking at it from the underside; 
     FIGS. 4 and 5 are views, similar to those of FIGS. 2 and 3, but showing a different embodiment of the tubular member. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The mixer shown in the drawing comprises a body 1 provided with a union 2 for the incoming warm water, a union 3 for the incoming cold water (this union 3 being shown with dashdotted lines because it is situated outside the plane of the cross-section), and a union 4 for the delivery of water having a regulated temperature. Within the body 1, a tubular member 20 maintained in position by means of a plug 5 separates the flow of warm water from the flow of cold water by means of an annular gasket 19 and allows said flows to enter its interior through end castellation-like denticulations 21 and 22 respectively. Slidable within the tubular member 20 is a cylindrical distributing valve 6 whose end edges define, with respect to the body 1 and the plug 5 respectively, throttled passages for the warm and the cold water respectively, which come in from the respective unions through the denticulations 21 and 22. The distributing valve 6 is connected to a thermometric bulb 7 mounted on a spring 8 in the body 1 and whose position is defined by a threaded member 9 screwed into the plug 5 and having housed therein, in a known manner, a strong safety spring 11. Connected to a tang 10 of the threaded member 9 is a knob 12 which allows one to control the rotation of the threaded member, thereby adjusting the axial position of the threaded member 9, the thermometric bulb 7 and the distributing valve 6 and consequently regulating the temperature which the thermostatic system, thus constituted, tends to maintain in the delivered water which laps the bulb 7. The operation of such thermostatic mixer is well-known in itself and does not need to be described specifically. 
     On occurrence of an increase of the temperature of the water being delivered, the bulb 7 expands and causes the lowering of the distributing valve 6 which throttles more the passage of the warm water, thereby compensating the temperature increase which has initiated the action of the system. 
     According to the invention, the passage apertures for the warm water, which in the present case are formed by the denticulation 21, are configurated in such a manner as to oppose to the flow a resistance which is substantially lower than that of the apertures for the cold water, which in the present case are formed by the denticulation 22. It follows that, the other conditions, namely the conditions of the warm and the cold water respectively, being equal, to obtain a determined temperature of the delivered water it is necessary that the position of the distributing valve 6 be adjusted, by means of the knob 12, in such a manner that the passage of the warm water be throttled more than it would be in a prior art mixer, whose inlet apertures for the warm and the cold water oppose a substantially equal resistance. That is to say that the distance of the lower edge of the distributing valve 6 from the cooperating surface of the body 1 is smaller than it would be in the absence of the characteristic according to the invention. It follows that on occurrence of an increase of the temperature of the regulated water, which increase generally is due to a sudden drop of the pressure in the inlet pipe of the cold water, the travel which has to be accomplished by the distributing valve in order to restore the equilibrium is much smaller and can be accomplished in a shorter period of time by virtue of the action of the thermometric bulb 7, thus reducing the disadvantage described in the preamble and limiting its consequences to a possible inconvenience, which, anyhow, will not be accompanied by any danger, or reducing and possibly eliminating altogether such inconvenience. 
     FIGS. 2 and 3 illustrate the way in which the different resistance opposed to the flow by the castellation-like denticulations 21 and 22 may be obtained, for instance, by making equal the projections of the two denticulations, but providing the denticulation 21 for the warm water with a smaller number of projections, which therefore will be spaced by larger passage recesses. 
     FIGS. 4 and 5, instead, illustrate how the same effect may be obtained by making equal the two denticulations 21 and 22, but providing a throttling ring 23 around the denticulation 22 for the cold water. 
     It is clear that the two provisions described above may also be adopted together, and also that other configurations may be utilized for achieving the desired effect, which configurations will appear obvious to those skilled in the art when becoming acquainted, through the present description, with the objects and means proposed by the invention. 
     It is to be understood that although a thermostatic mixer of the type provided with a separation tubular member having castellation-like denticulations has been specifically illustrated herein, the concept of the present invention may be applied to mixers having tubular members of different configurations, or without any tubular member at all, or provided with arrangements different from those envisaged herein for the passage and throttling of the warm water and cold water flows, without departing from the scope of the present invention.