LIQUID LEVEL MONITORING AND CONTROL APPARATUS

Abstract: A liquid level monitoring and control apparatus is described, which generates an alarm signal or a safety signal, discontinuing an operation such as heating, when the liquid level in a controlled vessel has reached a predetermined level. Several signals, similar or different, may be generated at different liquid levels. The operation of the apparatus may be based on various physical properties, such as optical, magnetic, acoustic, electrical and conductivity properties. The apparatus comprises a floating actuator, the level of which is determined by the level of the liquid in the vessel, a sensing assembly comprising at least a member which can be actuated by the actuator, means for guiding the vertical displacement of the actuator and means for issuing the desired signal or signals when the actuator reaches a level close to that of the actuatable member. The actuatable member can be displaced to set the predetermined level of the liquid as desired by the user. The apparatus can be so designed as to constitute a transportable kit comprising the actuator and the actuatable member. In a form of the invention, the actuator is mounted on a floating rod. In another form the floating actuator is accommodated within the vessel, the liquid level which is to be controlled, or within a liquid duct in communication with the vessel, and an actuatable switch is located outside the vessel and placed in the desired height.

Description: LIOUID LEVEL MONITORING AND CONTROL APPARATUS Field of the Invention This invention generally relates to liquid level monitoring and control apparatus, and paπicularly relates to such an apparatus that generates an alarm or other signal when the liquid level has reached a predetermined level. Background of the Invention Many types of liquid level sensing devices have been disclosed in the prior art. Such devices, which are usually based on magnetic, electrical-conductivity, acoustic or optical parameters, enable user manipulation of the positioning of the sensing elements for either facilitating the operation of the liquid level sensor itself or the issue of a sensible output at a desired liquid level in the monitored vessel, in accordance with one or more predetermined sensing elements. Thus, for example, US Patents Nos. 3,696,362 and 3,944,845 describe conducting liquid level control devices, wliich indicate when the level of a conducting liquid reaches the predetermined minimum level, while US Patent No. 4,354,180 describes an optical liquid level sensing probe. US Patents Nos. 3,849,771 and 4,771,272 describe portable self-contained liquid level alarm devices having a housing in which a floating maagnet actuates a reed switch. US Patent No. 3,702,910 describes a level sensing control device with a reed switch which can be rotatably adjusted to any position in respect of a magnetic member connected to a float member. Additional implementations of such magnetic devices have been described inter alia in US Patents Nos. 3,702,910; 3,823,328; 3,997,744; 3,978,299; 4,035,789; 4,066,858; 4,395,605; 4,458,118; 4,459,584; 4,499,348; 4,609,796; 4,748,299; 4,748,300; 5,103,673; 5,224,379; 5,426,271; 5,562,003; and 5,565,687. USP 5,565,607 describes an apparatus that comprises a linear series of switches, each of which is closed when in the proj imity of an actuating magnet movable along the series of switches. Movement of the magnet produces a progressive change in voltage on the output line, a resistance chain linked to the switches, as a cumulative signal indicating the position of the magnet. A cumulative signal represented in the magnet position relative to the series of switches can thus be generated. USP 4,771,272 discloses an indicator of a liquid level which comprises a pendant liquid level sensor suspended at a desired height within a vessel by means of flexible cable, said sensor including a hollow, elongated cylindrical housing closed at both the upper and the lower end by cylindrical cups providing the perforations to permit water to enter or exit. A cylindrical float is contained coaxially within the housing, and has a permanent magnet recessed into its upper surface. The switch is closed when the magnet rises sufficiently to contact or to almost contact it. Most of the liquid level monitoring and alarm systems described in the prior art, including those based on a floating magnet, are not versatile and usually have drawbacks and/or are not convenient for user manipulation. It is especially seen in cases in which the monitored vessel's interior is wholly inaccessible, such as the case of a sealed vessel holding hazardous material or when the content and/or prevailing conditions do not allow a simple and convenient user access and manipulation. Similar difficulties exist in the case of heated vessels, particularly in the case of a cocking pot or the like. It is often found in everyday coolάng operations that a heated liquid, e.g., soup, is left simmering on a heat source without supervision. It may happen that the cocking pot on the heat source has been forgotten, whereby the victuals being cooked or the cooking pot itself may be ruined and, more seriously, a hazardous situation may develop. There are known devices for automatically switching off an electrical water heater when the water level drops below the level of the heating element of the heater. Also, US Patent No. 4,673,925 describes an alarm device, for removably mounting onto the upper edge of a cooldng pot, which provides an alarm when the liquid contents of the cocking pot begin to boil, whilst US Patent No. 5,229,751 describes a coffee pot including an integrally provided alarm device for providing a time-based alarm indication in respect of the freshness of its liquid contents. Also, US Patent 5,341,728 describes an alarm device, which controls the cooker and indicates the end of cooking timing. In reality, only certain household containers, for example, electric kettles, are provided with liquid level sensors and automatic alarms or switch-off devices, while most cooldng pots and pans do not include such devices. This is primarily because the liquid level sensors and/or auto-switch devices of the art consume valuable space and interfere in cooking/cleaning operations. Moreover, even liquid level sensing devices currently used for cooking devices do not contain a simple and convenient means allowing the user, whenever he desires, to easily change the level at which the sensor will activate the alarm. It is a purpose of this invention to provide a liquid level monitoring and control apparatus that generates an alarm, a safety signal or other signal when the liquid has reached a predetermined level, or generates such sign.als at a plurality of predetermined levels. It is a still further object to provide such an apparatus that enables convenient user access to level setting components. It is a still further object of the present invention to provide a liquid level sensor that is exceptionally versatile, in that the same general structure of apparatus is suitable, with minor modifications, for obtaining a liquid-level apparatus whose operation can be based on various physical properties such as; optical, magnetic, acoustic, electrical and conductivity. It is a still further object to provide such an apparatus that may be designed so as to be usable with a variety of vessels of different sizes and shapes, with both open and sealed vessels, and with vessels with an interior inaccessible to user manipulation. It is a still further object to provide a novel and versatile liquid level sensor that can be readily adapted for a wide .range of applications. It is a still further object of the present invention to provide a liquid level apparatus tliat is applicable also for liquid containing solid materials. It is a still further object to provide a liquid level monitoring and control apparatus that is particularly suited for use with cooldng vessels. It is a still further object to provide an alarm .kit that is portable, transferable, and used interchangeably with a wide variety of vessels. It is a still further object to provide such an apparatus that is compact and inexpensive. It is a further object of the present invention to provide elements that are multifunction. Other purposes and advantages of the invention will appear as the description proceeds. Summary of the Invention The invention provides a liquid level apparatus for monitoring and control of a liquid level in a liquid-containing vessel (hereinafter briefly, "the liquid vessel" or "the vessel"), and for providing a signal for indicating when the liquid has reached a predetermined level, and if desired, activating one or more means including safety devices. In accordance to one aspect of the present invention the liquid-level apparatus comprises: a floating-rod assembly comprising of a rod conjugated to a float (hereinafter, briefly, "floating-rod") wherein in operation said floating-rod floatingly move, in response to changes in the level of said liquid, in such that the longitudinal axis of said rod is generally parallel to the vertical direction, and wherein the lower part of said rod is rigidly connected to said float while the upper end of said rod is exposed above said liquid. at least one displaceable and fixable actuator mounted on said rod, wherein said actuator is fixable at a user selected level, and wherein, in operation, after said actuator has been fixed at a certain position on said floating-rod, it will floatingly move together with said floating-rod, and wherein said actuator can cause an actuation of an appropriate actuatable member. means for displacing said actuator along the longitudinal axis of said rod and fixing it at a selected position on said rod. a sensing assembly comprising: a) at least one actuatable-member, wherein said actuatable-member can be actuated by said actuator once the level of said liquid reaches the predetermined level; b) an indicator; and c) a power supply, wherein said power supply energizes at least pan of said sensing assembly; and wherein said sensing assembly, preferably also comprising a control-unit, is issuing a signal once said actuatable-member has been actuated by said actuator. means for guiding and restraining the transition of said floating-rod to the vertical direction a support member, preferably mounted on the rim of said vessel, on which at least pan, preferably all components of said apparatus is mounted. a casing member, housing at least part, preferably all, components of said apparatus. Regarding to the actuator and actuatable-member pair (hereinafter, briefly, "actuation pair"), actuation pairs of various .kinds can be used in liquid-level apparatus designed according to the present invention. Those pairs can be based on various physical propeπies such as magnetic, optical, acoustic or electrical conductivity. Examples of such pairs are: a) a permanent magnet, as an actuator and actuatable magnetic switch, like a reed switch or a hall-effect switch (hereinafter, briefly, "magnetic switch"), as an actuatable-member, b) an optical reflector, as an actuator, and a controlled optical detector as the actuatable-member. In a prefeπed embodiment designed according to first aspect of the invention, the float, on which said rod is conjugated, is immersed at least in part within the liquid mass, while the actuator and the rest of the floating-rod are exposed above the liquid mass and preferably above its lid. The actuator is mounted on the substanti-ally vertically extending floating rod. The sensing assembly is located above the liquid mass, and preferably above the vessel, particularly over its lid, and preferably comprises a guide passage or passages for the floating rod. It comprises a box-like casing, which preferably encloses all components of the sensing assembly. A mutual, removable connection between said casing and said lid is preferably provided by matching structural features of said two elements. As has been said, the term "actuator" designates a component that is capable of actuating an actuatable member, generally a switch, when it enters a certain actuation range of said switch. While one of the prefeπed type of actuator is a magnet, and coπespondingly the switch is magnetically actuatable, other types of actuators, e.g. optical or mechanical, are comprised within the invention, and, if such are used, the switch will be actuatable by coπesponding physical stimuli. Also, the signal generated by the apparatus may be an alarm, e.g. acoustic or optical, and indicate that the level of the liquid has gone below a pre-selected level, or it may be a signal to a device, e.g. a pump or a heating device, associated with the liquid vessel, to stop the action which caused the liquid level to become too low or an action which has become undesirable or dangerous. In one mode of operation, after the lid was set on the rim of a vessel containing a liquid, the apparatus is mounted at the center of said lid (preferably through an aperture at the center of the lid) keeping the longitudinal axis of the floating-rod, generally, in the vertical position. At this stage, the floating-rod, which the lower part of it immerses in the liquid, start to float. Now, the exposed upper part of the floating-rod, which is above the lid, provides the user a continuous visual monitoring and indication about the liquid-level within said vessel. Now, with the .knowledge about the level of the liquid in the vessel, the user can decide about the exact location or selected level, on the floating-rod, where he or she would prefer to fix the displaceable actuator. When the liquid level drops, for example, to the pre-selected level, determined by the location of the actuator on said rod, the required signal will be generated. An apparatus designed according to first aspect of the invention is especially simple and versatile. Thus, e.g., embodiments can be designed that can operate on the basis of one or several physical properties. In many cases, in order to change the sensing principle of the apparatus from one physical property to another one, it suffices to replace the appropriate activation-pair, while leaving the other components of the apparatus unchanged. In other wards, the same general structure of apparatus, or, as may be said, the same backbone, is suitable, with minor modifications, for using it with various physical principles (optical, magnetic, acoustic, electrical conductivity, etc.), thereby providing an exceptional degree of versatility. In a number of embodiments of the present invention, a single actuator can actuate a single actuatable member, e.g. a switch, at least at two, significantly different, preselected activation levels of the liquid. Therefore, instead of using multiple actuators or multiple switches for generating signals at more than one pre-selected liquid level, a single set composed of an actuator and a switch can activate signals at more than one pre-selected level of said liquid. Thus, e.g., when such an apparatus is applied to a cooldng pot, an indication signal, like an alarm, is generated when the liquid level drops to a first pre-selected level, and a signal to shut-down the electrical heating of said vessel is generated when the liquid level drop further to a second pre-selected level. In order to apply the same apparatus for vessels of significantly different depth or liquid level, a long or an extendable floating rod is conveniently used. The extendibility of the rod can be achieved in various ways, e.g. by using a telescopic rod or by changing the position at which the rod is connected to the float. In principle, an apparatus designed according to such embodiment, can .function properly without any filtering unit. However, in cases where the vessel contains, in addition to liquid, material which might disturb the free vertical transition of the floating rod (which may well happen in a cooldng vessel) the floating rod has to be protected by adding a filtering unit. The mesh of said filter will be determined, mainly, according to the specific content of said vessel. .Also, when such an apparatus is used in a heated vessel containing liquid, vapor might be accumulated above the liquid (especially when a vessel is covered by a lid, as the usual case in cooking pots). In such cases, accumulation of liquid vapor around the passage of the floating rod might plug or disturb the free vertical transition of the rod, thereby causing malfunctioning of the apparatus. In order to prevent such plugging an appropriate outlet is preferably provided in the apparatus. An apparatus designed according to this aspect of the invention is mounted preferably on the lid of the vessel, but it can be mounted in the vessel by other means. Thus, for example, it can be hung on the upper rim of the vessel, or be appropriately supported at the bottom of the inside of the vessel. According to other, second, aspect of the present invention the liquid level apparatus comprises: a floating-magnet assembly comprising a floating actuator accommodated within said vessel or in a liquid duct in liquid communication with said vessel, which floats on said liquid and which is guided to move with the liquid level in a vertical path proximal to an internal wall of said vessel; and a sensing assembly, preferably located outside of said vessel, comprising; a) at least one displaceable and fixable actuatable member (hereinafter, briefly, "actuatable-switch"), wherein said switch is fixable at a user-selected level proximal to the vessel's, preferably, exterior surface and parallel to said vertical path of said floating actuator, and wherein said actuatable-switch can be actuated by said actuator once the level of said liquid reaches the predetermined level; b) an indicator; and c) a power supply, wherein said power supply energizes at least part of said sensing assembly; and wherein said sensing .assembly, preferably also comprising a control-unit, is issuing a signal once said actuatable-member has been actuated by said actuator. In one of the apparatus embodiments designed according this .aspect of the present invention, the floating actuator floatingly moves downwards or upwards, in response with the liquid level, along the interior wall of said vessel, for actuating the actuatable switch upon reaching a user-selected liquid level, to provide an output signal. There are two main configurations (modes) to constrain the transition of the floating actuator in close proximity to the vessel's interior wall surface and juxtaposed to said switches, located outside the vessel. According to one of the configurations (Mode A), which is particularly suitable for a large diameter vessel, the floating actuator is located within a sleeve-like filter which has free liquid flow communication with said vessel. According mode-A configuration, the sleeve-like member is of a filtering type and has dual .functions. In addition to serve as a guide for the vertical transition of the magnet, it is also a filtering unit for preventing some materials present in the vessel from entering inside the sleeve causing to the disturbance of the free transition of the floating magnet inside said sleeve. The sleeve-like member may be disposed within the vessel, or it may be positioned outside it but in flow communication with the vessel, so that the level of the liquid therein is essentially the same as in the vessel. According to another configuration (Mode B), which is particularly applicable to a vessel having a small cross-section, said actuator has a shape and dimension such that its outer rims are proximal to the interior side wall of the vessel, e.g., it may be an O-ring shaped actuator device disposed in a cylindrical vessel. In such a configuration (Mode B), the transition of the floating magnet is constrained by the vessel's interior wall to be generally vertical. As will be appreciated, Mode A or Mode B configuration may be chosen on the basis of the intended application. Thus, for example, wliile Mode A configuration will be typically applicable to large reservoirs, as well as for small vessels such as a cooking pot in a domestic kitchen, Mode B configuration is typically applicable to a vessel with a small cross-section. Also in this case, the actuation-pair can be based on JO- various physical properties, such .as optical or magnetic, although in the prefeπed embodinent a magnetic actuation-pair will the used, with a floating permanent magnet as the actuator and a magnetic switch as the actuatable switch. There are cases in which the sensing assembly may comprise two or even more actuatable switches. For example, in the case of a sensing assembly comprising two magnetic switches, the first of the two may be positioned at a first level, and the second may be positioned at a second level, below the first level, each of said switches issuing a signal to the control unit when the liquid level is such so as to bring a floating magnet to the level of that magnetic switch. The signal issued by the control unit may be different with respect to the two different levels. For ex.ample, when the liquid level reaches the first switch, an alarm may be generated, and when the liquid level reaches the second switch, the control unit may issue a signal to stop the action which causes the liquid level to go down, e.g., stop the heating in the case of a cooldng pot of kettle. On the basis of an embodiment according to the second aspect of the present invention, a magnet-based liquid level control kit with an alarm is provided. Said kit is comprised of two main units: a magnet assembly to be located inside the liquid vessel, and a sensing assembly to be attached, usually but not necessary, to the exterior wall of said vessel, wherein the magnet assembly and the sensing assembly can be attached to each other before applying them to the vessel or be packed as separate units. Said sensing assembly may include a control device, optionally, an alarm-generating circuit, and a support rack, on which one or more displaceable magnetic switches are positioned. Said .kit can be portable, transferable, and used interchangeably with a wide variety of vessels. Regardless of the configuration (Mode A or Mode B), there are various means for positioning and displacing said displaceable actuatable switch and fudng it at a user selected level. Thus, for example, a magnetic switch can be positioned on a support rack juxtaposed adjacent to said vessel's side wall exterior surface and displaceable along said support rack; or, alternatively, it can be attached directly onto the vessel's side wall exterior surface by attaching it at different levels along the side wall, e.g., by use of a hook and pile type fastener switch (e.g., VELCRO-type). In a number of apparatus embodiments, designed according to the second aspect of the invention, under controlled magnetic parameters, such as poles direction, magnetic strength and distances, a single magnetic switch can be actuated by a magnet, at least at two, significantly different, pre-selected activation levels of the liquid. Therefore, instead of using multiple switches for generating signals at more than one pre-selected liquid level, a single actuation-pair composed of a magnet and a magnetic-switch can activate signals at more than one pre-selected level of said liquid. Thus, e.g., when such an apparatus is applied to a cooldng pot, an indication signal, like an alarm, is generated when the liquid level drops to a first pre-selected level, and a signal to shutdown the electrical heating of said vessel is generated when the liquid level drop further to a second pre-selected level. In accordance with a further, third, aspect of the present invention, a removably mountable liquid level control apparatus is provided, wherein the control is based on measuring changes in one or more physical properties related to said liquid, be it the liquid itself or the vapor of that liquid. Examples of said physical properties are electrical conductivity, light reflection, or the like. According to the third aspect, the apparatus comprises: at least one displaceable sensing probe with a sensing tip for sensing a physical property related to said liquid; a sensing-tip displacement unit, which enables the user to position the sensing- tip at a selected level; and a control assembly, connected to said probe, for issuing a signal when said liquid reaches the level of said sensing-tip, wherein said control assembly typically contains a) a power supply; b) a detection system; and c) an indicator alarm, e.g., an audio or visual alaπn device. If an optical property is sensed, the sensing probe typically includes: a light emitter source which transmits light (UV, visible, IR) to the sensing tip; an optical receiver, which measures the reflected light coming from the sensing tip; and an optical waveguide which enables an optical communication between the sensing tip and the optical receiver. The liquid level control apparatus, according to this aspect, is provided with one or more displaceable optical sensing tips adapted for positioning at respective user-selected levels and a controller responsively coupled to said sensing tip or tips for providing an output signal for at least activating an alarm device when the level of the liquid reaches the user-selected level. The liquid level control apparatus preferably provides an additional output signal for stopping the action leading to a change in the liquid level, e.g., for switching off the heat source heating the cooking pot, thus filling an important need in both commercial and domestic kitchens for at least preventing victuals in a cooldng pot from being ruined by cooldng beyond a predetermined level. Apparatus designed according to the third aspect of the present invention, can be mounted on the vessel at different ways. Thus, for example, it might be hanged on the vessel's rim or, alternatively, it can be mounted on a lid covering said vessel, wherein the lid has a small hole, preferably at the center of the lid, through which the sensing tip is can reach the liquid. Regardless of the specific aspect at which the apparatus according to the present invention is designed, the signal issued by the liquid level apparatus may be an alarm signal to indicate to the user, for example, that the level of liquid has gone down to the selected level, e.g. an audio or a visual signal. Also, it may be a signal to a device associated with said vessel, to stop the action which caused the liquid level to lower, e.g. a heating device in case of a cooldng pot or a kettle, a pump in case of a storage container; or both. In addition, the liquid level monitoring and control apparatus, according to the present invention may be powered by a conventional power source (i.e. a battery or mains supply), or it may be powered by a thermoelectric power supply adapted for intimate contact with a heating source, either the heating source itself, such as an electric plate, a gas burner or the like, the hot surface of the cooking pot itself or hot surfaces, heated directly or indirectly by the heating source, and thereby produces the necessary electric power to energize at least part of the electric components of said apparatus. Such hot surfaces might be, for example, the vessel's wall or the lid that cover the heated vessel. Among the impo.rtant features which characterize a liquid level apparatus according to the present invention are included: the apparatus can be readily adapted for a wide range of applications, and to enable convenient user access to exterior disposed displaceable actuating-member to allow placing it at different levels, selected by the user. The liquid-level sensing system may be designed such as to be usable with a variety of vessels of different size and shape and made of various materials. the apparatus is easily adapted for both open and sealed vessels, and every vessel with an interior inaccessible to user manipulation for various reasons (e.g., vessels holding hazardous material and/or having prohibitive conditions, such as high temperatures, which do not lend themselves to convenient user manipulation of interior disposed magnetically actuatable switches). the liquid level monitoring apparatus preferably provides an additional output signal for stopping the action leading to a reduction in the liquid level, e.g., for switching off the heat source heating the cooldng pot, thus filling an impcrtant need in both commercial and domestic .kitchens for at least preventing victuals in a cooking pot from being ruined by cooldng beyond a predetermined limit. liquid level apparatus according to the present invention is applicable also for liquids containing solid materials. the apparatus is portable and transferable between, and used interchangeably with, a wide variety of vessels, not necessarily identical in shape or depth. - the apparatus is perfectly suitable to be used as a kit These and other objects and advantages of the present invention will become more apparent upon reference to the following specification when taken in conjunction with the accompanying drawing. Brief Description of the Drawings In the drawings: Figs. 1 A, B and C are respectively an axial cross-section of a liquid level monitoring and control apparatus embodiment designed to one aspect of the present invention, an enlarged, detailed cross-section of the sensing assembly, and a schematic horizontal cross-section of said assembly, seen from the top; Figs. 2A, B and C illustrate different types of actuators and coπespondingly different types of .actuatable switches which can be used as activation-pairs in the apparatus described in Fig. 1 ; Fig. 3 is an axial cross-section of an apparatus, similar to that described in Fig. 1 , comprising a theimoelectric power generator; Figs. 4A, B and C illustrate different ways of supporting a liquid level apparatus, similar to that described in FigJ, in a liquid vessel; Figs. 5A, B are, respectively, illustrate two similar liquid-level apparatus as described in Fig. 4B, with or without the tubular-like filter, while Fig. C is an enlarged, top view, of a hook by which the apparatus is mounted on the vessel's rim. Fig. 6 illustrates the application of a liquid level apparatus, similar to that described in Fig. 1 , to vessels of different sizes; Figs. 7A1, A2 and Bl, B2 illustrate two different ways of changing the length of the floating-rod assembly; in an apparatus similar to that described in Fig. 1. Figs. 8 A, B, Cl and C2 illustrate three different ways by which a single or double optical reflector can actuate an optical-detector at two, significantly different, pre-selected levels, in an apparatus as that described in Fig. 1 ; Figs. 9 A, B, C are vertical cross section views and Fig. D is a top view of another type of optical actuation-pair. Figs. 10 A, B illustrate, in perspective and perspective cross-section, respectively, a liquid level monitoring and control apparatus, according to Fig. 1, the various components of which are integrated into a kit; Fig. 11 is an exploded perspective view of some components of the kit described in Figs 10A and 10B. Fig. 12 is a perspective view of a cooking pot with a liquid level apparatus configured according to an embodiment of Mode A of the second aspect of the present invention; Fig. 13 is a close-up cross-sectional view of the liquid level control apparatus of Fig. 1; Figs. 14 and 15 are enlarged perspective views of the two components, the floating magnet device and the magnetic switch, respectively, of the liquid level control apparatus of Fig. 13; Fig. 16 shows two embodiments of the extendable sleeve-like member accommodating the magnetic device; Fig. 17 is a perspective view of a cooking pot comprising a liquid level apparatus, which is simile, but with some modifications, to the embodiment of Fig. 12; Fig. 18 is a vertical cross-section of an electric kettle fitted with a liquid level apparatus designed according to Mode-B configuration of the second aspect of the invention. Figs. 19 and 20 are enlarged perspective views of the two components, the floating magnet device and the magnetic switch respectively, of the liquid level control apparatus of Fig. 18; Fig. 21 shows a vertical cross-section of a medical infusion drip chamber equipped with an appropriate liquid-level control apparatus, according to the present invention; Figs. 22 and 23 are enlarged perspective views of two components, the floating magnet device and the magnetic switch respectively, of the apparatus in Fig. 21 ; Figs. 24A and 24B show two embodiments of a liquid reservoir fitted with a liquid level apparatus configured according to Mode-A and Mode-B, respectively, embodiments of the invention; Fig. 25 shows a longitudinal cross-sectional view of a liquid level apparatus kit designed according to Mode-A configuration; Figs. 26A and B are enlarged perspective views of the sensing unit and of the float of the liquid level vertical apparatus in Fig. 25; Fig. 27, illustrates a vertical cross-sectional view of another liquid-level control apparatus, configured according to Mode-A of the present invention. Fig. 28A and B are, respectively, perspective views of the apparatus shown in Fig. 27, and enlarged cross-sectional view for part of the sensing assembly. Fig. 29, is a perspective view of a liquid-level apparatus, similar to that of Fig. 28, comprising thermoelectric generator. Fig. 30 illustrates in perspective view another embodiment of liquid-level apparatus, similar to Fig. 27, in which almost all components of the sensing assembly are packaged within one compact compartment, and suspended by a sp.ring-leaf member; Fig. 31 is an opposite perspective view of Fig. 30; Figs. 32A, B and C illustrate in detail the sensing assembly of Fig. 30. Fig. 33, is a vertical cross-sectional view of liquid-level apparatus, similar to that of Fig. 27, in which the displaceable switch is located and displaced along the interior side of the vessel's wall; Fig. 34 is a perspective vertical cross-sectional view of the apparatus of Fig. 33; Fig. 35 A, B and C are vertical cross-sectional views of the floating magnet assembly, according to Mode-A configuration, showing its ability of turning it;. Fig. 36 is a partial vertical cross-section of a cooking pot fitted with an optical apparatus designed according to a third aspect of the present invention; Fig. 37 is a enlarged cross-sectional view of the sensing tip of the apparatus of Fig. 36; Figs. 38A and 38B are, respectively, a close-up perspective view and a cross-section of the control unit shown in Fig. 36; and Fig. 39 is a side cross-sectional view of an apparatus, similar to that presented in Fig. 36, mounted on a lid and conjugated to a thermoelectric generator. Detailed Description of Preferred Embodiments The apparatus of Fig. 1-10 illustrate several embodiments designed according to a first aspect of the present invention, which are also, particularly adapted to be integrated into a kit that can be portable, transferable and usable interchangeably with a wide variety of vessels. With reference now to Fig. 1 A, B and C, a cooking pot is generally indicated at 20 and contains a liquid 21 at a level 22. The pot is provided with a lid 23, at the center of which there is an aperture 38. The cooking pot is heated, e.g. by an electrical, unit not shown. A sensing assembly, generally indicated at 24, is located above the lid 23 and supported thereby. It is illustrated at a greater scale in the detail of Fig. IB. The sensing assembly 24 comprises a casing 26 with a cover 26', wherein within casing 26 are included the components of the sensing assembly. The displaceable actuator member 27, which is mounted on rod 36, is also displaceable along that rod and fixable at a selected level on rod 36 by the leaf-spring aπest member 44. For example, but not necessarily, the components of the sensing assembly may comprise a battery 28, a control device 29, an actuatable switch 30, and an alarm 31. The casing 26 has a downward projection 33, which passes through orifice 38 of the lid 23. It further comprises an aperture outlet 32, which in many cases is required for minimizing of condensed vapor, of said liquid, from interfering or disturbing the free floating transition of the rod 36. A float 35, of Fig. 1A, is rigidly attached to the rod 36, and in operation is at least partially submerged within the liquid 21. A tubular-like screen filter 34 suπound both the float and the portion of the floating rod below the lid 23 to prevent foreign particles from interfering with the free transition of the rod 36. For this purpose, the filter member 34 is preferably made of mesh material. The rod 36 passes through cylindrical orifice 37 of casing 26, which constitutes the guide assuring the vertical orientation and motion of the rod 36. Said rod 36 carries the actuator 27, positioned above the sensing device 24. Float 35, rod 36 and actuator 27 move vertically as the liquid level 22 changes. When the liquid level has become low enough for actuator 27 to be within activating distance of the actuatable-switch 30, this latter is actuated, and in turn activates the control device 29 included in the sensing assembly 24. Fig. 2A, B and C shows essentially the same liquid level monitoring and control apparatus of Fig. 1, with three different options of actuation-pairs, each based on different physical property. Fig. 2 A, illustrates one sort of optical activation-pair which includes optical reflector 45, as an actuator, and optical detector 46 as the actuatable member. In Fig. 2B, a magnetic actuation-pair is presented, with a permanent magnet 47 as an actuator and reed-switch 48 as an actuatable switch. In Fig. 2C, the actuation is mechanic, wherein the mechanical member 49 can press the actuatable electrical switch 57 to close an electrical circuit and to cause a signal activation. The embodiment of Fig. 3 differs from that of Fig. 1 essentially because a thermoelectric generator, generally indicated at 50, is connected to the sensing assembly and is applied to the lid 23 of vessel 20 to provide the required power, instead of, or in addition to, a battery. Fig. 4, which is similar to the apparatus of Fig. 1, illustrates various ways of positioning the apparatus in a cooldng vessel. In Fig. 4A, the apparatus disposed as in Fig. 1. In Fig. 4B, the apparatus is hung on the rim of vessel 20, by the hook 41. In Fig. 4C, the apparatus is supported in quite a different way, and precisely, a base 52 is placed on the bottom of vessel 20 and serves to support the tubular filter 34 .and to keep it vertical. Tubular filter 34, in turn, supports the sensing assembly 24. In these figures, the apparatus is equipped with magnetic activation pair, with magnet 27' as an actuator member and actuatable magnetic-switch. Fig. 5 A and 5B illustrate, respectively, apparatus similar to that described in Fig. 1 with and without a tubular-like filter 34. In these embodiments, optical actuation-pairs are used which include an optical reflector and an optical detector. Fig. C is a top view of the hook member 41 Fig. 6 is similar to Fig. 1, but shows a means for mounting the apparatus on a universal lid, wherein the universal lid 23' can be used for different sizes of vessels, though the dimensions of the liquid vessel may change. If the liquid vessel, as vessel 20, is of a size coπesponding to that of the lid, the situation of Fig. 6 is similar to that of Fig. 1, but the same lid with the same liquid level apparatus can be used with a liquid vessel of smaller size, as indicated by 20' in broken lines. Also, it is shown that by using .an appropriate coupling member, like the spring leaf 51, the apparatus can be mounted on lids with apertures of different diameter. In this embodiment, the aperture in the lid, which is indicated herein as 39, is larger than aperture 38 of Fig. 1, and, in order to firmly couple the sensing assembly 24 and the tubular-like filter 34 to lid 23', and to seal the vessel 20 at its top, a leaf spring 51 is provided. Fig. 7A1, A2 and 7B1 and B2 illustrate two different foπns of extended floating rods by which the operation range of the apparatus can be controlled. In Fig. 7A1 and 7.A2, the floating rod has a telescopic structure, viz. comprises an outer tubular component 36' and an inner rod component 36", onto which the magnet 27' is fixed. By relatively sliding tube 36' and rod component 36", the length of the exposed rod, on which the user can displace the actuator to a selected level, can be changed. In the drawings, that length has been increased from Fig. 7A1 to Fig. 7A2, and consequently, the displaceable range of the actuator along the rod was also increased. Practically, this change increases also the operation range of the apparatus. In Fig. 7B1 and 7B2, the same result has been obtained by rendering the float 35 vertically adjustable, with respect to the rod 36. The float may be attached to an intermediate point of the rod, as seen in Fig. 7B1, or to the end thereof, as seen in Fig. 7B2, in which latter case, once again, the operation range of the apparatus can be changed. Usually, from the viewpoint of convenience, when the apparatus is not in use or when the maximum length of the extendable floating rod is not required during the operation of the apparatus, it should be kept as short as possible. Fig. 8A, B, Cl and C2 illustrate the operation of three optical reflectors, as optical actuators, wliich can be applied in apparatus of Fig. 1. Member 60, which is part of the sensing assembly, includes a light source, e.g. a LED, which emits splitted focused light in two different directions 61 and 61 ' and two optical detectors 58 and 58'. Variously shaped reflectors 55, 62 and 63-64, the last of which are a pair, operate as actuators, by reflecting the light emitted by the LED. However, while reflectors 55 and 62 each has two optical reflection surfaces, each of reflectors 63 and 64 has only one optical reflection surface. The sensors function as switches, by activating the control device when they sense the reflected light. Elastic means, such as 55', 62' and 63' and 64', hold the reflectors in position along the rod 36, while being sufficiently yieldable to permit sliding them along the rod to set the activating level or levels. If one considers Fig. 8A, it will be apparent that no reflected light is sensed by the sensor 58 as long as the liquid level is so high that reflector 55 is above the upper position shown in the Fig. As the level becomes lower, the reflector will reach said upper position, and the light emitted by the LED will be reflected by a surface of the reflector onto the optical detector 58 and a signal will be generated. As the level becomes still lower, no light will be sensed by the sensors until the lower position, shown in broken lines in the figure, is reached, and then the light 61 ' will be reflected by another surface of the reflector onto the detector 58' and a second signal will be generated. The first signal may be an alarm and the second a safety sign.al. The operation of the embodiment of Fig. 8B is essentially the same and the drawing requires no further explanation. In the embodiment of Fig. 8C, on the other hand, two optical reflectors 63 and 64 are mounted on rod 36 at different levels and each reflector has s single reflecting surface. Once again two signals are generated at two different activating levels, but greater freedom is attained in setting the activating levels, because their difference does not depend only on the angles of the reflecting surfaces, as in Figs, 8A and B, but also on the distance between the two reflectors, which can be varied as desired. Fig. 9A, B, C are vertical cross-sectional views, and Fig. D is a top view, of another type of optical actuation-pair, wherein Figs. 9A, B and C illustrate, for the same sensing assembly 24", three optical situation with relative locations of the optical actuation pair, during the drop in the liquid level in the vessel (not shown). In the present optical embodiment, light source 60" and optical detector 58", which are part of the sensing assembly 24", are arranged in such way that light emitted from source 60" can reach the detector 58" when light blocker 27", the actuator, is out of the light path 61". Fig. 9A presents a situation when the liquid level, within the vessel, is quite high, such that optical blocker is above the light direction 61" and light 61 " hits the detector 58". Fig. 9B presents the situation when the liquid level dropped, to bring blocker 27" to the light path 61" to stop light 61 " from hitting detector 58", which as a result a signal is generated by the control unit, not shown, wherein such signal can be activating an alarm. As the level of the liquid continues to drop, blocker 27" reaches a lower level, presented in Fig. 9C, where it does not block, anymore, the light 61 " from reaching detector 58". At this point, the control unit can generate a second signal, for example, to shut-off the power supply of the heating source. Fig. 10A, and 10B .are perspective views of a kit designed according to the aspect described in Fig. 1. The kit, which can be applied to the lid of the vessel, as has been already shown before, is transferable from one vessel to another. In Fig. 10A, the kit is generally indicated at 66, and comprises a sensing assembly 24' an actuator magnet 27', and a tubular-like screen filter 34. Fig. 109B is a perspective axi.al cross-section of the kit 66, showing the float 35, the rod 36 and some components of the sensing assembly like the buzzer 72 and the reed switch 73. Fig. 11, is an exploded perspective view, mainly of the sensing assembly of the kit shown in Fig. 10A and 10B. The casing of the sensing assembly comprises a body 70 and a lid 71, provided with the openings for the aeration of the components of the sensing assembly, in order to avoid overheating, each opening having a size matching the cooling requirements of the underlying component. These components comprise a buzzer 72, a reed switch 73 and a battery 74. Fig. 12 to 26 illustrate several embodiments according to a second aspect of the invention. Reference is first made to Fig. 12-16, showing a cooldng pot 200 containing a liquid 201 at a level 202, provided with a lid 203 and an integral electric heating unit 204, receiving electric power through mains lead 206. Fixed to the cooldng pot is a liquid level control apparatus, generally designated at 208, comprising a magnetic switch assembly 210 disposed on the cooldng pot's exterior surface, a floating magnet assembly 212 in the cooking pot's interior, and a control apparatus 214, mounted on the cooking pot by means of a hook member 216. The magnetic switch assembly and the control apparatus, together, constitute in this case the sensing assembly. Magnetic switch assembly 210 consists of a support rod 217 and a displaceable magnetically actuated switch 218 mounted on the rod 217 by means of a sliding element 220, whiereby the switch can be fixed at various levels along rod 217. Rod 217 is composed of two parts, 217' and 217", one fitted telescopically into the other, to allow it to assume various lengths for fitting on different vessels. Floating magnet assembly 212 has a floating magnet retaining sleeve 224, which is the guide sleeve, and a floating magnet device 228, which is accommodated within sleeve 224. Sleeve 228 is made of net material and therefore in liquid flow communication with liquid 201 in cooking pot 200, and is supported in place by means of spring-leaf support members 226 and 227. The control apparatus comprises a control device 230, a retractable-type electrical wiring 232 and an indicator member 233, which, in this specific case, is an audio signal generator, e.g., a loudspeaker. As will be appreciated, the signal may be other than audio, e.g., a light signal. The apparatus further comprises a thermoelectric unit 234, wliich generates electricity by the heat provided by heating plate 204. In operation, the user sets the level of magnetic switch 218, as desired, and then, if the level of the liquid decreases such that the floating magnet member 228 is at the level of switch 218, an alarm signal is generated. Retaining sleeve 224 may have various configurations, of which two embodiments are shown in Fig. 16. Sleeve 240a-242a, shown at the right of Fig. 16, is comprised of a tubular net, and sleeve 240b-242b, shown at the left of Fig. 16, is comprised of a tube with a bottom open end, which in this specific case is fitted with a sieve 238, so as to assure that the magnet is retained therein. As can be seen, both sleeve members are comprised of two portions, 240a, 240b and 242a, 242b, with the former fitted into the latter in a telescopic manner, to allow the retaining sleeve member to assume various lengths, whereby it can be fitted into different containers. Similarly, the sensing and control assembly 230 is removable for fixing onto different containers. Fig. 17 illustrates an apparatus embodiment very similar to that of Fig. 1 1 but with some modifications. The difference between the embodiments of Fig. 17 and that of Fig. 12 lies in the presence, in Fig. 17, of circuit breaker 244, and a second magnetic switch 246, in addition to switch 218. Circuit breaker 244 provides the electric power supply to control apparatus 214', and is further capable of disconnecting the electric power supply to mains lead 206. In the case of this embodiment, if the liquid level falls to the level of magnetic switch 218, an alarm is generated. If the level is reduced further to the level of magnetic switch 246, in addition to an alarm, the control apparatus disconnects the electric supply to mains lead 206, whereby heating is terminated. It will be appreciated that the switching off of the heat source may be achieved by various means other than those shown. For example, in the case of a gas heater, the control apparatus may switch off the gas supply by providing an electric signal to an electric switch in the gas system. Reference is now made to Fig. 18, showing the electric kettle 250 containing a liquid 251 at a level 252, having a lid 253, and an integral heating element 254, connected to mains lead 256. The kettle has a hollow handle 258, which is in liquid flow communication with the interior of kettle 250, and accommodates a floating magnet member 260, shown in perspective view in Fig. 19. In this case, the magnet has the shape of an annulus. The hollow handle, in this case, is a guide sleeve. Fitted on the ej ternal surface of handle 258 is a liquid level sensing and control apparatus 262, comprising a telescopic sliding support member 264, a sensing and control device 266 which includes a magnetic switch 267 attached to a control member 268, shown in perspective view in Fig. 20. Thus, when the liquid level decreases to a level below that set by the user, an alarm signal is generated. .Another embodiment, according to Mode B of the second aspect of the invention, can be seen in Fig. 21. Liquid container 270, e.g., a medical infusion drip ch.amber containing an infusion liquid 271 at a level 272, having a liquid inlet 273 and a liquid outlet 274, accommodates a ring-shaped floating magnet member 276, shown in perspective view in Fig. 22, which has an outer diameter slightly less than the inner diameter of container 270. Liquid level control apparatus 280 is fitted onto container 270 by means of an adapter 282, and comprises a sliding support member 284, a sensing and control device 285, containing a magnetic switch 286 and a control device 288, shown in perspective view in Fig. 23. In this case, container 270 is both the liquid vessel and the guide sleeve, which is rendered possible by its reduced cross-section. The function of the liquid level apparatus is similar to that described in connection with the previous embodiments, and reference is made to the description therein for a more detailed explanation of the structure and function. Fig. 24A and 24B show two liquid reservoirs, 290 and 292, which are fitted each with liquid level control apparatus 293 and 293', respectively two different embodiments, and having respective liquid inlets 294 and 296, and respective outlets, 298 and 300. In Fig. 24 A, reservoir 290 has a floating magnet member 302, accommodated within a sleeve 304, within the reservoir, and a sensing and control unit assembly 306, as that described in Fig. 12. In distinction from Fig. 24A, the liquid level apparatus in the embodiment of Fig. 24B is very similar to that described in Fig. 18, with a magnetic accommodating tube, 308, accommodating magnet 302', but otherwise, the manner of the sensing and control assembly in the embodiment of Fig. 24B is essentially similar to that of Fig. 24A. Reference is now made to Fig. 25, showing an embodiment of a liquid level control apparatus kit of said second aspect of the invention. The liquid level apparatus kit 310 comprises: a floating magnet assembly 312, which includes a telescopic sleeve-like net 313, holding a floating magnet 314 and fitted at its bottom with a magnet support member 315 holding a magnet 316 and a sensing and control assembly 318, including a telescopic sliding support member 320, fitted at its bottom with a magnet 322 with its magnetic poles being such so as to be attracted to magnet 316, and a control device 324 accommodating a magnetic switch 326, shown in perspective view in Fig. 26. The floating magnet unit assembly 312 and the sensing unit assembly 318 are connected to each other by a pliable wire or band 328. In use of the liquid level apparatus kit 310, the floating magnet assembly 312 is positioned inside a vessel (not shown), while the sensing unit assembly 318, is positioned outside the vessel. The floating magnet assembly and the sensing and control assembly are kept in close proximity to the vessel's interior wall and to the exterior wall, respectively, and also to each other by the pliable wire or band 328 at the top, and by the two magnets 316 and 322 at the bottom. The function of the control apparatus kit 310 is similar to that described in connection with the previous embodiments, and reference is made to the description for a more detailed explanation. Fig. 27 illustrates another embodiment of liquid-level apparatus configured according Mode-A of the present invention. Fig. 28 illustrates a liquid vessel 400, partially shown; a guide screened sleeve 460, in which a floating magnet, comprising of a permanent magnet 465 encapsulated within float 466, is located; the housing and the suspensions of the various parts of the apparatus. The sleeve 460, preferably made of mesh material, has free flow communication with the liquid 401 in vessel 400. In this embodiment, components of the sensing assembly, is contained in a supporting housing 462, except the magnetic-switch 464 which is is housed in a base 463. The housing 462 also houses in, a strap 472 made of a couple of conjugated elastic stainless steel leaf springs which are electrically insulated from each other by an appropriate coating. The strap 472 has several, very important, functions: a) it supports the magnetic switch 464, by holding the magnetic switch housing 463; b) it enables to set the magnetic switch at a selected level; c) strap 472 serves also as the electrical connection between the magnetic switch to the other components of the sensing assembly located within housing 462; d) during operation, the elasticity of the leaf-spiings in strap 472 keeps the magnetic switch to be, always, in an intimate contact with the vessel's wall 400, to bring the magnetic switch as close as possible to the path of the floating magnet located inside the vessel. The adjustment of the magnetic switch 464 at any selected level is done can be done by drawing the strap 472 in or paying it out by its terminal portion 473, or by drawing the strap 472 through the window 474 of housing 462. The bending of strap 472 in housing 462, in addition of reducing the space of the apparatus, also prevents the strap 472 from sliding down by gravity. The plate 469, which is the lower part of the magnetic switch housing 463, keeps the magnetic switch from overheating by the heat-source (not shown) located, usually, under the vessel. Fig. 28A .and 28B, are perspective views of the items of Fig. 27, and with the same numbering of the items. As can be seen in Fig. 28B, all the components of the sensing assembly, except the magnetic switch 464, are compactly arranged inside the housing 462. In this specific embodiment described in Fig, 28, the components of the sensing assembly which are housed in housing 462, include: a battery 468 and a buzzer 470. The opening (window) 474 in housing 462 has a dual purposes: a) it is a place where the user can draw, by his finger, the strap 472 for adjusting the level of the magnetic switch 464; b) graduated marks (not shown) on the strap 472, which can be seen through the window 474, tell the observer what is the exact level of the activation point of the magnetic switch 464. Fig. 29 illustrates a similar apparatus of Fig. 28 with some modifications. In the embodiment of Fig. 29 the housing 462' does not contain a battery and a thermoelectric generator 480, located under magnetic switch 463' powers the buzzer 470. Like strap 472 of Fig. 28, strap 472' in the present embodiment is ,usually, comprised of at least two conjugated and electrically insulated straps. Strap 472, has several functions, which among them are included: a) it support the thermoelectric generator 480, which is hung on it; b) it enables the adjustment of the level of the thermoelectric generator 480 by a similar mechanism, described for the adjustment of the level of magnetic switch housing 463 of Fig. 28; c) strap 472' serves also as the electrical communication between the magnetic switch (not shown), the thermoelectric generator 480 and other parts of the sensing assembly, located in housing 462'. In addition, strap 472', which slidingly passes through magnetic switch housing 463', enables manual displacement, by sliding mechanism, of magnetic switch housing 463' and to fix it at a selected level. In this embodiment of Fig. 29, the thermoelectric generator 480 has dual functions. Firstly, it supplies power to the buzzer 470 .and secondly, since it is in close intimate contact with the wall of the heated vessel 400, it protects the magnetic-switch from overheating. That overheating can be caused by the heat source (not shown) located under vessel 400. Reference is now made to Fig. 30 to 32, which are perspective views of another embodiment similar, in some sort, to that embodiment described for Fig. 28. Contrary to Fig. 28, in the embodiment of Fig. 30 to 32 all of the elements of the sensing assembly are housed in a housing 482, and support housing 481 which is hung on the vessel's rim by a hook 467. In this embodiment, the sole function of housing 481 is to support strap 472'. The sensing assembly has the structure illustrated in Fig. 32, which shows an outer perspective view seen from two opposite directions in Fig. 32A and B, while it is seen in exploded view, divided into two parts, in Fig. 32C. As seen, housing 480 which has in both sides aeration openings 484 and 484' to prevent overheating, contains the reed switch 483, the battery 468 and a buzzer 470. The strap 472' is similar and has the same functions and operation modes as strap 472, which has been described in details for Fig. 27, except that in the embodiment of Fig. 30 the strap 472' is not used for electrical communication. Fig. 33 and 34 are vertical cross-sectional views which illustrate another embodiment, similar to the embodiment apparatus shown in Fig. 28, except that, in the embodiment of Fig. 33 and 34, the displaceable magnetic switch 464' and the strap 487, which hold and enables displacing and fixing switch 464 at a selected level, are located inside the vessel, usually immersed in the liquid and juxtaposition to the sleeve 460. Also, the mech.anism for adjustment the level of the magnetic switch 464 is based, in this case, on a rolling mechanism controlled by .knob 493 seen in Fig. 34. In the embodiment of Fig. 33 and 34, the battery and the buzzer (not shown) are contained within housing 482', which is provided with outlets 490 and 491. Strap 487, which is rolled within housing 482' and run to the magnetic switch 464 through outlet 490, is attached to the magnetic switch 464 and help, as will be explained, to displace and fix the switch at a selected level. In addition, strap 487 also serves as electrical communicator between magnetic switch 464 and other part of the sensing assembly located in housing 482'. Strap 486, which it is also rolled in housing 482' and .runs generally parallel to strap 487 and also controlled by l nob 493, passes through outlet 491, so that turning knob 493 will cause rolling or unrolling of straps 486 and 487 within housing 482'. However, in contrast to strap 487 where one of its ends runs inside vessel 400 and more precisely within rail 488 for supporting the magnetic switch 464, the coπesponding end of strap 486 runs outside the vessel 400. Rail 488, which is integrally connected to support 467', is the member within which strap 487 runs whenever the level of the displaceable switch 464 has to be adjusted. The rail 488 constrains the displacement of switch 464 to the vertical direction and keeps it in close proximity to the floating magnet path. Strap 486 located outside of vessel 400 serves as visual indicator. The location of the exposed end 486' of strap 486, which runs in close proximity to the vessel's wall, provides the observer with a visiral indication about the location of the usually unseen switch 464, located inside vessel 400. Fig. 35A, B and C are side views of part of the floating magnet assembly of Fig. 27, where the sleeve-like member can be pivotally rotated to increase the functional range of the apparatus. Fig. 35 A and B illustrate a screened sleeve 460 containing a floating magnet 466 within which a permanent magnet 465 is encapsulated at the top of float 466. Sleeve 460, which is provided with an axis-rod 477', is connected to hook 467 via tubular member 477, which is the lower part of hook 467, in such that sleeve 460 with its content can be pivotally rotated by axis 477'. Fig. 35C is the same as Fig. 35B except that in sleeve 460 with its content was rotated around pivot 277' by 180°. As can be seen, in Fig. 34B the transition range of the floating magnet within the sleeve is the range 461, which, practically, is one of the operation range of the apparatus. However, the coπesponding range according to Fig. 35C is the range 461 ' that enables another function rage for the apparatus. Practically, these two options, presented in Figs.35B and 35C, for positioning the sleeve, increase the functional range of the apparatus. .An embodiment of said third aspect of the invention is illustrated in Fig. 36 to 39. In Fig. 36, a cooldng pot 500, containing a liquid 501 to a level 502, having a lid 503, and which is seen herein heated by gas burner 504, is fitted with a liquid level control apparatus 506. Apparatus 506 has a control device 508, mounted on the cooldng pot by me.ans of a hook member 510, a sensing probe 512, and a thermoelectric unit 514, which provides electric power generated by the heat emitted by gas burner 504. As can be seen in the enlarged cross-sectional view in Fig. 37, sensing probe 512 contains two optical waveguides, 515 and 516, the distal ends of which, viz. the ends housed in a sensing tip, interact optically with a prism 520 or equivalent optical device. While waveguide 515 leads light emitted from light source 518, shown in Fig. 38B, to prism 520, the other waveguide, 516, leads light back from prism 520 to the photodetector 522 (see Fig. 38B). As long as the sensor tip is immersed in liquid, a certain amount of light will be dispersed into the liquid, as represented by aπow 524 in Fig. 37, and once the liquid level goes down below the sensing tip, more light will be reflected through waveguide 516 to the photodetector 522, and then an alarm signal will be generated. The structure of the control device 506 can be seen in Fig. 38A and 38B. It comprises an external housing 530 and an internal cylindrical housing 532, which is rotatable within the external housing. This rotation can be induced by means of control .knob 534. The sensing probe 512 is wound or has a pro.ximal segment which is wound onto internal housing 532, and thus, by rotation of knob 534, the probe, comprising the two waveguides and the sensor tip, can be extended or retracted through opening 538 in external housing 530, with a coπesponding change in the level of the sensor tip within the liquid, said level being the actuating level. In this embodiment, therefore, the prism or equivalent optical device, together with the waveguides, is the actuator, and the photodetector is the actuatable member. As can further be seen in Fig. 37B, in addition to the light source 518, which may be a light-emitting diode (LED) or a laser, and photodetector 522, the control device further comprises a control processor 526 and an alarm sign.al generator 528, e.g., an audio signal generator. Fig. 39, illustrates the same optical liquid-level apparatus of Fig. 36, except that, in the present embodiment of Fig. 39 the apparatus is mounted on a lid 503' of vessel 500'. The mounting of the apparatus on lid 503' is done through a passage 539 in lid 503'. In addition, thermoelectric generator 514', as a power supply, is conjugated to the apparatus. While specific embodiments of the invention have been described for the purpose of illustration, it will be understood that sldlled persons may carry the invention into practice with many modifications, variations and adaptations, without exceeding the scope of the claims.

Claims: CLAIMS 1. A liquid level apparatus for monitoring and control the liquid level in a liquid containing vessel and providing a signal when the liquid has reached a predetermined level, said apparatus comprising; - a floating-rod assembly comprising of a rod rigidly conjugated to a float wherein, in operation, said floating-rod floatingly move, in response to changes in the level of said liquid, in such that the longitudinal axis of said rod is generally parallel to the vertical direction, and wherein the lower part of said rod is connected to said float while the upper end of said rod is exposed above said liquid. - at least one displaceable and fixable actuator, which is one component of an activation-pair, mounted on said rod, wherein said actuator is fixable at a user selected level, and wherein, in operation, after said actuator has been fixed at a certain position on said floating-rod, it will floatingly move together with said floating-rod, and wherein said actuator can cause an actuation of an appropriate actuatable member. - means for displacing said actuator along the longitudinal axis of said rod and fixing it at a selected position on said rod. a sensing assembly comprising: a) at least one actuatable-member, wliich is the second component of said actuation-pair, wherein said actuatable-member can be actuated by said actuator once the level of said liquid reaches the predetermined level; b) an indicator; and c) a power supply, wherein said power supply energizes at least part of said sensing assembly; and wherein said sensing assembly, preferably also comprising a control-unit, is issuing a signal once said actuatable-member has been actuated by said actuator. - means for guiding and restraining the transition of said floating-rod to the vertical direction a support member, preferably mounted on the rim of said vessel, on which at least part, preferably all components of said apparatus is mounted. - a casing member, housing at least part, preferably all, components of said apparatus. 2. Apparatus according to Claim 1, wherein said actuator is annular-shaped slipped on said rod to be positioned coaxial to the longitudinal axis of said rod. 3. Apparatus according to Claim 1, wherein the same actuator can cause actuation of said actuatable-member at more than one pre-selected level, to generate more than one separate signals, wherein at least one of said actuation occurs when said actuator reaches a level which is higher than the level of said actuatable-member, and the other actuation occurs when said actuator reaches a level which is lower than the level of said actuatable-member. 4. Apparatus according to Claim 1, wherein said means for displacing and fixing said displaceable actuator, to hold it at a selected level on said rod, is based on a sliding mechanism 5. Apparatus according to Claim 1, wherein said mean, for displacing and fixing displaceable actuator at a selected level, is done by connecting said actuatable-member to a sliding-element provided with an aπest member allowing the sliding it along said rod and fixing it at a user selected level. 6. Apparatus according to Claim 1 , wherein said rod is removeably attached to said float. 7. Apparatus according to Claim 1 , wherein said floating-rod is extendible. 8. An apparatus according to claim 1, wherein structural features are provided in the casing of the sensing assembly and in the vessel lid for mutually and removably connecting them to each other. 9. Apparatus according to Claim 1, wherein said float is located inside a filter- like member, wherein said filter-like member has a free flow communication with said liquid while keeping out particles which might disturb the free vertical transition of said float within said filter-like member allowing a free vertical transition of said floating- rod. 10. Apparatus according to Claim 9, wherein the filtering is achieved by including a net-mesh type screen in said filter-like member. 11. Apparatus according to Claim 9, .wherein said filter-like member is removably attached to other component of said apparatus. 12. Apparatus according to Claim 1, wherein at least part but preferably most of components of said sensing assembly are located in a single compartment. 13. Apparatus according to Claim 1,. wherein said support member is a lid and wherein said lid is mounted on the rim of said vessel. 14. Apparatus according to Claim 1,. wherein said support member is a hook mounted on said vessel. 15. A casing member according Claim 1, having means for guiding and restraining the motion of said rod to allow, in operation, a free transition of said rod in a generally vertical direction along the longitudinal axis of said rod. 16. Apparatus according to Claim 1, having an appropriate outlet aperture for minimizing liquid-vapor condensation, resulting from said liquid, in some area of ht apparatus, wherein such vapor might disturb the free transition of the floating-rod. 17. Apparatus according to Claim 1, wherein said actuation-pair type is based on at least one physical property. 18. .An apparatus according to Claim 17, wherein said physical property is of a magnetic type. 19. An apparatus according to Claim 17, wherein said physical property is of an optical type. 20. An apparatus according to Claim 17, wherein said physical property is of an audio type. 21. An apparatus according to Claim 17, wherein said physical property is of an electrical conductivity type. 22. .An apparatus according to Claim 1 , wherein the same backbone, incuding the same casing and the same floating-rod assembly of said apparatus is compatible with different types of actuation pairs. 23. Apparatus according to claim 18, wherein at least one of said actuator is a permanent magnet and at least one of said actuatable-member is a magnetic switch. 24. Apparatus according to claim 17, containing at least one light source, preferably a LED; at least one optical detector functioning as said actuatable-member and at least one displaceable optical reflector functioning as said actuator having a reflection surface that can actuate at least one of said optical detectors. 25. Apparatus according to claim 24, wherein said optical reflector has at least two reflection surfaces wherein one of said surfaces causes generation of a signal when said optical reflector reaches one of the pre-selected level, preferably when said reflector is at a higher level than said optical detector, while the other of said reflection surfaces causes generation of another signal when said reflector reach another pre-selected level, preferably, when said reflector is at a lower level than the level of said optical detector.. 26. Apparatus according to claim 24, wherein at least two separate reflectors each separately displaceable along said rod, are mounted on said road at different level. Wherein the lower reflector actuate one of said optical detector corresponding to the higher predetermined level of said liquid and the higher reflector actuates the same or other optical detector coπesponding to the lower pre-selected level of said liquid. 27. Apparatus according to claim 20, containing at least one acoustic source at least one acoustic detector functioning as said actuatable-member and at least one acoustic reflector functioning as said actuator wherein said reflection surface can actuate at least one of said acoustic detectors. 28. Apparatus according to claim 27, wherein said optical reflector has at least two reflection surfaces wherein one of said surfaces causes generation of a signal when said acoustic reflector reaches one of the pre-selected level, preferably when said reflector is at a higher level than said optical detector, while the other of said reflection surfaces causes generation of another signal when said reflector reach another preselected level, preferably when said reflector is at a lower level than the level of said acoustic detector. 29. Apparatus according to claim 27, wherein at least two separate reflectors each separately displaceable along said rod, are mounted on said road at different level, wherein the lower reflector actuate one of said acoustic detector coπesponding to the higher predetermined level of said liquid and the higher reflector actuates the same or other acoustic detector coπesponding to the lower pre-selected level of said liquid. 30. Apparatus according to Claim 21, wherein said actuator is mechanical actuator and said actuatable-member is an electrical-switch with two electrical conductors, in such that once said mechanical actuator touch one of said conductor said electrical-switch is actuated, causing a signal generation. 31. A liquid level apparatus for monitoring and control the liquid level in a liquid containing vessel and providing a signal when the liquid has reached a predetermined level, the apparatus comprising: a floating-actuator assembly comprising a floating actuator member accommodated within said vessel or in a liquid duct in liquid communication with said vessel, which floats on said liquid and which is guided to move with the liquid level in a vertical path proximal to an internal wall of said vessel; and a sensing assembly, preferably located outside of said vessel, comprising; a) at least one displaceable and fixable actuatable-switch, wherein said switch is fixable at a user-selected level proximal to the vessel's, preferably, exterior surface and parallel to said vertical path of said magnet, and wherein said actuatable-switch can be actuated by said actuator once the level of said liquid reaches the predetermined level; and b) an indicator; and c) a power supply, wherein said power supply energizes at least part of said sensing assembly; and wherein said sensing assembly, preferably also comprising a control-unit, is issuing a signal once said actuatable- member has been actuated by said actuator. 32. Apparatus according to Claim 31, wherein the vertical movement of said floating actuator is guided by an elongated sleeve-like member situated proximal to the vessel's interior surface and having free liquid flow communication with said vessel. 33. Apparatus according to claim 32, wherein the sleeve-like filter member is pivotally suspended from a flexible support member and is rotatable about the suspension pivot point, in such that by flipping said sleeve, together with said floating- actuator, upside down, the functioning range of said apparatus can be changed. 34. Apparatus according to Claims 31 to 33, wherein said sleeve-like member is extendible. 35. Apparatus according to Claim 32, wherein said sleeve-like member is a filter- like member, keeping out particles present in said vessel which might disturb the free vertical transition of said floating actuator, from entering inside said filter-like member. 36. Apparatus according to Claim 31 , wherein said displaceable actuatable switch can be positioned directly onto the exterior wall of said vessel. 37. Apparatus according to Claim 31 , wherein said displaceable actuatable switch is positioned at a user selected level by a hook-and-pile type fastening means. 38. Apparatus according to Claim 31 , wherein said displaceable actuatable switch is attached to a support member. 39. Apparatus according to Claim 38, wherein said support member is extendible. 40. Apparatus according to Claim 38 and 39, wherein said displaceable actuatable switch is connected to a sliding element provided with an aπest member allowing the sliding of said magnetic switch along said support member and fixing it at a user selected level. 41. Apparatus according to Claim 38, wherein said actuatable switch is supported by a strap, preferably made of elastic stainless steel leaf spring, wherein said strap is preferably passing through a control housing and supported therein, in such a way that it may be paid out of the control housing or withdrawn into it, said strap being connected to said actuatable switch, whereby to adjust the level of said switch at a selected level. 42. Apparatus according to Claim 41, wherein said strap is served as the electrical communication between said switch and other parts of the sensing assembly. 43. Apparatus according to Claim 31, wherein each of the floating actuator assembly and the sensing assembly, are separate assemblies. 44. Apparatus according to Claim 31, wherein said floating magnet assembly and said sensing assembly are integrally connected to one another. 45. Apparatus according to Claim 31, wherein the floating actuator device has an external shape and diameter such that it is fitted snugly within the vessel, with the magnet device's external rims being in close proximity to the interior surface of said vessel 46. A liquid level Apparatus according to Claim 45, wherein said vessel is cylindrical and said floating actuator has an annular shape. 47. Apparatus according to Claim 46, wherein said vessel is a medical infusion drip chamber. 48. Apparatus according to Claims 45 and 46, wherein said floating actuator is disposed in a vertical tube which is located outside said vessel and which is in liquid- flow communication with said vessel. 49. Apparatus according to claim 31, wherein said floating actuator is a floating permanent magnet and said actuatable switch is a magnetic switch. 50. Apparatus according to claim 1 , wherein the physical property of the actuation-pair is of an optical type. 51. A liquid level monitoring and control apparatus, comprising: - at least one displaceable sensing probe having a sensing tip, for placing within the liquid inside said vessel, for sensing physical property related to said liquid; means by which said sensing-tip is displaced to allow the user to position the sensing tip at a selected level in said vessel; a control unit device connected to said sensing-tip and to a power supply, for issuing a signal when the level of said liquid reaches the predetermined level. 52. Apparatus according to Claim 51, wherein said physical property is electric conductivity. 53. Apparatus according to Claim 51, wherein the said physical property is an optical property related to said liquid and wherein the sensing probe includes a light emitter source which transmits light to the sensing tip, an optical receiver, which measures the reflected light coming from the sensing tip, and a waveguide which enables an optical communication between the sensing tip and the said receiver. 54. Apparatus according to any one of Claims 1, 31 and 51, wherein components of said apparatus is integrated to form a compact and transferable kit. 55. Apparatus according to any one of Claims 1, 31 and 51, wherein all components of the sensing assembly are integrated into a compact and transferable unit. 56. Apparatus according to any one of Claims 1, 31 and 51, wherein said vessel is a heated vessel holding liquid, to be heated. 57. Apparatus according to claim 56, wherein the liquid is water. 58. Apparatus according to Claim 56, wherein the vessel is a cooldng pot or a kettle. 59. Apparatus according to any one of Claims 1, 31 and 51, wherein said signal activates an alarm. 60. Apparatus according to any one of Claims 1, 31 and 51, wherein said signal interrupts the action which gives rise to a reduction in the liquid level. 61. Apparatus according to Claim 56, having a thermoelectric power supply, with a thermoelectric unit, for powering at least one electric component of said apparatus. 62. Apparatus according to Claim 61, wherein said thermoelectric power supply is heated directly by the heating source. 63. Apparatus according to Claim 61, wherein said thermoelectric power supply is attached to a hot surface, wherein said surface is heated as a result of said heating source. 64. Apparatus according to Claim 63, wherein said hot surface is hot walls of said vessel. 65. Apparatus according to Claim 63, wherein said hot surface is a lid to said vessel.

Inventors: ISSACHAR DAVID, ISSACHAR, DAVID
Applicants: ISSACHAR DAVID, ISSACHAR, DAVID
Application year: 1998
Main classification: G01F23
IPC codes: G01F23