referring to fig1 , there is shown a coffee machine 1 provided with a float switch 2 according to an embodiment of the invention . the coffee machine 1 comprises a water reservoir 3 into which the desired amount of water is filled for the preparation of coffee . a tube and / or hose system 4 adjoins the water reservoir 3 and functions to supply water to a filter holder 5 . the tube segment 6 which starts directly at the water reservoir 3 is connected to a float switch 2 according to the invention . the float switch 2 comprises an upper float casing part 7 and a lower float casing part 8 . the lower casing part 8 for the float is connected via an angled tube 9 to a heating unit 10 . a vertical tube 12 adjoins the heating unit 10 via a hose connection 11 . a seal 13 connects the vertical tube 12 to an overflow 14 which functions to conduct the water heated with the heating unit 10 into the filter body 5 . once it passes through a filter bag in the filter holder 5 , the liquid then flows into a glass carafe 15 . the glass carafe 15 rests on a warming plate 16 which is heated by an additional heating unit 17 . it follows from fig1 that the float switch 2 is arranged below the water reservoir 3 , within the tube system 4 , and does not determine the geometry of the water reservoir 3 . the water reservoir can thus be cleaned easily since there is no interference from a detection device for determining the water level . owing to the integration of the float switch 2 in the tube system , a simple and cost - effective design is created . the float switch 2 is shown in further detail in fig2 and 3 . a seal 8 is inserted between the upper casing part 7 and the lower casing part 8 . seal 8 is designed to seal the two casing parts , which are snapped together , against each other . a sensor 21 is installed in a tubular extension 20 that adjoins the underside 19 of the lower float casing part 8 . the sensor 21 is secured easily with the aid of an elastic clamp or spring 22 to prevent it from sliding out of the tubular extension 20 . fig1 and 12 show that the tubular extension 20 is provided with grooves or recesses 23 for inserting the elastic clamp 22 . the sensor 21 can thus be installed easily and can then be secured permanently in the installed position . a float 24 is located in the lower float casing part 8 . the float 24 illustrated in fig4 consists of a float body 25 and a float bottom 26 . these two components are joined with the aid of a cylindrical locking connection and are protected against penetrating water with the aid of an o ring 27 . a magnet 28 is arranged in the float bottom 26 . as shown in fig1 , this magnet 28 can be inserted easily into a holding space formed by ribs 29 that are arranged in a cross - shaped pattern . to ensure a secure function of the float switch 2 , the position of the magnet 28 cannot change . however , the snap - in connection between the float body 25 and the float bottom 26 is sufficient to lock in place the magnet 28 . once this locking connection is established , a spacer 30 that is formed onto an upper inside of the float body 25 is located at a very short distance to the magnet 28 , so that when the magnet 28 shifts it hits the spacer 30 , thus preventing a displacement of the magnet 28 in the float bottom 26 which would interrupt the function . a shown in fig5 and 7 , the water - carrying part of the float switch 2 consists of a supply tube 31 , a drain tube 32 , and a float guiding region 33 which is embodied similar to a bypass . the float guiding region 33 is formed by a casing wall of the lower float casing part 8 and a wall segment 34 that is embodied circular cylindrical . for this , the casing wall and the circular - cylindrical wall segment 34 are provided with narrow , vertically extending wall ribs 35 . the bottom region of the float guiding region 33 preferably contains four narrow , horizontally extending bottom ribs 36 . these bottom ribs 36 form the support surface for the float 24 . as a result , it is possible to embody the contact surface of the float 24 with the lower float casing part 8 with minimum dimensions . in this way , possible adhesion forces between the float 24 and the lower float casing part 8 can be minimized to ensure an uninterrupted upward movement of the float 24 . the bottom ribs 36 and the wall segment 34 are provided with chamfered surfaces for the unmolding during the production process . fig3 shows the situation where the water reservoir 3 and the float switch 2 do not contain water . in that case , the distance is at a minimum between the magnet 28 and the sensor 21 which reacts to the magnetic field of the magnet 28 . in this position , the sensor 21 transmits a corresponding signal to an electronic component , not shown herein , of the heating unit 10 . the electronic component in that case prevents current from flowing through the heating unit 10 , thus also preventing an overheating of the device if it no longer contains any water . if water is filled once more into the water reservoir 3 , the water is distributed throughout the tube system 4 of the coffee machine 1 , on the basis of the principle of communicating tubes . in that case , the float switch 2 is also filled with water . the float 24 is designed such that its total density is less than that of the water , thus resulting in buoyancy for the float 24 which then moves toward the top in the lower float casing part 8 . in fig7 , the float 24 is shown in this upper position . the buoyancy of the float 24 is limited by a stop face in the form of a rib 37 that is integrated into the upper float casing part 7 . as a result , the float 24 can only move in the float guiding region 33 and cannot tilt while in the upper position . for a secure function , the buoyancy of the float 24 should not be interfered with by frictional forces caused by contact with the wall of the lower float casing part 8 . this is ensured by the arrangement and the embodiment of the narrow vertical wall ribs 35 , wherein other types of guide mechanisms can also be provided . during the filling of water into the coffee machine 1 , the air in the water - carrying part of the device must be allowed to escape . to make it easier for the air in the float switch 2 to escape , one wall region 38 of the upper float casing part 7 is embodied cone - shaped above the float guiding region 33 . this cone - shaped wall region 38 ensures that during the filling in of water and the associated upward movement of the float 24 , the air in the float switch 2 can escape easily toward the top . the supply tube 31 is additionally connected to a separating rib 39 to ensure an easier discharge of the air . as a result , the air rising along the cone - shaped wall region 38 can rise toward the top along one side of the separating rib 39 while the inflowing water can flow in unhindered on the other side of the separating rib 39 . if no more water is added , then the water finally also flows out of the float switch 2 . to prevent residual water from remaining inside the float switch 2 , the bottom of the lower part 8 of the float casing is provided with a slanted drain surface 40 . the corresponding bottom region 41 is also embodied slanted in the drainage direction for the water , so that the water can drain out in the region of the circular cylindrical wall segment 34 . as a result , it is ensured that residual water in the float switch 2 can always drain securely in the direction of the drainage tube 32 , thereby avoiding micro - biological problems caused by residual moisture . it will be understood that the above description of the present invention is susceptible to various modifications , changes and adaptations , and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims
a device for the preparation of hot water includes a water reservoir , a tube system coupled to the water reservoir and a heating unit to heat the water passing through the tube system from the water reservoir . a float switch detects a water level in the water reservoir . the float switch includes a float arranged in the tube system to measure the water level in the water reservoir and a sensor responsive to the float to transmits a signal to an electronic component to activate the heating unit in dependence on the water level in the water reservoir .