Abstract:
A volume compensation device for a hot water heater composed of a water tank equipped with a cold water inlet and a hot water outlet, for heating and storing water, the device including: a bellows enclosing a variable volume chamber; a conduit connected for placing the chamber in flow communication with the interior of the tank; and a pressure or temperature controlled lifting mechanism coupled to the bellows for varying the volume of the chamber in response to a temperature related change in the volume of the water in the tank.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a volume compensation device for hot water heater including a water tank equipped with a cold water inlet and a hot water outlet, in which tank the water to be heated can be heated and stored. 
     Low pressure or open hot water heaters, as for example hot water storage devices, are constantly in communication with the atmosphere by way of an overflow pipe. The overflow pipe must never be closed because it must always be possible for water which expands when the contents of the water tank are heated to escape through the overflow pipe. The quantity of discharged overflow or expansion water is a function of the increase in temperature and the volume in the water tank. In most cases, the expansion water is discharged through the overflow pipe or through the tap or discharge faucet of a mixing arrangement suitable for low pressure devices. 
     This drop-by-drop discharge of expansion water results in calcium deposits at the discharge opening of the consumer tap and at the opening of the overflow pipe. On the one hand, such continuous dripping may annoy the consumer while, on the other hand, such calcium deposits also produce unsightly crust formations at the chrome-plated discharge pipes of the mixing device. Moreover, such deposits also reduce the discharge cross section of the overflow pipe. This may produce dangerous dynamic pressures. Regular and complicated decalcification with acid containing media is thus unavoidable. 
     German Pat. No. 3,040,450 discloses a hot water heater equipped with a volume compensation device for its water tank in which water can be heated and stored in a tank equipped with a cold water inlet and a hot water outlet. The water tank has an associated temperature responsive regulator with which the volume of the water tank can be changed according to the temperature-specific expansion of the volume of the stored water. This regulator is configured either as a temperature responsive, curvable, bimetal expandable bottom inserted into a wall region of the water tank, or the regulator is an expansion zone provided in an annularly circumferential wall region of the water tank, with the expansion of this zone in a direction axial to the plane of the ring being variable as a function of temperature. Alternatively, the regulator is variable in length as a function of temperature and is clamped in between two mutually facing, elastically deflectable membrane walls of the water tank. Moreover, the regulator may be variable in length as a function of temperature and may be supported at one end at a wall of the vessel and at its other end at a compressible membrane chamber disposed at the opposite wall of the water tank. According to another possibility, the regulator is variable in length as a function of temperature and is clamped in between two oppositely disposed walls of the water tank, with the water tank being provided with an annularly circumferential wall region around its longitudinal axis which is elastically expandable in the direction of the longitudinal axis. The regulator is then either a bimetal expansion rod, a bimetal strip or a hydraulic regulator which includes a cylinder equipped with a chamber containing a liquid which expands when heated and charges a membrane or a piston. 
     To equip such water tanks with curvable bimetal expansion bottoms or with membrane-like side walls in mass production requires enormously large expenditures for tools. Moreover, the introduction of a curved bimetal strip between two oppositely disposed elastically expandable walls of the water tank is handled, with respect to manufacturing technology, only with great difficulty and involves high installation costs. Since the water tank is subjected to constant mechanical changes in movement, only costly bronze sheet metal can be used as the wall material in such cases. If the otherwise customary thin copper sheets were used as the material for the tank, the water tank would tear open at the points of expansion after a relatively short period of operation because of these alternating mechanical stresses and would thus no longer be tight. The use of inexpensive plastic tanks, which must have relatively thick walls, is also impossible because of their relative rigidity. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide, by simple means, a reliably operating volume compensation device for a hot water heater which can be manufactured and installed at low cost and operates extremely reliably. 
     The above and other objects are accomplished, according to the present invention, by a volume compensation device for a hot water heater composed of a water tank equipped with a cold water inlet and a hot water outlet, for heating and storing water, which device includes: a bellows enclosing a variable volume chamber; conduit means connected for placing the chamber in flow communication with the interior of the tank; and pressure or temperature controlled lifting means coupled to the bellows for varying the volume of the chamber in response to a temperature related change in the volume of the water in the tank. 
     Advantageous further features of the invention are described below. 
     The advantages to be realized with the present invention are, in particular, that, instead of a change in the volume of the entire water tank, only a small part thereof, in the form of a membrane-like bellows, accommodates the maximum developing quantity of expansion water during the heating process. Then, practically no alternating pressure stresses develop, a fact which ensures a long service life for the water tank. Another advantage is that the use of inexpensive plastic water tanks is also possible. 
     Several advantageous embodiments of the invention are illustrated in the drawing figures and will be described in greater detail below with reference thereto. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal cross-sectional view of a low pressure hot water storage vessel for under-the-counter operation including a device disposed in the water inlet pipe for increasing the volume of the water tank according to an embodiment of the invention . 
     FIG. 2 is a longitudinal cross-sectional view of a low pressure hot water storage vessel for under-the counter operation including a bimetal device disposed in the middle of the bottom of the water tank for enlarging the volume of the water tank according to a further embodiment of the invention. 
     FIG. 3 is a longitudinal cross-sectional view of a low pressure hot water storage vessel for under-the-counter operation including a device disposed at the lower end of its water inlet pipe for enlarging the volume of the water tank according to a further embodiment of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The low pressure hot water heater shown in FIGS. 1-3 is designed as a hot water storage vessel for under-the-counter operation. This vessel includes an outer jacket 1 a cold water connection pipe or conduct 2 with inlet pipe or conduit 3 and inlet openings 3&#39;, a hot water connecting pipe or conduit 4 and a water tank or water storage container 5 having a bottom 6. The water tank 5 is enclosed on all sides and the bottom by thermal insulation 7, 7&#39;. At the bottom 6 of water tank 5 there is fastened a heating means or rod 8 in a manner not shown in detail. A temperature regulating element 9 keeps the contents of water tank 5 constantly at a preselected temperature. 
     Below the bottom 6 of water tank 5 there is a flanged area 10 for accommodating conventional electrical connection members (not shown) and member having controllable interior volume or a variable volume bellows 11. 
     FIG. 1 now shows an embodiment in which one end of a curved pipe or conduit 12 is fastened at the bottom or bottom wall 6 of water tank 5 while the other end of pipe 12 is introduced from the bottom into bellows 11 so that pipe 12 places the interior of tank 5 in communication with the interior of bellow 11. In this embodiment, bellows 11 is precisely centered below inlet pipe 3 ending in the bottom region of water tank 5 and is in communication with the contents of water tank 5. 
     A plunger 13 with a piston 13&#39; and a compression spring 14 are fastened to the upper side of bellows 11 and extend through a water-tight passage 15 into the lower end of inlet pipe 3 so that plunger 13 and piston 13&#39; are axially movable in pipe 3. To limit the upward stroke of plunger 13, the interior of inlet pipe 3 is shaped to present delimiting nubs 16. The plunger 13, piston 13&#39;, spring 14, and nubs 16 together are referred to as an automatic means for controlling the interior volume of the bellows 11. This automatic means, the bellows 11, and the connecting conduit 12 together are referred to as an overflow preventing means. 
     Upon initiation of a water withdrawal process, the dynamic pressure existing in inlet pipe 3 is utilized to move piston 13&#39; and its plunger 13 downwardly. This causes bellows 11 to be compressed and thus its volume to be reduced. The contents of bellows 11 are forced through curved pipe 12 into water tank 5 before cold water flows into tank 5. 
     Only when piston 13&#39; is in its lower position will it open inlet openings 3&#39; in inlet pipe 3 so that fresh water is able to flow into water tank 5. At the end of the water withdrawal process, plunger 13 is brought back into the illustrated rest, and closing, position by means of its compression spring 14. This simultaneously permits bellows 11 to expand. This expansion process is additionally supported by the static water pressure in tank 5. During this process, bellows 11 removes from water tank 5 the quantity of water which is reproduced by expansion when the contents of tank 5 are heated. That is, the water level existing in tank 5 is reduced by the amount which will be restored when the contents of tank 5 are heated, without expansion water now flowing out above hot water connection pipe 4. For this purpose, bellows 11 is dimensioned to have an available volume such that, in its expanded state, bellows 11 is able to hold at least four percent of the contents of tank 5. 
     In the embodiment shown in FIG. 2, a spirally wound bimetal strip 17 anchored firmly at the bottom 6 of tank 5 expands and compresses bellows 11 by way of a pull rod 18 fastened to the free end 17&#39; of strip 17 and to the bottom 11&#39; of bellows 11 so as to enlarge and reduce the volume of the bellows (these items together being referred to as an automatic means for controlling the interior volume of the bellows 11). The interior of bellows 11 is again in communication with the interior of tank 5 by way of a short pipe 19. Bellows 11, short pipe 19, pull rod 18, bimetal strip 17 (which together are referred to as an overflow preventing means) and heating rod 8 form a unit that can be introduced into tank 5 from the bottom in a manner which permits easy installation and replacement and is flanged to the bottom 6 of tank. 
     When the water in the lower part of the tank 5 is in a cold state, generally at the end of a water-withdrawal process, bimetal strip 17 is deflected upwardly and bellows 11 has its smallest volume. During the subsequent heating process for the contents of tank 5, bimetal strip 17 is deflected more and more downwardly and thus continuously increases the volume of bellows. In this way, the water level in tank 5 is prevented from rising and so is the escape of expansion water. To optimize the deflection of bimetal strip 17 during the heating process, the strip is provided with a heat return means via heat bridges or the like from heating rod 8. 
     FIG. 3 shows an embodiment in which inlet pipe 3 is a variable length rapid response member which expands and compresses bellows 11 by way of a lever mechanism 20. For this purpose, inlet pipe 3 is extended downwardly through a water-tight passage 15&#39; in the bottom 6 of tank 5 and is provided with an extension 21&#39;. Lever mechanism 20 is pivoted at the lower end 21 of this extension 21&#39; and at a bearing block 22 fixed to tank bottom 6. During each water-withdrawal process, inlet pipe 3 is cooled by the inflowing water and contracts to pivot the lever mechanism 20, due to its attachment to extension 21&#39;, in a direction to reduce the volume of bellows 11. When the contents of tank 5 are heated, inlet pipe 3 expands again, which results, in turn, in expansion of bellows 11 and thus in an increase in its available volume. The lever mechanism 20, extension 21&#39;, inlet pipe 3, and bearing block 22 together are referred to as an automatic means for controlling the interior volume of the bellows 11. This automatic means, the bellows 11, and the conduit 19 together constitute an overflow preventing means. A thermocouple (not shown) between heating rod 8 and inlet pipe 3 supports this process. 
     The invention now being fully described, it will be apparent to one of ordinary skill in the art that many changes and modifications can be made thereto without departing from the spirit or scope of the invention as set forth herein.