Fluid handling – Self-proportioning or correlating systems – Fuel controlled by boiler or water system condition
Patent
1997-01-15
1999-03-02
Bennett, Henry
Fluid handling
Self-proportioning or correlating systems
Fuel controlled by boiler or water system condition
251214, 251 58, F23N 100
Patent
active
058758070
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND AND SUMMARY OF THE INVENTION
The submitted invention concerns a fitting, especially as applied in a continuous flow water heater to control gas flow depending on water flow. Thereby the fitting has a gas control housing, a water control housing and a mechanical transmission which transmits a control motion, depending on the water flow and arising preferably from a Venturi tube and a membrane in the water control housing, extending initially from the interior of the water control housing, then outwards to a valve controlling the volume of gas within the gas control housing.
Fittings for continuous flow water heaters usually consist of gas and water components. In these fittings, gas control is activated by a hydraulic adjusting drive, which produces a particular stroke to control the volume of gas depending on the volume of water flowing through the fitting. Thereby the stroke starts mostly at particular minimal value, determined by the necessary volume of gas required to ignite the burner, and finishes at a particular maximum value which is determined by the technical layout of the gas burner and the heat exchanger.
As already discussed above and, for example, as shown in DR-PS 647 449, a control device, located in the water component, has a membrane through which the control housing is divided into chambers which are connected via pipes with parts of the fluid pipe which lies before and behind a pressure regulating valve. A gas pressure switch, located in the gas component, has a valve with a valve body which is moved by a further member. The membrane is controlled by pressure difference produced by a pressure regulating valve in a gas pipe leading to the burner. The control device is connected via a rod with a valve body belonging to the pressure regulating valve.
Another fitting for a continuous flow water heater is described in WO 94/00716. In this case, a control device, designated as a flow switch, is located in the water component and serves as a water deficiency safety device. This flow switch has a high pressure chamber and a low pressure chamber which are separated from each other by a membrane. The membrane is supported on a membrane plate rigidly connected with a rod which itself is sealed and leads out of the low pressure chamber. Thereby the membrane, membrane plate and rod form the adjusting drive for a gas volume control valve arranged in the gas component.
The construction of the fittings described in the above named patent documents have a problem in that the rod, serving to transmit the stroke, carries out an axial motion. Due to this axial motion, the rod transports water particles despite a seal being present. In order to prevent water particles getting into the gas control space, it is usually necessary that there be an air space between the water and gas control spaces. Additionally, the rod is made in two pieces. The problem still remains that by increasing rod stroke due to increasing water usage, a film of water on the rod is brought outside by the axial motion and assisted by the water pressure. This film of water evaporates in the air and leads to calcareous deposits on the rod. During the backstroke of the rod, due to decreasing water usage, this calcareous layer is drawn through the seal which damages the seal and thus leads to greater leakage. Furthermore, the control deviation of the continuous flow water heater is enlarged due to the increasing friction of the rod. Especially by the reduction of the volume of water flowing through, the volume of gas is no longer sufficiently reduced which leads to water temperatures being too high and the corresponding hazards to the user arise. The calcareous deposits can extend so far that the gas volume control valve remains open when the water supply is completely cut-off, which leads to destruction of the continuous flow water heater if special over-temperature protection device is not present.
By the employment of grease seals, double gaskets and ceramic guides, one can indeed delay these negative consequences but water tr
REFERENCES:
patent: 2126378 (1938-08-01), Feidler et al.
patent: 2258590 (1941-10-01), Merten
patent: 3327761 (1967-06-01), Rowell
patent: 4200258 (1980-04-01), Gliatas
patent: 4299373 (1981-11-01), Troyer
patent: 4457486 (1984-07-01), DeFrees
patent: 4655239 (1987-04-01), Kato
Bennett Henry
Kim Joanne Y.
Mertik Maxitrol GmbH & Co. KG
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