The invention relates to a tank drainage device for fresh water tanks on rail vehicles.
Rail vehicles, in particular passenger rail vehicles, frequently contain fresh water tanks for supplying sanitary units, galleys or the like. Because these tanks may contain drinking water, they are liable to freeze up if the vehicle is stationary for any length of time in cold weather conditions. While the vehicle is in operation, this danger does not exist because the tanks are generally arranged in the heated interior, typically in the ceiling above the sanitary unit. If the contents of a fresh water tank freeze, the vehicle cannot be used since the sanitary facilities are not operational and the vehicle needs to be warmed up in a heated hangar. Due to the large volumes of water, amounting to approx. 300 liters, such a process can take several days. If pipelines are damaged as a result of the water freezing, they have to be repaired. In order to solve this problem, rail vehicles containing fresh water tanks are fitted with automatic drainage devices which drain off a filled tank by means of a drainage valve if the temperature of the tank falls below a predefined level. These devices require an electrical power supply, which is provided by means of an onboard battery when vehicles are parked up. It is necessary to design said drainage devices as energy-efficient in order to enable the protection to be maintained over a relatively long period of time (several weeks). Furthermore, it is important that the drainage devices do not trip incorrectly, since such a vehicle (with empty fresh water tank) can be used only subject to severe restrictions or, as the case may be, the tank can be refilled only in certain stations.
The object underlying the invention is therefore to disclose a tank drainage device for fresh water tanks on rail vehicles which prevents false trips and is power-saving.
The object is achieved by means of a tank drainage device having the features recited in claim 1. Advantageous embodiments are the subject matter of dependent claims.
According to the basic concept of the invention, a tank drainage device is constructed for a fresh water tank of a rail vehicle, wherein a thermostatic switch is thermally coupled to the fresh water and, in the event of the temperature in the tank falling below a predefined temperature, triggers a timing element, which thereby opens a drainage valve for a predefined period of time, and wherein the thermostatic switch is arranged on a drainage line.
The advantage that is achievable by this means is that a fresh water tank of a rail vehicle is able to be drained automatically in the event of the temperature falling below a predefined minimum temperature.
According to the invention, a thermostatic switch is provided which is arranged in such a way that it is able to detect the temperature of the fresh water. In particular it is advantageous to arrange the thermostatic switch at those parts of the tank or drainage system which are first to become blocked by freezing water if the outside temperature drops. The drainage line discharges the water out of the railcar body into the outside environment and is immediately exposed to the ambient temperature, so the thermostatic switch should be arranged on said drainage line. Furthermore, a frozen drainage line would prevent the tank from being emptied in any case.
One embodiment variant of the invention provides using a thermostatic switch having a difference of less than 5 Kelvin between the turn-on value and the turn-off value. Conventional thermostatic switches have much greater switching point differences, with the consequence that the drainage process is initiated at much higher temperatures than necessary. Conventional thermostatic switches have neither the necessary switching point precision nor the necessary low switching point hysteresis. By using a thermostatic switch according to the invention (precision thermostatic switch) it is possible to dimension the tripping temperature considerably closer to zero degrees Celsius, typically to a value of two degrees Celsius. Such a thermostatic switch has a precision of one degree Celsius, which means that the drainage process is initiated between one and three degrees Celsius in any event.
Conventional thermostats, in contrast, must be set to much higher temperatures due to their imprecisions, a drainage process commencing already at approx. ten degrees Celsius in particularly unfavorable cases. Owing to the high precision of the thermostatic switch according to the invention, the turn-off threshold can be dimensioned to a value of four degrees Celsius, such that, given a precision of one degree Celsius, the thermostatic switch will interrupt the drainage process at any event in a temperature range between three and five degrees Celsius. Such a thermostatic switch has a difference of less than 5 Kelvin between the turn-on value and the turn-off value.
Conventional tank drainage devices are equipped with a device for measuring the fill level; such a device is not necessary in the case of the present invention. The advantage that is realizable by this means is that it is possible to achieve a reduction in the energy consumption of the tank drainage device, since in general the fill level is measured by means of an ultrasonic sensor and such a sensor requires electrical energy for its operation.
The current fill level of the fresh water tank is irrelevant in the case of the tank drainage device that is the subject matter of the present invention, since the thermostatic switch triggers a timing element which opens a drainage valve for a predefined period of time. Said period of time needs to be coordinated with the volume of the tank and the discharge volume per unit time through the drainage line in order to ensure that the tank is emptied in any event. In this case the timing element is typically required to be set to a drainage time of 30 minutes in the case of conventional tanks.
Another embodiment variant of the invention provides not to supply the energy supply of the timing element continuously with voltage, but likewise to take said energy supply from the signal transmitted by the thermostatic switch. In such a manner the energy consumption of the tank drainage device can be reduced to zero during the time up to the tripping (commencement of draining). A thermostatic switch has zero energy consumption, the timing element triggered by it consuming energy only during the drainage process, as also does the drainage valve actuated by the timing element. In such a manner a tank drainage device can be constructed which imposes only a minimum load on the vehicle power supply and as a result ensures the longest possible period of use of the tank drainage device for a specific battery capacity.
By way of example:
1 Tank
2 Drainage valve
3 Inlet
4 Outlet, drainage line
5 Supply line
6 Timing element
7 Thermostatic switch
8 Ultrasonic sensor
9 Control device
V Voltage supply
Number | Date | Country | Kind |
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A50433/2012 | Oct 2012 | AT | national |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2013/070502 | 10/2/2013 | WO | 00 |