ELECTRIC HEATING DEVICE

Abstract

An electric heating device for emitting a heated air flow, in particular for a sanitary room or washroom in a rail-borne vehicle, includes an air duct, a fan generating the air flow, a heating element heating the air flow and a first over-temperature switch. The first over-temperature switch can reversibly switch off the heating element when a first over-temperature is exceeded. A second over-temperature switch can irreversibly switch off the heating element when a second over-temperature is exceeded. The second over-temperature switch is disposed in a recess, depression or opening formed in the air duct. The second over-temperature switch has a disconnect or isolating switch to be thermally triggered for switching off the heating element. The thermally triggered disconnect or isolating switch can be triggered by a glass sphere or bead that breaks when the second over-temperature is exceeded.

Claims

1-10. (canceled)

11. An electric heating device for emitting a heated air current, the electric heating device comprising: an air duct having a recess formed therein; a fan disposed in said air duct for generating the air current; a heating element disposed in said air duct for heating the air current; a first over-temperature switch configured to reversibly switch off said heating element upon exceeding a first over-temperature; and a second over-temperature switch disposed in said recess and configured to non-reversibly switch off said heating element upon exceeding a second over-temperature; said second over-temperature switch including a thermally-triggered isolating switch for switching off said heating element, said thermally-triggered isolating switch having a glass sphere bursting upon exceeding the second over-temperature for triggering said thermally-triggered isolating switch.

12. The electric heating device according to claim 1, wherein the air current heats a sanitary room in a rail-borne vehicle.

13. The electric heating device according to claim 1, wherein said thermally-triggered isolating switch includes a switch and a switching mechanism having a switching element being prestressed by a spring, said switching element non-reversibly opening said switch upon triggering said switching mechanism.

14. The electric heating device according to claim 13, wherein said glass sphere holds a fluid expanding under an influence of heat and causing said glass sphere to burst upon exceeding the second over-temperature, and said switching element prestressed by said spring is triggered as a result of said glass sphere bursting.

15. The electric heating device according to claim 11, wherein said thermally-triggered isolating switch is disposed directly in a current path for supplying current to said heating element.

16. The electric heating device according to claim 11, wherein said air duct has an opening forming said recess, and a hat-shaped heat shield covers said opening.

17. The electric heating device according to claim 16, wherein at least one of said air duct or said hat-shaped heat shield is formed of sheet metal.

18. The electric heating device according to claim 11, wherein the air flow in the air duct flows in a flow direction being predetermined by said fan, and said recess is disposed upstream of said heating element in said flow direction.

19. The electric heating device according to claim 16, which further comprises: a two-part housing having first and second independent housing units disposed adjacent one another; said air duct being disposed in said first housing unit; said first and second over-temperature switches being disposed in said second housing unit; said opening being formed between said first housing unit and said second housing unit; and said hat-shaped heat shield being disposed in said second housing unit.

20. The electric heating device according to claim 19, wherein said housing units are two respective non-flammable troughs disposed one above the other.

21. A fan heater for heating a sanitary room in a rail-borne vehicle, the fan heater comprising: an electric heating device according to claim 11.

Description

EXAMPLES AND DRAWINGS

[0033] The invention is further explained hereinunder with the aid of preferred exemplary embodiments with reference to the attached drawings.

[0034] In the drawings:

[0035] FIG. 1 illustrates a rear view of an electric heating device in accordance with a first preferred embodiment of the invention, and

[0036] FIG. 2 illustrates a functional switching circuit of the exemplary embodiment shown in FIG. 1.

[0037] FIG. 1 illustrates an electric heating device 1 for rail-born vehicles in accordance with a first preferred embodiment of the invention. The figure illustrates essentially a rear view of the heating device 1 and the rear wall of a housing 16 is not illustrated.

[0038] It is evident from FIG. 1 that the heating device 1 comprises a two-part housing 16 having a first and a second housing unit 17, 18 that are embodied independently from one another. The housing units 17, 18 are embodied in the form of two non-flammable troughs that are arranged one above the other.

[0039] As is evident in the detail shown in FIG. 1, an air duct 2 is formed in the first housing unit 17 that is arranged at the bottom in FIG. 1. Furthermore, the housing unit 17 comprises an inlet 12 that is arranged on the right-hand side in FIG. 1 and an outlet 13 that is arranged on the left-hand side.

[0040] The air duct 2 extends between the inlet 12 and the outlet 13. A fan 3 is arranged in the air duct 2 and said fan produces an air flow in a flow direction 14, in FIG. 1 from right to left, in other words from the inlet 12 illustrated on the right-hand side to the outlet 13 illustrated on the left-hand side. The inlet 12 and the outlet 13 are embodied on the front face of the heating device 1 so that in the case of the rearward illustration they are covered in part by in each case a sheet metal guide 15.

[0041] As is illustrated in FIG. 1, the housing 16 comprises moreover a connection 19 for a data plug and also a mains connection 20 as a current supply.

[0042] The heating device 1 comprises a thermostat sensor 5 and a heating element 4 and they are both arranged in the air duct 2. A thermostat 6 for controlling the temperature of an air flow that is flowing out of the outlet 13 is positioned in the second housing unit 18 that is arranged at the top in FIG. 1. For this purpose, the temperature in the air duct 2 is ascertained by the thermostat sensor 5, a signal is transmitted to the thermostat 6 and on this basis the thermostat 6 controls the heating element 4 as explained in detail hereinunder.

[0043] The heating device 1 comprises furthermore a first over-temperature switch 8 that is embodied so as to be reversible. The first over-temperature switch 8 comprises a sensor 7 that is arranged in the air duct 2 above the heating element 4. The sensor 7 is embodied as a temperature sensor. As illustrated in FIG. 2, the current path 21 connects the heating element 4 to the mains connection 20. The first over-temperature switch 8 is embodied so as to interrupt the current path 21 in the case of an over-temperature being ascertained using the sensor 7.

[0044] Furthermore, an opening device 306 of the thermostat 6 is arranged in the current path 21. If the temperature that is ascertained by the thermostat sensor 5 exceeds a predetermined upper desired temperature, the current path 21 and consequently the current supply to the heating element 4 are interrupted by way of the opening device 306. If the temperature that is ascertained by the thermostat sensor 5 is below a predetermined lower desired temperature, the current path 21 is connected by way of the opening device 306 and the current supply to the heating element 4 is possible.

[0045] Moreover, an opening device 308 of the first reversibly switching over-temperature switch 8 is arranged in the current path 21. If the temperature that is ascertained by the sensor 7 of the first over-temperature switch 8 exceeds a first over-temperature, the current path 21 and consequently the current supply to the heating element 4 is interrupted by way of the opening device 308. If the temperature that is ascertained by the sensor 7 of the first over-temperature switch 8 is below the first over-temperature, the current path 21 is reconnected by way of the opening device 308 and the current supply to the heating element 4 can be resumed.

[0046] The heating device 1 comprises furthermore a second over-temperature switch 10 that is embodied so as to be non-reversible. The second over-temperature switch 10 comprises an isolating switch that is not illustrated separately in the figures. The second over-temperature switch 10 is arranged in the air duct 2 in the flow direction 14 upstream of the heating element 4. Since the over-temperature switch 10 is arranged in the flow direction 14 upstream of the heating element 4, during a problem-free operation only cold air flows through said over-temperature switch. The over-temperature switch 10 heats up in the event of a build-up of heat, in other words as the volume flow that is usually flowing through the air duct 2 reduces. The cause of such a reduction in flow can be by way of example a malfunction of the fan 3 or foreign bodies that are present upstream of the inlet 12 or outlet 13 or in the air duct 2.

[0047] The second over-temperature switch 10 is thermally connected to the isolating switch so that a switching procedure is triggered directly as a result of a thermal influence on the over-temperature switch 10. For this purpose, the isolating switch comprises a non-reversible switching mechanism that is not illustrated separately in the figures and a switch that is embodied in this exemplary embodiment as an opening device 310.

[0048] In detail, the switching mechanism comprises a switching element, which is prestressed by a spring, and a glass sphere that holds a fluid that can expand by way of thermal expansion. The glass sphere can be destroyed as a result of thermal expansion of the expandable fluid in the case of the second over-temperature being exceeded. The switching element that is prestressed by means of the spring can be triggered as a result of the destruction of the glass sphere. In this embodiment, the switching element is embodied as a bridge so as to open the opening device 310.

[0049] As is evident from the switching circuit illustrated in FIG. 2 showing the function of the heating device 1 illustrated in FIG. 1, the opening device 310 is arranged in the current path 21 of the heating element 4 so that the opening device 310 of the second over-temperature switch 10 interrupts the current path 21 upon being actuated. Owing to the fact that the isolating switch is actuated in a non-reversible manner, the interruption in the current path 21 is likewise non-reversible. During a problem-free operating mode, the opening device 310 of the second over-temperature switch 10 is closed.

[0050] Furthermore, FIG. 2 illustrates a loop circuit 24 of a signal/fault line that can be connected by way of connection clamps 23 to a monitoring or maintenance device. The loop circuit 24 can be interrupted by an opening device 308 of the first over-temperature switch 8 and consequently signal a malfunction to a monitoring or maintenance device.

[0051] As is evident from FIG. 1, the housing units 17, 18 are essentially separate from one another. Switching-on elements of the heating device 1 are arranged in the second housing unit 18, in other words the thermostat 6, the first over-current switch 8, the second over-current switch 10 and the clamp holder 11. Feedthroughs for supply lines for the thermostat sensor 5, the sensor 7, the heating element 4 and the fan 3 are arranged between the housing units 17, 18 in order to connect them to the switching-on elements. Furthermore, the housing units 17, 18 comprise a common opening 9, wherein the opening 9 is covered on the side of the second housing unit 18 by a hat-shaped heat shield 22. The hat-shaped heat shield 22 limits the extent to which the air flow can spread through the opening 9.

[0052] The opening 9 is located in the flow direction 14 upstream of the heating element 4 so that the part of the air flow that passes through the opening 9 is not heated during the problem-free operation.

[0053] In the event of a malfunction which causes a backlog of warm air against the flow direction 14, warm air passes through the opening 9 into the volume formed by the hat-shaped heat shield 22. The second over-temperature switch 10 that is arranged at this site becomes warm as a result of the backlog of air and interrupts the current path 21 if the second over-temperature is exceeded.