EP0624891B1 - Switching device for sacrificial anode - Google Patents

Abstract

A membrane (diaphragm) (6) is provided for an electrical switching device for indicating the consumption of a sacrificial anode in a water heater. In the event of consumption, the membrane (6) snaps over and triggers an indication via a contact body (14). In order to improve the functional reliability, an additional sealing body (10), which supports the contact body (14), is seated on the moving section of the membrane (6). <IMAGE>

Description

The invention relates to an electrical switching device for displaying the consumption of a sacrificial anode in a water heater, wherein a membrane is arranged in a measuring space connected to an interior of the sacrificial anode, which seals the measuring space from a contact chamber in which switching contacts located in a display circuit are arranged are connectable by means of a contact body movable with the membrane in a switching stroke.

Such a switching device is described in DE-GM 79 32 910. After a long period of operation, the sacrificial anode used to protect the water tank from corrosion in the water heater can be used up. Water can then enter the interior of the sacrificial anode, causing the membrane to bend under the action of the water pressure. This triggers a display signal that is an indication of the consumption of the sacrificial anode.

Such a display can only be expected after a long time, for example after a few years of operation of the water heater. It cannot be ruled out with certainty that the membrane has become leaky after such a long time, for example due to embrittlement. If this is done, then water can get into the contact chamber in the switching device according to DE-GM 79 32 910. On the one hand, this makes the membrane jumping around unsafe and, on the other hand, arises via the water an electrical connection between one of the live switch contacts and the water tank. The possibility of such a state does not meet safety requirements and can endanger the user. Otherwise, the water tank may also corrode in such a case if the water heater continues to operate due to the lack of a display signal.

In DE-GM 79 32 910, a simple contact bridge is provided as the contact body, which in the case of a display contacts the switch contacts. Such contacting appears in particular to be unreliable because, over time, oxide layers can form on the switching contacts and / or the contact body, which impair the necessary electrical contacting in an emergency. According to DE-GM 79 32 910, a two-point support of the contact bridge is provided on the switch contacts. If the contact bridge is displaced or tilted, contact may become unsafe.

In the older patent application P 42 40 591.2, an additional safety device is described for a switching device of the type mentioned at the outset, in which an earth contact is arranged in the contact chamber and lies outside the switching stroke of the contact body.

The object of the invention is to propose an electrical switching device of the type mentioned, the function of which is ensured even after a long time.

According to the invention, the above object is achieved in a switching device of the type mentioned at the outset in that a sealing body is seated on the movable section of the membrane and carries the contact body, the Sealing body seals the contact chamber against the membrane.

This considerably increases the safety of the switching device. If the membrane leaks in terms of water technology, the sealing body still seals the contact chamber from the measuring chamber when the sacrificial anode is consumed. So even with a leaky membrane, no water can get into the contact chamber, so that no undesired electrical short circuits can occur there.

If the membrane of the sacrificial anode is so far leaky that it no longer jumps under the water pressure that then occurs, then the further sealing body is displaced by the water pressure in such a way that it moves the contact body against the switching contacts, as a result of which the desired consumption is displayed.

The further sealing body can be stuck to the membrane. Preferably, however, the sealing body sits loosely on the membrane, so that when the membrane is so far leaky that it no longer bounces under the water pressure, it is rather moved under the water pressure and thereby moves the contact body to the switching contacts without the membrane having to take it with them.

The further sealing body can consist of a pressure plate and at least one sealing sleeve arranged on it or at least one sealing ring arranged on it. Preferably, however, the sealing body forms the pressure plate and the sealing sleeve in one piece.

In an embodiment of the invention, the sealing collar is arranged so that water breaking in through the membrane supports its sealing effect.

The figure shows a switching device for the display the consumption of a sacrificial anode schematically on average.

An electric water heater has an enamelled water container in which a sacrificial anode is arranged. In this there is an interior into which a connecting piece is screwed. The sacrificial anode is held on the water tank by means of the connecting piece.

Outside the water tank, an electrical switching device (1) is screwed onto the connecting piece by means of an internal thread (2). A sealing ring (3) is provided for sealing. The internal thread (2) is formed on a first housing part (4) of the switching device (1). An elastic membrane (6) made of plastic is clamped watertight between the first housing part (4) and a second housing part (5) of the switching device (1). The two housing parts (4, 5) are held together by means of a U-shaped ring (7). A measuring chamber (8) is formed in the first housing part (4) and is connected to the interior of the sacrificial anode via a channel (9).

On the middle, movable section of the membrane (6) sits a sealing body (10), which consists in one piece of a pressure plate (11) and a sleeve (12). It would also be possible to form the sealing body (10) in two pieces, the pressure plate (11) and the sleeve (12) each representing a separate component.

The outer circumference of the cuff (12) lies sealingly against the second housing part (5). It is movable in this. There is an intermediate chamber (13) between the membrane (6) and the sleeve (12). The sleeve (12) is arranged such that water entering the intermediate chamber (13) via the membrane (6) causes the sleeve (12) presses outwards on the second housing part (5) and thus increases their sealing effect.

In the second housing part (5), a contact disk (14) is fastened centrally to the sealing body (10) and is loaded by a compression spring (15) supported in the housing part (5). The contact disk (14) can carry a soft layer of tin.

In the second housing part (5) there is a contact chamber (16) between the sealing body (10) or the contact disk (14) and the housing part (5). Two switching contacts (17, 18) are arranged on the second housing part (5) and protrude into the contact chamber (16) with tips (19). Like the housing part (4), the housing part (5) consists of an electrically non-conductive plastic. The tips (19) lie in a plane essentially parallel to the contact disk (14), so that the contact disk (14), especially its tin layer, when the membrane (6) jumps over in its switching stroke (H) on the two switching contacts (17, 18) stops. If a three-point support is to be designed instead of this two-point support, then a stop lug can be formed on the housing part (5) in addition to the two tips (19).

The functioning of the switching device described when the sacrificial anode is consumed, i.e. when water penetrates into its interior and thus into the measuring space (8), is approximately as follows:

If the membrane (6) is still watertight when water enters the measuring chamber (8), then it jumps under the water pressure. It moves the sealing body (10) and thus the contact disk (14) so that it meets the switch contacts (17, 18), whereby the switch contacts (17, 18) are electrically connected. A signal lamp, not shown, now lights up. This is an indication of the need to exchange the Sacrificial anode.

If the membrane (6) is already porous when water enters the measuring chamber (8), or if it leaks when pressurized due to embrittlement, then water enters the intermediate chamber (13). Because of the sealing sleeve (12) of the sealing body (10), water from the intermediate chamber (13) cannot get into the contact chamber (16). Under the water pressure, the sealing body (10) is again moved so that the contact disk (14) meets the switching contacts (17, 18).

If the membrane (6) is so permeable to water when it enters the measuring chamber (8) that it can no longer jump around, the sealing body (10) becomes as described under the pressure of the water entering the intermediate chamber (13) postponed. He does not need to take the membrane (6) with him when he sits loosely on it.

Claims (6)

1. Electrical switch gear to indicate the consumption of a sacrificial anode in a hot water heater, where a membrane is installed in a measuring room which is connected to an interior room of the sacrificial anode, this membrane seals off a contact chamber which houses switching contacts which can be connected using contact bodies which can be moved by one lift of the membrane which activates the switch.
   This is characterised by the fact that a sealing body (10) sits on the movable section of the membrane (6) which carries the contact body (14), whereby the sealing body (10) seals the contact chamber (16) from the membrane (6).
2. Switch gear according to patent claim 1, characterised by the fact that the sealing body (10) sits loosely on the membrane (6).
3. Switch gear in accordance with claims 1 or 2, characterised by the fact that there is an intermediate chamber between a collar (12) ofthe sealing body (10) and the membrane (6), whereby if the membrane leaks, water enters this chamber and moves the sealing body in such a way that the contact body (14) hits the switch contacts (17, 18).
4. Switch gear in accordance to one of the above claims, characterised by the fact that the sealing body (10) has a pressure plate (11) and a collar (12).
5. Switch gear in accordance with patent claim 4, characterised by the fact that the sealing body (10) is made of one piece.
6. Switch gear in accordance with one of the above claims, characterised by the fact that the collar (12) is positioned in such a way that water flowing in supports its sealing functions.

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