The invention concerns a gas instrument comprising a housing for measurement and/or control devices, having a connecting branch on the housing to secure it on a gas supply line, in which a stop valve is provided in the connecting branch for the gas supply from the gas supply line and the stop valve has a closure portion which is under the influence of a spring member and the closing portion is kept in the open position by a melt substance.

The invention is used primarily in the case of those gas instruments which are used in large unit numbers for installations in housing.

In households, the gas instruments are connected via gas meters to the gas supply network. If the gas pressure in the gas supply network is too high, there is a requirement for the provision upstream of a gas control device which reduces the pressure and keeps it constant at the same time. For safety reasons, it is required that in the event of the occurrence of a harmful fire, a safety stop valve stops the gas flow through the fittings on the attainment of a predetermined and increased ambient temperature.

It is known that the prescribed safety stop valve should be installed in the housing which is resistant to the high temperatures caused in the event of fire and it is correspondingly expensive, and it contains the measuring and/or control devices. Such housings were until now made of sheet steel or of soft cast iron, which resist temperatures of up to 700°C and more, over a sufficiently long period. The costs of the production of such housings are high.

In addition, it is known that the requirements of the fire prevention regulations can be met in that between the end of the gas supply line and a measuring and/or control instrument, a separate thermally dissolving stop device should be inserted. In fact this proposal provides excellent safety in the event of fire, but the device which is needed additionally has substantial costs (DE 37 00 726 C2).

The object of the invention is to design a gas instrument which satisfies all the conditions which are required for safety against fire, without the production of its housing being connected with high costs.

For the solution of the problem as defined above, the point of departure is a gas instrument of the type described initially and the problem is solved in that the housing consists of a material, the resistance of which to the influence of fire is limited to 400°C and the connecting branch together with the stop valve withstand the long-term influence of an ambient temperature of at least 500°C.

The proposed design of the housing and the connecting branch with the stop valve has the effect that on the influence of a fire on the gas instrument, its housing together with the measurement and/or control devices in it initially becomes leaky even on a moderate increase of temperature and then it melts. But previously the stop valve on a lesser increase of temperature has already adopted its closed position from the open position, because of the melting in good time of the melting substance, and the gas supply is shut off directly at the end of the gas supply line. Because the connecting branch together with the stop valve still prevent the outflow of gas from the supply network because of its material properties, when the ambient temperature 500°C or has exceeded this temperature, the inventive gas instrument meets even the maximal security requirements.

Advantageously, the housing is made of aluminium pressure diecasting. This modus operandi is very favourable, and in particular for larger unit numbers, it supplies excellent strength and low weight. The resistance to temperature up to atmospheric temperatures of about 300 to 400°C is completely adequate.

When the gas pressure in the instrument only assumes small values, the housing can be made of a suitable plastic. The production is very economical, a high degree of adherence to the required dimensions is

achieved, even though the resistance to temperature can only be described as low. But this does not play any part in this case.

In an advantageous embodiment, the connecting branch and the stop valve together with its closing portion consist of brass.

Equally, it is an advantage when the connecting branch and the stop valve with its closing member consist of steel. Both brass as well as steel retain their form and their strength even at temperatures of 650°C for a sufficiently long period, at which steel is already in the dark red hot state.

Expediently, the closing portion has a valve closure cone, a valve rod wjaich supports it and which is longitudinally displaceable in a guide, a conical valve seat, a pressure spring as the spring member as well as a spring abutment on the valve rod. This design of the closing portion is simple in its construction and therefore it ensures a high degree of operating safety.

In order to increase safety against fire, the connecting branch has an internal thread for screwing in the gas supply line. This measure guarantees a safe and durable connection of the stop valve directly on the end of the gas supply line.

The connecting branch can have a flange to secure it on the housing. This makes the installation of the connecting branch on the housing easier.

As the melting substance, for example, a small cylinder of plastic or of a metal which melts at low temperature can also be used.

The melting substance can be placed between the rear side of the spring abutment and a pressure plate of a lever arm, which is pivotable by a safety member provided in the housing.

The invention will be explained below in the case of an embodiment on the basis of the enclosed drawing. The drawing shows a gas instrument in a greatly simplified, schematic illustration in a section.

The illustrated gas instrument has a housing 1 , a connecting branch 2 and a gas outlet 3.

The housing 1 contains measuring and/or control devices (which are not shown) as well as a safety member 4 (indicated by interrupted lines). This housing 1 consists of a material, the pressure stability and form stability of which against the influence of a harmful extemal fire are only guaranteed at temperatures which do not exceed about 400°C. This material is an aluminium pressure diecasting or a zinc diecasting; under certain preconditions and at pressures which are not too high it can also consist of a suitable plastic.

The connecting branch 2 which is arranged on a side wall 5 of the housing 1 is used for the supply of gas from a gas supply line 6 and is secured to the latter. The connecting branch 2 has an internal thread 7 for screwing in the end of the gas supply line 6, which is provided with an external thread. By means of a flange 8, the connecting branch 2 is firmly connected with the housing 1. In the connecting branch 2 there is a stop valve 9 to interrupt the gas supply into the fitting. This stop valve 9 has a closing member which is under the influence of a spring member 10 and which is kept in its open position (shown) by a melt substance 11.

The connecting branch 2 and the stop valve 9 are made of materials which provide them with a durable strength against the influence of ambient temperatures which amount to at least 500°C.

The stop valve 9 has a closing portion with a valve closing, cone 12, a valve rod 13, a guide 14, a valve seat 15, a pressure spring as the spring element 10 and a spring abutment 17.

The valve closing cone 12 is located on one end of the valve rod 13, which is mounted to be longitudinally displaceable in a guide 14, the conically formed valve seat .15 which interacts with the valve closing cone 12 is arranged on the inner wail of the connecting branch 2. The valve rod 13 is conducted through the aperture 16 of the valve seat 15. The pressure spring 10 is inserted between the spring abutment 17 which is provided on the other end of the valve rod 13 and a tangentially angled support arm 18 of the connecting branch 2, so that it keeps the stop valve 9 in the open position and gas can enter from the gas supply line 6 into the housing 1 and its devices.

The connecting branch 2 and the stop valve 9 with all their components consist of brass or of steel, which are both materials which withstand the long-term influence of 500°C and more as a result of a fire, without losing substantially as to their strength.

As the melt substance 11 , use is made of a small cylinder of plastic or another material which melts at temperatures between 70 and 150°C. This melt substance 11 is inserted between the rear side of the spring abutment 17 and a pressure plate 19 of a lever arm 20. The lever arm 20 is included among the safety members 4 and is activated by the latter when, for example, the gas pressure in the housing 1 or in the gas outlet 3 and/or in the gas installation which is connected with the gas outlet 3 becomes too high. The locking valve 9 is closed by pivoting the lever arm 20.

List of the reference numerals

1 housing

2 connecting branch

3 gas outlet

4 safety member

5 sidewall

6 gas supply line

7 internal thread

8 flange

9 stop valve

10 spring element

1 1 melting substance

12 valve closing cone

13 valve rod

14 guide

15 valve seat

16 aperture

17 spring abutment

18 support arm

19 pressure plate

20 lever arm