Mixing block for mixing a combustible gas mixture

Details Mixing block for mixing a combustible gas mixture Mixing block for mixing a combustible gas mixture

1986-06-23

1988-04-26

Schwadron, Martin P.

Combustion

Combustion bursts or flare-ups in pulses or serial pattern

137607, 431346, F16K 1118, F23N 524

Patent

active

047401524

DESCRIPTION:

BRIEF SUMMARY
PRIOR ART

The invention proceeds from a mixing block according to the type of patent claim 1. In the apparatuses particularly referred to for the thermal deburring of workpieces, which apparatuses are provided with such a mixing block, hydrogen and oxygen, for example, are admitted into pressure cylinders from a reservoir in order, then, to be pressed through the mixing block by gas pushing-in pistons, under considerable compression of up to 100 bar, into a combustion chamber which receives the workpieces to be deburred and which is closed so as to be gas-tight. When the gas mixture is ignited there is an explosion-like combustion. Temporary temperatures of up to several thousand degrees centigrade occur, during which undesired burrs melt away or burn away with the aid of a certain oxygen surplus.
The high pressures and temperatures occurring during the explosion-like combustion must be kept away from the gas pushing-in mechanisms and, for this reason, valves which close the boreholes so as to be gas-tight during the combustion process are arranged in the gas feed boreholes of the mixing block. For this reason, in a known valve arrangement a tappet is displaceably arranged in the gas feed boreholes for each component of the gas mixture to be pumped in and combusted, which tappet releases the gas throughput via the mixing and ignition duct to the combustion chamber in its one end position and, in its other end position, blocks the gas throughput in that it is pressed against the valve seat with a spherical valve surface by means of an external, correspondingly dimensioned force against the pressure occurring during the combustion process. Because of the high stressing of the valves, their construction, which is operationally reliable also for longer service life, brings about considerable difficulties which could not previously be removed with known constructions. Thus, particularly because of soiling of the valve seat, leakiness occurs which increases immediately because of the high thermal loading and leads to unusability of the valves. A plurality of valves are always affected in an apparatus; namely, the main valves, which are arranged in the gas feed boreholes, and at least one bleeder valve for letting off the gas mixture during ignition failures and the like, which is arranged in a borehole passing out of the gas feed borehole and leading outward.
It has been attempted to protect the valves by inserting boreholes between the mixing and ignition duct of the mixing block and the valves, which boreholes are of such a length that the volume of the gas components which are located in the boreholes and which are not combustible solely in themselves is sufficient to form a protective cushion which thermally insulates the valves and elastically intercepts the explosion pressure of the ignited gas mixture. However, it has been shown in practice that such a gas seal is not sufficient in every instance to completely keep away from the valves the factors disadvantageously influencing the service life of the valves (pressure, temperature, soiling). It is known, moreover, from DE-PS No. 24 40 041 to use a liquid seal, instead of a gas seal, for protecting the valves. In this instance, the gas feed boreholes are connected with the valve receiving boreholes via ducts, wherein the ducts and the valve boreholes are fillable, via another valve, with a liquid which is incombustible and substantially neutral relative to combustible gas. Indeed, such a liquid seal forms an effective protection against thermal overstressing of the valves, since the liquid absorbs the high temperatures occurring temporarily during the ignition of the gas mixture accompanied by inherent heating. However, it is not suited to keep away from the valves the high pressures occurring by means of the explosion of the gas mixture, since it maintains its volume. Moreover, the production of such a mixing block is considerably more complicated and more expensive than a comparable mixing block without a liquid seal.


ADVANTAGES OF THE INVENTION

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REFERENCES:
patent: 630315 (1899-08-01), Barclay
patent: 1151496 (1915-08-01), Pettis
patent: 3162238 (1964-12-01), Claywell et al.
patent: 3994668 (1976-11-01), Leisner et al.
patent: 4487576 (1984-12-01), Martini
patent: 4488865 (1984-12-01), Davis
patent: 4640678 (1987-02-01), Fraioli

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