Mixing arrangement for a combustible gas mixture

A mixing arrangement for mixing a combustible gas mixture consisting of at least two gas components for treatment of materials by means of temperature and pressure shocks, comprises for each gas component a feeding line discharging into a mixing chamber. At the discharge area of each of the feeding lines a jet arrangement is provided which forces gas flows discharged from the jet arrangement to take a shape and direction which enhance the admixture thereof before they enter the mixing chamber.

BACKGROUND OF THE INVENTION 
The present invention relates to a mixing block or arrangement for a 
combustible gas mixture fed to a combustion chamber of a device for 
treating workpieces. In the particularly related known installations for 
thermal deburring of workpieces a chemical process occurs due to the 
influence of heat. The material to be deburred is oxidized with oxygen and 
burnt. The heat shock which is required for deburring is generated by 
burning off a combustion gas-oxygen mixture, whereby hydrogen or natural 
gas or methane may be used as a combustion gas, for example so that the 
required energy is released and the gas mixture must be compressed before 
the igniting. This is usually performed with the aid of dosaging cylinders 
and gas push by the pistons of the cylinders. The admixing of the gas 
components and igniting of the gas mixture is performed in a mixing block 
which contains an ignition device for igniting the gas mixture as well as 
a mixing chamber. 
The proper igniting and rapid combustion of the gas mixture depends, among 
others, decisively from a good uniform admixing of the gas components in 
the area of location of the ignition device and the combustion chamber of 
the work piece finishing chamber. It is known from DE-OS No. 30 15 393 
that to improve the mixture preparation in that the feeding lines for the 
gas components discharge tangentially into the mixing space designed as a 
bore of the mixing chamber. Thus, a strong twisted flow is generated and 
thereby an intensive admixing of the gas components. Such a mixing block 
is relatively volumnious and correspondingly expensive in the geometry of 
the feeding lines and the mixing chamber, caused by the tangential input 
for the gas components. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide an improved mixing 
arrangement for mixing different gas components of a gas mixture to be fed 
into a combustion chamber of the device for treatment workpieces for 
example for deburring. It is a further object of the invention to provide 
a mixing block in which the gas flows before entering the mixing chamber 
are so shaped and deflected by a jet arrangement that an intimate and 
uniform admixing of the gas components occurs. Moreover, the jet 
arrangement in accordance with the invention is advantageous in that the 
feeding lines for the gas components and the mixing chamber are not fixed 
by a defined geometry with respect to their common arrangement, which is 
advantageous with respect to the size and the constructive design of the 
mixing block. 
It is particularly advantageous with respect to the cost effective 
manufacturing and compact mode of construction that the combustion chamber 
of a work piece finishing chamber is used as a mixing chamber, the walls 
of which are provided with receptacles for the jet arrangement and for an 
ignition device for igniting the gas mixture. It is known from DE-PS No. 
21 22 221 to use the combustion chamber of a work piece treatment chamber 
simultaneously as a mixing chamber for the gas components, however the 
feeding lines for the gas components which are shaped as parallel bores in 
the head portion of the treatment chamber discharge immediately into the 
combustion chamber, whereby the gases are insufficiently admixed. 
Preferably, the mixture preparation is performed by the jet arrangement 
which consists of a slotted nozzle feeding the gas component, preferably 
an annular slotted nozzle and a multihole nozzle for a second gas 
component directed to the gas flow discharging from the slotted nozzle. 
Due to this nozzle geometry the gas component discharging from the 
multihole nozzle is injected into the flow of the gas component 
discharging from the slotted nozzle. A good ignitable mixture is 
generated. For forming the annular slot a bore may be formed in the wall 
of the mixing chamber and an annular bolt made of heat resistant material 
may be centrically inserted therein. Such bolts are relatively small 
structural elements which can be simply made, and interchange of these 
bolts as highly stressed wear parts is possible with low costs. The end of 
the bolt facing the mixing chamber preferably extends beyond the wall face 
of the mixing chamber containing the bore for the bolt, whereby in the 
area of this extension the multiple hole nozzle is mounted in or on the 
bolt. Thus, additional structural parts for making the multiple hole 
nozzle are eliminated.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A treatment chamber for deburring work pieces is designated with the 
reference numeral 1 in FIG. 1. In the combustion chamber 2 of chamber 1 a 
work piece 3 to be deburred is placed. The work piece 3 rests on a locking 
plate 5 movable in the direction of the double arrow 4. Plate 5 is applied 
to the front face of the treatment chamber 1 before filling the combustion 
chamber 2 with a combustion gas-oxygen mixture and igniting the same. A 
packing 6 is provided between plate 5 and the front face. 
The gas components of the combustion gas-oxygen mixture are fed into the 
combustion chamber 2 which also is used as the mixing chamber by means a 
dosaging cylinder 7 for combustion gas and a dosaging cylinder 8 for 
oxygen by means of gas pushing piston 9 and 10. The pistons 9,10 are 
coupled with each other by means of a yoke 11, so that they execute 
strokes of the same magnitude under the influence of a force which engages 
on the yoke. 
Each pressure resistant feeding line 12, 13 extends from the dosaging 
cylinders 7,8 into a valve block 14 which consists of a massive metal 
block. The feeding lines 12, 13 each discharge into a connecting bore 15 
or 16 in the valve block 14 and subsequent bores 17 or 18. The bores 17,18 
merge into bores 19, 20 extending transversely through the head part of 
the treatment chamber 1. Bores 19, 20 feed the combustion gas and oxygen 
into the combustion chamber 2 of the treatment chamber. A spark plug 21 
(FIG. 2) is used for igniting the gas mixture contained in combustion 
chamber 2, whereby this spark plug is mounted in a socket 22 which is 
mounted in a bore 23 provided in the side wall of chamber 1. Valves 24,25 
or 26,27 are provided between bores 15,17 and 16,18, respectively. These 
valves are opened at the start of the gas pushing process and are closed 
again after the gas pushing process is finished when the pistons 9,10 have 
reached their end position and no gas is present in cylinders 7,8 any 
longer. 
A cylindrical bolt 29 made from heat resistant material is mounted in a 
central bore 28 of the head part of the treatment chamber 1. The bolt 29 
consists of two parts 30,31 which are welded together and have different 
diameters. The upper piece 30, whose diameter corresponds to that of bore 
28 is provided with an annular groove 32 into which bore 19 discharges 
which feeds the oxygen. Moreover, this upper piece 30 is provided with a 
central vertical bore 33 and a transverse bore 34 extending therefrom and 
providing the connection to bore 20 which feeds the combustion gas into 
the bolt 29. 
The lower piece 31 of bolt 29 has a somewhat smaller diameter than bore 28. 
Thus an annular slot 35 is formed, through which oxygen as the one gas 
component is fed into the combustion chamber 2, which also serves as the 
mixing chamber, by means of bore 19 and the annular groove 32. Thereby, a 
peripheral flow is generated encompassing the lower piece 31 of the bolt. 
The lower piece 31 has a pocket borehole 36 which is flush with the 
vertical bore 33 of upper piece 30. A plurality of radial bores 37 extend 
from bore 36 and discharge into the combustion chamber 2 in the area of 
the circumferential face of the lower piece 31. The end of the lower piece 
31 which faces the combustion chamber 2 has an extension a with respect to 
the wall face 38 of combustion chamber 2. Chamber 1 is provided with the 
bore 28 for bolt 29. Bores 37 form in extension a discharge into the 
combustion chamber. In the exemplified embodiment the bores 37 as 
illustrated are slightly inclined. Together, they are forming the multiple 
hole jet or nozzle arrangement which injects the combustion gas in a jet 
like manner into the oxygen-peripheral flow which discharges from the 
annular slot 35. Thus an intimate uniform admixing of the two gas 
components is obtained and a good ignitable mixture is formed. 
In the lower piece 31 of bolt 29 illustrated in cross section in FIG. 4 the 
radial bores 37 are closed by plugs 39. Bores 40 extend from radial bores 
37 and discharge tangentially into the combustion and mixing chamber 2. 
The discharging into chamber 2 takes place in the same direction of 
rotation. A strong twist flow is generated due to the tangential feeding 
of the gas jets which exit through bores 40. Thereby, an overlapping of a 
rotational flow with an axial flow occurs, whereby the axial flow is the 
jacket like gas flow which is formed by the annular slot 35. This results 
in an intensive admixing of combustion gas and oxygen and thereby a very 
easily ignitable mixture. 
Instead of mounting the jet arrangement in a work piece-treatment chamber 
the jet arrangement may also be provided in a separate mixing block which 
is flanged to the chamber treatment and provided with an ignition device 
as well as a mixing chamber, whereby a gas feeding line is provided 
discharging into the combustion chamber of the work piece-treatment 
chamber. The type of structure of the exemplified embodiment is also 
advantageous in that the combustion chamber of the work piece-treatment 
chamber is also the mixing chamber for the gas components, so that a 
separate block may merely contain the valves which close the gas feeding 
lines during the deburring process, thus separating the combustion chamber 
from the gas supply. The front face of the bolt 29 which faces the 
combustion chamber 2 acts as an impact face which protects the valve block 
14 against pressure and heat wave which is generated by the explosion of 
the gas mixture so as to protect its service life. 
By using a round bolt designed as a wear part a jet arrangement can be 
surprisingly realized so as to force a shape and direction of the gas 
flows which enhances the admixture thereof before entering the mixing 
chamber. The peripheral face of the bolt forms an annular slot nozzle 
together with the wall of the bore receiving the bolt for the one gas 
component, while the radial bores provided in the bolt form a multiple 
hole jet or nozzle which injects the discharging gas jets into the jacket 
like gas flow generated by the annular slot 35. 
The installation as illustrated in FIG. 1 is not only suitable for a 
thermal deburring of work pieces, but is also suitable for further fields 
of use. With such an installation the process of reticulating of foamed 
material in accordance with DE-Patent No. 15 04 096 or the process for 
removing of foam material, for example, in accordance with DE-Patent No. 
23 22 760 may be performed. There are many further field of use, wherein 
work pieces are finished by an explosive gas mixture. The scope of 
protection of the device in accordance with the invention naturally 
extends to these further field of use. 
It will be understood that each of the elements described above, or two or 
more together, may also find a useful application in other types of mixing 
blocks for combustible gas mixtures differing from the types described 
above. 
While the invention has been illustrated and described as embodied in a 
mixing block for a combustible gas mixture, it is not intended to be 
limited to the details shown, since various modifications and structural 
changes may be made without departint in any way from the spirit of the 
present invention. 
Without further analysis, the foregoing will so fully reveal the gist of 
the present invention that others can, by applying current knowledge, 
readily adapt it for various applications without omitting features that, 
from the standpoint of prior art, fairly constitute essential 
characteristics of the generic or specific aspects of this invention.