Deburring chamber for thermal deburring

A thermal deburring chamber has interchangeable inner parts exposed to wear backed by permanent parts providing support and cooling. The inner parts fit so as to permit some expansion without transmitting excessive thermal or mechanical shock to the backing members.

STATE OF THE ART 
In thermal deburring (also called thermochemical deburring), the pieces of 
work to be deburred are introduced into a deburring chamber. Combustion 
gas and oxygen are introduced into the deburring chamber via metering 
valves. The gas mixture is ignited in the chamber by an electric ignition 
device. When hydrogen is used as the combustion gas, the combustion 
produces water while releasing heat. The procedure runs its course within 
a few milliseconds. As a result of the heat being released, temperatures 
of approximately 3,000.degree. C. occur in the chamber. After the pieces 
of work have been deburred, the deburring chamber is opened and the pieces 
of work are replaced with new pieces of work which are to be deburred. 
The thermal deburring process causes an intentional removal of the material 
of which the work piece to be deburred is made, particularly at the edges. 
However, it is disadvantageous that there is also an unintended removal of 
material at the surfaces or portions of the deburring chamber forming its 
inner wall, this unintended removal being locally quite variable in 
severity. 
THE INVENTION 
Briefly, in order to deal more effectively with the erosion of the chamber, 
the chamber walls are made easily interchangeable and are designed subject 
to considerable wear. 
The deburring chamber according to the invention has the advantage over the 
prior art that tool costs in thermal deburring can be greatly reduced. 
Because parts of the deburring chamber which are subject to differing 
amounts of wear are embodied separately, relatively small units can be 
exchanged very easily and quickly. Since the deburring chambers operate 
with considerable cycling times (20 seconds, for instance), the deburring 
chamber walls are exposed to severe alternating thermal stresses, which 
can cause rupturing because of thermal shock and thus can cause a severe 
reduction in long-term rupture strength. The inner walls of the deburring 
chamber are subjected to a continuous alternating stress in synchronism 
with the cycle. The removal of material from deburring chamber parts can 
be of an order of magnitude of up to one millimeter per 50,000 deburring 
cycles. 
In this area, the deburring chamber according to the invention is therefore 
made up of easily exchangeable units which are subjected to relatively 
high wear. Such units are, in particular, the interior walls of the 
deburring chamber. 
A particularly advantageous deburring chamber design comprises an interior 
deburring chamber ring or sleeve with an upper portion or ceiling of the 
deburring chamber adapted thereto and an associated closing bottom plate. 
These three parts, adapted to one another, define the interior of the 
deburring chamber and represent those parts which are most subjected to 
wear. 
The inner parts of the deburring chamber are embodied, in terms of their 
strength, in such a manner that they are independently capable of 
withstanding the stresses which occur during thermal deburring. To this 
end, a clearance fit is provided between the inner deburring chamber ring 
and the outer cooling ring, in order to limit the continuous alternating 
temperature stress and accordingly the reduced long-term rupture strength 
to the part subject to wear. This principle is also applied to the upper 
portion of the deburring chamber, which when cold has a slightly inwardly 
curved shape but under temperature stress has a locking fit with the 
adapter located above it. However, a further form of embodiment of the 
deburring chamber provides that the inner ring is fitted into the 
surrounding cooling ring or some additional ring in such a manner that the 
surrounding ring absorbs the forces, while the inner ring is selected with 
a view solely to the factor of wear.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The deburring chamber 10 is defined by an inner sleeve-like ring 11 of the 
deburring chamber, an upper deburring chamber portion 12 and a closing 
plate 13, all serving as walls of the deburring chamber. The inner chamber 
ring 11 is surrounded by a cooling sleeve-like ring 14 having cooling 
coils 15. The ratio of the wall thickness of the inner ring to that of the 
cooling ring 14 is 2:3, by way of example. Because of the relative 
thinness of the walls of the inner portions of the deburring chamber, a 
large temperature drop in the walls is prevented from occurring. This 
results in a considerable reduction in thermal stress. The long-term 
rupture strength of the parts can thus be substantially increased. The 
cooling ring 14, like the inner ring 11, is manufactured of a 
chrome-nickel steel and embodied as a rupture safety device. The clearance 
fit between the inner ring 11 and the cooling ring 14 assures that no 
stresses occurring during the course of operation can be transmitted from 
the inner ring to the cooling ring. The cooling ring is accordingly not 
subjected to any alternating stress and is therefore not subject to wear; 
as a result, it can be used for safety purposes as a means of rupture 
prevention. 
Toward the top, the deburring chamber 10 is bounded by an upper deburring 
chamber portion 12. A seal 16 is disposed between the upper portion 12 and 
the inner ring 11 in such a manner that it is not exposed to direct 
temperature stress. An adapter or backing plate 17 is adapted to the upper 
deburring chamber portion 12. The upper adapter 17 is embodied similarly 
to the cooling ring 14. To this end, it is provided with cooling coils 18, 
which assume the function of cooling the upper portion 12 of the deburring 
chamber. In order not to subject the upper adapter 17 to alternating 
temperature stress (it is not a part subject to wear), the upper portion 
12 of the deburring chamber is embodied in such a manner that when cold it 
has an inwardly curved shape. The upper portion 12 of the deburring 
chamber expands only as the result of heating during thermal deburring and 
then has a locking fit with the upper adapter 17. 
The inner ring 11 and the upper portion 12 of the deburring chamber are 
clamped together by means of a tension bolt connection 17 between the 
upper adapter 17 and the cooling ring 14. The connection is pre-stressed 
by springs 20 in order to compensate for tolerances, expansion and the 
settling of the seal 16. The deburring chamber is supplied with combustion 
gas and oxygen by means of the gas connection 21. 
In its lower portion, the deburring chamber 10 is defined by the closing 
plate 13, which is connected with the inner deburring chamber ring 11 by 
means of a seal 22. A further lower adapter or backing plate 23, like the 
upper adapter or backing plate 17, assumes the function of connection to 
the machine frame, not shown in the drawing.