Method of making a grate plate

Metal working – Method of mechanical manufacture – Multiperforated metal article making

Reexamination Certificate

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Reexamination Certificate

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06266883

ABSTRACT:

The invention relates to a grate plate for installation in a grate apparatus for beat exchange between free-flowing material and treatment gas, particularly for fixing on a grate plate support in a grate cooler.
BACKGROUND OF THE INVENTION
It is generally known in the art for grate plates of the aforementioned type to be installed in various kinds of grate apparatus in which a free-flowing material, e.g. cement materials, ore materials and the like, are treated in the particular manner necessary with the aid of gases flowing upwards from the bottom through the layer of material. This treatment may for example be preheating, preburning, burning and above all cooling of the said materials.
In the as yet unpublished German Patent Application No. 195 37 904.7 a grate plate of approximately the aforementioned type is proposed which by its construction should achieve a particularly favourable and uniform flow through the material for treatment and thus an optimum heat exchange between material and treatment gas. For this purpose the document proposes that the gas flow channels be constructed like a pipe and approximately in zigzag form, and overall in the material transport direction they should extend obliquely from the lower face of the plate to the upper face of the plate.
A box-shaped grate base element with two lateral supporting flanges is also known from EP-B-O 167 658, in which the supporting flanges extend vertically and in the longitudinal direction of the plate and have attached to them in approximately ladder or dovetail form strip-shaped members which determine the surface and form between them gas slots which run through the entire width of the grate element. In each case two such ladder-shaped or fork-shaped structures consisting of lateral supporting flanges and strip members are put together in a complementary and form-locking manner in such a way that the strip members which extend parallel to one another form overall with the gas flow slots remaining between them a material support surface which is level on the top.
A grate cooler for cooling hot bulk material is disclosed in DE-A-37 34 043. In this document box-shaped grate plate supports are provided which have level upper cover plates each covered by an equally flat grate plate which is bent downwards at its front end. Slot-shaped gas flow openings are provided in the cover plate of the grate plate support and in the grate plate which is disposed flat above it, whilst slot-shaped connecting openings are formed between these two superimposed level plates as a connection between the gas flow openings. Since the gas flow openings in the two superimposed level plates are in each case displaced with respect to one another in the longitudinal direction of the plate, solids should be prevented from falling downwards through the gas flow openings in the event of a failure of the cooling gas supply, in which case throttle components can also be disposed in this system of openings.
In the two last-mentioned grate plate constructions it has been repeatedly found that the upper faces which come into contact with the material are still relatively susceptible to wear, and this is apparent particularly when relatively strongly abrasive material, such as is the case for example with cement clinker which is to be cooled, is to be transported along on the grate apparatus or a corresponding cooler grate and thereby to be cooled with cooling gas.
The object of the invention, therefore, is to make further improvements to a grate plate. In such a way that even in the case of strongly abrasive material, such as for example cement clinker or the like, the material carrier plate has a relatively long service life (high durability) and is distinguished by relatively favourable and economical manufacture.
SUMMARY OF THE INVENTION
In the construction of the grate plate according to the invention the material carrier plate thereof is produced from rolled steel plate material which is reworked or modified to high wear resistance, i.e. subsequently rendered highly wear-resistant, and the gas flow channels—viewed in vertical longitudinal section through the material carrier plate—are machined into this material carrier plate so that they extend substantially in a straight line and obliquely upward in the transport direction.
Rolled steel plate material which is reworked to high wear resistance is already known from general mechanical engineering for machine parts which are in danger of wear, but it has not been used hitherto for the construction of material carrier plates in grate plates of the said type. This is presumably because the material carrier plate of such a grate plate—particularly during the treatment of strongly abrasive material such as cement clinker or the like—is subject not only to high levels of attack by friction or wear but also to a considerable dead weight, so that correspondingly large plate thicknesses have been regarded as necessary, but they make the said plate material relatively expensive.
In the internal field trials on which the invention is based it was shown that the rolled steel plate material which is used according to the invention for the production of the material carrier plate and is subsequently rendered highly wear-resistant, and which in any case consists of a special alloy. brings with it an unexpectedly marked prolongation of the service life by comparison with the previously used partially tempered materials, that is to say it is considerably more wear-resistant than the previously known and used materials for these material carrier plates. Due to this fact the great advantage arises that in the grate plate according to the invention the material carrier plate can be produced from relatively thin plate material and can nevertheless have a longer service life than the known constructions. It is also advantageous that commercially available plate material, that is to say rolled steel plate material reworked to high wear resistance, can be used for the production of this material carrier plate.
In the material carrier plate produced in this way it is also regarded as particularly advantageous if—as already explained to some extent above—the gas flow channels are machined into this material carrier plate so that they extend substantially in a straight line and obliquely in the transport direction. This latter can occur in a relatively simple but very precise manner appropriately adapted to the particular requirements, above all by a special high-energy cutting process, as will be explained in greater detail below. The construction and alignment of the gas flow channels ensures a good penetration of the material situated on the material carrier plate by the gas to be delivered (e.g. cooling, air in the case of a cooler grate), and at the same time a certain conveying effect can also be achieved for the material to be transported along on the appertaining grate apparatus.
Since in this grate plate according to the invention the material, carrier plate—as already explained—can be produced from relatively thin plate material, it is advantageous to ensure stabilisation thereof so that no disruptive vibrations can build up during the operation of the appertaining grate apparatus, e.g. grate cooler. For this reason it is first of all provided that the basic plate body has within its outer frame structure a supporting structure made from reinforcing elements which connects parallel frame side parts firmly together, and on the reinforcing elements the material carrier plate is supported and at least partially fixed at locations between the gas flow channels. Thus this supporting structure connects parallel frame side parts, particularly the longitudinal side parts, firmly together with sufficient stability, the material carrier plate being additionally supporting with its lower face on the reinforcing elements of this supporting structure and in each case being at least partially fixed at locations between the gas flow channels. In this way it is also simultaneously ensured that the treatment gas or cooling ga

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