The present invention relates to a flexible connection for supplying cooling air to a movable grate element in a grate cooler, which comprises alternate rows of movable and stationary grate elements, and being designed for cooling of granular material subjected to heat treatment in a kiln, for example a rotary kiln.

When used in connection with a rotary kiln, the grate cooler will be mounted at the outlet end of the kiln for receiving the hot material which is discharged from the kiln and distributed across the grate surface of the grate cooler. The material is conveyed in a bed across the grate surface and thereby through the cooler by the reciprocating movement of the movable grate elements, while the material bed is simultaneously swept by cooling air from the perforated surface of the grate elements.

Grate elements of the above-mentioned kind are known i.a. from the description of the Danish patent application No. 1227/92. Since, generally, the material bed on the grate surface is not of a homogenous size, the cooling air is often separately fed to each single grate element and can thus be controlled for attainment of optimum cooling.

Consequently, this requires an air supply connection for each of the single grate elements, both the stationary and the movable elements.

Whereas it is not particularly difficult to supply air to the stationary grate elements, it is an essential requirement that the air connection for the movable grate elements has the required degree of flexibility so that the connection can follow the reciprocating movement of these grate elements.

Therefore, the flexible connection often consists of a flexible hose which may be of rubber or canvass or even of

stainless steel which will then be formed as an elastic bellows .

However, such flexible connections are exposed to wear and degradation due to the continuous bending strains, this being further aggravated by the exposure to the influence of very hot material which falls down between the grate elements .

The invention discloses a flexible connection of the abovementioned kind by which the aforementioned disadvantages are avoided or substantially reduced, and being characterized in that the connection comprises a rigid pipe with two end sections having a the wall thickness which exceeds that of the pipe and being rounded on their outer sides and mounted in a displaceable and tiltable manner in separate pipe sockets, of which the first is fixed to the movable grate element while the second is fixed to the stationary frame of the cooler.

A flexible connection of this kind does not have any parts which are exposed to abrasive and degrading bending strains, and, further, if at least the end sections are made of wear-resistant material, the service life of the connection can be extended, both with respect to wear resistance and increased resistance to hot down-falling material .

As additional protection against possible down-falling, hot material, the stationary pipe socket on the cooler frame may be shielded against such material by means of a collar on the pipe.

The invention is described in further details in the following by means of an example of a flexible connection according to the invention, and with reference to the

drawing, being diagrammatical, and showing a part of a grate cooler in longitudinal section and with a flexible connection according to the invention.

On the drawing is shown three grate elements 1, 2, 3 which in known manner overlap one another and of which the centremost element 2 can be moved to and fro as indicated by means of a double arrow 4. Through the movement of the movable grate element 2, the material 5 to be cooled is conveyed across the grate surface from the left-hand side to the right-hand side on the drawing as indicated by the arrow 6.

During the conveyance of material, the material is swept by cooling air which is blown up through the material via perforations 7 in the surfaces of the grate elements. Under the surface of each grate element there is an air chamber 8 which is fed with cooling air from the lower part of the cooler frame 9.

Whereas it is not particularly difficult to supply the stationary grate elements 1 and 3 with cooling air via rigid connections 10 and 11, the supply of cooling air to the movable grate element 2 requires a flexible connection which can follow the reciprocating movement 4 of this grate element .

The drawing shows an example of such a flexible connection 12 according to the invention, and it comprises a rigid pipe 13 having two end sections 14 and 15 which can be mounted in a displaceable and tiltable manner in two pipe sockets 16 and 17, of which the first 16 is fixed to the reciprocating grate element 2, whereas the second 17 is fixed to the cooler frame 9 which serves as air supply duct. If the rigid pipe 13 has a circular cross section, the end sections will advantageously be configured with a

spherical outer side.

The stationary socket 17 may be protected against hot downfalling material by means of a collar 18 fitted on the pipe 13.

The cross section of the rigid pipe may also . be rectangular, preferably square, and in such cases the end sections will not, of course, have a spherical outer side but will also be of rectangular or square configuratons, and the outer side will have the form of four cylindrical surfaces being perpendicular to one another.