US2414397A - Grate or burner - Google Patents

Description

v Jan. 14, 1947. F. P. D. scoT'r 2,414,397-

GRATE OR BU Filed Nov. 2, 1944 ATTOAIVE/S Patented Jan. 14, 1947 UNITED STATES PATEEQ GRATE R BURNER Francis Peto Dudley Scott, London, Engiand, as-

signor of one-half to Prior Stokers Limited,

London, England Application November 2, 1944, Serial No. 561,542

' In Great Britain November 9, 1943 1 Claim. 1

The duplex burner or grate of the present invention is of the kind in which fuel is fed to the bottom of and up into a. burner or grate with hollow walls or tuyres, provided with apertures near their upper margin through which combustion air is supplied, a single feed screw feeding both parts of the burner, one upon each side of a hollow longitudinal member. The feed screw terminates short of the end of the burner and a division plate at the end of the feed screw separates the two parts of the burner beyond the end of the feed screw. The forward motion of the fuel in this part of the burner i commonly up a slope designed to avoid excessive backward thrust on the feed screw and to maintain an even supply of fuel to the combustion zone. Agitating or stirring means may be incorporated at the end of the screw to help to keep the fuel moving. The hollow longitudinal member over the screw of the duplex burner is naturally designed to present as little resistance as is practicable having regard to the desired movement of the fuel, but there is a certain tendency to packing under the end of the screw because of the upward slope with a consequent upward thrust. There is also some tendency to side thrust, particularly when stirring means are used, and the fact that there is more resistance to the flow into the side of the longitudinal member where it would normally be greater tends to increase this. Moreover, with certain badly graded fuels there is found to be a tendency to unequal grading on the two sides of the burner; when the feeding worm is righthanded and therefore turning in a clockwise direction viewed from the forward end of the burner the fines tend to go more to the left-hand half and nuts more to the right-hand half of the burner as viewed from that end.

The present invention is designed to alleviate such conditions and includes several parts or features which tend separately and in combination to do so. One part of the invention includes the extension of the feed screw shaft under the longitudinal member into a forward bearing and preferably the use of a reverse thread of relatively very small diameter on the shaft extension. Another part includes the use of a feed screw located toward the side of the burner away from that where the fines would tend to predominate and an air duct led to the side remote from the feed screw, so that the initial pressure of the air is available on that side where fuel bed resistance tends to be greater and the arrangement is compact and economical of space. Other parts are embodied in a typical form shown upon the accompanying drawing. The parts for which a monopoly is desired are those delimited by the claim.

In the drawing- Fig. 1 is a perspective view from the forward end, broken away to show the construction and arrangement of parts, and v Fig. 2 is a diagrammatic view from the same end, making clear the preferred location of the feed screw and air duct.

The feed screw l is arranged to feed fuel through the feed tube 2 to the bottom of a trough 'I and up into the burner. The trough is of substantially \l shape in cross-section. The screw rotates clockwise as viewed and will consequently tend to feed a greater proportion of fines to the left-hand side 3 and of coarse to the right-hand side t of the trough. The two sides of the trough are separated by a substantially V shape longitudinal partition 5 which is curved down. at 6 to conform more or less with the upward curve of the bottom and the tapering down of the main feeding thread of the screw I. A plenum space i is formed outside the main casting 8 by brickwork 9 and supplies air over the longitudinal partition 5 and into the tuyre castings Ill. Air is supplied to the plenum space by an air duct II. It will be noted that the feed screw is oifset from the centre of the apparatus toward the side 4 of the burner to which a, greater proportion of the coarse fuel tends to be fed and that the air duct enters on the fines side i. The feed screw is extended into the forward bearing E2, the extension 33 being provided with a reverse thread it between the main thread and the bearing, to agitate and help to raise the fuel at the forward end of the trough.

In case fines get past the bearing length 15 of the extension a thread It of the same hand as the main thread may be formed on a portion of the extension within the bearing to feed them out at the end or through an aperture provided for them.

I claim:

A duplex burner including the combination of a trough of substantially V shape in cross-section with a rounded bottom, a substantially V shape longitudinal hollow partition for the trough providing upwardly diverging sides adapted to direct fuel upwardly, a tapered feed screw extending into the trough longitudinally thereof at the bottom to feed fuel upwardly to said sides, said partition being dependingly mounted so as to extend only partly into said trough and above the screw, means to supply air to the trough and into the hollow of the partition, the screw counteracting uneven burning of the fuel due to the resultant tendency to feed fines to one side and coarse fuel to the other side by reason of the screw being offset nearer to the side of the trough towards which the upper side of the screw rotates and said air supply being intensified on the side of the trough towards which the lower side of the screw rotates.

FRANCIS PETO DUDLEY SCOTT.

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