US1221125A - Air-supply to mechanical stokers. - Google Patents

Description

W; R. WOOD.

MR SUPPLY T0 MECHANICAL STOKERS.

APPLICATION men MAY 13. 1915.

1,821,125. Patented Apr. 3,1917.

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. WOOD.

AIR SUPPLY T0 MECHANICAL STOKERS.

APPLICATION FILED MAY 13' 19 15.

Patented Apr. 3, 1917.

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AIR-SUPPLY T0 MECHANICAL STOKERS.

Specification of Letters Patent.

Patented Apr. 3, 1917.

Application filed May 13, 1915. Serial No. 27,872.

To all whom it may concern:

Be it known that I, VVILFRED RO'rI-IERY Wooo, a citizen of. the United States of America, and a resident of London, England, have invented a certain new and useful Improvement in Connection with the Air- Supply to Mechanical Stokers, of which the following is a specification.

In mechanical stokers to which it is de sired to supply the air to the underside of traveling grates and maintain a pressure above that of the atmospheric pressure, considerable difficulty is frequently encountered in so arranging the air ducts which connect the stokers with the fan as to avoid a loss in the pressure set up by the fan, and also a loss of air through leakage. There is also considerable expense involved in the manufacture and arrangement of such ducts and occasionally it is found there is insufiicient roomfor a really practical arrangement.

There are also certain complications as regards connecting up. the ducts with the stokers. This is particularly the case with traveling grate (chain grate) stokers (and it is to this class that the present invention relates) which are usually so mounted on wheels, or otherwise, as to be capable of removal and replacement.

Among other proposals heretofore made is one to place a fan withinthe stoker itself, between the upper portion of the grate which carries the fuel in, and the lower or returning portion of the traveling grate. This proposal is almost impracticable owing to the dirt and dust causing serious wear 7 and trouble with the shaft driving the fan,

which it is necessary to run at a very high speed.

Further, in this posltion there is usually insufiicient room to place an efficient fan,

that is, a fan that would supply the necessary quantity of air without absorbing too much power. In this position too, the wearing parts are more orjless inaccessible.

It has further been proposed to employ a fan external to the furnace grate and de livering the air to the ash pit the position of the damper of such fan being regulated by the steam pressure in the boiler as is also the feed of fuel the arrangement being such that as the steam pressure rises the feed of fuel and air is decreased and as the pres sure falls both air and fuel are increased but such arrangement has not provided the essential for practical working namely the power to instantly alter the relative rates of fuel and air feed nor did it propose that separate fans mounted 'on the same shaft should deliver the air upon opposite sides of the grate and finally the arrangement did not permit of the removal of the grate and fans without breaking connections these being important features of the present invention.

According to this invention it is proposed to overcome the several difliculties described by mounting the fans on the stoker, that is, self-contained therewith or supported thereby, but in a position without instead of within the grate, and where high speeds are perfectly practicable, and all the parts are accessible and the shaft and fans so placed as to not present any inconvenience in the operation of the stoker, or aifect the accessibility to other parts of the stoker. At the same time the fans are placed in such a position as to enable short connections or ducts of a permanent character to be employed for carrying the air from the fans to the air chambers beneath the grate, and all these advantages may be gained by mounting the fans and prime mover if desired on the stoker hopper, or removable front plate.

The fans may be driven from a source of power not self-contained with the stoker, or they may be driven by a source of power such as an electric motor or by a steam turbine selfcontained with the stoker. In either case the mechanism which drives the stoker itself may be so connected up to the source of power that a variation in the speed of the prime mover gives a like variation to the speed of the grate. But a speed regulating apparatus between the stoker driving gear and the fans or the source of power should be employed so that the relative speed of grate and fans may be readily adjusted from time to time.

In a convenient construction according to the invention two fans are mounted on opposite sides of the hopper, these two fans being connected together by a shaft, also carrying an electric motor, or steam turbine, so as to secure a direct drive. Connected with the shaft is a worm reduction gear carrying at the bottom end of the worm wheel shaft a sprocket wheel, said sprocket wheel through the agency of a chain being caused to drive the stoker either direct or through a speed regulating gear.

From each fan a connection or duct is carried down the side of the hopper or front plate and into the side of the stoker, and in each connecting pipe an air gate is preferably arranged so that the supply of air to each side of the stoker, that is the supply of air from the two fans, may be regulated.

To enable the invention to be fully understood it will now be described by reference to the accompanying drawings, in' which 2.-

Figure 1 is a front elevation of a portion of 'a stoker having the invention applied thereto:

Fig. 2 is a side sectional elevation of same: and

Fig. 3 is a plan view thereof.

In the arrangement shown, two fans 1, 2, are mounted on opposite sides of the hopper 8, these two fans being connected by a shaft 4: also carrying an electric motor 5 supported on the brackets 6 so that a direct drive is secured. Connected with the shaft 4: is'a worm reduction gear 7 carrying at the bottom oftheworm wheel shaft a sprocket wheel 8. The sprocket wheel 8 is connected by a chain with a suitable speed regulating gear 9 which drives the stoker through the shaft 10 as indicated.

From each fan a connection or duct 11 is carried down the side of the hopper 3 to the opening 12 to the chamber beneath the grate 13. A pivoted air gate 1A is preferably arranged in each duct 11 so that the air supplied to each side of the grate by the fans may be. regulated.

The construction and arrangement of parts above described not only has the advantages set forth but also has others of great practical use in that it enables the dust and part of the heat of the boiler room tobe' effectively removed and such room ventilated and these points will be clearly understood if the prior practice is considered.

In hand firing furnaces with induced draft the dust of the boiler room is produced at or near the floor level, and the air being sucked into the ash pit ventilates the room,

and also carries away the dust, or a great deal of it. The same may be said of induced draft mechanical stokers, but these do not collect the dust to the same extent, since the dust is largely produced at the hopper where the coal is delivered either by shovel or by a chute.

With forced draft stokers, that is, stokers in which a pressure above the atmosphere is maintained beneath the fire, it has been customaryfheretofore to place the fans in such a position that they did not collect the dust or ventilate the boiler room where such collection and ventilation is needed, viz:

r is greater need with forced draft furnaces for such ventilation as compared with other types of furnaces, by reason of the fact that more dust is created. There is the impossibility of entirely confining the air beneath the grate, and also it is difficult, if not impossible, to prevent some back escape of gas and dust from the furnace itself.

Again, in traveling grate stokers it is an advantage that they should be made so that they can be removed from the furnace for repair of brickwork and repair of stokers: and they are, therefore, usually made portable, or semi-portable, say by mounting on wheels. With such construction as heretofore made there must be a joint between the air ducts and the stokers which must be broken at the time of removal of the stokers.

This joint is liable to leak and create dust and it otherwise presents difficulties as regards the removal of the stoker. As in the present invention the fans 1, 2, are placed on the stoker itself and at a point where the dust is formed, they will not only collect this dust, but they also, by taking away the warm air at these polnts, keep the room well ventilated. Furthermore, the fans 1, 2, being mounted, as shown, are connected up with the stoker in such a way that the stoker, fans, and ducts 11 are all removed from the furnace together without breaking joints.

Another point is that with this arrangement the power required to drive the fans 1, 2, is reduced, since the ducts 11 between the fans and the stoker are short and direct whereas with the old method of supplying air to the stokers the ducts were often long and tortuous, and connections with sharp bends were necessary in order to lead the air into the stokers. There was not only a considerable fall in air pressure between the fan and stokers, requiring fans to be run at higher pressure than will be required according to the present invention with a consequent increase of power, but there was also leakage in the ducts to be allowed for requiring still more power.

What is claimed is 1. In a furnace, the combination of a mechanical stoker, including a fuel support and a hopper, a fan or blower mounted adjacent the hopper whereby it is adapted to collect dust therefrom and withdraw heated air from adjacent the front of the furnace, and an air duct connecting the fan casing with a chamber below the fuel supporting surface of the stoker, all of said parts be ing bodily movable together from the furnace.

2. The combination of a mechanical stoker of the chain or endless grate type adapted to be bodily moved into and from a furnace, a hopper for supplying fuel to the grate, two fans supported on opposite sides ofthe hopper, gearing external to the stoker for driving the fans, and air ducts extending from the fan casings to a space beneath the fuel supporting surface of the grate, the hopper, fans and ducts being bodily movable with the Stoker.

3. The combination of a mechanical stoker of the chain or endless grate type, a hopper for supplying fuel to the grate, two fans supported at opposite sides of the hopper, a shaft external to the grate adapted to drive both fans, air ducts permanently connecting the fan casings and a space beneath the fuel supporting surface of the grate, and means for actuating the grate and rotating the fan driving shaft, the grate, hopper, fans and air ducts being adapted to be moved bodily as a unitary structure relative to a furnace.

4:. The combination of a mechanical stoker of the chain or endless grate type, a hopper for supplying fuel to the grate, two fans supported at opposite sides of the hopper, a shaft external to the grate adapted to drive both fans, air ducts permanently ing movable bodily as a unitary structure relative to a furnace.

5. The combination of a mechanical stoker of the chain or endless grate type, a hop per for supplying fuel to the grate, two fans supported at opposite sides of the hopper, a shaft external to the grate adapted to drive both fans, a prime mover on said shaft, means for actuating the grate geared to said shaft, and air ducts leading from the fan casings to a space below the fuel supporting surface of the grate, all of said parts being movable bodily as a unitary structure relative to a furnace.

In testimony whereof I have hereunto set my hand.

WILFRED ROTHERY WOOD.

Copies of this patent may be obtained for five cents each, by addressing the "Commissioner of Patents,

' Washington, D. G.

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