US 2845905 A
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8 1958 w. H. SMITH 2,845,905
BOILERS Filed Jan; 25, 1955 s Sheets-Sheet 1 lNl ffNTOR M1. LIAM H 544/171 Aug. 5 w. H. SMITH 2,845,905
BOILERS Filed Jan. 25, 1955 3 Sheets-Sheet 2 INVENTOR M /4AM! 6'M/7'1/ l/WENTOR /7'- 5M1 TH w. H. SMITH BOILERS 3 Sheets-Sheet 3 Aug. 5, 1958 Filed Jan. 25. 1955 BOILERS William Herbert Smith, East Molesey, England Application January 25, 1955, Serial No. iSfafiZh Claims priority, application Great Britain January 25, 1954 3 Claims. (Cl. 122-30) This invention relates to boilers for the supply of hot water or steam for domestic or light industrial processes. It is particularly concerned with boilers having a fuel hopper incorporated therein from which fuel is fed under gravity to the firebed to which air for combustion is fed by a fan operated under control of a thermostat in the water passages.
From one aspect, the invention provides a boiler having a hopper from which fuel is fed to a firebed through which air for combustion is forced by a fan in which a flue for the products of combustion extends upwardly from the fire bed and a water chamber is arranged in this flue so as to cause the flue gases to divide substantially equally through passages at rear and front of the Water chamber.
From another aspect, a boiler according to the invention comprises a casing enclosing a hopper from which fuel is fed to a fire bed, the rear wall of this hopper sloping upwardly and backwardly from the outlet for the fuel to form the front wall of a tapering flue passage the rear wall of which is formed by a partition which also defines with the rear Wall of the boiler a flue passage through which the flue gases after passing upwardly through the tapering passage pass downwardly to a flue outlet and a Water chamber arranged within the tapering flue passage shaped and arranged to direct the flue gases substantially equal fy through passages at front and back of the water chamber.
Preferably the lower end of the water chamber slopes upwardly and forwardly to direct the flue gases to the front passage and the upper end of the water chamber is substantially below the top edge of the partition.
According to another feature of the invention primary air for combustion passes through the fire bed and secondary air for combustion is supplied above the tire bed, both primary and secondary air being supplied by a fan and in which the ratio of primary to secondary air is controlled by an adjustably positioned valve in the path of the secondary air from the fan to above the fire bed.
The outlet of the fan supplying the forced draught is preferably controlled by a pivoted flap, biassed to the closed position and opened by the blast from the fan against an adjustable stop. The extent of closing of this flap is also controlled by an adjustable stop so that the amount of air supplied when the fan is not running can be controlled.
Other parts of the invention are embodied in the preferred form which will now be described in some detail with reference to the accompanying drawings in which Fig. 1 is a cross-section through the boiler,
Fig. 2 is a central section of the inner body of the boiler and,
Fig. 3 is a front view of this inner body.
In this form the boiler comprises an insulated outer casing 1 of substantially rectangular section within which is housed an inner body (see Figs. 2 and 3) formed to provide (with the outer casing) water passages and flues for the combustion gases.
At the front of the boiler is provided a fuel hopper 2 of Patented Aug. 5, 1958 ice which the rear wall 3 (comprising part of the inner body and formed with a water space 4) slopes upwardly from front to top. The base of the hopper is formed by a wall 5 (enclosing a water space 6) which slopes upwardly to define a throat 7 with the rear wall 3 and then slopes sharply downward to provide a sloping base 8 for the unburnt fuel.
The thickness of fuel on this base 8 is controlled by the edge 9 of a plate 10 attached to the rear wall 3 by a screw 11. The distance of the edge 9 from the base 8 may be adjusted, by sliding the plate 10 up or down the wall 3, to suit the type of fuel being used, the thickness of a bed of small fuel being less than that of one of large fuel. To increase the distance of the edge 9 from the combustion zone, the plate 10 is bent at its end so that its end portion is substantially perpendicular to the base 8.
Below the throat 7 is a fire grate which slopes upwardly from the rear towards the front. This grate comprises a number of fire bars 12 supported at their front ends by a cross bar 13 and at their rear ends on a bar 14 which is supported on springs from lugs 15 projecting from the side walls of the inner body.
A clinker ejecting ram 16 is reciprocable over the fire bars 12 by an oscillating crank 17 which can be operated manually or by an electric motor operated automatically in accordance with the output of the boiler.
Clinker is ejected by the ram over the front edge of the fire grate into an ashpan 18 housed in the base of the boiler and accessible for removal through ,a detachable cover 19.
Access to the fire space (immediately above the grate) is provided through an aperture 20 passing through a front water space 21. This aperture is closed by a hinged door 22 provided with a sighting glass 23. Holes 24 are provided in each side of the boiler through either of which may be inserted a gas poker for lighting the fire.
A double walled partition 25 providing a water space 26 projects upwardly from above the rear end of the grate towards the top of the boiler and forms with the sloping wall 3 a front flue 27 and with the rear wall 28 of the boiler (which is double to provide a water space 29) a rear flue 30. The rear flue 30 leads to a smoke box or outlet flue 31.
Within the front line 27 is a water chamber 32 which is shaped and positioned so as to ensure even division of the flue gases through the passages 33 and 34 at its front and back respectively. This is achieved partly by sloping the bottom 35 of the water chamber 32 upwardly towards the front and partly by terminating the water chamber 32 a sufiicient distance below the top of the central partition 25. The gases are thus encouraged to pass forwardly of the water chamber 32 and to impinge on the rear of the wall 3.
The front wall of the water chamber 32 is at a slightly less great slope than is the wall 3 so that the front passage 33 is narrower at the top than at the bottom and the rear wall of the water chamber 32 is sloped so that the rear passage 34- also narrows somewhat towards the top.
The rear flue 30 through which the gases pass downwardly is deep enough to increase eificiency by providing heat transfer surfaces but is short enough not to create sufiicient back pressure to negative the upward trend of the gases in the front flue 27. This is particularly important during periods when the boiler is idling on low loads under low flue depression.
At the head of the flues 27 and 3b is a space which is tapered inwardly on all four sides, to reduce heat losses and to permit gases to impinge on thesesides. This atrangement also assists the passage of water across the head of the water jacket.
In the top of the boiler above the head space is provided a flue cleaning aperture 36 closed by a cover 37. A flue brush may be passed through this aperture straight down either the passages 33 and 34 of the front flue 27 or the rear flue 30 so that flue sweeping is greatly facilitated.
The boiler is normally operated under forced draught supplied by a fan 38. The delivery side of which is connected to a chamber 39 behind the fire grate; The major part of the air passes below the fire grate and then upwardly through the fire bars and the fuel bed to the front flue 27 dividing on each side of the water chamber 32 to pass through the passages 33 and 34 to unite above the water chamber 32 and pass downwardly through the rear flue 30 to the smoke box 31 and so to the atmosphere.
Part of the air from the fan 38 is directed to above the fire bed, this secondary air being used for the combustion of unburnt gases arising from the grate. An aperture 40 connects the chamber 39 to a secondary air box 41 the outlet of which leads to the space above the fire bed and is controlled by a valve 42 operable by a handle 43 so that the amount of secondary air delivered can be controlled. The outlet 44 through which the secondary air enters the combustion space is directed downwardly (for example by being formed with a downwardly inclined lip) so that the secondary air is directed downwardly towards the fire bed. The path of the primary and secondary air is indicated in Fig. 1 by'the full-line arrows.
In the outlet of the fan 38 is an arrester flap 45- freely pivoted about a spindle 46. A rotary cam 47 acts as a stop to limit the amount by which this flap can be raised by the blast from the fan and this cam can be rotated to vary the amount of opening and so control the delivery of air when the fan is operating. Another stop 48 limits the extent to which the flap 45 can close the outlet from the fan and this stop can be adjusted by a lever 49. In this way the amount of air entering the tire bed during idling periods when the fan is not running can be regulated. This flap is biassed to the closed position and limits the combustion air to the boiler immediately the fan stops thereby reducing immediately the combustion rate when the predetermined thermostat setting (by which the fan is controlled), has been achieved. Furthermore the bias of the flap to the closed position prevents the flap opening under high flue depression which may occur for example on windy days and which would cause over-idling.
From the bottom of the smoke box 31, a duct (9 leads to the chamber 39 and so to the ash tray. This duct is normally closed by a shutter 51 so that fly dust and the like can accumulate at the bottom of the smoke box. The shutter 51 can when needful be pivoted about a spindle 52 by a handle 53 to allow the accumulated soot to fall into the ash tray.
The water passages of the boiler and the path of the water through them is seen best from Figs. 2 and 3 of the drawings in which the water path is indicated by the dotted arrows. The cold water enters (preferably from each side) at the bottom of the boiler into the side water passages 54 and front passage 21. Across the side passages 54 are deflectors 56 which direct the water into the water space 6 below the wall 5 whilst in the front passage 21, deflectors 57 prevent the water sneaking up the front instead of entering the water space 6. The water enters the bottom part of the space 6 and is directed, by baflles 58 projecting inwardly from each side, to the top part of the space 6. From the spacer the water passes back into the side passages, 54 and is directed by deflectors 59 into the lower part of the water chamber 32. Bafiles 6 0 projecting inwardly from each side direct the water inwardly and to the top of the water chamber from which it passes to the side walls. Water also passes from the side passages to the water space 4 of the wall '4 3, the water space 26 of the partition 25 and the water space 29 of the boiler rear wall 28. The hot water is taken from the boiler through the outlet 61 at the top of the boiler.
A thermostat 62 and thermometer 63 are provided near the top of the water passages. A safety valve 64 is provided and is arranged so that in the event of a blow off, it discharges water into the fire box by way of the hopper and so dowses the fire.
it will be appreciated that the invention is not restricted to the details of the preferred form which may be modified without departure from the broad ideas underlying them.
1. A boiler comprising a casing, means in said casing forming a fire chamber, a fuel hopper enclosed by said casing and having an outlet above said fire chamber through which fuel is fed from the hopper to said fire chamber, said hopper having a rear wall sloping upwardly and backwardly from said outlet, said rear wall forming the front wall of an upwardly directed tapering flue passage, a partition within said casing forming the rear wall of said flue passage and the front wall of a downwardly directed flue passage, the top of said partition lying below the top of said casing, said casing having a rear wall forming the rear wall of said downwardly directed flue passage, means forming an outlet flue to which the flue gases pass after passing upwardly through said tapering passage and said downwardly directed passage, wall means forming a water chamber within the tapering flue passage and defining with the front and rear walls thereof through passages each of which is in communication with the upper end of said downwardly directed flue passage, said through passages having substantially equal areas for directing the flue gases in substantially equal amounts to said downwardly directed flue passage, means forming passages for directing primary air for combustion through the fire chamber and secondary air for combustion above the fire chamber, a fan for supplying both primary and secondary air, and an adjustable valve in said passage forming means in the path of the secondary air from said fan to said fire chamber and controlling the ratio of primary to secondary air.
2. A boiler comprising a casing, means in said casing forming a fire chamber, a fuel hopper enclosed by said casing and having an outlet above said fire chamber through which fuel is fed from the hopper to said fire chamber, said hopper having a rear wall sloping upwardly and backwardly from said outlet, said rear Wall forming the front wall of an upwardly directed tapering fluea rear wall forming the rear wall of said downwardly;
directed flue passage, means forming an outlet flue to which the flue gases pass after passing upwardly through said tapering passage and said downwardly directed passage, wall means forming a water chamber within the tapering flue passage and defining with the front and rear walls thereof through passages each of which is in communication with the upper end of said downwardly directed flue passage, said through passages havingsubstantially equal areas for directing the flue gases in substantially equal amounts to said downwardly directed flue passage, said hopper rear wall, casing rear wall and partition all comprising double wall structures forming water spaces along said flue passages, means in said casing and adjacent each side thereof forming water jackets in communication with said water spaces and water chamber, means in said casing between said fire chamber and the bottom of said hopper forming a water chamber in communication with said water jackets, and baflile means in said water jackets directing water therefrom to said water spaces and water chambers.
5 3. A boiler according to claim 2, comprisng bafile means in said water chamber and spaces intermediate their height to circulate water therein, said jacket baffle means being disposed to direct water into the lower ends of said water spaces and chamber.
References Cited in the file of this patent UNITED STATES PATENTS 420,636 Switzer Feb. 4, 1890 6 Harpporte Dec. 3, 1907 Satchwell Dec. 19, 1950 Smith Apr. 1, 1952 FOREIGN PATENTS Denmark Oct. 1, 1928 Great Britain Oct. 27, 1939 Great Britain Mar. 14, 1940