The present invention relates to a device for controlling secondary air supply to a burner or a combustion chamber and is referred to as Secondary Burner Air Register and briefly as "SBAR" hereafter in the specification.
A "SBAR" device for use with a burner in the combustion chamber is useful to achieve optimum fuel-air ratio for burning in order to maximize efficiency of the burner. This device is also required to control secondary air flow to a burner in accordance with the furnace load. By efficient control of secondary air flow to a burner, problems associated with the furnace operation such as flame impingement in the tubes and maintenance of optimum level of oxygen in a furnace resulting in the minimization of undesirable gases being released to the atmosphere and other advantages known to persons in the art are possible to a great extent.
Various designs of devices for controlling secondary air to burners are known to the prior art. Most of such known prior art devices have a number of inherent disadvantages.
In general it has been observed that burner manufacturers do not give due importance to the design of the control devices for secondary air to a burner and as a result operation and maintenance are found to be troublesome and a major weak point in satisfactory operation of the burner as a whole.
For instance, due to proximity of a control device or "SBAR" to the flame and working environment of the combustion chamber it is exposed
to pollutants e.g. dirt, soot and overflow/seepage (spillage) of fuel oil from the burner tip which cause moving parts of its control mechanism to get jammed.
Over a period of time wear and tear on the drive mechanism for adjusting inflow of air of prior art devices, result in misalignment of louvers and therefore unequal opening thereof. Unequal opening of the louvers causes uneven distribution of air as well as inaccurate control of air flow which in turn results in improper and uncontrolled burning of fuel. Moreover, maintenance of prior art control or "SBAR" devices require complete shutdown of the burner/combustion chamber, causing substantial production losses.
All the afore-mentioned defects in prior art devices for control of secondary air to burners or "SBAR" are sought to be overcome by the present invention. Accordingly, objects of the present invention are to provide the following advantages:
1. Smooth flow and circumferential entry of secondary air to a burner thereby providing turbulence due to swirling motion of the entering air stream;
2. Circumferential entry of secondary air to cause turbulence which helps proper mixing of fuel/air mixture resulting in improved burning efficiency;
3. Protection of the driving mechanism which is through mechanical linkages that are insulated from any damage due to heat, dirt,
soot or overflow/slipages of fuel oil associated with the normal
operation of a burner; and 4. To provide control of secondary air flow over an infinite range of air
flow and ability to maintain a desired rate of flow of air to a burner.
The objects of the invention are achieved by the novel construction of a secondary air control device for use with a burner in a combustion chamber which will enable efficient control of the air flow to a burner and help in improving burner efficiency.
According, the present invention provides a device for controlling secondary air supply to a burner or a combustion chamber, said device comprising a cylindrical wall frame, for surrounding the combustion chamber and/or burner, spaced evenly along said cylindrical wall frame are a plurality of cutouts for entry of controlled secondary air to the combustion chamber, each of said cutouts having correspondingly sized openable/closable louvers hingedly mounted to the cylindrical wall, a driving mechanism, each of said louvers individually connnectible with said driving mechanism through a drive link connecting a said louver with said driving mechanism, each said driving link being selectively disconnectible from a said louver and replaceable by a lock link whereby desired number of louvers are lockable while other said louvers are operable to be opened to a desired degree so as to enable a controlled flow of secondary air to said burner, said driving mechanism comprising a set of combination rings, one slidable on top of another fixed ring secured to said circular wall frame, a drive wheel, universal joint and
lead screw coupled to said sliding ring so as to rotate said sliding ring back and forth and said drive links connected thereto alongwith the desired louvers to be operated, a concealed sliding means being provided between said two rings comprising a concealed guide channel provided intermediate said rings and inaccessible to outside pollutants, said concealed guide channel having therein rolling elements, a skirt attached to said circular wall frame and adapted to protect said driving mechanism from contaminants which could jam said driving mechanism.
The inventive device consists of a cylindrical main wall frame having a circular flange which is bolted to the floor of a combustion chamber having a burner fitted inside the cylindrical main wall frame. The cylindrical main wall has located thereon evenly spaced cutouts and corresponding number of louvers fitted to the wall surface by means of hinges.
Through mechanical linkage means the louvers are openable and closable to a desired degree. For convenience up to 50% of the louvers can be taken out of operation by replacing driving links of the driving mechanism connected thereto by a separate set of lock links.
The drive links and the lock links are so designed that they can be operated i.e. locked and unlocked without disturbing their respective functions. The lock links keep the respective louvers in closed condition when those louvers are taken out of operation for a desired mode of operation.
The driving mechanism for opening and closing of the louvers consists of a manually operable driving wheel, lead screw, universal joint and a combination set rings (one fixed and one sliding). The rings are oriented horizontally one above the other. The lower ring is fixed to the wall frame and the top ring is rotated by means of a driving wheel. The top ring is slidable on a set of steel balls or rollers and fixed guides. The steel balls or rollers are placed in a concealed groove in the rings so as to ensure dirt does not enter and jam movement of the sliding ring. One end of each drive link is connected to the sliding ring.
The louvers are connected with the sliding ring through a set of drive links having two pins on each link. The drive links are located on bushes fitted on the louvers at one end and the other end on the sliding ring. The louvers can be engaged or disengaged by lifting and rotating respective drive links in or out of engagement with the louvers.
A separate set of links called lock links are provided for locking alternate louvers in a closed configuration when desired. Similarly, the lock links are engagable or disengaged from the louvers by lifting and rotating the lock link in or out of engagement with the louvers.
A separate lock is provided in the lead screw for locking the driving wheel. By a half turn of the twist lock the louvers/driving mechanism is lockable in a fixed position so as to allow a constant desired flow of air to the burner.
Preferably, the combination set of rings, lead screw and universal joint are covered by a skirt made of sheet metal so as to protect these
features from contaminants such as soot, dirt and oil spillage. The metal skirt and the bottom ring are fitted to the cylindrical wall by means of bolts.
The invention will now be explained in detail with reference to the accompanying drawings by way of example in which :
Fig. 1 illustrates a front elevation of the novel device for controlling secondary air supply to a burner and is also referred to as a secondary burner air register (SBAR);
Fig. 2 is a top plan view of the control device or secondary burner air register;
Fig. 3 is a cross-sectional view on the line B-B marked in Figure 1;
Fig. 4 is a cross-sectional view on the line A-A marked in Figure 1;
Fig. 5 illustrates a half cross-sectional elevational view on the line C-C marked in Figure 2;
Fig. 6 illustrates sliding ring details;
Fig. 7 illustrates details of the bottom fixed ring;
Fig. 8 illustrates the metallic skirt which serves to protect the driving mechanism.
Also illustrated in sheets 3, 4 and 5 are individual parts and sections of the major figures.
In the preferred embodiments, Figure 1 illustrates an elevational view of the device for controlling secondary air supply also referred to as secondary burner air register (SBAR). The secondary air control device generally comprises a cylindrical wall frame 2 which surrounds the
combustion chamber. A plate-flange 1 attached to the cylindrical wall frame 2 is bolted to the combustion chamber floor or ceiling as convenient.
Spaced evenly along the circumference of the cylindrical wall 2 are a plurality of cutouts for entry of controlled secondary air to the combustion chamber. The amount by which the cutouts can be allowed to permit secondary air to enter the combustion chamber is controlled by the louvers 3 which are mounted by means of hinges 4 fixed to the cylindrical wall frame 2. The hinges 4 preferably are of the type consisting of a single pin which is covered by a cap washer which prevents entry of dirt or other matter which would cause sticking or jamming.
The opening and closing of louvers 3 are operated by a driving mechanism with a driving wheel 9 to enable simultaneous operation of desired number of louvers 3. Fixed to each louver 3 and the cylindrical wall frame 2 adjacent the louver 3 are a pointer 5 and scale 5A so as to indicate the extent of opening of each louver 3. A detail of the pointer and scale 5 and 5A are shown below Fig. 5.
The driving mechanism has the driving wheel 9 connected by means of universal joint 9A and a lead screw 9B
Manually operable driving wheel 9 is connected by means of the lead screw 9B, universal joint 9A and a combination set of rings 18 and 19 to the louvers 3. The rings 18 and 19 are oriented horizontally one above the other. The lower ring 19 is fixed to the cylindrical wall frame
2. Further details of the driving mechanism are given in the description hereafter.
Figure 2 depicts a top plan view of the device for controlling secondary air to the burner which will be located inside cylindrical wall frame 2. The plate flange 1 is shown attached to the wall 2 and may be bolted appropriately to the floor or ceiling as convenient.
Figure 3 depicts a cross-sectional plan view on the line B-B marked in Figure 1 and shows at hinges 4 spaced evenly around the cylindrical wall 2.
Figure 4 depicts a cross-sectional plan view on the line A-A marked in figure 1 and shows a lower portion of the device for controlling secondary air. In this figure driving links 6 and lock links 7 are illustrated. As shown driving links 6 are in the engaged position. These driving links 6 have to be disengaged from the driving mechanism 9 by lifting the desired driving links 6 from the pin-bush combination [11, 11 A]. Thereafter the desired louvers 3 are lockable by disengaging respective lock links 7 from their locked positions.
This is accomplished by rotating the lock links 7 and engaging them in the same bush 11A previously occupied by the disengaged driving link 6. Depending on the louvers 3 maintained in closed position by respective lock links 7, the air flow to the secondary burner air register is kept regulated.
Figure 5 is a half cross-sectional elevational view of the SBAR illustrating inside details of the louvers. Inward movement of the louvers
is prevented by the help of any known means such as a stopper fixed to the cylindrical frame 2.
Depicted below Figure 5 are details of various features such as the pointer 5 and scale 5A. Also shown are details of the locking lever 10, hand wheel 9, lead screw 9B, collar bolt (pin) 11 and other minor details are illustrated.
Figures 6 and 7 show the sliding ring and bottom ring as well as details and sections thereof. Sliding ring 18 is mounted to slide above the bottom ring 19 through the medium of a concealed sliding mechanism. The sliding mechanism may consist of steel balls and fixed rollers accommodated in a guide channel in the rings 18 and 19. The sliding rings 18 has fixed thereto collar pin and bush 11 and 11 A. The collar pin and bush 11 and 11A are fixed on a slotted elliptical guide hole 11B on the sliding ring 18 and it allows and guides to and fro movement of the top sliding ring 18. The bottom ring 19 is fixed to the cylindrical wall frame 2 by bolting. The top sliding ring 18 and fixed bottom ring 19 are coupled to each other by guide bolts. Cross-sections of the top sliding ring 18 are shown at three locations i.e. XX, YY and ZZ above Fig 6. A bush 12 is welded to the sliding ring 18 through which universal joint 9A of the driving wheel 9 [both shown in detail below Fig. 5] are attached.
Support bar 15 is welded to the bottom ring 19 for supporting the lead screw 9B of the hand wheel 9. Mounting bracket 16 enables fixing of the bottom ring 19 to the cylindrical frame 2. Collar pin 11 is fitted
through the hole 11C on the bottom ring 19. Steel balls or rollers 17 are placed in grooves which help the sliding ring 18 to slide freely on fixed bottom ring 19. Hand wheel 9 is connected to the cleat 14 of the bottom ring 19 through lead screw 9B and universal joint 9A.
To enable the driving mechanism to be protected from dust, dirt, oil spillage and any other contaminants and thereby prevent extra wear and tear or jamming of parts, there is a metal skirt 8 fixed to the cylindrical frame 2 through the medium of nuts and bolts so as to cover the entire driving mechanism. A moveable lid 8A is provided to cover lock lever 10.
Although the invention has been shown and described with respect to exemplary embodiments thereof, it should be understood by those skilled in the art that various changes, omissions, and additions may be made therein and thereto, without departing from the spirit and scope of the invention.

WE CLAIM:
1. A device for controlling secondary air supply to a burner or a combustion chamber, said device comprising a cylindrical wall frame, for surrounding the combustion chamber and/or burner, spaced evenly along said cylindrical wall frame are a plurality of cutouts for entry of controlled secondary air to the combustion chamber, each of said cutouts having correspondingly sized openable/closable louvers hingedly mounted to the cylindrical wall, a driving mechanism, each of said louvers individually connnectible with said driving mechanism through a drive link connecting a said louver with said driving mechanism, each said driving link being selectively disconnectible from a said louver and replaceable by a lock link whereby desired number of louvers are lockable while other said louvers are operable to be opened to a desired degree so as to enable a controlled flow of secondary air to said burner, said driving mechanism comprising a set of combination rings, one slidable on top of another fixed ring secured to said circular wall frame, a drive wheel, universal joint and lead screw coupled to said sliding ring so as to rotate said sliding ring back and forth and said drive links connected thereto alongwith the desired louvers to be operated, a concealed sliding means being provided between said two rings comprising a concealed guide channel provided intermediate said rings and inaccessible to outside pollutants, said concealed guide channel
having therein rolling elements, a skirt attached to/said circular wall frame and adapted to protect said driving mechanism from contaminants which could jam said driving mechanism.
2. A device as claimed in claim 1, wherein said circular wall frame is made of metal sheet having a flange fixed thereto, said flange being provided either at the top of said wall whereby said flange is securable to ceiling of said combustion chamber, said flange may also be provided at the bottom of said cylindrical wall and secured to floor of said combustion chamber, said louvers being connected to said wall frame by hinges, each of said hinges having a hinge pin with a cap portion which prevents entry of dirt or contaminants to the lower parts of the hinge and so prevent jamming or restriction in movement, said louvers openable in a circumferential manner on rotation of said sliding ring connected by respective drive links to said louvers, whereby entry of air to the burner(s) takes place in a circumferential manner.
3. A device as claimed in claim 1 or claim 2 wherein each said driving link consists of a bush and pin type joint, one part of said driving link fixed to said sliding ring and other part of said driving link removably fixed to a said louver opposite said hinged side, one of said driving link parts being liftable out of engagement with said other part so as to disconnect a said louver from said sliding ring of said driving mechanism.
4. A device as claimed in any of claims 1, 2 or 3 wherein said lock links have one end thereof fixed to said cylindrical wall adjacent said louver and other end thereof is engageable with the louver opposite said hinged side thereof, said lock link engageable in the part thereof previously engaged by a said drive link, said lock links enabling desired number of louvers to be retained in a closed position.
5. A device as claimed in any of the preceding claims wherein said combination rings of said driving mechanism are engaged with each other by means of a set of guide bolts, ellyptical holes in the sliding ring enabling the sliding ring to move back and forth under action of said driving wheel, universal joint and lead screw.
6. A device as claimed in any of the preceding claims wherein said driving mechanism is provided with a locking lever to enable said driving mechanism and said louvers to be locked in a desired position, so that a desired airflow is maintainable, a movable lid being provided so as to cover the locking lever from dust and spilt contaminants.
7. A device as claimed in any preceding claim wherein affixed to at least one said louver is a pointer and a scale is secured in relation therewith to enable indication of the degree of openness of the louvers by said driving mechanism.
8. A device for controlling secondary air supply to a burner or a combustion chamber substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.