Patent Abstract:
This invention discloses improvements to a damper of the type used in industrial applications to open and close ducts carrying noxious or corrosive materials, such as combustion by-products. The improvements include a linear rack and wheeled pinion system to raise and lower a damper blade plate and improvements to the seal cartridge to prolong the life of the seal membrane and to prevent galling between the blade plate and the seal cartridge or damper frame.

Full Description:
FIELD OF THE INVENTION 
     This invention relates to industrial dampers of the type used in flue gas ducting systems and, in particular, provides improvements to the type of damper utilizing a sliding blade mechanism and inflatable seal. 
     BACKGROUND OF INVENTION 
     The devices of the type disclosed herein are used principally in industrial settings having exhaust duct systems with large cross sectional dimensions wherein exhaust gases must be processed by scrubbers and/or precipitators before they can be released to the air through a smokestack. An example of use for the damper of the present system would be in a power plant where combustion by-products must be released. Such combustion by-products may contain sulfur dioxide, carbon monoxide, carbon dioxide and other noxious and corrosive compounds. In addition to corrosive compounds present in the exhaust gases, temperatures within the ducts may reach highs in the range of 300° to 700° F. 
     It is desirable in such settings that the flow of combustion by-products through individual ducts be interrupted at various times for the purpose of performing maintenance on the scrubbers and precipitators within the exhaust system. Therefore, a typical application of the damper of the present invention would be within a duct in an exhaust system from an industrial plant to isolate a scrubber and/or a precipitator from the normal flow of combustion by-products. Because the ducts carrying the combustion by-products may be relatively large, for example, on the order of twenty-five to four hundred square feet in cross sectional area, it is possible that maintenance workers may be required to physically enter the duct to perform maintenance operations. It is therefore necessary that a seal be provided such that combustion by-products do not leak past the damper and into the area where maintenance workers may be present. 
     Typical prior art dampers of the type for which improvements are shown by this invention consist of a frame which is secured inline in a duct carrying combustion by-products. A blade typically slides into the cross sectional area of the duct from an area outside of the duct to close the duct, thereby interrupting the flow of the combustion by-products past the damper. In addition, to better seal the duct against leaks of the combustion by-products past the damper blade, a seal within the damper contacts the blade and is forced against the blade by an inflation pressure provided by compressed air which may be inserted into a hollow area of the seal. To open the damper it is known in the art to evacuate the air from within the seal to cause the seal to collapse away from the blade, thereby allowing the blade to be retracted to open the duct. 
     Such a damper is shown in U.S. Pat. No. 4,561,472 (Dryer et al.). The damper of the &#39;472 patent is typical of those shown in the many patents of the prior art and improvements thereto are disclosed by this invention. Other similar dampers are also shown in U.S. Pat. No. 4,235,256 (Crawshay), U.S. Pat. No. 4,163,458 (Bachmann) and U.S. Pat. No. 4,022,241 (Fox). 
     One problem with the damper disclosed by Dryer et al. is that a failure of the seal may be precipitated by a failure of the compressed air system, which may allow the seal to deflate, thereby allowing combustion by-products to leak around the blade. A further problem with the prior art dampers of the type disclosed by Dryer et al. is that the blade, which may be subjected to differential pressure gradients and be relatively heavy, on the order of 4 plus tons, may contact the seal cartridge frame during retraction and engagement, causing galling to develop between the blade and the seal cartridge frame. This is particularly troublesome in corrosive environments where alloy materials must be utilized. Further, the mechanism for raising and lowering the blade in the prior art systems is prone to fouling by the collection of dust and dirt and through corrosion of the mechanism by continued exposure to the corrosive elements present in the combustion by-products. Lastly, the flexible seals of the prior art are typically permanently affixed to the frame of the damper, making it difficult to repair or replace the seal when necessary. These and other problems with the prior art are addressed by the current invention. 
     SUMMARY OF INVENTION 
     The device of the present invention is an improved damper of the type shown in the prior art and consists primarily of a frame which is provided with mounting flanges with holes sized for fasteners to attach to adjacent ductwork flanges. The invention includes a removable seal cartridge installed within and parallel to the frame. The seal cartridge inserts into the frame as a single unit, and may be removed and inserted through a lower access cover or a removable bonnet panel. A gasket may be attached to the seal cartridge and placed between it and the frame. 
     A bonnet is attached to the frame and is disposed directly above the frame, but outside of the cross sectional area of the duct. When the damper is in the open position, a blade plate is stored in the bonnet. When the damper is in the closed position, the blade plate translates into the area of the frame inside the duct with a motion which is essentially parallel to the frame. The bonnet provides an integrated area in which to store the blade plate when the damper is open and eliminates the need for seals between the lower frame section of the damper and the upper blade storage section of the damper. 
     In one improvement over the prior art, the opposing edges of the blade parallel to the direction of movement are formed into a rack system consisting of a toothed edge. The toothed edges of the blade plate engage with specially designed pinion wheels to impart a linear force to the blade plate thereby causing it to translate into and out of the area within the frame to open and close the damper, depending upon the direction of rotation of the pinion wheels. The invention employs circular pinions fabricated of pinion wheel sides fixated with a plurality of pinion pins. The pinion wheel sides also act as a guide for the blade plate as it translates into and out of the duct. The blade plate edges are each cut as a linear rack of a shape and dimension such that any thermal expansion of the blade is accommodated. The engagement of the pinion wheels with the blade is self-cleaning and virtually maintenance free. The use of pinion pins is an improvement over pinion gears in that solid matter and effects of corrosion do not deteriorate performance of the drive over time. 
     Compressed air is injected into or evacuated from the seal cartridge to operate the seal. The seal, when in the inflated position, engages the blade plate to form an air-tight barrier. When the air is evacuated from the seal cartridge, the seal collapses due to negative air pressure and the blade plate may be retracted into the bonnet. The seal cartridge is fitted with an air fitting for injection of compressed air into the seal cartridge and for evacuation of air from the seal cartridge. In another improvement over the prior art, the seal membrane of the present invention is able to maintain contact with the blade plate even in the event of a failure of the compressed air system, thereby providing a failsafe seal. 
     The seal cartridge is fitted with a blade guide composed of a hardened metal along which the blade plate rides as it translates into and out of the damper. The hardened metal blade guide prevents the cold welding or galling between the heavy blade plate and the seal cartridge which was a problem with prior art designs. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of the damper of the present invention installed in an attached duct. 
         FIG. 2  is an isometric view of the damper of the present invention. 
         FIG. 3  shows a cut-away close-up view of the pinion wheel and motor assembly. 
         FIG. 4  is a side sectional view of the seal cartridge. 
         FIG. 5  is an isometric cut-away view of the seal cartridge installed in the frame. 
         FIG. 6  is a front elevational view of the damper. 
         FIG. 7  is a rear elevational view of the damper. 
         FIG. 8  is a right elevational view of the damper. 
         FIG. 9  is a bottom view of the damper. 
         FIG. 10  is an isometric cut-away view of the accessory lifting mechanism for removing the seal cartridge from the frame. 
         FIGS. 11   a ,  11   b  and  11   c  are side elevational, front elevational and isometric views respectively of the pinion wheel construction. 
         FIG. 12  is a side cross section view of the damper having the blade plate in the open position. 
         FIG. 13  is a side cross section view of the damper having the blade plate in the closed position. 
         FIG. 14  is a schematic view of an exemplary system for inflating and deflating the air chamber of the seal cartridge. 
     
    
    
     DETAILED DESCRIPTION 
     The damper  1  of the present invention is shown in detail in  FIG. 2  and in situ installed in duct  2  in  FIG. 1 . Damper  1  consists essentially of frame  10 , having a lower section  5 , as shown in  FIG. 6 , disposed within the cross sectional area of attached duct  2 , and an upper section  6 , disposed adjacent to lower section  5  and outside of the cross sectional area of duct  2 . In a normal installation, upper section  6  will be above lower section  5 , but, in practice, there is no reason why upper section  6  cannot be disposed to the right, to the left, or below lower section  5 . Frame  10  can be attached to duct  2  by any conventional means known in the prior art, such as through the use of bolts or folded flanges. 
     Seal cartridge  12  is situated within lower portion  5  of frame  10 , as shown in  FIG. 5  and can be removed by opening seal access port  22 , located at the lower extremity of frame  10 , as shown in  FIG. 9 . Seal access port  22  allows seal cartridge  12  to be removed for maintenance and/or replacement. Seal cartridge  12  may also be removed for maintenance and/or replacement by use of a blade lift attachment  25 , shown in  FIG. 10 , which allows blade plate  16  to lift seal cartridge  12  out of frame  10  when bonnet  14  is removed. Blade lift attachment  25  is hooked over blade plate  16  and attached to holes defined in ears  74 , which are affixed to seal cartridge  12 . 
     When in place, seal cartridge  12  is secured to frame  10  via a series of bolts extending through holes defined in the bottom of U-shaped flange  62  (not shown) which align with a corresponding series of holes defined in frame  10 . The bolts are secured with nuts. Preferably, to reduce leaks of compressed air from air chamber  65 , the nuts are welded to the inside of U-shaped flange  62  around the holes defined therein. Alternatively, seal cartridge  12  may be secured within frame  10  by one or more clamps (not shown). 
     When in position within lower portion  5  of frame  10 , seal cartridge  12  provides an opening  13  through which material within attached duct  2  can flow when damper  1  is in the open position. 
     Upper portion  6  of frame  10  consists of enclosed bonnet  14  which will normally extend above and outside of attached duct  2 . Bonnet  14  houses blade plate  16  when damper  1  is in the open position, as shown in cross sectional view in  FIG. 14 . Bonnet  14  is integral with lower portion  5  and thereby eliminates the need for additional seals between frame  10  and blade plate  16 . 
     When damper  1  is in the open position, as shown in the cross-sectional view in  FIG. 13 , blade plate  16  is disposed within bonnet  14 , guided by frame members  24 , and area  13  in lower portion  5  of frame  10  is free of obstruction. To close damper  1 , blade plate  16  is translated into lower position  5  of frame  10 , and is situated between frame  10  and seal cartridge, occupying space  76  as shown in  FIG. 5 , thereby obstructing the flow of material through opening  13 . This is shown in a cross-section in  FIG. 12 . To provide an air-tight seal, seal membrane  70  is inflated with a compressed air to force it into contact with blade plate  16 . 
     Blade plate  16  is configured with a linear rack of toothed openings  17  on opposing sides thereof, which engage pinion wheels  18  disposed on opposite sides of frame  10  and extending through bonnet  14 . Pinion wheels  18  are housed in housings  20  which extend from the sides of bonnet  14 . In some embodiments of the invention, only one side of blade  16  may have linear rack  17  defined thereon and only one pinion wheel  18 . Such a configuration may be used, for example, where damper  1  is situated such that upper portion  6  of damper  1  extends from the side of duct  2  instead of from the top, and where the motion of blade plate  16  is horizontal as opposed to vertical. 
     Pinion wheels  18  are shown in  FIGS. 11   a - c , and consist of pinion wheel sides  84  attached radially with pinion wheel hub  80 , through which shaft  100  passes, and which, in turn, is eventually driven by motor  30  (see  FIG. 3 ). A plurality of pinion pins  82  are disposed between pinion wheel sides  84  at a point between pinion wheel hub  80  and the outer radius of pinion wheel sides  84 , and are held in place thereby. The actual number, size and spacing of pinion pins  82  may be varied without departing from the spirit of the invention, and is dependent upon, among other factors, the size and weight of blade plate  16 . The spacing, size and frequency of slots  17  in the linear racks located along the sides of blade plate  16  must, of course, correspond with the frequency, size and shape of pinion pins  82  in pinion wheels  18 . Additionally, hub  80  may be optional; pinion wheel sides  84  may be attached directly to the shaft of a motor or geared drive. 
     Rack  17  on each edge of blade plate  16  are cut of such a shape and dimension such that thermal expansion of blade plate  16  is accommodated. Pinion wheels  18  on either side of blade plate  16  counter rotate with respect to each other, thereby allowing blade plate  16  to move upward into bonnet  14  or downward into lower section  5  of frame  10 . The movement of blade plate  16  is guided by blade guide  24  and also by pinion wheel sides  84 , as shown in the cut-away view of  FIG. 3 . 
     Pinion wheels  18  are driven in counter rotating directions in the preferred embodiment by motor  30 , which is linked to drives  32 . Drives  32  for respective pinion wheels on the left and right side of damper  1  are connected by connecting rod  34 , and, optionally, by flexible joints (not shown) located between drives  32  and connecting rod  34 . Therefore, the motion of pinion wheels  18  is mechanically synchronized to insure that both sides of blade plate  16  are raised and lowered simultaneously. Alternate methods of rotating pinion wheels  18 , such as the use of varying number of motors and varying configurations of linkages are contemplated to be with the scope of this invention. 
     The engagement between pinion pins  82  and linear racks  17  is virtually maintenance free. The use of pinion pins  82  represents an improvement over the prior art pinion gears in that solid matter and the effects of corrosion do not deteriorate the performance of the drive over time. 
     Seal cartridge  12  is shown in detail in  FIGS. 4 and 5  and consists primarily of frame  10  upon which is mounted seal membrane  70 . Seal membrane  70  is composed, in the preferred embodiment, of a reinforced fluoroelastic material with reinforcing fibers oriented radially about the center of the seal. Fluoroelastomers (FKM) used in the preferred embodiment of the invention are of the type manufactured in the United States by Dupont Dow Elastomers, L.L.C. of Wilmington, Del. under the trade name Viton® and by Dyneon, L.L.C of Oakdale, Minn. under the trade name Fluorel®. FKM is often used as expansion joints in ducts. Preferably, the corners of seal membrane  70  are shaped as a quarter circle having a radius essentially compatible with the overall seal proportions. The reinforcing fibers in the seal membrane may be stainless steel, nickel alloy, fiberglass, polyester, Kevlar® or any other high-strength material. In some instances, it may be preferable that the reinforcing material be a corrosion-resistant material. 
     Seal membrane  70  is attached to U-shaped flange  62  using bolts  68   a  and  68   b  as shown in the cross-sectional view of seal cartridge  12  in  FIG. 4 , thereby forming air chamber  65 . Alternatively, welded studs may be used in place of bolts  68   a  and  68   b  to attach seal membrane  70  to U-shaped flange  62 . Compressed air can be forced into air chamber  65  or evacuated from air chamber  65  via air valve  19  shown in  FIG. 4 . Seal membrane  70  is shown in its normal position in  FIG. 4 . This positioning of seal membrane  70  is assumed in the absence of negative air pressure within air chamber  65 , that is, when compressed air is introduced into air chamber  65 , or when there is a neutral air pressure in air chamber  65 . As a result, the contact between seal membrane  70  and blade plate  16  will be maintained even in the event of a failure of the compressed air system, or in the event of a leak in air chamber  65 . Reference number  72  in  FIG. 4  shows the position of seal membrane  70  assumed when air chamber  65  is evacuated under negative air pressure. Position  72  of seal membrane  70  is assumed when blade plate  16  is translating from one position to another, to avoid contact between irregularities, rough surface areas or corrosion extant on blade plate  16  with seal membrane  70 , thereby further prolonging the life of seal membrane  70 . 
     Inner seal guide  64  and outer seal guide  66  prevent creasing of the fluorelastomer and therefore further prolongs the life of seal membrane  70 . The offset position of bolts  68   a , located on the inner surface of flange  62 , and  68   b , located on the outer surface of flange  62 , with respect to each other force seal membrane  70  to assume its normal (non-evacuated) position even during a loss of air pressure within air chamber  65 . 
     During the operation of damper  1 , air chamber  65  is evacuated under negative air pressure through air valve  19  and seal membrane  70  is drawn into position  72  against inner and outer seal guides  64  and  66  respectively, to avoid contact with blade plate  16  as blade plate  16  translates into or out of bonnet section  14 . If damper  1  is being closed, blade plate  16  moves into a position juxtaposed with seal cartridge  12  and in between seal cartridge  12  and frame  10 , to occupy space  76  shown in  FIG. 5 . As blade  16  is translating into this position, seal membrane  70  is held against seal guides  64  and  66  by negative air pressure within air chamber  65  to prevent contact with blade plate  16 . 
     Blade guide  60  is preferably welded to flange  62  and serves as a guide for blade plate  16  to ride along, further negating the possibility of contact between blade plate  16  and seal membrane  70 . Preferably, blade guide  60  is composed of a hardened metal or a soft metal having a hardened metallic coating, such that blade guide  60  has a hardness greater than that of blade plate  16 . When fully lowered into lower section  5 , blade plate  16  rests between blade guide  60  and frame  10  of damper  1 . When seal membrane  70  is inflated by the introduction of compressed air into air chamber  65 , seal membrane  70  engages blade plate  16  to form a seal. At this point, blade plate  16  may be not necessarily be in contact with blade guide  60 . Under normal operating conditions, i.e., when damper  1  is opened, air chamber  65  is either pressurized by compressed air within chamber  65  or by neutral air pressure within chamber  65 . In either case, seal membrane  70  should assume its normal, non-evacuated position. 
       FIG. 14  shows a schematic of a system used to inflate and evacuate air chamber  65  of seal cartridge  12 . Air supply  48  provides pressurized air which is stored in accumulator  50  through check valve  52 . Filter/regulator  46  filters the air of impurities and regulates the pressure. Seal air chamber  65  is inflated when three-way valve  42  is de-energized. To evacuate air chamber  65 , valve  42  is energized and air flow through ejector  44  causes air from air chamber  65  to be withdrawn. Note that the system shown in  FIG. 12  is only illustrative of one possible system for manipulating seal membrane  70 ; many other configurations well known in the prior art may also be used. 
     The illustrations, materials, and dimensions used herein are exemplary in nature only and are not meant to limit the scope of the invention, which is embodied in the claims which follow.

Technology Classification (CPC): 5