Patent Publication Number: US-2021172647-A1

Title: Airfoil blade and method of assembly

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a Divisional Application of U.S. Utility patent application Ser. No. 16/234,931, filed on Dec. 28, 2018, which is a Continuation-in-Part of U.S. Utility patent application Ser. No. 15/000,678 filed on Jan. 19, 2016 (now U.S. Pat. No. 10,208,982 issued Feb. 19, 2019), which itself claims priority to U.S. Provisional Application Ser. No. 62/106,868, filed on Jan. 23, 2015, all of which are hereby incorporated by reference in their entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to dampers and, more particularly, to an airfoil blade for a damper and a method of assembling an airfoil blade. 
     BACKGROUND OF THE INVENTION 
     Dampers have long been used in a variety of fluid handling applications to control the flow of various types of fluids. Typical uses of industrial dampers include the handling of process control fluids, the handling of fluids in power plants, and the handling of high speed fan discharge streams. Industrial dampers are usually subjected to relatively high pressures and must have considerable strength in order to be capable of withstanding the forces that are applied to them. 
     The damper construction normally includes a rigid frame which defines a flow passage controlled by a plurality of damper blades that each pivot between open and closed positions about a respective axle. The blades are often interconnected by a linkage which moves all of them in unison to control the fluid flow rate in accordance with the damper blade position. Although flat damper blades are often used, it has long been recognized that airfoil shapes can be used to enhance the fluid flow. Airfoil blades are thickest in the center at the pivot axis and taper toward each edge to present an aerodynamically efficient shape which minimizes turbulence and other undesirable effects such as noise generation and stresses on the flow passage and other components of the fluid handling system. 
     In the past, damper blades have been formed by bending multiple sheets of steel and joining them together to form an airfoil shape. Typically, in a separate step, a bead of silicone or other sealant may be manually deposited at the respective ends of each blade to provide for an air tight seal between the damper blades when in a closed position. In a further separate step, a bracket is mounted to each end of the blade, which is necessary to locate and accommodate an axle on which each blade pivots. As will be readily appreciated, however, existing airfoil blades are very time consuming and tedious to manufacture, requiring numerous and separate manual steps. In addition, existing blades often require additional strengthening ribs to bolster the blade under high speed flow, which may further increase the cost and labor involved. 
     Accordingly, it is desirable to provide an airfoil blade assembly that is easier, more cost effective, and less labor-intensive to produce than existing blades. 
     SUMMARY OF THE INVENTION 
     According to the present invention, an airfoil blade assembly includes a first shell member having a body having a first lock seam formed at one end thereof and a free distal end opposite the first lock seam, and a second shell member having a body having and a second lock seam formed at one end thereof and an a free distal end opposite the second lock seam. The second shell member is inverted with respect to the first shell member. The free distal end of the first shell member is captured within the second lock seam of the second shell member and the free distal end of the second shell member is captured within the first lock seam of the first shell member to lock the blades to one another. 
     According to another embodiment of the present invention a method of assembling an airfoil blade includes roll forming first and second shell members of the airfoil blade on a roll forming machine and depositing a sealant bead in an end seam of each of the shell members on the roll forming machine in an inline process. The method also includes joining two shell members to one another and crimping respective ends of each shell member to form a lock seam which captures a free edge of the opposed shell member therein to lock the shell members to one another. 
     According to yet another embodiment of the present invention, a damper assembly is provided. The damper assembly includes a frame, an axle rotatably mounted to the frame, and an airfoil blade assembly operatively mounted to the axle. The airfoil blade assembly includes an upper shell member and a lower shell member, wherein said lower shell member is invertedly disposed and connected to said upper shell member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of a flow control damper equipped with airfoil blades in a fully open position. 
         FIG. 2  is a cross-sectional view of an airfoil blade constructed according to an embodiment of the present invention. 
         FIG. 3  is cross-sectional view of a shell member of the airfoil blade of  FIG. 2 . 
         FIG. 4  is an enlarged, detail view of area A of  FIG. 3 . 
         FIG. 5  is a cross-sectional view of the shell member of  FIG. 3  after a roll forming operation. 
         FIG. 6  is a cross-sectional view of the shell member of  FIG. 3 , illustrating the insertion of a silicone bead in an end seam of the shell member. 
         FIG. 7  is a cross-sectional view of the shell member of  FIG. 3  after the end seam is closed. 
         FIG. 8  is a cross-sectional view of the shell member of  FIG. 3  after the shell member has been cut to length and locating apertures are punched in the shell member. 
         FIG. 9  is a cross-sectional view of the airfoil blade of  FIG. 2 , illustrating the joining of two shell members to one another. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     With reference to the drawings, reference numeral  10  generally designates an airfoil blade constructed in accordance with the present invention. With particular reference to  FIG. 2 , the airfoil blade is formed from a pair of relatively thin shell members  12 ,  14  which themselves may be formed from galvanized steel sheets. Each of the sheets is initially flat, and the sheets are bent into the shapes shown by suitable roll forming techniques. As illustrated in  FIG. 2 , the shell members  12 ,  14  are substantially identical and are manufactured in the same manner. As also shown therein, the upper shell member  12  essentially mirrors the lower shell member  14 , to which it is interconnected in the manner discussed hereinafter. 
     Each shell member  12 ,  14  includes an end seam  16  at one end thereof which is bent back upon the body of the respective shell member  12 ,  14  to provide a lock seam  18  which captures the free side edge  20  of the opposed shell member  12 ,  14 . By capturing the free side edges  20 , the two shell members  12 ,  14  are rigidly interlocked along both of their side edges  20 . The edges of the blade  10  are parallel. 
     The airfoil blade  10  has a hollow airfoil shape best shown in  FIG. 2 . The shell members  12 ,  14  form the walls of the blade  10 , and the shell members  12 ,  14  converge toward the interlocked edges to give the blade  10  a tapered profile. Center portions  22  of the respective upper and lower shell member  12 ,  14  are spaced apart from one another to provide the center portion of the blade  10  with a predetermined thickness. The blade  10  gradually tapers from the center portion toward each of the opposite edges. 
     Turning now to  FIG. 3 , a cross-sectional view of shell member  12  is illustrated. Shell member  14  is substantially identical to shell member  12  and is manufactured in a substantially identical manner, however only shell member  12  is being shown for clarity. As discussed above, shell member  12  may be formed from a sheet of galvanized steel in a roll forming operation. 
     The shell member  12  includes a first edge having a generally V-shaped end seam  16  and an opposed free edge  20 . The shell member  12  is generally arcuate in shape and has a center portion  22 . On opposing sides of the center portion  22 , downwardly depending legs are formed by bending the sheet of material back upon itself. In particular, a first depending leg or seam  24  is formed between the end seam  16  and the center portion  22  and a second depending leg or seam  26  is formed between the center portion and the free edge  20 . As shown, the height of the first depending leg  24  is greater than the height of the second depending leg  26 . The shell member  12  also includes a pair of spaced apart strengthening ribs  28  formed in the body of the shell member  12  adjacent to the center portion  22  and outside the legs  24 ,  26 , respectively. The ribs  28  are formed by corrugations in the shell member  12  and serve as stiffeners which enhance the strength of the airfoil blade  10 . Each rib  28  has a V-shaped configuration and extends into the interior of the blade  10 . 
     As therefore shown in  FIGS. 2 and 3  in total, the legs  24  and  26  of each shell  12 / 14  of the airfoil blade assembly  10  are preferably formed to be unequal in length so as to avoid any undesirable and damaging material deformation that can occur to the metal blank should the roll forming process that forms the airfoil blade assembly  10  be required to form both legs,  24  and  26 , to each be as long as the first depending leg  24 . 
     Moreover, by having legs  24  and  26  be of differing lengths, the assembly process is streamlined, whereby installers in the field can easily arrange the two halves/shells  12 / 14  of the airfoil blade assembly  10  in their proper orientation merely by ensuring that the shorter of the two legs, leg  26 , is always located on the outside of each of the legs  24  (as best seen in  FIG. 2 ). 
     It will therefore be readily appreciated that by forming legs  24  and  26  to be of uneven lengths the present invention ensures against material deformation, as well as providing a visual and structural guide for the final assembly of the airfoil blade  10 . 
     It will also be readily appreciated that the arrangement of legs  24  and  26  are such that, when shell  12  and shell  14  are mated to one another, each of the shorter legs  26  provides a significant strengthening and stiffening capability to the longer legs  24 . In just this fashion, the present invention provides the structurally robust, axially-aligned center portion  22 , as shown best in  FIG. 2 . In this regard, it is envisioned that leg  24  and  26  are generally formed to be unequal in length, preferably formed such that the shorter leg  26  is substantially half the length of the longer leg  24 , and more preferably that leg  24  is at least one third the length of leg  24 . 
     Known airfoil blade assemblies typically require the addition of one of more separate structures within the airfoil blade assembly to support an axial control rod disposed for movement of the airfoil blade assembly. In contrast, the present invention has recognized that by forming the structurally robust and axially-aligned center portion  22  via the nesting of legs  24  and  26 , it is possible to use these inner legs  24 / 26  to also provide the housing for any axial control rod disposed therein, without the use of any additional structure to the interior of the airfoil blade assembly  10 . 
     Indeed, as will be appreciated by one of ordinary skill, not only do the strengthening legs  24  and  26  of the present invention provide structural support for the airfoil blade assembly  10  as a whole, but by virtue of the nature of their construction, the legs  24  and  26  also provide a robust anchor point for any axial control rod disposed therein and used to move the airfoil blade assembly  10  between open and closed positions. 
     Still further, the structure of the center portion  22  of the airfoil blade assembly  10  is such that, as opposed to known axial control rods that extend the entire axial length of known airfoil blade assemblies, the current invention permits the use of shortened axial control rods which need only to be captured within the control portions  22  formed on distal ends of the assembled airfoil blade assembly  10 . Thus, robust nature of the center portion  22 , flowing from the structure and orientation of the legs  24  and  26 , promotes efficiency and reduces manufacturing costs by allowing shortened axial control rods to be used adjacent each distal end of the airfoil blade assembly  10  instead of longer, heavier and more expensive continuous rods running the axial length of the airfoil blade assembly, as is commonly known in the art. 
     As shown in  FIGS. 3 and 4 , the end seam  16  is generally V-shaped and has a first leg portion  30  that extends from the shell member body at a substantially ninety-degree angle, a second leg portion  32  that extends from the first leg portion  30  to form an angle, a, therebetween, and an arcuate tail portion  34  that extends from the second leg portion  32  over the open end of the end seam  16 . In an embodiment, the angle, a, is between approximately 10 and 20 degrees and, more preferably, is approximately 15 degrees. 
     With reference to  FIGS. 5-10  assembly of the airfoil blade  10  utilizing shell members  12 ,  14  is illustrated. As best shown in  FIG. 5 , shell member  12 , and the end seam  16 , strengthening ribs  28 , depending legs  24 ,  26  and center portion  22  thereof, are formed by repetitively bending, or roll forming, the sheet material on a single roll forming machine. 
     As the shell member  12  is suitably formed to the desired shape, and concurrent to the ongoing roll forming process, a bead of sealant  36 , such as silicone or vinyl, is then disposed along the length of the shell member  12  within the end seam  16 . Importantly, the sealant  36  is deposited in the end seam  16  as part of an in-line manufacturing process on the same roll forming machine on which the shell member  12  is formed. The same roll forming machine is then utilized to close the end seam  16 , as illustrated in  FIG. 7 . 
     As also shown in  FIGS. 5-10 , the bead of sealant  36  includes a tail  37 , captured within the seam  16 , further assisting in locating and fixing the bead of sealant  36  along the lateral edge of the airfoil blade assembly  10 . Indeed, as perhaps best seen in  FIG. 2 , seam  16  further includes an inwardly deformed locking tab  39 , further arresting the sealant bead  36  from undesirable movement or dislocation. 
     As will be readily appreciated by a review of  FIGS. 2 and 5-10 , the bead of embedded sealant  36  is not positioned or intended to prevent the entrance of moisture of contaminants into the body of the airfoil blade assembly  10  itself. Instead, the sealant bead  36  of the present invention is left exposed to run continuously along the lateral edge of, for example, each of the airfoil blade assemblies  10  shown in  FIG. 1 . As will therefore be readily appreciated, when the individual airfoil blade assemblies  10  are moved to their ‘closed’ position (they are shown in their ‘open’ position in  FIG. 1 ), the lateral edge of their respective planar faces will come into contact with the lateral edge of each adjacent airfoil blade assemblies. Thus, as will be appreciated, the sealant bead  36  disposed along each lateral edge of each of the airfoil blade assemblies  10  will become trapped between adjacent airfoil blade assemblies, thereby providing an elastic and resilient sealing member between such adjacent blade assemblies. 
     In stark contrast, known airfoil blade systems mechanically attach sealing members to the airfoil blade assemblies after the roll forming process is concluded, thus increasing the complexity, cost and manufacturing time of the resultant airfoil blade assembly. It is therefore an important aspect of the present invention that not only is the sealant bead  36  applied during the roll forming process, but it is done such that a portion/tail of the sealant bead is captured within a sealing seam already formed adjacent each lateral edge of the airfoil blade assembly  10 , thereby saving manufacturing costs and time. 
     The shell member  12  is then cut to a desired length, and apertures  38  are pierced in shell member  12  in the center portion  22  at cutoff, as shown in  FIG. 8 . In an embodiment, the apertures  38  are located approximately 1.25 inches from the leading and trailing edges of each shell member  12  (i.e., from the left and right edges of a completed shell member). Importantly, the formation of the shell members  12 , deposition of the sealant in the end seam  16 , closing of the end seam  16 , piercing of the apertures  38  and cutting the shell members  12  to the desired length is accomplished on a single machine without necessitating intervention or manipulation by an operator or technician. In an embodiment, the shell members  12 ,  14  are cut to a length of between approximately 8 inches and 60 inches, although the shell members  12 ,  14  may be cut to any length to form a blade assembly  10  having any desired span. 
     Once multiple shell members  12  are produced, an operator will collect the shell members  12 . One shell member is then flipped over on its backside (e.g., shell member  14  in  FIG. 9 ). A mating shell member  12  is then placed directly on top of shell member  14 , as shown in  FIG. 9 . A pin fixture  100  having pins  102  may then be placed on each end such that pins  102  extend through the apertures  38  in both shell members  12 ,  14  to properly locate and align the shell members,  12 ,  14  with one another. The airfoil blade  10  is then transferred to a bending/joining apparatus where the end seams  16  of each shell member  12 ,  14  are bent towards the center portion  22  (to close the ninety-degree bend between the shell member body and the first leg portion  30  of the end seam  16 ). This bending operation forms lock seams  18  which capture the free edges  20  of the opposed shell member  12 ,  14  therein. 
     This formation of the lock seams  18 , and capturing the free edges  20  of the corresponding shell member  12 ,  14 , respectively, therein, serves to lock the shell members  12 ,  14  to one another to form the completed airfoil blade assembly  10 . The pin fixtures  100  may then be removed and reused in the assembly of another airfoil blade. The completed airfoil blade assembly  10  is illustrated in  FIG. 2 . As shown, the sealant beads  36  are located on opposed edges (front and back), and opposed sides (upper and lower) of the blade assembly  10 . In an embodiment, the sealant beads  36  may be formed from silicone where the intended use for the damper blades  10  is in fire dampers. In other embodiments, the sealant bead may be formed from other materials, such as vinyl and the like, without departing from the broader aspects of the present invention. 
     Importantly, as best illustrated in  FIG. 2 , the opposed depending legs  24 ,  26  of each shell member  12 ,  14  define a longitudinal passageway or channel  40  for the passage of an axle, as hereinafter described. In particular, as shown in  FIG. 2 , the longer, first depending legs  24  extend from the shell member body from which they are formed substantially to the blade body of the opposed shell member. The shorter, second depending leg  26  of each shell member is configured to lie outside the first depending leg  24  of the opposing shell member, and functions to provide bolstering support for the first depending legs  24 , as illustrated in  FIG. 2  (i.e., the second legs  26  buttress the first legs  26 ). In this manner, the bolstering legs  26  help to maintain the structural rigidity of the first depending legs  24 , thereby maintaining the integrity and square form of the channel  40  during operation. Moreover, the four standing seams (i.e., the first and second depending legs  24 ,  26  of each shell member  12 ,  14 ) provide strength to the completed blade assembly  10  and provide a pocket for the axle, as discussed hereinafter. Accordingly, there is no need to utilize a separate bracket to locate the axle, which eliminates many of the tedious steps required for existing methods of assembly. 
     Referring to  FIG. 1 , once the airfoil blade assemblies  10  are constructed in the manner hereinbefore described, they may be dropped, one by one, into a rigid damper frame  200  having opposite sides  202 , a top portion  204 , and a bottom portion  206 . The frame  200  is normally installed in a fluid flow passage, a portion of which is formed by a damper opening  216  presented within the frame  200  between the sides and the top and bottom of the frame. 
     The axle  208  for each blade may then be slid through the frame  200  and through the channel  40  within each blade assembly  10 . In an embodiment, the axle may have a cross-section that is substantially similar to the square cross-section of the channel  40 , at least along the longitudinal extent where the axle is received within the channel  40 . In an embodiment, the axles  208  may be approximately ½″ in thickness and have a square cross-section. The axles  208  are supported for pivotal movement on the opposite sides  202  of the frame  200 . In particular, the axles  208  may be supported by round bushings that are themselves fixed in the frame  200 . As will be readily appreciated, the axle channel  40  formed in the blade assembly  10  keeps the blades from twisting on the axles under torque. 
     Each axle  208  may be rigidly connected to a crank arm  210 , and all of the crank arms  210  may be connected by a vertical linkage  212  pivoted at  214  to the crank arms  210 . This arrangement pivots the blade assemblies  10  in unison between the fully opened positioned shown in  FIG. 1  and the fully closed position in which the blades  10  are oriented vertically to close the damper opening. Other means of linking the axles  208  so that the blades  10  may be opened or closed in unison may also be utilized without departing from the broader aspects of the present invention. The damper blades  10  can be positioned anywhere between the fully opened and fully closed positions. 
     As discussed previously, and due to the provision and configuration of the depending legs  24 ,  26 , the need to utilize separate hardware to locate, secure and align each axle within each blade assembly  10  may be obviated. This eliminates costly and tedious manufacturing steps. The configuration of these legs  24 ,  26  also adds strength to the blade assembly  10  in comparison to existing blades. In addition, by roll forming the shell members and depositing the sealant bead  38  as part of an inline manufacturing process on a single machine, manufacturing efficiency and cost reductions may therefore be realized. 
     The enhanced stiffening of the center portion of the blade  10  provided by the legs  24 ,  26  and the ribs  28  eliminates the need to add separate reinforcement tubes or other reinforcement members. Because of the enhanced strength and resistance to deflection provided by the legs  24 ,  26  and ribs  28 , the sheet members  12  and  14  can be relatively light gauge sheet metal so that both the cost and the weight of the damper are reduced without sacrificing strength or other desirable performance characteristics. For example, acceptable results can be obtained from the use of 20 gauge coil stock, although other sheet thicknesses may also be utilized. 
     Also, as an alternative to utilizing a continuous axle  208  running from the center portion  22  adjacent one distal end of the airfoil blade assembly  10  to the center portion  22  adjacent the opposing distal end of the airfoil blade assembly  10 , the configuration of the center portion  22  of the present invention permits the use of two separate and non-continuous axle control rods, each captured with the distally located control portions  22  of the airfoil blade assembly  10 , thus reducing the material cost, weight and complexity of the airfoil blade assembly  10  of the present invention. 
     Although this invention has been shown and described with respect to the detailed embodiments thereof, it will be understood by those of skill in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed in the above detailed description, but that the invention will include all embodiments falling within the scope of this disclosure.