Abstract:
The present invention provides an apparatus for minimizing the blade opening between the blade shank of propeller and spinner in order to improve the overall efficiency of an aircraft and propeller system. The present invention consists of a two piece blade opening filler; the bulkhead insert which attaches to the bulkhead, and the spinner insert which maybe attached to bulkhead insert after installation of the propeller blade. The blade opening filler fills the blade opening between the spinner and blade shank while facilitating maintenance of the system.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a propeller system and more particularly to an apparatus which increases system efficiency by reducing losses caused by air moving through the blade opening between the spinner and blade shank. 
     A propeller system&#39;s, and thus an aircraft&#39;s overall aerodynamic efficiency is increased by incorporating a conical nose piece, known as spinner. The spinner covers the propeller hub and associated propeller control hardware and attaches to a bulkhead. The bulkhead separates the propeller system from the engine. Further, the spinner has blade openings through which extend the blade shank of the propeller blades. This spinner is designed to work with the blade design and engine nacelle to provide a low drag coefficient and improve aerodynamic efficiency. The spinner surface is often contoured to aid in achieving this goal. 
     In addition to designing for aerodynamic efficiency the spinner must facilitate maintenance of the propeller system, therefore, the spinner must be removable with the propeller blades installed. To achieve this goal, the blade opening in the spinner is continued on the bulkhead side of the blade shank. In addition, the blade openings must be sized to allow for rotation of the blade shank. Therefore, because the blade shank does not completely fill the blade opening, there is a blade opening between the blade shank and the edge of the spinner and bulkhead. Air flowing through this blade opening reduces the overall aerodynamic efficiency of the propeller system and thus the aerodynamic efficiency of the aircraft. 
     Typically, blade shank collars have been used to minimize the blade opening. A collar is placed around the blade shank such that when the blade is installed the collar can be aligned with the plane of the spinner surface. However, because the spinner surface is contoured and the blade is rotated about its longitudinal axis for various flight modes, the collar can only be optimized for a particular blade angle. Also, the blade collar has to be sized to leave a small gap between the collar and spinner to allow for movement in the blade shank induced by mechanical vibration and aerodynamic forces. 
     What is needed to overcome the deficiencies of the prior art is an apparatus to fill the opening between the propeller shank, spinner, and bulkhead of an aircraft for the various flight modes while allowing for maintenance of the propeller system. 
     Accordingly, it is the object of this invention to provide an aerodynamic blade opening filler that reduces the opening between the spinner and blade shank to improve overall propeller system/aircraft efficiency. 
     It is a further object of this invention to provide a blade opening filler that facilitates maintenance of the propeller system. 
     SUMMARY OF THE INVENTION 
     An improved propeller system is disclosed which improves aerodynamic efficiency by reducing the blade opening between the blade shank and the spinner and bulkhead. 
     In the preferred embodiment, a blade opening filler is inserted in the blade opening between the blade shank, spinner, and bulkhead. The blade opening filler consists of two subassemblies; a spinner insert and a bulkhead insert, allowing for ease of assembly and service. The spinner insert fills a first portion of the opening between the spinner and blade shank and the bulkhead insert fills a second portion of the opening between the blade shank and bulkhead. The bulkhead insert is attached to the bulkhead during assembly and the spinner insert fits around the blade shank of the already installed propeller blades and into the bulkhead insert. The spinner is attached to the bulkhead such the blade opening filler fills the blade opening. 
     In a second embodiment for use with oval or non-circular blade shanks, a collar may be installed around the blade shank on the hub side (interior) of the blade opening filler. Spring clips are then inserted which hold the collar against the blade gap filler to eliminate gaps while the propeller blade is rotated for various operational modes. 
    
    
     The above and other objects and advantages of this invention will become more readily apparent when the following description is read in conjunction with the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a &#34;Prior Art&#34; propeller system; 
     FIG. 2 is a partial cut away of a &#34;Prior Art&#34; propeller system with a collar installed; 
     FIG. 3 is a spinner assembly with the Blade Opening Filler of the present invention; 
     FIG. 4 is an interior view of the bulkhead insert; 
     FIG. 5 is a fight side view of FIG. 4; 
     FIG. 6 is a front view of the spinner insert; 
     FIG. 7 is a side view of the spinner insert; 
     FIG. 8 is an interior view of the Blade Opening Filler 
     FIG. 9 is a front view of the Blade Opening Filler 
     FIG. 10 is a propeller system with the Blade Opening Filler installed in the spinner assembly with the spinner partially cut away; 
     FIG. 11 is a cross-section of a non-circular blade root with a circular collar installed; 
     FIG. 12 is a propeller system with the spinner partially cut away with the Blade Opening Filler installed (partially cut away) and a collar installed on a non-circular blade root. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a prior art propeller system generally designated by the numeral 10. The typical propeller system comprises, a propeller hub (not shown) mounted to an engine shaft (not shown) such that the propeller hub is on the spinner side of the bulkhead 12. The propeller blades 14 are then inserted into the hub. The spinner 16 is then placed over the fully assembled hub and blade assembly to improve the aerodynamic efficiency of the propeller system 10. The spinner 16 has an interior surface facing the propeller and an exterior surface for directing the flow of air thereover. The spinner 16 is then attached to the bulkhead 12 by conventional means. 
     Blade openings 18, in the contour of the spinner, are necessary to allow the spinner 16 to fit over the fully assembled hub and blade assembly. The blade opening 18 must be sized to fit around the blade shank 20 of the propeller blade 14. Often the blade shank 20 is non-circular necessitating a blade opening 18 that is wide enough to allow for rotation of the propeller blade 14 about its longitudinal axis 11, running the length of the blade, as required for various flight modes. FIG. 2 shows the propeller blade 14 installed in the propeller system 10. Aerodynamic inefficiencies result from turbulence between the blade shank 20 of the propeller blade 14 and the spinner 16 in the area of the blade opening 18. 
     One way to minimize these losses is to fix a collar 24 to the blade shank 20. The collar 24 is positioned such that it follows the contour of the of the spinner 16 and bulkhead 12 to minimize the blade opening 18. However, the propeller blade 14 rotates about its longitudinal axis for various flight modes therefore the blade opening 18 can only be minimized for a pre-selected blade position. 
     FIG. 3 shows a propeller system, according to the present invention, generally designated by the numeral 30 which comprises a typical propeller system 30, and a blade opening filler 32 constructed in accordance with the present invention. 
     The blade opening filler 32, as shown in FIG. 3, is comprised of two major subassemblies, the bulkhead insert 34, and the spinner insert 36. The bulkhead insert 34 as seen in FIGS. 4 and 5 is a one piece plate, e.g. metal having 3 sections, two end sections 38 and a middle section 40. 
     The middle section 40 has length generally equal to the distance of blade opening 18 as measured at the interface 39 of the blade opening 18 and the bulkhead 12. The middle section also has exterior portion 41 that is contoured as shown in FIG. 5, such that when it is installed in the blade opening 18 between the blade shank 20 and the spinner 16 and the bulkhead 12, the middle section will form a generally smooth continuation of the exterior surface of the spinner 16. The middle section 40 has top edge 42 that is contoured to follow the outer circumference defined by the rotation of the blade shank 20 during operation. An adhesive strip, e.g. VELCRO strip 44 is located on the interior surface 43 of the middle portion 40 to hold the filler 34 in place during assembly of the propeller system 30. The VELCRO strip 44 attaches to a mating strip (not shown) located on the bulkhead 12. 
     The two end sections 38 are attached to and located at both ends of the length of the middle section 40. The two end sections 38 are positioned relative to the middle section 40 such that when the exterior portion 41 of the middle section 40 is flush with the exterior surface 17 of the spinner 16 the end sections 38 will conform to and abut the interior surface of the spinner 16. The length of the end sections 38, as measured along the mating surface 39 of the spinner 16 and bulkhead 12, extend under the spinner assembly 16 a sufficient distance to insure the bulkhead insert 34 will be held in place during operation. 
     Each end section 38 further contains through holes 46 such that when assembled between the spinner 16 and the bulkhead 12, conventional fasteners 63 may be inserted through the spinner 16 and bulkhead insert 34 into the bulkhead 12. 
     A bracket 60 is located on each end section 38 and extends a distance from the interior surface 43 of the end section 38. The bracket 60 located on an end section 38, is adapted in size and shape such that a tee shaped locking tab 50 of the spinner insert 36 shown in FIG. 6, and described herein, fits within the bracket 60. The bracket 60 shown in greater detail in FIG. 8 is adapted in size and shape such that a fastener, e.g. tie wrap 61 may be inserted through the bracket 60 and across the tee shaped locking tab 50 thus holding the tee shaped locking tab 50 against the interior surface 43 of the bulkhead insert 
     The spinner insert 36 is shown in greater detail in FIGS. 6 and 7. The spinner insert 36 is made of a flexible plastic material such as NYLON 6/6, that has sufficient stiffness to hold the spinner insert 36 against the inside surface of the spinner 16 when installed into the bulkhead insert 34 as described in the previous paragraph. The spinner insert 36 is generally horseshoe shaped and has the same general contour as the spinner 16. The spinner insert 36 generally consists of two sections, a first raised section 52 and a second lower section 54. The first raised section 52 has a width slightly less than the difference between the blade opening 18 and the circumference of the blade shank 20 as measured from the longitudinal axis the blade shank 20. The inner edge 53 of the first raised section 52 is nearest the circumference of the blade shank 20. The raised section 52 has an upper surface 55 that when installed in the spinner housing, as shown in FIG. 10 will form a continuation of the exterior surface of the spinner 16. 
     The lower sections 54 have protrusions 56 located on its upper surface 57. The protrusions 56 of the lower sections 54 are designed to conform to and abut the interior surface of the spinner 16 when the spinner insert 36 is assembled into the propeller system 30 of FIG. 3. 
     Extensions 58 are located on the ends of the spinner insert 36 such that when the spinner insert 36 fills the first portion of the blade opening 18 and the bulkhead insert 34 fills a second portion of the blade opening 18, the extensions 58 extend under the bulkhead insert 34. The width of each extension 58, is equal to the width of the raised section 52 with a distance between the outer edge of the extensions 58 equal to the blade opening 18 as measures along the intersection of the spinner 16 and the bulkhead 12. 
     T shaped locking tabs 50 are located on the lower sections 54 which are adapted in size and shape such that the locking tab 50 may be inserted between the brackets 60. 
     FIG. 10 shows an assembled blade opening filler 32 installed in a partially assembled propeller system. During assembly the bulkhead insert 34 is held to the bulkhead 12 by the VELCRO strip 44 pressed against a mating VELCRO strip (not shown) mounted on the bulkhead 12. The spinner insert 36 is the placed over the blade shank 20 such that the locking tabs 50 are inserted between the brackets 60 of tab insert slot 48. A fastener 61 is then inserted through the brackets and across the tee shaped locking tab 50 thus holding the spinner insert 36 against the bulkhead insert 34. The action of the fastener 61 also forces the extensions 58 against the bulkhead insert 34. 
     The spinner 16 is then placed over the assembled hub and blade assembly (not shown) and the blade opening filler :32. The spinner 16 covers the filler end sections 38 of the bulkhead insert 34 and the lower section 54 of the spinner insert 36. The raised section 52 of the spinner insert 36 and the middle section 40 of the bulkhead insert 34 are flush with the exterior and form a continuation of the contour of the spinner 16. The spinner 16 is fastened to the bulkhead 12 using conventional means such as a screw 63. The extensions 58 cooperate with the bulkhead insert 36 to hold the spinner insert 36 against the spinner 16. 
     In an alternate embodiment shown in FIG. 11, for non-circular or oval blade shanks, a collar 62 is fastened by conventional means e.g. bolt and nut (not shown) around the circumference of the blade shank 20 The collar is generally cylindrical in shape, with a first surface 64 that conforms to the surface of the blade shank 20 and a second surface 66 that forms a circumference that is a distance from the first surface 64 such that when the collar 62 is installed on the blade shank 20 on the hub side of the blade opening filler 32 the second surface extends under the spinner insert :36 and the bulkhead insert 34. 
     Spring clips 68 are inserted between the blade root 70 and collar 62 to allow the collar 62 to follow the contour of the spinner 16 and blade opening filler 32 during rotation of the propeller blade 14. 
     It should be understood by those skilled in the art that obvious structural modifications can be made without departing from the spirit or scope of the invention. Accordingly, reference should be made primarily to the accompanying claims, rather than the foregoing specification, to determine the scope of the invention.