Patent Publication Number: US-2015086379-A1

Title: Propeller blade assembly

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. §119 to British Patent Application No. 13171012, filed Sep. 26, 2013, the disclosure of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     Contemporary vehicles, such as hovercrafts, may include propeller blades to provide propulsive force. The propeller blades may be exposed to environments that erode portions of the propeller blades. Propeller failures may be caused by sand and stone nicks to the leading edge. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In one aspect, an embodiment of the invention relates to a propeller blade assembly, having a propeller blade having a leading edge, a replaceable guard selectively mountable to the propeller blade to cover at least the leading edge, and multiple fasteners selectively coupling the replaceable guard to the propeller blade and wherein at least one of the multiple fasteners does not extend beyond an exterior of the replaceable guard. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  is a schematic embodiment of an environment in which a propeller blade assembly may be used. 
         FIG. 2  is a top view of a propeller blade assembly according to an embodiment of the invention. 
         FIG. 3  is a cross-sectional view of a portion of a propeller blade assembly according to an embodiment of the invention. 
         FIG. 4  is an alternative cross-sectional view of a portion of the propeller blade assembly of  FIG. 3 . 
         FIG. 5  is a cross-sectional view of a portion of a propeller blade assembly according to another embodiment of the invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS OF THE INVENTION 
       FIG. 1  schematically illustrates a vehicle, more specifically a hovercraft  8 , in which a propeller blade assembly  10  may be used. It will be understood that the propeller blade assembly  10  may be used in any suitable vehicle and hovercraft.  FIG. 2  illustrates a propeller blade assembly  10  having a propeller blade  12 , a replaceable guard  14 , and multiple fasteners  16 . The propeller blade  12  may have an airfoil configuration. The propeller blade  12  may include a front surface  20  and a rear surface (not shown) bounded by a leading edge  22 , a trailing edge  24 , and a tip edge  26 , which extends between the leading edge  22  and the trailing edge  24 . 
     The replaceable guard  14  may be selectively mountable to the propeller blade  12  to cover at least the leading edge  22  of the propeller blade  12 . In the illustrated example, the replaceable guard  14  covers the leading edge  22  and the tip edge  26 . Further, the replaceable guard  14  has been illustrated as being multi-segmented although this need not be the case. In the illustrated example, two of the multiple segments are used to cover most of the leading edge  22  while a third is used to cover the tip edge  26 . Alternatively, in a multi-segmented configuration, a first segment may cover the leading edge  22  and a second segment may cover the tip edge  26 . It is contemplated that there may not be a replaceable guard  14  on the trailing edge  24 . 
     The multiple fasteners  16  may selectively couple the replaceable guard  14  to at least one of the front surface  20  and the rear surface (not shown). At least one of the multiple fasteners  16  will not extend beyond an exterior of the replaceable guard  14 . It is contemplated that all of the multiple fasteners  16  will not extend beyond an exterior of the replaceable guard  14 . In the illustrated example, multiple fasteners  16  operably couple the replaceable guard  14  to both the front and rear surfaces of the propeller blade  12 . More specifically, the multiple fasteners  16  alternate between the front and rear surfaces along a length of the propeller blade  12 . While no fasteners  16  have been illustrated as attaching the replaceable guard  14  to the rear surface at the tip edge  26  of the propeller blade  12  it will be understood that fasteners  16  may attach the replaceable guard  14  to the rear surface at such a location. 
       FIG. 3  illustrates one example of a portion of a propeller blade, replaceable guard, and fastener, which may be used in a propeller blade assembly including the propeller blade assembly  10 . As the propeller blade  112 , replaceable guard  114 , and fastener  116  are similar to those previously described, like parts will be identified with like numerals increased by 100, with it being understood that the description of the like parts of the propeller blade assembly  10  applies to the propeller blade assembly having the propeller blade  112 , replaceable guard  114 , and fastener  116 , unless otherwise noted. 
     As with the earlier described embodiment, the propeller blade  112  includes a front surface  120  and a rear surface  118  as well as a leading edge (not visible), a trailing edge (not visible), and a tip edge  126 . One difference is that the propeller blade  112  is illustrated as a composite body including a foam core  130 , a carbon and glass fiber layer  132 , and a polyurethane layer  134 . It will be understood that the propeller blade  112  may be formed in any suitable manner from any suitable material(s). Further, a foam insert  136  has been illustrated as being located between a portion of the propeller blade  112  and the replaceable guard  114 . An insert  140  may be bonded into a portion of the propeller blade  112  and sized to receive one of the multiple fasteners  116 . In the illustrated example, a block  142  has been moulded within the propeller blade  112  and the insert  140  is bonded into the block  142 . The block  142  may be formed from a composite such as a glass fiber and insert moulded into the propeller blade  112 . 
     By way of non-limiting example, the replaceable guard  114  has been illustrated as including a backer layer  150  and an erosion protection rubber layer  152 . It will be understood that the replaceable guard may be formed from any number of layers including a single layer. It will be further understood that the replaceable guard may be formed from any suitable material(s). 
     In the illustrated example, only a single fastener  116  has been illustrated; however, multiple fasteners may be included and may operably couple the replaceable guard  114  to the front surface  120  and/or the rear surface  118  of the propeller blade  112 . The fastener  116  is illustrated as including a rivet  160  selectively receivable in the insert  140  and a washer  162 . The replaceable guard  114  is clamped between the washer  162  and the insert  140  when the rivet  160  is received within the insert  140  and the fastener  116  does not extend beyond an exterior  164  of the replaceable guard  114 . By way of non-limiting example,  FIG. 4  illustrates the fastener  116  operably coupling the replaceable guard  114  to the rear surface  118 . 
       FIG. 5  illustrates an alternative propeller blade  212 , a replaceable guard  214 , and a fastener  216 . As the propeller blade  212 , replaceable guard  214 , and fastener  216  are similar to those previously described, like parts will be identified with like numerals increased by  100 , with it being understood that the description of the like parts of the propeller blade assembly  10  and the propeller blade  112 , replaceable guard  114 , and fastener  116  applies to the propeller blade assembly having the propeller blade  212 , replaceable guard  214 , and fastener  216 , unless otherwise noted. 
     One difference is that the fastener  216  has been illustrated as including a screw  260  that is at least partially threaded and sized to be threaded into the insert  240 . Another optional difference is that the insert  240  may be at least partially threaded and has been illustrated as being fully threaded. As with the previously described embodiment the fastener  216  includes a washer  262  and when assembled, the replaceable guard  214  is clamped between the washer  262  and the insert  240  when the screw  260  is threaded into the insert  240 . 
     The embodiments described above provide for a variety of benefits including that the embodiments above allow for an erosion protection guard to attach to at least a leading edge of a propeller blade in a manner that enables speedy replacement of an eroded guard using simple tools without damaging the propeller blade. In this manner, multiple guard changes may be made without replacement of the propeller blade and corrosion has no effect on its operation. In the above described embodiments, removal of the guard does not require any contact with the composite material of the propeller blade. Thus, the composite in the propeller blade will not be affected by guard fitting and removal. The internal insert spreads the clamping load of the rivet. Further, discontinuity with the airfoil is minimal as the fasteners are flush with or do not extend beyond an exterior of the replaceable guard. One contemporary design relies on the use of bolts with special nuts fitted from each side of a through bore in the propeller blade. The bolt heads and nuts extend above the guard and may corrode and erode making it difficult to remove them causing high replacement costs. In the above described embodiments, corrosion will have no effect and because the design is flush or below the guard erosion will be minimal. 
     To the extent not already described, the different features and structures of the various embodiments may be used in combination with each other as desired. That one feature may not be illustrated in all of the embodiments is not meant to be construed that it may not be, but is done for brevity of description. Thus, the various features of the different embodiments may be mixed and matched as desired to form new embodiments, whether or not the new embodiments are expressly described. All combinations or permutations of features described herein are covered by this disclosure. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.