Abstract A fan having curved flexible resilient blades which decamber with an increase in rotational speed and aerodynamic forces. Each of the blades has an overlying reinforcing strip in partial contact with a trailing sheet, which decambers as the rotational speed increases. The reinforcing strip and trailing sheet, which is of significantly thinner cross-section, are joined to each other and to a supporting arm extending from a central hub. The reinforcing strip preferably has a curved trailing decamber limiting portion and a curved bending limiting portion disposed along the inner side edge of the reinforcing strip and its decamber limiting portion. As the trailing sheet decambers it also makes progressive contact with the reinforcing strip in a direction toward the inner side edge of the sheet, thus reducing stress concentration at the intersection of the inner side edge of the sheet and the decamber limiting portion of the reinforcing strip.
In a fan having curved flexible resilient blades which decamber with an increase in rotational speed and aerodynamic forces, each of said blades comprising a reinforcing strip overlying and in partial contact with a trailing sheet, which decambers as rotational speed increases, joined to each other and to a supporting arm extending outwardly from a central hub portion, said trailing sheet being of significantly thinner cross-section than said reinforcing strip, said reinforcing strip comprising, a. a trailing decamber-limiting portion extending partially coextensively with a portion of said trailing sheet and at an acute angle to said sheet, and b. a bending limiting curved portion disposed along the inner side edge of said reinforcing strip and decamber-limiting portion whereby, as said trailing sheet decambers, progressive contact is made by said sheet with said reinforcing strip in a direction toward the inner side edge of said sheet, thus reducing stress concentration at the intersection of said inner side edge of said sheet and said decamber-limiting portion.
Claim 2
Dependent Claim
164 words
In a fan having curved flexible resilient blades which decamber with an increase in rotational speed and aerodynamic forces, each of said blades comprising a reinforcing strip overlying and in partial contact with a trailing sheet, which decambers as rotational speed increases, joined to each other and to a supporting arm extending outwardly from a central hub portion, said trailing sheet being of significantly thinner cross-section than said reinforcing strip, said reinforcing strip comprising, a. a trailing decamber-limiting portion extending partially coextensively with a portion of said trailing sheet and at an acute angle to said sheet, and b. a bending limiting curved portion disposed along the inner side edge of said reinforcing strip and decamber-limiting portion whereby, as said trailing sheet decambers, progressive contact is made by said sheet with said reinforcing strip in a direction toward the inner side edge of said sheet, thus reducing stress concentration at the intersection of said inner side edge of said sheet and said decamber-limiting portion.
Claim 3
Dependent Claim
43 words
A fan as called for in claim 1 wherein said (a) trailing decamber-limiting portion and said (b) bending limiting curved portion are both curved in a direction away from the surface of said trailing sheet which is in contact with said reinforcing strip.
Claim 4
Dependent Claim
29 words
A fan as cAlled for in claim 2 wherein said (a) trailing decamber-limiting portion and said (b) bending limiting curved portion are both curved, with equal radii of curvature.