Shroud for a rotor blade

Claim 2

For a rotor blade of the type used in gas turbine engines which has an airfoil disposed about a spanwisely extending axis and a shroud extending laterally from the airfoil, the improvement which comprises: a shroud having a laterally outward portion having a contact surface which adapts the rotor blade to engage a contact surface on an adjacent shroud of an adjacent rotor blade in the installed condition in the engine, a laterally inward portion extending between and integrally joined to the laterally outward portion and the airfoil for providing support to the laterally outward portion; wherein said inward portion of the shroud has a geometric contour, said geometric contour having dimensions that cause the inward portion of the shroud to exhibit a maximum fiber unit stress in a rotational force field that is nearly uniform throughout the lateral length of the inward portion of the shroud.

Claim 3

For a rotor blade of the type used in gas turbine engines which has an airfoil disposed about a spanwisely extending axis and a shroud extending laterally from the airfoil, the improvement which comprises: a shroud having a laterally outward portion having a contact surface which adapts the rotor blade to engage a contact surface on an adjacent shroud of an adjacent rotor blade in the installed condition in a gas turbine engine, a laterally inward portion extending between and integrally joined to the laterally outward portion and the airfoil for providing support to the laterally outward portion and having a laterally extending edge; wherein said inward portion of the shroud has a geometric contour such that, at any section taken through the shroud along a plane containing a line parallel to the edge and containing a line parallel to the spanwisely extending axis, said section has a maximum thickness at the airfoil, a minimum thickness at the outermost end of the laterally inward portion and said section tapers from the maximum thickness to the minimum thickness; wherein a filler material of less density than the shroud material is attached to the airfoil for aerodynamic smoothness; and wherein the said geometric contour has dimensions that cause the maximum fiber unit stress at the point of maximum thickness in a rotational force field to be approximately equal to to the maximum fiber unit stress at the point of minimum thickness.

Claim 4

For a rotor blade of the type used in gas turbine engines which has an airfoil disposed about a spanwisely extending axis and a shroud extending laterally from the airfoil, the improvement which comprises: a shroud having a laterally outward portion having a contact surface which adapts the rotor blade to engage a contact surface on an adjacent shroud of an adjacent rotor blade in the installed condition in a gas turbine engine, a laterally inward portion extending between and integrally joined to the laterally outward portion and the airfoil for providing support to the laterally outward portion and having a laterally extending edge; wherein said inward portion of the shroud has a geometric contour such that, at any section taken through the shroud along a plane containing a line parallel to the edge and containing a line parallel to the spanwisely extending axis, said section has a maximum thickness at the airfoil, a minimum thickness at the outermost end of the laterally inward portion and said section tapers from the maximum thickness to the minimum thickness; wherein a filler material of less density than the shroud material is attached to the airfoil for aerodynamic smoothness; and wherein the said geometric contour has dimensions that cause the maximum fiber unit stress at the point of maximum thickness in a rotational force field to be approximately equal to to the maximum fiber unit stress at the point of minimum thickness.

Claim 5

The invention as claimed in claim 1 wherein the shroud further has a laterally extending edge, an upper surface, and a lower surface spaced a distance T x ,y from the upper surface; wherein T x ,y.sbsb.1 is in a section taken through the shroud along a plane containing a line parallel to said edge, containing a line parallel to the spanwise axis and passing through a point y 1 and T x ,y.sbsb.1 has a magnitude T x .sbsb.1 y .sbsb.1 at a first location, and a magnitude T x .sbsb.2 y .sbsb.1 at a second location, the second location being laterally further away from the airfoil than the first location, the ratio T x .sbsb.2 y .sbsb.1 to T x .sbsb.1 y .sbsb.1 being less than one or equal to one in the support portion ##EQU1## and the ratio of T x .sbsb.2 y .sbsb.1 to T x ,y.sbsb.1 being greater than one or equal to one in the contact portion ##EQU2##

Claim 6

The invention according to claim 3 wherein a substantial part of the lower surface of the inward portion of the shroud in said section is linear.

Claim 7

The invention according to claim 3 wherein a substantial part of the lower surface of the inward portion of the shroud in said section is a curve which is defined by a second degree equation.

Claim 8

The invention according in the alternative to claim 1, claim 3, claim 4 or claim 5, wherein a filler material having a smaller density than the shroud material is joined to the shroud material for aerodynamic contouring.