Screw rotor machine and rotors therefor

Claim 2

A pair of cooperating rotors each having helical lands and intervening grooves with a wrap angle of less than 360* and adapted for rotation about parallel, spaced apart axes within the working space of a screw rotor machine, said working space including inlet and outlet ports and at least two parallel, intersecting bores whereby the rotors cooperate to define with the working space closed chambers for a working fluid moving from the inlet port to the outlet port as the rotors are rotated; one of said rotors being of the female type and formed so that a major portion of its lands and grooves lie inside its pitch circle and the flanks of the grooves have a generally concave profile; the other of said rotors being of the male type and formed so that a major portion of its land and grooves lie outside its pitch circle and the flanks of the lands have a generally convex profile; a the grooves on the female rotor being formed such that in a plane transverse to the longitudinal axes of the rotors, each groove includes: i. a central portion defined by a circular arc having its center outside the outside diameter of the female rotor and on a radial line from the center of the female rotor through the radially innermost point of the groove, ii. a first flank extending from said central portion to approximately the pitch circle of the female rotor and being defined by a curve generated by the male rotor, and iii. a second flank extending from said central portion to approximately the pitch circle of the female rotor and defined by a circular arc having its center outside the outside diameter of the female rotor on a line extending from the radially innermost point of the second flank through the center of the central portion and on the side opposite the second flank of a line from the center of the female rotor through the radially innermost point of said groove; b. the lands on said male rotor being formed such that in a plane transverse to the longitudinal axes of the rotors, each land includes: i. a first flank extending from substantially the root diameter of the male rotor toward the outside diameter of the male rotor which is defined by a curve generated by the female rotor, ii. a second flank extending from substantially the root diameter of the male rotor toward the outside diameter of the male rotor and having a major portion defined by a circular arc having a radius of curvature shorter than the radius of curvature of the second flank of the groove in the female and having its center inside the root diameter of the male rotor on a line extending from the radially outermost point of the second flank through the center of an arc connecting the radially outermost points of the first and second flanks, and iii. a minor portion of the second flank from the radially innermost point of the major portion of the second flank substantially to the male rotor root diameter being defined by a curve generated by the female rotor.

Claim 3

A pair of cooperating rotors according to claim 1 wherein when the relative rotational position of the rotors is such that a line connecting the centers of the male and female rotors passes through the radially innermost point on a groove in the female rotor and the radially outermost point of an adjacent land on the male rotor, the center of the major portion of the second flank of the land on the male rotor is on a line extending from the radially innermost point of the second flank of the groove in the female rotor to the center of the second flank of the groove in the female rotor and positioned between the center of the central portion of the groove in the female rotor and the center of the second flank of the groove in the female rotor.

Claim 4

A pair of cooperating rotors according to claim 2 wherein the lands on the female rotor include an addendum which lies outside the pitch circle of the female rotor and said addendum from the pitch circle to the outside diameter of the female rotor is defined by a circular arc so that from the pitch circle of the female rotor to the outside diameter of the female rotor, the first and second flanks of the grooves in the female rotor are defined by a circular arc.

Claim 5

A pair of cooperating rotors according to claim 3 wherein the first flank of the land on the male rotor is line generated by a portion of the circular arc extending from the pitch circle to the outside diameter of the first flank of the groove in the female rotor.

Claim 6

A pair of cooperating rotors according to claim 4 wherein the first flank of the groove in the female rotor is generated by the radially outermost point of the first flank of the land on the male rotor.

Claim 7

A pair of cooperating rotors according to claim 5 wherein the remaining portion of the second flank of the land on the male rotor is line generated By a portion of the circular arc extending from the pitch circle to the outside diameter of the second flank of the groove in the female rotor.

Claim 8

A pair of cooperating rotors according to claim 6 wherein the radially outermost points of the first and second flanks of the land on the male rotor are spaced apart a distance such that they substantially coincide with the radially innermost points of the first and second flanks of the groove in the female rotor and a sealing strip is positioned between the radially outermost points of the first and second flanks of the land on the male rotor and an arc connecting the radially outermost points will contact the sealing strip.

Claim 9

A pair of cooperating rotors according to claim 7 wherein the first and second flanks of the land on the male rotor include a circular arc connecting the flanks and the root of the male rotor and such arc has a radius of curvature approximately 80 percent of the radius of curvature of the circular arc defining the area from the female rotor pitch circle to the female rotor outside diameter of each flank of the groove in the female rotor.

Claim 10

A screw rotor machine apparatus for compressing an elastic working fluid comprising: a. a casing defining a working space including at least a pair of intersecting bores having parallel axes and a fluid inlet port and a fluid outlet port; and b. at least a pair of cooperating rotors each adapted to rotate in one of the bores of said casing and each having helical lands and intervening grooves with a wrap angle of less than 360*; c. said rotors being positioned to cooperate with each other and with said working space closed chambers for the working fluid moving from the inlet to the outlet as the rotors are rotated; d. one of said rotors being of the male type and formed so that a major portion of its lands and grooves lie outside its pitch circle and the flanks of the lands have a generally convex profile; e. the other of said rotors being of the female type and formed so that a major portion of its lands and grooves lie inside its pitch circle and the flanks of the grooves have a generally concave profile; f. the grooves of the female rotor being formed such that in a plane transverse to the longitudinal axis of the female rotor, each groove includes: i. a central portion defined by a circular arc having its center outside the outside diameter of the female rotor and on a radial line from the center of the female rotor through the radially innermost point of the groove, ii. a first flank extending from said central portion to approximately the pitch circle of the female rotor and being defined by a curve generated by the male rotor, and iii. a second flank extending from said central portion to approximately the pitch circle of the female rotor and defined by a circular arc having its center outside the outside diameter of the female rotor on a line extending from the radially innermost point of the second flank through the center of the central portion and on the side opposite the second flank of a line from the center of the female rotor through the radially innermost point of said groove; g. the lands on said male rotor being formed such that in a plane transverse to the longitudinal axis of the male rotor, each land includes: i. a first flank extending from approximately the root diameter of the male rotor toward the outside diameter of the male rotor which is defined by a curve generated by the female rotor, ii. a second flank extending from approximately the root diameter of the male rotor toward the outside diameter of the male rotor and having a major portion defined by a circular arc having a radius of curvature shorter than the radius of curvature of the second flank of the groove in the female and having its center inside the root diameter of the male rotor on a line extending from the radially outermost point of the second flank through the center of an arc connecting the radially outermost points of the first and second flanks, and iii. a minor portion of the second flank from the radially innermost point of the major portion of the second flank substantially to the male rotor root diameter being defined by a curve generated by the female rotor.

Claim 11

A screw rotor machine apparatus for compressing an elastic working fluid comprising: a. a casing defining a working space including at least a pair of intersecting bores having parallel axes and a fluid inlet port and a fluid outlet port; and b. at least a pair of cooperating rotors each adapted to rotate in one of the bores of said casing and each having helical lands and intervening grooves with a wrap angle of less than 360*; c. said rotors being positioned to cooperate with each other and with said working space closed chambers for the working fluid moving from the inlet to the outlet as the rotors are rotated; d. one of said rotors being of the male type and formed so that a major portion of its lands and grooves lie outside its pitch circle and the flanks of the lands have a generally convex profile; e. the other of said rotors being of the female type and formed so that a major portion of its lands and grooves lie inside its pitch circle and the flanks of the grooves have a generally concave profile; f. the grooves of the female rotor being formed such that in a plane transverse to the longitudinal axis of the female rotor, each groove includes: i. a central portion defined by a circular arc having its center outside the outside diameter of the female rotor and on a radial line from the center of the female rotor through the radially innermost point of the groove, ii. a first flank extending from said central portion to approximately the pitch circle of the female rotor and being defined by a curve generated by the male rotor, and iii. a second flank extending from said central portion to approximately the pitch circle of the female rotor and defined by a circular arc having its center outside the outside diameter of the female rotor on a line extending from the radially innermost point of the second flank through the center of the central portion and on the side opposite the second flank of a line from the center of the female rotor through the radially innermost point of said groove; g. the lands on said male rotor being formed such that in a plane transverse to the longitudinal axis of the male rotor, each land includes: i. a first flank extending from approximately the root diameter of the male rotor toward the outside diameter of the male rotor which is defined by a curve generated by the female rotor, ii. a second flank extending from approximately the root diameter of the male rotor toward the outside diameter of the male rotor and having a major portion defined by a circular arc having a radius of curvature shorter than the radius of curvature of the second flank of the groove in the female and having its center inside the root diameter of the male rotor on a line extending from the radially outermost point of the second flank through the center of an arc connecting the radially outermost points of the first and second flanks, and iii. a minor portion of the second flank from the radially innermost point of the major portion of the second flank substantially to the male rotor root diameter being defined by a curve generated by the female rotor.

Claim 12

A screw machine apparatus according to claim 9 wherein when the relative rotational position of the rotors is such that a line connecting the centers of the male and female rotors passes through the radially innermost point on a groove of the female rotor and the radially outermost point on an adjacent land on the male rotor, the center of the major portion of the second flank of the land on the male rotor is on a line extending from the radially innermost point of the second flank of the groove in the female rotor to the center of the second flank of the groove in the female rotor and positioned between the center of the central portion of the groove in the female rotor and the center of the second flank of the groove in the female rotor.

Claim 13

A screw machine apparatus according to claim 10 wherein the lands on the female rotor include an addendum which lies outside the pitch circle of the female rotor and said addendum from the pitch circle to the outside diameter of the female rotor is defined by a circular arc so that from the pitch circle of the female rotor to the outside diameter of the female rotor, first and second flanks of the grooves in the female rotor are defined by a circular arc.

Claim 14

A screw machine apparatus according to claim 11 wherein the first flank of the land of the male rotor is line generated by a portion of the circular arc extending from the pitch circle to the outside diameter of the first flank of the groove in the female rotor.

Claim 15

A screw machine apparatus according to claim 12 wherein the first flank of the groove in the female rotor is generated by the radially outermost point of the first flank of the land on the male rotor.

Claim 16

A screw machine apparatus according to claim 13 wherein the remaining portion of the second flank of the land on the male rotor is line generated by a portion of the circular arc extending from the pitch circle to the outside diameter of the second flank of the groove in the female rotor.

Claim 17

A screw machine apparatus according to claim 14 wherein the radially outermost points of the first and second flanks of the land on the male rotor are spaced apart a distance such that they substantially coincide with the radially innermost points of the first and second flanks of the groove in the female rotor and a sealing strip is positioned between the radially outermost points of the first and second flanks of the land on the male rotor and an arc connecting the radially outermost points will contact the sealing strip.

Claim 18

A screw machine apparatus according to claim 15 wherein the first and second flanks of the land on the male rotor include a circular arc connecting the flanks and the root of the male rotor which has a radius of curvature approximately 80 percent of the radius curvature of the circular arc defining the area from the female rotor pitch circle to the female rotor outside diameter of each flank of the groove in the female rotor.