ROTOR PROFILES FOR HELICAL SCREW ROTOR MACHINES

• US 3,787,154 A
• Filed: 05/24/1972
• Issued: 01/22/1974
• Est. Priority Date: 05/24/1972
• Status: Expired due to Term

• Current Assignee: Soren E.H. Edstrom
• Original Assignee: Soren E.H. Edstrom
• Inventors: Edstrom, Soren E. H.
• Primary Examiner(s): Myhre, Charles J.
• Assistant Examiner(s): Rutledge, W. H.
• Application Number:
  US05/256,237
• Time in Patent Office: 608 Days
• Field of Search: 418/201,150,197 74/462
• US Class Current: 418/201.3
• CPC Class Codes: F01C 1/084 Toothed wheels

Abstract

Asymmetric rotor profiles for cooperating helical screw type rotors for use in fluid compressors and motors. One flank of each gate rotor groove is formed partially as a concave curved surface defined by a circular arc having its radius center located outside the pitch circle of the gate rotor. The radially outermost portions of the gate rotor grooves are formed as convex curved surfaces defined by circular arcs. The other flank of each gate rotor groove and the flanks of the main rotor lobes are largely formed by traveling generation.

Claims

1. A pair of cooperating main and gate rotors having helical lobes and intervening grooves and adapted for rotation about parallel axes within a chamber formed in a helical screw rotor machine, said rotors having profiles defining the shape of said grooves and lobes formed in such a way that, in a plane transverse to the axes of rotation, said gate rotor grooves are formed to have:

a. a concave curved portion forming at least a part of a first groove flank and defined by a radius having its center outside the gate rotor pitch circle;

b. a convex curved portion on said first flank extending radially inwardly from said gate rotor pitch circle;

c. a concave curved portion forming at least a part of a second groove flank and being generated by a portion of said main rotor lobe tip; and

, d. a convex curved portion on said second flank extending radially inwardly from said gate rotor pitch circle; and

, said main rotor lobes having flanks which are substantially formed by traveling generation by said concave curved portion of said first flank and said convex curved portions forming said gate rotor grooves.

2. The invention set forth in claim 1 wherein:

said convex curved portion on said first flank extends from said gate rotor pitch circle to a meeting point with said concave curved portion on said first flank.

3. The invention set forth in claim 2 wherein:

said concave and convex curved portions on said first flank are tangent at said meeting point.

4. The invention set forth in claim 1 wherein:

said convex curved portion on said first flank is formed as a circular arc.

5. The invention set forth in claim 1 wherein:

said convex curved portion on said second flank extends from said gate rotor pitch circle to a meeting point with said concave curved portion which is traveling generated.

6. The invention set forth in claim 5 wherein:

said concave and convex curved portions on said second flank are tangent at said meeting point.

7. The invention set forth in claim 1 wherein:

said convex curved portion on said second flank is formed as a circular arc.

8. The invention set forth in claim 1 wherein:

said profile on said gate rotor groove comprises a concave curved portion forming the radially innermost part of said gate rotor groove which meets said concave curved portions on said first and second flanks and is tangent to said concave curved portions on said first and second flanks.

9. The invention set forth in claim 1 wherein:

said portion of said main rotor lobe tip comprises a curved portion which traveling generates said concave curved portion on said second flank.

10. The invention set forth in claim 9 wherein:

said curved portion on said main rotor lobe tip comprises a circular arc having a radius center located on a line which passes through the meeting point of the main and gate rotor pitch circles, on said line forming an angle with a straight line passing through the main and gate rotor axes of rotation.

11. The invention set forth in claim 1 wherein:

the profile of a gate rotor lobe includes a lobe tip portion formed as a curved surface defined by the pitch circle of said gate rotor and portions on said lobe tip on each side of said curved surface which slope radially inwardly from said pitch circle from respective meeting points with said curved surface.

12. A pair of cooperating main and gate rotors having helical lobes and intervening groove and adapted for rotation about parallel axes within a chamber formed in a helical screw rotor machine, said rotors having profiles defining the shape of said grooves and lobes formed in such a way that, in a plane transverse to the axes of rotation, said gate rotor grooves are formed to have:

a. a concave curved portion forming at least a part of a first groove flank and defined by a radius having its center outside the gate rotor pitch circle;

b. a convex curved portion on said first flank;

c. a concave curved portion forming at least a part of a second groove flank and being generated by a curved portion of said main rotor lobe tip; and

, d. a convex curved portion on said second flank;

said main motor lobes have flanks which are substantially formed by traveling generation by said convex curved portion of said first flank and said convex curved portions forming said gate rotor grooves;

said curved portion on said main rotor lobe tip comprises a circular arc having a radius center located on a line which passes through the meeting point of the main and gate rotor pitch circles, said line forming an angle with a straight line passing through the main and gate rotor axes of rotation, and said profile of said main rotor includes a flank portion which is traveling generated by said first flank and a straight line portion formed on said main rotor lobe tip, said straight line portion meeting said flank portion.

13. The invention set forth in claim 12 wherein:

said main rotor lobe tip includes a curved portion forming the radially outermost portion of said main rotor lobe which is disposed between said circular arc formed on said main rotor lobe tip and said straight line portion formed on said main rotor lobe tip.

14. The invention set forth in claim 13 wherein:

said curved portion forming the radially outermost portion of said main rotor lobe is a circular arc with a radius center at the main rotor axis of rotation.

15. A pair of cooperating main and gate rotors having helical lobes and intervening grooves and adapted for rotation about parallel axes within a chamber formed in a helical screw rotor machine, said rotors having profiles defining the shape of said grooves and lobes formed in such a way that, in a plane transverse to the axes of rotation, said gate rotor grooves are formed to have;

a. a concave curved portion forming at least a part of a first groove flank and defined by a radius having its center outside the gate rotor pitch circle;

b. a convex curve portion on said first flank;

c. a concave curved Portion forming at least a part of a second groove flank and being generated by a curved portion of said main rotor lobe tip; and

, d. a convex curved portion on said second flank;

said main rotor lobes have flanks which are substantially formed by traveling generation by said concave curved portion of said first flank and said convex curved portions forming said gate rotor grooves; and

, said profile of said main rotor includes a flank portion which is traveling generated by said first flank and a straight line portion formed on said main rotor lobe tip, said straight line portion meeting said flank portion.