Pair of conveyor worms for rotary positive-displacement pumps

A pair of conveyor screws for rotating positive-displacement pumps, the conveyor screws comprising multi-stage rotors including a rotor and a contra-rotor,

• wherein said conveyor screws comprise a screw spindle pump and rotate with zero contact between said conveyor screws, said conveyor screws being positioned within a housing and rotating at a same speed, said conveyor screws including teeth, said teeth having opposing flanks extending along a length of said teeth,
• said conveyor screws forming loss gaps and having a same thread depth, a same number of threads and flank profiles which are symmetrical, and
• said conveyor screws including a tooth base positioned below a flank profile reversing point and a tooth head positioned above said flank profile reversing point, wherein a profile-produced loss gap height in an axial section on a pitch circle is determined for a specific rotor diameter by shifting the flank profile reversing point as a function of a rotor pitch;
• wherein only stages nearest a suction side have an optimum profile-produced loss gap height.

A pump comprising:

• at least two intermeshed screws, said screws including a plurality of teeth, said screws having a pitch and a diameter;
• and
• a gap having a gap width formed between adjacent teeth of said teeth, wherein said gap width is determined by a profile reversing radius along said teeth,
• said profile reversing radius being positioned along said teeth depending on a ratio of said pitch to said diameter.

A screw pump comprising:

• first and second meshing screw rods counter-rotating at a speed within a bore of a casing,
• said first and second screw rods having a pitch, a predetermined number of starts and a thread depth,
• said first and second screw rods each comprising a helical gearing including teeth,
• each tooth of said teeth including a base, a tip and a pair of symmetrical opposing flank profiles,
• said flank profiles including a flank profile reversing radius, an addendum flank above said flank profile reversing radius and a tooth flank below said flank profile reversing radius,
• said thread depth comprising a distance between said tip and said base,
• said screw pump further comprising a plurality of leakage gaps between each said moth of said first meshing screw rod and each counter tooth of said second meshing screw rod, said leakage gaps having a width,
• wherein a radius of said flank profile reversing radius is variable such that said width of said leakage gaps is constant for a predetermined tooth tip diameter and a predetermined screw pitch.

A pump for pumping a substance formed by a method comprising steps of:

• providing at least two intermeshed screws, said screws having a pitch and a diameter;
• forming a plurality of teeth on said screws such that a gap is formed between adjacent teeth of said teeth, each tooth of said teeth having a profile reversing radius;
• determining a gap width of said gap for said substance;
• forming said gap width between said adjacent teeth by varying said profile reversing radius along said tooth as a ratio of pitch to diameter varies.