Screw pump with field refurbishment provisions

1. A screw pump ( 20 ), comprising:

at least two screws ( 40 ) having helical flights intermeshing with each other during rotation, and extending between inner and outer ends ( 44 and 42 );

a base ( 26 );

a shaft ( 50 ) for each screw ( 40 ), and extending between an inner end ( 68 ) and an outer end ( 74 ), as well as cantilevered from the base ( 26 ) proximate the inner end ( 68 );

each screw ( 40 ) formed with a hollow core ( 80 ) for receiving the shaft ( 50 ) such that the screw ( 40 ) slips onto the respective shaft ( 50 ) therefor over the outer end ( 74 ) thereof;

an axial clamping arrangement ( 56 ) intermediate each shaft ( 50 ) and screw ( 40 ), and operative to rotationally lock the shaft ( 50 ) and without a key or keyway;

wherein each shaft ( 50 ) is formed with and instep proximate the outer end, which produces a shoulder ( 74 );

wherein each axial clamping arrangement ( 56 ) comprises a pair of jaws ( 54 and 68 ) connected to or formed on the shaft ( 50 ), wherein at least one jaw ( 54 ) is movable and driven to produce clamping pressure;

wherein each movable jaw ( 54 ) comprises a ring ( 54 ) which fits inside the annular cavity between the necked-in shaft ( 50 ) beyond the shoulder ( 74 ) thereof and the core ( 80 ) in the screw ( 40 ) proximate the outer end ( 42 ) thereof; and

wherein the movable jaw ( 54 ) is driven by threaded rod engaged to the shaft ( 50 ) at the shoulder ( 74 ).

2. The screw pump ( 20 ) of claim 1 , wherein:

the axial clamping arrangement ( 56 ) is releasable such that, while released and not locked, timing between the screws ( 40 ) can be adjusted by rotationally slipping the screws ( 40 ) about the shafts ( 50 ).

3. The screw pump ( 20 ) of claim 1 , wherein:

wherein the axial clamping arrangement ( 56 ) is not only disposed intermediate the respective shaft ( 50 ) and screw ( 40 ) therefor but also disposed proximate the outer ends ( 74 and 42 ) thereof.

4. The screw pump ( 20 ) of claim 1 , wherein:

wherein the screw shaft ( 50 ) is stepped-in beyond the shoulder ( 74 ) and defines an annular cavity with the hollow core ( 80 ) in the screw ( 40 );

whereby this annular cavity provides working room for the introduction and functioning of the axial clamping arrangement ( 56 ).

5. The screw pump ( 20 ) of claim 1 , wherein:

each screw ( 40 ) is configured with an inner and outer seat ( 44 and 66 ) upon which the jaws ( 68 and 54 ) of the axial clamping arrangement ( 56 ) clamps onto.

6. A screw pump ( 20 ), comprising:

at least two screws ( 40 ) having helical flights intermeshing with each other during rotation, and extending between inner and outer ends ( 44 and 42 );

a base ( 26 );

a shaft ( 50 ) for each screw ( 40 ), and extending between an inner end ( 68 ) and an outer end ( 74 ) as well as cantilevered from the base ( 26 ) proximate the inner end ( 68 );

each screw ( 40 ) formed with a hollow core ( 80 ) for receiving the shaft ( 50 ) such that the screw ( 40 ) slips onto the respective shaft ( 50 ) therefor over the outer end ( 74 ) thereof;

a keyless locking mechanism ( 56 , 58 , 96 , or 98 ) intermediate each shaft ( 50 ) and screw ( 40 ), and operative to rotationally lock the screw ( 40 ) together without a key or keyway;

the screws ( 40 ) are produced of materials having coefficient of thermal expansion properties; and

the shafts ( 50 ) are produced of dissimilar materials having coefficient of thermal expansion properties that are higher in value than the coefficient of thermal expansion properties of the screws ( 40 ) across a temperature range from ambient to operating temperatures;

wherein the screws ( 40 ) and shafts ( 50 ) have a slip fit at ambient temperatures, and also have an interference fit at operating temperatures that further promotes the centering and positive locking of the screws ( 40 ) to their shafts ( 50 ); and

wherein the shaft ( 50 ) comprises a steel alloy and the screw ( 40 ) comprises a material with about zero percent (0%) thermal expansion over the temperature range from ambient to operating temperature.

7. The screw pump ( 20 ) of claim 6 , wherein:

keyless locking mechanism ( 56 , 58 , 96 , or 98 ) comprises any one of an axial clamping arrangement ( 56 ), a drift-free style of keyless bushing ( 96 ), a lift-style of keyless bushing ( 58 ), or a sink-style of keyless bushing ( 98 ).

8. The screw pump ( 20 ) of claim 7 , wherein:

the keyless locking mechanism ( 56 , 58 , 96 , or 98 ) comprises a combination of the axial clamping arrangement ( 56 ) with also one of the keyless bushings ( 58 , 96 , or 98 ).

9. A screw pump ( 20 ), comprising:

at least two screws ( 40 ) having helical flights intermeshing with each other during rotation, and extending between inner and outer ends ( 44 and 42 );

a base ( 26 );

a shaft ( 50 ) for each screw ( 40 ), and extending along an axis between an inner end ( 68 ) and an outer end ( 74 ), as well as cantilevered from the base ( 26 ) proximate the inner end ( 68 );

each screw ( 40 ) formed with a hollow core ( 80 ) for receiving the shaft ( 50 ) such that the screw ( 40 ) slips onto the respective shaft ( 50 ) therefor over the outer end ( 74 ) thereof;

an annular keyless locking mechanism ( 56 , 58 , 96 , or 98 ) intermediate each shaft ( 50 ) and screw ( 40 ), and operative to rotationally lock the shaft ( 50 ) and screw ( 40 ) together without a key or keyway;

each annular keyless locking mechanism ( 56 , 58 , 96 , or 98 ) comprising plural fasteners arranged in an annular pattern around the respective shaft ( 50 ) that twist to lock and untwist to unlock said annular keyless locking mechanism ( 56 , 58 , 96 , or 98 ) by twisting on respective axes that are arranged in said annular pattern around the respective axis of each annular keyless locking mechanism ( 56 , 58 , 96 , or 98 )'s respective shaft ( 50 ).

10. The screw pump ( 20 ) of claim 9 , wherein:

the annular keyless locking mechanism ( 56 , 58 , 96 , or 98 ) is releasable by untwisting the plural fasteners therefor on respective axes thereof that are arranged in an annular pattern around the axis of the shaft ( 50 ) such that, while released and not locked, timing between the screws ( 40 ) can be adjusted by rotationally slipping the screws ( 40 ) about the shafts ( 50 ).

11. The screw pump ( 20 ) of claim 9 , wherein:

wherein each annular keyless locking mechanism ( 56 , 58 , 96 , or 98 ) comprises at least four fasteners that twist to lock and loosen to unlock said annular keyless locking mechanism ( 56 , 58 , 96 , or 98 ) on four respective twisting axes arranged in an annular pattern around the respective axis of the respective shaft ( 50 ).

12. The screw pump ( 20 ) of claim 9 , wherein:

each shaft ( 50 ) is formed with and instep proximate the outer end, which produces a shoulder ( 74 ); and

wherein the screw shaft ( 50 ) is stepped-in beyond the shoulder ( 74 ) and defines an annular cavity with the hollow core ( 80 ) in the screw ( 40 );

whereby this annular cavity provides working room for the introduction and functioning of the annular keyless locking mechanism ( 56 , 58 , 96 , or 98 ).

13. The screw pump ( 20 ) of claim 9 , wherein:

the annular keyless locking mechanism ( 56 , 58 , 96 , or 98 ) comprises any one of an annular axial clamping arrangement ( 56 ), an annular drift-free style of keyless bushing ( 96 ), an annular lift-style of keyless bushing ( 58 ), or an annular sink-style of keyless bushing ( 98 ).

14. The screw pump ( 20 ) of claim 13 , wherein:

each annular axial clamping arrangement ( 56 ) comprises a pair of ring jaws ( 54 and 68 ) connected to or formed on the shaft ( 50 ), wherein at least one ring jaw ( 54 ) is movable and driven to produce clamping pressure.

15. The screw pump ( 20 ) of claim 14 , wherein:

each movable jaw ( 54 ) comprises a ring ( 54 ) which fits inside the annular cavity between the necked-in shaft ( 50 ) beyond the shoulder ( 74 ) thereof and the core ( 80 ) in the screw ( 40 ) proximate the outer end ( 42 ) thereof; and

wherein the movable jaw ( 54 ) is driven by the plural twist fasteners for said annular axial clamping arrangement ( 56 ), and the plural twist fasteners comprise threaded rod engaged to the shaft ( 50 ) at the shoulder ( 74 ).

16. The screw pump ( 20 ) of claim 9 , wherein:

the annular keyless locking mechanism ( 56 , 58 , 96 , or 98 ) for each shaft ( 50 ) comprises a combination of the annular axial clamping arrangement ( 56 ) with also one of the annular keyless bushings ( 58 , 96 , or 98 ) proximate each other on the outer end ( 74 ) or the respective shaft ( 50 ).

17. The screw pump ( 20 ) of claim 16 , wherein:

each annular keyless bushing ( 58 , 96 or 98 ) comprises a pair of collars which interfit with each other by respective conic tapered sections such that twisting the fasteners to lock the annular keyless bushing ( 58 , 96 or 98 ) causes the respective conic tapered sections to wedge into each other and provide a radial clamping force between the shaft ( 50 ) and screw ( 40 ); and

each annular keyless bushing ( 58 ) comprises plural provisions ( 60 ) independent of the twist fasteners to force apart the wedged together conic tapered sections to unlock said annular keyless bushing ( 58 ).