Screw pump and its components
Screw pump ( 2 ) comprising: a casing ( 3 ) with an inlet ( 30 ), an outlet ( 31 ) and a flow chamber ( 32 ) between the inlet and the outlet; at least two screws ( 4, 5, 6 ) housed in the flow chamber to force a fluid flow through the flow chamber from the inlet to the outlet; and a flexible coupling ( 11 ) connected to one of the screws to couple the screw to a drive motor ( 10 ).
1 . A screw pump comprising:
a casing with an inlet, an outlet and a flow chamber between the inlet and the outlet;
at least two screws housed in the flow chamber to force a fluid flow through the flow chamber from the inlet to the outlet; and
a flexible coupling connected to one of the screws to couple the screw to a drive motor,
wherein the flexible coupling includes a first axial end with a first coupling feature configured to engage with a shaft of a drive motor, and wherein the flexible coupling includes a second axial end with a second coupling feature engaged with a cooperating feature of the screw to which the flexible coupling is connected.
2 . The screw pump according to claim 1 , wherein the flexible coupling comprises a polyphthalamide material.
3 . The screw pump according to claim 1 , wherein at least one of the screws comprises a center shaft made of a first material on which the screw is molded from a second material that is less stiff than the first material.
4 . The screw pump according to claim 3 , wherein the first material is stiffer than the second material such that the at least one screw is reinforced.
5 . The screw pump according to claim 3 , wherein the first material comprises a metal.
6 . The screw pump according to claim 3 , wherein the center shaft comprises one or more anchoring features embedded in the second material to anchor the center shaft in the second material.
7 . The screw pump according to claim 6 , wherein the or each anchoring feature comprises an axial rib or spline that extends along at least part of the center shaft.
8 . The screw pump according to claim 6 , wherein the anchoring feature or features comprise(s) at least two anchoring features, or at least two groups of anchoring features, that are spaced along a length of the center shaft.
9 . The screw pump according to claim 1 , wherein the casing comprises a shell within which an insert defining the flow chamber is housed.
10 . The screw pump according to claim 1 , wherein each screw comprises a release coupling to restrict, when in use, rotation of the screw when it is being extracted from a molding tool.
11 . The screw pump according to claim 10 , wherein the casing comprises a shell within which an insert defining the flow chamber is housed, wherein the insert comprises at least one recess within which one of the release couplings is housed.
12 . A pump assembly comprising a pump according to claim 1 and a drive motor coupled to the flexible coupling to drive the screws so as to force a fluid flow through the flow chamber from the inlet to the outlet.
13 . The screw pump according to claim 1 , wherein the first coupling feature comprises a slot configured to house a protrusion on a shaft of the drive motor, and wherein the second coupling feature comprises a protrusion engaging the cooperating feature.
14 . The screw pump according to claim 13 , wherein the slot comprises a diametrical slot.
15 . The screw pump according to claim 14 , wherein the second coupling feature is rotationally offset by 90 degrees relative to the first coupling feature.
16 . The screw pump according to claim 1 , wherein the flexible coupling comprises a lubricated polymer.