Screw pump and its components
The disclosure relates to a 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, and at least two screws ( 4, 5, 6 ) housed in the flow chamber to force a fluid flow 5 through the flow chamber from the inlet to the outlet, wherein each screw ( 4, 5, 6 ) comprises a release coupling ( 45, 52, 62 ) to restrict, when in use, the rotation of the screw when it is being extracted from a molding tool.
1 . A screw pump comprising:
a casing with an inlet, an outlet and a flow chamber between the inlet and the outlet; and
at least two screws housed in the flow chamber to force a fluid flow through the flow chamber from the inlet to the outlet;
wherein each screw comprises a release coupling to restrict rotation of the screw when it is being extracted from a molding tool that molds the screw.
2 . The screw pump according to claim 1 , wherein the release coupling of at least one of the screws comprises at least one radial shoulder.
3 . The screw pump according to claim 1 , wherein the release coupling of at least one of the screws comprises a non-circular structure.
4 . The screw pump according to claim 1 , wherein the release coupling of at least one of the screws comprises an annular or partially annular structure.
5 . 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.
6 . The screw pump according to claim 1 , wherein the casing comprises a shell within which an insert defining the flow chamber is housed.
7 . The screw pump according to claim 6 , wherein the insert comprises at least one recess within which one of the release couplings is housed.
8 . The screw pump according to claim 6 , wherein the flow chamber is defined by a tubular wall of the insert that has a substantially constant wall thickness.
9 . The screw pump according to claim 6 , wherein the casing comprises a space between the shell and the insert.
10 . The screw pump according to claim 9 , wherein the space is separate from the flow chamber and is not part of it.
11 . The screw pump according to claim 6 , wherein the interface between the shell and the insert is designed to allow, when in use, circulating fluid to enter the space.
12 . The screw pump according to claim 6 , wherein the insert comprises one or more anti-rotation protrusions which engages with the shell to inhibit relative rotation between them.
13 . The screw pump according to claim 1 , comprising a flexible coupling connected to one of the screws to couple the screw to a drive motor.
14 . A pump assembly comprising a pump according to claim 13 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.
15 . The screw pump according to claim 2 , wherein the at least one radial shoulder extends in a radial direction outwardly past threads of the respective screw.
16 . The screw pump according to claim 15 , wherein the at least one radial shoulder includes at least one notch.
17 . The screw pump according to claim 16 , wherein the at least one notch includes two opposing notches.
18 . The screw pump according to claim 1 , wherein the release coupling comprises at least one hole creating a fluid passage with threads of the respective screw and the release coupling.
19 . The screw pump according to claim 18 , wherein the at least one hole comprises two opposing holes.
20 . The screw pump according to claim 5 , wherein the second material comprises a polymer.