Method of manufacturing a Coriolis mass flow rate sensor from a polymeric material
A method of manufacturing a Coriolis mass flowmeter from a polymeric material is described, in which a dynamically responsive manifold is fabricated from the same material as the flow sensor's flow-sensitive elements. The flowmeter is free of mechanical joints and adhesives. The manifold and flow-sensitive elements therefore do not slip or change their location relative one another, nor are they subject to differing degrees of thermal expansion that would otherwise undermine integrity, reliability, and/or accuracy of the boundary condition at the ends of the vibrating flow-sensitive elements.
1. A method for fabricating a Coriolis flowmeter from a single polymer material, the method comprising:
fabricating a dynamically responsive manifold from a first polymer material, the dynamically responsive manifold comprising:
a body,
at least four tubular port extensions integral to the body, each tubular port extension including a weld surface, and
at least one isolation plate integral to the body and the at least four tubular port extensions;
forming at least two flow-sensitive members by shaping at least two tubes to a predetermined shape, the at least two tubes made from the first polymer material, each flow-sensitive member including two open ends corresponding to two of the at least four tubular port extensions; and
welding each open end of the at least two flow-sensitive members to a corresponding weld surface of one of the at least four tubular port extensions,
wherein the at least two flow-sensitive members and the at least four tubular port extensions have a dimensional tolerance, and
wherein shaping at least two tubes to a predetermined shape comprises:
heating the respective tube to a temperature near a glass transition temperature of the first polymer material,
forming the tube into the predetermined shape,
maintaining the temperature for a time period, and
cooling the shaped tube.
2. The method of claim 1 , wherein welding each open end of the at least two flow-sensitive members to the corresponding weld surface of one of the at least four tubular port extensions occurs simultaneously.
3. The method of claim 1 , wherein the welding further comprises:
locally heating the weld surface of each of the at least four tubular port extensions to within a weld temperature range of the first polymer material;
locally heating each open end of the at least two flow-sensitive members to within the weld temperature range of the first polymer material; and
joining each open end to the corresponding weld surface simultaneously while each weld surface and each open end are within the weld temperature range of the first polymer material.
4. The method of claim 1 , wherein the tubular port extensions and the flow-sensitive members have an outside diameter that is approximately the same.
5. The method of claim 4 , wherein a tolerance of the outside diameter is +/−0.2 mm at each weld.
6. The method of claim 1 , wherein the welding forms an adhesive-free and contamination-free junction.
7. The method of claim 1 , further comprising: temporarily inserting a pin, during welding, to a location that is inside the at least two flow-sensitive members and the corresponding tubular port extension, the location corresponding to a polymer joint, the pin in intimate contact with the polymer joint to prevent polymer from the polymer joint from flowing into the flow-sensitive member.
8. An apparatus, comprising:
a dynamically responsive manifold, comprising:
a body of a first polymer material,
at least four tubular port extensions of the first polymer material, the at least four tubular port extensions integral to the body, and
at least one isolation plate of the first polymer material, the at least one isolation plate integral to the body and the at least four tubular port extensions;
at least two flow-sensitive members formed by shaping at least two tubes to a predetermined shape, the at least two tubes made from the first polymer material, each of the at least two flow-sensitive members having a first end and a second end, each of the first ends and the second ends corresponding to one of the at least four tubular port extensions, the at least two flow-sensitive members and the at least four tubular port extensions having a dimensional tolerance; and
at least four polymer welds, each of the at least four polymer welds connecting one of the first ends or one of the second ends of the at least two flow-sensitive members to the corresponding one of the at least four tubular port extensions,
wherein shaping at least two tubes to a predetermined shape comprises:
heating the respective tube to a temperature near a glass transition temperature of the first polymer material,
forming the tube into the predetermined shape,
maintaining the temperature for a time period, and
cooling the shaped tube.
9. The apparatus of claim 8 , wherein a wall thickness of each of the at least four tubular port extensions and each of the at least two flow-sensitive members is less than one millimeter.
10. The apparatus of claim 8 , wherein an inner diameter of the at least two flow-sensitive members is between two millimeters and four millimeters.
11. The apparatus of claim 8 , wherein a dimensional tolerance of each of the at least four polymer welds is within 0.2 millimeters.
12. The apparatus of claim 8 , wherein the at least one isolation plate is disposed between weld surfaces of the at least four tubular port extensions and the body of the dynamically responsive manifold.