US 2003/0079554 A1 · Method and apparatus for bonding a connecting ring to a flow tube and balance bar having different thermal coefficients of expansion in a Coriolis flowmeter

Abstract

A Coriolis flowmeter having a single flow tube surrounded by connecting rings and a balance bar whose ends are connected by the connecting rings to the flow tube. The balance bar has a thermal coefficient of expansion greater than that of the connecting rings and the flow tube. The outer circumferential surface of each connecting ring is tapered toward the axial center of the flow tube. The inner circumferential surface of the balance bar has a taper matching that of the connecting ring. The connecting ring can only partially inserted into the space between the flow tube and the balance bar when the assembly is at room temperature. Braze material is then applied to the visible ends of the surface common to the balance bar and the connecting rings as well as to the ends of the surface common to the connecting rings and the flow tube. The structure is heated to brazing temperature to braze these common surfaces. The greater thermal coefficient of expansion of the balance bar enables the tapered connecting rings to be fully inserted into the space between the balance bar and the flow tube so that the outer ends of the connecting rings are coplanar with the ends of the balance bar. Another embodiment has a step on the inner surface of the balance bar that limits the inward axial travel of the connecting rings. Another embodiment has an annular ring between the flow tube and the connecting ring to reduce the peak stress.

Claims39

Dependent claims

A Coriolis flowmeter having:

a flow tube;
connecting ring means having a center opening through which said flow tube extends;
a tubular balance bar coaxial with said flow tube and surrounding an axial portion of said flow tube;
said balance bar has a greater thermal coefficient of expansion than does said flow tube;
axial end portions of said balance bar coaxial with and surrounding at least a portion of said connecting ring means;
a radial inner circumferential surface of said connecting ring means coupled to an outer circumferential surface of said flow tube;
a radial outer circumferential surface of said connecting ring means is tapered with a decreasing radius in a first direction with respect to the axial center of said flow tube;
a radial inner circumferential surface of said end portions of said balance bar has a taper that matches said taper of said connecting ring means;
said connecting ring means is adapted to be partially inserted into ends of said balance bar prior to a brazing operation and then fully inserted into said balance bar during said brazing operation as said balance bar expands in diameter more than said connecting ring;
said tapered inner circumferential surface of said end portions of balance bar is adapted to be affixed by braze material to said tapered outer circumferential surface of said connecting ring means at the termination of said brazing operation.

7 more elements

A method of assembling a Coriolis flowmeter having a flow tube, a connecting ring means, and a tubular balance bar, said method comprising the steps of:

extending said flow tube through a center opening in said tubular balance bar;
positioning said flow tube so that said flow tube extends through a center opening of said connecting ring means and is coaxial with said balance bar;
positioning said connecting ring means so that axial end portions of said balance bar are coaxial with and surround at least a portion of said connecting ring means;
coupling an radial inner circumferential surface of said connecting ring means to said flow tube;
a radial outer circumferential surface of said connecting ring means is tapered in a first direction with a decreasing radius with respect to the axial center of said flow tube;
radial inner circumferential surfaces of said axial end portions of said balance bar have a taper that matches said taper of said connecting ring means;
and
said balance bar has a greater thermal coefficient of expansion than does said flow tube;
brazing said tapered inner circumferential surface of said end portions of balance bar to said tapered outer circumferential surface of said connecting ring means, said connecting ring means being axially moved within said balance bar during said brazing beyond the axial location within said balance bar prior to brazing.

6 more elements

Dependencies are inferred from the claim text.

Method and apparatus for bonding a connecting ring to a flow tube and balance bar having different thermal coefficients of expansion in a Coriolis flowmeter

Life of this patent

Method and apparatus for bonding a connecting ring to a flow tube and balance bar having different thermal coefficients of expansion in a Coriolis flowmeter

Life of this patent

Abstract

Claims39