Mass flow operating by the coriolis principle

Details Mass flow operating by the coriolis principle Mass flow operating by the coriolis principle

1990-01-08

1991-06-04

Goldstein, Herbert

Measuring and testing

Volume or rate of flow

Mass flow by imparting angular or transverse momentum to the...

G01F 184

Patent

active

050203800

DESCRIPTION:

BRIEF SUMMARY
The invention relates to a mass flow meter operating by the Coriolis principle comprising a mechanical oscillating system and an optical sensor means which detects the mechanical oscillations of the oscillating system and which has a light transmitter and a light receiver, the light of the light transmitter being transmitted to the light receiver by an optical waveguide means which comprises at least one quartz or sapphire rod and the light flux of which can be influenced by the oscillations.
In a mass flow meter of this type known from the published European patent application 0 262 573 the optical waveguide means consists of two sapphire rods, one of which is connected at one end to the light transmitter and the other of which is connected at one end to the light receiver. The other ends of the two sapphire rods are formed as total-reflecting prisms and spaced apart from each other in such a manner that the light flux emanating from the light transmitter and passing through the sapphire rod enters the other sapphire rod and is conducted by the latter to the light receiver. On the measuring tubes of the mass flow meter immersion tabs are mounted in such a manner that in dependence upon the deflections of the measuring tubes they project to a greater or lesser extent into the gap formed between the prismatically shaped ends of the sapphire rods. The advantage achieved with this arrangement is that the light transmitter and the light receiver can be accommodated in a protected manner at a distance from the oscillating measuring tube system, so that they are not exposed to pronounced temperature fluctuations when alternately cold and hot fluid flows through the measuring tubes. It is, moreover, avoided that the measuring tube system set in mechanical oscillations transmits undesired vibrations to the light transmitter and the light receiver or that the latter are attacked by a chemically aggressive fluid which may emerge from the measuring tubes. However, the sensitive sapphire rods of the optical waveguide means are exposed to such thermal, chemical and mechanical influences.
U.S. Pat. No. 4,173,393 describes an optical waveguide comprising a core of quartz, a cladding of glass and a protective coating of metallic glass. The protective coating of metallic glass is applied as a liquid which contracts more than the glass of the cladding when it solidifies, thereby placing the waveguide under constant compression which increases the resistance to fracture.
It is the problem underlying the invention to provide a mass flow meter operating by the Coriolis principle the optical waveguide means of which is distinguished by mechanical stability and resistance to corrosion and temperature.
According to the invention this problem is solved in that the or each quartz or sapphire rod of the optical waveguide means is surrounded by ceramic material or glass.
The ceramic material or glass surrounding the rods of the optical waveguide means improves the mechanical strength of the optical waveguide means and protects the quartz or sapphire rods of the optical waveguide means against chemical and thermal influences. The optical properties of the optical waveguide means are not affected by the embedding in ceramic material or glass, as ceramics or glass have a lower refractive index than quartz or sapphire. Particularly advantageous is the use of glass types suitable for industrial purposes, which glass types are suitable for bonding to sapphire and are chemically and thermally robust. Their refractive index is about 1.5 and is thus lower than that of sapphire.
An advantageous further development of the invention resides in the fact that the outside of the ceramic material or the glass is surrounded by a metal cladding. The chemical resistance and mechanical strength of the optical waveguide means is thereby further increased. The metal cladding also has the advantage that the optical waveguide means can now easily be secured to metallic objects, for example a metallic carrier housing.
Hereinafter ,an example of embodiment of

REFERENCES:
patent: 3912362 (1975-10-01), Hudson
patent: 4173393 (1979-11-01), Maurer
patent: 4778243 (1988-10-01), Finzel
patent: 4801897 (1989-01-01), Flecken
patent: 4828276 (1989-05-01), Abbott
patent: 4863234 (1989-09-01), Gladenbecit

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