JPS6122242Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical flow transmitter for a flowmeter, such as a positive displacement flowmeter.

Generally, the flow transmitter of a positive displacement flowmeter is a type of rotation detector that detects rotation proportional to the rotation of the flowmeter rotor, and usually uses a position detection type transmitter. Conventionally, this method involves rotating a highly conductive aluminum slit disk that is rotatably supported between a high-frequency oscillation coil and a receiving coil that faces each other. By detecting and amplifying the resulting high-frequency continuous signal from the receiving coil, the signal passing through the slit is converted into an electrical signal. In such a position detection type electrical transmitter, a constant level flow pulse signal can be obtained with high sensitivity even in the case of slow rotation with a low flow rate, but on the other hand, erroneous transmission may occur due to piping vibration even when the flow rate is stopped. To prevent this, positive feedback is applied to the amplifier circuit after detection to create a hysteresis effect.

Further, since such an electric flow rate transmitter consumes electric power, explosion-proof considerations are required when it is used in an explosion-prone area.

Furthermore, there are drawbacks such as being susceptible to external electrical noise during signal transmission. These drawbacks of electrical transmission methods can be solved by using light. However, the drawbacks of the position detection method,
In other words, problems such as erroneous transmission due to pipe vibration remain unsolved, and signal noise characteristics may be impaired due to dew condensation due to changes in environmental temperature. In order to compensate for these drawbacks, the present invention seals a transparent liquid inside the transmitter in a liquid-tight manner, and by adding viscous resistance to this transparent liquid, it is possible to prevent erroneous transmission due to minute vibrations and also to prevent dew condensation. Furthermore, changes in environmental temperature cause changes in internal pressure due to the difference in thermal expansion between the transmitter housing and the transparent liquid, which can cause liquid leakage at high temperatures. To prevent this, an elastic deformable body such as a bellows is provided to absorb the difference in thermal expansion to prevent an extreme increase in internal pressure. This idea consists of a rotatably supported slit plate, a light emitter/receiver that detects passage through the slits of the slit plate by transmission or reflection of light, an optical fiber cable connected to the light emitter/receiver, and an optical fiber cable connected to the light emitter/receiver. The transmitter housing is equipped with a transmitter housing, a transparent liquid sealed in the receiver housing, and an elastically deformable body such as a bellows that absorbs the thermal expansion of the transparent liquid.

Next, one embodiment of the flow rate transmitter of this invention will be described in detail with reference to the drawings.

FIG. 1 is a cross-sectional view of a flow rate transmitter, where 1 is a transmitter housing and 2 is a transmitter cover. The rotation of the flowmeter is
is transmitted to a bevel gear 8 fixed to the rotating shaft 7,
A slit plate 9 fixed to a rotating shaft 7 is rotated. On the other hand, light emitted from a light emitter (not shown) passes through the light emitting side of a two-wire optical fiber cable 6 fixed to the connector housing 4 with a cable retainer 5, passes through a connector 11, and enters the light emitting/receiving section 3. The light is transmitted through a single optical fiber cable 10 into a transparent liquid 17 sealed in the transmitter housing 1 to prevent erroneous rotation due to viscous resistance of the slit plate and to prevent condensation on the light emitting and receiving surfaces. Ru. The light that has passed through the notch in the slit plate 9 enters a single optical fiber cable 10 on the light receiving side of the light emitting/receiving section 3, and is connected to the connector 11.
After that, the light passes through the light receiving side of two optical fiber cables 6 and enters a light receiver (not shown), where it is photoelectrically converted into a flow rate pulse signal.

12 is a transparent liquid 1 attached to a plug 13.
7 is a bellows-type elastic deformable body that absorbs thermal expansion; 14 is a drain plug that seals in or extracts the transparent liquid 17; 15 is a ball bearing for bearing the rotating shaft 7; and 16 is an O-ring that seals the transparent liquid 17. .

FIG. 2 is a front view of the slit plate 9.

As mentioned above, according to this invention, by using a highly viscous liquid as the sealed liquid, erroneous rotation of the slit plate due to pipe vibration is prevented by viscous resistance, so there is no erroneous transmission, and the transmission method is optical. Therefore, it can be used safely in explosive hazardous areas and is not affected by electrical noise.

Furthermore, the light emitting and receiving surfaces are located in the sealed liquid and do not form condensation due to changes in environmental temperature, so signal noise characteristics are not impaired, and thermal expansion of the sealed liquid is absorbed by elastically deformable bodies such as bellows. Because
Since the pressure inside the transmitter housing does not rise abnormally, the sealed liquid will not leak.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an embodiment of this invention, and FIG. 2 is a front view of the slit plate of FIG. 1. 1... Transmitter housing, 2... Transmitter cover, 3...
...Light emitter/receiver section, 4... Connector housing, 6...
Optical fiber cable, 10... Optical fiber cable, 12... Elastic deformable body, 17... Enclosed liquid.

Claims (1)

[Scope of utility model registration request] A slit plate is rotatably supported so as to be rotated in proportion to the flow rate of the fluid to be measured, and the slit plate is arranged to detect passage through the slits of the slit plate by transmission or reflection of light. A transparent liquid is sealed in a transmitter housing that includes a light emitting and light receiving element, and an elastically deformable body such as a bellows that substantially absorbs a change in volume due to thermal expansion of the transparent liquid is arranged in parallel to the housing, and the light emitting and light receiving element is A flow transmitter characterized in that an optical fiber cable is connected to the flow transmitter.