Device for measuring the flow rate of a liquid

<img file="SE366206B_D0001.tif" />

PATENTS AND REGISTRATION OFFICE

IUTLÄ @@ i «IW6S§KBIFT mur 366 206 intci Å 61 b ​​5/02

Patent Application. No. 6575/71 Validity Day on Ans. widely available on

Ans. published and published on 22 IV 1974 Priority requested from 25 V 1970 (FR, 70 18962)

Received on 19 V 1971

V 1971 26 XI 1971

NV PHILIPS⁰ Incandescent lamp factories, EINDHOVEN, NL

Inventor: MJ Auphan, Courbevoie and JR Périlhou, Bourg-la-Reine, FR Orabud: S Skesson

Apparatus for measuring the flow rate of a liquid flowing through a duct by mixing with an auxiliary liquid of different temperature

The present invention relates to a device for measuring the flow rate of a fluid flowing through a duct, comprising an injection channel for an auxiliary fluid of a temperature other than the flowing liquid, the auxiliary liquid being manageable with the flowing liquid, while the device further comprises thermocouples for measuring the temperature. the flowing liquid, of the auxiliary liquid, and of the mixture of both said liquids.

Such a device is known from French patent specification 92,750. According to this patent, the flow rate of, for example, fluid flowing through a blood vessel is measured in that an auxiliary fluid whose temperature differs from that of the blood at a known rate is injected into the blood vessel. In order not to disturb the blood stream, at the same time, a certain amount of the mixture of blood and auxiliary fluid is taken from the blood vessel, whereby dc per unit time injected and withdrawn must be equal. The kundu device is provided with thermocouples for measuring the temperature difference between the blood, the auxiliary fluid and the mixture of blood and auxiliary fluid. These thermocouples are provided at suitable locations near the injection and the fluid withdrawal channels from the blood vessel.

0m fluid is drawn downstream from the injection channel, the flow rate D of the blood can be stated by the formula:

<img file="SE366206B_D0002.tif" />

Here, the temperature of the auxiliary liquid, Tg denotes the temperature of the mixture,

Tg the temperature, of the blood, and the rate at which the auxiliary fluid is injected.

In many cases, additional measures are required to achieve a &amp; od mixing between the flowing fluid and the auxiliary fluid. Such a patent discloses such a measure in the form of a stirrer consisting of one or more magnets which can be set in motion through a magnetic field generated outside the liquid channel. A disadvantage of this construction is that the operation of the agitator on difficult-to-access channels, such as deep-blood vessels, is hampered by the large air gap appearing in the magnetic circuit.

The present invention is intended to provide a structure which, regardless of the position of the liquid channel, enables a good mixing of the two liquids. This object is achieved according to the invention in that the device is provided with means for a pulsating supply of liquid.

Preferably, said means consists of an impulse pump which is connected via an inlet valve to a supply line for the auxiliary fluid and via an outlet valve to the injection channel.

Due to the pulsating supply of auxiliary fluid, the formation of the vortex formation in the vicinity of the two liquids occurs in the vicinity.

The invention is described in the following with reference to examples shown schematically in the accompanying drawing.

Fig. 1 shows schematically a device according to the invention.

Fig. 2 shows a cross-section through a pulse pump used in the device according to Fig. 1.

In Fig. 1, fluid flows at an unknown speed in the direction along the arrow 1 through a tube 3. Through an aperture needle 5 passing through the tube wall, an injection channel 7 in the form of a flexible tube is inserted into the tube 3. Over this injection channel, an auxiliary fluid flowing from a supply line 9 can be introduced into the tube at a speed which can be measured by means of a tube. known flow meter, which consists, for example, of a constriction 11 arranged in the injection channel, which results in a proportional decrease in pressure of the auxiliary fluid which can be measured by a pressure gauge 13.

The auxiliary fluid flows from the injection channel 7 in the direction of arrow 15 into the tube 3 and mixes with the fluid flowing in this tube. Above the bore needle 5, a portion of this mixture can be suctioned by a suction pump not shown. For measuring the temperature difference, thermocouples 17,19,21 and 23 are provided. Thermocouples 17 and 19 measure the temperature Tj of the auxiliary liquid and Tg of the mixture, respectively. They are connected to a measuring apparatus 25 which indicates the difference T „- T, Thermocouples 21 and 23 measure the temperature T- of the mixture, respectively 1 to Tg of the flowing liquid. They are connected to a measuring device 27 which indicates the difference Tg-Tg ·

In order to promote the mixing of the flowing liquid with the auxiliary liquid, the latter according to the invention is applied pulsed. For this purpose, the device is provided with a pulse pump 29 which is connected via an inlet valve 31 to the supply line 9 and over an outlet valve 33 to the injection channel 7, The pulse pump 29 (see Fig. 2) consists of a cylindrical housing 35 in which an axially compressible bellows 37 is present. By compressing the bellows 37, the pump compartment 39 present in the casing 35 will be enlarged, thereby opening the inlet valve 31 so that the auxiliary fluid flows from the supply line 10 into the pump compartment. Expansion of the heel 37 causes the pump compartment 39 to become smaller, thereby opening the outlet valve 33 so that liquid flows from the pump compartment 39 into the injection duct 7. The valves 31 and 33 are preferably designed as carbon valves.

The bellows 37 can be pulled elongated in that a rod 41 moves along the shaft to the chamber 35, thereby tensioning a spring 43 which ensures that the bellows 37 in the event of loss of the axial force on the rod 41 returns to its original position.

The rod 41 can be actuated in an axial direction with an arm 44 which is rotatable about an axis 45 and drives a gear 47, which cooperates with a gear 49, and is guided by two guide rollers 51 and 53, the gear 49 can be moved over one (not shown). The coupling is driven by an electric motor 55, whereby it begins to rotate in the direction of arrow 57. The coupling between the motor 55 and the gear 49 is, for example, an electromagnetic coupling known per se, which consists of a motor shaft connected to it. a continuous rotating disk and a disk connected to the gear, one of which contains an electromagnet which, when excited, connects the two discs to each other. If the excitation is excited by a pulse-shaped current, the gear 49 will always be driven for a shorter time, whereby the pin rod 47 moves in the direction of arrow 59. Thereby the arm 44 rotates to the left, thereby pushing the rod 41 into the housing 35. The bellows 37 are thereby pulled out and the pump space 39 is reduced. At the end of the coupling applied to the current pulse, the gear 49 will again be disengaged, whereby the force on the rod 41 will be lost and the spring 45 will restore the original state. By changing the length and frequency of the current pulses, the flow in the injection channel 7 can be influenced.

In order to prevent the coupling from receiving two too fast successive current pulses, a switch 61 actuated by the arm 44 is provided, which is exclusively closed when the arm is in a resting position. The switch 61 is provided in the power supply circuit and allows a new current pulse to be released only when the arm 44 is in a resting state.

366206 *