FR3110690A1 - Flowmeter comprising at least one tube with an internal grid - Google Patents

Abstract

The invention relates to a flow meter (100) for measuring a gas flow in a conduit (2, 3), and comprising a hollow tube (101, 102) provided with an internal grid (110) and intended to be inserted in the duct (101, 102), a module for measuring the differential pressure comprising at least one pressure sensor (105, 106, 140) intended to measure the pressure upstream and downstream of the grid (110), and a electronic card (104) making it possible to determine the flow rate of gas circulating in the conduit (2, 3) from the difference in the pressure measurements taken upstream and downstream of the grid (110). According to the invention, the grid (110) comprises at least two concentric cylindrical walls (111, 112, 113) arranged in the tube (101, 102) so that their axis of revolution is parallel to a longitudinal axis of the tube (101, 102), and in that the grid (110) has two upstream and downstream annular homogenization chamber (121, 122) arranged around the cylindrical wall (113) of larger dimension and in which each sensor (105 , 106, 140) will perform the pressure measurements. Figure for abstract: Fig. 5

Description

Flow meter comprising at least one tube with an internal grid

The present invention relates to a flowmeter comprising at least one tube provided with an internal grid.

In certain sensitive devices, such as ventilation devices for providing respiratory assistance to patients (these devices being commonly called "artificial respirators"), it is essential to be able to precisely control the flow rate of a gaseous air mixture /oxygen sent to an individual suffering from respiratory failure as well as the airflow expelled by this individual. Indeed, poor control of these flow rates could have harmful consequences for the patient.

Such a flowmeter must therefore be able to provide gas flow measurements that are reliable and precise, in a constrained environment.

A flow meter according to the invention is particularly but not exclusively suitable for measuring a gas flow circulating in a circuit of an artificial respirator.

The subject of the invention is a flow meter for measuring a gas flow in a conduit, and comprising a hollow tube provided with an internal grid and intended to be inserted into the conduit, a differential pressure measurement module comprising at least one sensor and intended to measure the pressure upstream and downstream of the grid, and an electronic card making it possible to determine the flow rate of gas circulating in the duct from the difference in the pressure measurements taken upstream and downstream of the grid.

According to the invention, the grid comprises at least two concentric cylindrical walls arranged in the tube so that their axis of revolution is parallel to a longitudinal axis of the tube, the grid having a plane of symmetry parallel to a plane materializing the section cross section of the tube and making it possible to distinguish an upstream part from which the upstream pressure measurement is carried out and a downstream part from which the downstream pressure measurement is carried out, each part comprising an annular homogenization chamber arranged around the concentric cylindrical wall of larger dimension and in which said at least one sensor of the module will carry out the pressure measurements. Such a flowmeter thus makes it possible to measure a gas flow in a conduit from the measurement of the pressure at two points of the gas flow located on either side of the grid. The principle of such a flowmeter is to use a grid whose particular shape will make it possible to create pressure drops and to obtain homogenization chambers in which there will be almost no gas circulation. The pressure measurements will be taken in these homogenization chambers, and will therefore be perfectly representative of the pressure prevailing in the duct because no gas circulation will disturb these measurements. The grid has an upstream part and a downstream part which are identical and from which upstream pressure measurements and downstream pressure measurements relative to said grid can be performed respectively. The tube is inserted into the conduit in which the gas circulates in order to perform the pressure measurements. The envelope of the grid has an overall cylindrical shape, the axis of revolution of which extends parallel to the direction of gas flow in the tube. The grid is fixed to an internal surface of the tube, and advantageously it is made in one piece with said tube to constitute with the latter one and the same piece. Preferably, the tube and the grid are made of plastic. It is also assumed that the tube and the grid are rigid parts. Advantageously, the tube comprises a cylindrical segment in which the grid is placed. According to a first alternative embodiment of a flowmeter according to the invention, the differential pressure measurement module may comprise a single pressure sensor comprising two tappings, one upstream of the grid and the other downstream of it. this. In this way, a single sensor makes it possible to perform both the pressure measurements upstream and downstream of the grid. According to a second variant embodiment of a flowmeter according to the invention, the differential pressure measurement module comprises two sensors, one dedicated to measuring the pressure upstream of the grid and the other dedicated to measuring the the pressure downstream of it.

According to a possible characteristic of the invention, the concentric cylindrical walls are fixed to an internal surface of the tube by several radial arms passing through said walls. In this way, there remains a plurality of passages for the gas between the cylindrical walls and the radial arms. Thanks to these radial arms, the cylindrical walls give the impression of being suspended in the tube. The presence of radial arms and concentric cylindrical walls creates pressure drops at the level of the grid.

According to a possible characteristic of the invention, the grid comprises three concentric cylindrical walls and six radial arms. This is a particular embodiment which is in no way limiting, but which makes it possible to carry out reliable and precise pressure measurements. The two cylindrical walls of smaller diameter serve to create pressure drop, and the third cylindrical wall of larger diameter also serves to create pressure drop and separates the central gas flow, from the homogenization chamber in which the pressure measurement will be taken.

According to a possible characteristic of the invention, the upstream part and the downstream part of the grid each comprise a plurality of plenum chambers distributed around the concentric cylindrical wall of larger dimension. These plenum chambers help to create pressure drop and to attenuate the gas flow, or even to eliminate it, upstream of the homogenization chamber so that there is no more gas circulation in said chamber. homogenization. Two consecutive plenum chambers of the upstream part or the downstream part are separated from each other by a free space constituting a passage for the gas flow evolving in the tube.

According to a possible characteristic of the invention, each plenum chamber consists of a solid quarter which is inserted between the larger concentric cylindrical wall and the annular homogenization chamber. These plenum chambers are preferentially in contact with the larger concentric cylindrical wall.

According to a possible characteristic of the invention, each plenum chamber of one of the two upstream and downstream parts of the grid is aligned with a plenum chamber of the other part along an axis which is parallel to the axis of revolution concentric cylindrical walls.

According to a possible characteristic of the invention, each plenum chamber is traversed by a hole extending parallel to the axis of revolution of the concentric cylindrical walls and allowing communication between the two plenum chambers of the two upstream and downstream parts which are aligned along said axis of revolution.

According to a possible characteristic of the invention, the plenum chambers of each of the two upstream and downstream parts of the grid are in communication with the corresponding homogenization chamber by means of radial passages. Advantageously, these passages are materialized by cylindrical channels.

The invention also relates to an artificial respirator comprising at least one flow meter having all or part of the preceding characteristics, arranged on at least one of the gas flow circuits chosen from the air supply circuit or a air/oxygen gas mixture to a patient, or the exhaled air return circuit from the patient.

Another object of the invention is a process for producing a flow meter according to the invention.

According to the invention, the method comprises a step of manufacturing the tube and the grid using a 3D printer. Indeed, the tube and the grid have shapes and dimensions that are compatible with manufacturing by 3D printing.

Another object of the invention is a flowmeter system making it possible to measure a gaseous flow in two parallel ducts.

According to the invention, said system comprises two flowmeters in accordance with the invention, said flowmeters being arranged relative to each other so that:
- the two tubes are parallel and connected to each other by a plate to which the electronic board is attached,
- the pressure sensors for measuring the pressure upstream and downstream of the grid of each duct are in contact with said card,
-each sensor is connected to the homogenization chamber of the corresponding part of the grid by means of a flexible pipe connecting to a hollow endpiece emerging from said tube and in communication with said homogenization chamber.

Such a system can for example be integrated into an artificial respirator in order to measure both the flow rate of a mixture of air and oxygen intended to be conveyed to a patient and the flow rate of air expelled by this patient. Such a system implements a single electronic card located between the two tubes to ensure the measurement of the gas flow in the two ducts. This arrangement thus makes it possible to limit the size of this flowmeter. In addition, such a system comprising the two tubes each equipped with the pressure drop grid and the two connection ends, as well as the plate can be produced using a 3D printer.

A detailed description of a preferred embodiment of a flowmeter according to the invention is given below, with reference to the following figures:

shows a perspective view of an artificial respirator comprising a flowmeter system according to the invention,

shows a perspective view of a flowmeter system according to the invention placed in an artificial respirator,

represents a perspective view of the flowmeter system alone,

shows a perspective view of a flowmeter according to the invention integrated into a flowmeter system, and in which part of the tube has been artificially removed in order to be able to view the interior of the flowmeter,

shows a perspective view from another angle of the flowmeter of Figure 4,

shows a front view of the inside of the tube of a flowmeter according to the invention, showing the shape of the pressure drop grid.

shows a side view of a flowmeter according to the invention integrated into a flowmeter system, and implementing a module for measuring the differential pressure comprising a single pressure sensor.

Referring to Figure 1, a flowmeter system 100 according to the invention can be integrated into an artificial respirator 1 intended to assist a person in respiratory distress. In the example illustrated, the respirator is a compact transportable respirator, it being understood that a flow meter according to the invention can be used in other types of device. Such a respirator 1 comprises a first conduit 2 for supplying an air/oxygen gas mixture intended to be routed to the patient, and a second conduit 3 intended to evacuate the air expelled by said patient. The ventilation of the air in the first duct 2 is carried out under the influence of a motorized fan fed upstream by air penetrating into an inlet mouth, this motorized fan pulsating air downstream towards the patient. An additional oxygen supply is carried out via pressurized oxygen. The air/oxygen mixture is produced by a connector promoting homogeneous mixing. The sending of the air/oxygen gas mixture to the patient is controlled by valves opening and closing the circuit according to the desired respiratory cycle. Within the artificial respirator 1, the two conduits 2, 3 are parallel and given the vital importance of controlling the gas flows circulating in said circuits 2, 3, it is essential to be able to measure their flow with reliability and precision.

Referring to Figures 2 and 3, a flowmeter system 150 according to the invention is designed in particular to be able to measure the gas flow in these two conduits 2, 3, and therefore connects two flowmeters 100 according to the invention. Such a system schematically comprises two straight and rigid tubes 101, 102, arranged parallel to each other. Each of these tubes 101, 102 is intended to be inserted into the gas duct 2, 3 considered, so as to constitute a section of this duct 2, 3. The two tubes 101, 102 are connected to each other by a flat plate 103 intended to support an electronic card 104 configured to measure the gas flow in each of said ducts 2, 3 from a differential pressure measurement provided by a differential pressure measurement module comprising at least one sensor 105, 106, 140 pressure. According to a first embodiment of a flowmeter 100 according to the invention, this module comprises two separate sensors 105, 106 per conduit 2, 3, one being provided for measuring the pressure upstream of the grid 110 and the other being provided to measure the pressure downstream of said grid 110.

Referring to Figure 7, according to a second embodiment of a flow meter 100 according to the invention, the differential pressure measurement module comprises a single pressure sensor 140 per conduit 2, 3 and having two tappings, the one upstream of the grid 110 and the other downstream of the latter to ensure a differential measurement of the pressure on either side of the grid 110. .

Referring to Figure 7, a sensor 145 for measuring the static pressure in the tube 101, 102 introduced into the conduit 2, 3, is placed on the electronic card 104 and is connected to a zone of said tube 101, 102 located upstream of the grid 110, by means of a pipe 146 which fits around an end piece 147 of this tube 101, 102. Referring to FIGS. 3 and 7, one 101 of the two tubes is shaped to be able to convey the gas flow of air and oxygen towards the patient in the direction indicated by the arrow 107, the other tube 102 being profiled to convey the air rejected by the patient in the other direction, as indicated by the arrow 108.

Referring to Figures 4, 5 and 6 each tube 101, 102 comprises a cylindrical zone 109 in which is housed a grid 110 pressure drop. This grid 110 is fixed to an internal surface of the cylindrical zone 109 of the tube 101, 102. The grid 110 comprises three concentric cylindrical walls 111, 112, 113 arranged in the tube 101, 102 so that their axis of revolution is coinciding with the axis of revolution of the cylindrical zone 109 of said tube 101, 102 in which it is housed. These three concentric cylindrical walls 111, 112, 113 are connected to the internal surface of the cylindrical zone 109 of the tube 101, 102 by means of six radial arms 120, each extending along a diameter of the internal channel delimited by the cylindrical zone 109 of tube 101, 102. These six arms 120 are evenly spaced so that two successive arms 120 make between them an angle of 60°.

This grid 110 has a plane of symmetry extending parallel to a plane materializing a cross section of the internal channel in which it is housed, this plane of symmetry making it possible to distinguish an upstream part 114 and a downstream part 115. The qualifiers “upstream” and "downstream" are to be considered in relation to the direction of propagation of the gas flow in the tube 101, 102. These two parts 114, 115 are identical, and constitute the zones from which the pressure measurements will be made upstream and downstream of grid 110.

The three concentric cylindrical walls 111, 112, 113 of the same part 114, 115 of the grid 110 comprise a first small wall 111, a second median wall 112 surrounding said first wall 111, and a third large wall 113 surrounding said second wall 112. The first wall 111 and the second wall 112 essentially serve to create pressure drop, while the third wall 113 not only creates pressure drop but also separates the central gas flow from the measurement zone. The three concentric walls 111, 112, 113 advantageously have the same thickness, and are preferably separated by annular spaces 116 having a constant thickness, which may or may not be equal to the thickness of said walls 111, 112, 113.

Referring to Figure 6, the third wall 113 is surrounded by six plenum chambers 117 in the form of solid quarters, regularly spaced around the third wall 113. Each quarter 117 is thus placed between two consecutive arms 120 being at the contact of said arms 120, and bears against an outer surface of the third wall 113 concentric. Two consecutive plenum chambers 117 are separated by a free space 118 located between two consecutive arms 120, this free space 118 constituting a passage for the gas flowing in the tube 101, 102. Each plenum chamber 117 of the upstream part 114 is aligned with a plenum chamber 117 of the downstream part 115 along an axis which is parallel to the axis of revolution of the three concentric walls 111, 112, 113, said two plenum chambers 117 being in contact with one another . It should be noted that the three concentric cylindrical walls 111, 112, 113 of one of the two parts 114, 115 are perfectly aligned with the three concentric walls 111, 112, 113 of the other part 114, 115.

Each plenum chamber 117 can be traversed by a hole 119 extending parallel to the axis of revolution of the three concentric walls 111, 112, 113, said holes 119 notably placing the two plenum chambers 117 of the two upstream and downstream 114, 115 of the grid 110, which are aligned along an axis which is parallel to said axis of revolution. These holes 119 make it possible to stabilize the flow in the plenum chamber 117 of the downstream part 115. These holes 119 also allow gas circulation in the tube 101, 102.

The plenum chambers 117 emerge radially into an annular homogenization chamber 121, 122, also called Kent chamber, surrounding said plenum chambers 117. The passage between each plenum chamber 117 and the homogenization chamber 121, 122 is carried out by means of a radial channel joining each of said plenum chambers 117 to the homogenization chamber 121, 122. Following in particular the passage of the gas through the plenum chambers 117, there is virtually no gas flow in the homogenization chamber 121, 122 and reliable and representative pressure measurements of the gas pressure prevailing in the tube 101, 102 can then be made in said homogenization chambers 121, 122.

For each upstream 114 and downstream 115 part, the homogenization chamber 121, 122 opens onto the wall of the cylindrical zone 109 of the tube 101, 102 by creating an opening. Referring to Figures 2 and 3, two hollow cylindrical ends 123, 124 are fixed on an outer wall of the tube 101, 102 vis-à-vis the openings of the homogenization chambers 121, 122 to be in communication with said openings .

Referring to Figures 2 and 7, said at least one pressure sensor 105, 106, 140 of the differential pressure measurement module, and intended to measure the pressure upstream and downstream of the grid 110 of each conduit 2, 3 in the homogenization chambers 121, 122, is placed on the electronic board 104 and is connected to the homogenization chambers 121, 122 by means of pipes 125, 126 which fit around the end pieces 123, 124.

Referring to Figure 7, when this module comprises a single pressure sensor 140 to measure the pressure on either side of the grid 110 of each conduit 2, 3, this sensor is placed on the electronic card 104 on the side of the conduit 2, 3 in which he will perform the pressure measurements104. This sensor 140 is thus connected to the two homogenization chambers 121, 122 of the upstream part 114 and of the downstream part 115 of the grid 110, by means of two pipes 125, 126 which fit around the end pieces 123, 124 of the corresponding tube 101, 102.

Referring to Figure 2, when the module comprises two separate pressure sensors 105, 106 per conduit 2, 3, one intended to measure the pressure upstream of the grid 110 and the other intended to measure the pressure in downstream of the latter, said two sensors 105, 106 are placed on the electronic card 104, on the side of the conduit 2, 3 in which the pressure measurements are to be carried out. Thus, a sensor 105 is connected to the homogenization chamber 121, 122 of the upstream part 114 of the grid 110, and the other sensor 106 is connected to the homogenization chamber 121, 122 of the downstream part of said grid 110, said connections being ensured by the pipes 125, 126 coming to fit around the corresponding end pieces 123, 124.

The signals sent by the pressure sensors 105, 106 to the electronic card allow the latter to determine the gas flow circulating in the tube 101, 102 from a differential measurement of the pressure carried out in the homogenization chamber 121 , 122 of the downstream part 115 and of the upstream part 114 of the grid 110.

The flowmeter system 150 comprising the two tubes 101, 102 each equipped with their grid 110 and the two end pieces 123, 124, and the junction plate 103 constitute a single and same part manufactured by means of a 3D printer.

In a non-illustrated variant embodiment of the invention, and in order to reduce manufacturing costs, these elements can be produced in one or more parts by injection.

Claims (11)

Flow meter (100) for measuring a gas flow in a conduit (2, 3), and comprising a hollow tube (101, 102) provided with an internal grid (110) and intended to be inserted into the conduit (101, 102 ), a differential pressure measurement module comprising at least one pressure sensor (105, 106, 140) and intended to measure the pressure upstream and downstream of the grid (110), and an electronic card (104) making it possible to determining the flow rate of gas circulating in the duct (2, 3) from the difference in the pressure measurements taken upstream and downstream of the grid (110), characterized in that the grid (110) comprises at least two walls concentric cylinders (111, 112, 113) arranged in the tube (101, 102) so that their axis of revolution is parallel to a longitudinal axis of the tube (101, 102), and in that the grid (110) has a plane of symmetry parallel to a plane materializing the cross section of the tube (101, 102) and making it possible to distinguish a upstream part (114) from which the upstream pressure measurement is made and a downstream part (115) from which the downstream pressure measurement is made, each part (114, 115) comprising a homogenization chamber (121 , 122) annular arranged around the concentric cylindrical wall (113) of larger dimension and in which said at least one sensor (105, 106, 140) of the module will perform the pressure measurements. Flowmeter according to Claim 1, characterized in that the concentric cylindrical walls (111, 112, 113) are fixed to an internal surface of the tube (101, 102) by several radial arms (120) passing through the said walls (111, 112, 113 ). Flowmeter according to Claim 2, characterized in that the grid (110) comprises three concentric cylindrical walls (111, 112, 113) and six radial arms (120). Flowmeter according to any one of Claims 1 to 3, characterized in that the upstream (114) and downstream (115) parts of the grid (110) each comprise a plurality of plenum chambers (117) distributed around the cylindrical wall concentric (113) of larger dimension. Flowmeter according to claim 4, characterized in that each plenum chamber (117) is constituted by a solid quarter which is inserted between the concentric cylindrical wall (113) of larger dimension and the annular homogenization chamber (121, 122) . Flowmeter according to any one of Claims 4 or 5, characterized in that each stilling chamber (117) of one of the two upstream (114) and downstream (115) parts of the grid (110) is aligned with a chamber calming (117) of the other part (114, 115) along an axis which is parallel to the axis of revolution of the concentric cylindrical walls (111, 112, 113). Flowmeter according to Claim 6, characterized in that each plenum chamber (117) is traversed by a hole (119) extending parallel to the axis of revolution of the concentric cylindrical walls (111, 112, 113) and allowing communicating the two plenum chambers (117) of the two upstream (114) and downstream (115) parts, which are aligned along said axis of revolution. Flowmeter according to any one of Claims 4 to 7, characterized in that the plenum chambers (117) of each of the two upstream (114) and downstream (115) parts of the grid (110) are in communication with the plenum chamber. corresponding homogenization (121, 122) by means of radial passages. Artificial respirator (1) characterized in that it comprises at least one flow meter (100) according to any one of the preceding claims, arranged on at least one of the gas flow circuits (2, 3) chosen from the circuit supplying air (2) or an air/oxygen gas mixture to a patient, or the air return circuit (3) exhaled from the patient. Process for producing a flowmeter according to any one of Claims 1 to 8, characterized in that it comprises a step of manufacturing the tube (101) and the grid (110) by means of a 3D printer. Flowmeter system (150) for measuring a gas flow in two parallel ducts (2, 3) characterized in that it comprises two flowmeters (100) in accordance with any one of claims 1 to 8, said flowmeters (100) being arranged so that:
- the two tubes (101, 102) are parallel and interconnected by a plate (103) to which the electronic card (104) is secured,
- the pressure sensors (105, 106, 140) for measuring the pressure upstream and downstream of the grid (110) of each tube (101, 102) are in contact with said card (104),
-each sensor (105, 106, 140) is connected to the homogenization chamber (121, 122) of the corresponding part (114, 115) of the grid (110) by means of a flexible pipe (125, 126) connecting to a hollow nozzle (123, 124) emerging from said tube (101, 102) and in communication with said homogenization chamber (121, 122).