MXPA00012295A - Fluidic oscillator, part designed to be incorporated in a fluidic oscillator and method for making such a fluidic oscillator - Google Patents

Abstract

The invention concerns a fluidic oscillator (21) symmetrical relatively to a longitudinal plane of symmetry (P), comprising a chamber (25) delimiting an oscillation chamber (27) and having an inlet and an outlet (45) through which the fluid flows and which are arranged along said plane (P) in one first direction said to be longitudinal (A), said inlet being shaped in the form of a narrow slot (57;93) in a second direction (B) said to be transverse to said plane (P), elongated in a third direction (C) parallel to said plane (P) and perpendicular to said first longitudinal direction (A), characterised in that said slot (57;93) is provided in a part (55;91) removable with respect to said chamber (25).

Description

A FLUIDIC OSCILLATOR, AN INSERTO FOR THE INCORPORATION IN A FLUIDIC OSCILLATOR, AND A METHOD FOR THE MANUFACTURE OF SUCH FLUID OSCILLATOR Description of the invention The invention relates to a fluidic oscillator which is symmetrical about a longitudinal plane of symmetry P comprising a housing defining an oscillating chamber and having an inlet opening and an outlet opening, through which the fluid flows , whose openings are in alignment with said plane P in a "longitudinal" direction, the entrance opening being implemented in the form of a groove that is narrow in a direction transverse to the plane P, and elongated in a direction contained in the plane P , and perpendicular to the longitudinal direction. Fluidic oscillators are well known. EP 0 381 344 describes a fluidic oscillator that operates based on the Coanda effect. The jet that arrives from an inlet nozzle, followed by an inlet channel itself spontaneously couples to one of the side walls and flows along the first and second main channels. A portion of the fluid that arrives from the inlet channel is purged by a reaction channel. This has the effect of detaching the jet from the wall and causing it to attach to the opposite wall. The phenomenon is repeated, thus giving rise to continuous oscillation in the inflow. The flow in the first and second main channels and in the reaction channel varies at a frequency that depends on the inflow speed. Figure 1 shows an example of a fluidic oscillator as seen from above. Oscillator 1 is symmetrical about a longitudinal plane of symmetry P and comprises a housing 3 defining an oscillation chamber 5 and an obstacle 7 received therein. The housing 3 has an inlet opening 9 and an outlet opening 11 in alignment in the plane P with the fluid flowing therethrough in the direction indicated by the arrows in the figure. The entry opening 9 is in the form of a groove of transverse size or "width" i_ which is small in comparison with a longitudinal dimension thereof, termed as its "height" h and which lies in a plane perpendicular to the plane of Figure 1 (see Figure 2). Conventionally, the width J_ is equal to approximately one fifth of the height h. This slot serves to transform a fluid flow into a fluid jet that oscillates transversely in a plane perpendicular to the plane P, for example in a plane parallel to that of Figure 1. To obtain good metrological operation from an oscillator, it is It is necessary that the oscillation of the fluid jet is under control, and in particular for the dimensions of the groove 9, that is determined precisely during the manufacture of the fluidic oscillator. The piece shown in Figure 1 is made of aluminum, for example, and is manufactured by molding and demolding operations. However, it is not possible to make the part directly with the dimensions merely by the molding and demolding operations. In this way, a piece that has been newly demoulded is subsequently machined in order to obtain the desired precision for its dimensions, and in particular for the dimensions of the slot 9. The machining performed in particular on the groove 9 of the piece as it is unmold, it is as shown in the front view in Figure 3. In this figure, the side portions 13 and 15 of the slot 9, as shown in dashed lines, define the traditional taper profile obtained after unmolding. The machining operation then consists in removing the portions 13 and 15 in discontinuous lines by means of a tool 17 such as a cutter that is inserted into the slot from above (as shown in Figure 3) or through the opening which opens out into the oscillation chamber 5. Notwithstanding, since the slot is elongated in its direction of height h and of narrow width 1_, the cutter 17 must be thin (for example, having a diameter of 16 mm to give a width! _ equal to 19 mm), and as a result no it is mechanically strong enough. Due to the fineness of the cutter, it can be subjected to mechanical vibration while it is being used, and as a result the surface condition of the inner portion of the groove is not completely under control over its full height, and in particular in ex. bottom thereof, for example close to the portion referenced 19 in Figure 3. In addition, due to its fineness, the cutter runs the risk of being damaged while in use. To avoid such damage, it is recommended to decrease the speed of machining, but that increases the duration of the operation of machining and thus increases the economic cost of it. Such measures are difficult to accept in an industrial environment. Further, while machining, when the cutter leaves the groove via the upstream portion thereof (represented by reference 21 in Figure 1) traveling in the opposite direction to the arrows in the figure, the tolerances in this portion that arrive directly of the demould, are poorly controlled. This can be harmful since the conditioning of the fluid flow in this region must be completely controlled.

The present invention seeks to remedy at least one of the aforementioned problems. The present invention thus provides a fluidic oscillator which is symmetrical about a longitudinal plane of symmetry P, comprising a housing defining an oscillating chamber and having an inlet opening and an outlet opening through which it flows the fluid, and which are in alignment in the plane P in a first "longitudinal" direction A, said inlet opening being formed in the form of a slot that is narrow in a second direction B extending transversely to the plane P, and elongated in a third direction C parallel to the plane P, and perpendicular to the first longitudinal direction A, the oscillator being characterized in that the slot is provided in an insert that is removable from the housing. In this way, the removable insert and the housing of the fluidic oscillator can be manufactured separately: the removable insert and more particularly the slot are manufactured with precision while the housing can be manufactured more closely.

It is sufficient during the molding and demolding operations to provide a cavity of large dimensions within the housing at the site where the slot is to be placed, and then roughly machine the walls of the housing defining the cavity, with a tool dimensions greater than the tool used in the prior art. The time required for the machining of the housing is thus reduced and the risk of damage to the tool is avoided. More precisely, the removable insert has two elongated side walls in the third direction C and spaced in the second direction B to define between them the dimension of the groove in the second direction, and also referred to as its width! _. The removable insert may have two end pieces perpendicular to the third direction C and located at the two opposite ends of the side walls, to define between the end pieces the size of the groove in the third direction, also referred to as its height h. According to a feature of the invention, the removable insert is inserted in a cavity provided in the housing, and of a transverse size d slightly larger than that of the insert. Advantageously, the removable insert has a notch formed in a peripheral area of the insert, and contained in a transverse plane defined by the second and third directions, the peripheral notch is designed to receive a sealing member that cooperates in particular with the walls of the housing that define the cavity. In yet another embodiment of the invention, the side walls of the removable insert run within the respective walls of the housing via at least one of its portions, and these also extend beyond the portions in the first "longitudinal" direction to project into of the oscillation chamber. In this way, the walls projecting inside the oscillation chamber serve to protect the jet of fluid formed in the groove from external influences that could disturb the oscillation of said jet. Advantageously, two corresponding sites are formed respectively on each of the end pieces, upstream of the slot for purposes of receiving an element that is suitable for changing the velocity profile of the fluid flow upstream of the slot. The invention also provides an insert for incorporation into a fluidic oscillator as described above, said part comprising two lateral webs which are elongated in a direction C and which are spaced in a direction B perpendicular to the direction C, in a manner such as to define a slot between them in the direction B. The insert can have two end pieces perpendicular to the direction C and placed on the two opposite ends of the side walls, in such a way as to define between the end pieces the size of the groove in the direction C. Advantageously, a groove is formed in a peripheral area of the insert and is contained in a plane defined by the first and second directions and, said Notch is designed to receive a sealing member. The side walls extend in a direction A perpendicular to a plane defined by the directions B and C in such a way as to project into the oscillating chamber of the fluidic oscillator, when the insert is incorporated therein. The invention also provides a method of manufacturing a fluidic oscillator that is symmetrical about a longitudinal plane of symmetry P, the oscillator comprising a housing defining an oscillation chamber and having an entry opening and an exit opening through the which fluid flows, and which are in alignment in the plane P in a first "longitudinal" direction, the inlet opening being formed in the form of a slot that is narrow in a second direction extending transversely to the plane P, and elongated in a third direction parallel to the plane P, and perpendicular to the first longitudinal direction, the method being characterized in that it consists of processing the housing by forming therein a cavity of transverse size greater than the transverse size of the housing. slot, in the manufacture separately from an insert and forming said slot in it, and inserting the insert in said cavity. More precisely, the method of the invention consists in the production of the fluidic oscillator housing by molding and unmolding operations and then machining the unmoulded housing. The method of the invention also consists in the production of an insert by means of molding and demolding operations. Other features and advantages appear from the following description, given purely by way of example limiting np, and elaborated with reference to the attached drawings, in which; Figure 1 is a diagrammatic plan view of a fluidic oscillator of the prior art; Figure 2 is a fragmentary perspective view on a larger scale, showing the fluidic oscillator of Figure 1 only with its slot shown in the figure; Figure 3 is a fragmentary front view on a larger scale, of the groove shown in Figure 2; . Figure 4 is a perspective view of the internal part of the central block of the fluidic oscillator, of the insert 55 with the groove formed therein, and of the obstacle 29, the part and obstacle of the block being separated; . Figure 5 is a perspective view on a larger scale, on the insert 55 shown in Figure 4; . Figure 6 is a view of the insert 55 in section on a plane parallel to the plane defined by the directions A and B in Figure 4; Figure 7 shows the insert 55 in section in the plane of Figure 6 inside the mold for its manufacture; . Figure 8 is a perspective view of yet another embodiment of the insert 55 of Figure 5; . Figure 9 is a view of the insert 91 of Figure 8 in section in a plane parallel to the plane defined by the directions A and B of Figure 4; . Figure 10 shows the insert 91 of the Figure 8 in a perspective view from the rear on a larger scale; Y . Figure 11 is a perspective view of the element 117 for insertion into the insert 91 of Figures 8 through 10. As shown in Figure 4 and given the complete reference 21, a fluidic oscillator is implemented in the form of a block central 23 whose upper wall forming the cover, has been removed.

The central block of the fluidic oscillator is symmetrical around a longitudinal plane of symmetry P (Figure 4). The central block comprises a housing 25 which defines an oscillation chamber 27. An obstacle 29 is designed to be placed in the oscillation chamber in the position marked by the arrow. The central block also has two passages 31 and 33 inclined in such a way as to form a V and each provided at one of its ends with a respective hole 35, 37 formed through the wall of the lower wall 38 of the central block. . The flow of the fluid passes through the holes 35 and 37 and along the following passages 31 and 33 before entering into the oscillation chamber 27. The passages 31 and 33 open within a cavity 39 which is defined in particular by the side walls 41 and 43 of the housing 25. From an end 27a "downstream" of the oscillation chamber 27, the side walls 41 and 43 extend parallel to each other and to the plane P, and then move away from the plane P to give the chamber a bulging shape, after which they close towards the plane P, extending perpendicular to it until they reach an opposite end "upstream" 27b of the oscillation chamber. The two ends 27a and 27b are in alignment in a first "longitudinal" A direction contained in the plane P. At the end 27a of the oscillation chamber 27, the side walls 41 and 43 are parallel to the plane P and between them they define an outlet opening 45 through which the fluid flows outwardly from the oscillation chamber 27. At the end 27b of the oscillation chamber, the side walls 41 and 43 are spaced apart from one another in a second direction B which it extends transversely to the plane P and thus defines the width d of the cavity 39. After this, the side walls 41 and 43 extend parallel to the plane P in an upward direction in the form of two wall portions 47 and 49 to define a fraction of the longitudinal dimension of the cavity 39, and these are then moved away from the plane P in the directions that are inclined in relation to the directions A and B to run towards the respective walls 51 and 53 defining the passages 31 and 33, respectively. The side walls 41 and 43 have a "height" dimension h which is in alignment with a third direction C perpendicular to the first two directions A and B, example way h can be equal to 91.3 mm. During the manufacture of the central block 23 of the fluidic oscillator, by means of molding and demolding of aluminum, for example, the side walls 41 and 43 and their extensions 47, 49 and 51, 53 are obtained with a conventional mold release taper of the type shown in the lines discontinuous in Figure 3. The central block is then machined with a cutter to eliminate the taper of demoulding on its side walls and obtain the desired dimensions. Since the width of the cavity 39 is much greater than the width of the inlet opening 9 towards the fluidic oscillator as shown in Figure 1, it is possible to use a cutter that is more robust than in the prior art to perform this machining operation, for example, a cutter having a diameter of 25 mm. The risks of damaging the cutter are thus avoided, and the length of time required for the machining operation is considerably reduced compared to the prior art. In addition, the side walls can be machined on their full height without difficulty. It should also be noted that this machining operation can be performed in a clearly "approximate" manner since the dimensions obtained after the machining of the side walls adjacent to the cavity 39, are not final dimensions facing the fluid flow, as it is explained later. As a result, the time required for the machining can also be reduced if the approximate machining is sufficient. As shown in perspective in the Figure 4 and in Figure 5, an insert 55 is designed to be inserted in the cavity 39 between the portions 47 and 49 of the side walls 41 and 43, and the width d_ of the cavity is slightly greater than the width of said insert.

This insert is also shown in Figure 6 in section on a plane containing the directions A and B, in a position where it is inserted between the wall portions 47 and 49. The width of the insert 55 may be 60 mm, for example , while the dimension d is equal to 61 mm, for example. The insert 55 has two side walls which are elongated in the third direction C and which are spaced along the second direction B to define a narrow slot 57 therebetween. This slot constitutes the inlet opening which is in alignment with the outlet opening 45 along the first direction A, and makes it possible for the flow of the fluid to be transformed into a jet which penetrates into the oscillation chamber 27. As shown in Figure 6, each of the side walls of the insert 55 has a respective portion 59 or 61 in alignment with the corresponding side wall 41, 43 of the housing, and between them these portions define the width 1_ as the slot 57, which is equal to 19 mm, for example.

The side walls of the insert 55 also include mutually parallel respective portions 63 and 65, which are also parallel to the plane P and which define the longitudinal dimension or length of the slot 57, and also two portions 67 and 69 that extend from the plane P in an inclined manner in relation to the directions A and B to run to the walls 51 and 53 of the passages 31 and 33. The insert 55 has two end pieces 71 and 73 implemented in the form of flat plates extending perpendicularly to the third dimension C, and located on the two opposite ends of the side walls of said insert, to define the height of the slot 57 between the end pieces, whose height corresponds to the dimension h. As shown in Figure 5, each end piece is of small thickness or height, and the lower wall 38 of the central block 23 has a shallow obstacle to registration with the cavity 39 (Figure 4) of a height corresponding to the thickness of the end piece 71. In a similar manner, a height obstacle corresponding to the thickness of the end piece 73 is provided in the cover (not shown) of the central block 23.

In addition, the insert 55 has a notch 75 formed in a peripheral zone of the insert and contained in a plane extending transversely to the plane P (Figure 4). This notch is designed to receive a sealing gasket 77 (shown in Figure 6) which is mounted in the notch before the insert 55 is inserted into the cavity 39. Figure 6 shows that the gasket 77 cooperates with the portions 47 and 49 of the side wall of the housing 25, to ensure that the fluid flow takes place by means of the slot 57 and does not infiltrate into the oscillation chamber between the portions 47, 49 and the insert 55. The package 77 also cooperates with the lower wall 38 of the central block and, in a manner not shown in the figures, with the cover of the central block. The insert 55 is made of plastic material, for example, by molding and demolding, using an injection mold of the type shown in Figure 7, where the insert can be observed in section on a plane parallel to that of Figure 6.

The mold comprises two mold cavity plates 79 and 81, one of which, the plate 81 defines the internal shape of the slot 57 and has two channels 83 and 85 which both serve to feed the liquid material into the empty internal areas of the mold in which the insert 55 is formed upon solidification. The mold also has two mold slides 87 and 89 which define the outer shape of the insert 55, including the peripheral notch 75. When the molding is determined, the slides 87 and 89 and the plates 79 and 81 of the mold cavity are moved to separate them in the directions shown by the arrows, and the insert 55 as it is unmoulded in this manner constitutes the final insert. It is particularly important to control the manufacturing tolerances for the insert 55 and also its surface condition, since the metrological properties of the fluidic oscillator depend on the quality of the fluid jet that is formed when passing through the insert (constant section, jet centered with relationship to the obstacle, ...), and this quality of the jet directly depends on manufacturing tolerances and the internal surface condition of portions 63, 65, 67, 69, 71, and 73. By way of example, the process of injection molding makes it possible to obtain precision of the order of one-tenth of a millimeter on the dimensions of the insert 55 while precision of only about five tenths of a millimeter is required in the manufacture of the central block from aluminum. Yet another advantage, associated with having an insert 55 that is separate from the housing, lies in the fact that the method of manufacture of the insert ~ 55 is repeatable and as a result the insert can be obtained with qualities that are repeatable over time, with which has a positive influence on the metrological qualities of the fluidic oscillator. The fact that the insert 55 is removable from the housing 25 and from the central block 23, makes it possible not only to simplify the maintenance, but also to exchange the insert 55 with a different insert having a groove of different width 1_, thus adapting it to a different range of flow velocities.

For example, the insert 55 having the dimensions defined above gives rise to a superior or head loss of 13 millibars (mbars) for a flow rate of 250 cubic meters per hour (m3 / h), and for the same higher loss , it is possible to increase the flow rate up to 300 m3 / h by increasing the width 1_ accordingly (by approximately 10%). The invention also has another advantage: since the manufacturing operations of the insert 55 and the housing 25 (for example the central block 27) are separated, accidental damage to the insert 55 during manufacture does not impair the manufacture of the complete fluidic oscillator. Figures 8 through 11 show yet another embodiment of the invention in which two additional independent features have been added. In this embodiment, the elements that remain unchanged in relation to Figures 4 to 7 retain the same references. As can be seen in Figures 8 to li, the removable insert 91 to be included in the housing 39 of the central block 23 of the fluidic oscillator shown in Figure 4, has two side walls that are elongated in the third direction C and that are spaced apart in the second direction B to define a narrow slot 93 between them. The side walls of the insert 91 are constituted of a plurality of portions: the portions 59, 61, 67, and 69 are identical to the portions of the insert 55 that have the same references, and two mutually parallel portions 95 and 97 which define the groove 93 itself and which projects from the transverse plane in which the portions 59 and 61 and the side walls 41 and 43 of the housing 25 are contained. These two side wall portions 95 and 97 which extend into the chamber of oscillation 27 of the central block 23, form a protective mesh for the fluid jet against the occurrence of turbulence by high pressure located in the zones defined by the portions 59, 95 on one side, and 61, 97 on the other side, and which contribute to divert the jet excessively. A fluidic oscillator provided with two side wall portions extending in the oscillation chamber is described in French patent application No. 97/13145 filed on October 17, 1997 by the Applicant. In a manner analogous to that described for the insert 55, the insert 91 also has two identical end pieces 99 and 101 positioned at the two ends thereof. Each end piece 99, 101 is equipped with a respective location 103, 105 positioned upwardly of the slot 93, and in the form of a portion delayed relative to the rest of the corresponding end piece. The two sites that are placed vertically one above the other have respective rectangular shapes, with the exception of the portions near the walls 67 and 69 that follow the profile of said walls, and which are extended in the direction A in the form of a notch 107 formed in the corresponding end piece. Each site has a central portion 109, 111 which is separated from the rest of the site by two empty spaces 106, 108 and 110, 112 which are aligned in the direction A and which serve to define respective tabs. The tabs 109 and 111 have respective holes 113 and 115 in vertical alignment with each other. An element 117 shown in perspective in Figure 11 is in the form of a flat plate 119 having a plurality of substantially rectangular portions 121a-121f partially cut from the rest of the plate in the middle portion thereof. The plate 119 has two flat portions 123, 125 at its ends that embrace the central portion, and the rectangular portions 121a to 121f extend at particular angles relative to the plane in which the flat portions 123, 125 extend. The plate 119 it is extended by a support 127 in the form of a straight prism of triangular section having two end faces opposite the end plates 129, 130 and provided with reespective studs 131. The end plates 129, 130 are complementary in profile to the sites 103 , 105. The element 117 is designed to be inserted in the insert 91 at the sites 103, 105, which are guided by the plates 129, 130 and the studs 131 cooperating with the holes 113, 115 to secure the element 117.

In order to make it possible for the element 117 to be mounted on the insert 91, it is important to ensure that the tabs 109, 111 possess a degree of elasticity. Once the element 117 has been installed in the insert 91 it serves to modify the velocity profile of the fluid flow upstream of the groove 93, by means of the portions 121a-121f which have an effect mainly on the central portion of the speed profile. Such an element may be necessary when the flow coming from above is not completely controlled. This element could also be very well adjusted to the insert 55.

Claims (14)

1. A fluidic oscillator that is symmetrical about a longitudinal plane of symmetry, comprising a housing defining an oscillating chamber and having an inlet opening and an outlet opening through which the fluid flows, and which are in alignment in the plane of symmetry in a first "longitudinal" direction, the entrance opening is made in the form of a groove that is narrow in a second direction that extends transversely to the plane of symmetry, and elongated in a third direction parallel to the plane of symmetry and perpendicular to the first longitudinal direction, the oscillator is characterized in that the slot is provided in an insert that is removable from the housing.

2. A fluidic oscillator according to claim 1, wherein the removable insert has two elongated side walls in the third direction and spaced in the second direction to define between them the dimension of the groove in the second direction, and also referred to as its width.

3. A fluidic oscillator according to claim 2, wherein the removable insert has two end pieces perpendicular to the third direction and located at the two opposite ends of the side walls, to define between said end pieces the size of the slot in the third direction, also referred to as its height.

. 4. A fluidic oscillator according to any of claims 1 to 3, wherein the removable insert is inserted in a cavity provided in the housing, and of a transverse size slightly larger than that of the insert.

5. A fluidic oscillator according to claim 4, in which the removable insert has a notch formed in a peripheral zone of the insert and contained in a transverse plane defined by the second and third directions, the peripheral notch is designed to receive a member of seal that cooperates in particular with the walls of the housing defining the cavity.

6. A fluidic oscillator according to claims 2 and 4, in which the side walls of the removable insert run in respective walls of the housing via at least one of its portions and these also extend beyond the portions in the first longitudinal direction. "to project inside the oscillation chamber.

7. A fluidic oscillator according to claim 3, wherein two corresponding sites are respectively formed on each end piece upstream of the slot for the purpose of receiving an element that is suitable for modifying the flow velocity profile of the running fluid above said slot.

8. A removable insert serving to transform a fluid flow in a fluid oscillation jet to be incorporated in a fluidic oscillator, according to any of claims 1 to 7, the insert comprises two side walls that are elongated in a third direction and which are separated in a second direction perpendicular to the third direction, in such a way as to define a slot between them in the second direction.

9. A removable insert according to claim 8, which serves to transform a fluid flow into an oscillating fluid jet, the insert has two end pieces perpendicular to the third direction and placed on the two opposite ends of the side walls in a manner such as to define between the end pieces the size of the groove in the third direction.

10. A removable insert according to claim 8, which serves to transform a fluid flow into an oscillating fluid jet, in whose insert a notch is formed in a peripheral zone of the insert, and is contained in a plane defined by the first and third directions, the notch being designed to receive a sealing member.

11. A removable insert according to any of claims 8 to 10, which serves to transform a fluid flow into an oscillating fluid jet, in whose insert the side walls extend in a first direction perpendicular to a plane defined by the second and third directions, in a manner such as to project into the oscillating chamber of the fluidic oscillator when the insert is incorporated therein.

12. A method for manufacturing a fluidic oscillator that is symmetrical about a longitudinal plane of symmetry, the oscillator comprises a housing defining an oscillating chamber and having an inlet opening and an outlet opening through which the fluid, and which are in alignment in the plane of symmetry in a first "longitudinal" direction, the inlet opening being formed in the form of a groove which is narrow in a second direction extending transversely to the plane of symmetry, and elongated in a third direction parallel to the plane of symmetry, and perpendicular to the first longitudinal direction, the method is characterized in that it consists in manufacturing the housing by forming therein a cavity of transverse size greater than the transversal size of the slot, in the manufacture separately from a removable insert and forming said slot in it, and inserting the insert removable in the cavity.

13. A method according to claim 12, which consists in preparing the housing of the fluidic oscillator by means of molding and unmolding operations and then machining the unmoulded housing.

14. A method according to claim 12 or 13, which consists in making the insert by molding and demolding operations.