Fluid handling – Processes – Cleaning – repairing – or assembling
Reexamination Certificate
2001-02-26
2002-06-25
Chambers, A. Michael (Department: 3753)
Fluid handling
Processes
Cleaning, repairing, or assembling
C137S269000, C137S826000, C137S833000, C137S315010
Reexamination Certificate
active
06408866
ABSTRACT:
The invention relates to a fluidic oscillator that is symmetrical about a longitudinal plane of symmetry P comprising an enclosure defining an oscillation chamber and having an inlet opening and an outlet opening through which the fluid flows, which openings are in alignment in said plane P in a “longitudinal” direction, said inlet opening being implemented in the form of a slot that is narrow in a direction transverse to said plane P, and elongate in a direction contained in said plane P and perpendicular to said longitudinal direction.
Fluidic oscillators are well known. Document EP 0 381 344 describes a fluidic oscillator operating on the basis of the Coanda effect. The jet coming from an inlet nozzle followed by an inlet channel attaches itself spontaneously to one of the side walls and flows along first and second main channels. A portion of the flow coming from the inlet channel is bled off by a reaction channel. This has the effect of detaching the jet from said wall and of causing it to attach to the opposite wall. The phenomenon repeats, thus giving rise to continuous oscillation in the incoming flow. The flow in the first and second main channels and in the reaction channel varies at a frequency that depends on the incoming flow rate.
FIG. 1
shows an example of a fluidic oscillator as seen from above.
The oscillator
1
is symmetrical about a longitudinal plane of symmetry P and comprises an enclosure
3
defining an oscillation chamber
5
and an obstacle
7
received therein.
The enclosure
3
has an inlet opening
9
and an outlet opening
11
in alignment in the plane P with the fluid flowing through them in the direction indicated by arrows in the figure.
The inlet opening
9
is in the form of a slot of transverse size or “width” l that is small compared with a longitudinal dimension thereof referred to as its “height” h and which lies in a plane perpendicular to the plane of
FIG. 1
(see FIG.
2
).
Conventionally, the width l is equal to about one-fifth of the height h.
This slot serves to transform a fluid flow into a jet of fluid that oscillates transversely in a plane perpendicular to the plane P, i.e. in a plane parallel to that of FIG.
1
.
To obtain good metrological performance from an oscillator, it is necessary for the oscillation of the fluid jet to be under control, and in particular for the dimensions of the slot
9
to be accurately determined during manufacture of said fluidic oscillator.
The piece shown in
FIG. 1
is made of aluminum, for example, and it is manufactured by operations of molding and of unmolding.
Nevertheless, it is not possible to make the piece directly with the desired dimensions merely by the operations of molding and unmolding.
Thus, a piece which has just been unmolded 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 slot
9
of the piece as unmolded is as shown in front view in FIG.
3
.
In this figure, side portions
13
and
15
of the slot
9
as shown in dashed lines flowing through them in the direction indicated by arrows in the figure.
The inlet opening
9
is in the form of a slot of transverse size or “width” l that is small compared with a longitudinal dimension thereof referred to as its “height” h and which lies in a plane perpendicular to the plane of
FIG. 1
(see FIG.
2
).
Conventionally, the width l is equal to about one-fifth of the height h.
This slot serves to transform a fluid flow into a jet of fluid that oscillates transversely in a plane perpendicular to the plane P, i.e. in a plane parallel to that of FIG.
1
.
To obtain good metrological performance from an oscillator, it is necessary for the oscillation of the fluid jet to be under control, and in particular for the dimensions of the slot
9
to be accurately determined during manufacture of said fluidic oscillator.
The piece shown in
FIG. 1
is made of aluminum, for example, and it is manufactured by operations of molding and of unmolding.
Nevertheless, it is not possible to make the piece directly with the desired dimensions merely by the operations of molding and unmolding.
Thus, a piece which has just been unmolded 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 slot
9
of the piece as unmolded is as shown in front view in FIG.
3
.
In this figure, side portions
13
and
15
of the slot
9
as shown in dashed lines define the traditional tapering profile obtained after unmolding.
The machining operation then consists in eliminating the dashed-line portions
13
and
15
by means of a tool
17
such as a cutter which is inserted in the slot from above (as shown in
FIG. 3
) or through the opening that opens out into the oscillation chamber
5
.
Nevertheless, since the slot is elongate in its height direction h and of narrow width l, the cutter
17
must be fine (e.g. having a diameter of 16 mm so as to give a width l equal to 19 mm), and as a result it is not strong enough mechanically.
Because of the fineness of the cutter, it can be subjected to mechanical vibration while it is being used, and as a result the surface state of the inside portion of the slot is not fully under control over its entire height, and in particular at the bottom thereof, i.e. close to the portion referenced
19
in FIG.
3
.
In addition, because of its fineness, the cutter runs the risk of being damaged while it is in use. To avoid such damage, it is recommended to slow down the rate of machining, but that increases the duration of the machining operation and thus increases the economic cost thereof.
Such measures are difficult to accept in an industrial environment.
Furthermore, while machining, when the cutter leaves the slot via the upstream portion thereof (represented by reference
21
in
FIG. 1
) traveling in the direction opposite to the arrows in said figure, the tolerances on this portion coming directly from unmolding are poorly controlled.
This can be harmful since the conditioning of the fluid flow in this region must be fully controlled.
OBJECTS AND SUMMARY OF THE INVENTION
The present invention seeks to remedy at least one of the above-mentioned problems.
The present invention thus provides a fluidic oscillator that is symmetrical about a longitudinal plane of symmetry P, comprising an enclosure defining an oscillation chamber and having an inlet opening and an outlet opening through which the fluid flows and which are in alignment in said plane P in a “longitudinal” first direction A, said inlet opening being made in the form of a slot that is narrow in a second direction B extending transversely to said plane P and elongate in a third direction C parallel to said plane P and perpendicular to said longitudinal first direction A, wherein said slot is provided in an insert which is removable from said enclosure.
Thus, the removable insert and the enclosure of the fluidic oscillator can be manufactured separately: the removable insert and most particularly the slot are manufactured with precision while the enclosure can be manufactured more approximately.
It suffices during the molding and unmolding operations to provide a cavity of large dimensions inside the enclosure at the site where the slot is to be placed and then to machine in approximate manner the walls of the enclosure defining said cavity with a tool of larger dimensions than the tool used in the prior art.
The time required for machining the enclosure is thus reduced and the risk of damaging the tool is avoided.
More precisely, the removable insert has two side walls elongate in the third direction C and spaced apart in the second direction B so as to define between them the dimension of said slot in said second direction, and also referred to as its width l.
The removable insert may have two endpieces perpendicular to the third direction C and located at the two opposite ends of said side walls so as to define bet
Carver Andrew
Hernoux Luc
Chambers A. Michael
Schlumberger Industries S.A.
Straub Michael P.
Straub & Pokotylo
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