Spray adapter designed to be fitted to a nozzle holder

Abstract

The invention relates to a spray adapter (28) intended for equipping a spray nozzle holder (10), characterized in that it comprises a spray nozzle (54), a body (38) having a pressurized liquid supply port (42) adapted to be connected to a mounting head (18c) of a nozzle holder (10), in place of a nozzle, an internal chamber (64) connected to said supply port (42) by an inlet circuit (66) for being supplied with pressurized liquid, and connected to the nozzle (54) by an outlet conduit (68) for supplying the nozzle (54) with pressurized liquid, and a control unit (62) mounted on the body (38) and adapted to vary the flow rate of the nozzle (54) by intermittently closing an outlet orifice (100) of the chamber (64) during an opening cycle. Closure. Abbreviated figure: Figure 1

Description

Title of the invention: Spray adapter designed to be fitted to a nozzle holder Scope of the invention

[0001] The present invention relates to the field of spraying.

[0002] The present invention will find advantageous applications in the agricultural and / or viticultural field, in particular by equipping an agricultural vehicle of the spreading vehicle type comprising a sprayer boom equipped with a plurality of spray nozzle holders. State of the art

[0003] In the agricultural and viticultural fields, sprayers are known, which are classically intended to spray products onto crops in liquid form.

[0004] We also speak of inputs.

[0005] Such sprayers are used for example to apply foliar fertilizers to crops or to treat crops against certain diseases and / or to control certain insects that are likely to damage the harvest.

[0006] For this purpose, sprayers are generally fitted to a motorized spreading vehicle such as a tractor, self-propelled vehicle or even an aircraft.

[0007] A sprayer generally comprises a boom which carries a plurality of nozzle holders, a storage tank containing the liquid to be sprayed, a circuit which is equipped with a pump and which supplies the nozzle holders with pressurized liquid.

[0008] Typically, each nozzle holder is equipped with one or more nozzles, a body which delimits a supply circuit connected to each nozzle, to supply each nozzle with liquid to be sprayed.

[0009] The different spraying devices are controlled independently by an electronic control device which includes a central computer.

[0010] The ramp which carries the nozzle holders can be several tens of meters wide and the nozzle holders can be fixed on the ramp for example about every fifty centimeters, or even every twenty-five centimeters.

[0011] The dimensions and spacings above are provided here purely as an indication and are in no way limiting or restrictive.

[0012] Thus, still according to this example, a spreading vehicle which is equipped with a forty-eight meter wide boom with a nozzle holder fixed every fifty centimeters will include a central computer capable of controlling in real time and independently ninety-six nozzle holders fixed on the boom.

[0013] Such control of the nozzle holders makes it possible to achieve localized spraying for spraying the field in a piecemeal fashion, that is to say on short sections of the field plot; it is therefore understood that the piloting of these localized nozzle holders may require simultaneous actuation of all the nozzle holders, as well as actuation of a single nozzle holder.

[0014] This is also referred to as nozzle-to-nozzle control.

[0015] From a theoretical point of view, this nozzle-to-nozzle control has many advantages: it makes it possible to reduce spraying costs and associated pollution by optimizing the use of the sprayed liquid.

[0016] Localized spraying also improves spraying accuracy by correctly spraying sections of the field according to actual needs.

[0017] On the other hand, the Applicant observed that, in practice, spraying nozzle by nozzle remains difficult to implement.

[0018] With current sprayers, it is indeed very difficult to ensure this localized spraying in a fully satisfactory manner because the configuration of the liquid circuit of the sprayer does not allow for a stable and controlled spray flow rate at the nozzle outlet.

[0019] Transition times are indeed observed when piloting a single nozzle holder.

[0020] These transition times are caused by an opening of the circuit, and / or a closing, which supplies the nozzle with liquid, resulting in a significant drop in pressure that does not allow for optimized spraying.

[0021] In "localized spraying" mode, the Applicant found that it was important to maintain a sufficient flow rate at the nozzle outlet without transition time so that the spraying would be optimal.

[0022] However, as explained above, a pressure loss is systematically observed in current circuits, which implies a transition time to reach the desired flow rate at the nozzle outlet.

[0023] Pulsed nozzle holders, also called pulsed nozzles, are also known as PWM nozzles, for the English acronym "pulse width modulation", or "pulse width modulation" in French.

[0024] The pulsed nozzle holders are electrically controlled by a control unit using pulse width modulation, or PWM, technology, capable of varying the flow rate of each nozzle by modulating the opening time during an opening / closing cycle of the liquid supply circuit of said nozzle.

[0025] Generally, pulsed nozzle holders have an opening / closing frequency of 10 to 100 Hertz.

[0026] In other words, it is understood here that each pulsed nozzle holder is capable of opening and closing 10 to 100 times per second.

[0027] The modulation of the nozzle flow rate is therefore achieved here by varying the duration of the opening of the nozzle supply circuit within an opening / closing cycle.

[0028] Theoretically, the use of pulsed nozzle holders is very advantageous because it allows for localized spraying.

[0029] On the other hand, in practical terms, the Applicant observes with today's pulsed nozzle holders that the size of the droplets exiting the nozzles is irregular and that the jet formed by the nozzle exiting the nozzle is not regular so that the surface to be treated by spraying is not properly treated with this type of pulsed nozzle holder, the properly treated surface may only represent a range of between forty and one hundred percent of the total surface.

[0030] The Applicant submits that, for these reasons, sprayers which are known to date and which use pulsed nozzle holders to spray a surface to be treated in a localized and independent manner can be improved. Description of the invention

[0031] The present invention aims to improve the situation described above.

[0032] The present invention aims in particular to resolve the drawbacks of the aforementioned prior art by proposing a nozzle holder adapter whose design makes it possible to limit the pressure drop of the liquid passing through the nozzle during the opening and closing cycle of the nozzle.

[0033] According to a first aspect of the invention, this objective, as well as others which will appear from reading the description that follows, is achieved with a spray adapter intended to equip a spray nozzle holder.

[0034] According to the present invention, such an adapter comprises: • a spray nozzle, • a body comprising a pressurized liquid supply inlet which is suitable for connection to a nozzle holder mounting head, in place of a nozzle, • an internal chamber which is connected to said supply outlet by an inlet circuit to be supplied with pressurized liquid, and which is connected to the nozzle by an outlet conduit to supply the nozzle with pressurized liquid, said outlet conduit being connected to the chamber by an outlet orifice, and • a control unit which is mounted on the body and which is adapted to vary the flow rate of the nozzle by intermittently closing said chamber outlet orifice during an opening-closing cycle.

[0035] The design of the adapter according to the invention makes it possible to approach the unit of piloting as close as possible to the nozzle in order to limit the length and volume of the outlet duct which connects the internal chamber and the nozzle.

[0036] According to other optional features of the invention, taken alone or in combination:

[0037] - the body has a three-branched shape, of which: a first branch which includes the feeding inlet, a second branch which carries the spray nozzle, and which extends along a spray axis, and a third branch which carries the piloting unit and which extends along an axis inclined relative to said spraying axis;

[0038] - the second arm which carries the spray nozzle is aligned with the first branch formed by the feed opening, following the spraying axis. This feature allows the adapter to spray along the same axis as a "classic" nozzle mounted on a nozzle holder fixing head;

[0039] - the third branch which carries the piloting unit and the second branch which carries the nozzle, form an obtuse angle. Such an arrangement allows the outlet duct to adopt a generally curved shape in the form of a circular arc whose radius of curvature is greater than a right-angled bent shape, which promotes the reduction of the volume of the outlet duct;

[0040] - the outlet conduit which connects the outlet orifice of the chamber to the nozzle present a curved shape, so as to limit the volume of said outlet duct. By curved shape we mean a straight shape, again to limit the volume of the outlet duct;

[0041] - the outlet conduit which connects the outlet orifice of the chamber to the nozzle present an angled shape (formed by two straight half-ducts connected together);

[0042] - the body is made in one piece (we speak of a monobloc body);

[0043] - the control unit varies the nozzle flow rate by closing the outlet orifice of the chamber intermittently during an opening-closing cycle, by implementing a technique known as pulse width modulation;

[0044] - the adapter's power supply port is designed to be mounted on a head of attachment of a nozzle holder, to allow the attachment of said adapter in place of a nozzle.

[0045] The invention also relates to a nozzle holder comprising an adapter of the type described above.

[0046] The present invention, through the various structural and functional technical features described above, makes it possible to solve the various technical problems of the prior art. In particular, it makes it possible to maximize the performance of PWM-type spray nozzles, which conventionally operate on a range of 40 to 100% of the duty-cycle while with the present invention it becomes possible to work on a range of 5 to 100% of the duty-cycle, which makes it possible to quickly achieve a perfect jet with a precise flow rate, even at low pressure (less than 50L / ha). Description of the drawings

[0047] Other features, purposes and advantages of the invention will become apparent from the following detailed description, for the understanding of which reference should be made to the accompanying drawings in which:

[0048] [Fig-1] is an overview in perspective which illustrates a nozzle holder equipped with two nozzles and an adapter according to the invention;

[0049] [Fig.2] is an exploded perspective view of the adapter of [Fig.1];

[0050] [Fig.3] is a detailed perspective view of the adapter body of [Fig.1];

[0051] [Fig.4] is a side view of the adapter of [Fig.1] which illustrates two axes of cuts;

[0052] [Fig.5] is a cross-sectional view along the median 5-5 axis of [Fig.4];

[0053] [Fig.6] is a cross-sectional view along axis 6-6 of [Fig.4];

[0054] [Fig.7] is a cross-sectional detail view of the adapter of [Fig.5], with the solenoid valve piston in the open position;

[0055] [Fig.8] is a cross-sectional detail view of the adapter of [Fig.5], with the solenoid valve piston in the closed position.

[0056] In the description and claims, the longitudinal, vertical and transverse terminology will be adopted without limitation with reference to the L, V, T trihedron indicated in the figures.

[0057] Also, the expressions "superior" and "inferior" will be used without limitation in reference to the upper and lower parts respectively of [Fig.1].

[0058] Also, the expressions "upstream" and "downstream" will be used without limitation in reference to the direction of flow of the liquid from upstream to downstream through the adapter.

[0059] Throughout all these figures, identical or similar elements are identified by identical or similar reference signs. Detailed description

[0060] Figure [1] shows a spray nozzle holder 10 which includes a body 12 on which a pivoting head 14 is mounted.

[0061] The pivoting head 14 comprises a central tubular portion 16 which extends along a longitudinal axis A, and three nozzle fixing heads 18a, 18b, 18c which each extend radially from the tubular portion 16, in a regularly angular manner.

[0062] Each fastening head 18a, 18b, 18c forms a male section 20a, 20b, 20c each equipped with two lugs, only the two lugs 22c of the third fastening head 18c are visible in [Fig.2].

[0063] The lugs are designed to ensure quick attachment of an added element, by a quarter turn bayonet type fixing.

[0064] Two of the three fixing heads 18a, 18b are equipped with a spray nozzle 24a, 24b respectively, each nozzle 24a, 24b being fixed to the associated fixing head 18a, 18b by a quarter-turn type nut 26a, 26b which cooperates with the lugs provided for this purpose.

[0065] The third fixing head 18c is equipped with a spray adapter 28 according to the invention, which is described below.

[0066] Also, the pivoting head 14 is pivotally mounted on the body 12 of the nozzle holder 10, around the axis A, between three angular positions in each of which one of the fixing heads 18a, 18b, 18c is activated, i.e. supplied with pressurized liquid.

[0067] This feature allows selection and activation of one of the fixing heads 18a, 18b, 18c, depending on the type of spraying desired.

[0068] According to the example described here, the fixing head which occupies an activated position is the third fixing head 18c which is oriented vertically downwards and which carries the adapter 28.

[0069] The nozzle holder 10 is intended to be mounted on a sprayer boom (not re shown) which is intended to be mounted on an agricultural machine (not shown), such as a tractor.

[0070] For this purpose, the spraying device 10 includes an annular flange 30 which includes a first fixed jaw 32 and a second movable jaw 34.

[0071] The second jaw 34 is articulated between an open position which allows the insertion of a transverse supply tube 36 into the flange 30 and a closed position, illustrated in [Fig.1], which ensures the supply of pressurized liquid to the nozzle holder 10.

[0072] For this purpose, the fixed jaw 32 delimits an orifice (not visible) which communicates with an internal circuit of the nozzle holder 10, which supplies the fixing head 18a, 18b, 18c occupying the activated position.

[0073] The adapter 28 according to the invention, shown in views 2 to 6, comprises a body 38 which generally has a three-pronged shape, and which is made in one piece.

[0074] A first branch 40 of the body 38 of the adapter 28 delimits a pressurized liquid supply mouth 42, which extends around a vertical spray axis B, perpendicular to the pivot axis A of the pivoting head 14 of the nozzle holder 10.

[0075] The supply port 42 is connected to the third mounting head 18c of the nozzle holder 10, to secure the adapter 28 to the nozzle holder 10 and to supply the adapter 28 in pressurized liquid.

[0076] For this purpose, the feed mouth 42 has a female shape complementary to the shape of each fixing head 18a, 18b, 18c of the nozzle holder 10.

[0077] Indeed, as can be seen in figures 2 and 3, the feed mouth 42 includes an internal cylindrical wall 44 which delimits two L-shaped grooves 46 each opening onto an upper edge 48 of the feed mouth 42, grooves 46 into which the two complementary lugs 22c of the third fixing head 18c are pushed in and locked at the end of the stroke.

[0078] A second branch 50 of the body 38 of the adapter 28 extends vertically along the spray axis B, coaxially with the first branch 40,

[0079] With reference to [Fig.2] and 5, the second branch 50 forms a fixing head which is provided with two lugs 52 and which is equipped with a spray nozzle 54.

[0080] The spray nozzle 54 is fixed by a quarter-turn type nut 56 which cooperates with the lugs 52 provided for this purpose, to ensure quick fixing of the nozzle 54 on the adapter 28.

[0081] It will be noted that an annular sealing gasket 58 is interposed axially between the free end of the second branch 50 and the nozzle 54.

[0082] Also, the adapter 28 forms a third branch 60 which carries a pilot unit 62 and which extends along an axis C inclined with respect to the spraying axis B.

[0083] With reference to figures 3, 5, 6 and 7, the adapter 28 includes an internal pressure regulating chamber 64 which is connected to the supply mouth 42 by an inlet circuit 66 to be supplied with pressurized liquid.

[0084] Also, chamber 64 is connected to nozzle 54 by an outlet conduit 68 to supply nozzle 54 with pressurized liquid.

[0085] The chamber 64 is formed by a breech 70 which has a generally stepped cylindrical shape, and which extends around the axis C.

[0086] The cylinder head 70 comprises a first downstream cylindrical section 72 which is received in a complementary housing 74 provided in the body 38 of the adapter 28, and a second upstream cylindrical section 76 which forms a shoulder 78.

[0087] The seal between the first section 72 of the cylinder head 70 and the housing 74 is achieved by a first O-ring 79a and a second O-ring 79b.

[0088] The shoulder 78 formed by the breech 70 is arranged opposite a radial face 80 of the free end of the third branch 60 of the body 38.

[0089] Also, according to [Fig.7], the second section 76 of the cylinder head 70 forms a bowl 82 which extends around the axis C and which opens axially opposite the pilot unit 62.

[0090] It should be noted that chamber 64 is delimited by basin 82.

[0091] According to Figures 3 and 5, the input circuit 66 which supplies chamber 64 comprises two inlet conduits 84 which are each formed by the body 38 of the adapter 28.

[0092] Each inlet conduit 84 extends from the supply mouth 42 to two holes 86 which are provided on the radial face 80 of the free end of the third branch 60 of the body 38, and which are arranged on either side of the housing 74.

[0093] Furthermore, with reference to Figures 6 and 7, the input circuit 66 comprises a plurality of passages 87 which cross the second section 76 of the cylinder head 70 and which are arranged around the axis C.

[0094] Each passage 87 extends from an inlet orifice 88 which opens into the chamber 64, to the shoulder 78 of the cylinder head 70, so as to supply the chamber 64 with pressurized liquid.

[0095] It will be noted that the shoulder 78 formed by the cylinder head 70 is axially spaced from the radial face 80 of the free end of the third branch 60 of the body 38, forming an annular cavity 90 in which the pressurized liquid circulates.

[0096] The cavity 90 is sealed by an O-ring 92 which is interposed axially between the shoulder 78 and the opposite radial face 80.

[0097] As can be seen in [Fig.7], the cylinder head 70 is fixed to the third arm 60 of the body 38 by a nut 94 which is screwed onto the third arm 60.

[0098] The outlet conduit 68, which supplies the nozzle 54 with pressurized liquid, includes a first channel 96 which is formed by the cylinder head 70, and a second channel 98 which is formed by the body 38 of the adapter 28.

[0099] The first channel 96 extends axially along axis C through the cylinder head 70, from a liquid outlet 100, which communicates with the chamber 64, to the free end of the first downstream section 72 of the cylinder head 70.

[0100] With reference to [Fig.7], the first channel 96 protrudes axially inside chamber 64, forming an annular seat 102 which delimits the outlet orifice 100 of chamber 64.

[0101] The second channel 98, visible in [Fig.5], has an upstream section 104 which is arranged axially opposite the free end of the first downstream section 72 of the cylinder head 70, in the extension of the housing 74 which receives the cylinder head 70.

[0102] Also, the second channel 98 has a downstream section 106 which opens into a radial face 108 of the free end of the second branch 50 of the body 38, to supply the nozzle 54 with pressurized liquid.

[0103] Finally, the second channel 98 has an intermediate section 110 which is interposed between the upstream section 104 and the downstream section 106, and which has a curved shape.

[0104] According to another aspect, the pilot unit 62 is adapted to vary the spray flow rate of the nozzle 54 by intermittently closing the outlet orifice 100 of the liquid from the chamber 64 during an opening-closing cycle.

[0105] For this purpose, the control unit 62 is equipped with a solenoid valve 112 comprising a body 114 which delimits a housing 116 in which a socket 118 is arranged.

[0106] The sleeve 118 extends axially along the axis C and includes a threaded section 120 which is screwed onto a threaded section 122 complementary to the peripheral wall of the cup 82 formed by the cylinder head 70.

[0107] As can be seen in [Fig.7], the seal between the solenoid valve 112 and the cylinder head 70 is ensured by an O-ring 124 which is interposed axially between an annular seat 126 formed at the entrance of the bowl 82 and a screwing wheel 128 of the sleeve 118.

[0108] Similarly, the seal between the sleeve 118 and the body 114 of the solenoid valve 112 is ensured by an O-ring 129a which is interposed axially between the wheel 128 and a first free end of the sleeve 118.

[0109] At the opposite end of the sleeve 118, the seal at the outlet of the housing 116 is ensured by an O-ring 129b which is interposed between the body 114 of the solenoid valve 112 and a plug 131 mounted on a second free end of the sleeve 118.

[0110] In addition, the solenoid valve 112 includes a generally cylindrical piston 130 which extends along the axis C, from a valve-forming head 132, which is arranged opposite the outlet orifice 100 of the chamber 64, to a tail 134 which is mounted in the sleeve 118.

[0111] The free end of the head 132 of the piston 130 has a circular obturating face 136 which extends perpendicularly to the axis C and which is intended to cooperate with the opposite seat 102, to obturate the outlet orifice 100 of the chamber 64.

[0112] For this purpose, the piston 130 of the solenoid valve 112 is mounted to slide between an open position shown in Figures 5 to 7, and a closed position shown in [Fig.8], during the opening-closing cycle.

[0113] In its open position, the piston 130 is retracted and allows the liquid to be sprayed to flow from the inlet circuit 66 to the nozzle 54, passing through the chamber 64 and the outlet conduit 68.

[0114] In its closed position, the piston 130 seals the outlet orifice 100 of the chamber 64 to prevent liquid from entering the outlet conduit 68.

[0115] The solenoid valve 112 is controlled by the control unit 62 which implements a technology called pulse width modulation, also known by the acronym PWM, so that the solenoid valve 112 varies the flow rate of the nozzle 54 by modulating the duration of opening of the outlet conduit 68 during an opening-closing cycle.

[0116] Typically, the solenoid valve has an opening-closing frequency of 10 to 100 Hertz. In other words, the solenoid valve is capable of opening and closing 10 to 100 times per second.

[0117] The applicant notes that in order to obtain a quality jet at the nozzle 54 outlet, the pressure of the liquid passing through the nozzle 54 must be substantially constant and must not not fall when the pilot unit 62 alternately closes and opens the outlet orifice 100 of the chamber 64 to vary the flow rate of the nozzle 54, during the nozzle opening-closing cycle.

[0118] Also, the applicant notes that a reduced volume of the outlet conduit 68 makes it possible to obtain a jet at the outlet of the nozzle 54 which is perfect, the volume of the outlet conduit 68 corresponding overall to the volume of liquid which is contained between the outlet orifice 100 of the chamber 64 and the outlet of the nozzle 54.

[0119] The adapter 28 according to the invention makes it possible to improve the quality of the jet at the outlet of the nozzle 54 compared to a nozzle holder whose pilot unit would be arranged upstream of the fixing heads 18a, 18b, 18c of the nozzles.

[0120] Indeed, the design of the adapter 28 according to the invention makes it possible to reduce the volume of liquid which is contained between the outlet orifice 100 of the chamber 64 and the outlet of the nozzle 54 by allowing the pilot unit 62 to be arranged as close as possible to the active nozzle 54, and thus to improve the quality of the jet at the outlet of the nozzle 54 on a nozzle holder 10 equipped with the adapter 28 according to the invention.

[0121] In addition, the outlet conduit 68 which connects the outlet orifice 100 of the chamber 64 to the nozzle 54 has a curved shape, generally in the shape of an arc of a circle, so as to limit the volume of the outlet conduit 68 compared to a right-angled bent shape.

[0122] Indeed, the expression "curved shape" here refers to a shape that is generally an arc of a circle as opposed to a shape bent at a right angle whose total length, and therefore volume, would be greater.

[0123] More specifically, the outlet conduit 68 has a curved shape over more than one third of its length, and about half of its length, as can be seen in [Fig.5].

[0124] Also, the third branch 60 which carries the pilot unit 62 and the second branch 50 which carries the nozzle 54 form an obtuse angle α, illustrated in [Fig.6].

[0125] In other words, the third branch 60 extends at a noticeably inclined angle towards the second branch 50.

[0126] This arrangement allows the outlet conduit 68 to draw a generally curved shape in the form of an arc of a circle whose radius of curvature is greater than that of a right-angled bent shape, which promotes the reduction of the volume of the outlet conduit 68.

[0127] Indeed, the developed length of a conduit in the shape of an arc of a circle is less than the developed length of a bent conduit.

[0128] The present invention also relates to a spraying device (not shown), in particular an agricultural vehicle-type spreading vehicle, which includes a spray boom equipped with a plurality of spraying systems of the type described above, according to the invention.

[0129] Naturally, the invention is described in the foregoing by way of example. It is it being understood that a person skilled in the art is able to carry out different variations of the invention without going out of the scope of the invention.

Claims

Claims

1. Spray adapter (28) provided for equipping a spray nozzle holder (10), characterized in that it comprises: - a spray nozzle (54), - a body (38) comprising a pressurized liquid supply mouth (42) which is capable of being connected to a fixing head (18c) of a nozzle holder (10), in place of a nozzle, - an internal chamber (64) which is connected to said supply mouth (42) by an inlet circuit (66) to be supplied with pressurized liquid, and which is connected to the nozzle (54) by an outlet conduit (68) to supply the nozzle (54) with pressurized liquid, said outlet conduit (68) being connected to the chamber (64) by an outlet orifice (100), and - a control unit (62) which is mounted on the body (38) and which is adapted to vary the flow rate of the nozzle (54) by closing said outlet orifice (100) of the chamber (64) intermittently during an opening-closing cycle.

2. Spray adapter (28) according to claim 1, characterized in that the body (38) has a three-branch shape, including: - a first branch (40) which comprises the supply mouth (42), - a second branch (50) which carries the spray nozzle (54), and which extends along a spray axis (B), and - a third branch (60) which carries the control unit (62) and which extends along an axis (C) inclined relative to said spray axis (B).

3. Spray adapter (28) according to claim 2, characterized in that the second branch (50) which carries the spray nozzle (54) is aligned with the first branch (40) formed by the supply mouth (42), along the spray axis (B).

4. Spray adapter (28) according to any one of claims 2 and 3, characterized in that the third branch (60) which carries the control unit (62) and the second branch (50) which carries the nozzle (54), form an obtuse angle (a).

5. A spray adapter (28) according to any preceding claim, characterized in that the outlet conduit (68) which connects the outlet orifice (100) of the chamber (64) to the nozzle (54) has a curved shape, so as to limit the volume of said outlet duct (68).

6. Spray adapter (28) according to any one of the preceding claims, characterized in that the body (38) is made in one piece.

7. Spray adapter (28) according to any one of the preceding claims, characterized in that the control unit (62) varies the flow rate of the nozzle (54) by closing the outlet orifice (100) of the chamber (64) intermittently during an opening-closing cycle, by implementing a technique called pulse width modulation.

8. A spray adapter (28) according to any preceding claim, characterized in that the feed mouth (42) of the adapter (28) is adapted to be mounted on a fixing head (18c) of a nozzle holder (10), to allow the fixing of said adapter (28) in place of a nozzle.

9. A nozzle holder (10) comprising an adapter (28) according to any preceding claim.

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