FR2667001A1 - Continuous-circulation spray system - Google Patents

Abstract

This system includes at least one spreader manifold (applicator) provided with a feed pipe supplying a plurality of spray nozzles each including a member (11) for closing the supply circuit of the associated nozzle, this system being of the type having continuous recirculation of the product to be spread, in the said feed pipe, and the said closure member being of the type which includes two sealed (fluidtight) chambers (15, 19) separated by an elastically deformable membrane (14), one (15) of these chambers communicating continuously with the said feed pipe so that the membrane acts as a shutter between this feed pipe and the associated spray nozzle, and the second (19) of these chambers communicating with an external pneumatic source (12) selectively controlled so as to urge the said shutter respectively in the closing direction, by putting this second chamber under pressure, or in the opening direction, by releasing the pressure in this same chamber. According to the invention, the said closure member furthermore comprises an elastic means (27) for continuously urging the shutter in the closing direction, this elastic means being calibrated so as to close the shutter when the pressure of the product to be spread becomes less than the normal spreading pressure and when the pressure of the pneumatic source becomes less than the pressure which would be necessary, in itself, to urge the shutter in the closing direction.

Description

Continuous circulation spray assembly
The present invention relates to an installation for spraying phytosanitary products of the continuous circulation type.

 There are essentially known, in the spraying technique, three types of circulation, illustrated respectively and schematically in FIGS. 1, 2 and 3.

 The simple or discontinuous circulation, illustrated in FIG. 1, consists of pumping the product to be spread 3 into a tank 1, by means of a pump 2, and of sending it to the pump outlet, via a tap 4, to a distributor 5 supplying a plurality of spreading booms 6, each comprising a feed pipe 7 supplying a plurality of spray nozzles 8, the supply of which is controlled by a respective closure member 9.

 The tap 4, depending on its position, allows the liquid delivered by the pump 2 to be sent either to a distributor 5 or to a recycling line when the spraying is interrupted.

 The closure members 9 generally consist of a calibrated spring valve coming into action as soon as the pressure of the product to be spread becomes less than a given threshold, corresponding to the pressure exerted by the spring.

 To stop spraying, the operator therefore switches the tap 4 so as to interrupt the supply of the distributor 5 and the booms 6; this maneuver then drops the pressure in the feeder pipes 7, which causes the consecutive closing of the valves of the closing members 9, with the final consequence of preventing the dripping of the nozzles.

 One of the major drawbacks of this system is that, in principle, as it is the closing of the supply valve which causes the action of the spring, after closing the product no longer circulates in the supply line , so that the products in suspension in the liquid to be spread tend to sediment and cause the clogging of the nozzles. This drawback is accentuated by the use of small nozzles, causing a very low flow speed in the booms, and which can even go so far as to cause deposits during spraying.

 The semi-continuous circulation system, illustrated schematically in Figure 2, is a variant of the previous one, designed to avoid the last aforementioned drawback, namely the risk of deposition during spraying. This system, as can be seen in the figure, is identical to the previous one, with the difference that the feeder pipe 7 ends in a pipe 10 returning to the tank 1.

 There is thus obtained a permanent flow of the liquid during spraying, and a substantially constant pressure in line with each nozzle.

 However, since the cut-off system is always the same, stopping the spraying again leads to immobilization of the liquid, which risks causing sedimentation.

 The third spraying mode, illustrated diagrammatically in FIG. 3, is the so-called continuous circulation mode, and is that to which the present invention relates.

 The circuit is comparable to that of FIG. 2, but the spraying is now cut off at each nozzle by a closure member II, different from the closure members 9 of the two previous modes.

 These closing members 11 are of a different type, which is generally a membrane system pneumatically controlled by a pressure source 12 connected by a compressed air line 13 to each of the devices 11. The spraying is not cut off. therefore more by controlling the tap 4, but by pressurizing the pipe 13, which will close the devices 11. It can thus be seen that, even in the absence of spraying, the feeder pipe 7 remains permanently supplied with the liquid under pressure.

 However, all the pneumatic closure systems hitherto marketed and used have the serious drawback of not preventing the dripping of the product when the device is at rest (that is to say that the pump 2 is not no longer supplied or that the tap 4 no longer directs the liquid towards the distributor 5) and that the air pressure in the pipe 13 becomes insufficient accidentally (leak, etc.) or negligently (forgotten by the operator pressurize line 13 even after the end of the spreading operation).

 In fact, in this case, despite the absence of liquid circulation, the feed pipe 7 and the return pipe 10 contain a non-negligible volume of liquid which will drip through the nozzles 8, in the absence of positive locking of the closing members. 11.

 For more than ten years that continuous circulation systems have existed, this drawback has persisted, and no technique has since been proposed to remedy it.

 The object of the present invention is precisely to provide a solution to this problem, by proposing a closure system. positive locking preventing any risk of leakage even in the absence of pressure in the pneumatic control line when the liquid circuit to be spread is at rest.

 This invention is all the more advantageous since regulations relating to the protection of the environment, in the course of preparation, must enact, in the case of the use of a continuous circulation system, the use of 'a positive locking means of the devices preventing any risk of such accidental pollution.

 Furthermore, as will be seen, the closure member proposed by the invention is of particularly simple structure, therefore economical to produce, and moreover it can be implemented by a slight modification of the current devices (adaptation of a part on a preexisting device), therefore without requiring significant modification of the system to pass from a simple or semi-continuous circulation to a continuous circulation.

To this end, the continuous circulation spraying assembly according to the invention, which is therefore of the type comprising at least one spreading boom provided with a feed line supplying a plurality of spray nozzles each comprising a closure member of the supply circuit of the associated nozzle, this assembly being of the type with continuous recirculation of the product to be spread in said feed pipe and said closure member being of the type comprising two sealed chambers separated by an elastically deformable membrane, a first of these
chambers communicating permanently with said feed pipe so that the membrane acts as a valve between this feed pipe and the associated spray nozzle, and the second of these chambers communicating with an external pneumatic source selectively piloted so as to urge said valve respectively in the direction of closing, by pressurizing this second chamber, or in the direction of closing, by releasing the pressure in this same chamber. is characterized in that said closure member further comprises an elastic means for permanently urging the valve in the closing direction, this elastic means being calibrated so as to close the valve when the pressure of the product to be spread becomes lower than the pressure spreading pressure and that the pressure of the pneumatic source becomes lower than the pressure which would be necessary, on its own, to urge the valve in the closing direction.

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Other characteristics and advantages of the invention will appear on reading the description below, made with reference to the accompanying drawings.

 It will be noted that, in the various figures, identical reference numerals denote functionally similar elements.

 Figures 1 to 3, above, describe, respectively and schematically, the principle of a discontinuous circulation system, semi-continuous circulation and continuous circulation (the present invention belonging to the latter type of circulation).

 FIG. 4 shows, in section, the structure of a pneumatic closure member of the conventional type for a continuous circulation system.

 FIG. 5 shows, also in section, a closure member according to the invention for a continuous circulation system, produced by modification of the pre-existing closure member of FIG. 4.

 Figure 6 shows, still in section, another embodiment of the invention.

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FIG. 4 shows a closing member 11 of known type, comprising an elastically deformable membrane 14 acting as a valve between a first chamber 15, connected by a channel 16 to the feed pipe for supplying fluid to be spread, and another channel 17 communicating with the spray nozzle. When the membrane rests on its seat 18, it closes the chamber 15, preventing the arrival of the liquid towards the nozzle.

 On the other hand, under the pressure of the liquid introduced into the channel 16, and in the absence of any other stress, it deforms up to the position illustrated in solid lines in the figure and lets this liquid pass to the nozzle, via channel 17.

 The device also comprises, on the other side of the membrane, a second chamber 19 which, in this example, is connected to the membrane 14 by a piston 20 and a second membrane 21 (but one could also provide for direct communication between the chamber 19 with the rear face of the membrane 14, which would give a functionally equivalent device).

 The chamber 19 is connected to a channel 22 communicating with the line 13 (FIG. 3) connecting with the source of air pressure.

Thus, when pressurized air is introduced into the chamber 19, the piston 20 is pushed back down, which causes the membrane 14 to lower, and therefore the liquid supply circuit to be spread to be interrupted. . Conversely, when the pressure in the chamber 19 is released, this circulation of the liquid can be restored under the effect of the pressure of the liquid.

 The whole of this device is housed in a housing comprising a body 23, a holding part 24 and a cover 25 tightened against the body by a clamping ring 26.

 The drawback of this device, as can easily be understood from FIG. 4, is that, in the rest position, if the pressure in the chamber 19 is released accidentally or inadvertently, the pressure of the residual liquid in the pipeline will cause an effacement of the membrane 14, and therefore a passage of the liquid from the channel 16 towards the channel 17, with as a consequence a dripping of this liquid by the nozzle.

 The present invention overcomes this drawback with a device, illustrated in FIG. 5, consisting essentially of a device similar to that of FIG. 4, but to which a return spring 27 has been added positively biasing the membrane 21 (and therefore the membrane 14 , via the piston 20) in the closing direction even in the absence of air pressure in the chamber 19.

 Most of the parts of the device in FIG. 4 can be kept; it suffices to replace the cover 25 by a suitable cover 28 containing the spring and a means for holding it, for example a clip 29.

 It can thus be seen that it will be very simple to transform a pneumatically controlled device (according to FIG. 4) into a device according to the invention (according to FIG. 5), by replacing the cover 25 with a suitable cover 28 comprising a spring.

 In the same way, it will be easy to transform devices with a simple spring-loaded valve (those used for systems with discontinuous or semi-continuous circulation) into a device according to the invention, by piercing the cover for holding the valve in order to adapt it. a pneumatic connector transforming the interior volume into a pneumatic control chamber in communication with the front face of the diaphragm forming a valve, the preexisting spring then playing the role of the complementary return spring 27.

 FIG. 6 represents another embodiment of the invention, in which the membrane 14 is unique, and directly separates the two chambers 15 and 19. The spring 27 then urges this membrane by means of a hollow piston 30 retained in the cover 28 by a shoulder 31, this piston being provided with an orifice 32 authorizing the communication of chamber 19 with passage 22.

FIG. 6 shows the membrane in the position it takes when the pressurized liquid is brought in via line 16.
When this liquid pressure decreases and the air pressure in the chamber 19 also decreases, the spring pushes, by its front face 33, the membrane to the position illustrated in dashed lines, thereby closing the liquid circuit and preventing any dripping of it through the nozzle.

Claims (1)

 CLAIM  A spraying assembly, comprising at least one spreading boom (6) provided with a feed line (7) supplying a plurality of spray nozzles (8) each comprising a member (11) for closing the supply circuit of the associated nozzle, this assembly being of the type with continuous recirculation of the product to be spread in said feed pipe and said closure member being of the type comprising two sealed chambers (15, 19) separated by an elastically deformable membrane (14), a first ( 15) of these chambers communicating permanently with said feed pipe so that the membrane acts as a valve between this feed pipe and the associated spray nozzle, and the second (19) of these chambers communicating with an external pneumatic source (12) selectively controlled so as to urge said valve respectively in the closing direction, by pressurizing this second chamber, or da ns the direction of closing, by releasing the pressure in this same chamber,  characterized in that said closure member further comprises an elastic means (27) for permanently urging the valve in the closing direction, this elastic means being calibrated so as to close the valve when the pressure of the product to be spread becomes less than normal spreading pressure and that the pressure of the pneumatic source becomes lower than the pressure which would be necessary, alone, to urge the valve in the closing direction.