GB2038154A - Device for applying doses of a liquid preparation to a ground surface - Google Patents

Abstract

A device for applying doses of a liquid preparation to a ground surface, particularly for selective treatment of plants, comprises at least one distribution pipe (1) having apertures (4) therein for the liquid preparation and also a plurality of screening caps (7), both carried by a displaceable frame (3). The distribution pipe (1) is movable between an operative position in which the apertures (4) are directed downwardly and an inoperative position in which the apertures (4) are directed upwardly and is provided with a drop collector (5), in order to prevent spilling of liquid during breaks in operation. A feeding pipe (6) may be present next to each distribution pipe (1), and several combinations of feeding pipe and distribution pipe may be mounted interchangeably on the frame. <IMAGE>

Description

SPECIFICATION Device for applying doses of a liquid preparation to a ground surface The invention relates to a device for applying doses of a liquid preparation to a ground surface, particularly for selective treatment of plants.

In agriculture and horticulture many liquid preparations are used, for example, for weed-control, growth inhibition or stimulation, for the control of bacteria, fungi, insects and many further similar purposes. The application of these preparations to a surface bearing plants is usually carried out by atomization or nebulation, which is successful in most cases. However, sometimes atomization of the preparation may be less appropriate, for example, in the event of an expensive preparation which has to be applied in small doses and at particular places or if a selective treatment of crops is desired, in which certain crops have to be treated, whereas other plants should not be treated. In the latter case atomization may be disadvantageous because drops of the preparation will also penetrate to the plants to be saved so that a different method of application has to be chosen.

Of late a device has become known by which a liquid preparation can be applied in doses to a ground surface. This known device comprises a frame movable along the ground and carrying a distribution pipe covering the whole width of the device. This distribution pipe can be connected with a supply of liquid preparation and has a row of dispenser apertures throughout its length for dispensing the liquid preparation in drops. Thus, during the movement of the device across a field a satisfactorily dosed rain of drops arrives at the plants. Beneath the distribution pipe and at right angles thereto a plurality of screening caps are fastened to the frame for protecting plants not to be touched by the liquid preparation.These screening caps ensure that during the run of the device certain plants are not touched by the liquid drops so that an overall selective treatment of crops can be carried out.

Although this known device operates satisfactorily, it can be improved in various aspects. It may, for example, be useful to take steps for avoiding spill of fluid from the device when turning the frame at the head land. Spilling of liquid would annul the effect of a satisfactory dosing and of a selective treatment.

Moreover, care should be taken that appreciable amounts of liquid should not trickle off the edges of the screening caps, since this would also be detrimental to the effect of satisfactory dosing. Further improvements will become evident from the following.

The invention has for its object to improve the known device in these respects so that an efficient operation is ensured.

The invention provides a device for applying doses of a liquid preparation to a ground surface, particularly for a selective treatment of crops, said device comprising a frame movable along the ground surface, at least one distribution pipe carried by said frame and adapted to be connected to a supply of liquid preparation and having a row of dispenser apertures for dispensing drops of the liquid preparation to the plants and a plurality of screening caps carried by said frame and being at right angles to the distribution pipe for protecting plants not to be treated by the preparation, said device being characterised in that the distribution pipe is adjustable at will between an operative position in which the dispenser apertures are orientated downwards and an inoperative position in which the dispenser apertures are turned upwards and in that a drop collector is provided on the distribution pipe at the side of the row of dispenser apertures.

The device according to the invention is eminently suitable for applying doses of a liquid preparation to a ground surface, since during the travel of the device across a field this preparation will be given off in the form of drops by the distribution pipe so that it will arrive in the correct doses at the plants to be treated at the desired places. The screening caps satisfactorily protect the plants not to be treated so that a selective treatment is ensured. Moreover, durr ing a turn of the device at the head land the risk of spilling liquid is practically eliminated. When the supply of liquid to the distribution pipe is cut off, the distribution pipe can be set in its inoperative position in which no liquid is any longer given off by the dispenser apertures.Any drop leaving the apertures during the displacement of the distribution pipe is effectively captured by the drop collector so that spilling of liquid is practically excluded. As soon as the device has been turned, the distribution pipe can be returned to its operative position and the supply of liquid can be released so that the device can be run in full operation along the next strip of land.

Consequently an important feature of the device is formed by the adjustability of the distribution pipe between an operative position and an inoperative position. This adjustability is preferably obtained by mounting the distribution pipe so as to be rotatable about its own axis, but if desired, the distribution pipe may be rendered pivotable about an axis parallel to the centre line of the pipe.

A further important feature is formed by the drop collector on the distribution pipe, which collector may generally have any suitable shape provided it is located at the side of the row of dispenser apertures.

It may be advantageous to arrange the drop collector on both sides of the row of dispenser apertures.

Satisfactory results have been obtained by a boxshaped drop collector surrounding the distribution pipe substantially completely with the exception of the dispenser apertures.

According to the invention further steps can be taken to prevent appreciable amounts of liquid preparation from dripping off the edges of the screening caps, which would spoil the satisfactory dosing effect and involve the same problems at the head land of the field. In a first embodiment these steps consists in that the row of dispenser apertures in the distribution pipe is locally interrupted and the screening caps are arranged beneath the intervals in the row of dispenser apertures. During operation only a small amount of liquid or no liquid at all will arrive at the screening caps or drip off along the edges thereof so that the satisfactory dosing is main tained and no problems are involved at the head land.

The use of local intervals of the row of dispenser apertures has, it is true, the disadvantage that the distribution pipe is then only suitable for use on fields where the distance between the rows of plants to be protected corresponds with the distance between the intervals in the tube. In practice, however, different distances between rows of plants are possible in dependence upon the kind of culture. The distance between rows of beet, for example, differs from that of corn. In order to render the device according to the invention suitable for use on all these kinds of crop two or more distribution pipes having each a different interval between the dispenser apertures can be mounted parallel to one another around a common pivotal shaft.When changing from one kind of crop to another the appropriate distribution pipe has to be moved into the correct position for dispensing drops and to be connected with the source of liquid. The turn about the common pivotal shaft can simultaneously serve to exchange the distribution pipes and to move a distribution pipe from the operative position into the inoperative position or conversely. As a matter of course, the use of two or more exchangeable distribution pipes brings about the necessity of a displaceability of the screening caps and therefore, the area of suspension of the screening caps to the frame is preferably variable.

Dripping of large amounts of liquid from the edges of the screening caps may be avoided in a further manner. In a second embodiment the distribution pipe comprises a plurality of separate pipe sections whilst the screening caps are suspended to the frame at the areas between these pipe sections. Also in this case only a small amount of liquid at all will get to the screening caps during operation or drip from the edges thereof, so that the satisfactory dosing of the preparation is maintained and no problems will occur at the head land.

In this embodiment the pipe sections must have their own liquid inlet. This can be ensured in a simple manner by connection of each of the pipe sections through a rigid connecting duct with a common supply pipe carried by the frame and extending parallel to the distribution pipe. By including in each connecting duct a non-return valve the risk of dripping or spilling from the separate pipe sections is drastically reduced. Of course, each pipe section is associated also in this case with a drop collector, whilst each pipe section can be adjusted between an operative position and an inoperative position, so that spilling is completely avoided. The latter adjustability is best obtained by mounting the pipe sections so as to be pivotable in common about an axis coinciding with or being parallel to the centre line of the supply pipe.When the pipe sections are turned, the supply pipe turns at the same time, which is no objection.

Also in this embodiment, in which the distribution pipe consists of a number of separate pipe sections, it is a disadvantage that the distribution pipe is adapted to a fixed distance between the rows of the plants to be protected. However, in order to enhance the flexibility of use matching different kinds of crop two or more combinations of distribution pipes and supply pipe with different lengths of pipe sections can be arranged parallel to one another around a common pivotal shaft so that for a change-over to a different crop and to a different distance between the rows the same device can be employed by turning a different combination of the supply pipe and the distribution pipe into the correct operational position.

The common pivotal shaft then serves again for exchanging the distribution pipes and for change of the pipe sections from the operative position to the inoperative position and conversely. Also in this case the area of suspension of the screening caps to the frame should, of course, be variable.

To both embodiments it applies that during a turn of the device at the head land of a field a slight shift of the liquid in the distribution pipe may always occur, the liquid being pushed to one end of the pipe. However, the resultant risk of emergency of liquid through the dispenser apertures does, however, not come true owing to the pivotability of the distribution pipe and to the presence of the drop collector. In the second embodiment said risk is substantially annulled owing to the assembly of separate pipe sections.

It will be obvious that a satisfactory operation of the device according to the invention, particularly with respect to the selective treatment of crops, is highly dependent upon the screening caps used for protecting the plants not to be treated during the travel across the land without causing damage of said plants. It has been found that the mode of suspension of the screening caps to the frame is very important for satisfactory operation. Though the suspension may be carried out in various ways, it is preferred to suspend the caps by means of two dual-hinge tie strips so that the caps can resiliently move upwards at any unevenness of the ground and will otherwise satisfactorily close around the rows of plants to be protected.

The invention will be explained further with reference to the drawing which shows a few embodiments by way of example.

Fig. 1 shows a first embodiment of the device in accordance with the invention in operation in a perspective view.

Fig. 2 is a sectional view taken on the line ll-ll in fig.

1.

Fig. 3 is a sectional view as that of fig. 2 of a varient of the embodiment shown in fig. 1.

Fig. 4 is a perspective view of the device in accordance with the invention in operation in a further embodiment.

Fig. 5 is a sectional view taken on the line V-V in fig. 4 on a strongly enlarged scale.

Fig. 6 is a sectional view like that of fig. 5 of a varient of the embodiment shown there.

Fig. 7 is a sectional view taken on the line VII-VII of fig. 4 on an enlarged scale.

Fig. 8 is an enlarged view of a detail of fig. 4.

Fig. 9 illustrates schematically the mode of attaching the device of fig. 4togetherwith the associated parts to a tractor.

Fig. 1 shows a simple embodiment of the device in accordance with the invention. This embodiment comprises a distribution pipe 1 covering the whole working width of the device and being rotatably journalled by means of stub shafts 2 in a frame 3.

Along its length the distribution pipe has a row of calibrated dispenser apertures 4 and it is substantially completely surrounded by a fox-shaped drop collector 5, which does not screen the dispenser apertures. The distribution pipe is provided with supply nipple 6 for the liquid.

Beneath the distribution pipe 1, at right angles thereto, a plurality of screening caps 7 are carried by the frame 3 by way of a tie stripS. Perpendicularly above said screening caps the row of dispenser apertures in the distribution pipe 1 is interrupted so that practically no liquid can get at the screening caps.

The device shown in fig. 1 may be moved manually or by machine, for which purpose the frame may be provided with ground wheels or be hitched to a vehicle. During operation the device of fig. 1 is run across a field in the direction of the arrows A and A'. The liquid preparation, for example, a weed killer is fed via the connecting nipple 6 to the distribution pipe 1 and distributed in correct doses in the form of a rain of drops on the field. The screening caps 7 extending in the direction of movement slide over and across given rows of plants and ensure that these rows of plants are not touched by the preparation. In this way the plants are selectively treated.

This may be important for saving rows of beet or maize, whereas all plants standing between said rows, for example, weeds, undesirable potato plants, have to be destroyed. Since the row of dispenser apertures is interrupted above the screening caps, practically no liquid will fall on the screening caps or drip from the edges thereof, so that a satisfactory dosing of the liquid is ensured.

When a broad strip of a field has been treated in this way, the device can be turned and used for the treatment of the next strip. During this turn care should, however, be taken to avoid spilling of liquid, since the preparation must not touch plants not to be treated. To this end the delivery of liquid preparation to the distribution pipe 1 is cut off and the distribution pipe is turned about its axis by means of a lever 9 in the direction of the arrow B into an (inoperative) position in which the dispenser apertures are turned upwards. In this position no liquid can any longer be delivered. If during the turn into the inoperative position drops should emerge from the dispenser apertures, they are captured by the drops collector 5 and retained thereby. In this way spilling of liquid is effectively avoided.When the device has been turned to be ready for a next operational run, the distribution pipe is turned back by means of the lever 9 from the inoperative position into the operative position and the feed of liquid preparation to the distribution pipe is re-established, after which the device can be run with uniform speed across the next strip of the field. The drops of liquid captured by the drop collector 5 during the turn of the distribution pipe 1 are given off to the plants at the begin ning of the next operational run and will not disturb the correct dosing.

Fig. 2 is an enlarged cross-sectional view of the distribution pipe 1 with the drop collector 5. The operative position, in which the dispenser apertures are directed downwards is shown in solid lines. It will be apparent that the pipe contains a liquid preparation 10, which is delivered in the form of drops 11 through the dispenser apertures 4. At the end of an operational run the liquid supply is shut off and the distribution pipe 1 with the drop collector 5 is turned in the direction of the arrow B' into the inoperative position (indicated by broken lines). It will be evident that any emerging drops will be satisfactorily collected by the drop collector 5.

Fig. 3 shows a sectional view like fig. 2 of a variant of the embodiment shown there. In this varient the distribution pipe 1 has a more or less rectangular cross-section and on both sides of the row of dispenser apertures 4 sloping faces 52 are provided to operate as drop collectors. The pipe 1 is adapted to turn in the direction of the arrow C and can thus be turned from the operative position shown into an inoperative position, in which the dispenser apertures are directed upwards. Also in this case the drop collector will prevent any undesirable dispensation of drops and the consequent spilling of liquid. Various othervarients of the shape of the drop collector may, of course, be designed.

In embodiment shown in fig. 1 the screening caps 7 and hence the intervals in the row of dispenser apertures 4 are spaced apart by a fixed distance. This involves that the device can only be used in those cases in which the distance between the rows of plants to be protected corresponds with the distance between the screening caps. In practice this distance between the rows may be different for different crops so that there is a need for devices having variable distances between the screening caps. In a variant of the device shown in fig. 1 (not shown) two or more distribution pipes having each a different distance between the intervals in the row of dispenser apertures can be mounted parallel to one another around a common pivotal shaft, which serves both for exchanging the pipes and for turning a pipe from the operative position into the inoperative position and conversely.Moreover, the area of suspension of the screening caps to the frame is rendered variable.

In such a variant the pipes can be readily exchanged and the screening caps can be easily displaced so that the device can be rapidly adapted to any distance between the rows of plants to be protected.

The fact that during the operation of the device practically no liquid will drip off the edges of the screening caps, means that during a turn of the device at the head land no liquid will be spilled from the screening caps. This applies to both the embodiment shown in fig. 1 and to the variants thereof.

Fig. 4 shows a further, more complicated embodiment of the device in accordance with the invention.

The distribution pipe 1, extending along the whole working width of the device, comprises a plurality of separate pipe sections 1 a, 1 b, .... . , each of which communicates through a rigid connecting duct 12 including a non-return valve 13 with a common supply pipe 14, covering the whole working width of the device and extending parallel to the pipe sections.

The supply pipe has a feeding nipple 15 for the liquid and is carried by means of stub shafts 16 by a frame 3 so that the combination of the supply pipe 14 with the pipe sections 1a, 1b, 1c. . whole can be turned about an axis coinciding with the centre lines of the stub shafts 16. Beneath the pipe sections of the distribution pipe 1 are arranged, at right angles thereto, screening caps 7, which are suspended by means of tie strips 17 at areas between the separate pipe sections to the frame 3.

Apart from the feeding pipe 14 a second feeding pipe 18 comprises through rigid connecting ducts 19 including each a non-return valve a series of distribution pipe sections ....... having a length differing from that of the pipe sections lea, . . . This combination of the feeding pipe 18 and the pipe sections 20a . . . is out of operation in the position shown, but, if desired, it can be switched on for working fields having different distances between the rows. The feeding pipe 18 is also journalled in the frame 3 by way of the stub shafts 16 and is pivotable about the same pivotal shaft as the feeding pipe 14. On the outer side of the stub shaft 15 shown a lever 21 is provided for carrying out the pivotal movement.

The frame 3 of the device of fig. 4 comprises retractable legs 22 and is intended for fastening to the front side of a tractor, by which it can be displayed horizontally in the direction of the arrow A.

In the sectional view of fig. 5 the two feeding pipes 14 and 18 with the associated parts are shown on an enlarged scale. The feeding pipe 14 communicates through a rigid connecting duct 12 including a nonreturn valve 13 with the pipe section 1 a of the distribution pipe 1, whereas the feeding pipe 18 communicates in a similar manner through a connecting duct 19 including a non-return valve 23 with a pipe section 20a of the distribution pipe 20. The nonreturn valves 13 and 23 have an internal diaphragm 24 and 25 respectively, whilst the connecting ducts 12 and 19 include furthermore a plate 26 and 27 respectively having a calibrated aperture for adjusting the passage. The pipe sections 1 a and 20a have a box-shaped drop collector 5 and 28 respectively, which surrounds the pipe section substantially completely with the exception of the dispenser apertures 4 and 29 respectively.In the position shown only the feeding pipe 14 communicates with a source of liquid, whereas the pipe section 1 a is in the operative position, the dispenser apertures 4 being directed downwards.

During operation the device shown in fig. 4 and 5 is moved in the directions of the arrows A across a field with plants, whilst the screening caps 8 glide along rows of plants which have to be protected. The liquid preparation, for example, a weed killer is fed through the feeding nipple 15 to the supply pipe 14 and from there through the connecting ducts 12 to the various pipe sections 1 a, 1 b, 1 c. . of the distribution pipe 1. Owing to the pressure of the liquid the non-return valves 13 are automatically held in the open state. The liquid preparation is delivered through the dispenser apertures 4 of the pipe section lea . . . in the form of drops so that the plants at the areas between the screening caps are uniformly treated with the preparation.Little or no liquid will fall on the screening caps so that a well-balanced dosing is ensured. The plants passing beneath the screening caps are completely protected, which ensures a selective treatment. At one end of the field, when the device has to be turned around, the supply of liquid to the feeding nipple 15is interrupted so that the fluid pressure in the connecting ducts 12 disappears and the non-return valves 13 close themselves automatically. The pipe sections .... then still hold a small amount of liquid 10, which must not be spilled.By turning the assembly of feeding pipes 14, 15 with the aid of the lever 21 in the direction of the arrow D through h 180", the pipe sections 1 a are removed into an inoperative position with the dispenser apertures 4 directed upwards so that no liquid can flow out. Any drops flown out during said turn are effectively captured by the drop collector 5.

As soon as the device has been turned and set in the correct position for treating a further strip of the field, the assembly of the feeding pipes 14, 18 is swung back into the initial position, after which the supply of liquid to the feeding nipple 15.is released and the device can be moved in full operation along the strip of land. The interval takes only little time and the liquid captured by drop collector 5 is normally delivered to the plants at the beginning of the new operational run without the balance of dosing being disturbed.

Since during operation practically no liquid flows away from the edges of the screening caps, the latter will not give rise to further dripping when the device is turned. Thus the risk of spilling is satisfactorily eliminated.

It is desired to exchange the distribution pipes at the end of a field, the same operations as described above are performed, that is to say, the supply of liquid is interrupted and the assembly of feeding pipes 14, 18 is turned. Thus the pipe sections lea . . .

are turned into the inoperative position and at the same time the pipe sections 1 0a are moved into the operative position. In addition the suspension area of the screening caps has to be shifted so that the screening caps 7 are located exactly between the pipe sections 201,20b... The device can then be passed to a further field where it matches the distance between the rows of plants to be protected and after the connection of the supply of liquid with the feeding pipe 18 it is directly ready for use.

It should be noted that instead of using two feeding pipes 14,18 with the associated distribution pipes and further parts a larger number of feeding pipes may be employed in the device. Fig. 6 shows such a variant, in which four feeding pipes 14,18,30,31 with the associated distribution pipe sections 1 a, 20a, 30a, 31 a, are mounted parallel to one another around a common pivotal shaft 34 and can be turned in the direction of the arrow D from an operative position into an inoperative position.

The sectional view of fig. 7 shows a small part of the feeding pipes and distribution pipes of figs. 4 and 5, the feeding nipples 15,35 of the feeding pipes 14, 18 being particularly apparent. This figure illustrates furthermore the mode of suspension of the screening caps 7. The screening caps 7 are fastened by means of inclined tie strips 17, 17 and vertical arms 36,36 of a framework 37, which is secured to the frame 3. The tie strips 17, 17 have double hinges 38, 38 so that the screening caps are resiliently suspended. When the frame is displaced forwardly, the screening caps will occupy a lowermost position by their weight so that they will satisfactorily screen the plants not to be treated with the liquid, whereas in the event of impact on an unnevenness they are readily lifted so that serious damage is avoided.The framework 37 is releasably fastened to the frame by means of a wedge 39a and a bolt 40. If the place of the screening cap has to be changed upon an exchange of distribution pipes, the connection can be disengaged and the framework can be refastened at a different place of the frame indicated by the wedge 39 of fig. 8.

Referring to fig. 9, the device 41 of fig. is hitched to the front of an agricultural tractor 42, which carries at the rear a hopper 43 for liquid preparation and a pump 44. Connecting ducts 45,46 are provided for carrying liquid from the hopper to the pump and from the pump to the device 41. By means of a control-cock 47 the feed of liquid to the device 41 can be regulated. This control-cock 47 serves in addition to actuate a hydraulic conduit 48, which acts upon a piston 49 forturning the distribution pipe in the device 41 and a hydraulic conduit 50 acting upon a piston 51 for lifting the device 41 at the initiation of the run across the field.

It will be obvious that within the scope of the invention many further variants are possible and that the embodiment shown are to be considered only by way of examples.

Claims (16)

1. A device for applying doses of a liquid preparation to a ground surface, particularly for a selective treatment of plants, said device comprising a frame displaceable along the ground surface, at least one distribution pipe carried by said frame and adapted to communicate with a supply of the liquid preparation and having a row of dispenser apertures for giving off the liquid preparation in the form of drops and a plurality of screening caps carried by the frame and being at right angles to the distribution pipe for protecting plants not to be treated with the preparation, characterised in that the distribution pipe is adjustable at will between an operative position in which the dispenser apertures are orientated downwards and an inoperative position in which the dispenser apertures are directed upwards and in that the distribution pipe is provided with a drop collector at the side of the row of dispenser apertures.

2. A device as claimed in claim 1, characterised in that the distribution pipe is rotatable about its own axis for the adjustment.

3. A device as claimed in claim 1, characterised in that for the adjustment the distribution pipe is pivotable about an axis parallel to the centre line of the pipe.

4. A device as claimed in claims 1 to 3, characterised in that the drop collector is provided on both sides of the row of dispenser apertures.

5. A device as claimed in claim 4, characterised in that the drop collector has a box-shaped design and surrounds the distribution pipe substantially com pletelywith the exception of the dispenser apertures.

6. A device as claimed in claims 1 to 5, characterised in that the row of dispenser apertures in the distribution pipe is locally interrupted and the screening caps are located beneath the areas of interruption of the row of dispenser apertures.

7. A device as claimed in claim 6, characterised in that two or more distribution pipes having each a different distance between the interruptions of the row of dispenser apertures are mounted parallel to one another around a pivotal shaft.

8. A device as claimed in claim 6 or7, character- ised in that the area of suspension of the screening caps to the frame is variable.

9. A device as claimed in claims 1 to 5, characterised in that the distribution pipe consists of a plurality of separate pipe sections and in that the screening caps are suspended to the frame at the areas between said pipe sections.

10. A device as claimed in claim 9, characterised in that the pipe sections of the distribution pipe each communicate through a rigid connecting duct with a common feeding pipe carried by the frame and extending parallel to the distribution pipe.

11. A device as claimed in claim 10, characterised in that each connecting duct includes a non-return valve.

12. A device as claimed in claims 9 to 11, characterised in that the pipe sections are in common pivotable about an axis coinciding with or extending parallel to the centre line of the feeding pipe.

13. A device as claimed in claims 9 to 12, characterised in that two or more combinations of a feeding pipe and a distribution pipe having different lengths of pipe sections are mounted parallel to one another around a common pivotal shaft.

14. A device as claimed in claims 9 to 13, characterised in that the place of suspension of the screening caps to the frame is variable.

15. A device as claimed in claims 1 to 14, characterised in that the screening caps are suspended to the frame by means of two dual-hinge tie strips.

16. Apparatus for applying doses of a liquid preparation to a ground surface substantially as hereinbefore described and illustrated with reference to any of the accompanying drawings.

16. A device for applying doses of a liquid preparation to a ground surface substantially as hereinbefore described and illustrated with reference to any of the accompanying drawings.

New claims or amendments to claims filed on 1013180.

Superseded claims 1-16.

1. Apparatus for applying doses of a liquid preparation to a ground surface, particularly for a selective treatment of plants, comprising a frame displaceable over the ground surface, at least one distribution pipe carried by the frame, communicable with a supply of the liquid preparation and having a row of dispenser apertures for dispensing the liquid preparation in the form of drops and a plurality of elongate screening caps carried by the frame and extending at right angles to the longitudinal axis of the distribution pipe for protecting plants not to be treated with the preparation, the distribution pipe being movable between an operative position in which the dispenser apertures are orientated downwards and an inoperative position in which the dis penser apertures are directed upwards, and the distribution pipe including or being located in a drop collector to collect drops of liquid issuing from the dispenser apertures when the distribution pipe is in its inoperative position.

2. Apparatus according to claim 1, in which the distribution pipe is rotatable about its longitudinal axis for movement between the operative and inoperative positions.

3. Apparatus according to claim 1, in which the distribution pipe is pivotable about an axis parallel its longitudinal axis for movement between the operative and inoperative positions.

4. Apparatus according to any one of claims 1 to 3, in which the drop collector is provided on both sides of the row of dispenser apertures.

5. Apparatus according to claim 4, in which the drop collector is trough-shaped design and surrounds the distribution pipe except on the side thereof at which the dispenser apertures are provided.

6. Apparatus according to any one of claims 1 to 5, in which the row of dispenser apertures in the distribution pipe is locally interrupted so that apertures of the row of dispenser apparatus are not provided vertically above the screening caps.

7. Apparatus according to claim 6, in which two or more distribution pipes having each a different spacing between the interruptions in the row of dispenser apertures are mounted parallel to one another around a pivotal shaft.

8. Apparatus according to claim 6 or claim 7, in which the relative positions of the screening caps on the frame is variable.

9. Apparatus according to any one of claims 1 to 5, in which the distribution pipe comprises a plurality of separate longitudinally aligned but axially spaced pipe sections and the screening caps are mounted on the frame at positions between adjacent pairs of the pipe sections.

10. Apparatus according to claim 9, in which the pipe sections of the distribution pipe each communicatethrough a rigid connecting duct with a common supply pipe carried by the frame and extending parallel to the distribution pipe.

11. Apparatus according to claim 10, in which each connecting duct includes a non-return valve.

12. Apparatus according to any one of claims 9 to 11, in which the pipe sections are pivotable together about an axis coinciding with or extending parallel to the centre line of the supply pipe.

13. Apparatus according to any one of claims 9 to 12, in which two or more combinations of supply pipe and distribution pipe having different lengths of pipe sections are mounted parallel to one another around a common pivotal shaft.

14. Apparatus according to any one of claims 9 to 13, in which the relative positions of the screening caps on the frame is variable.

15. Apparatus according to any one of claims 1 to 14, in which each of the screening caps is suspended on the frame by means of a pair of tie strips each including a pair of hinges.