GB2055534A - Machine for laying sheet material - Google Patents

Abstract

There is described a machine for laying sheet material on the ground comprising a support frame 50, a roll 60 of sheet material rotatably supported on the support frame, means 72, 76 for causing the marginal edges of the sheet material to be retained in or on the ground, and means 64, 66 for perforating the sheet material as it is unwound from the roll thereof and before it is placed in contact with the ground. <IMAGE>

Description

SPECIFICATION Machine for laying sheet material This invention relates to the laying of flexible material over land areas, and is especially concerned with the provision of a novel device for laying flexible material in strip form over an area of land.

Plastics films, for example polyethylene films, are finding increased use in agriculture and horticulture as soil coverings, with a view to increasing crop yield and improving plant growth. Opaque and translucent films are used as a "mulch", reducing weed competition and thereby improving the crop. Transparent films laid over a sown or growing crop raise soil temperature and aid plant growth, generally producing an earlier and consequently more valuable crop. In addition, any impermeable film laid over soil reduces the loss of water by evaporation and therefore reduces the quantity of water required to produce the crop. Plastics films are commercially available for most, if not ail, of these applications.

The "greenhouse" effect produced by laying a film over sown or planted soil is highly beneficial, but suffers the disadvantage that as the crop grows either the film is stretched, until it is finally ruptured by the rising crop, or the film does not "give" and therefore damages the crop. "Slack" may be put into the film at the time of laying, which can be taken up by the crop growth, a device for doing which is described in our U.K. Patent No: 1,504,967. Film may be laid with perforations which will allow a crop to respire and develop underneath, or with perforations through which the crop will grow. Both types of film may be degradable in a relatively short predictable time or may be relatively resistant to degradation and thus need removal.

The use of perforated film is carried out in one of two ways. In the first the film is perforated as part of the manufacturing process, and is supplied to the user in the form of a roll of perforated film. In the second, the actual film-laying machine is provided with perforating devices which puncture the laid film and at the same time make a small hole in the soil and deposit a seed in the hole.

The main disadvantage of the use of preperforated film is that it is expensive; the simultaneous perforating of film and sowing seeds through the formed holes involves the use of bulky and complex machinery. It is the object of the present invention to reduce the expense and complexity involved in the use of perforated plastics films.

According to the present invention there is provided a machine for laying sheet material on the ground comprising a support frame, a roll of sheet material rotatably supported on the support frame, means for causing the marginal edges of the sheet material to be temporarily retained in or on the ground, and means for perforating the sheet material as it is unwound from the roll thereof and before it is placed in contact with the ground.

By the means of the invention, the user if the sheet material need not purchase expensive perforated material. He purchases the less expensive unperforated material, and perforates it himself on site. The perforating means may comprise a simple mechanism which may be readily attached to and equally readily removed from any standard machine for laying film. Thus, for example, the perforating mechanism may be an attachment to the film-laying machine described in our U.K. Patent Specification 1,504,967.

In one embodiment the perforating means comprises two opposed rollers, between which the unperforated film is fed, one roller having spaced projections and the other having a surface upon which the projections act. This surface may for example be a resilient one, e.g. of rubber, or it may comprise spaced channels or recesses to accommodate the projections on the other roller. The projections may have cutting edges, and may for example take the form of cylindrical cutters.

Suitably the rollers are adapted to move in synchronism, and this may be achieved by providing them at their ends with friction surfaces e.g. rubber surfaces, or by means of suitable gearing.

Other devices for perforating the plastics film on the film laying machine include a spiked roller, i.e.

one having a multiplicity of spikes or needles each of which produces a tiny hole in the film, a hot gas gun (suitably several are used), which directs a tiny jet of hot gas, for example hot air, onto the plastic film to melt it locally and form a small hole, mutually opposed toothed wheels, reciprocating cutters, heated blades and wires. A further device for perforating the film comprises one or a series of flailing wires or cords attached to a central spinning disc or shaft. This lacerates the film on impact, and will be sited and operated at a distance from the film and a speed to give the requisite number and size of perforations in the film.

Another suitable device for perforating the film comprises a rotatable roller provided on its cylindrical surface with a series of spaced knife edges, each of which provides a slit on contacting the film. The knife edges are positioned on the roller in accordance with the desired spacing and configuration of the slits in the film. Thus, in a preferred embodiment the film is provided with two sets of perforations, one adjacent each marginal edge of the film, the long dimension of the slits extending laterally of the film.

Preferably the two sets of perforations will be separated by a distance between their midpoints substantially equal to the distance between two adjacent seed drills. In this way the perforated film may be laid over two adjacent seed drills, so that the plants or seeds placed therein will be able to grow up through the perforations.

Indeed, in a preferred machine according to the invention there are provided means for forming one or more drills, means for sowing seeds therein, and means for perforating the film and laying it over the seedcontaining drills such that the perforations lie substantially directly above the seeded drills.

As the seeds germinate and the seedlings begin to grow, they will push themselves upwards through the perforations in the film.

The film perforating mechanism, whatever its precise construction, is attached to the support frame in such a way that film being drawn from the supply roll and laid on the ground is subjected to the action of the perforating device before it is laid on the ground. As the film is laid on the ground its marginal edges are held in place, e.g. by soil being scooped by coulter blades on to the edges of the film or by those edges being forced into the soil by means of discs, and the film is therefore tensioned between the ground and the roll. The tension in the film as it is subjected to the perforating operation may require to be carefully controlled, in order to avoid splitting of the film.When the perforating device involves a rotatable element, as in the case of a roller having projections or knife edges, a braking mechanism associated with the rotatable element may be used to control the tension in the film.

In a preferred embodimentthe perforations take the form of elongate zig-zag or "W"-shaped slits, a row of each being formed just inwards of each marginal edge of the film. These may suitably be formed by two rotatable idler rolls journalled on the support frame, each having a series of surface-mounted "W"-shaped knife edges.

The film may be of any material which is known for use in agriculture/horticulture as a mulching andr plant growth-assisting medium. Polyethylene is particularly suitable for this purpose. The film may be translucent or opaque, e.g. transparent, green or black, or may have differently coloured portions, e.g.

a black central portion to resist the formation of weeds and translucent marginal portions to assist plant growth. What will when laid will be the underside of the film may be coated or impregnated with fertilisers, herbicides and the like, the activity of which will be realised when in contact with the soil or with water. The film may be a bio-degradable film or photo-degradable.

The invention is now illustrated by means of the accompanying diagrammatic drawings, in which: Figure lisa sketch showing the principle of one embodiment of the invention; Figure 2 is a view of a length of film in which the perforations take the form of elongated slits; Figure 3 is a view of a length of film showing another form of slit; and Figure 4 is a perspective view of machinery for perforating and laying film.

Referring to Figure 1, an unperforated film 1 of plastics material, e.g. polyethylene, is passed into the nip of coacting rollers, 2,3. The rollers, 2,3 at their ends are provided with friction, e.g. rubber, surfaces 4, whereby rotation of one roller causes the other roller also to rotate. Suitable gearing could take the place of surface 4. The surface of roller 3 is provided with a series of spaced cylindrical projections 5, each of which may have a cutting edge.

In one embodiment the projections 5 may have a diameter of 1 cm., and they may be spaced axially and circumferentially of the roller, between 5 and 15cm., apart.

Roller2 has a surface against which projections 5 can act without damage. Thus, the surface 6 of roller 2 may be of a resilient, e.g. rubber or sponge-like, nature, or may alternatively be provided with spaced channels or recesses in which the projections 5 may be accommodated.

The rollers 2,3 will be caused to move by the pull of the sheet material by the material-laying part of the machine, and as the sheet material passes bet ween the rollers it will be perforated, as shown at 7.

In an alternative embodiment, the non-cutting rol ler need only touch the cutting rnllratthe ends, and could therefore be narrower along the remainder of its length so that it cleared the cutters witftout recourse to the provision of rncesse 0 rcha-n ne-Is. It could indeed even be replaced by two separate shor ter rollels.

The perforating mechanism may be attached very simply to sheet laying machine such that described in Specification 1,504,967, so thatthe advantages of using perforated sheet materialB,as outlined able, may be had.

Figure 2 ofthe accompanying drawing is a schematic view of a length of plastics film 1 in which perforations in! the form of elongated slits 10 have been formed, for example, by a roller, around which the unperforatedfllm passes, having two series of knife edges provided around its circumference at either axial end thereof. The distance apart of the two series of slits corresponds approximately to the distance between adjacent seed drills. The length and distance apart ofthe individual slits depends to a large extent on the crop being sown. For example for sowing and growing maize, each slit 10 is suitably 22to 3 inches long and is spaced 1 to 12 inches from its two neighbours.

Instead of slits extending across the film, as shown in Figure 2, they may extend longitudinally of the film. Although only straight slits are shown by way of example, the slits may be of any suitable shape and the configuration of the perforating means, e.g.

the knife edges, will be chosen accordingly.

Figure 3 illustrates a length of film which is similar to that of Figure 2 but has zig-zag or "W" shaped slits 110. These may be formed by means of the machin, ery illustrated in Figure 4.

Figure 4 is a perspective view of machinery for putting the invention into effect, being a simple modification of the device illustrated in U.K. Specification No. 1,504,967. It comprises a frame 50, suitably of welded angle iron, on which are mounted connecting links 52 foattachment to a tractor or other motorised machine.Mounted on each side of frame 50 is an upstanding arm 54 having a bifurcated upper end 56. The upper ends 56 of arms-54 receive and rotatably support the shaft 58 of a stock roll- 6Q, of, for example, unperforated polythene sheet Mounted on the frame 50 forward of the arms 54 is a freely rotatable shaft 62 upon each end of which is fast a roller 64 each of which carries six "W"-shaped knife blades 66.

Attached to the rear of frame 50 are T-bars 68,70.

Bar 68 carries a rotatable disc 72 and bar 7Q carries a rotatable disc 74. Compacting rolters 76 (which need not necessarily have the "square" configuration shown in the diagram) are resiliently mounted on the rear ends of bars 68, 70 through linkages 78 pivotally attached to brackets 80 attached to the bars. The force exerted by rollers 76 on the sheetcovered soil is variable through spring tensioning devices 82 mounted on linkage 78.

In operation, a pair of furrow-forming devices, suitably mounted at the front end of the frame 50, but not shown here, form two parallel furrows, and seeds are deposited therein, also by a seed sower mounted on frame 50 if desired. Film from roll 60 is passed around rollers 64 and then onto the ground into which its marginal edges are forced by discs 72 and compacting rollers 76. As the film passes around the rollers 64 the knife edges 66 slit the film in the manner illustrated in Figure 3. The lines of slits correspond to the two furrows, and when the seeds germinate and the plants begin to grow they push themselves up through the slits.

If desired a certain amount of slack may be put in the film before laying, for example by means of an attachment to frame 50.

Claims (7)

1. A machine for laying sheet material on the ground comprising a support frame, a roll of sheet material rotatably supported on the support sheet frame, means for causing the marginal edges of the sheet material to be retained in or on the ground, and means for perforating the sheet material as it is unwound from the roll thereof and before it is placed in contact with the ground.

2. A machine as claimed in claim 1 wherein the perforating means comprise two opposed rollers, one having spaced projections on the surface thereof and the other having a surface on which the projections act.

3. A machine as claimed in claim 1 wherein the spaced projections have cutting edges.

4. A machine as claimed in claim 1 wherein the perforating means comprises one or more rollers rotatably mounted on the support frame, each roller having a series of surface-mounted knife edges.

5. A machine as claimed in claim 1, substantially as hereinbefore described with reference to Figure 1 or Figure 4 of the accompanying drawings.

6. A machine as claimed in any of claims 1 to 5 wherein said support frame also mounts a pair of furrow-forming members.

7. A machine as claimed in any of claims 1 to 6 comprising also a pair of seed distributing mechanisms.