WO2007144399A1

WO2007144399A1 - Grafting device and method

Info

Publication number: WO2007144399A1
Application number: PCT/EP2007/055886
Authority: WO
Inventors: Jan Bakker; Wim Struyck
Original assignee: Iso Groep Machinebouw B.V.
Priority date: 2006-06-14
Filing date: 2007-06-14
Publication date: 2007-12-21
Also published as: EP2112876A1; MX2008016073A; NL1031999C2; TW200812472A

Abstract

A grafting element (1) is described for automated grafting of plant sections. The grafting element (1) comprises an expanded tube that can be caused to contract both radially and axially onto the graft. The graft element (1) may be used in an automated grafting machine for automatically expanding the graft element (1) using air pressure or the like. A pre-expanded graft element (1) is also disclosed.

Description

GRAFTING DEVICE AND METHOD

The present invention relates generally to grafting devices and more particularly to devices for grafting together plant stem sections. The invention further relates to a method of grafting and a graft element to be employed in the method. Background of the Invention

It is well known in the fields of horticulture and fruit that a plant section of a preferred species of plant may be transplanted onto a section of a hardier species. The plant will then grow, having the qualities of the preferred species while enjoying benefits such as resistance to disease of the hardy species. The plant section of the preferred species to be grafted is referred to as the scion. The section of hardy plant onto which is grafted is generally called the root stock.

For certain plant races and species, grafting is systematic. Almost every rose plant consists of a scion of a selected species grafted onto a hardy root stock. Grape vines are also generally grafted. The process of grafting normally involves selecting appropriate scion and root stock sections, cutting the sections on a diagonal angle and bringing the diagonal faces of the graft together. The graft must then be held or supported sufficiently to allow the two sections to grow into one another. The graft should, where necessary, also be protected from the environment to prevent infection or damage. The process is generally labour intensive. In the past, the graft has been held together in various ways. One manner of grafting uses a conventional clothes peg to apply pressure to the graft. The use of such pegs is generally unsuitable for various reasons: the peg is relatively heavy for small plants (especially non-woody plants); each peg is relatively expensive; after use, the pegs must be removed and usually discarded; the overall success rate is low, leading to considerable wastage of plants, labour and space. Attempts have been made to produce specially adapted clips for grafting purposes. One such device is known from FR2693623 A which discloses a miniature clip formed of an elastic material. The clip is in the form of a slotted tube that can be opened and closed around a stem. The clip can also receive a support stick or splint, which may assist in supporting the graft. The clip is also considerably lighter than a clothes peg and more suited for use on soft-stemmed plants such as tomatoes and cucumbers. Nevertheless, individual placement of such clips by hand remains a time consuming occupation and can encourage the spread of plant diseases. It is also necessary to provide appropriately sized clips according to the size of the stem. A number of alternative devices have also been suggested. One device according to WO 95/21250 suggests the use of a reliable sleeve formed of an elastic material. The sleeve is initially in the form of a ring and is subsequently rolled out to cover the graft. The material of the sleeve may be biodegradable. Although, the device appears to be an improvement over the use of a clothes peg, its manufacture and deployment is relatively complex.

A further device for grafting vines is suggested in FR 1260228 A, which discloses a tubular element of a plastic or rubber material having a certain elasticity such as not to restrict growth of the plant stem. The tubular element is placed onto the root stock prior to grafting and after the graft is complete, may be lifted up to cover the graft. After the graft has healed, the tubular element may be cut away. The tubular element may be provided with holes to allow respiration of the graft and may also have incorporated fungicides or the like. Such manual grafting is both time consuming and subject to human error.

In the light of the problems associated with the prior art, it would be desirable to provide an alternative procedure for grafting. There is in particular a need for a grafting device that can simply and efficiently perform grafting on plants having stems of different dimensions and strengths. There is furthermore a need for a graft element that is easily applied and can support and protect the graft during the time taken for the graft to heal and can subsequently be disposed of. The grafting procedure should be cheap and simple to carry out while ensuring good graft success. It would also be desirable that the process be applicable to soft stemmed plants.

Statement of Invention

The present invention addresses these problems by providing a method of grafting together a first and a second plant section, comprising: providing a tubular graft element having a radially expanded state; inserting the first and second plant sections into the tubular graft element; and allowing the graft element to contract into intimate contact with the plant sections to retain and support them during healing. By providing the tubular graft element having an expanded shape, the plant sections may be easily inserted without risk of damage to the plant. Furthermore, plants sections of different dimensions and in particular, unmatched dimensions may be easily accommodated. On subsequently allowing the graft element to contract, the plant sections may be tightly held and also protected. The natural strength of the graft element may be sufficient to support the plant during healing or alternatively, further supporting elements may be used or integrated into the graft or graft element to provide additional support. The graft element may be formed of any suitable material that allows contraction from an expanded or enlarged state to a contracted state. Such materials may include shape memory materials or the like, responsive to temperature or other factors. Preferably, the graft element comprises a resilient tube e.g. made of an elastomeric material. Such materials have been found most desirable as they are relatively cheap. In this context, the term tube is intended to denote a closed tube i.e. one having a continuous perimeter. Such a closed tube is believed to be particularly advantageous in promoting healing. By maintaining pressure on the graft, fluids produced by the root section are retained and are at least partially prevented from escaping. The increased fluid pressure within the tube encourages the scion to drink. In one embodiment, such a tube may be brought into or held in the radially expanded state by applying a pressure differential between an interior and an exterior of at least a part of the tube. This may be achieved by pressurizing the inside of the tube to blow it up. Alternatively or additionally, a vacuum may be applied to an exterior of the tube to cause or assist it to expand. In a further embodiment, the graft element comprises radially extending gripping elements and may be brought into the radially expanded state by gripping the gripping elements and applying a radially directed force. This may be achieved by gripping an integrated profile provided on an exterior of the tube for this purpose. Alternatively, the gripping elements may be formed from a tube having an otherwise smooth exterior by folding or rolling back portions of the tube. Other devices that may be inserted into the interior of the tube to expand and retain it and subsequently withdrawn may also be used as appropriate. In an alternative embodiment, the tube may be held in a radially expanded state by molecular forces as may be the case with shape memory material or in the case of unvulcanised rubber. After insertion of the plant stems for grafting, the molecular forces may be released e.g. by a temperature change, electrical signal or by addition of a vulcanizing agent to unvulcanised rubber.

According to a particularly important aspect of the present invention, at least a portion of the graft element may also have an axially expanded state. In this manner, the graft element may contract both radially and axially into intimate contact with the plant sections, whereby an axial force is applied to bias the first and second plant sections towards one another. In general, when a plant stem is cut for grafting, root pressure in the root stock may cause the scion and root stock to be pushed apart. By applying an axial pressure, this may be prevented and improved healing may be achieved. Preferably, the method of allowing the graft element to contract comprises controlling the relative axial and radial contraction. The graft element may thus be allowed to first contract radially into contact with the plant sections. Thereafter, the axial tension may be released, which can thus be transferred to the plant sections to pull them together. An important aspect of the invention is the ability to control the contraction of the graft element as required.

According to a most favourable configuration of the invention, the graft element may be formed from a continuous tube by separating individual graft elements from the continuous tube. Such a method of forming graft elements is extremely efficient and cheap, in particular, when the graft elements are separated at the point of grafting in a substantially continuous process. A preferred method of separating the graft elements from the continuous tube is by applying tension to at least part of the tube and piercing that part with a sharp, such as a needle or blade. Other methods of separating e.g. using heat may also be used.

According to a yet further preferred form of the invention the material of the graft element is selected to degrade during the healing of the graft. A period of from 3 to 20 days may suffice for this purpose, depending upon the nature of the plant. The material may comprise natural rubber or similar compounds that are degraded easily when subjected e.g. to UV radiation. Alternative mechanisms such as heat, moisture additives and chemicals may be used to carefully adjust the period of degradation as required. In this context, degradation is intended to refer to loss of its physical properties. In particular, it has been found desirable that during the healing period, the graft element degrades at least to a point that its radial tension is substantially overcome. Most preferably, bio-degradable materials are used which may nevertheless remain present throughout the lifetime of the plant but which subsequently decompose with the plant.

According to a further aspect of the invention, a graft element may be provided comprising a material having incorporated beneficial agents for controlled release thereof. The agents may be generally beneficial to the plant such as minerals or may be specifically directed to improving the graft e.g. graft promoters or healing of the wound e.g. by preventing infection.

In a first exemplary embodiment of the invention, the method may comprise: inserting a section of a substantially continuous elastomeric tube into a cavity having a cross-section substantially larger than the tube and having corner spaces formed by at least partially movable cavity walls; applying pressure to an interior of the tube to expand it into contact with the cavity walls; moving the cavity walls to pinch the elastomeric tube in the region of the corner spaces; releasing the pressure in the interior of the tube; forming a vacuum in the cavity around an exterior of the tube; axially stretching portions of the tube extending from the cavity; severing the axially stretched portions adjacent to the cavity to form the tubular graft element.

The method may further comprise pressurizing the cavity around the exterior of the graft element subsequent to inserting the first and second plant sections into the tubular graft element in order to bring the graft element into initial contact with and centre the plant sections and moving the cavity walls to release the graft element from the corner spaces.

The present invention also relates to a graft element comprising a tubular section of elastomeric material having first and second ends, the tubular section being provided with radially extending gripping elements adjacent to at least its first and second ends. Preferably the elastomeric material comprises natural rubber. In order to provide the correct degree of support to the plant while avoiding strangulation or constriction, the material should preferably be susceptible to elongation to more than 400 %. It has also been found that a ratio of wall thickness to lumen diameter of between 0.35 and 0.7 is desirable. For use with soft stemmed plants, the graft element material may be substantially degradable on exposure to sunlight for a period of around 7 to 20 days, which is usually sufficient for the graft to heal. For woody plants, the period of degradation may be longer. The thickness and strength of the material may be selected to provide a particular amount of pressure on the graft. The fluid pressure on the graft may also be regulated by selecting a porous material that allows certain fluids to escape. This may also operate to perform a filtering function. In a most preferred embodiment, the gripping elements comprise a plurality of longitudinally extending profiles extending along the tubular section between the first and second ends to be gripped or retained by an expansion device. Such profiles may be easily manufactured by extrusion techniques.

The graft element may be supplied in a pre-extended state e.g. provided with appropriate clips or other retaining structure to maintain it in its extended state until the moment of use. Alternatively, it may be expanded at the point of use by means of a suitable machine or hand tool.

The present invention further relates to a grafting apparatus for applying a tubular graft element to join first and second plant sections, the apparatus comprising: expanding means for expanding the graft element; retaining means for retaining the graft element in an expanded state; control means for actuating the retaining means to retain and subsequently release the graft element thereby allowing the graft element to contract into intimate contact with the plant sections to retain and support them during healing of the graft. Preferably, the expanding means can expand the graft element both radially and axially. One manner of achieving this is by pneumatic means wherein the expanding means comprises a source of pressure and means to apply the pressure to an interior of the tubular graft element. The pneumatic pressure may also be combined with mechanical stretching of the tube. Although reference is made to the application of pressure within the tube, it will be evident to the skilled person that a vacuum provided on the exterior of the tube may also be used, at least partially, in expanding and retaining the graft element in its expanded state. Alternatively or additionally, other mechanical apparatus for expanding the graft element may of course be envisaged. Thus, grippers that pinch an exterior of the graft element or fingers that expand the graft element from within may be considered.

According to one functional embodiment of the apparatus according to the invention, the retaining means comprises a cavity having corner spaces formed by at least partially movable cavity walls. The cavity walls are movable to pinch portions of the graft element. The movable portions of the cavity walls are thus embodied as gripping elements that retain the graft element around its circumference in the radially expanded state. Use is made of pneumatic pressure to expand the graft element into the gripping elements, thus avoiding the need for the gripping elements to move in the radial direction. For many situations, the cavity is preferably separable or may be opened to allow the grafted plant to be laterally removed therefrom. For certain applications, a fixed cavity may be used whereby either a pre-expanded graft element or the grafted plant is removed axially.

According to a further feature of the inventive apparatus, a cutter may be provided for separating the graft element from a substantially continuous supply of graft element material. It has been found especially desirable to provide a continuous supply of graft element material and to cut it into individual sections at or near the point of forming the graft. In this manner, wastage may be kept to a minimum.

The grafting apparatus may further comprise transport elements for transporting the first and second plant sections and inserting them into the expanded graft element. The process of grafting may thus be substantially automated allowing greater efficiency, accuracy and speed in the placement of the plant sections into the graft element.

The grafting apparatus may also further comprise at least one knife for automatically cutting the ends of the first and/or second plant sections prior to inserting them into the expanded graft element. By ensuring that the plant sections are cut shortly before insertion, increased grafting success may be achieved. By automated cutting in combination with the use of transport elements, correct angular orientation of the respective first and second plant sections may be ensured. Traditional grafting requires the plant sections to be cut and joined on a diagonal angle. It is however noted that as a consequence of the axial bias that may be applied by the graft element, a butt joined connection may also be employed. Other rotationally symmetrical forms of cutting the plant sections may be used to improve healing of the graft and reduce the burden or accurately orienting the plant sections to one another.

The invention further relates to the provision of a graft comprising first and second axially aligned plant sections and a tubular graft element retained in both radial and axial tension around the first and second plant sections. As indicated above, the graft element preferably comprises a UV degradable elastomeric material. Most particularly, the plant sections forming the graft are soft stemmed plants. In this context, soft stemmed is intended to refer to non-woody plant stems. Especially suitable for this purpose are tomato, paprika, aubergine, and similar plants as well as plants such as melons and cucumbers. Although the invention has been described in relation to first and second plant sections, it may be understood that the invention may equally apply to the joining of three or more plant sections. Thus, two scions may be grafted to a single root stock using either a cylindrical shaped tubular graft element or using a specially shaped (e.g. Y-shaped) element. It may also be considered that three sections could be grafted together in series using the present invention, by placing a third stem section between e.g. an otherwise incompatible scion and root stock.

Brief Description of the Drawings

The invention will be described below with reference to a number of examples using an elastic tube or sleeve for grafting. Fig. 1 shows a pre-tensioned graft element according to the invention;

Fig. 2 shows a view of the graft element of Fig. 1 during the forming of a graft; Fig. 3 shows a graft machine according to the invention in exploded view; Fig. 4 shows the graft machine of Fig. 3 in its starting position; Figures 5 to 26 show all steps in the operation of the graft machine of Fig. 3 during the making of a graft;

Figures 27 to 29 show a second embodiment of a graft element according to the invention; Figures 30 to 36 show further embodiments of profiled graft elements according to the invention;

Figure 37 shows a second embodiment of a graft machine according to a further aspect of the invention; and

Figures 38 to 45 show a number of steps in the operation of the graft machine according to Figure 37.

Description of Illustrated Embodiments

Fig. 1 shows a graft element 1 for forming a graft according to the invention. Graft element 1 comprises a tubular piece of rubber which in its untensioned state has an outer diameter of 3,4mm, an inner diameter of 1,9 mm and a length of 15 mm. According to Fig. 1, graft element 1 is held in an open or tensioned condition by two split rings 3, 4. In its tensioned state, graft element 1 has an inner diameter of around 4 mm. The cut stem of a root stock 2 is inserted from one side into the open graft element. The cut stem of a scion 5 is inserted from the other side of the graft element.

From Fig. 2 it can be seen how the graft is formed by releasing the graft element onto the stems 2, 5. After positioning the stems 2, 5, the rings 3, 4 are pulled outwards. Rings 3, 4 are provided with extended fingers 7,8. The fingers 7 of ring 3 fit between the fingers 8 and can support against the ring 4 in order to maintain the graft element 1 in its tensioned state. The same applies for the fingers 8 of ring 4, which can support against ring 3. On retracting the rings 3, 4, the fingers 7, 8 can bend whereby the graft element 1 comes into contact with stems 2, 5. After releasing the graft element 1, the rings 3, 4 are removed from the stems 2, 5 and may be disposed of or reused. The positioning of the stems and the removal of the rings may take place by hand or may be automated.

The mounting of the graft element 1 on the rings 3, 4 is preferably performed by a graft machine 100. An example of a graft machine that can mount a flexible tube onto a tensioning structure is shown in Figs 3 and 4. This machine can also be used for directly forming a graft by stretching a graft element and then allowing it to contract onto the stems to be joined. This method of operation is explained in greater detail in relation to Figures 5 to 26. The graft machine 100 is shown in exploded view in Figure 3, from which the following elements can be recognised: mould 15, left piston 18, left pinch tube 19, sharp 20, piston front face 21, pin ring 22, pinch clamp 23, pinch ring 24, electromagnet 25 for retaining the pinch ring in gripping position, tube cutter 26, right piston 27, clamp 28 in piston 27, right clamp tube 29, movable clamp 30 in piston 27, tube guide-reel 31, electrically driven tube guide-reel 32, in-feed tube 33, weight adjustable tube guide-reel 34, electromagnet 35 to connect piston 27 with pinch clamp 23, and metallic part 36, which is integral with piston 27, for use with electromagnet 35.

Operation of the graft machine 100 is as follows. In the matrix 15, graft element 1 is inflated by means of compressed air. The graft element is formed of rubber and can be stretched to up to 400% of its length and diameter. After expansion, the graft element is held in its inflated state by means of vacuum while the root stock 2 and scion 5 are inserted into the matrix 15 from either side. Once they are correctly positioned, the vacuum in the matrix is stopped. In this manner the central section of the graft element is released onto the stems, it grips them gently. Thereafter the outer edges of the graft element are released whereby the complete graft element springs onto the stems 2, 5. The graft is complete. The matrix 15, which is formed in sections, is then allowed to open such that the graft can be removed.

Loading of the graft element takes place in a cycle comprising a number of steps. This will become clear in the light of Figs 4 to 28 which show the steps of the cycle. The starting position of the graft machine is shown in Fig. 4 whereby the following is to be seen: the pistons 18 and 27 are fully inwards, i.e. as far as the centre of the matrix; the tube 33, which passes through the centre of the piston 27, is sufficiently far forwards in piston 18; clamp 28 is gripping; clamp 30 is released; the tube transport, comprising clamp 30 and tube guide-reel 31 are inwards; the pinch tubes 19, right and left are fixed; the pin rings 22, left and right are inwards; the pinch clamps 23, left and right, are inwards, the pinch clamp magnets 35, left and right are off; the pinch retention magnets 25, left and right are off; the tube inflation valve (not shown) is off; the sharps 20, left and right are outwards; the tube cutter 26 is open; the matrix is closed; the matrix is located on the graft machine 100. In Fig. 5 compressed air P is blown inwards from the centre of the piston 18 whereby tube 33 becomes pressurised. The tube 33 is hardly expanded as it is constrained within the relatively narrow pinch tubes 19. Clamp 30 is also moved, together with tube guide reel 31, two steps outwards. See also Fig. 12. This has no influence on the tube 33 within the matrix 15. In Fig. 6 the pistons move outwards until their heads approach the end of the pin rings 22. These pin rings 22 comprise rings on which a plurality of pins 22 A are mounted in circular form. These pins 22A together form a sort of cage which provides adequate support for the tube 33 in its expanded state. By such a construction it is possible to actuate the pinch rings 24, which are located inside the cages, from the outside of the cage.

The pinch rings 24 are biased outwardly by springs (not shown) into engagement with an abutment (not shown) adjacent to the end of the pin rings 22. During the outwards movement of the pistons 18, 27, the tube 33 expands until it engages the inner surface of the matrix, and thereafter the inner surface of the pin rings 22. The tube 33 comprises a homogenous elastic material, whereby during inflation both the diameter and the length of the tube 33 can increase. In this manner, relatively little of the tube 33 is pulled from the pinch tubes during the movement of the pistons 18, 27.

Once the pistons 18, 27 stop at the end of the tube 33, their ends are level with the front of the pinch rings 24, and form effectively therewith a slightly larger piston. In Fig. 7 the pinch tubes 19 are retracted slightly, whereby a pinch space 19A is created between the pinch tubes and the pistons 18, 27. As a result of the pressure, the tube 33 is partially pushed into these spaces. Additionally, the pinch clamp magnets are activated, whereby the pistons 18, 27 are automatically mechanically connected to their respective pinch clamps. In Fig. 8 the pinch tubes are once again closed. Because the tube 33 was partially pushed into pinch spaces 19A between the pinch tubes and the pistons 18, 27, the tube is now pinched on both sides. At the same time, the pistons 18, 27 are moved inwards. Since the pistons 18, 27 are now connected by the pinch clamp magnets 35 to the pinch clamps 23, these are also moved inwards. The pinch clamps 23 in turn, push the pinch rings 24 inwards, whereby the tube 33 is rolled up on the outside of the pinch rings 24. This continues until the tube 33 is caught between the slanted sides of the pinch rings 24 and the slanted sides of the matrix 15. Between the pinch rings 24 and the pins 22 A of the pin ring 22, the tube 33 is formed into a fold. A certain quantity of air is held in these folds in a completely enclosed state. This air is useful on opening the pinch rings 24 (see Fig. 22 below) for ensuring that the tube 33 rolls off the pinch rings 24 rather than sliding off. In this manner the chance that an inwardly folded end of the tube remains after grafting is reduced.

In Fig. 9 the pinch retention magnets 25 are actuated whereby the pinching of the tube remains even after the pinch clamps are retracted. These are four magnets in total, since the matrix is split left and right and up and down. Furthermore, a vacuum is produced and supplied to the central part of the matrix 15 via channel 15 A. The inflated tube 33 is now surrounded by a vacuum, whereby the tube 33 remains expanded even if the air pressure within the tube is reduced. Because the matrix 15 is split, there will, in practice, always be some leakage and it is therefore desirable to continuously produce vacuum. It is of course also understood that with a non-split matrix, leakage would be so minimal that the tube would itself be able to hold a vacuum. At this point in time the compressed air supply from the centre of the piston 18 can be switched off and the interior of the tube is depressurised. In Fig. 10 the pinch clamp magnets 35 are switched off. In this manner, the mechanical connection between the pistons 18, 27 and the pinch clamps 23 is broken. The pinch clamps 23 are moved outwards. The pin rings 22 are moved outwards. The pistons 18, 27 are moved outwards. The tube 33 is thus stretched between the pinch tubes 19 and the pinch rings 24. In Fig. 11 the sharps 20 are moved inwards. At the point where the tube 33 is contacted by the sharps 20, the axial tension in the tube 33 is greater than the radial tension (in this state, the tube is stretched more in its length then in its diameter). As a result, the tube 33 tears from the point of piercing circumferentially in both directions. In Fig. 12 the sharps 20 are again retracted. The loading of the matrix 15 is thus complete. A free piece of tube 33 is now held against the matrix 15 by the co-operation of the pinch rings 24. This piece of tube will henceforth be referred to as graft element 1. Once it has been checked that the pinch clamps 23 and the pin rings 22 are completely retracted, the matrix is ready to depart to the grafting table. Now the matrix 15 departs with the graft element 1 to the grafting table where the actual grafting takes place. While it is away, a number of operations are performed. These operations are performed simultaneously with the actual grafting.

In Fig. 13 the clamp 30 is closed. Clamp 30 can be moved backwards and forwards in two steps, each with its own stroke. The tube guide reel 31 is also part of this mechanism and thus also moves with it in the delivery direction.

In Fig. 14 the clamp 28 opens. Prior to clamp 28 opening, there was a tension in the tube 33 between clamp 28 and the end of the piston 27. This tension was produced when, in Fig. 6, the pressurised tube 33 was partially withdrawn from the piston 27. A tension was also present in the tube 33 between clamp 28 and clamp 30 - the tension by which the tube 33 is delivered. This delivery tension is adjustable in order to avoid kinks in the tube 33. Once the clamp 28 is opened both of these tensions are equalised to an intermediate tension.

In Fig. 15 the clamp 30 together tube guide reel 31 is moved two steps inwards. In this manner, the tube 33 is partially compressed between the end of the piston and the clamp 30.

In Fig. 16 the pinch tubes 19 are opened. Hereby, the off cut 33 A remaining in the piston 18 is freed. In the piston 27, the tube 33 moves outwardly under the influence of the force described in relation to Fig. 15 above. This is desirable, not least in order to prevent that it should retract into the pinch space 19A at the front of the piston 27. Due to the expansion of the tube 33 there remains a slight cone 33B at its end. Were the tube 33 not to move forwards in the piston 27, then the cone would be difficult to remove from the pinch space 19A.

In Fig. 17 the pinch tubes 19 are once again closed. As there is no pressure within the tube 33, it is not pinched and the closure of the pinch tubes 19 has no influence on it. Simultaneously, clamp 28 is closed.

In Fig. 18 clamp 30 is opened. Clamp 28 and clamp 30 cannot be opened together in this procedure, as then the tube 30 would be drawn uncontrollably backwards by the weight on tube guide reel 34 (Fig. 3). Simultaneously, tube cutter 26 is actuated, whereby the tube 33 is cut ahead of the face of the piston 27. Furthermore, compressed air is blown into the centre of piston 18, whereby the off cut 33 A is blown away.

In Fig. 19 the compressed air to piston 18 is again switched off and the tube cutter 26 opened. Furthermore, clamp 30 together with tube guide-reel 31 is carried two steps outwards. This does not cause movement of the tube 33 within the head of the piston 27, since the clamp 28 is closed.

Figures 2OA, B, C show how a new length of tube 33 is subsequently loaded. In Fig. 20 A clamp 30 is again closed. Thereafter, in Fig. 2OB, clamp 30 together with tube guide-reel 31 is carried one step inwards. In so doing, the tension that was present in the tube between clamp 28 and clamp 30 ceases. In Fig. 2OC clamp 28 is again opened. This does not cause tube 33 to shift since both in front of and behind the clamp there is no tension in it. On completion of this step, the graft machine 100 is prepared, as completely as possible, for a subsequent loading cycle. In this state, it waits for a number of further operations of the machine that are necessary for the grafting operation. As soon as the matrix 15 has returned from the graft table, completion of the loading cycle can be continued.

Fig. 21 shows the matrix 15 during the delivery of the stems. In order to commence grafting, the vacuum is discontinued. Furthermore, air is delivered to the matrix 15 through channel 15 A, whereby the diameter of the graft element is reduced. On insertion of the root stock 2 and scion 5, these are lightly gripped and centred by the graft element Hn the middle section of the matrix 15. In Fig. 21 the stems are inserted into the already narrowed graft element 1. It is of course also possible to introduce air only after the stems have been introduced. A consequence of air introduction into the graft element 1 is that it is also subjected to an additional, controlled tension in the axial direction.

Thereafter, in Fig. 22, the pinch retention magnets 25 are switched off. The pinch rings 24 that were pressed against the matrix against the spring bias are thereby opened. On opening, the extremities of the graft element 1 spring onto the root - stock 2 and scion 5 to complete the actual grafting procedure. Since the middle section of the graft element 1 is already in contact with the stems prior to opening the pinch rings 24, a part of the axial tension remains. This tension is applied to the stems by friction as an axial force that forces the cut surfaces of the stems together in their lengthwise direction. On release of the graft element 1, the air supply to the matrix 15 is stopped. At the same time matrix 15 is opened whereby it is ready to return to the graft machine 100. In relation to Fig. 21 and 22 it is described how stems 2, 5 are introduced into the matrix 15. It is of course also understood that a tensioning structure could be applied in or around the graft element in order to produce a pre-tensioned graft element that could be subsequently used at another place or time..

In Fig. 23, the matrix 15 is again located between pistons 18, 27 in the graft element loading position of the graft machine 100.

As soon as the matrix 15 arrives at the graft machine 100, then, according to Fig. 24, the pistons 18, 27 are driven inwards. Furthermore, the pin rings 22 and the pinch clamps 23 are driven inwards.

In Fig. 25 clamp 30 together with tube guide-reel 31 are moved one step inwards. In this manner the tube is transported into the piston 18.

In Fig. 26 clamp 28 is again closed. On again reopening clamp 30, everything is once more in the initial state as described according to Fig. 4 and the cycle can begin again.

An alternative embodiment is shown in Fig. 27 to Fig. 29. In Fig. 27 a preformed tubular graft element 50 is used with enlarged upper and lower rims 51. Just as in the first embodiment, the graft element 50 is manufactured of rubber. The graft element is held on a graft machine by four grippers 54 and is pulled both in the radial and the axial directions (Fig 28). In this manner, the graft element 50 deforms into a square-like tube with a large opening (Fig 29). The enlarged graft element can now be moved to the grafting table to receive a root-stock and scion in the same manner as in the first embodiment. It will be recognized that these embodiments are susceptible to various modifications and alternative forms well known to those of skill in the art. For example, the graft elements as described above may alternatively be expanded by mechanical members inserted into the lumen of the elastic tube. Alternatively, the graft element of Fig 27 may be expanded by pneumatic force as in the first embodiment. A number of further alternative embodiments of a profiled graft element 60 are shown in Figs. 30 to 36. According to the embodiments of Figs. 31, 32, 33, 34 and 36, the graft element 60 comprises longitudinal ribs 62 that may be gripped by suitable grippers of a graft machine or hand tool in order to expand the graft element 60. Expansion may take place both radially and axially as required. According to the embodiments of Figs 30 and 35, longitudinal lobes 64 are provided for receiving suitable expansion members of a graft machine or hand tool. Although in each case, three ribs 62 or lobes 64 are shown, a greater number may be provided. The ribs 62 or lobes 64 may if desired be severed and removed on completion of the graft procedure. Additionally, the graft elements 60 of Figs 34 and 36 are provided with support retention channels 66 which may receive a suitable member for providing support to the graft or plant. The lobes 64 may also be used for this purpose. Although most embodiments are shown having a circular lumen 61 passing through the graft element 60, it is noted that the embodiment according to Figure 30 shows that a triangular lumen 61 may be provided. The skilled person will be aware that many alternative lumen cross-sections may be provided according to the required use, both in the case of Figures 30 to 36 and in relation to the earlier embodiments of Figures 1 to 29.

A second embodiment of a graft machine 200 is shown in Figure 37. Graft machine 200 is in particular adapted for operation with a profiled graft element 60 as shown in Fig. 32.

Graft machine 200 comprises a carrousel 202 having a scion supply 204, a rootstock supply 206 for transporting a plurality of plants carried in transport cups 208. Transport cups are for receipt of rooted plants and comprise stable, weighted cups that can be easily handled by automated machines. They are generally conventional and will not be described further. The carrousel 202 comprises an upper disk 210 onto which the scions are placed and a lower disk 212 which receives the rootstock supply 206. Graft machine 200 also comprises four grafting stations 212, of which only one is presently shown and described. The carrousel 202 is arranged to rotate relative to the grafting stations 212. It will be understood that the carrousel 202 may be provided with any number of grafting stations 212 and that the invention may also be performed without use of a carrousel. A conveyor 207 for removal of grafted plants 240 connects with lower disk 212. Each grafting station 212 comprises a scion inserter module 214, a matrix 215 having three pairs of jaws 216, a root stock inserter module 218 and a tube introducer 220. The scion inserter module 214 includes scion gripper 222, scion cutter 224 and scion centring device 226. Similar elements (not shown) are provided for the handling of the root stock. The tube introducer 220 is shown schematically and includes a tube cutter that operates by stretching a portion of graft element material and applying a sharp to the tensioned tube. This causes the oriented elastomeric material to tear as described above in relation to Fig. 11. Operation of the graft machine 200 will be described with reference to Figures 38 to 45.

Fig. 38 shows the jaws 216 in their fully open position. In Fig. 39, the jaws 216 are moved inwards and a graft element 60 is inserted and cut to length by tube introducer 220. Although three pairs of jaws 216 are shown arranged in a triangular configuration, it is understood that other jaw configurations may also be used according to the chosen form of graft element 60. It is also understood that the graft element 60 may alternatively be provided in pre-cut or pre-formed lengths. In Fig. 40, the jaws 216 close completely to grip the ribs 62 of graft element 60 and in Fig. 41, the jaws 216 are drawn apart to radially stretch the graft element 60 into an open position. At this point a scion 5 is gripped by scion gripper 222 and removed from a transport cup 208 on upper disk 210. The empty transport cup 208 continues rotating with carrousel 202 and will be collected and removed for reuse by suitable means (not shown). The scion 5 is then centred by scion centring device 226 prior to being cut by scion cutter 224. A similar procedure is performed with a root stock 2, although in this case, the root stock 2 remains in its transport cup 208.

As shown in Fig. 42, scion 5 is then introduced from above by scion inserter module 214 into the open graft element 60. Root stock 2 is introduced from below by root stock inserter module 218. Once correctly positioned, the jaws 216 are partially allowed to return causing the graft element 60 to partially close and centre the stems as shown in Fig. 43. Relaxing of the graft element 60 in the radial direction enables the next step in the procedure to be performed. In Fig. 44 the jaws 216 are operated to stretch the graft element 60 in an axial direction. As can be seen, each pair of jaws comprises five pairs of grippers 254. The grippers 254 can be axially spread with respect to one another within the matrix 215 to cause elongation of the graft element 60. At this point, the jaws 216 are then moved together and opened to release the graft element 60 onto the stems of the scion 2 and root stock 5. The axial extension of the graft element 60 is maintained due to friction against the stems causing the cut faces of the graft to be pulled towards each other as described earlier.

In Fig. 45, the graft element 60 has been released and the jaws are again fully opened such that the grafted plant 240 may be easily removed from the matrix 215. The grafted plant 240 together with its transport cup 208 proceeds on the lower disk 212 of the carrousel to a point where it is removed on conveyor 207. Many further modifications in addition to those described above may be made to the structures and techniques described herein without departing from the spirit and scope of the invention. Accordingly, although specific embodiments have been described, these are examples only and are not limiting upon the scope of the invention.

Claims

1. A method of grafting together a first and a second plant section, comprising: providing a tubular graft element in a radially expanded state; inserting the first and second plant sections into the tubular graft element; and allowing the graft element to contract into intimate contact with the plant sections to retain and support them during healing.

2. The method of claim 1, wherein the graft element comprises a resilient tube and the graft element is retained in the radially expanded state by gripping at a circumference of the tube.

3. The method according to any preceding claim, wherein the graft element comprises radially extending gripping elements and the method further comprises bringing the graft element into the radially expanded state by gripping the gripping elements and applying a radially directed force.

4. The method according to any preceding claim, further comprising axially extending at least a portion of the graft element, such that the graft element may subsequently contract radially and axially into intimate contact with the plant sections, whereby an axial force may be applied to bias the first and second plant sections towards one another.

5. The method according to any preceding claim, wherein the step of allowing the graft element to contract comprises controlling the contraction.

6. The method according to any preceding claim, wherein the graft element comprises a continuous tube and the method comprises separating individual graft elements from the continuous tube while subjecting the tube to axial tension.

7. The method according to any preceding claim, further comprising allowing the graft element to degrade during the healing of the graft.

8. The method according to any preceding claim, wherein the graft element comprises a resilient tube and the method comprises bringing the tube into the radially expanded state by applying a pressure differential between an interior and an exterior of at least a part of the tube.

9. The method according to any preceding claim, comprising: inserting a section of a substantially continuous elastomeric tube into a cavity having a cross-section substantially larger than the tube and having corner spaces formed by at least partially movable cavity walls; applying pressure to an interior of the tube to expand it into contact with the cavity walls; moving the cavity walls to pinch the elastomeric tube in the region of the corner spaces; releasing the pressure in the interior of the tube; forming a vacuum in the cavity around an exterior of the tube; axially stretching portions of the tube extending from the cavity; and severing the axially stretched portions adjacent to the cavity to form the tubular graft element.

10. The method according to claim 9, further comprising: pressurizing the cavity around the exterior of the graft element subsequent to inserting the first and second plant sections into the tubular graft element in order to bring the graft element into initial contact with and centre the plant sections; and moving the cavity walls to release the graft element from the cavity.

11. A graft element for joining together a first and a second plant section, the graft element comprising a tubular section of elastomeric material having first and second ends, the tubular section being provided with radially extending gripping elements adjacent to at least its first and second ends.

12. The graft element according to claim 11, wherein the material is susceptible to elongation to more than 400 % and has a ratio of wall thickness to lumen diameter of between 0.3 and 0.7 in the unexpanded state.

13. The graft element according to claim 11 or claim 12, comprising natural rubber and being substantially degradable on exposure to UV light.

14. The graft element according to any of claims 11 to 13, wherein the graft element is porous.

15. The graft element according to any of claims 11 to 14, wherein the graft element is provided with beneficial agents for controlled release thereof.

16. The graft element according to any of claims 11 to 15, wherein the graft element is additionally held in an axially extended state.

17. The graft element according to any of claims 11 to 16, wherein the graft element comprises a retaining structure to hold it in its extended state prior to use.

18. The graft element according to any of claims 11 to 17, wherein the gripping elements comprise a plurality of longitudinally extending profiles extending along the tubular section between the first and second ends to be gripped or retained by an expansion device.

19. The graft element according to any of claims 11 to 18, wherein the tubular section comprises a lumen of non-circular cross-section.

20. An apparatus for applying a tubular graft element to join first and second plant sections, the apparatus comprising: an expansion device for expanding the graft element and for retaining the graft element in an expanded state; and a control device for actuating the expansion device to retain and subsequently release the graft element thereby allowing the graft element to contract into intimate contact with the plant sections to retain and support them during healing of the graft.

21. The apparatus according to claim 20, wherein the expansion device can expand the graft element both radially and axially.

22. The apparatus according to claim 20 or claim 21, wherein the expansion device comprises a source of pressure and means to apply the pressure to an interior of the tubular graft element.

23. The apparatus according to any of claim 20 to 22, wherein the expansion device comprises a cavity having corner spaces formed by at least partially movable cavity walls, the movable cavity walls being movable to pinch portions of the graft element.

24. The apparatus according to any of claim 20 to 23, further comprising a device for separating the graft element from a substantially continuous supply of graft element material by applying tension to the graft element material and contacting with a sharp.

25. The apparatus according to any of claim 20 to 24, further comprising transport elements for transporting the first and second plant sections and inserting them into the expanded graft element.

26. The apparatus according to any of claim 20 to 25, further comprising at least one knife for automatically cutting the ends of the first and/or second plant sections prior to inserting them into the expanded graft element.

27. The apparatus according to any of claim 20 to 26, wherein the expansion device can be opened to allow its removal from a grafted plant.

28. A graft comprising: first and second axially aligned plant sections; and a tubular graft element according to any of claims 11 to 19 retained in both radial and axial tension around the first and second plant sections.

29. The graft according to claim 28 wherein the graft element comprises a UV degradable elastomeric material.