GB2233307A - Gripping and manipulating devices for plant tissue - Google Patents

Abstract

A device for gripping and manipulating a plantlet during micropropagation procedures, comprises a pair of cantilevered rollers (20 and 20A) projecting from a pair of support members (15 and 15A) which are pivotally mounted on a sub frame (11). The rollers are driven by respective stepper motors (23) and can be moved towards and away from each other by pivoting of the support members by means of a pneumatic cylinder (34). A plantlet can be gripped by controlled movement of the rollers apart and towards each other and can be lifted by rotation of the rollers in counter rotation. A further controlled movement can be applied by moving one of the rollers (20A) along the direction of its axis of rotation.

Description

GRIPPING AND MANIPULATING DEVICE AND HANDLING METHOD The present invention relates to a device for gripping and manipulating an item, in particular but not exclusively for transporting plant tissue from one work station to another and for planting a plantlet in a nutrient medium. The invention also relates to a method of handling a portion of plant tissue, and in particular but not exclusively a method of planting plant tissue into a nutrient medium for example plant shoots or parts of shoots for micropropagation.

Micropropagation of plants uses the techniques of plant tissue culture and applies them to the propagation of plants. Micropropagation normally uses either shoots or shoot tips or other vegetable plant organs as starting points. At its simplest, micropropagation consists initially of excising small pieces of actively growing tissue. Then, under sterile conditions, the pieces of tissue are transferred to a nutrient medium which supports plant growth. The plant material will finally develop into entire plantlets. These plantlets must then be weaned from the axenic conditions in which they have existed within the laboratory into viable, rooted plants capable of survival in conventional horticultural or agricultural environments.

The growth of plants from tissue culture is a technique which can produce large numbers of genetically identical plants, perhaps possessing a desirable quality such as disease resistance, in a short time. The tasks of dissecting and transplanting such plants are labour-intensive and repetitive, and the gains in speed, sterility and labour costs which could be achieved by the use of robots make automation an attractive prospect for the fast-expanding micropropagation industry.

However, automation is difficult, requiring methods of handling and robot guidance which can deal with the natural variability of biological objects.

The technique is labour-intensive, and four of the particularly important operations which are repeated frequently are (i) removing a plant from a container, (ii) cutting a required portion of plant tissue from the donor plant, (iii) transferring the cut portion of plant material, and (iv) placing the plant portion in a soft nutrient medium in such a manner that it stands upright.

As performed at present, the cutting operation normally consists of an operator holding the plant material by forceps on a sterilised card by one hand, and cutting the required portion of the plant by strokes of a scalpel, by the other hand. Commonly, the cuts are required to cut from the donor plant shoot, a node from which a side-shoot will develop from an axillary bud.

The cut portion is then transferred by forceps to the soft nutrient medium, which is in the nature of a gel, and the cutting is then manoeuvred so as to stand upright with the stem part of the cutting in the soft nutrient medium. The manoeuvering is normally carried out by the use of forceps.

Another task which needs to be repeated frequently in micropropagation is that of taking plantlets out of a nutrient medium, and transplanting the plantlet to a new nutrient medium, to take the plantlet to the next stage of growth.

The high cost of these labour-intensive operations has meant that micropropagation techniques have been limited to plant species which attract an adequate premium for greater uniformity or vigour, or are difficult or impossible to propagate from seed or cuttings. It is an object of the present invention to provide a device, apparatus and method for effecting operations involved in micropropagation techniques with greater speed and less reliance on operator skill. This will allow the benefits of micropropagation to be utilised in the growth of more plant species where it is at present prohibited by the costs involved.

In some aspects, the problem tackled by the present invention is that of picking up and transporting and delivering fragile and awkwardly shaped items, such as plant shoots or parts of shoots, or plantlets ready for planting in micropropagation.

According to the present invention in one aspect, there is provided a device for gripping and manipulating an item comprising a pair of cantilevered rollers, first drive means for moving the rollers together and apart to grip and release an item, and second drive means for driving at least one of the rollers in rotation so as to pick up or deliver an item gripped by the rollers.

Preferably the rollers are right circular cylindrical rollers and the axes of rotation of the rollers are parallel.

In some arrangements only one of the rollers may be driven, the other roller being mounted to be freely rotatable, and in operation being rotated by the effect of the first roller, but preferably the second drive means is arranged to drive each roller in rotation, with the rollers being driven in counter-rotation.

Preferably each roller is coupled to and driven by drive means individual thereto and individually controllable.

Conveniently the second drive means for rotating the rollers comprises two electrical stepper motors coupled one to each of the two rollers, conveniently by flexible couplings.

In one preferred arrangement the apparatus includes a sub-frame on which the rollers are mounted, each cantilevered roller projecting from a support member which is pivotally mounted on the sub-frame to pivot about an axis spaced from the axis of the roller such as to produce the said movement of the rollers together and apart. Conveniently the said first drive means is arranged to act between the two pivoted support members, for example a pneumatic or hydraulic ram may be coupled between the two pivoted support members. Preferably there may be provided biasing means biasing one of the support members towards a stop on the sub-frame, so that the position at which an item is held by the rollers is related to a datum position.

In accordance with an optional feature, there may be provided a third drive means for moving one of the rollers relative to the other roller substantially along the direction of the axis of rotation of the roller.

This allows rotation of an elongate item held by the rollers, about an axis aligned generally along the length of the elongate item. Conveniently the third drive means may comprise a gear engaging annular teeth on a support on which the roller is mounted.

The device according to the invention has particular application for use with plant tissue, for example plant shoots or parts of shoots for micropropagation, and also plantlets which have grown from such shoots. For example the device may be utilised in apparatus for transporting plant tissue from one work station to another, comprising a first work station, a second work station, a gripping and manipulating device as set out hereinbefore in accordance with the invention, and fourth drive means for moving the gripping and manipulating device relative to the work stations in such a manner as to pick up plant tissue at one work station, transport the plant material to the second work station, and release the plant material at the second work station.

In one form, such apparatus may comprise first presentation means for presenting a series of plantlets at the first work station, second presentation means for presenting a nutrient medium at the second work station, and control means for actuating the various drive means in such a manner as to pick up a plantlet at the first work station, transport the plantlet while gripped by the device to the second work station, and plant the plantlet in the nutrient medium at the second work station by action including rotation of the rollers in counter-rotation. By way of example the presentation means may in each case consist of a conveyor, and the control means may comprise a microcomputer.

The invention has particular application in robotic apparatus controlled automatically or semi-automatically by a vision guidance system. For example the apparatus may include camera means for producing image signals of the two work stations, the control means being arranged to operate the gripping and manipulating device in response to signals from the camera means.

In general, those aspects of the invention which have been described with reference to devices and apparatus according to invention, may also be provided with reference to methods of handling items in accordance with the invention, and vice versa.

In particular there may be provided in accordance with the present invention a method of handling a portion of plant tissue comprising gripping the plant tissue between a pair of rollers having resilient surfaces, and rotating the rollers in counter-rotation so as to move the plant tissue between the rollers.

The method may include moving the two rollers apart to release the plant tissue, or rotating the rollers until the plant tissue has been delivered from the rollers, or both steps may be used during the method.

The method is particularly applicable to planting plant tissue into a nutrient medium, and this may be done either by rotating the rollers so as to move the tissue between the two rollers onto or into a nutrient medium, or by the step of passing the plant tissue to a further plant handling means for onward transmission to the nutrient medium.

The method is particularly applicable in a robotic system of micropropagation, and may include the steps of picking up a portion of plant tissue by gripping the plant tissue between a pair of rollers having resilient surfaces, moving the plant tissue to a required location while gripped between the rollers, and releasing the plant tissue at the required location.

The method is particularly advantageous where the pair of rollers are cantilevered.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure la is a rear view of a device embodying the invention for gripping and manipulating a plantlet; Figure 1b is the same view as shown in Figure la but with the device in an open position ready to pick up a plantlet; Figure 2 is a front view of the device of Figures la and lbt shown when in the closed position of Figure la; Figure 3a is a side elevation of the apparatus of the preceding figures, with a part section through one roller of the device; Figure 3b is a side elevation of the apparatus shown in Figure 3a, but with a part section through a second roller of the device; and Figure 4 is a diagrammatic representation of the layout of apparatus for handling plant tissue, including a gripping and manipulating device embodying the invention of the form shown in the preceding figures.

Referring to Figures la to 3b, a gripping and manipulating device 10 has a sub-frame 11 with a main vertical flange 12 which carries two pivot assemblies 13 and 13A, each of which houses a pivot shaft 14 or 14A which protrudes rearwardly i.e. to the left in Figure 3a. Two main support members 15 and 15A are pivotally mounted on the vertical flange 12 of the sub frame 11, by means of the pivot shafts 14 and 14A. As shown in Figure 3a, the pivot shaft 14 extends through an aperture in the support member 15, to be secured by a nut 16. The pivot assembly 13 is arranged so that the support member 15 is freely pivotable about the axis of shaft 14. The second pivot assembly 13A has a similar shaft 14A on which is pivoted the second support member 15A.

As shown particularly in Figure 3a, the support member 15 comprises a main vertical flange 17, and a rearwardly extending horizontal flange 18 which leads to an end flange 19 which is inclined at a skew angle to the horizonal flange 18. The horizontal flange 18 and vertical flange 17 of the support member 15 are strengthened by a gusset 29, which is omitted from the side view of Figure 3a for simplicity. Protruding horizontally from the bottom of the vertical flange 17 is a rubber covered roller 20 which is rotatable about its longitudinal axis on a drive shaft 41 in a bearing 21 which is fixed relative to the flange 17. The roller 20 is coupled by a flexible drive, 22, for example a close coiled tension spring covered by a flexible plastics sleeve, to a geared electric stepper motor 23.

The stepper motor 23 is mounted on the inclined end flange 19 of the support member 15, so that the entire sub-assembly of roller 20, motor 23, and support member 15, can pivot together about the pivot shaft 14.

Thus there has been described with reference to Figures la, 2 and 3a, the left hand roller 20 in Figure 2, and the components associated with that roller, all pivotally mounted by pivot shaft 14 on the sub-frame 11. Considering Figure 2, it will be seen that the second roller 20A is supported in a similar manner on support member 15A which is pivoted about pivot shaft 14A on the sub-frame 11. Other components associated with the rotor 20A which correspond to the components associated with the rotor 20, are indicated by corresponding reference numerals followed by the reference letter A.

Certain features of the construction of the elements associated with the roller 20A are different from those associated with the roller 20. The support member 15A is coupled to the front flange 12 of the sub-frame 11 by a tension spring 24, which is linked between studs 25 and 26 on the sub-frame 11 and on the support member 15A, respectively. A further stud 27 acts as a stop which locates against a protruding finger 28 of the front flange 12 of the sub-frame 11. The effect of these components is to return the rollers 20 and 20A to a determinable datum position, relative to the sub-frame 11. Other features of the roller 20A will be described hereinafter.

As shown in Figures 2 and 3a, there is provided on support member 15 a further pivot shaft 30 which extends through the support member 15 into a pivot assembly 31, to be secured by a nut 32. The pivot shaft 30 passes through the support member 15 and forms a mounting plate 33 having a large central aperture (not visible). As shown in Figure la, there extends through the aperture in the mounting plate 33 a pneumatic cylinder 34 which is threaded externally and is secured to the plate 33 by nuts 35 and 36. The piston rod 37 of the pneumatic cylinder 34 extends away from the plate 33 towards the centre line of the device, where it is coupled by a coupling 38 to a corresponding piston rod 37A associated with the other roller 20A. The corresponding mounting of a pneumatic cylinder 34A is indicated by corresponding reference numerals, followed by the reference letter A.

The two pneumatic cylinders 34 and 34A, constitute first drive means for moving the rollers 20 and 20A together and apart so as to grip items to be manipulated by the device. Air is fed to the pneumatic cylinders 34 and 34A through conduits 40 and 40A respectively, and when such air is supplied, the support members 15 and 15A are moved apart by pivoting about the pivot shafts 14 and 14A, to the position shown in Figure lb. When the air pressure is removed, the rollers 20 and 20A move back together again, and return to the datum position by operation of the spring 24 in Figure 2. The pistons of the pneumatic cylinders are internally spring biased towards the retracted position and it is these springs which cause the support members 15 and 15A, and hence the rollers 20 and 20A, to move back together again when the air pressure is released.The spring 24 ensures the rollers return to the datum position.

The strength of the spring 24 is chosen to be sufficient to locate the rollers at the datum position, but not so great as to interfere with the operation of opening and closing the rollers. If the spring is so strong that the working pressure of the pneumatic cylinders cannot overcome its force then the roller 20A would not move at all. In fact this is not the case, as the retracting forces of the internal springs (not shown) in the pneumatic cyliners, together with the gravitational force on each roller assembly, ensure that when the system is at rest the rollers would reside more or less in the required datum position without any bias.

It is therefore only necessary for a light spring 24 to provide a positive bias onto the datum stop 27.

Referring to Figure 2, the sequence of events in use is as follows. When air pressure is applied to each cylinder, the roller 20 moves out on its pivot 13 until the boss of the pivot assembly 31 contacts the lower edge of the vertical flange,12. The roller 20A stays in the datum position during this phase, under the influence of the spring 24. At this point the roller 20 can move no further, and the roller 20A then pivots outwardly until the boss of the pivot assembly 31A also contacts the lower edge of the vertical flange 12. The whole assembly rests in this position whilst the air pressure is maintained. When the air pressure is released, the rollers return to the datum position in reverse sequence.

In addition to the rollers 20 and 20A being able to grip items by moving apart and together, items can also be gripped and manipulated by rotation of the rollers by the stepper motors 23 and 23A, which constitute second drive means for rotating the rollers in counter-rotation. Thus an item may be picked up either by the rollers 20 and 20A moving apart, and then back together again, and the rollers being moved upwardly, or by the item being positioned at the nip of the rollers, and being drawn upwardly by rotation of the rollers 20 and 20A. In some circumstances both actions may be used in order to pick up an item.

A typical operation of picking up a plantlet which is growing in an agar gel will now be described, using the two actions set out above.

A slight gap is provided between the rollers 20 and 20A when the two support members 15 and 15A are abutting each other with the air pressure released. This gap can be increased by rotation of the coupling 38 between the piston rods 37 and 37A of the pneumatic cylinders.

Conveniently the coupling 38 is a sleeve threaded onto both piston rods 37 and 37A with threads of opposite sense. The gap is adjusted to be such that the rollers 20 and 20A just grip a plantlet stem, without damage, when the two rollers are urged fully together upon release of the air pressure.

When the pistons are in the retracted position, the rollers 20 and 20A are positioned on either side of a datum plane which in Figure 2 is a vertical plane passing midway between the rollers 20 and 20A. In operation the rollers 20 and 20A are moved apart by the air pressure, and the entire device 10 is moved, for example by a robot, to a position in which the plantlet stem lies in the datum plane. The air pressure is then released from the pneumatic cylinders. First the support member lSA pivots downwardly until the roller 20A rests against one side of the plant stem. Then the support member 15 pivots downwardly until the roller 20 rests against the other side of the plant stem, the two rollers gently gripping the stem.Next the motors 23 and 23A are operated to rotate the rollers in counter-rotation and the plant is lifted gently from the agar nutrient material in which it is growing. When plant is free from the agar, the entire device 10 is moved by the robot to transfer the plantlet to the required new position. The plantlet can then be replanted in agar by reversing the steps set out above.

A third means of manipulating items gripped by the rollers is provided by an optional mechanism shown in Figures 2 and 3b. Figure 3b shows the same side view generally as Figure 3a, except that a section is shown through the far roller 20A. The drive to the roller 20A is the same as that to the roller 20, up to the drive shaft 41A which is rotatably mounted in the bearing 21A.

Referring to Figure 3a, the shaft 41 for the roller 20 continues as a plain circular section shaft on which the rubber roller 20 is fixedly mounted. In the case of the roller 20A shown in Figure 3b however the shaft 41A ends at its outer end in a square section drive shaft 42. On this is mounted an intermediate sleeve 43 which is slidable along the square section drive shaft 42. The rubber roller 20A is fixedly mounted on the sliding sleeve 43. At the inner end of the sleeve 43 (adjacent the bearing 21A) the sleeve is of increased cross section and is formed with a series of annular gear teeth 44 which are spaced apart along the sleeve 43 and extend annularly around the sleeve. The annular gear teeth 44 mesh with a cylindrical gear wheel 45 which is mounted (by means not shown) onto the support member 15A.A drive shaft 46 leading to the gear wheel 45 may be driven by a further stepper motor (also not shown) which is again fixedly mounted relative to the support member 15A.

The purpose of the mounting of the sleeve 43 is to allow controlled movement of the roller 20A along the direction of its axis. This enables controlled rotation of an item which is gripped by the two rollers 20 and 20A, about an axis generally vertical and lying between the two rollers 20 and 20A.

Thus it will be appreciated that the device described so far allows a number of different degrees of controlled movement of an item gripped between the two rollers. The entire device described so far is conveniently mounted on a moveable arm of a robotic system, so as to provide a flexible end effector of the robot.

Turning now to Figure 4, there is shown a diagrammatic representation, chiefly in plan view, of a robotic system for use in micropropagation of plants. A conveyor belt 50 carries a series of containers 51 containing plantlets during micropropagation. The conveyor 50 is operated intermittently and a container 51 is arrested at a work station 52 beneath the line of vision of a video camera 53 directed at a mirror 54. A micro processor (not shown) is linked to the output of the camera 53 and also to a gripping and manipulating device 10, which has been described with regard to the previous drawings, and which is mounted on a robot arm 55 also under the control of the central micro processor. It is to be appreciated that the conveyor 50, the containers 51, and the rollers 20, 20A are not drawn to the same scale.

The robot arm 55 is rotated as indicated by the arrows 56, until the rollers 20 and 20A are positioned over the work station 52. At the work station 52, the cantilevered rollers 20 and 20A are lowered by the robot arm 55 towards the container 51, with the rotors 20 and 20A fully apart. The rollers 20 and 20A are then brought together with a plantlet between the rollers, which grip the plantlet gently.

The rollers 20 and 20A are then rotated in counter rotation so as to draw the plantlet out of the nutrient medium, and the entire device 10 is raised from the container 51, with the plantlet gripped by the rollers 20 and 20A, which at that stage are not rotated.

The robot arm 55 is then rotated by 45 degrees and the plantlet is, for example, held in an area through which is blown filtered air indicated by the arrows 57.

At this stage, if required, unwanted material may be cut from the plantlet and unwanted items removed by the blast of filtered air.

The device 10 is then carried by further rotation of the arm 55 until the rollers 20 and 20a are brought to a second work station 53 over a second conveyor 54 which carries a series of further containers 51. The conveyor 54 arrests a container 51 at the work station 53 beneath the line of sight of a further video camera 60.

At the work station 53, the robot arm 55 is lowered, until the rollers 20 and 20A are just above the level of fresh nutrient medium. The rollers 20 and 20A are then rotated in counter-rotation in the opposite sense to that when picking up the plantlet, with the result that the plantlet is propelled downwardly and the plantlet is planted in the nutrient medium. When this has been achieved, the rollers 20 and 20A are moved apart and the robot arm withdraws the device 10 from the work station.

It is to be appreciated that the use of the device 10 shown in Figure 4 is merely exemplary and that many other steps in the micro propagating procedure can be achieved by use of the cantilevered gripping and manipulating arms 20 and 20A.

Claims (20)

1. A device for gripping and manipulating an item comprising a pair of cantilevered rollers, first drive means for moving the rollers together and apart to grip and release an item, and second drive means for driving at least one of the rollers in rotation so as to pick up or deliver an item gripped by the rollers.

2. A device according to claim 1 in which the second drive means is arranged to drive each roller in rotation, with the rollers being driven in counter-rotation.

3. Apparatus according to any preceding claim in which the apparatus includes a sub-frame on which the rollers are mounted, each cantilevered roller projecting from a support member which is pivotally mounted on the sub-frame to pivot about an axis spaced from the axis of the roller such as to produce the said movement of the rollers together and apart.

4. A device according to claim 3 in which the said first drive means is arranged to act between the two pivoted support members.

5. A device according to claim 3 or 4 including biasing means biasing one of the support members towards a stop on the sub-frame.

6. A device according to any preceding claim including third drive means for moving one of the rollers relative to the other roller substantially along the direction of the axis of rotation of the roller.

7. Apparatus for transporting plant tissue from one work station to another, comprising a first work station, a second work station, a gripping and manipulating device as set out in any preceding claim, and fourth drive means for moving the gripping and manipulating device relative to the work stations in such a manner as to pick up plant tissue at one work station, transport the plant tissue to the second work station, and release the plant tissue at the second work station.

8. Apparatus according to claim 7 comprising first presentation means for presenting a series of plantlets at the first work station, second presentation means for presenting a nutrient medium at the second work station, and control means for actuating the various drive means in such a manner as to pick up a plantlet at the first work station, transport the plantlet while gripped by the device to the second work station, and plant the plantlet in the nutrient medium at the second work station by action including rotation of the rollers in counter-rotation.

9. Apparatus according to claim 7 or 8 including camera means for producing image signals of the two work stations, the control means being arranged to operate the gripping and manipulating device in response to signals from the camera means.

10. A method of handling a portion of plant tissue comprising gripping the plant tissue between a pair of rollers having resilient surfaces, and rotating the rollers in counter-rotation so as to move the plant tissue between the rollers.

11. A method according to claim 10 including moving the two rollers apart to release the plant tissue.

12. A method according to claim 10 including the step of rotating the rollers until the plant tissue has been delivered from the rollers.

13. A method according to claim 10, 11 or 12 including the step of planting the plant tissue into a nutrient medium.

14. A method according to 13 including the step of rotating the rollers so as to move the plant tissue between the two rollers onto or into a nutrient medium.

15. A method according to claim 13 including the step of passing the plant tissue to a further plant handling means for onward transmission to the nutrient medium.

16. A method according to any of claims 10 to 15 including the steps of picking up a portion of plant tissue by gripping the plant tissue between a pair of rollers having resilient surfaces, moving the plant tissue to a required location while gripped between the rollers, and releasing the plant tissue at the required location.

17. A device for gripping and manipulating an item, substantially as hereinbefore described with reference to Figures la to 3b of the accompanying drawings.

18. Apparatus for transporting plant tissue from one work station to another, substantially as hereinbefore described with reference Figures la to 4.

19. A method of handling a portion of plant tissue, substantially as hereinbefore described with reference to Figures la to 3b.

20. A method of planting a portion of plant tissue, substantially as hereinbefore described with reference to Figures la to 4.