IE893854A1 - A device for gripping and cutting film - Google Patents

Abstract

The device, particularly for use with machines for wrapping large bales of fodder with a plastics film, comprises a gripping assembly having a fixed jaw 24 and a moveable jaw 23. The jaw 23 is mounted on a slidable rod 32 which is adapted to move the jaw 23 towards and away from the fixed jaw 24 to open or close the jaw assembly. The rod 32 is moved into the open position of the jaw assembly by means of an electrically operated linear actuator 45. The linear actuator on receipt of a first signal from an electric sensor moves the rod 32 into the open position of the jaw, while at the same time tensioning a spring 37 connected between the rod 32 and a fixture. The jaw assembly is held in the open position, against the bias of the spring, by a latch 48. On receipt of a second signal from electric sensor means the linear actuator tips the latch to release the spring thereby closing the jaws to grip the plastics material at 28, 29. The jaw 24 includes a blade 30 which at the same time cuts through the material. A turntable (6, Fig 3) and a tipping platform (4) of a bale-wrapping machine incorporating the device are each provided with electric sensors which serve to activate the linear actuator.

Description

A DEVICE FOR GRIPPING AND CUTTING FILM The present invention relates to a device for gripping and cutting film in the wrapping of an object with the film. The term film is intended to include sheeting, web material, strip material and the like sheet material suitable for wrapping objects. The invention is particularly suitable for use with machines for wrapping bales, such as large round bales, of silage, hay, straw and the like (hereinafter referred to as fodder) with a plastics film. Examples of bale wrapping machines of the kind described are disclosed in U.K. Patent Specifications Nos. 2191984A and 2228246, the contents of which are incorporated herein by way of reference.

Bale wrapping machines of the kind described comprise a wheeled chassis which may be towed by a tractor. The chassis carries a tipping platform which, in turn, supports a turntable. The turntable is rotatable about a vertical axis. The turntable carries a pair of spaced rollers each of which rotates about a horizontal axis. An endless belt is stretched between the rollers and rotates with the rollers. In order to wrap a large round bale of fodder material with plastics film, the round bale is lifted onto the turntable by means of lifting arms. The bale rests on the endless belt. The free end of a roll of plastics film is attached to the bale and the turntable is then rotated about a generally vertical axis to cause the sheet of film to be wrapped around the bale. However, if no movement of the bale about its longitudinal axis were to occur the bale would merely be wrapped with a single band having the thickness of the width of the plastics film. However, on each rotation of the turntable the endless belt is caused to move for a predetermined distance which, in turn, causes the bale to roll about its surface. This rolling of the bale on the belt - 2 allows a new area of bale to be wrapped by the film on each rotation of the turntable, thus eventually achieving a complete covering of the bale with a substantial degree of overlap of the plastics film.

The invention is concerned with a device which is intended to grip the free end of the film and to bring the film around the bale during the first two revolutions of the turntable. The device then releases the film to allow wrapping to continue. At the end of the wrapping operation the device again comes into contact with the film to grip the film and to cut the film so as to release the film from the bale. The film is then held in the gripping device ready for attachment to the next bale to be wrapped.

There are problems associated with known gripping and cutting devices which are mechanically or hydraulically operated. EP 0 367 529 A, for example, discloses an automatic round bale wrapper incorporating a device for gripping and cutting the plastics film in which the device is operated by a winding mechanism which tensions the gripping and cutting device step-wise at each revolution of a round bale table of the bale wrapper. Mechanical gripping and cutting devices of this kind are complicated in design and do not lend themselves to addition as a kit to existing bale wrapping machines. Hydraulic systems require hydraulic rotary couplings which tend to leak. Also they are not so efficient.

It is an object of the invention to provide an improved gripping and cutting device for the plastics film which is electrically operated.

Accordingly, the invention provides a device for gripping and cutting film in the wrapping of an object with the film comprising a gripping assembly having gripping means moveable from a closed position in which the gripping means is adapted to grip the plastics film to an open position in which the gripping means is adapted to release the film, cutting means adapted to cut the film on closure of the gripping means, and means for closing and opening the gripping means, wherein the means for opening the gripping means comprises an electrically operated - 3 linear actuator.

Preferably, the means for closing the gripping means comprises spring means which are adapted to be tensioned by the linear actuator on opening of the gripping means and subsequently released, by movement of the linear actuator, to close the gripping means and simultaneously to cut the film.

Suitably, the linear actuator has associated therewith signal means, the arrangement being such that on receipt of a first signal an actuator rod of the linear actuator is caused to move from a retracted position to an extended position to open the gripping means and simultaneously to tension the spring means, on receipt of a second signal by the linear actuator the actuator rod is caused to retract to an intermediate position, the spring means being maintained in a tensioned state by latch means, and on receipt of a third signal by the linear actuator the actuator rod is caused to retract further to trip the latch means and release the spring means.

The invention also includes a bale-wrapping machine having a device for gripping and cutting film as described above.

One embodiment of the invention is hereinafter described with reference to the accompanying drawings, wherein: Figures 1 to 4 show a side elevation of a bale wrapping machine fitted with the device of the invention, the bale wrapping machine being shown at different stages of its operation; Figure 5 is a front perspective view of a film gripping device of the invention shown in the fully retracted position; Figure 6 is a rear perspective view of the device of Figure 5 in the fully extended position; Figure 7 is a front perspective view showing the device in the fully - 4 extended position; Figure 8 is a rear perspective view of the device in a retracted position; Figure 9 is a plan view of a detail of Figure 5, showing the device in a closed position; Figure 10 is a plan view similar to Figure 9 showing the device in an 10 open position; Figure 11 is a sectional view of a linear actuator; Figure 12 is an elevation of a second arrangement of linear actuator 15 for use with the invention; Figure 13 is a plan view of the turntable of the bale-wrapping machine of Figures 1 to 4 showing details for the wiring of sensors; Figure 14 is a detail of the tipping platform showing the location of a sensor; Figure 15 is an elevation, to an enlarged scale, of part of the turntable of the machine of Figures 1 to 4 showing electrical connection means; and Figure 16 is a part-section on the lines A-A of Figure 9.

Referring firstly to Figures 1 to 4 of the drawings these show a bale 30 wrapping machine of the kind described in our U.K. Patent Specification No. 2228246.

The bale wrapping machine comprises a chassis 1 having a pair of wheels 2. The chassis is provided with a hitch 3 for attachment to a tractor.

A tipping platform 4 is mounted on the chassis 1. As best seen in Figures 3 and 4 the tipping platform is pivotally connected to a - 5 bracket 5 at the rear of the chassis 1 such that the tipping platform may be tipped from the horizontal position shown in Figures 1 and 2 to the fully tipped position shown in Figure 4.

A turntable 6 is mounted on the platform 4. The platform 4 is provided centrally with a main bearing 7 (see Fig. 16) which is bolted onto the platform. Main bearing 7 carries a central spindle 8 (see Figs. 15 and 16) of the turntable 6. The underside of the turntable 6 is fitted with wheels 9 which are adapted to run upon the upper surface of the tipping platform 4, as the tipping platform rotates. The platform 6 has a superstructure 10 on which are mounted a pair of spaced rollers 11. The rollers are mounted for rotation about horizontal axes. An endless belt 12 (see Fig. 4) is mounted rotationally about the rollers. The superstructure 10 is also provided with outwardly inclined arms 13 which define a cradle which is adapted to receive a large bale 14 of silage or other fodder for wrapping. The bale 14 is lifted into the cradle by means of a hydraulically-operated lifting arm (not shown) which extends laterally from the machine. When in the cradle, the bale 14 is carried on and is rotated by the belt 12. The top ends of the arms 13 are provided with rollers 18 which assist in positioning the bale 14 in the cradle.

Forwardly of the chassis 1 is mounted an upright 15 on which is mounted a film dispensing system 16. The dispenser system 16 includes a known dispenser and pretensioning unit through which sheeting of plastics film 17 is fed and stretched.

The film handling device of the invention is adapted to grip the free end of sheeting 17 and to wrap the sheeting around the bale 14 during the first two revolutions of the turntable 6. By this stage the film will have frictionally attached itself to the bale. The device then releases the sheeting which continues to wrap around the bale until the bale is fully wrapped. At the end of the wrapping step, the device again grips the sheeting 17, cuts the sheeting and holds the cut end of the sheeting ready for the next bale. - 6 The device of the invention is shown in more detail in Figures 5 to 11 and comprises a main frame 20 constructed from steel box section. The frame 20 is provided at each end with brackets 21 by means of which the device is mounted between the pair of arms 13, such that the device extends transversely of the cradle (see Figs. 1 and 2).

The device comprises a film gripper assembly 22 (shown in more detail in Figures 9 and 10) having two gripping or clamping means in the form of jaws 23,24. The jaws comprise an outer moveable jaw 23 which is substantially Z-shaped in plan and a fixed jaw 24. Fixed jaw 24 is attached to the frame 20 by a plate 25 which is welded to the frame 20. One side of the jaw 24 is provided with a pair of bosses 26 which house the ends of spring-mounted bars 27. The bars 27 carry at their other end a serrated gripping block 28, preferably made from a resilient material such as rubber. A spring 27a is coiled about each of the bars 27 and is interposed between the block 28 and the boss 26 so as to bias the block 28 outwardly way from the boss 26. The gripping block 28 is adapted to interengage with a complementary serrated block 29 on the opposite face of the jaw 23, also made from a resilient material such as rubber. The block 28 is formed with a plurality, preferably three, longitudinal ribs 28a, while the block 29 has a plurality of, preferably two, similar ribs 29a. When the jaws are in a closed position, as shown in Figure 9, the ribs 28a, 29a interengage, with the ribs 29a fitting into indents formed between the ribs 28a, thus provided a very firm grip on the plastics film 17, opposite the block 28.

A cutting blade 30 is mounted, opposite the block 28, between a blade holder 31 and the end of an angle bracket 31a bolted to the jaw 24.

The holder 31 is bolted to the bracket 31a, and the blade may be released and replaced by opening the bolts. A plate 30a is bolted to the side of the bracket 31a, opposite the blade, and acts as a blade guard.

The blade 30 is adapted to cut the sheeting 17 when the jaws are closed. It will be noted from Figure 9, that when the jaws 23,24 move - 7 to the closed position a flange portion 23a of the jaw 23 abuts the blade holder 31. This helps to tension the film to facilitate the cutting action. The cutting of the film is further facilitated by the arrangement in which the blade 31 slides along the outer surface of the flange portion 23a during cutting.

The moveable jaw 23 is fixed to the end a linearly moveable rod 32.

The rod 32 is slideably mounted in bearings 33,34 which are welded to the top of the main frame 20. The rod 32 protrudes through a circular aperture in the centre of the fixed jaw 24 so that the rod 32 and moveable jaw 23 may move independently of the fixed jaw 24.

As will be seen in Figures 5 to 8, a boss 35 is fixed by means of a pin to the rod 32 and travels with the rod. An upstanding bracket 36 is welded to the boss 35. A helical spring 37 is connected to the bracket 36 at one end, and at the other end to a bracket 38 which is welded to the end of the frame 20. The purpose of the spring 37 is to urge the rod 32 rearwardly so as to close the gripper assembly.

A pair of downwardly depending plates 39 are welded to the boss 35, each to an opposite side of the boss. A transverse boss 40 is bolted between the lower ends of the plate 39. The boss 35 and the rod 32 to which it is affixed, may be moved in an outwardly linear direction to open the jaw assembly by means of an electrically operated linear actuator 41.

The linear actuator 41 may be a commercially available actuator, for example an actuator of the type marketed by Warner Electric Ltd., England under part No. 9210-103-500. A cross-section of such an actuator is shown in Figure 11, and comprises an electric motor 42 which drives a screw shaft (or worm gear) 82, through the intermediary of inter-meshing gears 83, 84 and 85 housed in a gear box 43. The screw shaft 82 is disposed co-axially within a hollow actuator rod 44. The hollow rod 44 is provided with a recirculatory ball nut unit 86.

The balls in this unit engage between the threads of the screw shaft 82 so that rotation of the screw shaft 82 causes linear motion of the - 8 hollow shaft 44 in well known manner. The hollow rod 44 extends from a cylinder 45 which is slung beneath the main frame 20 by brackets 46.

Operation of the motor 42 causes the hollow rod 44 to move outwardly from the cylinder 45 (see Figs. 5 to 8). The rod 44 is shown in its retracted position in Figure 5 and in an extended position in Figure 7. A circular abutment disc 47 is fixed to the free end of the rod 44. The disc 47 abuts the plates 39 and transverse plate 40.

Thus, extension of the rod 44 from the cylinder 45 causes the plates 39,40 to move to the left (as shown in Fig. 5) together with the fixed boss 35 and the rod 32, from the position shown in Figure 5 to that shown in Figure 7, in which the gripper assembly 22 is fully open.

It will be appreciated that when the jaws 23,24 of the gripper assembly 22 are in the fully open position as shown in Figures 6 and 7 the helical spring 37 is fully stretched and is tending to pull the rod 32 back into the closed position. The gripper assembly is therefore locked in the open position by means of a latch 48 (see Figs. 6 and 8). The latch is pivoted by means of a pivot 49 on the frame 20. The latch is substantially right-angled in shape and has at one end an engagement portion which is adapted to engage with a pin 50 on the plate 39 (see Fig. 8). The latch is shown in the engaged position in Figure 6. The other end of the latch is pivotally connected to one end of a rod 51. The other end of the rod 51 is slideably mounted in a bracket 52 fixed to the main frame 20. A spring 53 positioned between the bracket 52 and an abutment 54 on the rod serves to bias the latch 48 into the closed position. A cam plate 55, which is attached to and moves with the disc 47 on the end of the actuator rod 44, is adapted to connect with a plate 56 fixed on the rod 51 to move the rod to the left, as shown in Figure 8, to open the latch.

The operation of the device of the invention will now be described. In order to prepare the bale wrapping machine for the wrapping of a bale, the turntable 6 is rotated to a position in which the film handling device of the invention is located at the front of the machine. The free end of the roll of plastics film 17 is held by the gripper - 9 assembly by locating the sheet between the blocks 28,29 of the jaws 23,24. The turntable 6 is then rotated anticlockwise through 90° to the position shown in Figure 1. A bale 14 is then lifted into the cradle of the machine by means of the lifting arm. The turntable is then rotated clockwise. This causes the film handling device of the invention to circle the bale 14 to commence wrapping the film 17 around the bale. As the turntable revolves electric sensors on the turntable pass over a magnetic device on the tipping platform (see Figure 13) and, after the second revolution of the turntable, an electrical signal is sent to the linear actuator 41. The actuator 41 begins operation to push out the rod 44 and thus move out the rod 32 and open the gripper assembly to release the film. By this stage the film has already attached itself to the bale 14 and the turntable 6 continues to revolve to completely wrap the bale in the plastics film.

Meanwhile, the rod 44 of the actuator 41 has reached the end of its stroke and the gripper assembly 22 is in the fully open position as shown in Figure 6. In this position, the latch 48 engages with the pin 50 to lock the assembly in the fully open position. At the same time a cam 58, which is fixed on a rod 59 moving with the actuator, actuates a change-over switch 60. This switch 60 causes the actuator to stop, and reverses the motor 42 to retract the rod 44. The abutment disc 47 thus disengages from the plate 40 and leaves the jaw assembly in the open position, as shown in Figure 6. In this position the jaw assembly is held open by the latch 48. As the actuator retracts, the cam 58 actuates a second limit switch 61 which gives a signal to the actuator to stop in this position, which is about 25mm from the fully retracted position.

When the bale 14 on the turntable 6 has been fully wrapped the platform is stopped with the platform rollers transverse of the cradle and with the device of the invention facing the front of the machine, as shown in Figure 2. Tipping of the machine then commences as shown in Figure 3. In this position, the sheet of film is aligned between the open jaws 23,24 of the gripper assembly. Thus, the plastics film is gathered up on the exposed portion of the rod 32. When the machine is - 10 almost fully tipped, a sensor located on the back end of the tipping platform 4 passes a magnet attached to the chassis which sends signals to the linear actuator 41 to cause the actuator rod 44 to travel in fully (This arrangement is shown in more detail in Figure 14). This causes the cam 55 and the rod 51 to push the plate 56 to the left, as shown in Figure 6, against the action of the spring 53 to release the latch 48. This permits the gripper assembly to close abruptly and with considerable force under the action of the spring 37. As the gripper assembly closes, the jaws 23,24 come together and the blade 30 cuts the plastics film. The tipping platform 4 continues to tip and the now detached bale is unloaded over the rear of the machine. Meanwhile, the free end of the cut film is held between the plates 28,29, and the rod 44 of the actuator has reached a fully retracted position where a third limit switch 63 acts as a cut-off switch for the actuator.

A second embodiment of a linear actuator 41 which may be used with the invention is shown in Figure 12, where like numerals denote like parts. In this arrangement the casing 45 of the linear actuator 41 is made from a metal such as aluminium. The limit switches 60, 61 and 63 are mounted directly on the metal housing at the desired positions.

Permanent magnets are attached to the worm gear 82 (not shown) within the housing 45. These activate the switches in the same manner as described above.

The position of the electric sensors on the turntable 6 which are used to commence operation of the actuator 41 to open the jaws 23,24, is shown in Figure 13. The sensors comprise two reed switches 84, 85 which are located beneath the turntable 6. The cabling from the switches 84, 85 extend upwardly through apertures in the turntable to a control box 86. Cabling 87, 88 leads from the control box to the actuator 41, and the microswitches 60, 61 and 63, respectively. A ring magnet (not shown) is located on the tipping platform 4 in a position below the reed switches 84, 85 such that when the turntable 6 rotates the reed switches 84, 85 pass over the magnet. The arrangement is such that on a first revolution of turntable 6 the first of the reed switches is activated as it passes over the ring magnet. On a second - 11 revolution of the turntable 6 the second reed switch is activated and the linear actuator is caused to open.

The switch arrangement for activating the actuator to trip the latch 48 at the end of the bale-wrapping operation is shown in more detail in Figure 14. When the bale or fodder has been wrapped the tipping platform 4 is tipped through the arc A about a pivot 90 on the bracket . A proximity switch reed contact 80 is attached to the underside of the tipping platform 4. When the tipping platform 4 is moved through the arc A the contact 80 moves along the arc B. This brings the contact 80 into proximity with a ring magnet 81 positioned along the arc B by means of a bracket 82 fixed to the chassis 1. The magnet 81 activates the contact 80 which in turn causes the linear actuator 41 to be activated. The ring magnet 81 and the bracket 82 are adjustable so as to enable the activation of the actuator 41 to take place at a desired point during the tipping operation.

Means for supplying electrical current from the tractor battery to the linear actuator means 41 is shown in Figures 15 and 16. As shown in these Figures, a pair of slip rings 65,66 are attached to the main spindle 8. The slip rings 65,66 are insulated from the spindle by an annular insulator 67. Electric current is conveyed to the slip rings 65,66 by brush assemblies 68,69. Each brush assembly comprises a pair of brushes 70,71 which are spring-loaded into contact with the slip rings by a spring 72 located between a pair of levers 73,74. One slip ring 65 carries current from the battery, and the other carries the signal from the proximity switch reed contact 80 on the tipping platform 4.

The gripping and cutting device of the invention may be built integrally with the bale-wrapping machine. It is also suitable for supply as a kit for attachment to existing machines.

Claims (17)

1. A device for gripping and cutting film in the wrapping of an 5 object with the film comprising a gripping assembly having gripping means moveable from a closed position in which the gripping means is adapted to grip the plastics film to an open position in which the gripping means is adapted to release the film, cutting means adapted to cut the film on closure of the gripping means, and means for closing 10 and opening the gripping means, wherein the means for opening the gripping means comprises an electrically operated linear actuator.

2. A device as claimed in claim 1, wherein the means for closing the gripping means comprises spring means which are adapted to be tensioned 15 by the linear actuator on opening of the gripping means and subsequently released, by movement of the linear actuator, to close the gripping means and simultaneously to cut the film.

3. A device as claimed in claim 2, wherein the linear actuator has 20 associated therewith signal means, the arrangement being such that on receipt of a first signal an actuator rod of the linear actuator is caused to move from a retracted position to an extended position to open the gripping means and simultaneously to tension the spring means, on receipt of a second signal by the linear actuator the actuator rod 25 is caused to retract to an intermediate position, the spring means being maintained in a tensioned state by latch means, and on receipt of a third signal by the linear actuator the actuator rod is caused to retract further to trip the latch means and release the spring means. 30

4. A device as claimed in any of Claims 1 to 3, wherein the gripping means comprises two jaws one of which is fixedly mounted and the other of which is moveable relative to the fixed jaw.

5. A device as claimed in Claim 4, wherein the jaws are each 35 provided with a resilient gripping block which has a ribbed surface and the blocks are adapted to interengage on closing of the jaws with the - 13 ribs on one block fitting into complementary indents in the other block so as to firmly grip the film.

6. A device as claimed in Claim 4 or Claim 5, wherein a cutting 5 blade is provided on one of the jaws which co-operates with a surface on the other jaw to cut the film on closing of the jaws.

7. A device as claimed in Claim 4, wherein the moveable jaw is mounted on a linearly moveable rod, wherein the rod is caused to move

8. 10 by the linear actuator from a first position in which the jaws are closed to a second position in which the jaws are open, a spring connected to the rod is adapted to be tensioned when the rod is moved into the open position of the jaws, latch means are provided to lock the jaws in the open position against the tension of the spring, and 15 trip means are provided to trip the latch means at the end of the wrapping operation so as to release the spring which in turn moves the rod to cause the moveable jaw to close on the fixed jaw so as to simultaneously grip and cut the plastics film. 20 8. A device as claimed in Claim 7 wherein the rod extends between the jaws in the open position of the jaws and in this position the rod serves as a support on which the film gathers to form a string for cutting. 25 9. A device as claimed in Claim 8 comprising an elongate frame, a fixed jaw secured to the frame, a rod moveable linearly of the frame moveable through an aperture in the fixed jaw, a moveable jaw attached to the end of the rod is such that the moveable jaw can be moved by the rod towards and away from the fixed jaw, a spring attached at one end 30 to the frame remote from the jaws, and at the other end to the rod, an electrically operated linear actuator attached to the frame and adapted to move the rod to open the jaws and simultaneously to tension the spring, latch means to lock the jaws in the open position against the tension of the spring, a first switch means associated with the 35 actuator to cause the actuator to stop when the jaws are fully open, and to retract, a second switch means which causes the actuator to - 14 retract to an intermediate position, and further switch means operable at the end of the wrapping operation to cause the actuator to fully retract to release the latch means. 5 10. A bale-wrapping machine fitted with a device for gripping and cutting film as claimed in any one of the preceding claims.

9. 11. A bale-wrapping machine having a chassis, a tipping platform pivotally connected to the platform, a turntable mounted for rotation 10 upon the platform and a conveyor means on the turntable such that a bale of fodder placed on the turntable may be rotated about both substantially horizontal and substantially vertical axes, a film dispensing means spaced from the turntable, and a device for gripping and cutting film mounted on the turntable, said device comprising a 15 gripping assembly having gripping means moveable from a closed position in which the gripping means is adapted to grip the plastics film to an open position in which the gripping means is adapted to release the film, cutting means adapted to cut the film on closure of the gripping means, and means for closing and opening the gripping means, wherein 20 the means for opening the gripping means comprises an electrically operated linear actuator.

10. 12. A bale-wrapping machine as claimed in Claim 11, wherein the turntable is provided with a first electric sensor means such that 25 after a pre-determined number of revolutions of the turntable a first signal is sent to the linear actuator to activate the actuator to open the gripping means, and wherein the tipping platform is provided with a second electric sensor means such that on tipping of the platform a signal is sent to the actuator to cause closure of the gripping means.

11. 13. A bale-wrapping machine as claimed in Claim 12 wherein the first electrical sensor means comprises switch means located beneath the turntable which are cooperable with a magnet located on a non-rotatable part of the machine located below the turntable.

12. 14. A bale-wrapping machine as claimed in Claim 12 wherein the second - 15 sensor means comprises an electric contact attached to the underside of the tipping platform which co-operates with a magnet fixed to the chassis on tipping of the platform.

13. 15. A bale-wrapping machine as claimed in Claim 12 wherein the mounting for the magnet is adjustable.

14. 16. A bale-wrapping machine as claimed in Claim 11 wherein the means for closing the gripping means comprises spring means which are adapted 10 to be tensioned by the linear actuator on opening of the gripping means and subsequently released, by movement of the linear actuator, to close the gripping means and simultaneously to cut the film.

15. 17. A bale-wrapping machine as claimed in Claim 16 wherein on receipt 15 of a first signal from the first electric sensor means an actuator rod of the linear actuator is caused to move from a retracted position to an extended position to open the gripping means and simultaneously to tension the spring means, on receipt of the second signal by the linear actuator the actuator rod is caused to retract to an intermediate 20 position, the spring means being maintained in a tensioned state by latch means, and on receipt of a third signal by the linear actuator from the second electric sensor means the actuator rod is caused to retract further to trip latch means and release the spring means. 25

16. 18. A bale-wrapping machine substantially as hereinbefore described with reference to the accompanying drawings.

17. 19. A device for gripping and cutting device substantially as hereinbefore described with reference to the accompanying drawings.