EP0142846B1

EP0142846B1 - Machine for automatically removing plastic wrapping from palletized loads

Info

Publication number: EP0142846B1
Application number: EP84113959A
Authority: EP
Inventors: Maurizio Chierighini; Franco Sisti
Original assignee: Leonardo SRL
Current assignee: Leonardo SRL
Priority date: 1983-11-21
Filing date: 1984-11-19
Publication date: 1988-05-11
Also published as: IT8323795A0; ATE34143T1; DE3471064D1; EP0142846A1; IT1165491B

Abstract

The invention concerns a machine capable of automatically cutting and removing normal plastic wrapping from palletized loads. The machine comprises a supporting structure (1, 2) for a vertically movable frame (3) provided with means (4) for horizontally and/or vertically cutting the plastic wrapping (9) of palletized loads (5). The horizontal cutting means (4) consist of a set of hot wire cutting members (4a) angularly reciprocating on respective carriages (18) which move on said frame (3), to the side of the wrapping (9). Two lateral cutting members (4b) subsequently make vertical cuts on the wrapping, whilst gripping members (34) remove the cut portions of the wrapping (9) and let them drop into collection boxes (7).

Description

This invention concerns a machine for automatically removing plastic wrapping material from palletized loads, and in particular, a machine capable of automatically and successively carrying out all the horizontal and vertical cutting operations according to a pre-established work procedure.
There are on the market numerous automated systems for wrapping palletized loads with plastic film, for example with polyethylene shrink-wrapping or extensible wrapping films, however at present no automatic systems or equipment for removing plastic wrapping from palletized loads while maintaining the stabilized condition of the packaged articles, are known; consequently, the cutting and removing of the covering must still be carried out by hand, with a considerable use of labour.
From WO-A-79 00 682 is known a machine for cutting strings or straps of palletized packings in which a cross bar is movable over the top wall of the packing, to position cutting members on opposite sides of the packing; the cutting members are in the form of downwardly movable cutting heads to hook and cutting the strap. No cutting of the wrapping sides is therefore possible with this apparatus, and no cutting is possible along horizontal planes or in different positions of peripheral sides.
US-A-3 889 442 discloses an apparatus for removing a shrinkable plastic wrapping from packages; the packages are conveyed towards stationary cutting members to make lengthwise cuts on opposite side walls; further cuts are made across the top wall and along vertically extending corners, forming flaps that are folded back in opposite directions to uncover the articles packaged. The cutters are in the form of pivotally supported knives actuated by a spring to bias against the wrapping.
From US-A-3 175 288 a cutting machine is known in which two cutter discs are used for slitting cartons; the spacing between the cutters is adjustable in accordance with the height of the carton to be processed. The rotary cutting discs oscillate horizontally while rotating, and the carton is manually moved to bring adjacent walls of the carton for slitting.
Furthermore GB-A-1 097 8559 discloses apparatus for opening the top of packages in which electrically heated bars make diagonal incisions on the top wall of the wrapping, forming flaps that are folded back by vacuum actuated clamping means.
However, some problems may occur when opening palletized packages in particular packages containing superimposed or stacked layers of articles, while handling the palletized packages after the wrapping has been removed. In particular, it is necessary to remove the side walls of the wrapping, while maintaining an upper portion defining a top cup which serves for stabilizing the unwrapped articles as they are conveyed towards a depalletizing machine. Furthermore, the cutting of the wrappings of palletized loads is a time consuming operation that must be performed in a short time, while assuring a correct cutting of all sides of the wrapping, avoiding uncut portions that will result in stretching and tearing.
The object of this invention is to provide a fully automatic machine for cutting the sides of plastic wrapping material on palletized loads in a single operation, for their subsequent use, while maintaining the load stationary and providing an upper cup-like wrapping portion for stabilization of the load.
A further object of the invention is to provide a machine of the aforesaid type which is capable of adapting to palletized loads of different height and which is capable of making cuts in the plastic wrapping material, along any given horizontal cutting level. These objects are achieved with the machine as claimed in claim 1.
According to a preferred embodiment means are provided in a machine as claimed in claim 1, by which it is possible to remove the sides of the plastic wrapping material, after the cutting.
This invention will appear clear from the following description, made with reference to the example of the accompanying drawings, in which:

Fig. 1 shows a frontal view of the machine;
Fig. 2 shows a plan view seen from above;
Fig. 3 shows a diagram of the movement of the frame supporting the cutting members;
Fig. 4 shows a plan view, from below, of the frame supporting the cutting members, in order to show their disposition;
Fig. 5 shows a cross-sectional view along the line 5-5 of the previous Fig. 4;
Figs. 6 and 7 show the details of a hot-wire cutting member and its supporting carriage;
Fig. 8 shows a cross-sectional view of the detail of one of the carriages supporting the arms which grip the plastic wrapping on the palletized load;
Fig. 9 shows a view of an embodiment of the vertical cutting member;
Fig. 10 shows a possible mechanical gripper for gripping the cut wrapping.

The machine comprises a rigid structure consisting of two lateral uprights 1 and an upper crossbeam 2, which define a cutting area of the plastic wrapping material of palletized loads, and which house the mechanical systems for the vertical movement of one or more supporting means for cutting members 4, for example a square or rectangular-shaped annular frame 3, provided with a pre-established number of cutting members 4, as described further on. Reference 5 indicates a palletized load which is situated beneath and axially aligned with the cutting member supporting frame 3, carried by a service conveyor 6, at either side of which are two boxes 7 for collecting the cut portions of the wrapping 9 which are gripped and removed from the load by means of two articulated arms 8 sliding along the upper crossbeam 2 of the structure of the machine.
The system for the vertical movement of the frame 3 supporting the cutting members, according to the simplified diagram in figure 3, comprises two vertical guide rods 10, fitted in the uprights 1, along each of which slide sleeves 11, which are connected by means of arms 12, to two opposite sides of the frame 3; each sleeve 11 is also connected to a branch of an endless chain 13, or equivalent drive mechanism, which winds around two gear wheels 14 and 15 situated at the ends of the aforesaid guide rod 10. The upper gear wheels 15 are interconnected by a drive synchronizing shaft 16, whilst one of the lower gear wheels 14 is driven by an electric motor 17.
By means of the above-described transmission, the annular frame 3 supporting the cutting members 4 can therefore be moved vertically, along the palletized load 5, from an upper position above the load 5 itself, to cutting positions below in correspondence with the pre-establised cutting heights or planes for the wrapping 9 of the load.
Figures 4 and 5 show a typical disposition of the cutting members provided on the movable frame 3 in the event of a square-shaped load. As can be seen, the frame 3 presents a similar conformation to that of the load 5, surrounding the latter peripherally.
The annular frame 3 is provided with a set of cutting members 4a for cutting the wrapping 9 horizontally, for example four horizontal cutting members 4a, one for each side of the annular frame 3, which follow each other peripherally around the frame itself, in a clockwise direction of movement. The annular frame 3 also comprises, on two opposite sides and in a central position of the sides, at right angles to the direction of movement of the load 5 on the conveyor 6, two cutting members 4b for cutting the wrapping 9 vertically, as explained further on.
Each horizontal cutting members 4a is mounted on its own carriage 18, which is movable along horizontal guides 19 (Fig. 7) secured in a plane below the frame 3. In the case illustrated, each carriage 18 is connected to one branch of an endless chain 19c which extends along one side of the frame, and the chains of the carriages are interconnected by means of pairs of idle gears 20 situated at the corners of the frame 3.
One of the pairs of gears is driven by a suitable geared motor 19a fitted on the frame 3 by means of a belt drive dimensioned so as to slip in the event of an overload or optionally comprising an equivalent slipping member.
Consequently, the horizontal cutting members 4a move simultaneously along their respective sides of the frame, peripherally around the load, slitting or cutting a corresponding portion of the wrapping 9.
In the case illustrated, the four horizontal cutting members 4a move simultaneously, at the same speed, as the palletized load is square in shape; therefore, gears of the same diameter are used. In the case of rectangular-shaped pallets, it is necessary to use different gears to move the cutting members on the long sides at a proportionately higher speea tnan tnat or tne cutting members on the short sides. In this case, and in general, it is preferable to use individual drive units for each cutting member or opposing pairs of cutting members so as to permit independent control with the appropriate cutting speed.
The vertical cutting members 4b are in a fixed position on the annular frame 3 and are controlled by a cylinder 21 situated in a plane above the frame 3, to move radially, that is to say, to move each cutting member 4b perpendicularly, to and from the face of the wrapping to be cut; such cutting members 4b are similar in conformation to the horizontal cutting members 4a and have their longitudinal axes sloping downwards, as shown in Fig. 5.
The cutting means 4, whether they be horizontal 4a or vertical 4b cutting members, may be of any type and supported in any way; according to a preferred embodiment, the cutting means 4 are of the hot-wire type, that is to say, as shown in figure 6, comprising a loop-shaped electric conductor 22 the two ends of which are connected to a source of electric power and are secured by means of bolts 23, or otherwise secured, to a plate 24 hinged to a pivot 25 on a slide 25a, so as to be able to rotate or reciprocate freely in either direction. One central, or two lateral return springs 26 keep the cutting member 22 orientated in a central position according to its longitudinal axis, that is to say, at right angles to the surface of the wrapping 9 to be cut; the springs 26 are consequently connected to pins 27 of the reciprocating plate 24 and respectively to pins 28 of the slide 25a. In particular, each cutting member, that is to say, each slide 25a, is connected to the rod of a control cylinder 30, situated on a plate 29, which acts normally to move the cutting member towards and away from the surface of the wrapping 9 to be cut.
Lastly, figure 8 shows how to support the hinged arms 8 for removing the cut wrapping. These arms 8, as shown in figures 1 and 2, consist of two pairs of arms hinged to a vertical rod 31 mounted on a respective carriage 32 shown in the cross-sectional view in figure 8, which is movable along horizontal guides 33 externally secured to the sides of the crosspiece 2. The hinged arms 8 are made to open and close against the wrapping of the load 5, by means of a control cylinder (not shown), or in any other way, and are provided with gripping members 34, for example, of the mechanical type, in order to grip and hold the edges of the cut wrapping 9 on the palletized load, during the cutting operations, as described further on. The carriages 32 supporting the hinged arms 8 can be made to slide along the guides 33 for example by means of pneumatic control cylinders 35 (only one shown) housed inside the crossbeam 2.
The machine operates in the following way: when the machine is at rest, the frame 3 supporting the cutting members 4 is completely raised above the palletized load 5 and with the carriages 18 at the end of their stroke, that is to say, in correspondence with the corners of the quadrilateral defined by the frame 3, in the case in question. The cutting members 4a moreover are in their forward position, capable that is, of interfering with the wrapping 9 to be cut, with the wire 22 under voltage.
The palletized load 5 covered by the wrapping 9 moves forward on the service conveyor 6 of the machine; two converging side panels (not shown), if necessary, bring the axis of the load 5 to coincide with the axis of the frame 3 of the machine and a photoelectric sensing means or limit switch stops the load 5, so that the transversal axis coincides with the transversal axis of the machine.
The frame 3 lowers until a photoelectric sensing means mounted on the frame itself, intercepts the top of the load 5 and stops the frame 3, by means of a control system, so that the cutting means 4a are on a lower plane then the top plane of the load 5.
At this point, the system for towing the carriages 18 is started up and each cutting element 4a contacts the corner of the load 5; as the carriage 18 advances, the cutting element automatically rotates, following the contour of the corner of the load.
It subsequentially runs along the entire side of the load until it reaches the opposite corner, the latter corner having been run, at the start, by the adjacent cutting element which had run the side at 90°. Consequently, each cutting element 4a runs the complete contour of one of the four corners once only, where there are generally very thick folds which form during the thermo-shrinking or wrapping process.
Optionally, as soon as the carriage 18 reaches the limit switch, it can be made to reverse direction and run backwards for a short distance which is sufficientto enable it to reach the corner situated at the end of the cutting stroke; after which the cylinder 30 causes the cutting element 4a to move back, the sliding direction is once again reversed, and the carriage travels back to the final limit switch, where the pneumatic cylinder 30 moves the cutting element 4a forward into the normal working position.
In this way, each corner can be re-cut by the cutting members. All the horizontal cutting members obviously work simultaneously to cut their respective portion or side of the wrapping 9.
Atthis point, the frame 3 is lowered, bringing the cutting members 4a in correspondence with the level of the plane which separates the load from the pallet. Exactly the same operations are carried out for cutting the wrapping at this level, as those previously described for cutting the wrapping at the higher level, but in the opposite direction.
As soon as these horizontal cutting operations have been carried out, the vertical cutting elements 4b, which are mounted on the frame 3 in correspondence with the longitudinal axis of the palletized load, are placed in position, and the frame 3 is raised up to the position of the upper cutting level, thus carrying out the vertical cut.
Before the two vertical cuts are completed, the articulated arms 8, which when at rest are close to the uprights 1, in an open position, are made to move forward closed until the pairs of gripping elements 34 come to rest against the wrapping 9 at the sides of the vertical cuts, and the gripping elements 34 are actuated to grip the vertical edges of the cut wrapping.
The vertical cut is completed, the cutting elements 4b are made to recede and the frame 3 returns to the rest position. The arms 8 open out and are made to move backwards towards the uprights 1 of the machine, each arm carrying with it half of the wrapping 9 which laterally covered the load.
At this point, the upper gripping elements loosen their grip so that the two portions of the wrapping fall forward, held by the lower gripping elements. After a short while, which corresponds to the time it takes for the wrapping to drop into the boxes 7, the other gripping elements also loosen their grip and the cut wrapping slips into the boxes 7.
With this system, the palletized load still keeps its upper wrapping cap which serves to stabilize the unwrapped load as it is conveyed towards the de-palletizing machine which normally removes the upper wrapping cap, remaining after the cutting, by means of an arm provided with suction pads.
According to a different embodiment of the vertical cutting members, shown in figure 9, the latter may be supported for a horizontal movement, towards and away from the plastic wrapping 9 to be cut, and for a vertical movement, so as the avoid possible interference with the horizontal cutting members, and in order to shift the vertical cutting member4b itself to the established starting point of the cut. This dual movement of the cutting member 4b can be achieved for example by means of a pair of double-acting control cylinders comprising a first horizontal-axis cylinder 36, mounted on the movable frame 3, the rod of which is provided with a block 37 guided along a plate 38. To said block 37 is, in turn, secured a second control cylinder 39 having a vertically arranged axis. Fixed to the lower end of the rod of the second cylinder 39, is a second block 40 provided with a pivoting pin 41 of the cutting member 4b, that is to say, of its supporting plate 42; a spring 43 is connected between a slide bar 44 for guiding the cylinder rod 39 and the plate 42 of the cutting member, which acts upon the latter to make it rotate upwards.
Lastly, figure 10 shows a possible embodiment of a gripper 34 for gripping the vertical cut edges of the plastic wrapping 9 to be removed from the palletized load. This gripper is movably supported by a relative arm 8, and is suitably pushed forward by a spring, as shown. In this connection, the gripper comprises a first jaw 45 held by a shank 46 sliding in the supporting arm 8 and thrust forward by a spring 46a; a second movable jaw 47 is held by a swivelling arm 48 controlled by a rotatory cylinder 49 secured to a plate 50 which is longitudinally movable with the shank 46 of the jaw 45.
The example described with reference to the figures of the accompanying drawings, illustrates a machine comprising a square-shaped frame and, more in general, an annular-shaped frame, provided with cutting members 4a acting upon all sides of the palletized load, and in particular, two horizontal cutting members 4a, acting respectively on the front and rear faces of the wrapping, with reference to the direction of movement of the load 5 on the conveyor 6, and two horizontal cutting members 4a acting respectively on the two sides or lateral faces of the aforesaid load; the vertical cutting members 4b and the grippers 34 for gripping and removing the cut wrapping, being preferably arranged on the sides at right angles to the direction of movement of the load, that is to say, in correspondence with the front and rear faces.

Claims

1. Machine for automatically cutting a wrapping (9) of plastic material from palletized loads (5) having lateral faces in which the load (5) with the plastic wrapping (9) is made to move on a conveyor (6) along a path and towards a cutting zone for cutting and removing the wrapping (5), the machine comprising a structure (1, 2) defining the cutting zone; cutting means (4) and a cutter supporting frame (3) vertically movable on said structure (1, 2) from an upper inoperative position to a lower operative position, characterized in that the cutter supporting frame (3) comprises an annular frame member, control means for moving the cutter supporting frame (3) from the upper inoperative position to a lower operative position in which the annular frame member surrounds the palletized load (5); said cutting means comprising first horizontal cutting members (4a) each movable on the aforesaid annular frame member (3) parallel to a respective lateral face of the wrapping (9), the machine further comprising control means and biasing means (26, 30) to move each horizontal cutting member (4a) towards and against the plastic wrapping (9), during each cutting operation.

2. Machine as claimed in claim 1, characterized by the fact that each horizontal cutting member (4a) is mounted on a carriage (18) movable along horizontal guides (19) on said annular frame member (3), and control means (19a, 19b, 19c) for simultaneously moving the carriages (18) on said annular frame member (3).

3. Machine as claimed in claim 1, characterized by the fact that each horizontal cutting member (4a) is mounted on a carriage (18) movable along horizontal guides (19) on said annular frame member (3), and control means (19a, 19b, 19c) for moving each single carriage (18) independently on said annular frame member (3).

4. Machine as claimed in claim 1, characterized by the fact that said frame (3) further comprise vertically acting cutting members (4b) for vertically cutting the plastic wrapping (9).

5. Machine as claimed in claim 4, characterized by the fact that the vertical cutting members (4b) are vertically movable, with respect to said supporting frame (3).

6. Machine as claimed in claim 1, characterized by the fact that each horizontal cutting member (4a) is movable along a cutting stroke comprising a peripheral side portion of the wrapping (9), which partially overlaps the peripheral side portion of an adjacent cutting member.

7. Machine as claimed in claim 1, characterized by the fact that each horizontal cutting member (4a) is pivoted to a supporting plate member to rotate angularly with respect to a central position, and by the fact that springs (26) are provided to bias said cutting member (4a, 4b) towards the central position and against the surface of the wrapping (9) to be cut.

8. Machine as claimed in claim 6, characterized by the fact that each horizontal cutting member (4a) is supported by a slider (24) movable at right angles to the cutting direction, towards and away from the plastic wrapping side (9) to be cut, said slides (24) being connected to a control cylinder (30).

9. Machine as claimed in any of the previous claims, characterized by the fact that said cutting means (4) comprise cutting members of the hot-wire (4a, 4b) type.

10. Machine as claimed in claim 1, characterized by the fact that the annular frame member (3) supporting the cutting members (4) is in the form of a square frame comprising a movable horizontal cutting member (4a) on each side of the frame (3).

11. Machine as claimed in claim 1, further characterized by comprising means (8, 34) for gripping and removing the cut wrapping (9).

12. Machine as claimed in claim 11, further characterized by the fact that said means (8, 34) for gripping and removing the cut wrapping (9) comprise articulated arms (8) provided with gripping members (34) for gripping the wrapping (9) and means (33, 35) for guiding and controlling said arms (8) from a condition close to, to a condition away from the wrapping (9) to be cut.

13. Machine as claimed in claim 12, characterized by the fact that said means (8, 34) for removing the wrapping (9) comprises articulated arms (8) hinged to a rod (31) supported by a carriage (32), said arms (8) being provided with gripping means (34) for gripping the wrapping (9); guide means (33) on said structure (1, 2) for said carriage (32), and control means (35) to move said carriage (32) and said articulated arms (8), from an advanced position with the arms (8) closed for gripping cut portions of the wrapping (9) on the palletized load (5), to a retracted position for releasing the removed portions of the wrapping (9).

14. Machine as claimed in claim 12, characterized by the fact that said means (34) for removing the cut wrapping (9) comprise pneumatic and/or mechanical gripping members (45, 47).