EP2392514A1

EP2392514A1 - Equipment for side wrapping of products with plastic film

Info

Publication number: EP2392514A1
Application number: EP11165480A
Authority: EP
Inventors: Massimiliano Ubertini
Original assignee: Messersi' Packaging Srl
Current assignee: Messersi' Packaging Srl
Priority date: 2010-05-27
Filing date: 2011-05-10
Publication date: 2011-12-07

Abstract

A plant for wrapping products with plastic film comprises a line (11) for conveying the products (12) in sequence and a vertical-wrapping station (13) which is arranged along the line. The station (13) comprises a wrapping system (14) with a strip of film arranged transversely with respect to the line so as to wrap a product which passes through the station. This wrapping system (14) is served by two loading systems which convey when operated a pair of reels to the wrapping system, selecting it from a plurality of pairs. A film change-over device picks up the film from a pair of reels conveyed into the operative position and joins it transversely with respect to the conveying line so that it is applied to the products by the wrapping system. It is thus possible to wrap products with different films by selecting the appropriate pair of reels. For example, the films may differ in height, so as to allow wrapping of products of varying height.

Description

DESCRIPTION

The present invention relates to a plant for side wrapping of products with plastic film, advantageously of the heat-shrinkable type.
Among the plants for performing wrapping with plastic film known from the prior art there are those which comprise a wrapping station (sometimes called "curtain" type station) in which a strip of film is stretched, in a vertical plane, transverse to the direction of movement of the product in the station. The product thus comes into contact with the strip and draws it along until it is partially wrapped by it. A pair of vertical blades are then operated in order to close the strip behind the product, weld its edges and cut it. The strip is then joined together again behind the wrapped product, so that it is ready to wrap the next product. In the case of heat-shrinkable film, the wrapped product is conveyed to a heat-shrinking station in order to complete the packing process. Since the height of the strip is related to the height of the product to be packaged (usually the strip must be folded over by a small, but not excessive amount onto the top and bottom faces of the product), in the case where it is required to package products of different height, separate packaging lines are required, i.e. one for each height, with not insignificant costs and dimensions. Alternatively, if the changes are occasional, it is possible to use only one line, enduring a somewhat long line stoppage in order to replace manually the rolls of film with those having a new height. The same problems occur if it is required to wrap the products with different types of film.
EP 0,183,676 describes a plant provided with a plurality of complete wrapping units. Each unit comprises two reels which are already joined together and spaced so as to form the strip of transverse film. The units are movable so that they may be inserted, from the top or from one side, transversely with respect to the product conveying line. The alternating movement of the units thus replaces a complete wrapping structure with another one. The system is, however, complex, bulky and excessively costly, not allowing the easy addition of other types of film.
US 2006/96244 describes a plant which has two wrapping units arranged vertically on top of one another so as to be able to wrap two strips of film of different heights simultaneously around each product. No valid suggestion is given as to how to use alternately several different strips.
The main object of the present invention is to provide a plant which allows the simultaneous management of different types of film rapidly and efficiently, for example for wrapping products which have a different height or in any case require one of these different types of film.
In view of this object the idea, according to the invention, is to provide a plant for wrapping products with plastic film as claimed in claim 1.
In order to facilitate the understanding the innovative principles of the present invention and its advantages with respect to the prior art, examples of embodiment applying these principles will be described below with the aid of the accompanying drawings. In these drawings:

Figure 1 shows a schematic plan view of a plant according to the invention;
Figure 2 shows a schematic front elevation view of the plant according to Figure 1;
Figures 3 and 4 show schematic plan views of grippers for gripping the film;
Figures 5 and 6 show a schematic side elevation view on a larger scale of film pick-up grippers in the plant according to Figure 1;
Figures 7-10 show schematic views, on a larger scale, of a film change-over sequence;
Figures 11, 12 and 13 show partially sectioned schematic plan views of a film cutting and joining device in the plant according to Figure 1;
Figure 14 shows a schematic side elevation view, on a larger scale, of a film cutting device in the plant according to Figure 1;
Figure 15 shows a perspective view of an advantageous embodiment of the plant;
Figure 16 shows a schematic perspective view, on a larger scale, of a plant loader;
Figure 17 shows a schematic front view of the plant shown in Figure 15;
Figure 18 shows a partially sectioned schematic plan view of a wrapping zone of the plant shown in Figure 15;
Figure 19 shows a schematic perspective view, on a larger scale, of a detail of the plant shown in Figure 15;
Figure 20 shows a schematic plan view similar to that of Figure 18, but of a possible variant.

With reference to the figures, Figure 1 shows a plant, denoted generally by 10, for wrapping products with plastic film.
The plant or equipment 10 comprises a line 11 for conveying in sequence products 12 to be wrapped with film. The products may be formed by packs of material arranged on a pallet so as to form a parallelepiped. For example, the packs may consists of bricks, paper-mill products, etc.
The conveying line is essentially of the known type and therefore will not be described or shown here in detail. It generally comprises a support surface on which the products are placed in order to be conveyed through the plant between a loading zone and an unloading zone. The line may advantageously be formed, for example, by means of a belt or chain conveyor.
The conveying line 10 passes through a vertical-wrapping station 13. As will be described in greater detail blow, the station has a system for performing "curtain" type side wrapping of a product 12 which passes through the station. The wrapping system 14 (of the type known per se) has a strip of film 15 which is arranged transverse to the line so as to wrap a product which passes through the station.
In order to form the system for side wrapping of the products, the station comprises two rolls of film 22 which are supported on their vertical axis and arranged on opposite sides of the conveying line. The portions of film which are unwound from the two rolls of the station are joined together to form the strip of film which is stretched transversely with respect to the conveying line. In this way, the product travelling on the conveyor comes into contact with the transverse strip of film and continuing its travel draws the film along with it and is partially wrapped on the sides. As can be seen more clearly in Figure 2, vertical welding blades 23 are arranged opposite each other on the two sides of the line and are movable towards each other for cutting and welding the strip of film around the product which passes through the station. During their movement towards each other the blades weld the film onto the rear part of the product (thus closing it around the product), cut the wound film and join together again the two portions in order to form again the transverse strip for wrapping the next product.
These blades comprise a known electric controlled-heating circuit for welding the portions of film which are brought into contact upon closure of the blades towards each other, as shown schematically in broken lines in Figure 2, after passing of the product. Advantageously, the structure of the station comprises a cross beam 33, between uprights 25 on the sides of the conveying line, along which the cutting and welding blades 23 travel when operated (by means of a motor 34 with a suitable known drive system) so as to move between the spaced apart non-operative position (shown in solid lines in Figure 2) for allowing a product to pass through and the operative position close together (shown in broken lines in Figure 2) for welding the film folded around the product and retained between the blades.
As can be clearly seen in Figure 1 again, on each side of the wrapping station the plant comprises loaders 100 which are equipped with a plurality of reels of film 22, which are each rotatably supported along their vertical axis 24 and are to be brought in pairs into the operative position 110 along the sides of the wrapping system. The loaders are driven by a suitable drive system (not shown in detail) so as to be able to convey when operated a desired pair of reels into the operative position 110.
The station also comprises means 111 which allow the free portions of the reels to be picked up in the operative position and conveyed to a joining unit 112 which is intended to form the continuous transverse strip of film and is used by the station during wrapping of the products. Advantageously, the station also comprises means 113 for cutting the strip so as to allow separation again of the reels so that they can be replaced by two other reels of the plurality.
Advantageously, the two loaders 100 are linear and parallel to the conveying line 11. Moreover, in each reel support seat the loader is provided with a device 114 for supporting and dispensing the free portion of the film.
Unwinding and recovery of the film can be performed by means of a motorized system 115 for managing rotation of the reel in the operative position. Advantageously there is one such motorized system for each loader, which is fixed in the operative position of the reels, and acts by means of tangential driving of the reel situated in the operative position. Tangential driving is advantageous for achieving better control over the peripheral speed of rotation of the reel.
Advantageously, an electronic apparatus for managing unwinding of the reel comprises, as will become clear below, a jockey arm system 16. The jockey arm is advantageously provided with spring steel plates which ensure that the film does not slip downwards when there is a slackening of the tension. Moreover, in order to prevent uncontrolled unwinding of the film, each reel has a support shaft 24 which is advantageously provided with disc brakes 117, as can be clearly seen in Figure 2.
Figure 3 shows in greater detail the means 111 which allow picking up of the free portions of the reels in the operative position and conveying thereof to the joining unit 112. These means 111 comprise fixed grippers 118 and mobile grippers 119. The fixed grippers consist of a plurality which are supported on the loader in each position for receiving a reel. These fixed grippers retain the free portion of film when the reel is not in the operative position. Advantageously they may be moved manually towards an outermost position with respect to the product conveying line so as to facilitate the manual insertion of the portion when a new reel is positioned on the loader (as shown in broken lines in Figure 7).
The mobile grippers 119 on the two sides of the station are supported so as to be driven between a pick-up position close to the fixed grippers and a position for joining the film (or gripping the film which is cut) close to the joining device 112 and cutting device 113. The mobile grippers advantageously travel along rails parallel to the cross beam 33 so as to be displaced from the reel loading zone to the zone for welding the opposite film portions.
As can be clearly seen in Figure 4 and also in Figures 5 and 6, the mobile grippers and the fixed grippers are advantageously formed by means of pairs of resilient flat lugs which project parallel from rotational spindles for closing and opening the grippers. The fixed-gripper lugs are staggered with respect to the mobile-gripper lugs so that they may be engaged inside each other, as can be clearly seen in Figures 4 and 6, so as to allow the film to pass from one pair of grippers to the other.
Advantageously, at least the mobile grippers have a supply of pressurised air which is emitted from a central duct 120 along the axis of rotation in a direction parallel to and passing over the lugs towards their free ends. This has been found to facilitate the corrected stretched arrangement of the portions of film between the grippers before they are closed.
Figures 7 to 10 show film change-over sequences.
In particular, Figure 7 shows (for one reel) the aforementioned position with the jockey arms and fixed grippers which are displaced outwards for introduction of the portion of film into the fixed grippers when assembly of a new reel on the loader is performed. The same operation is carried out in mirror fashion on the reels of the opposite loader. Then, the fixed grippers are brought back into the advanced operative position (as can also be seen in Figure 1) such that the reel is ready to be used when the loader moves it into the operative position 110.
Figure 8 shows two reels which are have reached the operative position and which must form the transverse strip 15.
In this condition, the fixed grippers 118 supply the station with respective portions of film 121. The mobile grippers 119 are then displaced so as to enter into the fixed grippers (Figure 9), grip the film, removing it from the fixed grippers (which open) so as to convey it towards the joining device (Figure 10) assisted if necessary by the drives 115.
The film is free to travel inside the fixed grippers and the mobile grippers are able to position the film in the vicinity of the welding and cutting unit 112, 113. Advantageously, just before reaching the position of the welding and cutting unit, the air jet on the mobile grippers is activated. This favours the vertical alignment of the film portion between the grippers. In the meantime, the jockey arm will rotate since the mobile grippers recall the film. Advantageously, by controlling the rotation of the jockey arm, the reel will be moved by means of the motor 115 so as to unwind the film, producing strong tensioning or pulling forces which would adversely affect normal operation of the machine.
The jockey arm will have the function of distributing the film uniformly and keeping it slightly pre-tensioned. Unwinding of the film will continue until the mobile grippers are in their end position and cause overlapping of the film portions.
The welding unit 112 is therefore activated and performs joining together of the left-hand portion with the right-hand portion. At this point the continuous transverse strip 15 has been formed, the welding and cutting unit returns into the rest position and the mobile grippers open so as to allow movement of the film when it is drawn by the pack passing through the machine. The machine is ready to receive the products to be wrapped with the film of the selected reels. Operation of the machine during the packaging operations are substantially conventional and will not be described further here.
When it is required to replace the pair of reels with another one (for example for a change in format of the film), the mobile grippers are positioned and grip the film in the vicinity of the cutting means 113.
The cutting unit 113 is operated and performs cutting of the film. At this point the film on the reels is divided again, with the free portions gripped between the respective mobile grippers. The mobile grippers retract until the film is inserted again inside the reel. At the same time, the reels are rotated by the respective drives 115 so as to be able to store the film again. When the mobile grippers are positioned again between the fixed grippers, the fixed grippers close and the movable grippers open. Finally, the mobile grippers move out from the fixed grippers so as to allow the loader to move into the position with the new desired reel. The reel joining cycle may then be performed as already described above and the machine is ready to operate again with the new reels. Figures 11, 12, 13 and 14 show in greater detail the cutting and joining means which, advantageously, are contained in the same cutting and joining device 150. Advantageously the device 150 comprises a welding unit 112 with a welding head 151 and a cutting unit 113 with a vertically sliding blade 152. The film is gripped between the unit and an opposite contact block 153 in order to perform welding or cutting.
In the case of welding, the welding head is heated and the blade is kept in the raised position so as not to interfere with the film (as shown schematically in Figure 14). The welding positioning device is shown in Figure 12.
In the case of cutting, the welding head is not heated and the blade is slid vertically so as to perform the cut, while the grippers 119 advantageously retain the portions. At least one of the two grippers 119 is advantageously retracted slightly in order to keep the film tensioned during cutting and facilitate the creation of a free portion for the next joining operation. The device in the cutting position is shown in Figure 13.
As shown in Figure 11, when the cutting and joining device is in the rest position, the open grippers are able to guide and facilitate movement of the film during the product packaging operations even if the film passes through the device.
The film driving system in the vicinity of the welding bars facilitates the movement of the film during wrapping of the pack.
Advantageously, the plant comprises 19 for controlling the plant, which manage operation of the plant and in particular displacement of the loaders so as to select the film which must be used. The control means 19 (for example, comprising a known electronic system with suitably programmed microcontroller) may receive selection commands from an operator or from a system for electronic detection of the incoming product.
In particular, if the reels are each equipped with film suitable for a different product height or height range, a sensor 20 may be provided, said sensor detecting the height of the incoming product before the station 13 and communicating this height to the control means 19 which may thus decide which pair of reels contains the film most suitable for wrapping the particular product and carry out the necessary replacement of the reels. Advantageously, the film used by the plant is of the heat-shrinkable type. In this case, the conveying line 11, after the wrapping station, reaches or passes through a known heat-shrinking station 21.
Figure 15 shows an advantageous embodiment of the plant where the side loaders 100 advantageously have a modular design. As can be clearly seen in Figure 16, each module (denoted generically by 200) comprises a box-shaped frame 201 which defines a parallelepiped for containing a reel 22. The modules may be designed all identical, suitable for receiving any reel between the maximum and minimum dimensions envisaged for the reels. The frame 201 supports the shaft 24 at the top and bottom ends, the braking system 117, the pre-tensioning jockey-arm system 116 and the fixed grippers 118. Suitable known electrical connection and fluid-dynamic systems allow each module to be supplied with the power necessary for operation and receive from each module signals of suitable sensors situated therein. For example, the jockey arms 116 may be controlled by pneumatic systems 205 so as to ensure correct pre-tensioning of the film, in turn controlling, via a known sensor, the drive means 115 for unwinding or rewinding the reel.
The modules are connected together (for example bolted together) so as to form a train which travels on special guides 202.
As can be clearly seen also in Figure 17, each module 17 advantageously has a rack segment 203 which is mounted horizontally close to the base. The rack segments of the modules arranged alongside each and connected to form a train thus create a single rack along the entire length of the loader 100. A motor 204 is provided in a suitable position (preferably alongside the station 13) and drives the rack so as to move the loader longitudinally along the guides 202 and bring the desired module 200 into the operative position for using the film on its reel, as already described above.
As can be clearly seen in Figures 17 and 18, the plant also comprises advantageously a further pair of jockey arms 206 which are provided along the path of the strip of transversely tensioned film and have the function of preventing vertical slipping of the strip during the product wrapping operations. As can be clearly seen also in Figure 19, these jockey arms 206 are formed by arms 207 which resiliently rotate around a vertical axis 209 by means of an actuator 208 and which support vertical tubes 210 over which the film passes. The jockey arms are situated close to the gripper zone.
The tubes 210 have suction slits 211 in the zone thereof over which the film passes, these slits being connected to a suction source (denoted by 212 in Figure 17). As can be seen in Figure 18, the film may pass over the tubes 210 in their vertical direction, but the suction prevents the film from slipping downwards when there is a reduction in the tension of the film owing to the welding operations. For example, during welding of the pack by means of the main welding blades 23, the film must be slackened so as to ensure that softening in the welding zone does not result in yielding of the film in this zone. During welding it is therefore advantageous for suction to be activated so as to keep the strip of film at the correct height in the plant, preventing it from sliding downwards.
The use of a suction system has been found to be particularly advantageous because it suitably retains the film without stress. Moreover, by acting on a single side of the film (differently, for example, from roller and counter-roller systems), it leaves suitably free the zone for the travel movement of the film conveying grippers during the joining operations.
Figure 20 shows a constructional variant of the suction jockey arms 206. According to this variant, suction jockey arms 306 are used where the suction tubes 210 (although being close to the gripper zone) are supported by arms 307 which rotate resiliently around a vertical axis 209 close to the mid-line of the wrapping station. As can be clearly seen in Figure 20, in this variant the arms 307 of the two jockey systems are in fact directed towards each other so that the axes 209 are close together. Advantageously it is thus possible to use an actuator 208 arranged centrally between the two jockey arms so as obtain their resilient movement. The greater resilient rotational leverage of the jockey arms improves their action on the strip of film. For example, with rotation of the jockey arms, the suction eyelets move in the plane of the film less than in the preceding solution, ensuring a better sucking action.
At this point it is clear how the predefined objects have been achieved. With a plant according to the invention it is possible to achieve a high degree of operational flexibility, quicker format change-over times and smaller dimensions, in particular in the vertical direction.
The system according to the invention offers the possibility of quick automated change-over of the reels which are available for the machine in the special store formed by the mobile loaders. The reels may be replaced by other new reels with a different format (i.e. height) if used up or with other formats and/or colours depending on the type of production required. It is sufficient for the reels for the required production to be preloaded by an operator in the predetermined receiving seats.
Advantageously, the driven reels are only those with the format being used by the machine, while the parked reels are stationary. In this way it is possible to perform easily replacement of the inactive reels without any danger since they are duly isolated from the moving parts of the machine. During this operation the machine may continue to work normally. The only operation prohibited is the format change-over operation, for obvious safety reasons.
The advantageous arrangement of the reels on two carriages which are situated on the right-hand side and left-hand side and which, during the change-over operations, move up and down with respect to the machine and along the sides of the conveyor result in a plant which is very compact and distributed along the sides of the conveyor in the longitudinal direction, without occupying valuable space in the side zones.
Obviously, the areas situated upstream and downstream of the machine and occupied by the store have a variable size depending on the capacity of the latter.
The use of stores with a modular structure advantageously results in a greater machine flexibility, the capacity of the stores being able to be expanded as required, without having to envisage already from the start relatively costly structures for many reels. Moreover, the modular nature of the structure results in lower design costs and easier and more rapid maintenance. For example, in the event of a malfunction of a store module, it may be quickly replaced in its entirety so as to avoid a longer machine downtime.
Obviously, the above description of the embodiments applying the innovative principles of the present invention is provided by way of example of these innovative principles and must therefore not be regarded as limiting the scope of the rights claimed herein. For example, the loaders are advantageously provided with reels of film for wrapping a varying product height or height range and the film is therefore selected depending on the height of the product to be wrapped.
However, the reels in the loader may have film with other varying characteristics, depending on specific wrapping requirements. For example, film with different colours or different physical and chemical properties may be provided. The plant according to the invention will however allow rapid selection of the desired film for each specific incoming product. Selection may be manual or controlled by suitable automatic or semiautomatic devices, also depending on sensing of the specific and predefined characteristics of the incoming product.
The number of reels which may be used may obviously be varied as required and different from that shown by way of example in the drawings. Moreover, although a substantially straight conveying line is preferable, other configurations are conceivable, also so as to be able to make use of spaces with a particular shape and reduce the dimensions of the plant in certain directions. The same is also applicable to the loaders. The suction jockey arms, as well as other plant components, may be used both with the generic loaders according to Figure 1 and advantageously with the modular loaders according to Figure 15, as can be easily imagined by the person skilled in the art on the basis of the description provided above.

Claims

Plant for wrapping products with plastic film comprising a line (11) for conveying the products (12) in sequence and a vertical-wrapping station (13) which is arranged along the line and provided with a wrapping system (14) with a strip of film stretched transversely with respect to the line so as to wrap laterally a product which passes through the station, the strip of film being unwound from two reels (22) situated in respective operative positions on the two sides of the station, characterized in that on the two sides of the station there are side loaders (100) which support a plurality of separate reels for moving them, when operated, between non-operative positions and said respective operative positions on the sides of the station, means (111) for picking up portions of film from two reels brought into said respective operative positions by means of the side loaders (100) being provided so as to supply said portions to joining means (112) for forming the said transverse strip.
Plant according to Claim 1, characterized in that the station comprises controlled means (113) for cutting the transverse strip so as to allow rewinding of the portions of film onto the respective reel and allow the loaders to change the reels in the operative position.
Plant according to Claim 1, characterized in that the loaders extend in a direction longitudinal with respect to the plant and parallel to the conveying line.
Plant according to Claim 1, characterized in that the pick-up means comprise, for each reel, fixed grippers (118) on the loader for retaining the respective portion and mobile grippers (119) in the station for gripping the portion from the fixed grippers of the reel in the operative position and conveying it to the means for joining to the corresponding portion unwound from the other reel in the operative position.
Plant according to Claim 1, characterized in that means (19) for controlling the plant operate the loaders and the station so as to select the reels which form the transverse strip of film which must be wrapped around a product passing along the line.
Plant according to Claim 1, characterized in that the station comprises vertical cutting and welding blades (23) which are arranged opposite each other on the two sides of the line and which are movable towards each other for cutting and welding the strip of film around a product which passes through the station and against the transverse strip.
Plant according to Claim 1, characterized in that the loaders are linear loaders which travel parallel to the conveying line so as to move in sequence the reels into said operative position.
Plant according to Claim 6, characterized in that the station comprises a cross beam (33) along which the cutting and welding blades (23) travel, when operated, so as to move between a spaced apart non-operative position allowing a product to pass through and an operative position close together for welding the film retained between the blades.
Plant according to Claim 1, characterized in that the film is heat-shrinkable and the conveying line, after the wrapping station, reaches or passes through a heat-shrinking station.
Plant according to Claim 1, characterized in that the side loaders are composed of modules (200) interconnected in a row, each module supporting a respective reel.
Plant according to Claim 10, characterized in that each module (200) comprises a support frame which supports a vertical shaft for rotation of the respective reel.
Plant according to Claim 11, characterized in that each module comprises a system (117) for braking rotation of the reel and/or a pre-tensioning jockey arm system (116).
Plant according to Claims 4 and 10, characterized in that each module comprises the said fixed grippers.
Plant according to Claim 1, characterized in that suction jockey arms (206) are present along the length of the transversely stretched strip of film for preventing vertical slipping of the strip during the operations for wrapping the product with the film.
Plant according to Claim 14, characterized in that the suction jockey arms comprise vertical tubes (210) with suction slits over which the transverse strip of film is intended to pass.
Plant according to Claim 10, characterized in that each module (200) comprises a rack segment (203), the rack segments of the modules interconnected in a row forming a rack having, engaged therein, a motor (204) for longitudinal movement of the loader so as to convey, when operated, a selected module into the operative position alongside the station.
Plant according to Claim 1, characterized in that each loader comprises for each reel a system (117) for braking rotation of the reel and/or a pre-tensioning jockey arm system (116).