HK1170464A - Method for feeding a supply station of a packaging unit with a new reel of sheet packaging material, sheet packaging material holder and lift truck - Google Patents

Description

Method for feeding a new roll of sheet packaging material to a supply station of a packaging unit, sheet packaging material holder and lift truck

Technical Field

The present invention relates to a method for feeding a new roll of sheet packaging material to a supply station of a packaging unit, as well as to a sheet packaging material holder and a lift truck.

Background

Many food products, such as fruit juice, pasteurized or UHT (ultra high temperature treated) milk, wine, tomato sauce, etc., are sold in packages made of sterilized packaging material.

A typical example of such a package is the parallelepiped-shaped package for liquid or pourable food products, known as Tetra Brik Aseptic (registered trademark), which is made by folding and sealing a laminated strip packaging material.

The packaging material has a multilayer structure generally comprising: a substrate for stiffness and strength, which may be defined by a layer of fibrous material (e.g., paper) or mineral-filled polypropylene material; multiple layers of heat-seal plastic material, such as polyethylene film, covering both sides of the base layer.

In the case of aseptic packages for long-storage products, such as UHT milk, the packaging material also comprises a layer of gas and light barrier material, such as aluminium foil or ethyl vinyl alcohol (EVOH) film, which is superimposed on a layer of heat-seal plastic material, and is in turn covered with another layer of heat-seal plastic material forming the inner face of the package eventually contacting the food product.

As is known, such packages are produced on fully automatic packaging devices having a supply station fed with a roll of sheet packaging material.

In more detail, a pair of rolls are mounted on a supply table, and each roll has a hollow core mounted on a spindle.

More precisely, the wrapping device processes the first roll while a new second roll is mounted on the supply station and remains idle during operation of the wrapping device.

During operation of the packaging device, the packaging material of the first roll slides within a slot defined by a first packaging material holder connected to a fixed part of the supply station.

In particular, a continuous tube is formed from a web of supplied packaging material in a packaging device; the web of packaging material is sterilized in the packaging unit, for example by applying a chemical sterilizing agent, such as a hydrogen peroxide solution, which is subsequently removed from the surface of the packaging material, for example by heating and evaporation.

The sterilized web is maintained in a closed, sterile environment, and is folded into a cylinder and sealed longitudinally to form a tube.

The tube is fed in a first vertical direction parallel to its axis and is continuously filled with the sterilized or sterile-processed food product and heat-sealed at equally spaced cross sections by two pairs of jaws to form pillow packs, each pillow pack having top and bottom transverse sealing bands, i.e. bands extending in a second direction orthogonal to the first direction. The pillow packs are separated by cutting the respective sealing bands and then fed to a folding station, where the pillow packs are folded to form respective packages.

When the packaging material of the first roll is almost completely unwound from the core and almost all the packaging material has passed through the slot of the first packaging material holder, the head movable within the supply station cuts the packaging material immediately downstream of the first packaging material holder. In this way, the first edge of the packaging material of the finished first roll is suspended from the first packaging material holder, while the second edge of the packaging material of the finished first roll remains in the supply station of the packaging device. In particular, the first and second edges are parallel to and spaced apart from each other.

When the packaging device is handling a first roll, the operator inserts the end of a new second roll into the slot of the second packaging material holder, thereby suspending the end from the second packaging material holder.

Furthermore, the operator performs a plurality of operations that prepare the joining of the end of the new second roll to the second edge of the packaging material of the finished first roll.

More precisely, the operator arranges the end of the new second roll at the supply station in the correct position with respect to the second packaging material holder and cuts the end along a diagonal. In this way, the operator forms the third edge of the new second roll; the third edge is positioned and shaped so as to perfectly match the second edge of the first roll.

At the end of these preparation operations, the third edge of the second roll is suspended from the second packaging material holder connected to the fixing means of the supply station.

After cutting the packaging material of the first roll, the head welds the second edge of the first roll to the third edge of the new second roll, so that the operation of the packaging device can continue to process the packaging material of the new second roll.

Again, the operator removes the core of the finished first roll and the wrapping material extending between the core and the first edge, and feeds the supply station with a new further roll of wrapping material.

The industry feels a need to meet the tolerance requirements for connecting the second edge of the finished first roll to the third edge of the new second roll, while reducing or even eliminating the presence of an operator at the supply station of the packaging unit.

Disclosure of Invention

The object of the present invention is to provide a method for feeding a supply station of a packaging unit with a new roll of packaging material, a packaging material holder and a lift truck, which method, holder and truck are designed to meet the above requirements in a straightforward and cost-effective manner.

According to the present invention, there is provided a method for feeding a new roll of sheet packaging material to a supply station of a packaging unit according to claim 1.

According to the present invention, there is provided a sheet packaging material holder according to claim 6.

Finally, according to the invention, there is provided a lift truck according to claim 12.

Drawings

Preferred non-limiting embodiments of the present invention will be described by way of example with reference to the accompanying drawings, in which:

figures 1 and 2 show in perspective view and in side view respective successive steps of a method for feeding a supply station of a packaging unit with a new roll of packaging material according to the invention;

fig. 3 is an enlarged perspective view of the stand of fig. 1, with parts removed for clarity;

figures 4 and 5 show a packaging material holder according to the invention in two different operating configurations in perspective view;

fig. 6 shows the packaging material holder, a part of the lift truck according to the invention, and the supply station of the packaging unit of fig. 2 from a different perspective with respect to fig. 4 and 5, with parts removed for clarity;

fig. 7 shows in an enlarged perspective view the pair of packaging material holders of fig. 4 to 6 coupled with the packaging device of fig. 1, with parts removed for clarity; and

figure 8 shows in perspective view a supply station of the packaging device of figure 1.

Detailed Description

Number 1 in figure 2 indicates as a whole a packaging unit for making sealed packages of a food product from a tube of sheet packaging material by processing a roll 3b of packaging material.

A plurality of packaging units 1 (only one of which is shown in fig. 2) are part of the packaging plant shown in fig. 1 to 3, limited to a storage station 2 (fig. 1 and 3) for a plurality of new rolls 3a of packaging material and a plurality of lift trucks 8 movable between the storage station 2 and a supply station 6 of the packaging units 1.

In more detail, new reel 3 a' and reel 3b are mounted on supply table 6. The roll 3b is processed by the packaging device 1 to form a package, while a new roll 3 a' remains idle during operation of the packaging device 1 (fig. 8). Once roll 3b is finished, the packaging material of new roll 3 a' is connected to the packaging material of finished roll 3b, finished roll 3b is unloaded from supply station 6, and a new roll 3a is loaded onto supply station 6.

In very simple terms, each roll 3a, 3 a', 3b comprises a hollow core 4 on which the sheet of packaging material is wound. Further, a mandrel 23 is inserted into the core 4.

The store station 2 comprises a plurality of supports 5 for supporting corresponding new rolls 3a of a supply station 6 feeding the packaging device 1.

Each lift truck 8 generally comprises a frame 7 and a pair of gripping arms 9 movable with respect to each other for gripping or releasing a corresponding new roll 3 a. Further, the clamp arms 9 of each lift truck 8 are rotatable about the horizontal direction integrally with each other, and are slidable in the vertical direction integrally with each other.

Furthermore, the lift truck 8 can be guided automatically within the packaging device. In particular, lift truck 8 may be laser guided.

Packaging unit 1 preferably produces sealed packages of pourable food products, such as pasteurized or UHT milk, fruit juice, wine, etc.

The packaging unit 1 can also produce sealed packages of such food products: the food product may be poured into the tube when producing the package and set after the package is sealed. An example of such a food product is a portion of cheese which melts when the package is produced and solidifies after the package is sealed.

The packaging material has a multilayer structure (not shown) and comprises a layer of fibrous material (usually paper) covered on both sides with respective layers of heat-seal plastic material, such as polyethylene. In the case of aseptic packages for long-storage products, such as UHT milk, the packaging material also comprises a layer of gas and light barrier material, such as aluminium foil or ethyl vinyl alcohol (EVOH) film, which is superimposed on a layer of heat-seal plastic material, and is in turn covered with another layer of heat-seal plastic material forming the inner face of the package eventually contacting the food product.

The tube is formed in a known manner by longitudinally folding and sealing a web (not shown) of heat-sealed sheet material, filled with sterilized or sterile-processed food products for packaging by means of a filling tube (not shown), and fed in a known manner not shown along a vertical path, heat-sealed and cut at equally spaced cross sections.

The supply station 6 generally comprises (fig. 2, 4, 6, 7 and 8) a frame 12 and support members (not shown) for rotatably supporting the spindles 23 of the new rolls 3 a' and 3b with respect to the frame 12.

During operation of packaging unit 1, the sheet packaging material of processed reel 3b passes through slot 10 of respective packaging material holder 11 fitted to frame 12 of supply station 6.

In contrast, only the end 52 of the sheet packaging material of the new roll 3 a' passes through the slot 10 of the other packaging material holder 11 fitted to the frame 12 of the supply station 6.

Furthermore, the supply station 6 comprises a head (not shown) movable within the frame 12. Such a head cuts the end of each roll 3b near the core 4 when the roll 3b is almost completely finished.

With reference to fig. 8, the head cuts the sheet packaging material adjacent to the core 4 immediately downstream of the holder 11 and along a diagonal relative to the feeding direction of the sheet packaging material.

In this way, the end portion adjacent to the core 4 of each finished roll 3b is divided by the head into a first portion 41 still wound on the core 4 and hanging from the holder 11 and a second portion 42 supported by the packaging device 1.

Referring to fig. 8 (left side), the head forms an end edge 50 on the first portion 41 of the terminated roll 3b and an end edge 51 on the second portion 42 of the terminated roll 3 b. More precisely, the edges 50, 51 are parallel, facing each other and spaced apart.

Subsequently, a new roll 3a is attached to the edge 51.

As will be apparent from the remainder of the present description, the operator performs a plurality of operations on the new reel 3a ' (3a) in preparation for connecting the new reel 3a ' (3a) to the edge 51 of the finished reel 3b (3a ').

In particular, the operator forms, by cutting, an edge 53 (fig. 5) in the end 52 of the new roll 3 a' (3a) opposite the relative core 4. This edge 53 is inclined and matches the configuration of the edge 51 of the finished roll 3b (3 a').

Once roll 3b (3a ') is finished, the head welds together edge 51 of finished roll 3b (3a ') and edge 53 of new roll 3a ' (3 a).

Referring to fig. 1 and 3, each support 5 comprises a frame 15, a pair of support elements 33 for supporting the spindle 23 of the stored reel 3a and a pair of connecting elements 17 supported by the frame 15.

More precisely, the frame 15 substantially comprises:

two horizontal base elements 16;

two horizontal elements 18 arranged parallel and higher than the elements 16; and

two uprights 19, each having a vertical portion 20 extending from the corresponding base element 16, a horizontal portion 21 arranged in parallel and supporting the relative connecting element 17, and an inclined portion 22 extending between the corresponding portions 20, 21.

The supporting elements 33 (only one of which is shown) have a trapezoidal cross section and are supported by the corresponding element 18 of the frame 15.

The connecting element 17 is supported by a portion 21 of the corresponding upright 19.

Advantageously, the holder 11 comprises a pair of pins 13 and a pair of pins 14, the pins 13 being releasably connectable to corresponding seats 25 (fig. 6 and 7, left) defined by the frame 12 of the supply station 6 or to seats 26 (fig. 3 and 5) defined by corresponding connecting elements 17 of the support 5, the pins 14 being releasably connectable to holes 43 (fig. 4 and 5) of a connecting structure 40 associated with the frame 7 of the lift truck 8.

Since the holder 11 can be releasably connected to both the frame 12 and the carriage 5, a preparation operation is performed on the new roll 3a at the carriage 6, and then the new roll 3a is moved toward the supply station 6.

The holder 11 further comprises two parallel plates 27, 28 defining a slot 10 therebetween, a pair of prism elements 29 and a support pin 14 projecting from a first side of the plate 27 facing away from the plate 28, and a pair of prism elements 30 and a support pin 13 projecting from a second side of the plate 27 facing away from the first side.

More precisely, pins 13, 14 have a cylindrical main portion 31 and a tapered end portion 32 extending from elements 30, 29, respectively.

The main portion 31 of each pin 13 comprises an annular groove 24, the annular groove 24 being adapted to cooperate with a spherical end of a respective dowel (not shown) housed in the respective seat 25, 26. More precisely, the dowel extends orthogonally to the relative seat 25, 26 and is spring-loaded towards a position in which it retains the relative pin 13 in the relative seat 25, 26.

In addition, each pin 14 includes a through hole 24' extending orthogonally to the axis of the associated pin 14, and the connection structure 40 further includes a hole 80 (fig. 4) orthogonal to and passing through the hole 43.

When the pin 14 engages the hole 43, the dowel, which is moved by the actuator 81 (FIG. 5), further engages the hole 80 and connects the connecting structure 40 to the holder 11.

The pins 13, 14 extend along respective axes A, B that are parallel to each other. More precisely, axis B is interposed between axes a.

Further, the retainer 11 comprises a pair of springs 35 wound on corresponding pins, the springs 35 being partially interposed between the plates 27 and 28 and loading the plate 28 against the plate 27.

In particular, the spring 35 is helical and extends along a corresponding axis C inclined with respect to the axis A, B.

More precisely, each axis C is interposed between relative axis a and corresponding axis B. Furthermore, the axis C is orthogonal to the plates 27, 28.

The plate 28 comprises a toothed appendage 37 on the surface facing away from the slot 10 (figure 6).

Supply station 6 comprises a variable-length actuator 39, actuator 39 in turn having an end 38 (fig. 6), end 38 engaging appendix 37 to move plate 28 away from plate 27 to allow sheet packaging material to pass through slot 10 during operation of packaging device 1.

In a completely similar manner, each carriage 5 comprises an actuator 39 of variable length, actuator 39 being adapted to move plate 28 away from plate 27 so as to allow the operator to arrange end 52 of roll 3a within slot 10 and with respect to holder 11 (fig. 5).

The connecting structure 40 comprises a plate 45 connected to an arm projecting from the frame 7 of the lift truck 8, a body 48 and a plurality of springs 47a, 47b interposed between the plate 45 and the body 48.

In particular, the arm is movable with respect to the frame 7 along three directions orthogonal to each other. Two directions lie in the plane of fig. 2, and the third direction is orthogonal to the plane of fig. 2.

More precisely, the body 48 extends on the opposite side of the plate 45 with respect to the frame 7 and defines a pair of through holes 43 (fig. 5) engaged by the pins 14 when the holder 11 is connected to the lift truck 8.

The springs 47a, 47b are four in number in the depicted embodiment and extend along respective axes D (fig. 5).

Two springs 47a have respective axes D on the same first vertical plane, and the other springs 47b have respective axes D on the same second vertical plane.

Each spring 47a is parallel to the associated spring 47 b.

Axis D is parallel to axis A, B.

Finally, the connecting structure 40 comprises a pair of springs 49, the springs 49 projecting from the body 48 on opposite sides of the plate 45 and having free ends opposite the body 48.

When pin 13 of holder 11 is connected to seat 25 of frame 12 and pin 14 is connected to connecting structure 40, spring 49 urges plate 27 against plate 27 (fig. 5) and against plate 28. Thus, when lift truck 8 is moved away from supply station 6, holder 11 is still connected to frame 12 by pins 13 inserted into seats 25.

In use, a new roll 3a is supported on the respective support 5 at the storage station 2 and the holder 11 is connected in a disengageable manner to the relative support 5 (fig. 1).

At the same time, the roll 3b is processed by the packaging device 1 while a new roll 3 a' remains idle at the supply station 6.

When the roll 3b processed by the packaging unit 1 is almost completely finished, the head of the packaging unit 1 cuts a portion of the sheet packaging material of the roll 3b adjacent to the core 4, downstream of the holder 11 previously connected to the frame 12 of the supply station 6. In this way, the head of the packaging unit 1 forms a portion 41 with a rim 50 depending from the holder 11. Furthermore, the head forms a portion 42 with an edge 51, which is supported by the packaging unit 1 downstream of the holder 11 (fig. 8).

At this stage, the head welds together the edge 51 of the finished coil 3b with the edge 53 of the new coil 3 a' already fitted to the supply station 6.

With reference to the holder 11 connected to the bracket 5, the pin 13 is inserted in the relative seat 26 of the connecting element 17 of the relative bracket 5. Specifically, the slot 24 is engaged by the ball-shaped end of the dowel to releasably secure the pin 13 within the seat 26.

In addition, the spindle 23 is inserted inside the core 4 of the corresponding new roll 3a and is supported by the relative support element 33.

For simplicity, the operation of the holder 11 and lift truck 8 is described below with reference to only one holder 11, only one new roll 3a and only one stand 5.

In particular, actuator 39 of bracket 5 moves appendix 37 (and therefore plate 28) away from plate 27 against the elastic action of spring 35.

In this way, the operator can easily insert the sheet packaging material of the new roll 3a into the slot 10 until it is suspended from the holder 11.

The operator performs a plurality of operations on the end 52 of the new roll 3 a. These operations are prepared for the subsequent connection of the end 52 of the new roll 3a with the edge 51 of the finished roll 3 a' (3b) processed by the packaging device 1.

More precisely, the operator checks the quality of the sheet packaging material, cutting the end portion 52 along a diagonal line with respect to the direction in which the sheet packaging material extends. In this way, the operator forms the edge 53. Furthermore, the operator arranges the sheet packaging material of the new roll 3a in a given position with respect to the position of the pins 13, so that the edge 53 will perfectly match the edge 51 of the finished roll 3 a' (3b) (fig. 3).

Once the operator has performed a preparation operation on the sheet packaging material of new roll 3a, actuator 39 of carriage 5 brings appendix 37 (and therefore plate 28) close to plate 27. In this way, the sheet packaging material of the new roll 3a is clamped firmly in the slot 10 of the holder 11.

Again, lift truck 8 separates holder 11 with finished reel 3b and relative core 4 from supply station 6.

More precisely, lift truck 8 approaches supply station 6 until hole 43 is engaged by pin 14 and moves away from supply station 6, detaching holder 11 with finished reel 3b from supply station 6.

When moved away from the supply station 6, the lift truck 8 disengages the pins 13 from the seats 25 of the supply station 6.

To feed packaging unit 1 with new roll 3a, another (or the same) lift truck 8 removes holder 11 together with new roll 3a with edge 53 from support 5, moves holder 11 together with new roll 3a from support 5 to supply station 6 of packaging unit 1, and finally connects holder 11 to frame 12 of supply station 6 and moves mandrel 23 of new roll 3a to the support members of supply station 6.

In more detail, lift truck 8 approaches holder 11, which is releasably connected to stand 5, until spring 49 abuts plate 27 and pin 14 of holder 11 engages hole 43 of connecting structure 40.

Specifically, actuator 81 moves the dowel further inward of bore 80 to connect connecting structure 40 to holder 11.

The lift truck 8 is then moved away from the support 5 with the attachment structure 40 releasably attached to the holder 11.

The springs 47a, 47b ensure that accidental vibrations do not affect the correct positioning of the edge 53 with respect to the holder 11, when the lift truck 8 moves the holder 11 together with the new reel 3a from the support 5 to the supply station 6. Furthermore, the spindle 23 of the new roll 3a is supported by the gripping arm 9.

Lift truck 8 with holder 11 and new reel 3a is brought close to supply station 6 and pins 13 of holder 11 are inserted in seats 25 of frame 12 in order to releasably connect holder 11 to frame 12.

In particular, during the movement of lift truck 8 towards supply station 6 and the connection of holder 11 to frame 12, spring 35 loads plate 28 towards plate 27, so as to clamp the sheet packaging material firmly within slot 10 and prevent edge 53 from changing its position with respect to holder 11.

After attaching the holder 11 to the frame 12, the lift truck 8 is moved away from the holder 11, thereby disengaging the pins 14 from the holes 43.

More precisely, when lift truck 8 moves away from supply station 6, the action of spring 49 pushes plate 27 against plate 28. Thus, the holder 11 is still connected to the frame 12 of the supply station 6 by the pins 13 inserted in the seats 25.

Once holder 11 is connected to frame 7 and core 4 of new roll 3a is coupled with relative spindle 23, edge 53 is cantilevered from holder 11 and has a shape perfectly matching edge 51 of roll 3 a'.

Once roll 3a 'is almost completely finished, the head of packaging unit 1 welds edge 51 of finished roll 3 a' to edge 53 of new roll 3 a. Actuator 39 of supply station 6 moves plate 28 away from plate 27 so as to allow sheet packaging material to move through slot 10, and operation of packaging device 1 continues to process the packaging material of new roll 3 a.

The advantages of the method according to the invention for feeding packaging unit 1 with new rolls 3a, as well as the advantages of holder 11 and lift truck 8, will be apparent from the foregoing description.

In particular, the method of feeding packaging unit 1 with new reel 3a and holder 11 and lift truck 8 according to the present invention allow to correctly arrange edge 53 of new reel 3a with respect to edge 51 of finished reel 3b, without requiring the presence of an operator at supply station 6.

In fact, the lift truck 8 can be easily controlled by the laser, so that the operator only needs to perform preparation operations at the support 5.

In this way, all the operations of unloading the finished reel 3b (3 a'), separating the new reel 3a from the cradle 5 and loading the new reel 3a to the supply station 6 can be fully automated.

Due to the fact that they are carried out at the support 5, the preparation operation becomes completely independent of the operation of the packaging unit 1. Thus, a first number of packaging units 1, for example ten, may be fed by using a second number of (for example five) racks 5, which is smaller than the first number of packaging units 1.

Due to the fact that the same pin 13 connects the holder 11 to the stand 5 or to the supply station 6 of the packaging unit 1, the operator can easily arrange the sheet packaging material of the new roll 3a in the correct position with respect to the seat 25 of the frame 12 by simply arranging this sheet packaging material with respect to the pin 14 of the holder 11.

Due to the fact that spring 35 urges plates 27 and 28 towards each other, sheet packaging material is firmly clamped within slot 10 when it is moved by lift truck 8 from stand 5 towards supply station 6 and when holder 11 is connected to frame 12 of supply station 6.

Thus, after the holder 11 has been removed from the stand 5 by the lift truck 8, the edge 53 of the new roll 3a remains in the correct position with respect to the edge 51 of the finished roll 3 b.

The presence of the springs 47a, 47b ensures that accidental vibrations do not negatively affect the position of the edge 53 of the new roll 3a with respect to the edge 51 of the finished roll 3.

Furthermore, the springs 47a, 47b allow to recover the alignment errors between the pins 13, 14 and the corresponding seats 25, 26 and holes 43, avoiding that the pins 13, 14 do not properly engage the seats 25, 26 and holes 43.

It is clear that modifications can be made to the method for feeding supply station 6 of packaging unit 1 with new reel 3a, as well as to sheet packaging material holder 11 and lift truck 8, without in any way departing from the scope of the present invention as defined in the appended claims.

In particular, the actuator 39 and the end 38 may be replaced by a cam and a follower, respectively.

Claims (15)

1. A method for feeding a supply station (6) of a packaging unit (1) with a new roll (3a) of sheet packaging material, characterized in that it comprises the steps of:

-releasably connecting a sheet packaging material holder (11) to a support structure (5);

-coupling the end (52) of the new roll (3a) with the holder (11), the holder (11) being in turn connected to the supporting structure (5);

-performing at least one operation on said end portion (52) which operation is ready to connect said end portion (52) to a first edge (53) of a finished roll (3 a', 3b) previously connected to said packaging unit (1);

-moving the new reel (3a) together with the holder (11) from the supporting structure (5) towards the supply station (6); and

-a fixing means (12) to releasably connect the holder (11) to the supply station (6) together with the new reel (3 a).

2. A method as claimed in claim 1, wherein said step of releasably connecting said holder (11) to a support structure (5) comprises the step of releasably connecting a first connecting member (13) carried by said holder (11) to a second connecting member (26) carried by said support structure (5); and said step of releasably connecting said holder (11) to a fixed part (12) of said supply station (6) together with said new reel (3a) comprises the step of releasably connecting said first connecting member (13) to a third connecting member (25) carried by said fixed part (12) of the supply station (6).

3. Method according to claim 2, characterized in that said step of performing comprises at least a step of arranging said end portion (52) in a given position with respect to said holder (11);

the step of moving the new roll (3a) together with the holder (11) and the step of releasably connecting the holder (11) together with the new roll (3a) to the fixing means (12) of the supply station (6) comprise the step of holding the end portion (52) in the given position with respect to the holder (11).

4. The method of claim 3, wherein the coupling step comprises the steps of:

-moving the first and second plates (27, 28) of the holder (11) away from each other;

-inserting said end (52) in said given position into a slot (10) defined by said first and second plates (27, 28); and

-bringing the two plates (27, 28) close to each other to clamp the end (52) firmly within the slot (10) in the given position.

5. The method according to claim 4, characterized in that said approaching step is performed by using elastic members (35) loading said first and second plates (27, 28) towards each other, and in that said moving away step comprises the step of moving one (28) of said first and second plates (27, 28) away from the other (27) of said first and second plates (27, 28) against the load of said elastic members (35).

6. A sheet packaging material holder (11) comprising a slot (10), through which slot (10) the sheet packaging material wound onto rolls (3a, 3b) can be slid, characterized by comprising:

-first releasable connecting means (13), said first releasable connecting means (13) being intended to connect said holder (11) either to a fixed part (12) of a supply station (6) of a packaging device (1) or to a supporting structure (5) of said rolls (3a, 3 b); and

-a second releasable connecting member (14), said second releasable connecting member (14) being for connecting the holder (11) to a lift truck (8).

7. Holder according to claim 6, characterized in that it comprises a first and a second plate (27, 28), which first and second plates (27, 28) define said slot (10) between them.

8. Holder according to claim 7, characterized in that it comprises a resilient member (35), said resilient member (35) in use loading the first and second plates (27, 28) towards each other into the following positions: in this position, the first and second panels (27, 28) firmly clamp the sheet packaging material within the slot (10).

9. Holder according to claim 8, characterized in that the resilient member (35) loads the first plate (27) against the second plate (28) when in use, and in that the second plate (28) integrally comprises a first element (37) movable away from the first plate (27).

10. A holder as claimed in any one of claims 7 to 9, characterized in that the first and second connecting members (13, 14) comprise a first and a second pin (13, 14), respectively; the first plate (27) supports the first and second pins (13, 14) on opposite sides thereof.

11. Holder according to claim 10, characterized in that the first pins (13) extend along respective first axes (a) parallel to each other and the second pins (14) extend along respective second axes (B) parallel to each other; the second axis (B) is arranged between the first axes (A).

12. A lift truck (8) comprising:

-a frame (7); and

-a gripping member (9), said gripping member (9) being supported by said frame (7) and being adapted to support a roll (3a, 3b) of sheet packaging material; it is characterized by comprising:

-a connecting structure (40), said connecting structure (40) being connected to said chassis (7) and being releasably connectable to a sheet packaging material holder (11), said sheet packaging material holder (11) in turn being coupleable with an end (52) of said roll (3a, 3 b).

13. Lift truck according to claim 12, characterized in that said connection structure (40) comprises:

-a plate (45), said plate (45) being connected to said frame (7);

-a body (48), said body (48) in turn comprising at least a hole (43), said hole (43) being releasably engageable by a pin (14) of said holder (11); and

-an elastic member (47a, 47b), said elastic member (47a, 47b) being arranged between said body (45) and said plate (48).

14. Lift truck according to claim 13, characterized in that said connection structure (40) comprises at least a first spring (49), said first spring (49) projecting from said body (45) on the opposite side of said plate (48) and having a free end which can abut against said retainer (11) in use.

15. Lift truck according to claim 13 or 14, characterized in that said elastic members (47a, 47b) comprise at least a first and a second spring (47a, 47 b); the first spring (47a), the second spring (47b) and the hole (43) extend along respective axes parallel to each other.