Equipment for measuring the quantity of film for coating of loads, method and control for measuring the quantity of the coating film.

The invention relates to equipment for measuring of the quantity of film used for wrapping of loads and to a method for measuring the used film and for its control.

The equipment can be built in film-wrapping machines, advantageously in stretch-wrapping machines.

In our age, the manufacturers economize on the usage of package materials not only for the reasons of economy but also for the reasons of environment saving, as well as for economy of material and energy.

The form of packing immediately contacting with the product, storing it, protecting it against light, air, vapor, or protecting the environment against the product, is regarded as primary packing.

The secondary packing is usually a collective packaging, which clamps together several primary packing units to a package, which can be easily handled or forwarded for a person. As regards the secondary packages, there are generally such points of view considered that it should be lifted with two hands by a person; in accordance with the rules of work safety of the most of countries, the package should not let the goods to fall to pieces, it should protect the product even in case of unloading and reloading several times, and it should fit into the car-boot of an average car. The secondary package as function has another very important role that it should include such a number of product units in primary packages and in such positions that utilizes the surface of the pallet used in the given region or by the business in one layer in the best possible way. The dimensions of the pallets are adapted to the transportation possibilities of the region, should it be ship, plane, railroad or road transport. The dimensions and orientation of the secondary package units are chosen in ideal case so, that they approach the dimensions of length and width of the pallet in one layer in the best possible way from below. It is advantageous to keep the length and width of the layers formed from the secondary package units within those dimensions of the pallet, because if a package unit hangs out from the contours of the pallet, as it is highly probable that it will be damaged during the loadings on the one hand, but, on the other hand, it is worth to utilize the area on the pallet in the best possible way from the points of view both of logistics and economy.

Generally, the secondary package should not protect the product against light, _v vapor or air, it is primarily destined to keep the primary packages together. Some of these package forms, not pretending to the completeness, should be mentioned such as shrink-wrapping (usage of heat-shrinking endless film on the previously arranged primary packages) or collecting box and wrap-around (typically in case of drinks in rectangular boxes).

The secondary packages usually lose their function in the trade process at the level of retail trade, where the buyers bring home the products only in primary package and the major part of the material of secondary packages is recycled. The same circulation applies to the tertiary packages, as well.

The stretch film package applied for wrapping of lateral and/or upper surfaces ^v of loads formed on pallets is usually tertiary package, more rarely secondary and only in extraordinary cases primary package.

The wrapping with stretch-film, as packaging process, is usually the last technological stage in the manufacturing plants; it is destined to keep the load together and to protect it against dust, precipitation and acts against property. It has only minimal aesthetic function, it is hardly utilized as surface for advertisement. Consequently, the wrapping with stretch-film, as cost, belongs mostly to the logistics, it represents requirement rather than added value, and the quantity of film used for a load unit should be minimal, meeting the requirements of properties, density, those of primary and secondary packages of the products, as well as the quality of transport, in ideal case.

The production plants usually know their average yearly consumption of film, regarding its distribution in time as even, or, in case of seasonal production, the film consumption can be proportional to the number of loads on the delivered pallets. It approaches the reality only in the case when the height of loads does not change. If the stretch-film wrapping machine uses a unit of film quantity to wrap a load of unit of height then it will use approximately twice as much film to wrap a load of two units of height at the same settings. Consequently, the number of loads on the delivered pallets does not give the trustworthy quantity of film used to wrap a unit of load formed on a pallet.

There is a great number of unit load wrapping apparatuses known in the practice.

Using a machine as described in the German publication of registration number DE 3633680 the load is put on a table and a shrink hood made of a shrinkable film is put on the load.

The load wrapped with the shrink hood is rotated by the table and a burner nozzle fastened on a vertically moving carriage shrinks the upper and lower parts of the shrink hood circularly and the lateral part along a screw line performing a programmed movement.

The application of the shrink hood provides appropriate protection to the load owing to the wrapping the upper part of the load.

The disadvantage of the machine is that the shrink hood must be made

<■ previously and put onto the load. The manufacturing of the cap requires manual labor, in addition the specific demand of film is great, as well as the energy requirement of the shrinking is also great enough.

The specific demand of film of the wrapping with stretchable film amounts approximately one fifth part of that of the shrink hood and the indispensable high energy requirement of the shrinking does not arise.

The common distinctive features both of the simplest hand-operated machines and the fully automated ones applied for the stretch wrapping with stretchable film are that they have a table for turning a load and a carriage applicable for the vertical movement of the film reel.

The above mentioned structural units of the machines make possible that the pre-stretched film wraps the load along a screw line as result of the turning movement of the load and the vertical movement of the film. The stretch of the film, the overlap and the number of film windings can be changed depending on the properties of the load and the requirements of fastening. The patent description of registration number of HUP 210302 discloses a very advantageously applicable machine enabling the stretch wrapping of loads with stretchable film also on the top surface of the load with the film applied for the wrapping of lateral surface.

The solution ensures the perfect protection of the goods through continuity of the stretched film, rendering unnecessary putting on a shrink hood in this way.

The essence of the machine according to the solution is that the film applied for stretch wrapping the lateral surface of the load by winding up along a screw line is led above the load and tilted from vertical position to horizontal one during the rotation of the load.

The film is then tilted back to the vertical position during a descending movement and the wrapping of the upper part is made in this way.

The machine according to the patent has a base frame, a table mounted in it and a mast fastened on the base frame.

A carriage vertically moving the film is mounted on the mentioned mast and bushings are formed on the carriage.

A shaft is inserted into the bushing and a reel of film is connected to the one end ' and a tilting actuator is connected to the other end of the shaft.

A sensor for the vertical (home) position and a sensor for the horizontal position are mounted on the base frame, triggering elements mounted on the table associated to the corners of the load, as operating elements controlling the tilting.

The disadvantage of the machine is that the stretch tension value can attain only the nearest digital value according to the step values, so it cannot be followed proportionally, consequently the tension of the film cannot be set precisely.

In the Hungarian utility model description of the registration number 4342 it ^ was set out to develop an apparatus, wherein it is complemented with a tilting film tension setting unit having pre-stretching rollers provided with a pre- stretching motor fastened to the frame of the film holding and pre-stretching unit, a guiding roller containing an arm with a roller, a stretch setting pneumatic pneumatic cylinder provided with an analogous displacement transducer, which cylinder has magnetic piston, and a frequency changer.

Using this apparatus, the measurement of stretching becomes more accurate, the intervention is faster and the hysteresis of stretching reduces.

The pre-stretching motor reacts faster, more accurately, with smaller redundancy to the increased tension, and the desired tension of the film can be better approached and kept during the whole time of wrapping .

The disadvantage of the apparatus is that the quantity of the used film cannot be measured while loads of different dimensions and shapes are wrapped, and the necessary film quantity cannot be previously determined by an estimated data.

It is another disadvantage that there is no possibility to form automatically a more economic pattern relatively to the previously set one, or to form a stronger one with more film requirement if desired, i. e. to the automatic regulation of the used quantity of film.

We set as target to develop an apparatus enabling measurement of used film quantity to be used for wrapping loads of different shapes of dimensions.

The invention relates also to a process for measuring, as well as to the regulation of the used film quantity.

The apparatus can be mounted into known film-wrapping machines, advantageously into stretch- wrapping ones.

A known film-wrapping machine serves for wrapping lateral and upper parts of loading units with stretchable film. It has a base frame, a table mounted in it and a mast fastened to the base frame, to which a carriage provided with a carriage motor is fastened vertically moving a film reel, a pin is led through it a tilting pneumatic cylinder is connected to the one end and the film reel is connected to the other end of the pin, a home position sensor and a horizontal position sensor are mounted on the base frame, tilting controlling triggers arranged < correspondingly to the corners of load and a base position trigger are mounted on the table, and it has a tilting film holding and pre-stretching unit fastened to the other end of the mentioned pin. The equipment according to the invention, which can be fitted into a film- wrapping machine and having a tilting film holding and pre-stretching unit, has pre-stretching rollers provided with one or more pre-stretching motors fastened to the frame, a guiding roller containing an arm with a roller, tension setting pneumatic cylinder provided with an analogous displacement transducer and having piston provided with magnet, furthermore a pressure regulator, where the film, wound down from the film reel, is led between pre-stretching rollers, optionally connected with a gear, and one of them or the two extreme ones are driven with a pre-stretching motor or two ones, then the film is led around a ^ guiding roller provided with a swing-arm turning around a center of rotation and having a roller, it is connected with the piston provided with magnet, mounted in the tension setting pneumatic cylinder and the piston provided with magnet is connected to the pressure regulator.

The characteristics of the apparatus are that the exterior rollers from among the pre-stretching rollers optionally complemented with leading rollers, the exterior ones are provided with rotation speed transducers and with rotation speed sensors or they are provided with bearings built together with rotation speed sensors, the former ones are connected by impulse connection to a controlling computer having a display and the latter is optionally connected by impulse connection to the motor turning the table, the one of the film carriage or both to the drive of the film holding and pre-stretching unit and to the film carriage motor.

The apparatus is applicable for the measurement of film quantity used to wrap loads having different dimensions and shapes, but it can be applied, in addition, for regulation of the film quantity after measurement, to increase or decrease the film quantity.

The equipment can be built in a known film-wrapping machine, where the table of the film- wrapping machine is driven with a table driving motor in one of its ^ advantageous embodiment, while the film holding and pre-stretching unit of the film wrapping equipment is provided with a drive in another advantageous embodiment. The invention relates also to a process for measuring quantity of film serving for wrapping loads and for regulating the quantity of film using the above mentioned apparatus.

The characteristics of the process are that the parameters of width, thickness and density of the wrapping film, the perimeter of curved surface of the pre- stretching roller the degree of pre-stretching, the slip coefficient between the film and the pre-stretching roller, the temperature of environment, the program of the pattern of film wrapping are fed into the controlling computer, then a load of arbitrary shape and dimensions is wrapped with film; the film is removed from the load at the end of wrapping and its mass is measured, this reference value is fed into the computer, then the film-wrapping is performed on a load of different dimensions and/or shape, using the same pre-stretching ratio, at the nearly the same temperature of environment, the actually used mass of foil is read from the display of the computer; in a case where it is desired to diminish or increase the actually used quantity of film, on a load of identical dimensions and/or shape, it should be fed the film quantity, to be actually used and the controlling computer sets automatically the overlap of spiral windings assigned to the desired economy of film or to the additional film quantity by means of changing the ratio between the rotational speed of the table turning motor and that of the film carriage motor or by means of changing the ratio between the rotational speed of the film pre-stretching drive and that of the film carriage motor, in a given case by means of changing the rotational speeds of the pre- stretching motors.

In the process of measurement the quantity of used film can be calculated from the product of the perimeter of curved surface of the chosen pre-stretching roller and the number of revolutions performed during the film wrapping process, the slip coefficient between the film and the pre-stretching roller, the current pre- stretching ratio and the temperature of environment should be taken into account in order to make exact measurement. The difference between the rotational speeds of the pre-stretching rolls of greatest and smallest rotational speeds, either measured or previously set on the controlling computer provide data about the pre-stretching ratio.

It is usually directly proportional to the ratio of sliding in characteristically normal conditions.

The controlling computer calculates greater film consumption when a greater pre-stretching ratio is chosen or set, because it compensates with a greater sliding coefficient to the greater pre-stretching ratio within the limit of elasticity. The actual elongation of the film will follow less and less the theoretic elongation ratio during increase of pre-stretching ratio. The controlling computer performs a similar compensation under influence of the temperature of environment. The film is stretchable in inverse proportion with the temperature of environment, but in contrary the breaking elongation is directly proportional to the temperature of environment (The film manufacturers determine the temperature limits of applicability of their products).

The process of regulation can be performed by an apparatus wherein the pre- stretching rollers have only one pre-stretching motor and the other one or more pre-stretching rollers are connected to the motor driven roller through a gear. In another embodiment of the regulation process each pre-stretching roller is driven by a motor.

There are different possibilities of economy in case of pre-stretching <. apparatuses with one motor drive than in case of embodiments with two motors. In case of embodiments with one motor drive the controlling computer controls the elements of the packing pattern, such as the pitch of screw line of the side wrapping, the numbers of upper lower and middle windings in quarter parts.

The controlling computer analyzes the ratio between the existing elements and the desired economy and automatically generates the ratios between the rotational speeds of table and the film holder and pre-stretching unit or that between the film holder and pre-stretching unit and the film carriage motor necessary for the number of windings with increased pitch inversely proportional to the desired economy. It is advisable to check the result in every case because the economy exceeding the optimal degree goes to diminish the stability, protection against dust or aesthetical value of the package.

The ratio between the overlap of winds generated by the pitch of screw-line of the film made in the wrapping cycle as starting base and the desired overlap can also be given as aimed economy, in this case the controlling computer will subtract a quantity corresponding to the ratio of the two overlaps from the quantity of the whole pattern of film-wrapping.

The process of regulation of film quantity assigned to the film pre-stretching unit with two motors has all the advantages of the process as described at the apparatus with one motor with the completion that the apparatuses with two motors are capable to make further savings of film.

It is reached in such a way that the film of unit length is automatically pre- stretched in arbitrary rate according to the commands of the software running in the controlling computer.

The machine according to the utility model is shown in the Figures 1 to 10. The Figures 1 to 4 and 9 show embodiments of the machine in top-side view wherein the table is motor-driven.

The Figures 5 to 8 show embodiments of the machine in top side view wherein the table does not turn but the film holding and pre-stretching unit is provided with a drive.

^ The Figure 10 shows side view of an embodiment of the equipment. The Figure 1 shows an advantageous embodiment of the machine in top view, wherein the table (2) is provided with a table turning motor (21).

In the Figure the base frame (1), the table (2) mounted in rotatable way in it, and the load (13) placed on the latter are shown.

A carriage (4) moving vertically the film reel (7) is fastened to the mast (3), which is fastened to the base frame (1) and bushings (5) are formed on the carriage (4). A pin (6) is led through the bushings (5) a tilting pneumatic cylinder (8) is connected to its one end and a film holding and pre-stretching unit (22) is connected to its other end.

A home position sensor (9) and a 10 horizontal position sensor are arranged on the base frame (1).

Tilting controlling triggers (12A, 12B, 12C and 12D) arranged according to the corners of load (14) and a home position sensor (9) are fitted to the table (2). Pre-stretching rollers (7 A) provided with a pre-stretching motor (20), a guiding roller (7B) comprising a swing-arm provided with a roller (7C), a tension setting pneumatic cylinder (16) provided with a piston provided with magnet ( 16 A) and an analogous displacement transducer (17) and a pressure regulator (18) are fastened to the frame of the film holding and pre-stretching unit (23) to the tiltable film tension setting unit (22).

<· The film wound down from the film reel (7) is led around the pre-stretching rollers (7A) connected together with a gear (19), one of them is driven by the pre-stretching motor (20), then the film is led around a guiding roller (7B) provided with an swing-arm with roller (7C) turning around a center of rotation. The swing-arm with roller (7C) is connected to a piston provided with magnet (16A) and the piston provided with magnet (16A) is in a tension setting pneumatic cylinder (16) provided with an analogous displacement transducer

(17) .

The piston provided with magnet (16A) is connected to a pressure regulator

(18) .

The table (2) is driven by a table driving motor (21).

The pre-stretching rollers (7 A) of the equipment are provided with rotation speed transducers (24A, B) and rotation speed sensors (25A, B).

They are connected with impulse connection to a computer (15) connected to a display (15A), which is connected to the table turning motor (21) and to the film carriage motor (30) shown in the Figure 10.

The rotation speed transducers (24A, B) on the pre-stretching rollers (7A) generate an impulse in each revolution in the rotation speed transducers (24 Α,Β), when they reach the sensing area of the rotation speed sensors (25 A, B), which impulse is sent to the controlling computer (15). The quantity of film can be read from the display (15A).

The product SM6 of the firm Bosch-Rexroth or the product named SMAT of the firm Festo are advantageously applied as analogous displacement transducer (17).

The gear (19) can be any one of usual type, advantageously one with chain, angle belt, gearwheels, timing belt etc.

In the case where the next cycles of film-wrapping the reduction or increase of the film quantity is desired, the controlling computer (15) changes the ratio between the speeds of rotation of the table driving motor (21) and the film carriage motor (30) (see in the Figure 10) and the assigned overlap of the film spiral (33).

The Figure 2 shows another advantageous embodiment of the machine in top- ' side view, where the table (2) is provided with a table turning motor (21).

This embodiment differs from the modification shown in the Figure 1 in that the pre-stretching rolls (7 A) are provided not with rotation speed transducers (24A,

B) and 25 A, B) rotation speed sensors but they are provided with bearings built together with rotation speed sensors (26).

The bearings built together with rotation speed sensor (26) generate several impulses depending on the construction in each revolution of a pre-stretching roller (7 A).

The Figure 3 shows a further advantageous embodiment of the machine in topside view, wherein the table (2) is provided with a table turning motor (21). This embodiment differs from the one shown in the Figure 1 in that it has three pre-stretching rollers (7 A) instead of two ones (7 A).

The two exterior pre-stretching rollers (7 A) from the three ones are provided with rotation speed transducers (24A, B) and rotation speed sensors (25A, B). The film is guided between the pre-stretching rollers (7A) by leading rollers (7D). An advantageous embodiment of the machine is shown in top-side view in the Figure 4, wherein the table (2) is provided with a table turning motor (21).

This embodiment differs from the one shown in the Figure 3 in that the two exterior pre-stretching rollers (7 A) from those ones are equipped with bearing built together with rotation speed sensors (26) instead of rotation speed transducers (24 A, B) and rotation speed sensors (26A, B).

A further advantageous embodiment of the machine is shown in top-side view in the Figure 5, wherein the film holding and pre-stretching unit (22) is provided with a drive of the film holding and pre-stretching unit (27).

This embodiment differs from the solution shown in the Figure 3 that the table (2) has not a drive.

The drive of the film holding and pre-stretching unit (27) is a film holding driving motor with turning ring (27A).

An advantageous embodiment of the machine is shown in top-side view the Figure 6 wherein the film holding and pre-stretching unit (22) is provided with a ^ drive of film holding and pre-stretching unit (27).

This embodiment differs from the one shown in the Figure 4 in that the table (2) has not a drive.

The drive of the film holding and pre-stretching unit (27) is an arm driving motor (27B) provided with a turning arm (29).

The turning arm (26) rotates the film.

An advantageous embodiment of the equipment is shown in top-side view in the Figure 6, wherein the film holding and pre-stretching unit (22) is provided with a drive of the film holding and pre-stretching unit (27).

An advantageous embodiment of the machine is shown in top-side view in the ' Figure 7, wherein the film holding and pre-stretching unit (22) is provided with a drive of the film holding and pre-stretching unit (27).

This embodiment differs from the solution shown in the Figure 5 in that it is provided with only two pre-stretching rollers (7 A) and it has no leading roller (7D). An advantageous embodiment of the machine is shown in top-side view in the Figure 9 wherein the table (2) is provided with a table turning motor (21).

This embodiment differs from the solution shown in the Figure 1 in that each pre-stretching roller (7 A) is provided with a separate pre-stretching motor (20). So a gear (19) between the two pre-stretching rollers (7 A) is not necessary. The difference between the rotation speeds of the two pre-stretching rollers (7 A) determines the pre-stretching ratio.

( An advantageous embodiment of the machine is shown in side view in the Figure 10, wherein the table (2) is provided with a table turning motor (21). In the Figure 10 are shown the base frame (1), the table (2) built in it in rotatable way and the load (13) placed on it.

A carriage (4) moving vertically the film is fastened to the mast (3) fastened to the base frame (1) and bushings (5) are formed on the carriage (4).

A pin (6) is lead through the bushings (5) and a tilting pneumatic cylinder (8) is connected to its one end and the film holding and pre-streching unit (22) is connected to its other end.

The carriage (4) is provided with a film-carriage motor (30).

The equipment is provided with a controlling computer (15), which is provided with a display (15A). The controlling computer (15) is connected by impulse connection with the pre-stretching motor (20), the table turning motor (21) and the film-carriage motor (30).

A spirally wound up film spiral (32) is on the load (13).

The invention relates also to a process for measuring quantity of film serving for wrapping loads and for regulating the quantity of film using the above described equipment.

The characteristics of the process are that the parameters of width, thickness and < density of the film, the length of perimeter of the curved lateral surface of the pre-stretching roller, the pre-stretching ratio, the slip coefficient between the film and the pre-stretching roller (7a) the temperature of environment and the program of film wrapping pattern are fed into the controlling computer (15), then a load (13) of arbitrary dimensions and shape is wrapped with film, the used film is removed from the load (13) at the end of the wrapping process and its mass is measured, this reference value is fed into the controlling computer (15), then the film wrapping is performed with the film of identical quality, identical pre-stretching ratio, at nearly the same temperature of environment with a load (13) of different dimensions and/or shape, the quantity of actually used quantity of film is read from the display (15A) connected to the controlling computer (15), and, in the case where the film quantity to be used should be reduced or increased to a load (13) of the same dimensions and/or shape, the ' actual value of film quantity desired to be used is fed into the controlling computer (15), and the controlling computer (15) automatically sets the overlap of the film spiral (33), together with changing the rotation speeds of the table turning motor (21), the film-carriage motor (30) or the drive of film holding and pre-stretching unit (27), the film-carriage motor (30), optionally the rotation speed of the pre-stretching motors (20) assigned to the desired economy of film quantity or to the additional film quantity.

The advantages of the equipment and process according to the invention are as follows:

The equipment is applicable to measure the film quantity used for wrapping loads of different dimensions and shapes, but it is applicable at the same time for automatic reduction or increase of the film quantity by means of a computer- aided controlling regulation.

List of notations

1 base frame

2 table

3 mast

4 carriage

5 bushing

6 pin

7 film reel

7A pre-stretching rollers

7B guiding roller

7C swing-arm with roller

7D leading roller

8 tilting pneumatic cylinder

9 home position sensor

10 horizontal position sensor

11 home position trigger

12 A, B, C D tilting controlling triggers

13 load

14 load corner

15 controlling computer

15A display

16 tension setting pneumatic cylinder 16 A piston provided with magnet

17 analogous displacement transducer

18 pressure regulator

19 gear

0 pre-stretching motor

1 table turning motor

2 film holding and pre-stretching unit 23 frame (of the film holding and pre-stretching unit) 24A, B rotation speed transducers

25 A, B rotation speed sensors

26 bearing built together with rotation speed sensor 27 drive of the film holding and pre-stretching unit

27A film holding driving motor with turning ring 27B arm driving motor

28 supporting roller

29 turning arm

30 film-carriage motor

32 film spiral

33 overlap of the film spiral