A METHOD AND AN APPARATUS FOR IMPROVING FUNCTIONING OF A WRAPPING MACHINE

Abstract: A method and an apparatus for improving the operating efficiency of a wrapping machine (10), by providing the wrapping machine (10) with two or more wrapping carriages (30a, 30b) or similar devices for two or more plastic film band rolls (31a, 31b), each of which can be taken into use in turn at any time. To permit a roll change, the wrapping machine is provided with a switch-over gripper (50) for gripping the end (33b) of the plastic film band (32b) coming from a full plastic film band roll (31b) and for pulling it onto a seaming gripper (40) before the wrapping of the next object (10) to be wrapped is started.

Description: A method and an apparatus for improving functioning of a rappϊ g machine METHOD OF THE INVENTION The present invention relates to a method for improving the operating efficiency of a wrapping machine, in which wrapping method at least two plastic film band rolls are placed inside the wrapping machine, plastic film band from at least one roll is wrapped about the object to be wrapped next, - after the object has been wrapped up, the plastic film band is seamed and severed, whereupon the next object can be wrapped, and that the wrapping action can be continued until the plastic film band on the roll has been used up. PRIOR-ART METHOD According to a prior-art wrapping method, the wrapping machine is stopped when the plastic film band on the roll has been used up. After that, the empty roll is replaced with a full one either manually or by means of an automatic roll changing mechanism. However, changing the roll always involves the waste of a considerable deal of valuable wrapping time. In a manual roll changing operation, first the safety screen of the wrapping machine is opened and then also the wrapping carriage inside the wrapping machine. The empty roll on the wrapping carriage is removed and replaced with a full roll. Finally, the wrapping carriage and the safety screen of the wrapping machine are closed. An automatic roll changing operation also takes a long time because even in this case the roll changing mechanism must first get the empty roll out of the stopped wrapping machine and then bring in a full roll to replace the empty one from outside the wrapping machine. APPARATUS OF THE INVENTION The invention also relates to an apparatus for improving the operating efficiency of a wrapping machine, said wrapping machine comprising - at least two wrapping devices, such as wrapping carriages, provided with plastic film band rolls to allow plastic film band to be wound about the object to be wrapped, and means for seaming and severing the plastic film band. PRIOR-ART APPARATUS A known solution is to provide the wrapping machine with an automatic device for changing the plastic film band roll, by means of which an exhausted plastic film band roll can be replaced with a full one. The change of rolls is performed with the wrapping machine in a fully inactive state. The changing mechanism extracts the empty roll from inside the wrapping machine and moves it out of the machine. After that, the changing mechanism takes a full roll onto the wrapping carriage inside the machine. However, the automatic roll changing mechanism is technically complicated and its operation takes a relatively long time because the wrapping machine has to be brought to a complete standstill for the duration of the roll change. The roll changing mechanism must first get the empty roll out of the wrapping machine and then bring in a full roll from outside the machine to replace the exhausted one. OBJECT OF THE INVENTION The object of the invention is to achieve a method and an apparatus for improving the operating efficiency of a wrapping machine which do not have the above-described disadvantages. FEATURES CHARACTERISTIC OF THE METHOD OF THE INVENTION The method of the invention is characterized in that, after one plastic film band roll has been used up, wrapping is continued from another, full plastic film band roll placed inside the wrapping machine. It is obvious that substantially faster operation is achieved if wrapping is continued from a roll already at hand than if a new roll has to be brought in from outside the wrapping machine. EMBODIMENTS OF THE METHOD OF THE INVENTION According to a preferred embodiment of the method of the invention, each plastic film band roll is placed on a separate wrapping device, and that after the plastic film band roll being used for wrapping has been exhausted, the wrapping operation is continued using another wrapping device which contains a full plastic film band roll. According to a second preferred embodiment of the method of the invention, the wrapping operation is started or continued using a wrapping device containing a full plastic film band roll by gripping the end of the plastic film band coming from the full plastic film band roll and locking it in place before starting the wrapping of the next object to be wrapped. FEATURES CHARACTERISTIC OF THE APPARATUS OF THE INVENTION The apparatus of the invention is characterized in that the wrapping machine comprises means for switching the wrapping process from an exhausted plastic film band roll to a full plastic film band roll. The means for switching the wrapping process from one roll to another are technically simple and therefore reliable in operation. EMBODIMENTS OF THE APPARATUS OF THE INVENTION A preferred embodiment of the apparatus of the invention is characterized in that the wrapping machine comprises at least two separate wrapping devices, such as wrapping carriages, containing a plastic film band roll, and that the wrapping machine is provided with a switch-over gripper for gripping the end of the plastic film band coming from a full plastic film band roll. A second preferred embodiment of the apparatus of the invention is characterized in that the switch-over gripper can be moved to a position near the end of the plastic film band coming from the plastic film band roll and in a direction away from said plastic film band end, and that a seaming gripper is placed near the path of the switch-over gripper, and that the seaming gripper has been arranged to grip the plastic film band drawn out from the plastic film band roll by the switch-over gripper. A third preferred embodiment of the device of the invention is characterized in that the wrapping device, such as wrapping carriage, containing a plastic film band roll is provided with a holder in which the end of the plastic film band is set so that it can be gripped by the switch-over gripper. EXAMPLES OF EMBODIMENTS In the following, the invention will be described by the aid of a few examples with reference to the attached drawings, wherein LIST OF DRAWINGS Fig. 1 presents a diagrammatic side view of a wrapping machine with two wrapping carriages. Fig. 2-4 present the wrapping machine of Fig. 1 at different stages of a roll change operation. Fig. 5 presents the wrapping machine of Fig. 1 at the start of a wrapping operation. Fig. 6 presents the wrapping machine of Fig. 1 in diagrammatic top view. DESCRIPTION OF THE DRAWINGS Fig. 1 presents a side view of a wrapping machine 10 for winding a plastic film band 32 about an object 60 to be wrapped, which is placed on a conveyor track 61. In this example, the wrapping machine 10 is a ring-type wrapping machine with a hoisting frame 20 vertically movable along vertical rails 21. Supported by support rollers 23 on the hoisting frame 20 is the rotating ring 22 of the wrapping machine 10, carrying two wrapping carriages 30a and 30b. Attached to the hoisting frame 20 is a seaming unit 40 provided with a gripper 41 for gripping the plastic film band as well as means for seaming and severing the plastic film band. Each wrapping carriage 30a and 30b carries a roll 31a, 31b of plastic film band 32a, 32b to be wound about the object to be wrapped 60. In the wrapping carriages 30a and 30b, the ends 33a and 33b of the plastic film bands are placed in holders 34a and 34b. The wrapping machine 10 further comprises a switch-over gripper unit 50, which moves horizontally on a slide 52. The switch-over gripper unit 50 is provided with gripper jaws 51 which can grip the plastic film band ends 33a and 33b in the holders 34a and 34b on the wrapping carriages 30a and 30b. In a roll change situation, the rotating ring 22 of the wrapping machine 10 is turned to a position such that the holder 34a of the a plastic film band end 33a on one of the wrapping carriages, in Fig. 1 wrapping carriage 30a, is aligned with the gripper jaws 51 of the switch-over gripper unit 50. Fig. 2 illustrates the initial stage of a roll change operation in the wrapping machine 10. At this point, the switch-over gripper unit 50 has been raised so that the gripper jaws 51 are at the level of the plastic film band ends 33a and 33b in the holders 34a and 34b of the wrapping carriages 30a and 30b. While the switch-over gripper unit 50 is moving horizontally on the slide 52, in Fig. 2 to the left, the gripper jaws 51 are opened. In Fig. 3 the gripper jaws 51 of the switch-over gripper unit 50 of the wrapping machine 10 have gripped the end 33a of the plastic film band. After that, the switch-over gripper unit 50 has moved to the right in Fig. 3 along the slide 52, so that the plastic film band end 33a has been released from the holder 34a. The jaws 51 of the switch-over gripper unit 50 have pulled the plastic film band end 33a and the plastic film band 32a off the roll 31a so that the plastic film band 32a has now reached the gripper 41 of the seaming unit 40. In Fig. 4, the gripper 41 of the seaming unit 40 of the wrapping machine 10 has engaged the plastic film band 32a and the gripper jaws 51 of the switch-over gripper unit 50 have been opened. This situation corresponds to a situation in a prior-art wrapping machine where the end of the plastic film band to be used for wrapping has been set into the gripper of a seaming unit to allow the wrapping to be started or continued from a new, full roll. In Fig. 5, the gripper 41 of the seaming unit 40 of the wrapping machine 10 has turned into a horizontal position in a known manner and the ring 22 with the wrapping carriages 30a and 30b has started to rotate, so the wrapping of the object 60 with plastic film band 32a has begun. At the same time, the switch-over gripper unit 50 has returned to its initial position, i.e. to the low position so that it is out of the way of the circulating wrapping carriages 30a and 30b. In Fig. 5, the object 60 is being wrapped with plastic film band 32a obtained from a roll 31a on wrapping carriage 30a. The roll 31b on the other wrapping carriage 30b attached to the rotating ring 22 is circulating with the ring but only as a stand-by roll ready for use when roll 31a is exhausted. When roll 31a runs out of plastic film band, the wrapping is continued using the roll 31b on the other wrapping carriage 30b. Roll 31b is put into active use by steps identical with those for roll 31a as illustrated in Fig. 2-4. However, since both rolls 31a and 31b are already within the wrapping machine 10, the roll change can be performed substantially faster and more effectively than in prior-art wrapping machines, in which the new roll is always brought in from outside the machine. Fig. 6 presents a simplified top view of the wrapping machine 10 in Fig. 1. As shown in the figure, the rotating ring 22 of the wrapping machine 10 is provided with two wrapping carriages 30a and 30b, each carrying a plastic film band roll 31a, 31b. The end of the plastic film band 32a, 32b on each roll 31a, 31b is placed in a holder 34a, 34b attached to the wrapping carriage 30a, 30b. Fig. 6 illustrates an initial situation in which each wrapping carriage 30a, 30b of the wrapping machine 10 is provided with a full plastic film band roll 31a, 31b. In preparation for the start of the wrapping action, the rotating ring 22 has been turned to an initial position such that the end 33a of the plastic film band 32a in the band holder 34a of the first wrapping carriage 30a is aligned with the jaws 51 of the switch-over gripper unit 50. Next, the switch-over gripper unit 50 moves to the left in Fig. 6 and the gripper jaws 51 grip the end 33a of the plastic film band 32a in holder 34a, as is also shown in Fig. 2. After that, the gripper jaws 51 pull the end 33a of the plastic film band 32a to the right in Fig. 6 so that the plastic film band 32a extends across the gripper 41 of the seaming unit 40. This situation is also illustrated in Fig. 3. The gripper 41 now engages the plastic film band 32a and the jaws 51 of the switch-over gripper unit 50 are opened, as is also shown in Fig. 4. After the switch-over gripper unit 50 has moved down to be out of the way of the wrapping carriages 30a and 30b, the machine can start wrapping the object 60 on the conveyor track 61 from the roll 31a on wrapping carriage 30a. ADDITIONAL REMARKS It is obvious to the person skilled in the art that different embodiments of the invention may be varied within the scope of the claims presented below. Thus, the invention is not limited to the ring-type wrapping machine presented in the drawings. In a corresponding manner, other types of wrapping machine can equally well be provided with two or more wrapping carriages or similar wrapping devices for winding a plastic film band, so that a substantially more effective roll change can be achieved.

Claims: CLAIMS 1. Method for improving the operating efficiency of a wrapping machine (10), in which wrapping method - at least two plastic film band rolls (31 a, 31 b) are placed inside the wrapping machine (10), plastic film band (32) from at least one roll (31 ) is wound about the object (60) to be wrapped next, after the object (60) has been wrapped, the plastic film band (32) is seamed and severed, whereupon the next object can be wrapped, and the wrapping action can be continued until all the plastic film band (32) on the roll (31) has been used up, ch a ra cte rize d in that after one plastic film band roll (31a) has been exhausted, the wrapping operation is continued from another, full plastic film band roll (31b) placed inside the wrapping machine (10). 2. Method as defined in claim 1, ch a ra cte rize d in that each plastic film band roll (31a, 31b) is placed in a separate wrapping device (30a, 30b), and that after the plastic film band roll (31a) being used for wrapping has been exhausted, the wrapping operation is continued using another wrapping device (30b) containing a full plastic film band roll (31b) . 3. Method as defined in claim 1 or 2, ch a ra cte rize d in that the wrapping operation is started or continued using a wrapping device (30a) containing a full plastic film band roll (31a) by gripping the end (33a) of the plastic film band (32a) coming from the full plastic film band roll and locking it in place before starting the wrapping of the next object to be wrapped. 4. Apparatus for improving the operating efficiency of a wrapping machine (10), said wrapping machine comprising at least two wrapping devices (30a, 30b), such as wrapping carriages, provided with plastic film band rolls (31a, 31b) to allow plastic film band (32a, 32b) to be wound about the object (60) to be wrapped, and means (40) for seaming and severing the plastic film band (32a, 32b) . c h a ra cte ri ze d in that the wrapping machine (10) comprises means (50) for switching the wrapping process from an exhausted plastic film band roll (31a) to a full plastic film band roll (31b). 5. Apparatus as defined in claim 4, cha ra cte ri ze d in that the wrapping machine (10) comprises at least two separate wrapping devices (30a, 30b) containing a plastic film band roll (31a, 31b), such as wrapping carriages, and that the wrapping machine (10) is provided with a switch-over gripper (50) for gripping the end (33b) of the plastic film band (32b) coming from a full plastic film band roll (31b). 6. Apparatus as defined in claim 4 or 5, c h a ra cte ri ze d in that the switch-over gripper (50) can be moved to a position near the end (33) of the plastic film band (32) coming from the plastic film band roll (31) and in a direction away from said plastic film band end, and that a seaming gripper (40) is placed near the path of the switch-over gripper (50), and that the seaming gripper (40) has been arranged to grip the plastic film band (32) drawn out from the plastic film band roll (31 ) by the switch-over gripper (50). 7. Apparatus as defined in claim 4, 5 or 6, c h a ra cte rize d in that the wrapping device (30), such as wrapping carriage, containing a plastic film band roll (31) is provided with a holder (34) in which the end (33) of the plastic film band (32) is set so that it can be gripped by the switch-over gripper (50).

Inventors: HERAVA ISMO, HERAVA, ISMO
Applicants: HERAVA ISMO, UNITED PACKAGING PLC, HERAVA, ISMO
Application year: 2001
Main classification: B65B11
IPC codes: B65B11