The present invention relates to a method and a device for transferring articles produced in a thermoforming mould towards a station to stack the articles thereby produced.
A method and a device according to the present invention can for example be utilized in thermoforming plants destined to produce hollow articles, such as cups, plates, trays or other such disposable products. These articles are produced from one or more thermoformable materials, such as polystyrene, polypropylene, polyethylene or the like, which are extruded in the form of a continuous sheet. In thermoforming processes, the articles produced with this technology are generally transferred to a subsequent processing station, for example a station to stack the cups.
In some prior art machines, the sheet exiting from the forming unit still carries the thermoformed articles with it to a cutting station, wherein the individual articles are separated from the rest of the sheet and transferred to the stacking station. Transfer of the articles is performed in this case with mechanical means that insert each of the articles into a corresponding guide duct to reach jets of air capable of propelling each article towards a stacking station.
In other prior art machines, for example machines of the type with a tilting half-mould, after separation from the rest of the sheet the thermoformed articles in the mould are ejected mechanically from the mould and deposited directly on stacking channels equipped with stop bosses or holding means, such as brushes, hooks or the like, or deposited directly on suitably shaped elements (also know as “male tools”) on which the articles are temporarily held during transfer.
These known systems have various drawbacks. Firstly, mechanical handling during the various stages of the transfer phases can cause damage to the articles. As well as influencing the quality of the final product, and increased production costs due to rejects, this can jeopardize the correct performance of the subsequent phases, for example correct stacking of the articles produced, and cause halts in production to restore the correct operating conditions of the production cycle.
Moreover, it is evident that the need to move various mechanical members in the various transfer stages can have a noteworthy incidence on the transfer speed of the articles, thus making known systems somewhat unsuitable for use in plants with high productivity levels.
Considering that the majority of articles produced with the thermoforming technology are destined for use with foods, the amount of mechanical handling can also cause noteworthy problems concerning hygiene.
The object of the present invention is therefore to provide a method for transferring articles produced in a thermoforming mould wherein mechanical handling of the thermoformed articles can be limited to as great an extent possible.
Another object of the present invention is to provide a method and a device that make transfer of the thermoformed articles extremely rapid.
These objects are obtained by a method according to claim 1 and a device according to claim 15. Further advantageous characteristics of the present invention are indicated in the dependent claims.
According to a first aspect of the present invention, a method is provided to transfer thermoformed articles, separated with respect to a sheet of thermoformable material, from a station for separation of the articles to a subsequent processing station, characterized in that each of the articles exiting from the separation station is picked up by suction and made to travel inside a corresponding duct by a condition of vacuum pressure produced in proximity to the inlet of the duct and inside this duct. In this way, the articles can be transferred in the ducts without any mechanical handling.
The condition of vacuum pressure is preferably produced by injecting pressurized air in an intermediate portion of the duct. Control and implementation of transfer of the articles is thus particularly simple, rapid and reliable.
The pressurized air can be implemented in the form of individual jets, or in the form of a blade of air.
According to a possible embodiment of the method of the present invention, each article is made to travel to the output of the corresponding duct and directed along one or more guide members. This is suitable, for example, for the production of small and medium sized cups, for which transfer to the subsequent processing station, for example a stacking station, can continue successively by gravity.
Alternatively, each article is deposited on a shaped element having form and dimensions essentially complementary to those of the article. The shaped element is movable between at least one position to receive the corresponding article and at least one position to release the article towards the subsequent processing station. This alternative embodiment is suitable to be utilized for large cups, or for plates or trays.
In accordance with a second aspect of the present invention, a device is provided to transfer the thermoformed articles, separated with respect to a sheet of thermoformable material, from a station to separate the thermoformed articles to a subsequent processing station, characterized by including means to produce a condition of vacuum pressure in proximity to the inlet of a transfer duct and inside this duct.
Further characteristics and advantages of the present invention shall become clearer from the description hereunder, provided with reference to the accompanying drawings, wherein:
It must be mentioned that, although five cavities and five corresponding ducts are visible in
The ducts 20a-20e are mounted on a supporting plate 30 through which pressurized air is fed simultaneously to all the ducts 20a-20e at pre-established times, that is in an interval of time during which the mould 10 is in the position wherein the various cavities are aligned with the ducts 20a-20e.
The supporting plate 30 is in turn mounted on a frame 40, connected to which are guide members 50 defining a separate route for each of the articles exiting from the corresponding duct to a subsequent processing station, for example a station to stack the cups.
When the mould 10 moves towards the position shown in
At this point, each of the cups is in a position sufficiently close to the inlet of the respective duct and the vacuum pressure produced in this area by the pressurized air fed into the duct allows the cup to be drawn by suction into the duct, as indicated in this case for the single cup 1a in
Air is injected at a pre-established pressure and maintained for a time sufficient to guarantee that the cups are ejected from the respective ducts and continue their travel through the guide members 50 to the subsequent processing station.
For example, during testing to perform transfer of cups with average dimensions (i.e. from 15 to 25 cc), the pneumatic circuit was supplied with pressures not exceeding 5 bar and maintained for around 1-2 seconds at each transfer cycle. With these values, it was possible to transfer cups that were fed with their closest edge at a distance not exceeding around 20 mm from the inlet of the corresponding ducts.
The phases to transfer a single cup (for example the cup 1a through the corresponding duct 20a) are shown in greater detail in the sectional views in
In
The nozzles 22 are preferably disposed in equidistant positions from the inlet and equally spaced from one another along the internal surface of the duct 20a. As an example, a single series of nozzles inside the duct 20a are shown, although, if necessary, several series of nozzles can be provided along the duct.
The pressurized air (arrows A) can for example be fed through suitable channels in the supporting plate 30 and directed at the nozzles 22 by inclined through holes 23, so that the jets of pressurized air P are inclined with respect to the axis of the duct.
This injection of air in the intermediate portion of the duct 20a allows a condition of vacuum pressure to be produced not only at the inlet 21 of the duct 20a, but also in the entire duct.
The cup 1a is thus drawn by suction into the respective duct 20a as shown in
Even after the upper edge of the cup 1a has moved beyond the series of nozzles 22 (
For the sake of clarity,
The operating principle is identical to the one indicated hereinbefore with reference to
The tray 200 may be held during movement, ensured for example by vacuum pressure produced between the tray 200 and the shaped element 60 through holes 61.
In
The cup 300 is thus drawn by suction and subsequently deposited on a shaped element 70, having the form of a truncate cone, which for example supports a suction cup 71 to temporarily hold the cup on the element 70. This element is also mounted on a supporting plate 75 which is movable together with the shaped element 70 between a position to receive the cup 300 (represented in
Various modifications and improvements may be made without departing from the scope of the present invention.
For example, as shown in
The continuous peripheral aperture 143 has a section inclined with respect to the axis of the duct 140, analogous to the inclined holes described hereinbefore.
In this embodiment it may be advantageous to vary the amplitude of the section of the aperture 143 so that, with the same feed pressure, the speed of the blade of air P injected into the duct can be varied and the conditions of vacuum pressure produced in proximity to and inside the duct can be influenced. This may be implemented in a particularly simple way by providing, for example, suitable means to vary the distance that separates the two contiguous portions of ducts 145 and 146, moving them towards or away from each other.
Number | Date | Country | Kind |
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MI2002A002566 | Dec 2002 | IT | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/IB03/05530 | 11/28/2003 | WO | 11/29/2005 |