The present invention concerns a device enabling stamping foil to be paid out with a view to storing it temporarily before its actual use in a stamping machine.
The invention finds a particularly advantageous, but not exclusive, application in the field of the fabrication of packaging for luxury goods.
It is known to print texts and/or patterns by stamping, that is to say by depositing by pressure on a support in the form of a sheet colored or metalized foil coming from one or more stamping foils commonly called metalized foils. In the industry, such a transfer operation is usually carried out by means of a platen press into which the printing supports are introduced sheet by sheet, while each stamping foil is fed continuously.
Each stamping foil is traditionally stored in the form of a spool, and it is a advance shaft that pays it out and circulates it through the stamping machine. In practice, this advance shaft is required to turn at variable speed given that in a platen press, by definition, the foil is fed sequentially. In concrete terms, this means that the rotation of the advance shaft consists in a more or less complex combination of accelerations, decelerations and time-delays.
The problem with this kind of arrangement is that it does not enable precise unwinding of the foil. A spool of stamping foil has a non-negligible mass and thus a relatively high inertia. It therefore proves particularly difficult for such a spool to track the succession of accelerations, decelerations and time-delays that is imposed by the advance shaft. This being so, it will not be possible to advance the stamping foil with the required precision, which in the end inevitably degrades the quality of the stamping. In other words, although it is preferable for a foil to be paid out at a substantially constant speed given the inertia of the spool that supports it, this is not compatible with the fact that the same foil is intended to circulate sequentially when acted on by a advance shaft turning at variable speed.
To solve this problem, it is possible to constitute a reserve of foil upstream of the advance shaft. In this regard, there is notably known a foil unwinding device that is placed between the spool and the advance shaft and that uses two series of diverting elements, the distance between which may vary as the foil advances. In concrete terms, the two series of diverting elements are disposed substantially face to face in such a manner as to define a foil circulation path the shape of which describes a succession of loops that respectively circumvent each diverting element on passing alternately from one series of diverting elements to the other. One of the series of diverting elements is mounted to be mobile relative to the other between a close together position in which the series of diverting elements are disposed in the vicinity of each other to define a foil circulation path of minimum length and a far apart position in which said series of diverting elements are disposed at a distance from each other in such a manner as to define a foil circulation path of maximum length. The foil unwinding device further includes means adapted to move the series of mobile diverting elements between the close together position and the far apart position as a function of the advance of the foil that is actually driven by the rotation of the advance shaft.
However, this type of foil unwinding device has the drawback that its operation is not free of jerks, notably during transient starting and stopping phases, but also during acceleration and deceleration phases. The unfortunate consequence of this is to limit the stamping speed of the platen press.
Thus the technical problem to be solved by the subject matter of the present invention is to propose a device for unwinding foil to accumulate at least one stamping foil upstream of a advance shaft, said device including on the one hand two series of diverting elements one of which is mounted to be mobile relative to the other between a close together position and a far apart position in such a manner as to define a foil circulation path of variable length and on the other hand means adapted to move the series of mobile diverting elements between the close together position and the far apart position as a function of the foil advance, which device would make it possible to avoid the problems of the prior art, notably by offering significantly more regular operation.
The solution in accordance with the invention to the stated technical problem consists in that the movement means are adapted to move the series of mobile diverting elements as a function of the rotation speed difference between the advance shaft that is intended to turn at variable speed and a rotary drive member that is meant to turn at a constant speed substantially equal to the average rotation speed of said advance shaft.
It is to be understood that throughout the present text the term diverting element generally designates any element capable of diverting the circulation of a foil. It may notably be static, such as an air diverting element, or intrinsically mobile, such as a rotary roller.
For its part, the concept of a series of diverting elements encompasses the situation in which there is only one diverting element, even though in practice the use of a plurality would be quasi-systematic. In concrete terms, the number of diverting elements will be chosen first and foremost as a function of the quantity of foil to be placed temporarily in reserve.
It is to be noted that the device of the invention for unwinding foil may be installed anywhere enabling both reception of the stamping foil coming from its place of storage and delivery of foil to the advance shaft associated with it. This notably means that this kind of foil unwinding device may equally well be positioned inside or outside the machine.
It is also important to point out that the foil unwinding device of the invention may equally well be associated with a single stamping foil driven by its own advance shaft or a plurality of foils coupled to a common advance shaft.
Be this as it may, the invention as so defined enables the prior art problem of jerks to be overcome, and thus real flexibility of operation to be achieved. It is consequently possible to operate the platen press at much higher throughputs than its prior art counterparts.
The present invention further concerns the features that will emerge during the following description considered separately and in all technically possible combinations.
This description, given by way of nonlimiting example, is intended to explain in what the invention consists and how it may be practised. The description is moreover given with reference to the appended drawings, in which:
For reasons of clarity, the same elements have been designated by identical references. Similarly, only elements essential for understanding the invention have been shown, diagrammatically and not to scale.
It will simply be pointed out that it is typically composed of a plurality of workstations that are juxtaposed to form a unitary assembly capable of processing a succession of printing supports in the form of sheets 10. Thus there are usually a feeder responsible for feeding the machine sheet by sheet, a feed table on which the sheets 10 are placed in a layer before being precisely positioned individually, a stamping station 1 adapted to deposit on each sheet 10 by hot stamping metalized foil coming from at least one foil 20, a waste recovery station for evacuating each spent stamping foil 20, and a delivery station adapted to restack the sheets previously processed. Conveying means 30 are further provided for moving each sheet 10 individually from the exit of the feed table to the receiving station, including through the stamping station 1. In an entirely standard manner, these conveying means 30 employ a series of clamp bars 31 that are mounted to be mobile transversely in translation via two trains of chains 32 disposed laterally on each side of the printing machine.
In this particular embodiment, chosen entirely by way of example, the sheets 10 are stamped by means of a standard platen press 40, to be more precise between an upper heating platen 41 that is fixed and a lower platen 42 that is mounted to be mobile to-and-fro vertically. Moreover, and in order to simplify an understanding of the invention, the stamping station 1 is here fed with only one stamping foil 20 wound around a spool 21 and driven by a advance shaft 50.
This foil unwinding device 100 comprises two series 110, 120 of diverting element rollers 111, 121 that are positioned substantially face to face. Everything is arranged so that these two series of diverting elements 110, 120 define a foil circulation path the shape of which describes a succession of loops that respectively circumvent each diverting element 111, 121 on passing alternately from one series of diverting elements 110 to the other series of diverting elements 120. Moreover, one series of diverting elements 110 is mounted to be mobile in translation relative to the other series of diverting elements 120. This mobility is operative between, on the one hand, a close together position I (
According to the present invention, the movement means 130 are adapted to move the series of mobile diverting elements 110 as a function of the rotation speed difference between the advance shaft 50 that is intended to turn at variable speed and a rotary drive member 131 that is meant to turn at a constant speed substantially equal to the average rotation speed of said advance shaft 50.
At this stage of the description, it is to be understood that the movement in translation of the series of mobile diverting elements 110 between the close together position I and the far apart position II may in theory take place along any trajectory. A rectilinear or curvilinear trajectory is notably considered here, and more generally any trajectory resulting from any combination of these two types of movement in translation.
According to another feature of the invention, the diverting elements 111, 121 of each series 110, 120 are separated transversely in pairs by empty spaces the dimensions of which are greater than those of the diverting elements 111, 121 of the other series 110, 120. This feature is intended to allow the diverting elements 111 of the mobile series 110 to pass between the diverting elements 121 of the static series 120. In this line of thinking, the series of mobile diverting elements 110 is moreover mounted to be mobile in translation between the close together position I (
In an analogous manner to what has been stated above, any type of trajectory may be envisaged a priori for the movement in translation of the series of mobile diverting elements 110 between the close together position I and the loading position III.
Be this as it may, such an arrangement greatly facilitates placing the foil 20 in the unwinding device 100. It suffices to cause the series of mobile diverting elements 110 to move to the other side of the series of static diverting elements 120, and then to insert the foil 20 linearly between said series of diverting elements 110, 120 (
In a particularly advantageous manner, the mobile diverting elements 111 are here disposed directly facing the empty spaces between the static diverting elements 121, both in the close together position I and in the loading position III. Everything is moreover arranged in such a fashion that the mobility in translation of the series of mobile diverting elements 110 between the two positions in question is along a substantially rectilinear trajectory.
The benefit of such an embodiment essentially lies in its simplicity. By offsetting the mobile diverting elements 111 transversely relative to the static diverting elements 121, the series of mobile diverting elements 110 is ideally positioned to be moved in a straight line. Such an operation proves particularly easy to carry out, given that a rectilinear movement in translation constitutes a movement that is relatively simple to generate and to guide.
The two series of diverting elements 110, 120 preferably lie in respective substantially parallel positioning planes. Everything is moreover arranged in such a manner that the mobility in translation of the series of mobile diverting elements 110 between the close together position I and the far apart position II, just as between said close together position I and the loading position III, is in a direction substantially perpendicular to said positioning planes.
The fact that the two series of diverting elements 110, 120 lie in two substantially parallel planes means on the one hand that the diverting elements 111, 121 of the same series 110, 120 are substantially coplanar and on the other hand that the corresponding two planes are equidistant. For its part the fact that the mobility in translation of the series of mobile diverting elements 110 is perpendicular to the two positioning planes implies that the mobile diverting elements 111 are offset transversely relative to the static diverting elements 120 and that they move in a straight line.
According to another feature of the invention, the series of mobile diverting elements 110 is fastened to a mobile support, forming a oscillatory member 140. Everything is moreover arranged in such a manner that the movement means 130 are in a position to move the oscillatory member 140 both between the close together position I and the far apart position II and between said close together position I and the loading position III.
In this line of thinking, the foil unwinding device 100 advantageously has guide means 150 that, as their name indicates, are adapted to guide movements of the oscillatory member 140 between the close together position I and the far apart position II, as well as between said close together position I and the loading position III.
As may be seen clearly in
According to another feature of the invention, the movement means 130 are adapted to move the series of mobile diverting elements 110 and the series of static diverting elements 120 closer together when the instantaneous rotation speed of the advance shaft 50 exceeds the average rotation speed of that same advance shaft 50, but also to move said series of mobile diverting elements 110 away from series of static diverting elements 120 when said instantaneous rotation speed falls below said average rotation speed.
In a particularly advantageous manner, the movement means 130 employ a rotary drive member 131 that is coupled to the oscillatory member 140 via at least one indirect transmission member 132 forming a differential. Everything is moreover arranged in such a manner that each transmission member 132 is also coupled in driving manner with the advance shaft 50. It is to be noted that in the context of the invention the term differential designates any mechanism capable of coupling in a driving manner rotary elements turning at different speeds. In the present instance, it is a question here of the advance shaft 50 that is intended to turn at variable speed and a rotary drive member 131 that is meant to turn at constant speed.
In the concrete embodiment of
It is to be understood here that the terms “front”, “rear”, “in front”, “behind” are to be understood relative to the direction of movement of the oscillatory member 140 and considering the forward direction as that which corresponds to the series of mobile diverting elements 110 moving away from the series of static diverting elements 120.
In this embodiment, the flexible transmission element 137 is constituted by a notched belt. It is nevertheless possible to use a smooth belt, a chain, a cable, etc.
When the advance shaft 50 turns at the same speed as the rotary drive member 131, the oscillatory member 140 remains immobile in a substantially central position relative to the first series of static pulleys 135 and the second series of static pulleys 136. This is on the understanding that the oscillatory member 140 can move only when the instantaneous rotation speed of the advance shaft 50 is different from its average speed.
Thus as soon as the rotation speed of the advance shaft 50 is about to exceed that of the rotary drive shaft 131, the belt portion 137 situated directly upstream of said advance shaft 50 pulls the oscillatory member 140 backward, i.e. in the direction of the series of static diverting elements 120. The mobile diverting elements 111 will then move toward the static diverting elements 121, thus enabling quick release of the required quantity of pre-paid-out foil 20.
On the other hand, when the advance shaft 50 is about to decelerate, its rotation speed will end up by falling below that of the rotary drive member 131. Each belt portion 137 situated directly upstream of said drive member 131 will then tend to pull the oscillatory member 140 forward, toward its initial central position. The consequence of this will be to generate movement of the mobile diverting elements 111 away from the static diverting elements 121 and therefore progressive reconstitution of the stock of pre-paid-out foil 20.
Thus the direction of movement of the oscillatory member 140 will depend on the evolution over time of the speed of the advance shaft 50, in other words whether it is a matter of acceleration or of deceleration. The speed of movement of the oscillatory member 140 will for its part be proportional to the intensity of the acceleration or the deceleration generated by the advance shaft 50. For its part, the amplitude of the movement of the oscillatory member 140 will be linked to the duration of the phase of acceleration or deceleration of the advance shaft 50, and thus the quantity of foil 20 actually in play.
According to another advantageous feature of the invention, each diverting element 111 of the series of mobile diverting elements 110 is coupled in rotary driving manner with a pulley of each first series of mobile pulleys 133 (
In this embodiment, as shown in
Of course, the invention is equally concerned with any stamping station 1 that is capable of depositing colored or metalized foil coming from at least one stamping foil 20 onto a succession of elements in the form of sheets 10 and that includes at least one foil unwinding device 100 as described above.
More generally, however, the invention further relates to any machine for processing elements in the form of sheets 10 that includes a stamping station 1 able to deposit on each sheet 10 colored or metalized foil coming from at least one stamping foil 20 and that further includes at least one foil unwinding device 100 as described above.
Number | Date | Country | Kind |
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11001601.1 | Feb 2011 | EP | regional |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP12/00654 | 2/15/2012 | WO | 00 | 8/23/2013 |