Abstract:
The invention relates to a device for accumulating flat material in flexible strip form, the device comprising an accumulator box having a bottom on which the strip accumulates, at least during accumulation stages, between two end walls and between two side walls that extend so as to face edges of the strip. The accumulator device includes at least one of the following means:
       rollers mounted idle close to the bottom and on which the strip rests during accumulation stages;   air-flow means for establishing a flow of air within the box towards the bottom of the accumulator box;   vibrator means for vibrating at least one of the side walls; and   adjuster means for adjusting spacing between the side walls.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is entitled to the benefit of and incorporates by reference essential subject matter disclosed in French Patent Application No. 11 51982 filed on Mar. 10, 2011. 
     FIELD OF THE INVENTION 
     The invention relates to a device for accumulating flat material in flexible strip form, e.g. a sheath of heat-shrink plastics material for fabricating heat-shrink sleeves on containers or on any other articles. 
     TECHNOLOGICAL BACKGROUND 
     In installations for covering containers or other articles in heat-shrink sleeves, it is useful to interpose an accumulator device between the reel carrying a heat-shrink sheath and the station where the sheath is used, with said accumulator device performing several roles. It enables variations in production rates to be absorbed, by avoiding the sheath being pulled too hard. It also enables the reel to be changed while leaving enough time for connecting a new sheath to the end of the old sheath. 
     Devices are known for accumulating flat material in flexible strip form, which devices comprise an accumulator box into which the strip penetrates and inside which it is laid flat to form a plurality of go-and-return plies. Such an accumulator device nevertheless suffers from certain drawbacks. Some flat materials tend to twist and do not take up spontaneously an arrangement in superposed plies, thereby leading to a shapeless jumble forming inside the box which can jam or damage the strip. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide an accumulator device of the accumulator box type in which the risk of twisting and of poor positioning of the strip is reduced. 
     In order to achieve this object, the invention provides a device for accumulating flat material in flexible strip form, the device comprising an accumulator box having a bottom on which the strip accumulates, at least during accumulation stages, between two end walls and between two side walls that extend so as to face edges of the strip, the accumulator device including at least one means for reducing the risk of the strip twisting inside the accumulator box. 
     According to the invention, the end wall closer to an inlet for the material into the accumulator box carries a deflector suitable for encouraging plies of material to form inside the accumulator box, the deflector being associated with vibrator means for causing the deflector to vibrate. 
     Associating the deflector with means for vibrating the deflector makes it much easier to cause the material to form flat plies, thereby limiting any risk of the flat material twisting, in particular when the material is a ply of heat-shrink plastics material for fabricating heat-shrink sleeves on containers, where such a material is not of uniform thickness and thus inevitably gives rise to problems when traveling through the accumulator box, with a risk of the sheath twisting that is increased in comparison with a flat material that is of uniform thickness. The invention is thus particularly adapted to limiting twisting in such a sheath. 
     In a preferred embodiment, the means for reducing the risk of the strip twisting inside the accumulator box are selected from:
         rollers mounted idle, at least in the vicinity of the bottom, and on which the strip comes to rest during accumulation stages;   air-flow means for establishing a downward flow of air inside the accumulator box;   vibrator means for vibrating at least one of the side walls; and   adjuster means for adjusting spacing between the side walls.       

     Various tests have shown that using one or more of these means makes it possible to further decrease the risk of the strip twisting inside the accumulator box. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The invention can be better understood in the light of the following description of particular embodiments of the invention given with reference to the figures of the accompanying drawings, in which: 
         FIG. 1  is a diagram of a circuit for flat material in strip form incorporating an accumulator device in a first particular embodiment of the invention, the box being partially cut away to show its inside; 
         FIG. 2  is an end view of the accumulator box of the accumulator device, one of the end walls being removed; 
         FIG. 3  is a perspective view of the accumulator device of  FIGS. 1 and 2 ; 
         FIG. 4  is a figure analogous to  FIG. 1  showing a diagram of a circuit for flat material in strip form incorporating an accumulator device in a second particular embodiment of the invention, during a stage of normal operation of the circuit; and 
         FIG. 5  is a figure analogous to  FIG. 4  showing the same circuit for flat material in strip form during a stage of material being accumulated in the accumulator box. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In a first particular embodiment shown in  FIGS. 1 to 3 , the accumulator device of the invention is for inserting in an installation that organizes the travel of a flat material in strip form, e.g. a sheath of heat-shrink plastics material. The circuit includes a reel  2  forming a source of strip material  1 . The strip  1  is then engaged in a damper device  3  having jumping rollers, comprising a series of stationary rollers  4  and a series of movable rollers  5  mounted on a lever  6  hinged on a pivot  7 , with the strip  1  extending between the rollers. The strip  1  is then taken towards an accumulator device  10  of the invention. 
     The device comprises an accumulator box  11  with the edges of the end wall  12 , of the ceiling  13 , and of the bottom  14  being shown in the figure. The accumulator box  11  is also closed by two side walls  30  that can be seen end-on in  FIG. 2 . In this example, the strip  1  enters into the accumulator box  11  via an opening  15  formed through the ceiling  13 , the strip being guided by a motor-driven inlet roller  16 . The strip leaves the box via an opening  17  formed in one of its end walls  12 , being guided by a motor-driven outlet roller  18 . 
     Naturally, the inlet and outlet rollers  16  and  18  are associated with backing rollers for pinching the strip  1  and forcing it to advance. In this example, an antistatic bar  19  is arranged at the inlet of the accumulator box  11  to prevent any static electricity accumulating in the accumulator box, since that might disturb stacking of the plies of the strip one on another. In a variant, the backing roller for the inlet roller  16  may be designed to be of the antistatic type. 
     The speed of rotation of the outlet roller  18  is naturally adapted to the rate at which the strip is required by the sleeving machine arranged downstream from the accumulator box  11 . The speed of rotation of the inlet roller  16  is normally adjusted to be identical to the speed of the outlet roller  18 , except during accumulation stages in which it is faster than the speed of the outlet roller  18 , thereby causing the strip to accumulate in plies inside the accumulator box  11 , as shown. During such a stage, the strand of strip leaving the accumulator box comes from a portion of the strip  1  that lies under the plies that have been built up by the strip  1 . Naturally,  FIG. 1  is diagrammatic, and the accumulator device  11  may have tens or even hundreds of plies forming inside the accumulator box  11 . It should be observed that the plies are placed one on another without any twisting by virtue of arrangements that are described in detail below. 
     The assembly operates as follows. During normal operation of the installation, the strip  1  is unreeled progressively from the reel  2  at the speed determined by the machine downstream from the accumulator device. The strip  1  then passes through the accumulator box  11  without building up heat. If, as a result of a level indicator  50  arranged close to the reel  2 , it is detected that the reel will soon be completely emptied, the inlet roller  16  is caused to rotate more quickly than the outlet roller  18  so that the strip is progressively accumulated in the accumulator box  11 . Once the reel has been completely emptied, an end-of-strip sensor  51  arranged upstream from the accumulator box  11  identifies the end of the strip, thereby causing the inlet roller  16  to be stopped. The end of the strip is then held stationary substantially above the accumulator box  11  where there is a splicing table (not shown). While the previously-accumulated strip is being delivered from the accumulator box  11 , an operator removes the empty reel and replaces it with a full reel. The start of the new strip is fed through the damper device  3  until it comes close to the end of the old strip. The operator then proceeds to splice the two strips together, and once they have been spliced together, the inlet roller  16  is once more set into rotation. The quantity of strip that is accumulated in the accumulator box  11  is adjusted to leave the operator sufficient time to change the reel and to splice the new strip to the old strip, with account being taken of the travel speed of the strip at the outlet from the accumulator box. 
     All of the above-mentioned rollers have axes of rotation that are parallel and that extend perpendicularly to a travel direction of the strip  1  (and thus also perpendicular to the side walls  30 ). 
     The arrangements of the invention relate more particularly to eliminating as much as possible, and in any event to reducing, the risk of the strip becoming twisted or poorly positioned inside the accumulator box  11 . 
     According to an aspect of the invention, the bottom  14  of the accumulator box  11  carries idler rollers  20  on which the strip  1  comes to rest during the accumulation stages. The idler rollers  20  make it easier for the strip to be extracted via the opening  17  by preventing it from being braked excessively by the weight of the accumulated plies of strip on top of the exiting strand. Naturally, the axes of rotation of the idler rollers  14  are parallel to the axes of rotation of the other rollers. 
     According to another aspect of the invention, the accumulator box  11  is fitted with air-flow means for encouraging proper positioning of the plies of strip inside the accumulator box  11  during accumulation stages. The air-flow means here comprise air extractors  21  that establish reduced pressure inside a compartment  22  arranged under the bottom  14  of the accumulator box  11 . The bottom  14  of the accumulator box  11  is perforated so that the suction as established in this way causes air to flow downwards inside the accumulator box  11  (i.e. towards the bottom of the accumulator box), as represented by arrows in  FIG. 1 , thereby tending to press the plies of the strip  1  against one another, and thus make it easier for them to stack up inside the accumulator box  11 . Naturally, it is appropriate to provide orifices in the ceiling  13  making air intake possible. 
     According to yet another aspect of the invention that can be seen more particularly in  FIG. 2 , the side walls  30  are provided with vibrators  31  serving to cause the side walls  30  to vibrate while the strip  1  is accumulating inside the accumulator box  11 . The vibration of the side walls  30  prevents the edges of the strip  1  from catching on the side walls, where that can lead to the strip  1  becoming twisted. Preferably, the side walls  30  are made of transparent material so as to make it possible to verify that the strips of ply  1  are properly stacked inside the accumulator box  11 . 
     According to yet another aspect of the invention, the side walls  30  are associated with adjustable spacer means  40  enabling the distance between the faces of the facing side walls to be adjusted so that the distance matches the width of the strip  1 , while leaving a small amount of clearance (typically a few millimeters for a strip having a width of ten centimeters). Each of the side walls  30  in this example is mounted on two supports  41  that co-operate via screw-and-nut type connections with respective shafts  42  (only one of which is visible in  FIG. 2 ) so as to rotate in a manner that is synchronized, e.g. by means of a belt. Each shaft  42  is received to rotate in a bearing  44  secured to the ceiling  13  of the box and is threaded with oppositely-handed threads at opposite ends such that rotating a shaft causes the two side walls  30  to move apart or towards each other symmetrically relative to a midplane along which the strip travels. For this purpose, one of the shafts  42  is fitted with a handle  43  for driving it. The side walls  30  are thus suspended from their supports  41 , thereby making them easier to vibrate by means of the vibrators  31 . 
     The arrangements of the invention serve to reduce the risk of the strip twisting in the accumulator box. The Applicant has been able to verify that the accumulator device is suitable for sheaths made of looped heat-shrink plastics material for use in fitting heat-shrink sleeves, with the sheaths being of various thicknesses (20 micrometers to 150 micrometers), and being made of various materials (polyvinyl chloride (PVC), polyethylene terephthalate (PET), oriented polystyrene (OPS), . . . ) traveling at speeds that are suitable for installing 20 to 600 sleeves per minute, the sleeves having heights in the range 15 millimeters to 250 millimeters. No twisting was observed. 
     In a second particular embodiment of the invention as shown in  FIGS. 4 and 5 , in which elements that are common with the embodiment described above have the same references plus one hundred, the strip  101  is taken to an accumulator device  110  that comprises an accumulator box  111 , with the edge faces of its end walls  112 , its ceiling  113 , and its bottom  114  being shown. The accumulator box  111  is also closed by two side walls that are not shown, with at least one of them being transparent. The strip  101  enters into the accumulator box  111  via an opening  115  formed in the ceiling  113 , being guided by a motor-driven inlet roller  116  associated with a backing roller. The strip leaves via an outlet  117  formed in one of the end walls  112 , being guided by an outlet roller  118 . 
     In this embodiment, a motor-driven extractor roller  160  is arranged on the outside for extracting the strip from the box  111 , the motor-driven roller  160  being associated with a brush  161  for maintaining constant tension at the outlet from the accumulator device. Furthermore, a choke  162  is arranged facing the outlet roller  118  to prevent a plurality of plies of strip exiting simultaneously. 
     The idler rollers  120  on which the strip rests can clearly be seen. In this embodiment, the idler rollers  120  are arranged not only close to the bottom  114 , but also along an outlet strand of the strip so as to facilitate exit of the strip, and air-flow means  121  can also be seen for establishing a vertical flow of air through the accumulator box  111 . 
     According to the invention, the end wall  112  opposite from the end wall having the outlet roller  118  is provided in this embodiment with a deflector  164  suitable for causing the strip to be put into plies, which deflector  164  is provided with a vibrator  165  for causing it to move so as to cause the plies to move towards the outlet of the accumulator box  111 . 
     In addition, the accumulator device is fitted with a level sensor  166  for managing some minimum level of plies within the accumulator box during an accumulation stage. The level sensor  166  serves to manage the speed of the inlet roller  116 . 
     The path followed by the strip upstream from the accumulator device  110  includes a reel  102  forming a source of strip  1 . The strip  1  is taken to the inlet of the accumulator box  111  by means of cylinders  167  and  168  forming air cushions and fitted with lateral guide rings for assisting in recentering the strip, in particular when using reels onto which the strip has been rewound. There can be seen the end of strip sensor  151  which is located in this embodiment immediately upstream from the deflector cylinder  168 , and also the level sensor  150  for sensing the amount that remains on the reel  102 . 
     The device of  FIGS. 4 and 5  is used as follows. 
     In normal operation, as shown in  FIG. 4 , i.e. when the level sensor  150  has not detected that the strip  101  will shortly cease to be delivered from the reel  102 , a slack portion  180  of strip is formed inside the accumulator box  111  by acting on the speeds of rotation of the inlet roller  116  and of the extractor roller  160 . For this purpose, it suffices on a temporary basis to cause the inlet roller to rotate faster than the extractor roller so as to generate said portion of strip that makes it possible to accommodate variations in the rate at which the strip is drawn out downstream from the accumulator device of the invention, but without thereby forming plies inside the accumulator box, in order to avoid any risk of the strip twisting. 
     This thus produces the same damping effect as in the above-described embodiment, but without using an external damper device. 
     During an accumulation stage as shown in  FIG. 5 , which stage is triggered when the level sensor  150  detects that the reel  102  will shortly be empty, plies are built up inside the accumulator box, as described above. The vibrating deflector  164  makes it easier to form plies by sending the strip towards the other end wall  112 . 
     The invention is naturally not limited to the above description. In particular, although the means of the invention as described are implemented in combination with one another, the invention also applies to embodiments in which at least one of said means is implemented. 
     Furthermore, some of the means shown in only one of the particular embodiments described may naturally be mounted on the other described embodiments, or on other variant embodiments of the invention. 
     Furthermore, said means may be varied in numerous ways. For example, although both side walls as described are fitted with a respective vibrator, it may suffice to vibrate only one of the walls. Similarly, although the spacer means cause the side walls to move symmetrically relative to a midplane, it is possible for only one of the side walls to be moved, providing the installation includes means for centering the strip in the space as defined in that way. 
     It is clear that the appropriateness of using a damper device (a jumping roller device as described above, or any other damper device), whether arranged upstream of the accumulator device or downstream therefrom, naturally depends on specific circumstances and on the characteristics of the installation. 
     While the present invention has been illustrated and described with respect to a particular embodiment thereof, it should be appreciated by those of ordinary skill in the art that various modifications to this invention may be made without departing from the spirit and scope of the present.