Abstract:
A machine for packing by wrapping a load (1) comprises a device for supplying a pre-drawn film (3) propelled with respect to a longitudinal axis (6) of the load (1) to be packed with a relative helicoidal movement, and a device for handling of the free end of the film (3) between two wrapping cycles in accordance with the invention comprises a plate (10) for holding of the film (3) against the load (1), the length of which is at least equal to the width of the film (3) used, and near one of the long edges of this plate (10), a pair of jaws (13, 14) mobile with respect to one another along this edge are provided to crumple and grip between them the portion of the film contained between the plate and the film-supply device.

Description:
FIELD OF THE INVENTION 
     This invention relates to a machine for wrapping a load. 
     BACKGROUND OF THE INVENTION 
     The techniques of packing a load by wrapping have as their principal function to endow the load formed as a pile with the necessary cohesion so as to preserve the stability of the pile at the time of its handling. 
     The method used to ensure this cohesion is a drawable film which is wound in the drawn state around the pile under a predetermined amount of low tension, the film having a tendency to retract slightly and to lie flat on the load. In general, at least two layers of winding are effected. 
     Among the machines used for the implementation of this packing technique, there are those in which the load revolves in relation to a fixed source of supply of pre-drawn film, and those in which the load is fixed, with the film-supply source revolving around such load. In these two categories, the film supply source comprises a spool of film combined with a pre-drawing device and is vertically mobile along its support (if the axis of the load is vertical) so as to be able to sweep the entire height of the load with a helicoidal winding. 
     The main problems still to be resolved for this type of machine relate to the beginning and end of a wrapping cycle. Indeed, at the beginning of each cycle, it is necessary to make the end of the film integral with the load so that the unwinding of this film results from the relative revolution of the load and the film-supply source. It is necessary, at the end of the cycle, to cut the film by &#34;attaching&#34; one of the ends to the load while the other end is preserved so as to then be applied to a subsequent load. 
     OBJECT OF THE INVENTION 
     This invention seeks to propose a simple device to ensure these functions at the beginning and end of the wrapping cycle, and in addition making it possible to improve the finishing quality of the packing and the speed of execution of such operations at the beginning and end of the cycle. 
     SUMMARY OF THE INVENTION 
     To this end, the purpose of the present invention is achieved through the provision of a machine for packing by wrapping of a load comprising a device for supplying a pre-drawn film, propelled in relation to a longitudinal axis of the load to be packed with a relative helicoidal movement, a device for handling the free end of the film between two wrapping cycles which consists of a plate for holding the film against the load, the length of which is at least equal to the width of the film used and, close to one of the long edges of this plate, a pair of jaws mobile with respect to one another along this edge so as to crumple and grip between them the portion of film contained between the plate applied to the load and the film-supply device. 
     These integral jaws movable with the film-holder plate on the load at the conclusion of wrapping offer several advantages. It will be recalled, first of all, that the principal function of this plate is to attach the end of the film to the load. This attachment may be accomplished either by pressure if the film is slightly adhesive or, most often, by thermo-sealing, the plate being capable of being heated. The first advantage of the jaws being integral and movable with the plate resides in the fact that they are located in the immediate area of this plate and their operation, which consists in gathering the film into a core, produces on this film, interactively with one of the edges of the plate, a tearing force which can be used advantageously to obtain free end of the film which is integral with the load very close to the attachment area. The finishing of the packing is thus greatly improved, as the loose-hanging end of the film, which at the time of handling or stocking constitutes a starting point for unwinding of the film if this end happens to become caught or to be pulled inopportunely in a malicious manner, is eliminated. 
     The second advantage of this arrangement resides in the possibility of stopping the wrapping at any point whatsoever on the outer surface of the load. Indeed, in the present machines, stoppage of the wrapping is most often implemented in a low position, after having passed the film through the last turn, by means of a clamp fixed in relation to the load with which it might be kept after cutting. 
     Another advantage of this arrangement resides in the fact that the film, when it is clamped between the jaws, is formed into a core which effectively transmits the pull which must be imposed on the film, specifically at the beginning of each wrapping cycle, which makes it possible to pick up speed rapidly without worrying about a break in the film. 
     In order to be able to apply the holding plate against the load with the film between the plate and the load, the plate and the jaws are installed at the end of a mobile support which is movable perpendicular to the axis of the load. In addition, so as to be able to select the level at which the wrapping will be stopped, the support is movable along a stationary guide parallel to the axis of the load. 
     In addition, the device comprises a clamp which is fixed with respect to the load and which is located at the level of one of its longitudinal ends, the positioning of which is, at the end of the wrapping cycle, located between the film-supply device and the film-gripping jaws, in the area of the path of these jaws at the time of the operation of the support with respect to the load. With the aid of this arrangement, it is possible to transfer the end of the film crumpled into the form of a core from the jaws to a fixed clamp so that the film delivered by the device supplying the pre-drawn film is ready to begin another wrapping cycle. 
     Finally, an additional feature of the present invention, which resides in the provision of a means for tearing of the film located between the jaws and the edge of the pressure plate, will be noted. This means for tearing, or more precisely for aiding or serving as a starting point for such tearing, can be a simple edge of the plate or a hot wire arranged between this plate and the jaws. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other features and advantages of the invention will be evident from the description thereof presented below, by way of example, and in reference to the attached drawings, in which like reference characters designate like or corresponding parts throughout the several views, and wherein: 
     FIGS. 1 to 5 are schematic perspective diagrams illustrating the various phases of functioning of the invention during a load-wrapping cycle; and 
     FIG. 6 is a general view of a wrapping device to which the methods of the invention are applied. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In FIGS. 1 to 5, a load 1 has been depicted, here in the form of a right-angled parallelepiped resting on its lower surface 2 on a support not illustrated in a machine which comprises a device for supplying a pre-drawn wrapping film 3, this device being depicted here simply by a spool 4 and a support 5 for the spool 4. 
     As recalled above, in accordance with this type of wrapping machine, either the load 1 revolves around its longitudinal axis 6 and the device for supplying of film 3 is stationary with respect to this axis 6 in a revolutionary orientation or mode but describes a reciprocating vertical movement along the support 5, or the load 1 is stationary and the device for supplying the film 3 revolves around the axis 6 while also undergoing a reciprocating vertical movement in relation to the load. In any case, it is this relative rotation of the load and the device for supplying the film 3 which produces the wrapping. 
     The machine of the invention comprises a fixed frame, a component 7 of which constitutes a slide for a support carrier 8 for an unfolding arm 9 for a plate 10 which is designed to hold the film 3 against the load 2 at the conclusion of the wrapping operation. The plate 10 is connected by a bracket indicated as 11 to a set of slides 12 for a pair of mobile jaws 13 and 14 which are movable along the set of slides 12 which is disposed parallel to one of the edges 10a of the plate 10. The set of slides 12, and consequently the jaws 13 and 14, are located between the plate 10, in the immediate area thereof, and the device for supplying the film 3. 
     In addition, the upper jaw 14 is equipped with a stirrup 15 in the direction of the film-supply device, this stirrup extending above the plane of the jaw 14 and having at its free end, perceptibly in the plane of the jaw 14, a finger 16 the function of which will be explained below. 
     When the wrapping operation is completed, the load 1 has its surface 1a disposed opposite the frame component 7. The automatic control mechanism of the machine adjusts the height of the carrier 8 and unfolds the arm 9 so that the plate 10 comes to rest on the surface 1a, pressing the film 3 onto this surface 1a as illustrated by the arrow A. Prior to this movement, the jaws 13 and 14 have been moved away from one another with the aid of a jack-type means of operation, along the slides 12, the distance separating them when they are disposed away from each other being greater than the width of the film 3 wrapped around the load 1. 
     As represented in FIG. 2, the jaws 13 and 14, when the plate 10 is held on the surface 1a of the load, are drawn closer to one another in accordance with the arrows B. 
     In accordance with a preferred mode of the present invention, each of the jaws preferably travels one half the distance which separates it from the other, but it is not outside the context of the invention to contemplate, for example, a fixed lower jaw 13 and a mobile upper jaw 14 which travels over the entire length of the slides 12. As the jaws draw closer to one another, the film 3 is crumpled between them and a pull is produced thereon which, as viewed in the figure, brings about its breaking or tearing at a location which is to the right of the side 10a of the plate 10. As a matter of fact, it may be desirable to implement this side 10a in such a way that it has a relatively hard, sharp edge so that, upon contact with this edge, at the time of crumpling of the film by the jaws 13 and 14, a starting point for breaking and a tearing of the film is produced. 
     It will be recalled that the plate 10 can be a thermo-sealing heating plate which can be activated in connection with the last turn of the film on the load. 
     The crumpled film held between the jaws 13 and 14 thus forms a sort of core which remains gathered together in a stump 17 outside the jaws with the aid of the finger 16 as illustrated by FIG. 3. 
     As a matter of fact, the condition of the machine depicted in this figure results on the one hand from the simultaneous lowering of the two jaws 13 and 14 to a position located at the lower portion of the slides 12, as the arrow C indicates, and on the other hand, the general descent of the carrier 8 and the spool 4 as indicated by the arrows D and E. Of course, prior to this operation of descent along the surface 1a of the load, there was a slight loosening of the plate 10 with respect to this surface through retraction of the unfolding arms 9 so as not to interfere with the wrapping covering the surface 1a of the load. 
     In the condition depicted in FIG. 3, the base of the spool 4 is located at the level of the finger 16 and the jaws 13 and 14, so that the finger 16 forces the film to come together along its lower edge which forms the portion of core 17 between this finger and the jaws 13, 14. 
     The presence of a clamp 18 which is borne by a support not depicted, integral with or joined to the support for the load 1 is also noted in FIGS. 1 to 5. This clamp 18 comprises two small plates 19 and 20 capable of being moved apart from one another and drawn together vertically. These small plates form jaws for this clamp which is located at the level of the lower surface 2 of the load on which the latter rests on its support. The control mechanism for opening and closing of the clamp 18 is conventional and will not be described. The clamp 18 is located near the side of the surface 1a of the load when the latter is stopped and between this surface and the frame component 7 which bears the carrier 8. 
     The automatic control mechanism of the machine which implemented the descent in accordance with arrows C, D and E of all the mobile equipment described above is such that at the end of such movements, as depicted in FIG. 3, the film stump 17 formed into a core is disposed opposite the two jaws 19 and 20 of the open clamp 18. A movement in accordance with the arrow F in FIG. 4 of the plate 10 in the direction of the carrier 8 introduces the film portion 17 in the form of a core between the two jaws 19 and 20. A detection of the presence of the core between the jaws 19 and 20 or a detection of the position of the mobile equipment in this intermediate position makes it possible to control the closing of the clamp on the film. When this closing is ensured, the jaws 13 and 14 can open and move away from one another along the slides 12, and the retraction of the deformable arm 9 can continue until achieving the configuration of the machine depicted in FIG. 5. 
     The wrapped load can then be extracted from the machine and a new load to be wrapped can be provided. Indeed it is noted in FIG. 5 that the clamp 18 holds the film 3 in a position such that the relative movement of the new load with respect to the film-supply device leads to the wrapping of the new load. When one or two helical turns are carried out, the clamp 18 opens and the portion of film which extends between the clamp 18 and the load 1 is released. To prevent this portion of film from hanging at the end of the wrapping, it can be advantageous to provide for a vertical blast of air under the load which has the effect of bringing this portion of released film back against the load so that the following turns succeed in keeping it there. 
     In variants of the present invention not depicted, it can also be contemplated that the clamp 18 is retractable between an upper level where it is in a service position, that is, capable of intercepting the film in the form of a stump or core 17, and a lower level located under the lower surface 2 of the load where it is retracted in order to permit, for example, the making of a very low turn which is to cover the lower edges of the load. 
     Likewise, and in case the load might rest on a revolving table, this table can comprise one or several other clamp 18 opposite each of the lateral surfaces of the load, which would make it possible to stop the wrapping opposite any surface whatsoever and in terms of the position of the load intake and discharge conveyors on the revolving table. If the clamp 18 is not installed in a retractable manner with respect to the lower surface of the load, it will be necessary to limit the number of clamps 18 to two arranged opposite two adjacent surfaces of the load so as to leave two load access and discharge sides free opposite these clamps. 
     FIG. 6 is an illustration of an industrial embodiment of a machine constructed in accordance with the invention, in which the load 1 rests on a revolving platen 21 while the device for supplying the film 3 and the carrier supporting the unfoldable arm, the plate 10 and the jaws 13 and 14, are installed so as to be vertically movable along a pole 22 integral with the frame of the machine. 
     There will be noted in this Figure, between the plate 10 and the slides 12 for sliding of the jaws 13 and 14, the presence of a heating wire 23 near which the jaws 13 and 14 can be drawn together, this heating wire constituting, when the plate 10 is held against one of the surfaces of the load 1, a means of starting the breaking of the film, which will be torn more easily when the jaws 13 and 14 draw toward one another. This hot wire can be replaced in accordance with a variant of the invention not depicted by a sharp edge which is supported by the wire and which can constitute a sort of fixed blade for cutting the film when the jaws 13 and 14 draw together. Of course, all the elements already described, with the same references, are found in this FIG. 6. 
     Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described herein.