Abstract:
The external conveyor supplying the trays coming from the filling machine is connected to a conveyor formed of parallel straps or belts, which has a greater length than the length of the group of trays of larger dimensions to be grouped together and which is provided in the end part with components inserted between the belts, a comb lifter of a length correlated with the length of said tray group to be formed, connected to lifting and lowering means with suitable acceleration and deceleration ramps. Upstream of the lifter, sensors are provided which detect the position in space of the trays arriving from the external conveyor in succession. A processing and control unit is provided to process the information arriving from said sensors.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to PCT International Application No. PCT/EP2013/062661 filed on Jun. 18, 2013, which claims priority to Italian Patent Application No. BO2012A000353 filed Jun. 26, 2012, the entirety of the disclosures of which are expressly incorporated herein by reference. 
     STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT 
     Not Applicable. 
     BACKGROUND OF THE INVENTION 
     The invention relates to machines designed to apply a closing film on trays containing a product, such as a food product, provided with a sealing and cutting station with opposing bells, between which groups of trays and an overhead section of film unwound from a coil are cyclically positioned and which, on command, are reciprocally closed to heat seal a portion of covering film on the upper edge of the trays, after possible conditioning of the atmosphere inside said trays, and then to separate around the perimeter, by cutting, the cover of each tray from the off-cut of surrounding film and which, lastly, are opened to prepare for offloading of the sealed trays and to prepare for removal of the off-cut of film, usually connected to a collection axis. These machines are provided upstream of said sealing station with a station which collects together and orders groups of trays to be inserted all together into said station, downstream of which a removal conveyor and pincer means are provided to perform simultaneously, with the sealing station open, transfer of groups of open trays from the first collection station to the second sealing and cutting station and sealed trays from said station to the final removal station. The invention relates in particular to the first tray collection station and cites as the prior art patent EP 334 266, which envisages said station being formed of a conveyor with intermittent motion, which stops cyclically to await the containers which are supplied to it by the unloading conveyor of the customer&#39;s machine, which fills the trays with the product. In certain cases, the trays contain liquid products, so it is necessary to make said changes in speed of the collection belt in an extremely gradual manner, with suitable deceleration and acceleration ramps, to prevent the liquid in the trays from overflowing or soiling the upper edge of said trays, prejudicing the successful outcome of the subsequent step of heat.sealing with the covering film. In order to overcome these problems, patent EP 680 880 describes how to perform said tray collection operation without the corresponding collection conveyor having to stop cyclically. This condition is obtained by arranging a compensation conveyor between the customer&#39;s collection conveyor and supply conveyor and by providing means of detecting the distance and speed of the trays inserted on said compensation conveyor, to guide the means of motion of said conveyor, so that it inserts the trays with a predetermined speed and position on the collection conveyor, which thus no longer needs to stop in succession, as indicated in EP 334 266, with the consequent advantages. 
     The second solution considered above considerably extends the length of the whole collection station, complicates its construction, considerably increases its costs and reduces its technological reliability, due to the major presence of sensors and all the processing and calculation means associated with them. 
     SUMMARY OF THE INVENTION 
     The invention is intended to overcome these and other limitations of the prior art with a solution as claimed in appended Claim  1 ) and the subsequent dependent claims, which envisages the use of a variable motion conveyor, which simultaneously performs the function of both compensation conveyor and collection conveyor and is formed of parallel straps or belts, which carries a comb lifter to the end part of them, inserted between the belts, and which is provided in the initial part with sensors which detect the position in space of the tray which arrives in succession from each row of the supply conveyor. A processing and control unit processes the information coming from said sensors, from a transducer which detects the advance speed of the conveyor belt and therefore the information of said trays and from software to which information relating to at least the dimensions of the trays to be closed is supplied each time. Said processing and control unit ensures that when the tray reaches the initial part of the comb lifter, in the lowered position, said lifter is raised by a small amount sufficient to release the tray from the movement of the conveyor belt and, when the second tray arrives upstream of the conveyor and in a specific position, the lifter itself lowers to allow the second tray which advances with the first tray and at a predetermined distance from it to enter it as well, and, when the second tray has entered onto the conveyor, this is raised and the cycle is repeated until the last tray of the group to be formed is lifted, in correspondence with which the lifer is raised with a higher run than the previous runs, sufficient to allow insertion below the tray group of the teeth of a comb, which, while the lifter is lowered to allow repetition of a new working cycle, takes over support of the trays and transfers them to the sealing and cutting station. The conveyor belt operates with variable motion and said cyclic lifting and lowering movement of the lifter occurs with acceleration and deceleration ramps such as to ensure the tray and the products they contain are influenced as little as possible by the changes in motion and remain in a stable position, even if liquid in nature. For this same purpose, it may also be envisaged that the lifter performs small horizontal translation movements during the lifting and lowering runs, so as to lift and lower the trays, respectively by taking them from and releasing them to the conveyor belt at speed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further characteristics and advantages of the invention will become more apparent from the following description of a preferred embodiment, illustrated by way of a non-limiting example in the figures in the three tables of drawings attached, wherein: 
         FIGS. 1, 2, 3, 4, 5, 6, 7  show the apparatus in schematic form, in side elevation and during the subsequent steps of its working cycle; 
         FIG. 8  shows a perspective and partial view of one of the combs for gripping and transferring the trays from the collection station to the sealing station; 
         FIGS. 9, 10 and 11  show the apparatus in transversal cross-section, as from the cross-section line of section IX-IX of  FIG. 1 , and with the lifter respectively in the lowered idle position, in the first lifting position for cyclic formation of the tray group and in the second lifting position for transfer of the tray group to the transfer comb; 
         FIG. 12  shows a side elevation and partial view of a construction variant of the apparatus. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The apparatus in question is now described in the version capable of managing two adjacent and parallel rows of small and medium-sized trays, coming from the same number of supply conveyors and which, if necessary, in the presence of large-sized trays, may be adapted to work on a single row of said trays. The apparatus must also be intended as protected if it is arranged to work on more than two parallel rows of trays or even on a single row. Having said this, with reference to  FIGS. 1 and 9 , it is specified that the apparatus comprises two straight and adjacent conveyors  1 ,  1 ′, horizontal and parallel to each other, each formed of a plurality of parallel belts  101 ,  101 ′, for example the Polycord® type, with round cross-section, having a good grip with the bottom of the trays, returned with the ends on pulleys  2 ,  2 ′ keyed onto shafts  3 ,  3 ′ supported rotating by the ends of a frame  4  and of which those downstream are connected to respective motion units  5 ,  5 ′ of the electronic speed control type and with an encoder, which may be governed independently when each conveyor works on its own row of trays V and which may be connected to each other by means of an electric shaft when the two conveyors  1 ,  1 ′ are combined to transport larger trays V 2 , as indicated respectively with a continuous line and with a broken line in  FIG. 9 , where  6 , 6 ′ denotes lateral and adjustable containment guides of the trays, while  7  denotes a central guide which may be removed when the trays V 2  to be processed have large dimensions and must simultaneously rest with the bottom on both conveyors  1  and  1 ′. With the left end for whoever is looking at  FIG. 1 , the conveyors  1 ,  1 ′ are connected to the customer&#39;s conveyors supplying the trays to be closed. The upper branch of the belts  101 ,  101 ′ of the conveyors  1 ,  1 ′ is maintained on a horizontal plane, for example by resting on transversal and coplanar rollers  8 , supported at the ends by the sides of frame  4 . The conveyors  1  and  1 ′ have a length correlated with the longest length of the group of trays to be cyclically formed, increased by the length of at least one of the longest trays to be processed and for the section which is destined to be used by the group of trays to be formed, said conveyors  1 ,  1 ′ are engaged longitudinally in the space between the belts  101 ,  101 ′, by vertical teeth arranged in the form of a comb  109 ,  109 ′ of lifters  9 ,  9 ′, which have a length equal and correlated to the length of the group of trays to be formed and which, with their distal end, are arranged at a short distance from the pulleys  2 ,  2 ′ of return of the final ends of the conveyors  1 ,  1 ′, said teeth  109 ,  109 ′ being arranged so as not to interfere with the levelling rollers  8  of the upper branch of the belts  101 ,  101 ′ of the conveyors  1 ,  1 ′. The tops of the teeth  109 ,  109 ′ are provided with elastomer inserts  10  which have a good grip on the bottom of the trays to be processed. By means of specific means described hereunder, the teeth  109 ,  109 ′ may be carried from a lowered idle position with their upper ends  10  just below the bottom of the trays transiting on the belts  101 ,  101 ′, as shown in  FIG. 9 , to a minimum raised position as shown in  FIG. 10 , where the teeth  109 ,  109 ′ raise the trays by the small amount necessary to distance them from the belts  101 ,  101 ′, to a position of maximum lifting as shown in  FIG. 11 , useful for creating between the bottom of the trays and the belts  101 ,  101 ′, a sufficient space to insert the gripping and transfer means described further on. The lifting and lowering means of the lifters  9 ,  9 ′, are such as to control these components with a variable motion, with the correct acceleration and deceleration ramps, as described further on. Returning to  FIG. 1 , it is noted that the control means of the lifters  9 ,  9 ′ are connected by means of wiring  11  to a processing and control unit  12 , which through the input  13 , is informed each time of the dimensions of the trays the apparatus must process, which by means of wiring  14  is connected to the means of motion  5 ,  5 ′ and to the relative encoders, which inform it of the speed of the conveyors  1 ,  1 ′, and which by means of wiring  15  is connected to sensors  16 , which form, for example, a vertical barrier of the optoelectronic type, with a reflector  116  upstream of the lifters  9 ,  9 ′, and which detects transit of the trays on the conveyors  1 ,  1 ′. The electronic unit  12  is provided with software which ensures functioning of the apparatus in the following manner. For the sake of brevity, the functioning of a single conveyor  1  is considered here, as functioning of the nearby conveyor  1 ′ is identical. At the start of the cycle, the conveyor  1  travels with its upper branch in direction F and the comb lifter  9  is in the lowered position, as shown in  FIGS. 1 and 9 . When the front edge in the direction of travel of the first tray V, indicated in  FIG. 1  with a broken line, is detected by the barrier  16 ,  116 , the processor  12  is able to control with precision the position in the subsequent space of said tray and when this reaches the initial part of the comb lifter  9 , this is raised by a small amount as shown in  FIGS. 2 and 10 , sufficient to release said tray from the movement of the conveyor belt  1  and, when the second tray V arrives upstream of the lifter  9  and in a specific position, said lifter is lowered as shown in  FIG. 3  to allow the second tray to enter above it, which advances with the first tray and at a pre-set distance from it and, when the second tray has also entered above the lifter  9 , as shown in  FIG. 4 , said lifter  9  is raised and the cycle is repeated until the last group of trays to be formed on said lifter  9  is raised. In other words, the trays are cyclically raised by the lifter  9 , so as to be maintained ordered one after the other and to await the next tray, while they are lowered onto the conveyor  1  to be grouped in increasing order and to be arranged increasingly above the aerial projection of the lifter  9 . If only two trays are to be positioned on the lifter  9 , as shown in the example in the drawings, when the second and last tray arrives, the lifter is raised with a higher run than the previous one, as shown in  FIGS. 5 and 11 , such as to allow insertion beneath the group of trays of the teeth  117  of a comb  17  (see also  FIG. 8 ) which, while the lifter  9  is lowered to allow repetition of a new working cycle, takes over support of the group of trays and, translating in a known manner, transfers them into the sealing and cutting station. The teeth  117  of the comb  17  are covered with a material which has a good grip on contact with the bottom of the trays, so that said trays do not move during transfer. It is clear that, on a change in height of the trays, it is unnecessary to perform any adjustment on the comb  17 , since said trays are always gripped on the bottom. The conveyor belt  1  operates with variable motion, so as to decelerate during transfer of the trays to the lifter  9 , which is also raised and lowered with suitable acceleration and deceleration ramps, such as to ensure stable positioning of the product packaged in the trays, even when liquid in nature, and the gravitational component acting on the packaged product in the lifting and subsequent lowering step also contributes to said stability. In order to better achieve the purpose of avoiding jolting the product in the trays, particularly if liquid in nature, it may also be envisaged that the lifter  9  is advanced with small horizontal translation movements during the lifting and lowering runs, so as to raise and lower the trays respectively by taking them from and releasing them to the conveyor belt  1  at speed. In order to achieve this purpose, it may also be envisaged that the teeth  109  of the lifter  9  are provided with sufficient horizontal clearance from the levelling rollers  8  of the conveyor  1  ( FIG. 1 ), or that said rollers  8  are replaced with straight guides  108  beneath each belt  101  and supported solely by the opposite ends of cross-bars  208  fixed to the frame  4 , so that the spaces between said belts  101  are completely free, and it may also be envisaged that the bottom plate  209  of the lifter (see  FIG. 2 ) is separate from an underlying support plate  209 ′ connected to the lifting and lowering means and is connected to this, with interposed guiding and sliding means  18 , so that the bottom plate  209  may perform a straight movement, even brief, in a parallel direction to the belts  101 , said bottom plate  209  being connected to the means of motion  19  carried by the lower plate  209 ′ and such as to impose on said plate  209  the small horizontal movements necessary to allow the teeth  109 ,  10  of the lifter  9  to pick up the trays at speed from the belts  101  of the conveyor  1  and then release them at speed to said belts, replicating the direction and advance speed of said belts. The number  114  denotes the wiring which connects the motion unit  19  to the processing and control unit  12  of  FIG. 1 . 
     With reference to  FIGS. 1 and 9-10 , the cyclic lifting and lowering means of the lifters  9 ,  9 ′ are described and, in this case, reference will be made for brevity&#39;s sake solely to the lifting means  9 , since lifting means  9 ′ are similar (see below).  FIGS. 1 and 9  show that the lower plate  209  of the lifter carries jointly a pair of vertical rods  20 , which project downwards and rest on an ideal vertical plane which is parallel to the direction of advance of the trays and said rods cross corresponding guide ferrules  21  integral to a beam  22  fixed to the frame  4  of the machine and said rods  20  are connected with the lower end by a cross-bar  23 , on the intermediate part of which, in  24 , the lower end of a pair of connecting rods  25  has its fulcrum, directed upwards and articulated with the upper end, in  26 , to the lower summit of a pair of triangular plates  27  which, with the upper summit, has its fulcrum, in  28 , on the middle line of the beam  22 . The third summit of the plates  27  is articulated in  29  to the stem  130  of a double-run actuator  30  which, with the opposite stem  230 , is articulated in  31  to an appendix  104  of the frame  4  of the machine. The actuator  30  is formed, for example, by the opposing union of the bodies of two small compressed-air cylinder and piston units, controlled by a solenoid valve unit  32  connected to the wiring  11  already discussed with reference to  FIG. 1 . The actuator  30  is provided with stop dampers.  FIG. 9  shows that, when the lifter  9  is in the lowered position, articulations  26 ,  28  are vertically aligned with each other, i.e. they are positioned at twelve o&#39;clock and at 6 o&#39;clock on a hypothetical clock, while articulation  29  is positioned at around 9 o&#39;clock and the stems  130 ,  230  of the actuator  30  are both extended. In order to raise lifter  9  with a short run, as shown in  FIG. 10 , the actuator  30  is controlled by retraction of one of the two stems, for example stem  230 , as shown in  FIG. 10 , with corresponding lifting of the cross-bar  23  and all the equipment associated with it. When lifter  9  must be raised with a long run, on the other hand, both stems  130 ,  230  of the actuator  30  are retracted, as shown in  FIG. 11 . It is clear how the solution described allows the acceleration and deceleration produced naturally by movement of articulations  26  and  29  on curved trajectories to be exploited, with the centre of rotation on the fixed and upper fulcrum  28 . 
       FIG. 1  shows that the control means of the lifter  9 ′ have the triangular plates  27 ′ turned in the same direction as those  27  of the mechanism described for lifter  9  and the possibility is envisaged of connecting articulations  29  and  26 ′ to each other by means of a tie rod  33 , in order to synchronise the movements of two lifters  9 ,  9 ′ when they are required to operate on large-sized trays V 2  which are resting simultaneously on the conveyors  1  and  1 ′. 
     It is also understood that the description relates to a preferred embodiment of the invention, to which numerous construction variants and changes may be made without deviating from the principle of the invention, as described and illustrated in the figures of the three appended tables of drawings and as indicated in the following claims. The references in brackets in the claims are purely indicative and do not limit the area of protection of said claims.