대표
청구항
▼
The invention claimed is: 1. A machine for packaging food products in trays which are sealed at the top with thermoplastic film, said machine comprising: a reel and film feeding means for controlled unwinding therefrom of film for closing the trays, the reel of film arranged with a horizontal axis thereby allowing the film to be unwound from the reel; first deviating means situated below the reel and around which the film is deviated for changing a path of the film from a descending path to a horizontal path, the first deviating means comprising a fixed...
The invention claimed is: 1. A machine for packaging food products in trays which are sealed at the top with thermoplastic film, said machine comprising: a reel and film feeding means for controlled unwinding therefrom of film for closing the trays, the reel of film arranged with a horizontal axis thereby allowing the film to be unwound from the reel; first deviating means situated below the reel and around which the film is deviated for changing a path of the film from a descending path to a horizontal path, the first deviating means comprising a fixed guide curved at the bottom and one or more rollers; second deviating means for altering a path of the film; rollers mounted on a vertically movable structure supporting a punching head on one end and fixed to a take-up beam supported rotatably in a projecting manner by a lug of a fixed frame of the machine on another end, the rollers being actuated by a roller motor, the roller motor, together with a film feeding motor, are actuated with constant control of torque wherein the film can be first stretched above the tray to be closed and then the film feeding motor can perform a small backward cyclical movement in order to limit the longitudinal waste of the film which during this step is also kept suitably stretched; counter-die means for supporting at least one tray horizontally, along an upper edge, with a predefined orientation and for displacing it horizontally underneath a horizontal section of film; welding means situated downstream of the first deviating means for welding the film sealingly onto an upper edge of the tray; means situated upstream of the first deviating means for blowing an appropriate quantity of modified atmosphere at appropriate pressure values into an open part of the tray which advances underneath the film until the tray has been completely sealed by the film; separating means for separating from the film, a portion of the film welded to the upper edge of each tray; collecting means for taking up the waste film produced by the separation means, the collecting means operating in conjunction with the film feeding means, whereby at least the section of film on the horizontal path advances continuously stretched both longitudinally and transversely; positioning means which at a start of a cycle supply and position correctly the trays to be closed in the counter-die means; lifting means which at an end of the cycle, raise the closed trays from the counter-die means; tray conveying means for conveying away the closed trays; and means for horizontally moving the counter-die means, which at the end of the cycle are adapted to bring the counter-die means back into a starting position for repetition of a new working cycle. 2. The machine according to claim 1, further comprising jockey wheel means disposed between the film feeding means and the first deviating means, with tensioning sensors, which provide extra play in a sufficient quantity of film to allow the small backward movement of the film, only with reversal in operation of the roller motor and so as to allow the use of the film feeding motor. 3. The machine according to claim 1, wherein closing trays are not subject to a modified atmosphere, wherein the blower is used to blow in clean air in order to remove from the tray the gases which are formed during welding of the film for closing the tray. 4. The machine according to claim 1, further comprising a vane provided transversely with respect to the path of the trays, upstream of the opening of the counter-die when the vane is stationary in a start-of-cycle position, the vane being associated with adjusting means, wherein, upon a variation in the shape or size of the trays, allow positioning of the vane immediately downstream of the tray which cyclically comes up against the barrier of the means for blowing the modified atmosphere and being associated with raising and lowering means which, when actuated, bring the vane from a low position for intercepting the trays to a high position which allows the trays to pass through and vice versa. 5. The machine according to claim 4, wherein the vane is supported by an arm mounted on a vertical slide actuated by a rectilinear actuator which in synchronism can bring the vane into the raised position, thereby allowing a tray to pass underneath it and then into a low stopped position of the trays, the machine further comprising a guide on which the vertical slide travels, the guide slidable on a pair of horizontal guides parallel to the longitudinal axis of a main conveyor and fixed at the ends to a part of the frame, a position of the vertical slide, on the horizontal guides, adjustable by means of a suitable system. 6. The machine according to claim 1, wherein, when the tray covered by the film passes thereunderneath, the welding means is adapted to heat-weld the film onto a perimetral edge of the tray, to close the tray in a sealed manner, the welding means comprising a welding roller with a round cross-section, parallel to the first deviating means, with a width suitably greater than the width of an upper edge of the trays to be closed, heated to an appropriate temperature, the welding roller being supported by raising and lowering means which, when actuated, is adapted to transfer the welding roller from a raised rest position to a low position where it makes contact an appropriate pressure on the film to be welded and being provided with rotation means which, during an active working phase, cause the weld roller to rotate at a peripheral speed identical to a linear speed of feeding of the tray with the film and in the same direction. 7. The machine according to claim 6, in which the welding roller may be actuated by a small electric motor which causes the welding roller to rotate during an active phase and/or at least when a carriage for conveying the tray is in the rest position, so as to avoid idle movements of the machine in the case where a tray is not immediately available in the loading station when the carriage returns into a start-of-cycle position. 8. The machine according to claim 6, wherein ends of the welding roller rotatably support the welding roller by a gantry, the gantry having a middle portion connected, via a cross-pin, to a fork member fixed to an end of an arm which is parallel to the welding roller and which at an other end of the arm is fixed to a slide which is slidable on a vertical guide which is fixed to the frame and biased upwards by a spring and which is adapted to be lowered by a rectilinear actuator comprising a cylinder and piston unit fixed with its body to a cross-member of the guide and connected to means which, during the active working phase of the welding roller, supply it with air at appropriate pressure values. 9. The machine according to claim 8, further comprising a fixed vane positioned downstream of the welding roller transversely above the horizontal path of the film and, differently from an upstream vane, the fixed vane being in a fixed position which is correlated based on a largest size of the trays which the machine is able to process. 10. The machine according to claim 8, wherein the arm is axially hollow so that it may be passed through by cables powering and controlling the welding roller, the cables passing through cable muffs and joined at their ends to the rotational means of the welding roller and to a probe mounted on the gantry and directed towards the welding roller, for detecting the operating temperature thereof. 11. The machine according to claim 10, in which one end of the welding roller has, keyed thereon, a toothed wheel, and hinged thereon, a first end of a toggle hingedly attached to the toothed wheel, and a second end of the toggle pivotably hinged to a part which is fixed to the frame, the part supporting a pair of toothed wheels rotatable and arranged integrally alongside each other, an outer one of the pair of toothed wheels meshing with an idle wheel which is situated on a hinged joint of the toggle and which meshes with the toothed wheel of the welding roller, an inner one of the toothed wheels meshing permanently with a horizontal rack fixed laterally to a side-wall of a carriage, a diameter of the pair of toothed wheels being related to an external diameter of the welding roller so that, when the carriage performs an active working stroke, the welding roller rotates in a direction for accompanying the carriage during displacement and at a peripheral speed equal to the linear advancing speed of the carriage. 12. The machine according to claim 1, wherein the separation means comprises a punching die supported by a raising and lowering means and directed downwards with a cutting punch which forms a rim able to circumscribe an edge of the closed tray supported by the counter-die at an end of its active displacement stroke, the cutting punch operatable in both a cold state or a heated state, the heated state provided via electric resistances embedded in a metal rim which supports the cutting punch, and temperature-measuring probes for controlling a power supply of the resistances according to predefined parameters. 13. The machine according to claim 12, wherein the punching die is supported with means which allow rapid replacement thereof, by one end of an arm which at the other end is fixed to a slide which is slidable on a vertical guide fixed to a side-wall of the frame and which in synchronism may be raised and lowered by means of a connecting rod and a crank actuated by an actuator fixed to the frame and the motor of which is controlled by a processor the connecting rod passing slidably through a hole provided in a pin mounted rotatably on the slide and the pin resting on a stop fixed onto the connecting rod which projects above from the pin with a portion supporting a spring situated between an end of the connecting rod and the, pin, wherein, as a result of the weight of the die and the slide, the pin rests constantly on the stop, whereas when, at the end of the downward stroke of the die, a punching rim of the die touches the film and presses the film against the insert of the counter-die, the connecting rod continues to travel a small distance downwards and stresses the spring which pushes the die downwards with a force such as to keep the film undergoing the punching operation firmly gripped. 14. The machine according to claim 13, further comprising means for ensuring that, in synchronism with the downward movement of the punching die, when the cutting punch grips a portion of film outside a weld and an upper edge of the tray onto a non-adhesive and elastic insert of the underlying counter-die, the lifting means is raised so as to raise the closed tray so that the film is cut by the cutting punch as a result of the combination of a compressive force of the cutting punch on the film and a tensile force exerted by the tray which is raised by the lifting means, while the film is retained between the cutting punch and an insert of the counter-die wherein, in sequence with raising of the lifting means, the punching die is also raised into a rest position, while the closed tray is positioned and kept above the counter-die by the lifting means which stops in an upper end-of-travel position. 15. The machine according to claim 1, further comprising an unloading conveyor downstream of the main conveyor, coplanar with the main conveyor, which is also supported by the frame of the machine and is connected kinematically to an end deviating roller of the main conveyor, by means of a gearing such that the unloading conveyor and the main conveyor are synchronized, in the same direction and at the same speeds. 16. The machine according to claim 15, further comprises photocell means which detect the passing movement of a tray between the main conveyor and the unloading conveyor and other photocell means for detecting the presence of a tray in front of the barrier of the blower and photocell means for detecting the presence of a tray against a movable vane, upstream of the moveable vane, the photocell means being connected to a processor so as to transmit to the processor the information relating to the presence or absence of the trays. 17. The machine according to claim 16, further comprising means so that, at a start of each working cycle, a carriage is situated upstream of the welding means with the lifting means in a high position, and means for ensuring that the machine, with correlated movements for activation of the conveyor and raising and lowering of a movable vane, may be automatically loaded with a tray which stops with a front side of the movable vane against the barrier of the blower which is now inactive, so as to be aligned correctly with its longitudinal axis relative to that of the conveyor, so as to ensure correct and future entry of the tray into a seat of the counter-die, and the conveyor stops and the movable vane remains in the low position when the loaded tray is detected by the specific photocell situated upstream of the blower and when an upstream tray reaches the movable vane and is detected by the specific photocell. 18. The machine according to claim 17, further comprising means so that, at the start of each operating cycle, the lifting means is lowered and the tray enters into the seat of the counter-die, while the specific photocell detects this condition and the cycle continues with raising of the vane and with activation of a horizontal displacement to the right of a carriage for conveying the trays, with lowering of the welding roller which rotates and welds the film onto the upper edge of the tray, while motors for unwinding the film from the reel and taking up the waste film downstream start to rotate in synchronism thereby feeding of the film in time with the tray and so as to keep it suitably stretched, wherein synchronism with welding of the film onto the tray, the blower is activated so as to introduce into the tray modified atmosphere which expels the ambient air and the gases which form during a welding operation. 19. The machine according to claim 18, further comprising means so that, during an active working stroke of the carriage, the main conveyor may be activated and the movable vane may be in synchronism raised and then lowered, for loading a subsequent tray upstream of the blower, while a final section of the main conveyor is shortened and expels any tray previously formed in the punching station towards the unloading conveyor which during this phase is also activated by rotation of the gearing for connection to the end roller of the main conveyor. 20. The machine according to claim 19, further comprising means, as a result of which, a speed of displacement of the carriage with the tray is such that the welding may be performed correctly and at the same time the gases inside the tray may be fully replaced. 21. The machine according to claim 19, further comprising means such that, at the end of an active displacement stroke of the carriage, when the tray situated on the counter-die has been closed above by the film and is centred with respect to the punching die which is in the raised position, the blower is deactivated in synchronism, the welding roller is raised in synchronism and the film feeding means are stopped, while in synchronism the punching die is lowered and is then raised following raising of the lifting means which positions the closed tray above the counter-die and remains in this position. 22. The machine according to claim 21, further comprising means so that, after raising of the lifting means, the carriage is displaced into a start-of-cycle position, while belts of the main conveyor are activated if it is required to replenish a tray upstream of the blower or otherwise remain at a standstill, while downstream and upstream sections of an upper portion of the main conveyor are lengthened and shortened respectively, wherein at the end of this displacement the counter-die with the lifting means still in a high position are arranged underneath the tray to be closed, which is retained between the movable vane and the blower and which is correctly oriented also by the movable vane for a subsequent working cycle of the machine, and during this phase wherein the tray which was closed during the previous cycle, which was separated from the film by the punch, which was previously raised by the lifting means and which was supported by the downstream portion of the main conveyor is retained in the punching station by a fixed vane so as to be able to evacuated during the subsequent working cycle. 23. The machine according to claim 22, further comprising means so that, during a return stroke of the carriage, motors driving the film are all or partly activated with a travel movement which is a reverse of an active working movement, so as to move the film backwards by an appropriate amount and so as to move adequately towards the first deviating means, an opening created in the film by a preceding operation involving punching a lid on a previously closed tray. 24. The machine of claim 23, further comprising optoelectronic sensors for reading indicia on the film. 25. A machine for packaging food products in trays sealingly closed at the top with thermoplastic film, said machine comprising: a reel and film feeding means for controlled unwinding therefrom of film for closing the trays; deviating means situated below the reel and around which the film is deviated for changing the film from a descending path to a horizontal path; counter-die means for supporting at least one tray horizontally, along an upper edge, with a predefined orientation and for displacing it horizontally underneath a horizontal section of film; welding means situated downstream of the deviating means for welding the film sealingly onto an upper edge of the tray; means situated upstream of the deviating means for blowing an appropriate quantity of modified atmosphere at appropriate pressure values into an open part of the tray which advances underneath the film until the tray has been completely sealed by the film; separating means for separating from the film, a portion of the film welded to the upper edge of each tray; collecting means for taking up the waste film produced by the separation means, the collecting means operating in conjunction with the film feeding means, wherein at least a section of film on a horizontal path advances continuously stretched both longitudinally and transversely; positioning means which at a start of a cycle supply and position correctly the trays to be closed in the counter-die means; lifting means which at an end of the cycle raise the closed trays; tray conveying means for conveying away the closed trays; and horizontal moving means for horizontally moving the counter-die means, which at the end of a cycle is adapted to bring the counter-die means back into a starting position for repetition of a new working cycle; wherein the horizontal path of the film between the deviating means is superimposed on a horizontal travel path of the trays feeding a main conveyor with belts over deviating rollers, a last one of the deviating rollers being connected to a drive unit controlled by a processor, an upper portion of the main conveyor having an intermediate depression with a length suitably greater than that of a largest tray to be processed, the intermediate depression being defined by belts of an upper portion of the conveyor being deviated so as to form a U-shaped path, over U-shaped path rollers which are rotatably supported by a carriage by which, by suitable means are adapted to be displaced horizontally and moved from a tray loading position into a position for unloading the tray and vice versa; and a flat and horizontal counter-die arranged in the intermediate depression, the counter-die being fixed to a carriage and with an upper side thereof being coplanar with an upper portion of the belts of the conveyor so that a tray is able to pass without obstacles from an initial section of the belts to the counter-die which is provided with an opening having a form and dimensions correlated to a body of the tray which is able to fit into the opening and may remain resting with its upper edge on a portion of the counter-die which circumscribes the opening, the carriage comprising a pair of side-walls which support the counter-die in a manner such that it may be easily and rapidly interchanged with other counter-dies upon a variation in the shape or size of the trays to be closed, and the side-walls are fixed together by special cross-members which comprise a bottom cross-member having, fixed thereto, a pair of vertical guides inside which corresponding rods slide, the rods being fixed at their top end to a cross-piece having, mounted thereon, a raising plate which, by means of a pneumatic cylinder and piston unit or other rectilinear actuator fixed with its body to the cross-member and connected with its stem to the cross-piece, actuatable to be raised inside the opening, in a manner coplanar with the die, or may be lowered. 26. The machine according to claim 25, in which an initial section of the upper portion of the main conveyor travels over a flat structure fixed to a frame of the machine and has a length sufficient to support at least one tray, and a final section of the upper portion of the main conveyor is free from obstacles underneath. 27. The machine according to claim 25, wherein the side-walls of the carriage are fixed to a middle part of a pair of horizontal rods which, at one end, are fixed to a slide and which, at the other end, support rollers with bearings sliding on a rail fixed to a frame of the machine, the slide being slidable on a pair of horizontal rods fixed at their ends to the frame which is in turn fixed to a side-wall of the base of the machine and on which a screw is rotatably mounted, parallel to the rods, the screw co-operating with a female thread housed inside the slide and able to be rotated in both directions and at an appropriate speed by a drive unit which is also fixed to the frame and provided with an electric motor for electronic speed and phase control, and sensors for detecting at least a rest position of the carriage and the high position of the lifting device. 28. The machine according to claim 27, further comprising a fixed sensor which produces a presence and consent signal for activation of a punching head, when the carriage with the counter-die reaches the end of the active working stroke. 29. The machine according to claim 27, further comprising a nozzle device immediately upstream of the deviating means, the nozzle device blowing the modified atmosphere into the tray which passes underneath it, so as to expel from the tray, the air using the modified atmosphere, the nozzle device having a curved form with a concavity directed towards the first deviating means, the nozzle device terminating at a short distance from an upper mouth of the trays which pass underneath the nozzle device. 30. The machine according to claim 29, in which the nozzles have an identical width and are spaced from each other by an amount substantially equal to the width, while the space occupied in plan view by the pair of the nozzles is suitably less than the internal width of the tray and the pair of nozzles is symmetrically arranged in the plan view projection of the tray, whereby the two flows of modified atmosphere supplied by the nozzles, after filling the internal and gradually increasing volume of the tray which advances and is gradually covered by the film, may flow back through the empty side spaces and through the empty middle space, preventing any entry of ambient air into the tray. 31. The machine according to claim 29, wherein the nozzle device is composed of a horizontal and hollow bar which is parallel to the deviating means and which at one end is fixed to support means and is connected to the means supplying the modified atmosphere under pressure and which at the other end supports and supplies with equal flows at least one pair of nozzles which are arranged alongside each other and oriented downwards with an appropriate inclination or with a concave curvature towards the deviating means so as to be at a suitable angle with respect to the horizontal surface and terminate with a respective discharge mouth at a short distance from the top of the trays which pass underneath them. 32. The machine according to claim 31, wherein the angle is between 10�� and 50��. 33. A machine for packaging food products in trays sealingly closed at the top with thermoplastic film, said machine comprising: a reel and film feeding means for controlled unwinding therefrom of film for closing the trays; deviating means situated below the reel and around which the film is deviated for changing the film from a descending path to a horizontal path; counter-die means for supporting at least one tray horizontally, along an upper edge, with a predefined orientation and for displacing it horizontally underneath a horizontal section of film; welding means situated downstream of the deviating means for welding the film sealingly onto an upper edge of the tray; means situated upstream of the deviating means for blowing an appropriate quantity of modified atmosphere at appropriate pressure values into an open part of the tray which advances underneath the film until the tray has been completely sealed by the film; separating means for separating from the film, a portion of the film welded to the upper edge of each tray; collecting means for taking up the waste film produced by the separation means, the collecting means operating in conjunction with the film feeding means, wherein at least a section of film on a horizontal path advances continuously stretched both longitudinally and transversely; means which at a start of a cycle supply and position correctly In the counter-die means the trays to be closed; lifting means which at an end of the cycle raise the closed trays; means for conveying away the closed trays; means for horizontally moving the counter-die means, which at the end of a cycle is adapted to bring the counter-die means back into a starting position for repetition of a new working cycle; and a nozzle device immediately upstream of the deviating means and the film which passes over them, the nozzle device adapted for blowing the modified atmosphere into the tray which passes underneath it, so as to expel from the tray, the air with the modified atmosphere, the nozzle device having a curved form with a concavity directed towards the deviating means, the nozzle device terminating at a short distance from an upper mouth of the trays which pass underneath it and being provided on a front side facing an initial section of a main conveyor with reliefs which form a barrier against which a tray cyclically stops and which in this condition with its body is correctly centred with the opening of the underlying counter-die stationary in the start-of-cycle position, wherein the nozzle device composed of a horizontal and hollow bar which is parallel to the first deviating means and which at one end is fixed to support means and is connected to the means supplying the modified atmosphere under pressure and which at the other end supports and supplies with equal flows to at least one pair of nozzles which are arranged alongside each other and oriented downwards with an appropriate inclination or with a concave curvature towards the deviating means so as to be at an angle of between 10�� and 50�� with respect to the horizontal surface and terminate with respective discharge mouths at a short distance from the top of the trays which pass underneath them.
