GB1574472A - Apparatus for stretch wrapping articles in thermoplastic film - Google Patents

Description

(54) APPARATUS FOR STRETCH WRAPPING ARTICLES IN THERMOPLASTIC FILM (71) We, IBARAGI SEIKI COMPANY LIMITED, a Company organised under the laws of Japan, of 5-5 Shinchujo-cho, Ibaragi-city, Osaka prefecture, Japan, do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement.- The present invention relates to a packing apparatus for packaging goods with a film of a themoplastic material such as a polyvinyl chloride, a butadiene rubber, or polyethylene. Such a film is flexible and may also be stretched. The present apparatus is constructed for using such a film having the above qualities.The invention seeks to provide a packaging apparatus, in which a film is stretched and applied to an article whilst in the stretched condition so that the article can be tightly packed by the film.

The present invention is particularly concerned to provide a means for efficiently extending said film while applying it to the article.

According to the invention there is provided a packaging apparatus for covering articles in a heat sealed wrapping of thermoplastic film comprising, conveying means for moving an article in a first predetermined longitudinal path; covering means including gripping means for gripping opposite side margins of a continuous supply of said film, for stretching said film laterally and longitudinally and drawing said film side margins along path inclined relative to said predetermined path so that the film is stretched and extended around the sides of, and underneath said article while the article is moving in said predetermined path; a sealing mechanism including a pair of opposed endless belts and heating means for sealing the opposite side margins of the film together under the article to enclose the article in a tubular envelope of film; cutting means including a pair of cutting rotors for severing the tubular film at locations between successive articles to provide leading and trailing tubular ends for each article; means for folding under said leading and trailing ends comprising conveyor side belts for engaging opposite sides of an article to convey the article in a second predetermined path away from said cutting means, endless chain drive means for moving a series of transverse rods in a path below said article parallel to said second path in the same direction as but at a speed greater than that of said article, a series of air inlets in a housing in communication with a vacuum source positioned below said transverse rods to draw the trailing end of film to a position in which said trailing end is capable of being engaged by one of said rods to fold said end against the underside of an article, means to engage the leading end of the film and fold it against the underside of an article; and a heating conveyor for applying heat and pressure to an area of the underside of an article to seal the folded ends in place.

An embodiment of the invention will now be Idescribed by way of example and with reference to the accompanying drawings, in which. Figure 1 is a side view of the packing apparatus of this invention, Figure 2 is a side view of a part of the apparatus, Figure 3 shows the relationship between a package and a film, Figure 4 is a plan view showing the relationship between each mechanism and a power unit, Figure 5 is a side view of a part of the apparatus.

Figure 6 is a plan view of a part of Figure 5, Figure 7 is a partially enlarged view of Figure 6, Figure 8 is a partially enlarged view of Figure 7, Figures 9 to 11 show an explanation of part of the present invention, and Figures 12 to 17 illustrate the packaging procedure.

As shown in the Figures, a typical package 1 comprises a dish-shaped container which is provided with fruit, fish, shellfish or other goods to be packed.

The apparatus to be described comprises of several mechanisms. The first mechanism has a means of conveying packages at uniform distances toward the film. The second mechanism has a means for covering several packages continuously provided by the conveyor with the film which moves in the same direction as the direction of conveying the package so as to wrap the packages with said film in a tubular configuration. The third mechanism has a means for cutting said tubular film at both ends of each package, the fourth mechanism has a means of turning said film ends down by air pressure and turning the film ends on to the bottom surface of the package and the fifth mechanism has a means of securing said turned-over ends to the bottom surface of the package.

As shown in Figure 1, the packaging apparatus comprises a stand 10 in which the various mechanisms are installed. The frame provided at the left-handside of the stand is for a conveyor 12 which feeds a package to a film wrapping stage. This conveyor 12 has a chain 13 continuously rotated within the frame 11 and conveys the package on the upper surface of the frame by pushers 14 spaced at uniform distances along the chain.

A pair of parallel rollers 15, 16 are mounted on the upper part of said stand. As shown in Figure 2 and Figure 5, a roll of film 3a is located above said rollers to provide a continuous supply of film. These rollers 15, 16 are provided so as to be able to freely rotate, but a damping or braking force is operated on at least one roller to prevent the roll of film from unwinding too freely. The film is transparent.

A secondary conveyor 17 is provided on the upper part of the stand under said rollers which support the film. This conveyor 17 is positioned at the outlet end of the conveyor 12 and is supported on the stand by the rollers 19, 20 of the endless chain conveyor 18.

A crumpling or folding mechanism which folds the film in to a barrel-shaped form is provided along the conveyor. The folding mechanism is shown in Figure 4 to Figure 8 in more detail.

As shown in Figure 6, a pair of endless chains 23 provided on both sides of the conveyor are supported by multiple chain wheels 26, 27, installed on a pair of base plates 24. Also, a number of clips 10 are mounted on the chains at equal distances from each other. The distance 25 between the chain wheels 26 supporting the chains at the inlet end is the same distance as the width of the film. At a point intermediate of the chain wheels, a distance 29 determined by tension wheels 28 is larger than said distance 25 so as to stretch the film prior to it being wrapped around the package. The pair of chains then move closer to each other, so that the chains are close together at the discharge end of the conveyor 17.

As shown in Figure 8, each clip 30 is provided with a projection 31 fixed to one part of a link 30a of the respective chain 23.

A rod 30c is slidably inserted within a tubular chain pin 30b. A movable projection 32 fixed to the upper end of said rod 30c is provided at an opposite position of said projection 31. The movable projection 32 is biassed towards the projection 31 by a coil spring 33 mounted on the rod 30c. The projections 31, 32 cooperate to grip the side margins of the film therebetween.

As shown in figures 1 and Figure 5, a pair of base plates 24 (shown in Figure 6) are located in an inclined position, one on each side of the conveyor 17. This inclination of the base plates 24 is such that they are higher at the inlet end than at the discharge end and the chains 23 are arranged in parallel with these base plates 24.

Under the chain wheels 26, 27 cams 34,35 are respectively fixed on the base plates, and throttle rollers 38 are respectively fixed on the upper side of driven rods 37.

As the side margins of the film are moved down the incline a package being moved by conveyor 17 is gradually enveloped in the film. At the end of the section the chain wheels 27 and hence the throttle rollers 37 are close together so that the side margins of the film are also held close together for entry into a final stretch- ing, closing and sealing mechanism 40. As shown in Figure 4, this mechanism includes a pair of centre-rotating belts 41. As shown in Figure 5, loops of said belts 41 run in a guide groove formed in the edge of a guide plate 42 for the most part, and the belts are supported by pulleys 43, 44. The pulley 43 supporting the belt 41 at the inlet end is connected to a shaft of a rotor 46 supporting one of a pair of flat belts 45 at an inlet end thereof. The discharge ends of said flat belts 45 are each supported on a respective rotor 47 above a respective pulley 44. One end of the guide plate 42 is located above the upper side of the throttle rollers 38, and heating rollers 48 are provided under the surface of said guide plate for heat sealing the side margins of a film together. An electric heater is provided within said heating rollers 48. A gear 50 is fixed to the lower part of a shaft 49 of each heating roller 48 and is connected with a gear 52 which is fixed to a driving shaft 51 of said pulley 44, so that the heating rollers 48 are rotated in synchronism with the pulleys 44.

As shown in Figure 1 and Figure 2, following the mechanism for closing and sealing into a tube around a package a mechanism is so provided to cut the barrelshaped film on each eide of the package.

This mechanism 58 comprises a pair of rotors 56, 57. The upper rotor 56 is provided with a sharp knife extending in the axial direction, and the lower rotor 57 is fixed with a base plate 55 formed as a flat plate, so that, when said knife and said base plate coincide with each other on each revolution of these rotors 56,57, the film therebetween is cut.

After the cutting mechanism, the apparatus is provided with a turning mechanism 60 which is adapted to turn the ends of the cut film on to the lower surface of the package 1. As shown in Figure 4, this mechanism includes a pair of side belts 61 which convey the package by gripping both sides thereof. The mechanism also includes a housing 62 within which a vacuum is provided so that the ends of the film round the package are pulled down on to the housing by air as shown in Figure 9. A plurality of transverse rods 63 are provided, the ends of which rods are supported by respectively endless side chains 64 which move the rods 63 at a faster speed than the conveying speed of the package. As shown in Figure 1 and Figure 4, under the belts 61 these chains are engaged by chain wheels 65 which are located upstream of the rotor 57 of said cutting mechanism.At the same time the downstream sides of the chains 64 are supported by chain wheels 66.

Since the rods 64 move faster than the package 1 the rods pick up the rear end 3c of the film round the package and draw it forwards until it lies against the undersurface of the package. The end 3c is carried by the vacuum in the housing 62 towards the housing to ensure that it is picked up by the rods 64.

As shown in Figure 2, the housing 62 is located within the loop of said chains 64.

This housing is connected with a vacuum pump 68 through a duct 67. Said housing is formed with a flat upper surface which is provided with air inlet holes 69. As shown in Figure 9, this housing is divided into a larger housing 71 on the upstream side and a smaller housing 72 on the downstream side through a valve 70 which is provided within the housing 62. The wall of said smaller housing 72 is provided with a number of air inlet holes 73 each of the rods 63 supported by the chains 64 are turned at the curcumference of said smaller housing 72 while the rods are revolved. As shown in Figure 2, a shaft 74 of the valve projects from the housing 62. A bell crank 75 fixed to the end of the shaft 74 is connected with a lever movably mounted near the cutting mechanism 51 through a connecting rod 77.The lever 76 contacts the circumference of a cam fixed to a shaft 78 of the rotor 57 which is provided below said cutting mechanism 51. Further, in the next part of said housing is located a shaft 80 which supports the chain wheels 66 positioned on both sides of said smaller housing 72, a counter roller 81 also being provided at this point.

As shown in Figure 1, after said roller 81, there is a conveyor 82 comprising a thin refractory belt 83 supported on a pair of pulleys, 84. 85. An electric heater 86 is provided within the loop of said belt 83.

A weighting roll 87 is provided at the upper side of said conveyor so as to increase adhesion between the lower surface of the package 1 and the upper surface of the belt 83 of said conveyor 82. Said weighting roll 87 consists of two rollers 89 which are supported on a frame 90. Said frame is movable supported on a column 92 by means of which it can be raised or lowered through a pair of parallel arms 91. Said rollers are formed of a flexible material such as an urethane foam, so as to easily deform corresponding to the formation of the package and its contents.

Movements of said packing mechanism and each mechanism of the device can be regulated in a desired sequence and a desired connection by a controlling means disposed within the power connection device shown in Figure 4. As shown in Figure 4, an electric motor is provided as the power source, and this driving power operates two power transmitting systems. One transmitting system is used to convey the film, and the other transmitting system is used to convey the packages.

An output shaft 96 of the motor 95 is connected with a reduction device 97 and transmits the driving effort to a variable change-speed gear 99 through a chain 98.

The transmitting direction for conveying the film described above is an output movement of this variable change-speed gear 99.

This variable change-speed gear 99 is provided with a handle 100 which variably adjusts its output speed. Firstly, the change gear 99 is connected with - a shaft 101 through a chain 102, so that the conveyor 17 is driven. Also, said shaft 101 is connected with a shaft 103 through a chain 102a. The shaft 103 is connected with further shafts 37 through bevel gears 104 (see Figure 5). Accordingly, equal movement is transmitted to the chains 231 on both sides of said conveyor. Also, said shaft 103 is connected with a further shaft 106 through a chain 105. The shaft 106 is connected with pulleys 44 through bevel gears 107, (see Figure 5). Accordingly, movement is respectively transmitted to the pair of belts 44, the pair of flat belts 45 and the pair of heating rollers 48.Further, said shaft 106 is connected with a shaft 109 through a chain 108.The shaft 109 is connected with the pair of side belts 61 through a bevel gear device 110. Accordingly, a driving force to convey the packages is transmitted to these belts. Further, said shaft 109 is connected with a shaft 112 through a chain 111, whereby a driving force is simultaneously transmitted to the heating conveyor 82.

Two endless side chains 121, 122 are engaged with an output shaft 120 of the reduction device 97. One side chain 121 is connected with a shaft 123 to drive the conveyor 12, so that a rotational movement at a predetermined speed proportional to the output of the reduction device 97 is transmitted to said conveyor 12. The other side chain 122 is connected by a variable differential gear 124 with a variable nonuniform speed change gear 126. Said differential gear 124 and the non-uniform speed change gear 126 is shown in Figure 10 and Figure 11 in detail. An epicyclic gear 130 and two gears 131-, 132 are supported with a shaft 129 rotatably mounted in a frame 128. In this case, said gear 131 is fixed to said shaft 129 through a key 133, and the epicyclic gear 130 and the output gear 132 are rotatably supported on the shaft 129 through ball bearings 134, 135.

Also, the number of teeth of said two gears 131, 132 are different. Epicyclic gears 137, 138 fixed to both ends of a shaft 136 rotatably supported with an eccentric part of said epicyclic gear are respectively engaged with said gears 131, 132. Further, a detent device 140 is used for the epicyclic gear 130. Said detent device 140 is adapted to engage between the teeth of the epicyclic gear 130 by the power of spring 141 so as to prevent idle rotation of the epicyclic gear 140. Also, a pinion fixed with the shaft of a handle 142 on the frame 128 is engaged with said epicyclic gear 130. Accordingly, when the input gear 1311 is rotated by the input of the chain 122, since the rotation of the epicyclic gear 130 is prevented by the detent device 140, the rotational movement of the input gear 130 is transmitted to the output gear 132 through the epicyclic gears 137, 138.In this case, the changed output, being in proportion to a number of epicyclic gear mechanisms at the both sides of the epicyclic gear is transmitted to the chain 125.

In Figure 11 by the rotation in an anticlockwise direction of the epicyclic gear 138 supported by the gear 130, the output gear 132 is rotated in a clockwise direction (see arrow direction). In these conditions, a pinion 143 is forced to be rotated by adjusting a handle 142 shown in Figure 10 against the power of spring 141 of the detent device 140. In Figure 11, if the epicyclic gear 130 is rotated in the clockwise direction by a chosen angle to change the position of the epicyclic gear 1318, the rotation speed is quickly reduced as the position of the gear is changed, so that, the transmitting speed toward the chain 125 can be reduced equally quickly. In other words, if the pinion 143 is rotated in a clockwise direction, the rotation speed of the chain 125 can be rapidly increased.

Said rotation transmitted to the chain 125 is further transmitted to the nonuniform speed change gear 126. This nonuniform speed change gear 126 is supported so that its shaft 147 with a bearing 146, can be displaced along a guide 145.

Said shaft 147 is engaged with said chain 125 through the chain wheel 148. A driving arm 149 fixed with one end of the shaft 147 is engaged with an arm 150 fixed to a shaft 156 of the rotor 57 of the cutting mechanism 51 through a pin 151. Said bearing 146 can be displaced along the guide 145 by controlling the screw rod 152 being engaged with said bearing 146. An eccentric dimension 153 can be adjusted by adjusting the eccentricity of the shafts 147,156.

The driving arm 149 driven by the chain 125 is continuously rotated at a constant speed, and said arm 150 is rotated at a non-uniform speed by the eccentricity of each shaft 147, 156. A rate of non-uniform speed during one rotation of the rotor 57 is increased in the proportion that the eccentric distance between the shafts 147 and 156 is changed to a larger direction. As shown in Figure 10, the rotors 56 and 57 are connected with each other by gears 154, 155. When the knife 54 contacts the plate 53, the slowest speed range corresponds to one rotation of an non-uniform rotation speed being transmitted to said rotors.

As shown in Figure 4, the rotor 57 of the cutting mechanism is engaged with the driving shaft 80 of the chains 64 through a chain 158. Said shaft 80 is engaged with the shaft of the trailing rotor 81 through a gear 159,160. The packing operation by the described devices of the embodiment is explained as follows.

As shown in Figure 5, in the folding mechanism which forms the film into a barrel-shaped tube, the clips 30 provided on the chains 23 are controlled by the operation of the cams 34, 35 at each end of chains 23 by rotation of the chains. As shown in Figure 8, when the clip 30 is in the range of operation of the cam 34, the movable projection 32 is pushed up through the rod 3c, so that the clip 30 is opened.

As shown in Figure 6, both ends of the film 3 are lead to the position where each clip of the chains is briefly opened. The edges of the film are pinched and the film is stretched in the direction of the arrows by the rotation of the chains, as it is conveyed. As shown in Figure 3 since the intermediate space 29 between the chains is larger than the width of the film, the film is also stretched width-wise while the film is stretched longitudinally.

On the other hand, as shown in Figure 2, the contents of the package contained in the dish 2 is fed toward the conveyor 17 at the correct speed and spacing by the conveyor 12. The conveyor 17 continuously delivers the packages to contact the lower surface of the film 3. Since the speed of the conveyor 17 corresponds with the moving speed of the film because of the common power transmitting system, when the package is fistly contacted with the film, there is no slip between the package and the film. As shown in Figure 5, the chain 23 is inclined. and the trailing end of this chain 23 is lower than the upper surface of the chain 18. of the conveyor 17. So that, as will be understood from the movements of Figure 12 and Figure 13, while the film is stretched outwardly, both edges are also downwardly extended.As shown in Figure 6. the chains 23 come into contact at the trailing side of the tension wheels 28 so that the film 3 is pulled over the circumference of the package gradually as shown in Figure 3 and Figure 14. Further, the package is conveyed to the mechanism 40 by which the film edges are sealed together, and while the film is sealed, is conveyed by being gripped on- its sides by the pair of flat belts 45 as shown in Figure 15. Prior to sealing, both edges of the film 3 are pinched between the pair of throttle rollers 38. Also, above the throttle rollers 38 both edges of the film 3 are pinched, by the rotation of a pair of endless belts 41. So that the diameter of said film at the circumference of the package is reduced, the film is simultaneously shrunk and sealed by the action of the heating rolls 48.

However, just before, the clips 30 holding the edges of the film are opened by the operation of the cam 35. (Figure 5). In the next station 58, as shown in Figure 2, the package is conveyed to the cutting mechanism where the film is cut between the packages, by cooperation between the knife 54 and the base plate 55. In this case, as shown in Figure 3, the length of the film being cut must be maintained appropriate to the length of the package, Also, the ends of the film 35 projecting ahead of and behind the package must be maintained at the correct length 3 irrespective of the length L1 of the packages. In response to variation in the length L1 of the package, the cutting length L is adjusted by the following method.As shown in Figure 4, in contrast to the situation where the package covered with the film is conveyed at a speed in proportion to the output speed of the gear 99; the rotor 57 of the cutting mechanism 58 is rotated by the power transmitting system at a speed which differs from the power transmitting system for conveying the film. By operating the handle 100 of said variable speed change gear 99, the conveying speed of the film is changed, and the length of the film between cuts is adjusted by changing the conveying speed of the film for each rotation of the rotor.

Since a space between each unit 14 in the conveyor is fixed, in the case of conveying a comparatively long package by the conveyer 12, the space between each package necessarily becomes smaller, whilst in the case of conveying shorter packages the space between each package become longer.

In the case of conveying the longer package, each package is fed onto the secondary conveyor 17 from the providing conveyor 12 the speed of the film conveying and secondary conveyor 17 being set faster than that of the conveyor 12. By increasing the conveying speed, the space between each package is enlarged. In the opposite case in case of conveying the shorter packages by decreasing the speed of conveyor 17 and the film conveying speed, the space between each package is adjusted to be shorter, So that, in response to the length of the package shown in Figure 3, the length of the leading and trailing ends L3 of film is always formed to a fixed length.However, in this case, since the film conveying speed is only adjusted without adjusting the rotation speed of the rotors 57 of the cutting mechanism, the knife 53t and the film may slip due to a difference between the rotation of the cutting knife 53 and the film conveying speed. Accordingly, an adjusting means is provided to synchronise the knife with the film conveying speed.

That is to say, as already mentioned in connection with Figure 10 and Figure 1.1, by adjusting the control handle 152 the rate of the non-uniform speed of each rotation of the rotors 56, 57 is changed. Also, the eccentric rate 153 is reduced as the rotors 56, 57 approach uniform speed of rotation.

When the film is cut, if the film is not cut equally between each package, the length of the ends of the film in Figure 3 become unbalanced so as to adversely affect the packing operation. The adjustment of the balance between the lengths of the ends of the film can be easily achieved while the packing machine is running by the following method. As described in Figure 10 and Figure 11, by operation of the handle 142 of the variable differential gear 124. the rotation speed of the chain 125 being continuously rotated can be rapidly adjusted.

Since rotation of the chain 125 is transmitted to the rotors 50, 57 of the cutting mechanism, the rotation speed of these rotors is adjusted to slower or faster speed quickly by operating said handle 142 so as to cut the film at the said point between the packages and to balance the length of the ends of the film as shown in Figure 3.

As described above, the package with the film cut off by the cutting mechanism 58 is moved to the turning mechanism 60 where the package is conveyed by being pinched between the pair of flat side belts 61. As shown in Figure 9, the package is conveyed as the same speed as the speed of the flat belts 61. The transverse rods 63 below the under-surface of the container are driven by the chain 64 at a higher speed than the conveying speed of the package.

The inside of the housing 62 is subjected to the operation of the vacuum pump 68 so that air is sucked into the housing through a number of air inlet holes 62 formed in the upper surface of the housing 62. The ends of the film are drawn down and the end 3c of the film projecting from the trailing end of the package is engaged with a rod which is being moved in the same direction as but at a higher speed than the conveying speed of the package. Accordingly, as shown in Figure 16 and Figure 17, the end 3c is turned against the bottom surface of the container 2 by the rod 63.

At this time, the film is longitudinally stretched. Also, the end 3b projecting from the leading end of the package is pulled between a rod 63 and the rotor 81 by the air pressure drawn in through the air inlet holes at the trailing side of the housing.

Then, the end 3b is turned on to the bottom surface of the container by the flat belt while the end is drawn between the rod and the rotor. At the same time, the film is stretched in the longitudinal direction.

As shown in Figure 2, the valve 70 is operated in correspondence with the timing of the cutting mechanism within the housing and the valve 70 is opened or shut between the small housing 72 and the vacuum pump 68. Then, as shown in Figure 9, when the end 3c turned under the trailing end of the package is passed on the air inlet hole 73 at the trailing side of the housing, the valve 70 is shut off, so that the film end 3c is prevented from peeling from the bottom surface of the container. The operation and timing of the valve 70 is adjusted by the fixed angle of the cam 79 against the rotor 57 in the dependence upon the length of the package.

In the next step, the package is moved toward the heating conveyor 90 from the turning mechanism 60 in Figure 1. An electric heater 86 is provided under the heat resistant belt 83 The film ends turned under the bottom surface of the container of the package are welded to the bottom surface of the container by transmitting the heat from the heater 86 through the belt 83. In this case, the package is pressed against the belt 85 by weight of the weighting roll 87 so as to increase the efficiency of the weld. Such extensible film, because the film has an inherently good welding rate, can be completely prevented from peeling from the bottom surface of the package by the welding effect described above.

WHAT WE CLAIM IS: 1. A packaging apparatus for covering articles in a heat sealed wrapping of thermoplastic film comprising, conveying means for moving an article in a first predetermined longitudinal path; covering means including gripping means for gripping opposite side margins of a continuous supply of said film, for stretching said film laterally and longitudinally and drawing said film side margins along a path inclined relative to said predetermined path so that the film is stretched and extended around the sides of. and underneath said article while the article is moving in said predetermined path; a sealing mechanism including a pair of opposed endless belts and heating means for sealing the opposite side margins of the film together under the article to enclose the article in a tubular envelope of film; cutting means including a pair of cutting rotors for severing the tubular film at locations between successive articles to provide leading and trailing tubular ends for each article; means for folding under said leading and trailing ends comprising conveyor side belts for engaging opposite sides of an article to convey the article in a second predetermined path away from said cutting means, endless chain drive means for moving a series of transverse rods in a path below said article parallel to said second path in the same direction as but at a speed greater than that of said article, a series of air inlets in a housing in communication with a vacuum source positioned below said transverse rods to draw the trailing end of film to a position in which said trailing end is capable of being engaged by one of said rods to fold said end against the underside of an article, means to engage the leading end of the film

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. the packing operation. The adjustment of the balance between the lengths of the ends of the film can be easily achieved while the packing machine is running by the following method. As described in Figure 10 and Figure 11, by operation of the handle 142 of the variable differential gear 124. the rotation speed of the chain 125 being continuously rotated can be rapidly adjusted. Since rotation of the chain 125 is transmitted to the rotors 50, 57 of the cutting mechanism, the rotation speed of these rotors is adjusted to slower or faster speed quickly by operating said handle 142 so as to cut the film at the said point between the packages and to balance the length of the ends of the film as shown in Figure 3. As described above, the package with the film cut off by the cutting mechanism 58 is moved to the turning mechanism 60 where the package is conveyed by being pinched between the pair of flat side belts 61. As shown in Figure 9, the package is conveyed as the same speed as the speed of the flat belts 61. The transverse rods 63 below the under-surface of the container are driven by the chain 64 at a higher speed than the conveying speed of the package. The inside of the housing 62 is subjected to the operation of the vacuum pump 68 so that air is sucked into the housing through a number of air inlet holes 62 formed in the upper surface of the housing 62. The ends of the film are drawn down and the end 3c of the film projecting from the trailing end of the package is engaged with a rod which is being moved in the same direction as but at a higher speed than the conveying speed of the package. Accordingly, as shown in Figure 16 and Figure 17, the end 3c is turned against the bottom surface of the container 2 by the rod 63. At this time, the film is longitudinally stretched. Also, the end 3b projecting from the leading end of the package is pulled between a rod 63 and the rotor 81 by the air pressure drawn in through the air inlet holes at the trailing side of the housing. Then, the end 3b is turned on to the bottom surface of the container by the flat belt while the end is drawn between the rod and the rotor. At the same time, the film is stretched in the longitudinal direction. As shown in Figure 2, the valve 70 is operated in correspondence with the timing of the cutting mechanism within the housing and the valve 70 is opened or shut between the small housing 72 and the vacuum pump 68. Then, as shown in Figure 9, when the end 3c turned under the trailing end of the package is passed on the air inlet hole 73 at the trailing side of the housing, the valve 70 is shut off, so that the film end 3c is prevented from peeling from the bottom surface of the container. The operation and timing of the valve 70 is adjusted by the fixed angle of the cam 79 against the rotor 57 in the dependence upon the length of the package. In the next step, the package is moved toward the heating conveyor 90 from the turning mechanism 60 in Figure 1. An electric heater 86 is provided under the heat resistant belt 83 The film ends turned under the bottom surface of the container of the package are welded to the bottom surface of the container by transmitting the heat from the heater 86 through the belt 83. In this case, the package is pressed against the belt 85 by weight of the weighting roll 87 so as to increase the efficiency of the weld. Such extensible film, because the film has an inherently good welding rate, can be completely prevented from peeling from the bottom surface of the package by the welding effect described above. WHAT WE CLAIM IS:

1. A packaging apparatus for covering articles in a heat sealed wrapping of thermoplastic film comprising, conveying means for moving an article in a first predetermined longitudinal path; covering means including gripping means for gripping opposite side margins of a continuous supply of said film, for stretching said film laterally and longitudinally and drawing said film side margins along a path inclined relative to said predetermined path so that the film is stretched and extended around the sides of. and underneath said article while the article is moving in said predetermined path; a sealing mechanism including a pair of opposed endless belts and heating means for sealing the opposite side margins of the film together under the article to enclose the article in a tubular envelope of film; cutting means including a pair of cutting rotors for severing the tubular film at locations between successive articles to provide leading and trailing tubular ends for each article; means for folding under said leading and trailing ends comprising conveyor side belts for engaging opposite sides of an article to convey the article in a second predetermined path away from said cutting means, endless chain drive means for moving a series of transverse rods in a path below said article parallel to said second path in the same direction as but at a speed greater than that of said article, a series of air inlets in a housing in communication with a vacuum source positioned below said transverse rods to draw the trailing end of film to a position in which said trailing end is capable of being engaged by one of said rods to fold said end against the underside of an article, means to engage the leading end of the film

and fold it against the underside of an article; and a heating conveyor for applying heat and pressure to an area of the underside of an article to seal the folded ends in place.

2. Apparatus according to claim 1, wherein said covering means comprises a pair of endless chains disposed on opposite sides of said film said gripping means comprise clips mounted on said chains and cam means for controlling closing and opening of said clips to respectively grip and release said film along the margins.

3. Apparatus according to claim 2 wherein said endless chains are further apart at an intermediate point than at their inlet ends so as to stretch the film while moving the film margins downwardly to cover the article on both sides.

4. Apparatus according to claim 1, 2 or 3 wherein said apparatus includes means for adjusting the positions at which the cutting means severs the tubular film to adjust the respective lengths of said leading and trailing ends of film.

5. Apparatus according to claim 4.

wherein said apparatus includes a supply conveyor for supplying articles at a predetermined rate to said conveying means, conveyor, said conveying means, said covering and stretching mechanism, said cutting means and said means for folding under the leading and trailing ends of film, said drive means including means to regulate the relative speed of said supply conveyor, said conveying and covering means and said cutting means in order to adjust the length of film covering each article delivered by the supply conveyor.

6. Apparatus according to claim 5, wherein said power transmitting means includes epicyclic gear means for transmitting power to said cutter means, said epicyclic gear means including planet gear means for transmitting power to an output gear connected to drive said cutting means, and means for shifting the angular position of the rotary axis of the planet gear means for adjusting the location at which the cutting means severs said film.

7. Apparatus according to any one of claims 1 to 6, wherein said housing is divided into a first housing connected with said air inlet holes and a second housing connected with a further number of air inlet holes provided in the end wall of the further housing, said valve being operated in association with said cutting mechanism, to close the connection between the second housing and the vacuum source when the trailing film end turned onto the bottom surface of the package passes over the end wall of the further housing.

8. Apparatus according to any one of claims 5, 6 or 7 wherein said cutting means includes a rotary knife and a coacting rotary anvil and means for rotating said knife and anvil in opposite direction synchronously at angular rates of speed which vary during each revolution.

S. A packing apparatus substantially as hereinbefore described with reference to, and as illustrated in the accompanying drawings.