US 3928941 A
A machine for wrapping articles is disclosed which forms a sheath of the wrapping material, which can be paper or shrink wrap, around each article. The machine comprises a main endless conveyor including a plurality of article supporting platforms which rise in step-like array towards a sealing section, travel horizontally through the sealing section, and then descend in step-like array. Anvils and heat-sealing bars on endless conveyors are guided from above and below into the gaps between the platforms to form the sheaths. The anvils, bars, and platforms move continuously, parallel to one another, and at the same speed through the sealing section. An arrangement which pulls back the wrapping material is provided to ensure that each sheath is a relatively tight fit. The upper conveyor carrying the anvils can lift away from the main conveyor should an article become wedged in the machine.
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Description (OCR text may contain errors)
United States Patent 1 in] 3,928,941 Singer [4 Dec. 30, 1975 l l MACHINE FOR WRAPPING ARTICLES  Inventor: Alec Singer, [4 Mountain Road, f Emmi'fer*Dnald Schra Claremom, Cape Town Cape AS81510!!! Exammer-Leon Gilden Province South Africa Attorney, Agent, or Firm-Ladas, Parry, Von Gehr,
' Goldsmith & Deschamps  Filed: Jan. 25, 1974 211 Appl. No.: 436,585 ABSTRACT A machine for wrapping articles is disclosed which forms a sheath of the wrapping material, which can be 0 ls l Foreign Apphanon Pmmty Dam paper or shrink wrap, around each article. The ma- Feb. l2, I973 SOUlll AfllCa 73/0978 Chine comprises a main endless conveyor including 3 Aug. l3, l973 South Africa 73/552l plurality of article pp g platforms which rise in step-like array towards a sealing section, travel hori-  8| 53/182 zomauy through the sealing Swim, and descend 865B ll/lg in step-like array. Anvils and heat-sealing bars on end- I l 0 53/28 less conveyors are guided from above and below into 98/158 the gaps between the platforms to form the sheaths. The anvils, bars, and platforms move continuously,  References cued parallel to one another, and at the same speed through UNITED STATES PATENTS the sealing section. An arrangement which pulls back 2,804,027 8/!957 Hecht 198/158 X the wrapping material is provided to ensure that each 3,122,467 2/!964 Hannon 53/180 X sheath is a relatively tight fit. The upper conveyor car- 9 |2/1964 Monflghafl 53/|82 X rying the anvils can lift away from the main conveyor 6/1965 F 53/82 should an article become wedged in the machine. 3,727,365 4/1973 Stohlqutst 53/l82 X 3,729,894 5/I973 Stohlquist 53/182 X 11 Claims, 7 Drawing Figures to r L l2 E 4 SF LT i HF o o 0 0 40 sec I55 U.S. Patent Dec. 30, 1975 Sheet 2 of3 3,928,941
Om NS US. Patent Dec. 30, 1975 Sheet 3 of 3 3,928,941
69 Q9 Q2 3. mg Na 3 a3 N3 ml 5 1P 1 [L 1 1. 6w 3 a 11 N9 1/1 0N 0w x m 0t &\ 1F; m J ow Q3 0N. s m on MACHINE FOR WRAPPING ARTICLES This invention relates to a method of and a machine for wrapping articles.
Wrapping machines are known in which the articles to be wrapped are placed one behind the other on a conveyor and are displaced through a wrapping station. Wrapping material in web form is supplied from two reels, the leading edges of the two webs of wrapping material being secured to one another. As the first article of the series moves through the wrapping station, it encounters the wrapping material which forms a curtain across its path. As the article is displaced, the web supplied from the upper reel is withdrawn from that reel and tends to overlie the article and the web supplied from the lower reel is also withdrawn from its reel and lies beneath the article. Scaling and severing elements then move into the gap behind said first article. The web of material above the article is thus forced into contact with the web of material below the article, the two webs are secured together and severing takes place to form a new leading edge. At this stage, the first article of the series has a sleeve of wrapping material around it, the sleeve being open at each lateral end, and the second article of the series is moving into engagement with the curtain which has now been re-formed.
The wrapping material is usually sheet synthetic plastics material and in this case the sealing and severing of the material is effected by means of heated elements which heat seal the webs together.
British patent specification No. 1,008,020 describes a machine of this type. This machine is, however, only suitable for use in wrapping articles of low profile. If the articles are tall and close together, then the severing and sealing elements which move in from above, as they enter the gap between each pair of articles, tend to strike the top edge of the rearmost article of the pair. Several ways have been proposed in which this problem may be overcome. Firstly, it has been suggested that the articles be widely spaced on the conveyor thereby to leave room for the upper sealing and severing elements to descend into the inter-article spaces. This is disadvantageous in that the articles emerging from the wrapping station have a very loose sleeve of material around them so that far more material is used for wrapping each article than is really required Another solution proposed is to adopt a stop start mechanism. In this connection reference may be made to a number of United States patent specifications in the name of Roger H. Stohlquist of which U.S. Pat. No. 3,727,365 is a good example.
In apparatus of the type of this Stohlquist patent, material in web form is again supplied from upper and lower reels, the leading edges of the two webs being joined to form a curtain. The article to be wrapped is fed forward into the curtain and displaces the joined leading ends of the webs forwardly with respect to the supply reels until the wrapping material both overlies and underlies the article. Forward movement of the article then ceases and sealing and severing elements are brought into co-operating relationship with one another behind the article. This has the effect of forming the rear heat sealed seam of the sleeve around the article and of forming the heat sealed seam which constitutes the new leading edge of the two webs of material. Relatively tight sleeves can be obtained with this type of machine but its main problem is that it is impos- 2 sible to run a stop-start machine at the sort of speeds that can be attained with a continuously operating machine. Furthermore, such a machine is subjected to considerable shocks in use due to the fact that the parts must be accelerated and decelerated very rapidly to obtain a reasonable output in terms of packages per minute. It must therefore be of sturdy construction and it follows that such machines are necessarily expensive.
A third solution to this problem involves bringing the sealing elements into a wide gap between articles and then accelerating the rearward article so that it overhauls the jaw in front of it and takes up a position close to the rear of that jaw. Stohlquist in his US. Pat. No. 3,729,894 has proposed a solution of this type. However, such a machine can only operate efficiently if the articles have a length substantially equal to the spacing between the sealing elements. If shorter articles are used the machine forms a slack wrap and wastes material.
The aim of the present invention is to provide an improved article wrapping machine which avoids the disadvantages and shortcomings of the prior art machines.
According to one aspect of the present invention, there is provided a method of wrapping articles comprising the steps of displacing the articles in spacedapart relationship along an article feed path, providing a partially formed sleeve of wrapping material around each article during movement thereof along said feed path, introducing into the spaces between articles members for completing the formation of the sleeves around the articles, and changing the direction of movement of said articles while said members are between the articles.
ln one form of the method, it comprises the step of displacing further members for forming the wrapping material into sleeves along a path which converges with the path along which the first mentioned members move and into co-operating relationship with the first mentioned members, the wrapping material being gripped between eo-operating firstmentioned and further members and being formed by the members into sleeves around the articles.
According to a further aspect of the present invention, there is provided a machine for wrapping articles, comprising means for displacing articles in spacedapart relationship along an article feed path having a change of direction therein, a plurality of members for forming wrapping material into sleeves around said articles, and means for guiding said members along a path which converges with said feed path before the change in direction thereof, the arrangement being such that the members, in use, enter the spaces between articles prior to the articles changing direction.
In a preferred form, said means for displacing articles maintains the articles, prior to the change in direction, in step-wise relationship to one another. Furthermore, it is preferred that said path comprises a first section and a second section with said change in direction between them, the second section being generally horizontal and said first section sloping upwardly towards it, said members converging with said article feed path from above.
In a specific constructional form, the means for displacing articles comprises a conveyor including a series of platforms on which the articles stand, said platforms being in step-wise relationship to one another prior to said change in direction and having their upper surfaces in the same horizontal plane after said change in direction.
A further plurality of members can be provided together with means for guiding said further plurality of members along a path which converges with the path along which the firstmentioned plurality of elements are displaced and into co-operating relationship with the firstmentioned plurality of members, the arrangement being such that wrapping material is gripped between each pair of co-operating members and formed into said sleeves.
In the shrink-wrap form of the machine (or any form which uses synthetic plastics material), the members are adapted to sever the synthetic plastics material and to form heat-sealed seams on each side of the line along which the synthetic plastics material is severed. In this form, the members of one plurality can each include at least three heated wires, the central wire being adapted to sever the material, and the outer wires being adapted to form said seams, and in which the member of the other plurality form anvils against which the member of said one plurality are pressed.
For a better understanding of the present invention, an embodiment thereof will now be described by way of example and with reference to the accompanying drawings, in which:
FIG. 1 is a diagrammatic side elevation of a machine for wrapping articles in heat-shrinkable film;
FIG. 2 is a plan view of the machine of FIG. 1 with certain upper parts of the machine omitted to show the underlying structure;
FIG. 3 illustrates, to an enlarged scale, a heat-sealing bar; and
FIGS. 4 to 7 are detailed side elevations, to a larger scale, and showing the sequence of steps during a sealing operation.
GENERAL LAYOUT The illustrated wrapping machine will first of all be described generally with reference to FIGS. 1, 2, and 3 and thereafter its operation will be described in detail with reference to FIGS. 4 to 7. The machine shown comprises an article feed zone 10 and a sealing zone 12, a series of articles A in the process of being wrapped being shown passing in spaced-apart relationship through the machine along its article feed path. These articles are wrapped by means of an upper film 14 of heat-shrinkable wrapping material fed from a reel 16 and a lower film 18 of the same material fed from a reel 20, the films I4 and 18 being heat-sealed together as will be described. The articles A exiting from the zone 12 enter a heat-shrink tunnel (not shown).
During their passage through the machine, the articles A are successively propelled by a series of pushers 22 carried on a pair of laterally spaced endless chains 24, carried and propelled by a series of parallel belts 26, and carried by a series of platforms 28. The platforms 28 form part of an endless conveyor generally indicated at 30, this conveyor turning at one end about sprockets 32 and at the other end about further sprockets (not shown) located at the far end of said tunnel. The main drive for the conveyor 30 is via these further sprockets and it will be understood that it is the upper run of the conveyor 30 which passes through the heatshrink tunnel. The returning, lower run passes beneath the tunnel.
Between the upper and lower runs of the conveyor 30 there is a further conveyor 34 which carries a spaced series of transverse heat-sealing bars 36. Above the conveyor 30 there is another conveyor 38 which carries a spaced series of transverse anvils 40 which co-operate with the bars 36. The conveyors 34 and 38 are driven from the conveyor 30 by chains C, and the three conveyors are driven so that, in the sealing section, generally indicated at 42, they travel from left to right as illustrated in FIG. 1, and at the same speed. The bars 36 and anvils 40 constitute members for forming the wrapping material into sleeves about the articles.
FILM FEED The film 14 passes from the reel 16 and is entrained around guide rollers 44. The roller 46 is a dancer roller, the ends of which are free to move in inclined guides 48 formed on the inner surface of the side plates P of the main frame MF of the machine. The dancer roller 46 is supported by the film 14 which, as will clearly be seen from FIG. I, passes under this roller.
The film 18 passes from the reel 20 around a guide roller 50, upwardly through the gap which exists between the chains 24 and the series of belts 26, and then to the right to join the upper film 14.
THE FEED SECTION Each pusher 22 is of generally I-shape (see FIG. 2) having an upright and two cross-bars 52 and 54. Opposite ends of the cross-bar 52 of each pusher are pivotally connected to the chains 24 as diagrammatically illustrated at 56 in FIG. 1. The other crossbar 54 carries two pusher blocks 58. A tab 60 forms an extension of the upright of the I on the opposite side of the bar 52 to the upright and co-operates with a fixed cam 62. A leaf spring 64 bears down on the upright of each pusher 22 as the parts of the chains 24 to which that pusher is secured pass from the lower runs to the upper runs around sprockets 66.
A table 68 extends over the chains 24 and is slotted at 70 (see FIG. 2), the uprights of the pushers 22 passing through this slot and the blocks 58 sliding on the upper surface of the table. Below the righthand end of the table 68 there is a pair of parallel sloping guides 72 with which the blocks 58 engage as they drop from the righthand end of the table. It will be noted that the guides 72 extend to the left beneath the chains 24 so as to limit downward movement of the free ends of the pushers.
Drive to the chains 24 and to a shaft 74 about which the belts 26 are entrained, is by way of chains 76 and 78 from the transverse shaft on which the sprockets 32 are carried. It is important to note that the rate at which the belts 26 are driven is slightly faster than the rate at which the platforms 28 are driven for a reason to be explained.
The conveyor 30 comprises the series of platforms 28 on which the articles stand and two laterally spaced chains 80 which are entrained around the sprockets 32 and around the driven sprockets at the far end of the tunnel. At the leading end of each platform (the righthand end while it is in the upper run as shown in FIG.
2) there is on each side thereof a block 82 which is pivotally connected to the platform and fixedly connected to a link of the adjacent chain 80. At the rear of each platform, and on each side thereof, there is an outwardly projecting arm 84 with a roller 86 at the end thereof. The rollers 86 run on lower guide tracks 88 and upper guide tracks 90. These tracks extend around practically the entire extent of the conveyor 30 and, in
conjunction with the rollers 86, hold the rear ends of the platforms in the desired position.
As will be seen from FIG. 2, the platforms 28 are, in plan, of open grid-like construction for lightness and to enable the film at the bottom of an article to be heated while that article is in the tunnel. The rear edge of each platform 28 is slotted at 92 so as to form a plurality of fingers 94, the slots 92 registering with the belts 26. As each platform rises towards the sealing section 42, the fingers pass around the outside of, and between, the forward, i.e. righthand, ends of the belts 26.
It will be noted from FIG. 1 that the guide tracks each have a steeply inclined upwardly extending section 96, a less steeply inclined section 98, a horizontal section at the sealing section 42, and a downwardly inclined section I02 after the sealing section. The sections I02 lead to horizontal sections which pass through the heating tunnel and hold the platforms 28 horizontal during their passage through the tunnel. Attention is directed to the path of the chains 80 which ensures that, the rollers 86 pass up the steeply inclined sections 96 of the tracks 90, the rear ends of the platforms are raised so that the platforms are lifted to horizontal from the steeply inclined position they are in the parts of the chains 80 to which they are attached round the sprockets 32. Thereafter the chains 80 and tracks 90 follow substantially parallel paths so that the platforms remain horizontal. Thus the article feed path has a number of different sections of which two are particularly important. During passage through the first of these the articles rise towards the sealing section 42 and then change direction to move horizontally through the section 42.
THE HEAT-S EA LING STRUCTURE The heat-sealing structure comprises the upper conveyor 38 carrying the anvils 40 and the lower conveyor 34 carrying the heat-sealing bars. Dealing firstly with the lower conveyor, this comprises a pair of chains 104 which are entrained around sprockets I06 carried on transverse shafts 108. The bars 36 are carried by the chains 104 and each bar comprises an elongated metal block (see FIG. 3) having its ends secured to the chains 104, a layer 112 of foamed plastics material, and a layer 114 of an insulating material such as TEF- LON, the foamed plastics material being sandwiched between the metal block and the layer of TEFLON. A terminal block 116, insulated from the metal block 110, is provided at one end of each bar 36 and a plurality of heating wires 118 are anchored to the terminal block 116 and extend longitudinally of the bar 110. The outer wire or wires I18 lie against the TEFLON layer 114. The end of the bar remote from the terminal block 116 is rounded and the wires extend around the curved face of the bar to the rear side thereof. The rounded configuration of the bar end can be obtained by machining the bar itself if desired but is preferably provided by mounting on the bar a rotatable pulley 120 having grooves in which the heating wires 118 are guided. On the rear side of the block 110, the wires 118 are connected to coil springs 122 which tension these wires and take up any extension which occurs on heating. The requisite second electrical connection to the wires 118 can be made via the coil springs 122 which have their other ends anchored to a terminal block (not shown) insulated from the elongated block 110.
The block 110 is wrapped in a sheet 124 of a material such as TEFLON so as to prevent direct contact occurring between all but the centre one of the heating wire 118 and the heat-shrinkable film.
The upper conveyor 38 comprises a pair of laterally spaced chains 126 to which opposite ends of the anvils 40 are attached. Each anvil comprises a metal bar hav ing a facing of foamed plastics material, the metal bar and foamed plastic being in a sleeve of an insulating material such as TEFLON. The anvils 40 are guided along a downwardly inclined path which converges with the upwardly inclined section of the conveyor 30 from above so that they enter the spaces between the articles.
Chain guides are shown at 128 for the chains 104, and at 130 for the chains 126. These guides ensure that upwardly directed and downwardly directed forces are exerted on the bars 36 and anvils 40 respectively in the sealing section 42 whereby the requisite pressure bc' tween these components is obtained.
ELECTRICAL SUPPLY TO THE HEAT-SEALING BARS Between the guides 128 (see for example FIG. 4) there is a pair of laterally spaced, parallel contactor bars 132. These bars are positioned between the chains 104 (see FIG. 2). Two microswitches I34 and 136 are provided for switching on and switching off current supply to one of the contactor bars 132. It will be understood that the other contactor bar is neutral. The microswitch 134 has an operating arm 138 which is positioned so as to be actuated by that one of the bars 36 approaching the sealing section 42 (see FIG. 4). The microswitch 136 has an operating arm 140 which is also arranged to be actuated by the bars 36 and is posi tioned so that it is actuated prior to each bar 36 exiting from the sealing section 42. Below each bar 36 there are laterally spaced brackets 142, and electrical shoes 144 are carried by these brackets. The brackets and shoes are not shown in FIG. 3. The shoes 144 are ar ranged so that they engage the contactor bars 132 as the associated bar 36 approaches the sealing section 42, and disengage from the contactor bars as the associated bar 36 exits from the sealing section. It will be noted that the shoes I44 engage the contactor bars before the microswitch 134 is actuated, and disengage from the contactor bars after the microswitch 136 has been actuated. This ensures that no arcing occurs.
It will be understood that the microswitches form part of a holding circuit and are not in the main supply circuit. Thus, upon the microswitch 134 being actuated, current is supplied to the heating wires of the sealing bar. this current then not being switched off until the microswitch 136 is actuated.
To avoid obscuring detail, only a minimum number of reference numerals have been applied to FIGS. 5 to 7. Similarly, while one of the sprockets about which the chains 80 are entrained has been shown in FIGS. 5 to 7, this sprocket has been omitted from FIG. 4.
ANVIL RELEASE If reference is made to FIG. 4, it will be noted that each anvil 40 has an upwardly projecting finger 146 and that a laterally projecting, fixed abutment 148 is provided which extends inwardly from the chain guide 130. The finger I46 encounters the abutment 148 as each anvil 40 and sealing bar 36 begin to separate as they leave the sealing section 42.
LIFTING ARRANGEMENT OF THE CONVEYOR 38 It will be noted from FIG. I that the conveyor 38 is shown in a lower, full line position and is also shown, in dotted lines, in a upper position. The sprockets 150, about which the chains 126 are entrained, are mounted on shafts 152 which are themselves mounted on a subframe SF of the machine. The sub-frame is pivotable about the axis of a shaft 154 on which the righthand sprockets 150 are mounted. An hydraulic cylinder 156 is secured between the main frame MP of the machine and the sub-frame SF by which the shafts 152 are carried. The connection between the sub-frame SF and the ram 158 of the hydraulic cylinder I56 is diagrammatically shown at 160, and is on the outside of the subframe SF. A one-way valve (not shown) is provided in the circuit of the hydraulic cylinder 156, the valve being arranged so as to allow hydraulic fluid to flow from the righthand end of the cylinder to the lefthand end as the ram 158 is retracted, but which prevents flow in the reverse direction. Thus, the hydraulic cylinder 156 offers little resistance to movement of the sub-frame SF in the upward direction as this causes the ram 158 to be retracted. However, once the sub-frame SF has lifted, the hydraulic cylinder prevents it being lowered until the valve is manually opened.
The front end of the subframe SF carries a pair of magents 162 and these magnets co-operate with steel or iron blocks I64 which are mounted on the insides of the main frame MF of the machine. These magnets cause a downward force to be exerted on the front end of the sub-frame SF, which force (plus its own weight) holds the sub-frame in the position in which the conveyor 38 is in the full line position illustrated.
THE ELECTRICAL SYSTEM The conveyor 30 is driven by an electric motor and the circuit of this motor is interlocked with the current supply circuit of the sealing bars 36. This ensures that, when movement of the conveyor 30 ceases, current is not supplied to the wires 118 of any sealing bar which happens to have the shoes I44 thereof in engagement with the contactor bars 132.
The reel 16 is driven by an electric motor 166 (FIG. 1) which is actuated on an on-demand basis. A microswitch 168 is associated with the dancer roller 46, and as this roller rises along the guides 48, which means that the film I4 is being drawn to the right, the microswitch 168 is actuated so that the reel 16 is rotated by the motor I66 to make further film available. The reel 20 is not driven and film from that reel is simply pulled off, as will be explained.
OPERATION The series of articles A, A1, A2, etc., to be wrapped, are placed, either manually or by an automatic feed apparatus, onto the table 68. As each one of the pushers 22 rounds the sprockets 66, the tab 60 thereof encounters the cam 62 which causes that end of each pusher at which the crossbar S4 is located, to lift suddenly to raise the blocks 58 above the level of the table 68. The leaf spring 64 limits upward movement of the pusher to prevent it turning over to a trailing position. Thus, as the pushers move along the upper run, the blocks 58 slide on the table 68 and propel the articles A onto the belts 26 in the desired spaced sequence.
It will be understood that the film 18 overlies the belts 26 and that each article A sandwiches the film between itself and the belts. Thus, movement of the article to the right with the belts, causes film to be drawn from the reel 20.
As each article A reaches the righthand end of the belts 26, the fingers of a platform 28 pass upwardly through the belts and lift that article (and the underlying film I8) off the belts. It will be understood that, by the time a platform 28 encounters an article, that platform has been guided by the rollers 86 and guide sections 96 and 98 to a horizontal position (see FIG. 1). The platforms 28 with the articles thereon rise steadily from the belts 26 to the sealing section 42. As they pass from the rising section to the sealing section, they change direction (to horizontal) so that there is now no longer convergence between the article feed path and the path along which the anvils 40 are guided, but instead these paths run parallel to one another through the sealing section 42.
In view of the fact that the platforms 28 rise as well as move to the right, the spacing between adjacent articles tends to increase more rapidly than it would if the platforms 28 simply moved to the right. By virtue of the slightly faster movement of the belts 26, sufficient film is drawn from the reel 20 to compensate for this. It will be noted that the platforms 28 are in step-like relationship to one another as they rise towards the sealing section 42 and, after changing direction to enter the sealing section 42, run parallel to the path of the anvils 40 with their upper surfaces in the same horizontal plane.
Turning now to the sealing sequence itself, this will be described with reference to FIGS. 4 to 7. FIG. 4 shows the condition which exists immediately after a seam S has been formed between the leading edges of the films l4 and 18. Immediately the film around the article Al has been severed from the film which is being wrapped around the article A2, the dancer roller 46 is operative to pull back the film 14, as indicated by arrow I in FIG. 4, to draw the film against the leading edge of the article A2. In FIG. 5 an anvil 40 and a sealing bar 36 are shown approaching the sealing sec tion 42, the anvil 40 having moved downwardly into the gap between the article A2 and the following article A3 (see FIG. 6). In the position illustrated in FIG. 5, the shoes I44 of the approaching sealing bar 36 have engaged the contactor bars 132 and the microswitch I34 has subsequently been actuated. Thus the current supply to the heating wires is on" and these wires are being preheated in preparation for sealing.
In the position illustrated in FIG. 6, the bar 36 and anvil 40 are about to come into co-operating relationship with the films 14 and 18 between them. It will be noted that the parts of the chains I04 and 126 on which the anvil 40 and sealing bar 36 are mounted, are coming into engagement with the guides 128 and 130 so as to ensure that the sealing bar and anvil are urged together with the necessary pressure. In FIG. 7, the bar 36 and anvil 40 are pressed into co-operating relationship with the films 14 and 18 between them so that sealing is thus taking place. The centre heating wire, not being covered by the TEFLON insulation, melts the films l4 and 18 so that separation occurs and simultaneously a closure seam S is formed on each side of the line along which severing occurs. Thus, a sheath of wrapping material is formed around each article. As the anvil 40 and sealing bar 36 separate (see FIG. 4
once more) the finger 146 encounters the abutment 148 which causes a sudden jerking motion to be imparted to the anvil 40. This ensures that the seam S does not adhere to the anvil which would result in the film 14 being pulled to the right, thereby preventing the dancer roller 46 being effective to pull back the slack material. It will be seen that, in the fully engaged position (see FIG. 7) the anvils 40 have moved downwardly with respect to the platforms 28 to a level in which their undersurfaces lie approximately in the plane of the upper surface of the platforms, and the bars 36 are immediately beneath the anvils.
The conveyors 30, 34, and 38 run continuously, and with a machine of the form illustrated, it is possible to ensure that the films l4 and 18 are wrapped relatively tightly around the articles A even before heat-shrinking is undertaken. This is achieved by virtue of the fact that the articles A rise towards the sealing section 42 and the anvils 40 descend towards the sealing section.
Because the conveyor 30 passes through the heatshrink tunnel, there are always products in the tunnel and as a consequence it is not possible to stop the main conveyor in the event of an article A being fed incorrectly into the machine and becoming wedged. Should this happen, an upward force is exerted on the subframe SF carrying the conveyor 38, and the moment the upward force exceeds the downward force exerted by the magnets/blocks 162, I64 and by the weight of the sub-frame SF, the sub-frame pivots upwardly about the shaft 154 to allow the improperly positioned article to pass. Once the article is through the sealing section 42, then the one-way valve of the hydraulic cylinder is actuated to enable the sub-frame SF to return to its operative position.
A sheet T of TEFLON (see FIG. 1) covers the sealing bars 36 as they approach the sealing section 42. As explained above, heating of the wires 118 takes place in advance and the sheet T prevents premature contact between the hot wires and the film.
The incorporation of the pull-back arrangement including the roller 46, enables the machine illustrated to handle articles of widely varying sizes without excessive slack resulting in the wrap. It does, however, mean that there must in each sealing and severing cycle be a period of time when the film is not gripped between a sealing bar and anvil. As will be understood from the above, it is during this period that the pull-back arrangement operates. Thus, the time available during which each sealing bar and associated anvil are in eooperating relationship, is short and this is one of the main factors in determining the speed at which the machine can run.
If, on the other hand, the machine is what can be termed a "single purpose machine, that is, it isintended to wrap articles which do not exhibit a wide variation in size, then the pull-back arrangement can be omitted and the sealing section 42 can be extended so that, at any one time, more than one pair of anvils and sealing bars are in contact with one another and there is always at least one sealing bar/anvil combination in engagement. This increases the time available to ensure that satisfactory sealing takes place and thus the machine can be run at higher speeds.
The machine thus far described is intended for wrapping articles with synthetic plastics material, specifically shrink wrap material, but it can be modified so as to be capable of wrapping articles in paper or other materials. In this form. the pull-back arrangement is bars 36 and anvils 40) contributes to the simplicity of the machine. However, if desired, the sealing bars 36 and the associated electrical supply system can be moved to the overhead position occupied by the upper conveyor 38, and the conveyor 38 removed. in this form, the leading edge parts of the platforms 28 constitute the anvils. This form of machine is less advantageous as it results in a slacker wrap and hence less economic use of the available material.
The arrangement illustrated, in which the platforms 28 rise, then travel horizontally and then descend gives rise to a simple form of machine. However, other layouts are possible. For example, the platforms could descend along an inclined path, travel horizontally and then rise, or descend along an inclined path, then descend vertically, and then descend along another inclined path lying beneath the first. This latter sequence could be reversed if desired. In all these possible layouts, the platforms change direction after converging with the anvils 40 (or the bars 36 if the positions of these components are interchanged) and then run parallel therewith.
If the articles to be wrapped are of relatively low profile, it is possible to construct a machine in which the stepped arrangement of the platforms 28 is omitted. In such a machine a conveyor belt moves upwardly towards the sealing region, then horizontally and then downwardly. Of course, such a belt must be apertured to enable the bars 36 and anvils 40 to cooperate.
I. A machine for wrapping articles comprising:
a. a plurality of supports for receiving articles and transporting the articles in spaced-apart relationship along an article feed path having a first linear portion intersecting with and obliquely disposed to a succeeding adjacent second linear portion, whereby a support transporting an article along the first linear portion of said article feed path will be in step-wise relationship with a a support transporting an article along said second linear portion;
a plurality of wrapping members for forming wrapping material into sleeves around said articles;
. means for guiding said wrapping members along a path which lies substantially in or parallel to the plane defined by said first and second linear portions and which converges with said article feed path before said first linear portion intersects with said second linear portion; and
d. driving means for moving said plurality of supports and said plurality of wrapping members along their respective paths continuously and in synchronism, the oblique disposition of said first and second linear portions being such in relation to the wrapping member guiding means that said wrapping members enter the spaces between adjacent articles while the trailing one of said adjacent articles moves along said first linear portion and while the leading one of said adjacent articles moves along said second linear portion, whereby said wrapping members avoid obstruction from the leading edge of said trailing article.
2. A machine according to claim I, in which said second linear portion is generally horizontal with said first linear portion sloping upwardly towards it, and in which said wrapping members converge with said article feed path from above.
3. A machine according to claim 2, in which said second linear portion of the article feed path is followed by a downwardly sloping third linear portion.
4. A machine according to claim 2, in which said plurality of supports are a series of platforms on which the articles stand, said platforms forming part of an endless conveyor connected in driven relation to said driving means and having their upper surfaces in the same horizontal plane while transporting said articles along the second linear portion of said article feed path.
5. A machine according to claim I, in which there is a further plurality of wrapping members, and means for guiding said further plurality of wrapping members along a path which converges with the path along which the firstmentioned plurality of wrapping members are displaced and into co-operating relationship with the firstmentioned plurality of wrapping members, the arrangement being such that wrapping material is gripped between each pair of co-operating members and formed into said sleeves.
6. A machine according to claim I, in which said wrapping members are adapted to sever synthetic plastics material and to form heat-sealed seams on each side of the line along which the synthetic plastics material is severed.
7. A maching according to claim 5, in which said wrapping members are adapted to sever synthetic plastics material and to form heat-sealed seams on each side of the line along which the synthetic plastics material is severed, and in which the wrapping members of one plurality each include at least three heated wires, the central wire being adapted to sever the material,
12 and the outer wires being adapted to form said seams, and in which the wrapping members of the other plurality form anvils against which the wrapping members of said one plurality are pressed.
8. A machine according to claim I, in which there is provided means for supplying two webs of wrapping material, one over and one under the articles, and means for taking up slack in the overlying web in the intervals between sleeve formation.
9. A machine according to claim 4, in which there is a further plurality of wrapping members, and means for guiding said further plurality of wrapping members along a path which converges with the path along which the firstmentioned plurality of wrapping members are displaced and into co-operating relationship with the firstmentioned plurality of wrapping members, the arrangement being such that wrapping material is gripped between each pair of co-operating wrapping members and formed into said sleeves, and in which the guide means for the two pluralities of wrapping members guides the wrapping members of the firstmentioned plurality downwardly with respect to the platforms to a level such that, in the second linear portion, their undersurfaces lie approximately in said horizontal plane, and guides the members of the second plurality upwardly so that their upper faces lie immediately beneath said undersurfaces.
l0. A machine according to claim 9, in which the two pluralities of wrapping members form part of endless conveyors, and in which the conveyor of which the firstmentioned plurality of members forms part, is mounted to enable it to lift away from said second linear portion of the article feed path.
11. A machine according to claim 1, in which said wrapping members are guided so as to run parallel to the article feed path along said second linear portion thereof.
i =1 l i