GB1569713A - Machine for sealing together superimposed webs - Google Patents

Description

(54) MACHINE FOR SEALING TOGETHER SUPERIMPOSED WEBS (71) We, PRATT MANUFACTURING CORP., a Corporation organized and exist- ing under the Laws of the State of Wisconsin, United States of America, of 3097 West Mill Road, Milwaukee, Milwaukee County, Wisconsin, United States of America, 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 : This invention relates machines for sealing together superimposed webs along laterally displaced lines extending longitudinally of the webs. Such machines have laterally spaced sealing wheels coacting with anvil wheels in opposed pairs above and below the webs to be sealed, and have been arranged to exert a suitable sealing pressure. In some cases, one or more of the wheels has been heated to provide a heat seal and, in other cases, pressure sensitive adhesive has been used. This requires pressure but not heat. In both cases, diffi- culty has been encountered due to minor abnormalities in the position and/or dimensions of one or both of the wheel pairs. For example, a single shaft supporting the sealing wheels might bow slightly to cause one wheel to be slightly farther away from the webs than the others. Also, the periphery of one or more of the wheels might be sufficiently eccentric to cause intermittent interruption or minor reduction in the sealing pressure along the line of seal, thus affecting the critical pressuretemperature-time relationship. Since a dimensional or positional abnormality as small as 0-001 inches can cause a defective seal, this presents a serious problem in packages used for the health industry or for food or anhydrous materials, as openings which might admit contaminating foreign matter, air or moisture would seriously affect the sterility, condition or usability of the contents.

The present invention provides a machine for sealing together super-imposed webs along at least three laterally spaced lines extending longitudinally of the webs, the machine having laterally spaced anvil wheels and pneumatic tyred sealing wheels on a single shaft coacting with the anvil wheels to exert sealing pressure on the webs along said lines, and means for regulating the pressure in the tyres, of the sealing wheels.

Embodiments of the invention will now be described further with reference to the accompanying drawings in which: Fig. 1 is a side elevational view of one embodiment showing a sealing wheel for sealing together super-imposed webs.

Fig. 2 is a sectional view taken on the line 2-2 of Fig. 1.

Fig. 3 is a similar sectional view of a second embodiment of the invention.

Fig. 4 is a diagrammatic perspective view of a machine showing three of the sealing wheels of Fig. 3 mounted on a common shaft and coupled through a rotary coupling to three separate air lines each having a pressure regulator.

Fig. 5 is a longitudinal sectional view of the rotary coupling used in the machine of Fig. 4.

Fig. 6 is a fragmentary view similar to a portion of Fig. 2 showing a modification.

Figs. 1 and 2 show a metal wheel 10 having a pneumatic tyre 12 for applying sealing pressure in a strip along webs 14. Tyre 12 is adapted to receive air under pressure through communicating bores 16 and 18 in wheel 10 and through a standard valve 20 which is attached within bore 16 by matching screw threads. Tyre 12 has outwardly- projecting beads 22 near its inner periphery which seat in matching grooves 24. The air pressure within tyre 12 presses beads 22 into grooves 24 to seal tyre 12 and help hold it in place on the wheel 10.

Wheel 10 has a central bore 26 within which a bronze bushing 28 is press fitted.

Wheel 10 and bushing 28 rotate freely on a shaft 30 which is supported by conventional means (not shown) in such a position that the tyre presses against the webs 14.

Webs 14 may be supported by a moving surface 32 which can be a portion of an endless belt or any other suitable support surface. One or both of the adjacent faces of the webs 14 may be coated with pressure sensitive adhesive in a strip positioned to be engaged by the tyre 12 so that the two webs 14 can be sealed together. Where pressure sensitive adhesive is employed, no heat is needed.

Fig. 4 shows three sealing wheels 34, 36 and 38 (in accordance with Fig. 3 and described below) mounted rigidly on a common rotatable shaft 40 to coact with three anvil wheels 42, 44 and 46 which are mounted on a common shaft 48. Shafts 40 and 48 are suitably supported on conventional supporting framework which is not shown in the drawings.

Two webs of packaging material 114 and 115 (Fig. 4) travel between the sealing wheels 3438 and anvil wheels 42-46 to seal the webs 114 and 115 along three laterally spaced lines or strips (a), (b) and (c), the center strip (b) in this instance being wider than the outer strips. The arrangement shown in Fig. 4 is used in a packaging machine in which items are inserted between webs of packaging material 114 and 115, which are then sealed both longitudinally on the strips (a), (b) and (c) and also transversely along lines not shown, and are then cut intermediate the width of central seal (b) and also along the trans- verse seals to separate the individual packages. However, the means for cutting the webs 114 and 115 into individual packages is not pertinent to this invention and is, therefore, not disclosed in the drawings.

One or both of the shafts 40, 48 may bow slightly so that the sealing pressure exerted by some wheels may vary from that exerted by other wheels. Also, it is possible, due to manufacturing imperfections or for other reasons, that certain wheels may be slightly out of round by different amounts.

To minimize the sealing pressure variations in response to these abnormalities, a pneumatic tyre 112 is mounted on each of the sealing wheels 34-38, each pneumatic tyre being connected to a separate compressed air line. Each of such lines may have its own pressure regulator as described hereinafter, or, alternatively, there may be a common source of compressed air with a single regulator instead of the three shown in Fig. 4.

Fig. 3 shows the pneumatic tyre 112 for back-up sealing wheel 38, which is similar in construction to the sealing wheel shown in Figs. 1 and 2 and has the same reference numbers increased by 100 for similar parts. Sealing wheel 38 differs from the previously described sealing wheel of Fig.

1 in having a compressed air conduit 52 communicating with bore 116 and extending through hollow interior 54 of shaft 40.

Sealing wheels 34-38 are slidably though rigidly attached to hollow shaft 40 and rotate therewith.

In the embodiment illustrated in Fig. 4, the pneumatic tyre for each of the back-up sealing wheels 34-38 is coupled via conduits 52, 56 and 58 through the hollow interior of shaft 40 to a three-way rotary coupling 60, and from coupling 60 via conduits 62, 64 and 66 to independent pressure regulators 68, 70 and 72, each of which is coupled to a conventional source of air under pressure. Pressure regulators 672 have manual adjustments 74, 76 and 78 and pressure gauges 80, 82 and 84. Each manual adjustment 74-78 is set to maintain the air pressure level desired for the corresponding tyre of sealing wheel 3438, as indicated on pressure gauges 80-84.

The pressure regulators 68-72 thereafter hold the pressure in the pneumatic tyres of sealing wheels 3438 with in a predetermined tolerance of the selected pressure levels. The independent pressure regulators and adjustments make it possible for each pneumatic tyre to be maintained, at a different pressure level if necessary to compensate for bowing of shafts 40 or 48 ar other abnormalities, but, as before mentioned, a common source of compressed air with a single regulator may be alternatively used.

Fig. 5 is a longitudinal sectional view of rotary coupling 6Q, which includes a core 86 which is mounted within a casing 88, these being bearings 90 and 92. Casing 88 has a hub 94 at one end which receives an end of shaft 40 and is rigidly secured thereto by set screw 96. Casing 88 rotates with shaft 40 while core 86 remains stationary.

-Care 86 contains three annular air ducts 13Q, 132 and 134 which are sealed from each other and from the ambient air by 0-rings 136-142. Conduits 52, 56 and 58 communicate with grooves 130-134 via elbow fittings 144, 146 and 148. Conduits 62-66 communicate with ducts 130-134 by way of ducts 150, 152 and 154 in core 86.

As casing 88 rotates, conduits 52, 56 and 58 continuously coupled to conduits 62, 64 and -66 through ducts 130-134 and 15e 154.

Core 86 in Fig. 5 may be lubricated by grease introduced through a grease fitting 156. There is also a packing 158 which is supported by a metal washer 160, a spring 162 between washer 160, and nut 164 within the end of casing 88, there being a set screw 168.

In the machine of Fig. 4, the webs 114 and 115 are drawn between sealing wheels 34-38 and anvil wheels 42-46 by suitable means such as an endless-belt 132. Anvil wheels 42-46 can be heated by conventional means not shown to effect a heat when a heat seal is required. Whether or not heat sealing is required, the pneumatic tyres on sealing wheels 34-38 compensate for positional abnormalities, and hold the sealing pressure relatively constant. This produces relatively uniform seals in spite of shaft bowing, out-of-round wheels, or other abnormalities.

In certain situations, particularly when there is heat sealing, it may be desirable to partially fill the tyre with a liquid as at 250 in Fig. 6. In this Figure like parts to those of Fig. 3 are designated by the same numerals preceded by a 2. The liquid is of a type which will bring about a more even distribution of heat when there is heat sealing. The liquid could be high temperature oil, water, a viscous medium or a metallic liquid such as mercury, for example. Air pressure from the duct 218 will also be used in the tyre so that there is controllable air pressure, just as in the forms of the invention of Figs. 1 and 3, but the pressure of the liquid will cause more even heat transfer.

In use, when the tyres are pressed against the webs, the tyres are compressed slightly but, because of the pneumatic pressure, provide play in both directions with regard to dimensional abnormalities. If a sealing wheel has a flat spot, the tyre may expand slightly to maintain sealing pressure as the flat spot passes over the web. If the sealing wheel has a bump, or if the shaft is displaced toward the web, the tyre may compress slightly. The air valve of Fig. 2 provides for maintenance of a suitable pressure for particular conditions. In the form of invention of Figs. 4 and 5, the pressure regulators automatically maintain suitable pressure for each tyre independently of the others.

WHAT WE CLAIM IS: 1. A machine for sealing together superimposed webs along at least three laterally spaced lines extending longitudinally of the webs, the machine having laterally spaced anvil wheels and pneumatic tyred sealing wheels on a single shaft aoacting with the anvil wheels to exert sealing pressure on the webs along said lines, and means for regulating, the pressure in the tyres of the sealing wheels.

2. A machine as claimed in Claim 1 in which said means for regulating the pressure in the tyres of the sealing wheels includes air ducts in said single shaft, a duct in each sealing wheel communicating at one end with a respective air duct and at its other end with the interior of its tyre, and means for independently introducing air under pressure into each of said air ducts.

3. A machine as claimed in Claim 2 wherein said means for introducing air under pressure into said air ducts includes a rotary coupling, a separate air line for delivering compressed air through said rotary coupling to the duct for each sealing wheel, and a pressure regulator for each separate air line.

4. A machine as claimed in Claim 1 as hereinbefore described with reference to the accompanying drawings.

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

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. In the machine of Fig. 4, the webs 114 and 115 are drawn between sealing wheels 34-38 and anvil wheels 42-46 by suitable means such as an endless-belt 132. Anvil wheels 42-46 can be heated by conventional means not shown to effect a heat when a heat seal is required. Whether or not heat sealing is required, the pneumatic tyres on sealing wheels 34-38 compensate for positional abnormalities, and hold the sealing pressure relatively constant. This produces relatively uniform seals in spite of shaft bowing, out-of-round wheels, or other abnormalities. In certain situations, particularly when there is heat sealing, it may be desirable to partially fill the tyre with a liquid as at 250 in Fig. 6. In this Figure like parts to those of Fig. 3 are designated by the same numerals preceded by a 2. The liquid is of a type which will bring about a more even distribution of heat when there is heat sealing. The liquid could be high temperature oil, water, a viscous medium or a metallic liquid such as mercury, for example. Air pressure from the duct 218 will also be used in the tyre so that there is controllable air pressure, just as in the forms of the invention of Figs. 1 and 3, but the pressure of the liquid will cause more even heat transfer. In use, when the tyres are pressed against the webs, the tyres are compressed slightly but, because of the pneumatic pressure, provide play in both directions with regard to dimensional abnormalities. If a sealing wheel has a flat spot, the tyre may expand slightly to maintain sealing pressure as the flat spot passes over the web. If the sealing wheel has a bump, or if the shaft is displaced toward the web, the tyre may compress slightly. The air valve of Fig. 2 provides for maintenance of a suitable pressure for particular conditions. In the form of invention of Figs. 4 and 5, the pressure regulators automatically maintain suitable pressure for each tyre independently of the others. WHAT WE CLAIM IS:

1. A machine for sealing together superimposed webs along at least three laterally spaced lines extending longitudinally of the webs, the machine having laterally spaced anvil wheels and pneumatic tyred sealing wheels on a single shaft aoacting with the anvil wheels to exert sealing pressure on the webs along said lines, and means for regulating, the pressure in the tyres of the sealing wheels.

2. A machine as claimed in Claim 1 in which said means for regulating the pressure in the tyres of the sealing wheels includes air ducts in said single shaft, a duct in each sealing wheel communicating at one end with a respective air duct and at its other end with the interior of its tyre, and means for independently introducing air under pressure into each of said air ducts.

3. A machine as claimed in Claim 2 wherein said means for introducing air under pressure into said air ducts includes a rotary coupling, a separate air line for delivering compressed air through said rotary coupling to the duct for each sealing wheel, and a pressure regulator for each separate air line.

4. A machine as claimed in Claim 1 as hereinbefore described with reference to the accompanying drawings.