Package making – Methods – Forming or partial forming a receptacle and subsequent filling
Reexamination Certificate
1999-10-29
2003-04-22
Smith, Scott A. (Department: 3721)
Package making
Methods
Forming or partial forming a receptacle and subsequent filling
C053S455000
Reexamination Certificate
active
06550225
ABSTRACT:
This invention relates to a method of, and an apparatus for, obtaining individual web sections from a web of sheet material, for example, to a method of, and apparatus for, forming bags from a length of a sealable sheet material.
In GB-A-1052701 there is described a method of making bags of a thermoplastic synthetic resin film comprising tube-making means including a pair of cooling means disposed between a guide roll and take-up rolls along the advancing direction of the film or films and in the vicinity of the edges at the two sides of the sheet or sheets to be sealed, the cooling means having a gap therein for cooling the films by the slidable movement of the films therethrough, heating means disposed in proximity of the film edges which protrude beyond the cooling means, and another cooling means disposed next following the heating means and on the same side as the heating means relatively of the film edges; a severing means for cutting the thermoplastic synthetic resin film tube whose edges have been completely sealed together by said tube making means, in predetermined lengths at right angles to the advancing direction of the film tube; and a bag bottom sealing means having heating means for fusing together the severed edge of the film tube. This bag bottom sealing means is provided at right angles to the tube-making and severing means; hence a conveying means consisting of an accelerating stacker and a direction-changing stacker is interposed between the tube-making and severing means and the bag bottom sealing means. In this arrangement the bag to be formed travels transversely to its former direction of motion and the bottom seal is formed in the new direction of the bag. This design is, by modern standards, incapable of achieving the high bag formation speeds desired today.
U.S. Pat. No. 4,005,970 teaches an apparatus for continuously producing seals in tube-shaped plastics film material comprising means for supplying the web of material, at least one heating beam travelling along with the web and subsequently returning, means for keeping the web mechanically tension-free at the location where it is warm, means for keeping the heated film layers one against the other up to a pressing station, said pressing station comprising two rollers at least one of which is provided with cooling means, and means for discharging the web. There is no description of what happens upon discharge of the web from the apparatus described, but since the web is to be formed into bags the web is presumably cut into bag lengths downstream from the apparatus described.
In U.S. Pat. No. 4,061,458 there is taught an apparatus for processing a web of material without a standstill. This has a pair of confronting transverse tools between which the web is guided. The tools are mounted on carriers guided in pairs on endless chains to follow a path composed of two parallel straight sections joined at the ends by semi-circular sections, the latter being relatively adjustable.
A bag-making machine is described in EP-B-0333726 in which the bags are defined by lines of perforation and weld lines. The cutting means used to form the perforations and the welding means are described as being separately connectible and disconnectible independently of other means.
U.S. Pat. No. 3,147,168 is concerned with manufacture of bags in the form of a series of connected bag sections open at their upper ends. It describes an apparatus in which registration of the seals between successive printed areas is maintained as the bags are formed. The bags are first sealed and then cut in turn from the web.
A similar principle is illustrated in U.S. Pat. No. 4,061,458.
GB-A-1147466 teaches a machine for making bags with an arcuate bottom using a conventional bag making machine which comprises in combination a mechanism for unwinding a film roll, a mechanism for transversely welding the unwound film at specified intervals in the longitudinal direction of the film, a mechanism for transversely cutting the welded film either in front of or behind the weld line thereby to form bags, and a mechanism for extracting the bags thus formed and collecting them in a specified place.
In modern day packaging there is a demand for machines that are capable of working at ever higher and higher speeds, while still producing packages with reliably formed seals and of neat appearance.
Roast and ground coffee is packaged in some countries in bags at atmospheric pressure so that the coffee more or less loosely fills the bag. However, in some countries the consumer is used to purchasing roast and ground coffee in vacuum packed packages. Such packages conventionally have a parallelepipedal shape, somewhat reminiscent of a brick. It is difficult to produce vacuum packages without unsightly wrinkles in the packaging material.
In order to facilitate the formation of a neat vacuum packed package of coffee, it is often packed in gusseted bags. These are typically formed from a tube of thermoplastic material which is itself made by sealing longitudinal edge portions of a web of thermoplastic sheet material one to another. The tube may then be provided with longitudinal creases so as to form a flattened tube at the lateral edges of which panel portions have been folded inwardly to form gussets. However, to form the bottom seal of a bag with gussets it is necessary to supply heat from a pair of opposed external heating bars through four layers of thermoplastic material, an operation that requires a significant time to perform, since the thermoplastic material is normally a relatively poor conductor of heat and it is at the inside surfaces that the thermoplastic material must be heated to welding temperature in order to form a reliable seal. Thus it may require the heating elements to be kept in contact with the outer faces of the flattened gusseted web for a period of from about 0.3 to about 0.75 seconds and under pressure in order to form a reliable seal, depending upon the thickness and thermal conductivity of the thermoplastic material.
An additional problem is that the web is usually preprinted with repeating patterns, each pattern providing advertising material and product information for each successive bag. Normally the web is printed with repeating registration marks for enabling the machine to be adjusted while it is running so that the bottom seals in the bags are in the correct relationship to the printed pattern and so that the bags are severed from the web with the printed information in the correct place thereon. By providing mechanisms for holding a portion of the web temporarily in a buffer along the path of the web and by arranging that at some point in the cycle of formation of each bag the sealing mechanism is out of contact with the web, then the correct print registration can be achieved by temporarily speeding up or slowing down the web as it passes through and between the various stages of the formation of a bag, so that the repeating printed pattern can be restored to the correct registration with the bottom seals. If the web is continuous, then in a high speed machine, the sealing section for forming the bottom seals of the bags may have to be relatively long, in order that each bag can spend sufficient time in contact with the heated elements and under pressure in order to achieve a reliable bottom seal. Once the bottom seal has been made, then the bags can be severed in turn from the web. However, if the speed of operation of the machine is sufficiently high that the time needed to form a reliable seal is greater than the interval between severing one bag and the next from the web, then in such an arrangement it is necessary to provide more than one set of sealing stations along the path of the bags in order to provide a sufficient sealing period for creating a reliable bottom seal and yet to permit print registration to be achieved. In this case a convenient place to achieve the necessary speed adjustment is in the middle of the bag bottom seal sealing section. However, if the heating elements part company from the outside of the
Cahill Michael John
Seaward David Robert
Jensen & Puntigam P.S.
Molins Plc
Nathaniel Chukwurah
Smith Scott A.
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