Package making – Progressively seamed cover web or web folds – With closing of web between package units
Patent
1998-02-02
1999-12-28
Johnson, Linda
Package making
Progressively seamed cover web or web folds
With closing of web between package units
533743, B65B 906
Patent
active
060065036
DESCRIPTION:
BRIEF SUMMARY
This invention is concerned with packaging machines of the type commonly referred to as vertical form fill and seal machines. In such machines, a web of packaging material is drawn along a former and then passes downwards in a tubular formation; the edges are then sealed longitudinally, after which horizontal seals are made at regular intervals to form individual packets. A measured quantity of product to be packaged is dropped into each packet before a top seal is formed by sealing jaws which simultaneously form the bottom seal of the next packet. The sealing jaws commonly include a cutting device which separates successive packets.
With some materials and in some circumstances, it is desirable to provide a stripping device to ensure that each measured quantity of the product passes downwards reliably into its packet before the top seal is formed. An example of a stripping device is described in European patent No. 165819. In that case cooperating stripping members are mounted on rotary sealing jaws and thus rotate at the same speed as the jaws. The present invention, on the other hand, allows stripping members to be driven at a greater speed than the sealing jaws while they are performing each stripping operation.
According to one aspect of the present invention, a packaging machine of the type described comprises a pair of sealing jaws for forming horizontal seals across the tubular packaging material at regular intervals, and a stripping device comprising a pair of conveyors mounted separately from and at the side of the sealing jaws (preferably at both sides) and carrying cooperating parallel stripping bars which are moved downwards by the conveyors, on opposite sides of the packaging material and ahead of engagement of the packaging material by the sealing jaws, to ensure that product being packaged drops down past the sealing jaws before the jaws act to form each seal. The reference to "the side of the sealing jaws" preferably applies to the position of the conveyor when viewed horizontally in a direction normal to the sealing surfaces of the jaws as they engage the packaging material.
In some packaging machines of this type it is also desirable to provide means to ensure that pieces of the product being packed do not fall into the seal area before the seal is formed. For that purpose the present invention may be adapted to provide, in addition to the stripping bars (or as an alternative), one or more pairs of product catching bars mounted on a pair of conveyors as described above. The product catching bars are brought close together by the conveyors carrying them, on opposite sides of the packaging material and in a region above the sealing jaws as they form each seal, to ensure that each quantity of product does not enter the bottom seal area before the seal is formed. The product catching bars may be carried by the same conveyors that carry the stripping bars, or by separate conveyors.
The term "bar" as used in this context embraces rollers which can rotate about their axes, as well as bars which are non-rotatably mounted on the corresponding conveyor or conveyors.
Catching or clamping bars carried by endless conveyors are disclosed in FR-A-2182006. The bars in that case have the purpose of preventing the weight of liquid (which is the product being packaged) bearing on each seal before it is securely formed.
This invention is particularly applicable to continuously moving packaging material and sealing jaws, the jaws being for example in a rotary form. However, it is in principle also applicable to machines based on horizontally reciprocating sealing jaws, the drive for the packaging material in this case being normally intermittent. In the case of continuous rotary-type sealing jaws, the path of the jaws may be such that the jaws remain in contact with the packaging material through a finite distance. Alternatively, in the simplest type of rotary arrangement the packaging material is only briefly engaged by the jaws while they are at about their 3 o'clock and 9 o'clock positions respectively; f
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Davison Clive
Kerry Malcolm Charles
Seaward David Robert
Johnson Linda
Molins, PLC.
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