GB2134879A - A sealed letter-packet and method for the manufacture thereof - Google Patents

Abstract

A sealed letter-packet is formed by manufacturing the cover around the contents 2, one side of the cover consisting of paper 1 and the other side of a thermoplastic plastic film 3, welding together the film and paper around the contents at all four edges 9, 10,11 and 12 of the packet and providing the packet with perforation 13 within one welding area. <IMAGE>

Description

SPECIFICATION A sealed letter-packet and method for the manufacture thereof Especially when sending direct advertising, it may be desirable that the content of the packets is immediately seen, and therefore, it is eligible if the cover of the packet is transparent. It is already known to wrap e.g. printed matter in plastic films, which are folded around and completely surround said printed matter. The plastic is then often preprinted for the intended purpose. The machines that are used are large and expensive and therefore, the number thereof is small. The method has mostly been used in large issues. It is also desirous to use paper for covers to advertising packets, while the paper is more rigid and gives a more letter-like impression. It is also easier to provide a simple print on paper, e.g. flexography (sender, postal marks, etc.).Furthermore, it is easy to write by hand on paper, e.g. another address or print an address thereon.

The present invention relates to a sealed letterpacket which may be manufactured at a low cost also in smaller issues and wherein one side of said packet is made of paper and the other side is transparent. The invention also relates to a method for the manufacture of the packet.

The invention will be further described below with reference to the accompanying drawings, in which Figure 1 illustrates a letter-packet according to the invention; Figure 2 is a section along the line A-A in Figure 1; Figure 3 is a plan view of a principal method of manufacture; Figure 4 is a section along the line B-B in Figure 3; and Figure 5 shown on an enlarged scale a part of the method of manufacture of Figure 4.

Figures 1 and 2 illustrate a complete letterpacker in CS-size, i.e. 229 x 162 mm. One side of the cover, made of paper, is provided with reference numeral 1, and may preferabiy have a relatively large weight to provide rigidness to the packet. The content of the packet has reference numberal 2 and 3 is the other side of the cover, made of transparent plastic film. The packet is limited by the edges 4, 5, 6 and 7 of the paper 1.

The plastic film is limited by the edges 4, 5, 6 and 8 of the paper 1. The plastic film is limited by the edges 4, 5, 6 and 8. Immediately within its edges, the plastic film is welded to the paper in the welding areas 9, 10, 11 and 12. The welding areas 9, 11 and 12 are 5 mm wide and the welding area 10 is 10 mm. The distance between the plastic edge 8 and paper edge 7 is here 2 mm.

The content is during manufacture pressed very close to the welding areas 10 and 11.

Immediately within the welding area 10 there is a perforation 13, which has a sharp inward curve 14 in the middle in order to provide a thumb grip after opening the packet by tearing off the strip outside the perforation, such that the content is easily withdrawn from the cover of the packet. The perforation is made such that the cuts in the plastic film are positioned straight above the cuts in the paper. A window 1 5 is punched out in the paper and covered by a plastic film 1 6. This plastic film is welded between the paper and the plastic film 3 in welding areas 9 and 11. If the paper has no window for addresses, an address is easily printed or written thereon.

In Figures 3-5 a method of manufacture is shown in principal. Two packets are here manufactured beside each other. Reference numeral 1 7 designates the horizontal central line of the manufacturing machine, which also coincides with the central line of the paper web.

Reference number 18 designates the content of a packet which in a known manner consists of a number of sheets. The content comes in the horizontal plane towards the central line 1 7 from both directions. Feeders 1 9 convey the content in the manufacturing direction of the machine. These feeders are well known from conventional enveloping machines. Here, they may be designated such that they slightly resiliently press the content forward as far as possible. Reference numeral 20 designates a paper web, the width of which is here 458 mm. Reference numeral 21 is a punch and 22 is a die fitting thereto. The punch is used to punch out a window for addresses in the paper web. The length of the window is 70 mm.

Reference numeral 23 designates a plastic film the width of which is 80 mm and which covers said window. For the purpose of clarity, only the lower row of packets 24 is shown provided with windows. Reference numeral 25 is a plastic film, the width of which is 455 mm. The paper web and plastic films are folded around the stationary rolls 26 and 27, the width of which is 470 mm.

Reference numeral 28 designates rubber-coated rolls which are movable up and down. A stationary reverse roll 29 is provided beneath said rubber rolls 28. A heating back 30, the width of which is 400 mm, is surrounded by two narrow supporting plates 31 and 32, the lower outer edges of which are rounded. Heating backs are in Figure 3 marked completely black. The heating back 30 as well as its side supports 31,32 are movable up and down.

The welding areas provided by the heating back 30 are designated 33. A sheet 34 beneath the paper web supports said web and serves as a holder-on for the heating backs. A 1 62 mm long heating back 35 is movable up and down. The welding area provided thereby is designated 36.

Reference numeral 37 and 38 designate perforating rules which are movable up and down and which when depressed, simultaneously perforate the plastic film and paper. The perforations 39 are designed such that the content is easily withdrawn from the cover. Two plate rails 40 and 41 are positioned above the paper web but beneath the content. There are two identical rails (not shown) on the machine which are disposed above the content but beneath the plastic film 25. The distance between a pair of rails shall be only somewhat greater than the thickness of the content 1 8.Feeders 42 operate between the paper web and plastic film and convey the content towards the central line 1 7 of the web and film respectively, adjacent to the welding area 36 provided by the heating back 35, whereby the content is disposed between the curved perforation in the plastic film and the corresponding curved perforation in the paper. The displacement towards the centre, amounts here to about 1 5 mm. The feeding may occur resiliently, such that the content with a slight pressure is pressed towards the nip defined by the plastic film and paper. Heating backs 43 and 44, having a length of 162 mm, are also provided with a 25 mm long part protruding perpendicularly to the length of said heating backs.A thin knife 45 is provided for cutting the welded web along the central line 1 7. Driving pulleys 46 and 47 are provided for pulling forward the welded web.

Reference numeral 48 designates a knife which is movable up and down and 49 is a printing unit for flexography.

The manufacture occurs in such a way that the driving pulleys 46, 47 for 0.5 seconds pull forward the welded web a partition, i.e. here 1 62 mm, whereafter the web is still for 0.6 seconds before a new forward pull occurs, and so on. While the web is still, the window is punched out by means of the punch 21; welding occurs by means of the heating back 30; the content 1 8 is pressed towards the stop defined by the plastic film and paper web being pressed together by the heating back 30 or the plate 31 outside the heating back; depression of the heating back 35 occurs, depression of the perforating rules 37, 38 occurs; printing of sender and postal marks occurs by moving the printing unit 49 upwards; insertion of the content towards the welding area 36 by means of the feeders 42 occurs; and depression of the heating backs 43, 44 and the knife 48 occurs, whereby two finished packets are formed which fall down on the conveyor belt 50. Immediately before a forward pull, the rolls 28 are pressed downwards, whereby the content is clamped between the plastic film 25 and paper web 20 and brought along therewith when pulled forward. During the forward pull, the welded web is separated into two by the knife 45.

When using rigid paper and a soft plastic film it is important, especially when the content is thick, that more plastic film than paper is fed, which is permitted in the present method, such that no tension occurs in the plastic film which later might curve the packets.

While the content during manufacture is pressed against a welding area in each direction, the opposite welding areas may come close to the content and thus, the content is sealed with a very small lapping space.

If the packet shall be opened in the perforation without difficulty, the cut part must be large which weakens the perforation. Then, the perforation is especially susceptible to that a corner engages it from the inside. Since the content is effectively sealed with a very small lapping space, this risk is eliminated.

If trimming of the paper web is to be avoided, it must have correct width from the beginning, i.e.

here 458 mm. Since the plastic film shall not extend beyond that, it may be somewhat narrower to compensate for deviations thereof. The welding area 12 is in any way sufficiently wide. It can hardly be seen that the plastic film does not reach to the edge of the paper, contrary to if the plastic film had reached beyond that.

The strip outside the perforation may be reinforced by laying in a strong strip. The paper web may be covered with plastic. The plastic film may be a laminate, as long as the side thereof facing the paper web is thermoplastic. Even if the packet primarily is intended to be transparent, a plastic film that is coloured or opaque or laminated with paper is sometimes preferable. The manufacture of the packets is the same and is as inexpensive. The paper web may be pre-printed either with an endless print or with such a print that the feeding is controlled by guide marks in a manner known per se. Instead of manufacturing two packets beside each other, it is of course possible to manufacture only one. The perforation may be provided earlier than what is shown in the drawings, either entirely or only the curved portions. Even if it for many reasons is desirable to stick to standard measures, it is of course possible to depart therefrom. The letter-packet may be manufactured in any size and the welding areas may be made more narrow than illustrated.

Claims (6)

1. A sealed letter-packet containing printed paper sheets or similar, characterised in that one outer side of the packet consists of a rectangular, relatively rigid paper (1), the edges (4, 5, 6 and 7) of which define the outer contour of the packet; that the other outer side of the packet consists of a thin thermoplastic plastic film (3); that the plastic film along all of its edges is welded to the paper in areas (9, 10, 11 and 12) immediately within the edges of the plastic film; that a perforation (13) of the plastic film and paper is provided parallel to one outer edge and immediately within the corresponding welding area; that the content (18) of the packet is sealed with a small lapping space between the welding areas (10 and 12) parallel to said perforation; and that the content (18) of the packet is sealed with a small lapping space between the welding areas (9 and 11) perpendicular to the perforation.

2. Letter-packet according to claim 1, characterised in that the middle portion of the perforation is curved inwardly (14) over the content.

3. Letter-packet according to claim 1, characterised in that the perforation cuts are common for plastic and paper.

4. Letter-packet according to claim 1, characterised in that a window for addresses is punched out in the paper and that a plastic film is positioned above said window on the inner side of the paper, which film is welded between the paper (1) and the other side (3) of the cover in the areas (9 and 11) within the outer edges (4 and 6) of the packet.

5. A method of manufacturing a letter-packet according to claim 1, characterised by inserting between a paper web (20) which is fed step-bystep and a plastic film (25) which is also fed stepby-step, the content (1 8) of the packet in the feeding direction in such a way that the content is pressed very close to the nip defined by the web and film engaging each other; welding together said web and said film close to the nip; feeding the paper web and plastic film together with the content clamped therebetween, a distance corresponding to the length of a packet; welding together further on in the feeding direction, the plastic film and paper on each side of the content parallel to the feeding direction; and making a cut off perpendicular to the feeding direction for providing the separate packets.

6. Method according to claim 5, characterised by welding together a welding area (36) parallel to the feeding direction; making a perforation immediately within this welding area by simultaneously cutting the plastic film and paper where the perforation is made with an inward curve towards the packet; displacing the content perpendicular to the feeding direction such that the content comes close to the welding area (36) at the perforation and between the curved perforations; and welding together the welding area on the opposite side of the content.