Plastic and nonmetallic article shaping or treating: processes – Carbonizing to form article – Agglomeration or accretion
Patent
1990-11-29
1992-04-28
Woo, Jay H.
Plastic and nonmetallic article shaping or treating: processes
Carbonizing to form article
Agglomeration or accretion
21912167, 21912172, 264154, 425142, 4251744, 425290, B23K 2610
Patent
active
051086697
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a process and an installation of manufacturing a perforated tubular plastic foil through the action of a laser beam.
DESCRIPTION OF PRIOR ART
Such a process for perforating a plastic foil using a laser beam is known. Plastic foils perforated with a laser beam in fact constitute a very suitable material for the production of bags for packing loose material in suitable quantities of, for example, 25 kg. Since in the filling of the bags with loose powder-type material this loose material is conveyed with air, after the bag has been filled a quantity of air is left behind between the particles of the powder material, and this air must be able to excape while leaving the powder material behind in the bag. Moreover, after filling, these perforations permitting a rapid deaeration must also be sealed quickly and as well as possible, in order to prevent loss of material and the penetration of moisture into the bag.
However, when a plastic tubular foil lying in a flat position is being perforated, it is difficult to obtain perforations of the desired size. If the plastic foil material to be perforated is too thick, a conical perforation being large at the entry side of the laser beam and small at the opposite side is produced. This means that in a tubular foil which is lying flat a relatively large or even too large a perforation is produced in the top layer of the foil, and a relatively small or too small a perforation in the layer of the foil underneath it, which is integral with the top layer of the foil on which the laser beam acts directly and first.
Another disadvantage is that when the tubular foil is lying flat the two layers of plastic lying closely on top of each other are together of such great thickness that the laser beam is difficult to focus over the entire thickness of the two layers of foil, which means that during the perforation with the laser beam melting of the perforation edges occurs.
In the case of perforating the plastic tubular foil with a layer of air between the two layers of plastic of the tubular foil the problem is that the laser beam is then not focused sharply enough, while the amount of energy for formation of the perforations becomes unacceptably high, and consequently too large perforations are formed and are, moreover, formed in imprecisely defined places.
In order to avoid these shortcomings U.S. Pat. No. 4,254,916 discloses a process of manufacturing a perforated tubular foil by means of a laser beam wherein the wall part of the foil to be perforated is guided in a perforation forming plane by sucking said wall part onto a supporting surface located outside the tubular foil, the remaining wall part of the tubular foil being held free from the wall part to be perforated.
However, this process presents the disadvantage that often the foil surface to be perforated is not tautly sucked onto the tubular foil supporting means situated outside the tubular foil. This involves the formation of creases in the foil surface leading to perforations at the incorrect position and/or with incorrect dimensions.
SUMMARY OF THE INVENTION
The object of the invention is now to provide a process of manufacturing a perforated tubular plastic foil through the action of a laser beam on the tubular wall of a tubular foil thereby forming perforations ranging from 50 to 250 .mu.m in size, and in which perforations of the desired size are obtained in the correct plane and with the correct dimensions, without melting of the perforation edges and without inadmissibly high energy consumption.
Thus, the invention relates to a process of manufacturing a perforated tubular plastic foil through the action of a laser beam on the tubular foil wall, forming perforations ranging from 50 to 250 .mu.m in size, wherein during the perforation action the wall part to be perforated and lying free from the remaining wall of the tubular foil is guided in a perforation forming plane on which the laser beam is founded, as known from U.S. Pat. No. 4,254,916, being character
REFERENCES:
patent: 3931491 (1976-01-01), Stumpf
patent: 4028525 (1977-06-01), Mominee et al.
patent: 4254916 (1981-03-01), Havens et al.
patent: 4511520 (1985-04-01), Bowen
patent: 4672168 (1987-06-01), Saunders et al.
Patent Abstracts of Japan, vol. 10, No. 277, May 1986, 61-99594(A).
Koopman Roelof
van Dijk Berend J.
Davis Robert B.
Wavin B.V.
Woo Jay H.
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