Electric heating – Metal heating – By arc
Reexamination Certificate
2000-03-20
2002-07-09
Elve, M. Alexandra (Department: 1725)
Electric heating
Metal heating
By arc
C219S121630
Reexamination Certificate
active
06417483
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention concerns a method and a device for welding the ends of tubular containers, in particular tubes, made from a thin-walled flat material which can be softened and melted by heat, wherein the tubular container is held such that the end to be welded is accessible and the tubular container is heated about a peripheral region at the accessible end to a temperature enabling welding and the heated end is pressed together along an elongated welding seam traveling transverse to the longitudinal extension of the container.
Many pourable or pasty media are packed in tubes e.g. cosmetics, tooth paste, shoe polish, creams and the like. The tubes can be made from a suitable malleable metallic, flat material. However, plastic has been utilized for same time, primarily for economical reasons.
Prior to sealing the end of the tubular container blank, the container is initially filled with the material to be packaged. The removal side is sealed with a suitable cap, such as a screw-on cap or the like. The fill end is sealed after filling. With malleable flat materials, the filling end has been conventionally folded along a line. Optionally, a linear pressing is effected in the end region. In this manner, an acceptable seal is guaranteed. However, this procedure cannot be used for plastics: the adjoined end must be welded or otherwise sealed.
DE 37 44 402 C2 discloses a method for sealing tubular containers made from plastic in which the end section is initially softened or melted in a suitable fashion through the introduction of heat prior to producing a sealing seam through pressing.
The softening is thereby effected by disposing a ring about the filling end provided with a series of nozzle openings, by means of which hot air is blown onto the outer wall of the filling end of the tube. Since a complete welding is normally required, substantial amounts of heat must be introduced externally, i.e. up to about 18 kW of electrical power. This method is prevalent in packaging technology today and is designated as the “hot-air” method.
In analogy to the hot-air method, a softening or melting of the end which is to be welded has been conventionally effected using ultrasound or microwave radiation.
All methods require the melting and subsequent pressing to be carried out in sequential product steps, since the device for melting the material cannot occupy the same space as the pressing device. In addition, it is normally necessary to cool down the initially heated tube following the pressing step, since undesirable plastic deformations could otherwise occur and the product might also be damaged by the heat. The additional effort associated with this cooling process makes the method extremely wasteful.
DE 22 61 388 describes a method for welding an end piece made from plastic to a tubular plastic body, with which a tubular section of the end piece is inserted into the tubular body. A laser is used to irradiate the outer side of the tubular body, whereby the tube rotates with the end piece. A pressing roller presses the warmed region together to effect a type of weldment.
SUMMARY OF THE INVENTION
It is the underlying purpose of the invention to create a method and a device for welding the ends of tubular containers, in particular tubes, which can be used for all types of tube plastic, which has low energy consumption and which guarantees a high production speed in a simple manner.
This purpose is achieved with a method for welding ends of tubular container filled with a pourable medium, in particular tubes, made from a thin-walled flat material which can be softened and melted by heat, wherein the tubular container is held such that the end to be welded is accessible and the tubular container is heated about a peripheral region at the accessible end to a temperature enabling welding and the heated end is pressed together along an elongated welding seam traveling transverse to the longitudinal extension of the container, wherein the tubular container is held stationary and a laser beam is directed, via a deflection element disposed outside of the tubular container, onto the inner wall of the tubular container, and the deflection element is set into rotation to heat the peripheral region.
The purpose is also achieved with a device for welding tubular containers filled with a pourable medium, in particular tubes, made from a thin-walled material which can be softened and melted by heat, having a holding device in which the tubular container is held such that the end which is to be welded is directed upwardly, and with a deflection element borne for rotation above the container and set into rotation via a rotational drive device, and with a laser whose beam is directed onto the deflection element in such a fashion that the laser beam coming from the deflection element is directed towards the inner side of the container proximate the open end to warm a peripheral region of the container, and with a pressing device for pressing together the upper end of the container to form a welding seam extending transverse to the axis of the container.
Naturally, the laser beam can only produce a light point or spot on the peripheral wall. Since a flat ring-shaped region extending about the periphery must be softened, a relative rotation between the laser beam and the container is necessary when only a laser light spot is used.
In the apparatus in accordance with the invention, the heating device comprises a laser whose beam is directed onto the inner peripheral wall. A rotational drive device rotates the laser beam relative to the tubular container by axially rotating an optical deflection element disposed outside of the container, about its own axis, with respect to the incident axis of the laser beam. The point of rotation of the deflection element is thereby disposed such that the point of reflection of the deflection mirror is precisely located on the rotational symmetry axis of the tubular container.
Direction of the laser beam onto the inner wall of the tubular container has the advantage that those regions of the tubular container are warmed which are directly utilized for welding.
A deflection mirror is preferentially utilized as the deflection element and is optimized to the associated wavelength. The deflection mirror is preferentially adjustable to change the deflection angle. A change in the deflection angle can permit adaptation to differing container diameters by varying the height of the laser light spot relative to the deflection mirror in the plane of rotation downstream of the deflection mirror. One can adapt to differing container radii relative to the central point of the deflection mirror through a relative upward displacement of the laser light spot (compared to containers having small radii) to compensate for the increased distance to the container wall. Instead of changing the deflection element angle, the deflection element can be linearly adjusted along the rotation symmetry axis of the tubular container to adjust the relative height of the laser light spot.
One should further note that rotation of a filled tubular container is disadvantageous for various reasons and the centrifugal forces associated with the required speed tend to push the product in a vertical direction towards and through the open end. For this reason, the laser beam or the deflection mirror are rotated. The average reflection point on the surface of the deflection mirror is preferentially rotated in the longitudinal axis of the tubular container.
Use of a suitable configuration for the laser deflection mirror and the container, with the deflection mirror being disposed outside of the tubular container, allows the tubular container to merely be positioned below the deflection mirror during production, prior to the warming and welding procedure.
Additional advantages result from the use of not one but two deflection mirrors. In this case, one deflection mirror is introduced onto the rotational symmetry axis of the tubular container such that this deflection mirror reflects the laser beam th
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