Tubular bagging machine

Details Tubular bagging machine Tubular bagging machine

1999-03-25

2001-01-02

Sipos, John (Department: 3721)

Package making

With means responsive to a sensed condition

Of package and filled receptacle closing or opening

C053S551000, C053S374800

Utility Patent

active

06167677

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to a tubular bagging machine, and more particularly to a tubular bagging machine with two cross-sealing jaws, which can be moved toward one another and thereby cross-weld a foil tube, a mechanism for moving the cross-sealing jaws, a transporting device for moving the foil tube and a longitudinal welding device for the foil tube, a filling device, a separating device for separating individual, filled tubular bags, a device for measuring the pressure of the cross-sealing jaws, and a machine control device.
BACKGROUND OF THE INVENTION
Such a tubular bagging machine is known from the EP-OS 0 469 105. The path of the cross-sealing jaws is in this machine fixedly specified by a machine controller. The cross-sealing jaws weld a foil tube transversely with respect to its transporting direction. The foil tube is welded by the cross-sealing jaws to create a cross-sealing seam after a product portion is fed into the foil tube.
It can happen in the case of certain product type that a product portion is not sufficiently compactly fed into the foil tube and therefore extends into an area of the foil tube to be cross-welded. In particular, relatively light, large-surface product particles like potato chips have the tendency to sail during free fall and thus result in a wide product swarm, the compactness of which can be very different from one product portion to the next product portion.
Product entrapped in a cross-sealing seam can result in a leaky tubular bag. Such a tubular bag is then removed from a packaging system. In particular in the case of smaller product entrapments in a cross-sealing seam it can additionally happen that the entrapment is not noticed and the defective tubular bag is forwarded for further packaging.
SUMMARY OF THE INVENTION
The basic purpose of the invention is to develop a tubular bagging machine of the above-described type in such a manner that large and small product entrapments in a cross-seam can be reliably recognized, and that upon recognition of such a product entrapment a signal can be produced.
The purpose is attained by providing a tubular bagging machine which has a device for recognizing product enclosed between the cross-sealing jaws, this device includes the cross-sealing jaws and the drive, the drive being a servomotor, the cross-sealing jaws consisting of a light metal, and has evaluating electronics for evaluating the performance characteristics of the servomotor and cross-sealing jaws and forwards these values dependent on the jaw position to the machine controller.
It is achieved with the tubular bagging machine of the invention that even small product entrapments in a cross-sealing seam can be reliably recognized, and that upon recognition of a product entrapment a signal can be produced.
The recognition of the product entrapment is done through a further evaluation of the performance resistance (characteristics) of the servomotor for driving the cross-sealing jaws and a comparison of this value with a desired value at the same jaw position at which the performance resistance was evaluated. If the momentary performance resistance is too high, a product entrapment in a cross-sealing seam to be welded and thus a product entrapment between the cross-sealing jaws can be determined. A measured performance resistance, which is too high, results in a reaction of the machine control or initially only in an error alarm. It is sufficient to evaluate one single momentary performance resistance. However, it is also possible to evaluate a plurality of momentary performance resistance. Several measurements of the momentary performance resistance during a cross-welding operation increase the precision of determining if a product entrapment has occurred.
Since the cross-sealing jaws consist of a light metal, they have in comparison to the commonly used steel clearly reduced dimensions, and the exactness for the measuring and evaluating of the performance resistance of the servomotor are clearly more exact than they would be if steel was used. A product entrapment recognition can only through this structure occur in a reliable manner.
Further, advantageous developments of the tubular bagging machine of the invention are below described.
A compact electronic construction is achieved when the evaluating electronics is integrated into the machine controller. Whereas, ease of servicing the tubular bagging machine is improved when the evaluating electronics is arranged separately from the machine controller.
A further advantage is achieved when the tubular bagging machine is a vertical tubular bagging machine since in the case of a vertical tubular bagging machine the danger of a product entrapment is greater than in a horizontal tubular bagging machine.
When the cross-sealing jaws are part of a rotating, continuously working jaw system, wherein the cross-sealing jaws rotate in opposite directions about respective axes, which extend parallel to one another, then the packaging speed can be greater than in a discontinuously functioning jaw system since a jaw standstill does not happen. In principal, however, it is possible to utilize the invention both in a continuously and also in a discontinuously working jaw systems.
The sensitivity regarding a product entrapment recognition is clearly increased when the cross-sealing jaw or a movable carrier of the cross-sealing jaw is made of a light metal, for example magnesium alloy. A magnesium alloy has a density of 1.7 kg/dm
3
which is clearly a lower density than steel, the density of which lies between 6.3 and 8.1 kg/dm
3
. Thus, the moved mass of a light metal cross-sealing jaw or carrier are clearly reduced when using a magnesium alloy. Since the sensitivity is increased at a decreasing mass, a very exact and thus also reliable product entrapment recognition can occur through the use of the magnesium alloy.
The thermal conductivity of the magnesium alloy (170 W/mK) is clearly higher than steel (15 to 45 W/mK) so that in addition the cross-sealing jaws have a clearly more exact and more even temperature than steel jaws along their sealing surfaces.
The momentary position of a cross-sealing jaw can be recognized by the servomotor through the operating time of the servomotor, which clearly simplifies recognizing the position of the cross-sealing jaws.
When both values of the jaw drive for the momentary jaw position and also corresponding values of the evaluating electronics are fed to the machine controller, then the machine controller can start a reaction to a product entrapment in a cross-sealing seam, for example, a bag expulsion operation, and thus the removal of the defective tubular bag from the further packaging processes.
When sensitivity for a product entrapment recognition is programmed in the evaluating electronics as a tolerable deviation of an actual measured value from a desired value for a value stored in the evaluating electronics, then the sensitivity for the recognition of a product entrapment can be changed. This is useful, for example, for changed machine parameters.
It is of interest in most cases that a product entrapment recognition is supposed to occur only within a certain jaw spacing since only at this jaw spacing, which lies, for example, near zero, a measurable increase of the jaw pressure occurs and is measured as the performance resistance. It is then advantageous when the jaw spacing is programmed in a range within which a product entrapment recognition occurs, in particular when a measurement of the momentary jaw pressure occurs at closed or almost closed cross-sealing jaw positions. The difference between actual value and desired value is in the case of a product entrapment the greatest in these positions.
In case of an error alarm because of a recognized product entrapment a machine stop can occur immediately so that the cause of the product entrapment can be determined and prevented in future packaging operations.


REFERENCES:
patent: 3778588 (1973-12-01), Bishel
patent: 3905174 (1975-09-01), Heisler
patent: 3925139 (1975-12-01), Simmons
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