Package making – Methods – Forming a cover adjunct or application of a cover adjunct to...
Reexamination Certificate
2000-05-08
2001-10-09
Vo, Peter (Department: 3721)
Package making
Methods
Forming a cover adjunct or application of a cover adjunct to...
C053S138400, C053S052000
Reexamination Certificate
active
06298635
ABSTRACT:
This invention relates to a method of setting up a machine for sealing closure clips between a stamp and a bottom tool, which for sealing the clip are first of all moved towards each other up to an adjustable sealing distance and are then moved away from each other. The invention also relates to a device for sealing closure clips between a stamp and a bottom tool.
BACKGROUND OF THE INVENTION
One application for methods as stated above and the corresponding device is the sealing of bag-shaped or tubular packages, such as for instance sausages. These are frequently sealed with U-shaped closure clips made of aluminum. High demands are made on the quality of such closure. It should not be so tight that the packaging casing is damaged when sealing the same. At the same time, however, the closure should be sufficiently tight, and during processing steps subsequent to the sealing of a sausage should not slip off the same. Due to these high demands made on the closure, the extent to which the clip is compressed upon completion of the sealing operation—subsequently referred to as clip height—must precisely be achieved for the respective type of package by adjusting a corresponding sealing distance. This is first of all effected empirically. Once the corresponding parameters for a type of product have been defined, they can be adjusted on the sealing machine. In the commercially available sealing machines it is generally possible to adjust the desired sealing distance. In most cases, a scale is provided, which provides for adjusting the same value for the clip height at a later date. Such sealing machine in the form of a desk top unit is known from DE-GM 19 33 066.
When the sealing machine has been adjusted to the corresponding product, the sealing operation is performed as follows:
First of all, a portion of a tubular casing is filled with the filling—for instance sausage meat. Subsequently, the filled sausage casing is pinched by two pairs of displacement shears. The same will then move away from each other axially with respect to the axis of the sausage and thus form a casing neck free from meat, which is disposed between the stamp and the bottom tool of the sealing machine. In the bottom tool, an open closure clip has been inserted. For sealing the closure clip, stamp and bottom tool are moved towards each other, so that the casing neck free from meat is seized by the open closure clip. Subsequently, the stamp impinges on the free legs of the U-shaped closure clip, bending the same about the casing neck. For sealing the casing neck, stamp and bottom tool first of all move towards each other, where they seal the closure clip and subsequently move away from each other, in order to release the closure clip. At the turning point of their movement, stamp and bottom tool have a sealing distance from each other which is decisive for the resulting clip height. The clip height of a sealed closure clip thus results from the actual sealing distance of stamp and bottom tool at the turning point between their movements towards each other and away from each other.
Since the system of levers moving stamp and bottom tool applies forces up to 2000 kg during the sealing operation, there will necessarily occur a certain wear. The resulting clearance is not considered when setting the sealing distance by means of the scale on the sealing machine. The consequence is that the scale reading does not correspond with the actual sealing distance and accordingly not with the actually resulting clip height either. Thus, the actually resulting clip height is not the originally determined desired clip height for which the sealing distance has been adjusted on the scale. Even during a current production, the wear caused by the clearance of the system of levers leads to the fact that the sealing distance of stamp and bottom tool is constantly increasing, so that the closure clips are sealed less and less tight and for instance during the subsequent processing of a sausage may slip off the same.
Accordingly, the users of such sealing machines are forced nowadays to newly check and possibly correct the tightness of the closure with each production start. However, the testing methods are quite specific and depend on the tester and thus are very subjective. The closure clip height very frequently lies below the required height for safety reasons, i.e. the closure clips are sealed too tight. As a result, the sealing machine is subjected to a much higher mechanical load than would actually be necessary, which leads to an increased wear and thus an early failure of the machine.
SUMMARY OF THE INVENTION
It is the object of the invention to be able to monitor the sealing distance independent of subjective influences. This object is solved by a method as stated above, where the sealing distance between stamp and bottom tool is detected by means of a sensor.
The gist of the invention consists in detecting the closure clip height actually obtained in operation as a result of the wear of bearings, etc. In accordance with the invention this is advantageously effected by measuring the sealing distance between stamp and bottom tool. This is based on the knowledge that the sealing distance between stamp and bottom tool is finally decisive for the quality of the closure. By indirectly measuring the sealing distance, all influences determining the sealing distance are considered as well, whereas on the other hand influences distorting the measurement result are avoided.
It is also conceivable to directly measure or change the sealing distance, in that the maximum sealing force is detected by means of a sensor, as is proposed by EP 0,467,020 A1. However, this variant has the disadvantage that the measurement also includes the friction forces occurring upon sealing the clip and the deformation resistance of the closure clip. The friction forces would be changed for instance by using greasy closure clips instead of dry ones.
A further advantage of the inventive method consists in that the sealing machine can be switched off automatically when no or two closure clips are present between stamp and bottom tool. In such cases, the required clip height is not achieved at all or exceeded with a correctly adjusted machine.
What is preferred is a method where for determining the sealing distance there is measured the distance between a distance sensor fixedly allocated to the stamp or the bottom tool and a reference surface fixedly allocated to the respective other part (bottom tool or stamp). This measurement is preferably effected in a contactless way, in order to avoid a mechanical wear and an unnecessary formation of noise.
The sealing distance is readjusted when the measured sealing distance lies outside a range of desired values for the sealing distance. This is preferably effected automatically. There is obtained a closed loop for monitoring the closure clip height during the operation, by means of which expensive production losses due to incorrectly sealed packages or undesired interruptions for readjusting the closure clip height can be prevented.
The adjustment of the sealing distance between stamp and bottom tool is for instance effected, as is known from DE-GM 19 33 066, by changing the geometry of the stamp drive. This can particularly easily be effected in that the sealing distance is adjusted by changing the length of a lifting rod in the stamp drive.
The inventive solution of the object also consists in a device as stated above, which includes a sensor for detecting a sealing distance between stamp and bottom tool as well as a means for adjusting the sealing distance between stamp and bottom tool. With such a device it is possible to determine the closure clip height while avoiding all possible points of wear, and the user can thus benefit from all advantages of the method in accordance with the invention.
In a preferred embodiment of the device the sensor is fixedly mounted with respect to the bottom tool or the stamp and corresponds with a reference surface fixedly mounted with respect to the respective other part (stamp or
Bienert Olaf
Ebert Detlef
Gerheim Manfred
Huynh Louis K.
Norris & McLaughlin & Marcus
Poly-Clip System GmbH & Co. KG
Vo Peter
LandOfFree
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