Plastic article or earthenware shaping or treating: apparatus – Means applying electrical or wave energy directly to work – Sonic or supersonic wave energy
Reexamination Certificate
2000-10-02
2003-01-21
Silbaugh, Jan H. (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Means applying electrical or wave energy directly to work
Sonic or supersonic wave energy
C425S445000, C156S580100, C156S580200
Reexamination Certificate
active
06508641
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a device for processing a continuously moving strip of material. In one such device, an ultrasonic generator unit having a sonotrode also has a facing counter tool, each of which is supported in a machine frame. The strip of material is passed through a gap between the sonotrode and the counter tool. A drive presses the sonotrode against the counter tool, with rigid and positive lock support on the machine frame.
Such a device is described in German Patent DE 195 26 354 C1. The processing includes, for example, reinforcement of a nonwoven made up of thermoplastic fibers, by melting the fibers in certain spots. In order to achieve an optimum processing effect, the distance between the sonotrode and the counter tool, i.e. the sheath surface of the relief applied to it, must be very precisely maintained. For this reason, the known device has a sensor that detects the gap height between the sonotrode and the counter tool, and the signal of this sensor is used to regulate the distance. However, precise and reliable detection of the gap height is a difficult undertaking and requires a complicated measurement device.
Adherence to a certain gap height must take place with such precision because any temperature variations at the sonotrode and the accompanying thermal expansions play a significant role. For this reason, a sensor that detects the temperature of the sonotrode is provided in the device according to German Patent DE 195 13 246 C2, and its signal is used to influence the gap height. However, only a partial aspect of the variable that changes the gap height is detected in this way, namely only the temperature-related displacements.
SUMMARY OF THE INVENTION
The present invention is directed to the task of better maintaining and controlling this gap height so as to provide a more uniform process.
This task is accomplished in the context of a counter tool that has a uniform embossing density. A force measuring member whose signal serves to regulate the drive is placed between the drive and the sonotrode.
By regulating the force exerted by the sonotrode, the other variables that influence the gap height are also detected. If the sonotrode becomes hot, and if the gap height decreases as a result, the force at the sonotrode increases, and the sonotrode has to be pulled back slightly from the counter tool. If the material thickness varies, this is expressed in variations in force, which can be evened out by means of the invention, so that a uniform processing effect is obtained once again.
The force measurement takes into consideration that variable that more or less includes the consequences of the other influence variables. Such a method of regulation takes place with a reference variable that is a direct determinant of the processing effect. In this connection, the measurement of force is significantly simpler, compared with a measurement of distance. At the same time, all the decisive factors are taken into consideration, in contrast to a measurement of temperature, which can only take into consideration the changes in gap height that are attributable to the temperature.
It is important that the sonotrode is supported rigidly, with a positive lock. What this means, of course, is a rigidity that can be achieved by the design, which prevents any elastic retraction of the sonotrode due to the forces transferred by the strip of material, to the greatest extent possible. As a result, there is no vertical swing response of the feed unit if the sonotrode is excited from the direction of the strip of material or the embossing roller. In this way, very high production speeds can be achieved.
However, the pressure force of the sonotrode can only be detected with sufficient accuracy, and used to regulate the gap, if the embossing density of the counter tool remains uniform, i.e. if there is always an equal number of embossing points (force concentration points) under the sonotrode foot as the rotating embossing roller, i.e. the counter tool, turns. The embossing density does not remain uniform, in this sense, if there are lengthwise ridges (parallel to the roller axis), for example, on the embossing roller. During the rotation of such an embossing roller, the force will vary, and there will be maximums at the locations of the lengthwise ridges. Here, the force cannot be clearly detected and used as the basis for regulation. Therefore a uniform, homogeneous embossing pattern, in accordance with a uniform bonding or perforation pattern, must be present, so that as the roller rotates, the contact is essentially constant.
If the force measurement is based on that variable that is a direct determinant of the processing effect, then regulation based on it is only optimal if it can detect the force free of any systematic errors.
To that end, the sonotrode can be moved along with the ultrasonic generator unit on a common carriage on a linear guide directed against the counter tool, with an additional carriage which can be moved on a linear guide on the side on which the drive engages. The force measuring member is arranged between the two carriages. This structure ensures that detection of the force remains free of lateral forces. Because the sonotrode carriage and the additional carriage are jointly guided on the straight-line guide, the force measuring member detects precisely and only those forces that act to press the sonotrode against the counter tool.
An important part of this design is the connection between the carriage at which the drive engages, and the machine frame; while this connection is variable in length, it becomes rigid at a certain length. Because of the rigid support of the sonotrode on the machine frame that is achieved in this way, the device is less sensitive to vibration than, for example, a pneumatic system for pressing the sonotrode down. Therefore the production speeds can be increased with this design of the drive.
German Patent DE 44 39 284 C2 discloses a sonotrode having rigid supports.
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Eduard Kusters Maschinenfabrik GmbH & Co. KG
Heckenberg Donald
Kenyon & Kenyon
Silbaugh Jan H.
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