Electrical generator or motor structure – Dynamoelectric – Linear
Patent
1998-05-05
2000-03-28
Ramirez, Nestor
Electrical generator or motor structure
Dynamoelectric
Linear
318135, 318 38, H02K 4100
Patent
active
060435712
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a linear-motor-driven transport installation, in particular a simultaneous stretching installation, in which linear-motor-driven carriages or tenter-clip carriages are advanced on a circulating track, and drive devices for carriages or tenter-clip carriages are provided, in particular for braking, on a return section of the track between a running-out zone and a running-in zone.
Linear-motor-driven transport installations, in particular stretching installations, are disclosed, for example, by U.S. Pat. No. 5,072,493, DE 29 30 534 A1, DE 195 10 281 C1 and U.S. Pat. No. 5,036,262 or U.S. Pat. No. 4,853,602.
These may concern synchronous, asynchronous or else hysteresis motor-operated linear drives.
As known, in such cases the circulating tenter-clip carriages are accelerated with increasing intensity from a running-in speed in the running-in zone in the following stretching zone, their distance from one another increasing. In a customary subsequent relaxation or setting zone, the speed of the tenter clips is reduced slightly with respect to the speed at the end of the stretching zone.
In the subsequent deflecting zone, and in particular on the return side, the tenter-clip carriages are again braked with increasing intensity down to the speed in the running-in zone.
To achieve appropriate film properties, during operation of the installation a specific speed profile is prescribed for the film side, in other words for the side on which the tenter-clip carriages grip the edge of the film, hold it securely and stretch it. Since it is intended that the speed of the installation can also be changed while production is in progress, and at the same time the number of tenter-clip carriages is constant during the operation of the installation, for this reason the following relationship must also hold even after a change in the speed profile ##EQU1## where x=position of the running carriage
On the basis of this relationship, the process control system is capable of determining the necessary decelerations in the braking zone and the required speed in the transporting zone for each operating state.
Thus, since in the case of such transport installations the total number of tenter clips is prescribed and can be changed only when the installation is at a standstill and, moreover, the number of tenter clips on the process and film side is already prescribed by the prescribed process conditions (namely the longitudinal stretching ratio), the difference from the total number of tenter clips on the return side of the installation (after the tenter clips have released the edge of the film) must be set and changed on this basis, according to the installation conditions. To be able in this case to accommodate any number of tenter clips on the return side, the average distance between the tenter clips must be variable, this distance being defined by the speed profile, as is described inter alia in U.S. Pat. No. 4,825,111.
In the case of the apparatus shown in U.S. Pat. No. 4,825,111, each tenter clip on the return side runs through three regions. In the first region, the tenter clips travel at constant speed, which corresponds to the final film speed. Thereafter, the tenter-clip carriages are decelerated in one or more stages. In the third region, the tenter-clip carriages again travel at constant speed, which is equal to the running-in speed. To set the average distances between the tenter-clip carriages appropriately on the return side, the limits between the regions are shifted. For this purpose, corresponding motors, which are capable of braking the tenter clips and/or continuing to maintain the transport of the tenter clips, are provided over the entire length of the return.
Against this background, the object of the present invention is to take the prior art cited above as a basis and, in a linear-motor-driven transport installation, optimize the braking on a return section of the carriages advanced along the linear-motor-driven transport installation.
The present invention makes it possible to reduc
REFERENCES:
patent: 3803466 (1974-04-01), Starkey
patent: 4220899 (1980-09-01), von der Heide
patent: 4769580 (1988-09-01), Goetz et al.
patent: 4825111 (1989-04-01), William et al.
patent: 4853602 (1989-08-01), Hommes et al.
Colvin R: "Magnetic Linear Drive Increases Speed of Biaxial Orientation Unit" Modern Plastics International, Bd. 26, Nr. 3, Mar. 1, 1996, p. 26/27 XP000587688 see figure 3.
Kreiner Rudolph
Oedl Gunter
Zintz Wolfgang
Bruckner Maschinenbau GmbH
Jones Judson H.
Ramirez Nestor
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