Textiles: cloth finishing – Expanding device for textile webs – Spreader
Patent
1997-12-03
1998-10-27
Vamatta, Amy B.
Textiles: cloth finishing
Expanding device for textile webs
Spreader
26 90, D06C 306
Patent
active
058263144
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a device for transversely (in the widthwise direction) stretching a stretchable web such as a film, a fibrous material or a net-like material.
BACKGROUND ART
The most popular device for transversely stretching the above described kind of web is a tenter. However, a tenter is large in size to require a wide space for the installation thereof and is generally expensive. Accordingly, there is proposed a device for transversely stretching a web which is small in size and simple in structure, wherein a pair of pulleys and a pair of belts are combined.
FIG. 7 illustrates a device for transversely stretching a flat web, which is disclosed in Japanese Examined Patent Publication No. 57-30368. In this device, a pair of pulleys 2, 2' having the same shape and same size are held in a cantilever manner on the same side in symmetry with each other relative to a center line 1, and driven for rotation at the same speed in the opposite directions in the same vertical plane, as shown by arrows. A pair of belts 3, 3' are arranged to circulate, starting from generally vertical and parallel path portions closer to the center line 1, through semi-circular portions guided by the lower halves or less of circumferences of the pulleys 2, 2' to the starting points via guide pulleys 5, 6 and 5', 6', respectively.
Releasing points of the belts 3, 3' from the circumference of the pulleys 2, 2' are determined by positions of the guide pulleys 5, 5' relative to axes of the pulleys 2, 2', and the tensions of the belts 3, 3' are adjusted by displacing the guide pulleys 6, 6' upward or downward. The lower semi-circular portions of the pulleys 2, 2' are immersed into a hot bath 9.
A web 10 to be stretched is fed along the belts 3, 3' running generally vertically downward, so that a center line of the web coincides with the center line 1 between the belts 3, 3', and on the side of the pulleys 2, 2' opposite to the cantilever shafts of the pulleys 2, 2'. Selvages of the web 10 are bent by selvage guides 11 and the bent portions are gripped between the belts 3, 3' and the pulleys 2, 2'. The selvages are pressed onto the circumference of the pulleys 2, 2' by the tension of the belts 3, 3' without slip, and the web is introduced into the hot bath 9 along divergent arcuate tracks as the pulleys 2, 2' rotate, so that a portion of the web 10 between the selvages is transversely stretched until the belts 3, 3' are released from the pulleys 2, 2'.
In the above mentioned prior art web stretching device, it is difficult to securely grip the selvages of the web. Although the selvage guide 11 is used for bending and guiding the selvages, either one of the selvages often drops off from the pulley in practice because of the heterogeneity of the web to be stretched, a slight difference or fluctuation in the gripping position or a slight difference in the pressure between both the assemblies of pulley and belt as well as the meandering movement inherent to web transportation. Thus, a stable operation of the device is difficult to achieve.
To solve the above drawback, as shown in FIG. 8, a device disclosed in Japanese Unexamined Utility Model Publication (Kokai) No. 57-16320 is provided with selvage pressing rolls 17, 17' for pressing the selvages of the web 10 onto the belts 3, 3' prior to the introduction of the web 10 to the pulleys 2, 2'. The grip reliability is somewhat improved, since the pressing rolls 17, 17' press the web 10 onto the belts 3, 3' without inclination, but the grip instability is not fundamentally solved. Also, according to this method, a wide salvage is necessary to obtain a large gripping force, with the result that the salvages which are not stretched increase to a great extent, and yield of the material and production cost are deteriorated.
SUMMARY OF THE INVENTION
An object of the present invention is to solve the above described problems of the prior art and to provide a device for transversely stretching a web by which effectively prevents the web from dropping from the grip
REFERENCES:
patent: 1238742 (1917-09-01), Butler
patent: 2988772 (1961-06-01), Horn
patent: 3509607 (1970-05-01), Fleissner
patent: 3807004 (1974-04-01), Anderson
patent: 3833973 (1974-09-01), Schwarz
patent: 4331624 (1982-05-01), Yazawa et al.
patent: 4349500 (1982-09-01), Yazawa et al.
patent: 5043036 (1991-08-01), Swenson
Aihara Kintaro
Kurihara Kazuhiko
Yazawa Hiroshi
Nippon Petrochemicals Company Limited
Polymer Processing Research Inst. Ltd.
Vamatta Amy B.
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