Clip with rocking bearing for stretching machines

Details Clip with rocking bearing for stretching machines Clip with rocking bearing for stretching machines

1991-12-27

1993-12-07

Crowder, Clifford D.

Textiles: cloth finishing

Expanding device for textile webs

Spreader

26 89, D06C 304

Patent

active

052673782

DESCRIPTION:

BRIEF SUMMARY
The invention relates to a clip for detachably holding a moving fabric web.
Clips are for clamping fabric webs, particularly sheet webs, when the sheets are moved horizontally. For example, in a device for stretching plastic sheet webs, a closed guiding device is provided on opposite sides of the web and is symmetrical to the conveying direction. A guiding device on which endless clip chain links or clip carriages are connected with one another are provided, the clips gripping the fabric or sheet web at the beginning of the device and moving it forward to the end of the device.
Clip levers on the clips are pivoted at the beginning of the device by appropriate operating links, into their closed locked position, in which they hold the fabric or sheet web clamped between a clamping piece and a clip table, and, at the end of the device into their open position, in which they again release the fabric or sheet web. The clips, according to the prior art, are provided with a pin bolt, which is supported in a journal bearing mounted on the clip body.
The manufacturing costs for such clips and clip bearings are considerable, particularly because their manufacture requires adherence to the highest of tolerances. This can readily be seen, for example, in that the plastic sheet webs to be clamped have a sheet thickness of up to about 2 microns. The required tolerance for the clips should therefore be at least 1 micron.
Furthermore, there is always the problem that the journal bearings, particularly in devices for stretching plastic sheet webs, become, over time and use, increasingly dirty. This leads to undesirable stiffness of the clip levers or, in extreme cases, even prevents a pivoting motion of the clip levers. The problem of dirt accumulation and deposits occurs especially when stretching sheets with high proportions of additives, such as those added to plastic sheets, for example, to prevent an antistatic charge, to increase sealing qualities and also to place barrier layers in the plastic sheet webs. The deposits from these additives in the bearings leads to dirt accumulation and sticking, by which the efficiency of the unit as a whole is reduced.
Cleaning and removing deposits of this type from the prior art clip levers is costly. While the actual clamping piece can often be cleaned by pivoting the clip lever into a cleaning position, the removal of the clip levers in total from the device is often necessary to effectively clean the pivot journals. This requires the removal of a whole clip carrier or clip body in order to gain access to the rotating shafts. The assembly and disassembly of the clips is thus time-consuming and expensive.
The object of this invention is therefore to overcome the disadvantages according to prior art and to create a clip that avoids sticking even should sheet deposits and dirt accumulation occur. It is also an object hereof to assemble and disassemble clips of this type much more easily than the clips of the prior art.
According to the present invention, a bearing arrangement of the clip lever is provided in the manner of a cradle, i.e., a swiveling axis body-free bearing arrangement. This cradle bearing arrangement can take place in the manner of a "knife-edge bearing" or in the manner of a "roller bearing". In such a knife-edge bearing, the knife edge tapers and lies in a wedge-shaped bearing surface. Consequently, when high surface bearing pressures occur, a self-cleaning action occurs. Accumulations of sheet deposits and dirt are automatically pressed out of these bearing surface areas. Accumulations of these types in this bearing surface area may have a certain lubricating effect and contribute to the reduction of friction. The bearing surfaces hereof do not have narrow cross sections that can become clogged or gummed up, and operating safety is also increased. Finally no further lubrication is necessary. As a further advantage, the cradle bearing enables the clip lever to have high opening and closing speeds and for this purpose requires only little opening force. A so-called

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patent: 1928930 (1933-10-01), De Juhasz
patent: 3748704 (1973-07-01), Schmidt et al.
patent: 3948508 (1976-04-01), Kanazawa
patent: 4658482 (1987-04-01), Lechner

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