Patent Application
20130092330
The present invention relates generally to industrial curtains used as environmental closures for openings through which traffic can still pass. The curtains generally comprise a plurality of strips suspended contiguously to each other from a hanger fixed adjacent to a top margin of the opening, each strip consisting essentially of a length of flexible material terminating adjacent to a lower margin of the opening. The present invention relates particularly to an improved configuration for the material forming the strips of such industrial curtains so that the electrostatic interaction between the strips is minimized.
Goods are often required to be transported from one area of a manufacturing or storage facility to another where one or the other of the areas is heated, air-conditioned or even refrigerated. Sometime other environmental concerns need to be addressed such as dust, fumes, smoke, dirt, or even noise. Where the traffic is only occasional, conventional doors can be employed to close any doorway between the two areas. Where the traffic is considerable, the use of conventional doors gives way to suspended flexible screens or curtains that inhibit the wholesale transfer of heated or cooled air from one area to the other yet still permit goods-transporting vehicles to pass through with little effort. Early screens were sometimes made of rubber as shown, for example, in U.S. Pat. No. 2,122,532. For safety reasons, it is desirable that the curtain be sufficiently transparent that one operating a transporting vehicle be able to see any hazard or obstruction that might exist on an opposite side of a screen before proceeding through. Persons on the opposite side of a screen also desire to be able to see oncoming transport vehicles so appropriate evasive action can be taken. Thus, plastic materials, which were more or less transparent, such as polyvinyl chloride and polyethylene, were adopted as the preferred materials for forming such screens as shown, for example, in U.S. Pat. Nos. 4,086,950; 4,095,642; 4,165,778; 4,232,725; 4,289,190; 4,367,781; 4,607,678; 5,127,460; 6,394,171; and 6,933,030.
Plastics such as polyethylene and polyvinyl chloride have two characteristics that have been recognized as detrimental to completely satisfactory performance in industrial doorway curtains. First, the plastic strips are often electro-statically attracted to each other so that they resist separation from each other as the goods and transporting vehicles attempt to pass through the curtain. This problem is particularly evident with the curtain is initially installed. Second, the plastics are generally much softer than the edges and corners of the transporting vehicles and goods packages that pass through the curtains. Thus, the curtain strips quickly become scuffed and scratched by the passing traffic to the point that the originally transparent strips become effectively opaque. In attempting to solve both of these and other related problems special overlapping attachments have been added to the strips, the edges of the strips have included bulbous enlargements, and ridges have been added to the body of the strips as shown, for example, in U.S. Pat. Nos. 4,086,950, 4,289,190 and 6,394,171. Despite these attempts to solve the problems of electrostatic attraction and visibility, the problems remain.
The present curtain strips attempt to directly address the problem of preventing scuffing and scratching of the strips of plastic forming the curtain thus ensuring substantially transparency of the strips and ensuring that vision through the strip is unimpeded while at the same time forming a curtain of minimal cost. A surprising and unexpected benefit has been observed in the present curtain strips of a demonstratively lower electro-static attraction to each other so that the frictional resistance to separation from each other as the goods and transporting vehicles attempt to pass through the curtain is much lower than prior art curtains.
The curtain strips can be formed to have a periodic variation in thickness in the width direction when viewed in cross-section comprising an alternating series of thicker portions separated from each other by thinner portions. The thicker portions can be of approximately the same width as the thinner portions. The thinner and thicker portions are united by narrower tapered regions of changing thickness. The narrower tapered regions of changing thickness can have a width of about ¼th the width of either the thinner or thicker portions. The thickness of the thicker portions can be about twice the thickness of the thinner portions. The lateral edges of the curtain strips are preferably of the same thickness as the thicker portions of the remainder of the strip. The curtain strips can be formed of any length appropriate for the dimensions of the doorway or other opening in which the strip curtain is to be deployed.
The strips consist essentially of a length of a flexible, substantially transparent material, such as polyvinyl chloride, having the desired longitudinal cross-section, which can be manufactured by way of a conventional extrusion process. The curtain strips can be assembled in an overlapping fashion as is conventional in such strip curtains. When such a strip curtain is constructed and deployed, a surprising effect is achieved of a demonstratively lower electro-static attraction between the strips so that the resistance to separation from each other as goods and transporting vehicles attempt to pass through the curtain is much lower than prior art curtains. Over time, the thicker areas of the curtain strips are observed to experience most of the frictional scuffing and wear while the thinner areas remain substantially transparent so as to give the curtain the desired visibility.
Other features of the present curtain strips and the corresponding advantages of those features will be come apparent from the following discussion of a preferred embodiment, which is illustrated in the accompanying drawings. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like referenced numerals designate corresponding parts throughout the different views.
An industrial traffic curtain 10 comprising a plurality of individually suspended strips 12 is shown installed in a doorway or opening 14 in
As shown in
When a strip curtain 10 is constructed and deployed using the strips 12 shown in
It can be seen from the graphs of
While these features have been disclosed in connection with the illustrated preferred embodiment, other embodiments of the invention will be apparent to those skilled in the art that come within the spirit of the invention as defined in the following claims.
