Fabric light control window covering

A fabric light control window covering in which fabric vanes are adhesively bonded between two sheer fabric sheets such that relative movement between the sheer fabric sheets in a direction perpendicular to the longitudinal direction of the fabric vanes changes the angle of the fabric vanes and, thus, controls the amount of light admitted through the shade. The vanes are bonded to the sheer fabric sheets in a manner which tends to bias the sheer fabric sheets together to the nonlight admitting position. Also, disclosed are methods and apparatus for manufacturing the above window covering. The method features linear application of adhesive to the vane material which provides for a uniform appearance in the finished product. A heat setting process and apparatus is disclosed in which the bonded layers of sheer fabrics and vanes are fed between belts over hot and cool surfaces, under uniform tension and pressure. This provides for heat setting of the layers of the window covering to a uniform temperature-size relationship without inducing wrinkles or distortion into the fabric during heat setting.

BACKGROUND OF THE INVENTION

The present invention relates to window coverings and, more particularly, to fabric window coverings provided with adjustable vanes for controlling the amount of light passing therethrough. The present invention also includes methods and apparatus for producing such a window covering.

Fabric window coverings are often preferred by consumers for a number of their features. The features most often considered desirable are the softer appearance relative to traditional Venetian blinds, the uniform appearance which they provide a window, and the insulating properties associated with cellular fabric shades.

Cellular fabric shades offering these features are known in the art. For example, U.S. Pat. No. 4,450,027 to Colson discloses cellular window coverings which may be made of fabric or film materials. In the process disclosed in the Colson patent, a flexible strip material is folded into a continuous longitudinal tube and the longitudinal folds thus created are permanently set by passing the tubing material around a heat setting wheel.

Adhesive is applied along one side of the flattened tubular material which is subsequently stacked by winding onto a rack having flat surfaces. The winding in this manner presses the adhesive to the next layer wound onto the rack to form a bonded unitary stack of closed tubular cells. When the ends are cut from the rack the stack may be expanded and the permanently set creases provide a neat and uniform outward appearance.

U.S. Pat. No. 4,732,630 to Schnebly discloses a modification to the Colson process described above. In the Schnebly patent a hot-melt adhesive is applied to one side of the tubular material. After the flat tubular strips have been stacked and cut, they are placed in an oven under pressure and the hot-melt adhesive is activated to bond the layers together.

Both of the above patents disclose window coverings which exhibit the desirable features discussed to this point. However, window coverings of that type lack one feature which is often desired by consumers. That feature is the ability to control the amount of light admitted through the window covering, similar to a traditional venetian blind. There have been some attempts to provide a fabric window covering with the ability to control the amount of light entering the room. However, these attempts have lacked one or more of the features discussed above and have been less than successful.

U.S. Pat. No. 3,384,519 to Froget discloses one such attempt. The window covering disclosed therein consists of two cloth layers spaced apart by movable parallel blades having each of their marginal edges heat-welded to one of the movable cloth layers. With this window covering, relative movement of the two cloth layers in a direction perpendicular to the blades changes the angle of the blade and thus controls the amount of light admitted through the article. A number of undesirable features of the Froget window covering derive from the fact that it is constructed utilizing a heat-welding process. First, this limits the fabrics which may be utilized to thermoplastic materials. Also, heat-welding necessarily requires a melting of at least some of the fibers of the materials bonded, thus providing an uneven outer appearance along the heat-welds and producing unwanted crimps or creases in the materials, which can result in fatigue failure. Further, heat-welding is a relatively slow process which may require six or more seconds to-create a bond over an extended length. This is too slow for application in high volume commercial production processes. Other drawbacks of the Froget window covering are that heat welds are limited in strength, especially at elevated temperatures experienced by an insulating type shade placed adjacent a sunlit window; and the difficulty in achieving uniformly straight heat welded joints over an extended length.

U.S. Pat. No. 2,865,446 to Cole discloses a window covering in which a long rectangular piece of fabric is doubled back upon itself and a plurality of pleated elements are placed between the folded over sheets. The pleated elements are an accordion-pleated fabric which extends when the two sides of the folded over fabric are moved relative to one another in ;a direction perpendicular to the accordion pleats. Such a window covering does not provide a uniform appearance because the accordion-pleated fabric located closer to the top of the window covering does not expand to the same extent as the fabric closer to the bottom of the window covering. Also, it is very difficult to ensure that such accordion-pleated fabric returns to its desired position after each expansion.

The construction of Cole inherently creates an undesirable feature if a woven type sheer fabric is used for the folded over, long rectangular piece of fabric. That undesirable feature is a moire effect or interference pattern which would result when light is viewed through the folded over fabric. The Froget window covering would also appear to have this drawback because the embodiment shown inFIG. 8of that patent appears to show front and back fabrics of the same material.

French Patent No. 1,309,194 discloses a curtain with variable opacity. In this curtain, screen or mesh parallel sides are provided with tiltable braids therebetween. The braids are said to be attached at their edges to the sides, however, no means for attachment is specified. The drawings appear to indicate a hinged type attachment and the specification ends by stating that the difficulties of construction are substantial.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide a fabric light control window covering comprising first and second parallel sheer fabric sides and a plurality of opaque or semi-opaque vanes extending between the sheer fabric sides with the vanes being angularly controllable by relative movement of-the sheer fabric sides.

Another object of the invention is to provide such a window covering which has a neat and uniform construction and outer appearance in all degrees of light control. In this respect a feature of the present invention is therefore adhesive bonding of the light control vanes to the sheer fabric utilizing linear application of the adhesive and, thus, a high degree of controllability of the adhesive application process and bonding of the vane. Such a feature provides advantages other than simply an improved outward appearance. The precisely uniform construction improves the operation of the blind by preventing warps or distortions from developing over the life of the blind.

Another object of the invention is to provide such a blind which operates with a high degree of repeatability, that is, always returns to the same appearance when closed. Thus, a feature of the present invention is attachment of the vanes to the sheer fabric sides such that the vanes tend to bias the window covering toward the minimum light admitting position. A further feature of the invention in this respect is a novel heat setting of the three layers together in order to provide a uniform and wrinkle-free shade at any temperature in subsequent use. These features allow the window covering to maintain its original shape and appearance even in the presence of temperature extremes encountered in a window environment.

A further object of the present invention is to provide methods and apparatus capable of producing the above window covering. One of the features of the present invention is adhesive bonding by means of adhesive linearly applied on the vane material. Linear application ensures a high degree of accuracy and provides uniform and straight adhesive lines. Another feature of the invention is the unique heat setting process utilizing hot and cold rollers and tension belts or hot and cold flat plates and belts to uniformly press the sandwiched fabrics during reheat setting and thus guarantee a wrinkle-free structure.

It is also an object of the present invention to provide such methods and apparatus which are suitable for high volume commercial type production. Features of the present invention which assist in this respect are adhesive bonding techniques which allow almost instantaneous bonding of the vane material and apparatus which allow for material changes without complete re-setup.

Accordingly, a fabric light control window covering according to the present invention comprises a first sheer fabric sheet, a second sheet fabric sheet disposed parallel to the first sheet, and a plurality of relatively opaque fabric strips adhesively bonded transversely between the sheet fabrics. Each strip has an edge portion bonded to the first sheet and an opposite edge portion bonded to the second sheet in a manner tending to bias the first and second sheets together. The window covering according to the present invention is movable between a closed position and an open position. The closed position is characterized by a central portion of the fabric strips being substantially parallel to the first and second sheer fabric sheets with the strips themselves being substantially planar. The open position is characterized by the central portion of the fabric strips being substantially perpendicular to the first and second fabric sheets and to the bonded edge portions of the strips themselves. Also, characteristic of this position is that portions of the strips between the bonded edge portions and central portions form smoothly cutting surfaces which are free of creases or sharp fold. In an alternative embodiment, the central portions of the fabric strips are substantially flat and longitudinally extending hinge or flex points are provided parallel to the bonded edge portions.

According to a preferred embodiment of the invention the method for manufacturing such a window covering generally includes the following steps. A first line of hot-melt adhesive is applied to the narrow strip material adjacent one edge on one side. A second line of hot-melt adhesive is applied to the narrow strip material adjacent the opposite edge on the opposite side. The narrow strip material is then cut to lengths equal to the width of the wider sheer fabrics and the cut lengths are separated to provide a space between them sufficient to allow for a subsequent processing step. The first sheer fabric is fed at a constant rate longitudinally in a direction perpendicular to the longitudinal direction of the cut strips. The first sheer fabric is also fed over the cut strips in close proximity thereto. As the first sheer fabric is fed, a portion is preheated to a temperature sufficient to form a tact bond with the hot-melt adhesive. Then, while continuously feeding the first sheer fabric at a constant rate, a portion of the first sheer fabric is stopped directly over one of the cut strips so that the cut strip may be pressed and bonded to the first sheer fabric without smearing the adhesive. In order to move the bonded strips out of the way of the next strip, the stopped portion of the first sheer fabric is advanced at a speed greater than the constant feed rate, followed by a reversing of the direction of travel of the formerly stopped portion to position the first sheer fabric for application of the next cut strip in an overlaying relationship to the previously applied cut strip. The second sheer fabric is then fed into mating contact with the cut strips which have been bonded to the first sheer fabric, thereby forming a sandwich of three layers. Almost immediately after feeding the second sheer fabric, the sandwich is heated under uniform pressure and tension to melt and force the hot-melt adhesive into the sheer fabrics, and set the layers of the sandwich at a uniform temperature-size relationship. Finally, the fabric sandwich is cooled under uniform pressure and tension, thereby permanently bonding the sheer fabrics to the cut strips without creating warps or wrinkles. The final, permanently bonded fabric can then be cut to desired lateral widths and/or trimmed along the lateral edges thereof.

Apparatus according to the invention generally comprises means for performing the above described method. In particular, the apparatus includes an adhesive applicator means comprising a heating block for melting the hot-melt adhesive. The heating block contains a gear pump which provides melted adhesive to nozzles at a rate proportional to the speed of feeding of the strip material. The heating block also is designed to melt only a small portion of adhesive in order to prevent yellowing while maintaining an adequate adhesive flow.

Included in the present invention is a means for positioning the first sheer fabric in order to stop a portion for application of a cut strip and then reposition and stop the fabric before the application of the next cut strip while maintaining a constant feed rate for the first sheer fabric. This portion of the apparatus comprises two dancer rollers around which the first sheer fabric runs. The dancer rollers are mounted on shafts which form the pivot points of a linkage around its frame. The linkage causes the dancer rollers to act in concert and the timing of the rotation of the linkage is controlled by an appropriately shaped cam member.

A heat setting means is provided in which the sandwiched layers of the window covering pass between first and second adjacent endless belts. The belts each run across hot and cool surfaces to successively heat and cool the window covering. In one embodiment, the hot and cool surfaces are rollers and tension induced in the belts causes a pressure to be exerted on the sandwiched layers, thus maintaining the layers under constant and uniform pressure at a tension significantly less than the tension induced in the endless belts. In another embodiment, the hot and cool surfaces are flat plates disposed opposite air plenums and the pressure exerted on the sandwiched layers is due to the biasing of the belts toward the flat plates by pressurized air supplied to the air plenums. Alternatively, the hot and cool surfaces may be pairs of oppositely disposed flat plates biased against the belts. Heat setting in these manners allows the sandwiched layers to be set to a uniform temperature and size relationship to prevent distortions in subsequent use.

Also, included in a preferred embodiment of the invention is a heat setting means wherein the first endless belt passes around a hot roller and the second endless belt passes around a cool roller. The location of the belts and rollers is arranged such that the second endless belt also passes around the hot roller outside of the first endless belt and the first endless belt passes around the cool roller for short distance outside of the second endless belt. With this arrangement the sandwiched layers of the window covering may be passed between the two belts, around the hot and cool rollers.

A hot knife cutting assembly is preferably provided to cut the final fabric to desired lateral widths and/or to trim the lateral edges, of the final fabric. The hot knife cutting assembly operates such that the three layer sandwich fabric is cut cleanly, without any heat sealing of the lateral edges of the individual fabric layers to one another.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawing and, in particular, first toFIG. 1, the method and apparatus according to the present invention may be explained in greater detail. Vane material is provided as a continuous strip material from supply roll12. Vane material10first passes around idler roller13mounted on frame14. The vane material then enters adhesive applicator assembly20, where adhesive nozzles21apply a thin line16of hot-melt adhesive to each side of the vane material10(seeFIG. 4). While the apparatus is explained below in connection with hot-melt adhesive, it should be readily appreciated that the same principles are generally applicable to other types of liquid adhesives.

In assembly20vane material10first passes around alignment roller22which is provided with raised edges in order to ensure proper alignment of the material. Vane material10next passes around backup roller23over which nozzle21is disposed. Backup roller23is mounted on arm24and shaft26which pivots in bearing25to allow for adjustment of the spacing between the glue nozzle21and vane material10on backup roller23. Preferably, the spacing is adjusted to provide a flat glue line as shown inFIG. 4. The flat profile of the adhesive lines provides greater control of the amount of adhesive applied and the degree of flow when subsequently squeezed between two materials. With a two inch wide vane material10, the dimensions of the adhesive lines are preferably about a height of 0.003 inches and a width of 0.060 inches.

Driven roller27is provided to assist in feeding the vane material and is positioned to ensure that vane material10has sufficient contact with backup roller23. By passing vane material10under stationary nozzle21, the adhesive lines are applied due to the linear motion of the vane material10in its longitudinal direction. In this manner great precision can be achieved in the application of the adhesive lines.

As illustrated inFIG. 4, adhesive line16ais disposed on vane material10adjacent one edge and on one side of the material. A second adhesive line16bis disposed adjacent the opposite edge on the opposite side of the material. The second adhesive line16bis placed on vane material10by utilizing the same components as just described arranged in a mirror image configuration and by doubling vane material10back over itself around the second backup roller23.

In a preferred embodiment of the present invention, the adhesive used is a copolyester hot-melt adhesive. This adhesive melts and flows at about 350.degree. F. and provides excellent strength over the temperature range to which the window covering will be exposed in use. It also provides a tack bond at slightly lower temperatures around 220.degree. F. which is useful in subsequent steps as described below.

This type of adhesive however does have the undesirable characteristic of yellowing when heated and maintained in a melted state for extended periods of time. In order to prevent yellowing, it is necessary to heat only a small amount of adhesive at a time. The present invention provides a novel system of adhesive application which eliminates this problem. Hot:-melt adhesive in the form of pellets is placed in hopper30. The pellets drop into caulking cartridge32which is provided with a pneumatic piston34that forces the pellets into heating block35. Electric heating elements36heat heating block35to melt a small amount of adhesive just before it is forced into a metering gear pump which pumps the adhesive into nozzles21. With this arrangement as little as four ounces of adhesive is melted at one time.

A gear pump, preferably a positive displacement pump, is disposed within heating block35to pump the melted adhesive to nozzles21. The gear pump is powered proportionally to the vane material10feed speed such that the amount of glue deposited on the vane material10remains constant at whatever speed the vane material is fed.

After leaving the adhesive applicator assembly20vane material10, with applied adhesive lines16a,16b, passes around idler rollers33and37. The vane material then travels around alignment roller38which has raised edges to align the vane material and a further idler roller39. Vane material10then travels into cutter assembly40.

Cutter assembly40is shown schematically in greater detail inFIG. 8. In the cutter assembly, vane material10first passes around an alignment roller41. Alignment roller41has raised edges similar to the other alignment rollers in order to guarantee the side-to-side alignment of vane material10. The vane material then passes between backup roller42and nip roller44. Nip roller44is mounted on a pivotable spring biased arm43in order to maintain a constant pressure against the backup roller42and prevent slippage of vane material10. Backup roller42is also a driven roller which pulls the vane material through the apparatus. Adjacent to backup roller42is cutting roller49. Blade50is disposed on the circumference of cutting roller49parallel to the roller axis. Cutting roller49and backup roller42are spaced apart a distance sufficient to prevent blade50from cutting vane material10on each rotation of the rollers.

Cutting roller49is rotatably mounted on bracket48which pivots on shaft51. After the desired length of fabric is fed around backup roller42, pneumatic cylinder46, mounted on bracket47and acting through linkage45, causes bracket48to pivot to the left so that blade50contacts and cuts material10to form individual vane strips10a. Linkage45comprises a clevis52attached to the end of the cylinder piston. Three connecting rods53,54and58are joined at pivot point56and are pivotably connected at clevis52, cutter assembly frame57and bracket48, respectively. The downward motion exerted by cylinder46causes pivot point56to move down and thus pivots bracket48to the left around shaft51.

Pneumatic cylinder46is controlled by a pneumatic valve (not shown) cooperating with the backup roller shaft. After the number of rotations of backup roller42corresponding to the desired length of vane material10, the pneumatic valve opens to actuate pneumatic cylinder46and thus move blade50to the cutting position. Backup roller42and cutting roller49are both driven rollers traveling at the same speed in order to prevent a scraping action of blade50along backup roller42.

In an alternate embodiment, nip roller44and biased arm43are eliminated. Instead, cutting roller49is surrounded by a squishable rubber liner having an outer diameter slightly greater than the radial extension of blade50and contacting backup roller42. The contact between the cutting roller rubber liner and backup roller42creates a nip for pulling fabric through the apparatus.

When air cylinder46causes bracket48to move slightly to the left to cut the vane material, the rubber liner is compressed against backup roller42to expose cutting blade50and thus cut vane material10.

After vane material10passes around backup roller42it falls onto vacuum belt62which is part of vacuum separator assembly60. InFIG. 8vane material10is shown slightly above belt62in order to clearly distinguish the two parts, in practice material10is pulled against belt62. Vacuum separator assembly60separates the cut strips10aof vane material in order to provide a sufficient distance between the strips to allow time for subsequent processing steps performed on the individual strips10a.

Vacuum belt62is provided with holes which are best seen inFIGS. 2 and 3. Vacuum belt62travels around drive wheel61, idler wheel63and idler wheel70which is mounted on screw tension adjustment67. Screw tension adjustment67allows the tension in vacuum belt62to be adjusted by turning screws67a. Vacuum belt62is supported along its top run62aby hollow frame64. The space within hollow frame64is evacuated by vacuum hoses69, thus causing a suction through the holes of vacuum belt62. This suction pulls the vane material against vacuum belt62as it comes off backup roller42.

In order to provide the spacing between the cut strips10aof vane material, vacuum belt62travels approximately twice as fast as the linear feed speed of vane material10. Thus, as the uncut vane material10passes backup roller42, it is pulled against vacuum belt62by the suction action. However, because it is moving at a slower speed, uncut vane material10slides along vacuum belt62. As soon as vane material10is cut by blade50, it is separated from the uncut vane material10due to the increased speed of the vacuum belt62. Nip roller65presses against vacuum belt62and is located a distance from the point of contact between blade50and backup roller42slightly less than the desired length of individual cut strips10a. Pneumatic cylinder66acts on arm68on which nip roller65is mounted in order to press nip roller65against Vacuum belt62. The actuation of air cylinder65is timed to correspond to that of pneumatic cylinder46such that at the precise moment vane material10is cut, nip roller65presses cut strip10aagainst vacuum belt62to ensure its separation from the uncut vane material. Vacuum belt62moves the cut vane strips10ato a position directly under first sheer fabric72.

The cutting assembly40and separator assembly60allow for successful handling of relatively soft fabrics for the vanes10a. This is a significant advantage over the prior art because soft fabrics provide a more pleasing appearance in the final product.

Referring toFIG. 3, first sheer fabric72is provided from supply roller74and fed around idler75, dancer roller76and preheat shoe78. The cut vane10ais carried beneath a portion of first sheer fabric72which is resting against preheat shoe78. Preheat shoe78heats first sheer fabric72to approximately 220.degree. F.

First sheer fabric72is fed with its longitudinal direction perpendicular to the longitudinal direction of the vane10a. The width of first sheer fabric72corresponds substantially to the cut length of vane10a.

When vane10areaches alignment with the opposite edge of first sheer fabric72, photo eye80senses the end of vane10aand activates kicker bar82. Kicker bar82is located on one side of vacuum belt62and directly below adhesive line16a. Kicker bar82pushes the front edge of vane10aupwards and presses adhesive line16abetween vane10aand the preheated first sheer fabric72. The combination of heat and pressure creates a tack bond between vane10aand first sheer fabric72, thus holding vane10ain place on first sheer fabric72. Kicker bar82then retracts downwards and out of the way of the next vane. Kicker bar82is mounted on a number of pneumatic cylinders83which provide the pressing force and accomplish the tack bond cycle within a span of about one-tenth of a second. First sheer fabric72with tack bonded vanes10a, as shown inFIG. 5, then moves around dancer roller84and idler roller86into heat setting assembly100.

In the window covering according to the present invention it is preferred to have the vanes slightly overlapping in the closed position in order to fully block the passage of light. This overlap requirement somewhat complicates the production of the window covering in order to prevent the subsequently attached vane from being adhered to the previous vane instead of the sheer fabric. In the present invention, dancer rollers76and84continuously reposition first sheer fabric72to solve this problem. The sheer fabric in the present invention is fed at a continuous rate and pulled through the apparatus by the heat setting assembly100. In order to facilitate understanding of the method and apparatus for positioning first sheer fabric72, the description is made with reference to a two inch wide vane material10. It should be readily appreciated that this is intended to in no way limit the present invention. Other vane material widths may be used with simple adjustments, apparent to those skilled in the art based on the disclosure contained herein.

With a two inch vane material, the overlap of the vanes is preferably about ¼ inch. Therefore, the first sheer fabric72is advanced a total of 1¾ inches for each vane10aapplied. In order to control and position first sheer fabric72, the first sheer fabric72runs around dancer rollers76and84. After a vane10ahas been applied, dancer roller76moves downward and dancer roller84moves to the left as shown inFIG. 3. This causes first sheer fabric72to be moved forward a total of 2¾ inches at a rate faster than that at which first sheer fabric72is actually being fed. The forward movement of 2¾ inches allows the tack bonded vane10ato move completely out of the way of the next vane to be applied. From this point, first sheer fabric72is moved backward one inch by the dancer rollers in order to assume the proper position of a total of 1¾ inches advancement. This positions the first sheer fabric72in place for the next vane10ato be applied.

As the backward motion occurs, air jets79blow a jet of air through first sheer fabric72on to applied vane10ato force it out of the way of kicker bar82. A number of air jets79may be positioned along the width of first sheer fabric72just after kicker bar82. Air jets79may provide a continuing airflow or may be timed to blow only during the backward motion of the dancers.

In order to maintain first sheer fabric72in a stationary position while the next vane10ais applied, dancer rollers84and76continue to move back slowly so as to exactly counter the effect of the forward pull of heat setting assembly100. Thus, first sheer fabric72between dancer rollers76and84remains briefly stationary. This prevents adhesive line16afrom being smeared when vane10ais applied to first sheer fabric72and also allows first sheer fabric72to become sufficiently preheated by remaining stationary on the preheat shoe78. Once kicker bar82tack bonds the next vane10ato first sheer fabric72the positioning process repeats.

In a preferred embodiment of the present invention a single motor drive system is utilized to power adhesive applicator assembly20, cutter assembly40, vacuum separator assembly60and heat setting assembly100. Dancer rollers84and76are also powered by this drive system. Dancer roller76is mounted on arms89which in turn are mounted on shaft88. Similarly, dancer roller84is mounted on arms85which in turn are mounted on shaft87. Shafts87and88extend through frame14as shown inFIGS. 1 and 2. Shafts87and88are linked together by arms90and91and connecting rod92which, together with frame14form a linkage. Arm91rides on cam93which is rotated by a shaft linked to the single motor drive system. Arm91is maintained in contact with cam93by extension spring94. Cam93is shaped to provide the motion of dancer rollers76and34just described.

As can be seen inFIG. 1, vacuum belt62extends beyond frame14at the left end of the apparatus. This allows for fast and easy changes of the vane material10. When a new vane material is placed on a supply roller12, its leading edge may be simply taped to the trailing edge of the last vane material. Then, when the cut strip containing the taped splice approaches first sheer fabric72, kicker bar82and the sheer fabric feed may be temporarily deactivated to allow the spliced portion of vane material to exit at the left side of the apparatus. When clean cut strips10aof vane material begin to exit at the left side, the sheer fabric feed and kicker bar82are reactivated. This allows quick changes of vane material without introducing flaws into the final product or requiring lengthy set up times.

Referring again toFIG. 3the remaining steps of the process may he explained. First sheer fabric72which passes around idler roller86has, vanes10atack bonded thereto in their final spaced relationship. Second sheer fabric96is fed from supply roller97around idler roller98and laid up against first sheer fabric72with tack bonded vanes10a. The three-layer sandwich of first sheer fabric72, vanes10aand second sheer fabric96travels over idler101, around heating roller102to cooling roller104and from there exits the apparatus as a finished fabric103. Heating roller102is maintained at a temperature of approximately 350.degree. F. At this temperature hot melt adhesive lines16a,16bare melted to form a permanent bond between the sheer fabrics72,96and vanes10a. Cooling roller104is maintained at a temperature of approximately 12020 F. and sets the hot-melt adhesive bonds.

In addition to providing an almost instant bond of high strength, the heat setting assembly provides a second function of equal importance. By running the three layers together around heating roller102at a temperature of 350.degree. F., the sheer fabrics and vane material are actually heat set to their new size and configuration at a uniform temperature-size relationship. The fabrics will thus hold this new size relationship with respect to one another unless subjected again to a temperature of 350.degree. F. or greater. The temperatures which normally would be experienced by this type of window covering in use generally do not exceed a 180.degree. F. Thus, the window covering according to the present invention will remain wrinkle-free at any normal use temperatures.

Additionally, the heat setting procedure allows for the use of fabrics which have not previously been heat set. Most fabrics are run through a heat setting process which sets the fibers and locks them to size in order to prevent shrinkage when subjected to heat in their normal applications. The heat setting apparatus of the present invention allows this preheat setting of individual fabrics to be eliminated, thus saving time and money in the fabric processing.

The present invention provides a further novel feature in order to ensure that a wrinkle-free final product emerges from heat setting assembly100. This feature is the use of endless tension belts106and108, respectively. First belt106travels around heating roller102and idler110mounted on shaft111. Second belt108travels around cooling roller104, idler112, mounted on shaft114, and idler101. Second belt108also travels around heating roller102outside of first belt106. Similarly, first belt106travels for a short distance around cooling roller104outside of second belt108. The three-layer fabric sandwich is pressed between the first and second belts106,108as it passes around heating and cooling rollers102,104. The first and second belts106,108are maintained at a much greater tension than the sandwich of sheer fabrics72,96and vanes10aas it passes therebetween. The tension in the belts has the effect of pressing together the belts around heating and cooling rollers102,104. This uniformly presses the finished fabric103as it is heat set and cooled, thus further eliminating the possibility for a wrinkled or warped final product. In a preferred embodiment, first and second belts106,108are polytetrafluoroethylene (TEFLON) coated fiberglass belts which have the required strength and exhibit the release characteristics of polytetrafluoroethylene.

Referring toFIG. 2, the tensioning of belts106and108is controlled by pneumatic cylinders120and122, provided in pairs on both sides of frame14. Pneumatic cylinders120act on shaft114which carries idler112and thus control the tension in cooling belt108. Pneumatic cylinders122act on shaft111on which idler110is mounted and thus control the tension in heating belt106. Both of cylinders120can be seen inFIG. 1. Slotted arms121and123ensure alignment of shafts114and111, respectively. Air supply to the cylinders is controlled by regulators128and129. The unwind tension of sheer fabric supply rollers74and97is controlled by pneumatic brakes124and125, which are regulated by regulators126and127, respectively. The pneumatic brakes and regulators allow the tension in the sheer fabrics to be precisely controlled during the steps of bonding the vanes and heat setting the layers together.

The rotation of heating and cooling rollers102,104is linked together by geared wheels132and134which are in turn driven by gears136and138linked to the drive system. Heating roller102may be heated by electric heating elements disposed around the internal diameter of the roller which is preferably formed as a hollow aluminum cylinder. Cooling roller104, also preferably formed as a hollow aluminum cylinder, may be cooled by forced air convection or in larger rollers by liquid cooling passages formed in the roller.

FIGS. 9,10and14illustrate alternative embodiments of the heat setting apparatus according to the present invention. InFIG. 9, first and second belts106aand108aare carried by rollers115aand110aand rollers113aand114a, respectively. Tension in belts106aand108amay be adjusted by the moving shafts111aand114ain the same manner as shafts111and114, explained above. Second sheer fabric96is again sandwiched with first sheer fabric72having tact bonded vanes10a. The sandwiched layers then run between belts106aand108a. Heating is provided by hot plates102aand cooling by cool plates104adisposed inside each of the belts. The plates are biased against the belts and sandwiched layers by springs116to ensure a uniform pressure on the sandwiched layers.

In the embodiment ofFIG. 10belts106aand108aare arranged generally as shown inFIG. 9. However, instead of hot plates102aa plurality of hot rollers102bare employed. Hot rollers102bare disposed inside each belt106awith the axes of the upper set of rollers offset between the axes of the lower set of rollers. The axes of the upper and lower sets are also located slightly closer together than the diameter of the rollers thus providing a slight wrap of the belts around each roller. The wrap around each roller creates a uniform pressure on the sandwiched layers between belts106aand108awhen tension is applied to the belts. In a preferred embodiment the rollers are positioned such that the belts wrap around an arc of approximately 20.degree. Rollers arranged in the same manner as hot rollers102bmay be used as cooling rollers or cooling plates104amay be employed.

In the embodiment ofFIG. 14, first and second belts106aand108aare arranged generally as shown inFIG. 9. However, instead of two hot plates102aand two cool plates104a, only one hot plate102cand one cool plate104cdisposed within endless belt108aare employed. The hot plate102cincludes an air chamber180and a plurality of air bleed holes182are formed through hot plate102c. The air bleed holes132provide fluid communication through the hot plate102cbetween the air chamber180and the upper surface of hot plate102c. Similarly, cool plate104cincludes an air chamber184and a plurality of air bleed holes186. Air plenums188,190are disposed within endless belt106aand are positioned opposite the hot plate102cand the cool plate104c, respectively. Each of the air plenums188,190is provided with flexible seals198around the lower edge thereof adjacent endless belt106a. Preferably, the hot plate102cand the cool plate104care wider than the belts106a,108aand the air plenums188,190are narrower than the plates and the belts.

Air is supplied to air plenum188and air chamber180of the hot plate102aby hot air blower192. More particularly, hot air blower192supplies air at a pressure of about 3 to 4 psi and a temperature of about 350 to 400.degree. F. to air plenum188through conduit193and to air chamber180through conduit194. Hot plate102cis also heated to a temperature of about 350.degree. by suitable means. Air is supplied to air plenum190and air chamber184of cool plate104cby cool air blower195. Air at a pressure of about 3 to 4 psi and ambient temperature is supplied by cool air blower195through conduit196to air chamber184and through conduit197to air plenum190. Cool plate104cis cooled to a temperature of about 120.degree. F. or lower, by suitable means such as water cooling.

The air pressure in the air plenums188,190pushes or biases the belts106a,108a, and the fabric sandwich103therebetween, toward the hot plate102cand the cool plate104c. In contrast: to the embodiments ofFIGS. 3,9and10, in the embodiment ofFIG. 14the tension in the belts106a,108ais not critical. In this embodiment, the pressure applied to the fabric sandwich103between the belts106a,108ais created by air pressure instead of tension.

The 3 to 4 psi of air introduced into the air plenums188,190pushes the belts106a,108aand the fabric sandwich103against the hot plate102cand the cool plate104c, respectively. This uniformly presses the finished fabric103as it is heat set and cooled. Pressurized air flowing through the air bleed holes provided in the hot plate102cand the cool plate104clifts the belt108aoff the hot and cool plates, preferably a few thousandths of an inch, to minimize friction between the belt108aand the plates to ensure uniform heating and cooling of the fabric sandwich103.

After the finished fabric103exits the apparatus as shown inFIG. 3, the finished fabric.103can be wound up in a roll for storage and subsequent processing into a finished window covering, or the finished fabric103can be immediately transported to trim the lateral edges of the finished fabric103and/or to cut the finished fabric103into desired lateral widths. A suitable hot knife cutting assembly is shown inFIG. 11. The hot knife cutting assembly300comprises a moving carriage302slidably or movably mounted on carriage rails304. A hot wheel knife cutter306is rotatably mounted on the moving carriage302and rotates in the direction indicated by arrow308. A shoe312carried by the moving carriage302holds the finished fabric103flat on the table Or support314until the fabric103is cut by the rotating hot wheel knife306. Depending upon the material of the first sheer fabric, the second sheer fabric and vanes of the finished fabric103, it may be possible to carefully control the temperature of the hot wheel knife306to prevent sealing of the lateral, cut edges of the three layers of the finished fabric103to one another due to the heat of the hot wheel knife306. However, preferably an air jet310connected to an air supply (not illustrated) is mounted on the moving carriage302. Air supplied through the air jet310blows onto the edge of the cut fabric103immediately after the cutting, and air from the air jet310lifts and opens the lateral edges of the fabric103to prevent: the edges of the fabric from sealing together. Instead of the air jet310, other suitable means for lifting and opening the finished fabric103along the cut edge thereof may be carried by the moving carriage302to immediately effect opening of the finished fabric immediately after it is cut by the hot wheel knife316. For example, mechanical opening means could be carried by the moving carriage to effect this opening.

The hot knife cutting assembly300may be employed to cut to the finished fabric103immediately after the finished fabric103has been produced, and prior to winding the finished fabric103into a roll for storage. Alternatively, the finished fabric103may be wound for storage and then, at a subsequent time or a different physical location, the finished fabric103from the storage roll can be cut using the hot knife cutting assembly300.

FIGS. 6 and 7illustrate a fabric light control window covering according to the present invention.FIG. 6illustrates the window covering in a fully open, light admitting position. In this position, each vane10ahas a central portion140which is substantially perpendicular to first and second sheer fabrics72,96. Edge portions142of the vane10a, which are bonded to the sheer fabrics are connected to central portion140by a portion141having a smoothly curving shape. The adhesive bonding process of the present invention allows portion141to be formed without creases or sharp folds. The smoothly curved nature of this portion, in the fully open position, allows the vane to retain its resiliency and thus tends to bias the sheer fabrics into a closed or drawn together position. This ensures that the window covering does not lose its shape over time from repeated opening and closing. Furthermore, creases along vanes10acan develop into failure points due to repeated bending inherent in the opening and closing of the window covering.

FIG. 7illustrates a possible method of deployment of a light control window covering according to the present invention. The window covering150is mounted on a head roller152. The bottom of the first sheer fabric72may be provided with decorative stiffener154. Second sheer fabric96is weighted by weight153. Rotation of head roller152causes relative movement between first and second sheer fabrics72,96in a vertical direction and thus an angular change in the orientation of vanes10ato let in or block out light as desired. First sheer fabric72need not be weighted because of the tendency to close imparted by the biasing effect of vanes10a.

FIGS. 6 and 7also illustrate the novel technique employed in the present invention for avoiding the appearance of a moire effect in window coverings of this type. With such window coverings, sheer woven fabrics having small interstices between the fibers provide a pleasant and desirable appearance for the first and second sheer fabrics72,96. However, when the same or very similar material of this type is used for the first and second sheer fabrics, a moire pattern is created by the fabrics when viewed in overlaying relationship. This moire effect is eliminated in the present invention by providing first and second sheer woven or knit fabrics of materials having differently sized, shaped and/or oriented interstices. According to the present invention, the moire effect is also avoided by using a non-woven sheer material as one or both of the first and second fabrics or by using a transparent plastic material as one or both of the first and second fabrics.

To avoid the undesirable moire effect when the first and second sheer fabrics of woven or knit material are viewed in overlaying relation in the window covering of the present invention, the first and second sheer fabrics must have different appearances when the sheer panels are viewed along an axis perpendicular to the plane of the first sheer fabric72and perpendicular to the plane of the second sheer fabric96. The required difference in appearance between the first sheer fabric72and the second sheer fabric96can be achieved in several different ways.

The first sheer fabric72can be a woven or knit fabric having interstices of one shape and the second sheer fabric can be a woven or knit material having interstices of a second shape. In one such embodiment shown inFIG. 7, a woven fabric employing fibers forming small square interstices is used as the second sheer fabric96. A material used for the first sheer fabric72may have fibers forming interstices which are smaller, the same size or larger than those of the second sheer fabric96. However, the fibers of the first sheer fabric72form interstices which are positioned as diamonds with respect to the second sheer fabric96. With this relationship between first and second sheer fabrics, the appearance of a moire pattern can be avoided.

In another embodiment, the first sheer fabric72can be a woven or knit fabric having interstices of one shape and size and the second sheer fabric96can be a woven or knit fabric having interstices of the same shape as the first sheer fabric but of a different size. In this second embodiment, shown inFIG. 6, the moire pattern may be avoided by providing a second sheer fabric96which has interstices which are smaller than those of first sheer fabric72without regard to the relative orientation or shape of the interstices. This also prevents the occurrence of interference leading to a moire effect. In practice, the first and second fabrics are selected so that the width of the interstices of the first fabric is far greater than the width of the interstices of the second fabric, thereby avoiding the moire effect.

It is also possible to use the same woven fabric for both the first and second sheer fabrics72,96, provided that the woven fabric is oriented differently in the two sheer fabrics72,96in order to provide the required difference in appearance. For example, with reference toFIG. 7, the woven fabric of second sheer fabric96has square interstices. The same woven fabric having square interstices can be used as the woven fabric of the first sheer fabric72by changing the orientation of the woven fabric by 45.degree. to provide the diamond shaped interstices of the first sheer fabric72. When the same woven fabric is used for both the first and second sheer fabrics72,96, the fabric for one of the sheer fabrics is cut on the bias so that the orientation of the interstices of that fabric is changed by an angular amount, e.g. roughly 45.degree. or 90.degree., sufficient to provide the required difference in appearance when the first and second sheer fabrics72,96are viewed along an axis perpendicular to the plane of both.

It is also possible to avoid the moire effect and provide the required difference in appearance by using a non-woven sheer material, such as a plastic material, for one of the sheer fabrics and a woven sheer material for the other of the sheer fabrics of the window covering. Alternatively, non-woven sheer materials, such as the same or different plastic materials, can be used for both the first and second sheer fabrics. A transparent plastic material can also be used as the first and/or second fabric. The use of a transparent material as at least one of the first and second fabrics also avoids the moire effect.

In another embodiment of the present invention, the second sheer fabric96is replaced by a series of sheer fabric strips156(FIG. 39) or a series of strings158(FIG. 38). A window covering of this embodiment can be made by the same process and apparatus as described above, however a series of parallel sheer fabric strips156or parallel strings158are fed to the apparatus from an appropriate supply toll instead of the second sheer fabric96. The use of a series of strings or sheer fabric strips in place of the second sheer fabric96provides a more “see-through” effect when the window covering is in the open position. However, because the overlapping configuration of the vanes is the same as that of a window covering having a second sheer fabric96, in the closed position a window covering comprising a plurality of strings or sheer fabric strips provides the same light blocking effect.

To achieve the gently curved structure of the vanes10ashown inFIG. 6, the vane material must have a certain degree of softness. As, a general principle, the wider the vanes10a, the stiffer the vane material can be. However, since a broad range of vane widths may be employed in window coverings in accordance with the present invention, it is difficult to precisely define an acceptable softness or stiffness range for the vane material.

A simple and effective physical test has been devised to determine whether a particular fabric is suitable for vanes having a specific vane width. The fabric being tested is allowed to hang over the edge of a table such that the distance from the edge of the fabric to the table top equals the desired vane width. If this length of fabric hangs substantially vertically, then it has sufficient softness for a vane of that vane width. For example, if a fabric is being tested for use as a 2″ wide vane, the edge of the fabric is extended 2″ beyond the edge of the table. If the extended 2″ of the fabric hangs substantially vertically from the table edge, it is suitable for use as a 2″ wide vane material in the structure shown inFIG. 6. If the extended 2″ of the fabric does not hang substantially vertically, the fabric is too stiff to produce 2″ wide vanes having the gently curved appearance ofFIG. 6.

Stiffer fabrics, i.e., those which do not hang substantially vertically over a table edge at the length of the desired vane width, can also be used as the vane material. However, if a stiffer fabric is used for the vanes, longitudinally extending hinge or flex points must be provided along the edges of the vanes. The use of a stiffer fabric provided with hinge points produces a window covering having a somewhat different appearance that the window covering shown inFIG. 6. This second embodiment of a window covering is shown inFIGS. 12 and 13. As seen inFIG. 12, vanes210ahave a straighter appearance and have a sharp bend at the hinge points212and214, rather than a gently curving portion141as shown inFIG. 6. The hinge points212,214are provided by score-compressing a stiff vane material, parallel to the longitudinal edges of the vane material. The score-compressed lines formed in the stiff vane material are spaced apart from the longitudinal edge of the vane-material a distance sufficient to allow the adhesive lines16a,16bto be applied to the vane material between the longitudinal edge of the vane material and the score-compressed line.

A structure similar to that shown inFIG. 12can also be produced using a relatively soft vane material, if desired. In this embodiment, a stiffening agent is printed onto the vane material in the central portion thereof to provide flatter vanes. The longitudinal edges of the vane material are left free of stiffening agent and the required hinge points are formed at the longitudinally extending edges of the printed on stiffening agent. The adhesive lines are applied to the longitudinal edges of the vane material, which longitudinal edges have been left free of stiffening agent.

According to another embodiment of the present invention, the vanes are formed of a black-out laminate material to maximize the room darkening effect of the window covering when the vanes are oriented in the closed position. A suitable black-out laminate material is a three ply laminate comprising a polyester film such as MYLAR sandwiched between two layers of a spun bonded or spun laced polyester non-woven material. Black-out laminates of this type are generally known in the art and have previously been used in other types of window coverings. Such a three ply laminate has, by virtue of its construction, a greater stiffness than most single ply materials. Accordingly, score-compressed hinge points, such as those shown inFIG. 12, could be provided in the black-out laminate vane material if necessary.

Alternatively, to produce a window covering of the present invention having a maximized room darkening effect, only a stiffened central portion of the vanes is formed from a black-out laminate material. The longitudinal edges of the vanes are left free of the black-out laminate to provide the required hinge points and flexibility along the edges of the vanes. When the blackout laminate is provided only on the central portion of the vanes, it is desirable to space the vanes closer together than described above in order to ensure that the black-out laminated central portions overlap when the window covering is closed, for maximum room darkening effect. For example, for a 25 inch wide vane with a 1½ inch wide black-out laminated central portion, the overlap of the vanes is preferably about 1¼ inch.

Another possible vane material is vinyl or a laminate of a non-woven material and a vinyl material. Generally, vinyl materials and laminates of non-woven material and a vinyl material provide an increased room darkening effect but are soft enough that score-compressed hinge points are not required. Of course, score-compressed hinge points could be provided if necessary.

As discussed with respect to the first and second sheer fabrics of the window covering, when two woven fabrics are viewed in an overlaying relationship, an interference pattern or moire effect can result. When a non-woven fabric is used for the vane material, the problem of a moire effect in the window covering when it is closed is avoided. In some instances, however, it may be desirable to use a woven or knit material for the vane material. A basic woven material will give a moire effect because this type of material has a very ordered orthogonal surface structure. To avoid a moire effect when the window covering having a woven or knit vane material is in the closed position, a crepe woven material can be used as the vane material because crepe woven materials have a much more randomly oriented surface structure. Alternatively, the surface of the woven or knit material can be altered to randomize the surface fibers, for example, by sanding, napping or calendarizing.

Window coverings having first and second sheer fabrics and vanes of various colors, and combinations of colors are contemplated within the scope of the present invention. For example, to provide a more transparent window covering in the open position, dark sheer material can be used for the first and second sheer fabrics because dark colors reflect less light than lighter colors. Similarly, white or light colored sheer materials provide a more translucent effect when the window covering is open.

The vanes may be the same color or a different color than the first and second sheer fabrics. A problem of glue line show-through has been experienced, however, when the vane material is a dark color and the first and second sheer fabrics are of a considerably lighter color or white. To overcome the problem of a dark glue line showing through a light colored sheer material when the vane is adhesively bonded to the first or second sheer fabric of the inventive window covering, a small amount of whitener, about 0.5 to 1.0% by weight, is added to the adhesive before it is applied to the vane material. A particularly suitable whitener is titanium dioxide. The addition of this whitening pigment to the adhesive eliminates the problem of dark colored glue lines being visible in a window covering wherein a dark colored vane is adhesively bonded to a lighter colored sheer fabric.

The description of the preferred embodiments contained herein is intended in no way to limit the scope of the invention. As will be apparent to a person skilled in the art, modifications and adaptations of the structure, method and apparatus of the above-described invention will become readily apparent without departure from the spirit and scope of the invention, the scope of which is defined in the appended claims.