Thermally movable plastic devices

Abstract

In accordance with the invention, thin bodies of plastic, such as sheets or strands, with substantially different thermal coefficients of expansion are laminated together to make plastic bodies which move in response to heat. The movable plastic bodies can be secured to a suitable base to make a variety of devices for amusement, temperature monitoring and display. Applications for amusement include a thermally blooming flower, a solar activated butterfly, and curling hair for a doll. Applications for temperature monitoring include safety lids for drinking cups, sunlight blockers including Venetian blinds, and ventilators.

Description

FIELD OF THE INVENTION

The present invention relates to plastic devices, and in particular, to plastic devices which move in response to heat, including Venetian blinds.

BACKGROUND OF THE INVENTION

It is well known that if two thin strips of metal having different thermal coefficients of expansion are laminated together, they will bend and straighten in a manner dependent on the temperature. This movement is because changes in temperature cause one strip to lengthen more than the other. Since both strips are bonded together, the only way this length difference can be accommodated is by curling. The standard equation for the bending of a bimetallic strip is: D=K(DT)(De)L²/t  (Eq. 1) where D is the distance the strip bends measured at the end of the strip, (DT) is the temperature difference relative to the temperature when the two layers were bonded, (De) is the thermal expansion difference, L is the length of the strip, t is the thickness, and K is a constant. Bimetallic strips are useful as thermometers and oven safety locks.

SUMMARY OF THE INVENTION

In accordance with the present invention, thin bodies of plastic, such as sheets or strands, with substantially different thermal coefficients of expansion are laminated together to make plastic bodies which move in response to heat. The movable plastic bodies can be secured to a suitable base to make a variety of devices for amusement, temperature monitoring and display. Applications for temperature monitoring include sunlight blockers.

The present invention provides sunlight blockers in the form of Venetian blinds, which also can act to reduce solar heat. The inventive blinds include a plurality of blades suspended from a head rail having means for mounting to a frame opening. Each of the blades is in contact with thermally movable bilayer louvers. The bilayer louvers include at least a first and a second polymeric component having coefficients of thermal expansion differing by more than 1×10⁻⁵. The movement of the bilayer louvers, attached to the blades, blocks or admits sunlight entering the room through the Venetian blind.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages, nature and various additional features of the invention will appear more fully upon consideration of the illustrative embodiments now to be described in detail in connection with the accompanying drawings. In the drawings:

FIG. 1 is a schematic cross section of a thermally movable plastic sheet;

FIGS. 2-7 illustrate thermally movable plastic devices for amusement;

FIGS. 8-12 illustrate thermally movable plastic devices for temperature monitoring and sunlight control; and

FIG. 13 shows a thermally movable plastic device for advertising display.

It is to be understood that these drawings are for purposes of illustrating the concepts of the invention and are not to scale.

DETAILED DESCRIPTION OF THE INVENTION

This disclosure is divided into four parts: Part I describes thermally movable plastic bodies; Part II describes thermally movable plastic devices for amusement; Part III describes such devices for temperature monitoring applications; and Part IV describes devices for display applications.

I. Thermally Movable Plastics

Referring to the drawings, FIG. 1 is a schematic cross section of a thermally movable plastic body comprising a sheet 10. The sheet 10 in its simplest form comprises two laminated sheets 11 and 12 of plastic having respective coefficients of thermal expansion which differ by more than about 1×10⁻⁵. Typical materials are polyethylene (thermal expansion coefficient about 8×10⁻⁵/F) and polyvinyl chloride (PVC) (expansion coefficient about 3×10⁻⁵/F). Typical thicknesses for each component layer vary from 1 to 10 mils in thickness.

The bending of the laminated sheet 10 follows the bimetallic strip bending equation (Eq.1), so thinner layers and materials with a large difference in expansion coefficient show the greatest heat induced movement. Plastics typically have larger coefficients (by a factor of 10) than most metals, providing a higher level of thermal sensitivity. Moreover plastics are inexpensively available in a wide range of colors, including clear, permitting a wide range of aesthetic effects.

The curling direction of sheet 11 can be controlled in a number of ways. In general, the sheet will bend away from the layer with the greater expansion coefficient. Some plastics such as polyethylene, exhibit biaxial expansion coefficients that differ in two directions. Biaxial expansion can result from stretching the plastic during manufacture, from inclusion of aligned, low-expansion fillers such as glass fibers, or from grooves or raised lines in the film. In general, the sheet 10 will curl along the direction of higher expansion coefficient. Depending on the shape of the film relative to the curl direction, a spiral can result upon heating.

The amount of curling is generally linear with temperature. The displacement D doubles with a doubling in the temperature difference (DT). A non-linear displacement can be achieved by preshaping the sheet 10 into an arc perpendicular to the direction of thermal curl. When heated, the sheet tries to expand and curl, but first must overcome the spring forces created by the initial arc. Once the temperature rise creates enough force, the sheet snaps open into a strong curl. Such preshaped sheets are useful, for example, in controlling valves to be open or closed at a particular temperature. Alternatively, nonlinear curling can be obtained by attaching a weight or small magnet to one end of the sheet. The sheet will not move until enough force is generated to overcome the weight or magnet.

Sheet 10 can be fabricated by any of a number of conventional laminating techniques. For example layers 11 and 12 can be bonded with a pressure sensitive adhesive such as a two-part epoxy. This has the advantage of room temperature fabrication. For example, PVC tape can be bonded to polyethylene sheets. Alternatively, the sheets can be attached together with heat or light sensitive adhesives.

The sheets 11 and 12 need not be chemically different polymers. Polyethylene, for example, exhibits a factor of five difference in expansion coefficient between low and high molecular weight versions. Thus sheet 10 could comprise low and high molecular weight polyethylene. It is even possible to dispense with Lamination by spraying a crosslinking agent on only one surface of a low or middleweight sheet, relying on the reaction of the agent through only a portion of the thickness to increase molecular weight on only one side and thus produce a thermally movable sheet.

The movable plastic bodies can also be formed as thin strips or strands. Strips can be made by forming sheets as described above and cutting them into narrow strips. Alternatively, heat movable strands can be made by co-injecting the two kinds of plastic through one nozzle, thereby ejecting a heat movable strand or fiber bilayer.

These thermally movable plastic sheets and strands can be used in a wide variety of applications. In general, the plastic is secured to a relatively rigid base, and the affect and application of the sheet depends upon the nature of the base.

II. Toy Applications

A. Blooming Flower

FIGS. 2A and 2B illustrate a device for amusement comprising a plurality of elongated oval (leaf shaped) pieces 20 of heat movable plastic secured around a common base 21 around a heat source 22 such as a low wattage light bulb. The pieces 20 can have one color on the underside, e.g. green, and another color on the top, e.g. red. The pieces 20 can comprise 2 mil polyethylene laminated to 2 mil PVC and the heat source can be a 7 watt bulb.

In use, the device behaves as a blooming flower. The pieces 20 can be oriented and arranged so that when the power of OFF, the pieces 20 curl around source 22, shielding it from view. This is illustrated in FIG. 2A. When the power is ON, heat from the source 22 causes the pieces 20 to curl away from the source, and the flower appears to bloom. This is depicted in FIG. 2B. The side of the leaf facing the source is preferably dark to absorb as much heat as possible.

B. Butterfly

FIGS. 3A and 3B depict a device to simulate a flying creature comprising a pair of generally oval pieces 30A and 30B of heat movable plastic secured on opposite sides of a generally cylindrical base 31. Advantageously 30A and 30B, in the flat condition, are sandwiched together, concealing the top surface. This is shown in FIG. 3B. In the curled condition shown in FIG. 3A, the wings open and the top surfaces are revealed. The pieces 30A and 30B can be imprinted on the top with a colorful pattern, such as that of a Monarch butterfly, and the body 31 can present a fuzzy texture such as that of a pipe cleaner.

In use, the device behaves as a butterfly. The pieces 30A and 30B can be oriented and arranged so that sunlight striking them causes them to open up like the wings of a butterfly. Animation can be achieved by providing a variable source of heat (not shown) such as an electrically powered heat source that cycles ON and OFF.

C. Opening Pyramid

FIGS. 4A and 4B show a device comprising a plurality of triangular pieces (40A-40D) of heat movable plastic with respective sides secured to sides of a polygonal base 41. The base 41 can include a display object 42. In the flat condition shown in FIG. 4A, the pieces 4DA-40D can come together in a common apex 43 to form a closed pyramid, concealing the display object 42. In the curled condition (FIG. 4B), the pieces open up, revealing the object 42. Optional struts (not shown) could be provided to assist alignment of the flat condition pieces. Suitable display objects could include imitation Egyptian artifacts or attractive minerals (not shown).

D. Curling Doll Hair

FIGS. 5A and 5B illustrate a device comprising a plurality of thin strips or strands 50 of heat movable plastic secured to an area on a generally ellipsoidal (head shaped) base 51. In the flat condition (FIG. 5A), the thin strips behave as flexible strands. In the curled condition (FIG. 5B), the strips or strands 50 behave as curled strands.

In use as doll hair, the strips or strands 50 can be oriented so that they will normally be curled. However, if placed under running cold water, the strands will straighten for grooming and styling. Upon drying they will revert to their curled state.

Strips can be made by cutting heat movable plastic sheets. Alternatively heat movable strands can be made by co-injecting two kinds of plastic through one nozzle, thus ejecting a bi-layer heat movable fiber.

E. Solar Motor

FIGS. 6A and 6B show a device comprising a plurality of strips 60 of heat movable plastic secured around the circumference of a circular ring or cylinder 61. The ring 61 is advantageously clear plastic and can be mounted to freely rotate on a central axle 62. In the flat condition, the strips 60 extend radially outward from the ring. In the curled condition (FIG. 6B), the strips bend radially inward.

In operation, the devices behaves as a solar motor When sunlight 69 strikes the ring, the exposed strips 60 bend, shifting the center of mass of the ring 61. The ring then rotates to bring the new center of mass under the axle 62. This movement, in turn, exposes a different set of strips to the sunlight. The cycle repeats, causing the ring to rotate continuously.

F. Artificial Plant Stems

FIGS. 7A and 7B depict a device comprising a thick strip or strand 70 of movable plastic having artificial flowers 71 and/or artificial leaves 72 secured to it. The strip or strand 70 is advantageously colored green and shaped to appear as an artificial plant stem. Advantageously, the artificial flowers and artificial leaves can also be made of thermally movable plastic.

In operation, the stem 70 behaves as a phototropic plant, moving from one position (FIG. 7A) to another (FIG. 7B) in response to sunlight. It can be oriented to follow the sun. The flowers 71 can bloom in the sun, and the leaves 72 can curl in the absence of light.

III. Temperature Monitoring Applications

A. Thermometer

FIG. 8 illustrates a thermometer comprising one or more of strips 80A-80G heat movable plastics suspended from a linear base 81 to hang in a parallel array. The strips are fabricated to curl at respectively different temperatures, e.g. temperatures spaced apart by about 5 degrees Fahrenheit. The strips are advantageously reflective (white or silver) to assure temperature readings are not by absorbed sunlight, and conveniently they are marked (not shown) with the temperature they indicate. Slightly conducting plastics are advantageous for minimizing the effect of static charges. In operation, the temperature can be indicated by the strip hanging vertically, with the remaining strips curled. Any number of strips can be used. A single strip can be used as an indicator of normal room temperature.

B. Non-Scalding Lid

FIGS. 9A and 9B depict a non-scalding lid 91 for a drinking cup 89 comprising a flap 90 of heat movable plastic attached to the lid under a drinking slot 92. The flap materials are chosen and oriented so that the flap closes off the slot 92 at high temperatures capable of scalding. At lower temperatures suitable for drinking, the flap curls away from the slot, permitting drinking. This device is particularly useful as a disposable coffee lid.

C. Heat Indicator for Drinking Cup

FIGS. 10A and 10B show a lid 100 for a drinking cup 101 including a warning flag 102 of heat movable plastic secured on top of the lid. The top of the flag 102 can be white indicating the contents and can be drunk and the bottom or underlying lid can be red with a warning message, e.g. “Too Hot”. When the contents of the container are cool enough to drink, the flag lies flat (FIG. 10A). When it is too hot, the flag curls up, exposing the warning message (FIG. 10B).

D1. Variable Sunlight Blocker

FIGS. 11A and 11B show a variable sunlight blocker comprising a sheet 110 of heat movable plastic in the form of louvers 111 adhered to a plane of transparent material such as window glass 112. As used herein, the term “louvers” refers to slats, or strips, that when opened, can allow air or light to enter into a room or enclosure. Advantageously, the plastic of the louvers is coated with light reflective material. Preferably, the sheet is placed in the center of a thermoplane window formed with a second glass plane 113. At low temperatures or low sunlight conditions (FIG. 11B), the louvers 111 let sunlight through the transparent material into a room. Alternatively, at higher temperatures (FIG. 11A), the louvers 111 curl and block the light, reducing the heat load on a room.

D2. Venetian Blind

In a preferred embodiment, the inventive louvers, as described above, are used in conjunction with a Venetian blind. The inventive Venetian blind acts to block sunlight and/or reduce the solar heating of a room without manual intervention.

The louvers of the present invention may be used with any conventional Venetian blind design known in the art. Examples of such designs are described in U.S. Pat. No. 3,633,646, U.S. Pat. No. 4,533,580, U.S. Pat. No. 4,817,698, U.S. Pat. No. 5,645,685 and U.S. Pat. No. 6,497,266, all of which are herein incorporated by reference.

FIGS. 11C and 11D depict an embodiment of the inventive Venetian blind in a low light condition and a bright light condition, respectively. FIGS. 11C and 11D show a cross-section of a Venetian blind with the room's exterior window to the left and the room to the right. The individual blades, 1141, are conventionally held in alignment by strings or fabric, 1133 and 1134, in a ladder formation. Although the illustration depicts the blades in vertical alignment, horizontal or other alignments known in the art also are contemplated. The blades are suspended from a head rail (not shown) by any conventional means known in the art. Optionally, a bottom rail (not shown) also is affixed to the blades or the strings aligning the blades.

The head rail is capable of being mounted to a frame opening (not shown). Any conventional mounting means may be used to mount the head rail to a frame opening, such as bracketing means. A “frame opening” refers to the physical space surrounding an aperture in a room, office, closet or any enclosure in a house, office building, other building type or structure. The opening of the frame opening may be covered by a transparent covering formed into a skylight, window or door. Preferably, the transparent covering is made of glass.

The blades, 1141, of the inventive Venetian blind are in contact with flat bilayer louvers of plastic material 1152, 1153, 1142, and 1143. These bilayers, 1152, 1153, 1142, and 1143, are attached to each of the blades, 1141, at one edge, as shown. One or more bilayer louvers may be attached to each blade. As is conventional in a Venetian blind, the blades can be made of metal, wood, plastic, fabric etc, and may be solid or a simple frame to carry and align the bilayer louvers.

The bilayer louvers are made from at least a first and a second polymeric component having coefficients of thermal expansion differing by more than 1.0×10⁻⁵. In one embodiment, the first polymeric component is polyethylene and the second polymeric component is polyvinyl chloride. In another preferred embodiment, the first polymeric component is polyethylene and the second polymeric component is polypropylene. In yet another preferred embodiment, the first polymeric component is low molecular weight polypropylene and the second polymeric component is high molecular weight polypropylene. Preferably, each polymeric component is greater than 1 mil in thickness. More preferably, each polymeric component is between 1 and 10 mils in thickness.

On a cloudy day, solar illumination rays, 1123, can pass through the Venetian blind FIG. 11C via an aperture. However, these rays will not create enough heat to cause the flat bilayer louvers, 1152, 1153, to bend. Alternatively, on a bright sunny day, rays, 1122, are absorbed by the bilayer louvers 1142, 1143 which heat and curl away from their supporting blade. The heating and curling of these bilayer louvers, 1142, 1143, act to block the entry of light into a room or other such enclosure. When the solar rays weaken, for example, as occurs when a cloud obscures the sun, or at night, the bilayer louvers, 1152, 1153, uncurl and permit light to again enter the room.

Other conventional structures also may be included with the inventive Venetian blind. For example, even though movement of the inventive bilayer louvers does not require human intervention, apparatus that allows for the manual movement of the inventive louvers and/or the inventive Venetian blind, also is contemplated. Hence, the blinds can be opened or closed manually by, for example, the rotation of a downwardly extending wand or handle, which extends from a head rail of an inventive Venetian blind. In one embodiment, the wand is connected to a rod passing into the head rail, generally with a universal-type joint, to allow the wand to be at a variety of different angles with respect to the head rail, while still allowing the wand to be rotated for turning the rod within the head rail.

Additionally, a pull-cord arrangement can be included with the inventive Venetian blind to raise or lower the blind. The inventive bilayer louvers do not interfere with the conventional operation of the Venetian blind. Lift cords may be attached to a bottom rail and extend upwardly through cord openings in the louvers, then into a head rail, and then lengthwise through the head rail via a cord lock. As is conventional, the operating portions of the lift cords can be pulled downwardly to raise a bottom rail and move the inventive louvers to a raised condition. The operating cords can be manipulated to release the cord lock and enable the lowering of the blind. (See, e.g. U.S. Pat. No. 5,573,054 for an example of this embodiment). These and other embodiments are well known to artisans in the window covering arts.

The inventive Venetian blinds have a variety of benefits. For example, unless a homeowner is available during the day to close the blinds when the sun hits a particular window, the blind will let in the sunlight and heat the room. The inventive Venetian blinds will not require the homeowner's presence to close the blind and prevent room heating. Likewise, damage to furniture, equipment or the like from sunlight passing through Venetian blinds can be prevented. Further benefits and uses can be envisioned by those of skill in the art.

E. Variable Ventilator

FIGS. 12A and 12B illustrate a variable ventilator comprising a sheet 120 of heat movable plastic cut to define an array of flags 121. The sheet is bonded onto an apertured support sheet 122, such as perforated masonite or flexible plastic, having holes 123 that line up under each flap. Each flap/hole combination forms a valve that lets air pass through at some temperatures and blocks air flow at other temperatures (FIG. 12A).

Such variable ventilators can be used to let air out of an attic in summer but seal it in winter. They can assist temperature regulation in greenhouses and coldframes. And, produced as large areas of clear plastic, they can assist in temperature regulation of entire gardens or even fields. The flaps would let in rain, yet still moderate temperature.

V. Display Applications

These devices also provide novel and attractive visual displays. For example, the opening pyramid of FIG. 4 can be used as a product display.

FIGS. 13A and 13B illustrate another display wherein a thermally movable plastic sheet 132 is partially attached to a display board 131 so that upon heating by a heat source 129 it will produce a three-dimensional effect. In the example shown, upon heating the sheet 132 curls like a wave. Light objects such as a simulated surfboard 133 can also be attached to the sheet 132 to enhance the three-dimensional affect.

It is to be understood that the above-described embodiments are illustrative of only a few of the many possible specific embodiments which can represent applications of the principles of the invention. Numerous and varied other arrangements can be made by those skilled in the art without departing from the spirit and scope of the invention.

Claims

1. A Venetian blind comprising a plurality of blades suspended from a head rail, the head rail having means for mounting to a frame opening; each of the blades contacting a thermally movable bilayer louver; the bilayer louver including at least a first and a second polymeric component, wherein said components have coefficients of thermal expansion differing by more than 1×10−5, and wherein movement of the bilayer louver varies the amount of light transmitted through the Venetian blind.

2. The Venetian blind of claim 1, wherein the opening of said frame is covered by a transparent covering selected from the group consisting of a window, a door and a skylight.

3. The Venetian blind of claim 1, wherein the movement of the bilayer louver indicates a bright light condition.

4. The Venetian blind of claim 1, wherein the movement of the bilayer louver indicates a low light condition.

5. The Venetian blind of claim 1, wherein the polymeric components are between about 1 and 10 mils in thickness.

6. The Venetian blind of claim 1, wherein the first polymeric component is polyethylene and the second polymeric component is polyvinyl chloride.

7. The Venetian blind of claim 1, wherein the first polymeric component is polyethylene and the second polymeric component is polypropylene.

8. The Venetian blind of claim 1, wherein the first polymeric component is low molecular weight polyethylene and the second polymeric component is high molecular weight polyethylene.