Patent Application
20160151962
This invention relates to hobby crafts, and particularly to a bracelet mold and to the use of the mold to produce a bracelet from a decorated strip of coated, heat-shrinkable, polystyrene film.
For about forty years, a popular hobby craft activity for both children and adults has been the production of three-dimensional objects from a heat-shrinkable sheet material known by the trademark SHRINKY DINKS, a registered trademark of K & B Innovations, Inc. The material consists of a sheet of thin plastic material that can be colored and/or cut out, and then heated to cause it to shrink and form thickened and hardened art forms. Typically the plastic sheet material is composed of a heat-shrinkable polystyrene base material coated with a water-insoluble, ink-receptive coating. The sheet material and some of its uses are described in U.S. Pat. No. 4,102,456, granted Jul. 25, 1978, and U.S. Pat. No. 6,157,865, granted Dec. 5, 2000. Coatings for the base material are described in U.S. Pat. No. 3,889,270 granted Jun. 10, 1975, U.S. Pat. No. 4,503,111 granted Mar. 5, 1985, U.S. Pat. No. 4,555,437 granted Nov. 26, 1985, U.S. Pat. No. 5,190,805 granted Mar. 2, 1993 and U.S. Pat. No. 5,206,071, granted Apr. 27, 1993. The disclosures of all of the aforementioned United States patents are incorporated by reference.
As supplied, the plastic sheet material is usually flat, and accordingly to form a wristband, bracelet, or the like, from a decorated strip of such material, it would be necessary to provide for a connection of one end of the strip to the other end. Heating the strip will cause it to curl, but, because shrinkage takes place unevenly, the result is usually not aesthetically acceptable.
There has been a need for a simple, convenient, and reliable way to utilize SHRINKY DINK sheet material to produce wearable jewelry in the nature wrist bands, bracelets and the like.
The mold in accordance with the invention comprises a block of silicone rubber having a bottom side and a top side parallel to the bottom side. A spiral slot is formed in said block, and open at the top side of the block and closed at the bottom side of the block. The spiral slot extends by at least two full turns, i.e., through an angle of at least 720°, and preferably 810°, around an axis that is in perpendicular relation to the top and bottom sides of the block A cover, preferably also made of silicone rubber, fits removably over the top side of said block, for enclosing the spiral slot.
Preferably, each of the bottom and top sides of the silicone rubber block has a central opening, and the central opening in the bottom side is connected to the central opening in the top side by a through passage. The spiral slot is preferably bounded by walls having a uniform thickness and extending from the bottom side of the block to the top side of the block.
The process for making a bracelet in accordance with the invention comprises inserting a strip of heat-shrinkable sheet material into a spiral slot in a silicone rubber mold, heating the strip while the strip is in the mold, thereby causing said strip to shrink, to become resilient, and to assume an arc-shaped configuration when relaxed, and removing the strip from the mold.
Preferably the spiral slot has a minimum radius not greater than 15 mm. and a maximum radius not greater than 25 mm. Ideally, the minimum radius of the spiral slot should be 15 mm, and its maximum radius should be 25 mm. The strip, in its arc-shaped configuration, can be expanded to receive an individual's wrist, and contracts by reason of its resilience to fit snugly but comfortably onto the individual's wrist.
A shown in
The mold body 10 is in the form of a block of silicone rubber having a flat bottom side 14 and a top side 16 in a plane parallel to the bottom side. The top side 16 has a central opening 18, and the bottom side 14 has a central opening 20, shown in
As seen in
The term “spiral” as used herein refers to a curve defined by a point on a radial line that rotates about a center, where the distance along the radial line from the center to the point increases at a rate proportional to the angle between the radial line and a fixed reference radial line extending through the center. That is, a spiral is defined in polar coordinates as a continuous portion of a curve r=kθ, where r is the distance from the center to the point, θ is the angle, and k is a constant.
As seen in
The uniform thickness of the spiral wall 24, promotes uniform heating of a heat-shrinkable strip placed in the spiral slot. The central passage 22 makes it possible for the inner part of the spiral wall to have the same thickness as its other parts.
The cover 12 is shaped to fit over the top of the mold body 10, and has a flange 32, which extends downward and is shaped to fit the upper portion of the outer wall of the mold body closely.
The height of the mold body, i.e., the distance from the bottom side 14 to the top side 16, is preferably about 32 mm, and the vertical height of the spiral slot 24 is slightly less, e.g., 30 mm.
To make a bracelet, a user can first decorate a coated strip 34 of heat-shrinkable material as shown in
The decorated strip, the length of which should be slightly less than the length of the spiral slot 24, e.g. about 250 mm, is placed into the spiral slot as shown in
If the spiral slot in the mold has these minimum and maximum radii, the radius of the relaxed, arc-shaped strip shown in
