Patent Application
20090072430
1. Field of the Invention
The present invention relates to a belt and systems for continuous vacuum forming having one or more belts in which the belt includes a heat absorbing material.
2. Description of Related Art
Continuous vacuum forming processes are known for shaping an extruded plastic sheet. U.S. Pat. No. 5,314,325 describes an apparatus for continuous vacuum forming in which hot plasticized material is drawn in contact with a flexibly resilient belt. The flexibly resilient belt includes a pattern form means thereon which is flexibly resilient. The resilience of the pattern form means allows it to pass around cylindrical rollers and be flexed while still retaining form.
U.S. Pat. No. 6,641,384 describes an apparatus for continuous vacuum forming of a hot plasticized material between a pair of rotating flexible belts in which one belt includes a plurality of teeth, which are received in a plurality of indentations of the other belt. Each of the belts includes a mold, which forms a channel when the belts are adjacent to one another. A vacuum is applied to at least one of the flexible belts for drawing material received in the channel of the belt and for alignment of the belts. Each belt can include a plurality of apertures, which are in fluid flow communication with a plurality of perforations of a flat support belt positioned over a vacuum manifold. The belts can be formed of a rubber material, or rubberized material, such as silicone rubber.
It has been found that in the above-described systems, heat is transferred from the hot plasticized material to the flexible belts. The absorption of heat in the belts can result in cracking of the belts.
It is desirable to provide an improved belt for operating a continuous vacuum forming system at high temperatures.
The present invention relates to a belt used in continuous vacuum forming. The belt comprises a heat absorbing material. In one embodiment, the heat absorbing material comprises graphite.
In one embodiment, a system for continuous vacuum forming a material includes the belt having a heat absorbing material. The belt is continuously rotatable with a flat support belt. The rotatable belt includes apertures therein. The support belt includes perforations therein. The flat support belt is fitted over rotatable rollers and the rotatable belt is fitted over the support belt. The rotatable belt receives the material to be vacuum formed. The belts are rotated by rotatable rollers over a vacuum means. The vacuum means provide a vacuum with the apertures in the rotatable belt and the perforations in the support belt for drawing the material against the rotatable belt.
In another embodiment, the system for continuous vacuum forming includes a pair of the belts having a heat absorbing material. The belts can be rotated using a plurality of teeth in one belt, which are received in a plurality of indentations of the other belt. A vacuum is applied to at least one of the belts for drawing material received between the belts and alignment of the belts. Preferably, a vacuum can be applied to both of the belts for improved alignment. Each belt can include a plurality of apertures, which are in fluid flow communication with a plurality of perforations of a flat support belt positioned over a vacuum manifold.
The invention will be more fully described by reference to the following drawings.
Reference will now be made in greater detail to a preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings. Wherever possible, the same reference numerals will be used throughout the drawings and the description to refer to the same or like parts.
Support belt 18 is positioned underneath rotatable belt 16. Upper surface 17 of support belt 18 contacts bottom surface 15 of rotatable belt 16. Rotatable belt 16 and support belt 18 extend around rollers 20 and 21. Rollers 20 and 21 are driven by driving means 22 to make rolling contact with bottom surface 19 of support belt 18. Vacuum means 23 applies a vacuum through vacuum manifold 24 to an area 25 between rollers 20 and 21.
Preferably, rotatable belt 16 is formed of a rubber material or a rubberized material and including an amount of a heat absorbing material. An example suitable heat absorbing material is graphite. The rubberized material can be silicon rubber. An example amount of the heat absorbing material used in rotatable belt 16 can be in the range of about 2% to about 10% by weight of the rubber or rubberized material. It will be appreciated that rotatable belt 16 can be used to replace the respective flexible belt described in U.S. Pat. No. 5,906,840, the details of which are herein incorporated by reference into this application.
Pattern 30 can be formed in rotatable belt 16, as shown in
Support belt 18 is preferably formed of a flat perforated metal material. For example, metal materials useful for forming support belt 18 include stainless steel, aluminum and nickel. A plurality of perforations 40 can be formed in support belt 18. For example, perforations 40 can have a diameter of about 1/32 of an inch to about 1/16 of an inch and can have a spacing between each perforation of about ¼ inch to about ½ inch. Apertures 32 are in fluid flow communication with perforations 40 to facilitate drawing of extruded material 11 onto top surface 13 of rotatable belt 16 by vacuum means 23. Vacuum means 23 can include grooved sheet 33 attached to vacuum manifold 24. Vacuum means 23 forms a vacuum along grooves 35 of grooved sheet 33.
In an alternate embodiment, extruded material 11 is received between upper belt 51 and lower belt 52 of dual belt continuous vacuum forming system 50, as shown in
Upper belt 51 and lower belt 52 are flexible patterned belts for applying a pattern to extruded shaped material 11. For example, the pattern can be a textured grain pattern. Preferably, upper belt 51 and lower belt 52 have a thickness of about 1 to about 2 inches to provide flexibility without cracking of the belts. Preferably, upper belt 51 and lower belt 52 are formed of a rubber of rubberized material including an amount of a heat absorbing material. A suitable example heat absorbing material is graphite. The rubberized material can be silicon rubber. An example amount of the heat absorbing material used in rotatable belt 16 can be in the range of about 2% to about 10% by weight of the rubber or rubberized material.
Referring to
Belt 16 or upper belt 51 and lower belt 52 allows respective continuous vacuum forming system 10 or dual belt continuous vacuum forming system 50 to operate at elevated temperatures. For example, continuous vacuum forming system 10 or dual belt continuous vacuum forming system 50 can operate at temperatures in the range of 140° F. to 400° F. without cracking of belt 16.
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 readily devised in accordance with these principles by those skilled in the art without departing from the spirit and scope of the invention.
