Abstract
Thermoforming apparatus and methods are described. To-be-formed polymeric material may be separated initially from a mold surface by a grid or support rail, avoiding the mold surface from drawing heat away from the material while it is being heated to forming temperatures. The grid may retract into the mold when no longer needed to support the material. Plugs or inserts about which material is formed may include skirts, allowing the formed material to be shaped so as to guide coins or other objects into cavities in which the coins or objects are held for presentation or display. Profile plates associated with the molds may include non-stick material on their sides intended to abut to-be-formed polymeric sheets in order to reduce possibility of transfer of printing from the sheets to the plates and reduce undesired transfer of heat from the plates to the sheets.
Claims
1. Apparatus for thermoforming a plastic material, comprising: a. a mold; b. means for supporting a plastic material in a first position remote from the mold and for repositioning the plastic material to a second position adjacent the mold, the plastic material defining integral first and second regions and the supporting means comprising a grid atop which the plastic material is configured to be placed; and c. means for selectively heating the first region to its forming temperature while maintaining the second region at less than its forming temperature when the plastic material is in the second position.
2. Apparatus according to claim 1 in which the supporting means further comprises at least one spring for biasing the plastic material toward the first position.
3. Apparatus according to claim 2 in which the mold defines an upper surface having at least one recess therein.
4. Apparatus according to claim 3 in which the at least one recess in the upper surface of the mold is configured to receive the grid when the plastic material is in the second position.
5. Apparatus according to claim 4 in which at least one pin protrudes from the upper surface of the mold, with the at least one spring being fitted about the at least one pin.
6. Apparatus according to claim 5 in which at least one plug protrudes from the upper surface of the mold, with the at least one plug being generally cylindrical in shape and having a side about which a skirt is formed.
7. Apparatus according to claim 6 in which the skirt forms an angle of approximately 135 with the side.
8. Apparatus according to claim 1 in which the grid comprises intersecting sets of bars.
9. Apparatus according to claim 5 in which the grid comprises intersecting sets of bars having at least one hole receiving the at least one pin.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) FIG. 1 is a perspective view of a mold useful with the present invention and illustrating various plugs and alignment pins protruding upward from its surface onto which a formable sheet may be placed.
(2) FIG. 2 is a perspective view of the mold portion of FIG. 1 together with a grid positioned on the alignment pins.
(3) FIG. 3 is a close-up view of the mold portion and grid of FIG. 2.
(4) FIG. 4 is a perspective view of an exemplary profile plate of the present invention having recesses that are not through-holes.
(5) FIG. 5 is a perspective view of the profile plate of FIG. 4 positioned atop an exemplary polymeric sheet and the grid of FIGS. 2-3.
(6) FIG. 6 is a perspective view of an exemplary polymeric sheet post-forming.
(7) FIGS. 7A-D are various views of a plug consistent with FIG. 1.
DETAILED DESCRIPTION
(8) Depicted in FIG. 1 are portions of a thermoforming apparatus including mold 10. Mold 10 may be similar to the mold of the Shanley, IV application and include a generally planar upper surface 14 and clamps 18. Protruding upward from upper surface 14 may be one or more plugs 22 and one or more alignment pins 26. Mold 10 preferably (but not necessarily) is made of aluminum, and plugs 22 function as three-dimensional objects about which sheets of polymer material are formed. Although not shown in FIG. 1, items such as heaters, actuators, and computerized controls also may be included as part of the thermoforming apparatus as needed. Pins 26 facilitate alignment of the to-be-formed material relative to the plugs 22.
(9) FIGS. 2-3 illustrate an exemplary grid 30 of the present invention. Grid 30 forms a support rail structure for a polymeric sheet and may include one or more holes 34 configured to align with pins 26. FIGS. 2-3 also detail springs 38 positioned about (at least) the pins 26 that are aligned with holes 34; the force of the springs 38 suspends grid 30 above upper surface 14, effectively providing an air gap between the two. Placing the polymeric sheet onto the top of grid 30, i.e. onto surface 42, thereby results in separation between the sheet and the upper surface 14 until the force of springs 38 is overcome.
(10) As shown at least in part in FIG. 2, grid 30 may comprise intersecting sets of bars 44 and have an overall size approximating the size of upper surface 14. Aluminum is a preferred material for grid 30, although other materials may be used instead. Preferably, although not necessarily, the total area of bars 44 of grid 30 is substantially less than the overall area of the grid 30. As long as grid 30 is able to prevent substantial sagging of a heated polymeric sheet, it should be satisfactory for its intended purposes.
(11) Also detailed in FIGS. 2-3 are recesses 46 formed in upper surface 14. Recesses 46 are formed complementary to grid 30 so that bars 44 may fit in the recesses 46 when the force of springs 38 is overcome. When bars 44 of grid 30 are so fitted, the polymeric sheet previously supported thereby instead will contact upper surface 14 so as to be able to be formed about plugs 22.
(12) FIG. 4 shows an exemplary profile plate 50 of the present invention. Plate 50 may generally be similar to the heat sink of the Shanley, IV application and include one or more cut-outs 54 through its depth, each of which preferably is approximately the size and shape of an associated plug 22. In an embodiment of the invention consistent with FIG. 4, however, plate 50 may omit through-holes for purposes of aligning with pins 26. Instead, it may contain downwardly-directed recesses configured to receive the pins 26, with the exterior 58 of one such recess being illustrated in FIG. 4 as protruding upward from upper surface 62 of plate 50.
(13) FIG. 5 illustrates relative positioning of grid 30 (albeit no longer visible in the drawing), polymeric sheet M (visible only through cut-outs 54), and profile plate 50 when the force of springs 38 is overcome. Upon this occurrence, bars 44 are fitted into recesses 46 so that grid 30 is flush with upper surface 14, sheet M contacts the upper surface 14 so as to be formed about plugs 22, and profile plate 50 remains atop the sheet M. A sample sheet M post-forming appears in FIG. 6. Like the formed sheet of the Shanley, IV application, sheet M may contain both formed portions 66 and unformed portions 70 and may be divided into multiple display holders or otherwise. Formed portions 66 typically comprise cavities for receiving coins or other objects for display, whereas unformed portions 70 typically include printed text or art work that remains undistorted notwithstanding having been subjected to elevated temperatures during the forming process. Sheet M need not necessarily have both formed and unformed portions 66 and 70, respectively, nor need it necessarily include printed text or art work.
(14) FIGS. 7A-D, finally, depict aspects of an exemplary plug 22 configured to be removably fitted into upper surface 14 of mold 10. Like the plugs of the Shanley, IV application, plug 22 may, if desired, be shaped generally as a cylinder and include section 74 comprising upper surface 78 together with side 82. Formed into side 82 may be one or more notches 86. Preferably three notches 86 are incorporated into side 82, with the notches 86 beneficially (although not necessarily) being angularly spaced evenly about the circumference of plug 22. As depicted in FIGS. 7B-D, notches 86 need not extend completely to upper surface 78although they may do so if desired.
(15) Detailed especially in FIGS. 7A-B and D is skirt 90 of plug 22. Skirt 90 exists about the circumference of section 74 at an end 94 of side 82 opposite upper surface 78 and forms an angle at its intersection with side 82 of preferably (although not necessarily) approximately 135. Effectively, skirt 90 may be a radiused extension of side 82. Existence of the skirt 90 essentially creates a controlled radius at the entry of each formed portion 66, reducing the tendency of the portion 66 to obstruct placement of a coin therein.
(16) As noted earlier herein, variants of the inventive technology may utilize through-holes in profile plates 50 instead of recesses or swap pins, holes, and recesses between the mold and plates 50. Additional variants of plates 50 may incorporate silicone tape material (or other non-stick material) on their sides that contact the polymeric sheets to help prevent undesired transfer of heat from plates 50 to the printed surfaces of the sheets. Persons skilled in the art will recognize that yet other variants may exist consistent with the concepts described herein and that acts of the thermoforming processes not described herein may be performed in the manners described in the Shanley, IV application or otherwise as desired.
(17) The foregoing is provided for purposes of illustrating, explaining, and describing embodiments of the present invention. Terms of direction and relative positioning (e.g. upper lower, upward, atop, etc.) are used to identify nominal or preferred, rather than absolute, relationships of components and may be modified as appropriate. Further modifications and adaptations to these embodiments will be apparent to those skilled in the art and may be made without departing from the scope or spirit of the invention.
