WO2001032399A1

WO2001032399A1 - Method and apparatus for thermoforming trim panels

Info

Publication number: WO2001032399A1
Application number: PCT/CA2000/001244
Authority: WO
Inventors: Walter P. Kornylo; Ronald R. Force
Original assignee: Magna Interior Systems, Inc.
Priority date: 1999-11-03
Filing date: 2000-10-25
Publication date: 2001-05-10
Also published as: AU1012901A

Abstract

A method and apparatus for forming an interior trim panel of an automotive vehicle. The apparatus comprises a lower mold having a lower mold cavity disposed vertically above the lower mold for movement between an open position spaced above the lower mold and a closed position in mating engagement with the lower mold. A plurality of vacuum ports (28) are disposed in the lower mold and extend between a vacuum opening disposed at the lower mold surface and a main vacuum line for applying vacuum pressure to the lower mold cavity. A fluid port (36) is disposed in the upper mold for supplying positive fluid pressure into the upper mold cavity and against the lower mold surface. The method includes the steps of placing a planar sheet of material (48) to be formed as the trim panel over the lower mold cavity defined by the contoured lower mold surface. Air from the lower mold cavity is evacuated from between the sheet of material and the lower mold surface to force the sheet of material to form at least partially to the contour of the lower mold surface to ensure that the entire sheet of material conforms to the contour of the lower mold surface of the lower cavity.

Description

METHOD AND APPARATUS FOR THERMOFORMING TRIM PANELS

Field of the Invention

The present invention relates to a method and apparatus for manufacturing a trim panel of an automotive vehicle, and more particularly, for forming a closed pattern grain definition in female vacuum formed interior trim panels.

Background of the Invention

Automotive interior trim panels typically include an outer layer made from moldable plastic and an inner layer of urethane foam that is usually sprayed onto the outer layer and allowed to harden to form a substrate for the trim panel. The outer layer is often made by a process known as female cavity mold vacuum forming. This process is commonly known in the art and is used extensively for applications of this type.

The female cavity mold vacuum forming process includes the use of a mold cavity which has vacuum ports distributed across the inner surface of the mold. A pre-heated sheet of a moldable plastic, typically a PVC/ABS blend, is laid across the mold. A plug is used to rough locate the plastic sheet within the mold. The plug is a three dimensional shape which corresponds to the shape of the mold.

Once the sheet is in place and the plug is advanced against the plastic sheet, a vacuum is activated to draw air in through the ports within the mold. The sheet is held against an outer perimeter of the mold such that no ambient air can enter. The vacuum ports draw out the air between the sheet and the mold surface creating a vacuum which draws the sheet tightly against the inner surface of the mold. The plug is needed to ensure that the plastic sheet is not overly stretched or otherwise deformed when the vacuum ports are activated. Specifically, the plug roughly positions the plastic sheet down into the female cavity mold, such that the sheet is roughly in place when the vacuum is activated and minimal stretching and deformation takes place.

This process works very well with a smooth mold. However when the mold includes a closed pattern grain, it is difficult to obtain consistent grain definition on the finished interior trim panel. A closed pattern grain is a predetermined pattern of indents, cavities, raised ridges, or the like, formed on the mold surfaces for forming a corresponding pattern on the outermost surface of the trim panel. In a mold with a closed pattern grain, the vacuum ports are typically located in selected grain locations at the bottom of the mold. When the vacuum is activated, the plastic sheet seals against the upper edges formed around the particular grains at the vacuum port locations. The result is that the air is not as effectively evacuated from between the plastic sheet and the mold. More specifically, in the grains which do not have vacuum ports, air is trapped within the grain preventing the plastic sheet from molding to the full depth of the grain. The final result is a trim panel that may have good grain definition at the grains where vacuum ports were located, and decreasing grain definition further from the grains with vacuum ports. Therefore, it is desirable to provide a method and apparatus for improving the grain patterns when forming an interior trim panel.

Summary of the Invention

Accordingly, the present invention relates to a method of forming a trim panel for an automotive vehicle comprising the steps of placing a planar sheet of material to be formed as the trim panel over a lower mold having a lower mold cavity defined by a contoured lower mold surface. Air is evacuated from the lower mold cavity between the sheet of material and the lower mold surface to force the sheet of material to form at least partially to the contour of the lower mold surface. A positive pressure is applied against the sheet of material to evacuate any remaining air from the lower mold cavity between the sheet of material and the lower mold surface to ensure that the entire sheet of material conforms to the contour of the lower mold surface of the lower cavity.

The present invention also relates to an apparatus for forming a trim panel of an automotive vehicle comprising a lower mold having a lower mold cavity defined by a contoured lower mold surface and an upper mold having an upper mold cavity disposed vertically above the lower mold for movement between an open position spaced above the lower mold and a closed position in mating engagement with the lower mold. A plurality of vacuum ports are disposed in the lower mold and extend between a vacuum opening disposed at the lower mold surface and a main vacuum line for applying vacuum pressure to the lower mold cavity. At least one fluid port is disposed in the upper mold for supplying positive fluid pressure into the upper mold cavity and against the lower mold surface. Brief Description of the Drawings

Advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: Figure 1 is a cross-sectional side view of a molding apparatus in an open position according to the present invention;

Figure 2 is a perspective view of a closed pattern grain formed on the mold surface of the molding apparatus;

Figure 3 is a cross-sectional side view of the molding apparatus with a plug seated on the lower mold of the molding apparatus;

Figure 4 is a cross-sectional side view of the molding apparatus in a closed position;

Figure 5 is a sectional view of the lower mold surface and sheet of material after vacuum pressure is applied to the lower mold during the process of the present invention; and

Figure 6 is a sectional view of the lower mold surface and sheet of material after positive air pressure is applied from the upper mold during the process of the present invention.

Detailed Description of the Preferred Embodiment

Referring to the Figures, wherein like numerals indicate like or corresponding parts throughout the several views, a molding apparatus used in the process of forming an interior trim panel of an automotive vehicle according to the present invention is generally shown at 10 in Figure 1. The molding assembly 10 includes a lower mold 12 forming a lower mold cavity 14 and an upper mold 16 forming an upper mold cavity 18. The upper mold 16 is aligned above the lower mold 12 for vertical movement between an open position spaced vertically above the lower mold 12 and a closed position in mating engagement with the lower mold 12. The lower mold cavity 14 is defined by a lower mold surface 20. The lower mold surface 20 of the lower cavity 14 is contoured to a predetermined shape which can be changed as desired according to the product being manufactured. The contour of the lower mold surface 20 creates the overall shape of the product being manufactured. Referring to Figure 2, the lower mold surface 20 of the lower cavity 14, in the preferred embodiment, also includes a closed pattern grain, generally indicated at 22, for forming a texture on the outer surface of the trim panel being manufactured. The closed pattern grain 22 may be defined by a number of indents, pockets, cavities, ridges, or the like, formed on the lower mold surface 20 of the lower cavity 14. The closed pattern grain 22 shown in Figure 2 is in the form of a pattern of symmetrical squares formed on the lower mold surface 20. The squares are define by a first plurality of spaced apart and parallel raised ridges 24 intersecting with a second plurality of spaced apart and parallel raised ridges 26. The first plurality of raised ridges 24 are generally perpendicular to the second plurality of raised ridges 26, the intersection of which form the symmetrical square pattern, or grain pattern, on the lower mold surface 20. The raised ridges 24, 26 will form corresponding channels in the outer surface of the molded trim panel. It should be appreciated that any variation from a perfectly smooth lower mold surface 20 will create a corresponding pattern in the molded trim panel. That is, the grain pattern may be symmetrical, non-symmetrical, square, circular or any desired shape or pattern on the mold surface 20 for forming a textured surface on the molded trim panel.

Referring to Figures 1 and 2, the molding apparatus 10 further includes a plurality of vacuum ports 28 disposed within the lower mold 12 for evacuating air during the molding process. The vacuum ports 28 extend from an opening 30, flush to the lower mold surface 20, to a main vacuum line 32. The main vacuum line 32 is connected to a vacuum pump 34 for creating vacuum pressure. The vacuum ports 28 are spaced apart and strategically located across the entire lower mold surface 20 of the lower mold cavity 14, however, a vacuum port 28 is not located within each square of the closed pattern grain 22. The upper mold 16 includes a fluid port 36 disposed therein connected to a fluid supply chamber 38 for supplying pressurized fluid to the upper mold cavity 18. The fluid may include any type of fluid which may be pressurized, or compressed, by the supply chamber 38. In the preferred embodiment, the fluid is air supplied from an air compressor or pump 38. Finally, the molding apparatus 10 includes a plug 40 disposed vertically above the lower mold 12. The plug 40 includes a contoured lower surface 42 which mirrors the contour of the lower mold surface 20 and a pair of locator recesses 44 for mating with

-A- locator pins 46 projecting from the lower mold surface 20 to locate and align the contoured lower surface 42 with the lower mold surface 20. The plug 40 may alternatively be fixed or movably attached to the upper mold 16.

The molding apparatus 10 is used in association with a method or process of forming an interior trim panel, and more particularly, for forming a closed pattern grain in an interior trim panel of an automotive vehicle. Specifically, referring to Figure 1, with the upper mold 16 in the open position spaced above the lower mold 12, the method includes placing a generally planar plastic sheet of material 48, preferably a PVC/ABS blend, against the lower mold 12 and over the lower mold cavity 18 adjacent the lower mold surface 20. The plastic sheet 48 is pre-heated to a predetermined temperature sufficient to allow the plastic sheet 48 to conform to the contour and grain pattern of the lower mold surface 20. The plug 40 is then placed above the plastic sheet 48 between the upper mold 14 and the lower mold 12. The plug 40 is pressed into the plastic sheet 48, either manually or by the upper mold 14, to force the plastic sheet 48 into the lower mold cavity 14 and roughly deformed against the lower mold surface 20, as shown in Figure 3. The plug 40 is aligned within the lower mold cavity 14 by mating alignment between the locator pins 46 within the locator recesses 44. At this point, the plastic sheet 48 is roughly the shape of the lower mold surface 20 of the lower mold cavity 14, but has not conformed to the more detailed features and shapes defined by the grain pattern 22 on the lower mold surface 20.

Once the plastic sheet 48 has been roughly located and formed within the lower mold cavity 14 by the plug 18, the upper mold 16 is lowered to the closed position into mating engagement with the lower mold 12, with an outer peripheral portion of the sheet 48 sandwiched therebetween, as shown in Figure 4. The upper mold 16 is sealed against the lower mold 12 in the closed position to fluidly seal both the upper mold cavity 18 and the lower mold cavity 14, with the sheet 48 and plug 40 therebetween. That is, the upper mold 16 seals the plastic sheet 48 to the lower cavity 14 to prevent any ambient air from entering or escaping from or between the lower cavity 14 and the plastic sheet 48. The upper mold 16 also creates a sealed upper mold cavity 18 above the plastic sheet 48 into which ambient air cannot enter or escape.

With the upper mold 16 in the closed position, the vacuum pump 34 is activated to draw vacuum pressure through the vacuum ports 28 and create a vacuum in the lower mold cavity 14 between the sheet 48 and the lower mold surface 20. The vacuum pressure evacuates the air between the sheet 48 and the lower mold surface 20 to draw the sheet 48 against the lower mold surface 20. That is, with the sheet 48 sealed between the engaged upper mold 16 and lower mold 12, no air can enter between the sheet 48 and lower mold cavity 20. Therefore, when the vacuum pump 34 is activated, the vacuum ports 34 create a vacuum within the lower mold cavity 14 between the lower mold surface 20 and the plastic sheet 48. Since the plastic sheet 48 is pre-heated, it can be molded and shaped as desired. The vacuum pressure draws the plastic sheet 48 tightly against the lower mold surface 20 of the lower mold cavity 14, thereby forcing the plastic sheet 48 to conform to the detailed contours of the lower mold surface 20. Pre-heating the plastic sheet 48 and using vacuum pressure to draw the air from between the plastic sheet 48 and the lower mold surface 20 helps to force the plastic sheet 48 to conform to the contours of the lower mold surface 20 of the lower mold cavity 14, and more specifically, to draw the plastic sheet 48 down into the grain pattern 22 within the mold surface 20 to achieve a high grain definition.

Referring to Figure 5, as the plastic sheet 48 is drawn downward toward the lower mold surface 20, the plastic sheet 48 seals against the upper edges of the raised ridges 24, 26 forming the grain pattern. Specifically, the plastic sheet 48 seals against the upper edges of the raised ridges 24, 26 forming the square grain patterns that do not include a vacuum port 28 therebetween. Air is trapped within the grains patterns that do not include a vacuum port 28 which prevents the plastic sheet 48 from fully molding, or forming, to the shape of the grain pattern. Therefore, as a final step, a positive pressure air blast is supplied by the fluid chamber 38, through the fluid port 36 and into the upper mold cavity 18, immediately following activation of the vacuum pump 34. The positive pressure air blast is preferably greater than the negative vacuum pressure created by the vacuum ports 28. For example, if the draw of the vacuum is 15 PSI, then the positive pressure of the air blast should be roughly 20 PSI. The vacuum and air blast pressures are chosen based on the material being molded, the contour of the lower mold surface 20, and the type of grain pattern on the lower mold surface 20. Alternatively, the positive pressure within the upper mold cavity 18 may be supplied by the vacuum pressure and vacuum pump 34. That is, the vacuum pressure which is created by the vacuum pump 34 may draw air through the ports 28 from the lower mold cavity 14 and exhausted through the port 36 in the upper mold 16 to create positive back pressure within the upper mold cavity 18 against the top of the plastic sheet 48. The positive pressure may be equal to the vacuum pressure or increased above the vacuum pressure by the vacuum pump 34 or air compressor 38. Thus, the pressure created by the vacuum pump 34 may be "recycled" for use as the positive pressure in the upper mold cavity 18.

Referring to Figure 6, the additional positive pressure exerted on the plastic sheet 48 forces the plastic sheet 48 deeper into the grain pattern along the lower mold surface 20 of the lower cavity 14, and forces trapped air to migrate to the grain patterns which include a vacuum port 28 where the air is then evacuated.

The additional step of providing a positive pressure air blast to the plastic sheet 48 forces the plastic sheet 48 to conform to the grain pattern within the lower cavity 14 so that consistent grain definition and visual appearance across the entire surface of the molded trim panel can be attained. Additionally, the positive pressure air blast will allow the lower mold surface 20 of the molding apparatus 10 to be designed with contours that have tighter radiuses and corners, as the positive air blast will force the moldable plastic sheet 48 against the lower mold surface 20 more effectively. The present invention provides a process whereby interior trim panels are produced with consistent closed pattern grain definition across the entire surface of the trim panel and features which are sharper and tighter than previously attainable.

The invention has been described in an illustrative manner, and it is to be understood that the terminology, which has been used, is intended to be in the nature of words of description rather than of limitation. Many modification and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced other than as specifically described.

Claims

What is claimed is:

1. A method of forming a trim panel for an automotive vehicle comprising the steps of: placing a planar sheet of material to be formed as the trim panel over a lower mold having a lower mold cavity defined by a contoured lower mold surface; evacuating the air from the lower mold cavity between the sheet of material and the lower mold surface to force the sheet of material to form at least partially to the contour of the lower mold surface; and applying a positive pressure against the sheet of material to evacuate any remaining air from the lower mold cavity between the sheet of material and the lower mold surface to ensure that the entire sheet of material conforms to the contour of the lower mold surface of the lower cavity.

2. A method as set forth in claim 1 further including the step of evacuating the air from the lower mold cavity between the sheet of material and the lower mold surface prior to applying the positive pressure against the sheet of material to evacuate any remaining air from the lower mold cavity.

3. A method as set forth in claim 2 further including the step of applying a plug against the sheet of material prior to evacuating the air from the lower mold cavity to preform the sheet of material into the lower mold cavity to the general contour of the lower mold surface.

4. A method as set forth in claim 3 further including the step of sealing the sheet of material against the lower mold to seal the lower mold cavity between the sheet of material and the lower mold surface.

5. A method as set forth in claim 4 further including the step of disposing an upper mold having an upper mold cavity against the lower mold to sandwich at least a portion of the sheet of material therebetween and sealing the sheet of material between the upper mold cavity and the lower mold cavity.

6. A method as set forth in claim 5 further including the step of applying the positive pressure through the upper mold into the upper mold cavity to force the sheet of material against the lower mold surface and evacuate any remaining air in the lower mold cavity between the sheet of material and the lower mold surface.

7. A molding apparatus for forming a trim panel of an automotive vehicle comprising: a lower mold having a lower mold cavity defined by a contoured lower mold surface; an upper mold having an upper mold cavity disposed vertically above said lower mold for movement between an open position spaced above said lower mold and a closed position in mating engagement with said lower mold; a plurality of vacuum ports disposed in said lower mold extending between a vacuum opening disposed at said lower mold surface and a main vacuum line for applying vacuum pressure to said lower mold cavity; and at least one fluid port disposed in said upper mold for supplying positive fluid pressure into said upper mold cavity and against said lower mold surface.

8. A molding apparatus as set forth in claim 7 further including a plug disposed between said upper mold and said lower mold, said plug having a lower contoured surface for mating with the contoured lower mold surface of said lower mold.

9. A molding apparatus as set forth in claim 8 further including a vacuum pump connected to said main vacuum line for applying vacuum pressure through said vacuum ports and into said lower mold cavity.

10. A molding apparatus as set forth in claim 9 further including a fluid supply chamber connected to said fluid port for supplying pressurized fluid through said upper mold and into said upper mold cavity.