This invention relates to improvements in integral skin foam objects, and more particularly to improvements in methods of making integral skin foam objects.
Integral skin foam objects are used in many applications, including steering wheels, instrument panels, console box lids and glove box lids, armrests and headrests, etc. For example, headrests have been used in motor vehicles for many years, and provide both a convenient place to rest an operator's head and also provide protection in the event of sudden changes in acceleration of the motor vehicle. Headrests also often are adjustably mounted to a seat to provide comfort adjustment. Generally, such headrests include cloth covered headrests and integral skin foam headrests. With cloth covered headrests, a foam or cushion like interior is shrouded by a cloth. Integral skin foam headrests have an exterior integral skin region with a low degree of foaming (often with a urethane paint applied to the molded part) and an interior region having a high degree of foaming. The foam material is typically polyurethane foam formed from a reaction of a polyol and an isocyanate. Known integral skin foam parts have had problems with exterior surface irregularities. These were manageable for part designs where part of the exterior surface was hidden from view. However, for parts where essentially the entire exterior surface is a “show surface” (visible to the user of the part), such surface irregularities prevented widespread use of integral skin foam technology without a cover. Therefore, it would be highly desirable to have an improved, low cost, method of making integral skin foam objects with improved show surface characteristics.
In accordance with a first aspect, a method for making an integral skin foam object in a mold mounted on a mold carrier is disclosed, comprising the steps of injecting a mixture of a polyol and an isocyanate into the mold, closing mold halves together, rotating the mold carrier about 80 to 110 degrees and allowing the mixture to react to form a polyurethane foam which fills the mold cavity. In accordance with another aspect, the mold clamping pressures are 300-600 psi, and the mold has upper and lower seals having widths of only about 0.25″ to 0.5″.
From the foregoing disclosure and the following more detailed description of various preferred embodiments it will be apparent to those skilled in the art that the present invention provides a significant advance in the technology of integral skin foam parts. Particularly significant in this regard is the potential the invention affords for providing a method of making a high quality integral skin foam part with an aesthetically attractive exterior or show surface. Additional features and advantages of various preferred embodiments will be better understood in view of the detailed description provided below.
It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various preferred features illustrative of the basic principles of the invention. The specific design features of the mold and method of making an integral skin foam part disclosed here, including, for example, the specific dimensions of the mold cavity will be determined in part by the particular intended application and use environment. Certain features of the illustrated embodiments have been enlarged or distorted relative to others to enhance visualization and clear understanding. In particular, thin features may be thickened, for example, for clarity of illustration. All references to direction and position, unless otherwise indicated, refer to the orientation illustrated in the drawings.
It will be apparent to those skilled in the art, that is, to those who have knowledge or experience in this area of technology, that many uses and design variations are possible for the mold and method of making an integral skin foam part disclosed here. The following detailed discussion of various alternative and preferred features and embodiments will illustrate the general principles of the invention with reference to a headrest suitable for use in automotive applications. Other embodiments suitable for other applications will be apparent to those skilled in the art given the benefit of this disclosure.
Referring now to the drawings,
Broadly, manufacture of an integral skin foam object or part as disclosed herein comprises preferably spraying or otherwise applying a mold release to the mold halves to help the part separate from the mold halves, and then spraying or otherwise applying each of the mold halves 16, 18 with a urethane paint. Once these steps are completed, a reactive two component mixture is introduced into the mold which, under mild heating, foams to fill the mold cavity. Generally greater foaming occurs in the center of the part, and the paint forms an integral skin to produce an aesthetically appealing show surface. A polyurethane foam part 14 is formed by reaction of two components: a polyol and an isocyanate introduced together into the mold. In the preferred embodiment shown in the Figs., the part 14 is an automotive headrest having a mounting insert 34, which during assembly is laid into proper alignment in the bottom mold half 18, typically after application of paint but prior to introduction of the two component mixture. The part 14 has a parting line 99 corresponding to where the mold halves meet. A heat gun 30 (
In accordance with another highly advantageous feature, the mold halves are closed together in a down position shown in
The mold halves 16, 18 have corresponding seals 26, 28 extending circumferentially around the mold cavity, as seen in
When the polyurethane foam object is removed from the mold, it is still warm, and the gas that creates the internal foam bubbles is naturally warm as well. To help equalize the pressure and reduce show surface irregularities, it has been found that in certain preferred embodiments a pressure equalization valve 32 may be inserted into the object, preferably at the area of the object formed adjacent the shim vent as seen in
The embodiments discussed were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to use the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.