MXPA97000364A - Coinjected automobile bumpers - Google Patents

Abstract

The present invention provides articles for absorbing and dissipating kinetic energy. These articles are formed by coinjection molding of a first thermoplastic material having good appareance and strength properties and of a second thermoplastic material having appearance and/or strength properties significantly inferior to those of said first thermoplastic material. The second thermoplastic material will generally form a core that is entirely surrounded by a skin consisting of said first thermoplastic material, although in some instances a portion of the finished article that will not be visible in use or is of special function may be constituted by exposed core material.

Description

"CO-INJECTED AUTOMOBILE BUMPERS" FIELD OF THE INVENTION The present invention relates to articles of plastic manufacture, and their production by injection molding techniques. More particularly, the present invention relates to articles, such as automobile bumpers and instrument boards that are produced by co-injecting at least two different grades of thermoplastic resins, such as polyolefins in mold forms that have been advantageously designed to Use the respective qualities of these thermoplastic resins.

• BACKGROUND OF THE INVENTION Extrusion and co-extrusion molding constitute well-known techniques for making articles that can be considered essentially "bi-dimensional" in configuration. The extrusion processes can be used to make long, straight, uniform rods; wires or complex bi-dimensional profiles that can then be cut to the desired length. The extrusion processes are limited by the nature of the shape of the pieces they will form. The use of inexpensive core materials in co-extrusion is * well known, but few automotive parts are manufactured with this process due to shape limitations. In extrusion and coextrusion processes, the plastic flows continuously through the bi-dimensional opening and then cooled in a water bath and finally cut to the desired length. A solid or hollow rod can be extruded, but it is impossible * Uncover the ends in extrusion processes. 10 Insertion or rolling (ie, internal / external) molding processes tend to have more complicated tools and longer cycle times than co-extrusion and co-injection processes. They also produce products that are physically more prone to warping than are the symmetrical coating / core / coating products that can < # produced by co-injection molding processes in accordance with the present invention. Perfectly straight pieces are rare in cars. When extrusion is used, the three-dimensional injection molded end caps are often used to complete the assembly. U.S. Patent Nos. 5,128,196, 5,087,488, 4,814,037, 4,546,022 and 4,405,557 disclose the processes of extrusion of sheet or profile that are not applicable to the formation of automotive parts of the types proposed by the present invention. In injection molding and co-injection, liquid plastics are injected into a three-dimensional mold where they are cooled and ejected once the mold is opened. Typical injection molding processes are described in U.S. Patent Nos. 5,057,266 and 4,925,100. The addition of the third dimension »Allows the production of complex shapes, attachments and significant design freedom. Even though there has been some limited co-injection molding activity with low cost cores, this has had very little commercial success. It has not been applied to the formation of automobile parts of the types proposed by this invention - namely, energy management parts. For example, Battenfeld GmbH of Meinerzhagen, Germany, a - * Leading producer of co-injection molding equipment promotes your equipment to be used in the manufacture of products such as housings for tooling carpentry, such as manual carpenter's brushes and circular saws, television housings, garden chairs and fins for boards to float on the waves. The applications in automobiles that Battenfeld discloses are for products such as fenders and reflectors of headlights front. In these automotive applications, Battenfeld # is related, in what refers to the present, only with the structural aspects of the core. Battenfeld does not disclose or suggest the use of low-cost low-cost core materials, as in the present invention.

COMPENDIUM OF THE INVENTION * The present invention provides a means by which relatively large quantities of inferior materials can be used internally in structures in applications that had never been thought possible without detrimental effects. In this way, the present invention provides an article for absorbing and dissipate the kinetic energy, whose article is formed by co-injection molding a first material / "- thermoplastic that has good appearance and good strength properties and a second thermoplastic material that has appearance and / or properties of resistance significantly lower than those of the first thermoplastic material. Preferably, the second thermoplastic material constitutes from 10 percent to 75 percent by volume of the article's mass. Unused internal material that can be used with greater advantage in accordance with the principles of the present invention is known as "painted re-corrected" thermoplastic olefin material. The term "painted re-rectified" refers to articles such as automobile bumpers which have been manufactured from thermoplastic polyolefins and painted and which have subsequently been ground to be used as a core material in accordance with the structural configurations of the present invention. j * Certain properties - for example, the Resistance - can be improved by using the painted re-corrected in accordance with the present invention. Appearance is the only significant property that is derived from the painted re-corrected core that will generally be made inferior to the use of a comparable core made of virgin material. When the piece in question is intended to be grain or low * Brightness, usually a relatively rough re-rectification will provide acceptable results. The appearance of an article with a painted re-corrected core, however, you can if you want to improve, by finer grinding of the painted re-corrected. In this way a perfect surface can be provided with co-injection for pieces of luster or high gloss. The articles that are provided through the The present invention is suitable for absorbing and dissipating kinetic energy. These articles are formed by co-injection molding a first thermoplastic material having good appearance properties and a second thermoplastic material having appearance properties that are significantly inferior to those of the first thermoplastic material. The second thermoplastic material will generally form a core that is entirely surrounded by a coating consisting of the first thermoplastic material, even though in some cases a The portion of the finished article may or may not be visible during use may be constituted by the exposed core material. Therefore, controlled introduction of the core material may be desirable in some cases. The second thermoplastic material can constitute up to 75 percent by weight of the mass of an article without significantly compromising its strength. The percentages by weight at the lower end of the scale will often be useful when the core is a foamed core. The conventional swelling agents, if If desired, they can be used to reduce the core weight. The foaming of the core in this manner has the additional advantage of counteracting surface depression signals, such as those that can be derived from the mold apparatus.

Items will typically be configured as complete or partial car bumpers, exterior trim, or energy management dashboard even though they may also be appropriate for non-automotive power management applications. In practice, both of the thermoplastic materials will usually be polyolefins. The first thermoplastic material can advantageously be constituted by a formulation # of polyolefin that has excellent appearance attributes and paint capacity such as ONTEX, which can be obtained from D &S Plastics International. The second thermoplastic material will usually consist of the painted re-rectified.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a cross section of a one-piece co-injectable bumper system according to the invention. Figure 2 shows a cross section of a co-injected foam core bumper cover to which an optional beam can be fixed by heat, vibration, ultrasonic stacking, adhesives or mechanical fastening.

Figure 3a shows a cross section of a bumper profile co-injected according to the invention. Figure 3b shows a photographic enlargement of a portion of the bumper profile of Figure 3a, indicating the location of the coating areas and core thereof. Figure 4a shows a cross section of a co-injected energy management instrument panel profile according to the invention designed to minimize the bath to the laminated metal of the surrounding body. Figure 4b shows a photographic enlargement of a portion of the profile of the energy management instrument panel of Figure 4a, indicating the location and dimensions of the coating areas and core thereof. Figure 5 shows a perspective view of a typical mold for co-injection molding of a bumper according to the invention. Figure 6 shows a cross-section of a typical mold for co-injection molding a partial or complete automotive instrument panel according to the invention. # thermoplastic. The materials of the core and the coating, in general, must be compatible - that is, adhere to one another - in order to reduce the danger of failure by delamination, even though in some cases the failure by delamination may not be a problem and , therefore, incompatible resins may be appropriate. In its broadest aspect, therefore, the present invention relates to any two or more '* thermoplastic resin systems. Resin systems which can be used in accordance with the present invention, therefore, include polyamides, such as nylon ("PA"), thermoplastic elastomers ("TPE"), polyesters, polycarbonates ("PC"), polyvinyl chloride ("PVC "), copolymers, such as acrylonitrile-butadiene-styrene ("ABS") and styrene-acrylonitrile ("SAN") and polyolefins, such as polypropylene ("PP"). Adhesion is clearly very good between products of the same type of compound # chemical, but if a material contains filler or cargo or other foreign matter, there may be a reduction in their adherence to each other. The following combinations of materials have been found to show excellent adhesion: PA66 / PA reinforced with glass, TPE / PP, PP / PP filled with talc, PC / ABS, PVC / ABS plasticised and SAN / PC. The thermoplastic material comprising the coating according to the present invention should - l - be essentially free of impurities. By the term "essentially free of impurities" is meant less than 3 percent of the unwanted substances that would affect the appearance, impact or shock resistance, elongation and similar properties of the resin. The core resin according to the present invention, on the other hand, may contain up to 25 percent impurity in addition to those substances such as ^ pigments and fillers or fillers that are used commonly in the automotive industry. The core resin also contains small amounts of "garbage", such as road dirt, insect residues and other items that may be associated with automotive parts under conditions of actual use. The above-described coating / core construction allows the use of the second thermoplastic material or core of the materials having cost advantages, but appearance and / or performance disadvantages, such as the painted re-rectification. He The first thermoplastic material or coating will probably be composed of polyolefins.

Bumpers and boards for instruments. As indicated above, the present invention is particularly suitable for the manufacture of automobile bumpers and energy management instrument panels. Figures 1 to 4 present schematic representations of typical product configurations for these articles. Figure 1 shows a cross-section of a one-piece co-injected bumper system according to the invention having a top thermoplastic polyolefin coating such as Ontex which is '* shows through thick dark lines and a core of a low-foamed material that is shown by the cellular structure. The low cost material can be selected from a variety of products, such as inexpensive thermoplastic polymers, including various types of polyethylene, scrap and recycle. The material Specially preferred for the core is that of recycled plastic automobile bumpers generally known as "painted re-corrected" thermoplastic material. The inexpensive material can be foamed with conventional swelling agents. The mold used for The manufacture of the bumper of Figure 1 will have a cavity corresponding in cross-sectional form to the exterior of the structure shown. An important feature of the present invention is the relatively large proportion of low cost material that can be incorporated unexpectedly in energy management articles without significant loss in energy management properties. As illustrated in the Figure, up to about two-thirds or even three-quarters of the article in volume may be constituted of low-cost materials, with the overall design of the article providing appropriate structural features to ensure an effective mixture of energy absorption and dissipation of energy. The present invention allows the production of car bumper configurations that are relatively thin. Figure 2, for example, shows a schematic cross-sectional view of a co-injected foam core bumper cover where about 50 percent of the article in volume is made up of low-cost foamed material. Due to the manner in which the bumper cover is configured, this bumper configuration will adequately dissipate energy. As indicated in Figure 2, however, this bumper configuration can be reinforced by stacking a beam to the same average heat, vibration, ultrasound, adhesives or mechanical fastening. Figure 3 demonstrates in detail that it can be achieved with co-injection molding in the context of a relatively large article, such as a car bumper. Figure 3b shows a photographic enlargement of a portion of the bumper profile that is slightly convoluted. Approximately 60 percent by volume of the bumper configuration of Figure 3 will be constituted of low cost painted re-rectification. Figure 4 demonstrates the detail that can be achieved with co-injection molding in the context of a , *? relatively small article, such as the boards of instruments for automotive energy management. As indicated in Figure 4, when the thickness of the ends of the article is less than about 75 percent of the nominal wall thickness, no core needs to be present in that locally thin area. A The thickness of a 3-millimeter piece can generally be made up of about 65 percent of the core, so typically, a 3.5-millimeter piece thickness typically can be made up of about 55 percent of the core. There is no thickness Minimum for co-ejection, but relative thickness changes within a part can be used to locate the core material. At least, a thickness of 4 millimeters is usually required to obtain the foam in the core. The flow distances for thin walls 25 could be similar to normal injection molding.

Correspondingly, conventional injection molding methods will typically be used in a thin wall context. A significant aspect of the invention is that inexpensive material cores can be used advantageously without significant loss in structural properties. Figure 4b shows a photographic enlargement of a portion of the instrument panel profile that is highly convoluted. Approximately 40 percent by volume of the The configuration of the instrument panel of Figure 4 will be constituted by a low cost painted re-rectification.

Rigidity and weight. 15 Stiffness can be calculated using the stiffness equation x = Mx (t) 3ma-Mm-P- where M is a constant for material X and t is the thickness of the specimen, the thickness of which is being determined. The constant for steel is 30,000,000; Y that for the plastic (thermoplastic polyolefin / polypropylene core coating) is typically 500,000. In extreme cases, it can be as high as 800,000 with a severity of 1.05 for higher weight savings, however. In this way, for a bumper of steel that has a thickness of 1.78 millimeters, Mx (t) 3 is 30,000,000 (.07) 3 or 10,290. In order to determine how thick a plastic bumper is (using the beam construction) it would have to be in order to have the same thickness as the 1.88 millimeter steel bumper, the equation becomes 10,290 = 500,000 (t) 3 which can be solved for t = 1.96 millimeters. Therefore, as is to be expected intuitively, a plastic bumper would have to be considerably thicker (even if not usable) than a steel bumper to have the same stiffness as a steel bumper. However, more important than the thickness in automobile construction is the weight - since most of the energy used by automobiles goes towards moving its weight. The weight savings of a plastic bumper that has the same stiffness as a steel bumper can be calculated as follows t plastic (density of plastic) t steel (density d steel) 6. 96 1.78 & 55 = 55% ~~ Therefore, the use of plastic materials molded in accordance with the present invention can result in a weight saving of more than 50 percent.

Molding processes. The co-injection molding processing according to the present invention may use conventional machinery and techniques such as those described in U.S. Patent Nos. 5,057,266 and 4,925,100, the total disclosure of which is expressly incorporated herein by reference. The unexpected benefit of the present invention lies in the application of the co-injection molding for the production and energy management articles, the designs of these articles and the forms of the molds to obtain and carry these designs to the optimum, and the thermoplastic resins that can be used to manufacture * These articles. The "sandwich" co-injection molding, that is, the molding of multiple materials when only the material is visible, it can be sinopsized in the following way. The material comes from two injection units and passes through a single nozzle as illustrated, for example, in Figure 7. Figure 7 shows a cross-sectional view of a generic molding system for co-injection molding of a dashboard for - automobile according to the invention. In Figure 7 is the body mold having a concave area corresponding in configuration to the outer surface of the instrument panel to be produced, 2 is the block containing a convex area that interacts with the concave area at 1 to form the mold cavity, 3 is the resin injection hole, 4 is the injection unit that supplies the first material through the hole 3 of resin injection and 5 is the unit of 0 injection that supplies the second material through the hole 3. The first unit injects the coating. The second unit injects the core material that forces the coating against the mold wall. The first unit 5 then injects more amount of the coating material to complete the molding and prepare for the next cycle. This process is explained in more detail below. Figure 5 shows a perspective view of a typical mold for co-injection molding of a bumper according to the invention. The mold of Figure 5 is a straight injection molding design wherein 1 is the mold body having a concave area corresponding in configuration to the outer surface of the bumper to be produced, 2 is the block containing an area convex that interacts with the concave area at 1 to form the mold cavity and 3 is the resin injection hole. As will be readily appreciated by those skilled in the art, many other types of molds and slides and plastic gates may be employed in accordance with the principles set forth herein. Figure 6 shows a cross section of a typical mold for co-injection molding of a partial or complete automobile instrument panel according to the invention. In Figure 6, the num1 is the workpiece cavity, 2 is the gate, 3 is the landfill bushing, 4 is the mold cavity, 5 is the mold core, and A is the area where the mold can be provided. Overflow channel to aid in core distribution. It is this mold configuration, the injection is made in the upper part of the piece to promote the presence of the high impact coating along the bottom of the piece. The distribution of the core can also be delayed by reducing the wall material along the bottom of the piece. The overflow channel will push the excess coating to the outside of the part where it can easily be trimmed. In interleaving molding, the mold is partially filled by the first injection unit so that the material in contact with the wall of the mold forms the coating of the product leaving a core still fluid. The second material is then injected by pushing the first remaining fluid material further forward continuing to form the coating while the second material progressively fills the interior of the component. If you inject an insufficient amount of first material, second material will be able to pass towards the extremities of the component forming the same the remaining coating. To prepare for subsequent injections, the second injection unit is stopped before the part has been completely filled, and the first injection unit is restarted from a partially advanced position. This second application of the first material completes the filling of the component, obscures the gate of the mold and cleans the injection nozzle of the machine downstream of the distribution system to ready it for the next cycle. During the next injection sequence of the first material, the change to retain the pressure can be carried out. The advantages of co-injection molding for thick section components include the fact that the less expensive and inferior materials can be used * for the core material, the pigments need to be used only with the coating material, all landfills and rejections can be recycled to the core material, the core materials with swelling agents remove the signs of surface depression leading to improved cooling and shorter cycles, the process temperature of the core material is normally adjusted to the minimum value necessary leading to less heat to be disbanded and, therefore, a reduction in cycle time, automatic separation of components and landfills within the mold design is possible due to the relatively smaller gate size requirement when the co-injection molding is carried out in opposition to the injection molding 5 of a single material that is being carried out, with high plasticization rates. A production benefit arises from the fact that the core material never comes into contact with the mold walls. The walls of the mold, therefore, are not subjected to wear that could otherwise be caused by hard particulate debris in the core material. The distribution of the core material is related to the position of the feed gate and the obstacles that the flow of the material will encounter. The core material is not necessarily used through the entire * piece. For example, to eliminate shrinkage in the flanged sections, it is sufficient to inject a foamed core only at these points. Although the present invention has been described with respect to certain specific embodiments in order to illustrate the principles thereof, other applications of the principles of the invention will readily occur to those skilled in the art based on the * present teachings. The present invention should be limited, therefore, only those modalities that are covered by the spirit and scope of the appended claims. *

Claims (17)

1. An article for cushioning and dissipating kinetic energy, the article is formed by co-injection molding a first thermoplastic material having good appearance properties and a second thermoplastic material having significantly inferior appearance and / or strength properties to that one. of the first thermoplastic material, wherein the second thermoplastic material constitutes from 10 percent to 75 percent by volume of the article's mass.

The article according to claim 1, wherein the first thermoplastic material is a polyolefin and forms a significant portion of an outer surface of the article.

3. The article according to claim 1, wherein the second thermoplastic material forms a core that is entirely surrounded by a coating consisting of the first thermoplastic material.

4. The article according to claim 3, configured as a car bumper or an energy management instrument panel. #

5. The article according to claim 1, wherein both thermoplastic materials are polyolefins.

6. The article according to claim 5, wherein the second thermoplastic polyolefin is a painted re-corrected polyolefin material.

7. An automobile bumper comprising a core of thermoplastic polyolefin material containing impurities, and a thermoplastic polyolefin coating that is essentially free of impurities, the coating surrounding at least a portion of the core.

The automobile bumper in accordance with claim 7, wherein the thermoplastic core polyolefin comprises painted rectified polyolefin material.

The automobile bumper according to claim 8, wherein the lining surrounds essentially all of the outer surfaces of the core, the bumper weighs 70 percent to 30 percent as much as a corresponding steel bumper that has comparable stiffness .

10. A car dashboard comprising a core of a thermoplastic polyolefin material containing impurities, and a thermoplastic polyolefin coating that is essentially free of impurities, the coating surrounding at least a portion of the core.

The automotive instrument panel according to claim 10, wherein the core thermoplastic polyolefin comprises a painted re-corrected polyolefin material.

12. The automotive dashboard according to claim 11, wherein the lining substantially surrounds all outer surfaces of the core, the instrument panel weighs 55 to 25 percent as much as the corresponding steel dashboard which has comparable rigidity.

13. A method for manufacturing an article for damping and dissipating the kinetic energy comprising the steps of sequentially (a) injecting a first thermoplastic material having good appearance and strength properties into a mold configured in the shape of the article to form a layer of the first thermoplastic material on the inner surface of the mold, (b) injecting a second thermoplastic material having properties of appearance and / or strength significantly inferior to those of the first thermoplastic material towards the mold, until the second thermoplastic material constitutes a about 10 percent to 75 volume percent of the final mass of the article, and (c) injecting an additional amount of the first thermoplastic material into the mold in order to complete the formation of the article in the mold.

The method according to claim 13, wherein the first and second thermoplastic materials are co-injection molded.

15. The method according to claim 14, further comprising injecting the first and second thermoplastic materials such that the second thermoplastic material forms the core of the article and the first thermoplastic material forms a coating 5 essentially surrounding the core.

16. The method according to claim 13, which further comprises selecting the first and second thermoplastic materials to be thermoplastic polyolefins.

17. The method according to claim 13, further comprising selecting the first thermoplastic material to be a thermoplastic polyolefin that is essentially free of impurities and selecting the second thermoplastic material to be - - a thermoplastic polyolefin material containing impurities. * * - 2 - RESUME OF THE INVENTION The present invention provides articles for damping and dissipating kinetic energy. These articles are formed by co-injection molding a first thermoplastic material having good appearance and strength properties and a second thermoplastic material having significantly less appearance and / or strength properties than those of the first thermoplastic material. The second thermoplastic material will generally form a core that is entirely surrounded by the coating consisting of the first thermoplastic material, although in some cases a portion of the finished article will not be visible during use or is of special function and may be made of the material of exposed core.