CA2194959A1 - Coinjected automobile bumpers - Google Patents
Coinjected automobile bumpersInfo
- Publication number
- CA2194959A1 CA2194959A1 CA002194959A CA2194959A CA2194959A1 CA 2194959 A1 CA2194959 A1 CA 2194959A1 CA 002194959 A CA002194959 A CA 002194959A CA 2194959 A CA2194959 A CA 2194959A CA 2194959 A1 CA2194959 A1 CA 2194959A1
- Authority
- CA
- Canada
- Prior art keywords
- thermoplastic
- core
- thermoplastic material
- component
- polyolefin
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/16—Making multilayered or multicoloured articles
- B29C45/1642—Making multilayered or multicoloured articles having a "sandwich" structure
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
- B60R19/00—Wheel guards; Radiator guards, e.g. grilles; Obstruction removers; Fittings damping bouncing force in collisions
- B60R19/02—Bumpers, i.e. impact receiving or absorbing members for protecting vehicles or fending off blows from other vehicles or objects
- B60R19/03—Bumpers, i.e. impact receiving or absorbing members for protecting vehicles or fending off blows from other vehicles or objects characterised by material, e.g. composite
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
- B60R19/00—Wheel guards; Radiator guards, e.g. grilles; Obstruction removers; Fittings damping bouncing force in collisions
- B60R19/02—Bumpers, i.e. impact receiving or absorbing members for protecting vehicles or fending off blows from other vehicles or objects
- B60R19/18—Bumpers, i.e. impact receiving or absorbing members for protecting vehicles or fending off blows from other vehicles or objects characterised by the cross-section; Means within the bumper to absorb impact
- B60R19/22—Bumpers, i.e. impact receiving or absorbing members for protecting vehicles or fending off blows from other vehicles or objects characterised by the cross-section; Means within the bumper to absorb impact containing mainly cellular material, e.g. solid foam
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
- B29L2031/00—Other particular articles
- B29L2031/30—Vehicles, e.g. ships or aircraft, or body parts thereof
- B29L2031/3044—Bumpers
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
- B60R19/00—Wheel guards; Radiator guards, e.g. grilles; Obstruction removers; Fittings damping bouncing force in collisions
- B60R19/02—Bumpers, i.e. impact receiving or absorbing members for protecting vehicles or fending off blows from other vehicles or objects
- B60R19/18—Bumpers, i.e. impact receiving or absorbing members for protecting vehicles or fending off blows from other vehicles or objects characterised by the cross-section; Means within the bumper to absorb impact
- B60R2019/1806—Structural beams therefor, e.g. shock-absorbing
- B60R2019/1833—Structural beams therefor, e.g. shock-absorbing made of plastic material
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
- B60R19/00—Wheel guards; Radiator guards, e.g. grilles; Obstruction removers; Fittings damping bouncing force in collisions
- B60R19/02—Bumpers, i.e. impact receiving or absorbing members for protecting vehicles or fending off blows from other vehicles or objects
- B60R19/18—Bumpers, i.e. impact receiving or absorbing members for protecting vehicles or fending off blows from other vehicles or objects characterised by the cross-section; Means within the bumper to absorb impact
- B60R2019/1886—Bumper fascias and fastening means therefor
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Injection Moulding Of Plastics Or The Like (AREA)
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
2~q4q57 ~ 9 5/ 08 61 3 Pl~ï ;;J
COih~ ~ AUTOMOBILE sUMPER8 FIELD OF THE INVENTION
S The present invention relates to plastic articles of manufacture, and to their production by injection molding techniques. More particularly, the present invention relates to articles such as automobile bumpers and fascias that are produced by coinjecting at least two different qualities of 10 thermoplastic resins such as polyolefins into mold shapes that have been designed to utilize the respective qualities of such thermoplastic resins to advantage.
BAC~KuuNB OF THE INVENTION
Extrusion and coextrusion molding are well known techniques for making components that may be regarded as essentially "two dimensional" in configuration. Extrusion 20 processes may be used for making long, straight, uniform rods, wires, or complex two dimensional profiles that may then be cut to length. Extrusion processes are limited by the nature of the shape of the parts that they can form.
Running inexpenslve core materials in coextrusion is well 25 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 two-dimensional opening and then cools in a water bath and is ultimately cut to length. One can extrude a solid or 30 hollow rod, but it is impossible to cap off the ends in extrusion processes.
Insert or laminate molding processes (i.e., inner/outer) tend to have more complex tooling and PEDC-64576 . 1 ~7~
WO96~1732 2 1 9 4 9 5 9 r~ 7 ~ - 2 -longer cycle times than coextrusion and coinjection processes. Also, they produce products that are physically more prone to warpage than are the symmetrical skin/core/skin products that can be produced by coinjection molding processes in accordance with the present invention.
Perfectly straight parts are rare in automobiles.
Where extrusion is utilized, three-dimensional injection molded endcaps are often used to complete the assembly. U.S. Patents Nos. 5,128,196, 5,087,488, 4,814,037, 4,546,022, and 4,405,557 disclose sheet or profile extrusion processe3 that are not applicable to the formation of automobile parts of the types contemplated by the present invention.
In injection and coinjection molding, liquid plastic(s) are injected into a three-dimensional mold where they cool and eject once the mold is opened.
Typical injection molding proce3ses are described in U.S. Patents Nos. 5,057,266 and 4,925,100. The addition of the third dimension allows for the production of complex shapes, att~l tS, and significant design freedom. Whlle there has been some limited coinjection molding activity with low cost cores, this has met with very little commercial success. It has not been applied to the iormation of automobile parts of the types contemplated by the present invention -- namely, energy management parts.
For instance, Battenfeld GmbH of Meinerzhagen, Germany, a leading producer of coinjection molding equipment, promotes its equipment for use in the manufacture o~ such products as housings for carpentry tools such as hand planes and circular saws, TV
housings, garden chairs, and fins ~or surfboards. The ~llt~ Ih;le applications that Battenfeld teaches are for such products as fenders and headlight reflectors.
2 1 9 4 9 5 9 ~ / 0 8 6 1 ~
t~ 'r3~y 1' In these automobile applications, Battenfeld is concerned, insofar as is relevant here, solely with the structural aspects of the core. Battenfeld neither teaches nor suggests the use of low quality, low cost core materials as in the 5 present invention.
SUMMARY OF TUE INVENTION
The present invention provides a means by which relatively large amounts of inferior materials can be used internally in structures in applications never before thought possible without deleterious effects. Thus, the present invention provides a component for absorbing and dissipating 15 kinetic energy, which component is formed by coinjection molding of a first thermoplastic material having good appearance and strength properties and of a second thermoplastic material having appearance andlor strength properties significantly inferior to those of the first 20 thermoplastic material. Preferably the second thermoplastic material constitutes from 10 to 75 % by volume of the component.
The unusual internal material that can be used to greatest advantage in accordance with the principles of the 25 present invention is known as "painted regrind" thermoplastic olefin material. "Painted regrind" refers to components such as automobile bumpers that had been made of thermoplastic polyolefins and painted and which have subsequently been ground up for use as core material in accordance with the 30 structural configurations of the present invention.
Certain properties -- for instance, strength -may be enh~n~e~ by the use of painted regrind in accordance with the present invention. Appearance is - 3 - ~C-64576.1 ~TJI1~ 9 5 / 0~ 61 21q495 9 lpl~ C ~ 3~
the only significa~t property deriving from the painted regrind core that will generally be inferior to the employment of a comparable core made of virgin material.
Where the part in question is intended to be grained or low 5 gloss, relatively rough regrind will generally give acceptable results. The appearance of an article with a painted regrind core, however, may if desired be ~nh~nc~d by finer grinding of the painted regrind. In this way, one can afford a perfect surface with coinjection for high gloss 10 parts.
The articles provided by the present invention are suitable for absorbing and dissipating kinetic energy. These articles are formed by coinjection molding of a first thermoplastic material having good appearance properties and 15 of 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 skin consisting of the first thermoplastic 20 material, although in some instances a portion of the finished article that may or may not be visible in use may be constituted by exposed-core material. Thus, controlled breakthrough of core material may be desirable in some instances. The second thermoplastic material can constitute 25 up to 75 percent by volume of a component without significantly compromising the strength thereof. Weight-percents at the lower end of the range will often be useful when the core is foamed. Conventional blowing agents may, if desired, be used to reduce the weight of the core. Foaming 30 of the core in this manner has the additional advantage of offsetting sinkmarks, such as those that might be derived from the mold apparatus.
P6DC- 64 576 .1 Wo96~1732 21 94 959 ~ A ~17 ~ - 5 -The articles will normally be configured as complete or partial automobile bumpers, exterior trim, or energy management fascia, although non-automotive energy management applications may also be appropriate. In practice, both of the thermoplastic materials will usually be polyolefins. The first thermoplastic material may advantageously be constituted of a polyolefin formulation that has excellent appearance and p~;~t~hil;ty attributes, such as ONTEX, which is available from D&S Plastics International. The second thermoplastic material will generally be constituted of painted regrind.
BRIEF DESCRIPTION OF T~E DRAWINGS
Figure l shows a cross-section of a one piece coinjected bumper system in accordance with the invention.
Figure 2 shows a cross-section of a foam core coinje-cted bumper cover, to which an optional beam may be attached by heat, vibration, ultrasonic staking, adhesives, or mechanical attachment.
Figure 3a shows a cross-section of a coinjected bumper profile in accordance with the invention.
Figure 3b shows a blow-up of a portion of the bumper profile of Fig. 3a, indicating the location of skin and core areas thereof.
Figure 4a shows a cross-section of a coinjected energy management fascia profile in accordance with the invention, designed to minimize damage to surrounding body sheet metal.
Figure 4b shows a blow-up of a portion of the energy management fascia profile o~ Fig. 4a, 2 1 9 4 ~ T~ - 9 5l ~ 8 6 1 . ~
indicating the location and dimensions of skin and core areas thereof.
Figure 5 shows a perspective view of a typical mold for coinjection molding a bumper in accordance with the S invention.
Figure 6 shows a cross-section of a typical mold for coinjection molding a partial or complete automobile fascia in accordance with the invention.
Figure 7 shows a cross-section of a generic mold system 10 for coinjection molding an automobile fascia in accordance with the invention.
DETAILED DESCRIPTION OF THE INVENTION
ThermoPlastic materials The present invention provides articles for absorbing and dissipating kinetic energy, preferably as components of vehicles such as automobiles. The components of the present 20 invention are formed by coinjection molding a first thermoplastic material having good appearance properties and a second thermoplastic material having appearance and/or strength properties significantly inferior to those of the first thermoplastic material. Generally, the second 25 thermoplastic material will constitute from 10 to 75 % by volume of the energy management component.
In practice, energy management components in accordance with the present invention will be configured such that the second thermoplastic material forms a core that is entirely 30 ~u~ruu--ded by a skin consisting of the first-thermoplastic material. The core and skin materials should generally be compatible -- that is, adhere to one another -- in order to -- 6 -- PEDC-645P6.1 2~ 9~959 W096~1732 r~l" ~
~ - 7 -reduce the danger of ~P1 ~mi n~tion~failure, although in some instances dPl~m;n~tion failure may not be of concern ~nd thus incompatible resins may be appropriate. In its broadest aspect, therefore, the , 5 present invention relates to any two or more thermoplastic resin systems. Resin systems that may be used in accordance with the present invention, therefore, include polyamide 8' such as nylons ("PA"), thermoplastic elastomers ("TPE"), polyesters, polycarbonates ("PC"), polyvinyl chloride ("PVC"), copolymers such as acrylonitrile-butadiene-styrene ("ABS") and styrene-acrylonitrile ("SA~"), and polyolefins such as polypropylene ("PP"). Adhesion is clearly very good between products of the same chemical type, but if one material ~nt~in~ fillers or other foreign matter, there may be a reduction in their adhesion to one another. The following material combinations have been found to shown excellent adhesion: PA66/glass-reinforced PA, TPE/PP, PP/talc-filled PP, PC/ABS, plasticized PVC/ABS, and SAN/PC.
The thermoplastic material that comprises theskin according to the present invention should be subst~nti~11y free of impurities. By "substantially free of impurities" is meant less than 3 percent of undesired substances that would affect the appearance, impact-resistance, elongation, and similar properties of the resin. The core resin in accordance with the present invention, on the other hand, may contain up to 25 percent impurities, in addition to such substances as pigments and fillers as are commonly used in the automotive industry. The core resin may also contain small amounts of "trash" such as road dirt, insect remains, and other such items that may become associated with automotive parts under actual use conditions.
WO96/01732 2 1 ~ ~ ~ 5 q ~". 17 The skin/core construction described above enables the use for the second thermoplastic material, or core, of materials that have expense advantages but appearance and/or performance disadvantages, such as painted regrind. The first thermoplastic material, or skin, will preferably be composed of polyolefins.
F -rs and fascias As indicated hereinabove, the present invention is particularly suitable for the manufacture of automobile bumpers and energy management fascias.
Figures 1-4 present schematic representations of typical product configurations~for such articles.
Figure 1 shows a cross-section of a one piece =~
coin~ected bumper system in accordance with the invention having a skin of premium thermoplastic polyolefin such as Ontex, shown by the thick dark lines, and a core of foamed low cost material, 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. Most preferred for the core is recycled plastic automobile =
bumpers, known generically as "painted regrind"
thermoplastic material. The low cost material can be foamed with conventional blowing agents. The mold used to make the bumper of Figure 1 will have a cavity that corresponds in cross-sectional shape to the outside of the structure shown. An important feature of the present invention is the=relatively large proportion of the low cost material that can nn~rectedly be incorporated into the energy management articles with no significant loss in energy management properties. As depicted in Figure 1, up to approximately two-thirds or even three-~uarters of the W096~1732 2 ~ 9 4 9 ~ 9 r~1/~ . I /
g _ article by volume may be constituted of the low cost material, with the overall design of the article providing appropriate structural features to ensure an effective mix of energy absorption and energy dissipation.
The present invention enables the production of automobile bumper configurations that are relatively thin Figure 2, for instance, shows a cross-sectional schematic of a foam core coinjected bumper cover, in which approximately 50% of the article by volume is constitute~ Df low cost foamed material Due to the manner in which the bumper skin is configured, this bumper configuration will adequately dissipate energy AB indicated in Figure 2, however, this bumper configuration may be reinforced by staking a beam thereto by means of heat, vibration, ultrasound, adhesives, or mechanical att~
Figure 3 demonstrates the ~Gt~;l;ng that can be achieved with coinjection molding in the context of a relatively large article such as an automobile bumper.
Figure 3b shows a blow-up of a portion of the bumper profile that is highly convoluted. Appr~ t~y 60~
by volume of the Pigure 3 bumper configuration will be constituted of low cost painted regrind.
Figure 4 demonstrates the detailing that can be achieved with coinjection molding in the context of a relatively small article such as automobile energy management fascias. AS indicated in Figure 4, where the th;~kn~s of the article's extremities are less than about 75~ of the nominal wall thickness, no core need be present in that locally thin area. A part thickness of 3 millimeters may generally be constituted of about 65~ core. Similarly, a part thickness of 3.5 millimeters may typically be constituted of a~out 55% core. There is no minimum WO96/01732 ~ 9~
thickness for coinjection, but relative thickness changes within a part may serve to localize the core =
material. At least 4 millimeters of thickness is usually required to obtain foam in the core. Flow distances for thin walls would be similar to standard injection molding. Accordingly, conv~nt;nn~l injection molding procedures may typically~be used in~
the thin-wall context. A significant aspect of the invention is that low cost material cores can profitably be used with no significant loss in structural properties. Figure 4b shows a blow-up of=a portion of the fascia profile that is highly convoluted. Approximately 40~ by volume of the Figure 4 fascia configuration will be constituted of low cost painted regrind.
Sti_fness ~n~ Wei~ht Stiffness may be calculated using the equation 5t;ffnf~RRx = My~t) in which 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; that for plastic (thermoplastic polyolefin skin/polypropylene core) is typicalIy 500,000. In extreme cases, it may be as high as 800,000, with a gravity of 1.05 for greater weight savings, however.
Thus, for a steel bumper having a th;~knf~R of 0 07 inches, MX(t)3 is 30,000,000(.07)3 or 10,290. In order to determine how thick a plastic bumper (utilizing beam construction) would have to be in order to have the same thickness as the 0.07 steel bumper, the equation becomes 10,290 = 500,000(t) 3 which can be solved for t = 0.274 inches. Thus, as would be intuitively expected, a plastic bumper would WO96/01732 2 1 q 4 9 5 9 P._l/L~ .
~ -- 11 -have to be subst~nti~lly (although not unusably) thicker than a steel bumper to have the same stiffness ~ as the steel bumper. However, more important than thickness in automobile construction is weight --since most of the energy used by automobiles goes into moving their weight. The weight savings of a plastic bumper having the same stiffness as a steel bumper may be calculated as follows:
t plastic (densit~ ~lastic~
t steel (density steel) 0.274 (1.1) 0.07 (7.8) .55 = 55~
Thus the use of plastic materials molded in accordance with the present invention can result in a weight savings of more than 50~.
Mol~;n~ ~rocesse~
Coinjection molding processing in accordance with the present invention can make use of conYPnt;~n~l machinery and techniques, such as those described in U.S. Patent No. 5,057,266 and ~7925,100, the entire disclosure of which are hereby expressly incor~orated by reference. The unexpected benefit of the present invention lies in the application of coinjection molding to the production of energy management articles, the designs of such articles and the shapes of the molds for obtaining and optim;~;ng such designs, and the thermoplastic resins that can be used to make such articles.
Coinjection ~sandwich". molding, i.e. multi-material molding when only one material is visible, may be synopsized as follows. Material comes from two injection units and passes through a single nozzle, as illustrated for instance in Figure 7. Figure 7 shows WO96/01732 2 1 ~ 4 ~ 5 ~
a cross-sectional view of a generic molding system for coinjection molding an automobile fascia in accordance with the invention. In Filgure 7, 1 i6 the mold body which has a concave area corr~Rp~n~;ng in configuration to the exterior surface of the fascia to be produced, 2 is the block cnnt~ining a convex area that interacts with the concave area in l to form the mold cavity, 3 is the resin injection port, 4 is the injection unit that delivers the first material through the resin injection port 3, and 5 is the injection unit that delivers the second material through port 3.
The first unit injects the skin. The second unit injects the core material which forces the skin against the mold wall. The first unit then injects more of the skin material to complete the molding and prepare for the next cycle. This process is explained in greater detail below.
Flgure 5 shows a perspective view of a typical mold for coinjection molding a bumper in accordance with the invention. The Figure 5 mold is a straight drop injection molding design, in which l is the mold body which has a concave area corresponding in configuration to the exterior surface of the bumper to be produced, 2 is the block r~nt~ining a convex area that interacts with the concave area in l to form the mold cavity, and 3 is the resin injection port. As those skilled in the art will readily appreciate, many other types of molds and plastic runners or gating may be employed in accordance with the principles set forth herein.
Figure 6 shows a cross-section of a typical mold for coinjection molding a partial or complete automobile fascia in accordance with the invention.
In Figure 6, l is the part cavity, 2 is the gate, 3 is 2 1 ~4~f ~9 the sprue bushing, 4 i8 the mold cavity, 5 is the mold core, and A iB the area in which an overflow channel may be provided to aid in core distribution. In this mold configuration, injection takes place at the top of the part to promote the preaence of high impact skin along the bottom of the part. Core distribution can be retarded further by necking down wallstock along the bottom of the part. The-overflow channel will push excess skin into a ~puddle" outside of the part where it may easily be trimmed off.
In sandwich molding, the mold iB partially filled by the first injection unit, BO that material in contact with the wall of the mold forms the skin of the product, leaving a still fluid core. The second material is then injected, pushing the 1 ;n;ng fluid first material further forward, rrnt;nning to form the skin, while the second material progressively fills the inside of the c, ~rnPrt.
Ii an insufficient amount of the first material is injected, the second material would be able to pass to the extremities of the r~ nPnt, itself forming the l~ ;n;ng skin. To prepare for subse~uent shots, the second injection unit is stopped before the part is completely filled, and the first injection unit is re, red from a partially advanced position. This second application of the first material completes the filling of the ~ -nt, obscures the mold gate, and cleans the machine's injection nozzle downstream of the'distribution system ready for the next cycle.
During the second sequence of injecting the first material, the changeover to holding pressure can take place.
Advantages of coinjection molding for thick section rrmrrnPnt.q include the fact that inferior and less expensive materials can be used for the core W096lOIn2 2 i ~ 4 ~ 5 q - 14 - 3r~
material, pigments need only be used with the skin material, all sprues and rejects can be recycled into the core material, core ~-t~r;~1 R with blowing agents eliminate sink marks, leading to improved cooling and shorter cycles, the proce~s temperature of the core material is normally adju~ted to the minimum value necessary, leading to les~ heat to dissipate and hence a reduction in cycle time, automatic separation of the ~_ ~nt~ and gprues within the mold design is possible due to the relatively small gate size re~uirement when coinjection molding, as opposed to single material injection molding, is being carried out, and high plasticizing rates. A production benefit arises from the fact that the core material never comes into contact with the mold walls. The mold walls, therefore, are not subject to the wear that might otherwise be caused ky 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 material will encounter. The core material is not necessarily used throughout the whole part. For instance, to eliminate shrinkage at ribbed sections it is sufficient to inject a foamed core only at these points.
While the present invention has been described with respect to certain specific embo~;m~nt~ in order to illustrate the principles thereof, other different applications of the principles of the invention will readily occur to those skilled in the art based upon the present t~h;ng~. The present invention should be limited, therefore, only to all those ~mho~;r t~
21 949~9 WO96/01732 . ~ 7 that are covered by the spirit and scope of the appended claims.
COih~ ~ AUTOMOBILE sUMPER8 FIELD OF THE INVENTION
S The present invention relates to plastic articles of manufacture, and to their production by injection molding techniques. More particularly, the present invention relates to articles such as automobile bumpers and fascias that are produced by coinjecting at least two different qualities of 10 thermoplastic resins such as polyolefins into mold shapes that have been designed to utilize the respective qualities of such thermoplastic resins to advantage.
BAC~KuuNB OF THE INVENTION
Extrusion and coextrusion molding are well known techniques for making components that may be regarded as essentially "two dimensional" in configuration. Extrusion 20 processes may be used for making long, straight, uniform rods, wires, or complex two dimensional profiles that may then be cut to length. Extrusion processes are limited by the nature of the shape of the parts that they can form.
Running inexpenslve core materials in coextrusion is well 25 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 two-dimensional opening and then cools in a water bath and is ultimately cut to length. One can extrude a solid or 30 hollow rod, but it is impossible to cap off the ends in extrusion processes.
Insert or laminate molding processes (i.e., inner/outer) tend to have more complex tooling and PEDC-64576 . 1 ~7~
WO96~1732 2 1 9 4 9 5 9 r~ 7 ~ - 2 -longer cycle times than coextrusion and coinjection processes. Also, they produce products that are physically more prone to warpage than are the symmetrical skin/core/skin products that can be produced by coinjection molding processes in accordance with the present invention.
Perfectly straight parts are rare in automobiles.
Where extrusion is utilized, three-dimensional injection molded endcaps are often used to complete the assembly. U.S. Patents Nos. 5,128,196, 5,087,488, 4,814,037, 4,546,022, and 4,405,557 disclose sheet or profile extrusion processe3 that are not applicable to the formation of automobile parts of the types contemplated by the present invention.
In injection and coinjection molding, liquid plastic(s) are injected into a three-dimensional mold where they cool and eject once the mold is opened.
Typical injection molding proce3ses are described in U.S. Patents Nos. 5,057,266 and 4,925,100. The addition of the third dimension allows for the production of complex shapes, att~l tS, and significant design freedom. Whlle there has been some limited coinjection molding activity with low cost cores, this has met with very little commercial success. It has not been applied to the iormation of automobile parts of the types contemplated by the present invention -- namely, energy management parts.
For instance, Battenfeld GmbH of Meinerzhagen, Germany, a leading producer of coinjection molding equipment, promotes its equipment for use in the manufacture o~ such products as housings for carpentry tools such as hand planes and circular saws, TV
housings, garden chairs, and fins ~or surfboards. The ~llt~ Ih;le applications that Battenfeld teaches are for such products as fenders and headlight reflectors.
2 1 9 4 9 5 9 ~ / 0 8 6 1 ~
t~ 'r3~y 1' In these automobile applications, Battenfeld is concerned, insofar as is relevant here, solely with the structural aspects of the core. Battenfeld neither teaches nor suggests the use of low quality, low cost core materials as in the 5 present invention.
SUMMARY OF TUE INVENTION
The present invention provides a means by which relatively large amounts of inferior materials can be used internally in structures in applications never before thought possible without deleterious effects. Thus, the present invention provides a component for absorbing and dissipating 15 kinetic energy, which component is formed by coinjection molding of a first thermoplastic material having good appearance and strength properties and of a second thermoplastic material having appearance andlor strength properties significantly inferior to those of the first 20 thermoplastic material. Preferably the second thermoplastic material constitutes from 10 to 75 % by volume of the component.
The unusual internal material that can be used to greatest advantage in accordance with the principles of the 25 present invention is known as "painted regrind" thermoplastic olefin material. "Painted regrind" refers to components such as automobile bumpers that had been made of thermoplastic polyolefins and painted and which have subsequently been ground up for use as core material in accordance with the 30 structural configurations of the present invention.
Certain properties -- for instance, strength -may be enh~n~e~ by the use of painted regrind in accordance with the present invention. Appearance is - 3 - ~C-64576.1 ~TJI1~ 9 5 / 0~ 61 21q495 9 lpl~ C ~ 3~
the only significa~t property deriving from the painted regrind core that will generally be inferior to the employment of a comparable core made of virgin material.
Where the part in question is intended to be grained or low 5 gloss, relatively rough regrind will generally give acceptable results. The appearance of an article with a painted regrind core, however, may if desired be ~nh~nc~d by finer grinding of the painted regrind. In this way, one can afford a perfect surface with coinjection for high gloss 10 parts.
The articles provided by the present invention are suitable for absorbing and dissipating kinetic energy. These articles are formed by coinjection molding of a first thermoplastic material having good appearance properties and 15 of 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 skin consisting of the first thermoplastic 20 material, although in some instances a portion of the finished article that may or may not be visible in use may be constituted by exposed-core material. Thus, controlled breakthrough of core material may be desirable in some instances. The second thermoplastic material can constitute 25 up to 75 percent by volume of a component without significantly compromising the strength thereof. Weight-percents at the lower end of the range will often be useful when the core is foamed. Conventional blowing agents may, if desired, be used to reduce the weight of the core. Foaming 30 of the core in this manner has the additional advantage of offsetting sinkmarks, such as those that might be derived from the mold apparatus.
P6DC- 64 576 .1 Wo96~1732 21 94 959 ~ A ~17 ~ - 5 -The articles will normally be configured as complete or partial automobile bumpers, exterior trim, or energy management fascia, although non-automotive energy management applications may also be appropriate. In practice, both of the thermoplastic materials will usually be polyolefins. The first thermoplastic material may advantageously be constituted of a polyolefin formulation that has excellent appearance and p~;~t~hil;ty attributes, such as ONTEX, which is available from D&S Plastics International. The second thermoplastic material will generally be constituted of painted regrind.
BRIEF DESCRIPTION OF T~E DRAWINGS
Figure l shows a cross-section of a one piece coinjected bumper system in accordance with the invention.
Figure 2 shows a cross-section of a foam core coinje-cted bumper cover, to which an optional beam may be attached by heat, vibration, ultrasonic staking, adhesives, or mechanical attachment.
Figure 3a shows a cross-section of a coinjected bumper profile in accordance with the invention.
Figure 3b shows a blow-up of a portion of the bumper profile of Fig. 3a, indicating the location of skin and core areas thereof.
Figure 4a shows a cross-section of a coinjected energy management fascia profile in accordance with the invention, designed to minimize damage to surrounding body sheet metal.
Figure 4b shows a blow-up of a portion of the energy management fascia profile o~ Fig. 4a, 2 1 9 4 ~ T~ - 9 5l ~ 8 6 1 . ~
indicating the location and dimensions of skin and core areas thereof.
Figure 5 shows a perspective view of a typical mold for coinjection molding a bumper in accordance with the S invention.
Figure 6 shows a cross-section of a typical mold for coinjection molding a partial or complete automobile fascia in accordance with the invention.
Figure 7 shows a cross-section of a generic mold system 10 for coinjection molding an automobile fascia in accordance with the invention.
DETAILED DESCRIPTION OF THE INVENTION
ThermoPlastic materials The present invention provides articles for absorbing and dissipating kinetic energy, preferably as components of vehicles such as automobiles. The components of the present 20 invention are formed by coinjection molding a first thermoplastic material having good appearance properties and a second thermoplastic material having appearance and/or strength properties significantly inferior to those of the first thermoplastic material. Generally, the second 25 thermoplastic material will constitute from 10 to 75 % by volume of the energy management component.
In practice, energy management components in accordance with the present invention will be configured such that the second thermoplastic material forms a core that is entirely 30 ~u~ruu--ded by a skin consisting of the first-thermoplastic material. The core and skin materials should generally be compatible -- that is, adhere to one another -- in order to -- 6 -- PEDC-645P6.1 2~ 9~959 W096~1732 r~l" ~
~ - 7 -reduce the danger of ~P1 ~mi n~tion~failure, although in some instances dPl~m;n~tion failure may not be of concern ~nd thus incompatible resins may be appropriate. In its broadest aspect, therefore, the , 5 present invention relates to any two or more thermoplastic resin systems. Resin systems that may be used in accordance with the present invention, therefore, include polyamide 8' such as nylons ("PA"), thermoplastic elastomers ("TPE"), polyesters, polycarbonates ("PC"), polyvinyl chloride ("PVC"), copolymers such as acrylonitrile-butadiene-styrene ("ABS") and styrene-acrylonitrile ("SA~"), and polyolefins such as polypropylene ("PP"). Adhesion is clearly very good between products of the same chemical type, but if one material ~nt~in~ fillers or other foreign matter, there may be a reduction in their adhesion to one another. The following material combinations have been found to shown excellent adhesion: PA66/glass-reinforced PA, TPE/PP, PP/talc-filled PP, PC/ABS, plasticized PVC/ABS, and SAN/PC.
The thermoplastic material that comprises theskin according to the present invention should be subst~nti~11y free of impurities. By "substantially free of impurities" is meant less than 3 percent of undesired substances that would affect the appearance, impact-resistance, elongation, and similar properties of the resin. The core resin in accordance with the present invention, on the other hand, may contain up to 25 percent impurities, in addition to such substances as pigments and fillers as are commonly used in the automotive industry. The core resin may also contain small amounts of "trash" such as road dirt, insect remains, and other such items that may become associated with automotive parts under actual use conditions.
WO96/01732 2 1 ~ ~ ~ 5 q ~". 17 The skin/core construction described above enables the use for the second thermoplastic material, or core, of materials that have expense advantages but appearance and/or performance disadvantages, such as painted regrind. The first thermoplastic material, or skin, will preferably be composed of polyolefins.
F -rs and fascias As indicated hereinabove, the present invention is particularly suitable for the manufacture of automobile bumpers and energy management fascias.
Figures 1-4 present schematic representations of typical product configurations~for such articles.
Figure 1 shows a cross-section of a one piece =~
coin~ected bumper system in accordance with the invention having a skin of premium thermoplastic polyolefin such as Ontex, shown by the thick dark lines, and a core of foamed low cost material, 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. Most preferred for the core is recycled plastic automobile =
bumpers, known generically as "painted regrind"
thermoplastic material. The low cost material can be foamed with conventional blowing agents. The mold used to make the bumper of Figure 1 will have a cavity that corresponds in cross-sectional shape to the outside of the structure shown. An important feature of the present invention is the=relatively large proportion of the low cost material that can nn~rectedly be incorporated into the energy management articles with no significant loss in energy management properties. As depicted in Figure 1, up to approximately two-thirds or even three-~uarters of the W096~1732 2 ~ 9 4 9 ~ 9 r~1/~ . I /
g _ article by volume may be constituted of the low cost material, with the overall design of the article providing appropriate structural features to ensure an effective mix of energy absorption and energy dissipation.
The present invention enables the production of automobile bumper configurations that are relatively thin Figure 2, for instance, shows a cross-sectional schematic of a foam core coinjected bumper cover, in which approximately 50% of the article by volume is constitute~ Df low cost foamed material Due to the manner in which the bumper skin is configured, this bumper configuration will adequately dissipate energy AB indicated in Figure 2, however, this bumper configuration may be reinforced by staking a beam thereto by means of heat, vibration, ultrasound, adhesives, or mechanical att~
Figure 3 demonstrates the ~Gt~;l;ng that can be achieved with coinjection molding in the context of a relatively large article such as an automobile bumper.
Figure 3b shows a blow-up of a portion of the bumper profile that is highly convoluted. Appr~ t~y 60~
by volume of the Pigure 3 bumper configuration will be constituted of low cost painted regrind.
Figure 4 demonstrates the detailing that can be achieved with coinjection molding in the context of a relatively small article such as automobile energy management fascias. AS indicated in Figure 4, where the th;~kn~s of the article's extremities are less than about 75~ of the nominal wall thickness, no core need be present in that locally thin area. A part thickness of 3 millimeters may generally be constituted of about 65~ core. Similarly, a part thickness of 3.5 millimeters may typically be constituted of a~out 55% core. There is no minimum WO96/01732 ~ 9~
thickness for coinjection, but relative thickness changes within a part may serve to localize the core =
material. At least 4 millimeters of thickness is usually required to obtain foam in the core. Flow distances for thin walls would be similar to standard injection molding. Accordingly, conv~nt;nn~l injection molding procedures may typically~be used in~
the thin-wall context. A significant aspect of the invention is that low cost material cores can profitably be used with no significant loss in structural properties. Figure 4b shows a blow-up of=a portion of the fascia profile that is highly convoluted. Approximately 40~ by volume of the Figure 4 fascia configuration will be constituted of low cost painted regrind.
Sti_fness ~n~ Wei~ht Stiffness may be calculated using the equation 5t;ffnf~RRx = My~t) in which 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; that for plastic (thermoplastic polyolefin skin/polypropylene core) is typicalIy 500,000. In extreme cases, it may be as high as 800,000, with a gravity of 1.05 for greater weight savings, however.
Thus, for a steel bumper having a th;~knf~R of 0 07 inches, MX(t)3 is 30,000,000(.07)3 or 10,290. In order to determine how thick a plastic bumper (utilizing beam construction) would have to be in order to have the same thickness as the 0.07 steel bumper, the equation becomes 10,290 = 500,000(t) 3 which can be solved for t = 0.274 inches. Thus, as would be intuitively expected, a plastic bumper would WO96/01732 2 1 q 4 9 5 9 P._l/L~ .
~ -- 11 -have to be subst~nti~lly (although not unusably) thicker than a steel bumper to have the same stiffness ~ as the steel bumper. However, more important than thickness in automobile construction is weight --since most of the energy used by automobiles goes into moving their weight. The weight savings of a plastic bumper having the same stiffness as a steel bumper may be calculated as follows:
t plastic (densit~ ~lastic~
t steel (density steel) 0.274 (1.1) 0.07 (7.8) .55 = 55~
Thus the use of plastic materials molded in accordance with the present invention can result in a weight savings of more than 50~.
Mol~;n~ ~rocesse~
Coinjection molding processing in accordance with the present invention can make use of conYPnt;~n~l machinery and techniques, such as those described in U.S. Patent No. 5,057,266 and ~7925,100, the entire disclosure of which are hereby expressly incor~orated by reference. The unexpected benefit of the present invention lies in the application of coinjection molding to the production of energy management articles, the designs of such articles and the shapes of the molds for obtaining and optim;~;ng such designs, and the thermoplastic resins that can be used to make such articles.
Coinjection ~sandwich". molding, i.e. multi-material molding when only one material is visible, may be synopsized as follows. Material comes from two injection units and passes through a single nozzle, as illustrated for instance in Figure 7. Figure 7 shows WO96/01732 2 1 ~ 4 ~ 5 ~
a cross-sectional view of a generic molding system for coinjection molding an automobile fascia in accordance with the invention. In Filgure 7, 1 i6 the mold body which has a concave area corr~Rp~n~;ng in configuration to the exterior surface of the fascia to be produced, 2 is the block cnnt~ining a convex area that interacts with the concave area in l to form the mold cavity, 3 is the resin injection port, 4 is the injection unit that delivers the first material through the resin injection port 3, and 5 is the injection unit that delivers the second material through port 3.
The first unit injects the skin. The second unit injects the core material which forces the skin against the mold wall. The first unit then injects more of the skin material to complete the molding and prepare for the next cycle. This process is explained in greater detail below.
Flgure 5 shows a perspective view of a typical mold for coinjection molding a bumper in accordance with the invention. The Figure 5 mold is a straight drop injection molding design, in which l is the mold body which has a concave area corresponding in configuration to the exterior surface of the bumper to be produced, 2 is the block r~nt~ining a convex area that interacts with the concave area in l to form the mold cavity, and 3 is the resin injection port. As those skilled in the art will readily appreciate, many other types of molds and plastic runners or gating may be employed in accordance with the principles set forth herein.
Figure 6 shows a cross-section of a typical mold for coinjection molding a partial or complete automobile fascia in accordance with the invention.
In Figure 6, l is the part cavity, 2 is the gate, 3 is 2 1 ~4~f ~9 the sprue bushing, 4 i8 the mold cavity, 5 is the mold core, and A iB the area in which an overflow channel may be provided to aid in core distribution. In this mold configuration, injection takes place at the top of the part to promote the preaence of high impact skin along the bottom of the part. Core distribution can be retarded further by necking down wallstock along the bottom of the part. The-overflow channel will push excess skin into a ~puddle" outside of the part where it may easily be trimmed off.
In sandwich molding, the mold iB partially filled by the first injection unit, BO that material in contact with the wall of the mold forms the skin of the product, leaving a still fluid core. The second material is then injected, pushing the 1 ;n;ng fluid first material further forward, rrnt;nning to form the skin, while the second material progressively fills the inside of the c, ~rnPrt.
Ii an insufficient amount of the first material is injected, the second material would be able to pass to the extremities of the r~ nPnt, itself forming the l~ ;n;ng skin. To prepare for subse~uent shots, the second injection unit is stopped before the part is completely filled, and the first injection unit is re, red from a partially advanced position. This second application of the first material completes the filling of the ~ -nt, obscures the mold gate, and cleans the machine's injection nozzle downstream of the'distribution system ready for the next cycle.
During the second sequence of injecting the first material, the changeover to holding pressure can take place.
Advantages of coinjection molding for thick section rrmrrnPnt.q include the fact that inferior and less expensive materials can be used for the core W096lOIn2 2 i ~ 4 ~ 5 q - 14 - 3r~
material, pigments need only be used with the skin material, all sprues and rejects can be recycled into the core material, core ~-t~r;~1 R with blowing agents eliminate sink marks, leading to improved cooling and shorter cycles, the proce~s temperature of the core material is normally adju~ted to the minimum value necessary, leading to les~ heat to dissipate and hence a reduction in cycle time, automatic separation of the ~_ ~nt~ and gprues within the mold design is possible due to the relatively small gate size re~uirement when coinjection molding, as opposed to single material injection molding, is being carried out, and high plasticizing rates. A production benefit arises from the fact that the core material never comes into contact with the mold walls. The mold walls, therefore, are not subject to the wear that might otherwise be caused ky 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 material will encounter. The core material is not necessarily used throughout the whole part. For instance, to eliminate shrinkage at ribbed sections it is sufficient to inject a foamed core only at these points.
While the present invention has been described with respect to certain specific embo~;m~nt~ in order to illustrate the principles thereof, other different applications of the principles of the invention will readily occur to those skilled in the art based upon the present t~h;ng~. The present invention should be limited, therefore, only to all those ~mho~;r t~
21 949~9 WO96/01732 . ~ 7 that are covered by the spirit and scope of the appended claims.
Claims (17)
What is claimed is:
1. An automobile component for absorbing and dissipating kinetic energy, said component being formed by coinjection molding of a first thermoplastic material having good appearance properties and of a second thermoplastic material having at least one of appearance or strength properties which are significantly inferior to those of said first thermoplastic material, wherein said second thermoplastic material constitutes from 10 to 75 % by volume of said component.
2. The component according to claim 1 wherein said first thermoplastic material is a polyolefin and forms a significant portion of an exterior surface of the component.
3. The component according to claim 1 wherein said second thermoplastic material forms a core that is entirely surrounded by a skin consisting of said first thermoplastic material.
4. The component according to claim 3 configured as an automobile bumper or energy management fascia.
5. The component according to claim 1 wherein both said thermoplastic materials are polyolefins.
6. The component according to claim 5 wherein said second thermoplastic polyolefin is painted regrind polyolefin material.
7. An automobile bumper comprising a core of thermoplastic polyolefin material which contains impurities, and a skin of thermoplastic polyolefin that is substantially free of impurities, said skin surrounding at least a portion of said core.
8. The automobile bumper according to claim 7 wherein the core thermoplastic polyolefin comprises painted regrind polyolefin material.
9. The automobile bumper according to claim 8 wherein said skin surrounds substantially all exterior surfaces of said core, and said bumper weighs from 70% to 30% as much as a corresponding steel bumper having comparable stiffness.
10. An automobile fascia comprising a core of thermoplastic polyolefin material which contains impurities, and a skin of thermoplastic polyolefin that is substantially free of impurities, said skin surrounding at least a portion of said core.
11. The automobile fascia according to claim 10 wherein the core thermoplastic polyolefin comprises painted regrind polyolefin material.
12. The automobile fascia according to claim 11 wherein said skin surrounds substantially all exterior surfaces of said core, and said fascia weighs from 55% to 25% as much as a corresponding steel fascia having comparable stiffness.
13. A method of making an automobile component for absorbing and dissipating kinetic energy which comprises the steps of sequentially (a) injecting a first thermoplastic material having good appearance and strength properties into a mold configured in the shape of said component so as to form a layer of said first thermoplastic material on the inner surface of said mold, (b) injecting a second thermoplastic material having at least one of appearance and strength properties which are significantly inferior to those of said first thermoplastic material into said mold until said second thermoplastic material constitutes from about 10 to 75 % by volume of the component, and (c) injecting a further quantity of said first thermoplastic material into said mold in order to complete the formation of said component in said mold.
14. The method of claim 13 wherein the first and second thermoplastic materials are co-injection molded.
15. The method of claim 14 which further comprises injecting the first and second thermoplastic materials so that the second thermoplastic material forms the core of the component and the first thermoplastic material forms a skin that substantially surrounds the core.
16. The method of claim 13 which further comprises selecting the first and second thermoplastic materials to be thermoplastic polyolefins.
17. The method of claim 13 which further comprises selecting the first thermoplastic material to be a thermoplastic polyolefin that is essentially free from impurities and selecting the second thermoplastic material to be a thermoplastic polyolefin material that contains impurities.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US27324194A | 1994-07-11 | 1994-07-11 | |
| US273,241 | 1994-07-11 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2194959A1 true CA2194959A1 (en) | 1996-01-25 |
Family
ID=23043127
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002194959A Abandoned CA2194959A1 (en) | 1994-07-11 | 1995-07-10 | Coinjected automobile bumpers |
Country Status (3)
| Country | Link |
|---|---|
| AU (1) | AU3125595A (en) |
| CA (1) | CA2194959A1 (en) |
| WO (1) | WO1996001732A1 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| IT1288648B1 (en) * | 1996-08-08 | 1998-09-23 | Nordica Spa | PROCEDURE FOR THE COINJECTION OF PLASTIC COMPONENTS PARTICULARLY FOR FOOTWEAR |
| EP1265742A4 (en) * | 2000-02-24 | 2003-05-07 | Conix Corp | Low-density injection-molded body components |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3991146A (en) * | 1974-04-01 | 1976-11-09 | Imperial Chemical Industries Limited | Method of encapsulating an insert in plastics material by injection molding |
| US5268226A (en) * | 1991-07-22 | 1993-12-07 | Diversitech Corporation | Composite structure with waste plastic core and method of making same |
-
1995
- 1995-07-10 CA CA002194959A patent/CA2194959A1/en not_active Abandoned
- 1995-07-10 AU AU31255/95A patent/AU3125595A/en not_active Abandoned
- 1995-07-10 WO PCT/US1995/008617 patent/WO1996001732A1/en active Search and Examination
Also Published As
| Publication number | Publication date |
|---|---|
| AU3125595A (en) | 1996-02-09 |
| WO1996001732A1 (en) | 1996-01-25 |
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| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued | ||
| FZDE | Discontinued |
Effective date: 20040712 |