CA1089896A - Protective and decorative molding construction - Google Patents

Abstract

PROTECTIVE AND DECORATIVE
MOLDING CONSTRUCTION

ABSTRACT OF THE DISCLOSURE

A molding suitable for use as a decorative and protective trim for motor vehicles, comprising an elongated plastic body bendable to conform to external contours of a vehicle and containing therein a plurality of parallel, laterally spaced, longitudinally extending wires bonded to the plastic and formed of metal wire having a low modulus of elasticity and which is capable of stretching beyond its elastic limit to take a permanent set when the molding is bent in, or at an oblique angle with respect to, a common plane occupied by at least two of the wires, thereby stabilizing the overall bent shape of the molding.

Description

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BACKGROUND OF THE INVENTION

Moldings of the type frequentl~r referred to as "trim strips", which are secured to the sides and other areas of motor vehicles to provide ornamentation and protection against minor dam-age are, in modern practice, commonly formed of a plastic which possesses elastomeric properties and other characteristics rendering it superior to the metal formerly used. Such moldings are normally formed of an extruded solid vinyl body, to which a chrome-like or ,.
other ~uitable ornamental surîacing is frequently applied, by tech-nlqucs already well known in the art. The plastic employed in moldings of the indicated nature intended for exterior installation, although elastomcric, i8 relatively stiff, and where body contours mi~ht rc~uirc its attachment in curved shape~, it frequcntly is not ~ .. ~ . .... .
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8~6 considcred practical, and metal may be substitutcd. Since thc plastic material is elastic, and has the "mcmory" which is characteristic of ~uch plastic~, it tends to return to its straight, extruded or initial form, and if it i9 installed on a curved surface, or is curved during installation, curved areas of the molding may tend to separate from the vehicle body. The metal moldings which were commonly used before the development of high-quality plastic moldings were normally preformed to desired contours by means of simple bending equipment prior to delivery to the body assembly line, the metal employed being of a character easily bendable beyond its elastic limit to the desired contouring so that it took a permanent set in the desired finished shape.
Such treatment has not been feasible ~vith plastic moldings of the in-dicated character, as heretofore commor~y constructed. The overall objective of the present invention is to provide an improved molding adapted for e~cternal use on motor vehicles and which consists pri-marily of a solid plastic body containing therein a unique arrangement of stiffening wires which are capable of being stretched lengthwise beyond their elastic limit when the molding is bent, the arrangement being such that the distorted wire~ then effectively hold the molding . in its bent contour.
A related object is to provide an improved plastic molding of li6ht weiaht and low cost which is readily bendable, and stable when bent, and wherein only a very small amount of metal is incorporated but the metal i9 effective to impart such stabilized characteristics Shereto.
A related object is to provide a moldin6 havin6 the indicated characteristics wherein the metal is completely embedded in the plastic and e~îectively prevented from corrodina.

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Anothcr object i9 to providc such an improved moldin6 which eliminates the need for post-cxtrusion gtress annealing opcr-ations, and which is ad~pted to be economically manufactured in high lrolume production by conventional technique~.
Still another object is to provide such an improved non-corrosive, relatively resilient molding having all of the advantages of modern plastic moldings and which, in addition, can be formed to stable contours by means of conventional types of bending fixtures, and will thereafter retain its bent form during shipment, installation and use.
Other objects and advantages will become apparent upon consideration of the present disclosure in its entirety.

BRIEF DESCRIPTION OF T~E
FIGURES OF DRAWING

Fig. I is a somewhat diagrammatic perspective view oi' a motor car provided with a molding, or so-called "trim strip", embodying the present invention;

Fig. 2 is a fragmentary elevational view, partly ~roken away, showing a portion of the molding on a larger scale;

Fig; 3 is a cross section of the molding on a still largcr ~cale; and Fig. 4 is a view similar to Fig. 3 showing a modification.

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DE:Tl~ILl3D Dl~SCl~Ir'TION OF rREFE:nnL~D
FORM.': OF TIIl. lNVI~NTION
.__ __ A motor vehiclc ~enerally designated V is dia6rammatically illuRtrated in Fig. 1 and ~hown as provided with a decorative and pro-tective molding ormcd in three sections, comprising a front section generally designated A secured to the front fender area, a mid section B 8ecured to the door of the vehicle as an aligned rearward continuation of section A, and a rear section C secured to the rear fender of the -vehicle as a further aligned rearward continuation. Sections A and C
include curved areaQ, respectively designated 11 and 12, which are bent upwardly in the plane of the molding to extend arcuately around and outline the upper portions of the two wheel cut-out areas 13, 14.
As best shown in Figs. Z and 3, the molding comprises an e~ctruded body generally designated 10 formed of a material such as polyvinylchloride having, typically, a durometer hardness of the order of 48, plus or minus 3, on the &ore D 8cale, 15 second delay method. ,, Although the specific configuration of the molding may of course vary, it is 8hown as of modified T cross section, having a central projecting rib or impact area 15. In such surface regions as may be desired for the sake of appearance, a chrome-like or other decorative coating may be applied to the outer surîace of the body, as diagrammatically indicated at ~7 and 18, An adhesive layer 16 i8 provided on thc bottom surface of the body 10, by means of which the molding is adapted to be secured to the 8urface of the vehicle body, A pair of parallel wires 20, 21 extend longitudinnlly within e.nd uninterruptedly throughout the length of the plasSic body 10. The wires are equidistant from me bottom sur~ce and ~r~ spaced a ~ub-stantial distance from each otller. The wire~ are- formed of a m~terial ~ - ~-- .

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85~ti havin~ a low modulus of elasticity but substantial strenE~th in compression, 8uch as a mild steel, aluminum, or so-called soft iron, and they are ~ncorporated in the body 10 by extruding the plastic material around them. The wires are initially coated with an epoxy phenolic acrylic primer or vinyl to metal adhesive such as *"Denflex 2392", manufactured ~y Dennis Chemical Co., to cause the plastic to bond thereto. Alterna-- ti~ely, or in addition, the wires may be mechanically interlocked with the plastic as by being roughened or provided with fine ridges or in-dentation~ which are too shallow to substantially affect its physical `~
properties but of sufficient depth to provide a mechanical interlock - between the plastic and the wire; The diameter, spacing, ductility and elastic modulus of the wire are such that when the molding is bent in t~e common plane occupied by the wires 20 and 21, as is necessary in the ca9e of the portions ll and 12 which bound the wheel cut-out -~
1~ areas 13 and 14, the radially outer wire (the wire 20 in the i~lustrated illstance) i9 stretched longitudinally beyond its elastic limit. Inasmuch as the radially inner wire (21 in the illustrated instance) is not com- -pre~sible to any material degree by 9uch bending of the molding in the manner indicated, it will be appreciated that the outer wire 20 and the ~20 plastic material lying radially outwardly from the innermost wire 21 are stretched lengthwise. Due to ~he low elastic modulus of the wire, -- the strain resulting from bending the molding in the manner indicated -~; causes a permanent elongation of the radially outer ~re sufficient to correspond to the increased peripheral length required to maintain the desired curvature, thc wire having been stressed beyond its elastic - limit so that it takes a pcrmanent set in the stretched condition. There-aftcr, thc wires stron~ty resist any tcndency of the moldin~ to return to thc strai~ht initial form, the effort of the plastic to straighten bein~
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resisted by tho rcaction of ~hc wire 20 to the longitudinal compression which is exertcd upon it by the plastic, inasmuch as the wire is hi6hly resi~tant to axial compression, while the wirc 21 is stressed in ter~ion and thereby also resists re~traightening of the molding. The molding accordingly preserves the contour imparted thereto by such bending in the plane of the wires.
Molding secffon~ such as the sections 11 and 12 illustrated in Fig. 1, constructed as herein disclosed, can ~e preshaped, much as in the case of the metal trim strips formerly used in such applications, and can be applied to the vehicle body without requiring the workmen to attempt to manually shape the molding or restrain it from straighteniry~
during installation. As noted above, this has frequently been impractical to attempt with previous types of plastic moldings. After attachment, any tendency of the bent molding to distort or separate from the body i~ effectively prevented by reason of the fact that it is stabilized in the bent ~hape by the interaction of the stretched ard unstretched wires 20, 21.
It wi~l be appreciated that the several variables which influence the abilib of the molding to retain its bent shape include the dimensions and configuration of the molding, the physical characteristics of the plastic, the dimensions of the wires, the spacing of the wires, and the physical characteristics of the wires. It is accordingly infeasible to attempt to derive a mathematical formula which will enable predicting positively whether plastic molding~ of various designs, with spaced wire~ therein, will retain thcir bent shape against the re-strai~htening effort of the plastic. However, it has been found relatively easy to empirically construct such moldings with parallel wircs arranged a9 shown and described, The drawings illu~trate in r~ropcr proportions .

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the succcssful moldin~ which has bcen constructcd. The body is formcd ot PVC of duromcter 48, mcasured as indicated above. The wires are , 031" diameter low carbon steel and bonded to the plastic by cementing as indicated abo~e. The dimensionQ designated by small letters in Fig.
3, in inches, are as follows.
a ~ . 650 b ~ . 355 c n ~ 260 d . 160 e=,27, f = .09 Such molding is readily bendable either by hand or on a bending machine, and wi,U hold its bent shape.
Although "tuo" or "a pair" of wires have been referred to, it will be understood that while the described function is inherently accomplished by the spaced wires, two or more may be used, and "pair" of course means "at least" a pair.
In addition, as brought out in Fig. 4, wherein parts corresponding to those of the first embodiment are designated by liXe reference numerals primed, one or more additional wires may be incorporated, located in different plane~, to stabilize bent formations in diffcrent planes. The molding lO' illustrated in Fig. 4 is shown as constructed in the same way as the moldin~ of the first-described embodiment, except for thc addition of a third wire 24 which 19 locnted on a ccntrni plane which is pcrpendicular to the basc and -at an oùtspnced position ncar thc top of thc impact rib l5'. Since the w1rc 24 i9 on the centcr plane, it does not interfere with bendin~
thc mhldin~ in thc planc of wires 20', 21', ina~muc1l as such bendin~

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applies no appreciable axial stre~s to thc wire 24. ~Iowevcr, if the .
-~- ~ moldin~g is bent in a plane at an angle to the common plane of wires r,"~
20~, 21', an effect analogous to that already described occurs, the ~
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,r~a ~ , radially outer wire or wires being stretched and the radially inner :~ - -; . .
~-- ~ire or wires placed in compression. If the molding is bent so as ,~, - .--, .
- to bow its ends toward the back (and toward the vehicle body), as for " -. :~ ~. ., .i - example to conform to a convex surface, the wire 24 is stretched and . . _ , . .
wires 20', 21' placed in compression.
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a further modification a fourth wire is added at the , ,,~ . "
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~';10 pos~tion shown in dotted lines at 25. The wires 24 and 25 will then, -, i;. ..
-` when the mol~;ng is bent perpendicularly or at an angle to the back ,:;- , . . .
- face (in or at an oblique angle to the plane of wire~ 24, 25), function -- similarly to the wires 20, 21 of the first embodiment ThisDetailed Description of Preferred Forms of the .. . .
~ i5 In~rentio4 and the accompanying drawings,. have been furnished in . --:: . .
~ ~ ~ - compliance with the statutorg- requirement to set forth the best mode : :.
: ~ contemplated by the invè~tor of carrying out the invention.
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Claims (3)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A bendable molding including an elongated polyvinylchloride body having a durometer of approximately 45 to 51 on the Shore D. scale, 15 second delay method, elongation of approximately 270% with a tensile strength of 3000 to 5000 P.S.I. and having embedded therein a pair of spaced parallel metallic wires extending lengthwise therein, means for securing said wires against longitudinal displacement with relation to the body, comprising an epoxy phenolic acrylic primer baked onto the wires and to which the body is bonded, the wires being formed of a material having a relatively low modulus of elasticity within the range of approx-imately 50,000 to 75,000 P.S.I. and capable of being stretched beyond the elastic limit thereof without fracturing when the body is bent in the common plane of said wires, whereby when the body is so bent, a radially outer wire is permanently elongated with relation to a radially inner wire and said wires thereafter oppose return of the molding to its pre-bent shape.

2. A molding as defined in claim 1 having a third wire in and also secured with respect to the body and parallel to the wires of said pair but spaced from the common plane occupied by the wires of said pair, said third wire being formed of a material capable of being stretched beyond its elastic limit when the body is bent in a plane which is at an angle to said common plane.

3. A molding as defined in claim 1 including a second pair of wires parallel to the first pair and lying in a second common plane which is at an angle to the first-mentioned common plane, the wires of said second pair also being secured with respect to the body and formed of a material capable of being stretched beyond its elastic limit when the body is bent in a plane which is at an angle to the first-mentioned common plane.