Fastening arrangement for plastic vehicle panel

The present invention relates to an arrangement for attaching a plastic panel to an automotive body metal substructure enabling controlled distortion free thermal expansion and contraction of the plastic panel relative to a metal substructure. The attaching arrangement comprises a plastic adjustable mounting block sized for initial insertion in an associated wide slot portion of a keyhole-shaped expansion and contraction slot. The block has a central abutment portion depending from an upper plate portion including lateral extending wings providing with the plate opposed grooves adapted to slidably engage a narrow trailing slot portion of the keyhole-shaped slot upon the blocks subsequent longitudinal rearward movement. The block has a vertically disposed longitudinally extending integral locating frangible finger extending longitudinally from the abutment portion adapted to engage the rearward transverse edge of the narrow slot portion allowing the precisely located block to be readily affixed by a fastener to the plastic panel. Upon the panel undergoing shrinkage the narrow slot portion transverse edge crushes the locating finger enabling the plastic panel and its associated blocks to slide fore and aft relative to the substructure to accommodate thermal movement of the panel.

This invention relates generally to a fastening arrangement for securing an 
elastomeric or plastic panel to a metal substructure portion of an 
automotive vehicle body and more particularly to such a fastening 
arrangement which allows for thermal distortion-free expansion and 
contraction movement of the plastic panel relative to the substructure. 
BACKGROUND OF THE INVENTION 
Various arrangements have heretofore been used for securing elastomeric 
parts to metal portions of motor vehicles. One such arrangement is found 
in the U.S. Pat. No. 4,792,475 issued Dec. 20, 1988 to Alfred A. Bien 
entitled Composite Joint Pad For Synthetic Resin Panels. The '475 patent 
discloses a mounting arrangement and method of manufacture for clamping 
synthetic resin panels to a workpiece such as a vehicle metal 
substructure. A composite joint pad has a plate-like metal bushing 
pre-molded therein. The bushing comprises a raised central embossment 
having an exposed portion terminating in an arcuate sectioned rim 
extremity positioned a predetermined distance outwardly from the bonding 
face of the pad. Upon the bushing exposed embossment being received in a 
panel aperture, the pad's face is bonded to a panel mating surface with 
the rim flush with an adjacent surrounding surface of the panel. As a 
result, the pad's arcuate sectioned rim is clamped to the substructure by 
means of a threaded fastener being overdriven in the bushing stem without 
causing stress on the panel. 
The U.S. Pat. No. 4,592,937 issued June 3, 1986 to Nagata et al. entitled 
Arcuate Side Molding discloses an arcuate resin plate side molding of a 
vehicle adapted to be attached to a curved surface of an automobile metal 
body avoiding holes being formed therein. The thermal expansion 
coefficient of the side molding is different from that of the automobile 
body. Therefore, the direct attachment of the molding to the metal body 
results in thermal deformation of the molding relative to the body, for 
example, in a hot day in summer. In the Nagata, et al. patent the molding 
comprises a resin plate having projections formed in the backside thereof, 
and an intermediate member provided with slots for receiving the 
projections of the resin plate. In assembling the resin plate and the 
intermediate member, the projections are inserted through the slots of the 
intermediate member, and then the tips of the projections are heat caulked 
to join the intermediate member to the resin plate. In this way the resin 
plate and the intermediate member are longitudinally slidable relative to 
each other. 
The U.S. Pat. No. 4,597,153 issued July 1, 1986 and U.S. Pat. No. 4,597,153 
issued July 16, 1986 to common inventor W. S. Zaydel disclose a method for 
mounting a plastic body panel on a vehicle underlying metal substructure 
together with the mounting structure therefore. The Zaydel patents 
disclose a fastener fixedly attaching one end portion of the plastic panel 
on the metal structure. A mounting block is slidably mounted on the metal 
substructure longitudinally spaced from the fastener to define a path of 
longitudinal movement of the mounting block toward and away from the fixed 
end portion of the plastic panel. A spring urges the mounting block to a 
certain longitudinal position and is yieldable to permit movement of the 
mounting block away from the certain longitudinal position. A fastener 
attaches the plastic panel to the mounting block so that the plastic panel 
is effectively supported in a manner enabling longitudinal movement 
relative to the fixed one end portion to accommodate thermal or 
hygroscopic growth of the plastic panel. 
The U.S. Pat. No. 3,875,661 issued Apr. 8, 1975 to Lindstrom et al. 
discloses a flexible subassembly for installation on a vehicle body. The 
Lindstrom subassembly includes a flexible elastomeric panel having a 
peripheral contour corresponding to a similar peripheral contour on the 
body, a plurality of square bosses on a mounting surface of the flexible 
panel, a rigid reinforcing panel disposed in juxtaposition with the 
mounting surface, and a plurality of apertures in the reinforcing panel 
corresponding to the bosses. Each aperture is larger than the 
corresponding boss in a direction parallel to the peripheral contour so 
that thermal expansion and contraction of the flexible panel is directed 
along the peripheral contour thereby to assure a continuous contour across 
the interface between the flexible panel and the body. 
The U.S. Pat. No. 4,564,232 issued Jan. 14, 1986 to Fujimori et al. 
discloses an automobile door with an inner plate and an outer plate 
wherein the outer plate has a panel formed from a synthetic resin. The 
panel is attached to a rigid metallic plate, such as steel, through a 
plurality of fastening holes formed in the longitudinal direction of the 
synthetic panel. One of the fastening holes near the forward end of the 
panel has a diameter substantially that of the fastening means. The 
remaining fastening holes are formed so as to allow longitudinal expansion 
and contraction of the synthetic panel. A lip portion is formed near the 
lower edge of the synthetic panel to engage with the inner plate of the 
door. 
The U.S. Pat. application Ser. No. 07/437,243 filed Nov. 16, 1989 now U.S. 
Pat. No. 4,973,102 issued Nov. 27, 1990, entitled "Fastening Arrangement 
For Plastic To Metal Parts", invented by Alfred A. Bien, and assigned to 
the assignee of the instant application. The Bien application discloses an 
improved arrangement for attaching a plastic panel and metal mounting 
strip sub-assembly to an automotive body metal substructure enabling 
controlled distortion free thermal expansion and contraction of the 
plastic panel relative to the mounting strip. The attaching arrangement 
comprises a metal spacing washer having a tubular sleeve portion formed 
with an integral frusto-conical spring flange. The washer sleeve portion 
free end extends through an elongated slot in the mounting strip and an 
aligned circular opening in the panel. A blind break-stem rivet is 
inserted through the washer bore and upon being set applies a 
predetermined axial clamping force biasing the washer flange into contact 
with the mounting strip. The rivet head undersurface may be provided with 
an annular locking ring adapted to engage the plastic panel outer surface. 
Upon the panel being heated to its thermal-relaxation temperature the 
locking ring is embedded in the softened plastic panel thereby reducing 
excess load on the washer spring flange in a tolerance self-compensating 
manner. 
SUMMARY OF THE INVENTION 
A primary object of the present invention is to provide an attaching 
arrangement for initial precise positioning of a plastic panel to a metal 
substructure of an automobile body along which the plastic panel may 
subsequently self-adjust by sliding relative to the metal substructure 
because of the different thermal expansion and contraction characteristics 
between the panel and the substructure. 
It is still another object of the present invention to provide an attaching 
arrangement as set forth above wherein a plurality of slidable plastic 
mounting blocks are received in associated aligned keyhole-shaped cut-outs 
or slots in a metal substructure whereby screw fasteners removably attach 
a plastic panel to each of the mounting blocks enabling the plastic panel 
and blocks to move conjointly longitudinally relative to vehicle body 
metal substructure accommodating both thermal expansion and contraction of 
the plastic panel. 
A still further object of the present invention is to provide an attaching 
arrangement as set forth above wherein each block having a frangible 
positioning finger adapted in its unyielding state to contact one 
transverse edge of its associated keyhole-shaped slot whereby the finger 
initially precisely positions its associated block on the metal 
substructure for ready attachment of a plastic panel by suitable fasteners 
while the finger being sufficiently weak in response to a compressive 
force being applied by the slot transverse edge providing a subsequent 
crushed state thereby enabling the block to slide in one direction to 
compensate for thermal contraction of the panel. 
The present invention discloses an arrangement for attaching long, thin 
sectioned plastic or synthetic panels such as a fender, for example, to a 
vehicle body metal substructure accommodating longitudinal expansion and 
contraction of the panel in a distortion or warpage free manner. A 
plurality of adjustable plastic or synthetic mounting blocks are provided 
for slidable reception in associated keyhole-shaped slots in the 
substructure. The mounting blocks comprise an upper rectangular plate 
portion having a width greater than the wide slot portion of a 
keyhole-shaped slot. The plate portion has a lower central abutment 
portion depending form the undersurface of the plate and sized for snug 
reception in the narrow slot portion of the keyhole-shaped slot. The 
abutment portion has its trailing transverse edge recessed a predetermined 
longitudinal distance from the trailing edge of the plate portion. 
The abutment portion is formed with a pair of laterally extending wings 
vertically spaced from the plate portion undersurface to define a pair of 
opposed grooves adapted to slidably receive associated side edges of the 
narrow slot portion such that the span of the wings is less than the width 
of the wide slot portion but greater than the width of the narrow slot 
portion. A vertically disposed integral frangible locating finger extends 
rearwardly from the abutment portion with its free end located just short 
of the plate's trailing edge. The finger is aligned in the vertically 
disposed longitudinally extending plane of symmetry of the mounting block 
such that its trailing free end is adapted to abut the closed transverse 
edge of the narrow slot portion to initially precisely position or index 
the block on the body substructure during a vehicle assembly line plastic 
panel mounting operation of the vehicle. 
A plurality of the mounting blocks, each having a vertical bore 
therethrough, are located in their indexed position in an associated one 
of a plurality of longitudinally aligned keyhole-shaped slots spaced along 
a portion of the vehicle substructure. To attach the panel a worker simply 
aligns the plurality of fastening holes in the plastic panel with 
respective underlying ones of the block bores and secures the panel by 
inserting screws through the aligned holes. The panel has one fastening 
hole near its rearward end which is aligned with a reference hole in the 
vehicle substructure. Upon receiving an anchoring screw through the panel 
fastening hole and the reference hole the plastic panel, together with its 
mounting blocks, is free to longitudinally expand away from and contract 
towards the vehicle substructure reference hole to accommodate thermal 
expansion and contraction. 
The vehicle is designed to withstand service temperatures ranging from 
-40.degree. to 180.degree. F. Thus, during subzero temperatures the 
plastic panel undergoes shrinkage or contraction causing each block 
indexing finger free end to be subjected to a compressive force by its 
associated keyhole-shaped slot transverse abutting edge. The frangible 
finger is sufficiently weak such that, upon a compressive force exceeding 
each finger's predetermined rigid and non-yielding state, the finger is 
crushed in its yielding deformable state enabling the panel and its blocks 
to move toward the anchoring screw. That is, each mounting block is free 
to slide rearwardly a required distance in its narrow slot portion whereby 
its closed edge deforms a corresponding segment of the frangible finger so 
as not to obstruct any shrinkage movement of the panel relative to the 
substructure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Turning now to the drawings, FIG. 1 shows a perspective view of a front 
portion of a vehicle body frame 10 adapted to receive a plastic panel 
member which in the disclosed embodiment is a front fender, generally 
indicated at 12. The fender 12 is formed from a suitable elastomeric or 
plastic material comprising an arcuate exterior portion 14 and an L-shaped 
integral angle portion comprising a vertical panel 16 and a horizontal 
panel portion 18. The horizontal panel portion has a plurality of 
longitudinally aligned uniformly spaced fastening holes 20 each adapted to 
receive respective self tapping threaded screw fasteners 22. 
The horizontal panel portion 18 is sized for flush reception on a metal 
planar portion of the vehicle frame substructure generally indicated at 
23. In the disclosed form the substructure planar portion is a horizontal 
sheet metal flange 24 formed or lanced with a plurality of expansion and 
contraction keyhole-shaped slots 26. As best seen in FIGS. 4, 5 and 6, the 
plastic fender 14 integral planar attachment panel 18 has a plurality of 
spaced uniform circular openings 20 aligned on a common longitudinal axis 
28. The plurality of the circular openings 20 are each adapted for 
alignment with an associated one of the plurality of keyhole-shaped slots 
26 formed in the flange 24 of the metal substructure 23. 
As best seen in FIGS. 3 and 3A each of the keyhole shaped slots 26 comprise 
a leading wide slot portion 30 having a predetermined first width and a 
trailing narrow slot portion 32 having a predetermined second width. It 
will be noted in FIG. 3A that each keyhole-shaped slot 26 has parallel 
opposed edges and is symmetrical about a longitudinal axis 28'. The wide 
slot portion 30 is shown connected to the narrow slot portion 32 by 
lead-in sloped edges 34 while the closed end of the narrow slot is defined 
by transverse edge 36 and the closed end of the wide slot portion 30 is 
defined by transverse edge 38. 
A plastic panel, such as the plastic fender 14, is made of urethane resin 
elastomeric material or the like which has thermal expansion and 
contraction rates substantially different from the metal substructure 23. 
Thus, a fastening arrangement is required that can be readily attached to 
a vehicle substructure that allows distortion free thermal growth and 
shrinkage of the plastic panel portion 18 relative to the metal 
substructure planar portion such as flange 24. 
With reference to FIGS. 10 through 15 a fastening arrangement further 
comprises a plurality of plastic adjustable mounting blocks generally 
indicated at 40. Each of the mounting blocks is formed symmetrical about a 
longitudinal axis 41 and comprises an upper generally rectangular plate 
portion 42 defining a forward transverse leading edge 44 and aft trailing 
transverse edge 46. The plate portion 42 has longitudinal side edges 48 
spaced at a predetermined width which a greater than the width of the wide 
slot portion 30. 
The adjustable mounting block 40 has a central longitudinally extending 
rectangular abutment portion 50 depending from the undersurface 52 of the 
plate portion 42. As best seen in FIG. 14 the abutment portion 50 has its 
aft or trailing surface 54 longitudinally recessed or set back a 
predetermined distance from the plate portion trailing edge 46. The 
abutment portion 50 has sides 56 formed with a pair of laterally extending 
wing portions 58 vertically spaced from the plate portion undersurface 52 
a predetermined distance so as to define therebetween a pair of opposed 
outwardly opening grooves 60. 
As best seen in FIG. 5 the grooves 60 are adapted to slidably receive 
associated longitudinal edge portions of the narrow slot portion 32. It 
will be noted in FIGS. 7 and 8 that the width between free edges 62 of the 
pair of wing portions 58 is less than the width of the wide slot portion 
30 and greater than the width of said narrow slot portion 32. Thus, as 
viewed in FIG. 3A the mounting block abutment portion 50 is initailly 
inserted in the wide slot portion 30 as the length of the abutment portion 
50 is slightly less than the length of slot portion 30. It will be noted, 
however, that the sloped lead-in edges 34 provide additional longitudinal 
space for the ready insertion of the abutment portion 50. The mounting 
block 40 is subsequently moved longitudinally into the narrow slot portion 
32 wherein the lead-in edges are slidably received in their associated 
grooves 60. 
The mounting block 40 is longitudinally advanced into the narrow slot 
portion 32 to its installation position shown in FIGS. 4 and 7. As seen in 
FIG. 10 a vertically disposed central locating finger 64 is formed 
integral on the undersurface 52 of the plate portion 42 and extends 
longitudinally forwardly from the aft edge chamfer 65 (FIG. 14) 46 aligned 
in the vertical plane of symmetry which includes the axis 41 of FIG. 12. 
The abutment portion face 54 has a rectangular recess 66 formed therein 
into which the locating finger 64 extends. 
With reference to FIG. 7 the locating finger is shown having a narrow or 
thin section 64 which is continuous with a thicker sectioned stem portion 
68 within the recess 66. The locating finger 64 free end 70 is shown 
contacting the closed transverse edge 36 of the narrow slot portion 32 to 
position the mounting block 40 in its installation indexed position. It 
will be appreciated that in FIG. 7 each adjustable mounting blocks 40 of 
FIG. 1 is located at its indexed position in its associated keyhole-shaped 
slot 26 with each block through bore 72 aligned with its associated hole 
20 in the subjacent substructure metal panel 24. The self-tapping screws 
22 are next threadably inserted in each of the mounting block bores 72 and 
their aligned holes 20. Accordingly, when the anchoring screw 22' (FIG. 1) 
is inserted in its hole 20' and aligned reference hole 74 the fender's 
plastic panel portion 18 is precisely located on the vehicle substructure 
23. 
As the fender panel portion 18 is fixed at its rearmost end by the 
anchoring screw 22' in metal flange reference hole 74 the panel 18 is free 
to expand in a forward direction from the screw 22' to accommodate thermal 
distortion free growth relative to the metal substructure. Thus, as seen 
in FIG. 7, the adjustable mounting block abutment portion 50 is partially 
indicated in an expansion position by phantom lines. The block 40, in its 
phantom line position, has slidably traveled forwardly toward the wide 
slot portion 30 of its keyhole-shaped slot 26 relative to the substructure 
metal flange 24. 
Upon the plastic panel portion 18 being subjected to a predetermined drop 
in temperature sufficient to cause contraction of the plastic material the 
panel will shrink rearwardly toward the anchor screw 22'. If shrinkage 
occurs with the adjustment blocks 40 in their index full line position of 
FIG. 7 applicant's invention results in the closed edge 36 of the metal 
flange 24 crushing the frangible plastic finger 64 by shearing or cutting 
the finger 64 at its longitudinal integral juncture 80 (FIGS. 10 and 14) 
with the undersurface 52 of the block plate portion 42. With reference to 
FIG. 8, as the plastic finger 64 is severed from the undersurface 52 
progressive rearward longitudinal travel of each of the adjustment blocks 
40 causes the severed portion of the finger 64 to yield and crush in an 
accordion fashion against the transverse edge end 36. Thus, the adjustable 
mounting blocks 40 uniquely accommodates longitudinal fore and aft thermal 
expansion and contraction of the plastic panel 18 relative to the metal 
flange 24. 
With reference to FIGS. 10, 11, and 12 it will be seen that the forward 
edge 44 and forward face 81 of the block abutment portion 50 have a 
radiused notch or cut-out 82 formed therein with outwardly or forwardly 
diverging side walls. Further, the block grooves 60, as seen in FIGS. 3 
and 7, are each tapered toward the narrow slot portion 32 such that the 
entrances or aft ends of the grooves 60 at the aft face 54 are 
transversely deeper than the forward ends of the grooves at the forward 
face 81. The tapered grooves 60 insure a close snug fit of the blocks 40 
in their associated narrow slot portions 32. Accordingly, the notch 82 
provides resilient flexibility enabling the block 40 to flex laterally 
inwardly, if necessary, accommodating for any out of tolerence conditions 
between the grooves 60 and the keyhole narrow slot portion 32. 
It will be further observed in FIG. 5 that the upper surfaces of the pair 
of wing portions 58 are sloped upwardly toward their outer ends to insure 
snug sliding reception of the narrow slot portion 32 within their 
associated grooves 60. With reference to FIG. 6 with the screw 22 fully 
driven home the wings upper surfaces are drawn-up flush with the underside 
of the metal flange 24. 
An alternative embodiment of the present invention is shown by the plastic 
adjustable mounting block generally indicated at 90 in FIGS. 16-19 of the 
drawings. Identical or corresponding portions of the mounting block 90 
will be indicated by the same numerals except that they will be primed. 
Accordingly, the mounting block 90 comprises an upper generally 
rectangular plate portion 42' defining a forward transverse leading edge 
44' and an aft transverse trailing edge 46'. The plate portion 42' has 
longitudinal side edges 48' spaced at a predetermined width which is 
greater than the width of the wide slot portion 30. 
The block 90 has a central longitudinally extending rectangular abutment 
portion 50' has its aft or trailing surface 54' longitudinally recessed a 
predetermined distance from the plate portion trailing edge 46'. The 
abutment portions 50' has sides 56' formed with a pair of laterally 
extending wing portions 58' vertically spaced from the plate portion 
undersurface 52' a predetermined distance so as to define therebetween a 
pair of opposed outwardly opening grooves 60'. 
The grooves 60' are adapted to slidably receive associated longitudinal 
edge portions of the narrow slot portion 32 in the same manner as the 
first embodiment of FIGS. 1-15. It will be noted in FIG. 16 that the plate 
portion 42' forward edge 44' has a radiused notch or cut-out 82' to 
provide resilient flexibility enabling the block 90 to flex laterally 
inwardly, if necessary, accommodating for any out of tolerance conditions 
between the grooves 60' and the keyhole narrow slot portion 32. 
It will be noted in FIG. 16 that the upper plate portion 42' has its aft 
edge 46' formed with a longitudinally extending U-shaped notch 92 formed 
symmetrical about the longitudinal axis of symmetry 41' of the block 90. 
Thus, the block 90, which is formed with a vertically disposed thin 
central frangible locating finger 94, such that the frangible finger 94 is 
cantilevered rearwardly from its thicker sectioned stem portion 68'. This 
is in counterdistinction to the form of the invention shown in FIG. 10 
wherein the finger 64 is formed with a longitudinal integral juncture 80 
with the undersurface 52 of the block plate portion 42. The cantilevered 
finger 94 is shown in FIG. 16 coextensive with the notch 92 in its 
unbroken state. Consequently, the finger 94 is more readily crushed by the 
transverse one edge 36 of the narrow slot portion 32 with the block 90 
sliding toward the edge 36 upon the fender panel portion undergoing 
thermal contraction such as during sub-zero temperatures. In its crushed 
state the finger 90 would be deformed in a manner similar to the crushed 
finger 64 shown in FIG. 8. It will be noted, therefore, that with all 
conditions of material and size being equal the cantilivered finger 94 may 
yield to its crushed state by a lesser compressive force than is required 
to crush the finger 64. It will also be noted that the U-shaped notch 92 
provides visual indication to the installer that the cantilevered finger 
free aft edge 96 is abutting the flange transverse edge 36 to insure 
correct location of the block 90. 
FIG. 18 shows the cantilevered finger 94 having its free end 96 recessed a 
slight distance from its trailing edge 46' so as to terminate at the lower 
edge of its aft edge chamfer 65'. Thus, by virtue of the locating finger 
94 being cantilevered rearwardly, it provides increased weakness to a 
predetermined compressive force as compared to the locating finger 64 of 
the embodiment of FIGS. 1-15. That is, as the fingers 64 must be sheared 
from the plate portion undersurface 52 a predetermined greater compressive 
force is required to crush the finger 64 than is required to crush the 
cantilevered finger 94. The embodiment of FIGS. 16-19 allows the finger 94 
to be more readily crushed by the transverse edge 36 of the keyhole-shaped 
slot 26 during shrinkage of the panel. 
While preferred embodiments have been shown and described to illustrate the 
invention, other embodiments will become to those skilled in the art. 
Accordingly, the scope of his invention is set forth in the following 
claims.