Wall panels

Disclosed is a constant contact panel interlock even during thermal expansion and contraction by providing flexible pins to bear on a tongue in a tongue and groove interlock and also by providing ramps for a bendable flange to slide over and bear on. Further, a material made of polypropylene with 20% calcium carbonate filler is used to form the panels, such material being sufficiently flexible at the temperatures common for panels exposed to direct sunlight (as on a roof or wall) to permit the pins or flange to bend without breaking and also being a material of much lower coefficient of expansion than pure polypropylene.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention is directed to interlocking wall panels, and more 
specifically to a composition of matter and physical structures to enhance 
thermal stability and reduce rattling, warpage and buckling. The prior art 
is generally found in Class 52. 
2. Description of the Prior Art 
The prior art is exemplfiied by the following patents: U.S. Pat. Nos. 
3,621,625; 3,783,570; 4,070,843; 4,102,106; 4,223,490 and West German Pat. 
No. 24 40 497. These previous patents have disclosed various methods of 
interlocking wall and roof panels. However, they have contributed little 
to the problems arising from thermal expansion and contraction after 
installation. 
In particular, U.S. Pat. No. 4,223,490 discloses panels that interlock via 
a tongue and groove arrangement and that have breakable pins for 
preventing the tongue from fully penetrating the groove during 
installation. Overcoming the thermal expansion is a critical factor in the 
marketability of this product because the panels will expand as much as 
5/8 of an inch over the 40 inch length at temperatures of 160.degree. F., 
which is easily attainable on hot sunny days. This expansion must be dealt 
with to prevent the panels from buckling away from the wall on which it is 
mounted. Then, upon thermal expansion after installation the expanding 
tongue breaks off the breakable pins and is able to penetrate farther into 
the groove, and upon contraction the tongue partially withdraws from the 
groove. This system of interlocking the panels, however, still has a 
problem of rattling due to the looseness of the tongue and groove joint. 
Also, the breakable nature of the pins may lead to a substantial number of 
the pins being broken off during shipment of the panels . This leads to 
misalignment of the panels upon installation and aggravates the rattling 
problem. 
Similarly, U.S. Pat. No. 4,070,843 has a short tongue and a wide groove 
interlock, but primarily relies upon the nailing of the panels to the roof 
or wall for stability. No compensation for thermal expansion is really 
provided, and rattling due to the loose nature of the interlock is likely. 
U.S. Pat. No. 3,073,570 provides a deep tongue and groove interlock, but 
fails to provide any expansion or contraction looseness so upon thermal 
expansion one would expect the panels to buckle. 
The interlock of U.S. Pat. No. 4,102,106 is essentially a tongue and groove 
with the groove being the space between a panel and the supporting wall or 
roof. As with the previous patents, the tongue and groove interlock is 
loose, and also no compensation for thermal expansion or contraction is 
provided. 
Lastly, West German Pat. No. 24 40 497 has an interlock similar to U.S. 
Pat. No. 4,102,106. And U.S. Pat. No. 3,621,625 has an interlock formed by 
again a tongue and groove but with the tongue wedging into the groove. 
However, no compensation for thermal expansion or contraction is provided, 
and thus one would anticipate buckling upon expansion and a loose 
interlock upon contraction resulting in rattling. 
SUMMARY OF THE INVENTION 
The present invention provides a constant contact panel interlock even 
during thermal expansion and contraction by providing flexible pins to 
bear on a tongue in a tongue and groove interlock and also by providing 
ramps for a bendable flange to slide over and bear on. Further, a material 
made of polypropylene with 20% calcium carbonate filler is used to form 
the panels, such material being sufficiently flexible at the temperatures 
common for panels exposed to direct sunlight (as on a roof or wall) to 
permit the pins or flange to bend without breaking and also being a 
material of much lower coefficient of expansion than pure polypropylene. 
Thus the present invention solves the problem in the prior art by providing 
an interlock which allows for thermal expansion and contraction yet avoids 
looseness.

DESCRIPTION OF THE FIRST PREFERRED EMBODIMENT 
Referring to FIG. 1, a wall 10 is shown with panels 12 and 14 already 
nailed to wall 10 and panels 16 and 18 ready to be positioned to engage 
panels 12 and 14 and each other and to be nailed to wall 10. Arrow 20 
shows the positioning of the panel 16 and arrows 22 and 24 shows the 
positioning of panel 18. Nails 30 (only the head visible in FIG. 1) driven 
through holes 31 (visible in FIGS. 2 and 3) secure panels 12 and 14 to 
wall 10, and after panels 16 and 18 are positioned nails will be driven 
through holes 32 in panel 16 and holes 34 in panel 18 to secure them to 
wall 10. 
FIG. 2 shows a cross-section of the engaging of panels 12 and 16 after 
panel 16 has been positioned in place and nailed to wall 10. Spacers 36 
behind holes 31 insure that flange 43 is spaced from wall 10 after 
nailing. 
The positioning of panel 16 to engage panel 12 is shown from the rear in 
FIG. 3 with wall 10 and nails 30 removed for clarity. Panel 16 is lowered 
as indicated by arrows 20 until flexible pins 40 abut the top edge 42 of 
flange 43 which forms the top portion of panel 12. In this position flange 
43 partially fills slot 44 formed by flange 46 and base 48 on panel 16. 
The engagement of flange 43 in the slot 44 holds the bottom portion of the 
panel 16 next to wall 10 because flange 43 of panel 12 is nailed to wall 
10 by nails 30. A large number of pins 40 eases installations. Using three 
flanges 46 and six pins 40 per foot of panel has proved convenient. 
After panel 16 has been positioned in place by engaging flange 43 of panel 
12, nails are driven through holes 32, thereby securing the top portion of 
panel 16 against wall 10. Thus it is seen that the upper and lower 
horizontal edge portions of panel 16 are held in a spaced relationship 
with wall 10. Further, the panel is provided with a plurality of spacers 
49 (illustrated in FIG. 4) which keep the central portion of panel 16 
spaced from wall 10. 
The vertical ends of panels 16 and 18 form an engaging tongue and groove 
when panels 16 and 18 are positioned for nailing to wall 10. This is 
illustrated in FIGS. 4 and 5. FIG. 4 shows a cross-section of engaged 
panels 16 and 18 illustrating the flanges 52 and 54 of panel 16 which form 
the groove engaging the tongue. A ramp 60 is provided for installation 
depth guidance and expansion contact. During installation flange 50 is 
inserted into the groove formed by flanges 52 and 54 until ramp 60 abuts 
flange 52. Ramp 60 has a rounded top portion 62 which will permit flange 
52 to bend and ride up on ramp 60 during thermal expansion and thereby 
insure frictional contact and eliminate looseness in the joint, as 
described below. 
For a panel 16 of length approximately 40 inches and of height 
approximately 18 inches, the top flange 43 is approximately 11/2 inches 
wide, flange 50 is approximately 3/4 inches wide, flange 52 approximately 
1 inch wide, flange 54 approximately 1/2 inch wide, and pins 40 
approximately 1/2 inch long although these dimensions of the flanges are 
in part determined by the particular pattern molded on the panel 16. For 
example, if a brick or stone pattern is molded, then the portions of the 
flanges visible after installation on wall 10 (portion 64 in FIG. 2 and 
portion 66 in FIG. 4) are to simulate the mortar between the bricks or 
stones. Thus these visible portions 64 and 66 must have dimensions 
compatible with such simulation. Panel 16 is preferably of an 80% 
polypropylene 20% calcium carbonate composition and of a thickness of 
approximately 0.090 inches. Panels made of such a compound are quite 
flexible above 100.degree. F., and thus permit flange 52 to bend and 
override ramp 60. Conversely, at installation temperatures the panels 
would be sufficiently rigid to resist overriding. During temperature 
changes panels 16 and 18 and all the other panels affixed to wall 10 will 
expand and contract; the primary effect is direct sunlight heating which 
typically raises the temperature of the panels from an abient of, say 
60.degree. F., to approximately 160.degree. F. 
In FIG. 4 it is seen that flange 50 will partially withdraw from the groove 
formed by flanges 52 and 54 upon a lowering of the temperature which 
causes a contraction of panels 16 and 18; whereas upon an increase in 
temperatures panels 16 and 18 will expand and flange 52 sill override ramp 
60 due to its rounded top 62 and height. This overriding bends flange 52; 
thus flange 52 presses against ramp 60 and keeps the joint tight. If 
flange 50 reaches the end of the groove formed by flanges 52 and 54, then 
further expansion by panels 16 and 18 causes them to buckle or bow out 
from wall 10. To avoid this buckling or bowing, the panels 16 and 18 are 
preferably made from a composition of 80% polypropylene and 20% calcium 
carbonate. This composition reduces the total horizontal expansion of 
panel 16 to less than approximately 1/4 inch over the temperature range 
30.degree. F. to 160.degree. F. and thus prevents flange 50 from reaching 
the end of the groove formed by flanges 52 and 54 upon expansion and also 
prevent flange 50 from disengaging from the groove formed by flanges 52 
and 54 upon contraction. 
The effects of temperature changes for expansion and contraction in the 
vertical direction are compensated for by pin 40 as follows. During 
installation panel 16 is lowered onto panel 12 so that flange 43 engages 
slot 44, and as shown in FIGS. 2 and 3 this engagement is limited by 
flange 43 abutting and slightly bending pins 40. With an increase in 
temperature panel 16 expands toward panel 12 and pins 40 bend so slot 44 
may move down on flange 43. Upon a decrease in temperature panel 16 will 
contracts upwards in FIG. 2 and flange 43 partially disengage slot 44. 
Pins 40 remains in contact with flange 43 except during low temperatures 
and thus provides tightness in the joint and eliminate any rattling of 
panel 16 about flange 43. 
DESCRIPTION OF THE SECOND PREFERRED EMBODIMENT 
For panels molded with patterns of shingles the vertical ends differ from 
panels molded with patterns of stone or brick because of the vertical 
continuity of shingle patterns as opposed to the primarily horizontal 
continuity of brick and stone patterns. Thus an alternative to the tongue 
and groove formed by flange 50 of panel 18 and flanges 52 and 54 of panel 
16 is the channel 74 in panel 70 and engage flange 76 of panel 72 as shown 
in FIGS. 6 and 7. FIG. 6 is a cross-sectional view. Channel 74 is formed 
by flange 78 and depending flange 80 in the vertical end of panel 70. 
Panel 72 is positioned to engage panel 70 by centering flange 76 in 
channel 74. To center flange 76 a pair of ramps 82 and 84 are formed in 
channel 74 with a space between them of approximately the thickness of 
flange 76. Upon installation panels 70 and 72 are positioned against the 
immediately adjacent panel below (this is analogous to panels 16 and 18 
being adjacent against panels 12 and 14 in the first preferred embodiment) 
and flange 76 of panel 72 is positioned in the gap between ramps 82 and 
84. Panel 70 is nailed to wall 10 prior to panel 72 being nailed to wall 
10. 
Upon changes in temperature the panels 70 and 72 expand and contract with 
the following results. Upon an increase in temperature, the panels 70 and 
72 expand towards each other and flange 76 rides up and over ramp 82 
because projection 82 is rounded and of a height measured from the bottom 
of channel 74 of approximately 0.080 inches. The thickness of the panels 
70 and 72 is approximately 0.090 inches throughout. Upon a decrease in 
climatic temperature, panels 70 and 72 contract away from each other, and 
flange 76 rides over ramp 84. 
The horizontal edges of panels 70 and 72 are similar to those of panels 16 
and 18, that is the lower edge of panel 70 has flanges analogous to flange 
46 forming slots analogous to slot 44 which engage an upper flange 
analogous to flange 43 on the immediately adjacent panel below. 
Panels 70 and 72 are essentially the same size as panels 16 and 18, that is 
18 inches high and approximately 40 inches long. Channel 74 is 
approximately 3/4 inches wide, and the width of flange 76 varies because 
of the slope of the molded shingle pattern. Use of a composition of 80% 
polypropylene and 20% calcium carbonate results in a panel of temperature 
change expansion and contraction which is small enough to permit flange 76 
to remain in channel 74. If pure polypropylene is used, then flange 76 
will likely be forced against one or the other sides of channel 74 upon 
expansion and contraction. 
Although particular embodiments of the invention have been shown and 
described in full here, there is no intention to thereby limit the 
invention to the details of such embodiments. On the contrary, the 
intention is to cover all modifications, alternatives, embodiments, usages 
and equivalents of the subject invention as fall within the spirit and 
scope of the invention, specification and appended claims.