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BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to transparent/translucent blocks as building materials used in commercial and residential construction and, more particularly, to ventilated interlocking blocks of manmade materials. 
   2. Description of Related Art 
   For decades, hollow glass blocks have been used to form interior or exterior walls or sections thereof in order to permit transmission of light through such walls. Usually, these glass blocks distort any images viewed therethrough or the blocks may be translucent to permit passage of light and yet provide a significant degree of privacy. For example, glass blocks have been used as part of a bathroom wall to permit transmission of light therethrough, particularly important if there are no windows in the bathroom, and yet provide privacy. In a commercial or private environment, walls or wall dividers have been formed of translucent hollow glass blocks to delineate floor space while accommodating light transmission therethrough to create a more airy and open environment without compromising privacy. 
   Hollow glass blocks serve the sought end result very well but several difficulties are created. First, the glass blocks are relatively heavy and generally are only permitted to be used under building codes in conjunction with supporting brick walls; conventional wood frame construction is generally considered of insufficient structural strength to support glass blocks. Second, transport of the glass blocks from a point of manufacturer to the end user is generally expensive because of the weight and the attendant crating and shipping costs. Third, in order to accommodate the change in pressure within the hollow part of the glass block due to temperature and elevational changes, the glass walls must be very thick. Fourth, assembling a wall or wall section of glass blocks requires a skilled artesian to properly align the glass blocks and to exercise skill in securing the glass blocks to one another with a binding agent. 
   To overcome the weight and handling difficulties attendant hollow glass blocks, hollow blocks of transparent/translucent manmade materials have been developed; hereinafter referred to as plastic blocks. These plastic blocks generally include interlocking elements to permit seating and rapid assembly. In some circumstances, depending upon the configuration and use of the plastic block, a binding agent must be used. The primary benefits of plastic blocks include light weight, ease of handling and installation, and relatively low cost. 
   The plastic blocks are hollow and the interior space is sealed against intrusion of foreign matter as well as air. In response to temperature changes or changes in elevation (primarily during shipping), the pressure within the plastic blocks increases and decreases proportionately. The pressure changes within the plastic blocks generally result in inward or outward flexing of the walls of the plastic block. Such flexing creates stresses within the plastic material. During cleaning with conventional cleaning agents, lines of stress become visually apparent. The resulting disfiguration becomes permanent and compromises the aesthetics of the wall or wall section formed of the plastic blocks. 
   SUMMARY OF THE INVENTION 
   The present invention is directed to ventilated transparent and/or translucent hollow plastic blocks having interlocking elements for rapidly building a wall or a wall section of such plastic blocks. Ventilation of the glass blocks to avoid imposing stresses on the walls of the glass blocks due to temperature changes and elevational changes is provided. In particular, equalization of pressure within each plastic block with the ambient pressure is provided by a single aperture disposed in the bottom edge of a mounted plastic block. 
   It is therefore a primary object of the present invention to provide a ventilated plastic block. 
   Another object of the present invention is to provide a ventilated translucent or transparent plastic block for use as a wall section. 
   Yet another object of the present invention is to provide a ventilated plastic block having interlocking elements for rapid snap together assembly with adjacent plastic blocks. 
   Still another object of the present invention is to provide is to provide a single aperture for ventilating a plastic block used in the construction of a wall. 
   A further object of the present invention is to provide a specifically located aperture in a translucent hollow plastic block to reduce the likelihood of condensation settling on the interior surfaces of the hollow plastic block. 
   A yet further object of the present invention is to provide a ventilated plastic block which precludes airflow therethrough while accommodating inflow and outflow through a common aperture due to changes in internal pressure resulting from temperature and elevational changes. 
   A still further object of the present invention is to avoid creation of stresses in the side walls of a transparent/translucent hollow plastic block due to temperature and elevational changes. 
   A still further object of the present invention is to provide a method for avoiding stressing the side walls of a hollow plastic block due to temperature and elevational changes. 
   These and other objects of the present invention will become apparent to those skilled in the art as the description there proceeds. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be described with greater specificity and clarity with reference to the following drawings, in which: 
       FIG. 1  illustrates a plurality of interlocked plastic blocks; 
       FIG. 2  is a cross sectional view taken along lines  2 — 2 , as shown in  FIG. 1 ; 
       FIG. 3A  is a cross sectional view taken along lines  3 A— 3 A, as shown in  FIG. 2 ; 
       FIG. 3B  illustrates a variant of the ventilation aperture shown in  FIG. 3A ; 
       FIG. 4  is a cross sectional view taken along lines  4 — 4 , as shown in  FIG. 3A ; 
       FIG. 5A  illustrates the two halves of a plastic lock prior to assembly; and 
       FIG. 5B  is a detailed view of the section encircled and identified with reference numeral  5 B shown in  FIG. 5A . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Interlocking unventilated plastic locks have been developed by the applicant, as illustrated and described in U.S. Pat. No. 5,836,125. The illustrations and writings contained therein are incorporated by reference herein. Accordingly, many of the features common with the present invention, particularly with respect to the interlocking and alignment elements, will be only summarily discussed as the details thereof are set forth in U.S. Pat. No. 5,836,125. 
   Referring to  FIG. 1  there is shown a plurality of interlocking plastic blocks  10 ,  10 A and  10 B which are preferably, but not necessarily, of acrylic material. Edge  12  of each plastic block includes two pairs of alignment tabs  14 A,  14 B and  16 A,  16 B. The tabs of each pair of these pairs of tabs are relatively widely spaced from one another as illustrated. Opposite edge  18  of plastic block  10  includes two pairs of alignment tabs of which tabs  15 A, 15 B are shown; these pairs of tabs are spaced closer to one another than pairs of tabs  14 A, 14 B and  16 A, 16 B. Edge  20  of each plastic block also includes two pairs of alignment tabs  22 A, 22 B and  24 A, 24 B. A spacing between the alignment tabs of these two pairs of tabs is less than the space between pairs of alignment tabs  14 A, 14 B and  16 A, 16 B and corresponds with the spacing of pairs of tabs  15 A, 15 B. Edge  26  of each plastic block includes two pairs of alignment tabs equivalent in spacing and location to pairs of alignment tabs  14 A, 14 B and  16 A, 16 B. Each of these alignment tabs bears against the inside surface of a corresponding one of circumferential flanges  30 ,  32  of an adjacent interlocking plastic block. Moreover, flanges  30 ,  32  serve as the bearing surfaces between adjacent blocks. Thereby, plastic blocks  10 ,  10 A and  10 B are easily assembled with one another in perfect alignment to form a wall section, window, divider, etc. 
   Generally, an assembly of plastic blocks is bounded by structure such as a strap or the like to ensure stability of the assembled structure wherein the structure is to be used. Additionally, a frame of wood, metal or other material may be used as a boundary within which the plastic blocks are mounted. A mastic or other binding agent may be used to secure the blocks to one another. 
   As particularly shown in  FIG. 2 , a snap fit mechanism may be incorporated to retain the blocks in place with one another during assembly. As the details of the snap fit mechanism are further described in U.S. Pat. No. 5,836,125 the following discussion will be relatively brief. Snap fit mechanism  40  may include a female receptacle  42  to be engaged by a male coupling  44 . The female receptacle includes a pair of cylindrical locking members  46 , 48  located at the extremity of respective wall members  50 , 52 . Male coupling  44  includes a cylindrical member  54  supported upon a wall member  56 . As shown in  FIG. 2 , the spacing between cylindrical members  46 , 48  of female receptacle  44  is less than the diameter of cylindrical member  54  of male coupling  44 . To permit penetration therebetween, wall members  50 , 52  of the female receptacle are resilient and sufficiently flexible to permit insertion and removal of the male coupling. As shown in  FIG. 1 , and other figures, each side of each plastic block may include a pair of snap fit mechanisms  40 . As further noted in  FIG. 1 , edge  12  supports a male coupling  44  and opposite edge  18  supports a female receptacle  42 . Edge  20  supports a female receptacle  42  and opposite edge  26  supports a male coupling  44 . Thereby, the plastic blocks will be oriented to locate bottom edge  18  of one plastic block adjacent the top edge of another plastic block. When such placement occurs, the alignment tabs will be properly mated and the corresponding snap fit mechanisms will be functional. 
   As particularly shown in  FIGS. 4 and 5A , each of the plastic blocks ( 10 ,  10 A,  10 B) is formed of two members  60 , 62 . Member  60  includes a four-sided side wall  64  and member  62  includes a similar four-sided side wall  66 . For structural reasons and to obtain a good bond between the members, side wall  64  includes a peripheral lip  68  that mates with a peripheral undercut  70  in side wall  66 . Upon mating and bonding members  60 , 62  with one another, an enclosed space is formed within the two members. 
   During transport of the plastic blocks, changes of elevation occur. Such changes of elevation would create a pressure differential between the space interior of each plastic block and ambient pressure. Unless each plastic block were vented, such pressure differential would cause the sides of the plastic block to flex in response to the degree of pressure differential. Similarly, during changes of the ambient temperature as a result of a plastic block being subjected to solar radiation, other source of heating or a cooling environment, the temperature within a sealed plastic block would change with a commensurate increase or decrease in pressure and the sides of the plastic block would flex in conformance therewith. 
   One of the reasons for having prior art glass blocks and prior art plastic blocks sealed is to prevent condensation to develop on the inside surfaces due to a change in temperature or ambient pressure by preventing air flow through such a block. However, it has been learned that the plastic blocks of the type illustrated and described herein can be vented to obviate a pressure differential between the interior of the plastic block and the ambient pressure and thereby prevent flexing of the sides of the plastic block. However, such venting must be configured to prevent cross flow within the plastic block. Furthermore, it has been learned that if the vent is on the bottom edge, any condensation that may develop, although unlikely, it can drain through the vent. 
   Referring particularly to  FIGS. 4 ,  5 A and  5 B, the vent developed for use with plastic block  10  will be described. Vent  80 , located in bottom edge  18  of plastic block  10  is formed by a slot  82  extending into side wall  66  past undercut  70 . Upon mating of side walls  64 , 66  lip  68  covers a part of slot  82  to the extent of the width of undercut  70 . The resulting vent is particularly shown in  FIGS. 2 and 3A . 
   Vent  80  accommodates a flow of air into and out of plastic block  10  as a function of changes in pressure outside or inside the plastic block. The vent is sized small enough to preclude any cross flow of air within the plastic block. That is, air can not enter at one location and depart at a different location. With such lack of cross flow within the plastic block, it has been learned that condensation within the plastic block will almost never occur. Yet, the use of a single vent of relatively small size will preclude flexing of the sides of the plastic block causing the stresses that ultimately will become visible upon cleaning the plastic block with conventional cleaning agents. 
     FIG. 3B  illustrates a variant  90  of vent  80 . A simple hole may be drilled in one or the other side walls of block  10  in edge  18  or may be formed therein during fabrication of the respective member  60 / 62 . Under certain circumstances, variant  90  may be formed post manufacturing by drilling a hole, as illustrated. 
   By experimentation, it has been learned that the size of vent  80  or variant  90  should have an area equivalent to a round hole having a diameter in the range of at least about 0.005 inches to about 0.25 inches. Optimally, the size of vent  80  or variant  90  should have an area equivalent to a circle having a diameter in the range of about 0.012 inches to about 0.015 inches to minimize the likelihood of inflow of moisture and yet permit an outflow of moisture if such inflow does occur. Thereby, an environment of trapped moisture will be eliminated. These area dimensions were developed as a result of significant testing during transport of the plastic blocks over roads having varying elevations and by subjecting them to temperature differentials over a period of time. 
   While the invention has been described with reference to several particular embodiments thereof, those skilled in the art will be able to make the various modifications to the described embodiments of the invention without departing from the true spirit and scope of the invention. It is intended that all combinations of elements and steps which perform substantially the same function in substantially the same way to achieve the same result are within the scope of the invention.

Summary:
A vented hollow translucent/transparent plastic block for use in wall construction includes a single aperture disposed along the lower edge of the plastic block for alleviating pressure within the plastic block and for discharging any condensation within the plastic block that may occur.