Title:
THROUGH- AND UNDER-DRAINING FLOORING MODULES
United States Patent 3802144
Abstract:
A through-draining and under-draining flooring structure for garages and the like comprised of grid-like plastic apertured square modules removably laid on a normal concrete floor over the major garage area with ramp modules at the edge of the major module array at the vehicle entrance; the square modules having a multiplicity of dependent like legs at grid bar junctions as well as integral marginal depressed apertured lugs along two adjacent sides for receiving feet of neighboring square modules, and also the feet of the ramp modules at the entrance edge of the array.
US Patent References:
Portable deck
Greulich - July 1944 - 2353398
Landing mat
McGuire - September 1953 - 2653525
Plastic floor coverings
Schnee - June 1954 - 2680698
Detachable link strap of synthetic plastic material
Kundert - December 1956 - 2775093
Constructional toy
Viken - May 1957 - 2791868
Portable deck
Greulich - July 1944 - 2353398
Landing mat
McGuire - September 1953 - 2653525
Plastic floor coverings
Schnee - June 1954 - 2680698
Detachable link strap of synthetic plastic material
Kundert - December 1956 - 2775093
Constructional toy
Viken - May 1957 - 2791868
Application Number:
05/280968
Publication Date:
04/09/1974
Filing Date:
08/16/1972
View Patent Images:
Export Citation:
Primary Class:
Other Classes:
428/131, 404/36, 52/177, 404/41, 428/53, 52/100
International Classes:
E01C11/22; E04F15/10; E01C11/00; E04C1/30; E04C2/10
Field of Search:
46/25,30,31 52/592,98,100,591,590,589 404/35,36,41
US Patent References:
Primary Examiner:
Faw Jr., Price C.
Assistant Examiner:
Radauzo H. E.
Attorney, Agent or Firm:
Golrick P. D.
Claims:
What is claimed is
1. A square or rectangular drainage flooring module adapted for laying interlocked with adjacent like modules in an array on a substantially flat and horizontal supporting surface, as a structure integrally molded of impact resistant plastic, comprising:
2. The module as described in claim 1, wherein each said lug is provided with a break-off weakening or cut-off guiding groove at its region of joining to the rest of the module.
3. The module as described in claim 1, wherein said feet are provided under respective intersections of the bars.
4. The module as described in claim 3, wherein a said foot is located beneath each intersection of bars.
5. The module as described in claim 1, wherein the cross section of said bars has equal sloped upwardly convergent sides between parallel flat top and bottom sides
6. The module as described in claim 5, wherein the projecting bar end portions terminate in end faces substantially complementary to the disposition of the outer side face of the said first bars.
7. The module as described in claim 1, wherein said feet are provided under respective intersections of said bars and
8. The module as described in claim 7, wherein feet are present under all said intersections.
9. For use in combination with a primary square module as described in claim 7 and located in a row of modules with their said lugs at an entrance edge of an array of said modules, a ramp module in form comprising:
10. The combination, with a substantially flat and unyielding and horizontal supporting surface, of a plurality of modules, each as described in claim 1, and arrayed in interlocked relation and supported on said surface.
1. A square or rectangular drainage flooring module adapted for laying interlocked with adjacent like modules in an array on a substantially flat and horizontal supporting surface, as a structure integrally molded of impact resistant plastic, comprising:
2. The module as described in claim 1, wherein each said lug is provided with a break-off weakening or cut-off guiding groove at its region of joining to the rest of the module.
3. The module as described in claim 1, wherein said feet are provided under respective intersections of the bars.
4. The module as described in claim 3, wherein a said foot is located beneath each intersection of bars.
5. The module as described in claim 1, wherein the cross section of said bars has equal sloped upwardly convergent sides between parallel flat top and bottom sides
6. The module as described in claim 5, wherein the projecting bar end portions terminate in end faces substantially complementary to the disposition of the outer side face of the said first bars.
7. The module as described in claim 1, wherein said feet are provided under respective intersections of said bars and
8. The module as described in claim 7, wherein feet are present under all said intersections.
9. For use in combination with a primary square module as described in claim 7 and located in a row of modules with their said lugs at an entrance edge of an array of said modules, a ramp module in form comprising:
10. The combination, with a substantially flat and unyielding and horizontal supporting surface, of a plurality of modules, each as described in claim 1, and arrayed in interlocked relation and supported on said surface.
Description:
In the prior patented art, as well as in actual commercial practice, relating to flooring, tiling pavements and the like, many modular structures of metallic, plastic, ceramic, or other suitable materials are known both for permanent and removable emplacement in array over areas for pedestrian or vehicle travel, or for other particular environments. Diverse shapes of modules have been designed to provide an interlock at times with a base or especially between modules to facilitate the emplacement in the appropriate array, to afford anti-skid surfaces or suitable playing surfaces, or to assure quick drainage of the floored or paved areas. Examples of early and more recent activity with diverse materials in grating type modules are presented respectively by the U.S. Pats. to Dean No. 70,076 and Becker et al., No. 3,438,312.
Although hereinafter an advantageous use of the invention and the description of particular modules are given in terms of a pavement or flooring applied on the concrete floor slab of say a residential garage, it is to be understood that the invention has advantageous applications as well for other purposes and environments.
The present invention though intended for a different primary use may be considered, for example, to be an improvement upon the modular structure and playing surface pavement modular array of Becker, insofar as it provides as principal structural elements, tile-like molded plastic modules of generally square form, presenting a grid-like top aspect with integral feet dependent from the grid-bar intersections, whereby a generally flat top surface with a large number of drainage apertures is provided and also draining under-flow space.
The square primary modules of the present invention further include, on two preferably adjacent sides, integral lateral lug means projecting at a level below that of the grid bars and adapted to receive feet of the other non-lugged sides of similar square modules in a firm interlock, which permits quick, ready laying yet easy removal; and by suitable orientation in a flooring array, also interlock with the appropriate disclosed ramp module elements.
Other particular advantageous aspects are disclosed in the following detailed description of one embodiment of the invention which provide ready through-drainage, decreased debris retaining top areas and anti-splash structure, durability, easy molding in thermoplastic or thermosetting plastic, facilitation of cutting in a convenient fashion not interferring with basic function or interferring with interlock, while presenting a good appearance, where for one reason or another modules must be cut especially where a horizontal dimension of the array is not an integral multiple of the module size.
The disclosed module and the flooring array assembled therefrom is especially useful as flooring for vehicle garage spaces, in view of its excellent characteristics for drainage of water and escape of debris from the top surface to, and also ready underdrainage along, an underlying supporting environmental surface of concrete or the like. Also as the modules are made of plastic compositions, in addition to functional features, a considerable range of colors is possible, offering the aesthetic advantage, especially for residential garages, of a more pleasing appearance.
Thus, as may arise where the vehicle is washed in the garage or after travel in the rain or especially on snowy or slushy roads, the liquid dripping and dirt or material falling from the car in great part escapes immediately or upon melting, through the module grid openings, maintaining a puddle-free, comparatively dry top surface.
Any residual dirt or debris which might remain on the grid bar top flats is easily hosed off the surface, readily escaping with the flush water through the apertures and then out across the surface of the underlying concrete floor.
Moreover, if there should occur beneath the modular array heavier debris accumulations which can not be readily flushed out by hosing with water, the array in whole or part is readily picked up and, after the flushing of the underlying surface, replaced.
It is the general object of the present invention to provide an improved through-drainage flooring structure and interlocking modular elements readily emplaced in an array to form said flooring.
Another object of the present invention is the provision of an improved grid-like module for through-drainage and under-drainage.
A still further object is to provide an interlocking primary module structure for the purposes described which is easily cut to smaller size as may be required without loss or impairment of the interlock function.
Other objects and advantages will appear from the following description and the drawings wherein:
FIG. 1 is a schematic or outline plan view of an array of flooring modules in accordance with the present invention, as laid, for example, in a vehicle garage;
FIG. 2 is a fragmentary plan view of a primary module with a portion of a ramp module interlockingly engaged therewith; and
FIG. 3 is a sectional view taken as indicated by the line 3--3 in FIG. 2.
In FIG. 1 of the drawings, illustrating one application of, and plastic modules for one embodiment of, the invention, there is represented in plan outline an array of primary modules P, generally square in their identical un-cut, i.e., as molded, form and covering from wall to wall say the concrete floor slab of a typical residential garage, along one edge of which, at the vehicle floor entrance, there is provided a co-operating end-to-end array of special molded ramp modules R.
The ramp elements are shown with their endwise abuttments as staggered relative to the column of the major or primary modules P with which they interlock as hereinafter described. These ramp modules, however, typically have a length equivalent to the length of the square side of the primary modules. Along one or more of the other three sides, the marginal row or column of the square modules may be cut to a required or desired smaller dimension as hereinafter described. The primary module may be considered as a flat plate body structure having the through-aperture, the bottom feet, the laterally projecting apertured lugs on two sides and stub projections from the other two sides, as hereinafter named.
As may be seen from FIGS. 2 and 3, the primary square module from above presents the appearance of a grid or grating of thick perpendicularly intersecting sets of equi-spaced like bars, designated 11 and 12, defining therebetween apertures 13 generally square in plan, with the top surface of the bars being flat and co-planar; while on the bottom of the bar intersections, preferably as here shown at all intersections, there are integral dependent, generally cylindrical, equi-spaced support feet 14.
Preferably the section of the bars is not rectangular, but trapezodial and upwardly tapering with parallel flat top and bottom surfaces, so that the equally but oppositely sloped lateral surfaces define the square openings 13 with opposed sides sloping downwardly convergently. This provides in the apertures a wider top area for liquid inlet access and drainage; comparatively speaking reducing debris-gathering flat area on the top of the module and correspondingly widening the bottom area of the bars, and to this degree, diminishing the openings to be found by liquid splashing upwardly from the underlying concrete slab. Rather then being hollow from the bottom ends, as might be desirable in some cases to diminish weight and also save material, the feet preferably are solid for strength and durability.
As seen in FIG. 2, two adjacent sides (each at times referred to as a straight edge or side, or bar side) of a module P are defined by a bar 11 and a bar 12 respectively, from each of which project like flat apertured interlock lugs 15 at a location downwardly offset so that their top surfaces occur at the level of or slightly below the plane of the bottom surface of the bars, to permit interlocking. As seen in plan view the lugs 15 occur in alignment with respective alternate bars 11 or 12, with the centers of their respective round, foot-receiving interlock eyes 16 being respectively spaced from the centers of the proximate feet 14, from the top regions of which they extend, by a distance equal to the spacing between adjacent feet. Since the feet are present at all bar intersections, at least on the outermost bars, and the lugs occur in alignment with bars, the bars having like equi-spacing in both sets, lugs are appropriately located to receive feet of adjacent modules for the possible mutual orientations, without further specifications on placement along the edges. A shallow groove may be provided at 17 along the projecting lugs so that they may be easily broken off or offer a guide for sawing if desired, there-by readily to produce a smooth edge.
Along the other remaining two sides of the module P, in effect the intersecting bars 12 (or 11) are carried out from the outermost bar 11 (or 12) in equal length projections 12a (or 11a), by an amount corresponding to the normal spacing between the sides of adjacent bars, the end of each such projection being downwardly inwardly sloped corresponding to the bar side slopes; so that when one module is brought with its projecting bar side against the lugged straight side of an adjacent module, alternating feet can be received down in and interlock with respective lugs, with the bar projections of one module aligned with the correspondingly oriented bars of the adjacent module and also extending close to the edge bar of the adjacent module as seen again in plan in FIG. 2, and in section in FIG. 3. The projections may be slightly shorter than the normal spacing between opposed faces or sides of adjacent bars affording clearance for convenience in molding and laying. In effect the square outline of a module P is defined by the ends of the projections, i.e., a line or vertical plane tangent to the ends of the projections in each of two sides, and by the respective bars at the other two sides.
The like ramp elements R are here shown in a form intended for the preferred manner of laying the array of primary modules to terminate in a row of projecting lugs across the vehicle opening or door of the garage, for convenience of installation operations as will appear.
Each ramp element R in effect integrally comprises at least two longitudinal bars 21, representing a full side dimension of one of the primary modules; intersecting shorter like transverse bars 22, providing one longitudinal module side with the typical projecting ends 22a as described for 11a, and 12a, and the other longitudinal side ramp projections 22c; and feet 24 and 24b. The feet 24 at the long bar from which 22a project are identical to feet 14 to serve interlock functions. From the other long bar and the respective feet 24b, the ramping projections 22c extend with outwardly decreasing triangular vertical sections, thus giving a solid support to the approach ramping surface, while yet providing adequate final outflow of the drainage space between the ramp elements 22c. Preferably one end of the ramp module has a straight edge with a lug at the end of the inner long bar, with the two long bars projecting beyond the short bar 22 at the opposite end.
It is to be understood that a manner of interlock between primary modules and between ramp and primary modules is that shown in FIG. 2 and especially in FIG. 3.
The illustrated module P has the interlock lugs 15 along adjacent sides, an arrangement by far preferred to disposition on parallel sides. For in installation, a first module P (full size or cut) can be layed at the corner of the area to be covered, oriented with the lugged sides disposed toward the interior of the area, so that when a first column is then built up by successively adding like oriented modules with feet of a projection-edged side of each engaged in a lugged side of the preceding module, the side of the completed first column toward the area interior presents a line of lugs from all the modules in the first column, wherein are readily engaged the feet of the parallel projection-edged module sides along the length of the next laid column as it is similarly built up.
With the modules here shown, where one dimension or the other of the garage or floor space to be covered is not an even multiple of module lengths, and cutting is desired for a row or column, the plastic modules are readily cut, for example with an ordinary saw or hacksaw, transversely through the ribs along a line passing through the apertures, thereby avoiding the necessity of cutting through the length of the rib, as would generally be required for such purposes by certain prior structure, while yet obtaining a good fill of the area.
Furthermore, if for some reason or another, cut modules might be desired in the midst of the array, such cutting may be so done that the lugged edges are retained on the module pieces to be installed, and further with the cuts made close to the adjacent bar portions of the parts to be removed; the interlock function is not destroyed; and an appearance of pattern continuation is obtained with little if any noteworthy difference from the general pattern.
Especially it should be noted that the interlocking system avoids undue stress upon the interlocking elements, since the lugs are essentially free of supporting contact with the overlying module and since the feet of the latter are bearing upon, hence the overlying module is supported by, the underlying slab.
It is obvious that as described in the introduction to this specification, ample flow space is provided for drainage and for escape of debris from the flooring top surface down through the apertures, and further ample under-space both for under-drainage and accommodation of heavier debris; that the modules have a form conducive to quick and easy installation, take-up and replacement, and to production from low cost tooling; while yet providing a sturdy durable flooring.
In addition to providing the through-drainage aperture configuration above noted, the described structure provides modules readily molded with low cost tooling, from plastic materials, e.g., Dupont's Delrin, or many other synthetic plastics of appropriate properties now available. Further to this end, it is to be understood that the feet may diverge from strict cylindrical form to have a slight taper as required for mold draft and easy release of elements from molds. Similar considerations may apply to other regions in accordance with known tooling and molded-part designing considerations.
Although hereinafter an advantageous use of the invention and the description of particular modules are given in terms of a pavement or flooring applied on the concrete floor slab of say a residential garage, it is to be understood that the invention has advantageous applications as well for other purposes and environments.
The present invention though intended for a different primary use may be considered, for example, to be an improvement upon the modular structure and playing surface pavement modular array of Becker, insofar as it provides as principal structural elements, tile-like molded plastic modules of generally square form, presenting a grid-like top aspect with integral feet dependent from the grid-bar intersections, whereby a generally flat top surface with a large number of drainage apertures is provided and also draining under-flow space.
The square primary modules of the present invention further include, on two preferably adjacent sides, integral lateral lug means projecting at a level below that of the grid bars and adapted to receive feet of the other non-lugged sides of similar square modules in a firm interlock, which permits quick, ready laying yet easy removal; and by suitable orientation in a flooring array, also interlock with the appropriate disclosed ramp module elements.
Other particular advantageous aspects are disclosed in the following detailed description of one embodiment of the invention which provide ready through-drainage, decreased debris retaining top areas and anti-splash structure, durability, easy molding in thermoplastic or thermosetting plastic, facilitation of cutting in a convenient fashion not interferring with basic function or interferring with interlock, while presenting a good appearance, where for one reason or another modules must be cut especially where a horizontal dimension of the array is not an integral multiple of the module size.
The disclosed module and the flooring array assembled therefrom is especially useful as flooring for vehicle garage spaces, in view of its excellent characteristics for drainage of water and escape of debris from the top surface to, and also ready underdrainage along, an underlying supporting environmental surface of concrete or the like. Also as the modules are made of plastic compositions, in addition to functional features, a considerable range of colors is possible, offering the aesthetic advantage, especially for residential garages, of a more pleasing appearance.
Thus, as may arise where the vehicle is washed in the garage or after travel in the rain or especially on snowy or slushy roads, the liquid dripping and dirt or material falling from the car in great part escapes immediately or upon melting, through the module grid openings, maintaining a puddle-free, comparatively dry top surface.
Any residual dirt or debris which might remain on the grid bar top flats is easily hosed off the surface, readily escaping with the flush water through the apertures and then out across the surface of the underlying concrete floor.
Moreover, if there should occur beneath the modular array heavier debris accumulations which can not be readily flushed out by hosing with water, the array in whole or part is readily picked up and, after the flushing of the underlying surface, replaced.
It is the general object of the present invention to provide an improved through-drainage flooring structure and interlocking modular elements readily emplaced in an array to form said flooring.
Another object of the present invention is the provision of an improved grid-like module for through-drainage and under-drainage.
A still further object is to provide an interlocking primary module structure for the purposes described which is easily cut to smaller size as may be required without loss or impairment of the interlock function.
Other objects and advantages will appear from the following description and the drawings wherein:
FIG. 1 is a schematic or outline plan view of an array of flooring modules in accordance with the present invention, as laid, for example, in a vehicle garage;
FIG. 2 is a fragmentary plan view of a primary module with a portion of a ramp module interlockingly engaged therewith; and
FIG. 3 is a sectional view taken as indicated by the line 3--3 in FIG. 2.
In FIG. 1 of the drawings, illustrating one application of, and plastic modules for one embodiment of, the invention, there is represented in plan outline an array of primary modules P, generally square in their identical un-cut, i.e., as molded, form and covering from wall to wall say the concrete floor slab of a typical residential garage, along one edge of which, at the vehicle floor entrance, there is provided a co-operating end-to-end array of special molded ramp modules R.
The ramp elements are shown with their endwise abuttments as staggered relative to the column of the major or primary modules P with which they interlock as hereinafter described. These ramp modules, however, typically have a length equivalent to the length of the square side of the primary modules. Along one or more of the other three sides, the marginal row or column of the square modules may be cut to a required or desired smaller dimension as hereinafter described. The primary module may be considered as a flat plate body structure having the through-aperture, the bottom feet, the laterally projecting apertured lugs on two sides and stub projections from the other two sides, as hereinafter named.
As may be seen from FIGS. 2 and 3, the primary square module from above presents the appearance of a grid or grating of thick perpendicularly intersecting sets of equi-spaced like bars, designated 11 and 12, defining therebetween apertures 13 generally square in plan, with the top surface of the bars being flat and co-planar; while on the bottom of the bar intersections, preferably as here shown at all intersections, there are integral dependent, generally cylindrical, equi-spaced support feet 14.
Preferably the section of the bars is not rectangular, but trapezodial and upwardly tapering with parallel flat top and bottom surfaces, so that the equally but oppositely sloped lateral surfaces define the square openings 13 with opposed sides sloping downwardly convergently. This provides in the apertures a wider top area for liquid inlet access and drainage; comparatively speaking reducing debris-gathering flat area on the top of the module and correspondingly widening the bottom area of the bars, and to this degree, diminishing the openings to be found by liquid splashing upwardly from the underlying concrete slab. Rather then being hollow from the bottom ends, as might be desirable in some cases to diminish weight and also save material, the feet preferably are solid for strength and durability.
As seen in FIG. 2, two adjacent sides (each at times referred to as a straight edge or side, or bar side) of a module P are defined by a bar 11 and a bar 12 respectively, from each of which project like flat apertured interlock lugs 15 at a location downwardly offset so that their top surfaces occur at the level of or slightly below the plane of the bottom surface of the bars, to permit interlocking. As seen in plan view the lugs 15 occur in alignment with respective alternate bars 11 or 12, with the centers of their respective round, foot-receiving interlock eyes 16 being respectively spaced from the centers of the proximate feet 14, from the top regions of which they extend, by a distance equal to the spacing between adjacent feet. Since the feet are present at all bar intersections, at least on the outermost bars, and the lugs occur in alignment with bars, the bars having like equi-spacing in both sets, lugs are appropriately located to receive feet of adjacent modules for the possible mutual orientations, without further specifications on placement along the edges. A shallow groove may be provided at 17 along the projecting lugs so that they may be easily broken off or offer a guide for sawing if desired, there-by readily to produce a smooth edge.
Along the other remaining two sides of the module P, in effect the intersecting bars 12 (or 11) are carried out from the outermost bar 11 (or 12) in equal length projections 12a (or 11a), by an amount corresponding to the normal spacing between the sides of adjacent bars, the end of each such projection being downwardly inwardly sloped corresponding to the bar side slopes; so that when one module is brought with its projecting bar side against the lugged straight side of an adjacent module, alternating feet can be received down in and interlock with respective lugs, with the bar projections of one module aligned with the correspondingly oriented bars of the adjacent module and also extending close to the edge bar of the adjacent module as seen again in plan in FIG. 2, and in section in FIG. 3. The projections may be slightly shorter than the normal spacing between opposed faces or sides of adjacent bars affording clearance for convenience in molding and laying. In effect the square outline of a module P is defined by the ends of the projections, i.e., a line or vertical plane tangent to the ends of the projections in each of two sides, and by the respective bars at the other two sides.
The like ramp elements R are here shown in a form intended for the preferred manner of laying the array of primary modules to terminate in a row of projecting lugs across the vehicle opening or door of the garage, for convenience of installation operations as will appear.
Each ramp element R in effect integrally comprises at least two longitudinal bars 21, representing a full side dimension of one of the primary modules; intersecting shorter like transverse bars 22, providing one longitudinal module side with the typical projecting ends 22a as described for 11a, and 12a, and the other longitudinal side ramp projections 22c; and feet 24 and 24b. The feet 24 at the long bar from which 22a project are identical to feet 14 to serve interlock functions. From the other long bar and the respective feet 24b, the ramping projections 22c extend with outwardly decreasing triangular vertical sections, thus giving a solid support to the approach ramping surface, while yet providing adequate final outflow of the drainage space between the ramp elements 22c. Preferably one end of the ramp module has a straight edge with a lug at the end of the inner long bar, with the two long bars projecting beyond the short bar 22 at the opposite end.
It is to be understood that a manner of interlock between primary modules and between ramp and primary modules is that shown in FIG. 2 and especially in FIG. 3.
The illustrated module P has the interlock lugs 15 along adjacent sides, an arrangement by far preferred to disposition on parallel sides. For in installation, a first module P (full size or cut) can be layed at the corner of the area to be covered, oriented with the lugged sides disposed toward the interior of the area, so that when a first column is then built up by successively adding like oriented modules with feet of a projection-edged side of each engaged in a lugged side of the preceding module, the side of the completed first column toward the area interior presents a line of lugs from all the modules in the first column, wherein are readily engaged the feet of the parallel projection-edged module sides along the length of the next laid column as it is similarly built up.
With the modules here shown, where one dimension or the other of the garage or floor space to be covered is not an even multiple of module lengths, and cutting is desired for a row or column, the plastic modules are readily cut, for example with an ordinary saw or hacksaw, transversely through the ribs along a line passing through the apertures, thereby avoiding the necessity of cutting through the length of the rib, as would generally be required for such purposes by certain prior structure, while yet obtaining a good fill of the area.
Furthermore, if for some reason or another, cut modules might be desired in the midst of the array, such cutting may be so done that the lugged edges are retained on the module pieces to be installed, and further with the cuts made close to the adjacent bar portions of the parts to be removed; the interlock function is not destroyed; and an appearance of pattern continuation is obtained with little if any noteworthy difference from the general pattern.
Especially it should be noted that the interlocking system avoids undue stress upon the interlocking elements, since the lugs are essentially free of supporting contact with the overlying module and since the feet of the latter are bearing upon, hence the overlying module is supported by, the underlying slab.
It is obvious that as described in the introduction to this specification, ample flow space is provided for drainage and for escape of debris from the flooring top surface down through the apertures, and further ample under-space both for under-drainage and accommodation of heavier debris; that the modules have a form conducive to quick and easy installation, take-up and replacement, and to production from low cost tooling; while yet providing a sturdy durable flooring.
In addition to providing the through-drainage aperture configuration above noted, the described structure provides modules readily molded with low cost tooling, from plastic materials, e.g., Dupont's Delrin, or many other synthetic plastics of appropriate properties now available. Further to this end, it is to be understood that the feet may diverge from strict cylindrical form to have a slight taper as required for mold draft and easy release of elements from molds. Similar considerations may apply to other regions in accordance with known tooling and molded-part designing considerations.