U.S. patent number 3,638,380 [Application Number 04/865,284] was granted by the patent office on 1972-02-01 for modular high-rise structure.
This patent grant is currently assigned to Walter Kidde Constructors Incorporated. Invention is credited to Joseph G. Perri.
United States Patent |
3,638,380 |
Perri |
February 1, 1972 |
MODULAR HIGH-RISE STRUCTURE
Abstract
The invention is directed to new and improved structural
concepts for so-called high-rise buildings, providing for optimum
utilization of prefabricated apartment modules and providing for
highly economic construction techniques and economic utilization of
space. The structure is of generally peristylar form, in that all
of the principal vertical support columns are located about the
exterior of the structure. A unique arrangement is provided for
supporting prefabricated apartment modules, comprising special
horizontal support beams, extending transversely in the structure
and which are supported at their ends by longitudinal beams
engaging the vertical support columns. The transverse beams are so
designed that their webs and flanges lie in two intersecting
planes, and T-beams are ideally suited for this purpose. The
prefabricated apartment modules are supported by their edges on the
transverse beams, in such manner that the webs and flanges of the
beams are received between very narrow vertical and horizontal
clearance spaces between apartment modules. To great advantage, the
longitudinal support beams of the peristylar structure are
comprised of Vierendeel trusses located at alternate story levels
of the structure and spanning a vertical distance of one story. The
arrangement of Vierendeel trusses is structurally advantageous and
has pleasing architectural characteristics.
Inventors: |
Perri; Joseph G. (New York,
NY) |
Assignee: |
Walter Kidde Constructors
Incorporated (New York, NY)
|
Family
ID: |
25345128 |
Appl.
No.: |
04/865,284 |
Filed: |
October 10, 1969 |
Current U.S.
Class: |
52/79.12;
52/653.1 |
Current CPC
Class: |
E04B
1/34807 (20130101); E04B 1/24 (20130101); E04B
2001/2484 (20130101); E04B 2001/2448 (20130101); E04B
2001/2457 (20130101); E04B 2001/2415 (20130101); E04B
2001/2496 (20130101); E04B 2001/2445 (20130101); E04B
2001/2481 (20130101) |
Current International
Class: |
E04B
1/24 (20060101); E04B 1/348 (20060101); E04h
001/04 () |
Field of
Search: |
;52/236,79 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Abbott; Frank L.
Assistant Examiner: Burke; Sam D.
Claims
I claim:
1. A modular high-rise structure for supporting a plurality of
apartment modules, in side-by-side relation on a plurality of story
levels which comprises
a. cooperating front and back pairs of vertical support columns
disposed at the front and back of the structure,
b. longitudinal support beams connected to and extending
horizontally between pairs of front columns and pairs of back
columns, and cooperating pairs of said longitudinal support beams
being disposed at the same story level in the structure,
c. said longitudinal support beams being spaced apart a distance
greater than of the front-to-back length dimension of said
apartment modules and having a length greater than the combined
width of the number of modules to be supported in side-by-side
relation to accommodate installation of said modules in a vertical
direction,
d. the vertical opening between adjacent longitudinal beams being
less than the vertical height of said apartment modules,
e. 1 plurality of transverse support beams of a length greater than
the front-to-back dimension of said modules, supported by and
extending between cooperating pairs of longitudinal support beams
for engaging and supporting said apartment modules,
f. said transverse support beams having one or more webs disposed
in a single vertical plane and one or more flanges disposed in a
single horizontal plane,
g. said transverse support beams being aligned with the lower
front-to-back edges of the apartment modules, with said
front-to-back edges being supported by flanges of said transverse
beams,
h. a horizontally adjacent pair of modules being supported along
adjacent lower edges by a transverse support beam having a pair of
horizontal flanges, and said adjacent modules being spaced apart a
distance less than the combined width of said flanges, the vertical
web of said beam extending between a pair of horizontally adjacent
modules and having an overall height greater than the space between
vertically adjacent modules,
i. the open spacing between horizontally adjacent transverse beams
being less than the width of said modules, and the open spacing
between vertically adjacent transverse beams being less than the
height of said modules,
j. whereby the modules of said structure may be positioned in a
compact configuration with the space between horizontally and
vertically adjacent modules being substantially smaller than the
overall horizontal and vertical dimensions of the supporting
beams.
2. The modular high-rise structure of claim 1, further
characterized by
a. said transverse beams being substantially of T-shaped cross
section,
b. at least the stem portions of said T-shaped beams being closely
received between the walls of adjacent apartment modules.
3. The modular high-rise structure of claim 2, further
characterized by
a. interior T-shaped beams being oriented with their stem portions
extending vertically downward between vertical walls of
horizontally adjacent apartment modules and with their crossbar
portions extending horizontally between vertically adjacent
apartment modules,
b. exterior T-shaped beams being oriented with their stem portions
extending horizontally between vertically adjacent exterior
apartment modules and with their crossbar portions disposed along
portions of the exterior vertical walls of vertically adjacent
exterior apartment modules.
4. A modular high-rise structure according to claim 1, further
characterized by
a. vertical truss beams extending between alternate pairs of
adjacent longitudinal support beams and forming Vierendeel truss
assemblies.
5. A modular high-rise structure according to claim 4, further
characterized by
a. the spacing of said vertical columns accommodating the
side-by-side placement of four apartment modules, and
b. said Vierendeel truss assemblies incorporating three vertical
beams aligned substantially with the spaces between adjacent
apartment modules.
6. A modular high-rise structure according to claim 1, further
characterized by
a. Vierendeel trusses connecting pairs of said columns at a
plurality of levels,
b. said Vierendeel trusses comprising vertically spaced pairs of
longitudinal support beams and vertical truss elements rigidly
connecting such pairs of beams,
c. said transverse support beams being transversely disposed and
being supported at their ends by horizontal beams of said
Vierendeel trusses.
Description
SUMMARY AND BACKGROUND OF INVENTION
The invention is directed to multiple-story, or so-called high-rise
buildings, and is intended particularly for, although perhaps not
necessarily limited to, high-rise apartment buildings intended for
human occupancy. One of the underlying objectives of the invention
is to enable more effective and efficient use to be made of
prefabricated, self-contained apartment modules in the construction
of high-rise apartment structures. To this end, it is an objective
of the invention to provide a structural framework for a high-rise
apartment which is most ideally suited for the installation of
prefabricated apartment modules, which greatly facilitates their
installation in the structure, and which provides for optimum
efficiencies of materials and space in the completed building.
In accordance with one specific aspect of the invention, a new and
advantageous structural framework is provided, for the reception of
prefabricated apartment modules, which is peristylar in its general
configuration. That is, the principal vertical supporting columns
are arranged and disposed about the exterior of the structure. Each
of the story levels of apartment modules is independently supported
by the framework of vertical columns, so that the apartment modules
themselves do not have any load-bearing function.
In the structure of the invention, the prefabricated apartment
modules desirably are boxlike units; they are self-supporting
structures, in that they do not rely upon the basic structural
framework of the building to retain their prefabricated
configuration, they can be handled independently by cranes, etc. In
accordance with one aspect of the invention, the structural
framework of the building is effectively floorless. Support for the
apartment modules at each story level is provided by special
support beams extending transversely in the structure and engaging
the apartment modules along their lower side edges. The transverse
beams are of greater length than the transversely disposed
apartment modules, and extend beyond them at both ends. The
transverse beams themselves are supported at their projecting end
extremities by other horizontally disposed beams extending
longitudinally in the structural framework between adjacent
vertical columns. Thus, in the structure of the invention, the
apartment modules are supported entirely by the special transverse
beams, which engage only the lower side edges of the modules.
As one of the advantageous features of the invention, the special
transverse beams are of a configuration in which the webs and
flanges lie in two intersecting planes, and most desirably, the
configuration is in the shape of a Tee. Thus, in the completed
structure, both the web and flange portions (crossbar and stem) of
the T-shaped beam may be received between closely spaced walls of
vertically and horizontally adjacent modules. A particular
advantage of this structure resides in the ability to install the
apartment modules in a "compact configuration," in which there is a
virtual minimum of clearance space between adjacent modules in both
the vertical and horizontal directions.
A further significant feature of the invention resides in the
utilization, in the structural framework of the building, of
Vierendeel trusses which extend longitudinally between vertical
columns, along the front and back of the framework. The Vierendeel
trusses are comprised of longitudinal beams which extend
horizontally, substantially at the levels of the horizontal planes
between adjacent story levels of apartment modules. A plurality of
vertical truss elements extend between and are rigidly secured to
pairs of these horizontal beams to form the Vierendeel trusses. As
a feature of the invention, the vertical truss members extend
between alternate pairs of the horizontal beams, so that the
Vierendeel trusses are located at alternate story levels at the
front and back sides of the high-rise structural unit. The use of
the Vierendeel truss provides adequate strength for the independent
support of each level of apartment modules and provides for
adequate lateral stability of the structure. From an architectural
standpoint, the Vierendeel truss has significant advantages in
providing for a substantially unobstructed view from the apartment
modules suspended in a structural framework of generally peristylar
configuration.
A further objective of the invention resides in the provision of a
structural framework, suitable for the independent support of a
large number of prefabricated apartment modules, wherein the
structural framework is the installation self-supporting to its
full height without the use of interior structural elements. By
this means, the entire structural "shell" may be constructed,
leaving a hollow framework with an open top. Prefabricated
apartment modules may then be lowered individually into the
interior of the framework and the overall structure completed in
successive story levels. The necessary transverse support beams may
also be inserted in successive story levels, as layers of the
apartment modules are installed. The structure of the invention
also contemplates, of course, that the installation of apartment
modules may be made more or less concurrently with the installation
of successive story levels of the framework.
For a more complete understanding of the above and other features
and advantages of the invention, reference should be made to the
following detailed description and to the accompanying
drawings.
DESCRIPTION OF DRAWINGS
FIG. 1 is a simple perspective view of a typical high-rise
apartment structure incorporating the principles of the
invention;
FIG. 2 is a top plan view of the structure of FIG. 1;
FIG. 3 is a vertical cross-sectional view taken generally along
line 3--3 of FIG. 2;
FIGS. 4 and 5 are enlarged, fragmentary cross-sectional views taken
generally along lines 4--4 and 5--5, respectively, of FIG. 2;
FIG. 6 is an enlarged, fragmentary cross-sectional view taken
generally along line 6--6 of FIG. 3;
FIG. 7 is an enlarged, fragmentary cross-sectional view taken
generally along line 7--7 of FIG. 2.
DESCRIPTION OF PREFERRED EMBODIMENT
Referring now to the drawing, and initially to FIG. 1 thereof,
there is shown a typical high-rise apartment complex incorporating
the principles of the invention. The complex includes a plurality
of structural units 10 which form the fundamental basic structure
of the invention and can be repetitively incorporated in a larger
structural complex in accordance with the specific requirements of
the installation. The structural unit 10 comprises four vertical
supporting columns 11-14 (see FIG. 2) arranged in peristylar
configuration, that is, about the exterior of the structure.
Desirably, the four columns are arranged to form the four corners
of a rectangle. For purposes of aiding the description, and without
implying any limitation, the pairs of columns 11-12 and 13-14 will
be considered as defining the "front" and "back" of the structure.
The sides are defined by pairs of columns 11-13 and 12-14.
Extending longitudinally between columns 11-12 and between columns
13-14, at the front and back of the structure, are horizontally
disposed support beams 15. The beams 15, like the columns 11-14,
desirably are of wide flange "I" section, of a weight and
proportion suitable for the load requirements. As reflected in FIG.
1, the longitudinally extending beams 15 are secured to the columns
11-14 at regularly spaced intervals up the entire front and back
faces of the structure. In accordance with the invention, spacing
of the successive beams 15 corresponds with the successive story
levels of the structure and, significantly, the beams are located
approximately at each of the floor levels of the structure.
In accordance with one important aspect of the invention, alternate
pairs of the longitudinally disposed beams 15 are rigidly connected
by a plurality of vertically disposed truss beams 16, such that the
assembly of a pair of beams 15 and their connecting vertical beams
16, rigidly secured to the vertical columns 11-12 and 13-14, form
Vierendeel trusses. As will be appreciated, the vertical dimension
of the trusses corresponds with the floor-to-floor dimension of one
story of the structure and, in the completed structure, such
Vierendeel trusses will extend between pairs of vertical supporting
columns at alternate story levels. The described utilization of
alternate story Vierendeel trusses provides lateral support for the
structural framework in the side-to-side direction and also, as
will hereinafter appear, provides an advantageous means for
supporting prefabricated apartment modules in the structure.
In the illustrated structure, suitable beams 17, typically wide
flange "I" beams, extend transversely between and are rigidly
connected to columns 11-13 and to 12-14, desirably at each floor
level of the structure. Diagonally disposed truss beams 18, 19 are
rigidly joined to the beams 17 to form "K-type" trusses between
side column pairs at each story level. This provides lateral
support for the structure in the front-to-back direction. If
desired, the front-to-back lateral support of the structure may be
provided by the use of transversely disposed Vierendeel trusses, in
place of the K-type trusses. However, since the trusses at the
sides of the structure do not, in the illustrated edifice at least,
have any significant vertical load-bearing function, the use of the
K-type truss for this purpose is considered economically
advantageous.
The structural framework unit described above is substantially
self-supporting. In this respect, it is contemplated that the
framework may, if circumstances warrant, be erected to its ultimate
height as a floorless structure, free of internal obstructions,
with prefabricated apartment modules subsequently being installed
by being lowered into the unobstructed interior. It is also
contemplated, of course, that the apartment modules may be
installed more or less concurrently with the erecting of the
framework. The more advantageous construction technique for a given
installation is a function of many factors, such as the ultimate
height of the edifice, availability of suitable life equipment,
etc.
As will be readily appreciated by reference to FIGS. 1 and 2, the
basic structural framework unit 10 is duplicated as appropriate in
the design of a specific apartment complex. Thus, as many basic
units 10 as desired may be arranged in side-by-side adjacency, in
which event all of the vertical columns on the "interior" sides of
units are utilized in common in the structures of adjacent units
(e.g., the pair of columns 12-14 of FIGS. 1 and 2). The basic
structural units may also be arranged in front-to-back adjacency,
as reflected in FIG. 2, but in that case it is often advantageous
to dispose the units in slightly separated relation, to form a
corridor or hallway space 20 between them. As will be appreciated,
significant design flexibility is afforded to accommodate the
economic, physical and other requirements of an installation and
also to provide freedom for the expression of architectural
tastes.
In accordance with a further important aspect of the invention, new
and advantageous means are provided for independently supporting a
plurality of apartment modules within the above-described
structural framework unit 10. The improved means comprise
supporting beams 22, 23 which are secured at their ends to the
horizontal beams 15 of the Vierendeel trusses and extend
transversely across the interior of the framework. As a specific
inventive feature, the transverse beams 22, 23 are so formed that
their webs and flanges are contained in two (only) right-angularly
intersecting planes. Most advantageously, T-section beams are
utilized for this purpose, although for some purposes an
"X"-section beam, with its webs and flanges in vertical and
horizontal planes, could be utilized.
As shown in FIG. 3, for example, an advantageous structure
according to the invention includes T-section beams 22, 23 of two
types. The T-beams 22 are utilized as "interior" beams, whereas the
T-beams 23 are utilized at the sides of the structural units and
may be identified as "exterior" beams.
In the structure of the invention a plurality of prefabricated
apartment modules 24-27 is supported within the otherwise "hollow"
structural framework in a closely spaced arrangement, descriptively
referred to herein as a "compact configuration." Thus a typical
edifice may incorporate prefabricated apartment modules of
"standardized" dimensions and rectangular configuration. These
modules are supported in the structure with their exterior
sidewalls 28 (FIG. 4) spaced apart not significantly more than
about 11/2 inches and thus are adapted closely to receive the
downwardly projecting, vertically disposed webs 29, forming the
"stem" portions of the "interior" transverse T-section beams 22.
The horizontal flanges 30, constituting the "crossbar" portions of
the T-beams 22 are spaced slightly above the exterior upper walls
31 of the apartment modules, sufficient to maintain a clearance
between the flanges 29 and the modules directly below when the
transverse beams 22 are under load. At the opposite sides of the
structure, the T-section transverse beams 23 (FIG. 5) are disposed
with their web or stem portions 32 extending horizontally inward,
slightly above the exterior upper walls 31 of the apartment modules
24, 27. The flange or crossbar portions 33 of the beams 23 extend
vertically upward and downward, with the lower portions extending
closely alongside the exterior sidewalls 28 of the apartment
modules.
In a complete edifice according to the invention, the lowermost
story of apartment modules may be supported by any suitable means,
such as a poured foundation, conventional beam structures and, if
desired, the special T-section beams 22, 23 described above.
However, more significant advantages are to be derived from the use
of T-section transverse supporting beams for the second and higher
story levels of apartment modules. Thus, after placement and
support in the frame structure of a lower story level of apartment
modules, a level of T-section transverse beams may be installed for
supporting the next higher story level of apartment modules. Since
all of the webs and flanges of the T-beam sections are contained
within two right-angularly intersecting planes, these webs and
flanges may be received between the walls of adjacent apartment
modules which are closely spaced in a "compact configuration," from
the standpoint of vertical as well as horizontal spacing. In this
respect, the term "compact configuration" refers specifically to
the fact that the vertical spacing between exterior top and bottom
walls of vertically adjacent apartment modules is less than the web
depth dimension of the interior support beams 22, and the
horizontal spacing between exterior sidewalls of horizontally
adjacent apartment modules is less than the horizontal dimension of
the flanges of the beams 22. Thus, in a practical embodiment of the
invention, utilizing apartment modules having exterior dimensions
of approximately 10 feet 8 inches in width by 8 feet 8 inches in
height by 21 feet in length, there typically may be an inch and a
half horizontal spacing between horizontally adjacent modules, and
about a 4 -inch vertical spacing between vertically adjacent
modules. At the same time, the overall web depth of the interior
T-section support beams may be on the order of 18 inches, and the
flange width on the order of 12 or 13 inches. At the edges of the
structure, the flange height of the T-section beams 23 may be on
the order of 16 inches, and the horizontal web depth dimension may
also be on the order of 16 inches.
By utilizing a beam configuration consisting of webs and flanges
intersecting in only two right-angularly disposed planes, these
transverse supporting beams 22, 23 may be nested within very narrow
spaces between apartment modules arranged in compact configuration.
This results in very significant efficiencies in space utilization,
particularly in respect of the utilization of vertical space. With
the structure of the invention, it is possible to realize a savings
of perhaps as much as 10 percent in the vertical space required to
contain an apartment module having an 8 -foot interior vertical
clearance. In more practical terms, this means that in an edifice
of around 20 or so stories in height, approximately two extra
stories of apartment modules may be contained within a structural
framework of given height, as compared to structures of more
conventional design.
In a typical structure according to the invention, containing
apartment modules of about 21 feet in length, the interior
clearance space between opposed pairs of Vierendeel trusses may be
on the order of 23 feet. The T-section transverse support beams
have a length dimension sufficient to span substantially the entire
distance between related pairs of the Vierendeel trusses and thus
will project beyond the ends of the modules. In the illustrated
structure (FIG. 7) mounting plates 34 are welded or otherwise
secured to the webs 35 of the horizontal truss beams 15, just below
the upper flanges 36 thereof. The mounting plates extend inwardly
into overlapping relation with the depending web sections 29 of the
interior T-section beams 22, and are secured thereto by bolts 37 or
other means. Advantageously, the upper surfaces of the T-beam
flanges 30 and the truss beam flanges 36 are substantially aligned
in a horizontal plane.
The exterior T-section beams 23 advantageously are secured directly
to the vertical columns 11-14. For this purpose, a mounting plate
38 is bolted to a flange 39 of the column and extends into
overlapping relation with the inside surface of the beam flange 33
below the web 32. Bolts 40 or other suitable means may be utilized
to secure the beam in position, in the manner shown in FIG. 6. As
reflected in FIG. 3, the exterior T-beams 23 are so mounted that
their horizontally disposed webs 32 are in a common plane with the
horizontally disposed flanges 30 of the interior T-beams, and
desirably also with the upper flanges of the truss beams 15,
17.
As reflected in FIG. 2, the apartment modules are supported in the
structure only along their lower lateral edges, by means of the
transverse beams 22, 23, a clearance space 41 being provided at
both ends of the apartment modules. In a structure such as
reflected in FIG. 2, where a plurality of structural units are
arranged in front-to-back adjacency, clearance spaces for any
apartment module having an interior access door, may be bridged
over by a suitable walkway (not shown) leading to the corridor
space 20. The clearance spaces for modules not having an interior
access door, or the clearance space alongside access door walkways,
may advantageously be utilized for plumbing, electrical service,
etc.
In the construction of a building, after a first story of apartment
modules has been suitably positioned and supported in the framework
structure, the transverse beams 22, 23 for the next successive
story are inserted into the structure and secured to the truss
beams 15 and columns 11-14, as previously described. The structure
is then ready to receive a second story level of apartment modules
(e.g., modules 42-45, FIG. 3), lowered one at a time into the
interior of the framework. To facilitate proper transverse
alignment of the modules within the structure, the interior T-beams
22 advantageously are provided with locating lugs 46 at a plurality
of locations along the length of the beams. Desirably, the lugs are
aligned with the vertical planes of the beam webs 29 and desirably
are about 1 inch in thickness for a module spacing of 11/2 inches.
At the sides of the structure, the modules are, of course, located
by the upward projection of the T-beam flanges 33.
After thus being rested on and supported by the T-beams, the
apartment modules may be suitably bolted or otherwise secured in
place, and the necessary electrical and plumbing connections, etc.,
may be made thereto. In many instances, a housing or office unit
may comprise more than one module, and there may, for example, be
standard prefabricated modules for such typical household units as
bedrooms, kitchens, etc. Where the housing or office unit does
consist of more than one module, appropriate interconnections,
provided for in the prefabrication, are made between the modules
after installation in the structure.
The construction of an entire building complex, regardless of its
height or lateral extent, proceeds substantially in the manner
outlined.
For optimum utilization of the techniques of the invention, the
free span of the Vierendeel trusses, between pairs of vertical
columns, may be on the order of 43 feet. This will accommodate the
support, over the span of the Vierendeel trusses, of four apartment
modules, disposed side-by-side in a compact configuration, where
the apartment modules have a 10-foot clear interior width and a
10-foot, 8-inch exterior width, and where a 11/2-inch separation
between modules is observed. In a structure as described, the
horizontal beams 15, which form the Vierendeel trusses, are spaced
approximately on 9-foot centers (vertically). Where four apartment
modules are supported over a free span, the thusly spaced
horizontal truss beams 15 may be interconnected by three vertical
truss beams 16, which are aligned with the spacing between adjacent
apartment modules. This specific arrangement provides an optimum
blend of functional and aesthetic considerations.
The structure of the invention represents a significant advance in
the construction of such high-rise structures as housing
apartments, office buildings and the like. The advantages in
utilizing prefabricated apartment modules is, of course,
self-evident, and the present invention provides an economical and
otherwise highly advantageous structural concept for the
utilization of such prefabricated modules.
An inventive feature of particular importance is the utilization of
supporting beams for the prefabricated modules which are arranged
to have their webs and flanges contained in two right-angularly
intersecting planes and serve to support the prefabricated modules
along their lateral lower edges. This arrangement is such that the
supporting beams, having principal web and flange dimensions as
large as necessary to safely perform their supporting functions,
may be nested within narrow spaces provided between adjacent
apartment modules arranged in compact configuration. In the
completed structure, a significant increase in useable space is
realized in relation to the overall cubic content of the
structure.
While Vierendeel trusses are well-known structural units, their use
in the specific manner and context of this invention is both new
and highly advantageous. The use of alternate story Vierendeel
trusses enables a plurality of apartment modules to be supported on
each story level of a stable peristylar framework solely by beams
extending under the lower lateral edges of the modules, while at
the same time providing for maximum unobstructed area at the front
of the structure. Thus, as will be evident in FIG. 1, the apartment
modules at alternate story levels are totally unobstructed at the
front. Between these totally unobstructed levels, the only
"obstructions" are the vertical beams 16 of the Vierendeel trusses,
which are disposed between adjacent apartment modules and, from a
practical standpoint, do not constitute a significant visual
obstruction.
Vierendeel trusses and T-section (or similar) transverse beams are
to great advantage utilized in combination, in the manner described
herein. However, there are also important advantages to be derived
from the use, in a similar context, of either one without the
other.
The structure of the invention significantly maximizes the extent
to which fabrication of components may be accomplished prior to
shipment to the erecting site. In addition to the obvious economies
to be realized from "factory" fabrication, important advantages are
derived by minimizing the use of field crews, which often must be
recruited to a large degree from the locale of the installation and
may not be available in the necessary numbers for the skills and
experiences desired.
It will be understood, of course, that the specific form of the
invention herein illustrated and described is intended to be
representative only, as certain modifications may be made therein
without departing from the clear teachings of the disclosure.
Accordingly, reference should be made to the following appended
claims in determining the full scope of the invention.
* * * * *