U.S. patent number 3,805,464 [Application Number 05/291,697] was granted by the patent office on 1974-04-23 for precast staircase.
This patent grant is currently assigned to Fabcon, Inc.. Invention is credited to David W. Hanson.
United States Patent |
3,805,464 |
Hanson |
April 23, 1974 |
**Please see images for:
( Certificate of Correction ) ** |
PRECAST STAIRCASE
Abstract
A precast reinforced concrete integral staircase adapted to be
installed as a unit to span the space between two landings is
formed of a deep U-shaped elongated beam member wherein the arm
portions of the U extend upwardly from the flat base of the U
defining the stairs to provide a supporting structure for the
stairs, which arms also become a rail for safety purposes during
construction and as a permanent rail thereafter.
Inventors: |
Hanson; David W. (Minneapolis,
MN) |
Assignee: |
Fabcon, Inc. (Savage,
MN)
|
Family
ID: |
23121433 |
Appl.
No.: |
05/291,697 |
Filed: |
September 25, 1972 |
Current U.S.
Class: |
52/190;
52/741.2 |
Current CPC
Class: |
E04F
11/022 (20130101) |
Current International
Class: |
E04F
11/022 (20060101); E04F 11/02 (20060101); E04f
011/14 () |
Field of
Search: |
;52/189,190,191,184-186,183,182,17,723 ;14/71,72 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
26,666 |
|
Oct 1953 |
|
SF |
|
1,166,294 |
|
Apr 1958 |
|
FR |
|
1,121,200 |
|
Jul 1956 |
|
FR |
|
215,342 |
|
Oct 1960 |
|
OE |
|
1,080,235 |
|
Dec 1954 |
|
FR |
|
1,082,834 |
|
Jan 1955 |
|
FR |
|
1,150,513 |
|
Jan 1958 |
|
FR |
|
1,161,495 |
|
Sep 1958 |
|
FR |
|
1,252,811 |
|
Dec 1960 |
|
FR |
|
172,886 |
|
Sep 1960 |
|
SW |
|
Primary Examiner: Sutherland; Henry C.
Assistant Examiner: Ruduazo; Henry E.
Attorney, Agent or Firm: Schroeder, Siegfried, Ryan &
Vidas
Claims
I claim:
1. A mobile unitary precast reinforced concrete staircase and
handrail of relatively low weight adapted to span a space between
horizontally and vertically spaced landings comprising a plurality
of U-shaped reinforcing rods spaced in generally parallel
relationship to one another with the arms and base portions of each
of said U-shaped rods being in a plane with the corresponding arms
and base portions of the balance of said U-shaped rods longitudinal
reinforcing rods extending generally transverse to said U-shaped
rods said longitudinal rods being in spaced and generally parallel
relationship to one another with a plurality of longitudinal rods
on each arm and on the base portion of said U-shaped rods and
welded to said U-shaped rods joining them to form a cage, concrete
encapsulating said cage to form a U-shaped beam member with the
concrete of the base of said U-shaped beam member forming a plane
on the lower side thereof and being configured on the upper
interior facing side thereof into a plurality of riser and tread
surfaces thereby defining a stairs, each of the arm portions of
said U-shaped beam extending upwardly from said stairs being
relatively thin in thickness and integral with said base portion
and having the overall shape of a parallelogram with the
longitudinal sides thereof parallel to the general plane of the
stairs, said arm portions having a height above said tread surfaces
corresponding to a hand rail height, the longitudinally remote ends
of said arm portions extending at least to each end of said stairs
and having an angle therewith so as to be substantially
perpendicular to the ground when said staircase is installed.
2. In combination first and second horizontally and vertically
spaced landings, the upper of said landings including a steel plate
fastened thereto adjacent the landing edge thereof, a unitary
precast reinforced concrete staircase of relatively low weight
spanning the space between said landings, said staircase comprised
of a unitary elongated U-shaped beam member of reinforced concrete,
the base portion of said U-shaped beam being configures on the
upper interior facing side thereof into a plurality of risers and
tread surfaces thereby defining a stairs, each of the arm portions
of said U-shaped beam being relatively thin in thickness and
integral with said base portion and having an overall shape of a
parallelogram with the longitudinal sides thereof parallel to the
general plane of the stairs, said arms having a height generally
corresponding to a hand rail height, the longitudinally remote ends
of said arms extending at least to each end of said stairs with the
upper ends of said arms extending beyond said stairs, the ends of
said arms having an angle with said stairs so as to be
substantially perpendicular to the ground when said staircase is in
the installed position, the portion of said arms extending beyond
the upper end of said stairs having a relieved portion at the lower
extended edge thereof constructed and arranged to engage an upper
surface of the landing, the relieved portion including an angle
iron covering the bearing surfaces of said relieved portion, said
angle iron being joined to reinforcing rods embedded in the
concrete of said staircase, said angle iron also being joined to
said steel plate on said upper landing to prevent movement thereof
with respect to said landing and the lower portion of said
staircase being in sliding engagement with the upper surface of the
lower landing.
3. A mobile unitary precast reinforced concrete staircase and
handrail of relatively low weight adapted to span a space between
horizontally and vertically spaced landings comprising: an
elongated U-shaped beam member comprised of a unitary body of
reinforced concrete; the base portion of the said U-shaped beam
having a plane surface on the outer side thereof and being
configured on the upper interior facing side thereof into a
plurality of risers and tread surfaces thereby defining a stairs;
each of the arm portions of said U-shaped beam being relatively
thin in thickness and integral with said base portion and having
the overall shape of a parallelogram with the longitudinal sides
thereof parallel to the general plane of the stairs, said arms
having a height generally corresponding to a hand rail height, the
longitudinally remote ends of the said arms extending at least to
each end of said stairs, the upper ends of said arms extending
beyond the topmost stair and having a relieved portion at the lower
extended edge thereof constructed to engage an upper surface of a
landing with the lower ends of said arms shaped to engage a surface
of a lower landing to thereby have said arms provide the principal
support for said stairs and the remote ends of said arms having an
angle with said stairs so as to be substantially perpendicular to
the ground when said staircase is installed.
4. A staircase in accordance with claim 3 wherein said relieved
portion includes a horizontal surface substantially on a plane with
the topmost stair tread, said horizontal surface being adapted to
provide the bearing surface for engagement with the upper surface
of a landing.
5. A staircase in accordance with claim 3 wherein said relieved
portion includes an angle iron covering the bearing surfaces of
said relieved portion, said angle iron being joined to reinforcing
rods embedded in the concrete of said staircase.
Description
The present invention is in the fluid of preformed structural
members for buildings and the like wherein component units of a
building are formed at a site remote from the actual building site,
transported to the building site as a unit and then installed to
form the building. More specifically, the present invention is
directed to a precast staircase member formed of reinforced
concrete adapted to be installed as an integral unit between two
landings.
The use of precast panels of concrete to form the floor and ceiling
is well known in the art and has found considerable usage in recent
years where apartment buildings and the like are to be erected in a
relatively short period of time. Precast concrete stairs for such
construction have not heretofore been available which include the
desirable features of great structural strength, relatively low
weight for easier handling and installation and which meet the
requirements of the Occupational Health and Safety Act. The Act
among other requirements makes it mandatory that where building
construction is being undertaken all stairways must be enclosed by
a railing to protect the workmen from injury due to falls off the
side thereof during the construction period for the building.
In accordance with the present invention there is provided a
staircase which possesses the necessary strength, is of relatively
light weight and has an integral part of its structure railing
members meeting the safety requirements. Briefly, the staircase of
the present invention involves a deep U-shaped elongated beam
member wherein the vertical portions of the beam form rails and
further provide the principal source of support of the stairs which
are suspended from the rail portions. The invention will be
understood from a study of the following specification and
drawings.
IN THE DRAWINGS
FIG. 1 is a perspective view of a staircase in accordance with the
invention shown spanning an opening between two landings;
Fig. 2 is an elevational view in cross section of the staircase of
FIG. 1;
FIG. 3 is a cross-sectional view along lines 3--3 of FIGS. 1 and
2;
FIG. 4 is an elevational view in cross section of a mold used in
forming the staircase of FIG. 1;
FIG. 5 is a sectional view of the mold of FIG. 4 along lines
5--5;
FIG. 6 is a side elevational view of a portion of the reinforcing
steel cage at the upper part of the staircase; and
FIG. 7 is a perspective view of a supporting plate and reinforcing
rods of FIG. 6.
In each of the several views like parts will be given the same
numerical designation.
In the drawings 10 generally designates a staircase in accordance
with the present invention. The staircase comprises a broad
flat-bottomed U-shaped beam wherein the arms of the U are
designated 11 and 12 respectively. The lower flat portion of the U
intermediate the arms forms the stairs 15. The upper portion of
staircase 10 rests upon a landing or upper floor 13 while the lower
portion of the staircase is supported by landing 14. Rails 11 and
12 have a relieved portion 16 and 17 respectively which is shaped
to engage floor 13. The lower portion of the staircase and rails 11
and 12 has a flat beveled portion 18 adapted to rest upon floor 14.
The entire staircase is formed in such a manner as to be a
one-piece cast reinforced concrete member.
Referring to FIG. 2 there is illustrated in cross-sectional view
the staircase in accordance with FIG. 1. As can be seen staircase
rail member 11 (and its corresponding rail 12) are of a
parallelogram configuration wherein the upper surface of the rails
is parallel to the general axis of the stairs and forms the
handrail portion thereof. The upper end of rail 11 extends
outwardly beyond the top stair 15' with the outermost edge 19 being
angled with respect to the stair so as to be perpendicular to floor
13. The lower edge 20 of rail 11 is similarly perpendicular to
bottom stair 15".
The flat base of the U-shaped beam comprises the stairs 15. The
lower side 29 is cast so as to present a flat smooth surface while
the upper side has been shaped to form the stairs 15. In the
construction of the staircase reinforcing rods of steel are
utilized. A partial showing is made in phantom in FIG. 2 of the
U-shaped reinforcing rods 21 which are joined as by welding to
stringer rods 22. Both rods 21 and stringers 22 extend the length
of the staircase to define the cage. Welding of the rods to form
the cage extending the length of staircase 10 is accomplished prior
to insertion of the rods into the mold, illustrated in FIGS. 4 and
5, to give additional strength to the overall construction.
As the staircase is a mobile unit adapted to be lifted into place
by a crane there is provided anchor nuts 23 which may, if desired,
be welded to the cage member formed of the reinforcing rods. These
anchor nuts are cast into place at the same time the concrete is
poured so as to be firmly embedded therein and in a manner so as to
support the weight of the stair when moving same. Bolt members (not
shown) are screwed into the anchor nuts for use when the stair is
to be moved about. Once the stair is installed the bolt members are
removed and the openings in the anchor nuts filled with a suitable
material so as to present a smooth surface in the finished
product.
The reader's attention is now drawn to FIGS. 6 and 7 which show
details of the reinforcing rod construction for the upper portion
of the reinforcing cage of the staircase. L-shaped reinforcing rod
24 is welded to an angle iron 25 which also has joined thereto rod
irons 26 which project inwardly into the concrete which will be
poured about the construction. Dotted outline 27 of FIG. 6
illustrates the final outer form of the poured concrete. The
function of angle iron 25 is to serve as a support and tie member
for the upper portion of staircase 10 in its joining to floor 13.
The dimensions of angle iron 25 are approximately the same as the
width of rails 11 and 12 and are positioned directly therebeneath.
The angle iron 25 thus provides a broad support structure for the
rail members which in turn act as the support for the stairs 15 and
adjacent concrete. In actual installation a plate of steel 28 is
cast into floor slab 13 when it is formed and when staircase 10 is
installed plate 25 is joined as by welding to plate 28, thus
insuring that the staircase does not slip out of position. The
lower portion of staircase 10 is not fixedly joined to floor 14 but
merely rests on flat surface 18 to permit movement due to expansion
and contraction arising from changes in temperature.
As illustrative of dimensions involved in the construction of a
staircase in accordance with the invention the following values may
be taken as typical. The staircase for complete spanning of an
interfloor distance of 9 feet has an overall length at the tread
portion of about 161/2 feet. The overall height of the rail
sections 11 and 12 is approximately 3 feet while the overall width
of the staircase is approximately 4 feet. The thickness of rail
sections 11 and 12 is approximately 3 inches. The minimum thickness
of concrete in the staircase between the back side 29 and bottom of
risers to stairs 15 is 3 inches. For a staircase with these
dimensions the weight would be approximately 2 tons.
Construction of a reinforced concrete stair without the use of the
U-shaped construction of the present invention would require as a
minimum thickness at least 7 inches of concrete between the base of
the risers to stairs 15 and the back side of the stair. This heavy
thickness of concrete, absent the deep U-shape construction of the
present invention, is necessary in order to make the stair
self-supporting of its own weight and the loads to be anticipated
in service. Through the use of the deep U-shaped construction of my
invention the stairs are supported, not by their own strength
alone, but are largely supported by hanging from the side rails 11
and 12 which form a high strength structural member for such
support. As has already been noted angle plates 25 are the
supporting surfaces for rails 11 and 12. Very little of the support
for the stairs portion results from the concrete along the length
of the stair. Rather, individual stairs are principally supported
from arms 11 and 12. The overall construction provides not only an
extremely strong construction but simultaneously provides an
integral railing with the construction which is immediately
serviceable as a safety factor during the construction period as
well as lending itself to a finished staircase appearance after the
building has been completed.
Referring now to FIGS. 4 and 5 there is illustrated respectively in
side elevational view and in cross-sectional view along lines 5--5
of FIG. 4 a mold for use in forming the staircase of the invention.
The mold is constructed of steel panel members which are joined
together as by welding to form a finished mold used in the inverted
staircase orientation as seen best in FIG. 5. The interior facing
surfaces of the mold are smooth and are treated with a suitable
release agent to minimize any tendency of the fresh concrete to
bond thereto. The arm portions of the mold 31 and 32 are shaped so
that the upper ends of rails 11 and 12 will be somewhat thinner
than the lower portion of the rails as an aid to releasing the rail
portions from the mold. The tread portions of the mold are formed
by angled sheets of steel which are welded to the side rail forming
portions of the mold.
The cradle of reinforcing steel rods, shown in the other views to
the drawings, is introduced into the mold chamber and concrete is
poured therein to surround the reinforcing rods. The open side of
the mold is then smoothed off to form the smooth back surface of
the staircase. After the concrete has become suitably set the mold
is freed from the now formed staircase.
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