U.S. patent number 3,851,431 [Application Number 05/351,190] was granted by the patent office on 1974-12-03 for cantilever stairstep construction.
Invention is credited to Harold I. Klein.
United States Patent |
3,851,431 |
Klein |
December 3, 1974 |
CANTILEVER STAIRSTEP CONSTRUCTION
Abstract
Reinforcement steel extends forwardly from flange portions of a
short length of metal channel stock into a concrete stairstep body.
A pair of tabs are bent rearwardly out from the web portion of the
channel member. An upper portion of a metal stringer is received
between said tabs and the tabs are welded around their free edges
to the sides of the metal stringer. Casting apparatus for the
stairstep includes a support frame which includes an intermediate
undersupport, contoured to follow the under portion of a stairstep
form. The form is a pan-type and is supported by the undersupport
and by edge portions which rest on the four sides of the frame. The
short channel mounting member is placed into the pan and its tabs
are directed through slots formed in a wall portion of the form on
opposite sides of the undersupport. When the web of the channel
member is positioned flat against such wall portion of the form
both it and the reinforcement steel connected thereto are properly
positioned within the form.
Inventors: |
Klein; Harold I. (Bellevue,
WA) |
Family
ID: |
23379947 |
Appl.
No.: |
05/351,190 |
Filed: |
April 16, 1973 |
Current U.S.
Class: |
182/217;
52/189 |
Current CPC
Class: |
B28B
23/005 (20130101); E04F 11/028 (20130101); E04F
11/116 (20130101); B28B 7/225 (20130101); E04F
2011/0209 (20130101) |
Current International
Class: |
B28B
7/22 (20060101); B28B 23/00 (20060101); E04f
011/14 (); E04f 011/16 () |
Field of
Search: |
;182/228
;52/189,182,751,752,753 ;403/391,398,399,400 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Machado; Reinaldo P.
Attorney, Agent or Firm: Graybeal, Barnard, Uhlir &
Hughes
Claims
What is claimed is:
1. In a precast concrete stairstep which includes an imbedded metal
mounting member which is weldable to an upper portion of a metal
stringer, for connecting the stairstep to the stringer, and from
which the stairstep projects in cantilever fashion, the improvement
comprising:
said metal mounting member being a length of channel stock having a
web and two flanges which project from the web forwardly into the
concrete, said mounting member also including two rearwardly
projecting elements of plate metal which are tabs bent out from
said web, leaving an opening in the web inwardly of each tab and
channel stock end portions outwardly of said tabs, and resulting in
said tabs having inner side surfaces which are perpendicular to the
web, said side surfaces being spaced apart a distance substantially
equal to the width of the stringer, to define a space therebetween
in which the stringer is received, each said tab presenting edge
portions which are weldable to side portions of the stringer, and
said web including a plate portion between the openings which rests
on the top of the stringer, and said stairstep also includes
reinforcement steel which is welded to said channels and projects
therefrom into the concrete, said reinforcement steel consisting of
a single loop of reinforcement steel which is welded along one side
only to the mounting member flange that occupies an upper position
on the metal stringer, and which extends over the other flange in a
plane that is generally parallel to the upper surface of the
stairstep, and a length of reinforcement steel which is bent into
the form of a shallow V, and is welded near its middle to such
other flange, and which extends upwardly from said other flange in
parallelism therewith.
2. Apparatus for casting a reinforced concrete stairstep of a type
including a mounting member having a pair of beam straddling
projections and a beam top contacting surface between said
projections, said apparatus comprising:
a support frame having four interconnected side and end members and
an intermediate undersupport;
a pan-type form insertable into said support frame and including
edge portions restable on the side and end members of said support
frame, and wall means restable on said undersupport having a pair
of slots formed therethrough on opposite sides of said intermediate
undersupport, sized to receive the projections from the stairstep
mounting member.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to reinforced concrete stairsteps of the
cantilever type, and more particularly to improvements in the
manner in which such stairsteps are mounted onto a stringer and in
the manner of casting such stairsteps.
2. Description of the Prior Art
It is old to construct a stairway from one or more stringers which
extend longitudinally of the stairway and to which precast
stairsteps are attached. A stairstep of this general type is shown
by U.S. Pat. No. 3,467,220, granted Sept. 16, 1969, to Frank B.
Smith and Steffan B. Harley. The stairway shown by this patent
includes preformed metal stairsteps which are bolted to the
stringer. However, it is old to make stairsteps of this type from
reinforced concrete, to embed a metal plate in said concrete, and
to attach the stairstep to a metal stringer by welding such plate
to the upper edge portions of the stringer.
A disadvantage of welding a flush plate wall to upper edge portions
of the stringer is that the welding torch must be directed towards
the concrete body of the stairstep. This results in undesirable
heating of the concrete which quite often weakens the concrete.
Also, considerable care must be taken to support the stairstep in a
substantially perpendicular position on the stringer as it is being
welded thereto.
SUMMARY OF THE INVENTION
Stairsteps of the present invention include a mounting member
having a pair of rearwardly extending metal tabs between which an
upper portion of a stringer is received. The free edge portions of
the tabs are welded to side portions of the stringer. Therefore,
the heat of the welding torch is not directed towards the concrete
body of the stairstep.
According to an aspect of the invention, the stairsteps are formed
in such a way that the mounting tabs are properly aligned relative
to the concrete body of the stairstep, so that when the stairstep
is installed onto a stringer the tabs function to correctly align
the stairstep, to hold it substantially perpendicular to the
stringer. Also, the tabs help to retain the stairstep on the
stringer before it is permanently secured thereto by welding.
The stairstep casting apparatus may comprise a support frame having
four interconnected side and end members and an intermediate
undersupport for a pan-type form which is insertable into said
frame. The form includes edge portions restable on the side and end
members of the support frame and wall means restable on the
undersupport. The wall means includes a pair of parallel slots
formed therein which when the form is in the support frame are
located on opposite sides of the intermediate undersupport. The
slots are sized to receive the mounting tabs which project
rearwardly from the stairstep mounting member. When such tabs are
located in the slots, and the web portion of the mounting member
between the tabs is flat against the form wall, the mounting tabs
are correctly aligned with respect to cavity for the concrete so
that the finished stairstep will be substantially perpendicular to
a stringer received between the tabs. Also, reinforcement steel
connected to the mounting member and projecting therefrom into the
cavity is properly positioned so that it will provide reinforcement
in the finished stairstep where reinforcement is needed.
These and other features of the invention will become apparent from
the following detailed description of the illustrated embodiment of
the invention.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a fragmentary isometric view of a cantilever stairway,
showing a reinforced concrete step in full line and a skeleton view
of a second step;
FIG. 2 is a fragmentary side elevational view of the stairway,
presenting a skeleton view of a single stairstep;
FIG. 3 is a cross-sectional view taken substantially along line
3--3 of FIG. 2;
FIG. 4 is an isometric view of an embodiment of the stairstep
mounting member;
FIG. 5 is an exploded isometric view of an embodiment of the
apparatus for casting the stairstep;
FIG. 6 is a cross-sectional view taken through the casting
apparatus, with a stairstep skeleton in place within such
apparatus;
FIG. 7 is a view like FIG. 6, but showing concrete in the form
cavity and showing a leveling member in its path of travel across
the top of the casting apparatus;
FIG. 8 is a view like FIG. 6 and 7, but showing the form removed
from its support frame and the stairstep being rotated out from
such form; and
FIG. 9 is a fragmentary top plan view of the mounting member inside
the form, showing the relationship of its mounting tabs to the
slots in the bottom wall of the form and to the intermediate
undersupport of the support frame.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIGS. 1 and 2, the type of stairway to which this
invention is directed comprises a longitudinal stringer 10 (or a
plurality of parallel stringers) and a plurality of stairsteps 12
which are spaced apart along the stringer 10 and are attached
thereto. This type of stairway is generally termed a "cantilever"
stairway. It includes rising portions throughout which the stringer
10 is set at an angle, as illustrated, and may include landing
portions (not shown) in which the stringer 10 is horizontal.
A rising portion of the stairway is illustrated and a stairstep
construction for such portion will be described. However, it is to
be understood that the invention applies as well to landing
sections of the stairway, and the term "stairstep" as used herein
is meant to mean a horizontal stair member within a landing section
as well as an individual stair member which is attached to a
sloping stringer.
Referring now to FIGS. 2-4 in particular, according to the present
invention, the stairstep 12 is formed to include a mounting member
14 which may be constructed from a short length of channel stock.
It comprises a web 16 and a pair of flanges 18, 20.
At two spaced apart locations, one side and both ends of an
elongated rectangular figure are cut through the web and the
material within such figure is bent rearwardly about the remaining
side to form a rearwardly extending mounting tab 22. The two
mounting tabs 22 are parallel and are spaced apart a distance
substantially equal to the width of the stringer 10.
As shown by FIG. 1 and 2, a rectangular loop 24 of reinforced steel
is welded to the flange 18 and a length of reinforcement steel 26
that is bent into the form of a shallow V is welded to the flange
20. The general plane of the loop 24 extends at an angle X relative
to the web 16 which is the angle necessary to result in the general
plane of the loop 24 being substantially horizontal when the member
14 is attached to a sloping stringer 10. Also, the position of the
loop 24 is such that its side and end parts are located in the
upper portion of the concrete stairstep body, so that they can
carry tension forces imposed on such body when a downward force is
applied on the stairstep 12.
The mounting member 14 and the reinforcement steel members 24, 26
together form a "skeleton" for the stairstep 12. When such a
skeleton 14, 24, 26 is embedded in the concrete body of the
stairstep the rear surface of the web 16 is substantially flush
with, or forms, a rear surface of the stairstep 12.
Herein, the upper surface of the concrete body is considered to be
a forward portion of the stairstep and any portion of the stairstep
which is generally on the opposite side of the stairstep from the
upper surface is considered to be a rear portion of the stairstep.
In the illustrated embodiment it is evident that the stairstep 12
includes a rear surface which forms the base of the step and which
is flat against the upper surface of the stringer 10. The rear
portion of a horizontal stairstep member may be directed
downwardly.
According to the invention, an upper portion of the stringer 10 is
snugly received between the mounting tabs 22. The mounting tabs 22
are welded to the side surfaces of the metal stringer 10 along
their free edges, as indicated at 28 in FIG. 2. The mounting tabs
22 help locate the stairstep 12 relative to the stringer 10 prior
to welding. They maintain it substantially perpendicular to the
stringer 10 and make it necessary to only restrain the stairstep 12
against sliding down the stringer 10 in order to keep it on the
stringer 10 while the welding is being done.
According to an aspect of the invention, each stairstep is
individually cast in a pan-like form 30 which may be constructed
from a suitable structural plastic material. The form 30 includes
wall means forming a mold cavity and an upper rim portion 32 which
rests on side and end members 34, 36 of a support frame 38. The
support frame 38 also includes an intermediate under support 40
which is contoured to follow the shape of the form 30 at its
location. As best shown by FIGS. 6 and 7, the form 30 includes a
rear wall portion 42 which when the form 30 is within the frame 38
rests on a sloping wall portion 44 of the undersupport 40.
The rear wall portion 42 of form 30 is formed to include a pair of
parallel slots 46 for receiving the mounting tabs 22 of the
mounting member 14 (FIGS. 6-8). When the form 30 is within frame 38
the inner borders of the slots 46 are substantially aligned with
the edges of wall 44. Thus, when the mounting member 14 is set in
place with its mounting tabs 22 in the slots 46, the wall 44 is
snugly received between the tabs 22. As a result, the concrete that
is poured into the form 30 will flow into the spaces above member
44 which were created when the tabs 22 were pushed out from the web
16, but the concrete will not leak out from the slots 44.
Preferably, the slots 46 are made to be slightly longer than the
tabs 22. This is so that after the concrete has sufficiently
hardened the stairstep 12 can be easily removed from the form 30 by
in effect rotating it out of the form 30 in the direction of the
arrow 48 (FIG. 8).
When the mounting member 14 is within the form 30, and the mounting
tabs 22 are extending through the slots 46 and the web 16 between
the mounting tabs is flat against the form wall 42, which in turn
is flat against the undersupport wall 44, both the mounting tabs 22
and the reinforcement steel 24, 26 are properly positioned with
respect to the concrete body of the stairstep 12. The mounting tabs
22 are substantially perpendicular to the longitudinal axis of the
stairstep 12. Hence, when the stairstep 12 is placed on a stringer
10 it is likewise substantially perpendicular to the axis of the
stringer. The rectangular loop of reinforcement steel 24 is located
in the upper portion of the concrete body so that it can carry the
tension stresses put into such upper portion when a downwardly
directed force is applied on the stairstep 12 by a person using the
stairway. The reinforcement bar 26 is positioned to carry both
bending and sheer stresses.
As shown by FIG. 7, a leveling member 50 may be moved across the
top of the form 30 to level the top of the stairstep.
An important advantage of the provisions of mounting tabs 22 in the
mounting member 14 is that the stairstep can be welded onto the
stringer 10 without it being necessary to direct the welding torch
directly towards the concrete body. Instead, the torch is directed
generally towards the side surfaces of the metal stringer 10. The
cutting of the tabs 22 from the web 16 provides an easy way to
construct the mounting member 14 or a disturbance to the flanges
18, 20 to which the reinforcement steel 24, 26 is welded. However,
in some installations it might be desirable to construct the
mounting tabs in some other manner.
It is to be understood that the illustrated embodiment is only one
form of the invention and the invention is not to be limited by the
details which are disclosed in the drawing and described above, but
is to be determined by an interpretation of the claims which
follow.
* * * * *