Note: Descriptions are shown in the official language in which they were submitted.
1 BACKGROUND OF THE INVENTION
,
1. Field of the Invention
This invention relates generally to a stairway
construction and more particularly, to a novel stairway
construction which consists of a plurality of elements
which interconnect to form an articulating, self-supporting
staircase.
2. Description of the Prior Art
It has been previously proposecl to provide a
stairway construction which consists of a plurality of
stairway support elements, each element having a horizontal
portion on which is mounted the stairway tread, and a
vertical portion, which extends upwardly from the
horizontal portion to interconnect with the element
immediately above and which extends downwardly from the
horizontal portion to interconnect with the element
immediately below.
The most difficult problem encountered with these
structures is to provide a self-supporting structure which
is safe and secure. Each element must be secured to the
adjacent element immediately above and immediately below
in such a manner to ensure safety, yet such construction
must be simple and easy to install onsite with minimal time
and tools being required. The structure must be designed
to be economical yet aesthetically pleasing and must have
the adaptability to be fully adjustable in height and in
orientation. Space and size restrictions must be able to
be accommodated for all possible installations.
1 The first attempt to provide such structures
utilized a central column to which riser and tread members
were attached. An example of such a structure is shown
in U.S. patent 3,964,222 granted on June 22, 1976 to
Geleijnse et al. Reference is also made to
U.S. patent 3,916,591 granted on November 4, 1975 to
Agterhot et al which uses a spindle to which the steps
are attached.
Free standing stairway cons-tructions have also
been attempted in the past. One such example is shown
in U.S. patent 3,473,275 granted on October 21, 1969 to
Lappin which shows a stairway comprising a series of
individual stair tread units, each connected by fasteners
such as bolts or screws to each others. Other more recent
constructions are shown in German Offenlegungsschrift
25 52 220 and German Offenlegungsschrift 2 129 753, U.S.
patent 3,908,325; U.S. patent 4,285,178, and Canadian
patent 1,005,964.
The principle concern of these patents and the
inventions disclosed herein reside in the problem of
securing the elements together in such a manner to provide
a safe and secure structure which will not fatique over
time. For example, Canadian patent 1,005,964 discloses
a structure which uses telescopically interengageable
metallic tubes as the vertical portions with bearing
members to clamp the tubes together. Steel balls are
used about -the bearing members to increase the clamping
effect.
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1 Various forms of clamps and bolts have also
be~n tried to prevent sagging of the structure over time.
~lowever, it has been found that all these structures
will fatigue over time and fail to meet the building
codes of many jurisdictions.
SUMMARY OF THE INVENTION
Accordingly, it isanobject of the present
invention to at least partially overcome these disadvant-
ages by providing a novel stairway construction which
consists of a plurality of elements, each element sup-
porting a step, which construction allows for a variety
of widths, materials and layouts of the elements. The
construction is sufficiently strong to comply with
building codes and yet is lightweight and easy to install
; 15 in a variety of configurations. Modularity of assembly
and ease of construction in any size or shape is achieved
with the present structure. The structure, when
assembled, forms an articulating, self-supporting stair~
case.
To this end, in one of its aspects, the inven-
tion provides an articulating, self-supporting staircase
which comprises a plurality of individual, interconnected
elements, each element having a tread and a riser,
and a wedge locking means to lock said interconnected
elements firmly together.
1 In another of its aspects, the invention further
provides an articulating, self-supporting staircase which
comprises a plurality of individual, interconnected elements,
each element having a tread and a riser, and a wedge
loc~ing means to lock said interconnected elements fully
together, wherein each tread is secured to the top of
each riser by means of a plurality of screws,
each screw extending upwardly through a boss
in said risqr, into said tread~ each riser except the
top riser having a conical protrusion extending upwardly
from the r~ar of a base, sa.id base having a plurality
of strengthening ribs therein and a strengthening box
therein which is enclosed by a plate, said base having
a tapering hole on the surface at the front thereof which
hole ls adapted to receive and retain the protrusion o~
the lower adjacent element, each protrusion having three
longitudinally slotted flattened sides; said wedge locking
means comprising three longitudinally ribbed wedges, each
wedge adapted to slide over one of said flattened sides
of said protrusion, a retaining ring adapted to retain
said wedge on said flattened sides, and a threaded bolt
adapted to be inserted through said hole and into the
protrusion o~ the riser to interconnect said adjacent riser,
and a washer on said bolt above said wedges on the lower
protrusion, whereby when said bolt is tightened, said
washer drives said wedge downwardly and firmly inter-
connects adjacent risers.
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l Further objects and advantages of the invention
will appear from the following description taken together
with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGURE l is a perspective view of the assembled
stairway construction of the present invention.
FIGURE 2 is a front perspective view of a riser
of the present invention.
FIGURE 3 is an exploded, bottom perspective
view of a riser and a tread of the present invention.
FIGURE ~ is an exploded view of the top riser
and a part of the tread of the present invention.
FIGURE 5 is an exploded view of two risers
and the means to lock two risers together.
FIGURE 6 is an exploded view of a view of figure
2.
FIGURE 7 is a cross sectional view of two
assembled risers and treads of the present invention.
DESCRIPTION OF THE PREFERRED EMBODI~ENT
Referring now to the drawings and in particular,
to figure l, the assembled stairway construction of -the
present invention comprises a plurality of elements 2
secured together to form an articulating, self-supporting
staircase.
Each element comprises a tread 4 and a riser 6.
The tread 4 is generally rectangular although variations
1 may be made ~ithin the scope of this invention. The tread
4 is secured to the riser 6 by any suitab]e means. As
shown in figures 3 and 4, one such means includes screws
8 which are inserted through holes 10 in the undersurface
of the riser 6. The screws 8 e~tend through the bosses 18
(see figure 4~ and into corresponding holes ~not shown) in
the bottom of the tread 4. The screws 8 are ~hen tightened
which pulls the tread 4 into contact with the riser 6.
Any desired decorative covering may be placed on the top
surface o~ the tread 4.
The riser 6 as shown in figure 2, comprises a
base 12 and a conical protrusion 14. The base 12 has been
cast in a particularly aesthetically pleasing shape but
may be made of any desired shape or outline as desired,
within the range of the present inven-tion. The base 12
has been hollowed out to reduce its weight and to reduce
its costs of manufacture. However, to impart the neces-
sary strength to the structure, ribs 16 are provided.
Bosses 18 are provided, preferably four in number, through
which screws 8 extend to retain the tread 4 in the desired
position.
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1 The ribs 16, in conjunc-tion with the side walls
of the base 12, form a box-like structure as best seen in
figure 2. Plate 20 is provided which is secured by screws
46 into bosses 44 to increase the strength of the base
12. A tapered opening 22 is provided in the forward
bottom portion of the base 12 which will accommodate the
conical protrusion 14 of the ad~acent riser 6, as will be
explained hereinafter. The tapered opening 22 extends into an
enlarged, recessed, boss 24 to which ribs 16 are joined~
Hole 26 is provided in the -top of the boss 24, the purpose
of which will be explained hereinafter.
The conical protrusion 14 extends upwardly
from the rear of the base 12 and the top surface is trun-
cated. The protrusion 14 is ~lattened on three sides as
shown in figure 5 . While the preferred embodiment has
three flattened sides 28, the invention is not so restrict-
ed and wi]l be operative with one or more flat sides.
Each of the flat sides 28 has a longitudinal slot 30 cut
therein.
Figure 5 illustrates the wedge lockin~ means
which is used to lock -two risers together. Three wedges
32 are provided and each wedge 32 is contoured to mate
with the inside tapered wall of the opening 22 as will be
explained hereinafter. Each wedge 32 has a rib 34 extend-
ing along its length and the rib 34 is constructed to fit
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1 with.in the slot 30 on each flattened side of -the pxotrusion
14. Retaining rings 38 (or any similar means such as
retaining clips) fi~ into transverse grooves 36 around
each wedge 32. Thus as shown in figure S in the assembled
position, the interaction between rib 34 and slot 30 only
allows vertical movement of the wedge 32.
A large, threaded bolt 48 is provided with a
hex head 50 which is adapted to fit through the hole
26 in the boss 24. A large washer 52 is placed on the
bolt 48 between the top of the conical protrusion 14 of
the underneath riser 6.
As shown în figure 4, th.e top riser 12 does
not have a conical protrusion and the tread 4 extends
over the surface of the riser 6. In the case of the toP
riser 12, the plate covers the entire box 21 as shown in
figure 4.
The assembly of the novel stairway construction
will now be explained. The first step is to assemble
the plate 20 on each riser 6. The plate 20 as shown in
figure 6, is orientated correctly and secured to the
riser as shown in figure 2. Screws 46 are secured th.rough
the hole 42 and inserted into the bosses 44. Since the
bosses 44 are below the planar surface of the riser, the
plate 20 sits inside the thus formed box there~y providing
a smooth top surace as shown in figure 2.
The wedges 32 are then each placed on a flattened
surface 28 of the conical protrusion 14 such that the rib
34 is keyed into the slot 30. The retaining rings 38
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1 are placed over the wedges 32 to secure the wedges in
place. The bolt 48 is then inserted through hole 26 in
boss 24 and washer 52 îs placed on the end of the bolt
48 which emerges through the hole 22. The end of the
bolt is then inserted into the top hole of the conical
protrusion 14.
The conical protrusion 14 of the lower riser
is then inserted into hole 22 of the upper riser as
shown in figure 7. The orientation and rise of each
riser is then adjusted and the bolt 48 is tightened. This
action drives the wedges downwardly along the key lined
walls of the conical section by the action of the washer
and the retaining rings 38 permit the necessary e~pansion
to occur. The process is then repeated for all the
desired risers. Treads 4 are then secured to the top of
each riser.
The stairway construction provides a very secure
and strong free-standing, self-supporting structure. The
riser is preferably of cast aluminum, or any other material
which possesses sufficient inherent strength and is quite
easy to cast. Most of the prior art devices were
found to be too brittle and not suitable. The aluminum
356 alloy does not suffer from fatigue over time.
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1 The particular wedge locking system of the
present invention provides notable improvements over the
prior art. Since the wedges,preferably cast of maleable
iron, are key lined to mate with the flattened surface
of the conical protrusion, they do not and cannot move
laterally. The wedges, as shown in figure 7, are
contoured to mate with the inside tapered walls of the
opening at the lower front of the adjacent casting. Once
the wedges are in place and the orientation of the risers
is set, the bolt is tightened which drives the wedges
downwardly. A noted advantage of this structure i5
that continued strengthening of the wedge lock system
occurs through use of the staircase. As weight is
applied to the tread by persons mounting the staircase,
; 15 pressure is applied which tends to tighten the wedge fit.
The present construction also provides for many
advantages over the prior art. It allows for full
variability of riser height within the normal range of
' staircase construction requirements. By adjusting the
height of thewedges and by tightening the bolt, the
height between adjacent risers may be controlled thereby
allowing for more variability in the height of the rlsers.
The device also allows for rotational adjustment
of the risers. The conical protrusion of each riser may
be adjusted rotationally within the opening of the upper
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1 riser before tightening. Therefore, by making such an
adjustment, the orientation of the "spinal column" shown
in figure 1 may be completely adjusted for a straight line,
a tight turn, a wide turn or any variation in between.
Also, identical curves may be produced between respective
risers if desired.
Maximum strength of the construction is also
achieved by use of the box structure and the plate on each
riser. This has been found to be sufficient to meet build-
ing codes in all jurisdictions.
The construction is also easily assembled on
site using a minimum number of tools and expertise. Simple
construction and assembly provides a notable advantage
over the prior art.
The inventor has constructed a stairway accord-
ing to the present invention and has subjected it to
various tests ~he stairway was made of AL~G 35 (Alcon
alloy 535.2) (trade mark) and had sufficient streng-th,
castability and finishing options.
Four basic tests were applied to the stairway~
These tests were as follows:
Test l: load test on a simple element to
determine bending strenyth.
Test 2: load test on two attached elements to
determine bending strength of the box
section.
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1 Test 3: same as test 2 but load applied to
edge of element.
Test 4: load tests on a stairway consisting
of 14 elements by applying an equal
load to each element in sequence from
step 2 to 12.
The loads on tests 1, 2 and 3 were applied with
a hydraulic jack and recorded ~ia a 10,000 lb load cell.
In test 4, each step was loaded with a deadweight of 838
lb (380 kg) and the deflection was measured on every second
step. For a final test, the maximum load was determined
by loading the weakest point in the structure (step 7)
until breakage occurred.
Two load applications were done in test 1.
The first used 4300 lbs and the second used 4800 lbs.
A physical inspection revealed no signs of fallure, i.e.
;; no cracks on any part of the element.
Test 2 used a bond applied in the mounting
point of the element using a maximum load of 2700 lbs. Test
3 used the same maximum load on the edge of each element.
No physical sign of failure on any part of the elements or
attachment points occurred.
For test 4, deflection readings were taken on
the outside edge of the steps and the results are shown in
Table 1. For the maximum load test, step 7 was loaded to
2650 lbs when breakage occurred in step 1.
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Table 1: Deflection Chart
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1 As shown by the test results, a very
satisfactory product was produced which meets all build-
ing codes.
While the invention discloses and describes a
preferred embodiment of the invention, i-t is to be under-
stood that it is not so restricted.
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