Freestanding stair assembly and riser therefor

A freestanding stair assembly which is simple and chemical to produce and assemble is disclosed. The assembly utilizes a plurality of interengagable tubular links each of which is provided with pair of axially directed parallel slots in the annular wall. The slots extend from one end of the link and are oriented and dimensioned so as to receive therein the other end of a superjacent link. The links may be rotated relative to each other to achieve a linear or a non-linear stairway. Each link is adapted to have a stair tread member secured thereto. Also each main slot may be provided with a locking slot in the annular wall which is perpendicular to the main slot. Each riser may than have a lower flange at the other end, which flange can engage with the locking slots as relative rotation of the risers is performed. The circumferential extent of the lower flange is such that adjacent risers are locked together thereby at any reasonable relative angular orientation. The uppermost and lowermost risers are adapted to be respectively secured to an upper support such as a joist, and a base support, such as a floor. With the invention a spiral staircase, for example, may be achieved without requiring a central support pole.

The present invention relates to a freestanding stair assembly in general 
and to a simple riser member therefor in particular. 
BACKGROUND OF THE INVENTION 
Freestanding stair assemblies are well known in the art, the most common 
being the spiral staircase having interengageable risers on each of which 
a stair tread is secured. Such spiral staircases often require a central 
vertical pole to which each tread, or each preformed riser assembly is 
secured. Such systems are complex and expensive. Other systems exist which 
avoid the use of a central stabilizing pole, such systems depending on the 
integrity of the interengagement between vertically adjacent riser members 
to achieve structural rigidity. An example of such an assembly is found in 
Canadian Pat. No. 1,005,964 (Hamm) issued Mar. 1, 1977. Another system 
which dispenses with a vertical pole is found in U.S. Pat. No. 3,491,498 
(Hughes, Jr.), issued Jan. 27, 1970 which shows links having serrated top 
and bottom edges and a sloped cylindrical wall. The serrated edges are 
intended to grip the stair tread although it is necessary to provide a 
hole in each tread for receipt of a cable which is stretched to apply a 
compressive load to the tread and riser assembly. Both of the 
aforementioned systems are expensive to produce and require considerable 
skill to assemble. Since such systems are aimed at the home handyman as 
well as at the general contractor it is desirable to provide a system 
which is simple to produce and assemble and which is also inexpensive at 
the retail level. 
SUMMARY OF THE INVENTION 
The present invention provides a freestanding stair assembly, and its riser 
component, which is simple and inexpensive to construct and which provides 
a structurally rigid assembly without requiring a vertical central 
stabilizing pole when the stair assembly is configured as a spiral 
staircase. 
The heart of the present invention is the riser, to which a stair tread may 
be secured. Any style of tread may be used whether rectangular for a 
straight staircase, or sectored for a spiral staircase. The treads may be 
formed of wood or metal or any other material that may suit the user. Each 
riser is interengageable with the immediately superjacent and the 
immediately subjacent riser, with the exception of course of the uppermost 
and lowermost risers respectively, and each riser may be simply rotated 
relative to the immediately adjacent riser to achieve any desired 
non-linear staircase effect. A linear, or straight line, staircase is of 
course easily achievable. The lowermost and uppermost risers are provided 
with appropriate means whereby those risers may be secured to suitable 
support surfaces, such as a floor and a joist respectively. 
As indicated hereinabove, each riser is simple in form and construction. 
Each riser is in the form of a tubular link of steel, cast-iron or any 
other suitable material and has a length appropriate to the height and 
aesthetics of the final stairway assembly. At one end thereof each riser 
may be provided with an outwardly projecting flange for the attachment of 
a tread thereto, as with screw-type fasteners. Extending parallel to the 
axis of the tubular link is a pair of slots which open at the one end. The 
slots are parallel to each other and each has a width which is slightly 
greater than the wall thickness of the link. The slots are 
circumferentially spaced apart and are shorter than one half the length of 
the link. The slots are dimensioned therefore and are spaced apart so as 
to be able to receive the annular wall of an immediately superjacent link 
therein. The interengaged links, when joined together in this fashion, may 
be oriented to produce a linear or straight-line assembly, or each link 
may be rotated relative to the immediately subjacent link to produce a 
non-linear assembly, such as a spiral staircase assembly. 
In summary of the above, therefore, the present invention may be broadly 
defined as providing a riser for a freestanding stair assembly comprising 
a tubular link member having an annular wall portion, tread securing means 
at one end of said wall portion, and a pair of axially extending parallel 
slots formed in said wall portion, said slots being open at said one end, 
being spaced apart circumferentially and being dimensioned to receive the 
other end of the wall portion of a superjacent riser. 
Furthermore, the present invention may be seen to encompass a freestanding 
stair assembly comprising a plurality of interengageable risers and a 
tread affixed to each riser, wherein each riser is a tubular link member 
having an annular wall portion, tread securing means at one end of said 
wall portion, and a pair of axially extending parallel slots formed in 
said wall portion, said slots being open at said one end, being spaced 
apart circumferentially and being dimensioned to receive the other end of 
the wall portion of a superjacent riser.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 illustrates the riser link 10 which is at the heart of the present 
invention. The link is tubular in cross-section and may be formed of 
steel, cast-iron, or any other material which will provide sufficient 
strength for the specific assembly to which it will be applied. Similarly, 
links may be produced in different heights and diameters so that the user 
may select appropriate links to meet his needs. 
Each link is defined by an annular wall 12 defining a central through 
passageway 14. At the top end, a flange 16 is formed, which flange 
projects outwardly and extends circumferentially about a major portion of 
the wall 12. The flange 16 is provided with a plurality of bores 18 which 
are adapted to receive fastening means which secure the tread 20 (FIG. 2) 
to the flange. The bore 18 could be smooth with a countersunk portion on 
the underside of the flange whereby wood screws could be driven upwardly 
into a wooden tread. The bores 18 could also be threaded so as to receive 
machine screws driven downwardly through the tread. 
FIG. 1 also shows a pair of blind slots 22 which are formed in the wall 12 
of the link 10. The slots 22 are spaced apart circumferentially and may 
extend downwardly a distance which is less than one-half the height of the 
link, the slots being parallel to each other and to the axis of the link. 
The width of each slot is slightly greater than the wall thickness of the 
link wall and, as seen in FIG. 2, each wall of each slot lies generally on 
an arc corresponding to the outer or inner wall surface of the superjacent 
link. For manufacturing purposes the walls of the slot may be straight as 
long as the width therebetween is as mentioned above. As seen clearly in 
FIGS. 1 and 2 the flange 16 terminates adjacent the outer walls of the 
slots, the portion of the wall 12 between the slots being devoid of any 
flange. 
At the lower end of each slot 22 is a second slot 24 which extends through 
the wall 12 at right angles to the slot 22 and parallel to the flange 16. 
As seen in FIGS. 1 and 3 slots 24 are directed toward each other and are 
coplanar. 
At the lower end of the link, projecting inwardly of the passageway 14 is a 
second flange 26. Flange 26 is a locking flange and has a thickness just 
slightly less than the height of each slot 24, as it is intended to 
cooperate therewith. Flange 26 extends around slightly less than one half 
of the inner circumference 14 and the lower surface thereof is coplanar 
with the bottom surface of the link 10. 
FIGS. 7 and 8 show a modification of the embodiment of FIGS. 1 and 3 
wherein the slots 30 extend away from each other from their respective 
slots 22. A lower flange 32 is provided on the outer wall 12 in the same 
manner as flange 16 and is also provided with through-bores 34. The flange 
32 could have the same circumferential extent as flange 16. 
The manner in which the riser links may be assembled together to form a 
staircase as depicted in FIGS. 4, 5 and 6 will now be described. It is 
seen that the links interengage and interlock to form the assembly. 
In order to assemble the links together a first link is slipped into the 
slots 22 of a subjacent link with the lower wall portion which is devoid 
of flanges being introduced into the slots. The superjacent link is slid 
down into the slots of the subjacent link until the lower wall surface 
meets the bottom of the slots. The links are then rotated relative to each 
other until the bottom flange 26 or 32 enters the slots 24 or 30. Rotation 
is continued until the desired relative angular orientation of the links 
is achieved, whether for a non-linear stairway (as in FIG. 4) or for a 
linear stairway (as in FIG. 5). The interengagement of the flanges 26 or 
32 with the slots 24 or 30 prevents any axial separation of the links once 
the desired relative orientation has been achieved and also prevents 
relative forward or backward movement between the links. The 
circumferential extent of the flanges 26 or 32 is sufficient to provide 
any appropriate and reasonable degree of non-linear orientation without 
unwanted separation of the links. 
If the embodiment of FIG. 1 is utilized, that is a plurality of links 
having the internal flange 26, it is necessary to provide a base link 36 
as shown in FIGS. 4, 5 and 6. Such a link has a lower flange 38 extending 
completely around the circumference, the flange 38 having through bores 40 
for accepting suitable fastening means 42 for securing the base link to 
the floor or other base support. The upper construction of the base link 
36 is otherwise identical to that of the link 10. 
If the embodiment of FIG. 7 is utilized then the through-bores 34 could be 
utilized to fasten any link to the floor or other support as the flange 32 
would then perform the same function as the flange 38 on a base link 38. 
With this embodiment it would not be necessary to provide a separately 
constructed base link and hence the manufacturing process could be 
slightly simplified. The links of this embodiment would be otherwise 
assembled in the same manner as the links of the first embodiment. 
With either embodiment it is necessary to provide an uppermost support link 
44 which is secured to a joist or other upper support 46 at the top of the 
stairwell. Such a link 44 would have a upper portion of the wall 12 sliced 
therefrom and replaced by a flat portion 48 welded or otherwise secured 
thereto. In order to permit the support link 44 to be assembled to the 
subjacent link 10 the lower edge of plate 48 must be spaced above the 
lower edge of the wall 12 a distance at least as great as the vertical 
distance between the lower surface of slot 24, or 30 and the top surface 
of the flange 16. The wall portion below the plate 48 may extend 
thereunder, if desired, terminating in a vertical face which is coplanar 
with the outer mounting face of the plate 48. As seen in FIGS. 4, 5 and 6, 
fasteners such as lag screws 50 secure the support link 44 to the joist or 
other support 46. 
When assembling a stairway utilizing riser links according to the present 
invention the desired number of links would be assembled together and the 
links rotated relative to each other until the desired configuration is 
achieved. All links may be assembled and oriented before securing the 
uppermost and lowermost links to their respective supports as the 
interlocking feature provided by the flanges 26, 32 and recesses 24, 30 
will keep the links together in the general desired orientation. 
Alternatively it would be possible to secure one of the uppermost or 
lowermost links to its respective support and to then assemble the links 
together one at a time, starting with the secured link, until the other 
securing link is assembled. It would, of course, be easiest to start with 
the lowermost link as the first secured link so as to avoid any difficulty 
when the time comes to assemble the last link to the assembly. Once the 
risers are positioned and secured as desired the tread members may be 
assembled to the risers in an appropriate fashion. In this regard it is 
noted that the treads have been omitted from FIGS. 4, 5 and 6 for clarity 
and that the tread on the uppermost link would normally be either spaced 
an appropriate distance below the upper floor surface or would be coplanar 
therewith. Such dimensioning would have to be taken into account when the 
stairway is designed. 
Since the height of each link is shown and the depth of the slots 22 is 
known it is a very simple exercise for the home handyman to ascertain the 
number of riser links that he will have to utilize. Whether a linear or a 
non-linear stairway is chosen will depend on aesthetics and/or the space 
available. 
In order to strengthen the assembled stairway each riser may be provided 
with a threaded bore 52 extending through the wall portion 12 and 
positioned between the slots 22 approximately midway between the top 
surface of the riser and the slots 24 or 30. Such bore 52 may receive a 
threaded bolt 54, shown in FIGS. 4 and 5, which bolt may be tightened 
against the inner wall of the superjacent riser. While not specifically 
illustrated the bolt 54 could be provided with a pointed end which, upon 
tightening of the bolt, would dig into the material of the inner wall of 
the superjacent riser to increase the locking strength thereof. Needless 
to say the bolt 54 would be tightened only after the desired stairway 
configuration has been finalized, the bolts after tightening preventing 
any unwanted relative rotation between interlocking risers. 
It is understood that modifications within the purview of a skilled person 
in the art could be introduced into the present invention and hence the 
protection to be afforded the invention should be determined by the claims 
appended hereto.