Improvements in Spiral Stairways.
Year: 1890

page_text: Date of Application, 22nd July. 1890-Accepted, 13th Sept., 1890
COMPLETE SPECIFICATION.
Improvements in Spiral Stairways.
A communication from abroad by CHRISTOPHER CLARKE, of Northamton, County of
Hampshire, State of Massachusetts, United States of America, Gentleman.
I, WILLIAM PHILLIPS THOMPSON, F.C.S., M.I.M.E. of the Agency for Foreign
Patent Solicitors, 6 Lord Street, Liverpool, & 6 Bank Street, Manchester, both in
the County of Lancaster, & 323 High Holborn, in the County of Middlesex, Civil
Engineer, do hereby declare the nature of this invention and in what manner the
same is to be performed, to be particularly described and ascertained in and by the
following statement :-
This invention relates to the construction of metallic sections adapted to be com-
bined to build up a complete spiral stairway, also said sections adapted to form, when
intended, a double spiral stairway from a common centre.
The object of the improvement is to provide means for building such stairways to
any desired height by the simple process of fitting together, the sections themselves
supplying the central core, as well as the risers and treads; and having also for their
object the construction of a double stairway at the same time, providing passages
isolated one from the other, and capable of being made smoke-proof and leading to
separate floors of a building.
The invention is fully illustrated in the accompanying drawings, in which :-
Figure 1 is a top plan view of a section for a single stairway.
Figure 2 is a side view of the same.
Figure 3 is a bottom plan view of the same.
Figure 4 is a top plan view of a section for a double stairway.
Figure 5 is a side view of the same in partial section.
Figuro 6 is the reverse of Figure 4.
Figure 7 is a perspective of two single sections.
Figure 8 is a plan view of six double sections combined.
Figure 9 is an elevation of six single sections combined, and
Figure 10 is a half section of a tower showing, in elevation a double stairway as
far as the second floor of a building continued as a single stairway to the third
floor.
A, is a cast metal section in one piece, comprising a sleeve with a larger and
smaller interior and exterior and an inner. and outer shoulder, as more particularly
shown in Figures 2 and 5, a tread c and a riser d both radiating from the sleeve b.
The sleeves b, when the sections A are combined, rest one upon the other and
bring the edge of the tread against the edge of the riser of the succeeding section, no
special skill being required to lay out and build a spiral stairway when all measurement
is thus dispensed with.
The core formed of sleeves b is a tube through which a bolt e, as shown at 9, may
be extended to draw and bolt the sections rigidly together; also room is left for a
stand pipe which may serve the purpose, at the same time, of a bolt for locking the
sections together.
In practice, a groove
is formed in one edge of the tread to receive the edge
of the adjacent riser in place of causing the riser to rest merely upon the surface
of the tread; as, by causing the treads and risers to interlock, a much firmer
structure is insured, and a supporting wall at the outer ends of the steps is not
essential; also the groove g facilitates the filling of the point with lead packing K
(Figure 7) when it is required to make the passage way smoke-proof, the treads
and risers of each section are integral and imperforate to make the stairway as
nearly smoke-proof as may be.
In Figure 8, the riser of one section is shown secured in the groove g of another.

page_text: B is a cast metal section in one piece, having a central sleeve & similar to that of
section A, with combined risers and treads c d radiating from opposite sides of said
sleeve, the risers (as more particularly shown in Figure 6) are joined to the treads
so that the successive combination of the sections will form two spirals of steps
around the same centre in the same direction, and starting from the same plane.
In Figure 8, six sections B are shown combined to extend the one fourth part of
a circle in plane.
With risers eight inches in height, by the time one half of a circle was completed,
or until the bottom of the twelfth step was over the top of the one marked L, a clear
space of eight feet, would be left as a passage way, which space would, of course,
remain constant as long as the two spirals were produced.
By means of these sections B so constructed, a double stairway can be built up
within a tower, to afford passages entirely isolated from each other and easily rendered
smoke-proof.
In practice, sections are set in lead or soft putty, and may then be drawn close
together, either as shown in Figure 9, or compressed, as shown in Figure 10, by
a nut upon the end of a rod extending from the roof of the tower (not shown)
within the sleeve of the top section of the stairway.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, as communicated to me by
my foreign correspondent, I declare that what I claim is:-
1. The general arrangement and construction of the risers and tread having an
eye or socket and grooves by which a continuous smoke-proof stairway is constructed,
substantially as described.
2. The arrangement and construction of the double tread and risers connected by
a central eye by which an independent double stairway is produced, substantially as
described.
Dated this 21st dove of July 1900
WM. P. THOMPSON & Co.,
Agents for the Applicant.