US3491498A - Spiral staircases - Google Patents

Description

Jan. :27, 1970 w. J. HUGHES, JR 3,491,498

SPIRAL STAIRCASES Filed July 12, 1968 2 Sheets-Sheet 1 J as V n V m:

W/LZ/FM Hus/1.55, JA.

Jan. 27, 1970 w. .1. HUGHES, JR

SPIRAL STAIRCASES 2 Sheets-Sheet 2 Filed July 12, 1968 INVENTOR ATTORNEY United States Patent 3,491,498 SPIRAL STAIRCASES William J. Hughes, Jr., 452 S. 19th St., Baton Rouge, La. 70806 Filed July 12, 1968, Ser. No. 744,419

Int. Cl. E04f 11/02 U.S. Cl. 52-187 8 Claims ABSTRACT OF THE DISCLOSURE A center-well type spiral staircase comprising an assembly of a plurality of individual tread members and a plurality of individual column sections, each section being interposed between and spacing a pair of adjacent tread members, said column sections being so configured and so placed and oriented with respect to the tread members between which they are interposed that they form a vertically ascending, roughly helical tread supporting column, and tension means extending through said tread members and column sections and being operative to place same under compressive force sufficient to secure and maintain them together as a fixed assembly.

This invention relates to improvements in spiral staircases and more particularly to an improved center-well type, as distinguished from a central-column or post type, of spiral staircase.

As conducive to a proper understanding of the persent invention, it is explained that while many designs of central-column or post type spiral staircases, according to which the treads radiate from and are supported from a central-column or post in cantilever fashion, have been devised, such are open to numerous objections, the principal of which are (l) the riser means employed must provide high step height in order to avoid low head room to the person ascending or descending the staircase; (2) the projection of the portions of the treads of the staircase disposed adjacent the central post or column is less than required for safety and/or convenience; and (3) no inner handrail is possible unless the diameter of the central column or post is abnormally large or unless the inner handrail is located outwardly from said central column a distance which necessitates an undesirable increase in the length of the treads.

While attempts to overcome the aforesaid objections to spiral staircases as conventionally manufactured are of record, such in general rely on a one-piece, continuous, helically configured tread-supporting column in place of a vertical supporting column, which latter can be and is usually made up in sections corresponding generally to riser height. While resort to the one-piece, continuous helical columnar element for supporting the treads was effective to a degree, such gave rise to other objectionable features. More particularly, the use of the one-piece and continuous helically configured support column not only necessitated factory configuration thereof but also gave rise to the requirement of the staircase employing same being assembled complete or substantially complete at some location other than at the location or site of installation, all of which made for high manufacturing costs and additional substantial inventory, shipping and installation costs. In short, resort to the one-piece continuous helical support column as the tread-supporting means of a spiral staircase rendered such a staircase economically non-feasible for large-scale use.

With the above in mind, a major object of the present invention is the provision of a spiral staircase of a design and structure which renders same capable of overcoming the objectionable features not only of the well known central column or post type of spiral stairway, but also of the more recently developed spiral stairway or staircase employing the one-piece factory fabricated, helically configured column for supporting the staircase treads.

More particular objects of the invention are the provision of a center-well type spiral staircase characterized by simple and practical design which makes for relatively inexpensive construction and economy in installation and which is moreover thoroughly dependable in use; the provision of an effective and practical spiral staircase employing a helical tread-supporting column of sectional construction; the provision of a spiral staircase of the laststated character wherein the sections making up the helical, tread-supporting column are of a nature and form lending themselves to prefabrication and to subsequent assembly at the site of installation of the final staircase; the provision of a spiral, center-Well type of staircase characterized by sectional construction and wherein the parts or sections making up the same may be prefabricated, packaged, shipped to and assembled at the site of installation at a cost substantially less than that involved in the fabrication, packaging, shipment and installation of staircases employing the one-piece continuous helical supporting column as described in the foregoing; and the provision of simple yet highly effective means for securing and thereafter maintaining said prefabricated parts and/ or sections in assembled relation at the site of installation.

The above and other objects and features of advantage of a center-well type spiral staircase according to the present invention will appear or be obvious from a consideration of the following detailed description thereof, taken with the accompanying illustrative drawings, wherein:

FIG. 1 is a side elevation of a fully assembled spiral staircase of the invention, with parts broken away in the interest of clarity;

FIG. 2 is a plan view of the spiral staircase of FIG. 1, as seen from the upper of the two fioors served thereby;

FIG. 3 is an exploded isometric view illustrating certain features of construction and a preferred means for and manner of connecting the lower end of the staircase shown in FIG. 1 to the lower of the two floors served thereby;

FIG. 4 is a view generally similar to FIG. 3, illustrating details of construction of the upper end of the staircase, and more especially of a preferred means and manner of securing and thereafter maintaining the column sections and tread members making up the staircase in compression; and V FIG. 5 is a detail of one of the column sections of the staircase shown in FIGS. 1 and 2 and which illustrates the side view configuration thereof.

Referring to the several views, it will be seen that a center-well type spiral staircase as herein proposed comprises: a plurality of individual tread members 10; a plurality of individual column-forming sections 12 serving both to support and to space said tread members; a staircase bottom-end fixture 14; tension means generally designated 16 for placing and "maintaining the assembly of tread members and column sections in compression; and a combined upper-end fixture and tension-applying means generally designated 18 (FIG. 4).

As best seen in FIGS. 2, 3 and 4, the tread members 10, which are preferably made of wood but which can also be made of other suitable materials, are shown to be of generally rectangular configuration, being of length, i.e. radial projection, and width corresponding to the length and width of the treads of staircases made in accordance with accepted architectural practice.

Referring in particular to FIGS. 3, 4 and 5, the individual column sections 12 illustratively take the form of truncated cylinders, i.e. sections of round pipe, having effective axial length corresponding to the height of conventional risers as used in staircase construction. However, rather than the column sections 10 having right-circular configuration as would be true if their upper and lower edges were disposed at right angles to their axes, said edges, while parallel to one another, are instead disposed at supplemental angles to their axes. Thus, when the individual column sections 12 are viewed in side elevation (as they are seen in FIGS. 1 and 4), they each have the configuration of a parallelogram and their open ends are shaped as ellipses.

Referring to FIG. 3, the aforesaid bottom-end fixture 14 preferably takes the form of a horizontal base plate fashioned from heavy-gauge metal plate stock, to which the lowermost column section designated 12a is rigidly aifixed as by welding. Said base plate is also generally rectangular in shape and mounts means such as bolts 22 whereby it may be secured by bolting to the floor slab 24 (FIG. 1) of the lower of the two floors served by the staircase under description. Preferably, the base plate 14 is masked from view by the finish floor designated 26 in FIG. 1, which as is conventional is applied over said floor slab, it being understood that other means for masking said plate may be employed.

Referring to FIG. 4, the aforesaid upper-end fixture is shown to comprise the uppermost column section designated 12b and a receptacle-like member 30 whose lower end portion is telescopically fitted into said column section 12b and whose upper end, which is open on top and provided with the marginal retaining flange 30a, extends through an aperture 32 provided therefor in the uppermost tread plate or member 10a, which latter is preferably set into and forms a part of the second or upper floor structure served by the staircase. A closure plate 34, which is disposed flush with the upper surface of said uppermost tread member 10a and is removably secured to said marginal retaining flange 30a, serves normally to close the open top of the receptacle-like member 30 but upon removal provides access to the interior space of said member.

Illustratively, the tension means 16 employed to place and thereafter maintain the staircase treads 10 and column sections sufficient to secure said treads and column sections in their assembled relationship comprises a plurality (two being shown) of cables 36 which are anchored at their lower ends to suitable attaching eyes 38 carried by the aforesaid base plate 14. Said cables extend upwardly from said base plate and thread through each of the individual column sections 12 and the tread members 10 as well, the latter for this purpose being provided either with a single through-hole large enough to accommodate all said cables or, as shown, with the through-holes 10h (FIG. 4) individual to the cables which are drilled or otherwise provided in the tread members adjacent the ends thereof to which the column sections are assembled, as will be hereinafter described in detail. At their upper ends the cables 36 are rigidly aifixed to externally threaded studs 40 which project in both directions through the closed bottom wall of the receptacle-like member 30 of the aforesaid upper-end staircase fixture 18, which wall, it is to be noted, is disposed at a right angle to the receptaclebody axis. Nuts 42 threaded on the upper ends of the studs 40 are disposed to bear on the inside surface of said closed bottom wall. When said nuts are turned in proper direction, said studs are translated axially upwardly, thus to tension the cables 36 and place the assembly of treads 10 and column sections 12 in compression.

Referring to FIGS. 4 and 5 in particular, means are provided on both the upper and lower edges of the column sections 12 for preventing any slippage or turning movement of said sections with respect to the tread members 10, between which they are interposed in assembly. Illustratively, such means takes the form of projecting serrations or teeth 12t on said edges which tend to bite into the tread surfaces with which they engage upon tensioning of the cables 36. Any other suitable means for preventing slippage or turning of the sections 12 may of course be substituted.

From what has been said in the foregoing, it will be appreciated that the staircase of the invention is one which is to be assembled at the site. Its assembly is relatively simple since basically it comprises proper placement and securement of the lower-end fixture 14 (base plate with its cable-anchoring eyes 38), fastening of the lower ends of the cables 36 to said anchoring eyes, progressive erection of the staircase by interposing column sections 12 between each pair of tread members 10, accompanied by threading of the cables 36 through the tubular column sections and holes 10h provided therefor in the treads 10, placement and securement of the uppermost tread 10a and the upper-end fixture 18 in the staircase well provided therefor in the upper-floor structure 42, afiixing the upper ends of the cables 36 within the studs 40, and tensioning said cables to place the stack of treads and column sections under compressive force sufficient to maintain the staircase fully assembled as in FIG. 1.

Of course, in addition to the aforesaid basic assembly steps, which are largely mechanical or routine erection steps, each column 12 must be properly positioned on the tread member 10 immediately below same and each such tread member and column-section set must be properly oriented with respect to similar tread member and column-section sets above and below same so as to achieve the center-well spiral configuration of staircase of the invention. More particularly, and as seen in FIGS. 3 and 4, each column section 12 must be placed on each ower tread member 10 in the particular position such that its inclined axis slopes away from the inner-end edge of said tread member; that its relatively innermost edge portion (which will be a point on its upper elliptically configured edge) is disposed approximately in vertical alignment with said tread-member inner edge; and that the greater length or major axes of its elliptically configured upper and lower edges will be approximately in the same vertical plane as that containing the longitudinal center line of said lower tread member. And furthermore, as best seen in FIG. 2, each of the sets of tread member 10 and its so positioned column section 12 must be turned with respect to each lower and upper tread member and column-section set at the particular angle such that the inclined axes of the column sections extend in substantial continuation of one another and along a roughly vertical helix having pitch determined in advance to provide both the necessary head room to a person ascending or descending the particular staircase and the desired tread projection, particularly adjacent the innermost ends of the tread members. Illustratively, for a fifteen-tread staircase that extends or spirals throughout an arc of 270", each tread member and column-section set will be turned 18 with respect to each upper and lower similar set, but such is variable within limits, as said angle of turn depends on factors such as spacing between floors, desired diameter of center well, projection of treads, etc.

If the so-assembled staircase is to be provided with railings, as is usually the case, inner and outer railings 50, 52 supported by spindles 50a, 52a may be installed after full assembly of the staircase per se. The railings are of conventional construction and thus require no detailed description here. However, it is pointed out that the design of the center-well spiral staircase of the invention is of advantage in that it permits of an inner railing, such without any undue increase of the length, i.e. radial projection, of the tread members 10.

Without further analysis, it will be appreciated from the foregoing that a center-well type staircase as described and illustrated achieves the objectives of the invention as outlined in the foregoing. More particularly, the shape and structure of the various parts making up a staircase as herein proposed are such that they may be factory prefabricated and thereafter packaged and shipped to the site of staircase installation at a fraction of the cost involved in the fabrication and shipment to the site of similarly configured saircases employing a one-piece, continuous, helical tread supporting column. The erection and assembly of the saircase from said prefabricated parts at the site of installation is also relatively simple since apart from the column section-to-tread placing operation and that of properly orienting the tread-member and colurnn-section sets with respect to adjacent sets, both of which can be assisted by templates or other mechanical aids, the assembly of the staircase to final form in the space provided for its insiallation is a routine operation requiring no special skill.

I claim:

1. A spiral staircase comprising: a generally vertically disposed assembly of a plurality of individual tread members and a plurality of individual column-defining sections; each said section being interposed between a pair of said tread members at the inner ends thereof and having vertical height as to space same in accordance with conventional staircase tread-spacing requirements; said column-forming sections having configuration in side elevation such that their axes are uniformly inclined to the vertical and being each so positioned on the lower tread member of each said pair spaced thereby that its axis is in the vertical plane containing the longitudinal center line of said lower tread member; each said columnforming section and said lower tread member of the pair thereof spaced thereby being displaced horizontallywith respect to each of the associated column-forming sections and tread members disposed immediately above and below same by a predetermined angle which is such that the axes of said plurality of individual column-defining sections extend in substantial continuation of one another and along a helix and which is further such that the tread members have requisite horizontal projection throughout substantially their full length; and means for securing said plurality of tread members and said plurality of column-defining sections together in rigid staircaseforming relationship.

2. A spiral staircase according to claim 1, wherein said securing means comprises cable means including means at one end for affixing same to the structure served by the staircase and including means at its other end for tensioning said cable means and thereby securing said tread members and column-defining sections in compression.

3. A spiral staircase according to claim 1, wherein column-defining sections incorporate means for preventing slippage or turning thereof following final staircase assembly.

4. A spiral staircase according to claim 1, wherein said column-defining sections have parallelogram configuration.

5. A spiral staircase according to claim 1, wherein said column-defining sections comprise lengths of round pipe whose end edges are parallel but are oblique to said axes of the sections.

6. A spiral staircase according to claim 5, wherein said end edges of the column-defining sections incorporate plural teeth-like projections adapted to sink into the surface of the pair of tread members with which each said column-defining section is associated responsive to securement of the tread members and column-defining sections.

7. A staircase according to claim 1, wherein means are provided at the lower end of said assembly of tread members and column-defining sections for securing the staircase to the lower of the floors served thereby.

8. A staircase according to claim 1, wherein means are provided at each of the lower and upper ends of the said assembly of tread members and column-defining sections for securing the staircase to the lower and upper floors served thereby.

References Cited UNITED STATES PATENTS 3,418,770 12/1968 Allmand 52-l87 1,726,133 8/1929 Wilson 52187 1,229,482 6/1917 Leclair 52--187 FRANK L. ABBOTT, Primary Examiner S. D. BURKE III, Assistant Examiner US. Cl. X.R. 52-228

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