Precast Staircase

Abstract

A precast reinforced concrete integral staircase adapted to be installed as a unit to span the space between two landings is formed of a deep U-shaped elongated beam member wherein the arm portions of the U extend upwardly from the flat base of the U defining the stairs to provide a supporting structure for the stairs, which arms also become a rail for safety purposes during construction and as a permanent rail thereafter.

Description

The present invention is in the fluid of preformed structural members for buildings and the like wherein component units of a building are formed at a site remote from the actual building site, transported to the building site as a unit and then installed to form the building. More specifically, the present invention is directed to a precast staircase member formed of reinforced concrete adapted to be installed as an integral unit between two landings.

The use of precast panels of concrete to form the floor and ceiling is well known in the art and has found considerable usage in recent years where apartment buildings and the like are to be erected in a relatively short period of time. Precast concrete stairs for such construction have not heretofore been available which include the desirable features of great structural strength, relatively low weight for easier handling and installation and which meet the requirements of the Occupational Health and Safety Act. The Act among other requirements makes it mandatory that where building construction is being undertaken all stairways must be enclosed by a railing to protect the workmen from injury due to falls off the side thereof during the construction period for the building.

In accordance with the present invention there is provided a staircase which possesses the necessary strength, is of relatively light weight and has an integral part of its structure railing members meeting the safety requirements. Briefly, the staircase of the present invention involves a deep U-shaped elongated beam member wherein the vertical portions of the beam form rails and further provide the principal source of support of the stairs which are suspended from the rail portions. The invention will be understood from a study of the following specification and drawings.

IN THE DRAWINGS

FIG. 1 is a perspective view of a staircase in accordance with the invention shown spanning an opening between two landings;

Fig. 2 is an elevational view in cross section of the staircase of FIG. 1;

FIG. 3 is a cross-sectional view along lines 3--3 of FIGS. 1 and 2;

FIG. 4 is an elevational view in cross section of a mold used in forming the staircase of FIG. 1;

FIG. 5 is a sectional view of the mold of FIG. 4 along lines 5--5;

FIG. 6 is a side elevational view of a portion of the reinforcing steel cage at the upper part of the staircase; and

FIG. 7 is a perspective view of a supporting plate and reinforcing rods of FIG. 6.

In each of the several views like parts will be given the same numerical designation.

In the drawings 10 generally designates a staircase in accordance with the present invention. The staircase comprises a broad flat-bottomed U-shaped beam wherein the arms of the U are designated 11 and 12 respectively. The lower flat portion of the U intermediate the arms forms the stairs 15. The upper portion of staircase 10 rests upon a landing or upper floor 13 while the lower portion of the staircase is supported by landing 14. Rails 11 and 12 have a relieved portion 16 and 17 respectively which is shaped to engage floor 13. The lower portion of the staircase and rails 11 and 12 has a flat beveled portion 18 adapted to rest upon floor 14. The entire staircase is formed in such a manner as to be a one-piece cast reinforced concrete member.

Referring to FIG. 2 there is illustrated in cross-sectional view the staircase in accordance with FIG. 1. As can be seen staircase rail member 11 (and its corresponding rail 12) are of a parallelogram configuration wherein the upper surface of the rails is parallel to the general axis of the stairs and forms the handrail portion thereof. The upper end of rail 11 extends outwardly beyond the top stair 15' with the outermost edge 19 being angled with respect to the stair so as to be perpendicular to floor 13. The lower edge 20 of rail 11 is similarly perpendicular to bottom stair 15".

The flat base of the U-shaped beam comprises the stairs 15. The lower side 29 is cast so as to present a flat smooth surface while the upper side has been shaped to form the stairs 15. In the construction of the staircase reinforcing rods of steel are utilized. A partial showing is made in phantom in FIG. 2 of the U-shaped reinforcing rods 21 which are joined as by welding to stringer rods 22. Both rods 21 and stringers 22 extend the length of the staircase to define the cage. Welding of the rods to form the cage extending the length of staircase 10 is accomplished prior to insertion of the rods into the mold, illustrated in FIGS. 4 and 5, to give additional strength to the overall construction.

As the staircase is a mobile unit adapted to be lifted into place by a crane there is provided anchor nuts 23 which may, if desired, be welded to the cage member formed of the reinforcing rods. These anchor nuts are cast into place at the same time the concrete is poured so as to be firmly embedded therein and in a manner so as to support the weight of the stair when moving same. Bolt members (not shown) are screwed into the anchor nuts for use when the stair is to be moved about. Once the stair is installed the bolt members are removed and the openings in the anchor nuts filled with a suitable material so as to present a smooth surface in the finished product.

The reader's attention is now drawn to FIGS. 6 and 7 which show details of the reinforcing rod construction for the upper portion of the reinforcing cage of the staircase. L-shaped reinforcing rod 24 is welded to an angle iron 25 which also has joined thereto rod irons 26 which project inwardly into the concrete which will be poured about the construction. Dotted outline 27 of FIG. 6 illustrates the final outer form of the poured concrete. The function of angle iron 25 is to serve as a support and tie member for the upper portion of staircase 10 in its joining to floor 13. The dimensions of angle iron 25 are approximately the same as the width of rails 11 and 12 and are positioned directly therebeneath. The angle iron 25 thus provides a broad support structure for the rail members which in turn act as the support for the stairs 15 and adjacent concrete. In actual installation a plate of steel 28 is cast into floor slab 13 when it is formed and when staircase 10 is installed plate 25 is joined as by welding to plate 28, thus insuring that the staircase does not slip out of position. The lower portion of staircase 10 is not fixedly joined to floor 14 but merely rests on flat surface 18 to permit movement due to expansion and contraction arising from changes in temperature.

As illustrative of dimensions involved in the construction of a staircase in accordance with the invention the following values may be taken as typical. The staircase for complete spanning of an interfloor distance of 9 feet has an overall length at the tread portion of about 161/2 feet. The overall height of the rail sections 11 and 12 is approximately 3 feet while the overall width of the staircase is approximately 4 feet. The thickness of rail sections 11 and 12 is approximately 3 inches. The minimum thickness of concrete in the staircase between the back side 29 and bottom of risers to stairs 15 is 3 inches. For a staircase with these dimensions the weight would be approximately 2 tons.

Construction of a reinforced concrete stair without the use of the U-shaped construction of the present invention would require as a minimum thickness at least 7 inches of concrete between the base of the risers to stairs 15 and the back side of the stair. This heavy thickness of concrete, absent the deep U-shape construction of the present invention, is necessary in order to make the stair self-supporting of its own weight and the loads to be anticipated in service. Through the use of the deep U-shaped construction of my invention the stairs are supported, not by their own strength alone, but are largely supported by hanging from the side rails 11 and 12 which form a high strength structural member for such support. As has already been noted angle plates 25 are the supporting surfaces for rails 11 and 12. Very little of the support for the stairs portion results from the concrete along the length of the stair. Rather, individual stairs are principally supported from arms 11 and 12. The overall construction provides not only an extremely strong construction but simultaneously provides an integral railing with the construction which is immediately serviceable as a safety factor during the construction period as well as lending itself to a finished staircase appearance after the building has been completed.

Referring now to FIGS. 4 and 5 there is illustrated respectively in side elevational view and in cross-sectional view along lines 5--5 of FIG. 4 a mold for use in forming the staircase of the invention. The mold is constructed of steel panel members which are joined together as by welding to form a finished mold used in the inverted staircase orientation as seen best in FIG. 5. The interior facing surfaces of the mold are smooth and are treated with a suitable release agent to minimize any tendency of the fresh concrete to bond thereto. The arm portions of the mold 31 and 32 are shaped so that the upper ends of rails 11 and 12 will be somewhat thinner than the lower portion of the rails as an aid to releasing the rail portions from the mold. The tread portions of the mold are formed by angled sheets of steel which are welded to the side rail forming portions of the mold.

The cradle of reinforcing steel rods, shown in the other views to the drawings, is introduced into the mold chamber and concrete is poured therein to surround the reinforcing rods. The open side of the mold is then smoothed off to form the smooth back surface of the staircase. After the concrete has become suitably set the mold is freed from the now formed staircase.

Claims

I claim:

1. A mobile unitary precast reinforced concrete staircase and handrail of relatively low weight adapted to span a space between horizontally and vertically spaced landings comprising a plurality of U-shaped reinforcing rods spaced in generally parallel relationship to one another with the arms and base portions of each of said U-shaped rods being in a plane with the corresponding arms and base portions of the balance of said U-shaped rods longitudinal reinforcing rods extending generally transverse to said U-shaped rods said longitudinal rods being in spaced and generally parallel relationship to one another with a plurality of longitudinal rods on each arm and on the base portion of said U-shaped rods and welded to said U-shaped rods joining them to form a cage, concrete encapsulating said cage to form a U-shaped beam member with the concrete of the base of said U-shaped beam member forming a plane on the lower side thereof and being configured on the upper interior facing side thereof into a plurality of riser and tread surfaces thereby defining a stairs, each of the arm portions of said U-shaped beam extending upwardly from said stairs being relatively thin in thickness and integral with said base portion and having the overall shape of a parallelogram with the longitudinal sides thereof parallel to the general plane of the stairs, said arm portions having a height above said tread surfaces corresponding to a hand rail height, the longitudinally remote ends of said arm portions extending at least to each end of said stairs and having an angle therewith so as to be substantially perpendicular to the ground when said staircase is installed.

2. In combination first and second horizontally and vertically spaced landings, the upper of said landings including a steel plate fastened thereto adjacent the landing edge thereof, a unitary precast reinforced concrete staircase of relatively low weight spanning the space between said landings, said staircase comprised of a unitary elongated U-shaped beam member of reinforced concrete, the base portion of said U-shaped beam being configures on the upper interior facing side thereof into a plurality of risers and tread surfaces thereby defining a stairs, each of the arm portions of said U-shaped beam being relatively thin in thickness and integral with said base portion and having an overall shape of a parallelogram with the longitudinal sides thereof parallel to the general plane of the stairs, said arms having a height generally corresponding to a hand rail height, the longitudinally remote ends of said arms extending at least to each end of said stairs with the upper ends of said arms extending beyond said stairs, the ends of said arms having an angle with said stairs so as to be substantially perpendicular to the ground when said staircase is in the installed position, the portion of said arms extending beyond the upper end of said stairs having a relieved portion at the lower extended edge thereof constructed and arranged to engage an upper surface of the landing, the relieved portion including an angle iron covering the bearing surfaces of said relieved portion, said angle iron being joined to reinforcing rods embedded in the concrete of said staircase, said angle iron also being joined to said steel plate on said upper landing to prevent movement thereof with respect to said landing and the lower portion of said staircase being in sliding engagement with the upper surface of the lower landing.

3. A mobile unitary precast reinforced concrete staircase and handrail of relatively low weight adapted to span a space between horizontally and vertically spaced landings comprising: an elongated U-shaped beam member comprised of a unitary body of reinforced concrete; the base portion of the said U-shaped beam having a plane surface on the outer side thereof and being configured on the upper interior facing side thereof into a plurality of risers and tread surfaces thereby defining a stairs; each of the arm portions of said U-shaped beam being relatively thin in thickness and integral with said base portion and having the overall shape of a parallelogram with the longitudinal sides thereof parallel to the general plane of the stairs, said arms having a height generally corresponding to a hand rail height, the longitudinally remote ends of the said arms extending at least to each end of said stairs, the upper ends of said arms extending beyond the topmost stair and having a relieved portion at the lower extended edge thereof constructed to engage an upper surface of a landing with the lower ends of said arms shaped to engage a surface of a lower landing to thereby have said arms provide the principal support for said stairs and the remote ends of said arms having an angle with said stairs so as to be substantially perpendicular to the ground when said staircase is installed.

4. A staircase in accordance with claim 3 wherein said relieved portion includes a horizontal surface substantially on a plane with the topmost stair tread, said horizontal surface being adapted to provide the bearing surface for engagement with the upper surface of a landing.

5. A staircase in accordance with claim 3 wherein said relieved portion includes an angle iron covering the bearing surfaces of said relieved portion, said angle iron being joined to reinforcing rods embedded in the concrete of said staircase.