US3601221A

US3601221A - Stairs

Info

Publication number: US3601221A
Application number: US881885A
Authority: US
Inventors: Guillermo Fuentes
Original assignee: Individual
Current assignee: Individual
Priority date: 1969-12-10
Filing date: 1969-12-10
Publication date: 1971-08-24
Anticipated expiration: 1988-08-24

Abstract

A staircase and method of constructing it wherein steps of generally triangular cross section have angles formed by the three sides determined in accordance with a prescribed formula, the steps mounted to a stringer with one side of the step substantially horizontal and a selected one of the two other sides mounted to the top of the stringer. The step mountings are located in accordance with the prescribed formula. The stringer is mounted between two floors inclined within a range of angles.

Description

United States Patent Guillermo Fuemw FOREIGN PATENTS 801,232 12/1950 Germany Primary Examiner-Reinaldo P. Machado Attorney- Kingsland, Rogers, Ezell, Eilers & Robbins ABSTRACT: A staircase and method of constructing it wherein steps of generally triangular cross section have angles formed by the three sides determined in accordance with a prescribed formula, the steps mounted to a stringer with one side of the step substantially horizontal and a selected one of the two other sides mounted to the top of the stringer. The step mountings are located in accordance with the prescribed formula. The stringer is mounted between two floors inclined within a range of angles.

PATENTED AUG24 I971 SHEET 1 [1F 2 STAIRS BACKGROUND or THE INVENTION carpenter must usually custom fit the stairs at the construction site. Also, the designs of staircases used prior to this invention often required custom fabrication of each staircase to insure proper fit and design. I

In this regard there is a formula well known in the art, which gives the relationship between the vertical distance between thefto ps of two successive steps and the effective width of the steps. This formula is 2R+T=25 inches, where R is the vertical distance in inches and T is the width in inches. Stairs designed in accordance with this formula give the most natural stepping arrangement. It has, also been found that the value of R should be-within the range of approximately 7-8 inches. Values of R outside this approximate range render the stairs uncomfortable for use.

Thus designers try generally to design stairs in accordance with the above formula and with values of R within this approximate range.

Therefore, it would be very desirable to design a staircase the. parts of which could be fabricated at the factory and which would fit any designrequirement within a specific range of values of R. For example, it would be desirable to design such a staircase which would fit any design requirement within R variations of from 7-8 inches and maintain the relationship of R to T, as prescribed by the formula-for any of these variations; This invention is such a staircase.

BRIEF SUMMARY OF THE'INVENTION The staircase of this invention includes one or more stringers mounted between the floors to be connected by the stairs. Also included are a plurality of steps or treads which are mounted to rest on the top of the stringer. The steps are of generally triangular cross section with one side of the step being substantially horizontal for use as the stepping surface, and the other two sides each being potential mounting surfaces. The angles formed by the sides of the steps are determined in accordance with the formula 2R+T=25 inches, as arefthe locations of the means for mounting the steps to the stringers. The stairs and stringers can be prefabricated and the mounting locations predetermined at the factory for a given range of values of R, so that installation at the job site can be accomplished quickly and easily and without the need to customize to particular design requirement (so long, of

- course, as the design requirement is within the range of R for which the stairs were fabricated). Stairs designed for ranges of R from 7-8 inches will nearly always fit the requirement since this isthe normal comfort range. A single-step design of this invention will accommodate this entire range and always maintain the formulated R-T relationship.

Because the stepping surface will vary approximately oneeighth' inch from horizontal over this range of R, adjustments may be provided to level the stepping surface. However, because the variation from horizontal is so slight, the adjustmentsmay be omitted if desired.

Various types of handrails may be mounted to the steps or stringers. Also, because the steps rest on the stringers, the stringers being merely for support, the stringers may be of any of several types and sizes. The steps themselves can be fabricated of any of several materials conventionally used.

BRIEF DESCRIPTION OF THE DRAWING 1 FIGS. 1-6 are schematic illustrations showing the stair construction ofthis invention for various stringer angles;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Because the stairs of this invention are designed to fit within a range of design requirements, it is first necessary to determine what the necessary range is. In this regard there is a for- I mula well known to the art, as follows: 2R+T=25 inches. This formula gives the relationship between R and T where R is the vertical distance between the tops of two adjacent stair steps and T is the effective width of the stepping surface of each of the steps. This formula is very old in theart, and formulates what has been found to be the most natural stepping arrangement, that is, where this relationship between R and T is not maintained the stairs are uncomfortable for use. Therefore, it is desirable in the design of any stairs to maintain this relationship. It'has also been found desirable to maintain R (the vertical distance between the tops of two adjacent steps) within a range of 7-8 inches, again it having been found that values of R less than 7 inches or greater than 8 inches result in an uncomfortable stair design. Therefore, by far the most common stair designs are designed in accordance with the above formula and with values of R ranging from 7-8 inches. Obviously, as R increases, the value of T decreases, and the angle of inclination between the stairs and the floors which it connects also increases. Therefore, as an example, it will be shown how one stair design of this invention can be used to accommodate all stair slopes as R varies between 7 and 8 inches, and still maintain the relationship between R and T set forth in the above formula.

Referring to F IG.. 1, there is shown schematically, two

steps

10 and 11, of generally triangular cross section mounted on a stringer 12. A line 13 represents the floor. The angle f is the angle between the stringer 12 and the floor 13. The

steps

10 and 11 have a substantially horizontal stepping surface b and mounting surfaces c and d. Each step has front and

rear edges

14 and 15 respectively as shown in the drawing. The distance A is the distance between the tops of the

steps

10 and 11, and the distance B is the width of the effective stepping surface of each of the steps. From the formula 2R+T=25 inches, where R is 7 inches, T is equal to 1 1 inches. With this information the value of the angle f can easily be determined using trigonometric equations as follows:

tanj -7/ ll=0.636 f=3230' In like manner the angle f can be determined for any value of R. Where R equals 8 inches, T is equal to 9 inches and the value of the angle f is given as follows: tan f=8/9=0.88, f= 4130. Hence it can be seen that as R varies from 7 to 8 inches, the angle f varies from approximately 3230 to 4130 and that the value of T varies between 1 1 inches and 9 inches.

values of R. This is particularly important because of what happens to the effective width of the steps as R, and, therefore, the angle of inclination of the stringer, increases.

In FIG. 1, A is 7 inches so that the effective width B, of the

steps

10 and 11 is ll inches in accordance with the formula 2R+T==25 inches, therefore, the steps are mounted so that the front edge 14 of the step 11 is vertically aligned with the back edge 15 of the step 10. This allows the entire width (l 1 inches) of the stepping surface to be used. FIG. 3 illustrates steps having the same dimensions and mounted the same distance apart on the stringer 12 with the same faces d resting on the stringer 12. With R equal to 7% inches the angle f equals 36. As the angle f varies from 3230 to 36 the front edge 14 of the step 11 will be caused to overlap the back edge 15 of the step 10 approximately three-quarter inch. This in effect reduces the efi'ective stepping surface B of the step 10 to 10% inches which is exactly in accordance with the formula 2R+T=25 inches. Hence, it can be seen that as the angle f increases the effective stepping surface B decreases to values which maintain the relationship between R and T in accordance with the formula.

Also, as the angle f increases, the stepping surface b will deviate from horizontal. That is, if the stepping surface b is horizontal when the angle f equals 34 it will slope to the front as f increases and to the rear as f decreases. Slight slopes to either the front or the rear are acceptable and even desirable in some cases, but excessive slopes such as for example, onefourth inch or more are not desirable. In this regard it is found that by using either side or d of the step as mounting surfaces, and by appropriately choosing the angles formed by the sides of the steps, the deviation j from horizontal of the stepping surface can be kept to a maximum of approximately one-eighth inch. Hence, as R varies between 7 and 8 inches the maximum deviation j from horizontal of the stepping surface of each of the steps will be approximately one-eighth inch in either the forward or rearward direction. Such a deviation is practically unnoticeable to the user and in some cases desirable for cleaning purposes.

This optimum condition can be obtained where the angle y between the stepping surface b and the surface d of each of the steps is approximately 34 and the angle x between the stepping surface b and the surface c is approximately 38. With a step so constructed the surface d is used for the mounting surface for angles of inclination between 3230 and 37 and the surface c is used as the mounting surface for angles of inclination between 37 and 4130. FIGS. 1-6 illustrate the deviations from horizontal of the stepping surface b between angles of inclination of 3230 and 4130. FIG. 1 shows a rearward deviation from horizontal of approximately oneeighth inch using mounting surface d and FIG. 6 shows a forward deviation from horizontal of approximately one-eighth inch using mounting surface c.

Hence, FIGS. 1-6 illustrate how one step design can accommodate stringer angles of from approximately 3230 to 4130 corresponding to values of R from 7-8 inches while maintaining the formulated relationship between R and T and with maximum stepping surfaces deviation from horizontal of approximately one-eighth inch.

FIG. 7 illustrates a typical stair design of this invention. There is shown a lower floor 30 and an upper floor 31, a stringer 32 is mounted to the

floors

30 and 31 by any suitable means such as

angle brackets

33 and 34. A tread or step 35 designed as described above, is mounted with its appropriate mounting surface 36 resting on the top of the stringer 32. The step 35 is fastened to the stringer 32 by any suitable means such as a bolt 37 and an inserted nut 38. A cover-board 40 may be inserted between the stringer 32 and the steps 35 if desired. The cover-board 40 is simply used to cover the space between the steps 35. A baluster 41 is mounted to the step 35 by various means as will be hereinafter described.

FIGS. 8 and 9 are schematic illustrations showing how wedges 20 can be inserted under either the bottom or top edge of the mounting surface to level the stepping surface where deviations occur. The wedges may be omitted if desired, since the maximum deviation of approximately one-eighth inch is practically unnotieeable.

FIG. shows the versatility of the stairs design of this invention in the materials from which the steps may be constructed. The step 43 is constructed from solid wood, such as oak. The step 44 has a molded plywood bottom 45 and a solid top 46. The step 47 has a molded plywood bottom 45 and a vinyl asbestos surface 48. The step 49 is fabricated of concrete with an exposed aggregate top 50. A mounting insert 51 is used for mounting the step to the stringer. The step 52 is constructed of concrete with a smooth surface 53 and inserts 54 in the side of the step for supporting the baluster. The step 55 is still another type of step fabricated from metal. This step is constructed of two angle brackets 56 each constructed in accordance with the design described above which are mounted on a pair of stringers (not shown). The stepping surface 57 is a metal grating. Holes 58 are provided on each of the mounting surfaces for mounting the brackets 56 to the stringers. In this embodiment, instead of wedges, leveling screws 59 are provided for leveling the stepping surface b of each of the steps. Holes (not shown) can be provided in the grating 57 for receiving balusters, which can then be mounted to the sides of the brackets 56. The step 60 shows a similar step construction only with the metal grating replaced by concrete slab 61. The concrete slab 61 is reinforced with a plurality of steel bars 62. A hole (not shown) may be provided in the concrete slab to receive a baluster for mounting to the angle brackets 56.

FIG. 11 shows a variety of stringers which may be used with this invention. The stringer 70 is composed of a 2X6 wooden support 71 with one-fourth inch plywood at the top 72 and bottom 73. The steps are mounted to the stringer with bolts 74 and angle brackets 75. A l 6 inch closure board 76 may be provided to hide the bolts 74.

Stringers

78 and 79 are other types of wood stringers similar to the stringer 70. The stringer 78 includes a maple core 80 between oak supports 81 and 82. The stringer 79 is fabricated simply of 2X6inch oak. The

stringers

90, 91, 92, and 93 are various types of metal stringers. The stringer is a metal angle stringer. The stringer 91 is a metal angle stringer with a metal cover plate 94 to hide the mounting bolts. The stringer 92 is a metal I-beam stringer, and the stringer 93 is a metal stringer of open web construction.

FIG. 12 illustrates various types of baluster mounts that can be used with the steps of this invention. The mount illustrates a baluster 101 mounted to the side of the step with lag bolts 102. The mount 103 illustrates a baluster 104 with a threaded end 105. The end 105 is inserted through a hole in the stepping surface b, and is threaded into an inserted nut 106. The mount 107 shows a baluster 108 inserted into holes 10? and 110 that extend through the stepping surface b and the unused mounting surface 111 of the step with a stop plate 112 for limiting the penetration of the baluster 108 into the step. Obviously, the balusters can be made of many different materials and can be used in combination with a great variety of hand rails.

Itshould now be evident that one of the features of this invention is the great variety of materials and accessories that can be used. This is particularly true of the stringers. Because the steps are not inserted into the side of the stringer as is done in many of the conventional step designs, it is possible to use stringers of substantially smaller cross section. In many of the old step designs the. stringers had to be 10 inches wide to accommodate the necessary width of the stepping surface. Notice in FIG. 11 that a stringer width of 6 inches is sufficient to support the steps of this invention resulting in substantial savings in, materials and expense.

Hence, this invention provides a stair construction that can be prefabricated with a great variety of materials and accessories to fit a wide range of design requirements without changing the stair design, and still maintain the formulated relationship between R and T.

Various changes and modifications may be made within the purview of this invention as will be readily apparent to those skilled in the art. Such changes and modifications are within the scope and teaching of this invention as defined by the claims appended hereto.

1. A stair construction for connecting adjacent floors comprising at least one stringer mounted between the two floors, a plurality of steps mounted on the stringer, each of the steps having a generally triangular cross section at least where the step is mounted on the stringer, one side of the triangle defining a substantially horizontal stepping surface and the other two sides defining potential mounting surfaces, the angles between each of the other sides and the stepping surface being such that with the step mounted to the stringer on one mounting surface the stepping surface is substantially horizontal through afirst prescribed range of stringer inclination angles, and with the step mounted on the stringer on the other mounting surface the stepping surface is substantially horizontal through a second prescribed range of stringer inclination angles, means associated with each of the other two sides and the stringer for mounting the steps to the stringer, with the select one of the other two sides resting on top of the stringer so that the stepping surface is nearest to horizontal, the stringer being mounted at an angle of inclination of any angle of theranges of angles.

2. The stair construction of claim 1 wherein the angles between the other sides and the stepping surface and the location of the mounting means are determined in accordance with the formula 2R+T=25 inches, where R is the vertical distance in inches between the tops of two successive stepping surfaces, and T is the width in inches of the effective stepping surface.

3. The stair construction of claim 2 wherein the second range of angles of inclination at which the stringer can be mounted is continuous with the first to define a continuous total range of stringer inclination angles.

4. The stair construction of claim 3 wherein the total range of stringer inclination angles is from approximately 32 to 42.

5. The stair construction of claim 2 wherein the angles formed by the other two sides and the stepping surface are approximately 34 and 38.

v 6. The stair construction of claim 2 including means for leveling the stepping surface.

7. The stair construction of claim 1 wherein the steps are of constant generally triangular cross section.

8. The stair construction of claim 1 wherein the mounting means associated with each of the other two sides and the sembly.

. variety of stringer inclinations comprising the steps of constructing a plurality of generally triangular cross section steps at least where the steps are mounted on a stringer, with one side of each of the steps defining a substantially horizontal stepping surface and the other two sides potential mounting surfaces, and with the angles formed by each of the mounting surfaces and the stepping surface determined in accordance with the formula 2R+T=25 inches, where R is the vertical distance in inches between the tops of two successive stepping surfaces, and T is the width in inches of the effective stepping surface, providing means for mounting the steps to a stringer with either of the mounting surfaces resting on the topof the stringer in accordance with the formula 2 R+T=25 inches, mounting the stringer between the floors to be connected by the stairs with an angle of inclination within a range of angles resulting in a deviation from horizontal of the stepping surface of approximately one-half of an inch or less with the steps mounted on the select one of the mounting surfaces which provides the most nearly horizontal orientation of the stepping surface, and mounting the steps with the select one of the two mounting surfaces resting on the top of the stringer so that the stepping'surface is nearest to horizontal.

10. The method of claim 9 wherein R varies from approximately 7-8 inches.

1 l. The method of claim 9 wherein the step of constructing a plurality of steps is performed with the angles formed by the mounting surfaces and the stepping surface being approximately 34 and 38.

12. The method of claim 9 wherein the step of mounting the steps comprises placing the steps in the mounting position on the stringer with the select one of the two mounting surfaces resting on the top of the stringer so that the stepp ng surface 15 nearest to horizontal, leveling the stepping surface as necessary and securing the steps to the stringer.

13. The stair construction of claim 2 wherein the angles between the other sides and the stepping surface are selected such that the maximum deviation of the stepping surface from horizontal through the ranges of inclination angles is approximately one-half inch.

Claims

1. A stair construction for connecting adjacent floors comprising at least one stringer mounted between the two floors, a plurality of steps mounted on the stringer, each of the steps having a generally triangular cross section at least where the step is mounted on the stringer, one side of the triangle defining a substantially horizontal stepping surface and the other two sides defining potential mounting surfaces, the angles between each of the other sides and the stepping surface being such that with the step mounted to the stringer on one mounting surface the stepping surface is substantially horizontal through a first prescribed range of stringer inclination angles, and with the step mounted on the stringer on the other mounting surface the stepping surface is substantially horizontal through a second prescribed range of stringer inclination angles, means associated with each of the other two sides and the stringer for mounting the steps to the stringer, with the select one of the other two sides resting on top of the stringer so that the stepping surface is nearest to horizontal, the stringer being mounted at an angle of inclination of any angle of the ranges of angles.

2. The stair construction of claim 1 wherein the angles between the other sides and the stepping surface and the location of the mounting means are determined in accordance with the formula 2R+T 25 inches, where R is the vertical distance in inches between the tops of two successive stepping surfaces, and T is the width in inches of the effective stepping surface.

4. The stair construction of claim 3 wherein the total range of stringer inclination angles is from approximately 32* to 42*.

5. The stair construction of claim 2 wherein the angles formed by the other two sides and the stepping surface are approximately 34* and 38*.

6. The stair construction of claim 2 including means for leveling the stepping surface.

8. The stair construction of claim 1 wherein the mounting means associated with each of the other two sides and the stringer are prelocated during the manufacture of the stair assembly.

9. The method of constructing a stair assembly to fit a wide variety of stringer inclinations comprising the steps of constructing a plurality of generally triangular cross section steps at least where the steps are mounted on a stringer, with one side of each of the steps defining a substantially horizontal stepping surface and the other two sides potential mounting surfaces, and with the angles formed by each of the mounting surfaces and the stepping surface determined in accordance with the formula 2R+T 25 inches, where R is the vertical distance in inches between the tops of two successive stepping surfaces, and T is the width in inches of the effective stepping surface, providing means for mounting the steps to a stringer with either of the mounting surfaces resting on the top of the stringer in accordance with the formula 2 R+T 25 inches, mounting the stringer between the floors to be connected by the stairs with an angle of inclination within a range of angles resulting in a deviation from horizontal of the stepping surface of approximately one-half of an inch or less with the steps mounted on the select one of the mounting surfaces which provides the most nearly horizontal orientation of the stepping surface, and mounting the steps with the select one of the two mounting surfaces resting on the top of the stringer so that the stepping surface is nearest to horizontal.

10. The method of claim 9 wherein R varies from approximately 7-8 inches.

11. The method of claim 9 wherein the step of constructing a plurality of steps is performed with the angles formed by the mounting surfaces and the stepping surface being approximately 34* and 38*.

12. The method of claim 9 wherein the step of mounting the steps comprises placing the steps in the mounting position on the stringer with the select one of the two mounting surfaces resting on the top of the stringer so that the stepping surface is nearest to horizontal, leveling the stepping surface as necessary and securing the steps to the stringer.