Patent Publication Number: US-7900403-B2

Title: Log staircase and a method of producing components for a log staircase

Description:
FIELD OF THE INVENTION 
     This invention relates to a log staircase and a method of producing components for a log staircase. 
     BACKGROUND OF THE INVENTION 
     The various components needed for installing a log staircase in a new log home or log building can be produced or fabricated at a manufacturer in a controlled environment. The manufacturer can produce the needed stringers, treads, etc. to specific dimensions such that the log staircase will have a particular length, height, angle of inclination, and a desired number of treads. The various components, including any needed fasteners, can then be bundled and shipped to the building site where the log staircase is to be installed. The installation of the log staircase into the new log home or log building can occur at an appropriate time in the construction cycle. This process has been successfully used in building log homes, many of which are located in remote areas. In the case of manufacturing internal and external log staircases, multiple C-shaped notches are formed in each of a pair of support stringers. Each of the C-shaped notches extends through more than half of the diameter of each stringer. Each tread or step is shaped to have a semicircular periphery with a flat surface. The flat surface forms the step portion of each tread. The semicircular periphery of each tread is designed to be positioned within one of the multiple C-shaped notches formed in each of the pair of stringers. During installation, the pair of stringers is secured in place between a lower level and an upper level. The semicircular periphery of each tread is then positioned in a pair of the C-shaped notches so as to bridge across the pair of stringers. Each tread is then shimmed and adjusted to obtain a horizontal alignment from left to right and from front to back. Once a tread is properly aligned, it is then secured in place by appropriate hardware, such as lag screws or bolts. 
     As is evident from the above description, the installation of such a log staircase normally requires two skilled laborers who have some previous experience with installing such log staircases. With each log staircase, it is very important that each tread or step be attached between the pair of stringers such that it lies in a horizontal plane from left to right and from front to back. Since the size and location of each C-shaped notch can vary depending upon the diameter of each stringer and because the semicircular periphery of each tread can also vary, it becomes necessary to shim and adjust each tread to obtain proper alignment. Each tread is then fastened in place to prevent movement, wobble, rotation or rocking. If the treads are not properly aligned, they can create a safety hazard to a person walking up or down the log staircase. Furthermore, if each tread is not horizontally aligned and evenly spaced from an adjacent tread, the log staircase will not pass building code. 
     Now, a log staircase and a method of producing components for a log staircase have been invented that allow a log staircase to be installed at a building site more quickly and efficiently, and in a manner that will satisfy building code. In addition, the log staircase can be installed by two persons that may not be skilled laborers in this task. 
     SUMMARY OF THE INVENTION 
     Briefly, this invention relates to an interior or an exterior log staircase. The log staircase includes an elongated stringer capable of angularly extending from a lower level to an upper level. The stringer has an outer circumference with one or more notches formed therein which do not extend through more than half of the diameter of the stringer. A protuberance extends upward from each of the notches. The log staircase also includes one or more treads each having a semicircular periphery with a flat surface. An opening is formed in the semicircular periphery and is aligned at an acute angle to the flat surface. The opening is capable of mating with one of the protuberances formed in the stringer to retain the flat surface of the tread crossways to the stringer. 
     In another embodiment, the log staircase includes a pair of elongated, spaced apart stringers. One stringer is aligned parallel to the other stringer and each stringer is capable of angularly extending from a lower level to an upper level. Each of the pair of stringers has an outer circumference with a number of notches formed therein. The notches do not extend through more than half of the diameter of each stringer. Each of the notches formed in one stringer is aligned horizontally along a common axis with one of the multiple notches formed in the other stringer. In addition, each of the notches has a protuberance extending upward therefrom. The log staircase also includes a number of treads each having a semicircular periphery with a flat surface. Each of the treads has a pair of spaced apart openings formed in the semicircular periphery with each of the openings being aligned at an acute angle to the flat surface. Each of the pair of openings is capable of mating with one of the protuberances formed in each of the stringers to retain each of the flat surfaces of the tread crossways to the pair of stringers. 
     The method of producing components for a log staircase includes selecting a pair of elongated, dried natural logs free of bark as stringers. Each of the pair of stringers has a length and an outer circumference with a relatively constant diameter extending along the length thereof. The outer circumference of one of the pair of stringers is similar in size to the outer circumference of the other stringer. The method also includes cutting a number of notches into the outer circumference of each of the pair of stringers. The notches do not extend through more than half of the diameter of each stringer. Each of the notches is longitudinally aligned with one another and each has a protuberance extending upward therefrom. Each of the notches formed in one of the pair of stringers is aligned horizontally along a common axis with one of the notches formed in the other stringer. The method further includes forming a predetermined number of treads equal to the number of notches formed in each of the pair of stringers. Each of the treads has a semicircular periphery with a flat surface. A pair of spaced apart openings is cut into the semicircular periphery of each of the treads and each is aligned at an acute angle to the flat surface. Each of the pair of openings is capable of mating with one of the protuberances formed in each of the pair of stringers. Lastly, the method includes gathering or bundling together the pair of stringers and the predetermined number of treads for shipment to a customer. 
     The general object of this invention is to provide a log staircase for connecting separate levels. A more specific object of this invention is to provide a method of producing components for a log staircase. 
     Another object of this invention is to provide an interior or an exterior log staircase which can be easily assembled at a building site. 
     A further object of this invention is to provide a log staircase for a log home or log building which requires less time to assemble at a building site. 
     Still another object of this invention is to provide a log staircase which allows each tread to be horizontally secured from left to right and from front to back to a pair of stringers. 
     Still further, an object of this invention is to provide a log staircase which utilizes a pair of openings formed in each of the treads wherein each opening is designed to mate with a protuberance formed in each of the pair of stringers to provide a secure attachment therebetween. 
     Other objects and advantages of the present invention will become more apparent to those skilled in the art in view of the following description and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a prior art log staircase showing a pair of log stringers each having multiple C-shaped notches cut therein which extend through more than half of the diameter of each stringer and with a semicircular tread removed to show a close up view of two of the C-shaped notches. 
         FIG. 2  is a perspective view of a log staircase installed between a lower level and an upper level and showing 13 semicircular treads secured to a pair of spaced apart log stringers. 
         FIG. 3  is a perspective view of an alternative embodiment of a log staircase having a single log stringer and two treads. 
         FIG. 4  is a perspective view of still another embodiment of a log staircase having three log stringers and two treads. 
         FIG. 5  is a side view of the log staircase shown in  FIG. 2  depicting how each tread is positioned relative to each log stringer and showing adjacent treads separated by a set distance. 
         FIG. 6  is a perspective view of a log stringer having an outer circumference with a number of notches cut therein, each notch having a protuberance extending upward therefrom. 
         FIG. 7  is a perspective view of a portion of the log stringer shown in  FIG. 6  depicting the configuration of one of the notches and the protuberance extending outward therefrom. 
         FIG. 8  is a top view of the portion of the log stringer shown in  FIG. 7   
         FIG. 9  is a cross-sectional view of the portion of the log stringer shown in  FIG. 7  taken along line  9 - 9 . 
         FIG. 10  is a side view of the portion of the log stringer shown in  FIG. 7  taken along line  10 - 10  depicting the side configuration of the notch and the protuberance. 
         FIG. 11  is a perspective view of the bottom surface of one of the treads shown in  FIG. 2  depicting a pair of spaced apart openings. 
         FIG. 12  is a perspective view of the left half of the tread shown in  FIG. 11  showing one of the openings. 
         FIG. 13  is a side view of the tread shown in  FIG. 12  taken along line  13 - 13  depicting the side configuration of the opening. 
         FIG. 14  is a top view of the tread shown in  FIG. 12 . 
         FIG. 15  is a cross-sectional view of the tread shown in  FIG. 12  taken along line  15 - 15 . 
         FIG. 16  is a perspective view of a portion of a log stringer and a portion of a tread showing an alternative embodiment for the notch and protuberance formed in the log stringer and an alternative embodiment for the mating opening formed in the tread. 
         FIG. 17  is an assembly view showing the tread and log stringer shown in  FIG. 16  mated together. 
         FIG. 18  is a cross-sectional view of  FIG. 17  taken along line  18 - 18 . 
         FIG. 19  is a cross-sectional view of  FIG. 18  taken along line  19 - 19 . 
         FIG. 20  is a perspective view of a portion of a log stringer and a portion of a tread showing another embodiment for the notch and protuberance formed in the log stringer and another embodiment for the mating opening formed in the tread. 
         FIG. 21  is an assembly view showing the tread and log stringer shown in  FIG. 20  mated together. 
         FIG. 22  is a cross-sectional view of  FIG. 21  taken along line  22 - 22 . 
         FIG. 23  is a cross-sectional view of  FIG. 22  taken along line  23 - 23 . 
         FIG. 24  is a perspective view of a portion of a log stringer and a portion of a tread showing still another embodiment for the notch and protuberance formed in the log stringer and still another embodiment for the mating opening formed in the tread. 
         FIG. 25  is an assembly view showing the tread and log stringer shown in  FIG. 24  mated together. 
         FIG. 26  is a cross-sectional view of  FIG. 25  taken along line  26 - 26 . 
         FIG. 27  is a cross-sectional view of  FIG. 26  taken along line  27 - 27 . 
         FIG. 28  is a perspective view of a portion of a log stringer and a portion of a tread showing a fourth embodiment for the notch and protuberance formed in the log stringer and a fourth embodiment for the mating opening formed in the tread. 
         FIG. 29  is an assembly view showing the tread and log stringer shown in  FIG. 28  mated together. 
         FIG. 30  is a cross-sectional view of  FIG. 29  taken along line  30 - 30 . 
         FIG. 31  is a cross-sectional view of  FIG. 30  taken along line  31 - 31 . 
         FIG. 32  is a perspective view of a portion of a log stringer and a portion of a tread showing a fifth embodiment for the notch and protuberance formed in the log stringer and a fifth embodiment for the mating opening formed in the tread. 
         FIG. 33  is an assembly view showing the tread and log stringer shown in  FIG. 32  mated together. 
         FIG. 34  is a cross-sectional view of  FIG. 33  taken along line  34 - 34 . 
         FIG. 35  is a flow diagram of a method of producing components for a log staircase. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 , a prior art log staircase  10  is shown which includes a pair of spaced apart log stringers  12  each having an outer diameter of approximately the same diameter. Each log stringer  12  has multiple C-shaped notches  14  cut therein. Each C-shaped notch  14  removes more than 50% of the material forming the outer diameter at that particular location. A number of wooden treads  16 , equal to the number of multiple C-shaped notches  14  formed in each log stringer  12 , are horizontally positioned across the pair of log stringers  12 . Each of the wooden treads  16  has a semicircular periphery  18  with a flat upper surface  20 . The semicircular periphery  18  of each wooden tread  16  is positioned in a pair of the C-shaped notches  14  and is secured in place by appropriate hardware (not shown), such as lag screw, bolts, etc. One drawback with this design is that the semicircular periphery  18  of each wooden tread  16  is not perfectly round and therefore is able to move, wobble, rotate and/or rock within the pair of C-shaped notches. Because of this, shims must be inserted and adjustment need to be made to ensure that each wooden tread  16  lies in a horizontal plane within a pair of the C-shaped notches  14 . Each wooden tread  16  must be horizontally aligned from left to right and from front to back. Furthermore, each wooden tread  16  must be at a set vertical distance from an adjacent wooden tread  16  in order to satisfy existing building code. Once the wooden treads  16  are properly adjusted, appropriate hardware is used to secure each of the wooden treads  16  to the pair of stringers  12 . 
     Referring to  FIG. 2 , a log staircase  22  is shown which can be either an interior log staircase or an exterior log staircase. By “interior log staircase” it is meant a log staircase that is installed within a home, building or other structure. By “exterior log staircase” it is meant a log staircase that is installed on the outside of a home, building or other structure. An exterior log staircase is usually exposed to the elements. The log staircase  22  includes at least one stringer  24  and one or more treads  26  secured to the stringer  24 . In  FIG. 2 , a pair of spaced apart elongated stringers  24 , each having approximately the same diameter, is depicted having thirteen treads  26  secured across the pair of stringers  24 . The pair of stringers  24  is aligned parallel to one another and they can be spaced apart by any desired distance. A distance of from about 1 foot to about 5 feet is common. The pair of stringers  24  is typically installed at an angle ranging anywhere from between about 20 degrees to about 55 degrees. The pair of stringers  24  angularly extends between a lower level  28  and an upper level  30 . For example, the lower level  28  can be a ground floor and the upper level  30  can be a second floor. Alternatively, the lower level  28  can be a basement, the ground floor, a first floor, a first landing, a second floor, etc. and the upper level  30  can be the first floor, a porch, a second floor, a second landing, an attic, etc. Wherever situated, the upper level  30  is located vertically above to the lower level  28 . 
     Each of the pair of stringers  24  is depicted as having an outer circumference and an overall cylindrical shape. By “outer circumference” it is meant a boundary line of a circle, figure, area or object. Each stringer  24  has a first end  32  and a second end  34 . Each of the stringers  24  has a longitudinal central axis X-X and a length l measured between the first and second ends,  32  and  34  respectively. The length l of a stringer  24  can vary depending upon the height, width and angle of inclination of the log staircase as well as the material from which each stringer  24  is formed. 
     As shown in  FIG. 2 , each stringer  24  is depicted as a full wooden natural log. The log can be from a hardwood tree or from a softwood tree. The log can come from various trees or shrubs, including but not limited to: conifers, white cedar, red cedar, Northern white pine, Norway or red pine, Southern yellow pine, lodge pole pine, jack pine, Douglas fir, hemlock, oak, maple, etc. By “conifer” it is meant any of various mostly needle-leaved or scale-leaved, chiefly evergreen, cone-bearing gymnospermous trees or shrubs, such as pines, spruces and firs. By “cedar” it is meant any of several Old World evergreen coniferous trees of the genus Cedrus, having stiff needles and large seed cones or any of several other evergreen coniferous trees or shrubs, such as the incense cedar or red cedar. In addition, each stringer  24  can be constructed of metal, iron, aluminum, a metal alloy, thermoplastics, composite materials, fiberglass, reinforced fiberglass, etc. or be formed from one or more materials that is covered or wrapped in a wood veneer or a material appearing to be wood. By “veneer” it is meant a thin surface layer, as of wood, glued to a base material or a decorative facing. Desirably, each stringer  24  is constructed from a full log that has had the bark removed. The log can be dried such as by air drying, kiln drying or by a combination of both air and kiln drying. The log can be left unfinished or it can be coated, stained or painted with a lacquer, shellac, a varnish or some other coating or paint. By “lacquer” it is meant any of various clear or colored synthetic coatings made by dissolving cellulose derivatives together with plastizers in volatile solvents and used to impart a high gloss to the surface. By “shellac” it is meant a thin varnish made by dissolving this substance in denatured alcohol, used to finish wood. By “varnish” it is meant a paint containing a solvent and an oxidizing or evaporating binder, used to coat a surface with a hard, glossy transparent film. 
     Optionally each stringer  24  can be a full wooden log that has been mechanically peeled to give it the appearance of having been hand peeled. In past years, logs were scraped with a hand tool, such as a draw knife, to remove the bark and/or to shape the diameter of the log. After the logs were peeled or scraped, they exhibited shave marks on the outer surface which are now considered to be aesthetically pleasing in appearance. In addition, most logs contain one or more cracks, checks, knots, etc. which will enhance the rustic appeal of the log but which do not compromise its structural integrity. Desirably, such cracks, checks, knots etc. should be left in their natural state and should not be covered up. 
     Still referring to  FIG. 2 , each stringer  24  has a diameter d which is relatively constant along its length l. The diameter d can range from between about 6 inches to about 13 inches. Desirably, the diameter d of each stringer  24  ranges from between about 8 inches to about 12 inches. More desirably, the diameter d of each stringer  24  ranges from between about 9 inches to about 11 inches. Most desirably, the diameter d of each stringer  24  is about 10 inches. Due to the removal of any bark and/or the mechanical peeling process mentioned above, the outer circumference of each stringer  24  will not be perfectly round and the diameter d will not be a constant from the first end  32  to the second end  34 . However, each stringer  24  will have a generally cylindrical shape of a relatively constant diameter d, plus or minus a couple of inches, from the first end  32  to the second end  34 . In addition, when two or more stringers  24  are utilized, each of the stringers  24  should have a diameter d and an outer circumference which are similar, although not identical, in size to the other stringers  24 . 
     Referring now to  FIG. 3 , a log staircase  22 ′ is shown having a single stringer  24  having two treads  26  secure to it. Each of the treads  26  extend crossways or perpendicular to the longitudinal central axis X-X of the stringer  24 . In addition, the upper tread  26  is vertically spaced a set distance above the lower tread  26 . 
     Referring to  FIG. 4 , a log staircase  22 ″ is shown having three spaced apart stringers  24  aligned parallel to one another. Two treads  26  are secure across the three stringer  24  in a crossways or perpendicular fashion relative to the longitudinal central axis X-X of each stringer  24 . Each of the three stringers  24  can be equally spaced apart from an adjacent stringer  24  or one of the stringers  24  can be aligned closer to one of the other stringers  24 , if desired. Similar to the embodiment shown in  FIG. 3 , the upper tread  26  is vertically spaced a set distance above the lower tread  26 . 
     Referring now to  FIG. 5 , a side view of the log staircase  22  is depicted. The log staircase  22  has a height h, a width w and an angle of inclination θ. The height h is measured as the vertical distance from the lower level  28  upon which the first end  32  of each stringer  24  rests to the upper level  30  which includes the height of the beams, supports, flooring, etc. used to construct the floor of the upper level  30 . The width w is measured as the horizontal distance between an outer edge of the first end  32  to an outer edge of the second end  34 . The angle of inclination θ is measured between the lower level  28  and the lower surface of each stringer  24 . The angle of inclination θ is depicted at approximately 38.5 degrees in  FIG. 5 . However, as mentioned above, the angle of inclination θ can vary to allow the log staircase  22  to fit within the dimensions provided by an architect. For safety reasons, the angle of inclination θ should not exceed 55 degrees. One will also notice that in  FIG. 5 , the elongated stringer  24  has a longitudinal central axis X-X and all of the thirteen treads  26  are secured to the stringer  24  such that they are all located on one side of the longitudinal central axis X-X. It should be understood that the number of treads  26  and the spacing between adjacent treads  26  can vary to suit one&#39;s particular requirements and the building codes of a particular jurisdiction. In  FIG. 5 , the log staircase  22  has a nominal spacing value n. The nominal spacing value n is the distance measured between the inward edge of a lower tread  26  and the lower edge of the adjacently located upper tread  26  at a point where the upper tread  26  intersects the outer circumference of the stringer  24 . The nominal spacing value n can vary to suit one&#39;s particular requirements. The nominal spacing value n can range from between about 3 inches and 5 inches. In  FIG. 5 , the nominal spacing value n is approximately 3.4 inches. 
     Phrased another way, each of the notches  36  formed in a stringer  24  should be spaced at least about 2 inches apart from an adjacent notch  36  when measured parallel to the longitudinal central axis X-X. Desirably, each of the notches  36  formed in a stringer  24  should be spaced at least about 2.25 inches apart from an adjacent notch  36  when measured parallel to the longitudinal central axis X-X. More desirably, each of the notches  36  formed in a stringer  24  should be spaced at least about 2.5 inches apart from an adjacent notch  36  when measured parallel to the longitudinal central axis X-X. When two or more stringers  24  are utilized, the notches  36  formed in each of the stringers  24  should be spaced at least about 2 inches apart from an adjacent notch  36  when measured parallel to the longitudinal central axis X-X. 
     Referring now to  FIGS. 6-10 , the elongated stringer  24  has a relatively constant diameter d and an outer circumference. The outer circumference can be approximately round, circular, oval, elliptical, have a racetrack configuration or have some other geometrical configuration. Typically, the outer circumference is irregular in shape and is not completely round or circular. This is especially true if the log has been subjected to a peeling process. The stringer  24  also has at least one notch  36  formed therein which does not extend more than 50% through the diameter of the stringer  24 . Desirably, the stringer  24  will have from between two to fifteen notches  36 . More desirably, the stringer  24  will have from between three and thirteen notches  36 . If the stringer  24  is used for an exterior staircase  22 , then it will usually have fewer notches  36  than if it was used to form an interior staircase  22 . One reason for this is that an exterior staircase  22 , such as from the ground to a porch will normally only have one to six steps while an interior staircase  22  spanning between a ground floor and the next upper floor will usually have eight to thirteen steps. 
     In  FIG. 6 , the stringer  24  is depicted as having four spaced apart notches  36  although additional notches  36  can be utilized if more steps are required. A notch  36  will be formed in each stringer  24  so as to correspond to the number of treads  26  required for a particular log staircase  22 ,  22 ′ or  22 ″. Desirably, from one to fifteen notches  36  are formed in a staircase  22 ,  22 ′ or  22 ″. More desirably, from two to thirteen notches  36  are formed in a staircase  22 ,  22 ′ or  22 ″. However, in some staircases  22 ,  22 ′ or  22 ″ more than fifteen notches  15  can be utilized. When two or more notches  36  are present, each notch  36  will be equally spaced apart from an adjacent notch  36 . The presence of multiple notches  36  can give each stringer  24  a scallop appearance. By “scallop” it is meant one of a series of curved indentations formed along at least a portion of the length of a member. 
     One can initially vary the size, configuration and height h 1  of the notches  36  one wishes to cut or machine into each stringer  24 . However, when a pair of stringers  24  is utilized to form a log staircase  22 , it should be understood that all of the notches  36  present in the pair of stringers  24  must be identical in size, configuration and height h 1 . As depicted in  FIG. 10 , each of the notches  36  has a height h 1  that should be less than half of the diameter d of the stringer  24  in which it is formed. Desirably, each notch  36  is formed with a height h 1  that is less than 30% of the thickness of the stringer  24 . More desirably, each notch  36  is formed with a height h 1  that is less than 25% of the thickness of the stringer  24 . By forming each notch  36  to be less than half of the thickness of each stringer  24 , one can obtain a stronger log staircase  22  and reduce the likelihood that the stringers  24  will flex during use of the log staircase  22 . Desirably, each notch  36  has a height h 1  of less than about 3.5 inches. More desirably, each notch  36  has a height h 1  ranging from between about 1.5 inches to about 3.5 inches. Even more desirably, each notch  36  has a height h 1  ranging from between about 2 inches to about 3 inches. Most desirably, each notch  36  has a height h 1  of about 2.5 inches. 
     It should be understood that when two or more log stringers  24  are utilized, each log stringer  24  is aligned parallel to one another and each has at least two, and desirably, multiple notches  36  formed therein as is shown in  FIGS. 2 and 4 . The multiple notches  36  formed in one log stringer  24  are horizontally aligned with the multiple notches  36  formed in the other stringer(s)  24 . Desirably, each notch  36  formed in one of the log stringers  24  will be horizontally aligned along a common axis with a notch  36  formed in the other log stringer  24 . 
     As best shown in  FIGS. 7-10 , the notch  36  is uniquely formed. In  FIG. 8 , the notch  36  has a length l 1  and a width w 1 . The length l 1  is measured parallel to the longitudinal central axis X-X while the width w 1  is measured perpendicular to the longitudinal central axis X-X. The length l 1  of the notch  36  is longer than the width w 1 . However, the length l 1  of the notch  36  could be less than or equal to the width w 1  depending upon the configuration of the notch  36 . In  FIGS. 7 and 8 , the notch  36  is depicted as having a partial oval configuration when viewed from the top. The notch  36  can be described as a concave cavity  38  having a squared off end  40  and a lower surface  42 . The lower surface  42  is rough in finish so that it can better grip a mating tread and prevent slippage therebetween. Desirably, the lower surface  42  contains small ridges, serration or corrugations to enhance its ability to grip and retain a mating tread. The concave cavity  38  is best depicted in  FIG. 10  when one views a notch  36  from the side. 
     Still referring to  FIGS. 7 and 8 , a protuberance  44  is positioned within the dimensions of the notch  36 . By “protuberance” it is meant something, such as a bulge, knob or swelling that protrudes upward or outward. Each protuberance  44  has a length l 2  and a width w 2 . The length l 2  and the width w 2  of each protuberance  44  is less than the length l 1  and the width w 1 , respectively, of the notch  36 . Each protuberance  44  can have any desired geometrical shape. In  FIG. 8 , the protuberance  44  is depicted as having a partial oval configuration when viewed from the top. The protuberance  44  extends upward from the lower surface  42  of the concave cavity  38 , see  FIG. 9 . The protuberance  44  has a convex shape extending across its width w 2 . As depicted in  FIG. 8 , the length l 2  of the protuberance  44  is of a greater dimension than the width w 2 . However, as will be understood by those skilled in the art, the length l 2  of the protuberance  44  could be less than or equal to its width w 2 , if desired, depending upon the overall configuration of the protuberance  44 . The length l 2  of the protuberance  44  is aligned parallel to the longitudinal central axis X-X of the stringer  24  in which it is cut or formed. 
     Referring to  FIGS. 9 and 10 , the protuberance  44  has an apex  46  which is located along a line that lies within the confines of the outer circumference of the stringer  24 . Desirably, the apex  46  of the protuberance  44  is aligned approximately parallel to the longitudinal central axis X-X of the stringer  24 . More desirably, the apex  46  of the protuberance  44  is aligned parallel to the longitudinal central axis X-X of the stringer  24 , see  FIG. 10 . The apex  46  of the protuberance  44  can be aligned flush with or be located within the confines of the outer circumference of the stringer  24 . In  FIG. 9 , one can see that the apex  46  is located a distance d 1  within the confines of the outer circumference of the stringer  24 . Desirably, the apex  46  is located a distance d 1  of from between about 0.1 inches to about 2 inches within the confines of the outer circumference of the stringer  24 . Desirably, the apex  46  is located a distance d 1  of from between about 0.75 inches to about 1.5 inches within the confines of the outer circumference of the stringer  24 . More desirably, the apex  46  is located a distance d 1  of at least about 1 inch within the confines of the outer circumference of the stringer  24 . The distance d 1  is measured perpendicular to a point which would be located on the outer circumference if the notch  36  was not present. 
     It should be understood that even though the apex  46  of the protuberance  44  has been explained above as being a line, it could also be a point. 
     Referring to  FIG. 10 , the notch  36  has a height h 1  which is measured from the bottom of the lower surface  42  to the outer circumference. This height h 1  can vary in dimension. Generally, for a stringer  24  having a diameter d of 13 inches or less, the height h a  of the notch  36  will range from between about 1.5 inches to about 3.5 inches. Desirably, the height h 1  of the notch  36  will range from between about 2 inches to about 3 inches. More desirably, the height h 1  of the notch  36  will be about 2.5 inches. The notch  36  can also be formed with a radius r. The notch  36  can have a radius r which ranges from between about 5 inches to about 9 inches. Desirably, the notch  36  can have a radius r which ranges from between about 6 inches to about 8 inches. More desirably, the notch  36  can have a radius r which ranges from between about 6.5 inches to about 7.5 inches. 
     It should be noted that the above described notch  36  and protuberance  44  design is now being referred to by the manufacturer who employs the inventors as a “DUAL COPE LOG STAIRWAY”. DUAL COPE LOG STAIRWAY is a State of Wisconsin registered trademark owned by The Armstrong Creek Company having an office at 612 C Avenue, Goodman, Wis. 54125. 
     Referring now to  FIG. 11 , a tread  48  is shown which is designed to be secured to two spaced apart stringers  24  which are aligned parallel to one another. The tread  48  can be half of a full wooden natural log cut lengthwise. The tread  48  is identical to the tread  26  shown in  FIG. 2 . The tread  48  can be formed from a log which is of the same species as the logs used for the stringers  24  or it can be of a different species. Desirably, the treads  48  and the stringers  24  are from the same tree species. The tread  48  has a half round appearance with a semicircular periphery  50  and a flat surface  52 . The semicircular periphery  50  may not be constant over its entire length. The tread  48  has a longitudinal central axis X 1 -X 1 . As with the stringers  24 , each tread  48  should have any bark removed and can be processed to have a peeled appearance. Each tread  48  has a diameter d 2  which will correspond to the width of the flat surface  52 . The diameter d 2  or the width of the flat surface  52  is aligned perpendicular to the longitudinal central axis X 1 -X 1 . The diameter d 2  of each tread  48  can range from between about 7 inches to about 14 inches. Desirably, the diameter d 2  of each tread  48  can range from between about 9 inches to about 13 inches. More desirably, the diameter d 2  of each tread  48  can range from between about 10 inches to about 12.5 inches. Even more desirably, the diameter d 2  of each tread  48  can range from between about 11 inches to about 12 inches. Typically, in designing a log staircase  22  to be both functional and aesthetically pleasing, the diameter d 2  or width of each tread  48  should be larger in dimension than the diameter d of each stringer  24 . Desirably, each of the pair of stringers  24  has a diameter d of at least 6 inches and the flat surface  52  of each tread  48  has a width that is at least 1 inch greater than the diameter d of each of the pair of stringers  24 . 
     Multiple treads  26  or  48  can be used to construct a staircase  22 ,  22 ′ or  22 ″. The number of treads  26  or  48  will vary depending upon the height h of the staircase  22 ,  22 ′ or  22 ″ and the vertical spacing between each of the treads  26  or  48 . Typically, the number of treads  26  or  48  used in a staircase  22 ,  22 ′ or  22 ″ can range from 1 to 25 treads  26  or  48 . Desirably, from one to fifteen treads  26  or  48  are present in each staircase  22 ,  22 ′ or  22 ″. More desirably, from two to thirteen treads  26  or  48  are present in each staircase  22 ,  22 ′ or  22 ″. 
     In  FIG. 11 , each tread  48  has a length l 3  which can vary for each log staircase. In the log staircase  22  shown in  FIG. 2  wherein a pair of stringers  24  is present, each tread  26  can have a length l 3  which can range from between about 2 feet to about 6 feet. Desirably, when the log staircase  22  utilizes a pair of stringers  24 , each tread  26  has a length l 3  of between about 3 feet to about 5 feet. In a log staircase  22 ′, such as that shown in  FIG. 3  having a single stringer  24 , each tread  26  can have a length l 3  which can range from between about 1 foot to about 3 feet. Desirably, when the log staircase  22 ′ utilizes a single stringer  24 , each tread  26  has a length l 3  of between about 1.5 feet to about 2.5 feet. In a log staircase  22 ″, such as that shown in  FIG. 4  having three stringers  24 , each tread  26  can have a length l 3  which can range from between about 6 feet to about 14 feet. Desirably, when the log staircase  22 ″ utilizes three stringers  24 , each tread  26  has a length l 3  of between about 8 feet to about 12 feet. 
     Referring to  FIG. 2 , the flat surface  52  of each tread  26  forms the upper portion of each step when assembled into the log staircase  22 ,  22 ′ or  22 ″. The semicircular periphery  50  of each tread  26  will form the lower or underneath portion of each step of the assembled log staircase  22 ,  22 ′ or  22 ″. 
     Returning to  FIG. 11 , one or more openings  54  are formed in the semicircular periphery  50 . The number of openings  54  will correspond to the number of stringers  24  the log staircase  22 ,  22 ′ or  22 ″ will utilize. For example, in  FIG. 3 , one opening  54  is formed in each tread  26 ; in  FIG. 4 , three openings  54  are formed in each tread  26 ; and in  FIG. 2 , two openings  54  are formed in each tread  26 . The openings  54  can vary in configuration. In  FIG. 11  each of the openings  54  has the appearance of a concave pocket. The openings  54  are aligned at an acute angle to the flat surface  52 . By an “acute angle” it is meant an angle of less than 90 degrees. In  FIG. 11 , two openings  54  are depicted, each spaced apart by the same distance that the pair of stringers  24  will be spaced apart. Each of the openings  54  is aligned perpendicular to the longitudinal central axis X 1 -X 1 . Each opening  54  is sized, shaped and configured to mate with one of the protuberances  44  formed in each notch  36  cut into the pair of stringers  24 . By “mate” it is meant to join closely. Desirably, each opening  54  can be machined or cut so as to be slightly larger in size, from between about 0.25 inches to about 0.0375 inches larger, than the protuberance  44  it will mate with. This small size difference provides for final adjustment of each tread  48  relative to the pair of stringers  24 . When each of the openings  54  mates with one of the protuberances  44  formed in each of the pair of stringers  24 , the tread  48  will be secured across the pair of stringers  24  such that the flat surface  52  of each tread  48  extends horizontally crossways relative to the pair of stringers  24 . By “crossways” it is meant to be or lie in a cross direction; across. Each tread  48  also has a first end  56  and a second end  58 . When each of the treads  48  is securely affixed across the pair of stringers  24 , the first and second ends,  56  and  58  respectively, will extend horizontally outward beyond the diameters d of each of the pair of stringers  24 . The distance that each of the first and second ends,  56  and  58  respectively, can extend outward beyond the diameter d of each of the pair of stringers  24  can vary but normally will range from between about 6 inches to about 2 feet, see  FIG. 2 . 
     Referring now to  FIGS. 12-15 , the left half of the tread  48  is shown to better depict the configuration of one of the openings  54 . As mentioned above, the opening  54  is configured as a concave pocket although other configurations can be used. In  FIG. 14 , the opening  54  has a width w 3  measured parallel to the longitudinal central axis X 1 -X 1 . The width w 3  can range from between about 4 inches to about 8 inches. Desirably, each opening  54  has a width w 3  which can range from between about 5 inches to about 7 inches. More desirably, each opening  54  has a width w 3  which can range from between about 5.5 inches to about 6.5 inches. 
     Still referring to  FIG. 14 , each opening  54  is at least partially surrounded by an enlarged pocket  60 . The enlarged pocket  60  can have any desired geometrical configuration. In  FIG. 14 , the enlarged pocket  60  is depicted as having at least a partial oval shaped perimeter. The enlarged pocket  60  extends outward from a portion of the openings  54 . Desirably, each enlarged pocket  60  extends outward in multiple directions from the periphery of at least a portion of the opening  54 . Each of the enlarged pockets  60  has a width w 4  which is at least about 1 inch larger than the width w 3  of the opening  54 . Desirably, each of the enlarged pockets  60  has a width w 4  which is at least about 2 inches larger than the width w 3  of the opening  54 . More desirably, each of the enlarged pockets  60  has a width w 4  which is at least about 2.5 inches larger than the width w 3  of the opening  54 . 
     Referring to  FIG. 15 , each enlarged pocket  60  can be formed with a radius r 1 . The enlarged pocket  60  can have a radius r 1  which ranges from between about 5 inches to about 9 inches. Desirably, the enlarged pocket  60  can have a radius r 1  which ranges from between about 6 inches to about 8 inches. More desirably, the enlarged pocket  60  can have a radius r 1  which ranges from between about 6.5 inches to about 7.5 inches. Each enlarged pocket  60  also has a height h 2  of less than about 1 inch. Desirably, each enlarged pocket  60  has a height h 2  of less than about 0.5 inches. The function of the enlarged pocket  60  is to mate with the concave cavity  38  of one of the notches  36  formed in each of the stringers  24 . By so mating, the tread  48  can be properly situated into one of the notches  36  and the protuberance  44  can be positioned within the opening  54 . During assembly of the treads  48  into the notches  36  formed in a pair of stringers  24 , builders caulk, an adhesive such as a construction adhesive, glue or some other kind of binding agent known to those skilled in the art, can be used to secure the two members  36  and  48  together. 
     The engagement between the protuberance  44  and the opening  54  is so precise that each tread  48  is horizontally positioned relative to a pair of stringers  24 . Each of the treads  48  will lie in a horizontal plane from left to right, from the first end  56  to the second end  58 , and from front to back. Many state building codes specify the range of tilt from front to back of each tread  48  that is permissible before a violation is cited. In some jurisdictions, the amount of tilt is limited to about 0.25 inches. The present invention eliminates the need to use shims to obtain a horizontally level tread  48 . By “shim” it is meant a thin, often tapered piece of material, such as wood, stone, or metal, used to fill gaps, make something level, or adjust something to fit properly. 
     Once one of the treads  48  is secured in respective horizontally aligned notches  36  between a pair of stringers  24 , a small diameter pilot hole (not shown) can be drilled from the underside of the stringer  24  such that it enters into the semicircular periphery  50  of a given tread  48 . A countersink or counter bore (not shown) can also be formed about the exterior surface of the pilot hole. By “countersink or counter bore” it is meant a hole with the top part enlarged so that the head of a screw or bolt will lie flush with or below the surface. The countersink or counter bore is sized to receive a wooden plug. A screw, such as a wood screw or a lag screw, or a threaded bolt (not shown) can then be screwed into the pilot hole to securely fasten the tread  48  to the stringer  24 . A wooden plug is then inserted into the countersink or counter bore and is cut and/or sanded down to blend in with the semicircular periphery  50  of the tread  48  such that it becomes unnoticeable. The wooden plug can be of the same wood used to construct the stringer  24 . Alternatively, a pilot hole can be drilled down through the flat surface  52  of the tread such that it enters the protuberance  44 . A countersink or counter bore can also be formed about the exterior surface of the pilot hole. The countersink or counter bore is again sized to receive a wooden plug. A screw, such as a wood screw or a lag screw, or a threaded bolt (not shown) can then be screwed into the pilot hole to securely fasten the tread  48  to the stringer  24 . A wooden plug is then inserted into the countersink or counter bore and is cut and/or sanded down to blend in with the flat surface  52  of the tread  48  such that it becomes unnoticeable. The wooden plug can be of the same wood used to construct the tread  48 . 
     Referring to  FIGS. 16-19 , another embodiment is shown depicting a portion of a log stringer  62  having a longitudinal central axis X 2 -X 2  and a portion of a tread  64  having a longitudinal central axis X 2 -X 2 . In this embodiment, called the wedge design, an oval shaped protuberance  44 ′ is formed in the log stringer  62  which is aligned perpendicular to the longitudinal central axis X 2 -X 2  of the log stringer  62 . In addition, an oval shaped opening  54 ′ is formed in the tread  64  which is aligned parallel to the longitudinal central axis X 2 -X 2  of the tread  64 . The opening  54 ′ is slightly larger in size than the protuberance  44 ′ to allow for minor adjustments, if necessary. The opening  54 ′ is intended to mate with the protuberance  44 ′ to secure the tread  64  to the log stringer  62 . An adhesive or glue can also be used, as was explained above to form a more secure attachment. 
     Referring to  FIGS. 20-23 , still another embodiment is shown depicting a portion of a log stringer  66  having a longitudinal central axis X 3 -X 3  and a portion of a tread  68  having a longitudinal central axis X 3 -X 3 . In this embodiment, called the slice design, a protuberance  44 ″ in the shape of a portion of a narrow disc is formed in the log stringer  66  and is aligned perpendicular to the longitudinal central axis X 3 -X 3  of the stringer  66 . In addition, a key shaped slot opening  54 ″ is formed in the tread  68  and is aligned parallel to the longitudinal central axis X 3 -X 3  of the tread  64 . The opening  54 ″ is slightly larger in size than the protuberance  44 ″ to allow for minor adjustments, if necessary. The opening  54 ″ is intended to mate with the protuberance  44 ″ to secure the tread  68  to the log stringer  66 . An adhesive or glue can also be used, as was explained above to form a more secure attachment. 
     Referring to  FIGS. 24-27 , a further embodiment is shown depicting a portion of a log stringer  70  having a longitudinal central axis X 4 -X 4  and a portion of a tread  72  having a longitudinal central axis X 4 -X 4 . In this embodiment, called the notch design, a notch  36 ′ is formed in the log stringer  66  which has a side wall  74 . The notch  36 ′ is aligned perpendicular to the longitudinal central axis X 4 -X 4  of the log stringer  66 . The side wall  74  functions as a protuberance  44 ,  44 ′ or  44 ″. In this embodiment, the periphery of the side wall  74  is flush with the outer circumference of the log stringer  70  instead of being inboard of it. In addition, a concave notch  76  is formed in the tread  72  and the longest dimension of the concave notch  76  is aligned parallel to the longitudinal central axis X 4 -X 4  of the tread  64 . The concave notch  76  is slightly larger in size than the notch  36 ′ to allow for minor adjustments, if necessary. The concave notch  76  is intended to mate with the notch  36 ′ to secure the tread  72  to the log stringer  70 . An adhesive or glue can also be used, as was explained above to form a more secure attachment. 
     Referring to  FIGS. 28-31 , still another embodiment is shown depicting a portion of a log stringer  78  having a longitudinal central axis X 5 -X 5  and a portion of a tread  80  having a longitudinal central axis X 5 -X 5 . In this embodiment, called the slot design, a protuberance  82  is formed within a concave cavity  38 ′ formed in the log stringer  78 . The long dimension of the protuberance  82  is aligned parallel to the longitudinal central axis X 5 -X 5  of the log stringer  78 . In addition, a key shaped slot opening  84  is formed in the tread  80  and the longest dimension of the key shaped slot opening  38 ′ is aligned perpendicular to the longitudinal central axis X 5 -X 5  of the tread  80 . The key shaped slot opening  84  is slightly larger in size than the protuberance  82  to allow for minor adjustments, if necessary. The key shaped slot opening  84  is intended to mate with the protuberance  82  to secure the tread  80  to the log stringer  78 . An adhesive or glue can also be used, as was explained above to form a more secure attachment. 
     Referring to  FIGS. 32-34 , a further embodiment is shown depicting a portion of a log stringer  86  having a longitudinal central axis X 6 -X 6  and a portion of a tread  88  having a longitudinal central axis X 6 -X 6 . In this embodiment, called the dowel design, a protuberance  90  is formed within a concave cavity  38 ″ formed in the log stringer  86 . The protuberance  90  is in the shape of a dowel rod which extends outward from the center of the log stringer  86  and is aligned perpendicular to the longitudinal central axis X 6 -X 6  of the log stringer  86 . In addition, an aperture or opening  92  is formed in the tread  88  and the aperture  92  is aligned perpendicular to the longitudinal central axis X 6 -X 6  of the tread  88 . The aperture  92  is slightly larger in size than the protuberance  90  to allow for minor adjustments, if necessary. The aperture  92  is intended to mate with the protuberance  90  to secure the tread  88  to the log stringer  86 . An adhesive or glue can also be used, as was explained above to form a more secure attachment. 
     Method 
     A method of producing components for a log staircase  22 ,  22 ′ or  22 ″ will now be explained. The method includes the steps of selecting a pair of elongated, dried natural logs. The logs can be conifer logs. Any bark that may be present on the logs is removed such that each log is free of bark. The logs can then be subjected to a peeling process where scraps are formed in the outer circumferences of each log to make it appear similar to a log that has been hand peeled using a draw knife. If the log staircase  22  requires a pair of stringers  24 , two logs of approximately the same outer circumference and diameter d are selected. No two logs will have a constant diameter but a relatively constant diameter will suffice. Each of the pair of stringers  24  has a length and an outer circumference which is relatively constant along its length. The outer circumference of one of the pair of stringers  24  will be similar in size to the outer circumference of the other stringer  24 . One or more notches  36  are cut or formed into the outer circumference of each of the pair of stringers  24 . Each of the notches  36  is longitudinally aligned with the other notches  36  and each notch  36  has a protuberance  44  extending upward or outward therefrom. Each of the notches  36  formed in one of the pair of stringers  24  is aligned horizontally along a common axis with one of the notches  36  formed in the other stringer  24 . The method also includes forming a predetermined number of treads  48  equal to the number of notches  36  formed in each of the pair of stringers  24 . Each of the treads  48  has a semicircular periphery  50  with a flat surface  52 . Each of the treads  48  has a pair of spaced apart openings  54  cut into the semicircular periphery  50  which are aligned at an acute angle to the flat surface  52 . Each of the pair of openings  54  is capable of mating with one of the protuberances  44  formed in each of the pair of stringers  24 . The method further includes gathering together the pair of stringers  24  and the predetermined number of treads  48  for shipment to a customer. 
     Optionally, the method can further include drilling apertures in each of the treads  48  such that the apertures are aligned with each of the openings or concave pockets  54 . The apertures can extend from the flat surface  52  of a tread  48  or from the underside semicircular periphery  50  of a tread  48 . A countersink or a counter bore can then be formed in the flat surface  52  of each of the predetermined number of treads  48 . Alternatively, the countersink or a counter bore can then be formed in spherical periphery  50  of each of the predetermined number of treads  48 . The countersink or counter bore will be coaxially aligned with one of the apertures and a wooden plug can be provided which can be inserted into the countersink or counter bore once a fastener has been inserted therein. The fastener will act to secure and retain the tread  48  to each of the stringers  24 . 
     The method can further include providing a number of fasteners which can be used to secure each of the predetermined number of treads  48  to each of the pair of stringers  24 . 
     While the invention has been described in conjunction with several specific embodiments, it is to be understood that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, this invention is intended to embrace all such alternatives, modifications and variations which fall within the spirit and scope of the appended claims.