CA2023574C - Articulating stairway - Google Patents
Articulating stairwayInfo
- Publication number
- CA2023574C CA2023574C CA 2023574 CA2023574A CA2023574C CA 2023574 C CA2023574 C CA 2023574C CA 2023574 CA2023574 CA 2023574 CA 2023574 A CA2023574 A CA 2023574A CA 2023574 C CA2023574 C CA 2023574C
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- stairway
- rails
- pair
- pairs
- parallel
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Abstract
An articulating stairway, having a first pair of horizontally spaced, parallel rails and a second pair of horizontally spaced, parallel rails aligned above the first pair of rails. A plurality of treads are provided, with each tread being pivotally connected between the first and second pairs of rails on two vertically aligned, parallel, horizontal axes. The axes remain vertically aligned as one end of the stairway pivots above or below the other end of the stairway, keeping the treads level throughout.
Description
~ ARTICULATING 8TAIRWAY
Field of the Invention This application pertains to an articulating stairway having stair treads which remain level as one end of the stairway articulates through a range of positions above, below or level with the other end of the stairway.
Background of the Invention There are a variety of situations in which it is desirable to extend a stairway between two levels which are vertically displaced by an unknown distance, or by a distance which changes over time. Consider, for example, a tidal water ship berthed adjacent a dock. The vertical displacement between the deck of the ship and the dock changes over time as the tides ebb and flow. The vertical displacement between the deck of the ship and the dock also changes over time as the ship is loaded and/or unloaded, whether the ship is in tidal water or not. If the ship is in tidal water its deck may be displaced through a vertical range of 50 or more feet by the combined effects the tide and the ship's load. That is, the deck of a fully loaded ship riding at low tide may be 50 feet or more lower than the deck of the same ship riding unloaded at high tide. It will thus be understood that large vertical displacements must be accommo-dated by stairways (gangways) which extend between a dock and atidal water ship berthed adjacent the dock.
The prior art has evolved a variety of stairway structures having treads which remain level while one end of the stairway is raised or lowered relative to the other end. For example, United States Patent No. 298,212 issued 6 May, 1884 for an invention of T. I. Knight entitled "Gangway For Ships"
provides a gangway in which a plurality of treads are pivotally connected between inner and outer pairs of parallel rails which swing past one another as one end of the gangway is raised or lowered relative to the other end. The structure is somewhat complex and therefore relatively expensive to construct.
-United States Patent No. 1,167,893 issued 11 January, 1916 for an invention of P. J. Fickinger entitled "Compensating Stairway" p~ovides a stairway having a somewhat complicated system of gears and chains for maintaining the treads level as one end of the stairway is raised or lowered relative to the other end. United States Patent No. 1,215,827 issued 13 February, 1917 for an invention of E. R. Lord entitled "Landing Steps" provides another stairway whose treads are kept level by lo a rather complex gear drive mechanism as one end of the stairway is raised or lowered relative to the other end. The mechanical complexity of the Fickinger and Lord structures increases their capital cost and also increases the risk of mechanical failure.
United States Patent No. 4,013,140 issued 22 March, 1977 for an invention of Jacques Pradon entitled "Safety Equipment" provides a stairway whose treads are pivotally connected between a single pair of lower, parallel "strings" such that the treads remain level as one end of the stairway is raised or lowered relative to the other end. The treads are fixed to uprights which are in turn pivotally connected to a pair of upper, parallel rails surmounted by a handrail. The "strings"
are pivotally connected at one end to a fixed support, but the ends of the upper rails are not fixed. The upper rails may therefore be displaced along their longitudinal axes. Such displacement would alter the plane of the treads, by tilting them away from the horizontal.
United States Patent No. 4,168,764 issued 25 September, 1979 for an invention of Tom Walters entitled "Level Step Stair Walkway" is similar to the Knight structure, in that the stair - treads are pivotally connected between inner and outer pairs of parallel rails which swing past one another as one end of the gangway is raised or lowered relative to the other end. The structure is relatively complex and expensive.
The present invention provides an mechanically simple, inexpensive, articulating stairway whose treads remain level as one end of the stairway articulates through a large vertical displacement range relative to the other end of the stairway.
Summary of the Invention In accordance with the preferred embodiment, the invention provides an articulating stairway, having a first pair of horizontally spaced, parallel rails and a second pair of horizontally spaced, parallel rails aligned above the first pair of rails. A plurality of treads are provided, with each tread being pivotally connected between the first and second pairs of rails on two vertically aligned, parallel, horizontal axes.
First and second pivot pins extend from the opposed ends of each tread to form one of the axes aforesaid. First and second risers project from the opposed ends of each tread. Third and fourth pivot pins extend from each of the risers to form the other axis.
The preferred embodiment of the invention may be alternatively characterized as providing an articulating stairway having a first pair of horizontally spaced, parallel rails and a second pair of horizontally spaced, parallel rails aligned above the first pair of rails, with a plurality of treads extending horizontally between the rails. A pair of risers project from the opposed ends of each tread. Each riser is pivotally connected between vertically aligned pairs of points on the first and second pairs of rails. The vertically aligned pairs of points remain vertically aligned as one end of the stairway pivots above or below the other end of the stairway.
The first and second pairs of rails are positioned such that vertical separation between the upper surfaces of the first pair of rails and the lower surfaces of the second pair of rails is a maximum when both ends of the stairway are level with one another; decreases as one end of the stairway pivots 202~S74 above or below the other end of the stairway; and, decreases to zero as one end of the stairway pivots to the maximum possible extent above or below the other end of the stairway.
First, second, third and fourth brackets are provided.
The respective brackets are pivotally connected between verti-cally opposed ends of one rail of the first pair of rails and one rail of the second pair of rails on two vertically aligned, parallel, horizontal axes.
Brief Description of the Drawinqs Figure 1 is an oblique pictorial illustration of an articulating stairway constructed in accordance with the preferred embodiment of the invention.
Figure 2 is a side elevation view of the articulating stairway of Figure 1 (viewed from the rear side of Figure 1).
In Figure 2, phantom lines are used to show the maximum extent to which the left end of the stairway may pivot above or below the right end of the stairway.
Figure 3 is an enlarged cross-sectional illustration taken with respect to line 3-3 of Figure 1 to provide details of the stair treads and the brackets which pivotally connect the vertically opposed rail ends together.
Figure 4 is an enlarged cross-sectional illustration taken with respect to line 4-4 of Figure 2 to provide further details of the stair treads.
Detailed Description of the Preferred Embodiment The drawings illustrate an articulating stairway 10 having a first pair of horizontally spaced, parallel rails 12, 14 and a second pair of horizontally spaced, parallel rails 16, 18 aligned above rails 12, 14 respectively. A plurality of stair treads 20, 22, 24, etc. are provided. As hereinafter described in greater detail, each tread is pivotally connected between the `. 2023574 first and second pairs of rails on two vertically aligned, parallel, horizontal axes such as axes 26, 28 illustrated in Figure 3 for tread 30. A handrail (shown in phantom outline in Figure 1) may be provided as a safety feature, and also to improve the structural integrity of stairway 10 (for example, by fixing a plurality of bracing struts between the handrail and the upper surfaces of rails 16, 18 as illustrated in Figure 2).
As best seen in Figure 4, a first pivot pin 32 extends from one end of stair tread 30 to pivotally engage within a reinforced aperture 34 in rail 14. A second pivot pin 36 extends from the horizontally opposed end of stair tread 30 to pivotally engage within reinforced aperture 38 in the horizontally opposed rail 12. Horizontally aligned pivot pins 32, 36 form horizontal axis 26. A first riser 40 projects upwardly at the end of tread 30 from which first pivot pin 32 extends. A second, identical riser 42 projects upwardly at the end of tread 30 from which second pivot pin 36 extends. A third pivot pin 44 extends from the upper end of riser 40 to pivotally engage within reinforced aperture 46 in rail 18. A fourth pivot pin 48 extends from the upper, horizontally opposed end of riser 42 to pivotally engage within reinforced aperture 50 in the horizontally opposed rail 16. Horizontally aligned pivot pins 44, 48 form horizontal axis 28. All of the stair treads are similarly pivotally connected between the first and second pairs of rails. The horizontal axes which intersect the first pair of rails 12, 14 lie in one plane;
and, the horizontal axes which intersect the second pair of rails 16, 18 lie in another plane parallel to the first plane.
As best seen in Figure 3, a bracket 52 is pivotally connected between the vertically opposed ends 54, 56 of rails 14, 18 on two vertically aligned, parallel, horizontal axes 58, 60.
Axis 58 lies in the same plane as the aforesaid horizontal axes which intersect the first pair of rails 12, 14; and, axis 60 lies in the same plane as the horizontal axes which intersect the second pair of rails 16, 18.
~ As best seen in Figure 2, the first and second pairs of rails are positioned such that the vertical separation between the upper surfaces 62 of the first pair of rails 12, 14 and the lower surfaces 64 of the second pair of rails 16, 18 is a maximum "a" when both ends of stairway 10 are level with one another.
The vertical separation decreases, as shown at "b", as one end of stairway 10 pivots above or below the other end of stairway 10. The vertical separation decreases to zero (i.e. the upper surfaces 62 of the first pair of rails 12, 14 contact the lower surfaces 64 of the second pair of rails 16, 18 as shown at "c") as one end of stairway 10 pivots to the maximum possible extent above or below the other end of stairway 10.
In operation, stairway 10 may, for example, be mounted on a suitable support structure atop a dock (not shown). If a ship (not shown) is berthed at the dock then one end of stairway 10 is extended, with the aid of a crane, and placed on the deck of the ship. The other end of stairway 10 remains on the dock, with provision being made for the dock end of the stairway to slide back and forth along the longitudinal axis of stairway 10 as stairway lo articulates in the following manner.
As the tides ebb and flow (assuming the ship to be in tidal water) and/or as the ship is loaded and unloaded, the vertical displacement between the dock and the ship's deck changes. Suppose for example that the ship is initially unloaded and riding at high tide. In this case the ship end of stairway 10 will likely be displaced vertically above the dock end of stairway 10 by a significant amount. Now, suppose that the same ship is fully loaded and riding at low tide beside the same dock.
In this case the ship end of stairway 10 will likely be displaced vertically below the dock end of stairway 10 by a significant amount. In between the two extremes aforesaid the ship end of stairway 10 is displaced vertically through a wide range of positions, relative to the dock end of stairway 10, with the dock end of stairway 10 sliding back and forth along the longitudinal axis of stairway 10. At all times the treads of stairway 10 are 202357~
kept level because they are supported, as aforesaid, by risers which are pivotally connected between vertically aligned pairs of axes intersecting the first and second pairs of rails, such that each vertically aligned pair of axes remains vertically aligned as one end of stairway 10 pivots above or below the other end of stairway 10.
As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifica-tions are possible in the practice of this invention withoutdeparting from the spirit or scope thereof. For example, instead of focusing on a horizontal "neutral" position, as heretofore assumed, one could instead focus upon a vertical neutral position. This could be accomplished by mounting the stair treads at positions rotated 90 with respect to the positions shown in the drawings, and by supporting one end of stairway 10 on a horizontal surface, so that the structure extended verti-cally upward from that surface. The upper end of the stairway could then be allowed to pivot off the vertical, to either side.
The stair treads would remain level because, in this orientation of the stairway, the risers are pivotally connected between horizontally aligned pairs of axes intersecting the first and second pairs of rails, such that each horizontal aligned pair of axes remains horizontally aligned as the upper end of the stairway pivoted to one side or the other relative of the lower end of the stairway. Accordingly, the scope of the invention is to be construed in accordance with the substance defined by the following claims by interchanging the terms vertical and horizontal as circumstances may require.
Field of the Invention This application pertains to an articulating stairway having stair treads which remain level as one end of the stairway articulates through a range of positions above, below or level with the other end of the stairway.
Background of the Invention There are a variety of situations in which it is desirable to extend a stairway between two levels which are vertically displaced by an unknown distance, or by a distance which changes over time. Consider, for example, a tidal water ship berthed adjacent a dock. The vertical displacement between the deck of the ship and the dock changes over time as the tides ebb and flow. The vertical displacement between the deck of the ship and the dock also changes over time as the ship is loaded and/or unloaded, whether the ship is in tidal water or not. If the ship is in tidal water its deck may be displaced through a vertical range of 50 or more feet by the combined effects the tide and the ship's load. That is, the deck of a fully loaded ship riding at low tide may be 50 feet or more lower than the deck of the same ship riding unloaded at high tide. It will thus be understood that large vertical displacements must be accommo-dated by stairways (gangways) which extend between a dock and atidal water ship berthed adjacent the dock.
The prior art has evolved a variety of stairway structures having treads which remain level while one end of the stairway is raised or lowered relative to the other end. For example, United States Patent No. 298,212 issued 6 May, 1884 for an invention of T. I. Knight entitled "Gangway For Ships"
provides a gangway in which a plurality of treads are pivotally connected between inner and outer pairs of parallel rails which swing past one another as one end of the gangway is raised or lowered relative to the other end. The structure is somewhat complex and therefore relatively expensive to construct.
-United States Patent No. 1,167,893 issued 11 January, 1916 for an invention of P. J. Fickinger entitled "Compensating Stairway" p~ovides a stairway having a somewhat complicated system of gears and chains for maintaining the treads level as one end of the stairway is raised or lowered relative to the other end. United States Patent No. 1,215,827 issued 13 February, 1917 for an invention of E. R. Lord entitled "Landing Steps" provides another stairway whose treads are kept level by lo a rather complex gear drive mechanism as one end of the stairway is raised or lowered relative to the other end. The mechanical complexity of the Fickinger and Lord structures increases their capital cost and also increases the risk of mechanical failure.
United States Patent No. 4,013,140 issued 22 March, 1977 for an invention of Jacques Pradon entitled "Safety Equipment" provides a stairway whose treads are pivotally connected between a single pair of lower, parallel "strings" such that the treads remain level as one end of the stairway is raised or lowered relative to the other end. The treads are fixed to uprights which are in turn pivotally connected to a pair of upper, parallel rails surmounted by a handrail. The "strings"
are pivotally connected at one end to a fixed support, but the ends of the upper rails are not fixed. The upper rails may therefore be displaced along their longitudinal axes. Such displacement would alter the plane of the treads, by tilting them away from the horizontal.
United States Patent No. 4,168,764 issued 25 September, 1979 for an invention of Tom Walters entitled "Level Step Stair Walkway" is similar to the Knight structure, in that the stair - treads are pivotally connected between inner and outer pairs of parallel rails which swing past one another as one end of the gangway is raised or lowered relative to the other end. The structure is relatively complex and expensive.
The present invention provides an mechanically simple, inexpensive, articulating stairway whose treads remain level as one end of the stairway articulates through a large vertical displacement range relative to the other end of the stairway.
Summary of the Invention In accordance with the preferred embodiment, the invention provides an articulating stairway, having a first pair of horizontally spaced, parallel rails and a second pair of horizontally spaced, parallel rails aligned above the first pair of rails. A plurality of treads are provided, with each tread being pivotally connected between the first and second pairs of rails on two vertically aligned, parallel, horizontal axes.
First and second pivot pins extend from the opposed ends of each tread to form one of the axes aforesaid. First and second risers project from the opposed ends of each tread. Third and fourth pivot pins extend from each of the risers to form the other axis.
The preferred embodiment of the invention may be alternatively characterized as providing an articulating stairway having a first pair of horizontally spaced, parallel rails and a second pair of horizontally spaced, parallel rails aligned above the first pair of rails, with a plurality of treads extending horizontally between the rails. A pair of risers project from the opposed ends of each tread. Each riser is pivotally connected between vertically aligned pairs of points on the first and second pairs of rails. The vertically aligned pairs of points remain vertically aligned as one end of the stairway pivots above or below the other end of the stairway.
The first and second pairs of rails are positioned such that vertical separation between the upper surfaces of the first pair of rails and the lower surfaces of the second pair of rails is a maximum when both ends of the stairway are level with one another; decreases as one end of the stairway pivots 202~S74 above or below the other end of the stairway; and, decreases to zero as one end of the stairway pivots to the maximum possible extent above or below the other end of the stairway.
First, second, third and fourth brackets are provided.
The respective brackets are pivotally connected between verti-cally opposed ends of one rail of the first pair of rails and one rail of the second pair of rails on two vertically aligned, parallel, horizontal axes.
Brief Description of the Drawinqs Figure 1 is an oblique pictorial illustration of an articulating stairway constructed in accordance with the preferred embodiment of the invention.
Figure 2 is a side elevation view of the articulating stairway of Figure 1 (viewed from the rear side of Figure 1).
In Figure 2, phantom lines are used to show the maximum extent to which the left end of the stairway may pivot above or below the right end of the stairway.
Figure 3 is an enlarged cross-sectional illustration taken with respect to line 3-3 of Figure 1 to provide details of the stair treads and the brackets which pivotally connect the vertically opposed rail ends together.
Figure 4 is an enlarged cross-sectional illustration taken with respect to line 4-4 of Figure 2 to provide further details of the stair treads.
Detailed Description of the Preferred Embodiment The drawings illustrate an articulating stairway 10 having a first pair of horizontally spaced, parallel rails 12, 14 and a second pair of horizontally spaced, parallel rails 16, 18 aligned above rails 12, 14 respectively. A plurality of stair treads 20, 22, 24, etc. are provided. As hereinafter described in greater detail, each tread is pivotally connected between the `. 2023574 first and second pairs of rails on two vertically aligned, parallel, horizontal axes such as axes 26, 28 illustrated in Figure 3 for tread 30. A handrail (shown in phantom outline in Figure 1) may be provided as a safety feature, and also to improve the structural integrity of stairway 10 (for example, by fixing a plurality of bracing struts between the handrail and the upper surfaces of rails 16, 18 as illustrated in Figure 2).
As best seen in Figure 4, a first pivot pin 32 extends from one end of stair tread 30 to pivotally engage within a reinforced aperture 34 in rail 14. A second pivot pin 36 extends from the horizontally opposed end of stair tread 30 to pivotally engage within reinforced aperture 38 in the horizontally opposed rail 12. Horizontally aligned pivot pins 32, 36 form horizontal axis 26. A first riser 40 projects upwardly at the end of tread 30 from which first pivot pin 32 extends. A second, identical riser 42 projects upwardly at the end of tread 30 from which second pivot pin 36 extends. A third pivot pin 44 extends from the upper end of riser 40 to pivotally engage within reinforced aperture 46 in rail 18. A fourth pivot pin 48 extends from the upper, horizontally opposed end of riser 42 to pivotally engage within reinforced aperture 50 in the horizontally opposed rail 16. Horizontally aligned pivot pins 44, 48 form horizontal axis 28. All of the stair treads are similarly pivotally connected between the first and second pairs of rails. The horizontal axes which intersect the first pair of rails 12, 14 lie in one plane;
and, the horizontal axes which intersect the second pair of rails 16, 18 lie in another plane parallel to the first plane.
As best seen in Figure 3, a bracket 52 is pivotally connected between the vertically opposed ends 54, 56 of rails 14, 18 on two vertically aligned, parallel, horizontal axes 58, 60.
Axis 58 lies in the same plane as the aforesaid horizontal axes which intersect the first pair of rails 12, 14; and, axis 60 lies in the same plane as the horizontal axes which intersect the second pair of rails 16, 18.
~ As best seen in Figure 2, the first and second pairs of rails are positioned such that the vertical separation between the upper surfaces 62 of the first pair of rails 12, 14 and the lower surfaces 64 of the second pair of rails 16, 18 is a maximum "a" when both ends of stairway 10 are level with one another.
The vertical separation decreases, as shown at "b", as one end of stairway 10 pivots above or below the other end of stairway 10. The vertical separation decreases to zero (i.e. the upper surfaces 62 of the first pair of rails 12, 14 contact the lower surfaces 64 of the second pair of rails 16, 18 as shown at "c") as one end of stairway 10 pivots to the maximum possible extent above or below the other end of stairway 10.
In operation, stairway 10 may, for example, be mounted on a suitable support structure atop a dock (not shown). If a ship (not shown) is berthed at the dock then one end of stairway 10 is extended, with the aid of a crane, and placed on the deck of the ship. The other end of stairway 10 remains on the dock, with provision being made for the dock end of the stairway to slide back and forth along the longitudinal axis of stairway 10 as stairway lo articulates in the following manner.
As the tides ebb and flow (assuming the ship to be in tidal water) and/or as the ship is loaded and unloaded, the vertical displacement between the dock and the ship's deck changes. Suppose for example that the ship is initially unloaded and riding at high tide. In this case the ship end of stairway 10 will likely be displaced vertically above the dock end of stairway 10 by a significant amount. Now, suppose that the same ship is fully loaded and riding at low tide beside the same dock.
In this case the ship end of stairway 10 will likely be displaced vertically below the dock end of stairway 10 by a significant amount. In between the two extremes aforesaid the ship end of stairway 10 is displaced vertically through a wide range of positions, relative to the dock end of stairway 10, with the dock end of stairway 10 sliding back and forth along the longitudinal axis of stairway 10. At all times the treads of stairway 10 are 202357~
kept level because they are supported, as aforesaid, by risers which are pivotally connected between vertically aligned pairs of axes intersecting the first and second pairs of rails, such that each vertically aligned pair of axes remains vertically aligned as one end of stairway 10 pivots above or below the other end of stairway 10.
As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifica-tions are possible in the practice of this invention withoutdeparting from the spirit or scope thereof. For example, instead of focusing on a horizontal "neutral" position, as heretofore assumed, one could instead focus upon a vertical neutral position. This could be accomplished by mounting the stair treads at positions rotated 90 with respect to the positions shown in the drawings, and by supporting one end of stairway 10 on a horizontal surface, so that the structure extended verti-cally upward from that surface. The upper end of the stairway could then be allowed to pivot off the vertical, to either side.
The stair treads would remain level because, in this orientation of the stairway, the risers are pivotally connected between horizontally aligned pairs of axes intersecting the first and second pairs of rails, such that each horizontal aligned pair of axes remains horizontally aligned as the upper end of the stairway pivoted to one side or the other relative of the lower end of the stairway. Accordingly, the scope of the invention is to be construed in accordance with the substance defined by the following claims by interchanging the terms vertical and horizontal as circumstances may require.
Claims (4)
1. An articulating stairway, comprising:
(a) a first pair of horizontally spaced, parallel rails;
(b) a second pair of horizontally spaced, parallel rails aligned above said first pair of rails;
(c) a plurality of treads, each tread pivotally connected between said first and second pairs of rails on two vertically aligned, parallel, horizontal axes;
(d) first and second pivot pins extending from opposed ends of each of said treads to form a first one of said axes;
(e) first and second risers projecting from said opposed tread ends;
(f) third and fourth pivot pins extending from said first and second risers to form the other of said axes; and, (g) first, second, third and fourth brackets, each bracket pivotally connected between vertically opposed ends of one rail of said first pair of rails and one rail of said second pair of rails on two vertically aligned, parallel, horizontal axes;
wherein said first and second pairs of rails are positioned such that vertical separation between the upper surfaces of said first pair of rails and the lower surfaces of said second pair of rails:
(i) is a maximum when both ends of said stairway are level with one another;
(ii) decreases as one end of said stairway pivots above or below the other end of said stairway; and, (iii) decreases to zero as one end of said stairway pivots to the minimum possible extent above or below the other end of said stairway.
(a) a first pair of horizontally spaced, parallel rails;
(b) a second pair of horizontally spaced, parallel rails aligned above said first pair of rails;
(c) a plurality of treads, each tread pivotally connected between said first and second pairs of rails on two vertically aligned, parallel, horizontal axes;
(d) first and second pivot pins extending from opposed ends of each of said treads to form a first one of said axes;
(e) first and second risers projecting from said opposed tread ends;
(f) third and fourth pivot pins extending from said first and second risers to form the other of said axes; and, (g) first, second, third and fourth brackets, each bracket pivotally connected between vertically opposed ends of one rail of said first pair of rails and one rail of said second pair of rails on two vertically aligned, parallel, horizontal axes;
wherein said first and second pairs of rails are positioned such that vertical separation between the upper surfaces of said first pair of rails and the lower surfaces of said second pair of rails:
(i) is a maximum when both ends of said stairway are level with one another;
(ii) decreases as one end of said stairway pivots above or below the other end of said stairway; and, (iii) decreases to zero as one end of said stairway pivots to the minimum possible extent above or below the other end of said stairway.
2. An articulating stairway, comprising:
(a) a first pair of horizontally spaced, parallel rails;
(b) a second pair of horizontally spaced, parallel rails aligned above said first pair of rails;
(c) a plurality of treads extending horizontally between said rails;
(d) a pair of risers projecting from the opposed ends of each of said treads, each riser being pivotally connected between vertically aligned pairs of points on said first and second pairs of rails;
(e) first and second horizontally aligned pivot pins extending from each of said pairs of risers to pivotally engage said first pair of rails; and, (f) third and fourth horizontally aligned pivot pins extending from each of said pairs of risers to pivotally engage said second pair of rails;
wherein:
(i) said vertically aligned pairs of points remain vertically aligned as one end of said stairway pivots above or below the other end of said stairway;
(ii) said first and third pivot pins are vertically aligned; and, (iii) said second and fourth pivot pins are vertically aligned.
(a) a first pair of horizontally spaced, parallel rails;
(b) a second pair of horizontally spaced, parallel rails aligned above said first pair of rails;
(c) a plurality of treads extending horizontally between said rails;
(d) a pair of risers projecting from the opposed ends of each of said treads, each riser being pivotally connected between vertically aligned pairs of points on said first and second pairs of rails;
(e) first and second horizontally aligned pivot pins extending from each of said pairs of risers to pivotally engage said first pair of rails; and, (f) third and fourth horizontally aligned pivot pins extending from each of said pairs of risers to pivotally engage said second pair of rails;
wherein:
(i) said vertically aligned pairs of points remain vertically aligned as one end of said stairway pivots above or below the other end of said stairway;
(ii) said first and third pivot pins are vertically aligned; and, (iii) said second and fourth pivot pins are vertically aligned.
3. An articulating stairway as defined in claim 2, wherein said first and second pairs of rails are positioned such that vertical separation between the upper surfaces of said first pair of rails and the lower surfaces of said second pair of rails:
(a) is a maximum when both ends of stairway are level with one another;
(b) decreases as one end of said stairway pivots above or below the other end of said stairway; and, (c) decreases to zero as one end of said stairway pivots to the maximum possible extent above or below the other end of said stairway.
(a) is a maximum when both ends of stairway are level with one another;
(b) decreases as one end of said stairway pivots above or below the other end of said stairway; and, (c) decreases to zero as one end of said stairway pivots to the maximum possible extent above or below the other end of said stairway.
4. An articulating stairway as defined in claim 3, further comprising first, second, third and fourth brackets, each bracket pivotally connected between an axis through one rail of said first pair of rails and a vertically aligned, parallel axis through the vertically opposed rail of said second pair of rails, wherein said axes remain vertically aligned and parallel as one end of said stairway pivots above or below the other end of said stairway.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US54327290A | 1990-06-25 | 1990-06-25 | |
| US543,272 | 1990-06-25 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2023574A1 CA2023574A1 (en) | 1991-12-26 |
| CA2023574C true CA2023574C (en) | 1994-10-11 |
Family
ID=24167301
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2023574 Expired - Fee Related CA2023574C (en) | 1990-06-25 | 1990-08-17 | Articulating stairway |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2023574C (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6256946B1 (en) * | 1999-10-04 | 2001-07-10 | Jack Kennedy Metal Products And Buildings, Inc. | Adjustable stairway for use with an overcast in a mine |
| CN110155269A (en) * | 2019-05-29 | 2019-08-23 | 浙江国际海运职业技术学院 | Autostairs peculiar to vessel |
| CN114135217B (en) * | 2021-10-13 | 2023-07-21 | 福建海电运维科技股份有限公司 | Boarding telescopic ladder |
-
1990
- 1990-08-17 CA CA 2023574 patent/CA2023574C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CA2023574A1 (en) | 1991-12-26 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |