Apparatus suitable for use as stairways, stepladders and the like

Apparatus for use as a stairway, stepladder and the like has a pair of upper stringers and a pair of lower stringers, all connected at one end to a top structure; and a series of treads, each of which is pivoted to the upper and lower stringers. The axes of articulation associated with the upper stringers are offset vertically from those associated with the lower stringers so that the stringers may be swung about their points of connection with the top structure, without the treads deviating from the horizontal into a horizontal position of the stringers, in which the upper stringers rest on the lower stringers. Support elements are articulated to the top structure, and an automatic latching apparatus is provided to interconnect the support members with the stringers.

BACKGROUND OF THE INVENTION 
This invention relates to an apparatus which may take the form of a 
stairway or pair of steps, the treads of which are always automatically 
maintained parallel to the ground regardless of the angle of the stringers 
relative to the ground. In consequence, when the apparatus is brought into 
a horizontal position, the treads form a substantially continuous plate. 
Apparatus is already known which includes treads which are maintained 
horizontal regardless of the angle of the apparatus, such apparatus being 
used particularly for gangways connecting harbour quays with floating 
bridges or launches which are at a lower level than the quays but which 
are vertically movable with the rising and falling tide. With such 
apparatus it is not necessary for the treads to form a continuous plate 
intended for receiving a large load, and for the load to be distributed 
over substantially the entire length of the two stringers so that one 
stringer shall rest upon the other. 
Ladders are also known, in which the stringers are pivotally mounted 
relative to a lower tread and a fixed, horizontal upper tread, as are 
ladders comprising a pair of fixed stringers, relative to which another 
pair is capable of being spread out or folded in. 
SUMMARY OF THE INVENTION 
An object of this invention is to provide such apparatus which is perfectly 
stable when resting upon the ends of the stringers and, when brought to 
the horizontal, forms a continuous and solid plate. 
A further object of the invention is to provide such apparatus in which 
each of the treads constituting the plate is supported by each of the 
stringers, the angle of the staircase being variable and not in any way 
leading to variations in absolute horizontality of the treads. 
Accordingly, the invention provides apparatus for use as stairs, steps and 
the like, comprising a first, lower pair of parallel, rectilinear 
stringers, a second, upper pair of parallel, rectilinear stringers; each 
stringer in the lower pair being disposed below and parallel to a 
respective stringer in the upper pair; a pair of horizontal, parallel arms 
between which first ends of the stringers are disposed, said first ends of 
the stringers being articulated to said arms about support arm pivot axes 
extending between the arms; the support arm pivot axis for the lower 
stringers being offset downwards by a predetermined vertical distance from 
the support arm axis for the upper stringers; a plurality of treads 
disposed between the stringers; each tread being pivoted to the lower 
stringers about a first tread pivot axis and to the upper stringers about 
a second tread pivot axis; the tread pivot axes associated with each 
stringer being spaced apart longitudinally of the stringer by distances 
approximately equal comparable to the widths of the treads, each of said 
treads being provided with at least one downwardly extending member 
adjacent one edge by way of which member the means of articulation between 
the tread and each lower stringer is supported, the first and second tread 
pivot axes for each tread being offset vertically by a distance 
approximately equal to said predetermined vertical distance between the 
support arm pivot axes, and more particularly, approximately equal to the 
sum of the distances, firstly between the upper longitudinal edges of the 
lower stringers and the support arm pivot axis of those stringers, and 
secondly between the lower longitudinal edges of the upper stringers and 
the support arm pivot axis of those stringers, thereby, when the stringers 
are pivoted relative to the arms the treads remain horizontal, and the 
lower longitudinal edge of each upper stringer rests upon the upper 
longitudinal edge of the respective lower stringer when the stringers are 
disposed horizontally. 
In the practical embodiment to be described herein, the spacing between the 
pivot axes along the stringers is slightly greater than the widths of the 
treads. 
The pivotal tread connection between each tread and the stringers can be 
achieved in two preferred ways; either by the use of two tubes integrally 
attached to each tread and slid onto bars fixed between the stringers, the 
treads carrying perpendicular, underlying, longitudinal flanges bearing 
against the tubes; or alternatively by the provision on the treads of 
perpendicular lateral flanges, through which there pass rods fixed to each 
stringer. 
The apparatus may alternatively be arranged so that it may be used as a 
pair of steps, from which condition it may be collapsed to form a wheeled 
structure suitable for use as a truck, trolley or barrow.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIGS. 1 and 2, apparatus in accordance with the invention may 
be made to occupy either an inclined position (FIG. 1) in which it serves 
as a flight of stairs, or a horizontal position in which it serves as a 
gangplank, or the like. In the inclined position a series of treads 8 are 
in vertically spaced arrangement, whereas in the horizontal position the 
treads are juxtaposed or are separated by small gaps. 
In these figures, parts of the apparatus have been depicted 
diagrammatically. Essentially the apparatus comprises a main frame 
consisting of a pair of spaced apart lower stringers 1, a pair of spaced 
apart upper stringers 2 and a pair of spaced apart support members or arms 
3, to each of which one stringer 1 and one stringer 2 are pivoted for 
movement about support arm pivot axes 4 and 5. Only one of each of the 
parts 1 to 3 is visible in FIGS. 1 and 2, the other ones of these parts 
being obscured from view. 
The treads 8 occupy positions between the two pairs of stringers, each 
tread being articulated to the lower stringers about tread pivot axes 6 
and to the upper stringers about tread pivot axes 7. Each tread is pivoted 
to the lower stringers by way of blocks or spacers 9. 
A fixed tread 3a is depicted as being provided between the arms 3 but this 
tread may be omitted in suitable circumstances. 
The support arm pivot axes or axes of rotation 4 and 5 lie in respective 
horizontal planes spaced by a predetermined vertical distance equal to the 
distance between horizontal planes in which lie the tread pivot axes 6 and 
7 of each tread 8. This spacing is also equal to the width of each of the 
stringers 1 or 2 in the case where these stringers are identical and where 
the centres of the pivot axes 6 and 7 lie on the median longitudinal lines 
of the stringers 1 and 2, respectively. This spacing is also equal to the 
height of the block or spacer 9. 
FIGS. 3 and 4 show one arrangement for mounting the treads 8 between the 
stringers, in which the tread pivot axes are provided by rods 10 which 
extend between the stringers and are held in place by nuts 13 screwed onto 
the ends of the rods and bearing against the stringers through washers 14. 
Each rod carries a tube 11 held fast with the associated tread by flanges 
12 embracing the tube. The flanges 12 associated with the upper stringers 
depend directly from the tread. The other flanges are formed on spacer or 
block 9 to offset these flanges in a vertical sense by the desired 
distance. 
Referring now to FIGS. 5 and 6, a second arrangement for mounting the 
treads 8 to pivot about tread pivot axes is achieved by forming or 
providing each tread with a depending flange or wall 16 at each end. Rods 
15 located in appropriate positions having regard to the amount of offset 
to be obtained extend between the respective stringers and through the 
walls 16. The ends of the rods are made rigid with the outer sides of the 
stringers, conveniently by upsetting using a rivetting tool for aesthetic 
reasons. The ends of the rods are thinned down so that only the part 17 
passes through the stringers and there is obtained a double blocking of 
the stringers 1 and 2 on the rods 15. 
A washer 18 prevents frictional contact of the walls 16 with the stringers 
1 and 2. These walls 16, as can best be seen in FIG. 5, are of a 
sufficient height to permit the pivot axis of the rod 15 of the stringer 1 
to be offset relative to the pivot axis of the rod 15 or the other 
stringer 2. 
In order to hold the apparatus in the erected condition it is equipped with 
elongate support members formed of two bars 19, 20 of flat or profiled 
section articulated between the horizontal arms. A support bar pivot axis 
21 of the support members or bars is provided between the arms 3, which 
axis does not intersect the median line of these elongate support members 
19 and 20, but is off-set from these members each of these members being 
provided with a post 22 (FIGS. 9, 10, 11) which carry the pivot rod so 
that the support members 19, 20 can swing from an upright position below 
the horizontal arms 3 (FIG. 7) to a rest position, above and parallel to 
the horizontal arms 3 (FIG. 8). 
Between the support members 19, 20, which will act as guide arms for the 
carriage, there are mounted a cross-bracing 23 and a transverse member 24 
perpendicularly to the support members 19 and 20. The transverse member 24 
may be a tube which serves for pushing or pulling the apparatus when in 
its collapsed, truck-forming condition. 
In this collapsed condition fixed wheels 25 mounted in brackets fixed upon 
the lower stringers 1, and steering wheels 26 mounted (by means not shown) 
in known manner below the fixed tread 10 make contact with the ground. 
When the apparatus is erected, i.e. set in its step-ladder forming 
condition, it is necessary to ensure that the stringers and support 
members maintain a given angle there between. To this end, a latching 
system is provided which can take any suitable form but which is 
preferably as shown in FIGS. 9 to 11, where there are provided four 
latching or blocking points, which are indicated by arrows 27 (FIG. 9), 
28, 29, 30 (FIG. 11). 
As shown in these Figures, a top step unit is formed by the horizontal arms 
3 these arms again interconnected by a tread or cross-member similar to 
tread 3a but shown here as comprising an upper plate 31 rigidly mounted on 
and extending between arms 3, and below which are mounted the pivots or 
spindles 4, 5 on which the stringers 1 and 2 are supported, and also the 
pivot, bar or spindle 21 for support members 19 or 20. Below the plate 31, 
arms 3 are interconnected by a plate 32, FIGS. 10 and 11, which is 
narrower, so that it, as shown, will not interfere with pivoting motions 
of the stringers. 
In the collapsed or carriage forming or rest position (FIG. 9) each lower 
stringer 1 is held to the pertaining upper stringer 2 by a latch 33 having 
a notch 34 in which is received a stop 35 projecting from the side of the 
stringer. It is not essential for this latching point (denoted by arrow 
27) to be provided but it has the advantage of preventing lifting of the 
opposite end of the top step unit when a heavy pressure is applied to the 
other end of said unit by the support members 19, 20, particularly when 
the apparatus is used as a trolley or barrow and more especially when it 
is not loaded. 
When the support members 19, 20 (FIG. 8) are swung up in the direction of 
arrow 36 (FIG. 9), they may be used as guide arms for the trolley formed 
by the apparatus. By then releasing the latch 33 and continuing the 
rotational movement of the support members 19, 20 in the direction of 
arrow 37 (FIG. 10), a roller 38 which interconnects the ends of these 
support members will come to bear against the lower stringers 1 and tend 
to turn them into an upright position (FIG. 10). This movement also 
results in the upper stringer being similarly turned. By still continuing 
to turn or rotate the support members 19 and 20 in the direction of arrow 
39, the set-up position shown in FIG. 11 is reached, in which the roller 
38 bears against and is stopped by the underside of the horizontal part 31 
of the top step unit (as shown at 29) as do the ends 40 of the lower 
stringers 1 (as shown at 29) and the ends 41 of the upper stringers (as 
shown at 30). As soon as this stopping position is reached, further 
turning or rotation is prevented so that a position cannot be reached in 
which there is an angle between the stringers and support members, smaller 
than the illustrated angle which is defined by this stopping of the 
support elements and stringers, as shown. To prevent re-opening of the 
apparatus, there is provided, preferably on each side, a latching arm 42 
which is fixed to the side of a respective one of the underlying stringers 
1. The arm 42 has a notch 43 which fits over a stop or pin 44 projecting 
from the internal face of a respective support member 19 or 20, so as to 
constitute a further latching point (shown at 28, FIG. 11). 
In order that the above described blocking and latching actions shall be 
automatic, the end 45 of the latch 33 is chamfered and the latch is hinged 
to pivot freely about the spindle 4. When the steps are being returned to 
the collapsed position, the end 45 will slide upon the stop 35 when a 
predetermined position has been reached (FIG. 10), so that later in the 
collapsed position (FIG. 9) the notch 34 will lie opposite the stop 35 so 
that the latch falls over the stop, unblocking being carried out 
automatically as indicated above. 
Similarly, the notch 43 is arranged to automatically receive the stop 44. 
The ensure this, the blocking arm 42, which pivots freely about a pivot 
spindle 6 of the lower stringer 1, extends beyond this spindle as far as 
the spindle 7 of the upper stringer 2, so that its end 46 abuts this 
spindle 7 (FIGS. 9 and 10) and so that the blocking arm 42 cannot fall 
into the vertical position but, on the contrary, will be maintained 
approximately horizontal, so that the chamfered end 47 of this arm, once a 
predetermined angle between the parts has been reached (exceeding that 
shown in FIG. 10) will abut against the stop 44 and finally the notch 43 
will fall onto the stop 44. 
Unblocking will not however be automatic but will be caused by raising the 
blocking arm or arms 42. 
As can be seen in FIG. 11, the ends 40 and 41 of the stringers 1 and 2 are 
also cut to a chamfer, to an angle determined so that they abut solidly 
against the internal face of the cross-member 31 of the top step unit. 
Nevertheless, to permit rotation of the upper stringers 2, it is necessary 
to provide a second cut-away portion 48 at the end 41 of these stringers. 
The same is true also for the end 49 of the support members 19 and 20, 
which must have a chamfered cut-away portion 50 so that it does not abut 
against the underlying stringers 1. 
To enable the steps to be easily moved while still erected two small 
rollers 51 (FIG. 7) are provided at the lower ends of the upper stringers 
2, so that, by slightly raising the steps by the top step unit it is 
possible to roll them along. 
If, in addition, it is desired to use the steps as a bench, the upper 
cross-member or tread 10 serving as a work table, it is preferable to 
equip the steps with a folding foot-rest platform 52, on which the workman 
can stand so as to stabilise the steps with his weight. This platform 52 
may, for example, be pivotally mounted by arms 53 on the transverse member 
24. 
In order to retain this platform when the apparatus is in the collapsed 
position, it is possible to provide a supplementary transverse member 54 
(FIG. 8) between the support members 19, 20. A hooking strip 55 attached 
to the end of the platform 52 can then engage this transverse member 54; 
the transverse member 54 can also act as the stop 44. 
When the steps are used as a bench, it is also possible to provide, as 
shown in FIG. 7, a tray 56 serving for setting out tools, and mounted on 
the pivot axes 6 of the lower stringers 1, so that, like the treads 8, the 
tray 56 is maintained horizontal whatever the position of the stringers 1. 
Although it is not in any way necessary to provide blocking for the support 
members 19, 20 or for the underlying stringers 1, these being absolutely 
prevented from continuing their rotation in the erected position (see 
arrow 29), the width of the lower horizontal part 32 of the top step unit 
3 can also be such that, as shown in FIG. 11, both the support members 19, 
20 and also the lower stringers 1 abut against the opposite ends of this 
horizontal part. 
The invention is of course not limited to the specific embodiments 
described and shown, and modifications may be made. In particular, the 
blocking system may be altered and accessories other than the rollers 51, 
foot-rest platform 52, and tool tray 56 may be provided. Attachment means 
(such as notches, screw threads or the like) may also be provided for one 
or more extension platforms, or for a vise. 
Moreover, although the apparatus can be made of any suitable material, it 
is preferably constructed of aluminium sections, enabling an extremely 
light device to be obtained having a very pleasing appearance. In this 
sense also, the connecting means, as can be seen in FIG. 8, are 
essentially for the various points of fixing, pivots, and axes of 
rotation, in the form of rivets flattened by a riveting die. In addition, 
the various axes of rotation and pivoting which require the use of washers 
are concealed either by the external face of the horizontal arms 3, or by 
the lateral sides 15. 
Of course, it will be appreciated that any other suitable top structure may 
be used in place of the arms 3, the only requirements for such structures 
being that the stringers (and if necessary, support members) can be 
connected to it with appropriate amounts of offset.