Fire escape to be attached to the outside of a building
BACKGROUND AND SUMMARY OF THE INVENTION 
     The purpose of this invention is a fire escape without the drawbacks characterizing the preceding state of the art, in particular a fire escape allowing the free access to the fire escape from the safety outlets on the single floors, allowing at the same time to reach the underlying floors following a regular staircase without sharp changes of direction and using steps having a comfortable rise and width. It is a further object of third invention to propose a fire escape made of prefabricated elements, unit composed and suitable without substantial modifications to different heights of the single storeys and of the buildings. An ulterior object of this invention is a fire escape whose access and outlet are always in the best possible position for allowing the rapid and unhindered evacuation of the fire escape in the event of danger. Finally, the here proposed fire escape is characterized by a surprising stability, by the possibility to erect it independently of the building, by requiring a minimum of base space. 
     The said objects and purposes are obtained according to this invention by a fire escape by having a platform interlocked with the safety outlet at an upper floor connected to a platform interlocked with the safety outlet at a lower floor by means of two supporting columns running along the whole height of the building and spaced from the facing and spaced among themselves, with the first column supporting the winders of a first turn of a spiral stair case, these winders being interposed with a series of straight steps supported by the first and/or the second column to reach a second group of winders forming another half turn of the spiral stair case supported by the second column and leading to the lower platform. 
     The here proposed invention uses for a fire escape of the here mentioned type all the advantages part of a classical spiral stair case, with the possibility, however, to adapt it freely to various heights of the floors of the building without having to change the ideal height of the single steps and allowing, in particular, the rapid access to the fire escape, and at the same time, from more than one safety outlet, one above the other one, but all in the same vertical plane. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The object conceived according to this invention will now be described more in detail for an embodiment thereof, without being limited thereto, given only by way of example, and on hand of the accompanying drawings in which: 
     FIG. 1 is a horizontal section through the fire escape along line I--I of FIG. 2, and 
     FIG. 2 is an elevation of the spiral stair seen along arrow II in FIG. 1. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As shown in FIG. 1, the fire escape indicated by 1 is arranged parallel to the front face 2 of a building, at the safety outlets 3 of the single floors lying all in the same vertical line, and connected to safety corridors 4 one to each floor. 
     Each safety outlet 3 is connected to a projecting platform 5 supported for example by two projecting brackets 6 fixed to the front 2. 
     Each platform 5 is still further supported by two columns 7 and 8 resting on foundations (not shown) provided at the foot of the building. The columns 7 and 8 are fixed at the angles 9 and 10 of the platform 5, spaced from the building 2; at the same time the said columns run parallel one to the other along the whole height of the building. 
     When to be used the fire escape 1 serves to descend from an upper platform 5 to a lower platform 5&#39;, as indicated by the arrow f. 
     Column 7 locked in the shown embodiment (FIG. 1) to the outlet 30 at the platform 5, carries also the steps 11 of a spiral staircase completing in direction of the arrow f a turn equal to 180°. The steps 11 are carried by the column 7 and supported in addition by spacer sleeves 12 inserted on the column 7 each spacer between two steps 11. 
     At the end of the series of steps or winders 11, in direction of the arrow f, we find a series of straight steps 13 supported in part by column 7, in part by column 8. These steps 13 are then followed by a further series of steps or winders 14 in the form of a spiral stair and in the same manner as described for the winders 11, supported by the column 8 and again separated and supported by spacer sleeves 15 seated on the column 8, one between each pair of winders. The platform 5 is provided with a railing 16, the same as the steps 11, 13, 14, with the railing schematically indicated by the uprights 17. 
     FIG. 2 shows the fire escape 11 between the two safety outlets 3 and 3&#39; of two adjacent floors. The two supporting columns 7 and 8, as shown to be parallel and support by means of the sleeves 12 and 15 both the platform 5 and platform 5&#39;, as well as the steps and winders 11, 13, 14 between the two platforms. 
     FIG. 2 also shows that the safety outlets 3, 3&#39;, in dashed outlines to distinguish them, are not at all obstacled by the supporting means or by the steps and winders of the stair and allow thus the quick, safe and free use of the fire escape 1 in the event of danger. To keep the drawings clear the railings which naturally are provided, are indicated only schematically at 16 for the platform 5 and at 17 for part of the steps. 
     A further advantage is that the straight steps 13 have a double width and can thus be anchored one to the other and to the respective columns 7 and 8, thus confering a major stability to the straight stretch. To allow the fire escape 1 to be adaptable to different heights (z) of the single floors, it is sufficient to increase or to diminish the distance (a) between the columns 7 and 8, with the therefrom ensuing possibility of inserting a greater number of steps 13 and thus varying the height (h) without having to modify the rise or the number of the winders 11, 14. This allows to realise fire escapes using modular prefabricated elements easily adapted to different heights in different buildings (from about 2.80 m to 4.20 m) maintaining at the same time the ideal rise (180-200 m) and width of the steps and winders, modifying only the distance (a) between the columns and therewith the number of straight steps 13 and the parameter (h).