Patent application title: SPIRAL STAIRCASE
Fausto Scherma (Santa Maria A Monte, IT)
IPC8 Class: AE04F11032FI
Class name: Static structures (e.g., buildings) stepped; e.g., stair helical type
Publication date: 2011-10-27
Patent application number: 20110258946
A spiral staircase comprises a central supporting element and a plurality
of steps which are connected to the supporting element at a first end,
there being two types of steps positioned in an alternating fashion, of
which a first type of step is substantially "L"-shaped and a second type
of step is substantially arrow-shaped.
7. A spiral staircase, comprising a central supporting element and a plurality of steps which are connected to the supporting element at a first end, the steps being of two types of steps positioned in an alternating fashion, wherein a first type of step is substantially "L"-shaped and a second type of step is substantially arrow-shaped, each type of step comprising at least one projection and one recess contributing to forming on the steps treadable portions, said at least one projection and one recess of the first type of step complementing said at least one projection and one recess of the second type of step, so as to increase the surface available for supporting the inside foot.
8. The spiral staircase according to claim 7, comprising a banister connected to a second end of the steps.
9. The spiral staircase according to claim 7, comprising spacer elements, designed to define a riser of the steps.
10. The spiral staircase according to claim 7, comprising a landing, having an edge shaped like one of the two types of steps.
11. The spiral staircase according to claim 8, comprising spacer elements, designed to define the riser of the steps.
 This invention relates to a spiral staircase. The widespread use of spiral staircases, in particular for internally connecting rooms which are on different levels of the same building, is mainly due to the fact that they have quite small plan dimensions. Especially in recent decades, this has fully satisfied the requirements of increasingly small homes.
 As is known, spiral staircases comprise a vertical central pole, along which steps are applied, at one free end of the steps. The series of steps describes a spiral in space, allowing people to ascend or descend the staircase by moving around the pole. The free ends of the steps usually support a banister which facilitates movements along the staircase, forming a support for users.
 Being used above all when there is limited space available, it is also undeniable that, for people of at least a normal build, the reduced width of the steps or, more precisely, the reduced distance between the central pole, which is the centre of the staircase, and the free end of the steps makes both ascending and descending the staircase rather difficult.
 These operations are further complicated by the fact that the distribution of the steps, combined with their compact dimensions, means that in many cases the surface available for supporting the sole of the foot, in particular the foot on the inside while descending the staircase, is reduced so much that it does not guarantee the stability needed during the movements.
 It is also important to consider that the distribution of the steps in a spiral staircase mainly depends on the staircase plan dimensions and on the riser, that is to say, the height separating two consecutive steps. Two steps which in plan view are separated by a round angle (360°) must be separated in terms of height by the space necessary (approximately two meters) to allow a person of average height to pass without the risk of striking his head on the higher step. Moreover, since the landing covers a large angle, this situation becomes critical close to the upper end of the staircase.
 Especially when the plan dimensions are compact, comparable to a circle with a diameter of 130/140 centimeters, or to a square having a side of similar length, in the current solutions an equivalent of the riser--tread ratio is very different from that which can be obtained with straight ramps and also noticeably unfavourable for the inside foot compared with the outside foot.
DISCLOSURE OF THE INVENTION
 This invention therefore has for an aim to eliminate the above-mentioned disadvantages.
 The invention, with the characteristics described in the claims, achieves this aim thanks to alternate positioning of two steps having different and complementary shapes.
 The main advantage of this invention is basically the fact that ascending and descending a spiral staircase is significantly facilitated. In particular, the surface available for supporting the inside foot when passing from one step to another is increased, guaranteeing users greater stability and balance.
 Moreover, the shape of the steps allows the achievement of an equivalent of the riser--tread ratio which is practically the same for the outside foot and the inside foot. In addition, the shape of the landing may allow an increase in the number of steps, reducing the riser and achieving an equivalent of the riser--tread ratio which is close to that which can be achieved with straight ramps.
 Finally, the structure of the invention guarantees the flexibility necessary for covering any height, thanks to a system for adjusting the height of the steps, for adapting to any plan shape (circular, square, etc.) and to the direction of rotation (clockwise or anti-clockwise), for production using any material (wood, iron, aluminium, etc.) or colour.
BRIEF DESCRIPTION OF THE DRAWINGS
 Further advantages and features of the invention are more apparent in the detailed description which follows, with reference to the accompanying drawings, which illustrate a preferred, non-limiting example embodiment of the invention, in which:
 FIG. 1 is a side view of the invention;
 FIG. 2 is a plan view of a first embodiment of the steps;
 FIG. 3 is a plan view of a pair of consecutive steps;
 FIG. 4 is a plan view of a second embodiment of the steps;
 FIG. 5 is a plan view of two embodiments of the landing.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
 In accordance with the accompanying drawings, the invention relates to a spiral staircase. It comprises a central supporting element (1) and a plurality of steps (2), which are connected to the supporting element (1) at a first end (2a). In particular, as shown in FIGS. 2 and 4, it comprises two types of steps (21, 22), where a first type of step (21) is substantially "L"-shaped and a second type of step (22) is substantially arrow-shaped. They are positioned along the staircase (10) in an alternating fashion, as shown in the detail in FIG. 3.
 The first type of step (21) comprises at least one projection (21a) and one recess (21b) which complement at least one projection (22a) and one recess (22b) of the second type of step (22). The projections (21a, 22a) and recesses (21b, 22b) contribute to forming on the steps (21, 22) treadable portions (21c, 22c) which are separate from portions (21d, 22d) that are not strictly necessary for achieving the advantages which the invention proposes. In this way, the "L"-shaped step (21) provides support only for the outside foot, whilst the arrow-shaped step (22) provides support only for the inside foot, both when a person is ascending and descending the staircase (10).
 The staircase (10) also comprises a landing (5), having an edge (5a) shaped like one of the two types of steps (21; 22). Obviously, depending on the shape of the edge (5a), anyone using the staircase (10) must begin stepping on it starting with the outside foot if the edge (5a) of the landing (5) is shaped like the arrow-shaped step (22), or with the inside foot if the edge (5a) of the landing (5) is shaped like the "L"-shaped step (21). In the latter case, it is possible to increase the number of steps (2), reducing the riser.
 For a complete overview, FIG. 1 also shows a banister (3), needed for safety reasons, connected to a second end (2b) of the steps (2), and spacer elements (4), designed to define the riser of the steps (2).
 The invention described above may be modified and adapted in several ways without thereby departing from the scope of the inventive concept. Moreover, all details of the invention may be substituted by technically equivalent elements.
 Obviously, in practice modifications and/or improvements are possible which are covered by the following claims.
Patent applications in class Helical type
Patent applications in all subclasses Helical type