ES2813124A1 - Stairlift for spiral or spiral staircases (Machine-translation by Google Translate, not legally binding) - Google Patents

Abstract

The stairlift for spiral or spiral staircases, shown in figure 1, allows its installation when the free space between the axis of said stairs and its opposite end does not exceed 50 centimeters. Said installation is achieved by using the inside of the shaft to house the tractor element of the platform that moves parallel to the steps. (Machine-translation by Google Translate, not legally binding)

Description

DESCRIPTION

Stairlift for spiral or spiral staircases

Technical sector in which the invention is framed

In keeping with the International Patent Classification (CIP), the invention that is the subject of the patent application is framed in:

Section B Various Industrial Techniques, Transportation

“B66 Elevation; lifting; towed

"B66B21 / 00 Classes of escalators or escalators

"B66B21 / 06 Spiral Type Escalators

The purpose of the invention is to transport people and / or things in a vertical direction where a spiral staircase - also called "spiral" - connects two or more levels in a building.

The mechanical devices that perform the aforementioned function are commercially called "stairlift".

Current state of the art

The elimination of architectural barriers in the building, which in some cases is mandatory by law, has made frequent the use of stair lifts to access from the street level to the entrance of buildings when there is not enough space to make a ramp. There are also stair lifts in hallways of houses so that people with reduced mobility are not forced to climb stairs. Already inside homes you can find stair lifts consisting of a chair or self-propelled platform that connects two or more levels (duplexes, single-family homes).

In all the cases mentioned so far, the stairlift consists of a mechanical device made up of a guide rail anchored to a wall that follows a path parallel to an ideal continuous line that joins the edges of the stair rungs. A self-propelled element that incorporates a chair or a platform jointly joined in order to transport a person sitting or standing, or something, moves on this guide rail, following the same route as the steps of the ladder. The self-propelled element is housed inside a rechargeable battery that supplies the energy necessary for movement. In the search for the antecedents of these devices, the INVENES, ESPACENET, LATIPAT and PATENTSCOPE databases were consulted, to which the OEPM website refers. The results obtained for section B66B21 / 00 are very numerous, highlighting the following:

ES2320211T3, WO2019011884 (A1), WO2018215238 (A1), US2017001837 (A1), EP3225581 (A1), EP3253704 (A1), EP3178770 (A1), EP3215450 (A1)

Patents are also related to this type of stair lift:

ES2128782T3, ES2374207T3, ES2177109T3, ES2309620T3

All the stairlifts referred to in the related patents require, for their material execution, that there is a minimum free distance between the guide rail and the opposite wall (or handrail, depending on the case) of 65 to 70 centimeters.

The background search conducted in section B66B21 / 06 specifically for spiral type escalators (spiral stairlift) did not return any results. This does not mean that it is not possible to install stairlifts on spiral staircases: in Spain a single model adaptable to this type of staircase is marketed, but it basically consists of a guide rail like those already mentioned, molded on the vertical axis from which they depart. the steps so that the self-propelled element slides on it. The minimum free distance for installation, measured from the guide rail to the opposite end, is still 65 to 70 centimeters.

Description of the invention

The spiral staircases referred to in section B66B21 / 06 of the CIP are usually found in old buildings, especially industrial ones, built in the first half of the 20th century and which have been converted into housing (so-called "lofts"). Spiral staircases, or spiral staircases, are generally metallic, with a circular plan that rarely exceeds 60 or 65 centimeters in radius, limited on their outer perimeter by a railing attached to tubes or vertical bars that connect two or more levels inside the buildings. They are also found in modern buildings of avant-garde design, with flying steps that seem to increase the available volume when in reality they only seek to occupy a minimum surface in vertical projection. This plan projection is reduced to a circle of only 50 or 55 centimeters radio.

The invention for which a patent is requested consists of a lifting platform that moves in a helical path so that at all times it remains parallel to the steps and at a constant distance from them. All spiral staircases have in common a fundamental structural element: the central axis from which the steps start. Figure 1 shows a perspective in which the handrail or surrounding element that supports the wide end of the steps has been omitted. It shows some elements of the elevator system whose patent is being requested.

The central axis (1) is a tube with a circular section from which the steps (2) start and which is rigidly attached to the base plate (3). This axis is the bearing element that supports all the static and dynamic mechanical stresses that are generated during the operation of the stairlift. The tube has a continuous helical groove (4) whose path is parallel to an ideal line that joins the anchoring points of each of the rungs. This slot enables the physical connection between a device housed inside the shaft (1) - and therefore not visible in figure 1 - and a horizontal lifting platform (5).

Figure 2 shows a perspective of the device housed inside the aforementioned shaft (1). This consists of a cylindrical piece (6) with an outer diameter somewhat less than the inner diameter of the tube (1). A through coaxial cylindrical bore (7) with a diameter approximately equal to one third of the diameter of the cylinder (6) has been drilled into this cylinder.

This piece (6) also has the following elements, all represented in the elevation and in the sections of figure 3 :

- three rings (8) equidistant from each other and integral with (6), located on the 95 perimeter of one of the flat faces of (6) that from now on we will call the upper face (visible in the elevation of figure 3 and in the perspective of figure 2)

- a minimum of three non-passing circular holes (9) equidistant from each other, drilled in the same straight section of the cylinder (6) and whose respective axes intersect the longitudinal axis of (6) as seen in the elevation and in the section a -a 'of figure 3 - a minimum of three non-passing circular holes (10) equidistant from each other, drilled in the same straight section of the cylinder (6) and whose respective axes intersect the longitudinal axis of (6) as seen in the elevation and in section b-b 'of figure 3 - a single threaded through circular hole (11) whose axis is in the median straight section of the cylinder (6) and also intercepts the longitudinal axis of the latter as seen in elevation y in section m-m 'of figure 3

Inside each of the non-through holes (9) and (10) are housed the following elements represented in figure 4 :

- in contact with the bottom of the hole, a spring (12) whose loop diameter is slightly less than the diameter of the hole

- a solid straight cylinder (13) whose diameter is slightly less than the diameter of the hole. The face that rests on the spring (12) is flat and perpendicular to the axis of the hole; the opposite face is also perpendicular to the axis of the hole and has a partial spherical recess (14)

- a sphere (15) with a diameter less than the diameter of the cylinder (13) that is partially housed in the recess (14) and that is in contact with the inner wall of the tube (1)

The set of elements (12), (13), (14) and (15) constitute what is called the spacer element (16).

In figure 5 -which is a straight section of the cylinder (6) coinciding with the straight section m-m 'of figure 3- the threaded through cylindrical hole (11) is represented with the associated elements. These are a threaded bar (17) that at one end reaches the edge of the hole (7) and at the other it protrudes from the tube (1) passing through the slot (4) extending until it is screwed into the platform (5). To prevent the threaded bar (17) from rubbing against the edges of the groove (4), a smooth bushing (18) is sandwiched between the two that can rotate freely around the bar (17). Parts (17) and (18) can also be seen in Figure 1.

Mounted between the platform (5) and the bushing (18) there is a set of parts -which does not appear neither in figure 5 nor in figure 1 - represented in figure 6 . A cylinder (19) provided with a longitudinal threaded through hole (20) is integrally attached to a prismatic piece with a trapezoidal section (21). This piece has a smooth cylindrical through hole (22) perpendicular to the trapezoidal faces of (21). The thread pitch of (20) is the same as that of the bar (17), in turn equal to that of the hole (11). In the right part of figure 6a the section made by the common longitudinal diametrical plane of the pieces (19) and (21) can be seen, and in the left part the right side view.

Adjusted to the smooth hole (22) there is a pin (22 ') that protrudes the same length on both sides of the part (21) and that fits inside the respective ball bearings (23). The left part of figure 6b shows the section made by the common longitudinal diametral plane of (19) and (21) with the bearings (23) mounted, and the right part the indicated section a-a '.

Figure 7 shows the assembly of the assembly represented in figure 6b. Figure 7a shows the longitudinal section made by the axis of the parts represented in figure 6 once they have been screwed into the bar (17), as well as their relative position with respect to the bushing (18) and the tube (1). The two edges of the groove (4) that appear correspond to the inner and outer surface of the tube (1), that is, to the edge or thickness of the tube. In figure 7b the section aa 'is represented which shows the relative position of the assembly with respect to the tube (1).

Figure 1 indicates the existence of a set (24) at the upper end of the central shaft (1). This set is a mobile head made up of the elements represented in Figures 8 and 9.

In figure 8 the longitudinal section of the assembly (24) that appears in figure 1 made by the longitudinal axis of the tube (1), in addition to its relative position with respect to this tube (1) and the cylinder (6 ). They appear:

- A cylindrical piece (25) with an outside diameter equal to the inside diameter of the tube (1) so that it fits and is flush with it. It has a through coaxial cylindrical bore (26) with a diameter equal to the inside diameter of a plain ball bearing (27). In addition, the part (25) has on its upper face a non-passing coaxial cylindrical recess with a diameter equal to the outer diameter of the flat bearing (27), so that the lower crown of the latter adjusts in the recess, leaving both flush and integral.

- the plain ball bearing (27) mentioned above

- a cylindrical piece (28) with an external diameter equal to the internal diameter of the tube (1). It has a through coaxial cylindrical hole (29) with a diameter equal to that of the hole (7) of the cylindrical part (6). In addition, the part (28) has on its lower face a non-passing coaxial cylindrical recess with a diameter equal to the outer diameter of the flat bearing (27), so that the upper crown of the latter adjusts in the recess, leaving both flush and integral. Finally, the cylindrical piece (28) has three equidistant through cylindrical holes (30) whose respective axes are located in a circle equidistant from the outer edge of the piece (28) and the edge of the hole (29) as shown in figure 9 - three pulleys (31) represented in figure 9 integral with the part (28), placed in a vertical position on its upper face so that the vertical of the bottom of their respective channels coincides on one side with the hole (29) and on the other hand with each of the holes (30). Figure 9a shows the pulleys fixed on the part (28) in plan and figure 9b shows the same section of the part (28) in figure 8, but with the pulleys that are integral with it.

Figure 10 shows the set of parts that make up the mobile head (24) already assembled at the end of the tube (1) as well as their relative position with respect to the cylinder (6).

Figure 11 shows in section perpendicular to the longitudinal axis of (1) -figure 1 la- the elements of the stair lift that are located at the lower end of the latter next to the base plate (3). Figure 11b shows the section according to a vertical plane containing the longitudinal axis of the tube (1). The elements are:

- A three-channel pulley (32) integral with the base plate (3) placed on it in a vertical position inside the tube (1) so that its vertical plane of symmetry coincides with a vertical plane of symmetry of the tube (1 )

- a cylindrical through hole (33) made in the wall of the tube (1) so that its axis is contained in the median vertical plane of the central channel of the pulley (32) and is tangent to said channel at its closest point to the motherboard (3)

Figure 11 also shows a TRACTOR ASSEMBLY THAT IS NOT PART OF THE STAIRCASE DEVICE WHOSE PATENT IS REQUESTED. This set is essential for the operation of the stairlift as it provides the driving force necessary for its operation, and can consist of a single-phase electric motor or a stepper motor that rotates in both directions governed by radio frequency.

The elements of the stairlift described throughout the epigraph are physically linked by three wire ropes (braided steel cables) identified by (34) as shown in figure 12 . Each one of them has an end hooked to a ring (8) and ascends inside the central axis (1), passes through the hole (26), through the interior of the plain bearing (27) and through one of the holes ( 30) to lodge in the bottom of the channel of the corresponding pulley (31) where the direction of its trajectory changes from vertical ascending to vertical descending. In its downward trajectory it passes first through the hole (29), then through the interior of the plain bearing (27), through the hole (26) and finally through the hole (7) of the part (6). It then continues its vertical downward trajectory until it reaches the three-channel pulley (32) where its trajectory changes from vertical to horizontal and goes outside the central axis (1) passing through the hole (33) made in it. The ends of the wire ropes that have remained outside the tube (1) are hooked to the tractor assembly. The element (35) is only a cover that protects the elements described above and that in its graphic representation coincides with the element (24) of figure 1.

Advantages of the invention

The described stair lift has a fundamental advantage over all currently existing stair lifts and especially over the only model marketed in Spain (and over similar ones marketed in other countries), namely: the free distance between the central axis from which the steps start and the structure on which the wide ends of these rest (or the very end of the steps, if they are flown) can be reduced to the minimum necessary value that the person or thing to be transported needs to occupy. In view of the current requirement of a minimum of 65-70 cm, it is possible to install a stairlift when only 45-50 cm of free space is available.

Furthermore, the described stair lift differs from -and improves- existing ones in that:

- It does not require a guide rail, which facilitates cleaning and results in the elegance of the design - It allows the use of a robust tractor unit, not specific for stairlifts, anchored to the base, fed directly from the electrical network and therefore avoiding the ease of periodic recharging, and being able to be hidden within an embellishing element

- uses mechanical safety elements that have been proven for more than a hundred years in the technology of conventional lifting devices: steel cables, pulleys, etc. - at the present time, the cost of installing a stair lift on a spiral staircase - when such installation is feasible - is between two and three times higher than that of installing on a conventional staircase. The model described will allow this cost to be substantially reduced by using, as will be explained later in the Preferred Embodiment section, standardized elements for all cases.

Explanation of the operation of the invention?

Figure 12 allows you to follow the explanation of the operation. Starting from the lowest position of the platform (5), that is to say when the movement of the stair lift is upward , the tractor unit pulls the wire ropes (34) towards itself, so that they move vertically down the inside of the central shaft (1) from the pulleys (31) to each of the pulley channels (32) passing through the hole (29), the interior of the plain bearing (27) and the holes (26) and (7). After the change of direction of movement in the pulleys (31), the ropes (34) hooked on the rings (8) drag the cylindrical piece (6) in an upward vertical direction, which in turn drives the platform (5).

At the same time as it performs the vertical upward movement, the cylindrical part (6) acquires a rotational movement around its longitudinal axis due to the fact that the bar (17) follows the path imposed by the helical groove (4) through which it is forced to slide. See Figures 1 and 5. The bushing (18) prevents, thanks to its free rotation around the bar (17), that it rubs against the edges of the groove (4), thus reducing the friction caused by the movement to almost nullify it. The platform (5) follows the same path as the bar (17) and moves parallel to itself and to the steps of the ladder.

Figure 13a shows how the cylinder (6) would react when subjected to the static force P supported by the platform (5). Said cylinder hangs from the three wire ropes (34) that are hooked to the rings (8) (a single wire rope has been represented for greater clarity of the figure) and when the platform (5) is loaded with the weight P the bar (17) it causes the longitudinal axis of the cylinder (6) - which coincided with the longitudinal axis of the tube (1) - to rotate around the point of intersection of said longitudinal axes with the axis of the bar (17). This situation is the one represented in figure 13a. The upper edge of the cylindrical piece (6) would come into contact with the inner surface of the tube (1) at a point located on the generatrix that passes through the bar (17) - and above the bar. Likewise, as a consequence of the rotation, the lower edge of the cylindrical piece (6) would come into contact with the inner surface of the tube (1) at a point located on the generatrix diametrically opposite to the one that passes through the bar (17) -and below from the bar. If this were to happen, the cylindrical piece (6) would wedge inside the tube (1) and it would be blocked.

To prevent this from happening - figure 13b - the set of parts (19) and (21) threaded to the bar (17) incorporates two ball bearings (23) that rest on the tube (1) on either side of the groove (4) so that, in movement, the trajectory of the bearings (23) always remains parallel to the groove (4). See figure 7b. The central axis (1) absorbs the pressure generated by the load of the platform (5) transmitted from it by the succession of pieces bar (17), bushing (18), piece (19) and ball bearing (23). In this way, the cylindrical part (6) maintains its longitudinal axis parallel to the longitudinal axis of the tube (1) at all times.

This tube (1), even if it is calibrated, has small variations in its internal diameter, the maximum and minimum values of which are specified in its manufacturing standard. The function of the spacer elements (16) in figure 4 is to absorb these small variations when the cylindrical part (6) moves inside the central axis (1) so that the longitudinal axis of (6) always remains parallel to the longitudinal axis of the tube (1). Due to the variation in their elongation, the springs (12) constantly press the solid cylinders (13) against the spheres (15) and these constantly press against the inner surface of the tube (1). The rotation of the spheres (15) on the partial recess (14) makes the friction between them and the inner surface of the tube (1) very small.

The angle of rotation of the cylindrical piece (6) around its longitudinal axis does not exceed 360 ° when the horizontal platform (5) passes from one level to the next higher level. The ends of the wire ropes (34) hooked to the rings (8) therefore rotate that same angle. In figure 12 it can be seen that in its change of trajectory from vertical ascending to vertical descending the wires (34) transmit the weight lifted by the platform (5) to the pulleys (31) pressing on the bottom of their respective channels. The upper crown of the flat ball bearing (27), which is integral with the cylindrical part (28), presses on the balls of said bearing. The rotation of the wire ropes (34) is transmitted to the assembly (24): the part (28) and the upper ring of the flat bearing (27) rotate on the lower ring of the flat bearing (27) fitted to the piece (25), both integral with the tube (1), at the same turning speed as the cylindrical part (6). In this way the wire ropes (34) move parallel to themselves and do not intersect.

There is, however, a torsion of each one of the wire ropes (34) on themselves along their entire length from the pulleys (31) to the pulley (32) on the base plate (3) since the latter two are integral , but this torsion is a maximum of 360 ° when the stairlift ascends one level - about three meters - or 720 ° when it ascends two levels, and it is absorbed without problem by the twisting of the wire rope.

When the movement of the stair lift is downward, the tractor unit rotates in the opposite direction to the one causing upward movement; The force that keeps the wire ropes (34) taut is now the sum of the weights of the cylinder (6) incorporating the spacer elements (16), plus those of the elements (17), (18), (19), (21) , (22 ') and (23), plus that of the platform (5), plus -where appropriate- that of the load transported by this platform. That said, the explanation of the operation of the invention is the same as when the stair lift displacement is upward.

Using the device

Starting from the lowest position of the platform (5), that is to say when it is at the foot of the ladder just above the base plate (3), a person standing on it will start the tractor unit with a remote control and the platform will raise. The linear speed of existing stairlifts is of the order of 7 centimeters per second; In the model described, it should be slightly lower, of the order of 5 cm / s, so that users do not lose stability with movement. Taking this fact into consideration, it is possible to add the elements shown in figure 14 to the platform (5). In conjunction with said platform, a pillar (36) can be arranged that supports a rotating seat (37) on which the user can sit and be transported as if climbing the steps on their back, with their knees oriented towards the steps they have just passed. For greater safety, the platform (5) can be equipped with two vertical bars (38) integral with it and placed in the rear corners - according to the upward movement - of the platform (5), so that the user can be moved subject to they.

At the aforementioned linear travel speed of about 5 cm / s, the stairlift will take between 65 and 70 seconds to cross two consecutive levels in a building.

The platform stop is also controlled with the remote control, the starting and stopping technology of the tractor unit being the usual and common for different industrial applications.

Preferred embodiment of the invention

The described stair lift can be mounted on existing stairs and, of course, on newly built stairs.

The installation in existing stairs -which would be the most frequent case- requires a previous taking of geometric data in situ both of the stair itself and of its envelope or box: height of each of the steps (which would be the riser in conventional stairs ), angle of separation of each of these, free distance from each rung anchor to its opposite extreme. It should be borne in mind that spiral staircases (which are almost always metal) used to be built adapting them to the available space in the building where they were located and they did not usually conform to any dimensional pattern.

The purpose of taking measurements is to define the trajectory of the continuous helical groove (4), which, as already mentioned, must be parallel to an ideal line that connects the anchor points of the steps (2) to the central axis (1) .

In the material execution of the stairlift, two phases must be distinguished after taking measurements in situ: the preparation in the workshop of all the elements that make up the device and their assembly on the existing staircase.

The workshop preparation of the different elements allows them to be standardized so that they are dimensionally the same for practically all existing spiral staircases. Only the platform (5) is likely to differ in dimensions in each stair, as well as the layout of the slot (4). The starting element is the tube that constitutes the central axis (1), being preferred the use of stainless steel tube with an external diameter 4 ”40S according to ANSI B-36.19, cut into 1 meter long sections on which the tracing and emptying the groove (4) so that, once all the sections have been spliced, its helical trajectory fulfills the condition of being parallel to the ideal line joining the inner ends of the steps (2). The rest of the elements of the stair lift can be the same in all cases, only varying the layout of the groove (4) and the measurements of the platform (5).

To carry out the assembly in situ of the elements prepared in the workshop, it is necessary to start by lowering each of the lower rungs of the existing ladder until the height of 1 meter is exceeded by three or four units; then the anchors to the central axis will be cut only from those rungs that are below the height of 1 meter and finally the central axis will also be cut below that height and also at ground level. After removing the cut shaft section, the steps (2) corresponding to it will be dimensionally adjusted so that they coincide with the measurement of the new central shaft (1) prepared in the workshop.

Once this is done, the base plate (3) will be placed, which will already have the three-channel pulley (32) mounted and the first section of the new central shaft (1) with the slot (4) previously emptied in the workshop and the drill will be fixed on it. cylindrical (33) made. The horizontal distance between the groove and the end of each of the rungs, previously defined, will always be the same. Once the verticality of the axis (1) and the horizontality of each of the steps have been verified, they will proceed to weld them to the mentioned axis and to weld the first section of the latter to the base plate (3).

For the assembly of the following sections of the central axis (1), proceed in the same way: lowering the steps, cutting their anchors in the next section of 1 meter of existing axis, cutting and removing this section, dimensional adjustment of the steps, placement of the new section of the central axis (1) prepared in the workshop, verticality and horizontality checks, fixing the steps by welding. In addition, the two new sections of the central axis (1) will be welded together.

Prior to the assembly of the last section, the assembly operations detailed below will have been carried out in the workshop and can be followed with the help of figure 12.

Inside this last section of tube (1) the cylinder (6) will have been inserted with the elements (12), (13), (14) and (15) associated to it that are shown in figure 4, and with each one of the wire ropes (34) attached to its corresponding ring (8)

- the bar (17) will have started to be threaded into the hole (11) and the cylinder (6) will have been fixed near the upper end of the pipe section (1) by tightening against it a threaded nut (not drawn in any figure) on the bar (17)

- the cylindrical part (25), the flat bearing (27) and the cylindrical part (28) will have been assembled in said section as shown in figure 12

- the wire ropes (34) will have been passed through the hole (26), bearing (27) and hole (30), each of them having been provisionally fastened to its corresponding pulley (31) with, for example, adhesive tape

- the free ends of the wire ropes (34) will have been attached to each other and to a weight, for example to a piece of bar with a diameter smaller than the diameter of the hole (7)

- The three free ends attached to the weight will have slid successively through the hole (29), the center of the bearing (27), the hole (26) and the hole (7), keeping each of the wire ropes provisionally attached to its corresponding pulley (31) with adhesive tape

The last section of the central axis (1) thus prepared will be mounted on the previous section and, once the verticality and horizontality checks have been made, the steps (2) will be fixed by welding. After welding the last section, the assembly of the central shaft (1) will be completed.

By removing the nut that retains the cylindrical piece (6), it will be released and it will slide down the interior of the central shaft (1), the ends of the wire ropes (34) reaching the base plate due to the dragging due to the aforementioned weight. Through the hole (33), the weight will be reached and it will be removed, then separating the three wire ropes (34) that will be placed in the corresponding channels below the pulley (32) to later fix them to the tractor unit. From that moment on, the adhesive tapes that kept them attached to the pulleys (31) can be removed.

To assemble the platform (5), the bar (17) must be screwed into the hole (11) as shown in figure 5. At the end of this bar outside the central shaft (1), the bushing (18) will slide and the Thread the part (19) with the bearings (23) already mounted. By slightly screwing or unscrewing the bar (17) in the hole (11), the final positioning of these bearings is achieved so that they remain as shown in figure 7b. This position will be ensured by tightening a nut -not drawn in any figure- against the piece (19). Lastly, the platform (5) will be screwed onto the free end of the bar (17) as shown in figure 5. The horizontal position of said platform will be secured with another nut - not drawn in any figure - tightly tightened against it.

The preferred embodiment described so far is the most suitable for the installation of stairlifts in existing spiral staircases. If it is desired to install it on a newly built staircase, the alternative embodiment described below is preferable.

Alternative realization. The upward (and downward) movement of the cylinder (6) that drives the platform (5) can also be achieved with a conceptually different mechanism from the one described so far and which in mechanical technology is known as a spindle nut. In essence, it consists of a long screw with a constant thread pitch called a spindle that is inserted into a nut and that when rotating produces the longitudinal displacement (rectilinear movement) of the nut into which it is screwed, while transmitting its torque. of torsion (rotational force) which is converted into linear translational force.

In the present invention that is the subject of the patent application, the cylinder (6) would be the equivalent of the nut, for which the hole (7) must have a channel hollowed out in its wall. In this way, said hole would have the equivalent of a fillet with a thread pitch that must be exactly equal to the thread pitch of the helix formed by the rungs (2) in their anchorage around the central axis (1). The existence of this thread pitch is precisely the reason for not recommending this alternative embodiment in existing spiral staircases since the aforementioned helix rarely has a constant thread pitch. In newly built stairs, however, the design and workshop manufacture of its elements allows the trajectory of the steps to be perfectly helical.

The spindle of the screw-nut mechanism would be the element that performs the function of dragging the cylinder (6) previously entrusted to the wire ropes (34) and elements associated with them. This spindle must have a thread of the same depth and pitch as the internal thread of the cylinder (6) so that it meshes perfectly with it. The length of the spindle should be almost equal to that of the central axis (1), which in this case would not have part (32) or parts (25), (27), (28), (31) and (34) assembled . Instead of these, others would be necessary, shown in figure 15 and detailed below (the spindle is not sectioned for a better understanding of the figure).

- at the upper end of the central shaft (1), a ball bearing (39) fitted to its inner face and to which the upper end of the spindle (40) will fit

- on the base plate (3) and integral with it a flat ball bearing (41) that will support the weight of the spindle (40)

- Above the lower support of the spindle (40), it must be provided with a mechanism (42) whose shaft (43) will mesh with a tractor unit that generates a torque that, applied to the shaft (43), will be transformed by the mechanism (42) in rotational movement of the spindle (40). This mechanism (42) may be a bevel gear, an endless screw, a Geneva wheel or any other mechanism that transmits a torque in a direction perpendicular to its own.

Given the great length of the spindle (40), which must be the same as that of the central axis (1), misalignment of the longitudinal axes of both due to buckling of the spindle (40) should not be ruled out. This dimensional deformation will not affect the operation of the device since the cylinder (6), now converted into the nut of the spindle nut mechanism, will behave at all times as an intermediate support for the spindle (40).

Claims (11)

1. Stairlift for spiral staircases consisting of a vertical round tube provided with a helical groove through which a horizontal axis emerges which, in its movement along said groove, drags a platform that can transport people or things. 2. Stairlift for spiral staircases according to claim 1, characterized in that the vertical tube is used to anchor the inner end of each of the steps. 3. Stairlift for spiral staircases according to claim 2, characterized in that the path of the groove is parallel to the line formed by the inner ends of the steps. 4. Stairlift for spiral staircases according to claim 3, characterized in that the horizontal axis is integral with a piece that slides inside the vertical tube. 5. Stairlift for spiral staircases according to claim 4, characterized in that the part incorporates mechanisms that keep it centered inside the tube. 6. Stairlift for spiral staircases according to claim 5, characterized in that the horizontal axis incorporates mechanisms that prevent the part from blocking inside the vertical tube. 7. Stairlift for spiral staircases according to claim 6 characterized by hanging the piece of cables to which it is hooked. 8. Stairlift for spiral staircases according to claim 7, characterized by splitting the cables of a mechanical pulling element outside the horizontal tube positioned in such a way that the cables are in tension both during operation and when standing still. 9. Stairlift for spiral staircases according to claim 6, characterized in that the part performs the function of a nut of a screw-nut mechanism. 10. Stairlift for spiral staircases according to claim 9, characterized in that it incorporates an end-to-end spindle of the vertical tube, inside it and meshing with the part that performs the nut function. 11. Stairlift for spiral staircases according to claim 10, characterized in that it incorporates a mechanism connected to the spindle that transmits the torque of a tractor unit to said spindle, turning it into a turn around its longitudinal axis.