Patent Publication Number: US-6712192-B1

Title: Staircase guide for a stairlift

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a staircase guide for a device for ascending a staircase, for instance a chair lift and so on, in addition to the device and also an assembly of staircase guide and device. 
     2. Description of the Related Art 
     Such staircase guides are generally known, wherein the staircase guide and the device co-act. The device comprises for instance a frame with a carrying element for people or goods and a drive connected to the frame. The staircase guide comprises a cylindrical tube to be adapted to a staircase shape. 
     The known staircase guides usually comprise two tubes which are both engaged by the drive or by the frame of the device in order to hold the carrying element, such as a chair, upright. Used as alternative in known staircase guides are guides of rectangular cross-section, one of which is then needed to hold the frame with the carrying element upright. 
     Known staircase guides with two cylindrical tubes have the drawback that the tubes must be situated at a constant distance relative to one another everywhere along the staircase. Much mounting material is furthermore required to arrange two cylindrical tubes. This is also the case for the material for the guides themselves. In addition, mounting of the circular tubes at mutually equal distances is difficult and time-consuming, wherein the correct alignment for both tubes must be found. Users moreover do not find the hereby created appearance very attractive. 
     Known staircase guides with a single staircase guide of substantially rectangular cross-section provide support possibilities on the frame of the device, so that the carrying element can be held upright, but are much more difficult to adapt to the course or an existing staircase. In the manufacture of such a guide of rectangular cross-section, bends arranged therein can form a considerable weakening when the great forces required are disadvantageously exerted for this purpose. Conversely, this tube better satisfies the aesthetic requirements of users. 
     SUMMARY OF THE INVENTION 
     The invention has for its object to obviate or at least reduce the drawbacks of the known art, for which purpose a staircase guide is provided which is distinguished in that one cylindrical tube is applied with at least one protrusion extending in longitudinal direction of the tube. The protrusion comprises an engaging surface for co-action with a drive element of the drive for the purpose of displacing the stairlift and a support surface for support of the drive by a support member in order to hold at least the carrying element upright. Elimination of the rotation degree of freedom thus results with a construction which can be realized in relatively simple manner. 
     In a staircase guide according to the present invention a single cylindrical guide is applied which is much easier to bend relative to a guide of rectangular cross-section. 
     With bending of the cylindrical guide the staircase guide is adapted to the shape or the progression of the existing staircase where the assembly of for instance stairlift as device and guide must be arranged. It is moreover possible to suffice with a single staircase guide where in the past two cylindrical guides were required in the known assemblies to hold for instance a carrying element of the device upright. Production and mounting are therefore both considerably simplified. The production costs are also reduced. Aesthetic aspects are hereby also improved. Teeth of a gear rack are thus not visible, and there is no danger of grease getting onto the clothing of people walking along the staircase guide. 
     It is noted that different protrusions can be provided, each fulfilling a function. A first protrusion can thus comprise the drive surface, while another protrusion forms the support surface. Although this entails a higher material consumption, such a configuration can be advantageously applied in respect of the distribution of forces round the cylindrical tube. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In a favourable embodiment the protrusion comprises a gear rack arranged on the tube. In this embodiment a toothed surface of the gear rack can form the engaging surface. A gear rack is per se a very favourable and simple embodiment for realizing the engaging surface. The toothed surface is herein preferably directed away from the tube in radial direction and the support surface comprises a side of the gear rack. Such an embodiment has the distinct advantage that the forces exerted by the drive on the toothed surface of the gear rack are directed through the central axis of the cylindrical tube. This produces a very favourable action of forces without the danger for instance of the drive losing grip on the gear rack or running off it in bends of the staircase guide. The drive is further relieved of load compared to an embodiment of the present invention wherein the toothed surface simultaneously forms the support surface and the engaging surface, since in such an embodiment the forces to prevent rotation of the frame on the cylindrical tube are exerted on the toothed surface by the drive, whereby the drive undergoes a higher load than only that necessary to cause movement of the stairlift. In such an embodiment a lighter motor can thus be applied and the gear rack and the other components of the drive can be adjusted hereto, which produces an overall lighter construction. This results in alleviation of the work of mounting and assembling personnel, which is favourable in the context of legislation relating to working conditions. 
     The present invention will be further described below with reference to an embodiment which is shown in 
     FIG.1 shows a perspective view of a stairlift on part of a staircase guide. 
     FIG. 2 shows in partly cut away perspective view a detail of the stairlift and guide shown in FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Identical or similar components or parts are designated in the different figures with the same reference numerals. 
     FIG. 1 shows an assembly  1  according to the present invention. This assembly comprises a stairlift  2  and a guide  3 . Guide  3  comprises a cylindrical tube  4 . Arranged on the underside of tube  4  is a gear rack  5 , the toothed surface of which is directed downward. Gear rack  5  thus extends in radial direction, wherein toothed surface  6  forms an engaging surface for engagement by the drive of stairlift  2 . Because the toothed surface is directed away from tube  4  in radial direction, a very favourable action of forces of the drive, to be further described hereinbelow, of stairlift  2  is obtained. 
     Downward extending side surfaces  7  are situated on either side of the toothed surface of gear rack  5 . These side surfaces  7  function as support surfaces in a manner to be further described hereinbelow. 
     Stairlift  2  comprises a frame  8  on which is arranged a carrying element designed as a chair  9 . 
     The frame comprises a device which determines the position of chair  9  and step-on platform  11  and which is driven by a motor  10 . This ensures that during displacement along the tube  4 , wherein this latter runs obliquely up or downward, the chair  9  and step-on platform  11  remain upright. The progression of the tube is for instance stored in a memory (not shown), wherein motor  10  is driven in order to hold chair  9  and the step-on platform upright along the length of tube  4 . 
     Motor  10  is arranged between frame  8  and chair  9  via a transmission comprising a gearbox  17 . Frame  8  comprises a superstructure  18  having thereon the chair  9  and a base part  19  containing the moving parts for stairlift  2 . Base part  19  and superstructure  18  are tiltable relative to each other under the influence of motor  10  together with gearbox  17 , wherein superstructure  18  and base part  19  are mutually connected for tilting on a shaft  20 . Gearbox  17  is arranged at a distance from shaft  20  between base part  19  and the superstructure and pushes or pulls superstructure  18  into a desired tilt position relative to base part  19  using a worm wheel rod  21  driven by motor  10 . 
     In base part  19  are arranged freely rotatable running wheels  13  which engage on the outer surface of tube  4 . The weight of the stairlift optionally having a person or goods thereon acts for the most part on the upper of the running wheels  13 , while the sideward orientated running wheel  13  serves substantially for reliable guiding. 
     The toothed surface  6  of gear rack  5  is engaged by a toothed wheel  14 , which is connected to a motor  16  via a shaft  15 . Motor  16  forms the drive, while toothed wheel  14  forms the drive element. Toothed wheel  14  extends between two slide blocks  12 , which are also situated on either side of gear rack  5 , i.e. at a short distance from or in contact with the side surfaces  7  of gear rack  5 . Side surfaces  7  of gear rack  5  thus form support surfaces for slide blocks  12 , which thus serve as support member for stairlift  2 . 
     A strip  22  is otherwise arrange- on at least one support surface  7 . This strip preferably has a low sliding resistance when slide blocks  12  support thereon. Strip  22  is then less essential when use is made of running wheels instead of slide blocks  12 . 
     In the embodiment with slide blocks  12  shown in FIG. 2, the stairlift is particularly suitable for a guide with few bends, since slide blocks  12  have a limited capacity to follow a bend. 
     In an embodiment (not shown) use can be made, instead of slide blocks  12 , of one or more than one running wheel which supports against the side surface  7  of gear rack  5  forming a support surface. Such an embodiment of the invention is better able to negotiate bends in tube  4  as a result of the limited contact surface between side surfaces  7  of gear rack  5  and the running wheels (not shown) which support thereon. 
     Because toothed wheel  14  engages the toothed surface  6  of gear rack  5  in a direction in the line of which the central axis of tube  4  is situated, a very favourable distribution of forces is obtained. The only load on motor  16  is that required to move stairlift  2  along the guide. If toothed surface  6  of gear rack  5  were to be situated laterally, i.e. at the position where in FIGS. 1 and 2 one of the side surfaces  7  of gear rack  5  is now situated, toothed wheel  14  would also be loaded with support forces, for which purpose a heavier motor would be required. 
     With the alignment of toothed surface  6  of gear rack  5  shown in FIG.  1  and in FIG.  2  and the corresponding positioning of toothed wheel  14 , a very favourable orientation of both components relative to each other is moreover obtained, particularly in bends, and, even if tube  4  or any other component were to display some play, the danger of toothed wheel  14  of toothed surface  6  running off the gear rack or losing grip is minimized. 
     The present invention is described in the foregoing with reference to a single embodiment thereof. The invention is however not limited hereto, but is defined as the combination of measures of the main claim. The dependent claims relate to preferred embodiments. A number of protrusions, also embodied or designed otherwise than as gear rack, can thus also be arranged on the tube, wherein each of the protrusions fulfils a separate function, i.e. supporting or driving. A solution other than gearbox  17  with motor  10  can be chosen, also within the scope of the present invention, for holding upright the chair and the associated components, such as the step-on platform. Tube  4  can be solid or hollow, although a hollow tube  4  is of course the easier to bend without unacceptable losses of strength etc. When use is made of a toothed wheel  14  for the driving, the toothed surface of the gear rack can be replaced with an array of successive notches in tube  4 , in which notches engage the teeth of toothed wheel  14 . In such an embodiment a different protrusion must be provided to support stairlift  2 . There are thus many other variants and alternative embodiments within the scope of the present invention which will occur to the skilled person after perusal of the foregoing.