Field of application of the invention

The present invention relates to elevators in general and in particular to a reticular frame of an elevator cabin or elevator platform with hidden corner joints.

Review of the known art

Figure 1 shows a frame 1 of an elevator cabin or elevator platform, of which only the metal base 4 is shown for simplicity. The frame 1 is a parallelepiped reticular structure formed of metal bars 2, called uprights and cross members, converging three by three at eight corner joints 3. Each of these joints has three arms orthogonal one to another converging in a common vertex. The ends of the bars 2 are joined to respective arms of respective corner joints 3. The frame 1 in particular comprises:

four cross members 2a the ends of which are joined, two by two, to two arms of a respective joint 3 of a first group of four, forming a rectangular supporting structure for the metal base 4 of the cabin;

- four uprights 2c one end of which is joined to the third arm of a respective joint 3 of the first group;

four cross members 2b the ends of which are joined, two by two, to two arms of a respective joint 3 of a second group of four, forming a rectangular supporting structure for the roof of the cabin; the other end of the uprights 2c being joined to the third arm of a respective joint 3 of the second group.

Each orthogonal arm of a joint 3 consists of two walls joined at 90° along a common longitudinal edge, contiguous to the walls of two other arms forming the common vertex. The corner joint thus obtained presents an external surface and an internal surface that delimits a seat for connection of the ends of the cross members 2a (or 2b) and of the upright 2c converging there. The metal bars 2 comprise walls joined at 90° along a common longitudinal edge forming a tubular structure whose ends are in contact with the internal surface of the seat into which they fit in the respective corner joints. The connection of cross members 2a and 2b and of upright 2c to the corner joint 3 is made outside the bars by means of screws the engage with threaded bushes (not seen in the figure) inserted in said bars.

According to the description, the corner joints 3 project beyond the metal bars 2 inside the hoistway 5 for as much as the total thickness of the metal sheet of which they are made (usually about 4 mm) and the thickness of the screw head. This creates a problem affecting the proper functioning of the system. When the cabin is at a floor, the distance between the threshold of the cabin and that of the floor must be extremely short for reasons of safety. For European Community regulations, this distance can be set by norms harmonized with the directive concerned and, particularly for elevators, it must be of 35 mm or less, while for elevator platforms it must be of 20 mm or less. In cabins with only one access, the 4 mm projection of the corner joints reduces the space needed for correctly operating the system, increasing the risk of contact between the cabin and the structure 6 of the door 7 on the floor side, a risk already increased by the hoistway 5 being inevitably out of plumb, and by the tolerances allowed for civil works.

Figure 2 shows a cross section of an elevator plant that employs the frame in Figure 1 in a two-door cabin , namely with doors in two opposite walls. Seen inside the hoistway 5, to the right of the figure, is a cross section of a hydraulic lifting apparatus and a lateral direct telescopic piston, with T-shaped slide guides 8 for the cabin fixed to opposite walls of a U-shaped bracket 9 anchored to the wall 10 of the hoistway 5. The frame 1 is rigidly joined to car sling which includes sliding blocks (not shown in the figure) that slide along guides 8.

In an installation of this kind as shown in Figure 2, the risk of contact referred to above doubles because there are two doors on opposite sides of the cabin. A further defect in these reticular-structured frames, according to the prior art, consists in the fact that, according to the way the ends of the bars 2 are fitted into the respective seats in the joints 3, said seats can be only partly occupied by the bars 2 thus creating spaces between bar ends. In this case small blocks of polyethylene must be fitted in between said ends.

Purpose of the invention

The purpose of the present invention is therefore to overcome the above drawbacks and propose a reticular-structured frame with corner joints that do not further extend into the hoistway beyond the metal bars forming part of the frame.

Summary of the invention

To achieve this purpose, subject of the present invention is a frame for an elevator cabin or elevator platform comprising:

longitudinal metal bars respectively called uprights and cross members;

- metal corner joints having three arms, orthogonal one to another, joined to respective ends of said cross members and said uprights, to form a rigid reticular structure;

- means for fixing said bars to the arms of said corner joints,

wherein, according to the invention:

each metal bar includes a longitudinal cavity delimited by walls of which at least two, orthogonal one to another, form a seat at each end of the bar to house an arm of a respective corner joint, said arm having two walls respectively in contact with said at least two orthogonal walls, as described in claim 1.

Further characteristics of the present invention, considered innovative, are described in the dependent claims. In accordance with a first embodiment of the invention with corner joints of bent and welded sheet metal, each orthogonal arm of a corner joint consists of two walls joined at 90° along a common longitudinal edge, either bend or welding, the two walls of each arm being contiguous to those of the other two arms at a common vertex. Each arm of the corner joint therefore has an external surface in relation to the trihedron delimited by the three arms converging at the common vertex. Consistent with the above, coupling between joints and related bars is such that the external surface of each arm of the corner joint is in contact with the surface of said two walls, the one orthogonal to the other, inside the cavity of the respective bars. As the corner joint is completely contained in the seats present in the cross members and in the corresponding upright, the distance between the threshold of the cabin and that of the floor is not adversely affected, thus overcoming the drawback present in the known art, the length of the cross members remaining unaltered. According to one aspect of the first embodiment, the crosswise sections at the two ends of each cross member converge at 45°, so that the edges of contiguous cross members can match together.

To enable the cross members converging in a vertex to match at 45°, there are two longitudinal clefts starting from respective edges of the horizontal wall of said cross members which lies adjacent to two respective uprights, fitted into each of said clefts is the edge of a wall of the vertical arm of a corner joint fixed to a said respective upright.

In accordance with a second embodiment of the invention wherein the corner joints are obtained by die-casting, each corner joint comprises a parallelepiped block from which said arms depart, orthogonal to three faces of the block with a common vertex, leaving free a pedestal round each arm to receive the edge of one end of the bar joined to that arm, the width of the pedestal being such that the faces of the block opposite to those from which the arms engaged in seats present in the respective cross members depart are flush with the walls of the bars contiguous to said faces.

According to an aspect of the second embodiment, especially for very heavy cabins, the arms of the corner joint are solid prismatic bars having at least two walls orthogonal one to another in contact with the surface of the two walls the one orthogonal to the other inside the cavity of the respective bars. The advantage is the same as that obtained with the first embodiment.

Alternatively, a vertical arm comprises a longitudinal groove aligned with a hole that passes through said block for insertion of a tie-rod whose ends are bolted against the walls of opposite corner joints, further increasing the rigidity of said reticular structure.

According to one aspect of the invention, common to the two embodiments, there are longitudinal grooves in the uprights and in the cross members to house the edges of the panels forming the walls of the elevator cabin or elevator platform. In the second embodiment there is a parallelepiped cavity on each edge of the block comprised between pairs of arms for insertion of a corner of the wall panel.

According to one aspect of the invention, in the metal bars and in the arms of the corner joints are holes reciprocally aligned for insertion of said fixing means, said fixing means do not project beyond the external surface of the wall of said metal bars.

According to another aspect of the invention, the fixing means include flat- headed screws.

According to another aspect of the invention, the metal bars are aluminium extrusions whose walls are lightened by longitudinal cavities lying parallel to said seat.

According to another aspect of the invention, the lightener cavity does not continue into the part crossed by said fixing means comprising a flat-headed screw.

According to another aspect of the invention, the fixing means include lowered head screws.

Advantages of the invention

Thanks to the innovations included in the invention, the advantage compared with known systems consists in reducing the bulk of the reticular structure of the frame of the cabin, which otherwise might become critical in many installations. This also facilitates assembly of the elevator allowing for hoistways imperfectly realized or out of plumb, especially in cases where the cabin has two doors on opposite sides.

On account of the shape of the corner joints and of the way in which they join cross members to uprights, no empty spaces are left between the metal bars at the vertices of the frame. There is thus no need for polyethylene filler blocks and the frame is all the more stable as a consequence.

The profile of the arms of the joint need not necessarily be strictly complementary to the internal profile of the uprights and of the cross members into which it is inserted; all that is needed is to respect the coupling at the two I walls, orthogonal one to another, of the seat that houses each arm. This makes it possible to couple the joint of the frame with uprights having different internal profiles.

In cases of cabins and hoistways with transparent walls (for example, to allow passengers to see outside the cabin), a further aesthetic advantage consists in > the fact that arms of the corner joints are invisible.

Short description of the figures

Further purposes and advantages of the present invention will be clear from the following detailed description of an example of its realization and from the attached drawings provided solely for explanatory reasons and in no way

) limitative, wherein:

Figure 1 is a perspective view of a reticular-structured frame of an elevator cabin and an elevator platform, according to the known art.

Figure 2 shows a cross section of an elevator system wherein the cabin has two doors on opposite sides, realized with the frame in Figure 1.

5 Figure 3 is a plan view of a semifinished product made of sheet metal for realization of a corner joint forming part of a reticular frame according to the present invention.

Figure 4 is a perspective view from the front of the corner joint obtained by bending and welding the sheet metal in figure 3.

) Figure 5 is a side view of the corner joint in Figure 4.

Figure 6 is a perspective view of the corner joint in Figure 4 with the arms partially inserted in metal bars. Figure 6a is a cross section of the bars in Figure 6.

Figure 7 is a perspective view of a reticular frame according to the present invention, realized using corner joints like that in Figure 4 to join metal bars like those in Figure 6.

Figure 7a is a longitudinal section according to plane A-A in Figure 7.

Figure 8 is a perspective view, of a corner joint according to the invention, alternative to the joint in Figure 3.

Figures 9 to 11 are plan views, respectively side, rear and from below, of the corner joint in Figure 8.

Figure 12 is a perspective view of the corner joint in Figure 8 with two arms completely inserted in two respective metal bars, and the third arm partially inserted in a third bar.

Figure 13 is a perspective view of a reticular frame alternative to the frame in Figure 7, realized using corner joints like that in Figure 8 for joining metal bars like those in Figure 12.

Figure 13a is a longitudinal section according to plane B-B in Figure 13.

Detailed description of some preferred forms of realizing the invention

In the following description identical parts that appear in different figures can be marked with the same symbols. In explaining a figure reference may be made to parts not shown in that figure but in previous ones.

Figure 3 shows a metal sheet 20 laid flat, cut in the form of a cross with arms of equal length lying along orthogonal axes 20a and 20b. Two arms 23 and 24, orthogonal one to another, are of a length half that of the remaining arms 21 and 22. The axes 20a and 20b are symmetrical in relation to arms 21 and 22. One side of arms 23 and 24, respectively 23b and 24b, is therefore disposed along a respective axis 20a and 20b, and the two sides cross one another at the centre of the cross at a circular hole 33. The metal sheet in this example is galvanised steel and is about 4 mm thick. In each full width arm, 21 and 22, there are four hexagonal holes of equal size, respectively 25 and 29, disposed symmetrically in relation to a longitudinal axis, aligned, two by two, parallel to said axis. The distance between the aligned holes and their distance from the shorter side are the same for arms 21 and 22. The positions of the hexagonal holes 30, 32 respectively present in the shorter arms 23, 24, are the same as for those in arms 21, 22 on one side only in relation to the longitudinal axes 20a and 20b.

The metal sheet 20 is a semifinished piece to be used to make a corner joint 40 (Figure 4).

Figure 4 shows the corner joint 40 obtained from the metal sheet 20 after two 90° bends have been made in opposite directions along axes 20a and 20b, and a weld 41 along matching sides 23b and 24b. Following these operations three arms 42, 43, 44 orthogonal one to another will be formed and converge at a common vertex 33. Arm 42 consists of two walls, 21c and 21d, joined at 90° along a bend 21b. Arm 43 consists of two walls, 22c and 22d, joined at 90° along a bend 22b. Arm 44 consists of two walls, 23 and 24, joined at 90° along the welded edges 23b and 24b. Bends 21b and 22b and the welded edges 23b and 24b converge at the vertex 33 of the trihedron formed by arms 42, 43 and 44.

Figure 5 shows that holes 29 in arm 43 occupy the same positions as holes 30 and 32 in arm 44. The same positions apply to holes 25 in arm 42.

Figure 6 shows joint 40 with its arms 42 and 43 placed horizontally and arm 44 vertically. Horizontal arms 42 and 43 are seen partially inserted inside the longitudinal cavities 45a and 46a present in two metal bars, respectively 45 and 46, acting as cross members in the interconnections to be seen in Figure 7. The vertical arm 44 is also shown partially inserted inside a longitudinal cavity 47a present in a metal bar 47 acting as an upright in the interconnections to be seen in Figure 7.

Figure 6a shows the form taken by metal bar 47 at any non-terminal cross section. The same figure, and its description, also apply to bars 45 and 46. Metal bar 47 comprises four walls 50, 51, 57, 60 orthogonally joined one to another to define the longitudinal cavity 47a for housing the vertical arm 44 of corner joint 40. The extrusion mould for bar 47 is shaped so that the walls 50, 51, 57, 60 are lightened by longitudinal cavities 48 separated by partition walls 55, narrower than the width of the cavity, in the form of ribs to achieve the same rigidity as the solid wall. The longitudinal walls 57 and 60 have a common edge 63 widely bevelled to 45°; the two cavities 48 at either side of the bevelled edge 63 are open outwards so that, together with the partition walls 55, they form two longitudinal grooves 66 and 67 to house the edges of respective panels forming the walls of the cabin.

Referring again to Figure 6 it will be noted that the external surface of contiguous walls 23, 24, orthogonal one to another, of the vertical wall 44 inside the cavity 47a of upright 47, is in contact with the surface of the hollow walls 50, 51 having a common edge opposite the bevelled edge 63. Similarly, the external surface of contiguous walls 22c and 22d, orthogonal one to another, of horizontal arm 43, inside the cavity 46a of cross member 46, is in contact with the surface of the hollow walls 50, 51 these having a common edge opposite to the bevelled edge 63. Also similarly, the external surface of contiguous walls 21c and 2 Id, orthogonal one to another, of horizontal arm 42, inside cavity 45a of cross member 45, is in contact with the surface of walls 50, 51 having a common edge opposite the bevelled edge 63. The width of the walls of the arms is substantially equal to the width of the face of the walls of the metal bar with which they are in contact.

The first crosswise terminal sections 68 and 69 of cross members 45 and 46 engaging the horizontal arms 42, 43 of the corner joint 40, are inclined at 45° in relation to the longitudinal axis so that, once assembled as seen in Figure 7, the edges of the above sections 68 and 69 match. The second terminal sections of cross members 45 and 46 (not shown) are inclined at 45° in the opposite direction in relation to the first terminations 68 and 69. A first terminal section 70 of upright 47, engaging the vertical arm 44 of corner joint 40, rests against the horizontal wall 57 of the respective cross members 45 and 46 (when assembled as in Figure 7); the same may be said for the other termination of upright 47.

Present in the horizontal hollow wall 57 of cross members 45 and 46, is a respective longitudinal cleft 57a into which fit the vertical walls 23 and 24 of arm 44, with terminations 68 and 69 of cross members 45 and 46 matching at their respective edges at 45°. Wall 50 of upright 47 is crossed through by two holes 71 and 72 aligned with holes 30 present in the wall 23 of the vertical arm 44 of corner joint 40. Similarly, the wall 50 of cross members 45 and 46 is crossed through by two holes (61 in Figure 7a) aligned with holes, respectively 25 and 29, in the horizontal walls 21d and 22d of horizontal arms 42 and 43.

Figure 7 shows a frame 80 of an elevator cabin or elevator platform (for simplicity, only the metal base 82 is shown) obtained by assembling the components already described. It will be seen that the frame 80 is a parallelepiped reticular structure made of metal bars that converge, three by three, at eight corner joints identical to joint 40. Frame 80 comprises in particular:

four lower cross members 81 (including metal bars 45 and 46) fixed two by two as will be seen in Figure 7a to corresponding horizontal arms 42 and 43 of the respective corner joints 40 of a first group of four, forming a rectangular supporting structure for the metal base 82 the edges of which fit into the grooves 67;

four uprights 84 (including metal bar 47) fixed at one end to corresponding vertical arms 44 of respective corner joints 40 belonging to the first group; four upper cross members 83 fixed, two by two, as will be seen in Figure 7a to corresponding horizontal arms 42 and 43 of the respective corner joints 40 of a second group of four, forming a rectangular supporting structure for the metal roof of the cabin, the edges of which fit into the grooves 67. The other end of uprights 84 is fixed to corresponding vertical arms 44 of respective corner joints 40 belonging to the second group, forming angular supporting structures for the panels of the side walls of the cabin. The lower and upper edges of said panels are fitted into grooves 66 of cross members 81 and 83, respectively lower and upper, while the lateral edges are fitted into grooves 66 and 67 in the uprights 84.

Figure 7a shows a preferred type of join for joining the metal bars, uprights 84 and cross members 81 and 83, to the corresponding arms 42, 43 and 44 of the respective hidden corner joints. For this join flat headed screws are used, therefore lying flush with the external surface of bars 81, 83 and 84 and further reducing encumbrance in the elevator shaft. The use of flat-headed screws makes it necessary to fill a short terminal length of the cavities in the walls of the extruded bars beforehand and after that make the holes. The filling material, described as MR, may be the aluminium itself or else a thermosetting resin sufficiently rigid to avoid deformation of the wall when the screws are tightened. As an alternative, lowered head screws may be used without altering the extruded profiles but this involves a slight encumbrance in the hoistway.

In Figure 7a the connection may be seen between the horizontal wall 21d of arm 42 of the joint 40 and wall 50 of the lower cross member 45. Wall 50 is solid around the hole 61, aligned with hole 25 in wall 2 Id. Filling is continued for a length that goes from the edge 68 to beyond the hole 61. A hexagonal nut 52 is set in the hole 25 and there welded to wall 2 Id. Hole 61 is not threaded and has an initial flared section to receive the flared head of a screw 62 that screws into the nut 52.

As seen in Figures 7 and 7a nothing projects from the external surface of the bars to the inside of the elevator shaft.

Figure 8 shows a corner joint 90 obtained from die-cast aluminium using a special die. The corner joint 90 comprises a block 91 substantially cubic in shape, from three faces 92, 93, 94 of which, each consecutive to the other twos, three respective arms 95, 96, 97 project orthogonally from a central position; said arms are of equal length, but could also be of different lengths. Arms 95, 96 97 are prismatic in shape with an octagonal base corresponding to a square with bevelled vertices, the sides of which are disposed parallel to the edges of block 91. Arm 97 comprises a longitudinal parallelepiped groove 97d open towards arm 95, delimited by three contiguous walls 97a, 97b, and 97c starting from an external wall 97a. Groove 97d communicates with an unthreaded hole 101 that passes through block 91 in the direction of the groove. Passing through arm 95 is a pair of unthreaded holes 98 parallel to arm 97, disposed along the centre line of arm 95. Passing through arm 96 is a pair of unthreaded holes 99 parallel to arm 97, disposed along the centre line of arm 96. Passing through the wall 97a of arm 97 is a pair of unthreaded holes 100 parallel to arm 96, disposed along the centre line of wall 97a.

Three parallelepiped cavities 102, 103, 104 are made in block 91 on the edges comprised between the pairs of consecutive faces from which arms 95, 96, 97 depart. Cavity 102 in particular is comprised between arms 95 and 96; cavity 103 between arms 96 and 97, and cavity 104 between arms 95 and 97. Cavities 103 and 104 are realized in a substantially central position on respective edges. Cavity 102 is realized starting from a substantially central position and extending as far as face 1 11 (Figure 11) of block 91 opposite face 94. The vertex of block 91 comprised between three cavities 102, 103, 104 is bevelled to form an equilateral triangular surface 108.

Figure 9 is a plan view of joint 90 from the side of face 92 of block 91 in Figure 8. It will be seen from Figure 9 that wall 97b is crossed through by a pair of unthreaded holes 109 parallel to arm 95, disposed along the centre line of wall 97b. The distance of holes 109 from the face 94 of block 101 is equal to the distance of holes 100 from the same face, and similarly equal to the distance of holes 99 from face 93.

Figure 10 is a plan view of joint 90 of Figure 8 from the side of face 1 10 opposite to face 93. Looking at Figure 10, it will be seen that the distance of holes 98 of arm 95 from face 92 is equal to the distance of holes 100 and 109 from face 94. Holes 98, 99, 100 and 109 are therefore at the same distance from the faces of block 91 from which the arms containing them extend.

Figure 11 is a plan view of joint 90 in Figure 8 from the side of face 1 1 1 opposite face 94, after joint 90 has made a clockwise rotation of 90°. It will be seen from Figure 11 that the diameter of hole 101 is practically equal to the distance between walls 97a and 97c, and is tangential to wall 97b.

Figure 12 shows joint 90 with its arms 95 and 96 disposed horizontally and arm 97 disposed vertically. The figure shows two identical bars 120 and 121 used as cross members, and a third identical bar 122 used as an upright in the interconnections that will be seen in Figure 13. < The cross members 120 and 121 differ from cross members 45 and 46 in Figure 6 solely because of not having terminations inclined at 45°. The walls of bars 120, 121, 122 delimit three respective identical longitudinal cavities 120a, 121a and 122a equal to the cavities in the bars in Figure 6.

Referring to Figure 12, it will be seen that arm 95 is partially inserted inside the cavity 120a, while arms 96 and 97 are not shown since they are completely inserted in the respective cavities 121a and 122a of bars 121 and 122.

The faces of arms 95 and 96 parallel or orthogonal to the edges of block 91, and one of the bevelled edges are respectively in contact with the walls and with the bevelled edge that delimit cavities 120a and 121a present in the cross members 120 and 121. The walls 97a, 97b and 97c of arm 97 are respectively in contact with the walls that delimit the cavity 122a present in upright 122. The faces of block 91 , opposite faces 92, 93 and 94 from where the arms 95, 96, 97 depart, are flush with the walls of bars 121 and 122 contiguous to said faces. The height of block 91 is equal to that of the cross members 120 and 121. Further, cavity 103 is as wide as the groove 66 in cross member 121 and as groove 67 in upright 122, and is contiguous to said grooves.

Two holes, 128 and 129, pass through the wall of upright 122 in contact with wall 97b of the grooved arm 97, said holes being aligned with holes 109 in said wall 97b. Similarly, two holes (130 in Figure 13a) pass through the wall of cross members 120 and 121 opposite the respective grooves 66, said holes being aligned with holes, respectively 98 and 99, of the horizontal arms 95 and 96.

Figure 13 shows a frame 140 of an elevator cabin or elevator platform (of which, for simplicity only the metal base 142 is shown) obtained by assembly of the components seen in Figures 8 to 12. It will be noted that the frame 140 is a reticular structure parallelepiped in shape, consisting of metal bars converging three by three at eight corner joints 145 identical to joint 90. Frame 140 comprises in particular:

four lower cross members 141 ( including metal bars 120 and 121), fixed two by two, as will be seen in Figure 13a, to corresponding horizontal arms 95 and 96 of respective corner joints 145 (including joint 90) of a first group of four, to create a rectangular supporting structure for the metal base 142, the edges of which are inserted in grooves 67 and the vertices of which are inserted in the cavities 102 in the blocks of the joints 145;

four uprights 144 (including the metal bar 122) fixed at one of their ends to corresponding vertical arms 97 of respective corner joints 145 belonging to the first group;

four upper cross members 143 fixed two by two, as will be seen in Figure 13a, to corresponding horizontal arms 95 and 96 of the respective corner joints 145 of a second group of four, forming a rectangular supporting structure for the metal roof of the cabin, the edges of which are inserted in grooves 67 with the vertices inserted in the cavities 102 in the blocks of joints 145. The other end of the uprights 144 is fixed to corresponding vertical arms 97 of respective corner joints 145 belonging to the second group, to form supporting corner structures for the panels of the lateral walls of the cabin. The lower and upper edges of said panels are inserted in grooves 66 of respectively lower and upper cross members 141 and 143; the lateral edges of said panels are inserted in grooves 66 and 67 of uprights 144; the vertices of said panels are inserted in cavities 103 and 104 in the blocks of corner joints 145.

The bevelled vertices 63 of cross members 141 and 143 and of uprights 144 converge in the triangular bevelled surface 108 present in blocks 91 of corner joints 145.

The frame 140 also comprises four tie-rods (not shown in the figures) each of which is placed in the longitudinal cavity 122a of the respective upright 144 passing through: the hole 101 in the block 91 of a lower corner joint, the longitudinal slot 97d in the vertical arm 97 of the lower corner joint, the longitudinal slot 97d in the vertical arm 97 of an upper corner joint and, lastly, the hole 101 in block 91 of the upper corner joint. The tie-rods are bolted to the two threaded ends emerging from the respective blocks 91 of corner joints 145, respectively lower and upper, to sustain the rigid base 142 of the cabin, this too helping to increase structural rigidity of the frame 140.

Figure 13a shows a type of preferred connection of the metal bars, uprights 144 and cross members 141 and 143, to the corresponding arms 95, 96, 97 of the respective corner joints 145. For this connection flat-headed screws are used, these lying flush with the external surface of bars 141, 143, 144 and further reducing encumbrances in the elevator hoistway. The use of flat-headed screws needs prior filling of a short terminal length of the cavities contained in the wall of the extruded bars, followed by execution of the holes. The filling material, described as MR, can be the aluminium itself or a thermosetting resin of sufficient rigidity to avoid deformation of the wall which might be caused by tightening the screw. Alternatively lowered head screws can be used without altering the extruded bars, though this may slightly increase encumbrances in the elevator hoistway.

Referring to Figure 13 a, the connection can be seen between arm 95 of the joint 90 and the wall 50 of the lower cross member 120. The wall 50 is solid round the hole 130 aligned with hole 98 in arm 95. Filling is continued for a length from the edge 124 to beyond the hole 130. A threaded bushing 146 is set in the hole 98. Hole 130 is not threaded and its initial length 147 is flared to receive the flat head of a screw 149 that engages in the bushing 146. As will be seen from Figures 13 and 13a, the external walls of the bars are flush with the faces of the blocks of joints contiguous to said faces and there is nothing that can project from the external surface of the bars to the inside of the elevator shaft.

Based on the description given of an example of a preferred realization, it is clear that some changes can be made by an expert in the field without thereby departing from the sphere of the invention as will appear from the following claims.