System for guiding and supporting a leaf of a platform-access door

A system for guiding and supporting a leaf of a platform-access door capable of moving relative to a fixed panel in a horizontal translational movement in a plane of the leaf between open and closed positions, includes a rail extending in a direction of the horizontal translational movement, a first set of rollers collaborating with the rail with and being made up of: a main roller in contact with a lower bearing surface of the rail; first and second secondary rollers which are vertically offset from one another and are respectively in contact with the lower bearing surface and with an upper bearing surface of the rail and are spaced from the main roller.

This application claims priority to International Application No. PCT Application No. PCT/FR2016/051995 filed Jul. 29, 2016; and French Patent Application No. 1557442 filed Jul. 31, 2015; the entire contents of each are incorporated herein by reference.

The invention relates to a guiding and support system for a leaf of a platform screen door, and to a platform screen door equipped with such a guiding and support system.

The platform facades make it possible to isolate the platform deck as such from the traffic line along which the platform extends, when there is no traffic on said traffic line. However, when a train, e.g. a rapid transit train, is parked at the platform along the platform, the platform facade must allow the users access to the cars of the parked train. For that, the platform facade comprises a series of screen doors arranged so as to extend facing access doors of the train likely to be parked along the platform. As is known per se, a platform screen door forms a module which comprises at least one fixed part and an associated sliding leaf which can be moved between an open position and a closed position (and vice versa) in a horizontal direction in the plane of the leaf and substantially parallel to a platform edge coping on which the screen door is positioned. In open position, the leaf at least partly frees an opening allowing passage for the users adjacent to the fixed part of the screen door. In closed position, the leaf blocks this opening. For that, a guiding and support system is provided between the fixed part and the associated sliding leaf, together with a motor drive to move the sliding leaf in its translational movements between the open and closed positions.

Generally, the platform screen doors comprise two pairs of fixed part/sliding leaf positioned symmetrically in mirror-fashion. The two fixed parts are separated from one another by a door threshold, the assembly delimiting the opening allowing passage for the users. The two sliding leaves can then be moved according to horizontal translational movements in the plane of the leaves which are symmetrical to one another between the closed position and the open position and vice versa. Each of the sliding leaves has a guiding and support system and an associated motor drive.

Also, the standards imposed for the platform screen doors require the provision of at least one guiding and support system which allows:

a resistance to the pumping effect induced by the passage of a train on the traffic line along the platform facade, therefore along the screen door equipped with the guiding and support system;

a resistance to wind;

a resistance to possible thrust induced by the users that may be located on the platform deck;

a support for the weight of the sliding leaf linking the guiding and support system to the associated fixed part.

Such guiding and support systems are illustrated for example in the document JP 2010-105547. It emerges that such guiding systems require numerous moving parts or parts rubbing against one another. This increases the complexity of the maintenance interventions and increases the risks of failure. This then involves a high manufacturing and servicing cost.

One aim of the invention is to provide a guiding and support system for a sliding leaf of a platform screen door which is simpler and less costly to produce and to service.

To this end, according to the invention, a guiding and support system is provided for a leaf of a platform screen door, the leaf being able to be moved in relation to a fixed panel by a horizontal translational movement in a plane of the leaf between open and closed positions in which the leaf at least partly frees or blocks an opening adjacent to the fixed panel, comprising:

a rail extending in a direction of the horizontal translational movement

a first set of rollers cooperating with the rail to guide it and support it in the horizontal translational movement, each roller of the set of rollers comprising an axis of rotation at right angles to the plane of the leaf, the first set of rollers consisting:

of a main roller in contact with a bottom bearing surface of the rail,

of first and second secondary rollers offset relative to one another in at least one vertical direction and in contact respectively with the bottom bearing surface of the rail and a top bearing surface of the rail, the first and second secondary rollers being positioned at a distance from the main roller in the direction of the horizontal translational movement and in the direction of a transition from the closed position to the open position.

Advantageously, but optionally, the guiding and support system according to the invention offers at least one of the following additional technical features:

the second secondary roller is situated between the main roller and the first secondary roller;

the second secondary roller is offset in the direction of the horizontal translational movement in relation to the first secondary roller;

the system comprises a second set of rollers intended to laterally guide the rail in a horizontal direction at right angles to the direction of the horizontal translational movement;

the second set of rollers comprises a first pair of rollers positioned at the level of one out of the main roller and one of the secondary rollers;

the second set comprises a second pair of rollers positioned at the level of the other out of the main roller and one of the secondary rollers;

the first set of rollers comprises an additional roller in contact with the top bearing surface of the rail and positioned vertically to the main roller;

the main roller comprises two rollers positioned one behind the other in the direction of the horizontal translational movement;

the bottom and top bearing surfaces comprise rolling tracks inscribed in a circle so as to form a pivot function between the rail and the first set of rollers; and

the rollers of the first set of rollers are mounted to be translationally mobile on their axis against elastic limiting means, the elastic limiting means forming calibrated springs.

According to the invention, there is also provided a platform screen door comprising a threshold, a first fixed panel and a first leaf that can be moved in relation to the first fixed panel by a horizontal translational movement in a plane of the leaf between open and closed positions in which the first leaf at least partly frees or blocks an opening adjacent to the first fixed panel, as well as a guiding and support system for the first leaf having at least one of the preceding technical features.

Advantageously, but optionally, the screen door according to the invention has at least one of the following additional technical features:

the rail is secured to the first leaf and the first set of rollers is secured to the first fixed panel;

the guiding and support system is situated in a bottom part of the screen door;

the screen door comprises:a second fixed panel, separated from the first fixed panel by the opening and the threshold;a second leaf that can be moved in relation to the second fixed panel by a horizontal translational movement in a plane of the leaf between open and closed positions in which the second leaf partly frees or blocks the opening, the horizontal translational movement of the second leaf being symmetrical to the horizontal translational movement of the first leaf; anda guiding and support system for the second leaf having at least one of the preceding technical features;

the screen door comprises a driving mechanism for the leaves comprising a driving motor, two flexible elongate driving elements fixed crosswise, the driving motor driving just one of the two flexible elongate driving elements, one of the flexible elongate driving elements comprising two ends fixed respectively to a left end of the rail of the guiding and support system for the first and second leaves and the other of the flexible elongate driving elements comprising two ends fixed respectively to a right end of the rail of the guiding and support system for the first and second leaves;

the flexible elongate driving elements run partly in or under the threshold;

the flexible elongate driving elements are belts, chains or cables;

the driving motor is situated in the bottom part of one out of the first and second fixed panels; and

the driving motor is positioned under the rail of the guiding and support system for one out of the first and second fixed panels.

Referring toFIG. 1, as has been indicated in the preamble to this description, a screen door1comprises, here, from one end to the other, a first emergency door4, a first fixed part3, a first sliding leaf2associated with the first fixed part3, a second sliding leaf2, a second fixed part3associated with the second sliding leaf2, and a second emergency door4. In a variant embodiment, the first and second emergency doors4can be fixed panels. A door threshold6separates the two fixed parts3from one another and delimits with it an opening adjacent to the fixed access parts3. The first and second sliding leaves are mounted to be horizontally translationally mobile in the plane of the sliding leaf over the fixed part3which is associated with them via a guiding and support system8according to the invention. Thus, each sliding leaf can assume a closed position in which it at least partly blocks the adjacent opening and an open position in which it at least partly frees the abovementioned adjacent opening. In addition, the two sliding leaves are driven by symmetrical and, preferably, synchronized translational movements.

It should be noted that the guiding and support system8according to the invention is positioned, here, in the bottom part of the screen door, and therefore of the fixed part3and of the sliding leaf2that it links. In addition, as will be seen later, the motor drive mechanism of the sliding leaves2is itself also situated in this bottom part. In a variant embodiment, the guiding and support system8and/or the motor drive mechanism can be situated in any part of the screen door and therefore of the fixed part3and of the associated sliding leaf2.

Referring now toFIG. 2, there now follows a more detailed description of the guiding and support system8,8′ according to the invention. Here, the first guiding and support system8according to the invention allows the first sliding leaf2to be mounted on the first fixed part3of the screen door1and the second guiding and support system8′ according to the invention allows the second sliding leaf2to be mounted on the second fixed part3of the screen door1. The two guiding and support systems8and8′ according to the invention are symmetrical in mirror-fashion. The first guiding and support system8according to the invention comprises a rail11and a rail support20. The second guiding and support system8′ according to the invention comprises a second rail12and a second rail support30. The rails11and12are, here, identical and the rail supports20,30are symmetrical in mirror-fashion. Hereinbelow, only the first guiding and support system8according to the invention will be described, the description applying mutatis mutandis to the second guiding and support system8′ according to the invention.

Referring toFIGS. 5 to 8, the rail is an extruded section and is preferably fixed onto the sliding leaf2. In cross section, the rail11is, as illustrated here, overall of rectangular form. As a variant, other forms are possible. Therefore, here, it comprises a top wall115, an outer sidewall (on the right inFIG. 7) connected to the top wall115. The rail11comprises a bottom wall118connected on a side edge to the outer sidewall116. The bottom wall118comprises a bottom bearing surface1181and a top bearing surface1182. The rail11further comprises an inner sidewall117(on the left inFIG. 7) connected by a top edge to the top wall115. The inner sidewall117extends vertically only over a top part of a height of the section of the rail11. Since the inner sidewall117and bottom wall118are not directly connected to one another, they define a longitudinal opening making it possible to interface the rail11with a rail support20.

The rail support20comprises a plate23forming a base that makes it possible to fix the rail support20onto the platform edge coping. It comprises a first post22fixed onto the plate23and extending by protruding therefrom vertically. On one side of the first post22, the rail support comprises a main roller221mounted free to rotate on the first post22on an axis of rotation at right angles to a plane of the sliding leaf2, here horizontal. Also, the first post22comprises, at a top, a first pair of rollers225mounted to be rotationally mobile on the first post22according to a vertical axis of rotation. The first pair of rollers225is positioned at the level of the main roller221, line therewith, here. When the rail11is positioned in the rail support20, the bottom bearing surface1181of the bottom wall118of the rail11comes to bear on the main roller221. At the same time, the inner sidewall117is received between the two rollers225of the first pair of rollers225.

The rail support20comprises a second post21fixed onto the plate23, at a distance from the first post22, and extending by protruding therefrom vertically. On one side of the second post21, the rail support comprises first211and second212secondary rollers mounted free to rotate on the second post21on an axis of rotation at right angles to a plane of the sliding leaf2, here horizontal. The second secondary roller212is positioned at a distance, vertically, from the first secondary roller211such that a distance e between a high point of a rolling surface of the first roller211and a low point of a rolling surface of the second secondary roller212is equivalent to a thickness of the bottom wall118of the rail11, with a functional clearance. Thus, when the rail11is positioned in the rail support20, the top bearing surface1182of the bottom wall118of the rail11comes to bear on the second secondary roller212, and the bottom bearing surface1181of the bottom wall118of the rail11comes to bear on the first secondary roller211. Also, horizontally, the second secondary roller212is offset from the first secondary roller211such that the second secondary roller212is located between the first secondary roller211and the main roller221in a direction of movement of the rail11. Also, the first211and the second212secondary rollers are, here, in one and the same plane as the main roller221. As a variant, they are in different but parallel planes. Furthermore, the second post21comprises, at a top, a second pair of rollers215mounted to be rotationally mobile on the second post21according to a vertical axis of rotation. The second pair of rollers215is positioned at the level of one of the first211and second212secondary rollers, in line therewith, here. In the present case illustrated in the figures, the second pair of rollers215is positioned in line with the first secondary roller211. When the rail11is positioned in the rail support20, the inner sidewall117is received between the two rollers215of the second pair of rollers215. Obviously, the first pair of rollers225is aligned with the second pair of rollers215.

Thus, a first set of rollers is formed by the main roller221and the first211and second212secondary rollers. The prime role of this set of rollers is to support the sliding leaf2and to guide it during its transitions from the closed position to the open position and vice versa. The main roller221supports twice the weight of the sliding leaf2: to this end, it has a diameter greater than a diameter of the secondary rollers211,212. The secondary rollers211,212ensure that the sliding leaf2does not tilt in its plane regardless of the position that it occupies.

Similarly, a second set of rollers is formed by the first225and second215pairs of rollers. The prime role of this second set of rollers is to laterally guide, in a horizontal direction at right angles to the direction of the horizontal translational movement of the sliding leaf2, the rail11fixed to the sliding leaf2. That makes it possible to take up the loads due to the pumping effect and to crowd thrust, or even wind thrust, which are applied to the sliding leaf2.

In the screen door1according to the invention, the rail support is positioned in the fixed part3associated with the sliding leaf2that the guiding and support system8according to the invention links, such that:

the first post22is on the side of the opening adjacent to the fixed part3of the screen door1according to the invention;

the second post21is on the side of the fixed part3, opposite the adjacent opening, that is to say on the side of the emergency door4, in the case illustrated here.

The guiding and support system8according to the invention as has just been described comprises fewer moving parts since the number of rollers has been reduced, in particular for the first set of rollers. In addition, none of the parts involved in the guiding and the support of the sliding leaf2rubs with the rail11: there are only bearings. Thus, the servicing costs are minimized, and the mechanical efficiency is close to 1, which generates energy savings.

According to a variant embodiment, the rollers of the first225and second215pairs of rollers can be replaced by friction skids, for example made of PTFE (polytetrafluoroethylene).

In one embodiment, the main roller221can be replaced by two smaller rollers, for example similar to the rollers211and212. That makes it possible to standardize all of the rollers used: which simplifies the manufacturing and maintenance.

According to another embodiment, an additional roller2214can be associated with the main roller221on the first post22. In this case, the two main221and additional rollers are positioned on the first post22in a way similar or symmetrical to the positioning of the two secondary rollers211and212on the second post21. That makes it possible to prevent a tilting, in its plane, of the leaf in open position in some situations.

In one embodiment, the main221and secondary211and212rollers (as well as the possible additional roller) are chevron-shaped rollers, rolling on a rounded rolling track formed on the surfaces1181and1182of the rail11. That allows for a self-centering of the leaf2on said rollers.

In another embodiment, the main221and secondary211and212rollers (as well as the possible additional roller) can be adjusted in position, particularly according to their axes of rotation, in order to allow an adjustment of the verticality of the leaf2as well as the alignment thereof in relation to the other leaf2of the screen door1.

As an example, the four preceding embodiments are illustrated concomitantly in a second embodiment of a support and guiding system80according to the invention which will now be described with reference toFIGS. 9 and 10.

The first set of rollers2210,211and212of the support and guiding system80will be described first. It comprises a main roller2210and first211and second212secondary rollers. The main roller2210here comprises two rollers2211and2212positioned one behind the other in the direction of movement of the rail1100. The two rollers2211and2212are identical. In addition, preferentially but optionally, they are similar to the secondary rollers211and212in size and/or in shape. Also, the two rollers2211and2212are mounted, at least rotationally mobile about their own axis, on a link plate2213. This link plate2213is itself mounted to be rotationally mobile on the first post22. That makes it possible to ensure a contact with the rail1100regardless of the orientation thereof in relation to the first post22, and thus ensure an optimal distribution of the loads of the leaf2on the two rollers2211and2212, regardless of the positioning of the rail1100and therefore the leaf2in relation to the first post22.

Also, illustrated here, the first set of rollers further comprises an additional roller2214associated with the main roller2210on the first post22. The two main2210and additional2214rollers are positioned on the first post22in a way similar or symmetrical to the positioning of the two secondary rollers211and212on the second post21. In particular, according to the embodiment illustrated inFIG. 9, the additional roller2214is situated on the vertical to the axis of rotation of the link plate2213of the main roller2210. That makes it possible to prevent a tilting, in its plane, of the leaf in open position in some situations.

The support and guiding system80according to the present invention includes a rail1100of extruded section and fixed type, when mounted on the leaf2. The rail1100includes a first zone1102which is intended to cooperate with the first set of rollers211,212,2210,2214. For that, the rail1100includes, in the first zone1102, a rolling track formed on the top surface1182aof convex form, here in the form of a circular arc. The rail1100further includes a rolling track formed on the bottom surface1181aalso of convex form, here, once again, in the form of a circular arc. The rolling tracks formed on the top surface1182aand formed on the bottom surface1181aare, here, symmetrical and mirroring one another.

In a particular embodiment, the rolling tracks formed respectively on the top1182aand bottom1181asurfaces of the guiding rail1100are inscribed in a circle, so as to produce, in operation, a pivot function with the rollers: thus, a defect of verticality of the leaf2generates no load in the rollers.

Also, the rail1100comprises a second zone1101, adjacent to the first zone1102, in which:

the rail1100is fixed to the leaf2

the rail1100comprises a runner1103in the form of an inverted “U”, the runner1103extending parallel along a longitudinal axis of the rail1100.

The runner1103, upon installation, is intended to slidingly receive, between the branches of the “U”, abutment-forming means27situated, here, at a free end of a transmission part26fixed to the second post21, at the level of a base thereof in the vicinity of the plate23. A transmission part26is also provided similarly on the first post22. In both cases, the free end bearing the abutment-forming means27extends facing and at a distance from the main roller2210and the first secondary roller211respectively. An operating clearance is provided between the abutment-forming means27and the branches of the “U” so as to allow a limited relative movement of the abutment-forming means27in a lateral direction within the runner1103.

Also, the various rollers211,212,2211,2212and2214are, here, chevron-shaped rollers. In fact, as illustrated inFIG. 10, a rolling surface2112of the secondary roller211has a concave shape in section which takes the form of a chevron. The same applies for a rolling surface2122of the other secondary roller212. These rolling surfaces2112and2122, in operation of the support and guiding system80according to the present invention, come to bear and roll on rounded rolling tracks respectively formed on the surfaces1181aand1182aof the rail1100. That allows for a self-centering of the leaf2on the rollers as well as the possibility of transmitting lateral loads from the leaf2to the posts21and22.

The various rollers of the first set of rollers are, each, mounted to be rotationally mobile on their associated post21or22and to be mobile with limited translation along their axis of rotation. These translational movements along the axis of rotation of the rollers are performed against elastic limiting means28. These elastic limiting means28here are stacks of Belleville spring washers, two adjacent Belleville spring washers being positioned in mirror-fashion one against the other. Furthermore, in the embodiment illustrated inFIGS. 9 and 10, a similar stack of Belleville spring washers is positioned on either side of each of the rollers. Thus, for each of the rollers211,212,2211,2212and2214, there are two stacks of Belleville spring washers for each roller axis. Such a system constitutes a spring casing. Each stack28of Belleville spring washers behaves like a calibrated spring.

Thus, when the leaf2undergoes a lateral load, for example following a gust of wind, a crowd thrust or a pumping effect dur to the passage of the train, the latter generates a lateral movement of the leaf2. The lateral load is transmitted to the rail1100fixed to the leaf2. Because of the shape of the rolling surfaces of the rollers of the first set of rollers cooperating with the convex rolling tracks1181and1182of the rail1100, the lateral load is transmitted to the rollers which are moved translationally according to their axis of rotation against the elastic limiting means28as long as the induced lateral movement remains less than the operating clearance between the abutment-forming means27and the branches of the “U” shape of the runner1103. The lateral load is transmitted to the posts21and22.

Also, because each stack28behaves like a calibrated spring, as long as the lateral load which tends to generate a lateral movement does not exceed the calibration value of the stacks28, there is no lateral movement and the abutment-forming means27serve no purpose. If the lateral load increases, the calibration force is exceeded, the Belleville spring washers are crushed, the rollers slide on their axis, and the leaf is moved laterally until the abutment-forming means27come to bear against one of the branches of the “U” shape of the runner1103.

If the lateral load is such that the lateral movement induced is greater than the above operating clearance, then the abutment-forming means27come to bear against one of the branches of the “U” shape of the runner1103: a portion of the lateral load is transmitted to the posts21and22via the rollers and the elastic limiting means28, the other portion of the lateral load is transmitted to the posts21and22via the abutment-forming means27and the transmission part26. Such a structure makes it possible to protect the first set of rollers from a significant lateral load. In addition, such a structure makes it possible to also produce a lateral guidance of the leaf2in a movement thereof, which replaces the second set of rollers formed by the rollers of the first225and second215pairs of rollers of the embodiment previously described of the support and guiding system8,8′ according to the invention.

Also, the various rollers2210,2214,211and212of the first set of rollers can be adjusted in terms of position, particularly in terms of height. For that, the axis of the rollers211,212,2210and2214is received respectively in an oblong opening, here vertical,2111,2121,2217and2216formed in a thickness of the associated post21,22. Means2110,2120,2215for adjusting the position in the oblong opening are provided for this purpose. Here, the position adjustment means are bolts screwed into the thickness of the posts21,22and of which one end emerges in the oblong opening at right angles to the axis of the rollers and comes to bear against the latter.

In another variant embodiment, the guiding and support system8is backed up, in a top part of the fixed part3and of the leaf2, by a complementary guiding system comprising a rail and sets of rollers/skids similar in structure to the second set of rollers/skids215,225. That makes it possible to reinforce the resistance to the lateral loads that the leaf2can be subjected to because of the wind, the pumping effect or crowd thrust.

There now follows a description, referring toFIGS. 2 to 4, of a driving mechanism40making it possible to move the sliding leaves2of the screen door1according to the invention in a synchronized manner.

The driving mechanism40comprises a driving motor41. It is positioned, here, between the posts of the rail support30, under the rail12. It drives a motor pulley42in rotation. The driving mechanism comprises a first51and a second52flexible elongate driving element. The flexible elongate driving elements51and52can be belts, cables or even chains. The flexible elongate driving elements51,52are mounted crosswise, the driving motor41directly driving only one52of the flexible elongate driving elements51,52.

The first flexible elongate driving element51is fixed, at a first end111, e.g. a left end of the first rail11and, at a second end121, e.g. a left end of the second rail12. Return pulleys441,442,443,444make it possible to tighten and define a run for the first flexible elongate driving element51, particularly partly under the door threshold6so as to run the first flexible elongate driving element51under the opening adjacent to the fixed parts3of the screen door1according to the invention. For that, two return pulleys443and444are situated at the first fixed part3and two return pulleys441,442are situated at the second fixed part3, as is illustrated inFIG. 3. In a variant embodiment, the return pulleys441and442can be one and the same return pulley. Each pair of pulleys443,444and441and442can be offset relative to one another in a horizontal direction, as is illustrated for example inFIG. 4for the pair of pulleys443,444.

Similarly, the second flexible elongate driving element52is fixed, at a first end112, e.g. a right end of the first rail11and, at a second end122, e.g. a right end of the second rail12. Once again, return pulleys431,432,433,434make it possible to tighten and define a run for the second flexible elongate driving element52, in particular partly under the door threshold6so as to run the second flexible elongate driving element52under the opening adjacent to the fixed parts3of the screen door1according to the invention. For that, two return pulleys433and434are situated at the first fixed part3and two return pulleys431,432are situated at the second fixed part3, as is illustrated inFIG. 3. In a variant embodiment, the return pulleys433and434can be one and the same return pulley, as is illustrated inFIG. 4. In another variant embodiment, the pulleys431and432can be one and the same return pulley. Each pair of pulleys433,434and431and432can be offset relative to one another in a horizontal direction.

In addition, here, the second flexible elongate driving element52cooperates with the motor pulley42to be driven by the driving motor41.

The two flexible elongate driving elements51,52are positioned and run side by side, the set of the return pulleys431,432,433,434being axially offset to the set of the return pulleys441,442,443,444. Thus, it is possible to mount pulleys of both sets on one and the same axis, as is illustrated inFIG. 4for the pulleys433/434and443. In addition, since there are only two flexible elongate driving elements51,52which run side by side in the threshold6, the section of the threshold6is consequently very small, and therefore its bulk in the civil engineering work is also very small: that simplifies the preparation of the civil engineering work at the platform edge coping and the installation of the complete screen door1module.

In operation, that will be illustrated for the transition from a closed position to an open position of the sliding leaves2with reference toFIG. 3, the motor pulley42driven by the driving motor41by a rotational movement R meshes with the second flexible elongate driving element52which is then moved according to a movement D52. This movement D52of the second flexible elongate driving element52has the effect of pulling on the end112of the second flexible elongate driving element52. That then drives the first rail11in a movement D11and consequently the end111of the first flexible elongate driving element51. The latter then performs a movement D51along its run which has the result of pulling on the end121of the first flexible elongate driving element51. Consequently, the second rail12is set in motion according to a movement D12, opposite and symmetrical to the movement D11of the first rail11. The second rail12then drives, in its movement D12, the end122of the second flexible elongate driving element52, thus looping a driving loop formed in succession by the second flexible elongate driving element52, the first rail11, the first flexible elongate driving element51and the second rail12.

Thus, very simply, the two sliding leaves2are set in motion between their opening and closing positions by a single driving motor41, while ensuring a perfect synchronization between the two sliding leaves2. That avoids the use of two motor drive systems and two control systems (one for each leaf).

A variant embodiment of the driving mechanism40is illustrated and described in the document CN203361842U to which reference can be made for more comprehensive information, if necessary.

Obviously, it is possible to apply numerous modifications to the invention without in any way departing from the scope thereof.