FR2511655A1 - Disposable towel roll dispenser - has grip moved moved against paper on cylinder by operating linkage handle - Google Patents

Abstract

The dispenser feeds disposable towels from rolls, having a cylinder (4) on a horizontal axis in the bottom of a housing, which drives the roll (13) to be dispensed, resting on it, in the opposite direction. The cylinder is indexed in one direction by an external handle, the paper from the roll passing part-way round it to an opening in the housing. A grip (7) parallel to the cylinder axis (4b) moves between a position bearing against the paper on the cylinder and one clear of it under the action of a linkage (5,6) operated by the handle, while a lock (9,9a) also operated by the handle, secures it in the first position.

Description

Apparatus for dispensing sheet product, especially paper towel rolls

The present invention relates to sheet product dispensing apparatuses available in the form of continuous webs presented in rolls, such as paper towels, of the type comprising, in a casing, a cylinder with a horizontal axis which, on the other hand, is arranged at the lower part of this casing, so that a roll to be dispensed can rest on this cylinder for being driven by the latter in rotation in opposite direction, and q ;; f, on the other hand, is periodically rotated in a given direction, with the aid of an actuating member accessible from outside the casing, a dispensing opening being formed in the lower part of the casing so that the sheet of product of the roll is extends between this roll and this opening by wrapping the cylinder on a part of its periphery
With this arrangement, the user actuates the external operating member, for example constituted by a lever, which, rotating the cylinder, simultaneously moves the sheet of product wrapping the latter to make it out, through the opening of distribution;; a section that the user can then separate, for example using a saw has on the edge of the opening.

 Devices of this type are already known, for example described by the French patents 80 06 105 and 80 06 108 of the applicant.

 However, it is found that in these devices, a simple freewheel is disposed between the outer actuating member and the drive cylinder and it is the travel allowed to this actuator which alone causes the distribution of the section. desired product integer corresponding to the current or standard length of use, without the user having to exert on this section a traction, which is moreover almost impossible since, once the previous section separated from the sheet, the The free end of this element does not protrude out of the dispensing opening. I1 is, moreover, provided against a cylinder which comes to rest freely under its weight, against the drive cylinder, so as to be driven by it in the opposite direction and to advance with him the pinch sheet between them. Finally, the apparatus comprises, when the roll is wound on a cylindrical support, a support member which is constituted by the edge of a rocking block on which, in course of der ulement, the roll rests at the same time as on the Cylinder drums, which, when the roll is empty, can disappear in time than the aforementioned counter-cylinder to allow evacuation of the cylindrical support of the roll.

Therefore, in the case of these known devices,
It is sufficient for the user to actuate as many times as he wants the actuator so that the device sucks suc cessively a corresponding number of sections of product that the user does not separate them and can recapare in together. It can thus steal a large length of the roll, if not a complete roll, for its own use. The same result can be obtained by pulling continuously on the first section resulting from the opening if the user has Be careful not to separate with the saw and this is also the method that is the most embarrassing, because in the previous case the manufacturer can always provide a timer system or even coin mechanism on the actuator to allow a new actuation of the latter, which limits the temptation at this level.

 This is why the present invention aims to provide an apparatus on which this continuous extraction of the web, by traction on the first standard section provided and not separated, is no longer allowed.

 For this purpose, the subject of the invention is an apparatus of the type in question, characterized in that it further comprises, on the one hand, a gripping element parallel to the axis of the cylinder and mounted movably between a pinch position in which it is in contact with a generatrix of this cylinder, on the path of the product web, and an erase position in which it is spaced apart, and secondly means for moving this pinch element connected to the driving cylinder and moving this element from its first position to the second, and vice versa, under the effect of two parts of the rotation stroke of the respectively associated cylinder and not associated with the active stroke of the actuating member, while it is also provided means for immobilizing the displacement means, in the pinching position of the movable member, and the outer actuating member is associated with these immobilizing means so as to to be able to release them during his active race.

 With this arrangement, in the initial position, the movable element is in pinch position and the user has no possible action on the product web.

 He must then actuate the maneuvering organ. following a movement which comprises on the one hand an arming stroke which brings it into position to cooperate with the cylinder displacement means, and on the other hand an active stroke during which it acts on the immobilizing means of these moving means for releasing them, then on these moving means themselves to rotate the cylinder on a stroke which allows the pinching element to come into its second erasing position, while during the race When the immobilization means have been released, the cylinder has slightly dragged the free edge of the sheet so as to cause it to appear free between the cylinder and the pinching element.

The user can then seize this free edge of the web and pull it, which causes unwinding of the product roll and a new rotation of the cylinder on a stroke (not associated with the active stroke of the actuating member) which leads to the displacement means to bring the movable member into its pinch position The traction of the web by the user is then blocked by this pinch and if he continues to shoot, the more he pulls, the stronger the blockage, which therefore requires that it separates, for example by means of a saw disposed on the edge of the opening, the section of the sheet from which it has taken place during the preceding movement of traction. it is then necessary for a new user, or the same, to actuate the external operating member again to release the immobilizing means and to further reduce the pinch element to the erased position, which allows it to pull at its turn the tablecloth to get a new at the stretch. Thus, it is in no case possible to pull the web continuously.

 To this main advantage is added the fact that this device no longer has a counter cylinder and that it is therefore easy to avoid the use of a rubber of particular quality, very expensive, which was necessary in known devices to achieve the cylinder and the contrecylindre, which had the disadvantage, however, in use, to charge electricity and skate.

 Particularly advantageously, the pinch element may consist of a section of a product guide flap, which is articulated on a horizontal axis facing the path of the product web on the cylinder. Preferably, the guiding flap is curved and turns its concavity towards the cylinder, which promotes guiding the free edge of the web of a new roll during the commissioning thereof.

 In addition, advantageously, the dispensing opening may be arranged on the housing in front of the drive cylinder and the guide flap may be arranged below this cylinder, so that its pinching element is situated approximately in view of the lower generatrix of this cylinder, which has the great advantage of allowing a passage of this flap from the pinch position to the erasing position under the sole effect of gravity, once the imputsion has been given by the release of the immobilization means. In this case, the axis of the shutter is preferably disposed behind the cylinder opposite to the latter, the distribution opening.With this same provision of the dispensing opening to the before the cylinder, it is advantageously provided that the driving means are arranged so that the cylinder moves at its lower part from the rear to the front, so that the end of the sheet is always directed towards this opening , especially when commissioning a new roll. The latter must also be placed in the casing so as to be able to move in rotation in the opposite direction of the latter under the rotational drive communicated to it by the cylinder, the lap thus following a path S of the roller than the distribution opening. This arrangement increases the length of the contact path of the web on the cylinder and thus ensures optimum training of this web.

 Preferably, the free edge of the guide flap can extend, beyond its gripping element, into the dispensing opening and this free edge comes into contact with one of the edges of this opening when the movable element is in pinch position. This contact thus ensures, if the need arises, a second immobilization of the extracted product, it is of very clear net, to the extent that advantageously, a saw is disposed on one of the two elements constituted by the free edge of the flap and the edge opposite the opening. In addition, this same contact prevents any intempest sv water penetration.

 In known apparatus, the counter-cylinder being supported by its weight against the drive roll, in the case where the rolls of product are wound on cylindrical cores or sports, it was necessary to provide a extraction element, such as a ribbon, fixed on this support or on the end of the wound web, in order to be able to pull this support between the cylinder and the counter-cylinder by lifting the latter so that the traction force is supplied .

Advantageously, in the case of the present invention, the stroke of the pinching element and the dimension of the dispensing opening are both greater than the diameter of a roller support, which allows the Xvacuati-on free of this support once the whole sea roll: used. In the case of a guide flap, the axis of the latter is preferably located at a distance from the drive roller which is also greater than the diameter of the roller support.

 It can also be advantageously provided on the housing an additional support element against which the roller can rest at the same time as on the drive cylinder and which is arranged relative to the vertical plane passing through the axis of this cylinder , opposite the path of the product web on the cylinder and at a distance from this plane greater than a roll radius. This arrangement ensures a constant maintenance of the roller, even when its diameter is significantly reduced, in support above the cylinder and without risk that this roller slips, under the effect of the traction of the user, to come wedge between the cylinder and the pinching element (or its support that constitutes the flap I guiding: .preferably, contr com support can between provided on the opposite face of the housing, at a distance from the support element substantially equal to a roll diameter, which ensures a perfect initial placement of the roll.

Advantageously also, in the case where a roll introduction door is provided on the front face of the housing, the support element is arranged on this door itself.

 In a particular embodiment of the invention, the means for displacing the pinching element may comprise at least one rod disposed in a plane perpendicular to the axis of the cylinder and connecting the pinching element to an off-center point. a wheel which is rotated by the cylinder. The means for immobilizing these displacement means in the pinching position of the movable element are preferably constituted by a positioning of the point of attachment of the link on the wheel such that, when the pinch element is in position pinching, this fixing point is located in the vicinity of the top dead center of the connecting rod-crank constituted by this rod and this wheel.Very advantageously, it can be provided that the immobilizing means comprise removable abutment means on which an element of the wheel-link assembly is supported in said top dead center position. Therefore, it has a precise mechanical stop that makes it impossible to pass the dead point, even under the effect of a very forceful traction of the user on the product web.

 Preferably, the means for releasing the immobilizing means may be constituted by an arm carrying a pawl and articulated on the axis of the wheel and which can be displaced by the external actuating member, between said stitch position high death in which the pawl rests freely on the wheel which is then made in the form of a toothed wheel, and another position from which it can rotate this gear. Preferably, a return spring is disposed between this arm and the casing, so as to automatically ensure that this drive in rotation of the toothed wheel. In this case also, lotto maneuver is advantageously constituted by a lever attached to the arm and parallel to the axis of the wheel.

 Also preferably, in the case where there is provided abutment means, these are constituted firstly by a fixed abutment on the housing and being outside the path of the end of the rod opposite the flap and secondly by a finger hinged to the arm, so that its end can be interposed between this stop and this end of the link.

 Particularly advantageously, it can be provided that the wheel for moving the pinching element has the same axis as the cylinder and is directly integral in rotation thereof, which considerably reduces the machining operations and therefore the cost price, especially in the case of a gear wheel, since only one wheel is sufficient, and may possibly be of a standard model commercially available, while the known devices currently required several gears very expensive a machined.

Other features and advantages of the invention will emerge from the description which follows, by way of non-limiting example, and with reference to the appended drawings in which:
FIG. 1 shows a perspective view of an apparatus according to a particular embodiment, according to the invention, the closure case of this apparatus being assumed removed.

 FIG. 2 is a perspective view of the apparatus with its housing, but door open.

 FIG. 3 is a right view of this apparatus, in the rest position, housing removed and taken in section along the plane of symmetry of the apparatus.

 FIG. 4 also shows a right view, but taken outside the inner frame of the housing.

 - Figs. 5 and 6 show views similar to that of FIG. 4 illustrating different positions of the drive mechanism during operation of the apparatus.

 The apparatus shown in the figures comprises a housing which consists of a fixed part or frame 1 and a removable closure housing 2. The frame comprises a back plate intended to be fixed on a wall and which carries laterally, on its two sides, two vertical support flanges ld, lc which have a roughly rectangular shape. The closure casing 2 has a shape enabling it to surround the frame, and more particularly the flanges 1b and 1c, so that its own lateral faces 2a delimit with these flanges the mechanism housing chambers. , in addition to upper and lower faces, a front face which comprises on the one hand an access door 2b articulated on its lower edge, and on the other hand, below this door, an opening 3 extending over any its width and having on its upper edge a paper cutting saw 3a.

 There is provided, between the two flanges 1b and 1c, and at their lower part, a drive cylinder 4 which is journalled on these flanges, its diameter being such as to leave a free space at least at the rear , towards the wall la. This cylinder is made in the form of a hollow metal drum, the surface of which provides a series of small projections 4a, for example consisting of punctures.

 The axis 4b of this cylinder passes through the flanges 1b and 1c, so as to carry at its ends two wheels of the same diameter, one of which is smooth, while the other 5 bears on its periphery teeth 5a asymmetrical flanks. . These two wheels bear on their outer plane face, and on the edge thereof, each a drive finger 5b of the same radial arrangement.

 These fingers 5b are journalled at one end of two rods 6, arranged in vertical planes parallel to the wheels 5 and which are oriented downwards.

These rods are joined at their lower ends by a transverse rod 6a parallel to the axis 4b of the cylinder.

 Between the two flanges 1b and 1a, there is also arranged a guiding flap 7, oriented parallel to the axis 4b of the cylinder and which is articulated at one end on an axis 7a, fixed at the rear of the chassis substantially at said axis 4b of the cylinder. From this axis, the flap curves downwards, so as to turn its concavity towards the cylinder 4, and to have a free end 7b which, in the rest position of FIGS. 3 and 4, is approximately horizontal after having followed the outline of the cylinder 4 for a short length, the length of the flap being such that its end comes (FIGS 3 and 4 practically in contact with the saw 3a, while> cylinder 4 and the flap 7 are arranged sufficiently above the upper mower 2c of the housing to allow the opening of the flap to be described later.On the area of the flap which is situated directly below the lower generatrix of the cylinder 5, is welded rod 6a which connects the rods, and it is also provided on its upper side with one or more compressible pads 7c, for example rubber.

 As shown in Figs. 3 and 4 which illustrate the position "rest" of the apparatus, when the flap 7 is raised, with its front end 7b in the vicinity of the saw 3a, the rods 6 are to be inclined slightly with respect to the vertical, to the forward and downward, the rod 6a entangling slightly offset forwardly with respect to the lower generatrix of the cylinder, while the rod is oriented very exactly diametrically with respect to the wheel 5 and the cylinder 4.

 Each of the mechanisms thus constituted by a wheel or a toothed wheel 5 and a connecting rod 6, is a mechanism which functions, as will be seen later, in the manner of a crank-handle assembly, and it is disposed in each of the mechanism chambers, located on either side of the flanges lb and lc.

 The right mechanism, which comprises the toothed wheel 5 ~ is completed by release means which are constituted by an arm 8 which is disposed between the toothed wheel 5 and the flange 1c, is articulated at one end on the axis 4b of the cylinder and is oriented upward, in the same orientation as the link 6, however projecting upward beyond the end of this link. On its upper end is articulated a finger lying downwards and whose free end is located between the upper end of the rod (Fig. 4) and a fixed stop 9a fixed on the flange 1c backwards. and above the wheel 5, at a height sufficient not to be in the path of the link 6, as will be described later.

Between the point of articulation of the finger 9 and the wheel 5, the arm 8 carries in addition, hinged on it, a ratchet tooth 8a which can engage behind the steep front flank of one of the teeth 5a of the wheel 5 and is held there by means of a support spring 8b (Fig. 1). A return spring 10 finally connects the upper end of the arm 8 to the rear of the flange 1c in a direction approximately perpendicular to that of the arm. A second pawl 11 is pivotally mounted on the flange 1c at the rear of the wheel 5 and below the abutment 9a, so that it can also engage under the action of another spring. support lia, behind the steep flank of another tooth 5a of the wheel.Il is further provided an actuating rod 12, parallel to the axis 4a of the cylinder and which is fixed at one end on the arm 8, between the pawl 8a and the finger 9 and which extends on the side of the device to pass through an opening in a circular arc 12a formed in the lateral face 2a of the closure housing, while this rod has at its free end, located at the outside the device, a manual 12b operation button. In the rest position shown in FIG. 2, the rod 12 is located at the rear end of the opening 12a.

 As shown in Fig. 2 and 3, there is disposed within the housing, between the flanges lb and the, a first roll of. paper 13 wound on a cylindrical support 13a in the ant-clockwise direction (right view of the apparatus). This roll is supported on the one hand, on a bearing element 14 attached to the door 2b of the closure housing (and having a substantially vertical portion facing the axis of the roll, extending by a inclined advance which comes to rest on the roller), and secondly, on an upper generatrix of the cylinder 5, so that the axis of this roller is disposed in front of the vertical plane passing through the axis of the This first roller is held in this advanced position, at least when it is full, by a counter-support plate 15 fixed to the rear wall of the apparatus (and having a vertical portion above the level of the roll, extending downwardly by an inclined advance located at a distance from the support 14 substantially equal to the diameter of the roll). It is also possible to have, above this first roll 13, a second roll 16, wound in the same direction and which rests, on the one hand, on the first roll, and on the other hand, on the vertical part of the counter -support 15.

 Because of its anticorrosive winding (seen from the right), the sheet of the roll 13 passes over the cylinder 4, at their contact generatrix, to wind around about a semicircle, clockwise, around it. cylinder 4 and move forward in the opening 3 of the housing.

The operation of the apparatus thus described is as follows
The apparatus being in the rest position as shown in Figs. 3 and 4, the free end 13b of the web of the roll 13 is flush with the saw 3a and the free edge 7b of the flap 7, between these two elements. Even if the user had already extracted a section of paper 13b during a previous maneuver, if he thinks to try not to separate it on the saw 3a and tries to keep pulling on the sheet, the more effort that it applies is large, the more the paper tends to drive the cylinder and the locking of the mechanism on the stop assembly that constitutes the finger 9 and the abutment t3 is ensured; it must therefore separate the section 13b and operate the control button 12b.

 This button then moves the arm 8 forward, its pawl 8a and the stop finger 9 to the extreme front position 8 'shown in FIG. 5 in dotted lines. Therefore, the finger 9 releases the rod 6 and the arm 8 'is armed, the pawl 8a coming to engage behind a tooth Sa of the wheel 5 to drive it under the effect of the return spring 10 when the the user abruptly releases the button 12b. In this rapid return movement, the finger 9 violently hits the end of the rod 6 and thus communicates to it and the toothed wheel a pulse that makes him leave his top dead position and come very quickly, with the cylinder 4 and the flap 7, in the position of FIG. 6 where the flap 7 reaches a position erased down under the combined effect of the pulse of the finger 9 and its own weight.In this position, the finger 9 carried by the arm came under the action of the spring 10, bearing against the stop 9a and the pawl 8a is engaged behind another tooth 5a of the wheel, while the second pawl 11 has also come into engagement behind a tooth located lower. In the drive movement of the cylinder 4 by the wheel 5 during the first part of the active stroke of the cylinder (which corresponds to the return of the arm 8 by the spring 10 and therefore is associated with the movement of the operating rod 12) this cylinder has rotated with it the roller 13 and the front end 13b of the web has advanced into the wedge space which has opened between the cylinder 4 and the flap 7.

 The user can then grab the edge 13b and pull it forward (arrow f, Fig. 6). In this traction movement, the sheet that winds on the cylinder 4 is always integral with the latter by means of the friction elements that constitute the projections 4a (which could also be achieved by other means, for example by For example, a rough surface such as a layer of paper will be seen during this movement of traction, the roller 13 continues to be deviated, and because of the frictional connection, the cylinder 4 is effectively rotated, in the same The cylinder itself drives the toothed wheel 5, this movement being free since the pawls 8a and 11 are raised in the passage and this rotation of the wheel drives the rod 6 upwards. Otherwise identical for the two links 6, simultaneously causes a progressive raising of the flap 7, and this up to the position already illustrated in Figure 4 in which the links have reached the alig 4b of the cylinder, which alignment can be defined as constituting the top dead center of the connecting rod-crank constituted by the wheel 5 and the rod 6. This movement also corresponds to a second part of the cylinder stroke 4 which is not associated with the active travel of the operating rod 12.

 In this same position of FIG. 4, the flap 7 has been raised to the point where the rubber stamp (s) 7c firmly compress the end 13b of the ply on the lower generatrix of the cylinder 4, which completes, if need be, the additional traction prohibition on the sheet already provided by the presence of the stop assembly 9-9a.

 The user then has, outside the opening 3, a section of web 13b having a suitable standard length, and it is sufficient for him to separate this stretch of sheet by tearing it on the saw 3a which equips the edge superior of the opening.

 It should be noted that the inner end of the product web is glued, or otherwise secured, to the roll support 13a, so that when the roll has been used to its last stretch, the user who pulling this last section simultaneously drives with it the roller support which then passes between the flap 7 and the cylinder 4 to be permanently extracted and discarded.

 It is therefore absolutely clear that such an apparatus does not make it possible to continuously extract the sheet of paper and that the sections can only be obtained successively. The mechanism is, moreover, perfectly simple and a relatively lower manufacturing cost than that of known devices (this being in particular dG with the presence of a single gear).

Claims (19)

 10) - Sheet product dispensing apparatus available in the form of continuous webs presented in rolls, of the type comprising, in a housing (1-2), a cylinder (4) with a horizontal axis which, on the one hand, is disposed at the bottom of this housing, so that a roll to be dispensed (13) can rest on the cylinder to be driven by the latter in rotation in opposite direction, and which, on the other hand, is periodically rotated in a given direction, with the aid of an operating member (12) accessible from outside the housing, a dispensing opening (3) being formed in the lower part of the housing so that the roll of product sheet it extends between this roller (13) and this opening (3) by wrapping the cylinder (4) on a part of its periphery, characterized in that it further comprises, on the one hand, a pinch element (7). -7c) parallel to the axis (4b) of the cylinder and mounted movably between a position pinch in which it is in contact with a generatrix of this cylinder, on the trajectory of the sheet (13b) of product, and an erasure position in which it is spaced apart, and secondly means means ôe displacement ( 5-6) of this gripping element (7-7c) connected to the driving cylinder (4) and moving this element from its first position to the second, and vice versa, under the effect of two parts of the stroke of rotation of the cylinder (4), respectively associated and not associated with the active travel of the actuating member (12), while there is further provided means (9-9a) for immobilizing the displacement means (5). -6), in the pinch position of the movable member (7), and the outer actuating member (12) is associated with these immobilizing means (9-9a) so as to be able to release them during its active race.  20) - Apparatus according to claim 1, characterized in that the clamping element (7) is constituted by a section of a product guide flap, which is articulated on a horizontal axis (7a) located opposite the path the web (13b) of product on the cylinder (4).  30) - Apparatus according to claim 2, characterized in that the guide flap (7) is curved and turns its concavity towards the cylinder (4).  40) - Apparatus according to any one of claims 2 and 3, characterized in that the dispensing opening (3) is disposed on the housing (1-2) in front of the drive cylinder (4) and the flap guide (7) is disposed below this cylinder, so that its pinch element (7c) is located approximately opposite the lower generatrix of this cylinder.  50) - Apparatus according to claim 4, characterized in that the axis (7a) of the flap (7) is disposed behind the cylinder (4), opposite to it, the opening of distribution (3).  60) - Apparatus according to any one of claims 4 and 5, characterized in that the drive means (5-6) are arranged so that the cylinder (4) moves at its lower part from the rear to the 'before.  70) - Apparatus according to any one of claims 2 to 6, characterized in that the free edge (7b) of the guide flap (7) extends, beyond its gripping element (7c), into the dispensing opening (3) and this free edge comes into contact with one of the edges (3a) of this opening (3) when the flap (7) is in the pinch position.  80) - Apparatus according to claim 7, characterized in that a saw (3a) is disposed on one of the two elements constituted by the free edge of the flap (7) and the edge opposite the opening (3) .  90) - Apparatus according to any one of claims 1 to 8, characterized in that the stroke of the nip member (7c) and the size of the dispensing aperture (3) are both greater than to the diameter of a roll holder (13a).  100) - Apparatus according to claim 9, when dependent on claim 1, characterized in that the guide flap (7) is located at a distance from the drive roller (4) which is greater than the diameter of the support ( 13a) of the roll.  110) - Apparatus according to any one of claims 1 to 10, characterized in that there is provided on the housing (1-2) an additional support element (14) which is arranged relative to the vertical plane passing by the axis of the cylinder (4), opposite the path of the product web (13b) on the cylinder and at a distance from this upper plane h a roller radius (13).  120) - Apparatus according to claim 11, characterized in that a counter-pressing (15) is provided on the opposite face of the housing 1-2) at a distance from the support element (14) substantially equal X ur roll diameter (13).  130> - Apparatus according to any one of claims-tions 11 and 12, characterized in that, in the case where a door (2b) for introducing rollers is provided on the front face of the housing (? .- 2) the support element (14) is arranged on this door itself.  140) - Apparatus according to any one of claims 1 to 13, characterized in that the displacement means (5-6) of the clamping element (7c) may comprise at least one rod (6) arranged in a plane perpendicular to the axis of the cylinder (4) and connecting the pinch element to an eccentric point (5b) of a wheel (5) which is rotated by the cylinder  150) - Apparatus according to claim 14, characterized in that the means (9-9a) for immobilizing these displacement means in the pinch position of the movable member (7) are preferably constituted by a positioning of the point for fixing (5b) the rod (6) on the wheel (5) such that, when the pinching element (7c) is in the pinch position, the fixing point (5b) is located in the vicinity of the top dead center of the biellemanivelle assembly constituted by this rod (6) and this wheel (5).  160) - Apparatus according to claim 15, characterized in that the immobilizing means (9-9a) comprise stop means (9-9a) on which a member (6) of the wheel-link assembly is based in said top dead center position.  170) - Apparatus according to any one of claims 15 and 16, characterized in that the means for releasing the immobilizing means may be constituted by an arm (8) carrying a pawl (8a) and articulated on the axle of the wheel (5) and which can be moved by the outer actuating member (12) between said top dead center position in which the pawl (8a) rests freely on the wheel (5) which is then realized in the form of a toothed wheel, and another position from which it can rotate this gear.  180) - Apparatus according to claim 17, characterized in that a return spring (10) is disposed between the arm (8) and the housing (1-2).  190) - Apparatus according to any one of claims 17 and 18, characterized in that the actuating member (12) is constituted by a lever attached to the arm (8) and parallel to the axis of the wheel (5). ).  200) - Apparatus according to any one of claims 17 to 19, characterized in that the stop means (9-9a) consist on the one hand by a fixed stop (9a) on the housing (1-2) and being outside the path of the end of the rod (6) opposite the flap (7) and secondly by a finger (9) articulated on the arm (8) so that its end can be interposed between this stop (9a) and this end of the rod (6).  210) - Apparatus according to any one of claims 14 to 20, characterized in that the larva (5) of displacement of the clamping element (7c) has the same axis as the cylinder (4) and is directly integral with rotation of it.