EP0181804B1 - Automatic angular positioning device for a plurality of rotative indexing machine components, and machine, particularly a franking machine, comprising such a device - Google Patents

Description

The invention relates to automatic angular positioning devices for indexable rotary members of machines, in particular office machines, packaging machines and, more generally, machines where the angular position of one or more members needs to be settled.

The invention applies, in particular, to the automatic positioning of the printing rollers, in a postal franking machine, the printing drum of the machine itself constituting a rotary support for the printing rollers, the indexing allows the "enhancement" of the machine for each franking operation.

Such a small machine comprises: a frame, a main rotary shaft mounted for rotation in the frame, a printing drum carried by said shaft and in which printing wheels are rotatably mounted on a transverse shaft and carry toothed pinions in engagement, each with a first corresponding rack secured to a rod mounted for longitudinal sliding in said main shaft, while a second longitudinal rack secured to each of said rods is engaged with one of several individual coaxial toothed wheels of enhancement command.

In certain known devices, in particular that described in US Pat. No. 4,398,458, each of the rods is controlled by a stepping motor. Each of these stepper motors, to be easily accommodated in the machine, must be small and can therefore only provide a low torque. It follows the risk of breakdowns by loss of step when the rods and the wheels are impeded in their movement by the printing ink, which requires frequent cleaning. Furthermore, the axial arrangement of the rods imposes complicated transmissions between them and the printing wheels.

In other devices, such as that described in US Patent No. 3,965,815, the print wheels are positioned by independent gears successively engaged with a toothed wheel. The toothed wheel is rotatably mounted in a carriage movable parallel to the common axis of the pigs and it is controlled by a single stepping motor. The movement of the carriage is ensured by two electromagnets, excited together or separately, to rotate the levers connected to the carriage by an axis transforming the rotation into translation. There remain here a large number of mechanical connections whose inertia limits the speed of movements and requires two large electromagnets. Finally, the number of carriage positions is limited to four, representing the combinations of two two-state electromagnets.

In other devices, such as that described in US Patent No. 4,050,374 (French 2,355,659), the rods are successively controlled by a first stepping motor whose axis slidingly carries a carriage driven transversely by a second stepper motor. The second stepper motor, despite its simplicity, is bulky and expensive.

The object of the invention is to provide an automatic device for positioning indexable rotary members of a machine, in particular printing knobs for a postage franking machine, which does not have the aforementioned drawbacks of the embodiments mentioned more high.

• - une roue dentée commune de commande d'indexation solidaire d'une tige cylindrique de commande d'indexation parallèle à l'axe desdits organes rotatifs indexables,
• - un arbre rotatif primaire de commande d'indexation constitué par une douille cylindrique formant cage à billes dans l'alésage de laquelle la tige peut coulisser et tourner,
• - un palier pour l'arbre rotatif primaire, qui est porté par un support mobile seulement dans la direction de l'ensemble des organes rotatifs indexables et dont l'alésage présente une gorge annulaire, les billes étant engagées partiellement dans cette gorge annulaire ainsi que dans des gorges hélicoïdales pratiquées dans la surface cylindrique de la tige,
• - un moteur électrique pas à pas dont l'arbre est lié en rotation à l'arbre rotatif primaire de commande d'indexation,
• - des doigts d'immobilisation sollicités élastiquement respectivement contre les dentures des organes rotatifs indexables,
• - des moyens pour immobiliser temporairement la tige de commande d'indexation, en rotation seulement,
• - des moyens pour immobiliser temporairement la tige de commande d'indexation, en coulissement seulement,
• - des moyens pour repousser temporairement le doigt d'immobilisation de l'organe rotatif indexable sélectivement en prise avec la roue dentée commune de commande d'indexation et pour verrouiller angulairement, dans le même temps, les autres organes rotatifs indexables, et
• - des moyens de commande des déplacements du support précité, comportant un seul électro-aimant, lesdits moyens étant adaptés à deplacer ledit support dans une première position dans laquelle la rotation du moteur pas à pas provoque un déplacement axial de la tige et de la roue dentée commune bloquées en rotation, pour la sélection de l'organe rotatif à indexer, ou dans une seconde position, dans laquelle la rotation du moteur à pas provoque une rotation de la tige et de la roue dentée commune immobilisées en translation pour l'indexation de l'organe rotatif sélectionné.

To this end, the device according to the invention comprises:

• a common gear for indexing control secured to a cylindrical rod for indexing control parallel to the axis of said indexable rotary members,
• a primary rotary indexing control shaft constituted by a cylindrical bushing forming a ball cage in the bore of which the rod can slide and rotate,
• a bearing for the primary rotary shaft, which is carried by a movable support only in the direction of all of the indexable rotary members and whose bore has an annular groove, the balls being partially engaged in this annular groove as well as in helical grooves made in the cylindrical surface of the rod,
• - a stepping electric motor whose shaft is linked in rotation to the primary rotary indexing control shaft,
• immobilizing fingers elastically urged respectively against the teeth of the indexable rotary members,
• means for temporarily immobilizing the indexing control rod, in rotation only,
• means for temporarily immobilizing the indexing control rod, in sliding only,
• means for temporarily repelling the immobilizing finger of the indexable rotary member selectively engaged with the common toothed indexing control wheel and for angularly locking, at the same time, the other indexable rotary members, and
• means for controlling the movements of the aforementioned support, comprising a single electromagnet, said means being adapted to move said support in a first position in which the rotation of the stepping motor causes an axial displacement of the rod and of the wheel common toothed locked in rotation, for the selection of the rotary member to be indexed, or in a second position, in which the rotation of the stepping motor causes a rotation of the rod and the common toothed wheel immobilized in translation for indexing of the selected rotary member.

Thanks to this particular design, it is possible to produce a reliable, economical and inexpensive device.

The subject of the invention is also machines, in particular postal franking machines, which include an automatic angular positioning device for indexable rotary members having the characteristics set out in the present application.

The invention will be better understood on reading the description which follows and on examining the appended drawings which show, by way of example, an embodiment of the invention.

• - la figure 1 est une vue de face d'une machine d'affranchissement postal dont les molettes d'impression sont mises à valeur par un dispositif automatique suivant l'invention,
• - la figure 2 est une vue en plan du dispositif de mise à valeur des molettes d'impression, en position de repos,
• - la figure 3 est une coupe verticale faite suivant la ligne III - III de la figure 2,
• - la figure 4 est une vue analogue à la figure 2, mais le dispositif étant en position de mise à valeur d'une molette d'impression,
• - la figure 5 est une coupe verticale faite suivant la ligne V - V de la figure 4,
• - la figure 6 représente, à plus grande échelle, la partie centrale de la figure 5,
• - la figure 7 est une coupe faite suivant la ligne VII - VII de la figure 6,
• - la figure 8 est une coupe faite suivant la ligne VIII - VIII de la figure 4, et
• - la figure 9 est une coupe faite suivant la ligne IX - IX de la figure 8.

In these drawings:

• FIG. 1 is a front view of a postal franking machine, the printing wheels of which are enhanced by an automatic device according to the invention,
• FIG. 2 is a plan view of the device for enhancing the print wheels, in the rest position,
• FIG. 3 is a vertical section taken along line III - III of FIG. 2,
• FIG. 4 is a view similar to FIG. 2, but the device being in the position for enhancing a printing wheel,
• FIG. 5 is a vertical section taken along the line V - V of FIG. 4,
• FIG. 6 represents, on a larger scale, the central part of FIG. 5,
• FIG. 7 is a section taken on line VII - VII of FIG. 6,
• FIG. 8 is a section taken along line VIII - VIII of FIG. 4, and
• - Figure 9 is a section taken on the line IX - IX in Figure 8.

The postal franking machine shown from the front, as a whole, in FIG. 1, comprises a frame 1 in which is rotatably mounted a main shaft 2 which supports a printing drum 3; the franking folds 4, placed on a table 5 integral with the frame 1, are pushed, one by one, between two drive rollers 6, 7 which lead them between the rotary printing drum 3 and a support roller 8 ; they emerge franked from the machine at the location of arrow 9. The printing drum is driven, each time for one revolution, by a motor to which we will return later. A body 11 includes the device for enhancing the print wheels which is generally designated by 12 and will be described in detail below. The body still contains, in particular, the control and reading members, such as: a keyboard 14, an indicator of the postage value 15, a totalizer of the postage values 16, and a postage meter 17. movements of the various elements of the automatic enhancement device are provided by a stepping electric motor 18 and by an electromagnet (not shown in this figure) in response to the information given on the keyboard, under the control of a set microprocessor electronics and peripherals (not shown) which will not be described in detail, because it is not part of the invention.

In Figures 2 and 3, there is, on a larger scale, the main shaft 2 which rotates in two bearings 19, 20 and carries the drum 3 in which are mounted the print wheels 21a, 21b, 21c, 21d , four in number, for example, corresponding to the digit, units, tens, hundreds and thousands of postage values to be made; these knurls are mounted for rotation on an axis 22 orthogonal to the direction of the main shaft 2 and they are integral, respectively, with toothed pinions 23a, 23b, 23c, 23d whose teeth are engaged, respectively, with first racks 24a, 24b, 24c, 24d, integral with longitudinal rods, 25a, 25b, 25c, 25d adapted to slide in corresponding longitudinal grooves cut in the main shaft 2.

Each rod such as 25b, for example, is provided with a second rack 27b engaged in itself with an indexable rotary member constituted by an individual toothed wheel for enhancement control, 28b (see also Figure 8). In the present case where the machine comprises four printing rollers, there are therefore four individual toothed wheels for enhancement control 28a, 28b, 28c, 28d, respectively, but to simplify the representation, in FIG. scale, only three have been shown 28a, 28b, 28c. These toothed wheels are mounted idly on an axis 30 fixed transversely in the main shaft 2 in a direction parallel to that of the axis 22 which carries the printing knobs and they are - kept locked in each of their positions, which correspond to numbers in the printing position of the rollers, by locking fingers, such as the finger 31 b (FIG. 6) for the wheel 28b, all these fingers being pivotally mounted on a common transverse axis 32 carried by the shaft main 2 and being resiliently biased against the teeth of the wheels by springs such as 33b. Between the individual cogwheels for enhancing control, washers 35 are interposed, the outside diameter of which is equal to the bevel diameter of said cogwheels, that is to say the diameter of the circumference which passes through the vertices of their teeth; we will come back to the role of these washers later.

With each of the individual cogwheels for enhancing control 28a to 28d, a common cogwheel for indexing or enhancement control 37 can be selectively engaged 37 made integral, for example by means of a pin 38 (see in particular FIGS. 6 to 8), of a cylindrical rod for indexing or setting control 39 located in the same transverse geometric plane P1 as the axis of the individual toothed wheels 28a to 28d and parallel to said axis. The rod 39 is mounted, at one of its ends, in a primary rotary indexing or enhancement control shaft 41 (FIGS. 8 and 9) constituted by a cylindrical bushing forming a ball cage 42 and in which it can rotate and slide longitudinally; the amplitude of the sliding movement of the rod 39 is limited by an adjustable stop 40. The primary shaft 41 is mounted in a bearing 44 whose bore has an annular groove 45; the balls are partially engaged in this annular groove as well as in helical grooves 46 formed in the cylindrical surface of the rod 39. The bearing 44 is mounted in a support 47 which can approach or move away from the set of toothed wheels individual enhancement control commands 28a to 28d by a pivoting movement of an axis 48, the two ends of which are respectively mounted in two legs 51, 52 secured to a structure 53 fixed in a removable manner in the frame 1. The other end of the rod 39 can rotate and slide freely in the support 47. The support 47 can pivot under the action of an electromagnet 55 (Figure 5) carried by the structure 53 and whose movable armature 56 is adapted to push an arm 57 integral with the support 47, against the force of a return spring 58. The amplitude of the oscillating movements of the arm 57 is limited, precisely, by two stop screws to lock nut 61, 62.

When the support 47 occupies its inactive lower position which is that shown in FIGS. 2 and 3, a tooth of the common toothed gear for controlling the enhancement 37 is engaged in a groove 65 (see also FIGS. 6 and 7) parallel to the axis of said wheel and formed in a guide 66 carried by the structure 53; it follows that the rod 39, integral with said wheel, is immobilized in rotation. In this same position, the fingers such as 31 b resiliently returned by the springs such as 33b, immobilize all the individual gear wheels for enhancing control.

When the support 47 occupies its high active position which is that shown in FIGS. 4 to 8, the common gear wheel for enhancement control 37 is released from the groove 65. In addition, the common gear wheel 37 is engaged between the two washers 35 which are located on either side of the individual wheel against which the common wheel is engaged, so that said common wheel 37 and the rod 39 are blocked in translation. It follows that a rotation of the rod 39 is capable of rotating this wheel and, consequently, of indexing the individual toothed wheel and the corresponding printing wheel. In addition, means are provided for selectively releasing the finger such as blocking 31 b of the individual wheel considered, as well as safety means for additional blocking, respectively axial and or angular, of the rod 39 and or of the individual toothed wheels. other than the currently selected wheel, such as 28b, for example. To this end, the two cheeks 71, 72 of a yoke 73 are crossed by the enhancement control rod 39 and enclose the common toothed wheel 37; the yoke 73 has a rib 74 permanently engaged in a guide groove which, in this example, consists of the groove 65 in which a tooth of the common toothed wheel can already engage. When the support 47 is in the low position, the rib 74 of the yoke 73 is engaged in the bottom of the groove 65, and a tooth of the common wheel 37 engaged in the upper part of said groove, while in the high position of the support, the tooth of the common wheel is out of the groove, but the rib of the yoke is still engaged in the upper part of the groove, and, in addition, portions of toothing 77, 78 of the two cheeks 71, 72 of the yoke, respectively, are in axial contact with at least one of the washers 35 and are engaged in the teeth of the two individual toothed wheels 28a, 28c which are located on either side of the selected individual wheel 28b and which, consequently, the rod 39 is positively blocked in rotation, being on its side, blocked in translation. Finally, a protuberance 79 of the yoke 73 in the high position, pushes a bent extension, such as 81 b, of the corresponding finger 31 b for example, for immobilizing the selected individual wheel 28b, so as to allow it to d 'be indexed.

The electric stepping motor 18 (FIGS. 1, 2, 4) is fixed to a console 83 secured to the frame of the machine and its shaft 84 is connected to the primary shaft 41 by a universal joint, from Oldham or Cardan joint. example, indicated in 85.

The drive motor for one revolution of the main shaft 2 which carries the printing drum is indicated at 87.

The operation of the machine is as follows:

After the last fold franking operation, the print wheels 21 a, 21 b, 21 c, 21 d remained at their respective values Va-0, Vb-0, Vc-0 and Vd-0. We will assume that it is now necessary to frank a fold to a different value for which some, at least, of the print wheels must be indexed to a new value. We are going to designate the values that the knobs must now have by Va-1, Vb-1, Vc-1 and Vd-1.

Currently, the machine is at rest and the various members of the automatic enhancement control device occupy the positions shown in FIGS. 2 and 3, that is to say that the common gear wheel for enhancement control 37 is out of range of the individual toothed wheels 28a, 28b, 28c, 28d by the fact that the rod 39 occupies its advanced position as far as possible against the stop 40. In addition, the electromagnet 55 is not excited, so that the support 47 occupies its low position and that, consequently, a tooth of the common wheel 37 is engaged in the groove 65; it follows that the rod 39, integral with this toothed wheel, is blocked in rotation.

• - le moteur pas à pas 18 est mis en marche dans le sens, et du nombre de pas convenables, pour que la tige 39 (figures 4 à 9), immobile en rotation comme on vient juste ce le rappeler, subisse un mouvement de coulissement vers l'arrière (c'est-à-dire en s'éloignant de la butée 40) pour amener la roue dentée commune 37 en regard de la première roue dentée individuelle 28a, sous l'effet de la rotation de la couronne de billes 42 emprisonnées dans l'épaisseur de l'arbre tubulaire primaire 41 relié à l'arbre 84 du moteur, et engagées partiellement, à la fois dans les gorges hélicoïdales 46 de la tige 39 et dans la gorge annulaire 45 du palier fixe. Puisque la tige 39 ne peut pas tourner, elle est en effet, obligée de coulisser axialement.
• - l'alimentation de l'électro-aimant 55 déplace son armature 56 et provoque le pivotement du bras 57 jusqu'à la butée 62 (figure 5) et par la même, la montée du support 47, ce qui assure l'engagement de la roue dentée conmune 37 dans la roue dentée individuelle 28a (on peut se référer aux figures 6 et 7 qui correspondent à la sélection de la roue dentée individuelle 28b) et son dégagement de la rainure fixe 65, ainsi que le dégagement du doigt 31a a de blocage de cette roue individuelle et, au contraire, le blocage de la roue individuelle suivante 28b dans laquelle est engagée la portion de denture 77 de la chape 73. La tige 39 est maintenue immobile en translation par le fait que le flasque 71 de la chape 73 est embrassé par les rondelles 35 enfilées sur l'axe 31 de part et d'autre de la roue individuelle 28b et que cette roue individuelle est portée par l'arbre principal 2 de la machine qui, d'une manière classique, est toujours bloqué en rotation dans une position d'attente prédéterminée entre deux opérations d'affranchissement.
• - le moteur pas à pas 18 est mis en marche dans le sens et du nombre de pas convenables pour que la tige 39 (immobile en translation) subisse un mouvement de rotation d'amplitude telle que la roue dentée individuelle 28a fasse passer la molette d'impression 21 a de la valeur Va-0 à la valeur Va-1 par l'intermédiaire de la chaîne cinématique qui comporte: la crémaillère 27a, la tige 25a, la crémaillère 24a et le pignon denté 23a. La tige 39 ne peut, en effet, que tourner sur elle-même sous l'influence du mouvement de rotation de l'arbre primaire 41 qui entraîne les billes 42 dans un mouvement circulaire dans la gorge 45 du palier fixe.
• - l'alimentation de l'électro-aimant 55 est coupée (figure 3), le bras 57 est repoussé par le ressort 58, le support 47 descend, la roue dentée commune 37 se dégage de la roue dentée individuelle 28a, la portion de denture 77 se dégage de la roue dentée individuelle 28b et le doigt 31a a s'engage dans la roue denté individuelle 28a qui vient d'être indexée. En même temps, la roue dentée commune 37 s'engage à nouveau dans la rainure fixe de blocage 65.
• - les mêmes séquences que celles qu'on vient de décrire en détail pour l'indexage de la première molette 21 a, se reproduisent pour l'indexage de chacune des autres molettes 21 b, 21c et 21d. Il est bien évident cependant que, si la valeur d'affranchissement de l'une ou de plusieurs des molettes n'a pas à être modifiée, les séquences correspondant à leur mise en valeur ne s'effectuent pas.

The new postage value is dialed on the keyboard 14 (FIG. 1); it appears in the viewfinder 15. We then press the "V" key designated by the reference numeral 10 in FIG. 1 and, from this moment, all of the operations for setting up the print wheels will be carried out automatically under the control of the electronic microprocessor device , by executing the following series of sequences:

• - the stepping motor 18 is started in the direction, and of the number of suitable steps, so that the rod 39 (FIGS. 4 to 9), stationary in rotation as we have just recalled, undergoes a sliding movement backwards (that is to say away from the stop 40) to bring the common toothed wheel 37 opposite the first individual toothed wheel 28a, under the effect of the rotation of the crown of balls 42 trapped in the thickness of the primary tubular shaft 41 connected to the shaft 84 of the motor, and partially engaged, both in the helical grooves 46 of the rod 39 and in the annular groove 45 of the fixed bearing. Since the rod 39 cannot rotate, it is in fact forced to slide axially.
• - the power supply of the electromagnet 55 moves its armature 56 and causes the arm 57 to pivot to the stop 62 (FIG. 5) and by the same token, the rise of the support 47, which ensures the engagement of the common toothed wheel 37 in the individual toothed wheel 28a (reference may be made to FIGS. 6 and 7 which correspond to the selection of the individual toothed wheel 28b) and its release from the fixed groove 65, as well as the release of the finger 31a a blocking this individual wheel and, on the contrary, blocking the following individual wheel 28b in which is engaged the toothing portion 77 of the yoke 73. The rod 39 is held stationary in translation by the fact that the flange 71 of the yoke 73 is embraced by the washers 35 threaded on the axis 31 on either side of the individual wheel 28b and that this individual wheel is carried by the main shaft 2 of the machine which, in a conventional manner, is always locked in rotation in a predetermined waiting position mined between two postage operations.
• - The stepping motor 18 is started in the direction and the number of suitable steps so that the rod 39 (stationary in translation) undergoes a rotation movement of amplitude such that the individual toothed wheel 28a causes the thumb wheel d printing 21 has the value Va-0 to the value Va-1 via the kinematic chain which comprises: the rack 27a, the rod 25a, the rack 24a and the toothed pinion 23a. The rod 39 can, in fact, only rotate on itself under the influence of the movement of rotation of the primary shaft 41 which drives the balls 42 in a circular movement in the groove 45 of the fixed bearing.
• the power supply to the electromagnet 55 is cut off (FIG. 3), the arm 57 is pushed back by the spring 58, the support 47 descends, the common toothed wheel 37 emerges from the individual toothed wheel 28a, the portion of gear 77 emerges from the individual gear 28b and the finger 31a has engages in the individual gear 28a which has just been indexed. At the same time, the common toothed wheel 37 engages again in the fixed locking groove 65.
• - The same sequences as those just described in detail for indexing the first wheel 21 a, are repeated for indexing each of the other wheels 21 b, 21c and 21d. It is obvious, however, that if the postage value of one or more of the knobs does not have to be modified, the sequences corresponding to their enhancement are not performed.

In the position for which the common toothed wheel 37 is opposite the second individual toothed wheel 28b, which is the case shown in Figures 6 to 8, said common toothed wheel 37 is trapped axially between the two washers 35 located on either side of the individual toothed wheel 28b while the two portions of teeth 77 and 78 of the yoke 73 are engaged with the two individual toothed wheels 28a and 28c, respectively and embrace the pair of washers 35 above. For the other axial positions of the common toothed wheel for the selection of the individual wheels 28c and 28d, it is obviously necessary to transpose the relative positions of the various elements which have just been taken into consideration.

When all the knobs are in their desired franking positions, the stepping motor 18 is set in motion in the direction and the number of suitable steps to bring the rod 39, then locked in rotation by the common toothed wheel 37, to its advanced position against the stop 40 (Figures 2 and 3); the common toothed wheel 37 is therefore again away from the group of individual toothed wheels 28a to 28d.

-The main shaft is rotated for one turn under the action of the motor 87 as soon as the franking fold is introduced into the machine. The counter 17 (FIG. 1) advances by one unit and the total of the values of the envelopes already franked appears in the viewfinder 16.

The machine is ready for franking of a new fold at the same value. In the event that the postage value should be modified, we would then proceed to the maneuvers that have just been explained above in detail.

With a view to simplifying the construction of the machine, facilitating the programming of its microprocessor and reducing inertia, the common toothed wheel 37 for enhancing control is advantageously given a number of teeth equal to 10 and, at the same time time, the axial spacing between the individual toothed wheels 28a to 28d is chosen equal to one tenth of the pitch of the helical grooves 46 of the rod 39, so that the number of steps which the rotor of the motor 18 must rotate is the same for an axial selection operation of an individual toothed wheel only for indexing a tooth of these wheels.

The invention can generally be applied to the selection and indexing of moving parts having teeth with which the power take-offs are aligned.

Claims (9)

1. A device for automatic angular positioning of a plurality of indexable rotary machine elements, said device comprising:

- a common indexing-control gear-wheel (37) rigidly fixed to a cylindrical indexing-control rod (39) which is parallel to the axis of said indexable rotary elements (28a, 28b, 28c, 28d),

- a rotating primary shaft (41) for indexing control constituted by a cylindrical sleeve forming a ball cage (42), the cylindrical control rod aforesaid being capable of displacement in sliding and rotational motion within the bore of said ball cage,

- a bearing (44) for the rotating primary shaft (41), said bearing being carried by a support (47) which is capable of moving solely in the direction of the series of indexable rotary elements (28a, 28b, 28c, 28d), the bore of said bearing being provided with an annular groove (45) and the balls (42) being partially engaged in said annular groove as well as in helical grooves (46) formed in the cylindrical surface of said cylindrical control rod,

- an electric stepping motor (18), the shaft (84) of said motor being rotationally coupled to the indexing-control rotating primary shaft (41),

- locking-fingers (31a, 31b, 31c, 31d) elastically biased respectively against gear-teeth of the indexable rotary elements (28a, 28b, 28c, 28d),

- means (65) for temporarily locking the indexing control rod (39), solely against rotational motion;

- means (35) for temporarily locking the indexing control rod (39), solely against sliding motion,

- means (73) for temporarily thrusting-back, the finger (31a, 31b, 31c, 31d) for locking the indexable rotary element (28a, 28b, 28c, 28d) which is selectively in meshing engagement with the common indexing-control gear-wheel (37) and for angularly locking the other indexable rotary elements at the same time, means (55, 56, 57, 58) for controlling the displacements of the support (47) aforesaid comprising a single electro-magnet,

- said means being adapted to move said support (47) into a first position, in which the rotation of the stepping motor (15) produces an axial displacement of the rotationally locked rod (39) and common gear-wheel (37), for selecting the rotary element to be indexed (28a, 28b, 28c, 28d), or into a second position, in which the rotation of the stepping motor (18) produces a rotational displacement of the translationally locked rod (39) and common gear-wheel (37), for indexing the selected rotary element.

2. A device according to claim 1, characterized in that the indexable rotary elements (28a, 28b, 28c, 28d) are constituted by coaxial individual gear-wheels for controlling the value-setting of the printing-wheels (21 a, 21 b, 21 c, 21 d) of a postal franking machine which comprises a frame (1), a main shaft (2) rotatably mounted in said frame, a printing drum (3) which is carried by said shaft and in which the printing-wheels (21 a, 21 b, 21 c, 21 d) are rotatably mounted on a cross-shaft (22) and carry toothed pinions (23a, 23b, 23c, 23d) each disposed in meshing engagement with a first corresponding toothed rack (24a, 24b, 24c, 24d) mounted for longitudinal sliding motion in said main shaft, whilst a second longitudinal toothed rack (27a, 27b, 27c, 27d) is rigidly fixed to each of the first toothed racks and is in meshing engagement with one of the aforesaid individual coaxial value-setting control gear-wheels (28a, 28b, 28c, 28d).

3. A device according to claim 1, characterized in that the means for temporarily locking the indexing control rod (39), solely against rotation, consist of a stationary guide (66) provided with a groove (65) which is parallel to said indexing control rod and in which is engaged one tooth of the common indexing-control gear-wheel (37) when said gear-wheel is not engaged against one of the indexable rotary elements (28a, 28b, 28c, 28d).

4. A device according to claim 1, characterized in that the means for temporarily locking the indexing control rod (39) solely against sliding motion consist of washers (35) which are interposed between the indexable rotary elements (28a, 28b, 28c, 28d) and the external diameter of which is equal to the addendum circle diameter of said rotary elements.

5. A device according to claim 1, characterized in that the means for temporarily thrusting-back the finger (31 a, 31 b, 31 c, 31 d) for locking the indexable rotary elements (28a, 28b, 28c, 28d) selectively in meshing engagement with the common indexing-control gear-wheel (37) and for angularly locking the other indexable rotary elements, at the same time, consist respectively of a projecting portion (79) adapted to thrust- back respective extensions (81 a, 81 b, 81 c, 81 d) of the locking fingers and of gear-teeth portions (77 - 78) adapted to engage in the gear-teeth of the indexable rotary elements with which the common indexing-control gear-wheel (37) is not engaged, said projecting portion and said gear-teeth portions being incorporated in a yoke (73) in which the cheeks (71 - 72) of said yoke are traversed by the indexing control rod (39) and embrace the common indexing-control gear-wheel (37), said yoke being provided with a rib (74) continously and freely engaged in a groove (65) of a stationary guide (66) which is parallel to the indexing control rod (39).

6. A device according to claims 4 and 5, characterized in that the means for temporarily locking the indexing control rod (39) solely against sliding motion, further comprise the lateral faces of the gear-teeth portions (77, 78) which cooperate with corresponding lateral faces of the washers (35) interposed between the indexable rotary elements (28a, 28b, 28c, 28d).

7. A device according to claim 1, characterized in that the coupling between the indexing-control primary shaft (41) and the shaft (84) of the stepping motor (18) for positioning the indexable rotary elements is constituted by a universal joint (85) such as an Oldman coupling or a cardan joint.

8. A device according to claim 1, characterized in that the common indexing-control gear-wheel (37) is provided with ten teeth and in that the pitch of the helical grooves (46) of the coupling between the indexing-control rotating primary shaft (41) and the shaft (84) of the stepping motor (18) is equal to ten times the distance between the geometrical midplanes of two adjacent indexable rotary elements (28a, 28b, 28c, 28d).

9. A device according to claim 1, characterized by its utilization in postal franking machines.

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