WO2010112774A1

WO2010112774A1 - Device for detecting torque, printer and operating method

Info

Publication number: WO2010112774A1
Application number: PCT/FR2010/050613
Authority: WO
Inventors: Denis Montagutelli
Original assignee: Aps Engineering
Priority date: 2009-04-02
Filing date: 2010-03-31
Publication date: 2010-10-07
Also published as: EP2414266A1; FR2943946B1; EP2414266B1; CN102387974A; FR2943946A1; CN102387974B

Abstract

Aside from a printer and an operating method, the invention relates to a device for detecting torque for an electric motor drive for winding a printer belt about a driveshaft (8) rotated by a transmission means thanks to a motor shaft driven by an electric motor (1), the transmission means comprising at least two rotatable wheels with peripheral gears. According to the invention, the transmission means comprises at least one planet gear (3, 3', 3a, 3b, 3'a, 3'b) translatably movable relative to another so-called geared wheel (4, 6) with which it meshes and which is stationary, said planet gear moving in parallel to the periphery of the geared wheel, said planet gear being connected to a stationary point of the device by resilient return means (5) for bringing the movable planet gear back into a predetermined rest position in the absence of motor torque or, when motor torque is present, the belt freely runs without resistance, said movable wheel leaving said rest position when a resistance of the belt to winding is present, said device further comprising a means (7) for detecting the translatable movement of the planet gear.

Description

TORQUE DETECTION DEVICE. PRINTER AND METHOD OF

OPERATION

The present invention relates to a torque sensing device for a motorized electric drive of a reel / rewinder of a printer paper web, a printer and a method of operation of such a printer.

Devices for controlling the drive of the paper webs in the printers are generally implemented in order to avoid, in particular, blocking of drive motors and / or tearing of the paper web. These devices may also be useful for better delivery of printed coupons or self-adhesive labels. For the latter, one generally uses a roll of a strip of treated paper having on one side self-adhesive labels, the treatment being intended to ensure a weak adhesion of the labels on the paper strip and thus to allow the easy removal of the labels of with the roll of paper.

The control of the drive here relates more particularly to the means for detecting that a certain tension of the paper web has been reached. FR2 846 595 discloses a mechanical device based on the movement of a movable arm retained by a spring and over which the paper web passes. Other devices are also known in which the current supplied to the motor for driving and / or rewinding of the paper web is measured and it is made to limit or cut this current if a threshold is exceeded. current.

The present invention provides a device combining mechanical means and electrical / electronic means. It relates more particularly to a torque detection device for a motorized electric drive of a reel of a printer paper web, a winding shaft ensuring the winding of the paper web, said winding shaft being rotated by a transmission means by a motor shaft driven in rotation by an electric motor, the transmission means having at least two peripheral gear wheels rotatable.

According to the invention, the transmission means comprises at least one gear wheel gear which is movable in translation relative to another, said gear wheel, that it meshes and which is fixed, said movable satellite wheel can move parallel to the periphery of the gear meshing by remaining therein, said translatable satellite wheel being connected to a fixed point of the device by means of an elastic return means intended to bring the moving satellite wheel into a rest position determined by the absence of engine torque or when, in the presence of a driving torque, the winding of the paper is freely made without resistance of said paper web, said moving wheel leaving this rest position when a resistance of the paper web to the winding is present, said device further comprising a means for detecting the displacement in translation of the satellite wheel. Finally, the term "translation" is understood here as a displacement along a curve which is circular, in this case the periphery of the geared wheel.

In the context of the invention, the term "paper" in "paper web" should be understood broadly and the invention is in fact applicable to any type of web material that can be used in a printer as direct or indirect 'impression. Likewise, the terms upstream (print reel side) and downstream are to be considered in relation to the direction of use of a strip of paper that is printed to produce labels (or keep the print journal).

In various embodiments of the invention, the following means can be used alone or in any technically possible combination, are employed: the elastic return means is a spring,

- the spring is a spiral spring, (watch regulator type or galvanometer reminder)

- the spring is a coil spring, (coil spring)

- the spring works in compression, (the displacement of the satellite wheel causes compression of the spring) - the spring works in extension, (the displacement of the satellite wheel causes an extension of the spring)

the electric motor is a stepping motor,

the detection means is all or nothing,

the detecting means is proportional to the movement of the at least one satellite wheel; the detecting means comprises at least one electromechanical switch (push-button (s) of end (s) of travel);

the detection means comprises at least one optoelectronic sensor,

the detection means comprises at least one potentiometric sensor,

the detection means comprise at least one magnetic sensor, (I.L.S or Hall + magnet effect)

the detection means comprises an optoelectronic sensor activated when the at least one satellite wheel is in its rest position,

the detection means comprises an optoelectronic sensor activated when the at least one satellite wheel has left its rest position and is at a predetermined point of its translation, the at least one satellite wheel is rotated by the motor and said at least one satellite wheel and the motor are mounted on the same mobile support, said satellite support, said satellite support being connected to the fixed point of the device via the return means elastic and being kept freely rotatable coaxially with the axis of rotation of the meshing wheel,

the device comprises a satellite wheel fixed on the driving shaft and an intermeshing wheel fixed on the winding shaft; the device comprises a first planet wheel meshing with a first gear wheel and a second planet wheel meshing with a second gear wheel; the two planet wheels meshing moreover with each other and the two intermeshing wheels being coaxial with each other, one of the two meshing wheels being driven by the motor and the other meshing wheel driving the winder, the motor being fixed, and the two satellite wheels are mounted on the same mobile support, said satellite support, said satellite support being connected to the fixed point of the device via the elastic return means and being kept free in rotation coaxially with the axes of rotation of the two intermeshing wheels,

the first and the second satellite wheels are one and the same satellite wheel meshing with the two intermeshing wheels; the device comprises two pairs of satellite wheels, the two satellite wheels of each pair being integral with one another, a first satellite wheel of the first pair meshing with a first gear wheel and a first gear wheel of the second pair meshing with a second gear wheel, the second planet wheels of the two pairs meshing moreover with each other and the two meshing wheels being coaxial with each other, one of the two meshing wheels being driven by the motor and the other gear wheel driving the winder, the motor being fixed, and the two pairs of satellite wheels are mounted on the same mobile support, said satellite support, said satellite support being connected to the fixed point of the device via the elastic return means and being kept freely rotatable coaxially with the axes of rotation the two meshing wheels, - the two satellite wheels of each pair have different diameters,

- The two satellite wheels of each pair are one and the same wheel.

The invention also relates to a printer comprising a reel of a paper web with a device as described. In variant embodiments of the printer:

the printer comprises, upstream of the reel in the direction of travel of the paper web, an upstream driving means of the paper web pinching said paper web so that when the upstream driving means is inactive, said strip of paper is blocked (or at least difficult to pull),

- the printer is a thermal printer,

the printer is a self-adhesive label printer, a means for detaching the labels being disposed upstream of the reel and downstream of the upstream drive means, said means being a deflection stop on which the paper web runs. , the deflection of the strip of paper leading to the detachment of the labels arranged on said strip (the labels because of their mechanical properties and the fact that the glue of the label does not adhere strongly to paper tape that is processed for this, tend to continue in the original direction of the paper tape, forward direction that the latter does not undergo the deflection) - the drive means upstream of the paper web comprises a stepper motor, the motorized electric drive of the winder comprises a stepper motor and the printer comprises means allowing to maintain substantially constant the tension of the paper web between the upstream drive means and the winder.

The invention also relates to a method of operating a printer such as a printer according to the description, an electric motor which is a stepper motor, a detection means which is activated when the at least one satellite wheel left its rest position and is at a predetermined point of its translation, and such that when the detection means is activated stopping the progression of the stepping motor.

The present invention, without it being so limited, will now be exemplified with the following description of embodiments and implementation in connection with: Figure 1 which is a diagram of a first embodiment FIG. 2 is a diagram of a second exemplary embodiment with (at least) two satellite wheels and two meshing wheels, FIG. 3 which is a first perspective view (view from FIG. the front) of a third embodiment, Figure 4 which is a second perspective view (front view) of the third embodiment, Figure 5 which is a third perspective view and against-dive (View from the rear) of the third embodiment, Figure 6 which is a fourth perspective view and downward (seen from the rear) of the third embodiment.

The device of the invention makes it possible to measure / detect a torque which is a function of the combination essentially of a (if any) active torque of the winding motor tending to the winding of the paper strip and of a (if any) torque tending to prevent said winding (depending on the operating conditions: winding motor active or not, active tape drive motor or not ...). Under certain operating conditions, the device of the invention also makes it possible to prevent unwinding of the strip of paper that has been wound up.

The present invention is particularly interesting in its applications to thermal printers on paper webs and in particular those intended for print self-adhesive labels. Indeed, because of the structure of a thermal printer, the paper web is pinched by a drive roller, the band being generally clamped between the drive roller and the thermal printing head. The paper web is therefore retained when the drive roller is not operating and it is therefore difficult to pull it downstream of the drive roller. In addition, with regard to self-adhesive labels, it is useful to recover by rolling the strip of paper backing labels, as and when, after detaching the adhesive labels. Note that this operation of recovering a paper web by winding can also be useful in the case of control strips / cash register, printed in the stores or distributors and which are stored in the printer of the cash register or the distributor while the ticket printed on another tape is given to the customer. The present invention is also of interest because, by implementing geared wheel transmission means, it also allows the choice of a transmission ratio between the driving motor of the winder, the motor shaft in this case , and the winding shaft of the paper roll. This is possible by selecting an arrangement and ratios of matched gear wheels diameters. It is also possible to implement one (two gear wheels only) or several stages (more than two gear wheels) in the transmission. We will see in the following description several embodiments with arrangements and transmission stages more or less important. The device of the invention is therefore more particularly implemented on the reel of the paper web which is arranged downstream of the drive roller and the printing area of / on said paper web. The detection device, in connection with a paper tape reel, by its ability to detect a tension on the paper web, a tension which causes resistance to winding, makes it possible in particular to ensure a sufficient tension of the web. bandaged. It is understood that once the sufficient voltage is reached, it can be maintained and if it is desired to reduce it there are two possibilities: to operate the winder in the opposite direction or to activate (more) the roller of training.

The use of a stepper motor for the motor of the winder is particularly interesting in the context of the invention. Indeed, thanks to the device of the invention, there is no loss of pitch during winding or unwinding. In particular, in a printer comprising a printing mechanism controlled also by a stepping motor, the latter provides a known length of paper to the device of the invention, which is similar to a rewinder and which is placed downstream of the printing mechanism (there is no loss of step in the printing and therefore the printed length is directly proportional to the number of steps performed by the engine of the printing mechanism). With this data and the number of steps performed by the motor of the rewinder, as well as the design data (reduction, ...) it is easy to deduce the current diameter of the rewound paper. It becomes possible to estimate the quantities of paper remaining, used, etc. For more precision one can possibly correct these calculations taking into account the angular difference of position of the satellite which moved between the beginning and the end of the measurement.

This data is particularly useful because it makes it possible to convert the constant-torque reel device of the invention into a particular operating mode into a constant-voltage rewinder in another mode of operation, since it is possible, on the basis of diameter information thus deduced, change the angular setpoint of the satellite to, during rewinding, increase the rewinding torque to allow to keep the paper tension constant throughout the printing of the roll. This characteristic is particularly useful in the case of a label printer because, in addition to other geometrical characteristics of the system (deflection of the strip carrying the labels in particular), the quality of the delamination is also a function of the tension exerted on the strip carrying the labels (the treated paper label holder). In particular, if this voltage is kept fixed or substantially fixed, a constant delamination quality will be obtained irrespective of the diameter of the upstream label roll and regardless of the position of the label in the roll. However, one of the problems encountered in conventional single friction printers is that the tension on the paper is very high at the beginning of the roll (small rewind diameter) and sometimes too low at the end of the roll (large rewind diameter). The first exemplary embodiment, shown diagrammatically in FIG. 1, essentially implements a satellite wheel 3 and an intermeshing wheel 4. The intermeshing wheel 4, which can turn in rotation, which is fixed on the chassis of the printer and which is rotated by the satellite wheel 3, is preferably directly related to the winding shaft of the paper web of the printer. The satellite wheel 3, which can rotate and is more mobile in translation relative to the printer frame, is preferably directly driven by a motor 1, preferably step by step, and the satellite wheel 3 is then attached to the motor shaft of the motor. Therefore, the motor must also be mobile in translation and is therefore fixed on a mobile support that can oscillate, said satellite support 2, whose attachment point, free in rotation relative to the printer frame, is located at the axis of rotation of the geared wheel 4 so that the satellite wheel 3 can have a path parallel to the periphery of the gear wheel 4. With this arrangement, the satellite wheel 3 remains engaged on the gear wheel 4 all the along its translation.

An elastic return means, preferably a spring 5, is arranged between the mobile satellite support 2 (carrying the engine 1 and the satellite wheel 3) and a fixed point of the printer frame in order to bring back the satellite support 2 and therefore the satellite wheel, at a predefined rest position in the absence of constraints tending to move said satellite wheel. This rest position may correspond to a balance of forces between the spring (or a absence of return force of the spring, the latter then being relaxed, at rest) and the other possible forces or correspond to an arrival of the support against a fixed stop (whose position is possibly adjustable) fixed on the frame while the spring is always tense.

A means for detecting the displacement in translation of the satellite wheel is implemented in the form of an optoelectronic sensor 7. In an advanced embodiment, the sensor 7 is proportional in that it detects the translation angle of the sensor. satellite support

2. Alternatively, the sensor may be all or nothing and, for example with detection of light beam cutoff and for this purpose, a cover is fixed on the movable support 2 and can cut off the light beam of the sensor which is fixed, attached to the printer chassis when the mobile stand is moving.

It is understood that when the motor 1 is activated for winding the paper web, the satellite wheel 3 and therefore the satellite support 2 can move along the periphery of the gear wheel 4 depending in particular on the resistance to winding opposed by the paper web and the restoring force of the resilient biasing means. It should be noted that the term printer chassis in the context of the invention refers to a fixed structural element of the printer and that it may as well cover the general frame of the printer as a frame of a printer. part of the printer such as a prefabricated module comprising the device of the invention as will be explained later.

The second exemplary embodiment, shown diagrammatically in FIG. 2, implements at least two planet wheels 3, 3 'meshing with each other and an intermeshing wheel 4, 6 with a satellite wheel, a 6 of the intermeshing wheels being driven by the engine of FIG. drive 1 which is this time fixedly fixed on the frame of the printer. The intermeshing wheels 4, 6 rotatable are fixed on the printer frame and are coaxial. The planet wheels 3, 3 'which can turn in rotation are also movable in translation parallel to the peripheries of the intermeshing wheels 4, 6 and are on an oscillating mobile support, said satellite support 2, connected to a fixed point of the printer frame. by a return means, a helical spring 5 in this example. The point of attachment of the satellite support 2, free to rotate relative to the printer frame, is located at the axis of rotation of the gear wheel 4 so that the planet wheels 3, 3 'can have a parallel path at the peripheries of the meshing wheels 4, 6. With this arrangement, the planet wheels 3, 3 'remain in engagement with their corresponding meshing wheels 4, 6 throughout their translation. As before, a means for detecting the translational movement of the satellite wheels is implemented. In this example, the detection means is an optoelectronic sensor 7 in relation to the satellite support 2 carrying the planet wheels 3, 3 '. In the second example of embodiment which has just been presented, it has implemented intermeshing wheels 4, 6 which have different diameters, this to facilitate the visualization of the various elements of the device. It is understood that these diameters can be other and, by example, equal. It may be the same for the diameters of the satellite wheels. For the same reason it was implemented in this example that two planet wheels 3, 3 'meshing with each other. It is also understood that other equivalent functional configurations are possible and, for example, a single satellite wheel carrying two gears to engage on the two intermeshing wheels or more than two satellite wheels. Due to the arrangement of the elements, the meshing wheels are superimposed.

Thus, in an alternative embodiment of this second example, especially in the case where the two intermeshing wheels have the same diameter, a single satellite wheel (by equivalence to two satellite wheels of the same diameter, superimposed) can be implemented. The third exemplary embodiment, shown in FIGS. 3 to 6, implements four planet wheels 3a, 3b, 3'a, 3'b in the form of two pairs 3a, 3b and 3'a, 3'b, in a pair the two satellite wheels being secured together to rotate together. The two pairs of planet wheels are intermeshing each other 3a, 3'b so that the first pair rotates the second pair. The two pairs being made of satellite wheels, they can move in translation while remaining meshed with each other. A satellite wheel 3b, 3'a of each pair meshes with a corresponding meshing wheel 6, 4 which is rotatable but fixed to the printer frame. A first 6 of the two intermeshing wheels is driven by a motor gear 9 driven by the motor shaft of the motor 1 and the second intermeshing wheel 4 drives the winding shaft which comprises a mandrel 8 for receiving the paper roll which is going to to wrap it up.

The pairwise satellite wheels, which can therefore turn in rotation, are therefore more mobile in translation parallel to the peripheries of the meshing wheels and are on an oscillating mobile satellite support 2 connected to a fixed point of the printer frame by means of recall, a helical spring 5 in this example. As before, a means for detecting the translational movement of the satellite wheels is implemented. In this example, the detection means is an optoelectronic sensor 7 in relation to the satellite support 2 carrying the satellite wheels. The sensor is reflective and not broken beam in this example. As before, the two intermeshing wheels are coaxial with each other and the satellite support 2 is articulated in rotation about their axis of rotation. Figures 4 and 6 is further shown a housing 10 in which in particular the satellite wheels and their satellite support and the meshing wheels are arranged. The elastic return means, the spring 5, is fixed at one of its two ends at a fixed point of this housing 10. The engine 1 is also fixed on the housing 10. The various rotatable members, in particular gear wheels and support satellite, are mounted on the housing. For the latter, 2, the rotating mobile satellite wheels, are mounted on said satellite support 2 and can be seen in Figure 5, the bosses 1 1 and 1 1 'for the axes of each pair of satellite wheels protruding from the face rear of said satellite support 2. This explains the existence of a niche 12 elongated in an arc extending beyond the back of the housing 10 Figure 6 so that the boss / bosses can circulate freely. Thus, the bosses 1 1, 1 1 'made in the plastic of the satellite support 2 allow the insertion of the reported axes of the satellite gear wheels (metal inserts of the satellite wheels) over a sufficient length. These metal shafts are present to ensure good behavior of the gear and reduce the diameter of the axis of rotation of each pair of planet wheels.

Preferably, the device of the invention is in the form of a prefabricated module 13 that can easily be fixed functionally on the frame / chassis of the printer. Likewise, it is preferable for the gear wheels to be protected from the environment (dust, paper debris, hair, etc., which can block the gears) and thus be disposed within a closed or substantially closed housing at least one times in the printer. The introduction of a module 13 as shown in Figures 4 and 6 with its housing 10 in the printer ensures the closure of the housing because it is placed against a wall of the printer frame. The module 13 can be fixed on the frame of the printer by screwing, latching, gluing or any other means. The latching means visible on the module housing are here intended to fix a small interconnection card not shown for reasons of simplification. Preferably, the mounting of the module is done with screws through the chassis of the printer, frame which is in the form of a metal base plate, and through holes in the housing which are in particular visible on the Figure 4. The materials used for the elements of the device are selected from metals, metal alloys, simple plastics or composite, loaded or not. The gears can be self-lubricating or you can add grease.

In general, when the / the satellite wheels are in the rest position, the elastic return means, preferably a spring, can be claimed (or precompressed as the case may be) or not. Means for adjusting said pretension (precompression) may be implemented to modify the sensitivity / detection threshold of the device. In a variant, there is a means for adjusting the stiffness of the elastic return means in order to adjust the sensitivity / torque detection level of the device of the invention. It has also been seen that such an adjustment can be obtained by moving a stop of the frame intended to stop the mobile support at its rest position as this can create a prestressing of the elastic return means.

Preferably, the means for detecting the displacements of the satellite wheel (s) is functionally integral with the mobile satellite carrier which carries the said satellite wheel (s). For example, in the case of an on-off detection means with an electromechanical sensor of the push button switch type, an actuating finger can be carried by the mobile support, which finger will press the fixed button which is fixed on a printer chassis. For example, in the case of an on-off detection means with an optoelectronic sensor of the light beam cutoff type, a cover may be worn by the mobile support, which cache will cut the beam of the fixed sensor which is fixed on a frame of the printer.

In another case, the detection is by reflection on a reflective zone of a light beam. In particular, in the embodiment shown, the sensor is optoelectronic and the response of the sensor is linear because the reflecting surface is on a curve (a circle in this case) whose center is offset with respect to the axis of rotation. of the satellite support 2 which, in this case is also the rewind shaft. Thus, depending on the position angle of the satellite, the distance between this reflecting surface and the sensor varies. The optoelectronic sensor is used as a proximity sensor, reflecting the angle of the satellite. Note that in the case where the reflecting surface is on a curve parallel to the displacement of the sensor, the reflective surface may have a substantially triangular shape, so that the reflection varies depending on the position of the sensor along the triangle.

It is understood that all the equivalent arrangements are also considered (sensors on the mobile support for example) and that all types of sensors can be used (magnetic, optical, mechanical).

Other detecting means (paper defect, etc.) and / or effectors (paper cutting, etc.) can be implemented in the printer. In addition to the thermal printing itself, the electronic or computer control means of the printer allow the control of the means including motor printer according to the conditions detected by the sensor / sensors of the printer.

As regards the operating modes of a printer comprising the device, it is understood that they can be various according to needs. In any case, the possibility of detection of torque, in particular a rewinding resistance, makes it possible to block the winding motor, for example by remaining in a particular position, once a certain level of torque has been detected. . In variants, it is possible to provide a slight rollback of the winding motor when the detection is carried out or, again, the activation of the drive motor of the paper strip to relax the paper web a little. To this end, electronic and computer means are implemented, in particular in the form of a wired logic and / or programmed and / or a computer program for controlling the various effectors (including engines) of the printer according to sensor measurements (including that of the invention) and external orders (printing instructions / data to be printed).

Claims

1. Torque sensing device for a motorized electric drive of a reel of a printer paper web, a winding shaft (8) for winding the paper web, said winding shaft being driven into rotation by a transmission means by means of a motor shaft driven in rotation by an electric motor (1), the transmission means comprising at least two peripheral gear wheels rotatable, characterized in that the transmission means comprises at least a gear wheel (3, 3 ', 3a, 3b, 3'a, 3'b) which is movable in translation relative to another, said gear wheel (4, 6), which it meshes and which is fixed, said mobile satellite wheel being able to move parallel to the periphery of the gear meshing while remaining therein, said translatable satellite wheel being connected to a fixed point of the device by means of an elastic return means (5) intended to bring the moving satellite wheel back to a determined rest position in the absence of a driving torque or when, in the presence of a driving torque, the winding of the paper web is carried out freely without resistance of said paper web, said moving wheel leaving this rest position when a resistance of the paper web to the winding is present, said device further comprising a means (7) for detecting displacement in translation of the satellite wheel.

2. Device according to claim 1, characterized in that the at least one satellite wheel (3) is rotated by the motor (1) and that said at least one satellite wheel and the motor are mounted on the same mobile support, said satellite support (2), said satellite support being connected to the fixed point of the device via the elastic return means and being kept freely rotatable coaxially with the axis of rotation of the gear wheel (4).

3. Device according to claim 2, characterized in that it comprises a satellite wheel

(3) fixed on the motor shaft and an impeller (4) fixed on the winding shaft.

4. Device according to claim 1, characterized in that it comprises a first (3) satellite wheel meshing with a first (6) gear wheel and a second (3 ') satellite wheel meshing a second (4) gear wheel, both satellite wheels (3, 3 ') meshing with each other and the two meshing wheels (4, 6) being coaxial with each other, one (6) of the two intermeshing wheels being driven by the motor (1) and the other (4) intermeshing wheel driving the reel (8), the motor being fixed, and in that the two satellite wheels are mounted on the same mobile support, said satellite support (2), said satellite support being connected to the fixed point of the device via the elastic return means and being kept free in rotation coaxially with the axes of rotation of the two intermeshing wheels (4, 6).

5. Device according to claim 4, characterized in that the first and second satellite wheels are a single satellite wheel meshing with the two meshing wheels.

6. Device according to claim 1, characterized in that it comprises two pairs (3a, 3b) (3'a, 3'b) of satellite wheels, the two satellite wheels of each pair being integral with each other, a first ( 3b) satellite wheel of the first pair meshing with a first (6) meshing wheel and a first (3'a) satellite wheel of the second pair meshing with a second (4) meshing wheel, the seconds (3a, 3'b) satellite wheels the two pairs meshing moreover with each other and the two intermeshing wheels being coaxial with each other, one (6) of the two meshing wheels being driven by the motor (1) and the other (4) meshing wheel driving the winder ( 8), the motor being fixed, and the two pairs of satellite wheels are mounted on the same mobile support, said satellite support 2, said satellite support being connected to the fixed point of the device via the elastic return means (5) and being kept freely rotatable coaxially with rotational axes n of the two meshing wheels.

7. Printer characterized in that it comprises a motorized electric drive reel of a paper web with a torque detection device according to any one of the preceding claims and upstream of the winder in the direction of scrolling the paper web, an upstream driving means of the paper web pinching said paper web so that when the upstream driving means is inactive, said paper web is blocked.

8. Printer according to claim 7, characterized in that it is a thermal printer.

9. Printer according to claim 7 or 8, characterized in that it is an adhesive label printer, a label detachment means being disposed upstream of the reel and downstream of the upstream drive means, said means being a deflection stop on which the paper web is traveling, the deflection of the strip of paper leading to the detachment of the labels arranged on said strip.

10. Printer according to claim 7, 8 or 9, characterized in that the upstream drive means of the paper web comprises a stepper motor, the electric motorized drive of the winder comprises a stepper motor. and that the printer has means for keeping substantially constant the tension of the paper web between the upstream drive means and the winder.

1 1. A method of operating a printer, characterized in that a printer according to one of claims 7 to 10 is used, an electric motor which is a stepper motor, a detection means which is activated when the at least one satellite wheel has left its rest position and is at a predetermined point of its translation, and in that when the detection means is activated stopping the progression of the stepping motor.