WO2008092943A1

WO2008092943A1 - Device to detect the advance of a belt

Info

Publication number: WO2008092943A1
Application number: PCT/EP2008/051237
Authority: WO
Inventors: Vincenzo Chiarelli; Gianni Chiodo; Lorenzo Duroux; Andrea Vito Antonio Garramone
Original assignee: Sferal World Wide Technology Srl
Priority date: 2007-02-02
Filing date: 2008-02-01
Publication date: 2008-08-07
Also published as: CN101627284A; EP2115393A1; CN101627284B; ITUD20070020A1

Abstract

A device to detect the advance of a belt (11) with respect to its container (12) comprises a rotating element (13) associated with the belt (11), which rotates by one revolution each time the belt (11) advances by a determinate amount, and magnetic detection means (16) able to detect the presence, or the variation, of a magnetic field so as to generate a corresponding electric signal. The rotating element (13) comprises at least a permanent magnet (19), able to rotate with it, and the magnetic detection means (16) is disposed in a fixed position with respect to the rotating element (13), in correspondence with a peripheral zone of the rotating element (13), in order to detect the rotations of the permanent magnet (19) and generate the electric signal.

Description

"DEVICE TO DETECT THE ADVANCE OF A BELT"

FIELD OF THE INVENTION

The present invention concerns a device to detect the advance of a belt with respect to its container, and in particular of an inked belt with respect to the cartridge that contains it.

BACKGROUND OF THE INVENTION

A device is known, for detecting the advance of an inked belt with respect to the cartridge that contains it, which comprises a rotating element that is associated with the belt so that it rotates by one revolution each time the belt itself advances by a determinate amount. In this way, by detecting the number of rotations of the rotating element, it is possible to determine, with a good level of precision, the amount of belt that has advanced, for example with respect to the printing member outside the cartridge. In the known device the rotating element comprises a foil made of a metal that allows the magnetic flux to pass and which is shaped so as to define one or more spokes, which depart in a radial manner with respect to an axis of rotation. The spokes of the foil are associated with a Hall effect magnetic sensor, disposed in a fixed position, and consisting of a permanent magnet and a detection element, able to detect the variation in the magnetic flux generated by the permanent magnet. In this way, the rotation of the foil causes, with its spokes, the selective variation of the magnetic flux generated by the permanent magnet and the consequent generation, due to the Hall effect, of corresponding electric signals by the detection element. However this known device has the disadvantage of having the rotating foil, associated with the belt, "on board" the cartridge, while the magnetic sensor is mounted on the frame of the printer, in a fixed position, or "off board". This means that an imperfect assembly of the cartridge in the printer causes incorrect positioning of the rotating foil with respect to the fixed magnetic sensor, with consequent errors in the generation of said electric signals and hence in the detection of the advance of the belt.

US-A-4,718,683 discloses a signal transducer for detecting a limited linear displacement between a fixed part and a movable part. The transducer includes a flexible traction member, the length of which defines the maximum relative travel between the two parts, having one end anchored to the fixed part and another end connected to the movable part, and a return spring that tends to rotate the movable part in the opposite sense of rotation when the two parts move linearly toward each other. The transducer further includes sensor means indicative of the angular position of the rotor relative to the fixed part and hence of the relative position of the two parts. The transducer is actually mounted on one of the parts of which the detection is made, so that the accuracy of the detection is conditioned by the precision of the reciprocal assembly.

One purpose of the present invention is to achieve a device to detect the advance of a belt with respect to its container, which is precise and which is not excessively influenced by a possible imprecise positioning of the container with respect to the machine on which it is mounted, for example a printer, in the case of a cartridge for an inked belt.

Another purpose of the present invention is to achieve a device to detect the advance of a belt with respect to its container, which allows to encode, in a simple and economic manner, the type of belt and/or container on which said device is mounted. The Applicant has devised and perfected the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.

SUMMARY OF THE INVENTION

The present invention is set forth and characterized essentially in the independent claim, while the dependent claims describe other innovative characteristics of the invention.

In accordance with the above purposes, a device to detect the linear, continuous and incremental advance of a belt with respect to its container, around a roller driven in rotation by the belt, comprises a rotating element associated with the belt, able to rotate by one revolution each time the belt advances by a determinate amount, and magnetic detection means, disposed in a fixed and remote position with respect to said rotating element and able to detect the presence, or the variation, of a magnetic field so as to generate a corresponding electric signal.

According to a characteristic feature of the present invention, the rotating element is integral with said roller and comprises at least a permanent magnet, able to rotate therewith. Said magnetic detection means is located in correspondence with a peripheral, fixed and remote zone with respect to the rotating element in order to detect the rotations of the permanent magnet and to generate said electric signal.

Thanks to the remote positioning of the detection means with respect both to the belt and to the container, the detection is not influenced by the reciprocal assembly of the two parts, so that no errors in the detection arise from a wrong mounting position between the belt and the relative container.

According to one form of embodiment of the present invention, said magnetic detection means comprises a Hall effect sensor, disposed on a ferromagnetic element, which channels thereon the flux of the magnetic field generated by the permanent magnet.

According to another form of embodiment of the present invention, the magnetic detection means advantageously comprises a Giant Magnetoresistive

Sensor (GMR), or an Anisotropic Magnetoresistive Sensor (AMR), both known sensors, each of which is able to detect the presence, or absence, of the magnetic field generated by the permanent magnet when this moves closer thereto.

The rotating element can be associated both with a member for drawing the belt, for example consisting of a drawing roller associated with the shaft of an electric motor, and, advantageously, to a roller driven by the belt. In this second case, in fact, the reciprocal sliding of the belt and the roller is prevented. Furthermore, according to a first form of embodiment of the present invention, the rotating element consists of a single permanent magnet, in the shape of a bar pivoted in the center and with the polar expansions N and S at its ends.

According to a variant, the rotating element has a plurality of radial arms, for example four disposed in a cross, with the polar expansions N and S of the permanent magnet disposed at the ends of the radial arms. The radial arms can all be of the same length, or have different lengths.

According to another characteristic feature of the present invention, the permanent magnet consists of a disc made of magnetic rubber and polarized in its - A -

peripheral zone in a selective manner, so as to define in this way an identifying code along its circumference, which can be "read" and therefore interpreted by said magnetic detection means.

According to another characteristic feature of the present invention, an electromagnet, able to be selectively energized, is associated with the magnetic sensor, on the opposite side with respect to the rotating element; this electromagnet allows to pre-polarize the sensor and take it to a useful linear zone for the correct detection of the rotation of the rotating element. In this way it is possible to perform an automatic, or programmed, calibration of the magnetic sensor, making the device according to the present invention independent from any magnetic field present in the surroundings of the device.

The pre-polarizing magnetic field, obtained with the electromagnet, can also be generated by a second permanent magnet, fixed, with characteristics equivalent to those of the electromagnet. In this way, with the device according to the present invention, it is possible not only to detect the advance of a belt with respect to its container, but also to memorize information concerning the belt in the rotating element, such as for example its length, its type (made of fabric, polythene, re-chargeable, and other), and/or concerning its container. BRIEF DESCRIPTION OF THE DRAWINGS

These and other characteristics of the present invention will become apparent from the following description of some preferential forms of embodiment, given as a non-restrictive example with reference to the attached drawings wherein:

- fig. 1 is a schematic view, partly sectioned, of a device according to the present invention;

- figs. 2 to 10, including figures 2a and 3a, schematically represent some forms of embodiment of the device according to the present invention;

- figs. 11 to 16a represent some electric signals generated by the magnetic sensors of the device according to the present invention. DETAILED DESCRIPTION OF A PREFERENTIAL FORM OF

EMBODIMENT

Fig. 1 schematically represents a device 10 according to the present invention, able to detect the advance of a belt 11 with respect to its container 12. The belt 11 and the container 12 can be of any known kind and are not relevant for the purposes of the present invention. Thus, for example, the belt 11 can be an inked belt for an impact printer, not shown in the drawings, and the container 12 can be the relative cartridge. The device 10 comprises a rotating element 13, connected to a roller 15, held adherent to and driven in rotation by the belt 11, in order to rotate by a complete revolution each time the belt 11 advances by a determinate amount, equal to the development of the circumference of the roller 15. In this specific case, the roller 15 is integral with said roller 15 and is advantageously not linked to the kinematism of the motor drawing the belt 11, which can be of any known type and is not shown in the drawings, as it is not relevant for the present invention. In this way, wrong signals of correct functioning are prevented, as the device 10 supplies an output only if the belt 11 actually advances with respect to the container 12. Advantageously, the rotating element 13 is provided, at least on its peripheral zone, with at least a permanent magnet 19 (figs. 2-10).

The device 10 also comprises a magnetic sensor 16, mounted on a fixed part 20, consisting for example of the frame of the printer on which the cartridge 12 is mounted. The magnetic sensor 16 is mounted in a remote position with respect both to the belt 11 and to the container 12.

The magnetic sensor 16 is able to detect the presence of the magnetic field generated by the permanent magnet, or by the permanent magnets, 19 present in the rotating element 13, so as to generate a corresponding electric signal SG (figs. l l-16a), consisting of impulses I, which can be both positive and negative, or only positive, as will be described in detail hereafter.

Figures 2 to 10 show, as an example, some forms of embodiment of rotating elements 13 and of the relative permanent magnets 19, all coming within the scope of the present invention, it being understood that countless other forms of embodiment of the rotating elements 13 are possible, always remaining within the scope of the present invention.

In particular, in the forms of embodiment shown in figs. 2 and 3 the rotating element 13 consists of a single permanent magnet 19 shaped as a bar, pivoted in the center and with its polar expansions N and S at its ends.

In fig. 2 the magnetic sensor 16 is of the Hall effect type and is mounted on a U-shaped ferromagnetic element 21 fixed to the fixed part 20, not shown in the drawing. In this specific case, the ferromagnetic element 21 has a length equal to that of the permanent magnet 19.

In fig. 3, on the other hand, the magnetic sensor 16 is a Giant Magnetoresistive sensor (GMR) or an Anisotropic Magnetoresistive sensor (AMR), and is mounted directly on the fixed part 20, without any ferromagnetic element, as it is not necessary. According to a variant, shown schematically in figs. 2a and 3a, an electromagnet 23 is associated with the magnetic sensor 16, of the GMR or AMR type, on the opposite side with respect to the rotating element, with a selectively chargeable coil 25. The electromagnet 23 allows to pre-polarize the magnetic sensor 16 and take it to a linear zone useful for the correct detection of the rotation of the rotating element 13. The electromagnet 23 can be replaced by a fixed permanent magnet, with equivalent characteristics and not shown in the drawings.

In the forms of embodiment shown in figs. 4, 5 and 6 the rotating element 13 consists of a permanent magnet 19 shaped like a cross, with four arms at 90° with respect to each other, at whose ends the polar expansions N and S are disposed. In particular, the arms can all have the same length, as in fig. 4, or different lengths, as in figs. 5 and 6. In this specific case, the magnetic sensor 16 is of the Hall effect type and is mounted on a ferromagnetic element 21. The latter can have a length equal to that of the permanent magnet 19 (figs. 4 and 5) or half of it (fig. 6). It is clear that the Hall effect magnetic sensor 16 can be replaced by a GMR or AMR type sensor.

In the forms of embodiment shown in figs. 7, 8, 9 and 10 the rotating element 13 consists of a disc 22 of magnetic rubber, which has permanently polarized peripheral zones which act as permanent magnets 19, that is, as polar expansions N and S. Alternatively, the disc 22 can be made of non-magnetic material, for example plastic, with the magnetic rubber disposed in the peripheral zones that define the polar expansions N and S.

The size of each polar expansion N and S and the distance between them determine different electric signals S (figs. 15 and 16) by the magnetic sensor 16. In these cases too, the magnetic sensor 16 is of the Hall effect type (figs. 7, 9 and 10) and is mounted on a ferromagnetic element 21, or a GMR or AMR type (fig. 8). In the diagrams in figs. 11 to 16a, each signal SG generated by the magnetic sensor 16 corresponds to a complete rotation of the rotating element 13. The time needed to complete a complete rotation by the rotating element is represented on the x-axis, while the y-axis shows the values of the impulses I. The number of impulses I generated by the magnetic sensor 16 during each complete rotation of the rotating element 13 is equal to the number of polar expansions of the latter. Furthermore, the shape of the impulses I (height and width) and the time interval between them are defined by the presence and shape of permanent magnets 19 present in the rotating element 13.

In particular, the shape of the waves of the signals S in figs. 1 1, 12, 13, 14, 15 and 16, which are bipolar and have both positive and negative impulses I, refer to a Hall effect magnetic sensor 16. When, instead, the magnetic sensor is of a

GMR type, the corresponding wave shapes are mono-polar, with only positive impulses I, as shown in figs. 11a, 12a, 13a, 14a, 15a, 16a. The presence of the pre-polarization electromagnet 23 (or the equivalent permanent magnet), if current is passed through it, allows to obtain bipolar wave shapes (figs. 11, 12,

13, 14, 15 and 16) also with GMR sensors.

Figs. 11 and 11a schematically show an electric signal SG generated by the magnetic sensor 16 in figs. 2 and 3, respectively 2a and 3a.

Fig. 12 schematically shows the electric signal SG generated by the magnetic sensor 16 in fig. 4.

Fig. 13 schematically shows the electric signal SG generated by the magnetic sensor 16 in fig. 5.

Fig. 14 schematically shows the electric signal SG generated by the magnetic sensor 16 in fig. 6. Fig. 15 schematically shows the electric signal SG generated by the magnetic sensor 16 in figs. 7 and 8.

Fig. 16 schematically shows the electric signal SG generated by the magnetic sensor 16 in figs. 9 and 10. Figs. 12a, 13a, 14a, 15a and 16a schematically show the electric signal S generated by each magnetic sensor 16 of the devices 10 shown, respectively, in figs. 4 (12a); 5 (13a); 6 (14a); 7 and 8 (15a); 9 and 10 (16a), in the hypothesis that the magnetic sensor is a GMR type. It is clear that modifications, simplifications and/or additions of parts may be made to the device 10 as described heretofore, without departing from the scope of the present invention.

It is also clear that, although the present invention has been described with reference to some specific examples, a person of skill in the art shall determinately be able to achieve many other equivalent forms of device to detect the advance of a belt, with respect to its container, having the characteristics as set forth in the claims and hence all coming within the scope of protection defined thereby.

Claims

1. Device to detect the linear, continuous and incremental advance of a belt (1 1) with respect to its container (12) around a roller (15) driven in rotation by said belt (11), the device comprising a rotating element (13) associated with said belt (1 1), able to rotate by one revolution each time said belt (11) advances by a determinate amount, and magnetic detection means (16) able to detect the presence, or variation, of a magnetic field so as to generate a corresponding electric signal (SG), characterized in that said rotating element (13) is integral with said roller (15) and comprises at least a permanent magnet (19), able to rotate therewith, and in that said magnetic detection means (16) is disposed in a fixed and remote position with respect to said rotating element (13), in correspondence with a peripheral zone of said rotating element (13) in order to detect the rotations of said permanent magnet (19) and to generate said electric signal (SG).

2. Device as in claim 1, characterized in that said magnetic detection means (16) comprises a Hall effect sensor, disposed on a ferromagnetic element (21), which channels thereon the flux of the magnetic field generated by said permanent magnet (19).

3. Device as in claim 1, characterized in that said magnetic detection means (16) comprises a Giant Magnetoresistive sensor (GMR), or an Anisotropic

Magnetoresistive sensor (AMR).

4. Device as in claim 3, characterized in that an electromagnet (23), with a selectively energizable coil (25), is associated with said magnetic sensor (16), of the GMR or AMR type, on the opposite side with respect to said rotating element (13).

5. Device as in claim 3, characterized in that a second permanent magnet is associated with said magnetic sensor (16), of the GMR or AMR type, on the opposite side with respect to said rotating element (13).

6. Device as in any claim hereinbefore, characterized in that said permanent magnet (19) has the shape of a bar pivoted at the center and with polar expansions (N and S) at its ends.

7. Device as in any claim hereinbefore, characterized in that said permanent magnet (19) comprises a plurality of radial arms, and has the polar expansions (N and S) disposed at the ends of said radial arms.

8. Device as in claim 7, characterized in that there are four of said radial arms, disposed at 90° with respect to each other, so as to form a cross.

9. Device as in claim 7 or 8, characterized in that said radial arms all have the same length, or different lengths.

10. Device as in any claim hereinbefore, characterized in that said permanent magnet (19) consists of a disc (22) at least partly made of magnetic rubber and polarized in its peripheral zone in a selective manner, so as to define, along its circumference, the polar expansions (N and S) of said permanent magnet (19).

11. Device as in any claim hereinbefore, characterized in that said rotating element (13) is associated with a roller (15) driven by said belt (11).