The present invention relates to a guide system for a conveyor belt.

In general, the invention can be usefully applied in all machines or conveyor systems that envisage the use of a conveyor belt for which a precise advancement which is constant over time along a rectilinear direction is required.

In particular, but not exclusively, the invention can be usefully applied in an ink jet decorator for decorating ceramic tiles.

As is known, an ink jet decorating machine for ceramic slabs or tiles comprises an inkjet printing head, located in a certain position, below which a conveyor belt is positioned, configured to lead the tiles or slabs to be decorated below the ink jet printing head. The belt moves continuously, so that the slabs or tiles are decorated during movement, while they transit below the printing head.

It is known that, to obtain a precise decoration, it is necessary to know at all times, in a very precise way, the position of every point of the conveyor plane with respect to a fixed reference system. This is necessary so that every pixel of the decoration, i.e. every drop of ink emitted by the printing head, is positioned in a predefined point of a given ceramic slab or tile positioned on the conveyor plane.

In particular, in the event of a conveyor belt on which the objects to be printed are positioned, it is necessary for the latter to precisely follow a predefined route. In order for this to happen, the path followed by the conveyor belt must have a known and repeatable course in every point thereof. In the longitudinal sense, i.e. the advancement direction, the positioning precision is guaranteed by the belt drawing system. In the transverse direction, i.e. perpendicular to the advancement direction, the conveyor belt is instead free to move.

As is known, the longitudinal edges of the conveyor belt are not perfectly rectilinear and parallel, mainly because of the trimming process by which they are made. The errors on the longitudinal edges are substantially due to a deviation with respect to a longitudinal direction, a deviation that can lead to a change of direction of the belt, a variation in the width of the belt or a combination of the two errors.

In current guide systems it is possible to contain the error due to the change of direction, using rails or other lateral guide devices. Instead it is not possible to effectively contain the change in width of the conveyor belt. This is because the rails or lateral guides must be located at a distance such as to enable the passage of the sections with the maximum width. In this way, the sections of the conveyor belt with the minimum width are not effectively guided.

The aim of the present invention is to offer a guide system for a conveyor belt that makes it possible to overcome the drawbacks of currently available guide systems.

The main but not only advantage of the present invention is that it enables both errors due to a change of direction and errors due to a change of width of the conveyor belt to be effectively contained.

Additional features and advantages of the present invention will become more apparent from the following detailed description of an embodiment of the invention, illustrated by way of non-limiting example in the appended figures, in which: figure 1 shows a schematic plan view of the guide system according to the present invention, in a first operating configuration; figure 2 shows the guide system of figure 1 in a second operating configuration; figure 3 shows a second embodiment of the guide system according to the present invention.

The guide system according to the present invention is particularly effective for guiding a conveyor belt (T) along a predefined advancement direction (X), but not only for this.

A conveyor belt substantially means a flat and flexible element, movable along an annular path defined by two or more idler rollers, rotating about axes of rotation preferably parallel and horizontal to one another. At least a main section of the annular path followed by the conveyor belt is a section along which the transport of objects takes place. Preferably, the main section is substantially horizontal and parallel to the advancement direction (X). At least along the main section, the conveyor belt (T) defines a conveyor plane for the objects. Such conveyor plane is preferably horizontal. The appended figures schematically illustrate the main section of the conveyor belt (T) and the conveyor plane defined thereby. In the following description, reference is made to the conveyor belt (T) to indicate the main section of the conveyor belt (T) itself.

The conveyor belt (T) has a prevalent extension, or length, directed substantially parallel to the advancement direction (X), at least along the section intended to transport objects. The conveyor belt (T) also has a width, measured perpendicularly to the advancement direction (X), which substantially defines the distance between the two lateral edges of the conveyor belt (T).

Overall, the conveyor belt (T) is supported by a load-bearing frame, not illustrated in detail, which also supports the idler rollers which define the path followed by the belt (T) itself, the motor systems and other parts possibly arranged for the operation of the conveyor belt (T).

The guide system according to the present invention comprises a first guide (2) and a second guide (3), each of which is arranged to be positioned in contact with a respective side of the conveyor belt (T). In a possible embodiment, the first and the second guide (2,3) are in the form of prismatic elements provided with a longitudinal axis oriented substantially parallel to the advancement direction (X), except for any oscillations that can take place during operation. Preferably, but not necessarily, the first and the second guide (2,3) are provided with sliding elements, e.g. skids, rollers or castors, positioned so as to be in contact with the sides of the conveyor belt (T).

In another possible embodiment, not illustrated, the first and the second guide (2,3) are in the form of rollers or castors, with axes of rotation oriented so as to enable rotation in contact with the lateral edges of the conveyor belt (T). For example, in the event in which the latter is lying on a horizontal plane, at least along the section intended for transporting objects, the axes of rotation of the rollers or castors which define the first and the second guide (2,3) are vertical.

Advantageously, the first and the second guide (2,3) are movable, at least partially, towards and away from one another. Preferably, but not necessarily, the first and the second guide (2,3) are movable with respect to one another between a position of maximum mutual distance and minimum mutual distance. This enables the guides (2,3) to be able to adapt to conveyor belts (T) of different widths, or to follow the errors and deviations of the lateral edges of a conveyor belt (T).

The first and the second guide (2,3) are associated with a support frame (F), not illustrated in detail, which can be associated with or be part of the overall support frame of the conveyor belt (T).

Advantageously, the guide system according to the present invention comprises a transmission kinematic mechanism (4), which connects the first and the second guide (2,3) to one another. Such transmission kinematic mechanism is configured to transmit, to at least a portion of the first guide (2) and to at least a portion of the second guide (3), symmetrical movements with respect to a central plane (P). In a possible embodiment of the transmission kinematic mechanism (4), the movements transmitted to at least one portion of the first guide (2) and to at least one portion of the second guide (3) are rectilinear, and are therefore equal and opposite in direction, perpendicularly to the central plane (P). In another possible embodiment, the movements transmitted to at least one portion of the first guide (2) and to at least one portion of the second guide (3) are shaped like the arc of a circle, with centres arranged in turn symmetrically with respect to the central plane (P).

In other words, the transmission kinematic mechanism (4) is structured to transmit to the first and to the second guide (2,3), or at least to respective portions, a symmetrical movement at least with respect to a central plane (P)-

An actuator (5) is arranged to exercise a thrust on at least one from between the first and the second guide (2,3), which tends to move a portion of the guides (2,3) themselves towards one another. In other words, the thrust exercised by the actuator (5) is directed and/or oriented so as to move the first and the second guide (2,3), or at least respective portions of the first and the second guide (2,3) towards one another.

By arranging the first and the second guide (2,3) so that the central plane (P) is positioned to contain the advancement direction (X), and substantially perpendicular to the conveyor belt (T), it is possible to keep the latter substantially aligned with the advancement direction (X). In other words, by arranging the first and the second guide (2,3) so that the central plane (P) contains the advancement direction (X), and is substantially perpendicular to the conveyor plane defined by the conveyor belt (T), it is possible to keep the latter substantially aligned with the advancement direction (X).

In fact, the first and the second guide (2,3) are placed to the sides of the conveyor belt (T), and, at least a portion of each of them, is pushed into contact with a respective side of the conveyor belt (T) by the actuator (5). In the event in which the sides of the conveyor belt (T) are not rectilinear and/or not parallel, at least a portion of the first guide and at least a portion of the second guide (2,3), pushed by the actuator (5) to move towards one another symmetrically with respect to the central plane (P) which contains the advancement direction (X), are kept in contact with the conveyor belt (T) obliging it to stay, in turn, aligned with the transport direction (X).

In a possible embodiment, the transmission kinematic mechanism comprises a first rod (41 ) and a second rod (42), each of which is hinged both to the first guide (2), and to the second guide (3) about axes of rotation (a,b,e,g) parallel to one another. In other words, the first rod (41 ) is hinged to the first and to the second guide (2,3) about respective axes of rotation (a,g) parallel to one another. The second rod (42) is hinged to the first and to the second guide (2,3) about respective axes of rotation (b,e) parallel to one another. Preferably, the axes of rotation (a,b,e,g) of the two rods (41 ,42) are parallel to the central plane (P). Preferably, the axes of rotation (a,b,e,g) of the two rods (41 ,42) are perpendicular to the conveyor plane defined by the conveyor belt (T).

The first rod (41 ) and the second rod (42) are arranged in crossed directions to one another on a plane perpendicular to the axes of rotation (a,b,e,g). Preferably, the first and the second rod (41 ,42) are arranged symmetrical with respect to the central plane (P).

Preferably, the first guide (2) and the second guide (3) rotate about respective axes of rotation (c,d) parallel to one another and parallel to the axes of rotation (a,b,e,g) of the first and the second rod (41 ,42). In other words, the axis of rotation (C) of the first guide (2) is located in an intermediate position between the axes of rotation (a,e) respectively of the first rod (41 ) and of the second rod (42). The axis of rotation (D) of the second guide (3) is located in an intermediate position with respect to the axes of rotation (b,g) respectively of the second rod (42) and of the first rod (41 ).

As depicted in figure 2, by making the first guide (2) rotate in the clockwise direction, about the respective axis of rotation (C), an equal rotation, but in the opposite direction, is necessarily transmitted to the second guide (3), about the respective axis of rotation (D). Two end front areas (21 ,31 ) of the two guides (2,3) are therefore pushed towards one another and towards the conveyor belt (T), with symmetrical displacements with respect to the central plane (P), while two rear end areas (22,32) are moved away from one another. In this way, the conveyor belt (T) is kept aligned with the advancement direction (X) and centred with respect to the central plane (P). In a further embodiment, illustrated in figure 3, the transmission kinematic mechanism comprises two bars (61 ,62) slidable along a transverse direction (Y). Such transverse direction (Y) is oriented transversally with respect to the advancement direction (X). Preferably, the transverse direction (Y) lies on a horizontal plane. Preferably, the transverse direction (Y) is perpendicular to the advancement direction (X).

The first guide (2) is associated with a first bar (61 ), whereas the second guide (3) is associated with a second bar (62).

The first and the second bar (61 ,62) are provided with a rectilinear toothing (61 a, 62a), i.e. they are provided with a rack, whose primitive is substantially parallel to the transverse direction (Y). The transmission kinematic mechanism (4) comprises a toothed wheel (63), arranged so as to mesh with both of the rectilinear toothings (61 a, 62a). In particular, the toothings (61 a, 62a) are facing one another. The toothed wheel (63) is interposed between the two toothings (61 a, 62a), meshing with both. In this way, the sliding by a determined length of one of the two bars (61 ,62) along the transverse direction (Y) is transmitted to the other bar (61 ,62) for the same length, but in the opposite direction. The sliding movements of the bars (61 ,62) are therefore symmetrical with respect to the axis of rotation of the toothed wheel (63).

By arranging the transmission kinematic mechanism (4) so that the axis of rotation of the toothed wheel (63) intersects the advancement direction (X) and is perpendicular to the latter, and so that the transverse direction (Y) is perpendicular to the advancement direction (X) and lies on the conveyor plane defined by the conveyor belt (T), i.e. is substantially horizontal, it is possible to keep the conveyor belt (T) aligned with the advancement direction (X).

As in the solution previously described, also in this solution the first and the second guide (2,3) are placed to the sides of the conveyor belt (T), and, at least a portion of each of them, is pushed into contact with a respective side of the conveyor belt (T) by the actuator (5). In the event in which the sides of the conveyor belt (T) are not rectilinear and/or not parallel, at least a portion of the first guide and at least a portion of the second guide (2,3), pushed by the actuator (5) to move towards one another symmetrically with respect to the central plane (P) which contains the advancement direction (X), are kept in contact with the conveyor belt (T) obliging it to stay, in turn, aligned with the transport direction (X).

Preferably, the actuator (5) comprises an elastic means, associated with at least one from between the first guide (2) and the second guide (3).

In the embodiment of the transmission kinematic mechanism (4) comprising the first and the second rod (41 ,42), the actuator (5) may be, for example, in the form of a torsion spring, concentric to the axis of rotation (C) of the first guide (2) or to the axis of rotation (D) of the second guide (3). In particular, the torsion spring can be interposed between one of the two guides (2,3) and a support part of the transmission kinematic mechanism (4) and/or of the conveyor belt (T). Alternatively to the torsion spring, the actuator (5) may be in the form of a helical spring, associated with one of the two guides (2,3) and/or with one of the rods (41 ,42) positioned so as to exercise an eccentric thrust with respect to the axis of rotation (C,D) of the guide (2,3) with which it is associated. In both cases, the actuator (5) is able to make one from between the first or the second guide (2,3) rotate, with a determined torque, about the respective axis of rotation (C,D).

In the embodiment of the transmission kinematic mechanism (4) comprising the two bars (61 ,62) provided with respective toothings (61 a, 62a) and toothed wheel (63), the actuator (5) may be, for example, in the form of a torsion spring, concentric to the axis of rotation of the toothed wheel (63). In particular, the torsion spring can be interposed between the toothed wheel (63) and a support part of the transmission kinematic mechanism (4) and/or of the conveyor belt (T). Alternatively to the torsion spring, the actuator (5) may be in the form of a helical spring, associated with one of the two guides (2,3) and/or with one of the bars (61 ,62) and positioned so as to exercise a thrust which has at least one component directed along the transverse direction (Y). In both cases, the actuator (5) is able to make both bars (61 ,62) slide so as to move the first and the second guide (2,3) towards one another.