BACKGROUND OF THE INVENTION

The present invention relates to the technical field concerning automatic machines for manufacturing and packaging of disposable articles of tissue paper or another similar absorbing material, into interfolded packs.

In particular, the invention concerns a device for moving folding arms in an interfolding machine, aimed at obtaining such interfolded packs of disposable articles, beginning from continuous strips of the material being used.

BRIEF DESCRIPTION OF PRIOR ART

It is known that different types of disposable paper articles, such as handkerchiefs, napkins, towels, toilet paper, etc. are often sold in the form of sheets, packaged in packs made of a certain number of folded sheets, stacked one over another and interfolded. This means that each sheet is folded by the aforesaid machine so as to obtain two or more folding flaps, and then it is stacked so that the flaps of adjacent sheets of the stack are co-penetrating. For example, in the case of three flaps folding, the first flap of a sheet is contained in the folding of the previous sheet and, the first flap of the subsequent sheet is in turn contained between the second and third flaps. In this way, during the use, by removing a sheet from the pack of articles, also the first flap of the subsequent sheet is freed. This facilitates the subsequent withdrawing of the latter.

The conventional, most common interfolding machines include a plurality of rollers material from which the articles are obtained, dimensionssheetdirectionroller partially overlays the sheet

At the outlet of the folding rollers, the partially overlaid sheets are taken by a pair of comb-like oscillating devices, provided with a plurality of folding arms, parallel to one another, that separate the overlaid portions of two subsequent sheets from each roller and form the interfolded stack. The folding arms move along a close trajectory that includes a first extreme position, in which the arms are introduced into suitable grooves made in the folding rollers, and a second extreme position, in which the arms protrude outwards of the aforesaid rollers, taking with them a flap of the forthcoming sheet to put it on the stack being formed.

The known comb-like devices are hinged on axes parallel to the folding rollers and are generally moved in step relation with the sheets forward movement on the rollers, by means of a mechanism equipped with connecting rod-crank assemblies operated by cam guides. The driving action derives from the interfolding machine main drive, by means of known mechanical transmission devices.

A suitably studied cam profile allows the folding arms to execute their movements with required timing and to increase, reduce or even set to zero their movement speed, depending on the position occupied in the close trajectory.

A disadvantage of the conventional driving mechanisms of the above mentioned comb-like devices derives from the fact that the inertia of these mechanisms components, in particular of the cams and connecting rod-crank assemblies imposes quite serious limits to the folding arms working speeds.

OBJECTS OF THE INVENTION

Another important drawback of the known driving mechanisms derives from the fact that it is necessary to change the cam group each time it is requested to change the trajectory of the folding arms, or the timing in which such trajectory is followed.

It is an object of the present invention to propose a device for driving the folding arms in an interfolding machine, which is capable of defining the trajectory thereof in a way substantially independent from the presence of the cam mechanisms, and thus capable of obtaining higher working speeds with respect to those allowed by the conventional driving devices.

Another object of the invention is to propose a driving device capable of allowing immediate variations which can be realized simply by the folding arms trajectories, by the timing, with which the trajectories are followed, and by both characteristics.

A further object of the invention is to propose a driving device that is extremely precise and reliable.

SUMMARY OF THE INVENTION

The above mentioned objects are wholly obtained in accordance with the contents of the claims, by a device for driving the folding arms of comb-like folding means along a closed operation path, used on the interfolding machine for the production of interfolded packs of sheets of tissue paper or another material, mounted on a frame situated in the lower part of the machine.

A connecting rod-crank transmission assembly is mounted on the frame and connected to the above mentioned comb-like, aimed at driving the latter along the closed operating path.

The driving device comprises also a main motor, aimed at supplying at least a part of mechanical power necessary to drive the comb-like, and a supplementary motor, of controlled rotation speed, aimed at cooperating with the main motor in driving the comb-like.

An epicycloidal differential, connected mechanically to the main and supplementary motors and to the transmission assembly, receives at the inlet the rotational mechanical power generated by the main and supplementary motors, respectively, and supplies at the outlet the corresponding rotational mechanical power to the transmission assembly as the combination of the energy received from the inlets.

A control unit is also provided in the interfolding machine for adjusting the rotation speed caused by the supplementary motor depending on the position assumed by the folding arms in the above mentioned operating path.

BRIEF DESCRIPTION OF DRA WINGS

The characteristics of the invention, as they will become apparent from the claims, are pointed out in the following detailed description, with reference to the enclosed tables of drawings, in which:

Figure 1 is a schematic side view of the main structure of an interfolding machine, equipped with a pair of folding assemblies; Figure 2 is a prospective view of one of the folding assemblies of Figure 1, provided with the folding arms driving device obtained according to a first embodiment of the present invention; Figure 3 is a top view of the folding assembly of Figure 2; Figure 4 is a top view of the folding assembly in a second embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

With reference to Figure 1, the main operating means of a machine 100 for interfolding sheet articles 1, such as, for example, towels made of tissue paper, are illustrated schematically.

The interfolding machine 100 comprises, according to a known technology, a pair of counter-rotating cutting rollers 101a, 101b, a corresponding pair of folding rollers HOa, HOb, likewise counter-rotating and arranged below the cutting rollers 101a, 101b, and corresponding folding assemblies, which comprise a pair of comb-like folding means 2 arranged below the folding rollers 110a, 110b.

The comb-like 2 comprises substantially a plurality of folding arms 3 mounted parallel one to another and equidistant on a shaft 4 rotating on its axis (see also Figure 2). The shaft 4 is mounted parallel to the axis of the corresponding folding roller HOa, 110b, so that each folding arm 3 is equidistant from the surface thereof.

The folding arms 3 are aimed at oscillating periodically, in a suitable phase relation with the rotation of the folding rollers 110a, 110b, along a closed operating path, which allows them to detach the towels 1 from the same folding rollers HOa, HOb, to withdraw them and fold them according to folding schemes, likewise known.

With reference to Figures 2 and 3, the folding arms 3 are driven along the above mentioned operating path by a driving device 10, made according to a first embodiment of the present invention.

The driving device 10 comprises a frame 10a, situated below the corresponding folding roller 110a, 110b, which receives, in its front part, the above mentioned folding means 2, putting them in a position parallel with respect to the aforesaid rollers. The device 10 comprises also motor means 50, having electronically controlled speed and whose structure and conformation constitute the basis of the invention. hi the aforesaid first embodiment, the motor means 50 comprise first of all main motor means 51, mounted at an end of the frame 10a, aimed at supplying at least a part of the mechanical power necessary to move the comb- like 2, as it will become evident from the following part of the description. The main motor means 51 are constituted by a derivation from the interfolding machine 100 general drive, in the drawings schematized simply with a shaft and a pulley, connected to a mechanical transmission assembly 31 by means of a belt 11. It is to be noted that substantially this derivation speed cannot be controlled, at least, in particular, having regard to the driving device 10, and therefore it is to be considered steady.

The transmission assembly 31 includes a phaser-overgear transmission box device 32 of known type, which is connected, by means of a further belt 33 and a pair of pulleys, to an end of a shaft 34 supported by the frame 10 parallel to the shaft 4 of the comb-like 2.

At the opposite end, the shaft 34 is connected, by means of a pulley and a transmission belt 35, to differential adjustment means 20, made of a mechanical epicycloidal differential.

In particular, the transmission belt 35 engages with a first power intake 21 of the aforesaid differential 20, provided in the moving casing thereof.

The differential 20 used, as already mentioned, comprises advantageously a device, commercially available on the market, that includes a first power intake 21 in correspondence to its moveable casing, a second axial power intake 22 and a power take-off 23, likewise axial and aligned with the axis of the second intake 22.

The differential 20 is mounted on transversal supports made in the frame 10 with the axis parallel to the axes of the shaft 4 of the comb-like 2 and of the shaft 34 of the transmission assembly 31.

The output of supplementary motor means 55 is connected axially with the second power intake 22, said supplementary motor means 55 being mounted on one of the transversal supports of the frame 10 and aimed at cooperating with the above mentioned main motor means 51 to drive the comb- like 2. In particular, the supplementary motor means 55 comprise advantageously a brushless type motor, whose angular position, and consequently, whose instantaneous velocity in both directions can be controlled with extreme accuracy, and therefore allow to define its instantaneous velocity and position by means of a programmable control unit. In any case, the aforesaid type of motor is not to be considered limiting or exhaustive. An excellent electronic control of the rotation speed can be obtained also with other types of electric motor, for example with an asynchronous motor or a stepping motor.

Ultimately, the differential 20 is aimed, according to the invention, at receiving at the intake the rotational mechanical power from the main motor 51 and from the supplementary brushless motor 55, and at supplying at the output the rotational mechanical power with the rotation speed defined by the combination of the rotation speed imposed by the main motor 51 on the first power intake 21 and on the second power intake 22.

An output transmission shaft 14, connected axially to the take-off 23 of the differential 20, is in turn connected mechanically to mechanical transmission means 13, aimed at driving the comb-like folding means 2.

The mechanical transmission means 13 comprise substantially a connecting rod-crank assembly consisting of a connecting rod 13a, coupled at one end to a crank 13b, made in the aforesaid transmission shaft 14, and with the opposite end of the connecting rod 13a connected eccentrically to the shaft 4 of the comb-like 2. In this way, a complete rotation of the output transmission shaft 14 corresponds to a cycle of oscillation of the folding arms 3, which brings the latter to cover the above mentioned closed operating path, with a known conformation.

According to the operation of the above described driving device, the main motor 51 works in a substantially conventional way, with constant rotation speed, and defines the basic driving speed of the folding arms 3, by means of the mechanical transmission assembly 31, the casing of the differential 20 and the connecting rod-crank assembly 13.

The rotation speed of the supplementary motor 55, in turn, is defined depending on the position assumed by the folding arms 3 along the closed operating path, by means of a suitable program stored in the control unit of the interfolding machine 100, or in a dedicated control unit of the device 10. The rotation speed induced by the supplementary motor 55 in the second power intake 22 of the differential 20 is then added, at the output on the corresponding power take-off 23, to the rotation speed induced by the main motor 51, if the rotation directions of the two motors are concordant, and subtracted therefrom if the supplementary motor 55 is driven to rotate in the direction opposite with respect to that of the main motor 51.

Consequently, it seems evident that the possibility offered by the brushless supplementary motor 55 to control and define its instantaneous position and velocity point per point, allows to impose to the folding arms 3 any acceleration or deceleration with respect to the basic speed, requested to modify the timings of the folding arms 3 intervention on the sheets 1 to fold.

Such timings can be also advantageously changed simply and immediately, also in the production line, varying only the parameters of the control program of the supplementary motor 55.

A second embodiment of the invention is illustrated in Figure 4. In such an embodiment the supplementary motor means 55 include a first brushless motor 55a and a second brushless motor 55b, mounted symmetrical with respect to the mechanical transmission and conversion assembly 13 with the respective axes being aligned.

The differential transmission means 20, in turn, include a first mechanical differential 20a and a second mechanical differential 20b, both of epicycloidal type, mounted respectively opposite to each other on related transversal supports of the frame 10a and aligned axially with each other and with the aforesaid supplementary motors 55a, 55b.

The differentials 20a, 20b are provided, respectively, with a first power intake 21a, 21b, in correspondence to their respective casing, connected to the main motor 51 by means of a pair of transmission belts 35a, 35b, operated together by the mechanical transmission assembly 31, in a way quite similar to what has been already described with reference to the first embodiment of the invention, with a second power intake 22a, 22b, connected to the supplementary motors 55a, 55b, and with a power take-off 23a, 23b arranged in axis with respect to the second power intake 22a, 22b.

The power take-offs 23a, 23b are in turn connected at the opposite sides to the mechanical transmission and conversion means 13.

The rotation speed of the supplementary motors 55a, 55b is defined and made synchronous by a program stored in the control unit of the interfolding machine 100, so that both motors cooperate in identical way to change the speed and acceleration of the folding arms 3 along their closed operating paths.

The advantages related to the use of a double supplementary motor drive as defined in the second embodiment of the invention, derive mainly from the fact that in this way it is possible to use components of smaller dimensions, with limited size increase and obtaining at the same time a substantial cost reduction.

According to another embodiment of the above described invention, that does not change substantially the already illustrated working principles, and that is not illustrated in the figures, since of immediate comprehension, the above mentioned motor means 50 comprise a single motor, aimed only at operating the driving device 10, of the electronically controllable speed type, whose shaft is connected directly to the above mentioned outlet shaft 14. The rotation speed of the motor 50 in this case is controlled directly by the programmable control unit of the interfolding machine 100 or of the device 10. hi this way, the constructive simplicity characteristics of the whole driving system of the device 10 are improved. A drawback of such further embodiment lies in the fact that the motor 50 can present some inertia problems, when the accelerations and decelerations necessary for a full control of the folding arms 3 functionality are to be reached for very high production speeds. The choice to use one embodiment of the invention with respect to other described ones is in any case subjected to suitability evaluation in function of the productivity and performance requirements of the device 10 in each single case.

It is understood that what above has been described as a pure not limiting example. Therefore, possible modifications and variations of the invention are considered within the protective scope of the present technical solution, as described above and claimed below.