Embossing system

Abstract

An embossing system including: an embossing unit with at least one embossing roller arranged to emboss a web of paper intended to be joined with a further web by gluing; and a gluing unit associated with the embossing unit, with a tank containing the glue used to perform the gluing and a glue dispensing device including a cliche roller adapted to distribute by contact the glue contained in the tank on one of the webs while the embossing is performed, the cliche roller rotating with a pre-fixed angular velocity around an axis parallel to said at least one embossing roller. The system further includes: a sensor to produce electrical signals having amplitude and/or frequency related to the vibrations at which the cliche roll is instantaneously subject.

Claims

1. An embossing system comprising: an embossing unit with at least one embossing roller arranged to emboss a web of paper intended to be joined with a further web by gluing; and a gluing unit associated with the embossing unit, with a tank containing glue used to perform said gluing and a glue dispensing device comprising a cliche roller adapted to distribute by contact the glue contained in the tank on one of said webs while the embossing is performed, said cliche roller rotating with a pre-fixed angular velocity around an axis parallel to said at least one embossing roller; and further comprising: a sensor to produce electrical signals having amplitude and/or frequency related to the vibrations at which said cliche roller is instantaneously subject, while the cliche roller rotates around said axis; a control unit that during operation of the embossing system receives instantaneous data of the amplitude and/or frequency of signals produced by said sensor and compares them with reference data contained in a file previously acquired by testing the embossing unit and the gluing unit in conditions of regular and respectively non-regular distribution of the glue on the cliche roller, said reference data comprising a first set of amplitude and/or frequency data representative of normal vibrations and a second set of amplitude and/or frequency data representative of abnormal vibrations respectively, the control unit being programmed to generate an alarm signal if at least an instantaneous datum of amplitude and/or frequency of the signals produced by said sensor corresponds to at least a datum of amplitude and/or frequency of the second set.

2. An embossing system according to claim 1, wherein the data of the first and second set of data are acquired by means of the sensor which produces the instantaneous data in an operating phase of the embossing system.

3. An embossing system according to claim 1, wherein said sensor detects the vibrations of a shaft of the cliche roller, and the axis of the cliche roller coincides with said axis of rotation.

4. An embossing system according to claim 1, wherein said alarm signal activates a procedure of slowing or stopping of the embossing system controlled by the control unit.

5. An embossing system according to claim 1, wherein the cliche roller and the embossing rollers are driven by respective drive units, and said alarm signal activates a procedure of slowing or stopping of said drive units controlled by the control unit.

6. An embossing system according to claim 1, wherein the gluing unit is mounted on a relative support which allows the removal of the gluing unit from the embossing unit by means of an actuator, and said alarm signal activates the actuator so determining said removal.

7. An embossing system according to claim 1, wherein the control unit generates said alarm signal if the instantaneous data of amplitude and/or frequency of the signals produced by the sensor correspond to the data of the second set for a predetermined number of times in an interval of time which is also predetermined.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 schematically represents an operative unit for embossing and gluing two plies of paper material usable in a paper converting plant according to the present invention;

(2) FIG. 2 represents a simplified block diagram of a system for controlling the operating unit shown in FIG. 1;

(3) FIGS. 3 and 4 schematically represent a possible time course of the amplitude of the signal produced by the sensor (2);

(4) FIG. 5 schematically represents the signal produced by the sensor (2) in the frequency domain.

DETAILED DESCRIPTION

(5) The operating unit (OU) schematically represented in FIG. 1 comprises a pair of embossing rollers with relative counter-rollers (G1, G2) arranged vertically overlapped, i.e. with the corresponding rotation axes horizontally oriented and aligned along the same vertical axis. The unit (OU) also comprises a glue distributor with a tank (T), an anilox roller (AR) and a cliché roller (CR) whose axes are parallel to those of the embossing rollers. The tank (T) contains the glue used to glue together two plies of paper material (V1, V2) supplied by respective reels placed on unwinders (not shown in the drawings) arranged upstream of the unit (UO) with respect to the direction (A) from which the same plies (V1, V2) come. The latters, passing between the embossing rollers and the relative counter-rollers (G1, G2), are embossed. The anilox roller (AR), rotating around its own axis, picks up the glue from the tank (T) and transfers it to the cliché roller (CR) which, in turn, distributes it on the ply (V1) subjected to embossing by the respective roller and counter-roller (G1). The ply (V1) will therefore stick to the ply (V2) treated by the roller and by the counter-roller (G2) forming the web (W) that comes out of the unit (OU) along the direction (AW) to feed a rewinder (RW), prepared downstream, which wind the web (W) to produce logs destined to be cut transversely to obtain rolls of toilet paper, kitchen paper etc. In general, the cliché roller and the anilox roller have different rotation speeds to allow the glue to be dosed differently depending on the product to be produced. The structure and operation of such an operating unit are known to those skilled in the art. The structure and operation of the rewinders as well as the structure and operation of the unwinders are also known. Alternatively, according to a scheme also known to those skilled in the art, in the unit (OU) a ply (V2) is not embossed. In this case, the roller and the counter-roller of the couple (G2) form a guide device for the ply (V2) which remains smooth and is glued to the ply (V1) which is instead embossed. Normally, the gluing unit (T, AR, CR) is positioned on a respective support structure (S) which allows it to be placed in operative position (set-up in which the cliché roller CR is coupled to an embossing roller) and in inoperative position (set-up in which the cliché roller CR is spaced from the embossing roller to which it is instead approached in the operating phase).

(6) According to the present invention, the aforesaid operating unit (OU) is controlled by a programmable control unit (1) which controls the motors (M1, M2) which determine the rotation of the embossing rollers and of the relative counter-rollers (G1, G2), the motors (MA, MC) of the anilox (AR) and cliché (CR) rollers, and the actuator (AS) which determines the movement of the mobile support (S) of the gluing unit (T, AR, CR). A sensor (2) able to detect the vibrations of the cliché roller (CR) is connected to a corresponding input of the control unit (1). For example, said sensor (2) is an accelerometer of the SKF CMSS2200 type. For example, this sensor (2) detects the vibrations of a bearing supporting one end of the cliché roller (CR) shaft in such a way as to detect the vibrations of the shaft itself. The sensor (2) produces electrical signals representative of the vibrations to which the cliché roller (CR) is subjected during its operation. In other words, the electrical signals produced by the sensor (2) are signals of amplitude and frequency determined by the vibrations of the cliché roller (CR).

(7) In a step of carrying out the control system object of the present invention, the operating unit (OU) is operated under normal conditions (i.e. under conditions of proper lubrication of the cliché roller CR which receives glue from the anilox roller AR in sufficient quantity to guarantee lubrication), and in conditions of poor lubrication (i.e. in conditions of insufficient lubrication of the cliché roller CR which receives glue from the anilox roller AR in insufficient quantity to guarantee a correct lubrication), detecting the vibrations of the cliché roller (CR) in each of these operating conditions specially reproduced. Preferably, said vibrations are detected with the same sensor (2) subsequently used during operation of the system. Said measurements, i.e. the amplitude and/or frequency of the signals produced by the sensor used to detect the vibrations of the cliché roller (CR), are recorded in a data file (DB) which is used by the control unit (1) as further indicated below. For example, the file (DB) can be registered in a memory section of the control unit (1). In practice, during the formation of the file (DB), both normal and abnormal operating conditions of the unit (OU) are reproduced and data of amplitude and/or frequency of electrical signals produced by the vibrations of the cliché roller (CR) are recorded by a transducer that converts such vibrations into electrical signals. The data thus recorded are then used as a reference model in the phase of actual productive use of the operational unit (OU). In fact, during operation of the unit (OU), the control unit (1) continuously receives the data corresponding to the signals produced by the sensor (2) and compares them with the data of the file (DB). If the data related to the vibrations detected by the sensor (2) correspond to the data of the file (DB) representing anomalous operating conditions, the control unit (1) intervenes on the motors (M1, M2, MA, MC) to slow down the rotation of the rollers connected to them or also to stop the rotation thereof. In the latter case, the control unit (1) can also be programmed to drive the actuator (AS) so as to distance the gluing unit (T, AR, CR) from the embossing rollers.

(8) FIG. 3 schematically represents the time course of the electrical signal (SH) produced by the sensor (2) during operation (operational use phase) of the unit (OU). The dotted lines (UL, LL) represent the upper (UL) and lower (LL) limits of a field within which the amplitude (y) of the signal (SH) may vary over time (t) without the unit of control (1) generate any alarm signal. The values (UL, LL) are determined in the testing phase of the unit (OU) and represent two limit values of the signal amplitude (SH) detected in conditions of correct lubrication of the cliché roller (CR). In the example shown in FIG. 3, at time t1 the signal amplitude (SH) is outside the field (UL-LL). Therefore, at time t1, the control unit (1) generates the alarm signal which determines the activation of the programmed procedure (slowing down or stopping the system).

(9) Alternatively, with reference to FIG. 4, the control unit (1) can be programmed to generate said alarm signal if the signal trend (SH) is such that the limit values (UL, LL) are exceeded for a predetermined number (N) of times in a time interval (ΔT) also pre-established. In the example of FIG. 4 the signal (SH) is outside the limits (UL, LL) for more than 20 times in the time interval Δt=t2−t1. If Δt≥ΔT and the preset value for the number (N) is equal to 20, then the control unit (1) generates the alarm signal that determines the activation of the programmed procedure (slowing down or stopping the system).

(10) FIG. 5 schematically represents the instantaneous values (a) of the signal produced by the sensor (2) as a function of the frequencies (f). In this graph a possible distribution (DF) is qualitatively shown, showing a limit value (aL) assumed as reference for the control unit (1), similarly to what previously stated with reference to the amplitude data of the signal produced by the sensor (2).

(11) From the foregoing description it is evident that an embossing system according to the present invention comprises: an embossing unit with at least one embossing roller (G1; G2) arranged to emboss a web of paper (V1; V2) intended to be joined with a further web (V2, V1) by gluing; a gluing unit associated with the embossing unit, with a tank (T) containing the glue used to perform said gluing and a glue dispensing device (GD) comprising a cliché roller (CR) adapted to distribute by contact the glue contained in the tank (T) on one of said webs (V1, V2) while the embossing is performed, said cliché roller (CR) rotating with a pre-fixed angular velocity around an axis (x) parallel to said at least one embossing roller (G1; G2); a sensor (2) apt to produce electrical signals having amplitude and/or frequency related to the vibrations at whom said cliché roll (CR) is instantaneously subject, while the same rotates around said axis (x); a control unit (1) that receives instantaneous data of the amplitude and/or frequency of the signals produced by said sensor (2) and compares them with reference data contained in a file (DB) previously acquired by testing the embossing unit and the gluing unit in conditions of regular and respectively non-regular distribution of the glue on the cliché roller (CR), said reference data being constituted by a first set of amplitude and/or frequency data representative of normal vibrations and a second set of amplitude and/or frequency data representative of abnormal vibrations respectively, the control unit (1) being programmed to generate an alarm signal if at least an instantaneous datum of amplitude and/or frequency of the signals produced by said sensor (2) corresponds to at least a datum of amplitude and/or frequency of the second set.

(12) In practice, the details of execution may in any case vary in an equivalent manner as regards the individual elements described and illustrated, without departing from the scope of the solution idea adopted and therefore remaining within the limits of the protection conferred by the following claims.