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(11) | EP 0 036 193 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | A paper transport device for label printing machines or the like |
| (57) The device according to the present invention comprises a set of rollers supporting
and guiding the band of overprintable material to the writing station and beyond to
rewinding, and a band transport device moved by step-motor (7) providing for drawing
said band through a drawing roller (4) in the intervals between the writing of one
line and the next, making electronically controlled and preset intermittent angular
rotations, a friction rewinding means (6) being provided. |
[0001] This invention relates to a device for unwinding and rewinding reels of labels or other self-adhesive documents in the form of continuous modules which are mounted on a siliconized support, said device being adapted for use along with overprinting machines of electronic type. Particularly, the invention is concerned with the separation of the label from its support or backing during the rewinding process.
[0002] The overprinting machines for self-adhesive labels or the like at present commercially available are basically in the following overprint types.
a - Frame-mounted inked matrix, which is carried out by typewriting the text on a typewriting machine.
b - Inked matrix with conposable metal letters of the printing type. These matrices may be planar or rotary cylinder matrices.
c - Needle writing head (printer of a processor) scanning the whole label surface.
[0003] All of these embodiments provide the displacement or shifting of the label or the like when overprint is being carried out, or at the immediately preceding moment, but in any case by a spacing equal to an entire label at a time, by using an A.C. or D.C. motor. This motor moves the paper only once by a full pitch (a pitch includes a label and the inter space between two successive labels) using this space as a reference. This is because the force required for separating the label or the like from its support or backing can be effected only by a motor developing a certain torque.
[0004] In the first two of the above mentioned cases, a text conposition requires some time which does not allow the use of this type of machines for limited series of labels. The use of these printing machines becomes particularly difficult when producing labels, in which the variability of the text to be written and the number of variables is such that the amount of identical labels is so small to require the use of writing units of the type used on priners for processors, thus excluding preformed planar matrices or cylindrical matrices with composition of metal or synthetic letters. The use of these printing machines should also be avoided when the paper transport cannot be carried out by the punched side bands as in the printers.
[0005] In the last case, is that when using the needle head for printing, its movement along two perpendicular directions for scanning the whole label or the like, would render the machine highly expensive and too complicated.
[0006] Therefore, it is the object of the present invention to provide a transport device for a label printing machine or the like, which is extremely simple.
[0007] It is another object of the invention to develop a substantial torque during the winding up step for separating the self-adhesive label from its support cr backing
[0009] Jhe above mentioned objects have been accomplished by carrying out the paper transport by means of an electronically controlled step-motor, while a friction rewinding means provides the required torque for carrying out the separation of a label or the like from its support or backing.
[0010] The device carrying out the above described conditions is particularly a device comprising a set of rollers supporting and guiding the band of overprintable material to the writing station and beyond to rewinding, and a step-motor for the band transport, which provides for carrying the band along through a drawing roller in the intervals between the writing of a line and the next line, effecting electronically controlled and preset intermittent angular rotations, a friction rewinding means being provided.
[0011] According to a first embodiment, said friction rewinding means is driven through a clutch by said step-motor.
[0012] A second embodiment contemplates that the rewinding means is provided by a continuously rotating motor, which preferably trasmits a high constant torque through a clutch. Thus, the paper transport is obtained by means of a constant high torque as defined by the clutch calibration; this torque is substracted by (band stop) or added with (band movement) the torque developed by the step-motor.
[0013] For the paper sliding alignment, the adjustable orientation for at least one roller or for the whole writing plane is provided.
[0014] Another preferred solution provides that the friction rewinding means is of high adherence or knurled, and particularly the label band is caused to slide with the labels facing the outer surface of the roller forming the friction rewinding means.
[0015] An improvement to the invention is obtained by carrying out the several kinematic movements of the rollers by means of toothed pulleys and belts, whereby the mutual angular position is assured.
[0016] Another improvement to the invention is obtained by providing that the angular rotation by each pitch of the step-motor will cause the advancement of the reel by a full writing height, or preferably- by a full fraction of the minimum writing height provided.
[0017] Some unrestrictive embodiments of the device according to the invention have been outlined in Figs. 1 and 2, showing perspective views of two embodiments according to the present invention.
[0018] Referring to the embodiment of Fig. 1, there are shown an unwinding roller 1, an idle roller 2 acting as a damper for the pulls due to each single forward movement of the step-motor, the writing plane 3, that is the plane on which the needle writing head (not shown for the sake of sinplicity) will write, the drawing roller 4 coated with a knurling 4b providing a high adherence, the counter-drawing roller 5 also knurled, the rewinding roller 6, the step-motor 7, the drawing belt 8 for the latter, the drawing clutch 9 which can be adjusted by a spring, the reel 10 of labels to be overprinted, the recovery reel 11, and the photocell 12 for signalling the label end.
[0019] In the embodiment according to Fig. 2, the corresponding pieces or elements have been denoted by the same reference numerals. However, said roller 4 is provided with a coating 4a having a high adherence, for example rubber. Moreover, at 13 the D.C. rewinding motor has been denoted, at l4 the plane on which the brush 15 bears and improves the adherence of the label band on roller 4, 16 counter-rollers, 17 the clutch adjusting knob, and 18 the cam for the angular adjustment of the writing plane.
[0021] The writing unit has not been shown in the drawing as it comprises a conventional needle head and a conventional inked ribbon, both of the type used on the printers of microprocessors. The electronics governing the control of the motor and photocell has also not been shown in the drawing.
[0022] The two figures of the drawing show two versions of the same device. They basically differ as in Fig. 1 (the most elementary version) there is only one motor 7, while in Fig. 2 the rewinding motor is also shown. In the case of Fig. 2, the movement of the label band occurs when the torque of the rewinding motor 13 adds to the moving torque of the step-motor 7. Stop occurs when the stop torque of the step-motor 7 is subtracted from the torque of the rewinding motor 13. The torque of the rewinding motor 13 is defined by the calibration of clutch 9 and remains constant for a given calibration of the clutch.
[0023] In order that a good operation be assured, it is necessary in both embodiments to meet some conditions, and namely:
a - the velocity ratio between said motor 7 and drawing roller 4 should be constant. This is obtained by using toothed pulleys and belts (solution shown in the drawing), or by gears.
b - the band to be overprinted should not skid relative jo the drawing roller 4. This condition is of extreme importance since it is the angular displacement of roller 4 that determines the distance or spacing-between the writing lines, and accordingly the graphic setting of the label. In the drawings two different solutions are shown, in Fig. 1 the band is compressed between two knurled rollers 4 and 5 pressed to each other by a spring (not shown), while in Fig.2 the roller 4 is coated with rubber and the counter-roller 5 is knurled.
c - the recovery of the overprinted band should be assured. This condition is true
both in case of labels which are rewound after overprint, and for "dispensed" labels
(separated from the siliconized support or backing and withdrawn). In the second case,
only the support or backing is recovered. The two alternatives shown differ just in
the solution of this condition.
In Fig. 1 the rewinding roller 6 is drawn so that the portion of circumference developed
by said roller 6 at each rotation of motor 7 is larger than the corresponding portion
developed by said roller 4. In Fig. 2 the roller 6 is drawn by motor 13 (a D.C. or
A.C. motor) continuously rotating at a speed such as to provide the condition shown
in Fig. 1. Thus by recovering the roller 6 to a higher degree than that allowed by
roller 4, the provision of clutch 9 is required enabling pulley 9' to rotate . and
roller 6 to be blocked when the band is tensioned. In the embodiment according to
Fig. 2, there the knob 17 is shown allowing the adjustment of the spring for said
clutch 9.
d - the label band should always be tensioned throughout its path.
This condition has already been fulfilled between the rollers 4 and 6 in accordance
with the foregoing at the preceding paragraph. In order to obtain such a condition,
the dampening roller 2 is provided in Fig. 1, which roller is rockable about a fulcrum
2' in order to recover any "catenary curve" of the band at each start of said motor
7 to conpensate for the pull which would occur due to inertia of reel 10. To prevent
said inertia from allowing a larger "catenary curve" than the recovery capability
of roller 2, roller 1 is clutched on its shaft in order to facilitate the stop thereof.
In Fig. 2 a brush 15 has been inserted for pressing the label band on plane 14, this
further assures the adherence of the band to said roller 4 and 16.
e - during its unwinding, the band should not be subje ccted to side shifting.
[0024] This is a difficult condition to obtain since the band is restrained throughout its path, to assure a perfect parallelism among all of the members on which such a band slides or runs would be expensive. The condition is obtained providing that at least one of said members (1, 2, 4, 5, 6, 16 or writing plane 3) allows an angular adjustment of its geometrical axis. In the drawings, such members are in Fig. 1 respectively the counter-roller 5, the 5a of which may move in the slot 5b, while in Fig. 2 the writing plane 3 is moved by the cam 18.