CONTINUOUS BAND CENTERING DEVICE, IN PARTICULAR FOR BLISTER PACK PRODUCING MACHINE

Abstract: A device for centering a continuous band (2) driven through a series of working stations (7, 8) in a movement direction (D) includes at least one pair of rollers (12) rotatably carried with vertical axes, at the ends of arms (15). The arms (15) are pivoted along corresponding vertical axes on both sides of the band (2) symmetrically with respect to a longitudinal middle axis (A). The arms (15) are equipped with levers (23) for driving the arms (15) into symmetrical oscillation by limited angles. The arms (15) are subjected to the action of springs (22) which keep the rollers (12) touching the opposite sides of the band (2), so as to center the band (2) with respect to the movement direction (D).

Description: CONTINUOUS BAND CENTERING DEVICE, IN PARTICULAR FOR BLISTER PACK PRODUCING MACHINE FIELD OF THE INVENTION The present invention relates to the handling of bands, e.g. blister bands used in blister pack producing machines . More in particular, the present invention relates to a device for centering a continuous belt, from which a blister band is obtained. DESCRIPTION OF THE PRIOR ART Blister pack producing machines have been heretofore proposed as forming blisters in a continuous band made of thermoformable material and afterwards, filling the obtained blisters with products. The blister band filled with products is then covered with the closing band, welded together with it and cut, so as to obtain single blister packs. The band of thermoformable material unwinds from a reel and is moved, on a horizontal plane and in a horizontal direction, through a pre-heating station, then through a forming station, where suitable means make the blisters therein. It is necessary that the longitudinal axis of the band of thermoformable material be maintained centered with respect to the band movement direction, when it is in the region of the forming station. The lateral displacement of the band with respect to the movement direction would cause wrong blisters positioning during the thermoforming operation, which would result in problems with filling of the blisters with products, since the filling means are usually centered on the band longitudinal axis. A lateral displacement of the band could be caused by the pulling action exerted thereon or by even small faults of the band, e.g. not perfectly constant thickness or width thereof . In order to avoid any band displacement, blister packs producing machines are equipped with suitable guiding means, against which the band abuts, and which maintain the band centered upstream and downstream of the blister forming means . The mutual distance between the guiding means is adjustable manually, so as to allow the change over operation when a band of different size is used. However, the band size change requires an expensive manual intervention and very often other adjustments are needed to compensate the band manufacturing tolerance. SUMMARY OF THE INVENTION The object of the present invention is that of avoiding the above mentioned problems by proposing a device which automatically maintains constant the centering of a continuous band with respect to the band movement direction, in particular to be used in machines equipped with working stations through which the blister band passes, especially blister packs producing machines. Another object of the invention is to propose a universal device, i.e. a device which automatically centers the blister band independently from the band size and the type of machine to which the device is applied. A further object of the invention is to propose a centering device, whose structure is simple and which is functional and which can be easily applied to known blister packs producing machines. The above mentioned objects are obtained, in accordance with the contents of the claims, by means of a device for centering a continuous band, with the band fed through at least one working station in a movement direction, the device including: at least one pair of rollers, which are rotatably carried with vertical axes at the ends of arms, said arms being pivoted, about corresponding vertical hinge axes on both sides of said band symmetrically with respect to a longitudinal middle axis; means for mutual engagement of said arms, said mutual engagement means provoking an angularly limited symmetrical oscillation of said arms; elastic means acting on said arms for keeping said rollers touching the opposite sides of said band, so as to center said band with respect to said movement direction. BRIEF DESCRIPTION OF THE DRAWINGS The characteristic features of the invention are pointed out in the following description, with particular reference to the enclosed drawings, in which: Figure 1 is a schematic lateral view of a blister pack producing machine equipped with the proposed blister band centering device; Figure 2 is a vertical section view of the proposed centering device; Figure 3 is a corresponding plan view thereof. BEST MODE OF CARRYING OUT THE INVENTION With reference to the above described figures, the reference numeral 1 indicates a blister pack producing machine, which makes blisters in a continuous band 2 of thermoformable material and subsequently fills the obtained blisters with respective products. The band 2 of thermoformable material unwinds from a reel 3, rotating about a horizontal axis 4, and is driven on a horizontal plane by transmission rollers 5, 6. During its movement on the horizontal plane in a horizontal direction D, the band 2 passes through a preheating station 7 and then through the blister forming station 8. At the outlet of the blister forming station 8, the band 2 engages with a guide 9, which helps to turn the belt, so that the open blisters are turned upward in the subsequent filling station, which is not shown. Devices 10, 11 for centering the band 2, in particular its median longitudinal axis A, with respect to the band movement direction D, are situated upstream of the preheating station 7 and downstream of the blister forming station 8, respectively. The centering device 10 situated upstream of the preheating station 7 includes a pair of rollers 12 (Figure 2) which are carried at the ends of arms 15 on respective pins 13 having vertical axes . The pair of rollers can rotate by interposition of rolling bearings 14. Actually, the rollers 12 of the centering device 10 shown in Figure 2, include pairs of rollers 12a, 12b which rotate on respective pairs of coaxial axles 13a, 13b, so as to engage, as will be explained later, corresponding parts 2a, 2b of the band of thermoformable material unwinding from the reel 3 (see Figure 2) . The part 2a of the band extends on the horizontal plane of the working stations 7 and 8 in the direction D. The arms 15 of the rollers 12 are pivoted on support means 17 by spindles 16 having vertical axes. The support means 17 are fastened to the stationary frame of the machine, on the opposite sides symmetrically to the median longitudinal axis A. More precisely, each spindle 16 is rotatably carried inside a sleeve 19 by means of rolling bearings 18. In its middle part, the sleeve 19 forms a ring-like flattening 19a, whose wider part is turned upwards. A spiral-like torsion spring 22 is fastened at one end to the sleeve 19 and at the other end to the top of the spindles 16 protruding from the sleeves 19, on a ring 21. The arms 15 are equipped with square angled levers 23, which engage with each other at their free ends (Figure 3) by means of a peg 24 extending vertically from the first lever 23 and engaging with a corresponding slot 25 made in the second lever 23. However, the two levers can be coupled in different ways, e.g. toothed sections and the like. The mutually coupled levers 23 are aimed at driving the arms 15, subjected to the elastic reaction of the spring 22, into angularly limited rotation and symmetrically, so as to maintain the rollers 12 touching the opposite sides of the band 2 in order to center the latter with respect to the movement direction D thereof. The elastic reaction force of the spring 22 can be suitably adjusted by changing the angular position of the sleeve 19 with respect to the spindle 16, by rotating the sleeve 19 by a predetermined angle. The reached position is kept stable by sprung balls 26, mounted in positions diametrically opposite, in corresponding seats made in a ring 27, which is fastened to a cover 28 of the support 17. The sprung balls 26 engage elastically a series of recesses 29 made in the flattening 19a of the sleeve 19, and arranged along a circumference. The sleeve 19 is axially held by a ring nut 30 which engages the upper surface of the ring 27. Therefore, these rollers 12, which act on opposite sides of the band 2 and are carried by oscillating arms 15, maintain, stressed by the elastic reaction of the springs 22, the median axis A of the band 2 automatically centered with respect to the movement direction D, as clearly seen in Figure 3. If the size of the thermoformable band is changed, the device automatically adjusts the centering, without necessity of any manual adjustment. Actually, the arms 15 can oscillate by limited angles, about the axes of the relative spindles 16, so as to keep the rollers 12 touching the band sides, as seen in Figure 3, where broken line 20 indicates a wider band and broken line 120 indicates the corresponding position assumed by the rollers, as a consequence of the arms 15 oscillation. It is to be noted that the automatic centering is guaranteed by the fact that the arms 15 which carry the rollers 12 oscillate symmetrically by the same angles, due to their mutual coupling obtained by the levers 23. A second centering device 11, functionally analogous to the just described device 10, is situated downstream of the forming station 8, considering the advancement direction D. The rollers 12 of the second centering device 11 feature each one a groove 31, in which the band 2 is guided (Figure 1) . The groove 31, situated substantially on the horizontal plan, on which the band 2 moves, prevents the band 2 from being raised during its movement in direction D. Therefore, the device obtained according to the present invention solves the problem of automatic centering of a continuous band with respect to this band movement direction, particularly in blister packs producing machines . This allows to change the band size without manual adjustments, which results in higher productivity and avoids expensive manpower. It is also to be pointed out that the band width changes are automatically registered by the proposed device, which also efficiently contrasts the forces acting on the band, which tend to displace it with respect to the movement direction D. Another advantage of the proposed centering device results from its simple structure, functionality and easy applicability to known blister packs producing machines. The proposed device has been described with reference to a blister packs producing machine, to which it is applied; however, the device can be advantageously used in all cases in which it is necessary to center a band, passing through a series of working stations, with respect to movement direction. It is understood that what above has been described as a pure and not limitative example, therefore possible constructive modifications remain within the protective scope of the present technical solution, as described above and claimed below.

Claims: CLAIMS 1. A device for centering a continuous band, with the band (2) fed through at least one working station (7,8) in a movement direction (D) , the device being characterized in that it includes: at least one pair of rollers (12), which are rotatably carried with vertical axes at the ends of arms (15), said arms (15) being pivoted, about corresponding vertical hinge axes on both sides of said band (2) symmetrically with respect to a longitudinal middle axis (A) ; means (23) for mutual engagement of said arms (15), said mutual engagement means provoking an angularly limited symmetrical oscillation of said arms (15); elastic means (22) acting on said arms (15) for keeping said rollers (12) touching the opposite sides of said band (2), so as to center said band (2) with respect to said movement direction (D) . 2. A device, according to claim 1, wherein said mutual engagement means (23) of said arms (15) include respective levers, a first lever and a second lever respectively, protruding from said arms (15) and featuring respective free ends, said levers being set in mutual engagement at said free ends . 3. A device, according to claim 2, wherein said levers (23) engage with each other by a peg (24) extending vertically from said first lever (23) and engaging with a corresponding slot (25) made in said second lever (23). 4. A device, according to claim 1, wherein each one of said arms (15) is pivoted on a respective spindle (16) and said elastic means (22) include each a respective torsion spring having one end fastened to a top of said spindle (16), with another end of said elastic means being fastened to a related support sleeves (19), through which said spindle (16) passes axially. 5. A device, according to claim 4, wherein said sleeves (19) can be rotated with respect to the related spindles (16) by a predetermined angle, to adjust the elastic reaction force of said torsion springs (22) . 6. A device, according to claim 5, including sprung balls (26) seated in a ring (27) coaxial with each of said sleeves (19), for engaging elastically a plurality of recesses (29) made in a flattening (19a) of said sleeve (19), said flattening (19a) kept in abutment against said ring (27), so that the angular position of said sleeves (19) is fixed. 7. A device, according to claim 1, wherein each of said rollers (12) include pairs of rollers (12a, 12b) which rotate on respective pairs of coaxial axles (13a, 13b), so as to engage corresponding parts (2a, 2b) of said band (2) of thermoformable material unwinding from a reel (3) in said movement direction (D) . 8. A device, according to claim 1, wherein said rollers (12) feature a groove, in which said band (2) is guided, with said groove (31) being situated on the horizontal plane, on which said band (2) moves in direction (D) .

Inventors: GAUDENZI RODOLFO, GAUDENZI, RODOLFO
Applicants: GAUDENZI RODOLFO, IMA SPA, GAUDENZI, RODOLFO, I.M.A. INDUSTRIA MACCHINE AUTOMATICHE S.P.A.
Application year: 2000
Main classification: B65H23
IPC codes: B65H23