PNEUMATIC CLAMPING MANDREL FOR CORELESS WEB WINDING MACHINES AND POSITIONING DEVICE THEREOF

Abstract: The invention concerns a mandrel (1) suitable for coreless web winding machines. The mandrel lodges two expanders (2, 3) pneumatically acted by means of cylinders (4, 5). One of the expander is suitable for gripping and clamping the leading edge of the band to be wound for obtaining coreless rolls. The invention includes, in combination, a device for the transport of the leading edge of the band to the clamp of the mandrel.

Description: PNEUMATIC CLAMPING MANDREL FOR CORELESS WEB WINDING MACHINES AND POSITIONING DEVICE THEREOF The field of application of the present invention concerns the winding machines of webs or tapes made of paper or plastic material . In particular, the subject of the present invention is a mandrel, which is mountable on the aforesaid said machines, specifically addressed for making coreless rolls of said webs or tapes , in cooperation with means for the positioning of the webs in order to automatically insert their initial edges into the suitable seats of the mandrel . At the present state-of-the-art, machines for winding rolls or bobbins of web-like materials, like paper or plastic, use mandrels whereon a support of plastic or other material suitable for such a function, usually of cylindrical shape, is inserted and thereto the initial edge of the web to be wound is fixed ; the necessity of such a support is dictated either by the final use of the rolls, for example in labeling machines, either, also, by the difficulty of winding the webs without said support in a totally automatic way. Some methods for winding coreless rolls of paper, in particular toilet paper, are already domain of the state-of- the-art, as disclosed by WO 96/28079 and US 3,853,279. In the cited documents the front edge of the band to be wound is wetted for being sticked to the winding mandrel , so as to obtain a temporary gluing to said mandrel at least for its first two or three rotations : said rotations form the suitable anchoring for winding the web, while avoiding its sliding from the mandrel . Further applications concerning webs with a core previde partxcrular glues tσ fix the front edge of the band to the mandrel ; such glues evaporate or dissolve during the winding operation . The use of bands or tapes without core is often requested. In fact, the use of a core, besides being more costly for the cost of the core itself, complicated in many cases the charging and replacing of rolls in distributors, like i.e. in the automatic labeling machines , in some tele ax machines and in some distributors of toilet paper. Furthe.rmore , the use of the core, when it is not dictated by its function, comports longer winding time to obtain the rolls and more complex operations , due to the necessary fixing of the front edge of the web material to the core and the insertion of the latter on the mandrel , which are manual operations ; also , the reliability of the production process, due to (whenever the securing of the initial edge should fail) the possible slipping of the paper about the core, would be affected. The present invention solves the above mentioned problems by means of a mandrel configured for being actuated by pneumatic means and which overcome the need of the core of millboard or other material by means of clamps for gripping the leading edge of the web . Similar solutions are provided by leaf-type air shafts, as in US 3,863,857, by using expansible elements : the complexity of the expansible mandrels of the prior-art is nevertheless a limitation for what concerns their reliability and their costs . Furthermore, the composite structure of prior-art expansible mandrels complicates their maintenance and reduces their life-cycle, reducing as well their ability to strengths at high rotation speed. More examples of such composite mandrels are given in US 5,123,604 and US 4,195,792. The mandrel of the present invention vis-a-vis the prior-art improves the clamping system for gripping the leading edge of the web material to be wound and allows the complete automation of the operation of leading the front edge to the mandrel clamping system and of securing it for initial winding . Said automation is achieved by means of a transport system which cooperates with the mandrel and suitable for leading the front edge of the web towards the clamping system and providing automatic insertion into the slot of the mandrel clamps , as better described below . The main embodiment of the invention and its functioning is better e.xplained by means of Figureures , whereas - Figure 1 shows the cross-section of the clamping mandrel and its elements of the preferred embodiment. - Figure 2 shows the plant of the clamping mandrel and the shape of its body for lodging the various working elements . - Figure 3 and 4 illustrate the longitudinal and perspective view of the mandrel. - Figure 5 , 6 and 7 represent the phases of working of the mandrel . - Figure 8 represents the schematic view of the web winding machine for the understanding of the mechanism of the present invention, for what concerns the leading of the band edge towards the mandrel . - Figure 9 shows in details the mechanism of insertion of the band into the mandrel . In the cylindrical body of the mandrel 1 of Figure 1, two seats 13 and 14 are shaped for lodging respectively the expander 2 and the clamping expander 3 , actuated by pistons 4 and 5 ; a duct 6 for the adduction of compressed air is drilled along the axes of the body of said mandrel 1. The duct 6 is communicating with the series of seats 7, therein said pistons 6 , 7 are lodged as illustrated by Figure 2. The number of pistons and their spacing is determined by the length of mandrel 1 , so as to assure that expanders 2 and 3 are actuated for its entire length without misalignments. The preferred embodiment of the mandrel , as from Figure 3 , shows the duct 6 closed by the cap 8 so to form a closed chamber, wherein the pressurised air exercises pressure on the pistons 4 and 5 lodged in seats 7. To the end of securing said chamber 7 by air-tightness under pressure, pistons 4 and 5 are provided, respectively, by O-rings 15 and 16. The expander 2 is connected to pistons 4 by means of screws 9 : these screws 9 are calibrated for allowing between said pistons 4 and said expander 2 a clearance 10 of the order of some tenth of millimeter ; said clearance 10 allows a freedom degree in the positioning of said expander 2 for an easier lock of the opening 13 of the mandrel during the expansion phase . The expander 3, which acts as a clamp, is let disconnected from pistons 5, and therefore, when it is in idle state (absence of pression in chamber 6) it falls by gravity, leaning against the shaped wall of mandrel 1 and so letting a greater opening between itself and the interior wall 13 of the shaped cavity of said mandrel 1. Said expander 3 , which in the closed position (expansion) grips the leading edge of the web, is provided along its length with a rubber or plastic string 12 apt to secure a better grip of said leading edge of the web. Mandrel 1 is crossed in each of the seats 7 of the pistons 4 and 5 , and in correspondence with duct 6 , by plugs 11 acting as separators of pistons 4 and 5, in order to avoid that in the opening phase (e.xpiration of air from duct 6) said pistons 4 and 5 would close entirely the hole 6 , so compromising its functioning : in fact in the following phase of expansion, the compress air in the so obstructed duct 6 would impede the outwardly pushing of pistons 4 and 5. The working of the mandrel of the present invention may be better understood by means of Figures 5,6,7. As from Figure 5 at the beginning of each winding process of web material in rolls , it is created in the duct 6 a decompression and pistons 4 and 5 are then sucked towards the interior of mandrel 1. A transport and positioning mechanism, hereinafter better described, leads the front edge of the web into the slot 13, between the clamping expander 3 and the internal wall of the mandrel, as shown in Figure 6. Subse-quently, it is admitted compressed air which acting on pistons 4 and 5 pushes outwardly the eapanders 2 and 3, so that the external walls of the eacpanders adhere with the internal walls of the shaped seats of mandrel 1 and, indeed, closing air-tigthnessly the opening of said mandrel 1. The clamping expander 3 grips and holds the band to be wound during the rotation of mandrel 1 till the completion of the entire roll . When the roll is formed, the evacuation of air from duct 6 makes pistons to be moved by depression towards the interior of mandrel 1 ; the expander 2 it is retracted and the expander 3 falls, by gravity, against the internal wall of its seat while opening the slot 13 and so allowing the easy slipping of the mandrel 1 of the roll . Although the above described operation could be effected by using a single clamping expander, the embodiment of the present invention makes use of two expanders in order to , when the winding is completed, help removing the roll from the mandrel : the second expander 2, when retracted, creates an embossed zone on the external surface of mandrel 1 so impeding the adhesion of the first turn of the roll to said mandrel and its possible unwinding. The automatic insertion of the leading edge of the web into slot 13 of clamp 3 of mandrel 1 is made possible by means of positioners 17 and 18, fixed about the axis of guiding rollers 20 and 21 as described in Figures 7 and 8. A block 19, comprising two guiding rollers 20 and 21, lifts up at the initial phase of winding, and displaces from the initial position 22 to the position 23 next to the mandrel 1 ; at the same time the arms 17 and 18, fixed on the axis of rollers 20 and 21 rotate in order to precisely position the leading edge of the web for the insertion into slot 13 of the open clamp 3. Once the initial zone of the band to be wound is inserted into slot 13 , compressed air is let in duct 6 : pistons 4 and 5 are pushed outwardly and clamp 3 closes ; mandrel 1 starts then the revolution for the winding cycle of the roll . The positioning of mandrel 1 is obtained by means of mechanical phasers ; said phasers are transmission organs comprising a heart shaped cam acted by pistons : the concave zone of said cam corresponds to the idle mechanism of rotation of the mandrel, which, therefore, stops always in the same angular position. The displacement of block 19 and of the arms 17 and 18, in order to insert automatically the front edge of the web into slot 13 of clamp 3 , are pneumatically controlled and coordinated by means of microprocessors, so as the control of the adduction and emission of air phases of the compressed air in duct 6. All pneumatic functions of the mandrel of the present invention, in combination with the positioning system of the leading edge of the web , are performed by the normally installed compressors on the winding machines of the type described, whereas additional air paths and valves are controlled by the above said microprocessors . Mandrel 1 is set to the right angular position for the automatic insertion of the leading edge of the web by means of a pneumatically controlled heart shaped cam. The above description it is not a limit to other possible embodiments that the mandrel of the present invention can permit without addition of the described subject matter ; also, the pneumatic control of the expanders should not be considered as narrowing the disclosure by excluding different electro-mechanical embodiments based on the same principe which do not extend the present subject matter. The same application of the mandrel of the invention to web winding machines cannot be intended a limit to applications for clamping front edge of webs in different apparatus , like i.e. fax machines and printers .

Claims: CLAIMS 1- A cOainbination of a mandrel and a device for positioning a leading edge of a band next to said mandrel preferably for coreless web winding machines characterised in that the cylindric body of said mandrel (1) is provided of two seats (13,14) lodging a first expander (2) and a second clamping expander (3) , said seats (13,14) are in communication, by means of cylindric seats (7) shaped transversally to the body of said mandrel (1) , with a duct (6) coaxial to the longitudinal axis of said mandrel (1) , said duct (6) being closed by a cap (8) ; a first series of pistons (4) and a second series of pistons (5) are lodged in saids seats (7) in correspondance , respectively, with a first expander (2) and a second clamping expander (3) ; the device for positioning the leading edge of a band next to said clamping expander (3) comprising a first arm (17) fixed to the axes of a first guiding roller (20) and a second guiding roller (21) , said second arm (18) being of a length superior to said first arm (17) in order to obtain the exact angle of insertion of the leading edge of said band into clamp (3) of said mandrel (1) , said expanders (2,3) acted pneumatically outwardly the said mandrel (1) by compressed air admitted in duct (6), whereas said expanders (2,3) are acted inwardly said mandrel (1) by suction of air from said duct (6) . 2- The combination according to claim 1 characterised in that said mandrel (1) is provided of pins (11) in a median position of seats (7) in correspondance of duct (6) , said pins (11) acting as separators of pistons (4,5) for freeing said duct (6) during the phase of air suction. 3- The combination according to claim 1, characterised in that the clamping expander (3) of mandrel (1) is provided with a plastic or rubber string (12) along its length on the closure wall of said expander (3) , in correspondance with the internal closure wall (14) 4- The combination according to claim (1) characterised in that pistons (4,5) are provided with O-rings for air tigt ness under pressure in seats (7) . 5- The combination according to claim (1) characterised in that arms (17,18) and positioning device (19) are pneumatically controlled, whereas the angular position of mandrel (1) for the insertion of the leading edge of the web is controlled by a mechanical phaser comprising a pneumatically acted heart shaped cam, the concave zone thereof corresponding to the idle position of the rotation mechanism of mandrel 1.

Inventors: PRATI PIETRO, PRATI, PIETRO
Applicants: MEC PRATI PIETRO OFF, PRATI PIETRO, OFFICINA MECCANICA PRATI PIETRO, PRATI, PIETRO
Application year: 1998
Main classification: B65H
IPC codes: B65H75