Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
  • B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
  • B29C55/04—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets uniaxial, e.g. oblique
  • B29C55/08—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets uniaxial, e.g. oblique transverse to the direction of feed
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
  • B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
  • B29C55/10—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial
  • B29C55/12—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial biaxial
  • B29C55/16—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial biaxial simultaneously
  • B29C55/165—Apparatus therefor

Definitions

• the present invention relates, in general, to the technical field of stretching films of synthetic material.
• This invention relates, more particularly, to a motorized drive device for a transverse stretching system for plastic films, of the type of those using, for holding, transporting and stretching the film, grippers successive supported and guided by rails, and driven forward by endless chains connecting the clamps.
• the invention relates, even more particularly, to a device which, in this context, ensures the forward drive of the chains provided with clamps.
• Bi-oriented synthetic material films are obtained from an extruded ribbon, after melted material has been deposited on a cooled casting drum so as to slow down the crystallization of the film and allow it to be stretched. ulterior.
• the extruded ribbon then passes through a longitudinal stretching machine, in which the stretching is carried out on the principle of a speed differential between different successive cylinders.
• the ribbon then passes through a transverse drawing machine, in which the ribbon is held by clamps mounted on chains, the spacing of which gradually increases.
• This type of stretching is perfectly suitable for films made of many synthetic materials such as polypropylene, polyester, and it is therefore widely used in industry.
• Another important step in the process for manufacturing bi-oriented synthetic material films is the so-called transverse stretching phase which occurs inside a large oven.
• two chains equipped with clamps and guide members move on side rails, first, in parallel and until the film has reached the desired temperature, then, thanks to an adjustment of the guide rails, moving away from each other symmetrically so as to ensure a transverse stretching of the film.
• the guide rails After stretching, the guide rails again become parallel or slightly convergent, so as to allow either the crystallization of the stretched film, or, possibly, its thermal relaxation.
• the important and incompressible parameters of the process are for example the residence times in the preheating zone of the oven necessary for the film to be heated to the core, and therefore stretches homogeneously, which requires the elongation of the preheating zone, or the progressiveness of the stretching which requires that the stretching zone be lengthened, and finally the maintenance, at a higher production speed, of a heat-stabilization time sufficient to ensure complete crystallization and therefore the stability of the films produced, which requires the elongation of the heat-stabilization zone.
• the extension here desirable of the transverse stretching machines is not without posing many problems which are mainly of double nature:
• the drive of the chains which ensure the synchronization of the clamps on the guide elements is traditionally done from toothed wheels driven by suitable reducers by a motorized shaft located on the side of the outlet of the machine, the return of the mobile assembly consisting of the chain and clamps being made at the entrance of the oven by another toothed wheel not driven allowing the return of the chain / clamps, that it again enters the oven ensuring the transport of the film.
• the driven toothed wheel located at the outlet of the oven must therefore ensure the drive of the assembly consisting of the chain and the clamps, not only for the strand which is inside the oven, but also for the return strand , or over a length approximately twice that of the machine concerned.
• This toothed wheel must therefore transmit a driving force to the chain, the result of which is a tension on the chain which must be greater than the forces opposing this movement, which are the mechanical frictions as well as the stretching forces of the film. .
• the subject of the invention is a drive device for a transverse stretching system for plastic films, of the kind indicated in the introduction, which is essentially characterized in that it comprises, for driving each endless chain connecting the clamps, at least two large-diameter drive gear wheels, ie a drive gear wheel located at the front end of the "go" strand of the chain, and another drive gear wheel located at the rear end of the "return” strand of the chain, with each toothed wheel being associated with motorized means for driving this wheel in rotation, and the motorized drive means associated respectively with the two toothed wheels being synchronized with each other .
• a first arrangement at the base of the invention consists in using large gear wheels, much larger than the current dimensions which are diameters from 1 meter to 1.5 meters, the gear wheels driving the chains of the device object of the invention having a diameter greater than 1.5 meters.
• a second basic arrangement of the invention consists in using, for a chain, two toothed drive wheels, either a wheel located at the inlet of the transverse stretching system, and a wheel located at the outlet of the same system. of stretching, the two toothed wheels being driving, since each of them has its own rotational drive means.
• These drive means are in particular, for each drive gear, a servo electric motor, the two associated motors respectively with the two toothed wheels being synchronized in speed, and controlled so that the torque necessary for driving the chain is distributed substantially equally between the toothed wheel located at the entry of the transverse drawing system and the gear wheel located at the exit of the transverse stretching system.
• the drive device object of the invention, makes it possible to halve the tension to which the chain is subjected.
• the transverse drawing machine can therefore be used at high speed, keeping the classic design of the chain / clamps assembly.
• each large toothed drive gear consists of an outer ring, with teeth adapted to the chain to be driven, and a fixed support part, the crown and said support part finding themselves linked to each other by a set of balls or rollers ensuring rotational guidance of the outer crown, while the support part is fixed horizontally to a frame. Thanks to this arrangement, the support part being fixed perfectly horizontally to a rigid frame, it is ensured that the outer ring of the wheel, which guides and drives the chain, is also held in a perfectly plane horizontal, despite a large diameter.
• each large-diameter drive gear has internal teeth, of diameter close to the external diameter of said wheel, teeth with which a relatively small diameter drive pinion engages, itself driven in rotation from the motor means associated with the toothed wheel considered.
• This mode of drive, by a motor pinion engaged with an internally toothed ring has the additional advantage of producing a speed reducer, the reduction ratio of which is all the greater as the diameter of the toothed wheel drive is large, and that the diameter of the motor pinion is on the contrary small.
• the drive pinion rotates at relatively high speed, so that it can either be driven in rotation directly by the output shaft of the engine associated with the wheel in question, or be driven in rotation by means of a reduction gear, with or without angle gear, reducer which is relatively small.
• Figure 1 is a very schematic overview, in plan from above, of a drawing machine provided with the device object of the invention
• Figure 2 and a perspective view of a toothed wheel and its rotational drive device
• Figure 3 is a vertical sectional view of this drive device.
• Figure 1 gives a very schematic overview of a transverse film stretching machine.
• the film 2 to be stretched is transported along the arrow F, so as to pass successively through the successive zones (here not detailed) of an enclosure, regulated in temperature, in which the longitudinal and then transverse stretching takes place of the film 2.
• To maintain and transport the film 2 it is held, by its two opposite edges, by means of pliers whose structure is known and can, in particular, be in accordance with that described in the aforementioned French patent No. 2 686 041.
• These clamps are carried by two endless chains 3, arranged symmetrically with respect to the longitudinal axis of the drawing machine, and driven along arrows respectively F1 and F2.
• Each endless chain 3 has an active part, which is its inner strand 4, the return of the chain 3 being provided by its outer strand 5.
• the two inner strands 4, belonging respectively to the two chains 3, in particular have divergent parts which correspond to the transverse stretching zone of the film 2.
• This drive device is describes, in what follows, for only one of the two chains 3, taking into account the perfect symmetry of the system.
• the drive device comprises two toothed drive wheels 6 and 7, of vertical axis A and B respectively, therefore located themselves in a horizontal plane, that is:
• a first toothed wheel 6 located at the outlet of the drawing machine, in other words at the front end of the inner strand or "go" strand 4;
• a second toothed wheel 7 located at the entrance to the stretching machine, in other words at the rear end of the outer strand or "return" strand 5.
• the two drive toothed wheels 6 and 7 have a large diameter D , greater than 1.5 meters, and whose order of magnitude is for example from 1.5 meters to 2.5 meters.
• the toothed wheel 6 proper comprises an outer ring 8, provided with an external toothing 9 adapted to the characteristics of the endless chain 3 to be driven, which chain passes over this external toothing 9.
• the external crown 8 is integral with a flange central 10.
• Beneath the outer ring 8 is concentrically mounted a ring 11 with internal toothing 12, serving to drive the wheel 6 in rotation.
• the assembly constituted by the two concentric rings 8 and 11 is mounted rotating by means of a set of balls 13, carried by a horizontal support 14 belonging to a fixed frame 15, the set of balls 13 also holding the wheel tooth 6 in a horizontal plane.
• the frame 15 supports an electric servo motor 16, the output shaft 17 of which is arranged horizontally drives a gear reducer 18, with angle gear.
• the vertical output shaft 19 of the reduction gear 18 carries a motor pinion 20 of relatively small diameter, which engages the internal toothing 12 by forming an additional reduction stage, for the rotational drive of the toothed wheel 6 from servo motor 16.
• the endless chain 3 is driven by the two toothed wheels 6 and 7, motorized as just indicated, the servo motors respective 16 of the two wheels 6 and 7 being synchronized.
• the first toothed wheel 6 thus pulls the "go" strand 4 of each endless chain 3, while the second toothed wheel 7 pulls the "return” strand 5 of this chain 3.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Shaping By String And By Release Of Stress In Plastics And The Like (AREA)
• Registering, Tensioning, Guiding Webs, And Rollers Therefor (AREA)
• Advancing Webs (AREA)
• Gear Transmission (AREA)
• Devices For Conveying Motion By Means Of Endless Flexible Members (AREA)

Applications Claiming Priority (2)

Publications (1)

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• 2003
  • 2003-06-02 FR FR0306635A patent/FR2855452B1/fr not_active Expired - Fee Related
• 2004
  • 2004-05-27 EP EP04767195A patent/EP1631437A1/de not_active Withdrawn
  • 2004-05-27 US US10/553,785 patent/US7322078B2/en not_active Expired - Fee Related
  • 2004-05-27 JP JP2006508344A patent/JP2007526965A/ja not_active Withdrawn
  • 2004-05-27 WO PCT/FR2004/001318 patent/WO2004108395A1/fr active Application Filing
• 2011
  • 2011-12-26 JP JP2011283960A patent/JP5559137B2/ja not_active Expired - Fee Related

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Non-Patent Citations (1)

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