AN APPARATUS FOR SECURING FITTINGS IN A THERMOPLASTIC FOIL WEB

Abstract: An apparatus for manufacturing a foil web of a thermoplastic with locally secured fittings (21), for use as tarpoulins or similar articles, comprises an extruder head (1) with an entirely or mainly downwards directed ejection orifice and two counterrotating rollers (25, 26) with a nip for calibrating the extruded foil (22). In a feeding device with a vertical supply magazine (10) a stack of fittings (5) is accommodated which by means of a guiding duct (2) may be guided into a discharge duct (3) extending towards the roller nip. The guiding device is electrically operated and an electrically controlled stop member (15) with an associated fitting sensing element (12) are arranged at the lowermost end of the discharge duct (11-15) towards the roller nip (24) for accurate control of the supply of fittings to the roller nip and monitoring the presence of fittings in the discharge duct. The discharge duct is arranged in such a relationship to said counter rotating collers (25, 26) that each fitting is supplied from the mouth of the discharge duct (25) to the roller nip (24) by a substantially free fall.

Description: An apparatus for securing fittings in a thermoplastic foil, eb. The invention relates to an apparatus for manu¬ facturing a foil web of a thermoplastic with locally secured fittings for use as tarpaulins or similar ar¬ ticles, comprising an extruder head with an entirely or mainly downwards directed ejection orifice and two counterrotating rollers or similar members arranged be¬ low the ejection orifice, at least one of said rollers or members being cooled, said rollers or members for¬ ming between them a nip for calibrating the extruded foil, and a feeding device with an entirely or mainly vertical supply magazine for accomodating a stack of fittings, a discharge duct extending from the bottom of the supply magazine in a direction towards the roller nip and a guiding device for guiding the lowermost fit¬ ting in the magazine into the discharge duct. An apparatus of this kind, which is used for ex- " ample for the fastening of eyelets in a plastic foil web, which is subsequently to be cut in suitable lengths for production e.g. of tarpaulins for covering purposes in construction works is known from DK- published patent application No. 130 239. In this prior art apparatus the guiding device formed as a reciprocating slide is driven by a hydrau¬ lic or pneumatical working cylinder and the discharged duct of the feeding device is arranged and designed in such a way that the supplied fittings are guided from the mouth of the duct towards the roller nip by the cooled roller. Thereby, it is only possible to obtain a relati¬ vely inaccurate positioning of the fitting in the foil web, since the velocity with which the fittings are supplied from the mouth of the discharged duct is main¬ ly determined by the stroke velocity of the slide. SUBSTITUTE SHEET ISA/SE 2 The ejection of fittings may thereby in an un¬ predictable way take place at such a velocity, that the fittings strike holes in the soft foil web. When a number of feeding devices arranged on a 5 line in the axial direction of the rollers are used for fastening fittings along a corresponding line in the foil web -in one operation, local differences in the surface character of the cooled roller has moreover led to a releatively inaccurate supply of the fittings of 10 the roller^ nip. Whereas these disadvantages have to a certain extent been acceptable in case of foil tarpaulins for singular use, they are not acceptable, when a greater number of tarpaulins are used for covering in construc- 15 tion works and arranged with overlapping edges since the said inaccuracies entail that the eyelets along the overlapping edges cannot be positioned opposite each other. It is the object of the invention to provide 20 an apparatus of the kind referred to, by which the said disadvantages are avoided so that the fittings are po¬ sitioned with a great accuracy in the foil web and at a substantially higher working speed than has been pos¬ sible in the above mentioned prior art apparatus, while 25 at the same time a very high safety against mal¬ function, e.g. failing supply of fittings from one or more of a number of feeding devices, is obtained and thereby a considerable reduction of the rejection per¬ centage. 30 TO achieve this an apparatus according to the invention as characterized in that the guiding device is electrically operated and an electrically controlled stop member with an associated fitting sensing element are arranged in the vicinity of the lowermost end of 35 the discharge duct towards the roller nip for accurate control of the supply of fittings to the roller nip and minitoring the presence of fittings in the discharge duct, the discharge duct being arranged in such a re¬ lationship to said counter rotating collers that each fitting is supplied from the mouth of the discharge duct to the roller nip by a substantially free fall. Thereby, in addition to a more accurate control of the movement per se of the guiding device the advan¬ cement of fittings from the mouth of the discharge duct to the roller nip will be independent of the movement of the guiding device as well as the surface character of the roller and may thereby be controlled with a uniform and constant speed in such a way that damage to the foil web is avoided also in cases, where a great number of feeding devices are arranged on a line in the axial direction of the rollers. Moreover, by means of the fitting sensing member it is to a large extend made sure that a fitting will always be present in the discharge duct prior to opera¬ tion of the controlled stop member. This safety may be further improved in that a further controlled stop member with an associated fit¬ ting sensing element is arranged as a buffer device a distance above said stop member, said sensing element being connected via a control circuit to an operating device for said guiding device. In the following the invention will be further explaned with reference to the schematical drawing in which, Fig. l shows an example of a tarpaulin with lo- cally fastened eyelets cut out from a reinforced thermoplastic foil web, Fig. 2 and 3 shows an example of an eyelet fit¬ ting, Fig. 4 a preferred embodiment of an apparatus according to the invention, and Fig. 5 a simplified control diagram. Fig. 1 shows an example of a tarpaulin 20 cut out from a net reinforced web of thermoplastic foil such as polyethylene foil having a rectangular shape and be¬ ing provided with eyelet fittings 21 fastened at se- parated positions along all edges of the tarpaulin. In Fig. 2 and 3 an example is shown of an eye¬ let fitting 21 in the form of a flat circular disc with a central eyehole extending through approximately one third of the diameter of the disc. As shown in Fig. 3 the thickness of the disc decreases towards a rather thin edge at the circumference of the disc such as known per se from the above-mentioned Danish published patent application No. 130239. The eyelet fitting 21, which is preferably ma- nufactured from a cast moulded plastics constitutes, howeever, only an example of such fittings, which may be fastened to a foil web by means of an apparatus ac¬ cording to the invention. As further possible forms of such fittings, which may also be manufacatured from me- tal or other materials, shackles, buckles or hooks may be mentioned. In the embodiment of the apparatus shown in Fig. 4 the foil web 22 consisting of a thermoplastic is extruded from an extruder head 1 formed as a wide slit ejector and having a downwards directed ejection orifice 23 towards the roller nip 24 between two counterrotating rollers 25 and 26 arranged below the ejection orifice, at least one roller 25 being a cooled roller. The apparatus comprises a tubular and substanti¬ ally vertical supply magazine file arranged above the cooled roller 25 for accomodating a stack of eyelet fittings 21 having a form as shown in Figs. 2 and 3. By means of a reciprocating slide 2 operated by an electric motor 12 with an associated gearbox through a connecting rod mechanism not shown and having an upwards directed projection 27 matching the central hole in the eyelet fittings 21, the lowermost fitting in the stack in the magazine 5 may be guided outside the magazine to a position, in which it is detached from the slide 2 by means of a detaching device 4 and at the return movement of the slide 2 falls down in the upper end of a slidlike discharge duct 3. The discharge duct 3 extends mainly linearly through an inclination of substantially 70° with the horizontal downwards towards the roller nip 124 with its mouth positioned immediately above the roller nip. At its mouth the duct 3 has a guiding plate 28 for accurate guiding the direction of an eyelet supplied from the duct towards the roller nip 24. In the vicinity of the lowermost end of the discharge duct 3 an electrically controlled stop member 15 is arranged and immediately above this a sensing element 14 for sensing the presence of a fit- ting 21 at the position in the duct 3 determined by the stop member 15. At a position upstream in the duct 3 a further electrically controlled stop member 29 with an asso¬ ciated sensing element 30 is arranged as a buffer de- vice. In order to sense the height of the stack of fittings in the magazine 5 a sensing element 7 is provided in connection therewith. For the purpose of manually moving the entire feeding device the magazine 5 is further provided with a handle 6. By means of a locking device 8 the feeding device may be locked in any desired position along a mounting bar 10 extending parallel to the axial di- rection of the rollers 25 and 26, on the other side of which a yardstick may be provided for accurate po- sitioning of a number of feeding devices side by side on a line parallel to said axial direction. The feeding devices may be positioned as closely on the mounting bar 10 as the width of the individual feeding device allows e.g. with a mutual separation down to 14 cms. As shown in the diagram in Fig. 5 several fee¬ ding devices may be controlled by means of a common electronic control device 32 such as a P C/PPC- control circuit receiving signals from sensing elements 7, 14 and 30 in each feeding device and generating energizing signals for the motor 12, the detaching de¬ vice 4 and for release of the stop members 15 and 29 in response to such signals. An alarm device 33 may be connected to the control device 32 for generating a visual and/or acu- stical alarm signal, when the height of the stack of fittings in the supply magazine 5 of a feeding device falls below a level corresponding to the position of the sensing element 7. Correspondingly, the control device may be programmed to generate an alarm signal if no fitting reaches the stop member 29 in spite of repeated operation of the motor 12 and the detaching device 4. The control device 32 may be programmed for accurate positioning of fittings in the foil web 22 in any desired configuration, e.g. also along diagonal lines as shown at 34 and 35 in Fig. 1. In itself, generation of the reciprocating move- ment of the slide 2 by means of a connecting rod mec¬ hanism operated by an electric motor provides high sa¬ fety for the slide to gripping the lowermost eyelet in the stack of fittings in the magazine 5 during each stroke and for detaching this eyelet from the slide by means of the detaching device 4 since the relevant extreme positions of the slide correspond to the dead points in the connecting rod movement. A further improved safety may be provided by a arranging the control device to operate the electric motor 12 so as to be briefly stopped in diametrically opposite rotor positions corresponding to said extreme positions. The electric motor 12 may be a controlled DC- motor or a step motor, in which latter case a high accuracy may be obtained by adjustment of the pulse shape and frequency for the control pulses.

Claims: P A T E N T C L A I M S 1. An apparatus for manufacturing a foil web of a thermoplastic with locally secured fittings (21) , for use as tarpoulins or similar articles, comprising an extruder head (1) with an entirely or mainly downwards directed ejection orifice and two counterrotating rol¬ lers (25,: 26) or similar members arranged below the ejection orifice, at least one of said rollers or mem¬ bers (25) being cooled, said rollers or members forming between them a nip for calibrating the extruded foil (22), and a feeding device with an entirely or mainly vertical supply magazine for accomodating a stack of fittings (5), a discharge duct (3) extending from the bottom of the supply magazine in a direction towards the roller nip and a guiding device (2) for guiding thelowermost fitting in the magazine into the discharge duct, c h a r a c t e r i z e d in that the guiding de¬ vice is electrically operated and an electrically con¬ trolled stop member (15) with an associated fitting sensing element (12) are arranged in the vicinity of the lowermost end of the discharge duct (11-15) towards the roller nip for accurate control of the supply of fittings to the roller nip and monitoring the presence of fittings in the discharge duct, the discharge duct being arranged in such a relationship to said counter rotating collers (25, 26) that each fitting is supplied from the mouth of the discharge duct (25) to the roller nip (24) by a substantially free fall. 2. An apparatus as claimed in claim 1, c h a - r a c t e r i z e d in that a further controlled stop member (29) with an associated fitting sensing element (30) is arranged as a buffer device a distance above said" stop member (15), said sensing element (30) being connected via a control circuit to an operating device for said guiding device. 3. An apparatus as claimed in claim 2, c h a - r a c t e r i z e d in that an alarm device (33) is connected to said control circuit for actuating an alarm when no fitting has been guided on to said fit- ting sensing element (30) after several repeated opera¬ tions of the guiding device. 4. An apparatus as claimed in any of the precee- ding claims c h a r a c t e r i z e d in that said discharge duct (3) extends substantially linearly from said feeding device to a mouth at a short distance from the roller nip, a guide plate (28) being arranged at the mouth for accurately guiding the direction of the fittings. 5. An apparatus as claimed in claim 4 c h a - r a c t e r i z e d in, that the discharge duct (3) has an inclination of substantially 70° with respect to the horizontal. 6. An apparatus as claimed in any of the prece¬ ding claims c h a r a c t e r i z e d in, that the feeding device with associated discharge duct (3) is mounted for lateral displacement in the axial direction of the rollers and for being locked in any desired po¬ sition. 7. An apparatus as claimed in any of the prece- ding claims c h a r a c t e r i z e d in that a sensing element (7) is arranged at said suipply magazine (5) for sensing the heigth of the stack of fittings. 8. An apparatus as claimed in claim 2 c h a - r a c t e r i z e d in, that the guiding device (2) with associated operating device comprises a reciproca¬ ting slide, which via a connecting rod is operated by an electric motor (12) so as to be briefly stopped at its two extreme positions, in which it grips the lower¬ most fitting (21) from the stack of fittings in the supply magazine and delivers said fitting at the upper end of the discharge duct by means of an electrically controlled detaching member (4) . 10 9. An apparatus as claimed in any of the prece¬ ding claims c h a r a c t e r i z e d in that a number of fitting devices with associated discharge ducts ar¬ ranged in predetermined positions along the axial di- rection of the rollers are controlled by a common PLC/PPC control unit.

Inventors: SOELBECK PETER, SOELBECK, PETER
Applicants: POLYSHEET AS, POLYSHEET A/S
Application year: 1990
Main classification: B29C67
IPC codes: B29C31, B29C47, B29C65, B29C70, B29L7, E04G21