FR2513802A1 - Ribbon cable mfg. machine using heated, grooved rollers - uses plastics extruder to inject hot plastics around planar array of parallel conductors prior to passing between grooved rollers - Google Patents

Abstract

The machine has a wire feeder which provides copper wires (12) parallel to each other in a coplanar array which runs over heated rollers (67,68). As extrusion machine (69) extrudes hot plastic around the layer of wires to provide the insulation between them. The rollers have cupped circular grooves around the periphery, and act one against the other to compress the hot plastic around the array of wires. The wires tend to move to the grooves, ensuring even spacing, and the plastics cools around the wires with a thin layer left between individual wires to ensure their attachment one to the other. One of the rollers has an associated cutter which lies parallel to the axis of the roller and is used to cut the flat cable to length. The depth of the groove closest to the cutter is less than 70% of that of furthest grooves.

Description

Device for manufacturing flat seams by calendering with lateral shearing
The invention relates to a device for manufacturing flat cables by calendering with lateral shearing. It applies in particular to the manufacture of electric cables comprising a large number of metallic conductors insulated from each other.

Known devices for the manufacture of such cells are described, for example, in French patent No. 2,189,833
(Philips) or British Patent No. 815,573 (Sumitomo). A flat sheet of parallel wires is guided in the axis of an extrusion assembly delivering hot plastic material on either side of this wire sheet. The assembly, which is still hot, is clamped between two fluted calendering rollers, which weld to each other, in the intervals between the wires, the two plies of plastic material located on either side of the ply of wires, and which give the cable its final shape.

 In this type of device, the flow rate of the extrusion assembly always varies a little during manufacture. This results, on the one hand, in small variations in thickness of the insulating sheath around the wires, which is not troublesome in practice, and on the other hand, random and unacceptable lateral burrs.

That is why we use shearing devices mounted at the ends of the calender rolls.

 The known manufacturing devices of the kind described above have various drawbacks such as - accumulation of plastic material against the rollers, - localized excess thicknesses of the fabricated cable, particularly on the edges thereof, - or air inclusions in the cable in contact with the wires, in the welding plane.

 The purpose of the present invention is to avoid excess thickness of the cable on its edges, air inclusions and any accumulation of plastic material.

 It relates to a device for manufacturing flat cables with wire guides, this device comprising -means for continuously supplying a flat sheet of parallel metal wires moving parallel to themselves in a "longitudinal" direction towards a downstream side " of the device for constituting the conductive cores of the flat cable to be manufactured, - an extrusion assembly for extruding hot plastic around this layer of wires, - two calendering rollers whose axes are parallel to this layer of wires and perpendicular to the wires, these two rollers being arranged opposite one another on either side of this ply surrounded by the hot plastic material, so that these rollers compress this plastic material together and thus ensure, in the intervals between wires, a weld between the plastic material located on one side of the sheet and that located on the other side, - at least one of these rollers comprising a succession of grooves circular hollow separated by raised grooves, so that these grooves form on the plastic insulating sheaths in succession following the width of the flat cable and connected to each other by connecting strips of lesser thickness formed by the pressure of the grooves, - these rollers being provided with a shearing device locally compressed the hot plastic material to cut it and form an edge of the flat cable, - this device further comprising a wire guide disposed near and upstream of the calender rollers to guide each of the ply wires to one of these grooves so as to place this wire in the axis of the plastic sheath formed by this groove, - and means placed downstream of the calender rolls to drive the cable flat thus formed, - this device being characterized in that at least one groove of these rollers in the vicinity of the shearing device has a depth reduced so that , at a distance from this shearing device, the depth of the grooves is sufficient to be able to absorb a temporary excess flow rate of the extrusion assembly by forming sheaths of increased height on the metal wires, and that, in the vicinity of the shearing the depth of the grooves is small enough to prevent a permanent excess height of these sheaths due to the fact that the shearing device laterally repels hot plastic.

 Using the attached diagrammatic figures, a device according to the invention will be described below, without implied limitation.

 The elements which correspond on several of these figures are designated therein by the same reference signs.

 FIG. 1 represents a view of the extrusion and calendering assemblies of this device in section through a median longitudinal vertical plane, that is to say passing through the median line of the ply of wires which constitutes the cores of the cable manufactured .

 FIG. 1A represents a detail on an enlarged scale of FIG. 1, this detail showing the wire guide.

Figures 2, 3, 4, 5, 6, 10 and 11 show partial views of this device in section through planes II-II,
III-III, IV-IV, VV, XX and XI-XI of FIG. 1, respectively, these planes being vertical transverse, that is to say perpendicular to the wires, the scale being enlarged in FIG. 5.

 FIG. 6 represents a detail on an enlarged scale of FIG. 4.

 Figures 7 and 8 show views of the assembly of the same device according to the invention, respectively in side view and from above.

 FIG. 9 represents a cross section of a flat cable manufactured using the device according to the invention.

 In accordance with FIG. 1, a device according to the invention comprises an extrusion assembly G9 itself comprising two superimposed extrusion heads, an upper head 21 and a lower head 21 ', supplied with hot plastic material by a extruder G21 (see Figure 3) whose axis is horizontal transverse, that is to say perpendicular to the plane of Figure 1.

A guide assembly G6 guides a horizontal sheet 12 of parallel copper wires which advance in the direction of their lengths passing between the two heads 21 and 21 '. The words "downstream" and "upstream" will be used below with reference to the direction of movement of these wires, the direction of these wires being called "longitudinal", and the horizontal perpendicular direction being called "transverse".

 Each of these heads provides a strip of hot plastic material 23 above and 23 ′ below the layer of wires 12, the assembly then passing between the rollers 67 and 68 of a calendering assembly G10. The axes of these rollers are horizontal transverse.

 The guide assembly G6 comprises a frame 18 disposed upstream of the two extrusion heads and carrying in cantilever a beam-shaped slide 11 which extends downstream, passes in the interval between these two heads without touching them, and carries at its end downstream of these heads a wire guide 14 which individually guides each of the wires of the ply 12. Each of these wires passes for this purpose through a guide orifice formed by a slot 15 dug in the upper edge of the wire guide, this edge being covered with a cover 13 which is removably attached to it and closes the upper opening of the slots.

 This cover 13 extends over the slide 11 at a certain distance upstream from these slots (see FIG. 1) so as to allow this removable fixing to be produced by screwing its upstream part 13a onto two raised lateral edges 11a of the slide. The latter is in fact constituted by a U-shaped steel profile, the two branches of the U constituting these two raised edges. The wire guide 14 also extends upstream of these slots on the slide but its upper edge, in which the slots 15 are hollowed out, occupies only its downstream end and protrudes above its upstream part 14a. The wire guide is also fixed to the slide by screwing its upstream part 14a.

 The lower surface of the wire guide 14 rises and the upper surface of the cover 13 lowers towards their downstream end, which are arranged cantilevered beyond the downstream end of the slide 11, this so as to decrease the vertical thickness of the guide assembly in the vicinity of the rollers 67 and 68, and thus allow the wire guide to be brought as close as possible to these rollers despite the small gap which then remains between the two plies of plastic material 23 and 23 ' extruded by heads 21 and 21 '.

 The lower face of the slide 11 is provided in its transversely median part with a rack 11b (see FIG. 1 and 10) which cooperates with a drive pinion 18a carried by the frame 18 to allow the slide to move forward and backward, screw 18c allowing the blocking of the slide when it is in the guide position.

 The adjustment of the guide position is ensured by opposing adjustment screws 18d, 28f, 18g, 18h and 18j acting on an intermediate frame 18k at the rear end of the slide (see Figure 11).

 We will now give a nomenclature of the main elements of the G9 extrusion and calendering G10 assemblies.

EXTRUSION ASSEMBLY (see figures 2 and 3) 21: prismatic upper head in several elements.

22: passage for the wire guide assembly between the head
lower and upper head.

23: Upper strip of thermoplastic coating material
son.

23 ': Lower strip of the same material.

24 Adjustable upper lip of the extrusion slot of the
upper strip 23, the lower lip 24a of this slot
being fixed.

25: Adjustment corner of the upper lip 24, the adjustment of
the thickness of the slot being made by displacement of this
corner perpendicular to the plane of Figure 1.

26: Heating resistors.

27: Thermal regulation probe.

The lower head is symmetrical with the upper head by
relative to the horizontal plane of the layer of wires 12, the
elements of the lower te being designated by the same
reference numbers as the symmetrical elements of the
upper head by adding only an apostrophe, the
head 21 ′ being for example symmetrical with head 21.

28 Body of the extruder (see figure 3) feeding the two
extrusion heads.

29: Extrusion screw pushing the hot plastic towards
internal chambers 32 and 32 'of the extrusion heads.

30: Head support collar and material distribution.

31: Distribution channel and top / bottom distribution of
hot plastic.

32: Internal chamber of the upper head.

33-34 Two counter-screws for adjusting the position of the
upper corner 25 (Figure 2).

35: Two lip tilt adjustment screws
upper 24.

36: Two screws pulling the upper lip 24 against the corner 25
to block the upper lip in height
24.

37: Graduation marking of the strip thickness adjustment
23.

38: Set of screws and elastic washers for plating the
upper lip 24 against the upper head.

33, 34, 36 and 33 ', 34', 36 'allows to increase or decrease
the thickness of the two strips of extruded material, while
ensuring uniformity and equality of thickness of the two
bands.

CALENDERING ASSEMBLY (see Figures 1 and 4) 50: Support frame.

51: Lower tilting support (tilting allows
lower the lower roller 68 to then allow
its lateral clearance for maintenance or adjustment).

52: Lateral carriage.

53: Longitudinal carriage carrying the calender roll
inferior.

54: Upper calender roller support lever.

55: Upper roller lifting cylinder.

56: Lowering cylinder for the two rollers.

57: Lateral transfer cylinder of the rollers.

58 Light boot to allow visual control of the position
wire operation in the cable thanks to the semitrans
plastic appearance.

59: Screw for longitudinal positioning of the rollers.

60: Manual lever for lifting the upper roller to allow
to position each wire laterally in relation to the
rollers.

61: Safety stop to prevent excessive approach
rollers.

62: Clevis with oblong eye to ensure the connection between the udder
tone of jack 55 and lever 54 when you want to raise the
upper roller and to avoid all risk at the same time
action on this lever during cable manufacturing.

63: Upper roller bearing.

64: Lower roller bearing.

65 Top roller axis.

66: Lower roller axis.

67: Upper calender roller.

68: Lower calender roller.

69: Shear ring carried by the upper roller.

70: Shearing washer carried by the lower roller
(this ring and this washer cut the excess material
plastic on the edges of the cable during manufacture and
constitute said lateral shearing device of the
cable, the ring 69 being pushed axially by a
spring 69a so that its bevelled face 69b comes to rest
the hot plastic against the outer edge of the
washer 70 which acts as a knife) 69a: Pushing spring of the ring 69 69b: Tapered bevelled face of the ring 69, the top of the
cone being on the axis of the upper roller and on the same side the
ring that this roller 69c: Spring support nut 69a 70a Washer locking sleeve 70 against one end
of the lower roller 70b: Sleeve locking nut 70a 71 ': Nut.

72: Spring washer.

73 roller alignment screen for setting the
grooves of the two rollers facing each other well
other.

74-: Counter pressure weight defining the pressure applied
by the rollers on the plastic.

75: Counterweight cable.

76: Cable finished.

We will now describe the operation of the calendering assembly, first of all during the preparation of manufacture:
On the frame 50 is mounted a set of cross-motion carriages allowing the following maneuvers - lateral release of the assembly, using the jack 57, acting on the carriage 52, previously released by the simultaneous action of the jacks 55 and 56 which respectively raises the upper roller and lowers the lower roller.

- longitudinal positioning of the calenders at a horizontal distance from the extrusion slots, to control the removal of the material, this using the screw 59
The calender rollers are free to move in the vertical direction. They are however kept perfectly aligned in the transverse direction.

 The stop 61 prevents them from colliding with one another.

 At the start of cable manufacturing, the two rollers being open, the wire guide loaded with wires is advanced. The wires are conventionally hooked to a pulling cord itself driven by the track G15 of the line (that is to say between drive bands G15a and G15 located on the production line downstream of the assembly of calendering, according to Figures 7 and 8).

 The start of the extruder leads to the appearance of two strips of plastic material (polyvinyl chloride) which are pressed manually on the sheet of wires and driven by the latter.

 The bringing together of the rollers achieves the profiling of the plastic material under the action of the counterweight 74 which precisely defines the pressure applied by the rollers to the strips of plastic material.

 The absence of positioning stops in the vertical direction allows the rollers to automatically adjust according to variations in the flow rate of the extrusion heads, that is to say the thickness of the extruded bands, and makes it possible to absorb all thickness variations without affecting the distance between the conductors.

 The two calendering rollers 67 and 68 are identical.

They each have circular grooves 102 which follow one another along the length of the roller and are separated by circular grooves in relief 104, the grooves of one roller being opposite those of the other. Each of the grooves 804 carries a weakening net 106 projecting over the entire perimeter of the median circle of its summit band 105.

 These grooves form in relief plastic sheaths B1, B4 coating the wires F (see FIG. 9) and the grooves form flat connecting strips of lesser thickness joining the sheaths. As for the weakening nets, they form grooves in the plastic S allowing easy tearing of the finished cable between two conductive wires coated by their sheaths.

 At least one groove 102-1 of these rollers 67, 68 in the vicinity of the shearing device 69, 70 has a reduced depth so that, at a distance from this shearing device, the depth of the grooves is sufficient to be able to absorb a temporary excess of flow rate of the extrusion assembly by forming sheaths B of increased height on the metal wires F, and that, in the vicinity of the shearing device, the depth of the grooves is sufficiently small to prevent a permanent excess in height of these sheaths in this is because the shearing device laterally repels hot plastic.

 Preferably the depth E1 of the groove 102-1 closest to the shearing device 69, 70 is less than 70% of that E4, ES of the grooves 102-4, 102-5 remote from this device and several grooves 102-1 , 102-2, 102-3 in the vicinity of the shearing device 69> 70 have a reduced depth, this depth gradually increasing from the shearing device and then becoming constant.

 Preferably the number of grooves 102-1, 102-2, 102-3 with reduced thickness is at least two and at most four.

 Preferably, the sides 103 of the grooves 102 are connected at an obtuse angle to the top strip 105 of the grooves, this strip and these sides being seen in section for a plane passing through the axis of the roller 67, this so that the area of this connection constitutes an edge capable of completely applying the hot plastic material against the part of the surface of each wire close to the plane passing through the axes of all the wires F. In the example shown the connection angle is straight. If the connection is not made by a sharp edge, its average radius of curvature is less than 10% of the width of the top strip.

 The effect of the arrangements which have just been described as to the shapes of the grooves and grooves appears on the finished cable (see fig. 9). The sheath B1 closest to the shearing device has, in section, an almost rectangular shape due to the filling under pressure of the groove 102-1, itself of rectangular section, while the incomplete filling of the deep grooves 102-4 and following leads to a naturally rounded B4 sheath shape.

 One of the rollers could of course be produced without grooves or grooves if one wanted to manufacture a flat cable with a smooth face.

 The dimensions of the finished cable are given - in transverse pitch of the conductors, by the pitch of the grooves of the rollers, account having to be taken of the shrinkage of the material after calendering, the extent of the lateral shrinkage depending on the distance between the outlet of the heads extrusion and rollers, - in thickness by the ratio of the flow rate of the thermoplastic material to the cable running speed.

 it should be understood that the sets for guiding the extrusion and calendering threads belong to a larger set which includes other elements and which will now be described briefly because these other elements are in themselves well known to one skilled in the art.

 A "creel" G1 (coil support frame) (see FIGS. 7 and 8) carries at most sixty coils G2 supplying the wires G3 to be coated which are guided, towards the guide assembly G6 (FIG. 1). After passing through the extrusion assembly G9 supplied with plastic by a group G5 and by the calendering assembly G10, these wires coated in the plastic constitute the flat cable 76. They then pass successively (see FIG. 7) through an air cooling gutter G12 in which they are supported by rollers G13, a cooling tank G1 #, a light boot G4, a marking device G11, the pulling track G15 in which the cable 76 is clamped between the flexible bands G15a and G15b a cable receptacle G16 and a control device G18 preceding a reel G20.

 We also see in Figure 8 the extruder G21.

 By way of example, the following values can be given for the manufacture of a cable in accordance with FIG. 9 and consisting of sixty electric conductor wires with seven strands of 0.13 mm in diameter forming a strand of 0.39 mm regularly spaced 1.27 mm pitch and coated in a 0.2 mm thick sheath and made of polyvinyl chloride charged with kaolin at 2.5% by weight with 34% of a phthalate pastifier.

- Thickness of the extrusion slot: from 0.5 to 0.6 mm, - Width of the extrusion slot: 2.20 mm, - Total plastic flow rate: 1800 to 2000 gr / mmr depending on the size of waste, - Temperature at the outlet of the die, 1700C, - Temperature of the rollers 1200C, - Diameter of the rollers at the top of the grooves, 55 mm, - Width of the grooves: 1.37 mm - Width of the grooves: 0.55 mm - Depth of successive grooves from the shearing device
El = 0.9 Z = En
E2: 1.2 Z = E (n-1)
E3 = 1.5 Z = E (n-2)
E4 = ES = ..... = E (n-3) = 1.75 Z - n being the number of grooves and Z = 0.2 mm the desired thickness of the sheath, - Scrolling speed 20 m / mn - Pressure force between the rollers 25 kg, - Sheath shrinkage coefficient, 8%
The number of conductive wires can reach 100 with diameters between 0.16 16 and 6 mm. These conductors are multifilament if their diameter exceeds 0.8 mm.

 The pitch of these conductive wires can be between 0.4 and (several mm), with an edge (extreme lateral part of the lagoon) equal to at least 0.6 mm. The total width of the cable can reach 85 mm. The presence of grooves S allows subsequent separation of the cable into several cables of smaller widths, by simple manual or mechanical tearing. It is also easy to choose a thickness which is sufficiently small for the sheath to allow electrical contacts to be made by perforating the sheath by the pins of the insulation displacement connectors. The ratio of the width of the cable to its thickness can be greater than 100.

 The coated wires according to the invention may already each have a first individual insulating sheath, and be asymmetrically coated. These wires can be of different types in the same cable. It should be understood that the word wire used here designates all kinds of flexible linear elements capable of being coated in an extrudable material. These "wires" can be not only electrical conductors, but also optical fibers, mechanical steel traction wires, pipes for transporting a fluid, etc. the sheath may include a central zone without wires so as to allow its fixing, in particular by stapling.

 The plastic used must be extrudable. The following materials can in particular be used - polyvinyl chloride (PVC) - fluoroethylene-propylene (FEP) - perfluoroalkoxy (PFA) - ethylene tetrafluoroethylene (ETFE) - ethylene chlorotrifluoroethylene (ECTFE) - polyolefins (polyethylene). ..) - polyurethanes and polyamides thermosetting materials provided that they are extrudable such as elastomers.

 The rollers 67, 68 are normally made of bronze. However, in the case of hot tacky plastics such as polyurethanes and polyamides, the rollers can be coated with a slightly adhesive material, for example polytetrafluoroethylene (PTFE).

Claims (8)

1 / Device for manufacturing flat cables with wire guide, this device comprising - means for continuously supplying a flat sheet (12) of parallel metal wires (F) moving parallel to themselves in a "longitudinal" direction towards a downstream side "of the device for constituting the conductive cores of the flat cable to be manufactured, - an extrusion assembly (G9) for extruding hot plastic around this layer of wires, - two calender rollers (67, 68), the axes are parallel to this ply of wires and perpendicular to the wires, these two rollers being arranged opposite one another on either side of this ply surrounded by hot plastic, so that these rollers compress between them this plastic material and thus ensure, in the intervals between wires, a weld between the plastic material located on one side of the sheet and that located on the other side, - at least one of these rollers (67) comprising a succession circular hollow grooves (102) separated by raised grooves (104), so that these grooves form on the plastic insulating sheaths in relief (B) succeeding each other along the width of the flat cable and connected to each other by connecting strips (L) of lesser thickness formed by the pressure of the grooves, - these rollers being provided with a shearing device (69, 70) locally compressing the hot plastic to cut it and form an edge of the cable flat, - this device also comprising a thread guide (14) disposed near and upstream of the calender rollers to guide each of the threads (F) of the ply (12) towards one of these grooves (102) so as to place this wire in the axis of the plastic sheath formed by this groove, - and means (G15) placed downstream of the calender rolls to drive the flat cable thus formed, - this device being characterized in that at least one groove (102-1) of these rollers (67, 68) on the road sinage of the shearing device (69, 70) has a reduced depth so that, at a distance from this shearing device, the depth of the grooves is sufficient to be able to absorb a temporary excess flow rate of the extrusion assembly by forming sheaths (B) of increased height on the metal wires (F), and that, in the vicinity of the shearing device, the depth of the grooves is small enough to prevent a permanent excess height of these sheaths due to the fact that the shearing device laterally repels hot plastic. 2 / Device according to claim 1, characterized in that the depth (El) of the groove (102-1) closest to the shearing device (69, 70) is less than 70% of that (E4, E5) grooves (102-4, 102-5) remote from this device. 3 / Device according to claim 1, characterized in that several grooves (102-1, 102-2, 102-3) in the vicinity of the shearing device (69, 70) have a reduced depth, this depth gradually increasing from of the shearing device. 4 / Device according to claim 3, characterized in that the number of grooves (102-1, 102-2, 102-3) with reduced thickness is at least two and at most four. 5 / Device according to claim 1, characterized in that these rollers are provided with a pressure device (74) tending to bring them closer to each other with a constant force while allowing them to move apart 'from each other under the action of a temporary excess thickness of the strips (23, 23') of extruded plastic. 6 / Device according to claim 1, characterized in that the flanks (103) of the grooves (102) are connected at an angle not obtuse to the top band (105) of the grooves, this band and these flanks being seen in section for a plane passing through the axis of the roller (67), this so that the zone of this connection constitutes an edge suitable for completely applying the hot plastic material against the part of the surface of each wire close to the plane passing through the axes of all the wires (F).  7 / Apparatus according to claim 6, characterized in that the average radius of curvature of said connection is less than 10% of the width of said top band, this connection preferably being made by a sharp edge. 8 / flat cable obtained by the device of claim 1, this cable comprising - a flat sheet of parallel zetallic wires (F) - sheaths (B1, B4) of plastic material coating these wires - and connecting strips (L) uniting these sheaths, - this cable being characterized in that at least one sheath (B1) at the edge of the cable has, in section, a shape substantially different from the naturally rounded shape of the sheaths (B4) at a distance from the edges of the cable , while having a substantially equal thickness.