US 3769697 A
Method and apparatus for manufacturing long lengths of flexible waveguides which have an inner wall of a helically wound insulated conductor covered by insulating or metal tape over which a thermoplastic sheath is extruded, in which the insulated conductor is wound in a helix and advanced successively through tape winding and sheath extruding machines at a rate which permits each operation to be continuous. Subsequent to the extrusion of the sheath it is cooled and the waveguide is wound on a bobbin. Armoring and protective layers may be added to the waveguide prior to or subsequent to winding of the waveguide on the bobbin.
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Description (OCR text may contain errors)
United States Patent [1 1 Priaroggia et al.
[ METHOD AND APPARATUS FOR THE CONTINUOUS MANUFACTURE OF A FLEXIBLE WAVEGUIDE  Inventors: Paolo Gazzana Priaroggia, Milan;
Antonio Portinari, Sesto San Giovanni, both of Italy  Assignee: Industrie Pirelli Societe Per Azioni Centro Pirelli, Milan, Italy  Filed; May 3, 1971  Appl. No.: 139,633
 Foreign Application Priority Data May 8, 1970 Italy 24300 A/70  References Cited UNITED STATES PATENTS 3,391,525 Ostennann 57/9 Nov. 6, 1973 Primary Examiner-Charles W. Lanham Assistant ExaminerCarl E. Hall Attorney-Brooks, Haidt & Haffner  ABSTRACT Method and apparatus for manufacturing long lengths of flexible waveguides which have an inner wall ofa helically wound insulated conductor covered by insulating or metal tape over which a thermoplastic sheath is extruded, in which the insulated conductor is wound in a helix and advanced successively through tape winding and sheath extruding machines at a rate which permits each operation to be continuous. Subsequent to the extrusion of the sheath it is cooled and the waveguide is wound on a bobbin. Armoring and protective layers may be added to the waveguide prior to or subsequent to winding of the waveguide on the bobbin.
4 Claims, 1 Drawing Figure METHOD AND APPARATUS FOR THE CONTTNUOUS MANUFACTURE OF A FLEXIBLE WAVEGUIDE The present invention concerns method and apparatus for the manufacture of a flexible type of helical waveguide in a continuous manner and in relatively long lengths.
Examples of the types of waveguides to which the invention applies are shown and described in our copending application (P-333), filed concurrently herewith and entitled Improved Helical Waveguide. Such waveguides have an internal helix of insulation covered metal which is covered with a layer of insulating or metal tape. A'sheath in the form of a layer'of thermoplastic material is extruded over the layer of tape, and such sheath is normally covered by an armor, such as a layer of wires. Normally, also, the armor is covered by an external protective layer, such as a layer of impregnated jute or a layer of thermoplastic material. Although said application shows only the use of metal strap for the helix, this invention is equally applicable to the manufacture of helical waveguides having a helix made of a conductor having a different cross-section, e.g. circular.
The process in use up to the present time for the manufacture of helical waveguides enables the manufacture of sections of guide having only a limited length of a few meters and which, during installation, have to be connected together using a corresponding number of joints which, even though the connecting operation is carried out with the utmost care, produces points of discontinuity that inevitably lead to losses in transmission of the main wave mode.
Such known process comprises winding on a mandrel a helical coil of insulated wire with the turns in good alignment and near to one another and in subsequently covering the resulting helix with a sheath of synthetic resin.
The present invention aims at providing a process for the continuous manufacture of flexible helical wave guides, the length of which is limited only by the capacity of the take-up bobbin, so that in an installation the joints are reduced to a minimum and consequently the losses due to discontinuities decreases.
In particular, the present invention aims at providing a process for the manufacture of a flexible type of helical waveguide, by means of which the helix is formed by winding a conductor on a suitable device, characterized by the fact, that it consists in the continuous formation of this helix while simultaneously moving it along in the direction ofits axis at a speed synchronized with that of the formation of a synthetic resin sheath thereon by extruding the material of the sheath on the advancing helix.
A further object of the invention is to provide apparatus designed to carry out the process according to the invention, characterized by the fact that such apparatus comprises: a wire-distributor head on a device designed to receive the helix being formed and to guide it in the direction of its axis, a pressure and pulling device designed to adjust the speed of movement of the helix and synchronize it with the formation speed, and following such-device at least one extrusion head for extruding a sheath on the advancing helix.
The attached drawing illustrates by way of a nonlimiting example, a presently preferred embodiment of the invention, and such drawing, I
The FIGURE represents diagrammatically a production line including apparatus which permits the process to be carried out according to the invention.
The production line and apparatus shown in FIG. 1 comprises a wire-distributor head 10, a device 11 designed to receive the helix being formed and guide it onwards. The device 11 is, for example, a mandrel either fixed or, if desired, rotating on its own axis which extends for length starting with the helical waveguide formation up to a point at which the helix is stabilized. A pressure and waveguide pulling device 12 is arranged around the mandrel 11, and the devicelZ preferably is composed of four drive elements, each including a continuous elastic belt 20 extending around two rollers 21, at least one of which is driven so that the portion of the belt which contacts the helix 24 moves the helix from left to right as viewed in FIG. 1. The number of these drive elements can obviously be different from four or the pulling device 12 could be another conventional pulling device.
A lapping head 13 is situated downstream from the device 12 and is followed in order, by an extruder 14 and a cooling bath 15, containing a second pulling device 16 for the adjustment of the axial load on the waveguide. Such device 16 as in the case of pulling device 12, comprises four elements, each comprising an elastic belt 22 moved by at least one ofa pair of rollers 23. As with the pulling device 12, the number of elements making up the pulling device 16 could be different from four or the device 16 could be another known type of pulling device.
A rotatable bobbin 18 takes up the waveguide 17 at the end of the manufacturing process.
The forming head 10 rotates around the mandrel 1 1 and winds on the latter helix-24 of metal strap or wire made of insulated conductive material (for example, enamelled metal strap or copper wire), so that the turns are wound in perfect close relation, one with the other. The head 10 may wind only a single insulated conductor on the mandrel 11 or could wind simultaneously on to the mandrel 11 a plurality of insulated conductors with their turns interposed and in contact in the event that for construction reasons the helices called for a higher winding pitch than that obtained with only one.
The helix resulting from the simultaneous winding on to the mandrel 1 l of a plurality of insulated conductors is called a multi-start helix. The multi-start helix could also be obtained by uniting a number of metal straps and subsequently winding the element obtained on the mandrel.
The helix 24 on coming out from the forming head 10 is gripped between the elements constituting the pressure and pulling device 12 which, by the belts 20 moved by the rollers 21, force the helix to advance at a speed which is synchronized with that ofthe formation of the helix. The device 12, in addition to being an adjusting unit which enables the advancing speed to be the same as the speed of the helix formation, is also a device which permits the necessary pressure to be applied to the turns of the helix to keep them perfectly adjacent for the whole of their travelling time towards the next production phase of the waveguide.
Downstream of the device 12, the helix 24 is immediately covered with a wrapping 25 of tapes made of a suitable material, for example plastic or metallic, by the lapping head 13 rotating round the axis of the helix. As shown in the drawing, the width of the tape 25 is greater than the distance between corresponding points on adjacent turns of the helix 24.
The helix wrapped in this way enters the extrusionhead 14, where it is covered with a sheath 26 of thermoplastic resin (for example polyethylene or polyvinylchloride.) At this point, the waveguide is complete and it is subsequently passed into the cooling bath l and into the device 16 for the regulation of the axial drive applied to it. v
The application of armoring and protective layers to the waveguide, if required and which have the object of making the sections less liable to changes during the bending and laying operations, can be carried out directly on the line in a subsequent operation, either between the cooling bath and the take-up on the bobbin 18, or in a subsequent operation after the take-up phase. I
It is evident that with the process and the apparatus of the present invention it is possible to manufacture a continuous flexible waveguide of relatively long length, the lengthusually being limited only by the size of the take-up bobbin or storage means.
What is claimed is:
l. A method for continuously manufacturing a flexible waveguide having an inner wall formed by a helically wound conductor and a tubular sheath of synthetic resin therearound, said method'comprising winding a helical conductor into a helix with contacting turns around a support at a first position while simultaneously advancing said helix in the direction of its axis, removing said helix from said support in a direction axially thereof as the helix is formed and advancing and guiding said helix as it is formed to a second position located in said direction with respect to said support while maintaining the turns of the helix in the relation in which they were wound, said advancing, guiding and maintaining being performed by roller means located between said first and second positions, extruding a sheath of synthetic resin around said helix at said second position as it is advanced and synchronizing the rate of winding and advance of said helix as well as the rate of extrusion of the resin of said sheath so that the waveguide is formed continuously with the desired sheath therearound.
2. A method as set forth in claim 1 wherein said waveguide has a layer of plastic tape intermediate said helix and said sheath, said tape having a width greater than the distance between corresponding points on adjacent turns of said helix, said method further comprising wrapping said tape over the turns of said helix intermediate the point of formation of said helix and the extrusion of said sheath therearound, the wrapping of said tape being synchronized with the advance of said helix so that the waveguide is formed continuously.
3. Apparatus for continuously manufacturing a flexible waveguide having an inner wall formed by a helically wound conductor and a tubular sheath of synthetic resin therearound, said apparatus comprising a support for said helix, a wire-distributor head for winding said conductor in a helix with contacting turns around said support, means for feeding said helix from said support in a direction axially of said helix, means in said direction with respect to said head for receiving said helix from said support, for maintaining the turns of said helix in the desired relative positions and for advancing said helix in the direction of the axis thereof at a speed synchronized with the rate at'which said helix is formed, and an extrusion head in said direction with respect to said advancing means for receiving said helix and extruding said sheath thereover as said helix is continuously formed and advanced.
4. Apparatus as set forth in claim 3 further comprising a tape lapping head for wrapping tape on said helix disposed intermediate said advancing means and said extrusion head.