FR2506661A1 - APPARATUS FOR THE CONTINUOUS PRODUCTION OF EXTRUDED TUBES REINFORCED BY A METAL WIRE HELD - Google Patents

Abstract

An apparatus for extruding a pipe reinforced with a helically wound metal wire is provided. The helically wound metal wire (13) is fed along a mandrel (4), which is rotatable about its axis and can also be moved along the axis. The helically wound wire (13) is fed from a group of rollers (16), which are arranged around the mandrel (4), contact the wire (13) and are rotatable about their own axes as well as about the mandrel axis. The wire (13) consequently reaches into the plastics extrusion head (1), into which the end of the mandrel (4) extends and bears a free-wheel bush (7) there. There, the metal wire (13) is embedded in the plastic.

Description

 The invention relates to an apparatus for the continuous production of extruded tubes, reinforced by a metal wire wound in a helix.

 Apparatus intended for manufacturing tubes of the above type is already known. Thus, for example, the German patent application DAS 1 160 167 describes an apparatus in which: the metallic armor wire is fed continuously, in a rectilinear movement, to an extrusion head; the metal wire is force-guided by geometrical coupling, up to the # feeding point of the plastic material, where it is incorporated therein; the metal wire is driven by the tubular mass pushed along a calibration path, where the plastic is pressed and calibrated.In this device, the metal wire moves along a fixed mandrel, a certain part of which is hollow, this mandrel being connected by one end to the extruder and having at the end of its cavity a series of slots through which escapes the plastic which comes to wrap and drown the helical wire. The main drawback of such an apparatus is the existence of the hollow mandrel, in which each time a work stoppage or interruption, a large amount of plastic material solidifies and is difficult to remove subsequently .

 The French patent 810 638 describes an apparatus which does not suffer from the above drawback. This apparatus comprises a rotary mandrel, provided on a certain part with a helical groove and surrounded, but at a distance, by a fixed, concentric sheath. The helically wound wire engages in the helical groove of the rotating mandrel and, due to the friction on the fixed sheath, the wire moves axially until it reaches the point of feeding the plastic where it is embedded. At the level of the region where the wire is embedded and the tube is formed, the rotary mandrel carries, mounted idly on this mandrel, a calibration sleeve provided with a recessed or recessed part. The disadvantage in this device is that, during its movement, the metal wire is subjected to a significant friction which quickly wears out the fixed sleeve, and which can lead to the wire breaking.

 Also known, from Italian patent 987 983, an apparatus for the production of the same type of tubes. In one of its modes of implementation, this device corresponds to the device illustrated in the aforementioned French patent, from which it differs only in that, instead of the crazy forming sleeve, this device has a fixed axis at the end of the rotary mandrel. The displacement system used, which is analogous to the system according to the French patent, has the same defects and drawbacks as this patent. In order to partially eliminate the friction between the metal wire and the fixed sleeve, the latter is replaced, in its terminal part, by a bronze bushing, which poses problems of assembly, price and substitution, since the The bronze bushing is itself susceptible to wear. In addition, to reduce the tightening effect that can be exerted on the mandrel by the spring, a mandrel with a relatively large axial length and therefore very bulky has been used. . In the other embodiment of the Italian patent, the roles are reversed between the mandrel (which is fixed in this case), and the sleeve surrounding it (sleeve which rotates on the other hand and which is provided with a groove helical). The principle, on which this second solution is based, corresponds to the principle of the German patent mentioned above, and the same drawbacks as those of the first solution remain.

 The present invention relates to an apparatus intended for the production of extruded tubes, armed with a metallic wire wound in a helix, an apparatus which makes it possible, by means of a judicious reduction of friction, to eliminate the drawbacks of the previous solutions, described in this who is before.

 The above object is achieved according to the invention by an apparatus of the type comprising a mandrel extending to an extrusion head and a device for continuously feeding, in a straight line, a metal wire wound in a helix, the along the mandrel towards the extrusion head where the wire is embedded in the plastic; the apparatus is essentially characterized in that the device, making it possible to advance the metal wire, acts on this wire by means of a series of rollers arranged # around the mandrel, and moved by means which drive the rollers rotating about their own axis and the axis of the mandrel.

 According to an advantageous aspect of the invention, the mandrel is mounted so as to allow it to rotate around its own axis from motor means placed under the control of at least one sensitive member which detects the diameter of the propeller formed by the metallic wire.

 According to a characteristic of the invention, the channel or channels, established in the extrusion head for conveying the plastic material into the annular intermediate forming space receiving the end of the mandrel, are directed in a direction approximately perpendicular to the axis of the mandrel.

 Advantageously, the mandrel carries, mounted idly on the terminal part of the mandrel, in a manner known per se, a sleeve or sleeve, preferably made of polytetrafluoroethylene, which internally delimits the intermediate forming space.

The invention will be better understood with the aid of the following detailed description, relating to one of its preferred modes of implementation, shown by way of purely illustrative example, in no way limiting, in the appended drawings, in which
Fig. 1 is a schematic view in axial section of the apparatus according to the invention, and
Fig. 2 is a sectional view along the line II-II in FIG. 1.

 Referring to the figures above, it can be seen that there has been designated generally, by reference 1, an extrusion head connected to a conventional extruder for plastics, to one or more screws. The plastic material, fed by the extruder, enters along arrow A, in a substantially conical passage 2 of decreasing section, which opens into a substantially annular chamber 31 located in a plane substantially perpendicular to the longitudinal axis of a mandrel 4 described in more detail later. The conical passage 2 can be divided into several channels by means of intermediate pieces or longitudinal bridges which make it possible to maintain the two parts 1A and 1B of the head 1 at the necessary spacing distance.

 The annular chamber 3 opens into the passage 5 for forming the reinforced extruded tube, designated by 6. The forming passage is delimited externally by the wall of the hole formed in the part 1A of the extrusion head and, internally, by a sleeve or socket 7, made of polytetrafluoroethylene, mounted so as to be able to rotate on the free end 8 of the mandrel 4, where the socket is held axially by a flange 9 secured by means of screws (not visible) on the head of said mandrel.

 Approximately at the point where the annular chamber 3 opens into the forming passage 5, a chamfer 11 marks the beginning of a collar 10 mounted on the mandrel and which extends over part of this mandrel, ending in a chamfer 12 on the other side. The outside diameter of this collar is substantially equal to the inside diameter D of the helix 13 formed by the metallic armor wire 14, a wire which is wound in a helix around the mandrel by a winding machine known per se, which removes the wire from a reel. This winding machine is well known in the art, so there is no need to describe it here.

 The collar 10 delimits, on a certain part of this collar adjacent to the chamfer 11, an internal annular cylindrical passage, delimited externally by the wall 14 of a hole coaxial with the mandrel, formed in the part 1B of the extrusion head 1. The diameter of this hole is substantially equal to the outside diameter D 'of the propeller 13, which obviously has the purpose of preventing the plastic material supplied by the extruder from flowing to the left - that is to say say in the opposite direction of the forward movement of the propeller 13 - instead of flowing to the right as it should be (with reference to Figure 1).

 To cause the longitudinal displacement of the propeller 13 to the right, there is provided a supply device, designated by 15 as a whole, which is mounted in part 1B of the extrusion head 1, according to the example illustrated .

The device in question comprises four or a greater number of rollers 16 placed at equal angular distances from one another around the mandrel 4, and established to act on the thread of the propeller 13 at the level of the collar 10, these rollers being very close to the surface of the collar. In the particular position of FIG. 2, the regions of the propeller 13, subject to the action of the rollers 16, are designated by B. The rollers act on the propeller 13 by their parts of larger diameter called flanges in the continued and designated by 50, 51, 52, 53. As can be seen in FIG. 1, these flanges are offset axially with respect to one another at the rate of approximately 1/4 of the diameter of the metal wire, which corresponds to the pitch of the propeller 13, when the turns of the latter are approached or approached until contact, as happens in the annular zone delimited between the collar 10 and the wall 14. In addition, although not shown in the drawings, the longitudinal axes
Z of the rollers are preferably not parallel to the longitudinal axis of the mandrel 4 but very slightly oblique (order of the fraction of a degree) relative to this axis, so that said rollers are substantially tangent to the last of the close turns, at points B.

This inclination of the axes of the rollers is equal and in the same direction for all the rollers. The rollers 16 mounted mad inside a cage 17 which is rotatably supported, in any known manner, in the part 1B of the extrusion head. The cage 17 carries at one end a toothed ring 18 which is actuated from a geared motor 21 by means of a toothed wheel 20 and chain 19. Through this mechanical connection, the cage 17 and, consequently , the rollers 16 are driven in rotation around the mandrel in the direction of the arrow X in FIG. 2.

 In the cage 17 is rotatably mounted an actuating member 22, which is axially hollow, that is to say substantially tubular, this member carrying an internal toothed ring 23 with which pinions 24 integral in torsion with the rollers 16 engage. The toothed crown 23 is produced so as to take account of the small inclination of the axes of the rollers 16, by providing for this purpose, for example, clearances, or by giving a barrel shape to the teeth of the crown. The rotation of the member 22 is such that the rollers rotate about their axis in the direction of the arrows J of FIG. 2. This rotation is imparted from the gear motor 21 mentioned above, via a transmission which comprises the toothed wheel 25, the chain 26 and the external toothed crown 27 carried by the member 22. The angular speed of the drive member 22 is greater than the speed of the cage 17; it is chosen in such a way that at each turn of the cage, the rollers 16 accomplish, by any point of their part or zone acting on the propeller 13, a path equal to the development of a turn of the propeller.

 In this way (that is to say, thanks to the forced double rotation of the rollers 16), when the propeller 13 meets the plastic material arriving in the forming path of the chamber 3, the propeller is incorporated into the material, without being subject to dangerous voltages.

 The mandrel 4 is mounted so as to be able to rotate and move axially in supports 30 placed upstream of the point where the metal wire 14 is wound in the helix 13. The axial displacement of the mandrel 4 can be achieved by means of a screw 31 capable of being blocked, guided through a fixed threaded ring 32 and carrying a plate 33 interposed between two collars 34 inside the mandrel 4. This arrangement allows the mandrel to be able to rotate around its own axis. This rotation of the mandrel 4, which is not strictly necessary, but which can be useful, is printed to it by means of a toothed wheel 35, wedged on the mandrel and connected by a chain 36 to a toothed wheel 37 mounted on the output shaft of an adjustable speed motor 38, which is associated with a reduction gear if necessary. The motor speed can be adjusted by an electronic control circuit 39 as a function of a signal reaching this circuit through a potentiometer 40 whose cursor is connected to a pallet 41 movable against the action exerted by springs, this pallet being applied against the propeller 13. The arrangement provides for the use of two or three paddles 41, placed at angular distances therebetween and each cooperating with a potentiometer, the potentiometers being able to be connected in series or in parallel. In essence, the paddles detect a variation in the diameter of the propeller 13 and control the motor 38 so as to compensate for this variation, which is due to a difference between the speed of the propeller 13 absorbed by the plastic material and the speed propeller supply.

 It has in any case been found that a slow speed of rotation of the mandrel 4, even when the adjustment circuit is absent, goes to the benefit of the quality of the product. In the alternative, the control circuit just described could act on the production speed of the machine forming the propeller, instead of acting on the mandrel 4.

 The operation is as follows.

 A conventional winding machine forms the propeller 13 on the mandrel 4. The propeller moves axially under the effect of the device 15 which sends it to the annular space, delimited between the collar 10 and the wall 14, where the propeller turns are packed. Where this annular space widens, at or near the exit from chamber 3 through which the plastic material escapes, the turns unfold and are enveloped by the material. The reinforced tube is formed in the forming path 5 existing inside the extrusion head 1, and the tube thus formed is put into a coil after cooling.

Claims (10)

Claims  1. Apparatus for the continuous production of extruded tubes, reinforced by a helically wound metal wire, which comprises a mandrel extending to an extrusion head and a device for continuously advancing, in a straight line, a metallic wire wound in a helix, along the mandrel, towards the extrusion head where the helical wire is embedded in the plastic material, characterized in that the device, advancing the wire, acts on the metal wire through a series rollers arranged around the mandrel, the rollers being driven by actuating means which cause rotation about their own axis and the axis of the mandrel.  2. Apparatus according to claim 1, characterized in that the rollers are rotatably mounted in a cage which is operatively connected with the actuating means.  3. Apparatus according to claim 1, characterized in that the rollers are operatively connected with the actuating means through toothed couples.  4. Apparatus according to claim 3, characterized in that the toothed couples comprise a pinion integral in torsion with each roller and a toothed crown, the toothed crown being moved by the actuating means and the pinions meshing with the toothed crown.  5. Apparatus according to one of the preceding claims, characterized e e that the ring gear is rotatably mounted inside the cage and is coaxial therewith, the cage and the ring gear being both traversed by the mandrel.  6. Apparatus according to one of the preceding claims, characterized in that the mandrel is mounted so as to be able to rotate it around its own axis from the driving members.  7. Apparatus according to claim 6, characterized in that the drive members are placed under the control of at least one sensitive member established to check the diameter of the metal wire wound in a helix.  8. Apparatus according to one of the preceding claims, characterized in that the or the channels bringing the plastic into the tube forming channel where the end of the mandrel ends, are substantially perpendicular to the mandrel.  9. Apparatus according to one of the preceding claims, characterized in that the mandrel carries, mounted idly on the end portion of the mandrel, an annular body.  10.Apparatus according to one of the preceding claims, characterized in that the mandrel can be moved axially.