IL23899A - Method and apparatus for the production of a continuous plastic envelope on bars,pipes and the like - Google Patents

Description

A ΜΕΤΙ-ΟΏ AND APPARATUS FOR THE PRODUCTION OF A CONTINUOUS PLASTIC ENVELOPE ON BARS. PIPES AND THE LIKE nain m o^ ^O ns**^ ¾pnm nsTisn firms .mtnsa The invention relates to a method for the production of a continuous plastic envelope on rods, bars, pipes and the like, in which the plastic emerges in a known manner under pressure from an extruder head and envelopes a corresponding core profile.

I the methods for enveloping a core profile with a plastic envelope known up to now the extruder head had to be closely adapted to the profile bar to be enveloped which led to considerable costs since the necessary working steps were extended.

The invention shows a method and a device avoiding this disadvantage.

Furthermore it has been very difficult up to now in the known methods to homogenize the plastic before covering the core profile. The invention avoids also this disadvantage.

Moreover the invention shows a method and a device by which a plastic envelope may be produced in a continuous production method with an extruder head, which plastic envelope is produced with different colours along its periphery.

The methods known up to now have also the disadvantage that the plastic envelope must always be in close contact with the core profile to be enveloped. The invention shows a novel method and a device in which the ready plastic profile may differ from the core profile.

Further advantages of the invention are a considerable increase of the output speeds at the extruder head. These have been between 1 to 2 m per minute in the machines used up to how, whereas 6 to 8 m per minute may be produced easily by the method according to the invention.

Thus the invention relates to a method for the production of a continuous plastic envelope on rods, bars pipes and the like and is characterized in that the plastic fed under pressure to an extruder head arranged in a press means emerges independently from the core profile to be enveloped for example with a tube-like configuration. Thus a considerable simplification of the production of the parts for the extruder head is guaranteed.

In the method according to the invention a profiling means may be provided behind the press means, looking in the feed direction of the core profile, for giving the desired profile to the plastic tube.

The feed speed of the core profile and the plastic tube may be equal or different at the seating area of the plastic tube on the core profile. The feed speed of the core profile may also be higher on this point than that of the plastic tube.

In order to increase the production speed and to guarantee a more uniform seating respectively adhering of the plastic covering to the core profile, a heating means according to the invention may be provided before the press head means looking in the feed direction of the core profile, which heats the core profile to be enveloped by the plastic.

Moreover a milling means may be arranged before the press head means, looking in the feed direction of the core profile, in which the endless fed rod, bar, pipe and the like, may be milled to the desired core profile.

Behind the milling means, but before the press head means, looking in the feed direction of the core profile, a primer application means may be arranged for priming the core profile on its surface and thus smoothing it.

According to the invention a cutting means may preferably be arranged behind the profiling means, which cuts the rods, bars, pipes and the like provided with a plastic envelope to the desired length. A simple circular saw may for instance be used for this.

The core, i.e. the endless fed rod, the bar, the pipe and the like, may be composed of one or several pre-grooved or pre-profiled parts of equal or different lengths which may be staggered with respect to each other. A bar may for instance be composed of three single bars situated one at the side of the other and glued together which may have every limited length; care must, however, be taken to stagger the joins with respect to each other so that the bar has a sufficient mechanical stability.

The device according to the invention for effecting #he method comprises a press head means provided with an extruder head; the plastic tube emerging from the extruder head is not only adjustable with respect to its wall thickness but is also adjustable with respect to the exfcentricity of the inner wall periphery in relation to the outer periphery, so that an adaptation of the plastic tube to the desired final plastic profile is guaranteed. The invention allows to provide even rectangular core profiles with a plastic envelope having the prescribed cross-section area at the desired points by using an extruder head having a conical inner head part and having an outer head part, being the only component to be According to the invention it is moreover possible to feed to the extruder head additionally a plastic material of another colour than that ϋ,βά by the main worm press .

The extruder head according to the invention is detachably arranged in the press head means. The press head means contains a guiding means for guiding the core profile to be enveloped with plastie material. The guiding means carries a guide body for the plastic material on its exterior periphery and may moreover support so-called guide fins for the plastic material. Furthermore colour guide fins may be provided on the periphery of the guiding means if coloured envelopes are desired. The guiding means itself carries a conical head part at its front extremity and is provided with bores extending in an axial direction for receiving heating cartridges. Besides these bores continuous botes are provided in an axial direction which extend also through the conical head part in the same direction, the space between the core profile and the plastic tube being either connected with the atmosphere or with a vacuum pump which contributes to guaran- teeing not only a plastic envelope on the core profile, but also a removal of steam, generated by the heat of the press head means and the hot plastio materi if core profiles composed of wood with a wet surface are used.

Thus it is avoided that the plastic material inflates before it has come into , =a^=seaAia^=-i- contact with the core profile.

In order to homogenize the plastic material an ex- changeable filter may be provided according to the invention between the guiding means and the output of the worm press which allows a cleaning of the filter without interrupting the production process. The filter means maybe heatable.

The extruder head consists of the conieul head part fastened on the guiding means and of an adjustable and exchangeable mouth-piece. This mouth-piece may be provided e on its inner priphery with ribs or grooves extending in an axial direction. The extruder head is furthermore provided with a retaining ring having tangential holes for receiving heating rods.

The above-mentioned vacuum pump is connected opposite to the extruder head to the holes extending continuously in an axial direction through the guiding means. e housing of the press head means may be provided at the level of the colour guide fins with at least one hole for the feed of the coloured plastic material and with a press for this coloured plastic material, '^he coloured plastic material may of course also be injected hydraulically or by some other means at this poin?. The press head means is provided with several spaced holes on its periphery for receiving heating rods. The holes may of course be arranged also in such a way that hot steam may be fed through them.

The profiling means according to the invention has guiding track provided with holes, slots and the like and exhaust pipes for building up a vacuum at specific points of the plastic envelope. Thus it becomes possible that the plastic material is in contact with the core profile in the points the plastic material is in a certain distance from the core profile so that finally a plastic profile is obtained which is not identical with the core profile, but differs from this.

The profiling means may furtheron contain a cooling means so that the core profile enveloped by plastic material leaves the profiling means in According to the invention the profiling means may also be configurated in such a way that the guiding track resiliently supported by springs or the like, so that it is ¾¾a^©¾B&==oi=^¾¾¾n^gewB=3^^ able to ield laterally.

The invention is to be described by means of an embodiment.

Pig. 1 shows a summary of the arrangement of the different means for a method for producing a continuous, plastic envelope on an endless rod which consists of single assembled wood bars; Pig. 2 the press head means with the extruder head and a -worm press; Pig. 3a and 3b the guiding means with the plastic guiding Fig. 7,8 and 9 different mouth-pieces of the extruder head; Fig. 10 and 11a plan views of the extruder head with guiding Fig. 1 2 is a specific filter means between the worm press and the guiding means; Fig. 1 3 the exchangeable filter means and Fig. 14 examples of different profiles produced.

Fig. 1 shows the basic arrangement of the different means as they are for example used in the method for the production of a plastic envelope on rods which are composed of single wood bars. An endless rod 1 is fed in the direction of the arrow 2. This endless rod may be assembled in a magazine means and be laminated in such a way that the joints are staggered as shown in the drawing. This rod is milled to the desired core profile in a milling means 3. A priming means 4, i.e. a means to apply an undercoatd or primer, is arranged priming means behind this milling means, in which /the surface of the endless rod is primed and thus smoothed properly. After leaving the priming application means the endless rod enters a heating means ί in which it is preheated. It may, of course, be pre-heated already in the priming application means 4 in order to assure a better and more rapid wetting of the surface by the primer and may then be brought to the desired temperature in the heating means 5· The press head means is shown at 6, to which a worm press 7 is screwed on one side, from which plastic material under pressure is pressed into the press head means. An additional worm pressaand the like for introducing a plastic material having another colour has been indicated in phantom lines on the press head means 8. The extruder head is shown at 9. The plastic material engages with the core profile at 10 at the entry of the profling means 1 1 . A cutting means 1 2 is provided behind length the profiling means 1 1 , which may be adjustable to different by means of the device 1 3. 1 2 may e¾-g« contain a circular saw Pig. 2 shows the press head means 6 with the worm press 7 and the extruder head 9. The plastic material flows through special guiding channels at 14 out of the worm press to the press head means, he rods arranged at 15 may be hollow in their interior and be provided with a heating means. The plastic material then flows in the direction of arrows 16 to the filter means 17 provided with filters 18 and 19. The filter means 17 is provided with bores 20, which may receive electrical heating cartridges or may be formed so that hot steam can be fed through jtshem. The plastic material then flows in the direction of arrow 21 and finally enters chamber 22.

The core profile respectively the endless rod 1 is fed in the direction of arrow 23. The whole press head means is heated by heating means as e.g.. indicated at 24. ¾e extruder head also has a retaining ring 25 provided with bores 26 through which a heating fluid may be fed. These bores may, of course, also r beceive heating cartridges extending in a tangential direction. The endless rod 1 is retained in its position by the guiding means 27. This guiding means 27 carries a conical head part 28 at its front end. This conical head part is part of the extruder head 9. mouth A corresponding c-miitttHr-piece 29 is arranged around the conical head part 28, which is fastened by intermediate rings 30 and 31 and the retaining ring 25. Because of the pressure acting ,the plastic material which has already filled chamber 22 now emerges between the conical head part and the mouth-piece 29 from the extruder head in the direction of arrow 21 in a tube-like, conical form as shown by 32. It engager at point 33, where it is desired, with the core profile respectively the endless rod 1 and enters then the profiling means 11 at 10. f the endless rod consists of assembled wood rods as in the illustrated example, it may be that vapours are evolved on the surface of the rod, which fill the space 34.

In order to avoid that the plastic tube 32 inflates between the emergence from the extruder head 9 and the entry at 10 into the profiling means, axially extending continuous bores 35 are foreseen in the conical head part 28, which extend into the guiding part 27 and have there been designated with 36.

These bores finally open into a space 37 to which a vacuum pump may be connected, so that an inflation of the plastic tube is avoided at 32 and an engagement of the plastic tube at point 10 situated at the entry side of the profiling means is not only promoted, but is also effected with the desired continuity.

Fig. 3a and 3b shows again the guiding means 27 with the conical head part 28 and the continuous bores 36 extending in an axial direction for exhausting the vapours from space 34. The guiding means 27 is furtheron provided with bores 38 receiving heating cartridges so that the endless rod respectively the core profile 1 is heated from the exterior and the plastic material from the interior.

A guide body 39 for the plastic material is fastened on the guide part 27 having at its surface guiding fins 40 for the plastic material in order to dtistribute the e plastic material in a uniform manner around the p iphery of the guide part 27 and thus around the conical head part, which The guide part 27 may also be provided with colour guide ins 41 , between which a plastic material of another colour than that of the material coming from the main worm press may be injected at 42. By a sufficiently high pressure at be==^¾a««= 42 it is avoided that the plastic material coming from the main wotm press passes between the colour guide fins41 so that this pl¾t©o= space is occupied only by the additional plastic material which is then taken along by the main material G¾§P©*S^ in the direction of arrow 43.

It is possible to provide a further set of such colour guide fins together with another injection p¾.aoe for d coloured plastic material in a spaced relation to the first one on the periphery of the guide part 27.

Pig. 4 shows the injection of the coloured plastic material. Plastic material is introduced into auxiliary press means 45 in the direction of arrow 44, out of which the coloured plastic material is fed into the press head means in the direction of arrox* 46.

Fig. 5 and 6 show the profiling means 11. The plastic tube enters at point 10 and is introduced between the pairs of guide track 48 and 56. From point 10 omrords it engages at the desired points with the core profile 1.

The guide track 48 has holes 49 x*hich open into a space 50 which may be connected with a vacuum pump by means of a channe 51. Compressed air may also pumped through guide tracks 48 for obtaining a cooling action. The part 52 of the guide track has a cooling means in its interior which guarantees that the envelope hardens sufficiently at the guiding means 48 so that it emerges at point 53 in finished condition. This the necessary means also contains ^ F&t& riswb connections 54 for cooling water or cooling air.

The pair of guide tracks 48 is resiliently supported by springs 55 according to the invention so that it is able to yield in a vertical direction.

As is clear from Pig, 6 the pair of lateral guide tracks 56 is retained by a spring 57 and thus yieldably supported. Thus a certain elasticity of each one of the pairs of guide tracks is guaranteed and therewith a compensation of irregularities in the thickness of the plastic envelope may be obtained which may occur a± especially at the start of the device when more or less hardened parts are present in the plastic material.

As already mentioned with reference to Pig. 5 the guide track 48 may be formed with holes 49 connected with a vacuum pump so that the plastic material envelope is sucked recess&S (vide Pig. 6) off from d««^©*=pia¾¾¾ 58 of the core profile/and engages at its exterior wall with the guide track 48.

Fig. 7 shows a specific embodiment of mouth-piece 29 provided with grooves 59 for producing a specially formed plastic envelope together with retaining rings 30 and 31.

Pig. 8 finally shows a plan view of the mouth-piece 29 of Fig. 7.

Pig. 9 shows a mouth-piece 29 without grooves.

Pig. 10 shows a plan view of the extruder head, looking in a direction opposite to the feed direction of core profile 1 , and of guiding means 27.

Fig. 11a shows the same view as Pig. 10, the conical head part being, however, provided with ribs on its exterior periphery.. The lower view again shows a lateral view of this head part with ribs 60.

Pig, 11b shows the head part of Pig. 11a in a 90° turned position.

Fig, 12 shows a filter means in perspective view as shown already in Fig. 2. The two heating rods are shown at 20 in the holes of the filters 18 and 19, which are arranged in corresponding holes 61 and 62 of the filter parts 63 and 64.

Fig. 13 finally shows a detachable filter unit comprised of a filter 65 and of a filter 66 shown in its operative position. Electrical heating cartridges 67 which are connected to the mains by a plug 68 are also provided for heating the plastic material. The filter means may be displaced laterally together with the whole frame 69, its path of movement being limited in the one direction by a stop face 70. Another stop face (not shown) is arranged in the other direction. By means of this double filtet means it is possible to maintain one filter always in the path between the worm press and the guiding means whereas the other filter may be demounted and so to have a continuous production.

Fig. 14 shows a series of different possibilities of enveloping a core with plastic material.

Fig. 14a shows a core assembled from two core partial bars which/ has been profiled in the milling means 3 and smoothed at its surface by the primer application means 4. This core is covered with plastic material of uniform thickness around its periphery according to the embodiment of Fig. 14b using an extruder head from which the plastic tube emerges with approx. circular configuration. ¥ith a special form of the inner surfaces of the profiling means 11 it is possible to obtain a series of different 'shaped plastic envelopes varying from the core profile as shown in Fig. 14c, d and e. For example the plastic envelope of Fig. 14c shows a slight variation from that of Fig. 14b only ¾¾¾¾¾¾ f^oflF¾h¾=^ =: xo¾¾:^ whereas it is provided according to Fig. 14d with ribs on the outside or as shown in Fig. 14e, with ribs not only on the outside but also with inwardly projecting ribs. Fig. 14f-k and Fig. 141-p show similar examples based on the same principle. Sxgx x x-Sxxgain XhHKSXHHXXX-fck It must be hoted as particularly remarkable that the sha e or cross section of the plastic material envelope thus produced departs from the shape or cross section of plastic material tube emerging from the extruder with an approx. circular configuration, i.e. in which the plastic material tube has not yet received the final profile when leavin shaped approximately similar the extruder head, but has only been/¾-d¾pt?e¾L=a^r-ex-i-itta-ti-v-e to the final envelope profile with regard to its wall thickness and cross sectional shape.

Claims (10)

C L A I S :

1. A method for producing a continuous plastic coating on elongated articles of uniform cross-section comprising, forming a pliable plastic tube of substantially annular cross^-section having an inner diameter larger than the outer diameter of the artifile to be coated, feeding the article coaxially -with said plastic tube, conforming the cross-section of said pliable plastic tube to the cross-section of said article, and cooling said plastic tube whereby to form a hardened plastic coating on said article.

2. Apparatus for producing a continuous plastic coating on elongated articles of uniform cross-section comprising an extrusion head, an annular extrusion nozsle in said head for the formation of a pliable plastic tube, a bore through said extrusion head, coaxial with and within said annular nozzle for the passage of the article to be coated, at least one passage through said extrusion head communicating with the area betveen the nozzle outlet and the coaxial bore and connectable to a source of vacuum, and profiling means having a passage adapted to receive said plastic tube and the article to be coated and to conform the cross-section of the tube to that of the article, said profiling means including means to cool said plastic whereby to produce a hax'dened plastic coating on said article.

3. Apparatus as claimed in claim 2, wherein the profiling means comprises at least one independently movable element forming a wall of a passage adapted to receive said elongated article and plastic tube, said element being resiliently maintained in position.

4. Apparatus according to claim 2, wherein predetermined sections of the rall of the passage in said profiling means are provided wit apertures connected to a source of vacuum.

5. Apparatus according to claim 2 , wherein said extrusion head is provided with an exchangeable filter for plastic material to be fed to said annular nozzle.

6. Apparatus according to claim 5, wherein said filter consists of a slide including two filter plates adapted to be selectively placed in operable position.

7» An apparatus according to claim 2, wherein means a heating/for the core profile to be enveloped by the plastic is provided before the pross head means looking in the feed direction of the core profile.

8. An apparatus according to claim 2, wherein a milling means for the endless fed rod, bar, pipe and the like, to be milled to the desired core jrofile, is arranged before the press head means looking in the feed direction of the core profile.

9· An appe-ratus according to claim 2 and the foregoing claim, wherein behind the milling means a priming means for priming the core profile on its surface is arranged.

10. An apparatus according to claim 2, wherein behind the profiling means a cutting means is arranged to cut the rods, bars, pipes enveloped with plastic to the desired lengths. Tel-Aviv, 4th of July, 1965 AGENT FOR APPLICANT