GB2070623A

GB2070623A - Methods and apparatus for disintegrating plastics and/or rubber materials

Info

Publication number: GB2070623A
Application number: GB8103308A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1980-02-05
Filing date: 1981-02-03
Publication date: 1981-09-09
Also published as: DE3103311A1; NO155609B; FI69774B; IT8167151A0; NO810383L; JPS56121733A; DK45681A; FR2474893A1; IT1143357B; FI810286L; SE8100221L; FI69774C; AU6664481A; NL8100554A; SE452281B; NO155609C

Abstract

A method of disintegrating plastics and/or rubber material, such as the plastics and/or rubber casings of metal cores, for the purpose of recovering the metal from scrap cables for example. The material to be disintegrated is cooled to a temperature at which it becomes brittle. The embrittled material is then subjected in at least one station to mechanical oscillations which cause the material to disintegrate. The oscillations suitably have a frequency in excess of 30 Hz and an amplitude of about 2-3 mm. The oscillations can be imparted with the aid of a vibratory device with which the embrittled material is brought into contact.

Description

SPECIFICATION Methods and apparatus for disintegrating plastics and/or rubber materials The present invention relates to methods of disintegrating plastics and/or rubber materials such as the plastics and/or rubber casings of metal cores, wherein the plastics and/or rubber material is cooled to a temperature at which it becomes brittle and is then disintegrated. The invention also relates to apparatus for carrying out the methods.

A method has long been sought whereby the rubber or plastics casings of metal cores, such as copper and aluminium cores of insulated cables, copper pipes and the like, can be separated from the cores in a simple and rapid manner, and whereby; in addition to completely separating the casing material from the metal core, the various constituents can also be accurately separated in a ready manner, so that both the metal and the casing material can be re-used.

The method most used earlier has been to burn away the casing material. This method, however, results in the generation of air contaminants which are injurious to the environment, and is now forbidden. Furthermore, when using said method the casing materials cannot be re-used. In another known method, the electric cables were subjected to fragmentation, i.e. were cut or hacked into pieces so small that most of the insulating material automatically fell from the conductors.

This method, however, is relatively time consuming and expensive, besides creating large separation problems.

In British patent specifications Nos. 1 303 1 67 and 1 407 996 there are described methods in which the casing material is first cooled to a temperature at which it becomes brittle, whereafter it is worked mechanically. A serious disadvantage with the apparatus used in accordance with the first mentioned patent specification No. 1 303 1 67 is its relatively complicated design, which includes both a hammer unit and a following separating drum. If, for example, there enters the apparatus at any time a material which has not been sufficiently cooled, the apparatus will become clogged and blocked by an adhering mass which is difficult to clear.The risk of heating the cooled material excessively is also created by the fact that a substantial portion of the kinetic energy represented by the hammer is converted to thermal energy in the casing material. Further, the necessity of using relatively short pieces of conductor, or core, material leads to serious separation problems, especially in the case of thin metal conductors, and hence the plastics and rubber material recovered does not have the desired quality (purity), whereby the value of the material is greatly reduced.

In the method described in the other of the aforementioned British patent specifications, i.e.

No. 1 407 996, a continuous length of conductor is advanced in an apparatus, and successive parts of said length are worked intermittently, with a combined hammer and cutting head. This apparatus has the following disadvantages.

Because the mode of operation is intermittent and because only one conductor length can be worked at a time, the working speed or capacity is low.

The method is best suited for large cables, and cannot be applied efficiently with very thin cables or with cables containing a plurality of separate, insulated conductors. Further, the hammer means must be accurately set relative to the dimensions of the cable being treated, and the cable must have a relatively long length.

The main object of the invention is to provide a method and apparatus of the kind mentioned in the introduction which do not have the aforementioned disadvantages and with which plastics and/or rubber material can be continuously disintegrated in a ready manner, e.g.

for separating plastics and/or rubber casings from metal cores, irrespective of the length, size and number of cores of the workpiece; and with which a plurality of workpieces can be treated simultaneously.

The invention is based on the concept of replacing the known technique of embrittling the casing material and then disintegrating said material with the aid of hammer or cutting tools, with a technique in which, in at least one station, the embrittled casing material is subjected to mechanical oscillations which cause said material to disintegrate. The oscillations comprise pressure waves or pressure pulsations of a constant frequency and which individually possess insufficient energy to crush the material but which when caused to propagate through the material in the form of a substantially continuous mechanical oscillation result in the disintegration of the material as a result of the vibrations therein.

Preferably, the frequency of the oscillations exceeds 30 Hz.

The oscillations can, for example, be imparted with the aid of a vibratory means with which the objects from which the casing Is to be removed are brought into contact. Preferably, the objects are caused to pass between a vibratory plate and a fixed support surface. This permits a large number of cables to be processed simultaneously in the space between the plate and said support surface.

By mounting the vibratory plate on a spring suspension, the size of the gap will automatically adjust to the dimensions of the workpieces, e.g.

the cable, thereby enabling the apparatus to be used for workpieces of different sizes, without needing to reset the apparatus. Tests have shown that the aforesaid oscillations can be effectively transmitted between the different layers of a cable or bunch of cables, and hence the method according to the invention enables the insulating material to be removed effectively also from multiconductor cables comprising several separate insulating casings within an outer casing, and will even allow cables to be processed several at a time. When applying the invention, substantially complete separation is obtained between the metal and the insulation material, thereby to render the recovered material more valuable than that recovered with previously known methods.

In a particularly preferred embodiment of an apparatus according to the invention, there is used a vibratory plate which is suspended from springs arranged at mutually opposite end portions of the plate, and the vibrations are induced in the plate at a location which is closer to the springs at the upstream end portion than the others, and the plate is so arranged that the workpieces to be treated are introduced into a gap between said one end portion of the plate and a fixed support surface. Among other things, this means that in the case of not readily worked casings, energy will be stored in the down stream springs and will be restored with a certain transmission ratio, to the upstream edge of the plate and give rise to an increased abutment force.Preferably, at least said upstream end portion of the plate forms an angle with the support surface, which means that a cable, or workpiece, will be treated progressively in a tapering gap, which is of particular advantage in the case of multicore cables.

Other features of the invention are set forth in the accompanying claims.

The invention will now be described in more detail with reference to the accompanying drawings, in which Figure 1 is an overall view of a plant for disintegrating the insulating casings of cables when applying a method according to the invention, and Figure 2 is a detailed view of a vibratory apparatus according to the invention incorporated in the plant illustrated in Figure 1.

In Figure 1 the reference 1 identifies generally part of a straightening apparatus having a severing means 2. The straightening apparatus comprises a plurality of rollers 3, which co-act to straighten an incoming cable 4. Such straightening apparatus are known and will not be described in detail here.

As shown in Figure 1 , the straightened and severed cable lengths 5 are introduced into a cooling line 6. In practice the position of the straightening apparatus is 900 to that shown in the Figure, so that said cable lengths are oriented transversely of the cooling line 6. The cooling line comprises an elongate insulating housing 7 connected to a funnel-shaped infeed section 8 for receiving the severed cable lengths 5. Arranged for rotation in the infeed section 8 is a rotary vane feeder 9, for feeding batches of cable lengths 5 into the cooling line. The feeder 9 co-acts with plunger means 1 0 for the continued feed of cable lengths 5 through the cooling line. In order to facilitate this further feed of cable lengths 5, the cooling line may slope downwardly relative to the horizontal.

Discharging into the cooling line 6 are a number of pipes 1 through which liquid nitrogen flows from a container 12. So as to cool the cable lengths 5 effectively, a number of fans 13 are provided to ensure that the nitrogen is effectively circulated in the cooling line 6. The line 6 is also provided with a suction fan 14, for evacuating the gas in a controlled fashion. The provision of the rotary vane feeder 9 prevents uncontrolled losses of coolant.

The temperature in the cooling line 6 is sensed by means of one or more temperature sensors 1 5 arranged to cooperate with an amplifier 1 6 which produces an electric signal corresponding to the temperature sensed by said one or more sensors 1 5. This signal is compared in a comparator unit 1 7 with a set-point temperature reference 1 W. The comparator 1 7 is arranged to produce a control signal which controls a control valve 1 9 in the delivery line from the nitrogen container 12. By means of this control equipment it is possible to hold the various sections of the cooling line 6 at the desired temperature level.

Cable lengths 5, the casings of which are now brittle as a result of being cooled, are fed from the line 6 to an apparatus in which the embrittled casing material is disintegrated. The disintegrating means comprises a vibrator unit 20, into which the rigid cable lengths 5 are fed by means of a plunger means 21.

Referring now to Figure 2, it will be seen that the vibrator unit 20 comprises a vibrator plate 22 which is suspended from two upstream and two downstream springs 23 and 24 respectively. In turn, these springs are mounted on beams 25 whose downstream ends can be swung about a fixed shaft 26. The upstream ends of the beams 25 are mutually connected by a rod 27. In the illustrated embodiment, for the purpose of adjusting the height of the upstream ends of the beams 25, said ends are arranged to slide in slots in fixed holders 28 and to be locked in selected positions therein.

Arranged on the plate 22 is a vibrator, which in the illustrated embodiment comprises two unbalanced fly wheels 29 driven by an electric motor, not shown. Vibrations of the desired amplitude and frequency can be obtained by suitable adjustment of the weight, balance and peripheral speed of rotation of the fly wheels 29, in a manner known per se. The vibrator is located nearer the upstream springs 23 than the downstream springs 24.

The reference 30 identifies a fixed support surface which merges at the downstream end of the vibrator with a gid structure comprising elongate rods 31. Located beneath the grid 31 is a receptacle 32 for receiving disintegrated casing material, while a receptacle 33 is located at the terminal end of the grid, for collecting the metal cores 34 in said cable lengths.

In operation, a batch of straightened and severed cable lengths 5 embrittled in the cooling line 6 are fed into the gap between the vibrator plate 22 and the fixed support surface 30, by, means of the plunger 21. The decreasing height of the gap between said plate and support surface results in the progressive working of the casing of the incoming cables during their passage through said gap. Because the casing material is completely stiff, good propagation of the vibrations produced by the vibrator plate 22 is obtained through all the casings in all the cables, so that both the outer casings and the separate casings around individual conductors are effectively disintegrated by the oscillations in the material. The apparatus can also effectively work thin conductors arranged in bunches, i.e. the conductors can be fed to the apparatus in several layers.

Because of the manner in which plate 22 is suspended and the vibrator situated on said plate, when not-readily worked or large cables, or large bundles of conductors, are fed into the apparatus, the upstream end of the plate is lifted, thereby compressing the springs 23 and expanding the springs 24. The energy thus stored in the rear springs 24 is then restored with a given transmission ratio, determined by the position of the vibrator on the plate 22, in the form of a downwardly acting force on the forward end of the plate. The increased abutment force thus obtained facilitates disintegration of the casings of the lengths of cable fed to the vibrator. Good results have been achieved in tests in which the vibrator was so placed on the plate 22 that the ratio of the distances between the vibrator and the upstream and downstream springs, respectively, was 1:4.

Thus the illustrated spring suspension of the vibrator plate 22 enables the disintegrating means to be used effectively with cables whose respective diameters vary within wide limits; and results in an increased abutment force against cables of large diameter or cable-casings which are not readily worked. When the cables to be processed have excessively large diameters, the upstream end of the plate 22 can be raised, with the aid of setting means 27 and 28.

The flywheels 29 of the vibrator are arranged to rotate in the direction of arrow A, so as to advance automatically the cables 5 in the gap between the plate 22 and the support surface 30. The vibratory movement of the plate 22 also creates a winnowing effect, which effectively forces the disintegrated casing material through the grid formed by rods 31, down into the receptacle 32.

When carrying out tests, very good results were obtained when the vibrations created by the plate 22 had an amplitude of 2-3 mm and a frequency of 50 Hz. Despite this relatively low amplitude, a good disintegrating effect was obtained, even in the case of cables having a relatively large casing thickness, which illustrates that the apparatus does not operate by conventional crushing, but that the relatively high frequency is also of decisive significance. The frequency should not be lower than about 30 Hz, inter alia from the point of view of mechanical design, and frequencies higher than 50 Hz can also be used. In those tests carried out, the frequency used was 50 Hz, since this frequency can be readily obtained in practice, with the use of an electric motor.The fact that the apparatus does not function as a conventional crusher is also borne out by the low power required. In the aforementioned tests, the vibrator was driven with a power input of only 500 W, with good effect. In order to increase the capacity of the apparatus, however, a higher input power should be applied, for instance 1 to 1.5 kW. Under all circumstances, however, the power input will be very low per kilogram of disintegrated material, when compared with the power required by conventional apparatus designed for the same purpose.

This low power input means that there is no risk of the casing material being heated excessively as the lengths of cable pass through the vibrator. Heating of the casing material has in practice been found to be so low that several vibratory devices can be arranged in series, if so desired.

A very important advantage afforded by the invention is that the casing material can be removed completely from the metal cores. This means that the metal and casing material recovered in the apparatus has a high commercial value. Since a plurality of cable lengths can be worked simultaneously over the whole of their lengths, the capacity of the apparatus is very high.

The apparatus is also very easy to handle and of simple construction. Normally no adjustments are required when processing cables of respective different dimensions.

In the illustrated embodiment the severed cable lengths 5 are fed to the apparatus transversely.

The lengths are suitably in the order of one metre.

Both shorter and longer cable lengths can be processed, however. It is also possible to feed a plurality of continuous cable lengths axially through a vibratory apparatus according to the invention. The cable may be arranged to run from reel to another during its passage through a cooling line and vibratory apparatus according to the invention. In this way the metal core can be recovered in one single length and may optionally be re-used without first being resmelted.

The aforedescribed embodiment of the cooling line is only to be considered as an example, since it can be modified as desired. Further, the gaseous nitrogen may be replaced with another gas, depending on the desired cooling temperature, which is determined by the casing material. This is well known to the man of average skill in this field, and will not be dwelt upon here. The vibrator unit may also be modified, and, for example, may be arranged for scanning movement relative to the fixed support surface.

The use of vibrations for disintegrating plastics and rubber material in accordance with the invention may also be practiced for removing casings from, for example, plastic-coated copper tubes and the like. Other objects may also be broken up by means of the method and apparatus according to the invention, such as vehicle tyres and the like. These are first divided into smaller pieces, which are then embrittled and passed through a vibratory apparatus according to the invention, where the brittle rubber material is disintegrated.

The invention can also be modified in other respects while the common feature of all embodiments is the use of mechanical oscillations for disintegrating rubber and/or plastics material which has been rendered brittle by cooling. The oscillations can be produced by means of a vibratory apparatus or in some other way, e.g. by powerful compressed-air impulses or the like.

Claims

1. A method of disintegrating plastics and/or rubber material, comprising cooling the material to be disintegrated to a temperature at which it becomes brittle, and disintegrating the embrittled material in at least one station by subjecting it to mechanical oscillations which cause the material to disintegrate.

2. A method according to claim 1, comprising subjecting said embrittled material to oscillations having a frequency above 30 Hz.

3. A method according to claim 1 or claim 2, comprising imparting said oscillations with the aid of a vibratory means with which the embrittled material is brought into contact.

4. A method according to claim 3, comprising passing the embrittled material between a vibrating plate and a fixed support surface.

5. An apparatus for disintegrating plastics and/or rubber material, said apparatus comprising means for cooling the material to be disintegrated to a temperature at which said material becomes brittle, and means arranged to subject said embrittled material to mechanical oscillations which cause said material to disintegrate.

6. An apparatus according to claim 5, wherein the frequency of said oscillations exceeds 30 Hz.

7. An apparatus according to claim 5 or claim 6, wherein the amplitude of said oscillations is approximately 2-3 mm.

8. An apparatus according to any of claims 5 to 7, wherein said means for subjecting said embrittled material to mechanical oscillations comprises a vibratory plate arranged at a short distance above a fixed support surface to form a gap-like passage therebetween through which the embrittled material is intended to pass while in contact with both said vibratory plate and support surface.

9. An apparatus according to claim 8, wherein the vibratory plate is suspended from springs arranged at mutually opposite end portions of said plate; the oscillations are applied to the plate closer to the springs at the upstream end portion thereof; and at least this upstream end portion of the vibratory plate forms an angle with the support surface.

10. An apparatus according to claim 9, wherein the distances between that position on the vibratory where the vibrations are applied and the springs at respective end portions of said plate are in a ratio of about 1:4.