Process for the continuous separation of discarded hygiene articles into their components

There is provided a process for the continuous separation of discarded hygiene articles into their components, namely flock and/or cut absorbent materials on the one hand and sheet coverings on the other comprising first tearing the discarded hygiene articles into large pieces and then conducting the pieces over an oscillating sieve surface, preferably over an oscillating sieve device having decreasing mesh widths with the smallest mesh width being so selected that the flocculent and/or cut absorbent material still can fall through while the large pieces of torn covering are always carried off as sieve residues.

BACKGROUND OF THE INVENTION 
The invention is directed to a process for the continuous separation of 
discarded hygiene articles into their components, namely flocculent and/or 
cut absorbent material on the one hand and sheet coverings on the other. 
In the production of hygiene articles for one time use, the so-called 
discardable or single use hygiene, articles such as diapers, sanitary 
napkins, sick bed linings or the like there always occur a certain 
proportion of defective goods. This so-called scrap as a rule is 
unmarketable and increases the cost of production since it results in the 
lost of ultimately valuable raw material. 
In view of the overall scarcity and above all, increase in expense of raw 
materials it is of considerable importance to recover scrap material. This 
is also true for hygiene articles of the type mentioned whose absorbent 
material for the most part consists of flocculent cellulose and whose 
covering or coverings for the most part consist of (synthetic resin) film 
and fleeces. For a reworking these must with the finished hygiene article, 
including the scrap goods, next be separated to a unit of combined 
components. 
There has already been proposed by the applicant a process and an apparatus 
for this purpose, see German OS No. 27 03 063. The process consists of 
conveying the hygiene article discontinuously into the entrance area with 
carriers rotating at high peripheral speed, whereby the covering synthetic 
resin films are torn off and unwound and enclosed cellulose set free and 
drawn off with suction and subsequently the synthetic resin films are 
dissolved with cutting up of the carriers and are separately drawn off 
with suction. 
Accordingly, to the known process, however, it is only possible to work 
discontinuously which does not permit the throughput of large amounts per 
unit of time. Furthermore, the sheet coverings must be further cut up 
before they again can be free and can be removed. Naturally this means a 
proportionately high mechanical expense. 
This is the starting point for the invention. It is based on the problem of 
developing a process which permits the continuous separation of discarded 
hygiene articles into their components, namely flocculent and/or cut 
absorbent materials on the one hand and sheet coverings on the other. 
Thereby the process should permit a high throughput without too great a 
mechanical expense. 
SUMMARY OF THE INVENTION 
This problem is solved according to the proposal of the invention in a 
surprisingly simple manner by first tearing the discarded hygiene article 
into large pieces and then conducting them over an oscillating sieve 
surface, preferably over an oscillating sieve device with decreasing mesh 
widths with the smallest mesh width being so selected that the flocculent 
and/or cut absorbent material still can fall through while the large 
pieces of torn covering are always carried off as sieve residue. 
The tearing in each case need only take place until the absorbent material 
falls out of the sheet coverings. The mechanical expense for this can be 
held proportionately low. Suitable tools or apparatus for the tearing for 
example are so-called bale breakers or bale tearers such as are employed 
for breaking up cotton balls in spinning mill operations. 
The true separation takes place subsequently with the help of known 
oscillating sieves (or screens) wherein the flocculent material is finally 
recovered in each case as screen undersize and the coverings in each case 
recovered as sieve residue. This process step can be accomplished in many 
variations. In the simplest case a simple oscillating sieve is sufficient. 
Suitably the transportation of the sieve goods is effective over the 
oscillating sieve surface by the oscillating sieve itself which for this 
purpose can be inclined particularly in the transportation direction. 
The sharpness of separation increases first with the length of the 
oscillating sieve, however, above all can be increased by using an 
oscillating sieve device with decreasing mesh widths. For this purpose 
several oscillating sieves can be arranged in succession and the sieve 
undersize in each case again be led to the subsequent oscillating sieve 
via a chute, slide, a conveying belt, etc, while the sieve residue in each 
case is immediately separated and removed in common. 
Especially simple and advantageous is an oscillating sieve device with 
several oscillating sieves arranged one above the other. Thereby the sieve 
undersize without further help in each case goes to the next smaller 
oscillating sieve where a further separation occurs into absorbent 
material and coverings. 
The sieve residue of each sieving step is always collected on the sieve 
surface until it goes over a wall of the oscillating sieve and can fall 
downwardly where it can be collected in a chute, slide, on a conveyor 
belt, etc. and removed. With the sieve residues in each case it is a 
matter of formerly sheet covering which, according to the degree of 
comminution, earlier or later accumulate as sieve residue, i.e. the 
smaller the coverings are torn the more frequently they can still pass 
through individual oscillating sieves with the absorbent material and the 
later they form a sieve residue. Thereby the smallest mesh width is so 
chosen that finally only absorbent material can fall through. 
Finally the process can also be carried out advantageously with oscillating 
sieves whose mesh widths continuously decrease within the same oscillating 
sieve. 
As a result the invention permits the use of a continuous stream of 
material so that a higher throughput is attained. The mechanical expense 
needed is proportionately small since for the true separation there are 
essentially needed only large surface oscillating sieves worth the price. 
Compared with the above mentioned known discontinuous process besides 
there can be eliminated the inclusion of compressed air conveyor systems 
as well as an air deposition with filtration. Through this there is saved 
a considerable expense, furthermore, the development of noise is lower. 
According to a further proposal of the invention a fine separation is also 
possible in which even the portion of formerly sheet coverings still are 
separated which are torn so exceptionally small that they are able up to 
the final to pass through the screen area together with the absorbent 
material. The process consists of leading the flocculent and/or cut 
absorbent material together with any remaining residual covering after the 
sieves past on an electrostatically loaded surface, preferably of a 
conveyor belt. 
The process uses known electrostatic effects whereby there is assumed 
components with different dielectric constants. This assumption with the 
hygiene articles of interest here in general is true. 
The sharpness of separation can be further increased by simultaneously 
disintegrating the material stream with approach to the electrostatically 
charged surface which for a conveyor belt means that this should be 
carried out in addition to a linear motion with a crushing motion. 
Below there is described a preferred example of the invention and the 
invention will be further explained therethrough. 
The process can comprise, consist essentially of or consist of the steps 
set forth.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The scrap from the discardable disposable hygiene articles is first 
supplied to a bale tearer and torn therein into large pieces. Next the 
mixture of absorbent material and coverings is fed by means of a conveyor 
belt to the first, i.e., uppermost oscillating sieve (screen) of a 
multistage oscillating sieve device. Below this oscillating sieve there 
are located further oscillating sieves with successively decreasing mesh 
widths. 
Dependent on the motion of the oscillating sieve the material stream 
migrates over the sieve surface of the oscillating sieve whereby the sieve 
residue in each case at the end of an oscillating sieve goes beyond its 
wall and then was caught and removed. This was continued from stage to 
stage until after the last oscillating sieve there only remained available 
as sieve undersize flocculent and/or cut absorbent material without its 
sheet coverings and this was removed. 
The oscillating motion of each individual oscillating sieve as well as its 
length and mesh widths are so laid out that always only sheet coverings go 
over the wall at the end of each oscillating sieve, i.e. substantially 
freed from flocculent and/or cut absorbent material. The coverings are 
carried away by means of conveyor belts and pressed by means of known 
process to transport bales for a further processing. The flocculent and/or 
cut absorbent material in contrast can be again supplied directly to the 
production process for new discardable hygiene articles.