US2564880A

US2564880A - Apparatus for compressing thermoplastic masses

Info

Publication number: US2564880A
Application number: US9581A
Authority: US
Inventors: Colombo Roberto
Original assignee: Individual
Current assignee: Individual
Priority date: 1944-02-15
Filing date: 1948-02-19
Publication date: 1951-08-21
Anticipated expiration: 1968-08-21
Also published as: BE478479A; DE879914C; GB628468A; CH250430A; NL68958C; FR958938A

Description

Allg 21, 1951 R. COLOMBO 2,564,880

APPARATUS FOR COMPRESSING THERMOPLASTIC MASSES Filed Feb. 19, 1948 v FQ l.

. INVENTOR alvcirv 67020122170 Patented ug. 21,; 1951 UNITED STATES PATENT OFFICE.

APPARATUS FOR COMPRESSING THERLMTPLASTIC lMASSES Roberto Colombo, Turin, Italy Section 1, Public Law 690, August 8, 1946 Patent expires February 15, 1964 3 Claims. Al

This invention relates to an apparatus for the compression of plastic masses more particularly in extrusion presses.

It is well known that many synthetic resins, before they can be reduced to articles of manufacture, are in a pulverulent condition and have a very low apparent specific weight. In order to utilise them, either in the form of pressing powders or for the manufacture of proled articles it is necessary previously to incorporate therein softening, plasticizing agents, or pigments, filling substances and so on. It is therefore necessary thoroughly to mix these synthetic resins, .generally at a temperature over 100 C. and 'under a high pressure, in order to mix the raw materials with the auxiliary ingredients. The methods employed heretofore for this preliminary treatment of plastic masses are based upon the use of solvents, mixers and, finally, extrusion presses.

This invention relates to a device of the latter class which affords the following advantages over those employed heretofore:

1. Thorough mixing of the ingredients,

2. Strong power of reduction of the specific volume from the initial pulverulent to the final compact state,

3. Production of very high pressures at the outlet of the material,

4. Extreme simplicity of the apparatus which is strong and inexpensive, easily cleaned, which is important when colours of type of material under treatment when going over from one colour of type of material under treatment to another,

5. Large output with inexpensive means.

It is essential to fulfill all these requirements for obtaining articles of manufacture of constant quality and having the best properties.

The apparatus comprises a central body of conical spiral shape, which is moved eccentrically and parallel to itself within a chamber in the shape of a conical screw. The movement performed by the central body is only a circular movement of its axis parallel to itself, so as to displace the turns of the conical spiral of the inner element within the turns of the conical spiral of the stationary outer element, thereby gradually displacing the line of contact of the various turns over the full quadrant. As the diameter on each turn of the inner element is smaller than the diameter on the corresponding turn of the outer element, a chamber is formed between the two turns in which, by effect of the above described movement, the material is rapidly pushed forward as it is strongly compressed through the correspondingly rapid reduction in volume of the chamber confined by one turn with respect to the volume of the chamber limited by the preceding turn. The pitch of both spirals, the inner and outer one, is of course the same. Moreover, the above-mentioned difference in diameter between the cooperating turns of the two inner and outer elements has to be twice the eccentricity of the movement performed by the inner element. The material which has been admitted in a pulverulent condition through the inlet situated near the largest diameter of the outer element, will issue in a thoroughly mixed and considerably compressed condition through the outlet near the front end at which the inner and outer conical spirals abut. The desired compression is of course determined by the axial extent of the steps of the helices and the output of the machine by the pitch of the spiral. A baclrflow of material from the outlet towards the inlet is impossible, since each turn of the inner element contacts along a line parallel to the axis of said inner element with the corresponding turn cf the outer element. When it is desired to compress the material to a still higher degree, the inner and outer conical spirals are given a pitch gradually decreasing from the inlet towards the outlet end.

When high compressions are not required, but it is desirable to convey a large quantity of material under a relatively low pressure, the pitch of the spiral may increase from the inlet towards the outlet, thereby gradually increasing the section of the chamber between the two screws.

The apparatus is either heated or cooled, depending upon the nature of the material treated.

The accompanying drawing shows by way of example one particular construction of apparatus according to the invention.

Figure 1 is an axial view of the inner conical helix;

Figure 2 is an axial section of the outer conical helix;

Figure 3 is a sectional View of the assembled apparatus with the members adapted to impart the above described movement to the inner and outer element, respectively.

Fig. 4 is a partial section of Fig. 3 on line IV-IV.

Referring to these drawings l denotes the inner conical helix and 2 the outer casing of the apparatus in which the outer conical helix 3 is formed, having on each winding the same pitch as the inner helix I, but of a larger diameter, the difference 3a between the two diameters being twice the eccentricity of the movement of the element I with respect to the element 2. 1n Figure 3, the inner helix I is in the position in which its turns are in contact with those of the outer helix 2 along a stepped line (shown underneath the axis in the section plane in which the gure is drawn) whilst in the diametrically opposed position there is the largest section of the chamber C formed between the turns of the two elements I and 2; the inner element I has a journal 4 the axis of which is indicated by X--X and on which the worm wheelV with an eccentric axis Y-Y is mounted through a co-axial bushing 5, and receives motion through an endless screw 1, Figi 4. The worm screw 6 is guided through the interposition of rollers 8 on the rings 9 and the axial thrust is supported by the disc I with the interposition of balls I I. Due to the eccentricity of the worm wheel 6 and its annular supports II with respect to the journal 4 on which said wheel is mounted, a movement parallel to itself is imparted to the journal 4, resulting in the displacement of its axis X-X about the axis Y-Y which brings about a similar movement of the inner conical helixfrI with respect to the element 2. The material is fed into the inlet I2 and discharged through the drawing-die I3 formed in the casing 2 in its front portion, strongly compressed because of the rapid reduction of the helical chamber through which it is fed. The apparatus is of extreme simplicity, since it consists of only three parts which are of simple construction and easily dis-assembled.

The constructiona1 details of the apparatus may be varied from the example shown and described, without departing from the scope o this invention.

What I claim is:

l. Apparatus for mixing and compressing plastic masses, comprising an inner spiral member mountedV on a cylindrical journal, an outer spiral member having its turns equalling in axial extent associated turns of said inner member, the diameter of the turns of the inner member dii"- fering from the diameter of the associated 'turns 45 of the outer member by a constant value, means for holding the axis of said inner member parallel to the axis of the outer member, means for revolving the axis of said inner member about the axis of said outer member, so that each turn of the inner member constantly contacts along a line parallel to the axis of said member with the associated turn of the outer member, means for preventing rotation of the inner member about its own axis, the turns of said inner member coming progressively into contact with those of the outer member, thereby pushing forward and compressing the material entering at the outer periphery of the spiral of the outer member and issuing centrally at the front end thereof.

2. Apparatus for mixing and compressing plastic masses, as claimed in claim 1 wherein the pitch of the inner and outer member gradually decreases from the inlet towards the outlet end, in order to increase the compression of the ma; terial;

3. Apparatus for mixing and compressing plas; tic masses, comprising an outer spiral member, a ring xed to said outer spiral member, a worm wheel mounted on said ring through the interposition of rollers, said worm wheel being eccentrically bored, means for actuating said worm wheel, a bush in the eccentric bore in said worm wheel, a cylindrical journal in said bush, an inner spiral member xed to said cylindrical pivot and having its turns equalling in axial extent the associated turns of said outer member, the diameter of the turns of the inner member diiering from the diameter of the associated turns of the outer member by a constant value, each turn of the inner member constantly contacting along a line parallel to the axis of said inner member with the associated turn of the outer member, means for preventing rotation of the inner member about its axis.

ROBERTO COLOMBO.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,353,917 Lambert Sept. 28, 1920 1,904,884 Royle Apr. 18, l933 2,343,529 Brown Mar. '7, 1944