GB1560352A - Extruders - Google Patents

Description

(54) IMPROVEMENTS IN OR RELOCATING TO EXTRUDERS (71) We. VEB ERSTE MASCHINEN FABRIK KARL-MARX-STADT, a corporation organised under the laws of the German Democratic Republic, of 58-60 Kurt-Berthel Strasse, Karl-Marx-Stadt, German Democratic Republic, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The invention relates to a cylinder for an intersecting twin screw extruder, more especially for processing thermoplastics materials, comprising two bores which are parallel in the cylinder housing and which intersect one another and into which bushings, having a wear-resistant internal surface, have been inserted.

It is known to provide the internal cylinder surface of twin screw extruders with a wear-resistant layer of appropriate materials, that is to say to armour it, in ordEr to reduce to a large extent the wear occurring on the internal cylinder surface during the processing of plastics materials.

It has proved to be a suitable appropriate measure for the increase of the duration of use of the cylinders to design the cylinders as cylinder housings and to insert into the double bores respectively shaped bushings which are provided with a wearresistant internal surface.

The insertion of bushings into the cylinder housing has given rise to problems which could partly not yet be solved satisfactorily.

For example, one problem consists in joining the bushing surfaces, which have been cut in accordance with the shape of a circle segment, to jointed cut surfaces, which are located in the gusset area of the two bores, so that there do not arise on the butt joint any gaps into which the plastics material penetrates and decomposes. Fur thermore, the bushing cut surfaces, which taper to form a narrow tongue in the gusset area, should be of great strength, so as to prevent the edges from chipping and also to withstand wear in a satisfactory manner.

It has furthermore proved to be necessary to secure the inserted bushings in their position against rotation.

On a known twin screw extruder, there are inserted in the cylinder housing wearresistant bushings which are connected by welding seams in the gusset throats. To this end, there are arranged in the throats individual chambers by means of welding seams, which alternate in the longitudinal direction with smoothly jointed bushing surfaces.

This constructional form of the bushings avoids the troublesome gaps on the butt joints of the bushings, which are cut out in the shape of circle segments, and ensures easy insertion of the bushings into the cylin eer housing as well as an easy exchange thereof.

The disadvantages of the gusset tips, which are formed by the cut surfaces and which are heavily stressed, as is known, still exist in this constructional form of the bushing. Another disadvantage proves to be the great wall thickness of the bushings that is necessary in order to provide the chambers in the gusset throats and to keep within narrow limits the changes in form andlor position occurring on the bushings as a result of thermal stresses during the welding.

There is known another twin screw extruder into whose cylinder housing simple wearing bushings have been inserted. The wearing bushings consist of sleeves which are cut out in a sector-like manner and of gusset forming wedge-shaped inserts which are inserted between the sleeve cut surfaces.

Bolted joints which are passed through the cylinder housing brace the wedge-shaped inserts, and thus also the bushings, in the cylinder housing.

The high expenditure relative to manu facturing technique for the production of the individual parts as well as the internal shape of the cylinder housing are disadvantageous in this construction of the inserted wearing bushings. Nor can the described constructional form eliminate the known gaps along the butt joints between the sleeves and the wedge-shaped inserts.

The invention preferably assists in reducing the expenditure relating to the manufacture of the wear-reistant bushings, in preventing the penetration of plastics material into the gaps of the joints, and consequently in eliminating the qualityreducing properties of the plastics material with respect to the extrudlate, the plastics material having decomposed in the gaps, as well as in simplifying the insertion and replacement of the bushings in order to lower the expenditure relative to maintainance and servicing and to increase their useful life with respect to wear.

The present invention may provide wearresistant bushings for the cylinder of a twin screw extruder, whose inserted bushings have table gussets, due to a special design of the surfaces of cut, and whose bushings are arranged in the cylinder houing so that a rotation and/or axial displacement of the bushings and the formation of gaps are impossible.

According to the present invention there is provided a cylinder for a twin screw extruder, more especially for the processing of thermoplastics materials, comprising two bores (2), which are parallel in the cylinder housing and which intersect one another longitudinally in a sectional plane (11) and into which there are inserted bushings, which are each radially cut out in the shape of a sector and which are provided with a wear-resistant internal surface, characterised in that a radially cut surface (9) of each bushing (3,4) is formed as an abutting surface (5) at one arcuate end of the sector; and at the other arcuate end of the sector the radially cut surface (10) of each bushing (3,4} is formed as one surface of a gusset tip (7) whose other surface is defined by the internal surface (6) of the other bushing at the sectional plane (11) of intersection of the bores (2); and the bushings it3,4) being arranged in the bores (2) of the cylinder housing (1) relative to one another in such a way that there is provided a support of the abutting surface (5) of each bushing (3,4) on the external surface (8) of the other bushing (4,3); and a flush transition (12) is provided between the internal surfaces (6) of each bushings (3i4) and the cut surface of the other bushing (4,3) which forms the said one surface of the gusset tip.

An advantageous development of the pre sent invention consists in providing the bushings with an improved support of the abutting surfaces on the bushing external surfaces with a shoulder which corresponds in its width to the thickness of the bushing wall.

An additional advantageous development of the present invention consists in that the radially cut surfaces defining the abutting and gusset tip surfaces are arranged alternately along the length of each bushing.

An additional advantage of the present invention for the production of a wearresistant layer on the gusset tip consists in providing, on the internal surface of the uncut bushing blank a groove which during the application of a wear-resistant material on the internal surface of the bushing, is also filled with this material. The radially cut surface is then made at the place of the groove so that the gusset surface with the wear-resistant layer is present when the bushing has been cut out.

For a firm connection of the two bushings, provision is made for a soldered or welded seam being provided in the gusset throats.

The advantages of the invention over the known prior art consist in that the manufacturing of the bushings as well as the difficulty of their insertion into the cylinder housing and the exchange thereof are simplified and in that the bushings are provided with a stable gusset formation which results in a longer resistance to wear.

Due to the connection of the bushings as well as the position in which they are installed in the cylinder housing, the formation of gaps along butt joints is avoided, a quality-retdtucing effect on the extrudate of any material decomposed in the gaps thus being prevented. Furthermore, the position of the bushings in the cylinder housing is secured against rotation and displacement.

The invention will now be explained in detail with reference to an exemplified em embodiment. In the accompanying drawings: Fig. 1 shows, in a partical section, a view of the cylinder housing with the bushings inserted, Fig. 2 shows the details -"X" shown in Fig. 1, in an enlarged illustration, Fig. 3 shows the details "X" shown in Fig. 1, in an enlarged illustration, but as an embodiment with a shoulder on the external surface of one bushing, Fig. 4 shows a view of a bushing with abutting surfaces and gusset tips which are arranged alternate along the length of the bushing, Fig. 5 shows a view of the interconnected bushings, Fig. 6 shows the section A-A accormding to Fig. 5, Fig. 7 shows the section B-B according to Fig. 5, Fig. 8 shows, in an enlarged illustration, the detail "X" shown in Fig. 1 comprising a soldered or welded seam, Fig. 9 shows a front view of the bushing blank with a groove arranged on the internal surface, Fig. 10 shows, in an enlarged illustration, the detail "Y" of the bushing blank shown in Fig. 9, In Fig. 1, the cylinder housing 1 comprising two parallel bores 2, which intersect one another in the sectional plane 11 and into which the bushings 3, 4, which are provided with a wear-resistant internal surface 6, are inserted, is shown in a partical section. Each bushing 3A comprises a pair of radial cut surfaces 9,10.

The Fig. 2 shows, in an enlarged illustration, the detail "X" shown in Fig. 1. The radial cut surfaces of each bushing 3, 4 are formed as an abutting surface 5 at one arcuate end of the sector and at the other arcuate end of the sector as one surface of a gusset tip 7 whose other surface is formed by the internal surface 6 of the other bushing at the sectional plane 11. The bushings 3, 4 being arranged in the bores of the cylinder housing relative to one another in such a way that there is provided a support of the abutting surface 5 of bushing 3 on the external surface 8 of the bushing 4. Between the internal surfaces 6 of the bushings 3,4 is provided a flush transition 12.

Fig. 3 shows the detail "X" shown in Fig.

1, in an enlarged illustration, of an alternative embodiment in which the support of the abutting surface 5 of bushing 3 on the external surface 8 of the bushing 4 can be seen. The external surface 8 of the bushing 4 being advantageously provided for an improvement of the support with a shoulder 13 which corresponds in width to the thickness of the wall of bushing wall 3.

Fig. 4 shows a view of a bushing 3, which is cut out with abutting surfaces 5 and gusset tips 7, being arranged alternately along the length of bushing 3. The projecting surfaces are designed as gusset tips 7 and the recessed surfaces as abutting surfaces 5.

Fig. 5 shows a view of the bushings 3A which have been joined together in accordance with the alternating arrangement of the flush transitions 12.

Fig. 6 and Fig. 7 show the sections A-A and B-B according to Fig. 5, the upper gusset tip 7 and the lower gusset tip 7 respectively being formed by the bushing 3 and the bushing 4 respectively.

Fig. 8 shows the detail "X" in an enlarged illustration according to Fig. 1. For a firm interconnection of the bushings 3 and 4, a soldered or welded seam 16 is provided in the gusset throat 15.

Fig. 9 shows, in a front view, the bushing 3 in its blank state without the sector shaped cut-out. On the internal surface 6, there is located in an appropriate position a groove 14, which is filled with wear resistant material.

Fig. 10 shows the detail "Y" according to Fig. 9 in an enlarged illustration. The bushing 3 is cut out at the point where the groove 14 is positioned, so that on this way a wear-resistant gusset tip 7 with the internal surface 6 is formed.

WHAT WE CLAIM IS: 1. A cylinder for a twin screw extruder, more especially for the processing of thermoplastics materials, comprising two bores (2), which are parallel in the cylinder housing and which intersect one another longitudinally in a sectional plane (11) and into which there are inserted bushings, which are each radially cut out in the shape of a sector and which are provided with a wear-resistant internal surface, characterised in that a radially cut surface (9) of each bushing (3A) is formed; as an abutting surface (5) at one arcuate end of the sector; and at the other arcuate end of the sector the radially cut surface (10) of each bushing (3,4) is formed as one surface of a gusset tip (7) whose other surface is defined by the internal surface (6) of the other bushing at the sectional plane (11) of intersection of the bores (2); and the bushing (3,4) being arranged in the bores (2) of the cylinder housing (1) relative to one another in such a way that there is provided a support of the abutting surface (5) of each bushing (3,4) on the external surface (8) of the other bushing (4,3); and a flushing transition (12) is provided between the internal surfaces (6) of each bushings (3,4) and the cut surface of the other bushing (4,3) which forms the said one surface of the gusset tip.

2. A cylinder as claimed in Claim 1, characterised in that the external surfaces (8) of each bushing (3A) are provided with a shoulder (13) for abutment with the abutting surface (5) of the other bushing.

3. A cylinder as claimed in Claims 1 and 2, characterised in that the radially cut surfaces (9,10) defining the abutting and gusset tip surfaces (5 and 7) extend alternately along the length of each bushing (3,4).

4. A cylinder as claimed in Claims 1 to 3, characterised in that there is arranged on the internal surface (6) of each bushing (3,4) prior to cutting the abutting and gusset tip surface a groove (14) which, is filled with wear-resistant material, at which one of the cuts is effected to form the said one surface of the gusset tip with the wearresistant material after the sector-shaped cut-out of the bushings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. Fig. 5, Fig. 8 shows, in an enlarged illustration, the detail "X" shown in Fig. 1 comprising a soldered or welded seam, Fig. 9 shows a front view of the bushing blank with a groove arranged on the internal surface, Fig. 10 shows, in an enlarged illustration, the detail "Y" of the bushing blank shown in Fig. 9, In Fig. 1, the cylinder housing 1 comprising two parallel bores 2, which intersect one another in the sectional plane 11 and into which the bushings 3, 4, which are provided with a wear-resistant internal surface 6, are inserted, is shown in a partical section. Each bushing 3A comprises a pair of radial cut surfaces 9,10. The Fig. 2 shows, in an enlarged illustration, the detail "X" shown in Fig. 1. The radial cut surfaces of each bushing 3, 4 are formed as an abutting surface 5 at one arcuate end of the sector and at the other arcuate end of the sector as one surface of a gusset tip 7 whose other surface is formed by the internal surface 6 of the other bushing at the sectional plane 11. The bushings 3, 4 being arranged in the bores of the cylinder housing relative to one another in such a way that there is provided a support of the abutting surface 5 of bushing 3 on the external surface 8 of the bushing 4. Between the internal surfaces 6 of the bushings 3,4 is provided a flush transition 12. Fig. 3 shows the detail "X" shown in Fig.

1, in an enlarged illustration, of an alternative embodiment in which the support of the abutting surface 5 of bushing 3 on the external surface 8 of the bushing 4 can be seen. The external surface 8 of the bushing 4 being advantageously provided for an improvement of the support with a shoulder 13 which corresponds in width to the thickness of the wall of bushing wall 3.

Fig. 4 shows a view of a bushing 3, which is cut out with abutting surfaces 5 and gusset tips 7, being arranged alternately along the length of bushing 3. The projecting surfaces are designed as gusset tips 7 and the recessed surfaces as abutting surfaces 5.

Fig. 5 shows a view of the bushings 3A which have been joined together in accordance with the alternating arrangement of the flush transitions 12.

Fig. 6 and Fig. 7 show the sections A-A and B-B according to Fig. 5, the upper gusset tip 7 and the lower gusset tip 7 respectively being formed by the bushing 3 and the bushing 4 respectively.

Fig. 8 shows the detail "X" in an enlarged illustration according to Fig. 1. For a firm interconnection of the bushings 3 and 4, a soldered or welded seam 16 is provided in the gusset throat 15.

Fig. 9 shows, in a front view, the bushing

3 in its blank state without the sector shaped cut-out. On the internal surface 6, there is located in an appropriate position a groove 14, which is filled with wear resistant material.

Fig. 10 shows the detail "Y" according to Fig. 9 in an enlarged illustration. The bushing 3 is cut out at the point where the groove 14 is positioned, so that on this way a wear-resistant gusset tip 7 with the internal surface 6 is formed.

WHAT WE CLAIM IS: 1. A cylinder for a twin screw extruder, more especially for the processing of thermoplastics materials, comprising two bores (2), which are parallel in the cylinder housing and which intersect one another longitudinally in a sectional plane (11) and into which there are inserted bushings, which are each radially cut out in the shape of a sector and which are provided with a wear-resistant internal surface, characterised in that a radially cut surface (9) of each bushing (3A) is formed; as an abutting surface (5) at one arcuate end of the sector; and at the other arcuate end of the sector the radially cut surface (10) of each bushing (3,4) is formed as one surface of a gusset tip (7) whose other surface is defined by the internal surface (6) of the other bushing at the sectional plane (11) of intersection of the bores (2); and the bushing (3,4) being arranged in the bores (2) of the cylinder housing (1) relative to one another in such a way that there is provided a support of the abutting surface (5) of each bushing (3,4) on the external surface (8) of the other bushing (4,3); and a flushing transition (12) is provided between the internal surfaces (6) of each bushings (3,4) and the cut surface of the other bushing (4,3) which forms the said one surface of the gusset tip.

2. A cylinder as claimed in Claim 1, characterised in that the external surfaces (8) of each bushing (3A) are provided with a shoulder (13) for abutment with the abutting surface (5) of the other bushing.

3. A cylinder as claimed in Claims 1 and 2, characterised in that the radially cut surfaces (9,10) defining the abutting and gusset tip surfaces (5 and 7) extend alternately along the length of each bushing (3,4).

4. A cylinder as claimed in Claims 1 to 3, characterised in that there is arranged on the internal surface (6) of each bushing (3,4) prior to cutting the abutting and gusset tip surface a groove (14) which, is filled with wear-resistant material, at which one of the cuts is effected to form the said one surface of the gusset tip with the wearresistant material after the sector-shaped cut-out of the bushings.

5. A cylinder as claimed in Claims 1 to

4, characterised in that the bushings (3,4) are connecting in a gusset throat (15) by a soldered or welded seam (16).

6. An extruder cylinder, substantially as described herein with reference to and as illustrated by the accompanying drawings.

7. A cylinder as claimed in Claim. 1, substantially as hereinbefore described.