CA2150595A1 - Plastifying and injection unit for injection moulding machines used to manufacture rubber or plastic articles - Google Patents
Plastifying and injection unit for injection moulding machines used to manufacture rubber or plastic articlesInfo
- Publication number
- CA2150595A1 CA2150595A1 CA002150595A CA2150595A CA2150595A1 CA 2150595 A1 CA2150595 A1 CA 2150595A1 CA 002150595 A CA002150595 A CA 002150595A CA 2150595 A CA2150595 A CA 2150595A CA 2150595 A1 CA2150595 A1 CA 2150595A1
- Authority
- CA
- Canada
- Prior art keywords
- screw
- plastifying
- ahead
- chamber
- injection unit
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 238000002347 injection Methods 0.000 title claims abstract description 38
- 239000007924 injection Substances 0.000 title claims abstract description 38
- 239000004033 plastic Substances 0.000 title claims abstract description 28
- 238000001746 injection moulding Methods 0.000 title claims abstract description 14
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 8
- 239000000463 material Substances 0.000 description 6
- 239000007787 solid Substances 0.000 description 5
- 238000000034 method Methods 0.000 description 4
- 239000007858 starting material Substances 0.000 description 4
- 239000000654 additive Substances 0.000 description 3
- 238000005054 agglomeration Methods 0.000 description 3
- 230000002776 aggregation Effects 0.000 description 3
- 230000008901 benefit Effects 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 238000004140 cleaning Methods 0.000 description 2
- 239000000945 filler Substances 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 1
- 230000004927 fusion Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 230000008439 repair process Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000001360 synchronised effect Effects 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/17—Component parts, details or accessories; Auxiliary operations
- B29C45/20—Injection nozzles
- B29C45/24—Cleaning equipment
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/17—Component parts, details or accessories; Auxiliary operations
- B29C45/46—Means for plasticising or homogenising the moulding material or forcing it into the mould
- B29C45/53—Means for plasticising or homogenising the moulding material or forcing it into the mould using injection ram or piston
- B29C45/532—Means for plasticising or homogenising the moulding material or forcing it into the mould using injection ram or piston using a hollow injection ram co-operating with a coaxial screw
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2021/00—Use of unspecified rubbers as moulding material
Landscapes
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Mechanical Engineering (AREA)
- Injection Moulding Of Plastics Or The Like (AREA)
- Extrusion Moulding Of Plastics Or The Like (AREA)
- Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
Abstract
A plastifying and injection unit for injection moulding machines that are used to manufacture rubber or plastic articles with a plastifying screw (13) that can rotate within a screw cylinder (14) and move axially into a chamber (5) ahead of the screw, which has at its end that is proximate to the chamber (5) ahead of the screw a non-return valve that can move synchronously with it; that ahead of the non-return valve (27), as viewed in the direction of flow of the plastified rubber or plastic, there is a sieve-like filter device (28) that completely covers the unobstructed cross-section for the flow of plastified rubber or plastic, this being so arranged that it can move synchronously with the plastifying screw (13) and the non-return valve (27) into the chamber (5) that is ahead of the screw.
Description
21~0S95 -A PLASTIFYING AND INJECTION UNIT FOR
INJECTION MOULDING MACHINES USED TO
MANUFACTURE RUBBER OR PLASTIC ARTICLES
The present invention relates to a plastifying and injection unit for injection moulding machines that are used to manufacture rubber or plastic articles, this having the distinguishing features set out in the preamble to patent Claim 1.
Plastifying and injection units of this kind are described, for example, in German patents DE 32 47 272 C2, DE 37 02 191 C2, DE 37 17 735 C1, and DE 40 38 843 C2. These are used, on the one hand, to convert the rubber or plastic material that is introduced into the end of the screw cylinder that is remote from the injection mould, from a solid to a free-flowing form by the rotary motion the plastifier screw and, on the other hand, to inject the plastified rubber or plastic that has accumulated in the chamber ahead of the screw in the chamber(s) of the injection mould by the actual movement of the plastifying screw in said chamber, and do this within a specified time interval--that is as short as possible--at a specified pressure. When this is done, the non-return valve that is installed prevents the plastified rubber or plastic from flowing back into the screw cylinder during the injection process, instead of flowing into the chamber(s) of the mould.
The particular advantage of this plastifying and injection unit is that it requires fewer moving parts than an arrangement that consists of a special plastifying unit and an additional injection unit that is supplied from thisi this is economical in any case, and it also requires less space than a two-part arrangement consisting of a 21 5t~5~1~
plastifying unit and an injection unit, and this brings economic advantages as well. Nevertheless, in the case of the integrated plastifying and injection units discussed above, it is a disadvantage that, even after no fewer than ten years of use and development, they still make no provision for balancing out--at least in part--any differences in the plastified rubber or plastic, which is moved into the chamber ahead of the screw, with respect to its degree of fusion and/or the degree to which it is mixed with additional substances that are first introduced into the plastifying cylinder with the starting material; neither do they make it possible to trap any starting material that is inadequately fused or any possible agglomerations of additional materials--in particular mineral materials--or any foreign bodies that may happen to get into the plastifying screw prior to them reaching the sprue runner or the sprue runner system that forms part of the mould chamber(s). Very often, however, this means that in less serious instances the composition of the rubber or plastic materials that are produced is different so that they are of inferior quality, with the result that if their quality is in doubt, they have to be discarded; in more serious cases this will result in the screw runner or screw runner system, or the associated nozzle(s) becoming blocked, which will mean that the whole injection moulding system will have to be shut down so that it can be cleaned, which entails considerable cost both with respect to time and money.
In the case of plastifying screws used for continuously plastifying rubber or plastic to be fed to wide slot nozzles that are used to manufacture films or panels, or to supply blow moulds used to manufacture hoses, it has been known--at least since the publication of British patent GB 1 011 950--that it is possible to arrange a fixed, replaceable sieve-Z15~59~
like filter in the form of a strainer at the outlet of theplastifying cylinder; nevertheless, it was impossible to use such an arrangement for the integrated plastifying and injecting units discussed herein, in the form in which it was disclosed, for this would have meant arranging such a filter device at the outlet of the chamber located ahead of the screw. Were this done, however, during each injection procedure the filter device would be subjected to considerable pressures generated by the plastified rubber or plastic that has to be expelled from the chamber ahead of the screw, as opposed to the situation when continuous plastification is carried on, when there are very small differences in the pressure at the output of the plastifying cylinder; given that pressures of 2,000 bar are not unusual in injection moulding machinery, this would result in immense amounts of wear and thus to frequent replacement of the filter device, with all the associated and wasteful machine downtime for the required repair and maintenance operations, to say nothing of the fact that solid components in the plastified material--such as inadequately melted starting material, agglomerations of (fine) grain additives, and/or foreign bodies--are forced into the filter device with considerable amounts of kinetic energy, and these very soon block or destroy said filter device.
For this reason, it is the task of the present invention to describe a filter device for plastifying and injection units as described in the preamble to patent Claim 1 that can, on the one hand, even out, as far as possible, minor differences within the plastified rubber or plastic that moves into the chamber ahead of the screw with respect to the degree to which it is melted and/or mixed with additives before it reaches the chamber ahead of the screw, and, on the other, to so trap solid components such as inadequately 215G5~
melted starting material and~or agglomerations of (fine) grain additives and/or foreign bodies that are contained in the plastified rubber or plastic that these can be removed by occasionally cleaning the filter device so that the filter device is then once again fit for use.
The present invention solves this problem using the features set out in the defining portion of Claim 1.
In this connection, it is particularly advantageous that a sieve-like filter device, which completely covers the unobstructed cross-section for the flow of the plastified rubber or plastic, is arranged ahead of the non-return valve, as viewed in the direction of flow, in such a way that it can be moved into the chamber ahead of the screw synchronously with the plastifying screw and the non-return valve, because by this means the whole of the plastified rubber or plastic passes through a sieve-like filter device before it reaches the chamber ahead of the screw, and this subjects it to yet another internal mixing process and, on the other hand--depending on the mesh size of the sieve-like filter device--any solid or almost solid components that may be present in the material are removed by being trapped therein. This takes place without the sieve-like device being subjected to the considerable pressures that cause so much wear, and which are generated by the plastified rubber or plastic that is driven from the chamber ahead of the screw into the chamber(s) of the mould. In this case, the plastified rubber or plastic passes through the sieve-like filter device only at a small pressure differential during each particular period when the chamber ahead of the screw is being filled, this flow being cut off by the non-return valve during each injection phase. Most surprisingly, during operation of the plastifying and injection unit according to the present invention, there has been an additional and extremely advantageous effect, namely, that the sieve-like filter device results in a very effective de-gassing of the plastified rubber or plastic, when the gas that accumulates in the area between the sieve-like filter device and the non-return valve can be removed from the plastifying and injection unit by means of a de-aerating device of a known type. This results in a further improvement of the rubber or plastic articles that are manufactured, and ensures that they are all of the same quality.
In a further development of the plastifying and injection unit according to the present invention, it is advantageous that the sieve-like filter device be replaceable, since a design of this kind, for example, a filter device consisting of two semi-annular filter frames with corresponding sieve inserts, which can be secured on the tip of the plastifying screw, between the threads that end there and the non-return valve, by screws or snap fasteners of the known kind, also makes it much simpler to clean the sieve-like filter device when this becomes necessary, particularly if an additional sieve-like filter device of this kind is available, so that the operation of the injection moulding machine has to be interrupted only in order to expose or recapsulate the tip of the plastifying screw, for example, by temporary removal of part of the plastifying cylinder, and to replace the sieve-like filter devices from each other, when the actual cleaning of the sieve-like filter insert can take place outside the injection moulding machine once operation has been resumed.
In a special embodiment of the plastifying and injection unit according to the present invention it is also an - 21S05~5 advantage that the plastifying screw can be moved into the chamber ahead of the screw together with the screw cylinder, because then access to the sieve-like filter unit is made much simpler and quicker since the device for the synchronized movement of the plastifying screw and the screw cylinder into the chamber ahead of the screw is so designed that it can move the end of the plastifying screw that protrudes into the chamber ahead of the screw and the screw cylinder out of this synchronously as well, it being additionally advantageous if the sieve-like filter device and the non-return valve can be held by the screw cylinder in a defined position in front of the end of the plastifying screw that faces the chamber ahead of the screw.
Also advantageous is one embodiment of the present invention in which the screw cylinder has at its end that is proximate to the chamber that is ahead of the cylinder a cap-like extension that is configured as the cylinder head of the piston-cylinder unit that comprises the screw cylinder and the chamber ahead of the screw, which is used to inject the plastified rubber or plastic into one or a plurality of mould chambers, and which is connected releasably to the screw cylinder, which holds the sieve-like filter device and the non-return valve in a pre-set position ahead of the end of the plastifying screw that is proximate to the chamber ahead of the screw in its inner chamber, and which incorporates an outlet opening for the plastified rubber or plastic that is directed towards the chamber ahead of the screw, since this design greatly reduces the time required to replace a filter device that is to be cleaned by a fully functionable filter device, this being particularly so if, on one hand, an easily accessible quick release, screw, or direct thread connection of the known type is used to lock the cap-like extension on the screw cylinder and, on the - 21~05~!~
other hand, the sieve-like filter device is positioned within the cap-like extension simply by two suitable stops between the non-return valve, the cap-like extension, and the nearest end of the screw cylinder. In this case, it has been found that replacement times in the order of one to two minutes can be achieved, when this can also be carried out at normal operating temperatures because of the simplicity of the operation, whereas corresponding measures, for example, replacing the non-return valve or parts thereof in injection moulding machines according to the prior art have normally require from 30 minutes to an hour.
Also advantageous is a development of the plastifying and injection unit according to the present invention in which a sieve-like filter device comprises a plurality of screens that are of metallic mesh that are held in a frame of a suitable design in a pre-determined arrangement since such devices are known in principle and have been tested so that, on the one hand, they do not lead one to anticipate any problems during manufacture or in operation or when they are cleaned and, on the other hand, they are simple to handle and can thus make replacement much simpler in a plastifying and injection unit of the type discussed herein, particularly if the frame consists of two panel-like holders that incorporate suitable openings and which accommodate the screen that is of metallic mesh in a jointly formed recess and are assembled with this by means of known fastenings, for example, screws or bolts, to form a packet-like block.
One embodiment of the plastifying and injection units according to the present invention is shown in the drawings appended hereto. These drawings show the following:
- 21~0$95 Figure 1: a vertical cross-section through the parts of a rubber injection moulding machine of the known type, which is shown diagrammatically, with an installed sieve-like filter device between the mould end of the plastifying screw and the non-return valve that is arranged ahead of thisi Figure 2: an enlarged section from Figure 1 showing details of a sieve-like filter device according to the present invention and the manner of its arrangement in the area of the mould end of the associated plastifying screw.
Figure 1 shows the part that is seated on the upper end 1 of a closing device--not shown explicitly herein for purposes of greater clarity--of a rubber injection moulding machine of the type described, for example, in German patent DE 40 38 843 C2. This comprises a plastifying unit 2 and a drive unit 4 that is formed as a piston-cylinder arrangement 3 for injecting a plastified mixture of rubber into the mould cavity or cavities that are arranged in the closing device (not shown herein), as well as a cylinder block 6 that forms a chamber 5 ahead of the screw, a reversing device 7 that is adjacent to this, and the injection nozzle 8 that is held by this, the latter opening out into a sprue runner or the appropriate inlet of a sprue runner system (not shown explicitly herein). The cylinder block 6, the reversing device 7 with the injection nozzle 8 and the end of the piston rod 10 of the drive unit 4 for injecting the plastified material, which in this instance is a plastified mixture of rubber but which, in a suitable injection moulding machine, can also be plastified plastic, which is remote from the piston 9 are friction fitted on the upper end 1 of the closing device by means of a recess 11.
21SQS9~
Essentially, the plastifying unit 2 comprises a plastifying screw 13 that is connected to a rotary drive 12 and a screw cylinder 14 that encloses this, the latter supporting a stop bridge 15 on which tension rods fit; these are not visible in the present drawing, and they lie in a horizontal plane with the screw cylinder 14. Their other ends are friction fitted to stops 16 on the sliding cylinder housing 17 of the drive assembly 4 for the injection process. At the end of the plastifying screw 13 that is remote from the chamber 5 ahead of the screw, there is a filler opening 18 for the introduction of strips 19 of raw material into the screw cylinder 14. The end area 20 of the plastifying screw 13 that faces the chamber 5 that is ahead of the screw has both a non-return valve and a sieve-like filter device according to the present invention, and this is so configured that it acts in the chamber 5 ahead of the screw as a piston for inserting the plastified material through the reversing device 7 and the injection nozzle 8 into the mould chamber or chambers, if the cylinder housing 17 of the piston cylinder unit 13 is moved in a direction away from the chamber 5 that is ahead of the screw.
Figure 2 is a detailed drawing of one possible embodiment of the end area 20 of the plastifying screw 13. In this, the screw cylinder 14 that encloses the plastifying screw 13 has a cap-like extension 21 on its open end that is proximate to the chamber 5 which, in the embodiment shown, is locked by means of a direct threaded connector 22 to the screw cylinder 14. This locking can, of course, be effected by any other suitable means, for example, by screw connections that are radial to the axis of rotation of the plastifying screw 13, by appropriately oriented spring-loaded bolts, bayonnet-type connectors or similar quick-release devices.
In its area that is remote from the end of the plastifying _ g _ 215~S9!j -screw 13, the cap-like extension 21 has an outlet opening 23 which, when the cap-like extension 21 exerts pressure on the plastified rubber (or plastic) material that has accumulated in the chamber 5 ahead of the screw is closed off by a non-return valve 27 that in this instance consists of a ball 24, a cage 25, and a valve seat 26.
~ithin the internal space of the cap-like extension 21, between the end of the screw cylinder 14 and the valve seat 26, there is a sieve-like filter device 28 according to the present invention, and this consists of two panel-like holders 30, 31 that have suitable openings 29, and of a plurality of screens 33 that are of metallic wire mesh and are arranged one behind the other in a recess 22 that is formed by the panel-like holders 30, 31. The whole of the sieve-like filter device 28 is assembled to form a packet-like block by means of suitable fastening elements 34, and this is positioned in the example shown solely by lying against surfaces of the screw cylinder 14, the cap-like extension 21 and the valve seat 26 that are formed as stops within the overall arrangement that is shown. This permits very rapid replacement of a filter device 28 that is to be cleaned by a fully functional filter device of the identical kind, particularly if the piston-cylinder arrangement 3 that is shown in Figure 1 is so designed that they not only draw the end area 20 of the plastifying screw 13 which normally always protrudes into the chamber 5 ahead of the screw deeper into the chamber 5 ahead of the screw but, if needs be, can also be completely withdrawn from said chamber.
The present patent does not relate solely to the embodiment that has been explained and is illustrated in Figures 1 and 2 with respect to a plastifying and injection unit according to the present invention. It also applies to any possible 215Q59~
embodiment of the type of plastifying and injection unit discussed herein which can be characterized by the features set out in patent Claim 1.
Reference index 1 upper end of the closing device of a rubber-injection moulding machine 2 plastifying unit 3 piston-cylinder arrangement 4 drive unit for injection chamber ahead of screw 6 cylinder block 7 reversing device 8 injection nozzle 9 piston piston rod 11 receptacle 12 rotary drive 13 plastifying screw 14 screw cylinder stop bridge 16 stops 17 cylinder housing 18 filler opening 19 strips of raw material the end area of the plastifying screw that is proximate to the chamber ahead of the screw 21 cap-like extension 22 screw fastener 23 outlet opening 24 ball cage 26 valve seat 27 non-return valve 28 sieve-like filter device 29 openings 30,31 panel-like holders 32 recess 33 screen of metallic mesh 34 connectors
INJECTION MOULDING MACHINES USED TO
MANUFACTURE RUBBER OR PLASTIC ARTICLES
The present invention relates to a plastifying and injection unit for injection moulding machines that are used to manufacture rubber or plastic articles, this having the distinguishing features set out in the preamble to patent Claim 1.
Plastifying and injection units of this kind are described, for example, in German patents DE 32 47 272 C2, DE 37 02 191 C2, DE 37 17 735 C1, and DE 40 38 843 C2. These are used, on the one hand, to convert the rubber or plastic material that is introduced into the end of the screw cylinder that is remote from the injection mould, from a solid to a free-flowing form by the rotary motion the plastifier screw and, on the other hand, to inject the plastified rubber or plastic that has accumulated in the chamber ahead of the screw in the chamber(s) of the injection mould by the actual movement of the plastifying screw in said chamber, and do this within a specified time interval--that is as short as possible--at a specified pressure. When this is done, the non-return valve that is installed prevents the plastified rubber or plastic from flowing back into the screw cylinder during the injection process, instead of flowing into the chamber(s) of the mould.
The particular advantage of this plastifying and injection unit is that it requires fewer moving parts than an arrangement that consists of a special plastifying unit and an additional injection unit that is supplied from thisi this is economical in any case, and it also requires less space than a two-part arrangement consisting of a 21 5t~5~1~
plastifying unit and an injection unit, and this brings economic advantages as well. Nevertheless, in the case of the integrated plastifying and injection units discussed above, it is a disadvantage that, even after no fewer than ten years of use and development, they still make no provision for balancing out--at least in part--any differences in the plastified rubber or plastic, which is moved into the chamber ahead of the screw, with respect to its degree of fusion and/or the degree to which it is mixed with additional substances that are first introduced into the plastifying cylinder with the starting material; neither do they make it possible to trap any starting material that is inadequately fused or any possible agglomerations of additional materials--in particular mineral materials--or any foreign bodies that may happen to get into the plastifying screw prior to them reaching the sprue runner or the sprue runner system that forms part of the mould chamber(s). Very often, however, this means that in less serious instances the composition of the rubber or plastic materials that are produced is different so that they are of inferior quality, with the result that if their quality is in doubt, they have to be discarded; in more serious cases this will result in the screw runner or screw runner system, or the associated nozzle(s) becoming blocked, which will mean that the whole injection moulding system will have to be shut down so that it can be cleaned, which entails considerable cost both with respect to time and money.
In the case of plastifying screws used for continuously plastifying rubber or plastic to be fed to wide slot nozzles that are used to manufacture films or panels, or to supply blow moulds used to manufacture hoses, it has been known--at least since the publication of British patent GB 1 011 950--that it is possible to arrange a fixed, replaceable sieve-Z15~59~
like filter in the form of a strainer at the outlet of theplastifying cylinder; nevertheless, it was impossible to use such an arrangement for the integrated plastifying and injecting units discussed herein, in the form in which it was disclosed, for this would have meant arranging such a filter device at the outlet of the chamber located ahead of the screw. Were this done, however, during each injection procedure the filter device would be subjected to considerable pressures generated by the plastified rubber or plastic that has to be expelled from the chamber ahead of the screw, as opposed to the situation when continuous plastification is carried on, when there are very small differences in the pressure at the output of the plastifying cylinder; given that pressures of 2,000 bar are not unusual in injection moulding machinery, this would result in immense amounts of wear and thus to frequent replacement of the filter device, with all the associated and wasteful machine downtime for the required repair and maintenance operations, to say nothing of the fact that solid components in the plastified material--such as inadequately melted starting material, agglomerations of (fine) grain additives, and/or foreign bodies--are forced into the filter device with considerable amounts of kinetic energy, and these very soon block or destroy said filter device.
For this reason, it is the task of the present invention to describe a filter device for plastifying and injection units as described in the preamble to patent Claim 1 that can, on the one hand, even out, as far as possible, minor differences within the plastified rubber or plastic that moves into the chamber ahead of the screw with respect to the degree to which it is melted and/or mixed with additives before it reaches the chamber ahead of the screw, and, on the other, to so trap solid components such as inadequately 215G5~
melted starting material and~or agglomerations of (fine) grain additives and/or foreign bodies that are contained in the plastified rubber or plastic that these can be removed by occasionally cleaning the filter device so that the filter device is then once again fit for use.
The present invention solves this problem using the features set out in the defining portion of Claim 1.
In this connection, it is particularly advantageous that a sieve-like filter device, which completely covers the unobstructed cross-section for the flow of the plastified rubber or plastic, is arranged ahead of the non-return valve, as viewed in the direction of flow, in such a way that it can be moved into the chamber ahead of the screw synchronously with the plastifying screw and the non-return valve, because by this means the whole of the plastified rubber or plastic passes through a sieve-like filter device before it reaches the chamber ahead of the screw, and this subjects it to yet another internal mixing process and, on the other hand--depending on the mesh size of the sieve-like filter device--any solid or almost solid components that may be present in the material are removed by being trapped therein. This takes place without the sieve-like device being subjected to the considerable pressures that cause so much wear, and which are generated by the plastified rubber or plastic that is driven from the chamber ahead of the screw into the chamber(s) of the mould. In this case, the plastified rubber or plastic passes through the sieve-like filter device only at a small pressure differential during each particular period when the chamber ahead of the screw is being filled, this flow being cut off by the non-return valve during each injection phase. Most surprisingly, during operation of the plastifying and injection unit according to the present invention, there has been an additional and extremely advantageous effect, namely, that the sieve-like filter device results in a very effective de-gassing of the plastified rubber or plastic, when the gas that accumulates in the area between the sieve-like filter device and the non-return valve can be removed from the plastifying and injection unit by means of a de-aerating device of a known type. This results in a further improvement of the rubber or plastic articles that are manufactured, and ensures that they are all of the same quality.
In a further development of the plastifying and injection unit according to the present invention, it is advantageous that the sieve-like filter device be replaceable, since a design of this kind, for example, a filter device consisting of two semi-annular filter frames with corresponding sieve inserts, which can be secured on the tip of the plastifying screw, between the threads that end there and the non-return valve, by screws or snap fasteners of the known kind, also makes it much simpler to clean the sieve-like filter device when this becomes necessary, particularly if an additional sieve-like filter device of this kind is available, so that the operation of the injection moulding machine has to be interrupted only in order to expose or recapsulate the tip of the plastifying screw, for example, by temporary removal of part of the plastifying cylinder, and to replace the sieve-like filter devices from each other, when the actual cleaning of the sieve-like filter insert can take place outside the injection moulding machine once operation has been resumed.
In a special embodiment of the plastifying and injection unit according to the present invention it is also an - 21S05~5 advantage that the plastifying screw can be moved into the chamber ahead of the screw together with the screw cylinder, because then access to the sieve-like filter unit is made much simpler and quicker since the device for the synchronized movement of the plastifying screw and the screw cylinder into the chamber ahead of the screw is so designed that it can move the end of the plastifying screw that protrudes into the chamber ahead of the screw and the screw cylinder out of this synchronously as well, it being additionally advantageous if the sieve-like filter device and the non-return valve can be held by the screw cylinder in a defined position in front of the end of the plastifying screw that faces the chamber ahead of the screw.
Also advantageous is one embodiment of the present invention in which the screw cylinder has at its end that is proximate to the chamber that is ahead of the cylinder a cap-like extension that is configured as the cylinder head of the piston-cylinder unit that comprises the screw cylinder and the chamber ahead of the screw, which is used to inject the plastified rubber or plastic into one or a plurality of mould chambers, and which is connected releasably to the screw cylinder, which holds the sieve-like filter device and the non-return valve in a pre-set position ahead of the end of the plastifying screw that is proximate to the chamber ahead of the screw in its inner chamber, and which incorporates an outlet opening for the plastified rubber or plastic that is directed towards the chamber ahead of the screw, since this design greatly reduces the time required to replace a filter device that is to be cleaned by a fully functionable filter device, this being particularly so if, on one hand, an easily accessible quick release, screw, or direct thread connection of the known type is used to lock the cap-like extension on the screw cylinder and, on the - 21~05~!~
other hand, the sieve-like filter device is positioned within the cap-like extension simply by two suitable stops between the non-return valve, the cap-like extension, and the nearest end of the screw cylinder. In this case, it has been found that replacement times in the order of one to two minutes can be achieved, when this can also be carried out at normal operating temperatures because of the simplicity of the operation, whereas corresponding measures, for example, replacing the non-return valve or parts thereof in injection moulding machines according to the prior art have normally require from 30 minutes to an hour.
Also advantageous is a development of the plastifying and injection unit according to the present invention in which a sieve-like filter device comprises a plurality of screens that are of metallic mesh that are held in a frame of a suitable design in a pre-determined arrangement since such devices are known in principle and have been tested so that, on the one hand, they do not lead one to anticipate any problems during manufacture or in operation or when they are cleaned and, on the other hand, they are simple to handle and can thus make replacement much simpler in a plastifying and injection unit of the type discussed herein, particularly if the frame consists of two panel-like holders that incorporate suitable openings and which accommodate the screen that is of metallic mesh in a jointly formed recess and are assembled with this by means of known fastenings, for example, screws or bolts, to form a packet-like block.
One embodiment of the plastifying and injection units according to the present invention is shown in the drawings appended hereto. These drawings show the following:
- 21~0$95 Figure 1: a vertical cross-section through the parts of a rubber injection moulding machine of the known type, which is shown diagrammatically, with an installed sieve-like filter device between the mould end of the plastifying screw and the non-return valve that is arranged ahead of thisi Figure 2: an enlarged section from Figure 1 showing details of a sieve-like filter device according to the present invention and the manner of its arrangement in the area of the mould end of the associated plastifying screw.
Figure 1 shows the part that is seated on the upper end 1 of a closing device--not shown explicitly herein for purposes of greater clarity--of a rubber injection moulding machine of the type described, for example, in German patent DE 40 38 843 C2. This comprises a plastifying unit 2 and a drive unit 4 that is formed as a piston-cylinder arrangement 3 for injecting a plastified mixture of rubber into the mould cavity or cavities that are arranged in the closing device (not shown herein), as well as a cylinder block 6 that forms a chamber 5 ahead of the screw, a reversing device 7 that is adjacent to this, and the injection nozzle 8 that is held by this, the latter opening out into a sprue runner or the appropriate inlet of a sprue runner system (not shown explicitly herein). The cylinder block 6, the reversing device 7 with the injection nozzle 8 and the end of the piston rod 10 of the drive unit 4 for injecting the plastified material, which in this instance is a plastified mixture of rubber but which, in a suitable injection moulding machine, can also be plastified plastic, which is remote from the piston 9 are friction fitted on the upper end 1 of the closing device by means of a recess 11.
21SQS9~
Essentially, the plastifying unit 2 comprises a plastifying screw 13 that is connected to a rotary drive 12 and a screw cylinder 14 that encloses this, the latter supporting a stop bridge 15 on which tension rods fit; these are not visible in the present drawing, and they lie in a horizontal plane with the screw cylinder 14. Their other ends are friction fitted to stops 16 on the sliding cylinder housing 17 of the drive assembly 4 for the injection process. At the end of the plastifying screw 13 that is remote from the chamber 5 ahead of the screw, there is a filler opening 18 for the introduction of strips 19 of raw material into the screw cylinder 14. The end area 20 of the plastifying screw 13 that faces the chamber 5 that is ahead of the screw has both a non-return valve and a sieve-like filter device according to the present invention, and this is so configured that it acts in the chamber 5 ahead of the screw as a piston for inserting the plastified material through the reversing device 7 and the injection nozzle 8 into the mould chamber or chambers, if the cylinder housing 17 of the piston cylinder unit 13 is moved in a direction away from the chamber 5 that is ahead of the screw.
Figure 2 is a detailed drawing of one possible embodiment of the end area 20 of the plastifying screw 13. In this, the screw cylinder 14 that encloses the plastifying screw 13 has a cap-like extension 21 on its open end that is proximate to the chamber 5 which, in the embodiment shown, is locked by means of a direct threaded connector 22 to the screw cylinder 14. This locking can, of course, be effected by any other suitable means, for example, by screw connections that are radial to the axis of rotation of the plastifying screw 13, by appropriately oriented spring-loaded bolts, bayonnet-type connectors or similar quick-release devices.
In its area that is remote from the end of the plastifying _ g _ 215~S9!j -screw 13, the cap-like extension 21 has an outlet opening 23 which, when the cap-like extension 21 exerts pressure on the plastified rubber (or plastic) material that has accumulated in the chamber 5 ahead of the screw is closed off by a non-return valve 27 that in this instance consists of a ball 24, a cage 25, and a valve seat 26.
~ithin the internal space of the cap-like extension 21, between the end of the screw cylinder 14 and the valve seat 26, there is a sieve-like filter device 28 according to the present invention, and this consists of two panel-like holders 30, 31 that have suitable openings 29, and of a plurality of screens 33 that are of metallic wire mesh and are arranged one behind the other in a recess 22 that is formed by the panel-like holders 30, 31. The whole of the sieve-like filter device 28 is assembled to form a packet-like block by means of suitable fastening elements 34, and this is positioned in the example shown solely by lying against surfaces of the screw cylinder 14, the cap-like extension 21 and the valve seat 26 that are formed as stops within the overall arrangement that is shown. This permits very rapid replacement of a filter device 28 that is to be cleaned by a fully functional filter device of the identical kind, particularly if the piston-cylinder arrangement 3 that is shown in Figure 1 is so designed that they not only draw the end area 20 of the plastifying screw 13 which normally always protrudes into the chamber 5 ahead of the screw deeper into the chamber 5 ahead of the screw but, if needs be, can also be completely withdrawn from said chamber.
The present patent does not relate solely to the embodiment that has been explained and is illustrated in Figures 1 and 2 with respect to a plastifying and injection unit according to the present invention. It also applies to any possible 215Q59~
embodiment of the type of plastifying and injection unit discussed herein which can be characterized by the features set out in patent Claim 1.
Reference index 1 upper end of the closing device of a rubber-injection moulding machine 2 plastifying unit 3 piston-cylinder arrangement 4 drive unit for injection chamber ahead of screw 6 cylinder block 7 reversing device 8 injection nozzle 9 piston piston rod 11 receptacle 12 rotary drive 13 plastifying screw 14 screw cylinder stop bridge 16 stops 17 cylinder housing 18 filler opening 19 strips of raw material the end area of the plastifying screw that is proximate to the chamber ahead of the screw 21 cap-like extension 22 screw fastener 23 outlet opening 24 ball cage 26 valve seat 27 non-return valve 28 sieve-like filter device 29 openings 30,31 panel-like holders 32 recess 33 screen of metallic mesh 34 connectors
Claims (8)
1. A plastifying and injection unit for injection moulding machines used to manufacture rubber or plastic articles, with a plastifying screw that can rotate within a screw cylinder and move axially into a chamber ahead of the screws, which has at its end that is proximate to the chamber ahead of the screw, with a non-return valve that can move synchronously with it, characterized in that ahead of the non-return valve (27), as viewed in the direction of flow of the plastified rubber or plastic, there is a sieve-like filter device (28) that completely covers the unobstructed cross-section for the flow of plastified rubber or plastic, this being so arranged that it can move synchronously with the plastifying screw (13) and the non-return valve (27) into the chamber (5) that is ahead of the screw.
2. A plastifying and injection unit as defined in Claim 1, characterized in that the sieve-like filter device (28) is replaceable.
3. A plastifying and injection unit as defined in Claim 1 or Claim 2, characterized in that the plastifying screw (13) can be moved into the chamber (5) ahead of the screw together with the screw cylinder (14).
4. A plastifying and injection unit as defined in Claim 3, characterized in that the sieve-like filter device (28) and the non-return valve (27) can be held by the screw cylinder (14) in a defined position ahead of the end (20) of the plastifying screw (13) that is proximate to the chamber (5) ahead of the screw.
5. A plastifying and injection unit as defined in Claim 3 or Claim 4, characterized in that
6. A plastifying and injection unit as defined in Claim 5, characterized in that the sieve-like filter device (28) is positioned within the cap-like extension (21) solely by suitable stops between the non-return valve (27), the cap-like extension (21) and the nearest end of the screw cylinder (14).
7. A plastifying and injection unit as defined in one of the Claims 1 to 6, characterized in that the sieve-like filter device (28) consists of a plurality of screens (33) that are of metallic mesh and which lie one behind the other and are which are held in a prescribed arrangement by a frame of suitable design.
8. A plastifying and injection unit as defined in Claim 7, characterized in that the frame consists of two panel-like holders (30, 31) that incorporate suitable openings (28) which accommodate the screens (33) of metallic wire mesh in a jointly formed recess (32) and which are assembled by means of known connectors ( 34), for example, screws or bolts, to form a packet-like block.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE4419405A DE4419405C2 (en) | 1994-06-03 | 1994-06-03 | Plasticizing and injection unit for injection molding machines for the production of rubber or plastic articles |
| DEP4419405.6-16 | 1994-06-03 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2150595A1 true CA2150595A1 (en) | 1995-12-04 |
Family
ID=6519697
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002150595A Abandoned CA2150595A1 (en) | 1994-06-03 | 1995-05-31 | Plastifying and injection unit for injection moulding machines used to manufacture rubber or plastic articles |
Country Status (4)
| Country | Link |
|---|---|
| CA (1) | CA2150595A1 (en) |
| DE (1) | DE4419405C2 (en) |
| FR (1) | FR2720676A1 (en) |
| IT (1) | IT1275446B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114506016B (en) * | 2022-04-18 | 2022-06-21 | 烟台爱开天隆模塑有限公司 | Nozzle special for injection molding of plastic product of airplane seat |
| AT525547B1 (en) * | 2022-07-11 | 2023-05-15 | Engel Austria Gmbh | filter device |
Family Cites Families (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1242329A (en) * | 1959-08-17 | 1960-09-30 | Mach Foucher | Improvements made to plastic molding machines |
| FR1290323A (en) * | 1961-03-03 | 1962-04-13 | Improvements to pre-plasticization injection devices | |
| US3248469A (en) * | 1961-08-28 | 1966-04-26 | Phillips Petroleum Co | High shear visbreaking method and apparatus |
| FR1339308A (en) * | 1962-11-16 | 1963-10-04 | Triulzi S A S A | Screw extruder for plastics |
| FR1564783A (en) * | 1968-02-23 | 1969-04-25 | ||
| DE2524746A1 (en) * | 1975-06-04 | 1976-12-16 | Gerhard Prof Dr Ing Schenkel | Synthetic material injector with worm plasticiser - has filter flushed by force opened and closed back pressure valve |
| AR215981A1 (en) * | 1978-02-09 | 1979-11-15 | Dart Ind Inc | NOZZLE FOR INJECTION MOLDING PLASTICS |
| DE3247272A1 (en) * | 1982-12-21 | 1984-06-28 | Krauss-Maffei AG, 8000 München | BACKFLOW LOCK |
| GB8510185D0 (en) * | 1985-04-22 | 1985-05-30 | C R M Design Services Ltd | Nozzle for injection moulding thin rubber articles |
| DE3702191A1 (en) * | 1987-01-26 | 1988-11-03 | Kloeckner Ferromatik Desma | BACKFLOW LOCK FOR PLASTICIZING AND SPRAYING UNITS FOR INJECTION MOLDING MACHINES |
| DE3717735C1 (en) * | 1987-05-26 | 1988-02-18 | Krauss Maffei Ag | Non-return valve for a plastication screw |
| WO1992005939A1 (en) * | 1990-10-06 | 1992-04-16 | Seiki Corporation | Process and apparatus for injection molding with melt filtration |
| DE4038843A1 (en) * | 1990-12-06 | 1992-06-11 | Kloeckner Ferromatik Desma | PLASTICIZING AND SYRINGE UNIT FOR RUBBER INJECTION MOLDING MACHINES |
-
1994
- 1994-06-03 DE DE4419405A patent/DE4419405C2/en not_active Expired - Fee Related
-
1995
- 1995-05-26 IT ITMI951094A patent/IT1275446B/en active IP Right Grant
- 1995-05-31 CA CA002150595A patent/CA2150595A1/en not_active Abandoned
- 1995-05-31 FR FR9506456A patent/FR2720676A1/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| DE4419405A1 (en) | 1995-12-07 |
| ITMI951094A1 (en) | 1996-11-26 |
| IT1275446B (en) | 1997-08-07 |
| DE4419405C2 (en) | 1996-11-21 |
| ITMI951094A0 (en) | 1995-05-26 |
| FR2720676A1 (en) | 1995-12-08 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued |