CA2076480A1 - Plasticizing assembly for use in an injection molding machine - Google Patents
Plasticizing assembly for use in an injection molding machineInfo
- Publication number
- CA2076480A1 CA2076480A1 CA 2076480 CA2076480A CA2076480A1 CA 2076480 A1 CA2076480 A1 CA 2076480A1 CA 2076480 CA2076480 CA 2076480 CA 2076480 A CA2076480 A CA 2076480A CA 2076480 A1 CA2076480 A1 CA 2076480A1
- Authority
- CA
- Canada
- Prior art keywords
- cylinder
- plasticizing
- plasticizing cylinder
- section
- feed screw
- 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
Classifications
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- 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
- B29C45/58—Details
- B29C45/60—Screws
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- 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
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- 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
- B29C45/23—Feed stopping equipment
- B29C45/231—Needle valve systems therefor
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- 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
- B29C45/58—Details
- B29C45/62—Barrels or cylinders
Landscapes
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Mechanical Engineering (AREA)
- Injection Moulding Of Plastics Or The Like (AREA)
Abstract
ABSTRACT
PLASTICIZING ASSEMBLY FOR USE IN AN INJECTION MOLDING MACHINE
In a plasticizing assembly for use in an injection molding machine, which assembly comprises a low-pressure chamber, which contains the feed screw, connecting means are provided, which connect the plasticizing cylinder or a rear section of a bipartite plasticizing cylinder and connect also the nozzle body or a forward section of a bipartite plasticizing cylinder in part of its length and is secured to the plasticizing cylinder or to its rear section. The forward section enlarges at least the low-pressure chamber. As a result, a replacement of the nozzle body or of the forward section of the plasticizing cylinder can be effected and it is possible to supply energy at a higher rate without being dependent on the energy supplied by heating cuffs.
PLASTICIZING ASSEMBLY FOR USE IN AN INJECTION MOLDING MACHINE
In a plasticizing assembly for use in an injection molding machine, which assembly comprises a low-pressure chamber, which contains the feed screw, connecting means are provided, which connect the plasticizing cylinder or a rear section of a bipartite plasticizing cylinder and connect also the nozzle body or a forward section of a bipartite plasticizing cylinder in part of its length and is secured to the plasticizing cylinder or to its rear section. The forward section enlarges at least the low-pressure chamber. As a result, a replacement of the nozzle body or of the forward section of the plasticizing cylinder can be effected and it is possible to supply energy at a higher rate without being dependent on the energy supplied by heating cuffs.
Description
Reference to Related Application A patent application entitled "Plasticizing Assembly for use in an injection molding machine" filed for Karl Hehl on February 24,1992, bearing Serial No. 07/840,194 contains subject matter related to the subject matter of the present application.
BACKGROUND OF THE INVENTION
1. Field of the Invention This invention relates to a heatable plasticizing assembly for use in an injection molding machine, which assembly comprises a heatable nozzle body, a rotatable feed screw, and a plasticizing cylinder defining at least a cylindrical low-pressure chamber, which contains said feed screw, which is provided at its forward end with a back flow valve, wherein the low-pressure chamber comprises a cylindrical portion and is connected with the nozzle body by an axially extending portion tapering from said cylindrical portion to the diameter of the nozzle passage, and said cylinder and nozzle body are connected by connecting means.
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2076~80 The term "low-pressure chamber" describes a chamber which is disposed behind the back flow valve and during the injection of molten plastic material into the injection mold is hermetically sealed from the high-pressure chamber by said valve. The high-pressure chamber has the largest volume when the feed screw is inits rearmost position. That rearmost position differs from an actual rear position of the feed screw, which actual rear position is determined by the quantity of plastic material requirea for a given molding to be made.
BACKGROUND OF THE INVENTION
1. Field of the Invention This invention relates to a heatable plasticizing assembly for use in an injection molding machine, which assembly comprises a heatable nozzle body, a rotatable feed screw, and a plasticizing cylinder defining at least a cylindrical low-pressure chamber, which contains said feed screw, which is provided at its forward end with a back flow valve, wherein the low-pressure chamber comprises a cylindrical portion and is connected with the nozzle body by an axially extending portion tapering from said cylindrical portion to the diameter of the nozzle passage, and said cylinder and nozzle body are connected by connecting means.
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2076~80 The term "low-pressure chamber" describes a chamber which is disposed behind the back flow valve and during the injection of molten plastic material into the injection mold is hermetically sealed from the high-pressure chamber by said valve. The high-pressure chamber has the largest volume when the feed screw is inits rearmost position. That rearmost position differs from an actual rear position of the feed screw, which actual rear position is determined by the quantity of plastic material requirea for a given molding to be made.
2. Description of the Prior Art A plasticizing assembly of the type described first herein-before is known from U.S.Patent 4,886,439.
In conventional plasticizing assemblies the effective length of the feed screw usually does not exceed 20 times the diameter of said screw. On the other hand it is often desired to increase the production rate of the injection molding machine by a supply of heat at a higher rate to the plasticized plastic material. In known injection molding machines this can be accomplished only by a supply of a higher electric power to the heating cuffs although the p~wer which can thus be supplied cannot be increased indiscriminately.
U.S.Patent 4,886,439 suggests to connect the nozzle body to the plasticizing cylinder by means of a sleeve, which is adapted to be screw-connected to the plasticizing cylinder and applies an axial pressure to the nozzle body. In that case the force required to . : , 20764~0 loosen the connecting sleeve is much stronger than the force required to loosen each screw of the plasticizing cylinder described first hereinbefore. Practice has shown that such a connecting sleeve can be loosened only with the aid of a heavy implement consisting, e.g., of a fork spanner, and it is often necessary to strike against the implement in order to loosen said sleeve. Besides, it is often necessary to replace the nozzle body in the premises of the user of the injection molding mach;ne and to have that operation performed by personnel of such user or by service technicians of the manufacturer of the machine. A replace-ment of the nozzle will give rise to problems particularly when properly skilled labor and proper implements are not available or when it is necessary to transport heavy implements to remote sites of injection molding machines, e.g., in countries which are not highly developed industrially.
The related and above identified patent application describes connecting means for connecting the nozzle body to the plasticizing cylinder with a plurality of fixing screws, which are screwed in a plurality of angularly spaced apart tapped bores on a circular line. A connecting sleeve surrounds the plasticizing cylinder and the nozzle body adjacent to the gap between them and is formed with the tapped bores, which consist of through bores to abutment faces of the plasticizing cylinder.
Further, it is well known from U.S.Patent 4,842,507 to use a bipartite plasticizing cylinder comprising two separate parts. In this assembly the rearward part of the plasticizing cylinder has a 2076~80 smaller diameter and a smaller width in the clear than the forward part of the plasticizing cylinder. The rearward part dips in the separate forward part like a telescope. This assembly does not permit a simple and quicker replacement of a nozzle body or of a forward section of a bipartite plasticizing cylinder.
SUMMARY OF THE INVENTIQN
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It is an object of the invention to provide a plasticizing assembly which is of the kind described hereinbefore and which permits the nozzle body or a forward section of a plasticizing cylinder to be replaced and which permits energy to be supplied at a higher rate to the plastic material in a simple manner.
In a plasticizing assembly which is of the kind described first hereinbefore that object is accomplished in that a forward section having a rearwardly facing surface and an inside peripheral surface elongates the plasticizing cylinder and connecting means placed at a rearward end of the forward section and corresponding to the connecting means of the nozzle body are capable for connecting the forward section to the connecting means of the-plasticizing cylinder, when the nozzle body is aside, and cooperate with the connecting means of the plasticizing cylinder, and at least said low-pressure chamber of the plasticizing cylinder is enlarged by the inside peripherical surface of the low-pressure chamber.
In that plasticizing assembly the nozzly body is displaced and replaced by a forward section of the plasticizing assembly.
If such modular assemblies are provided, the plasticizing cylinder may comprise rear and forward cylinder sections and the forward cylinder section may be connected to the rear cy~inder section by means which are similar to those connecting the nozzle body to the forward cylinder section. In such an assembly comprising a bipartite plasticizing cylinder the plastic material will be plasticized and homogenized to a higher degree because it flows along a longer path so that moldings of higher quality can be made, particularly because the longer plasticizing cylinder permits more kinetic or thermal energy to be supplied to the plastic material.
According to a preferred feature of the invention a connecting sleeve is secured to the plasticizing cylinder and surrounds the plasticizing cylinder adjacent to the forward portion of the high-pressure chamber and axially overlaps the nozzle body or a forward section of a bipartite plasticizing cylindeP in part of its length, and the fixing screws which are axially supported by the screw threads of tapped bores of the connecting sleeve have end faces bearing on abutment faces of the nozzle body or of the forward section.
207648~
In that plasticizing assembly the screw threads by which the fixing screws force the nozzle body or the forward cylinder section against the plasticizing cylinder are screwed in the internal screw threads of the tapped bores of the connecting sleeve and are remote from those portions of the nozzle body and the plasticizing cylinder which are heated to critically high temperatures. In that case the screw-threaded joint connect~ng the connecting sleeve and the plasticizing cylinder is not eliminated for a replacement of the nozzle and constitutes a heat transfer bridge but the temperature adjacent to the fixing screws is far below the temperatures in the nozzle body and the plasticizing cylinder. An ingress of any corrosive gases evolved from the plasticized plas~ic material as far as to the screw threads of the fixing screws is virtually precluded so that the interengaging screw threads cannot stick together.
As a result, the nozzle body and the forward cylinder section can be replaced by an exertion of a much smaller physical force and by means of an implement which is light in weight and can easily be handled, particularly because the contact pressure which is required for a tight seal is applied by means of a large number-of fixing screws so that the manual force which is exerted on the implement is distributed to a large number of fixing screws and the implement which is required can be carried along by the technician~ e~g., in a briefcase or in a small bag.
According to a preferred feature of the invention each of the confronting end faces of the nozzle body and of the plasti-2076~8~
cizing cy1inder is finish-machined only in a relatively small annular area, which adjoins the inside peripheral surface of the plasticizing cylinder, respectively.
In that case much lower contact pressures will be required for a tight seal between the finish-machined end faces of the nozzle body or of the forward cylinder section, on the one hand, and of the plasticizing cylinder or its rear section, on the other hand, because said contact surfaces are relatively small or the nozzle body is so long that it entirely surrounds the high-pressure chamber regardless of the position of the feed screw so that the gap between the nozzle body and the plasticizing cylinder will always adjoin the low-pressure chamber. As a result~ the replacement of the nozzle will be further facilitated because much lower contact forces are required to ensure a tight seal so that the stresses in the interengaging screw threads will also be reduced.
According to a preferred feature of the invention the forwar~ cylinder section of the bipartite plasticizing cylinder is provided at its forward end with means for connecting said forward cylinder section to said nozzle body, the rear cylinder section of the bipartite plasticizing cylinder is provided at its forward end with similar means adapted to connect said nozzle body to said rear cylinder section, and said nozzle body is provided with connecting means for connecting said nozzle body selectively to said connecting means of said forward cylinder section and to said connecting means of sa-id rear cylinder section. In that case the nozzle body can be detached from the forward cylinder section and another nozzle body can be mounted on the forward cylinder section or the forward cylinder section may be omitted and the same nozzle body or a different one may be mounted on the rear cylinder section, which now constitutes the entire plasticizing cylinder.
Alternatively, an integral nozzle body may be used, which~has a length that is equal to the total length of the nozzle body and the forward cylinder section previously employed.
According to a preferred feature of the invention the forward and rear cylinder sections are provided at corresponding positions with bores which open on the outside peripheral surface of the plasticizing cylinder and are adapted to receive means such as temperature sensors and a valve needle.
According to a preferred feature of the invention the plasticizing assembly comprises a valve needle for sealing the nozzle passage of the nozzle block and means for actuating said valve needle, which actuating means comprise a lever, which is pivoted to said rear cylinder section on a pivotal axis~ a forward actuating rod, which is pivoted to said lever at a distance from said pivotal axis and is rigidly connected to said valve needle, and a rear actuating rod, which is pivoted to said pivoted lever at a distance from said pivotal axis, and said valve needle extends through a needle-guiding bore in said forward cylinder section, and when said nozzle body is directly mounted on said rear cylinder section said valve needle extends through a needle-guiding bore in said rear cylinder section, said forward actuating rod is shorter than the one used in the plasticizing assembly comprising said forward cylinder section, said lever is shorter than the one used in the plasticizing assembly comprising the forward cylinder section, and said rear actuating rod is pivoted to said lever at the same distance from said first pivotal aXis as in the plasticizing assembly comprising said forward cylinder section. In that case only two components of the actuating means must be changed for a conversion of an assembly comprising a forward cylinder section to one in which said forward cylinder section has been omitted, whereas the same heating means, valve means and other control means can be used in both embodiments.
According to a preferred feature of the invention the feed screw contained in the bipartite plasticizing cylinder extends also in the forward cylinder section and the arrangement is such that the contacting end faces of the forward and rear cylinder section adjoin the low-pressure chamber regardless of the position of the feed screw.
Ac~ording to a preferred feature of the invention the feed screw contained in the bipartite plasticizing cylinder is provided with at least one feed screw extension, which is provided on the rear with a stem which is similar to the stem of the back flow valve and extends into a socket of the feed screw or of another feed screw extension and each of said extensions is formed in its forward end face with a socket for receiving the stem of another 2076~80 extension or the stem of the back flow valve. Said extension or one of said extensions may consist of a mixing mernber, which may comprise mixing disks, which extend at right angles to the axis of the plasticizing cylinder and have approximately the same diameter as the feed screw and are formed in their rims with grooves which are angularly offset in adjacent ones of said disks.
In such arrangements the feed screw or feed screw assembly comprising the feed screw extensions may have a length which is about 25 times the diamter of the feed screw. The extensions may consist of screw sections or of mixing members. Regardless of the nature of a given extension, the provision of mating stems and sockets will ensure that the feed screw means can be increased in length in a simple manner in that the components of the feed screw assembly are connected by screw-threaded joints which are similar to the joint by which the back flow valve is connected to the feed screw means. In the feed screw assembly an extension consisting of a mixing member may be mounted directly on the feed screw proper or on a screwlike extension mounted on the feed screw proper.
By means of a feed screw extension consisting of a mixing member as described above, the plastic material can be more thorough~y mixed, e.g., in order to admix coloring materials.
Whereas conventional mixing members often consist of mixing arms, the present mixing member comprises mixing disks which occupy almost the entire cross-section of the otherwise free space within the plasticizing cylinder. To nevertheless permit a thorough mixing and a feeding of the plastic material said mixing disks are formed in their rims with grooves, which are angularly offset on 2~76~80 adjacent mixing disks so that said grooves are disposed on helical lines and permit the plastic material to pass through the mixing member in said grooves. The helix angle of the helix defined by said grooves is smaller than the helix angle of the feed screw so that the swirl imparted to the plastic material by the feed screw will inherently be disturbed and a more intense mixing will thus be effected.
Besides, the gap between the forward and rear sections of the plasticizing cylinder is disposed sufficiently to the rear and always adjoins the low-pressure chamber even when the back flow valve has been retracted, usually by three times the diamter of the feed screw, to a rearmost position.
In a preferred embodiment of the invention there is used a kit of components for use in an injection molding machine, which kit comprises, plasticizing cylinder having a forwardly facing surface and an inside peripheral surface adapted to define a low-pressure chamber, forward cylinder section having a second forwardly facing surface and a second rearwardly facing surface and an inside peripheral surface adapted to define the low pressure chamber, and at least one nozzle body defining a nozzle passage and having a rearwardly facing surface, wherein the plasticizing cylinder and the nozzle body, on the one hand, and the plasticizing cylinder and the forward cylinder section and the nozzle body, on the other hand, are adapted to be assembled to constitute plasticizing assemblies.
207648~
The kit also comprises feed screw means adapted to be dispo-sed in the low-pressure chamber and to be movable along the plasticizing assembly between rearmost and foremost positions, first connecting means for connecting the nozzle body to the plasticizing cylinder, one one hand, and to the forward section, on the other hand, and second connecting means for connecting the forward section to the plasticizing cylinder, wherein the first and second connecting means are identical.
The manufacture of said embodiment will not involve substantially higher costs because they can be manufactured as modular assemblies comprising only a few different components so that only a relatively small number of components must be kept in stock and may be provided with the same heating means, nozzle valve means and other control means.
BRIEF DESCRIPTION OF THE DRAWING
Figure 1 is a side elevation showing partly in vertical section a plasticizing assembly comprising a plasticizing cylinder.
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Figure 2 is a side elevation showing partly in section the plasticizing assembly comprising a bipartite plasticizing cylinder.
Figure 3 is an enlarged view showing the back flow valve.
~ 13 -, 2076~80 Figures 4 and 5 are enlarged views showing different forwurd sections of a bipartite plasticizing cylinder.
Figure 6 shows a feed screw assembly composed of components shown in Figures 3 to 5.
Figure 7 is an elevation like Figure 2 without a forward section.
Figure 8 is an elevation like Figure 7 with a closable nozzle body.
Figure 9 is an elevation like Figure 2 and shows a plasti-cizing assembly comprising a nozzle valve and valve-actuating means.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Illustrative embodiments of the invention will now be described in detail with reference to the drawing.
During the injection molding operation, a feed screw 12 in the heated plasticizing cylinder 10 feeds the plasticized plastic material into a high-pressure chamber H in front of the feed screw 12 as the latter is yielding back. The feed screw 12 is then axially advanced to inject the plastic material through the nozzle passage 16 into an injection mold. During that forward stroke of the feed screw 12~ a back flow valve R mounted on the feed screw 12 at its forward end is effective to seal the continuouslydecreasing high-pressure chamber H from the low-pressure chamber N, which contains the feed screw 12. The high-pressure chamber H
has a cylindrical rear portion extending in the plasticizing cylinder 10 and a forward portion, which tapers in the nozzle body 11 to the diameter of the nozzle passage 16 and merges into the latter. The nozzle body 11 and the plasticizing cylinder 10 or the forward section 14 of a biparite plasticizing cylinder 10, 14 have finish-machined confronting end faces 11b and 14b or 10b and adjacent to said end faces the parts 10 and 11 are connected by a large number of angularly spaced apart fixing screws 21 disposed on a circular line. The forward section 14 is connected to the rear section 10 of the bipartite cylinder adjacent to finish-machined end faces by similar fixing screws 121 arranged on a circular line. Adjacent to the forward portion of the high-pressure chamber H the plasticizing cylinder 10 or the rear cylinder section 10 is surrounded by a connecting sleeve 23 or 123, which surrounds also the nozzle body 11 or the forward cylinder section 14 and is secured to the plasticizing cylinder 10 if it is integral or to the forward section 14 of a bipartite plasticizing cylinder 14, 10. To that end, internal screw threads of the connecting sleeve 23 or 123 are screwed onto and axially supported by external screw threads lOa' or 14a' of a flange 10a or 14a of the plasticizing cylinder 10 if it is integral or of the forward section 14 of a bipartite plasticizing cylinder. The fixing screws 21 and 121 extend at an angle of about 45 to the axis z-z of the cylinder and the fixing screws 21 extend through a radial flange 23a of the connecting sleeve 23 and are secured at internal threads 23b or 123b. The free end portions of the fixing screws 21 or 121 extend into recesses llc or 14c formed in the nozzle body 11 or in the forward section 14 of a bipartite plasticizing cylinder (see Figures 2, 9). The abutment faces llc' and 14c' are disposed at the bottom of the recesses llc and 14c.
Instead of the connecting sleeve 23 or 123 and the fixing screws 21 or 121 other connecting means may be used. For example forward cylinder section 14, plasticizing cylinder 10 and nozzle body 11 may be screwed together or a connecting sleeve may surro~nd the parts to be connected as known in the art. Essentially the connecting means of the forward cylinder section 14 must be able to cooperate with the connecting means of the plasticizing cylinder 10.
The nozzle body 11 has a forwardly facing annular shoulder, which is in snug contact with an end face 23a' of the flange 23a.
The end face 23a' is at right angles to the axis z-z of the cylinder. The nozz1e body 11 is surrounded in part of its length by an axial flange 10a of the plasticizing cylinder 10.
The back flow valve R comprises an annular seat 13b, which is secured to the forward end face of the feed screw 12 or of the feed screw assembly which will be described hereinafter with referen~e to Figures 5 and 6, a head 13~ which is connected by a stem 13c to the feed screw 12 or feed screw assembly and axially spaced from the seat 13b, and a sealing ring 13a, which is axially slidably mounted between the seat 13b and the head 13 and radially protrudes from the seat 13b. To prevent a back flow of the plastic material from the high-pressure chamber H, the sealing ring 13a is 2076~80 in sealing contact with a forward end face of the annular seat 13b, as is shown, e.g., in Figures 2 and 6.
An adequate seal of the gap between the nozzle body 11 and the plasticizing cylinder lU or the forward cylindrical section 14 in spite of a lower contact pressure can be ensured in that the contacting end faces 11b, lOb, 14b of the nozzle body Il the plasticizing cylinder 10 and the forward cylindrical section 14 are finish-machined only in a small annular area, which adjoins the inside peripheral surface of the plasticizing cylinder 10.
The length of the plasticizing assembly can be increased in that the plasticizing cylinder is bipartite and consists of a rear section 10 and a forward section 14, which is connected to the rear section by an additional connecting sleeve 123, which is screwed on the external screw threads lOa' of the flange lOa of the rear section 10 and is thus connected to the connecting means provided on the rear section 10. That additional connecting sleeve 123 surrounds the plasticizing rear section 10 adjacent to the low-pressure chamber N so that the gap between the end faces 14b', lOb will not adjoin the high-pressure space H even when the feed screw ~2 is in its rearmost position. Basically also the gap between the end faces 11b and 14b of nozzle body 11 and forward section 14 will adjoin the low-pressure chamber N.
The rear end portion of the forward section 14 is similar to the rear end portion ot the nozzle body 11 in that the contacting end faces lOb and 14b' of the rear and forward sections of the , - ~' plasticizing cylinder abut in a recess 10c of the forward end face 10b of the rear section 10 so that the cylinder space which accomodates the feed screw 12 is defined by a continuous peripheral surface. The forward section 14 is provided at its forward end with a flange 14a, which has external screw threads 14a' and a forward end face 14b. The external screw threads 14a' are screwed into the internal screw threads of the connecting sleeve 23, which is connected to the nozzle body 11 by the means described hereinbefore. Alternatively, the nozzle body may be integrally formed with the forward section of the bipartite plasticizing cylinder.
In the embodiment shown in Figure 9 a nozzle body of the plasticizing assembly is provided with a nozzle valve. To permit the use of a nozzle valve whenever it is desired the rear section and the forward section 14 of the bipartite plasticizing cylinder are provided each with bores 10d, 10e, 10f and 14d, 14e, 14f, respectively, which are not utilized in the arrangement of Figure 2 and may be used to accomodate temperature sensors and a valve needle 17. As a result, the nozzle passage can be sealed by a valve needle regardless of the use of an integral plasticizing cylinder 10 or a bipartite plasticizing cylinder 10, 14. As is apparen-t from a comparison of Figures 8 and 9 it is sufficient in the arrangement shown in Figure 9 to replace the lever 19 shown in Figure 8 by the longer lever 19', to which the forward actuating rod 18' can be pivoted on a lower level than the forward actuating rod 18 in Figure 8. The forward actuating rod 18' is longer than the forward actuating rod 18. In spite of that conversion, the rear actuating rod 20 is pivoted to the levers l9 and 19' at the 2~7~48~
same distance from the axis S on which the lever is pivoted to the plasticizing cylinder 10 or the rear section lO
thereof.
The longer plasticizing cylinder may accommodate either a longer feed screw or a feed screw assembly, which comprises a normal feed screw 12 and at least one feed screw extension 15. The feed screw assembly is longer than the feed screw 12 by five diameters of the feed screw 12 so that the length of the feed screw assembly is 25 times the diameter of the feed screw. Whereas the stem 14c of the back flow valve is normally held in the socket 12a in the forward end face of the feed screw 12, a similar stem of feed screw extension 15 may be fixed in said socket 12a. Each feed screw extension 15 is formed in its forward end face with a similar socket 15a, which is used to accommodate a stem 15c of a preceding feed screw extension 15 or the stem 13c of the back flow valve. The homogenizirg and mixing action can be intensified in that the feed screw assembly comprises a feed screw extension which consists of a mixing member.
In the present embodiment the mixing member comprises mixing disks 15b, which extend at right angles to the axis z-z oF the cylinder and have approximately the same diameter as the feed screw 12. To permit the plastic material to flow through the mixing disks, the latter are formed in their rims with grooves 15b' and the grooves 15b' of adjacent disks 15b are angularly offset so that the grooves 15b' are arranged on helices and the plasticized plastic material is forced forwardly from the feed screw 12 through said grooves. The helix angle of the helix on .
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which said grooves are disposed is smaller than the helix angle of the feed screw 12 so that the swirl imparted to the plasticized plastic material by the feed screw 12 is interrupted in the mixiny feed screw extension and the mixing action is thus intensified.
Energy can be supplied to the plastic material in the plasticizing assembly not only by the heating cuffs 27 and 27' provided on the nozzle body 11 and the rear section 10 'of the plasticizing cylinder but also by the heating cuff 27 " on the forward section 14 of the plasticizing cylinder. The plasticizing cylinder 10 is surrounded by a protective guard 30.
In those embodiments showing the bipartite plasticizing cylinder it may be understood, that the plasticizing cylinder also could consist of more than only two parts, which may be connected in the same manner as the forward and the rearward parts of the plasticizing cylinder shown in the embodiments.
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In conventional plasticizing assemblies the effective length of the feed screw usually does not exceed 20 times the diameter of said screw. On the other hand it is often desired to increase the production rate of the injection molding machine by a supply of heat at a higher rate to the plasticized plastic material. In known injection molding machines this can be accomplished only by a supply of a higher electric power to the heating cuffs although the p~wer which can thus be supplied cannot be increased indiscriminately.
U.S.Patent 4,886,439 suggests to connect the nozzle body to the plasticizing cylinder by means of a sleeve, which is adapted to be screw-connected to the plasticizing cylinder and applies an axial pressure to the nozzle body. In that case the force required to . : , 20764~0 loosen the connecting sleeve is much stronger than the force required to loosen each screw of the plasticizing cylinder described first hereinbefore. Practice has shown that such a connecting sleeve can be loosened only with the aid of a heavy implement consisting, e.g., of a fork spanner, and it is often necessary to strike against the implement in order to loosen said sleeve. Besides, it is often necessary to replace the nozzle body in the premises of the user of the injection molding mach;ne and to have that operation performed by personnel of such user or by service technicians of the manufacturer of the machine. A replace-ment of the nozzle will give rise to problems particularly when properly skilled labor and proper implements are not available or when it is necessary to transport heavy implements to remote sites of injection molding machines, e.g., in countries which are not highly developed industrially.
The related and above identified patent application describes connecting means for connecting the nozzle body to the plasticizing cylinder with a plurality of fixing screws, which are screwed in a plurality of angularly spaced apart tapped bores on a circular line. A connecting sleeve surrounds the plasticizing cylinder and the nozzle body adjacent to the gap between them and is formed with the tapped bores, which consist of through bores to abutment faces of the plasticizing cylinder.
Further, it is well known from U.S.Patent 4,842,507 to use a bipartite plasticizing cylinder comprising two separate parts. In this assembly the rearward part of the plasticizing cylinder has a 2076~80 smaller diameter and a smaller width in the clear than the forward part of the plasticizing cylinder. The rearward part dips in the separate forward part like a telescope. This assembly does not permit a simple and quicker replacement of a nozzle body or of a forward section of a bipartite plasticizing cylinder.
SUMMARY OF THE INVENTIQN
.
It is an object of the invention to provide a plasticizing assembly which is of the kind described hereinbefore and which permits the nozzle body or a forward section of a plasticizing cylinder to be replaced and which permits energy to be supplied at a higher rate to the plastic material in a simple manner.
In a plasticizing assembly which is of the kind described first hereinbefore that object is accomplished in that a forward section having a rearwardly facing surface and an inside peripheral surface elongates the plasticizing cylinder and connecting means placed at a rearward end of the forward section and corresponding to the connecting means of the nozzle body are capable for connecting the forward section to the connecting means of the-plasticizing cylinder, when the nozzle body is aside, and cooperate with the connecting means of the plasticizing cylinder, and at least said low-pressure chamber of the plasticizing cylinder is enlarged by the inside peripherical surface of the low-pressure chamber.
In that plasticizing assembly the nozzly body is displaced and replaced by a forward section of the plasticizing assembly.
If such modular assemblies are provided, the plasticizing cylinder may comprise rear and forward cylinder sections and the forward cylinder section may be connected to the rear cy~inder section by means which are similar to those connecting the nozzle body to the forward cylinder section. In such an assembly comprising a bipartite plasticizing cylinder the plastic material will be plasticized and homogenized to a higher degree because it flows along a longer path so that moldings of higher quality can be made, particularly because the longer plasticizing cylinder permits more kinetic or thermal energy to be supplied to the plastic material.
According to a preferred feature of the invention a connecting sleeve is secured to the plasticizing cylinder and surrounds the plasticizing cylinder adjacent to the forward portion of the high-pressure chamber and axially overlaps the nozzle body or a forward section of a bipartite plasticizing cylindeP in part of its length, and the fixing screws which are axially supported by the screw threads of tapped bores of the connecting sleeve have end faces bearing on abutment faces of the nozzle body or of the forward section.
207648~
In that plasticizing assembly the screw threads by which the fixing screws force the nozzle body or the forward cylinder section against the plasticizing cylinder are screwed in the internal screw threads of the tapped bores of the connecting sleeve and are remote from those portions of the nozzle body and the plasticizing cylinder which are heated to critically high temperatures. In that case the screw-threaded joint connect~ng the connecting sleeve and the plasticizing cylinder is not eliminated for a replacement of the nozzle and constitutes a heat transfer bridge but the temperature adjacent to the fixing screws is far below the temperatures in the nozzle body and the plasticizing cylinder. An ingress of any corrosive gases evolved from the plasticized plas~ic material as far as to the screw threads of the fixing screws is virtually precluded so that the interengaging screw threads cannot stick together.
As a result, the nozzle body and the forward cylinder section can be replaced by an exertion of a much smaller physical force and by means of an implement which is light in weight and can easily be handled, particularly because the contact pressure which is required for a tight seal is applied by means of a large number-of fixing screws so that the manual force which is exerted on the implement is distributed to a large number of fixing screws and the implement which is required can be carried along by the technician~ e~g., in a briefcase or in a small bag.
According to a preferred feature of the invention each of the confronting end faces of the nozzle body and of the plasti-2076~8~
cizing cy1inder is finish-machined only in a relatively small annular area, which adjoins the inside peripheral surface of the plasticizing cylinder, respectively.
In that case much lower contact pressures will be required for a tight seal between the finish-machined end faces of the nozzle body or of the forward cylinder section, on the one hand, and of the plasticizing cylinder or its rear section, on the other hand, because said contact surfaces are relatively small or the nozzle body is so long that it entirely surrounds the high-pressure chamber regardless of the position of the feed screw so that the gap between the nozzle body and the plasticizing cylinder will always adjoin the low-pressure chamber. As a result~ the replacement of the nozzle will be further facilitated because much lower contact forces are required to ensure a tight seal so that the stresses in the interengaging screw threads will also be reduced.
According to a preferred feature of the invention the forwar~ cylinder section of the bipartite plasticizing cylinder is provided at its forward end with means for connecting said forward cylinder section to said nozzle body, the rear cylinder section of the bipartite plasticizing cylinder is provided at its forward end with similar means adapted to connect said nozzle body to said rear cylinder section, and said nozzle body is provided with connecting means for connecting said nozzle body selectively to said connecting means of said forward cylinder section and to said connecting means of sa-id rear cylinder section. In that case the nozzle body can be detached from the forward cylinder section and another nozzle body can be mounted on the forward cylinder section or the forward cylinder section may be omitted and the same nozzle body or a different one may be mounted on the rear cylinder section, which now constitutes the entire plasticizing cylinder.
Alternatively, an integral nozzle body may be used, which~has a length that is equal to the total length of the nozzle body and the forward cylinder section previously employed.
According to a preferred feature of the invention the forward and rear cylinder sections are provided at corresponding positions with bores which open on the outside peripheral surface of the plasticizing cylinder and are adapted to receive means such as temperature sensors and a valve needle.
According to a preferred feature of the invention the plasticizing assembly comprises a valve needle for sealing the nozzle passage of the nozzle block and means for actuating said valve needle, which actuating means comprise a lever, which is pivoted to said rear cylinder section on a pivotal axis~ a forward actuating rod, which is pivoted to said lever at a distance from said pivotal axis and is rigidly connected to said valve needle, and a rear actuating rod, which is pivoted to said pivoted lever at a distance from said pivotal axis, and said valve needle extends through a needle-guiding bore in said forward cylinder section, and when said nozzle body is directly mounted on said rear cylinder section said valve needle extends through a needle-guiding bore in said rear cylinder section, said forward actuating rod is shorter than the one used in the plasticizing assembly comprising said forward cylinder section, said lever is shorter than the one used in the plasticizing assembly comprising the forward cylinder section, and said rear actuating rod is pivoted to said lever at the same distance from said first pivotal aXis as in the plasticizing assembly comprising said forward cylinder section. In that case only two components of the actuating means must be changed for a conversion of an assembly comprising a forward cylinder section to one in which said forward cylinder section has been omitted, whereas the same heating means, valve means and other control means can be used in both embodiments.
According to a preferred feature of the invention the feed screw contained in the bipartite plasticizing cylinder extends also in the forward cylinder section and the arrangement is such that the contacting end faces of the forward and rear cylinder section adjoin the low-pressure chamber regardless of the position of the feed screw.
Ac~ording to a preferred feature of the invention the feed screw contained in the bipartite plasticizing cylinder is provided with at least one feed screw extension, which is provided on the rear with a stem which is similar to the stem of the back flow valve and extends into a socket of the feed screw or of another feed screw extension and each of said extensions is formed in its forward end face with a socket for receiving the stem of another 2076~80 extension or the stem of the back flow valve. Said extension or one of said extensions may consist of a mixing mernber, which may comprise mixing disks, which extend at right angles to the axis of the plasticizing cylinder and have approximately the same diameter as the feed screw and are formed in their rims with grooves which are angularly offset in adjacent ones of said disks.
In such arrangements the feed screw or feed screw assembly comprising the feed screw extensions may have a length which is about 25 times the diamter of the feed screw. The extensions may consist of screw sections or of mixing members. Regardless of the nature of a given extension, the provision of mating stems and sockets will ensure that the feed screw means can be increased in length in a simple manner in that the components of the feed screw assembly are connected by screw-threaded joints which are similar to the joint by which the back flow valve is connected to the feed screw means. In the feed screw assembly an extension consisting of a mixing member may be mounted directly on the feed screw proper or on a screwlike extension mounted on the feed screw proper.
By means of a feed screw extension consisting of a mixing member as described above, the plastic material can be more thorough~y mixed, e.g., in order to admix coloring materials.
Whereas conventional mixing members often consist of mixing arms, the present mixing member comprises mixing disks which occupy almost the entire cross-section of the otherwise free space within the plasticizing cylinder. To nevertheless permit a thorough mixing and a feeding of the plastic material said mixing disks are formed in their rims with grooves, which are angularly offset on 2~76~80 adjacent mixing disks so that said grooves are disposed on helical lines and permit the plastic material to pass through the mixing member in said grooves. The helix angle of the helix defined by said grooves is smaller than the helix angle of the feed screw so that the swirl imparted to the plastic material by the feed screw will inherently be disturbed and a more intense mixing will thus be effected.
Besides, the gap between the forward and rear sections of the plasticizing cylinder is disposed sufficiently to the rear and always adjoins the low-pressure chamber even when the back flow valve has been retracted, usually by three times the diamter of the feed screw, to a rearmost position.
In a preferred embodiment of the invention there is used a kit of components for use in an injection molding machine, which kit comprises, plasticizing cylinder having a forwardly facing surface and an inside peripheral surface adapted to define a low-pressure chamber, forward cylinder section having a second forwardly facing surface and a second rearwardly facing surface and an inside peripheral surface adapted to define the low pressure chamber, and at least one nozzle body defining a nozzle passage and having a rearwardly facing surface, wherein the plasticizing cylinder and the nozzle body, on the one hand, and the plasticizing cylinder and the forward cylinder section and the nozzle body, on the other hand, are adapted to be assembled to constitute plasticizing assemblies.
207648~
The kit also comprises feed screw means adapted to be dispo-sed in the low-pressure chamber and to be movable along the plasticizing assembly between rearmost and foremost positions, first connecting means for connecting the nozzle body to the plasticizing cylinder, one one hand, and to the forward section, on the other hand, and second connecting means for connecting the forward section to the plasticizing cylinder, wherein the first and second connecting means are identical.
The manufacture of said embodiment will not involve substantially higher costs because they can be manufactured as modular assemblies comprising only a few different components so that only a relatively small number of components must be kept in stock and may be provided with the same heating means, nozzle valve means and other control means.
BRIEF DESCRIPTION OF THE DRAWING
Figure 1 is a side elevation showing partly in vertical section a plasticizing assembly comprising a plasticizing cylinder.
.
Figure 2 is a side elevation showing partly in section the plasticizing assembly comprising a bipartite plasticizing cylinder.
Figure 3 is an enlarged view showing the back flow valve.
~ 13 -, 2076~80 Figures 4 and 5 are enlarged views showing different forwurd sections of a bipartite plasticizing cylinder.
Figure 6 shows a feed screw assembly composed of components shown in Figures 3 to 5.
Figure 7 is an elevation like Figure 2 without a forward section.
Figure 8 is an elevation like Figure 7 with a closable nozzle body.
Figure 9 is an elevation like Figure 2 and shows a plasti-cizing assembly comprising a nozzle valve and valve-actuating means.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Illustrative embodiments of the invention will now be described in detail with reference to the drawing.
During the injection molding operation, a feed screw 12 in the heated plasticizing cylinder 10 feeds the plasticized plastic material into a high-pressure chamber H in front of the feed screw 12 as the latter is yielding back. The feed screw 12 is then axially advanced to inject the plastic material through the nozzle passage 16 into an injection mold. During that forward stroke of the feed screw 12~ a back flow valve R mounted on the feed screw 12 at its forward end is effective to seal the continuouslydecreasing high-pressure chamber H from the low-pressure chamber N, which contains the feed screw 12. The high-pressure chamber H
has a cylindrical rear portion extending in the plasticizing cylinder 10 and a forward portion, which tapers in the nozzle body 11 to the diameter of the nozzle passage 16 and merges into the latter. The nozzle body 11 and the plasticizing cylinder 10 or the forward section 14 of a biparite plasticizing cylinder 10, 14 have finish-machined confronting end faces 11b and 14b or 10b and adjacent to said end faces the parts 10 and 11 are connected by a large number of angularly spaced apart fixing screws 21 disposed on a circular line. The forward section 14 is connected to the rear section 10 of the bipartite cylinder adjacent to finish-machined end faces by similar fixing screws 121 arranged on a circular line. Adjacent to the forward portion of the high-pressure chamber H the plasticizing cylinder 10 or the rear cylinder section 10 is surrounded by a connecting sleeve 23 or 123, which surrounds also the nozzle body 11 or the forward cylinder section 14 and is secured to the plasticizing cylinder 10 if it is integral or to the forward section 14 of a bipartite plasticizing cylinder 14, 10. To that end, internal screw threads of the connecting sleeve 23 or 123 are screwed onto and axially supported by external screw threads lOa' or 14a' of a flange 10a or 14a of the plasticizing cylinder 10 if it is integral or of the forward section 14 of a bipartite plasticizing cylinder. The fixing screws 21 and 121 extend at an angle of about 45 to the axis z-z of the cylinder and the fixing screws 21 extend through a radial flange 23a of the connecting sleeve 23 and are secured at internal threads 23b or 123b. The free end portions of the fixing screws 21 or 121 extend into recesses llc or 14c formed in the nozzle body 11 or in the forward section 14 of a bipartite plasticizing cylinder (see Figures 2, 9). The abutment faces llc' and 14c' are disposed at the bottom of the recesses llc and 14c.
Instead of the connecting sleeve 23 or 123 and the fixing screws 21 or 121 other connecting means may be used. For example forward cylinder section 14, plasticizing cylinder 10 and nozzle body 11 may be screwed together or a connecting sleeve may surro~nd the parts to be connected as known in the art. Essentially the connecting means of the forward cylinder section 14 must be able to cooperate with the connecting means of the plasticizing cylinder 10.
The nozzle body 11 has a forwardly facing annular shoulder, which is in snug contact with an end face 23a' of the flange 23a.
The end face 23a' is at right angles to the axis z-z of the cylinder. The nozz1e body 11 is surrounded in part of its length by an axial flange 10a of the plasticizing cylinder 10.
The back flow valve R comprises an annular seat 13b, which is secured to the forward end face of the feed screw 12 or of the feed screw assembly which will be described hereinafter with referen~e to Figures 5 and 6, a head 13~ which is connected by a stem 13c to the feed screw 12 or feed screw assembly and axially spaced from the seat 13b, and a sealing ring 13a, which is axially slidably mounted between the seat 13b and the head 13 and radially protrudes from the seat 13b. To prevent a back flow of the plastic material from the high-pressure chamber H, the sealing ring 13a is 2076~80 in sealing contact with a forward end face of the annular seat 13b, as is shown, e.g., in Figures 2 and 6.
An adequate seal of the gap between the nozzle body 11 and the plasticizing cylinder lU or the forward cylindrical section 14 in spite of a lower contact pressure can be ensured in that the contacting end faces 11b, lOb, 14b of the nozzle body Il the plasticizing cylinder 10 and the forward cylindrical section 14 are finish-machined only in a small annular area, which adjoins the inside peripheral surface of the plasticizing cylinder 10.
The length of the plasticizing assembly can be increased in that the plasticizing cylinder is bipartite and consists of a rear section 10 and a forward section 14, which is connected to the rear section by an additional connecting sleeve 123, which is screwed on the external screw threads lOa' of the flange lOa of the rear section 10 and is thus connected to the connecting means provided on the rear section 10. That additional connecting sleeve 123 surrounds the plasticizing rear section 10 adjacent to the low-pressure chamber N so that the gap between the end faces 14b', lOb will not adjoin the high-pressure space H even when the feed screw ~2 is in its rearmost position. Basically also the gap between the end faces 11b and 14b of nozzle body 11 and forward section 14 will adjoin the low-pressure chamber N.
The rear end portion of the forward section 14 is similar to the rear end portion ot the nozzle body 11 in that the contacting end faces lOb and 14b' of the rear and forward sections of the , - ~' plasticizing cylinder abut in a recess 10c of the forward end face 10b of the rear section 10 so that the cylinder space which accomodates the feed screw 12 is defined by a continuous peripheral surface. The forward section 14 is provided at its forward end with a flange 14a, which has external screw threads 14a' and a forward end face 14b. The external screw threads 14a' are screwed into the internal screw threads of the connecting sleeve 23, which is connected to the nozzle body 11 by the means described hereinbefore. Alternatively, the nozzle body may be integrally formed with the forward section of the bipartite plasticizing cylinder.
In the embodiment shown in Figure 9 a nozzle body of the plasticizing assembly is provided with a nozzle valve. To permit the use of a nozzle valve whenever it is desired the rear section and the forward section 14 of the bipartite plasticizing cylinder are provided each with bores 10d, 10e, 10f and 14d, 14e, 14f, respectively, which are not utilized in the arrangement of Figure 2 and may be used to accomodate temperature sensors and a valve needle 17. As a result, the nozzle passage can be sealed by a valve needle regardless of the use of an integral plasticizing cylinder 10 or a bipartite plasticizing cylinder 10, 14. As is apparen-t from a comparison of Figures 8 and 9 it is sufficient in the arrangement shown in Figure 9 to replace the lever 19 shown in Figure 8 by the longer lever 19', to which the forward actuating rod 18' can be pivoted on a lower level than the forward actuating rod 18 in Figure 8. The forward actuating rod 18' is longer than the forward actuating rod 18. In spite of that conversion, the rear actuating rod 20 is pivoted to the levers l9 and 19' at the 2~7~48~
same distance from the axis S on which the lever is pivoted to the plasticizing cylinder 10 or the rear section lO
thereof.
The longer plasticizing cylinder may accommodate either a longer feed screw or a feed screw assembly, which comprises a normal feed screw 12 and at least one feed screw extension 15. The feed screw assembly is longer than the feed screw 12 by five diameters of the feed screw 12 so that the length of the feed screw assembly is 25 times the diameter of the feed screw. Whereas the stem 14c of the back flow valve is normally held in the socket 12a in the forward end face of the feed screw 12, a similar stem of feed screw extension 15 may be fixed in said socket 12a. Each feed screw extension 15 is formed in its forward end face with a similar socket 15a, which is used to accommodate a stem 15c of a preceding feed screw extension 15 or the stem 13c of the back flow valve. The homogenizirg and mixing action can be intensified in that the feed screw assembly comprises a feed screw extension which consists of a mixing member.
In the present embodiment the mixing member comprises mixing disks 15b, which extend at right angles to the axis z-z oF the cylinder and have approximately the same diameter as the feed screw 12. To permit the plastic material to flow through the mixing disks, the latter are formed in their rims with grooves 15b' and the grooves 15b' of adjacent disks 15b are angularly offset so that the grooves 15b' are arranged on helices and the plasticized plastic material is forced forwardly from the feed screw 12 through said grooves. The helix angle of the helix on .
- .
which said grooves are disposed is smaller than the helix angle of the feed screw 12 so that the swirl imparted to the plasticized plastic material by the feed screw 12 is interrupted in the mixiny feed screw extension and the mixing action is thus intensified.
Energy can be supplied to the plastic material in the plasticizing assembly not only by the heating cuffs 27 and 27' provided on the nozzle body 11 and the rear section 10 'of the plasticizing cylinder but also by the heating cuff 27 " on the forward section 14 of the plasticizing cylinder. The plasticizing cylinder 10 is surrounded by a protective guard 30.
In those embodiments showing the bipartite plasticizing cylinder it may be understood, that the plasticizing cylinder also could consist of more than only two parts, which may be connected in the same manner as the forward and the rearward parts of the plasticizing cylinder shown in the embodiments.
. -.:
Claims (21)
1. In a plasticizing assembly for use in an injection molding machine, which assembly comprises a plasticizing cylinder having a forwardly facing surface and an inside peripheral surface defining at least a low-pressure chamber and having connecting means placed at its forward end, a nozzle body internally defining a nozzle passage and having a rearwardly facing surface and being provided with heating means and connecting means placed at its rearward end connecting said nozzle body to said connecting means of said plasticizing cylinder said low-pressure chamber having a cylindrical portion in said plasticizing cylinder and tapering in said nozzle body to the diameter of said nozzle passage and merges into said nozzle passage and said assembly further comprising feed screw means disposed in said low-pressure chamber and movable along said plasticizing assembly between rearmost and foremost positions, the improvement residing in that a forward section having a second rearwardly facing surface and an inside peripherical surface elongates said plasticizing cylinder, connecting means placed at a rearward end of said forward section are adequate to said connecting means of said nozzle body and are capable for connecting said forward section to said connecting means of said plasticizing cylinder, when the nozzle body is aside, and cooperate with said connecting means of said plasticizing cylinder, and at least said low-pressure chamber of said plasticizing cylinder is enlarged by said inside peripherical surface of said forward section.
2. The improvement set forth in claim 1, wherein said plasticizing cylinder and said nozzle body define in front of said low-pressure chamber a high-pressure chamber, which has a cylindrical portion in said plasticizing cylinder and tapers in said nozzle body to the diameter of said nozzle passage and merges into said nozzle passage.
3. The improvement set forth in claim 1, wherein one of the parts consisting of said plasticizing cylinder and said nozzle body is formed with a plurality of anularly spaced apart abutment faces disposed on a circular line and facing away from the other of said parts, said connecting means comprise means defining a plurality of angu-larly spaced apart tapped bores, which are disposed on a circular line, and a plurality of fixing screws, which are screwed in and axially supported in respective ones of said tapped bores and are under initial stress to force said forwardly and rearwardly facing surfaces against each other under a contact pressure, and comprise a connecting sleeve, which surrounds said plasticizing cylinder and said nozzle body adjacent to said forwardly and rearwardly facing surfaces and is connected to the other of said parts and is formed with said tapped bores, which consist of through bores open to respective ones of said abutment faces, and said fixing screws bear on respective ones of said abutment faces.
4. The improvement set forth in claim 1, wherein said one part consists of said nozzle body and said other part consists of said plasticizing cylinder.
5. The improvement set forth in claim 1, wherein said forwardly and rearwardly facing surfaces are finish-machined only in an annular area which adjoins said inside peripheral surface of said plasticizing cylinder.
6. The improvement set forth in claim 1, wherein a valve needle for selectively sealing said nozzle passage is slid-ably mounted in a needle-guiding bore, which is formed in said nozzle body and opens into said nozzle passage, said plasticizing cylinder is formed with a second bore, which is aligned with and communicates with said needle-guiding bore and valve-actuating means are provided, which comprise a lever, which is pivoted to said plasticizing cylinder on a pivotal axis, a rear actuating rod, which is pivoted to said lever at a distance from said pivotal axis, and a forward actuating rod, which is pivoted to said lever at a distance from said pivotal axis and extends in said second bore and is rigid with said valve needle.
7. The improvement set forth in claim 1, wherein said plasticizing cylinder comprises a rear cylinder section and a forward cylinder section, which is formed with said forwardly facing surface and with said second rearwardly facing surface, said rear section is formed with a second forwardly facing surface, one of said cylinder sections is formed with a plurality of second angularly spaced apart abutment faces disposed on a circular line and facing away from the other of said cylinder sections, a second connecting sleeve is provided, which surrounds said cylin-der sections adjacent to said second forwardly and rearwardly facing surfaces and is connected to said other cylinder section and is formed with a plurality of second angularly spaced apart through bores, which are open to respective ones of said second abutment faces, and a plurality of second angularly spaced apart fixing screws are screwed in and axially supported in respective ones of said second tapped bores and under initial stress bear on respective ones of said abutment faces to force said second forwardly and rearwardly facing surfaces against each other under a contact pressure.
8. The improvement set forth in claim 7, wherein said one cylinder section consists of said rear section and said other cylinder section consists of said forward section.
9. The improvement set forth in claim 7, wherein said second connecting sleeve comprises a second radial flange, said other cylinder section is formed with a plurality of second angularly spaced apart recesses, which are define by said second abut-ment faces, and said fixing screws extend at an angle to the axis of said cylinder through said second radial flange.
10. The improvement set forth in claim 7, wherein said rear cylinder section is formed at its forward end with a socket defined at its bottom with said second forwardly facing surface and said forward section extends into said socket, and said rear and forward sections have flush inside peripheral surfaces defining a space which accommodates said feed screw means.
11. The improvement set forth in claim 7, wherein said rear and forward cylinder sections are provided with similar bores for accomodating temperature sonsors.
12. The improvement set forth in claim 7, wherein a valve needle for selectively sealing said nozzle passage is slid-ably mounted in a needle-guiding bore, which is formed in said nozzle body and opens into said nozzle passage, said forward section of said plasticizing cylinder is formed with a second bore, which is aligned with and communicates with said needle-guiding bore, and valve-actuating means are provided, which comprise a lever, which is pivoted to said rear section of said platicizing cylinder on a pivotal axis, a rear actuating rod, which is pivoted to said lever substan-tially at a predetermined distance from said pivotal axis, and a forward actuating rod, which is pivoted to said lever at a second distance from said pivotal axis and extends through said second bore and is rigid with said valve needle.
13. The improvement set forth in claim 7, wherein said rear section of said plasticizing cylinder is formed with a third bore, which has the same inclination to the axis of said cylinder as said needle-guiding bore, said nozzle body is adapted to be connected directly to said rear section of said plasticizing cylinder so that said third bore is aligned with and communicates with said needle-guiding bore, said lever is adapted to be replaced by a second lever, which is pivoted to said rear section of said plasticizing cylinder on said pivotal axis and is adapted to be pivoted to said rear actuating rod substantially at said predetermined distance from said pivotal axis, and a second forward actuating rod which is rigid with said valve needle is adapted to be pivoted to said second lever at a distance which is smaller than said second distance from said pivotal axis.
14. The improvement set forth in claim 1, wherein said feed screw means comprise a feed screw formed at its forward end with a socket, and extension means comprising a rearwardly extending first stem, which is detachably mounted in said socket, and are formed at their forward end with a second socket, and a back flow valve is provided, which has a rearwardly extending second stem, which is detachably mounted in said second socket.
15. The improvement set forth in claim 14, wherein said extension means comprise a feed screw extension consisting of a mixing member, compri-sing a plurality of mixing disks, which are at right angles to the axis of said plasticizing cylinder and have approximately the same diameter as said feed screw and have rims formed with angularly spaced apart grooves, which are angularly offset in adjacent one of said mixing disks.
16. The improvement set forth in claim 7, wherein said forward and rear cylinder sections define said inside periphe-ral surface of said plasticizing cylinder and said forwardly and rearwardly facing surfaces are finish-machined only in an annular area, which adjoins said inside peripheral surface.
17. A kit of components for use in a plasticizing cylinder for use in an injection molding machine, which kit comprises, plasticizing cylinder having a forwardly facing surface and an inside peripheral surface adapted to define a low-pressure chamber, forward cylinder section having a second forwardly facing surface and a second rearwardly facing surface and an inside peripheral surface adapted to define said low-pressure chamber, and at least one nozzle body defining a nozzle passage and having a rearwardly facing surface, wherein said plasticizing cylinder and said nozzle body, on the one hand, and said plasticizing cylinder and said forward cylinder section and said nozzle body, on the other hand, are adapted to be assembled to constitute plasticizing assemblies, said kit also comprises feed screw means adapted to be disposed in said low-pressure chamber and to be movable along said plasticizing assembly between rearmost and foremost positions, first connecting means for connecting said nozzle body to said plasticizing cylinder, on one hand, and to said forward section, on the other hand, and second connecting means for connecting said forward section to said plasticizing cylinder, wherein the first and second connecting means are identical.
18. A feed screw assembly for use in a plasticizing assembly for use in an injection molding machine, which feed screw assembly comprises a feed screw formed at its forward end with a socket, and extension means comprising a rearwardly extending first stem, which is detachably mounted in said socket, and are formed at their forward end with a second socket, and which feed screw assembly is provided with a back flow valve which has a rearwardly extending second stem, which is deta-chably mounted in said second socket.
19. A feed screw assembly as set forth in claim 18, wherein said exten-sion means comprise a plurality of feed screw extensions, each of which is provided with a rearwardly extending stem detachably mounted in one of said sockets and is formed at its forward end with a socket containing one of said stems.
20. A feed screw assembly as set forth in claim 18, wherein said exten-sion means comprise a feed screw extension consisting of a mixing member.
21. A feed screw assembly as set forth in claim 20, wherein said mixing member comprises a plurality of mixing disks, which are at right angles to the axis of said plasticizing cylinder and have approximately the same diameter as said feed screw and have rims formed with angularly spaced apart grooves, which are angularly offset in adjacent ones of said mixing disks.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE4130287A DE4130287A1 (en) | 1991-02-23 | 1991-09-12 | PLASTICIZING CYLINDERS ON A PLASTIC INJECTION MOLDING MACHINE |
| DEP4130287.7 | 1991-09-12 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2076480A1 true CA2076480A1 (en) | 1993-03-13 |
Family
ID=6440407
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2076480 Abandoned CA2076480A1 (en) | 1991-09-12 | 1992-08-20 | Plasticizing assembly for use in an injection molding machine |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0531652A3 (en) |
| JP (1) | JPH05301263A (en) |
| CA (1) | CA2076480A1 (en) |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2255162A1 (en) * | 1973-12-20 | 1975-07-18 | Piot Henri | Extrusion barrel assembled from tubular elements - to facilitate change or renewal of selected sections |
| US4154536A (en) * | 1977-07-25 | 1979-05-15 | Beloit Corporation | High efficiency injection molding screw |
| JPH03121823A (en) * | 1989-10-05 | 1991-05-23 | Komatsu Ltd | Screw for injection molding machine |
| DE4105731C1 (en) * | 1991-02-23 | 1992-06-04 | Karl 7298 Lossburg De Hehl | |
| DE4130287A1 (en) * | 1991-02-23 | 1993-04-01 | Karl Hehl | PLASTICIZING CYLINDERS ON A PLASTIC INJECTION MOLDING MACHINE |
-
1992
- 1992-07-09 EP EP19920111688 patent/EP0531652A3/en not_active Withdrawn
- 1992-08-20 CA CA 2076480 patent/CA2076480A1/en not_active Abandoned
- 1992-09-14 JP JP27082292A patent/JPH05301263A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| EP0531652A3 (en) | 1993-05-05 |
| EP0531652A2 (en) | 1993-03-17 |
| JPH05301263A (en) | 1993-11-16 |
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