INJECTION MECHANISM FOR MOLDING PLASTICS

Abstract: The invention relates to an injection mechanism for molding plastics, comprising at least one injection bushing (2), at least one lower needle valve (26), which is supplied by the injection bushing (2) with molten plastics and opened by the pressure of the molten plastics during injection, further comprising heating means (7, 8, 11) and cooling means (15) adjacent to the flow path of the plastics, control means for maintaining the plastics at an adjusted temperature, further control means for injecting the molten plastics into at least one mold cavity (6) via a corresponding injection aperture (5), and for the closing of the mold cavity (6) after finishing the injection, wherein for improving this mechanism, especially for facilitating very small center distances, only one plunger (30-36) within a heated distributor block (1) is provided, which actuates several needle valves (26), situated at different locations within the distributor block (1) for supplying the molten plastics to the mold cavity (6) via one single injection bushing (2), an injection nozzle (9) and several lower injection openings (10, 5).

Description: INJECTION MECHANISM FOR MOLDING PLASTICS The invention relates to an injection mechanism according to the introductory portion of claim 1. In injection molding arrangements for injection molding of products of plastics or other materials, these products are usually injected by way of a runner which is provided with a sprue. The injected products are then removed from this runner. If it is desirable to omit the runner, an arrangement is used with which it is possible to utilize runnerless injection molding. In such an arrangement for runnerless injection molding of products, one or more injection nozzles are assembled to a heated distributor block, which is geometrically separated from the injection machine, and the molten plastics are flowing from the injection molding machine through radially extending distributor channels in the heated distributor block downward through the injection nozzles and by way of the injection aperture into the product cavity. The products which are injection molded in this fashion may exhibit injection spots which can very negatively influence the function or the appearance of the products to be injection molded. In order to mold products which absolutely must not exhibit injection spots, needle valves must be utilized, which are installed in the injection nozzles respectively in the heated distributor block these needle valves must be opened at the beginning of the injection into the cavity of the molten plastics and will close off the injection apertures in the product cavity after completion of the entire injection cycle. The botton point of each needle valve is forcibly driven into the conical injection aperture of the product cavity and, as is well known, the most critical function of such an arrangement lies in the injection aperture, where improper functioning can cause costly break down of the injection machine or imperfections in the molded product. The lower apertures of the injection nozzle are separated from the cavity plate by an air space, which is filled with plastics and which provides a thermal insulation between the hot nozzles and the cold cavity plate. In injection molding arrangements for the production particularly of products of small dimensions, this arrangement requires several injection nozzles. Until the present time the minimal center distances between individual needle valves are determined by their activating mechanism, each needle valve is activated separately and for this a certain minimal space is required. The center distances in the injection arrangement for small products to be injection molded is therefore entirely dependant on the minimal center distance which can be attained with separately activated needle valve mechanisms. Until the present time injection nozzles for this purpose have been designed such that for each selection of the manner of injection or the injection aperture, a different injection nozzle is required. The manners of injection can be among others, the so-called open nozzle, the nozzle provided with a fixed body in the injection aperture; the nozzles provided with a fixed, heated torpedo; a nozzle which is provided with a needle valve. Up to the present, a conscious selection is also required concerning the application of the manner of injection, if the applicable injection nozzle is placed centrally in the injection mold or if the injection nozzle is used in a hot runner design. Up to now, it is also necessary for the processing of certain types of plastics to make a conscious selection of the manner of injection, to commit to a certain type injection nozzle. It is evident that many types of injection nozzles must be purchased, in most cases with different dimensions and matching heights, thus not universally interchangeable. In injection molding arrangements for the production particularly of small products, this arrangement requires several injection nozzles. Up to the present time, the minimum center distances of the individual injection apertures are determined by the sizes of the injection nozzles to be used, resulting in a minimum distance. It is the object of the invention to avoid the'disadvan- tages of the above-mentioned large variety of the injection nozzles to be used, and to facilitate very small center distances in an injection mechanism according to the introductory portion of claim 1, that means, in an injection mechanism for molding plastics, comprising at least one injection bushing, at least one lower needle valve, which is supplied by the injection bushing with molten plastics and opened by the pressure of the molten plastics during injection, further comprising heating means and cooling means adjacent to the flow path of the plastics, control means for maintaining the plastics at an adjusted temperature, further control means for injecting the molten plastics into at least one mold cavity via a corresponding injection aperture, and for the closing of the mold cavity after finishing the injection. The object of the invention is solved by the features of the characterizing clause of claim 1, wherein only one plunger within a heated distributor block is provided, which actuates several needle valves, situated at different locations within the distributor block, for supplying the molten plastics to the mold cavity via one single injection bushing, an injection nozzle, and several lower injection openings. Preferred embodiments of the invention are described in the attached subclaims. The purpose of this invention is among other things to facilitate very small center distances. In this inven tion this purpose is realized in that several needle valves are placed at very small center distances (minimum center distance is 3 mm) from each other in a single injection-nozzle, which is provided with as many lower apertures as the injection nozzle contains needle valves. These needle valves are then activated by a plunger, which obtains a movement as described in claims 1 through 5 and in which the plunger has been placed in the heated distributor block to which the injection nozzle (5) is assembled. In applying such an injection nozzle several products can be injection molded with a single injection nozzle or a single large product can be injection molded through a single injection nozzle in several places, the injection nozzle being provided with needle valves in both cases. The main advantage of this new application is, in addition, that the needle valves are directly activated by a single plunger which is located in the heated distributor block and that this way a smaller dimension in height for assembly in an injection molding arrangement can be attained. The realization of this construction is such that this combination, plunger, needle valve, injection nozzle and heated distributor block, after assembly is one entity and can therefore be held within very close tolerances. Another additional essential advantage is that in applying several injection nozzles, every plunger in the heated distributor block is activated and controlled according to claims 2, 4 and 5, separately from outside the injection molding arrangement, also during the injection molding process. Because the design of the invention is realized and described in the claims, the important advantage is obtained that the needle valves can be exchanged or their axial positions can be adjusted, this latter case through the use of a spacer bushing underneath the head of the needle, without the necessity to disassemble the injection molding arrangement. To simplify the assembly and disassembly of these needles the axially adjustable guide bushing in the plunger is prevented from rotating in that it is provided with one or more flat spots, which are in contact with one or more corresponding flats in the plunger. Another purpose of the invention is to reduce the center distances of the locations where injection occurs through the use of a single injection nozzle as described above, but without utilizing needle valves. In order to allow the full realization of the above parts of the invention and this aims at an injection molding arrangement which works 100% properly and maintainance-free, the parts described below will be required as part of and the application of the invention. Because the injection nozzle has several lower apertures which protrude with respect to it and since it is necessary to place the lower apertures as close as possible to each other, but because it is desirable to obtain a correct location of the lower apertures with respect to the points of injection in the cavity plates, a spacer and centering bushing is used, which correctly centers the injection nozzle as a whole in the cavity plate, so that the lower injection apertures are placed exactly opposite the points of injection. In injection molding of certain types of plastics, e.g. polycarbonate, P.V.C., acetate, nylon, acrylics and other high value plastics, which have a norrow processing range as far as melting temperature is concerned, within which these are still easy to process, especially in the region of the lower apertures, it is necessary to keep the temperature'constant and at the correct value in this region. This is mainly realized through the fabrication of the injection nozzle from a material with high heat conductivity, e.g. beryllium copper and through the heating of this by a cast-in, plastic-tight heater element, provided with a thermocouple, placed as close as possible to the lower aperture. Further, care has to be taken that little heat is lost through conduction from the injection nozzle to the cavity plate. In order to realize this, the spacer and centering bushing has been designed as shown in the attached drawings, figures 1 through 6. In order to further reduce heat conduction losses from the heated distributor block and the injection nozzle, the heated distributor block is not in contact with the front plate of the injection molding arrangement, but assembled directly by way of the spacer and centering bushing to the cavity plate with high quality socket head cap screws. In this manner, a compact unit of the above-mentioned parts is obtained through which in the locations of the surfaces of contact of the spacer and centering bushing with the cavity plate the unit pressure against each other is so large (but still allowable) that no plastics can leak through to the outside and thus a proper closure is obtained. Making the surface of contact of the injection nozzle which is in contact with the heated distributor block, barge with respect to the length of the injection nozzle, facilitates a proper and regular heat exchange between them, through which it even becomes possible, during the processing of plastics with a wide melting temperature range, to perform injection molding without heating the injection nozzle separately, all required heat is then coming from the heated distributor block and will flow easily to the lower injection apertures, because of the large area of contact with the injection nozzle. This is thus only possible with a small ratio of length to diameter. To obtain a proper closure between these two parts, a special gasket has been placed around the distributor channel. Because the above-mentioned surfaces are in flat contact only, the heated distributor block can expand freely as a result of the heat to be supplied to it and thus slide freely over the surface of the injection nozzle. According to the subject matter of the invention, a single injection nozzle is provided with a heating element and a thermocouple and has one or more lower nozzles, as many as there are injection apertures, with a free exit opening, and in which one or more externally adjustable fixed needles can be placed or omitted, or one or more externally adjustable needle valves. All above-mentioned manners of injection can be realized in placing the injection nozzle centrally in the injection molding arrangement or installing this injection nozzle in a hot runner design. In order to facilitate full utilization of the abovementioned parts of the invention through which a 100% break down free injection arrangement is aimed at, the parts which are required for the application of the invention and will be part and parcel of it, will be described below. Because the injection nozzle contains several lower injection apertures which protrude with respect to it and if it is necessary to place the lower injection apertures as close to each other as possible, and to obtain the correct location of the lower apertures with respect to the injection openings in the cavity plates, a spacer and centering ring can be utilized here, which insures proper centering of the entire. injection nozzle with respect to the cavity plate so that the lower injection apertures are placed exactly opposite the injection openings. If it is necessary to injection mold a certain type of plastics such as polycarbonate, P.V.C., acetate, nylon, acrylates and other high quality plastics which have a narrow range of processing parameters such as melting temperature within which these can be properly processed especially in the vicinity of the lower aperture, care should be taken that at this location the temperature remains constantly at the correct value. This is attained mainly in producing the injection nozzle from a material with high heat conductivity,e.g. beryllium copper and in heating this by means of an integrally cast, plasticstight heating element, provided with a thermocouple which should be placed as close as possible to the lower nozzle. Further, care should be taken not to lose too much heat through conductivity of the injection nozzle with respect to the cavity plate. To realize this, the spacer and centering ring is designed as shown in the attached drawings Fig. 1' through 7'. In order to further reduce heat conduction losses from the heated distributor block and the injection nozzle, the heated distributor block is not installed against a front plate of the injection molding arrangement, but bolted directly against the cavity plate via the adaptor plate or installation unit by means of the above-mentioned spacer and centering ring, with high strength socket head cap screws. In this manner, a compact assembly of the above-mentioned parts is obtained, so that at the location of the surfaces of contact of the spacer and centering ring with the cavity plate the unit pressure with respect to each other is so large (but still allowable) that'this way no plastics can leak to the outside and thus the proper closure is obtained. Making the surface of contact of the injection nozzle with the heated distributor block large with respect to the length of this injection nozzle results in proper and uniform heat exchange which even makes it possible in- processing those plastics which have a large melting range, to injection mold without separately heating the injection nozzle. All heat thus emanates from the heated distributor block and flows easily via the large area of contact of the injection nozzle to the lower injection apertures. Thus this is only possible with small length to diameter ratios. To obtain the proper closure between these two parts the distributor channel is surrounded by a special gasket. Because the above surfaces are in plane contact, the distributor block is free to expand as a result of the added heat and can slide freely over the surface of the injection nozzle. The invention will now be illustrated with the aid of drawings for several application examples, in which: Fig. 1 - a cross-section through part of an arrangement for injection molding of plastics, provided with a single needle valve and in which the plunger has been placed in the heated distributor block, as part of the invention. Fig. 2 - a cross-section of Fig. 1, taken through the center line of the needle valve. Fig. 3 - a cross-section as shown in Fig. 2, but this time of a manifold application as covered in the invention. Fig. 4 - a cross-section of a needle valve, activated by a plunger,applied centrally located in an injection molding arrangement and against which the injection nozzle of the injection machine is directly placed,'as part and parcel of the invention. Fig. 5 - a cross-section as shown in Fig, 4, but now in manifold application, as part of the invention. Fig. 6 - a cross-section of a part of an arrangement for injection molding of plastics which is provided with a single needle valve and in which the plunger is placed within a part of a channel block which is not directly heated by a heating element, such as is, among other, the case in the runnerless injection molding arrangement "THE COOL ONE", marketed by DME in the U.S.A. which has its European Headquarters in Mechelen, Belgium. Naturally, this can also be used in a manifold application in accordance with the invention. Fig. 1' - a cross-section of the injection molding mechanism with a free injection aperture, placed centrally in an injection arrangement as part and parcel of the invention. Fig. 2' - a cross-section of the injection molding mechanism with a free injection aperture, placed in a hot runner injection molding arrangement, as part and parcel of the invention. Fig. 3' - a cross-section of the injection molding mechanism with a free injection aperture, in which opening has been placed a fixed needle which can be adjusted externally, which mechanism is placed centrally in an injection molding arrangement as part and parcel of the invention. Fig. 4' - a cross-section of the injection mechanism, with a free injection aperture, in which has been placed a fixed needle which is externally adjustable, which mechanism has been placed in a hot runner injection molding arrangement, as part and parcel of the invention. Fig. 5' - a cross-section of the injection molding mechanism, with a free injection aperture, in which an externally adjustable needle valve has been placed, which is placed in a hot runner injection molding arrangement, as part and parcel of the invention. Fig. 6' - a cross-section of the injection mechanism, with several free injection apertures in which an externally adjustable needle valve has been placed, which is placed in a hot runner injection molding arrangement, as part and parcel of the invention. Fig. 7' - a cross-section of Fig. 6' running through the center line, as part and parcel of the invention. In the above mentioned figures, starting with Fig. 1, number 1, are indicated part of the entity of the heated distributor block of an injection molding arrangement, with injection nozzle 2 through which the molten plastics enter the injection molding arrangement from the injection machine by way of distributor channels 3 and 4 and injection aperture 5 is injected into the form cavity 6. The injection bushing 2 is provided with band heater element 7 and the heated distributor block 1 is provided with heater cartridges 8. Against the heated distributor block has been placed the injection nozzle 9 provided with distributor channel 4, which in turn is provided with the lower injection aperture 10. In the injection nozzle has been placed a cast-in heater element 11, provided with a thermocouple 12. This thermocouple should be located nearest the vicinity of the lower aperture, because this is the critical point as far as keeping the molten plastics in the space between the lower aperture 10 and the recess 13 in the form cavity plate 14, at the proper temperature. Near the lower aperture the plastics material is kept warm respectively warms up or cools off, depending on the temperature control of the injection nozzle. Because the temperature of the injection nozzle can be controlled externally by means of an installed thermo couple, the temperature of the lower aperture can be managed accurately. This is of great importance in injection molding of so-called engineering materials having a narrow processing temperature range, in which the molten plastics are either too cold and resistant to flow or too hot and thus are burnt and become unfit for use. On the side of recess 13 in form cavity 14 the molten plastics are cooled off locally because the form cavity plate is cooled off by a cooling fluid in cooling channels 15. Because in the described system the temperatures of both above-mentioned sides 10 and 13 can be controlled and particularly at the location of side 10, injection molding with the described system will be performed without problems. The closure between the injection nozzle and the heated distributor block is obtained by a special gasket 16. In order to incur as little as possible heat conduction losses, a spacer and centering bushing 17 is placed between injection nozzle 9 and the form cavity plate 14, realized as shown in the attached drawings Fig. 1 through 6. Mathematically it can be shown that this design provides 6 to 10 times less heat conductivity and therefore also 6 to 10 times less heat loss. In order to assemble the injection nozzle accurately opposite the the injection opening 5, the spacer and centering bushing 17 is used. The injection nozzle is centered with respect to the rim 18 in the spacer and centering bushing, which in turn is centerd in the form cavity plate 14 with respect to the diameter 19. The surfaces 20 and 21 of the spacer and centering bushings 17 will have to be coaxial within predetermined tolerances. Installing the spacer and centering bushings provides airspace 22 between bushing 17 and injection nozzle 9, this spacer 22 will be fiLled with plastics and will provide the proper thermal insulation between both men tioned parts 9 and 14. The installation of the spacer and centering bushing 17 also provides an air gap 23 resulting in a secord thermal insulation between injection nozzle 9 and form cavity plate 14. Installing injection nozzle 9 with high quality socket head cap screws 24 in the heated distributor block by way of the spacer and locating ring 17 on form cavity plate 14 , such a large, but still allowable,pressure is obtained on surface 25, that this results in an absolute closure against leakage of the molten plastics from the distributor channels 3 and A. Installation of the socket head cap screws also pulls the heated distributer block 1 against injection nozzle 9 also here resulting in the proper closure as well as the proper heat flow from the heated distributor block in the direction of the injection nozzle. Because mentioned parts are connected with each other by means of the socket head cap screws 24, the heated distributor block 1 does not need to be supported by a clamping plate of the injection molding arrangement, so that here also there are no contacting surfaces resulting in heat losses and the installation height of the injection molding arrangement can be kept smaller. Correct adjustment should result in location of the front surface of the needle 26 of which the front end is cylindrical or nearly cylindrical, in the same plane as the surface of the product cavity of the injection molding arrangement. At the start of the injection process, space 28 above the plunger is vented to atmosphere at the slime time at the start of the injection cycle the pressure to which the molten plastics are subjected will press needle 26, which is assembled to guide bushing27 via the surface of the enlarged part of bushing 27 against frictional resistance, moving it a distance of about 4 mm, so that the molten plastics can enter the product cavity 6 by way of the injection opening 5. The travel of needle 26 is limited through contact of the shoulder of the guide bushing 27 against a surface in the bore in the heated distributor block. As soon as the injection cycle has been terminated, the pressure in the distributor channels 3 and 4 will increase no longer and if the injection nozzle 57 of the injection machine (see Fig. 6), after termination of the injection cycle, is pulled back in the injection bushing 2, the existing pressure in the distributor channels 3 and 4 will be reduced rapidly and if there exists a proper fit between the injection nozzle and the injection bushing a vacuum will even result in the distributor channels. The instant the total injection cycle will be terminated, a signal from within the injection machine will cause compressed air to press on surface 29 of the plunger existing of parts 30 and 31. In the plunger the guide bushing 27 has been installed which is secured against turning and in the guide bushing in turn the needle 26 is installed. The compressed air causes a force to act through which the plunger and thereby the needle 26 are moved downward with great force and speed, so that the injection opening 5 is closed and the front end of the needle 26 is caused to lie in one plane with the out side surface of the form cavity 6. As was described above, at the beginning of the injection of plastics, the compressed air is vented and the space: 28 above surface 29 will lose its pressure. The hightness of the closure of the point of the needle valve in the injection opening is not critical, because during the closed condition of the needle valve, no large pressure differences are occuring, so that closure against a ring-shaped surface of minor dimension (about 0.5 mm) suffices. In order to minimize wear during operation, the edge of the bottom front surface of the needle is provided with a radius of about o.2 mm, in addition, the corresponding inside edge of the injection aperture in the recess 13 is chamfered. The plunger consisting of parts 30 and 31 which are held together by socket head cap screws 33 are located with respect to each other through the accurate male-female fit 34 between the two, in addition the plunger contains a gasket ring 32. Guide bushing 27 is installed in the plunger with ample clearance but secured against rotation with cap screw 35, so that independant guiding of the plunger assembly as well as guide bushing 27 with respect to each other are assured. Leakage around the plunger is prevented by the gasket 32 and after completion of its travel, surface 36 of the plunger will be in contact with surface 37 of the heated distributor block, so that air which could escape around the gasket 32, should it become worn, is stopped anyway. Should, after a time, seats 36 or 37 become damaged, the compressed air is still up against closure 38. The parts 30, 31 and 27 can easily be manufactured to the required tolerances, since they have a round geometry, this also goes for the corresponding bores for these parts in the heated distributor block. For convenient assembly and disassembly of the plunger and the needle valve, the heated distributor block 1 is provided with a cover 39, which is attached by means of socket head cap screws 40. This has the advantage that in case of break down in the described system, assembly and disassembly can be executed easily during the injection molding process, without having to remove the injection molding arrangement from the injection machine. The closure against leakage of the molten plastics around the guide bushing 27 in the heated distributor block is obtained by an accurate fit of the one part within the other and by a large ratio of length versus diameter. To prevent wear in the heated distributor block, guide bushing 27 is heat treated, so that the hardness of the latter is lower than that of the distributor block. Should some molten plastics leak through, it will be collected in groove 41 from where it will run out via channel 42 and tube 43. This drainage will be facilitated during admittance of compressed air to the plunger since during the plunger's downward travel air within the space 58 is compressed and expelled by way of channel 59 and tube 43 causing a partial vacuum in channel 42. In Fig. 2 and 3 it can be seen that the lead wires from the heater element and the thermocouple are brought to the outside through installed tube 44 to prevent damage in assembly and should leakage of molten plastics take place. Compressed air is supplied and vented through tube 45. In Fig. 3 the application of a manifold design of the injection nozzle with several needle valves is shown. To this design the operation and all applications and characteristics of the single design as mentioned above and to be mentioned below, are applicable, subject to the condition that the injection nozzle has to be secured against rotation outside the diameter of the spacer and centering bushing. In Fig. 4 and 5 the design of the central location is shown to which the premises as mentioned in Fig. 3 are also applicable. The parts 46 are band heater elements. With reference to Fig. 6, the operation of a design in which the plunger is placed within a not directly heated 'distributor block 60 is described. To this design the operation and all applications and characteristics of the single and manifold design as mentioned above and to be mentioned below are applicable. The molten plastics within this distributor block are kept at the proper temperature by heated tubes 47. The above-mentioned injection nozzle 9 is now composed of parts 48, 49 and 50. The heater element 11, controlled by the internally installed thermocouple 12, will keep this injection nozzle at the desired temperature. To reduce heat conduction losses, part 49 contacts the distributor block 60 only with the narrow edge 51 which also goes for part 50 with edge 52. Because part 49 is heated and is made from a highly conductive material, e.g. beryllium copper,the molten plastics which flow from distributor channels 53 to part 49, will flow to injection aperture 5 from distributor channels 54 and 55, whence to the product cavity. Above, in Fig. 1 through 6, preferential designs of the single and manifold needle valves have been described in accordance with the invention, however, it will be evident that within the framework of the invention several variations of the details are possible. Those parts which in accordance with the drawings have been designed to be operated with Allen wrenches, may be suited for operation with other tools, such as a screw driver. Moreover, the plunger can be activated as described in claims 1 through 6. The needle valve 26 may be installed directly in the plunger, in which case guide'bushing 27 is eliminated and the plunger must be made double acting. The injection nozzle can also be composed from parts such as 48, 49 and 50. In the above-mentioned figures starting with Fig. 1', the reference number 8' indicates the installation plate of the injection mechanism with injection opening 21' through which the molten plastics enter the injection mechanism from the injection machine and are injected via the distributor channels 20' and 2' and the injection aperture 11' into the cavity 22'. Against installation plate 8' has been placed the injection nozzle 1', which has been provided with distributor channel 2' running into the injection aperture 3'. The injection nozzle has been cast around a heater element 4' which is provided with thermocouple 5'. This thermocouple should be located as closely as possible in the vicinity of the lower aperture, because this is the critical point as far as the correct temperatures of the molten plastics are concerned. The molten plastics fill the space between the lower aperture 3' and the recess 6' in the cavity plate 7'. Near the lower aperture the plastics are kept warm, are heated or cooled depending on the temperature control of the injection nozzle. Because the temperature of the injection nozzle can be controlled externally by virtue of the installation of a thermocouple, the temperature of the lower aperture can be exactly regulated. This is of extreme importance in injection molding of the so-called technical plastics which have a narrow processing temperature range, in which the molten plastics are either too cold and thus flow very difficult or too hot and thus burn out and are destroyed. In the recess 6' in the cavity plate 7" the molten plastics are cooled off because the cavity plate is cooled by means of a coolant flowing in cooling channels. Because in the described system## the temperature of both mentioned sides 3' and 7' can be regulated and especially side 3',it will be possible to injection mold with the described system without problems. The closure between the injection nozzle and the installation plate 8' is obtained by the special gasket 9-'. In order to restrict heat losses as much as possible, a spacer and centering ring 10' is placed between injection nozzle 1' and cavity plate 7', which is designed as shown in the attached drawings, Fig. 1' through 7'. It can be proven mathematically that this design reduces heat conduction 6-10 times and thus reduces heat losses 6-10 times. In order to place the injection nozzle exactly opposite the injection aperture 11', the spacer and centering ring 10' is utilized. On one end the injection nozzle is centered on edge 12' in the spacer and centering ring, which in turn is centered in the cavity plate 7' on diameter 13'. Surfaces 14' and 15' of the spacer and centering ring 10' therefore will be coaxial with each other within predetermined tolerances. Installation of the spacer and centering ring results in an air space 16' between ring 10' and the injection nozzle 1'. This space 16' will be filled with plastics resulting in the proper thermal insulation between abovementioned parts 1' and 7'. Installation of the spacer and centering ring 10' also results in an air space 17', providing a second thermal insulation between injection nozzle 1' and cavity plate 7'. In assembling the injection nozzle 1' by means of high strength socket head cap screws and the spacer and centering ring 10', to cavity plate 7',- such a high unit pressure (but still allowable) is obtained on surface 19', that this results in absolute closure against leakage of molten plastics from distributor channels 2' and 20'. Installation of the socket head cap screws pulls installation plate 8' against the injection nozzle as well, also resulting in proper closure as well as proper heat flow from the injection nozzle in the direction of the installation plate. To obtain proper centering of parts 1' and 8', a centering ring 23' is installed whereas-an exchangeable bushing 24' has been installed in installation plate 8'. In Fig. 2', the injection molding mechanism of Fig. 1' has been installed such that the injection nozzle 1' is placed against the heated distributor block 25' (hot runner beam) and the installation plate 8' is placed on the heated distributor block. The installation plate 8' is provided with a centering edge 43' which fits accurately within the centering bore 44' in the hot runner beam 25'. With the socket head cap screws placed in the installation plate (not shown here but shown in Fig. 4', ref. no. 35'), the heated distributor block 25' and the injection nozzle 1' are bolted to the cavity plate 26'. Thus it is possible to utilize the injection molding mechanism shown in Fig. 1', which is here placed centrally in an injection molding mechanism in a hot runner design in that the hot runner beam is placed between installation plate 8' and injection nozzle 1', without the necessity to make any changes at all in parts 1' and 8'. In Fig. 3', the injection molding mechanism shown in Fig. 1' has been installed such that here the injection molding mechanism has been provided with an externally adjustable fixed needle 27'. In removing bushing 24' of Fig. 1' and in replacing this by needle bushing 28', #an injection molding mechanism is obtained with a free injection aperture provided with an externally adjustable fixed needle. The needle bushing has been provided with several bores 29', through which the molten plastics flow from the injection molding machine via injection aperture 21' and the distributor channels 2' and 20' to the cavity 22'. In the needle bushing 28' a needle is installed which has been threaded on one end and provided with a hexagon socket. It is secured by means of the lock screw 30'. In order to close the threaded hole, cap 31' has been installed. The needle can now be moved in the injection aperture 32' to such extend that on the product to be injection molded no objectionable spot will result. In order to center the needle in the injection aperture 32', the lower part 3' of the injection nozzle 1' has been designed such that the needle is centered between several points 33'. It is even possible to make the fit between the needle and the centering points so close that the needle is in contact with the centering points and this results in flow of heat from the lower part of the nozzle 3', which is heated by the heating element in the nozzle, to the lower tip 34' of the needle to such a temperature that the plastics in injection aperture 32' can not freeze, and the aperture thus remains open. To obtain a proper heat flow via the needle to point 34', the needle is made of a high conductive material such as beryllium copper. Fig. 4' is the injection molding mechanism of Fig. 3', installed such that here the injection nozzle 1' is placed against the hot runner beam 25' and the installation plate 8' containing the needle bushing 28', needle 27', and the lock screw 30', is placed on the hot runner beam. Installation plate 8' has a centering edge 43' which fits accurately in the centering bore 44' of hot runner beam 25'. This centering and the centering ring of the injection nozzle via the spacer and centering ring in the cavity plate, causes needle 27' to be aligned with the injection aperture, with the socket head cap screws 35' in the installation plate 8', the hot runner beam and the injection nozzle are bolted against cavity plate 26'. Here again the injection molding mechanism of Fig. 1' and 3' which are installed centrally in an injection molding arrangement, can be utilized in a hot runner design through placement of the hot runner beam between installation plate 8' and the injection nozzle 1', without any change to parts 1', 8' and 28'. In Fig. 5' the injection mechanism has been installed such that here again the same injection nozzle 1' has been utilized on top of which the hot runner beam 25' has been placed, to which the needle valve as part of assembly 36' has been assembl#.The entire assembly being bolted to the cavity plate 26' by means of the socket head cap screws 35'. The needle valve contained in assembly 36' has been described in connection with Fig. 1-6 of the present application. The injection mechanism described here, with one or more needle valves, has been installed here in a separate assembly 36', such that this can be manufactured more readily in series production. The alignment of the assembly 36' on the hot runner beam has been designed in the same manner and the same dimensions as described in Figs. 2' and 4'. Here also the needle valve 27' is aligned between several centering points 33' such as described in Fig. 3, this to obtain perfect location of the needle valve above the injection aperture 37', which must close'bff, so that the injection opening will not wear on one side only. In Figs. 1' through 5' identically the same injection nozzle 1' is utilized, as a complete unit as described in Fig. 1'.#It is therefore possible to realize all existing types of injection molding with one and the same injection nozzle, if this is placed centrally in an injection molding arrangement as well as if this is placed in a hot runner injection molding arrangement. The selection of a fixed pattern of installation bolts 38' (shown in Fig. 4') renders this injection mechanism universally applicable. In Figs. 6' and 7' the design is shown of a manifold application of an injection molding arrangement with an injection nozzle 45' containing manifold lower apertures 3', in which are placed several needle valves 27'. For the manifold design, the operation of all above-mentioned and hereafter to be mentioned applications and characteristics of the single design, shown and described in Figs. 1 ' through 5', are applicable to this manifold design, subject to the condition that the injection nozzle 45' besides the alignment via spacer and centering ring 46', has been provided with spacer and centering ring 40'. For the description of the operation of this mentioned needle valve reference is made to the description of Figs. 1 through 6 of this application. Above, in Figs. 1' through 7' preferential designs of a single and manifold injection mechanism have been described according to the invention, but it is evident that within the framework of the invention, several variations of the design details are possible. - The parts which are conceived according to the drawings for servicing with the aid of Allen wrenches, can be conceived for servicing with other tools such as a screw driver.

Claims: CLAIMS: 1. Injection mechanism for molding plastics, comprising at least one injection nozzle (9.) , at least one lower needle valve (26), which is supplied by the injection bushing (2) with molten plastics and opened by the pressure of the molten plastics during injection, further comprising heating means (7, 8, 11) and cooling means (15) adjacent to the flow path (3, 4) of the plastics, control means for maintaining the plastics at an adjusted temperature (12, ...), further control means for injecting the molten plastics into at least one mold cavity (6) via a corresponding injection aperture (5), and for the closing of the mold cavity (6) after finishing the injection, c h a r a c t e r i z e d in that only one plunger (30-36) within a heated distributor block (1) is provided, which actuates several needle valves (26), situated at different locations within the distributor block (1), for supplying the molten plastics to the mold cavity (6) via one single injection bushing (2), an injection nozzle (9) and several lower injection openings (10, 5). 2. Injection mechanism according to claim 1, c h a r a c t e r i z e d in that the injection nozzle is a manifold version, which contains several needle valves which are supplied by an single injection bushing and furnish plastics to several corresponding 'injection . . apertures. 3. Injection mechanism according to claim 1 or 2, c h a r a c t e r i z e d in that the plunger is actuated pneumatically, hydraulically or by one or more springs. 4. Injection mechanism according to one of claims 1 to 3, c h a r a c t e r i z e d in that the motion of the plunger is derived from a mechanism outside the part in which the injection mechanism is installed. 5. Injection mechanism according to one of claims 1 to 4, c h a r a c t e r i z e d in that the plunger must be double acting if the needle valves are placed directly in this plunger and through which the guide bushing (27) may be omitted. 6. Injection mechanism according to one of claims 1 to 5, c h a r a c t e r i z e d in that the needle valves are not opened by the pressure of the molten plastics but by the movement of the plunger. 7. Injection mechanism according to one of claims 1 to 6, c h a r a c t e r i z e d in that the plunger is provided with a gasket, which can withstand a tempe rature of at least 4000C and of which the mechanical properties of the gasket composed of carbon alloy do not deteriorate. 8. Injection mechanism according to one of claims 1 to 7, c h a r a c t e r i z e d in that the plunger has a shoulder (36) which contacts seat (37) in the heated distributor block (1) after each stroke, such that the compressed air or the hydraulic fluid under pressure, cannot pass or escape, after wear of the closure and should both the gasket and the closure between surfaces (36, 37) not function properly any longer after prolongated operation, a close fit (38) between parts (1, 31) provide a third barrier. 9. Injection mechanism according to one of claims 1 to 8, c h a r a c t e r i z e d in that the plunger is composed of two parts (30, 31) to form an integral unit which can be removed and installed in the bore through the rear surface of the heated distributor block (1) which bore is closed off by cover (39) which is fastened to the heated distributor block (1) by socket head cap screws. 10. Injection mechanism according to one of claims 1 to 9, c h a r a c t e r i z e d in that the needles (26) are attached to one or more guide bushings (27) which are axially moveable in the heated distributor block (1). 11. Injection mechanism according to claim 10, c h a r a c t e r i z e d in that the guide bushing (27) has a collar at its front end functioning as a stop to the stroke of the needle valves, respectively the plunger to which the guide bushing (27) is attached by means of a socket head cap screw; the presence of this collar provides an enlarged surface against which the injection pressure of the molten plastics can act resulting in a large force for opening the needle valves; the presence of this collar also allows the other part of the guide bushing to be of small diameter ensuing in a large ratio of length vs diameter which has to prevent leakage of molten plastics by virtue of the close fit between the two parts (1) and (27). 12. Injection mechanism according to claim 1#, c h a r a c t e r i z e d in that the guide'bushing has been attached to the plunger leaving clearance so that this way an independant true fit of both the guide bushing and the plunger are assured, this guide bushing is provided with one or more flat spots corresponding with one or more flat spots in the plunger so that the guide bushing can be prevented from turning during assembly or disassembly. 13. Injection mechanism according to one of claims 1 to 12, c h a r a c t e r i z e d in that a standard commercially available pin having a cylindrical or conical head is used as a needle valve (26) and the needle valve is attached to the guide bushing (27) by means of one or more lock screws (65) and locked in the desired position. 14. Injection mechanism according to one of claims 1 to 13, c h a r a c t e r i z e d in that the guide bushing (27) is provided with one or more recesses (41) in which plastics leakage, should it occur, can collect and be expelled through a channel (42), this channel is connected to channel (59) coming from the underside of the bore in which the plunger is located and when compressed air is admitted to the upper surface of the plunger, the plunger will move downward and expel the air below the piston along the channel (59) and tube (43), this way the pressure is lowered in channel (42) so that the collected material in above recess(es) can flow easily to the outside. 15. Injection mechanism according to one of claims 1 to 14, c h a r a c t e r i z e d in that the needle valves are not attached in the guide bushing (27), but directly in the plunger, so that the guide bushing (27) can be omitted if desirable. 16. Injection mechanism according to one of claims 1 to 15, c h a r a c t e r i z e d -in that the injection nozzle (9) is provided with a heating element with thermocouple (12) either integrally cast or not and that the injection nozzle (9) can be composed of different materials and in which the part which contains the distributor channel (s) is always made from highly conductive material such as beryllium copper and the connecting wires are protected by tube (44). 17. Injection mechanism according to one of claims 1 to 16, c h a r a c t e r i z e d in that as many lower nozzles or injection openings (10, 5) are contained in the manifold version as there are needle valves (26). 18. Injection mechanism according to one of claims 1 to 17, c h a r a c t e r i z e d in that in the manifold version without needle valves (26) also with one injection bushing.(2) or one injection nozzle (9) more than one product can be injected or one larger product can be injected in several locations. 19. Injection mechanism according to one of claims 1 to 18, c h a r a c t e r i z e d in that the functioning, the characteristics and the realization are also applicable to a model placed centrally in the injection molding mechanism, both for the single and the manifold versions which is shown in figures 4 and 5. 20. Injection mechanism according to one of claims 1 to 19, c h a r a c t e r i z e d in that the functioning, the characteristics and the realization are also applicable to a version, in which the plunger and the injection bushing or the injection nozzle, respectively, are placed in a distributor block (60) which is not directly heated by a heating element of an injection molding mechanism such as the COOL ONE Rnnerless injection system by DME Company which is shown in figure 6 and the description of how it functions. 21. Injection mechanism according to one of claims 1 to 20, operated either with or without needle valves (as shown in figures 1 through 6), c h a r a c t e r i z z# e d in that the complete injection mechanism consists of, is composed of, and is assembled from parts 1 through 65, in so far as the parts compose and are applicable to the selected version and of which the functioning, the characteristics and the application have been explained in one or more of the above claims and mainly as defined in the description and/or figures. 22. Injection mechanism according to claim 16, c h a r a c t e r i z e d in that the part containing the distributor channel is covered for procession of corrosive plastics with a protective surface layer and the connecting leads are protected by a tube (44). 23. Injection mechanism according to one of claims 1 to 22, c h a r a c t e r i z e d in that the injection nozzle (1') can be provided with one ore more fixed needles (27' ) which can be externally adjusted, in which the points of these needles enter the injection aperture and thereby prevents that the product receives an injection point. 24. Injection mechanism according to one of claims 1 to 22, c h a r a c t e r i z e d in that the injection nozzle (1') can be provided with one or more needle valves (27') which can be adjusted externally, in which the points of the needle valves (27') close the injection aperture after injection so that at the location of injection a amooth surface is obtained. 25. Injection mechanism according to one of claims 1 to 24, c h a r a c t e r i z e d -in that the injection nozzle (1') is provided with a locating and centering sleeve (10'-40'; 471 to obtain proper alignment and heat insulation with respect to the cavity plate (26'), (as illustrated in figure 1' through 7'). 26. Injection mechanism according to one of claims 1 to 25, c h a r a c t e r i z e d in that an adaptor plate t8') has been installed on the injection nozzle (1') by means of which it is assembled to the cavity plate with socket head cap screws (18') when located centrally in an injection molding arrangement and when applied to a hot runner mold; wherein this adaptor plate is placed on the hot runner beam and the injection nozzle (1' ) is placed in the bottom of the hot runner beam, wherein in this case it is not necessary to make assembly holes in the hot runner beam (25'). 27. Injection mechanism according to claim 26, c h a r a c t e r i z e d in that within the adaptor plate (81) can be placed a separate bushing (241) (as shown in figure 11) and a needle bushing (28') (as shown in figures 3'and 4t, both these bushings fitting closely in bores made in the adaptor plate (8'). 28. Injection mechanism according to claim 26, c h a r a c t e r i z e d in that the adaptor plate (8') is assembled to the injection nozzle (1') with socket head cap screws (18 ) and is provided with a centering shoulder which fits accurately in a centering bore in the hot runner beam (25'), or when centrally located this centering shoulder is contained in a centering ring which fit accurately around a centering shoulder of the injection nozzle (1'). 29. Injection mechanim according to one of claims 26 to 28, c h a r a c t e r i z e d in that the adaptor plate (8') contains bolt holes in a standardizèd pattern (38'), through which the injection nozzle (1') and the hot runner beam (25' ) are attatched to the cavity plate ( 26'), wherein the choice of a standardized pattern allows universal application to all modes of injection molding. 30. Injection mechanism according to claim 27, c h a r a c t e r i z e d in that within the needle bushing (281) several bores (2µ) have been made, through which the molten plastics flow from the injection molding machine by way of injection opening (218) and the distributor channels (2,' 205 to the cavity (22'). 31. Injection mechanism according to claim 27, c h a r a c t e r i z e d in that the needle bushing (28') contains a needle (27') provided with screw thread (39') and an internal hexagon (39' ), which screw thread fits within the internal screw thread (39') in the needle bushing (28'), such that the needle (27' ) is adjustable and can be locked in any position by means of one or more set screws ( 30'). 32. Injection mechanism according to one of claims 27 to 31, c h a r a c t e r i z e d in that the bore (30') within the needle bushing (28') containing the screw thread ( 30') is closed off with a cap (31' )( as shown in figure 3') so that no plastics can enter the bore ( 30'), and also improves the flow pattern of the entering molten plastics. 33. Injection meachnism according to one of claims 27 to 32, c h a r a c t e r i z e d in that the needle bushing (28') is provided with a collar ( 42'), which is clamped with a light press fit between the injection nozzle (1') and adaptor plate ( 8' ) in order to obtain the proper heat conductivity, also for this purpose the needle bushing has been made from a highly conductive material, i.e. beryllium copper, which can be provided with a protective surface in case corrosive plastics are processed and the collar also causes the needle bushing (28') to be centered correctly in the adaptor plate ( 8' ) so that the needle is centered accurately in the middle of the distributor channel (2') and injection aperture (32'). 34. Injection mechanism according to claim 28, c h a r a c t e r i z e d in that the hot runner beam ( 25') has been provided with a centering bore ( 44') for proper centering of the adaptor plate (8) and assembly (36'), in which the needle valve ( 27') has been installed, this way a simple exchange between both parts is possible, assembly (36') has the same bolt hole pattern as has adaptor plate (8'). 35. Injection mechanism according to claim 34, c h a r a c t e r i z e d in that the assembly (365 contains a pneumatically operated needle valve ( 27') according to claims 1 to 21 (figures 1 to 6), wherein the assembly (36') is included to simplify manufacture in series, thus becoming more universally applicable, and to make this assembly containg a needle valve ( 27') more fitting for the injection mechanism, such that it can be easily exchanged with adaptor plate (8') also, adaptor plate (8') and assembly (36') have centering shoulders of the same dimensions and bolt hole patterns 38'), according to claims 28 and 29. 36. Injection mechanism according to one of claims 1 to 35, c h a r a c t e r i z e d in that the functioning, the characteristics and the realization are also applicable to a version with several injection apertures (11'-34'-37') contained within one injection nozzle (1') or injections nozzles (45'),which has as many lower. nozzles (3') or apertures respectively with free flow apertures ( 2'), fixed ajudstable needles or adjustable needle valves ( 27' ) as it has injection openings (11'-34'-37'k wherein a version with needle valves can be externally adjusted (as shown in figures 6' and 7'). 37. Injection mechanism according to claim 36, c h a r a c t e r i z e d in that the lower injection apertures (3') have separate locating and centering rings (40') which help to align the injection nozzle (45') and allow the molten plastics to fill the air space (41') and assist in forming a proper closure between the lower injection apertures (3') and the cavity plate (26' ) so that no leakage of plastics can occur, further this locating and centering ring (40') has the same function as the locating and centering ring (10') ( as shown in figure 1). 38. Injection mechanism according to one of claims 22 to 37 (and described in connection with figures 1' through 7') , c h a r a c t e r i z e d in that an applicable injection mechanism exists, built up and assembled from parts 1' through 46'. insofar as these parts are part of and are applicable to the selected version and of which the functioning, the characteristics and the application are explained in one or more of the above claims, and mainly as set forth in the description and/or in figures 1¯through 71

Inventors: SCHOUENBERG, HENDRIKUS JACOBUS ELISABETH
Applicants: SCHOUENBERG, HENDRIKUS JACOBUS ELISABETH
Application year: 1980
Main classification: B29F1
IPC codes: B29C45