Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
  • B29C45/03—Injection moulding apparatus
  • B29C45/04—Injection moulding apparatus using movable moulds or mould halves
  • B29C45/06—Injection moulding apparatus using movable moulds or mould halves mounted on a turntable, i.e. on a rotating support having a rotating axis parallel to the mould opening, closing or clamping direction
• • 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
  • B29C45/03—Injection moulding apparatus
  • B29C45/04—Injection moulding apparatus using movable moulds or mould halves
  • B29C45/06—Injection moulding apparatus using movable moulds or mould halves mounted on a turntable, i.e. on a rotating support having a rotating axis parallel to the mould opening, closing or clamping direction
  • B29C2045/067—Injection moulding apparatus using movable moulds or mould halves mounted on a turntable, i.e. on a rotating support having a rotating axis parallel to the mould opening, closing or clamping direction one mould being openable during clamping of the other moulds

Definitions

• the invention relates to the field of injection molding and, particularly, to an injection molding machine for making plastic articles.
• Typical injection molding procedures involve the injection of molten resin into a mold, cooling the resin until it is sufficiently solid to be removed from the mold, opening the mold, ejecting the molded article, closing the mold and clamping the mold closed for the next cycle. It can be appreciated that the injection molding unit is idle during a substantial part of this cycle, particularly while the part is cooling and is then ejected from the mold.
• U.S. Patent No. 5,040,969 describes a system wherein resin is injected into a first mold and held to begin cooling while resin in a second mold completes cooling and the part is ejected. The injection unit then moves to the second mold and fills the second mold with resin while the resin in the first mold completes cooling and is ejected.
• the molding
• U.S. Patent No. 3,830,613 discloses a process wherein molds are shuttled in and out of an injection molding station.
• each mold carries its own mold opening/closing device, which adds to the cost and complexity of the device due to the duplication of elements.
• shuttle devices in general, if more than two molds are to be used, some molds must be skipped over during shuttling, resulting in additional idle time for the injection molding unit.
• U.S. Patent No. 2,327,227 discloses a rotatable horizontal circular plate carrying a plurality of equally spaced small molds which are successively indexed to a clamping and injection station. The molds are opened and closed by a cam and roller arrangement. With this design, however, excessive time is required when larger molds are used. Further, the use of a rotating table complicates the connection of the molds to services such as electric, control, power, cooling water, air, and hydraulic oil which are essential with large or modern complex molds.
• U.S. Patent No. 2,333,056 discloses another system wherein a rotatable horizontal table is used. Molds are opened and closed with dedicated hydraulic actuators which are operated by a stationary cam. Such a structure requires duplication of the hydraulic actuators and also is limited as to the mold size for which it can be used. Further, hy ' raulic fluid and electric power are supplied through rotary connections such as annular rings or chambers fixed to the rotatable table, or electrical brushes contacting a central strain rod of the device. These connections become too complex when large molds are used which require numerous electric, control, power, hydraulic, air, and cooling connections to operate the various heaters, temperature sensors, cooling systems, and hydraulically movable elements contained therein.
• 3,574,894 discloses another apparatus where molds are carried by a rotating table.
• the molds are opened and closed by rods having rollers contacting a cam below the lower half of the mold. Clamping is accomplished by a hydraulic cylinder also located below the table and molds.
• a hydraulic cylinder also located below the table and molds.
• An injection molding machine for large molds is supplied by Italtech. This device shuttles two molds into and out of an injection station. Two opening/closing stations are provided, one on each side of the injection station. A single robot removes articles from both opening/closing stations. Thus, this apparatus requires duplication of the mold opening/closing station, and also is subjected to excessive wear due to the relatively long distance the robot must travel.
• the principal object of the present invention to provide an injection molding machine wherein large molds can be unidirectionally rotated so as to de-synchronize the molding cycle and reduce idle time of the injection molding unit.
• the invention is drawn to an injection molding apparatus which comprises a plurality of stations for preparing injection molded articles; a rotatable table carrying at least two molds, the table being positioned so that rotation of the table serially indexes the at least two molds to the plurality of stations; means for supplying services to the at least two molds including on-board control means for distributing services to the at least two molds, the on-board control means being mounted to the table and connected to the supplying means and the at least two molds, whereby services are distributed from the supplying means to the at least two molds through the on-board control means.
• Each mold preferably has a mold parting line dividing the mold into mold elements
• the plurality of stations preferably includes an injection molding station having means for injecting a molten material into a mold and having a primary clamp means for clamping and sealing the mold elements during injection, and an ejecting station having mold opening means for opening and closing the mold elements.
• the apparatus preferably includes a main control means for issuing commands to and receiving information from the on board control means, the main control means being operatively connected to the on board control means and being mounted substantially stationary relative to the rotatable table, whereby commands are distributed to the at least two molds from the main control means through the on board control means.
• connection between supplying means and on board control means, as well as the connection between main control means and on board control means are made by a rotary connection means so that connection is maintained through rotation of the on board control means relative to the substantially stationary supplying means and main control means.
• Fig. 1 is a perspective view of an injection molding apparatus according to the invention
• Fig. 2. is a schematic view of an injection molding apparatus according to the invention.
• Fig. 3 is a schematic view of an alternate embodiment of the invention.
• Fig. 4 schematically illustrates a preferred embodiment of a rotary connection for fluid services, according to the invention
• Fig. 5 schematically illustrates a preferred embodiment of a rotary connection for electrical services
• Figs. 6-8 illustrate cycle times for various embodiments of unidirectionally rotating tables
• Fig. 9 schematically illustrates a top view of a table with three molds and stations, according to the invention
• Fig. 10 schematically illustrates a top view of a table with four molds and stations
• Fig. 11 illustrates a clamping device for clamping an injection molding unit to a mold, according to the invention
• Fig. 12 illustrates an alternate embodiment of a primary clamp for clamping molds during injection.
• the invention relates to an injection molding apparatus 10 for injection molding articles in molds 12.
• molds 12 are disposed on a rotatable table 14 and rotated between stations so as to de-synchronize the injection molding procedure and reduce idle time of various elements of the system.
• An injection molding station 16 is positioned relative to table 14 as well as an ejecting station 18.
• molds 12 are filled at injection molding station 16, and table 14 is rotated while molds 12 are cooled and indexed on table 14 to ejecting station 18 where each mold 12 is opened, the molded article is removed, and the mold is closed and indexed to the injection molding station 16 to be filled again.
• molds 12, especially large and/or complex molds typically require numerous electrical and fluid connections for power, control, hydraulic oil, air, cooling water and the like (collectively aferred to herein as services) .
• Such connections must be made through a rotary connection, as table 14 rotates and the source of most services is stationary, and does not rotate with table 14.
• the number of rotary connections is minimized by providing a unit for on-board control and distribution of services mounted to the table, as will be thoroughly discussed hereinbelow.
• table 14 is preferably rotatably mounted to a central tie bar or strain rod 20 which may suitably be mounted to a frame 22 as shown.
• Molds 12 typically have a mold parting line 24 dividing mold 12 into a stationary mold element 26 which may be conventionally mounted to table 14, and a movable mold element 28 which can be displaced, for example at ejecting station 18, so as to remove molded articles from mold 12.
• Injection molding station 16 preferably includes a primary clamp unit 30 which serves to clamp mold elements 26, 28 of molds 12 in injection molding station 16 and thereby seal the mold elements along mold parting line 24 during injection.
• Injection molding station 16 also includes an injection molding unit 32 which may be of any conventional type.
• Injection molding unit 32 serves, in well known manner, to inject molten material such as resin into molds 12, where the molten material is cooled and is eventually removed in at least partially solid form.
• Injection molding unit 32 is preferably mounted on a carriage 34 as shown. Carriage 34 allows injection molding unit 32 to be vertically and laterally positioned, relative to table 14, to accommodate molds 12 having differing sizes and configurations. Such positioning of injection molding unit 32 may be accomplished, for example, through vertical and lateral runners 35, 37 mounted to carriage 34, as schematically shown in Fig. 1, or in any other suitable and convenient manner.
• injection molding unit 32 could be adjusted to different molds being run together on the same table 14 so as to cyclically produce different articles, if desired. Further, two or more injection units 32, each injecting a different resin, could be shuttled into and out of alignment with each successive mold 12, or each injection unit 32 could sequentially inject successive molds, to produce a different part in each mold.
• a mold opening and closing unit 36 is preferably disposed over table 14, preferably over ejecting station 18. Mold opening and closing unit 36 serves to open molds 12 when they have cooled sufficiently so that cooled injection molded articles can be removed and mold 12 can be prepared for the next shot of resin at injection molding station 16. Mold opening and closing unit 36 is preferably mounted to tie bar 20, and is preferably positionable in the vertical direction to accommodate molds of different heights. Mold opening and closing unit 36 may also desirably be rotatably disposed on tie bar 20 so that unit 36 can be positioned over any desired station around table 14, thereby rendering the system more versatile particularly for use with different numbers and configurations of molds on table 14.
• table 14 is rotated through any conventional means such as belt drive 38 so as to serially index molds 12 from station to station, thereby cyclically filling molds and ejecting cooled molded articles.
• Table 14 is preferably rotated unidirectionally. That is, it is rotated in one direction rather than the oscillation movement utilized by much of the prior art. In this manner, idle time of injection molding unit 32 is significantly reduced as molds do not need to be passed over during indexing as is necessary with oscillating tables.
• the present invention is especially well suited to use with molds which are large and complex. Such molds require numerous connections for power, hydraulic oil, air and cooling fluid, and the like, which are generally and collectively referred to herein as services.
• table 14 is to be unidirectionally rotated, the source or sources of the services must be connected to table 14 through a rotary connection in order to accommodate the rotation of molds 12 on table 14.
• large and complex molds require a large number of rotary connections which cause the rotary connection to be prohibitively complex.
• the number of rotary connections is minimized by providing an on board controller 40 mounted to table 14 as shown schematically in Figs. 1-3. According to the invention, a minimal number of connections are made from the various service supply sources, collectively referred to as services supply source 42, to on board controller 40.
• a single individual connection for each service is provided.
• On board controller 40 serves to distribute these services among molds 12.
• On board controller 40 contains valves, manifolds, electrical relays and/or switches, junction connections, communication nodes, and the like for distributing the flow of services between source 42 and molds 12.
• numerous electrical, hydraulic and cooling connections of each mold 12 are made to on board controller 40 which is substantially stationary relative to molds 12 since both controller 40 and connection thereto are mounted to and rotate with table 14.
• most service connections are standard connections for the particular service, and may be of any type conventionally used to connect two relatively stationary elements.
• a main controller 44 is also preferably provided and connected to on-board controller 40, as shown in Fig. 2, for issuing commands to and receiving feedback from on board controller 40. In this manner, commands and feedback can be distributed to rotating molds 12 from relatively stationary main controller 44 through on board controller 40 with only a minimal number of rotary connections.
• main controller 44 is individually connected to elements of apparatus 10 which are also relatively stationary, such as injection molding unit 32, primary clamp unit 30, mold opening/closing unit 36, and any other element desirable such as, for example, a robot 46 for removing articles from opened molds and the like. It should be noted that main controller 44 may alternatively be partially or entirely incorporated into on board controller 40 if desired.
• on board controller 40 may preferably include a control unit 48 for relaying commands from main controller 44 to a control/monitoring unit 50 for controlling, distributing, and monitoring flow of services to individual molds 12.
• Control unit 48 also serves to relay feedback from molds 12, control/monitoring unit 50, and various other on table functions 52 to main controller 44.
• Control/monitoring unit 50 receives services from services supply 42 using a minimal number of rotary connections, schematically illustrated at 63.
• Fig. 2 illustrates these various operative connections with single lines for command/feedback connections, and with double lines for other "services" connections.
• Fig. 3 illustrates a further preferred embodiment of the invention, similar to that of Fig. 2, wherein operative connections are further simplified by the provision of local controllers 56 on mold units 12a to provide local control of some functions of each mold 12a.
• Local controllers 56 serve to relay commands from main controller 44, via control unit 48, to local control/monitor units 58 for directly controlling services supplied to individual molds 12. Miscellaneous on table functions 52 are controlled from control unit 48 through on table function controller 60 and on table function control/monitor unit 62 as shown.
• Rotary connections of services and command/feedback may be accomplished through any means known in the art.
• Figs. 4 and 5 illustrate a preferred embodiment of such a connection.
• Fig. 4 illustrates a rotary connection 63 for connecting flow of services from stationary sources of the services to molds and other elements rotating on table 14, preferably through on board controller 40.
• Connection 63 includes an inner sleeve 64, mounted on central tie bar 20, and an outer sleeve 65, rotatably disposed around inner sleeve 64 and fixed to table 14.
• Inner sleeve 64 has one or more ports 66 for connection to services supply source(s) 42. Since inner sleeve 64 is non- rotatably mounted to stationary central tie bar 20, a direct connection from ports 66 to the supply source 42 of each service, which source is also stationary, can be made.
• Outer sleeve 65 also has a number of ports 67 for connection of fluid services with on board controller 40.
• outer sleeve 65 rotates with table 14, simple and direct connection of the various fluid services can be made to on board controller 40.
• Flow of fluids is conducted from stationary inner sleeve 64 to rotating outer sleeve 65 as follows.
• Each port 66 of inner sleeve 64 which is to be used to convey a fluid preferably leads to a passage 68 which passes through the wall 69 of inner sleeve 64 to a radially oriented opening 70.
• Each port 67 of outer sleeve 65 communicates with an inner ring 71 formed in an inside surface of outer sleeve 65.
• Inner ring(s) 71 are formed on outer sleeve 65 so as to align with respective openings 70 of inner sleeve 64.
• fluids may flow from a port 66 through a passage 68 to opening 70 of inner sleeve 64, then into ring 71 of outer sleeve 65 and to a port 67 of outer sleeve 65 to on board controller 40. Since most fluid connections require an inlet and an outlet to on board controller 40, two paths similar to that described above may be provided on rotary connection 63, one for incoming fluids on their way to on board controller 40, and the other for returning fluids to source(s) 42 or some other fluid recycling or gathering point. It should be pointed out that the foregoing structure allows communication between stationary opening 70 of stationary inner sleeve 64 and a respective inner ring 71 which rotates around opening 70.
• a number of seal rings 78 may be disposed between the inner surface of outer sleeve 65 and the outer surface of inner sleeve 64. Rings 78 are preferably arranged above and below respective inner rings 71 of outer sleeve 65 so as to prevent leakage of the various fluids to be conveyed. Connection of electrical, command, and/or power services are made in a similar manner.
• a port 66a is preferably provided for receiving wires 72 connected to the sources of the various foregoing services. Wires 72 are passed through a passage 73 defined in wall 69 of inner sleeve 64 to connect with respective contacts 74. Contacts 74 are arranged so as to extend radially through wall 69 so as to contact conductive rings 75.
• Rings 75 are fixed to stationary inner sleeve 64.
• Outer sleeve 65 has a number of contacts 76 mounted thereto for connection to on board controller 40. Each contact 76 rotates with outer sleeve 65 and table 14, and has a conductive brush 77 for contacting a respective conductive ring 75. In this manner electric, power, and command services are conveyed between stationary source 42 and rotating on board controller 40. Contacts 76 and brushes 77 may be attached to posts 79 for proper arrangement adjacent to a desired ring 75.
• Fig. 5 is a section taken through the rotary connection 63 of Fig. 4, and further illustrates the aforesaid elements of this structure.
• Fluids flow from port 66 (Fig. 4) to passages 68 and, as shown by the arrows of Fig. 5, fluids then flow through opening 70 and into ring 71 of outer sleeve 65.
• the fluid then flows through ring 71, as further illustrated by the arrows of Fig. 5, to reach port 67 which connects and conducts fluids to on board controller 40 for distribution to various molds 12.
• the typical injection molding cycle can be divided into three basic time periods. These time periods are (1) the time required to clamp a mold, inject resin and hold, and unclamp mold; (2) allow resin to cool; and (3) open mold, eject article and load inserts, if any, and close mold.
• a mold In a unidirectionally rotatable table such as that of the present invention, a mold must remain at each station for a period of time equal to the longest time required at any one station.
• the cycle can be made more efficient by reducing the total time required at the station at which the longest time is required. For example, consider the following cycle breakdown:
• Fig. 6 graphically illustrates the sequence and timing of these operations for each mold at each station. For example, mold set 1 cools for 8 seconds in station 1, for 2 seconds during indexing, and then for 4 seconds in station 2 before it is opened in station 2. Mold set number 2 goes through substantially the same sequence, but is 180 degrees out of phase for each machine cycle compared to mold set 1.
• the cycle time for a three station embodiment (assuming the same indexing time) with one station (for cooling only) between the injection and ejecting station would be 14 seconds.
• the cooling time would be distributed as follows: 4 seconds at station 1 since the mold begins to cool immediately after injection, and the hold time cannot be delayed, 2 seconds during indexing from station 1 to station 2, 8 seconds at the cooling station between injection and ejecting stations. (The mold is actually in station 2 for 12 seconds, but has cooled sufficiently after 8 seconds to be removed.)
• the last 4 seconds in station 2 are unnecessary, but unavoidable since now the longest operation is at the ejecting station, and is 12 seconds.
• the time to open eject/insert and close the molds in the preceding example now determines the cycle time of the machine. If the tasks can be split by adding another station to divide the ejecting and insert loading between two stations as described below, then further unit cycle time reductions are possible.
• Fig. 9 schematically illustrates a top view of a table 14 having three molds 12 equally spaced thereon.
• Stations disposed around table 14 include injection molding station 16, ejecting station 18, and, according to the invention, a cooling station 86 serially disposed after injection molding station 16 and before ejecting station 18. Since the cooling period is generally the longest of the three time periods, cooling station 86 allows this period to be broken up over several stations, thus shortening the time which must be spent at any one station, namely, the station where all cooling would otherwise take place. In this manner, idle time of the injection unit is reduced.
• Fig. 10 illustrates an embodiment similar to Fig. 9, where a fourth station 88 is provided for loading inserts, when desired, into molds 12 before injection molding.
• Inserts may be additional mold pieces, or composite materials to be laminated with other materials, or any other of numerous conventionally known inserts.
• the longest time period may now typically be the time required to open mold 12, eject the article, load an insert, and close mold 12.
• insert loading station 88 is preferably provided to further shorten the time spent by each mold 12 at ejecting station 18 and, thereby, to increase the output of the machine.
• Insert loading station 88 may preferably be arranged relative to table 14 so that molds are indexed from ejecting station 18, where articles are ejected, to insert loading station 88, for the loading of an insert, and thence to injection molding station 16 for the injection of resin.
• An additional mold opening unit may be supplied for insert loading station 88 so as to open the mold for insertion of the insert.
• injection molding station 16 preferably includes a clamping unit for clamping injection unit 32 to molds 12 for injection of molten resin.
• Fig. 11 illustrates such a clamping unit 90, for firmly holding nozzle 94 of injection unit 32 in sealing contact with a sprue 92 of a mold 12.
• Such a clamping unit 90 may include two jaws 91 pivotably mounted to injection unit 32.
• Each mold 12 preferably has indentations 93 arranged on sprue 92 for receiving jaws 91 so that injection unit 32 and nozzle 94 can be firmly held to sprue 92 of mold 12.
• Jaws 91 pivot in the direction indicated by the arrows in Fig. 11.
• jaws 91 pivot away from each other to disengage from sprue 92 of a mold 12 that has been filled with resin.
• a new mold 12 is then indexed into alignment with injection unit 32, and jaws 91 are then closed and pivoted toward each other to engage indentations 93.
• Fig. 11 is an example of a suitable clamping structure. Any known conventional clamping structure could be used. Examples of suitable embodiments of such a clamping structure are set forth in U.S. Patent No. 5,044,927 to DiSimone et al, issued September 3, 1991 to the assignee of the present application.
• primary clamp unit 30 is preferably disposed above injecting molding station 16 in position to clamp individual molds 12 when they are to be filled.
• Primary clamp unit 30 is preferably slidably mounted, for example on tie bars 20 and 98, so as to be vertically positionable. In this manner, primary clamp unit 30 can be adjusted to clamp molds of different sizes.
• Mold opening and closing unit 36 may also preferably be mounted to tie bar 20 in a slidable manner so as to likewise be vertically positionable and therefor adjustable to molds of different sizes.
• Primary clamp unit 30 preferably has a fixed base 100 and a movable platen 102, and a piston 104 for displacing platen 102 relative to base 100. In this manner, platen 102 is displaced between a clamping position wherein a clamping force is applied to molds in injection molding station 16, and an undamped position wherein a mold can be indexed out of, and into, injection molding station 16.
• mold opening and closing unit 36 preferably has a fixed base 106 and a movable platen 108, and a piston 110 for displacing platen 108 relative to base 106.
• platen 108 can be displaced between an open position wherein a mold 12 is opened and molded articles can be removed (or inserts loaded) , and a closed position wherein the mold is closed.
• pistons 104, 110 are desirable. Clamping at injection molding station 16 generally requires a short stroke, since molds at this station do not need to be opened, but this clamping requires a large force to resist forces resulting from high injection pressures and provide proper sealing of the mold. Alternatively, opening/closing the mold at ejecting station 18 or insert loading station 88 requires a relatively long stroke, as the mold must be opened sufficiently to allow articles/inserts to be removed/inserted. Piston 110 for mold opening and closing unit 36 does not, however, require a force of the magnitude of the clamping force.
• piston 104 allows piston 104 to be provided with a short stroke and a large piston area, as desired, while piston 110 is provided with a long stroke and a relatively small piston area.
• Such a configuration optimizes the operation of each piston and provides a more efficient use of space and hydraulic fluid than a single piston having both a long stroke and a large piston area to provide motive means for both units 30, 36.
• Piston 104 of primary clamp unit 30 may alternatively include a plurality of independently operable pistons 104a (See Fig. 12) spaced between fixed base 100 an movable platen 102. In this manner, different clamp forces can be applied to different locations or portions of a mold. This feature is desirable for injection/compression molding and/or gas assist molding, as well as any other type of operation wherein a non- symmetrical loading of the mold is desired.

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Mechanical Engineering (AREA)
• Injection Moulding Of Plastics Or The Like (AREA)
• Moulds For Moulding Plastics Or The Like (AREA)

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• 1994
  • 1994-10-12 WO PCT/US1994/011566 patent/WO1995011792A1/en not_active Application Discontinuation
  • 1994-10-12 EP EP94931821A patent/EP0724514A1/de not_active Ceased

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