CA2280599A1 - Melt transfer system and bushing assembly therefor - Google Patents
Melt transfer system and bushing assembly therefor Download PDFInfo
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- CA2280599A1 CA2280599A1 CA 2280599 CA2280599A CA2280599A1 CA 2280599 A1 CA2280599 A1 CA 2280599A1 CA 2280599 CA2280599 CA 2280599 CA 2280599 A CA2280599 A CA 2280599A CA 2280599 A1 CA2280599 A1 CA 2280599A1
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- melt
- platen
- transfer
- shear
- transfer system
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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
- B29C45/26—Moulds
- B29C45/32—Moulds having several axially spaced mould cavities, i.e. for making several separated articles
- B29C45/322—Runner systems for distributing the moulding material to the stacked mould cavities
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- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Mechanical Engineering (AREA)
- Moulds For Moulding Plastics Or The Like (AREA)
Abstract
A melt transfer system is provided for a stack mold. The melt transfer system includes a first bushing assembly defining at least a portion of a first runner passage and a second bushing assembly defining at least a portion of a second runner passage, the first and second runner passages being in communication with each other when the melt transfer system is in a flow position and the first and second runner passages being sealed to communication by the bearing surface of the opposing first or second bushing assembly when the melt transfer system is its a sealed position at least one of said bushing assemblies being moveable with an actuation between said flow position an,d said sealed position.
Description
usizsiaa xiow ia:aa r~Ax Ti : MELT TRANSFER SYSTEM ~USHIN~G ASSEMsLY THEREFOR
~'I>~LD OF THfi NATION
xhe present invention relates to injection molding and in particular to a melt transfer system for a stack mold.
»A P THE
In a stack mold, pressurized melt must be conveyed across 2~
paxting line between two platens that are displaceable relatitre to each other. A melt transfer system is required ire order to control the flow of the pressurized melt depending opt whether the platens are in contact with 1Q each other or are separated.
A valve gated melt transfer system, such as is disclosed ltx U.S. Patent 4,244,909, contxols the flow of melt between platens using a combination of valve date units. ,A disadvantage with valve gated melt transfer systems is that pressure variances within the melt passages are experienced due to the presence of the v2~lve pins.
A, thermal gated melt transfer system, such as disclosed in LT.S. 4,5$6,887, controls the flaw of melt between platens by a cøui,binatioxi of heated xiozzles. A disadvantage with thermal gated melt transfer systerms is that the flow of pressurised melt is impeded by the relatively small diameter gate defined in each heated nozzle and there is a delay associated with cooling and rernelting the melt itx the gate for each molding cycle.
There is a need for a melt transfer system to be developed for stack molds that ovexcome the above problern,s and that is relatively simple in its construction and effective in its operatiori_ _2_ SUM__M_A_1tY OF TH1? _ ~N'IiON
The present invention provides an improved system and method. for conducting pressurised melt between platens in a stack mold.
ht one aspect the invention provides a melt transfer system for a stack mold having a first platen and a second platen, the second platen moving between an open position and a closed position relative to the first platen and cooperating with the first platen to define at least one meld cavity when in said closed position, the z~nelt transfer system campri.sing:
1a a first runner passage defined ix1 the first platen for cor<ductxng a pressiui.zed melt from a melt inlet to a first shear gate;
a sECOnd runner passage defined in the second platen for conducting said pressurized melt from a second shear gate to a distribution manifold;
a first bushing assembly defining at least a portion of said first runner passage arid having a first bearing surface into which said first shear gate is defined;
a second bushing assembly defxx~ing at least a portion of said second runner passage and having a second bearing surface into which 2D said second shear gate is defined, said fixst and second bearing surfaces contacting each other when said first axed second platens are in a closed position;
means for movit<g at least one of said first and second bushing assemblies betweezt a flow position, where said first and second platens are in a dosed position and said first and second shear gates are in communication to facilitate flow of pressurized melt from said first runner passage to said second runnex passage, a~xd a shear positian, where melt at said first shear gate is sheared by said second bearing surface an melt at said second shear gate is sheared by said first bearing surFace to u-pz~event flow of pressurized melt from said first runner passage to said second runner passage.
DESCRTP1'rI'lN OF THE DRAWINGS
For a better understanding of the present invention, and to show more clearly how it may be carried into effect, zeference will now be made by way of example to the acconnpanying drawings.
The drawings show preferred embodimen-t$ of the present invention, i~.t which:
1D Pig. I is a partial sectional view of a melt transfer system in accordance with the present invention disposed in a pordon of a stack mold, the melt transfer system being in a flow position;
Fig. 2 is a sectional view of the melt transfer system of Fig. x as viewed along lines 2-2, with the melt transfer system in a sealed position;
Fig. 3 is a sectional vi.Ew of the melt transfer system of Fig. 1 as viewed along lines 3-3, with the melt transfer system it< a flow position;
Fig. 4 is a sectional view of the melt transfer system of Fig. 1 as viewed along lines 3-3, with the melt transfer system in a sealed position;
Fig, 5 is a partial sectional view of a second embodiment of a xxtelt transfer system in accordance with the present invention disposed ix~
a portion of a stack ixtald, the melt transfer system being its a flow position;
Pig. 6 is a sectional view of the melt transfer system of Fig. 5 as viewed along lines 6-6, with the melt transfer systenn in a sealed position;
Fig. 7 is a sectional view of the melt transfer system of Fig. 5 as viewed along lines 7-7, with the pelt transfer system ire a ~tow position;
as vieweu aivng Ames i-i, with the melt txansrer system in a flow position;
Fig. 8 is a sectional view of the melt transfer system of Fig. 5 as vlewecl along lines 7-7, with the melt transfer system in a sealed position.
Fig. 9 is a partial sectional view of a third embodiment of a melt transfer system in accordance with the present invention disposed in a portion of a stack mold, the melt transfer system beix~g in a flow positiort;
Fig. 10 is a sectional view the melt transfer system of Fig. 9 with the melt transfer system in a sealed position;
Fig. 11 is a perspective view of a transfer bushing assembly for the melt transfer system of Fig. ~;
Fig. 1,2 is a side view of the transfer bushing assembly of Fig.
11;
Fig. 13 Xs a flop view of the transfer bushing assembly of Fig.
11;
Fig. 14 is a sectional view of the transfer bushing assembly as viewed along lines 14-14 of Fig. 13;
Fig. 15 is sectional view of the traxxsfer bushing assembly as viewed along limes 15-15 of Fig. 12; and, Fig. 16 is a sectional view of the transfer bushing assembly as viewed along fines 16-16 of Fig. 12.
hlr Referring to the Figures, a melt t~'~nsfer system in accordance ?5 with the present invention is shown gez~exally at 20. The melt transfer systexxt 20 is located within a stack mold (or multi-level mold) 22. Stack mold 22 has a plurality of cavities (not shown) located on a first parting line ?4 and on a second parting line (not shown). The first parting line ?4 exteztds between a statioztary platen 26 and a cezttral moving platen 28 and the second pardx~g line (not shown) extends between the central moving ~uua uamaiaa mmv la:~~ rHa - - .- .-_g., platen 28 and a secondary moving platen (not shown). $taek xnQlds 22 of this type are well known in the art, as described in U.S. Patent Nos.
4,212,626 and 4,244,909 to Gellert, both of which are incorporated herein by reference.
A molding rnachixie inlet 30 is defined in fhe stationary platen 26 to accept the nozzle (not shown) of an injection molding machine. In communication with molding machine inlet 30 is a heated runner system $2, which is heated by heater windings 34 or any other means known in the art sufficient to maintain the melt therein at a desired temperature. Runner system 32 comprises a first runner passage 36, in stationary platen 26, aztd a second runner passage 38, in central moving platen 28, in communication with a distribution manifold 40.
Runner passages 36, 38 communicate via front and second shear gates ~2, 44. Manifold 4~ communicates with ear.~h mold cavity (not shown) via a nozzle 46 having a thermally gated mold cavity gate 48.
The melt transfer system 20 comprises a first transfer nozzle 60 and a first transfer bushing assembly 62 in stationary platen 26 and a second transfer nozxle b4 and second transfer bushix~g assembly 66 in central moving platen 28. Each transfer bushing assembly 62, 6G has a planar bearing surface 68 for contactiieg the planar bearing surface 68 of fine opposing transfer bushing assembly 62, 66.
The first and second transfer bushing assemblies 62, 66 are movably supported in the platens 26, 28 with bolt fasteners 70 extending through slots 72 defined in retainer r;ngs 74 tl,.at extend about the circumference of the transfer bushing assenriblies 62, 66. The first and second transfer bushing assemblies 62, bb each include a neck 76 that is rotatably received by a collar 78 defined itl the corresponding first and second transfer nozzles 60, 64. The first transfer nozzle 60 is secured to the stationary platen 26 with a bolt fastener 80 extending through an opening usizsies xiur id:au rvx -. ----_g_ 82 defined in a locating ring $~ mounted to a back plate 86. The second 'd' transfer bushing assembly 64 is mounted to the distribution manifold 40 with tW ended bolts 88.
Lever arrn Z00 is disposed on the second transfer bushing assemmbly C6 for pivotally receiving a cammd 102 secured by a pin 104. The carnrod 102 is actuated by a piston and cylinder assembly 106. '1,'he piston and cyl~der assembly 106 is controlled, synchronized and actuated by a central processing unit {Cl'U) of the molding machine (not shown). As is well known in the art, the Cl?U synchronizes actuation with mold and ~a x0 injeciion cycles, as further described below. Actuation of the piston and cylinder assembly 10& causes the ramrod 102 to extend or retract and in turn move the lever arm 100 to rotate the second transfea bushing assembly 66 about rotation axis 108 relative to the first transfer bushing assembly fit. A pin 110 extends fronn the first transfer bush3rtg assembly 62 into the stationary platen 26 to secure the first transfer bushing assembly 62 from. moving relative to the stationary platen 26.
While the preferred embodiment provides for rotary movement of the second transfer bushing assembly 66 by the ramrod 102, it is contemplated that the first transfer bushing assembly 62 could be moved in addition to or instead of uiovement of the second transfer bushing assembly 66 movement (ie. by conxteeting a piston and cylinder assembly 106 and ramrod 1.02 to the first transfer bushing assembly 60).
Furthermore, it is contemplated that one or both of the first and second transfer bushing assemblies 62, 66 could be moved linearly instead of rotationally relative to each other. Tn such case, the transfer bushing assemblies 62, 66 woxlld be supported in a track (not shown) to guide the linear movement and the piston and cylinder assembly 106 would be connected to the traxtsfer bushing assemblies 60, 66.
emu umz~isa xiur ie:as r~ax ... _.. dull Each transfer bushing assembly 62, 66 defines a melt channel having a center portion 120 and an eccentric portion 122 extending respectively along parallel axis 7.08 and 124 and fluidly connected by a transverse portion 126. The center portion 120 extends along the rotation axis 108 for the second transfer bushing assembly 66. When the melt transfer system 20 is in a flow position, with the platens 26, 28 in a closed position, as shown in Figures 1 and 3, the shear gates 42, 44 of the respective eccentric portions 1Z2 align to permit melt to flow between the first and second transfer bushing assemblies 62, 66. When the melt transfer systenn 20 is moved to a sealed position, as shown in Figures 2 and 4, the melt is sheared and the gates 42, 49: are closed by the bearing surface 68 of the opposing transfer bushing assemblies 62, 6b. At the same time as the melt transfer system 20 is moved to a sealed position, a decompression is impaxted in the first xunner passage 36 to control drool at the gate 42 when the mold is parted at parting line 2~4. Decompression is imparted in the runner passage 36 by any means knowm in the art such as retracting the barrel of the nozzle (not shown) of the injection moldixtg machine.
The operation of melt transfer system 20 is synchronized with nnold injection as will now be described. RefErring to Figures 7, and 3, the CPU moves the mold to place the platens 26, 28 into a closed position and the CPU then actuates piston and cylinder assembly 106 to move transfer bushing assembly 66 and in turn shear gate 44 to its "flow"
position relative to first txansfer bushing assembly 62 and gate 42. rn this position, pressurized melt xs permitted is to flow from the molding machine sequentially through first runner passage 36, across parting line 24, through second runner passage 38 and into manifold 40 for delivery to the mold cavities. Once the mold cavities are filled, the molding pressure is maintained to apply a packing pressure, as is lcvown inn the art.
lZeferring to Figixres 2 and 4, upon completion of the packir~g phase, the CPU actuates piston and cylinder assembly 106 to move second _g_ transfer bushing assembly 66 to a "sealed" position relative to first transfer bushing assembly 62. The pressurized melt is sheared at the first shear gate 42 and the first shear gate 42 is closed by the bearing surface 68 of the second transfer bushing assembly b6. The CPU at the same time retracts the barrel of the injection nozzle (not shown) of the injection molding machete to impart a decompression in the melt in fihe first runner passage 36. The stack mold 22 nnay now be opened (under control of the CPU), along first parting line 24 and second parting line (not shown) to permit 'x the molded parts to be ejected from the mold 22. The decompression imparted in the first runner passage 36 prevents melt from drooling from the first shear gate 42. Ch~tce the molded parts have been, ejected from the nnold 22, the mold 22 may be closed axtd the molding machine readied for the next mOldin~ Cycl~.
Referring to Pigures 5 to 8, a second embodiment of the melt transfer system in accordance with the present invention is shown at 20.
For convenience, corresponding elements to those described above have bEC'n give~t corxespanding reference numerals. 'f'he second embodiment of melt transfer system includes a mechanical shut off system 140 fox shutting off the back pressure to the melt to reduce drool xt the shear gates 42, 44 so that plasb'tfication with some back pressure of the plastification scre~nr of machine can take place to reduce cycle time.
The shut aff system comprises divided runner passages 142 defixted in the first and second rulzner passages at interfaces 144 betweext the transfer nozzles 6Q, 64 an,d the transfer bushing assemblies 6z, b6.
The first and second transfer bushing assemblies b2, 66 each include lever arms 100 For pivotally engaging cam,rods 102 that are actuated by piston and cylinder assemblies 106. The actuation of piston and cylinder assemblies 106 by ~FU causes first transfEr bushing assembly 62 to rotate in a first direction 146 and the second transfer bushing assembly' b6 _9_ to rotate in a second direction 148 that is opposite to the first direction 146.
Rotation of the transfer buehung assemblies 62, b6 causes the divided.
rurvzter passages 142 to become closed by bearing surfaces 150 defined on the collar 7$ az~d neck 76 of the transfer nozzles 60, 64 and transfer bushing assemblies 62, 66 at interfaces 144.
ht use, the CPU actuates the piston and cylinder assemblies 106 to rotate each of the first and second bushixtg assemblies 62, 64 in opposing directions 146, 148 to between a flow position and a sealed positxoz~. The synchronization of the movement of the transfer bushing assemblies 62, 6d with the remaining operations in the molding process is equivalent to the process as described above. Since the second embodiment of melt transfer system 2p includes a mechanical shut off system 140, it is not necessary for the CPU to actuate retraction of the nozzle barrel to ixxtp~rt a decompression of the melt.
lZefet't'1ng to Figztres 9 to 16 a third embodiment of the melt transfer syste~nn in accordance with the present invention is shown generally at 200. Por convenience, corresponding elements to those described above have been given corresponding refexen.ce z~uzr~.exals.
The melt transfer system 200 includes transfer bushing assemblies 202 mounted to transfer nozzles 204 in each of the platexis 2b, 28. Transfer nozzles 204 include heater windings 34 to control the teznperaturc of the melt in the first and second rtuuier passages 36 and 3S.
The transfer bushing assemblies each include a shear face 206 that extends parallel to the direction of movement 20$ of the platens 26, 2$. Shear gate 210 is defined in the shear face Z06 to permit the transfer pf melt between platens 26, 28 when the platens are in the flow position. ~'he shear gates 210 are guided into a.ligr<ixtent by cam surfaces 212 and abutment surfaces 214 when the platens 26, 28 move from an open _ ~0 _ position to a closed position.
Referring to Figure 13, it may be seen that runner passage 36, 3$ has inwrardly tapered walls 216 adjacent to the shear gate 210. The tapered walls define sharp comers that assist in shearing the rxtelt when the platens 26, 2$ are moved from a closed position to an open position.
Furthermore, the tapered walls 21b cause a plug to be formed by the exposed melt located at the shear gate 210 when the meld is waved to its open position. The plug prevents melt from drooling from sheax gate 2i0 when the mold is in its open position.
Referring to Figures 14-16 it may be seen that the runner passage 36, 38 defined ixt the transfex bushing assembly 202 varies in cross sectional shape along its length. This reduces shear stress oxi the melt as it passes along the runner passage 36, 3$ and reduces the pressure variances along the length of the runner passages at points where the runnier passage changes direction.
It is to be understood that what has been described is a preferred embodiment to the invention. If the in~rention nonetheless is susceptible to certain changes and alternative embadimeztts fully comprehended by the spirit of the invex<tion as described above, and the scope of the claims set out below.
~'I>~LD OF THfi NATION
xhe present invention relates to injection molding and in particular to a melt transfer system for a stack mold.
»A P THE
In a stack mold, pressurized melt must be conveyed across 2~
paxting line between two platens that are displaceable relatitre to each other. A melt transfer system is required ire order to control the flow of the pressurized melt depending opt whether the platens are in contact with 1Q each other or are separated.
A valve gated melt transfer system, such as is disclosed ltx U.S. Patent 4,244,909, contxols the flow of melt between platens using a combination of valve date units. ,A disadvantage with valve gated melt transfer systems is that pressure variances within the melt passages are experienced due to the presence of the v2~lve pins.
A, thermal gated melt transfer system, such as disclosed in LT.S. 4,5$6,887, controls the flaw of melt between platens by a cøui,binatioxi of heated xiozzles. A disadvantage with thermal gated melt transfer systerms is that the flow of pressurised melt is impeded by the relatively small diameter gate defined in each heated nozzle and there is a delay associated with cooling and rernelting the melt itx the gate for each molding cycle.
There is a need for a melt transfer system to be developed for stack molds that ovexcome the above problern,s and that is relatively simple in its construction and effective in its operatiori_ _2_ SUM__M_A_1tY OF TH1? _ ~N'IiON
The present invention provides an improved system and method. for conducting pressurised melt between platens in a stack mold.
ht one aspect the invention provides a melt transfer system for a stack mold having a first platen and a second platen, the second platen moving between an open position and a closed position relative to the first platen and cooperating with the first platen to define at least one meld cavity when in said closed position, the z~nelt transfer system campri.sing:
1a a first runner passage defined ix1 the first platen for cor<ductxng a pressiui.zed melt from a melt inlet to a first shear gate;
a sECOnd runner passage defined in the second platen for conducting said pressurized melt from a second shear gate to a distribution manifold;
a first bushing assembly defining at least a portion of said first runner passage arid having a first bearing surface into which said first shear gate is defined;
a second bushing assembly defxx~ing at least a portion of said second runner passage and having a second bearing surface into which 2D said second shear gate is defined, said fixst and second bearing surfaces contacting each other when said first axed second platens are in a closed position;
means for movit<g at least one of said first and second bushing assemblies betweezt a flow position, where said first and second platens are in a dosed position and said first and second shear gates are in communication to facilitate flow of pressurized melt from said first runner passage to said second runnex passage, a~xd a shear positian, where melt at said first shear gate is sheared by said second bearing surface an melt at said second shear gate is sheared by said first bearing surFace to u-pz~event flow of pressurized melt from said first runner passage to said second runner passage.
DESCRTP1'rI'lN OF THE DRAWINGS
For a better understanding of the present invention, and to show more clearly how it may be carried into effect, zeference will now be made by way of example to the acconnpanying drawings.
The drawings show preferred embodimen-t$ of the present invention, i~.t which:
1D Pig. I is a partial sectional view of a melt transfer system in accordance with the present invention disposed in a pordon of a stack mold, the melt transfer system being in a flow position;
Fig. 2 is a sectional view of the melt transfer system of Fig. x as viewed along lines 2-2, with the melt transfer system in a sealed position;
Fig. 3 is a sectional vi.Ew of the melt transfer system of Fig. 1 as viewed along lines 3-3, with the melt transfer system it< a flow position;
Fig. 4 is a sectional view of the melt transfer system of Fig. 1 as viewed along lines 3-3, with the melt transfer system in a sealed position;
Fig, 5 is a partial sectional view of a second embodiment of a xxtelt transfer system in accordance with the present invention disposed ix~
a portion of a stack ixtald, the melt transfer system being its a flow position;
Pig. 6 is a sectional view of the melt transfer system of Fig. 5 as viewed along lines 6-6, with the melt transfer systenn in a sealed position;
Fig. 7 is a sectional view of the melt transfer system of Fig. 5 as viewed along lines 7-7, with the pelt transfer system ire a ~tow position;
as vieweu aivng Ames i-i, with the melt txansrer system in a flow position;
Fig. 8 is a sectional view of the melt transfer system of Fig. 5 as vlewecl along lines 7-7, with the melt transfer system in a sealed position.
Fig. 9 is a partial sectional view of a third embodiment of a melt transfer system in accordance with the present invention disposed in a portion of a stack mold, the melt transfer system beix~g in a flow positiort;
Fig. 10 is a sectional view the melt transfer system of Fig. 9 with the melt transfer system in a sealed position;
Fig. 11 is a perspective view of a transfer bushing assembly for the melt transfer system of Fig. ~;
Fig. 1,2 is a side view of the transfer bushing assembly of Fig.
11;
Fig. 13 Xs a flop view of the transfer bushing assembly of Fig.
11;
Fig. 14 is a sectional view of the transfer bushing assembly as viewed along lines 14-14 of Fig. 13;
Fig. 15 is sectional view of the traxxsfer bushing assembly as viewed along limes 15-15 of Fig. 12; and, Fig. 16 is a sectional view of the transfer bushing assembly as viewed along fines 16-16 of Fig. 12.
hlr Referring to the Figures, a melt t~'~nsfer system in accordance ?5 with the present invention is shown gez~exally at 20. The melt transfer systexxt 20 is located within a stack mold (or multi-level mold) 22. Stack mold 22 has a plurality of cavities (not shown) located on a first parting line ?4 and on a second parting line (not shown). The first parting line ?4 exteztds between a statioztary platen 26 and a cezttral moving platen 28 and the second pardx~g line (not shown) extends between the central moving ~uua uamaiaa mmv la:~~ rHa - - .- .-_g., platen 28 and a secondary moving platen (not shown). $taek xnQlds 22 of this type are well known in the art, as described in U.S. Patent Nos.
4,212,626 and 4,244,909 to Gellert, both of which are incorporated herein by reference.
A molding rnachixie inlet 30 is defined in fhe stationary platen 26 to accept the nozzle (not shown) of an injection molding machine. In communication with molding machine inlet 30 is a heated runner system $2, which is heated by heater windings 34 or any other means known in the art sufficient to maintain the melt therein at a desired temperature. Runner system 32 comprises a first runner passage 36, in stationary platen 26, aztd a second runner passage 38, in central moving platen 28, in communication with a distribution manifold 40.
Runner passages 36, 38 communicate via front and second shear gates ~2, 44. Manifold 4~ communicates with ear.~h mold cavity (not shown) via a nozzle 46 having a thermally gated mold cavity gate 48.
The melt transfer system 20 comprises a first transfer nozzle 60 and a first transfer bushing assembly 62 in stationary platen 26 and a second transfer nozxle b4 and second transfer bushix~g assembly 66 in central moving platen 28. Each transfer bushing assembly 62, 6G has a planar bearing surface 68 for contactiieg the planar bearing surface 68 of fine opposing transfer bushing assembly 62, 66.
The first and second transfer bushing assemblies 62, 66 are movably supported in the platens 26, 28 with bolt fasteners 70 extending through slots 72 defined in retainer r;ngs 74 tl,.at extend about the circumference of the transfer bushing assenriblies 62, 66. The first and second transfer bushing assemblies 62, bb each include a neck 76 that is rotatably received by a collar 78 defined itl the corresponding first and second transfer nozzles 60, 64. The first transfer nozzle 60 is secured to the stationary platen 26 with a bolt fastener 80 extending through an opening usizsies xiur id:au rvx -. ----_g_ 82 defined in a locating ring $~ mounted to a back plate 86. The second 'd' transfer bushing assembly 64 is mounted to the distribution manifold 40 with tW ended bolts 88.
Lever arrn Z00 is disposed on the second transfer bushing assemmbly C6 for pivotally receiving a cammd 102 secured by a pin 104. The carnrod 102 is actuated by a piston and cylinder assembly 106. '1,'he piston and cyl~der assembly 106 is controlled, synchronized and actuated by a central processing unit {Cl'U) of the molding machine (not shown). As is well known in the art, the Cl?U synchronizes actuation with mold and ~a x0 injeciion cycles, as further described below. Actuation of the piston and cylinder assembly 10& causes the ramrod 102 to extend or retract and in turn move the lever arm 100 to rotate the second transfea bushing assembly 66 about rotation axis 108 relative to the first transfer bushing assembly fit. A pin 110 extends fronn the first transfer bush3rtg assembly 62 into the stationary platen 26 to secure the first transfer bushing assembly 62 from. moving relative to the stationary platen 26.
While the preferred embodiment provides for rotary movement of the second transfer bushing assembly 66 by the ramrod 102, it is contemplated that the first transfer bushing assembly 62 could be moved in addition to or instead of uiovement of the second transfer bushing assembly 66 movement (ie. by conxteeting a piston and cylinder assembly 106 and ramrod 1.02 to the first transfer bushing assembly 60).
Furthermore, it is contemplated that one or both of the first and second transfer bushing assemblies 62, 66 could be moved linearly instead of rotationally relative to each other. Tn such case, the transfer bushing assemblies 62, 66 woxlld be supported in a track (not shown) to guide the linear movement and the piston and cylinder assembly 106 would be connected to the traxtsfer bushing assemblies 60, 66.
emu umz~isa xiur ie:as r~ax ... _.. dull Each transfer bushing assembly 62, 66 defines a melt channel having a center portion 120 and an eccentric portion 122 extending respectively along parallel axis 7.08 and 124 and fluidly connected by a transverse portion 126. The center portion 120 extends along the rotation axis 108 for the second transfer bushing assembly 66. When the melt transfer system 20 is in a flow position, with the platens 26, 28 in a closed position, as shown in Figures 1 and 3, the shear gates 42, 44 of the respective eccentric portions 1Z2 align to permit melt to flow between the first and second transfer bushing assemblies 62, 66. When the melt transfer systenn 20 is moved to a sealed position, as shown in Figures 2 and 4, the melt is sheared and the gates 42, 49: are closed by the bearing surface 68 of the opposing transfer bushing assemblies 62, 6b. At the same time as the melt transfer system 20 is moved to a sealed position, a decompression is impaxted in the first xunner passage 36 to control drool at the gate 42 when the mold is parted at parting line 2~4. Decompression is imparted in the runner passage 36 by any means knowm in the art such as retracting the barrel of the nozzle (not shown) of the injection moldixtg machine.
The operation of melt transfer system 20 is synchronized with nnold injection as will now be described. RefErring to Figures 7, and 3, the CPU moves the mold to place the platens 26, 28 into a closed position and the CPU then actuates piston and cylinder assembly 106 to move transfer bushing assembly 66 and in turn shear gate 44 to its "flow"
position relative to first txansfer bushing assembly 62 and gate 42. rn this position, pressurized melt xs permitted is to flow from the molding machine sequentially through first runner passage 36, across parting line 24, through second runner passage 38 and into manifold 40 for delivery to the mold cavities. Once the mold cavities are filled, the molding pressure is maintained to apply a packing pressure, as is lcvown inn the art.
lZeferring to Figixres 2 and 4, upon completion of the packir~g phase, the CPU actuates piston and cylinder assembly 106 to move second _g_ transfer bushing assembly 66 to a "sealed" position relative to first transfer bushing assembly 62. The pressurized melt is sheared at the first shear gate 42 and the first shear gate 42 is closed by the bearing surface 68 of the second transfer bushing assembly b6. The CPU at the same time retracts the barrel of the injection nozzle (not shown) of the injection molding machete to impart a decompression in the melt in fihe first runner passage 36. The stack mold 22 nnay now be opened (under control of the CPU), along first parting line 24 and second parting line (not shown) to permit 'x the molded parts to be ejected from the mold 22. The decompression imparted in the first runner passage 36 prevents melt from drooling from the first shear gate 42. Ch~tce the molded parts have been, ejected from the nnold 22, the mold 22 may be closed axtd the molding machine readied for the next mOldin~ Cycl~.
Referring to Pigures 5 to 8, a second embodiment of the melt transfer system in accordance with the present invention is shown at 20.
For convenience, corresponding elements to those described above have bEC'n give~t corxespanding reference numerals. 'f'he second embodiment of melt transfer system includes a mechanical shut off system 140 fox shutting off the back pressure to the melt to reduce drool xt the shear gates 42, 44 so that plasb'tfication with some back pressure of the plastification scre~nr of machine can take place to reduce cycle time.
The shut aff system comprises divided runner passages 142 defixted in the first and second rulzner passages at interfaces 144 betweext the transfer nozzles 6Q, 64 an,d the transfer bushing assemblies 6z, b6.
The first and second transfer bushing assemblies b2, 66 each include lever arms 100 For pivotally engaging cam,rods 102 that are actuated by piston and cylinder assemblies 106. The actuation of piston and cylinder assemblies 106 by ~FU causes first transfEr bushing assembly 62 to rotate in a first direction 146 and the second transfer bushing assembly' b6 _9_ to rotate in a second direction 148 that is opposite to the first direction 146.
Rotation of the transfer buehung assemblies 62, b6 causes the divided.
rurvzter passages 142 to become closed by bearing surfaces 150 defined on the collar 7$ az~d neck 76 of the transfer nozzles 60, 64 and transfer bushing assemblies 62, 66 at interfaces 144.
ht use, the CPU actuates the piston and cylinder assemblies 106 to rotate each of the first and second bushixtg assemblies 62, 64 in opposing directions 146, 148 to between a flow position and a sealed positxoz~. The synchronization of the movement of the transfer bushing assemblies 62, 6d with the remaining operations in the molding process is equivalent to the process as described above. Since the second embodiment of melt transfer system 2p includes a mechanical shut off system 140, it is not necessary for the CPU to actuate retraction of the nozzle barrel to ixxtp~rt a decompression of the melt.
lZefet't'1ng to Figztres 9 to 16 a third embodiment of the melt transfer syste~nn in accordance with the present invention is shown generally at 200. Por convenience, corresponding elements to those described above have been given corresponding refexen.ce z~uzr~.exals.
The melt transfer system 200 includes transfer bushing assemblies 202 mounted to transfer nozzles 204 in each of the platexis 2b, 28. Transfer nozzles 204 include heater windings 34 to control the teznperaturc of the melt in the first and second rtuuier passages 36 and 3S.
The transfer bushing assemblies each include a shear face 206 that extends parallel to the direction of movement 20$ of the platens 26, 2$. Shear gate 210 is defined in the shear face Z06 to permit the transfer pf melt between platens 26, 28 when the platens are in the flow position. ~'he shear gates 210 are guided into a.ligr<ixtent by cam surfaces 212 and abutment surfaces 214 when the platens 26, 28 move from an open _ ~0 _ position to a closed position.
Referring to Figure 13, it may be seen that runner passage 36, 3$ has inwrardly tapered walls 216 adjacent to the shear gate 210. The tapered walls define sharp comers that assist in shearing the rxtelt when the platens 26, 2$ are moved from a closed position to an open position.
Furthermore, the tapered walls 21b cause a plug to be formed by the exposed melt located at the shear gate 210 when the meld is waved to its open position. The plug prevents melt from drooling from sheax gate 2i0 when the mold is in its open position.
Referring to Figures 14-16 it may be seen that the runner passage 36, 38 defined ixt the transfex bushing assembly 202 varies in cross sectional shape along its length. This reduces shear stress oxi the melt as it passes along the runner passage 36, 3$ and reduces the pressure variances along the length of the runner passages at points where the runnier passage changes direction.
It is to be understood that what has been described is a preferred embodiment to the invention. If the in~rention nonetheless is susceptible to certain changes and alternative embadimeztts fully comprehended by the spirit of the invex<tion as described above, and the scope of the claims set out below.
Claims (13)
1. A melt transfer system for a stack mold having a first platen and a second platen, the second platen moving between an open position and a closed position relative to the first platen and cooperating with the first platen to define at least one mold cavity when in said closed position, the melt transfer system comprising:
a first runner passage defined in the first platen for conducting a pressurized melt from a melt inlet to a first shear gate;
a second runner passage defined in the second platen for conducting said pressurized melt from a second shear gate to a distribution manifold;
a first bushing assembly defining at least a portion of said first runner passage and having a first bearing surface into which said first shear gate is defined;
a second bushing assembly defining at least a portion of said second runner passage and having a second bearing surface into which said second shear gate is defined, said first and second bearing surfaces contacting each other when said first and second platens are in a closed position;
I means for moving at least one of said first and second bushing assemblies between a flaw position, where said first and second platens are in a closed position and said first and second shear gates are in communication to facilitate flow of pressurized melt from said first runner passage to said second runner passage, and a shear position, where melt at said first shear gate is sheared by said second bearing surface an melt at said second shear gate is sheared by said first bearing surface to prevent flow of pressurized melt from said first runner passage to said second runner passage.
a first runner passage defined in the first platen for conducting a pressurized melt from a melt inlet to a first shear gate;
a second runner passage defined in the second platen for conducting said pressurized melt from a second shear gate to a distribution manifold;
a first bushing assembly defining at least a portion of said first runner passage and having a first bearing surface into which said first shear gate is defined;
a second bushing assembly defining at least a portion of said second runner passage and having a second bearing surface into which said second shear gate is defined, said first and second bearing surfaces contacting each other when said first and second platens are in a closed position;
I means for moving at least one of said first and second bushing assemblies between a flaw position, where said first and second platens are in a closed position and said first and second shear gates are in communication to facilitate flow of pressurized melt from said first runner passage to said second runner passage, and a shear position, where melt at said first shear gate is sheared by said second bearing surface an melt at said second shear gate is sheared by said first bearing surface to prevent flow of pressurized melt from said first runner passage to said second runner passage.
2. A melt transfer system as claimed in claim 1, wherein at least one of said first and second transfer bushing assemblies is rotatable by said moving means about an axis, and wherein said first or second shear gate defined in said rotatable first or second transfer bushing assembly is eccentric to said rotation axis.
3. A melt transfer system as claimed in clay 2, wherein said first or second runner passage defined through said rotatable first or second transfer bushing assembly is coaxial with said eccentric gate.
4. A melt transfer system as claimed in clam 2, wherein said first or second runner passage of said rotatable first or second transfer bushing assembly has a center portion that extends along said rotation axis and an eccentric portion that extends along a center axis of said eccentric first ar second gate, said eccentric portion and said center portion being communicatively connected by a transverse portion.
5. A melt transfer system as claimed in claim 2, wherein each of said first and second runner passages has a center portion extending along said rotation axis and an eccentric portion extending along a second axis that is parallel to and eccentric from said rotation axis, said center portion and said eccentric portion being communicatively communicatively by a transverse portion, and wherein said first and second shear gates are defined respectively in said first and second bearing surfaces at said eccentric portions of said first and second runner passages.
6. A melt transfer system for a stack mold having a first platen and a second platen, the second platen moving between an open position and a dosed position relative to the first platen and cooperating with the first platen to define at least one mold cavity when in said closed position, the melt transfer system comprising:
a first transfer nozzle and a first bushing assembly disposed in said first platen to define at least a portion of a first runner passage for conducting a pressurized melt from an inlet to a first shear gate, said first bushing assembly having a first bearing surface into which said first shear gate is defined;
a second transfer nozzle and a second bushing assembly disposed in said second platen for defining at least a portion of a second runner passage for conducing said pressurized melt from a second shear gate to a distribution manifold, said second bushing assembly having a second bearing surface into which said second shear gate is defined, said first and second bearing surfaces contacting each other when said first and second platens are in a closed position;
means for supporting at least one of said first and second transfer bushing assemblies in said first and second platens for movement relative to said first and second transfer nozzles;
means for moving at least one of said first or second bushing assemblies relative to said first or second transfer nozzles between a flow position, where said first and second platens are in a closed position and said first and second shear gates are aligned to facilitate flow of pressurized melt from said first runner passage to said second runner passage, and a sealed position, where said first shear gate is sealed by said second bearing surface and said second shear gate is sealed by said first bearing surface to prevent flow of pressurized melt from said first runner passage to said second runner passage.
a first transfer nozzle and a first bushing assembly disposed in said first platen to define at least a portion of a first runner passage for conducting a pressurized melt from an inlet to a first shear gate, said first bushing assembly having a first bearing surface into which said first shear gate is defined;
a second transfer nozzle and a second bushing assembly disposed in said second platen for defining at least a portion of a second runner passage for conducing said pressurized melt from a second shear gate to a distribution manifold, said second bushing assembly having a second bearing surface into which said second shear gate is defined, said first and second bearing surfaces contacting each other when said first and second platens are in a closed position;
means for supporting at least one of said first and second transfer bushing assemblies in said first and second platens for movement relative to said first and second transfer nozzles;
means for moving at least one of said first or second bushing assemblies relative to said first or second transfer nozzles between a flow position, where said first and second platens are in a closed position and said first and second shear gates are aligned to facilitate flow of pressurized melt from said first runner passage to said second runner passage, and a sealed position, where said first shear gate is sealed by said second bearing surface and said second shear gate is sealed by said first bearing surface to prevent flow of pressurized melt from said first runner passage to said second runner passage.
7. A melt transfer system as claimed in claim 6, wherein a divided portion is defined in at least one of said first and second runner passages at an interface between said respective first or second transfer nozzles and said first or second bushing assemblies, said divided portion defining a plurality of passages for conducting said pressurized melt, said passages in said first or second transfer nozzle communicating with said passages in said first or second transfer bushing when said system is in said flow position, and said passages being sealed from communication with said system in said sealed position.
8. A melt transfer system as claimed in claim 7, wherein at least one of said first and second transfer bushing assemblies in rotatable by said moving means about an axis, and wherein said first or second shear gate defined in said rotatable first or second transfer bushing assembly is eccentric to said rotation axis,
9. A melt transfer system as claimed in claim 8, wherein said first or second runner passage defined through said rotatable first or second transfer bushing assembly is coaxial with said eccentric gate.
10. A melt transfer system as claimed in claim 8, wherein said first or second runner passage of said rotatable first or second transfer bushing assembly has a center portion that extends along said rotation axis and an eccentric portion that extends along a center axis of said eccentric first ore second gate, said eccentric portion and said center portion being communicatively connected by a transverse portion.
11. A melt transfer system as claimed in claim 8, wherein each of said first and second runner passages has a center portion, extending along said rotation axis and an eccentric portion extending along a second axis that is parallel to and said eccentric from said rotation axis, said center portion and said eccentric portion being communicatively connected by a transverse portion, and said first and second shear gates are defined respectively in said first and second bearing surfaces at said eccentric portions of said first and second runner passages.
12. A method of transferring melt in a stack mold having a first platen and second platen, the second platen moving between an open position and a closed position relative to the first platen and cooperating with the first platen to define at least one mold cavity when in said closed position, the method comprising the steps of:
moving at least one of the first platen and the second platen into said closed position to define said at least one mold cavity;
moving a melt transfer system disposed in said stack mold into a flow position, said melt transfer system having a first bushing0 assembly defining at least a portion of a first runner passage in said first platen for conducting a pressurized smelt from an inlet to a first shear gate, and a second bushing assembly defining at least a portion of a second runner passage in said second platen for conducting said pressurized melt from a second shear gate to a distribution manifold, said first and second shear gates being in communication to facilitate flow of pressurized melt from said first runner passage to second runner passage when said system is in said flow position;
moving at least one of said first and second bushing assemblies from said flow position to a sealed position where said first shear gate is sealed by a second bearing surface located on said second transfer bushing assembly and said second shear gate is sealed by a first bearing surface located on said first bearing assembly; and moving at least one of the first platen and the second platen into said open position to eject any molded parts from said at least one mold cavity after the melt has set.
moving at least one of the first platen and the second platen into said closed position to define said at least one mold cavity;
moving a melt transfer system disposed in said stack mold into a flow position, said melt transfer system having a first bushing0 assembly defining at least a portion of a first runner passage in said first platen for conducting a pressurized smelt from an inlet to a first shear gate, and a second bushing assembly defining at least a portion of a second runner passage in said second platen for conducting said pressurized melt from a second shear gate to a distribution manifold, said first and second shear gates being in communication to facilitate flow of pressurized melt from said first runner passage to second runner passage when said system is in said flow position;
moving at least one of said first and second bushing assemblies from said flow position to a sealed position where said first shear gate is sealed by a second bearing surface located on said second transfer bushing assembly and said second shear gate is sealed by a first bearing surface located on said first bearing assembly; and moving at least one of the first platen and the second platen into said open position to eject any molded parts from said at least one mold cavity after the melt has set.
13. A method as claimed in 13 wherein, one of said first or second bushing assemblies is moved rotatably relative to the other of said bushing assemblies to move said system between said flow position and said sealed position.
Priority Applications (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2280599 CA2280599A1 (en) | 1999-08-23 | 1999-08-23 | Melt transfer system and bushing assembly therefor |
| CA 2284955 CA2284955A1 (en) | 1999-08-23 | 1999-10-04 | Melt transfer system and transfer bushing therefor |
| AU68128/00A AU6812800A (en) | 1999-08-23 | 2000-08-22 | Melt transfer system and bushing assembly therefor |
| PCT/CA2000/000973 WO2001014118A1 (en) | 1999-08-23 | 2000-08-22 | Melt transfer system and bushing assembly therefor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2280599 CA2280599A1 (en) | 1999-08-23 | 1999-08-23 | Melt transfer system and bushing assembly therefor |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2280599A1 true CA2280599A1 (en) | 2001-02-23 |
Family
ID=4164014
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2280599 Abandoned CA2280599A1 (en) | 1999-08-23 | 1999-08-23 | Melt transfer system and bushing assembly therefor |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2280599A1 (en) |
-
1999
- 1999-08-23 CA CA 2280599 patent/CA2280599A1/en not_active Abandoned
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