Injection unit with telescopic melt coupling

Abstract

In one aspect, an injection unit for an injection molding machine having a hot nozzle with a gate. The injection unit includes a heated melt tube configured to deliver a continuous stream of melt, a shot pot assembly, and a telescoping melt link. The shot pot assembly is configured to convert the continuous stream of melt from the heated melt tube into a batch for a cycle shot and is translatable between a gate engaged position and a gate disengaged position. The telescoping melt link is configured to deliver melt from the heated melt tube to the shot pot assembly and has a variable length. The variable length telescoping melt link allows the shot pot assembly to translate relative to the heated melt tube between the gate engaged position and the gate disengaged position while maintaining a fluid melt interconnection between the heated melt tube and the shot pot assembly.

Description

TECHNICAL FIELD

[0001] The present invention relates to injection molding, and more particularly, to an injection unit having a telescoping melt coupling. BACKGROUND

[0002] An injection unit of an injection molding machine can include an extruder and at least one shot pot. The extruder typically includes at least one screw that rotates within a heated barrel to convert solid molding material, such as pellets of plastic or resin, into a stream of molten molding material ("melt"). The shot pot accumulates melt from the extruder and periodically injects the accumulated melt into a mold via a nozzle. The nozzle is shaped and sized to connect with a sprue (e.g., a nozzle bushing) of a hot runner so as to define a fluid melt connection therewith. Each injection of melt received from the shot pot via the nozzle and sprue is delivered via a channel of the hot runner to a plurality of cavities within the mold, where molded articles are formed.

[0003] The injection unit can translate between a production position and a purge position.

[0004] In the production position, the nozzle tip engages (connects with) the sprue so as to form a fluid melt connection therewith through which melt from the shot pot is periodically injected. The term "production position" is meant to refer to the fact that the injection unit is in this position when the injection molding machine is actively producing molded articles.

[0005] In the purge position, the injection unit is moved away from the hot runner. The nozzle tip is separated or disengaged from the nozzle bushing, thereby breaking the fluid melt connection between the injection unit and the hot runner. This separation prevents melt expelled from the injection unit nozzle from entering the hot runner. Instead, melt expelled from the nozzle can simply fall into a waste collection container to be discarded. Purging can be performed, for example, when the melt in the injection unit has become contaminated or can have degraded in some way. This can occur, for example, when the machine is idle for an extended period of time or when the temperature of the accumulated melt exceeds a threshold temperature at which undesirable melt byproducts or impurities, such as acetaldehyde, can form. SUMMARY

[0006] In one aspect of the application, an injection unit for an injection molding machine having a hot nozzle with a gate is provided, the injection unit comprising: a heated melt tube configured to deliver a continuous stream of melt; a shot pot assembly comprising at least one shot pot, the shot pot assembly configured to convert the continuous stream of melt from the heated melt tube into a batch for a cyclic injection, the shot pot assembly translatable between a gate-engaged position and a gate-disengaged position; and a telescoping melt coupling configured to deliver melt from the heated melt tube to the shot pot assembly, the telescoping melt coupling having a variable length to allow the shot pot assembly to translate relative to the heated melt tube between the gate-engaged position and the gate-disengaged position while maintaining a fluid melt interconnection between the heated melt tube and the shot pot assembly.

[0007] In some embodiments, the telescoping melt coupling comprises: a sleeve; and a sheath slidable about the sleeve between an extended position and a retracted position while maintaining a seal with the sleeve to substantially contain melt.

[0008] In some embodiments, the injection unit further comprises at least one sleeve heater configured to heat the sleeve of the telescoping melt coupling; and at least one sheath heater configured to heat the sheath of the telescoping melt coupling, wherein the at least one sleeve heater and the at least one sheath heater are independently controllable.

[0009] In some embodiments, the at least one sleeve heater is operable to deactivate upon the sleeve of the telescoping melt coupling transitioning from the extended position to the retracted position.

[0010] In some embodiments, the injection unit further comprises a plurality of heaters for heating the heated melt tube, wherein the plurality of heaters, the at least one sleeve heater, and at least one sheath heater are collectively operable to define a monotonically increasing temperature gradient along the heated melt tube and the telescoping melt coupling in a downstream direction. The monotonically increasing temperature gradient may, for example, be linear or exponential.

[0011] In some embodiments, the at least one sleeve heater comprises at least one of: a cartridge heater embedded in the sleeve; and an infrared heater adjacent to the sleeve.

[0012] In some embodiments, the at least one sleeve heater comprises a pair of infrared heaters on opposite sides of the sleeve.

[0013] In some embodiments, the at least one sleeve heater comprises a plurality of cartridge heaters embedded in a wall of the sleeve.

[0014] In some embodiments, the at least one sleeve heater comprises both a cartridge heater embedded in the sleeve and an infrared heater adjacent to the sleeve.

[0015] In some embodiments, one of the at least one cartridge heater and the at least one infrared heater acts as a primary heater for the sleeve, and the other of the at least one cartridge heater and the at least one infrared heater acts as a failsafe heater for the sleeve configured to activate in the event of a failure of the primary heater.

[0016] In some embodiments, the telescoping melt coupling defines a spherical connection mating face that conforms to a sphere centered along an axis of the telescoping melt coupling.

[0017] In some embodiments, the spherical connection mating face is defined at an upstream end of the sleeve, and the injection unit further comprises a stationary annular melt tube coupling fluidly interconnecting the heated melt tube and the sleeve, the annular melt tube coupling having a downstream end defining a spherical connection mating face that is complementary to the spherical connection mating face of the sleeve. The two spherical connection mating faces collectively allow for angular axial misalignment of the telescoping melt coupling relative to the heated melt tube without compromising the fluid melt interconnection.

[0018] In some embodiments, the sleeve has an annular flange extending radially from an upstream end thereof, and the injection unit further comprises a locking ring attached to the annular melt tube coupling, the locking ring defining an annular space containing the annular flange therein to allow for limited longitudinal movement of the sleeve.

[0019] In some embodiments, the injection unit further comprises a biasing element between the locking ring and the annular flange configured to bias the spherical connection mating face of the sleeve against the spherical connection mating face of the annular melt tube coupling.

[0020] In some embodiments, the injection unit further comprises a static mixer between the telescoping melt coupling and the shot pot assembly.

[0021] In another aspect of the invention, there is provided an injection molding machine comprising a hot nozzle having a primary gate; and an injection unit comprising a heated melt tube configured to deliver a continuous melt stream; a shot pot assembly configured to convert the continuous melt stream into a batch for cyclic injection, the shot pot assembly being translatable about the heated melt tube between a gate-engaged position and a gate-disengaged position; and a telescoping melt coupling configured to deliver melt from the heated melt tube to the shot pot assembly, the telescoping melt coupling having a variable length to allow the shot pot assembly to translate relative to the heated melt tube between the gate-engaged position and the gate-disengaged position while maintaining a fluid melt interconnection between the heated melt tube and the shot pot assembly.

[0022] In some embodiments, the telescoping melt coupling includes a sleeve and a spool slidable relative to the sleeve between an extended position and a retracted position while maintaining a seal with the sleeve to substantially contain a melt, and the injection molding machine further includes: at least one sleeve heater configured to heat the sleeve of the telescoping melt coupling; at least one spool heater configured to heat the spool of the telescoping melt coupling; and a controller configured to deactivate the at least one sleeve heater or the at least one spool heater when the spool transitions from the extended position to the retracted position.

[0023] In some embodiments, the injection molding machine further includes a ball joint configured to allow angular axial misalignment of the telescoping melt coupling relative to the heated melt tube without compromising fluid melt interconnection between the heated melt tube and the shot pot assembly.

[0024] Other features will become apparent from the following description in connection with the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0025] The non-limiting embodiments will be more fully understood in view of the drawings, wherein:

[0026] Figure 1 depicts a partial cutaway elevation view of a conventional injection unit in a production position;

[0027] Figure 2 depicts a partial cutaway elevation view of a conventional injection unit of Figure 1 in a purge position;

[0028] Figure 3 is a top isometric view of an injection molding system including an injection molding machine and a molded material recycling machine;

[0029] Figure 4 is a perspective view of a molded article produced by the injection molding system of Figure 3 ;

[0030] Figure 5 is an elevation view of an injection unit of the injection molding machine of Figure 3 in a production position;

[0031] Figure 6 is a longitudinal cross-section of a portion of the injection unit of Figure 5 , including a telescoping melt coupling as it appears when the injection unit is in a production position;

[0032] Figure 7 is a top perspective view of a portion of the injection unit of Figure 5 as it appears when the injection unit is in a production position;

[0033] Figure 8is a top perspective view of the support frame and telescoping melt coupling supported thereby as they appear when the injection unit is in the purge position, isolated from the remainder of the injection unit;

[0034] Figure 9 is a perspective view of the support frame and telescoping melt coupling supported thereby as they appear when the injection unit is in the production position; Figure 8 is a top perspective view of a portion of the support frame including the telescoping melt coupling;

[0035] Figure 10 is a top plan view of a portion of the support frame including the telescoping melt coupling as they appear when the injection unit is in the production position; Figure 8 is a top plan view of a portion of the support frame including the telescoping melt coupling;

[0036] Figure 11 is a perspective view of Figure 6 is a longitudinal cross-section of the telescoping melt coupling of

[0037] Figure 12 is an exploded view of the telescoping melt coupling of Figure 7 showing its sleeve and bushing components;

[0038] Figure 13 is a perspective view of a portion of the sleeve of Figure 12 showing the male spherical connection joint mating face defined at the upstream end of the sleeve;

[0039] Figure 14 is a longitudinal cross-section view of a portion of the sleeve of Figure 13

[0040] Figure 15 is a perspective view of a longitudinal cross-section of the spherical connection between the upstream end of the sleeve of Figure 12

[0041] Figure 16 is an elevation view of the heated melt tube, showing the heater array and associated heating zones of the melt tube, isolated from the remainder of the injection unit;

[0042] Figure 17 is a longitudinal cross-section of the telescoping melt coupling and downstream components showing an additional plurality of heating zones as they appear when the injection unit is in the production position;

[0043] Figure 18 is a simplified three-dimensional schematic of the melt flow path defined within the injection unit of Figure 5 as it appears when the injection unit is in the production position;

[0044] Figure 19 schematically depicts a cross-section through the injection unit as the first shot pot of the dual shot pot assembly of the injection unit is discharging melt and the second shot pot of the dual shot pot assembly is being refilled;​​Figure 18 Melt flow along the melt path;

[0045] Figure 20 The schematic depiction shows the passage at a point in time shortly after the first jet can is being refilled and the second jet can is discharging the melt. Figure 18 Melt flow along the melt path;

[0046] Figure 21 When the injection unit is in the purge position Figure 5 The longitudinal cross-section of the injection unit includes a portion of the telescopic melt connector;

[0047] Figure 22 When the injection unit is in the purge position Figure 21 Top perspective view of a portion of the injection unit;

[0048] Figure 23 It is defined as the situation when the injection unit is in the purge position, the first injection can is discharging melt, and the second injection can is being refilled. Figure 5 A simplified three-dimensional schematic diagram of the melt flow path within the injection unit; and

[0049] Figure 24 The schematic depiction shows the passage at a point in time shortly after the first jet can is being refilled and the second jet can is discharging the melt. Figure 23 The melt flow along the melt path.

[0050] The accompanying drawings are not necessarily drawn to scale and may be illustrated using dashed lines, graphical representations, and fragmentary diagrams. In some cases, details that are unnecessary for understanding these embodiments or that make other details difficult to perceive may have been omitted. Detailed Implementation

[0051] In this document, any use of the term "exemplary" should be understood as meaning "an example of...", without necessarily implying that the example is preferred or optimal in some way. Terms such as "down," "right," and "left" may be used to describe features of some embodiments in this specification, but should not be construed as necessarily implying the orientation of the embodiments during manufacture or use.

[0052] Figure 1 A partial cross-sectional front view depicting a portion of a conventional injection molding machine 90, including an injection unit 100 and a hot runner 150.

[0053] The injection unit 100 includes an extruder 102, a feeder 110, and an injection can assembly 122.

[0054] The extruder 102 is operable to receive molding material in solid (e.g., pelletized) form, to plasticize the molding material into a molten form, and to extrude the resulting melt in a continuous stream. The extruder includes at least one screw housed within a heated barrel driven by a screw actuator.

[0055] The material feeder 110 is a device that supplies solid molding material 114 to the extruder 102. The feeder can operate, for example, as a metered feeder or as a continuous feeder. The molding material 114 can be a combination of virgin molding material and recycled molding material, such as polyethylene terephthalate (PET) and recycled PET (rPET). Alternatively, the molding material 114 can be 100% recycled molding material.

[0056] The shot tank assembly 122 is a device that transforms the continuous stream of melt from the extruder 102 into batches for cyclic injection into the hot runner 150. The depicted shot tank assembly 122 is a dual shot tank assembly that includes two shot tanks and associated melt tubes and valves configured to operate out of sequence with one another. While one shot tank is accumulating melt from the extruder 102, the other shot tank is “shot” injecting previously accumulated melt into the hot runner 150 via the nozzle 127 of the injection unit 100.

[0057] It will be appreciated that the position of each of the extruder 102, the feeder 110, and the shot tank assembly 122 of the injection unit 100 is fixed relative to the rest.

[0058] The injection unit 100 is slidably mounted to the fixed base 130, as Figure 1 schematically illustrated. The slidable mounting allows the injection unit 100 to translate on its base 130 toward and away from the hot runner 150 between a production position and a purge position, as will be described below.

[0059] Figure 1 Further schematically depicted is a portion of the hot runner 150 into which melt from the injection unit 100 is periodically injected. As shown, the hot runner 150 includes a gate bushing 152 (a form of a gate) for receiving the tip of the nozzle 127. The gate bushing 152 is schematically illustrated in cross-section in Figure 1 . The hot runner 150 also includes a distribution channel for conveying melt from the gate toward a plurality of molding cavities of a mold, none of which are explicitly illustrated. The hot runner 150 is fixed (does not move) relative to the base 130 of the injection unit 100.

[0060] In Figure 1In the middle, the injection molding machine 90 is depicted with the injection unit 100 in a production position. In this position, the tip of the nozzle 127 engages (i.e., connects) the gate bushing 152 of the hot runner 150. This engagement creates a fluid melt connection between the injection unit 100 and the hot runner 150 through which periodic injections of melt are delivered into the multiple cavities of the mold for production of molded articles. This is the position of the injection unit 100 during normal operation of the injection molding machine 90.

[0061] Figure 2 The injection molding machine 90 is depicted with the injection unit 100 in a purge position. When the injection unit 100 is in this position, the nozzle 127 is disengaged from the gate bushing 152. Any melt expelled by the shot pot assembly 122 with the injection unit 100 in this position will fall downward to be discarded as waste. This position of the injection unit 100 can alternatively be referred to as a maintenance position, as it can facilitate access to certain components of the injection molding machine 90 (e.g., the gate bushing 152) for routine maintenance of the injection molding machine 90.

[0062] To move the injection unit 100 from the production position of Figure 1 to the purge position of Figure 2 , the injection unit 100 is translated along its fixed base 130 away from the hot runner 150. It will be appreciated that because the extruder 102, the feeder 110, and the shot pot assembly 122 including the injection unit 100 are in fixed relationship to one another, all of these components move together during translation. Because the feeder 110 remains positioned to supply solid molding material 114 to the extruder 102, the injection unit 100 is able to continue to produce and expel melt while in the purge position.

[0063] As noted above, the particulate material 114 in the feeder 110 can include or be recycled molding material. The rationale for using recycled material can include, for example, one or more of the following: recycled material can be less expensive than virgin material; recycled material can be considered environmentally friendly; and use of recycled material is marketable.

[0064] Recycled plastic or resin molding material pellets can be produced by large commercial plastic recycling machines. Such machines typically input post-consumer plastic material and process the material through a series of stages to produce solid pellets of purified recycled material. These stages can include cutting, compacting, melting, degassing, filtering, and pelletizing stages. The machines can employ, for example, solid state polycondensation (SSP) or liquid state polycondensation (LSP) technology. Commercially available examples of such recycling machines include, at the time of writing, The produced and from Next Generation Recyclingmaschinen GmbH (NGRTM ) of P:REACT TM System.

[0065] When using such machines to produce solid pellets of recycled material for injection, the recycled material must be melted a second time before forming a new molded article: once during recycling (in a recycling machine as described above), and then again when the pellets of recycled material are melted in the extruder of the injection machine (e.g., extruder 102) during injection. Each time energy is consumed to heat the material to its melting point.

[0066] To improve energy efficiency, it can be desirable to supply newly recycled molten material to an injection molding machine as a melt rather than as solid pellets. This not only avoids the need for pelletizing equipment in the recycling machine, but also eliminates the need for an extruder in the injection molding machine to melt the pelletized recycled material. Energy efficiency is estimated to improve by about 30%.

[0067] However, direct supply of molten recycled material from an external melt supplier to the injection unit of an injection molding machine can be problematic in certain respects. Machines that produce recycled melt tend to be large and bulky, and can have complex shapes. As a result, it can not be easy to place such recycled melt machines near an injection molding machine, which itself can be large, bulky, and can have incompatible shapes. As a result, the recycled melt machine and the injection molding machine can be separated by a substantial distance. Long distance transport of molten molding material is prone to problems such as temperature variations within the stream of transported melt and / or formation of harmful byproducts, such as acetaldehyde, due to the molten PET being held in a molten state, particularly at higher temperatures.

[0068] Another potential problem with direct flow connection of melt from an external melt supplier, such as a separate material recycling machine, to an injection unit can be the resulting constraint on the mobility of the injection unit. As discussed above, conventional injection units supplied by integral feeders can be configured for translational movement between an away-from and toward hot nozzle position and a maintenance position. Many conventional injection units (e.g., injection unit 100 of P:REACT® and Figure 1 and 2 Injection unit 100 of P:REACT®) have integral material feeders that are fixed relative to the shot pot assembly, which becomes easy in part due to this fact. In contrast, because material recycling machines can be fixed due to their size and weight, injection units directly supplied by melt from such machines will not be as easily configured.

[0069] The inventors considered various approaches for maintaining the mobility of the injection unit while maintaining fluid connection with the upstream melt source. One approach - a flexible tube - was rejected due to the irregular shaping of the inner surface of the flexible tube, which can undesirably affect melt flow, and due to insufficient ability to withstand high melt pressures. Another approach - the use of multiple connecting tubes with ball and socket joint connections - was rejected due to undesirably being expensive, complex, and due to defining an undesirably long melt path.

[0070] Figure 3 An exemplary injection molding system 200 that addresses at least some of the foregoing issues is depicted in isometric top view. The injection molding system 200 includes an injection molding machine 300 that is directly supplied with melt by a stationary reclaimer 400. The injection molding machine 300 incorporates structure that allows the injection unit's shot pot assembly to translate between a production position and a maintenance position without breaking the fluid melt connection with the reclaimer 400, as will be described below.

[0071] The depicted injection molding machine 300 is used to injection mold preforms from a molding material, such as PET. Figure 4 An exemplary preform 500 that can be produced by the injection molding machine 300 is depicted in perspective view. Referring to this figure, it can be seen that the preform 500 has an elongated tubular body 502, a dome-shaped closed base 504, and a neck finish 506 that bounds a neck of the preform 500 near its open end 508. The preform 500 is intended to be subsequently blow molded into a container, such as a beverage bottle, using equipment not depicted or described herein. Other embodiments can produce other types of molded articles.

[0072] Referring again to Figure 3 It can be seen that the injection molding machine 300 includes a housing 302 that houses a clamp unit, a stationary platen 303, a movable platen, and a mold mounted therebetween. The housing 302 also houses a hot runner 305 for directing molding material into the cavities of the mold. Of the above-listed components of the injection molding machine 300, only the stationary platen 303 is visible in Figure 3

[0073] The injection molding machine 300 also includes an injection unit 304. The injection unit includes a shot pot assembly 306, a heated melt tube 314, and a telescoping melt coupling 320, all of which are located atop a stationary base 307. Other components of the injection unit 304 that are not visible in Figure 3

[0074] ​​The spray can assembly 306 is a dual spray can assembly comprising two spray cans 308 and 310 arranged side by side. The spray cans 308 and 310 are configured to operate independently of each other: when one of the spray cans 308 or 310 accumulates the incoming melt from the recovery unit 400, the other spray can 310 or 308 is sprayed through the nozzle 325 of the spray can assembly 306. Figure 3 It is not visible in the text, but as described below, Figure 5 (As shown) the previously accumulated melt injection volume is injected into the hot runner 305. The injection can assembly 306 may, for example, be similar to the dual melt accumulator described in U.S. Patent No. 9,352,503 entitled “A Method for Controlling a Melt Accumulator in an Injection Molding Machine,” which is incorporated herein by reference. The injection can assembly 306 is shown in more detail in the following figures described below.

[0075] The spray can assembly 306 is slidably mounted to the fixed base 307. In this embodiment, a wear pad 309 on the underside of the spray can assembly 306 facilitates the sliding of the assembly 306 on top of the surface of the base 307 in response to the longitudinal force generated by the carriage cylinder 311. Therefore, the assembly 306 can be longitudinally translated between a production position and a purging position, as described below. Figure 3 In the diagram, the spray can assembly 306 is shown in the production position. When the spray can assembly 306 is in the production position, the injection unit 304 can also be considered to be in the production position. This is true even though some parts of the injection unit 304 (e.g., the heated melt tube 314 described below) are actually fixed.

[0076] For clarity, Figure 3 The mutually orthogonal dimensions X, Y, and Z shown refer to the transverse, longitudinal (axial), and vertical dimensions, respectively. Any depiction of dimensions X, Y, and / or Z in the following figures will be consistent with... Figure 3 Consistent.

[0077] Figure 3 The heated melt tube 314 is intended to receive melt from the output melt tube 402 of the machine 400 and guide the melt toward the spray can assembly 306. The heated melt tube 314 is composed of a belt heater array as described below ( Figure 3 (Not visible in the middle) Heating. Tube 314 and heater are housed together within cover 315. For safety and heat preservation reasons, cover 315 is provided, including insulating material (e.g., blanket). Cover 315, together with melt tube 314 and associated heater array, is supported by support column 316 fixedly mounted to fixed base 307 of injection unit 304. It should be understood that the heated melt tube 314 is therefore fixed, i.e., unlike the injection can assembly 306, it is not longitudinally movable.

[0078] An extendable melt coupling 320 is disposed between the heated melt pipe 314 and the spray tank assembly 306. The extendable melt coupling 320 is extendable, i.e., has a variable length. This allows the spray tank assembly 306 to be translated longitudinally between a production position and a purge position without breaking the fluid melt connection between the spray tank assembly 306 and the fixed heated melt pipe 314. In Figure 3 The extendable melt coupling 320 is covered by a cap 322, and is therefore not visible.

[0079] The injection molding machine 300 is controlled by a controller 351 based in part on human operator input. The controller 351 includes at least one processor in communication with volatile or non-volatile memory storing computer readable program code stored on a tangible medium 319 (e.g., ROM, optical disk, USB drive, or magnetic storage medium). In some embodiments, the computer readable program code can be transmitted to the memory via a modem or communication adapter communicatively coupled to a network (e.g., a wide area network such as the Internet). The controller 351 may, for example, be an industrial PC, such as a Core TM i processor of model CP22xx Panel PC.

[0080] Control instructions can be input by an operator via a human machine interface (HMI) 352, which may, for example, be a multi-functional touch screen forming part of or coupled to the controller 351. The HMI 352 allows a human operator to control the operation of the injection molding machine 300, including movement of the spray tank assembly 306 between the production position and the purge position, as will be described below. In Figure 3 The human operator 350 is depicted by an icon that is generally proportional relative to the size of the injection molding machine 300, providing a general sense of the scale of the depicted embodiment.

[0081] The molded material recycling machine 400 converts post-consumer molded material (e.g., PET) into purified molten molded material (e.g., rPET) for reuse. The recycling machine 400 can process the molded material through a series of stages, including compaction, melting, degassing, and filtration stages. The machine may, for example, be a Engineering Recycling Maschinen und Anlagen Ges.m.b.H. of 2318t machine. The purified molded material is output from the recycling machine 400 in molten form via a melt pipe 402. It will be appreciated that the description of the recycling machine 400 in Figure 3 is a schematic representation that is not necessarily drawn to scale and does not reflect the typical complexity of the machine 400.

[0082] Figure 5 depicts Figure 3 a front view of the injection unit 304 with covers 315 and 322 removed. Figure 6 is a front view of a longitudinal cross-section of a portion of the injection unit taken along Figure 3 line 6-6 of FIG. 6, the injection unit including the telescoping melt coupling 320. Figure 7 is a top perspective view of a portion of the injection unit 304 including the telescoping melt coupling 320. In Figure 5 , 6 and 7, the telescoping melt coupling 320 is shown in a production (i.e., extended) position.

[0083] Referring to Figure 5 , the heated melt tube 314 is supported between a support post 316 and a support frame 324. The support frame 324 is a rigid, fixed structure that supports and houses the telescoping melt coupling 320.

[0084] In Figure 8 , 9 and 10, the support frame 324 and the telescoping melt coupling 320 are shown in isolation from the rest of the injection unit 304. Figure 8 The support frame 324 is depicted in a top perspective view with the telescoping melt coupling 320 in a purge position. Figure 9 and 10 depict the support frame 324 in a top perspective view and a top plan view, respectively, with the telescoping melt coupling 320 in a production position.

[0085] Perhaps best seen in Figure 8 , the support frame 324 has a base 326 and an upper portion 328. The base 326 is configured to be connected to the base 307 of the injection unit 304, for example as shown in Figure 5 and 6 . The upper portion 328 of the support frame 324 has three adjoining upright walls: a transverse wall 330 and two adjoining longitudinal walls (side walls) 332, 334. The walls 330, 332, and 334 collectively form three sides of an open box, the missing wall of which is furthest from the heated melt tube 314. As will be appreciated, the open downstream end of the box allows the telescoping melt coupling 320 to extend longitudinally into Figure 9 and 10 the production position of FIGS. 6 and 7.

[0086] Referring to Figure 8 , 9And 10, the annular melt tube connector 338 is fixedly mounted in a circular aperture 336 passing through the transverse wall 330 of the support frame 324 for fixation. The melt tube connector 338 fluidly interconnects the downstream end of the heated melt tube 314 with the upstream end of the sleeve 340 portion of the telescopic melt connector 320 (e.g., see...). Figure 6 The connector 338 has an annular flange 339 that is wider than the bore 336, which abuts the inner surface of the wall 330 (e.g., see...). Figure 9 and 10 ).

[0087] Locking ring 341 (in) Figure 9 and 10 (Also visible in the image) It is attached to the downstream end of the annular melt tube connector 338. The locking ring 341 holds the sleeve 340 in place while allowing it limited movement, as described below.

[0088] The support frame 324 also has a pair of inward-facing infrared heaters 342, 344, which are respectively mounted in the side walls 332, 334, located on the side of the sleeve 340 (see...). Figure 8 , 9 And 10). When the telescopic melt connector 320 is in Figure 9 and 10 When the sleeve is extended or in the production position, these infrared heaters 342 are designed to use infrared radiation to heat the sleeve 340. This is done to ensure that any conveyed melt is maintained at the required temperature. As described below, this embodiment also uses a cylindrical heater as a redundant mechanism for heating the sleeve 340.

[0089] Telescopic melt connector 320 in Figure 11 and 12 A separate illustration is shown in the image. Figure 11 It is the longitudinal cross-section of the melt connector located in the extended production position. Figure 12 This is an isometric exploded view of the telescopic melt connector 320, in which the annular melt tube connector 338 is attached to the upstream end of the sleeve 340.

[0090] like Figure 11 and 12 As shown, the telescopic melt connector 320 has two main components: a sleeve 340 and a tube 360. These two components are slidably engaged with each other in a telescopic manner, wherein the tube 360 ​​slides around the sleeve 340. The extension and retraction of the telescopic melt connector 320 allows the length of the longitudinal fluid melt path thus defined to be within the extension length L1 (e.g., ...). Figure 11 (as shown) and contraction length L2 (as shown) Figure 8adjustment between the extended production position of the telescoping melt link 320 (shown in FIG. 3) and the collapsed purge position of the telescoping melt link 320 (shown in FIG. 4), where Li > L2. In this embodiment, the sleeve 360 slides longitudinally back and forth around the sleeve 340, which remains substantially fixed. The tight fit between the sleeve 340 and the sleeve 360 facilitates the formation of a substantially melt-tight seal between the two.

[0091] When the spray tank assembly 306 is in the production position of FIGS. 1 Figure 5 , 6 and 7, the telescoping melt link 320 extends to a length Li. Conversely, when the spray tank assembly 306 is in the purge position of FIGS. 1 Figure 21 and 22 (described below), the telescoping melt link 320 collapses to a length L2. Thus, the extended and collapsed positions of the telescoping melt link 320 can be referred to as its production and purge positions, respectively.

[0092] Referring to FIG. 3, Figure 11 the sleeve 340 and the sleeve 360 have inner diameters Di and D2, respectively, where Di < D2. The outer diameter of the sleeve 340 is slightly smaller than the inner diameter D2 of the sleeve 360. The dimensions of these components allow them to slidably engage one another as described above, but substantially prevent the leakage of melt therebetween.

[0093] The passage defined by the sleeve 340 flares outwardly at its downstream end. This flared portion 349 can limit the formation of areas of slow-moving or stagnant melt that might otherwise form, for example, if the widening of the inner diameter were more abrupt.

[0094] Referring to FIG. 3, Figure 11 the sleeve 360 is surrounded by three aligned three-belt heaters 362A, 362B, 362C (collectively, heaters 362). These heaters heat the sleeve 360 circumferentially to maintain the melt flowing through the sleeve 360 at a desired temperature. In this embodiment, the heaters 362A, 362B, and 362C are activated both when the telescoping melt link 320 is in the extended production position of FIG. 3 and when the telescoping melt link 320 is in the collapsed position of FIG. 4. Figure 11 Figure 8 Referring to FIG. 3,

[0095] Referring to FIG. 3, Figure 12 it can be seen that the outer surface of the sleeve 340 has a plurality of annular ridges 343 defined therein. The ridges 343 define a sealing surface with the interior of the sleeve 360, which substantially contains the melt. A central flat undercut region 345 bounds a space in which any melt that leaks, for example, due to wear of the components over time, can collect. Any collected melt can be periodically drained through a drip port 365 in the sleeve 360 (see FIG. 4). Figure 11

[0096] ​​As noted above, when the telescoping melt coupling 320 is in the extended or production position, in addition to the infrared heaters 342, 344 shown Figure 8-10 A cartridge heater is also used to heat the sleeve 340 of the present embodiment, in addition to the infrared heaters 342, 344 shown. In one embodiment, the cartridge heater and the infrared heaters are both activated simultaneously whenever the telescoping melt coupling 320 is in the extended position. In another embodiment, one of the two types of heaters can act as the primary heater, and the other type of heater can act as a failsafe heater that activates in the event of a failure of the primary heater. Some embodiments can employ only one of the two types of heaters, as each type is advantageous in different ways. For example, infrared heaters can be more expensive, but can be more maintenance or replacement if defective. Cartridge heaters, as shown in Figure 13 and 14 .

[0097] Figure 13 is an isometric view of the upstream end of the sleeve 340, showing the radially protruding proximal ends of three cartridge heaters 348A, 348B, and 348C (collectively or generically referred to as cartridge heaters 348). Each cartridge heater 348 is a narrow cylindrical resistive element, with a diameter of approximately 50% of the wall thickness of the sleeve 340. Each of the three heaters 348 is oriented longitudinally and embedded into the wall of the sleeve 340, as shown in the longitudinal cross-section of Figure 14 . Embedding the heaters 348 into the wall of the sleeve 340 facilitates heating of the sleeve 340 by conduction. Moreover, this embedding avoids any interference with the slidable engagement of the bushing 360 on the outer surface of the sleeve 340 or with the flow of melt on the inner surface of the sleeve 340.

[0098] In the present embodiment, the three cartridge heaters 348A, 348B, 348C are equally spaced around the circumference of the sleeve 340. As such, each of the three cartridge heaters 348 is offset by 120 degrees from each of the other cartridge heaters along the circumference of the sleeve 340. In view of this arrangement, only the first cartridge heater 348A is visible in the longitudinal cross-section of Figure 14 . A longitudinal channel can be drilled into the sleeve wall between adjacent cartridge heaters to accommodate a thermocouple or other form of temperature sensor. The protruding end of each heater 348A, 348B, and 348 extends radially at a right angle to the embedded portion of the heater (see Figure 13 ), and terminates in a pair of wires for powering the heater.

[0099] It has been found that the use of three embedded longitudinal cartridge heaters 348A, 348B, 348C (equally spaced as described) heat the sleeve 340 sufficiently uniformly around its circumference by conduction to maintain the desired melt temperature. This is taking into account the thermal conductivity of the material from which the exemplary sleeve 340 is made, which can be steel, nichrome 135M, or the like. Alternative embodiments can use a different number or shape of cartridge heaters, for example depending on the efficiency of the heaters, the thermal conductivity of the material from which the sleeve is made, or other factors, or can heat the sleeve 340 in another manner.

[0100] It will be appreciated that the cartridge heaters 348 are redundant to the infrared heaters 342, 344 (see Figure 9 , 10 and 11). The redundancy is intended to provide flexibility in heating the sleeve 340 when the telescoping melt coupling 320 is in the production position. The cartridge heaters 348 heat the sleeve 340 internally by conduction, and the infrared heaters 342, 344 heat the sleeve 340 externally by radiation. The cartridge heaters 348 can be activated together with, or alternatively to, the infrared heaters 342, 344.

[0101] Referring to Figure 11 and 13 , it can be seen that the upstream end of the sleeve 340 has an annular flange 379 extending therefrom. This flange 379 facilitates the connection of the sleeve 340 to the annular melt tube coupling 338, as will be described below.

[0102] Referring back to Figure 5 , 6 and 7, it will be appreciated that the telescoping melt coupling 320 is longitudinally aligned, i.e. coaxial, with the heated melt tube 314 of the injection unit 304. The inventors believe that there is some risk that the telescoping melt coupling 320 can become angularly misaligned with the longitudinal axis of the heated melt tube 314 over time, given the forces that can be imparted to the telescoping melt coupling 320 during use. That is, the downstream end of the telescoping melt coupling 320 can be raised, lowered, or laterally displaced relative to the upstream end of the telescoping melt coupling 320 that is connected to the annular melt tube coupling 338. The forces that can cause this effect can include one or more of: bending moments from repeated extension and contraction of the coupling 320 as the shot pot assembly 306 is reciprocated between the production position and the purge position; thermal expansion of components of the injection unit 304; and manufacturing tolerances of these components. These factors can have a compounding effect. In particular, given the fact that only one end of the telescoping melt coupling 320 is attached to the support frame 324 - the upstream end being attached at the annular melt tube coupling 338 by the locking ring 341 - the longitudinal axis of the telescoping melt coupling 320 can stop being parallel to the longitudinal axis of the heated melt tube 314 over time.

[0103] In view of this risk, the connection between the telescoping melt coupling 320 and the annular melt pipe coupling 338 has been designed as a ball joint, as best seen in Figure 14 and 15 The upstream end of the sleeve 340 and the immediately adjoining mating face of the annular melt pipe coupling 338 have complementary surfaces 370, 372. The surfaces 370, 372 are consistent with a sphere S that is centered generally along the axis AA (see Figure 14 and 15 ) of the sleeve 340, which is also the axis of the telescoping melt coupling 320. In the present embodiment, the surface 370 of the sleeve 340 is slightly convex, and the complementary surface 372 of the annular melt pipe coupling 338 is slightly concave. In alternative embodiments, this relationship can be reversed. The result is a ball-and-socket type joint between the two components 340, 338. This ball joint allows the telescoping melt coupling 320 to pivot universally, at least to a limited extent, relative to the annular melt pipe coupling 338, without compromising the fluid melt interconnection, i.e., with minimal melt leakage. This can promote robustness and cost efficiency, and can minimize operational downtime of the injection molding system 200.

[0104] In the present embodiment, the complementary surfaces 370, 372 of the ball joint are biased away from one another. More particularly, the locking ring 341 has an annular shoulder 346 on its upstream side. The annular shoulder 346 faces the annular flange 339 of the annular melt pipe coupling 338, creating an annular space 347 below the shoulder 346. The annular flange 379 of the sleeve 340 is enclosed within this annular space 347. The relative dimensions of these components allow a limited degree of longitudinal movement of the annular flange 379 within the annular space 347. A coil spring 377, as a form of biasing element, also occupies the annular space 347, compressed between the locking ring 341 and the annular flange 379. The spring 377 is preloaded to a degree that can be adjusted by appropriate tightening or loosening of the bolts 381 that hold the locking ring 341 to the coupling 338. The coil ring 377 can have an outward taper, and the annular flange 379 can have an inverse taper, i.e., can widen outwardly in a complementary manner.

[0105] The pressure of the compressed spring 377 against the annular flange 379 urges the upstream end of the sleeve 340 against the annular melt pipe coupling 338. The combined bias of the spherical surface 370 against the complementary spherical surface 372 can help to prevent leakage of pressurized melt from the ball joint. It will be appreciated that the bias of the melt flow through the telescoping melt coupling 320, the coil spring 377, is continuous.

[0106] The telescoping melt coupling 320 is also designed to limit melt leakage from the ball joint in another way when operated in the extended or production position. The telescoping melt coupling 320 is arranged so that the exposed end of the (narrower) sleeve 340 is upstream of the exposed end of the (wider) sleeve 360, rather than the other way around. This arrangement has the effect that when pressurized melt flows through the extended telescoping melt coupling 320, the melt pressure within the downstream sleeve 360 will exert a force on the upstream (Y) dimension on the upstream sleeve 340 that partially occupies the sleeve 360. The upstream directed force on the sleeve 340 can increase the pressure with which the ball joint face 370 of the sleeve presses against the complementary face 372 of the annular melt tube coupling 338. This increased pressure supplements the biasing force created by the disc spring 377, which can be thought of as precisely maximizing the protection against ball joint leakage when it is most needed: when pressurized melt is flowing through the telescoping melt coupling 320.

[0107] It will be appreciated that the aforementioned force from the pressurized melt pushing on the sleeve 340 in the upstream direction can be significant during injection unit operation. The support frame 324 can be designed to resist this force and thereby protect the upstream melt source (e.g., the heated melt tube 314 and the upstream tube 402) from damage. For example, the structural members of the support frame 324 can be made of a suitably strong material. In addition, the base 326 of the support frame 324 can be well secured to the base 307 of the injection unit 304, for example using a number of bolt fasteners as shown.

[0108] Referring again to Figure 6 It will be seen that the injection unit 304 also includes a static mixer 380 in the melt path immediately downstream of the telescoping melt coupling 320. The purpose of the static mixer 380 is to improve the uniformity of the melt in terms of its temperature and viscosity after it has been conveyed through the tube 402, heated melt tube 314, and telescoping melt coupling 320 over a considerable distance of the molding material recycling machine 400. The static mixer 380 may, for example, have a structure as described in U.S. Patent No. 7,198,400, which is incorporated herein by reference. That is, the mixer 380 can include a mixer body having first and second arrays of interengaging and interconnecting channels formed therein that connect between and provide a swirling flow path between flow faces at the ends of the mixer body. The first and second arrays of channels can be interconnected such that the boundaries of adjacent interengaging channels overlap to form a mixing entrance.

[0109] The injection unit 304 also includes a downwardly sloped melt tube 382 in the melt path immediately downstream of the static mixer 380 Figure 6 ) The melt tube 382 conveys the melt into the injection pot assembly 306, which is described below in connection with Figure 18Various melt tubes are described.

[0110] The injection unit 304 is configured with multiple heaters along the melt path from the molding material recovery machine 400 to the spray tank assembly 306. These heaters are used to maintain the delivered melt at an optimal temperature under the control of the controller 351. The optimal temperature at various stages along the melt path can depend on various factors, such as the type of molding material, including its viscosity at various temperatures and the risk of temperature-based melt degradation (e.g., formation of acetaldehyde) at various temperatures, energy efficiency considerations, melt residence time in the spray tank, and other factors. The optimal temperature at various stages along the path can ultimately be a compromise among these sometimes competing factors, and can vary among embodiments.

[0111] The melt from the example molding material recovery machine 400 Figure 3 is output at a first temperature Tl, referred to as its recycle temperature. In this embodiment, this recycle temperature Tl is lower than a second target temperature T2 for injection of the melt into a mold, referred to as its injection temperature. If the molding material is rPET, the recycle temperature Tl can be, for example, about 270 degrees Fahrenheit, and the injection temperature can be, for example, about 285 degrees Fahrenheit.

[0112] In this embodiment, the multiple heaters along the melt path of the injection unit 304 are grouped in fourteen successive zones, labeled Zl through Zl4, in the downstream direction. These zones are depicted as Figure 16 and 17 Each zone can include at least one independently controllable heater and temperature sensing device. In this embodiment, the majority of the selected heaters are belt heaters, as they are suitable for encircling the relevant melt tube in that zone. However, some zones employ other forms of heaters, such as infrared heaters 342, 344 and cartridge heater 348, which are used to heat the sleeve 340 of the telescoping melt coupling 320 in zone ZlO Figure 17 , described below. The types of heaters used in alternative embodiments can vary.

[0113] Referring to Figure 16 , a front view of the heated melt tube 314 is depicted. Starting from the right side of the upstream end Figure 16 , eight heater zones Zl through Z8 are defined in sequence along the melt tube 314. Most of the zones have uniform lengths. However, zones Zl, Z3 and Z8 are shorter than the other zones. In this embodiment, the lengths of the heater zones are determined at least in part by the heat absorption and / or heat dissipation of the melt tube in that zone. For example, zone Zl includes the coupling flange 385, and zone Z8 includes the annular melt tube couplings 338, each of which is shorter than the other zones. Figure 16The other areas absorb and / or dissipate more heat from the tube.

[0114] Turning to Figure 17 , a longitudinal cross-section of the telescoping melt coupling 320 and downstream components of the injection unit 304 is depicted when the shot pot assembly 306 is in the production position. Starting from the upstream end (right side of the figure), six heater zones Z9-Z14 are defined in sequence along the melt path. The reason for the variation in length of these zones is similar to that described above in connection with Figure 17 Figure 16 In this embodiment, all zones use band heaters except for zones Z9 and Z10. Zone Z9 uses a cartridge heater in this embodiment.

[0115] The heaters can be controlled by the controller 351 to define a monotonic increasing temperature gradient in the zones Z1-Z14. The temperature gradient may, for example, be linear, exponential, or otherwise, as appropriate for the embodiment at issue. For example, the temperature gradient can be selected so as to minimize melt degradation or yellowing by keeping the melt at as low a temperature as possible for as long as possible while maintaining the viscosity of the molding material used at least at a threshold level. The temperature gradient can take into account the duration required to heat the melt and its residence time in the melt path.

[0116] Figure 18 is a simplified three-dimensional schematic of the melt flow path defined within the injection unit 304 when the shot pot assembly 306 is in the production position. The line L-L divides the components of the injection unit 304 into two groups: fixed components and translatable components.

[0117] The fixed components of the injection unit 304 include the heated melt tube 314 and the sleeve portion of the telescoping melt coupling 320. These components are fixed, as shown, with the support column 316 anchored to the floor. For the sake of clarity, the sleeve 340 is considered fixed herein, despite its limited ability to travel longitudinally, in view of the significantly greater degree of longitudinal travel that the translatable components are capable of between their production and purge positions. Figure 18

[0118] Figure 18 ​​The remaining components of the injection unit 304 depicted are translatable in the direction depicted by the double-headed arrow T. Translatable components include the sleeve 360 portion of the telescoping melt coupling 320, the stationary mixer 380, the downwardly sloped melt tube 382, and the spray pot assembly 306. Within the spray pot assembly 306, a network of melt tubes are translatable as a unit. These melt tubes include the upper cross melt tube 390, the vertical melt tubes 392 and 394, the axial melt tubes 396 and 398, and the lower cross melt tube 399. The spray pots 308 and 310 and the nozzle 325 are also considered part of the spray pot assembly 306 and are translatable with the aforementioned components.

[0119] It will be appreciated that as the translatable components of the injection unit 304 are translated uniformly toward or away from the stationary components, the telescoping melt coupling 320 expands and contracts axially in the Y-dimension. Figure 18 In this manner, the fluid melt connection from the heated melt tube 314 to the spray pot assembly 306 is maintained regardless of whether the injection unit 304 is in a production position (as shown in Figure 18 ) or a purging position (as shown in Figures 21 to 24 , as described below).

[0120] Figure 19 and 20 The manner in which melt is dispensed from the spray pots 310 and 308 during normal production of molded articles is schematically depicted, with the injection unit 304 in a production position, for example, as shown in Figure 6 . In this position, the nozzle 325 of the spray pot assembly 306 engages the gate bushing 335, thereby forming a fluid melt connection therewith (see, for example, Figure 6 ).

[0121] It will be appreciated that when the telescoping melt coupling 320 is in the expanded production position of Figure 19 , the sleeve heater 362 Figure 12 and the sleeve heaters 342, 344, and 348 Figure 9 and 13 will be on.

[0122] Figure 19 The first stage of the injection cycle is depicted. In this stage, the spray pot 310 is venting previously accumulated melt into the mold via a melt path defined by the axial melt tube 398, the lower cross melt tube 399, and the nozzle 325. This process is shown in Figure 19The middle section is indicated by the dashed arrow DD. Simultaneously, another injection tank 308 is refilled with melt continuously supplied by the heated melt pipe 314 via a melt path defined by the telescopic melt connector 320, mixer 380, downward-sloping melt pipe 382, ​​upper transverse melt pipe 390, vertical melt pipe 392, and axial melt pipe 396. This process is indicated by the dashed arrow RR. It should be understood that all these melt paths are defined in part by the appropriate control of the distribution valve (not depicted) of the dual injection tank assembly 306 by the controller 351.

[0123] exist Figure 20 In the subsequent stages of the injection cycle shown, the situation is reversed. The spray can 308 discharges the previously accumulated melt into the mold via a melt path defined by the axial melt pipe 396, the lower transverse melt pipe 399, and the nozzle 325, as indicated by the dashed arrow DD. Simultaneously, another spray can 310 is refilled with melt continuously supplied by the heated melt pipe 314 via a melt path defined by the telescopic melt connector 320, the mixer 380, the downward-sloping melt pipe 382, ​​the upper transverse melt pipe 390, the vertical melt pipe 394, and the axial melt pipe 398, as indicated by the dashed arrow RR.

[0124] Figure 21 and 22 The injection unit 304 is depicted, wherein the injection can assembly 306 is in the purge position. More specifically, Figure 21 and 22 These are longitudinal cross-sections and top perspective views of a portion of the injection unit 304, including the telescopic melt connector 320 and the nozzle 325.

[0125] When the spray can assembly 306 moves from the production position to the purging position, the nozzle 325 separates from the gate bushing 335, thereby breaking the fluid melt connection between them. The tip of the nozzle 325 can be retained within a recess 441 in the outer surface of the pressure plate 303. Any melt discharged while the nozzle 325 is in this position will not enter the hot runner 305.

[0126] Movement of the shot tank assembly 306 to its purging position will cause the telescoping melt coupling 320 to collapse, i.e., the sleeve 340 will become substantially nested with the sleeve 360. When the telescoping melt coupling 320 reaches its collapsed position, the sleeve heaters 342, 344, and 348 are deactivated, e.g., under control of the controller 351. The rationale for deactivation is that with the sleeve 360 substantially overlapping the sleeve 340, the sleeve heater 362 will be sufficient to heat the sleeve 340. As such, the melt in the telescoping melt coupling 320 can be maintained at a desired temperature without the risk of temperature overshoot from overlapping heaters. In some embodiments, only the infrared sleeve heaters 342, 344 are deactivated when the telescoping melt coupling 320 collapses, with the cartridge heater 348 remaining active. The collapsed position can be detected, e.g., by a position sensor of the injection unit 304.

[0127] Figure 23 and 24 The manner in which melt is dispensed from the shot tanks 310 and 308 during purging of the injection unit 304 with the shot tank assembly 306 in the purging position is schematically depicted. Referring to Figure 23 , a first phase of the injection cycle is depicted. Operation of the shot tank assembly 306 in this phase is the same as that shown above in Figure 19 , with the exception that the stream of melt DD exiting the nozzle 325 falls as waste. Figure 24 A subsequent phase of the injection cycle is depicted. Operation of the shot tank assembly 306 in this phase is the same as that shown above in Figure 20 , with the exception that the stream of melt DD exiting the nozzle 325 again falls as waste, rather than being injected into the sprue bushing 335.

[0128] Various alternative embodiments are contemplated.

[0129] While the above-described embodiments contemplate use of recycled molding material for molding articles, alternative embodiments can use virgin molding material in whole or in part.

[0130] The above-described example telescoping melt coupling embodiments are used in conjunction with a shot tank assembly having two shot tanks, i.e., a dual shot tank assembly. It will be appreciated that telescoping melt couplings can be used in alternative injection unit embodiments that employ other types of shot tank assemblies. For example, one alternative shot tank assembly can have only a single shot tank with an upstream buffer for buffering incoming melt as the shot tank will earlier accumulate shots of melt for injection into the sprue for molding a batch of articles.

[0131] In at least some of the above embodiments, the sleeve heater is deactivated and the jacket heater remains active when the telescoping melt coupling moves from the extended position to the retracted position. In some embodiments, this can be reversed. That is, the jacket heater can be deactivated and the sleeve heater can remain active when the telescoping melt coupling moves from the extended position to the retracted position.

[0132] Other modifications can be made within the scope of the following claims.

Claims

1. An injection unit (304) for an injection molding machine (300) having a hot nozzle (305) with a gate (335), the injection unit comprising: a heated melt tube (314) configured to deliver a continuous stream of melt; a shot pot assembly (306) including at least one shot pot, the shot pot assembly configured to convert the continuous stream of melt from the heated melt tube into batches for cyclic injection, the shot pot assembly translatable between a gate-engaged position and a gate-disengaged position; and a telescoping melt link (320) configured to deliver melt from the heated melt tube to the shot pot assembly; wherein the telescoping melt link includes: a sleeve; and a sheath slidable about the sleeve between an extended position and a retracted position while maintaining a seal with the sleeve to substantially contain melt; at least one sleeve heater configured to heat the sleeve of the telescoping melt link; and at least one sheath heater configured to heat the sheath of the telescoping melt link.

2. The injection unit of claim 1, wherein the telescoping melt link has a variable length configured to maintain a fluid melt interconnection between the heated melt tube and the shot pot assembly between a gate-engaged position and a gate-disengaged position.

3. The injection unit of claim 2, wherein the at least one sleeve heater and the at least one sheath heater are independently controllable.

4. The injection unit of claim 3, wherein the at least one sleeve heater is operable to deactivate upon the sheath of the telescoping melt link transitioning from the extended position to the retracted position.

5. The injection unit of claim 3, further comprising a plurality of heaters for heating the heated melt tube, wherein the plurality of heaters, the at least one sleeve heater, and the at least one sheath heater are collectively operable to define a monotonically increasing temperature gradient in a downstream direction along the heated melt tube and the telescoping melt link.

6. The injection unit of claim 5, wherein the monotonically increasing temperature gradient of the heated melt tube and telescoping melt link is linear.

7. The injection unit of claim 5, wherein the monotonically increasing temperature gradient of the heated melt tube and telescoping melt link is exponential.

8. The injection unit of claim 1, wherein the telescoping melt link defines a spherical connection mating surface conforming to a sphere (S) centered along an axis (AA) of the telescoping melt link. ​ 9. The injection unit of claim 8, wherein the spherical connection mating face is defined at an upstream end of the sleeve, and further comprising a fixed annular melt tube coupling (338) fluidly interconnecting the heated melt tube with the sleeve, the annular melt tube coupling having a downstream end defining a spherical connection mating face complementary to the spherical connection mating face of the sleeve, the two spherical connection mating faces collectively allowing axial angular misalignment of the telescoping melt coupling relative to the heated melt tube without compromising fluid melt interconnection.

10. The injection unit of claim 9, wherein the sleeve has an annular flange (379) extending radially from an upstream end thereof, and further comprising a lock ring (341) attached to the annular melt tube coupling, the lock ring defining an annular space (347) containing the annular flange therein to allow limited longitudinal movement of the sleeve.

11. The injection unit of claim 10, further comprising a biasing element between the lock ring and the annular flange, the biasing element configured to bias the spherical connection mating face of the sleeve against the spherical connection mating face of the annular melt tube coupling.

12. An injection molding machine (300) comprising: a hot runner (305) with a main gate (335); and an injection unit (304) comprising: a heated melt tube (314) configured to deliver a continuous melt stream; a shot pot assembly (306) configured to convert the continuous melt stream into batches for cyclic injection, the shot pot assembly being translatable relative to the heated melt tube between a gate-engaged position and a gate-disengaged position; and a telescoping melt coupling (320) configured to deliver melt from the heated melt tube to the shot pot assembly; wherein the telescoping melt coupling comprises: a sleeve; and a sleeve tube slidable about the sleeve between an extended position and a retracted position while maintaining a seal with the sleeve to substantially contain melt; wherein the injection molding machine further comprises: at least one sleeve heater configured to heat the sleeve of the telescoping melt coupling; and at least one sleeve tube heater configured for heating the sleeve tube of the telescoping melt coupling.

13. The injection molding machine of claim 12, wherein the telescoping melt coupling has a variable length configured to maintain fluid melt interconnection between the heated melt tube and the shot pot assembly between a gate-engaged position and a gate-disengaged position.

14. The injection molding machine of claim 13, wherein the injection molding machine further comprises: a controller (351) configured to deactivate the at least one sleeve heater or the at least one sleeve tube heater when the sleeve tube transitions from the extended position to the retracted position. ​ 15. The injection molding machine of claim 13, further comprising a ball joint configured to allow angular axial misalignment of the telescoping melt coupling relative to the heated melt tube without compromising the fluid melt interconnection between the heated melt tube and the injection pot assembly.

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