The present invention relates to an apparatus for molding, and more particularly to an injection molding machine with a material injection system and a mold clamping system.
The invention relates to injection molding machines, such as the type that produce heat cured or thermo-setting materials such as but not limited to silicone rubber. Thermoset injection units are typically built upon a screw based injection system originally designed for thermoplastic polymers. A typical thermoplastic injection system first takes material in a pellet form from a hopper and feeds it into a heated barrel where a screw rotates to convey, compress, and mix the material before plunging to force the material into the mold cavity where the material cools to become solid in order to make a part. Upon the introduction of thermoset materials, the thermoplastic injection system was adapted to inject thermoset material using many of the same elements. A typical thermoset injection first takes material in a liquid form under pressure and feeds it into a barrel where a screw rotates to convey the material before plunging to force the material into the mold cavity where the material is heated to cure and become solid in order to make a part.
In plastic injection molding, plastic pellets are pre-heated in a hopper then a screw in a heated barrel turns and strokes the material into the mold. When switching materials or colors the entire injection system needs to be dismantled to fully clean the screw, barrel, nozzle and all components that come in contact with the material. Purging techniques exist but are not sufficient to completely clear out the injection system. An injection system tear down and cleaning can typically take a full day leaving the injection molding machine unavailable for production. These same plastic molding machines are used to mold thermoset materials like liquid silicone rubber (“LSR”) with some minor modifications. However, a complete tear down for cleaning is still required for both material change over and at the end of the production run since the material could cure to the point of locking the components together if left in the machine for days. Cleaning uncured thermoset material from injection components is more involved and time consuming as solvents are often needed to remove the sticky material that is comparable to tree sap.
At least one thermoset injection system has been developed to address these concerns by redeveloping a system from the ground up with a removable injection module that contains all or substantially the entire material flow path downstream from the material supply. For example, an injection molding machine with a removable injection module is shown in U.S. Pat. No. 10,239,246 entitled INJECTION MOLDING MACHINE, which issued Mar. 26, 2019 to Burton et al, which is incorporated herein by reference in its entirety. Injection molding machines incorporating the teachings of U.S. Pat. No. 10,239,246 to Burton provide a variety of notable advantages over other systems, particularly in connection with the use of liquid silicone rubber.
Other innovations in thermoset injection systems have been focused on keeping the material at a low enough temperature before it is injected so it will not cure before entering the mold cavity. One innovation is to build a mold in more than two plates with insulation material between the plate where the thermoset material first enters the mold and the heated mold cavity plate. One disadvantage of this approach is that is can increase the cost and complexity of the mold design. A further innovation is to pump liquid through cavities in the plates to be cooled allowing a large amount of heat to be removed. One disadvantage of conventional liquid cooling systems is that they are not configured to work with injection molding systems with removable injection modules.
Other innovations are focused on reducing the amount of voids in the final product due to trapped air or additional processes to remove extra material called flash. A typical mold has small passages to allow air inside the mold cavity to escape as material enters the mold cavity. Molds designed this way may produce parts with trapped air if material enters the mold cavity faster than the air can escape. It is undesirable to have voids in the part as it may adversely affect the physical properties or the aesthetics. Molds designed this way may also produce parts with additional material, called flash, if the material flows into the passages meant to allow the air to escape. It is undesirable to have flash on the part as it may require additional processing to remove. U.S. Pat. No. 10,239,246 to Burton provides an embodiment in which a vacuum system in integrated into the injection molding system. In one embodiment, the vacuum system includes a vacuum sleeve that is fitted around the nozzle of the injection module. The vacuum sleeve is capable of operatively engage the mold cavity to draw a vacuum in the mold cavity before the nozzle is seated. Once the desired vacuum is achieved, the nozzle can be seated to close off the mold cavity while it remains under vacuum. Material can then be introduced into the mold through the nozzle with the vacuum helping to draw material into the mold cavity and provide improved part quality.
A need exists to enhance the type of injection molding systems that have removable injection modules to include a cooling system and to do so without losing the ability to include an effective vacuum system.
The present invention provides an injection molding system generally including an injection frame and a removably attached injection module. The injection frame includes an integrated liquid cooling system to cool a portion of the injection module and help to prevent material from curing the injection module prior to injection in to the mold. The liquid cooling system is integrated into the injection frame such that the injection module can be installed and removed from the injection frame without manipulation of the liquid cooling system.
In one embodiment, the liquid cooling system is configured to cool at least a portion of the nozzle of the injection module. In such embodiments, the injection frame may include a carrier plate configured to releasably receive the injection module in such a way as to arrange the nozzle in operative association with the liquid cooling system automatically as the injection module is installed on the injection frame.
In one embodiment, the liquid cooling system includes a liquid coolant supply that moves coolant through the cooling system by a pressure differential. For example, coolant may be introduced into the cooling system under positive pressure and/or withdrawn from the cooling system under negative pressure. In one embodiment, the liquid cooling system includes an inlet port for receiving a supply of coolant from the liquid coolant supply and an outlet port for returning coolant to the liquid coolant supply. The inlet and outlet ports may be affixed to the injection frame.
In one embodiment, the injection frame includes a nozzle sheath configured to receive the nozzle when the injection module is mounted to the injection frame. The nozzle sheath may be configured to be generally coextensive with the nozzle extending from nozzle base to nozzle tip.
In one embodiment, the exterior of the nozzle and the interior of the nozzle sheath cooperatively define one or more liquid flow paths through which a cooling liquid may be moved to cool the nozzle.
In one embodiment, the liquid cooling system includes a pair of seals that define an interior space to receive the cooling liquid. In one embodiment, the pair of seals includes an inner seal that forms a leaktight seal between the base of the nozzle and the nozzle base and an outer seal that forms a leaktight seal between the nozzle sheath and the tip of the nozzle.
In one embodiment, the external shape of the nozzle and the internal shape of the nozzle sheath are configured to define separate supply and coolant return paths. The coolant supply path may extend from the base of the nozzle sheath to the tip of the nozzle and the coolant return path may flow from the tip of the nozzle back to the base of the nozzle sheath.
In one embodiment, the nozzle base defines an inlet recess for supplying liquid to the coolant supply path and outlet recess for returning liquid from the coolant return path.
In one embodiment, the exterior of the nozzle and the interior of the nozzle sheath are shaped to define a longitudinally extending coolant supply path and a longitudinally extending coolant return path. For example, the interior of the nozzle sheath may be tubular and the exterior of the nozzle may be polygonal with the vertices of the polygon closely interacting with the interior of the nozzle sheath to define a plurality of longitudinal passages. More specifically, the interior space defined between the interior of the sheath and each side of the polygon may form a longitudinally extending passage capable of functioning a liquid flow path.
In one embodiment, the interior of the nozzle sheath is circular in cross section and the exterior of the nozzle is hexagonal in cross section. In this embodiment, the external dimensions of the nozzle and the internal dimensions of the nozzle sheath are selected so that the vertices provide a sufficient seal with the nozzle sheath to define six longitudinal flow paths.
In one embodiment, the nozzle tip may include a plurality of longitudinally extending flutes (or grooves) that allow liquid supplied through the coolant supply path to flow around the nozzle tip and into the coolant return path.
In one embodiment, the inlet port is in fluid communication with the base of the nozzle sheath through a first portion of the circumference and the outlet port is in fluid communication with the base of the nozzle sheath through a second portion of the circumference.
In a second aspect, the present invention provides an injection molding system having a vacuum system for drawing air from the mold cavity prior to injection. In one embodiment, the vacuum system includes a vacuum sleeve that is situated about the nozzle sheath. For example, the vacuum sleeve may be fitted coaxially about the nozzle sheath. The inside diameter of the vacuum sleeve may be larger than the outside diameter of the nozzle sheath to define an intermediate air flow path. A vacuum source may be coupled to the distant end of the vacuum sleeve to allow air to be drawn through the mold end of the vacuum sleeve.
In one embodiment, the vacuum sleeve extends beyond the nozzle sheath and the injection nozzle in a direction toward the mold. This allows the vacuum sleeve to engage the mold before the injection nozzle as the injection molding system is shuttled toward the mold. The vacuum sleeve may include a seal on the mold end. The seal is configured to create and air tight seal between the vacuum sleeve and the mold face. In one embodiment, the vacuum seal is created around the injection nozzle inlet so that the mold cavity is in fluid communication with the vacuum sleeve. As a result, when a vacuum is applied, air is drawn from the mold cavity.
In one embodiment, the vacuum sleeve is retractable to allow it to move into the injection molding system as the injection molding system moves farther forward to bring the nozzle into engagement with the mold inlet. The vacuum sleeve may be telescopically received within a sleeve base and may be capable of extending and retracting with respect to the sleeve base during operation of the system.
In one embodiment, the injection molding system includes a spring that urges the vacuum sleeve away from the sleeve base into its forward-most position, but is capable of compressing to allow the vacuum sleeve end to move telescopically into the sleeve base into a retracted position. The spring may be a coil spring that is fitted coaxially over the nozzle sheath and engages the innermost end of the vacuum sleeve end. In an alternative embodiment, the vacuum sleeve may be immovable, but it may include a seal that is capable of compressing, collapsing or otherwise allowing the injection nozzle to move into engagement with the mold after the vacuum has been drawn.
In use, the injection molding system may be moved forward toward the mold until the seal on the vacuum sleeve, but not the nozzle tip, has touched the mold face. In this position, the vacuum sleeve is sealed against the mold face in communication with the nozzle inlet. Since the nozzle tip has not yet contacted the mold face, a partial vacuum can then be drawn at the rear end of the vacuum sleeve to extract air from the mold cavity through the sprue at the nozzle inlet. While the mold cavity is held under vacuum, the injection molding system can be moved farther forward toward the mold until the nozzle tip seals against the mold face. During this second stage of travel, the vacuum sleeve remains sealed against mold face, but retracts into the injection system. Once in this position, the mold cavity is held under vacuum by the seal between the nozzle tip and the mold shut off surface. Material can be injected into the mold cavity under the aid of the partial vacuum. Since air can often be evacuated from the cavity very quickly, the motion to move the nozzle tip towards the mold may be continuous. In other words, a desired vacuum is achieved from time when the nozzle sleeve seal first contacts the mold face and the nozzle tip engages the nozzle seat and seats against the mold while under continuous motion.
The present invention provides a simple and effective injection molding system that is particularly well-suited for use with liquid silicone rubber (“LSR”) material. The releasably attachable injection module can be easily cleaned or swapped out with another injection module to run a different material or color for the same or different mold tool. Once removed from the injection molding system, the injection module may be placed in cold storage to prevent curing of material between uses to avoid cleaning altogether. All of these options prevent machine down time and related costs due to material change over. The incorporation of actuators into the carrier plate reduces the size, weight and complexity of the injection module. It also facilitates the use of interchangeable injection modules because each injection module is not required to include its own set of actuators. Attachment and removal of the injection module can be facilitated with quick attachment structures to couple the actuators to the movable components in the injection module. The liquid cooling system helps to prevent material from curing in the injection module prior to injection into the mold. The liquid cooling system may be fully integrated into the injection frame so that the injection module can be attached and removed without the need to manipulate the liquid cooling system. When implemented, the vacuum system reduces the force required to inject material into the mold cavity and helps to improve part quality. Integration of a retractable vacuum sleeve provides an effective structure that is highly reliable and can operate with limited additional components. If desired, the liquid cooling system may implemented so that it can operate to cool at least a portion of the injection module during all steps of the molding process, for example, including the steps of filling the injection module with material, applying a vacuum to the mold cavity, injecting material into the mold cavity and waiting for the material to cure in the mold.
The present invention is described with reference to various alternative embodiments. In one illustrated alternative embodiment, the present invention is incorporated into a horizontal mold press. In this embodiment, the present invention includes a variety of alternative components, including an alternative injection module and an alternative clamping system. Although this embodiment includes a variety of alternative components, it should be understood that these alternative components are not limited to use in connection with one another as shown and described in connection with the horizontal mold press embodiment, but instead may be used individually or in essentially any combination.
These and other features of the invention will be more fully understood and appreciated by reference to the description of the embodiments and the drawings.
Before the embodiments of the invention are explained in detail, it is to be understood that the invention is not limited to the details of operation or to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention may be implemented in various other embodiments and of being practiced or being carried out in alternative ways not expressly disclosed herein. In addition, it is to be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items and equivalents thereof. Further, enumeration may be used in the description of various embodiments. Unless otherwise expressly stated, the use of enumeration should not be construed as limiting the invention to any specific order or number of components. Nor should the use of enumeration be construed as excluding from the scope of the invention any additional steps or components that might be combined with or into the enumerated steps or components. Any reference to claim elements as “at least one of X, Y and Z” is meant to include any one of X, Y or Z individually, and any combination of X, Y and Z, for example, X, Y, Z; X, Y; X, Z; and Y, Z.
Overview.
An injection molding machine in accordance with an embodiment of the present invention is shown in
In the illustrated embodiment, the injection module 18 includes a nozzle 32 for delivering material to the mold 13 and the liquid cooling system 700 is configured to move a cooling liquid over at least a portion of the nozzle 32. In this embodiment, the cooling system 700 includes a nozzle sheath 706 mounted to the injection frame 16. The nozzle sheath 706 defines an interior configured to receive the nozzle 32 as the injection module 18 is mounted to the injection frame 16. In this embodiment, the intermediate space between the nozzle 32 and the nozzle sheath 706 defines a chamber 708 around the exterior of the nozzle 32 and nozzle tip 34 to receive cooling liquid. For example, inner and outer seals 720 and 722, respectively, may be disposed toward opposite ends of the nozzle 32 to assist in forming the intermediate sealed chamber 708. In the illustrated embodiment, the intermediate chamber 708 is configured to define a coolant supply path 710 through which liquid coolant is moved along the nozzle 32 to the nozzle tip 34 and a coolant return path 712 through which coolant returns from the nozzle tip 34 along the nozzle 32.
In the illustrated embodiment, the injection frame 16 generally includes a mounting plate 21 that supports an injection module receiver 22 and a plurality of actuators that are configured to move the injection frame 16 toward and away from the mold 13 and to operate the various parts of the injection module 18. The injection module 18 is releasably attached to the injection module receiver 22. The injection module 18 includes at least a portion of the material flow path from the material supply connection 20 to the mold 13, including the nozzle 32 and the nozzle tip 34. When desired, the injection module 18 can be removed from the injection frame 16. This allows the injection module 18 to be easily cleaned or, if not empty, to be placed in a refrigerated location where the material inside the injection module 18 will not cure for an extended period. It also allows the interchangeable use of different injection modules 18 on the same injection molding system 14.
The injection molding system 14 may also include a vacuum system 36 for drawing air from the mold cavity 15 prior to injection. In this embodiment, the vacuum system 36 includes a vacuum sleeve 38 that is situated about the nozzle sheath 706. The vacuum sleeve 38 extends forwardly beyond the nozzle 32 so that the vacuum sleeve 38 contacts the mold 13 prior to the nozzle tip 34. The vacuum system 36 also includes a vacuum source (not shown) for applying a partial vacuum to the vacuum sleeve 38. In the illustrated embodiment, the vacuum sleeve 38 is retractable with respect to the nozzle 32. The injection molding system 14 of the illustrated embodiment includes a spring 40 that urges the vacuum sleeve 38 into its forward-most position, while allowing the vacuum sleeve 38 to move rearwardly as the injection frame 16 is moved from the vacuum position to the injection position. In use, the injection frame 16 may be moved toward the mold into the vacuum position in which the vacuum sleeve 38, but not the nozzle 32, is engaged with the mold 13. In this position, the vacuum source may be operated to create a partial vacuum within the mold cavity 15. While the mold cavity 15 is held under vacuum, the injection frame 16 can be moved farther toward the mold 13 until the nozzle tip 34 seals against the mold face. During the second stage of travel, the vacuum sleeve 38 remains sealed against the mold face while retracting into the injection frame 16 as spring 40 is increasingly compressed. Once the injection frame 16 has been moved into the injection position, material can be injected into the mold cavity 15 with the aid of the partial vacuum.
Although the present invention is described in the context of a conventional horizontal mold press, it should be understood that the present invention can be incorporated into a wide range of molding machinery, including a variety of alternative vertical and horizontal presses. The various cylinders incorporated into the present invention may be pneumatic cylinders, hydraulic cylinders or essentially any other actuators capable of providing reciprocating motion.
Directional terms, such as “vertical,” “horizontal,” “top,” “bottom,” “upper,” “lower,” “inner,” “inwardly,” “forward,” “rearward,” “outer” and “outwardly,” are used to assist in describing the invention based on the orientation of the embodiments shown in the illustrations. The use of directional terms should not be interpreted to limit the invention to any specific orientation(s).
General Construction and Operation.
As noted above, an injection molding system in accordance with the present invention may be configured to operate with a wide variety of different press and mold assemblies. In the illustrated embodiment, the injection molding machine 10 includes a generally conventional horizontal mold press 12 that supports a mold 13 with an internal mold cavity 15. The injection molding system 14 is operatively associated with the mold press 12 and is configured to selectively introducing material into the mold 13 to form a part in the shape of the mold cavity 15. For purposes of disclosure, the injection molding machine 10 is described with a horizontal mold press 12 (or horizontal die set) having a mold 13 that is assembled and formed from self-aligning rapid tooling inserts and frames, such as those made by DME and Progressive Components. Given that the horizontal mold press 12 and associated mold assembly are generally conventional, they will not be described in detail. However, the general structure and function of the mold press 12 will be described with sufficient detail to facilitate disclosure of the present invention.
Referring now to
As noted above, the present invention includes an injection molding system 14 configured to introduce material into the mold 13 supported in the mold set 12. Referring now to
For purposes of disclosure, the present invention is described in the context of a clamping system that is affixed to the mold press 12 and is operable to selectively move essentially the entire injection molding system 14 toward and away from the mold press 12. For example, as perhaps best shown in
As noted above, the injection molding system 14 may be incorporated into a wide range of alternative mold presses. By way of example and not limitation, the present invention may be incorporated into the different press and mold assemblies disclosed in U.S. Pat. No. 10,239,246 entitled INJECTION MOLDING MACHINE, which issued Mar. 26, 2019 to Burton et al, which is incorporated herein by reference in its entirety.
In the illustrated embodiment, the injection molding system 14 generally includes an injection frame 16, an injection module 18 and a material reservoir 20 attached to the injection module by a supply connection. The injection frame 16 includes a generally includes a mounting plate 21, an injection module receiver 22 and a plurality of actuators that are configured to move the injection frame 16 toward and away from the mold 13 and to operate the various parts of the injection module 18. The mounting plate 21 is movably mounted to the guide rods 200 and functions as a carrier for the various components of the injection molding system 14. In this embodiment, the mounting plate 21 is configured to receive and support the injection module receiver 22, the nozzle clamp cylinders 76, the guide sleeves 202 and the injection rod actuator 90 as shown and described below. The design and configuration of the mounting plate 21 may vary from application to application, but in the illustrated embodiment is a somewhat rectangular vertically-extending plate with a horizontal lip extending from its lower end.
In the illustrated embodiment, the injection module receiver 22 is mounted to the outer face of the mounting plate 21 and is configured to removably receive the injection module 18. In the illustrated embodiment, the injection module receiver 22 generally includes a receiver plate 210 for removably seating the injection module 18, a manifold clamp 212 for securing the injection module 18 in the injection module receiver 22, a valve actuator 82 for operating the rotational valve 84 in the injection module 18 and a nozzle base 214 that closes the inner end of the injection module receiver 22. The receiver plate 210 defines a seat 66 for removably receiving the main body of the injection module 18. A pair of guide rails 68a-b may extend along opposite sides of the seat 66 where they can be received in corresponding guide slots 70a-b defined in the injection module 18 (See
The manifold clamp 212 includes a needle cylinder 350 that operates to extend and retract the needle 148 extending through the interior of the nozzle 32. As shown in
In the inner side of the injection module receiver 22 is closed by a nozzle base 214. The nozzle base 214 supports the nozzle sheath 706 and the receiver insert 218. More specifically, the nozzle base 214 defines a stepped circular through-hole 220 that receives the enlarged circular head 222 of the nozzle sheath 706 (described in more detail below). An O-ring seal 224 is fitted between the head 222 and the stepped through-hole 220. The receiver insert 218 is generally disc-shaped and is secured in the stepped through-hole 220 over the head 222. For example, the receiver insert 218 may be secured to the nozzle base 214 in the stepped through-hole 220 by a plurality of screws 225. O-ring seals may be fitted around each screw 226. Further, a large O-ring seal 228 may be fitted between the receiver insert 218 and the nozzle base 214. In this embodiment, the receiver insert 218 includes a throat 230 that receives the pinion bearing assembly 232 (described below). An O-ring seal 234 may be fitted between the bearing assembly 232 and the pinion insert 236 (described below).
The valve actuator 82 is configured to operate the rotational valve 84 in the injection module 18. In the illustrated embodiment, the valve actuator 82 includes a linear actuator that provides rotational movement of the rotational valve 84 through a rack-and-pinion arrangement. Referring now to
The illustrated rotational valve actuator 82 is merely exemplary and it may be replaced by other actuators configured to operate the valve. For example, other types of rotary valve actuators may be used. As another example, a linear actuator may be used when the injection module 18 includes a linear valve (rather than rotary valve). In some applications, no valve actuator may be necessary. For example, the injection module valve arrangement may include one or more directional valves (e.g. a rotational valve or rotary valve) or it may include one or more check valves. In an alternative embodiment, a check valve (not shown) may be provided at the material supply connection 20 to allow material into the manifold as the injection rod 92 is retracted then allow material to be ejected from the manifold through the nozzle 32 when the injection rod 92 is extended while preventing material from going back the way it came.
The injection module receiver 22 includes an integrated liquid cooling system 700 that provides a structure for circulating a liquid coolant over at least a portion of the nozzle 32. In the illustrated embodiment, the liquid cooling system 700 is integrated into the injection frame 16 so that the injection module 18 can be installed and removed from the injection frame 16 without manipulation of the liquid cooling system 700. The liquid cooling system is configured to circulate a liquid coolant over at least a portion of the nozzle 32 of the injection module 18. The portion of the nozzle 32 receiving the liquid coolant may vary from application to application.
In the illustrated embodiment, the liquid cooling system 700 is integrated into the injection module receiver 22 such that the nozzle 32 and nozzle tip 34 come into operative association with the liquid cooling system 700 automatically as the injection module 18 is installed in the injection receiver 22. The liquid cooling system 700 of the illustrated embodiment includes a nozzle sheath 706 having an interior configured to receive the nozzle 32 when the injection module 18 is mounted to the injection frame 16. The nozzle sheath 706 of the illustrated embodiment is generally coextensive with the nozzle 32 extending from the nozzle base 214 over the nozzle tip 34 (See
In the illustrated embodiment, the liquid cooling system 700 generally includes the nozzle sheath 706 that is fitted through the nozzle base 214, a receiver insert 218 that is affixed to the nozzle base 214 over the nozzle sheath 706 and a plurality of liquid coolant passageways that guide liquid coolant (See
Referring now to
In the illustrated embodiment, the liquid cooling system 700 includes a liquid coolant supply (not shown) that moves coolant through the cooling system 700 by a pressure differential. For example, coolant may be introduced into the cooling system 700 under positive pressure and/or withdrawn from the cooling system under negative pressure. In the illustrated embodiment, the liquid cooling system 700 includes an inlet port 702 for receiving a supply of coolant from the liquid coolant supply and an outlet port 704 for returning coolant to the liquid coolant supply. Referring now to
It should be noted that, in the illustrated embodiment, the nozzle 32 and the nozzle tip 34 are carried by the rotational valve 84 and therefore rotate approximately ninety degrees as the rotational valve 84 is rotated between the fill and inject positions. As a result, the cooling system 700 is configured to accommodate this rotational movement. As noted above, the hexagonal outer shape of the nozzle 32 in this embodiment defines six potential flow passages along the length of the nozzle 32. As the nozzle 32 rotates, different potential flow passages move into operative alignment with the inlet gap 242 and the outlet gap 244. As this occurs, the different potential flow passages that align with the inlet gap 242 become the coolant supply path 710 and the different potential flow passages that align with the outlet gap 244 become the return coolant supply path 710. Further, the nozzle tip 34 includes flutes 716 aligned with each of the potential flow passages (See
The injection frame 16 also includes an injection rod actuator 90 that is configured to operate the injection rod 92 in the injection module 18. More specifically, the injection rod actuator 90 is operatively coupled to the exposed end of the injection rod 92 that extends from the injection module 18 and is capable of reciprocating motion that allows it to extend and retract the injection rod 92 with respect to the injection module 18. For example, the injection module 18 may be filled with material by operating the injection rod actuator 90 to retract the injection rod 92 and receive material from the material supply connection 20 into the interior of the injection module 18. Once the injection module 18 is filled, the material may be ejected from the injection module 18 and into the mold 13 by operating the injection rod actuator 90 to extend the injection rod 92 and force the material from the interior of the injection module 18 through the nozzle 32 and into the mold 13. The design and configuration of the injection rod actuator may vary from application to application. However, the injection rod actuator 90 of the illustrated embodiment generally includes a motor 432, a ball screw 436, a drive nut 434, a drive plate 438 and a pair of guide rods 428 (See
The injection rod actuator of this embodiment is merely exemplary and it may be replaced by essentially any other linear actuator capable of providing the injection rod with the desired motion, which in this embodiment is reciprocating linear motion. If desired, the injection rod actuator may also include a load cell configured to allow the control system to dynamically measure force applied to the injection rod 92 to derive injection pressure for a specific diameter injection rod 92.
As noted above, the injection module 18 is removable attachable to the injection molding system 14. This provides a number of advantages. For example, it allows the injection module 18 to be removed for cleaning and allows installation of interchangeable injection modules 18 on the same machine. It also allows an injection module that has not been emptied to be moved into a storage environment that impedes curing and may facilitate use of the material later. For example, with LSR, the injection module 18 may be removed and placed in cold storage to impede curing of the LSR. In the illustrated embodiment, the injection module 18 forms the material flow path from the material supply connection 20 to the mold 13. As a result, removal of the injection module 18 constitutes removal of essentially all of the material within the injection molding system 14, excluding (in this embodiment) only that material that is contained in the material supply connection 20. The injection module 18 of the illustrated embodiment will now be described in more detail with reference to
The injection cylinder 150 is mounted to the lower end of the manifold 140. For example, the injection cylinder 150 may be threaded to the bottom end of the manifold 140. While the manifold 140 and injection cylinder 150 are threaded in this embodiment, other types of connections may be employed, such as a bayonet connection. In some applications, the manifold 140 and injection cylinder 150 assembly may be replaced by a single one-piece component. The injection cylinder 150 defines an internal bore configured to seat the injection rod 92. In this embodiment, the injection rod 92 includes an enlarged head 93 that is movably seated within the injection cylinder 150 and an extended tip that extends into the longitudinal bore 600. In this embodiment, a pair of seals are fitted around the circumference of the head 93 to create a leaktight seal with the injection cylinder 150. Although the injection rod 92 of the illustrated embodiment includes a cylindrical rod that moves linearly, the injection rod 92 may have alternative constructions. For example, the injection rod may alternatively be a screw configured to rotate within the internal bore.
The rotational valve 84 of the illustrated embodiment is configured to seat within the manifold 140. In this embodiment, the rotational valve 84 is rotatably fitted within cross-bore 144 and includes seals 146 toward opposite ends. In this embodiment, the rotational valve 84 includes a valve cap 516 and a valve base 517 that are installed into the cross-bore 144 from opposite sides and joined together, for example, by threading. An O-ring seal 580 is fitted into a counter-bore in the valve cap 516 to create a leaktight seal between the valve cap 516 and the exterior surface of the needle 148. In this embodiment, the valve base 517 generally includes a tapered outer end 502, a through passage 504, a cross passage 506, an annular seat 508 and an inner end 510 with a pair of drive flats 402 (See
The nozzle assembly is coupled to the rotational valve 84. In this embodiment, the nozzle assembly includes the nozzle 32, the nozzle tip 34 and a needle 148 mounted for reciprocating longitudinal movement within the nozzle 32. In this embodiment, the nozzle 32 is an elongated tubular structure having an outer end that is threadedly (or otherwise) secured to the valve base 517. The nozzle 32 defines a cylindrical internal bore 33 through which the needle 148 extends. In this embodiment, the outer surface of the nozzle 32 is configured to assist in defining one or more coolant flow paths between the nozzle 32 and the nozzle sheath 706. For example, the outer surface of the nozzle 32 is hexagonal and the combination of flats and corners of the hexagonal structure interact with the circular internal surface of the nozzle sheath 706 to define six longitudinally extending passages. An O-ring seal 720 is fitted into an annular recess in the nozzle 32 and to form a leaktight seal between the outer surface of the nozzle and the inner surface of the receiver insert 218 as described in more detail below. As noted above, the outer end of the needle 148 is coupled to the valve cap 516 by a spring and a thrust bearing assembly that biases the needle 148 in an outward position and facilitates rotation when the needle 148 is under load from the needle cylinder 350.
In the illustrated embodiment, the needle 148 is fitted within the rotational valve 84 and the nozzle 32. In the illustrated embodiment, the needle 148 is concentrically and coaxially disposed with the internal bore 512 in the rotational valve 84, the internal bore 538 of the nozzle 32 and the internal bore 540 of the valve cap 516. As noted above, a thrust bearing assembly is fitted over the outer end of the needle 148 (See
The nozzle tip 34 is installed on the inner end of the nozzle 32, for example, by threading. The nozzle tip 34 is shaped to fit closely with the nozzle seat 35 in the mold face and defines a tapered internal bore 182 that aligns with the mold gate when the seated. The tapered internal bore 182 is configured to receive the tapered head 184 of the needle 148. When the needle 148 is extended, the head 184 of the needle 148 closes and sealed the nozzle tip 34, and when the needle 148 is retracted, a gap is formed between the head 184 of the needle 148 and the tapered internal bore 182, which allows material to flow out of the nozzle tip 34 and into the mold 13 (Compare
As described above, the injection molding system 14 may include a vacuum system 36 that can be used to draw a vacuum in the mold cavity 15 prior to injection of material (See
Although the illustrated embodiment includes a vacuum sleeve 38 disposed about the nozzle sheath 706, this configuration is merely exemplary and the vacuum system may include essentially any alternative arrangements capable of coupling a vacuum source to the material inlet of the mold. For example, instead of a vacuum sleeve disposed coaxially about the nozzle sheath, the vacuum system may include alternative structure capable of being operatively coupled to a vacuum source and of creating a vacuum seal at the material inlet. For example, the alternative structure may include a vacuum outlet, such as an air line or other fluid flow path, that is physically separate from the nozzle and the nozzle sheath or that is integrated with the nozzle or the nozzle sheath in an arrangement different from that of the illustrated coaxial vacuum sleeve 38. It should also be noted that a vacuum system in accordance with the present invention may be integrated into essentially any injection system and is not limited to use with an injection system having a removably attachable injection module.
As noted above, the injection molding system 14 includes a material supply connection 20 for supplying material to the injection module 18 (See
In use, the injection molding system 14 is movable between a retracted position, a vacuum position and an injection position. In the retracted position, the nozzle 32 and vacuum sleeve 38 are moved rearwardly away from the mold 13. In the vacuum position (shown in
As described above, the present invention may be implemented in a wide variety of alternative embodiments. The illustrated mold press 12 is merely exemplary, and the present invention may be implemented using other types or styles of presses (horizontal and vertical) that might interface with an injection system or clamping system according to the present invention. Further, the present invention is described in the context of a mold assembly having a pair of mold parts that, when closed, cooperatively define a mold cavity having the shape of the desired molded article. The present invention may, however, be incorporated into injection molding machines that include other types of mold assemblies, including different numbers and combinations of mold parts. For example, although not shown, the mold may include heaters cartridges.
Operation of the illustrated embodiment will now be described. Operation of the injection molding machine 10 can be generally divided into the following stages: (a) closing the mold, (b) clamping the mold, (c) applying a vacuum to the mold, (d) injecting material in to the mold, (e) curing the molded part and (f) opening the mold and ejecting the molded part. These general stages represent one method for operating the injection molding machine 10. The injection molding machine 10 may be operated in accordance with an alternative method. For example, in some embodiments, the injection system 14 may be used without the vacuum functionality. In such embodiments, the vacuum structure may be eliminated or simply not be used.
In this embodiment, the cooling system 700 may be used to provide cooling to the injection module 18 during part or all of the manufacturing process. In typical applications, the cooling system 700 is operated during the entire manufacturing process, including the time between cycles. During operation, liquid coolant is introduced into the cooling system 700 via inlet port 702, the coolant flows from the inlet port 702 through the nozzle base 214 and into the inlet channel 248 in the receiver insert 218. The coolant follows the inlet channel 248 to the inlet gap 242 and then in the coolant supply path 710 defined in the chamber 708. The coolant flows along the exterior surface of the nozzle 32 though the coolant supply path 710 eventually reaching the nozzle tip 34. At the nozzle tip 34, the coolant flows through the flutes 716 aligned with the coolant supply path 710 into the space surrounding the nozzle tip 34. The coolant then flows along the exterior of the nozzle tip 34 to the flutes 716 aligned with the coolant return path 712. The coolant passes through those flutes 716 and then flows along the exterior surface of the nozzle 32 through the coolant return path 712. The returning coolant flows through the outlet gap 244 and into the outlet channel in the receiver insert 218. The coolant flows along the outlet channel to the throughbore in the nozzle base 214 to exit the cooling system 700 via the outlet port 702. The coolant is supplied to the inlet port 702 under positive pressure and/or withdrawn from the outlet port 704 under negative pressure produced at the coolant source. In this embodiment, coolant is circulated continuously, but it may in alternative embodiments be circulated intermittently as desired. The cooling system 700 and/or the coolant source may include a cooling system for reducing the temperature of the coolant.
Description of the remaining operation of the injection molding machine 10 will begin with the mold press 12 in the closed position and the injection molding system 14 moved away from the mold press 12. As noted above, the mold press 12 is generally conventional and may be opened and closed using conventional techniques and apparatus. Accordingly, the process of opening and closing the mold is not described in detail. Once the mold assembly is closed and the desired clamping force is applied, the injection module 18 is filled with material, for example, liquid silicone rubber (“LSR”). Before filling the injection module 18, the needle cylinder 350 is extended, thereby causing the needle 148 to move inwardly (e.g. toward the mold) to close the outlet end of the nozzle tip 34. To prepare the injection module 18 to receive material, the rotational valve 84 is moved into the fill position (See
Once the injection module 18 is filled, the injection molding system 14 is moved into the vacuum position and a vacuum is applied to the mold cavity. As noted above, the vacuum system is optional and the vacuum step may eliminated as desired. To move the injection molding system 14 into the vacuum position, the clamp cylinders 76 are moved until the injection system 14 is in the position shown in
Following application of the desired vacuum, the injection molding system 14 is moved into the injection position and material is injected into the mold assembly more freely since the air inside has been extracted. More specifically, the nozzle clamp cylinders 414 are operated to move the injection molding system 14 into the injection position by re-applying air pressure on one set of ports and exhausting the other and fully extending the pneumatic cylinders 414 into the position shown in
In typical applications, it may be desirable to retain the injection system 14 in the injection position until the material has had sufficient time to cure in the inlet portion of the sprue. Once the material is sufficiently cured, the injection system 14 may be moved away from the mold assembly to the open position by operation of nozzle clamp cylinders 414. The mold press 12 remains clamped until the material has sufficiently cured. The mold halves are typically fitted with heater cartridges and thermocouple sensors for heat cured LSR material. The heater cartridges controlled with a temperature controller such as the systems offered by Omega Engineering. Mold tools are typically brought up to a set temperature such as 300 degrees F. for fast curing of LSR material. An additional control system may include a timer and may be programmed to wait a predetermined period for curing before opening the mold press 12. Non-heat cured materials may be cured using the appropriate curing methods. For example, UV-cured LSR is cured with only ultraviolet light at room temperature. No heater cartridge, sensors or temperature control system are needed for UV-cured LSR. Instead, special mold materials, such as clear acrylic, are created to allow a UV light source in to the mold assembly to cure the material.
When the molded part is sufficiently cured, the mold press 12 is opened using conventional techniques and apparatus. For example, the mold press 12 may be opened, the parts of the mold may be separated and the molded part may be removed from the mold. As noted above, the mold press 12 may include a conventional ejector assembly to assist in separating the molded part from the mold cavity 15.
As can be seen, the illustrated injection molding machine 10 includes a removably attachable injection module 18 that can be readily removed and cleaned with greater ease. A spare (pre-cleaned) injection module could also be used to swap out one in the machine 10 that needs cleaned reducing material change over time to minutes. In this embodiment, the injection module 18 includes all components that come in contact with the material being molded so no cleaning of machine components are required. The present invention is not, however, limited to embodiments in which injection modules includes all the components that contact the material. Further, in this embodiment, the injection module 18 is removably attachable to the machine 10, which allows it to be cleaned more easily. In this embodiment, the machine 10 provides all of the mechanisms used to actuate the injection process, including moving the injection rod 92, traversing the nozzle 32 to and from the mold 13, rotational valve 84 operation and seating and unseating the needle 148 inside the nozzle tip 34. This means that the actuators do not need to be duplicated in each injection module, thereby reducing overall cost when interchangeable injection modules are used. The injection module 18 design shown is for liquid silicone rubber (“LSR”) and uses an injection rod. Components of the injection module 18 that come in contact with the material are the injection rod 92, the inlet fitting 142, inside bores of the manifold assembly 480, the rotational valve 84, the inside bore of the nozzle 32, the exterior of the needle 148 and the inside of the nozzle tip 341. The injection module can be readily cleaned without the solvents typically needed to clean injection systems. When the injection module components are disassembled, the individual parts are relatively small with straight through holes. Further, O-rings are positioned to protect the material from contacting the threads. Placing the assembled injection module or the individual components into a small oven and bake curing the LSR can be achieved in minutes. Once the material has cured it, turns into rubber cylinder shaped pieces that can be pulled or pushed out of their respective bores (e.g. the manifold bore). Cured material on exterior surfaces like the needle or injection rod can simply be peeled away. Once the cured material is removed from the components, the injection module can be re-assembled and ready for use. Although all of the actuators are carried by the machine rather than the injection module in the illustrated alternative embodiment, this is not strictly necessary and the present invention may be implemented with one more of the actuators integrated into the injection module.
An alternative embodiment of the present invention is shown in
The injection module 18′ of this embodiment includes modifications centered primarily around an alternative needle 148′ (see
Referring now to
As with injection module 18, the needle 148′ is carried by the rotational valve 84′. As perhaps best shown in
In this embodiment, the head 800 of the needle 148′ is configured to automatically couple with the needle cylinder 350′ when the manifold clamp 212′ is closed and automatically decouple from the needle cylinder 350′ when the manifold clamp 212′ is opened. To facilitate this automatic feature, the needle cylinder 350′ is fitted with a latch assembly 806 that is configured to be interfitted with the head 800. As perhaps best shown in
In the illustrated embodiment, the latch assembly 806 includes a bearing 810 to facilitate rotational movement of the needle 148′ relative to the latch assembly 806, which occurs, for example, when the rotational valve 84′ is rotated between the fill and inject positions. In operation, the bearing 810 provides a single point of contact with the head 800, which allows close to friction-free rotation. In the illustrated embodiment, the bearing 810 is a steel ball bearing that is fitted into the interior of the latch 808 and protrudes a small amount into the C-shaped channel 814 to engage the center of the head 800. As perhaps best shown in
In operation, the latch assembly 806 couples the needle 148′ to the needle cylinder 350′ so the needle 148′ travels during extension and retraction of the needle cylinder 350′. This eliminates the need for needle return spring 368. To help ensure proper alignment between the latch 808 and the head 800 of the needle 148′ when the needle cylinder 350′ is not powered, an alignment spring 836 is fitted between the needle cylinder 350′ and the latch 808. The alignment spring 836 applies a bias that urges the latch assembly 806 away from the needle cylinder 350′ into the outermost position where it will be laterally aligned with the head 808 when the needle 148′ is in the closed position. The alignment spring 836 is a compression spring with sufficient spring force to move the latch assembly 806 to the desired position when the needle cylinder 350′ is not in operation.
As noted above, the alternative embodiment of
Additionally, in this embodiment, the manifold 140′ defines a longitudinal bore 600′ having the same diameter as the internal bore 850 of the injection cylinder 150′. As a result, the injection rod 92′ is capable of being extended into the longitudinal bore 600′. This eliminates the need for a piston head 93 with a reduced-diameter extended tip, instead allowing the injection rod 92′ itself to move into the longitudinal bore 600′ to drive material from the manifold 140′.
As discussed above in connection with injection molding system 12, the injection rod 92 is moved by an injection rod actuator 90, and the system is designed so that the injection rod 92 easily couples to the injection rod actuator 90 when the injection module 18 is installed in the receiver 22. The embodiment of
As described above in connection with injection module 18 and injection rod actuator 90, the rod end 95′ may be fixed to the drive plate 438′ using essentially any attachment arrangement.
The above description is that of current embodiments of the invention. Various alterations and changes can be made without departing from the spirit and broader aspects of the invention. This disclosure is presented for illustrative purposes and should not be interpreted as an exhaustive description of all embodiments of the invention or to limit the scope of the claims to the specific elements illustrated or described in connection with these embodiments. For example, and without limitation, any individual element(s) of the described invention may be replaced by alternative elements that provide substantially similar functionality or otherwise provide adequate operation. This includes, for example, presently known alternative elements, such as those that might be currently known to one skilled in the art, and alternative elements that may be developed in the future, such as those that one skilled in the art might, upon development, recognize as an alternative. Further, the disclosed embodiments include a plurality of features that are described in concert and that might cooperatively provide a collection of benefits. The present invention is not limited to only those embodiments that include all of these features or that provide all of the stated benefits, except to the extent otherwise expressly set forth in the issued claims. Any reference to claim elements in the singular, for example, using the articles “a,” “an,” “the” or “said,” is not to be construed as limiting the element to the singular.
Number | Date | Country | |
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62855020 | May 2019 | US |