INJECTION MOLDING APPARATUS

A linear actuator for use in an injection molding apparatus is provided. The linear actuator comprises an electric motor including a drive shaft; an anti-rotation mechanism including a restrictor and a captive member, the captive member attached to the pin, the restrictor and the captive member arranged for translating a rotational motion of the drive shaft to a linear motion of the captive member, and by extension the pin, relative to the restrictor; and an adapter coupling the drive shaft with the captive member to enable the drive shaft to transmit the rotational motion of the drive shaft and to be readily decoupleable from the captive member without needing to separate the captive member from the pin.

FIELD OF THE INVENTION

The invention relates generally to an injection molding apparatus and, in particular, to an injection molding apparatus using a linear actuator.

BACKGROUND OF THE INVENTION

In injection molding, a melt delivery body such as a nozzle is used to dispense melt from a source into a cavity of the mold for creating an article therein. In a valve gated system, a pin, disposed and axially slideable in the melt channel of the nozzle, is used to control the flow of melt dispensed by the nozzle. Some valve gated system uses electric motors to drive the pin.

It is desirable to be able to separate the electric motor from the pin without having to separate the pin from the nozzle.

BRIEF SUMMARY OF THE INVENTION

An aspect of the present application provides, in an injecting molding apparatus comprising a nozzle and a pin slideably disposed in the nozzle to control the flow of melt dispensed by the nozzle, a linear actuator comprising: an electric motor including a drive shaft; an anti-rotation mechanism including a restrictor and a captive member, the captive member attached to the pin, the restrictor and the captive member arranged for translating a rotational motion of the drive shaft to a linear motion of the captive member, and by extension the pin, relative to the restrictor; and an adapter coupling the drive shaft with the captive member to enable the drive shaft to transmit the rotational motion of the drive shaft and to be readily decoupleable from the captive member without needing to separate the captive member from the pin.

The drive shaft is readily decoupleable from the captive member without needing to separate the captive member from the pin by moving the drive shaft axially away from the captive member.

The adapter can include an externally threaded sleeve coupling the drive shaft with the captive member, the captive member can include an internally threaded channel corresponding to and engaging with the external thread of the externally threaded sleeve.

An external thread of the externally threaded sleeve can be ACME thread.

The drive shaft can have a non-circular cross-section and the externally threaded sleeve can include a non-circular channel for receiving and engaging the drive shaft therein.

The adapter can include a non-circular sleeve and the externally threaded sleeve can include a non-circular channel for receiving and engaging the non-circular sleeve therein, the non-circular sleeve attached to the drive shaft.

The cross-section of the non-circular sleeve can be “D” shaped.

The cross-section of the non-circular sleeve can be a polygon.

The cross-section of the non-circular sleeve can be hex shaped.

The non-circular sleeve can be attached to the drive shaft via a screw.

The non-circular sleeve can be attached to the drive shaft via an adhesive.

The linear actuator can further comprise a bearing wherein the externally threaded sleeve can include a flange at an end proximal to the electric motor and the bearing can be located between the flange of the externally threaded sleeve and a cover for absorbing the axial load acting on the threaded sleeve in a direction towards the motor.

The linear actuator can further comprise an o-ring situated between the flange of the externally threaded sleeve and an end of the captive member proximal to the electric motor.

The restrictor can define a spline channel and the captive member can include a spline shaft corresponding to and engaging the spline channel to enable the captive member to be axially but not rotationally movable relative to the restrictor.

The restrictor can define a non-circular channel and the captive member can include a non-circular shaft corresponding to and engaging with the non-circular channel of the restrictor to enable the captive member to be axially but not rotationally movable relative to the restrictor.

The adapter can include a ball screw having a threaded shaft and a ball assembly, the threaded shaft coupled to the drive shaft and the ball assembly attached to the captive member.

The drive shaft can have a non-circular cross-section and the threaded shaft of the ball screw can include a non-circular channel for receiving and engaging the drive shaft therein.

The adapter can include a non-circular sleeve and the threaded shaft of the ball screw can include a non-circular channel for receiving and engaging the non-circular sleeve therein, the non-circular sleeve attached to the drive shaft.

The linear actuator can further comprise a bearing wherein the threaded shaft of the ball screw can include a flange at an end proximal to the electric motor and the bearing can be located between the flange of the threaded shaft of the ball screw and a cover for absorbing the axial load acting on the threaded shaft of the ball screw in a direction towards the motor.

The linear actuator can further comprise an o-ring situated between the flange and the ball assembly.

DETAILED DESCRIPTION OF THE INVENTION

Specific embodiments of the present invention are now described with reference to the figures. The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be restricted by any expressed or implied theory in the present disclosure. In the description, “downstream” is used with reference to the direction of mold material flow from an injection unit of an injection molding apparatus to a mold cavity, and also with reference to the order of components, or features thereof, through which the mold material flows from the injection unit to the mold cavity, whereas “upstream” is used with reference to the opposite direction.

FIG. 1is a side view of an injection molding apparatus10including an injection unit15, a mold assembly20, and a clamping unit25. Referring toFIG. 2, mold assembly20includes a moving half30and a stationary half35. Clamping unit25is configured to move moving half30towards stationary half35to close mold assembly20and away from stationary half35to open mold assembly20. Moving half30includes a core plate40and a stripper plate45. Stationary half35includes a cavity plate50, a manifold plate55housing a manifold60, and, depending on the application of injection molding apparatus10, other plates62for housing other components of mold assembly20. In the embodiments of the present application, other plates62include an actuator plate63for housing actuators64(seeFIG. 3). (Persons of ordinary relevant skill in the art would appreciate that injection molding apparatus10can have one or more actuators64.) According to the embodiments of the present application, actuators64are linear actuators (and will henceforth be referred to individually as linear actuator64and collectively as linear actuators64). Mold assembly20is bounded by a clamp plate72on each end thereof (seeFIG. 2).

Manifold60is a melt delivery body, which, depending on the application of injection molding apparatus10, can include a network of melt channels (not shown) for distributing melt from injection unit15to nozzles68(and will henceforth be referred to individually as nozzle68and collectively as nozzles68). Core plate40includes cores65. Cavity plate50includes cavities70(and will henceforth be referred to individually as cavity70and collectively as cavities70).

In operation, clamping unit25closes mold assembly20and clamps mold assembly20shut, in a closed position, to prevent mold assembly20from opening under the pressure of melt being injected, by injection unit15, into cavities70. With mold assembly20clamped in the closed position, melt is injected in to space75, shaped and dimensioned to create an article (not shown), between core65and corresponding cavity70. When the article is ready to depart mold assembly20, the article clings to core65. To remove the article from core65, mold assembly20opens allowing stripper plate45to move upstream to eject the article from core65.

FIG. 3is a side sectional view of actuator plate63, according to an embodiment of the present application. Linear actuator64includes an electric motor80for providing a rotational motion to drive linear actuator64and a drive mechanism85to convert the rotational motion of electric motor80to a linear motion of pin90.

FIG. 4is a sectional view of a downstream end of nozzle68with pin90in the open position, according to an embodiment of the present application. Nozzle68includes a melt channel95and an opening100, through which melt105traveling in melt channel95, in a direction D (i.e., downstream), exits nozzle68(i.e., dispensed from nozzle68) into space75(seeFIG. 2). Pin90can be used to control the flow rate of melt105through opening100by obstructing melt flow through opening100. In the open position, pin90is retracted from opening100allowing melt105to flow substantially unobstructed through opening100(seeFIG. 4). In the closed position, pin90is extended downstream to block opening100preventing melt105from flowing through opening100(seeFIG. 5). The axial movement E of pin90is effected by linear actuator64. (In some injection molding apparatuses, not shown, a pin regulates the amount of melt flowing into the cavity by blocking an opening at a gate insert located immediately upstream from the cavity. In injection molding apparatuses where the opening is part of the gate insert, the opening is commonly referred to as the gate.)

FIG. 6is a side sectional view of drive mechanism85, according to an embodiment of the present application.FIG. 7is an exploded view of linear actuator64. Referring toFIG. 6andFIG. 7, drive mechanism85includes an anti-rotation mechanism110having a restrictor115and a captive member120. Restrictor115and captive member120are arranged for translating a rotational motion of drive shaft125of electric motor80to a linear motion of captive member120, and by extension pin90, relative to restrictor115. Referring toFIG. 6, captive member120can be attached to pin90via an externally threaded nut126threaded with a threaded channel127of captive member120at a downstream end128of captive member120. Nut126includes a channel129to receive pin90therethrough.

Linear actuator64also includes an adapter130coupling drive shaft125with captive member120to transmit the rotational motion of drive shaft125to captive member120and to enable drive shaft125to be readily decoupleable from captive member120without needing to separate captive member120from pin90. In particular, drive shaft125is readily decoupleable from captive member120by moving drive shaft125axially away (e.g., in a direction G) from captive member120(seeFIG. 15). In one embodiment, adapter130includes an externally threaded sleeve135having an external thread145for coupling drive shaft125with captive member120(seeFIG. 7) by engaging an internally threaded channel140of captive member120(seeFIG. 6). In some embodiments, external thread145of externally threaded sleeve135is an ACME thread. (Persons of ordinary relevant skill in the art would appreciate that external thread145can cover a partial portion or the entire length of externally threaded sleeve135. See, for example,FIG. 7andFIG. 9)

In the embodiment illustrated byFIG. 7, adapter130includes a non-circular sleeve150and externally threaded sleeve135includes a non-circular channel155, matching the geometry of the cross-section of non-circular sleeve150, for receiving and engaging non-circular sleeve150therein. When non-circular sleeve150is received in non-circular channel155, non-circular channel155prevents non-circular sleeve150from rotating relative to externally threaded sleeve135but permits non-circular sleeve150to move axially, when an axial force is applied to non-circular sleeve150, e.g., pulling non-circular sleeve150away from or pushing non-circular sleeve150towards externally thread sleeve135. Non-circular sleeve150can be attached to drive shaft125by a screw, an adhesive, welding or other equivalent means. When assembled, with non-circular sleeve150attached to drive shaft125, non-circular sleeve150fits snugly in, but can readily be separated from, non-circular channel155, an arrangement that not only enables drive shaft125to rotate externally threaded sleeve135, which in turn causes captive member120to move axially relative to restrictor115but allows drive shaft125to be readily decoupleable from captive member120by moving electric motor80, and by extension drive shaft125, in direction G (seeFIG. 15). (That is, the friction between non-circular sleeve150and non-circular channel155couples non-circular sleeve150with non-circular channel155. Separating non-circular sleeve150from non-circular channel155merely requires a substantially axial force to overcome the friction coupling non-circular sleeve150with non-circular channel155.) Because pin90is attached to captive member120, axial movement of captive member120results in axial movement of pin90.

FIG. 8is an exploded view of a partial linear actuator with a drive shaft125aof electric motor80magnified, according to an embodiment of the present application. In the embodiment illustrated byFIG. 8, drive shaft125ahas a non-circular cross-section and externally threaded sleeve135includes non-circular channel155, matching the geometry of the cross-section of drive shaft125a, for receiving and engaging drive shaft125atherein. (In the embodiment illustrated byFIG. 8, non-circular sleeve150is absent from adapter130.) When drive shaft125ais received in non-circular channel155, non-circular channel155prevents drive shaft125afrom rotating but permits drive shaft125ato move axially therein. When assembled, drive shaft125afits snugly in, but can readily be separated from, non-circular channel155, an arrangement that not only enables drive shaft125ato rotate externally threaded sleeve135, which in turn causes captive member120to move axially relative to restrictor115but allows drive shaft125ato be readily decoupleable from captive member120by moving electric motor80, and by extension drive shaft125a, in direction G (seeFIG. 15). (That is, the friction between drive shaft125aand non-circular channel155couples drive shaft125awith non-circular channel155. Separating drive shaft125afrom non-circular channel155merely requires a substantially axial force to overcome the friction coupling drive shaft125awith non-circular channel155.)

Externally threaded sleeve135can include a flange160in the upstream portion thereof. Linear actuator64can include a bearing165located between flange160of externally threaded sleeve135, a cover260upstream of flange160, and a retainer ring261(partially retained in a groove inside restrictor115) to divert the axial load acting on drive shaft125away from drive shaft125to retainer ring261(seeFIG. 6). Cover260retains contents of restrictor115within restrictor115.

In the embodiment ofFIG. 7, restrictor115defines a spline channel170and captive member120includes a spline shaft175corresponding to and engaging spline channel170to enable captive member120to be axially but not rotationally movable relative to restrictor115. Consequently, when externally threaded sleeve135rotates in internally threaded channel140, external thread145engages the thread of internally threaded channel140of captive member120and because captive member120is restricted from rotating relative to restrictor115, captive member120moves linearly relative to restrictor115in the form of movement E (see.FIG. 4andFIG. 5).

Referring toFIG. 6, in some embodiments, linear actuator64can include an o-ring210situated between a downstream surface215of flange160and an upstream surface of its nearest downstream neighbour (e.g., captive member120,120aand ball nut205) to reduce the risk of the adjacent opposing surfaces of the respective neighbouring components from jamming into each other when linear actuator64is in the open position. For example, in the embodiment illustrated byFIG. 6, o-ring210can be used to prevent captive member120from jamming with downstream surface215of flange160. O-ring210can be housed in a washer211. O-ring210can be made of rubber, silicone, or equivalents thereof.

FIG. 9,FIG. 10, andFIG. 11illustrate another embodiment of drive mechanism85ofFIG. 7, referenced as drive mechanism85a. The reference numbers used inFIG. 7are used to identify like components inFIG. 9,FIG. 10, andFIG. 11. Components of drive mechanism85athat are alternatives to their respective counterpart components of drive mechanism85bear the same reference number as their counterpart components except suffixed by the letter “a”. Drive mechanism85adiffers from drive mechanism85in that anti-rotation mechanism110aincludes restrictor115aand captive member120ain place of restrictor115and captive member120, respectively. Restrictor115adefines a non-circular channel180and captive member120aincludes a non-circular shaft185corresponding to and engaging with non-circular channel180of restrictor115ato enable captive member120ato be axially but not rotationally movable relative to restrictor115a(seeFIG. 11).

FIG. 12,FIG. 13, andFIG. 14illustrate yet another embodiment of drive mechanism85ofFIG. 7, referenced as drive mechanism85b. The reference numbers used inFIG. 7are used to identify like components inFIG. 12,FIG. 13, andFIG. 14. Components of drive mechanism85bthat are alternatives to their respective counterpart components bear the same reference number as their counterpart components except suffixed by the letter “b”. In the embodiment illustrated byFIG. 12,FIG. 13, andFIG. 14, adapter130bis an alternative to adapter130ofFIG. 7. Adapter130bincludes a ball screw190having a threaded shaft195and a ball assembly200having a ball nut205. Ball screw190defines a non-circular channel192(seeFIG. 14) at an end193proximal to electric motor80to couple ball screw190to drive shaft125. Ball screw190can be coupled to drive shaft125via non-circular sleeve150. In embodiments with drive shaft125a(seeFIG. 8) having a non-circular cross-section corresponding to non-circular channel192of ball screw190, non-circular sleeve150is omitted and ball screw190can be coupled directly with drive shaft125avia the insertion of drive shaft125adirectly into non-circular channel192of ball screw190. Ball assembly200can be attached to captive member120bby threading ball assembly200to captive member120bor equivalents thereof. Bearings240,245facilitate rotation of ball screw190during the closing and opening of pin90, respectively. Flange160bcan be integral with ball screw190(seeFIG. 12andFIG. 13) or a separate piece (referenced as250inFIG. 18) coupled to ball screw190. Screws255can be used to secure cover260to restrictor115b(seeFIG. 18). Screws265can be used to secure restrictor115bto actuator plate63(seeFIG. 18).

In operation, electric motor80, via drive shaft125, rotates externally threaded sleeve135to impart axial movement E on pin90(seeFIG. 4) to effect closing (seeFIG. 5) or opening of opening100(seeFIG. 4). The direction of movement E of pin90depends on the angular direction of rotation of drive shaft125. Similarly, for the embodiment illustrated byFIG. 12, electric motor80, via drive shaft125, rotates ball screw190to impart axial movement E on pin90to effect closing (seeFIG. 5) or opening (seeFIG. 4) of opening100.

Referring toFIG. 16andFIG. 17, in some embodiments, captive member120can include a pin head slot220with an opening225for receiving a pin head230of pin90into pin head slot220. Pin head slot220has a generally T-shaped cross-section to capture pin head230therein. With pin head230captured in pin slot220, axial movement of captive member120is translated into axial movement of pin90. Pin head slot220can facilitate the removal of actuator plate63from the injection molding apparatus10without needing to also remove pins90therefrom. With other components separated from captive member120and removed from actuator plate63, captive member120can be moved radially in a direction H (i.e., away from opening225) to clear pin head230from pin head slot220so that captive member120can be separated from actuator plate63by moving captive member120in the upstream direction (i.e., in a direction I). With captive member120removed from actuator plate63and bore 235 sized large enough to allow pin head230to pass therethrough, actuator plate63can be separated from the remainder of stationary half35without needing to remove pins90therefrom. (A person of ordinary skill in the art would appreciate that captive members120aand120bcan also be facilitated with pin head slot220.)

By coupling electric motor80with captive member120, via adapter130,130b, electric motor80can be decoupled from captive member120by moving electric motor80(and by extension, drive shaft125) axially away from captive member120(i.e., in direction G) (seeFIG. 15) without needing to separate captive member120from pin90. In injection molding that uses a hot runner, when an electric motor driving an actuator fails, it may be necessary to cool the melt delivery bodies such as the manifold and the nozzles down, to service the malfunctioned electric motor. However, when plastic, in melt delivery bodies, cools, the plastic hardens and can seize the pins, a condition that may require excessive force to remove the pins from the melt delivery bodies. The present application allows pin90to remain in the melt delivery bodies while electric motor80is separated from injection molding apparatus10by axially moving electric motor80away from captive member120(seeFIG. 15).

While various embodiments according to the present invention have been described above, it should be understood that they have been presented by way of illustration and example only, and not limitation. It will be apparent to persons of ordinary relevant skill in the relevant art that various changes in form and detail can be made therein without departing from the scope of the invention. It will also be understood that each feature of each embodiment discussed herein, may be used in combination with the features of any other embodiment. For example, adapters130,130a,130bcan interchangeably be paired with anti-rotation mechanisms110,110a, the pairing illustrated by the figures are for providing example pairings, persons of ordinary relevant skill in the art would appreciate that other pairings are possible. For another example, adapter130bcan be paired with anti-rotation110a. Thus, the breadth and scope of the present invention should not be limited by the above-described exemplary embodiments, but should be defined only in accordance with the appended claims and their equivalents.