Hot runner system having active material

According to an aspect, there is disclosed a hot runner system (100), comprising: a first surface (205) being elastically deformable; a second surface (210) forming, in cooperation with the first surface (205), a melt-leakage gap (215) being located between the first surface (205) and the second surface (210); and an active material (220) being: (i) coupled with the first surface (205), (ii) held normally stationary, (iii) configured to be operatively coupled with a signal source (225), and (iv) configured to elastically deform in response to receiving a signal from the signal source (225), upon elastic deformation of the active material (220), the first surface (205) becomes moved toward the second surface (210) such that a size (235) of the melt-leakage gap (215) becomes controlled.

TECHNICAL FIELD

The present invention generally relates to molding systems, and more specifically the present invention relates to hot runners and molding systems having hot runners.

BACKGROUND OF THE INVENTION

U.S. Pat. No. 4,017,237 (Inventor: WEBSTER; Published: Apr. 12, 1977) discloses a mold provided with a pair of cavities interconnected by a runner to a common entry point. One of the cavities is gated whereby plastic may be injected into this cavity only by applying ultrasonic energy to the gate.

U.S. Pat. No. 4,120,921 (Inventor: WEBSTER; Published: Oct. 17, 1978) discloses a mold provided with a pair of cavities interconnected by a runner to a common entry point. One of the cavities is gated whereby plastic may be injected into this cavity only by applying ultrasonic energy to the gate.

U.S. Pat. No. 7,072,735 B2 (Inventor: SMITH; Published: Jul. 4, 2006) discloses a method and apparatus for controlling an injection molding machine having a first surface and a second surface including a piezo-ceramic sensor configured to be disposed between the first and second surface. The piezo-ceramic sensor is configured to sense a force between the first surface and the second surface, and to generate corresponding sense signals. Transmission structure is coupled to the piezo-ceramic sensor and is configured to carry the sense signals. Preferably, a piezo-ceramic actuator is also disposed between the first surface and a second surface, and is configured to provide an expansive force between the first surface and a second surface in accordance with the sense signals.

U.S. Pat. No. 7,165,958 B2 (Inventor: JENKO; Published: Jan. 23, 2007) discloses a method and apparatus provided for sealing interfaces within an injection mold having a first surface and a second surface including an active material actuator configured to be disposed in a manner suitable for generating a force between the first surface and the second surface. The active material actuator is configured to generate a force in response to sense signals from a transmission structure. Methods and apparatus are also provided for centering a nozzle tip within a gate opening, and adjusting tip height of a nozzle tip with respect to a gate opening, also using active material inserts.

U.S. Pat. No. 7,293,981 B2 (Inventor: NIEWELS; Published: Nov. 13, 2007) discloses a method and apparatus for compressing melt and/or compensating for melt shrinkage in an injection mold are provided. The apparatus includes a cavity mold portion adjacent a cavity plate, a core mold portion adjacent a core plate, a mold cavity formed between the mold portions, and at least one piezo-ceramic actuator disposed between either or both of the core plate and the core mold portion and the cavity plate and the cavity mold portion. A controller may be connected to the at least one piezo-ceramic actuator to activate it, thereby causing the mold cavity volume to decrease, compressing the melt.

United States Patent Application Publication Number 2005/0236725 A1 (Inventor: NIEWELS et al; Published: Oct. 27, 2005) discloses a method and apparatus for controlling an injection mold having a first surface and a second surface including an active material element configured to be disposed between the first surface and a second surface. The active material element may be configured to sense a force between the first surface and the second surface, and to generate corresponding sense signals. Transmission structure is coupled to the active material element and is configured to carry the sense signals. Preferably, an active material element actuator is also disposed between the first surface and a second surface, and is configured to provide an expansive force between the first surface and a second surface in accordance with the sense signals. The method and apparatus may be used to counter undesired deflection an/or misalignment in an injection mold.

United States Patent Application Publication Number 2005/0236726 A1 (Inventor: NIEWELS; Published: Oct. 27, 2005) discloses a method and apparatus for controlling a vent gap in a mold for an injection molding machine are provided, and include an active material insert configured to regulate the degree of opening of the vent gap. The active material insert is configured to be actuated in response to signals from a controller, so as to selectively block the opening of the vent gap during the molding process. Wiring structure is coupled to the active material insert, and is configured to carry the actuation signals. Melt flow sensors may also be provided to aid in regulating the vent gap, and may be connected to the controller in order to provide real-time closed loop control over the operation of the vent gap. Preferably, the methods and apparatus are used as part of a system for controlling the flow of melt within a mold cavity.

United States Patent Application Publication Number 2005/0236727 A1 (Inventor: NIEWELS; Published: Oct. 27, 2005) discloses a method and apparatus for applying a force to a portion of a surface of a mold component are provided. An injection mold has a core insert, a side acting core insert, and a piezo-ceramic actuator. The amount of force needed for sealing a surface of said side acting core insert to a portion of a surface of said core insert is determined, and a piezo-ceramic actuator is actuated so as to supply the force to seal the side acting core insert against the core insert during a molding operation. A piezo-ceramic sensor may be provided to sense a force between the side acting core insert an the core insert, and to generate corresponding sense signals. Wiring structure is coupled to the piezo-ceramic sensor and is configured to carry the sense signals.

United States Patent Application Publication Number 2005/0236729 A1 (Inventor: ARNOTT; Published: Oct. 27, 2005) discloses a method and apparatus for applying a vibration and/or oscillation to melt within an injection mold including at least one stable surface within the mold, at least one movable surface within the mold, at least one active material element affixed to each stable surface, and adjacent to each movable surface. In use, a control means repeatedly energizes the at least on active material element, wherein the repeated energizing of the at least one active material element generates vibration and/or oscillation in the melt. In the method, at least one active material element is activated intermittently to move the at least one movable surface with respect to the at least one fixed surface. In the apparatus, a wiring conduit is coupled to the active material insert, and is configured to carry vibration signals to the at least one active material element.

United States Patent Application Publication Number 2005/0238757 A1 (Inventor: NIEWELS et al; Published: Oct. 27, 2005) discloses a method and apparatus for assisting the ejection of molded parts from a mold having a first surface and a second surface including an active material actuator configured to be disposed between the first surface and a second surface. The active material actuator is configured to provide an expansive force between the first surface and the second surface in response to actuation signals, pushing the surfaces apart. Transmission structure is coupled to the active material actuator and is configured to transmit the actuation signals. The molded part may be ejected upon initiation of the actuation signal, or upon withdrawal of the actuation signal.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provided a hot runner system (100), comprising: a first surface (205) being elastically deformable; a second surface (210) forming, in cooperation with the first surface (205), a melt-leakage gap (215) being located between the first surface (205) and the second surface (210); and an active material (220) being: (i) coupled with the first surface (205), (ii) held normally stationary, (iii) configured to be operatively coupled with a signal source (225), and (iv) configured to elastically deform in response to receiving a signal from the signal source (225), upon elastic deformation of the active material (220), the first surface (205) becomes moved toward the second surface (210) such that a size (235) of the melt-leakage gap (215) becomes controlled.

According to a second aspect of the present invention, there is provided a molding system (500), comprising: a hot runner system (100), including: a first surface (205); a second surface (210) forming, in cooperation with the first surface (205), a melt-leakage gap (215) being located between the first surface (205) and the second surface (210); a signal source (225); and an active material (220) being coupled with the first surface (205), the active material (220) being configured to be coupled with the signal source (225), and the active material (220) being configured to, in response to receiving a signal from the signal source (225), move the first surface (205) toward the second surface (210) such that a size (235) of the melt-leakage gap (215) may be controlled at a position being located proximate to the active material (220).

A technical effect of the aspects of the present invention is provision of a seal between hot runner components in a hot runner system100to control and/or to prevent the leakage of melt in a melt leakage gap215being located between two adjacent surfaces by way of using an active material220.

The drawings are not necessarily to scale and are sometimes illustrated by phantom lines, diagrammatic representations and fragmentary views. In certain instances, details that are not necessary for an understanding of the embodiments or that render other details difficult to perceive may have to been omitted.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

FIG. 1depicts the cross-sectional view of the hot runner system100. By way of example, the hot runner system100has a nozzle, such as a valve gate nozzle110and/or a thermal gate nozzle115connected with the hot runner system100and a mold120. The hot runner system100is used in a molding system500, which is depicted inFIG. 5. It will be appreciated that the hot runner system100(and the molding system500) may include components that are known to persons skilled in the art, and these known components will not be described here; these known components are described, at least in part, in the following text books (by way of example): (i) “Injection Molding Handbook” by Osswald/Turng/Gramann (ISBN: 3-446-21669-2; publisher: Hanser), (ii) “Injection Molding Handbook” by Rosato and Rosato (ISBN: 0-412-99381-3; publisher: Chapman & Hill), (iii) “Runner and Gating Design Handbook” by John P. Beaumont (ISBN 1-446-22672-9, publisher: Hanser), and/or (iv) “Injection Molding Systems” 3rdEdition by Johannaber (ISBN 3-446-17733-7).

FIGS. 2A,2B and2C depict the views of the hot runner system100ofFIG. 1. Referring toFIGS. 2B and 2C, the hot runner system100includes: (i) a first surface205, (ii) a second surface210, and (iii) an active material220. The first surface205is elastically deformable. The second surface210forms, in cooperation with the first surface205, a melt-leakage gap215located between the first surface205and the second surface210. The active material220is: (i) coupled with the first surface205, (ii) held normally stationary, (iii) configured to be operatively coupled with a signal source225, and (iv) configured to elastically deform in response to receiving a signal from the signal source225. Upon elastic deformation of the active material220, the first surface205becomes moved toward the second surface210such that a size235of the melt-leakage gap215becomes controlled.

While the typical mechanism of the piezoelectric material is the application of a mechanical stress to generate a voltage across the material, piezoelectric materials also show the opposite effect, called ‘converse piezoelectric effect’, whereby the application of an electric field, or a signal, from the signal source225, creates mechanical deformation in the piezoelectric material. It is this converse piezoelectric effect of an active material220which is used to enable the embodiments of the aspects of the present invention.

Referring toFIG. 2B, a manifold bushing245has a bushing hole250extending through the manifold bushing245and the bushing hole250receives a valve stem260. The manifold bushing245also has a bushing groove255encircling, at least in part, the bushing hole250, and the active material220is received in the bushing groove255.

The first surface205, which is an integral part of the manifold bushing245, faces the second surface210. The first surface205is made elastically deformable due to the proximate placement of the bushing groove255to the melt-leakage gap215, thereby creating an annular wall270therebetween. The annular wall270is sufficiently thin to allow flexure of the annular wall270between the bushing groove255and the first surface205. The manifold bushing245includes an alloy which is described further below.

The size235of the melt-leakage gap215may be variable and is determined by the amount of movement of the active material220and hence the amount of movement of the first surface205toward the second surface210.

The second surface210is the outer surface of a valve stem260which is configured to reciprocate within a bushing hole250that is defined by the bushing groove255so that the second surface210moves relative to the first surface205. The bushing hole250extends through the manifold bushing245. The bushing groove255is defined on a top side or top face of the manifold bushing245, and it will be appreciated that the bushing groove255may be defined on a bottom side or a bottom face of the manifold bushing245.

FIG. 2Bdepicts the active material220in a non-active state, whileFIG. 2Cdepicts the active material220in an active state. Referring toFIG. 2C, the active material220is configured, in response to receiving the signal from the signal source225, to urge the first surface205toward the second surface210so that the first surface205seals (and makes contact with) with the second surface210thereby preventing a flow of a melt273along the melt-leakage gap215, as shown inFIG. 2C.

It will be appreciated that the size235of the melt-leakage gap215between the first surface205relative to the second surface210may result in partial closure, when the active material220receives the signal from the signal source225. For the case where the active material220is in the non-active state, the size235of the melt-leakage gap215is preferably no greater than 0.1 mm, to preclude excessive flexure of the annular wall270. For the case where the active material220is in the active state, the size235of the melt-leakage gap215is preferably no less than 0 mm, for a size-on-size fit (no gap) between the first surface205and the second surface210.

According to a non-limiting variant, the active material220is configured to, in response to receiving the signal from the signal source225, urge the first surface205toward the second surface210so that the first surface205remains offset from the second surface210thereby varying an amount of a flow of a melt273along the melt-leakage gap215.

FIG. 2Adepicts the active material220as it is arranged (by way of example in accordance with a non-limiting variant) in an active material array265in the bushing groove255. The active material array265includes a plurality of active material220. When the active material array265receives the signal, the active material array265exerts forces along radial directions of a valve stem260relative to a longitudinal axis of a valve stem260, so that the force extends from the first surface205toward the second surface210in a more or less substantially uniform manner.

To facilitate elastic deformation of the first surface205, the manifold bushing245is made from a material (or an alloy) which may include, by way of example, a variety of high strength steel alloys, such as (but not limited to) H-13. The annular wall270is preferably no less than 0.5 mm thick, to preclude fracture of the wall, and preferably no greater than 3.0 mm thick, to permit elastic flexure of the wall in response to activation of the active material220.

The signal source225is capable of supplying a high voltage (low current) source of electricity to the active material220. According to a non-limiting variant, timing of the signal source225may be tied into the molding cycle of the injection molding machine, such that the following sequence may be observed: (i) the valve stem260opens flow path into the mold120, (ii) the active material220moves toward the valve stem260creating a seal, (iii) the plastic injection pressure is increased to fill and pack the mold120(iv) the plastic injection pressure is decreased (v) the active material220relaxes, releasing hold of valve stem260, and (vi) the valve stem260closes flow path into mold120.

The exact timing of this sequence may be altered according to the molding application, however, it is likely that the valve stem260may not be opened or closed with the active material220activated. While this sequence may incur some cycle time penalty, active materials220react extremely quickly to an applied voltage, and thus it is expected that any impact on cycle time would be minimal.

According to a non-limiting variant, a seal is not created between the first surface205and the second surface210, but rather a permitted amount of bleeding of the melt273from the melt-leakage gap215may be desired. By way of example, a valve gate nozzle110requires a thin film of lubrication between the first surface205and the second surface210, in the form of the melt273, to prevent seizure of the valve stem260in the bushing hole250.

FIGS. 3A and 3Bdepict the hot runner system100according to the second non-limiting embodiment. The second surface210is (an outer surface of) an integral part of a nozzle380, and the first surface205is integral to a gate insert370. A nozzle tip372, in fluid communication with the nozzle380, permits a melt273to flow out of the hot runner system100and into a gate bubble360of the gate insert370and ultimately exit through a gate365. The melt273is also allowed to flow into a gap390between the nozzle380and the nozzle tip372to act as an insulative layer to minimize thermal conduction therebetween.

The gate insert370has a nozzle bore375extending into the gate insert370. The nozzle bore375receives the nozzle380. The gate insert370also has a gate insert groove356which receives the active material220in the form of the active material array265, (which is depicted inFIG. 2A). The active material array265is held in place in the gate insert groove356via a cover385. The cover385is, in turn, secured against the gate insert370by the proximity of a manifold plate395.

FIG. 3Adepicts the active material220in a non-energized state such that the melt-leakage gap215exists between the first surface205and the second surface210. When the active material array265receives the signal, the active material array265imparts a force along a direction extending radially from a longitudinal axis of a nozzle380to control the size235of the melt-leakage gap215, as shown inFIG. 3B(FIG. 3Bdepicts the active material220in an energized state). The size235of the melt-leakage gap215is preferably no greater than 0.1 mm, to preclude excessive flexure of the annular wall270and preferably no less than 0 mm, for a size-on-size fit (no gap) between the first surface205and the second surface210.

To facilitate elastic deformation of the first surface205, the gate insert370is made from a material which may include, by way of example, a variety of gate insert materials known to those skilled in the art, such as (but not limited to) H-13. The thickness of the annular wall270is preferably no less than 0.5 mm, to preclude fracture, and preferably no greater than 3.0 mm, to permit elastic flexure.

FIGS. 4A and 4Bdepicts the hot runner system100according to the third, non-limiting embodiment. The second surface210is the outer surface of the valve stem260. The second surface210is configured to reciprocate within the bushing hole250, and the first surface205, which is the inner surface of a wedge seal hole495. The wedge seal490has a wedge seal hole495extending through the wedge seal490, for receiving the valve stem260. The wedge seal490is also engaged in a bushing cavity485of the manifold bushing245. The wedge seal490is made from a material which may include, by way of example, a variety of high strength steel alloys, such as (but not limited to) H-13 and CPM9V, or high temperature thermoset/thermoplastic materials such as (but not limited to) polyimides or Celazole® Polybenzimidazole.

A positioning nut400is configured to threadably engage with the manifold bushing245to secure and locate the active material220, and the positioning nut400also has a positioning nut hole402therethrough for reciprocating movement of the valve stem260. The positioning nut400is made from a material which may include, by way of example, a variety of high strength steel alloys, such as (but not limited to) H-13 and CPM9V. A bushing bore487is centrally located in the manifold bushing245to house the active material220, and a bearing surface403of the positioning nut400is configured to secure and locate the active material220atop the wedge seal490located in the bushing cavity485.

FIG. 4Adepicts the active material220and the wedge seal490in a non-energized state, whereby the size235of the melt-leakage gap215is at a maximum. Conversely,FIG. 4Bdepicts the active material220having received the signal from the signal source225such that the size235of the melt-leakage gap215is reduced. The deformation of the active material220forces the wedge seal490into the confined space of the bushing cavity485thereby deforming the wedge seal490such that the wedge seal hole495is constricted around the valve stem260thus controlling the size235of the melt-leakage gap215.

FIG. 5depicts a schematic representation of the molding system500, which includes any one of the hot runner systems100ofFIGS. 1 to 4B, inclusive, and a mold120.

The description of the non-limiting embodiments provides non-limiting examples of the present invention; these non-limiting examples do not limit the scope of the claims of the present invention. The non-limiting embodiments described are within the scope of the claims of the present invention. The non-limiting embodiments described above may be: (i) adapted, modified and/or enhanced, as may be expected by persons skilled in the art, for specific conditions and/or functions, without departing from the scope of the claims herein, and/or (ii) further extended to a variety of other applications without departing from the scope of the claims herein. It is understood that the non-limiting embodiments illustrate the aspects of the present invention. Reference herein to details and description of the non-limiting embodiments is not intended to limit the scope of the claims of the present invention. Other non-limiting embodiments, which may not have been described above, may be within the scope of the appended claims. It is understood that: (i) the scope of the present invention is limited by the claims, (ii) the claims themselves recite those features regarded as essential to the present invention, and (ii) preferable embodiments of the present invention are the subject of dependent claims. Therefore, what is protected by way of letters patent are limited only by the scope of the following claims: