GB2638981A

GB2638981A - Active vacuum venting system

Info

Publication number: GB2638981A
Application number: GB2403127.0A
Authority: GB
Inventors: Rochman Arif; Refalo Paul; Mifsud Sarah; Zahra Olaf; Pretty Keith
Original assignee: TOLY PRODUCTS Ltd; Universita ta Malta UM
Current assignee: TOLY PRODUCTS Ltd; Universita ta Malta UM
Priority date: 2024-03-04
Filing date: 2024-03-04
Publication date: 2025-09-10
Also published as: WO2025186126A8; WO2025186126A1; GB202403127D0

Abstract

An active vacuum venting system for a moulding system comprising a mould having an unsealed mould cavity 114, the venting system comprising a vacuum source; and at least one vent connector 200 to connect the vacuum source to the mould cavity, wherein the vacuum source evacuates the mould cavity during supply of moulding material into the cavity. A vacuum controller may be provided with an evacuation signal generator and may be programmed to control the vacuum source to selectively evacuate the cavity. At least one sensor may be provided, such as a contact, proximity, or pressure sensor. A gas source may be provided to introduce gas into the cavity responsive to the at least one sensor detecting ejection of an injection moulded product from the mould cavity. A vent channel 112 or venturi channel may provide access to the cavity. One or more vent inserts (figure 5a-5f) may be removably inserted into the vent channel to modify a vent area of the channel. An injection moulding system, a moulding system, and a method of operating a venting system are also provided.

Description

ACTIVE VACUUM VENTING SYSTEM

The present disclosure relates to an active vacuum venting system with a computerised vacuum control system for moulding processes, such as plastic injection moulding, and compression moulding, in which sealing of the mould cavity is not required.

Injection and compression moulding processes are commonly used methods for mass fabrication of complex plastic parts.

According to a first aspect of the invention, there is provided an active vacuum venting system for use in a moulding system comprising a mould having an unsealed mould cavity, the active vacuum venting system comprising: a vacuum source (e.g. a vacuum generator); and at least one vent connector configured to, in use, connect the vacuum source to the mould cavity, wherein the vacuum source is configured to, in use, evacuate the mould cavity during injection of the moulding material into the mould cavity.

The present disclosure of the invention relates to an active vacuum venting system that does not require a fully sealed mould cavity, regardless of the size and shape of the part to be moulded and the layout of the cavity. The present invention provides the benefit of a reliable reduction in air traps while requiring minimal modification (e.g. machining) of the mould, requiring no sealing or a partial sealing of the mould cavity, and remaining relatively low cost. Furthermore, a moulding system based on the active vacuum venting system of the present invention may be provided by building a new moulding system from scratch or by retrofitting the active vacuum venting system to a pre-existing moulding system while requiring little to no modification or reconfiguration of the pre-existing moulding system.

In embodiments of the invention, the active vacuum venting system may include a vacuum source controller and an evacuation signal generator. The vacuum source controller may be programmed to control the vacuum source to selectively: evacuate the mould cavity responsive to an evacuation start command generated by the evacuation signal generator; and stop evacuating the mould cavity responsive to an evacuation stop command generated by the evacuation signal generator.

The active vacuum venting system may include at least one sensor. The evacuation signal generator may be configured to generate the evacuation start command or the evacuation stop command responsive to the at least one sensor detecting a predefined state of the moulding system. The evacuation signal generator may be configured to generate the evacuation start command responsive to the at least one sensor detecting a moulding material supplier being at or within a predetermined distance of the mould.

The evacuation signal generator may be configured to generate the evacuation start command responsive to the at least one sensor detecting assembly of a plurality of mould portions of the mould to form the mould cavity. The assembly of the mould portions involves the closing of the mould. The detection of the assembly of the mould portions may involve the detection of the initiation of the assembly of the mould portions, or the completion of the assembly of the mould portions. The at least one sensor may be or may include, but is not limited to, one or more contact or (non-contact) proximity sensors configured to detect motion or displacement.

The at least one sensor may be or may include a pressure sensor. The evacuation signal generator may be configured to generate the evacuation stop command responsive to the pressure sensor detecting a pressure in the mould cavity reaching or passing a threshold vacuum level.

The vacuum source may be configured to, in use, begin evacuating the mould cavity before injection of the moulding material into the mould cavity.

In further embodiments of the invention, the active vacuum venting system may include a gas source (e.g. a compressed gas source) configured to, in use, introduce gas into the mould cavity. Such gas introduction may be referred to as "blowback".

The active vacuum venting system may include a gas source controller and a gas introduction signal generator. The gas source controller may be programmed to control the gas source to selectively: introduce the gas into the mould cavity responsive to a gas introduction start command generated by the gas introduction signal generator; and stop introducing the gas into the mould cavity responsive to a gas introduction stop command generated by the gas introduction signal generator.

The active vacuum venting system may include at least one sensor. The gas introduction signal generator may be configured to generate the gas introduction start command or the gas introduction stop command responsive to the at least one sensor detecting a predefined state of the moulding system. The gas introduction signal generator may be configured to generate the gas introduction start command responsive to the at least one sensor detecting disassembly of the mould cavity into a plurality of mould portions of the mould. The disassembly of the mould cavity involves the opening of the mould. The detection of the disassembly of the mould cavity may involve the detection of the initiation of the disassembly of the mould cavity, or the completion of the disassembly of the mould cavity. The gas introduction signal generator may be configured to generate the gas introduction start command responsive to the at least one sensor detecting movement of an ejector plate of the mould towards the mould cavity. The gas introduction signal generator may be configured to generate the gas introduction stop command responsive to the at least one sensor detecting ejection of an injection moulded product from the mould cavity. The gas introduction signal generator may be configured to generate the gas introduction stop command responsive to the at least one sensor detecting retraction of an ejector plate of the mould away from the mould cavity. The at least one sensor may be or may include, but is not limited to, one or more contact or (non-contact) proximity sensors configured to detect motion or displacement.

In still further embodiments of the invention, the vacuum source may be reconfigurable or controllable to adjust its evacuation rate. The vacuum source may be reconfigurable or controllable to adjust its evacuation rate to different values corresponding to different cavity volumes of the mould cavity and/or different air volumes to be evacuated from the mould cavity. The vacuum source may be reconfigurable or controllable to adjust its evacuation rate to different values corresponding to different volumetric supply speeds of the moulding material and/or different melt flow rates of the moulding material.

There may be provided a moulding system comprising: a mould having an unsealed mould cavity; and an active vacuum venting system according to any one of the first aspect of the invention and its embodiments. The moulding system may be, for example, an injection moulding system, or a compression moulding system. Preferably the moulding system further includes a moulding apparatus including a moulding material supplier for supplying a moulding material into the mould cavity.

In embodiments of the invention, the moulding system may include at least one active vent channel formed in a body of the mould, the at least one active vent channel providing access to the mould cavity. The at least one active vent channel may be formed in the body of the mould at a dead-end region of the mould cavity. The at least one active vent channel may be unitary with the body of the mould. The at least one active vent channel may be machined into the body of the mould. The at least one active vent channel may be a venturi channel but may be another type of channel in other embodiments.

The vacuum source may be configured to, in use, evacuate the mould cavity via the at least one active vent channel. The gas source may be configured to, in use, introduce gas into the mould cavity via the at least one active vent channel.

In embodiments of the invention, the moulding system may include one or more vent inserts. The or each vent insert may be removably inserted into or combined with the at least one active vent channel so as to modify an area of the at least one active vent channel.

According to a second aspect of the invention, there is provided a method of operating an active vacuum venting system for use in a moulding system comprising a mould having an unsealed mould cavity, the active vacuum venting system comprising: a vacuum source; and at least one vent connector configured to, in use, connect the vacuum source to the mould cavity, wherein the method includes the steps of: supplying a moulding material into the mould cavity; by the vacuum source, evacuating the mould cavity during supply of the moulding material into the mould cavity.

The features and advantages of the first aspect of the invention and its embodiments apply mutatis mutandis to the second aspect of the invention and its embodiments.

The method may include the step of controlling the vacuum source to selectively: evacuate the mould cavity responsive to an evacuation start command; and stop evacuating the mould cavity responsive to an evacuation stop command. The method may further include the step of generating the evacuation start command or the evacuation stop command. Preferably the method may include the step of generating the evacuation start command or the evacuation stop command.

The method may include the step of generating the evacuation start command or the evacuation stop command responsive to detection of a predefined state of the moulding system. The method may include the step of generating the evacuation start command responsive to detection of a moulding material supplier being at or within a predetermined distance of the mould. The method may include the step of generating the evacuation start command responsive to detection of assembly of a plurality of mould portions of the mould to form the mould cavity. The detection may take the form of proximity, motion, displacement or contact detection.

The method may include the step of generating the evacuation stop command responsive to detection of a pressure in the mould cavity reaching or passing a threshold vacuum level.

The method may include the step of beginning evacuation of the mould cavity before injection of the moulding material into the mould cavity.

In the method of the invention, the active vacuum venting system may include a gas source (e.g. a compressed gas source) for introducing gas into the mould cavity. The method may include the step of, by the gas source, introducing gas into the mould cavity.

The method may include the step of controlling the gas source to selectively: introduce the gas into the mould cavity responsive to a gas introduction start command; and stop introducing the gas into the mould cavity responsive to a gas introduction stop command. Preferably the method may include the step of generating the gas introduction start command or the gas introduction stop command.

The method may include the step of generating the gas introduction start command or the gas introduction stop command responsive to detection of a predefined state of the moulding system. The method may include the step of generating the gas introduction start command responsive to detection of disassembly of the mould cavity into a plurality of mould portions of the mould. The method may include the step of generating the gas introduction start command responsive to detection of movement of an ejector plate of the mould towards the mould cavity. The method may include the step of generating the gas introduction stop command responsive to detection of ejection of an injection moulded product from the mould cavity. The method may include the step of generating the gas introduction stop command responsive to detection of retraction of an ejector plate of the mould away from the mould cavity.

The detection may take the form of proximity, motion, displacement or contact detection.

The method may include the step of, by the gas source, introducing gas into the mould cavity via at least one active vent channel. The method may include the step of, by the vacuum source, evacuating the mould cavity via at least one active vent channel. Exemplary details of the at least one active vent channel are described with respect to the first aspect of the invention and its embodiments and elsewhere throughout the specification.

The method may include the step of removably inserting/combining one or more vent inserts into/with the at least one active vent channel so as to modify an area of the at least one active vent channel.

The method may include the step of reconfiguring or controlling the vacuum source to adjust its evacuation rate, preferably to different values corresponding to different cavity volumes of the mould cavity, different air volumes to be evacuated from the mould cavity, different volumetric supply speeds of the moulding material and/or different melt flow rates of the moulding material.

The active vacuum venting system of the invention allows gaps in the mould, such as between mould portions (e.g. mould halves) or between ejector pins and their bores, to function as passive vents that allow air to escape the mould cavity until the gaps are sealed by the flowing injection material melt.

The active vacuum venting may be achieved preferably, but not limited to, by, e.g., using the Venturi effect to create a vacuum using compressed air rather than a vacuum pump and tank, therefore reducing the size requirements of the active vacuum venting system. Additionally, the active vacuum venting system may have a blow-back function, using the gas source, to blow gas through the at least one active vent channel in order to clear them of remaining injection material melt or melt contaminants to avoid them becoming clogged, and to aid in part ejection.

It will be appreciated that the use of the terms "first" and "second", and the like, in this patent specification is merely intended to help distinguish between similar features and is not intended to indicate the relative importance of one feature over another feature, unless otherwise specified.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, and the claims and/or the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and all features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

Preferred embodiments of the invention will now be described, by way of non-limiting examples, with reference to the accompanying drawings in which: Figure 1 shows a view of a mould; Figure 2A shows a close-up view of a connection; Figure 2B shows a close-up view of an active vent channel; Figure 3 shows a view of an injection moulding system according to an embodiment of the invention; Figure 4 shows a detailed view of a vacuum control system; Figures 5a to 5f show optional active vent inserts with different vent areas; Figure 6 shows a flowchart of an evacuation process according to an embodiment of the invention; and Figure 7 shows a flowchart of a gas introduction process according to an embodiment of the invention.

The figures are not necessarily to scale, and certain features and certain views of the figures may be shown exaggerated in scale or in schematic form in the interests of clarity and conciseness.

The following embodiments of the invention are exemplarily described with reference to an active vacuum venting system used in an injection moulding system. It will be appreciated that the active vacuum venting system of the invention may be used with other moulding systems, such as compression moulding systems.

In an embodiment, the injection moulding system of the current invention comprises a mould having a mould cavity, an injection moulding apparatus, a vacuum source controller and a vacuum source. In some embodiments the vacuum source may use the Venturi effect to generate a vacuum and evacuate the mould cavity. Further embodiments may include: a gas source controller that is separate from or integrated with the vacuum source controller, and a gas source (such as a compressed air source). A combination of active vent channels machined into the mould and passive vent channels ensure that air is not trapped inside the mould cavity during injection moulding.

The injection moulding apparatus further comprises a moulding material supplier in the form of an injector. The mould cavity may be formed of at least two mould portions which are held or packed together to form the mould cavity. The current invention does not require a seal between the mould portions of the mould during the injection moulding step. Some embodiments may make use of a partial seal between the mould portions. The current invention allows for the injected plastic melt to effectively "seal itself" inside the mould cavity.

An exemplary mould for use in the injection moulding system of the present invention is shown in Figure 1. In the pictured embodiment, the mould has two mould portions 116, 118. The first mould portion 118 is held stationary throughout the manufacture of moulded parts, while the second mould portion 116 is movable. During injection and cooling of the polymer the two mould portions 116, 118 are held together without a seal therebetween so as to form a mould cavity 114. The mould cavity 114 is shaped such that injected polymer melt will fill the mould cavity 114 and solidify during cooling to form the desired moulded product with a shape corresponding to the shape of the mould cavity 114.

To manufacture a moulded polymer part, in the pictured embodiment, the second mould portion 116 is brought together with the first mould portion 118 to form the mould cavity 114. The injector is brought towards the mould and, once it is within a predetermined distance from the mould, an evacuation signal is sent to a vacuum controller. The vacuum controller commences evacuation of the mould cavity 114, wherein the air is evacuated through at least one vacuum hose 104. The at least one vacuum hose 104 is connected to the mould cavity 114 via corresponding connections and active venting channels 112 machined into the mould. To commence fabrication the injector injects polymer melt into a sprue 102 of the mould. The polymer melt fills the mould cavity 114 and self-seals the mould portions 116, 118 to become air-tight.

There is a tendency in injection moulding for air traps to form within the mould cavity during injection of the polymer melt. Air traps give rise to troublesome manufacturing errors in the finished product, such as empty gaps/spots in the surface of the finished product where no plastic melt has entered, empty regions/voids inside the plastic, and surface defects such as burn marks, low weld line strength, and high residual stresses.

The quality of the finished plastic part is paramount for many applications, and it can be difficult to remove defective parts during quality control.

Potential solutions to the air trap related problems include design and processing solutions, altering the mould design to include passive venting in regions which are last to fill or to include large vents which allow trapped air to escape, or adjusting the moulding conditions by injecting melt at a higher pressure. The earlier solutions require significant modifications on both part and mould, while the last solution causes high residual stresses in the moulded parts.

The present invention presents an alternative solution in the form of an active vacuum venting system with integrated air evacuation and gas introduction controls. This is easier to implement compared to the previous example solutions, which are additionally not always effective at increasing quality and yield. Unlike the example solutions, the present invention does not require seals in the mould nor does it require extensive redesign of moulds or injection moulding apparatus.

In an embodiment, the active vent channels 112 are targeted towards known or anticipated "dead end regions" in the mould cavity 114 where air is commonly trapped. The vacuum evacuation removes the air from the mould cavity 114 via these active vent channels 112 and thereby causes the plastic melt to fill the mould cavity 114 more completely. This allows for more complicated shapes to be reliably formed with less manufacturing errors that would have otherwise arisen due to air traps.

The pictured embodiment includes ejector pins 120, an ejector pin retainer plate 122 and an ejector plate 124. The ejector pins 120 are attached to one side of the ejector pin retainer plate 122, while the ejector plate 124 is attached to the other side of the ejector pin retainer plate 122. When the injection of the polymer melt is underway, the ejector pins 120, ejector pin retainer plate 122 and ejector plate 124 are positioned such that the ejector pins are flush with the interior wall of the mould cavity 114 and that polymer melt does not enter the channels through which the ejector pins 120 extend. The ejector pins 120, ejector pin retainer plate 122 and ejector plate 124 are configured to be movable so as to move the ejector pins 120 into the mould cavity 114 and thereby push a finished injection moulded product out of the mould cavity 114. More specifically, movement of the ejector plate 124 towards the mould pushes the ejector pin retainer plate 122 and ejector pins 120 in the same direction. The ejector pins 120 can be retracted from the mould cavity 114 via movement of the ejector plate 124 in the opposite direction, which in turn causes the ejector pin retainer plate 122 and ejector pins 120 to also move in the opposite direction.

The mould portion 118 is configured to be fixed in position throughout the injection moulding process. The mould portion 116 is configured to be movable. In the pictured embodiment, the mould cavity 114 is formed by bringing the movable mould portion 116 in abutment with the fixed mould portion 118. Other embodiments include at least one further mould portion such that there is a plurality of mould portions which are brought together to assemble a mould cavity rather than the two mould portions 116, 118 shown in Figure 1.

An embodiment of a connection from the vacuum source hose to the mould cavity is shown in Figure 2A. In the pictured embodiment, the connection 200 comprises a pipe fitting or hose 202 and a threaded connector 204 with a threaded part 206. In some embodiments the threaded connector 204 may be wholly threaded throughout its length. In other embodiments, the threaded part 206 may be a relatively small portion of the threaded connector 204.

The hose 202 is attached to the mould by means of the threaded connector 204. In the pictured embodiment, the hose 202 is connected at its other end to the vacuum source so as to channel gas from the mould cavity 114 during evacuation, and to channel gas from a gas source to the mould cavity 114 during gas introduction. The threaded end is configured to be long enough to provide a secure connection of the hose and connector to the mould during evacuation and gas introduction.

Figure 2B shows a view of an exemplary active venting area 210. In the pictured embodiment, there is an active vent channel 212 unitary with the mould which is directed towards releasing the air from an air trap region 218 of the mould cavity 214.

A vent insert may be inserted (e.g. push fit) into or combined with the active vent channel 212 so as to modify an internal area of the active vent channel 212. In some embodiments, a vent insert may not be necessary to achieve the desired rate of evacuation of the mould cavity 114. In other embodiments, a vent insert may be configured with a different vent size and/or shape so as to achieve a different vent area or evacuation rate. In further embodiments, vent inserts of different shapes and dimensions may be used to target different regions of the mould cavity 114.

An embodiment of the invention includes active vent channels machined into the mould cavity targeted at regions which are susceptible to air traps. These regions include "dead end" regions, where the shape of the mould cavity means that, once the entrance to that section of the mould cavity has been filled by polymer melt, there is no route for the trapped air to escape. The active vent channels of the present application provide a route by which this air might be removed so as to allow the polymer melt to fill the mould entirely. In some embodiments, the active vent channels are machined into a pre-existing mould so as to adapt a pre-existing injection moulding system to become the injection moulding system of the present invention. In other embodiments, the mould is designed with the present injection moulding system in mind, and the active vent channels may be included in initial designs for the mould. In other embodiments, active vent channels in existing moulds may be adapted for use with the injection moulding system of the present invention. In some embodiments, at least one active vent channel is a venturi channel.

Figure 3 shows an embodiment of the current invention. The injection moulding system 300 includes an injector 320, a mould 310, a gas source 308 and a vacuum control system 400. In some aspects, the gas source may be a compressed air source. An embodiment of the injection moulding system includes an evacuation signal generator, shown as being exemplarily integrated with a sensor 312, which relays an evacuation signal to a vacuum source controller 402 of the vacuum control system 400 when the injector 320 is at or within a predetermined distance from the mould 310. Some embodiments include the evacuation signal generator being configured to generate an evacuation start or stop command upon the sensor 312 detecting a predefined state of the injection moulding system. For example, the sensor may be a contact sensor and the predefined state may be the assembly of a plurality of mould portions to form the mould cavity. In another embodiment, the sensor 312 is a proximity sensor and the pre-defined state is the injector 320 being at or within a pre-defined distance of the mould 310. In other embodiments, the predefined state may be the proximity of the mould portions 116, 118 to one another. In other aspects, the evacuation signal generator may form part of the vacuum control system.

In a further embodiment the active vacuum venting system may include a gas introduction signal generator, shown as being exemplarily integrated with a sensor 314, which relays a signal to the vacuum source controller 402 upon detection of a predetermined state, action or threshold. In this regard the vacuum source controller 402 also functions as a gas source controller, although in other embodiments the vacuum source controller 402 and gas source controller may be configured as separate controllers. The gas introduction signal generator may be configured to generate a gas introduction signal in response to a sensor 314 detecting a pre-determined state of the injection moulding system. For example, the sensor 314 may be a movement/motion/proximity sensor and the pre-determined signal may be, but not limited to, the movement of the ejector plate 124 towards the mould cavity 114, which results in the movement of the ejector pins 120 into the mould cavity 114. In other embodiments, the pre-determined state may be the ejection of an injection moulded product from the mould cavity 114. In yet other embodiments, the predetermined state may be the disassembly of the mould cavity 114 into a plurality of mould portions of the mould. In other aspects, the gas introduction signal generator may form part of the vacuum control system.

Upon receipt of the gas introduction signal, the gas source controller controls the gas source 308 to initiate a "blow-back" of gas through the injection moulding system 300.

In some cases, introduction of gas into the system will ensure that the active vent channels are clear of solid or melted polymer material and ready for the next injection cycle. In embodiments where the gas is compressed air, the additional pressure from the introduction of compressed air will clear blocked vents. In some embodiments, the predetermined action is the movement of the ejector plate 124 away from the mould cavity 114, which results in movement of the ejector pins 120 to eject the finished injection moulded product from the mould cavity 114. In another embodiment, the predetermined action is the withdrawal of the injection unit 320 from the mould. In a further embodiment, it is the extraction of the injection moulded product from the mould cavity 114.

In further embodiments, the sensor may be replaced with another kind of sensor or is a proximity sensor located elsewhere adjacent the injection moulding system. For example, the sensor may be a pressure sensor that is configured to measure the pressure inside the mould cavity and the evacuation signal generator relays an evacuation signal when the pressure inside the cavity reaches a predetermined threshold. In yet further embodiments, the evacuation signal generator may relay an evacuation signal to the vacuum source controller 402 upon the sensor detecting that the injection of polymer melt into the mould has commenced.

A detailed view of an embodiment of the vacuum source controller 402 programmed to control the vacuum source and receive signals from the sensors 412, 414 and signal generators of the injection moulding system 300 is shown in Figure 4. The vacuum control system 400 comprises a vacuum source controller 402 (which in this embodiment also functions as a gas source controller), a system status display 404, and a vacuum generator 410 connected via connector 422 to the gas source 308 and via connector 424 to the moulding apparatus 410. The vacuum source controller 402 is in communication with the evacuation signal generator associated with the sensor 412 and with the gas introduction signal generator associated with the sensor 414. The vacuum source controller 402 is configured to receive vacuum control and gas introduction signals respectively, to interpret the signals and to instruct the vacuum generator 410 and gas source 308 to commence evacuation or blow-back based on the interpreted signals.

In some embodiments, the vacuum source controller 402 is configured to control the speed of evacuation or gas introduction. In some embodiments this is achieved by controlling the vacuum source. Some embodiments of the vacuum controller 400 may include a compressed air flow/pressure regulator 426 between the vacuum generator 410 and the vacuum hose connector 422. In other embodiments, the programmable vacuum controller 400 may further include a suctioned air flow/pressure regulator 428 between the vacuum generator 410 and the mould hose connector 424 for regulating the air flow between the vacuum generator and the mould cavity. Further embodiments of the present invention include an optional silencer 406 attached to the vacuum generator 410 for noise reduction.

A compressed air flow regulator and a suctioned air flow regulator may be configured manually to regulate the air flow. Additionally, the vacuum source controller 402 may be configured to control them according to a set of fabrication parameters which may depend on: the size or volume of the moulding apparatus mould, the viscosity of the plastic melt, the size of volume of at least one active venting channel machined into the mould, and the vent size or area of a vent insert in the at least one active venting channel.

In some aspects, through the use and programming of the vacuum control system, sensors and signal generators, the evacuation and gas introduction may be substantially or completely automated based on predetermined signals and thresholds. Placement of the sensors and signal generators allow for a bespoke choice of predetermined system states which trigger the sensors and cause the evacuation and gas introduction stages to begin. In this manner there is a reduced need for user input and thereby results in increased efficiency.

The gas source controller may be further configured to, in the case of a blockage of the vents or hoses, increase the pressure of the gas being introduced to the mould cavity until either the blockage is cleared or a maximum safe level is achieved. This function requires that at least one of the sensors and signal generators is configured to detect the blockage and relief of said blockage. As an example, the sensor may be a pressure sensor located in or near the active vent channel, and the predetermined state which triggers the signal generator may be the pressure in the active vent channel exceeding a threshold.

Exemplary embodiments of vent inserts 500a, 500b, 500c are respectively shown in Figures 5a, 5b, 5c, 5d, 5e and 5f.

Figure 5a shows a first embodiment of a vent insert 500a, while Figure 5b shows the insertion of the vent insert 500a into the mould portion 116. The vent insert 500a comprises a circular base on which a narrower cylindrical projecting member is mounted. Air is evacuated through the clearance between the cylindrical projecting member and the mould portion 116. The degree of evacuation can be altered by changing the diameter and shape of the cylindrical projecting member in order to modify the clearance between the vent insert 500a and the mould portion 116.

Figure 5c shows a second embodiment of a vent insert 500b, while Figure 5d shows the insertion of the vent insert 500b into the mould portion 116. The vent insert 500b comprises a rectangular parallelepiped base on which a narrower rectangular parallelepiped is mounted. An elongated groove is formed in the narrower rectangular parallelepiped, and is configured to be in communication with the active vent channel 212. Air is evacuated through the elongated groove. The degree of evacuation can be altered by changing the width and length of the elongated groove.

Figure 5e shows a third embodiment of a vent insert 500c, while Figure 5f shows the insertion of the vent insert 500c into the mould portion 116. The vent insert 500c comprises a circular base on which a narrower cylindrical projecting member is mounted. A bore is formed to extend through the cylindrical projecting member, and is configured to be in communication with the active vent channel 212. Air is evacuated through the bore. The degree of evacuation can be altered by changing the diameter and shape of the bore.

Each vent insert 500 has a narrow vent width/gap to avoid flash formation on the moulded parts or vent clogging, while the length of the vent gap may be varied to increase the area of the active vent channels, thus increasing the air evacuation rate. In some aspects, the reduced width/gap of the active vent channel may reduce the negative aesthetic impact of the manufacturing process on the finished injection moulded product. The use of the vent insert reduces the need for machining on the mould if, for example, the type of polymer is changed and the melts have different viscosities or flow rates or volumetric injection speeds, or if a previously existing mould is to be used with the system described herein. In further embodiments, the vent insert may have a different sized active vent to suit a different polymer viscosity or evacuation rate. Further, some embodiments may include a variety of vent inserts of different dimensions and/or shapes to target different areas of the mould cavity which may benefit from smaller or larger active vent channels. In some aspects, this may reduce the need for machining of the mould itself.

In aspects of the invention, the vacuum source controller may adjust an evacuation rate of the vacuum source to different values corresponding to, for example, different volumes of the mould cavity and/or different melt viscosities of the injection material.

A method of using the active vacuum venting system in the injection moulding system is described below with reference to the flow diagrams of Figures 6 and 7.

In some aspects, the method may be broadly described as having two portions: the injection portion, an example of which is shown in Figure 6, and the gas introduction portion, an example of which is shown in Figure 7.

An exemplary injection portion of the method as shown in Figure 6 is as follows: Step 1. A plurality of mould portions is brought together to form the seal-less mould cavity.

Step 2. The injector moves towards the mould.

Step 3. A sensor 312, 412 associated with the evacuation signal generator senses a predetermined evacuation state, which causes the evacuation signal generator to communicate an evacuation start command to the vacuum source controller.

Step 4. The vacuum source controller sets a timer of predetermined length. Step 5. The vacuum source controller initiates evacuation of the mould cavity by controlling the vacuum source, which is in the form of a vacuum generator.

Step 6. Polymer melt is injected into the mould cavity by the injector.

Step 7. The polymer melt is drawn into the cavity with the help of the evacuation of air from the mould cavity. Air is pulled through the active venting channels to allow polymer melt to fill the mould entirely. As the polymer melt is drawn into the cavity, it passively seals the mould cavity without the need for additional sealing components. Additional polymer melt may be injected into the mould cavity to account for material shrinkage and backflow.

Step 8. The vacuum source controller waits for one of two predetermined signals. Upon elapsing of the timer, or upon a predetermined vacuum pressure threshold being reached inside the mould cavity, the evacuation signal generator generates and communicates an evacuation stop command to the vacuum source controller which then switches the vacuum generator off.

Step 9. The system then waits for the polymer melt to cool for a predetermined time.

Step 10. Upon elapsing of the cooling time, the mould is disassembled or opened.

Step 11. The ejector pins extend into the mould cavity.

The sensor 312, 412 in communication with the evacuation signal generator may be a proximity sensor, a pressure sensor, a contact sensor, or another sensor where appropriate. There may be more than one sensor and more than one predetermined evacuation state of the injection moulding system. The predetermined evacuation state of Step 3 above resulting in the generation of the evacuation start command is the injector being within or at a predetermined distance to the mould. In other embodiments, the predetermined evacuation state resulting in the generation of the evacuation start command may be the assembly of the plurality of mould portions of the mould to form the mould cavity. In further embodiments, the predetermined evacuation state resulting in the generation of the evacuation stop command may be the pressure reaching or passing a threshold vacuum level. In yet further embodiments, a different predetermined evacuation state may be selected according to user requirements.

An exemplary gas introduction portion of the method of using the present active vacuum venting system is shown in Figure 7 and is as follows: Step 1. A sensor 314, 414 associated with the gas introduction signal generator detects the movement of the ejector plate leading to the extension of the ejector pins (for example Figure 6, Step 11).

Step 2. The gas introduction signal generator then generates and communicates a gas introduction start command to the gas source controller.

Step 3. The gas source controller sets a timer of predetermined length.

Step 4. The gas source controller initiates introduction of gas, e.g. compressed air. to the mould 310 via the active vent channels.

Step 5. The finished injection moulded product is pushed by the ejector pins protruding into the mould cavity and by the gas pressure.

Step 6. Upon elapsing of the timer or the detection of the ejector pins retracting, the gas source controller stops the introduction of gas into the moulding apparatus.

Step 7. The finished injection moulded product is now ejected.

The sensor 314, 414 in communication with the gas introduction signal generator may be a proximity sensor, a pressure sensor, a contact sensor, or another sensor where appropriate. There may be more than one sensor and more than one predetermined gas introduction state of the injection moulding system. The predetermined gas introduction state in Step 2 of Figure 7 is the extension of at least one ejector pin into the mould cavity, which may be detected by sensing the movement or displacement of the ejector plate, but the predetermined gas introduction state may be another state. In some embodiments, the predetermined gas introduction state may be the disassembly of the plurality of mould portions. In other embodiments, the predetermined gas introduction state may be a threshold pressure in the mould cavity, withdrawal of the injector, ejection of an injected moulded product from the mould cavity, or another system state which suits the unique requirements of a user.

In some embodiments, upon completion of the gas introduction portion, the injection portion of the method may begin again such that the method is a repeating cycle of injection and gas introduction. In this manner, the production of finished injection moulded products may be substantially continuous without compromising the quality of the finished injection moulded products.

There is an ever-increasing need for moulding systems which can more reliably eliminate air traps and increase yield. Other current solutions require sealing and excessive machining of the moulds and are high in cost and low in efficacy. The present invention disclosed herein offers a solution to reducing air traps and provides a means for preventing vent blockages in the active venting channels.

The listing or discussion of an apparently prior published document or apparently prior published information in this specification should not necessarily be taken as an acknowledgement that the document or information is part of the state of the art or is common general knowledge.

Preferences and options for a given aspect, feature or parameter of the invention should, unless the context indicates otherwise, be regarded as having been disclosed in combination with any and all preferences and options for all other aspects, features and parameters of the invention.

Claims

CLAIMS1. An active vacuum venting system for use in a moulding system comprising a mould having an unsealed mould cavity, the active vacuum venting system comprising: a vacuum source; and at least one vent connector configured to, in use, connect the vacuum source to the mould cavity, wherein the vacuum source is configured to, in use, evacuate the mould cavity during supply of moulding material into the mould cavity.
2. An active vacuum venting system according to Claim 1 including a vacuum source controller and an evacuation signal generator, wherein the vacuum source controller is programmed to control the vacuum source to selectively: evacuate the mould cavity responsive to an evacuation start command generated by the evacuation signal generator; and stop evacuating the mould cavity responsive to an evacuation stop command generated by the evacuation signal generator.
3. An active vacuum venting system according to Claim 2 including at least one sensor, wherein the evacuation signal generator is configured to generate the evacuation start command or the evacuation stop command responsive to the at least one sensor detecting a predefined state of the moulding system.
4. An active vacuum venting system according to Claim 3 wherein the evacuation signal generator is configured to generate the evacuation start command responsive to the at least one sensor detecting a moulding material supplier being at or within a predetermined distance of the mould.
5. An active vacuum venting system according to Claim 3 or Claim 4 wherein the evacuation signal generator is configured to generate the evacuation start command responsive to the at least one sensor detecting assembly of a plurality of mould portions of the mould to form the mould cavity.
6. An active vacuum venting system according to any one of Claims 3 to 5 wherein the at least one sensor is or includes a contact or proximity sensor configured to detect motion or displacement.
7. An active vacuum venting system according to any one of Claims 3 to 6 wherein the at least one sensor is or includes a pressure sensor, wherein the evacuation signal generator is configured to generate the evacuation stop command responsive to the pressure sensor detecting a pressure in the mould cavity reaching or passing a threshold vacuum level.
8. An active vacuum venting system according to any one of the preceding claims wherein the vacuum source is configured to, in use, begin evacuating the mould cavity before supply of the moulding material into the mould cavity.
9. An active vacuum venting system according to any one of the preceding claims including a gas source configured to, in use, introduce gas into the mould cavity.
10. An active vacuum venting system according to Claim 9 wherein the at least one vent connector is configured to, in use, connect the gas source to the mould cavity.
11. An active vacuum venting system according to Claim 9 or Claim 10 including a gas source controller and a gas introduction signal generator, wherein the gas source controller is programmed to control the gas source to selectively: introduce the gas into the mould cavity responsive to a gas introduction start command generated by the gas introduction signal generator; and stop introducing the gas into the mould cavity responsive to a gas introduction stop command generated by the gasintroduction signal generator.
12. An active vacuum venting system according to any one of Claims 9 to 11 including at least one sensor, wherein the gas introduction signal generator is configured to generate the gas introduction start command or the gas introduction stop command responsive to the at least one sensor detecting a predefined state of the moulding system.
13. An active vacuum venting system according to Claim 12 wherein the gas introduction signal generator is configured to generate the gas introduction start command responsive to the at least one sensor detecting disassembly of the mould cavity into a plurality of mould portions of the mould.
14. An active vacuum venting system according to Claim 12 or Claim 13 wherein the gas introduction signal generator is configured to generate the gas introduction start command responsive to the at least one sensor detecting movement of an ejector plate of the mould towards the mould cavity.
15. An active vacuum venting system according to any one of Claims 12 to 14 wherein the gas introduction signal generator is configured to generate the gas introduction stop command responsive to the at least one sensor detecting ejection of an injection moulded product from the mould cavity.
16. An active vacuum venting system according to any one of Claims 12 to 15 wherein the gas introduction signal generator is configured to generate the gas introduction stop command responsive to the at least one sensor detecting retraction of an ejector plate of the mould away from the mould cavity.
17. An active vacuum venting system according to any one of Claims 12 to 16 wherein the at least one sensor is or includes a contact or proximity sensor configured to detect motion or displacement.
18. An injection moulding system according to any one of the preceding claims wherein the vacuum source is reconfigurable or controllable to adjust its evacuation rate.
19. An injection moulding system according to Claim 18 wherein the vacuum source is reconfigurable or controllable to adjust its evacuation rate to different values corresponding to different cavity volumes of the mould cavity.
20. An injection moulding system according to Claim 18 or Claim 19 wherein the vacuum source is reconfigurable or controllable to adjust its evacuation rate to different values corresponding to different air volumes to be evacuated from the mould cavity.
21. An injection moulding system according to any one of Claims 18 to 20 wherein the vacuum source is reconfigurable or controllable to adjust its evacuation rate to different values corresponding to different volumetric supply speeds of the moulding material and/or different melt flow rates of the moulding material.
22. A moulding system comprising: a mould having an unsealed mould cavity; and an active vacuum venting system according to any one of the preceding claims.
23. A moulding system according to Claim 22 further including: a moulding apparatus including a moulding material supplier for supplying a moulding material into the mould cavity.
24. A moulding system according to Claim 22 or Claim 23 including at least one active vent channel formed in a body of the mould, the at least one active vent channel providing access to the mould cavity.
25. A moulding system according to Claim 24 wherein the at least one active vent channel is formed in the body of the mould at a dead-end region of the mould cavity.
26. A moulding system according to Claim 24 or Claim 25 wherein the at least one active vent channel is unitary with the body of the mould.
27. A moulding system according to Claim 26 wherein the at least one active vent channel is machined into the body of the mould.
28. A moulding system according to any one of Claims 24 to 27 wherein the at least one active vent channel is a venturi channel.
29. A moulding system according to any one of Claims 24 to 28 wherein the vacuum source is configured to, in use, evacuate the mould cavity via the at least one active vent channel.
30. A moulding system according to any one of Claims 24 to 29 when dependent from any one of Claims 9 to 16, wherein the gas source is configured to, in use, introduce gas into the mould cavity via the at least one active vent channel.
31. A moulding system according to any one of Claims 24 to 30 including one or more vent inserts, wherein the or each vent insert is removably inserted into or combined with the at least one active vent channel so as to modify a vent area of the at least one active vent channel.
32. A method of operating an active venting system for use in a moulding system comprising a mould having an unsealed mould cavity, the active vacuum venting system comprising: a vacuum source; and at least one vent connector configured to, in use, connect the vacuum source to the mould cavity, wherein the method includes the steps of: supplying a moulding material into the mould cavity; by the vacuum source, evacuating the mould cavity during supply of the moulding material into the mould cavity.