Patent Description:
Injection molding is a manufacturing process in which molten material is injected into a mold cavity and hardens into a product that takes the shape of the mold cavity. Injection molding is used to manufacture parts for a variety of applications. Examples of materials used injection molding are thermoplastic and thermosetting polymers, metals, glass, and elastomers. Over the lifespan of the injection mold, the surfaces of the mold cavity are subjected to wear that affects the quality of the molded parts.

Document <CIT> aims to accurately and simply attach a mold stocker and a mold replacing robot device to an injection molding machine so as to obtain dimensional precision and flatness without performing adjustment. For this purpose, an attaching bracket is placed on tie bars guiding a slide of a movable platen so as to straddle them from above and, with this mount state kept, the attaching bracket is fixed to a fixed platen to attach a mold replacing robot device and mold stockers to the upper surface of the attaching bracket through an attaching stand.

Document <CIT> discloses a molding system that includes a plurality of cavity portions or core block assemblies attached to a mold plate and a plurality of core portion or core block assemblies attached to a second mold plate, and a plurality of stripper rings or thread split-slide assemblies attached to a stripper plate assembly. The stripper plate assembly includes a main stripper plate with one or more stripper plate panels coupled thereto that are translatable away from the main stripper plate during installation of at least the core portions or core block assemblies. The one or more stripper plate panels may be translatable to fold, outwardly swing, and/or slide relative to the main stripper plate to clear any core portions or core block assemblies that may have been previously installed.

A system according to the present invention is set out in claim <NUM>. A combination according to the present invention, comprising an injection mold and the system is set out in claim <NUM>. A method according to the present invention is set out in claim <NUM>. Further advantageous embodiments of the present invention are set out in the dependent claims.

According to the present invention, a combination comprising an injection mold and a system according to the present invention is provided. The injection mold comprises an outer shaping surface and an inner shaping surface that cooperate to define a mold cavity; a mold body that comprises the outer shaping surface; and a moveable core that comprises the inner shaping surface, wherein the core is configured to be grasped by an automated core changing tool. Such an injection mold can be maintained automatically. For example, the core can be automatically switched out by an automated core changing tool in contrast to manual disassembly of the injection mold.

Preferably, the core comprises a clamping section configured to be grasped by the automated core changing tool and configured to engage a securing element that secures the core to the mold body. The clamping section can preferably include a groove or recess.

Preferably, the core and the mold body are configured to cooperate and center the core relative to the mold body.

Preferably, the core comprises a plurality of assembled parts.

Preferably, the core comprises a shaping section that comprises the inner shaping surface and a detachable support section that connects the body of the core to the mold body.

According to the present invention, a system for an injection mold comprises a gripper; a holder that comprises a plurality of slots, each configured to hold a mold core; and a controller configured to control the gripper in response to receiving a core change signal to disassemble a core from the injection mold, deposit the disassembled core in one of the plurality of slots of the holder, retrieve a core stored in a different one of the plurality of slots of the holder, and connect the core to the injection mold. Such a system can automatically maintain an injection mold and reduce defects in the parts molded using the injection mold. For example, the system can be configured to run automatically, without external intervention by a user.

Preferably, the controller is configured to receive the core change signal from an injection molding machine comprising the injection mold, wherein the core change signal is generated based on a number of injection cycles of the injection molding machine.

According to the present invention, the system includes a sensing device configured to sense a property of the mold core assembled in the injection mold, wherein the core change signal is generated in response to a sensor signal. The sensing device can preferably comprise one or more cameras configured to sense scratches or defects on a surface of the mold core. Preferably, the sensing device is configured to detect a presence of at least a part of the mold core based on inductance or capacitance. The sensing device can preferably comprise an optoelectronic device configured to detect a presence of at least a part of the mold core. The sensing device can preferably alternatively or additionally comprise one or more cameras configured to detect scratches or defects on a surface of one or more parts molded by the injection mold.

The present invention also combines the injection mold and the system described above.

According to the present invention, a method comprises disconnecting, using a gripper, a core from an injection mold in response to a core change signal and depositing the disconnected core; retrieving, using the gripper, a replacement core; connecting, using the gripper, the replacement core to the injection mold; and sending an enable signal to a controller of an injection molding machine that comprises the injection mold. Such a method can automatically maintain an injection mold and avoid defects in the parts molded using the injection mold.

Preferably, the method includes receiving the core change signal from the controller of the injection molding machine based on a number of molding cycles.

According to the present invention, the method includes detecting, using a sensing device, whether the core connected to the injection mold is intact and receiving the core change signal from the sensing device.

Preferably, the method includes detecting, using a sensing device, scratches or defects on the core and receiving the core change signal from the sensing device.

Preferably, the method includes molding, using the injection mold, one or more parts; detecting, using a sensing device, scratches or defects on the molded parts; and receiving the core change signal from the sensing device.

Preferably, retrieving a replacement core comprises retrieving a replacement core that has the same structure as the disconnected core.

The details of one or more implementations of the subject matter of this specification are set forth in the accompanying drawings and the subsequent description.

Referring to <FIG>, an injection mold <NUM> defines a mold cavity <NUM>. The mold cavity <NUM> has the inverse shape of a molded part (not shown), meaning that the surfaces of the mold cavity <NUM> give the molded part its shape. Molten material for forming the part is injected at an inlet <NUM> that is connected to a vertical passage or sprue <NUM>. The molten material flows down the sprue <NUM>, through a runner <NUM>, and into the mold cavity <NUM> via a gate <NUM>. Although the implementation illustrated in <FIG> has one mold cavity, one gate, one runner, and one sprue, some implementations may include multiple mold cavities and a corresponding network of sprues, runners, and gates. Once the molten material has solidified inside of the mold cavity <NUM>, actuators (not shown) open the injection mold <NUM> along a mold parting line <NUM> to retrieve the part. Although not shown in <FIG>, the injection mold may include an ejector assembly to help remove the molded part from the mold. An ejector assembly may include one or more knockout pins attached to an ejector plate and a motor that drives the ejector plate.

The mold cavity <NUM> includes a pair of forming or shaping surfaces <NUM>, <NUM>. The molten material enters the mold cavity <NUM> and hardens onto the shaping surfaces <NUM>, <NUM>. Once the material has solidified, the bond between the hardened material and the shaping surfaces <NUM>, <NUM> is broken in order to remove the molded part. This repetitive process causes the shaping surfaces <NUM>, <NUM> to wear at a faster rate than the rest of the mold <NUM>.

An outer shaping surface <NUM> corresponds to the outer surface of the finished part. In the illustrated example, the outer shaping surface <NUM> is formed by first and second cavity plates <NUM>, <NUM> and a first holder plate <NUM> that is described in more detail below. Depending on the geometry of the mold cavity <NUM>, a single cavity plate may be sufficient to form the outer shaping surface <NUM>, or more than two cavity plates may be necessary to form the outer shaping surface <NUM>. In the illustrated example, the runner <NUM> and gate <NUM> are formed in second cavity plate <NUM>, and the sprue <NUM> extends along both cavity plates <NUM>, <NUM>. The shape and placement of the sprue <NUM>, the runner <NUM>, and the gate <NUM> depends on the mold geometry and the properties of the molten material (e.g. viscosity) and may therefore be different than illustrated in <FIG>.

An inner shaping surface <NUM> corresponds to the inner surface of the finished part. In the illustrated example, the inner shaping surface <NUM> is formed by a core <NUM>. More specifically, the core <NUM> includes a shaping section <NUM> (<FIG>) that is inserted into the space or void formed by the first and second cavity plates <NUM>, <NUM>. In other words, an outer surface <NUM> of the shaping section <NUM> is also the inner shaping surface <NUM> of the mold cavity <NUM>. The core <NUM> is supported by the first holder plate <NUM> that also forms part of the outer shaping surface <NUM>, a second holder plate <NUM>, and a core clamp <NUM>. The first and second holder plates <NUM>, <NUM> and the core clamp <NUM> are described in more detail in reference to <FIG>.

Generally speaking, the injection mold <NUM> thus comprises a cavity section <NUM> and a core section <NUM> that meet along mold parting line <NUM> (<FIG>). Although not illustrated, the injection mold <NUM> may also include clamping or support plates that compress the mold parts together, an alignment mechanism that aligns the cavity section <NUM> and the core section <NUM>, or both.

<FIG> is an enlarged view of a core <NUM> that is similar to the core <NUM> shown in <FIG>. The core <NUM> includes a shaping section <NUM> and a supporting section <NUM>. The shaping section <NUM> extends from a first end <NUM> of the core <NUM> and is arranged in the void formed by the first and second cavity plates <NUM>, <NUM> of the cavity section <NUM>. The outer surface <NUM> of the shaping section <NUM> forms the inner shaping surface <NUM> of the mold cavity <NUM> when the core <NUM> is installed in the core section <NUM> of the injection mold <NUM>. The supporting section <NUM> maintains the position of the core <NUM> when the core <NUM> is installed in the core section <NUM> by engaging the first and second holder plates <NUM>, <NUM> and the core clamp <NUM>. In other words, the supporting section <NUM> does not directly form the mold cavity <NUM> and does not include a shaping or forming surface. The supporting section <NUM> extends from a second end <NUM>, towards the shaping section <NUM> and the first end <NUM> of the core <NUM>.

Unlike the core <NUM> in <FIG>, the core <NUM> in <FIG> has multiple assembled parts, as shown in the enlarged partial cross section X of the tip <NUM>. More specifically, the core <NUM> includes a body <NUM> and a removable pin <NUM> that are connected by a threaded connection <NUM>. In the illustrated example, the removable pin <NUM> may be used to mold a small hole (e.g. diameter of less than or equal to <NUM>) in the finished part. For example, the outer shaping surface <NUM> may have a small recess that mates with an end surface <NUM> of the pin <NUM>. Due to its small diameter, the pin <NUM> is more prone to breakage than the body <NUM> of the core <NUM>. By forming the pin <NUM> and the body <NUM> as separate parts, the pin <NUM> can be made of a harder material than the body <NUM> or replaced when broken. In other implementations, the shaping section <NUM> and supporting section <NUM> may be formed by separate parts, since the shaping section <NUM> is more susceptible to wear than the supporting section <NUM>. A dotted line <NUM> schematically indicates, for example, a screwed connection between the shaping and supporting sections <NUM>, <NUM>. The placement of the connection line <NUM> may not necessarily coincide with the transition between the shaping and supporting sections <NUM>, <NUM>, e.g., to avoid a visible line or break in the molded part.

The supporting section <NUM> includes a centering device <NUM> and a clamping section <NUM>. The centering device <NUM> aligns the core <NUM> and the first holder plate <NUM> when the core section <NUM> is assembled. In the illustrated example, the centering device <NUM> is a conically-shaped part of the outer surface <NUM> that matches a conically-shaped surface <NUM> in the first holder plate <NUM> (<FIG>). However, the centering device <NUM> may also a centering pin or other similar device. Due to the conically-shaped surface that forms the centering device <NUM>, the supporting section <NUM> has a larger outer diameter than the shaping section <NUM>. However, implementations that include a different centering device <NUM> (e.g. a centering pin) may include a core <NUM> that has a substantially constant outer diameter along its entire length. In such implementations, the core section <NUM> may include a single core plate with a cylindrical bore or passage that receives the core <NUM>.

The clamping section <NUM> is located adjacent the second end <NUM> and engages the core clamp <NUM> shown in <FIG>. In the illustrated example, the clamping section <NUM> includes a peripherally extending groove <NUM> that receives a pair of jaws of the core clamp <NUM>. However, there are other ways to releasably connect the clamping section <NUM> and the core clamp <NUM>. For example, the core <NUM> may include a pull stud bolt that is threaded into a hole in the body <NUM>, similarly to the pull stud bolts used to connect milling cutters to CNC machines. In such implementations, the core clamp <NUM> may include a collet or a ball-type device to engage the enlarged head of the pull stud bolt.

Referring now to <FIG>, an injection mold <NUM> similar to the example illustrated in <FIG> is shown in an open state. In other words, the cavity section <NUM> and the core section <NUM> are separated along the mold parting line <NUM> to expose the inner shaping surface <NUM>, i.e. the surface <NUM> of the shaping section <NUM> of the core <NUM>. As described above, the repetitive process of removing molded parts from the core <NUM> may cause scratches on the surface <NUM> that diminish the quality of the molded parts. The core <NUM> may also become cracked, or an additional part, such as the pin <NUM> (not shown), may break or be missing. In order to minimize such potential defects, a sensor system <NUM> is illustrated. The sensor system <NUM> includes one or more sensing devices <NUM> that are communicatively coupled to a controller <NUM>.

In the illustrated example, the sensing devices <NUM> are cameras trained on the outer surface <NUM> of the shaping section <NUM> of the core <NUM>. The cameras are configured to send image data to the controller <NUM>, and the controller <NUM> uses software to determine the presence of scratches, cracks, or missing parts. Although the illustrated cameras are focused on the core <NUM>, in some implementations, the cameras of the sensing system may be used to screen the molded parts for defects resulting from scratches, cracks, or missing parts. In implementations including a camera, the camera may capture one or more images after every injection molding cycle. If the mold or molded parts passes the quality test (e.g. no scratches are detected), the controller <NUM> may determine that the core <NUM> is fit for use.

Instead of cameras, other types of devices may form the sensing devices of the sensor system <NUM>. For example, the sensor system <NUM> may include a photoelectric sensor that senses the presence of a part such as the pin <NUM>. For example, a through-beam photoelectric sensor may be arranged so that the pin <NUM> is located within the line-of-sight of the receiver, blocking the light beam from reaching the receiver. When the pin <NUM> is broken or missing, the beam of light may extend from the transmitter to the receiver, sending a signal to the controller <NUM>.

In some implementations, the sensing devices <NUM> may include proximity sensors. The proximity sensors may be optical proximity sensors that detect the presence or absence of the pin <NUM>. The proximity sensors may also use inductance or capacitance to detect the presence or absence of the pin <NUM>, based on the material of the pin (e.g. metal).

The sensor system <NUM> may also include a combination of different sensing devices. For example, a camera may be used to check for scratches, while an induction or capacitive proximity sensor detects the presence of the pin <NUM>.

When the sensor system <NUM> detects a defect in the core <NUM>, the core <NUM> can be switched before defects occur in the molded parts. Referring to <FIG>, an automated core changer system <NUM> includes a mover <NUM>, a rack <NUM>, and a controller <NUM>. In <FIG>, the mover <NUM> is schematically illustrated as a pair of jaws that grip the clamping section <NUM> of the core <NUM>, for example, the peripheral groove <NUM>. When the injection mold <NUM> is in its open state, the controller <NUM> may send signal to the mover <NUM> to begin the core change operation. Although the controller <NUM> is illustrated separately from the controller <NUM> of the sensor system <NUM>, they may also be one and the same, i.e. the sensor system <NUM> is optionally incorporated into the core changer system <NUM>. The controller <NUM> may be a standalone device that is separate from the control system (not shown) for the injection molding machine, making it possible to retrofit the core changer system <NUM> to an existing injection molding machine. However, it is also conceivable that the injection molding machine's control system also implements the control operations for the core changer system <NUM>, the sensor system <NUM>, or both.

The controller <NUM> may then control the mover <NUM> to engage the clamping section <NUM> of the core <NUM> installed in the core section <NUM> of the injection mold <NUM>. The mover <NUM> then loosens the installed core <NUM> by an appropriate movement, e.g., gently twisting or pulling the core away from the core section <NUM>.

After initially loosening the core <NUM> to avoid damage to the core section <NUM>, the mover <NUM> moves the used core to the rack <NUM>. In the illustrated example, the rack <NUM> has a plurality of slots 208a-208c that each hold a core 34a-34c. Although the cores 34a-34c are shown to be identical, the rack <NUM> may hold differently shaped cores, and the core changer system <NUM> is used to automatically change the cores and thus the shape of the mold cavities.

After depositing the used core in an appropriate slot <NUM>, the mover <NUM> then moves to a different slot <NUM> to retrieve an undamaged core <NUM>. For this purpose, the controller <NUM> may be communicatively coupled to the rack <NUM>. Alternatively, the mover <NUM> may communicate the positions of the damaged and undamaged cores to the controller <NUM> without the rack <NUM> being communicatively coupled to the controller <NUM>.

The mover <NUM> guides the tip <NUM> of the core through a passage formed by the conical surface <NUM> in the first holder plate <NUM> and a cylindrical opening <NUM> in the second holder plate <NUM>. Once the conical centering surface <NUM> of the core <NUM> and the surface <NUM> of the first holder plate <NUM> engage, the core <NUM> and the first holder plate <NUM> are centered. At this point, the jaws of the mover <NUM> may release the core's clamping section <NUM>, and the core clamp <NUM> engages the clamping section <NUM> to keep the core <NUM> in place. As described, the mover <NUM> forms an automated core changing tool.

Once the core clamp <NUM> engages the core's clamping section <NUM>, the controller <NUM> may send a signal to a controller of an injection molding machine (not shown) that the injection mold <NUM> is ready for use.

Although the core changer system <NUM> is described in relation to the core design illustrated on the implementations of <FIG>, the core changer system <NUM> can be used with any type of core that has a clamping section that can be gripped by the mover <NUM>. For example, the mover <NUM> may include a magnet or vacuum suction device that engages the clamping section of a core. Furthermore, although the mover <NUM> and the core clamp <NUM> are illustrated as separate parts in <FIG>, in some implementations, the core clamp <NUM> may also form the mover <NUM> for the core changer system <NUM>.

The described core changer system may automatically switch the core in an injection mold and automatically render it fit for use. In some implementations, the core may be switched after a predetermined number of injection mold cycles. For example, the controller of an injection molding machine may send a signal (e.g. a core change signal) to the controller <NUM> to instigate the core switching process. In some implementations, the core may be switched in response to a signal provided by the controller <NUM> of the sensor system <NUM>. In both implementations, the core switching process may minimize defects in subsequent molded parts by providing a new and intact core in the injection mold.

In some implementations, the core switching process may be instigated based on the number of production cycles and in response to input from the sensor system. Some implementations may be configured to generally instigate the core switching process after a particular number of molding cycles. Once the pre-determined number of cycles has been reached, sensor input may be used to determine whether to trigger a core change. For example, if a camera continues to capture image data of a scratch-free or intact core, the system may be configured to postpone the core switching process.

Referring to <FIG>, a schematic overview of a method <NUM> of automatically changing an injection mold core in an injection molding machine is shown. At <NUM>, a core is disconnected from an injection mold using a gripper in response to a core change signal and depositing the disconnected core. At <NUM>, a replacement core is retrieved, also using the gripper. For example, the replacement core may have the same structure as the core that was disconnected from the injection mold. At <NUM>, the gripper is used to connect the replacement core to the injection mold. At <NUM>, an enable signal is sent to a controller of the injection molding machine. The enable signal communicates to the controller of the injection molding machine that the mold core has been replaced and the injection molding process can restart. By automatically changing one of the parts of the injection mold that is most susceptible to wear, the method may reduce the overall downtime of the injection mold and improve the efficiency of the molding process.

According to different implementations, the core change signal may originate from different sources. For example, the core change signal may be received from the controller of the injection molding machine based on a number of molding cycles. Some implementations of the method use a sensing device to detect whether the core connected to the injection mold is intact (e.g. whether part of the core is missing), and the core change signal is based on this detection. In some implementations, a different sensing device may be used to detect scratches, dents, or cracks, and the core change signal is based on the detection of the core's scratches, dents, or cracks. Similarly, a sensing device may be used to quality test for scratches or defects on the parts molded by the injection mold, and the core change signal may be based on this quality control of the molded parts.

In some implementations, the method may include multiple forms of quality control that are performed after every molding cycle, and the core change signal may be obtained based on the combined input of the multiple sensing devices. For example, a first sensing device may sense an irregularity on a part of a mold core, and a second sensing device may show that the irregularity does not have an impact on the molded parts. In such a case, the input of the second sensing device may be used to override the first sensing device to avoid a premature core switching operation. In other cases, one input may override the other input and instigate a core changing operation. For example, the number of injection molding cycles may be below a predetermined threshold that triggers a core change signal, but input from a sensing device that detects a defect on the molded part may nonetheless trigger the core change signal.

Although the illustrated implementations show a single mold cavity and a single mold core, the general concept may be implemented for an injection mold that includes multiple mold cavities and multiple cores that are changed as described above.

Claim 1:
A system (<NUM>) for an injection mold (<NUM>) comprising:
a gripper (<NUM>);
a holder (<NUM>) that comprises a plurality of slots (208a-208c), each configured to hold a mold core (<NUM>, 34a-c);
a controller (<NUM>) configured to control the gripper (<NUM>) in response to receiving a core change signal to
disassemble a core (34a) from the injection mold (<NUM>),
deposit the disassembled core (34a) in one of the plurality of slots (208a-208c) of the holder (<NUM>),
retrieve a core (34b, 34c) stored in a different one of the plurality of slots (208a-208c) of the holder (<NUM>), and
connect the core (34b, 34c) to the injection mold (<NUM>), characterized in
a sensing device (<NUM>) configured to sense a property of the mold core (<NUM>, 34a-c) assembled in the injection mold (<NUM>), wherein the core change signal is generated in response to a sensor signal.