Self-sufficient sequential locking device for injection molding tool

Embodiments of the invention provide a self-sufficient sequential locking device and an injection molding tool. The self-sufficient sequential locking device comprises an elongate body having two ends which are provided with first and second inner engagement elements respectively; first and second outer engagement elements selectably engageable with the first and second inner engagement elements respectively for alternatively establishing a first or a second connection by rotation of the elongate body between a first position in which the first connection is secured and the second connection is simultaneously releasable, and a second position in which the second connection is secured and the first connection is simultaneously releasable, and first and second locking element respectively cooperable with the first and second inner engagement element for securing the first connection when the elongate body is in the first position or the second connection when the elongate body is in the second position.

FIELD OF INVENTION

The invention generally relates to injection molding, especially a self-sufficient sequential locking device which is able to secure/release different parting lines/layers/surfaces (hereinafter referred to as “parting lines”) of an injection molding tool according to a predetermined sequence without the need for external actuator or controller.

BACKGROUND

Injection molding using sequential technology is also named as Tandem technology which requires an exclusive sequential locking device/latch for alternately securing or releasing two parting lines of the injection molding tool in sequence to increase productivity of injection molding processes.

However, the existing locking devices/latches for injection molding tool require external actuators or controllers for their operation, e.g. a hydraulic system, or an air pressurized system, which not only significantly increase the manufacturing, installation and/or operating costs of the locking device and the injection molding tool, but also may cause some other problems/constraints relating to manufacturing or operation of the injection molding tool.

In a first example of an existing locking device, a hydraulic system is used to activate the sequence of the locking latch. The hydraulic system may be a subsystem from an injection molding tool incorporating the locking device or an external hydraulic generator. However, hydraulic system may not be suitable for production of plastic parts dedicated to medical devices which have to be contamination-free. As hydraulic system requires use of oil, this could contaminate the produced plastic parts and thereby rendering the produced parts unsuitable for medical usage.

In a second example, an air pressurized system is used to activate the sequence of the locking device. However, production room pressure is typically at six bars, and this would impose a constraint on the power generated by the air pressurized system. To increase the power generated by the air pressurized system, piston diameter may be increased or multiple cylinders may have to be installed in the sequential molding tool. Either way, there would be a substantial increase in the size or height of the sequential molding tool incorporating the locking device.

In a third example as illustrated in UK patent GB 2470285 B, to activate the sequential molding tool, a double locking device is used to generate a movement in a perpendicular direction to the opening of the sequential molding tool such that one side of the device is released and at the same time, the other side is secured. A simple pneumatic device may be used in this solution since it requires less pressure from the piston. However, as the double locking device has to be installed on the external side of the sequential molding tool, the double locking device tends to cover the whole central area of the sequential molding tool, which removes the possibility of adding all the cooling input and output suitable for the sequential tool and restraining perfect optimization of the cycle time in some circumstances.

In a fourth example, an electro-magnetic latch is used to activate the sequential molding tool. This solution removes the need for oil associated with a standard hydraulic system. However, as the heat generated by the electromagnets would cause unexpected thermal expansion, insulators and possibly extra cooling channels would be required to isolate other parts of the sequential tool from the electromagnetic latch. This would inevitably increase the size of the sequential molding tool if thick plates are used as insulators or cooling channels.

It is therefore desirable to provide a self-sufficient sequential locking device for an injection molding tool, which addresses the above and other problems.

SUMMARY OF INVENTION

Embodiments of the invention provide an entirely mechanical self-sufficient sequential locking device which is suitable for an injection molding tool, e.g. a sequential molding tool or an overmolding tool. The sequential locking device is configured to practise an alternating sequence of locking and unlocking (securing and releasing) at each side of the device such that one side is locked while the other side is simultaneously unlocked. This alternating securing and releasing of two sides of the sequential locking device is actuated by mechanical engagement or disengagement of its own components instead of an additional actuator. When the sequential locking device is used in an injection molding tool, the mechanical engagement/cooperation in the sequential locking device for actuating alternating securing and releasing of two sides of the sequential locking device is solely actuated by alternating securing and releasing of two side portions in the injection molding tool, without requiring any external control.

According to a first aspect of the invention, a self-sufficient sequential locking device is provided. The self-sufficient sequential locking device comprises:an elongate body having two ends which are provided with a first and a second inner engagement element respectively;a first and a second outer engagement element selectably engageable with the first and second inner engagement elements respectively for alternatively establishing a first or a second connection by moving the elongate body between a first position in which the first connection is secured and the second connection is simultaneously releasable, and a second position in which the second connection is secured and the first connection is simultaneously releasable, anda first locking element cooperable with the first inner engagement element for securing the first connection when the elongate body is in the first position and a second locking element cooperable with the second inner engagement element for securing the second connection when the elongate body is in the second positionwherein the moving of the elongate body between the first and the second position is mechanically actuated by engagement of the first outer with the first inner engagement element or the second outer with the second inner engagement element.

In one embodiment of the first aspect wherein the sequential locking device is incorporated in an injection molding tool, engagement of the first outer with the first inner engagement element or the second outer with the second inner engagement element to alternatively establish the first or the second connection, is solely actuated by alternating securing and releasing of parting lines in the injection molding tool.

Further, the cooperation of the first locking element with the first inner engagement element or the second locking element with the second inner engagement element to alternatively secure the first or the second connection is solely actuated by alternating securing and releasing of parting lines in the injection molding tool.

According to a second aspect of the invention, an injection molding tool is provided. The injection molding tool comprises a central portion, first and second side portions releasably coupled to the central portion; anda self-sufficient sequential locking device as mentioned above,wherein the elongate body of the locking device is incorporated at the central portion of the injection molding tool, the first outer engagement element and the first locking element of the locking device are incorporated at the first side portion; and the second outer engagement element and the second locking element of the locking device are incorporated at the second side portion,wherein when the elongate body is in a first position, the first connection is secured by the first locking element such that the first side portion is locked to the central portion, while the second connection is releasable such that the second side portion is releasable from the central portion; andwhen the elongate body is in the second position, the first connection is releasable such that the first side portion is releasable from the central portion, while the second connection is secured by the second locking element such that the second side portion is locked to the central portion.

In one embodiment of the second aspect, the injection molding tool is a sequential molding tool.

In another embodiment of the second aspect, the injection molding tool is an overmolding tool, wherein the central portion includes a core plate of the overmolding tool, the first side portion includes a back plate and a spacer plate which is remote from the central portion, and the second side portion includes a cavity plate.

According to a third aspect of the invention, a method for sequentially locking first and second side portions of an injection molding tool to an central portion thereof is provided. The method comprises:using alternating securing and releasing of the first and second side portions of the injection molding tool,engaging, in alternating sequence, the first outer engagement element with the first inner engagement element to establish the first connection, and the second outer engagement element with the second inner engagement element to establish the second connection, by moving the elongate body between the first position and the second position; and cooperating, the first locking element with the first inner engagement to secure the first connection when the elongate body is in the first position, and cooperating the second locking element with the second inner engagement to secure the second connection when the elongate body is in the second position.

According to a fourth aspect of the invention, a method for installing a self-sufficient sequential locking device to an injection molding tool which includes a central portion, and a first and a second side portion releasably coupled to the central portion is provided. The method comprises:incorporating an elongate body of the locking device at the central portion of the injection molding tool;incorporating a first outer engagement element and a first locking element of the locking device at the first side portion; andincorporating a second outer engagement element and a second locking element of the locking device at the second side portion, such thatalternating securing and releasing of the first and second side portions in the injection molding tool actuates engagement of a first outer with a first inner engagement element or a second outer with a second inner engagement element to alternatively establish a first or a second connection, and cooperation of the first locking element with the first inner engagement element or the second locking element with the second inner engagement element to alternatively secures the first or the second connection.

As the self-sufficient sequential locking device is an entirely mechanical system without the need for any additional activator or controller, the above-identified problems faced by existing locking devices/latches will be solved. Specifically, the manufacturing, operating and installation cost of the sequential locking device and/or the injection molding tool will be greatly reduced. Accordingly, production costs (for producing injected plastic parts) by such injection molding tools will be reduced. Further, the sequential locking device is suitable for producing components of medical devices since no hydraulic system is required to activate the locking device and therefore no oil contamination will be introduced to the manufactured articles. Furthermore, the size of the sequential molding tool will not be substantially increased, and the installation of the injection molding tool is simplified since no external activator or control is required. Also, the operation of the injection molding tool will become easier as no configuration parameters need to be pre-defined and pre-set during installation or adjusted during operation thereof.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

In the following description, numerous specific details are set forth in order to provide a thorough understanding of various illustrative embodiments of the invention. It will be understood, however, to one skilled in the art, that embodiments of the invention may be practiced without some or all of these specific details. It is understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to limit the scope of the invention. In the drawings, like reference numerals refer to same or similar functionalities or features throughout the several views.

Self-Sufficient Sequential Locking Device

Structure of Self-Sufficient Locking Device

FIG.1is a full isometric view of a self-sufficient sequential locking device10according to one embodiment of the invention.FIG.2Ais a sectional view of the self-sufficient sequential locking device10inFIG.1.FIGS.2B and2Care isometric views of the locking device10and illustrate the detailed structure of the locking device10and sequential operation of the locking device10. The structure of the sequential locking device10will be described in detail below referring toFIGS.1, and2A to2C.

Referring toFIGS.1and2A, in this embodiment, the sequential locking device10includes left and right outer engagement elements100aand100b, a shaft200, left and right inner engagement elements300aand300b, and left and right locking elements330aand330b. As shown inFIG.2A, the left and right inner engagement elements300aand300bare attached to the shaft200by screws310aand310brespectively to form an elongate body. It should be noted that in some other embodiments, the elongate body may be an integrally formed component, i.e. the shaft200is integrally formed with the left and inner engagement elements300aand300b, or the left and right inner engagement elements300aand300bare attached to the shaft200by other suitable attachment means.

To realize the self-sufficient sequential operation of the locking device10, the left and right outer engagement elements100aand100bare configured to alternately engage with the left and right inner engagement elements300aand300brespectively to trigger a movement, e.g. rotation, of the elongate body between a first position and a second position. When the elongate body is in the first position, a left connection between the left outer engagement element100aand the left inner engagement element300ais established and secured, while a right connection between the right outer engagement element100band the right inner engagement element300bis releasable; and when the elongate body is in the second position, the right connection is established and secured, while the left connection is simultaneously releasable.

Referring toFIGS.2A and2B, in this embodiment, each of the left and right outer engagement elements100a/100bincludes a tubular structure, an engagement means120a/120band fixed stoppers (103a,104a)/(103b,104b). The engagement means120a/120band the fixed stoppers (103a,104a)/(103b,104b) are provided on an inner surface of the tubular structure of the corresponding outer engagement element100a/100b. The engagement means120a/120bin this embodiment includes a projection member and a resilient means121a/121b, e.g. a spring. The resilient means121a/121bbiases the projection member to abut against the inner engagement element300a/300bwhen the inner engagement element300a/300bis received by the outer engagement element100a/100b.

Referring toFIGS.2B and2C, each of the left and right inner engagement elements300aand300bincludes a tubular structure and a pair of self-retracting stoppers (320a,321a)/(320b,321b) provided thereon. On the outer surface of the tubular structure of each inner engagement element300a/300b, there are provided a straight groove301and a helicoidal groove302fluidly coupled to the straight groove301through a circular groove303.

The engagement means120a/120bprovided on the outer engagement element100a/100bis biased by the resilient means to abut against the helicoidal groove302on the inner engagement element300a/300b, and adapted to engage with/move along the helicoidal groove302to rotate the elongate body between the first position and the second position such that the left connection and the right connection are secured in alternating sequence. The engagement means120a/120bis also adapted to engage with/move along the straight groove on the inner engagement element300a/300bfor releasing the left or right connection in accordance with the alternating sequence.

Referring toFIGS.2A to2C, the left and right locking elements330aand300bare releasably cooperable with/insertable into the left and right inner engagement elements300aand300brespectively for securing the left connection when the elongate body is in the first position and securing the right connection when the elongate body is in the second position. In this embodiment, each of the left and right locking elements330a/330bincludes an insertion portion and a resilient means331a/331bfor biasing the insertion portion into a corresponding inner engagement element300a/300bto secure the first or second connection.

When the elongate body is in the first position (referring toFIG.2B(1)), the left locking element330ais inserted into the tubular structure of the left inner engagement element300ato prevent the retraction of the self-retracting stoppers (320a,321a). Thus, the left connection is secured by the engagement of the self-retracting stoppers (320a,321a) with the fixed stopper (103a,104a). Similarly, when the elongate body is in the second position (referring toFIG.2B(4)), the right locking element330bis inserted into the tubular structure of the right inner engagement element300bto prevent the retraction of the self-retracting stoppers (320b,321b). Thus, the right connection is secured by the engagement of the self-retracting stoppers (320b,321b) with the fixed stopper (103b,104b).

Referring toFIG.1orFIGS.2A to2B, the locking device10may further include a manual rotation activator202provided on the shaft200. With this manual rotation activator202, the elongate body of the locking device10may be manually rotated. Further, both the right and left connection of the locking device10may be secured simultaneously by manually operating the manual rotation activator202to prevent releasing of any connection during installation or transportation of the locking device10, or for any other purposes.

Sequential Operation of Self-Sufficient Locking Device

For explanation of the sequential operation of the locking device10, it is assumed that in this embodiment as shown inFIG.2B(1), the initial position of the elongate body is in the first position and the initial position of the locking device10is in “Position D-A”. In “Position D-A”, the left side of the locking device10is in position D and the right side of the locking device10is in position A as shown inFIG.2C(1). When the left side is in position D, the left connection between the left outer engagement element100aand the left inner engagement element300ais secured by engagement of self-retracting stoppers (320a,321a) with the fixed stoppers (103a,104a). When the right side is in position A, the engagement means120bis ready to move along the straight groove, and the self-retracting stoppers (320b,321b) are not engageable with the fixed stoppers (103b,104b) due to their relative positional relationship such that the right connection is releasable.

In the first step of the sequential operation, as shown inFIG.2B(2), the locking device10moves from “Position D-A” to “Position D-B”. In “Position D-B”, the elongate body is kept in the first position and the left side of the locking device10is kept in position D, while the right side of the locking device10moves to position B as shown inFIG.2C(2), in which the right connection between the right outer engagement element100band the right inner engagement element300bis released, i.e. the right outer engagement element100bis disengaged from the right inner engagement element300b.

In the second step of the sequential operation, as shown inFIG.2B(3), the locking device10moves from “Position D-B” to “Position D-C”. In “Position D-C”, the left side of the locking device10is kept in position D, while the right side of the locking device10moves to position C as shown inFIG.2C(3), in which the right outer engagement element100bstarts to engage with the right inner engagement element300b, i.e. move along the helicoidal groove on the right inner engagement element300b, to trigger rotation of the elongate body from the first position to the second position.

In the third step of the sequential operation, as shown inFIG.2B(4), the locking device10moves from “Position D-C” to “Position A-D”. In “Position A-D”, the elongate body is rotated about 90 degrees from the first position to the second position, the left side of the locking device10moves to position A and the right side of the locking device10moves to position D as shown inFIG.2C(4). When the left side is in position A, the engagement means120ais ready to move along the straight groove, and the self-retracting stoppers (320a,321a) are not engageable with the fixed stopper (103a,104a) due to their relative positional relationship. Thus, the left connection between the left outer engagement element100aand the left inner engagement element300ais releasable. When the right side of the locking device10is in position D, the right connection between the right outer engagement element100band right inner engagement element300bis secured by engagement of the self-retracting stoppers (320b,321b) with the fixed stopper (103b,104b).

In the fourth step of the sequential operation, as shown inFIG.2B(5), the locking device10moves from “Position A-D” to “Position B-D”. In “Position B-D”, the elongate body is kept in the second position and the right side of the locking device10is kept in position D, while the left side moves to position B, in which the left connection between the left outer engagement element100aand the left inner engagement element300ais released, i.e. the left outer engagement element100ais disengaged from the left inner engagement element300a.

In this embodiment, the fixed stoppers (103a,104a)/(103b,104b) provided on the inner surface of the outer engagement element100a/100binclude a recess-protrusion structure as shown inFIG.2DandFIG.2E(1)-(4).FIG.2Dprovides front views of the locking device10and illustrates the left side of the locking device10in position A and position D to clearly show the relative positional relationship between the self-retracting stoppers (320a321a) and the fixed stoppers (103a,104a).

When the locking device10is in position A, the self-retracting stoppers (320a321a) are aligned with the recesses (101a,102a), i.e. not receivable into the recesses (101a,102a) and thereby are not engageable with the fixed stoppers (103a,104a). As this prevents disengagement of the left outer engagement element100afrom the left inner engagement element300a, the left connection is thus releasable in position A. When the locking device10is in position D, the self-retracting stoppers (320a,321a) are rotated to be perpendicular to the recesses (101a,102a) such that the self-retracting stoppers (320a,321a) are extendable therein and engageable with the fixed stoppers (103a,104a). As this prevents disengagement of the left outer engagement element100afrom the left inner engagement element300a, the left connection is thus secured.

Referring toFIG.2E(1) to (4), the right side of the locking device10is taken as an example to explain the cooperation of the locking element300a/300bwith the inner engagement element300a/300b. In this example, the locking element330bincludes an insertion portion having a front part, middle part and an end part, and the resilient means331b, e.g. a spring. The inner engagement element300bincludes a tubular structure which provides a channel for receiving the inserted locking element as well as the self-retracting stopper (320b,321b) provided on the tubular structure.

When the right side is in position A, the elongate body is in the first position in which the right connection between the right outer engagement element100band the right inner engagement element300bis releasable. Referring toFIG.2E(1), in this position, the locking element330bis completely received into the channel of the right inner engagement element300. The self-retracting stopper320bis in an extended state and aligned with the corresponding recess101b, i.e. not receivable into the recess101b, thereby the self-retracting stopper320bis not engageable with the corresponding fixed stopper103b. Accordingly, the right connection between the right outer engagement element100band the right inner engagement element300bis ready to be released.

In position B shown inFIG.2E(2), the right outer engagement element100bis disengaged from the right inner engagement element300b.

Position C inFIG.2E(3) shows that the right outer engagement element100bstarts to engage with the right inner engagement element300balong the helicoidal groove302to establish the right connection and trigger rotation of the elongate body from the first position to the second position. During this process, the extension of the self-retracting stopper320bis constrained by the fixed stopper103bthereby allowing only part of the right locking element330bto be inserted into the right inner engagement element300bsuch that the resilient element331bis in a compressed state.

When the right side of the locking device10is in position D shown inFIG.2E(4), the self-retracting stopper320bis received into the recess101b, which allows for further extension of the self-retracting stopper320b. Thus, the insertion portion of the right locking element330bis biased by the resilient element331bto further insert into the right inner engagement element300band the self-retracting stopper320bis further pushed into the recess101bsuch that the extended self-retracting stopper320bis engaged with the fixed stopper103bto secure the right connection.

Sequential Molding Tool Including a Self-Sufficient Sequential Locking Device

FIG.3shows a partial sectional view of a sequential molding tool01including a self-sufficient sequential locking device10according to a first embodiment of the invention. In this embodiment, the self-sufficient sequential locking device10is used in a sequential injection molding process.

As shown inFIG.3, the sequential molding tool01includes a central portion30, left and right side portions20and40, and a self-sufficient sequential locking device10. The elongate body of the locking device10is provided at the central portion of the molding tool01; the left outer engagement element and left locking element of the locking device10are provided at left side portion20; and the right outer engagement element and right locking element of the locking device10are provided at the right side portion40.

A first layer of the molding tool01is defined as the parting line between the left side portion20and the central portion30, and the second layer is defined as the parting line between the central portion30and the right side portion40. When the elongate body of the locking device10is in a first position, the left side of the locking device10secures the first layer, i.e. the left side portion20is locked to the central portion30, while the second layer is releasable, i.e. the right side portion40is releasable from the central portion30. When the elongate body is in a second position, the first layer is releasable, i.e. the left side portion20is releasable from the central portion30, while the right side of the locking device10secures the second layer, i.e. the right side portion40is locked to the central portion30.

The left side portion20further includes a guide bush first layer09assembly inserted inside the core plate first layer02, and the right side portion40includes a guide bush second layer06inserted inside the core plate second layer05. The central portion30includes guide pin second layer07and guide pin first layer08assembly in their respective cavity plate second layer04and cavity plate first layer03. As it is well known, these guiding components are mounted on the sequential molding tool01to guide movements of the side portions20and40relative to the central portion30along a predetermined direction and to constrain or prevent movements of the side portions20and40along other directions. Also, these guiding components are used to securely attach the central portion30on the sequential molding tool01to prevent the central portion30from floating and falling away from the sequential molding tool01.

At the central portion30, the sequential molding tool01is further provided with a tool access opening50which is aligned with the manual rotation activator202provided on the shaft200of the sequential locking device10to allow manual control of shaft rotation.

The manual rotation activator202may be operated by a simple device such as a screwdriver or lever to control rotation of the shaft200. Thus, the user can manually control securing and releasing of the two side portions of the sequential molding tool01. As any repetitive lifting action on a self-sufficient sequential locking device10in a sequential molding tool01from top to bottom or vice versa will invert the releasable layer and the secured layer of the locking device10, it is necessary to ensure the securement of each part of the sequential molding tool01by the manual rotation activator202during such lifting actions or transportation to prevent accidental release or dropping of any part of the molding tool01.

In a sequential molding tool01which is installed with multiple self-sufficient locking devices10, the user can control the rotation of each shaft200through a manual rotation activator provided on each of the locking devices10. To safely transport, displace or dismantle a sequential molding tool which incorporates these sequential locking devices10, the whole sequential molding tool01must be secured completely, which may be realized by only rotating one of the manual rotation activators in the molding tool01, i.e. by inverting the releasable layer and the secured layer of only one of the locking devices10. Of course, to further improve the safety for transportation, displacement and dismantlement of the sequential molding tool, it is preferable to rotate more than one manual rotation activator in the molding tool in case any one of the rotated manual rotation activators becomes reactivated accidentally during transportation or dismantling of the sequential molding tool.

In an example, referring toFIG.2A, the shaft200of the elongate body is rotatably coupled to the central portion30via left roller guiding device201aand right roller guiding device201b. The left and right roller guiding devices201aand201bare securely disposed within the central portion30by screws, and the left and right outer engagement elements100aand100bare securely disposed within the left and right side portions of the sequential molding tool01by the screws110aand110b. All the screws for fastening the sequential locking device10extend along an axial direction of the shaft200within the sequential molding tool01. As such, heads of the screws are not accessible unless the left and right side portions of the sequential molding tool10are in an opening state. Therefore, it could be not convenient to uninstall the locking device10from the sequential molding tool01.

To conveniently uninstall the locking device10from the sequential molding tool01, another installation method of the sequential locking device is provided. Referring toFIG.4, a left roller cover209aand a right roller cover209bare provided at the central portion30for covering and fixing the left and right roller guiding device201aand201brespectively. The left and right roller covers209aand209bare securely attached to a surface of the sequential molding tool01by their respective left roller cover screw210aand right roller cover screw210bwhich extend along a direction perpendicular to the surface of the sequential molding tool01and to the axial direction of the shaft200such that heads of the screws210aand210bare accessible anytime from outside of the sequential molding tool01. Similarly, the left and right outer engagement element100aand100bare covered and disposed within the left and right side portions20and40of the sequential molding tool01by a left and a right outer engagement element cover211aand211brespectively. The left and right outer engagement element covers211aand211bare securely attached to the surface of the sequential molding tool01via screws212aand212brespectively, wherein the screws212aand212bextend along a direction perpendicular to the surface of the sequential molding tool01and the axial direction of the shaft200.

In addition, a safety screw203is further provided to fix the shaft200to the central portion of the sequential molding tool10for further reinforcing the securement of the sequential molding tool01and thereby preventing any accidental rotation of the shaft200during lifting or transporting of the sequential molding tool01.

FIG.5is a partial sectional view of a sequential molding tool01as shown inFIG.3. The cavity plate thickness206inFIG.5refers to a cumulative width of the cavity plate first layer03and cavity plate second layer04. As it is well known, both the cavity plate first layer03and cavity plate second layer04include hot runner systems, which are used to control the balancing of the flow of the resin during the injection phase. To perform this task, the hot runner systems are required to be maintained at an appropriate temperature, in which balancing of each injection nozzles will be independently adjusted. However, the temperature of the hot runner systems could increase by contact and radiance from the heat of its surrounding area, which could cause an increase of the cavity plate thickness206.

To solve this problem, a few cooling channels are provided inside both cavity plate first layer03and cavity plate second layer04, which can re-adjust the temperature to conform to the requirement of the resin, typically equivalent to a neutral temperature.

However, the temperature of a hot runner system may reach a high value when the resin is injected inside the sequential molding tool01, and the cooling process can require temperatures higher than eighty (80) degrees Celsius, which may cause thermal expansion incompatible with any adjacent mechanical parts in the sequential molding tool01. To prevent this unexpected thermal expansion, a left insulator204aand a right insulator204bcould be provided in the sequential molding tool01for shielding the left roller cover201aand right roller cover201brespectively from thermal expansion. Accordingly, the shaft200is also insulated from thermal expansion by being not in contact with both cavity plate first layer03and cavity plate second layer04. To further adequately control thermal expansion, two small clearances are provided at the axial contact area with both left insulator204aand right insulator204b. The requested value of the left gap205aand right gap205bwould be determined based on the basic calculation referring to the differential temperature between both cavity plate first layer03and cavity plate second layer04and the ambient temperature of the self-sufficient sequential device10.

Overmolding Tool Including a Self-Sufficient Overmold Latch

In the above embodiments, the self-sufficient sequential locking device10is used in sequential or tandem injection molding process, however, in the second embodiment of the invention, it will be explained that the self-sufficient sequential locking device can also be applied to an overmolding process.

As it is well known, an over-molding process requires the installation of at least one insert inside the overmolding tool before proceeding with the sequence of injection molding, and a typical moment selected to feed the mold with this insert is generally after the ejection of the over-molded product from the overmolding tool. It would be easy to understand that such sequences are time-consuming given that this feeding will require an additional time during an open/close session in the overmolding process.

Furthermore, it will be explained below how a double layer can be used to re-root the overmolding process during a cooling time to introduce at least one new insert inside the overmolding tool.

FIGS.6A-6Dare sectional views of an overmolding tool900in four different positions in an overmolding process according to the second embodiment of the invention. Referring to theFIGS.6A to6D, the overmolding tool900includes:a moldbase having four plates: spacer plate901, back plate902, core plate903, and a cavity plate904;a self-sufficient overmold latch11provided in the moldbase;an ejection system including bottom ejector plate905, top ejector plate906and ejector pin910, a core940within a series of inserts including back insert920and next insert921, and an overmolded insert922provided inside an injected part930which is delimited by a cavity950on the right side of the overmolding tool900.

As shown inFIG.6A, the self-sufficient overmold latch11has similar structure and function as the self-sufficient sequential latch10. The elongate body of the latch11is provided at the core plate903which is the central portion of the overmolding tool900. The left outer engagement element and left locking element of the latch11are provided at the back plate902and the spacer plate901, which are the left side portion of the overmolding tool900, wherein the back plate902is adjacent to the core plate903while the spacer plate901is located remotely from the core plate903. The right outer engagement element and right locking element of the latch11are provided at the cavity plate904which is the right side portion of the overmolding tool900.

FIG.6Aillustrates a sectional view of the overmolding tool900at a closing station with the self-sufficient overmold latch11being in position A-D in which, the left layer between back plate902and core plate903is releasable/openable and the right layer between the core plate903and the cavity plate904is secured by the right side of the latch11. In closing station, the positions of the bottom ejector plate905and top ejector plate906are defined by two parameters: X defining a gap between the extreme left side of spacer plate901and the extreme left side of the bottom ejector plate905; and Y defining a gap between the extreme right side of the top ejector plate906and the extreme left side of the back plate902, i.e. maximum ejection stroke requested for ejecting the Part30. The dimension of X is exactly equal to the thickness of one insert.

FIG.6Billustrates a sectional view of the overmolding tool900in a loading station with a self-sufficient overmold latch11being in position B-D in which the left layer between back plate902and core plate903is opened and the right layer between core plate903and the cavity plate904is secured. It should be noted that the overmolding tool900reaches this position at the end of an injection holding stage during a cooling time for the injected part930to an acceptable release temperature. During this cooling time, the left layer is opened and the tool900is loaded with a new insert923on a backside of the core plate903using a conventional robot. In this position as shown inFIG.6B, the new inserts923are ready to join to both back insert920and next insert921located inside the core940. The injected part930and its overmolded insert922are still enclosed during this cooling stage by the cavity950. The other components on the top right side such as the core plate903within the double guide pin908, and the cavity plate904including its guide bush cavity plate909are still in the same secured position. The parameter X has been reduced to zero, accordingly the parameter Y is increased to Y+X, which is caused by a shift of the ejector pin910away from the core plate903at a value equal to the thickness of one insert.

FIG.6Cillustrates a sectional view of the overmolding tool900in a pre-opening station with a self-sufficient overmold latch11being in Position D-A, in which the left layer between back plate902and core plate903is secured and the right layer between core plate903and the cavity plate904is releasable/openable. It should be noted that the closing session of the left layer will activate the possibility to open the right layer.

In this position, the moldbase including the spacer plate901, the back plate902, the core plate903, and cavity plate904are again in a closing position. The double guide pin908realigns the left and right layers via the guide bush back plate907and the guide bush cavity plate909. The bottom ejector plate905and the top ejector plate906have been maintained in the same position as inFIG.6B. It will be easy to understand that during the closing session the ejector pin910pushed the new insert923to establish a perfect alignment with the back insert920and the next insert921, while the injected part930and its overmolded insert922are still enclosed between the core940and the cavity950and ready to be ejected from the tool900when a predetermined cooling time has been reached. It should be noted that during this ejection, the dimension Y+X will decrease to zero before being reinitialized to its initial value Y and resetting the dimension X.

FIG.6Dillustrates a sectional view of the overmolding tool900in a releasing station with the self-sufficient overmold latch11being in Position D-B in which the left layer between the back plate902and the core plate903is secured and the right layer between the core plate903and the cavity plate904is opened. In this position, two different sequences will be introduced: the first one is related to the injected part930and the overmolded insert922, and the second one is that the ejector plates move back to the initial positions. As shown inFIG.6D, in this position, the spacer plate901, the back plate902, and the core plate903are in closed position with the double guide pin908providing the realignment via the guide bush back plate907. The cavity plate904within the guide bush cavity plate909is now in opening session, i.e. the right connection of the self-sufficient overmold latch11is released. The injected part930within the overmolded insert922is now detached from the core940and the cavity950, and ready to fall on a conveyor or be evacuated by a robot arm. The bottom ejector plate905and top ejector plate906have moved back to their initial positions as represented by parameters X and Y. The ejector pin910has been shifted towards the core plate903during the ejection of the new insert923and the following back insert920and next insert921. It is to be understood that after the closing of the right layer of the overmolding tool900, the self-sufficient overmold latch11will be alternated again, and the overmolding tool900will be ready for a new injection phase as introduced inFIGS.6A to6D.

As will be appreciated from the above, embodiments of the invention provide an entirely mechanical self-sufficient sequential locking device, which can be applied to both sequential injection molding and overmolding processes. With this self-sufficient sequential locking device, two layers of an injection molding tool are configured to be closed and opened in an alternating sequence without the need for external actuator or controller, as the securing or release of two sides of the sequential locking device are mechanically actuated by the engagement or disengagement of the corresponding outer engagement element with the corresponding inner engagement element, and both the engagement of the corresponding outer and the corresponding inner engagement element, and the cooperation of the locking element with the corresponding inner engagement element are solely actuated by alternating securing and releasing of two side portions in the injection molding tool, without requiring external control. Since no external actuator or controller is required, the manufacturing, operating and installation costs of the sequential locking device and the injection molding tool will be significantly reduced. Accordingly, plastic parts can be produced by the injection molding tool at a lower cost. Further, as the sequential locking device is a completely mechanical system, the user/manufacturer does not need pre-defined, pre-set, or pre-adjusted configuration parameters during the installation or operation of the injection molding tool, and thus the setup and operating of the injection molding tool will become more predictable and simplified. In addition, the sequential locking device can be fully integrated into the sequential molding tool or overmolding tool without causing substantial change in the size of the injection molding tool.

It is to be understood that the embodiments and features described above should be considered as examples and not restrictive. Many other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the invention. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. Furthermore, certain terminology has been used for the purposes of descriptive clarity, and not to limit the disclosed embodiments of the invention.

TABLE OF REFERENCE NUMERALS IN DRAWINGS01Sequential Molding Tool02Core Plate First Layer03Cavity Plate First Layer04Cavity Plate Second Layer05Core Plate Second Layer06Guide Bush Second Layer07Guide Pin Second Layer08Guide Pin First Layer09Guide Bush First Layer10Self-Sufficient Sequential Locking device11Self-Sufficient Overmold Latch20Left Side Portion30Central Portion40Right Side Portion50Tool Access Opening100aLeft Outer Engagement Element100bRight Outer Engagement Element101aFirst Recess in Left Outer Engagement Element102aSecond Recess in Left Outer Engagement Element101bFirst Recess in Right Outer Engagement Element102bSecond recess in Right Outer Engagement Element103aFirst Fixed Stopper in Left Outer Engagement Element104aSecond Fixed Stopper in Outer Engagement Element103bFirst Fixed Stopper in Right Outer Engagement Element104bSecond Fixed Stopper in Right Outer Engagement Element110aScrew for Left Outer Engagement Element110bScrew for Right Outer Engagement Element120aLeft Engagement Means120bRight Engagement Means121aSpring of Left Engagement Means121bSpring of Right Engagement Means200Shaft201aLeft Roller Guiding Device201bRight Roller Guiding Device202Manual Rotation Activator203Safety Screw204aLeft Insulator204bRight Insulator205aLeft Gap205bRight Gap206Cavity Plates Thickness209aLeft Roller Cover209bRight Roller Cover210aLeft Roller Cover Screw210bRight Roller Cover Screw211aLeft Engagement Element Cover211bRight Engagement Element Cover212aLeft Engagement Element Cover Screw212bRight Engagement Element Cover Screw300aLeft Inner Engagement Element300bRight Inner Engagement Element301Straight Groove302Helicoid Groove303Circular Groove310aScrew for Left Inner Engagement Element310bScrew for Right Inner Engagement Element320aFirst self-retracting Stopperon Left Inner Engagement Element320bFirst self-retracting Stopper on Right Inner Engagement Element321aSecond self-retracting Stopper on Left Inner Engagement Element321bSecond self-retracting Stopper on Right Inner Engagement Element330aLeft Locking Element330bRight Locking Element331aSpring of Left Locking Element331bSpring of Right Locking Element900Overmolding Tool901Spacer Plate902Back Plate903Core Plate904Cavity Plate905Bottom Ejector Plate906Top Ejector Plate907Guide Bush Back Plate908Double Guide Pin909Guide Bush Cavity Plate910Ejector Pin920Back Insert921Next Insert922Overmolded Insert923New Insert930Injected Part940Core950Cavity