Decelerated ejector pin system and method for operating the same

A decelerated ejector pin system in an ejector half of an injection mold, that molds a molded part. The ejector half has at least one lifter, a core plate, a pin plate, an ejector bar, a base plate, and at least one ejector pin. The decelerated ejector pin system includes at least one further ejector pin to be moved and decelerated through the core plate. The decelerated ejector pin system has at least one sleeve that is actuated by the core plate for decelerating the further ejector pin. A spring is disposed in the ejector bar. At least one stop pin supports the further ejector pin and compresses the spring, and a cap attaches to the stop pin for pre-stressing the spring.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an apparatus for de-molding injection molded parts, more specifically, to an injection mold which requires lifters to de-mold the part, has a part cavity that is shallower than the lifter cavity detail depth, requires a controlled ejection due to the part geometry (i.e.: part texture or cavity depth), or has limited space in the ejection system. The invention also relates to a method for ejecting a part having an embedded ejector pin.

2. Description of the Related Art

It is prior-art practice, for example, in the case of injection molds, which use lifters to create desired part features, to use embedded ejector pins to hold a molded part stationary in the lifter de-molding axis. The embedded ejector pin allows the molded part to separate from the lifter. This practice has the disadvantage that the molded part is stuck to the embedded pin at the end of the ejection cycle. A molded part that is not ejected is very disadvantageous because it can lead to a disruption of the cycle, defective part(s) when the injection mold closes on the non-ejected part, and thus a lower productivity.

In order to deal with this problem several solutions have been proposed in the prior art. One solution is to use an air blow-off to blow the part off of the embedded ejector pin. This solution has the disadvantages that there is no control of the part when it is blown off and that air blow-offs generate dirt in the injection mold. Another solution is the use of a robot to remove the parts. This solution has the disadvantages of a large capital expense, longer cycle times, and additional maintenance costs. A third solution is to have an operator manually remove the parts. This solution has the disadvantages of inconsistent cycle times, longer cycle times, and additional labor costs.

Accordingly, prior art ejector systems have the disadvantages that they do not provide a satisfactory solution for removing an embedded ejector pin from a molded part.

SUMMARY OF THE INVENTION

It is accordingly an object of the invention to provide an ejector system and a method for ejecting a part having an embedded ejector pin which overcome the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which provides an ejector system for a mold requiring embedded ejector pins that is easily manufactured, easy to maintain, is durable, and reliable.

With the foregoing and other objects in view there is provided, in accordance with the invention in an ejector half of an injection mold, for molding a molded part. The ejector half has at least one lifter, a core plate, a pin plate, an ejector bar, a base plate, and at least one ejector pin. A decelerated ejector pin system includes at least one further ejector pin to be moved and decelerated through the core plate. At least one sleeve is actuated by the core plate for decelerating the further ejector pin. A spring is disposed in the ejector bar and at least one stop pin supports the further ejector pin and compresses the spring. A cap is attached to the stop pin for pre-stressing the spring.

In accordance with another feature of the invention, the further ejector pin has a head and a shaft. The sleeve has a head and is located on the shaft of the further ejector pin and a counter bore formed in the core plate actuates the sleeve by engaging the sleeve head.

In accordance with a further feature of the invention, the stop pin has a head and a shaft, the shaft of the stop pin is disposed inside the spring, and the head of the further ejector pin rests on the head of the stop pin for compressing the spring.

In accordance with an added feature of the invention, a screw attaches the cap to the stop pin.

In accordance with an additional feature of the invention the further ejector pin is longer than the at least one ejector pin.

With the objects of the invention in view, there is also provided in an injection mold having an ejector half for molding a molded part in an injection molding machine with ejector drive system. The ejector half, includes a core plate that has a cavity formed therein. A retainer plate is disposed adjacent the core plate. An ejector bar is disposed adjacent the retainer plate. A base plate is disposed adjacent the ejector bar. At least one ejection pin is mounted in the retainer plate and is moveable through the core plate. At least one lifter has a cavity detail forming a feature in the molded part and the lifter is moveable through the core plate. At least one further ejector pin is to be moved and decelerated through the core plate and projects into the cavity. At least one sleeve is actuated by the core plate for decelerating the further ejector pin. A spring is disposed in the ejector bar. At least one stop pin supports the further ejector pin and the stop pin is located inside the spring and compresses the spring. A cap is attached to the stop pin for pre-stressing the spring.

In accordance with yet another feature of the invention, the further ejector pin is longer than the at least one ejector pin.

In accordance with yet a further feature of the invention, the ejector pin and the further ejector pin are moveable through the core plate on an ejection axis.

In accordance with yet an added feature of the invention, the lifter is moveable through the core plate on an axis at an angle with respect to the ejection axis.

In accordance with yet an additional feature of the invention, the further ejector pin has a head and a shaft. The core plate has a counter bore formed therein. The sleeve has a head and is located on the shaft of the further ejector pin. The counter bore actuates the sleeve by engaging the sleeve head.

In accordance with still another feature of the invention, the stop pin has a head and a shaft. The shaft of the stop pin is disposed inside the spring. The head of the further ejector pin rests on the head of the stop pin and compresses the spring.

In accordance with still a further feature of the invention, a screw attaches the cap to the stop pin.

With the objects of the invention in view, there is also provided in an injection mold having an ejector half for molding a molded part in an injection molding machine with ejector drive system. The ejector half includes a core plate having a cavity formed therein. A retainer plate disposed adjacent the core plate. An ejector bar is disposed adjacent the retainer plate. A base plate disposed adjacent the ejector bar. At least one ejection pin is mounted in the retainer plate and is moveable through the core plate. At least one further ejector pin is to be moved and decelerated through the core plate and projects into the cavity. At least one sleeve is actuated by the core plate for decelerating the further ejector pin. A spring is disposed in the ejector bar. At least one stop pin supports the further ejector pin and compresses the spring. A cap is attached to the stop pin for pre-stressing the spring.

With the objects of the invention in view, there is also provided, a method of producing molded parts in an injection molding press during a cycle. The method includes providing an injection mold with an ejector half as described above. Clamping the injection mold and injecting material into the at least one cavity. Timing out a cooling stage of the cycle. Unclamping and opening the injection mold. Moving the ejector bar for ejecting the molded part from the injection mold. Decelerating the further ejector pin after the lifter cavity detail is de-molded from the molded part and de-molding the molded part from the further ejector pin.

In accordance with another mode of the invention, the material injected into the at least one cavity forms a part around the lifter cavity detail and the at least one further ejector pin.

In accordance with a further mode of the invention, a continuing movement of the ejector pins completely de-molds the at least one further ejector pin from the molded part and allows the molded part to be dropped clear of the injection mold.

With the objects of the invention in view, there is also provided, a method for ejecting a part from an injection mold having at least one embedded ejector pin. The method includes moving a plurality of ejector pins and the at least one embedded ejector pin through a core plate, and decelerating the at least one embedded ejector pin.

The prior art does not disclose a method for ejecting a part from an injection mold that has an embedded ejector, where one of the ejector pins is decelerated.

With the objects of the invention in view, there is also provided, a method for ejecting a part from an injection mold having at least one lifter with a cavity detail. The method includes embedding at least one ejector pin in the part, moving a plurality of other ejector pins and the at least one ejector pin through a core plate, and decelerating the at least one ejector pin.

The prior art does not disclose a method for ejecting a part from an injection mold that has a lifter with a cavity detail, where an embedded ejector pin is decelerated.

With the objects of the invention in view, there is also provided, a method for producing molded plastic parts in an injection molding machine during a cycle. The method includes providing an injection mold with an ejector half, a core plate, at least one cavity formed in the core plate, at least one lifter with a cavity lifter detail, ejector pins, and at least one further ejector pin projecting into the at least one cavity. Clamping the injection mold together and injecting material into the at least one cavity. Timing out a cooling stage of the cycle. Unclamping and opening the injection mold. Moving the ejector pins, the lifter, and the further ejector pin out of the core plate. The further ejector pin remains embedded in the part. Initiating a stopping of the further ejector pin, while the ejector pins continue to de-mold the part from the decelerated ejector pin. Further moving the ejectors for completely de-molding the further ejector pin from the molded part and allowing the molded part to be dropped clear of the injection mold.

In accordance with an additional mode of the invention, the further ejector pin holds the part and allows the lifter cavity detail to move along a lifter de-molding axis, while retracting from the molded part.

Although the invention is illustrated and described herein as embodied in a decelerated ejector pin system and a method of using the same, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the figures of the drawing in detail and first, particularly, toFIG. 1thereof, there is seen part of an ejector half41of an injection mold45(FIG. 11) according to the invention. The injection mold45can be used in any common injection-molding press (not illustrated) that properly corresponds to the size of the mold.

The ejector half41of the mold45includes a core plate or B-plate13, an ejector system40, and a bottom clamp plate or base plate16. The core plate13includes a molding cavity17, which has a depth C.

The ejector system40, is a mechanical assembly that is free to move relative to the ejector half41of the mold45and is actuated by the injection-molding press to de-mold at least one molded part22(FIG. 2). The ejector system40includes a pin plate or retainer plate14, an ejector bar15, at least one lifter11, ejector pins7, and at least one decelerated ejector pin system18(FIGS. 8 and 10). The term “decelerated” is used to indicated that when the “decelerated” ejector pin system18is initiated, a “decelerated” ejector pin5is mechanically stopped while the rest of the ejection assembly continues to move to complete the de-molding process.

The lifter11, a decelerated ejector pin or further ejector pin5, and the ejector pins7are mounted in the pin plate14and are actuated along an ejection axis E by the ejector bar15, which is actuated by an ejector system of the injection molding press, to eject the molded part22. The decelerated ejector pin5, and the ejector pins7slide through the core plate13, along the ejection axis E to eject the molded part22. The lifter11moves through the core plate at an angle α to the ejection axis E. The lifter11includes a cavity detail12that is molded into the molded part22. The cavity detail12has a depth D, which is the depth that the cavity detail12creates in the molded part22. As the press opens the mold and the lifter11moves out of the core plate13, the cavity detail12de-molds from the molded part22along a lifter de-molding axis A.

The decelerated ejector pin system18includes a decelerated ejector pin5with a head25and a shaft35. The decelerated pin5projects into the cavity17and is embedded into the molded part22to prevent the molded part22from moving along the lifter de-molding axis A. A sleeve6is provided on the ejector pin shaft35at the pin plate14. The sleeve6has a head26. A stop pin3is provided that has a head23and a shaft33. The decelerated ejector pin5is located on the head23of the stop pin3. The head23abuts a spring4that is located in the ejector bar15and held in place between the ejector bar15and the head23to pre-stress the stop pin3. The shaft33of the stop pin3is located inside the spring4. The stop pin3and the spring4are retained in the ejector bar15by a cap1and screw2.

As can be seen inFIG. 5the sleeve6mechanically stops the decelerated ejector pin5by making contact with a counter bore20provided in the core plate13. Alternatively, it is possible to eliminate the counter bore20if stroke limiters (not illustrated) are used in the mold45. The stroke limiters are required when the stroke needed to eject the part is less than the ejection stroke available. If stroke limiters are used to positively stop the pin plate14and the ejector bar15before they reach the core plate13the counter bore20can be eliminated.

The operation of the device during a molding cycle will be described with respect to the drawings and the above-provided description.

FIGS. 1 and 11show the ejector half41of the mold45in the initial stage or clamped position of the injection mold of the cycle. In the clamped position the injection mold45is ready to be injected with melted plastic material from the press for forming the part22.

FIG. 2shows that the injection mold45is still in the clamped position and the plastic material has been injected into the cavity17to form the part22. The clamped position is maintained until the part has cooled sufficiently to be ejected. It is shown in the enlargedFIG. 3, that after the injection of plastic material is completed, the decelerated pin5is embedded in the part22. Also, it is shown inFIG. 2that the plastic surrounds the cavity detail12of the lifter to create the desired part feature.

FIG. 4shows a first stage of ejection, initiated by the press, where the lifter and the ejectors begin to move out of the core plate13. The decelerated ejector pin5remains embedded in the part22, to hold the part on the decelerated ejector pin5, which allows the lifter cavity detail12to move along the lifter de-molding axis A, while de-molding from the molded part22.

FIG. 5shows a second stage of ejection where the lifter is completely de-molded from the part22and the deceleration of the decelerated ejector pin5is initiated. The sleeve6makes contact with the core plate13, which pushes down on the head25of the decelerated ejector pin5. The decelerated ejector pin5in turn presses down on the stop pin3, which compresses the spring4. The ejector pins7continue to move the part off of the decelerated ejector pin5, which is decelerated due to the compression of the spring4.FIG. 6shows an enlarged view of the initiation of the deceleration of the decelerated ejector pin5.

FIG. 7shows a third stage of ejection, where the ejectors7have continued to move and decelerated ejector pin5is completely de-molded from the molded part22. The spring4has been further compressed and the amount of deceleration P of the decelerated ejector pin can be seen.FIG. 8shows an enlarged view of the stop pin3compressing the spring4during the third stage of ejection.

FIG. 9shows that the momentum of the ejectors7has propelled the molded part22off of the ejectors7and the injection mold is ready to begin a new molding cycle.

FIG. 10also shows an enlarged view of the decelerated ejector pin system18returned back to its original state ready for the injection stage of the process.