Figure 6-56 shows a mold structure for accelerated ejection of a button product with an inverted inner side. After mold opening, lower ejector plate 6 and upper ejector plate 7 move together, driving central ejector pin 5 and two ejector pins 8 to eject product from mold core. At this time, plastic part is still tightly wrapped around central ejector pin 5. Ejection continues until rocker arm 4 contacts stop block 1, stopping its movement and rotating clockwise. This rotation lifts upper ejector plate 7 through ejector block 3, accelerating ejection of ejector pins 8 and forcefully removing plastic part from central ejector pin. This completes the entire ejection process.

 

Figure 6-56 Button Mold Diagram
1 - Stop Block; 2 - Hex Screw; 3 - Ejector Block; 4 - Rocker Arm; 5 - Center Ejector Pin; 6 - Lower Ejector Plate; 7 - Upper Ejector Plate; 8 - Ejector Pin.

For some irregularly shaped plastic parts, using a single fixed-stroke ejection during mold opening may not guarantee synchronous demolding of product. Product may easily deform or be difficult to eject. In this case, an additional ejection stroke is needed at specific locations (edges or rounded corners) of product to ensure synchronous ejection with irregularly shaped ejector pins. This additional ejection stroke requires one or more sets of (push rods, push plates) accelerated ejectors to add an ejection stroke and complete synchronous demolding of product. Accelerated ejection is a special ejection method different from secondary ejection. Main difference is that it overcomes ejection pause of secondary ejection, achieving synchronous accelerated ejection. Therefore, accelerated ejection can effectively shorten ejection time and ensure that product does not deform. Figure 6-57 shows a lever-type accelerated ejection with a single ejector pin. Note that in this design, diameter of accelerating ejector pin must not be less than 5mm.
When mold has deep ribs or requires a large demolding force, plastic part cannot completely detach from mold after a single ejection. Manual demolding or an additional ejection mechanism is needed, preventing automated injection molding. Using an accelerated ejection mechanism easily solves these problems without adding complex mold structures, such as a secondary ejector plate mechanism.

Principle of lever-type accelerated ejection is shown in Figure 6-57. Accelerating push rod shown in Figure 6-57(a) has a spring for return, resulting in less lateral force during ejection. Accelerating push rod shown in Figure (b) relies on a rotating block for return, resulting in greater lateral force during ejection. During ejection, limiting pin touches plate B, causing rotating block to rotate, thus accelerating accelerating push rod on its head forward to complete secondary ejection. After mold closing, spring-controlled ejector pin and rotating block return to their original positions. Because lever-type accelerated ejector pin bears lateral force during acceleration, its diameter cannot be too small; minimum diameter is 5mm, and most use ejector pins with a diameter of 6mm or more.

 

Figure 6-57 Lever-driven accelerated ejection
An example of lever-type accelerated ejection is shown in Figure 6-58. Plastic part is a capacitor shell, shaped like a rectangular shell, with decorative patterns requiring a fixed mold slider for core pulling. Internal edges have raised ribs requiring a lifter for demolding. Mold layout is 1 ejector pin and 2 ejectors, requiring fully automatic molding and automatic drop of plastic part. Ejection elements for plastic part are a lifter and a pusher pin. After ejection, capacitor shell becomes stuck on lifter and is difficult to remove, even with increased ejection stroke. In this mold, lifter stroke is limited, and it is necessary to avoid collision between two lifters. Therefore, an accelerated pusher pin 3 is designed to solve fully automatic ejection problem.
After mold opening, fixed mold's inclined slide block completes core pulling, and plastic part attaches to moving mold. Lifter and accelerator push rod 3 push plastic part out of core, while lifter simultaneously completes undercut demolding. After ejection stroke reaches 72.35mm, upper surface of rotating block 6 touches end face of accelerator limit rod 4, causing rotating block 6 to rotate counterclockwise, driving accelerator push rod 3 to accelerate ejection, thus demolding plastic part from lifter. Before mold closing, ejector insert 2 pulls the entire ejection system back to its original position. Support rod 7 touches inclined surface of rotating block 6, causing rotating block to rotate and reset.

 

Figure 6-58 Capacitor casing lever-type accelerated ejection
1-Ejection limit block; 2-Ejector insert; 3-Accelerating push rod; 4-Accelerating limit rod; 5-Pin; 6-Rotating block; 7-Support rod; 8-Pressure block; 9-Screw

Single push rod accelerated ejection mechanism uses a gear and rack rotation mechanism, providing an additional ejection stroke of more than 15.8mm. Utilizing simple linear motion, stroke and ejection speed of push rod, push rod core, and the entire ejection device are increased. During ejection and return, movement is smooth and without excessive impact force.
Figure 6-59(a) shows a rack and pinion type single push rod accelerated ejection, composed of an ejector housing, drive rack, ejection rack, push rod fixing nut, acceleration limit rod, reset screw, gear, torsion spring, and elastic retaining ring for hole. Ejection process is shown in Figure 6-60. Figure (a) shows mold closed state; Figure (b) shows state at the start of ejection, before accelerated ejection begins; Figure (c) shows state at the end of accelerated ejection. This ejection utilizes elastic force of a torsion spring to achieve accelerated ejection. Torsion spring is mounted on push plate, and each accelerated ejector pushes one accelerated push rod. Upon mold closing, internal spring force resets ejector. Single push rod accelerated ejector is designed only for push rods that need accelerated ejection, without affecting other push rods. It occupies less mold space, is easy to use, and provides smooth ejection. Number of single push rod accelerated ejectors can be determined based on number of push rods requiring acceleration, or only one can be designed for standalone use. When designing and installing torsion spring, it is important to note that torsion spring needs to be pre-compressed at a 90° angle.

 

Figure 6-59 Gear and rack type accelerated ejection

 

Figure 6-60 Single push rod accelerated ejection