Base-ejection devices

Ejector locations. Ejection devices for plastic parts can range from screwdrivers used to pry parts out of a hand mold to mechanized stripper plates and elaborate mechanisms which also retract collapsible cores. All of them share one common characteristic they exert pressure on a newly formed part. That pressure can distort the part to the point of disturbing its function or appearance if it occurs while the part is still too soft to withstand it. Therefore, the processor must delay ejection until the moldment can endure it. The more ejectors there are, the more ejection surface there is to distribute that pressure and the sooner the part can be removed from the mold, thereby shortening the molding cycle. However, ejectors cost money and leave marks on the surface of the moldment. Therefore, there is a mold cost associated with a faster molding cycle. (Differences between bidders on a project are often based on variations in cooling and ejection systems.) Additional ejectors leave more marks on the surface and their number and location may be limited by functional and appearance concerns. 

A die stamping was produced in just one action. Stock (2) was fed into die (1) and the deformation to obtain a cup was performed by a stamp (3) which moved in a sleeve (4) driven by a piston of a hydraulic cylinder. The strain obtained was measured with strain gauge (5). The temperature of the deformed alloy was maintained by heating device (7) and controlled with sensor (8). After the deformation was completed shedder (9) driven by a piston (10) of hydraulic cylinder (11) ejected the cup. The whole press ram rested upon base (12). 

A phototransistor or photodiode may also be used to detect visible fight. Both devices have p-n junctions. In the photodiode the photon ejects an electron from the p semiconductor to the n semiconductor. The electron cannot cross back across the p-n junction and must travel through the circuitry, an ammeter to return to the p material. In a phototransistor, usually an npn type, the base (p-type semiconductor) is enlarged and photosensitive. Photons dislodge electrons that act as if a potential was applied to the base. This results in an amplified flow of electrons proportional to the number of photons striking the base (Fig. 5.11). 

In a linear ion trap one of the most efficient ways to perform mass analysis is to eject ions radially. Hager [60] demonstrated that, by using fringe field effects, ions can also be mass-selectively ejected in the axial direction. There are several benefits for axial ejection (i) it does not require open slits in the quadrupole, (ii) the device can be operated either as a regular quadrupole or a LIT using one detector. A commercial hybrid mass spectrometer was developed based on a triple quadrupole platform where Q3 can be operated either in normal RF/DC mode or in the LIT ion trap mode (Fig. 1.24). 

Fig. 4 Schematic of an ion trap MS instrument. This device consists of two endcap electrodes (entrance and exit) and a ring electrode. An ion trap MS separates ions based on mass-to-charge ratio (m/z). Once ions are introduced into the ion trap MS, the radiofrequency (rf) amplitude is increased so that ions are sequentially ejected (by increasing mass) and detected. This type of MS provides a routine (i.e., benchtop) and sensitive detector using either GC and LC interfaces. Furthermore, this instrument provides a unique format for multiple stages of MS analysis (MS ). (Courtesy of ThermoFinnigan, San Jose, CA.)...

Inkjet printing technology can be used with an electrohydrodynamic spraying technique (24). A conventional electrohydrodynamic inkjet device is based on DC voltage and requires two electrodes a nozzle electrode and an extractor electrode. However, this device suffers from drawbacks such as electrical breakdown. A more stable jetting technique uses the extractor electrode alone without the nozzle electrode and AC voltage. Thus, a continuous ejection of droplets can be obtained due to AC voltage. 

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