Single Stroke, Mechanically. Operated

Closeup of single stroke, mechanically operated, electrodecontrol assembly... 

Ref 13, p 3, the needle is moved down by means of single-stroke, mechanically-operated electrode- control assembly, preadjusted so that the gap is less than that required for the discharge. The procedure with,this device (which,is reproduced here as Fig El3) prevents any loss of energy by sparking at the switch, minimizes the effects of leakage in the system, and allows only one spark to occur... 

What Inspect the clutch/break mechanism, anti-repeat features, single stroke mechanism, auxiliary equipment, and other parts and safeguards on power presses to ensure safe operating condition and adjustment. 

Reciprocating pumps are those most commonly used in high performance Ic. The single-piston type usually has inlet and outlet check valves with some mechanism such as variable stroke frequency to minimize the effect of pump pulsations. Dual-piston pumps operate with the pistons 180° out of phase to minimize pulsations. For this system to work optimally, the piston units must be identical. 

A discernible trend in modem pump design is towards the use of very small pistons (stroke volume around 100 pi). These tiny pistons have to be operated at very high driving speeds, to provide the flow rates required in analytical HPLC. However, when they are used in combination with electronic feedback pulse control mechanisms, as described above, they can provide extremely stable solvent delivery characteristics. Such is the efficacy of this approach that single piston pumps designed in this way are able to easily out-perform older dual piston pumps, and are consequently beginning to account for a major part of the LC pump market. 

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