A stored energy printer is a

computer printer A printer is a peripheral machine which makes a durable representation of graphics or text, usually on paper. While most output is human-readable, bar code printers are an example of an expanded use for printers. Different types of printer ...

that uses the energy stored in a spring or

magnetic field A magnetic field (sometimes called B-field) is a physical field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular ...

to push a hammer into a

ribbon A ribbon or riband is a thin band of material, typically cloth but also plastic or sometimes metal, used primarily as decorative binding and tying. Cloth ribbons are made of natural materials such as silk, cotton, and jute and of synthetic mate ...

to print a dot. It is a type of impact printer. As compared to

dot matrix printer Dot matrix printing, sometimes called impact matrix printing, is a computer printing process in which ink is applied to a surface using a relatively low-resolution dot matrix for layout. Dot matrix printers are a type of impact printer that p ...

s that print a single column of dots at a time, this printer generally creates an entire line of dots at a time. Therefore, it is also known as a

line matrix printer A line matrix printer is a computer printer that is a compromise between a line printer and a dot matrix printer. A line matrix printer prints page-wide lines of dots at a time, building up a line of text by printing lines of dots. Applicatio ...

. An advantage of this technology is its low running costs: printer hammers have a lifespan of millions to billions of dots, and ink is transferred using conventional typewriter-style ribbons.

Technology

The most common printer to use this technology was the line-matrix printer made by

Printronix Printronix is an American supplier of Industrial Print Solutions, Industrial Laser Printers and line and dot matrix printers. Printronix is based in Irvine, California, and operates across 14 offices worldwide. Products Printronix's printers are ...

and its licensees. In this type, the hammers are machined from an oval of magnetically permeable stainless steel, and the hammer-tips form vertical rows. The hammers are arranged as a "hammerbank"; a type of comb that oscillates horizontally to produce a line of dots. The original technology was patented by Printronix in 1974. The

tungsten carbide Tungsten carbide (chemical formula: ) is a carbide containing equal parts of tungsten and carbon atoms. In its most basic form, tungsten carbide is a fine gray powder, but it can be pressed and formed into shapes through sintering for use in in ...

hammer is brazed to the center-top of a

leaf spring A leaf spring is a simple form of spring (device), spring commonly used for suspension (vehicle), suspension in wheeled vehicles. Originally called a ''laminated'' or ''carriage spring'', and sometimes referred to as a semi-elliptical spring, e ...

. The top of this stiff spring is initially held back by a

magnet A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, steel, nickel, ...

ic pole-piece. To produce a dot, an

electromagnetic coil An electromagnetic coil is an electrical Electrical conductivity, conductor such as a wire in the shape of a wiktionary:coil, coil (spiral or helix). Electromagnetic coils are used in electrical engineering, in applications where electric curre ...

wrapped around the pole-piece neutralizes the magnetic field, causing the spring to release the hammer and hit the ribbon and the paper behind it, leaving behind the printed dot. Character matrix printers have also been produced.

Improvements

Recent designs have performed complex optimizations in the magnetic circuit, and eliminated unwanted

resonance Resonance is a phenomenon that occurs when an object or system is subjected to an external force or vibration whose frequency matches a resonant frequency (or resonance frequency) of the system, defined as a frequency that generates a maximu ...

s in the spring. The result was a near-doubling of speed. Other improvements include the use of

electrical discharge machining Electrical discharge machining (EDM), also known as spark machining, spark eroding, die sinking, wire burning or wire erosion, is a metal fabrication process whereby a desired shape is obtained by using electrical discharges (sparks). Material is ...

to produce complex, three-dimensional hammers that trade-off the magnetic circuit, mechanical resonances, and printing speed. Normal wear occurs on the pole piece when the spring rubs against it as it returns. This eventually requires the pole pieces to be reground and recertified. However, using hexavalent

chrome plating Chrome plating (less commonly chromium plating) is a technique of electroplating a thin layer of chromium onto a metal object. A chrome plated part is called ''chrome'', or is said to have been ''chromed''. The chromium layer can be decorativ ...

on the pole-piece, combined with careful design, more than doubles speeds and improves life-span, allowing approximately a billion impressions per hammer.

References

Computer peripherals Computer printers Impact printers Printing technology {{computing-stub