Spring plunger
Spring-loaded device for indexing, locating, positioning
A spring plunger or detent spring is a spring-loaded mechanical part to ease indexing, positioning, securing, and disassembling of objects without losing parts. The spring force keeps the pin in position during normal use.
Typically, it is a machine part consisting of a hollow cylinder with an internal compression spring acting on a pin. The pin may, for example, be shaped as a rod with either a cylindrical or rounded tip (broadly categorized as a spring plunger), or a spring-loaded ball (ball plunger) if the spring acts against a ball.
01Manufacture
Spring plungers can be supplied as a complete unit that is mounted into the workpiece by screwing into threads, or in a pluggable version that is pressed into the workpiece. The sleeve is usually made of free machining steel.
Alternatively, it can be made directly into the workpiece by drilling and tapping a hole, then inserting a pin (or ball), spring, and finally a set screw.
The spring force is tuned for the intended use. In spring plungers with a screw, the spring pressure can be adjustable within a certain working range.
Different plungers may require different tools for installation, such as a hex key, socket wrench, or flathead screwdriver. Blind hole mounting variants may have tool slots on the same side as the pin.
02Materials
At high temperatures or when the parts are exposed to aggressive chemicals, plastic balls or balls made of corrosion-resistant materials such as silicon nitride can be used. The threaded sleeve is then typically made of stainless steel instead of carbon steel.
03Use
Spring-loaded plungers have a wide range of uses.
Some spring plungers are designed to be handled only when assembling or occasionally adjusting equipment. Other spring plungers are designed to be routinely manipulated (for example, to adjust the angle of a utility bench), and may have an integrated operating lever that is pushed in (push pin plungers) or a lever that is pulled out to manipulate the object (pull pin plunger).
Similar principles are used in spring-loaded valves and valve stems (including safety valves), or automatic ejectors on firearms.
Mechanics
Spring plungers can be used, for example, to lock levers in different positions. Spring-loaded plungers with anti-twist protection enable screwless fastening.
Electronics
A pogo pin is a type of electrical connector mechanism widely used in modern electronics. Compared to other electrical connectors, they have better durability and are more resistant to mechanical shock and vibration.
Archery
In modern archery, an archery plunger allows the arrow to be deflected as it is fired from the bow. It allows for adjusting the arrow's relative position on the arrow rest. By adjusting the stiffness and position of the plunger, the arrow can be adjusted to fly with the best possible flight, so that it travels straight.
Sources and credits
This article is adapted from the Wikipedia article “Spring plunger”, written by its contributors and licensed under CC BY-SA 4.0. Fathomly has changed the layout, removed citation markers, navigation and maintenance notices, and adjusted punctuation. This adapted version is shared under the same license. For references, see the original article.
Images, from Wikimedia Commons:
- Kolbempumexplar.jpg by de:user:anton, CC BY-SA 2.5
- WeightBenchSide.jpg by No machine-readable author provided. Amcbride~commonswiki assumed (based on copyright claims)., CC BY-SA 3.0
- Assembly Structure Pogo Pin.png by C.C.P. Contact Probes Co. Ltd., CC BY-SA 4.0
- Button-recurvebogen-1.jpg by Hartmut Stoepler, CC BY-SA 4.0
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