Editing Poppet valve (section)

== Design ==
[[File:Poppet valves activated by two mechanisms.gif|thumb|right|Piston engine with an automatically actuated intake valve (in red), and a cam-activated exhaust valve (in blue)]]

The poppet valve is different from both slide and oscillating valves. Instead of ''sliding'' or ''rocking'' over a seat to uncover a port, the poppet valve lifts from the seat with a movement [[perpendicular]] to the plane of the port. The main advantage of the poppet valve is that it has no movement on the seat, thus requiring no lubrication.<ref>{{Cite book|last=Fessenden|first=Charles H.|title=Valve Gears|year=1915|publisher=McGraw Hill |location=New York|pages=[https://archive.org/details/valvegears00fessrich/page/159 159]–168|url=https://archive.org/details/valvegears00fessrich|url-status=live|archive-url=https://web.archive.org/web/20160603231938/https://archive.org/details/valvegears00fessrich|archive-date=2016-06-03}}</ref>

In most cases it is beneficial to have a "balanced poppet" in a direct-acting valve. Less force is needed to move the poppet because all forces on the poppet are nullified by equal and opposite forces. The solenoid coil has to counteract only the spring force.<ref>{{Cite book|last=Wahl|first=Philipp |title=Piston spool valves and poppet valves |year=2013|publisher=Festo AG & Co. KG |location=Esslingen |url=http://www.festo.com/net/lt_lt/SupportPortal/Downloads/320845/291660}}</ref>

Poppet valves are best known for their use in internal combustion and steam engines, but are used in general pneumatic and hydraulic circuits where a pulsed flow control is wanted. The pulse can be controlled by a combination of differential pressure and spring load as required.

[[Presta valve|Presta]] and [[Schrader valve]]s used on pneumatic [[tire|tyres]] are examples of poppet valves. The Presta valve has no spring and relies on a pressure differential for opening and closing while being inflated.

Poppet valves are employed extensively in the launching of [[torpedo]]es from [[submarine]]s. Many systems use compressed air to expel the torpedo from the [[Torpedo tube|tube]], and the poppet valve recovers a large quantity of this air (along with a significant amount of seawater) in order to reduce the tell-tale cloud of bubbles that might otherwise betray the boat's submerged position.<ref>{{cite book |title=Torpedo Tube Manual | isbn=9781935327639 |url=https://books.google.com/books?id=-oAVAgAAQBAJ&dq=poppet+valve+torpedo&pg=PA63 |via=Google Books| last1=Navy | first1=U. S. | date=February 2009 | publisher=Lulu.com }}</ref>