Editing Poppet valve

{{Short description|Type of valve}}

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A '''poppet valve''' (also sometimes called '''mushroom valve'''<ref>{{Citation|title=Dyke's Automobile and Gasoline Encyclopedia|author=A.L. Dyke|year=1921|publisher=St. Louis, A. L. Dyke |url=https://archive.org/details/dykesautomobile00dykegoog |url-status=live |archive-url=https://web.archive.org/web/20160611051701/https://archive.org/details/dykesautomobile00dykegoog |archive-date=2016-06-11}}</ref>) is a [[valve]] typically used to control the timing and quantity of petrol (gas) or vapour flow into or out of an engine, but with many other applications.

It consists of a hole or open-ended chamber, usually round or oval in cross-section, and a plug, usually a disk shape on the end of a shaft known as a valve stem. The working end of this plug, the valve face, is typically ground at a 45° bevel to seal against a corresponding [[valve seat]] ground into the rim of the chamber being sealed. The shaft travels through a [[valve guide]] to maintain its alignment.

A pressure differential on either side of the valve can assist or impair its performance. In '''exhaust''' applications higher pressure against the valve helps to seal it, and in '''intake''' applications lower pressure helps open it.

==Etymology==
The word [[poppet]] shares [[etymology]] with "[[puppet]]": it is from the [[Middle English]] ''popet'' ("youth" or "doll"), from [[Middle French]] ''poupette'', which is a [[diminutive]] of ''poupée''. The use of the word ''poppet'' to describe a valve comes from the same word applied to [[marionette]]s, which, like the poppet valve, move bodily in response to remote motion transmitted linearly.<ref>{{Cite web |url=http://www.merriam-webster.com/dictionary/poppet |title='''Poppet''' at Merriam-Webster |publisher=Merriam-webster.com |access-date=2011-12-06 |url-status=live |archive-url=https://web.archive.org/web/20111017220959/http://www.merriam-webster.com/dictionary/poppet |archive-date=2011-10-17 }}</ref><ref>{{Cite web |url=http://www.merriam-webster.com/dictionary/puppet |title='''Puppet''' at Merriam-Webster |publisher=Merriam-webster.com |access-date=2011-12-06 |url-status=live |archive-url=https://web.archive.org/web/20120112111206/http://www.merriam-webster.com/dictionary/puppet |archive-date=2012-01-12 }}</ref> In the past, "puppet valve" was a synonym for ''poppet valve'';<ref>{{Cite web |url=http://www.websters-online-dictionary.org/Pu/Puppet+valve.html |title='''Puppet valve''' from 1913 Webster's dictionary |publisher=Websters-online-dictionary.org |access-date=2011-12-06 |url-status=dead |archive-url=https://web.archive.org/web/20060221143245/http://www.websters-online-dictionary.org/Pu/Puppet+valve.html |archive-date=2006-02-21 }}</ref><ref>{{Cite web |url=http://patimg1.uspto.gov/.piw?Docid=00339809&homeurl=http%3A%2F%2Fpatft.uspto.gov%2Fnetacgi%2Fnph-Parser%3FSect1%3DPTO1%2526Sect2%3DHITOFF%2526d%3DPALL%2526p%3D1%2526u%3D%25252Fnetahtml%25252FPTO%25252Fsrchnum.htm%2526r%3D1%2526f%3DG%2526l%3D50%2526s1%3D0339809.PN.%2526OS%3DPN%2F0339809%2526RS%3DPN%2F0339809&PageNum=&Rtype=&SectionNum=&idkey=NONE&Input=View+first+page |title=U.S. Patent No. 339809, "Puppet Valve", issued April 13, 1886 |publisher=Patimg1.uspto.gov |access-date=2011-12-06 |url-status=live |archive-url=https://web.archive.org/web/20170110090901/http://patimg1.uspto.gov/.piw?Docid=00339809&homeurl=http%3A%2F%2Fpatft.uspto.gov%2Fnetacgi%2Fnph-Parser%3FSect1%3DPTO1%2526Sect2%3DHITOFF%2526d%3DPALL%2526p%3D1%2526u%3D%25252Fnetahtml%25252FPTO%25252Fsrchnum.htm%2526r%3D1%2526f%3DG%2526l%3D50%2526s1%3D0339809.PN.%2526OS%3DPN%2F0339809%2526RS%3DPN%2F0339809&PageNum=&Rtype=&SectionNum=&idkey=NONE&Input=View+first+page |archive-date=January 10, 2017 }}</ref> however, this usage of "puppet" is now obsolete.

== 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>

== Usage in internal combustion engines ==
[[File:4StrokeEngine Ortho 3D Small.gif|thumb|right|upright|Poppet valves in a typical [[overhead camshaft engine]] ]]
{{more citations needed|section|date=March 2022}}

Poppet valves are used in most [[piston engine]]s to control the flow of intake and exhaust gasses through the [[cylinder head]] and into the [[combustion chamber]]. The side of the poppet valve which sits inside the combustion chamber is a flat disk, while the other side tapers from the disk shape to a thin cylindrical rod called a "valve stem".

=== Materials and durability ===
In a typical modern mass-production engines, the valves are solid and made from steel [[alloy]]s. However some engines use hollow valves filled with [[sodium]], to improve [[heat transfer]].

Many modern engines use an aluminium cylinder head. Although this provides better heat transfer, it requires steel [[valve seat]] inserts to be used; in older [[cast iron]] cylinder heads, the valve seats are often part of the cylinder head. A gap of {{convert|0.4|-|0.6|mm|in|3|abbr=on}} is present around the valve stem, therefore a valve stem [[oil seal]] is used to prevent oil being drawn into the intake manifold and combustion chamber. Typically, a rubber lip-type seal is used. A common symptom of worn valve guides and/or defective oil seals is a puff of blue smoke from the exhaust pipe at times of increased intake [[manifold vacuum]], such as when the throttle is abruptly closed.

Historically, valves had two major issues, both of which have been solved by improvements in modern [[metallurgy]]. The first was that in early internal combustion engines, high wear rates of valves meant that a [[valve job]] to regrind the valves was required at regular intervals. Secondly, [[Tetraethyllead#In motor fuel|lead additives]] had been used in petrol (gasoline) since the 1920s, to prevent [[engine knocking]] and provide lubrication for the valves. Modern materials for the valves (such as stainless steel) and valve seats (such as [[Stellite]] and [[inconel]]) allowed for leaded petrol to be phased out in many industrialised countries by the mid-1990s.

===Sodium Cooled Exhaust Valves===
Exhaust valves are subject to very high temperatures and in extreme high performance applications may be [[sodium]] cooled. The valve is hollow and filled with sodium, which melts at a relatively low temperature and, in its liquid state, convects heat away from the hot valve head to the stem where it may be conducted to the cylinder head. Common in second world war piston engines, now only found in high performance engines.<ref>{{cite web |last1=Cameron |first1=Kevin |title=Some Facts About Sodium-Filled Valves |url=https://www.cycleworld.com/story/bikes/some-facts-about-sodium-filled-valves/ |website=Cycle World |publisher=Octane Media, LLC |access-date=9 July 2023 |date=22 April 2020}}</ref>

=== Actuation method ===
{{see also|Camshaft}}
Early engines in the 1890s and 1900s used an "automatic" intake valve, which was opened by the vacuum in the combustion chamber and closed by a light spring. The exhaust valve had to be mechanically driven to open it against the pressure in the cylinder. Use of automatic valves simplified the mechanism, but [[valve float]] limited the speed at which the engine could run, and by about 1905 mechanically operated inlet valves were increasingly adopted for vehicle engines.

Mechanical operation is usually by pressing on the end of the valve stem, with a spring generally being used to return the valve to the closed position. At high engine speeds ([[revolutions per minute|RPM]]), the weight of the [[valvetrain]] means the valve spring cannot close the valve as quickly enough, leading to [[valve float]] or ''valve bounce''. [[Desmodromic valve]]s use a second rocker arm to mechanically close the valves (instead of using valve springs) and are sometimes used to avoid valve float in engines that operate at high RPM.

In most mass-produced engines, the [[camshaft]](s) control the opening of the valves, via several intermediate mechanisms (such as [[pushrod]]s, [[roller rocker]]s and [[valve lifter]]s). The shape of the cams on the camshaft influence the [[valve lift]] and determine the timing of when the valves open.

=== Number and location of valves ===
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{{see also|Multi-valve}}

Early [[flathead engine]]s (also called ''L-head engines'') saw the valves located beside to the cylinder(s), in an "upside down" orientation parallel to the cylinder.<ref>{{Cite web |url=http://www.fsoc.co.uk/ |title=fsoc |website=fsoc |access-date=24 April 2018 |url-status=live |archive-url=https://web.archive.org/web/20180318113101/https://www.fsoc.co.uk/ |archive-date=18 March 2018 }}</ref> Although this design made for simplified and cheap construction, the twisting path of the intake and exhaust gasses had major drawbacks for the airflow, which limited engine RPM<ref>{{Cite web |url = http://www.rucenterprises.com/Clinton/A_Handy_Guide_To_Clinton_Engines.pdf |title = A Handy Guide to Clinton Engines |date = 1956 |access-date = October 2, 2015 |page = 2 |quote = R. P. M. 2200&nbsp;— 3600 |url-status = live|archive-url = https://web.archive.org/web/20151003194636/http://www.rucenterprises.com/Clinton/A_Handy_Guide_To_Clinton_Engines.pdf |archive-date = October 3, 2015 }}</ref> and could cause the engine block to overheat under sustained heavy load. The flathead design evolved into [[IOE engine|intake over exhaust (IOE) engine]], used in many early motorcycles and several cars. In an IOE engine, the intake valves were located directly above the cylinder (like the later ''overhead valve engines''), however the exhaust valve remains beside the cylinder in an upside down orientation.

These designs were largely replaced by the [[overhead valve engine|overhead valve (OHV) engine]] between 1904 until late-1960s/early-to-mid 1970s, whereby the intake and exhaust valves are both located directly above the cylinder (with the camshaft located at the bottom of the engine). In turn, OHV engines were largely replaced by the [[overhead camshaft engine|overhead camshaft (OHC) engines]] between 1950s until 1980s. The location of the valves is broadly the same between OHV and OHC engines, however OHC engines saw the camshaft located to the top of the engine with the valves and OHC engines often have more valves per cylinder. Most OHC engines have an extra intake and an extra exhaust valve per cylinder (four-valve cylinder head), compared with the design of two valves per cylinder used by most OHV engines. However some OHC engines have used three or five valves per cylinder.
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== Usage in steam engines ==
[[File:PuppetValve.png|right|thumb|upright|Balanced poppet valve from U.S. Patent 339,809. High pressure steam enters at ''A'' and exits at ''B''. The valve stem ''D'' moves up to open the valve discs ''C''.]]

[[James Watt]] was using poppet valves to control the flow of steam into the cylinders of his [[beam engine]]s in the 1770s. A sectional illustration of Watt's beam engine of 1774 using the device is found in Thurston 1878:98,<ref name="Thurston 1878 98">{{Cite book|last=Thurston|first=R.H.|title=A History of the Growth of the Steam Engine|year=1878|publisher=Appleton & Co.|location=New York|pages=[https://archive.org/details/cu31924031167632/page/n123 98]|url=https://archive.org/details/cu31924031167632}}</ref> and Lardner (1840) provides an illustrated description of Watt's use of the poppet valve.<ref>{{Cite book|last=Lardner|first=Dionysius|author-link=Dionysius Lardner |title=The steam engine explained and illustrated|year=1840|publisher=Taylor and Walton|location=London |pages=[https://archive.org/details/steamengineexpla00lardrich/page/189 189]–91 |url=https://archive.org/details/steamengineexpla00lardrich |url-status=live |archive-url=https://web.archive.org/web/20131004215524/http://archive.org/details/steamengineexpla00lardrich |archive-date=2013-10-04}}</ref>

When used in high-pressure applications, for example, as admission valves on steam engines, the same pressure that helps seal poppet valves also contributes significantly to the force required to open them. This has led to the development of the balanced poppet or [[double beat valve]], in which two valve plugs ride on a common stem, with the pressure on one plug largely balancing the pressure on the other.<ref>Jacques Mouchly, Valve and Valve Gear for Locomotives and Other Engines, U.S. Patent 1,824,830, issued Sept. 29, 1931.</ref><ref>Herman G. Mueller, Steam Engine Valve, U.S. Patent 1,983,803, issued Dec. 11, 1934.</ref> In these valves, the force needed to open the valve is determined by the pressure and the difference between the areas of the two valve openings. [[Frederick Ellsworth Sickels|Sickels]] patented a valve gear for double-beat poppet valves in 1842. Criticism was reported in the journal Science in 1889 of equilibrium poppet valves (called by the article the "double or balanced or American puppet valve") in use for paddle steamer engines, that by its nature it must leak 15 percent.<ref>Criticism by E.N. Dickerson in lecture to the Electric Club of New York 17/01/1889, reported by Science vol.13 No.314, Feb 8 1889 p.95 [https://www.science.org/doi/pdf/10.1126/science.ns-13.314.94 sciencemag.org]</ref>

[[File:231-E-41-d.jpg|left|thumb|upright=1.15|Oscillating poppet valve on one of Chapelon's rebuilt [[4-6-2]] locomotives]]
Poppet valves have been used on [[steam locomotive]]s, often in conjunction with [[Hugo Lentz|Lentz]] or [[Caprotti valve gear]]. British examples include:
* [[LNER Class B12]]
* [[LNER Class D49]]
* [[LNER Class P2]]
* [[LMS Stanier Class 5 4-6-0]]
* [[BR standard class 5]]
* [[BR Standard Class 8|BR standard class 8 71000 Duke of Gloucester]].

[[Sentinel Waggon Works]] used poppet valves in their steam wagons and steam locomotives. Reversing was achieved by a simple sliding [[camshaft]] system.

Many locomotives in France, particularly those rebuilt to the designs of Andre Chapelon, such as the [[SNCF 240P]], used Lentz oscillating-cam poppet valves, which were operated by the Walschaert valve gear the locomotives were already equipped with.

The poppet valve was also used on the American [[Pennsylvania Railroad]]'s [[PRR T1|T1]] [[duplex locomotive]]s, although the valves commonly failed because the locomotives were commonly operated in excess of {{Convert|160|km/h|-1|abbr=on}}, and the valves were not meant for the stresses of such speeds. The poppet valves also gave the locomotive a distinctive "chuffing" sound.

One poppet valve design was invented in 1833 by American E.A.G. Young of the [[New Castle and Frenchtown Turnpike and Railroad Company|Newcastle and Frenchtown Railroad]]. Young had patented his idea, but the [[1836 U.S. Patent Office fire|U.S. Patent Office fire of 1836]] destroyed all records of it.<ref>{{Cite book|last=White|first=John H.|title=A History of the American Locomotive|year=1979|publisher=Courier Corporation|location=North Chelmsford, MA|pages=145}}</ref>

==See also==
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* [[Double beat valve]]
* [[List of auto parts]]
* [[Pneumatic valve springs]]
* [[Reed valve]]
* [[Relief valve]]
* [[Rotary valve]]
* [[Sleeve valve]]
* [[Safety valve]]
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==References==
{{Reflist}}

{{Automotive engine}}
{{Steam engine configurations}}

{{DEFAULTSORT:Poppet Valve}}
[[Category:Engine valves]]