The Info List - Poppet Valve

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A poppet valve (also called mushroom valve[1]) is a valve typically used to control the timing and quantity of gas or vapour flow into an engine. It consists of a hole, usually round or oval, and a tapered plug, usually a disk shape on the end of a shaft also called a valve stem. The portion of the hole where the plug meets with it is referred to as the 'seat' or 'valve seat'. The shaft guides the plug portion by sliding through a valve guide. In exhaust applications a pressure differential helps to seal the valve and in intake valves a pressure differential helps open it. The poppet valve was most likely invented in 1833 by E.A.G. Young of the Newcastle and Frenchtown Railroad. Young patented his idea but the Patent Office fire of 1836 destroyed all records of it.[2]


1 Etymology 2 Operation

2.1 Internal combustion engine

2.1.1 Valve
position 2.1.2 Valve

2.2 Steam engine

3 See also 4 References

Etymology[edit] 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 marionettes, which – like the poppet valve – move bodily in response to remote motion transmitted linearly.[3][4] In the past, "puppet valve" was a synonym for poppet valve;[5][6] however, this usage of "puppet" is now obsolete. The valve stem moves up and down inside the passage called guide, which is fitted in the engine-block. the head of the valve called valve face, is generally grounded to 45 degrees angle, so as to fit properly on the value seat in the block and prevent leakage Operation[edit] The poppet valve is fundamentally different from 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.[7]

This animation shows a pressure activated poppet valve (red), and a cam activated poppet valve (blue), in a cylinder of an internal combustion engine.

valves in action at the top of the cylinder

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[8]

valves are used in many industrial processes, from controlling the flow of milk to isolating sterile air in the semiconductor industry. However, they are most well known for their use in internal combustion and steam engines, as described below. Presta and Schrader valves used on pneumatic tyres are examples of poppet valves. The Presta valve
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 torpedoes from submarines. Many systems use compressed air to expel the torpedo from the tube, and the poppet valve recovers 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.[9] Internal combustion engine[edit] Poppet
valves are used in most piston engines to open and close the intake and exhaust ports in the cylinder head. The valve is usually a flat disk of metal with a long rod known as the 'valve stem' attached to one side. In early internal combustion engines (c1900) it was common that the inlet valve was 'automatic', i.e. opened by the suction in the engine and returned 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 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 revolutions per minute (RPM), the inertia of the spring means it cannot respond quickly enough to return the valve to its seat between cycles, leading to 'valve float' also known as 'valve bounce'. In this situation desmodromic valves can be used which, being closed by a positive mechanical action instead of by a spring, are able to cycle at the high speeds required in, for instance, motorcycle and auto racing engines . The engine normally operates the valves by pushing on the stems with cams and cam followers. The shape and position of the cam determines the valve lift and when and how quickly (or slowly) the valve is opened. The cams are normally placed on a fixed camshaft which is then geared to the crankshaft, running at half crankshaft speed in a four-stroke engine. On high-performance engines, the camshaft is movable and the cams have a varying height so, by axially moving the camshaft in relation with the engine RPM, the valve lift also varies. See variable valve timing. For certain applications the valve stem and disk are made of different steel alloys, or the valve stem may be hollow and filled with sodium to improve heat transport and transfer. Although a better heat conductor, an aluminium cylinder head requires steel valve seat inserts, where a cast iron cylinder head would often have employed integral valve seats in the past. Because the valve stem extends into lubrication in the cam chamber, it must be sealed against blow-by to prevent cylinder gases from escaping into the crankcase, even though the stem to valve clearance is very small, typically 0.04-0.06 mm, so a rubber lip-type seal is used to ensure that excessive oil is not drawn in from the crankcase on the induction stroke, and that exhaust gas does not enter the crankcase on the exhaust stroke. Worn valve guides and/or defective oil seals can often be diagnosed by a puff of blue smoke from the exhaust pipe on releasing the accelerator pedal after allowing the engine to overrun, when there is high manifold vacuum. Such a condition occurs when changing gear. In multi-valve engines, the conventional two-valves-per-cylinder setup is complemented by a minimum of an extra intake valve (three-valve cylinder head) or, more commonly, with an extra intake and an extra exhaust valve (four-valve cylinder head), the latter meaning higher RPM are, theoretically, achievable. Five valve designs (with three inlet and two exhaust valves) are also in use. More valves per cylinder means improved gas flow and smaller reciprocating masses may be achieved, leading to improved engine efficiency and, ultimately, higher power output and better fuel economy. Multivalve engines also allow for a centrally located spark plug, which improves combustion efficiency and reduces detonation. Valve
position[edit] In very early engine designs the valves were 'upside down' in the block, parallel to the cylinders. This was the so-called L-head engine design, because of the shape of the cylinder and combustion chamber, also called 'flathead engine' as the top of the cylinder head was flat. The term preferred outside America (though occasionally used there too) was sidevalve; hence, its use in the name of the UK-based Ford Sidevalve Owners' Club.[10] Although this design made for simplified and cheap construction, it had two major drawbacks; the tortuous path followed by the intake charge limited air flow and effectively prevented speeds greater than 3600 RPM,[11] and the path of the exhaust through the block could cause overheating under sustained heavy load. This design evolved into ' Intake
Over Exhaust', IOE or F-head, where the intake valve was in the head and the exhaust valve was in the block; later both valves moved to the head. In most such designs the camshaft remained relatively near the crankshaft, and the valves were operated through pushrods and rocker arms. This led to significant energy losses in the engine, but was simpler, especially in a V engine
V engine
where one camshaft can actuate the valves for both cylinder banks; for this reason, pushrod engine designs have persisted longer in these configurations than others. More modern designs have the camshaft on top of the cylinder head, pushing directly on the valve stem (again through cam followers, also known as tappets), a system known as overhead camshaft; if there is just one camshaft, this is a single overhead cam or SOHC engine. Often there are two camshafts, one for the intake and one for exhaust valves, creating the dual overhead cam, or DOHC. The camshaft is driven by the crankshaft - through gears, a chain or a timing belt. Valve
wear[edit] In the early days of engine building, the poppet valve was a major problem. Metallurgy
was lacking, and the rapid opening and closing of valves against cylinder heads led to rapid wear. They would need to be re-ground in a process known as a 'valve job'. Adding tetraethyllead to the petrol reduced this problem somewhat, the lead coating the valve seats would, in effect, lubricate the metal. In more modern vehicles and properly machined older engines, valve seats may be made of improved alloys such as stellite and the valves themselves of stainless steel. These improvements have generally eradicated this problem, and helped make unleaded fuel the norm. Valve
burn (overheating) is another problem. It causes excessive valve wear and defective sealing, as well as engine knocking (the hot valve causes the fuel to prematurely ignite). It can be solved by valve cooling systems that use water or oil as a coolant. In high performance or turbo charged engines sometimes sodium filled valve stems are used. These valve stems then act as a heat pipe. A major cause of burnt valves is a lack of valve clearance at the tappet; the valve cannot completely close. This reduces its ability to conduct heat to the cylinder head via the seat, and may allow hot combustion gases to flow between the valve and its seat. Burnt valves will cause a low compression in the affected cylinder and loss of power. Steam engine[edit]

Balanced Poppet
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

Oscillating Poppet
on one of Chapelon's rebuilt 4-6-2 locomotives.

James Watt
James Watt
was using poppet valves to control the flow of steam into the cylinders of his beam engines in the 1770s. A sectional illustration of Watt's beam engine of 1774 using the device is found in Thurston 1878:98,[12] and Lardner (1840) provides an illustrated description of Watt's use of the poppet valve.[13] 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.[14][15] 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. 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.[16] Poppet
valves have been used on steam locomotives, often in conjunction with 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 71000 Duke of Gloucester.

Sentinel Waggon Works
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 T1 duplex locomotives, although the valves commonly failed because the locomotives were commonly operated in excess of 160 km/h (100 mph), and the valves were not meant for the stresses of such speeds. The poppet valves also gave the locomotive a distinctive "chuffing" sound. See also[edit]

Double beat valve Reed valve Relief valve Rotary valve Sleeve valve Safety valve


^ A.L. Dyke (1921), Dyke's Automobile and Gasoline Encyclopedia  ^ White, John H. (1979). A History of the American Locomotive. North Chelmsford, MA: Courier Corporation. p. 145.  ^ "'''Poppet''' at Merriam-Webster". Merriam-webster.com. Retrieved 2011-12-06.  ^ "'''Puppet''' at Merriam-Webster". Merriam-webster.com. Retrieved 2011-12-06.  ^ "''' Puppet
valve''' from 1913 Webster's dictionary". Websters-online-dictionary.org. Archived from the original on 2006-02-21. Retrieved 2011-12-06.  ^ "U.S. Patent No. 339809, " Puppet
Valve", issued April 13, 1886". Patimg1.uspto.gov. Retrieved 2011-12-06.  ^ Fessenden, Charles H. (1915). Valve
Gears. New York: McGraw Hill. pp. 159–168.  ^ Wahl, Philipp (2013). Piston
spool valves and poppet valves. Esslingen: Festo AG & Co. KG.  ^ Torpedo
Tube Manual https://books.google.com/books?id=-oAVAgAAQBAJ&pg=PA63&lpg=PA63&dq=poppet+valve+torpedo&source=bl&ots=sFId7gUss-&sig=WbdzrI7eoVvnua_Dg6QqNUQUFrI&hl=en&sa=X&ei=j7RwU-eaNpKCogTj4oCgCg&ved=0CEsQ6AEwCA#v=onepage&q=poppet%20valve%20torpedo&f=false ^ http://www.fsoc.co.uk/ ^ "A Handy Guide to Clinton Engines" (PDF). 1956. p. 2. Retrieved October 2, 2015. R. P. M. 2200 - 3600  ^ Thurston, R.H. (1878). A History of the Growth of the Steam Engine. New York: Appleton & Co. p. 98.  ^ Lardner, Dionysius (1840). The steam engine explained and illustrated. London: Taylor and Walton. pp. 189–91.  ^ Jacques Mouchly, Valve
and Valve
Gear for Locomotives and Other Engines, U.S. Patent 1,824,830, issued Sept. 29, 1931. ^ Herman G. Mueller, Steam Engine Valve, U.S. Patent 1,983,803, issued Dec. 11, 1934. ^ 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 http://www.sciencemag.org/content/ns-13/314/94.full.pdf

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Reciprocating engines and configurations


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I2 I3 I4 I5 I6 I7 I8 I9 I10 I12 I14


F2 F4 F6 F8 F10 F12 F16

V / Vee

V2 V3 V4 V5 V6 V8 V10 V12 V14 V16 V18 V20 V24


W8 W12 W16 W18

Other inline

H U Square four VR Opposed X X24 Junkers Jumo 222



Cylinder head
Cylinder head
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Automotive engine

Part of the Automobile series

Basic terminology

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float Variable valve timing


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Portal Category

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Steam engines

Operating cycle

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Savery Engine (1698)

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Newcomen Memorial Engine
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Fairbottom Bobs
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Elsecar Engine

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Kinneil Engine
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Richard Trevithick

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Murray's Hypocycloidal Engine
Murray's Hypocycloidal Engine
(1805) Salamanca (1812)


Porter-Allen (1862) Ljungström (1908)

See also

Glossary of steam locomotive components History of steam road vehicles

Cugnot's fardier à vapeur (1769) Murdoch's model steam carriage (1784)

Lean's Engine Reporter List of steam technology patents Modern steam Stationary steam engine Timeline of steam power Water-returning engine

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Aircraft piston engine components, systems and terminology


Mechanical components

Camshaft Connecting rod Crankpin Crankshaft Cylinder Cylinder head Gudgeon pin Hydraulic tappet Main bearing Obturator ring Oil pump Piston Piston
ring Poppet
valve Pushrod Rocker arm Sleeve valve Tappet

Electrical components

Alternator Capacitor discharge ignition Dual ignition Electronic fuel injection Generator Ignition system Magneto Spark plug Starter


Air-cooled Aircraft engine
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