A poppet valve is a valve consisting 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. For other uses see Valve (disambiguation. For the electronic component see Thermionic valve. The shaft guides the plug portion by sliding through a valve guide. In most types of Reciprocating engines a valve guide is provided for each Poppet valve in the Cylinder head. In most applications a pressure differential helps to seal the valve and in some applications also open it.
Presta and Schrader valves used on air-filled tires are examples of poppet valves. The Presta valve is a Valve commonly found in high Pressure road style and better mountain Bicycle Tires although it is now used on all The Schrader valve, invented by August Schrader in the 1890s consists of a Valve stem into which a valve core is threaded and is used on virtually all This article is about tires used on road Vehicles including pneumatic tires and solid tires. The Presta valve has no spring and relies on a pressure differential for opening and closing while being inflated.
Poppet valves are a very robust and resilient construction for use in industrial directional control valves. They are usually very tolerant of typical air line contaminants (rust, scale, etc) when used in compressed air service. Compressed air This type of valve construction is typically characterized as being a high flow, fast acting design due to the large flow paths through the body that can be opened quickly. Think of a poppet valve very much like a stopper or plug in a bath tub drain. When the plug is pulled, the flow path opens quickly and the area that opens is quite large. The large opening of a poppet allows particulate to pass through the valve easily.
Poppets are only one of several different types of construction used in the manufacture of industrial directional control valves. Poppet valves are characterized by having a movable element (the poppet) that is used to direct the flow of fluid through the valve body. The poppet inside is moved via a stem that pushes the poppet off its seat allowing a flow path (in the case of a two-way, normally closed valve), or closing off a flow path by pushing the poppet onto a seat (in the case of a two-way normally open valve). The stem is moved by some sort of actuator (typically a pilot, manual, mechanical or solenoid operator). A solenoid is a three-dimensional Coil. In Physics, the term solenoid refers to a loop of wire often wrapped around a Metallic core which In the case of a pilot actuator, a piston chamber is pressurized by a fluid or gas, causing a piston to push down on the stem. In the case of manual operation, some sort of device such as a knob, lever, or pedal is actuating the stem via human force. Valves actuated by manual force are often referred to as "human interface" devices. Mechanical operators such as a stem extension, roller, or a cam roller are actuated by the actual process in which the valve is installed. Actuation of the stem via a solenoid can be achieved in one of two ways. When using a direct solenoid, the actual electro-mechanical force pushes directly on the stem to open the poppet. In the case of a solenoid/pilot actuator, the solenoid only controls the flow of a gas (typically compressed air) or liquid into and out of a pilot chamber (discussed above) which moves the stem.
When the operator force is removed from the stem on a normally closed valve, a spring pushes the poppet towards the seat in the body and is assisted by the flow through the valve. Once the poppet reaches the seat, the inlet pressure assists in keeping the poppet seated bubble tight. On normally open valve models, the flow through the valve assists a spring in pushing the valve off its seat to return it to the open condition.
Poppet valves such as illustrated here feature a design that incorporates a seal that is crimped into the poppet's sealing face. The seal materials that are used include various types of rubber, plastics or other exotic polymers which are chosen based on type of medium and operating conditions. Parameters that affect seal material choices would include operating pressure, temperature extremes, chemical composition of the gas or liquid passing through the device, environmental concerns, etc. In some cases, the entire poppet may be made from exotic polymers rather than just the seal insert.
Typical models of poppet valves would include two-way (either in a normally closed or normally open configuration) and three-way operation for filling and exhausting functions from one device. 
Poppet valves are used in many industrial process from controlling the flow of rocket fuel to controlling the flow of milk. Milk is an opaque white liquid produced by the Mammary glands of female Mammals (including Monotremes.
Poppet valve applications include:
Specific applications include:
Poppet valves are used in most piston engines to open and close the intake and exhaust ports in the cylinder head. A reciprocating engine, also often known as a piston engine, is a Heat engine that uses one or more reciprocating Pistons to convert Cylinder head porting refers to the process of modifying the intake and exhaust ports of an Internal combustion engine to improve the quality and quantity of the gas flow In an Internal combustion engine, the cylinder head sits atop the cylinders and consists of a platform containing part of the Combustion chamber and the The valve is usually a flat disk of metal with a long rod known as the valve stem out one end. The stem is used to push down on the valve and open it, with a spring generally used to close it when the stem is not being pushed on. Desmodromic valves are closed by positive mechanical action instead of by a spring, and are used in some high speed motorcycle and auto racing engines, eliminating 'valve float' at high RPM. In general mechanical terms the word desmodromic is used to refer to mechanisms that have different controls for their actuation in different directions MotorCycle is the title of a 1993 album by Rock band Daniel Amos, released on BAI Records. Auto racing (also known as automobile racing, motor racing or car racing) is a Motorsport involving Racing Cars It Valve float is an adverse condition which occurs when the Poppet valves on an Internal combustion engine Valvetrain do not remain in contact with the
For certain applications the valve stem and disk are made of different steel alloys, or the valve stems may be hollow and filled with sodium to improve heat transport and transfer. An alloy is a Solid solution or Homogeneous mixture of two or more elements, at least one of which is a Metal, which itself has Sodium (ˈsoʊdiəm is an element which has the symbol Na( Latin natrium, from Arabic natrun) atomic number 11 atomic mass 22 In Physics, heat, symbolized by Q, is Energy transferred from one body or system to another due to a difference in Temperature
The engine normally operates the valves by pushing on the stems with cams and cam followers. A cam is a projecting part of a rotating Wheel or shaft that strikes a Lever at one or more points on its circular path A tappet in Mechanical engineering is a projection which imparts a linear motion to some other component within an assembly 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. The camshaft is an apparatus often used in Piston engines to operate Poppet valves It consists of a cylindrical rod running the length of the Cylinder bank The crankshaft, sometimes casually abbreviated to crank, is the part of an Engine which translates reciprocating Linear Today Internal combustion engines in cars, Trucks motorcycles aircraft construction machinery and many others most commonly use a four-stroke cycle. On high performance engines e. g. used in Ferrari cars, the camshaft is movable and the cams have a varying height, so by axially moving the camshaft in relation with the engine RPM, also the valve lift varies. Ferrari SpA is an Italian Sports car manufacturer based in Maranello, Italy See variable valve timing. Variable valve timing, or VVT, is a generic term for an Automobile Piston engine technology
In very early engine designs the valves were 'upside down' in the block, parallel to the cylinders - the so called L-head engine because of the shape of the cylinder and combustion chamber, also called 'flathead engine' as the top of the cylinder head is flat. A cylinder is the central working part of a Reciprocating engine, the space in which a Piston travels A combustion chamber is the part of an Engine in which Fuel is burned A flathead engine or sidevalve engine (sometimes called a flatty) is an Internal combustion engine with valves placed in the engine block In an Internal combustion engine, the cylinder head sits atop the cylinders and consists of a platform containing part of the Combustion chamber and the Although this design makes for simplified and cheap construction, it has two major drawbacks; the tortuous path followed by the intake charge limits air flow and effectively prevents speeds greater than 2,000-2,500 RPM, and the travels of the exhaust through the block lead to excessive overheating under sustained heavy load. Cylinder head porting refers to the process of modifying the intake and exhaust ports of an Internal combustion engine to improve the quality and quantity of the gas flow This design therefore evolved into 'Intake Over Exhaust', IOE or F-head, where the intake valve was in the block and the exhaust valve was in the head; later both valves moved to the head. The intake over exhaust (IOE engine also known as F-head and pocket valve, is a Four-stroke Internal combustion engine of primitive design
In most such designs the camshaft remained relatively near the crankshaft and the valves were operated through pushrods and rocker arms. An overhead valve (OHV engine, also called pushrod engine or I-head engine is a type of Piston engine that places the Camshaft Generally referred to within the Internal combustion engine of automotive marine motorcycle and reciprocating aviation engines the rocker arm is a reciprocating lever This led to significant energy losses in the engine, but was simpler, especially in a V engine where one camshaft can actuate the valves for both cylinder banks; for this reason, pushrod engine designs persisted longer in these configurations than others. A V engine is a common configuration for an Internal combustion engine. Piston engines are typically arranged with their pistons in rows moving inside individual cylinders
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. A tappet in Mechanical engineering is a projection which imparts a linear motion to some other component within an assembly Overhead camshaft, commonly abbreviated to OHC, Valvetrain configurations place the engine Camshaft within the Cylinder heads above the Often there are two camshafts, one for the intake and one for exhaust valves, creating the dual overhead cam, or DOHC. Overhead camshaft, commonly abbreviated to OHC, Valvetrain configurations place the engine Camshaft within the Cylinder heads above the The camshaft is driven by the crankshaft - through gears, a chain or a rubber belt. The crankshaft, sometimes casually abbreviated to crank, is the part of an Engine which translates reciprocating Linear A Belt is a looped strip of flexible material used to mechanically link two or more rotating shafts
In the early days of engine building, the poppet valve was a major problem. Metallurgy was not what it is today, and the rapid opening and closing of the valves against the cylinder heads led to rapid wear. Metallurgy is a domain of Materials science that studies the physical and chemical behavior of metallic elements, their intermetallic compounds, and their They would need to be re-ground every two years or so, in an expensive and time consuming process known as a valve job. A valve job is an operation which is performed on any Four stroke cycle, Internal combustion engine, the purpose of which is to clean up the mating surfaces of the Adding tetra-ethyl lead to the petrol reduced this problem to some degree as the lead would coat the valve seats, in effect lubricating the metal. Tetra-ethyl lead, abbreviated TEL, is an organometallic compound with the formula ( CH3CH2)4 Pb. Valve seats made of improved alloys such as stellite have generally made this problem disappear completely and making leaded fuel unnecessary. Stellite alloy is a range of Cobalt - Chromium Alloys designed for Wear resistance
Poppet valves have also been used on steam locomotives, often in conjunction with Lentz or Caprotti valve gear. A steam locomotive is a Locomotive powered by Steam. The term usually refers to its use on Railways but can also refer to a "road locomotive" Hugo Lentz (July 21 1859–March 21 1944 was an Austrian Mechanical engineer, born in South Africa. The Caprotti valve gear is a type of Steam engine Valve gear invented by the Italian Arturo Caprotti. The valve gear of a Steam engine is the mechanism that operates the inlet and exhaust Valves to admit Steam into the cylinder and allow exhaust British examples include:
Sentinel Waggon Works used poppet valves in their steam wagons and steam locomotives. Sentinel Waggon Works Ltd was a British company based in Shrewsbury, Shropshire that made steam powered lorries ("road locomotives" Reversing was achieved by a simple sliding camshaft system. The camshaft is an apparatus often used in Piston engines to operate Poppet valves It consists of a cylindrical rod running the length of the Cylinder bank
The D Slide Valve was a form of Rectilinear slide valve for use in rotative Steam engines invented by William Murdoch and patented in 1799. A piston valve is a device used to control the motion of a Fluid along a tube or pipe by means of the Linear motion of a Piston within The sleeve valve is a type of Valve mechanism for Piston engines distinct from the more common Poppet valve. A safety valve is a Valve mechanism for the automatic release of a gas from a Boiler, Pressure vessel, or other System when the pressure The relief valve is a type of Valve used to control or limit the Pressure in a system or vessel which can build up by a process upset instrument or equipment failure The relief valve is a type of Valve used to control or limit the Pressure in a system or vessel which can build up by a process upset instrument or equipment failure A Corliss steam engine (or Corliss engine) is a Steam engine, fitted with Rotary valves and with Variable valve timing, invented by and named