Piston valve
Encyclopedia
Fluid
In physics, a fluid is a substance that continually deforms under an applied shear stress. Fluids are a subset of the phases of matter and include liquids, gases, plasmas and, to some extent, plastic solids....
along a tube or pipe
Pipe (material)
A pipe is a tubular section or hollow cylinder, usually but not necessarily of circular cross-section, used mainly to convey substances which can flow — liquids and gases , slurries, powders, masses of small solids...
by means of the linear
Linear
In mathematics, a linear map or function f is a function which satisfies the following two properties:* Additivity : f = f + f...
motion of a piston
Piston
A piston is a component of reciprocating engines, reciprocating pumps, gas compressors and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from...
within a chamber or cylinder
Cylinder (engine)
A cylinder is the central working part of a reciprocating engine or pump, the space in which a piston travels. Multiple cylinders are commonly arranged side by side in a bank, or engine block, which is typically cast from aluminum or cast iron before receiving precision machine work...
.
Examples of piston valves are:
- The valves used in the valve gearValve gearThe 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 steam to escape, respectively, at the correct points in the cycle...
of many stationary steam engineSteam engineA steam engine is a heat engine that performs mechanical work using steam as its working fluid.Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be...
s and most steam locomotiveSteam locomotiveA steam locomotive is a railway locomotive that produces its power through a steam engine. These locomotives are fueled by burning some combustible material, usually coal, wood or oil, to produce steam in a boiler, which drives the steam engine...
s. - The valves used in many brass instrumentBrass instrumentA brass instrument is a musical instrument whose sound is produced by sympathetic vibration of air in a tubular resonator in sympathy with the vibration of the player's lips...
s. - The valves used in pneumatic cannons.
Steam engines
Leicester and Swannington Railway
The Leicester and Swannington Railway was one of England's first railways, being opened on 17 July 1832 to bring coal from collieries in west Leicestershire to Leicester.-Overview:...
, manufactured by The Horsely Coal & Iron Company in 1833, shows a very early use of the piston valve. Piston valves had been used a year or two previously in the horizontal engines manufactured by Taylor and Martineau of London, but did not become general for stationary or locomotive engines until the end of the 19th century.
In the 19th century, most steam locomotive
Steam locomotive
A steam locomotive is a railway locomotive that produces its power through a steam engine. These locomotives are fueled by burning some combustible material, usually coal, wood or oil, to produce steam in a boiler, which drives the steam engine...
s used slide valves
D slide valve
The slide valve is a rectilinear valve used to control the admission of steam into, and emission of exhaust from, the cylinder of a steam engine.-Use:...
to control the flow of steam into and out of the cylinder
Cylinder (steam locomotive)
The cylinders of a steam locomotive are the components that convert the power stored in the steam into motion.Cylinders may be arranged in several different ways.-Early locomotives:...
s. In the 20th century, slide valves were gradually superseded by piston valves, particularly in engines using superheated
Superheater
A superheater is a device used to convert saturated steam or wet steam into dry steam used for power generation or processes. There are three types of superheaters namely: radiant, convection, and separately fired...
steam. There were two reasons for this:
- With piston valves, the steam passages can be made shorter. This reduces resistance to the flow of steam and improves efficiency
- It is difficult to lubricateLubricationLubrication is the process, or technique employed to reduce wear of one or both surfaces in close proximity, and moving relative to each another, by interposing a substance called lubricant between the surfaces to carry or to help carry the load between the opposing surfaces. The interposed...
slide valves adequately in the presence of superheatedSuperheaterA superheater is a device used to convert saturated steam or wet steam into dry steam used for power generation or processes. There are three types of superheaters namely: radiant, convection, and separately fired...
steam
The usual locomotive valve gears, e.g., the Stephenson valve gear
Stephenson valve gear
The Stephenson valve gear or Stephenson link or shifting link is a simple design of valve gear that was widely used throughout the world for all kinds of steam engine. It is named after Robert Stephenson but was actually invented by his employees....
, Walschaerts valve gear, and Baker valve gear
Baker valve gear
Baker valve gear was the main competitor to Walschaerts valve gear for steam locomotives in the United States. Strictly speaking it was not a valve gear but a variable expansion mechanism adapted to the Walschaerts layout replacing the expansion link and sliding die block...
, can be used with either slide valves or piston valves. Where poppet valve
Poppet valve
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. The shaft guides the plug portion by sliding through a valve guide...
s are used, a different gear, such as Caprotti valve gear
Caprotti valve gear
The Caprotti valve gear is a type of steam engine valve gear invented in the early 1920's by Italian architect and engineer Arturo Caprotti. It uses camshafts and poppet valves rather than the piston valves used in other valve gear...
is needed.
Brass instruments
Brass instrument
A brass instrument is a musical instrument whose sound is produced by sympathetic vibration of air in a tubular resonator in sympathy with the vibration of the player's lips...
s, particularly the trumpet-like members of the family (cornet
Cornet
The cornet is a brass instrument very similar to the trumpet, distinguished by its conical bore, compact shape, and mellower tone quality. The most common cornet is a transposing instrument in B. It is not related to the renaissance and early baroque cornett or cornetto.-History:The cornet was...
, flugelhorn
Flugelhorn
The flugelhorn is a brass instrument resembling a trumpet but with a wider, conical bore. Some consider it to be a member of the saxhorn family developed by Adolphe Sax ; however, other historians assert that it derives from the valve bugle designed by Michael Saurle , Munich 1832 , thus...
, saxhorn
Saxhorn
The saxhorn is a valved brass instrument with a conical bore and deep cup-shaped mouthpiece. The sound has a characteristic mellow quality, and blends well with other brass.-The saxhorn family:...
, etc.).
Other brass instruments use rotary valve
Rotary valve
A rotary valve is a type of valve in which the rotation of a passage or passages in a transverse plug regulates the flow of liquid or gas through the attached pipes. The common stopcock is the simplest form of rotary valve...
s. notably the orchestral horn
Horn (instrument)
The horn is a brass instrument consisting of about of tubing wrapped into a coil with a flared bell. A musician who plays the horn is called a horn player ....
s and many tuba
Tuba
The tuba is the largest and lowest-pitched brass instrument. Sound is produced by vibrating or "buzzing" the lips into a large cupped mouthpiece. It is one of the most recent additions to the modern symphony orchestra, first appearing in the mid-19th century, when it largely replaced the...
models, but also a number of rotary-valved variants of those brass instruments which more commonly employ piston valves.
The first piston-valved musical instruments were developed just after the start of the 19th century. The Stölzel valve (invented by Heinrich Stölzel
Heinrich Stölzel
Heinrich David Stölzel was a German horn player who developed some of the first valves for brass instruments. He developed the first valve for a brass instrument, the Stölzel valve, in 1814, and went on to develop various other designs, some jointly with other inventor musicians...
in 1814) was an early variety. In the mid 19th century the Vienna valve was an improved design. However most professional musicians preferred rotary valves for quicker, more reliable action, until better designs of piston valves were mass manufactured in towards the end of the 19th century.
Pneumatic cannons
A piston valve can also refer to a 2-way 2-position, pilot-operated spool valve. The term is extremely popular among spud gun enthusiasts who often build homemade piston valves for use in pneumatic cannons. Valves are typically constructed primarily from pipe fittings and machined plastics or metals.The inside of a piston valve contains a piston that blocks the output when the valve is pressurized, and a volume of air behind the piston. When the pressure behind the piston is released the piston is pushed back by the force of the pressure from the input. This allows the valve to be opened by a much smaller pilot valve, with speeds faster than possible with just a manually operated valve. Functionally these types of valves are comparable to quick exhaust valves.
This type of piston valve is also sometimes referred to as a back-pressure valve.
See also
- Angle seat piston valveAngle seat piston valveAn angle seat piston valve is a pneumatically-controlled valve with a piston actuator providing linear actuation to lift a seal off its seat. The seat is set at an angle to provide the maximum possible flow when unseated. Angle seat piston valves are particularly suited to applications where high...
- Corliss valve
- D slide valveD slide valveThe slide valve is a rectilinear valve used to control the admission of steam into, and emission of exhaust from, the cylinder of a steam engine.-Use:...
- Poppet valvePoppet valveA 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. The shaft guides the plug portion by sliding through a valve guide...
- Rotary valveRotary valveA rotary valve is a type of valve in which the rotation of a passage or passages in a transverse plug regulates the flow of liquid or gas through the attached pipes. The common stopcock is the simplest form of rotary valve...
- Sleeve valveSleeve valveThe sleeve valve is a type of valve mechanism for piston engines, distinct from the usual poppet valve. Sleeve-valve engines saw use in a number of pre-World War II luxury cars and in USA in the Willys-Knight car and light truck...
- Slide valve
External links
- Early valve designs
- Why was the valve invented?
- Elements of Brass Instrument Construction with good discussion of valve types and history
- Visual explanations of some types of piston valve
- Kinematic Models for Design Digital Library (KMODDL) – Movies and photos of hundreds of working mechanical-systems models at Cornell University. Also includes an e-book library of classic texts on mechanical design and engineering.