Trip valve mechanisms are a class of

steam engine A steam engine is a heat engine that performs mechanical work using steam as its working fluid. The steam engine uses the force produced by steam pressure to push a piston back and forth inside a cylinder. This pushing force can be trans ...

valve gear 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 steam to escape, respectively, at the correct points in the cycle. It can also serve as a reversing g ...

developed to improve

efficiency Efficiency is the often measurable ability to avoid wasting materials, energy, efforts, money, and time in doing something or in producing a desired result. In a more general sense, it is the ability to do things well, successfully, and without ...

. The trip mechanism allows the inlet valve to be closed rapidly, giving a short, sharp

cut-off A cut-off, battle jacket, battle vest or kutte in heavy metal subcultures, is a type of vest or jacket which originated in the U.S. military, specifically the Army Air Corps, where pilots and other aviation personnel would collect patches or o ...

. The valve itself can be a

drop valve The double-beat valve, drop valve or equilibrium valve is a type of poppet valve arranged to allow it to be opened against a high pressure with a minimum of force. One of its uses is in steam engines to admit steam to the cylinders and to release t ...

or a

Corliss valve Corliss is both a surname and a given name. People Given name * Corliss Lamont (1902–1995), American philosopher, political activist, and philanthropist * C. C. Moseley (1894–1974), American aviator and aviation businessman * Corliss Palmer ( ...

. Trip valve gear was applied to larger

stationary engines A stationary engine is an engine whose framework does not move. They are used to drive immobile equipment, such as pumps, generators, mills or factory machinery, or cable cars. The term usually refers to large immobile reciprocating engines, pr ...

. It was not used in transport applications,An exception was the very early

London Steam Carriage The London Steam Carriage was an early steam-powered road vehicle constructed by Richard Trevithick in 1803 and the world's first self-propelled passenger-carrying vehicle. Cugnot had built a steam vehicle 30 years previously, but that had been ...

(1803) which had a form of trip gear. as it was not suitable for high speed. The trip point of the valve mechanism, and therefore the cut-off, would be adjusted either manually or automatically by the

governor A governor is an administrative leader and head of a polity or political region, ranking under the head of state and in some cases, such as governors-general, as the head of state's official representative. Depending on the type of political ...

. The valve is opened by the mechanical valve gear mechanism, and when the trip gear trigger releases the mechanism the valve is snapped closed, usually by a spring acting against a

dashpot A dashpot, also known as a damper, is a mechanical device that resists motion via viscous friction. The resulting force is proportional to the velocity, but acts in the opposite direction, slowing the motion and absorbing energy. It is commonly us ...

Advantages of a Trip Valve Gear

When using the Corliss and other trip valve gears, the possible advantages are: # By allowing the inlet-valves to open quickly, full boiler-pressure can be established in the cylinder early in the stroke. # Due to how quickly the inlet-valve closes, the area of the work-diagram is increased. This is due to a sharp corner at the cut-off point rather than a rounded curve. When a rounded curve is present here the pressure from wire-drawing is lowered gradually due to the gradual closure of the valve. # Due to this gear being created for engines designed to be regulated by varying admission, it has an advantage of making terminal pressure low. These engines secure this regulation without creating irregularities in exhaust functions due to them always having multiple-valve engines. # Adjusting these independent valves can be easy if variations at both ends of the cylinder is something that is wanted. # Due to the small amount of motion and period of rest for the steam-valves after they have closed helps to reduce the friction in the valve-gear which in turn decreases the loss of power.

Disadvantages of a Trip Valve Gear

The trip valve-gear, which is almost always a multiple valve-gear, has the potential to face the following disadvantages: # Many times, these gears have multiple complicated parts. # Engines which are created with these complicated gears can be expensive. # The limitation of rotative speed or the number of revolutions which are caused by the need for engaging catches and valves can be a down fall in these valve-gears. # It is important for this valve to release prior to the valve reaching its greatest point of opening. This is an issue due to the way it limits the range.

Footnotes

References

Engine valves Steam engines {{Mech-engineering-stub