Figure415 Stepped-thread interrupted-screw breech block

An Asbury Mechanism opens and closes the

breech Breech may refer to: * Breech (firearms), the opening at the rear of a gun barrel where the cartridge is inserted in a breech-loading weapon * breech, the lower part of a pulley block * breech, the penetration of a boiler where exhaust gases leav ...

of heavy artillery for reloading with a projectile and bags of

propellant A propellant (or propellent) is a mass that is expelled or expanded in such a way as to create a thrust or other motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicles, the e ...

. It was widely used for

naval artillery Naval artillery is artillery mounted on a warship, originally used only for naval warfare and then subsequently used for naval gunfire support, shore bombardment and anti-aircraft roles. The term generally refers to tube-launched projectile-firi ...

of the

world war A world war is an international conflict which involves all or most of the world's major powers. Conventionally, the term is reserved for two major international conflicts that occurred during the first half of the 20th century, World WarI (1914 ...

s and similar

coastal artillery Coastal artillery is the branch of the armed forces concerned with operating anti-ship artillery or fixed gun batteries in coastal fortifications. From the Middle Ages until World War II, coastal artillery and naval artillery in the form of c ...

and

railway gun A railway gun, also called a railroad gun, is a large artillery piece, often surplus naval artillery, mounted on, transported by, and fired from a specially designed railroad car, railway wagon. Many countries have built railway guns, but the ...

s. The device was invented at the

Washington Navy Yard The Washington Navy Yard (WNY) is the former shipyard and ordnance plant of the United States Navy in Southeast Washington, D.C. It is the oldest shore establishment of the U.S. Navy. The Yard currently serves as a ceremonial and administrativ ...

in 1916 by draftsman Dorsey Frost Asbury. It is sometimes called a Smith-Asbury mechanism by the

United States Navy The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...

in recognition of Asbury's supervisor, Lieutenant Commander George Leonard Smith, USN. Large caliber breech-loading artillery became practical with French development of the obturator by Charles Ragon de Bange in 1872; and speed of reloading was improved by adaptation of the

interrupted screw Breech from Russian 122 mm M1910 howitzer, modified and combined with 105 mm H37 howitzer barrel An interrupted screw or interrupted thread is a mechanical device typically used in the breech of artillery guns. It is believed to have be ...

breech plug, which was later further improved by

Axel Welin Ernst Martin Axel Welin (10 November 1862 – 27 July 1951), was a Swedish inventor and industrialist. He was married to Agnes Welin from 1889. Axel Welin studied at the Royal Institute of Technology in Stockholm from 1879 to 1884. Between ...

in 1890 as the

Welin breech block The Welin breech block was a revolutionary stepped, interrupted thread design for locking artillery breeches, invented by Axel Welin in 1889 or 1890. Shortly after, Vickers acquired the British patents. Welin breech blocks provide obturation for ...

and adopted by the Swedish. Asbury used gearing to fully open a Welin breech by linking the unscrewing, withdrawing and swinging clear movements into one continuous action.

Sources

* {{US Patent, 1185964A Artillery components