![cover image](https://wikiwandv2-19431.kxcdn.com/_next/image?url=https://upload.wikimedia.org/wikipedia/commons/thumb/8/8a/Joyvalvegear.png/640px-Joyvalvegear.png&w=640&q=50)
Joy valve gear
Valve gear for steam engines / From Wikipedia, the free encyclopedia
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Joy valve gear is a type of steam locomotive valve gear, designed by David Joy (3 March 1825 – 1903), Locomotive and Marine engineer, and patented (no. 929) on 8 March 1879.[1] The British patent has not been found but the US patent (US252224 of 10 January 1882) has.[2] Joy's gear is similar to Hackworth valve gear but has a compensating mechanism which corrects for "the slight inequality in the motion of the valve arising from the arc of the lever".[3]
![Thumb image](http://upload.wikimedia.org/wikipedia/commons/thumb/8/8a/Joyvalvegear.png/640px-Joyvalvegear.png)
The drawing (right) shows the Joy gear as applied to a London and North Western Railway locomotive.[4] The US patent shows several modifications of the gear. In figure 6 of the patent, one of the levers has been replaced by a slide.
On 10 January 1882, Mr. Joy received U.S. Patent No. 252,224 for the invention.