Wiegand's Patent Model of a Variable Eccentric for a Steam Engine Cut-Off Valve – ca 1857
date: label: date made
content: 1857
label: patent date
content: 1857-09-29
name: label: inventor
content: Wiegand, S. Lloyd
notes: label: Description
content: This model was filed with the application to the U.S. Patent Office for Patent Number 18,311 issued to S. Lloyd Wiegand of Philadelphia, Pennsylvania on September 29, 1857. The patent was for an improved mechanism to operate the cut-off valve gear for steam engines.
label: Description
content: Wiegand's design provided a means of adjusting the point in the power stroke of the engine’s piston at which high pressure steam being fed to the cylinder was cut off. This was desirable as power was extracted from the expansive force of the steam after the valve closed. This saved fuel by avoiding continuing use of high pressure steam. Wiegand provided a means of adjusting the point of cut-off while the engine was running. This was not new; others such as B. H. Wright and George Corliss had patented devices to do so. Both Wiegand and Wright based their designs on variable eccentrics. In a variable eccentric, the amount of eccentricity, or offset from the shaft center, can be varied by a control mechanism.
label: Description
content: The method to accomplish this consisted of an inclined metal slide that varied the amount of eccentricity as a lever was moved causing the slide to move through a slot in the eccentric wheel. Wiegand's claim was that his design for the first time allowed such adjustments to be made regardless of whether the engine was operating in forward or reverse. In the image of the model the lever operating the steam inlet valve would rest upon the top of the eccentric which is the thin cylinder to the right center.
label: Description
content: The patent model is constructed of brass and mounted on a hammered brass plate which is mounted on a wooden base. The brass base plate is inscribed “S. Lloyd Wiegand, Philadelphia, PA.” The control lever is shown at the left. The miniature hand crank at the right was intended to demonstrate the movement of the cut-off mechanism. Diagrams showing the complete design of the patent can be found in the patent document online at the United States Patent and Trademark Office website, www.uspto.gov.
place: label: place made
content: United States: Pennsylvania, Philadelphia
label: associated place
content: United States: Pennsylvania, Philadelphia
topic: label: Subject
content: Patent Models
label: Subject
content: Steam Engines
setName: label: See more items in
content: Work and Industry: Mechanical and Civil Engineering
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content: Engineering, Building, and Architecture
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content: Patent Models
label: Exhibition
content: Power Machinery
label: Exhibition Location
content: National Museum of American History
publisher: label: Related Publication
content: Frank A. Taylor. Catalog of the Mechanical Collections of the Division of Engineering United States National Museum, Bulletin 173
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: MC.308659
label: catalog number
content: 308659
label: accession number
content: 89797
label: patent number
content: 18,311
objectType: label: Object Name
content: engine, steam, valve gear. model
label: Object Name
content: patent model, valve, steam engine cut off
physicalDescription: label: Measurements
content: overall: 7 in x 3 in x 13 in; 17.78 cm x 7.62 cm x 33.02 cm