FACTOID # 22: South Dakota has the highest employment ratio in America, but the lowest median earnings of full-time male employees.
 
 Home   Encyclopedia   Statistics   States A-Z   Flags   Maps   FAQ   About 
   
 
WHAT'S NEW
 

SEARCH ALL

FACTS & STATISTICS    Advanced view

Search encyclopedia, statistics and forums:

 

 

(* = Graphable)

 

 


Encyclopedia > Geneva drive

The Geneva drive is a mechanism that translates a continuous rotation into an intermittent rotary motion. It is an intermittent gear where the drive wheel has a pin that reaches into a slot of the driven wheel and thereby advances it by one step. The drive wheel also has a raised circular blocking disc that locks the driven wheel in position between steps. Image File history File links Geneva_mechanism_6spoke_animation. ... Rotation of a plane, seen as the rotation of the terrain relative to the plane (exposure time 1. ... Spur gears found on a piece of farm equipment. ...


The name derives from the device's earliest application in mechanical watches, Switzerland and Geneva being an important center of watchmaking. The geneva drive is also commonly called a Maltese cross mechanism due to the visual resemblance. A pendulum clock uses a pendulum as its time base. ... Geneva (pronunciation //; French: Genève //, German: //, Italian: Ginevra) is the second most populous city in Switzerland, and is the most populous city of Romandy (the French-speaking part of Switzerland). ... Maltese Cross The Maltese cross is identified as the symbol of the Christian warrior. ...


In the most common arrangement, the driven wheel has four slots and thus advances for each full rotation of the drive wheel by one step of 90° (360/4 = 90). If the driven wheel has n slots, it advances by 360/n° per full rotation of the drive wheel. A degree (in full, a degree of arc, arc degree, or arcdegree), usually symbolized °, is a measurement of plane angle, representing 1/360 of a full rotation. ...

The mechanism needs to be well greased; it is often enclosed in a grease box. Image File history File links Geneva_drive. ...

Contents


Uses and applications

One application of the Geneva drive is in movie projectors: the film does not run continuously through the projector. Instead, the film is advanced frame by frame, each frame standing still in front of the lens for 1/24 of a second (and being exposed twice in that time, resulting in a frequency of 48 Hz). This intermittent motion is achieved using a Geneva drive. (Modern film projectors may also use an electronically controlled indexing mechanism or step motor, which allows for fast-forwarding the film.) The first uses of the Geneva drive in film projectors go back to 1896 to the projectors of Oskar Messter and Max Gliewe and the Teatrograph of Robert William Paul. Previous projectors, including Thomas Armat's projector, marketed by Edison as the Vitascope, had used a "beater mechanism", invented by Georges Demenÿ in 1893, to achieve intermittent film transport. 35 mm Kinoton movie projector in operation. ... Look up second in Wiktionary, the free dictionary. ... The hertz (symbol: Hz) is the SI unit of frequency. ... 1896 (MDCCCXCVI) was a leap year starting on Wednesday (see link for calendar). ... Thomas J. Armat (1866 - September 30, 1948) was an American mechanic and inventor, a pioneer of cinema best known through the co-invention of the Edison Vitascope. ... Thomas Alva Edison (February 11, 1847 – October 18, 1931) was an American inventor and businessman who developed many devices which greatly influenced life in the 20th century. ... 1893 (MDCCCXCIII) was a common year starting on Sunday (see link for calendar). ...


Geneva wheels having the form of the driven wheel were also used in mechanical watches, but not in a drive, but rather to limit the tension of the spring, such that it would operate only in the range where its elastic force is nearly linear. If one of the slots of the driven wheel is obscured, the number of rotations the drive wheel can make is limited. In watches, the "drive" wheel is the one that winds up the spring, and the Geneva wheel with four or five spokes and one closed slot prevents overwinding (and also complete unwinding) of the spring. This so-called Geneva stop or "Geneva stop work" was the invention of 17th or 18th century watchmakers. A wrist watch A watch is a small portable clock that displays the time and sometimes the day, date, month and year. ... It has been suggested that Coil spring be merged into this article or section. ... (16th century - 17th century - 18th century - more centuries) As a means of recording the passage of time, the 17th century was that century which lasted from 1601-1700. ... (17th century - 18th century - 19th century - more centuries) As a means of recording the passage of time, the 18th century refers to the century that lasted from 1701 through 1800. ...


Other applications of the Geneva drive include the pen change mechanism in plotters, automated sampling devices, indexing tables in assembly lines, and so on. This article or section does not cite its references or sources. ...


Internal Geneva drive

Internal Geneva drive
Internal Geneva drive

Besides the external Geneva drive shown in the diagram above, there is also an internal Geneva drive. The more common form is the external Geneva drive because it can be built smaller and can withstand higher mechanical stresses. The axis of the drive wheel of the internal Geneva drive can have a bearing only on one side. The angle by which the drive wheel has to rotate to effect one step rotation of the driven wheel is always smaller than 180° in an external Geneva drive and always greater than 180° in an internal one, where the switch time is therefore greater than the time the driven wheel stands still.
Image File history File links Interior_Geneva_drive. ... Image File history File links Interior_Geneva_drive. ... Figure 1  Stress tensor In physics, stress is a measure of the internal distribution of force per unit area within a body that balances and reacts to the loads applied to it. ...


See also

A dwell cam is an intermitant motion mechanism that alternates forward and return motion with holding position. ...

External links


  Results from FactBites:
 
Geneva drive: Information from Answers.com (643 words)
Geneva wheels having the form of the driven wheel were also used in mechanical watches, but not in a drive, rather to limit the tension of the spring, such that it would operate only in the range where its elastic force is nearly linear.
In watches, the "drive" wheel is the one that winds up the spring, and the Geneva wheel with four or five spokes and one closed slot prevents overwinding (and also complete unwinding) of the spring.
The angle by which the drive wheel has to rotate to effect one step rotation of the driven wheel is always smaller than 180° in an external Geneva drive and always greater than 180° in an internal one, where the switch time is therefore greater than the time the driven wheel stands still.
  More results at FactBites »

 
 

COMMENTARY     


Share your thoughts, questions and commentary here
Your name
Your comments

Want to know more?
Search encyclopedia, statistics and forums:

 


Press Releases |  Feeds | Contact
The Wikipedia article included on this page is licensed under the GFDL.
Images may be subject to relevant owners' copyright.
All other elements are (c) copyright NationMaster.com 2003-5. All Rights Reserved.
Usage implies agreement with terms, 1022, m