tailieunhanh - Mechanisms and Mechanical Devices Sourcebook P4

RECIPROCATING AND GENERAL-PURPOSE MECHANISMS GEARS AND ECCENTRIC DISK COMBINE IN QUICK INDEXING An ingenious intermittent mechanism with its multiple gears, gear racks, and levers provides smoothness and flexibility in converting constant rotary motion into a start-and-stop type of indexing. It works equally well for high-speed operations, as fast as 2 seconds per cycle, including index and dwell, or for slowspeed assembly functions. The mechanism minimizes shock loads and offers more versatility than the indexing cams and genevas usually employed to convert rotary motion into start-stop indexing. . | __CHAPTER 4 RECIPROCATING AND GENERAL-PURPOSE MECHANISMS GEARS AND ECCENTRIC DISK COMBINE IN QUICK INDEXING Connecting rod Both stops and dwell are adjustable. An ingenious intermittent mechanism with its multiple gears gear racks and levers provides smoothness and flexibility in converting constant rotary motion into a start-and-stop type of indexing. It works equally well for high-speed operations as fast as 2 seconds per cycle including index and dwell or for slow-speed assembly functions. The mechanism minimizes shock loads and offers more versatility than the indexing cams and genevas usually employed to convert rotary motion into start-stop indexing. The number of stations stops per revolution of the table can easily be changed as can the period of dwell during each stop. Advantages. This flexibility broadens the scope of such automatic machine operations as feeding sorting packaging and weighing that the rotary table can perform. But the design offers other advantages too Gears instead of cams make the mechanism cheaper to manufacture because gears are simpler to machine. The all-mechanical interlocked system achieves an absolute time relationship between motions. Gearing is arranged so that the machine automatically goes into a dwell when it is overloaded preventing damage during jam-ups. Its built-in anti-backlash gear system averts rebound effects play and lost motion during stops. How it works. Input from a single motor drives an eccentric disk and connecting rod. In the position shown in the drawing the indexing gear and table are locked by the rack the planet gear rides freely across the index gear without imparting any motion to it. Indexing of the table to its next position begins when the control cam simultaneously releases the locking rack from the index gear and causes the spring control ring gear to pivot into mesh with the planet. This is a planetary gear system containing a stationary ring gear a driving planet gear and a sun index .