Chap.6 intermittent mechanisms
Chap.6.1 Ratchet mechanisms
Chap.6.2 Geneva mechanisms
Chap.6.3 Cam-type index mechanisms
Chap.6.4 Intermittent gearset
Chap.6.1 Ratchet mechanisms
Working principle,
Driving pawl Holding pawl
Driven
ratchet
Frame
Type of the ratchet mechanisms
Silent ratchet mechanisms
Externally meshed
Internally meshed
Ratchet rack
Fixed direction
Changeable direction1,2
Single function
Double function
External
Internal
Tooth ratchet mechanisms
Internally meshed
Ratchet rack
Externally meshed
Double function
Silent ratchet mechanisms
Application
? 1,Intermittent motion（牛头刨床的间歇送进机构）
? 2,Safety lifting mecjanism（卷扬机制动机
构）
? 3．转位、分度（手枪盘分度机构）
? 4,Clutch 超越离合（钻床的自动进给机构）
Chap.6.2 Geneva mechanisms
Driving plate
Driven geneva wheel
Working principle,
Type of the geveva mechanisms
Planar geneva mechanisms
Spherical geneva mechanisms
external geneva mechanisms
internal geneva mechanisms
Compared to the ratchet mechanism
The angular velocity of a geneva mechanism should
not be too high,The rotation angle of a geneva wheel
for each cycle can not be adjusted,
The Geneva mechanism has no rigid impulse and
motion is smoother,Geneva mechanisms can be
used to drive rotating tables with large moments of
inertia,
Application
? Widely used in the Automatic machine and
instruments,
? Projection Machine
Chap.6.3 Cam-type index mechanisms
? It is used in machines which need to
transmit indexing motion or
intermittent motion between two
crossed shafts,
? Two types,
Cylindrical-cam index mechanisms
Hourglass –cam index mechanisms
Advantages,Disadvantages and
Application
? It can transmit motion smoothly and
their dynamical characteristics are very
good,Noise and vibration is very low,
? Any ratio between motion time and
dwell time can be designed,and
positional accuracy is high and reliable,
? Used in high-speed,high-accuracy index
mechanisms,The hourglass-cam index
mechanism has higher index accuracy,
Chap.6.4 Intermittent gearset
Type
? External
? Internal
Application
? Rack
? gearset