Page 404 - Analysis and Design of Machine Elements

Analysis and Design of Machine Elements
382
as a coupling. Springs 4 are used to preset engagement speed by providing correct
tension during assembly.
An overrunning clutch or directional clutch transmits torque from the driving shaft
to drive shaft only in one direction. In the opposite direction, the driven shaft is in
overrun condition, with no torque transmitted. The ratchet and pawl is a simple device
permitting alternate engagement and disengagement of rotating members. In a more
high-precision machine, an overrunning clutch can be used. As shown in Table 13.3, the
clutch has an inner ring 1 with cam profiles around the periphery and an outer ring 2.
When the driving shaft rotates in the driving direction, or when the driving shaft rotates
faster than the driven shaft, the bolts and springs 3 ensure the rollers 4 are wedged tightly
between the outer ring 2 and inner ring 1 and thus transmit torque. When the driving
shaft rotates in the opposite direction, or when the driven shaft rotates faster than the
driving shaft, the rollers 4 move out of engagement, and no torque is transmitted, thus
protect equipment from damage due to over speeding [1]. There are usually between
three and four rollers and the greater the number of rollers, the higher the torque that
canbetransmitted.

References

1 Mott, R.L. (2003). Machine Elements in Mechanical Design, 4e. Prentice Hall.
2 Hindhede, U., Zimmerman, J.R., Hopkins, R.B. et al. (1983). Machine Design Funda-
mentals: A Practical Approach. New York: Wiley.

3 Collins, J.A. (2002). Mechanical Design of Machine Elements and Machines: A Failure
Prevention Perspective, 1e. New York: Wiley.
4 Mancuso, J.R. (1986). Couplings and Joints: Design, Selection, and Application.New
York: Marcel Dekker.
5 Pu, L.G. and Ji, M.G. (2006). Mechanical Design, 8e. Beijing: Higher Education Press.
6 Juvinall, R.C. and Marshek, K.M. (2011). Fundamentals of Machine Component
Design, 5e. New York: Wiley.
7 Xu and, Z.Y. and Qiu, X.H. (1986). Machine Elements, 2e. Beijing: Higher Education
Press.
8 Wen, B.C. (2015). Machine Design Handbook, 5e, vol. 3. Beijing: China Machine
Press.
9 Oberg, E. (2012). Machinery’s Handbook, 29e. New York: Industrial Press.
10 Budynas, R.G. and Nisbett, J.K. (2011). Shigley’s Mechanical Engineering Design,9e.
New York: McGraw-Hill.

Problems

Review Questions

1 How can one transmit power to or from a rotating shaft?

2 What are the characteristics of a universal coupling? How could one assemble a pair
of universal couplings?