Chapter 11 : Simple Lifting Machines „„„„„ 185

185

Simple Lifting

Machines

11.1. INTRODUCTION

In the last chapter, we have discussed the

principles of lifting machines. Now in this chapter,

we shall discuss the applications of these principles

on a few lifting machines.

11.2. TYPES OF LIFTING MACHINES

These days, there are many types of lifting

machines which are available in the market. But the

basic principle, on which all these machines are based,

is the same. It will be interesting to know that engineers

who have designed (or invented) these machines have

tried to increase the velocity ratio of their respective

lifting machines. A little consideration will show, that

if the efficiency of a machine remains almost the same,

11

CHAPTERCHAPTERCHAPTERCHAPTERCHAPTER

Contents

1. Introduction.


2. Types of Lifting Machines.


3. Simple Wheel and Axle.


4. Differential Wheel and
   Axle.


5. Weston’s Differential Pulley
   Block.


6. Geared Pulley Block.


7. Worm and Worm Wheel.


8. Worm Geared Pulley Block.


9. Single Purchase Crab
   Winch.


10. Double Purchase Crab
    Winch.


11. Simple Pulley.


12. First System of Pulleys.


13. Second System of Pulleys.


14. Third System of Pulleys.


15. Simple Screw Jack.


16. Differential Screw Jack.


17. Worm Geared Screw Jack.