574
�KINEMATICS OF MACHINERY.
�chain. Both are placed upon the link 6 '7, and give a very near
approximation to the required motion. Compound (C") chains are
also employed in numerous modifications as weighing machines.
The skew screw-chain (<7$^P^), which we examined in 154, has also come lately into use in the " dogs " used upon the face plates of lathes,* &c., in several forms.
Another example which is in place here is that of the reverted wheel-chain ((7 z2 OJj'), which we examined in 105. 1 must content myself here with merely mentioning this : we have already
seen what an immense number of me- chanisms are formed from the chain
j n"\ , 2 <-v-
As a fifth and last example we shall take the chain shown in a general form in Fig. 431, which gives us some very notable mechanisms. It is a combined chain consisting of the simple spur- wheel chain (O t C') with two links, each p ra 430 containing two parallel cylinder pairs,
added to the two wheels. The chain lias therefore five links and six pairs, the latter being the cylinder pairs
���Fri. 431.
1, 2, 3, 4, 5 and the pair 6 of the form (C 2 ). We may write it shortly as (0JQ) and in full :
6 d 1 a 2 I 3 c 6
ii
..
�d 5 e 4 c
- See for example Danbtiry's drill-chuck, Scientific American, vol. xix. (1373)
p. 215.
�
