284 J. ALFRED GRIFFITHS. 



these instruments, but in the illustration (Fig. 5) a more carefully 

 designed instrument is shown, which may be used for many purposes. 



The three parts of the mechanism are fixed in one frame, and 

 in the illustration the front plate is supposed to be removed, and 

 with it the ordinary dial work on the hour arbor C. The large 

 sector N moves with a long range outside the back plate, has a 

 steady axis of the full breadth of the frame at the base and rests 

 at zero against the stop P, a light spring assisting and balancing 

 its return stroke. The motion of the prime mover is communi- 

 cated to the pulley T by a cotton thread from any convenient 

 rotating part, and by the worm S drives the wheel R and the 

 friction roller Q bearing against the sector N, and continually 

 drags the pen Y away from zero. The front pivot of the arbor of 

 Q bears in the front plate of the clock, and the wheel R (of one 

 hundred teeth) remains continually in gear with the worm S. 

 The back pivot of R Q however is carried in a swinging bearing 

 attached to a branch of the lever V "W which is centred in cocks 

 so as to clear the wheel R and the sector N. A light spring holds 

 down the lever W and presses the roller Q against N, except when 

 the lever end W is lifted by the revolution of the snail K. If the 

 motion of T is speeded too fast for the size of the paper, at the 

 upper limit of the pen stroke the roller Q passes over the clearance 

 Z and grinding is avoided. 



The tripping train* B, G, H, K, is driven from the inner end 

 of the mainspring, and the time trainf A, C, D, E, F, from the 

 outer end of the spring, and winding may be done at any time 

 between the tripping moments without stopping the action. 

 Separate springs might be used for the two trains, but a single 

 spring ensures a constant proportion between the power available to 

 lift the lever I J and the friction at the main tripping pallets L. 



On the snail arbor K is an arm K L (shown dotted), with a 

 detent pin at its end gearing alternately with one of two pallets L 



„ m , , , Mainspring 8 8 8 



* The numbers may be:— B=84teeth X ^gj X h^o x sISTk 



Mainspring 25 8 8 6 



A =84 teeth. ~ C=64 D=6U E=48 scape, 15 teeth 



