DESCRIPTION OF THE DIVIDING ENGINES 693 



advanced a space equal to the desired distance between the rulings. 

 This is done by the cams operating the pawl-levers (26 and 40), which 

 cause the pawl (41) to rise to a pre-determined position corresponding 

 to one or more teeth of the graduated ratchet head, then to engage this 

 wheel and, being now forced down to its normal position, to cause the 

 wheel and the feed-screw, to which it is attached, to turn through a 

 small definite angle. The rotation of the screw causes the nut to 

 advance towards the ratchet head; and the nut pushes forward the 

 plate-carriage to which the plate to be ruled is secured. The engine 

 being now at the end of its return stroke, the diamond is lowered into 

 contact with the plate, and is ready for ruling the next line. These 

 operations are repeated until the requisite number of lines is ruled. 

 During each cycle of operations a slight additional motion is imparted 

 to the nut and thus to the plate-carriage by means of the corrector 

 mechanism, in order that any periodic errors of the screw, screw-head, 

 etc., may be eliminated. 



The ruling-carriage with its diamond holder moves along truncated 

 V-ways, as shown in the cuts, the surfaces in contact being the 

 steel ways and the box-wood linings to the grooves on the carriage. 

 These box-wood linings press against both the sides and the top of the 

 ways and are adjustable. The plate-carriage moves along V-ways, the 

 surfaces in contact being the steel ways and the cast-iron carriage. 

 These two pairs of ways are accurately at right angles to each other. 



DETAILED DESCRIPTIONS 



I. Mechanism connecting the plate-carriage and the nut. See Fig. 5. 

 The plate-carriage carries a thrust collar (20) through which the 



feed-screw passes freely. It is held in position by pins engaging in the 

 top and bottom of the plate-carriage. The thrust of the nut in advan- 

 cing is communicated by two lugs, one on each side of the nut casings 

 (21), to two correspondingly located screw-heads in the thrust collar; 

 and, finally, screw-heads in the top and bottom of the thrust-collar 

 transfer the thrust to correspondingly located lugs (22) in the plate- 

 carriage. 



II. Pawl mechanism. See Fig. 4. 



The degree of rotation imparted to the graduated ratchet-head de- 

 pends upon the number of teeth the pawl engages in each revolution 

 of the main-shaft and may be varied by altering the size of the cams 

 (46 and 47) on which the pawl-levers 26 and 40 rest. The pawl-lever 



