The Trials of Self -binding Harvesters at Chester. 717 
the compressor jaw have their lower ends suspended by links 
from under the lower portion of the frame, while their centres 
are actuated by a pair of cranks formed in continuation of the 
main square driving-shaft. 
The needle, which is of the usual curved shape, is keyed on 
to a crank shaft which traverses the machine fore and aft, and 
is actuated by a short rod which connects the crank formed on 
the needle shaft with one on the cam disc hereafter mentioned. 
The buttor and the packers are always running, but while the 
sheaf is gathering and forming, the binding machinery, the 
separators, and the ejector are at rest ; but as soon as the sheaf 
has attained the required size it automatically raises a tripper and 
throws into action a driving-pawl, which sets the binding 
machinery to work. This is accomplished by the following 
arrangement. 
On the forward end of the main square driving-shaft, and 
just in front of the packer cranks, is a pinion which runs loose on 
its shaft, and drives by means of a spur wheel a sprocket-wheel 
keyed on to a short shaft, and which, by the agency of a pitched 
chain, drives a sprocket-wheel, fixed on the knotter spindle, 
which actuates the knotter and the ejectors. A crank pin in 
the arm of the sprocket-wheel, by a connecting-rod, operates 
the needle, and a cam disc on the sprocket-wheel, through a 
rocking-lever and a connecting-rod, lowers the compressor for 
the sheaf to be discharged. The loose pinion on the main shaft 
is driven by a clutch formed of a crosshead fixed on the main 
shaft, and carrying on its ends driving rollers. Either of these 
may engage into a tripping pawl consisting of a short lever, 
which revolves with the loose pinion, rocks on a pin pro- 
jecting from its side, and is kept in a radial position by a spiral 
spring similarly fixed, and acting on the tail end of the pawl. 
In this position one of the rollers at the end of the driving-arm 
falls into a recess formed in a projection on the side of the pawl, 
and carries the pinion round with it. But if the revolution of 
the driving pawl be stopped by a tripper arrangement it is 
turned out of its radial position, and the rollers on the driving 
arm then clear the driving recess, and the motion of the pinion 
and with it that of the binding machinery ceases. The tripper 
gear consists of a rocking lever attached to a short fore and aft 
spindle, on to which is keyed a lever, which in its normal 
position is depressed and, striking against the tripper pawl, 
prevents its revolution ; and in order that this may be done with 
as little shock as possible, the end of the lever terminates in a 
spring arrangement, which not only allows of a certain amount 
of yield, but by the reaction of the spring serves also to take 
