A, fig. 139. The lock is here to be seen in its normal or 'set ' condition,
with its catch in position to hold the loop of the bow-string.
Fig. 139. - The Lock with Its Working and Other Parts,
Fitted, and One of the Side-Plates of Its Casing Removed to show the Interior
Action of the Lock. Half full size.
The curved catch of the lock, i.e. the upper part of the tumbler (A,
fig. 138, previous page), stands above the side-plates at the forward end
of the casing. This catch is smoothly rounded at its edges so that it may
hold the bow-string without cutting it.
The upright iron at the lever end of the lock is the base of the peep-sight
(M, fig 115, p. 178). As this piece has no connection with the movements
of the lock, its upper part is here omitted.
B, fig. 139. The lock as it appears when the trigger (T, fig. 115, p.
178) in the stock of the cross-bow has been pulled to release the bow-string.
This trigger, which swings loosely in the stock of the crossbow, presses
back the projecting end of the lock-trigger. This allows the long end of
the sear to escape from the little step in the lock-trigger against which
it rested, as it did in A, fig. 139. At the same moment, the strain of
the bow-string on the catch of the tumbler causes the tumbler and the short
end of the sear to disengage where they were previously interlocked, the
loop of the bow-string being, of course, then instantly set free from the
It will be seen that the short end of the sear and the notch in the
tumbler are slightly sloped (fig. 138, previous page), where they fit against
one another when the lock is set, as it is in A, fig. 139. This causes
these parts to separate directly the long end of the sear and the trigger
of the lock are clear of each other. To reset the lock, all you need do
is to push the tumbler upwards into the position shown in A, fig. 139.
The shoulder in the tumbler, which may be seen immediately below its
upper part or catch, comes against the short end of the sear when the lock
is set free and thus prevents the tumbler from turning too far round.
By pressing down the small knob fixed on the top part of the lock-trigger,
it can be utilised to free the bow-string.