SHAFTS
THERE ARE TWO TYPES OF SHAFTS :--
hollow shaft
This shaft is the main shaft carrying all the linkages including
two prismatic pairs in the open position of the umbrella.initially
in the closed position this shaft is held against the lower catch.
When this catch is released shaft moves up relative to the base
shaft due to force applied on this shaft by inner shaft spring
which is in compressed position initially.During this movement of
shaft umbrella doesn't open up too much,but after moving a certain distance
safe enough to allow the umbrella to open up without hurting the
user this shaft gets engaged with upper catch.At this instant
there starts a relative motion between this shaft and
links of prismatic pairs.
base shaft
This is the lower shaft carrying the whole weight of the umbrella.
Both the catches are on this shaft. The cross section of the shaft
is not circular but has two guideways at 180 deg to each other
provided for the alignment of the hollow shaft so that it finds catches
on its path.
start
mechanism
springs
linkages
catches