Patent ID: 7097156
Filing Date: 2006-08-29
Classification: B66D

Abstract:
1. A safety device of an air balancing hoist comprising: a housing including a chamber in which compressed air is induced/discharged by an operation of a push button switch; a first end cap, mounted at one end of the housing, for tightly closing the chamber, where a manifold for inducing and discharging the compressed air into the chamber is formed on an outer side surface; a piston connected in the housing to be slidably reciprocated; a ball screw penetrating the piston and having both ends fixed against rotation in the housing; a reel drum having one end fixed to be rotatable by a bearing fixed on the piston and a second end fixed on a ball nut connected to the ball screw, for rotating along the ball screw; a ratchet wheel of ring shape mounted on an inner side surface of a second end cap formed at the other end of the housing; a braking rotor mounted inwardly in the ratchet wheel to be rotatable around the second end cap; a braking shaft having one end connected to a fixing hole formed on the reel drum and a second end is fixed on the rotor; and a braking pawl having one end elastically inserted in the braking rotor to be pivotable in a circumferential direction and a second end fixed by a hinge on the braking rotor, wherein the push button switch comprises: an up lever and a down lever for controlling a supply and a discharge of the compressed air in the chamber; a body mounted on a passage connected with an entrance and an exit of the compressed air and provided with a cylinder for selectively opening and closing the entrance and the exit of the compressed air as a spool is slidably moved when operating the up lever and the down lever; and a stroke control member, mounted on the body to control the stroke of the up lever, for preventing the up lever from being suddenly fast operated at more than a predetermined pressure.