Stepless speed change electric chain block
Number of patents in Portfolio can not be more than 2000
United States of America Patent
Stats
-
Dec 20, 1988
Grant Date -
N/A
app pub date -
May 26, 1987
filing date -
May 23, 1986
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
A stepless speed change electric chain block includes a DC motor for driving a load sheave. The chain block comprises a phase control circuit having a variable resistor, a capacitor, a two-way trigger diode, and a triode AC switch for receiving alternating current from alternating power source to control it in phase, a full-wave-rectifier for receiving alternating current controlled in phase in the phase control circuit to convert it into direct current which is supplied into the DC motor, and mechanical brake means provided in a transmission between the DC motor and the load sheave for braking rotation of the load sheave in a winding-off direction. With this arrangement, as the speed setting for winding operation is effected only by the phase control circuit, so that the constitution of the block is simplified and inexpensive in comparison with the prior art. All the supplied power is effectively utilized for operating the chain block. A load is always wound-off at a set speed safely and is securely held at the stopped position during the stoppage of the chain block.
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