Multi-column lifting apparatus and synchronization control device for same
AssigneeGebr. Hofmann KG
InventorHorst Hegenbart
Life of this patent
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Abstract
A lifting apparatus of the type having a number of columns supporting a load platform each column driven by an electrical, polyphase current motor whereby sensors on each column, for example potentiometers, produce a signal indicating the height of that column. The signals are applied to a comparator which in turn provides an output to one or more electronic switches, such as a triac or thyristor having a diode connected in parallel with it for conducting current in an opposite direction, each such switch connected to a winding of a motor to control the current applied so as to reduce any difference in height among the columns.
Claims12
A lifting apparatus comprising
- a plurality of columns, a respective carriage vertically movable along each column,
- means supported by the carriages for carrying a load to be lifted,
- a respective electrical polyphase current motor operable to move each said carriage,
- a sensing means operatively associated with each said column and operable to deliver an electrical signal depending on the height of lift of the respective carriage,
- comparing means connected to said sensing means for receiving and comparing said signals, and
- an electronic polyphase current switch controllable by the comparing means and actuated thereby, when there is a difference between the signals from the sensing means, to supply a reduced current to the respective one of said motors.
A control circuit for a lifting apparatus having a plurality of movable columns and a motor associated with each said column for moving that column comprising:
- sensing means coupled to each said column for producing an electrical signal which varies as a function of the height of that column,
- comparator means connected to said sensing means for receiving said signal and producing a control signal indicating differences in height between said columns and
- control means connected to said motors and said comparator means for varying the current applied to the motors and accordingly the speed of the motors to reduce differences in height between said columns, including a thyristor having its anode and cathode connected to a motor winding and its gate connected to said comparator means and a diode connected in parallel to said thyristor for conducting current in an opposite direction.
Dependencies are inferred from the claim text.