Lifting Device For An Overhead Projector Which Has A Constant Velocity During The Upward And Downward Movement
First Claim
1. A lifting device, comprising:
- a lifting unit;
a drive unit connected with the lifting unit to control operation of the lifting unit; and
a braking unit connected with the drive unit to control operation of the drive unit;
wherein the braking unit includes;
a microprocessor;
a control circuit connected with the microprocessor;
a changeover switch connected with the control circuit and the drive unit; and
a control switch connected with the microprocessor and the changeover switch;
the control circuit of the braking unit includes a first transistor, a second transistor, a first connecting terminal and a second connecting terminal;
the first transistor of the control circuit is connected with a power supply and is connected with the first connecting terminal;
the second transistor of the control circuit is connected with a ground side and is connected with the second connecting terminal;
the control switch of the braking unit includes a relay;
the relay of the control switch has a coil connected with the microprocessor.
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Accused Products
Abstract
A lifting device includes a lifting unit, a drive unit connected with the lifting unit to control operation of the lifting unit, and a braking unit connected with the drive unit to control operation of the drive unit. The braking unit includes a microprocessor, a control circuit connected with the microprocessor, a changeover switch connected with the control circuit and the drive unit, and a control switch connected with the microprocessor and the changeover switch. Thus, the drive unit is rotated normally in the positive direction to lift the overhead projector and is rotated at a slower speed in the reverse direction to lower the overhead projector so that the overhead projector is kept at a constant speed during the lifting and lowering process and is moved upward and downward smoothly and stably.
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Citations
5 Claims
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1. A lifting device, comprising:
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a lifting unit; a drive unit connected with the lifting unit to control operation of the lifting unit; and a braking unit connected with the drive unit to control operation of the drive unit; wherein the braking unit includes; a microprocessor; a control circuit connected with the microprocessor; a changeover switch connected with the control circuit and the drive unit; and a control switch connected with the microprocessor and the changeover switch; the control circuit of the braking unit includes a first transistor, a second transistor, a first connecting terminal and a second connecting terminal; the first transistor of the control circuit is connected with a power supply and is connected with the first connecting terminal; the second transistor of the control circuit is connected with a ground side and is connected with the second connecting terminal; the control switch of the braking unit includes a relay; the relay of the control switch has a coil connected with the microprocessor. - View Dependent Claims (2, 3, 4, 5)
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Specification