Drive mechanism for telescopic linear actuator
A telescopic linear actuator includes a rotational drive mechanism specially adapted and assembled within a tubular housing to reduce noise and vibration of the actuator during its operation. The rotational drive mechanism includes an electric motor adapted for low current operation, a gearbox containing a planetary gear axially connected to the motor with a stepped-up gear ratio, and a drive screw member operatively connected to the gearbox to extend longitudinally through the tubular housing. The drive screw is provided with a specially configured threaded surface formed along the screw member having a reduced thread count and associated increased thread pitch to operatively engage and drive a movable piston member through the tubular housing.
1. A telescopic linear actuator for movement of an article coupled thereto in opposite longitudinal directions with reduced noise levels, comprising:
a tubular housing substantially cylindrical in form and having a longitudinal axis; and
a rotational drive assembly contained within the tubular housing, the rotational drive assembly comprising an electric motor reversible in rotational operation, a planetary gearbox connected to the electric motor and having a stepped-up gear ratio to provide increased torque, and a drive screw member engaged with the planetary gearbox.
2. A telescopic linear actuator according to claim 1 , further comprising a piston arm connected to the drive screw member of the rotational drive assembly and made to move thereon in alternate directions longitudinally through the tubular housing.
3. A telescopic linear actuator according to claim 1 , wherein the electric motor is regulated in the rotational operation thereof to run effectively at reduced motor speeds below normal motor specifications.
4. A telescopic linear actuator according to claim 3 , wherein the reduced motor speeds of the electric motor are below 2000 rpm.
5. A telescopic linear actuator according to claim 3 , wherein the stepped-up gear ratio of the planetary gearbox is increased to a level inversely proportional to the reduction in the motor speed of the electric motor.
6. A telescopic linear actuator according to claim 1 , wherein a thread count along the drive screw member is approximately one thread per inch.
7. A telescopic linear actuator for linear movement of an article coupled thereto in opposite longitudinal directions with reduced noise levels, comprising:
a tubular housing;
a rotational drive assembly contained within the tubular housing, the rotational drive assembly including:
a reversible electric motor with a motor output,
a planetary gearbox connected to the motor output, and
a drive screw engaged with the planetary gearbox; and
a piston arm connected to the drive screw and displaceable by rotation of the drive screw,
wherein the reversible electric motor is connected to a variable power supply and configured to operate at regulated input currents below those normally specified resulting in a slower motor speed.
8. A telescopic linear actuator according to claim 7 , wherein the planetary gearbox is configured such that a ratio between rotation of the reversible motor and rotation of the drive screw is stepped-up.
9. A telescopic linear actuator according to claim 8 , wherein the planetary gearbox is configured such that the ratio is stepped-up to a level that increases actual torque output to match a required torque output at normal motor operating speeds.
10. A telescopic linear actuator according to claim 8 , wherein the ratio is stepped-up to a level inversely proportional to a percentage reduction in the motor speed.
11. A telescopic linear actuator according to claim 7 , wherein the slower motor speed of the reversible electric motor is below 2000 rpm.
12. A telescopic linear actuator according to claim 7 , wherein a thread count along the drive screw is approximately one thread per inch.
13. A method of operating a telescopic linear actuator including a tubular housing and a rotational drive assembly contained within the tubular housing, wherein the rotation drive assembly includes a reversible electric motor with a motor output, a planetary gearbox connected to the motor output, and a drive screw engaged with the planetary gearbox, the method comprising:
connecting the reversible electric motor to a variable power source; and
operating the reversible electric motor at regulated input currents below those normally specified resulting in a slower motor speed.
14. A method according to claim 13 , further comprising stepping up a gear ratio of the planetary gearbox to provide increased torque.
15. A method according to claim 14 , wherein the step of stepping up the gear ratio comprises stepping up the gear ratio by an amount inversely proportional to a percentage reduction in the motor speed.