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electric worm gear screw jacks
Motorized Electric Screw Jack Actuators Price

Electric screw jack actuators  is a basis jack-up part, accomplish the functions such as lifting, drop, push and inverting through worm gear drives screw.

electric worm gear screw jack lift
Two-set Linkage Screw Jack System

Two-set linkage screw jack system can be "L", I and T configuration.  It usually consists bevel gearbox, screw jack, electric motor, gear reducer, hand wheel, pillow block bearing, jaw coupling, line shafting.

 Automatic Screw Jack Lift System
Good Performance Screw Jack Lift System

Screw jack lift system structures include miter gearboxes, screw jacks, electric motor or gear reducer, hand wheel, pillow block bearings, jaw couplings and line shaftings.  Screw Jack System Features: 1. Heavy duty, self-locking, positioning precision, uniform lifting speed, fully synchronization, easy installation, easy operation 2. Two screw jacks system, three screw jacks system..forty screw jacks system. 3. Extremely high capacity requirements of need very precise up or down control. It's of high mechanical, they are an excellent choice when hydraulic, pneumatic or chain systems are prohibitive choices. 4. Widely used in wood working machines, plastics processing machines, textile machines, assembly equipment in the automobile and aircraft industries, food and beverage production equipment as well as packaging machines.

acme ball screw jacks screw lift
Four-set Linkage Screw Jacks System

Four-set linkage screw jack system can be  I and T configuration, transmission efficiency can be 85% .

worm screw jack lift table
High Efficiency Worm Gear Screw Jack Systems

Screw jack lift system structures include miter gearboxes, screw jacks, electric motor or gear reducer, hand wheel, pillow block bearings, jaw couplings and line shaftings.

SE enclosed housing slewing drive
Slewing Drive for Aerial platform

Slewing drives are powered with hourglass worm technology for maximum gear torque and the smoothest rotation.

Worm Gear Slewing Drive
Slewing Drive WE Series

WE Series Slewing drive is combined by the curved tooth slewing ring and worm, gear and worms are more touch supply larger torque.

spiral bevel gear unit
HD Series Spiral Bevel Gearbox

HD Series spiral bevel gearbox is hexahedron,which can fit different direction mounting.

worm gear ball and acme screw jacks
Worm Gear Screw Jack with reducer and motor

Screw jack is used in applications where linear motion is required. Lifting of any load, pushing or pulling of mechanical equipment, adjusting of tight clearances of mechanical parts can be done by screw jacks.

Spiral Gear screw jack
High-speed Lifting Bevel Gear Screw Jack

High-speed lifting bevel gear screw jacks are partly completed machines and intended for installation in complete machines or to be used for assembly with a totality of machinery to create systems.The bevel gear transmission makes high lifting speeds and a high duty cycle possible.

acme mechanical screw jacks lifts
Trapezoidal Machine Screw Jacks 5Ton

Worm Gear Machine Screws Jacks are common worm gear screw jacks,can be upright or inverted,with anti-rotation or self-locking functions.

high efficiency electric lift cylinder
Energy Saving Electric Linear Actuator with DC Motor

An Electric Linear Actuator is an actuator that creates motion in a straight line, in contrast to the circular motion of a conventional electric motor.

right angle bevel gearboxes
T Series Bevel Spiral Gearbox

T series bevel gearbox is standardized with many varieties. The deceleration ratio is 1:1, 1.5:1, 2:1, 2.5:1 and 3:1, which are all actual transmission ratios.

Acme Screw Linear Actuator
ACME Screw Linear Actuator with AC Motor

A Electric Linear Actuator is a mechanical device that converts energy (power from air, electricity or liquid) to create motion in a straight line.

ball screw electric cylinder
Ball screw lifting electric linear actuator

An electric linear actuator is a device that converts the rotational motion of a motor into linear motion – that is push and pull movements.

News
Screw Jacks' Self-locking Property

2018-12-07



Compared with some other types of jack,the Worm gear machine screw jack has an important advantage that is it is self-locking, which means when the rotational force on the screw is removed, it will remain motionless where it was left and will not rotate backwards, regardless of how much load it is supporting. This makes them safer than the hydraulic jack itself, for example, if the force on the hydraulic actuator is released accidentally, it will move backwards under load.

self-locking screw jack actuator

Then what is "self-locking"? Let us see the following information.


Large frictional forces cause most screws in practical use to be "self-locking", also called "non-reciprocal" or "non-overhauling". This means that applying a torque to the shaft will cause it to turn, but no amount of axial load force against the shaft will cause it to turn back the other way, even if the applied torque is zero. This is in contrast to some other simple machines which are "reciprocal" or "non locking" which means if the load force is great enough they will move backwards or "overhaul". Thus, the machine can be used in either direction. For example, in a lever, if the force on the load end is too large it will move backwards, doing work on the applied force. Most screws are designed to be self-locking, and in the absence of torque on the shaft will stay at whatever position they are left. However, some screw mechanisms with a large enough pitch and good lubrication are not self-locking and will overhaul, and a very few, such as a push drill, use the screw in this "backwards" sense, applying axial force to the shaft to turn the screw.

A push drill, one of the very few mechanisms that use a screw in the "backwards" sense, to convert linear motion to rotational motion. It has helical screw threads with a very large pitch along the central shaft. When the handle is pushed down, the shaft slides into pawls in the tubular stem, turning the bit. Most screws are "self locking" and axial force on the shaft will not turn the screw.


This self-locking property is one reason for the very large use of the screw in threaded fasteners such as wood screws, sheet metal screws, studs and bolts. Tightening the fastener by turning it puts compression force on the materials or parts being fastened together, but no amount of force from the parts will cause the screw to untighten. This property is also the basis for the use of screws in screw top container lids, vises, C-clamps, and screw jack lifts. A heavy object can be raised by turning the jack shaft, but when the shaft is released it will stay at whatever height it is raised to.


A screw will be self-locking if and only if its efficiency η is below 50%.

Whether a screw is self-locking ultimately depends on the pitch angle and the coefficient of friction of the threads; very well-lubricated, low friction threads with a large enough pitch may "overhaul".


Now come back to screw jacks. In the case of large shocks, the self-locking function of the lift may be invalidated. Worm gear screw lift self-locking function depends on the following parameters:

• The size of the lead
• Different gear ratios
• Lubrication
• Friction coefficient
• Environmental effects such as high or low temperature, vibration, etc.
• Installation location
Ball screw type and large pitch of the trapezoidal screw series without self-locking function. Therefore, in these cases must use the appropriate brake or brake motor. For smaller guides
(Single line), providing a limited self-locking function. Self-locking function depends on the specific situation.


Learn  more about self-locking screw jacks at www.ludetransmission.com

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