When facing with the need to lift, lower, push or pull a load,especially a heavy load and hold it in the correct position, as crew jack or multiple screw jack system may provide the best linear motion solution when considering its performance/cost ratio. There are 3 main types of screw jacks:machine/worm gear screw jacks,ball screw jacks, and bevel gear screw jacks. Within these, there are 3 subcategories related to the mode of operation: Translating, Keyed, and Rotating/Traveling nut.  Let's see how these three subcategories move in below ,

In order to know if a screw jack or screw jack system could be a solution for your application, you will need to consider which type of screw jack to select. There are worm gear screw jacks, bevel gear screw jacks and ball screw jacks, and each has several different options and configurations.

To determine the type of screw jack that is best for your application, you need to consider several factors, including: load, self-locking capabilities, travel rate or travel speed, efficiency, accuracy, duty cycle and price,etc.

The double-section screw structure consists of two screws and two nuts. The diameter of the first-stage screw is larger than that of the second-stage screw. There is a keyway on the first-stage screw, and the inner hole of the worm gear is a through hole with a keyway. When the worm gear rotates counterclockwise, the key structure drives the first-stage screw to rotate. A nut with an internal thread is installed above the turbine and fixed on the top of the box. It cooperates with the thread of the first-stage screw. The screw and the nut produce relative movement, and the screw rises or falls. The second-stage structure is also a combination of a pair of nuts and screws. The secondary nut is connected to the primary screw and rotates and rises and falls with the primary screw. The secondary screw is connected to the user’s equipment. The screw does not rotate, but only rises and falls.

1. The primary and secondary screws have the same axis;
   
2. Compact structure, small size, saving space and cost;
   
3. Reduce the weight of the overall platform, reduce the output power of the drive source, energy saving and environmental protection;
   
4. Double the speed. Compared with a single-section screw, the speed is twice that of a single-section screw at the same input speed;
   
   
   

The screw jack system is widely used in situations with long spans and excessive loads. The use of screw jacks typically involves a multi-unit synchronized configuration. This approach ensures that the load on each individual screw jack does not exceed its capacity, guaranteed sychronized movement of all units to prevent lateral forces, and ehances overall stability and safety of the solution.

The desigan phase for a synchronized screw jack system is crucial,requiring customers to provide relvent data and considering installation space, operating conditions, limit switches, and other aspects. However, after completion and production delivery, on-sit installation at the customer's premises is equally important. We need to pay attention to various issues such as center height alignment,coaxiality, guide devices,and gearbox orientation determination.

Today we want to discuss how to avoid excessive deviations during the multi-unit screw jack system.First, let's start with the perparation steps: After receiving the screw jacks from the customer, it's necessary to ensure that the output and input shafts of units like gearbox and motors are at the same horizontal level. If there is a difference in center height, you can chosse to add appropriate thickness washers to make them consistent. When connecting with couplings or connection rods, it's necessary to calibrate coaxiality to prevent tilting or binding situations.

If a lifting platform is required, attention must be paid to its installation. We need to ensure that the mountibng surface of the screw or nut is at the same horizontal heigth, and the mounting surface of the screw jack should also remain level.Additionally, adjust the mounting holes of the screw head(or nut mounting holes)so that they align with the mounting holes of the support platform before installation installing it. It's important to note that during installation,lateral forces should not be applied to the screw. Lastly, to avoid excessive deviation when multiple screw jack system are installed, we must confirm that there are no errors in the dimensional deviations of each axis before connecting the equipment.Before assembling the screw jack with the driven source and other devices., check for dimensional deviations in shaft diameters,keys, and keyways to prevent damage to bearings from over-tightening or affect power transmission from under-tightening.After installation, lubricate all necessary parts and conduct test runs.If any issues arise during testing, immediately stop operation and only restart once everything is confirmed to be normal.

Screw stability verification: known load 100KN, stroke 500mm, speed 60mm/min, no guide rail, usage coefficient 1.5, low operating frequency, calculated model For (Heavy Duty Electric Linear Actuator model SCA200-V1-500-FL-P2):

lifting Screw specification Tr80*12

1. Known conditions

Load F=100KN=100,000N

Stroke S=500mm

Speed v=60mm/min

Usage coefficient K=1.5

Screw specification Tr80*12 (diameter 80mm, pitch 12mm)

2. Analysis of screw force

The screw mainly bears the axial load, so we need to calculate the stress of the screw under the axial load.

• Screw diameter d=80mm=0.08m

•Screw cross-sectional area A=π (2d)2= π(20.08)2=0.005027㎡

•Axial load Fax=K*F=1.5×100,00N=150,000N

3. Calculation of screw stress

Screw stress o =AFax=0.00502715000=2983866.67Pa

4. Check the stability of the screw

For the stability of the screw, we mainly pay attention to whether it will flex. Since the screw is usually installed on the fixed bracket and its length is relatively short (500mm), the possibility of buckling is relatively small. However, in order to evaluate more accurately, we can use Euler's formula to estimate the critical bending load of the screw.

1. Screw length=500mm=0.5m

2. The elastic modulus of the screw material E (set to steel, E≈210GPa=210×109Pa)

3. Screw moment of inertia I=π 64d4= π64×(0.08)4=2.01062×10-7m4

Eular critical load Fcr can be calculated by the following formula:

Fcr=12 π2EI=(0.5)2π 2×210×109×2.01062×10-7=2,649,444.44N

Because Fax=150,000N＜Fcr=2,649, 444.44N, the screw is stable under axial load.

5. Summary
After calculation, it is confirmed that the screw (specification is Tr80*12) equipped with the linear actuator model SCA200-V1-500-FL-P2 is at a load of 100KN, stroke of 500mm, speed of 60mm/min, and a coefficient of use of 1.5 And the linear actuator is stable under the condition of low working frequency.

The transmission ratio of a worm gear screw lift (often just called a worm gear) refers to the ratio between the number of turns the worm (the driving gear) makes for one complete revolution of the worm wheel (the driven gear). This ratio dictates how much mechanical advantage is gained through the system, and also influences the speed reduction and torque increase.

Factors Related to the Transmission Ratio:

1. Lead of the Worm:

   • The lead is the distance the nut (or worm wheel) moves along its axis per one complete revolution of the worm. It plays a direct role in the transmission ratio.
   • A higher lead results in a faster movement of the worm wheel, but with a higher mechanical advantage (lower ratio) as the gear ratio is influenced by how far the worm travels per turn.

2. Number of Teeth on the Worm Wheel:

   • The number of teeth on the worm wheel relative to the number of threads on the worm also affects the ratio.
   • In general, the more teeth on the worm wheel relative to the worm, the lower the transmission ratio.

3. Number of Threads on the Worm:

   • Worms can have one or more threads (called single-start or multi-start worms).
   • A multi-start worm will reduce the transmission ratio, as each turn of the worm moves the worm wheel by a larger distance.

4. Pitch of the Worm:

   • The pitch (distance between adjacent threads) also influences the ratio. A finer pitch (smaller thread spacing) typically results in a higher transmission ratio.

5. Friction and Efficiency:

   • Worm gears have a high frictional contact between the worm and the worm wheel, which can influence the effective transmission ratio, especially at higher loads.
   • Efficiency is typically lower in worm gears compared to other types of gears, which can cause some discrepancy between the theoretical and actual ratio.

How to Calculate the Transmission Ratio:

The transmission ratio can be calculated using the following formula:

Where:

• $Z_w$ = Number of teeth on the worm wheel.
• $Z_s$ = Number of starts (threads) on the worm.

Example:

If the worm wheel has 40 teeth and the worm has a 2-start thread, the transmission ratio would be:

This means for each full rotation of the worm, the worm wheel will turn 1/20th of a rotation.

Additional Considerations:

• Self-locking feature: Worm gears often have a self-locking property, where the worm can drive the worm wheel but the worm wheel cannot drive the worm. This property comes into play in applications like screw lifts where load holding is important.

Regardless of whether it is a standard electric linear actuator, a small-sized actuator, or even a micro actuator, these devices have seen strong development and application across various industries. One common aspect of their use is their significant role in the renewable energy sector. Here, we will focus on the development of electric actuators in the field of photovoltaic (PV) power generation.

1. Reasons for Applying Electric Actuators in the Photovoltaic Industry
The idea of using electric linear actuators in PV systems emerged due to the high cost of solar panels, which greatly limited the widespread adoption of such products. Under these circumstances, there was a strong need for alternative products, leading to further development of electric electric linear actuators.

2. Development of Electric Actuators in the PV Industry
From the early stages of technology to the present day, photovoltaic power generation has evolved from expensive solar cells to more cost-effective polycrystalline silicon cells, with a significant expansion in application fields. During this process, the use of components has also changed. In the past, fixed brackets were mostly used in power generation systems. However, the current trend has shifted toward actuator-based tracking systems.

3. Recognition of Electric Actuators in the PV Industry
Due to the high efficiency and stability of actuator-based tracking systems, they have received widespread recognition from both the government and industry peers. This has further encouraged investment in this area, ushering in a promising period of development for electric linear actuator tracking systems.

4. Categories of Electric Actuator-Based PV Tracking Systems
This power generation model can be broadly classified into two main types: single-axis linked tracking systems and dual-axis tracking systems. Regardless of the type, electric linear actuators serve as the driving force for these tracking systems. Because of this, strict requirements are placed on their service life—they must match the lifespan of the solar panels in order to maximize the overall efficiency of the PV power generation system.

The gear ratio (also called the transmission ratio) of a worm gear screw jack refers to the ratio between the rotational speed of the worm and the rotational speed of the screw, usually expressed as the ratio of the worm's speed to the screw's speed. The gear ratio directly affects the speed and output torque of the screw jack.

Meaning of Gear Ratio:

Definition of Gear Ratio:
The gear ratio (Transmission Ratio) is the transmission ratio between the worm wheel and the worm, usually represented by the ratio of the number of teeth on the worm wheel to the number of threads on the worm. For example, if the worm wheel has 50 teeth and the worm has 10 threads, the gear ratio would be 5:1.

Impact on Speed:
The gear ratio determines the relationship between the rotational speed of the worm and the screw. The larger the gear ratio, the slower the worm's speed and the slower the screw's lifting speed. Therefore, a higher gear ratio will slow down the screw's movement, which is suitable for applications requiring precise control. A lower gear ratio will result in faster screw movement, which is suitable for quick lifting needs.

Impact on Torque:
The larger the gear ratio, the greater the torque transmitted from the worm to the screw. In cases of heavy loads, a larger gear ratio can provide higher output torque, allowing the jack to support heavier loads.

• Low Gear Ratio (e.g., 1:1 or 3:1) typically provides higher speed but lower output torque, making it suitable for light load, high-speed applications.

• High Gear Ratio (e.g., 10:1 or 20:1) provides greater torque, making it suitable for applications requiring higher load capacity and precision, but with slower speed.

Gear Ratio and Application Scenarios:

Higher Gear Ratio (e.g., 20:1, 30:1):

• Suitable for high-load, low-speed applications. Due to lower speed, it provides greater torque, making it ideal for heavy-duty equipment or precision-controlled applications, such as precision lifting platforms and large machinery.

• Typical Applications: Lifting platforms, heavy-duty cranes, precision machinery.

Lower Gear Ratio (e.g., 3:1, 5:1):

• Suitable for light-load, high-speed applications. Due to the smaller gear ratio, the speed is higher, but the torque is lower, making it suitable for applications that require faster movement but are not designed for heavy loads.

• Typical Applications: Light-duty conveyor systems, automated production lines, etc.

Impact of Gear Ratio on Self-locking Performance:

Worm gear screw jacks often feature a self-locking function, meaning that when the worm stops turning, the friction generated by the engagement between the worm and the worm wheel prevents the load from automatically sliding down. When the gear ratio is larger, the self-locking ability is stronger, because the engagement angle between the worm and the worm wheel is greater, making it more difficult for the load to move in the opposite direction.

The load capacity of servo electric cylinders cannot be very high mainly due to the following reasons:

4. Efficiency issues: High loads can reduce the operational efficiency of the electric cylinder, causing increased heat generation. Excessive load may also affect the effectiveness of the cooling system, raising the system temperature and shortening the lifespan of the electric cylinder.

Therefore, when selecting a servo electric cylinder, it is essential to choose a model that matches the specific application requirements. Ensuring the load remains within the design limits of the cylinder is critical to avoid overload and ensure reliable operation.

1. Snow melting principle of heating cable

Electro thermal conversion

The alloy resistance wire inside the cable generates heat after being energized (the surface temperature is generally 40-50℃), and melts the snow through heat conduction, thereby preventing the formation of ice dams.

Self-regulating technology (some high-end models)

Due to the use of PTC materials, the lower the temperature, the lower the resistance, and the greater the heat output, thus achieving automatic power regulation, saving energy, and achieving optimal safety.

Zone control

The system uses temperature and humidity sensors or intelligent controllers and only starts in snowy weather or low temperatures to reduce energy consumption.

2. Installation steps and precautions

•  Preparation before installation

Land use planning

Cover eaves, gutters and other areas prone to snow and ice accumulation. It is recommended to use "inverted W" or "snake" wiring.

Cable selection

Power: generally 15~30W/m (appropriately adjusted according to cold climate, the recommended value in the north is ≥25W/m).

Type: It is best to use self-adjusting cables to prevent overheating and damage to roof materials.

• Installation

Surface cleaning

Remove debris from the roof and ensure that the cable is close to the roof.

Cable fixing

Fix with special clips or high-temperature resistant tape, maintaining a spacing of 30 to 50 cm.

Avoid drilling directly with a nail gun to avoid damaging the insulation layer.

Installation in the gutter

The cable is laid at the bottom of the ditch and can be covered with a metal sheath to prevent mechanical damage.

Electrical connection

Connect the cable to the GFCI (leakage protection) socket and seal the waterproof junction box.

It is recommended to use an independent circuit to avoid overload.

3. Safety tips

The cable spacing is ≥5cm and overlapping is prohibited. Avoid using flammable materials (such as asphalt membrane; use high-temperature resistant models).

Test the insulation resistance (≥1 MΩ) after installation.

Two suggestions and purchase points:

•  Purchase settings

Power: 20-30 W/m (higher value for very cold areas)

Voltage: 220V (home use) or 24V (safety low voltage)

Protection level: IP68 (waterproof and dustproof)

Warranty period: ≥10 years

• Maintenance and energy-saving tips

Regular inspection

Test the cables for normal operation before winter every year and clean up all dead leaves.

Smart control

Use a Wi-Fi thermostat (such as Honeywell T6) to start and stop remotely or trigger automatically.

Energy-saving tips

Use electricity only during the day (take advantage of freezing and thawing at night).

Choose the time of electricity use according to the electricity rate sharing area.