A The double clevis screw jacks(double clevis trunnion) are furnished with a clevis at both ends. Double-clevis jacks have less load capacity than the other common mounting configurations. A double-clevis jack has pivots or clevises at both ends: one on the screw tip and one on the end of the protection tube. This tends to weaken it as a column by creating eccentric loads on the screw. This eccentricity tends to increase with greater distance and higher loading. For this reason, double-clevis jacks are limited both in capacity and maximum length. Double-clevis mounting differs from trunnion mounting because the pivot is located farther from the jack body. The Column Loading charts do not apply for this mounting.

When to Choose Screw Jack with Clevis End on Both Ends?
When freedom of movement in two axes is required, a double clevis screw jack may be used, which  incorporates a special clevis end bottom pipe and a standard clevis end on the lifting screw. Machine screw jack and ball screw jacks from 1ton to 25 ton load capacities canbe supplied with double clevis end jacks .Double clevis jacks are always made from upright jacks. Stroke lengths are limited based compression loads. It can be used in angle tilt adjustments, moving a load through an arc, tracking antennas, hinged doors or air dampers etc. Below is a application in solar pannal. In this application, the linear motion is provided by a double clevis machine screw jack.

A There are 3 main types of screw jacks: worm gear machine screw jacks, worm gear ball screw jacks, and bevel gear screw jacks. Within these, there are 3 subcategories related to the mode of operation: Translating, Keyed, and Rotating nut. They have different types in relation to the application. Understanding each of the designs is foundational to selecting the suitable type for your specific applications.

Machine screw jacks that are properly selected and maintained will reliably lift, position, support or hold industrial loads for years. Incorporating them into mechanized applications is a fairly simple matter once jack designs are understood. The basic components of machine screw jacks are lifting screw, gear set, and thrust bearing.

Ball screw jacks include ball nuts that are about 90% efficient so the jacks require much less energy to lift an equal load than their machine screw jack counterpart. They are NOT self-locking so a brake motor needs to be included in the drive system and hand wheels are not a recommended option. Mechanical worm gear ball screw jack, available with translating lifting screw or lifting nut. Standard lifting screw length up to 6 m. Not self-locking, must be combined with a brake arrangement. Ball Screw jack with Translating Lifting Screw. Ball Screw jack with Lifting nut.

Bevel Gear Screw Jacks offer higher efficiency and greater speed than other mechanical worm gear screw jacks. As an added benefit, bevel gear jacks also act as right angle gearboxes, making them an ideal choice for multi-jack systems. There are no "standard" travel lengths and each bevel gear screw jack is built to specification. All high bevel gear screw jacks are equipped with hardened, sharpened and spiral toothed bevel gear transmissions for high lifting speed and greater duty cycle. Bevel Gear Machine Screw Jacks incorporate the use of a trapezoidal acme screw. Bevel Gear Screw Jack systems are ruggedly designed and produced in standard models with load handling capacities 20 tons. They may be used individually or in multiple arrangements.

Rotating Screw Jack(Nut Traveling): A rotating jack has a lifting screw that moves a nut as it turns. The lifting screw is fixed to the worm gear. This causes the load, which is attached to the travel nut, to move along the lifting screw.
Translating Screw Jacks: A translating jack has a lifting shaft that moves through the gear box. A nut is integrated with the worm gear such that the worm gear nut rotate together. When the lifting screw is held to prevent rotation, the lift shaft will move linearly through the gear box to move the load.
Keyed Screw Jacks for Non-Rotation: A feature can be added to a machine screen jack to prevent lifting screw rotation. This type of jack is referred to as a "keyed jack" and is available in upright and inverted models. A keyed jack has a keyway machined along the length of the lifting screw. A matching key is fastened to the cover of the jack which will eliminate lift shaft rotation.
Double Clevis Screw Jacks are used when it is necessary to move a load through an arc, such as tracking antennas, hinged doors or air dampers, Machine Screw and Ball Screw Jacks from 1 ton to 35 ton capacities can be supplied with double clevis mounts. One clevis is welded to a heavy duty stem cover, which is welded to the housing. Double clevis designs are available with optional accessories such as boots, motor mounts, right angle reducers, motors, encoders and rotary limit switches.
Anti-backlash Screw Jacks are used wherever reversible load conditions require precision positioning control. Adjustable backlash Screw Jack models are available to reduce backlash. The unit allows the lash between the drive sleeve and the Work Screw thread(1) to be accurately controlled by the relative position of the upper (2) and lower (3) drive sleeves. Adjustment of the cover (4), by loosing set Screws (5), changes the relative distance between the sleeves. This change in distance compensate for any slash. Axial backlash should be minimized but not completely eliminated, the result would be a lock-up of the Jack. When top plate touch the Jack body, the Jack wear is at the limit and Jack shall be revised.

Self locking machine screw jacks with anti-backlash and ball screw jacks must be considered separately, as the normal backlash will vary due to different constructions. Ball screw jacks do not have an anti-backlash option similar to the machine screw jacks. Instead for zero or reduced axial play ball screw jacks can be ordered with a pre-loaded ball nut.

A Self-locking is a term used to describe jacks that require power to move in either direction. They hold their position when power to the system is off. This makes them inherently safer than hydraulic jacks, for example, which will move backwards under load if the force on the hydraulic actuator is accidentally released. A standard type screw jack made from a worm gear and trapezoidal thread configuration. Self-locking capability (self-holding) can be used at any position within the stroke.

A brake motor is usually NOT required to hold position on self-locking machine screw jacks. Hand wheels in a variety of diameters. They are recommended for self-locking jacks and actuators and can be mounted directly to the jack input shaft.

For Ball Screw Jacks, they are NOT self-locking and require a brake motor to hold position. A brake should also be included for applications that expose the jack or actuator to vibration. They are NOT suited for manual operation.

Bevel gear jacks with single lead screws provide the benefits of a self-locking screw, and bevel gear jacks with double lead screws offer even greater travel speed. Safe design using self-locking. There is a self-locking effect from using a screw jack, which allows maintenance of the screw shaft even during unexpected power cuts.

A Most prevalent are worm gear screw jacks because they can lift heavy loads with little input torque. The large mechanical advantage is through a worm gear ranging from 5:1 to 40:1 in combinations with lead screw or a ball screw.

Ball screw jacks differ from machine screw jacks in a few key ways. Machine screw jacks are typically used to move heavy loads in low-duty-cycle setups and low-speed applications. Because it uses an acme screw it can (in some cases) self-lock to resist backdriving as well — meaning it will hold position without the presence of power or a mechanical brake. In contrast, ball screw jacks are common where higher speeds and duty cycles are needed. In addition, because of the higher efficiency of the ball screw (compared to a machine screw) ball screw jacks can decrease motor horsepower and other electrical requirements.

There are two basic types of screw jacks of which a few additional styles originate. First, there are translating screw jacks. These types of screw jacks use a lift shaft or screw that travels into or out from the worm gear box. The lift shaft can either protrude from the mounting flange side of the gearbox or from the top side of the worm gear box. Secondly, are rotating type screw jacks. In this style, the lift shaft remains stationary and a lifting nut moves along the lift shaft. Much like the translating screw jacks the screw can also protrude down from the mounting flange or up from the top of the jack. To produce translation of the lift shaft or nut, both configurations must be secured to prevent rotation. Where this is unfeasible, keyed screw jacks are an option.

A Worm Gear Screws Jacks can provide long duty life, high load capacity and flexible design. They come in two major categories, Ball Screw and Machine Screw. In this post, we hope to help you identify the best type for your application.

Ball Screw Jacks use a ball screw and nut made from hardened alloy steel with bearing balls carrying the load between nut & screw. This rolling action reduces the friction between nut and screw, permitting smooth and efficient load movement that requires approximately 1/3 less torque than a machine screw jack with the same load.

Machine Screw Jacks incorporate an alloy or sometimes stainless steel worm which drives a high strength bronze worm gear, or drive sleeve. The worm shaft is supported on anti-friction tapered roller bearings with external seals that prevent lubrication loss. The drive sleeve can also be supported on tapered roller bearings, or ball thrust bearings. Rotation of the drive sleeve causes the acme thread lifting screw to translate or rotate, depending on the jack configuration.

Both types can be metric, come in several types (Upright, Inverted, Upright Rotating and Inverted Rotating) and multiple jacks can be laid out in H, U, T and In-Line arrangement. You can also employ multiple jacks in tandem, depending on the physical design and size of the equipment, its stiffness and the guide system. This will, however, introduce challenges with drive, alignment and synchronization. Any jack system is limited by multiple constraints: load capacity, duty cycle, horsepower, column strength, critical speed, type of guidance, brake motor size and ball screw life. To properly size your jack for these constraints, application information must be collected.

A Bevel Gear Jack System offers higher efficiency, greater speed, longer duty cycle capabilities and multiple configurations than other Mechanical Worm Gear Jack System. As an added benefit, bevel gear jacks also act as miter boxes, making them an ideal choice for multi-jack systems. The system's make it a diverse product that suits a variety of applications. Bevel gear jacks with single lead screws provide the benefits of a self-locking screw, and bevel gear jacks with double lead screws offer even greater travel speed.

Although worm gear jacks are sufficient for large loads that are infrequently moved, bevel gear jacks offer more flexibility and programmable options  for a wider range of applications.
Bevel gear jack systems don't come with standardized travel lengths, so each one can be built to specification. Bevel screw jacks come available in machine and ball screw models. Machine screw jacks use a trapezoidal acme screw that offers a low backlash between the nut and screw. Ball screw jacks use hardened bearing balls that allow for smooth and efficient movement of the load. Bevel gear jacks have the capability to run continuously at 100-percent efficiency without overheating. Because of the greater efficiency and rolling action, the ball screw can operate at higher speeds or increased duty cycle when compared with the machine screw jack.

Available in three jack configurations, bevel gear screws can move along the lift shaft in a variety of ways to meet customer expectations:
Translating- The translating configuration has a lifting shaft that moves through the gear box. A nut is integrated with the bevel gear such that the bevel gear and nut rotate together. When the lift shaft is held to prevent rotation, the lift shaft will move linearly through the gear box to move the load.
Rotating- A rotating jack has a lift shaft that moves a nut as it turns. The lift shaft is fixed to the bevel gear. This causes the load, which is attached to the travel nut, to move along the lift shaft.
Keyed- The lift shaft of a translating style jack must be attached to something which prevents the lift shaft from rotating. If it is not, the lift shaft (and the load) will turn and not translate. A feature can be added to a machine screw jack to prevent lift shaft rotation. This type of jack is referred to as a "keyed jack" and is available in translating models.  Anti-rotation is accomplished by a square guide attached to the screw translating inside a square stem cover attached to the jack. The square stem tube is supplied with lube fittings.

Worm Gear Jack Systems are sufficient for large loads that are infrequently moved, Bevel Gear Jack Systems offer more flexibility and programmable options  for a wider range of applications. A mechanical worm gear jack is used where precisely controlled linear movement and positioning are needed. We manufacture two main types of mechanical screw jacks, they are machine screw jacks or ball screw jacks. The design is based on our standard worm gear drives and provides the freedom to mount units in all positions, on a floor, wall or ceiling, for example. Multiple jacks can operate in a group with a shared drive motor, coupled by bevel gears, clutches and transfer shafts. All sizes are available with a variety of gear ratios to ensure the best possible match with the desired movement and precision. A number of versions are also offered with a self-locking action, meaning that the jack locks itself to ensure safety, and no energy is needed to support the load. Complete accessories: bellow, anti-backlash design, safety nut, ball screw, limit switch, overload clutch, potentiometer, encoder, brake, hand-wheel, mounting accessories. Note: Worm gear screw jacks with multi-start screws are also available for applications with high lifting speeds. These versions run at a considerably lower screw speed and better efficiency for the same lifting speed.

A Worm Gear Screw Jack includes Machine Screw Jack and Ball Screw Jack. The key components of mechanical worm gear screw jacks are: trapezoidal lifting screw and lifting nut(machined screw jacks), or ball screw and ball nut(ball screw jacks), worm screw, worm gear and gear housing. The most common screw jack is the worm gear screw jack, also referred to as machined screw jacks because the acme, or trapezoidal, lead screw is machined. In addition to the low cost and self-locking characteristics, another advantage of machine screw jacks, and all screw jacks, is the mechanical advantage achieved through the internal gear ratio resulting in the ability to lift, lower, push or pull a significant load with a relatively small amount of torque on the drive shaft. Ball screw jacks incorporate a ball screw instead of a machined screw and a ball nut, which activates the screw. The advantage of ball screw jacks and the rolling action of their design is greater efficiency, up to 60%, which is much greater than machined screw jacks. Because of their efficiency ball screw jacks can be used in heavier duty cycle applications. They also provide good positional accuracy in high speed applications. One potential disadvantage is that ball screw jacks are not self-locking and will require a brake or motor with enough holding torque to prevent the ball screw from back-driving.

Worm gear machine screw jacks offer precise positioning, uniform lifting speeds and capacity up to 120 tons. Standard model configurations include upright or inverted units with translating or rotating lifting screws. End configurations include top plate, plain, threaded, and clevis ends.
Worm gear ball screw jacks lift and precisely position loads up to 35-tons. Upright or inverted jacks. Select from standard lead and high lead ball screw jacks models to meet your travel speed and ball nut life requirements. These ball screw jacks require up to two-thirds less input torque to move the load than similarly rated machine screw jacks. They require a brake motor or external locking device to hold position.

Bevel Gear Screw Jacks: Bevel gear design eliminates the need for miter gear boxes in multi-jack systems. This design allows higher travel speeds and higher duty cycles. Single-lead machine screw bevel gear jacks are considered self-locking and the lower internal gear ratio permit faster travel speeds (and higher duty cycles) than worm gear screw jack counterparts. Bevel ball jacks achieve fast travel speeds and are rated for near continuous operation.
Bevel Gear Jacks, available in 2.5-ton to 50-ton static capacities, offer higher efficiency and greater speed than other mechanical screw jacks. As an added benefit, bevel gear jacks also act as miter boxes, making them an ideal choice for multi-jack systems. As many as three output shafts may be specified for mounting motors, limit switches, readout devices and other accessories. Bevel gear jacks with single lead screws provide the benefits of a self-locking screw, and bevel gear jacks with double lead screws offer even greater travel speed.
Bevel Ball Actuators, available in 3-ton to 15-ton static capacities, are designed for near-continuous duty operation. These are ours fastest jacks. Available in Translating and Rotating designs, bevel ball actuators act as miter boxes, making them an ideal choice for multi-jack systems. As many as three output shafts may be specified for mounting motors, limit switches, readout devices and other accessories.

A A screw jack is a gearbox assembly (either worm gear or bevel gear) and a transmission product (lead screw, ball screw or roller screw) which through use of a motor is used to convert rotary into linear motion. They can be used to push, pull, tension, lock, unlock, tilt, pivot, roll, slide and lift or lower loads, anything from a few kilos to thousands of tonnes. Screw jacks are essential components of automated machines. Safety and legislative concerns encourage automation of the handling and lifting of heavy loads, especially in regions where workplace and health and safety legislation has been developed.

What Is Screw Jack? A jackscrew, or screw jack, is a type of jack that is operated by turning a lead screw. It is commonly used to lift moderately heavyweights, such as vehicles; to raise and lower the horizontal stabilizers of aircraft; and as adjustable supports for heavy loads, such as the foundations of houses. A screw jack consists of a heavy-duty vertical screw with a top-mounted load table that is screwed into a threaded hole in a stationary support frame with a wide base on the floor. A rotating collar on the head of the screw has holes into which the handle, a metal rod, fits. When the handle is turned clockwise, the screw moves further out of the base and lifts the load resting on the load table. In order to withstand large loads, the screw is usually formed with Acme threads.

The trend to electromechanical actuation screw jacks from hydraulic actuation. Screw jacks typically work in heavy-duty applications. The competing technology at high loads is usually hydraulics. However, the hydraulics are less energy efficient than the electromechanical actuation by screw jacks. Hydraulic systems waste energy when the fluid circulates at constant pressure, regardless of how much work is required by hydraulic positioning. A hydraulic jack or ram requires constant pressure to hold its position when a load is held in place. In contrast, an electric motor used to drive a spindle lift truck consumes energy only when it is driving the load to a required position.
The advantages of electro-mechanical screw jacks over hydraulic can be summarized by: Demand for increased safety, in the event of power loss, screw jacks can be self-locking. Demand for machinery that operates with better energy efficiency. Demand for machinery that operates greater levels of precision. Machinery that requires less maintenance. Machinery that requires less manual intervention to set up processes. Increased range of actuation in terms of variable positioning. Accurate and smooth delivery of force. Cleaner machinery.

Types Of Screw Jack: There are 3 main types of screw jacks: machine/worm gear screw jacks, ball screw jacks, and bevel gear jacks. Within these, there are 3 subcategories related to the mode of operation: Translating, Keyed, and Rotating/Traveling nut.
* Translating Screw Jack: The rotation of the worm wheel acts directly on the lead screw and the lead screw moves linearly. If the end of the lead screw is not fixed (depending on customer requirements), the lead screw will tend to rotate due to the friction between the screw threads.
* Keyed Screw Jack: As above, but the lead screw is wedged so that it cannot turn. This is important if the lead screw end is not to be attached to the load. Both encrypted and non-encrypted transmission screws are commonly used in applications where more than one screw jack is attached to a common load.
* Rotating Screw Jack: The lead screw is attached to the worm wheel so that rotation of the worm wheel causes the lead screw to rotate, thereby sliding the nut along the lead screw when the nut is attached to the load.

The translation speed of a screw jack is influenced by the number of times the screw spindle is started. With single start screw jacks, the system is normally self-locking because the friction angle of the threads is greater than the helix angle. i.e. an axial force exerted on the screw does not result in rotation. This is not the case with a multi-start screw because the angle of friction may be less than the angle of lead.