A Look at Screw Jacks
Screw jacks are a common tool found wherever there is a need to lift, position, align, or hold a load. Their reliability and synchronization makes them applicable to a broad range of uses that alternative methods of handling are unable to accomplish. Their applications span across markets such as steel works equipment, water processing, pharmaceutical, medical and laboratory equipment, packaging equipment, nuclear, aerospace, and general mechanical handling. Screw jacks are also finding new uses as alternatives to traditional pneumatic and hydraulic systems. In this blog, we will cover screw jacks, their working principles, and types.
Screw jacks are devices used to convert rotational motion into linear motion. To do this, they use the properties of a screw thread that provide a mechanical advantage, such as their ability to amplify a force. A screw jack may incorporate a machine cut lead screw or ground ball screw to assist in transferring rotational energy into linear energy. In either case, the worm screw acting on the lead screw converts rotation into linear motion via the worm wheel. In the machine screw type, the worm wheel acts directly on the lead screw. In the ball screw jack type, the worm wheel acts on the ball screw via the ball nut which actuates the lead screw.
Of the two, the ball screw type provides greater efficiency between the input and output. It also allows for greater actuation speeds and is generally more durable due to its low friction. However, ball screw jacks are not self-locking and their initial outlay is larger. Nevertheless, their improved efficiency offsets this against smaller drive train components and results in a significant reduction in the necessary power.
Many applications do not necessitate the added expanse of a ball screw jack as they do not require continual drive. During configuration of a screw jack, the frequency of actuation is predicted and the appropriate screw jack is selected based on this. Aside from the worm drive systems, bevel gear systems can also be used to convert rotation into linear motion. This would provide greater efficiency to the screw jack, making it a rolling contact rather than a sliding contact. However, this will likely come at a greater initial cost and will not work in as many scenarios as worm drives.
Types of Screw Jack
There are many variations of screw jacks available depending on a specific need. These can be both machine screw jack or ball screw jacks and are generally chosen based on the architecture of the system they are being fitted with. The most common types of screw jacks are:
- Translating Screw Jack: The rotation of the worm wheel acts directly on the lead screw, which translates linearly. Unless the end of the lead screw is fixed, the lead screw will rotate due to friction between the screw threads.
- Translating Keyed Screw Jack: This is the same as a translating screw jack, except it is keyed so it cannot rotate. This is important as the lead screw end is not affixed to the load.
- Rotating Screw Jack: The lead screw is fixed to the worm wheel such that the worm wheel causes rotation of the lead screw when the nut is attached to the load.
- Translating Screw Jack System: This is a system of six screw jacks wherein the lead screw ends are attached to a common load. Clearance is required under the bottom mounting plane of the jack body to accommodate the translating screw cover.
- Rotating Screw Jack System: This is a system of four screw jacks in which the lifting nuts translate. Clearance under the bottom mounting plane of the jack body is not required but allowance must be made in the lifting plate design to allow the plate to pass over or past the lifting screw.
For screw jacks of all types and much more, look no further than NSN Axis. Owned and operated by ASAP Semiconductor, we can help you find all types of parts for the aerospace, civil aviation, defense, electronics, industrial, and IT hardware markets. Our account managers are always available and ready to help you find all the parts and equipment you need, 24/7-365. For a quick and competitive quote, email us at sales@nsnaxis.com or call us at 1-269-264-4495. Let us show you why we consider ourselves the future of purchasing.
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