As opposed to the worm drive systems discussed here, a bevel gear system could be used to convert rotation to linear motion. This might offer greater performance to a machine screw jack due to it producing a rolling contact instead of the sliding contact of worm drive elements. It could, however, come at a larger initial cost and does not cover as higher ratio range as worm drives.
Also known as power screws, lead screws come with a number of different types of thread profile which are suitable for different applications. Acme lead screws are described by their trapezoidal thread profile and 29° flank angle and are commonly within American Imperial machine screw jacks. An alternative solution to the Acme business lead screw in a machine screw jack will be a square lead screw.
European or other international screw jacks utilise a trapezoidal lead screw with a 30° flank angle and complies to an ISO metric regular.
Ball screw jacks require the thread of the business lead screw to get a profile that allows for the travel of the balls. To improve load distribution and minimise put on, the ball screw monitor has a gothic arch profile.
Recognition of the trapezoidal screw thread originates from the fact that it is simpler to machine and is therefore more economical than square and ball screw thread forms. Additionally, due to the large area of contact between the lead screw threads and the worm wheel, there is certainly a large load carrying capability. This results in high friction which is certainly detrimental to efficiency but also means the system is more likely to be self-locking. This low performance implies that this kind of screw jacks are more suitable for non-continuous or intermittent operation.
Many applications usually do not warrant the excess expenditure of a ball screw jack since they do not require continual drive. In configuring a screw jack a prediction is made of the frequency of actuation and this will point to the correct screw jack to end up being selected.
Translating Design Jacks are most often selected. With this style, a driven insight worm acts on an internal worm gear causing the lifting screw to increase or retract. Operation requires that rotation of the lifting screw end up being prevented. This rotation it restrained whenever several jacks are linked with the same load.
Keyed Design Jacks are utilized any time rotation of the lifting screw isn’t restrained. For example, when you need to lift the jack to meet up a load. This is one way they work: An integral, fixed to the jack casing and inserted into a keyway milled in to the length of the lifting screw forces the lifting screw to translate without rotating.
Keyed For Travelign Nut Style Jacks (KFTN) are another choice. These jacks possess a fixed duration lifting screw that rotates. Loads are attached to a flanged “journeying” nut that translates up and down the length of the rotating screw. This kind of jack is well suited for applications that cannot accommodate a screw security tube or that want a flush mount
The worm wheel acts on the ball screw (via the ball nut) which actuates the lead screw. This system offers greater performance between the insight and the useful result compared with a machine screw jack. Furthermore, it allows for greater actuation speeds and, because of the low friction, is quite durable. However a ball screw jack isn’t inherently self-locking and, because of its improved precision components, the initial outlay is better. The resulting improved performance however implies this could be offset against smaller drive train components and a significant reduction in the necessary power.