Instead of the worm drive systems discussed here, a bevel gear system could possibly be used to convert rotation to linear motion. This would offer greater performance to a machine screw jack due to it making a rolling contact instead of the sliding contact of worm drive parts. It could, nevertheless, 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 business lead screws are described by their trapezoidal thread profile and 29° flank angle and are commonly found in American Imperial machine screw jacks. An alternative to the Acme 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 position and complies to an ISO metric standard.
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 wear, the ball screw monitor includes a gothic arch profile.
Popularity of the trapezoidal screw thread comes from the fact that it’s easier to machine and is therefore less expensive than sq . and ball screw thread forms. Additionally, due to the large area of contact between your business lead screw threads and the worm wheel, there is definitely a sizable load carrying capacity. This results in high friction which is harmful to efficiency but does mean the system is much more likely to end up being self-locking. This low performance implies that such screw jacks are more suitable for non-continuous or intermittent operation.
Many applications usually do not warrant the extra expenditure of a ball screw jack since they do not require continual drive. In configuring a screw jack a prediction is constructed of the frequency of actuation which will point to the appropriate screw jack to end up being selected.
Translating Design Jacks are most often selected. With this style, a driven input worm acts on an internal worm gear causing the lifting screw to increase or retract. Operation requires that rotation of the lifting screw become prevented. This rotation it restrained whenever two or more jacks are linked with the same load.
Keyed Style Jacks are used any moment rotation of the lifting screw is not restrained. For example, when you must lift the jack to meet up a load. This is one way they work: An integral, fixed to the jack casing and inserted right into a keyway milled in to the amount of the lifting screw forces the lifting screw to translate without rotating.
Keyed For Travelign Nut Design Jacks (KFTN) are another option. These jacks have a fixed size lifting screw that rotates. Loads are attached to a flanged “vacationing” nut that translates up and down the length of the rotating screw. This kind of jack is ideal for applications that cannot accommodate a screw protection tube or that require 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 input and the useful result weighed against a machine screw jack. In addition, it allows for greater actuation speeds and, because of the low friction, is very durable. However a ball screw jack isn’t inherently self-locking and, because of its enhanced precision components, the initial outlay is better. The resulting improved performance however implies this is often offset against smaller sized drive train elements and a significant reduction in the necessary power.