Page 17 - Joyce - Jacks, actuators and systems

ENgiNEERiNg iNFORmATiON FAQ

8. Can I buy a jack with a clevis on both 14. What is screw lead error? The deviation 20. What do I need to consider when
ends? Yes. When freedom of movement from the mathematical lead expressed in ordering a bellows boot to protect
in two axes is required, a double clevis jack inches per foot cumulative. the lifting screw?
may be specified.
- Closed height dimensions may increase
- Double clevis jacks incorporate a clevis 15. What is the amount of lead error in when boots are added.
machined or pinned on the screw end and a standard lifting screw? Rolled Acme - The customer must specify boot collar
also a clevis welded to the protection tube.
screws have up to .010 in/ft cumulative diameter when ordering bellows boots
Screw travel is limited. Contact Joyce/ error, milled Acme screws have up to 0.003 for KFTN jacks.
Dayton for more information. in/ft cumulative error; and ball screws have - Zippered boots are also available.
up to 0.007 in/ft cumulative error. Contact
- Electric cylinders, integrated actuators, Joyce/Dayton for more information. - Special boot material is available.
and linear actuators are also available with
a clevis on both ends. - Horizontal screw applications may
require boot guides.
16. Are Joyce/Dayton jacks and actuators Contact Joyce/Dayton for more information.
9. What is meant by “self-locking”? user-serviceable? The level to which
Self-locking is a term used to describe products can be serviced in the field
jacks that require power to move in either varies from product to product. Refer 21. Are jacks and actuators corrosion-
direction. They hold their position when to the product Operation & Maintenance resistant? Stainless steel jacks are
power to the system is off. See page 10 Manuals or contact Joyce/Dayton for inherently corrosion resistant. All
for more details. more information. exposed surfaces are stainless steel
and aluminum bronze. Most other jacks
can be modified with special finishes,
10. What if the jack is not self-locking? 17. What motor options are available? coatings, and seals. Contact Joyce/Dayton
A brake is required on the input shaft of Motor options vary among product lines. with your requirements. See page 179.
any jack that may lower under load (ball Customers can use AC 3-phase, AC
screw jacks, WJ500 jacks, double-lead single-phase, DC motors, international
Acme screw jacks, integrated actuators, voltage motors and others. Let us know 22. What is a follower nut assembly and
and electric cylinders that are more your requirements. when is it helpful to have one?
than 30% efficient). See page 10 for Follower nut assemblies allow customers
more details. The motors on linear actuators are an to gauge the wear on the wormgear screw
integral component. They are available thread of translating jacks and on the
in 120 VAC, or 12 VDC.
traveling nut screw thread of KFTN jacks.
11. How much side load can be placed This allows customers to replace the
on a screw jack? Standard jacks and nut before its threads wear too thin to
actuators are not designed for dynamic 18. What is the clutch on a linear actuator support the design load. These assemblies
side loads. The load must be positioned and how is it used? A screw clutch generally consist of a gear nut or traveling
axially. Static side loads are limited. Contact device is an option on linear actuators nut pinned to a second nut of dissimilar
Joyce/Dayton for technical assistance. (if they do not have limit switches). This material. A preset gap separates the two
See page 10 for more details. device allows the screw to turn if the nuts. As the wormgear or traveling nut
actuator is operated against a hard stop. threads wear, the preset gap narrows.
This is an emergency protection device, The assembly is replaced when the gap
not to be used repeatedly as an end of measurement reaches the design limit.
Follower Nut DesignsFollower Nut Designs
12. How much backlash is in a machine
screw jack? In machine screw jacks travel stop. Follower nut assemblies are designed
KFTN JackKFTN Jack
Translating JackTranslating Jack
there are two types of backlash: worm for specific applications. Contact Joyce/
to wormgear backlash (typically 8-15° Dayton for more information.
worm rotation), and lifting screw to nut 19. Are limit switches preset? No. Direction of Load
Direction of Load
backlash, sometimes called endplay
(up to 0.020 inches on new standard jacks). - Shaft-mounted rotary cam limit switches Follower NutFollower Nut
Refer to the JAX program or contact must be set to the required positions Internal Internal
®
Joyce/Dayton for more information. during installation. Wormgear Wormgear External External
Traveling NutTraveling Nut
- Limit switches on linear actuators must be
set after the actuators have been installed Follower Nut
Follower Nut
13. Can I reduce machine screw in order to tailor the stop position to the
backlash? Yes, screw backlash can individual application.
Direction of LoadDirection of Load
be adjusted on translating and keyed
style machine screw jacks via one of Translating Jack KFTN Jack
the following anti-backlash options:
standard split-nut design; A90 external
nut adjustment; or A95 design. Refer
to catalog pages 180-181 or contact
Joyce/Dayton for more information.
Custom products are available • Contact Joyce/Dayton with your requirements 17
800-523-5204 sales@joycedayton.com joycedayton.com