This standard provides guidelines for the design,
rating and application of globoidal wormgearing
mounted with axes at a 90 degree angle. This type of
gearing is called double enveloping wormgearing in
the United States, but the term globoidal is more
commonly used worldwide.
This standard discusses the two main categories of
globoidal wormgearing manufactured in industry
today: the traditional Hindley designs, and the more
recently developed full contact designs. The standard
presents the formulas for calculating general
gearset proportions for the globoidal designs and a
rating procedure for Hindley designs. It does not
provide a detailed or complete procedure for the
design of gearsets and the cutting tools required.
Globoidal wormgearing of the Hindley design has
been used in industrial applications for over 200
years. The manufacturers of Hindley wormgearing
have each designed and built their own tooling to
manufacture the gearing. TheHindley design uses a
common base circle to form all of the tooth profiles.
The worm thread is generated by a cutting edge
(line) rotating in a single plane.
Themore recently developed full contact designs do
not use a constant base circle to form the tooth
profiles. The worm thread is generated in multiple
planes by a generating surface. The manufacturers
of full contact gearing have each conducted their
own research, and the details of their designs are
proprietary to each company. This design may
provide increased load carrying capability over the Hindley design, but a standard rating method for full
contact designs has not been established.
1.1 Types of reducers
This standard provides information pertaining to
globoidal wormgear speed reducers of the following
specific types:
-- single reduction reducers incorporating globoidal
wormgearing;
-- multiple reduction reducers incorporating globoidal
wormgearing in each stage of reduction;
-- the wormgear portion of multiple reduction reducers
incorporating globoidal wormgearing with
other types of gearing.
1.2 Speed limitation
The velocity factor table in this standard provides
data for sliding velocities up to 6000 feet per minute.
For velocities in excess of 6000 feet per minute, the
manufacturer should be consulted.
Where the sliding velocity of the worm thread
exceeds 2000 feet per minute, additional consideration
must be given to the lubrication of gears and
bearings. Special lubricants and a pressurized
lubrication system may be required.
1.3 Included ratios
The input power formulas for globoidal wormgearing
apply for ratios of 3:1 and greater. Engineering
practice dictates that ratios in excess of 74:1 should
be discussed with the manufacturer.
1.4 Exceptions
Wildhaber plane enveloping globoidal gearing is not
covered in this standard.
This standard does not pertain to globoidal wormgearing
used as speed increasers. For such
applications, the manufacturer should be consulted.
1.5 Intended use
The equations and values presented provide a
general approach to design and rating. Deviations
from the methods and values stated in this manual
may be made when justified by experience, testing
or more specific analysis. It is intended for use by
experienced gear designers capable of selecting
reasonable values based on their knowledge of the performance of similar designs and the effect of such
items as lubrication, deflection, manufacturing tolerances,
metallurgy, residual stresses and system
dynamics. It is not intended for use by the
engineering public at large.