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Acceleration Time When a
motor is used to accelerate a rotating load, acceleration time
is the response time of the motor to bring the load from zero
to normal running speed
Actual Torque The actual
torque required to drive a machine. It is the torque measured
at the input shaft of a machine being driven.
AGMA American Gear Manufacturers
Association. Composed of member companies who manufacture speed
reducers, enclosed gear drives, open gearing, and gear type shaft
couplings. They establish standards for the design and application
of gear products. The combined experience of the company members
and technical members assures gear users that products will perform
satisfactorily when built, selected, and tested in accordance
with AGMA standards.
Ambient Temperature The temperature
of the air around the power transmission
equipment in operation.
Auxiliary Drive Belt, chain,
or gear drive used with a gear motor or speed reducer to provide
additional speed reduction and/or torque multiplication.
Axial Thrust Load The external
loading of force acting lengthwise along a shaft.
Back Drive A condition in
which the drive (or prime mover) is driven by the load rather
than driving the load. An example might be when a high inertia
load, such as a fly wheel, is decelerating down to slower speed
or complete stop.
Backlash The amount by which
the width of a tooth space exceeds the thickness of the engaging
tooth.
Center Distance When applied
to speed reducers, it is the distance between the
centerlines of the input (high speed) shaft and the output (low
speed) shaft. Shaft centerlines may be parallel or at right angles
to each other. Center distance is often used to designate a single
reduction worm gear speed reducer, such as 1.33", 1.75"
Double Reduction A multiple
reduction unit containing two stages of gear reduction housed
in a single enclosure. The overall speed reduction (ratio) is
the product of the gear ratios provided by the individual stages.
Duty Cycle The relationship
between operating and rest time. When applied to gear
reducers, duty cycle is usually referred to as continuous or
intermittent duty.
Continuous Duty The ability
of a geared unit to operate continuously within its
rated capacity without exceeding the temperature limits of its
lubricating system.
Intermittent Duty A geared
unit which has a specific operating time limit (min/hr) to prevent
exceeding the temperature limits of its lubricating system. This
limit is often
specified as a percentage. (A 25% duty cycle indicates a maximum
total operating time of 15 minutes each hour).
Efficiency An expression
of the amount of power delivered at the output of a power transmission
system as a percentage of the amount of power supplied to the
system's input side.
Gears Machined elements that
transmit motion and power by means of successively
engaging teeth. When two gears run together, the one with the
larger number of teeth is called the GEAR, and the one with the
smaller number of teeth is called the PINION. Most common gear
types available are helical, spur and worm gears.
Types of Gears:
Helical Gears Gears that are cylindrical in form and
mesh between parallel
centerlines. Their teeth are cut at an angle, called the helix
angle, across the face of the gear.
Spur Gears Gears that are
cylindrical in form and mesh between parallel centerlines
with teeth cut straight across gear face.
Worm Gears Gears that consist
of a screw like worm and its mating gear. Both are
cylindrical in form and mesh at right angles to each other. The
WORM is the driving
component and is identified by one or more teeth in the form
of screw threads wrapped around a cylinder (similar to barber
pole stripes). The WORM GEAR, also called Worm-Wheel, is the
driven component and has teeth similar to those of a helical
gear with the top of its teeth curved inward to mesh with the
worm.
Gear Ratio Described below
for helical, spur, and worm gears.
Helical and Spur Gears Ratio of number of teeth on driven gear
divided by the
number of gear teeth on driving gear (pinion).
Worm Gears The ratio of the
number of teeth on the Worm gear (Worm-Wheel)
divided by the number of threads or "starts" on the
worm.
Hand of Drive The location
of the output shaft of a reducer relative to its input shaft.
It is generally expressed as left-hand or right-hand, though
some reducer manufacturers use codes or symbols to designate
shaft arrangement.
Horsepower (HP) A measure
of the ability to do work. It can be applied to either linear
(straight-line) or rotary (circular) motion.
Inertia (WR) A measure of
the resistance of an object to accelerate or decelerate.
Inertial Load A load, such
as a fly wheel or other heavy rotating object, which tends to
oppose acceleration up to rated speed or deceleration to stop.
Input Horsepower The amount
of power applied to the input shaft of a reducer by the prime
mover. The input horsepower rating assigned to a reducer represents
the maximum amount of power the reducer is capable of handling.
Load The burden imposed on
a drive system by the equipment or machine being driven.
There are three types:
Constant Torque The load
torque remains constant over the speed range, while the horsepower
required varies directly with speed. This type of load is usually
the result of friction related to sliding or rolling motion.
Industrial equipment of this type include conveyors, hoists,
and similar general machinery.
Variable Torque The load
torque and the horsepower both vary as speed is
changed; as speed increases, torque and horsepower both increase
in some related manner. Examples include some types of mixers,
positive displacement and centrifugal pumps, air moving fans,
and blowers.
Constant Horsepower The load
horsepower remains constant over the speed range, while the torque
required decreases as speed increases. Constant horsepower loads
commonly are found on metal cutting or removing equipment such
as saws, lathes, and milling machines.
Load Classifications Loads
can be classified by the degree of shock or impact they impose
on the drive system. There are two main classifications.
Uniform Steady Load Loads
that are essentially smooth, shock or impact free.
Equipment that normally exhibit this type of load include filling
and bottling machinery,
uniformly loaded or fed conveyors, and printing presses.
Shock Loads Loads that transmit
shock or abrupt peak loads back to the driver
(power source-motor, gear motor, or reducer) and often repeat
on a regular or cylindrical basis. Shock loads may be categorized
as light, moderate, or heavy. Equipment that exhibits this type
of load are conveyors not uniformly fed, agitators for liquids
and solids, tumblers, and variable density mixers.
Mechanical Rating The maximum
power or torque that a speed reducer can transmit, based on the
strength and durability of its components.
NEMA National Electrical
Manufacturers Association. Organization that sets standards of
performance and dimensions for the motor industry.
Overall Drive Ratio The ratio
of input speed (RPM) to output speed (RPM). Overall drive ratio
is normally expressed as (x):1
Overdrive An interchangeable
term for back drive.
Overhung Load The side or
radial force applied at right angles to a drive motor,
gear motor, or reducer shaft. This force results from a gear,
pulley, or sprocket that the drive's bearing and shaft must support
without damage while transmitting power.
Pinion The input or driving
gear that meshes with an output or driven gear.
Prime Mover The machine that
provides input power to a drive. The most frequently encountered
prime movers include electric motors, internal combustion engines,
hydraulic and air motors.
Radial Load An interchangeable
term for overhung load.
Rating Tables Tables that
define the capacity of a given size or type of reducer when operating
under a given set of conditions.
Reducers The basic types
are described below.
C-Face Reducer Allows for
direct coupling to a motor. Motor shaft fits into a
hollow input shaft on the reducer. Motor face bolts to the flange
on the reducer. Both
reducer flange and motor face are designed to dimensions by NEMA
standards.
Indirect Drive Reducer (Open Shaft Reducer)
Allows for the prime mover to be mounted away from the reducer.
It contains an input shaft extension which accommodates the use
of pulleys or flexible couplings.
Parallel-Shaft Reducer A
speed reducer (C-Face or Open-Shaft) having an input shaft and
output shaft parallel to each other. These reducers contain spur
and/or helical gearing.
Right Angle Reducer A speed
reducer (C-Face or Open-Shaft) having an input shaft and output
shaft at right angles to each other. Worm gear reducers are the
most common right angle reducers.
Self-Locking A condition
commonly associated to worm gear speed reducers. A worm gear
reducer is said to be self-locking when its output worm gear
cannot drive the worm.
Service Factor Has two meanings:
Service Factor Motors The
service factor listed on the motor nameplate refers to a measure
of the reserve margin built into the motor. Motors rated over
1.0 SF have more than normal margin, and are used where unusual
conditions are likely to occur, such as high or low voltage or
momentary overload.
Service Factor Speed Reducers
When applied to speed reducers, service factor is a number (multiplier)
that redefines basic torque requirement of a load. It adjusts
basic torque requirement to a service rating for the reducer
by compensating for load classifications, duty cycle, and type
of prime mover.
Single Reduction A unit containing
a single stage gear reduction housed in an enclosure, such as
a worm gear reducer.
Speed Ratio The ratio or
relationship of input speed divided by the output speed. Speed
ratio is normally expressed as (x):1
Thermal Rating For speed
reducers, this is a rating indicating that maximum input
horsepower that can be supplied to drive a reducer and the output
torque that can be
transmitted continuously without exceeding the temperature limits
of the gear lubricant.
Thrust The force acting lengthwise
along the axis of a shaft either towards or away from it.
Torque Twisting force that
tends to cause rotation. For explanations of Running (Full Load)
Torque and Starting Torque as it pertains to gear motors, see
the Power Transmission section.
Triple Reduction A multiple
reduction unit containing three stages of gear reduction housed
in a single enclosure. Follows the same principles of the double
reduction unit except it has an additional stage of gearing.
Worm "Start" Beginning
of thread on a worm pinion as seen from the end of the worm shaft.
Worm Thread The tooth of
the worm that winds around the shaft to give it a screw like
appearance (similar to barber pole stripes). The worm can have
one or multiple threads.
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