NORD Drivesystems B1000 - Manual (Page 798)

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PRODUCT OVER
VIEW
G1000 – Subject to Change Without Notice
Key Features
UNICASE™ Construction
UNICASE™ Construction refers to an overall design
concept that allows proper alignment of the gear
meshes and the bearings. All of the main drive train
components are contained in a one-piece housing.
All bearing bores, pilots, and registers of the housing
are machined in one set-up. First, the foot or inspec-
tion cover is machined. The housing is then positioned
from this fi rst cut to machine all remaining features.
Specially designed, dedicated fi xtures are used to hold
the castings rigidly and accurately for machining. This
assures positive bearing and gear alignment.
Covers or openings are minimized, reducing the num-
ber of potential leak paths, and subsequently the
probability of a leak occurring. A standard Failure Ef-
fects and Modes Analysis (FEMA) shows that this is
the best design. Although this type of design tends to
make assembly more diffi cult, it results in a superior
product. Fortunately, NORD has specially designed
tools to assure proper, effi cient assembly.
All covers and openings are un-stressed access panels,
or are positioned with a large pilot diameter. An un-
stressed access panel is the best, because there are no
forces trying to break the seal between the compo-
nents.
In no case is a bearing bore split even if it is internal
to the reducer. Designs with split bearing bores re-
quire bolts to hold the bore together. It is common
for bearings to fail due the outer face being improp-
erly supported, causing a stress riser at seams in bear-
ing bores.
AUTOVENT ™ Breather
When a gear reducer is operated intermittently, it warms
up while operating and cools down after being shut off.
The oil expands when it heats up and compresses the air
inside the housing, resulting in a positive pressure that
could cause the oil seals to rupture if left unregulated.
Conversely, when the oil is cooling, it will reduce in
volume, and outside air, and potentially humidity and
dirt, will enter the reducer. A small concentration of
water in mineral oil will cause foaming, will reduce the
lubricating properties of the oil, and will promote a
rapid degradation of the lubricant’s chemistry. Internal
components, such as bearings and gears, may quickly
be damaged by a small quantity of these contaminants
alone or in combination with caustic or corrosive fl uids.
The Autovent ™ operates like a check-valve to allow
the reducer to dissipate internal pressure during
warm-up, while preventing lubricant contamina-
tion during cooling. A spring presses a ball against
a machined orifi ce until the heating of the oil and
air inside the reducer exceeds 2 psi. Between 2 and 3
psi, the spring compresses and the ball is displaced, al-
lowing pressure to escape. The internal pressure then
drops below 2 psi, the spring elongates, and the ball
returns to its initial position, sealing the unit. As the
reducer continues to cool, the unit will temporarily
develop a slight vacuum.
NORD Gear supplies all reducers, except those that
are “lubricated for life”, with an Autovent
™ as a stan-
dard feature. In addition, the Autovent ™ gives NORD
Gear the ability to ship reducers and gear motors with
factory-fi lled lubricant. Since the spring keeps the
valve tightly closed regardless of the reducer’s orien-
tation, the unit can be inverted during shipment and
not develop an oil leak. A metal canopy protects the
ball and spring from damage. During operation, oil
splash and mist are generated. In contrast to the Au-
tovent
™ breather, an open breather can allow these
to migrate out, resulting in an undesirable brownish
stain around the vent plug.
Labyrinth Spring