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2021-01-24 13:49
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2021年1月24日发(作者:milky)

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英文原文

Rolling Contact Bearings
The
concern
of
a
machine
designer
with
ball
and
roller
bearings
is
fivefold
as
follows:(a) life in relation to load; (b) stiffness,tions under load; (c) friction;
(d) wear; (e) noise. For moderate loads and speeds the correct selection of a standard
bearing
on
the
basis
of
a
load
rating
will
become
important
where
loads
are
high,although
this
is
usually
of
less
magnitude
than
that
of
the
shafts
or
other
components
associated
with
the
bearing.
Where
speeds
are
high
special
cooling
arrangements
become
necessary
which
may
increase
fricitional
drag.
Wear
is
primarily associated with the introduction of contaminants,and sealing arrangements
must be chosen with regard to the hostility of the environment.

Because the high quality
and low price of ball
and roller bearing depends on
quantity production,the task of the machine designer becomes one of selection rather
than
design.
Rolling-contact
bearings
are
generally
made
with
steel
which
is
through-hardened to about 900HV
,although in many mechanisms special races are not
provided and the interacting surfaces are hardened to about 600HV
. It is not surprising
that,owing to the high stresses involved,a predominant form of failure should be metal
fatigue, and
a
good deal of work is
based on
accept
values of life
and it
is
general
practice
in
bearing
industry
to
define
the
load
capacity
of
the
bearing
as
that
value
below which 90 percent of a batch will exceed life of one million revolutions.

Notwithstanding the fact that responsibility for basic design of ball and roller
bearings rests with he bearing manufacturer, the machine designer must form a correct
appreciation of the duty to
be performed by the bearing and be concerned not
only
with bearing selection but with the conditions for correct installation.

The
fit
of
the
bearing
races
onto
the
shaft
or
onto
the
housings
is
of
critical
importance because of their combined effect on the internal clearance of the bearing
as
well
as
preserving
the
desired
degree
of
interference
fit.
Inadequate
interference
can induce serious trouble from fretting corrosion. The inner race is frequently located
axially by against a shoulder. A radius at this point is essential for the avoidance of
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stress
concentration
and
ball
races
are
provided
with
a
radius
or
chamfer
to
follow
space for this.
Where
life
is
not
the
determining
factor
in
design,
it
is
usual
to
determine
maximum loading by the amount to which a bearing will deflect under load. Thus the
concept of
applied to a bearing, which is either stationary or subject to slight swiveling motions,
without
impairing
its
running
qualities
for
subsequent
rotational
motion.
This
has
been determined by practical experience as the load which when applied to a bearing
results in a total deformation of 0.0025mm for a ball 25mm in diameter.
The successful functioning of many bearings depends upon providing them with
adequate
protection
against
their
environment,
and
in
some
circumstances
the
environment
must
be
protected
from
lubricants
or
products
of
deterioration
of
the
bearing design. Moreover, seals which are applied to moving parts for any purpose are
of
interest
to
tribologists
because
they
are
components
of
bearing
systems
and
can
only be designed satisfactorily on basis of the appropriate bearing theory.
Notwithstanding
their
importance,
the
amount
of
research
effort
that
has
been
devoted to the understanding of the behavior of seals has been small when compared
with that devoted to other aspects of bearing technology.
Lathes


Lathes are widely used in industry to produce all kinds of machined parts. Some
are
general
purpose
machines,
and
others
are
used
to
perform
highly
specialized
operations.
Engine lathes
Engine
lathes,
of
course,
are
general-purpose
machine
used
in
production
and
maintenance
shop
all
over
the
the
world.
Sized
ranger
from
small
bench
models
to
huge heavy duty pieces of equipment. Many of the larger lathes come equipped with
attachments not commonly found in the ordinary shop, such as automatic shop for the
carriage.
Tracer or Duplicating Lathes
The
tracer
or
duplicating
lathe
is
designed
o
produce
irregularly
shaped
parts
automatically. The basic operation of this lathe is as fallows. A template of either a flat
or three-dimensional shape is placed in a holder. A guide or pointer then moves along
this
shape
and
its
movement
controls
that
of
the
cutting
tool.
The
duplication
may
include
a
square
or
tapered
shoulder,
grooves,
tapers,
and
contours.
Work
such
as
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motor shafts, spindles, pistons, rods, car axles, turbine shafts, and a variety of other
objects can be turned using this type of lathe.
Turret Lathes
When machining a complex workpiece on a general-purpose lathe, a great deal
of time is spent changing and adjusting the several tools that are needed to complete
the work. One of the first
adaptations of the engine lathe which made it suitable to
mass
production
was
the
addition
of
multi-tool
in
place
of
the
tailstock.
Although
most turrets have six stations, some have as many as eight.

High- production
turret
lathes
are
very
complicated
machines
with
a
wide
variety of power accessories. The principal feature of all turret lathes, however, is that
the tools can perform a consecutive serials of operations in proper sequence. Once the
tools have been set and adjusted, little skill is require to run out duplicate parts.

Automatic Screw Machine

Screw
machines
are
similar
in
construction
to
turret
lathes,
except
that
their
heads
are
designed
to
hold
and
feed
long
bars
of
stock.
Otherwise,
their
is
little
different
between
them.
Both
are
designed
for
multiple
tooling,
and
both
have
adaptations for identical work. Originally, the turret lathe was designed as a chucking
lathe for machining small casting, forgings, and irregularly shaped workpieces.

The
first
screw
machines
were
designed
to
feed
bar
stock
and
wire
used
in
making small screw parts. Today, however, the turret lathe is frequently used with a
collect attachment, and the automatic screw machine can be equipped with a chuck to
hold castings.

The
single-spindle
automatic
screw
machine,
as
its
name
implies,
machines
work on only one bar of stock at a time. A bar 16 to 20 feet long is feed through the
headstock spindle and is held firmly by a collect. The machining operations are done
by
cutting
tools
mounted
on
the
cross
slide.
When
the
machine
is
in
operation,
the
spindle and the stock are rotated at selected speeds for different operations. If required,
rapid reversal of spindle direction is also possible.

In
the
single-spindle
automatic
screw
machine,
a
specific
length
of
stock
is
automatically fed through the spindle to a machining area.

At this point, the turret
and cross slide move into position and automatically perform whatever operations are
required.
After the machined piece is
cut
off, stock is
again
fed into the
machining
area and the entire cycle is repeated.

Multiple-spindle
automatic
screw
machines
have
from
four
to
eight
spindles
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located
around
a
spindle
carrier.
Long
bars
of
stock,
supported
at
the
rear
of
the
machine,pass
though
these
hollow
spindles
and
are
gripped
by
collects.
With
the
single spindle machines, the turret indexes around the spindle. When one tool on the
turret is working, the others are not. With a multiple spindle machine, however, the
spindle itself index. Thus the bars of stock are carried to the various end working and
side
working
tools.
Each
tool
operates
in
only
one
position,
but
tolls
operate
simultaneously.
Therefore,
four
to
eight
workpieces
can
be
machined
at
the
same
time.
Vertical Turret Lathes


A vertical
turret
is
basically a turret
lathe that has been stood on its
headstock
end. It is designed to perform a variety of turning operations. It consists of a turret, a
revolving
table,
and
a
side
head
with
a
square
turret
for
holding
additional
tools.
Operations performed by any of the tools mounted on the turret or side head can be
controlled through the use of stops.
Machining Centers
Many
of
today's
more
sophisticated
lathes
are
called
machining
centers
since
they are capable of performing, in addition to the normal turning operations, certain
milling
and
drilling
operations.
Basically,
a
machining
center
can
be
thought
of
as
being
a
combination
turret
lathe
and
milling
machine.
Additional
features
are
sometimes included by the versatility of their machines.
Numerical Control
One
of
the
most
fundamental
concepts
in
the
area
of
advanced
manufacturing
technologies is numerical control(NC). Prior to the advent of NC, all machine tools
were manually operated and controlled. Among the many limitations associated with
manual
control
machine
tools,
perhaps
none
is
more
prominent
than
limitation
of
operator skills. With manual control, the quality of the product is directly related to
and limited to the skills of the operator. Numerical control represents the first major
step away from human control of machine tools.


Numerical
control
means
the
control
of
machine
tools
and
other
manufacturing systems through the use of prerecorded, written symbolic instructions.
Rather
than
operating
a
machine
tool,
an
NC
technician
tool
to
be
numerically
controlled,
it
must
be
interfaced
with
a
device
for
accepting
and
decoding
the
programmed instructions, known as a reader.


Numerical
control
was
developed
to
overcome
the
limitation
of
human
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operators,
and
it
has
done
so.
Numerical
control
machines
are
more
accurate
than
manually operated machines, they can produce parts more uniformly, they are faster,
and
the
long-run
tooling
costs
are
lower.
The
development
of
NC
led
to
the
development of several other innovations in manufacturing technology:
1.

Electrical discharge machining.
2.

Laser cutting.
3. Electron beam welding.
Numerical
control
has
also
made
machines
tools
more
versatile
than
their
manually
operated
predecessors.
An
NC
machine
tool
can
automatically
produce
a
wide
variety
of
parts,
each
involving
an
assortment
of
widely
varied
and
complex
machining processes. Numerical control has allowed manufacturers to undertake the
production
of
products
that
would
not
have
been
feasible
from
an
economic
perspective using manually controlled machine tools and processes.

Like
so
many
advanced
technologies,
NC
was
born
in
the
laboratories
of
the
Masschusetts
Institute
of
Technology.
The
concept
of
NC
was
developed
in
early
1950s with funding provided by the force. In its earliest stages, NC machines
were able to make straight cuts efficiently and effectively.
However,curved
paths
were
a
problem
because
the
machine
tool
had
to
be
programmed to undertake a series of horizontal and vertical steps to produce a curve.
The shorter is straight lines making up the steps, the smoother is the curve. Each line
segment in the steps had to be calculated.




This
problem
led
to
the
development
in
1959
of
the
Automatically
Programmed Tools(APT) language. This is a special programming language for NC
that uses statements similar to English language to define the part geometry, describe
the cutting tool configuration, and specify the necessary motions. The development of
the
APT
language
was
a
major
step
forward
in
the
further
development
of
NC
technology. The original NC systems were vastly different from those used today. The
machines
had
hardwired
logic
circuits.
This
instructional
programs
were
written
on
punched paper, which was later to be replaced by magnetic plastic tape. A tape reader
was used to interpret the instructions written on the tape for the machine. Together, all
of
this
represented
a
giant
step
forward
in
the
control
of
machine
tools.
However,
there were a number of problems with NC at this point in its development.




A
major
problem
wad
the
fragility
of
the
punched
paper
tape
medium.
It
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was common for the paper tape containing the programmed instructions to break or
tear during a machining process. This problem was exacerbated by the fact that each
programmed instructions had to
be return through the reader.
If it was necessary to
produce 100 copies of a given part,it was also necessary to run the paper tape through
the
reader
100
separate
times.
Fragile
paper
tapes
simply
could
not
withstand
the
rigors of a shop floor environment and this kind of repeated use.



This led to the development of a special magnetic plastic tape. Whereas the
paper
tape
carried
the
programmed
instructions
as
a
series
of
holes
punched
in
the
tape, the plastic tape carried the instructions as a series of magnetic dots. The plastic
tape
was
much
stronger
than
the
paper
taps,
which
solved
the
problem
of
frequent
tearing and breakage. However, it still left two other problems.



The most important of these was that it was difficult or impossible to change
the instructions entered on the tape. To make even the most minor adjustments in a
program
of
instructions,
it
necessary
to
interrupt
machining
operations
and
make
a
new tape. It was also still necessary to run the tape through the reader as many times
as there were parts to be produced. Fortunately, computer technology became a reality
and soon solved the problem of NC associated with punched paper and plastic tape.
The
development
of
a
concept
known
as
direct
numerical
control(DNC)solved
the
paper
and
plastic
tape
problems
associated
with
numerical
control
by
simply
eliminating
tape
as
the
medium
for
carrying
the
programmed
instructions.
In
direct
numerical
control
machine
tools
are
tied,
via
a
data
transmission
link,
to
a
host
computer. Programs for operating the machine tools are stored in the host computer
and
fed
to
the
machine
tool
as
needed
via
the
data
transmission
linkage.
Direct
numerical control represented a major step forward over punched tape and plastic tape.
However, it is subject to the same limitations as all technologies that depend o a host
computer.
When
the
lost
computer
goes
down,
the
machine
tools
also
experience
downtime. This problem led to the development of computer numerical control.
The
development
of
the
microprocessor
allowed
for
the
development
of
programmable
logic
controllers(PNC)and
microcomputer.
These
two
technologies
allowed for the development of computer numerical control(CNC). With CNC, each
machine tool has a PLC or a microcomputer that serves the same purpose. This allows
programs
to
be
input
and
stored
at
each
individual
machine
tool.
It
also
allows
programs to be developed off-line and download at the individual machine tool. CNC
solved the problems associated with downtime of the host computer, but it introduced
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another
known
as
data
management.
The
same
program
might
be
loaded
on
ten
different being solved by local area networks that connect microcomputer for better
data management.
CNC machine tool feed motion systems

CNC machine tool feed motion systems, especially to the outline of the control
of movement into the system, must be addressed to the movement into the position
and velocity at the same time the realization of two aspects of automatic control, as
compared with the general machine tools, require more feed system high positioning
accuracy and good dynamic response. A typical closed-loop control of CNC machine
tool feed system, usually by comparing the location of amplification unit, drive unit,
mechanical
transmission
components,
such as feedback and testing of several
parts.
Here as mechanical gear-driven source refers to the movement of the rotary table into
a linear motion of the entire mechanical transmission chain, including the deceleration
device, turning the lead screw nut become mobile and vice-oriented components and
so on. To ensure that the CNC machine tool feed drive system, precision, sensitivity
and
stability,
the
design
of
the
mechanical
parts
of
the
general
requirement
is
to
eliminate the gap, reducing friction, reducing the movement of inertia to improve the
transmission accuracy and stiffness.
In addition, the feeding system load changes in
the
larger,
demanding
response
characteristics,
so
for
the
stiffness,
inertia
matching
the requirements are very high.

Linear Roller Guides

In
order
to
meet
these
requirements,
the
use
of
CNC
machine
tools
in
general
low-friction
transmission
vice,
such
as
anti-friction
sliding
rail,
rail
rolling
and
hydrostatic guideways, ball screws, etc.; transmission components to ensure accuracy,
the use of pre-rational,
the form
of a reasonable support to
enhance the
stiffness
of
transmission; deceleration than the best choice to improve the resolution of machine
tools
and
systems
converted
to
the
driveshaft
on
the
reduction
of
inertia;
as
far
as
possible
the
elimination
of
drive
space
and
reduce
dead-zone
inverse
error
and
improve displacement precision.


Linear Roller Guides outstanding advantage is seamless, and can impose
pre-compression. By the rail body, the slider, ball, cage, end caps and so on. Also
known as linear rolling guide unit. Use a fixed guide body without moving parts, the
slider fixed on the moving parts. When the slider moves along the rail body, ball and
slider in the guide of the arc between the straight and through the rolling bed cover of
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Rolling Road, from the work load to non-work load, and then rolling back work load,
constant circulation, so as to guide and move the slider between the rolling into a ball.
Bridge Crane
Bridge
crane
is
having
an
elevated
track
running
in
a
bridge-type
crane,
also
known as the crane. Bridge Crane in the laying of the bridge on both sides along the
elevated track on the vertical run, lifting trolley along the bridge laying on the track in
the horizontal operation, a scope of work of a rectangle, it can take full advantage of
having the space below lifting materials from the ground equipment hindered.

Bridge
Crane
widely
used
in
indoor
warehouses,
factories,
wharves
and
open
storage yard and other places. Able to carry items, stood up, lifting status, and adjust
operations,
mainly
for
the
workshop,
sections
and
steel
production
lines
yard,
etc..
Lifting
capacity
usually
in
the
10
to
100
t.
Bridge
crane
itself
for
horizontal
movement, the winch frame for the vertical movement of the winch suspended from
the hook for vertical movement, the direction of movement of three of the crane can
work. In order to prevent bridge crane driver not clear in the specific hook campaign,
on the ground are equipped with lifting the general command or folder, put hook. If
hanging
overhead
crane
hoisted
electromagnetic
lifting
plate,
often
operated
by
the
drivers themselves. Bridge cranes can be divided into general overhead crane, simple
girder bridge crane for bridge crane and metallurgical three.

Ordinary
general
overhead
crane
from
lifting
trolley,
having
run
institutions,
having composed of a metal structure. Lifting up from the car and from institutions,
agencies and the car running small frame consists of three parts.

Lifting bodies, including the motor, brakes, reducer, and the pulley drum group.
Motor through the reducer, driven rotating drum so that the wire rope around 42.50 or
42.50
down
to
lifting
weights.
Small
frame
is
from
the
brackets
and
install
or
run
agencies and institutions, such as car parts rack, usually welded structure.

Crane running the driving mode can be divided into two categories: one category
is the concentrated drive, which uses a motor-driven initiatives on both sides of the
drive shaft driven wheel; were driven to another, that is, on both sides of the initiative
the wheels with a motor drive. Small, medium and larger overhead crane with brake,
and motor reducer combination into one of the
ordinary from the overhead crane for easy installation and adjustment, often drive the
use of universal - axis.

Crane
normally
used
only
four
active
and
driven
wheels,
if
a
great
weight,
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increase
common
approach
to
reduce
wheel
round
pressure.
When
more
than
four
wheels,
must
adopt
a
balanced
hinged
frame
device
so
that
the
crane
load
evenly
distributed in the wheels.

Bridge
metal
structure
from
the
main
sorghum
and
sorghum-composed
of
the
main
beam
is
divided
into
single-and
double-girder
bridge
having
two
categories.
Single-beam bridge from the main beam and a single on both sides of the span at the
end
of
sorghum,
dual-beam
bridge
by
the
two
main
sorghum
and
sorghum-component.

Liang Liang Gang and the end of the link-beam ends with wheels, for supporting
an elevated bridge in the running. A main beam welding on track for the lifting trolley
running. Having the structure of the main beam type is more a typical box structure,
the four truss structure and fasting truss structure.

Box
structure
can
be
divided
into
two-track
box
girder,
partial
double-track
box-beam, single-bias-rail box and several main sorghum. Dual-track box girder is the
extensive use of a basic form, the main beam from the upper and lower flange on both
sides
of
the
plate
and
vertical
web
composition,
layout
rail
car
in
the
center
of
the
flange plates online, and its simple structure , manufacturing convenient, suitable for
mass production, but larger forces.

Partial tracks box-girder and partial double- track box-section of the main beam
are
from
the
upper
and
lower
ranges
flange
plates
and
thick
web
of
the
main
components,
rail
car
in
the
main
web
layout
above,
the
short
Xiangbenna
omit
the
stiffening plate, which tracks box-side main beam from a wide flange box instead of
the
main
sorghum
two
main
sorghum,
respect
smaller,
but
more
complex
manufacturing.

4 truss-type structure from four plane truss structure into a closed space, in the
general
level
of
the
surface
Truss
shops
follow
plate,
light
weight,
rigidity,
but
compared
with
other
structures,
and
its
dimensions,
creating
more
complex,
fatigue
lower intensity, has been less productive.

Partial fasting truss structure similar to the main tracks box-girder from the four
components
of
a
closed
steel
structure,
in
addition
to
the
main
web
for
the
Solid
shaped beam, the other three plate in accordance with the design requirements cut into
many windows, forming a no-ramps Fasting Truss, in the lower level of the surface
occupied
by
taking
truss
plate,
cranes
and
the
operation
of
electrical
equipment
installed in the bridge house, lighter forces, the overall stiffness, and that in China is a
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more widely used type.

General
overhead crane
used mainly
driven power, the
general
is
in
the
driver
indoor manipulation, but also remote control. From the weight of up to 500 tons, up to
60 m span.

Simple
beam
bridge
crane
known
as
sorghum
cranes,
and
the
structure
and
composition of ordinary bridge crane similar to a weight, span and speed are smaller.
Bridge
is
the
main
sorghum
or
other
steel
I-beam
and
plate
steel
girder
section
composed
of
simple,
hand-pull
or
electric
hoist
accompanied
by
gourd
simple
as
lifting trolley car, the car usually in the word sorghum run on the next flange . Bridge
can
be
elevated
along
the
orbit,
but
also
along
the
elevated
suspension
in
the
following orbit, such as a crane hoisted sorghum crane.

Metallurgical
dedicated
bridge
crane
in
the
steel
production
process
can
be
involved in a specific process operation, and its basic structure and general overhead
crane
similar,
but
in
small
vehicles
are
equipped
with
lifting
the
work
of
special
agencies
or
devices.
This
feature
is
the
work
of
a
crane
used
frequently,
poor,
working-level higher. Dual-beam bridge crane factories on the track along the vertical
direction
of
movement,
the
lateral
movement
and
trolley
movements
campaign
to
hook
work.
Applied
to
machining
and
assembly
shop,
a
metal
structure
workshop,
mechanical workshops, metallurgy and casting workshop and warehouse type lifting
work. With scores from the weight of the form, molecular weight mainly Gouqi, the
denominator as vice Gouqi weight. There are five main types.

Casting Crane: for the lifting of hot metal into Mixer, furnaces and molten steel
into
lifting
equipment
or
continuous
ingot
steel
ingot
mould
used.
Sheng
barrels
lifting the car, a flip- sheng, deputy trolley barrels, and other auxiliary work.

Tongs
crane:
Using
tongs
high
temperature
steel
ingot
will
be
vertically
being
lifted onto a deep soaking pits, or put it out the car shipped spindles.

Stripper
Crane:
an
ingot
from
the
mandatory
extrusion
ingot
mold.
There
are
special small car Stripper devices, spindles Stripper under way and the shape of the
model:
Some
Stripper
crane- is
attributable
to
suppress
billets,
ingots
filed
with
the
clamp module; Some of the clamp punctured ingot mould, with Ingot filed small pair
of pliers.

Feeding Crane: Charge will be added to the open hearth furnace. Trolley bottom
of the column with the pick-and inciting material to me and it into the furnace. The
main column to bypass the vertical axis rotation, pick-and rotary can swing from top
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to bottom. Deputy car repair furnace for such auxiliary operations.

Forging
Crane:
to
meet
with
hydraulic
forging
large
workpieces.
Trolley
displayed on the main hook up special feeder to support and flip the workpiece; Vice
car used to lift the workpiece.

Dual-beam bridge crane, the biggest
weight from 100 tons, the hook-and-grab,
electromagnetic, metallurgical cranes, quenching crane, manual double girder bridge
crane,
electric
hoist
double
girder
overhead
crane
with
the
crane
unit
JB
/
T14405

bridge
crane
standard,
the
quality
of
products
to
JB/T53442

overhead crane product quality grade
of starting up and running with the car running on the bridge, a metal structure for the
double-girder box form. From the characteristics of the device in accordance with the
classification
for
the
hook,
grab,
electromagnetic
and
multipurpose
bridge
crane,
mainly for the mines, factories, wharves and warehouses, and other material handling
operations
frequent
stops,
as
a
crane
quenching
equipment,
a
high-speed
heat
treatment
process
of
decline .
Metallurgical
casting
molten
steel
crane
to
transport
packet is indispensable than smelting industrial equipment. The use of modern means
of
science
and
technology,
will
enable
any
crane
structure
with
a
jump-speed
performance. Can be used with high-level rotating hook for stacking operations.

Single-girder
bridge
crane,
the
largest
weight
of
10
tons
from,
hook-and-grab,
electromagnetic, flying single-girder bridge crane, manual single- girder bridge crane
with
the
crane
unit
JB/T1306

single-girder
bridge
Crane

JB/T2603
electric single-girder overhead crane hoisted the
is characterized manual or electric hoist monorail car along the main beam under the
flange I-beam operation, material handling operations, normally used for workshops,
warehouses and other material handling operations, which manual does not allow for
single-girder crane No electricity or power occasions. Grab motor with the monorail
or bulk materials can also be used to grab operations, the unit crane compact structure,
operational
flexibility,
can
be
used
to
ground,
can
also
be
used
to
operate
the
cab.
Special circumstances can also be used for remote operation. Industrial production or
storage is indispensable equipment.

Crane
normal
working
hours
to
allow
a
lifting
of
the
greatest
quality
as
rated
starting weight. Rated crane hook from the hook and the weight does not include the
fixed pulley group themselves. Grab sucker and electromagnetic devices, such as the
quality of admission included in the ratings from the weight. In accordance with the
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