爱你到底机械工程专业英语 李光布

2021年1月19日发(作者：顾瑛)
























Keys
，
Couplings and Seals
A key is the machinery component placed at the interface between a shaft and the hub of a
power
—
transmitting element for the purpose of transmitting torque(see Figure 1
．
6(a))
．
The
key is demountable to facilitate assembly and disassembly of the shaft system
．
It is installed in
an axial groove machined into the shaft
，
called a keyseat
．
A similar groove in the hub of the
power
—
transmitting
element
is
usually
called
a
keyway
，
but
it
is
more
properly
also
a
keyseat
．
The
key is typically installed into the shaft keyseat first
；
then the hub keyseat is aligned with the
key
，
and the hub is S1
．
d into position
．

Figure 1
．
6 Parallel keys
1
．
Square and Rectangular Pa rallel Keys




The most common type of key for shafts uD to 6
．
5 inches in diameter is the square key
，
as
illustrated in Figure 1
．
6(b)
．
The rectangular key(illustrated in Figure 1
．
6(c))is
recommended for larger shafts and is used for smaller shafts where the shorter height can be
tolerated
．
Both the square and the rectangular keys are referred to as parallel keys because
the top
，
bottom and the sides of the key are parallel
．





The keyseats in the shaft and the hub are designed so that exactly one
—
half of the height of
the key is bearing on the side of the shaft keyseat and the other half on the side of the hub
keyseat
．

2
．
Couplings




The term coupling refers to a device used to connect two shafts together at their ends for
the purpose of transmitting power
．
There are two general types of couplings
：
rigid and flexible
．

1)Rigid Couplings




Rigid couplings are designed to draw two shafts together tightly so that no relative motion
can occur between them
．
This design is desirable for certain kinds of equipment in which
precise alignment of two shafts is required and can be provided
．
In such cases
，
the coupling
must be desioned to be caoable of lransmittina the
．
tnrn=Ip in thpthoft
。
A typical rigid coupling is
shown in Figure 1
．
7
，
in which
flanges are mounted on the ends of each shaft and are drawn
together by a series of bolts
．
The load path is then from the
driving shaft to its flange
，
through the bolts
，
into the mating
flange
，
and out to the driven shaft
．
The torque places the
bolts in shear
．
The total shear force on the bolts depends on
the radius of the bolt circle and the torque
．





Rigid couplings should be used only when the alignment
of the two shafts can be maintained very accurately
，
not only
at the time of instaIIatjOn but aIsO during Operation Of the



Figure 1
．
7

Rigid c
。
upling
machines
．
If significant angular
，
radial
，
or axial misalignment
occurs
，
stresses that are difficult to predict and that may lead to early failure due to fatigue will
be induced in the shafts
．
These difficulties can be overcome by the use of flexible couplings
．

2)Flexible Couplings




Flexible couplings are designed to transmit torque smoothly while permitting some axial
，

radial
，
and angular misalignment
．
The flexibility is such that when misalignment does occur
，

parts of the coupling move with little or no resistance
．
Thus
，
no significant axial or bending
stresses are developed in the shaft
．


Many types of flexible couplings are available commercially
．
Each of them is designed to
transmit a given limiting torque
．
The manufacturer
’
S catalog lists the design data frOm which
you can choose a suitable coupling
．
Remember that torque equals power divided by rotational
speed
．
So for a given size of coupling
，
as the speed of rotation increases
，
the amount of power
that the coupling can transmit also increases
，
although not always in direct proportion
．
Of
course
，
centrifugal
effects
determine
the
uDDerIimjtnfsnpp
—
course
，
centrifugal
effects
determine the upper limit of speed


3
．
SeaIS


Seals are an important part of machine
apply
：

design in situations where the following conditions
●
Contaminants must be excluded from critical areas of a machine
．

●
Lubricants must be contained within a space
●
Pressurized fluids must be contained within a component such as a valve or a hydraulic
cylinder
．



Some of the parameters affecting the choice of the type of seal ink system
，
the materials
used
，
and the details of its design are as follows
：

●
The nature of the fluids to be contained or excluded
．

●
Pressures on both sides of the seal
．

●
The nature of any relative motion between the seal and the mating cOmpOnents
．

●
Temperatures on all parts of the seal ing system
●
The degree of sealing required Is some small amount of leakage permissible?
●
The nature of the solid materials against which the seal must act
：
corrosion potential
，

smoothness
，
hardness
，
wear res istance
．

●
Ease of service for replacement of worn seal ing elements




l he number of designs for sealing systems is virtually limitless
，
and only a brief Overview
will be presented here
．
Often-designers rely on technical information provided by manufacturers
of complete sealing systems or specific sealing elements
．
Also
．
in critical Or unusual situatiOns
，

testing of a proposed design is advised
．

A
键和轮毂轴之间的界面下的机械组件

电发送单元，用于传递转矩的目的（见图
1.6
（一）
）
。

关键是可拆除的，以方便组装和拆卸的轴

的安装在

加工成轴的轴向槽，称为一个
keyseat.A
类似的凹槽中的枢纽

动力传递元件，通常被称为一个键槽，但它是更适当地还设有一个

第一密钥通常安装到轴的键槽，轮毂键槽对齐与

键，和轮毂
S1.d
入到位。

图
1.6
并行键


和矩形霸
rallel
键


最常见的类型的键轴
UD
到
6.5
英寸直径的平方的键，

矩形键（图
1.6
（
c
）条中所示）是图
1.6
（
b
）条中示出。

建议使用较大的轴，用于较短的高度可以减小轴


正方形和长方形的键被称为平行键，因为

的顶部，底部和两侧的键是平行的。