Types Of Mechanical Keys- Design Of Keys, Keyways

机械钥匙简介：

Akeyis the piece inserted in an axial direction between a shaft and hub of the mounted machine element such as pulley or gear etc.,

• keys are used to prevent relative rotation but sometimes may allow sliding movement along the shaft if required.

• Keys are temporary fastening and are always made of mild steel because they are subjected to shearing and compressive stresses caused by the torque they transmit.

• A keyway is the groove cut in the shaft or hub to accommodate a key. Keyways can be milled horizontally or vertically.

Functions of Key:

a) To transmit torque from shaft to hub of the mating element such as the pulley, gear, etc.
b)To prevent relative motion between the shaft & mating machine element

Types Of Keys:

There is a large variety of machine keys and they may be classified under four broad headings:

沉没的钥匙，
平键，
Saddle keys
别针或圆形键

Sunk keysmay be further classified into the following categories:

(a) Rectangular sunk keys

Rectangular sunk keys are shown in figure- They are the simplest form of machine keys and may be either straight or slightly tapered on one side. The parallel side is usually fitted into the shaft.

(b) Gib head sunk keys

吉布头键are ordinary sunk keys tapered on top with a raised head on 一侧使其去除方便。

（c）羽毛钥匙

羽毛钥匙is used when one component slides over another. The key may be fastened either to the hub or the shaft and the keyway usually has a sliding fit.

(d) Woodruff keys

A woodruff key is a form of sunk key where the key shape is that of a truncated disc, as shown in the figure-. It is usually used for shafts less than about 60 mm diameter and the keyway is cut in the shaft using a milling cutter. It is widely used in machine tools and automobiles due to the extra advantage derived from the extra depth. Steel keys are widely used in securing machine parts such as gears and pulleys.

Saddles keys分类为：

Hollow saddle key
平鞍钥匙

A flat key,如图所示 - 用于轻负载，因为它们完全取决于夹具的摩擦。这些键的侧面是平行的，但顶部略微锥形，适合贴合。这些钥匙有大约沉没钥匙厚度的一半。

一个马鞍钥匙，如图所示 - 与扁平钥匙非常相似，除了底侧凹入以适合轴表面。这些键也具有摩擦握把，因此不能用于重负荷。简单的销可以用作传输大扭矩的键。在这些情况下，在轴上发生了很少的应力浓度。

Round Keysare sub-classified as,

平行销钉
Taper pin

Lewis keys,如图所示 - 昂贵，但提供优质的服务。

它们可以用作单个或双键。当它们用作单个键时，定位取决于轴的旋转方向。

样条轴和轮毂：

当需要沿着轴滑动时，使用花键轴。这些轴主要用于滑动齿轮应用，如在飞机的汽车齿轮箱和螺旋桨轴中。

•通过这意味着传输的电源在给出的键数量之间同样划分

•一个花键轴，其中切割平衡纵向槽，这些凹槽之间的金属形成花键或均匀深度的羽毛。 great strength and security against total failure than by using a single key.

Design Consideration of key :

1) Power to be transmitted.
2）合适的紧张性
3）连接的稳定性

4) Cost
5) Crushing failure of key:
6) shearing failure of key
7）钥匙的材料，轴应相同，但钥匙应弱于轴。

Application Of Mechanical Keys :

1）沉没钥匙：used for heavy-duty application
a) Rectangular sunk key:for preventing rotation of gears and pulleys on the shaft
b) Gib headed key:used where the key to be removed frequently.
c）羽毛钥匙：Machine tool
2) Saddle key:用于轻型或低功率传输
3）圆形关键：Used for low Power drive
4) Splines:Where providing axial movement between the shaft and mounted member

Keyway Design :

Effect of Keyway on strength of shaft:

键槽是在轴上或毂上加工的槽，以容纳钥匙。它由垂直或水平铣刀切割。
一点考虑将显示切入轴的键槽降低了轴的承载能力。
这是由于键槽的角落附近的应力集中和轴的横截面积的减小。它其他单词，轴的扭转强度降低。
以下对键槽的弱化效果的关系基于实验结果
H.F. Moore。e = 1-0.2(w/d)-1.1(h/d)

where e = Shaft strength factor.
w = Width of the keyway,
d =轴的直径，和
H =键槽的深度=键的厚度（t）/ 2
It is usually assumed that the strength of the keyed shaft is 75% of the solid shaft, which is somewhat higher than the value obtained by the above relation.