Fig. 2598.
[Fig. 2598][37] represents a cone friction clutch pulley. The outer half is a working fit upon the shaft, but is secured against end motion by the collar d. The sliding half is coned and covered with leather as shown at c c, the outer half being coned to correspond. The sliding half is driven by a feather fast in its bore, and sliding in a feather-way or spline in the shaft.
[37] From The American Machinist.
The driving power of the device is obtained by means of the friction of the coned surfaces. The less the angle x of the cones the more power transmitted with a given pressure of the internal to the external cone.
On the other hand, however, this angle may be so little that the external cone will not release the internal one when the end pressure on the latter is removed.
The object is, therefore, to so proportion the angle x of the cones that their friction will be a maximum, while the internal cone may be moved endwise and unlocked from the external without undue effort or strain at the moving clutch bar e. If the angle be 30 degrees, the clutch will release itself when the lateral pressure is removed. If the angle be 25 degrees the internal cone will require a slight lateral pressure to release it. If the angle be 20 degrees, the internal cone cannot be released by end pressure applied by hand.
The transmitting capacity of the clutch depends upon the pressure applied to maintain the cones in contact, and therefore upon the leverage of the clutch bar, whose fork end is shown in section at e.
It is desirable that the end pressure be as small as possible, because of the friction between e and the hub of the sliding half of the pulley.