cone clutch

CONE CLUTCH

In a cone clutch, contact surfaces are in the shape of cones, as shown in Fig.7.6. The two cones - outer cone (cup) A and infer cone (cone) B - are in contact when the clutch is engaged. The contact is complete and tight with the help of compression springs. Thus torque is transmitted during engagement of clutch through friction cones from driving shaft to driven shaft. For disengaging, the clutch of the cone B is pulled back by means of a lever system compressing the springs. There is only one pair of friction surface in these cone clutches. The slope angle a is vary from 8° to 15°.

1. Torque Transmitted on the Cone Clutch

Consider a pair of friction surface as shown in Fig.7.7(a). Fig.7.7(b) shows a small

elemental ring of radius r and thickness dr.

Let

p = Normal intensity of pressure on friction surface, 

2α = Cone angle,

α = Semi-cone angle or face angle of the cone or the angle of the friction surface with the axis of the clutch,

r1 and r2 = Outer and inner radius of friction surfaces respectively,

Since the area of contact of a pair of friction surface is a frustum of a cone, therefore the torque transmitted by the cone clutch is the same as truncated conical pivot bearing as discussed in Section 6.16, Chapter 6.

1. Considering Uniform Pressure Theory

Similar to the truncated axial pivot bearing, for uniform pressure, we get

2. Considering Uniform Wear Theory

Similar to the truncated conical pivot bearing, for uniform wear, we get 

p × r = C and W = 2π C (r1 − r2)

Note 

1. Axial force required at the engagement of clutch is given by

2. Axial force required at the disengagement is given by

2. Formulae Summary

Table 7.1 summarises the expressions used for calculating torque transmitting capacity for various clutches.

Table 7.1. Formulae Summary

Example 7.14 

Determine the axial force required to engage a cone clutch transmitting 25 kW of power at 600 rpm. Average friction diameter of the cone is 400 mm, semi-cone angle 12° and coefficient of friction 0.25.

Given data: 

P = 25 kW = 25 × 103 W; N = 600 rpm; D = 400 mm or R = 200 mm 0.2 m; α = 12°; μ = 0.25.

Solution:

Normal load acting on friction surface can be obtained by

The axial force required to engage the cone clutch is given by

Example 7.15 

The following data relate to a cone clutch: minimum and maximum surface contact radii are 125 mm and 150 mm respectively; semi-cone angle allowable normal pressure is 14 × 104 N/m2; μ = 0.25. Find: (a) the axial load, and (b) the power transmitted, if the speed is 700 rpm. Assume uniform pressure.

Given data: 

r1 = 125 mm = 0.125 m; r2 = 150 mm = 0.15 m; α = 20°; μ = 0.25; pn = 14 × 104 N/m2; N = 700 rpm

Solution:

 (a) Axial load transmitted to the clutch:

We know that the axial load acting on the clutch,

(b) Power transmitted:

We know that the torque transmitted for the uniform pressure,

Example 7.16

A leather faced conical friction clutch has a cone angle of 30°. If the intensity of pressure between the contact surface is limited to 0.35 MPa and the breadth of the conical surface & not to exceed one third the mean radius, find the dimension of contact surfaces to transmit 22.5 kW at 2000 rpm. Assume uniform rate of wear and take coefficient of friction as 0.15.

Given data: 

2α = 30° or α = 15°; pn – 0.35 MPa = 0.35 × 106 N/m2; b = R/3; P = 22.5 kW = 22.5 × 103 W; N = 2000 rpm; μ = 0.15

Solution: 

We know that for uniform wear the axial force,

The torque transmitted for uniform wear is given by

Example 7.17

A cone clutch is to transmit 7.5 kW at 900 rpm. The cone has a face angle of 12°. The width of the face is half of the mean radius and the normal pressure between the contact faces is not to exceed 0.09 N/mm2. Assuming uniform wear and the coefficient of friction between contact faces as 0.2, find the main dimensions of the clutch and the axial force required to engage the clutch.

Given data: 

P = 7.5 kW 7.5 × 103 W; N = 900 rpm; α = 12°; b = R/2; pn = 0.09 N/mm2 = 0.09 × 106 N/m2; μ = 0.2

Solution:

Main dimensions of the clutch:

We know that for uniform wear the axial force,

The torque transmitted for uniform wear is given by

Axial force required to engage the clutch:

Normal load acting on friction surface (Wn) can be obtained by

Now the axial force required to engage the cone clutch is given by