Couplings and clutches

Couplings are attachments whereby shafts are connected to each other or with parts free-mounted on shafts (gears, pulleys) for transmitting torque. Couplings are either fast, which means that the coupled parts can be disengages only by being disassembled after stopping the machine, or disengaging type in which the driven shaft can be connected and disconnected at will, the driving shaft rotating continuously. Accordingly, the couplings are divided into fast couplings and clutches.

Fast couplings:

1.Closed couplings calling for strict axial alignment of the connected shafts

2.Compensating couplings permitting parallel and angular misalignment of shafts, and their axial displacement owing to linear expansion or contraction as the temperature rises or falls.

Compensating couplings are, in turn, classified as rigid couplings, i.e., having no elastic elements and transmitting possible jerks and shocks along with the torque, and flexible couplings absorbing part of jerks and shocks. The elastic members of flexible couplings are various types of springs, cylindrical bars and nonmetallic (rubber, leather) parts.

It should be noted that all closed couplings are, at the same time, rigid couplings.

Clutches:

1. Friction clutches, i.e.m those engaging two machine members owing to the forces of

friction.

2. Jaw clutches.

Friction clutches may have working (friction) surfaces of different shapes and, correspondingly, they are known as friction disc clutches.

The jaw clutch consists of two members slipped on the ends of the shafts connected. One clutch member is rigidly fixed on the shaft while the other member can be shifted along the shaft over a guide feather by a rontrol lever.

Apart from couplings and clutches designed for perma­nent or controllable connection between the pieces of shaft­ing, there are safety couplings intended, in the main, to protect a machine against breakdown in case of an emergency overload or excessive speed.

The safety coupling may be installed to supplement the torque-transmitting coupling, though the functions of both may be combined in one coupling.

There is a great number of couplings in current use.

The sleeve coupling is the simplest form of closed fast couplings. It consists of a steel or cast-iron sleeve fitted with an interference on the ends of the shafts being connected. The coupling is secured on the shafts and trans­mits torque by means of feathers, taper keys, or taper pins. This type of coupling is simple in design and manufacture.

2. Make up a plan in the form of questions.

3. Give the summary of the text according to your plan in a written form.

IV Comprehensive skills.

1. Read and remember.

1. charitable – неможливість

2. controversial – суперечливий

3. ridicule – насміхатися, насмішка

During the 1920s, however, the Ford Motor Company lost much of its popularity with the American public. When other manufacturers introduced more stylish, relatively inexpensive cars, Ford automobile sales began to drop. Though he closed his factories for 18 months in 1927-28 to prepare for a new Ford car, the Model A, he never regained his position of leadership in the car industry.

As owner of the Ford Motor Company, Henry Ford accumulated more than $1 billion. Between the years 1908 and 1947, when he died, he contributed more than $40 million to charitable causes, such as public hospitals, and research institutions. He established the Ford Foundation which continues to support various programs in education, media, and culture.

A controversial figure, Ford saw his ideas adopted and applied throughout the world. Yet Ford himself was frequently the target of criticism.

Without a doubt, however, Ford was a technological genius. Not a great inventor he was able to borrow ideas and apply them to new uses. In bringing the automobile to the average worker, he altered the structure of society, its cities, and the nations of the world.