What is the internal structure and principle of a refrigerator compressor? Why the compression pump they are supported by three springs and not fixed dead inside?

Introduction of the working principle of the compressor:

The working principle of the compressor is very simple, the motor drives the piston to reciprocate by driving the crankshaft and connecting rod. When the piston moves down, the cylinder hole to form a negative pressure and open the suction valve, so that the refrigerant flow into the cylinder hole (Figure a). When the piston moves up, the pressure in the cylinder bore rises. When the pressure is higher than the pressure at the discharge end, the discharge valve opens and the refrigerant is discharged from the compressor (Figure b). Vapor flow is non-continuous, with suction only as the piston moves down, and exhaust only a short time before the piston reaches the top of the cylinder.

There is just one cylinder, and three springs are used to support, dampen