Principle Behind Shock Absorber

Shock absorber can be better called as an energy-absorbing device that works on the conversion of energy principle for stopping moving load with minimum load rebound and shock to the load and to surrounding equipment. To stop a moving load smoothly, is necessary in motion control. Different types of instruments like rubber snubber, a compression spring, and a dashpot is used for stopping the moving load. These instruments accomplished their tasks by absorbing energy.

In spring and snubber, energy is stored and when they are compressed the energy is released thereby resulting in a rebound. In a dash pot on the other hand if a force acts against the piston, it encounters high resistance from the fluid at the beginning of the stroke, then much less as the piston retracts. However there is a limitation in working of spring, snubber and dashpots. These instruments do not dissipate the energy uniformly. The energy is transferred to he load uniformly only in the case of shock absorber. Take the case when in all the above mentioned instruments (snubber, dashpots, springs and shock absorber) the same amount of kinetic energy is absorbed. In this situation the energy will be dissipated at differing rates.

The kinetic energy of the load is converted into heat by the Shock absorbers which is transferred into the atmosphere. There is no rebound in shock absorbers. The potentially dangerous shocks are prevented from reaching to equipment.

The design of a normal shock absorber is quite simple to understand. Generally speaking, a shock absorber contains double-walled cylinder. There is a space between the concentric inner and outer walls, a piston, some means of mechanical return for the piston, and a mounting plate. The piston can be mounted externally around the piston rod or internally on the inside of the cylinder body. In inner cylinder wall many orifices are drilled. The cylinder contains the fluid which is devoid of air as the bubbles may reduce the efficiency of the shock absorber. The movement of the piston inside, forces the fluid through the orifices in the inner cylinder wall. The orifice is closed as the the piston retracts thereby reducing the effective metering area, and maintaining a uniform deceleration force as the load loses its energy.

The pressure of the fluid remains constant which provides constant resistance to the load. Since the kinetic energy of the load becomes zero, the load slows to a stop. Also as the shock absorber stores no energy, there is no rebound. The shock absorber returns to its position after the load is removed. The piston is pushed by the spring outward and open a check valve. This permits the flow of fluid from behind the piston to the space the piston was in its retracted position.

While mounting care must be taken to to bolt the shock absorbers to a non-flexing mounting structure. External stop is also necessary for providing a firm positioning point, and for preventing the shock absorber piston from bottoming out at the end of its deceleration stroke. Usually an external stop is required to prevent damage both to their product and to the user's equipment. Shock absorber can be mounted through a drilled hole. The mounting can be secured by using stop collar.