The complete range of IZMAC shock absorbers and rate controllers covers the most varied requests and applications. Starting from the smaller self-compensating threaded size M5, we can choose different sizes and threads, both for the adjustable and self-compensating models, arriving at the large decelerators for extreme applications. Rate controllers are also available, both unidirectional and bidirectional with separate regulation.
The various models are divided as follows:
Mini Self-Compensating Shock Absorbers - sizes from M4 to M36
Mini Adjustable Shock Absorbers - sizes from M10 to M36
Medium Self-Compensating Shock Absorbers - sizes from M33 to M115
Medium Adjustable Shock Absorbers - sizes from M33 to M85
Safety Buffers - sizes from Ø 65 mm to Ø 120 mm
Heavy Loads Buffers - sizes from Ø 90 mm to Ø 275 mm
Unidirectional Speed control (damped) - strokes from 13 to 51 mm
Bidirectional Rate Control - strokes from 50 to 250 mm
Crash Dampers - aluminum or plastic
Compact Shock Absorbers - sizes from M16 to M25
Main construction characteristics:
The shock absorber is composed externally of an impact head, stem, threaded body and lock nut. If adjustable, an adjustment dial is present.
The impact head is the part that comes into contact with the object to be decelerated, ensuring a reduction in noise thanks to the polyurethane insert. It also works as a mechanical stop on the front bushing of the shock absorber at the end of the stroke. It is possible to request the shock absorber without such head, in which case the impact occurs on the front part of the steel stem and the decelerated object goes to mechanical stop directly on the front bushing of the decelerator, pushing the stem back to the end of the stroke.
The body of the shock absorber is fully threaded for easy installation and better dissipation of the heat generated.
If the shock absorber is adjustable, there is an adjustment dial which is used to divide the oil passage orifices, thus varying the hardness of the decelerator.
The lock nut allows the threaded body of the shock absorber to be installed and securely fixed to the machine structure.
The interior of the decelerator consists of a piston, non-return valve, high pressure chamber with multiple orifices, accumulator, return spring and oil.
Energy absorption theory
Upon impact, the piston slides inside the high pressure chamber pushing the oil and generating an increase in pressure on the non-return valve which closes. The oil is then pushed out of the high pressure chamber through the calibrated orifices generating a reaction force on the piston. The accumulator positioned outside the high pressure chamber is compressed to compensate for the difference in volume of the stem at the stroke end. Energy is converted into heat during oil leakage through the orifices. At the end of the stroke, the internal spring pushes the stem towards the initial position. The internal pressure is zeroed and the non-return valve opens, allowing the oil to return quickly to the high pressure chamber during the stem reset.
The shock absorbers are designed with multiple orifices and can be self-compensating or adjustable.
Self-compensating shock absorbers
Self-compensating shock absorbers are available in different hardnesses and do not have the possibility of being adjusted. Each hardness corresponds to a different range of "effective mass" determined by the different diameter of the orifices, smaller for the models with greater hardness and gradually larger for models with lower, or softer, hardness. During the stroke, the piston closes the orifices one by one allowing a constant linear deceleration.
The self-compensating model is normally preferred when the mass, the impact speed and the forces involved are already defined and certain in the design phase.
Adjustable shock absorbers
The adjustable shock absorbers allow the calibration of the hardness, or the partialisation of the orifices, directly during installation. By the adjustment dial it is possible to vary the hardness of the decelerator. The presence of 12 adjustment steps allow a very precise calibration and the grub screw ensures the maintenance of the chosen adjustment even in the presence of vibrations on the structure.
The adjustable model is normally preferred when the mass, impact speed or forces involved are not defined with certainty during the design phase and deceleration must be optimized during installation and commissioning.