Features:
Rugged design
Smooth functioning
Reliable operation
Introduction:
Telescopic cylinders ore specially designed hydraulic cylinders that provide on exceptionally long output travel from o very compact retracted length. Typically, the collapsed length of a telescopic cylinder is 20% to 40, of the fully extended length depending on the number of stages.
This feature is very special for machine design engineers when a conventional single-stage rod-style actuator does not fit in on application to produce the required output stroke.
Telescopic cylinders are usually powered by hydraulics, but some special light duty designs ore powered by compressed air.
Design and Technical Terminology:
Showing the telescopic principle, an object collapsed (top) and extended (bottom), providing more reach
Telescopic cylinders are designed with a series of steel tubes of progressively smaller diameters nested within each other
The largest diameter sleeve is tolled the main or barrel
The smaller inner sleeves are called the stages
The smallest stage is often called the plunger
The cylinders ore usually mounted M machinery by pivot mounts welded to the end or outer body of the barrel as well as on the end of the plunger
Telescopic cylinders con be built with as many os 6 stages
Six stages seem to be a practical design limit as stability problems become more difficult with larger numbers of stages
Telescopic cylinders require o careful design
Basic Design -Types of Telescopic Cylinders:
Telescopic cylinders can usually be classified into two basic designs: Single acting and double acting. A number of other special designs also exist including a hybrid single / double acting design and a constant speed, constant thrust design.
Single Acting:
Single acting telescopic cylinders are the simplest and most common design
As with a single acting rod style cylinder the single acting telescopic cylinder is extended using hydraulic pressure, but retracts using external forces when the hydraulic pressure is removed and relieved to the reservoir
This external retraction force is usually gravity acting on the weight of the load
This external weight must obviously be sufficient to overcome the friction and mechanical losses within the machine design even after the work portion of the machine cycle has been accomplished. In the example above of the dump truck, the weight of the dump body now raised at an angle of 60°, but empty of the load, most be enough to force the UN-pressurized hydraulic fluid out of the cylinder and cause it to retract to the fully collapsed position.
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