Telescopic cylinders are a special design of a hydraulic cylinder or pneumatic cylinder as well as pulley system which provide an exceptionally long output travel from a 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.Some pneumatic telescoping units are manufactured with retracted lengths of under 15% of overall extended unit length.This feature is very attractive to machine design engineers when a conventional single stage rod style actuator will not fit in an application to produce the required output stroke.
Heavy duty telescopic cylinders are usually powered by oil hydraulics, whereas some lighter duty units could also be powered by compressed air.
Telescopic cylinders are also referred to as telescoping cylinders and multi-stage telescopic cylinders.
An application for telescopic cylinders commonly seen is that of the dump body on a dump truck used in a construction site. In order to empty the load of gravel completely, the dump body must be raised to an angle of about 60 degrees. To accomplish this long travel with a conventional hydraulic cylinder is very difficult considering that the collapsed length of a single stage rod cylinder is approximately 110% of its output stroke.[It would be very challenging for the design engineer to fit the single stage cylinder into the chassis of the dump truck with the dump body in the horizontal rest position. This task is easily accomplished, however, using a telescopic style multi-stage cylinder.
Common Uses for Telescopic Cylinders
Telescopic hydraulic cylinders are suited to applications where force space is limited and a traditional welded rod cylinder will not fit. They are used in platform lifts, dump hoists, dump lifts, and pack/eject functions. If your application needs a linear force applied over a long distance, telescopic hydraulic cylinders are an excellent choice for many different types of equipment:
Dump trucks
Garbage trucks
Transfer trailers
Construction equipment
Agricultural equipment
Industrial mobile vehicles.
Types of Telescopic Hydraulic Cylinders
Single-acting, double-acting, and combination telescopic cylinders are available to meet your equipment's specifications. While each type of telescopic cylinder shares many advantages and usages, it is essential to understand the differences between each configuration.
Single-Acting Telescopic Cylinders
Single-acting telescopic cylinders feature a straightforward design that uses hydraulic pressure to extend and gravity or other external force to retract. They tend to have a larger outer diameter than rod cylinders and deliver reliable, long-lasting performance. They are often applied in dump trucks, platform truck/trailers, and similar equipment.
Double-Acting Telescopic Cylinders
Double-acting telescopic cylinders use hydraulic pressure to extend and retract. They are ideal for applications where gravity cannot assist in moving loads due to horizontally mounted cylinders or other factors. Double-acting cylinders are often used in non-critical positioning applications, refuse vehicles, and transfer trailers.
Combination Telescopic Hydraulic Cylinders
As implied by their name, combination telescopic cylinders feature plunger rods that can be single or double-acting, utilizing hydraulic pressure for a portion of the stroke and retracting through gravity or other external force. These multi-stage telescopic cylinders are often found in large mobile drilling rigs and other heavy-duty applications.
