Telescopic tube

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Telescope telescope

A telescopic tube is a mostly cylindrical object, which is characterized by the fact that individual elements of reduced diameter are pushed into one another. This reduces the volume during transport, but a greater usable length is available at the point of use. Typical areas of application are tripods and cranes, but also the collapsible tube of telescopes, from which the name is derived.


A telescopic tube consists of two or more cylindrical or prismatic, possibly also slightly conical, partial tubes lying coaxially inside one another . Each of the inner telescopic parts can be pulled out axially from the next larger one, which therefore directly envelops it. Each extension ends with a stop or lock in a position in which the function of the telescopic tube as a whole is still secured, i.e. it guarantees support, bending force or tightness. With telescopic fishing rods, the - soft - stop and the locking is done by frictional rotation under tension through the somewhat conical shape of the tubes. Photo tripods from the first half of the 20th century had cylindrical brass tubes with a longitudinal groove that prevents them from twisting, so that a locking ball from the inner tube can precisely snap into a hole in the outer tube under spring pressure. In order to push the multi-stage telescopes back together, it was enough to press the ball with the thumb nail on the thickest extension and push it together, because the balls on the thinner tubes are sufficiently pressed in by the edge of the thickest tubes after next. With this construction, extracting only a partial number of the mostly three or four elements required first extracting all and then loosening and inserting the thinnest element. Ski poles made of aluminum round tube can be locked continuously: turning the inner part spreads clamping jaws via a thread that adhere to the inside of the outer tube. With aluminum round tube photo tripods, the thickest extension must be drawn first. It is locked using a knurled union nut on the outer tube. Folding levers can be operated a little faster, but they do not require round profiled tubes.

Photo tripod with telescopic tubes as a tripod

Surveyor stands are also locked by folding levers, each of the three legs is formed at the top by two parallel aluminum round tubes (or vibration-damping wooden rods), between which a block with two semi-cylindrical grooves slides. The telescopic tube principle is not implemented axially, but mirror-symmetrically and flat. Very old photo tripods and easels sometimes have a similar wing nut-clamped extension of wood between two wooden cheeks, which can also be combined with another folding step.

Strong truck-mounted crane arms are higher than wide in cross-section for high buckling and bending resistance with a horizontal overhang under the weight of the load. The telescopic extension is hydraulically driven on the inside, up to about five extensions are locked using hydraulic cross bolts. For good rolling or sliding guidance, the top and bottom of the box profile are convex, semicircular or bent, stiffened as required and weight-minimized by welded-on metal sheets.

Lighting and camera masts for film, photo, surveillance and construction sites only carry a relatively light load and are often pneumatically raised and thus cleanly vertically.

The single-stage vacuum cleaner telescopic tube is often made of steel, aluminum or plastic and is secured against twisting. It can be released at the push of a button and engages in a groove about every three centimeters of length adjustment.

Slab props for concrete slab construction can be adjusted with a pin through punched transverse holes and adjusted and clamped with a thread.

A minimum overlap from element to element of twice the diameter or more in the longitudinal direction is required for low wobbling play and good transmission of forces. If a telescopic tube is only used to protect against contamination by dust, as a contact protection or optical cover, it can also be made delicately on machines, around the air spring of an office swivel chair or on the handy telescopic telescope and pulled out to a very small residual overlap.

It is precisely from this construction of a lens telescope with an extendable tube , which also allows focusing, that the name telescope tube comes .

The telescopic tube is a technical extension of an arm (cantilever) in the form of a tube in order to be able to reach, bridge or fix a desired distance variably .

Telescopic tubes of a telescopic rod

Well-known telescopic tube applications are:

Lifting platform

In box form, e.g. B. square, rectangular, trapezoidal or triangular, telescopic tubes are used for: