Telescopic hydraulic cylinders, sometimes called multi-stage cylinders, are a type of linear actuator consisting of a series of tubular rods called sleeves. The sleeves (usually four or five) sequentially decrease in diameter and are nested inside of each other.
Once hydraulic pressure is introduced to the cylinder, the largest sleeve (called the main or barrel) is extended first. Once the cylinder barrel has reached its maximum stroke, the next sleeve, usually referred to as a stage, begins to extend. This process continues until the cylinder reaches its last stage, called the plunger.

There are two different types of telescopic hydraulic cylinders—single-acting cylinders and double-acting cylinders. Single acting, by far the most common, work by using gravity or some other external force to retract the stages of the cylinder. As soon as pressure is released from the cylinder, the force of the load pushes oil out of the system and the cylinder retracts.

While pneumatic telescopic cylinders exist, hydraulic power is much more common, especially when heavy loads are being moved. With a collapsed length typically between 20-40% of the fully extended length, telescopic hydraulic cylinders are used when extension needs to be originated from a tight space. This extension capability creates a longer working stroke than would be possible with a single stage rod-style actuator. These capabilities, along with the power to handle very heavy loads, make dump trucks, lifts and garbage trucks some of the most common applications for telescopic cylinders.

What is a telescopic hydraulic cylinder?最先出现在Bos-Hyd。

A hydraulic cylinder works on the principle of pressure difference. The hydraulic cylinders can be broadly categorised into:

1. Single acting cylinders –Where the pressure can be applied only in one direction and the return of the piston is either by gravity or other means such as pulling back (A bicycle air pressure filling pump).
2. Double acting cylinders – in these cylinders the pressure can be applied from both the sides. The other side acts as the return side (low pressure) in the forward stroke and acts as the main side (high pressure) in the return stroke. This cylinder has openings on both sides to allow for hydraulic oil to enter and exit (return to tank) from both sides alternately as per the stroke (forward or return).

The hydraulic basically acts on the simple principle of Force and pressure.

Force (F) = Pressure (P)*Area (A)

The force exerted on the cylinder piston rod of the cylinder is equal to the pressure of the hydraulic oil multiplied by the area of the piston. The force exerted on the piston in the forward (main) stroke is higher than the force on the other side of the piston since the pressure on the other side is very low (equal to the tank or reservoir pressure). This difference in force results into the movement of the piston towards one end of the cylinder tube and the subsequent movement of cylinder rod out of the cylinder or inside the cylinder as the case may be (double acting). The piston rod is attached to the piston and may be considered integral with the piston since they both move together only.

The main parts of a double acting hydraulic cylinder are:

1. Cylinder tube
2. Piston
3. Piston Rod
4. Head End Cover (Cylinder Head)
5. Piston Seal (Part of cylinder seal kit which also contains the dust seal fitted in head end cover)
6. Attached pipes (to entry and exit ports on the cylinder tube)

Further, once the piston moves to one end of the cylinder tube and still the hydraulic oil pressure is applied then the pressure gets relieved through a pressure relief valve located in the hydraulic system which is set to a predetermined pressure value. Moreover, if there is an internal leak (the seal may be cut inside and allow the oil to leak to the other side of the piston although no leakage may be visible from the outside) in the piston seal then the pressure gets relieved from there before the relief valve setting is reached and in such a case, the cylinder does not create the force which it normally creates. It basically underperforms. If this happens, then the piston seal kit needs to be replaced.

What are single acting & double acting hydraulic cylinders?最先出现在Bos-Hyd。

Hydraulic cylinder is a hydraulic actuator that converts hydraulic energy into mechanical energy and performs linear reciprocating motion (or swing motion). It has a simple structure and reliable operation. When it is used to realize reciprocating motion, the reduction device can be eliminated, and there is no transmission gap, and the movement is stable, so it is widely used in hydraulic systems of various machines. The output force of the hydraulic cylinder is directly proportional to the effective area of the piston and the pressure difference on both sides; the hydraulic cylinder basically consists of a cylinder barrel and a cylinder head, a piston and a piston rod, a sealing device, a buffer device and an exhaust device. The buffer device and exhaust device depend on the specific application, and other devices are necessary.

Bos-Hyd is a professional manufacturer in hydraulic cylinder and assembly products , we have more than 23 years experience, honed tube ,hard chrome bar, hollow chrome bar are also our hot selling products, any needs ,please feel free to contact us.

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The wide application of hydraulic cylinders最先出现在Bos-Hyd。

High-pressure cylinders are ideal to safely transport and use store compressed gases. Bos offers many sizes of high-pressure gas cylinders and tube trailers made of aluminum and steel.

Bos Hyd offers a variety of packaging options for both specialty gases and industrial gases. We provide numerous sizes of high-pressure compressed gas cylinders with various volume capacities for any application. Cylinder packs are also available for applications requiring multiple cylinders of compressed gas. In addition, We offers liquid gas mixtures in high-pressure piston cylinders. For larger quantities of hydrogen and helium, high-pressure tube trailers are available. While most of our gas cylinders remain the property , we also fill customer-owned cylinders provided they meet all appropriate safety requirements.

What is high pressure cylinder?最先出现在Bos-Hyd。

A hydraulic cylinder (also called a linear hydraulic motor) is a mechanical actuator that is used to give a unidirectional force through a unidirectional stroke. It has many applications, notably in construction equipment (engineering vehicles), manufacturing machinery, and civil engineering.

Hydraulic cylinders get their power from pressurized hydraulic fluid, which is typically oil. The hydraulic cylinder consists of a cylinder barrel, in which a piston connected to a piston rod moves back and forth. The barrel is closed on one end by the cylinder bottom (also called the cap) and the other end by the cylinder head (also called the gland) where the piston rod comes out of the cylinder. The piston has sliding rings and seals. The piston divides the inside of the cylinder into two chambers, the bottom chamber (cap end) and the piston rod side chamber (rod end / head end).

Flanges, trunnions, clevises, and lugs are common cylinder mounting options. The hard chrome rod also has mounting attachments to connect the cylinder to the object or machine component that it is pushing or pulling.

How does hydraulic cylinder work?最先出现在Bos-Hyd。

Cylinder Design And Repair最先出现在Bos-Hyd。

What is the solution of hydraulic cylinder scratch? In the process of using hydraulic cylinder, it is inevitable to encounter some hydraulic cylinder scratches, which will affect the normal use of hydraulic cylinder, but also affect the production efficiency. Hydraulic cylinder manufacturers introduce the solution of hydraulic cylinder scratch.

Solutions of hydraulic cylinder scratch:

The surface of the inner hole of the hydraulic cylinder may be scratched during use. The following article, to introduce the solution of the hydraulic cylinder scratch.

1. After the material is cured, the material is repaired above the guide rail surface with a fine grindstone or scraper, and the construction is completed.

2, with oxygen acetylene flame roast scratch parts (control the temperature, so as not to surface annealing), the perennial metal surface of the oil baked off, baked until no sparks splash.

3, with Angle mill surface treatment will scratch harm, grinding depth of more than 1mm, grinding groove along the guide rail, dovetail groove. The holes at both ends of the scratch are deepened to change the stress.

4, with absorbent cotton dipped in acetone or anhydrous ethanol to clean the surface.

5. The material has a performance of 24 hours at 24℃. In order to save time, it can be heated by halogen tungsten lamp, the temperature increases by 11℃, the curing time is shortened by half, and the curing temperature is 70℃.

Bos Hyd produces the hydraulic cylinder ,hydraulic ram and air cylinder , the product cover metallurgy, the mine, lift heavy objects, transportation, ships, forging and stamping, casting, coal petroleum, chemical industry, scientific research, war industry and so on.

What is the solution of hydraulic cylinder scratch最先出现在Bos-Hyd。

For many types of machinery, a welded rod cylinder has a long enough reach to perform the required function. On equipment where a longer reach is needed, a telescopic cylinder does what a welded rod can’t. Its ability for a longer extension makes it perfect for dump trucks, garbage trucks, and other heavy-duty construction equipment.

Telescopic hydraulic cylinders have a design that works with various equipment types. Though commonly used in construction equipment and dump trucks, you will also find them on military vehicles, offshore drilling equipment, and countless other places.

Whether you need a telescopic cylinder versus a welded rod design depends on your equipment design and application. Here are situations where you should consider using a telescopic hydraulic cylinder:

You require a longer stroke length than a welded cylinder can provide
The equipment where you plan to install the cylinder is compact or you are working with confined spaces
The application requires achieving a specific elevation or angle.

How Do Telescopic Cylinders Work?最先出现在Bos-Hyd。

At times cylinder rods can get damaged by external objects as the chrome rod extends out of the barrel on extension and this can leave it prone to damage.

Depending on how bad the damage is, we can repair it in 3 different ways, we can polish if they are not too deep and the chrome is still intact, we can strip off the old chrome and electroplate (re-chrome) the damaged rod or we can manufacture a totally new rod from scratch.

If the barrel of the cylinder is scratched, scored, marked then honing of the barrel should always be considered after inspection of the surface in the barrel. If the cylinder barrel has any defects, dings, scores, wear marks/shiny spots these areas need to be carefully investigated and honed to clean up.

The most standard and universal type piston seal designs usually allow for a barrel that is 0.305mm over size on diameter. If the barrel damage is excessive there are a couple of options, manufacture, and machine up another barrel on a lathe and use as much of existing parts off the old barrel as possible or purchase another barrel from an OEM (Original Equipment Manufacturer).

You want to hone the barrel oversize until it cleans up and manufacture a new over-sized piston. This last option might sound unconventional but it is extremely time and cost-efficient. Most seal designs can be stretched to within a specified limit.

Honing of hydraulic cylinder barrels can be done by either manual hand honing or on a specialized hydraulic cylinder hone machine with the appropriate tooling and stones. Specialized hydraulic cylinder hones are large and require a fair level of operator knowledge the get the best performance and surface finish on the cylinder barrel.

How Do You Repair Hydraulic Cylinder Scratches?最先出现在Bos-Hyd。

The great advantage telescopic hydraulic cylinders have over any other type of cylinders is their ability to provide an exceptionally long stroke from a compact initial package. The collapsed length of typical telescopic cylinders varies between 20% to 40% of their extended length. Thus, when mounting space is limited, and the application needs a long stroke, a telescopic cylinder is a logical solution.

For example, assume a dump body needs to be tilted 60° in order to empty completely. If the body or trailer is fitted with a conventional rod-type cylinder — with a one-piece barrel and stroke long enough to attain that angle — the dump body could not return to a horizontal orientation for highway travel because of the cylinder’s length, even when fully retracted. A telescopic cylinder easily solves this problem.

Telescopic hydraulic cylinders are relatively simple devices, but their successful application requires an understanding of this components’ idiosyncrasies. Knowledge of how telescopic cylinders work and which special application criteria to consider will enable you to design them safely and economically into equipment.

Main and stages
As the name infers, telescopic cylinders are constructed like a telescope. Sections of steel tubing with successively smaller diameters nest inside each other. The largest diameter section is called the main or barrel; the smaller-diameter sections that move are called stages; the smallest stage is also called the plunger. The maximum practical number of moving stages seems to be six. Theoretically, cylinders with more stages could be designed, but their stability problem would be daunting.

Telescopic cylinders normally extend from the largest stage to the smallest. This means the largest stage — with all the smaller stages nested inside it — will move first, and complete its stroke before the next stage begins to move. This procedure will continue for each stage until the smallest-diameter stage is fully extended. Conversely, when retracting, the smallest-diameter stage will retract fully before the next stage starts to move. This continues until all stages are nested back into the main.

Basic types

As with conventional cylinders the two basic types of telescropic hydraulic cylinders are single- and double-acting. Single-acting telescopic cylinders extend under hydraulic pressure and rely on gravity or some external mechanical force for retraction. Single-acting cylinders are used in applications where some form of load is always on the cylinders. The classic single-acting telescopic applications are dump trucks and dump trailers. Pressurized oil extends the telescopic cylinder to raise one end of the dump body. When pressure is released, the weight the dump body forces oil out of the cylinder, it retracts.

Double-acting telescopic cylinders are powered hydraulic in both directions. They can be used in applications where neither gravity nor external force can retract the cylinder. They are well suited to non-critical positioning applications requiring extension and retraction movement of a substantial load.

How does telescopic hydraulic cylinders work?最先出现在Bos-Hyd。