The first section of the type and characteristics of the hydraulic cylinder

Hydraulic piston-cylinder: the cylinder piston rod can be divided into double and single rod type of construction, its installation have fixed cylinder and the piston rod fixed in two ways.

Dual fluid cylinder: the cylinder piston rod ends are double with a piston rod into the cylinder and piston rod fixed two fixed installation form.
Single rod cylinders: single piston rod hydraulic cylinder with a piston at one end only, bi-directional movement of the piston can get a different speed and output power, and its passage connection diagram shown in Figure 3.2.

Plunger hydraulic cylinder:

Swing cylinders:

Telescopic hydraulic cylinder:

Section IV of the hydraulic cylinder structure

Hydraulic cylinders generally consists of the main part of the rear end cover, cylinder, piston rod, piston assembly, the front cover, etc; in order to prevent oil leakage or leakage from the high pressure chamber to the low pressure chamber to the hydraulic cylinders, the cylinder with end caps, piston and the piston rod, the piston and cylinder, between the piston and the front cover is provided with sealing means outside front cover, it is also equipped with anti-dust;? After a quick return to prevent the piston stroke end strike cylinder head, hydraulic the ends of the cylinder is also provided a buffer means; sometimes need to set up an exhaust system

Cylinder and end cap connections:

(1) flange connection, simple structure, easy processing, reliable connection, but requires the cylinder ends have sufficient wall thickness to installed by bolts or screws screwed. Cylinder ends generally with casting, upsetting or welding made of thick outer diameter, it is commonly used as a form of connection.

(2) half-ring connection, into outer half-ring connection and a half-ring connecting the two connection type, half-ring connection technology is good, reliable connection, compact structure, but weakened the cylinder strength. Semi-ring joint application is very common, often used in seamless steel cylinder with end caps connection.

(3) threaded connection with connection of two external and internal threads, which is characterized by small size, light weight, compact, but the cylinder end structure is more complex, this connection type is generally used for small form factor requirements lightweight occasions.

(4) connecting rod type, simple structure, good technology, versatility, but the larger size and weight of the cover, after the force rod will stretch longer, affecting the sealing effect. Not only applies to the length of the low pressure hydraulic cylinder.

(5) welded connection, high strength, create a simple, but easy to cause cylinder deformation during welding.
 
 Cylinder is the main cylinder, which is commonly used in the hole boring, reaming, rolling or honing precision machining manufacturing process, the surface roughness in 0.1mm ~ 0.4mm, the piston and seals, bearing smooth slide, thus ensuring the sealing effect, reducing wear and tear; cylinder liquid to be under great pressure, therefore, should have sufficient strength and rigidity.

 End caps mounted on both ends of the cylinder, to form a closed oil chamber and the cylinder, the same fluid under great pressure, and therefore, the end cap and the connecting member should have sufficient strength. It is necessary to consider the strength of the design, but also the process of selecting a better structure.
 
 Guide sleeve from the piston rod or plunger guide and support the role of some of the hydraulic cylinder guide sleeve does not directly cover the hole with a guide, this simple structure, but the cover must be replaced after wear.

Piston assembly sealing:

Piston device is designed to prevent leakage of hydraulic oil. The basic requirements of the sealing device is a good sealing performance, and with the increase of pressure can automatically improve sealing, in addition, the frictional resistance to small, oil, corrosion resistance, wear resistance, long life, create a simple, easy accessibility . Cylinder mainly ring seal, there are several kinds of O-ring, V-shaped, Y-shaped and modular, with its materials for the oil and rubber, nylon, polyurethane, etc.

 (1) O-ring

O-ring of circular cross section, mainly for static sealing. O-ring installation convenient, cheap, within in the temperature range, but with lip seals, movement greater resistance workout O ring sealing principle

After the O-ring into the seal groove, the cross-section by compressed deformation. In the absence of fluid pressure, by the elastic O-ring on the contact surface produce a pre-contact pressure to achieve an initial seal, when the pressure in the sealed chamber filled with oil, the role of fluid pressure, O-ring groove pressed against the side seal increased surface contact pressure, improving the sealing effect. Any form of seal during installation, you must ensure appropriate pre-compression, is too small can not be sealed, is too large, the friction increases, and easy to damage, so the installation seal groove dimensions and surface accuracy must be relevant manuals The data presented strictly guaranteed. In the dynamic seal, when pressure is greater than 10MPa, O-ring will be extruded into the gap and damage the O-ring ring need to set the low side for this Teflon or nylon, having a thickness of 1.25 ~ 2.5mm, two-way by the pressure, two? will be added ring, prone to twisting when the seal, it is generally not a separate movement for cylinder seals (can be used in combination with other seals).

(2) V-ring:

Sectional shape of the V-shaped ring, V-shaped sealing device is a pressure ring, V-ring and the support ring. When the working pressure is higher than 10MPa, increase the number of V-ring, improve the sealing effect. When installed, opening V-Ring should be facing high pressure side

V-ring good sealing performance, high pressure, long life, by adjusting the pressing force for optimum sealing effect, but the larger size of the V-shaped structure friction and sealing device, primarily for piston reciprocating seals it suitable for working pressure of P> 50MPa, working temperature conditions.

3) Y (Yx) ring:

Y-ring Y-shaped cross section, is a lip seal. It is a seal, better stability and pressure resistance, small friction, long life seals, it is quite common. Y-ring is mainly used for sealing reciprocating motion, depending on the aspect ratio of the cross-section, Y-ring can be divided into two broad sections and a narrow section of the form, as shown in Figure 3.12 to a wide cross-section Y-ring

Sealing rings depends on its lips close contact with the surface of the coupling, and a greater contact pressure oil under pressure effect, to seal the purpose. When the fluid pressure increases, the lip surface with stick more tightly coupled, the contact pressure higher and better sealing performance.

When the Y-ring installation, lip
 
Coping with a high-end surface side hydraulic pressure, when the pressure changes in the larger, higher sliding speeds, to use the support ring to secure the seal.

 Wide cross-section Y-shaped ring are generally applicable to the working pressure P <20MPa occasions; Y-ring narrow section generally applies to the working pressure P <32MPa at work
 

 4 buffer means: (c) variable throttle trough (d) throttle test

When the large mass of the cylinder drive unit for rapid reciprocating motion, since the great kinetic energy of moving parts, and therefore the hydraulic cylinder when the piston is moved to the end, it will collide with the cap, and an impact and noise. This mechanical impact not only cause damage to the relevant part of the hydraulic cylinder, and will cause other related mechanical damage. To prevent such hazards, ensure safety, measures should be taken to buffer of the hydraulic cylinder velocity control.

 
When the piston is moved to its end, the cushion plunger is initially inserted into the cushion hole side of the cylinder, is formed between the piston and the cylinder end of the closed space, the remaining oil trapped in the chamber from the throttle hole can squeeze or the cushion plunger and hole groove between the throttle ring gap of the extrusion, resulting in a back pressure forcing the movement of the plunger brake deceleration achieve buffering. Importers now widely used in the cylinder can be adjusted for one - way throttle cushioning effect.
 
 5 exhaust:

Hydraulic drive system is often mixed with air, the system unstable, vibration, crawling or pediment phenomenon, serious cause the system not working properly. Therefore, the design of hydraulic cylinders, we must consider excluding air.
 
 For less demanding hydraulic cylinders, are often not designed specifically for the exhaust, but the port is arranged at the highest ends of the cylinder, which would also make the air with the oil discharged into the tank, then overflow from the tank, for speed stability require high hydraulic cylinders and large hydraulic cylinders, the highest point in the hydraulic cylinder is often set up special exhaust, exhaust plugs, exhaust valve.
 
After loosening the locking screw plugs or exhaust valves, low pressure reciprocating movement several times, the oil will be discharged with the bubbles, the air discharge after tightening the screws, hydraulic cylinders can be normal!