Working principle and operating characteristics of double-acting cylinder

Among all kinds of cylinders, piston-type single-rod cylinders are widely used, called ordinary cylinders. Ordinary cylinders can be divided into single-acting cylinders and double-acting cylinders according to the working principle of the cylinder. In the market, double-acting cylinders are used in mechanical automation equipment. It has a wide range of applications. Basically, cylinders can be made into double-acting cylinders, such as standard cylinders, rodless cylinders, thin cylinders, mini cylinders, finger cylinders, sliding cylinders, dual-axis cylinders, free installation cylinders, clamping cylinders, three-axis cylinders , Vacuum cylinders, needle cylinders, heavy-duty cylinders.
Double acting pneumatic cylinder refers to a cylinder that can input compressed air into two chambers to realize bidirectional movement. Its structure can be divided into double piston rod type and single piston rod type. Double piston type, cushion type and non-cushion type, etc., such cylinders are widely used.
Ordinary double-acting cylinders are generally composed of cylinder barrels, front and rear cylinder heads, pistons, piston rods, seals and fasteners. The cylinder barrel is fastened and locked by 4 tie rods and nuts between the front and rear cylinder heads (not shown in Figure 24). There is a piston connected with the piston rod in the cylinder, and a piston sealing ring is installed on the piston. In order to prevent air leakage and the intrusion of external dust, the front cylinder head is equipped with a seal ring and a dust ring for the piston rod. This double-acting cylinder is divided into a rod cavity (referred to as head cavity or front cavity) and rodless cavity (referred to as tail cavity or rear cavity) by the piston.
①Working characteristics of double-acting cylinder
a. There is output force in both directions
b. The output force of the return stroke is smaller than the output force of the extension, and the difference is the product of the pressure and the cross-sectional area of ​​the piston rod.
c. In the extended position and the return position of the piston, the distance between the piston support ring and the guide sleeve is different.
d. The piston rod cannot bear radial load.
e. In order to make the output force during the return stroke large enough, the diameter of the piston rod is generally small
f. Simple structure, excellent performance
②Application range of double-acting cylinder: all linear motions that require output force in two directions, and the output force
Double-acting cylinders can be used where the requirements are not too great.
③Classification of double-acting cylinders
a. Single rod type. Common type
Such as SU standard cylinder, DNC standard cylinder, SC standard cylinder
b. Double rod type. The pressure area on both sides of the piston is equal, and the movement stroke and output force on both sides are equal. Both sides of this cylinder can do external work. In this way, the guiding function of the cylinder is improved due to the guide sleeves at both ends. The distance between the two guide sleeves is constant, so it can bear a small radial load; the effective area on both sides of the piston is equal, so the output forces in the two directions are equal.
Such as TN double shaft cylinder, CXMS double shaft cylinder, TD double shaft cylinder
④Application range: occasions with radial load; occasions where the output force requirements in the two directions are equal, occasions where back pressure is required to stop; occasions where a signal element needs to be installed on the other side of the cylinder, etc.
Precautions for use of double-acting cylinders:
A double acting pneumatic cylinder is not the same as a double-barrel cylinder. Affected by the piston rod, the thrust generated by the rodless cavity is greater than the thrust generated by the rod cavity (the force of the piston rod is greater than the force of the piston rod retract ), the design of pneumatic circuit needs to be considered. In use: the normal lubrication of the cylinder must be ensured, and the oil mist device on the pneumatic triplet must not cut off the oil to avoid premature wear of the piston cylinder (some imported cylinders can be operated without oil lubrication due to the pre-coated grease on the piston) , But once the cylinder has been lubricated, it must be ensured that the lubrication continues and the lubrication cannot be interrupted). The double-acting cylinder requires clean compressed air. When the cylinder joint is sealed with raw material tape, it must be wrapped around the threaded part of the joint to prevent the raw material tape from clogging the air holes.

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