Take the single piston rod double acting cylinder most commonly used in the pneumatic system as an example. The typical structure of the cylinder is shown in the figure below. The utility model is composed of a cylinder barrel, a piston, a piston rod, a front end cover, a rear end cover, a sealing element, etc. The interior of the double acting cylinder is divided into two chambers by the piston. The cavity with piston rod is called rod cavity, and the cavity without piston rod is called rodless cavity. When the compressed air is input from the rodless chamber, the rod chamber exhausts, and the pressure difference between the two chambers of the cylinder acts on the piston to overcome the resistance load and push the piston to move, making the piston rod stretch out; When the rod chamber is used for air intake and the rod chamber is used for air exhaust, the piston rod will be retracted. If the rod cavity and the rod free cavity alternately intake and exhaust, the piston can realize reciprocating linear motion.
Structure and working principle of mechanical contact rodless cylinder
The mechanical contact rodless cylinder has a groove in the axial direction of the cylinder pipe, and the piston and slide block move on the upper part of the groove. In order to prevent leakage and prevent dust, polyurethane sealing tape and dust-proof stainless steel tape are used to fix the opening on the cylinder heads at both ends, and the piston frame passes through the groove to connect the piston and sliding block. The piston is connected with the slider to drive the actuator fixed on the slider to realize reciprocating motion.
This cylinder is characterized by:
1) Compared with ordinary cylinder, the installation position can be reduced by 1/2 under the same stroke;
2) No anti rotation mechanism is required;
3) It is applicable to cylinder diameter of 10~80mm, and the maximum stroke can reach 7m when the cylinder diameter is ≥ 40mm;
4) High speed, standard type can reach 0.1~0.5m/s; High speed type can reach 0.3-3.0m/s.
Its disadvantages are:
1) Poor sealing performance, easy to cause leakage. The medium pressure valve must be selected when using the three position valve;
2) In order to increase the load capacity, the guide mechanism must be added due to the small load force.
Structure and working principle of magnetic rodless cylinder
The piston drives the moving body outside the cylinder block to move synchronously through magnetic force, and its structure is shown in the figure. Its working principle is to install a set of permanent magnetic rings with high strength magnetism on the piston. The magnetic line of force acts on another set of magnetic rings which are sleeved outside through the thin wall cylinder. Because the two sets of magnetic rings have opposite magnetism, they have strong attraction. When the piston is pushed by air pressure in the cylinder barrel, the magnetic ring sleeve outside the cylinder barrel is driven to move together under the action of magnetic force, and the thrust of the cylinder piston must adapt to the suction of the magnetic ring.
Structure and Working Principle of Rack and Pinion Swing Cylinder
The rack and pinion swing cylinder is a kind of swing cylinder that rotates the gear through the rack connected to the piston. Its structural principle is as follows. The piston only moves in a reciprocating straight line, with less friction loss. The efficiency of gear transmission is high, and the efficiency of this oscillating cylinder can reach about 95%.
Blade type swinging cylinder and its working principle
The structural principle of the single blade oscillating cylinder is as follows. It is composed of blade shaft rotor (output shaft), stator, cylinder block, front and rear end covers, etc. The stator and cylinder block are fixed together, and the blade and rotor are connected together. There are two air paths on the stator. When the left path is used for air intake, the right path is used for air exhaust. The compressed air pushes the blade to drive the rotor to swing clockwise. On the contrary, swing counterclockwise. The blade type oscillating cylinder has small volume and the lightest weight, but it requires high manufacturing accuracy, is difficult to seal, has large leakage, and has large contact area of dynamic seal, large friction resistance loss of seals, and low output efficiency, less than 80%. Therefore, it is limited in application, and generally only used in situations where the installation position is limited, such as fixture rotation, valve opening and closing, workbench rotation, etc.