According to the structure of the commonly used hydraulic cylinder, it can be divided into three types: the hydraulic cylinder of sanitation garbage truck has various structural forms, and its classification methods are also various: according to the movement mode, it can be divided into linear reciprocating movement and rotary swing type; According to the action of liquid pressure, it can be divided into single action type and double action type; According to the structure form, it can be divided into piston type, plunger type, multi-stage expansion sleeve type, gear rack type, etc; According to the installation form, it can be divided into tie rod, earring, foot, hinge shaft, etc; According to the pressure grade, it can be divided into 16MPa, 25MPa, 31.5Mpa, etc.

　　Hydraulic cylinder (engineering machinery)

　　Piston type

　　Only one end of a single piston rod hydraulic cylinder has a piston rod. As shown in the figure is a single piston hydraulic cylinder. Both inlet and outlet oil outlets A and B can be connected with pressure oil or return oil to realize bidirectional movement, so it is called double acting cylinder.

　　Piston can only move in one direction, and its reverse movement is done by external force. But its stroke is generally larger than that of piston type hydraulic cylinder.

　　Working principle of piston hydraulic cylinder

　　Piston hydraulic cylinder can be divided into two structures: single rod type and double rod type. The fixing mode is fixed by cylinder block and piston rod. According to the action of hydraulic pressure, there are single action type and double action type. In a single acting hydraulic cylinder, pressure oil is only used for one cavity of hydraulic cylinder, and the cylinder can move in one direction by hydraulic pressure, while the reverse direction movement is realized by external force (such as spring force, self weight or external load); The movement of piston in two directions of double acting hydraulic cylinder is achieved by alternating oil inlet of two chambers and by the action of hydraulic pressure.

　　It only has piston rod on one side of piston, so the effective area of two cavities is different. At the same time, the piston velocity is different with different cavity oil; At the same time, the oil supply pressure is different when the load force to be overcome is different. Or after the system pressure is set, the two directions of the hydraulic cylinder of sanitation garbage truck can overcome different load forces.

　　Plunger type

　　(1) Plunger hydraulic cylinder is a single acting hydraulic cylinder, which can only realize one direction movement by hydraulic pressure, and the return of plunger depends on other external forces or the weight of plunger;

　　(2) The plunger is supported by the cylinder liner and does not contact with the cylinder liner, so the cylinder liner is easy to process, so it is suitable for long stroke hydraulic cylinder;

　　(3) The plunger is always under pressure when working, so it must have enough rigidity;

　　(4) The plunger is often heavy, and it is easy to drop due to its own weight when placed horizontally, which causes unilateral wear of seal and guide, so it is more advantageous to use vertically.

　　Telescopic

　　The expansion hydraulic cylinder has two or more stages of piston. The sequence of piston extending out in the telescopic hydraulic cylinder is from large to small, while the order of no-load retraction is generally from small to large. The expansion cylinder can achieve a long stroke, but the retraction time is short and the structure is compact. This kind of hydraulic cylinder is commonly used in engineering machinery and agricultural machinery. There are several piston moving once. When each piston moves one by one, its output speed and output force are all changed.

　　Swing type

　　Swing hydraulic cylinder is the executive component of torque output and realize reciprocating motion, which includes single blade, double blade, spiral swing and other forms. Blade type: stator block is fixed on cylinder block, and blade and rotor are connected together. According to the oil direction, the blade will drive the rotor to swing back and forth. The spiral swing type is divided into two kinds: single screw swing and double spiral. Now double helix is more commonly used. The linear motion of piston in the hydraulic cylinder is transformed into a compound motion of linear motion and rotation motion by two screw pairs to realize the swing motion.