Based on the structural forms of commonly used hydraulic cylinders, they can be categorized into three types: The structural forms of hydraulic cylinders in waste collection vehicles are diverse, with various classification methods: They can be divided into linear reciprocating motion and rotary oscillating motion according to the mode of movement; into single-acting and double-acting according to the action of hydraulic pressure; into piston type, plunger type, multi-stage telescopic sleeve type, gear rack type, and others according to the structural form; into pull rod, ear ring, base foot, hinge shaft, and others according to the installation form; and into 16MPa, 25MPa, 31.5MPa, and other pressure grades.

Piston

The single piston rod hydraulic cylinder has a piston rod only on one end. Both ends have oil inlets and outlets, A and B, which can be connected to pressure oil or return oil, allowing for bidirectional movement, hence it is called a double-acting cylinder.

Pistons can only move in one direction, with their reverse movement requiring an external force. However, their travel distance is generally greater than that of piston-type hydraulic cylinders.

Principles of Piston-Type Hydraulic Cylinder Operation

Piston hydraulic cylinders are available in two types of structures: single rod and double rod. The fixation methods include body fixation and piston rod fixation. They are categorized into single-acting and double-acting based on the pressure fluid's action. In single-acting hydraulic cylinders, pressure fluid is supplied to only one chamber, enabling single-direction movement through the fluid pressure. The opposite direction is achieved by external forces, such as spring force, gravity, or external loads. Conversely, double-acting hydraulic cylinders utilize alternating fluid supply to both chambers, completing movement in both directions through the fluid pressure's action.

The piston rod is only present on one side of the piston, resulting in different effective action areas between the two chambers. With the same fuel supply volume, the piston's movement speed varies depending on which chamber is being fed; similarly, with the same load force to overcome, different fuel supply pressures are required when different chambers are fed, or, after the system pressure is set, the load forces that can be overcome by the hydraulic cylinders of the waste collection truck in both directions differ.

Piston

A plunger-type hydraulic cylinder is a single-acting hydraulic cylinder that can only achieve motion in one direction due to hydraulic pressure; the return stroke of the plunger requires the force of an external agent or the weight of the plunger itself.

2. The piston is supported by the cylinder sleeve without contacting it, making the sleeve easier to machine, thus suitable for long-stroke hydraulic cylinders.

3. The plunger is constantly under pressure during operation, thus it must possess sufficient rigidity.

4. Plunger weights are often substantial, and when placed horizontally, they tend to sag due to their own weight, leading to uneven wear on sealing components and guide elements. Therefore, vertical usage is more advantageous.

Reversible

Telescopic hydraulic cylinders feature two or more stages of pistons. The extension sequence of the pistons in a telescopic hydraulic cylinder is from large to small, while the retraction sequence when unloaded is generally from small to large. These cylinders can achieve a longer stroke, but are shorter and more compact when retracted. They are commonly used in construction and agricultural machinery. With multiple pistons moving in a single stroke, the output speed and force change as each piston moves sequentially.

Swing

The oscillating hydraulic cylinder is an actuator that outputs torque and achieves reciprocating motion, coming in various forms such as single-Blade, double-Blade, and spiral oscillation. In the blade-type design, the stator block is fixed to the cylinder body, while the blades are connected to the rotor. Depending on the direction of the incoming oil, the blades drive the rotor to oscillate reciprocally. The spiral oscillation type includes single and double spiral oscillations, with the double spiral being more commonly used. It converts the straight-line motion of the piston inside the hydraulic cylinder into a compound motion of linear and rotational motion through two spiral pairs, thereby achieving oscillating movement.