A hydro pneumatic press is a press machine that is powered by a compressed air cylinder with closed hydraulic circuits. This very mechanism that the press machine applies allows attaining the requested loads with a stroke which is triggered when the piston gets a resistance. It is a system that combines the advantages of both pneumatic and hydraulic systems; the hydro pneumatic system has the pneumatic power and the hydraulic control. A hydro pneumatic press can be used in multiple metal forming operations such as assembling, drawing and marking, cutting, pressing, folding, and riveting. This type of press is efficient and more cost effective than a traditional hydraulic press machine.
The way a conventional pneumatic press works is by utilizing the potential force of a pneumatic press comes from a compressed air or gas. There is typically an electrical powered unit that sets the pneumatic press into motion and feeds compressed air into the cylinders or tubes that connect to the actual press machine. When the compressed air fills the cylinders, the resistance pressure forces the movement of the press machine. The movement of the press machine refers to the downward movement of the ram on the press.
Once the movement is complete, the gas inside the cylinder will then evacuate through the exhausted valves and the mechanical spring coils in the cylinder will push the piston back into its previous position. When the piston is repositioned, a full cycle of the pneumatic mechanism is complete. The pneumatic press machines are the mostly widely applied type of press machine in industrial applications to date since the pneumatic system is able to generate powerful force in a relatively faster pace.
The press machine that applies hydraulic system has the benefits such as the ease of operation and accuracy of the control and of course the power it can generate. The ease of operation comes from fewer moving parts that the system contains. The hydraulic system is able to generate a great amount of constant force and torque. Though the hydraulic press is able to generate greater pressing force for heavy duty applications, the speed that the mechanism works is slower than other kinds of power systems.
The hydraulic system works on the principle of Pascal’s law, which discusses that when pressure is applied to a confined fluid, the pressure change takes place throughout the entire fluid. In a hydraulic press, there is a piston rod that works as a pump which provides a force to a small area. There is another piston with a larger area which generates a larger force when the pressure changes. The hydraulic system is able to move heavier loads and provide greater force. However, there is a chance of fluid leakage of a hydraulic system.
The operation of a hydro pneumatic system is carried out by the hydro pneumatic cylinders which the stroke is divided into three basic parts: the fast approach, the working stroke and the return stroke. These parts are controlled by the moving components inside the system. Within a hydro pneumatic system, there are two pneumatic chambers and a hydraulic chamber. These chambers are divided by a pneumatic piston and a hydraulic piston. The two pistons are connected, so any motion of the pneumatic piston must be translated to an equal motion of the hydraulic piston.
The control valve injects compressed air into the pneumatic chamber and the air drives the pneumatic piston to move. The actuation and descent of the pneumatic piston is quick, and hence this part is called the fast approach. When the pneumatic piston reaches the second pneumatic chamber, a distributor will be triggered and injects the compressed air into the hydraulic piston chamber. The plunging shaft compresses oil and increases power here. The power transition from compressed air to oil is called the working stroke. The return stroke refers to the return of the pistons to their previous positions.
The working stroke is essential in the operation of a hydro pneumatic system. The compressed air fills the first pneumatic chamber and forces the pneumatic piston to move between the two pneumatic chambers. Consequently, the piston in the hydraulic chamber moves as well. In turn, the oil inside the hydraulic chamber from one side of the cylinder into the other and a greater force is generated.
The primary advantage that a hydro pneumatic press has is its economy. A hydro pneumatic press does not need the regular hydraulic components or specialized hydraulic oil. As a result, the machine is less expensive. The use of compressed air in the hydro pneumatic press allows a quicker approach and retraction. Therefore, the typical downfall of slow working speed that a hydraulic press has is eliminated.
In addition, less maintenance is required when applying this type of press machine. The reason is that the sealing components of a hydro pneumatic system are simple. They are basically the identical sealing components that people tend to find on a pneumatic press. With these components, the other downfall of a hydraulic press is also removed. The leakage of fluid is less likely to take place on a hydro pneumatic press.
Due to the simplicity of the design, a hydro pneumatic system is reduced profoundly in size. This way, the press that applies this very system can be used in more applications than a typical hydraulic press. With the compact size, a hydro pneumatic machine is space efficient. On top of that, a hydro pneumatic system requires less energy to operate comparing to the hydraulic system and the pneumatic system, which makes it more applicable for certain applications.
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