Rapid traverse hydraulic cylinder with power stroke
Press cylinder, Hydraulic cylinder with rapid traverse function
Rapid traverse cylinders are used when a very high force is required over a short stroke range when starting up the hydraulic cylinder. For the remaining travel of the hydraulic cylinder, a higher travel speed is required, but a smaller force is sufficient for this.
The advantage of these rapid traverse cylinders is that a smaller power unit can be used, as the power for the increased force and the rapid traverse is not required at the same time. In addition, the rapid traverse function can shorten the working cycles of the machine.
- One hydraulic cylinder - two force curves
- Energy-saving: less power required for rapid traverse
- Increased productivity due to higher working cycles
Applications for rapid traverse cylinders
Foundry, Die casting, Press engineering
Such dual-force cylinders with rapid traverse function are used, among other things, in foundry operations or in press construction, hence the designation "press cylinder with integrated rapid traverse":
Foundry and Die casting
To open the casting mould, increased force is needed to release the mould from the components - to "tear it open" - so that the mould can be opened. Once the mould has been released, only a little force is required, but the rapid traverse cylinder should return the remaining opening stroke as quickly as possible.
Press engineering
A high force is necessary for the pressing process. Applying of the high pressing force usually takes place just before the end position of the hydraulic cylinder. During the rest of the movement, the press cylinder runs with a much reduced load; among other things, it is only necessary to keep the space free for loading with parts.
Function
Rapid traverse cylinder in retraction direction with power stroke at the beginning of stroke
The rapid traverse cylinder, that applies the high force on tension, automatically pressurised (p2) the effective surface of the additional piston (A3) during the return stroke. As long as the additional piston is in contact with the piston surface (A2), the piston rod retracts with great force until the additional piston hits the internal end stop. From this moment on, the piston rod (A2) can retract faster to the desired position, as its effective area is smaller. The additional piston can either be pressurised actively via port p3 or moved passively by the piston rod using an air filter and leakage oil line.
| Formula symbols | |
| A1 / p1 | Extension stroke |
| A2 | Rapid traverse |
| A3 / p2 | Power stroke |
Function
Rapid traverse cylinder in extension direction with power stroke at the end of stroke
The rapid traverse cylinder, that applies high force on pressure, has a hollow bore piston rod. An additional rod with a small effective area (A3) is located inside this rod. For rapid extension, the small rapid traverse surface (A3) is pressurised (p3). During this rapid traverse, the fluid required to fill the large chamber for the power stroke is provided by using of a pre-fill valve or with low pressure (p1). The power stroke with the large area of the piston rod (A1) can be switched on hydraulically at any time and at any position.
| Formula symbols | |
| A1 / p1 | Power stroke - fill/ pressure port |
| A3 / P3 | Rapid traverse |
| A2 / p2 | Return stroke |