HYDRAULIC CYLINDERS WITH SPECIAL FEATURES
Doppelrohrzylinder sind Hydraulikzylinder mit einer ganz speziellen Bauform. Konstruktiv sind sie so aufgebaut, dass zwei Zylinderrohre ineinander verbaut und druckfest gegeneinander abgedichtet sind.Diese können auch für große Hübe hergestellt werden.
Das Kennzeichen von Doppelrohrzylindern ist die Rundbauweise mit einem Flansch auf einer Seite. Der Flansch befindet sich entweder auf der Stangen- oder auf der Kolbenseite. An diesem Flansch sind beide Anschlüsse für Vor- und Rückhub angebracht und an diesem wird der Zylinder auch befestigt.
Doppelrohrzylinder erweisen sich immer dann als sinnvoll, wenn durch längere Hübe und den Einbau in größere Formen eine Seite des Hydraulikzylinders schlecht zugänglich ist und sich somit beide Anschlüsse auf einer Seite befinden sollen.
CORE PULL UNIT
Core pull units are hydraulic cylinder designed with a guide that can apply high linear forces and very precise motion. They are especially well suited for injection molding applications. In this arrangement of guide and cylinder, the unit „pulls“ out the core of an injection molding tool with great force. Because here the hydraulic cylinder „pushes“ with its entire piston surface – and not just with the ring surface, as is otherwise typical for pulling motions . In this manner it applies 1 .6 times the force with the same pressure conditions. Thus, a smaller piston diameter can be selected.
Core pull units also save space, and can absorb very strong side forces and torques. Both of these are important requirements for building optimal tooling solutions in injection molding.
TWO-FORCE CYLINDER – PUSHING
There are certain applications in which very different motion characteristics lead to an optimal manufacturing process. In practice it can be observed that in some applications high (breakaway) forces are required at the beginning of a motion, and then comparatively low forces are needed for the remaining motion. In such cases the cylinders are designed for the largest force that has to be applied.
As a more cost-effective alternative to this, AHP Merkle has developed two-force cylinders, which are designed so that they can execute various force and speed profiles. This is possible through the use of two concentric piston rods running one inside the other. Their advantage is the high force generated at the beginning of the motion, and the subsequent automatic switching to higher travelling speeds at the same flow rate.
TWO-FORCE CYLINDER – PULLING
In this hydraulic cylinder option with stepwise force and motion characteristics the linear drive is designed for pulling. Here, too, two concentric piston rods run one inside the other. First a large piston with a correspondingly large ring surface receives pressure, which results in high force generation and low speed. Once the large piston is located at the housing wall and the pressure is only acting on the ring surface of the smaller piston, the force is reduced, and at the same time the travelling speed of the cylinder increases.
In contrast to the „Two-Force Cylinder – pushing“, the option „Two-Force Cylinder – pulling“ develops the greatest force when the piston rod is extended.
Two-force cylinders are for the most part always customer-specific solutions. This means that AHP Merkle adapts the changeover point from high force to high speed in accordance with individual customer requirements.
Multiposition cylinders are designed for moving to defined positions between the forward and return end positions. Multiposition cylinders are a simple, robust and especially economical alternative to complex servo or proportional cylinders with the associated control technology.
From a design standpoint, these are compact cylinder units that are arranged one after the other. First piston rod 1 moves to the end position, at the same time also pushing forwards all of the piston rods located in front of it, and thus reaching position 1.
To get to position 2, pressure is now applied to piston rod 2. The start and end positions of each individual stage can be detected via position switches.
BLOCK CYLINDER WITH NON ROTATING PISTON ROD
In hydraulic cylinders, the piston rod can rotate. In order to prevent such rotation of the piston rod, the design has to be adapted. To do this, an element that is not visible from the outside is build into the piston rod; this element guides the piston rod and thus prevents it from rotating. In such solutions the hydraulic cylinder is somewhat longer.
However, when a component is mounted on the piston rod it has to be fixed in place. Please note that the non rotating piston rod is only dimensioned for the internal forces of the cylinder.
OTHER SPECIAL DESIGN REQUIREMENTS (S)
AHP Merkle’s extensive range of cylinders has grown consistently over the course of decades . Many cylinder options in the standard catalog have come about as a result of individual customer projects. Today, a high degree of flexibility in the development and construction of hydraulic cylinder solutions is still one of AHP Merkle‘s main areas of expertise.