Safety edges are found, for example, on lift tables with extension platforms. If a drive is used to extend these extensions, sensor safety edges which react to a touch are attached to their tips. This ensures that the extensions of the lift table do not present any danger of crushing.
Scissor lift table
The term scissor lift table describes a lifting structure in which the up and down movement of the platform is generated by a scissor structure.
In the most widespread variant, the hydraulic scissor lift table, the ends of the lifting cylinders are each connected to one of the two sections of the scissors. The extended cylinders cause the scissors to stand at a steeper angle, thus raising the platform. The retracting cylinders then lower the platform.
Self-supporting base frame
When a lift table is loaded, high point loads act in the area of the locating and non-locating bearing. In non-self-supporting base frames, these forces can lead to permanent deformation or it can even break the structure.
To prevent this from happening, non-self-supporting base frames must be underlaid in the bearing area. The underlay assists in transferring the force directly from the scissors to the ground and no longer exert stress on the base frame.
It is not necessary to underlay self-supporting base frames. The base frame is sturdy enough to absorb all the forces that occur. Except for the flat lift tables, all our lift tables are equipped with a self-supporting base frame.
Sensor clock control
The term sensor clock control describes a special form of lift table control, which is mainly used for the automatic loading of production machines with metal sheets.
Automated production machines are often dependent on the exact positioning of the material to be machined. A good example in this regard is the feeding of an articulated robot. The robot uses suction cups to pick up a sheet of metal from a pallet and carries out the pre-programmed bending. The robot expects the sheet to always be at the same height, so lift tables are often used for feeding, with the lift table consistently raising the stack of sheets every time. The current height of the stack of sheets is detected by a light barrier, for example. When the robot takes a metal sheet from the pallet, the light barrier is released and the lift table receives the command to lift a piece again until the light barrier is engaged again. This synchronised lifting is referred to as sensor clock control.
Spindle lift tables
Spindle lift tables are a particular type of scissor lift tables. The lifting movement is generated by a mechanical spindle. One of its advantages is that no hydraulic oil needs to be used. However, this type of lift table usually requires more energy than hydraulically operated lift tables.
A detailed analysis of the different types of lift tables can be found in the article about Lift table types and their advantages and disadvantages.
When an electric motor is started, the rotor must first be accelerated from standstill into a rotating movement. This requires a higher torque than during normal operation.
As the torque of an electric motor is dependent on the current consumed, a relatively high current can be measured during the starting process. This current is called the starting current. The starting current can be a multiple of the later operating current. This high current must be taken into account when the electrical components are designed.
In the technical field, the term start-up means the commissioning of all necessary systems and components to bring an entire plant from standstill to operating condition.
When we speak of the start-up situation, we mean any situation in which the lift table is moved from standstill to a state of motion. In these situations there are some special technical features that must be taken into account when designing and adjusting the components. A good example of this is the protection of the electric motor. This must be so slow that the starting current does not cause the trip switch to trip.
Stopping accuracy is the tolerance with which, for example, a lift table reaches its predefined position.
In some applications, it is necessary to reach the landings with millimetre precision for process-related reasons. In a scissor lift table with only two stops, this is easily possible without further equipment. At the bottom landing the platform is simply aligned by means of the mounting bolts, while the top landing is adjusted by a stop for the floating bearing rollers.
If there are more than two landings, additional equipment usually have to be used. The use of roller switches is usually not recommended because of their soft switching point and the inaccuracy associated with this. Depending on the application, it is therefore more likely to fall back on additional supports, locking bolts or a combination of several inductive sensors.
According to the European standards, all steels which are not directly used as tool steel are called structural steel. They have a low alloy and carbon content (the carbon content is about 0-0.6%).
Structural steels are generally considered to have good weldability, are inexpensive and can be stress-relief annealed. Because of their good price-performance ratio, their main field of application is in general steel and mechanical engineering. The minimum tensile strength that can be achieved is usually less than 500 N/mm2.
Structural steels are identified by the letter S and their yield strength is given in N/mm2.
Common structural steels are S 185, S 235 JR, S 235 JRG1, S 235 JRG2, S 275 JR and S 355 JR.
Surface-mounted control unit
Depending on whether the control unit is installed under the plaster or on top of it, it is called a surface-mounted or flush-mounted control unit. The installation of flush-mounted control units is more expensive, but it usually has a more high-end look. If the control unit is outside the field of vision, or in commercial and industrial operations, more cost-effective surface-mounted control units are normally used.
Surface specifications in technical drawings can be used to provide information on the type of machining and the roughness of workpiece surfaces.
In some applications, the mere specification of normal dimensions, shape and position tolerances is not sufficient to guarantee the functionality of the workpiece. For example, the sealing effect of an installed part can fail if the surface is too rough. In such cases, surface specifications are usually used to determine the desired roughness value and the type of machining to be used to remove the material.