Dark operate
Dark operate or light operate designates the wires of a light barrier.
A light barrier usually has four wires. In addition to the two wires for the power supply, there are the two signal lines. If the signal of the light-operate line is interpreted, the light barrier acts as an NC contact. An interpretation of the dark-operate line acts similarly to a normally open contact.
An interpretation of the light barrier would accordingly produce the following signal states:
| Operating mode | Light barrier occupied | Light barrier free |
|---|---|---|
| Light operate | 0 signal | 1 signal |
| Dark operate | 1 signal | 0 signal |
Dead man's controls
Dead man's control refers to a specific type of control where a button must be kept pressed in to execute a movement.
This type of control is often used in scissor lift tables for the up and down movement of the platform. The lifting or lowering movement only takes place as long as the corresponding button is kept pressed in. If the system operator releases the button, the plant stops in the position the lift is at that moment. This is intended to further increase plant safety.
Double-acting cylinders
In single-acting cylinders, only one side of the piston is pressurised with the hydraulic fluid. This means that the cylinder can be extended by the hydraulic power unit but not retracted again. An external force, such as the dead weight of the lift table or the payload, is needed to effect the return movement.
In double-acting cylinders, both sides of the piston are pressurised with the hydraulic fluid. This means that both the retracting and extending movement can be carried out by the hydraulic power pack.
Lift tables are mostly equipped with single-acting cylinders. Exceptions are, for example, hydraulic loading flaps on a loading lift table, scissor lifts with lightweight structures or suspended lift tables.
Double stroke
In the lift table industry, a double stroke refers to a complete lifting and lowering process of the scissor lift. The lift table manufacturer often asks the potential customer to specify how many double strokes per hour or per day.
This information is important when designing the lifting platform. If many lifting and lowering operations are performed, it may be necessary to use a more robust design, central lubrication or similar.
Drawing of assemblies
The individual parts or sub-assemblies are shown in an drawing of assemblies in their assembled state.
In contrast to drawings of single parts, the drawing contains item numbers and parts lists. If necessary, the drawing of assemblies also contains information about processing steps which may only be carried out after the individual parts/sub-assemblies have been assembled.
Furthermore, the drawing of assemblies does not contain the dimensions of a single component, but concentrates on the connection dimensions and main dimensions to be observed.
Duty cycle
The duty cycle is used for technical components that may not be operated continuously. The reason for this can be, among other things, that the occurring heat loss cannot be dissipated.
The maximum duty cycle can be specified in three ways:
1. Abbreviation for an operation mode (e.g.: S1 for continuous operation)
2. Percentage
3. Percentage and time interval
If only a percentage value is given, it refers to a time span of 10 minutes. With a duty cycle of 10 percent, the component may only be operated for one minute at a time and must then rest for nine minutes.
In the third case, the percentage always refers to the specified time value.
