Background and requirements
In bus production, work on the vehicle roof is regularly required along several production lines. To ensure that these tasks can be carried out safely, ergonomically and without any loss of time, a continuous, easily accessible work area spanning the entire length of the vehicle is required, which should be adaptable to varying bus lengths.
Against this backdrop, a roof working platform roof access platforms that covers four production lines was designed for and assembled at HESS AG, has a total length of 23 metres and can be flexibly configured during operation. In addition to adaptability, the project required a central control system, production-line-specific control points and a comprehensive access, interlocking and rescue concept.
In addition, the control system for material supply to the various components on the roof was integrated, and the use of wheel clamps to lift the buses for various work steps was enabled.
An additional requirement arose from the integration of the system into an existing hall: the roof working platform was partially integrated into the hall’s existing supporting structure. In doing so, the structural requirements of the existing building and the operational fire safety concept had to be taken into account, particularly with regard to penetrations, clearances and material/cable routes.
Implementation: Roof working platform with electrically operated extensions
The main task involved the installation of four 23-metre-long, double-sided roof working platforms. The working areas can be adjusted to the respective bus lengths using electrically driven extensions on the left and right sides. The extensions are designed in segments of varying lengths – 3, 5 and 6 metres – so that the working surface can be precisely defined according to the vehicle length.
The extension can be extended by up to 550 millimetres, allowing the platforms to be positioned in a controlled manner towards the vehicle. A rubberised contact strip, which runs the full length of each segment, serves a protective function: upon contact with the vehicle, movement is immediately and sensitively halted to protect both the system and the vehicle from damage.
The transitions were designed as a slip-resistant, close-meshed steel grating with R10 slip-resistance. This creates a robust, practical surface, particularly in areas where movement, changes of direction or transitions occur. Plug-in handrail segments are integrated along a length of around 14 metres on the extensions, ensuring that the fall protection follows the respective platform configuration.
The integration with the hall beams and the routing of the technical components were implemented in such a way as to comply with the existing building’s fire safety requirements.
Control and operation: Clear access per line
The roof working platform is controlled via a central control cabinet configured in collaboration with HESS AG. This cabinet houses the drives, safety circuits and logic enable functions. For day-to-day operations, a central control station in the form of a control panel has been installed at the respective stairwell for each production line.
This ensures that the key functions are available at the point where access begins and the roof working platform is moved into the working position. At the same time, responsibility for operation remains clearly assigned for each line. In addition, a traffic light system for entry control is integrated, with signals linked to the home position. Only when the extensions are fully retracted and the roof work platform is in the home position are vehicle entry and exit authorised.
Overall, this combination of a central, line-specific control station and clear status display helps to reduce unnecessary walking distances and waiting times. At the same time, it prevents operating errors and enables the workstations along the four roof working platforms to be used efficiently and economically in the planned cycle.
Access, locking and escape routes
Two access doors have been installed per roof working platform, secured by an electromechanical door lock. The lock is designed to support escape and emergency release functions in addition to the regular operating mode. Furthermore, connecting doors have been installed between lines 1/2 and 3/4. These can only be opened once the two associated roof working platforms, including the vehicle, have been fully set up. This ensures that crossings are used exclusively in a defined, safe state.
An emergency descent ladder has also been installed at the end of each roof work platform, which likewise features an electromechanical door locking system with escape and emergency release functions.
Access and fall protection: consistent and practical
Access is provided via an ergonomic staircase with handrails on both sides. For added guidance, the first and last steps are clearly marked in accordance with industry standards. To accommodate the length of each vehicle, individually adjustable front and rear fall protection barriers were developed and integrated into the roof working platforms.
Material supply and process integration
Pallet storage spaces have been installed at each roof working platform to ensure a synchronised material supply. These are designed to withstand loads of up to 500 kg and are secured by a safety concept featuring two doors: one door is used for loading goods and is operated from below, whilst the other door is located at the top and is used for unloading goods.
The use of the wheel clamps is also integrated into the safety system. The circuitry and controls are designed so that the wheel clamps can only be adjusted or deployed when the platforms are retracted and the roof working platform is in its home position.
Advantages of the roof working platform at a glance
Flexible positioning of work areas on the vehicle
Electrically operated side extensions allow for controlled access to the vehicle and create safe, ergonomic working conditions along the entire roof edge.
Significant improvement in workplace safety
Sensitive safety features such as contact strips, locking systems, clearly defined system statuses, and emergency descent and rescue concepts reduce risks in day-to-day work.
Efficient and synchronised production processes
Centralised control and line-specific control points minimise travel and waiting times and support the structured use of workstations along the production lines.
Uninterrupted access along the entire length of the vehicle
A 23-metre-long work area enables comfortable and ergonomic work on the vehicle roof without interruptions.
Optimised material supply directly at the workstation
Integrated pallet storage bays and coordinated safety mechanisms ensure a reliable supply to the assembly areas in line with the production cycle.
High adaptability to existing building structures
The roof working platform was integrated into the existing hall structure in accordance with structural and fire safety requirements.
Ergonomic and practical working environment
Safe access points, slip-resistant flooring and individually adjustable fall protection systems support comfortable and safe working conditions during daily operations.
Future-proof solution for multiple production lines
A single system covers four lines simultaneously, thereby providing a scalable infrastructure for long-term production requirements.