Switching devices are key components in demolition and deconstruction technology, in rock excavation and in natural stone extraction. They control the energy flow, enable functions, interlock movements, and safeguard processes. In hydraulic applications of Darda GmbH – from rock and concrete splitters to concrete demolition shears, through to combination shears, Multi Cutters, steel shears and tank cutters – switching devices form the interface between the operator, the hydraulic power pack and the work tool. Precise, robust, and safe switching is a prerequisite for controlled work on the construction site, during building gutting, in special demolition, and in tunnel construction.
Definition: What is meant by switching device
A switching device is a mechanical, electrical, or hydraulic device for targeted switching on, off, and changeover of functions and energy flows. It can be implemented as a switch, pushbutton, lever, valve, relay, or contactor, and takes on tasks such as start/stop, reversal of direction, selection of operating modes, as well as interlocking and emergency stop. In hydraulic systems, the term also includes directional and pressure valves, control blocks, and operator units that route the flow and pressure to the actuators — for example, cylinders of concrete demolition shears or rock and concrete splitters. Switching devices are distinct from control systems: while controls react continuously to deviations, switching devices set defined states, often binary (on/off) or stepped/proportional.
Design and operating principle
The typical chain is: the operator actuates a control element (pushbutton/joystick), the switching device converts the signal into a switching action that addresses the hydraulic power pack and the valves; as a result, oil flows to the work tool. In detail, switching devices consist of the operator element (ergonomic, suitable for gloved operation), the signal section (electrical or hydraulic), the power section (e.g., 4/3 directional valve), protective components (pressure relief valve, check valve), and indication/acknowledgement. On concrete demolition shears, the device switches between opening, closing, and holding; on rock and concrete splitters, between approach, pressure build-up, and relief. Proportional circuits allow sensitive movements; on/off circuits are particularly robust.
Switching devices in hydraulic systems
Hydraulic switching devices control the flow from the hydraulic power pack (hydraulic power units) to the A and B ports of the actuators. The directional valve defines the direction of movement, throttle or flow control valves influence the speed, and pressure valves protect the system against overpressure. On concrete demolition shears, the switching enables rapid closing with controlled force build-up; on rock and concrete splitters, it provides a clear separation between fast approach and powerful splitting mode. In rock demolition and tunnel construction, check valves and counterbalance valves are common to hold loads safely and prevent unintended movements.
Directional valves and switching logic
Directional valves (2/2, 3/2, 4/2, 4/3) are actuated by hand lever, mechanical cams, pneumatics, or solenoids. Poppet valves seal with low leakage; spool valves offer good flow characteristics. A center position can unload to tank, lock actuators, or unload the pump. For combination shears, Multi Cutters, and steel shears, a defined center position is helpful to hold the tool safely; for tank cutters, an unloading center position can reduce heating.
Pressure and flow control
Pressure relief valves provide protection, pressure-reducing valves stabilize subcircuits. Flow control valves and throttles influence speed; this is crucial to position a concrete demolition shear with control, or to bring the splitting wedge of rock splitters into position without jerk. Proportional valves offer sensitive control but require clean hydraulics and suitable electrical actuation.
Electrical and electronic switching devices
Electrical switching devices range from the main switch and motor protection switch on the hydraulic power pack, to pushbuttons and selector switches, and on to relays and contactors for solenoid valves. The wiring often includes emergency stop circuits, operating mode selectors (e.g., manual/automatic), and feedbacks (signal horn, lights). In noisy environments, clearly tactile switches and unambiguous feedback are important so the operator can safely recognize the switching state.
Operator concepts and ergonomics
Control pendants, hand levers, foot switches, or radio controls are chosen depending on the application. In building gutting, handy operator units with good feedback make operation easier under changing visibility conditions. For special deployments, an emergency stop button must be arranged for easy reach. Large, non-slip controls support gloved operation; clear pictograms avoid confusion between open/close or approach/split.
Safety and recognized rules of technology
Safety circuits follow a risk assessment. Common are positively guided emergency stop pushbuttons, interlocks against unintentional actuation, mandatory reset after emergency stop, and clearly defined center positions on valves. Degrees of protection (e.g., IP protection against dust/water), EMC compatibility, vibration and shock resistance are particularly relevant in concrete demolition, in rock excavation, and in tunnel construction. Legal and normative requirements are context-dependent; in case of doubt, the applicable, generally recognized rules of technology should be observed and assessed by competent experts.
Switching device and energy efficiency
Appropriate switching logic can save energy: an unloading center reduces waste heat, standby switching avoids idling, and coordinated flow control prevents unnecessary throttling losses. With concrete demolition shears, energy demand drops when holding functions are implemented depressurized; with rock and concrete splitters, a clean changeover between approach and splitting pressure reduces cycle time and oil temperature.
Selection criteria for construction site and deconstruction
Selection is based on the tool, the hydraulic power pack, the environment, and the operator concept. For a robust, user-friendly switching device, the following points are practical:
- Environment: dust, moisture, temperature range, vibration
- Operation: glove compatibility, tactile feedback, clear labeling
- Hydraulic data: working pressure, flow rate, case-drain behavior, return pressure
- Electrical: supply voltage, fusing, EMC, connectors
- Safety: emergency stop, interlocks, defined center position
- Maintenance: accessibility, filtration system, contamination tolerance
- Compatibility: interfaces to concrete demolition shears, rock splitting cylinders, and other tools
Sizing and design
Valve nominal sizes, switching times, and pressure losses must be matched to the tool. For rock and concrete splitters, fast switchover between low- and high-pressure circuits is important; concrete demolition shears require switching that is sensitive during positioning and powerful during cutting. Electrical coils must match the supply; cable runs should be short and protected.
Integration in systems of Darda GmbH
In typical system architectures of Darda GmbH, the hydraulic power pack provides the energy supply, while the switching devices are arranged on the power pack or on the tool. A main switch with motor protection, an operator panel with pushbuttons or levers, a control block with directional, pressure, and flow control valves, as well as an emergency stop circuit are often found. On concrete demolition shears, switching selects between opening, closing, and holding; on rock and concrete splitters, between positioning, pressure build-up, and relief. For combination shears, Multi Cutters, steel shears, and tank cutters, additional interlocks or operating modes (e.g., fine mode/coarse mode) may be added depending on the application.
Maintenance, inspection, and troubleshooting
Regular visual and functional checks increase availability. These include: leak inspection, checking of actuation paths, testing the emergency stop, inspection of connectors and cables, filter changes as specified, and functional testing under load. Clean oil and correct electrical connections are crucial for precise switching operations.
Typical fault patterns and causes
- No function: main switch off, fuse tripped, emergency stop not reset, defective coil or relay
- Slow movement: contaminated filters, throttle too narrow, voltage drop at the coil, insufficient flow
- Jerking/drifting: air in the system, internal leakage in the valve, missing load-holding valves
- Heating/loud noises: throttling losses, cavitation, bypass permanently open
- Unclear switching positions: worn operator elements, stiff spools, faulty feedback
Practical examples from application areas
In concrete demolition and special demolition, a two-stage circuit on the concrete demolition shear ensures that the jaws close quickly at first and then apply powerful force. In rock demolition and tunnel construction, safe changeover on the hand valve of rock and concrete splitters enables switching from fast approach to the splitting process without pressure spikes. In building gutting, a well-positioned control pendant on Multi Cutters facilitates work in confined spaces. In natural stone extraction, a sensitive proportional control helps position splitting wedges precisely to make clean use of predetermined fracture lines. For special deployments, robust emergency stop and interlocking concepts are important when visibility and access are limited.
Terminology differentiation within the system
The switching device sets defined states (e.g., open/close); the control system coordinates sequences (e.g., order of approach and pressure build-up); protective devices limit the consequences of faults (e.g., overcurrent or overpressure protection). In hydraulic systems for concrete demolition shears and rock and concrete splitters, these functions interlock: the hydraulic power pack delivers energy, the switching device directs the flow, the control system organizes the sequence, and protective components keep the system within the safe range.