Switching device

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. As core elements of the operating concept, they contribute directly to process reliability, productivity, and repeatable quality in demanding environments.

Definition: What is meant by a 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. In practice, variants range from momentary to latching actuation, from purely manual to solenoid-operated designs; fail-safe behavior, defined neutral positions, and clear feedback are essential characteristics.

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. Clean routing of signals, adequate power reserve in the valve stage, and unambiguous center functions reduce misoperation and wear.

• Operator element: grip geometry, resistance, and detents designed for accuracy and fatigue-free use
• Signal section: clear logic, suppression of interference, and suitable plug-in connectors
• Power section: valve sizing aligned to flow and pressure, low pressure drop at nominal flow
• Protection: pressure limitation, load-holding where required, and defined relief paths
• Indication: status lights or mechanical position feedback for rapid verification

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. Suitable contamination control, short hose runs with low back pressure, and correctly tuned counterbalance valves help avoid oscillations, pressure spikes, and oil heating.

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. Clearly identified center functions and reproducible detents improve operational safety during setup and frequent changeover.

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. Viscosity and temperature influence valve behavior; compensation measures and correct orifice selection maintain predictable motion across operating conditions.

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. Surge suppression for inductive loads, proper fusing, and strain-relieved cable routing extend service life and prevent nuisance trips or chattering of contactors and control inputs.

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. Where radio is used, robust pairing procedures and a fallback to cabled operation increase availability in areas with interference or signal shadowing.

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. Clear documentation, labeling of functions and flows, and lockable isolating devices support safe maintenance and setup.

• Interlocking logic: prevents conflicting movements and unintended energization
• Diagnostics: feedback of switching states and faults for rapid, traceable troubleshooting
• Isolation: safe de-energization and depressurization before interventions
• Environment: enclosure selection and cable protection matched to dust, moisture, and shocks

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. Additional measures include pressure cut-off at target force, accumulator-assisted peak coverage, and temperature-conscious warm-up routines to reach optimal viscosity swiftly.

Selection criteria for the 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
• Connection strategy: hose lengths, quick couplers, and permissible back pressure at return
• Documentation: circuit diagrams, labeling scheme, and spare-parts concept

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. Acceptable pressure drop at nominal flow, coil duty cycle at elevated temperature, and defined hysteresis ensure reproducible dynamics and long service life.

Integration in the 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. Modular valve blocks, clear port labeling, and preassembled harnesses simplify commissioning and reduce the potential for misconnections on site.

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. Documented inspection intervals, traceable fault logs, and timely replacement of wear parts prevent creeping performance loss.

1. Bleed air after interventions and verify defined neutral positions
2. Measure switching times and compare against specification
3. Check pressure settings under load and at operating temperature
4. Record results and trends to plan maintenance proactively

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
• Pressure spikes on changeover: incorrect sequence control, counterbalance valve set too high
• Unintended movement: pilot leakage, damaged centering springs, or sticking spool

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. In cold environments, warm-up strategies and viscosity-appropriate throttling prevent sluggish response and ensure consistent splitting and cutting behavior.

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. Clear separation of roles, consistent naming, and coherent documentation support efficient setup, operation, and servicing.