Aerospace Switch Technology

Negative Rate Disk Springs

• The negative rate disk spring is the heart of the operating pressure switch; it’s the mechanism that allows the whole switch device to operate for thousands and thousands of cycles. Basically, it is a convex disc spring with a center hole—shaped like a doughnut. The disk spring snaps to a concave shape when it reaches a certain pressure. It then snaps back when pressure is released.
• Negative rate disc spring technology is significantly superior to other older pressure switch technologies, such as bellows, bourdon tubes, or basic metal diaphragms. Our technology gives the switch two simple operating states: a basic “on” or “off.” There’s no “elastic creep deflection” that is seen with conventional pressure switch designs.
• The snap action of the Hydra-Electric disc spring eliminates “tracing” of fluctuating pressures. This technology also prevents effects from surge pressures or pump ripples, which give false signals. Our units are resistant to contact chatter, vibration, or premature fatigue. Plus, the set points remain very constant with this design.

Snubbers

• One common issue with pressure switches is the fact that quick and temporary pressure spikes in hydraulic lines may cause false signals or premature actuation of the switch. These pressure spikes can be caused by pump ripple, where the on-off cycle of a pump causes rapid pressure variations. Hydra-Electric solves this problem by installing pressure snubbers inside our products that impede fluid flow and allow pressure to rise and fall more slowly inside the switch. This permits proper activation of the switch at the design pressure levels.

Materials

• Since pressure switches need to be long lasting and durable, they have to be machined out of solid stainless steel or aluminum. Hydra-Electric utilizes multi-axis CNC machines to lathe and bore rod material down to finished component shapes. Common stainless materials used are 304, 347 and 17-4PH alloys, while the aluminums include alloys such as 2024T and 6061.
• Seals and O-rings help keep the units sealed, and they are generally made from aerospace-grade thermoplastic elastomers. Electric connectors involve common aerospace insulator and conductor materials. Durable interior components including negative rate disk springs and force transfer arms are made from hardened stainless steel or Ni Span C. Overall, we use only high grade, durable materials.