Safety Relays with Force Guided Design

A traditional electromechanical relay consists of a set of contacts that open or close, depending on their arrangement and the coil voltage. A Riese safety relay’s contact design is mechanically interlocked. Mechanically interlocking the contacts enables the relay’s behavior to operate in a predetermined fashion and is achieved by either applying the mechanical interlock or force guiding the contact set.

The design using a mechanical bar interlinking all the contacts assures that all normally open (N/O or Form A) contacts don’t close if the normally closed (N/C or Form B) contacts don’t open. If the contacts of either the N/O or the N/C type are welded shut, the bar prevents the opposing contact type from operating. Therefore, when a relay contact fails to open, the opposing (or other) contacts don’t close enabling a monitored state of the relay.  This design is the heart of RIESE SAFETY RELAYS and provide detection of a single fault, redundancy in the contacts and monitoring of the safety devices. In addition, the N/C and N/O contact may not be closed simultaneously.

When experiencing a fault, a safety relay’s contacts go into an undefined state. In the event that a relay contact welds together or fails to open, fault tolerance is achieved by allowing all the possible contact sets to open to a gap larger than 0.5 millimeters. This is the minimum contact set for a safety relay consists of a Form A (N/O) and Form B (N/C) contact.

With automated machines and processes, hazardous motion is typically present posing potential danger. The goal of any safety circuit, is to provide protection  for the operator, the machine, and even the processes. The use of Riese Safety Relays with force guided, redundant, monitored circuit design results in reduced danger, control reliability, single fault tolerance and improved safety.

Installing safety devices such as guards and gates, light curtains, safety mats, pull cord switches, foot switches, two hand control devices etc….. Don’t in and of themselves create a safe machine.  It is the use of the Riese Safety Relay behind these devices that assure the output from any of these safety devices is correctly and reliably sent to the stopping control circuit.