While a Google search of “dead mans switch” brings with it a host of interesting non-engineering references, we concern ourselves today with the ones related to the more pedestrian and technical meaning: Operator Presence Detection. The phrase “Dead Man’s Switch” was originally coined by engineers at the turn of the century who were running electric streetcars and trains. These devices do pretty much what the name implies: they prevent a disaster if the equipment operator suddenly dies or becomes incapacitated. Indeed, deployment of dead-man devices in the USA saw great increase after the famous Malbone Street Subway Crash in Brooklyn in 1918 which killed over 70 people. Today throughout the world, trains and rail transit vehicles universally employ these devices. In more civilized society, this application is commonly called “Operator presence detection”, and these switch based devices are used on a wide variety of equipment as fail-safe mechanism. When the fail-safe condition is detected the make or break of the circuit is designed to bring operation back to a safe state such as reducing motor idle speed, applying brakes, or sounding alarms. Applications of Operator Presence Detection At CPI, we’ve seen variations of our E1 limit switches used in a wide variety of these fail-safe applications.
A few primary factors bring equipment manufactures to our door time and time again for dead man switch and indeed many general fail-safe switch applications:
CPI E1115 – This is a commonly used low profile switch bracket with a “simulated” roller, ideal for under the seat applications. As such it is unobtrusive making for good ergonomics at the seat. The switch itself can be specified in a wide variety of standard electrical configurations and lead lengths. CPI E1134 – Roller Level Flush Mount switch. Similar to above but with a hard nylon roller. Parameters such as travel length, current rating, and electromechanical endurance are customizable. CPI has achieved endurance qualifications over 5 million cycles with this basic roller limit switch design. CPI E1085 – This is a Flush mount bracket on a “dual switch” configuration allowing two separate circuits to be controlled during a fail-safe event. All the same comments with regard to switch customization and electrical parameters apply, but to both switches. Here are some useful links:
At CPI we’ve been making high endurance waterproof switches for over 70 years from our factory here in East Hanover New Jersey. We’ve made switches for US Military Vehicles, Navy Ships, and Construction Vehicles, not to mention pleasure boats, lawn mowers, and even mountain bike racers. When companies get fed up with the performance of a cheap, offshore-made switch in a critical application, they typically come to us. In production quantities our prices are competitive with the offshore guys, but with none of the field problems. Our engineers see to that during a rigorous qualification of switches which are made right here in the USA. With CPI you have both off-the-shelf and full custom options for your switch design. Call us today. Make the switch to CPI. http://www.cpi-nj.com This content was originally posted at https://www.cpi-nj.com/blog/dead-mans-switch-the-electrical-one/ Manufacturers of dump bodies, lift gates, cranes, municipal and emergency vehicles, mobile construction equipment, and utility vehicles are some of CPI's best and most loyal customers for our waterproof switch product line.
But it often doesn't start that way! It's easy for manufacturers to fall into the trap of thinking that inexpensive offshore-made switches that claim to be waterproof will do the job in their application. However common problems includes loss of seal integrity, mounting problems, and short electromechanical endurance under real-world conditions leading to expensive in-warranty repair issues. Its that kind of frustration which generally leads engineers to our door. Read more about how common work-vehicle systems have been improved after the other guy's waterproof switch didn't cut it.
For more information on all our waterproof switch products visit us on the web at http://www.cpi-nj.com/waterproof-switches This content was originally posted at https://www.cpi-nj.com/blog/work-trucks-work-better-with-cpi-switches/ |
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