Thursday 28 January 2016

Who Invented the Seismic Switch for Elevators?

What is a Seismic Switch?

One of the general public’s biggest fears, related to vertical transportation, is the prospect of being trapped inside an elevator during an earthquake. The industry has dedicated time and resource to reducing the likelihood of this happening. The earliest earthquake detection devices were called Seismoscopes and were invented in China during the second century, long before vertical transportation was an established industry. In the twentieth century earthquake detection became part of the vertical transportation industry in the form of a Seismic Switch. A Seismic Switch is a device that can disable or de-activate an elevator in the event of an earthquake. Seismic switches can enhance elevator passenger safety by the early detection of earthquakes.

How Do Seismic Switches Work?

A Seismic Switch works by monitoring seismic energy made up of Seismic Waves. Seismic Waves are waves of energy that travel through the earth’s layers and are the result of an earthquake, volcano or an explosion. When the device detects fluctuations above a certain level it returns the elevator to the nearest floor and the doors open allowing passengers to get out. The switches are triggered by the preliminary P-waves of an earthquake. P-waves arrive before the more dangerous S-waves arrive. Seismic switches are also known as seismic triggers.

Who Invented the Seismic Switch for Elevators?

Larry D Miller invented the Seismic Switch for elevators in 1975. His US patent filed in that year described his invention as a ‘Tuned ground motion detector utilizing principles of mechanical resonance.’ This was to become the vertical transportation industry standard, CHV -1. Larry was chief designer at Seismic Switch Inc., a company that has since installed over 10,000 devices. Other manufacturers within the vertical transportation industry including industry giant Otis have created and installed their own versions of Seismic Switches. Otis’ product is called a Seismic Sensor.

Since the 1970s Seismic Switches have become a mandatory requirement in earthquake prone countries for buildings with elevators. Most earthquake activity occurs in the following regions: West coasts of South and Central America and from the Northern USA to Alaska, the Aleutians, Japan, China, the Philippines, Indonesia and Australasia. Japan is possibly the most earthquake prone country in part due to its 110 active volcanoes and the fact that 4 of the world’s tectonic plates converge in Japan. Seismic Switches have become an integral part of elevator systems in all of the countries mentioned.

Dunbar and Boardman is the lift, escalator and access equipment consultancy. Are you currently planning a project that will involve vertical transportation? We would be happy to discuss with you. Give us a call on T +44 (0) 20 7739 5093 or send us an email via to start the conversation. We look forward to hearing from you.

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