On the surface, the mechanics of door closers seem pretty straightforward.
“A door closer makes sure your door…closes,” explains Matt Burstein, Senior Sales and Purchasing Manager with Sentinel Door Controls.
But that is just the beginning.
Door closers are the mechanical devices that close a door after someone opens it. An integral component in all commercial buildings, in the United States, door closers are required on all entrances and exits as well as on fire safety doors.
Door closers have two primary functions. First, they control the door as it opens and closes, protecting the opening and preventing the door from closing too quickly or slamming, potentially causing injury. Second they provide security.
“Door closers are essential life safety and security components,” says Dave Gray, General Manager of Norton Door Controls. “The best lock in the world becomes ineffective if the door closes most of the way but doesn’t latch.”
May the force be with you
In a manual closing, as you open the door to enter, the resistance you feel is the compressing of a spring in the closer. Also, you are moving hydraulic fluid that is used to manage the speed of the door. This prevents the door from swinging open. When the door is released, the energy stored in the same spring then pushes the door shut. Hydraulic fluid controls the closing and prevents the door from slamming shut.
Leaking hydraulic fluid – as a result of abuse or a design flaw – is the most common reason for door closers to fail over time.
“Manufacturing assembly processes play a big part in maximizing closer life,” says Gray. “At Norton we have used techniques such as vibratory processing of internal parts to reduce wear, closer oil with anti-wear additives developed specifically for door closers, and careful selection and testing of seal material to improve closer life.”
Design issues of door closers are often related to their efficiency and there has to be enough force to overcome resistance and successfully close the door. “To determine the proper closer to be used you must factor in issues such as friction and resistance. What is the size and weight of the door? Is the door dragging on the carpet, for example? An effective closer must overcome a multitude of forces to have a satisfactory closing action,” says Gray.
Concealed or exposed
Another design challenge comes because most door closers must be mounted at the top of a door, or on the frame. “Closers are usually exposed,” says Burstein. “As a result, vandalism can be a problem and you can’t always control people from hanging things off them.”
Door closers are either surface mounted, the kind everyone sees, or overhead concealed within the door’s frame, Burstein explains. On a larger scale, there are also floor closers, heavy duty closers installed in the floor that control large, heavy doors.
“But an advantage of the surface mounted closers is that they tend to last longer,” Burstein says. “The concealed closers or floor closers only have so much hydraulic fluid and that can run out. A surface mounted closer can last forever if it’s not tampered with.”
Gray advises customers to think of their door closers like a car’s brake system. Both use pistons and hydraulic fluid and provide a safety benefit to the user. But, just as with a car’s brakes, for a door closer to work properly, fluid levels must be maintained for a long time, typically 10 years or more without service.
With the goal of combining efficiency, long life and ease of operation, Norton has developed the new Trinity door closer. It stands out from other traditional door closers because it uses a combination of electronics, hardware and software to self regulate, adjusting itself in changing environments.
In many commercial applications, door closers must be manually re-adjusted to compensate for seasonal changes, explains Gray. “When you install a door closer, you set it up properly to ensure it closes the door reliably on the latch without slamming and that it does not swing back and hit the wall on opening”
Door closers may need to be readjusted to ensure effective closing throughout the changing seasons and resulting shifts in temperature and air pressure within a building.
The Trinity saves time and expense by readjusting itself.
“Over time, if the closer senses the door is not shutting at the same speed that you originally set it up, it will self adjust to compensate back to the original setting.” And the Trinity does this without requiring costly installation or regular battery replacement. The act of opening the door turns a pinion that runs a generator which in turn powers the electronics that control the closer.
“A lot of people can make a basic door closer,” says Gray. “There hasn’t been a lot of change in the technology for the past 100 years. But, for a door closer to really be efficient and to last? That takes careful selection of materials and precision in manufacturing.”
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