Door closers are one of the most taken for granted hardware items. People push doors open, then let the door go and fully expect the door to slowly and quietly shut behind them. According to the dictionary, 'taken for granted' means to underestimate the value of a person or thing. This description certainly fits the lonely door closer. Nobody looks up to watch a door closer in action until that unlikely day when their door does not close properly and people look around to see what is causing the problem.
It is said that the first elementary design for a door closer was developed in the 19th century by necessity to prevent the noise of slamming doors during religious services. A gentleman named Lewis Norton received a patent for his door closer invention in the mid 1880s and founded a company to manufacture his product. His first invention was pneumatic and attempted to control the speed of air escaping from a chamber. Lewis Norton later changed to a more dependable hydraulic door closer design. This design controlled the movement of a piston through liquid and stands as the basis for commercial door closer designs in use today. More than a century later the Norton name still stands for quality in the many available Norton door closer products.
In its most elementary form a door closer consists of a piston enclosed in liquid, a spring to drive the piston through the liquid, and a valve to control the movement of the piston. As a closed door is moved, an automatic relief valve is opened, the piston can freely move through the liquid, and the door can be opened for ingress or egress. As spring pressure begins to close the door, the automatic relief valve closes and a second control valve begins restricting the flow of liquid. Liquid passing through the control valve is directed to a channel which leads the liquid to the other side of the piston in preparation for the next opening cycle.
For many years commercial door closers were often referred to as 'Pot' style door closers. A large vertical chamber contained a flat coiled spring and a smaller horizontal section contained the piston unit. Door closers were known for their utilitarian purpose with no thought to visual esthetics.
The Norton 7500 door closer chosen for this article is a new class of door closer often referred to as 'Streamline.' While the piston, spring and valve operating system is similar to Pot door closers, the compression spring is horizontally enclosed in a common chamber with the piston. This eliminates the large vertical spring chamber and presents a much more pleasing esthetic look on the door. Norton still makes Pot style door closers, now called 'traditional' closers, which are used in limited applications where customers may desire an old-time look.
Basic Streamline door closers contain a spring with set spring strength. A door closer is designated by size. Basic door closers must be specifically ordered according several criteria such as door size, door weight, possible ADA regulations and weather conditions. Basic door closers usually contain one adjustment valve. The single adjustment valve can control general closing, often called 'sweep', and final latching speed.
Norton 7500 Series
Norton 7500 multi size door closers provide versatility for almost any application situation. The first noticeable feature is shafts which project. One 7500 door closer body can be used for left hand or right hand operation by attaching the door closer arms to the shaft end required.
The standard Norton 7500 door closer unit contains four adjusting screws. Helpful adjustment instructions are permanently affixed inside the cover case. The first valve on the left provides latch speed adjustment for final closing of the door. The valve second from left provides sweep adjustment to set general closing rate of the door to retain heat or air conditioning conditions within the building while being slow enough to allow people to be clear the opening ahead of the closing door.
The valve on the extreme right is for setting the backcheck. A backcheck setting is designed to prevent the door from being moved violently against an obstruction or wall either by wind or people which could cause damage to the door. The valve second from the right sets the opening angle at which the backcheck cushioning begins. The casting space second from the left is used when optional delayed closing is required.
Another Norton 7500 adjustment can be made at the round end of the closer unit where an 11/16" adjustment nut is located. Door closer sizes can vary from 1 (light spring pressure) to 6 (heavy spring pressure). Norton 7500 door closers can be set to operate at any spring pressure from 1 to 6 depending on individual door requirements. A chart included in the instruction sheet shows how many turns to be made to achieve desired operation depending on door size and exterior or interior usage. A maximum of 16 1/2 turns of the adjustment nut can be made.
Finally, each Norton 7500 door closer contains a regular arm assembly and a soffit plate used for parallel arm installations. 7500 door closers can be mounted in the regular position with the door closer on the door and the rod and shoe assembly attached to the top jamb.
If the 7500 door closer must be mounted on the side opposite the hinge pins, there are two alternatives. First, the door closer can be mounted on the top jamb with the rod and shoe mounted to the door. A second alternative is to replace the shoe with the soffit plate, then use a parallel installation with the door closer mounted to the door and the soffit plate mounted to the header. Optional hold open and slide track arm assemblies are available.
Full instructions are included with each 7500 series door closer showing installation instructions, adjusting instructions and drawings of standard, top jamb and parallel installations. Full size installation templates can be downloaded from: www.nortondoorcontrols.com.
Norton 7500 door closers have exceeded 25 million cycles as witnessed and verified by UL and have a 25 year limited warranty.
For further information contact your local locksmith distributor or Norton Door Controls, an ASSA ABLOY Group company. 800-338-0965, www.nortondoorcontrols.com.
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