Various types of door closer assemblies have heretofore been designed which will cause a door to close once it has been opened. Many such door closers include a pneumatic check such as an air escape valve designed to control the closing velocity of the door. A common problem which has occurred with door closers is caused by the fact that a strong closing force is needed to completely close and latch the door, but, it is too difficult to distort the spring to open the door, persons of limited strength such as the young, the elderly or infirm find it difficult to adequately open the door. In addition, in the event the closing force is high, there is a tendency for the door to close too rapidly and slam shut unless the door is equipped with a check devise which dissipates enough energy to adequately control the closing velocity. Another problem encountered by prior art door closers is the fact that it is necessary to accommodate the opening of the door more than 90.degree. from the closed position and generally at least 100.degree. . The use of conventional door closers requires the use of a door frame or door jam bracket having a length of approximately 3" in order to prevent the extended rod from hitting and being bent by the door when the door is fully opened.
U.S. Pat. No. 2,932,847 to Quinn discloses a modified door closer in which attachment to the door is provided through a secondary, leaf type spring. However, the spring is attached to the door at a point located outwardly of the airbleed end of the cylinder. Thus, as the door is opened, this spring tends to pull the door toward the cylinder. The novel geometry provided by the present invention is not suggested.
The present invention provides a door closer assembly which overcomes many of the shortcomings of the prior art door closers. Specifically, it is an object of the present invention to provide a door closer in which the door closing force does not diminish as the door closes to the extent experienced with conventionally mounted door closers. In a further embodiment of the invention a door closer construction is provided in which the closing force on the door actually increases as the door closes. A further advantage of the present invention is the ability to use a very short jam bracket of 11/2" or less in length.
These and other objectives are achieved by the use of the configuration by which the closer is mounted to the door bracket through a pivot near the rod end of the closer rather than the opposite or air bleed end. A further embodiment of the present invention utilizes a single leaf type helper spring which approximately triples the latching force while greatly reducing the closing force in all "door open" positions. A further object of the invention is to provide such a door closer in which a self-lubricating plastic cup seal is employed which may be economically injection molded from a low friction plastic.