1. Field of the Invention
The present invention is an air damper that is low cost, has a low torque requirement, and makes a good seal when the blades of the air damper are closed.
2. Description of the Related Art
Air dampers with multiple blades that rotate to modulate air flow have one common problem. That problem is that they are difficult to make seal properly. This problem has several contributing factors.
First, there is air leakage between adjacent blades when the blades do not fully and tightly close. To address this problem, closer tolerances can be introduced between adjacent blades or seals can be provided on the blades. Closer tolerances and seals between blades create higher manufacturing costs and create higher friction between adjacent blades which requires more torque being applied to the blades in order to fully close them.
Various types of seals have been used on adjacent blade edges to try to seal between the blades, but these seals still require that the blades to be fully closed in order to properly seal. There is often some “play” in the closure mechanism so that the blades often do not fully close, but instead are still partially open when they are suppose to be in their closed position. Even with seals on the blade edges, if the seals do not engage the adjacent blades prior to the blades being fully closed, they will not seal between the blades.
Also, there is air leakage between the ends of the blades and the supporting damper frame. This leakage is due to the fact that existing side seal designs are have high leakage rates and because the lengths of the blades may not be cut precisely square, may not be cut at uniform lengths and may not be cut so that there are close tolerances between the ends of the blades and the frame.
The present invention addresses all of these problems. The present invention is provided with a blade seal that is square in cross sectional configuration. The blade seal is provided on the blade edges so that the blade seal engages the adjacent blade early, before the blades are fully closed, i.e. in their parallel, aligned orientation. The reason the blade seal engages the adjacent blade early is that the diameter of the diagonal of the square seal is longer than the length of the side of the square seal.
Thus, the square configuration blade seals make it unnecessary to remove the “play” from the closure mechanism in order to fully seal between adjacent blades and makes it unnecessary to have precise parallel alignment of the blades in order for the seals to engage.
The blade seal attachment to the damper blade is preferably constructed of a plastic such as polypropylene, nylon or ABS plastic to which sponge rubber is bonded. The plastic used is preferably polypropylene. Polypropylene is rigid, low friction, and dimensionally stable so that it maintains its length once it is cut to the desired length. The sponge rubber is flexible and capable of sealing against the adjacent blades.
Also, the present invention is provided with a side seal mechanism that seals and stops air leakage between the ends of the blades and the damper frame even when the blades are not completely closed, cut precisely square, when the blades are not cut at uniform lengths and when the blades are not cut so there are close tolerances between the ends of the blades and the frame.
The present invention provides an air damper with three advantages: it is low cost to make and operate, it has low torque requirements, and it provides a good seal. Previous air dampers may have been able to provide one or two of these advantages, but none have previously been able to provide all three of these advantages in the same unit.