Chimney draft control valve

Abstract

The chimney draft control valve has a baffle plate suspended inside a housing, between an inlet opening and a valve seat inside that housing. The baffle plate is suspended to a pivot axis for pendulum movement toward and away from the valve seat and for checking a draft in a chimney when a vacuum pressure in that chimney is high. A spring is affixed to the housing and to the baffle plate for controlling an amplitude of the pendulum movement of the baffle plate in moderate to strong wind conditions. A dampening device is affixed to the housing, to the baffle plate and to the spring for controlling a period and amplitude of the pendulum movement of the baffle plate and a free vibration in the spring.

Description

FIELD OF THE INVENTION [0001] This invention pertains to chimney draft control devices and more particularly it pertains to a damper-type flue gas control valve having in combination a mass, a spring and a damper, to control the draft in a chimney to which an oil stove is connected. BACKGROUND OF THE INVENTION [0002] The efficiency of a pot-type oil stove depends to a great extent on the draft in the chimney to which the stove is connected. A high wind above the chimney, for example, is known to put out the flame in the pots of these stoves, whereby the oil can fill and overflow the pot, leading to dangerous spills. It is believed that these oil stoves would be more widely used if better draft control devices would be available for installation thereon. [0003] Most draft control devices available commercially are similar to each other wherein each has a baffle plate pivoted on a horizontal axis. Generally, one or more counterweights are affixed to the plate, to move the centre of gr...

AI Technical Summary

Benefits of technology

"The present invention relates to a chimney draft control valve that can maintain a constant negative pressure inside a chimney, regardless of weather conditions. The valve has a baffle plate mechanism that includes a mass, a spring, and a dampening device. The spring is selected to control the movement of the baffle plate in high wind conditions, while the dampening device removes any free vibration in the baffle plate. The valve can adjust its position to different chimney conditions and can be installed in a horizontal, vertical, or right angle elbow flue pipe. The invention ensures that the movement of the baffle plate is proportional to the vacuum pressure inside the chimney and is not affected by other factors such as free vibration or the natural frequency of the spring."

Problems solved by technology

A high wind above the chimney, for example, is known to put out the flame in the pots of these stoves, whereby the oil can fill and overflow the pot, leading to dangerous spills.

Therefore, when the wind above a chimney is unsteady, the baffle plate oscillates like a pendulum, letting irregular amounts of air pass through the chimney, and causing a fluttering draft through the stove.

It is believed that the combination of these two vibrations on the baffle plate is the primary cause of air fluttering in a flue gas passage.

The field of chimney draft control devices is a limited one wherein few changes were made to a basic concept since a far past.

Because of its natural frequency, however, the spring changes the characteristics of the free vibration but does not eliminate it.

On the other hand, a damper attenuates the free vibration, but does not provide a linear response to a forced vibration.

It is for these reasons, basically, that the prior flue gas dampers are difficult to predict or to calibrate.

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