Averaging Temperature Responsive Apparatus

1. Field of the Invention

In air conditioning systems wherein air is delivered through ducts, there is often a need to measure the average temperature of the air passing through the duct. If a single temperature responsive element is used in one portion of the duct, the air stratification or mixing of the air is not always sufficient that the temperature with a single positioned temperature responsive element provides a true temperature of the total air passing through the duct.

2. Description of the Prior Art

Averaging temperature responsive apparatus for use in an air conditioning duct have had various forms. For many years a wire wound Balco temperature responsive resistance element where the wire is wound on a long support element which when inserted into the side of a duct would extend transversely across the duct to be impinged upon by the air flowing through the duct and thus provide an average temperature reading of the air. Such elements were not only expensive to manufacture but in many cases did not provide a true averaging temperature measurement.

Another form of averaging temperature responsive apparatus makes use of a tubular air conduit which is long enough to extend transversely across the duct. The conduit has either a continuous slit opening or a plurality of inlet openings on the upstream side and at least one opening on the downstream side. Positioned adjacent the downstream opening is a temperature responsive element so that as the air entering the upstream openings passes through the conduit and mixes, the temperature of the air as sensed by the temperature responsive element provides an average temperature of the air in the duct. Such prior art devices depend on pressure differential to promote air movement down the tube to the sensing element.

The present invention is concerned with an averaging temperature responsive apparatus which has improved performance over the prior art responsive apparatus. An elongated conduit or tubular duct is made to be adapted to be mounted transversely in an air duct. The tubular conduit has a plurality of inlet openings on the upstream side spaced across its length and at least one outlet opening on the downstream side. Adjacent the downstream opening is a temperature responsive sensing element to respond to the temperature of the air passing by the element. The upstream openings are formed by cutting the tubular duct at spaced positions and bending a portion of the duct inward to provide a sloping surface for diverting or redirecting the air flow, as it impinges upon the conduit, in a direction into the opening and along the conduit toward the exhaust opening. The redirecting of the air down the tubular duct sustains the air velocity near its original velocity and also promotes turbulence and better mixing of the air before it contacts the sensing element. With the sloped inlet surface for each of the openings, an improved sampling of the air takes place across the duct and thus the measurement of the average temperature is more accurate as the air moves by the temperature responsive element.

FIG. 1 is a schematic representation of an air duct with a fan for moving air through the duct to impinge upon the averaging temperature responsive apparatus,

FIG. 2 is a cross-sectional view of the averaging temperature responsive apparatus showing the temperature responsive element and the inlet openings on the upstream side of the element,

FIG. 3 is a cross-sectional view of the apparatus of FIG. 2 showing the vent portion of the conduit for inducing air flow into the conduit from the opening,

FIG. 4 is a perspective view of one of the openings of the apparatus of FIG. 2,

FIG. 5 is a cross-sectional view of the opening shown in the apparatus of FIG. 2, and

FIG. 6 is an elongated apparatus.

Referring to FIG. 1, the improved averaging temperature responsive apparatus 10 is shown mounted in a duct 11 through which air flows under the power of a fan 12. The duct of FIG. 1 is a schematic showing and obviously could be any air conditioning duct where air moves through the duct under the power of some control fan apparatus.

The averaging temperature responsive apparatus of FIG. 1 is shown in cross-sectional view in FIG. 2. A channel member or tubular conduit 13 is made sufficiently long to extend transversely across various sizes of air conditioning ducts such as shown in FIG. 1. Conduit 13 is closed at both ends 14 and 15. A plurality of inlet openings 20 on the upstream side of the conduit 13 are spaced along the length of the conduit to receive air passing as shown by the arrow 21. At least one outlet opening 22 on the downstream side of the conduit 13 provides for the exhausting of the air as it enters the plurality of inlet openings 20. Mounted adjacent the exhaust opening 22 is a temperature responsive element 23 which might be a temperature responsive resistance element or thermistor or any type of temperature measuring thermostat which would respond to the temperature of the air as it passes along the conduit 13 and exhausts from opening 22. Element 23 might be connected to an appropriate type of measuring or control apparatus over the wires 24. While opening 22 and element 23 are shown at one end near the end 15 which is mounted on duct 11, the opening 22 and element 23 might be placed at various positions along the conduit 13 to provide an exhausting of the air which enters the inlet opening 20.

Each of the inlet openings 20 is made by cutting the duct 13 at a plurality of locations 25 and bending the surface of the duct inward to provide an inclined or projection surface 30 to divert the air flow as it impinges upon the inclined surface 30 into the opening 31 as shown in FIGS. 4 and 5. A cross-sectional view of the inclined surface 30 is shown in FIG. 5. Surface 30 directs the incoming air down the duct toward element 23. The incoming air is maintained at its original velocity to assist in the temperature sensing operation. The inclined surface can be shaped to promote turbulence to mix the air in tube 13 to a better mixture and thus a more accurate averaging temperature measurement.

Duct 13 can be made of a plurality of sections as shown in FIG. 6. Each section is short enough to make a convenient shipping package for ease in marketing; however, many sections such as 13 and 13' can be coupled together with a cap 14' to enclose the end of section 13'. Often the average temperature across a six foot air duct is desired. If so, several sections of conduit can be connected together using conduit 13 with a sensing element 23, several sections of conduit 13 with a suitable connecting means and a cap 14'. The shape of openings 25 could be varied depending on the force needed to direct the air down duct 13' and 13.

When the averaging temperature responsive apparatus 10 is placed in a duct with the openings 20 upstream to be impinged upon by the air moving through the duct, the air is redirected into the hole 31 by the sloped surface 30 and a vector of force to aid the air flow through the conduit 13 to the exhaust opening is present. With such a sloped or inclined surface 30 of each of the openings 20, a better sampling of air is provided across the duct to be provided for the averaging temperature measurement by element 23 as the mixed air is assisted to flow through the conduit 13 in a turbulent mixing manner to exhaust from the opening 22.