Refrigeration – Automatic control – Of external fluid or means
Patent
1980-10-10
1982-11-09
Wayner, William E.
Refrigeration
Automatic control
Of external fluid or means
236 49, 474 11, F25D 1704
Patent
active
043578063
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
BACKGROUND OF THE INVENTION
The present invention relates generally to variable air volume systems for maintaining a desired temperature range within buildings and, more particularly, to an improved controller for enabling the required air volume to be supplied.
In variable air volume systems for cooling the interiors of buildings, the cooling coils are maintained at a substantially constant temperature by a continuously operating compressor while a controller establishes the volume of air forced through the cooling coils and distributed throughout the building to maintain a desired temperature range. This controller is connected to operate a speed changing means which results in fan speed changes to vary the volume of air. The inputs to the controller are means sensing temperature of the areas of the building being cooled and a feedback indicative of the speed of the fan.
In some prior variable air volume systems, a heat cycle is provided before the cooling is introduced. In some systems, direct current drives the fans, some have eddy current drive means, while others use two speed motors with variable inlet vanes. The alternating current fan drive and controller of this invention operate with a significantly shorter payback period than the above alternatives. This invention further contributes considerable amounts of energy saved. Since the power consumed is a function of the cube of the fan speed, the variable speed provides fan operation at speeds substantially below maximum a considerable part of the operating time. The initial cost is low; and the maintenance requirements, efficiency at partial loads, overload capacity, complexity of controls, and the requirements of maintenance training are favorable to the structure of this invention.
In the prior art, the variable pitch split pulley transmission system was utilized in cooling of engines such as is shown in U.S. Pat. No. 3,872,842 issued Mar. 25. 1975 to Jackson C. Medley. In the application of such speed changing mechanism to air conditioning systems, as in the present invention, unique control circuitry is contributed.
SUMMARY OF THE INVENTION
This invention incorporates: a variable speed means for the fan providing an infinite number of fan speeds; and a controller capable of providing precise fan speed operation to accurately control the temperature within a building. The variable speed fan drive is a fixed-center belt drive. It consists of a mechanically adjustable driver pulley, a spring loaded driven pulley, a variable speed belt and mounting collets for the pulleys. An integrally mounted servo-motor adjusts the pitch of the driver pulley. The driven pulley, being spring loaded, automatically adjusts to pitch diameter changes of the driver pulley to maintain proper belt tension while providing infinitely adjustable fan speeds.
The controller provides for connection to existing sensing means such as thermostats, pressure gauges and the like to accept therefrom an analog input to produce an output which signals to the servo-motor with a positive output to speed up the fan, with no pulse to remain constant, or with a negative output to slow down the fan. A feedback signal from the shaft of the fan provides a reference signal that is compared with a signal indicative of the temperature of the area to be cooled to determine the succeeding operation of the system. Adjustments determine the maximum and minimum speeds of the fan as well as a deadtime interval which is representative of the temperature variation that is acceptable before a speed change is effected. The output of the controller is applied to the servo-motor and effects speed changes by adjusting the pitch of the driver pulley.
Also, provision is made for controlling a return system when the supply cooling air could cause doors to close or windows to be blown out. This return system control is coupled to the input controller and provides a percentage differential so that the return air is removed at a rate slightly slower than the supply air.
It is, therefore, an obj
REFERENCES:
patent: 2130995 (1938-09-01), Henney
patent: 3349785 (1967-10-01), Duffy
patent: 3653589 (1972-04-01), McGrath
patent: 3887000 (1975-06-01), Pinckaers
patent: 3954018 (1976-05-01), O'Berto
patent: 3964675 (1976-06-01), Euchner, Jr.
patent: 4072268 (1978-02-01), Perris
Harris Charles G.
Mora Erwin P.
Singh Mahendra P.
Solberg David P.
Dana Corporation
Lucke Robert C.
McDonald Frank B.
Wayner William E.
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