US2808488A - Air conditioning unit and control - Google Patents

Description

1957 s. J-. LEVINE AIR CONDITIONING UNIT AND CONTROL Original Filed Jan. 5, 1952 Inventor: Samuel J. Levine Hi5 Attorney.

Unite States Patent Ofifice 2,808,488 Patented Oct. 1, 1957 AIR coNnrrroNlNo UNIT AND CONTROL Samuel J. Levine, l est Grange N. 3., assignor to General Electric Company, a corporation of New York Original application January 5, 1952, Serial No. 265,153, now Patent No. 2,711,681, dated June 21, 1955. Di vided and this appiication September 17, 1954, Serial No. 456,741

3 Claims. (Cl. 200-440) This application is a division of application Serial No. 265,138, filed January 5, 1952 (now Patent 2,711,681), in the name of Samuel J. Levine and assigned to the same assignee as the present invention.

This invention relates to air conditioning apparatus and particularly to air conditioning units for ofiice buildings and the like.

Office buildings, for example, may be provided with air conditioning units supplied with preconditioned air from a central plant but also providing individual control for the oliices through the operation of blowers installed in units in each omce for circulating air from the central plant and from the room over heat transfer surfaces in the unit. It is desirable that all the units in the building be under control of the central plant so that the entire system may be shut down from the central plant. Such shutdowns may be desirable in ofiice buildings, for example, over the week end; however, it is also desirable that individual ofiices be conditioned although the entire system is not in operation so that such offices in use when the over-all system is not in operation may be air conditioned. Accordingly, it is an object of this invention to provide an air conditioning system including individually controlled units for rooms of the building and providing over-all control from the central plant and a selectively controllable arrangement for conditioning individual rooms when the over-all plant is not in operation.

It is another object of this invention to provide an improved control system for air conditioning units.

It is a further object of this invention to provide an improvedcontrol device for air conditioning units which is simple in operation and affords selective control of the unit.

Further objects and advantages of the invention will become apparent as the following description proceeds, and the features of novelty which characterize the invention will be pointed out with particularity in the claims anmated to and forming a part of this specification.

In carrying out the objects of this invention, an air conditioning unit of the type comprising a heat transfer surface and electric motor driven blowers for circulating air over the surface is arranged to receive air under pressure from a suitable source and is provided with a control mechanism for actuating the blower motor upon the occurrence of a predetermined pressure in the air supply. The control further includes a manually operated element for starting the motor in the absence of air pressure in the supply, this latter control being biased to its neutral position and being retained in its motor actuating position by a latching mechanism which is released whenever air pressure is restored in the inlet to the unit. An installation of a plurality of such units may thus be controlled by supplying air under pressure to all of the units, but individual units may be actuated in the absence of such pressure by operation or" the manual control. A further selective control is provided so that the motor may be stopped even though the air pressure control is actuated.

For a better understanding of this invention, reference may be had to the accompanying drawing in which Fig. 1 is a front elevation, partly in section, of an air conditioning unit embodying this invention; Figs. 2 and 3 are end views or the unit of Fig. 1; Fig. 4 is a diagrammatic view of a plurality of units of the type shown in Fig. 1 arranged in a multizone installation; Figs. 5 and 6 are enlarged elevation and side views, respectively, of the control mechanism employed in the unit of Fig. 1; Fig. 7 is a diagrammatic illustration of the electric circuit employed in the conditioner of Fig. 1; and Figs. 8 and 9 are enlarged detail views, taken On the line 88 of Fig. 5, illustrating the two positions of the manual control switch of the control.

Referring now to the drawing, the air conditioning unit shown in Figs. 1, 2 and 3 comprises a casing 10 in the upper portion of which is arranged a heat transfer unit 11 of the finned coil type arranged to receive heat transfer liquid from a suitable supply through intake and discharge connections 12 and 13. Air may be circulated over the unit it by operation of a pair of centrifugal blowers 14 and 15 driven by an electric motor 16, as indicated by dotted lines in Fig. 1. Room air is admitted to the unit through an opening 17 at the bottom of the casing and flows throu h a filter 18 to the blower inlets. Fresh air, preferably conditioned in the central plant, is supplied under pressure through an inlet 19 and flows through a series of perforated battle plates 20 and into an elongated silencer tube 21 from which it flows into the space below the filter 18, as indicated at 22. Thus the fresh air is mixed with the return air and enters the blower inlets to be circulated over the heat transfer surface 11.

The unit may be employed either for heating or cooling, suitable equipment being provided in the central plant to supply either heating or cooling liquid to the unit 11. When the unit is employed for cooling, moisture condensed on the surface of the unit 11 flows into a trough 23 and then through a drain connection 24 to a collecting funnel 25 under which may be placed a container or plumb ing connection (not shown). When the unit is employed for heating, the air supplied under pressure from the central plant may be preheated, and when the system is employed for cooling, this air may be precooled thereby removing the major portion of the moisture from the fresh air before it is distributed to the units.

The general arrangement of the units in an ofiice building, for example, is shown in Fig. 4 where three units 10 have been illustrated arranged to receive conditioned air under pressure from a central plant 26 through a supply duct 27 connected through risers 23 to the inlets 19 of the units it). Each of the units is provided with a control device 29 which is arranged to ener ize the motor 16 Whenever air is supplied under pressure to the inlet 19 and further, in the event that air is not being lied, these controls are provided with manually adjustable members to operate the motors although central plant air is not available. The central plant arrangement for supplying heating or cooling fluid to the heat transfer units 11 has not been illustrated in order to avoid further complication of the drawing. It will be apparent that all of the units may be conditioned for operation by supplying air under pressure through the conduit 27, but that in the event the central air conditioning system is shut down, as over a week end, individual ofiices may be controlled manually.

The control 29 is provided with a pressure tube or connection 39, shown in Figs. 1 and 2, which provides communication between the control and the air supply inlet 19. The details of the control are shown in Figs. 5 and 6. The pressure tube 30 is connected to a chamber 32 within an expansible chamber device 33 which includes a movable diaphragm 34 biased to its low pressure position by a spring 35 mounted between the diaphragm and a wall 36 2,soe,ass

of the device 33. The chamber 32 is formed by a wall 37 of the device 33 which is mounted in engagement with the back wall of the casing of the device 29 indicated at 38. An electric switch 39 is mounted on a bracket 40 on the wall 36 and includes a switch arm 4]; arranged in the path of a plunger 42 mounted on the diaphragm When a predetermined pressure prevails in the chamber 32, the plunger 42 moves toward and engages the arm 41 and moves it to the left to actuate the switch. The arm 41 is resiliently urged toward its right-hand position, as illustrated in Fig. 6, by a suitable spring biasing means (not shown), the switch being of the well-known snap acting type which is biased to its open position. The switch 39 is connected in the circuit of the motor to in the manner illustrated in Fig. 7. The motor 16 may be supplied with current from lines 45 through the switch 39 and a manual switch 46, shown in its off position. When the switch 46 engages either of a pair of terminals 47 and 43 of a reactor 49, the motor is connected across the lines 45 upon closing the switch 39. When the switch 46 engages the contact 47 the motor is operated at full speed, and when it engages the contact 48 the reactor 49 is placed in series with the motor which then runs at reduced speed.

During periods when the majority of the offices in the building are unoccupied and there is no demand for heating, it may happen that in severe winter weather the temperature becomes abnormally low. It is desirable to prevent reduction of the temperature below some predetermined value and an arrangement is provided so that the fans may be started when room temperatures fall too low. The heat exchange coil is supplied with warm water at all times, and in order to circulate the air over the coil and prevent too great a reduction in room temperature a thermostat Si) is provided in the control which engages a contact 51 at the desired minimum temperature and connects the motor for reduced speed operation through the reactor 49 even though the switches 39 and 46 are open. By preventing too great a reduction in temperature in the unused rooms, the general ambient temperature within the building is prevented from falling to too low a value.

From the foregoing, it is readily apparent that all of the units in a building such as that illustrated in Fig. 4 may be controlled by supplying air under pressure through the duct 27; however, during the idle periods of the overall system when air is not being supplied under pressure from outside the room it may be desirable to operate an individual unit, and for this purpose a manual control having a knob 52 is provided to close the switch 39 al though the diaphragm 34 is in its right-hand position and the plunger 42 out of engagement with the switch. The knob 52 is secured to a shaft 53 mounted in a bracket 54 secured to the wall 36 of the device 33. A cam 56 is secured to the end of the rod 53 and acts as a stop against which the switch arm 41 bears when the plunger 42 is disengaged. The cam 56 is eccentric in form, as illustrated in Figs. 8 and 9, its normal position being shown in Fig. 8 and corresponding to its position as shown in Figs. and 6. The cam 56 is urged to this position by a coil spring 57 having one end engaging the bracket 54 and its other end hooked about a post 58 on the rod 53. This spring biases the cam 56 to its position as shown in Fig. 8 wherein the cam engages the plate 36 at 59. The cam 56 includes a notched or relieved portion 60 in its periphery remote from the rod 53, and when the knob 52 is turned to rotate the rod 53 in a clockwise direction, as viewed in Fig. 8, the notch 60 engages the switch arm 41 and thereby retains the cam 56 in the position shown in Fig. 9, the arm 41 being urged against the cam by the bias of the switch arm and preventing rotation of the shaft 53. Thus the motor may be actuated by closing the switch 39 even though air under pressure is not available at the inlet 19. This enables the occupant of an individual room to control the circulation of air in that room whether or not the central plant air supply is in operation. Whenever the central plant is again placed in operation, the plunger 42 moves the switch arm 41 to the left out of engagement with the cam, which thereupon is returned to its position of Fig. 8 by the biasing spring 57, thereby restoring the unit to automatic control. it will be understood that the switch arm 41 is moved to its switch closing position by movement of the cam 56 to the position as shown in Fig. 9 but may be urged beyond the position for initial closing of the switch by the switch bias upon operation of the plunger 42.

From the foregoing, it is readily apparent that a simple and effective arrangement has been provided for controlling air conditioning units in multizone installations while making possible individual control of the units when the central plant automatic control is not in operation, thereby providing a system which is flexible in operation, particularly for installations involving a great many separate zones normally supplied with fresh air from a common central source.

While a particular embodiment of the invention has been illustrated including specific details of structure, modifications will occur to those skilled in the art and it is not desired to limit the invention to the specific structure illustrated, and it is intended to cover by the appended claims all modifications which fall within the spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A pressure responsive switching mechanism comprising an electric switch having an operating arm, an expansible chamber device having a movable wall member, means dependent upon a predetermined fluid pressure in said device for utilizing movement of said wall member to actuate said switch arm, means for biasing said arm against such movement, a movable stop for said switch arm having a first position for limiting the movement of the arm by said biasing means of said arm, means for moving said stop to a second position against said biasing means to actuate said switch, spring means for biasing said stop to said first position, and means on said stop for engaging said switch arm and retaining said stop in said second position and affording release of said stop and return to said first position upon operation of said switch arm by said expansible chamber device.

2. A pressure responsive switching mechanism comprising an electric switch having an operating arm, an expansible chamber device having a movable wall member, means dependent upon a predetermined fluid pressure in said device for utilizing movement of said wall member to actuate said switch arm, means for biasing said arm against such movement, a rotatable stop biased to a first position in the path of said switch arm for limiting the movement of said arm by the biasing means of said arm, means for rotating said stop to a second position to move said arm against its biasing means for actuating said switch, and a catch on said stop for engaging said arm in the second position of said stop to retain said switch in its actuated position, said pressure dependent means being arranged to move said switch arm out of engagement with said catch whereby said stop is returned to its first position upon a predetermined movement of said movable wall member.

3. A pressure responsive switching mechanism comprising an electric switch having an operating arm and means biasing said arm to its switch opening position, said arm being movable from its switch opening position to a switch closing position and affording further movement of the arm after the switch has been closed, an expansible chamber device having a movable wall member, means dependent upon a predetermined fluid pressure in said device for utilizing movement of said wall member-to actuate said switch arm against the bias thereof, a movable stop for said switch arm having a first position for limiting the movement of said arm in the switch opening direction, means for moving said stop to a second position to move said switch arm to its switch closing position, means for biasing said stop to its first position, and means utilizing engagement of said stop and said switch arm in the second position of said stop for retaining said stop in said second position and for releasing said stop upon further movement of said arm beyond said switch opening position by operation of said expansible chamber device.

References Cited in the file of this patent UNITED STATES PATENTS Sundh July 14, 1903 Bowar Ian. 12, 1951 Greenawalt Mar. 2, 1954 Senn Mar. 9, 1954

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