US3443588A - Damper means in air supply units or the like - Google Patents

Description

May 13, 1969 E. J. BANKO 3,443,588

DAMPER MEANS IN AIR SUPPLY UNITS OR THE LIKE Filed Oct. 24, 1965 Sheet of 2 g 8O 18 -23 g2 18 2s w k 5 1O ZZ-- 3O 15 Z I70 21 0 gm 24.. Z0 O o10210304060607080q o 16 59c: .Dnnmpflmcs-pesqea-Omy b 29 A u H W I7. 12 0 15 flow HQ "19 5 Z?) 20 L21 1/2 Q R Z4 3 3 (4 18 Tl I00 17 I 12 0 Q; 17a 20 is t 2 F 0" i 12 0 w 24 g I 50 3 53 :2

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Anne vars May13, 1969 E. J. BANKO v 3,443,588

DAMPER MEANS IN AIR SUPPLY UNITS OR THE LIKE Filed Oct. 24, 1965 Sheet g of 2 i E i 7. T H D T W i. 8 12 O 1s-- 3 g 32 O g 12 Q '5 i 5 14 x Y 12 v o1ozow4o607oa99o 7 files 00MPe 4/me-0;6ms0m/ 3 Ti E .60 I s 51 W Q18 23 i 3 A V 5 E INVENTOR;

62 5 1 fowmo J (SHIV/ 0 United States Patent 01 ice 3,443,588 DAMPER MEANS IN AIR SUPPLY UNITS OR THE LIKE Edward J. Banko, Colonia, N.J., assignor to Aero-Flow Dynamics, Inc. (The Wing Company Division), Linden,

N.J., a corporation of New York Filed Oct. 24, 1965, Ser. No. 504,433 Int. Cl. F17d 1/10; F28f 27/02; F24f 13/04 U.S. Cl. 137-601 Claims ABSTRACT OF THE DISCLOSURE Control arrangements for fiat damper system in a face and by-pass type air heater unit, providing concurrent differential movement as between the face passage, dampers and the dampers on the smaller width by-pass passages when moved to positions between their respective full open and full closed POSitiOnS with linkage means for effecting a variable rate of movement of one of said dampers so that, at all damper settings, the air pressure drop across the unit is substantially the same. See disclosure for particular arrangements, including four-bar linkage control for both face and by-pass dampers and having particular lengths and angular relationships of its comstated results.

This invention relates to air supply units or the like in which adjustable dampers proportion the flow of admitted air between passages for conditioning admitted air, as by heating or cooling the same, and passages through which admitted air by-passes the conditioning passages. More particularly, the invention relates to an improved manner of operation of such dampers for improving the overall operation of the supply unit.

Although the invention was made in connection with attempts to improve air flow proportioning and regulation in space heater units of the so-called integral face and bypass type and therefore will be described in connection with such use, the invention may be useful in other applications, such as in fluid conditioning units in general, and whose primary function is other than heating, and in connection with face and by-pass equipment which is not integrally arranged as, for example, in equipment providing separated fluid conditioning and fluid by-pass arrangements.

A conventional integral face and bypass air heater unit includes a series of parallel air passages for conducting air from a source, such as the atmosphere or a room of a building or the like, to another area where the air will be used, such as a 'room of the building or the confines of a work processing area as, for example, a paint spraying chamber situated on an assembly line. The alternate of the parallel air passages contain heating coils, sometimes called blast coils, for heating any air passing therethrough by contact of the air with the surfaces of the coils, and such alternate passages are therefore called face passages. The remaining interstitial air passages of the unit are plain, and are called by-pass passages since they are utilized for by-passing air around the face passages. It is usual to provide an air blower on either the upstream or the downstream side of the face and by-pass passages to promote the flow of air through the unit.

It is conventional to employ adjustable dampers to control or proportion the amount of air which may fiow through the face and by-pass passages since, depending upon the air temperature desired to be established or maintained within the space being supplied as compared with the temperature of the air at the air source, all or only a portion of the incoming or admitted air may be passed through either the face or the by-pass passages.

3,443,588 Patented May 13, 1969 Thus, temperature regulation of the air which has passed through the air supply unit is achieved without the necessity for adjusting the amount of heat supplied to the heat ing coils within the face passages. Known types of adjustable dampers as are employed in such air heating units are exemplified by United States Letters Patent Number 2,521,866 issued Sept. 12, 1950 to Ott, and Number 3,107,724 issued Oct. 22, 1963 to Horn et al. In this connection, it will be noted that the Ott apparatus involves the use of fiat-type dampers, whereas the dampers in the Horn et al. apparatus are curved.

As referred to in the Horn et al. patent, one of the difficulties in prior damper arrangements in such units was the inability of the damper system to provide a minimum and substantially constant resistance to air fiow through the unit throughout the range of such modulation of the flow as is provided by the adjustable dampers. That is, it is desirable, and in some modern applications of such air supply units it is extremely important, that the air pressure drop through both the face and the by-pass passages shall remain substantially constant regardless of the damper-effectuated proportioning of all or only a part of the total supply of air through either of them. The V-shaped, curved dampers when mounted on such units and operated in the manner disclosed by Horn et al. are very effective in overcoming the deficiencies of prior damper arrangements in this regard, and do provide more constant pressure drop characteristics in such air supply units. However, the Horn et al. curved-type dampers, so arranged and mounted for operation, involve relatively high costs of manufacture as compared with the previously conventional, but less desirable, flat damper arrangements.

Accordingly, it is intended by the present invention to provide an adjustable damper system which, when utilized in face and by-pass type fluid conditioning units, will achieve all of the benefits of the curved type damper arrangement of Horn et al., yet which will effect appreciable savings in the manufacturing costs of such units. One of the ways in which manufacturing costs may be reduced is by eliminating the rolling operations as are necessary to form the curved dampers themselves and, accordingly, it is intended that the present invention will only require the use of the less costly fiat type dampers'as were known prior to Horn et al.

Whereas the Horn et al. air supply unit effects substantially constant pressure drop regardless of damper position by altering the configuration of the dampers themselves while providing for concurrent and equal movement of the dampers which control the face and the by-pass passages, the present invention contemplates achieving the same or better results by differential movement as between the dampers which control the by-pass passages and the dampers which control the face passagesin such air supply units. As previously noted, the invention contemplates that these results may be achieved in a flat damper system, although it will be understood that, additionally, the otherwise flat configuration of the dampers might be altered for other reasons.

Briefly describing the invention in its preferred embodiment, the integral face and by-pass air heater unit includes a plurality of parallel and alternately adjacent face passages and by-pass passages through which movement of air is induced, as by a fan or air blower at either the upstream or downstream side of the unit. Considering the total volume and rate of flow of air which is intended to pass through the unit, and also the flow losses and resistance which will occur as the air passes through the heating coils of the face passages, the transverse or inlet area dimensions of the face passages and the by-pass passages, respectively, are determined in accordance with the requirements that either the total face passage area or the total by-pass passage area shall be capable of accommodating all of the air flow when the other is fully closed; that the inherent drop in air pressure as the air passes through the face passage areas shall be a practical minimum; and that the pressure drop through the bypass passage areas when the face passage areas are closed shall equal the pressure drop through the face passage areas when the by-pass passage areas are closed.

In such an arrangement of alternate face and by-pass passages the invention provides an adjustable damper system for modulating the flow of air between the face passages and by-pass passages, the damper system being such that substantially the same pressure drop occurs across the the unit when the dampers, which are situated at the inlet ends of the respective face and by-pass passages, are adjusted to any relative positioning for proportioning the flow of air between the two types of passages.

The damper system provides a fiat damper, hingedly mounted for arcuate pivotal movement about an axis of its length, at the air inlet side of each face passage and each by-pass passage. The range of pivotal movement of each damper is ninety degrees, and the planes of the dampers, in each of the respective sets of dampers which control the face and by-pass passages, are disposed at ninety degrees with respect to the planes of the dampers in the other set when either the face passages or the bypass passages are fully closed. However, control of the movement of the damper sets is such as to provide differ ential movement between the face passage dampers and the by-pass passage dampers when adjustment is made to proportion the total air flow between the face and the bypass passages. Thus, at any intermediate position of the damper sets, the face passage dampers and the by-pass passage dampers are not disposed at ninety degrees with respect to the other. The differential movement and resulting repositioning is such as to avoid the establishment of areas of insufiicient air flow to either the face or the by-pass passages as occurs when using conventional fiat damper arrangements of the type in which the face passage dampers and by-pass passage dampers are disposed at ninety degrees with respect to each other throughout the range of their movement. That is, as regards the relative positioning of the flat type face passage dampers and by-pass passage dampers with respect to each other at any position, the arrangement is such as to establish fiow areas at the face passage and by-pass passage inlets which produce substantially the same air pressure drop across the unit as is produced by the damper arrangement in any other position.

Although a cam arrangement might be used, such relative movement of the damper sets is achieved in the preferred embodiment of the invention by the features of the comparatively uncomplicated damper control linkage which promotes the concurrent but differential movement of both sets of dampers. The linkage arrangement includes damper arms of equal length respectively attached to, and extending perpendicularly from the pivotal axis of each damper. These damper arms in each of the respective damper sets extend parallel to each other and are each pivotally connected to a damper rod whose movement thus controls the movement of all of the dampers in the set. In addition, a face passage damper crank arm is attached to, and extends perpendicularly from the pivotal axis of one of the face passage dampers, and a by-pass passage damper crank arm is attached to and extends similarly from one of the by-pass passage dampers. At their projecting ends, the crank arms are pivotally connected to a damper control bar which induces concurrent arcuate movement of one responsive to arcuate movement of the other.

The crank arms are of unequal lengths, however, and are disposed in particular angular relationship with respect to each other within the vertical plane of their movement. In the preferred embodiment to be described, the ratio of the length of the face passage damper crank arm to the by-pass passage crank arm is 1.666; the fixed 4 angle of disposition of the face passage damper crank arm to the plane of the face passage damper to which it is attached is 15; and the fixed angle of disposition of the by-pass passage damper crank arm to the plane of the by-pass damper to which it is attached is 40. These relationships induce the referred to differential movement between the concurrently moving dampers in the respective damper sets. Moreover, and as will later be more fully understood, the intended relative movement of the face and by-pass dampers provides what is referred to as a quick opening by-pass at the time when the face passage dampers initiate their closing movement, such having been found to be of particular consequence towards achieving constant pressure drop through all of the passages throughout the range of damper operation.

In addition to the previously referred to advantages in an air supply unit, the invention also achieves elimination of end dampers and rod arrangements as were previously necessary in, for example, the Horn et al apparatus; affords minimum adjustment requirements both during manufacture and at the time of installation of the air supply unit; simplifies the damper control arrangement by elimination of so-called helper springs, brackets, cranks, and thru shafts in the linkage; and results in the requirement of smaller damper drive motors, and in some applications the use of only one damper motor instead of two as would otherwise be required.

An additional and important advantage of the damper system in, for example, an air heater unit is that it produces a more linear temperature modulation characteristic throughout the range of damper adjustment, such resulting in more accurate control of the temperature of discharged air.

These and other objects, features and advantages of the invention will become more readily apparent from the following detailed description thereof, when taken together with the accompanying drawings in which:

FIGURE 1 is a diagrammatic showing in sectional side elevation of an integral face and by-pass air heater unit having an adjustable flat damper system in accordance with the preferred embodiment of the invention;

FIGURE 2 is a similar diagrammatic showing, to an enlarged scale, of one pair of face and by-pass dampers in a damper system in accordance with the invention to illustrate its manner of operation;

FIGURE 3 is a graph showing the desired angular position relationships between the face dampers and bypass dampers of the damper system of the invention as compared with those of previously known fiat damper systems;

FIGURES 4, 5 and 6 are diagrammatic showings, to a reduced scale, of further embodiments of the invention;

FIGURE 7 is a graph illustrating two characteristics of an air heater unit embodying the invention as compared with the same characteristics of the air heater unit were it equipped with the previously known damper system; and

FIGURE 8 is a graph illustrating a third characteristic of an air heater unit embodying the invention as compared with the same characteristics of the air heater unit were it equipped with the same type of previously known damper system.

Referring to FIGURE 1, there is shown diagrammatically, in cross-sectional side elevation, an integral face and by-pass type air supply unit heater, generally designated by reference numeral 10. The unit heater 10 is usually mounted in upright position as shown, and is utilized as a means through which air flows, for example, from an atmospheric air source A into a room area R. In typical application an air supply fan (not shown) is situated on either the upstream side (area A) or the downstream side (area R) of the unit to induce the flow of air therethrough in well known manner.

The unit heater 10 includes a usually rectangular frame 11, which determines the air opening of the unit,

the frame having a plurality of fixed and parallel partitions 12 which are usually horizontally arranged as shown to provide alternate face passages 13 and by-pass passages 14 for dividing the flow of air as it passes through the unit. The face passages 13 contain conditioning elements 15 for conditioning any air which passes therethrough, and therefore the passages 13 may also be generally referred to as conditioning passages. In the embodiment being described, the elements 15 are air heating elements, such as finned type steam, hot air, or electric heating coils, which furnish heat at a constant rate determined by any pre-selected heat rating for the unit. The by-pass passages 14 are utilized to by-pass all or a portion of the total air supply around the heating elements 15 so that no adjustment of the heat rate to the elements 15 is required when the air supply is to be delivered to the area R at any of the possible variety of temperatures afforded by adjustment of the unit 10.

The respective air inlet areas of each of the air passages 13, 14 is determined in accordance with the requirement that, considering the volume and velocity of the air which the unit heater is intended to deliver which in turn is determinative of the number and general size of the passages 13, 14, the loss in air pressure or air pressure drop as occurs across the unit when the air flows only through all of the face passages 13 shall be substantially equal to the air pressure drop across the unit when the air flows only through all of the by-pass passages 14. As will be noted from the drawings, such requirement results in the height F of each of the face passages 13 at its inlet area being greater than the height B of each of the by-pass passages 14, the inlet areas of the face and by-pass passages being each rectangular in shape and of equal length, and the respective face passage inlet areas being equal to each other as are the respective by-pass passage areas. Such difference as between these respective inlet areas is due to the presence in the face passage areas 13 of the heating elements which restrict the flow of air therethrough to a determinable extent, as is well known. For the purposes of illustration, in the example shown by FIGURE 1, the total inlet area of the five face passage 13 is 922 square inches and the total of the four by-pass passage areas is 714 square inches, considering that the length dimension (not shown) of each of these areas is inches.

Air temperature adjustment of the air flowing through the unit heater 10 is made by adjusting the positioning of the damper system with which the unit is provided, and which is generally indicated by reference numeral 16. The damper system 16 is a pivotable damper system which includes two sets of dampers, concurrently operable, one set being a ganged arrangement of face dampers 17, and the other set being a similar arrangement of bypass dampers 18. Each of the dampers 17, 18 is a flat type damper having length and width equal to the rectangular shaped inlet area of the air passage, either face or by-pass, which it is intended to close. As indicated by the drawing, each of the face dampers 17 is mounted for arcnate pivotal movement about its central longitudinal axis 17a which corresponds with the midpoint of the height of the face passage 13 in which it is mounted, all of the face dampers 17 being ganged together by means of a face damper rod 19 to which each of the parallel extending and equal length face damper arms 20 are pivotally connected, as at the respective pivot points 21. Similarly, a bypass damper rod 22 connects the equal length by-pass damper arms 23 at their respective pivot points 24 for concurrent pivotal movement of the by-pass dampers 18 to which the respective arms 23 are attached, the dampers 18 being mounted in the same manner for pivotal movement on their respective axes 18a within the respective by-pass passages 14. As indicated by the drawing, the respective planes of the dampers in each set are parallel to each other at all damper positions within the ninety-degree (90) range of arcnate pivotal movement of the respective dampers in opening or closing the air passage with which it is associated. It will further be noted that the by-pass dampers 18 are arcuately offset with respect to the planes of the face dampers 17 such that, when the face passages 14 are fully closed, the by-pass passages 13 are fully open, and vice versa.

Concurrent but differential movement of both damper sets is eifectuated by pivotal connection, at respective pivot points 25, 26, of a face damper crank arm 28 and a bypass damper crank arm 29 to a damper control bar 30 as shown, the crank arms 28 and 29 each being attached to one of the dampers of the damper set with which it is associated so that the damper moves therewith. It should be here noted that the crank arms 28 and 29 are of unequal length, and are not parallel to each other. The damper system 16 is actuated by either motor or pneumatic or hydraulic means (not shown) via a damper drive link 31 which is pivotally connected to either the face damper rod 19 at one of its pivot points 21, as shown, or to the bypass damper rod 22, or to the damper control bar 30, or to any other arm element in the linkage system as may be appropriate.

As shown in FIGURE 1, when the face dampers 17 are in their fully closed position closing all of the inlet areas of the face passages 13, the bypass dampers 18 are in their fully opened position permitting maximum air flow through the by-pass passages 14. Further, and as indicated by the full line showing in FIGURE 2, the range of arcuate movement of either the face dampers 17 or the bypass dampers 18 is However, the unequal lengths and relative angular positioning with respect to each other of the crank arms 28 and 29 induce what is referred to herein as differential movement as between the dampers 17 and 18 when the damper system is actuated by, for example, pushing upwardly on the drive link 31 (see FIGURE 1). That is, assuming the link 31 to be pushed upwardly to effect a maximum swing of the face dampers 17 from their fully closed positions as shown in FIGURE 1 to their fully opened positions as indicated by the full lines in FIGURE 2, the by-pass dampers 18 will move arcuately at a. different and non-uniform rate, as compared with the rate of movement of the face dampers 17 from their fully opened positions as shown in FIGURE 1 toward their fully closed positions as indicated by full lines in FIGURE 2. For reasons as will be later more fully understood, in the preferred embodiment of the invention as is being described, it has been found that, to achieve the differential movement of the dampers which will provide substantially constant pressure drop across the unit 10 regardless of the setting of the damper system 16, the face damper crank arm 28 should be disposed at an angle x (FIG. 1) of 15 with respect to the plane of the face damper 17 to which it is attached; the by-pass damper crank arm 29 should be disposed at an angle y (FIGURE 1) of 40 with respect to the plane of the by-pass damper 18 to which it is attached; and the length of the face damper crank arm 28 should be 1 /3 times the length of the bypass damper crank arm 29. In the embodiment shown, the actual length of either of the crank arms 28, 29 is irrelevant so long as this ratio as between the respective lengths obtains. The differential movement as between the dampers 17 and 18 which is obtained by the linkage arrangement illustrated in FIGURE 1 actually is an efficient compromise of the theoretically ideal differential movement as can be achieved by either the cam actuation or the motor actuation embodiments of FIGURES 4 and 5, respectively. However, the linkage arrangement of FIG- URE 1 is preferred since it is less costly to manufacture and maintain.

The proper relative angular positioning and ratio of lengths as between the crank arms 28 and 29 will be understood from the following discussion and illustration of the general principles of the invention as compared with the operation of the fiat damper system which has been previously incorporated in such unit heaters.

Though not specifically illustrated, the typical fiat damper system as previously incorporated in unit heaters provided for concurrent and equal angular movement of the face and by-pass dampers between their fully opened and fully closed positions as respectively indicated by the full line showings in FIGURES 1 and 2. That is, the control rod 30 and crank arms 28, 29 were omitted, and all of the dampers 17, 18 were ganged together for movement whereby, at any damper position, the by-pass dampers 18 were always disposed in 90 offset relation with respect to the face damper 17. Thus, for example, when the face dampers 17 were pivoted to their 45 or half-opened positions, the by-pass dampers 18 were also pivoted to their 45 positions; when the face dampers 17 were 60 toward full open, the by-pass dampers 18 were pivoted 60 towards their closed position; and so forth. However, such concurrent movement of the damper causes the air pressure drop as measured across the unit heater to vary considerably depending upon the setting in this respect of the damper system. As plotted against degrees of opening of the face dampers, this change in air fiow resistance is shown by curve 1 of FIGURE 7. For comparative purposes as will be later more fully appreciated, the total open area of flow through the unit having such a conventional damper system is plotted against degrees of opening of the face dampers in curve 2 of FIGURE 7, the unit having a maximum total face passage area of 922 square inches and a maximum total by-pass passage area of 714 square inches. These total open areas, as well as the respective open areas of the face passages and by-pass passages for possible damper settings using such conventional fiat damper system are also tabulated in the following Table 1.

TABLE 1.CONVENTIONAL FLAT DAMPER SYSTEM OPE RATION Degrees Open area Degrees B.P.D Open area by-pass Total open F.D. open open face (in!) (in?) area (in!) In order to achieve substantially constant pressure drop across the unit at all damper system settings for proportioning all or a portion of the air flow through the face and by-pass passages, the position relationship of the face and by-pass dampers with respect to each other at any damper system setting must be such as will establish a total area of opening through the unit which presents the same total resistance to air fiow as occurs at any other setting. It has been found that this requirement results in the further requirement that the damper position relationship must establish a sudden, or quick-opening of the by-pass dampers as the face dampers achieve a limited degree of movement from their opened position towards their closed position.

Considering the referred to basic unit heater which has face passage maximum inlet areas totalling 922 square inches and by-pass passage maximum inlet areas totalling 714 square inches (which affords equal pressure drop across the unit heater when either the face passages or the by-pass passages are fully open), the necessary angular position of opening of the by-pass dampers 18 is computed for each assumed angle within the range of opening of the face dampers 17 such that the total area of opening through the unit heater is within the range of from 714 to 922 square inches. Using as a target the minimum total area of 714 square inches, these ideally required angles 8 of opening of the by-pass dampers 18 are tabulated in the following Table 2:

TABLE 2.IDEAL ANGULAR RELATIONSHIP BETWEEN FACE DAMPERS AND BY-PASS DAMPERS Face pas- Required Req'd. B.P. B.P.D.open

F.D. open sage area total area passage angle reqd. angle (in?) (in!) area (in?) (deg.)

These ideally required respective angles of opening of the by-pass dampers 18 for each angular setting of the face dampers 17 are plotted as curve .1 of FIGURE 3.

These required angular relationships between the face dampers 17 and the by-pass dampers 18 for all settings of the damper system can be precisely produced by either a cam actuated damper system as diagrammatically illustrated in FIGURE 4, or by a motor actuated damper system as diagrammatically shown in FIGURE 5.

Referring first to FIGURE 4 as illustrative of a possible cam actuated arrangement, the face damper arm 20 is slidably connected to a face damper cam follower arm 40, and the by-pass damper arm is slidably connected to a by-pass damper cam follower arm 41. The cam follower arms 40 and 41 are mounted for pivotal movement at the respective pivot points 42, 43, the movement being responsive to rotation of the respective face damper and by-pass damper actuator cams 44, 45 which are interlocked for concurrent and equal rotative movement as, for example, by the rod 46 lWhlCh is pivotally attached to each. Each follower arm 40, 41 is spring biased into engagement with its respective C3111). 44, 45, as by the respective springs 47, 48. The cam track 44a on which the follower arm 40 rides and the linkages 40, 20 are such that of rotation of the cam 44 pivots the face damper 17 between its fully opened and its fully closed position within the face passage (not shown) within which it is situated. The cam 44 is rotated by means not shown. The by-pass damper cam track 45a is configured such that the by-pass damper 18 is concurrently pivoted the number of degrees shown in either Table 2 or on curve 1 of FIGURE 3 as corresponds with the position of the face damper 17, the by-pass damper movement being responsive to the movement of the follower arm 41 which engages the cam track 45a.

Referring to FIGURE 5, it will be understood that the same results may be achieved by the use of separate damper actuator motors 49, 50 which are sequenced, as by a known type of sequencing means S, to produce the desired relative positioning of the face dampers 17 and the bypass dampers 18. The motors 49, 50 may be either electric or pneumatic or hydraulic in nature, and their respective outputs may be connected to the damper arms 20, 23 in any convenient manner, such as by rack and pinion means, etc. (not illustrated.) If electric motors, one would drive the face dampers 17 and also a potentiometer arrangement serving as the sequencing device S which would produce positioning signals for driving the by-pass damper motor. If pneumatic or hydraulic, the motor sequencing unit S might be a needle valve type or other similar regulating device which IWOlJld drive the by-pass damper motor in the desired manner responsive to movement of the face damper motor.

However, as previously noted it is more desirable to utilize the linkage arrangement shown in FIGURE 1 for moving the dampers 17 and 18 in the desired manner. In view of the known limitations of directly connected linkage systems, a close approximation of the ideal damper positioning relationship is achieved without undue complexity in the four-bar linkage system of the preferred embodiment by disposing the face damper crank arm 28 at an angle of 15 within the plane of movement with respect to the face damper 17 to which it is attached, by disposing the by-pass damper rcrank arm 29 at an angle of 40 within the plane of movement with respect to the by-pass damper 18 to which it is attached, and by making the length of the face damper crank arm 28 equal to 1 /3 times the length of the bypass damper crank arm 29, as shown in FIGURE 1. In the basic unit heater which has been used as illustrative, the air flow areas through the unit as are produced by the linkage system of FIGURE 1 are tabulated inthe following Table 3:

TABLE 3.FLOW AREAS PRODUCED BY LINKAGE SYSTEM OF FIGURE 1 Degrees Face pas- By-pass Degrees F.D. 13.1. sage open passage open Open area open open area (in!) area (in!) total (in?) As a convenience in determining SUlCl'l modification of the ideal curve 1 of FIGURE 3, the respective open areas of the face passages and the by-pass passages as shown in Table 2 may be plotted against the respective angles of opening of the dampers, such graph not being illustrated herein. For comparison with the ideal curve 1, the angles of by-pass damper opening for respective angles of opening of the face dampers are plotted as curve 2 on FIG- URE 3, and it will be noted that curve 2 follows curve 1 as nearly as possible, as compared with the straight line relationship of curve 3 of the same figure, the latter representing the relative damper positioning in the conventional damper system. Similarly, the total open passage area of the unit for all settings of the damper system is plotted as curve 3 of FIGURE 7 for comparison with curve 2 of that figure, and it will be noted that the flow areas through the unit are more uniform for all such settings as compared with the conventional damper system.

The operation of the damper system 16 is illustrated in FIGURE 2. The full lines show the face damper 17 in full open position while the by-pass damper 18 is fully closed. Referring to Table 3, upon movement of the face damper 17 an arcuate distance of towards its closed position so that its open angle a is 85, the by-pass damper 18 moves to an open angle b equal to and when the face damper 17 is moved to its open angle a of 60, the by-pass damper 17 moves to its open angle [7 equal to 50; these being representative relative positions for the purpose of illustration.

The direct connected linkage damper system 16 of the preferred embodiment causes the pressure drop across the unit heater 10 to be more uniform for all damper settings in the manner shown by curve 4 of FIGURE 7. This substantially constant pressure drop may be compared with curve 1 of that figure which, as previously noted, shows a substantial variation in the pressure drop as is produced using the conventional fiat damper system.

In addition, the air temperature rise through the unit having the damper system 16 is more uniform throughout the range of face damper opening as compared with the same unit having the conventional flat damper movement. This is graphically illustrated by FIGURE 8 wherein curve 1 represents the temperature rise produced by operation of the conventional system as expressed as a percent of maximum rise, and the more linear curve 2 is that for the linkage system of the present invention.

It will be further noted that the damper system afforded by the invention may be used in face and by-pass systerns which are not integral, such as in the face ano bypass system of FIGURE 6 wherein the by-pass passages 61 of the system are externally located with respect to the face passages 62. That is, so long as the by-pass dampers have differential movement relative to that of the face passage dampers such that the total flow area across the system presents substantially constant air flow resistance throughout the range of such movement, the results of the invention are achieved, and can be achieved by control of the damper movement either by the linkage arrangement, or the cam actuator arrangement, or any of the motor actuated arrangements as have been described.

What is claimed is:

1. A gas supply unit comprising a face passage presenting a gas inlet area, a by-pass passage presenting a gas inlet area, and a damper system for proportioning the fiow of gas between the respective of said face and by-pass passage inlet areas, said face passage having gas conditioning means therein presenting resistance to the flow of gas therethrough and said face passage inlet area being larger than said by-pass passage inlet area by an amount such that the pressure drop in a given flow of gas through said face passage when its said inlet area is fully open is substantially equal to that of the same flow of gas through said by-pass passage when its said inlet area is fully open, and said damper system comprising a face damper mounted for movement between open and closed positions respectively fully opening and fully closing said face passage inlet area, a by-pass damper mounted for movement between open and closed positions respectively fully opening and fully closing said by-pass passage inlet area, said by-pass damper being in its said closed position when said face damper is in its said open position and, further, being in its said open position when said face damper is in its said closed position, and damper positioning and differential movement means connected to said 'face and by-pass dampers and adapted to move one of said dampers at one rate to respective positions between its said open and closed positions and to move the other of said dampers at a varying rate to respective positions thereof between its said open and closed positions correlated to said respective positions of said one damper whereby, when said one damper is in any said position, the position of said other damper is such that the total area of opening of said face and by-pass inlet area is substantially within the range of from an amount equal to said by-pass passage inlet area to an amount equal to said face passage inlet area.

2. A gas supply unit according to claim 1, wherein said face and by-pass dampers are each mounted for arcuate pivotal movement.

3. A gas supply unit according to claim 2, wherein said face and by-pass dampers are each of the substantially fiat type.

4. A gas supply unit according to claim 3, wherein said face and by-pass dampers are each mounted for said arcuate pivotal movement about a central axis thereof, said axis being disposed centrally of said inlet area of the passage with which the damper is associated.

5. A gas supply unit according to claim 1, wherein said face and by-pass dampers are each mounted for arcuate pivotal movement about an axis thereof, and said damper positioning and movement means comprises a first crank arm of given length extending from said bypass damper, a second crank arm extending from said face damper, said second crank arm having length which is greater than said given length of the first crank arm, and means connecting said crank arms to provide concurrent movement thereof.

6. A gas supply unit according to claim 5, wherein said length of the scecond crank arm is substantially equal to one and two-thirds (1 /3) times said given length of said first crank arm.

7. A gas supply unit according to claim 5, wherein said first crank arm is rigidly attached to said by-pass damper and extends perpendicularly with respect to said axis of the latter, and said second crank arm is rigidly attached to said face damper and extends perpendicularly with respect to said axis of the latter, said first and second crank arms having angular disposition with respect to a corresponding reference on the respective dampers to which they are attached, said angular disposition of the first crank arm with respect to said by-pass damper being different from said angular disposition of the second crank arm with respect to said face damper.

8. A gas supply unit according to claim 7, wherein said face and by-pass dampers are each of the substantially flat type, said first crank arm being disposed at an angle of substantially forty degrees (40) with respect to the plane of said by-pass damper, and said second crank arm being disposed at an angle of substantially fifteen degrees (15) with respect to the plane of said face damper.

9. A gas supply unit comprising a plurality of alternately adjacent face passages and by-pass passages, and a. damper system for proportioning the flow of gas between said face and by-pass passages, said face and by-pass passages having substantially equal length, and the respective of said face passages having means therein presenting resistance to the flow of gas therethrough which is substantially equal to the resistance presented in each other face passage, the respective of said face passages having substantially equal inlet areas determined by said length and respectively equal height, and the respective of said by-pass passages having substantially equal inlet areas determined by said length and respectively equal height, said height of each face passage inlet area being larger than said height of each by-passage inlet area by an amount such that the pressure drop in a given fiow of gas through all of said face passages when their said inlet areas are fully open is substantially equal to that of the same flow of gas through all of said by-pass passages when their said inlet areas are fully open, and said damper system comprising a face damper set and a by-pass damper set, said face damper set comprising a substantially flat type damper mounted for arcuate pivotal movement substantially adjacent said inlet area of each said face passage, and said by-pass damper set comprising substantially flat type damper mounted for arcuate pivotal movement substantially adjacent said inlet area of each said by-pass passage, each said damper set further including a damper rod pivotally connected to all of said dampers within the set for concurrent pivotal movement in parallel relation with respect to each other over a range of 90 between respective open and closed positions of the dampers with respect to the said passage inlets with which they are associated, and linkage means connecting said damper sets to provide substantially concurrent movement of one of said damper sets at a varying rate with respect to a given rate of movement of the other damper set whereby the dampers in either damper set are in their closed positions when the dampers of the other damper set are in their said open positions and whereby at any intermediate position of either damper set the position of the other is such that the total area of opening of all of said face and by-pass inlet areas is substantially within the range of from an amount equal to the total of said by-pass inlet areas to an amount equal to the total of said face passage inlet areas, said linkage means connecting said damper sets comprising a first crank arm of given length firmly attached at one of its ends to one of said dampers of the by-pass damper set and extending perpendicularly with respect to the axis of said pivotal movement of said damper to which it is attached and, further, being disposed at an angle with respect to the plane of said damper to which it is attached, a second crank arm firmly attached at one of its ends to one of said dampers in the face damper set and extending perpendicularly from the axis of said pivotal movement of said damper to which it is attached and, further, being disposed at an angle with respect to the plane of said damper to which it is attached, said second crank arm having length which is greater than said given length of the first crank arm, and said respective angles of disposition of said first and second crank arms being diffierent from each other, and a single rod pivotally connected to and between each of the respective opposite ends of said first and second crank arms to provide concurrent movement thereof.

10. A gas supply unit according to claim 9, wherein said length of the second crank arm is substantially equal to one and two-thirds (1%) times said given length of said crank arm, said angle of disposition of said first crank arm being substantially forty degrees (40), and said angle of disposition of said second crank arm being substantially fifteen degrees (15 References Cited UNITED STATES PATENTS 2,521,866 9/1950 Ott -103 X 2,884,228 4/1959 Jorgensen 165-103 X 2,891,576 6/1959 Kennedy 137-601 X 2,976,884 3/1961 Kurth et al 137601 X 3,027,918 4/ 1962 Robra 137-601 X 3,107,724 10/1963 Horn et al. 165-103 X 3,331,394 7/1967 Hefier et a1 137--601 X 3,346,013 10/1967 Reichow 137-628 FOREIGN PATENTS 714,990 9/1931 France.

ALAN COHAN, Primary Examiner.

DENNIS H. LAMBERT, Assistant Examiner.

US. Cl. X.R. 98-41; 165l03

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