US2184701A - Damper regulator - Google Patents

Description

J. P. KRIECHBAUM ET AL 2,184,701

DAMPER REGULATOR Filed Jan. 2, 1956 I a w w Patented Dec. 26, 1939 PATENT OFFICE omen REGULATOR John P. Kriechbaum and Carl G. Kronmiller,

Minneapolis, Minn., assignors to Minneapolis- Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application January 2, 1936, Serial No. 57,221

2 Claims.

Our invention relates to a new and novel damper regulator, and more particularly to one in which means are provided for moving the dampers to afiring position when desired.

In systems for the automatic control of furnaces it is common to employ a damper motor for actuating the dampers, which damper motor is under the control of some condition responsive device, such as a room thermostat. In such systems the dampers are usually moved from a position wherein the check damper is open and the draft damper is closed to a position I in which the opposite condition exists, depending upon whether the temperature or other control-- ling condition is above or below the desired value. In firing a furnace, it is necessary that the check damper be closed to prevent the escape of smoke from the firing door during the firing operation.

In certain types of furnacesit is, furthermore, necessary that both the check door and the draft door be closed during this firing operation. It, accordingly, is common to provide means in the basement for moving the dampers to a position in which either the check damper alone or both dampers are closed. Such, means commonly takes the form of a basement switch which causes the motor to run until the dampers are in the desired position. The objection to this arrangement is that the furnace attendant will quite likely forget to 'move the basement switch back to the position under which the furnace is under the control of the room thermostat. Various complicated arrangements have; accordingly, beenprovided for returning the damper motor 35 to the control of the room thermostat a predetermined period of time after the switch has been moved to firing position. These arrangements not only greatly add-to the expense of the damper motor but rely upon timingmeans which tend to get out.of order I Another class of damper motors is provided with means for declutching the damper actuating arm from the motor so as to permit the dampers being manually moved to any desired firing position. In this class of motors, provision has been made for automatically returning the motor 1 to the control of the condition responsive'device by causing the act of declutching to energize the motor and run the same to a, position wherein the damper actuating device was automaticably reclutched with the motor and was returned to automatic control. One difficulty with this type of device is that it involves more effort upon the" part of the operator. 'A further and even more serious objection is that the presence of the furnaceand a room thermostat.

' such movement has been initiated.

A further object of the present invention is to provide a damper motor having a manual 10 switching means for causing the motor to rotate the dampers through a desired firing position and to continue such rotation until the dampers have reached a position determinedtby the value of the controlling condition. e

Other objects of the invention will be apparent from the accompanying description, claims and drawing.

The single figure of the drawing schematically shows our damper motor associated with a 20 Referring to said drawing, a conventional furnace is indicated by the reference numeral II. This furnace is shown as being of the hot air type, although it is to be understood that it may be of any conventional form. The furnace is shown as hav ing the usual hot 'air pipes l2, a stack pipe iii, a fuel door H,. a draft door l5 and a check damper IS.

The damper motor comprises a motor I! having a rotor l8 and a field winding IS. The motor is connected through reduction gearing 20 with a shaft 2|. The shaft 2| is provided at its opposite ends with crank arms 22 and 23. Crank arm 22 is connected through a chain or'equivalent de- 5 vice 24 with the draft damper l5, and crank arm 23 is similarly connected through a chain 25 with the check damper l6. It will be noted that the chain 24 is provided with a certain amount of slack when the crank 22 is in its downward switch arms 30 and 3|, respectively. Switch arm 30 is adapted to move-into engagement with a contact 32 and switch arm 3| is adapted to be moved into engagement with either contact 33 or a contact 34. Switch arms 30 and 3t and their respective contacts constitute what may be termed a maintaining switch, the function of which will be apparent from the following de- Gr1pt1on, The cam '21 is provided with two cam toes and 36 spaced at points 180 apart, so that switch 36 is separated from contact 32 every 180 of rotationof shaft 2|. Cam 28 is provided with an elongated cam toe 31 which is adapted to hold switch arm 3| in engagement with contact 34 during a considerable period of rotation of shaft 2|. The toe 31 of cam 28 is so located that switch arm 3| is moved to the position wherein it is in engagement with contact 34 before the cam toe 35 is operative to move contact 36 out of engagement with contact 32.

Power for actuating the motor is supplied by a step-down transformer 38 having a line voltage primary 39 and a low voltage secondary 46. The primary 36 is connected to line wires 4| and 42.

The thermostat which controls the operation of the damper motor is designated generally by the reference numeral 43. This thermostat is of a conventional form and comprises a bimetallic element 44 to which is attached contact arm 45. Contact arm 45 is adapted to be engaged with either contact 46 or contact 41. The bimetallic element is so designed that upon the temperature dropping below the value desired the contact arm .45 will be moved into engagement with contact 46, while upon the temperature rising to the desired value the contact arm will be moved into engagement with contact 41. Thus, contact 46 may be referred to as the "cold contact and contact 41 as the hot contact. While we have shown a room thermostat as a controlling condition responsive switch, it will be understood that any other suitable form of controlling condition responsive switch may be employed. Thus a device which is responsive to the water temperature in the case of a hot water heating system, or to the steam pressure in the case of a steam heating system, may be employed.

A basement switch is generally designated by the reference numeral 48. This switch is shown as comprising a stationary contact 49 and a movable switch blade 56. The switch blade 56 is mounted on a rotatable member 5| which may be provided with a knob 52 for conveniently rotatin member 5| manually to bring the switch arm 56 into en agement with contact 46, as shown in dotted lines in the drawing.

As shown in the drawing, our damper con trnller and the various members associated therewith are in the position assumed when the temperature in the room is at the desired value. In this position, the draft damper I5 is closed and the check damper I6 is open so that the dampers are'acting to retard a draft in the furnace. With the dampers in this position, a condition will eventually be reached wherein the temperature adiacent the thermostat 43 falls below the desired value. Upon this taking place, contact arm 5 will be moved into enga ement with contact 48. This will cause the following circuit to be established through the field winding IQ of the motor l1: From one end of secondary 46, throu h conductor 53. bimetallic element 44. contact arm 45. contact 46, conductor 54. contact 34, switch arm 3|, conductors 55. 56 and 51. field winding l9 and conductor 56 to the other terminal of secondary 46. This will cause motor IT to rotate with the result that shaft 2| is rotated in the direction of the arrow 66. After a very slight initial rotation of the shaft 2| fswitch arm 36 will be allowed to move into engagement with contact 32. Upon this taking place, the following maintaining circuit for field winding I9 is established-: .From one end of secondary 46, through conductor 59, conductor 60, cont c 32,

switch arm 36, conductor 51, field winding l9 and conductor 58 back to the other terminal of secondary 46. It will be noted that the maintaining circuit just traced does not depend upon the engagement of contact arm 45 with contact 46 so that even if contact arm 45 should be separated from contact 46 after the motor has started its rotation, such rotation will continue. This rotation of motor l1 and the resultant rotation of shaft 2| will continue until switch arm 36 is moved out of engagement with contact 32 by the cam toe 36. By the time this takes place, the cam 28 will be in a position such that switch arm 3| is resting upon the heel of the cam 28 so that it isno longer in engagement with contact 34, being now in engagement with contact 33. Thus, both the initial engergizing circuit and the maintaining circuit are interrupted so that rotation of shaft 2| and the resultant movement of the dampers is stopped unless in the meantime, contact blade 45 has moved into engagement with contact 41. In this new position of shaft 2| crank arm 22 is in its uppermost position and crank arm 23 is in its lowermost position so that draft damper His new open and check damper i6 closed.

The new position of the dampers causes combustion to be accelerated so as to increase the temperature of the space to be heated. This will continue until the temperature of said space has risen sufliciently that contact 45 is moved into engagement with contact 41. Upon this taking place, the following energizing circuit for field winding l9 will be established: From one end of secondary 46, through conductor 53, bimetallic element 44, contact arm 45, contact 41, conductor 62, contact 33, switch arm 3|, conductors 55, 56 and 51, field winding l9 and conductor 58 to the other terminal of secondary 46. The establishment of this circuit through field winding I9 will cause rotation of 'the motor i1 and the resultant rotation of shaft 2| with the result that cam 21 will be moved so as to allow switch arm 36 to again move into engagement with contact 32 after a very slight initial rotation of the shaft. This re-engagement of the switch arm 36 with contact 32 will result in the reestablishment of the previously traced maintaining circuit so that, as in the previous case, the motor will continue to rotate even though the arm 45 should move away from the contact 41. As in the preceding case,.this rotation will continue for 180 until switch arm 36 is again moved out of engagement with contact 32, the parts then being in the position shown in the drawing. Before this separation of switch arm 36 from contact 32 takes place, switch arm 3| has been moved out of engagement with contact 33 and into engagement with contact 34 by coming into engagementwith the toe 31 of cam 28.

The operation of the basement switch of our regulator will now be described. Assuming that the parts are in the position shown in the drawing, and it is desired to fire the furnace, the knob 52 is rotated so as to cause member 5| to be ro- 4 tated until switch arm 56 is in engagement with contact 48 asshown in dotted lines in the drawing. Upon this engagement taking place, the following energizing circuit will be established through field winding i9: From one end of secondary 46, through conductors 59 and 64, contact 49, switch arm 56, member 5|, conductors 65, 56 and 51, field winding i9 and conductor 58 to the other terminal of secondary 46. This will cause rotation of motor i1 and. the resultant rotation of the shaft 2| so that, as in the previously described cases, where the energizing circuit is established by reason of the engagement.

be limited to any particular speed of rotation,

it has been found satisfactory to provide a reducing gear such that it requires two minutes for the shaft to rotate through 180". The actuation of the basement switch will, accordingly, cause the shaft 2| to be slowlyrotated with the result that damper i6 is slowly moved to a closed position and the slack in chain 24 is slowly taken up. After a comparatively short period of time, during which the operator can be-preparing to fire, dampers l5 and I6 will both be closed. The operator may now proceed to fire the furnace without any danger of smoke issuing from the fire door I4. Due to the relatively slow speed of rotation of shaft 2| ample time is provided for firing the furnace before damper |5 has opened appreciably. Moreover, in the case of the majority of furnaces, no trouble is encountered with smoke issuing from the fire door even if the draft damper I6 is opened so long as the check damper is closed. Thus, assuming a two minute cycle,

such as mentioned above, the operator has two minutes in which to complete his firing operation between the time that check damper I6 is first movedto a closed position until the time that it is again moved towards an open position.

As mentioned previously, shaft 2| is provided with a cam 29. This cam is provided with two cam toes 66 and 61 which'are adapted to engage cam toe 68 of member 5|. Thus. rotation of the shaft 2| will cause one or the other of the cam toes to move ,into engagement with a shoulder 68 on member 5| if the member is in the position indicated in dotted lines in the drawing, in which the basement switch 48 is closed. The engagement of these cam toes' will cause rotation of member 5| about its axis and a resultant separation of switch arm 50 from contact 49. While we have shown the cam toes 66 and 61 as displaced from cam toes 35 and-3B of cam 21, it is to be understood that cam toes 6G and 61 may be located at any desired point so long as they are sufficiently displaced from the cam toes 35 and 36 to permit the switch arm 30 to move into engagement with contact 32 to establish the maintaining circuit before switch arm 50 is separated from contact 49.

The result of cam 29 moving switch arm 50 out of en agement with contact 49 is that the motor. is returned to the control of the thermostat 43'. Thus, if the parts were initially in what unusual one and that ordinarily the con-' tact arm is in engagement with either contact 46 or 41. Thus, ordinarily when the dampers are in the position indicated in the drawing switch arm 45 would be in engagement with the "hot contact 41. Accordingly, after the shaft has rotated and switch arm 30 was separated from contact 32 by engagement with the cam toe 35, the energization of the motor would be continued by reason of an energizing circuit being established through contact 33 and switch arm 3| so that the motor would continue to rotate until the dampers are again in the position shown in the drawing. Thus, the shaft 2| would be rotated through 360 during 180 of which, as explained previously, the dampers are in a position suitable. for firing. I It will be seen that we have provided an exvision is made for moving the dampers to a firing position and returning the damper motor to automatic control without the use of complicated declutching arrangements or timing mechanisms. It will be seen that we have provided a damper motor wherein the basement switch removes the motor from control of the thermostat for only a short period and returns the same automatically to control of the thermostat during the movement of the damper actuating device to the desired position. i

While we have shown a specific embodiment of our invention, it will be understood that this is for purposes of illustration and that our invention is to be limited only by the scope of the appended claims.

-We claim as our inventioni 1. In combination, a furnace, dampers therefor movable between draft retarding and draft producing positions, a damper actuating device, a motor, non-releasable connections between said motor and said damper actuating device to cause movement of the latter by the former, means responsive to a condition for initiating movement of said motor upon said condition assuming an undesired value, means for maintaining said motor in operation until the dampers have assumed either said draft retarding or draft pro} ducing position depending upon the value of said condition, further motor controlling means norprior to actuation of said further controlling means, said connections between said motor and said damper actuating device'including means to cause said motor to drive said dampers suflicient- 1y slowly that ample time is provided for firing while said dampers are passing through said firing range.

2. In combination, a furnace, dampers therefor movable between draft retarding and draft producing positions, a motor, connections between said motor and said dampers effective upon continuous movement of said motor in one direction to causelsaid dampers to be moved successively back and forth slowly between said draft retarding and draft producing positions, means responsive to a condition for initiating. movement of said motor upon said condition assuming: an

tremely simple damper regulator in which prov able to a second position wherein it is operativeto initiate movement of said motor independently of said condition responsive means, and means driven by said motor for moving said further controlling means back to said first position after said motor is under control of said maintaining means whereby said motor slowly operates both of said dampers through a firing range and, if the condition responsive device remains in the same controlling position, back to the position occupied prior to actuation of said further controlling means, the speed of movement of said dampers by said motor being sufliciently slow that ample time is provided for firing whi 1e said dampers are passing through said firingrange. JOHN P. JQQIECHBAUM. CARL G. KRONMIILER.

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