US2363748A - Condition control apparatus - Google Patents

Description

Nov. 28, 1944. J. E. RoBB 2,363,748

CONDITION CONTROL` APPARATUS FIedAug. 8, 1942 BY Joss/ll #0515,

Patented Nov. 28, 1944 zsa'us coNnmoN coN'raoL APPARATUS Joseph E. Robb, Lawrence, Kans., asslgnoi' to Minneapolis-Honeywell Regulator Company, y Minneapolis, Minn., a corporation of DelawareA Application August 8, 1942, Serial No. 454,149

13 Claims. (Ci. 236-9) This invention relates to the condition control art lbut more particularly to improvements in condition control apparatus specially applicable to great advantage in temperature control systems-of the type employingdamper regulated furnaces.

It is usually customary in such systems to'provide a motor operator for driving the dampers between draft-increasing and draft-retarding positions, and to also provide automatic means responsive to a condition or conditions indicative of a need ;for regulation of the furnace to "initiate operation of the motor operator. It is usually desirable in the use of such furnaces to further provide a manually operable basement switch in control of the motor operator for moving the dampers to a tlring" position during the stoking or ilring of the furnace. Since the most ideal firing position of the dampers is generally considered to be the draft-increasing posi- .tion thereof, and since attendants frequently inadvertently leave the basement switch in this position, the furnace is in a'condition to develop dangerously high temperatures.

Accordingly, various prior art means have been devised-first, to move the dampers to their draft-retarding position independently of the basement switch position, and second, to return v the basement switch to its initial position. Some of these prior art devices have comprised auxilary time switches operable after a time period to return the b asement switch to its initial position. Others have provided time delay arrangements inherent in Athe apparatus employed Vto attain the above first and second objectives. Others have provided declutching arrangements of the motor operator whereby the dampers are released and may be manually moved to the iring posttion, such movement initiating a follow-up motor action. Still other means have combined the basement switch with apparatus a firing position when the switch is manually moved into a position in which a standard furnace thermostat controls subsequent motor action, and the subsequent motor action is utilized to return the switch to its initial position under power of the motor operator. In accordance with the invention the motor operator and switch are combined in a imitar! structure, and simple and inexpensive driving connections are provided between them for producing the function described above. With this arrangement, the motor operator may be used in control systems not employing the furnace thermostat without materially increasing the cost of the motor operators above that of operators not equipped with the switch return feature.

Accordingly, a broad-obiect'of the present in vention is to generally provide improvements in the construction and arrangement of apparatus employed in temperature control systems of the type described, promoting increased economy of construction and emciency in operation. A

Another object of the invention is to provide an improved motor operator for use with a damper regulated furnace comprising an electric motor and a manually operable switch movable into a position to initiate a motor action moving a damper into a firing position, the switch being operable when in such position 'to place subsequent motoraction under control of a standard furnace thermostat, and a motor operator comprising driving connections between the motor and the switch whereby motor vaction initiated by the furnace thermostat returns the manual switch to its initial position.

A further object of this invention is the provision of a motor operator having an electric motor, and a shaft driven thereby through a sequence of one-half revolution movements, having also a manual switch for initiating motor action to drive the shaft through one of the movements, and further having driving connections between the shaft and switch whereby subsequent movement of the shaft returns the switch to its initial position.

A still further object of this invention is to provide, in a motor operator having an electric motor, a manual switch for initiating motor operation and simple; reliable, and inexpensive driving connections between the motor and switch whereby the switch is returned to its initial position under power of the motor upon subsequent motor action.

Other objects and advantages of the invention Ain turn is provided with a terminal 43.

schematically discloses the improved motor oper- I ator as used in a temperature control system employing a damper regulated furnace.

Referring to the drawing, the numeral I generally designates a conventional furnace of the hot air type having a bonnet II and the usual draft and check dampers I2 and I3, respectively. The draft damper I2 is associated with the combustion chamber of the furnace in the usual manner, and the check damper I3 is mounted on the stack I4 which communicates with the combustion chamber, also in the usual manner. Leading from the bonnet`I l is a duct I5 through which heat generated in the bonnet is transferred to a space I8. A return duct. I1 is provided through which the cold air in the space is returned to` the bonnet.

A motor operator generally designated by the numeral I8 is provided for driving the dampers I2 and I3 between draft-increasing and draft-retarding positions. The motor operator I8 comprises a motor which may be of the unidirectional inductive motor type having a squirrel cage rotor I8 and a single winding 20 for actuating the rotor. The rotor I8 drives an operator shaft 2I through a reduction gear train 22, thedirection of rotation being indicated by the arrows' 23. The operator shaft 2l carries a pair of diametrieally opposed operator arms 24 and 25 which are connected to the dampers I2 and I3 by suitable chain and pulley connections 25 and 21, respectively. Thus, when the arms 24 and 25 are in the position shown, the dampers are in their full line positions which provides a draft-retarding condition of the furnace III. When the arms 24 and 25 are in their dotted line positions, the dempers I2 and I3 are in their dotted line positions which provides a draft-increasing condition of the furnace I0.

In order to limit the movement of the shaft 2i to 185 movement to thereby providemovement of the dampers between the draft-increasing and draft-retarding positions, a pair of limit switches 28 and 29 are provided which are actuatable by the shaft 2 I. The switch 28 comprises a fixed contact 30 engageable by a movable contact 3i carried by a blade 32. The blade 32 is provided with a follower 33 which rides upon the peripherial surface of a cylindrical cam 34 secured to the shaft 2|. The cam 34 is provided with an indentation 35 which when aligned withV the follower 32 receives the same to open the switch 28. in like manner, the switch 29 cornprises a fixed contact 36 engageable with a movable contact 31 which is carried by a blade 38. The blade 38l carries a follower 39' which rides upon a-cylindricai cam 40 secured to the shaft 2I. The cam 4II has an indentation 4I which receives the follower 39 when aligned therewith to open the switch 29. Since the indentations 35 and 4I are diametrically opposed, it will readily be seen that but one of the switches 28 and 29 will be opened at any one time. Also, since the indentations are small compared to the peripheral surface of the cams 34 and 48, slight movement of the shaft 2l provides a closed condition of the switches for the greater part of one-half a revolution. Thus, by this arrangement, as will` hereinafter appear, the switches 28 and 28 provide a means for maintaining the energization of the motor winding 20 once the energization has been initiated. The fixed contacts 30 and 36 are connected by a suitable conductor 42 whlih e switch blades 32 and 38 are similarly provided with terminals 44 and 45, respectively.

Means hereinafter to be described are provided for short-circuiting the terminals 43, 45 when the switch 29 is open to complete a circuit through the switch 28 for energizing the 4winding 20 to drive the dampers to their draft-increasing position. The means is also arranged to short-circuit the terminals 43, 44 when the switch 28 is open to establish a circuit for energizing the winding 20 through the switch 29 to drive the dempers to their draft-retarding position.`

The motor operator I8 further comprises a manual switch 46 which is manually movable into three positions indicated by the legends open automatic and closed The switch 46 comprises a switch arm 41'which is engageable with a. fixed contact 48 when in the automatic position, is engageable ywith a fixed contact 49 when in the open position, and is engageable with a fixed contact 5I) when in the Qclosed position. As will hereinafter-appear, when the switch arm 41 is in engagement with the contact 48 a thermostat 5I located in the space I8 is provided for shortcircuiting the terminals 43, 45 upon a decrease in temperature below a desired value and for shortcircuiting the terminals 43, 44 upon an increase in the space temperature above the desired value to initiateenergization of the winding 20. When the switch` arm 41 is moved into engagement with the contact 43, the terminals 43 and 45 are short-circuited to complete a circuit to the winding 20 to move the dampers to a draft-increasing position, and when the switch arm 41 is moved` into engagement with the contact 50 the terminals 43 and 44v are short-circuited to complete a circuit to the winding 20 to move the dampers to a draft-retarding position. Also, as'will hereinafter appear, when the switch arm 41 is placed in the open position, further motor operation is placed in control of a furnace thermostat gener ally designated by the numeral 52. When the furnace temperature rises to a dangerously high value, the thermostat 52 short-circuits the terminals 43, 44 to drive the dampers to their draftretarding position.

I'he switch 'arm 41 is pivotally mounted at 53, the pivotal axis 54 extending generally parallel to the axis of the shaft 2I. The arm 41 is providedl with an extension 55 which extends from the switch arm 41 in such a manner that when the arm 41 is in the automatic position the extension 55 just clears the path of movement 55 of an arm 51 secured to the shaft 2| for rotation therewith. As previously stated, when the switch arm 41 is moved to the open position the shaft 2l rotates 180. Such movement of switch arm 41 brings its extension 55 to the dotted line position. The movement ofthe dempers brings them into draft-increasing position. With this motor movement, the arm 51 moves to its dotted line position. Further slight movement of arm 51 will cause it to engage extension 55. Accordingly, as the arm 58 moves from its dotted line to full line position, it drives the switch arm 41 back to its full line position, thus providing a return of the manual switch 45 to its automatic position under power of the motor for a purpose hereinafter to appear.

The thermostat 5I is of the three wire type comprising a bimetallic element 58 to which is secured an actuating blade 53. The blade 58 carmotor winding 20, conductor 14, a conductor 15 xcontacts Si, 60, blade 59, element 58, conductor 'ries a movablel contact 60 which is engageable with spaced fixed contacts 8| and 82. -Upon a decrease in temperature from a desired value, the blade 59 moves in the direction of the legend C for causing an engagement of the contacts 60 and 6|. Upon a rise in temperature above the desired value, the blade moves in the direction of the legend H to cause engagement of the con- 'tacts S0 and 62. l

The furnace thermostat 52 comprises a helical bimetallic element B3 which is inserted in the bonnet il. On a rise in furnace temperature the element 63 actuates a rod 64 which in turn rocks a mercury switch in a counter-clockwise direction. The mercury switch comprises a glass envelope 85 provided with two pairs of electrodes 66, 61 and B8, 69 engageable by a globule of mercury 10 carried in the envelope 65. The electrodes 61 and 68 are connected together to provide a common terminal as shown in the drawing.

The motor winding 20 is energized by a stepdown transformer comprising a primary winding 1| connected to a suitable A. C. source of power and a secondary winding 12.

In operation, with the parts in the positions as shown, the thermostat 5| is satised and the heat supplied by the furnace is just sufficient to oifset the loss from the space I6. Upon a drop in temperature from the desired value, the contact 60 engages the contact 6| to provide a circuit for energizing the motor winding 2B. This circuit may be traced as follows: from the top side of the secondary 12 through a conductor 13,

16, contact 48switch arm 41, a conductor 11, electrode `65, mercury 10, electrode 61, a conductor 18, conductor 42, contacts 30, 3|, switch blade 32, and av conductor 1S back to secondary 12.

Upon energizationof winding 20, the shaft 2iv rotates sufficiently in the direction of arrow 23 tormove the follower 39 out of engagement with the indentation di, thereby closing the switch 29 to establisha maintaining circuit for the Winding 2G. This circuit may be traced as follows: from the top side of the secondary 12 through the conductor 13, winding 2b, conductor 14, switch arm 38, contacts 31, 36, conductor 42, contacts Sii and 3|,Y switch blade 32, and conductor l@ back t'o secondary 12. The shaft 2| then continues to rotate until the switch 28 is opened, at which time the dampers have been driven to their draft-increasingposition. The furnace l0 then operatesto provide additional heat to the space i5. After a time, the thermostat 5| will begin to feel the effect of the additional heat supplied and under ordinary circumstances would move in the direction of'legend H to close the contact 60, 62. If, however, the temperature in the bonnet Il increases until it reaches a dangerously high value before the room thermostat is satisfied, the mercury switch will b e rotated counter-clockwise by the element 6,3 toclose a circuit through electrodes .68 and 69. This completes a circuit for energizing the winding as follows: from the top side of the transformer 12, through conductor 13, the winding. 20, conductor 14, switch blade 38, contacts 31, 36, conductor 42,= conductor 18, electrode 68, mercuryj10, electrode 69. and a conductor 80 back to secondary 12.` Upon energization of the winding 20, the dampers are returned to their draft-retarding position, where they remain until the temperature in the bonnet drops below the value at which thermostat 52 is set to act. Thereupon thel mercury switch returns to the position as shown in the ligure, and if the room thermostat is still calling for heat, the circuit previously traced to the winding 20 again causes a motor action to drive the dampers tol their draft-increasing position. It will be seen that any circuit completed to the winding 2D through the switch 46 or thermostat 5| for the purpose of opening the draft of the furnace must be completed through the electrodes 66, 61 of the thermostat 52. However, when the dangeri ously high furnace temperature is reached the electrodes B6, 61 are no longer shorted by the mercury 10. Consequently, the switch 46 and the thermostat 5l are unable to initiate a motor operation to again drive the dampers to a draftincreasing position while the high furnace temperature exists. As will hereinafter appear, the motor operation initiated by the thermostat i2 to return the dampers to a draft-retarding position is utilized to return the manual switch arm 41 to the automatic position when it has inadvertently been left in the open position. l

Assuming the room temperature is raised suilciently before the furnace temperature became excessive. the contact Sii moves out of engagement with the contact'i and into engagement with the contact 62 to establish a circuit for energizing the winding 2B. This circuit may be traced as follows: from. the top side of secondary 12 through conductor 13, winding 20, conductor 1d, switch blade 38, contacts 31, 36, conductor 42, conductor 1t, electrode 61, mercury 10, electrode Sii, conductor 11, switch arm 41, contact 118,v conductor 16, element 5E, blade 59, contacts Sii, 62, a conductor 8i, and conductor 19 back to the secondary 12. Upon energization of the winding 2@ the motor then drives the dampers to their draftretarding position.

In stoking or ring the furnace, it is desirable to move the dampers to their `draft-increasing position. For this purpose, the manual switch,

l into the open position. This completes a circuit to the winding 2d as follows: from the top side of the secondary 12 through conductor 13, winding 2|) conductor 1d, a conductor 82, switch arm 41, conductor 11, electrode 65, mercury "iii, electrode 61. conductor 1d conductor 42, contacts 3d. 3l, switch blade 32, and conductor 19 back to the secondary 12. The motor 20 is then energized to drive the dampers to their draft-increasing pcsitiorr After `the firing of the furnace has been completed the attendant usually moves the switch arm 41 back to the automatic position in which position, as previously pointed out, the thermostat5| will initiate a motor operation if the temperature of the space I6 is at the desired value or when the temperature rises to the desired value to drive the dampers to their draftretarding position. Ii the attendant desires that the dampers be moved to their draft-retarding` position immediately, he may move the switch arm 41 to the closed position which establishes a.

circuit for energizing the-winding 20 as follows: from the top side of the secondary 12 through a conductor 13, winding 20, conductor 14. switch blade 38, contacts 31 and 3G, conductor 42, conductor 18, electrode 61, mercury 10, electrode 66,

Aconductor` 11. switch arm 41 contact 5|), a conductor 83. and conductor 19 back to secondary Winding 20 is then energized providing a 12. motor action which drives the dampers to their draft-retarding position. y

\ It frequently happens that the attendant inadvertently leaves the switch arm 41 in the open position after firing 4the furnace. As previously stated, this movement of the switch 46 takes the motor operator out of control of the thermostat 5I and places it in control of the thermostat I2. Thus, with the dampers in their draft-increasing position the furnace l develops the dangerously high temperature referred to. hereinabove which actuates the thermostat 52 to cause a motor action driving the dampers to their draft-retarding position. As previously pointed out, during this motor action the arm 51 on the shaft 2iengages the extension 55 from the switch arm 41 to drive the switch arm 41 back to its automatic position to again place further motor action under the normal control of the room thermostat I and limit control 52.

From the foregoing, itis now apparent that I have provided a motor operator well adaptable to fulfill the objects of the invention set forth hereinabove.' While I have disclosed but a single embodiment of. my invention, I contemplate all such further embodiments and structural modifications thereof as-would naturally occur to those skilled in the art without departing from the spirit of the invention as defined by the appended claims. f ,i

I claim as my invention:

1. In a temperature control system, a furnace for heating a. space, dampers on the furnace movable between draft-increasing` and draftretarding positions, a unidirectional motor operator for driving the dampers between said draftincreasing and draft-retarding positions, a thermostat in the space for initiating operation of the motor operator in accordance with varial tions of the space temperature from a desired value, a manually operable switch associated th the motor operator movable between a first tion in whichthe thermostat'completes a circuit through the switch for the Acontrol of said dampers according to the temperature in said space, a second position in which the switch completes a circuit to the motor operator independently of the thermostat, said motor operatoroperating to drive said dampers to a draftincreasing position when said switch is manually moved to said second position, and a third position in which the switch completes another circuit to the motor operator independently of the thermostat to move said dampers to adraft retarding position, a thermostat associated with the furnace and, responsive to a predetermined temperature thereof for initiating4 operation of the motor operator independently of the space thermostat and manual switch when the same is in said second position to drive the dampersl to a draft-retarding position, and operative connections between the motor operator and manual switch operable to positively move the switch to the rst position thereofonly when the motor operator moves said dampersinto said draftretarding position.

2. In a temperature control system, a furnace for heating a space, dampers on the furnace source of power. and electrical connections between the source of power, manual switch, furnace thermostat, space thermostat, motor switch means, and motor providing a first circuit in 5 which motor operation is initiated by the room thermostat for control of said dampers according to the temperature in said space when the manual switch is in said first position, said connections providing a second circuit in which motor operation is initiated by the manual switch independently of the room thermostat to move said dampers toa draft increasing position when the manual switch is moved to said second position, said connections providing a third circuit in which motor operation is initiated by a manual switch independently of the room thermostat to move said'dampers to draft retarding position when the manual switch is moved .to said third' position and said connections providing a fourth circuit in which motor operation is initiated `by the flurnace thermostat independently of the space thermostat andV vmanual switchv when the manual switch is in said second position, and driving connections between the motor and manual switch operable to move-the manual switch y from said second to said first position when the motorcoperation is initiated by said fourth circuit.

- -3. Ina temperature control system, a furnace for heating a space, dampers-on the furnace i mpvable between draft-increasing and draftretarding positions, a motori operator for driving said dampers between said draft-increasing and draft-retarding-positions, said operator. com- 5 prising switch means. for maintaining a circuit `erable switch associated with the motor movable between first, second, and third positions, a source of power, and electrical connections ybetween the source of power, manual switch, iurnace thermostat, space thermostat, motor switch means, and motor providing a first circuit in lwhich motor operation is initiated by the room thermostat when the manual switch is in said first position, said first circuit including the A source, of power, motor, space thermostat, manual switch, furnace chermiat, and motor switch means, said connections providing a second circuit in which motor operation is initiated by the manual switch independently of Athe room thermostat to move said dampers to a draft increasing position when the manusi switch is moved to Nsaid second position, said second circuit including the source of power, manual switch, furnace thermostat, and motor switch means, said connections providing;

move said dampers to a draft retarding posiltion when the'manual switch is moved to said thirdI position, said third circuit including the movable' between draft-increasing and draftfc source of power, motor, motor switch means, fura responsive thermostat, a manually operable switch associated with the motor movv nace thermostat, and said manual switch and said connections providing a fourth circuit in which motor operationfis initiated by the furnace thermostat independently of the space 70. thermostat and manual switch when the manual switch is in said second position, said fourth circuit including the source of power, motor, and motor switch mea s, and driving connections between the motor 'd manual switch operable able between first, second and third positions, a 15 to move the switch from said. md t0 Said first a third circuit in which 4 motor operation is initiated by the manual switch independently of the room thermostat to A position when' the motor operation is initiated by said fourth circuit.

4. In a temperature control system a-space to beheatedI heat exchange means for heating said space,v a member controlling said heat exchange means, said member having rst and second positions respectively adapted to increase and decrease the output of said heat exchange means, motor means operating said member, iirst heat' responsive means in said space selectively actu- Y ating said motor means to operate said member into said rst and said second positions, means manually operable to a rst, second and third position for controlling the operation of said member,` said member being operable by said iirst heat responsive means when said manual means is placed in said first position, said member being operable to supersede said rst heat responsive means to move said member to its first position when said manual means is placed insm'd second position, said manual means being operable to supersede said rst heat responsive means when said manual means is placed in said third position to actuate said motor means to move said member into its said second position and second heat responsive means in heat transfer relation with said heat exchange means superseding said first heat responsive means and said manually operable means and actuating said motor means to operate said member only into said second position, said manually operable means being positively disengageable from operative relation by operation of said member only from said first position to said second position.

5. hi a temperature control system a space to be heated, heat exchange means for heating said space, a member controlling said heat exchange means, said member having ilrst and second positions respectively adapted to increase and decrease the output of said heat exchange means, unidirectional motor means operating said member, rst heat responsive means in said space selectively actuating said motor means to operate said member into said rst andsaid second positions, means manually operable to a1 iii-st, second and third position for controlling the operation or' said member, said member being operable by said irst. heat responsive means when said manual means is placed in said rst position, said member being operable to supersede said rst heat responsive means to move said member to its rst position when said manual means is placed in said second position, said manual means being operable to supersede ilrst heat responsive means when said manual means is placed in Ysaid third position to` actuate said motor means to mve said member into its said second position, and second heat responsive means in heat transfer relation with said heat exchange means superseding said first heat responsive means and said manually operable means and actuating' said motor means to operate said member only into said second position, said manually operable means being positively disengageable from operative relation by operation of said member only from said first position Vto said second position.

6. In combination, a. motor operator comprising, motor means .and `an operator shaft driven thereby through a cycle lhaving distinct succes- 'sive rst and second positions; a manually operable control member having iirst, second and third positions; said manual member being operably connected 'to said motor means for-the control thereof, and means carried by said shaft and adapted to positively move said control member from said rst position to said second position only during said second portion of said cycle of said shaft.

'7. In combination, a motor operator comprising, motor means and an operator shaft unidirectionally driven thereby through a cycle having distinct successive rst and second positions, a-

l0 manually operable control member having rst, second and third positions; said manual member being operably connected to said motor means for the control thereof, and means carried by said shaft and adapted to positively move said control member from said first position to said second position only during said second portion of said cycle of said shaft.

8. In combination, a motor operator comprising, motor means and an operator shaft driven 2o thereby through a cycle having distinct successive rst and second portions, said shaft having rst and second positions successively attained by moving through said iirst and second portions of said cycle, a manually operable control member having first, second and third positions; said manual member being operably connected to said motor means for the control thereof, and means carried by said shaft and adapted to positively move said control member from said rst position to said second position only during said second portion ci said cycle of said shaft.

9. In combination, a motor operator comprising, motor means and an operator shaft unidirectionally driven thereby through a cycle having distinct successive rst and second portions, said shaft having iirst and second positions successively attained by movement through said first and second portions of said cycle, a manually operable control member having first, second and third positions; said member being operably connected to said motor means for the control thereoi, and means carried by said shaft and adapted to positively move said control member from said first position to said second` position only during the second portion of said cycle of said shaft.

10. In a temperature control system, a furnace for heating a space, dampers on the furnace movable between draft-increasing and draft-retarding positions, a motor operator for driving the dampers between said draft-increasing and draftretarding positions, a thermostat in the space for initiating operation of the motor in accordance with variations of thel space temperature from a desired value, a manually operable switch associated with the motor movable to a rst position in which the thermostat completes a. circuit through the switch and to a second position in which the switch completes a circuit to the motor independently of the thermostat, said motor operating to drive said dampers to a draft-increasing position` when said switch is manually moved to said second position, a thermostat in heat transfer relation with the furnace and responsive to a predetermined temperature thereof for initiating operation of the motor independently of the space thermostat and manual switch when the same is in said second position to drive the dampers to a draft-retarding position, and operative connections between the motor operator and manual 70 switch operable to return the switch to the iirst position thereof only when the motor operates to move said dempers into said draft-retarding position.

11. In combination, amotor operator compris- 76 ing, motor means and an operator shaft driven thereby through a cycle having distinct successive first and second positions: a manually operable control member having first. second and third positions; said manual member being operatively connected to said motor means, said control member being operable in said third position to only move said shaft from said nrst to said second position. l

12. In a condition control system. a space whose condition is to be aiected.- a unit for aecting the condition of said space, eiements'of said unit being movable between two positions, motor means operable to move said elements between a hrst position and a second position, a manual member loperably associated with said motor means for controlling the position of said elements, said menber being adapted for movement to one of three positions.

13. In a temperature control system, a furnace for heating a space, dampers on the furnace movable between draft-increasing and draft-retarding positions, a thermostat in the space for initiating operation of the motor in accordance with variations ofthe space temperature from a desired value, a manually operable switch assov4ciated with the motor movable to'a first position in which the motor is responsive to the space thermostat for initiating the operation of the motor to move the dampers to draft-increasing or draft-retardins position, a second position in which the motor drives the dampers to afdraftfrom said second to said first position only when the motor operates to nove said dempers into draft-retardins position. l

JOSEPH E. ROBB.

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