US2422496A - Control device for draft regulators - Google Patents

Description

June 1?, 1947. c. H. MORROW CONTROL DEVICE FOR DRAFT REGULATORS Filed Jan. 4, 1945' 2, Sheets-Sheet 1 FTc-b. L

INVENTORQ Cumanca HMonRow man/2m.

' June. 17, 1947. c. H. MORROW 2,422,496

CONTROL DEVICE FOR DRAFT REGULATORS Filed Jan. 4, 1945 2 Sheets-Sheet 2 Face. 5. INVENTOR.

CLnRsNcE, H. Mo'maow FTTOtMaEY Patented June 17,1947

UNITED STATES OFFICE CONTROL DEVICE FOR DRAFT REGULATORS Application January 4, 1945, Serial No. 571,239

3 Claims.

This invention relates to control or operating mechanism for a furnace draft stabilizing damper. It is an improvement upon the construction shown, described and claimed in Patent No. 2,381,437, for Control means for draft regulators, granted August '7, 1945, to Morris W. Crew and George A. Short, to which referenc may be had for more complete understanding of certain of the features, if not completely described or shown here,

The control mechanism of said patent includes an operating member movable back and forth between two positions and driven in one direction by an electric motor of such form as to permit it to stall without injury, and in the opposite direction by suitable power means, such as a spring, said operating member being connected to the damper by disconnectible parts, all of the said parts being constructed and arranged so that with the mechanism in stand-by position and the motor deenergized, upon a thermostatic call for more heat, the motor is energized and drives the operating member in one direction to suddenly release the damper for normal stabilizing action during the period while the burner operates. When the demand for more or additional heat is satisfied, the motor circuit is deenergized and the operating member then is moved in the opposite direction by the power spring or other power source connected thereto, to slowly return the parts to their original position. Such mechanism includes speed reducing gearing driven by the motor and certain latch and holding devices.

The present invention has for its object to improve the mechanism of said patent by the inclusion in the operating connections between the motor and operating member of a floating coiled spring clutch so arranged that driving relation from the motor to the operating member, or vice versa, is permitted in one direction only, as will more fully appear hereinafter, for the purpose of distributing the wear on the speed reducing gears uniformly over their entire periphery, instead of limiting it to only a part of the teeth; which prevents gear clash and the impact of the momentum of the motor armature upon the gear teeth when the parts come to rest, with possible damage of the gears, as heretofore; and which avoids any possibility of bounce or return of the parts by reverse motion with consequent inaccuracy and possible faulty operation of the latching and disconnectible operating parts.

Further objects of the invention in part are obvious and in part will appear more in detail hereinafter.

Cal

In the drawings, which represent one suitable embodiment of the invention, Fig. 1 is a longitudinal sectional elevation through a furnace damper provided with my improved control, the front wall of the control casing being omitted to expose interior parts;

Fig. 2 is a similar view, showing the parts in another position;

Fig. 3 is a detail sectional view illustrating the speed reducing gear;

Fig. 4 is a sectional elevation on a larger scale, on the lin d, Figs. 1 and 3, showing the oneway clutch;

Fig. 5 is a detail end view from the right in Fig. 4; and

Fig. 6 is a sectional plan view on the line 6-6, Fig. 5.

Complete description of all of the parts of the mechanism is unnecessary, since reference may be had to said patent where that is desirable or necessary. It will suffice for this application to refer to many of the parts in a general way, as follows:

l0 indicates a damper mounted for pivoting movement in a sleeve-like frame or housing ll adapted for connection to a pipe leadingfrom a furnace to the stack for controlling the flow of the check draft. Fig. 2 represents the stand-by position, in which the damper is held wide open, while Fig. 1 illustrates the position the parts assume upon a call for heat or more heat, the damper being free for normal stabilizing action.

Movement of the damper to one or the other of its positions is produced by an operating member l2, movable back and forth between two positions, as by reverse swinging motion about a pivot. The operating member shown, as in said patent, is a two-armed device, one arm of which, I3, is connected by disconnectible connections, indicated generally at M, to a link l5 connected to the damper. The disconnectible connections cooperate with a pivoted latch It. The other arm I! of the operating member is connected to a suitable source of power, such as the tension spring IS.

The spring it always tends to move member l2 in the counterclockwise direction, Fig, 1. It may also be driven in the clockwise direction by an electric motor, marked generally M, which drives the shaft 26, around the axis of which member I2 turns, by means of speed reducing gearing shown more or less diagrammatically in Fig. 3, and including a series of large gears 2| and small pinions 22, the drive being from the motor shaft 23 to.

the first small pinion, then to a large gear, and so on to the final slow speed shaft 20.

With the arrangement described, as in the patent before referred to, the parts lie in the positions shown in Fig. 2 upon a stand-by. The electric motor is deenergized and the parts are held in the stand-by position by the tension of spring I8 and the engagement of pivot 24, about which link swings, with the end of the slot 25 in said link.

Upon a call for heat or more heat by the thermostat (not shown) said thermostat closes the motor circuit and the motor immediately begins to rotate in a direction to turn member I 2 in the clockwise direction. Practically immediately, the disconnectible connections separate and the damper is released and. moves promptly to its position shown in Fig. 1, for normal stabilizing action. finally the second arm of member l2, to which spring [8 is secured, engages the stop 26, with the parts in the position shown in Fig. 1. There they remain until the call for heat is satisfied, whereupon the motor circuit is opened. The motor, of course, is of the ordinary clock motor type, capable of being stalled without injury, as described in said patent.

When the motor circuit is opened spring [8 begins to turn member I2 in the opposite direction, also driving the rotor of the electric motor reversely through the speed reducing gearing, the latter serving to retard motion of member I2 and delay the completion of motion of the damper to the stand-by position shown in Fig. 2.

According to the present invention, for purposes and advantages to be later referred to I introduce into the dliVil'lg connections between the electric motor and operating member 2 a one-way or overrunning clutch device or mechanism, of special form, and so arranged, that driving effect may be produced from the speed reducing gearing to member l2, or reversely from member l2 to the The motor continues to rotate until j speed reducing gearing, but in each case only in one direction.

The mechanism is relatively small, space being at a premium in and around the space at the hub of lever l2. Accordingly I provide a very compact and improved spring clutch which may be made and operatively assembled with the other parts by simple operations and at low cost.

The drawings show for the purpose one suitable form of spring clutch illustrated in detail in Figs. 4, 5 and 6. As illustrated the end of the slow motion shaft 2% is left plain, except for a small diameter cross hole 39 to receive a securing cotter pin 3 I. Around the shaft is sleeved a coiled clutch spring 32 having its inner end plain, at 33, and its outer end bent tangentially to form an operating arm 34.

Spring 32 is housed or enclosed in the cavity 35 of a sleeve-like hub 36 permanently fastened to and forming the hub of lever [2, the outer end of said hub being provided with a slot 37 to receive the operating arm 36. Cavity 35 at its inner end is slightly enlarged, at 38, to house the plain inner end of the spring clutch and avoid any sticking effect such as might be caused by a rough end of the spring riding on metal of the hub.

The turns of the coil spring are fairly close together and said coil has such internal diameter that it is a snug fit upon shaft 20. In other words all of its turns at all times are in actual contact with a light frictional drag upon the shaft surface. The direction of twist, right or left, is such that When the hub is held stationary, as in Fig. 5,

4 clockwise rotation of the slow speed shaft 20 tends to close or wind the coils more tightly about the shaft, while shaft rotation in the opposite direction tends to open up the coils and free them from the shaft. Thus, the spring serves as a one-way driving clutch, permitting driving effect from shaft 28 to the hub, or vice versa, but in each case in one direction only.

With the construction described, assuming the parts in the stand-by position Fig. 2, and that the thermostat has called for heat or more heat and thus has closed the motor circuit, the motor begins to turn in the clockwise direction Fig. 1. Practically immediately the disconnectible parts are disconnected, as in said patent, and the damper promptly moves to the position shown in Fig. 1, for normal stabilizing action. The motor continues to operate, turning shaft zfi'and driving hub 36 through the spring clutch in the clockwise direction Fig. 5, and turning member 12 until it engages the stop 26. Thereupon movement of member [2 stops, and through the clutch fully prevents further advance or rotation of the motor rotor and reducing gear. The parts are held in this position, with the motor stalled, so long as the motor is energized.

When the call for heat is satisfied, the thermo-,- stat opens the motor circuit, as before described, and the spring 18 becomes the operating power source, exertin its effect through member l2 upon the hub 36, driving it in the counterclockwise direction Fig. 5 and through the clutch 7 spring also turning shaft 20, the reducing gearing, and the motor rotor in the reverse direction from before. This operation continues until finallythe parts reach the position shown in Fig. 2, with the pin 24 at the end of the slot 25 and forming a positive stop for motion of member l2. However, the one-way clutch now permits the shaft 20, speed reducing gearing and the motor rotor to continue to rotate until the force and tendency to move have been expended in friction. The parts are then ready for the next cycle of operations.

The mechanism avoids. any possible rebound effect as the parts reach the stand-by position of Fig. 2. Heretofore, when the shaft 28' has" been positively connected to member I2, so that the two parts always rotate together, when the, parts reach the stand-by position,-driven by the force of spring 8, at the moment of impact of the pivot pin 24 with the end of the slot 25, the heavy force of the rotating motor armature causes it to rebound, as it were, so, that in actual practice it may rotate reverselyv as much as 10 or 15 revolutions. has been sufiicient to unlatch the disconnectible parts and permit false operation or motion ofthe ing in the hub and the provision of the cross slot for its introduction into the device. v v

The construction described is simple, durable, effective. and not liable to get out of order, and may be applied both to new control devices-cor; as replacement parts for those already, in use-.

This rebound effect sometimes Further advantages of the invention will be apparent to those skilled in the art.

What I claim is:

1. Apparatus of the character described, comprising an electric motor, speed reducing gearing driven by the motor and including a slow running shaft member, an operating device having a hub member surrounding the shaft memher, power means connected to the operating device to positively turn it about the shaft axis, and a coil spring surrounding and closely fitting the shaft, one end of said spring being free and the other end being connected to one of said members, said spring serving as a one-way clutch between said members permitting drive through said spring of said operating device by said motor in one direction only or of the motor by said operating device in the opposite direction only.

2. Furnace damper control mechanism of the character described, comprising, in combination, a damper, an operating device movable back and forth and having a disconnectible connection to said damper, an electric motor, speed reducing gearing driven thereby and including a slow running shaft, and a coil spring surrounding and closely fitting said shaft, one end of said spring being free and the other end being fastened to said operating device and power means efiective directly upon said operating device and tending to move it reversely to its movement by the motor, said spring serving as a one-way clutch for establishing driving connection through it'between the motor and operating device.

6 V a 3. Control means for a furnace draft stabilizing damper, comprising an electric motor adapted while energized to be stalled without injury thereto, means operatively connecting said motor and damper and having stand-by and damper release positions, said connecting means including speed reducing gearing connected to the motor rotor and including a slow running shaft, an operating device connected to the damper and movable back and forth and having a hollow hub surrounding said shaft, power means effective upon said device and tending to move it reversely to its movement by the motor, and a coiled spring surrounding the shaft and housed within the hollow hub and having one end connected to said hub and the other end free, said spring serving as a one-way clutch between said reduction gearing and operating device to permit drive by either to the other in one direction only.

CLARENCE H. MORROW.

REFERENCES CITED 9 The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,021,413 Gille Nov. 19, 1935 2,381,437 Crew et a1 Aug. 7, 1945 2,169,168 Shipley Aug. 8, 1939

Images