US2222990A

US2222990A - Motor operated mechanism

Info

Publication number: US2222990A
Application number: US180179A
Authority: US
Inventors: Sylvanus C Shipley; Cyr Benjamin
Original assignee: Honeywell Inc
Current assignee: Honeywell Inc
Priority date: 1937-12-16
Filing date: 1937-12-16
Publication date: 1940-11-26
Anticipated expiration: 1957-11-26

Description

2 1940- .s. c. SHIPLEY Efr AL MOTOR OPERATED MEcHANIsM Filed Dec. 16, 1957 3 Sheets-Sheet l /YIMUYlflJ/ A/ diz lvanus d. Shiple y Benjamin (yr (W W M 1940- s. c. SHIPLEY EI'AL MOT-OR OPERATED MECHANISM Filed Dec. 16, 1937 3 Sheets-Sheet 2 m/Uf/Mfo m/ Sylvanzw C. Shipley Ben Jamln Cy)" W fi M 1940- s; c. SHIPLEY ET AL 2,222,990

MOTOR OPERATED MEGHANI SM Filed Dec. 16, 1937 s Sheets-Sheet 5 L- Ill J ylvanws U. Sh ipley Benjamin Cy)" W MM Patented Nov. 26, 1940 UNITED STATES PATENT OFFICE MOTOR OPERATED MECHANISIVI Application December 16, 1937, Serial No. 180,179

Claims.

This invention relates to a motor operated mechanism and more particularly to one of the type wherein an element is biased to one position and is moved against its bias and held in a sec- 5 and position by the continued energization of a motor.

In many arts, it becomes necessary to move a controlling element between two positions, one of which is a safe position and the other of which is an active position. An example of such an element is a valve controlling the flow of fuel to a burner. When the valve is closed, it is in a safe position inasmuch as the continued maintenance of the valve in that position does riofoause I an unsafe condition to be created. When the valve on the other hand is in open position, it is in an active but unsafe position inasmuch as if the valve continues in that position, the burner may cause an overheating of the device heated thereby. Another such example of an element which is movable between a safe and an unsafe position is an electric switch. Such a switch is often used to control heating apparatus or apparatus whose continued operation under some circumstances may be undesirable. Where such elements are controlled by power operated devices, which in turn are controlled by automatically electrically operated controlling systems, it becomes highly imperative that some means be provided for insuring that these elements are moved to their safe position in the event of power failure. It is, accordingly, a common practice in certain arts to have the element biased towards a safe position and moved by an automatically controlled electric motor to its active position, the biasing means being effective in the event of power failure to return the element to its safe positionv An art in which this principle is used to a considerable extent is the valve art, particularly where the valves are used for the control of a heat producing medium. In this case, the motor operating the valve is thermostatically controlled.

One very serious difliculty which has been encountered, however, in such motorized valves is that it is necessary to maintain the motor continually energized when the valve is in its open position. This results in the motor heating up with the result that there is a tendency for the bearings to stick, Inasmuch as such a motor usually operates the valve through a reduction gear train, any tendency of the motor to stick, no matter how slightly, offers a decided resistance to the return of the valve by the spring. inasmuch as the spring, in order to return the valve, must rotate the entire gear train and motor, By reason of the fact that the motor is connected to the high speed end of the gear train, it must be rotated at a relatively high speed. It is impossible to overcome this difficulty by merely increasing 5 the tension of the spring since this in turn results in the necessity of a much larger motor, which in turn gives olT more heat when maintained in its energized position. As a result of this situation, considerable dimculty has been experienced in the past with valves of this type sticking in open position and causing an excessively overheated condition, which in certain instances have resulted in fires.

'It will be readily apparent that the same difficulty would be experienced in the operation of any element biased to a safe position by means of an electric motor.

An object of the present invention is to provide a device of this type wherein upon initial movement of the apparatus, in the reverse direction, the element is disconnected from the motor so that the biasing means is able to return the element unimpeded by the motor.

A second object of the present invention is to provide means in such an arrangement to stop the return movement of the motor at a point such that sufficient lost motion will exist in the connecting means to insure the establishment of a maintaining circuit during the taking up of such 30 lost motion.

Further objects of the present invention will be apparentfroma consideration of the accompanying specification, claims and drawings, of which:

Figure 1 is a vertical sectional View of the motor operated mechanism taken substantially along the line of Figure 2;

Figure 2 is an end elevational view of the same looking from the left in Figure 1 and showing the cover for the mechanism in section, the section being taken along the line 2-2 of Figure 1;

Figure 3 is a side elevational view looking from the right in Figure 2 with certain portions being shown in section along the line 3-3 of Figure 2 and with the terminal block and binding post being shown in broken lines as though transparent;

Figure 4 is a diagrammatical view of the structure shown in Figures 1 to 3 and including the electrical control system therefor, and

Figure 5 is a detailed view of a portion of the valve operating mechanism in the position it assumes when the valve is in its open position.

While the invention is not so limited, the same has been illustrated as applied to the operation of a valve for controlling the now of gas to a burner.

Referring now to Figures 1 to 4, the control valve generally designated at 9 has a valve casing l0 having outlet andinletopenirigs H and i2, respectively. The valve casing ID has a transverse wall l3 having a port opening it therein which is encompassed by an annular shoulder to form a valve seat l5. The valve member comprises a valve disc l6 adapted to seat on the annular seat l5, reinforcing washers i1 and i9 flanking the valve disc I6, said valve disc I6 and said reinforcing washers i? and 59 being securely clamped together by means ofa plug i9 and a nut 29 screwed thereon,

Extending into theflpl s s J! of the valve member is a valve stem 2|, the plug l9 and the valve stem 2| having holes to receive a pin 22 to secure the valve stem 2| and plug I! together in fixed relation. Mounted in an annular groove in the valve stem 2| is a split ring 23 which supports a spring retainer member 24. A spring 25 rests in the spring retainer member 24 and abuts against an abutment plate 28 tar normally urge the valve member toward its 1-; Located adjacent the upper portion of tho slve casing I0 are a disc 21, a packing washer 1.4. and a sup-= port 29 which are secured togei and to the abutment disc 26 by means oi rivets 39. 3| designates a clamping nut, screw-threaded on the upper portion of the valve casing M to hold the support 29 in fixed relation to the valve casing I0.

Extending through the abutment disc 26, the disc 21, the washer 28, and the support 29 and secured thereto is a sleeve guide member 32 through which the valve stem 2| slida tends outwardly from the valve casing order to effectively seal the valve i9 leakage of fluid therefrom a diaphragm is secured to the outer end of the valve stem 2| by clamping the diaphragm 3"! between a nut 34 and a washer 35, the clamping action being efiected by a nut 38 screwed on the screwthreaded portion 33 of the valve stem 2|. The outer edge of the diaphragm 31 is clamped cctween the support 29 and a base 39 by means of screws 39.

Mounted on the base 38 by means of screws 42 are two upright, spaced parallel plates 40 and 4|, the plates 40 and 4| being held in spaced relation by bolts 43 cooperating with nuts 45 to clamp the plates 40 and 4| against spacer mem bers 44.

A motor of any known type, generally designated at 45, is secured to and spaced from the vertical plate 40 by means of screws 41 and spacers 48. The motor shaft extends through the plate 40 and has a motor pinion 49 located on the end thereof. Located between the plates 40 and 4| and driven by the motor pinion 49 is a reduction gear train, comprising a gear 59 engaging the motor pinion 49, a gear 52 engaging a pinion 5| integral with the gear 50 and a gear 54 engaging a pinion 53 integral with the gear 52. The gears and pinions are suitably mounted and spaced between the upright parallel plates 40 and 4| by means of bearings 55.

By means of a pivot pin 59 and spacers 50, a lever 58 is pivoted between the plates 40 and 4| and by means of a pivot pin 6| and spacers 92 the lever 58 is pivoted to a U-shaped bracket 63, which bracket 63 is secured to the valve stem 2| by a nut 64 screwed on the screw-threaded engages the pin 9|.

portion 33 of the valve stem 2| whereby movement or the lever 58 in a clockwise direction about its pivot pin 59 causes opening of the valve 9.

A pawl member 66 is pivotally secured by means of a pivot pin 61 to the lever 58. This pawl member intermediate the length thereof is provided with a shoulder portion 68 which is adapted to cooperate with a pin 69 secured to plate 40. The pawl member 86 is biased into engagement with pin 69 by means of a spring 10 surrounding the pivot pin 61 and whichengages at one end the pawl member and at its other end a pin 'Hsecured to the lever 58. The pawl member 96 is also provided with a hook portion 12 at a point somewhat above the shoulder portion 68. This hook portion 12 is designed to cooperate with a pin 14 carried by the gear 54- in the low speed end of the gear train. The upper end of the pawl member 66 is bent forwardly as at 15 and has pivotally secured thereto a member 16. This member is provided with a transversely extending tooth engaging member ll, which under certain circumstances engages the tooth of the gear so as to disengage the hook portion 12 from pin id. The member 16 is provided at its outer end with a curved extension 19 which is adapted to engage the fixed pin 43 to limit outward movement of member '19 and consequently of pawl member 66.

Secured to pawl member 66, as best indicated in Figures 1 and 2, particularly the latter, is a spring member 89. This spring member is rig idly secured at its lower end to the pawl memher and is curved at 8| at its upper end. This curved upper and Bi of the spring member 89 is adapted to engage the pin 14 of gear 54 upon movement of the gear in valve closing direction.

The gear 54 is secured to a shaft 85. Also mounted on this shaft, as indicated in Figures 2 and -3, is a pair of collar members 86 and 81.

Collar member is rigidly secured to the shaft 85 whereas collar 81' is slidably but non-rotat ably secured thereto. A cam member 99 is located between the collar members 89 and 81. A spring 99 bears against the collar member 81 and urges the same against the cam member 98 to clamp the same between collar members 86 and 8?. In this manner, cam member 88 is frictionally connected to shaft 85 so as to rotate therewith when its motion is unimpeded. The cam member 89 is provided adjacent its upper portion with a notch 99 which is adapted to cooperate with a pin 9| secured to the plate 4|. The pin 9| effectively serves to limit the movement of cam 88. Thus upon rotation of the motor in either direction, cam 88 is initially rotated until a respective shoulder of the notch The cam member 88 is employed for actuating a, maintaining switch. This maintaining switch consists of a fixed contact carrying member 93 and a movable contact carrying member 94. Movable contact carrying member 94 is pivotally mounted to plate 4| at 95 and has attached thereto an elongated resilient member 96 which engages a pin 91 se cured to a terminal plate 33. This terminal plate 83, which in Figure 3 is shown as if transparent, is secured to plate 4| by screws 82 and spacers 94. The resilient member 96 serves to bias contact carrying member 94 away from fit) bers 93 and 94 are provided with contacts I00 and IN," respectively, and upon the cam follower 98 engaging the toe portion 99 of cam member 88, upon clockwise rotation of the cam member, contacts I00 and I01 are moved into engagement with. each other. The action of the maintaining switch is, accordingly, that upon initial movement of the motor in valve opening direction, contacts I00 and IIII are moved into engagement with each other, and upon an initial movement of the motor in valve closing direction, the contacts I00 and IOI are separated from each other. The function of this maintaining switch will be more apparent from the subsequent description.

Surrounding the mechanism is a cover member I05. This cover member slides over the edge of the base member 38 at its lower end and is held in position at its upper edge by a bolt and nut assemblage secured to plate 40 and generally indicated by the reference numeral I08. This cover can be conveniently removed when desired by unscrewing the nut of the fastening means Hi8.

The lever 58 projects through the cover I05, as indicated in Figures 1 and 3. The righthand portion thereof, as viewed in these figures, provided with a plurality of holes I08. These holes are for the purpose of attaching a chain, or similar member thereto, for operating a damper by means of lever 58. This function of t .maticaily illustrated. in Figure 4. While the primary purpose of lever 58 extending through the cover is to actuate a damper or othe the same time furnishes a means we may be manually actuated in er failure. Inasmuch as it is one inexperienced with the art operate the valve under such circumstances, the shoulder 58 is provided for the purpose preventing such opening of the valve without removal of cover I05, as will be explained in more detail later. Upon removal of cover H15, shoulder 68 can be withdrawn from the path of pin 69 by engaging a thumb piece I H] on the pawl member 68. When this is done, it is possible by hearing down on the right-hand end of the lever 58 to move the valve towards open position. A plunger member H2 is provided for the purpose of holding lever 58 in its valve open position when it is so moved manually. The plunger H2 is slidable in a bearing member H3 and is provided at its inner end with a collar member II4 which is designed to be moved into the path of lever 58. A collar II5 of insulating material is secured to plunger II2. Extending between this collar H5 and a supporting plate 45 is a spring IIG, which spring serves to bias plunger II2 to the position shown in Figure 2 wherein collar member H4 is out of the path of movement of lever 58. Secured to the terminal plate 83 is a fixed contact member H8. Cooperating with this contact member H8 is a movable contact member i I9. Movable contact member H9 is biased into engagement with fixed contact member H8 but is normally prevented from moving into engagement with contact member M8 by reason of the collar |I5 which is biased by the spring IIIi. It will be noted that collar H5 is in engagement with contact member Hi When the plunger is in. its normal position shown in Figure 2. The contact members H8 and H9 form the two contacts of a r auxiliary apparatus, extension recycling switch, as will be more apparent from the subsequent description. I

In Figure 4, a portion of the apparatus is shown schematically together with the control system for operation of the motor. The motor 46 is shown in the present figure as being of the shaded pole induction type. The motor comprises a stator core I25 upon which is located a field winding I26. The core I25 is formed with the two pole portions I21 and I28 which are split. Opposite halves of the two pole portions are provided with shading rings I29 and I30 of any conventional construction. A rotor I3I of the conventional squirrel cage type is rotatably mounted between the pole portions I21 and I28.

A thermostat is shown as forming the controlling switch. This thermostat is indicated gen erally by the reference numeral I35. This thermostat consists of a contact arm I38 which is secured to a bimetallic element I31. The contact arm I38 is designed to engage fixed contacts I38 and I39. The contact I38 is spaced farther from contact arm I38 than contact member I39. The result is that upon movement of contact arm I38 in the direction of contacts I38 and I39, the contact I39 is engaged first. Simi larly, on movement of contact arm I36 in the opposite direction, the arm I38 separates first from contact I38. Bimetallic element I31 is arranged so that upon a temperature fall, the contact arm I38 is moved to the left.

Power is supplied for operation of the system by a step-down transformer I40. This transformer comprises a line voltage primary HI and a low voltage secondary I42. The line voltage primary I is connected to-line wires I43 and I44 leading to a suitable source of power (not shown). A switch comprising a switch blade I46 and a fixed contact I41 is provided for manually interrupting the power supplied to the motor when it is desired to place the valve out of operation for a considerable period of time. I In this figure, the lever 58 is shown as connected to the secondary air damper of a gas burner. This damper is for the purpose of controlling the admission of secondary air to the burner. The damper is generally indicated by the reference numeral I50 and is pivoted to the casing I5I surrounding the gas burner. Only a portion of this casing is shown in the drawing. A chain I52 is shown as extending between the damped I50 and the lever 58.

The other elements of Figure 4 are shown schematically and correspond to elements shown and described in connection with Figures 1 to 3, and inasmuch as they bear the same reference characters as the corresponding elements in Figures 1 to 3, it is believed that a further description of these elements in connection with Figure 4 is unnecessary.

Operation Various elements are shown in the position which they occupy when the thermostat I35 is in a position wherein it is not calling for the valve to be opened. Where the valve controls the flow of gas to a burner. as in the present instance, this position of the thermostat will be the position which it assumes when the tempera-- ture is above the desired value. Let it be assumed now that the temperature begins to fall by reason of the valve being closed. This will cause movement of contact blade I35 to the left causing it to successively engage contacts I39 and I38. The engagement with contact I39 has blade I36. bimetallic As soon. however, as the engagement I38 is eifected, the following circuit no effect. of contact is established: from the right-hand terminal of secondary I42 through conductor I55, contact I41, switch blade I46, conductor I56, conductor I51. contact I39, contact; arm I36, contact I38, conductors I58 and I59, field winding I26, and conductor I60 to the other terminal of secondary I42. The result of the establishment of this circuit is that the motor becomes energized causing gear 54 to be rotated through the various elements of the gear train for reasons to be subsequently explained. The pin 14 at the time this movement is started will be in approximately the position indicated in solid lines in Figure 4. The rotation of gear 54 which will take place in a clockwise direction will result in the pin 14 similarly being moved in a clockwise direction away from hook 12. It will be readily apparent that upon slightly less than 360 of revolution of gear 54, the same will be brought into engagement with the under surface of the hook portion 12 of pawl member 66. Before, however, such engagement of pin 14 with hook portion 12 occurs, the cam member 88 will be moved in a direction to close contacts I00 and IOI, as previously explained. The engagement of these con- Iacts will result in a new circuit being established to field winding I26 as follows: from the righthand terminal of secondary I40 through conductor I55, contact I41, switch blade I46, conductor I56, conductor I51, contact I39, switch element I31, conductor I62, contacts IOI and I00, conductors I63, I64, and I59, field winding I26, and conductor I60 to the other terminal of secondary I42. It will be noted that the last traced circuit is independent of contact I38. Thus, even though the temperature should rise slightly to cause disengagement of switch I36 with contact I38, the motor will not be stopped. It will thus be seen that the temperature differential is required between the stopping and starting of the motor. In this manner, any chattering of the thermostat will not result in rapid energization and deenergization of the motor.

As previously indicated, the continued rotation of gear 54 in a clockwise direction results in the engagement of pin 14 with the hook portion 12. As soon as such engagement takes place, further rotation of gear 54 results in pawl member 66 being raised upwardly and moving the valve towards open position. Due to the fact that the pin 14 follows an arcuate path, the pawl member 66 will be swung outwardly by the pin 14 thus enabling shoulder 68 to clear the stop pin 69. The position of pawl member 66 shortly after it passes pin 69 is shown in dotted lines in Figure 4. After shoulder 68 has thus cleared pin 69, the pawl member 66, the lever 58, and the valve will be free to continue to move upwardly. Such upward movement will continue until the lever 58 engages the pin 69. at which time the various elements will assume the position shown in solid lines in Figure 5, which corresponds to open position of the valve. The motor will be effective thereafter to conlinue to hold the valve, or other actuated element, in its uppermost position. It is to be understood that the gas admitted by the valve to the burner is lighted by a pilot light, or some other conventional igniting means.

At the same time that the valve is moved to its open position, a downward movement of the right-hand end of the lever 58 results in sec ondary air damper I50 being moved to open position. It will be noted that this damper is biased to open position so that as soon as the lower end of lever 58 moves down, the weight of damper I50 is able to move the damper to open position. The opening of the secondary air damper permits air to be admitted to the burner to support combustion.

The continued admission of gas to the burner by reason of the valve being held in open position eventually results in the temperature to which thermostat I is subjected rising to the point where the switch blade I36 separates not only from contact I38 but also from contact I39.

When this occurs, both circuits to the motor field I winding I26 are interrupted so that the motor is completely deenergized. The biasing spring 25 is thereupon effective to rotate lever 58 and, through the pawl member 66, the gear train and the motor in the reverse direction towards valve closed position. It will be noted that the under surface of tooth engaging member 11 is free of any sharp projections so that as long as the gear 54 is rotating in clockwise direction, the tooth engaging member 11. merely rides over the surfaceof the teeth. As soon as gear 54 starts to rotate in the reverse direction, the tooth engaging member 11 engages the teeth of gear 54 so that member 16 and consequently pawl member 66 are pushed to the left. It will be readily apparent that after such movement of pawl member 66 to the left continues for a relatively short distance, the hook portion 12 is disengaged from pin member 14, as shown in dotted lines in Figure 5. The disengagement of hook portion 12 from pin 14 effectively interrupts the connection between the valve and the motor and gear train. The result is that the valve, the lever 58. and the pawl member 66 are free to move downwardly independently of the gear train and motor. Moreover, such return movement is accomplishedquite rapidly so as to insure an abrupt closing off of the gas to the burner.

Due to the fact that the gear train has some momentum imparted to it by the relatively limited motion thereof before the hook 12 is disengaged from pin 14, the gear train and motor will contime to rotate after such disengagement. If it were possible for pin 14 to clear the upper edge of hook member 12, pin 14 might well be left in a position to close to the under side of hook portion 12 that upon energization of the motor the engagement of pin 14 with hook 12 would take place before a maintaining circuit could be established by closure of contacts I00 and IOI. Moreover, if such rotation continues sufficiently far in a counter-clockwise direction, it might engage pawl member 66 at the upper end thereof and move pawl member 66 outwardly so that shoulder 68 clears the pin 69, whereupon it would be possible for someone to manually open the valve without removal of the cover. In order to guard against either of these contingencies, the hook portion 12 is provided with an upper surface which is slightly recessed, as indicated at I61. Moreover, the spring 80 is provided which. as previously stated, has a curved end 8I. Upon pin 14 rotating in a counter-clockwise direction after hook 12 has been disengaged therefrom, the pin 14 first strikes the spring 80. The effect of this spring is to yieldably halt further movement,

of the gear. In the majority of cases, pin 14 will never move into engagement with the upper surface of hook portion 12. However, if it does, it

engages the same and moves downwardly into the recess portion I61 so that any further movement thereof is effectively retarded. In tins manner, it is assured that a substantial movement of the gear 54 is necessary upon reenergization of the motor before the pin I4 again engages the under side of the hook portion I2.

The amount of movement of gear 54 in the reverse direction which is required to move hook member I2, off of pin I4 is so slight that even if motor 46 has a decided tendency to stick, the chances are that such movement will still take place. Thus, the motor bearings may be sufliciently sticky that the valve would otherwise creep back a certain distance, and then by reason of the fact that the spring 25 would be under less tension, such movement of the valve would be stopped entirely. With the present invention, it is necessary to have only a small amount of such movement before the valve is disengaged entirely from the motor to assure closing of the valve. Due to the fact that spring 25 is most highly compressed when the valve is in fully open position, the probability is very great that a small amount of such movement will take place.

As previously indicated, it is considered undesirable in many instances for the average user to be able to manually open the valve by merely grasping the right-hand end of lever 58 and moving the same downwardly. For this reason, the shoulder 68 is provided which, if an attempt is made to open the valve in this manner, will engage pin 69 to prevent such movement. The service man or other person skilled in the operation of the equipment, however, can manually open the valve by merely removing the cover I85. When the cover is removed, it is possible to manipulate the thumb piece I ID to swing the pawl 66 to the left and move shoulder 68 out of the o path of pin 69. It is then possible to move the valve to open position by depressing the righthand end of lever 58.

The outer portion of member I6 is curved outwardly as at I8, as previously indicated. This outwardly curved portion is designed to engage with pin 43 so that when thumb piece I I8 is manually manipulated, there is no danger of pawl 66 being moved so far to the left that the toothed follower II of member I6 rides off of the gear and 50 drops down on the left-hand side of the gear.

lever 58 in valve open position, the contact members I I8 and I I9 are moved into engagement. As previously indicated, these contacts constitute a recycling switch. The purpose of this is to insure that the valve is again placed under control of the thermostat as soon as power is restored. Closure of these contact members I I3 and I I9, as best indicated in Figure 4, results, as soon as power is restored, in the following energizing circuit to the field winding I26: from the right-hand 70 terminal of secondary I42 through conductor I55,

contact I41, switch blade I46, conductor I56, conductor I10, contact members H8 and H9, conductors III, I64,and I59, field winding I26, and conductor I60 to the other terminal of secondary 75 I42. It will be noted that the circuit just traced is independent of the thermostat so as to insure that this circuit will be established immediately upon the restoration of power. While the position which the valve assumes when manually moved towards open position and held in this position by the plunger II2 has been previously referred to as the valve open position, this position is not the same as the complete valve open position to which the valve is moved by the motor. In other words, plunger I I2 is designed to hold the left-hand end of lever 58 in a position where it is not entirely in engagement with pin 69. Accordingly, as soon as the motor is reenergized, the gear 54 is rotated so as to cause reengagement of pin I4 with book portion I2 of the pawl member 66. The continued rotation of gear member 64 causes the lever 58 to be moved to the full open position shown in. Figure 5. When this occurs, lever 58 is moved away from the collar member II4 so that plunger H2 is free to move to its normal position through the action of biasing spring H6. The movement of plunger I I2 to the right results in a separation of contact members H8 and H8 so that the circuit last traced to motor field winding I26 is interrupted. The motor is thereupon again under the sole control of thermostat I85 and either stays energized or becomes deenergized, depending upon the then position of the thermostat.

It will be seen that the present invention provides an improved means of insuring the closing of a valve or other element biased to a safe position upon deenergization oi the actuating motor, even though the motor or associated connecting elements offer such resistance to turning that the biasing means would not normally be able to completely move the operated element to its safe position. By reason of the device of the present invention, it is accordingly possible to obtain the advantages of a device which is biased to a safe position and moved to another position and held there only upon the continued energization of the actuating means and at the same time avoid the disadvantage thereof arising from the tendency of such mechanisms not to return to their safe position upon the deenergization of the actuating means.

While a specific embodiment of the invention has been shown for purposes of illustration, it is to be understood that the invention is limited only by the scope of the appended claims.

We claim as our invention:

1. In combination, an element to be operated movable between a safe first and an active second position, means biasing said element toward said safe first position, motor means, connecting means between said motor means and said element, said motor means being operative upon continued energization of said motor means to move said element toward and hold the same in said active second position, said biasing means being operative upon deenergization of said motor means to move said element, said connecting means, and said motor in the reverse direction toward said first position, and means operative in response to such movement toward said first position to render said connecting means inoperative, said last mentioned means being actuable by energy of said biasing means whereby said element is returned by said biasing means to said safe first position independently of said motor means.

2. In combination, an element to be operated movable between a safe first and an active second position, means biasing said element toward said safe first position, motor means, a reduction gear train having its high speed end connected to said motor means, connecting means between the low speed end of said reduction gear train and said element, said motor means being operative upon continued energization of said motor means to move said element toward and hold the same in said active second position, said biasing means being operative upon deenergization of said motor means to move said element, said connecting means, said gear train, and said motor in the reverse direction toward said first position, and means actuable by such movement toward said first position to render said connecting means inoperative whereby said element is returned by said biasing means to said safe first position independently of said motor means and said gear train.

3. In combination, an element to be operated movable between a. safe first and anactive second position, means biasing said element toward said safe first position, motor means, connecting means between said motor means and said element, said connecting means comprising cooperating pin and hook members, one connected to said element and the other actuated by said motor means, said motor means being operative upon continued energization of said motor means to move said element toward and hold the same in said active second position, said biasing means being operative upon deenergization of said motor means to move said element, said connecting means, and said motor in the reverse direction toward said firstposition, and means responsive to such movement toward said first position to disengage said hook and pin members whereby said element is returned by said biasing means to said safe first position independently of said motor means.

4. In combination, an element to be operated movable between a safe first and an active second position, means biasing said element toward said safe first position, motor means, a reduction gear train having its high speed end connected to said motor means, connecting means between said motor means and said element, said connecting means comprising cooperating pin and hook members, said hook member being connected to said element and said pin member being secured to the gear at the low speed end of said gear train, said motor means being operative upon continued energize-tion of said motor means to move said element toward and hold the same in said active second position, said biasing means being operative upon deenergization of said motor means to move said element, said connecting means, said gear train, and said motor in the reverse direction toward said first position, and means operative in response to such movement toward said first position to disengage said hook member from said pin member whereby said element is returned by said biasing means to said safe first position independently of said motor means and said gear train.

5. In combination, an element to be operated movable between a safe first and an active second position, means biasing said element toward said safe first position, motor means, a reduction gear train having its high speed end connected to said motor means, connecting means between the low speed end of said reduction gear train and said element, said motor means being operative upon continued energization of said motor means to move said element toward and hold the same in said active second position, said biasing means being operative upon deenergization of 75 said motor means to move said element, said connecting means, said gear train, and said motor in the reverse direction toward said first position, and means operated by said gear train in response to movement thereof in the reverse direction to render said connecting means inoperative whereby said element is returned by said biasing means to said safe first position independently of said motor means and said gear train.

6. In combination, an element to be operated 1 movable between a safe first and an active second position, means biasing said element toward said safe first position, motor means, a reduction gear train having its high speed end connected to said motor means, connecting means between said 15 motor means and said element, said connecting means comprising cooperating pin and hook members, said hook member beingconnected to said element and said pin member being secured to the gear at the low speed end of said gear train, said motor means being operative upon continued energization of said motor means to move said element toward and hold the same in said active second position, said biasing means being operative upon deenergizatlon of said inc- 5 tor means to move said element, said connecting means, said gear train, and said motor in the reverse direction toward said first position, and means associated with said hook member, engaging an element of said gear train, and oper- 30 ative in response to movement of said gear train in the reverse direction to disengage said hook member from said pin member whereby said element is returned by said biasing means to said safe first position independently of said 33 tor means, said motor means being operative 45 upon continued energization of said motor means to move said element toward and hold the same in said active second position, said biasing means being operative upon deenergization of said motor means to move said element, said connecting means, and said motor in the reverse direction toward said first position, and means responsive to such movement toward said first position to disengage said hook and pin members whereby said element is returned by said biasing means 55 to said safe first position independently of said motor means, and means for yieldablylimiting the coasting of said motor and said gear train after said connecting means has been rendered inoperative.

8. In combination, an element to be operated movable between a first and a second position, means biasing said element toward said first position, rotary electrical motor means, a reduction gear train having its high speed end con- 65 nected to said motor means, connecting means between said element and said gear train, said connecting means comprising a first member carried by said gear train at the low speed end thereof and a second member connected to said 0 element and lying in the path of said first member when said gear train is rotated by reason of the energization of said motor, a control switch including a pair of insecurely engageablecontacts, a maintaining switch movable to closed circuit means operative upon engagement of said pair of contacts of said control switch to cause energization of said motor, second circuit means operative upon closure of said maintaining switch to establish a circuit to said motor independently of said pair of contacts, said motor means bein operative upon continued energization of said motor means to move said element toward and hold the same in said second position, said biasing means being operative upon deenergization of said motor means to move said element, said connecting means, said gear train and said motor in the reverse direction toward said first position, means operative in response to movement of said motor in the reverse direction by said biasing means to render said connecting means temporarily ineffective whereby said element is returned by said biasing means to said first position independently of said motor means, and means for terminating the coasting movement of said gear train before thefirst member of said connecting means carried thereby is in a position where forward movement thereof would cause immediate engagement of the second member of said connecting means therewith whereby it is necessary for a sufllciently large movement of said motor and gear train to take place before engagement of said members of said connecting means that the closure of said maintaining switch is assured prior to the engagement of said members.

9. In combination, an element to be operated movable between a first and a second position, means biasing said element toward said first position, rotary electrical motor means, a reduction gear train having its high speed end connected to said motor means, connecting means between said element and said gear train, said connecting means comprising a first member carried by said .g'ear train at the low speed end thereof and a second member connected to said element and lying in the path of said first member whens'aid gear train is rotated by rea- 'switch to establish a circuit, to said motor independently of said pair of contacts, said motor its means being operative upon continued energization of said motor means to move said element toward and hold the same in said second position, said biasing means being operative upon deenergization of said motor means to move said element, said connecting means, said gear train and said motor in the reverse direction toward said first position, means operative in response to movement of said motor in the reverse direction by said biasing means to render said connecting means'temporarily ineffective whereby said element is returned by said biasing means to said first position independently of said motor means, and means for terminating the coasting movement of said gear train at a point such that the two members of the connecting means are in a relative position such that sufficient movement of the motor and gear train is required upon reenergization thereof before reengagement of said members to insure the closure of said maintaining switch before such reengagement.

10. In combination, an element to be operated movable between a first and a second position, means biasing said element toward said first position, electrical motor means, connecting means between said element andv said motor means, said connecting means comprising interengaging members, one driven by said motor means and the other connected to said element,

' a control switch including a pair of insecurely engageable contacts, a maintaining switch movable to closed position upon initial movement of said motor, circuit means operative upon engagement of said pair of contacts of said control switch to cause energization of said motor, second circuit means operative upon closure of said maintaining switch to establish a circuit to said motor independently of said pair of contacts, said motor means being operative upon continued energization of said motor means to move said element toward and hold the same in said second position, said biasing means being operative upon deenerglzation of said motor means to move said element, said connecting means, and said motor in the reverse direction toward said first position, means operative in response to movement of said motor in the reverse direction by said biasing means to render said connecting means temporarily ineffective whereby said element is returned by said biasing means to said first position independently of said motor means, and means for terminating the return movement of said motor at such a point that the two members of the connecting means are in a relative position such that sufiicient movement of the motor is required upon reenergization thereof before reengagement of said members to insure the closure of said maintaining switch before such reengagement.

11. In combination, an element to be operated movable between a safe first and an active second position, means biasing said element toward said safe first position, motor means, connecting means between said motor means and said element, said motor means being operative upon continued energization of said motor means to move said element toward and hold the same in said active second position, said biasing means being capable upon deenergization of said motor means of moving said element, said connecting means, and said motor means in the reverse direction toward said first position, and means operative as a result of the deenergization of said motor means to render said connecting means inoperative whereby said element is returned by said biasing means to said safe first position independently of said motor means, said means operative as a result of the deenergization of said motor means being so constructed and arranged as to utilize the force of said biasing means to render said connecting means inoperative,

12. In combination, an element to be operated movable between a safe first and an active second position, means biasing said element toward said safe first position, motor means, a reduction gear train having its high speed end connected to said motor means, connecting means between the low speed end of said reduction gear train and said element, said motor means being operative upon continued energization of said motor means to move said element toward and hold: the same in said active second position, said biasing means being capable upon deenerglzation of said motor means of moving said element, said connecting means, said gear train, and said motor in the reverse direction toward said first position, and

means actuable by energy of said biasing means upon deenergization of said motor to render said connecting means inoperative whereby said element is returned by said biasing means to said safe first position independently of said motor means and said gear train.

13. In combination, an element tobe operated movable between a safe first and an active second position, means biasing said element toward said safe first position, motor means, disengageable connecting means between said motor means and said element, said motor meansbeing operative upon continued energization of said motor means to move said element toward and hold the same in said active second position, said biasing means being operative upon deenergization of said motor means to move said element, said connecting means, and said, motor in the reverse direction toward said first position, andmeans actuable by such movement toward said first position to disengage said connecting means whereby said element is returned by'said biasing means to said safe first position independently of said motor means and gear train.

14. In combination, an element to be operated movable between a safe first and an active second position, means biasing said element toward said safe first position, motor means, connecting means between said motor means and said element, said motor means being operative upon continued energization thereof to move said element to said active second position, said biasing means being operative to move said motor means, said connecting means, and said element in reverse direction when said motor means is denergized in a manner to impart momentum to said motor means, said connecting means being of a 5 one-way type permitting freedom 01' movement of said motor means in reverse direction and means arranged to resist and limit the amount of movement of said motor means in reverse direction, said last mentioned means being ineflective to resist movement of said element, connecting means and motor means toward said safe first position.

15 In combination; an element to be operated means including said biasing means for returning said element to said safe first position, and

means operative in response to the initiation of such movement toward said first position to release said transmission means whereby said element is returned by said biasing means tosaid saie first position independently of said transso mission means.

SYLVANUS C. SHIRLEY, BENJAMIN CYR.