US2418537A - Electric circuit breaker - Google Patents

Description

April 8, 1947. M. a. WOOD ELECTRIC CIRCUIT BREAKER Filed Jan. 7. 1944 Patented Apr, may

UNITED STATES PATENT OFFICE ELECTRIC CIRCUIT BREAKER Morris B. Wood, Newbury, Mass.

Application January '7, 1944, Serial No. 517,383

14 Claims. 1

The present invention relates to electrical circuitbreakersand is herein illustrated as embodied in a compact form of circuit breaker adapted for use where available space is limited, under conditions of excessive vibration such as in internal combustion engine driven vehicles and in which a current responsive tripping element is employed, comprising a bimetallic strip or other device of relatively low actuating power.

In internal combustion engine driven vehicles, particularly in aircraft, space and weight limitations are extremely restricted and instrumentalities for electric control of such craft and for indicating the operating conditions must be constructed durably to withstand vigorous vibration, often at high periodicities and intensities. In the construction of electrical switches or circuit breakers, electrical contacts of suitable durability for the prevailing conditions have necessitated the development of a metal alloy in which minimum pressure must be maintained between contacts composed thereof to render its use practical. To insure an adequate contact pressure between electrical contacts composed of such an alloy, mechanism for establishing and maintaining such pressure is essential. The construction oi a circuit breaker requires further, a current responsive element capable of holding the pressure on. the contacts and of releasing the pressure reliably when the current increases above a permissible predetermined minimum value With limited available space conditions the simplest expedient is to eliminate all motion modifying linkages in the contact actuating mechanism and to arrange the current responsive element in direct acting relation to the member for actuating the electrical contacts. Where high current carrying capacities the contacts and compactness are required the most practical current responsive element is a bimetallic thermostatic strip heated by current passing through the circuit breaker, If a "Dime-- tallic strip is used in direct acting relation to the contacts of a circuit breaker employing a minimum contact pressure alloy of well known characteristics, irictional effects resulting from the pressure applied to the contacts may be so high as to require greater power to release the pressure than is readily obtainable, or, as a result of heating a bimetallic strip within safe temperature limits such frictional eficcts may result in inaccurate response to increases of current, particularly under conditions of violent vibration in the circuit breaker,

The objects of the present invention are to avoid the difficulties above referred to and to provide a more compactly constructed electric cuit breaker capable of carrying and interrupting higher current values reliably and accurately than heretofore with the use of a bimetallic strip as a directly acting contact holding and contact pressure releasing element. Other objects are to improve generally the construction and of operation of an electrical circuit breaker and to provide a simple light weight operating nicchanism therefor which will be effective and at same time be durable under conditions oi violent vibration as well as being easily adjustable with out complicated or expensive forms of constrncw tion.

An electrical circuit breaker comprising the present invention, according to these and other objects, is provided with a bimetallic strip type current responsive tripping element to hold the circuit of the breaker closed and to release the pressure required to hold closed a pair of contacts composed of a well known alloy having a marked decrease in current carrying capacity below a predetermined minimum contact pressure and being actuated by ashiftable rectangular slide for imparting the closing pressure to the contacts, the mounting for and construction of the slide being arranged to offer inherent friction in moving the member under the pressure of the contacts whereas the holding pressure of the bimetallic element on the actuating member causes a substantially smaller increase of. friction than produced by the pressure of the contacts and may even cause a decrease in friction but not to the full amount of friction of the actuating memher in its mounting. These results are obtained in the illustrated embodiment of the invention by arranging the slide with a first arm struck out of its central portion projecting transversely of the slide for supporting the pressure of the contacts and a second arm on the slide extending in the opposite direction from the first arm and engaging the bimetallic element and an actuating button at the other end of the slide.

While this feature of the invention is particularly useful in a circuit breaker employing a. bimetallic type tripping element it may also be utilized to advantage in a circuit breaker having other types of maximum current responsive elements or even in a manually actuable device for releasing the shiftable contact closing members of a circuit breaker. Since the pressure of the contacts causes the predominant proportion of the friction between the shiftable contact closing and actuating slide and its mounting according to this feature of the invention, installations in which the circuit breaker is subject to violent vibration tend to increase the pressure on the contacts and consequently less pressure on the current responsive element is needed to keep the contacts closed. This result is obtained as a reult of minute vibratory movements between the contact actuating member and its mounting. With each minute vibratory movement the friction on the actuating member is built up while the pressure on the contacts increases. The increased friction retards the vibratory movement of the actuating member in a direction to release the built up pressure, thereby reducing the holding pressure of the actuating member on the current responsive element, which reduction in holding pressure does not cause a reduction in the amount of friction of the actuating member in its mounting to such an extent as does the increased contact pressure from vibration. Thus, the action of vibration increases the contact presure and relieves the holding pressure on the current responsive element, both of which effects are desirable.

Where a bimetallic current responsive element is employed, a convenient shape for the element is a strip formed with a simple U, one arm of the U being secured to the frame or housing for the circuit breaker and the other arm acting as a latch engaging the contact actuating member to hold it in circuit closing position. As illustrated, the arm of the bimetallic strip engaging the actuating member is toed out to form an angular surface against which the actuating member is pressed while closing the contacts to prevent substantial side thrust on the actuating member in a direction transversely of the guideway for said member from increasing the friction of the member in its mounting. From this construction and arrangement an easily operated circuit breaker is provided in which there is no danger of the contacts being moved to partially closed positions and being held in such positions by friction of the control actuating member produced by transverse thrust of the bimetallic strip on the contact actuating member before the member is properly latched by the strip. As hereinafter described, the arm of the U strip which is secured to the frame of the circuit breaker has connected with it an adjusting device accessible for manipulation outside the circuit breaker frame.

Further features and advantages of the invention will become apparent to those skilled in the art from the following description and appended claims taken in connection with the accompanying drawings, in which Fig. 1 is a sectional view of an electrical circuit breaker having a bimetallic excessive current responsive tripping strip and embodying the features of the present invention;

Fig. 2 i a viewin side elevation of a portion of the frame or casing of the circuit breaker illustrated in Fig. 1;

Fig. 3 is a perspective view of the shifting contact actuating member of the circuit breaker;

Fig. 4 is a detail view of the contact actuating member illustrating diagrammatically the distribution of forces applied to the actuating member while the contacts are being held closed by the bimetallic strip, and

Fig. 5 is a partially sectional view of a modified terminal.

The circuit breaker illustrated in the drawings is of exceptionally compact and light weight construction intended primarily for use in protecting electrical circuits of aircraft where available space is at a premium and where all moving parts are subject to violent and prolonged periods of relatively high-frequency mechanical vibration. Such vibration is particularly destructive of heavily constructed parts under conditions of minute looseness, and wear consequently is excessive. To avoid the natural effects of vibration and wear it is common practice to fit moving parts tightly together both to avoid movement of one part on another and to impose a motion retarding frictional effect on the parts. 'Iightly fitted parts, however, frequently cause erratic operation in a circuit breaker and consequent failure of other devices which must be protected against heavy current flow.

The illustrated circuit breaker comprises a hollow rectangular frame or casing in of insulated material having one end open, with mounting flanges or lugs projecting beyond the contour of the frame at the sides. All of the operating parts are inserted through the open end of the frame and are easily secured to the frame in assembled relation. After assembly a cover or face plate I2 is attached to the open end of the frame by hollow clamp bolts 14 passing through perforations in the cover and mounting lugs.

The operating parts of the circuit breaker include the contacts l6 and IS, a shiftable contact actuating member 20 having an integral insulating resetting button 22 projecting from its upper end through a loose fitting opening in the cover l2. A U-shaped bimetallic excessive current responsive strip 24 forms a latch for the actuating member 20 and a circuit opening tension spring 26 is stretched between the contact actuating member 20 and an anchor pin 21 having its ends disposed in open ended side notches in the frame, one of which notches is indicated at 28 in Fig. 1.

The contacts i6 and l 8 are composed of a highpercentage silver and refractory metal containing composition which is sintered or otherwise alloyed. This type of alloy is particularly effective in use where high current carrying capacities are desired but in order to obtain satisfactory results the contacts must be forced together by relatively heavy pressure and the pressure maintained at a high intensity.

The contact actuating member 20 is constructed in the form of a rectangular slide engaging a guideway formed by parallel ribs 30 projecting towards each other from the inner opposite side surfaces of the frame, the shifting movement of the slide being retarded by inherent friction between the engaging surfaces of the slide and guideway. For ease and simplicity of manufacture the actuating member is composed of brass plate stock to one reduced end of which the button 22 is molded and the frame and guideway 30 of suitable molded material to which a friction producing substance such as wood fiber has been added. To actuate the contacts, the contact I8 is fastened to a laterally extending arm 3| struck out of a central opening in the member 20 and the other contact I6 is mounted on a U-shaped leaf spring 32 screwed to the base of the frame l0 together with an angular terminal plate 34 provided with a screw clamp fitting projecting through a slot in the base. The leaf spring 32 is disposed inside the frame with its arms extending at substantially right angles to the guideway for the slide.

It will be noted that in general arrangement the circuit breaker is constructed in a symmetriand the bimetallic current responsive latching strip at the other side, thus enabling a central location for the button and actuating member. Also the bimetallic strip 24 is arranged with its bend adjacent to the open end of the frame where the best cooling action occurs and with its arms substantially parallel to the slide where it occupies a minimum of space. However, the minimum pressure under which the contacts will conduct current without substantial heating is so high as compared to the holding and releasing power of the bimetallic strip when heated by excessive current flow, that the circuit may not be opened promptly where the strip acts directly as a holding latch on the contact actuating member unless special provision is made for lightening the pressure on the strip. Various friction reducing expedients or pressure multiplying mechanisms have heretofore been applied to circuit breakers to avoid the necessity oi. holding the pressure on the contacts by a direct acting bimetallic strip but these mechanisms are subject to looseness, lost motion, high inertia and frequent failure from mechanical causes, particularly under conditions oi. excessive vibration. y a

In order to avoid the necessity of employing such expedients or mechanisms, according to the principal feature of the present invention, the contact actuating member 20 has been so arranged in its mounting guideway 30 that the friction in the guideway acts in a novel and advantageous manner rather than in a manner requiring increased operating forces to be applied to the actuating member for overcoming the friction. Thus, a low powered bimetallic latching strip may be employed acting directly to resist the contact opening movement of the actuating member without the interposition of other expedients.

As will be apparent from Fig. 1 of the drawings, the arm 3| of the slide member 20 on which the contact I8 is mounted, extends a substantial distance to the right from the center line of the slide portion of the member, the contact i8 being made fast to the outer end of the arm. Thus, the'force on the contact 18 under upward pressure of the contact l6 and the tension of the spring 26 exert a torque moment on the slide member tending to twist it about a transverse axis in its guideway 30. This torque moment greatly increases the friction of the slide in the guideway with each incremental increase.

of contact pressure. approaching a value of friction with sufficiently increased contact pressure where the slide will become jammed against further movement in either direction. With condi-.

tions of excessiv vibration of the actuating slide 6 parallel relation to the guideway at the side opposite the contacts, with a screw clamp fitting: projecting through the base of the frame to the outside. The other arm of the U-shaped strip which forms the latching terminal is teed out with an angle approaching 45 and engages the beveled end of a latching arm 38 bent from the lower end of the slide member 20 in a direction opposite to the arm 3|, the arrangement being such that downward movement of the slide merrr bar in closing the contacts will press the toes. out foot with substantial force downwardly rather than laterally so that the friction of the slide member in the guideway 30 will not be increased to a prohibitive point before the contacts are closed. The latching foot of the strip 24 engages the arm 38 at a position where the mechanical re sistance offered by the latching foot increases the friction of the slide member in its guideway, ai though not to the extent exerted by the pressure of the contacts. The length of the arm 38 is shorter than the arm 3i on the slide member and is engaged by the bimetallic strip closer to the center line of the slide, so that the resultant torque moment on th slide member has a sub-- stantial effect on the friction of the slide menu ber, much greater than simple lateral pressure on the slide. Also, since the resistance of the bimetallic strip is less than the pressure of the contacts, the reaction on the strip is still further reduced from that required to hold the full force of the contacts and spring 26. This arrange ment is of advantage not only in reducing the pressure on the bimetallic strip but also to aid member in its guideway, the slide tends to seek a position of equilibrium where the frictional retardation is equal the forces applied to the member. The vibrating movements of the slide member thus always increase the pressure on the contacts with a cramping or pumping action of the slide member in its guideway. .As a consequence, a relatively light holding force only is needed to retain the actuating slide member Ell in contact closing position, thus freeing the bimetallic strip for easy movement towards unlatchlng position in case of excessive current flow.

The U shaped bimetallic strip 24 has one arm fastened by a rivet straight terminal plate 36 adjustabiy secured within the frame ill in during releasing movement of the strip when heated by excessive currents.

To insure that the points of application of forces producing the torque moment on the slide member will not be modified adversely by the action of the contact operating spring 26, the lower end of the spring is connected to the arm by a lug located in line with the center of the contacts so as to add to the force on th slide member at the proper position relatively to the center line of th slide member.

The circuit through the circuit breaker is as follows: from terminal plate 34, to leaf spring 32, contacts l6 and I8, arm 3|, slide 20, arm 38. a flexible jumper 40, bimetallic strip 24 and out through the terminal plate 36. When the button is manually held in closed position it is desirable to short circuit the bimetallic strip 24 against currents which would normally cause the breaker to trip open. As a means to short circuit the strip 24 under momentary heavy current flow, the terminal plate 36 has secured to it an angular contact arm 42 to be engaged by the lower surface of slide arm 38 when the slide member is fully depressed. For similar purposes the tenninal plate 34 has a projection 44 designed to contact with the upper end of the leaf spring 32 beneath the contact l6, when the slide member is fully depressed, thus shunting oif destructive currents from the spring 32 also.

Referring now to Fig. 4, the forces applied to the contact actuating slide member 20 are represented by weighted vectors. Assuming the combined force of the contacts and of the openina spring 26 to be 15 units, this force will be offset in part by a mechanical couple each component force of which will be equal to 9 units acting on the guideway 38. Assuming a frictional coeificient of 1, the mechanical couple will produce friction requiring a pressure of 9 units which will relieve the holding resistance required to maintain the contacts together with the result that only 6 units of holding force will be required of the. bimetallic strip 24. A force of 6 units may easily be held by the strip and will not affect the releasing action of the strip adversely. When subjected to violent vibration, the momentum of the slide member and button tend to decrease the holding resistance required by the bimetallic strip further as explained above.

To adjust the position of the bimetallic strip and its releasing action. the terminal plate 36 is rigidly secured along its central portion to an enlargement in the frame by a screw 46. the head of which is exposed outside the frame, passing through the plate into a threaded opening in the Contact arm 42. Above the enlargement an exposed adjusting screw 48 passes through the end wall of the frame into a threaded opening of the terminal p ate 36. Rotation of the adjusting screw forces the rounded head of the rivet 35 against the inner wall of the frame and hows the terminal plate 38, changing the position of the bimetallic strip. Thus, the bulge formed by the rounded head of rivet 35 acts as a fulcrum about which the bimetallic strip is moved while being adjusted. Permanent adjustment is assured by soldering the screws 46 and A8 to a perforated clip 50 mounted on the outer surface of the frame beneath the heads of both the screws 46 and 48.

The releasing movement of the bimetallic strip tends to reduce the friction of the contact actuating member. This follows from the frictional force and sliding movement of the toeti out end of the strip as it rides along the arm 33 to release the contact actuating member. Although this force does not fully offset the friction of said member on its guide, it is of advantage since it assists in a rapid opening of the contacts when the releasing action once starts.

Referring to Fig. 5, the frame In and slide 20 are the same as illustrated in the other figures but the bimetallic strip indicated at 52 is formed with a larger bend at its upper end and a longer tocd out latching foot at its lower end. The angle between the latching foot and upper bent end is made more acute than that in the bimetallic strip 24. Instead ofconnecting the flexible jumper 54 beneath the bimetallic strip it i connected above the latching foot and passes through the central opening in the slide and above the arm 3 i. By this construction the bimetallic strip 52 is bent through an angle of substantially more than 360 degrees with the result that. the latching footof the strip is given an unlatching v ment which has a component in a direction to release the pressure on the foot and thus provide a more accurate response than otherwise.

To provide space for the angle of the bimetallic strip 52 when moved to unlatching position, the strip is secured to a terminal plate 56 having a rectangular perforation 58 in which the angle of the strip may be received.

The perforation 58- is formed between the securing screw 48 and the adjusting screw 48 to provide a weakened section which will bow more read y than when of solid construction. The

' on at which the bowing occurs will be uniunder all conditions. The reduction of currying capacity of the terminal plate v.tinding the perforation there is a t Zing a rivet head as a fulcrum the bimetallic strip is adjustably e perfoiation 58 is not objectionable moved with the terminal plate 56, the late 55 is formed with an angular slotted head 60 within which the strip 5-2 is confined and the head presses against the end wall of the frame ID to provide an adjusting fulcrum for the plate. Thus a, secure fastening construction with adequate bearing surface on the frame wall is provided.

The nature and scope of the invention having been pointed out and a specific embodiment having been described, what is claimed is:

1. In an electric circuit breaker, a pair of contacts, the electrical conductivity of which is effective only above a predetermined contact pressure, the combination of contact actuating means comprising a rectangular shiftable fiat metal slide for pressing the contacts together, a frame having guideways for the side edges of the slide, a first arm struck out of the center of the slide projecting transversely from the slide for support-ing the pressure of the contacts, a second arm bent from one end of the slide in the opposite direction from the first arm, a bimetallic strip engaging the second arm of the slide to hold the slide against the pressure of the contacts and to release the slide upon excessive current flow and a resetting button at the other end of the slide.

2. In an electrical circuit breaker, an insulating hollow frame, a pair of contacts in the frame, contact actuating means within the frame and a current responsive bimetallic strip in the frame acting to hold the contacts closed and to release the contacts upon excessive current flow, the combination with means for adjusting the position of the bimetallic strip comprising a terminal plate secured along its central portion to the frame with one end projecting from the frame and the other end to which the bimetallic strip is fastened supported by the inner wall of the frame and an adjusting screw pasing through the wall of the frame into threaded engagement with the terminal plate to bow the terminal plate against the frame in changing the position of the bimetallic strip.

3. In an electrical circuit breaker, an insulating hollow frame, a pair of contacts in the frame, contact actuating means within the frame and a current responsive bimetallic strip in the frame acting to hold the contacts closed and to release the contacts upon excessive current flow, the combination with means for adjusting the position of the bimetallic strip comprising a terminal plate within the frame projecting from the frame to which the bimetallic strip is fastened, an adjusting screw passing through the wall of the frame to how the terminal plate in changing the position of the bimetallic strip, means for fastening the bimetallic strip to the terminal plate and an exposed screw for rigidly securing the terminal plate within the frame, said fastening means being forced by the adjusting screw against the inner wall of the frame to cause said fastening means to act as a fulcrum about which the bimetallic strip moves while being adjusted.

4. In an electrical circuit breaker an insulating hollow frame, a pair of contacts in the frame, contact actuating means within the frame and a current responsive bimetallic strip in the frame acting to hold the contacts closed and to release the contacts upon excessive current flow, the combination with means for adjusting the position of the bimetallic strip comprising a perforated terminal plate to which the bimetallic strip is fastened within the frame and an adjusting screw passing through the wall of the frame to bow the terminal plate along the perforated portion in changing the position of the bimetallic strip, of a fastening for the bimetallic strip on the plate, an exposed screw engaging the plate for rigidly securing the plate within the frame in a position to cause the fastening to act as a fulcrum about which the bimetallic strip moves while being adjusted and a perforated soldering clip on the outer surface of the frame beneath the heads of both the securing and adjusting screws.

5. In an electrical circuit opener, an insulating frame, a contact, a leaf spring mounted in the frame for supporting the contact, an actuating slide, a second contact fastened to the slide, a

guideway for the slide in the frame and a current responsive strip engaging the slide to hold the contacts closed, the combination with means for short circuiting the bimetallic strip when the slide is depressed comprising an arm arranged to be engaged by the slide and a projection for contacting the leaf spring beneath the contact there- 6. In an electrical circuit opener, an insulating frame, a contact, a leaf spring mounted in the frame for supporting the contact, a slide having oppositely disposed laterally extending arms, a second contact on one of the arms of the slide, a guideway for the slide in the frame and a current responsive bimetallic strip engaging the other arm of the slide to hold the contacts closed, the combination with means for short circuiting the bimetallic strip when the slide is depressed comprising a contact arm arranged to be engaged by the bimetallic strip engaging arm of the slide and a projection for contacting the leaf spring beneath the contact thereon.

'7. In an electrical circuit breaker, the combination with an insulating hollow frame, a pair of contacts in the frame, contact actuating means within the frame and a current responsive bimetallic strip in the frame acting to hold the contacts closed and to release the contacts upon excessive current flow, of means for adjusting the position of the bimetallic strip comprising a terminal plate to which the bimetallic strip is fastened at one end having a perforation comprising a weakened section and an adiusting screw passing through the wall of the frame into contact with the plate adjacent to the perforation to bow the terminal plate along its weakened section in changing the position of the bimetallic strip.

8. In an electrical circuit breaker, the combination with an insulating hollow frame, a pair of contacts in the frame, contact actuating means within the frame and a current responsive bimetallic strip bent through an angle of substantially more than 360 degrees and formed with an angular latching foot to hold the contacts closed and to release the contacts upon excessive current flow, of supporting means for the strip comprising a perforated terminal plate to which the bimetallic strip is fastened at a location to cause the angle of the latching foot to enter the perforated portion of the terminal plate when the foot moves to unlatching postion.

9. In an electrical circuit breaker, the combination with an insulating hollow frame, a pair of contacts in the frame, contact actuating means within the frame and a current responsive bimetallic strip bent through an angle of substantially more than 366 degrees and formed with an angular latching foot to hold the contacts closed and to release the contacts upon excessive current flow, of supporting means for the strip comprising a perforated terminal plate to which the bimetallic strip is fastened at a location to cause the angle of the latching foot to enter the perforated portion of the terminal plate when the foot moves to unlatching position an adjusting screw passing through the Wall of the frame to bow the terminal plate along its perforated portion in changing the position of the bimetallic strip.

10. In an electrical circuit breaker, the com-- bination with an insulating hollow frame, a pair of contacts in the frame, contact actuating means within the frame and a current responsive bl metallic strip bent through an angle of substantially more than 360 degrees and formed with an angular latching foot to hold the contacts closed and to release the contacts upon excessive current flow, of supporting means for the strip comprising a perforated terminal plate to which the bimetallic strip is fastened at a location to cause the angle of the latching foot to enter the perforated portion of the terminal plate when the foot moves to unlatching position and means for providing a shunt current path about the perforated portion of the terminal plate in cluding screws passing through the frame and a clip outside the frame for conducting current between the screws.

11. In an electrical circuit breaker, a frame having a guideway, a shiftable slide in the guideway and a pair of electrical contacts actuated by the slide, in combination with a U--shaped bimetallic current responsive strip, one arm of which is secured in the frame in substantially parallel relation to the guideway and the free arm of which at the other side of the bent portion engages the slide to hold the contacts closed and a U-shaped contact supporting leaf spring mounted in the frame at the side of the slide opposite to the bimetallic strip with its bend adjacent to the slide while in contact closing position and with its arms projecting away from the slide substantially at right angles to the slide, one of said arms being secured to the frame and the other carrying one of the contacts.

12. In an electrical circuit breaker, an open ended frame having a guideway, a shiftable slide in the guideway and a pair of electrical contacts actuated by the slide, in combination with a U-shaped bimetallic current responsive strip inside the frame disposed with its bend adjacent to the open end of the frame at one side of the slide and with its arms substantially parallel to the guideway for the slide and a U-shaped leaf spring, on one of the arms of which one of the contacts is mounted and the other arm of which is secured inside the frame at the other side of the slide, said spring being disposed with its bend adjacent to the slide while in contact closing position and with its arms projecting away from the slide substantially at right angles to the slide.

13. In an electrical circuit breaker, a frame having a centrally located guideway, a shiftable slide in the guideway and a pair'of electrical contacts actuated by the slide, in combination with a pair of U-shaped members, one on each side of the slide in the frame comprising a bimetallic current responsive strip and a contact supporting leaf spring, the bimetallic strip being secured' in the frame with its arms substantially parallel to the slide and the contact spring secured in the frame with its arms substantially at right angles to the slide.

14. In an electrical circuit breaker, a pair of electrical contacts, a frame having a guideway and contact supporting means in the frame, in combination with contact actuating means com- 'prising a. rectangular substantially flat metal MORRIS B. WOOD.

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

UNITED STATES PATENTS Number Name Date 1,492,967 Donle May 6, 1924 2,150,013 Von Hoorn Mar. 7, 1939 1,704,379 Aichele Mar. 5, 1929 2,153,517 Field Apr, 4, 1939 1,743,807 Carter Jan. 14, 1930

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