US2759426A

US2759426A - Rotary pump

Info

Publication number: US2759426A
Application number: US547433A
Authority: US
Inventors: Oscar C Blomgren; Jr Oscar C Blomgren
Original assignee: Tuxco Corp
Current assignee: Tuxco Corp
Priority date: 1955-11-17
Filing date: 1955-11-17
Publication date: 1956-08-21
Anticipated expiration: 1973-08-21

Description

Aug. 21, 1956 BLOMGREN 2,759,426

ROTARY PUMP 4 Sheets-Sheet 1 Filed Nov. 17, .1955

INVENTORS OSCAR C. BLOMGREN OSCAR c. BLOMGREN, JR. av 6 0 ATT'YS Aug. 21, 1956 I QCBLOMGREN ETAL 2,759,426

ROTARY PUMP Filed Nov. 17, 1955 4 Sheefs-Sheet 2 INVENTORS. OSCAR 4C. BLOMGREN OSCAR C. BLOMGREN, JR.

Aug. 21, 1956 Q a BLOMGREN ET AL 2,759,426

ROTARY PUMP Filed Nov. 17, 1955 4 Sheets-Sheet 3 INVENTORS: a OSCAR c. BLOMGREN K) P ATT'YS OSCAR c, BLOMGREN,JR.

United States Patent '0 i ROTARY PUMP Oscar C. Blomgren and Oscar C. Blomgren, (in, Evanston, IlL, assignors to Tuxco Corporation, North Chicago, 11]., a corporation of Illinois Application November 17, 1955, Serial No. 547,433

12 Claims. (Cl. 103-42) This invention relates, in general, to rotary pumps and is particularly directed to a pump of this character having a novel design which utilizes fewer parts, is more economical to manufacture and yet, is more efficient than those heretofore known.

Heretofore, rotary pumps have been constructed with shafts supporting the liquid propulsion member, thus necessitating shaft holes in the housing, as well as bearings for the shafts. Difficulty has been incurred in manufacturing these pumps accurately because of the necessity of properly aligning the shafts, the bearings and the holes in the housing through which the shafts pass.

Since all of these parts had to be accurately machined, the chance for multiplication of small errors has been very great. inaccuracies, even though small, have caused wear on the moving parts, and particularly the propulsion members themselves. pump immediately begins to lose its efliciency thereupon requiring replacement of parts and excessive maintenance.

The rotary pump of the present invention eliminates many of the parts, such as the conventional shafts, bearings and shaft holes in the housing, thus making it unnecessary to maintain the close tolerances necessary heretofore. The elimination of these parts also enables the device to be manufactured more economically; and the pump of the present invention has been found to operate more efiiciently than those of conventional design.

It is, therefore, a principal object of the present inven tion to provide a rotary pump having a novel construction and arrangement of parts designed to overcome th disadvantages set forth above.

Another object of the invention is to provide a rotary pump wherein the liquid propulsion member thereof is mounted for rotation in thrust-torque bearings of an unconventional design.

A further object of the invention is to provide a rotary pump wherein the propulsion members have accurate alignment and lack of vibration, due to the provision of thrust-torque bearings which are supported in the bore of the pump housing and which, themselves, rotatably support the rotating propulsion members.

Still another and more specific object of the invention is to provide a rotary pump wherein each gear provides its own bearing surfaces against the housing and the end plates of the housing, thereby avoiding the necessity of using shafts, shaft holes and lubrication provisions.

A still further specific object of the invention is to provide a rotary gear pump wherein a drive gear is supported within a housing by having the hubs of the gear supported in thrust-torque bearings which are stationary, and wherein a meshing idler gear is also supported in the housing by having its hubs supported in thrust-torque bearings rotatable therewith, said bearings being supported within the bores of the housing so that the peripheries thereof become the torque bearing surfaces, and the faces thereof become the thrust bearing surfaces against the end plates on the housing.

Another object of the invention is to provide a rotary 2,759,426 Patented Aug. 21, 1956 gear pump having a drive gear and an idler gear supported in thrust-torque bearing members wherein one or more of such bearings are mounted for yieldable axial movement in response to an excessive fluid pressure, thereby relieving such pressure.

A still further and more specific object of the invention is to provide a gear pump wherein the bore of the housing within which the idler gear is supported, is counterbored at each side thereof for the depth of the thrusttorque bearing members, and each counterbore is provided with a plurality of roller bearings positioned in parallel relation with the axis of the bearing members, whereby wear on the surface of the recess is minimized, 0 completely eliminated.

The foregoing and numerous other important objects,

'ice

. advantages and inherent functions of the invention will As soon as such wear begins the become apparent as the same is more fully understood from the following description, which, taken in connection with the accompanying drawings, discloses preferred embodiments of the invention.

Referring to the drawings:

Fig. 1 is a perspective view of a rotary gear pump e bodying the present invention;

Fig. 2 is an exploded view, in perspective, of a gear pump embodying the present invention and illustrating a preferred form thereof;

Fig. 3 is an exploded perspective view of the drive and idler thrust-torque bearing members which are positioned at each side of the gears;

Fig. 4 is an enlarged, vertical sectional view through the rotary gear pump embodying the present invention;

Fig. 5 is a vertical, transverse sectional view taken along the plane of line 5-5 of Fig. 4;

Fig. 6 is a perspective view of a rotary gear pump embodying a modified form of the present invention;

Fig. 7 is an exploded perspective view illustrating the parts of a rotary gear pump embodying a modified form of the invention;

Fig. 8 is an enlarged, exploded perspective view of the thrust-torque bearing members as utilized in the modified form of the invention shown in Fig. 7;

Fig. 9 is an enlarged, vertical sectional view through the gear pump embodying the modified form of the invention shown in Fig. 7;

Fig. 10 is a vertical sectional view taken along the plane of line 10--10 of Fig. 9; and

Fig. 11 is an enlarged, fragmentary sectional view illustrating a detail of the modified form of the invention, and particularly that portion of Fig. 10 which is encircled and identified by the numeral 11.

The primary features of the present invention are the provision of a rotary pump wherein a housing is provided with an internal bore or bores to enable it to independently support bearing members at each side thereof. The liquid propulsion member or members are each provided with hubs, which hubs are received within and supported by the aforesaid bearing members. The usual fluid inlet and outlet are provided in the housing, in order that fluid may be pumped therethrough. The assembly is then completed by providing gaskets at each side of the housing together with cover plates secured thereto. The only shaft utilized in the assembly is a drive shaft which passes through one of the cover plates and is keyed to the propulsion member. Thus it becomes unnecessary to support the propulsion member or members by shafts, thereby eliminating the necessity of drilling shaft holes through the end plates.

The term thrust-torque bearing members is applied to the bearings utilized in the pump of the present invention, to designate bearings which take both thrust and torque. Thus the bearings themselves are supported'in bores within the housing and the peripheries thereof transmit the torque of the propulsion member to the housing and thus act as torque bearings. Also, the thrust of the propulsion member is transmitted through the bearings and to the cover plates on the housing so that they also act as thrust bearings; thus the term thrust-torque bearing members is utilized in the specification and claims herein to denote a bearing member which is capable of transmitting both thrust and torque from the propulsion member of the pump to the housing of the pump in its assembled condition.

The invention, in its broader aspects, is applicable to rotary pumps regardless of the specific type of liquid propulsion member utilized. For example, pumps using paddles, jet wheels, a series of blades, screws, or gears as the propulsion member, may have the thrust-torque bearing members of the present invention applied to hubs thereon and be supported in a bore or bores within the housing and thus eliminate supporting shafts and bearings and consequent expense of manufacture and maintenance.

Thus, although the drawings and description herein relate specifically to a rotary gear pump, it will be understood that this is primarily by way of example as one form of liquid propulsion member and is not intended to be limiting in any way, since the other forms above mentioned are included in the term liquid propulsion member.

Referring now, more particularly to the drawings, and especially to Figs. 1-5, inclusive, the housing of the pump is indicated by the numeral 1 and is provided with the fluid inlet and

outlet openings

2 and 3. The interior of thehousing is machined so as to provide an upper circular recess or bore 4 and a lower circular recess or bore 5, which are in communication with each other, due to the passageway 6 extending therebetween.

A drive gear 7 is positioned within the upper circular recess 4, and this drive gear is provided with hubs 8 and 9 at each side thereof. In the preferred form of the invention, these hubs 8 and 9 have a diameter substantially equal to the root diameter of the gear itself. The drive gear 7 is provided with an opening therethrough for the reception of the drive shaft 10 which is keyed to the drive gear 7 in any suitable manner. As will appear more fully hereinafter the drive gear is supported solely by the thrust-torque bearing members. The drive shaft does not act as a support but merely drives the drive gear. In the present instance, a connecting pin 11 is shown as extending radially through the drive gear 7 and into the drive shaft 10, so that rotation of the shaft will impait rotation to the drive gear 7.

An idler gear 12 is positioned for rotation within the lower circular recess in the housing and is provided with the

hubs

13 and 14 at each side thereof. These

hubs

13 and 14 are likewise of a diameter which is substaifiially equal to the root diameter of the idler gear ltse The thrust-torque bearing members for the drive gear 7 are indicated by the numeral 15 and, from Fig. 2, it will be noted that one such bearing is provided at each side of the drive gear. Reference to Fig. 3 will clarify the preferred construction of each drive gear bearing member, wherein it will be noted that the periphery thereof is circular throughout the same distance as the circular portion of the recess 4 in the housing in which it is located. The bearing is then provided with

downward projections

16 and 17, and an intermediate concave recess 18. These

projections

16 and 17 are adapted to abut the sides of the connecting passageway 6 within the housing, and thus prevent the bearings 15 from rotating. Each bearing 15 also has a central Opening therethrough for the reception of a hub 8 and 9 on the drive gear 7. It will thus be evident that when the two bearing members 15 are 'supported within the housing in the recess 4, and the hubs of the drive gear 7 are received therein, they will form independent bearing supports for the drive gear.

The bearing member positioned at each side of the idler gear 12 is indicated by the numeral 20, and is completely circular, with an opening 21 therethrough, for the reception of a hub of the idler gear. The external diameter of each bearing 20 is such that it will fit snugly within the lower circular recess 5 in the housing.

A pin 22 is provided for each bearing member 20 and is adapted to be received by an axially extending opening 23 in the bearing and a similar, aligned opening 24 in the idler gear 12. These pins may be seen more clearly in their assembled relationship by viewing Fig. 5.

Thus, the bearings 20 are fixed to the idler gear 12 so that they will rotate therewith. The bearings 15 are held against rotation, and the concave recess 13 therein has substantially the same radius as the bearings 20, so that a portion of the bearings 20 will be received thereby during rotation thereof.

The outer diameter of each of the thrust-torque bearing members 15 is substantially equal to the outer diameter of the drive gear, so that the gear teeth will have a snug fit within the recess 4, and the torque will be transmitted to the housing. The outer diameter of each of the thrust-torque bearing members 20 is substantially identical with the outer diameter of the idler gear 12, so that the teeth thereof will engage the machined internal surface of the housing, and the torque will be transmitted to the housing through the bearing member.

The material out of which these thrust-torque bearing members is made may be any suitable self-lubricating substance. One of the preferred materials is that which is commercially known as Teflon, which is a polymer of tetrafluorethylene. They may also be formed of such material as sintered bronze, molded graphite and stainless steel. If the fluid being pumped is not aqueous, then nylon is suitable.

The hub members 8 and 9 on the drive gear, and 13 and 14 on the idler gear, may be made of bronze. It is preferred that the hubs on the idler gear be made of sintered bronze containing graphite.

The pump, as thus constructed for pumping most fluids, needs no additional lubrication, and therefore, lubricating openings into the housing have not been shown.

The assembly of the pump is completed by providing a gasket 25 at one side thereof and a cover plate 26. At the opposite side of the housing there is provided a similar gasket 27 and a cover plate 28. The plate 26 is held in place and mounted at one side of the housing by means such as the screws 29, which extend through openings in the gasket 25 and are received by the housing. The cover plate 28 is likewise mounted at the opposite face of the housing by means such as the screws 30.

The plate 28 is provided with an opening 31, which extends through a threaded boss 32 formed as an integral part of the plate. Suitable packing 33 is inserted within the space between the boss 32 and the shaft 10, which is forced into sealing engagement with the shaft by a member 34 and held in place by means of the lock nut 35 and cap 36.

I It will be noted that only one shaft hole is provided and that is only to accommodate the drive shaft 10 which does not act as a bearing or support. In view of the manner of mounting the gears in the bearing membersas above described, the idler gear needs no shafts or shaft holes, whereupon all bosses to accommodate shafts and shaft bearings can be eliminated. The construction, therefore, provides important savings in materials, as well as space.

The modified form of the invention, as illustrated more particularly in Figs. 6l1 inclusive, is basically and primarily the same as that above described and illustrated in Figs. 1-5, inclusive. Figs. 6ll inclusive, however, illustrate two specific variations in structure which may be utilized under certain circumstances, if desired,

Wlllllllwwu I depending upon the use to which the pump may be put. In these figures of the drawings, similar parts have been indicated by the same numerals. The pump housing, for example, is indicated by the numeral 1 and is provided with the same fluid inlet and

outlet

2 and 3 as; described above. The interior of the housing is machined to form the recess 4 for the reception of the drive gear 7.

The lower recess or bore 5 is the same as that heretofore described, except that counterbores 37 and 33 are provided at each side of the housing of larger diameter than the bore 5, having a depth substantially equal to the thickness of the bearing members 20.

As may be more clearly seen by viewing Figs. 9 and 10, each counterbore extends through an are somewhat less than 360, and at each end terminates in a

shoulder

39 and 40 adjacent the passage 6. A plurality of roller bearings 41 are inserted into each

counterbore

37 and 38 and extend between the shoulders 39 and 4h. The purpose of these roller bearings is to reduce or eliminate wear on the interior surface of the housing, which might otherwise occur due to the inertia of the idler gear. Certain uses to which the pump might be put, depending upon the fluid flow therethrough, may cause the idler gear to wear down into the housing, resulting in looseness between the teeth of the gears. The provision of the roller bearings 41 will prevent this from occur ring and may be desirable in certain instances. Although a set of roller bearings for each thrust-torque bearing member has been illustrated, it might be desirable, in some instances, to provide only one set of roller bearings extending the full width of the housing.

The arc through which the rollers are positioned is not critical, and may extend throughout an arc of between 90 and 270.

Another feature which is particularly adapted for use as a part of the present invention, and which may be desirable under certain operating conditions, is one which is adapted to relieve an excess of fluid pressure. This feature involves a modified form of the drive gear thrust torque bearing member. The bearing member is indicated in the various figures by the numeral 42, and in general appearance and outline is similar to that heretofore described. It is provided with an internal opening 43 which is adapted to receive the hub 8 on the drive gear '7. The periphery 44 of the bearing is circular and of substantially the same diameter as the recess 4, so that it may be received therein. The bearing is also provided with the

downward extensions

45 and 46, having the concave, arcuate recess 47 therebetween to receive the periphery of the idler gear bearing member 20.

The outer face of the bearing member 42 is provided with a plurality of circumferentially spaced recesses 48, each of which is adapted to receive a small coiled C0111 pression spring 49.

The cover plate 50, has formed on the inner face thereof, a recess 51 having the same contour as the hearing member 42. When the pump is assembled, with the gasket 52 on one side of the housing 1 and the cover plate 50, the outer ends of the springs 49 will bear against the base of the recess 51. This relationship may be more clearly seen by viewing Figs. and 11.

The opposite side of the pump housing will be arranged as described above, with the drive gear bearing and the idler gear bearing in place and assembled with the gasket 27 and cover plate 28.

In the normal operation of the pump the springs 49 will urge the bearing member 42 inwardly into contact with the ends of the gear teeth on the drive gear 7, as shown in Fig. 10. Under conditions of excessive fluid pressure, the bearing 42 may be forced outwardly against the compression of the springs 49 to the position shown in Fig. 11, whereupon the fluid passing through the pump may be received by the annular passage 53 provided be- 7 tween the inner face of the bearing 42 and the ends of the gear teeth on the drive gear 7. This will relieve the excessive pressure, and when the conditions which initially created the pressure are obviated, then the springs 49 will urge the bearing 42 back to its normal position, as shown in Fig. 10. Movement of the bearing 42 is less than the depth thereof so that its sealing contact with the lower bearing member 20 will not be disturbed.

Although the modifications, including the roller bearings 41 and the axially movable bearing 42, have been illustrated as being embodied in the same construction, it will be obvious that one or the other may be utilized independently, if so desired.

If the use to which the pump is to be put makes it desirable or necessary to have lubrication, then suitable oil holes may be provided in the cover plates. For example, the cover plate 28 may have opening 54 therein, and the cover plate 50 may have an opening 55 for the attachment of suitable fixtures to apply lubrication to the gears within the housing. Rotary pumps of present known constructions, wear so rapidly that any lubricant on the inner faces of the cover plates will be washed out in a short time by the liquid being pumped. In the present construction such wash-out of the lubricant is eliminated because of the close seal between the thrusttorque bearing members and the gears, and between each other.

From the foregoing description, it will be evident that the shafts and shaft bearings of the conventional rotary gear pump have been eliminated, thus also eliminating costly manufacturing procedures which require close tolerances and perfect alignment as between such shafts and their bearings. The elimination of shaft holes in the cover plates makes it unnecessary to machine the internal surfaces thereof, thereby permitting the cover plate to be stamped from sheet stock rather than cast.

In actual practice a pump embodying the basic features of the present invention has been proven to have greater priming ability and increased gear life, even with no lubrication whatsoever. The normal service maintenance requirements of conventional rotary gear pumps have been totally eliminated. Furthermore, the packing gland problem requiring frequent tightening of the packing nut, due to wear, has also been eliminated because the packing gland used in combination with the present invention does not act as an auxiliary hearing as it has heretofore. In fact, the Wear characteristics of all moving parts are greatly improved with the present construction.

In many instances pumps are designed for use in multiple. That is, a plurality of propulsion members and housings are placed side by side and operated in tandem. With the present invention this can be accomplished in much less space, with less weight, and requiring less driving power than has been possible heretofore with other pump constructions presently known, because a plurality of housings and propulsion members therein can be placed side by side between two cover plates and bolted together.

It is thought that the invention and its numerous attendant advantages will be fully understood from the foregoing description, and it is obvious that numerous changes may be made in the form, construction and arrangement of the several parts without departing from the spirit and scope of the invention, or sacrificing any of its attendant advantages, the forms herein disclosed being preferred embodiments for the purpose of illustrating the invention.

The invention is hereby claimed as follows:

1. In a rotary pump, a housing, fluid inlet and outlet openings in the walls of said housing, intersecting parallel bores through said housing, a drive gear in one of said bores and an idler gear in the other of said bores in mesh with said drive gear, a non-rotatable annular thrust-torque bearing member at each side of said drive gear and supported by said one bore, an annular shoulder fixed to said bearing members, a drive shaft on which said drive gear mounted for rotation therewith, an annular bearing member at each side of said idler gear and supported by the walls of said other bore, an annular shoulder fixed to said idler gear on each side thereof and received by said last named bearing members, whereby said last named bearing members provide the sole support for said idler gear, and means for fixing said last named bearing members to said idler gear for rotation therewith.

2. The combination of elements defined in claim 1 combined with closure members at the sides of said housing against which said bearing members abut, whereby the peripheries of said bearing members become torque bearing surfaces, and the outer faces thereof become thrust bearing surfaces. 3. The combination of elements defined in claim 1, combined with yieldable means normally urging at least one of said non-rotatable bearing members against the adjacent face of the drive gear, whereby excessive pressure within the pump will move said bearing member in an axial direction away from the drive gear against the pressure exerted by said yieldable means, thereby to relieve such excessive pressure.

4. In a rotary pump, a housing, fluid inlet and outlet openings in the walls of said housing, intersecting parallel bores through said housing, a drive gear in one of said bores and an idler gear in the other of said bores in mesh with said drive gear, a non-rotatable annular thrusttorque bearing member at each side of said drive gear and supported by said one bore, the outer diameter of each said bearing member being substantially equal to the outer diameter of said drive gear, an annular shoulder fixed to said drive gear on each side thereof and received by said bearing members, a drive shaft on which said drive gear is mounted for rotation therewith, an annular bearing member at each side of said idler gear and supported by the walls of said other bore, the outer diameter of said last named bearing members being substantially equal to the outer diameter of said idler gear, an annular shoulder fixed to said idler gear on each side thereof. and received by said last named bearing members, whereby said last named bearing members provide the sole support for said idler gear, and means for fixing said last named bearing members to said idler gear for rotation therewith.

5. In a rotary pump, a housing, fluid inlet and outlet openings, in the walls of said housing, intersecting parallel bores through said housing, a drive gear in one of said bores and an idler gear in the other of said bores in mesh with said drive gear, a non-rotatable annular thrust-torque bearing member at each side of said drive gear and supported by said one bore, an annular shoulder fixed to said drive gear on each side thereof and received by said bearing members, the diameter of each said shoulder being substantially equal to the root diameter of said drive gear, a drive shaft on which said drive gear is mounted for rotation therewith, an annular bearing member at each side of said idler gear and supported by the walls of said other bore, an annular shoulder fixed to said idler gear on each side thereof and received by said last named bearing members, whereby said last named bearing members provide the sole support for said idler gear, the diameter of the shoulders on said idler gear being substantially equal to the root diameter of said idler gear, and means for fixing said last named bearing members to said idler gear for rotation therewith.

6. In a rotary pump, a housing, fluid inlet and outlet openings in the walls of said housing, intersecting parallel bores through said housing, a drive gear in one of said bores and an idler gear in the other of saidbores in mesh with said drive gear, a non-rotatable annular thrusttorque bearing member at each side of said drive gear and supported by said one bore, the outer diameter of each said bearing member being substantially equal to the outer diameter of said drive gear, an annular shoulder fixed to said drive gear on each side thereof and received u by said bearing members, the diameter of each said shoulder being substantially equal to the root diameter of said drive gear, a drive shaft on which said drive gear is mounted for rotation therewith, an annular bearing member at each side of said idler gear and supported by the Walls of said other bore, the outer diameter of said last named bearing members being substantially equal to the outer diameter of said idler gear, an annular shoulder fixed to said idler gear on each side thereof and received by said last named bearing members, whereby said last named bearing members provide the sole support for said idler gear, the diameter of the shoulders on said idler gear being substantially equal to the root diameter of said idler gear, and means for fixing said last named bearing members to said idler gear for rotation therewith.

7. The combination of elements defined in claim 6, wherein said last named means includes axially extending pins through said last named bearing members and said idler gear.

8. The combination of elements defined in claim 6, combined with closure members at the sides of said housing against which said bearing members abut, whereby the peripheries of said bearing members become torque bearing surfaces, and the outer faces thereof become thrust bearing surfaces.

9. In a rotary pump, a housing, a fluid inlet and outlet openings in the walls of said housing, intersecting parallel bores through said housing, a drive gear in one of said bores and an idler gear in the other of said bores in mesh with said drive gear, a non-rotatable annular thrust-torque bearing member at each side of said drive gear and supported by said one bore, an annular shoulder fixed to said drive gear on each side thereof and received by said bearing members, a drive shaft on which said drive gear is mounted for rotation therewith, an annular bearing member at each side of said idler gear and supported by the Walls of said other bore, an annular shoulder fixed to said idler gear on each side thereof and. received by said last named bearing members, whereby said last named bearing members provide the sole support for said idler gear, and axially extending pins through said last named bearing members and said idler gear, whereby said last named bearing members and said idler gear will rotate together.

10. I a rotary pump, a housing, fluid inlet and outlet openings in the walls of said housing, intersecting parallel bores through said housing, a drive gear in one of said bores and an idler gear in the other of said bores in mesh with said drive gear, a non-rotatable annular thrusttorque bearing member at each side of said drive gear and supported by said one bore, an annular shoulder fixed to said drive gear on each side thereof and received by said bearing members, a drive shaft on which said drive gear is mounted for rotation therewith, a counterbore at each side of said other bore, a plurality of roller bearing members in each said counter-bore, an annular bearing member at each side of said idler gear and supported on said roller bearing members, an annular shoulder fixed to said idler gear on each side thereof and received by said last named annular bearing members, whereby said last named annular bearing members provide the sole support for said idler gear, and means for fixing said last named bearing members to said idler gear for rotation therewith.

11. The combination of elements defined in claim 10, combined with yieldable means normally urging at least one of said non-rotatable bearing members against the adjacent face of the drive gear, whereby excessive pressure within the pump will move said bearing member in an axial direction away from the drive gear against the pressure exerted by said yieldable means, thereby to relieve such excessive pressure.

12. The combination of elements defined in claim 10, wherein the outer diameter of each said non-rotatable bearing members is substantially equal to the outer diam- References Cited in the file of this patent UNITED STATES PATENTS 638,853 Snyder Dec. 12, 1899 10 Egersdorfer Apr. 26, 1927 Edwards Sept. 19, 1933 Ungar Apr. 1, 1941 Ungar May 18, 1943 Tucker May 9, 1944 Maisch Nov. 25, 1952