US2662483A - Rotary vane pump - Google Patents

Description

Dec. 15, 1953 F, E SMITH ETAL 2,662,483

ROTARY VANE PUMP Filed Sept. 25, 1948 2 Sheets-Sheet l fo/222 zaza/ay Dec. 15, 1953 F. E. SMITH Erm. 2,662,483

ROTARY VANEI PUMP Filed Sepc. 25, 1948 2 Sheets-Sheet 2 Hal-5,5

Patented Dec. 15, 1953 Frederick E. Smith, Cleveland Murray, Macedonia, Thompson Products, Inca corporation of Ohio Heights, and John Ohio, `assignors to gClevelaiflul,` Ohio, a

Application September 25, 1948, Serial No. 51,172 9 Claims.` (Cl. 10S-136) This `invention relates to improvements in the construction of rotary Vane type pumps, and particularly to an economically manufacturable rotary vane pump capableoi not only quieter I'but also longer operation Ibefore.replacement of the Wearable components of the pump is required.

A `feature of this invention is the construction o'f a rotary vane pump in such manner that the vane-carrying rotor is supported in cantilever fashion within a pump casing. The slots in whichV the@ rotor Vanes are mounted project throughv the axial end face of the rotor and hence permit the vanesv to be mounted Hush with such axial end face. Inletand outlet ports are then provided in v'an` end wall for the casing immediately adjacentl to theaioresaid end face of the rotor and a thrust plate of antifriction material is interposed Ibetween vthev end face of the rotor andthe aforestated ported end wall for the casing. Such thrust plate not only provides bearing support for the rotor and rotor vane elements, but is apertured or recessed to pro.- vide fluid communication Abetween the rotor varies and the -inlet and outlet ports in the casing end wall. The thrust lplate is further ap ertured to -Ibypass aportion of the discharge fluid pressure generated by ther pump to the center of the rotor wherein the bypassed 'fluid `is effective to urge-the rotor vanes outwardly into snug engagement with the pumpingl chamber.

Stil-l another featureof thisinvention is the initial shaping or preforming of the tips ofthe blades of vanes of Aa rotary vanenpump in such manner that lsuch' tipsv initially have a coni-iguration conforming to' the tip configuration eventually achieved by a worn blade. In particular, the initial tip configuration ofthe vane peripheralv wall of the is such as toprovide a large surface engagement of the t-ip of the vane with that l portion of the kannular pumping chamber wall in the vicinity o'f the? inlet port, and at all other portions `of the-pumping chamber wall, lesser area contact is maintained, approaching aline con-4 tact. Such .construction permits the pump to #be initially operated at its maximum eliciency and `not only-'makes the pump-substantially quieter in its initial operation but ,results in `a substantially longer life of the wearable components Vof the pump due to elimination ofall possibility of scouring the annular pumping chamber wall by the limited area fr1ctional contact therewith suiered by Vanes tional tip configuration.

'Still another feature of this invention is the provision of an improved cheek valve arrangement for automatically-bypassing a portion of the discharge fluid into the inlet of the pump when the discharge pressure exceeds a' predetermined maximum. Furthermore, the construction of this invention permits convenient adjustment of the pump discharge pressure by adjustment of the spring` the check valve.

Accordingly, it is an object of this invention to provide an improved rotary vane pump eonstruction characterizedhy the unusual simplicity of manufacture and assembly of its compo nents, quieter operation, and longer life of the wearing parts of the pump than has heretofore been possible of attainment.

A particular object of this invention is the provision of a rotary vane pump construction wherein a thrust plate of antifriction material is interposed between an axial end face of a varied rotor and a ported endewall or cover for the pump casing, and wherein such thrust plate not only defines apertures providing communication between the inlet and discharge ports and the varied portion of the pump rotor, but also deiines a uid `passage for bleedinga portion ofthe discharge fluid` pressure into the central portion of the rotor slots in which the vanes are mounted, thus urging `the vanes outwardly into snug engagement with thevannular wall of the pumping chamber.

Still another'Y object ofthis invention is the provision of a simplied adjustable bias check valve `arrangement for effecting control of the discharge pressure of a-pump by selective bypassing of a portion of the fluid from the discharge side of the pump to the inlet side ofthe pump.

The specic nature of the invention as wellfas other `objects and advantages thereof will become apparent to those skilled-inl the art from the `:following detailed. description of the annexed sheets of drawings which, by way of preferred example only, illustrate one specic embodiment of the invention.

On the drawings:

Figure-l is a .front end elevational view of. an asssembled rotary vane pump vunit embodying this invention.

Figure 2 lis a sectional view taken along the plane II-II of Fig. 1.

Figure l3 is a sectional 4view `taken along.- ythe plane III- III of Fig. 2.

Figure 4 is an elevational View,

Partly ,in section, of the rear endpf the pump with the end cap removed from the vane casing.

VFigure 5is a greatly enlarged scale, side elevaacca-118e a tional view of a vane or blade element of a pump construction in accordance with this invention.

As shown on the drawings:

The major elements of the pump are assembled within a generally cup-shaped metallic casing II) which denes a large cylindrical chamber IOa. The base portion Ib of the casing I is centrally apertured, as indicated at Ic, to accommodate a conventional uid sealing unit I2 for journaling the shaft portion IIe of a rotor II. The unit I2 includes an inner ring in sealing engagement with an end face or shoulder between the rotor portions IIb and IIc. An outer casing of the seal I2 seats tightly in the bore IGC. At spaced intervals around its periphery, casing I0 is provided with projecting ears or lugs wel which are apertured as at Ille to permit the convenient mounting of the pump on a panel or similar supporting surface.

An outturned radial flange I0 f is formed at the mouth of the casing IE) and an end cap I3 is bolted to the flange If to enclose the chamber a. A plurality of bolts I4 are employed for this purpose and a gasket I5 is interposed between the planar end face i3d of end cap I3 and the flange If of casing I.

Within the chamber Illa, a sleeve type bearing I6, which is preferably formed of molded graphitic material, is snugly inserted, seating against the bottom wall Ib of the casing I0. An annular liner I1 of suitable non-corrosive metallic material is then mounted in the chamber Illa, abutting against the axial end face of the sleeve bearing I5. Liner I'I is provided with a pump bore Ila of desired contour, the axis of which is eccentrically disposed with respect to the axis of cylindrical chamber Illa. The bore IIa thus defines a pumping chamber for a rotary vane pump in conventional fashion.

The rotor II constitutes a unitary, cylindrical Imember having an enlarged head portion I Ia disposed within the pumping chamber bore I'Ia, an intermediate diameter bearing portion I Ib which is journaled in the bore IEa of bearing sleeve I6, `and a reduced diameter shaft portion IIc which, as has already been mentioned, projects out of casing I0 through a sealing unit' I2. The project- =ing end of rotor II is connected to a suitable driver (not shown).

Since the rotor I I is journalled in only a single bearing sleeve I6 located on only one side of the `pumping chamber Ila, the rotor II is of the cantilever type with the impeller or vane components being located on the projecting head portion IIa of the cantilever type rotor II.

The head portion Ila has a plurality of circumferentially spaced slots, here shown as two slots IId disposed at 90 with respect to each other, milled entirely through said head portion and opening both in the axial end face of the rotor head portion and in the peripheral wall surface. Shiftable vanes or blades I8 are then mounted in the slots I Id. Such vanes are of sufcient axial length so as to have their axial end faces I8a disposed substantially flush with the axial end face of the rotor. Two of such blades or vanes I8 are mounted in each of the slots IId and the inner end portion of each of the blades I8 is reduced in Width as indicated at Ib so that such may be assembled in overlapping relationship n the intersecting rotor slots IId without interference.

The radial length of the blades I8 is such as to insure that such blades will contact the eccentrically disposed peripheral wall of the pumping chamber bore I'Ia. The outer tips I8c of th blades I8 are shaped in a peculiar fashion as will be described in more detail later.

As best shown in Fig. 3, the end cap I3 defines a pair of spaced passages I3b and I3c which at one end open in the planar end face i3a of the end cap I3 to function as inlet and outlet ports I3d and I3e respectively (Figure 3) for the pumping chamber I'Ia, and at their other ends connect with threaded counterbores I3f and I3g, which respectively receive threaded nipples I9 for effecting the connection of the pump in a fluid system in conventional fashion.

In accordance with this invention, a thrust plate 20 of disk-like configuration is mounted intermediate the outer axial end face of liner I1 and the planar end face I3a of the end cap I3. Such thrust plate is preferably formed of antifriction material which, for example, may comprise molded graphite. As best shown in Fig. 4, the thrust plate 20 has segmental portions of the periphery cut away or apertured as indicated at 20a and 20h to respectively provide fluid communication to the inlet and outlet ports I3d and I3e in planar end face I3a of the end cap I3. In this manner, the inlet and discharge ports are placed in communication with annularly spaced regions of the vaned head portion I Ia of the rotor II. Because of the fact that the thrust plate 20 is formed of anti-friction material, only a few ten thousandths of an inch clearance relationship with axial end face I Ie of the rotor is necessary, thus minimizing fluid leakage along such end face while at the saine time maintaining the frictional resistance to the rotation of the rotor at a minimum. Thrust plate 20 not only provides anti-friction thrust bearing support for the rotor II against axial displacement, but also provides antifriction guide surfaces for guiding the radial movements of the vanes I8 within the rotor slots IId.

In accordance with this invention, the thrust plate 2i) may be further provided with a central hole 20c which communicates with the center of the intersecting rotor slots IId. Furthermore, a radially extending passage '20d is then formed in thrust plate 20 providing fluid communication between the center hole 20c and the discharge port I3e of the pump. With this arrangement, a portion of the pressured fluid is withdrawn from the discharge side of the pump and applied to the radially inward faces of the vanes I8. Since the vanes I8' are snugly mounted within the rotor slots IId, such pressure is effective in maintaining an outward bias upon the blades I8, such tending to maintain the tip ends of the blades in snug engagement with the peripheral wall of the pumping chamber.

To retain the liner I1, and hence the eccentric pumping chamber bore Ila in proper angular relationship with respect to the inlet and outlet ports, an axially extending pin 2I is provided which passes through suitable aligned holes in the liner I1, thrust plate 20, gasket I5 and the outer end thereof projects into a recess I3h formed in the planar end face of the end cap I3. Hence, once the end cap I3 is assembled to the pump, the liner is maintained in fixed angular relationship with respect to the inlet and discharge ports.

As will be recognized by those skilled in the art, since the pumping vanes or blades I8 are being rotated about an axis which is eccentric with respect to the pumping chamber bore IIa, it is not possible to provide any form of arcuate surface which will achieve a large area rsur-face engagement with all portions of the Apumping chamber bore Ilotl as the particular blade rotates therearound. In rotary vane pump constructions heretofore known it 'has been customary to round olf the-tp ends of the blades It prior to the initial assemblage of thel pump and to use'materials'which are not supposed to Wear. However, no known material will resist Wear Idur-ing severe pumping conditions and predesigned rounded contours cannot be maintained.-

InA accordance with this invention, the tip ends of the'blades i8 are preferably preformed to a conguration closely resembling that attained by the blade tips intheir worn condition, i. e., after substantial operation in the pump. Since the discharge vpressure is continuously maintained against the inner faces of the blades i8, irrespectiveof the angular position of the blades, it followsY that the region of greatest blade tip pressure against the pump'chamber bore exists adjacent the inlet port of the pump, for in this regionthevfull pressure diiferential between the inlet and discharge sides of the pump is effective to urge the blades IS radially outwardly into engagement with the pumping chamber bore. all other angular positions 0f any particular blade I8 in the pumping chamber bore, less radial pressure is maintained on the blades, due to the fact that aninwardly dir sure is produced upon the blade tips.

We have observed that the tip configuration ci a worn blade invariably includes substantially cylindrical segment surface coniiguration extending from the trailing edge of the blade toward and past the mid-region of the blade. `Such configuration is indicated at |88 in the enlarged scale view of the blade i8 shown in Figure Furthermore, the curvature of this cylindrical segmental surface portion Isc. substantially con- ,W

formsv to the curvature of the-pumping bore surface Ila in the vicinity of the inlet port. Thisnaturally follows from the fact that the same region produces the greatest radial pressure between the blade tip and the pumping cham-berA bore. As a result, in conventional ro.-

tary vane pump constructions wherein the conguration of the blade tip was `merely rounded olf withl a radius having geometric relation with other dimensions of the vanos, rotor and pump chamber, the initial operation of the pump would produce an excessive wear or such blade tip portions until they achieved a connguraticn 'ap-- proaching that shown in Figure 5. Such rapid Wear-'was due to the fact that substantially only line contact was being maintained between the blade tip-'and the pumping bore surface. Hence, the conventional pumps have not only been sluggish and inefficient in their initial operation until wear-in of the blade tips is. accomplished, but they have been substantially noisier in initial operation.

Accordingly, as indicated above, this invention contemplates that the tip surfaces of the blades iS'will be preformed to a configuration substantially resembling the coniguration assumed by pumpfblades after a break-in period of operation oi?V the pump. A suitable configuration, illustrated in Figure 5 of the drawings, includes a cylindrical segment surface portion ite which extends from the trailing edge of the blade toward and past the mid-region of the blade. In addition, a planar, chordal surface ilf is formed on the blade tipl extending from the leading edge of the blade toward the mid-region of the blade but intersecting the cylindricalsegment surface cted component of presi l8f-on the leading side of the mid-region of the blade. If desired, the surface if can. be curved, since it corresponds tothe original contour of a conventional blade.

The radius of curvature of the cylindrical segmental surface portion iBe of the blade tip` is selected so as to substantially conform to the curvature of the eccentric pumping chamber bore surface Ila in the region of the inlet port. This, ofcourse, does not mean that the. radius of curvature of cylindrical segment surface IlleY is swung about the axis of rotor il, for it must behremembered that the axis of rotation of the blades lil'is substantially offset from the axis of the pumping chamber bore surface Ila.

When the blades I3 are formed of an antifriction material such as a molded graphite product, and the described tip coniiguration is applied to such blades, it has been found that the pump will immediately achieve substantially its maximum operating efficiency and will not only be much quieter in operation, but will opei'ate for longer periods of time with` less weai of the blades I8 and the pumping chamber bore surface Ila than conventional constructions. The eliminationof the necessity for wearing in the proper bladetip configuration obviously eliminates all possibility of scratching or gouging the pumping chamber bore surface llc during the initial operation of the pump.

A still further desirable feature of the pump embodying this invention is the incorporation of an adjustably biased check valve to permit the selective control of the discharge pressure of the pump. As best shown in Fig. 3, the end cap I3 has `a transverse hole ISIC formed therein which is in direct communication between the passages lh and itc connecting with the inlet and discharge ports i3d and lite respectively. A larger diameter hole iim, which, in elfect, constitutes a counterbore of the hole i is drilled into the end cap l@ from the side adjacent the inlet passage ISb. This counterbore portion ISm is threaded to receive a bolt-like adjusting member 22. The inner end of adjusting member 22 has an integral rod-like extension 22a thereon which mounts one end of a valve spring 23'. At the other end of spring 2t, -a valve element 2d is mounted. Valve element E!! is of bolt-like conliguration and has a head portion 2daarranged to overlie the hole l3k, and an integral shank portion 2li-b which is snugly inserted within the end coils of spring 23.

With the described arrangement, the valve 24 is obviously maintained in spring-pressed closed engagement with the hole itk, but the bias of spring 23 is opposed by the iiuid pressure existingk in the discharge passage idc. Whenever the discharge iiuid pressure exceeds the bias of spring 23, the valve Zit will be moved oil? its seat and suilcient fluid permitted to bleed from the discharge to the inlet side of theA pump so as to maintain the discharge pressure below a predetermined maximum.

The adjusting member 22 may obviously vary the effective bias of the spring 23, hence the elfective discharge pressure of the pump, by rotation of such member in the threaded counterbore I3m. A lock nut 25 and a cap nut 25' are mounted on the projecting portion of the adjusting member 22 to permit such member to be locked to the end cap i3 in any selected adjusted position. Gaskets are placed between the nuts 2li` and 2iv and between the cap i3 and nut. 25;

While not limited thereto, we have found it tures of construction and operation. Each of the components of the pump is readily manufacturable and the pump may be assembled without requiring any special tools or skill. The performance of the pump is maintained more uniform throughout its entire useful life and the useful life of the wearing parts of the pump is substantially improved. Furthermore, the pump embodies conveniently adjustable means for regulating the discharge pressure of the pump to suit varying application.

It will, of course, be understood that various details of construction may be modified through a wide range without departing from the principles of this invention and it is, therefore, not the purpose to limit the patent granted hereon otherwise than necessitated by the scope of the appended claims.

We claim as our invention:

l. A rotary vane pump comprising a hollow casing defining a chamber having a substantially planar end Wall, said casing having inlet and outlet ports opening in said end wall, means defining a pumping chamber within said chamber and adjacent to said end wall, a rotor shaft having radial vane slots therethrough opening in both the peripheral surface and one end face of said rotor shaft, a bearing in said casing spaced from said chamber and journaling said rotor shaft as a cantilever for rotation in said chamber with said slotted portion disposed in said pumping chamber and said one end face of said rotor shaft opposed and parallel to said chamber end wall, vanes in said vane slots cooperating with said pumping chamber, and a thrust plate of antifriction material disposed intermediate said one end face and said chamber end wall, said thrust plate having apertures therethrough respectively aligned with said inlet and outlet ports.

2. A rotary vane pump comprising a hollow casing defining a cylindrical chamber having a substantially planar end wall, said casing having inlet and outlet ports opening in said end wall, a liner mounted in said chamber and defining an eccentrically disposed pumping chamber adjacent to said end Wall, a rotor shaft having a planar end face and having radial vane slots therein opening in both the peripheral surface and said planar end face, a bearing in said casing spaced from said chamber and journaling said rotor shaft as a cantilever for rotation in said chamber with Said slotted portion disposed in said pumping chamber and said planar end face of said rotor shaft opposed and parallel to said chamber end wall, vanes radially shiftable in said vane slots and cooperating with said pumping chamber, and a thrust plate of antifriction material disposed intermediate said planar end face and said chamber end wall, said thrust plate having apertures therethrough respectively aligned with said inlet and outlet ports, said thrust plate also defining a fluid passage communicating between said outlet port and the bottom surfaces of said vanes, whereby pump outlet pressure is applied to said vanes to urge said vanes radially outwardly into engagement with said liner.

3. A rotary vane pump comprising a hollow casing defining a cylindrical chamber having a substantially planar end wall, said casing having inlet and outlet ports opening in said end wall, a liner mounted in said chamber and defining an eccentrically disposed pumping chamber adjacent to said end wall, a rotor having radial vane slots therein opening in both the peripheral surface and one end face of said rotor, means journaling the other end of said rotor in said casing for rotation in said chamber with said slotted portion disposed in said pumping chamber and said one end face of said rotor opposed and parallel to said chamber end wall, vanes radially shiftable in said vane slots and cooperating with said pumping chamber, and a thrust plate of antifriction material disposed intermediate said one rotor end face and said chamber end wall, said thrust plate having apertures therethrough respectively aligned with said inlet and outlet ports, said thrust plate also having a central hole communicating with said rotor vane slots and a radial hole communicating between said central hole and said aperture which is aligned with said discharge port, whereby pump outlet pressure is applied to said vane through said thrust plate to urge said vanes radially outwardly.

4. A rotary vane pump comprising a hollow casing defining a cylindrical chamber having a substantially planar end wall, said casing having iniet and outlet ports opening in said end wall, a liner mounted in said chamber and defining an eccentrically disposed pumping chamber adjacent to said end wall, a rotor having radial vane slots therein opening in both the peripheral surface and one end face of said rotor, means journaling the other end of said rotor in said casing for rotation in said chamber with said slotted portion disposed in said pumping chamber and said one end face of said rotor opposed and parallel to said chamber end Wall, vanes radially shiftable' in said vane slots and cooperating with said pumping chmber, and a thrust plate of antifriction material disposed intermediate said one rotor end face and said chamber end Wall, Said thrust plate having apertures therethrough respectively aligned with said inlet and outlet ports, said thrust plate also defining a fluid passage communicating between said outlet port and the bottom surfaces of said vanes, whereby pump outlet pressure is applied to said vanes to urge said vanes radially outwardly, each of said vanes having a tip surface comprising a cylindrical segment surface extending from the trailing edge of the vane to a mid region thereof, and a planar chordal surface extending from said mid region to the leading edge of the blade, said cylindrical segment surface having a curvature selected to substantially correspond to the curvature of the annular pumping wall in the vicinity of the pump inlet port, whereby large area surface engagement of the blade tip is achieved in the vicinity of the inlet port.

5. In a rotary vane pump, a casing, a pumping chamber therein, a rotor extending into said pumping chamber and aligned coaxially therewith, a bearing in said casing spaced axially from said pumping chamber and journaling one end of said rotor for rotation in said pumping chamber, the innermost end of said rotor terminating in a hub portion having a planar end face, said pumping chamber having a bore providing a pumping cavity eccentrically offset relative to the axis of said pumping chamber and said rotor, a

plurality of radially aligned vanes slidably mounted in said hub portion of said rotor and arranged to be rotated in said pumping cavity with the ends thereof in engagement with said casing, and a disc of anti-friction material in said casing adchamber forming a thrust plate concurrently engaging the sides of said vanes and said planar end face of said hub portion, whereby said rotor comprises a rotatable cantilever shaft in said casing, said casing having inlet and outlet openings and said thrust plate being apertured in registry with said inlet and outlet openings and together with said casing forming an inlet and an outlet at angularly spaced portions of said vanes tion of said rotor.

6. A pump comprising a casing means having a bore therein and a pumping chamber at one end of said bore eccentrically offset relative to the axis of said bore, a shaft journaled in said a planar end face at one end in said pumping chamber, said one end shaft having radially aligned intersecting slots formed therein. a vane in each slot, said vanes being arranged to slidably engage the walls of said pumping chamber upon rotation of said shaft, and a disc-shaped thrust plate made of anti-friction material in said pumping chamber abutting said vanes and said planar end face, said thrust plate and said casing means having openings formed therein providing an inlet and an outlet for said pump at angularly spaced apart portions of said pumping chamber.

7. A pump comprising a casing means having a bore therein and a pumping chamber at one end of said bore eccentrically offset relative to the axis of said bore, a shaft journaled in said bore and having a planar end face at one end thereof in said pumping chamber, said one end of said shaft having radially aligned intersecting slots formed therein, a vane in each slot, said vanes being arranged to slidably engage the Walls of said pumping chamber upon rotation of said shaft, and a disc-shaped thrust plate made of anti-friction material in said pumping chamber abutting said vanes and said planar end face, said thrust plate and said casing means having openings formed therein providing an inlet and an outlet for said pump at angularly spaced apart portions of said plate having a passage extending from said outlet to said intersecting slots to pressure load said vanes radially outwardly.

8. A pump comprising a casing means having a bore therein and a pumping chamber at one end of said bore eccentrically offset relative to the axis of said bore, a shaft journaled in said bore and having a planar end face at one end thereof in said pumping chamber, said one end of said shaft having radially aligned intersecting slots formed therein, a vane in each slot, said vanes being arranged to slidably engage the Walls of said pumping chamber upon rotation of pumping chamber, said thrust said shaft, and a disc-shaped thrust plate made of anti-friction material in said pumping chamber abutting said vanes and said planar end face, said thrust plate and said casing means having openings providing an inlet and an outlet for said pump at angularly spaced apart portions of said pumping chamber, said thrust plate having a passage extending from said outlet to said intersecting slots to pressure load said vanes radially outwardly, each of said vanes having a segmental tip portion engaging the casing Walls of said pumping chamber and being shaped to provide a substantially cylindrical surface configuration conforming substantially to the curvature of said pumping chamber at said inlet and extending from the trailing edge toward and past the mid region of said vane.

9. In rotary vane pump, a shaft having a planar end face on one end thereof, said shaft being radially slotted at said one end, a plurality of radially aligned sliding vanes in said slotted portion of said shaft, a bearing adjacent the other end of said shaft, a casing means surrounding said shaft and supporting said bearing to journal said shaft as a rotatable cantilever rotor, said casing means providing a Dumping chamber to receive said vanes and being eccentrically offset from the axis 0f said shaft, and a plate made of anti-friction material abutting the sides of said vanes and said planar end face, said vanes each having a segmental tip portion engaging said casing means at said pumping chamber and being shaped to provide a, substantially cylindrical surface conguration extending from the trailing edge toward and past the mid region of each of said vanes, said casing means and said plate together providing an inlet and an outlet port at angularly spaced portions of said pumping chamber, said segmental tip portions each conforming substantially to the curvature of said pumping chamber in the vicinity of the inlet port.

FREDERICK E. SMITH. JOHN F. MURRAY.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 383,811 Hoyt May 29, 1888 1,580,713 Ensign Apr. 13, 1926 1,675,079 ZisCh June 26, 1928 1,743,585 Wiltse Jan. 14, 1930 1,943,561 Staley Jan. 16, 1934 2,055,296 Lane Sept. 22, 1936 2,098,652 Buckbee Nov. 9, 1937 2,255,785 Kendrick Sept. 16, 1941 2,326,803 Samiran Aug. 17, 1943 2,417,349 Colbaugh Mar. l1, 1947 2,455,303 Grate Nov. 30, 1948 2,460,047 Von Wangenheim Jan. 25, 1949 2,470,987 Johnson May 24, 1949 2,491,670 Lipman Dec. 20, 1949

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