US2909325A

US2909325A - Sprinkler head

Info

Publication number: US2909325A
Application number: US648594A
Authority: US
Inventors: Edwin J Hunter
Original assignee: Individual
Current assignee: Individual
Priority date: 1957-03-26
Filing date: 1957-03-26
Publication date: 1959-10-20
Anticipated expiration: 1976-10-20

Description

E. J. HUNTER SPRINKLER HEAD Oct. 20, 1959 2 Sheets-Shea?l l Filed March 26, 1957 INVENTOR. bn/mf d /f//vrf'e BY @wg CDA- QTTOEWEV E. J. HUNTER SPRINKLERVHEAD Oct. 20, 1959 2 Sheets-Sheet 2 Filed March 26, 1957 R O T N E V m y ZW/Af dbb/V756 BY @Q C@ MMM 77'06/1/57 United States Patent Office y 2,909,325 l Patented Qct. 20, 1959 This invention relates to sprinkler heads, more particularly to lawn sprinklers of the pop-up type and included in the objects of this invention, are:

First, to provide a sprinkler head wherein a small water turbine Wheel rotating at relatively high speed effects slow rotation of the sprinkler nozzle means by a unique wobble tube and precession drive means involving `a yminimum of moving parts, yet effecting a drastic -speed reduction between the turbine wheel and the sprinkler nozzle means.

Second, to provide 'a sprinkler head wherein a large number of relatively small jets are discharged radially :from the rotating sprinkler nozzle means, some of which are interrupted or spoiled so that the spray pattern is substantially uniform.

Third, to provide a sprinkler head which incorporates a novel sprinkler jet control means that may be predetermined to cause sprinkling of a full circle or any selected arc of a circle, such as but not limited to a three-quarter, half, or quarter circle, and wherein, irrespective of the arc, whether a full circle or less, the coverage per unit area is constant; for example, the quantity of water applied to a full circle is four times the quantity applied to a quarter circle, thus insuring uniform coverage, although an installation may require fu-ll circle and various partial circle -sprinkler heads.

Fourth, to provide a sprinkler head which has a relatively large sprinkling radius, but which has a relatively low rate of application of water so that run-olf is minimized and the capacity of the supply system is correspondingly reduced; that is, the control valves, pipe lines, and ttings servicing a series of sprinkler heads may be of minimum size, and the demand on the water supply is minimized so that installation costs and operating expenses of a sprinkler system utilizing the sprinkler head is correspondingly reduced.

Fifth, to provide a sprinkler head of the pop-up type wherein the sprinkler nozzle means includes` a novel seal operative when the sprinkler head is shut olf, to prevent drainage of residual water from the lowermost sprinkler heads of a sprinkler system, to prevent dirt getting into the sprinkler heads, and to prevent algae and lime growth which develop in the presence of water standing in a sprinkler head.

Sixth, to provide a sprinkler head of the pop-up type which is selfcleaning during the extension and retraction movements of the sprinkler nozzle means so that the sprinkler head is maintained in operative condition.

Seventh, to provide a `sprinkler head which is so designed as to provide a screen or iilter of substantial area to minimize clogging of the sprinkler head, and which is further so arranged that the sprinkler head may be quickly serviced without aggravating the danger of dirt entering the sprinkler head.

With the above and other objects in view as may appear hereinafter, reference is directed to the accompanying drawings in which: l i

Figure 1 is a side View of the sprinkler head shown in its extended position.

Figure 2 is a a side View thereof, partially in eleva-Y tion and partially in section, with the sprinkler head shown in its retracted position, the sprinkler casing and cap being shown in section.

Figures 3, 4, 5, and 6 are transverse sectional views of the sprinkler nozzle means, Figure 5 being taken through 5 5 of Figure 7 -showingga half-circle sprinkler, whereas Figures 3, 4, and 6 arecorresponding transverse sectional views showing respectively a full circle, three-quarter circle, and one-quarter circle sprinkler.

Figure 7 is an enlarged` longitudinal sectional View' through 7 7 of Figure 1, showing the sprinklerhead in its extended position. k

Figure 8 is an enlarged transverse sectional view through 8-8 of Figure 7, showing particularly the precession drive for the sprinkler nozzle.

Figure 9 is 'an enlarged fragmentary sectional View through 9--9 of Figure 8. v

Figure l() is a transverse sectional view through 10-10 of Figure 7.

Figure 1l is ya transverse sectional View through 1111 of Figure 7.

The Vsprinkler head includes a cylindrical casing 1 `having a reduced lower end which is internally screwthreaded to form a water inlet 2 arranged for connection to a water supply line.l The other or upper end of the casing is open and receives a `cap 3= having a marginal flange which iits over the casing. The casing and'cap are joined by a screwthread connection 4.

Centered in the cap 3 and extending into the casing is a tubular slide bearing 5 A riser 6 is slidable within the c-asing and is arranged to protrude from the capv 2.

The riser includes a tubular stein 7 axially slidable in the bearing 5. The llower extremity of the bearing is internally beveled and the stem is provided with a mating beveled stop shoulder 8, which seals against the end of the bearing when the riser is extended.

The lower end ofthe stem is enlarged to form a rotor housing 9 having an open lower end. A return spring 10 is interposed between the Vupper side of the rotor housing and the cap 3 to urge the stem 7 from its extended position shown in Figures 1 and 7 to its retracted position' shown vin Figure 2. The upper end of the housing is provided with an external flange 11 guided within the walls of the casing. The flange 11 is notched and the interior of the casing is provided with longitudinal ribs 12 which prevent rotation of the riser 6.

The lower end of the rotor housing 9 is closed by a rotor base 13 which forms with the interior of the housing a rotor chamber 14. A pin shaft 15 extends concentrically Within the rotor housing and journa'lled thereon is a rotor 16 having radial blades. i

The surrounding walls of the rotor housing are provided with several nozzle oriiices 17 directed tangentially toward the rotor. Water jettingl tangentially inwardly through the orifices turn the rotor 16 at relatively high speed. The rotor blades` are canted or slightly helical in a direction to produce a Islight downward force component to maintain the rotor seated on the base 13.

A cylindrical screen 18 surrounds the rotor housing 9 between the flange 11 and rotor base 13. The walls of the rotor housing are relieved behind the screen to provide ample access to the nozzle orifices 117.

Provided at the vupper axial end of the rotor V is an eccentric boss `,19 which iits into a socket 20 formed in the lower end of a wobble 'tube 21 which extends upwardly into the tubular stem 7. Above the socket 20 the wobble tube is closed by a partition. The remainder of the tube forms a flow duct 22 accessible through perforations 23 in the side walls of the" wobble tube. A cross pin Z4 extends loosely lthrough a pair ofthe perfrations. The extremities of the cross pin 24 are restrained by longitudinal grooves 25 formed within the tubular stem 7. The tube 21 is thus free to wobble or gyrate as the eccentric and rotorturn, but the Vtube cannot turn.

The upper portion of the wobble tube is reduced slightlyv kIn order to preselect the arc of a circle to be sprinkled,

the upper end of the wobble tube isnotched to expose a preselected arc of port slits, leaving a valve lip which closes the other ports. l

Thus, if a quarter-circle sprinkler is desired, the lip, designated 28, occupies three quarters of a circle, as shown in Figure 6. If a half-circle sprinkler is desired, the lip, designated 29, occupies a half-circle as shown in Figures and 7. If a three-quarter circle sprinkler is desired, the lip, designated 30 occupies one quanter of a circle, as shown in Figure 4. If the lip is omitted, a full circle -sprinkler is provided as shown in Figure 3. By preselecting the arcuate extent of fthe valve lip, any complementary arc of a circle may be sprinkled. Y

Fitted on the precession sleeve 26 below the ring of port slits 27 is a nozzle ring 31 having avfrusto-conical upper surface. Fitted over the sleeve 26 and secured thereto by a screw 32 is a nozzle cap 33.A The under side of the nozzle cap is frusto-conical to mate the nozzle ring 31, and is provided with radiating nozzle slots which form with the nozzle ring 31 radiating nozzle passages 34. The nozzle cap 33 is so secured on the sleeve 26 that the passages 34 register with the port slits 27.

Above the passage 34, the nozzle cap is provided with an upwardly directed and slightly flaring rim 35, the base end of which is equal to the external diameter of the tubular stem 7. Depending from the rim 35 in front of several of the nozzle passages 34 are rudimentary spoiler tongues 36. In the construction illustrated twelve nozzle passages and four spoiler tongues are provided. The spoiler tongues break upthe corresponding water jets and serve to produce uniform distribution of water.`

The upper end of the tubular stem 7 terminates below thevnozzle ring 31-and is provided at its upper end with a 4 small internal shoulder 37. Fitted within the'upper end portion of the stern is a precession ring 38 having an internal ilange 39 under the shoulder 37. A seal ring 40 is interposed between the ring 38 and the sleeve 26.

The lower edge of the precession ring 38 is beveled inwardly to form an annular drive lip 41. The precession sleeve 26 is provided with an external flange I42, the upper peripheral portion of which forms a drive shoulder 43 which bears against the drive lip 41.

It will be observed that the wobble tube 21 and the precession sleeve thereon tend to wobble or gyrate about an approximate point located within the internal flange 37 and seal ring `4t); that is, the common axis of the wobble `tube and precession sleeve generates an acute conical iigure of revloution about the axis of the tubular stem 7. The axis common to the wobble tube and precession sleeve forms a small acute angle with the axis ofthe tubular stem 7 and the precession ring 38 fixed therein. The plane deined by the drive shoulder 43 occupies a correspondingly small angular relation with the plane dened by Ithe drive lip 41. The shoulder and drive lip thus contact at one point which precesses around the drive shoulder and drive lip as the wobble tube is gyrated by the eccentric 1,9.

The radial distance (designated X in Figure 9) between the point of contact of the drive lip and drive shoulder and the axis of the wobble tube 21V is less Vthan the radial distance Y between this point and the axis of precession ring. Consequently, the circumference of the .4 circle described on the drive shoulder is correspondingly less than the circumference of the drive lip. Assuming no peripheral slippage between the drive shoulder and drive lip, the precession sleeve will turn relative to the wobble tube with each gyration through a small are corresponding to the differences in circumferences determined by radii X and Y. The differences in circumference are, in fact, only a few thousandths of an inch; consequently, the precession sleeve turns only a slight amount with each gyration of the wobble tube. It is feasible by this means to provide a speed reduction between the rotor and the precession sleeve of between /1 and 300/1; thus the rotor may turn at, for example, 3000 r.p.m. and cause the precession sleeve to turn between 30 and 10 r.p.m. Other speed ratios may be utilized by predetermining the ratios of the radii X and Y.

The precession ring 38 is preferably made of harder material than the precession sleeve, and the drive lip 41 may be relatively sharp, approximately 25 included angle, so as to wear` an annular groove 44 in the drive shoulder 43. This groove will have the radius X. In so wearing a groove the drive connection is improved. Although the force of the drive connection is limited, it is ample to effect rotation of the sleeve on Ithe wobble tube so that the jets of water issuing from the nozzle passages rotate accordingly.

The necessary contact pressure between the drive shoulder and drive lip is maintained by fthe upward force on the precession sleeve due to the water pressure within the wobble tube exerted against the closed end of the precession sleeve. In order to protect the drive connection between :the drive shoulder and drive lip, a seal ring 45 may be provided between the sleeve 26 and 4the riser stem 7.l

Operation of the sprinkler head is as follows:

When the sprinkler is inactive, the riser is retracted as shown in Figure 2. As was pointed out hereinbefore, the rim 35 of the nozzle cap ares slightly; furthermore, the nozzle cap is preferably formed of yieldable plastic material so that when the riser is retracted, the Irim 35 wedges into the upper end of the slide bearing 5 to seal the sprinkler head. Thus, when the sprinkler is inactive, low pressure water is prevented from seeping out of the sprinkler and dirt is excluded from entering.

When the springler is activated, water pressure acting on the area of the riser stem 7 overcomes the force of the spring, causing the riser to extend -to the position shown in Figures l and 7. During the extension of the riser, some water leaks through the side bearing 5, washing the riser stem. This also occurs during retraction of the riser. In order to minimize the possibility of sand particles wedging between the riser stern and the upper end'of the slide bearing, an annular V-groove 46 is formed at the upper end of the slide bearing which forms an annular deflecting lip. When the riser is extended, the shoulder 8 seats against the lower end of the slide bearing and stops flow of water therethrough.

As soon as the nozzle head is clear of the cap 3, water flows through the screen 18 and is jetted by the nozzle orifices 17 against the rotor 16, causing the wobble tube 21 to gyrate, and producing a slow precession of the sleeve 26. Water discharges upwardly from the rotor between the wobble tube and riser stem, then through the perforations 23 into the flow duct 22. The water then ilows radially through the port slits 27 and nozzle passages 34.

As represented in Figures 3, 4, 5, and 6, the spray pattern may be a full circle, or any predetermined part of a circle; by spoiling four of the twelve jets, sprinkling of the area adjacent the sprinkler head is assured. In fact, with the arrangement illustrated, the coverage per square foot within the sprinkling circle is remarkably uniform. Furthermore, this uniformity is not sacrificed when the sprinkler is arranged to cover a portion of a circle. By reason of the fact that the number of sprinkling jets in operation are reduced in proportion to the reduction in arc sprinkled, the coverage per square foot remains constant, Whether a quarter circle is sprinkled or a full circle is sprinkled.

Although a large number of iets are employed, they are purposely small so that the capacity ofthe sprinkler head in gallons per minute discharge is much less than is the common practice. The water lis discharged, however, at high velocit-y so that the radius of coverage, and consequently, the spacing between sprinkler heads may be at a maximum. As a consequence, the rate of coverage per square foot of area is maintained suiciently low that run-olf is greatly reduced; that is, the percentage of the water which soaks into the soil is high. By changing the angle of the nozzle passages, and by altering the size of the rotor nozzle orifices, the capacity and radius may be predetermined. The characteristics of the sprinkler head set forth above are evidenced by the following table:

When the supply of water is shut off, the spring returns the riser 6 to its retracted position. Immediately, at the start of the return movement, a small amount of water ows upwardly through the slide bearing 5 to wash the riser stem. The nozzle cap is drawn into the upper end of, and seals, the slide bearing on completion of the retraction movement.

Although a particular embodiment has been shown and described, the invention is not limited thereto but includes the constructions, combinations, and karrangements embraced in the appended claims.

I Claim:

l. A sprinkler head, comprising: a tubular stem; a ow tube mounted therein; a nozzle sleeve rotatably mounted on said flow tube and having radiating discharge nozzle elements at its upper end beyond said tubular stem communicating with said flow tube; means for positioning said ilow tube and nozzle sleeve in an axis inclined relative to the axis of said tubularstem and for gyrating said llow tube and nozzle sleeve in said inclined axis about the axis of said tubular stem; and precession drive means incorporating mating elements carried by said sleeve and stem to cause precession of said sleeve about said inclined axis of said flow tube as said iiow tube gyrates.

2. A sprinkler head as set forth in claim l, wherein: said flow tube includes means operative as said nozzle sleeve rotates thereon to close successive nozzle elements during their passage through a preselected arc of travel thereby to cause the discharge from said nozzle elements to be limited to a complementary arc.

3. A sprinkler head, comprising: a tubular stem; a flow tube mounted therein; a nozzle sleeve rotatably mounted on said ow tube and having radiating discharge nozzle elements at its upper end beyond said tubular stem communicating with said ow tube; means for positioning said dow .tube and nozzle sleeve in an axis inclined relative to the axis of said tubular stem and for gyrating said flow tube andvnozzle sleeve `in said inclined axis about the axis of said tubular stem; and axially confronting annular shoulders on said sleeve within said stem mutually engageable as said flow tube and nozzle sleeve gyrate -to describe circles of contact of different circumference thereby to cause slow precession of said nozzle sleeve relative to said tubular stem,

y4. A sprinkler head, comprising: a tubular stem; a flow tube mounted therein; a nozzle sleeve rotatably mounted on said lowtube and having radiating discharge nozzle elements at its upper eri'd beyond said tubular stem communicating with said ow tube; means for positioning said ow'tube and nozzle sleeve in an ax-is inclined relative to` the axis of said tubular stern and for gyrating said flow tube and nozzle sleeve in said inclined axis about the axis of said tubular stem; axially confronting annular shoulders on saidsleeve within said steiri mutually engageable as said flow tube and nozzle sleeve gyrate to describe circles of contact of differentl circumference thereby to` cause slow precession of said nozzle sleeve relative to said tubular stem; and valve means for limiting discharge from each of said rotating nozzle elements to a predetermined arc of travel.

`5. A sprinkler head, comprisingf a tubular stem; a ilow tube mounted therein; yieldable mounting means intermediate the ends of said ow tube restraining said flow tube against rotation about its longitudinal axis; a nozzle sleeve rotatably mounted on the upper end of said flow tube and having radiating discharge nozzle elements at its upper end beyond said tubular stem communicating with said flow tube; a water actuated turbine and eccentric drive operated thereby, said eccentric drive engageable with the lower end of said flow tube to incline said flow tube relative to said tubular stem and gyrate said inclined flow tube and nozzle sleeve thereon about the axis of said tubular stem; and precession drive means incorporating mating elements carried by said sleeve and stem to cause precession of said nozzle sleeve relative to said tubular stem. v

6. A sprinkler head comprising: a casing structure adapted to be connected to a water supply line; a tubular stem slideably mounted in said casing structure and responsive to water pressure in said housing to move to an extended position; yieldable means for retracting said stern on reduction in water pressure in said housing; a iiow tube mounted in said tubular stem; a nozzle sleeve rotatably mounted on said ilow tube and having radiating discharge nozzle elements at its upper end beyond said tubular stem communicating with said flow tube; seal means between said nozzle sleeve and stem; eccentric means engageable with said flow tube to dispose said flow tube at an axis inclined relative to the axis of said tubular stem; drive means for said eccentric means lto cause said inclined axis to generate a conical ligure of revolution about the axis of said tubular stem, thereby to cause said flow tube and nozzle sleeve thereon to gyrate; and precession drive means incorporating mating elements carried by said sleeve and stem to cause precession of said nozzle sleeve relative to said tubular stem.

7. A sprinkler head as set forth in claim 6 wherein: yieldable means restraining said flow tube against rotation, whereby said nozzle sleeve in its precession rotates thereon; said flow tube includes means operative as said nozzle sleeve rotates thereon to close successive nozzle elements during their passage through a preselected arc of travel, thereby to cause the discharge from said nozzle elements to be limited to a complementary arc.

8. A sprinkler head comprising: a casing structure adapted tolbe connected to a Water supply line; a tubular stem slideably mounted in said casing structure and responsive to water pressure in said housing to move to an extended position; yieldable means for retracting said stem on reduction in water pressure in said housing; a ilow tube mounted in said tubular stem; a nozzle sleeve rotatably mounted on said flow tube and having radiating discharge nozzle elements at its upper end beyond said tubular stern communicating with said flow tube; seal means between said nozzle sleeve and stem; drive means engageable with sa'id ow tube to cause said iiow tube and said nozzle sleeve thereon to generate a conical figure of revolution about the axis of said tubular stem; and axially confronting annular shoulders on said sleeve and within said stem mutually engageable as said ow tube and nozzle sleeve generate said conical ligure of revolution to describe circles of contact of diierent circumference thereby to cause slow precession of said sleeve about the axis of said flow tube.

9. A sprinkler head comprising: a casing structure adapted to be connected to a Water supply line; a tubular stem slideably mounted in said casing structure and responsive to water pressure in said housing to move to an extended position; yieldable means for retracting said stem on reduction in water pressure in` said housing; a flow tube mounted in said tubular stem; a nozzle sleeve rotatably mounted on said ow tube and having radiating discharge nozzle elements at its upper end beyond said tubular stem communicating with said flow tube; seal means between said nozzle sleeve and stem; a water turbine unit mounted in said casing structure and including an eccentric drive engageable with said ow tube to dispose said ow tube and nozzle sleeve at an axis inclined relative to said tubular sleeve whereby on rotation of said eccentric drive, said flow tube and nozzle sleeve gyrate to define a conical ligure of revolution about the axis of said tubular stem; and precision drive means incorporating mating elements carried by said sleeve and stem to cause slow precession of said nozzle sleeve relative to said tubular stem.

l0. A sprinkler head comprising: a casing structure adapted to be connected to a water supply line; a tubular stem slideably mounted in said casing structure and responsive to water pressure in said housing to move to an extended position; yieldable means for retracting said stem on reduction in water pressure in said housing; a turbine housing at the inner end of said stem within said casing structure and axially movable with said stem, said turbine housing having turbine nozzle ports therein forming means of communication between the interior of said casing structure and said stem; a turbine wheel mounted in said housing operable by water issuing from said nozzle ports; a rotary spray head closing the upper end of said stem; and speed reducing means interconnecting said tube and said rotary spray head. v

11. A sprinkler head as set forth in claim 10 wherein: said rotary spray head includes a yieldable seal means engageable with said casing structure as said stern is retracted to seal said casing structure against outow of low pressure water and entrance of deleterious matter.

12. In a sprinkler head, a rotary spray unit, comprising: a llow tube; a sleeve capping said ow tube and rotatably mounted thereon, said sleeve having a plurality of radially directed water discharge ports; and spoiler elements protruding into the water streams issuing from selected ports.

13. A sprinkler head comprising: a ow tube; a sleeve capping said ow tube and rotatably mounted thereon, said sleeve having a plurality of radially directed water discharge ports; spoiler elements protruding into the water streams issuing from selected ports; means for supporting said flow tube for non-rotational gyrating movement; means for gyrating said flow tube; and means for causing procession of said sleeve about said ow tube as said flow tube gyrates.

14. In a sprinkler head, a rotary spray unit, comprising: a flow tube; a sleeve capping said flow tube and rotatably mounted thereon, said sleeve having a plurality of radially directed water discharge ports; spoiler elements protruding into the water streams issuing from selected ports; said ow tube having an arcuate projection positioned to close successive discharge ports as said sleeve rotates, -whereby water tlow is shut off within an arc deiined by said projection.

15. A sprinkler, comprising: a tubular stem having a longitudinal axis and an internal precession shoulder; a

rotary nozzle means having a longitudinal axis in acute angular relation to said tubular stem axis, said nozzle means being disposed within said stern and including an external precession shouldere in angular and eccentric relation to and engageable with said internal precession shoulder, said nozzle means projecting beyond said stem and having a nozzle port; means for gyrating the longitudinal axis of said nozzle means about the axis of said tubular stem'to cause precession of said external precession shoulder relative to said internal precession shoulder and corresponding rotation of said nozzle means relative to said tubular sleeve; and means for supplying water to said nozzle port.

16. A sprinkler, comprising: a tubular stem having a longitudinal axis and an internal precession shoulder; a rotary nozzle having a longitudinal axis in acute angular ,relation to said tubular stem axis, said nozzle means being disposed within said stem and including an external precession shoulder in angular and eccentric relation to and engageable with said 'internal precession shoulder, said nozzle means projecting beyond said stem and having a nozzle port; a tubular journal for said nozzle means having a longitudinal axis coincident therewith; means for gyrating the common axis of said journal and said nozzle means about the axis of said tubular stem to cause precession of said external shoulder relative to the internal shoulder of said tubular stem; and means for supplying water through said tubular journal to said nozzle port.

17. A sprinkler, comprising: a tubular stem having a longitudinal axis and an internal precession shoulder; a rotary nozzle having a longitudinal axis in acute angular relation to said tubular stern axis, said nozzle means being disposed within said stem and including an external precession shoulder in angular and eccentric relation to and engageable with said internal precession shoulder, said nozzle means projecting beyond said stem and having a nozzle port; a tubular journal for said nozzle means having a longitudinal axis coincident therewith; a water actuated turbine and an eccentric rotated thereby, said eccentric engageable with said journal to cause gyration of the common axis of said journal and nozzle means about the axis of said stern thereby to cause relative precession of said precession shoulders; and means for supplying water to said nozzle port through said journal.

18. A sprinkler, comprising: a tubular stem having a longitudinal axis and an internal precession shoulder; a rotary nozzle means having a longitudinal axis in acute angular -relation to said tubular stem axis, saidv nozzle means being disposed within said stem and including an external precession shoulder, said nozzle means projecting beyond said stem and having a plurality of radiating nozzle ports; a tubular journal for said nozzle means and having a longitudinal axis coincident therewith, said journal having an arcuate valve extremity closing a portion of said nozzle ports; means for gyrating the common axis of said journal and nozzle means about the axis of said tubular stem to cause precession of said external shoulder relative to said internal shoulder whereby said nozzle means is caused to rotate; means for restraining said journal against rotation whereby, upon rotation of said nozzle means, said nozzle ports are covered and uncovered successively by the arcuate valve extremity of said journal; and means for supplying water through said journal and uncovered nozzle ports.

References Cited in the tile of this patent UNITED STATES PATENTS 1,753,841 Thompson Apr. 8, 1930 1,821,579 Rader Sept. l, 1931 2,639,191 Hruby May 19, 1953 2,739,839 Greener Mar. 27, 1956