US2614495A - Fuel injection system for reversible internal-combustion engines - Google Patents

Description

Oct. 21, 1952 P. E. WlENE FUEL INJECTION SYSTEM FOR REVERSIBLE INTERNAL-COMBUSTION ENGINES Filed June 24, 1946 5 Sheets-Sheet 1 P. E. WIENE 2,614,495

5 Sheets-Sheet 2 w \A m Oct. 21, 1952 FUEL INJECTION SYSTEM FOR REVERSIBLE INTERNAL-COMBUSTION ENGINES Filed June 24, 1946 .Znv 6151301 T17. Ei6=1v r Oct. 21, 1952 wlENE 2,614,495

FUEL INJECTION SYSTEM FOR REVERSIBLE INTERNAL-COMBUSTION ENGINES Filed June 24, 1946 5 Sheets-Sheet 5 5 Sheets-Sheet 4 M! b/ ////j P. E. WlENE Oct. 21, 1952 FUEL INJECTION SYSTEM FOR REVERSIBLE INTERNAL-COMBUSTION ENGINES Filed June 24, 1946 mw A M Oct. 21, 1952 P. E. WIENE 2,614,495

FUEL INJECTION SYSTEM FOR REVERSIBLE INTERNAL-COMBUSTIONENGINES Filed June 24, 1946 5 Sheets-Sheet 5 M W FIG. I5

Q C Q 0 Y Q 3 \\\\\\\\\\\\\V\\\\\\\ FIG. l8

the; e in i Patented Oct. 21, 1952 FUEL, INJECTION SYSTEM FOR REVERSIBLE INTERNAL-COMBUSTION ENGINES Poul ltmil Wieh'e, Copenhagen, Denmark Application as 24, 1946, Serial No. 679,016

In Denmark June 16, 1945 Section 1, Public Law 690, August 3, 1946 Patent expires June 16, 1965 4 Claims.

in reversible inti-nal conibiistion engines it has for the actua of the fulinlecti'dn humps tee the general ractice it r se two difie'rent ecn'roi cams, for ahead workingiand for astern working res'nectively, or the same control cam hasfben tis'ed for both direction's d f rotation, but it has then been necessary'diiringthereversing to give the control cam an angular turn in relation to the crank shaft. A

Fuei injection systems, are, ,riowev'e' also known for reversible internal combnstion engines in hich neither thefabpli'cation of, a double set of pump cams noran angnia eisp aeement of the hump 'ca'ms at the reversing needed care being taken while atpiym e single unalteiable set of pum cams that a fuel oil pump, which at ahead working supplies fuel oil to acert'ain "cyl inner or a certain combustionspa'ceor groups of such cylinders or spaces, willat 'astern working supply fuel oil to another or other cylinders or combustion spaces. i t i N I, i I V The present invention relates to such an injection system which more particularly defined is" of the kind where the communication between the various fuel oil pumps and the fuel injection valves served by the latter controlled by control member's, e. g; cocks, valves, Sl idd VaflVeS} or distributors, which at the reversing arerevefrsed or changed over in such a waythat at astern y'vorking each fuel oil pump is connected to the injection valve or val ves of another or other cylinders or combustion spaces than at ahead working. 7 U I.

The mem er driving the fuel Oil pump isin that case so constructed that at astern workin'g'it can effect injection at thenronerpoints for the partic 'ular other e'yimaei or cylinders or combustion spaces without thefu'l oil pump being reversed. A's normally the fuel oil pumps are drivenby means of control earns; the part of the pump cane-1 cam which at ahead working forms the rear side or the descent-is then so shaped that at astern working it can function as ascent.

The above mentioned cocks, waives; V slide valves, or distributors which are changed over at the reversing are in manyicase's to remain in the same position during the working of the engine for along time, viz; aslong: as the working is in the same; direction, e. g; in ajmarine engine during the whole of the time when the ship goes ahead without being manoeuvered, The

said control members areon acco int of this subjected. to stickhrgsothfit it: may happen that he c i e e v s ii sud en y j e sri espi f e a ae ians t the reversing desired thus cannot be effected.

The purpose, of the invention is to makean injection system of the said kind safe and reliable in its functioning by the said control members which are reversed at the reversing being made or mounted in such a way that one may be certain that they cannot, by sticking in the penises when the working of the engine takes pra'ce'in one and the same direction and in which they consequently do not function, prevent a reversing from being effected when such a reversing is needed. i k In accordance with this the invention is first and foremost characterized in that the said ec t'ro1 members which are changed over at the reversing arearranged for being put into a metion, which is difierent to their normal 'rn'o'tion while functioning, during the periods in which they do not function as reversing members. i

The invention may be carried into effect in the way that the said control members which are changed over'atthe reversing, which members may e. g. be constructed as slide valves meta porated in the tops of normal fuel oil pumps, are furnished wither connected with a kind of rock- I ing device by means of which the control them hers can be given a suitable motion preferablyin another direction or in another way than the one in which the control members are moved at the reversing. By means of such a rocking device, it will be possible to ascertain or to control the state of the control members at any desired time. Such control may be made at suitable intervals and especiallyat a suitable time before, manoeuvring is expected to take place. the control members do not stick, it is 'of course good, but if they should stick then there will be time for remedying this calamity by again getting the; control members operable so that they may function when the reversing is to be carried out, H

The invention can also be carried into eifect in the way thatthe said control members which are changed over at the reversing are connected with, shaped in, or form part of members; which during the working of the engine are constantly or often moved, as eg, fuel pun no pistons or contingently slide valves which distribute the fuel oil from a pump orapump pressure pipe to several injection valves. By this embodiment of the invention is attained that, without havingto be influenced by hand, the said control ine mbers are, moved constantly or frequently during the working and will thusbe prevented fromsticiring,

When the said control members are combined.

- with the rnei oil ump pistons, these may in ac.-

cordance with the invention be performed in part in a way normal per se with oblique cuttingofi edges for the determination of the length of the injection period, in part with recesses and/or bores out of regard to their functioning as the said control members which are changed over at the reversing, the pistons bein connected with or under the influence of members, by means of which they can be adjusted, in part for ordinary regulation of the injection, in part for reversing of the engine.

In accordance with a further development of the invention each of or one or more of the said control members or of the pistons in the fuel oil pumps functioning as such control members may furthermore have recesses, bores, or similar shaped parts for the control of the communication conduit, the so-called astern conduit, from the pump which during astern Working is to supply fuel oil to the injection valve which the particular control member or pump piston normally serves. This arrangement serves for avoiding the drawback as regards increased lost work of the fuel oil pumps and an irregular injection process (e. g. after-injection or so-called stealthy opening of the injection valve) which might arise when communication conduits of a greater length are used if these, While out of use, were only cut off at the end nearest the pertaining pump.

It is especially in such embodiments where long communication conduits (astern conduits) are used that the risk of accumulation of air asserts itself, which risk can be reduced or avoided, in part in a way known per se by the conduits being placed with a suitable declination, in part by utilization of the natural leakage of the slide valves for producing a constant slight oil flow through the conduits to an outlet, whereby the conduits are vented. As, however, the natural leakage Will generally be insufficient for the said purpose, there may expediently in accordance with the invention be formed slits or fine channels in the slide valves, Whereby a flow can be produced artificially to an outlet through the conduits, especially the conduits which may for a long time remain unused. The procuring of such an artificial fiow will at the same time entail that the slide valves are kept oiled to a certain degree, which may also prevent them from sticking.

The invention is illustrated on the accompanying drawing, where Fig. 1 schematically shows an injection system of the kind to which the invention refers, there being for the sake of simplicity only shown the application of the system for two cylinders in a two-stroke engine, of which besides the cylinders and the fuel oil pumps with the communication conduits is also shown the shaft with the pump cams, in side elevation,

Fig. 2 the pump cans, in end view,

Fig. 3 the pertaining crank positions,

Figs. 4, 5 and 6 in a similar way as Figs. 1, 2, and 3 an injection system of the said kind in a three-cylinder engine,

Fig. 7 likewise schematically another embodiment of a three-cylinder engine, where distribution slide valves are used,

Fig. 8 at a larger scale such a distribution slide valve with pertaining slide valve liner in longitudinal section,

Fig. 9 a section on line IX-IX in Fig. 8,

Fig. 10 part of an embodiment with a control slide valve incorporated in the top of a fuel oil pump and a rocking device for the said slide valve,

Figs. 11 and 12 sections on lines XI-XI and XII-XII respectively in Fig. 10,

Fig. 13 part of an embodiment with a fuel oil pump the piston of which is furthermore shaped as a control slide valve,

Figs. 14, 15, and 16 sections on lines XIVXIV, XV-XV, and XVIXVI respectively in Fig. 13,

Fig. 17 the surface of the piston in evolution, and

Figs. 18 and 19 likewise in evolution two other embodiments of a pump piston constructed as control slide valve.

The injection system shown schematically in Figs. 1-3 serves for in a simple way illustrating the principle of such a system by its application on two cylinders in a two-stroke engine, the cranks I and 2 of which are displaced 180 in relation to each other. A1 and A2 designate two fuel oil pumps driven by pump cams B1 and B2 respectively. The pertaining engine cylinders are designated by C1 and C2, and their injection valves are in communication each with its fuel pump through conduits L1 and L2, in which there are valves H1 and H2. Furthermore a pair of extra conduits Z1 and Z2 are mounted, the former of which connects the pump A1 with the cylinder C2, While the latter conduit connects the pump A2 with the cylinder C1. In the conduits Z1 and Z2 valves h1 and h2 respectively are fitted.

During ahead Working the valves H1 and H2 are open, while the valves h1 and h2 are closed, so that the pump A1 supplies the cylinder C1 and the pump A2 the cylinder C2. At reversing the former valves are closed while the valves hi and in are opened, so that now the pump A1 supplies the cylinder C2, while the pump A2 supplies the cylinder C1.

The shaft carrying the pump cams B1 and B2 has hereby not been adjusted by axial or rotational displacement but as it is in positive connection with the crank shaft it is only rotated in the opposite direction of before just as is the case with the crank shaft of the engine. The injection can nevertheless be effected in the proper Way, the pump cams being in the well known manner constructed so that the part of them, which at ahead Working forms the rear side or descent for one cylinder can function as ascent for another cylinder at astern working.

During the reversing there is, on the other hand, efiected a reversing or change over of the valve system H1, H2, hi, and h2. Instead of valves, cocks or slide valves may be used or contingently a single slide valve or distributor.

In the schematically shown Fig. 1, the letters C1 and C2 may alternatively-instead of two different engine cylinders-designate the top end and the bottom end, respectively, of one and the same engine cylinder of a double-acting engine.

In Figs. 4-5 is shown how the injection system may be arranged'for a three-cylinder engine, the cranks l, 2, and 3 of which are displaced in relation to each other. The designations used in Figs. 4 and 5 correspond to the designations used in Figs. 1 and 2.

During ahead working the valves H1, H2, and H3 are open, while the valves h1, h2, and he are closed, so that each of the three fuel pumps A1, A2, and A3 supply fuel oil to the nearest cylinder, C1, C2, and C2 respectively, During astern working the former valves are closed, while the latter are opened, whereby the pump A1 will be made to supply the cylinder C2, the pump A2 the cylinder C3, and the pump As the cylinder C1, viz. through the extra conduits Z1, Z2, and Z3, which these may be;

s tuate hematite-whiter the :tenewms be 'fill'e'ci eastern schaeits.

e dil'i'ifitsdfic'rs, howevet, stem the drawhhhlt t e cistern cohduit 'Z" I m: the valve h the: ump Asto theoonduit L1, whichlea'os to the cylinder wiflhmo during ehehd Working be ii comhihhieh'tioh'with the said ihjettion echduit rto the cyliiider 'ci-froih the i hei hump 1A1! h ch ci-tctimst iicewili cease crease th lost work of the fuel some and red eethe regularity of injection; 'Outof' reg-std to this there-may as n in Fig; *E'H- liififlhfid an extra valve-k3 in he-esterh cohort-it h st'the' end "or the letter farthest from: the-pdmp As; valve opens and closes iii time with the verve mend coiitrehy to the valve In esi'rhimrwey valves-lei 702 may" he'iittedete'ridscf the cistern conduits h veives kr, its, arid Ice-mew he construe-ted hhtometicei actin noh rieturn retires, end 'c'vi'd'ed' with "skirts, so that the hertoihihs "estcrh ochdoitsare wholly or partly feiie'ved wheh thev'alvesclose; 7

on "account or the faetth'atthe-three v'elves H, h, and R: are to be actuated at the s'hfhre-time they may also be substituted by a, lide valve whi" h-performs fih'funotihs of an the-valves. in the embodmeht shown in Fig.- 7 threesuch distrihiitioh 'vslresGi, G2, and G3 are mounted which substitute-the nine velves shown in Fig. 4. Each of the fuel pumps is connected with its slide valve through a discharge" conduit or, at,

and. as" respectively; and from each of the slide valves ii'ijetiofi conduits c1, c2, and crrespectiveiy lead to the pertaining engine cylinders. The slide valves fir'i' furthermore interconne ted through conduits; of which the ones leading from theslideva-ive-Gi to the s'll'devalves' G2 and G3 are designated-by or and g3 respectively;

In Fig. 8 one of the s1idev'a1tes, viz. theslide vewech is shown together wit the pertaining slidev'alvc li'nr' and the conduits eh' chenh' 1s terminating in the latter, there being besides the conduits a'i, c g2; and 03 already 1'Jrient-ir' ne'd.

shown it pair of channels M; which serve as outlet conduits. The slide v'ezive G1 has fingflshabped turnihg's 1)- ehd- E" besides two-axial i 'iued cut I csss and F situated diametrically oppos te to each other, such as a pears from Figs.

a and-9L I In the position of the slide valve shown in Fig. ii the 011 passesfr'om t e pump A1 through the Conduita1 and th tu'r'ningD to theconduit er and from thereto the-cylinder Cir, aild'thetwo other slide valves G 2 and G3 leadin a corres ond his manner the oil direct from the hi -hips Arena hate the pertaining c h ders c2 and;'C3' respec-- tively'. it; however, the slide; valve Gris dismsced to the left in Fig, 8, so that the rhiued out recess F is in line with both the cohd'uit d1 dhd the cenduit gs; the oil from the aririi mwil throoeh the milled' ont recess Fioe led to the slide v ive G2 through thecchdiiit as an from the slide veive- (is to the cylinder ('31:, vvl'iile the' oil" from the hump As will through the onduit as be led to thmilld out fecoSs'F iii the slide veiveer shown and from there through the conduit or to the cylifid'ei" Ci. cor espondingly the oil will from the iiiimp Aib'e directed to the oyll'nde'f'cs through the slide traits-Gs.

The tuhiihes or grooves E'serve for theacourhii'ldfiion of leak-oil from the ti'ifiiing' D, which leek-oil can pass away through thecohdiiit' e to the slide valve G2. correspondingly, leak -oil hint-gr tot H I v r ined-outieeess- F"'-it is-' 1e'e1 to the outlet 'Heiebvh perm-merit vehhh'g eisthe ssterh' coiri'skld ii -earths slide valve Gethioughfth' ochlid' verve eh, where-thi oujgh' the The cache, vehres, or I slide vsives mentioned above; which eretcibe-cheheed cveret'the revetsms; the ih accordance with the invention as eheedy hientienedhrieneed for bein able to they-control whetherthey stick'or'hot."

in Figs; "1'0- -12- hertore-normal fuel {comp is shown, the top" of which a slid valve; G1; has been ihcorpor'itted, the function .of'which is simil'ei to that of the-slide valve G1 in accordance with Figs; 8- 'aiid 9; but which cit reversing instead of heihedishleced in its longitudinal direction is turned around its tit; 90?; which turhihg is caused bymeahs of the ma oeuv'erihg member designated by In' this mbodifnent the slide valve may for the prevention of sticking b' moved' littl in its longitudinal direction. Normaily'it'is hel'd-fest-ih fih position shown in Fig.

10 undef'th influence of the eccentric v'ih comimdeh'th-Slid valve so the-t he-who makes- "the control can either hear the motion or' feel it.

Th6 dSighafii0nusd in Figs. 10 12 correspend 36 those usedin Fig. 8,131.18 '(idnduibm, 110W- ever, having been disl'oc'e'nseol with on account of the fact that; the 'Slid waive G1 is incorporated in the pump A1 proper. The Suction opening of the letter is designated by s; In the position of the 'slido'valve G1 showfi in Figs. 10 1-2 th 011 15 Ied ffom the pump A1 direct tb-th cylinder C91 through the milled-out recess D in the slide valve and the passage or in the liner; When the slidvalveis turned 90 from the position shown, {3H8 IOWi" part of the Slide valve cuts 013:" the communication to the passage m, but at the same time a c mmunication is through themilled out recess D opened to the pas age gs, so that the oil is led to the cylinder Ct-through the slide't'ralve G2 situated in the top of the fuel pump A: (not shown). At the some fiin'l there will through the milled-out r'css' F be established et'communicatioh between the pas:- sages gt and c1, so that the oil led from thepump A2; throughthe slide" valve Gs (not shown) to the passage Us is through the milled-out recess F 'ehd the passage or let to the oylindehcr. The passage he can as shown in Figs. 10 and 11 expediehtiy be divided and terminate ih two pieces situated diametricallyopposite to each other, so thdfi'fiofi 's'iiied load of-the slide valve is avoided;

in this empo di'rhe t shown 1h Figs. lit-1'7 the danger of" stiokihg of the slide valve member is avoided or at ahyrat oo'nsidrablyd'e'cioased bytheslid valvebeing formed in the fuel pump pistoh proper; which isc'onsta'ntly in motion dini'ri 'the worhineof the en ine. The pump isteh .and in the starting position, the suction openings S being in line with the mouths of the milled-out recesses between the, oblique edges'K, so that the pump pressure space T will constantly be in communication with the suction openingsS. If the piston is turned to one side, which corresponds to ahead working, the oil will through the milled-out recesses D be led to the passages Cm, which lead to the cylinder 01, while, when the pump piston is turned to the other-side, corresponding to astern working, the oil will be led to the passages 02, which lead to the cylinder (32. There might be only a single passage Cla and .a single passage 02, but these passages are exa communication from the pump A3 through the passage as to the cylinder C1 through a passage (31b. I

The mode of operation must be supposed to appear most clearly by viewing the evolution of the surface of the piston shown in Fig. 17, in

which the eight holes in the pump liner S, S,

cm, 02, Cla, 02, as, and Clb are drawn in their proper places in relation to the piston, when the latter is at the bottom in the starting position.

The upper milled-out recesses shown, which ccmprise the milled-out recesses between the oblique edges K and the milled-out recesses connected therewith, are constantly in communication with the pressure space T of the pump, while the two lower milled-out recesses F and F which are interconnected through the transverse bore N are cut off from the pressure space T. If the piston is turned so that the suction openings S get in line with the lines -25), the mouths of the passages Cla will get in line with the lines Zii2l, i. e. move along these lines in relation to the pump piston, if this is imagined stationary and the liner, movable up and down, so that the passages 012. are thus constantly in communication with the pressure space T. During the part of the pump stroke where the openings S are cut off, the oil will thus be pumped through the passages Cla. to the cylinder C1. At the same time the passages 02 will be cut off, as in relation to the pump piston their mouths-move along the lines 22-43, and the communication between 7 the passages on and on, will likewise be cut off, as in relation to the pump piston the mouths of these passages move along the lines 23-24. By turning the piston to the opposite side the former communications will, on the contrary, be cut off, while the latter communications are open.

The construction of the fuel pump piston shown in Figs. 13-17 entails that the piston gets a rather considerable length. This may be avoided by omission of the lower milled-out recesses, a nonreturn Valve as valve is in Fig.4: being used as a substitute for these, but it may, however, also be avoided by the piston being constructed as shown in evolution in Fig. 18 or in Fig. 19.

In Fig. 18 the placing of the four necessary holes in the pump liner S, 01, c2, and (13 are shown in the position which they take up in relation to the piston when the latter is at bottom in the starting position. The milled-out recesses to the left at the top are constantly in communication with the pressure space T of the pump, so that all the oil is pumped back to the suction passage. If the pump piston is turned tothe right in Fig. 18, which is illustrated best if all of the fourliolesqare imagined moved to the left,

the suction opening S will during part of thepump stroke be covered by the hatched surface to the left of the recess between the oblique edges K, so

that the oil is from the pressure space T forced tion opening S will during part of the pump stroke be covered by the hatched surface to the left of the milled-out recess D, for a longer or shorter time dependent on the angle of turning.

The oil will then escape through the hole 02,

which gets in line with the milled-out recess D,

and be led to the cylinder Cz. At the same time the hole as, which is in communication with the fuel pump As, will get in line with the milled-out recess F, so that the oil from the pump As can flow to the cylinder C1 through the bore N which connects the milled-out recess F with the upper milled-out recess F, in line with which the hole .31 will now be.

The milled-out recesses F and F shown in Fig. 18 need at normal astern working not be as high as the whole stroke of the pump, the pump As only working when the pump A1 approaches and has nearly reached its bottom position. Thecase may, however, be imagined that the piston in the fuel pump A1 sticks, which will then happen in the top position, and in that case the pump A: will not be able to get rid of its oil unless it is provided with a safety valve. Furthermore the height of the milled-out recessD' corresponds only to the effective pump stroke. The embodiment in accordance with Fig. 18 furthermore has the drawback that the pump piston is not balanced, as the large unsymmetrical milled-out recesses will produce a side thrust on thepiston,

' so that the latter and the pump liner aresubjected to an increased wear. In practice a construction will therefore be preferred which requires a somewhat greater building length, e. g. as indicated by Figs. 13-17, where all the milledout recesses are symmetrical around the axis. On the other hand the milled-out recesses need not be symmetrical in relation to a plane, as the Fig. 19 is in fact practically speaking balanced, the two milled-out recesses being placed diametrically opposite to each other and their areas being equal or at any rate very nearly equal. In this construction there is only one suction opening S, but otherwise the principle and mode of operation correspond to those described in connection "with Figs. 13-17 and Fig. 18. One hole or is shown in communication with the cylinder C1 and two holes 02 and c2 with communication to the cylinder C2. Of these the hole 02' is not-at small loads in constant communication with the pressure space T during astern working, but it serves for relieving the pump piston, as during ahead working it constantly counteracts the pressure. from the hole c2.

The fuelpump pistons can e. g. by means of a gear transmission or in other suitable ways be moved by being actuated by a handle, the central position of which corresponds to the stop position or the starting position. When the handle is turnedto one side, the pump is adjustedfor supplying fuel oil for ahead. working, while the cylinders get. injections for astern working when the handle is turned to the other side. 7

I claim:

1. In a fuel pump, the combination of a cylinder having an inlet and a pair of outlet ports; a piston reciprocable in said cylinder; and a valve member in said cylinder having a passage therein for selectively connecting said inlet port with said outlet ports, respectively, when said valve member is in two positions relative to said cylinder, said valve member being adapted to have a first movement for adjustment about the longitudinal axis of said cylinder, and to have a second movement for adjustment axially, and by one of said movements to be brought into and out of said two positions to effect continuous supply of fuel by successive reciprocation strokes of said piston through the outlet port to which said passage is connected, and by the-other of said movements to be conditioned for movement from one of said positions to the other one of said positions to prevent sticking of said valve member.

2. A fuel pump, as claimed in claim 1, in which said valve member constitutes a part of the said piston.

3. In a fuel pump, the combination of a cylinder having an inlet and a pair of outlet ports; a piston reciprocable in said cylinder; and a valve member in said cylinder having a passage therein for selectively connecting said inlet port with said outlet ports, respectively, when said valve member is in two adjusted positions relative to said cylinder, said valve member being adapted to be adjusted axially of the cylinder into and out of said positions, to effect continuous supply of fuel by successive reciprocation strokes of said piston,

through the outlet port to which said passage is connected, and said valve member being also adapted tobe adjusted about the longitudinal axis of the cylinder to be conditioned for its axial adjustment, to prevent sticking of said valve member.

4. In a fuel pump, the combination of a cylinder having an inlet and a pair of outlet ports; a piston reciprocable in said cylinder; and a valve member in said cylinder having a passage therein for selectively connecting said inlet port with said outlet ports, respectively, when said valve member is in two adjusted positions relative to said cylinder, said valve member being adapted to be angularly adjusted about the longitudinal axis of the cylinder into and out of said positions, to effect continuous supply of fuel by successive reciprocation strokes of said piston, through the outlet port to which said passage is connected,

and said valve member being also adapted to be adjusted axially of said cylinder to be conditioned for its angular movement, to prevent sticking of said valve member.

PO-UL EMIL 'WIENE.

REFERENCES CITED UNITED STATES PATENTS Number Name Date 171,390 Knowles Dec. 21, 1875 853,785 Henry May 14, 1907 1,293,564 Sjoman Feb. 4, 1919 1,377,139 Murphy May 3, 1921 1,512,805 Roucka Oct. 21, 1924 1,595,458 Doolittle et al Aug. 10, 1926 1,897,302 Crimmel Feb. 14, 1933 1,908,396 Albright May 9, 1933 1,951,340 Bohuslav 1 Mar. 20, 1934 2,083,020 High June 8, 1937 2,286,928 Pipkin, Jr June 16, 1942 2,326,958 Marais Aug. 17, 1943 2,360,093 Ainslie et al Oct. 10, 1944

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