US2645210A - Steam generator - Google Patents

Description

y 14, 1953' R. L. HARRIS ETA]. 2,645,210

STEAM GENERATOR Filed May 22, 1948 4 Sheets-Sheet 1 FllEi l xaer/l flax-x73 BY Mara/.9 la/Avpa July 14, 1953 R. 1.. HARRIS ETAL 2,645,210

STEAM GENERATOR Filed May L2, 1948 4 Sheets-Sheet 2 mmvroxs inter/Z. barr/ls //J M 3 Mara/.9 [0/71/40 '23 i I /a/ %Q July 14, 1953 R. HARRIS EI'AL ,6 5,210

STEAM GENERATOR Filed May 22, 1948 4 sheets-sheet s IN VEN TOR! fade/v A flarr/Ls BY Mara/s la/firap y 1953 R. L. HARRIS ETAL 2,645,210

STEAM GENERATOR Filed May 22, 1948 4Sheets-Sheet 4.

- INVENTORS I Fade/.7 Z. f/orr/ia Y 4/4/40: 0/72/40 FJLE E Patented July 14, 15 953 UNITED-STATES PATENT OFFICE" 7 s'r EAM GENERATOR Robert L. Harris and ,Marcus Lotlir'op, erkeley,

Calif., assignors"to".Yuba Manu faeturingcomv any, Salli-Francisco, Calif., a corporation of California "App a a May 22, 1948, Serial No. 28,548

- 8 Claims. .(Cl. 122-9240 Our invention relates to relativelylight, mod-- erate size steam generators usefulin many different environments, eithe'r'st'ation-ary or portable, but especially adapted for vehicular use. The generator is of the series tube, or forced" circulation type in which a'relatively small body of water is confined for heating in a longtube, the fluid flow being from end of the tubeto the other end from which steam is discharged; It is customary to supply sufiicien-t heat to the tube with respect to the quantity of water that the' issuing steam is superheated While various different designs of forced circulationor series tube generators are well-known and have numerous advantages, there are certain major disadvaritages which render them difilcult to" utilize underv some circumstances. The manufactureof the tube convolutions is relatively difficult in small, sizes especially where the configuration of the.

tubing is intricate and where sharp bends of relatively heavy tubing must be'made'. It is" customary to weld lengths of tubing together end to end in order to get a sufiiciently' long fluid path and often the welds come at an inopport'une location both for bending of the tubing and for thermal reasons In many designs of series tube or forcedcirculation generators, the flowfioilliquid, such as water, with respect to the flow of heatingfluid, such as hot products of combustion does not yield a particularly high thermal transfer eflicier'icy'.

Additionally, there often is a relatively large loss of heat from the unit by radiation or conduction to the surroundings. Again, in the endeavor to make a very compactly arranged generator, tub ing or fastenings or other parts are often buried within much additional tubing so that in the event of a tubing failure or a leak or even for inspection, it is extremely difficult to get at someparticularly at high outputs, is a severe mechan ical loss since the introduced liquid must be pumped to an initial pressure considerably higher than the pressure of the discharged steam.

There are other disadvantages of forced circulation orseries tube typegenerators in addi' tion to those mentioned to offset the, inherent advantages. Y

I't is'therefore an object of our invention in general to improve generators of the forced circulation or, series tube type.

Another object of our invention is to overcome the various disadvantages mentioned. Another object of thein vention is to improve thef thermal characteristics of a forced circula-v tion type generator.

A furtherobject of the invention is to provide better liquid-and steam flow characteristics.

A furtherob ject of th invention is to provide a generator readily manufactured, readilyserviced and readily repaired.

O-ther objects together with the foregoin 'have been attained in the embodiment of the inventionldescribed'in the following description and illustrated in the accompanying drawings in which 4 T f Figure 1 is for the mostpart a sideelevation on a longitudinal and vertical median plane, portions of the structure being shown in side eleva tion and a part of the generator beingremoved in order to reduce; the size of figure;

FigureZ' is a cro'ss section, the planes of which are indicated by the lines ll-+2 of Figure 1.

Fiigu re 3 is a cross-section to an enlarged scale of the structure disclosed by' sectioning" the mechanism on the line offFigure l.

Figure t is a front elevation of the generator with the blower mechanism removed.

Figure't'i is a rear elevation of the generator, part of the rear cover being broken away to disclosethe interior construction.

Figure 6 is, a side elevation, partially diagram matic, of the forward portion of the generator with various of the internal elements thereof withdrawn in different amounts to illustrate the telescoping relationship of the parts.

In its preferred form the steam generator of 7 our invention comprises; a central cylindrical combustion tube supplied with a heating medium sucli'as productsof combustion and arranged with a first helical conduit encompassing the tube, the'conduit being for the purpose of con ducting liquid or steam or bath. A cylindrical insulating jacket surrounds the conduit to confine heat while a cylindrical tube surrounds the insulating jacket and is spaced from it in order to provide an annular gas passage therebetween in communication with the combustion tube. A

plurality of conduits are arranged along side each other and are wound in a second helix encompassing the insulating jacket with all of the tubes being connected together at one end and to one end of the helical conduit. The second helix is disposed in the gas passage. Fluid is introduced into the several conduits of the second helix and flows through them and then through the first helical conduit.

As disclosed herein, the steam generator is especially designed for use in a steam power plant of the type disclosed in our co-pending application entitled Steam Power Plant, filed May 1, 1948, Serial No. 24,656, Patent No. 2,596,968, dated May 20, 1952. In that power plant the steam generator is approximately of a size to furnish two hundred engine horse power and supplies steam at about nine hundred degrees Fahrenheit temperature and fifteen hundred pounds per square inch discharge pressure. In that environment, the generator is disposed with its axis 6 in a horizontal plane and is provided with a blower l which is a separate and detachable unit to furnish air for combustion. In the outlet of the blower l is disposed a burner mechanism 8 including a spark plug 9 for igniting the fuel. The blower and burner mechanism is no part of the present invention, it being illustrated merely as a convenient source of supply for the requisite quantities of burning fuel and air mix ture and products of combustion.

The blower and burner unit is provided with an outlet flange I l by means of which it is connected to the forward end of a combustion tube I2. This tube is a composite structure including a metallic sleeve [3 of generally circular cylindrical contour, several times its diameter in length, and of relatively thin, heat resistant metal, preferably a metal containing a high percentage of nickel and chromium.- The sleeve [3 at its forward end merges with a metallic housing [4 joined to a front annular metallic plate [6 to which the fiange H is secured. The blower I and the tube l2 are both located coaxially or concentrically with the axis 6. Between them the plate and the housing 14 provide a space in which insulation I1, preferably glass wool or the like, is packed. The shape of the housing I4 is such as to afford an appropriate gas passageway from the blower and burner mechanisminto the inside of the sleeve [3 and is also of an appropriate contour so that a flange remains at the outside margin of the disc I6. The products of combustion enter the tube l2 with a great deal of turbulence, and travel through the sleeve I3 from left to right, as indicated by the gas fiow arrows in Figure 1.

At a convenient interval from the inlet end of the tube [2, there is provided a closure l8 in order to bar further axial travel of the products of combustion. This closure comprises a pair of metallic sheets [9 and 2i, the latter being conical to avoid undue warping, between them enclosing a space filled with insulation 22. The sheets are preferably welded to the sleeve l3 and are tacked in rather lightly so that they can readily be removed in the event it is necessary to gain access to the immediate'vicinity of the right hand end of the tube. The sheet 2| especially is in the direct path of the products of combustion and runs at a relatively high temperature being effective to intercept and to vaporize any particles of liquid fuel which are not vaporized in passing through the remainder of the sleeve I3.

In order to permit the gases to escape from the interior of the central combustion tube l2, the down-stream end thereof is interrupted to provide a plurality of apertures 23 of maximum extent for gas flow yet leaving bridge straps 24 to hold the down-stream end of the tube I2 in position so that the entire combustion tube and its forward insulation [1 and its rearward insulation 22 are in effect one manufacturing and servicing unit. This structure is therefore conveniently fabricated of simple sheet metal shapes and is readily replaced in the event long continued combustion eventually destroys the tube material.

In accordance with our invention, we provide means for absorbing heat from the products of combustion but such heat absorbing means is arranged so that its contained fluid, generally liquid and finally steam, flows in a countercurrent direction to the direction of flow of the combustion gases. Consequently, immediately surrounding the combustion tube 12 is disposed a first helical conduit 26 or tube. While this tube is termed a first conduit, it is actually the final conduit for the steam fiow. It includes a central section 21 which is a regular helix made up of relatively thick walled, large diameter tubing wound so that its helix axis can be disposed coincident with the axis 6. The inner diameter of the helix formed by the first conduit section 2! is slightly larger than the outer diameter of the sleeve so that the sleeve can be slidably moved into and out of position within the helix.

The outflow end of the helical section 21 is provided with a deflected portion 28 leading through a notch 29 cut in the end of the combustion tube assembly and terminating in a fitting 3I. The inflow end of the first helical section 21 is provided with a convolution 32 passing around the end plate [9 and terminating in a central fitting 33. While the forward convolution 28 extends radially outward from the body 21 of the helix, the rearward convolution 32 extends radially inwardly of the helix. This arrangement permits the combustion tube 12 to be axially moved into telescoped relationship with the helical conduit 26 or to be Withdrawn therefrom without interference. This relationship is especially illustrated toward the left hand end of Figure 6.

In order to hold the first helical conduit i2 in its desired position, in order to make it readily producible to precision standards and to avoid strains in it due either to excessive welding or to thermal stresses developed during changes in temperature when in use, we provide it with a support channel 36 or rib. This channel is lightly tacked by welding to each convolution of the helix 2'! or to alternate convolutions. Thus the general helical form of the first conduit 26 is largely maintained by the channel 33 but the convolutions are individually free to expand and contract circularly and axially with respect to each other under manufacturing and operating conditions. Since the coil 21 does not receive any substantial amount of heat conduction from active combustion by gases but rather is heated by radiation from the sleeve l3 and by metal conduction, there is no particular space left between turns of the helix, and they are made as close together as conveniently possible.

To prevent the undesired travel of heat radially outward from the sleeve l3 and the coil 21, an insulating jacket 31 of generally cylindrical form is provided around the coil and is disposed with its axis coincident with the axis 6. The insulating jacket 31 includes a front plate 38, overlapped by the flange portion of the plate 16, and an adjacent annular, sheet aware metal housing 3!! to confine a ring of insulating material .41. The insulating bodieslfl and Al. effectively block heat flow from the forward end of the structure. From the housing 4| there extends an inner cylinder metal tube or sleeve 42 overlying the outside of the helical section of the conduit 25 in freely sliding relationship and an outer sheet 53 which is conical and converges away from the forward end of the structure finally to unite with the sheet .42. In the space between the sheets 42 and 43 is disposed a mass of thermal insulation 46. Since the gases adjacent the forward end of the, combustion tube l2 are hotter than those near the rearward end thereof, the layer of insulation 46 is correspondingly thick at theforward end andthinat the rearward end. In addition to the forward insulatio-n body 4|, there is provided a rearward body 41 of insulation confined by. a rear plate 48 and a sheet metal, annular housing 49. I]? desired, bridges 50 of metal span the space 5!, otherwise existing between the rearward end of the sheet 42 and the housing 49 so that the entire insulating jacket 37 is manufactured and operates as a unit.

To facilitate manufacture and also .properly to relate the insulating jacket with the remaining part of the mechanism, the jacket along one side or along one element of its approximatelycylindrical contour is provided with a metallic channel 52. At its opposite ends, the channel enters and is fastened to the'metal work of the insulating housings 39 and 49 and serves as a sort of backbone for the insulating jacket affording support and stiffness in addition to that yielded by the general constru'ction of the device. The upturned channel 52 is designed also to. serve as a support and guideway or track for the downturned channel 36 of the helical coil section 21 so that the coil can be slid into an accurately located position as shown in Figure 6 within the insulating jacket 31. The

channels 36 and 52 being in nested relationshipv afford not only an adequate support so that the vertical spacing of the conduit and of the jacket is correct but also establish thev relative lateral location of the members. The channels do not,

however, afford all of the support against lateral displacement, some being furnished by the fit of the housing [4 within the housing 39 at the forward end and the fit of the housin I9 at the rearward end of the tube within the housing 49. Thus the jacket and helical coil are related to each other and are held in suchrelationship by the fastenings 53'at the forward endon the tube in one direction and then after passing through the opening 23 is back upon itself in a reverse direction. The annular gas passage 56 is defined not only by the outer portion of the first insulating jacket but likewise by the inner portion of a second insulating jacket 5'l having an approximately cylindrical configuration disposed coaxially with the remaining part of the structure. This jacket 5'! is approximately a reversal of the first jacket 31. At its forward end it includes a plate 58 overlapped by the plate 38 and cooperating with an annular metallic jacket 59 to enclose insulation 6|. closure so formed by bridges 62 over an annu- Joined to the enthe gas on all sides.

lar opening $3 are :an inner sheet 64 --and an" outer sheet 66. Both of the sheets are slightly conical to increase rigidity and to afford a proper enclosure for. the circularly or annularly' enlarging gas passage 56. ated betweenthe inner and outer sheets and 'at 'the rearward end in an inturned, metalclad insulating flange H overlying and in .slidable relationship with the housing 49. 'In addition to the relatively small bridges 62, the parts of the second .or intermediate insulating jacket, 51- are related by a channel 12 which engages both of the ends of the jackets and serves as a support and alining device.

To supplement the'heat exchange surface and to act as a continuation of the first helical conduit '26 and to occupy a space within the gas pasonly to-three, and especially since each ofthern is preferably provided with its own separate liquid supply by an. individual force pump, the generator acts according to forced circulation or series tube principles. v

Each of the tubes 14, 15 and'l-B, which make up the helical member 13, is brought radially in-. ward into a fitting 18 detachablyjoined by axialmovement to the fitting .33 on the axis 5, the tubes 14, 15 and 16 passing outwardly through notches 19 provided in the insulating flange H for that purpose. The convolutions of the helix 13 are wound With slight spaces between them in order that the gases flowing over them can pass between the individual turns of the helix. Since the annular gas-passageway 56 is defined by the conical walls 44 and .64, the gas passes progressively from-the inside of the helix 13 to the outside thereof as ittravels generally axially from the right hand end to the left hand end of the passageway. In this way the heat transfer is eifectuated in a countercurrent direction with each of the tubes receiving heat from The forward end of the helix I3 is formed by convolutions 81 of the individual tubes turned radially outward and passing through notches in the plate 38. Fittings 82 are disposed on the outer portions of the tubes so that an adjacent coil can be fastened. The

direction of flow is through the helix (3 from the fittings 82 at the forward end thereof to the backward end through the fitting 18 and the fitting 33 and then forwardly through the inner helix to the fitting 3|.

To hold the helix 13 in position and to support it,'we join it to a section of generator tubing 34 which takes the place of a channel and also serves as a protected conduit to take the steam from the fitting 3| to the rear of the generator where it is to be utilized. The tube 84 extends parallel to the axis 6 and at its forward end is turned radially outward through a notch in the Insulation 1.61 is .situ- Rather, it is preferably comprised of i mostat tube 89 is Welded to the side of the tube 84 and extends forwardly through the plate I6. This arrangement is such that while the helical coil 28 is continuous with the multiple coil 84 for conducting steam, it can also be detached therefrom by disconnecting the fitting 3| from the fitting 86 so that the inner helix can be withdrawn axially for detachment or can be reassembled by axial movement until the front plates and the fittings 3| and 86 register and can be secured together. After the other interior structure has been withdrawn, the helix I3 together with the steam tube 84 and the thermostat tube 89 can be axially withdrawn toward the left in Figure 1 since its r arward portions extend radially inward and pass readily through the center part of the generator. The rearward end of the steam tube 84 being turned radially inward passes along with the helix I3 through the center part of the structure.

Gases which traverse the length of the passage 56 are again reversed to travel around the outside of the insulating jacket 51. To provide an outer gas passageway 9|, there is situated in substantially even spacing from the outer sheet 66 of the insulating jacket 51 a conical inner sheet 92 of an outer insulating jacket 93. This is externally defined by a circular cylindrical.

shell 94 of metal confining a body 96 of insulation between it and the sheet 92. The outer shell 93 is continuous and terminates at its forward end in an annular metal plate 91 engaged by fastenings with the plate 58. At its rearward end, the outer shell merges with a metallic ring 98 at appropriate intervals carrying spacers 99 in sliding engagement with the outer portion of the sheet 66 of the jacket 51. The jacket 93 is provided with a base channel IilI extending for substantially the full length thereof along the bottom and parallel to the axis 6 being conveniently joined in fabrication with the metallic covers for the insulation. The gas passageway BI is connected, except for the bridge 62, with the gas passage 56 at its forward end and at its rearward end provides an annular opening I03 for the release of spent products of combustion. The products of combustion in the outermost passageway of the assembly are the coolest and lose a minimum amount of heat through the insulation 96 to the atmosphere.

In order to utilize the heat transferring capabilities of the gas within the passage 9I, we provide a third, outer helical coil I05. This coil is made of three tubes laid side by side and at their forward ends emerging with convolutions I01, I08 and I09 respectively, bent radially outward. These are provided with fittings III detachably joined in an axial direction with the fittings 82. At their rearward ends, the tubes of the helix I06 emerge in terminals H2, H3 and H4, each one extending through suitable check valves to its own individual plunger pump. The cold liquid for evaporation enters through the extensions H2, II 3 and H4 at the right hand or exhaust end of the gas passage HI and travels through the helix toward the left in Figure 1, finally entering the intermediate coil at the fittings 82. The coil or helix IE6 is generally circular cylindrical and is wound with the convolutions slightly spaced apart so that the gas traveling through the passageway 9I transfers from the inside of the helix to the outside thereof through the individual interstices between the turns and thus each of the convolutions is surrounded with the heating medium.

To keep the outer helix in position and to serve as a support without confining it unduly against minor adjustments due to thermal changes, an internal longitudinal channel H6 is welded to each convolution or to each few convolutions and serves as a frame for the outer helical coil. The channel H6, as especially shown in Figure 6, is readil received and is slidable within the channel I2 incorporated with the intermediate insulating jacket 51. The coil I06 is thus located and held, being additionally supported by the outwardly extending portions near the fittings III where they pass through notches in the forward plate 91 and in the plate 58.

The exhaust products of combustion, having given up asmuch heat as possible to the coldest water entering the inlet end of the helix I06, are gathered in a closure housing I2I secured to the rearward pate 98 of the outer jacket and comprised of two halves secured together by fastenings I22. These halves overlie the sides of the emerging steam pipe 84 and likewise overlie a plug I23 through which the inlet terminals H2, H3 and H4 extend. From the housing I2I an adapter I24 extends to serve as an outlet conduit for the exhausted gas.

The liquid to be evaporated, usually water, enters the coldest portion of the generator at the outside helix through the pipes H2, II 3 and H4 and travels in parallel turns. It is subjected to hotter and hotter products of combustion as it advances. The liquid then flows through the parallel tubes constituting the intermediate cylindrical helix. This in turn traverses in counterfiow relationship, the increasingly hot intermediate gas passage insulated from the outer gas passage. Finally the liquid emerges from the parallel tubes and flows through the single, inner, helical coil enveloping the combustion tube containing the hottest products of combustion. While the term liquid has been used, at some point, in its travel, the liquid changes to steam and may become a dry gas. Steam from the hottest end of the central helix is discharged for use.

Each of the helical coils is a generally cylindrical arrangement, and they and the combustion tube and the insulating jackets are all as-- sembled in an axially slidable, and telescopic relationship. Being all fastened only at one end, the forward end, to each other, they are not only readily withdrawn each from within the others by sliding on the channels provided, but they are also freely expandable lengthwise. The individual turns of the helixes are fastened at only great intervals on their periphery so that they themselves are free to expand and contract under thermal changes. The insulation in a radial direction is several layers thick and the temperature difference between layers is relatively small so that very little heat is lost to the atmosphere.

Since the forward and the rearward walls of the generator are provided with insulation, the entire mechanism is substantially enclosed with thermal insulation. In the event of excess scaling, the tubes being quite simple in shape and of relatively inexpensive material, can be withdrawn and replaced with new, scale-free helical coils. The various shapes, being relatively simple, are readily fabricated without any sharp bends or obscure welds. Any portion of the generator can readily be inspected by withdrawing it from the assembly.

We claim:

1. A steam generator comprising a jacket substantially in the shape of a circular cylinder disposed with its axis substantially horizontal, a rail projecting inwardly of and extending along the bottom of said jacket, a conduit in the shape of a helix disposed within said jacket and having its successive convolutions resting on said rail, means for sending fluid to be heated through said conduit, a channel extending inwardly and longitudinally of and secured to the bottom of said helix, a second jacket substantially in the shape of a circular cylinder disposed with its axis substantially horizontal within said helix and resting on said channel to transmit the weight of said second jacket through said channel and said helix to said rail, and means for sending heating gases between said jackets and over said conduit.

2. A steam generator comprising a jacket substantially in the shape of a circular cylinder disposed with its axs substantially horizontal, a rail projecting inwardly of and extending along the bottom of said jacket beneath said axis, a conduit in the shape of a helix disposed within said jacket and having the lower outer portion of its successive convolutions touching and resting upon the upper surface of said rail to transfer the weight of said helix to said rail, the axis of said helix being substantially coincident with the axis of said jacket, and means bearing downwardly on the lower inner portion of said helix above said rail for holding said helix against shifting on said rail.

3. A steam generator comprising an outer jacket substantially in the shape of a circular cylinder open at both ends, an inner jacket substantially in the shape of a circular cylinder disposed within said outer jacket and spaced therefrom to leave an annular gas passage therebetween, a flange at one end of said inner jacket overlying said gas passage and the adjacent end of said outer jacket, there being a notch in said flange, a helical coil in said gas passage and having a front terminal portion extending axially through said notch and a rear terminal portion extending axially from said gas passage fasteners for removably securing said flange and said outer jacket, and spacers at the other end of said outer jacket extending across parts of the adjacent end of said gas passage on either side of said rear terminal'portion and in sliding abutment with said inner jacket.

4. A steam generator comprising a horizontal outer jacket having an interior surface substantially in the shape of a frustum of a cone, an inner jacket having an exterior surface substantially in the shape of a frustum of a cone, said inner jacket being disposed substantially coaxially within said outer jacket to leave a conical gas passage annular in cross-section therebetween, a conduit having successive convolutions in the shape of a cylindrical helix disposed substantially coaxially within said gas passage with one end of said helix adjacent said exterior surface and the other end of said helix adjacent said interior surface, and a rail extending inwardly along the bottom of said outer jacket and having an axially extending top portion parallel to said axis in supporting relationship with the bottom portions of the successive convolutions of said helix.

. 5. A steam generator comprising a lower, horizontal rail, a conduit in the shape of a helix having several convolutions about a horizontal axis, a rib disposed parallel to said axis and extending beneath the lower portion of and secured in direct supporting relationship to several convolutions of said helix and adapted to rest on said rail for 10 axial sliding movement thereon, said convolutions being supported solely by said rib and thereby being free to expand and contract, and means for holding said rib on said rail against said sliding movement and against lateral and rotary displacement.

6. A steam generator comprising a central combustion tube, a first helical conduit encompassing said tube, a cylindrical jacket surrounding said conduit, means for preventing combustion gas flow between said combustion tube and said jacket, a cylindrical tube surrounding said jacket and spaced therefrom toprovide an annular gas passage, a second helical conduit en compassing said jacket and disposed in said gas passage, means for establishing communication in series between the interior of said combustion tube and said gas passage, and means for connecting said first and said second helical conduits for fluid flow in series therethrough.

7. A steam generator comprising a central combustion tube, a first helical conduit encompassing said tube, a cylindrical jacket surrounding said conduit, means for preventing combustion gas fiow between said combustion tube and said jacket, a cylindrical tube surrounding said jacket and spaced therefrom to provide an annular gas passage, means for establishing communication in series between said gas passage and said combustion tube, a plurality of conduits alongside each other and arrangedin a second helix encompassing said jacket and disposed in said gas passage, and means for connecting said plurality of conduits together at one end and to one end of said helical conduit.

8. A steam generator comprising a circular cylindrical outer jacket having an axis, a rail projecting inwardly of and extending along the wall of said outer jacket parallel to said axis, a conduit in the form of a helix disposed within said outer jacket and having its successive convolutions supported on said rail for sliding movement axially along said rail, a circular cylindrical inner jacket disposed within and supported on said conduit for sliding movement axially along said helix, and separable interconnections for holding said outer and inner jackets and said conduit against said sliding movement.

ROBERT L. HARRIS. MARCUS LOTI-IROP.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 760,784 Fournier 1- May 24, 1904 1,271,487 Reid July 2, 1918 1,446,521 Smith Feb. 27, 1923 1,583,557 Josse May 4, 1926 1,737,712 Gazelle Dec. 3, 1929 1,818,057 Ferrier, Jr. Aug. 11, 1931 1,980,301 Stewart Nov. 13, 1934 1,992,305 Love Feb. 26, 1935 2,115,567 Anderson Apr. 26, 1938 2,189,532 Garson etal. Feb. 6, 1940 2,223,856 Price Dec. 3, 1940 2,245,332 Dufault June 10, 1941 2,256,882 Sebald Sept. 23, 1941 2,273,767 McCollum Apr. 17, 1945 FOREIGN PATENTS Number Country Date 740,226 France Nov. 12, 1932

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