US2568948A - Pan type heat exchanger - Google Patents

Description

Sept. 25, 1951 w, CART-[ER 2 ,568,943

PAN TYPE HEAT EXCHANGER Filed Sept. 28, 1945 2 Sheets-Sheet l #3 Q INVENTOR. 3 g 20 WILLIAM G.CMrrm.

A ATTORNEY.

Sept. 25, 1951 w, CART R 2,568,948

PAN TYPE HEAT EXCHANGER Filed Sept. 28, 1945 2 Sheets-Sheet 2 IN VEN TOR. WILLIAM G. CARTTER.

ATTORNEY.

Patented Sept. 25, 1951 UNITED STATES PATENT OFFICE 2,568,948 PAN TYPE HEAT EXCHANGER William G; Cartter, Monrovia, Calif., assignor to Afliliated' Gas Equipment, Ina, Cleveland, Ohio, a corporation of Delaware Applications eptmber 28, 1945, Serial No. 619,113

claims. (01. 126-355) My invention relates to water heaters, and more particularly to recirculating water heaters of an automatic continuous fiow type which may b combined with a hot water storage tank or the like.

Various types of water heaters are known, in which the heat from the combustion of a fuel is directed against tubes or coils containing water to be heated. In these heaters the water to be heated is contained in the tubes or coils under greater than atmospheric pressures so that the construction of the heater must withstand greater than atmospheric pressures. The heat of combustion is not wholly utilized, and the hot gases of combustion are for the most part drawn past the heating tubes or coils with substantial velocity andcontain a considerable amount of heat when they are discharged from the heater.

I have developed a water heater in whichthe heating of the Water may take place at atmospheric pressure and in which the heat from a burning fuel or heating coil is retained in contact with the water heating surfaces until virtually its entire energy is absorbed by the water.

By my invention the water to be heated is subjected to layers or cushions of heating or com'-" bustion gases at successively higher temperatures as the heating progresses. The temperature differential between the heating gases upon the es-'- cape from the heater and the temperature of the incoming unheated water is at a minimum, the gases'of combustion'before their escape f'rom'the heater acting to pre-heat the colder incoming Water.

It is an object of my invention toprovide a gravity flow water heater in which the water may be retained at atmospheric pressure-during the heating process.

It is a further object of my invention-to provide an improved water heater in which the heat ing gases are retained in migrant layers'in a series of stages, and wherein the water is pro-'- gressively heated in several stages.

A'further object of my invention is to provide a-water heater in which water is retained in broad shallow layers above layers of gases of combustion, and in which the water is subjected to progressively hotter layers of heating gases at successively lower layers or levels as th water descends from a higher to a lower level.

A further object of my invention is to provide a water heater in which the water to be heated and-which, ata predetermined level, fiows'into 8 second fiat receptacle forsubjection' to the heat,

of escaping gases of combustion at successively lower levels and higher temperatures, until said water is heated to a desired temperature in the lowermost flat receptacle.

A further object of my invention is to provide a water heater comprising a stack of fiat recep bination with means maintaining a continuous supply of hot water under pressure in the stora'ge't'anks. I

Another object of my invention is to provide an improved'system of water heating comprising a storage tank operatively connected to an improved water heater and associated with means for maintaining-a continuous supply of hot water under pressure in saidstorage tank and in which the heating of the water may take place under atmospheric pressure.

A further object of my invention is to provide a novel water heater of high efiiciency provided with a stack of individually replaceable flat containers having staggered openings for the upward circulation of gases of combustion, said containers being slidably arranged in tiers within an insulated casing, said casing having a hinged door for the replacement of said containers, individ: ual removable covers for the containers and ad- J'ustable Wiers or overflows in the containers controlling the depth and circulation of Water therein, said overflows being widely spaced from inlets provided in each container, requiring the water to travel a maximum distance over a horizontal heating surface in its course through the heater.

Other objects and advantages will appear and be brought out more fully from the following descriptionconsidered with reference to the ab.-

:companying drawings throughout which like parts are designated by'like numerals.

In the drawings: Figure 1 is a vertical sectional view of my im proved'waterheater taken'o'n thelin'e ll of' Figure-2.;

Figure 1A is an enlarged sectional view taken on the line |AIA of Figure 1.

Figure 2 is a horizontal sectional View of my water heater taken on the line 2-2 of Figure 1.

Figure 3 is a front view of a drawer incorporated in my water heater.

Figure 4 is a vertical sectional view taken on the line 44 of Figure 1.

Figure 5 is an elevational View of a Water heating system incorporating my improved heater.

Figure 6 is a sectional view of a discharge sleeve and nipple taken on line 6-6 of Figure 1.

Figure 7 is a detailed sectional view on the line I-I of Figure 2.

Figure 8 is a detailed sectional view on the line 88 of Figure 2.

Figure 8a is an enlarged fragmentary elevational view similar to Figure 8 illustrating the slotted construction of an adjustable weir.

Referring more particularly to the drawings:

My improved heater 28preferably comprises an insulated box-like casing 2| having an outer wall 22 and inner wall 23 provided therebetweenwith' a suitable insulating material 24, such as glass wool, asbestos, mineral wool, or the like. A nipple 25 may slidably extend through a sleeve 26 fitted in the top of the heater 20. Feed water from any sources of supply is introduced into the heater through the nipple 25. At the lower right hand side of the heater 20 (Figure 1) is an opening 26' provided with a collar 21 through which a pipe 28 conducts heated water to a point of'use or accumulation, as hereafter more fully set forth.

20 through openings 3| fitted with collars '32 through which the pipes 30 are slidable, being removably supported upon a U-shaped bracket at their inner ends.

side of the heater (Figure 1). Suitable burners 4| are appropriately spaced along and supported" by the gas pipes 30. Any suitable fuel or source of heat may be used in lieu of gas, as electricity, oil, or other liquid-fuel.

The casing 2| may be mounted upon channel irons or other suitable supports 42, and may be ported at the top for the installation of a fiue for the escape of gases of combustion. A door may be supported upon hinges 5| and preferably extends across an entire side of the heater to form the front wall or casing thereof.

Air ducts may be provided in the bottom of the heater 20 between elongated fabricated spacers 56 supported upon angles 51 extending along the front and back of the heater 20.

' Horizontally disposed within the casing 2| are flat pans 60, 6| and 62 supported in vertical spaced relationship as upon angles 65 affixed to the inside of the casing 2|, preferably along the sides and back thereof.

The fiat pans 60, 6| and 62 are fitted with flues I0 extending through their bottoms at staggered intervals relative to the fiues 10 in any adjacent upper or lower pans 60, 6|, and 62. One corner of the pans 60, 6| and 62 may be set off by di- The gas pipes 30 leadinto" the heater from a manifold '40 at the left hand 62 respectively. Said covers are formed with formed with a weir I62 in a corner of the pan 6| diagonal from the weir I00 in pan 60.

The upper pan 6|] receives the feed water nipple 25 in a corner of the pan diagonally opposite from an outletor overflow 86 provided in the corner of the pan 60 by the diagonal partition 15, Said nipple 25 extends through an opening in the cover of the pan 60 where it may be fitted with a grommet 83. The outlet chamber 90 formed by the diagonal partition I5 is fitted with a drain 9| incorporating the dependent nipple 92 by means of a split joint 93 sealably compressing a packing 94, as best illustrated in Figure 6. The packing 94 may be compressed between the walls of the drain 9| and the nipple 92 by axial manipulation or threading of said slip joint in a well known manner. The overflow pipe 86 extends through the bottom of the outlet chamber 90 adjacent the drain 9| and projects for a suitable distance above the bottom of the pan 60. The overflow pipe 86 may be fitted with a nipple 81 at the.

8| on the second pan 6| so that water flowing by gravity through the overflow 86 or the drain 6| empties into the second pan 6| in a corner of said pan 6| diagonally opposite from the feed water inlet 25, but in a similar manner to said inlet 25.

Nipples I64 and I65 are respectively connected to the drain 84 and overflow in a similar manner to the nipples 92 and 91, and empty into a corner of the lower pan 62 diagonally opposite from the weir I00.

Diagonally opposite from the drain 84 and the overflow 85 is an overflow chamber IID formed by a corner of the lower pan 62 and the wall 'I! bounding said corner. The wall Il may be formed with a weir II5 by which to establish the height of the water within the lower pan 62. The overflow chamber III is provided with a drain H6 and an overflow II'I, preferably extending above the water level established by the weir H5. The drain H6 and overflow III depend into a collector I20 which is fitted with a cover I22 provided with holes to receive the drain H6 and overflow II'I, respectively, in a manner similar to the receipt of the nipples 92 or 91 by the cover 8| of the intermediate pan 6|, as hereinabove set forth. The pipe 28 conducts the heated water from thecollector I20 to any point of storage or use. An auxiliary overflow comprising overflows 98, preferably fitted with nipples 99, may be installed in vertical series to permit a rapid withdrawal of water into the storage basin 2H) in case of a failure of the normal circulating and drainage system within the heater 20. Such auxiliary system may be constructed in a similar manner to the overflow pipe 8.6. and nipple 91, for example.

In. addition to each of the fixed weirs, such as I 00, I filand II5, I may provide. an extra adjustable weir gate 1452 (Figures 7. and 8). which may be afiixed to either or all or the. diagonal partitions I5, i8 and El, as. by means of screw fasteners I24 extending through holes. I25, whereby the water level in the several pans may be readily adjusted. Suitable packing (not shown) may be. provided to. prevent leakage around the adjustable weir. To facilitate the raising or lowering of the weir gate, I42, vertically disposed slots I241 may be provided therein.

Thus, it will be seen that the water maintained in the heating. pans. such as. pan 61,. may be maintained at any desirable level below the cover 8| by loosening the screws I24 which are. threaded into, the diagonal partition I6 and raising or lowering the adjustable. gate. I42 as. by means of vertical slots I24, then. tightening said screws Such adjustment changes, the level of the top edge of the gate I42. with. respect. to the weir I32 of the stationary partition I6, and governs the water level in the pans.

It is an important feature of. my improved heater that the several parts thereof may be individually removed or replaced as follows: The hinged door 50, which may be. held in closed position by releasable clips, I33 pivotally secured as by bolts I3I, may be swung open to expose the inside of the heater 2i]. The pans 6.0, BI and $2 may be slid out in the manner of drawers guided upon the side angles 65. All waterconducting nipples may be made axially slidable, and may be retracted and disengaged from their respective grommets. The drain H6 and the overflow II'I may be withdrawn from the collector cover I22, as by disengaging the. pipe 28 from the collector I20 whereby the collector will be free for removal from its supporting bracket I2I when the pan 62 is raised to re.- tract the drain Hi5 and the overflow Ill. The pan 62, unless raised to remove these last-named structures from their engagement with the collector cover I22, will obviously not be removable from the heater as contemplated.

Each of the pans 60, BI and 62 is locked into position by means of individual latches I32 depending through openings I33 in the front angles,

I35. Upon disengaging said pivoted latches I32 from said openings I33, the individual pans 6.0, 5| and 62 may be slid outwardly through the front of the heater, whereupon the covers. 80, BI and 82 ma be conveniently removed for cleaning or replacment.

The gas pipes 30 which are held in position by the arcuate notches I40, formed in the side angle I4I, may be pulled through the openings 3! after the removal of the burners 4| from their referably threaded engagement with the gas pipes 39. The elongated spacers 5B are removable individually or together by lifting them from their angled supports 51.

The operation of the described embodiment of my improved Water heater is as follows: Combustion in the burners QI may be supported byv a fuel, such as gas, entering the gas pipe 30 through the gas manifold 40 and by air entering underneath the heater by way of the air ducts 55. The heated air and the products of combustion from the burners 41 rise and continuously form a blanket or cushion of hot gases and flame against the bottom of the lowermost pan 62 whereby thewater in said lowermost pan-is heated. The fluestheheated gases upwardly through the lower-- most pan- 62 until the'gases. strike the bottom of the intermediate pan 6| atpoints between the flues 84 in said intermediate .pan which are in staggered relationship to the flues in the lowermost pan 62. A layer of hotgascs is thereby formed beneath the intermediate pan 6|, whereby the water in the intermediate pan 6 I is heated. The hot gaseous layer below the intermediate pan 6|. is conducted upwardly through the panfil in a-likemanner, striking the bottom of the upper pan B0 and-forming a similar layer of hot gasesbelow. the uppermost pan fill, by virtue of which the water in the uppermost pan Ellis heated. The flues I0 in the uppermost pan 60- finally con-- duct the gases upwardly towards thev flue: 45 through which the spent gases may escape into the atmosphere.

The. circulation of the hot. gases upwardly In the operation of m heater, condensation may occur upon the top of the covers 8| and 82. In view of the factthat said covers are not in. contact with the water in the bottoms of the pans, the covers willbe intensely hot so thatcondensate will immediately vaporize and pass out with the products of: combustion. The pans may be made of any suitable material; either ferrous or. non-ferrous. The upper surfaces of' the covers are preferably bright and heat-reflective to reflect and intensify the heat upon the bottoms of the pans for greater economy and efiiciency of heat utilization. The bottomsof the pans on the other hand are preferably blackened for better heat absorption.

Tests have shown that when a proper relationship of. delivered. heat to heating surfaces, including volume and depth of the treated water, is achieved, the efiiciency of heat transfer is exceedingly high, such that the hand may be placed in the path of the escaping gas through the main flue. 355. without discomfort. In my improved heater the feed water is'preferably retained and heated atatmospheric pressures, but the pans 60, GI and 62 ma be continuous withthe gen eral water circulatory systems and maintained thereby at'the same pressures. Heating under atmospheric pressures has important advantages; such for example, as avoiding large internal pressures which tend to burst conventional closed pressure systems.

Asan example only of a system which may provide the environment for my improved water heater, I may utilize an improved hot water storage tank 200, a pressure regulating valve 2i3I, my improved hot water heater 20, and a circulating pump 203- driven by a motor 205. Water in'thetank 200' is circulated throughthe above named elementsby way of the feedwater pipe 206 and the tank return pipe 2Il'I in-the direction indicated; by the arrows. Interconnected W-ith'said return pipe 201 is a preferably insulated-overflow stor age-basin210which is connected to the=pump 2&3"

by said return pipe 201. Heatedwater from the heater 20 circulates through the overflow storage basin 210 for keeping the pump 203 primed, and to act as an overflow reservoir for;the heater 20, as hereinafter described.

The pressure regulating valve 201 is installed between the storage tank 200 and the heater 20 so as to admit water from the tank 200 into the heater when the manual valve 211, adjacent to the heater, is in open position, provided that the water in the tank 200 is under a sufficient predetermined pressure. The pump 203 is positioned in the return line 201 between the heater 20 and the tank 200 to circulate heated water from the heater 20 and the basin 210 back into the tank 200. A check valve 213 is installed between the pump 203 and the tank 200 to prevent a return flow from the tank 200 into the pump.

The tank 200 is provided with a cold water supply line 215 equipped with a manually operable valve 216 and a check valve 211, the latter being operative to prevent a back flow from the tank 200 into the cold water supply line 215. .A hot water service line 219 equipped with a manually operable valve 220 leads from the top of the tank 200 to any point of use.

A thermostat 222 may be installed in the tank 200 interconnected in an electrical circuit 224 which includes a manual switch 111. This circuit 224 is also interconnected to the motor 205 through 'an automatic switch 226, and is further interconnected to a solenoid control 228 operating a plunger 229 against the tension of a coil spring 230, and automatically controlling a fuel valve 231.

The operation of the illustrative system incorporating my improved water heater is as follows: Water enters the tank 200 through the cold water supply line 215 under the pressure of the water main until the tank 200 is filled, at which time the water will leave the tank 200 through the service line 2 I 9, unless that line is closed as by the valve 220.

The tank 200, now being filled with water under main pressure, can not discharge by way of the return line 201 due to the check valve 213. The pressure regulated valve 201 is set to prevent the flow of water through the line 206 on account of the static head within the tank 200.

When the pump 203 is in operation, a sufficient pressure is built up within the tank 200 to force the water from the tank through the feed water line 206, and through the regulating valve 201 into the top of the heater 20. The feed water is discharged from the nipple 25 into the topmost pan until the water has reached a suflicient level in said pan 50 to overflow the weir 100 or the overflow 86. After passing over the weir 100, the water enters the intermediate pan 61 by way of the outlet 91 and nipple 92, or the overflow 85 and nipple 91, until a suflicient level has been reached in the pan 51 to flow over the weir 102, whence the water is conducted through the outlet 84 and nipple 104, or through the overflow 85 and nipple v closed, current may flow in the conductor 224 but v said cur n is broken yt e be mostat 22: um

less the water within the tank 200 falls below a desired predetermined temperature. When the water falls below such predetermined temperature, the thermostat contacts close permitting a flow in the conductor 224 which thereupon actuates the coil of the automatic switch 226. This switch is normally held open and in an elevated position by means of its coil spring 226' but upon its coil being energized, the switch 226 closes the contact points 220" permitting a flow through conductor 226a, motor 205 and conductor 225b, energizing the motor 205 which operates the pump 203 drawing heated water from the basin 210 and forcing the same into the tank 200 by means of thepipe 20'1.

Simultaneously with the closure of the switch 225, current may flow through the circuit 226d and 2260 and return to switch 111, thereby actuating the solenoid 228 to operate the plunger 229 against the tension of the coil spring 230 so as to fully open the fuel control valve 231 and ignite the burners 41. Thus there is set up a potentially continuous cycle in the water system through the conduit 206, the heater 20, the basin 210, the pump 203 and conduit 201.

This system of continued fluid and electrical flow is interrupted when the water in the tank exceeds a desired predetermined temperature. 'lhereupon the thermostat 222 breaks the circuit in the conductors 224 and 224' de-energizing the coil in the switch 225 and the coil of the solenoid 220 whereupon the spring 226 breaks the electrical circuit to the motor 205 and spring 230 closes valve 231. This system is then substantially cle-energized except for the flow of the suflicient amount of fuel through the valve 231 or an equivalent construction to provide a pilot light, not shown, by which the burners may be ignited upon reenergizing the system as aforesaid.

The pump 203 delivers water to the tank 200 at a higher pressure than that of the main, but the check valve 21! installed in the cold water supply line 215 prevents the water from returning into the main.

It is to be noted that the novel form of heater disclosed herein permits a maximum utilization and conversion of fuel for heating the water. Moreover, the structural arrangement contemplates a facile increase or decrease in the number ;of pans or water heating elements, or alteration facilitate cleaning of the parts and to carry out the demouritable structure of the heater generally, but the fact that the cover and other parts are separable and demountable is not intended as a limitation, but merely as a preferable form and arrangement.

Important also is the adjustability of the flow and depth'of water within the pans, as by means of the weirs and outlets. The rate of heating, the temperature of the water and the capacity of the heater may, for example, be altered by varying the rate of output of the burners, the depth of theiwater within the pans, the number and size of the pans, or the number and arrangement of the inlets, outlets and/or vents within the pans. In addition, heating may be accomplished under atmospheric conditions, whether within or without the casing. As a consequence of these and other considerations, it is believed that this inventionlrepresents a revolutionary dc velopment and departure in the art of water heaters, particularly of the-circulating type.

It is very important in any form of the invention that the water level be maintained in the pans below the top thereof :so that water is not in contact with the top of the pan. This should prevail whether the pans are open to atmospheric pressure or are sealed shut. The top of each pan being thus exposed to the high temperatures of the air in the area above and adjacent to the top of the pan and out of contact with the water in the pans becomes super heated. Such super heat is primarily derived from the products of combustion circulating through the fiues of Figure 1 and secondarily reflected or radiated heat from the bottom of the pan immediately above. The tops of the pans are thus heated to a relatively high temperature. Therefore any moisture in the space above the pan is vaporized and passes out with the products of combustion elimi-' nating condensation which otherwise might foul the heater and possibly contaminate the heated water. Also, radiant heat from the pan top is directed downwardly to some extent and conserves the heat of the water below, thereby increasing the over-all efiiciency of the heater.

Although I have herein shown and described my invention in what I have conceived to be the most practical and preferred embodiment, it is recognized that departures may be made therefrom within the scope of my invention, which is not to be limited to the details disclosed herein, but is to be accorded the full scope of the claim so as to embrace any and all equivalent structures.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A heat exchanger comprising a housing; a plurality of substantially fiat pans adapted to hold water and slidably disposed in said housing in vertical spaced relation, a plurality of conduits disposed through each of said pans and positioned in offset relation with respect to each adjacent pan adapted to form a tortuous path for heated gases, whereby said gases are caused to wipe substantially all of the bottom of each of said pans, water supply means adapted to supply water to be heated to one corner of the upper of said pans, means in the opposite corner of each of said pans adapted to conduct said water by gravity to each successively lower pan whereby said water is caused to travel diagonally across each of said pans before descending to the next lower pan, said last-named means comprising a sleeve of relatively large diameter depending from the bottom of each of said pans respectively, a sleeve of relatively smaller diameter disposed in said larger sleeve, sealing means disposed between said sleeves adapted to frictionally retain said smaller sleeve in position, whereby said smaller sleeve may be telescoped upwardly into said larger sleeve to permit removal of each of said pans, and means for maintaining a predetermined level of said water in each of said pans, said lastnamed means comprising a weir adapted to partition said corner in which said water conducting means is disposed from the rest of said pan.

2. A heat exchanger comprising a housing, a plurality of substantially fiat pans adapted to hold water and slidably disposed in said housing in vertical spaced relation and independently supported therein, a plurality of conduits disposed through each of said pans and positioned in ofiset relation with respect to each adjacent pan adapted to form a tortuous path for heated gases,

10 whereby said gases are caused to wipe substantially all of the bottom of each of said pans, water supply means adapted to supply water to be heated to one corner of the upper of said pans, means in the opposite corner of each of said pans adapted to conduct said water by gravity to each successively lower pan whereby said water is caused to travel diagonally across each of said pans before descending to the next lower pan, said lastnamed means comprising a sleeve of relatively large diameter depending from the bottom of each of said pans respectively, a sleeve of relatively smaller diameter disposed in said larger sleeve, sealing means disposed between said sleeves adapted to frictionally retain said smaller sleeve in position whereby said smaller sleeve may be telescoped upwardly into said larger sleeve to per- 'mit removal of each of said pans, and means for adjustably maintaining a predetermined level of said water in each of said pans, said last-named means comprising a weir having an adjustable weir gate adapted to partition said corner inwhich said water conducting means is disposed from the rest of said pan.

3. In a heat exchanger having a housing, a plurality of pans adapted to contain water and having a bottom, side walls and a top slidably disposed and independently supported in said housing in vertically spaced relation, and means disposed through each of said pans defining a tortuous path for hot gases, means adapted to define a water conduit from each of said pans to each successively lower pan, said means comprising a sleeve of relatively large diameter disposed through the bottom of each of said pans, a sleeve of relatively small diameter disposed through the top of the next subjacent pan concentric with said larger sleeve, and sealing means disposed between said sleeves adapted to frictionally engage said smaller sleeve, whereby said smaller sleeve may be telescoped in said larger sleeve in upper or lower position, said smaller sleeve being free from the top of said next subj acent pan when in its upper position, thereby permitting free removal of each of said pans.

4. In a heat-exchanger having a housing, a plurality of pans adapted to contain water and having a bottom, side walls and a top slidably disclosed and independently supported in said housing in vertically spaced relation, and means disposed through each of said pans defining a tortuous path for hot gases, means adapted to define a water conduit from each of said pans to each successively lower pan, said means comprising a sleeve of relatively large diameter disposed through the bottom of each of said pans, a sleeve of relatively small diameter disposed through the top of the next subjacent pan concentric with said larger sleeve, and sealing means disposed between said sleeves adapted to frictionally engage said smaller sleeve, whereby said smaller sleeve may be telescoped in said larger sleeve in upper or lower position, said smaller sleeve being free from the top of said next subjacent pan when in its upper position, thereby permitting free removal of each of said pans, and means for maintaining a constant water level in each of said pans, said means comprising a weir adapted to partition said water conduit off from the balance of said Dan.

5. In a heat exchanger having a housing, a plurality of pans adapted to contain water and having a bottom, side walls and a top slidably disposed in said housing in vertically spaced relation, and means disposed through each of said pans defining a tortuous path for hot gases, means adapted to define a water conduit from each of said pans to each successively lower pan, said means comprising a sleeve of relatively large diameter disposed through the bottom of each of said pans, a sleeve of relatively small diameter disposed through the top of the next subjacent pan concentric with said larger sleeve, and sealing means disposed between said sleeves adapted to frictionally engage said smaller sleeve, whereby weir having an adjustable weir gate adapted to partition said water conduit off from the balance of said pan.

WILLIAM G. CAR'I'IER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Number Name Date Turner et al. June 29, 1897 Deardufi Feb. 8, 1898 Lewis Nov. 28, 1905 Goodrich Oct. 15, 1907 Pinal Mar. 9, 1920 Owens Mar. 22, 1921 Manning et al May 10, 1921 Walters Dec. 30, 1924 Katzinger Sept. 15, 1925 Acton May 13, 1930 Nissen Apr. 19, 1932 FOREIGN PATENTS Country Date Great Britain of 1884 Great Britain Apr. 19, 1928

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