US2630165A

US2630165A - Liquid fuel burner construction

Info

Publication number: US2630165A
Application number: US70219A
Authority: US
Inventors: Resek Marc
Original assignee: Perfection Stove Co
Current assignee: Perfection Stove Co
Priority date: 1946-06-03
Filing date: 1949-01-11
Publication date: 1953-03-03
Anticipated expiration: 1970-03-03

Description

March 3, 1953 M. RESEK LIQUID FUEL. BURNER CONSTRUCTION 2 SHEETS-SHEET 2 1 105 Original Filed June 5, 1946 INVEN TOR. Marc flesek :iinin Patented Mar. 3, 1953 UNITED STATES PATENT OFFICE LIQUID FUEL BURNER CONSTRUCTION Marc Resck, Cleveland Heights, Ohio, assignor to Perfection Stove Company, Cleveland, Ohio, a

corporation of Ohio 14 Claims. 1

This invention relates to improvements in the construction of heaters, more particularly those of the liquid fuel burning type.

The invention was conceived and developed as a part of an engine heating apparatus for use on automotive vehicles, as disclosed in my copending application Serial No. 674, 012, filed June 3, 1946, now Patent No. 2,509,399, and of which this application is a division.

The general object of the invention is the production of a relatively simple and very substantial and serviceable construction for heaters of the liquid fuel burning class.

Another object is to provide a liquid fuel burner of the bowl type that will operate efficiently and produce a clean flame throughout its entire range of operation, including lowest and highest fires.

Additional objects and advantages will appear as I proceed to describe the invention in detail by reference to the accompanying drawings wherein like characters designate like parts in the several views.

In the drawings, Fig. 1 is a side elevational view of the heater with certain parts shown in section, in offset planes, as indicated by the line l-| of Fig. 2; Fig. 2 is a plan view of the heater, partly in section, as on the line 22 of Fig. 1; Fig. 3 is a perspective view, with parts broken away, of the lower assembly of the heater construction, including the burner bowl and the fuel feed and control means, and Fig. 4 is a plan view of the electrical igniter.

The heater construction, designated generally by the reference numeral I, consists of two major assemblies. As best illustrated in Figs. 1 and 3, the bottom assembly includes a burner bowl that is denoted, generally, by the reference numeral 2. The top portion of the bowl is formed by a cylindrical wall 3 and an integral annular top wall 4, the relatively large central opening of which is surrounded by a depending flange 5. Secured to and spaced from the wall 4, by a suitable number of connectors 6, is the annular portion 1? of a throat member 8 that is flared outwardly at its upper end and terminates in a cylindrical flange 9, the body portion of the throat member being of approximately the same diameter as the wall 3 of the burner bowl. The inner edge of the annular portion I is curved upwardly and thence downwardly to provide a flange l9 that is spaced radiallyinwardly from and is surrounded by the previously mentioned flange 5. The space between the annular portion "I of the throat member 8 and the top wall of the burner bowl 2 forms a secondary air passage II.

The lower end of the wall 3 is telescoped into a slightly enlarged portion of a cylindrical wall 12 of a bottom member Hi, the lower end of which constitutes the bottom wall It of the burner bowl. Projecting upwardly through a circular opening at the center of the bottom wall 15 is a tube l0, shown as flared outwardly at its lower end a short distance below the plane of the adjacent portion of said bottom wall. The joints between the walls 3 and E2, and between the wall l5 and the tube it, are made secure and liquid tight by welding or other means. Above its telescoping connection with the wall 3, the wall I2 is flared outwardly and then continues upwardly as a cylindrical wall iii of about the same diameter as the flange 9 of the throat member 8. The top portion of the wall It is desirably convergent, as indicated at 19.

Surrounding the lower portion of the burner bowl is a cup-like shell 20, the cylindrical edge wall 2i of which fits over the lower portion of the wall 18 of the member 14, While the top edge portion of the wall 2| is oflfset outwardly to provide between itself and the top portion of the wall [8 a channel 22 that contains :a gasket 23 of packing material. The perimeter of the shell 20 is divergent, as shown at 24, to provide, with the previously mentioned portion [9, a flared entrance to the channel 22. The wall H is secured to the wall IS in any suitable manner, as by welding. Surrounding a large central opening in the bottom of the shell 20 is an upstanding fiange 25 that is engaged with the bottom wall of the burner bowl. When the burner is in operation, the bottom of the bowl is protected from the atmospheric temperature by the shell 20, so that it will not be chilled to such an extent as to adversely affect vaporization of the liquid fuel in the bowl. Above its connection with the bottom member [2, the peripheral wall 3 of the burner bowl is provided with air admitting openings 26.

30 denotes, generally, an electrical igniter unit that is separably connected to the: bottom assembly or, more specifically, to the bottom of the shell 20. Said igniter, shown in vertical section in Fig. l and in plan View in Fig. 4, consists of a base 3|, desirably formed from sheet metal to provide a closure for the tube it. The central area of the base 3! is embossed upwardly to provide, between cylindrical portions of different diameters, an annular seat 34 which is adapted to bear against the flared lower end of the tube Hi. The end portions 35 of the base 3! have laterally opening and inwardly enlarging notches 36 that are equally spaced from the axis of the elevated central portion 31 of the base and are in diametrical alignment therewith. One side of each end portion of the base, opposite its notch 36, is turned downwardly to provide a wing 38. Secured to and depending from the bottom of the shell 20 are studs 40, to the threaded lower ends of which are applied nuts 4|. Slidable on each of the studs 40 is the apertured frusto conical upper end of a thimble 42 that is urged upwardly along the stud by a spring 43 that surrounds the stud and is compressed between said upper end and the nut M. The studs are so placed that when the igniter unit is presented to the bottom assembly with the elevated central portion 31 of its base piloted in the bottom of the tube It and with the seat 34 engaging said tube, the studs are in the orbital path of the notches 36. Now, upon turning the base by applying force to the wings 38, the slightly embossed portions of the base about the notches 36 override the complementarily shaped upper ends of the thimbles 42, the springs 43 now acting to urge the base upwardly against the tube l6.

Extending through apertures in the central elevated portion 3'! of the base 31 are posts as and 46, the latter being insulated from the base by a bushing 41 and a washer 58 of insulating material. Any suitable expedient may be employed to otherwise secure the posts 35 and 45 to the base 3 I, the post 45 being insulated from the base in the manner just described, while the post 425 is grounded to the base, The upper ends of the posts, shown as flattened, are turned laterally and spread apart; and supported by and between said ends, and electrically connected thereto, is an igniter element 553, desirably consisting of a coil of electrical resistance wire. A wick of asbestos or other non-combustible absorbent material surrounds, and desirably extends slightly above, the tube 16, and, by capillary action, conducts liquid fuel from the bottom of the bowl upwardly into vaporizing and lighting relation to the igniter 59.

Liquid fuel feeding and control means, designated generally by the reference numeral 52, constitutes a part, of the lower assembly, although, in detail, it. forms no part of the present invention, Description thereof, suflicient for the present disclosure, will be made hereinafter.

The upper assembly of the heater includes a cylindrical casing 55 that is only slightly greater in, diameter than the peripheral flange 9 of the throat member 3. This casing is engaged downwardly over said member and has its lower end projected into the channel 22 and seated against the gasket 23. Apertured lugs 56 are secured to and extend outwardly from the casing 55 near the lower end thereof, and these lugs are adapted to align, vertically, with bifurcated lugs 5! that are secured to and extend laterally from the lower portion of the bottom shell 20. Bolts 58 have their threaded upper ends engaged upwardly through the apertures of the lugs 56 and thereabove are threaded through nuts 59 that are nonrotatably supported by the lugs 56. The bolts 58 have winged heads 6% that repose beneath the bifurcated lugs 5'! when the bolts are engaged within the notches thereof, washers being interposed between'the heads 6t and the lugs 51. By turning the bolts by means of their heads 6d, the upper and lower assemblies of the heater may be drawn firmly together with the joint 4 between them sealed by the gasket 23. The bolts are desirably retained against complete withdrawal from the nuts 59 by cotter pins 6| that extend through holes in the bolts. The upper end of the casing 55 is shown as surrounded by an inwardly turned stiffening flange 65, and surmounting the casing in an annular top 66 having its central opening surrounded by an upstanding flange El. The latter flange is adapted to have attached to it by suitable means a flue or conduit for carrying ofi the products of combustion, as will be readily understood, and as shown in the parent application. For attaching the heater to a part of a vehicle or other support is a mounting plate '10, shown in dotted lines in Fig. 1 and in full lines in Fig. 2. The top 66 is provided with an opening i5 through which the action of the burner may be observed, or by way of which a taper may be inserted for lighting the burner in case the electrical igniter fails. A cover it is hingedly connected to the top 65 and normally closes said opening.

A flat ring 18 is suitably connected to and extends inwardly from the wall of the casing 55 immediately above the throat membert. Within a combustion chamber formed by the portion of the casing above said ring is disposed, in spaced relation to the walls of the casing, a circulating and heat exchanging unit 80. This unit, in the present embodiment, consists of an outer dome 8! and an inner dome $2, the latter being inserted upwardly into the former and having its lower end flared outwardly and welded or otherwise secured to the corresponding end of the outer dome. Flues 83 have their reduced ends sealed within aligned openings in the circular top walls of the inner and outer domes. Internally threaded

spuds

85 and 86 have their inner ends secured within apertures in the peripheral wall of the outer dome 8i and form, respectively, the inlet and the outlet for the liquid circulating space between the domes. 81 is a bar of relatively heavy stiff metal which has its ends rigidly fastened to the spuds 85 and 8E, and adjacent the spuds said bar has threaded apertures in which are engaged screws 88, shown as fitted with lock washers, the screws being projected through registering holes in the wall of the casing 55. By this means, the circulating unit 88 is securely fastened to the casing 55 in spaced relation to the peripheral wall thereof so that products of combustion rising into the combustion chamber may pass upwardly through and about the unit and out through the central opening of the top 56. The purpose of the ring #6 is three-fold. It imparts roundness and rigidity to the casing 55, insuring easy insertion of the throat member 8.; it directs the major portion of the rising products through the circulating unit 88, and it prevents air that escapes from the plenum chamber, later to be described, about the flange 9, from rising directly into the space about the circulating uni-t. Such air is deflected inwardly by the ring and mingles with the products.

Secured to one side of the casing 55-, adjacent the top thereof, is a bracket 96 that supports an air impeller or blower 9|, and an electric motor 92 by which the fan or rotor of the air impeller or blower is driven. The casing 93 of the blower encloses the fan or rotor 94, shown in dotted lines in Fig. 2. The outlet. of the blower casing 533 communicates, through a conduit 95 and a fitting 96, with aplenum chamber l-BG set off within the casing 55 by the enlarged upper ends of the throat member 8 and the bottom member I4 of the burner bowl, the casing wall having an opening in the form of a horizontal slot wherewith the outlet end of the fitting 96 registers.

It is apparent from the foregoing that when the electric motor 92 is energized, air will be drawn from the atmosphere through the usual inlet opening (not shown) of the casing 93 and forced through the conduit 95 and fitting 96 into the plenum chamber IEO, thereby to supply primary air to the burner bowl through the perforations 26, and secondary air thereto through the passage I I, said secondary air being directed downwardly into the bowl by means of the flange Ill.

The liquid fuel feeding and control means 52,

.previously referred to as a part of the lower assembly, is rigidly secured, through brackets I04 and I85, to the side of the bottom shell of the lower assembly. This liquid fuel feeding and control means includes a casing I06, and the interior of the casing is separated by a transverse partition [ill into a receiving compartment I08 (Fig. 3) and a delivery compartment I09. As previously pointed out, the structural features of the liquid fuel feeding and control means form no part of the present invention, although it may be briefly explained, by reference to Fig. 3, that liquid fuel is delivered from a suitable source through a filter I I0, and by way of a float controlled valve II I, to the receiving compartment I I38; and it is carried over the partition I ill by a wick siphon I I5 that straddles said partition and is adapted to be vertically adjusted by a lever Ilia, pivotally connected to a bracket Ill that surmounts the casing lflfi, and which lever has one of its ends connected, by a pivot member IIB, to the upper end of an actuator III] of the wick carrier I20.

Communicative connections are provided between the delivery compartment I09 and the burner bowl 2, and in the present instance these connections include a valve casing I which has its inlet end sealed within an aperture in the bottom of the casing I06. The connections are completed by a pipe I25 that leads from the outlet of the valve casing I25, through an opening in the shell 20, and has its end remote from said valve casing sealed within an aperture in the bottom member I2 of the burner bowl. An air tube I 23 is desirably incorporated in the burner bowl for admitting air from the plenum chamber IE6 (or more specifically from the secondary air passage I I) to the region immediately above the bottom wall of the bowl in the immediate vicinity of the fuel supply pipe I26. This insures complete vaporization of the fuel, including its heavier constituents that are otherwise liable not to vaporize and to accumulate within the bottom of the bowl. A valve I (Fig. 3) occupies the valve casing I25 and it is urged upwardly by a spring I34, compressed between the valve and a screw cap I that is applied to the lower end of the valve casing, so as to engage the tapered upper end of the valve with a seat I35. A relatively long stem I31 rises from the valve I33 through the inlet end of the casing I25 and projects an appreciable distance into the delivery compartment 9 in the path of a lug I38 on the wick carrier I23. When the wick carrier is depressed enough to lower the bottom portion of the wick below the liquid fuel level in the receiving compartment I38 and thereby cause a feeding of the fuel over the partition I01 into the delivery compartment I99, the 111;! I38 engages the valve stem I34' and depresses and unseats the valve I30, thereby to permit the liquid fuel to pass on from the delivery compartment through the valve casing and the pipe I26 to the burner bowl. For a full and complete description of this liquid fuel feeding and control means, reference is made to the aforesaid Patent No. 2,509,399.

Having thus described by invention, what I claim is:

1. A heater construction including an upper assembly and a lower assembly; the lower assembly comprising a burner bowl, a throat member surmounting said bowl, the throat member consisting of an annular wall having a portion of approximately the same diameter as the bowl and flared outwardly adjacent its top to a diameter substantially greater than that of the burner bowl, an element surrounding the burner bowl and including an annular wall portion which extends outwardly and upwardly and is of substantially the same diameter within the distance of its upwardly extending portion as the top portion of the throat member, an annular wall surrounding said element and having a circumferential portion spaced radially from the corresponding portion of said element to provide an. upwardly opening channel; the upper assembly comprising a casing that fits down over the throat member and has its lower end disposed within said channel, means for admitting air to the space enclosed by the casing between said throat member and said element, the burner bowl having openings for admitting air from said space to the bowl, and means binding the upper and lower assemblies together.

2. A heater construction according to claim 1, wherein a body of packing material occupies the bottom of said channel wherewith the lower end of the casing has sealing contact.

3. A heater construction including an upper assembly and a lower assembly; the lower assembly comprising a burner bowl, a throat member surmounting said bowl, the throat member consisting of an annular wall having a portion of approximately the same diameter as the bowl and flared outwardly at its top to a diameter substantially greater than that of the burner bowl, said bowl incorporating an element having a peripheral annular wall portion which extends outwardly and upwardly and is of substantially the same diameter within the distance of its upwardly extending portion as the top portion of the throat member, an annular wall surrounding said peripheral annular wall portion and having the region adjacent its top spaced radially from the corresponding region of said peripheral annular wall portion to provide an upwardly opening channel; the upper assembly comprising a casing that fits down over the throat member and has its lower edge disposed within said channel, means for admitting air to the space enclosed by the casing between said throat member and said peripheral annular wall portion, said bowl being provided with means for admitting air from said space to the bowl, and means binding the upper and lower assemblies together.

4. A heater construction including an upper assembly and a lower assembly; the lower assembly comprising a burner bowl, a throat member surmounting said bowl, the throat member consisting of an annular wall having a portion of approximately the same diameter as the burner bowl and flared outwardly at its top to a diameter substantially greater than that of the burner bowl, an element surrounding the substantially the same diameter within the distance of its upwardly extending portion as the top portion of the throat member, an annular wall surrounding said element and having its top portion spaced radially from the corresponding portion of said element to provide an upwardly opening channel; the upper assembly comprising a casing that fits down over the throat member and has its lower edge disposed Within said channel, means for admitting air to the space enclosed by the casing between said throat member and said element, the burner bowl having openings for admitting air from said space to the upper portion of the bowl, means for delivering liquid fuel to the bottom of the bowl, an air supply tube arranged with its receiving end in said space and its discharge end adjacent the portion of the bottom of the bowl to which the fuel is delivered, and means binding the upper and lower assemblies together,

5. A heater construction including an upper assembly and a lower assembly; the lower assembly comprising a burner bowl having a top wall provided with a relatively large opening, a throat member consisting of an annular wall having a portion of approximately the diameter of the bowl and extended inwardly at its lower end to define an opening registering with that of said top wall, means securing said member to said top wall in spaced relation thereto and in such manner as to permit circulation of fluid through the space between the member and the top wall, the throat member being flared outwardly at its top to a diameter substantially greater than that of the burner bowl, an element surrounding the bowl and including an annular wall portion which extends outwardly and upwardly and is of substantially the same diameter within the distance of its upwardly extending portion as the top portion of the throat member, an annular wall surrounding the annular wall portion of said element and having its top region spaced radially from the corresponding region of said annular wall portion to provide an upwardly opening channel; the upper assembly comprising a casing that fits down over the throat member and has its lower edge disposed within said channel, means for admitting air to the space enclosed by the casing between said throat member and the annular wall portion of said element, means for delivering liquid fuel to the bottom of the bowl, an air supply tube hav= ing its upper end projected through the top wall of the burner bowl and opening into the space between said wall and the throat member, the lower end of the tube being adjacent the portion of the bottom of the bowl to which the fuel is delivered, and means binding the upper and lower assemblies together.

6. A heater construction including an upper assembly and a lower assembly; the lower assembly comprising a burner bowl section having a top wall provided with a relatively large opening, a throat member consisting of an annular wall having a portion of approximately the diameter of the bowl and extended inwardly at its lower end to define an opening registering with that of said top wall, means securing said mem ber to said top wall in spaced relation -thereto and in such manner as to permit circulation "of fluid through the space between the member and the top wall, the throat member being flared out= wardly at its top to a diameter substantially greater than that of said burner bowl section, an element forming the bottom 0': the burner bowl and having an annular peripheral wall portion which extends outwardly and upwardly and is of substantially the same diameter within the distance of its upwardly extending portion as the top portion of the throat member, an annular wall surrounding the annular wall portion of said element and having its top region spaced radially from. the corresponding region of said annular wall portion to provide an upwardly opening channel; the upper assembly comprising a casing that fits down over the throat member and has its lower edge disposed within said channel, means for admitting air to the space enclosed by the casing between said throat member and said element, means for delivering liquid fuel to the bowl, and means bindin the upper and lower assemblies together.

7; A heater construction including an upper assembly and a lower assembly; the lower assembly comprising a burner bowl having a top wall provided with a relatively large opening, a throat member consisting of an annular wall having a portion or approximately the diameter of the bowl and extended inwardly at its lower end to define an opening registering with that of said top wall, means securing said member to said top wall in spaced relation thereto and in such manner as to permit circulation through the space between the member and the top wall, the throat member being flared outwardly at its top to a diameter substantially greater than that of the burner bowl, an annular bottom member incorporated with the burner bowl and including a peripheral wall portion which extends outwardly and upwardly and is of substantially the same diameter within the distance of its upwardly extending portion as the top portion of the throat member, an annular shell surrounding the bottom member and having its top edge in about the plane of that of the peripheral wall portion of the bottom ncember and spaced therefrom to provide an upwardly opening channel; the upper assembly comprising a casing that fits down over the throat member and has its lower edge disposed within said channel, means for admitting air to the space within the casing between said throat member and said bottom member, and means binding the upper and lower assemblies together. 7

'8, A heater construction including an upper assembly and a lower assembly; the lower assembly comprising a burner bowl having a top wall provided with a relatively larger opening, a threat member consisting of an annular wall having a portion of approximately the diameter of the burner bowl and extended inwardly at its lower end to define an opening registering with that of the top wall, means securing said member to said top wall in spaced relation thereto and in such manner that fluid may circulate through the space between said member and the top wall, the throat member being flared outwardly at its top to a diameter substantially greater than that of the burner bowl and terminating in a cylindrical flange, an annular bottom member incorporated with the burner bowl and including a peripheral wall portion which extends outwardly and thence upwardly and is of substantially-the same diameter within the distance of its upwardly extending portion as the aforesaid flange of the throat member and disposed approximately in axial alignment therewith, an annular shell surrounding the bottom 9 member and having a peripheral cylindrical wall that fits over the peripheral wall portion of said bottom member, the edge portion of the'cylindrical wall of the shell being oifset outwardly to provide between itself and the adjacent region of the peripheral wall portion of the bottom member an upwardly facing channel; the upper assembly comprising a cylindrical casing that fits down over the throat member and has its lower edge engaged within the aforesaid channel, means for admitting air to the space within the casing between said throat member and said peripheral wall portion of the bottom member, and means binding the upper and lower assemblies together.

9. A heater construction according to claim 8, wherein said means for binding the upper and lower assemblies together consists of sets of lugs extending radially from the upper and lower assemblies, those of each set being in substantially vertical alignment, and tie bolts cooperating with said lugs for drawing the assemblies toward each other.

10. A heater construction according to claim 9, wherein packing material occupies the bottom of said channel, and the lower edge of the casing has sealing contact with said material.

11. A heater construction including an upper assembly and a lower assembly; the lower assembly comprising a burner bowl having a top wall provided with a relatively large opening, a throat member consisting of an annular wall having a portion of approximately the diameter of the bowl and extended inwardly at its lower end to define an opening registering with that of said top wall, means securing said member to said top wall in spaced relation thereto, the throat member being flared outwardly at its top to a diameter substantially greater than that of the burner bowl, an annular bottom member incorporated with the burner bowl and, including a peripheral wall portion which extends outwardly and upwardly and is of substantially the same diameter within the distance of its upwardly extending portion as the top portion of the throat member, an annular shell surrounding the bottom member and having its top edge in about the plane of the top edge of said peripheral wall portion of the bottom member and spaced therefrom to provide an upwardly opening channel; the upper assembly comprising a casing that fits down over the throat member and has its lower end disposed within said channel, means for admitting air to the space within the casing between said throat member and said peripheral wall portion of the bottom member, means binding the upper and lower assemblies together, liquid fuel feeding means constituting a part of the lower assembly, and communicative connections between said means and the burner bowl.

12. A heater construction including an upper assembly and a lower assembly; the lower assembly comprising a burner bowl, a throat member surmounting the burner bowl, the throat member consisting of an annular wall having a portion of approximately the same diameter as the bowl and flared outwardly at its top to a diameter substantially greater than that of the burner bowl, an annular bottom member incorporated with the burner bowl and including a peripheral wall portion which extends outwardly and upwardly and is of substantially the same diameter within the distance of its upwardly extending portion as the top portion of the throat member, an annular wall surrounding the top region of said peripheral wall portion of the bottom member and spaced therefrom to provide an upwardly opening channel; the upper assembly comprising a casing that fits down over the throat member and has its lower end disposed within said channel, means for admitting air to the space within the casing between said throat member and said peripheral wall portion or" the bottom member, the burner bowl having openings for the passage of air from said space to the burner bowl, means binding the upper and lower assemblies together, means for supplying liquid fuel to the burner bowl, the burner bowl having a bottom opening, a tube rising within the burner bowl and sealed to the bottom wall thereof about said opening, a seat surrounding the lower end of the tube, a closure for engagement with said seat, yielding means removably supporting the closure and urging it against said seat, and an electrical igniter carried by the closure and projecting upwardly through said tube.

13. A heater construction including an upper assembly and a lower assembly; the lower assembly comprising a burner bowl, a threat member surmounting said bowl, the throat member consisting of an annular wall having a portion of approximately the same diameter as the bowl and flared outwardly at its top and shaped to form a cylindrical flange having a diameter substantially greater than that of the burner bowl, said bowl incorporating an element having a peripheral wall portion which extends outwardly and upwardly and is of substantially the same diameter within the distance of its upwardly extending portion as the top of the throat member, an annular part surrounding the peripheral wall portion of said element and having its top region spaced radially from the corresponding region of said peripheral wall portion to provide an upwardly opening channel; the upper assembly comprising a casing having a cylindrical peripheral wall that fits down over the throat member and has its lower edge disposed within said channel, a ring-like member extending inwardly from said peripheral wall of the casing immediately above the throat member, means for admitting air to the space enclosed by the casing between said throat member and said element, the burner bowl having openings for admitting air from said space to the upper portion of the bowl.

14. A heater construction according to claim 1, having combined therewith an air impeller that forms a part of the upper assembly and the outlet of which has communicative connection with said space, and liquid fuel feeding and control means incorporated with the lower assembly and having communicative connection with the burner bowl.

MARC RESEK.

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

UNITED STATES PATENTS Number Name Date 2,342,272 Hayter Feb. 22, 1944 2,369,999 Behrendt et a1 Feb. 20, 1945 2,393,232 Breese Jan. 22, 1946 2,393,411 Resek Jan. 22, 1946 2,418,622 Chadwick Apr. 8, 1947 2,431,456 Bock Nov, 25, 1947