US3053246A

US3053246A - Hot air heater

Info

Publication number: US3053246A
Application number: US802095A
Authority: US
Inventors: Arnold A Kosarin; Basil A Kosarin
Original assignee: Individual
Current assignee: Individual
Priority date: 1959-03-26
Filing date: 1959-03-26
Publication date: 1962-09-11
Anticipated expiration: 1979-09-11

Description

Sept. 1 l 1962 A. A. KosARlN ETAL 3,053,246

HOT AIR HEATER Filed March 26. 1959 3 Sheets-Sheet 1 @wapa/4A A. A. KosARlN E'rAl. 3,053,246

Sept. 11, 1962 HOT AIR HEATER 5 Sheets-Sheet 2 Filed March 26, 1959 lllllllvlloi Sept. 11, 1962 A. A. KosARlN ETAL. 3,053,246

HOT AIR HEATER Filed March 26, 1959 3 Sheeizs-.SheecI 3 l TL- E l l l I a1- l al /76 z iff/l o n /Jf 116 l .lao/:r i i i ff 42 /Lm L32 I acl "5@ I 1L 4 u 4@ INVENTUM ,4R/vwo 4. wwwa/N BY @Aww 4. mamie/N 3,053,246 HUT AIR HEATER Arnold A. Kosarin and Basil A. Kosarin, both of 7310 Woodward Ave., Detroit, Mich. Filed Mar. 26, 1959, Ser. Noa 802,095 7 Claims. (Cl. 126-110) This invention relates to hot air heaters such as industrial heaters for heating large spaces either directly or by blowing the warm air through ducts which discharge at locations remote from the heater.

The primary object of the invention is the provision of a heater which can be manufactured and sold at competitive prices and which, at the same time, will overcome a number of faults of present-day heaters, as well as incorporating a number of added features not found in commercially available heaters, which altogether lead to a more eicient and longer life heater.

Another object of the invention is the provision of a heater having a combustion chamber located in the air stream to be heated and which is of such configuration as to promote the ilow and distribution of the hot gases burning therewithin so that the walls of the chamber are uniformly heated and which configuration will at the same time prevent the formation of dead air pockets around the outer surface of the chamber. In realizing this object, the combustion chamber is of generally polygonal configuration and specifically of hexagonal configuration. The gases of combustion enter the chamber in a direction normal to the hexagonal shape and just prior to entry have imparted to them a circular motion so that upon entering the chamber they are swirling in a direction around the inside of the combustion chamber and as the gases spread radially to contact the walls of the chamber, they are deflected from wall portion to wall portion of the hexagonal shape of the chamber and evenly distribute their heat to the walls of the chamber. In addition to eliminating dead air pockets around the outside of the chamber which would result in the formation of hot spots, and the promotion of the swirling pattern of the hot gases within the chamber to eect an even distribution of the heat thereof to the walls of the chamber, the hexagonal shape provides excellent structural strength for the chamber.

Another object of Ithe invention is the provision of a floating combustion chamber which allows the chamber to expand and contract under varying temperatures without damage thereto, such as at the joints of the wall portions comprising the chamber. To accomplish this object the chamber is so supported that it may expand and contract relative to its supporting framework.

Another object of the invention is the elimination of strain and stresses on the combustion chamber by the weight of the burner assembly. The conventional practice is to hang or support the burner assembly on a wall of the chamber which results, upon repeated heating and cooling of the chamber, in the wall assuming a permanent bend of deformation, in turn changing the direction of the flame entering the chamber from the burner. In the instant invention the burner assembly is carried by framework independent of the combustion chamber wall with the chamber expansible and contractible relative to the burner.

Another object of the invention is the provision of a bank of economizer tubes which are so connected between and to their headers that the forces of expansion between the tubes and headers do not impose deleterious strains and stresses either upon the tubes, headers, or joints therebetween. This object is realized by forming the joints between the headers and tubes by swaging the tubes in the headers rather than by welding or some other rigid connection, the swaged joint permitting expansion and contraction between the tubes and headers While maintaining a tight seal.

Another object of the invention is the provision of means in the economizer tubes which is inexpensive both in cost and installation and which will create turbulence of the hot gases in the tubes so that the gases transfer a greater portion of their heat to the tubes than would be the case without such means, and with such means of a construction that does not materially restrict the cross sectional area of the tube thereby reducing the hot gas ow therethrough.

Other objects of the invention include the provision of baffles adjacent the bank of economizer tubes which ensure a uniform air flow through the bank; and the provision of radiation shields for directing air upwardly around the combustion chamber and which split the air stream to form walls of insulating air adjacent the outer surfaces of the heater.

Other objects, advantages, and meritorious features will more fully appear from the following description, claims, and accompanying drawings, wherein:

FIG. 1 is a perspective view of a heater embodying our invention;

FIG. 2 is a longitudinal cross sectional view through the heater shown in FG. 1 taken above the blower chamber;

FIG. 3 is a cross sectional view at the front of the heater taken along the line 3--3 of FIG. 2;

FIG. 4 is a cross sectional view taken substantially along the line 4-4 of FIG. 2;

FIG. 5 is a cross sectional view at the burner-receiving aperture of the heater taken on the line 5 5 of FIG. 2;

FIG. 6 is a fragmentary view showing the means for supporting ythe radiation shields; and

FIG. 7 is a sectional view showing the swaged connection of an economizer tube in a wall of a header.

The illustrative embodiment of the invention shown in FIG. l includes a heater casing 10 into which the air to be heated is drawn through a screen 12 at the bottom of the casing and expelled through

discharge openings

14, 16, and v18 at the top of the casing by blower means 20 which includes an electric motor 22. The heater casing is built upon and around a frame generally indicated at 24. The casing includes

opposed end walls

26 and 28 and

opposed side walls

30 and 32. These walls, if desired, may be removably connected together to afford access to the interior of the casing. They form a relatively air-tight enclosure through which the air to be heated passes. In the lbottom of the casing the blower means 20 is supported in any convenient fashion.

Above the blower means and -supported on the framework 24 of the heater is the heat exchanger apparatus which includes a combustion chamber 34 and a bank of economizer tubes 36. The air forced up through the casing =by the blower means 20 strikes the -bottom of the combustion chamber and passes around the chamber and around and through the bank of economizer tubes and is thereby heated before leaving the casing through the

openings

14, 16, and 18. The combustion chamber and economizer tubes are heated by a burner assembly generally indicated at 38. This burner assembly in the form shown in the drawings is of the oil-burning type but it should be understood may be replaced with a fuel gas burning type or any other suitable burner. The burner assembly is supported on the heater as hereinafter described.

The :combustion chamber 34 and the lbank of economizer tubes 36 are supported on the frame 24 of the heater in such fashion that expansion and contraction of the combustion chamber and bank of tubes does not im- 0 pose a strain upon the chamber and bank as a result of termed a four-point floating suspension within the heater. In addition the bank of tubes is capable of expansion and contraction relative to the headers between and to which the tubes are secured so that deleterious strains will not be set up between the headers and the tubes.

The combustion chamber as shown in FIGS. 1, 3, and 4 is of generally polygonal configuration in cross section and specifically of hexagonal configuration. While the hexagonal conliguration is an irregular hexagon, regular hexagonal shapes to suit specific applications may be desirable. The chamber includes opposed

side wall portions

42 and 44 and opposed top and

bottom portions

46 and 48, such portions being integrally secured together at their meeting edges -as by welding along top and

bottom joinder lines

60 and 62, respectively. The

side walls

42 and 44 are bent at lines 45, see FIG. 3, to converge upwardly to joinder line 60, and are also bent along lines 47 to converge downwardly to the joinder line 62. The upward air ow striking bottom wall portion 48 of the combustion chamber will split along the line 62. Because line 62 is narrow and relatively sharp, no dead air pockets will form along line 62 or at any other place on the bottom wall portion 48 giving rise to hot spots as frequently occurs with cylindrical or airfoil shaped chambers.

The front of the chamber is closed by an end wall 50 secured to the side and top and bottom wall portions as by Welding or the like. The rear of the combustion chamber is closed by a header generally indicated at 52. The lower portion of the header forms a rearward extension of the combustion chamber and is closed by rear wall 51. The sides 56A and 58 of the header taper at the bottom and the rear wall is bent to overlie this taper as at 53 and is suitably welded to sides 56 and 58. This tapering portion 53 of the rear wall serves to deflect air upwardly along the rear of the header, between it and rear casing wall 28. The header 52 communicates with the interior of the combustion chamber so that hot gases in the chamber can ow into the header and thence into the tube bank. Above the combustion chamber the header is closed at the front by a tube receiving wall 63, and at the rear by a removable panel 65 to afford access to the tube bank for cleaning purposes. The top of the header is closed by plate 66 to which a lifting eye 67 may be secured. The convergence of the sides S6 and 58 of the header above the lines 60 is not as` great as the convergence of the upper wall portion 46 of the combustion chamber as shown in FIGS. 3 and 4 nor do the side walls 56 and 58 meet at a line of joinder as do the wall portions 46 at the line 60 as shown in FIG. 1. However, the convergence of the sides S6 and 58 of the header is substantially parallel to the convergence of the

upper portions

68 and 70 of the side walls of the heater casing as shown in FIG. 3.

The bank of economzer tubes is provided with another header generally indicated at 72. This header does not communicate with the interior of the combustion chamber but is structurally connected thereto. It includes front and rear walls '69 and 71, the latter receiving the tubes, a bottom wall 73 of the same shape as the top wall portion 46 of the combustion chamber but spaced thereabove, and

side walls

75 and 77 closed by a top 79, all being securely Welded together as a unit. A lifting eye 80 may be secured to top 79. The side walls converge upwardly from lines 81 to the top 79. Header 72 is rigidly supported on the frame of the heater by a pair of upwardly extending

supports

74 and 76 each formed of channel-shaped material rigidly secured as by welding at the bottom to the frame 24 of the heater and secured as by Welding at the upper ends to opposite sides of header 72.

Between headers 52 and 72 is the bank of economizer tubes. The tubes are supported by the headers. Each tube is swaged at opposite ends within apertures in opposed walls of the headers. A fragment of the tubereceiving header wall 71 is shown in FIG. 7 with an economzer tube at 82, and the mouth of the tube swaged thereof.

4 outwardly at 84 at one side of the plate, and at 85 the tube is swaged outwardly on the other side of the plate. Between the outwardly swaged portions 84 and 85 the tube has been expanded to seal against the passage of the hot gases of combustion yet not so much as to prevent slight axial elongation and contraction of the tubes. No welding or the like is used to secure the ends of the tube in the headers. As a result of the swaged connection the tubes are allowed slight axial elongation and contraction relative to the header wall 71 such that any substantial strain is kept out of the tubes and the header wall as a result of the expansion and contraction of the tubes and the heater.

The rearward end of the combustion chamber and, in turn, the header 52, is oatingly supported on the frame of the heater by a pair of upwardly extending channelshaped members S6 and 88, each secured rigidly at its lower end to the frame 24 of the heater and slidably connected to the sides of the combustion chamber. The slidable connection between the

members

86 and 88 and the combustion chamber is effected by pins 90 each rigidly secured to a plate 92 in turn welded to the side of the combustion chamber with the pin extending through a `slot formed in the upper end of each member. It is apparent that this oating support will allow the combustion chamber to expand and contract with the pins 9) sliding in the slots. The slots in

members

86 and 88 and the pins 90 provide two of the four floating points of suspension for the combustion chamber.

The forward end of the combustion chamber is floatingly supported at two points by a pair of

pins

94 and 96 secured respectively to the upper and lower lines of

joinder

60 and 62 of the combustion chamber as by welding and received in brackets 98 and 100 respectively ysecured to the header 72 and the frame 24 of the heater. The

pins

94 and 96 are slidable through the brackets so that upon expansion and contraction of the combustion chamber, the pins slide allowing relative movement between the brackets and the combustion chamber.

It is now apparent that we have provided a support for the heat exchanger apparatus which will allow the same tov expand and contract relative to the heater frame without setting up strains therebetween which will lead to breakage of weld joints or fracture of the metal walls of the heat exchanger apparatus. It is also apparent that by the swaged connection between the tubes and the headers, each tube may expand and contract relative to the headers, combustion chamber, and to other tubes without causing strains which might otherwise be damaging to the entire assembly.

In order to cause a turbulence of the hot gases passing through the economzer tubes, a strip of expanded metal 102 which has been twisted to present a spiral formation, is inserted in each of the tubes to extend from end to end The expanded metal spirals serve to create a turbulence of the hot gases causing greater heat transfer to the walls of the tubes. The expanded metal does not materially reduce the cross sectional area of the tubes and therefore the hot gases may ow therethrough without any appreciable reduction in gas ow.

The front wall 69 of header 72 is provided with an outwardly extending flue pipe 106 to which may be connected an induced draft blower or the like 108 having a suction pipe 109 telescoped in the ue pipe 106. The pipe 106 is welded to the front wall 69 of the header and supported by a burner supporting framework generally indicated at 110 in FIG. 3. The burner framework is provided with a pair of transverse members 112 and 114 which embrace the pipe 106 and carry the weight of the blower. The framework also includes a pair of vertically extending

members

116 and 118 between and to which members 112 and 114 are secured, with

members

116 and 118 rigidly secured at their lower ends to tne frame 24 of the heater.

Bolts 119 or the like, shown in FIGS. 1 and 5, support the burner assembly 38 and extend completely through the front wall 26 of casing 18 and into a plate 116 secured to the

vertical members

116 and 118 of the burner supporting framework 110 so that the weight of the burner is taken on the framework 110 rather than upon the front wall 50 of the combustion chamber. The burner is slidably received through an aperture 128 in the front wall 58 of the combustion chamber. A cylindrical boot 122 may lbe secured as by welding in aperture 120. The burner assembly is provided with a burner pipe 124 which slidably extends into the boot 122. Suitable heat-resistant gasket material such as asbestos or the like 126 encircles the pipe 124. The packing is disposed between the

uprights

116 and 118, and the front wall 26 of the heater casing with the bolts 119 extending through the packing and connected to the uprights as particularly shown in FIG. 5. An apertured plate 128 through which the pipe 124 extends overlies the front wall 26 of the heater casing and is welded to the burner pipe 124 and carries the burner assembly on the bolts 119. It is apparent that upon expansion and contraction of the combustion chamber relative to the frame of the heater, the forward wall 50 of the combustion chamber may slide relative to the burner pipe 124 of the burner assembly. It is also apparent that the weight of the burner assembly is carried by the burner framework 114B rather than by the front wall t) of the combustion cham-I ber.

In order -to direct the air steam upwardly around the combustion chamber and `also to provide a wall of insulating lair adjacent the

walls

26, 28, 30, and 32 of the heater casing, we have provided

radiation shields

138 and 132 at the sides of the combustion chamber and shields 134 'and 136 at the front and rear of the combustion chamber. The shields are individually supported by L-shaped tabs 138 pressed out of the shields, as shown particularly in FIG. 6, `and spot-welded or otherwise secured at convenient places to the walls or the heater casing as shown in FIGS. 2 and 5. These tabs allow the shields to expand and contract without causing an undue strain on the connection between the shields and the heater casing. The tabs will llex slightly under expansion and contraction of the shields. It will be noted that the lower edge of each of the radiation shields is inwardly deflected as at 140 and this inward deflection serves to guide a portion of the air rushing through the heater casing between the shields and the outer wall of the casing to provide an insulating wall of air which will keep the exterior of the casing relatively cool.

In order to assure a uniform distribution or air flow 'through the bank of economzer tubes we provide a pair of air vane assemblies at each side of the combustion chamber just below the bank of tubes. These assemblies are indicated at 142 and 144. Each comprises a hat strip of metal lying in a plane parallel with that of the upwardly converging wall portions 46 of the combustion chamber and secured to the adjacent economzer tubes with each provided with a series of depending vanes 146 spaced `apar-t longitudinally therealong and secured thereto in any convenient fashion -as by welding. The plates and the vanes serve to direct Ithe air ow upwardly `beneath the bank Iof economzer tubes as clearly shown in FIG. 4. It will be noted that each vane `assembly extends outwardly beyond the

sides

42 and 44 of the combustion chamber a distance such that it meets the adjacent radiation shield.

Baifles are secured to the combustion chamber as at 148, 150, and 152 above a clean-out pipe 154 which communicates with the interior of the combustion chamber lat the rear. A pair of

bales

156 and 158 are also secured to the chamber above

theburner opening

156 and 158. These battles serve to cause an air ow across the upper surfaces of the clean-out pipe 154 and burner pipe 124 preventing the lformation of hot spots therein.

6 Air deflectors and 162 are also provided improving the lair ow efficiency out of the casing through the

discharge apertures

14, 16, and 18. In dotted arrows the iiow of hot gases through the combustion chamber and bank of economzer tubes is shown.

As mentioned in the object paragraphs, the hexagonal shape of the combustion chamber promotes the flow of the gases of combustion therewithin. The burner assembly 38 is provided in the Iburner pipe 124 with a. series of vanes or the like which impart Ito the gases a swirling circular motion. Such motion is indicated at G in PIG. 4. As the gases expand upon entering the chamber, they strike the walls thereof and bounce from one wall portion to another around the combustion chamber as they move from the burner end thereof toward the rear end to pass upwardly through the header at the rear end and into the economzer tubes. Because the hot gases tend to bounce in their spiraling motion from one wall portion to another of the hexagonally shaped chamber, they -tend to evenly distribute their heat to the walls of the chamber, such heat distribution being so superior to the conventionally square or rectangularly shaped chambers that we have found the chambers may be made of ordinary steel, rather than stainless steel, and still comply with the safety requirements tor Icombustion chambers. As mentioned hereinbefore, such hexagonal shape also eliminates the formation of dead air pockets around the outer surface of the chamber preventing the formation of hot spots.

What we claim is:

l. In a hot air heater: a casing defining an enclosure, means for moving air to be heated through said enclosure, an elongated combustion chamber generally polygonal in cross section disposed in the enclosure with a pair of opposed vertices lying in an imaginary plane extending substantially parallel with the direction of air movement through the enclosure, means for supporting the chamber within the casing including a supporting member at each side of the chamber with a portion of each supporting member confronting a portion of the chamber, one of said confronting portions provided with a `slot extending in a direction lengthwise of the chamber and the other confronting portion provided with a pin extending into the slot and cooperating therewith to provide a freely movable connection allowing expansion and contraction of the chamber along its length without imposing strains thereon between the chamber and the casing.

2. In a hot air heater: a casing defining an enclosure, means `for moving air to be heated through said enclosure, through which `air to be heated moves, an elongated combustion chamber generally polygonal in cross section disposed in the chamber with a pair of opposed vertices lying in an imaginary plane extending substantially parallel with the direction of air movement through the enclosure, means for supporting the chamber within the casing including a supporting member at each side of the chamber with a portion of each supporting member confronting a portion of the chamber, one of said confronting portions provided wifth `a slot extending in a direction lengthwise or the chamber and the other confronting portion provided with a pin extending into the slot and cooperating therewith to provide a shiftable connection allowing relative movement between the chamber 4and said means upon expansion and contraction of the chamber, `an economzer tube assembly disposed above the combustion chamber and in communication with the interior of the chamber, said assembly including a pair of opposed headers, said assembly including a plurality of economzer tubes extending between and each slidably sealingly received at opposite ends in the headers allowing relative movement between the ltubes and headers upon axial expansion and contraction of the tubes, and a burner assembly projecting through a wall of the combustion chamber.

3. In a hot -air heater: a casing dening an enclosure; means rfor moving air to be heated through said enclosure; a combustion chamber in the casing in the path of air movement; an economizer tube assembly disposed above the chamber and including a pair of headers, one adjacent each end of the chamber; one of said headers rigidly connected to and communicating with the interior of `the chamber, means extending between and connected to the other header and the chamber suspending the chamber from such header, said means including an apertured member slidable along a pin extending lengthwise of the chamber and allowing relative movement between the chamber `and header only in a direction lengthwise of the chamber, first frame means supporting the last-mentioned Vheader in the casing, second frame means ,supporting the opposite end of the chamber in the casing from the last-mentioned header, and a freely shiftable connection between the chamber and the second frame means and including a pin extending transversely of the chamber and a slot within which the pin is received extending in a direction lengthwise of the chamber and allowing relative `shiftable movement between the second frame means and chamber upon expansion and contraction of the chamber.

4. In a hot air heater: a casing providing an enclosure through which air to be heated moves; means for creating `an air flow upwardly through ithe enclosure; a combustion chamber in the casing having opposed sides and end walls, a bottom wall, and an inverted V-shaped top wall; an economizer tube assembly disposed above and adjacent `the top of the chamber, said assembly including a pair of headers one adjecent each end of the chamber with one of the headers communicating with the interior of the chamber; a bank of economizer tubes extending between and communicating with the interior of the headers, said tubes arranged in a generally inverted V-shaped pattern conforming to the inverted V- shaped top of the chamber and spaced above the chamber; and air deecting means at the sides of the chamber and below the bank of tubes and extending beyond the sides of the chamber toward the casing for catching and deeeting air rising along the sides of the chamber upwardly along the inverted V-shaped top and beneath the tube bank.

5. In -a hot air heater: a casing `defining an enclosure, means for moving air to be heated through said enclosure; a combustion chamber in the casing and in the path of air movement through the casing; said chamber having a V-shaped bottom and an opposed inverted V- shaped top; parallel side walls extending between and joining the extremities of the V-shaped top and bottom; end walls joining the top and bottom and side walls, said chamber disposed inV the casing such that the V-shaped bottom faces in the direction of and divides an air stream moving through the casing such that the air stream passes along the diverging sides of 'the V-shaped bottom and Ialong the parallel sides of the chamber; an air deector spaced inwardly from the casing and extending along the extremities of the inverted V-shaped top where Ithe top joins the parallelV sides of the chamber and extending beyond the parallel sides into the air stream to catch air moving over the surfaces of such sides and deflect such air inwardly and upwardly over and against the surfaces of the inverted V-shaped top.

6. In a hot air heater: a casing dening an enclosure; means for moving air to be heated through the enclosure; a combustion chamber in the path of air movement through the casing; said chamber having a V-shaped bottom and an opposed inverted V-shaped top; parallel side walls extending between and joining the extremities of the V-shaped top and bottom; and walls joining the top and bottom and side walls, said chamber disposed inthe casing such that the V-shaped bottom faces in the direction of and divides an air stream moving through the casing such that the air stream passes along the diverging sides of the V-shaped bottom and along the parallel sides of the chamber; an air deector extending along the extremities of the inverted V-shaped top where the top joins the parallel sides of the chamber and extending beyond the parallel sides into the air stream to catch air moving over the surfaces of such sides and deflect such air inwardly and upwardly over the surfaces of the inverted V-shaped top; said end walls of the chamber disposed adjacent but spaced inwardly from confronting end walls of the casing; and the V-shaped bottom of the chamber at one end being closed by a wall extending angularly downwardly and toward the opposite end of the chamber to deflect air between said one end and the adjacent confronting wall of the casing.

7. In a hot air heater: a casing defining an enclosure through which air to be heated moves; a combustion chamber in the path of air movement through the casing; said chamber having a V-shaped bottom and an opposed inverted V-shaped top; parallel side walls extending between and joining the extremities of the V-shaped top and bottom; end walls joining the top and bottom and side walls, said chamber disposed in the casing such that the V- shaped bottom faces in the direction of and divides an air stream moving through the casing such that the air stream passes along the diverging sides of the V-shaped bottom and along the parallel sides of the chamber; an air deflector extending along the extremities of the inverted V-shaped top where the top joins the parallel sides of the chamber and extending beyond the parallel sides into the air stream to catch air moving over the surfaces of such sides and deect such air inwardly and upwardly over the surfaces of the inverted V-shaped top; a bank of economizer tubes arranged spaced above the inverted V-shaped top of the chamber with all of the tubes disposed directly above the chamber and with the air deflectors delecting air into the space between the inverted V-shaped top and the tube bank; a header rigidly connected to and communicating with the interior of the chamber at one end thereof and into which the tubes are sealingly received at one end; a second header at the opposite end of the chamber connected thereto for suspending and allowing relative shiftable movement lengthwise of the chamber between the header and chamber and into which the opposite ends of the tubes are sealingly received; means in the casing supporting said one end of the chamber for shiftable movement upon expansion and contraction of the chamber; and means in the casing supporting said second header for shiftable movement upon longitudinal expansion and contraction of the tubes.

References Cited in the le of this patent UNITED STATES PATENTS 130,913 Gaston Aug. 27, 1872 1,056,373 Segelken Mar. 18, 1913 1,644,180 Croan Oct. 4, 1927 1,862,219 Harrison lune 7, 1932 1,936,003 White Nov. 2l, 1933 2,070,427 Faunce Feb. 9, 1937 2,149,182 Powers Feb. 28, 1939 2,160,269 Iorolemon May 30, 1939 2,353,606 Watts July 11, 1944 2,669,297 Sherman Feb. 16, 1954 2,800,126 Costello et al. July 23, 1957 2,836,169 Reilly May 27, 1958 2,857,906 Davidson et al Oct. 28, 1958 2,979,050 Costello Apr. 11, 1961 2,984,235 Johnson et al. May 16, 1961 FOREIGN PATENTS 568,038 Belgium June 14, 1958