US2683209A

US2683209A - Electric unit heater

Info

Publication number: US2683209A
Application number: US168057A
Authority: US
Inventors: Beckjord William Edward
Original assignee: Individual
Current assignee: Individual
Priority date: 1950-06-14
Filing date: 1950-06-14
Publication date: 1954-07-06
Anticipated expiration: 1971-07-06

Description

W. E. BECKJORD ELECTRIC UNIT HEATER July 6, 1954 2 Shets-Sheet 1 Filed June 14, 1950 INVENTOR. Will 1AM FOWARD Eff/(J01?!) July 6, 1954 w, BECKJQRD 2,683,209

ELECTRIC UNIT HEATER Filed June 14, 1950 2 Sheets-Sheet 2 MrWM/J Patented July 6, 1954 UNITED STATES PATENT OFFICE 3 Claims.

This invention relates to an electric space heater of the dark or non-glow type and more particularly to a heat transfer unit adapted to convert electrical energy. into heatenerg-y.

. The prior art illustrates a great many-electrical'heating devices in which electric energy is converted into heat. energy. Most of these units provide a great many heated surfaces or blades that are small in area, extremely small in cross section and are generally spaced closelytogether. The surface temperature of the blades closely spaced blades. In the forced air space heaters there is a great deal of heat provided over small blades in close relationship to restrict the forced air draft that is blown through the While the air is immediately between or surrounding-the highly heated blades or fins. Whereas, in applicants device I have found that it is desirable to provide a greater'spacing between blades or fins to provide a greater area for theblades or fins that are to be heated and to control or reduce the surface temperature of the blades or fins and permit a natural flow of air between and around the heated-surfaces. Thus the air-flowing through a convector heater of applicantside sign will have a gradient, that is, there is a definite gradient of the temperature of the air entering theheater, the air flowing through the heater and the air exhausted from the heater.

- An object of this invention is to provide a heat transfer unit which may be multiplied in various-forms to fit the necessary heat requirements forpractically any installation.

A further object of this invention is to provide a convector heater which will transfer the heat energy from a given electrical resistance'to a maximum volume of air with the greatest degree of efiiciency.

Another object of this invention is to provide a convector'heater which will convert electrical energy into heat energy to heat a maximum volof unrestricted heated air.

A further object of this vide a predetermined heating surface in a con- A still further object of this invention is to provide an electrical convector heater with a time-distance factor for the column of air passing through the heater by designing a multiple of a unit that will produce the maximum volume of heated air with a given electrical resistance.

A still further'object of this invention is to provide a convector heater which will instigate a natural circulation ofair through the heater to produce the largest volume of heated air at a predetermined temperature.

A further object of thisinvention is to provide a convector heater which will instigate a natural circulation of air through the heater over a maximum length of heated surface that is' designed to come to a specific surface temperature with a iven electrical resistance.

A further object of this invention is to provide a convector" heater that'is constructed of a plurality of heater units which are so located in the heater to permit the heater to bedivided horizontally in inches so that the heater is cdm prised of a plurality of unitinches and all factors relating to one unit inch may be multiplied according to the horizontal and or vertical dimension of the heater. r i 1 It is-an object of this invention to provide an electrical space-heater in which a plurality of fins or blades are formed of'a large area to permit a natural flow of air without restricting the flow and in' which the surface temperature of the fins'or blades is of a predetermined temperature that will not overheat the air adjacent to the fins or blades and will encourage the natural flow of air'as it becomes heated passing through the heater. 1

It is afurther'object of this'invention to heat a large volume of air toa moderate temperature and thus circulate the heated air until the total volume of air is heated to a uniform temper ature. Y

It is a further object of this invention to heat a large volume "of air to a uniform" temperature and at the same time avoid hotspots and a tem perature gradient in the space heated.

Another object of this invention is to heat a large volume of air to a 'moderate temperature and circulate thisair'while being heated to avoid the natural tendency of overheated air to rise and pocket against the ceiling of the heated space.

Further objects of this invention may be apparent by reference to the accompanying detailed description and the drawings in which Fig. 1 illustrates an elevational view of the heater,

. per se must Fig. 2 is a cross sectional view taken on line 2-2 of Fig. 1,

Fig. 3 is a cross sectional view taken on line 3-3 of Fig. 1,

Fig. i is a schematic illustration of various combinations of the heater units and the wiring diagram for the operation of said units.

Fig. 5 is a top plan view of a heater strip and its heating blades,

Fig. 6 is a cross sectional view taken on line 6-6 of Fig. 5,

Fig. '7 is a plan view partly in section of a heater element,

Fig. 8 is a side elevational view of two heater units positioned in spaced relationship similar to that illustrated in Fig. 1,

Fig. 9 is an isomeric view illustratinga unit inch measurement taken on Fig. 8,

Fig. 10 is an isometric view similar to Fig. 9 but illustrating another embodiment of the plate structure,

Fig. 11 is a schematic illustration of a further combination of the heater units and Fig. 12 is a schematic illustration of a still further combination of the heater units.

Although applicant hasillustrated a space heater H in Figs. 1, 2 and 3 this is by way of example, in fact the preferred example which incorporates the features of this invention. The general design of the space heater ll illustrated is a departure from the prior art as the heater unit be mounted in a very definite relationship to the air passage through the heater and the location and spacing of the air duct about the heater must be exactly as illustrated and described herein to produce the maximum efiiciency expected of this heater. The space heater i I may be considered as a portable unit or a stationary unit according to the installation as the only requirement is to permit plugging the electrical conduit into the line for the power source. The structure of the heater H is according to Figs. 1, 2 and 3 comprised of a hollow boxlike housing [2 enclosed on three sides with a back 14 and a pair of sides 15 and I6 and an enclosed top H. The back l4 and sides l5 and I6 may be formed as illustrated in Fig. 3. N3 of the heater is spaced slightly above the supporting floor line and is comprised of a solid portion 59 and a grill opening 20. 2! and 22 are mounted to the inner wall surface of the front portion [9 slightly below the central axis of the heater. The brackets 21 and 22 are generally L shaped andare provided with apertures 23 for mounting the electrical heating unit and apertures 24 to permit affixing the brackets to the inner side of the portion l9. It will be noted that the inner wall is provided with an angular shoulder 25 also provided with an aperture to receive a bolt or such affixing device that must be aligned with the aperture 24 of the bracket. An electrical heating unit Si? is provided and mounted within the heater and supported between the brackets 21 and 22 being affixed to these brackets by bolts 3% which are affixed through the apertures 23. The heater unit 39 in this particular embodiment is comprised of a pair of strip heater elements 33 upon which a plurality of metal blades as are mounted in a predetermined spaced relationship. In this particular design we have employed a pair of 500 watt strip heater elements 33, however the strip heater elements are provided in various sizes (as illustrated in Fig. i) and we may similarly provide a pair of 250 watt units D (Fig. 4) and The front panel A. pair of brackets i illustrated in in such installation we would design the cabinet to be half the length of the cabinet illustrated using the shorter units mounted in exactly the same relationship. We may similarly use a pair of 1000 watt units E (Fig. 4) and in such instance we would install them in the same relationship but the cabinet would be twice the length of the present cabinet illustrated. Various combinations of heater elements may be provided as Fig. 4, that is, with the cabinet as illustrated we may provide one heater element A (Fig. 4) of 500 watts which is made up of multiples of half a unit inch, whereas with the units B as illustrated which are made up of multiples of a unit inch, and when it is desirable we may use three 500 watt units C which would be made up of multiples of one and one half unit inch. We may combine other strips of less or greater wattage to provide heater elements as desired. In any case whether we use a single element as in A or triple elements as in C each element is to be connected to the source of electrical supply as illustrated in Fig. 4 and of course the elements and line may be connected through a thermostatic element is that may be situated at a proper point in the space to be heated and thus the heater elements will be turned on and 01? according to the demand for heat.

Although we have shown a so called electrical strip element as our heating means we are not limited to this type of element. We may construct a similar type element but in any case the element will simply be comprised of a resistance embedded in a refractory material and properly encased in a steel sheath. Elements are also constructed in tubular form but for the purposes of this invention we have selected the strip element with both terminals located at one end of the strip as illustrated in Fig. '7. This strip 33 is comprised of a nickel chromium alloy resistor embedded in a special refractory which is compacted to maximum density under pressure. The strip is fired in a furnace at 1500 F. to semivitrify. The strip is then enclosed in a steel sheath and the ends of the resistance wire are connected to suitable screw type terminals which are fastened to and insulated from the steel sheath. The strip illustrated in Fig. '7 is a 500 watt element to be used on a volt system. In Fig. 5 we have illustrated a plan view of one of the strips as utilized in the space heater of Fig. 1. It is comprised of a strip element 33 as described upon which a plurality of fins 3A are mounted in equal spaced relationship over the length of the strip. Referring to Fig. 6 the fins 34 are provided with a cutout portion or notch 37. and an aperture 38. As illustrated, the plate is fitted over the strip with the notch 3'5 surrounding the strip 33. The assembly is then placed in a mold and a molten metal poured to embed the strip 33 and the metal will pass through the apertures 38 to form a continuous bar in the form illustrated in Fig. 6, thus forming the strip 33 and plates as in an integral relationship. We have found that the plates 3 may be made of various metals or other heat conducting materials but in this instance we have provided aluminum and by actual test we have found that one square inch of aluminum surface at 220 F. standing vertically in free air has a heat loss equivalent to .425 plus or minus watts of electrical resistance. Any given material has a certain ability to conduct heat, consequently the cross sectional area of a heat dissipating plate such as 3% must be thick plus) enough'so that the plate will have the ability to conduct 100% of the heatsupplied by th'eleme'nt to the surface of the plate to be dissipated by convection to the surrounding air. In this heater we have designed a relatively thick Y inch aluminum plate with an area A XB for example approximately eight inches high and six inches wide formed into an integral unit with the electrical strip and by test it is designed to bring the surface temperature to approximately 220 F. Another factor that we consider of importance in the design of this space heater is the so-called time-distance factor which we define as: A function of time and distance for a predetermined volume of air to be heated while moving by natural convection from the time it first comes in contact with the heated blade until it leaves contact with the heated blade. This time distance function is such in my unit inch section of heater that the temperature of the predetermined volume of air leaving the heater will be approximately the same temperature as the heated blade.

In applying the convector heater as illustrated in Fig. 1 to the problem of heating any predetermined cubage of space it was necessary to design a unit of measure that is the same through any cross section of this heater and which may be multiplied through the combination of strip elements and their associatedplate structure as defined in this invention. One of the factors that must be controlled is the depth of the cabinet H. The depth C from the inside of the front panel to the inside of the back (clear space) must be at least the depth of the plates 34 plus the thickness of the core of the heating unit. This allows for an unrestricted passage of air over the heater units.

Another factor is the height of the intake air opening D at the bottom of cabinet H which must be equal to at least the width of the plates 34.

A still further factor is the free area E of the grill 2!] which is the discharge opening for the heated air. This must be at least more than the width of the blade to allow an unrestricted flow of warm air from the cabinet.

A further factor is as illustrated in Fig. 2 wherein there is provided a slanting baflle that extends across the cabinet running from just above the heating units to the upper edge of the discharge grill 29. The distance F perpendicular to the baflle from the lower inside edge of the discharge opening must be at least equal to the distance across the blades. Although we have shown this baflle (Fig. 2) as the preferred form we may similarly utilize the same heater, that is, the same components and dimensions but without the baffle and in such instance the discharge grill 20 will be positioned in the top H. Thus, the heated air will be discharged upward instead of outward into the room as illustrated in Fig. 2.

In the design of the cabinet the length of the intake and discharge openings is generally not less than four inches longer than the length of the finished heater unit.

The above factors contribute to the efficient operation of the heater and they are the foundation for the unit of measure that we have determined throughout the heater illustrated and throughout any and all combinations of the heater that may be designed to carry out this invention. This unit of measure we have termed as a unit inch. The unit inch rule forms the basis for all multiples of these heaters and permi'ts the application of this heater, to solve tli'e heating of any heating problem. The unit inch rule may be stated as follows; Oneunit inch lof the heater is made up of a surfacedisposed vertically in a column of free air one inch wide, said surface being heated to a predetermined temperature by an electrical resistance which consumes 50:20 watts of electricity. The unit inch is clearly illustrated in Figs, 8, 9 and lO,"thatis, with a pair of heating elements according to Fig-.1 we may lay out a one inch cross section as shown at XX in Fig. 1 andas shown at 3X)? in Fig. 8. This unit inch taken through the heater elements is illustrated in an isomeric viewin Fig. 9 and in Fig. 10 we ,have similarly shown a unit inch measure but Fig. 10 illustrates a further embodiment of thisinvention in which we have provided a center strip 33 and a pair of heater plates 34A and 34B associated with the strip 33. The plates are providedwith a hub structure 39 which surrounds the strip 33 and these plates may be bolted together or mounted in any manner to hold the platesin a tight fitting relationship with the strip 33. The design of the unit, that is, by using two plates one above the other instead of one plate is primarily from a production or manufacturing viewpoint.

Fig. 11 illustrates a further embodiment in which we have arranged the heater elements in the same relationship one above the other, but we have doubled the unit inch by spacing an additional pair of units in adjacent relationship. We may similarly combine a plurality of units in any desired relationship and at the same time retain the basic requirements (the necessary area of plate and wattage density of electrical resistance) of the unit inch rule.

Fig. 12 illustrates a further arrangement in which we have provided a pair of units of narrower plate width, in which we retain the wattage density according to the unit inch rule. The only reason for reducing the width of the plate is to permitthe installation of the unit in a limited space. This becomes necessary when the unit is built into a wall structure. In such installation there is very little width between the outer and inner wall area or with internal walls between the two wall surfaces but there is plenty of height permissible. The elements illustrated in Fig. 12 are designed especially for this type of installation In the application of this form of heater to a house, it is found that the basement and first floor should be designed with multiples of the unit" inch that are made to the basic size in wattage and to the basic size on heated surface area. Whereas the second and third floor or attic may be equipped with heaters designed to the one half unit inch with basic wattage and heated surface designed to the high limit. Where it is desirable to increase the performance, the heater should be designed to the high limit on wattage and to the basic limit on area of heated surface.

This heater may also be designed for an installation where it is primarily a booster heater and in such case the heater should be designed to the high limit on wattage and to the basic or low limit on square inches of heated surface.

Although we have shown one form of space heater in which we have reduced the heating element to a prescribed dimension which we call the unit inch, we may vary the general form of the space heater, that is,

in length, height, width see 01:, shape without departing from the spirit of this" invention. Similarly we may vary the form and size of the plates but retainthe necessary :areaf'and wattage density, to. comply with the unit inch rule. Similarly although we have '11- lustr'ated and described a particular form of strip ,heat'e'r'and. heat dissipating plates that are the means of arriving at, the watts or electrical resistance that are to be combined'with the square inches of heat radiating surface to provide the most efficient form of heater under the unit inch'rule, we may similarly vary "the type and'wattage' of the strip "elements or the thickne'ss and size of the heating plates without defparting from the "spiritof this invention and this invention shall'beflimited only by the appended Q1 aim'S."i '?What is claimed'i's:

L i li'jAn'electric unit heater comprising a plurality of electric heating strip elements and mounting'means for said elements including a casing in which said elements are disposed, each of said elements mounted in horizontal relationship to said casing, said heating-elements spaced from Tall sides of said casing and free of contact there- 7 with, said elements having a plurality of rectangular fin shaped blades disposed at right angles to said strip element, said blades spaced one inch apart and held in this spaced relationship by a molten poured core that surrounds said strip heater and anchors said blades in their positioned relationship, said positioned relationship providing a unit inch spacing of said blades so that said heater is made up of a multiple of unit inch sections, each unit inch of the heater providing said blades disposed vertically in a column of free air one inch wide, said blades being heated to a predetermined temperature and controlled by an electrical'resistance, the blade shape and area being designed for the wattage of electricity consumed by the heater based upon a consumption of 50:20 watts of electricity of each unit inch, and means to predetermine the length of time it takes a predetermined volume of air contained within the designed unit inch to be heated while moving by natural convection from the time it first comes in contact with the heated blade until it leaves contact therewith.

2. An electric heater of the convection type comprising a casing, provided with an, air inlet and an air outlet port, a plurality of electrical heating elements arranged in said casing in horizontal relationship to said casing, one above the otherand adjacent the air inlet thereof, said electrical elements being comprised of a central heating core running the length of said elements and a plurality of spaced heat dissipatingiblades that are disposed at right angles to said heating core, said heating core positioned in the lower portion at each blade, said blades mounted in a predetermined one inch spaced relationship, said blades being relatively thick in cross section at their root and tapering to their tipto conduct per cent of the heat supplied to the surface of said electrical heating elements, said heating elements spaced from all sides of said casing and free of contact therewith, means for supporting said electric heating elements within said casing.

3. An electric unit heater comprising an electric heating strip element and mounting means for said element including a casing in which said element is disposed, said element mounted in horizontal relationship to said casing, said heat-' ing element spaced from all sides of said casing and free of contact therewith, said element having a plurality of rectangular fin shaped blades disposed at right angles to said strip element, said blades spaced one inch apart and held in this spaced relationship by a molten poured core that surrounds said strip heater and anchors said blades in their positioned relationship, said positioned relationship providing a unit inch spacing of said blades so that said heater is made up of a multiple of unit inch sections, each unit inch of the heater providing said blades disposed vertically in a column of free air one inch wide, said blades being heated to a predetermined temperature and controlled by an electrical resistance, the blade shape and area being designed for the wattage of electricity consumed by the heater based upon a consumption of 50:20 watts of electricity of each unit inch, and means to predetermine the length of the time it takes a predetermined volume of air contained within the designed unit inch to be heated while moving by natural convection from the time it first comes in contact with the heated blade until it leaves contact therewith.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date' 1,660,218 Burgher Feb. 21, 1928 1,892,882 Gannon et a1. Jan. 3, 1933 2,062,466 Marr Dec. 1, 1936 2,080,800 Wiegand May 18, 1937 2,473,783 Brown, Jr. June 21, 1949 FOREIGN PATENTS Number Country Date.

834,128 France Aug. 8, 1938