US2235764A - Heater - Google Patents

Description

L. P. HYNES March 18,1941.

HEATER Filed NOV. l0. 1938 2 Sheets-Sheet l March 18, 1941. L p, HYNES 2,235,764

HEATER Filed Nov. lO, 1938 2 Sheets-Sheet 2 Patented Mar. 1s, 1941 UNITED STATES PATENT OFFICE HEATER Application November 10, 1938, Serial No. 239,855

8 Claims.

This invention is a heater unit of a type capable of use in an electric heater assembly, preferably in a group arrangement, although not limited to any specific arrangement of such groups.

One of the 'objects of the invention is to provide a substantial and compact heater unit designed to present a minimum restriction to air flow, and at the same time to obtain a very large resistance-coil-surface, approximately all of which will be exposed to an air stream flowing over the coils. A fur-ther object is to provide a heater unit including a plurality of flat dielectric sections, ilexibly supported in such manner as to provide a relatively wide, at, and well insulated backbone for the resistor coils mounted thereon, and sol constructed and arranged that the same may be readily and easily assembled or disassembled as loccasion may require.

In electric heaters now in common use and of the type employing an assembly of a plurality of heater units, a serious problem is presented by the overheating of fan, motor and other parts by the stored heat remaining in said units after the current is shut off. Where a plurality of heater units are massed within a chamber with a concentrated delivery of energy suited to an air blast, another danger emanating from the stored heat is that some emergency condition may arise to stop the flow of air due to failure of the fan 30 to function, or due to some mechanical impedance of air flow, such for instance as that caused by the closing of a damper. Under these circumstances, it is imperative that ow of electric power to the heaters be instantly stopped. Other- Wise, there would be a destructive temperature rise, and creation of a possible fire hazard. Automatic safety thermal devices must be employed to cut off the current every time any undue temperature-rise occurs. Any excessive stored heat would cause too great a rise of temperature, due

to high thermal storage, even though a normal action of stopping the fan would also cut off the source of power. This means that a sensitive and d proper thermal protective device would be operated every time the fan is stopped normally and that the system would be automatically thrown out of f circuit with the source of power until someone re-established it manually. To meet these conditions, the present invention has for one of its objects the `designing of a heater unit so constructed and arranged that the resistor wire itself does not have very great mass. In other words, the said resistor wire has a great deal of surface area in proportion to its mass, with a very low capacity for heat storage, so

that it will not run at a very high normal temperature and will very quickly lose heat when the power is shut off.

Another object of the invention is to provide an assembly of heater units which may be readily adapted to a variety of bus bar arrangements, so that the units may be properly connected for any desired type of installation.

The invention will be hereinafter fully set forth and particularly pointed out in the claims.

In the accompanying drawings:

Figure 1 is a front elevation illustrating a group of heater units each constructed in accordance with the invention. Figure 2 is a side elevation of one of the units, parts being broken away, and parts being shown in section. Figure 3 is a side view of one of the dielectric sections, and Figure 4 is an end view thereof. Figures 5 and 6 are perspective views illustrating one of the end pieces, viewed respectively from opposite v sides thereof. Figure 7 is a side elevation of one of the metal supporting bars, and Figures 8 and 9 are opposite end views of the group illustrated in Figure 1, showing one form of bus bar arrangement. Figure 10 is a sectional view illustrating an assembly designed to be removably inserted into an air duct.

Referring to the drawings, A designates a heater unit comprising a flat metal bar l0 having an opening H in each end thereof. tudinal edges of the bar are provided with shoulders l2 which are outwardly offset from the body of the bar in such manner as to overhang the flat surfaces thereof. Said offset shoulders may be formed in any desired manner. mounted upon the bar l0 are a plurality of dielectric sections S constructed of any desired material, but preferably of porcelain. Each of said sections consists of a body, preferably of approximately oblong form in side elevation, and having its inner edge provided with a longitudinal groove i4. Said groove is slightly enlarged at the interior thereof by laterally extended portions, as indicated at I5. The groove i4 and its laterally extended portions I5 are complemental to the cross section of the bar IQ and the shoulders l2 formed on the edges thereof, so that each dielectric section S may be interlocked with a bar by bringing the groove into engagement with the end of the latter and then sliding the section along the bar. The interlocking arrangement is such, that the sections S are free to slide along the edges of bar I, but are anchored against lateral movement with respect to said bar. It will be observed that the dielectric sections S are The longi- Slldably arranged in two sets, which respectively engage the olset edges of the bar II), and are maintained in spaced relation with respect to each other. It will also be observed that each section S is provided with transverse surface grooves I6 which are arranged diagonally so as toprovide seat portions for the resistor element R. It is to be understood that the bars I0 are slightly resilient, so as to protect the unit from shocks, but sui'iciently stiff to provide a substantially rigid support for the porcelain parts.

The sets of dielectric sections S are held in position against endwise movement by means of end pieces E, each of which is formed of any suitable dielectric material, preferably porcelain, and is provided with a slot 20 through which an end of the bar I0 may be passed. The inner face of each end piece E is provided with an offset portion 2 I. The width of said end pieces is increased at both ends, as indicated at 23 to provide suicient body to receive the holes 22. The end pieces are prevented from sliding `oi of the bar I 0 in any desired manner, but for purposes of illustration cotter pins 24 are employed, which eX- tend through suitable holes in the bar I0.

It will be observed that the vend pieces E are of suchdesign that they may be used at either end of the bar I0, except that the oifset portion 2| of each end piece must be reversed with respect to that of the companion end piece secured to the same bar. Thus, while the end pieces are in proper position, the two sets of dielectric sections S are held in spaced relation with respect to each other, and in such manner that the surface grooves I 6 of the sets of sections are in register with each other and practically form and maintain a helical seat for the resistor R. By this arrangement the two sides of the bar are insulated with individual pieces of porcelain, so that'the resistor R may be wound on the supporting sections S as a continuous coil.

The resistor R may be of any desired material, but for purposes of illustration it is shown in the form of a, helically coiled wirewound in helical coils aroundv the insulator sections S, as shown in the drawings. The terminals of the resistor are secured to terminal screws 25 carried in the holes 22 of each of the respective end bars E.

As illustrated in Figures 1, 8 and 9, a plurality of units A may be arranged in an assembly, and in this connection it is to be understood that the particular arrangement shown is intended solely for illustrative purposes, and Without any intent to speciiically limit the invention in this respect. It is to b-e understood that the unit arrangement is subject to a very wide variation, well within the spirit of the invention and in ways well understood in the art. In assembling a plurality of the units, metal rods 30 are passed through the registering end openings II of the bars I0 of a plurality of aligned and relatively spaced units A. Said units are held in relatively spaced relation by means of spacing sleeves 3| loosely mounted on said rods and interposed between said bars IB. The ends of the rods 30 are preferably screw threaded so as to be engaged by suitable nuts 32, so as to hold the rods 30 against endwise movement, suitable supporting lugs 33 being also secured in place by the same nuts.

In the form shown in the drawings the assembly of units is arranged for a 220 volt, three phase, star arrangement. That is, the terminal screws at one end of the assembled units are connected by a single bus bar 34 and the other ends are connected in pairs by shorter bus bars 35.

Each of the bus bars 35 is provided with a binding post 36 to which the electric Wires may be connected.

It will readily be seen that any desired cornbination of interconnecting busses can be arranged by which heating elements may be connected in series or parallel in any desired way, thus giving a very flexible and substantial method of making reliable connections to suit different types of power service conditions.

In Figure 10 is illustratedan assembly unit designed to be inserted within an air duct. Referring to said iigure, 40 designates an air' duct shown in cross section and having an opening 4I in one side thereof, said opening being provided with inturned flanges 42. Arranged to close said opening is a dielectric panel 43 Which supports an open sided metal frame 44, and secured to said frame by lugs 33 is the assembly X which may be of any desired arrangement, said assembly being made up ofl a plurality ofthe heater units A in a manner already described. The panel board is provided-With electric terminals which are connected with' the heater units byv suitable conductors in a manner already described. The panel board is provided witha box 46 positioned to cover said terminals. In practice, the unit is inserted through the hole 4I and supported within the duct 40yby means of the panel board 43 which also acts as a'closurefor the opening in the duct.

'The advantages of theinvention will be readily understood by those skilled in the art to which it belongs. For instance, itwill be observed that a very simple and inexpensive type of heater unit is provided, which is constructed of a plurality of dielectric sections flexibly supported in such manner as to provide a relatively wide, flat and well insulated backbone for the resistor coil, whereby :there is a minimum of restriction to air ow, and atthe same time it is possible to obtain avery large resistance surface. A further and very important advantage isthat a heater unit is provided which has a. very low capacity for heat storage, due to the manner in which the dielectric sections vare supported with respect t0 each other. Another factor is that the resistor wire itself does' not have a very great mass, but a large surface area in proportion to its mass, and therefore does not run at a very high temperature, so that it very quickly loses heat when the power is shut oil. A further advantage is that any numberof the heater units hereinabove described may be arranged in aunitary assembly which may be handled as a single unit, and in which the arrangement is suchas to be readily adaptable for any desired bus bar arrangement. An important advantage is thatthe resistor is supported by a plurality of relativelysmall dielectric sections having surface grooves which are maintained in register in a simple and eflicient manner. Because the dielectric sections are of small size and each one is mounted independently without pressure binding them against veach other, they are able to-stand mechanical shocks much better than larger sections would. They also permit of a exibility of motion and also expansion and contraction, all of which are of great importance in practical operation. It is even possible to mount the dielectric sections in the form of a ring by bending the exible bar upon which they are'm'ou'nted after the sections have been slipped on its edges. Therefore, an important advantage is` gained'because it is jnot desirable to tightly cement or otherwiseattach the dielectric sections to the bar. In other words, they must be fre-e to yield under mechanical tensions or under expansion and contraction, due to heating and cooling. An important advantage of the interlocking relation between the dielectric elements and the flat metal supporting bar lo is that said sections may be securely held in place while the resistor is being wound around them, thereby greatly facilitating the winding operation. For instance, to efficiently place the resistor in position, it is necessary to mount the assembled unit in a rotatable support of a winding machine, and to revolve it in order to wind the resistor around it. Obviously, the dielectric sections would fall off during this operation except for the interlocking feature.

Having thus explained the nature of the invention and described an operative manner of constructing and using the same, although without attempting to set forth all of the forms in which it may be made, or all of the forms of its use, what is claimed is:

l. A heater unit for electric heaters comprising a flat bar, a plurality of sets of approximately identical dielectric sections loosely mounted on the edges of said bar independently of each other, and having portions extending over the faces of the latter, each of said sections having inclined resistor receiving seats, said sections being arranged in two relatively spaced groups, one at each longitudinal edge of the bar, means for maintaining said dielectric sections of each set in offset relation with respect to those of the other set so that the surface grooves thereof provide `an approximately continuous resistor seat from one end of the unit to the other, said bar and said sections having interlocking means for preventing separation of said sections of each group from said bar, and a continuous resistor element located in said surface grooves.

2. A heater unit for electric heaters comprising a flat bar, a plurality of identical dielectric sections loosely mounted on the edges of said bar independently of each other, and having portions extending partially over the side faces of the bar, each of said sections having inclined surface grooves extending continuously on the outside thereof from one side edge to the other sid-e edge, said dielectric sections being arranged in two relatively spaced groups, one at each edge of said bar, means for maintaining said dielectric sections of each group in offset relation with respect to those of the other group, so that the surface grooves of all of the sections of the two groups provide an approximately continuous helical resistor seat from one end of the unit to the other, said bar and said sections having interlocking means for normally preventing separation of said loosely mounted dielectric sections from said bar, and a continuous resistor element seated in said approximately continuous helical resistor seat.

3. A heater unit for electric heaters comprising a flat bar, a plurality of approximately identical dielectric sections loosely mounted on the longitudinal edges of said bar independently of each other and each section having portions enclosing the side surfaces of the bar adjacent an edge thereof, said dielectric sections each having inclined surface grooves, said dielectric sections being arranged in two relatively spaced groups, one at each edge of the said bar, means for maintaining the dielectric sections of each group in offset relation with respect to those of the other group so that the surface grooves provide a helicalresistor seat from one end 'of the unit to the other, the enclosing portions of said dielectric sections and said har having complemental interlocking means to normally prevent separation oi said dielectric sections with respect to said bar, and a continuous resistor element seated in said surface grooves.

4. A heater unit for electric heaters comprising a fiat bar having widened longitudinal edges, a plurality of approximately identical dielectric sections loosely mounted on the bar independently of each other and each having a longitudinal groove with internal longitudinal offsets complemental to the bar and the widened edges thereof, each of said dielectric sections having inclined surface grooves, said sections being arranged in two relatively spaced groups, one at each edge of said bar, said widened edges of said bar and the complemental portions of the edge grooves of the dielectric sections preventing separation of the sections from said bar and from each other except by longitudinal movement of the sections with respect to the bar, means for maintaining said dielectric sections of each group in offset relation with respect to those of the other group, so that the surface grooves of the sections of the two sets provide a resistor seat from one end of the unit to the other, and a continuous resistor element seated in said surface grooves.

5. A heater unit for electric heaters comprising a fiat bar, a plurality of approximately identical dielectric sections loosely mounted on the bar independently of each other and engaged with the longitudinal edges of said bar, each of said sections having inclined surface grooves, said sections being arranged in two relatively spaced groups, one at each longitudinal edge of the bar, duplicate end pieces anchored to said bar and so positioned as to normally prevent endwise movement of the dielectric sections, each end piece having an offset portion cooperating with the offset of the other piece to maintain the dielectric sections of the respective groups in off-set relation with respect to each other so that the surface grooves of the sections of the two sets are in register, said bar and said sections having complemental interlocking means for normally preventing separation of said dielectric sections from said bar, and a resistor element wound around said unit and seated in said surface grooves,

6. A heater unit for electric heaters comprising a dat bar of slight flexibility, said bar having widened longitudinal edges, a plurality of approximately identical dielectric sections having internal seats complemental to the edge portions of said bar, the dielectric members being loosely mounted on said bar and independently of each other, each of said sections having inclined surface grooves, said sections being arranged in two relatively spaced groups, one at each edge of said bar, said widened edge portions of said bar and the complemental seats of said dielectric sections being so constructed and arranged as to normally prevent separation of the dielectric members from said bar and from each other, means for maintaining the dielectric sections of each group in offset relation with respect to those of the other group so that the surface grooves of the sections of the two groups provide an approximately continuous helical resistor seat from one end of the unit to the other, and a resistor element located in said seat.

7. An electric vheater comprising a plurality of units each consisting of a flat bar carrying a relatively spaced aligned units, each unit including a slightly ilexible flat bar, a plurality of identical dielectric sections loosely mounted on the edges of said bar and having interlocking slidable engagement therewith, and a continuous resistor Wound around and engaging the dielectric sections, support rods engaging the ends of the aligned flat bars, means carried by said rods for maintaining the units in relatively spaced relation, means for releasably holding said units in said relatively spaced relation, and bus bars connected to the terminals of said resistors.

LEE P. HYNES.

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