US3436014A - Heater calculator - Google Patents

Description

`April 15 1969 R. P. OCHONICKY l 143,436,014" l v I HEATER CALCULATOR FileaNov. 17, 196e 4APT-i1 l, 1969 RP. QcHoNlcKY 3,436,014

HEATER CALCULATOR v Filed NOV. 17, 1966 sheep 2 @f2 J jvzz/e/' y 20k/@Caf my? United States Patent O 3,436,014 HEATER CALCULATOR Robert P. Ochonicky, Bensenville, Ill., assignor to Continental Sensing Incorporated, Melrose Park, Ill., a corporation of Illinois Filed Nov. 17, 1966, Ser. No. 595,078 Int. Cl. G06c 27/00 U.S. Cl. 23S-78 ABSTRACT F THE DISCLOSURE A disc type calculator for storage, display and computation of data relative to electrical heaters. The calculator includes four rotatable discs stacked in coaxial relationship, and a pair of pointers, one rotatable and one fixed with respect to the smallest or uppermost disc. The smallest disc and the third largest and largest discs bear graduated scales which, in cooperation with the pointers, permit calculation of heater surface temperature and power per unit area of heater surface as functions of heater length, diameter and total power. The largest disc also bears a pattern of indicia which, in cooperation with a corresponding overlying pattern of apertures in the second largest disc, permits a determination of the availability of heater types which will, for a desired diameter and length, yield a desired total power.

7 Claims This invention concerns a heater calculator and, more particularly, a calculator for storing, computing, and displaying data relative to cylindrical metal-sheathed electric heaters.

One type of electric heater construction is characterized by an outer cylindrical metallic sheath. Such heaters are available in a wide range of lengths and sheath diameters. There may also be a wide range of styles and types, depending upon numerous factors such as sheath material, heating element size, configuration and resistance, voltage rating, heat output per unit length, etc. It should be apparent that the cataloguing of such a wide range of styles, types and sizes is a complex matter, as is the proper selection of a particular heater for a particular design application Accordingly, it is an object of this invention to provide a heater calculator which enables ready access to heater specifications.l

An additional object of this invention is a heater calculator which is capable of computing heater sheath surface temperature and heat output per unit heater sheath surface area from pre-selected values of required heat output, heater length and sheath diameter.

A further object of this invention is to provide a heater calculator capable of indicating the availability of heater styles and types which will provide a desired value of heat output at a given value of heater length and sheath diameter.

Another object of this invention is to provide a heater calculator capable of computing heater current and resistance at a given value of power and voltage.

It is also an object of this invention to provide a heater calculator which is easily manipulated, compact, and which can be inexpensively constructed from convenient materials.

A fuller understanding and appreciation of the foregoing objects, aswell as others, will be gained from a consideration of the remainder of the specification and the claims, with illustrative reference to the drawings in which:

FIGURE 1 is a plan view of a heater calculator constructed in accordance with the invention;

FIGURE 2 is a cross-sectional view taken on the line 2-2 of FIGURE 1;

FIGURE 3 is a fragmentary View, partially broken away and somewhat enlarged, of the heater calculator illustrated in FIGURE l; and

FIGURE 4 is an exploded view of the heater calculator depicted in FIGURE 1, showing the configuration and interrelationship of the parts.

In general, the present invention is directed to a heater calculator which comprises a plurality of discs and transparent pointers arranged in a coaxial, stacked configuration. The discs and pointers are secured by suitable means in such a way that they are free to rotate about their common axis, each being rotatable relative to at least the next adjoining one. The discs vary in diameter so that each of the larger discs can accommodate circular graduated scales which will not be obscured by the next adjoining smaller disc. The graduated scales are laid out and positioned relatively to one another so as to permit certain computational operations on relevant data by suitable manipulation of the discs and pointers. In particular, the graduated scales represent data corresponding to total heat output (or electrical power consumption), total heater length, heater sheath diameter, heater sheath surface temperature and heat output per unit area of heater sheath surface. Additionally, there may be scales representing total electrical current and resistance. One of the discs also has marked thereon a pattern of indicia which represents available heater types. The next adjoining smaller disc has a corresponding pattern of apertures overlying the pattern of indicia; this arrangement permits selective viewing of the underlying indicia.

Given desired values for total heat output, heater length, and heater sheath diameter, a heater calculator constructed in accordance with the present invention will indicate at a glance Whether a heater type and style exists which will provide the required total heat for the desired length and diameter. If such a type and style exists, then further manipulation of the calculator Will indicate the resultant values of heater sheath surface temperature and heat output per unit area of heater sheath surface which may be expected.

Referring specifically to the drawing and with particular reference to FIGURES l, 2 and 4, there is shown a heater calculator 10 which is constructed in accordance with the present invention. A set for four discs 20, 30, 50 and 60 are stacked coaxially atop one another in order corresponding to the diameter of the discs. Disposed between the discs 30 and 50 is a transparent pointer 40 which likewise has its semicircular end 42 positioned coaxially with respect to the discs 20, 30, 50 and 60. A second transparent pointer 62 is rigidly attached to the disc 60 and extends radially to the periphery of the disc 20, as does the pointer 40.r As shown in the drawing, the pointer 62 is formed integrally with the disc 60. This need not be the case, however, since the only requirement is that the pointer 62 bear a fixed angular relationship to the disc 60. This relationship could be achieved in numerous other ways, as for example, by constructing the pointer 62 in the same manner as the pointer 40 and then securing the pointer 62 to the disc 60 to prevent rotational movement therebetween.

As best shown in FIGURES 2 and 4, the discs 20, 30, 50 and 60 and the pointer 40 are mounted so as to be mutually rotatable vabout their common axis. A rivet 70, having a plurality of spring arms 71 and 72 at each end thereof, passes through the respective axial holes 21, 31, 51, 61 and 41 in the discs 20, 30, 50I and 60 and the pointer 40. A washer 73 rests against the exposed sur-face of the disc 60 and a corresponding washer 74 rests yagainst the exposed surface of the disc 20. The spring arms 71 and 72 exert pressure against the washers 73 and 74, respectively. In this manner, a constant resilient force is exerted on the discs 20 and 60, tending to urge them together and consequently tending to maintain the entire stack of discs and pointers in a snug relaionship. The tension exerted by the spring arms 71 and 72 should be suliicient to provide enough friction between the discs and pointers to prevent accidental rotation, but not so great that the components cannot be easily rotated by the operator. The rivet 70 and its associated members are illustrated simply as one suitable means for maintaining the discs and pointers in the proper coaxial relationship, and are not intended to be exhaustive of the many means for accomplishing the same result. For example, means could be provided to Vary the -force exerted by the spring arms 71 and 72, such as a screw, etc.

As best shown in FIGURE 1, the disc 20v has a number of graduated scales marked near the periphery thereof. The scale 22 contains indicia representative of heat or electrical power in watts. The scales 23` and 24 respectively contain indicia representative of current in amperes and resistance in ohms. As will become apparent below, the scales 22, 23 and 24 bear a predetermined spatial relationship which permits ready computation of any two values of watts, amperes or ohms when the third value is given along with a given voltage.

The disc 20 also has marked near its periphery three scales 25,26 and 27 which contain indicia representative of heater sheath surface temperature in degrees Fahrenheit. The necessity for three such scales will become apparent hereinafter when the operation of the calculator is described. Also included on the disc is a graduated scale 28 which contains indicia representative of wa-ttts per -square inch of heater sheath surface.

As best seen in FIGURE 3, the disc 20 includes a pattern of indicia 29 which underlie the disc 30. These indicia 29 are representative of heater types and serve to indicate the availability of such types for a particular design application, as will become apparent below.

As can be seen in FIGURE l, the disc 30 is of a diameter sufficiently large to cover completely the pattern of indicia 29 on the disc 20, but sufficiently small that the scale 28 on the disc 20 is not obscured. The disc 30 itself has marked near its periphery a graduated scale 32 which contains indicia representative of heater length in inches.

Also included on the disc 30 is apattern of apertures 33. As shown in the drawing, each pair of apertures 33 has associated with it indicia representative of heater sheath diameter in inches. In addition, each member of each pair of apertures 33 has associated with it indicia representative of a heater style. The apertures 33 permit viewing of the indicia 29 on the disc 20, as will become apparent when the operation of the calculator 10 is described.

The disc 50 has a diameter sufficiently small that none of the yapertures 33 on the disc 30 are obscured thereby. Marked near the periphery of the disc 50 is a graduated scale 52 consisting of indicia repersentative of heater length in inches. Also marked near the periphery of the disc 50 is an index arrow 53.

Disposed between the discs 30 and 50 is the transparent pointer which extends radially from the common axis to approximately the periphery of the disc 20. Incorporated into the pointer 40 is a reading reference line 43. The line 43 is of a length sufficient to enable simultaneous registry with indicia in scales 52, 32, 24, 23 and 22. As the pointer 40 is rotated, the line 43 will always lie along a radius of the discs 20 and 30; accordingly, if the line 43 were extended, it would transect the common axis of the discs -and pointer.

The disc 60 lies atop the disc 50 and has marked near the periphery thereof a graduated scale 64 which consists of indicia representative of heater sheath diameter in inches. Note that the diameter of the disc 60 is of sufficient size so that the index arrow 53 on the disc 50 just meets the periphery of the disc 60 and the graduated scale 52 on the disc 50 is not obscured.

The transplant pointer 62 which, as indicated above, is constructed to maintain a xed angular position with respect to the disc 60, likewise extends radially to approximately the periphery of the disc 20. Incorporated in the pointer 62 is a reading reference line 63 which is of sufficient length to enable simultaneous registry with the scales 25, 26, 27 and 28. The line 63, like the line 43, will always lie along a radius of the discs 20 and 30 as the disc 60 is rotated.

The operation of the heater calculator 10 may now be described with specific reference to FIGURE l. It may be assumed, for example, that in a particular application for an electric heater a total heat output of 500 watts is required. It may further be assumed that in such applica- Iltion, dimensional limitations and requirements indicate a heater length of inches and a heater sheath diameter of .125 inch. An example of the operation of the heater calculator 10, using these parameters, is depicted in FIGURE l.

The lirst step is to set the reading reference line 43 of the transparent pointer 40 at 500` watts on the scale 22. The disc 30` is then rotated until the reading reference line 43 registers with 100 inches in the graduated scale 32. Since .125 inch is the desired heater sheath diameter, the operator then looks to the pair of apertures 33 in the disc 30 which correspond to that figure. If an indicium 29 appears in either of the pair of apertures 33 associated with the .125 inch sheath diameter ligure, this indicates that a heater type is available which will yield a total heat output of 500 watts for a length of 100 inches and a sheath diameter of .125 inch at volts. For example, if the indicium` U should appear in the aperture 33 which is associated with the style designation A and B, this would indicate that 100 inches of heater type U, style A or B would yield 500` watts at 115 volts.

Proceeding on the assumption that a heater type exists which will yield 500 watts for 100 inches heater length and .125 inch sheath diameter at 115 volts, it is possible to calculate heater sheath surface temperature and heat output per unit sheath surface area in the following manner. With the reading reference line 43 set at 500l watts on the scale 22 and 10() inches on the scale 32, as indicated above, the disc 50 is then rotated until the line 43 also registers with 100 inches 0n the scale 52. The disc 60 and the pointer 63, which always maintain the same angular relationship, are then rotated until the index arrow 53 of the disc 50 registers with .125 inch on the scale 64. This latter step constitutes the final setting of the heater calculator |10 and the resultant values of watts per square inch of heater sheath surface and heater sheath surface temperature in degrees Fahrenheit can be determined. As shown in FIGURE 1, the reading reference line 63 of the transparent pointer 62 shows a value of approximately 13 watts per square inch of heater sheath surface on scale 28. This means that a 100 inch length of a heater type which has a sheath diameter of .125 inch and which will yield a total of 500 watts at 115 volts will also yield a per unit area heat output of approximately 13 watts per square inch of sheath surface. It should be apparent that the values in the scale 28 are easily computed by calculating the total surface area of the heater (using the given values of length and sheath diameter) and dividing the total heat output in watts by this iigure.

It will be noted that the scales 25, 26, and 27 all relate to heater sheath surface temperature, and that the reading reference line 63 will in each case transect all three. The proper temperature scale, however, can be determined on the basis of the heater sheath diameter. Note that the scale 26 bears the indication that it is to be used for sheaths having a diameter between .062 inch and .125 inch. Accordingly, since .125 inch is the diameter used 1n the present example, scale 26 is the relevant temperature scale, and line 63 indicates an expected surface temperature of approximately 730 F.

The necessity for three temperature scales 25, 26 and 27 is explained by the fact that electrical heaters of the type under consideration will normally be employed in a non-vacuum environment and will thus be subject to natural convection. It will be understood, of course, that heater surface temperature can readily be calculated by employing the well known Stefan-Boltzmann law, which states that the rate of heat radiation varies as the fourth power of the surface temperature. In the present case, since the heater is obviously not a perfect black-body, the expression of the Stefan-Boltzmann law will include a factor representative of the emissivity of the material used to form. the sheath. In addition, since the heater will be operating under non-vacuum conditions, the effect of natural convection must be considered. Thus, the expression of the Stefan-Boltzmann law will also include a term which is representative of the surface heat transfer coefficient due to natural convection. In the case of cylindrical objects, such as the heaters under consideration, this coefficient varies in accordance with the diameter. Therefore, in order to be completely accurate, it Iwould be necessary to provide a temperature scale for each available value of heater sheath diameter. IHowever, it has been found that dividing the available heater sheath diameters into three groups and providing a separate scale 25, 26 and 27 for each group furnishes adequate precision for surface temperature computations.

Should an indicium from the pattern of indicia 29 fail to appear in one of the pair of apertures 33 which is associated with the .125 inch diameter figure, then it becomes necessary to adjust the disc 30 until such an indicium does appear. This manipulation will result in a slightly different reading at the reference line 43 for heater length on the scale 32. Typically, however, it will not be necessary to make an unduly large adjustment in the heater length characteristic in order to arrive at a heater type and style which would yield the desired total heat output. Since heater length will often be the most flexible design parameter, the foregoing adjustment will probably be the most commonly employed. It should be understood, however, that the other parameters (sheath diameter and total heat output) may also be adjusted in order to arrive at an approximately suitable heater type and style.

It should be noted that in the heater calculator depicted in FIGURE 1 the scales 22, 23 and 24 bear an interrelationship, calculated in accordance with Ohms law, based on operation at 115 volts. Thus, when the reading reference line 43 registers with 500 watts on scale 22, it also registers with approximately 4.3 amperes on scale 23, which would be the expected current when the heater is operated at 115 volts, and with approximately 26 ohms on scale 24, which is the expected value of resistance under such conditions of operation. It should be understood, however, that the scales 22, 23 and 24 could be interrelated on the basis of any commonly encountered voltage. Also if the scales 22, 23 and 24 are arranged for expected operation at a particular voltage Value, and if a different voltage is actually used, nomograms may be provided for easy conversion of values.

It should be further understood that the units described herein are exemplary only, and the scales could be graduated in terms of any desired system of units. The use of watts, inches and degrees Fahrenheit was chosen herein merely -because such units are commonly employed in connection with electric heaters.

The materials used for the discs and pointers in the heater calculator 10 can vary over a wide selection. It has been found that a relatively stiff paper is an excellent material for construction of the discs since the scales may be readily printed thereon. The paper might be coated with plastic for durability, or the discs might be entirely constructed from plastic, metal or other suitable materials. The pointers 40 and 62, of course, must be transparent so that the indicia underlying them .are not obscured. Again, plastic constitutes an excellent material for this purpose. The reading reference lines 43 and 63 may be embedded within the pointers 40 and 62, or may be scribed or inked thereon.

Although the heater calculator 10 constructed in accordance with the present invention has been described with the requisite particularity, the disclosure is of course only exemplary. Consequently, numerous changes in the details of construction and in the size, configuration and arrangement of components, materials and units will be apparent to those familiar with the art and may be resorted to -without departing from the scope of the invention as set forth in the following claims.

I claim:

1. A device for storing, computing and displaying data relative to cylindrical metal-sheathed electric heaters, said device comprising: a first disc having marked near the periphery thereof a plurality of graduated scales, at least a first of said scales consisting of indicia indicative of power, at least a second of said scales consisting of indicia indicative of power per unit area of heater sheath surface, and at least a third of said scales consisting of indicia indicative of heater sheath surface temperature for a predetermined range of heater sheath diameters, and also having marked thereon a predetermined pattern of indicia indicative of available heater types, said pattern of indicia lying wholly within the boundary defined by the innermost of said graduated scales;

a second disc lying coaxially atop said first disc, said second disc having a diameter sufficiently large that said pattern of indicia on said first disc is covered but sufficiently small that the innermost of said graduated scales on said first disc is not covered, said second disc having marked near the periphery thereof a fourth graduated scale consisting of indicia indicative of heater length, and also having a predetermined pattern of apertures lying wholly within the boundary defined by said fourth graduated scale, said apertures being positioned for selective registry with certain of the indicia on said first disc, each of said apertures having associated therewith indicia indicative of available heater styles and heater sheath diameters;

a third disc lying coaxially .atop said second disc, said third disc having a diameter sufficiently small that said pattern of apertures on said second disc is not covered, said third disc having marked near the periphery thereof an index mark and a fifth graduated scale consisting of indicia indicative of heater length;

a fourth disc lying coaxially atop said third disc, said fourth disc having a diameter sufficiently small that said fifth graduated scale and said index mark on said third disc are not covered, said fourth disc having marked near the periphery thereof a sixth graduated scale consisting of indicia indicative of heater sheath diameter;

a first transparent pointer disposed between said second and third discs, mounted coaxially atop said second disc and extending radially of said discs to approximately the periphery of said first disc, said first pointer defining a first reading reference line extending radially of said discs and of sufiicient length to transect said first, fourth and fifth graduated scales;

a second transparent pointer extending radially of said discs to approximately the periphery of said first disc, said second pointer defining a second reading reference line extending radially of said discs and of.

Sufficient length to transect said second and third graduated scales, said second transparent pointer having a fixed angular position relative to said fourth disc;

and means for mounting said discs and said first pointer rotatably about a common axis so that each is independently rotatable relative to each of the others;

said graduated scales, said pattern of indicia, said pattern of apertures, said index mark and said fixed angular position of said second pointer bearing a predetermined spatial relationship such that when said first reading reference line registers with a desired value 'of power on said first scaleand a desired valueof heater length on said fourth scale an indicium from said pattern of indicia will appear in that one of said apertures corresponding to a desired heater style and sheath diameter, if and only if a heater type is available which will yield the desired power at the desired heater length and style and heater sheath diameter;

and if such a heater type is available then when said first reading reference line registers with said desired value of heater length on said fifth scale and when said index mark registers with said desired value of heater sheath diameter on said sixth scale, said second reading reference line will register with the resultant values of power per unit area of heater sheath surface on said second scale and heater sheath surface temperature on said third scale.

2. A device as defined in claim 1, wherein said first disc also has marked near the periphery thereof a seventh graduated scale consisting of indicia indicative of electrical current, said seventh and said first scales bearing a predetermined spatial relationship such that when said first reading reference line registers with said desired value of power on said first scale, said first reading reference line will also register with the resultant value of electrical current on said seventh scale.

3. A device as defined in claim 1, wherein said first disc also has marked near the periphery thereof an eighth graduated scale consisting of indicia indicative of electrical resistance, said eighth and said first scales bearing a predetermined spatial relationship such that when said first reading reference line registers with said desired value of power on said first scale, said first reading reference line will also register with the resultant value of electrical resistance on said eighth scale.

4. A device as defined in claim 1, wherein said third scale comprises a plurality of sub-scales, each of said subscales consisting `of indicia indicative of heater sheath'surface temperature for a predetermined range of values 0f heater sheath diameter.

5. A device as defined in claim 1, wherein said third scale comprises a plurality of sub-scales, each of said sub-scales consisting of indicia indicative of heater sheath surface temperature for a predetermined value of heater sheath diameter.

6. A device as defined in claim 2, wherein said first, second, third, fourth, fifth, sixth and seventh graduated scales are respectively indicative 0f the units watts, watts per square inch, degrees Fahrenheit, inches, inches, inches and amperes.

7. A device as defined in claim 3, wherein said first, second, third, fourth, fifth, sixth and eighth graduated scales are respectively indicative of the units watts, watts per square inch, degrees Fahrenheit, inches, inches, inches and ohms.

References Cited UNITED STATES PATENTS 2,328,881 9/1943 Saunders 23S-78 2,433,984 1/1948 De Vries 23S-78 3,013,720 12/ 1961 Steinkoenig 23S-78 3,360,195 12/1967 Fisher 23S-78 3,363,836 1/1968 Lee v.. 23S- 78 STEPHEN I. TOMSKY, Primary Examiner.

U.S. Cl. X.R.

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