US 3588493 A
Description (OCR text may contain errors)
United States Patent lnventor Robert G. Nordquist Springfield, Ohio Appl. No. 724,688
Filed Apr. 29, 1968 Patented June 28, 1971 Assignee Grimes Manufacturing Co.
Urbana, Ohio PROJECT ING LAMPS HAVING REFLECTOR WHICH FORM RECTANGULAR PATTERNS OF LIGHT Primary Examiner-Samuel S. Matthews Assistant Examiner- Richard M. Sheer AuomeyMarechal, Biebel, French & Bugg ABSTRACT: Projecting lamps are formed with reflectors which define, beyond the region of image inversion, a square or rectangular light pattern. A conventional reflector is divided into four arcuate separate segments. Each is angularly outwardly offset from the position which it would normally occupy in the conventional reflector, with respect to the central axis, resulting in the displacement of radiant energy patterns in superimposition. Since the reflector is divided along straight lines the image portions form a correspondingly straight line pattern, which may be rectangular or square, at all regions beyond image inversion, with the number of sides of the pattern of light corresponding to the number of reflector segments. The resulting pattern is substantially uniform in intensity from corner to corner and has an area which is smaller than the area formed by the conventional reflector by a factor of pi.
SHEET 1 OF 5 FIG-I FIG-2 ART i l l0 PRIOR IN VE/V TOR ROBERT G. NORDQUIST A TTORNEYS PATENTED JUN28 I9?! SHEET 2 OF 5 PATENTEU JUN28 m:
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PATENIED JUN28 Ian SHEET 5 UF 5 PROJECTING LAMPS HAVING REFLECTOR WHICII FORM RECTANGULAR PATTERNS OF LIGHT BACKGROUND OF THE INVENTION Projecting reflector-type lamps have variously employed compromises in order to provide a light pattern of desired characteristics and shapes. Where a uniform light pattern is desired, such lamps often have been specially modified in order to reduce the hot spot which is frequently formed by the use of conventional reflectors, by the use of such extras as prismatic lenses, diffusers and filament shields. Even then, the achieving of a uniform light pattern over a relatively small area, with the lamp positioned at a substantial distance from the area, has frequently required the use of auxiliary lenses and the like. Alternatively, only a small portion of the available light is permitted to pass from the lamp resulting in inefficient use of the lamp's output.
In some instances, for example in the US. Pat. of Clark, No. 1,248,456 of 1917, light patterns have been formed on a given or fixed plane by the use of a segmented reflector in which the reflector parts were directed inwardly from their normal position toward the reflector axis to form an overlapping or composite pattern of light in a given shape prior to image inversion. Such a system must be so designated to form the desired shape at a given distance of focal length from the detector, since at all other focal lengths, a different shape will necessarily be produced. Such converging beams necessarily diverge into space and form a meaningless pattern at locations beyond the desired focal plane for which the reflector is designed. Thus, the systems as shown in the Clark patent are generally limited for use where the plane to be illuminated is at a fixed location and is relatively close to the light source, such as the film plane in a slide projector.
SUMMARY OF THE INVENTION The present invention is directed to lamps and reflectors in which the output of a radiant energy source, such as a light source, is utilized in a highly efficient manner in order to illuminate an area or a field with substantially constant and uniform illumination, at varying distances from the reflector. This is achieved in the present invention by displacing discrete segments of a reflector in such a manner that corresponding portions of the field are caused partially to overlap in a pyramid or column beyond the region of image reversal, to form a pattern which has a regular geometric shape, with straight sides, such as a square, a rectangle or a triangle, and with uniform illumination to the corners. A further benefit of the present invention resides in the fact that the radiant energy may be directed with a substantially decreased included anglle, as compared to that of a conventional reflector, resulting in the illumination of a given area at a correspondingly increased distance.
It is accordingly an important object of the present invention to provide a lamp or a reflector which directs a straightsided regular geometric beam of radiant energy in a composite pattern of uniform light values. Generally the resulting beam forms a pattern with dimensions which are substantially less than those of an ordinary pattern formed with the conventional paraboloidal or ellipsoidal reflector.
A further object of this invention is the provision of a lamp which forms a square or rectangular pattern of light which is illuminated to substantially constant light values throughout the area of illumination, and even into the corners.
A further object of the invention is the provision of a universal lamp or reflector and bulb or filament combination which is adapted to a wide variety of uses, such as providing rectangular or square illuminating as a reading light for aircraft passengers, as an evacuated envelop type of internal reflector lamp for illuminating pictures, buildings, or the like, as a head lamp for an automobile, or for general illumination, and for a wide variety of additional uses where uniform illumination over a controlled area, without hot spots, is desired.
Another object of this invention is the provision of a reflector adapted for use with a point or generally localized source of radiant energy, such as a tungsten filament, which produces a pyramid or shaft of light of uniform, straight-sided geometric shape at all transverse planes beyond the region of image reversal.
Still a further object of the invention is the provision of a reflector and an illuminating lamp incorporating such a reflector in which the reflector itself is formed of a plurality of reflector segments each having the surface configuration of a conventional reflector, such as spherical, paraboloidal, or ellipsoidal, and in which at least some of the segments are displaced from the position which they would occupy in such a conventional reflector angularly outwardly in relation to the point source and reflector axis to form a composite shaft of illumination beyond the region of image reversal which has a predetermined geometric shape and light values.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is an elevational view of a portion of an airline passenger cabin showing the application of the present invention to the reading lights;
FIG. 2 shows, in perspective, a conventional lamp employing an off-focus parabolic reflector, and the expanded pattern formed on a transverse plane of illumination;
FIGS. 3A--3D depict four arcuate segments of the lamp of FIG. 2 and the corresponding quadratures of light which would be projected therefrom on a transverse plane;
FIG. 4 is a further perspective showing the composite pattern produced by a reflector made according to this invention;
FIG. 5 is a diagram showing one of the reflector segments of FIG. 3 positioned in the normal manner, and the light pattern therefrom; I
FIG. 6 is a diagram similar to FIG. 5 showing the same segment after it has been displaced in accordance with this invention;
FIG. 7 is a vertical section through a reflector made in accordance with the present invention with displaced segments substantially in the manner shown in FIG. 8 to produce the composite pattern as shown in FIG. 4;
FIG. 8 is a plan view of the reflector as viewed along the lines 8-8 of FIG. 7, with the bulb removed;
FIG. 8A is a fragmentary transverse section through the reflector taken generally along the line 8A-8A of FIG. 8;
FIG. 9 is a diagram of light projection from the reflector of FIGS. 7 and 8 in which views A-A through E-E represent the light patterns at the respective transverse plane positions showing stages of the image reversal and confluence into a pyramid of regular shape;
FIG. 10 shows the manner of applying the present invention to a tilted-revolved ellipsoidal reflector segment;
FIG. 11 is a vertical section through an evacuated lamp constructed according to this invention;
FIG. 12 is a plan view of the back of the lamp of FIG. 11;
FIG. 13 is a vertical section through a modified form of the invention embodied in a squared reflector, which may be preferred where space is limited;
FIG. 14 is a plan view looking into the reflector of FIG. 13 and showing in broken line form the portions of the normal circular reflector which have been eliminated;
FIGS. 15, I6 and 17 are projection diagrams showing the manner in which the squared reflector may be modified in accordance with the present invention, in which FIG. 15 represents a normal pattern for such a reflector with a superimposed circular pattern shown for the purpose of comparison;
FIG. 16 is a perspective view showing the portion of the pattern formed by one quadrant of the reflector of FIG. 15;
FIG. 17 shows the composite pattern produced by the four displaced and tilted reflector segments;
FIG. 18 is a plan view of the reflector of FIG. 17; and
FIGS. 19 and 2t]! illustrate a further modification of the present invention as applied to a reflector for producing an elongated rectangular pattern, in which FIG. 19 represents the pattern before applying the teachings of this invention, and FIG. 2b represents the modified rectangular composite produced by a four segment reflector.
DESCRIPTION OF PREFERRED EMBODIMENTS Referring to the drawings which illustrate preferred embodiments of the invention, a typical illustration of one use of a lamp constructed according to the present invention may be that of a reading light for a large aircraft. In this case, a portion of the aircraft cabin 110 is shown with individual reading lamps III which project downwardly from the cabin ceiling onto a target area which may be defined by reading material 12 and 113. In the case of passenger reading lamps for aircraft, as an example, it is important that the target area be illuminated with the most efficient use of the wattage available from the reading lamp, in order to reduce the electrical load and heating caused by the lamps, and to hold the weight at a minimum. With large cabins as currently designed, the distances of projection between the target areas 12 and 113 and the lamps iii are increasing and, as an example, where 3040 inches of projecting distance has been common in the past, in larger aircraft such as the Boeing 747, this distance is increasing to the range of 6080 inches while the target area remains at 18 inches across. Therefore, the necessity for confining the light and for forming a pattern of uniform illumination becomes even more critical.
The arrangement and operation of the present invention can be more readily understood by referring first to the diagrams of FIGS. 2 and 3 in which FIG. 2 shows a conventional paraboloidal reflector 20, which has an off-focus filament light source. If the filament, defining the source of light, is positioned at the focal point of a parabola, a hot spot will be formed at the center of the projected pattern, and this is a common arrangement of spot lights, flashlights, and the like. With an axial filament, an infinite number of filament images are revolved about the axis of the parabola which intersect at the axis.
A well-known technique for eliminating the hot spot is to move the parabola off focus by moving the filament forwardly or toward the open end of the parabola, thereby expanding the filament image while, at the same time, moving the filament image off from the center to one side of the pattern, with filament image inversion. This is shown in FIG. 2 in which the filament image 21 is defined by concentric rings 22 as a convenience of illustration, on a transverse illumination plane. The concentric rings 22 illustrate the fact that an axial coiled filament will be observed as rings of light due to the fact that light tends to be concentrated somewhat at the filament loops.
The pattern of radiation produced by the off-focus parabola, in many instances, is undesirable since it frequently has too wide a spread in relation to its distance from the projecting reflector 20. Thus, while the technique of off-focus parabola may be used for general illumination it is often quite unsatisfactory where light or other radiation is required on a more discrete and localized area and/or over a greater distance of projection.
The views of FIGS. 3A-3D, 4i, 5 and 6 illustrate the manner in which an off-focus parabolic reflector of the type shown at 20 in FIG. 2 may be modified according to this invention to provide a square pattern of radiation on a transverse plane, which pattern has substantially uniform intensity values throughout its area and which is substantially smaller than the original circular pattern of light. In these views the filament rings 22 have been omitted for clarity.
In FIGS. 3A3D, the reflector 20 of FIG. 2 is shown as being divided into four equal arcuate segments or quadrants, and the corresponding quadrature segments of the field or pattern on a transverse plane, shown in full lines, are those which would be formed by the respective quadrants. Therefore, a
quadrant 2th: of the reflector 20 forms the portion of the pattern of FIG. 2 identified by the'letters DAC in FllG. 3A. The segment DAC is one-fourth of the pattern produced by the complete reflector 20, is expanding with increasing distance from the reflector segment 20a, and is reversed in position relative to the reflector since it is observed beyond the region 2d of image inversion.
Similarly, the quadrants 20b of the reflector 20 forms the image or pattern segment DEC, the quadrant 20c forms the segment RCA and the quadrant Zfld forms the light segment BDA.
in the present invention, each of the reflector segments 2%- -2d is displaced outwardly from the position it occupies in a conventional reflector, as shown in H6. 5 to the position shown in FIG. 6, by movement substantially about the axis 2 of the filament, to displace the respective quadrant of illumination diagonally approximately a distance equal to onehalf the radius of the original pattern circle. The same relative diagonal displacement is effected for each of the quadrants b, c and a. In other words each quadrant is displaced in such a manner as to displace its resulting pattern, beyond the region of image inversing, in a diagonal direction, with the result that a composite square pattern is produced at all transverse planes beyond the region of image inversion as shown at 30 in F IG. 3.
Referring more particularly to FIG. i, it will be seen that the square pattern 30 is formed with four comers A, B, C, and D. it will also be noted that these four corners were previously at the center of the circular light pattern prior to displacement of the reflector quadrants. In other words, the radius of the original pattern, as defined by the line A, D of FIG. 3A, is now one side of the rectangular pattern 30. Therefore, by definition, the rectangular pattern 1%) has an area which is smaller than the area of the original circular pattern by a factor pi. It will also be seen that the rectangular pattern is now a composite of four overlapping segments of the original circular pattern, by reason of the outward displacement of the four quadrants of the reflector 20.
The four corners A, B, C, and D of the rectangular pattern 30 are uniformly illuminated since these corners were formed from the center of the circular pattern. In fact, the entire area of the pattern 30 tends to be generally uniformly radiated or illuminated due to the substantial overlap of the individual superimposed patterns, as shown in FIG. 4.
As previously noted, each of the quadrants of the reflector 20 are revolved or displaced substantially about an axis 25 defined at the filament center. For each quadrant, this results in a slight outward movement, in the manner shown in FIG. 6, to achieve the displacement required.
A composite complete reflector 35 may be made by joining together at 36 each of the several displaced reflector quadrants. The reflector 35 in FIG. 7 includes a bulb socket 37 and a bulb 38 with an axial, forwardly displaced filament 39. Since there would be a wedge-shaped gap or space between the adjacent edges of reflector segments formed by modifying a conventional symmetrical reflector, these may be eliminated by merely continuing the development of the curvature in an arcuate sense in each of the reflector segments to cause the segments to meet along joining lines 36 so that each individual segment represents, in the completed reflector 35, slightly more reflecting surface than a true quadrant. Alternatively, the spaces or regions which would be formed between the segments may be otherwise suitably filled or even left open, without departing from the scope of the invention or adversely affecting the operation thereof.
Reflector 35, thus completed, remains of generally circular configuration as shown in FIG. b and produces a square pattern of radiation as shown at W in FIG. 4. Since this pattern is smaller than that of the original circle from which it has been developed, it may be projected over a correspondingly longer distance to cover the same area. Since the efficiency of the reflector has been substantially unimpaired or even increased, the amount of luminous flux over the area 30 is at least the same as that which was previously available over the original circular area. In other words, the rectangular pattern of uniform intensity has been achieved with no decrease in efiiciency. In many cases, such a rectangular pattern is more ideally suited for illuminating a lap or reading area, since magazines, books and the like lend themselves to a square or rectangular illumination, with less spill-over into adjacent areas. The uniform pattern is thus achieved without the necessity of adding auxiliary lenses or diffusing shields over the reflector. It may be desirable to incorporate a filament shield to reduce the direct radiation, as well known in the art.
FIG. 9 shows the field patterns of reflected energy (on an enlarged scale) at a series of transverse planes with the reflector 35. Section A-A shows the pattern of reflected radiation from a reflector prior to field inversion. The fields formed area are erect images of the four quadratures of the reflector. Section 8-8 shows that a portion of the field has passed through inversion. Field inversion takes place over an axial distance rather than at a point due to the fact that the filament has some finite dimension, and is preferably axially displaced in this embodiment as previously described. Section C-C is taken about midway through field inversion and shows that approximately one-half of the flux field of each reflector segment has been inverted. Section D-D shows the further progression of inversion, and section E-E shows the completed inverted and composite geometric, straight-sided pattern. This pattern of Section 5-5 will retain its relative shape in all transverse planes further from the reflector 35.
It will be seen by reference to the sections of FIG. 9 that the projecting system of this invention requires only a small opening or openings forward of the reflector. If desired, a single correspondingly small aperture may be employed for each reflector segment, such as four hour-glass-shaped apertures properly positioned to pass the radiant energy in plane C-C, without loss of efficiency, permitting a variety of decorator treatments when the invention is embodied in illuminating lamps and the like.
The present invention may be applied to any noncollimating, image inverting projecting reflector system. Thus, it may be applied, for example, to the tilted revolved elliptical reflector, as shown in FIG. 10. A reflector generated by a tilted ellipse is a well-known technique for providing illumination over a circle of large diameter in relatively short projection distances. It is formed by employing a section of an ellipse,
such as the section 40 shown in FIG. 10, in which the section is on a tilted or inclined ellipse axis 42. Once the tilt of the ellipse has been established, the reflector is then "generated" by revolving the line section of the ellipse about the focal point 43 defined by the bulb filament.
FIG. shows a one quadrature section 40 of such a revolved ellipse reflector and the resulting quadrature 44 of light in relation to the entire pattern of light which is produced by this type of reflector. It will be seen that a relatively large circular pattern is normally produced. This reflector can be modified in the manner taught above by tilting the ellipse section 40 about the point 43 at the bulb filament to displace the segment ABC inwardly by a distance equal to one-half the radius of the circular pattern. The remaining reflector sections are similarly displaced diagonal to form the composite rectangular pattern in the manner described in connection with FIG. 4. Again, the resulting square pattern of light has relatively constant light values and has a height and length which is equal to the original radius of the circular pattern and therefore, is smaller than the circular pattern by a factor of pi.
The present invention is, of course, not limited to electric lamps with separate bulb and reflector elements as shown in FIGS. 7 and 8. It may advantageously be applied to an integral evacuated lamp such as shown at 50 in FIGS. 11 and 12. Here, the integral reflector portion 52 is reflectorized and is made up of quadrants 52a, b, c, and d, in the manner previously described. The glass envelope may be closed by an annular portion 54 and a bottom clear segment 55. The encircling portion 54 is of spherical configuration, and the center of the sphere is designed as the center of the filament 56. The spherical portion 54 operates to increase the efliciency of the lamp 50 by reflecting the filament image into the displaced segments of the reflector 52 for reflection outwardly into the pattern, as defined by the line 58, for example.
A squared" reflector may be desirable in many installations where size is a limiting factor. For example, if an opening permits the insertion of a reflector with a maximum dimension of 3 inches, and if the other dimensions permit, it may be more efficient to insert a 3-inch square reflector within the opening rather than a 3-inch diameter circular reflector. This would be particularly true of a rectangular opening. Therefore, under some circumstances, a more efficient reflector can be made by applying the teachings of the present invention to a squared reflector.
A circular reflector can be "squared" by lopping off the sides, substantially in the manner shown for the reflector 60 in FIGS. 13 and 14. This result can be achieved by forming a reflector 60 which has a surface of a symmetrical true reflector but in which excess material has been removed off the sides, as shown by the broken lines 60' in FIG. 14. The conventional pattern 61 which is thus produced by a reflector squared" in this manner is shown by the full lines in FIG. 15.
The reflector 60 of the type shown in FIGS. 13 and 14 can be modified in the manner which has been described above and thus divided into a plurality of segments, such as the seg ment 60a of FIG. 16, each segment forming a corresponding segment 62 of the whole pattern 61. As the reflector 60 is divided into four equal segments, the pattern segment 62 will represent exactly one-fourth of the original pattern 61. The individual segment 60a can thus be displaced outwardly, substantially in the manner described in connection with FIGS. 5 and 6, to displace the pattern segment 62 to the broken line position as shown in FIG. 16. When each of the segments are thus displaced, a new integrated rectangular pattern is formed, as shown at 65 in FIG. 17, by a composite reflector 66, shown in FIG. 17 and in greater detail in FIG. 18. The pattern which is thus formed in this embodiment is a square, which has onefourth the area of conventional pattern 61 of FIG. 15, with substantially uniform light values thereover. As in the case of the previously described embodiments, the pattern 65 is formed only beyond the region of image inversion, and retains its shape in all transverse sections beyond inversion. The reflector 66 shown in FIG. 18 resembles, in construction, the reflector 35 shown in FIGS. 7 and 8, but has increased efficiency for a given size due to the fact that the four corners 67 increase the effective area of the several quadrants providing a somewhat increased overall reflector area as compared to the substantially round type of composite reflector shown in FIGS. 7 and 8.
It is not necessary, in the practice of this invention, to form a square pattern using a reflector of four segments. When a squared" reflector 66 is employed as shown in FIG. 18, the individual reflector sections can be positioned in such a manner as to form a rectangular pattern 70 such as shown in FIG. 20. In FIG. 19, the pattern 61 prior to modification corresponds to the same pattern shown in FIG. 15. In this case, the individual segments 62 are moved along a diagonal as shown by the arrows 72, in such a manner that the two patterns on the right-hand side, are moved diagonally to form a composite pattern 74 (FIG. 20) on the left-hand side, while the opposite sections on the left-hand side are similarly moved diagonally, by controlled outward displacement of the corresponding reflector quadrants to move the respective pat terns to the right-hand side into a single square 75. The composite pattern 70 is therefore an integrated rectangular pattern, as shown in FIG. 20, with substantially uniform light values thereover.
The pattern 70 has particular value in that the left-hand margin 77 and right-hand margin 78 were formed along the vertical centerline 79 of the original pattern 60 but with the portion in one section furthest from the geometric center of the pattern positioned in overlying relation with the corresponding portion of the adjacent section which was nearest the center. In other words, the arrangement of FIG. automatically integrates variations in the field intensity, and provides an elongated or rectangular pattern from a generally circular or squared reflector. The patterns thus formed may be used to illuminate buildings, or as head lamps for automobiles, or aircraft landing lights or particular aircraft or ship position or collision warning lights.
By controlling the amount and degree of overlapping of the images from the several segments of a reflector, after image inversion, special effects can be obtained such as trapezoidal patterns for illuminating buildings from the ground. In addition, the invention is not limited to the use either of four quadrants, as shown in the preferred embodiments, or round or squared" reflectors. The teachings of the invention may be applied to oval reflectors or to rectangular reflectors, and these may be divided into three or more segments and the patterns suitably integrated to form images, in all transverse planes beyond the region of image inversion, which are regular, geometric, with straight sides corresponding in number to the number of reflector segments employed.
The present invention is not limited to the projection of visible light rays from suitable sources, and may be used to project any type of a ray obeying the normal optical laws of reflection. For this purpose, ultraviolet and infrared rays may be controlled, as well as very short wave length electromagnet waves, such as millimeter radar.
The terms circularly symmetrical and symmetrical reflector" as used herein and in the claims refers to the quality of an ordinary reflector which presents the same angle to direct rays from an axially positioned source in all corresponding angular portions about the central axis thereof, such as, for example, spherical, parabolic and revolved tilt-elliptical reflectors, and variations thereof.
While the forms of apparatus herein described constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise forms of apparatus, and that changes may be made therein without departing from the scope of the invention, which is defined in the appended claims.
1. A reflecting system for directing radiant energy in controlled spatial relation, comprising a generally localized source of radiant energy, a concave noncollimating image inverting reflector positioned with respect to such energy source to direct energy therefrom outwardly of said reflector with said source being positioned generally on a central axis of said reflector, said reflector comprising a plurality of arcuate concave segments of a whole symmetrical reflector with each of said segments being displaced generally radially outwardly of said axis from the position it would occupy in such a symmetrical reflector in such a manner as to direct a corresponding portion of the radiant energy outwardly therefrom with the discrete image from each reflector passing through inversion at a common transverse region, said displacement of said segments forming inverted images which lie on paths which converge and which form, in all transverse planes beyond image inversion, a geometric pattern of such energy having straight sides, with the number of said sides corresponding to the number of said segments.
2. The device of claim 1 in which said segments are portions of a revolved tilted ellipse.
3. The device of claim l, in which each of said segments is displaced as if by outward by rotational movement about a transverse axis through said source.
4. The device of claim l in which said pattern is rectangular and is smaller than corresponding circular pattern of the circularly symmetrical reflector by a factor of pi.
5. The reflecting system of claim 1 in which said energy comprises luminous flux.
6. The reflecting system of claim 1 in which said reflector is formed into four said segments of substantially equal arcuate dimension.
7. The system of claim 10 in which said segments are related to the axis to form a square pattern.
8. The system of claim 6 in which said segments are related to said axis to form a rectangular pattern.
9. The system of claim 1 in which the reflecting surfaces of said segments are segments of surface generated by a revolved tilted ellipse.
10. The system of claim l in which the reflecting surfaces of said segments are segments of a paraboloid, and in which said source is displaced forwardly of the normal focus of such paraboloid.
11 The system of claim 1 in which said source is a tungsten filament of an electrical lamp and in which said reflector is formed as an integral part of the lamp.
12. A light projecting apparatus comprising an electric filament forming a localized source of light, a noncollimating image inverting concave reflector positioned to direct light from said filament outwardly with said filament being positioned generally on a central axis of said reflector, said reflector being divided into four arcuate segments with each of said segments having a surface curvature which forms an arcuate section of a symmetrical reflector, with each of said segments being displaced generally radially outwardly of the position which it would occupy in such a symmetrical reflector to direct a corresponding portion of the light outwardly therefrom with inversion of the filament image and forming in all transverse planes beyond image inversion a substantially square pattern of light.
H050 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 3.588.493 Dated June 28. 1971 Inventor(s) Robert G Nnrdqniqi' tified that error appears in the above-identified patent It is cer and that said Letters Patent are hereby corrected as shown below:
Column 5, line 14, "area" should be deleted.
Column 8, line 23, "10 should be 6.
Signed and sealed this 21 st day of March 1972.
ROBERT GOTTSCHALK EDWARD I LFLETCHER, JR.
Commissioner of Patents Attesting Officer