US3434777A - Attachment for stereomicroscopes - Google Patents

Description

March 25,1969 L. J. 'sANT'mocco ETA-L 3,434,777

ATTACHMENT FOR STEREOMICROSCOPES Filed Oct. 31. 1966Sheet 1 of 6 FIG. 1

INVENTORS LOUIS J. SANTIROCCO JOACHIM A. RITTER .ATTO N Y March 25, 1969 L. J. SANTIROCCO ET AL ATTACHMENT FOR STEREOMI CROSCOPES Sheet 13 of 6 Filed Oct. 31. 1966 N OE n ATTORNEY March 25, 1969 ET 3,434,777

ATTACHMENT FOR STEREOMICROSC OPES Filed Oct. 51. 1966Sheet 3 or e v INVENTORS LOUIS J. SANTIROCCO BY JOACHIM A. RITTER ATTOR EY March 25, 1969 L'-.J. SANTIROCCO ETAL 3,434,777

ATTACHMENT FOR STEREOMICROSCOPES Filed Oct. 31, 1966 0,555-- 'I i A a I II I 42 50 55 41 45 43 FIG. 5

,f .54 FIG. 7

INVENTORS 5e LOUIS, J. SANTIROCCO BY JOACHIM A. RITTER TT NEY March 25, 1969 L. J. SANTIROCCO ETAL 3,434,777

ATTACHMENT FOR STEREOMICROSCOPES Filed Oct. 51, 1966Sheet 5 of e n4 IIO- 100x- FIG. 9

ATToRNza March 25', 1969 SANT'RQCCQ ET 3,434,777

ATTACHMENT FOR STEREOMICRQSCOPES Filed'o'ct- :51. 1966 Sheet INVENTORS LOUIS J. SANTIROCCO JOACHIM A. RITTER Anode? United States Patent 3,434,777 ATTACHMENT FOR STEREOMICROSCOPES Louis J. Santirocco, Greece, and Joachim A. Ritter, Irondequoit, N.Y., assignors to Elgeet Optical Company, Inc., Rochester, N.Y., a corporation of New York Filed Oct. 31, 1966, Ser. No. 590,987 Int. Cl.G02 27/22 US. Cl. 350-436 12 Claims ABSTRACT OF THE DISCLOSURE A stereoscopic attachment for a stereomicroscope is disclosed having two lens holders rotatably mounted in it, and two objective carrying arms swingably mounted on it. Each lens holder has a prism at each end and an intermediate reflecting member which may also be a prism. Each arm has an opening at its free end, and a right angular prism registering with the opening. A second right angular prism at the pivotable end of each arm registers with an opening through the bearing on which the arm swivels. An objective is removably mounted in each arm between and in registry with its prisms. A roof prism reflects the light traveling through each arm into the associated lens holder, and from the lens holders the light is reflected by prisms into the eyepieces of the stereomicroscope.

The present invention relates to optical systems, and more particularly to optical image rotating devices. In a still more specific aspect, the invention relates to a stereoscopic attachment for stereomicroscopes with image rotating capability.

For map making, and for study of terrain as, for instance, enemy-occupied territory, it is usual for airplanes on a photographic mission to take a series of pictures, each having approximately a sixty percent overlap of the next succeeding and the next preceding picture. For study purposes, successive pictures may be placed under a stereomi-croscope having a stereoscopic attachment with a rotational feature so as to permit alignment of successive images of an object with one another for viewing through the microstereoscope. This gives, in effect, a three-dimensional view of the object.

Heretofore Pechan, Schmidt, or Dove prisms have been used as image rotating devices. These will invert and revert the image. Moreover, for mounting them on a microscope, the structure becomes usually rather bulky, long, wide and deep. This makes them costly.

One object of the present invention is to provide an image rotating stereoscopic attachment for stereomicroscopes, which will be smaller and less costly, than previously known such attachments.

Another object of the invention is to provide a stereoscopic attachment of the character described which will permit the use of interchangeable objectives, allowing different magnifications.

Another object of the invention is to provide an optical system for stereoscopicattachments which will permit image rotating and which can be used with divergent or convergent light as well as with parallel light.

More broadly stated, another object of the invention is to provide a prism arrangement for image rotating devices which will permit a greater tolerance of angular deviation, which is easily adjustable in all planes, and with which the mechanical dimensions may be kept to a minimum.

A further object of the invention is to provide an image rotating device of the character described which is compact enough to be used in compact optical instruments like telescopes, mciroscopes, and the like.

Other objects of the invention will be apparent hereinafter from the specification and from the recital of the appended claims, particularly when read in conjunction with the accompanying drawings.

In the drawings:

FIG. 1 is a vertical sectional view through a stereoscopic attachment built according to one embodiment of this invention, the arms of this attachment being shown in folded position, and the objective carried by one of these arms being removed therefrom;

FIG. 2 is a vertical sectional view through a stereoscopic attachment for stereomicroscopes made according to another embodiment of the invention, the objectives being shown mounted in both arms;

FIG. 3 is a section, laid out in a plane, through the device of FIG. 2 with parts removed for clarity of illustration, both arms being shown extended outwardly;

FIG. 4 is a bottom plan view of one of the arms with the lenses removed therefrom;

FIG. 5 is an axial sectional view of one of the objective lens barrel assemblies;

FIG. 6 is a side elevation of this objective lens barrel;

FIG. 7 is a transverse section showing a lens barrel mounted in its arm;

FIG. 8 is a fragmentary view showing the means for locking either the attachment of FIG. l or FIG. 2 to a stereomicroscope;

'FIG. 9 is a diametral transverse parts shown in FIG. 8;

FIG. 10 is a fragmentary sectional view showing how either attachment may be secured, with the illustrated locking means, to a stereomicroscope;

FIG. 11 is a view showing the prisms in the image rotating portions of both attachments and illustrating diagrammatically their action;

FIG. 12 is a similar view illustrating an alternative arrangement of prisms and a mirror in an image rotating device built according to a modification of the invention; and

FIG. 13 is a view similar to FIGS. 1 1 and 12 illustrating a still further arrangement of prisms for an image rotating device.

In the embodiment of the invention illustrated in FIG. 1 of the drawings, there are two arms pivotally mounted on the body of the attachment for swinging movement about parallel vertical axes, each, through 360". Each arm has an objective lens barrel mounted in it for removal and exchange so that objectives of different magnification can be substituted and employed. In each arm there are mounted two prisms, disposed, respectively, at opposite ends of the objective lens barrel. One of the prisms of each arm registers with the annular bearing or trunnion on which the arm pivots. Mounted in the body of the attachment above each trunnion and in registry with its bore is a roof prism. Mounted in the body ofthe attachment, also, are two rotatable lens holders, each of which carries, at one end, lenses registering with one of the roof prisms. Mounted in each lens holder, also are three cooperating prisms. A double convex lens is mounted in the other end of each lens holder for transmitting light therefrom to a fixed prism, one of which is associated with each lens holder. Between these two fixed prisms is another fixed prism which cooperates with both. Light entering each arm is reflected by the prism at the free end of the arm through the objective lens barrel to the prism at the pivot of the arm, and thence through the associated roof prism and the associated lens holder to one of the fixed prisms. The light reflected by the two fixed prisms is reflected to the intermediate fixed prism, whence it passes into the two barrels or tubes of the stereomicroscope to which the attachment is secured. The

section through the Patented Mar. 25, 1969 t axes of rotation of the lens holders are inclined to one another; and the three prisms in each lens holder are so disposed to one another that the reflected light, in efiect, travels in a straight line through the lens holder. The arms can be swung on the body to dispose the prisms at the free ends of the arms and the openings in the arms, through which light enters these prisms, over the portions of the photographs which are to be viewed. By rotation of the lens holders two photographic views of an object can be aligned so that when viewed through the microscope they will appear enlarged and three-dimensional.

The attachment shown in FIG. 2 is similar to that illustrated in FIG. 1, differing only in the respect that for more precise rotary adjustment of the lens holders, each lens holder is adjustable also through manipulation of a pair of hypoid gears instead of being merely rotatable manually by a knurled ring secured to the lens holder.

Instead of using three cooperating prisms in each lens holder, two prisms and a mirror may be substituted therefor, as shown in FIG. 12, the mirror being disposed between the two prisms to reflect light from one prism to the other.

Instead of using a mirror with the two prisms, a third prism may be disposed instead between them, as shown in FIG. 13. This last embodiment is particularly useful for various types of optical instruments including telecopes, and the like.

Referring now to the drawings by numerals of reference, denotes a casing having abody section 12 and acover portion 14 secured to the body section by screws 15. Rotatably mounted on the body section by annular trunnions orjournals 17 are twoarms 18. Mounted in eacharm 18 is aprism 20 and aprism 21.

The arms and the parts mounted therein are identical. Hence the structure and parts of only one arm will be described in detail here.

Theprisms 20 are mounted in their respective arms onledges 22 and 23 and are held in place in the arms byend plates 24. Arubber gasket 25 may be interposed between each of theplates 24 and the adjoining side of the associatedprism 20. Each of theprisms 21 is mounted on agasket 27 and held in place by thering bushing 17.

Each of thebushings 17 has aperipheral rib 30 and is mounted by means of this rib on a preloaded ball hearing, which comprises a lower ring 31, anupper ring 32 and lower and upper sets ofballs 33 and 34, respectively. Thering 32 threads rotatably into thehousing section 12 in order to preload the bearings. A setscrew 36 serves to lock eachring 32 in adjusted position. This setscrew is aligned with thefastening screw 15 so as to be readily accessible. Eacharm 18 is threaded to its ring bearing to rotate therewith and is secured in position by asetscrew 37.

The arms are adapted to carry identical objectives mounted betweenprisms 20 and 21. The objectives are interchangeable so as to permit interchanging objectives of diflerent magnifications from .5 x for instance, through .'75 and l to 2x.

A typical objective is shown in FIGS. 5, 6 and 7 at 40. It comprises ahousing 41 in which are mounted thelenses 42, 43, 44, 45 and 46. One end of the housing provides a seat forlens 42. Aspacer ring 48 is disposed betweenlenses 42 and 43.Lens 44 is mounted in aring 51 against which lens 45 seats. A spacer ring 53 is interposed betweenlenses 45 and 46. A spacer ring 55 holdslens 46 in place; and anannular nut 57, which threads intobarrel 40, serves to hold all the lenses and rings in place in the lens barrel. For ease in handling, the side walls of the housing are provided with diametrally opposedrectangular recesses 49. At one end each housing has aledge 50.

Eacharm 18 has a cylindricallybored chamber 54 in which the associatedlens barrel 40 is adapted to be mounted; and it is formed with twoopposed ledge portions 56 at opposite sides, respectively, of thechamber 54. Eachchamber 54 is open at its bottom as indicated at 52.

To mount an objective in an arm, therecesses 49 in thebarrel 40 are registered with theledges 56 of thechamber 54, and the objective is pushed up through theopening 52 into the arm. The objective is then slid axially in thechamber 54 so that therecesses 49 in the objective 40 are offset axially of theledges 56 in the arm. Thus, each lens barrel assembly will :be held from dropping out of its arm. A leaf spring 58 (FIGS. 1, 4 and 7), which is secured byscrews 59 to one of theledges 56, and which presses down on the base of the lens barrel, serves to hold the lens barrel frictionally in place in the arm.Ledge 5% of the lens barrel engages underledge 23 of its arm when the lens barrel is in proper position in the arm. Theledge 50, which is at one end only of the lens barrel insures that each lens barrel is put in its arm in proper end-to-end position.

Light enters the system through a circular opening 6t) in each arm. This opening registers with theprism 20 of the arm.

Rays of light entering theopening 60 in each arm are reflected byprism 20, pass through the objective 40, and are reflected by theprism 21 through the bore of thebearing ring 17 onto a roof prism es, whence they are reflected through thefield lenses 66 and 67 into a lens barrel 69. Mounted in this lens barrel are threelens prisms 76, 72 and 74.

The two lens barrels 69 and the parts mounted therein are identical. Hence only one lens barrel 69 and its parts will be described in detail here.

Thelenses 66 and 67 are fixed and held in place by the ring clamp 76 which is threaded onto thering member 77 that is fastened in any suitable manner to a seat 78 which is secured to thehousing 1 Thelenses 70, 72 and 74 are so designed and mounted that light passing through the lenses as and 67 is directed to lens and is reflected inlens 70 twice tothe lens '72, and from lens 72 to the lens '74 and fromlens 74 is reflected, as shown by the arrows in FIG. 11. The light thus travels, in effect, in a straight line through prisms 7t], 72 and 74. Fromprism 74, the light passes through a doubleconvex lens 30 into aprismatic lens 82. The straight line of effective travel of the light throughprisms 70, 72, 74 coincides with the axis of lens barrel 69. Eachlens 80 is secured in a ring 31 that is threadedly fastened on the lens barrel 69; and this lens is held in thering 81 by aring nut 83.

Twoprismatic lenses 82, which are silvered at 88, are disposed at opposite sides of theprismatic lens 84 with the result that the light is reflected from theprisms 82 into the objectives 164 (FIG. 10) of the stereomicroscope, to which the attachment is secured, as shown by the broken line and arrow in FIG. 11.

Each of the lens barrels 69 is rotatable by means of aknurled ring 85 that is secured to the barrel in any suitable manner. Rotation of the lens barrel permits rotating the image seen through the lens system associated with this lens barrel. A click stop in the form of aball 86, which is resiliently urged into engagement with peripheral recesses on thering 85, serves to hold thering 85 and the barrel 69 in any adjusted position. The ball is urged into the engaging position by acoil spring 87.

Each lens barrel 69 is rotatably journaled in thehousing 12 by aball bearing 99, which surrounds the barrel at one end, and by aball bearing 91, which surrounds thering 81.

Theclick stop 86 not only holds each barrel in any adjusted position, but by feeling the clicks it is possible to precisely position each lens barrel in the housing.

To precisely align the prisms 7t '72 and 74 of each set, theblock 95, on which each prism 72 is mounted, is made adjustable in the associated lens barrel 69. A stud 96 is threaded into each block $5 and passes through an enlarged hole 97 in the corresponding lens barrel. Threescrews 98 are threaded into the associated lens barrel 69 and disposed equiangularly about the stud 96. Each of these screws has a pointed end engaging the associatedblock 95. By adjustment of these screws, theblock 95 can be tilted, to precisely adjust each prism 72 relative to the associatedprisms 70 and 74 so as to have the light beams, which are reflected from aprism 70, reflected by associatedprisms 72 and 74 in such mnaner as to in etfect pass in the desired straight line through these prisms, as shown by the arrows in FIG. 11.

The attachment is secured to the stereomicroscope by a pair ofslidable clamp members 100, 101 (FIGS. 8, 9 and which are recessed, as indicated at 102 and 103, to permit light rays to pass from the attachment into the tubes orbarrels 104 of the stereomicroscope, These clamping members are manipulated by arotary ring member 105 which has two diametrally disposed knurled lugs orprojections 106 thereon by which it may be manipulated. Thering 105 is connected bypins 107 with the clampingmembers 100 and 101. These pins engage in straight inclined slots 1-08 in the clamping members so that when the ring is rotated in one direction, the clamping members are moved away from one another to clamp the attachment to the stereomicroscope, and when the ring is rotated in the opposite direction, the clamping members are released. In clamping position, the clamping members engage at their outsides in an internal groove 109 (FIG. 10) formed in the cover orhousing 117 of the stereomicroscope as shown in FIG. 10.

The clamping members slide in dove-tailedguideways 110 machined into the block orplate 113 On which thering 105 is rotatable. The plate or block 113 is fastened to the attachment byscrews 112 which pass through holes 112' in theblock 113.Pins 114 in the stereomicroscope engage inholes 114 in the block orplate 113 to locate the attachment precisely on the stereomicroscope.

For finer adjustment of the image rotating part of the attachment than is possible with the attachment of FIG. 1, a construction, such as shown in FIGS. 2 and 3, may be used. This attachment is identical with the attachment of FIG. 1 except that each lens barrel 69 may be precisely adjusted by means of a hypoid gear andpinion 115, 116. The hypoid pinion is mounted on a shaft 118 which is journaled by means of the bearingportions 119 and 120 inplates 121 and 122, respectively, that are connected in any suitable manner to thebody 12. A dowel 124 and screw 125secure plates 121 and 122 tobody 12 which forms part of the mount for theprisms 82 and 84. Aknurled knob 126 is fastened to one end of each shaft 118; and aknurled knob 128 is connected to the opposite end of each shaft 118 bystud 129 which is integral with theknob 128 and is threaded into the portion 119 of the shaft. Aball 130, which is urged by acoil spring 131 into engagement with equiangularly spacedrecesses 132 in a collar portion of eachknob 128, serves as a click stop to hold the hypoid pinion in any adjusted position and also as a means for assisting in quickly locating the desired position of rotation of the associated barrel 69.

Thehypoid gear 115 itself is journaled on the barrel 69 and is frictionally connected thereto by aball 135 which is constantly urged byspring 136 into engagement with one of the equiaugularly spaced recesses in the back of the gear. This produces enough friction to take the barrel 69 along with thegear 115 when the gear is rotated. However, it permits independent rough adjustment of the barrel by rotating it by means of theknurled portion 85.

The section of FIG. 3 is a developed sectional view, the axes of the two lens barrels 69 which are, of course, inclined to one another, being shown in a common plane.

In FIG. 3, thearms 18 are shown swung to 90 positions. Each can be rotated through 360 to view any portion of any picture beneath the microstereoscope.

Instead of using the prism arrangement shown in FIGS. 1 and 2, a prism arrangement such as shown in FIG. 12 may be used. Here twoprisms 140 are employed, each of which is a 30, 60, prism. These two prisms are used in conjunction with amirror 142, which takes the places of the prism 72.. The sides of the two prisms enclosed by the 90 and 30 angles, have to be silvered in order to obtain reflection. When mounted in the manner shown in FIG. 12, reflections are obtained which produce image rotation along an undeviated optical axis when aligned properly. Alignment of the unit can be obtained by shifting and tilting the mirror since it is not fixed or cemented to the prisms.

This arrangement can replace the conventional dove prism since its mechanical perimeter is almost equal to that of a dove prism and its length is somewhat shorter. This unit has the advantage over dove prisms, however, that it can be used with divergent or convergent beams of light as well as with parallel beams.

In the rotating system of FIG. 12, if the aperture A=1 and the refractive index n=l.517, then 0=60, p=30, w=90, 1/:180, B=1.73205, 0:2, D=2B'=3.4641,

=A=1.000, and G=1.15469. The light path in this system equals t=5.19608; and t/n=4.0l554. F and D are related to each other. If n, the refractive index of the glass, is changed, l/n is the only dimension that is affected, since n is related to t/n.

To further shorten the mechanical length of the image rotating system, two 45 prisms in conjunction with a 90 prism may be used. As shown in FIG. 11 this, however, will increase the mechanical perimeter of the system to that of a Pechan prism.

The prism arrangement shown in FIG. 11, which is that illustrated in FIGS. 1 and 2, will work exactly like the prism arrangement of FIG. 12 but here the mirror is replaced by a 90 prism 72 which makes t/n shorter.

If the aperture diameter A=1 and the refractive index 11:1.517, 6=45, p=11230', w==, and H=0.02202, then B=l.7250, C=1.100, G=l.00'0, F=1.4l42l, D=2.4672. The light path in this system equals t=4.40038; and t/n=2.9l434.

FIG. 13 shows a still third image rotating system which has all of the advantages of the previously described systems, and, in addition, since the t/n value equals the overall distance or D value, this arrangement can be placed in any existing instrument without changing the dimensional configurations of it. In other words, this system can be used on any microscope regardless of the tube length of the microscope without change in the tube length. Here A=l.0, 0z=60, 5:30", :90", 6=180, and H=0.02202. Then B=l.73051, C='2.0,

E=l.l547, F=1.0, t=5.1961 and t/n-=3.46383.

There are various crown glasses available which are close to the mean index of 1.49998 of this system, such as K-ll, BK3, BK-4, BK-lO, K-IO, etc.

This last-described image rotating system may be used on various optical instruments such as telescopes, microscopes, and the like.

With any of the attachments described and their lens systems with its 360 image rotation feature, randomly oriented uncut film can readily be viewed and analyzed.

While the invention has been described in connection with different embodiments thereof, it will be understood that it is capable of further modification, and this application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth, and as fall within the scope of the invention or the limits of the appended claims.

Having thus described our invention, what we claim is:

1. A stereoscopic attachment for stereo microscopes, comprising: a body,

two hollow arms pivoted on parallel axes on said body, and each having a free end opposite from said pivot an objective lens mount in each arm,

an optical, image-rotating device associated with each arm, and aligned therewith the two image-rotating devices being rotatably mounted in said body and each comprising a rotary lens barrel open at both ends, two prisms disposed in operative relation to the two ends of the barrel, respectively, and a reflecting member disposed between the two prisms to reflect light from one prism to the other so that the light travels in the direction of the axis of the respective barrel,

the free end of each arm having an opening therein for admitting light into each arm,

a first reflector mounted in each arm in optical registry with its opening for reflecting light into one end of the associated objective lens mount,

a second reflector in each arm optically aligned with said first reflector and objective lens for reflecting light received from said first reflector into one end of the associated lens barrel, and

means optically aligned with said two lens barrels for reflecting the light therefrom into a stereomicroscope to which the attachment is secured.

2. An attachment as claimed inclaim 1, wherein the means for reflecting light from said opposite ends of the two barrels into a stereomicroscope comprises a central prismatic lens and two other prismatic lenses disposed each with one side contiguous to opposite sides, respectively, of said central prismatic lens, the sides of said other prismatic lenses which are contiguous to the sides of said central prismatic lens being silvered to reflect the light into the two objectives, respectively, of the stereomicroscope.

3. An attachment as claimed inclaim 1, wherein:

(a) wherein each arm has a cylindrical bore for the section thereof, in which the objective lens mount is mounted,

(b) each objective lens mount is cylindrical, and

(c) for the purpose of insertion of each objective lens mount into its arm, the arm has an opening therein of substantially the same length and diameter as the lens mount, each arm has two ledges formed at opposite sides of its bore projecting thereinto, and each objective lens mount has diametral recesses at opposite sides thereof, whereby each lens mount may be inserted in its arm by aligning its recesses with the ledges of the arm, and the lens amount may be held in the arm after insertion thereinto by moving the lens mount axially to offset the recesses axiall from the ledges.

4. An attachment as claimed inclaim 1, wherein eacl: arm is pivotable through 360 about an axis perpendicular to the optical axis of the associated objective lens mount on an annular bearing through the bore of which light passes from the arm to the rotary lens barrel.

5. An attachment as claimed inclaim 4, wherein:

(a) each arm has a ring bearing member secured to it whose bore is coaxial with the pivotal axis of the arm,

(b) said ring bearing member has an external peripheral rib, whose opposite sides are of concave profile,

(c) two ring race members are mounted in said body at opposite sides respectively of each ring bearing member to be coaxial therewith, and

(d) ball bearings are mounted between each race member and the opposed side of the associated ring hearing member,

(e) one of said race members of each pair of cooperating ring race members being adjustable axially in said body to adjust the load on said bearings.

6. An attachment as claimed inclaim 1, wherein the means for admitting light into the free end of each arm and for reflecting it into the associated objective lens mount includes an aperture in the arm and a prism registering optically both with said opening and with said one end of said objective lens mount.

7. An attachment as claimed inclaim 6, wherein the means for directing light from each objective lens mount into one end of each rotary lens barrel includes another prism.

8. An attachment as claimed inclaim 4, wherein the means for directing light from each objective lens mount into said one end of each rotary lens barrel includes another prism disposed in its arm to reflect the light through the bore of said annular bearing.

9. An attachment as claimed in claim 8, wherein the means for directing light from each objective lens mount into one end of each rotary lens barrel includes a roof prism disposed in said body to reflect the light passing through said bearing into said one end of the associated lens barrel.

10. An attachment as claimed inclaim 1, wherein:

(a) the two prisms in each lens barrel are 30 prisms, and

(b) the reflecting member is a plane mirror having its reflecting surface opposed to the hypotenuse sides of these two prisms.

11. An attachment as claimed inclaim 1, wherein:

(a) the two .prisms in each lens barrel are 45 prisms,

and

(b) the reflecting member is a 90 prism.

12. An attachment as claimed in claim 11, wherein the refractive index of the prisms in each lens barrel are so selected that the length of the light path through the prisms divided by the refractive index of the glass is equal to the overall length of the prism system.

References Cited UNITED STATES PATENTS 973,438 10/1910 Janda 350-88 1,521,339 12/1924 Taylor 35038 2,406,798 9/1946 Burroughs 350-286 2,456,521 12/1948 Maxwell 350-53 2,866,382 12/1958 Gruner et al 350-137 3,030,857 4/1962 Shumway 35023 FOREIGN PATENTS 637,198 5/1950 Great Britain. 911,827 11/1962 Great Britain.

DAVID SCHONBERG, Primary Examiner.

PAUL R. GILLIAM, Assistant Examiner.

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