US2566998A - Bucky grid and method of making same - Google Patents

Description

Sept; 4, 1951 s. w. STRICKMAN BUCKY GRID AND METHOD OF MAKING SAME Filed Nov. 5, 1948 I -"L L L IL L Patented Sept. 4, 1951 UNITED STATES PATENT OFFICE Samuel" W. Str'ickinan, Kew Gardens, N. Y., as-

' signor of; one-fourth to Charles El-Bloom, Glen Ridge N. J and 9ne=fourth to Harry G. Bier: man, New Rochelle, N. Y..

Application-November 5, 1948, Serial'Nm' 58,580

several ways, one of which utilized lead strips which were attached to a sheet or canvas or the like and equally spaced. Such a structure was mounted so as to move through an arc in order to obtain alig ulatidfi. Such a structure was inaccurate in that itwas difficultto uniformly space the lead' Stripsand they were not'fi'rmly held on the" canvas. The angulation caused a substantial absorptionof primary rays and formed distortd images on the due to the unequal dista'lice of the grid fr m the 1' Another type of grid consisted" in a series of alternate strips" of wood and lead. it was quite difficult to make the lead strips suiificientlythin to be highly errecuv'and it was also diflicult to form" a' coherent body because sausractoryperhefit'ifigl" of" lead t6- Wdod w s difficult This structure had disadvantages in that becauseaof the relative thickness of the leadstrips shadows were'for'm'edon the film. The ratio of the length of the' wood strips to the space between adjacent strips was relatively low,-being.- about-3 01 4 to 1". Because of this secondary rays passed through the wood and dimmed the-imager nlso i'nthe fabrication it was difiicult to handle the many relatively thin slices or strips of lead and wood so that wrinkling or buckling or undesired shifting tools placewith the result that a large proportion of the grids so; made-were defective. Also-,the thinneststrip of lead thatcould be conveniently handled was-.060 inch, and the'thinnest strips of wood were about .090 inch: Such a grid had the additional disadvantage that it tended toabsorb water which caused warping of the grid and-a--distortion--of theimage on the film.

The present-invention is-intended and adapted to overcome the difficulties and the disadvan tages inherentin prior structures of the'type described,- itbeing'. amongthe -objectsof thepresent invention-to provide a Bucky gridwhich ishighly effective operation;- which casts substantially no shadow on the film-and which is non=warp mg.

It-is also among=the objects of thepreseiitinventionto provide a=--Bucky' grid which is strong and may be subjected to rough hand-lingl without; deterioration, which has a long life irr- 9" claims. (01:250-63) mar use, wherein very high ratios of length of lead to space therebetween is obtained, and is substantially impervious to water.

It is still further among the objects of the present invention to provide a method of; makiiig a Bucky grid which. is simple and effective, rapid and which greatly decreases the cost' of manufacture.

In practicing the present invention, there is provided a sheet or strip of a synthetic resinous or plastic material, which is transparent to X-rays and is relatively thin. The thickness of said plastic material need not be over .030 inch and may be as low as .003 inch. Upon this surfacethere is sprayed a mixture of finely divided lead particles and a readily volatile organic liquid which has the property of causing selling of the-surface of the plastic material. Various solvents known in the art are eminently suitable for the presentpurpose .but the solvents must be chosen so that the proper amount and character of gelling. of the surface is obtained. Among the solventssuitable for the purpose are ethylene dichloride, ethyl alcohol, acetone, ethyl acetate, methyl acetate, methyl ethyl ketone, dibutyl ether; octene, cycloheptane, monochlorpentane, butyl acetate and others. The manner ofapplication-ofthe suspension is set forth fully in my co-pe'nding application Serial No. 53,285, filed October '7, 1948; entitled Method of- Producing Go'nduct'ing Surfaces. Said application describes a; process wherein metal particles suspended in said volatile Iiquid'areagitated to form auniform suspension and immediately sprayed onto" the" mastic material under at least 20 pounds per square inch pressure to atomi'ze the liquid and to cause substantially complete vaporization'thereof, said vaporized liquid causing g elliiig of the plastic material without any solution thereoflthe particles being forced partially mm the plasticmaterial and being anchored therein by evaporation ofthe liquid within 5 seconds. v

The spraying leaves a thin layer of powdered lead -onthe surface ofthe plasticmaterial with the powder anchored ontothe surface to form a substantially complete and uniform film anchored therein. This film maybe in the order of .001 inch or thicker, if desired, and as high as .OBO'inch; The strip sotreated may be sprayed on the Ol l 'osite facewitl'i a solvent for the plastic material in'oider'to'soften the same and render it adhesive. A serie's' of sheets are then stacked and compressed; wherebythey-become cemented together and the"- solvent is allowed to evaporate.

Usually the ratio of the Width of the strips to the thickness of the layer is from 3-25 to l.

In the accompanying drawings constituting a part hereof and in which like reference characseconds the bulk of the gelling liquid has evapo rated and the strip is turned over to expose the opposite surface. Ethyl alcohol is sprayed thereon sufiicient to wet said opposite surface and to cause initial solution thereof. A series of such strips are immediately stacked, compressed and dried.

Example 2 The base strip is made of cellulose acetate composition such as is ordinarily used for mo- 7 tion picture film. It is placed on a surface and ters indicate like parts,

Fig. 1 is a perspective view of a fragment of a strip used in the present invention;

Fig. 2 is an exploded view showing a series of strips ready for assembly to form a grid;

Fig. 3 is a front elevational view of a completed grid made in accordance with the present invention, being partly broken away;

Fig. 4 is a top plan view of a grid of different form, and

Fig. 5 is an end view of a modified form of strip before being assembled into a grid.

In practicin the present invention, there is provided a strip l which is of the proper width for the depth of a grid, or it may be a multiple of such depth. There is sprayed onto the surface thereof a mixture of lead powder in a highly volatile organic liquid which is capable of gelling the surface of strip 1 to form a film or layer 2 on the surface thereof.

The opposite surface 3 of the strip is treated with a solvent so as to cause incipient solution of said surface, and a series of such strips are assembled as shown in Fig. 2, placed in contact and held under sufficient pressure to cause close contact of the several strips. The body thus formed is dried to remove the volatile solvent, whereby all of the strips are cemented together.

Acasing or cover 4 is formed around the grid thus produced, said cover being of a similar synthetic plastic material which may be formed by casting or pressure molding. The casing adequately protects the grid from outside contamination and from the entrance of moisture.

-. InFig. 4 is shown a circular grid which is formed from a single or multiple strip of considerable length of the type shown in Fig. l, and having the under-surface treated with a solvent 3. The strip is rolled to give the desired number of convolutions and held under compression until the solvent has evaporated.

In order to form an angular grid, there is provided a strip 6, as shown in Fig. 5, which has a trapezoidal cross-section. A film or layer 1 is deposited therein in the manner described above.

A series of such layers may be assembled as in Fig, 3, or a single longer strip may be assembled as in Fig. 4 to give an angular Bucky grid.

The following are specific examples of the operation of the present invention:

Example 1 The sheet or strip consists of a resin which is a copolymer of vinyl acetate and vinyl chloride.

-It is sprayed with a suspension having the following composition:

A sufiicient amount is sprayed onto the surface so as to provide a layer of lead anchored therein of a thickness of about .002 inch. After a few is sprayed with a composition as follows:

Lead (powdered 300 mesh) gms 45 Acetone cc 200 A sufiicient amount is sprayed so that the lead filmis about -.001 inch thick. A series of such strips are immediately stacked before the solvent has had an opportunity of completely evaporating. Pressure is applied and the gelling liquid allowed to become dispersed and evaporated, during which'it renders the contacting layers sufficiently adhesive so that a solid mass'is obtained. The mass is placed in'a mold and a covering of a water-resistant plastic may be heatsealed around the grid, or aplastic may be cast and caused to polymerize around the grid, or a solution thereof cast about it. The solvent is allowed to evaporate, thus forming a seal or cover for the grid.

There are numerous advantages inherent in the present invention in that the method of operation is simple and semi-skilled workers can readily produce the grid. There is very little wastage and very few defective grids formed in the process. The cost of operation is much lower than the cost of previous methods. The grid is strong and may be subjected to hard usage without deterioration. The grid is much more effective than those of the prior art in that it practically eliminates shadow on the film and practically completely absorbs secondary rays.

Although the invention has been described setting forth several specific embodiments thereof, the invention is not limited to such details as many variations in the operation may be introduced within the principles herein set forth. For instance in place of the plastic materials specifically mentioned, other materials either thermoplastic or thermosetting may be used, such as the alkyl methacrylates, including methyl methacrylate, polystyrenes, various cellulose derivatives such as cellulose ether and carboxy methyl cellulose, alkyd resins, phenol formaldehyde resins and many others. It is necessary that suitable gelling agents and solvents be used with such-plastic materials. The lead usually is of a mesh greater than and as high as 350 but coarser or finer lead powder is equally suitable. Lead layers of even less than .001 inch in thickness may be obtained.

Compounds of lead such as lead oxide are suitable, it being essential that whatever compound is used shall be opaque to X-rays. It may even be feasible in some cases to utilize a solution of a leadsalt, such as lead acetate in acetone, and spray the solution instead of the suspension.

Depending upon the character of the base material, the solvent and the gelling agent may be the. same or different compounds or mixtures. The spray mixture may in some cases havea small proportion of a film-forming material therein compatible with the base. It is not necessary to spray the mixture previously formed but the lead andthe liquid may be applied separately accepts but suificiently close together so as to anchor the lead into the surface of the strip. Other bases with-a synthetic adhesive in -the nature of a plastic material to provide a surface on which the lead powder may be anchored.

When forming a grid by pressing the laminations together, care must be taken to avoid distortion of the lead layer. The initial lead layer may be increased in thickness by electroplating lead thereon. In order to obtain a layer of highly uniform thickness, the metallized strips may be wiped by a felt or similar roll. A circular grid may be formed by cutting a circle from the grid shown in Figs. 2 and 3. These and other changes may be made within the spirit of the invention which is to be broadly construed in accordance with the claims appended hereto.

I claim:

1. A Bucky grid comprising contacting strips of non-metallic, X-ray transparent, synthetic plastic material, each strip having a thin layer of particles of lead anchored in the surface thereof resulting from the spraying of a uniform suspension of said particles in a highly volatile organic liquid free from adhesives under at least pounds per square inch pressure to atomize said liquid to cause gelling of said surface without solution thereof, said particles being partially embedded in said surface, said strips being cemented together, said strips being in the form of a helix.

2. A Bucky grid comprising contacting strips of non-metallic, X-ray transparent, synthetic plastic material, each strip having a thin layer of particles of lead anchored in the surface thereof resulting from the spraying of a uniform suspension of said particles in a highly volatile organic liquid free 20 pounds per square inch pressure to atomize said liquid to cause gelling of said surface without solution thereof, said particles being partially embedded in said surface, said strips being cemented together, and a casing of said plastic material surrounding said grid.

3. A Bucky grid comprising contacting strips of non-metallic, X-ray transparent, synthetic plastic material, each strip having a thin layer of particles of lead anchored in the surface thereof resulting from the spraying of a uniform suspension of said particles in a highly volatile organic liquid free from adhesives under at least 20 pounds per square inch pressure to atomize said liquid to cause gelling of said surface without solution thereof, said particles being partially embedded in said surface, said strips being cemented together, the cross-section of said strip being rectangular.

4. A Bucky grid comprising contacting strips of non-metallic, X-ray transparent, synthetic plastic material, each strip having a thin layer of particles of lead anchored in the surface thereof resulting from the spraying of a uniform suspension of said particles in a highly volatile organic liquid free from adhesives under at least 20 pounds per square inch pressure to atomize said liquid to cause gelling of said surface without solution thereof, said particles being partially embedded in said surface, said strips being cemented together, the cross-section of said strip being trapezoidal.

5. A method of making a Bucky grid which comprises providing a strip of non-metallic, X-ray transparent, synthetic plastic material,

from adhesives under at least '6 spraying .onto1thesurface thereof a mixture con sisting essentially of particles of lead suspended in an organic highly volatile liquid capable of gelling the surface of said strip without dissolw ing said surface, the pressure of spraying being sufficient to cause said particles to become partially embedded in said gelled surface, :said mixture being free from adhesives, causing the particles tobecome anchored in said surface so gelled bytheevaporation of said liquid from said gelled surface in'a few seconds, then-assembling 'aplu rality of said strips.

6. A method of making a Bucky grid which comprises providing a strip of non-metallic, X-ray transparent, synthetic plastic material, spraying onto the surface thereof a mixture consisting essentially of particles of lead suspended in an organic highly volatile liquid capable of gelling the surface of said strip without dissolving said surface, the pressure of spraying being sufficient to cause said particles to become partially embedded in said gelled surface, said mixture being free from adhesives, causing the particles to become anchored in said surface so gelled by the evaporation of said liquid from said gelled surface in a few seconds, electroplating said surface with lead, then assembling a plurality of said strips.

'7. A method of making a Bucky grid which comprises providing a strip of non-metallic, X-ray transparent, synthetic plastic material, spraying onto the surface thereof a mixture consisting essentially of particles of lead suspended in an organic highly volatile liquid capable of gelling the surface of said strip without dissolving said surface, the pressure of spraying being sufficient to cause said particles to become partially embedded in said gelled surface, said mixture being free from adhesives, causing the particles to become anchored in said surface so gelled by the evaporation of said liquid from said gelled surface in a few seconds, applying a readily volatile solvent to the opposite surface of said strip to provide a cement, then assembling a plurality of said strips.

8. A method of making a Bucky grid which comprises providing a strip of non-metallic, X-ray transparent, synthetic plastic material, spraying onto the surface thereof a mixture consisting essentially of particles of lead suspended in an organic highly volatile liquid capable of gelling the surface of said strip without dissolving said surface, the pressure of spraying being sufficient to cause said particles to become partially embedded in said gelled surface, said mixture being free from adhesives, causing the particles to become anchored in said surface so gelled by the evaporation of said liquid from said gelled surface in a few seconds, then assembling a plurality of said strips, and covering the assembly with a water-resistant plastic.

9. A method of making a Bucky grid which comprises providing a strip of non-metallic, X-ray transparent, synthetic plastic material, spraying onto the surface thereof a mixture consisting essentially of particles of lead suspended in an organic highly volatile liquid capable of gelling the surface of said strip without dissolving said surface, the pressure of spraying being sufficient to cause said particles to become partially embedded in said gelled surface, said mixture being free from adhesives, causing the particles to become anchored in said surface so gelled by the evaporation of said liquid from said gelled surface in a few seconds, then assembling a plu- Number REFERENCES CITED 5 The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 10 1,149,974 Chisholm Aug. 10, 1915 8 Name Date Richardson Mar. 6, 1923 Loebell Aug. 25, 1925 Sawford Mar. 22, 1927 Freeman June 28, 1938 Freeman Oct. 18, 1938 Millenaar Dec. 7, 1943 Keller Apr. 6, 1948 Armstrong Nov. 14, 1950

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