US2133183A - Electrical insulation - Google Patents

Description

0d. 11, 1938. A RD ET AL 2,133,183

ELECTRICAL INSULATION- Original Filed Aug. 22, 1933 2 Sheets-Sheet l Oct. 11, 1938. F. J. BAIRD ET AL 2,133,183

ELECTRICAL INSULATION Original Ei led Aug. 22, 1933 2 Sheets-Sheet 2 Iii-7- Patented Oct. 11, 1938 ELECTRICAL INSULATION Fred J. Baird, Toledo, and Allen L. Simison,

Newark, Ohio,

assignors to Owens-Illinois Glass Company, a corporation of Ohio Application August 22, 1933, Serial No. 686,270 Renewed August 13, 1936 ZZ CIaimS.

Our invention relates to electrical insulating material adapted for a wide variety of uses in the field of electrical insulation. In its preferred form, the insulating material comprises fine glass wool which may be molded into various forms,

and which may also be felted or matted and compresed. rolled or woven into sheets and impregnated with a suitable binding material or materials. The sheets of glass wool fabric or felt in. may also, for some p p ses and uses, have applied thereto a thin surface layer of insulating material oi! the character and for purposes hereinafter, set forth.-

Among the objects of our invention are the 5 following: To provide an electrical insulating material which may be either molded or made in the form of sheets of varying thickness and which is inexpensive to manufacture, which possesses high insulating qualities, which has no high dielectric resistance and Strength so that it is not easily broken down by disruptive electrical charges, which will withstand comparatively high temperatures without destruction or deterioration, which has elasticity and compressibility g adapting it for various uses for which a comparatively incompressible material is unsatisfactory. The invention in one of its forms provides an insulating material made in sheet formation from raw materials which lend themselves to wide variations in the thickness, compressibility, elasticity, fineness and other desired properties of the finished product, and which adapt it to a wide variety of uses.

A further and specific object of the invention is to provide an insulating material of the character indicated which is particularly adapted for in armatures, commutators and other parts of electric generators and motors. At the present time mica is extensively used as an insulating material in such equipment. The insulating segments used in the commutators and which are interposed between the copper bars or segments of such commutators are usually made of mica. This applies to most, if not all, of the higher grade commutators. Mica is a mineral which always contains invisible metallic impurities and microscopic clefts that weaken its insulatin properties and render it comparatively unreliable. The methods of treating the raw material to prepare it for use as an insulator are costly and the resultant product expensive. The mica has certain physical properties which are detrimental to its use as insulating segments for commutators or in similar situations. The thin laminae or layers of mica which comprise the insulating segments tend to slip when subjected to the high pressure applied to them in assembling the commutator bars, making the assembling operations difficult and also making it difficult to reliably hold the parts in assembled 5 position. when these mica segments are placed between the commutator bars they must be undercut, or in other words, the mica at the surface of the commutator must be cut down below the adjoining copper bars in order to prevent 10 excessive arcing. When thecommutator bars during use wear down to the level of the mica, further undercutting of the latter becomes necessary.

An object of our invention is to overcome the 16 above noted difiiculties and objections to the use of mica by providing an insulating material which is inexpensive to manufacture, which when assembled with the commutator bars will retain its position without liability of slipping, and 20 which in use will wear down as rapidly as the adjoining copper bars and thereby eliminate the necessity of undercutting or other special treatment to avoid excessive arcing.

An aim of the present invention is to provide 5 an insulating material which when used with commutator segments as a substitute for mica, practically eliminates the usual shorts between adjoining commutator bars and also minimizes the time and labor involved in testing the com- 30 mutators for such shorts. It is customary to test each two adjoining commutator bars at comparatively high voltages which may range from volts to 440 volts, or considerably higher. When any short occurs during this test, scraping 35 of the mica segment, or other manipulation, is necessary. This involves much time and labor and whenit has to be frequently repeated in testing a single commutator. Such shorts are due in part of the surface conductivity of the mica, 40 and to various other factors. The present invention provides an insulating material which is substantially free from these objections, and which in use has been found to practically eliminate shorts and thus greatly reduce the 4.5 labor involved in testing the commutator.

A further difficulty encountered with the use of mica for commutator segments is due to the fact that in finishing the commutator with a cutting tool there is a. tendency for the edges of the mica do to project above the commutator bars. This necessitates a sanding or other operation. An object of our invention is to overcome this dimculty by the provision of a material which turns even with or below the copper. is

A further feature of the insulating material forming the subject-matter of our invention, which renders it superior to mica for use in electricmotors and generators and in various other situations, relates to its flexibility and compressibility. Thus, for example, in building commutators, thisproperty permits a wide tolerance in the thickness both of the insulating material and the commutator bars. Mica has very little compressibility so that when the commutator is assembled difliculty is often experienced in compressing or drawing it down to specified dimensions. This difliculty is overcome by the present invention.

A further object of the invention is to provide an insulating material which when used for insulating the various parts of electric motors and generators will successfully and permanently withstand the combined eifects of temperature changes and continuous vibration to which it is subjected in use. With the materials which at present are generally used as insulating materials it appears to be impossible to build a motor with the parts held together so securely that looseness of parts will not develop in time. The heat and continuous vibration gradually misplaces and destroys the insulation, causing weakness and a final break down. This trouble is aggravated by the wid temperature variations and sometimes high temperatures to which the motor is subjected. An aim of our invention is to overcome these objections and provide an insulating material which, owing to its elasticity, flexibility,

heat resisting qualities and high insulating values, permits the motor to be compactly built in a manner to withstand vibration, high temperatures and temperature variations without deterioration, thereby greatly prolonging the life and eiiiciency of the motor and adapting it for use in situations and under conditions where it would be impractical or impossible to use motors in which other materials are employed and relied on as the insulating material.

Cheap substitutes for mica, such as cotton cloth, paper and other organic materials impregnated with a binder, are extensively used in the manufacture of armatures and other electrical equipment. Such materials are inferior and unsatisfactory.. Paper and cotton cloth carbonize at high temperatures so that their insulating value is destroyed as well as their physical properties. The present invention provides an inexpensive insulating material which is not destroyed and does not deteriorate at high temperatures and which meets the requirements of a high grade insulating material.

Other objects of the invention will appear hereinafter.

In the accompanying drawings:

Fig. 1 is a perspective view of a sheet of insulating'me erial made in accordance with our invention.

Fig. 2 is a fragmentary sectional view of the sheet on an enlarged scale.

Fig. 3 a fragmentary view of an electric armature showing particularly the commutator.

Fig. 4 is a perspective view of an insulating segment of the commutator.

Fig. 5 is a part sectional perspective view of the commutator.

Fig. 6 is a sectional view of an insulatingring or collar.

Fig. 7 is a face view of the same. r

Fig. 8 is a perspective view of an insulating tube.

Fig. 9 is a sectional perspective viewshowing a stator,

Fig. 10 is a perspective viewshowing slot cell insulation. 7

Fig. 11 is a perspective view of an armature coil and shows a method of applying insulating material thereto.

Fig. 12 is a view of a cord made of our insulating material.

Fig. 13 is a. perspective view of a piece of cloth or fabric made of the insulating material.

Fig. 14 is a perspective view of a woven insulating tube.

Fig. 15 is a sectional view of a condenser.

- Fig. 16 is a view of an electric cable wrapped with insulating material made in accordance with our invention. I

The insulating material may be made in the form of sheets in of varying sizes, shapes and thickness, which sheets may be stamped or cut to provide pieces of insulating material of various sizes and shapes, depending upon the particular uses to which the invention is tobe put. In general terms, the sheet of insulating material comprises a body of glass wool l I which is matted or felted and compressed to provide a sheet of desired thickness, a binder of insulating material with which the woolis impregnated and, if desired, an outer layer 12 of thin sheet material covering both surfaces of the sheet Ill.

The glass wool II which forms the body of the insulating material consists of individual flbers or strands of glass, the fineness of which may vary as hereinafter pointed out. These fibers are woven, matted, felted, or otherwise manipulated to form an elastic compressible body or mass of wool. The particular methods of making such material are not a part of the present invention, but one such method may be briefly stated as follows: Small streams of molten glass are blown by air or steam which is applied at a high pressure and draws the glass out into fine threads or filaments which are instantaneously solidified while suspended in the air and accumulate to form a mass known as glass wool. The wool is spread uniformly on a conveyor or the like and transferred thereby to rolling equipment by which it is rolled and compressed to the desired thickness and density. For many uses to which the insulation is put, it is desirable to apply a suitable binding material, either before or after the rolling or compressing operation.

The insulating material which is used as a binding medium for the wool may consist of shellac, phenolic condensation product (commonly known under the trade name Bakelite) latex, rubber, rosin, silicate of soda, varnish, either bake drying or air drying varnish, or some other material, or a combination of such materials, depending on the specific properties and results desired, which evidently will vary to a considerable extent with the particular use to which the insulation is to be put. We have found that very satisfactory results are obtained with the use of either shellac or a phenolic condensation product, as a binding medium alone or in combination with other materials, throughout a wide range of uses for which the insulating material is adapted. The binding material may be used in suflicient quantity and have sufficient body to fill or substantially fill the interstices of the wool base and thereby provide a dense, compact, impervious sheet having high tensile strength and permanency of shape, and which at the same time is elastic and compressible.

A small amount of latex may be used as a binding material in combination with either shellac or a phenolic condensation product, as it is found that the latex materially improves the product. Particularly, it greatly increases its flexibility without detrimentally affecting the dielectric properties and electrical resistance of the product. The latex also renders the material easier to cut or work with tools, admitting of smooth clean cut edges, free from chipping and breaking.

The fineness of the glass wool may be varied through rather a wide range, depending upon the particular uses to which the material is to be put and the specific results desired. Generally speaking, superior results are obtained with wool, the fineness of which comes within the range of .0001 to .002 of an inch in diameter of the individual filaments. Wool of this fineness can be more readily compressed than a coarser wool and results in a superior product. If a coarse wool is used, compression tends to crush the glass, particularly where the fibers cross each other. For certain uses, however, the wool may be somewhat coarser than that above indicated,

the diameter of the filaments ranging, for example, up to several hundredths of an inch in diameter.

The sheet ill of insulating material may be provided on both its upper and lower surfaces with a thin layer or sheet of insulating material I2 such as tissue paper, regenerated cellulose (known in the trade as Cellophane"), or other material. This surface layer serves to, materially stiffen the sheet and also protects the body of the insulating material. Further, it facilitates the stamping or cutting of the sheet into smaller pieces, permitting such pieces to be cut or stamped with a sharp clean edge. The surface layer i2 is of particular value when handling the pieces of material in large numbers, as, for example, insulating segments for commutators, as it materially facilitates the ease with which the insulating segments are assembled. It provides a smooth surface which facilitates the assembly of the insulation with the commutator bars. We have found that regenerated cellulose is a superior material for the above purposes. It is to be understood, however,

that the sheet material ll may be used without the surfacing material, and this is sometimes preferable, particularly where it is desirable to cause the insulation to firmly adhere to the commutator bars or other surfaces to which it is applied.

The binding material with which the wool is impregnated, as, for example, shellac or phenolic condensation product, may be so applied as to impregnate the entire mass, or it may be applied in a manner to penetrate only part way through the mass. When the binder is applied only to the surf ce portions of the sheet it may serve simply s a binder to retain the size and shape of the material, the interior layer or portion of glass wool which is not impregnated with the binder serving to produce the necessary resistance to the passage of electric current.

' Although the glass wool for general purposes may be matted or felted as above described, other arrangements 'of the glass may be employed. Thus, the individual strands may be laid in parallel-or/and jackstraw arrangement or pattern. The parallel strands of glass may be laid or built up in layers with the strands in the several layers parallel with one another, or with the strands in the layers at constantly varying angles one to another. Spun glass may also be used. The glass wool in whatever form used should be free from iron, moisture or other impurities or materials which would interfere with its efficiency as an electrical insulator.

In Figs. 3 to 11, we have shown adaptations of our invention for use in electric motors and generators. The machine comprises an armature l and a commutator I], mounted on a rotating shaft. The commutator may be of conventional form and construction, except as regards the particular insulating material used. It comprises an annular series of copper bars or segments it with interposed segments or layers IQ of insulating material. The individual segments I! (Fig. 4) may be stamped from a sheet Ill. The parts of the commutator may be assembled in the usual manner. The properties of the insulating material as heretofore pointed out especially adapt it for this use.

As shown on Fig. 5, the commutator comprises a central metal sleeve or spool surrounded by the copper bars l8 and insulating segments IS. The metal sleeve 30 is surrounded by a tube ll (Figs. 5 and 8) which may comprise a strip of the sheet material Ill, or may be molded or formed to size. The bars l8 and segments iii are clamped in position by a V-shaped metal ring 32 and the metal sleeve 30. V-shaped collars or rings 33 and 33 of insulating material are interposed between the copper segments l8 and the parts 30 and 32. The rings 33 and 33' may be molded or otherwise formed of glass wool impregnated with a binding material, as herein described.

The flexibility and compressibility of the insulating segments permit a comparatively wide tolerance in the thickness of the parts and at the same time permit them to be compactly assembled. The flexibility and compressibility of the -material permits it to readily conform to any irregularities in the surfaces with which it contacts. This feature is of value not only in connection with commutators and other parts of dynamo-electric machines but in various other situations, as it enables the insulating material when compressed to conform to surfaces of an irregular nature, such as rough cast surfaces, rough machined surfaces, semi-machined surfaces, warped surfaces, etc., and maintains a practically complete contact with its mating surfaces.

The flexibility and compressibility of the insulating sheet also builds up a frictional resistance, due to its compression against mating members when assembled, which resistance opposes any tendency for the material to be thrown or moved out of position, as, for example, by centrifugal force when used with a commutator rotating at a high speed. The frictional resistance when the material is assembled under compression, results in stability or absence of movement of the insulation relative to the part to which it is applied, prevents slipping, creeping or crawling of the insulation whether used with rotating or nonrotatlng parts, and also when subjected to vibration or heat. By omitting the smooth surface layers i2 from the insulating material, the frictional resistance is increased and may be further augmented by the use of an adhesive material or binder, so that the insulation will adhere with tenacity to the surfaces to which it is applied.

The insulating material composed of glass wool or glass wool felt with a binder such as above described has been found to be heat resistant -to an extent which renders it satisfactory for use in commutators and in other situations where it =may be subjected to temperatures which may range as high as 750 to 1000 F.

It is important that the commutator when completed shall have the parts firmly and securely united to form a rigid structure in which there can be no movement of one part relative to another. If, for example, any movement of an insulating segment takes place so as to project even slightly beyond the adjoining bars, it results in arcing and a destructive action which soon ruins the commutator. In accordance with our invention, the glass wool is impregnated with a binder, as, for example, shellac or phenolic condensation product, which when cold results in a comparatively stifl' sheet. When the commutator is assembled, heat is applied which softens the material to a certain extent, sufficient to permit compression in the manner above described, the material, however, retaining sufficient stiffness and resistance to compression to permit the assembled commutator parts to be subjected to the high pressure which is applied for firmly uniting and compacting the parts. While under this pressure, the commutator is subjected-to a heating or baking process by which the more volatile parts of the binding material are driven off and such material hardened. The result of this method of treatment is a commutator in which the copper bars and insulating segments are firmly united in substantially an integral piece or unit so that it is practically impossible for relative movement or displacement of the parts when the commutator is in use.

Analternative method of applying the insulating binder to the glass wool as used, for example, in commutators, consists in dipping or spraying the wool with the insulating varnish or binder at the time the material is installed or assembled in the commutators.

Fig. 11 shows an armature coil 35 and a me'hod of winding the coil with strips 36 of glass wool insulating material. These strips may be cut from sheets of insulation II] or may consist of strips of tape cut from a woven fabric such as shown in Fig. 13, or made of strands of spun glass wool woven into tape. V

Fig. 9 illustrates a stator made up in the usual manner of iron sheets or laminations 31, provided with slotted cells 38 for receiving the coils. Insulating pieces 39 shaped to fit the cells 38 provide insulation for the coils within said cells.

Fig. 12 illustrates a cord made of glass wool. The fine individual fibers of glass wool are spun into strands H. A plurali'y of these strands are wrapped to form a strand or cord 42. These cords in turn may be combined to form a rope or cord- 43. The spun strands or cords may be woven or fabricated into the form of a sheet 44 (Fig. 13). The methods of making the fabric 44 from glass wool may be substantially the same as used in the mapufac'ure of cotton or woolen fabrics and need not be herein described in detail. The fabrics thus made from glass wool may be used as an insulation for the various specific purposes to which our insulation is applied, as hereinbefore described, and for many other purposes. The

glass wool fabrics can be made and are adapted for use without a binding material or othermaterials combined therewith. For insance, such glass wool fabric without other ingredients may be used as the sole insulating material in an electric motor such as above described, with the result that the motor can withstand extremely high temperatures indefinitely without injury and is practically fireproof. For certain uses, however, it is preferable to impregnate or treat the fabric with latex, shellac, phenolic condensation product or other materials, ora combination of such materials.

Fig. 14 shows a tube made of woven or braided glass wool. The tube may, if desired, be impregnated with a binding or stiifening material so that it will retain its shape independently of the article to which it is applied. It may also have a coating either internally or externally, or both, of any suitable surfacing material as varnish, shellac, regenerated cellulose, woven cotton or silk or the like. Such tubes are adapted for use in various situations. For example, they may be used as indicated in Fig. 3 for insulating the leads or terminal wires of the armature coils between the armature and commutator.

Fig. 15- illustrates the use of our insulating material in a condenser comprising metal plates 2| and 22 with interposed sheets 23 of the insulating material.

Fig. 16 shows an electric cable 25 and an outer coat or wrapping 26 of insulating material. As shown, the insulation consists of a strip of glass wool woven tape or strips cut from sheet ID of suitable width wound spirally on the cable. Other methods of applying the material may be employed, such as a plastic material composed of glass wool and a binder applied and baked to form under heat or pure glass wool retained by a binding tape. A cord made of glass wool (Fig. 12) may be wound as in Fig. 16 and reiained with a coating of varnish or other covering such as lead, cotton or silk, or a combination of these materials. Such material can be applied as a covering to the cables when the latter are manufactured, or may be used for splicing joints in the field, with either underground or overhead construciion. The flexibility and compressibility of the insulation together with its permanency or freedom from deterioration, and other characteristic properties, make it a satisfactory insulating maerial for covering cables or other electrical conductors.

The insulating materials herein set forth are suitable for use in the insulating field generally, including numerous other situations than those herein specifically mentioned. For example, glass wool may be used as an insulator between the copper windings of a pancake coil in an electrical welding machine, to be installed either before or after dipping or to besprayed with an insulating varnish at the time of its installation between the coils. In general, the insulating materials herein set forth may be used in the electrical insulation field wherever mica or similar products are used, such as paper, glass, rubber, shellac treated fiber board, phenolic condensation product, cotton cloth and producs of a similar nature. Glass wool or wool impregnated with an insulating binder may be drawn, molded or otherwise formed into many shapes and sizes coming within its physical application as an insulator in electrical work.

Modifications may be resorted to within the spirit and scope of our invention.

What we claim is:

1. An insulating material in sheet form comprising a body of matted glass wool, a binder of electrically non-conducting material impregnating said body, and a thin sheet layer of impervious insulating material covering said body.

2. An insulating material in sheet form comprising a body of flexible, compressible, matted glass wool, an insulating material impregnating and filling the interstices of said wool and forming a binder therefor, said binder and the body of wool impregnated therewith being flexible and compressible, and a thin surface coating of flexible material overlying and secured to said body.

3. A flexible, compressible sheet of insulating material comprising a matted body of flexible, compressible glass wool and a binder consisting of shellac with which said wool is impregnated.

4. A flexible, compressible sheet of insulating material comprising a body of flexible, compressible, matted glass wool and a binder consisting of shellac with which said wool is impregnated, said sheet having a surface layer of regenerated cellulose.

5. A sheet of insulating material comprising a body of matted glass wool and a binder of insulating material impregnating the surface portions of the wool and penetrating only part way through the sheet, leaving an interior layer of the wool free from said binder.

6. An electrical insulating material comprising a body of matted glass wool, latex forming a coating for the individual fibers of the wool, and an insulating binder with which said body of material is impregnated.

7. An electrical insulating material comprising a body of matted glass wool, latex forming a coating for the wool fibers, and an insulating binder comprising phenolic condensation prodnot with which said body is impregnated.

8. An electrical insulating material comprising a body of matted glass wool, latex forming a coating for the wool fibers, and an insulating binder comprising shellac with which said body s regnated.

9. An electrical insulating material comprising a body consisting of a mat of highly compressible, elastic glass wool, latex forming a coating for the wool fibers, and an insulating binder comprising phenolic condensation product and shellac with which said body is impregnated.

10. An insulating material in sheet form comprising a body of matted glass wool, a flexible material forming a coating for the individual fibers of the wool, and a binder of electrically nonconducting material impregnating said body.

11. An insulating material in sheet form comprising a body of matted glass wool, a flexible material forming a coating for the individual fibers of the wool, and a binder of electrically non-conducting material impregnating and filling the interstices oi said body.

12. An insulating material in sheet form'comprising a body of matted glass wool, latex form- 8 a coating for the individual fibers of the wool, and a binder of electrically non-conducting material impregnating said body.

13. An insulating material in sheet form comprising a body of matted glass fibers of microscopic fineness, a binder of electrically non-conducting material impregnating said body, and a thin sheet layer of impervious insulating material covering said body.

14. An insulating material in sheet form comprising glass fibers of great fineness not more than .0001 to .002 inch in diameter and of great length to provide flexibility, compressibility and mass integrity to the body. said fibers being matted together to form a compressible and flexible integral body, and a binder of electrically non-conducting material impregnating said body.

15. A flexible, compressible sheet of insulating material comprising a matted body consisting of glass fibers of not more than about .0001 to .002 inch in diameter and of a length, flexibility and resiliency to provide a flexible, compressible, integral body, and a binder consisting of shellac with which said body is impregnated.

16. A sheet of insulating material comprising a body of glass fibers of great fineness not more than .0001 to .002 inch in diameter and of great length to permit said fibers to mutually interlace with one another and provide flexibility, compressibility and mass integrity to the body, said fibers being intermatted to form an integral body, and a binder of insulating material impregnating the surface portions of said sheet and penetrating only part way through the sheet. leaving an interior layer of said fibers free from said binder.

17. An insulating material comprising long, flne glass fibers intertwisted into threads, and said threads woven into a fabric having strength, flexibility and pliability, and a surfacing material of electrically nonconducting substance at least partially impregnating said insulating material.

18. As an insulating material comprising threads of intermatted glass filaments having a. fiber diameter of great fineness, not more than about .0001 to .0004 inch in diameter, and of great length to provide flexibility and strength to the threads, said threads being interwoven to form a fabricated article having great: flexibility and strength and being capable of being wound around a fine wire.

19. As an insulating material comprising threads of intertwisted glass filaments having a fiber diameter of great fineness, not more than about .0001 to .0004 inch in diameter, and of great length to provide a flexibility and strength to the threads, said threads being interwoven to form a fabricated article having great flexibility and strength and being capable of being wound around a fine wire.

20. Ar: insulating material in sheet form comprising a resilient, flexible, fabricated body of glass fibers of microscopic fineness, a binder of electrically nonconducting material impregnating said body, and a thin sheet layer of impervious insulating material bonded to and covering said body.

21. An insulating material in sheet form comprising glass fibers of great fineness not more than .0001 to .001 inch in diameter and of great length, giving flexibility and compressibility to the body, said fibers being fabricated to give mass integrity and strength to said body as a whole, and a thin sheet layer of impervious insulating material covering said body and bonded thereto.

22. A soft, resilient and flexible electrical insulating material in sheet form, comprising glass fibers of miscroscopic fineness intertwisted to form threads, said fibers being of sumcient length to permit said intertwisting and to give great strength to the threads, said threads being woven into the form of a tape, and a thin sheet of cellulose base material overlying said tape and 7 bonded thereto.

' FRED J. BAIRD.

ALLEN L. SIMIBON.

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