Document jgEqNpz7d3BM9VJem8rKaNM8O

FILE NAME Keene KNE DATE 1953 Mar 31 DOC KNE004 DOCUMENT DESCRIPTION US Patent - Insulating Material amee* ra , a ? os, phi 2,633,433 e tm i PE UNITED UNITED UNITED UNITED STATES PATENT OFFICE ote 2,633,433 INSULATING MATERIAL Frederic H. Hollenberg Jr. Wyndmoor Pa assignor to Exldwin Company Trenton N. J. a corporation of New Jersey . No Drawing Application May 2 1946 Serial No. 666,807 11 Claims CL 117 126 inorganic .2 I enter section and the resin may even be sub- The present invention relates to an insulating material of unusual and im- stantially confined to the outer sections be pretared by any process Abre proved properties and to a wet process of pro- The product may thermosetting resin and bentonite in ducing the same and more particularly it in which a medium is incor- relates to an insulating sheet material which is addition the presence of an aqueous porated in incrganic ficrous material the fibres characterized by its resistance In of which are interfelted in an aqueous suspension the invenison relates to an aquecus resinous com thereof and in which the resin after its associa- position which is available for use in the produc- tion in the interfelted web is converted by heat tion of inorganic fibrous insulating material pos- 10 the infusible insoluble stage Since the ben- sessing water and resistant properties to in the inorganic fibrous One object of this invention is to provide an which while tonite is incorporated material in the presence of an aqueous medium bentonite and the final inorganic fibre insulating materizi high flexural strength the water will swell the relatively light possesses electrical product will contain bentonite in its swollen is waterproof fireproof and has high state and thermal insulating values In the preferred embodiment of the invention Another object is to furnish an insulating ma- the sheet of insulating material which is sub- terial which possesses in addition to other desir- to heat to convert the resin is formed able properties resistance and which if the combustion tem- jected from an aqueous suspension of the fibrous mato remove water raised at one portion to 20 terial by the use of a screen perature of the resin will provide a barrier pre- therefrom Preferably the thermosetting resin venting propagation of thermal decomposition in and bentonite are mixed with the aqueous sus- adjacent portions of the product pension of the inorganic bres for example in A further object is to provide an insulating the beater or the mixing or agitating tank or the material comprising inorgarde fibrous material head box but if desired & soluble liquid resin bentonite the latter 25 be added to the inter- bentonite may e synthetic resin binder and and the ingredient imparting resistance and other feited web for example to the wet fibre on the destrable properties to the product and which screen or subsequently If de- product may be made by an economical and producing sired instead of forming the interfelted web from commercially practical process Still another object of the invention is to pro- se vide an insulating matenal in the production of which various types of thermosetting resins in- cluding a soluble resin even in a very dilute solution may be used and in which the white water may be utilized to make up new stock solutions 35 Still another coject is to provide & resinous composition comprising a soluble thermosetting resin in solution in an aqueous medium and a retardant in suspension therein which composition is available for use in the production of 40 insulating material of improved properties Other objects will be apparent from a con- sideration of this specification and the claims The insulating material of the present in- vention comprises an interfelted web of inor- 45 ganic fibrous material and a synthetic resin in its insoluble fusible stage and bentonite incorporated in said interfelted web the resin and bentonite providing resistance and fireresistance respectively to the product as will bereinafter be discussed In cue preferred em- bodiment the resin and bentonite are distributed substantially throughout the interfelted web mating uniformly product Mena but nacin nacin in in if desired the the contacmontam the mating mating mating mating mating may have them them for for th th the an aqueous suspension by use of a screen & smaller amount of water may he employed and the resulting suspension may then be deposited either continuously on a conveying system or batch into forms As will hereinafter ap- pear other additives such as a supplemental retardant a foaming agent a bentonite- viscosity reducing agent or both may advants- geously be added at a sultable point in the process By inorganic fibres is meant what is generally known in the industry as glass wool mineral rock or slag wool and asbestos fibres and all these will be referred to generally herein as fibres Any one of these fibrous materials may be used advantageously in the process the use of mineral wool being generally preferred and mixtures of any two or all of them in varying proportions may be utilized For example portions of long fibre asbestos such as amosite may be advantageo'isly mixed with glass wool or rock wool or both to provide additional strength to the Anished board In the case of the use of the glass or rock wool either fibre or loose wool or what is known in the trade as granulated or nodulized water ot ng orn ge te gold co a cart a a ... ets ee 2,633,433 a * a . ty One wool is prepared by nodulizing the wool on a bustion It can be seen therethf atoifrae ny rotary screen which also removes the major par- portion of the binder is raised to the combustion TD EN tion of the shot that is the glass granules of fiberized material When fibre wool temperature of the resin thermal decomposition will spread throughout the entire product unless is used a large percentage of the shot is ad- some is means provided to prevent such action vantageously removed in the process for ex- The presence of the bentonite in the finished a product serves as the means preventing the ete ample by a riffe box The removal of the major portion of the shot is important since obviously for propagation of thermal decomposition through substantial quantities of it will seriously alter the the product Bentonite acts as an excellent fire- fe weight of the finished board without changing 10 retardant for all the various types of thermo- the volume appreciably In the preferred embodiment of the invention setting resins that may be used in the production of the insulating material since the bentonite granulated or nodulized wool is employed since the finished product will have lower thermal ~ anductivity lower density greater strength and better handling properties as compared to a product made from fibered wool Mixtures provides a mechanical barrier between the portion of the product which has been bustion point of the resin and product tions In the event the raised to the comthe adjacent por is subjected to & temperature sufficiently high to cause fusion of of fibered and nodulized wool may be used the bentonite the fused bentonite then serves as if desired the barrier This condition occurs during the By thermosetting resin is meant any syn- 20 application of the insulating material to a metal thetic resin in an initial stage of polymerization starface by metal pins since in such a process the which is convertible by heat to the insolubline- fusible state Such resins may be used in any one of the three following forms 1 as an aque- pins are welded to the metal surface Thus if the material is ignited at one portion the combustion will not spread to other portions due ous solution of a soluble liquid thermo- 25 the barrier provided by the bentonite setting resin 2 as an aqueous emulsion of a The bentonite is used in any particular case insoluble thermosetting resin in liquid in an amount to provide the desired resist- form and 3 es an aqueous dispersion of a insoluble thermosetting resin in a dry 30 powdered Snely divided form Mixtures thereof ^nceto the product The amount employed wili be dependent on the quantity ofrest in the product When optimum resistance is de- may also be used if desired The first two forms contain liquid resins as distinguished from the sired the amount of bentonite will usually exceed the resin content for example with a product powdered resin of the third form While any of the thermosetting resins or mix- whereas containing % resin about % bentonite may be present whereas with a resin content of % the tures thereof may be employed for example bentonite content may only be about % formaldehyde formaldehyde formaldehyde and formaldehyde As previously stated if desired the fireretardant characteristics of the bentonite may the use of a formaldehyde resin that is be supplemented by the presence in the product & resin produced by reacting a phenol with a formaldehyde substance is preferred Examples of the phenc's are phenci cresol and xieuol and examples of formaldehyde substances are formaldehyd~ paraformaldehyde of another retardant While various cherai- fire cals having retardant properties may be used with the bentonite zinc ammonium phosphate has been found to be particularly effective The choice of the particular supplemental retard- and netetramive The usua extenders or mod^>lerssuch as Vin^olresin which Ent employed will depend upon its ability to be used in the process without undesirable reaction is a thermoplastic hydrocarbon resin derived from wood containing phenol alde with the reci anrd to be retaiinnethde fin- ished material Certain substances having fire- hyde and ether groups Iresinate which is merely an emulsion of the above described Vinsol resin in water and the like may be included in 50 the resinous composition Bentonite is a generic term covering colloidal retardant properties are notavailable for use due to their reactivity with the resin for example zinc borate may be used with a powdered resin but not with the liquid resin due to its reactivity with the latier clays that have an affinity for water and swell in the presence thereof and any of the various grades of bentonite such as sodium- potassium calcium- or magnesium bentonites may be used in the production of the product of the invention Advantageously a bentonite with & high absorptive capacity is employed and as stated the bentonite will be present in the product in a swollen state Regardless of the type of resin employed the presence of bentonite either alone or with other fire retardants in the the - finished insulating material serves to render product resistant The resins used in this process being af a coinbustible nature will undergo thengal decompusi- The proportions of inorganic fibre resin and bentonite in the finished product may vary widely but since these three ingredients are associated in the presence of water the relative amounts thersof will depend upon the particular type of process used in the preparation of the product Generally Generally the finished material will contain from about 55 to about 97 of incrganic fibre from about % to about 30 of the converted resta and from about % to about 25 of ben- tonite Insulating material baving particularly properties advantageous may contain from sbout 70 to about 97 of inorganic Ebre from about from about 25 of to % to about10% from the converted resin and about 18 of bentonite for in- tion when subjected to high temperatures even stance from 85 to 90 fibre % to % resin when the resin is incorporated with the inorganic and % to 35 bentonite In a typical example fibrous material the finished product The in- To the moulating material contains 87 rock rooi organic fibres fu the finished product form an insulating blanket over the resin particles preventing the heat of combustion from being dissi- pated and poh Pade due vine to the presence of 171966 12,8 metais van the Abres vastuu pari tig a aitr we fibre % of a formaldehyde resta converted to its infusible insoluble state and % of bentonite in another example the finished prodn^t entiained 02 of rock wool flore % of a ae Fe fbn SIVUAYTPat dehyda resto andand -2,63 ,48 5 -2,633,488 6 5 - 6 % of bentonite When a supplemental fire- tonite particles in suspensiaonnd % by weight ae - ats retardant is included in the product the amount of resin solids in solution after dilution with the thereof may vary from a very small amount for water employed in the process is desired it is not example a few tenths of a per cent up to 5 necessary to use an initial resin solution having & Ee or even more based on the weight of the resin 6 dilutability of at least 14 to 1 but a solution of a ere and the amount employed in any particular case dilutability ratio of less than 14 to 1 may be em- wili be determined by the degree of supplemental * ployed provided the dilutability ratio is greater retarding action desired than about L. Thus the bentonite wlli serve te 2 The insulating material of the present inven- to convert a precipitatable solution into s tion is characterized not only by resistance 10 Land proofness but also by high electrical and thermal insulation values It is further- - characterized by high flexural strength sound precipitatable solution It is to be understood that the resin content of the solution or suspension after the dilution by the water in the process may vary widely for absorbing properties and resistance to vibration example from about 1to about 20 by Referring to resistance a sample of the 16 weight of resin solids and that an initial resin insulating material of the invention was found to have absorbed less than % water in an atmos- solution to provide such resin content will be employed This is also the case when a resin phere of 95 relative humidity at a temperature emulsion or dispersion is used of 120 F. Even when the material was sub- Likewise the bentonite content of the resin- merged in cold hot or boiling water it did not 20 water medium after the dilution by the water in deteriorate and after the wet insulating material the process may vary widely for example from was dried the original strength was retained about % to 18 by weight of bentonite and an Tests of the product by the Columbin tem- initial amount of bentonite to provide such quan- perature method showed no evidence of burning tity will be employed The bentonite is prefer- Furthermore the product is characterized by its 25 ably moistened with sufficient water to swell it Alacr, ease of handling and may be utilized with a minimum of dusting and breakage and there- fore with practically no industrial health hazard before it is incorporated with the water medium When bentonite is employed in the upper portion of the range for example about ern The product may therefore be used in any application where such properties are desirable The weight per cubic foot of the product may % and above the viscosity of the medium is high 30 and with relatively thick products difficulty may he encountered in removing excess liquid from vary over a wide range depending upon the proc- the interfelted web when a screen is used in the ess steps employed in its production as will here-- formation thereof In order to decrease the vis- inafter be described and usually the weight per cosity of the medium particularly when more cubic foot will be between about 6 and 25 pounds 35 than about % bentonite is present it has been When the product is to be used as an insulating eave material for ships or in other applications where a light weight product is desired the weight per found that this may be accomplished by the indinsion in the water medium of a small amount of a soluble polyphosphate for example ELAR cabic foot is advantageously between about 6 and 10 pounds sodium or potassium hexametaphosphate tetra40 phosphate or pyrophosphate sodium tetraphos- As previously stated various processes may be phate being preferably employed When & used in the preparation of the product and the soluble polyphosphate is employed some of it at particular process depends on whether en aque- least will be present in the finished lest 043 solution an emulsion or a dispersion is verted product The amount employed may vary Initially employed Furthermore when an aque- 4545 from a few tenths of a per cent up to % or more ous salution is employed the process depends on based on the weight of the bentonite The pre- whether the resin will remain in solution when ferred range is from about 0.5 to about 15 the solution is brought into contact with the water employed in the process or whether the resin will precipitate under such conditions These two types of initial aqueous solutions are termed precipitatable and Tesin- precipitatable respectively When bentonite is included in the aqueous solution of the resin the dilutability of the solution without precipitation of the resin is markedly increased so that a solution which is normally precipitatable may become upon the inclusion of the bentonite the precipitatable type In a typical case where it is desired to employ a precipitatable solution and to pro- vice a solution after dilution with the water em- resin ployed in the process of % by weight of solids an itutial solution containing 70 resin solids and having a difutability of at least 14 water to 1 solution by weight is employed Ina typical case where it is desired to employ a provide precipitatable solution and to a suspension containing % by weight of precipi- tated resin solids after dilution with the water employed in the process an initial solution con- taining 70 resin solids and having a dilutability of less than 14 water to 1 solution by weight ts used Illustrative of the effect of bentonite if solution containing % to 10 by weight of ben- Thus in a typical case where an % suspension of bentonite after dilution by the water in the process was used and % of sodium tetraphos- phate was present the viscosity was reduced ap- proximately to that of 3,5 bentumite concentration In the case where the suspension of fibre bentonite and resin is sufficiently concen- trated so that it is not necessary to remove excess 65 water by a screen the use of a polyphosphate is usually not required since a high viscosity is an advantage by The process is preferably carried out by mix- ing the resin and the bentonite with the in- so organic fibrous raaterial before the interfelted web is formed and in this type of process the precipitating solution the resin emul- sion or resin dispersion may be added to the 65 beater mixing or agitating tank or bead or delivery box to the screen used to form the web If desired instead of using a screen to form the web a conveyor or stationary form may be emplayed In this case the use of granulated 73 mineral wool is advantageous In the case a precipitating solution a precipitating solution or a resin emulsion is used the interfelted web after its formation for instance on the forming screen or after y removal therefrom either before or after drying - . . , ee 2,538,433 ns 8 an aqueous may be treated with medium con- the wat interfelted web is placed upon pallets a -taining the resin and bentonite Since the web which support it in a flat form and are dengned Shea is formed from a suspension of the inor- to impart impart to the web a smooth flat surface The ganic fibrous material it is a water web pallets are placed on cars and the cars in turn me t and as is usual in water webs the major por- are dryini a dn ryig ng tunnel The drying tunnel NS tion of the fibers therein are oriented in a plane is usually kept at a temperature of between 250 substantially parallel to the plane of the web or F. and 550 F. preferred range being between sheet If the dried sheet is treated it may or 300 F. to 350 F. At this temperature the water wen may not be wet prior to the application of the is evaporated and the resin is converted to the carrying medium but of course if a pre- cipitated resin is desired the product must con- tain suficient water to cause a precipitation of the resin when a precipitatable solution is Infusible Insoluble state The length of time of treatment is a function of the temperature employed and usually requires three hours or mare slight increase in resin the employed Furthermore if desired instead of When the interfelted web contains a resin treating the interfelted web with an aqueous which is soluble in the residual water associated medium containing both the resin and the with the web there is a tendency during the dry- bentonite the bentonite may be incorporated ing cycle for such resin to migrate to the outer with the fibres prior to the interfelting step or surface This migration results in a product that subsequently thereto and after drying the prod- has a strong outer crust but a softer inner oct may be treated with an aqueous solution or core emulsion for example by spraying dipping or while such a product is at times desirable the passing the solution or emulsion through the use of bentonite has the further advantage when product a product having a substantially uniform distri- When a precipitatable solution is ap- bution of resin is desired since when using such plied to the interfelted web whether it be on soluble resin the bentonite reduces the amount of the forming device or subsequently the water 27 migration so that from a practical standpoint associated with the web and the displaced water very little occurs although there usually is a is drawn through the web as filtrate Since the concentration on presence of the water in the web raises the outer surface This slight increase is beneficial since it dies in the fibre very com- amount of water in the resin solution above the particles of critical dilution ratio the resin is precipitated 30 pletely and provides a finished product which is from the solution and is dispersed throughout easier to handle In fact in cases where the the wet web product has been cut to size before conversion of The interfelted web of organic fibrous materisk whether the resin be associated with the Abres prior to the formation of the web or thereafter is advantageously formed on the screen of an Oliver filter or other type of revolving screen squipped with vacuum compartmenbtust if de- sired the web may be formed on the usual the resin then the slight migration provides & product in which the surfaces thereof including the edges and ends are neatly sealed Regardless of the particular form of aqueous resin medium employed it will be desirable to recirculate the water removed through the screen This is particularly important when a cylinder type of paper machine or on the screen of a Fourdrinter machine Thereafter the web is subjected to the action of a pressure roll or rolls in order to compact it to some extent and to smooth the surface and after the treatment with the bentonite and resin as described the interfelled web is dried and heated to convert the resin to the insoluble infusible state In the preferred embodiment of the invention the inter- felted web is formed by the process described in Patent No. 1,865,069 except when granulated or ~ nodulized wool is employed the riffle box may be omitted As stated the use of pressure rolls is recommended since they serve to establish the thickness of the product at a predetermined point For example in the preparation of 55 a one inch board the suction may be applied so that the stock will build up an interfelted web of approximately one and eighth inches and by passing under the pressure rolls the thickness may be reduced to one inch When the stock solution delivered to the screen contains the resin and bentonite as well as the inorganic fibrous material the solution may foara and if this condition is encountered a suitable reducing agent may be added 65 The interfelt web is subsequently heated to dry the web and convert the resin to the infusible Insoluble state and the product may be cut to the desired size for example by means of circular 70 discs revolving at high speed either before or after the drying and heat treatment The in- terfelted material may be heated by any suitable means and the temperature of the treat- ment will depend upon the partialar resin preseut in the interfelted structure Advantageously 75 precipitating solution is employed since the resin and bentonite content of the white water remains substantially constant Such a solution is normally relatively unstable and there is a tendency for the resin upon standing to sepa- rate from the solution The use of beatonite in such a solution however makes it possible to obtain resin solutions stable over a period of months and in fact the stability of such a solntion increases toon aging The stability imparted to such a solution by the bentonite therefore makes + possible to recover and reuse the white water As stated previously one object of the invention is to provide a resinous composition comprising & soluble thermosetting resin in solution in an aqueous aqueous medium and bentonite suspended therein which composition is useable in the produc- tion of insulating material In making such a compositicomoposintion it is desirable to first suspend the bentonite in water to swell it and than to incor- porate it with the resin solution The concen- trations of bentonite and resin in the solution may correspond to those of the solution to be used in the production of the insulating material such for example as those given above but it is advan- tagies to make a core concentrated solution for example a solution containing from 20 to 50 of resin and from 10 to 40 of bentonite and then to dilute this solution at the time of its use The presence of the bentonite stabilizes the resin as hereinbefore described Considerable modification is possible in the proportions of the constituents of the insulating material of the invention as well as in steps whe ons anoe ne Bn, aes AF - TONS IT wool and asbestos fibres and mixtures thereof between about % and about 18 of bentonite ~. formaldehyde formalde- and electrical in- between about % and about 10 of synthetic ee high flexural strength heat thermosetting condensation product selected tn ting valves fireproofness and waterproofness from the group consisting of comprising in the form of an interfelted web an hyde formaldehyde formalde- ce of inorganic fibres selected from h^fide and formaldehyde condensation intimate mixture the group consisting of glass wool mineral wool 10 products in the infusible insoluble state and and asbestos fibres and mixtures thereof be- zinc ammonium phosphate said bentonite said tween about % and about 18 of bentoni aend synthetic thermosetting condensation product between about % and about 10 of a synthetic and said zinc ammonium phosphate being molec- thermosetting condensation product selected ularly interspersed with each other at least the from the group consisting of formulde- 15 major portion of said inorganic fibres being ori- hyde formaide- ented in a plane substantially parallel to the hyde and formaldehyde formaldehyde condensation plane of the interfelted web and said bentonite " products in the infusible insoluble state said being present in an amount in excess of said syn- bentonite and sald synthetic thermosetting con- thetic thermosetting condensation product densation product being molecularly interspa 20 8. The product of claim 7 wherein the syn- with each other at least a maior portion of said thetic thermosetting condensation product is a inorganic fibres being oriented in a plane substan- formaldehyde resin and wherein the in- tially parallel to the plane of the interfelted web organic fibres are granulated mineral wool fibres and said bentonite being present in an amount in 9. The product of claim 1 wherein the inor- excess of said synthetic thermosetting conden- zanic fibres are a mixture of asbestos fibres and sation product 2. The product of claim 1 wherein the syn- thetic thermosetting condensation product is a mineral wool fibres 10. The product of claim 1 wherein the inorganic fibres are a mixture of asbestos fibres and phenol formaldehyde resin wherein the mor- 3. The product of claim 1 glass wool fibres 11. The product of claim 1 wherein the inor- ganic fibres are mixture glass wool fibres ganic fibres are mineral wool fibres 4. The product of claim 1 wherein the syn- thetic thermosetting condensation product is a . resin and wherein the in- a of and mineral wool fibres FREDERICK E HOLLENBERG JL formaflodremhyadledehyde eee organic fibres are granulated mineral wool fibres 5. An insulating material characterized by REFERENCES CITED high Bexural strength heat and electrical in- The following references are of record in the sulating values freproofonfesasnainndtewrafteeltrepdrowoefbneasn s file of this patent ~ comprising in the form of inorganic fibres selected UNITED STATES PATENTS intimate mixture 40 from the group consisting of glass wool mineral Number Name Date wool and asbestos abres and mixtures thereof 300.946 Carey -..-- - 1884 June 24 _~~-- between about % and about 18 of bentonite 1,160,362 Baekeland .._.-.-- Nov. 16 1915 between about % and about 10 of a synthetic 1,887,726 Weber --- Nov. 15 1932 thermosetting condensation product selected 1,949,087 Squiers Feb. .--__--~ 27 1934 1934 from the group consisting of formalde- 1,969,156 Schuttler ..--.--- Aug. 7 - formalde- 2,011,915 Seigle . Aug. 20 1935 hyde and formaldehyde condensation 2,040,348 Victor et al .----. May 12 1936 hyde in the infusible insoluble state and a - 2,101,449 Party - Dec. 7 1937 psorloudbulcetsalkali metal polyphosphate said benton- 2,122,514 Crocker s---... July 5 1928 -- and said synthetic thermosetting condensa- 2,164,316 Plummer .---.-..- Dec. 26 1939 ite tion product being molecularly interspersed with 2,105,272 2,105,272 Ehlers -- Mar. 26 1940 each other at least a major portion of said in- 2,221,420 Clarvos et al Nov. 12 1940 --. organic Abres being oriented in a plane substan- 2.251.236 Shipp -.- _.. Aug. 5 1941 tially parallel to the plane of the interfelted weh 2,266.638 Hauser Dec. -----.--_~ 16 1941 and said bentonite being present in an amount 2,298,295 Hyatt ---..___----- Oct. 13 1942 in excess of said synthetic thermosetting con- 2,319,033 Bernstein et al . M. ay 11 1943 densation product 2,330106 Bernstein et al Sept. 21 1943 6. The product of claim 5 wherein the syn- 2,335,103 . Borgin -- _ Nov. 23 1943 Cassel thetic thermosetting condensation product is a 2.543.541 wee Feb. 29 1944 resin wherein the inor- 2,345,965 Fiedler _ -a. Apr. 4 --. 1944 formaldehyde ganic fibres are mineral wool fibres and wherein 2,367,181 Bernstein et al - Jan. 16 1945 the soluble polyphosphate is sodium tetraphos- 2,376,595 Hood .. . May 22 1945 phate 2,376,687 Goldstein et al May ... 22 1945 7. An insulating material characterized by 2,316,588 Goldstein et al -- M.ay 22 1945 high flerunni strength heat and electrical in- 2,385,384 Schroy aoe Sept. 25 1945 ulating values Areproofness and waterproofness 2,500,635 Courtright -- Mar. 14 1950 comprising in the form of an interfelted web ~ me es Me te Ul ene ee -- + IS oor: . Patent No, 2,633,433 Certificate of Correction | Certificate 4 Patent Patent No. 2,633,433 2,633,433 H. 1953 1953 1953 HOLLENBERG 2,633,433 FREDERICK FREDERICK H. HOLLENBERG HOLLENBERG HOLLENBERG hereby above hereby certified certified FREDERICK that appears printed JR printed specification of the numbered numbered correction correction above Column Column 7 core read 66 interfelt more , read be follows line 67 for 67, that Letters said Letters Patent should be above Tead corrected corrected Patent Patent of the read case as corrected corrected that that the the Office D. Patent Patent [sraL} a a a hres MURPHY THOMAS F. Assistant Commissioner Ys Commissioner of Patents. - Patenteg March March 31 Certificate Certificate Correction ; oe pee a ee TO wee ee wo It is It i FREDERICK FREDERICK HOLLENBERG Jr. No, the above HOLLENBERG It has appears numbered above above numbered numbered patent and showing has showing fault been made that occurred occurred correction faith and was not the of Patent Office said mistake mistake read | requiring follows fault the said mistake ; Patent Column Column line line No. 1,865,049 for The The said Patent though o^' Signed Signed patent should 7th and sealed this 7th dadyayoJfulAy.D1.953 . i 865, ate 7 . ead 7 ai , : . Ce oe _ ; . | Commissioner Patents, Commissioner Assistant Assistant . ; Assistang a = aaas . ae aa a of ; coat ; 5 _ i i