US3492232A

US3492232A - Aqueous lubricants for metal working

Info

Publication number: US3492232A
Application number: US600384A
Authority: US
Inventors: Milton Rosenberg
Original assignee: Cincinnati Milling Machine Co
Current assignee: Milacron Inc
Priority date: 1966-12-09
Filing date: 1966-12-09
Publication date: 1970-01-27
Anticipated expiration: 1987-01-27
Also published as: DE1644875C3; CH496081A; DE1644875B2; SE342831B; ES348079A1; GB1216988A; DE1644875A1

Description

United States Patent US. Cl. 25249.3 19 Claims ABSTRACT OF THE DESCLOSURE Aqueous compositions containing 0.1 to by weight of an aqueous phase of a polyester of a polyoxyalkylene glycol having a degree of polymerization of 4 to 200, said alkylene groups having from 2 to 4 carbon atoms, and the dimer of a fatty acid having from 16 to 26 carbon atoms, and the process of their use in the rolling and machining of metals.

This invention relates to lubricating compositions useful in the working of metals, both ferrous and non-ferrous, by such methods as rolling, forging, and drawing. In another aspect, the present invention relates to cooling fluids useful in the machining of ferrous stock. More particularly, the present invention relates to aqueous lubricating compositions of particular value in the rolling of non-ferrous metals.

It is well-known from the prior art that non-soluble oils such as straight mineral oils or their emulsions are not completely satisfactory for the rolling of non-ferrous metals such as, in particular, aluminum and aluminum alloys, although for lack of any better composition they are widely employed for such purpose. Straight mineral, vegetable, or animal oils lack the required cooling properties necessary in, of example, the hot rolling of aluminum, and leave undesirable residues on the rolled plate Or sheet. Rolling fluids based on light petroleum fractions tend to ignite when used at desirable high speeds in the cold rolling of aluminum. Oil emulsions, frequently also referred to as soluble oils, although providing cooling capacity, have the undesirable property of allowing aluminum oxide to be transferred from the aluminum sheets to the rolls and then back to the sheets. This causes the aluminum sheets being rolled to be marked and to have a duller finish, frequently referred to as stain. Additionally, metal can stick to the rolls, aggregate, and cause deformati n which can become serious enough to require regrinding of the rolls. This phenomenon is generally referred to as pick-up. In the cold rolling of nonferrous metals, such emulsions frequently have insuflicient lubricity to permit rolling at high speeds or with high reductions. Other allied problems occur in the cold working of ferrous metals such as steel and the like.

It is, therefore, an object of the present invention to provide improved aqueous lubricants for the working of metals.

It is another object of the present invention to provide rolling fluids for non-ferrous metals.

It is a further object to provide cutting fluids.

Yet another object of the present invention is to provide aqueous lubricants of improved lubricity, reduced staining, reduced pick-up, and improved stability at elevated temperatures.

Still another object is to provide rolling fluids which can be employed at high speeds.

Other objects will become apparent from the following disclosure and claims.

The aqueous lubricants of the present invention basically comprise aqueous solutions of 0.1 to 20% by Weight of the aqueous phase of a polyoxyalkylene glycol polyester of a dimer fatty acid, wherein the polyoxyalkylene glycol has an average degree of polymerization of a least 4 and preferably from 4 to about 200 and the alkylene group contains from 2 to 4 carbon atoms. The term solution as employed herein is meant to include not only true solutions but also the type of macromolecular dispersions obtained with hydrophilic materials. The term polyester is meant to define compounds which, on the average, contain more than one ester group per molecule.

Since both the dimer acid and the polyoxyalkylene glycol are difunctional, the esterification of the acid with the polymeric glycol results, generally, in a complex mixture of compounds including the partial ester of the glycol and the acid, the cyclic diester and the linear polyester, which in turn can vary widely in the degree of polymerization. The polyesters which can be employed in the present aqueous lubricating compositions are all liquid esters of polyoxyalkylene glycols and preferably polyethylene glycols and dimer fatty acids which dissolve in water to form stable solutions. Extremely high molecular weight polyesters of the fatty dimer acid and the polyoxyalkylene glycol, often referred to as superpolyesters, are solids and do not readily dissolve in water and hence are not preferred. The solubility of the polyester to form a stable solution at room temperature, when employed in the concentrations indicated above as being useful in forming the aqueous lubricants of the present invention, is readily established experimentally. The useful polyesters employed in the aqueous lubricants of the present invention can further be defined in terms of the process by which they are prepared. Thus, suitable polyesters of dimer fatty acids and polyoxyalkylene glycol are prepared by a condensation reaction at elevated temperatures at molar ratios of glyc0l-toacid varying from 0:8 to 2.0 and preferably from 1.0 to 1.5. The esteriflcation is continued until from 50 to 90% of the theoretical water, formable as a result of the complete reaction of all available hydroxyl groups with all available acid groups, and preferably from to of the theoretical water, has been distilled out of the reaction mixture.

Although the polyesters employed in the aqueous lubricants of the present invention form stable solutions in the required concentrations which can be employed as such as aqueous lubricants in the rolling of non-ferrous metals or as cutting fluids in the machining of ferrous metals, it is generally preferred to employ the polyesters in.

combination with a surfactant. Thus, the addition of other ingredients such as inorganic salts and the like normally employed in either cutting or rolling fluids tends todecrease the stability of the solution. Additionally, the high pressures and shears involved also affect the stability. The concentration of the surfactant can vary from 1 to 25% by weight of the mixture of the polyethylene glycol polyester and surfactant. Although both cationic detergents such as quaternary ammonium compounds, amine salts, and other nitrogeneous bases, and anionic detergents such as secondary alkyl sulfates and alkali metal or alkaline earth metal sulfonates can be employed, the preferred surfactants are nonionic detergents. Particularly suitable nonionic detergents are based on polyoxyalkylones and include polyoryethylene dioleate, polyoxyethylene stearate, polyoxyethylene monobutyrate, polyoxyethylene monobutyl ether, polyoxyethylene dinonyl phenol ether, polyoxyethylene sorbitan monooleate, polyoxyethylene t-octyl phenol ether, and others which have been described in the literature.

The dimer acids employed in the formation of the polyesters employed in the aqueous lubricants of the present invention are obtained by the polymerization of unsaturated fatty acids having from 16 to 26 carbon atoms,

or their ester derivatives. The polymerization of fatty acids to form the dimer fatty acids has been described extensively in the literature and thus need not be amplified here. The preferred dimer acids employed in the formation of the polyester are those which have 36 carbon atoms such as the dimer of linoleic acid and eleostearic acid. Other dimer acids having from 32 to 54 carbon atoms can be similarly employed. The dimer acids need not be employed in pure form and can be employed as mixtures in whirh the major constituent, i.e. greater than 50%, is the dimer acid and the remainder is unpolymerized acid or more highly polymerized acid such as trimer and tetramer acid. Preferably, the dimer Kacid content is greater than 75%. Such compositions are commercially available under the trademark Empol and T extilana.

The polyoxyalkylene glycols erterified with the dimer acids are polyoxyalkylene diols having a degree of polymerization of 4 to about 200, in which the alkylene group contains from 2 to 4 carbon atoms. Suitable polyoxyalkylene glycols include polyethylene glycols, polypropylene glycols, polybutylene glycols, poly(ethylenepropylene) glycols and poly(ethyenebutyene) glycols. The polyoxyalkylene glycols are commercially available, and can be obtained in varying degrees of polymerization. The preferred polyoxyalkylene glycols are polyethylene glycols. It is to be recognized that the degree of polymerization employed in the definition of the polyoxyalkylene glycol is an average degree of polymerization and that a polyoxyalkylene glycol having an average degree of polymerization of 10 can contain polyethylene glycols varying in their degree of polymerization from 3 to 20. Nevertheless, the average degree of polymerization best reflects the properties of polyoxyalklene glycol. It is critical, from a standpoint of obtaining a lubricant having the desired degree of lubricity and solubility, to employ polyoxyalkylene glycols having a degree of polymerization of at least 4. Esterification products of dimer fatty acids and ethylene glycol or diethylene glycol, for example, when dispersed in water do not result in compositions which have the lubricity and solubility characteristic of the compositions of the present invention. Thus, polyesters of diethylene glycol and the dimer ester do not disperse in water when added in concentrations of 5 volume percent and are therefore unsuitable as metal lubricants in aqueous media. When employed in mixtures of aqueous and non-aqueous oil lubricants, these esters tend to migrate into the oil phase thereby removing desired lubricating properties from the aqueous phase. Even the addition of a surfactant does not result in lubricating compositions which exhibit the surprising combination of properties discovered in the novel compositions of the present invention. Polyoxyalkylene glycols which have degrees of polymerization in excess of 200 are generally not employed because the molecular weight of the resulting polyester makes the solubilization of the ester diflicult. Greatly preferred are polyoxyalkylene glycols and particularly polyethylene glycols which have a degree of polymerization of 4 to 30.

The esterification of the dimer acid with the polyoxyalkylene glycol is carried out by heating agitated mixtures of the dimer acid and the polyether glycol at temperatures of 100 to 300 C. with removal of Water formed as a result of the esterification. Optionally, the reaction can be conducted in the presence of inert diluents, and preferably those which form azeotropes with water. Preferred reaction temperatures are from 200 to 250 C. The polyether glycol and the dimer acid are, as indicated above, employed in a molar ratio of glycol-to-acid of about 0.8 to 2.0, and preferably 1.0 to 1.5. Although it is not essential, the reaction is preferably conducted in the presence of an acid catalyst such as sulfuric acid, alkyl sulfonic acidr, aryl sulfonic acids, or various phosphorous acids. Preferred catalysts are aryl sulfonic acids such as p-toluene sulfonic acid.

The water distilled out of the reaction mixture is condensed and serves as a means of controlling the extent of the esterification in the reaction mixture. Thus, on the basis of the reagents charged, the theoretical amount of water formed by the reaction, if all the hydroxyl or all the carboxyl groups are esterified, can be calculated. By comparing the actual water condensed out of the reaction mixture with the theoretical water, the degree of completion of reaction can be calculated. As indicated above, the reaction is continued until at least 50% of the theoretical water, and preferably until from 70 to of the theoretical water, has been distilled out. In general, the reaction is not continued beyond the level. The resulting polyester can be further characterized by its acid value and hydroxyl value, the determination of which is well-known to those skilled in the art.

It is to be understood that the dimer acid polyesters employed in the present invention can be directly employed in the form of aqueous solution with or without a surfactant as lubricants, or that such compositions can be further modified by the addition of other components to enhance the utility of the aqueous lubricant of the present invention in particular applications. The addition of such modifiers tends, in general, to enhance one area of utility of the aqueous lubricants of the present invention and can, correspondingly, detract from the use of modified compositions in other areas of utility. Hence, it is not surprising that compositions specifically formulated as rolling fluids are not as satisfactory as cutting fluids. Additives which can be used to modify the aqueous lubricants of the present invention include corrosion inhibitors, inclusive of which are alkylolamines such as mono-, di-, or tri-ethanolamine and alkali metal nitrites or chromates such as sodium, or potassium nitrite and potassium chromates. Suitable corrosion inhibitors include those which are effective in protecting not only the work piece but also the machine tool. Such corrosion inhibitors are generally employed in a concentration of 0.01 to 20% by weight of the total composition. Another type of additive frequently employed in rolling and cutting fluids is a bactericide such as o-phenyl phenol. The polyesters of dimer fatty acids forming the base of the aqueous lubricants of the present invention can further be combined with other lubricants suitable for use in metal working. Thus, phosphate esters, such as tricresyl phosphate, are useful additives in rolling oils because they increase the bite of the rolls without reducing the lubricity of the composition. Phosphate esters are generally employed in a range of 0.01 to 10% by weight of the total composition. Additionally, mineral or fatty oils such as have been used heretofore in aqueous lubricants can be combined with the dimer esters. The term fatty oils as employed herein is to be broadly interpreted as including natural, vegetable and animal, oils as well as synthetic esters, alcohols, amines and nitriles of fatty compounds having from 8 to 26 carbon atoms. Such oils can constitute up to 75% of the water-free concentrate of the lubricant. Since such oils are insoluble in water, an emulsifying agent is generally employed in combination with such oils when employed in the compositions of the present invention, although such is not essential.

In a preferred embodiment of the present invention the described dimer esters are em loyed in aqueous rolling fluids for the cold rolling of non-ferrous metals. In concentrated form (i.e., without water) the rolling fluid contains from 20 to 75% by weight of the concentrate of the polyether glycol dimer acid polyester, from 20 to 75% of a fatty oil and from 5 to 25% of an aromatic phosphate ester. The fatty oil as indicated above can be an ester of a fatty acid having from 8 to 26 carbon atoms or it can be an alcohol, amine, or nitrile derived from such acid. The preferred esters are the lower (C C alkyl or alkylol monoesters of fatty acids such as methyl oleate, ethyl stearate, glyceryl monostearate, methyl laurate, and the like. The phosphate esters useful in forming the rolling oils are phosphate esters which contain an aromatic moiety in the ester radical and preferably a benzene or substituted benzene moiety in the ester radical. Aromatic phosphate esters are well-known in the art and are commercially available. Particularly preferred are the phosphate partial esters. In using the phosphate partial esters, it is generally preferred to employ such in combination with a weak base, such as dialkanolamine or trialkanolamine, which not only neutralizes the acidity in the phosphate ester by forming salt therewith, but furthermore, is a corrosion inhibitor. The described concentrate when employed as rolling oil is diluted With water to concentrations in the range of 0.1 to 20% by weight. In such dilute form the described rolling oils based on the polyether glycol polyester of dimer fatty acids exhibit superior stability at elevated temperatures (140l50 F.). The diluted fluid can be passed through a 2 micron glass fiber filter without clogging the filter; or affecting the stability of the fluid; nor are any ingredients removed by such filtration.

The aqueous lubricating compositions of the present invention constitute a significant improvement over prior art aqueous lubricating compositions used as rolling oils or cutting fluids. Although generally handled and stored as liquid concentrates, they readily dilute to the desired concentration, i.e. 0.1 to 20% by weight of the aqueous phase. In such dilute form the compositions are homogeneous and exhibit superior lubricity. They are stable at elevated temperatures and do not break down when used at high relative speeds of work piece to tool. The measurement of lubricity and the correlation of such measurement with actual end-use performance are not always successful, although a qualitative comparison can be established. One of the methods of measuring lubricity is the measurement of the film strength in which a rotary surface is pressed against a stationary surface under increasing pressures, the rotating surface being in contact during part of its revolution with a reservoir of the lubricant being tested. The pressure at which the surfaces seize, expressed in p.s.i., is considered the film strength of the lubricant tested. The equipment employed to measure the values discussed hereinafter was an Alpha Molykote Tester operated at a speed of 334 surface feet per minute, unless otherwise indicated. With a steel block having a Rockwell C Hardness of 57 to 60, the use of a 1 weight percent solution of the dimer ester resulted in film strengths of 21,600 to 33,600 p.s.i. Tests made with 0.5% and 0.25% concentrations resulted in film strengths of 31,500 p.s.i. and 28,000 p.s.i, respectively The use of water alone resulted in almost immediate seizure With an aluminum block instead of the steel block a 1% solution of the dimer ester produced a film strength of about 14,000 p.s.i., while a 0.25% solution resulted in film strength of about 12,600 p.s.i Oil emulsions such as used heretofore in the rolling of aluminum and containing about 5% of oil resulted in film strengths of 5,000 to 8,000 p.s.i. The addition of 1% of the polyethylene glycol dimer polyester raised the film strength to about 21,000 p.s.i.

The aqueous lubricants of the present invention, particularly when formulated as rolling fluids for aluminum, result in rolled products which have less marks, a shinier finish, and fewer stains than obtained with the oil emulsions heretofore employed.

The preparation and the properties of the aqueous lubricating compositions of the present invention are further illustrated by the following examples, in which all units of quantity are by weight unless otherwise indicated.

EXAMPLE 1 Into a three-neck round-bottom flask mounted in an electric mantle and equipped with stirrer, thermometer, condenser, and Dean-Stark Trap are charged 3 moles of a The procedure of Example 1 is repeated using equimolar quantities of the dimer acid and the polyethylene glycol and 1% by weight of the reaction mixture of ptoluene sulfonic acid. The resulting polyethylene glycol polyester has an acid value of 50 and a hydroxyl value of 5.5.

EXAMPLE 3 The procedure of Example 1 is repeated using equimolar concentrations of the glycol and a dimer acid commercially available as Empol 3020R, containing 73% of C dimer acid and 22% of C trimer acid. The resulting polyester has an acid value of 32.5 and a hydroxyl value of 23.3.

EXAMPLE 4 The procedure of Example 1 is repeated using equimolar concentrations of the glycol and a dimer acid commercially available as Empol 1016, containing 87% of C dimer acid and 13% of C trimer acid. The resulting polyester has an acid value of 25.7 and a hydroxyl value of 21.8.

EXAMPLE 5 An aqueous lubricating composition is made up containing the following components:

Percent Polyester of Example 1 5.44 Triethanolamine 3.02 Sodium nitrite 3.62 Sodium salt of o-phenyl phenol 0.78

Nonionic surfactant, ethylene oxide condensate of t-octyl phenol, commercially available as Triton Xl02 1.81 Partial phosphate ester of the adduct of 3-10 moles of ethylene oxide with one mole of dinonyl phenol, commercially available as Gafac RM15O 0.6 Water 84.73

This aqueous lubricant is then further diluted and tested in concentrations of 4% by volume as an aluminum rolling fluid on a 2 high mill rotated at 90 surface feet per minute. The mill is set for 50% reduction with a commercial hot rolling emulsion in water. Reductions of 52.5% are obtained over the range of concentrations. The resulting rolled sheet exhibits minimized pick-up and high gloss.

EXAMPLE 6 An aqueous lubricant concentrate is made up having the following components:

Parts Mineral oil, Saybolt viscosity 48 43.35 Vegetable oil, a mixture of oleate esters 27.4

Cationic surfactant Aerosol C61, an ethanolated alkyl guanidine amine complex 3.375 Nonionic surfactants, ethylene oxide condensates of alkyl-substituted phenols 15.40 Corrosion inhibitor, diethanolamine 0.47 Bactericide:

t-butylbenzoic acid 0.74 o-phenyl phenol 0.74 Polyester of Example 3 5.00

Phosphate ester, Gafac RM-S 10 3.375

The concentrate is diluted with water as indicated below and employed in the rolling of aluminum on a two High- Stanat mill rotated at 90 surface feet per minute. The mill is set for 50% reduction with mineral oil. The reduction obtained at various concentration levels is shown:

Concentration: Reduction, percent 52 2.5% 52 1.6% 52 EXAMPLE 7 An aqueous lubricant concentrate is made by admixing 87% of the polyester of Example 4 with 13% of an ethylene oxide condensate of t-octyl phenol, a nonionic surfactant commercially available as Triton X165, The concentrate is diluted With water and employed in the rolling of aluminum as indicated in Example 5. The following reductions are obtained at the concentrations indicated:

Concentration: Reduction, percent 73 5% 64 2.5% 60 EXAMPLE 8 A polyester of equimolar quantities of dimer acid and a polyethylene glycol having a degree of polymerization of is prepared by the procedure of Example 1. The polyester is dissolved in a 1% concentration in water and employed as a cutting fluid. A 4340 steel, Rockwell C. 30, tube is turned with tungsten carbide tools containing 2% or 6% cobalt. The workpiece is rotated at 400 s.f.m. The tool feed is 0.004 i.p.r. and the total and the total cutting time is 80 seconds. With the 6% cobalt cutting tool total flank wear is 0.0098 in. and total crater wear 0.0289 in. as compared to 0.0126 in. and 0.0319 in., respectively, for water alone. With the 2% cobalt tool the total flank Wear is 0.0114 in. and the total crater wear is 0.0257 in. as compared to 0.0115 and 0.0309 for water alone.

EXAMPLE 9 The Alpha Molykote Tester was employed to measure cup wear and block wear of a standard 2 g. block of annealed 5086 aluminum, at varying speeds and at a normal load of about 600 lbs. using a commercially available mineral (50 SUS) oil containing about 10% of a fatty oil. The following results were obtained:

Cup speed, ($1111.) Cup wear (g) Block wear, (g)

The following rolling fluids were prepared:

Fluid A.-Rolling Fluid of Example 6 in 20% concentration in water.

Fluid B.R0lling Fluid of Example 6 in 10% concentration in water.

Fluid C.This fluid was prepared by admixing the These fluids were tested in the Molykote Tester as indicated above and the following results were obtained:

Cup speed Fluid Cup wear Block wear (s.i.m.) (g.) is) 1, 008 A 0. 0000 0. 0088 1, 008 B 0. 0010 0. 0077 C 0. 0003 0. 0130 The foregoing results show the significant reduction in wear on both the machine tool and the workpiece obtained with the compositions containing the polyether glycol polyesters of dimer acids.

The foregoing examples have illustrated the preparation of the dimer acid polyethylene glycol polyesters and the utilization of such in the :formation of the aqueous lubricants of the present invention. As will be apparent from the foregoing examples, substantial improvements in the end-use performance result when the polyesters of the present invention are employed in aqueous lubricants, whether employed as such, modified for particular application, or employed in combination with oil emulsion. Various alterations and modifications will be apparent to those skilled in the art, particularly with respect to the formulation of specific lubricants designed for particular applications by the addition of modifiers. The foregoing description of specific embodiments of the present invention is not intended as limiting the invention thereto which broadly comprises the use of polyesters of polyethylene glycol and dimer fatty acids in the form of aqueous solution as lubricants in the working of metals.

What is claimed is:

1. In the process for working metals the step comprising lubricating the metal with an equeous lubricant composition containing 0.1 to 20% by weight of the aqueous phase of a polyester of a polyoxyalkylene glycol having a degree of polymerization of 4 to 200, said alkylene groups having from 2 to 4 carbon atoms, and the dimer of a fatty acid having 16 to 26 carbon atoms, wherein said polyester is obtained by the condensation of 0.8 to 20 moles of polyoxyalkylene glycol per mole of acid, said condensation being conducted until 50% to of the theoretical water has been removed.

2. The process of claim 1 wherein the alkylene group is ethylene.

3. The process of claim 2 wherein the polyester is employed in combination with a surfactant, said surfactant constituting from 1 to 25% by weight of the mixture of surfactant and polyester.

4. The process of claim 1 wherein the dimer acid is a C dimer acid.

5. The process of claim 3 wherein the surfactant is a nonionic surfactant.

6. The process of claim 5 wherein the surfactant is an ethylene oxide condensate.

7. The process of claim 3 wherein the lubricant contains a corrosion inhibitor.

8. The process of claim 7 wherein the corrosion inhibitor is an alkylolamine.

9. The process of claim 7 wherein the corrosion inhibitor is an alkali metal nitrite.

10. The process of claim 7 wherein the corrosion inhibitor is a combination of alkylol amine and alkali metal nitrite.

11. The process of claim 1 wherein the lubricant contains a lubricating oil selected from the class consisting of mineral, vegetable, and animal oils.

12. The process of claim 11 wherein the lubricating oil is an ester of a fatty acid having from 8 to 26 carbon atoms.

13. The process of claim 1 wherein the aqueous lubricant composition contains 1 to 20% by weight of an alkali metal nitrite, and 5 to 20% by weight of an alkylolamine, based on the weight of lubricant composition.

14. The process of working metals of claim 1 wherein aluminum is rolled.

15. The process of working metals of claim 1 wherein ferrous metals are machined.

16. In the process for working metals the step comprising lubricating the metal with an aqueous lubricant composition substantially free of lubricating oils containing 0.1 to 20% by weight of the aqueous phase of a polyester of a polyoxyalkylene glycol having a degree of polymerization of 4 to 200, said alkylene groups having from 2 to 4 carbon atoms, and the dimer of a fatty acid having 16 to 26 carbon atoms, wherein said polyester is obtained by the condensation of 0.8 to 2.0 moles of polyoxyalkylene glycol per mole of acid, said condensation being conducted until 50% to 90% of the theoretical water has been removed.

17. The process of claim 16 wherein the alkylene group is ethylene.

18. The process of claim 16 wherein the dimer acid is a C dimer acid.

19. An aqueous metal working lubricant concentrate comprising a mixture of from 20 to 75% by weight of the mixture of the polyester of a polyethylene glycol having an average degree of polymerization of 4 to about 30 and a C dimer acid, said polyester being obtained by the condensation of said glycol with said acid in a molar ratio of from 1.0 to 1.5 until from 70 to 85% of the theoretical water has been removed; from 20 to 75 by weight of the mixture of an ester of a fatty acid having from 8 to 26 carbon atoms and from 5 to 25% by weight of the neutral mixture of the alkylolamine salt of an aromatic partial phosphate ester.

References Cited UNITED STATES PATENTS 2,625,509 1/1953 Laug 252495 X 2,470,405 5/1949 Leland 252-49.5 X 2,914,477 11/1959 Cafcas et al -2 25249.5 X 3,000,826 9/1961 Gililland 252493 3,057,890 10/1962 De Groote 260-407 3,117,929 1/1964 McCoy et al. 25249.5X 3,287,273 11/1966 Furey et al. 25257 DANIEL E. WYMAN, Primary Examiner W. CANNON, Assistant Examiner US. Cl. X.R. 252 49.5, 57