US2713167A - Cold weather clothing - Google Patents

Description

July 19, 1955 w. E. cowlE ErAL 2,713,167

COLD WEATHER CLOTHING Original Filed May 25, 1950 3 Sheets-Sheet 1 9% fw l5 N/Bu/P E. Cou/5 ARTHUR E- BL ou//v July 19, 1955 w. E. cowIE Erm.

com WEATHER CLOTHING 3 Sheets-Sheet 2 Original Filed May 25, 1950 JvvE/vrof? A//L Bw? L'. Cow/E.

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July 19, 1955 w. E. cowlE E rAL 2,713,167

COLD WEATHER CLOTHING Original Filed May 25. 1950 5 Sheets-Sheet 3 ATT 3 United States Patent Otiiee 2,713,167 Patented July 19, 1955 COLD WEATHER CLOTHING Wilbur Elliott Cowie, Ottawa, Ontario, and Arthur Eugene Blouin, Crystal Bay, Ontario, Canada, assignors to Her Majesty the Queen in the right of Canada as represented ly th Minister of National Defence, Ottawa, Ontario,

ana a Original application May 25, 1950, Serial No. 164,086, now Patent No. 2,656,586, dated October 27, 1953. Divided and this application October 19, 1953, Serial No. 386,927

Claims priority, application Canada May 28, 1949 3 Claims. (Cl. 2 2) body clothing and tested under servere operational conditions in the Arctic. The novel pile fabrics and body clothing so produced are considered to constitute a notable improvement over fabrics and fabric clothing hitherto available for cold Weather protection and even to sur pass in performance the caribou fur clothing of admitted excellence evolved by the Eskimos through centuries of experience with the Arctic climates.

The several characteristics of our improved fabrics, which characteristics are to a certain extent inter-related, will be discussed under separate headings, as follows:

FROST REMOVAL We are satisfied that the superiority of Wolverine hair can adequately be accounted for solely on the basis of its mechanical properties. Furs not yet studied may possess similar mechanical properties but, of those tested, Wolverine guard hair bre is unique in exhibiting all the following qualities:

(a) A high tensile strength,

(b) A firm anchorage to the pelt,

(c) A smooth surface, and

(d) The greatest lament diameter within the Carnivora order, with consequential exposure of less surface to ice per given Weight of hair.

The average measured characteristics of the guard hairs of certain of the different furs investigated are shown in Table l as follows:

Table l constant Wo1verine Muskmt Whggga caribou nigh Low Length, in inches 2. 93 l. 33 1. 58 2. 64 Wolverine-" Muskrat. Diameter, in inches." 0. 00378 0. 00232 0. 0106 0. 0094 W- T. Deer Do. Weight per inch, in

gms i- 0. 00017 0. 000063 0. 00013 0. 00012 W01verine Do. Density (g111s./cc.) 0.93 0. 91 0. 088 0. 080 do Do. No. of guard hairs per in 1, 888 2, 740 6, 660 Tension in lbs. on

Scott Tester 0. itl/1% 0. 05/0. 55 04/0. 55" Wolverine Caribou.

must be so designed that such accumulations may periodically be removed.

The accumulation of frost Within the insulating layers may of course be prevented by enclosing them within a water impermeable envelope but this has not so far proved to be practical. In regard to the periodic removal 0f frost it has long been known to employ a fur rutf around the edge of a parka to protect the face of the wearer under polar climatic conditions and periodically to remove from the ruif frost formed by condensation of moisture exhaled in the breath and a consistent preference has been shown for Wolverine fur as an edge trimming. This preference has been ascribed to various factors but appears in general, to be based upon the superior frostshedding or de-icing properties of Wolverine fur. Thus, While Wolverine fur collects frost or ice in the same way as any other fur, When the frost has changed to ice it may be removed by knocking and brushing without detriment to the fur, whereas most other furs are permanently harmed by this treatment.

We have investigated the chemical and physical characteristics of Wolverine hair and of the hair of a number of other fur-bearing animals, to ascertain Why Wolverine fur is superior to others in shedding frost and We have surveyed and evaluated the several other factors bearing upon the construction of a pile fabric which is to be capable of affording adequate protection to the wearer under polar climatic conditions.

As a result of our investigations a variety of pile fabrics have been constructed which have been fashioned into A standard Scott tester (used for measuring the tensile strength of fabrics) Was employed for determining the tensile strength of the various hair fibres and our results show that it takes a pull of 0.18 lb. (81.7 gms.) to break a. single 1%" long Wolverine hair weighing 0.00017 gm./ inch, which corresponds approximately to a filament of 60.25 denier. The tensile strength of Wolverine hair is therefore shown to be about 1.36 gms. per denier. Only very short samples were available for the tests, the lengths of the samples being dependent upon the length of guard hair as it Was taken from the pelt, Which in the case of Wolverine Was 1%" in most cases. To correctly evaluate the utility of a particular hair in shedding frost, the strength of the anchorage must of course be considered as Well as the tensile strength of the hair fibre but our results clearly indicate Wolverine guard hair to be much higher in tensile strength than any other fur tested.

THE PILE FILAMENTS Our experiments have pointed to the desirability of a pile fabric having monotilaments firmly anchored to the ground cloth, to withstand the stress of combing and brushing to remove matted frost, and to the employment of pile filaments selected with regard to the following special characteristics:

(i) They should be straight, should have a smooth surface and should be substantially uniformly distributed over the fabric surface,

(ii) They should have a tensile strength of not materially less than that of Wolverine fur guard hair,

(iii) They should retain their flexibility and strength at polar sub-zero temperatures and preferably down to temperatures at least at low as 60 F.,

(iv) They should have a low-moisture-,absorption capacity at high relative humidities (i. e. less than that of cotton fibre),

(v) They should have a stiffness sufficient to maintain themselves in a substantially separate condition to resist compression and felting of the pile so as to allow it to be combed or beaten to removeV accumulated frost.

The pile filaments to be employed in accordance with the invention preferably consist of extruded non-cellulosic thermoplastic filaments preferably selected from the group comprising the polymeric amides (known generically as nylon), or the vinyl resins comprising, for example,.the copolymers of vinyl chloride and vinyl acetate (known for example, under the registered trademark Vinyon) or the vinylidene chloride polymers (known, for example, under theregistered trademark Saran). Alternatively, polyacrylonitrile fibres (known under the 4 The overall bulk density of the pile is also largely iniiuenced by the overall weight of the fabric. In the course of our experiments it has been determined by trial in the Arctic that clothing which weighs more than 12 to 14 lbs., including handgear and footgear, tires the wearer rapidly in proportion to the increase in weight. The Vmaximum practicable weight of body clothing for the conditions envisaged is of the order of l to l2 lbs. It is, therefore, of critical importance that the bulk density of the fabric be held to a minimum, which calls for the employment 4 required insulation.

trademark Orion) have characteristics suitable for use Y in accordance with the invention.

Of the foregoing materials, high tensile nylon filaments have proved eminently satisfactory in practice and fully satisy the prescribed special characteristics in being straight, in having a smooth substantially cylindrical surface, in having an average moisture regain of 6.30% at relative humidities as high as 90% (approximately half that of cotton under similar conditions), in possessing a high tenacity (about 5 to 7 grams per denier dry and about 4.4 to 6 grams per denier Wet), and in retaining their strength and in showing only slight increase in elongation' at temperatures as low as 80 C.

Nylon filaments are further particularly suited for use as a pile thread in clothing fabrics in being inert and clean, in possessing no harmful toxological properties and in being relatively incapable of supporting the growth of mildew, fungi or bacteria.

PILE FILAMENT DENIER VAs previously stated, the pile filaments should have a tensile strength not materially less than that of woly verine fur guard hair and a stiffness sufficient to maintain themselves in a substantially separate condition to resist compression and felting. We have determined that a l0- deniermonolament with characteristics similar to that Y of nylon is about the lowest denier pile filament which is suitable for use in oui improved fabric. The optimum denier is the stiffest monofilament which can be worn in comfort towards the skin; we estimate this to be at to denier when no underclothing is worn to about 50 or possibly 75 denier with underclothing.

THE PILE STRUCTURE v The thermal insulation of the fabric is determined, inter alia, by thethickness and state of immobility of the air layer trapped within the pile and, therefore, varies with the length of the pile. Moreover, if the fabric is subject to conditions of use tending to fiatten the pile, the thermal insulation depends also upon the ability of the pile to resisticompression and to return to its original condition when the compression load is removed. The ability of a pile fabric to retain its thickness under intermittent compression loading is thus a functionof the stiffness and resilience of the pile filaments and also of the overall bulk density of the pile, which varies as the number of the pile threads. The nature of the ground cloth employed, the

ldenier of the pile thread, the resistance of the pile thread In setting the physical limits of pile structures whichk will yield fabrics sufficiently warm for body clothingl under polar conditions, we have studied the structure of various furs and we have selected caribou as a standard Y of excellence, proved by centuries of use by the Eskimo to be the most suitable for body clothing in the Arctic winter, toV be attained or surpassed. The features which render caribou skin so desirable are its low bulk, stiffness and weight combined with adequate warmth and its ability to withstand the conditions of service over a period of months while on the trail. Thus, Stefansson states in his Arctic Manual (1945) that As protection against the weather of the various seasons, the Eskimos lhave developed on the whole better garments than probably any people in history and further, caribou is the best of all native Arctic materials for winter cloths. For use in pile fabrics required for insulating purposes larve diameter, low density, tightly packed filaments are desirable such as occur naturally in caribou fur which Y has 6660 guard hairs per square inch with a diameter of 0.024 cm. and a density of 0.080. Wolverine guard hair on the other hand, has a diameter of 0.0096 cm. and, therefore, to maintain the same proportion of diameter to number of hairs as caribou, should have 16,700 guard hairs per square inch. However, the controlling factor is the overall bulk density, as that is a measure of the weight of the material for a given amount of insulation, and the specific gravity of caribou guard hair is only a fraction of that of Wolverine and of artificial filaments possessing the required tensile strength so that it is necessary to use a proportionately lower denier of synthetic filament to obtain theoptimum bulk density of the pile fabric. With these considerations in mind we have experimented with a number of pile fabrics utilizing artificial pile warp threads of different denier selected with regard to the special characteristics for frost-removal discussed above and packed to different degrees and we have` found that pile fabrics possessing appropriate thermal insulation, light weight, flexibility and low bulk density can be obtained byemploying a number of pile filament ends per unit area of fabric which is of the same order as that of the guard hair in caribou fur.

Good thermal insulation can, however, be obtained notwithstanding that the number of pile filamentsV per unit area of fabric varies between wide limits, provided that a corresponding adjustment is made in Ythe denier of 'the filaments. The practical limitsof filament count have been found to coincide approximatelyY with the range 2500 to 18,500 filament ends4 per square inch of pe area.

To assist in arriving at approximate packing densities using filaments of different denier we have formulated an approximate rule relating the number of filament ends per square inch of pile area and the denier of filaments concerned; the rule provides that the number, N, of filament ends per square inch of pile area should beof the order of the quotient of the expression k/d, where k has a value between 200,000 and 300,000 and d is the denier of the filaments, the filaments being considered as solid and as having a specific gravity approximating to that of dry nylon fibres (i. e. of the order of 1.14). In the present specification the expression number-of filaments per square inc connotes the total number of individual pile filament ends which stand out from the ground cloth. Thus, supposing a pile warp thread is used consisting of 220 denier' 16 filament thread used singly, each tuft then consists of a bundle of 16 filaments anchored in the ground cloth intermediate their ends. There will thus be a total of 32 filament ends standing out from the ground cloth for each tuft. Assuming the number of separate tufts per square inch to be 482, the total number of lament ends per square inch is given by 32 482=15,422.

PILE LENGTH The weight per unit area of the fabric is, of course, approximately proportional to the pile length (other factors remaining constant) and it is essential in using the fabric for body clothing for the climatic conditions in question, to keep the pile length at a minimum consistent with securing the required thermal insulation. We have established that a relatively short pile is adequate to immobilize the air within the pile to provide the required thermal insulation. While there is no sharply defined lower limit for pile length, our experiments indicate that the minimum pile length for inner garments for Arctic wear is of the order of 1A inch, The thermal insulation of the clothing is almost directly proportional to the pile thickness and we have determined by test that an Eskimo type construction must consist of two 1A inch pile layers to be effective in the Arctic winter climate. the practical lower limit of pile length is considered to be 1A inch. The foregoing pile thicknesses are also such as to allow the clothing to follow the contours of the body more closely by compressing the pile to some degree on the inside garment over protruding irregularities of the body. It is of advantage to us thicker piles (for example up to about 3/1, inch) for extreme cold, in which case the pile filaments should be selected at a larger diameter and of the filament range to maintain adequate compression resistance and to keep the pile in an erect unmatted condition. Under the latter conditions it is also advantageous to use hollow or cellular pile tilaments to assist in keeping the weight of the clothing below the limit of tolerance, i. e. l5 lbs.

AIR AND VAPOUR PERMEABILITY The air and water vapour permeability of the ground cloth of the fabric is of critical importance for body clothing under polar climatic conditions. The lower limit of air permeability of the fabric is, of course, zero and is preferable if it can be attained without unduly decreasing the water vapour permeability. When the fabric is to be used for clothing in areas subject to high velocity winds of the order of more than 25 miles per hour at subzero temperatures, it is of prime importance that the air permeability be not greater on the average than about 5 cubic feet per square foot of fabric per minute, as measured at a pressure differential of 1/2 inch of water in the Schiefer and Boyland apparatus described in Research Paper R. P. 1471 of the Journal of Research of the United States Department of Commerce, National Bureau of Standards, vol. 28, May 1942. At lower velocity winds the air permeability may be somewhat higher but should be maintained at a value not in excess of cubic feet/square foot/minute, measured as above, for use in Wind velocities from miles per hour down to l0 miles per hour. The air permeability of caribou clothing skin measured by the above method ranges from about 0.5 to about 6.0 cu. ft./ sq. ft./minute.

The water vapour permeability should on the other hand be as high as possible consistent with a low air permeability and should preferably be not less than a dry tanned deer or caribou skin as set forth hereinafter. There is no sharp demarcation of desirable vapour permeability but vapour impermeable materials produce an undesirable accumulation of moisture within the clothing.

For inner layers in moderately cold climates k As a minimum requirement, the pile' fabrics should have a water vapour transmission per square metre per single layer per hour of 20 grams for a vapour pressure difference of 10 mm. of mercury, of 50 gms. for a vapour pressure difference of 40 mm. of mercury and of 80 gms. for a vapour pressure difference of mm. of mercury, measured at body temperature on one side 'and 0 C. on the other side.

The desired limits of air and vapour permeability may be achieved while simultaneously securing good anchorage of the filaments to the ground cloth and without adding substantially to the overall weight of the fabric by a controlled application of a cementing or bonding agent of suitable viscosity to the ground cloth. As bonding agent, we may employ pre-vulcanized or vulcanizable natural, synthetic or reclaimed rubber, coated from aqueous emulsion or from solution onto the back of the woven fabric so as lightly to impregnate the back and to form a thin continuous liquid film over the backing. The rubber bonding agent must have a high viscosity, of the order of 1500 centipoises, so that it does not penetrate the backing and run into the pile. The coated rubber is then dried, or cured and dried, and the amount of rubber applied is so controlled that the drying process ruptures the thin liquid lm over the larger pores in the backing thereby providing passages for vapour transmission. The weave of the ground fabric ensures that sufficient pores are available for the required vapour transmission and that the pore size is small enough to keep the air permeability down to the required limits. The rubber also locks the pile laments firmly to the backing and the light penetration of the rubber into the ground cloth reduces the water absorbency of the ground cloth. An amount of rubber not exceeding 1 ounce (avoirdupois) per square yard of fabric has been found to provide excellent lament anchorage and to give air and vapour permeability within the required limits.

'Ihermoplastic bonding agents may alternatively be employed in emulsion or in solution. The required low air permeability of the backing may also be achieved without impregnation by a uid bonding agent either by the closeness of the weave of the ground cloth or by using thermoplastic fibres in the backing yarns and by passing the fabric back-down over heated rolls to flatten out the filaments and to seal up the back of the fabric.

While our experiments have shown that pile fabrics having an air permeability not greater than 5 cubic feet per minute are suitable for body clothing under the most severe conditions of a polar winter, it should be understood that pile fabrics which are substantially impermeable to air are also within the scope of the invention provided that the required vapour permeability limits are conserved. The overall weight of such substantially airirnpermeable structures is, however, in general greater than that of the equivalent air-permeable structures which latter constructions are accordingly preferred on the basis of Weight.

PILE WEAVE The pile thread may be woven into the ground cloth by the well-known cut pile weaving technique and the so-called W-weave is preferred as enhancing the anchorage of the pile filaments.

THE GROUND CLOTH The weave of the ground cloth is susceptible to wide variation but should be selected having regard to the following special characteristics:

(a) High flexibility with a low weight,

(b) High tensile strength per thread to withstand weaving stresses,

(c) High tensile strength per unit cross section to withstand wearing stresses, and

(d) A low moisture absorbency.

A cotton-warp and a cotton-filled ground cloth has given good results, a nylon-warp and a cotton-filled Vmoisture absorbency of nylon.

CLOTHING CONSTRUCTION The flexibility of the pile fabric when made into body clothing should be high to provide ease of movement and to conserve the energy of the wearer for work tasks. The drapeY of the fabric is also important in ensuring that when made into clothing it does not hang too far from the body and leave voids beneath. Such voids chill the wearer due to convection currents and to excessive ventilation due to flapping of the clothing when the wearer moves. The wearer should lalso have little consciousness of the bulkof the clothing and in this respect the resistance to compression under the armpits and around'the joints is important. To achieve perfection the clothing should Vsimulate the fluidity of air.

We have established that ymaximum flexibility, the required drape, minimal consciousness of bulk and minimal resistance to compression can be achieved by the Eskimo style of garment comprising two layers of pile fabric in a back-to-back construction. With this arrangement, the resistance to motion across the face of the pile is very slight as small forces at right angles to the pile filaments easily deflect the pile and allow movement of the contacting body relative thereto. The ends' of the pile filaments move in the direction of the deliecting force and when flattened presents the smooth rounded surface of the sides of the laments to the contacting object.` Such material has very little tendency to snag on surrounding objects and allows the wearer to reach,

1 or enter bodily into areas diliicult of access-to the wearer of conventional flat Woven fabric clothing,

In order that ythe invention may be more fully understood, several Vexamples of pile'fabric constructed` in accordance with'the invention will now be described, the construction being illustrated in Figures l, 2 and 3 in which:

Figure l is a diagrammatic'plan-view of the face of the pile fabric greatly enlarged to showv the fabric and pile structure. f

Figure 2 is a cross-sectional elevation of the fabric weftways on the line 2 2 of Figure l and Figure 3 is a cross-sectional elevation of the fabric warpways on the line 3 3 of Figure l.

A specific embodiment of body clothing intended for the ground Ycloth and constitute the pile and the total number of upstanding pile lament ends is thus given by x-y-z where z is the number of individual filaments per tuft. In the various speciiic constructions described hereinafter, the total number of upstanding pile filament ends per square inch is calculated from the expression by substituting the values for x, y and z given in each example.

The back of theground cloth also carries a rubber coating 16 or other bonding agent applied as previously described in an amount not exceeding l ounce (dried weight) per square yard of fabric. The coating 16 is so thinly distributed that the texture of the warp and filling l yarns is clearly visible and apparent to the touch. Nevertheless, the carefully controlled application of a bonding agent in this small amount is adequate to provide air and vapour permeabilities within the required limits and firmly to anchor the pile threads in the ground cloth.

Specific examples of pile fabrics constructed in accordance with the invention areas follows:

EXAMPLE I 3A nylon pile, cotton ground cloth Backing: l

Warp 2/30 carded cotton, 48 ends/ inch (x). V Filling l/ l2 carded cotton, 72 picks/ inch (y). Weight 0.4 lb./square yd. Pile:

Length 3%: inch. Weave W, warp thread. Material Nylon; 75 denier monolament. Filaments/tuft Six (z). Filament ends in.2 3460 (approx.). Fabric weight 2.8 pounds/square yd. Air permeability 2.0 to 5.0 cu. ft. of air/sq.

ft./min. (Schieffer and Boyland). VBonding agent Rubber applied to the back of wear in the polar regions and consisting of pile fabric pursuant to the invention Will also be described with reference to Figures 4 and 5 in which:

' Figure 4 shows the inner garments of a parka and trousers assembly,

Figure 5 shows the assembly completed by the addition of an outer parka and outer trousers, and

Fig. 6 isa sectional View along the line 6 6 of Fig.- 4.

The pile fabric shown diagrammatically in Figures l to 3 consists of a ground cloth made up of warp yarns 11 Yand weft picks or filling yarns 12, and a pile comprising `a plurality of individual tufts 13 of pile warp yarns beaten Vup in a tight W-weave with the weft yarns. The tuftsV 13 are distributed uniformly over the ground cloth and in the direction of Vthe warp there is one tuft for every six weft or lilling yarns, giving a ratio of l to 6 for tufts to picks, and in the direction of the weft, there is one tuft for every two ground warp yarns. If the number of warp ends per inch is designated by x and the number of filling yarns per inch is designated by y, the

total number of tufts per square inch is then given by cale nel@

0f lilaments which stand substantiallyvstraight out from the ground cloth and weighing l oz./sq. yd.

ln the construction of Example I, each tuft consists of six filaments giving twelve filament ends per tuft upstanding fromY the ground cloth. Applying the parameters of Example I ink the formula N=k/d, we have d equal to 75 and N equal to 3460, giving a k value of 259,500.

l EXAMPLE II 1%6" nylon pile-cotton ground cloth ft./ minute.

9 onding agent Rubber, applied to the back of the ground cloth and weighing 1 oz./sq. yd.

The construction of Example Il affords sixty-four lament ends per tuft standing out from the ground cloth. Substituting in the expression N=k/d, d is equal to 220/ 16, and k is then equal to:

EXAMPLE 111 3/a nylon pile-cotton ground cloth Backing:

Warp 2/ 30 carded cotton, 62 ends/ inch.

Filling 1/40 carded cotton, 92 picks/ inch.

Weight 0.24 lb./sq. yd.

Pile:

Length 3A; inch.

Weave W, warp thread.

Material Nylon; 220 denier, 16 lament used singly.

Filaments/tuft Sixteen.

Filament ends in.2 15,400 (approx).

Fabric weight 15.4 02s./ sq. yd.

Air permeability 2.0 to 5.0 cu. ft. of air/sq.

ft./minute.

Bonding agent Rubber, applied to the back of the ground cloth and weighing 1 oz./sq. yd.

ln the construction of Example III, k is equal to 211,750.

EXAMPLE IV nylon pilenylon and cotton ground cloth Backing:

Warp denier, 68 lament nylon,

64 ends/ inch.

Filling l/40 carded cotton, 104 picks/ inch.

Weight 0.24 1b./sq. yd.

Pile:

Length B; inch.

Weave W, warp thread Material Nylon; 220 denier, 16 lament used singly.

Filaments/tuft Sixteen.

Filament ends in.2 17,700 (approx.).

Fabric weight 17.1 ozs./sq. yd.

Air permeability 1.0 to 4.0 cu. ft. of air/sq. t./

minute.

Bonding agent Rubber, applied to the back of the ground cloth and weighing 1 oz./sq. yd.

In the construction of Example IV, k is equal to 243,375. The conductivity factor of the material of Example IV has been measured and found to be 0.58 B. t. u./hour/per sq. ft./inch thickness.

EXAMPLE V f/s nylon pile-nylon ground cloth Backing:

Warp 140 denier, 68 filament nylon, 62 ends/inch. 25 turns/inch. Filling denier spun nylon, 103

picks/inch. Weight 4.8 ozs. per square yard.

Pile:

Length 3A; inch.

Weave W, warp thread Nylon; 215 denier, 17 filament Material used singly.

Filaments/tuft Seventeen.

Filament ends in.2 17,700 (approx).

10 Fabric weight 18.3 ozs./square yd. l Air permeability 0.4 cu. ft. of air/sq. ft./min'. Bonding agent Rubber, synthetic, applied to the back of the ground cloth and weighing 1 oz./sq. yd.

The pile fabric may be treated, for example, after weaving and before or after bonding, depending upon the bonding agent employed, by a chemical surface agent to give the fabric a high degree of water repellency and a low water absorption. The silicones, such as amino silane or the methyl chloro silanes, having a high contact angle with water have been found to serve as suitable surface agents. The amino silanes may be applied from solution or in the form of the liquid per se and the methyl chloro silanes may be applied from emulsion. Thus, the Woven pile fabric may be immersed in a 1% solution of amino silane in carbon tetrachloride and then passed through Wringer rolls under pressures of the order of 200 lbs. per inch width of fabric and afterwards through a curing oven at 350 F. for four minutes. The weight of silicone applied is about 1/2 oz./sq. yd. on a 5% pile fabric. The chemical surface agent lmay alternatively be applied to the yarn before Weaving.

The calculated overall bulk densities of pile fabrics constructed in accordance with Examples I to V are as follows:

Lbs/cu. ft. Example I 6%", 75 denier filaments) 5.0 Example II (1%6 pile, 13.7 denier filaments) 2.7 Example III pile, 13.7 denier laments) 3.4 Example IV pile, 13.7 denier lilaments) 3.8 Example V 0% pile, 12.6 denier laments) 4.1

The bulk densities set forth above were calculated from the weight of fabric per square yard given in Examples I to V by multiplying the weight per square foot of fabric by the number of the thicknesses of fabric required to iill a foot cube without compressing. It will be appreciated that the bulk density calculated as above will be inversely proportional to the pile length where the construction of the backing and the density of the pile are constant.

The bulk density of caribou skin varies somewhat according to the pelt and the rigour of the dressing treatment but has a value from about 3.75 to about 5.3 lbs./cu. ft. The pile fabric in accordance with the invention thus has a b'ulkdensity which is closely comparable with the best values obtained for caribou, and which is substantially constant over an extreme range of lament denier.

The pile Warp yarns employed in Examples I to V hereof are composed of a plurality of filaments twisted together in some degree to assist the Weaving process. The nylon yarn employed is, however, such that no permanent twist remains in the pile yarn after the pile warp threads have been cut following weaving by the known cut pile processes and, as a result, the filaments separate from each other to produce a very regular pile structure with the individual filaments spaced uniformly throughout the pile for a substantial portion of their free length. In order to achieve the necessary pile count in accordance with the invention, the pile warp yarns have to be beaten up very tightly in the weft yarns. As a result of this beating up, the individual iilaments of the weft yarns become displaced from their twisted cylindrical condition in the region of the bottoms of the W tufts, and become spread out into a ribbon formation where they bend over the weft yarns of the backing. The pile filaments are thereby individually exposed to the bonding agent so facilitating their rm anchorage in the ground cloth and the bonding agent is extended so that the required air and vapour permeabilities can be secured with a minimum weight of bonding material.

The vapour permeabilities of representative samples of caribou skin and of our improved pile fabrics have been measured in terms of their water-vapour transmission t perate clothing.

Table 2.-Caribou skins as used in clothing 12 the extreme outward fibres may be placed under considerable tension. The mechanical moment so inducedis proportional to the tensile stress multiplied by the thick- Y ness of the'material which becomes an appreciable factor O W in the utility of temperate clothing. Temperature and H2O Temperature and H2 vaatervapour Y vapour pressure on pour pressure on pile transmission The design prmc1 p1e employed m temperate dthmg back Y side 1s not, therefore, satlsfactory for polar reglon clothing as Y the restrictive forces increase as an appreciable power of C. mln-Hg C. mmHg gmsJhln/m.2 the thickness involved. If possible, the forces involved l0 should be relatively independent of the thickness and as o 29 9.6 63 should be a minimumyalue, well within the tolerance 24 25 13.8 22 levels 21 18.6 21 11.2 23 f 5 38.5 51 0 4.6 115 The foregoing criterlon 1s ach1eved in Esknno clothing 8 jg ge consisting of two caribou skinslworn back-to-back. ln 3s 5o -20 9.8 55 i5 this assembly only the two skins themselves oier resiste ance to bending and the distance between theextreme VTable 13E- Nylon pile fabrics Temperature and H2O Temperature and H2O Y vapour pressure on vapour pressure on vtggr Fabric type back pile 51de C. mm. Hg C. mm. Hg gms./hr./1:u.Z

Example n, wie" pue; 28.5 29 28.5 9.9 so rubberized 3s 50 3s 9.9 62 as -6 3.0 259 Example IV, pile Y not; rubberized, air permeability to 80 cu. fr. 38 50 0 4. 6 220 Example IYV, S/ pile; I 27 27 27 13.5 26 rubberized 3s 50 0 4. s 194 A Y l as 5o -19 1.o 202 Example V, is pile;

rubberized 38 50 -16 1. 15 293 Y Vltrwill be noted that vapour permeabilities for the nylon pile rfabrics given above all compare favourably with Ythose of caribou. The all nylon structure of Example V is particularly good in having a high water-vapour Y transmission rate and an extremely low air permeability Ydiners in'two main respects' from temperate clothing,

namely, in its greater thickness, and -in the occurrence of frost within the boundaries of the clothing.v l

The thickness .of Eskimo clothing is required Vto provide the necessary thermal insulation but the means by which the necessaryY thickness is achieved differs radically from the measures taken' for thepsame purpose, in ternin temperate clothing, the thickness determines to some extent the stiiness of the fabric and bresof these skins relative to the overall thickness of the insulation, is-comparatively small. On the outer side of the parka assembly, the hair olers no resistance to bend- K compressed thereby allowingvfreedom of movement to the joints without restriction. Y l Y s Notwithstandingthe desirable properties of caribou clothing, it is diiCult-tofremove frost from caribou hair without damage to the hide, since caribou guard hair therindividual has becomeaccustomedfto andtolerant of( Y Mbo where M bzbending moment,

' E=modulus of elasticity,

l=moment of inertia, Y Y C=radius of curvatureto which the neutral axis' is flexed.

While the forces at playfare relatively inconsequential in temperate clothing, they become appreciable when the thickness of the clothing approaches the order of two inches, as the magnitude of the moment of inertia' varies as the cube of the distance between the extreme fibres.

Although temperate clothing is usually` made up of at,

least vtwo layers, thereby diminishing the forces involved by slip between the layers, slip is most resisted where most required, namely, in the area of the joints, so that does not possess'the'grequisite tensile strength. FrostV revrnoval is, however, essential'r since thevmoisture exuded from the body is not 'all carried away by convection currents next to the wearers skin to escape by way of vari-Y ousopenings; much of this moisturepermeates the inner parka and this moisture eventually passes through theVV f inner parka .where it'reaches turbulent currentsV of air between thei inner and outer parkas.V When the wearer retires toY a sleeping bag at night after shedding his clothing, his `1parka freezes and the frost must be beaten out Y in the morning before it can be put on.L Nevertheless, the

assembly of caribou skins, back-to-back has, until now, provided body clothing of otherwise excellent characteristics, the back-to-back assembly serving to give more than mere freedom of movement. The improved pile fabrics of the invention'enable full advantage tobe taken of the known Eskimo type of backto-back assembly without the disadvantages hitherto attending the use ofcaribou skins, and enables other advantages tobe gained. Y Y Y Referring now to the accompanying drawings, as shawn in Figure 4, the body clothing consists of an upper inner parka 21 covering the head, arms'and torso and extending to about the crotch. The. head covering consists of an integral hood 22 'provided with a `narrow face opening which hood is fairly close-fitting, and particularly so around the face.l VInner pants 23 cover the body from the waist downwards (as shown in dotted lines in Figure 13 4) and extend approximately to the ankles. The skirt of the inner parka 21 is worn outside the inner pants 23. The parka 21 and pants 23 may conveniently be made from a pile fabric as set forth in Examples III, IV or V hereof and the pile should be turned towards the skin of the wearer.

The skirt of the parka 21, as well as the ends of the sleeves and the face-opening of the hood 22 are each trimmed with ruffs comprising a pile fabric as herein described and having a pile comparable with that of Wolverine fur or longer. Pile fabric as described in Examples Il, III, IV or V hereof but having a pile length of about 3 inches may conveniently be used for the ruifs 24, 2S and 26.

The outer garments of the body clothing are shown in Figure and are of a size larger than the inner garment so as to provide a loose t. They comprise an outer parka 27 covering the head, arms and torso and extending again to about the crotch. As in the inner parka, the head covering is integral with the parka 27 and is provided with a narrow face opening trimmed with a ruff 28 consisting, for example, of a pile fabric as set forth in Examples I, II, III, lV or V but having a pile length of the order of 4 inches. Outer pants 29 are also provided extending from the waist downwards terminating slightly below the top of muklliks 30 so as to provide a short portion which may be tucked inside the mukluks. The outer parka 27 and pants 29 may conveniently be made from a pile fabric as described in Examples III, IV or V hereof and the pile should be turned outwards as shown.

The clothing is completed by mitts 31 which may consist of back-to-back layers of the fabrics of Example III, IV or V or of a single layer of such pile fabric, pile outwards worn over due mitts and a foot covering consisting of felt insoles, due socks, dutlle Vamps all covered by the mukluks 30 which consist of a single layer, pile outwards of the pile fabric of Examples III, IV or V joined integrally with a flexible moccasin-like shoe portion 32 made, for example, of moosehide or other exible dry-tanned good quality leather -giving a good wearing surface.

The inner and outer garments should be relatively loosefitting to maintain an appreciable air space between the inner and outer garments. The inner and outer parkas, therefore, provide elongated bell-shaped insulation around the body with ventilation from the bottom or skirt controlled by the degree of activity of the wearer. Due to the difference in specific gravity between the warm air next to the body and the outside air, the warm air remains within the parka system in spite of the open bottom to the skirts. The back-to-back assembly produces a remarkably flexible body clothing with high insulating qualities and good frost-removal characteristics.

No inner and outer boundary layer of cloth is necessary in this system (no other clothing need be worn beneath the inner garments) and a low weight and a low apparent bulk of body clothing can thus be secured combined with high flexibility. lf insulating qualities and air and vapour permeability are maintained at the necessary levels, the most important considerations in polar clothing are bulk, flexibility and weight, and clothing as described with reference to Figures 4 and 5 satises all three criteria.

The marginal utility of men operating in the extreme cold of the polar regions is low under the best conditions. Hitherto, no textile fabric clothing has been devised which could be worn for long periods under polar climatic conditions approaching the utility of Eskimo clothing. Body clothing constructed as described with reference to Figures 4 and 5 has, however, been worn by Eskimos in the Arctic and has been declared by them to be as good as their traditional caribou clothing.

A number of field tests have been made in the Arctic with body clothing made from pile fabric according to Examples III, IV and V for various periods under various conditions of activity, and at exposures down to F. and with wind velocities up to 50 M. P. H. Representative results obtained with one subject over several days are set forth in Tables 4, 5 and 6 below.

Table 4 Dufle vamps. Canvas mukluks, with moosehide soles. Dufde mitts. Nylon pile mitts.

Date and Weather Activity Temperatures in clothing F.)

Comfort during Test 10 Feb. Clear with good visibility.

-29 F. Wind SE 16 M. P. H.

l1 Feb. 25 F.

and sunny.

Light wind. Clear 12 Feb. 12 F. Wind S. 16 M. P. H.

Clear. Y

15 Feb. -18 F. Wind N. 29 M. P. H.

lear sky. 16 Feb. 19 F. Wind N. 26 M. P. H.

Clear sky. Driving snow.

17 Feb. 43 F. Wind NW. 30

P.H. Drivingsnow.

19 Feb. ft2 F. Wind N.

Bright and Clear.

light.

20 Feb. 31 F. Wind light. Bright and clear.

Light exercise walking down and mto Wind over snow covered ice on lake.

Medium work. Shovelling hardpacked snow for 2% hours.

Hard work. Pulling heavily loaded sled over level but rough ice and snow surface.

Cross country walk over hilly country for 2 hrs.

Light exercise. Walking on airstrip.

Working at clearing snow around igloo.

Walk over hilly country to visit traplines, approx. 4 hours walk.

Pulled Sledge loaded to lbs. over rough snow for 5 miles. Tried to keep below sweating level.

(Thetmocouples outside pyjama tops): back of neck, 76; Left m-pit, 90; Back, 70; Stomach,

(Thermocouples outside pyjama tops): Back of neck, 83; Left 'im-pit, 93; Back, 76; Stomach,

(Thermocouples outside pyjama tops): Back of neck, 80; Left arm-pit, 85; Stomach, 63; Kidneys, 73.

Weather conditions prevented Thermocouple measurements. (Thermocouple harness over pyjama tops): Back of neck, 8 81; Left arm-pit, 89; Stomach,

68; Kidneys, S4.

N ot taken.

(Thermocouple harness next to body): Back of neck, 72; Left arm-pit, 92; Back, 92; Stomach,

(Thermocouple harness next to skin):.l3ack of neck, 77; Left am-prt, 94; Back, 87; Stomach,

Comfortable in general, but back cool. Hands and feet warm. Finger tips cool. Face cold when Walking into wind.

Comfortable. No draughts anywhere. Hands and feet warm.

Warm and sweating while working.

No draughts except when standmg waiting for T. C. measurements. Hands sweating.

Warm at all times. Hands and feet warm. Froze tip of nose.

Comfortable in rst part of exercise. Cool on second part. Fraz/.e side of nose.

Comfortable generally. Face cold. Eyelashes froze together at times. Feet warm. Hands wann except thumb where pile is compressed by shovel handle.

Comfortable walking. Hands and feet Warm. Nose froze 5 times during the walk. Body cooled rapidly when standing still at traps.

Very comfortable. Feet warm but sore because of ill-htting inscles. Hands too Warm. Hoar frost appeared on pile.

Vcool a little.

VIn these tests, skin temperatures were measured by way of copper-constantan thermocouples supported on an elastic harness. The couples terminated in a socket on Vthe clothing and could be connected, when required, to a Vplug joined by leads which extended into a warmed room housing the measuring equipment. Under Vthe conditions of the tests, the skin temperature measurements were not accurate to more than about 11 F. lsince it was difficult to `keep thermocouples in contact with the skin and the subject had to keep comparatively still While the measurements are made which inactivity allowed him to However, the figures show the general trend of the temperature under the clothes and are lower, not higher than the true skin temperatures. lIt is to be noted that certain of the temperature figures are for the thermocouples next to the skin and others are for thermo- V couples just outside the underclothing.

A typical experiment was as follows: The subject dressed after all his clothing had been weighed, first putting on the thermo'couple harness either next to his skin or over his underclothes. When completely dressed his total'weight was measured. He then performed some task, such as dragging a loaded sled from a known distance'. At the end of this work his skin temperatures were `measured and he was reweighed and his observations concernirig the clothing were recorded. "By these means, data were collected regarding the warmth of the clothing under various conditions (Table 4), the changes in weight from day to day (Tables 5A and 5B) and the overall change in weight during the tests (Table 6).

Table 5A.-Changes in weights of clothing during'test Subject: A

Date 10 Feb. 11 Feb. 12 Feb. 15 Feb. 16 Feb.

Garments (Weights in grams):

Inner and outer parkas.- 3, 000 3, 000 2, 950 2, 950 3, 075 Inner and outer punts 1, 920 l, 930 l, 910 l, 910 l, 9G() Pyjama tops.. 285 290 280 Iusoles Dule socks... 610 610 696 605 Dule Vamps.. s M ulluks 380 400 420 460 495 t$ 30o 335 33o Athletic suport 77 77 Balaclava 108 118 120 Man and Garments (in lbs. and ozs.):

Before test. 183/3 182/5 132/7 18H/11 After test; 183/3 182/5 181,/

Table 5B.-C'haftges in weights of clothing during test Subject: A (continued) Date 17 Feb. 19 Feb 20 Feb.

Garments (weights in grams):

Inner and outer parkas 3, 3,150 3, 1GO Inner and outer pants 1, S70 1, 965 1, 955 Pajama tops 290 Insoles Dutle socks 515 480 Dule vampsm. Kumiks 370 ldukluks Q i 395 4G() Duffle mrt z Pile mitts. 40 33" Balaclava Woolen gloves Man and Garments:

Before test 179/12 177/13 After test 179/13 177/2 aud demonstrate that polar clothing constructedy as de-v 16` Table 6 [Clothes were worn from February 8 to 21. They were then doffed and weighed. Later they were room dried and reweighed] The low airepermeability of the fabrics in accordance with the invention leads to outstanding uniformity of temperature within Vthe suiting; this fact was strikingly demonstrated during Vearly eld tests by one subject who woreV a suit of fabric according to Example IV butin which the rubber bonding agent Was inadvertently insufficient so giving rise to a highly permeable fabric. This observer was forced to take shelter after l5 minutes exposure; on the other hand a similar suit with fabric of the required air permeability Was very warm while walking at a wind chill of 2300 kg. Cals./ sq. m./hour, expressed in terms of the Wind -Chill Tables appearing rfor example in Measurements of dry atmospheric cooling in sub-freezing temperatures, by Siple and Passel, Pro-V ceedings of American Philosophical Society, vol. 89, No. 1, 1945. Y

From the above andotherfpractical tests we conclude thata pile Vfabric of the invention made into Eskimo type i clothing is adequate for survival under the worst conditions encountered. Under-somewhat milder conditions,-

the wearer would be able to .work in relative comfort even though the totalV Weight of the clothing is only aboutl 14 lbs.

Moisture accumulation in the clothing worn for long periods is not considered to be serious. The high water vapour permeability of the fabric was clearly shown by the collection of boar-frost on the outer pile hairs when the wearer was Vworking hard, pointing to the fact thatv a considerable amount of water vapour had passed completely through the Yfabric layers. y

It is necessary, of course, to give the clothing more care than is customary in normal, temperate region, life.

Thus, snow and frost should always be beaten out of j the garments and ice should be removed from the parka ruff after wear. If this is done, and the outer garment hung up to dry,.quite considerable drying can occur evenV` in the conditions inside a snow-house with a maximum air temperature of around +25 F.

The field tests have proved satisfactory in all respects scribed above of pile fabric of Examples Ill, IV and V with pile lengths ranging from 1A to inches provides the required thermal protection to the wearer with -mini imum bulk and stillness and combines thebest features of caribou With those of Wolverine and results in clothing which is superior in performance to any cold weather suiting yet devised. AV saving in weight of ten pounds has been achieved over non-native clothing of limited comparable performance with aremarkable improvement in exibility.

What we claim as our invention is:

1. Flexible, lightweight body clothing for wear in the polar regions comprising, an inner loosetittingY garment adapted to be worn adjacent the skin, and an outer similar garment of a size larger than said inner garment so as to provide a loose t when Worn over the inner garment, each of said garments being comprised of a flexible ground cloth of interlaced yarns and a pile surface having substantially smooth-surfaced articial filaments anchored in interlaced relationship thereto, said laments having a denier per filament Within the range of about l0 to 75 and being flexible at and retaining their strength at the sub-zero temperatures obtaining under polar conditions, and having a tensile strength per lament greater than about l.36 gms. per denier and exhibiting low moisture absorption at high relative humidities, said pile fabric having a structure modied from the original to provide pores to give to the fabric a low transmission rate less than substantially l0 cubic feet per square footh per minute at 1/2 inch Water pressure dierential, said inner garment having the pile surface on the body side and said outer garment having the pile surface on the outside.

2. Flexible, lightweight body clothing for Wear in thc polar regions comprising an inner leose-iitting garment having a bifurcated lower portion and a head covering adjacent the skin, and an outer garment having a bifurcated lower portion of a size larger than said inner garment so as to provide a loose t When Worn thereover, each of said inner and outer garments being formed of a textile pile fabric comprising a flexible ground cloth of interlaced yarns and a pile surface having substantially smooth-surfaced artiiicial iilaments anchored in interlaced relationship thereto, said laments having a denier per ilament Within the range of about l0 to 75 and being exible at and retaining their strength at the sub-zero temperatures obtaining under polar conditions and having a tensile strength per lament greater than about 1.36 gms. per denier and exhibiting low moisture absorption at high relative humidities, said pile fabric having a structure modiiied from the original to provide pores to give to the fabric a low transmission rate less than substantially l0 cubic feet per square foot per minute at 1/2 inch Water pressure differential, said inner garment having the pile surface on the body side and said outer garment having the pile surface on the outside, and the face opening of the head covering being trimmed with a ruit' formed of the said textile pile fabric, the free length of the pile of which is about three inches.

3. Flexible lightweight body clothing as claimed in claim 2 in which the said ruii is arranged on the inside and the outside of the inner garment at the said face opening.

References Cited in the tile of this patent UNlTED STATES EATENTS 2,438,933 Markin Apr. 6, 1948 2,642,571 Brown June 23, 1953 2,656,536 Cowie et al Oct. 27, 1953

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