High elastic modulus bandage

A high elastic modulus, cohesive bandage comprising partially extended spaced aligned elastic yarns sealed between two thin nonwoven fibrous webs by means of a polymeric binder is disclosed. The bandage provides joint support without imposing undue constriction. A method of supporting and/or providing compressive force to a mammalian limb including supporting suspensory ligaments and flexor tendons in the leg of a horse is also described.

DETAILED DESCRIPTION OF THE INVENTION 
As shown in FIG. 1, elastic yarns 10 from a beam 11 are unwound under 
tension controlled by driven press roll 12 and through comb 14. Thin 
non-woven fibrous webs 15 and 17, from supply drums 16 and 18, 
respectively, or directly from the forming machine, if desired, are 
brought into contact with the yarns and with each other between 
rubber-covered squeeze roll 19 and knurled steel squeeze roll 20, the 
latter dipping into a pan 21 containing a fluid binder mixture 22 and 
depositing the binder mixture throughout the web 17. The composite web 
passes directly into a drying oven 24 and thence between pull drums 25 and 
26. The web next passes around roll 27, between heating platens 28 and 29, 
around idler rolls 31 and surface winder roll 30, and is wound up to form 
stock roll 32. 
Squeeze rolls 19 and 20 rotate at a considerably greater surface speed than 
does beam 11, and the yarns 10 are accordingly stretched a corresponding 
amount. This stretch is maintained by operating pull drums 25 and 26 and 
turn-around drum 27 at approximately the same speed compared with rollers 
19 and 20. Surface winder roll 30 and wind-up drum 32, however, are again 
operated at a slower speed to permit shrinkage of the web as it passes 
between the heater platens 28 and 29. The composite web 34, which is 
smooth as it reaches the roll 27, becomes increasingly puckered or shirred 
as it passes through the heating zone, the result being further indicated 
in FIG. 2. 
The heat supplied by the platens 28 and 29 is sufficient to cause 
considerable fuming of the sheet material and to relax the structure 
sufficiently to permit the elastomeric yarns to retract and produce the 
desired degree of puckering or shirring as controlled by the speed of the 
surface winder roll. The temperature may be regulated by adjusting both 
the energy input to the platens and the distance between the platens and 
the web. In a typical installation for producing a finished web, the 
electrically heated platens are each 48 inches high, and are spaced 
between six and nine inches from the web. The platens are operated 
600.degree. F. at idle and 525.degree. F. when the web is running. The 
duration of the heat treatment may be regulated, for a given length of 
platen, by adjusting the speed of travel of the web, sufficient time being 
provided to permit retraction of the web to the desired degree. The 
platens are maintained at a temperature sufficient to keep the web taut 
during the shrinking operation between rolls 27 and 30 at the speed 
indicated but not so high as to cause deterioration of the web as 
evidenced by excessive fuming and discoloration thereof. The length of the 
relaxed web after retraction will be within the range of about one-third 
to about two-thirds the fully extended length. The elastic yarns are 
initially stretched to a length of about three to five times (and 
preferably three to three and one-half times) their fully relaxed length 
(the ratio of stretched length to relaxed length of the yarns is referred 
to as the draw ratio), and are permitted to relax only partially during 
the puckering step. Nevertheless, the shirred product is dimensionally 
stable, the heat treatment serving to provide an effective degree of 
heat-setting or stabilizing, and neither shrinks nor expands when allowed 
to stand at normal temperatures and under no external stress; and it 
returns to such dimensions when first stretched and then permitted to 
retract. 
The thin fibrous matts are conveniently prepared on a carding machine or on 
a "Rando-Webber" machine. Matts of polyester or rayon staple fibers or 
mixtures are preferred. The fibers are desirably of about 1.75 denier and 
about 1.5 inch in length, and the matt is about 0.25 to 0.50 oz./sq. yd. 
or about 5-10 lb. per 320 sq. yd. These very thin matts are fragile and 
flimsy, but show surprising strength when combined in composite structures 
of the type and in the manner hereinabove indicated. The matt as first 
formed is preferably reinforced by lightly treating it with a compatible 
bonding agent. As an example, the reinforced matt may consist of 75 parts 
by weight of polyester staple fibers and 25 parts of polyethyl acrylate, 
the latter being applied at the forming machine by saturating with a 
dilute emulsion of the polymer, removing the excess between squeeze rolls 
and drying in an oven. 
Concentrated natural rubber latex is preferred as the impregnating and 
bonding or unifying medium. Other elastomers or blends of elastomers 
having similar properties may be used. The dried rubbery residue, although 
presenting a slightly tacky feel, does not adhere to the skin, but 
cohesively bonds to itself with sufficient force to hold the contacting 
layers together against reasonably high shearing stresses. The 
impregnating and bonding materials may be used without further 
modification, but will ordinarily be blended with pigments or other visual 
modifiers. 
In an illustrative example, the yarns 10 are 700 denier spandex spaced 18 
ends per inch of width and each of the webs 15 and 17 consists of a 
polyester matt (0.3 oz/ yd..sup.2). Centrifuged natural rubber latex at 
61% concentration (available under the trade designation "GNL 200" from 
Goodyear Tire and Rubber Company) serves as the fluid binder mixture 22. 
In order to provide the desired elasticity, the spandex beam 11 is run at 
41% of the line speed (rolls 19 and 20). To help insure good lamination at 
the desired draw ratio, the oven 24 and rolls 25, 26 and 27 are 
over-speeded 13% relative to the line speed. In order to allow the web to 
relax in the shrink tunnel (platens 28 and 29), rolls 30 and 32 are run at 
45% of the line speed. The total draw ratio contributed by the tension of 
the elastic yarn on the beam and the further stretch resulting from the 
speed differential between beam 11 and rolls 19 and 20 is about 3.5. The 
resulting sheet material was slit into bandages 4 inches wide and 5 yards 
long (stretched dimensions). This material is referred to as Example 1 in 
the discussion below. 
In one preferred method of the invention, a bandage of the invention is 
applied to the front leg of a horse in a series of FIG. 8's extending 
below the fetlock joint as low as the coronary band, and above the fetlock 
joint as high as the knee. This provides support for the suspensory 
ligaments and flexor tendons, thereby reducing the potential for injury 
due to hyperextension of the fetlock joint. The bandage is applied at 
about 50% of its usable stretch. Most preferably, three layers of FIG. 8's 
are employed and vertical splints which comprise folded lengths of the 
bandage of the invention are inserted between the first and second and 
second and third layers of the applied bandage. The splints are placed 
over the posterior part of the leg directly over the tendon and ligament 
structure. 
The physical characteristics of the bandage of Example 1 of the invention 
were measured. The F.sub.n values measured as described below (except that 
three replicates instead of the stated five replicates were run) show that 
the bandage of Example 1 exhibits an F.sub.125 /F.sub.50 value of less 
than five. The bandages of the invention are seen to exert a useful 
compression force in the usable range of 25% to 100% elongation while 
still maintaining the ability to stretch an additional 50% while in use 
without exerting an unduly high compressive force which could constrict 
circulation and cause physical damage to a horse's leg. 
This performance has been borne out in university clinical trials and 
repeated field trials where horses, legs have been wrapped with the 
bandage of Example 1 by various trainers using varied techniques followed 
by normal race activity. The bandage has provided support without imposing 
undue constriction and has shown good durability during races. 
Specifically, when used at racing speed the bandage has been shown in some 
horses to reduce the drop of the fetlock joint, stabilize the stride and 
reduce distal limb vibration in the swing phase. 
It is contemplated that the bandage of the invention would have utility in 
other mammals in addition to horses. For example, it is anticipated it 
could be used as a compressive and/or support bandage on humans, 
particularly in the field of sports medicine. 
TENSILE AND ELONGATION MEASUREMENTS 
This procedure uses stress-strain tester "MTS-810" available from Materials 
Testing Systems, Minneapolis, Minn., to determine F.sub.n modulus values. 
The F.sub.n modulus value is the force required to elongate the test 
specimen a certain percent (n) from the unstretched length. The machine 
conditions were set at a gauge length of 50 mm, a crosshead speed of 50 
inches/min. Data was collected with a digital oscilloscope utilizing a 
twelve-second total sampling period. A 1" wide by 8" long sample was razor 
cut from a bandage. In order to minimize the incidence of jaw breaks, 
masking tape tabs were applied so that one tab was located in each jaw of 
the apparatus. The sample was clamped between the jaws, the crosshead was 
started and the stress plot was recorded, the F.sub.n values were 
calculated from the stress plot and the F.sub.125 /F.sub.50 ratios were 
calculated. The F.sub.125 and F.sub.50 values used in computing F.sub.125 
/F.sub.50 values recited in the claims are the average of five independent 
determinations. This procedure is derived from ASTM D 882-80a, 
incorporated herein by reference.