Title:
Disposable surgical mask
United States Patent 3884227


Abstract:
This improvement in surgical masks provides a tissue barrier layer or ply between the filter and the inner ply facing of a disposable surgical mask for the purpose of stopping spicules from the filter from working their way through the inner facing ply, and to add some stiffness to the mask so that the mask has less tendency to collapse when the wearer inhales. The barrier tissue adds wet strength to the mask for protection against breakdown of the non-woven inner ply when moistened by the breadth of the wearer; and the added stiffness provided by the barrier ply also reduces the flexing of the filter which causes increase in the number of spicules which become detached from the filter.



Inventors:
Lutz, William A. (Rumson, NJ)
Zipf III, Frederick W. (Rumson, NJ)
Application Number:
05/327311
Publication Date:
05/20/1975
Filing Date:
01/29/1973
Assignee:
BLESSINGS PRODUCTS, INCORPORATED
Primary Class:
International Classes:
A41D13/11; (IPC1-7): A61M15/00
Field of Search:
128/146
View Patent Images:
US Patent References:
3664335SURGICAL FACE MASK1972-05-23Boucher
3613678FILTRATION MASK1971-10-19Mayhew
3603315SURGICAL FACE MASK1971-09-07Becker



Primary Examiner:
Gaudet, Richard A.
Assistant Examiner:
Recla, Henry J.
Attorney, Agent or Firm:
Sandoe, Hopgood & Calimafde
Claims:
What is claimed is

1. A disposable surgical mask comprising pleated plies of sheet material with the pleats extending across the face of the mask, binding covering the pleats at their ends, stitching through the binding and pleated material securing the pleats closed at the ends of the mask, the plies including inner and outer facings for the mask, a ply of filter material behind the front facing, the filter being made of material from which spicules of the filter become loosened during use of the mask, and a ply of barrier material between the filter and the inner facing of a porosity that stops spiclues of the filter from reaching the inner facing during use of the mask, and the barrier ply being made of tissue paper having a porosity of from 200 to 800 cu. ft./min (Gurley Permometer), a basis weight between 7 and 10 lbs./2880 sq. ft. and comprising at least 50% long fiber, and a wet strength of about 580 (machine direction) and 200 (cross direction) gms./inch.

2. The disposable surgical mask described in claim 1 characterized by the porosity being between 400 and 600 cu.ft./min.

3. The disposable surgical mask described in claim 1 characterized by the pleats extending horizontally across the mask and having overlaps that unfold to increase the vertical width of the mask at its mid section more than between 50 and 100% of the vertical width when the pleats are folded, and all of the plies being in contact with one another and similarly pleated.

4. The disposable surgical mask described in claim 3 characterized by the barrier coat being made of tissue paper having a porosity between 400 and 600 cu.ft/min. and a wet strength above 290 (machine direction) and 100 (cross direction) grams/inch, and having a basis weight of 7 to 10 lbs/2880 sq. ft.

5. The disposable surgical mask described in claim 1 characterized by the barrier ply being made of tissue paper that has greater stiffness than either the inner or the outer facing and providing added stiffness to the mask to hold the mid portion of the mask away from a wearer's face when the pleats are open and the mask is being worn.

6. The disposable surgical mask described in claim 1 characterized by the barrier ply being made of tissue paper that has greater wet strength than the inner facing to prevent wet-out of the mask by the breadth of the wearer.

7. The disposable surgical mask described in claim 1 characterized by the barrier ply being made of tissue paper that lies against the filter and that stiffens the mask so that the filter is reinforced against excessive flexing and thereby to reduce breakage of portions of the filter material with resulting increase in the number of spicules from the filter.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION

The typical disposable surgical mask is composed of three basic parts: inner and outer facings of non-woven fabrics or similar material between which is sandwiched the filter media of micro-fibre glass. To these, of course, the various bindings, ties, etc. are attached to form the mask.

The micro-fibre glass media can and does cause irritation to the face of the wearer as a result of the abrading action of tiny spicules of glass working their way through the inner facing of the mask. While the irritation is superficial and transitory, it is a serious annoyance to all users of micro glass filter masks, and the same could be true of masks using other fibres for the filter.

None of the commonly used inner facing materials offer adequate protection against glass strike-thru. The mask of this invention uses a fourth ply or barrier between the inner facing and the filter media. A tissue with certain characteristics best meets the needs.

The barrier must be light in weight so as not to add noticeably to the weight of the mask. It has to be strong enough to resist the penetration of the glass spicules and to have a density and porosity suitable for this purpose. The barrier ply must, however, have high enough porosity so that breathability of the mask is not noticeably diminished and it must have a wet strength that resists breakdown from moisture resulting from the breath of the wearer.

Other objects, features and advantages of the invention will appear or be pointed out as the description proceeds.

BRIEF DESCRIPTION OF DRAWING

In the drawing, forming a part hereof, in which like reference characters indicate corresponding parts in all the views:

FIG. 1 is a front view, partly broken away and in section, of a surgical mask made in accordance with this invention;

FIG. 2 is a sectional view taken on the line 2--2 of FIG. 1;

FIG. 3 is a view showing the mask of FIG. 1 with the pleats extended as they are when the mask is worn by a user of the mask; and

FIG. 4 is a greatly enlarged sectional view taken on the line 4--4 of FIG. 1.

DESCRIPTION OF PREFERRED EMBODIMENT

FIG. 1 shows a surgical mask 10 which is formed of four plies of material. The first ply is an outer facing 12, preferably formed of non-woven fabric. The second ply is a filter 14 made of micro-fibre glass.

The third ply is a barrier tissue 16 for preventing spicules of glass from the filter 14 from reaching an inner facing 18 which comprises the fourth ply of the mask.

The plies 12-18 are secured together at their top edges 20 by binding 22 which is folded over the top edges 20; and the binding 22 is secured to the plies 12-18 by stitching 24. This stitching also holds the plies 12-18 together at their upper ends. A similar binding 22 with stitching 24' is applied bottom edge of the mask 10.

When the mask is in its folded or flat condition, all of the plies 12-18 lie against one another and they are pleated as shown in FIG. 2. Because of the scale of the drawing in FIG. 2 it is not practical to attempt to show the individual plies; and the assembly of the plies 12-18 is indicated in FIGS. 2 and 3 by the reference character 28. FIG. 2 shows the way in which the assembly of plies 28 is pleated to form pleats 32 and 34.

Referring again to FIG. 1 there is binding 36 folded over both the right hand and left hand edges of the plies 12-18; and this binding is secured to the plies 12-18 by stitching 38. This stitching 38 holds the plies with the pleats 32 and 34 folded along both sides of the mask. The pleats can be opened up and the assembled plies 28 form into an arch at the center portion of the mask. This arch flattens out toward both sides of the mask but provides an arched center for space ahead of the wearer's nose and to keep the mid portion of the mask out of contact with the wearer's face. In accordance with conventional practice, there is a maleable metal strip 42 adhered to the front facing of the assembled plies 28. This metal strip is bent down manually around the wearer's nose to cause the top of the mask to conform to the contour of the wearer's face, thereby preventing the formation of large gaps between the top of the mask and the wearer's face on opposite side of the wearer's nose. At the bottom of the mask, the binding 22' will lie close to and in contact with the wearer's chin and cheeks when the bottom edge of the mask is pulled against the wearer's face by straps 44 which are extensions of the binding 36. The upper part of the mask is held against the wearer's face by other straps 46 which are also extensions of the binding 36. This construction is conventional and no further description of it is necessary for a complete understanding of this invention.

FIG. 4 shows the assembled plies 28 on a greatly enlarged scale so that the individual plies can be shown in section. The outer facing 12 and the inner facing 18 of the mask are preferably made of non-woven material such as cellulose with a porosity of at least 200, and preferably approximately 500 cubic feet or more per minute per square foot (Gurley peromometer). The preferred embodiment of the invention has the outer facing 12 and the inner facing 18 made of cellulosic non-woven fibers held together with a binder.

The filter 14 is of conventional construction. Such filter medium is made exclusively from preselected and wet cleaned Vinyon and microglass fibers with less than 1.2% by weight of non-allergenic latex binder. These filters contain no cellulose or other natural materials. Typical properties are coverage - 98 square feet per pound; thickness - 0.0085 inch at 7 - 9 pounds per square inch (Tappi method); tensile strength - machine direction, 225 grams per inch, cross-machine direction - 150 grams per inch; permeability - 60 cubic feet per minute per square foot at 0.5 inches water; filtration efficiency - 95% minimum in accordance with military specification M-36431B. These specifications are given merely by way of illustration.

Glass filters are almost universally used for disposable surgical masks even though those glass filters have the objection that spicules of glass become detached from the filter media and penetrates through the inner facing of the mask so that they contact with and irritate the skin on the face of the person wearing the mask. In spite of the irritating effect caused by the glass fiber filter media in disposable masks, the extremely effective filtering obtained from such glass fiber masks is so much better than any other inexpensive filter medium known at the present time that glass filters continue to be used in spite of the objection to them caused by the breaking off of spicules of glass.

Glass fiber filter media for face masks are available from C. H. Dexter Co., Windsor Locks, Conn.; and Strathmore Paper Co., Westfield, Mass.

This invention is not limited to masks made with the particular glass filter media described above, but can be used with any mask which has a glass fiber filter media which presents the same problem of glass spicules penetrating an inner facing that contacts with the face of the person wearing the mask.

The barrier tissue 16 is made of a special tissue which is commonly referred to in the trade as "tea bag paper". This paper is extremely light in weight; as low as seven pounds in basis weight, one commercial grade is 7.25 pounds per 2,880 square feet. The light weight is obtained without sacrifice of strength by making the paper with long fibers. The length of fibers is preferably approximately 5 to 6 millimeters and in any event more than 4 millimeters. These long fibers add greatly to the strength of the paper and lighter paper can be obtained by using hemp fibers. The paper used for the barrier layer 16 is preferably made with at least 50% of its long fibers in excess of approximately four millimeters.

Tests show that such paper with long fibers has a strength about twice as great as paper with short fibers. This strength is important in preventing the glass spicules from working their way through the barrier ply 16.

The porosity of the barrier layer 16 should not be less than 200 cubic per minute per square foot since lower porosity reduces the breathability of the overall mask to an unacceptable limit. This porosity is necessary in order to offset the relatively low porosity of the glass fiber filter which is ordinarily only about 60 cubic feet per minute per square foot. The preferred embodiment of the invention uses a barrier sheet 16 having a porosity of approximately 550 cubic feet per minute per square foot.

In the preferred construction the strength of the paper used for the barrier ply 16, by virtue of its long fibers, has approximately twice the strength of wood pulp paper of the same weight, and a maximum porosity of about 800.

The paper used for the barrier ply 16 is a paper that is ordinarily made with raw manila hemp which has a fiber length about twice that of wood fiber normally used in paper making. As previously explained, it is the fiber length that gives the unusually high strength to weight ratio and a porosity of the paper used for the barrier ply 16. The fibers of this paper are usually combined with a resin such as poly-amide for wet strength and binding. It is possible to use heat sealable fibers and resins in the sheet, but experiments indicate that this is not desirable for the face mask barrier tissue 16.

Other fibers than manila hemp can be used in the construction of the paper, such as rayon or sisal fibers, either separately or in combination with each other and with hemp, and some short fiber can be used, but the long fiber content of the paper should not be less than 50%.

"Tea bag paper" suitable for the barrier ply 16 can be purchased from the C. H. Dexter Co., Windsor Locks, Conn., and also from Peter J. Schwitzer, Division of Kimberly-Clark Corporation, New York City, N.Y.

When a mask is worn for an extended period of time, the inner facing 18 becomes soaked with moisture caused by the exhaling of the wearer of the mask. This moisture accumulation, when it becomes excessive, causes the inner facing 18 to "wet-out". This expression is used to designate a condition in which air can no longer pass through the inner facing and with the result that the inner facing will pull apart unless there are adequate areas of dry facing 18 beyond the wetted area to permit ready passage of air each time the wearer exhales.

The barrier ply 16, being made of tissue paper, instead of non-woven fabric, is somewhat stiffer than the non-woven fabric of the inner facing 18 and thus adds stiffness to the ply assembly so that it will remain in an arched condition, as shown in FIG. 3, more effectively and thus maintain the arch holding it away from the wearer's face even though the breathability of the mask becomes somewhat impaired after extended use and as a result of moisture accumulation on the plies.

It is not satisfactory to omit the inner facing ply 18 and let the barrier tissue 16 contact with the face of the wearer of the mask. The barrier tissue 16 is much rougher than the non-woven inner facing 18 so that the omission of the inner facing 18 makes the mask uncomfortable to wear.

The use of the combination of the barrier ply 16 with the inner facing 18 seems to make the mask of this invention more effective in stopping glass spicules. Experiments made with a plurality of layers of non-woven facing material 18 did not effectively stop glass spicules from working through the mask and contacting with the face of the wearer. Other experiments with the inner facing ply 18 next to the glass fiber filter 14 and with the barrier tissue 16 on the inside surface of the mask effectively stopped the glass spicules but such a construction is unsatisfactory because of the roughness of the barrier tissue 16 as compared to the inner non-woven material of the inner facing 18. The construction as shown in FIG. 4 is, therefore, the most effective and at the same time the most comfortable construction for the mask.

The barrier tissue has a basis weight between 6.75 and 7.75 lbs. per 2880 sq. ft. and preferably about 7.25 lbs. per 2880 sq. ft. Porosity has been described above. Tensile strength is preferably about as follows:

Dry oz./in. Machine direction 2825 Cross direction 970 Wet Machine direction 580 Cross direction 200

The lower limit for both dry and wet strength is not less than 60% of these preferred values.

Tests made on the mask of this invention indicate that air for inhaling and exhaling by someone wearing the mask of this invention, passes through the mask more easily with the barrier layer in the mask than without it (all other structure being the same). Applicant has not yet discovered the reason for this phenomena.

The preferred embodiment of this invention has been illustrated and described but changes and modifications can be made and some features can be used in different combinations without departing from the invention as defined in the claims.