Underpad for incontinent patients

An absorbent underpad for use on an article of bedding includes a liquid impervious backing sheet, a liquid permeable upper facing sheet adhered to the backing sheet about the edges thereof, and an interior absorbent pad combination comprising upper and lower tissue layers generally coextensive with the boundarees of the underpad, a pair of spatially separated barrier strips formed of super-absorbent material between the tissue layers, and a non-woven transfer layer along the central region of the upper tissue layer adjacent the upper facing sheet. The plies of the tissue layer are formed with a crepe-like irregular surface oriented to develop a wicking action directed along the layers in a transverse direction, toward the absorbent barrier strips.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to absorbent pads and, more particularly, to such 
pads which are designed for protecting bedding against soiling by 
incontinent patients, principally for use on beds in hospitals, nursing 
homes and the like. 
2. Description of the Related Art 
Various approaches to solving the problem of protecting bedding from 
incontinent patients are known in the prior art. For example, rubber 
sheets have been used, usually placed over a mattress and underneath the 
lower cloth sheet on a bed. While they serve the primary purpose of 
protecting the mattress, they are extremely uncomfortable for the patient. 
Hospital underpads have been developed as a preferable alternative to the 
rubber sheet. Since these underpads are more comfortable for the patient 
to lie on in direct contact with, they are placed on top of the lower 
sheet, thereby protecting it as well as the mattress. One type of hospital 
underpad which has long been on the market comprises a plurality of soft, 
fibrous tissue layers backed by a soft, waterproof polyethylene backing 
layer. The four edges of the backing layer are turned and/or sealed. The 
absorbent tissue layers are uniform and lump free, and provide maximum 
absorbency and dispersion of liquid. Runoff or leakage is prevented by 
virtue of the sealed edges. Instead of the fibrous tissue layers, some 
underpads are formed of packed tissue or fluffed wood pulp. These hospital 
underpads are provided in appropriate sizes to cover the vulnerable area 
underneath the patient and are available in individual packs for ease of 
stocking and handling. 
The turned edges of the hospital underpads just described present an upper 
surface of polyethylene or polypropylene backing which frequently comes in 
contact with the patient's skin where it can create "hot spots" or cause 
skin breakdown, resulting in bedsores which sometimes lead to a type of 
cancer. Bedsores are a serious problem with longer term bedridden 
patients, particularly the elderly. Statistics on the subject indicate 
that some 30,000 patients die of complications from bedsores every year. 
The problems are exacerbated with underpads that do not have the liquid 
absorbent capacity needed for comfort or which are not changed often 
enough. 
Some of these hospital underpads are equipped with adhesive strips of 
pressure-sensitive tape or plastic melt or the like on the exposed surface 
of the backing layer in order to hold the underpad in place underneath the 
patient without bunching up or displacement from the desired position of 
maximum effectiveness. In some examples of the prior art, the bottommost 
absorbent layer is adhesively laminated to the impervious backing sheet. 
In an effort to improve the absorbent capability of hospital underpads, 
variations have been developed in which wood pulp is interspersed with the 
soft fibrous tissue layers. Sometimes, a super-absorbent powder is mixed 
with the wood pulp in homogeneous distribution within the pad. 
Unfortunately, if such pads are left with a patient too long, the filling 
with liquid develops a slimy combination of the wood pulp, super-absorbent 
powder and urine that is particularly likely to cause skin breakdown if 
left in contact with the patient's body. Thus such arrangements, even 
though more absorbent, still do not provide a completely satisfactory 
answer to the problem of developing an absorbent underpad for incontinent 
patients. It is desirable, therefore, to provide a novel construction for 
hospital underpads which increases the absorbent capacity of the product 
to a significant extent over that of presently known absorbent underpads. 
SUMMARY OF THE INVENTION 
In brief, arrangements in accordance with the present invention provide an 
absorbent underpad for use on beds in hospitals, nursing homes, and the 
like which develops an improved capability for liquid absorption by virtue 
of its novel structural configuration as well as its use of particular 
absorbent materials. The underpad basically comprises an uppermost layer, 
a bottom or backing layer and a plurality of intermediate layers to 
establish the liquid absorbent capability of the pad. In one preferred 
embodiment, the backing layer is a thin sheet of impervious polypropylene 
plastic, as is the case with presently known underpads. However, the edges 
are not folded over on top of the uppermost layer of the pad but instead 
are adhered along the underside of the uppermost layer by separate narrow 
lines of glue extending along the two side edges of the pad between the 
two outermost layers. 
The upper layer of the underpad is a porous layer, permeable to liquid, of 
open weave, spun-bonded sheet, hydrophobic material, preferably of 
polypropylene facing. Directly underneath that is a transfer layer of 
non-woven polyester hydrophilic material which allows liquid to pass 
through readily into the inner layers of the pad but impedes any passage 
of the liquid in the opposite direction. Next, along the inner side of the 
transfer layer, is an upper layer of tissue. The upper surface of the 
transfer layer, being next to the uppermost layer, tends to draw liquid 
through the open weave. However, the lower surface of the transfer layer, 
being next to the upper tissue layer, does not exhibit the same tendency, 
thus accounting for the directional transfer of liquid therethrough. 
The upper tissue layer comprises a plurality of plies of thin, soft, 
fibrous tissue which are formed together to constitute the upper absorbent 
tissue layer next to the transfer layer. This combination of the one-way 
liquid passage effected by the transfer layer and the absorbency of the 
adjacent tissue layer achieves the very beneficial result that the pad 
develops a feeling of dryness along its upper surface, even though it may 
have only recently been wet. 
Beneath the upper tissue layer and extending lengthwise of the underpad is, 
preferably, a pair of spatially separated strips of laminated 
super-absorbent polymer powder material. These laminated strips, 
preferably about 2" wide and extending virtually the full length of the 
pad, serve as barriers to any liquid which passes by capillary action 
outward from the central region of the pad or inward from the side edge of 
the pad and complete the absorption of the liquid in the side areas of the 
pad which are generally outside the region where the patient's body rests. 
On the underside of these barrier strips is a lower tissue layer, 
essentially identical to the upper tissue layer. 
The upper and lower tissue layers are formed of as many as ten plies of 
highly absorbent tissue, fabricated with a crepe construction which is 
aligned transversely of the pad to establish a preferential direction for 
the capillary action for liquid which is absorbed within the tissue 
layers. Together with the barrier strips between them, the upper and lower 
tissue layers form a sort of sandwich. The combination of the transversely 
directed wicking action in conjunction with the super-absorbent barrier 
strips along the sides of the pad serves to direct the liquid away from 
the central region of the pad, the area where the patient's body is most 
likely situated, to near the edges where the liquid is absorbed. Thus the 
central region of the pad is kept reasonably dry, even though the pad may 
have a substantial amount of liquid within it, and so enhancing the 
comfort of the patient who is lying on the pad and within the bed. As an 
added aspect of comfort to the patient, the removal of liquid from the 
center makes the upper facing layer feel dry to the touch. 
The barrier strips are of laminated absorbent material, comprising upper 
and lower thin layers of absorbent tissue with super-absorbent powder 
distributed in a generally random fashion between them. These barrier 
strips are available commercially from Gelock, Inc., Pine Lake Industrial 
Park, Dunbridge, Ohio 43414. 
Absorbent underpads of the type involved in the present invention are 
commonly made in a range of sizes which may be 17-1/2.times.24", 
23.times.24" or 23.times.36". In one particular embodiment of an underpad 
in accordance with the present invention, the pad is approximately 
291/2"square. About 1/2" in from each side edge of the pad is a glue line 
extending the length of the pad, sometimes referred to as the "machine 
direction", which adheres the side edges of the pad together between the 
upper spun-bonded permeable sheet and the lower polypropylene plastic 
impervious backing layer. The internal components of the pad--the upper 
and lower tissue layers with the side barrier strips which make up the 
sandwich construction to direct the liquid flow within the pad--are 
closely contiguous to the side edge glue lines but terminate short of the 
top and bottom edges of the pad by about 21/2" on each upper and lower 
edge. The tissue layers extend to within approximately 1/2" of the side 
edges while the intermediate barrier strips are spaced about three or four 
inches therefrom. This arrangement provides a region where the external 
surface layers are loosely and somewhat intermittently adhered together 
with sufficient space in the inner pad region to provide some leeway at 
the ends for the cutting blade as it separates the individual pads during 
fabrication. It will be understood that the pads are formed from rolls of 
the respective layer elements on a production line. 
The upper, or inner, surface of the polypropylene backing layer is sticky, 
and this is effective to accomplish the adherence of the upper spun-bonded 
facing layer to the polypropylene backing layer at the longitudinal ends 
of the pad where these two layers come in contact. The stickiness of the 
inner surface of the polypropylene backing layer is accomplished by 
spraying glue fibers on the upper surface of the backing sheet at 
intervals along the production line corresponding to the interpad area 
where the slitting will occur. There is a slight overlap of the sticky 
surface with the location of the tissue layers within the pad so that the 
ends of the bottom tissue ply also adhere to the surface, thereby serving 
to hold the internal components of the pad in position. 
In a second preferred embodiment of the invention, the impervious backing 
layer is replaced by a non-woven, spun-bonded sheet which has a certain 
degree of porosity. In both embodiments, the upper facing layer comprise 
1/2 ounce spun-bonded material which is sprayed with a surfactant that 
facilitates the passage of liquid therethrough. The backing layer of the 
second embodiment, however, is formed of heavier 11/4 ounce spun-bonded 
material without the surfactant treatment. This is almost impervious to 
water but is permeable to air. The second embodiment of my invention finds 
particular application in use with air beds, such as are used for burn 
victims, patients with ulcerated skin, etc. These air beds have a core of 
beads or sand which permit air at a slightly elevated pressure to flow 
through them from the bottom up, thereby assisting in drying the skin. The 
porosity of the heavier non-woven backing layer without any surfactant 
treatment is such that the pressurized air passes through, but only the 
slightest bit of moisture can penetrate the backing layer from the upper 
side. This serves to prevent any "strike through" of moisture from the pad 
to the bed. This embodiment is typically slightly longer than the first 
embodiment described hereinabove. Dimensions of this underpad are 
preferably 291/2 " wide by 351/2" long with the lengths of the individual 
components of the underpad being adjusted accordingly. 
During assembly of the constituent components of the underpad as it 
proceeds along the production line, the interior laminations of the upper 
and lower tissue layers with the side strip barriers between them are 
loosely secured together by longitudinal lines of pressure bond stitching 
spaced approximately two to four inches apart. As is known in the art, 
this pressure bond stitching is formed by running a serrated wheel under 
load along the tissue layers, thus penetrating and compressing them 
sufficiently to create the lines of pressure bonds. 
The transfer layer is approximately as long as the tissue layer sandwich 
but is somewhat narrower, being located along the center of the pad, 
generally equidistant from the side edges. The width of the transfer layer 
is sufficient to overlap and cover the side barrier strips. In the 
particular 291/2" square embodiment of the invention referred to 
hereinabove, the transfer layer is approximately 171/2" wide and the side 
barrier strips are about 2" wide and spaced about 6" from the side edges, 
leaving a space between the strips of about 131/2".

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
As shown on FIG. 1, a conventional hospital underpad 10 of the prior art is 
positioned for use on the lower sheet 12 of a hospital bed 14. The 
underpad 10 comprises an absorbent central area 16 with sealed 
longitudinal edges 18 and lateral edges 20 which are formed by folding 
over the backing layer and sealing it along the upper edge surface of the 
upper sheet. This may be considered to exemplify the prior art, such as 
that which is the subject of the O'Connell patent 4,097,943. 
The preferred embodiments of the present invention, as best shown in the 
schematic views of FIG. 2 (a partially broken away plan view) and FIG. 3 
(an exploded view) show an underpad 100 comprising a backing layer 102 and 
an upper layer 104 between which are a transfer layer 106, an upper tissue 
layer 108, and a lower tissue layer 110, the tissue layers being separated 
by a pair of spaced-apart absorbent strips 112. The arrow 114 indicates 
the longitudinal direction of the underpad 100. The cross hatching and 
other marking on the respective components in FIG. 2 is not intended to 
indicate any particular construction but is merely to emphasize the 
different individual components. 
The upper spun-bonded sheet 104 is sufficiently open as to appear partially 
transparent, at least to the extent that the outline of the upper tissue 
layer 108 is discernible through it, particularly against the darker 
background of the blue polyethylene backing sheet 102 (see FIG. 2). The 
upper and lower sheets 102, 104 are secured together along the side edges 
120, 122 by lines of glue 124, 126 and, at the top and bottom ends 121, 
123, by the stickiness of the glue fibers sprayed on the inner surface of 
the backing layer 102 in the end regions 126, 128. The regions of sprayed 
glue fibers generally extend in the areas 126A and 128A, thereby providing 
a slight overlap with the tissue layers 108, 110 with the result that the 
lower tissue layer 110 adheres to the backing layer 102. 
The transfer sheet 106 is shown in the breakaway view of FIG. 2 as being 
immediately beneath the upper facing sheet 104. The breakaway at line A 
corresponds to a peeling away of the upper facing sheet 104, thereby 
exposing the transfer sheet 106 overlying the upper tissue layer 108. The 
breakaway at line B corresponds to the peeling away of the transfer sheet 
106 and the upper tissue layer 108 in the corner of the pad below the line 
B. This displays one of the barrier strips 112 having an overlap with the 
transfer sheet 106 (shown between lines A and B). The lower tissue layer 
110 is shown below the barrier strip 112. An optional second barrier strip 
112A is indicated by broken line outline alongside the strip 112. The 
relative juxtaposition of the respective elements making up an underpad 
100 may be clarified by reference to the end sectional view of FIG. 4. 
The crepe construction of the tissue layers 108, 110 is represented in the 
enlarged schematic view of FIG. 5. This shows a portion 130 of one of the 
plies of the tissue layer 108 or 110 having an irregular, crepe-like 
surface with numerous surface irregularities 132 in the form of 
embossments and depressions. These are generally aligned in the transverse 
direction and are created by running the individual tissue plies in the 
transverse direction over a doctor blade configured to develop the crepe 
irregularities 132 of FIG. 5. As a consequence of this surface 
configuration, moisture which is absorbed in the tissue layers is directed 
by capillary action to migrate in the transverse direction of the pad 100 
toward a barrier strip 112. Since the superabsorbent barrier strip readily 
soaks up any moisture which reaches it through the tissue layers 108, 110, 
a gradient wicking action in the tissue layers channels the liquid in the 
transverse direction toward the barrier strip 112 associated therewith. 
The construction of a barrier strip 112 is illustrated schematically in 
FIG. 6. As shown therein, the strip 112 comprises an upper layer 140 and a 
lower layer 142 which carry between them, generally randomly distributed 
throughout, a plurality of clumps 144 of super-absorbent powder. The 
strips 140, 142 with the powder between them are pressed together so as to 
serve as a carrier for the super-absorbent powder. Because of this 
structural configuration, the strips 112 effectively serve as a barrier to 
any liquid against passing a strip 112, at least until the strip 112 is 
fully saturated. 
The second preferred embodiment of my invention as described hereinabove 
may be represented by the same drawing FIGS. 1-5 used to show the first 
embodiment, since the appearance as depicted is essentially the same. The 
difference resides in the backing layer 102 which for the second 
embodiment is designated 160. Instead of being impervious polypropylene as 
in the first embodiment, the backing layer is a heavier sheet of 
spun-bonded material, untreated with a surfactant such as that used in the 
upper facing sheet 104, which is permeable to air at an elevated pressure 
but resistant to the transfer of water. This finds application on air beds 
for burn patients, the elderly, etc. 
Arrangements in accordance with the present invention are capable of 
absorbing a substantial quantity of liquid while still feeling dry to the 
touch and thus provide an effective underpad for the stated purpose. These 
pads have been found to be more effective than those which are known 
heretofore. A quantity of water equal to the contents of two coffee cups 
may be poured into the center of one of these pads and it will be totally 
absorbed within a very short time, leaving the surface of the upper facing 
layer essentially dry to the touch. This high liquid absorption capability 
is the result of the materials used, the components employed in the pad 
and the structural configuration of the respective elements. 
This is a considerable improvement over pads over which use wood fiber 
fluff as the absorbent material, even when it is mixed with 
super-absorbent powder. In the fluff pads, the fibers are not connected 
and the water tends to puddle, sometimes interacting with the 
super-absorbent powder to develop a slime along the surface of the pad. 
The laminated barrier strips of the present pads prevent the water from 
going through, thereby eliminating the likelihood of hydraulic pressure 
from weight of the patient's body on the absorbent material forcing liquid 
through the backing layer to contaminate the air bed with which it is 
used. 
Although there have been described hereinabove various specific 
arrangements of an underpad for incontinent patients in accordance with 
the invention for the purpose of illustrating the manner in which the 
invention may be used to advantage, it will be appreciated that the 
invention is not limited thereto. Accordingly, any and all modifications, 
variations or equivalent arrangements which may occur to those skilled in 
the art should be considered to be within the scope of the invention as 
defined in the annexed claims.