CA1287279C - Nonwoven screen for odorless animal litter unit - Google Patents

Abstract

ABSTRACT OF THE INVENTION
The combination of a sorbent pad laminate and a litter device for the collection of animal urine having a bottom sheet layer of moisture impermeable material, overlying the base of the device, an intermediate sorbent layer of material having a high sorbency capacity for urine and a top claw resistant screen means. The bottom sheet layer and top screen means are bonded to each other along at least a substantial portion of the periphery of the screen means. The screen means is a urine permeable, flexible member of nonwoven material which is substantially inert to urine, formed of strands randomly fused together at their intersections and having sufficient tear strength to withstand the clawing action of a cat.

Description

1~3727~

1 NONWOVEN SCREEN FOR O~ORLESS ANIMAL LITTER UNIT

3 Technical Field 4 This invention relates to improvements in the rip proof screen for an odor preventing, disposable, sorbent pad-liner for an animal 6 litter unit, and more particularly to a non-woven screen for use in 7 combination with a sorbent padding, a liquid impermeable liner, a lit-8 ter container and litter.
9 Brief Description of the Prior Art Many domestic animals frequently use litter boxes for the 11 elimination of body wastes. The boxes are usually filled with various 12 kinds of sorbent granular materials such as sand, cat litter and the 13 like, and must be periodically emptied and cleaned, which are somewhat 14 objectionable tasks, since the sorbent granular material must be re-placed and the boxes cleaned each time.
16 Cats, the most frequent users of litter boxes, present a urther 17 problem in that the urine of the feline has the most severe tendency 18 to produce a pervasive odor problem. Apparently, cat urine contains 19 the highest content of urea which, when allowed to stand for any length of time in any litter material, releases an ammonia odor. In 21 any event it is the odor associated with cat urine which is one of the 22 most objectionable factors in the ownership of a cat.
23 In order to eliminate the odor caused by cat urine, the litter 24 box must be changed frequently, this being an expensive, laborious and messy job.

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1 Many patents have issued on devices for the lndoor use by cats, 2 such as U.S. Patent No. 3,233,588. The lnventlon dlsclosed ln this 3 patent employs the use of a screen whlch ls placed on top of the cat 4 lltter. Thls patent does ease the problem of dlsposlng of anlmal excrement, by merely ]i~ting the screen and disposing of the feces 6 lying on top. It does not however, contend with the problem of the 7 odor created by the urine. The unit must be perlodically emptied of 8 its sorbent granules and thus only partly contents with the elimlna-9 tlon of the mess and labor lnvolved. U.S. Patent No. 3,809,013 ls similar, except tha-t a stack of llners ls placed under the lltter.
ll When the lltter becornes soiled, the liner ls llfted, the lltter fll-12 ters through screen covered holes ln the cente. of the llner and the 13 litter ls reused with the next liner. Agaln, the excrement is dis-14 posed of neatly, however -the odor problem remains.
U.S. Patent 3,284,273 discloses an absorbent pad which can be 16 used in comblnatlon wlth anlmals. Although thls pad does contaln ab-17 sorbent capabllitles, the odor from the urlne of the anlmal ls L8 trapped, much as in the standard cat Litter. The pad :is not deslgned 19 for repetitive, long term use in a cat box but rather to retain the urine in a disposable pad, by mopping up pools of urine left on 21 floors or in cages, etc.
22 U.S. Patent No. 3,476,083 discloses the use of deodorizing sub-23 stances which are placed in the bottom of the receptacle. A screen is 24 placed a short distance above, on which lies the standard kitty lit-ter. The upper compartment receives the solid and liquid excreta, 26 retains the solids and absorbs the bulk of the liquid allowing the ex-27 cess liquids to drain through to the lower compartment. Although ~f~ 7 2 7 9 1 providing sorne neutraliz-ing of the ammonia odor by deodorizing the 2 urine which cannot be absorbed by the litter, it does not provide an 3 effect-ive means for deodorizing the bulk of the urine which has been 4 trapped in the litter. The disposal of all the litter creates a sub-stantial expense to the owner and the cleaning of the lower compart-6 ment would be unpleasantly laborious and rather messy. The spilling 7 of the deodorizing substances (lime is suggested) would be objec-8 tionable as well as possibly harmful to the person handling the con-9 tainer if by chance some of the chemical substance was to come in con-tact with the skin.
11 Patent 3,752,121, Brazzell, discloses a tray which holds a ab-12 sorbent mat covered with artificial grass. "Below the artiEicial 13 grass 31 and its backing sheet 32 there is provided a liquid absorbing 14 pad 33 which may be composed of a plurality of layers of absorbent paper and/or a pad of absorbent fibers to absorb any liquid which 16 seeps through the apertures in the artiEicial grass backing sheet."
17 The Brazzell patent also recommends using a deodorizer after the 18 animal has used the unit (deodorizer included with the unit at time of 19 purchase). The purpose of the Brazzell absorbent layers is to hold the urine, encasing it between a bottom "impervious layer" and a top 21 "non-absorbant or impervious layer" of artificial grass. The entrap-22 ment of the urine allows for bacteria to grow, causing odor. This 23 bacteria growth prevents use of the pad for long periods of time.
24 While many additional patents could be cited regarding other variations of disposal systems, types of granular litter and con-26 tainers none of systems of these patents have been found to overcome 27 both the problem of odor and provide an easy, economical and con-. :

' 7 ~ 3 1 venient disposal and replacement. By way of contrast, U.S. patent 2 4,469,046 discloses and claims an effective means for handling the 3 foregoing problems. Ilowever, due at least in part to the cost of 4 producing a protective screen having the requisite characteristics, the protective screen is a major cost item in the system of the 6 patent.
7 Summary of the Invention 8 It has now been found that the protective screen of the 9 aforenoted patent can be further improved through the use of a non-woven screen which provides economic advantages over other types of 11 screen material while, surprisingly, being capable of providing the 12 rip resistant characteristics of a protective screen as required in 13 the system of the aforenoted patent. Thus, in the instant invention 14 the foregoing problems are overcome and an easy to use, low cost, odorless, disposable absorbent pad system for use in animal litter box 16 is provided.
17 The odorless animal litter box can be a container as disclosed 18 and claimed in U.S. patent 4,469,046, which locks in place the sorbent 19 pad system, or a standard litter box, which can be combined with any affixing methods as disclosed in co-pending applications. The sorbent 21 pad system includes a protective screening and a moisture impermeable 22 liner. The protective screening is capable of withstanding the claw-23 ing action of an animal such as a cat, thus protecting the sorbent 24 pad and the moisture impermeable liner. The sheet layer of sorbent material, positioned between the screen and the moisture impermeable 26 material, has length and width dimensions equal to or less than that 27 of the screen. The moisture impermeable material is at least equal to ' ' ' ~ Z~7Z79 1 the length and wldth dimensions o:E the screen and they are sealed or 2 affixed to each other along at least a substantial portion of the 3 peripheral edge of the screen, or if substantially the same dimen-4 sions, at their common peripheral edge. The screen is a flexible mem-ber formed of strands bonded at their intersections and is formed of a 6 material which is substantially inert to urine.

8 The advantages and objects of the invention will become apparent 9 and the invention will be more fully understood from the following specification, particularly when read in conjunction with the draw-11 ings, wherein:
12 FIGURE 1 is a perspective view of the assembled unit in accor-13 dance with the present invention;
14FIGURE 2 is an exploded fragmentary view of the sorbent pad of 15the instant invention;
16FIGURE 3 is a fragmentary plan view of a screen for use with the 17instant invention; and 18FIGURE 4 is an enlarged vlew o:E a port:ion of the screen of 19 FIGURE 3.
20DETAILED DESCRIPTION OF T~IE INVENTION
21 In order to provide a clear understanding of the instant inven-22 tion, the various aspects of the invention are hereinafter described 23 in detail.

The granular material as employed in the instant invention is 26 utilized to satisfy the digging instinct of the animal and therefore 27 need not provide absorptive qualities. Consequently, inexpensive .

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' ~f37~7~3 1 material.s, such as clay, can be used in accordance with individual 2 preferences. Unl-ilce the commonly employed systems in which the 3 granular material must be used in quantity to provide the required 4 absorptive qualities and digging qualities, minimal quantities of the granular material can be used. The absorpt:ion quality of the layer 24 6 can provide the total or the predominant desiccation effect.
7 The litter material is commonly in granular form and must be in 8 moisture transfer contact with the underlying sorbent material so that 9 the urine can be drawn from the litter material into the sorptive layers. It should be noted that the terms sorbent, absorbent and ad-11 sorbent, in so far as they are used in regard to the present invention 12 are essentially used interchangeably. The use of a surfactant on the 13 screen material can enhance the moisture transfer capability of the 14 screen and is essential in combination with hydrophobic or low hydrophilicity materials.

17 The absorptive elements can be any material such as paper, 18 tissue, pulp starch and related polymers, etc. which can disperse the 19 liquid quickly, thus providing a large surface area for evaporation of moisture. In order to maintain a moisture free environment, it is 21 necessary to evaporate from 5 to 20 ml. of liquid each time the system 22 is used by the cat.
23 Examples of sorbent materials are those manufactured by Dow 24 Chemical, disclosed in U.S. Patent 4,117,184 and marketed under the designation DWAL 35 R. The Dow Chemical product is available as a 26 laminate which has an indicated minimum liquid sorbency capacity of 28 27 grams per gram of laminate.

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J~'7~79 1 Alternatively, the super absorbent can be a hydrophilic polymer 2 which has the ability to absorb and hold urine, such as the National 3 Starch and Chemical Corporation product sold under the registered 4 trademark PERMASORB.
Another example oE an absorbent is the materlal sold under the 6 trademark WATER-LOCK by Grain Processing Corp.
7 A ground paper pulp absorptive material has been found to 8 provide a combination of high sorbency, high surface area and low 9 cost. The large surface area provides for rapid urine evaporation and consequently is extremely effective in odor prevention.
ll Toxic chemicals or biologically active ingredients are not only 12 unnecessary but preferably are avoided. U.S. patent 4,494,482 as-13 signed to Proctor and Gamble relies on the use of 5000 to 30,000 ppm 14 of a halogenated aromatic hydrocarbon bacteriostat in a sorbent pad to effectively control odor development. It has been found that if the 16 sorbent material has the ability to sorb the urine, distribute the 17 urine rapidly throughout its mass, and evaporate the urine faster 18 than the bacteria can act on the urine, then the bacteria from the 19 feces cannot grow in the absorptive layer because they are dried out and die or become dormant. Consequently, chemically or biologically 21 active additives are not only unnecessary but undesirable.
22 Whereas, in conventional litter boxes, two to three inches of 23 litter are required, in accordance with the present invention less 24 than one inch of litter, and preferably no more than about one half inch, provides the desired results.

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1 A flexible, screen like mesh or permeable or semi-permeable 2 membrane is utilized to prevent the animal from clawing through to the 3 sorbent layer. The screen material must, therefore, exhibit suffi-4 cient strength to with stand the clawing action of the animal. Even though the screen is disposable, it is critical that the screen be 6 made of a material which is relatively inert to urine thereby prevent-7 ing rapid corrosion of the screen material, resultant odors and chemi-8 cal activity. Some of the preferred materials of construction include 9 polyester and polypropylene. Particularly in the case of hydrophobic materials, a surfactant must be used to prevent the screen from acting 11 as a liquid transfer barrier. While the particular surfactant which 12 is used is not narrowly critical, by way of illustration the surfac-13 tant can be a non-ionic surfactant such as Tergitol. The mesh-like 14 screen or netting 19 can be formed by the spun bonding process as well known in the art. While it would appear that screens formed by this 16 process would not be capable of providing the required claw rip resis-17 tance without resorting to such a high material density that moisture 18 transfer would be either precluded or severely restricted and cost 19 would be excessive, it has been found that a critical balance of properties can be achieved.
21 Structural integrity of the screen can be achieved by any of the 22 known means which yields bonding of the strands at their intersec-23 tions, as for example, through fusion of strands at the cross-over 24 points or any other means which precludes relative movement of the strands.

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1 Figure I :illustrates the assembled unlt: lO of the instant :lnven-2 tion. The sorbent unit 12 is inserted into t:he container unit l6, 3 preferably with the screen reg:ion at least covering the inner walls of 4 the container 16. As illustrated the sorbent unit 12 completely covers the interior of the container and overlies the outer walls.
6 The granular material 20, which can be sorbent or non-sorbent, is 7 placed on top of the sorbent unit 12 to provide the animal with the 8 necessary scratching materials, if so required. The granular material 9 would not be required if the unit was being used for a dog or other animal which did not have the scratching instinct. Adhering and/or 11 fastening systems, such as adhesive tape, elastic, etc. are described 12 in co-pending applications and can be combined with the nonwoven 13 screen disclosed herein in order to hold the sorbent member in place.
14 The sorbent layer 24 preferably is about coextensive with the bottom of the container 16.
16 Figure 2 shows a cross-section of the layers which form the sor-17 bent unit 12. The outer layer 22 which is a thin plastic sheet of a 18 material such as polypropylene or polyethylene prevents waste from 19 making contact with the box and doubles as a bag when disposing of the soiled litter. The sorbent layer 24 is formed from a super sorbent 21 material as previous stated herein.
22 The protective layer 26 is made from a durable, non-woven tissue 23 substance. If a binder is used for either the fabric of the tissue 24 layer or other layer, it must be of a non-water soluble material. The protective screen 18 is of a flexible, durable substance which : ~ ' - ~

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1 prevents the animal Erom scratching through to the bottom layers.
2 The granular rnaterial 20 is placed on top of the sorbent urlit as pre-3 viously described herein.
4 The screen 60 of Figure 3, is formed of strands 63 and 64 which are crossing one another in a random order, as well known in the non-6 woven art. The instinct of cats to scratch at fabric puts a heavy 7 stress on the screen and the clawing action can puncture or separate 8 the strands to the point that the sorbent material 24 which underlies 9 the screen can become exposed to the claws and torn apart. Since it is essential that the urine is free to pass through the screen and any 11 intermediate layers, such as one or more layers of tissue paper, to 12 the sorbent material, neither the screen nor the intermediate layers 13 can offer restriction to the urine flow. For this reason, the screen 14 must have sufficient porosity and liquid resistance that beading or pooling of urine does not occur. The intersections of the cross 16 strands are shown in Figure 4, to be fused, as for example by means of 17 heat. The nonwoven screening does not have woven fabric strands but 18 rather strands placed one layer over the other, at random angles, 19 prior to fusing. It has been found that th:is type of nonwoven struc-ture can withstand intense claw:ing without separation of strands, 21 thereby, protecting the inner layers from the claws of the cat. In 22 this regard it is noted that the openings 14 of the screen 18 of 23 Figure 4, must represent a very high percent of the area of the screen 24 as compared to the area occupied by the solid area of the screen.
The desired ratio has been found to be more reliably attainable with 26 screens having strands fused at their intersections than by any other - ~ .

~ 2~37~79 1 means. It must be understood that the opening cannot be so large that 2 the cat can claw at the underlying layers. It is this later fact 3 which results in the difficulty in attaining the required porosity.
4 Nonwovens have been known in the fabric industry for many years and have many uses. A nonwoven can be used to reinforce a weaker 6 component, as for example in filtration systems and air filters and is 7 well known for its light weight strength and versatility. While they 8 are tested for many specific properties, the properties listed below 9 are those which are critical to the instant application:
Abrasion resistance - the ability to resist pilling and weaken-11 ing of certain sections to rubbing.
12 Air Permeability - the measure of the ease with which air will 13 pass through a fabric. It is measured in cubic feet of air passing 14 through a square foot of fabric in a minute at a given pressure dif-ferential across the fabric.
16 Burst Strength - measures the ability of a fabric to resist rup-17 ture by pressure. Burst strength is expressed in pounds per square 18 inch of fabric. Specimens are clamped in rings and a diaphragm is ex-19 panded against the fabric until the fabric bursts.
Tear Strength - - the measure of the force necessary to tear a 21 fabric. It is expressed in pounds. In the trapezoid tear test, 22 notched specimens are clamped in jaws and loaded until the fabric rips 23 apart.
24 Repellency - the ability to resist sorbtion of a liquid sub-stance.
26 Chemical and environmental resistance - the ability to resist 27 penetration by chemicals, insects, mildew and bacteria.

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1 The Eabric used in the instant lnvention requires a high abra-2 sion resistance to avoid pilling or wearing thin in certain sections.
3 A fabric which pills from the rubbing of the animals paws would be un-4 acceptable as the pilled fabric would attach itself to the animal's paws and be tracked through the premises. AEter some use of the lit-6 ter unit, the pilled fabric could have sorbed small amounts of urine, 7 which would be objectionable to users. The wearing thin of certain 8 sections could lead to weakening of the screen and possible tearing, 9 allowing access to the under layers.
The criteria of the bursting strength and tear strength are im-11 portant to prevent ripping. The pressure exerted by an animal, espe-12 cially by a cat, can put stress on the fabric in diagonal, horizontal 13 and vertical directions simultaneously. If the protective screen is 14 torn, the animal has access to the urine filled sorbent layer. The destruction of this layer by animal claws would be very undesirable.
16 The sorbent layer must be allowed to dry out and the bacteria 17 aerated to the maximum extent. Thus, the air permeability of the 18 fabric is critical as air is required to prevent the accumulation of 19 liquid urine and its odor, through evflporation and the maintenance of an aerobic environment. Since a flow of air in and out of the sorbent 21 layer must occur, it is also essential that the quantity of litter 22 employed does not produce an adverse effect.
23 The liquid repellency of the fabric allows all the urine to pass 24 through the fabric onto the sorbent layer and prevents the urine from bein8 sorbed into the fabric. The addition of surfactants allows the 26 liquid waste to pass through to the sorbent layer while preventing 1 beading or puddling. The chemical and bacteria, etc. repellency of 2 the fabric prevents the corrosion of the fabric by the urine as well 3 as bacteria build up within the fabric.
4 The weight per mil of fabric is an important factor to regulate in order to prevent the fabric from adding unnecessary weight and cost 6 to the litter pad unit. However it is an indication of the Eabric 7 strength and cannot be compromised in an effort to reduce weight of 8 the unit. The minimum thickness would be about 2.5 mils, with a maxi-9 mum requirement of about 7 mils. The preferred weight would be be-tween 80 and 170 grams per square yard, the mil to gram ratio would Il naturally vary depending upon the fabric or screening used.
12 The process used to form the nonwoven can be any of the known 13 processes, such as dry formed, wet formed, melt blown, thermal bonded, 14 etc., however the spunbonded and spunlaced tend to come closest to meeting the criteria of the instant invention.
16 The adhesion of the nonwoven fabrics to the pad unit can be by a 17 number of methods such as pressure sensitive glue, sonic welding, heat 18 seal, hot melt, etc.

Cats can exert about 4-8 pounds of force with each paw. This 21 force is greatly magnified at the tip of the cats pointy claws. The 22 claws are not sharp like ra~or blades, but rather, are very pointy.
23 It is the ability of these points to first puncture, then be pulled 24 over a surface via the 4-8 lb force, repeatedly, that can puncture, abrade and tear certain materials. Various nonwoven, spun bonded 26 nylon and polyester sheets of varying strength were subjected to 27 puncture and tear tests as follows:

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7"3 -- 14 _ 1 A steel block containing four sharp fish hooks, sim~llating cats 2 claws, was placed on the surEace of varying strengths of clifferent 3 types of selected nonwoven.s. Those nonwovens that allowed the hooks 4 to immediately penetrate through the material were rejected. The sharp points of the hooks were able to immediately penetrate the flat 6 sheets due to pore sizes that were too large, or because the inter-7 sections were too weak to hold the small pore opening. Next the ac-8 ceptable sheets were placed on a rack 90` to the floor. The hooks 9 were pushed into the nonwovens being tested until penetration was com-pleted. Next, a 6 lb weight was added to the device to simulate a 11 cats pull.

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' r37279 1 The following observations were made;
2 weight of screen PUNCTURE TEAR
3 (o~mce/sq. yd) screen A screen A screen B screen C
4 1.0 - - +
1.5 6 2.0 7 + = tear or puncture 8 - = no tear or puncture 9 Screen A is a spun bonded nylon sold under the trademark. Cerex by Monsanto and was found to provide the best puncture and tear 11 resistance in the range from .85 to 2.0 o~./sq. yd. Screen B is 12 a product sold under the trademark Lutradur LD 7230, by 13 Lutravile and screen C is a product sold under the trademark 14 Reemay by DuPont.
Under actual in use field tests, the performance predicted by 16 the simulated tests were achieved. In the narrow range from about 1 17 to about 1.5 oz./sq.yd. the optimum performance-cost factor relation-18 ship is achieved. The weight of at least .85 o~./sq. yd. is required 19 to achieve the required performance while, at above 2 oz./sq. yd. the cost becomes undesirably high. As the fabric increases in thickness 21 so does its rigidity, with increasing manufacturing difficulties in 22 ratio to the added thickness. In higher weight fabric the performance 23 degenerates because of the loss of air permeability, as will become 24 evident from the following chart.
Screen Weight Grab Tensile Tear Strength Mullen-(cfm/sq.
26 o~/sq. Strength Dir- burst ft.) Air 27 yard Mach.- Trans.Mach. Trans. (psi.) Per-. ..
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1 meability 3 A 1 35 22 11 8.5 42 450 4 B 1.5 54 34 16 12 58 250 C 2 80 5~ 21 16 80 160 6 D 1.4 32 28 12 13.5 32 302 8 Screen D was l.utrabond 1045 and screen C was DuPont 9 Reemay 2200.
In the 1 to 2 oz. range Screen A was found to be accept-11 able in its ripproof qualities as well as in its air per-12 meability. In selecting a ripproof nonwoven the following chart the 13 guidelines which predict acceptability:

Preferred Acceptable 16 Grab Tensile Strength 17 Machine Direction : >35 >20 18 Transverse Direction: >20 >15 19 Tear Strength Machine Direction : >10 >6 21 Transverse Direction: >8 >6 22 Mullen Burst : >40 >15 23 Air Permeability : >150 >100 .

' ~ 2r~7z79 1 A further benefit derived from the use of a non-woven fabric is 2 the wicking action of the long strands of the screen. The wicking 3 action serves to transfer urine from the sorbent pad 24 to the atmos-4 phere by conveying the liquid out from under the litter and up the sides of the sorbent unit 12.
6 The efficacy of the wicking action of the screen is greatest in 7 combination with a non-absorben-t litter since the absorbent litters 8 tend to retain the liquid and counteracts the effect of the sorbent 9 unit. The following chart illustrates the evaporation efEect of the sorbent unit when used alone and in combination with a s-tandard ab-11 sorbent clay litter. In this case the screen was treated with a sur-12 factant sold under the trademark Triton X-100. The sorbent unit was 13 placed in a litter container with the absorbent section overlying the 14 bottom of the container and the screen region extending up the sides of the container. The test was conducted at 73 degrees F. and 74 %
16 relative humidity. In the test, 300 ml. of water was added to the 17 test unit and the net weight change was periodically measured.
18 It should be noted that the + changes indicate a weight increase 19 undoubtedly due to the clay being hygroscopic and absorbing moisture from the atmosphere.

-: ' -;37279 1 TIMr in hours 2 __ ___________________________________ 4 2 IN. +3.2 +1.3 + .5 +.7 +1.2+3.5 +.7 2" + L +3.4 +1.6 +1.5 +.6 +1.1+2.2 +.8 6 1" + L +1,9 0 -1.8 -4.8 -2.3 -7.0 -3.0 7 .5"+ L -1,9 -3,2 -9.1 -8.5 -4.8-12.9 -3.9 8 .25"+L -3.7 -4.4-9.9 -10.9 -6.1-14.6 -3.1 9 LINER -19.2 -16.5-44.9 -47.2 -25.0-66.5 -10.0 W~TER -1.0-.7 -.9 -na -2.1 -2.2 -.4 12 The wicking of the water up the sides of the screen to the top 13 of the litter container was visually evident.
14 It is readily apparent from the foregoing that the use of two inches of an absorbent litter can actually retard the moisture 16 evaporation, apparently due -to the lLtter serving as a moisture bar-17 rier between the sorbent unit and the atmosphere. In actual use it 18 has been found that the clawing and scratching of the cats tends to 19 expose regions of the screen or at least greatly reduce the amount of litter covering certain regions of the screen. ~lthough the ideal 21 system would be free of litter the cats tend to reject a litter con-22 tainer which is totally litter free. The use of a non-absorbent lit-23 ter which does not pack, or conversely, which permits the sorbent unit 24 to "breath" minimizes the adverse effects of standard litters.

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Claims (21)

1. In the combination of a sorbent pad laminate for the collection of animal urine, comprising:
a bottom sheet layer of moisture impermeable mater-ial; and intermediate sorbent layer of material having a high urine surbency capacity;
a top claw resistant screen means, said bottom sheet layer and said top screen means being bonded to each other along at least a substantial portion of the periphery of said screen means, the improvement comprising:
said screen means being a urine permeable, flexible member of nonwoven fabric which is substantially inert to urine, formed of strands randomly fused together at their in-tersections and having sufficient tear strength to withstand the clawing action of a cat and sufficiently small holes size to protect said sorbent layer and said sheet layer of moisture impermeable material from being torn by animal claws.

2. The sorbent pad screen means of claim 1 wherein said strands forming said nonwoven fabric cross one another at random angles.

3. The sorbent pad laminate of claim 2 wherein liquids pass through said screen means to be sorbed in said sorbent layer without being sorbed by said screen means.

4. The sorbent pad laminate of claim 3 wherein said screen means further has a grab tensile strength greater then 20 psi, in the machine direction, and a grab tensile strength greater than 15 psi in the transverse direction.

5. The sorbent pad laminate of claim 3 wherein said screen means further has a machine direction strength greater than 6 psi, and a transverse direction tear strength greater than 6 psi.

6. The sorbent pad laminate of claim 5 wherein said screen means has length and width dimensions which are at least equal to that of said sorbent layer.

7. The sorbent pad laminate of claim 3 further having a mullen burst strength greater than 15 psi.

8. The sorbent pad laminate of claim 1 whereby said screen means has a weight of between 0.85 ounces per square yard and 2 ounces per square yard.

9. The sorbent pad laminate of claim 8 wherein the screen means air flow is not less than 100 cfm/sq.ft.

10. The sorbent pad laminate of claim 8 wherein said nonwoven fabric of said screen means is treated with a surfac-tant.

11. The sorbent pad laminate of claim 10 wherein said litter granules are substantially non-urine sorbent and are less than about two inches deep.

12. The sorbent pad laminate of claim 1, further compri-sing a layer of tissue paper between said sorbent means and said screen means.

13. The sorbent pad laminate of claim 1 further compris-ing litter granules, said litter granules overlying said top claw resistant screen means.

14. The sorbent pad laminate of claim 1 further compris-ing securing means, said securing means being affixed to said moisture resistant sheet layer opposite said sorbent layer.

15. The sorbent pad laminate of claim 14 wherein said securing means is pressure sensitive adhesive tape.

16. In the combination of a litter device for use with cats and sorbent pad laminate means for the collection of ani-mal urine, comprising: a litter device having a base and walls, sorbent pad laminate means for the collection of animal urine, and litter on said sorbent pad laminate means.
wherein said sorbent pad laminate means includes a. a bottom sheet layer of moisture impermeable material, said sheet layer being in contact with said base and walls of said litter device;
b. an intermediate sorbent layer of material having a high sorbency capacity for urine, said sorbent layer being in contact with said sheet layer;
c. a top claw resistant screen means, wherein said screen means and said moisture impermeable material are substantially immovable with respect to each other, the improvement comprising said screen means being a flexible member of fabric formed of strands randomly fixed at their inter-sections forming a nonwoven fabric which is sub-stantially inert to urine and having sufficient tear strength to withstand the clawing action of a cat and sufficiently small hole size to protect said sorbent layer and said sheet layer of moisture impermeable material being torn by animal claws.

17. The combination of claim 16 further including litter granules overlying said top claw resistant screen means.

18. The combination of claim 17 wherein said litter granules are substantially non-urine sorbent and is less than about two inches deep.

19. The combination of claim 17 further comprising se-curing means, said securing means fixing said sorbent pad laminate means to said litter device and preventing relative movement of said sorbent pad and said self supporting struc-ture which can be cause by the clawing action of an animal.

20. The combination of claim 17 wherein said litter device is a self supporting structure.

21. The litter device of claim 20 wherein said self sup-porting structure is made of paperboard.