Securing means for odorless animal litter unit
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of application Ser. No. 573,958, filed Jan. 26, 1984, which application is a continuation-in-part of U.S. Pat. No. 4,469,046, issued Sept. 4, 1984, which application is a continuation-in-part of application Ser. No. 909,256, filed May 24, 1978, now abandoned, the subject matter and description of which is incorporated herein by reference thereto, as through set forth herein in detail. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to improvements in a unique odor preventing, disposable, absorbent pad and liner for an animal litter unit, and more particularly to an improved combination of adhesive attachment and plastic litter pad liner to be utilized in combination with an animal litter container. 
     2. Brief Description of the Prior Art 
     Many domestic animals frequently use litter boxes for the elimination of body wastes. The boxes are usually filled with various kinds of absorbent granular materials such as sand, cat litter and the like, and must be periodically emptied and cleaned, which are somewhat objectionable tasks, since the absorbent granular material must be replaced and the boxes cleaned each time. 
     Cats, being the most frequent users of litter boxes, present a further problem in that the urine of the feline has the most severe tendency to produce a pervasive odor problem. Apparently, cat urine contains the highest content of urea which, when allowed to stand for any length of time in any litter material, releases an ammonia odor. In any event, it is the odor associated with cat urine which is one of the more objectionable factors in the ownership of a cat. 
     In order to eliminate the odor caused by cat urine, the litter box must be changed frequently, this being an expensive, laborious and unpleasant job. 
     Many patents have issued on devices for the indoor use by cats, such as U.S. Pat. No. 3,233,588. The invention disclosed in this patent employs the use of a screen which is placed on top of the cat litter. This patent does ease the problem of animal excrement, by merely lifting the screen and disposing of the feces lying on top, it does not however, contend with the problem of the odor created by the urine. The unit must be periodically emptied of its absorbent granules and thus only partly contents with the elimination of the mess and labor involved. U.S. Pat. No. 3,809,013 is similar, except that a stack of liners is placed under the litter. When the litter becomes soiled, the liner is lifted, the litter filters through screen covered holes in the center of the liner and the litter is reused with the next liner. Again, the excrement is disposed of neatly, however the odor problem remains. 
     U.S. Pat. No. 3,284,273 discloses an absorbent pad which can be used in combination with animals. Although this pad does contain absorbent capabilities, the odor from the urine of the animal is trapped, much as in the standard cat litter. The pad is not designed 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 floors or in cages, etc. 
     U.S. Pat. No. 3,476,083 discloses the use of deodorizing substances which are placed in the bottom of the receptacle. A screen is placed a short distance above, on which lies the standard kitty litter. The upper compartment receives the solid and liquid excreta, retains the solids and absorbs the bulk of the liquid allowing the excess liquids to drain through to the lower compartment. Although providing some neutralizing of the ammonia odor by deodorizing the urine which cannot be absorbed by the litter, it does not provide an effective means for deodorizing the bulk of the urine which has been trapped in the litter. The disposal of all the litter creates a substantial expense to the owner and the cleaning of the lower compartment would be unpleasantly laborious and rather messy. The spilling of the deodorizing substances (lime is suggested) would be objectionable as well as possibly harmful to the person handling the container if by chance some of the chemical substance was to come in contact with the skin. 
     U.S. Pat. No. 3,752,121, Brazzell, discloses a tray which holds a absorbent mat covered with artificial grass. &#34;Below the artificial grass 31 and its backing sheet 32 there is provided a liquid absorbing 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 seeps through the apertures in the artificial grass backing sheet.&#34; The Brazzell patent also recommends using a deodorizer after the animal has used the unit (deodorizer included with the unit at time of purchase). The purpose of the Brazzell absorbent layer is to hold the urine, encasing it between a bottom &#34;impervious layer&#34; and a top &#34;non absorbent or impervious layer&#34; of artificial grass. The trapment of the urine allows for bacteria to grow, causing odor. This bacteria growth prevents use of the pad for long periods of time. 
     While many additional patents could be cited regarding other variations of disposal systems, types of granular litter and containers none of these patents overcome both the problem of odor and easy, economical and convenient disposal and replacement. 
     In applicant&#39;s U.S. Pat. No. 4,469,046 and pending application Ser. No. 573,958 the foregoing problems of odor, economics and convenience were overcome and an easy to use, odorless, disposable absorbent pad containing animal litter box were disclosed. The patent discloses and claims a locking means for preventing relative movement of the litter pad device and the litter box. 
     Since it is the pad structure which prevents the urine odor any urine trapped between the box and the moisture impermeable liner of the pad structure will cause odor. It is therefore imperative that the urine be deposited on the pad structure and that the pad remain fixed in place at all times. 
     SUMMARY OF THE INVENTION 
     It has now been found that the tendency of the sorbent pad laminate to slide when used in standard litter boxes can be eliminated without the use of the special container of the aforenoted U.S. Pat. No. 4,469,046. 
     In accordance with the present invention the foregoing problem is overcome by use of a pressure sensitive adhesive on the moisture impermeable liner. The liner is thus secured to a litter container. The sorbent pad prevents the odor ordinarily caused by the action of bacteria on urine in the litter container through rapid evaporation. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The advantage and objects of the invention will become apparent and the invention will be more fully understood from the following specification, particularly when read in conjunction with the drawings, wherein: 
     FIG. 1 is a plan view of the litter pad unit in accordance with the present invention; 
     FIG. 2 is a perspective view of the litter pad unit positioned in a litter box; 
     FIG. 3 is a plan view of another embodiment of the moisture impermeable liner in accordance with the present invention; 
     FIG. 4 is a plan view of an additional embodiment of the litter pad unit in accordance with the present invention; 
     FIG. 5 is a fragmentary side view of the moisture impermeable liner of FIG. 4 placed in a litter box; 
     FIG. 6 is a fragmentary plan view of a tape of the instant invention; 
     FIG. 7 is a further fragmentary plan view of the tape of FIG. 6; 
     FIG. 8 is a fragmentary plan view of litter pad unit with the side folded in preparation for disposal; 
     FIG. 9 is a perspective view of an additional adhesive tape; 
     FIG. 10 is a perspective view of an another embodiment of the adhesive tape; and 
     FIG. 11 is a top view of a non-custom box with an alternate taping method; 
     FIG. 12 is an exploded fragmentary view of the absorbent pad of the instant invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 illustrates the litter pad structure 10 with the impermeable liner 12, longitudinal tape 14 and the optional transverse tape 16. The longitudinal tape 14 and the transverse tape 16 are located at the peripheral edges of the impermeable liner 12 and affixed to the impermeable liner 12 by means predetermined in manufacture. There are various means for affixing the determined tape to the impermeable liner 12 that are well known in the prior art. The use pressure sensitive adhesives with absorbent pads is well known in the diaper art, as evidenced for example, by U.S. Pat. No. 4,505,706. Although the function of the adhesive means in the instant invention is unrelated the use in the diaper art, the manufacture of the adhesive is analogous and from that standpoint, the disclosure of U.S. patent is incorporated herein by reference. 
     The longitudinal tape 14 and the transverse tape 16 can be of the type disclosed hereinafter or of a type standard to the industry. Although reference is made herein to a tape, it should be understood that the term is intended to cover both the use of a pressure sensitive adhesive directly on the liner and a pressure sensitive adhesive carried on both sides of a carrier sheet. The only prerequisite for the tape being that the side which is in contact with the impermeable liner 12 must not be easily removable from said impermeable liner 12, while the side which will be affixed to the litter box must be readily removable. The nature of the materials to which they are being adhered will facilitate in this prerequisite as the tape will be more easily removed from the hard plastic from which litter boxes are typically made, as compared to the softer, more readily adhered to material of the plastic liner. In the event that adhesive which covers any of the tapes referred to herein and placed next to the litter box is not readily removable, the tape will tend to stick to the box and tear the impermeable liner 12 or accumulate in the bottom of the litter box. The tearing of the impermeable liner 12 will allow the interior of the litter pad structure 10 to come in contact with the bottom of the litter box, preventing evaporation of the urine, allowing for odor build up and necessitating a clean up operation. 
     In addition to the various tapes disclosed herein for use with the litter pads, many other means of strip adhesives as known in the art can be applied, including hot melt and cold adhesives. Double sided pressure sensitive tape with a release strip, such as commonly employed in the art can be used. The adhesive can be applied by roller, gravure head, etc. onto the bottom of the liner as it is passed over production equipment. A release film, such as waxed paper strips can then be applied over the tacky cold adhesive to prevent adhesion to undesirable surfaces. 
     The litter box system 18, of FIG. 2 shows the litter pad structure 10 placed in the litter box 20. In this figure, the dramatic difference between the use of a pressure sensitive adhesive in the diaper art and in association with litter pads, become evident. Prior to placement the protective strip on the longitudinal tape 16 is removed, exposing the adhesive and permitting adhesion of the horizontal tape 16 to the litter box 20. In this embodiment the bottom 11 of the litter pad structure 10 is loose and the litter pad structure 10 is only affixed to the litter box 20 at the edges. Litter granules 15 are then placed on the bottom 11 of the litter pad structure 10 to provide a cat with a medium to which it can apply a clawing action. The pressure sensitive adhesive strip 16 is shown to not merely hold the litter pad structure 10 in place, but of even greater importance, the overlying flap regions 22, 24, 26, and 28 of the litter pad structure 10, are held in place. Thus, the pressure sensitive adhesive serves to enable the litter pad structure 10 to conform to the shape and size of the litter box. 
     FIG. 3 illustrates an additional embodiment of the litter pad structure 30. This embodiment provides for the inner vertical tapes 38 and inner horizontal tapes 39 to be added to the outer vertical tapes 34 and outer horizontal tapes 36. The inner vertical tapes 38 and inner horizontal tapes 39 should be positioned on the impermeable liner so as to be adhered to the bottom of the litter box, this will further secure the litter pad structure 30 to the bottom of the litter box as well as around the edges. The obvious disadvantage of the additional tape would be cost of manufacture. However, the added convenience and improved holding power versus added cost of manufacture would be the primary factors in determining the amount of adhesive employed. 
     In FIG. 4 the small litter pad structure 40 fits the bottom of the litter box 50, leaving the sides uncovered. It is preferable that the small litter pad structure 40 be slightly larger than the bottom of the litter box 50, as shown in FIG. 5, to prevent seepage of urine between the litter box 50 and the small litter pad structure 40. The small litter pad structure 40 has the vertical tapes 44 and horizontal tapes 46 attached to the impermeable liner 42, as previously described. The addition of tapes as illustrated in FIG. 3 or any subsequent Figures can easily be incorporated with the embodiment of FIG. 4. 
     FIG. 6 illustrates one type of tape to be used with most embodiments of the litter pad structure 10. The tape 60 is affixed to the impermeable liner 72 of the litter pad structure 70 as previously described. The adhesive strip 66, FIG. 7, is covered and protected from exposure by the first protective strip 62 and second protective strip 64. For use as disclosed herein it is necessary for the first protective strip 62 and second protective strip 64 to be of a tear proof flexible material, such as used for the impermeable liner 12. This heavier construction will prevent the first protective strip 62 and second protective strip 64 from tearing when used as described herein. The first protective strip 62 and second protective strip 64 are divided by the perforated line 68. The perforated line 68 allows the the first protective strip 62 and second protective strip 64 to be separated when required for tieing while allowing for one piece application at the time of manufacture. A short distance from one end of the perforated tape 60 is the peel resistant line 69. The peel resistant line 69 can be created by a heat seal, stitched area or other method convenient to manufacture in order to prevent the first protective strip 62 and second protective strip 64 from being completely removed from the tape 60. For most effective use of this embodiment, the tape 60 should be placed in from the outer edges, approximately two inches, to allow for fold over space, as described further herein. This is especially effective when used in combination with standard peel off tape for the outer horizontal and vertical strips and horizontal strips and the disclosed tape 60 for the inner vertical strips. 
     In FIG. 7 the first protective strip 62 and second protective strip 64 are shown lifted up and away from the tape 60 exposing the adhesive tape 66. The first protective strip 62 and second protective strip 64 can be stored under the impermeable liner 72 until the litter pad structure 70 is ready for disposal. When the litter pad structure 70 is ready for disposal, the sides are folded in, as illustrated in FIG. 8, at the line created by the adhesive strip 66, thus preventing leakage of the litter. The litter pad structure 70 is then rolled, in the direction of arrow A creating the &#34;bed roll&#34; effect as shown in FIG. 9. The litter pad structure 70 can then be tied by use of first protective strip 62 and second protective strip 64 for a neat and conveniently disposed of package. 
     FIG. 10 is an additional tape embodiment illustrating a reverse tab tape 90. The tape 90 has a double sided adhesive coated tape 94 with one of its sides adhered to the impermeable liner 12 at time of manufacture. The exposed side of the adhesive tape 94 is covered with a removable protective strip 96 to prevent its adhering to unwanted objects. In the embodiment illustrated in FIG. 10 the reverse tab tape 90 extends beyond the edge of the impermeable liner 12. The extensions section of the reverse tab tape 90 is provided with a bottom protective strip 98 and a top protective strip 96 which prevent the adhesive tape 94 from unwanted adhesion. The extension section can be folded under the impermeable liner 12 if desired, however care must be taken not to interfere with the adhesion of the adhesion tape 94 to the litter box. The litter pad structure 10 is adhered to the litter box by removal of the top protective tape 92 and exposure of the adhesive tape 94, as previously described. At time of disposal the litter pad structure 10 is folded and rolled, as described in FIGS. 8 and 9 and the bottom protective strip 98 is removed from the reverse tab tape 90 revealing the adhesive strip 94. The adhesive strip 94 is affixed to the impermeable liner 12 of the rolled litter pad structure 10, securing the structure 10 into a neat, disposable roll. Although it is preferable that the reverse tab tape 90 extend over the edge of the impermeable liner 12 to allow for easier access, it can be positioned so that the edge of the reverse tab tape 90 is flush with the edge of the impermeable liner 12. In embodiments positioning the reverse tab tape 90 flush with the edge of the impermeable liner 12, the bottom protective strip 96 is not required as the entire reverse tab tape 90 can be adhered to the litter box. 
     FIG. 11 is an alternate tape embodiment 110. The tape 110 is manufactured longer than the impermeable liner 12 so as to extend beyond the edge approximately two inches. The protective strip 116 covers the adhesive tape 114 only to the stop line 113. The remaining adhesive tape 114, from the edge of the protective strip 116 at stop line 113 to its end is provided with a separation strip 118. A protective strip 119 is placed on the adhesive tape 114 extending from the fold line 115 at the edge of the impermeable liner 12 to the end in order to prevent sticking of the tape 110 to the litter box. The extended tape is folded at the fold line 115 onto the unprotected adhesive strip 114, thereby placing the protective strip 118 in contact with the adhesive tape 114. The protective strip 116 covering the adhesive strip 114, until removed for use, extends only up to the edge of the folded over section of the excess tape 110. The separation strip 118 prevents the adhesive strip 114 from sticking to itself and allows for easy removal of the folded section. At time of disposal adhesive strip 114 is opened up to to extend the folded over section of the tape 110 beyond the litter pad structure 10. The litter pad structure 10 is folded and rolled as previous described in FIGS. 8 and 9. The protective strip 119 is then removed and the adhesive surface 114 exposed, allowing attachment to the impermeable liner 12 as previously described. 
     FIG. 12 illustrates an alternate method is which to secure the litter pad structure 10 to the litter box 100. Individual adhesive strips 102, having two adhesive sides covered by protective strips, are provided in an &#34;unstripped&#34; form. The first side of the protective strips can be removed, revealing the adhesive area and individual adhesive strips 102 can then be affixed at various desired positions within the box. The outer protective covering can then be removed and the litter pad structure 10 secured thereupon. This method allows for the user to secure the litter pad structure 10 to unconventional boxes or to heavily secure a cat&#39;s favorite clawing spot and is especially suited to disposable boxes. The individual tapes also save manufacturing costs in that they use less tape and the tape does not have to be previously affixed to the impermeable liner 12. 
     In order to provide necessary background regarding the absorbent pad of FIG. 13, the following information is provided. 
     GRANULAR MATERIAL 130 
     The granular material 130 as employed in the instant invention is utilized to satisfy the digging instinct of the animal and therefore need not provide absorptive qualities. Consequently, inexpensive materials, such as clay, can be used in accordance with individual preferences. Unlike the commonly employed systems in which the granular material 130 must be used in quantity to provide the required absorptive qualities and digging qualities, minimal quantities of the granular material can be used, as illustrated in the charts supra. The absorption quality of the layer 24 can provide the total or the predominant desiccation effect. 
     The litter material is commonly in granular form and must be in moisture transfer contact with the underlying absorbent material so that the urine can be drawn from the litter material into the sorptive layers. The use of a surfactant on the screen material can enhance the moisture transfer capability of the screen and is essential in combination with hydrophobic or low hydrophilicity materials. 
     ABSORBENT LAYER 124 
     The absorptive elements can be any material such as paper, tissue, pulp starch and related polymers, etc. which can disperse the liquid quickly, thus providing a large surface area for evaporation of moisture. In order to maintain a moisture free environment, it is necessary to evaporate from 5 to 20 ml. of liquid each time the system is used by the cat. 
     Examples of absorbent materials are those manufactured by Dow Chemical under U.S. Pat. No. 4,117,184. The Dow Chemical laminate has an indicated minimum liquid absorbency capacity of 28 grams per gram of laminate. 
     Alternatively, the super absorbent can be a material such as the National Starch and Chemical Corporation product sold under the registered trademark Permasorb. The National Starch product is a hydrophilic polymer which has the ability to absorb and hold urine. There is a significant reduction in urine odor and pH level in the presence of Permasorb. 
     Another example of an absorbent is the material sold under the trademark Water-Lock by Grain Processing Corp. 
     A ground paper pulp absorptive material has been found to provide a combination of high absorbency, high surface area and low cost. The large surface area provides for rapid urine evaporation and consequently is extremely effective in odor prevention. 
     Toxic chemicals or biologically active ingredients are not only unnecessary but preferably are avoided. U.S. Pat. No. 4,494,482 assigned to Proctor and Gamble relies on the use of 5000 to 30,000 ppm of a halogenated aromatic hydrocarbon bacteriostat in an absorbent pad to effectively control odor development. It has been found that if the sorbent material has the ability to absorb the urine, distribute the urine rapidly throughout its mass, and evaporate the urine faster than the bacteria can act on the urine, then the additives are not only unnecessary but undesirable. 
     Bacteria from the feces cannot grow in the absorptive layer because they are dried out and die or become dormant. It is the bacteria which is capable of breaking down the urine which cause the strong volatile odor commonly associated with cat litter boxes, the dry environment of the sorbent material effectively prevents odor. The high absorption capacity of the super absorbent polymers, such as available from Dow Chemical, do not provide an advantage over a pulp fiber, due to the high rate of evaporation of urine from the fiberous material. As previously stated, the instant invention requires substantially less granular material for each use and requires fewer changes, saving further on granular use. Whereas, in conventional litter systems two to three inches of litter are required, in accordance with the present invention less than one inch of litter, and preferably no more than about one half inch, provides the desired results. 
     SCREEN MATERIALS 
     A flexible, screen like mesh or permeable or semi-permeable membrane is utilized to prevent the animal from clawing through to the absorbent layer. The screen material 128 must, therefore, exhibit sufficient strength to with stand the clawing action of the animal. Even though the screen is disposable, it is critical that the screen be made of a material which is relatively inert to urine thereby preventing rapid corrosion of the screen material, resultant odors and chemical activity. Some of the preferred materials of construction include polyester and polypropylene. Particularly in the case of hydrophobic materials, a surfactant must be used to prevent the screen from acting as a liquid transfer barrier. While the particular surfactant which is used is not narrowly critical, by way of illustration the surfactant can be a non-ionic surfactant such as Tergitol. The mesh-like screen or netting 128 can be formed by the spun bonding process as well known in the art. While it would appear that screens formed by this process would not be capable of providing the required claw rip resistance without resorting to such a high material density that moisture transfer would be either precluded or severely restricted and cost would be excessive, it has been found that a critical balance of properties can be achieved. The absorptive layer must be protected from the tearing action of the claws. For example, the screen of Vander Wall, U.S. Pat. No. 3,476,083, would be totally inoperative to prevent tearing of the absorptive layer or the plastic moisture barrier. 
     The use of a loose screen-like fabric is unacceptable because the mesh can be varied as a result of the force of the animal&#39;s claws. Accordingly, the reference to mesh size is intended to indicate the effective size under actual use conditions rather than a `temporary` size which can be readily altered by the animal. 
     The screen used in the instant invention requires a high abrasion resistance to avoid the fabric from pilling or wearing thin in certain sections. The criteria of the bursting strength and tear strength are important to prevent ripping. The pressure exerted by an animal, especially by a cat, can put stress on the fabric in diagonal, horizontal and vertical directions simultaneously. If the protective screen is torn, the animal has access to the urine filled absorbent layer. The absorbent layer must be allowed to dry out and the bacteria should be aerated to the maximum extent. Thus, the air permeability of the fabric is critical as air is required to prevent the accumulation of liquid urine and its odor, through evaporation and the maintenance of an aerobic environment. The liquid repellency of the fabric allows all the urine to pass through the fabric onto the absorbent layer and prevents the urine from being absorbed into the fabric. The chemical and bacteria, etc. repellency of the fabric prevents the corrosion of the fabric by the urine as well as bacteria build-up within the fabrics. 
     FIG. 13 shows, in exploded form, a cross-section of the layers which form the absorbent unit 120. The outer layer 122 which is a thin plastic sheet of a material such as polypropylene or polyethylene prevents waste from making contact with the box and doubles as a bag when disposing of the soiled litter. The sorbent layer 124 is formed from a super absorbent material as previous stated herein. 
     The protective layer 126 is made from a durable, non-woven tissue substance. If a binder is used for either the fabric of the tissue layer or other layer, it must be of a non-water soluble material. The protective screen 128 is of a flexible, durable substance which prevents the animal from scratching through to the bottom layers. The granular material 130 is placed on top of the absorbent unit as previously described herein. 
     The foregoing description of adhesive strip placement, quantities and lengths have been used herein as examples for illustration purposes and in no way limit the scope of the invention. Any combination of placement, quantity and length of any double sided adhesive tape can be incorporated in the instant invention and to describe all combinations would be too lengthy. Additionally, the instant invention can be combined with any of the co-pending applications, i.e. disposable bag, non-woven screen and/or disposable carton.