Abstract:
A cat litter box has a solid bottom, vertical sides and a top with an opening to admit a cat. The height of the vertical sides is such that a cat can reach the top with its forepaws by standing on its hindlegs. The box is low enough that a cat would have easy access to the box, yet is deep enough to prevent the escape of litter or excreta from the box during use by a cat.

Description:
FIELD OF THE INVENTION 
     The present invention relates to an improved cat litter box. Many patents have been issued for a wide range of containers for cat litter. Almost without exception, these litter boxes have had structures that facilitated entry by the cat, requiring the cat to exert a minimum of effort to enter and use the box. As a result, these litter boxes have not been able to retain the litter in the box when the cat seeks to bury its excreta. As all cat owners know, it is an instinctive reaction for cats to scratch the litter after relieving themselves. Frequently the litter is thrown out of the box by vigorous scratching. Moreover, male cats are particularly prone to spray their urine out of conventional litter boxes. 
     What is required for a clean and efficient litter box is one that cats cannot throw the litter from and from which no urine or faeces escapes. Preferably such a litter box should also prevent litter from being tracked out of the box on the cat&#39;s feet. 
     DISCUSSION OF THE PRIOR ART 
     As mentioned above, there are many patents extant for cat litter boxes. Searches of the prior art have produced dozens of such patents. In the United States Patent Office Classification System, Class 119 and its various subclasses seem to be entirely devoted to cat litter boxes. These patent documents extend over a period of many years with many attempts made to come up with the ideal litter box. Such efforts range from Lowe, Jr. U.S. Pat. No. 3,310,031 of Mar. 21, 1967, to McCauley U.S. Pat. No. 5,329,878 of Jul. 19, 1994. Lowe Jr. recognized that the box should be rectangular, and that the walls at the ends of the box should project upwardly from the side walls &#34;to a substantial height thereabove&#34;, (column 2, lines 58 and 59). 
     Unfortunately, cats do not conform to the wishes of designers of litter boxes. A box with low sides and high ends, and no shelf as defined above, will not retain litter or urine. Litter will be sent flying by vigorous scratching, and male cats will urinate over the low sides. 
     Similarly, McCauley U.S. Pat. No. 5,329,878 provides a box for a pot belly pig, a creature not known for its ability to jump. Thus an inclined ramp is provided in one end of the box. Here again this design would not meet the criteria for a cat litter box. Litter and urine would not be retained in such a box if used by a cat. 
     Other United States Parents which have been studied in order to assess the patentability of the present invention include the following: 
     
         ______________________________________U.S.Pat. No.  Date     Inventor    Title______________________________________3,085,550  04/16/63 Crawford    Cat Sanitary                       Container Enclosure3,771,493  11/13/73 Chandor     Litter And Waste                       Receptacle For Small                       Pet Animals3,793,989  02/26/74 Clark       Deodorized Pet Relief                       Station3,831,557  08/27/74 Elesh       Cat Litter Box3,990,397  11/09/76 Lowe, Jr.   Sanitary Pet Box Structure4,271,544  06/09/81 Hammond     Animal Commode4,279,217  07/21/81 Behringer   Liner For A Litter Box4,541,360  09/17/85 Higgins et al                       Disposable Animal                       Litter Box4,548,160  10/22/85 Feitelson   Cat Litter Box4,553,671  11/19/85 Cheesman    Tear-open                       Compartmented Cat                       Litter Container4,627,382  12/09/86 Muzzey      Disposable Litter Box4,640,225  02/03/87 Yananton    Odorless Animal                       Litter Unit4,646,684  03/03/87 Embry       Animal Waste Container4,696,257  09/29/87 Neary et al Self Drying Pet Litter Box4,766,845  08/30/88 Bavas       Cat Litter Pan System4,771,731  09/20/88 Derx et al  Litter Box4,813,376  03/21/89 Kaufman et al                       Cat Litter Tray4,838,202  06/13/89 Neu         Animal Litter Container4,848,274  07/18/89 Yananton    Odorless Animal                       Litter Unit4,852,518  08/01/89 Yananton    Odorless Animal                       Litter Unit4,858,561  08/22/89 Springer    Pet Litter Enclosure4.926,794  05/22/90 Yamamoto    Domestic Pets&#39;                       Chamberpot4,972,800  11/27/90 Bennett et al                       Pet Litter Box5,167,204  12/01/92 Nussle      Litter Box5,195,464  03/23/93 Mutter      Animal Litter Station5,211,133  05/18/93 Foley       Litter Saver Device5,218,930  06/15/93 Casmira     Litter Tray Apparatus5,220,885  06/22/93 Goetz       Litter Box5,272,999  12/28/93 Nussle      Litter Box______________________________________ 
    
     SUMMARY OF THE INVENTION 
     All of the above desirable characteristics are provided by the litter box of the present invention. This improved litter box requires cats to enter by using their natural jumping abilities, entering through the top of the box, which has no side openings, and no doors or flaps to admit cats, except by entry from above. The walls of the litter box of the invention are sufficiently tall that a cat standing inside on the litter is surrounded by an unbroken wall, as high as the cat&#39;s shoulder when standing. 
     It will be appreciated by cat owners that cats are cautious creatures. Accordingly, no cat will jump into a box if it cannot first see into the box to determine the safety, and cleanliness of the interior of the litter box. It has been determined that if the cat can stand on its back legs with its forepaws on the top edge of the box, so that it can inspect the interior of the box before entry, that the cat will enter once it is satisfied that the box is acceptable to it. The necessity of jumping over the wall of the box is no impediment to cats. Even elderly cats of 20 plus years readily use the litter box of the invention. 
     Thus the present invention is directed to an improved litter box in which the exterior wall is approximately the height of the shoulder of the average cat when standing on its back legs, and the interior height above the normal bed of litter is greater than the height of a cat&#39;s shoulder when standing on all four legs. A shelf or ledge around the top of the walls is highly desirable for assisting the cat to enter and exit the box. Typical dimensions of a box meeting these criteria are: overall height of box 14.5 inches (36.8 cm), width 16 inches (40.6 cm), length 22 inches (55.9 cm) and the shelf around the top of the box 1.5 inches (3.8 cm), with an opening of 13 by 19 inches (33 cm by 48.3 cm) in the top of the box. The depth of the litter bed would typically be 3 inches (7.6 cm). 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the improved cat litter box of the present invention; 
     FIG. 2 is a top plan view of the litter box of FIG. 1; 
     FIG. 3 is a side elevation of the litter box of FIG. 1; 
     FIG. 4 is an end elevation of the litter box of FIG. 1; 
     FIG. 5 is a longitudinal section of the litter box of FIG. 1 on the line 5--5 of FIG. 2; 
     FIG. 6 is a transverse cross-section on the line 6--6 of FIG. 2; 
     FIG. 7 is a partial section of the left hand side wall of FIG. 6; 
     FIG. 8 is an enlarged fragmentary view of the joint of FIG. 7; 
     FIG. 9 is a section through the joining clip holding the upper and lower sections of the litter box together; and 
     FIG. 10 is a side elevation of a second embodiment of the present invention in which the proportions of the upper and lower portions of the litter box are different than in FIG. 3. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The litter box of the present invention represents a simple yet elegant solution to the problems associated with conventional litter box designs. As shown in FIG. 1, the litter box 10 includes a solid bottom 11 (FIG. 2), upright sides 12, 13, 14 and 15 and a shelf 16 forming an opening 17 in the top of the box 10. 
     Preferably the box 10 is formed of upper and lower portions U and L which can, for example, be molded from a suitable translucent plastic polymer. The upper and lower portions are of identical size and shape, except for the opening 17 in the upper portion, and the solid bottom 11 of the lower portion. Thus it would be possible to mold both portions from the same mold by inserting a plate in the mold for forming the opening 17 when molding the upper portion U. The two halves of the litter box 10 are joined by a series of clips 18 which are formed of resilient material that damps the halves of the litter box together. 
     From the top view of FIG. 2 the shelf or rim 16 can be clearly seen. Also raised panels 19, 20 and 21 are shown in this view, which serve to strengthen the bottom of the box 11, in a technique well known to those skilled in the plastic molding art. FIGS. 2, 3 and 4 are three views of the basically rectangular box 11, the specific shape being chosen for moldability and strength, while permitting the completed box to be molded in two halves from a single mold. Since the upper and lower sections are of identical, but inverted shape they may be nested for shipment by inverting the upper half into the lower half. Obviously several complete boxes can be nested together for shipping, and assembled at the point of sale. 
     The cross-sections of FIGS. 5 and 6 show the assembled components of the litter box 11 held together by clips 18. Litter 22 is shown in the box to a depth, for example, of 3 inches (7.6 cm). 
     As will be evident to those skilled in the art of plastic molding, the litter box of the invention may also be molded as a solid box having a top opening, and formed, for example, by blow molding from polyethylene. Such a manufacturing process could form the box without the opening 17 in the box as molded and the opening 17 would then be cut in the top of the box to complete the litter box. 
     A further advantage of the two part litter box is the possibility of removing the upper half so that the box may be used for an injured cat which could not enter the assembled box by jumping over the tall wall of the assembly. Similarly, the top may be removed for training a kitten to use the box. Kittens quickly learn to jump and the top could be reattached once the kitten had grown to a size to enter over the top of the assembled box. The owner of the box will also find it convenient to remove the upper portion from the lower portion when replacing the litter in the box. It is much easier to pour litter from the box once the upper portion has been removed. 
     A suitable litter is placed in the box typically to a depth of 3 inches (7.6 cm), when the litter box is put into use, as shown in FIGS. 5 and 6. Experience has shown that the best type of litter to use in a cat litter box is the dumping type of material, which has the property of the particles adhering to each other when moistened. Such litter is easy to maintain in clean condition by regular removal of clumped material, and can be obtained in either odorless or scented forms. 
     FIG. 9 shows the clip 18 as extruded, for example, from a suitable resilient plastic material. When applied to the upper and lower halves of the litter box, they are held securely together to prevent the escape of litter or urine from the joint between the halves. Obviously these clips would not be required for a one piece box. 
     FIG. 10 illustrates an alternative embodiment of the two piece litter box, which for aesthetic reasons has the lower portion L formed as taller than the upper portion U. The overall height of the box is the same as the first embodiment. The joint between the two portions is above the median height of the assembled box, for example, 8.25 inches (21 cm) above the base, and the upper portion is therefore 6.25 inches (15.8 cm), so the total height is still 14.5 inches (36.8 cm). 
     It is important, however, that the overall height of the box be such that a cat standing on its hind legs can just reach the shelf 16 with its forepaws, and see into the box before jumping inside. If the box is lower than this, then when litter is added there is a risk that the cat when standing inside may urinate over the shelf, or may be able to scatter litter over the shelf while burying its excreta in the litter. The design of this litter box is predicated on the facts that cats are inherent jumpers and climbers, cats are also naturally curious, and can&#39;t resist jumping into boxes, cats often have a need for privacy when eliminating, and finally a tall box provides a sense of security for the cat while in the box. 
     These considerations led to the design of a litter box with entry and exit achieved through an opening in the top of a tall four-sided box. All prior art litter boxes assume that the cat must enter the box by stepping over the side, just as a human would enter a room through a door. The litter box of the present invention has been designed around the way in which cats think, rather than imposing anthropomorphic limitations in the design. The top only entry of a tall box is entirely unknown in the prior art. All previous cat litter box designs in which the box was open at the top were of shallow proportions. None of the prior inventors recognized the benefits of a tall box which the cat jumps into, and from which no excreta and litter escapes. Incredibly, no-one prior to the present inventors has recognized the importance of the dimensions of a cat litter box as well as the necessity for top entry. If any litter should be stuck to the cat&#39;s paws after using the box, the act of jumping from the box contributes to removal of litter from the paws, leaving almost all of it in the litter box.