Self-cleaning pet litter box

A pet litter holding device which facilitates removal of animal waste and re-use of the litter includes a stationary base and a drum rotatively supported by the base. The drum is bounded by an enclosing wall which terminates in lateral extremities equipped with flanges that slidably embrace the base. A sieving panel isolates solid and clumped litter during rotation of the drum. A funnel region of the enclosing wall directs the isolated waste material downwardly to an exit spout adapted to hold a disposable plastic bag that receives the waste material.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention concerns a pet litter box having improved means for 
sieving the litter and disposing of the pet waste. 
2. Description of the Prior Art 
A known problem with the ownership of house pets, particularly cats, is the 
unpleasant and sometimes noxious odors and fumes associated with pet 
waste. Conventional waste boxes are frequently used for collecting pet 
waste in a quantity of litter so as to reduce the pet waste odor in the 
environment surrounding the box. Such boxes include an open tray which 
retains a quantity of litter accessible to the pet. The litter is provided 
so that the pet may bury the waste within the litter. The litter also 
helps shield the odors and contain the fumes of the pet waste until the 
combined litter and waste are removed from the box and placed in a 
receptacle for disposal. 
The litter changing process, however, requires a significant amount of 
human contact with the waste box, and waste residue, odor and fumes. 
Contact with pet waste is undesirable as it may cause toxoplasmosis, which 
is known to cause miscarriages, and may be spread from a pregnant woman to 
her child, possibly resulting in neurological and ocular problems in the 
child. Also, the pet waste, litter dust, and waste fumes can be noxious to 
people leading to nausea and lung infections. 
Two methods are typically employed for maintaining conventional waste 
boxes. In the first method, the pet is allowed to deposit waste in the 
litter box over the course of several days until the litter is saturated. 
Once the litter is saturated with waste, the combined litter and waste is 
discarded, resulting in the use of unnecessary quantities of litter. In 
the second method, the operator, using a hand scoop, removes contaminated 
portions of the litter. In each method the operator is placed in close 
proximity to the waste, odor, fumes, and dust. Additionally, when waste 
boxes are used by pets, litter is often kicked out by the pet and is also 
scattered out of the box as the pet steps out of the box, further wasting 
litter, and requiring more cleaning. 
Recently, clumping litter, which has finer granules than conventional 
litter, has been developed. Clumping litter, generally consisting of 
granular inorganic clays, forms hardened lumps out of solid and liquid pet 
waste. These lumps may be separated from the clean litter by sieving. 
Although clumping litter is more expensive than conventional litter, the 
ability to remove liquid waste from the litter lengthens the amount of 
time that the litter may remain in the litter box, and results in an 
overall reduction in litter costs. In the interest of securing greater 
utilization of the more expensive clumping litter, some sort of cleaning 
and re-use of the litter is generally indicated. However, use of a hand 
scoop does not provide sufficiently thorough cleaning. 
Several pet waste boxes have been developed which attempt to address the 
problems listed above. Such devices generally provide a chamber for 
collecting pet waste in a quantity of pet litter, and are able to separate 
the waste from the litter by sieving. 
U.S. Pat. No. 5,402,751 to Chevrotiene concerns a litter box equipped with 
a removable lid having a sieving screen. Rotation of the box separates out 
the solid and clumped debris, and deposits it into the lid which then must 
be removed by hand, dumped and stored separately, whether soiled or 
cleaned, until its next use. 
U.S. Pat. No. 5,394,833 to Glass discloses an animal waste disposal 
apparatus adapted to be positioned directly above a litter box. The 
disposal apparatus, of considerable size, filters the litter, which falls 
downwardly into a waiting empty litter box. Removed solids and clumps are 
channeled to a collection bag. Though potentially effective, the falling 
litter would be expected to produce a dust problem. 
U.S. Pat. No. 5,507,252 to Ebert concerns a rotative litter box having a 
built-in sieving screen. Rotation of the box separates the waste debris 
and deposits it in a tray which is manually removed for disposal of its 
contents. 
U.S. Pat. No. 5,509,379 to Hoeschen discloses a litter box having a 
rotating cylinder equipped with a perforated sieving surface. The 
perforated surface, during rotation, removes solid and clumped waste and 
conveys it to a collection chamber which must be manually removed for 
emptying. 
U.S. Pat. No. 5,551,375 to Flores relates to a litter box having a 
rotatable cylindrical drum equipped with a sieve screen and a removable 
collection drawer. Rotation of the drum achieves deposition of the solid 
and clumped waste into the collection drawer. 
It is notable that the prior art devices discussed above do not efficiently 
utilize space. For example, the various means for separating and removing 
waste from litter employed in the prior art devices have required the use 
of relatively large and clumsy chambers in order to provide sufficient 
interior room for use by a pet. 
Therefore, a significant and heretofore unsolved need exists to provide a 
pet waste box having an improved means for separation of pet waste from 
litter, and minimizing human exposure to the waste and its odors or 
surfaces contaminated with the waste. There exists an additional need to 
provide a pet waste box which minimizes dust generation during a sieving 
operation, and which reduces the amount of litter which might scatter out 
of the device. Furthermore, there exists the need to provide a pet waste 
box which more efficiently utilizes space. 
It is accordingly an object of the present invention to provide a litter 
holding device which facilitates separation of solid and clumped animal 
waste from litter material confined within said device. 
It is another object of this invention to provide a device as in the 
foregoing object which minimizes human contact with the animal waste or 
surfaces contaminated therewith. 
It is a further object of the present invention to provide a device of the 
aforesaid nature which is of relatively small size and easy to manipulate 
for the purpose of removing animal waste therefrom. 
It is yet another object of this invention to provide a litter box of the 
aforesaid nature which minimizes dust and odor production during the 
separation of animal waste from the litter. 
It is a still further object of the present invention to provide a litter 
box of the aforesaid nature which is not intimidating to pets and is of 
durable and simple construction amenable to low cost manufacture. 
These objects and other objects and advantages of the invention will be 
apparent from the following description. 
SUMMARY OF THE INVENTION 
The above and other beneficial objects and advantages are accomplished in 
accordance with the present invention by a litter holding device 
comprising: 
a) a stationary base comprised of a bottom panel and two spaced apart 
facing side panels upwardly emergent from said bottom panel and provided 
with identical arcuately-shaped recesses centered upon a lateral axis 
parallel to said base, said side panels each bounded in part by exterior 
surfaces and facing interior surfaces, and 
b) a drum rotatively supported by said base and comprised of an enclosing 
wall having inside and outside surfaces, a portion of said wall having a 
circular cylindrical configuration centered upon said lateral axis, said 
drum terminating in front and rear planar lateral extremities, said front 
extremity having an attached front flange panel having a large circular 
animal access portal centered therein, said rear extremity having a rear 
flange panel disposed in parallel relationship to said front flange panel, 
said front and rear flange panels serving to embrace said side panels in 
sliding contact with the exterior surfaces thereof 
c) a sieving panel disposed within said drum and extending laterally 
between said flanges, said sieving panel having leading and trailing 
extremities and 
d) a funnel region outwardly directed from the enclosing wall adjacent the 
trailing extremity of said sieving panel, and terminating in an exit 
spout. 
In a preferred embodiment, a storing chamber is disposed upon the outside 
surface of said enclosing wall in overlying relationship with said sieving 
panel, said storing chamber bounded in part by an external panel having a 
leading extremity which is tangentially emergent from said outside 
surface, and a trailing extremity spaced circumferentially away from said 
sieving panel and radially spaced from said enclosing wall.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIGS. 1-6, an embodiment of the litter-holding device or 
"litter box" of the present invention is shown comprised of a stationary 
base 10 and drum 11 rotatively supported by said base. 
Base 10 is of metal or rigid plastic construction, and comprised of 
horizontal bottom panel 12 of substantially rectangular perimeter, and 
paired spaced apart parallel flat side panels 13 upwardly emergent from 
said bottom panel and terminating in upper extremities 14. In preferred 
embodiments, the side panels are continuous integral extensions of the 
base panel, as components of a monolithic base structure. The side panels 
are provided with identical arcuately shaped recesses 15 centered upon a 
lateral axis 19 parallel to said bottom panel and residing in a vertical 
plane that bisects said bottom panel. Said recesses 15 are preferably of 
circular shape except for an upper portion which opens onto the upper 
extremity of the side panels. Such manner of construction facilitates 
engagement of drum 11 with the base, as will be shown hereinafter. Side 
panels 13 are further characterized in being bounded in part by exterior 
surfaces 16 and facing interior surfaces 17. 
Drum 11 is defined by an enclosing wall 41 having inside and outside 
surfaces 20 and 21, respectively. A portion of said wall has a circular 
cylindrical configuration centered upon axis 19. Enclosing wall 41 extends 
between front and rear planar lateral extremities 22 and 23, respectively. 
Front extremity 22 has attached thereto a vertically disposed front flange 
panel 24 having a large circular animal access portal 25 centered therein. 
Rear extremity 23 has attached thereto a vertically disposed rear flange 
26. Said front and rear flanges serve to embrace said side panels in 
sliding contact with the exterior surfaces 16 thereof. 
A sieving panel, in the form of a zone of perforations 27, is incorporated 
into enclosing wall 41. Said zone has leading and trailing extremities 28 
and 29, respectively, spaced apart between 35 and 50 degrees of the 
contour of the cylindrical portion of the drum. The preferred, illustrated 
type of perforation is a grate-like array of elongated slots disposed as 
arc-like portions of the circumference of enclosing wall 41 in orthogonal 
relationship to axis 19. The zone of perforations extends between both 
lateral extremities of the drum. 
A funnel region 30 is outwardly directed from the drum adjacent the 
trailing extremity of the zone of perforations, and terminates in an exit 
spout 31. Said funnel region is defined by surfaces 47 and 48 which 
converge upon exit spout 31 in directions respectively parallel to and 
orthogonal to axis 19. 
The convergence angle A of surfaces 47, shown in FIG. 3, is between 120 and 
160 degrees. Convergence angles smaller than 120 degrees, which produce a 
steeply defined funnel region, displace exit spout 31 too far from 
enclosing wall 41. Convergence angles larger than 160 degrees produce a 
shallow funnel region which does not efficiently convey solid waste from 
the drum to exit spout 31. 
In the exemplified embodiment, a storing chamber 32 is disposed upon the 
outside surface 21 of enclosing wall 41 in overlying relationship with 
said zone of perforations. Said storing chamber is bounded in part by an 
external panel 33 having a leading extremity 34 which is tangentially 
emergent from outside surface 21 of said enclosing wall, and a trailing 
extremity 35 circumferentially advanced from the trailing extremity 29 of 
said zone of perforations. Storing chamber 32 is further bounded by end 
wall 42 and opposed lateral walls 44. The volume of storing chamber 32 is 
such as to be able to hold the entire batch of litter 37 that normally 
resides in drum 11. In alternative embodiments, the storing chamber may be 
replaced by a region which transiently accommodates sieved litter while 
drum 11 is rotated. 
In the use and operation of the exemplified embodiment of the litter box of 
the present invention, when the drum is in the position shown in FIG. 1 
wherein exit spout 31 is upwardly directed, litter is disposed upon the 
bottom of drum 11. In this position of use, the cat or other animal is 
able to enter drum 11 through access portal 25 and make use of the litter. 
When it is desired to remove solid and clumped animal waste 38 from the 
litter, drum 11 is manually rotated in the counter clockwise direction. 
Such motion causes unclumped litter to pass by sieving action through the 
slots in the zone of perforations, and become confined within storing 
chamber 32. The solid and clumped waste 38 is caused to move downwardly by 
gravity effect into funnel region 30 and thence to exit spout 31. A 
disposable plastic bag 39 is caused to removably engage spout 31. When the 
waste 38 has entered bag 39, the direction of rotation is reversed. With 
the clockwise motion that restores spout 31 to its initially uppermost 
position, clean litter that was stored in chamber 32 now passes back 
through the slots of said zone of perforations, and comes to rest in the 
bottom of the drum, thereby restoring the device to the starting or use 
state. The bag 39, containing the separated waste is easily detached from 
spout 31 and disposed of. A retaining lip 45 may be disposed atop spout 31 
to facilitate securement of the bag with the aid of a rubber band. Drum 11 
and base 10 are preferably fabricated of durable, washable plastic 
material such as thermoplastic polymers amenable to shaping by injection 
molding techniques. 
While particular examples of the present invention have been shown and 
described, it is apparent that changes and modifications may be made 
therein without departing from the invention in its broadest aspects. The 
aim of the appended claims, therefore is to cover all such changes and 
modifications as fall within the true spirit and scope of the invention.