Abstract:
A litter box has two unit assemblies and a waste receptacle. The first unit assembly has three components: an unenclosed litter compartment allowing animals&#39; ingress and egress to/from the unenclosed compartment in one of multiple directions to deposit waste material; a compartment to temporarily hold filtered litter; and a pivotally mounted and/or flexible screen that filters out waste material from the litter that is being communicated away from the unenclosed litter compartment and toward the temporary compartment. The second unit assembly is a support base that has a motor mounted on the support base that manipulates the first unit assembly, and contains a motion sensor and controller that actuates the motor. The waste receptacle is a rectangular, box-shaped container with an open top into which animal waste is deposited. When a controller associated with the device detects the presence of an animal through use of a motion sensor, a process is started whereby the controller waits for a predetermined amount of time to start a physical cycle. If the presence of an animal is detected again before the physical cycle starts, the process is aborted and restarted. Once the physical cycle is started, the first unit assembly is partially rotated by the motor. This rotation of the first unit assembly relative to the vector force of gravity causes the combination of litter and waste to move away from the unenclosed litter compartment, and toward the temporary compartment. The screen filters litter and waste being communicated toward the temporary receptacle, only allowing filtered litter to enter the temporary receptacle, and forcing waste solids to pass by the temporary compartment and into the waste receptacle. The motor then reverses, allowing the filtered litter in the temporary receptacle to be communicated back into the unenclosed litter compartment to its original location by passing through and under or back through the screen.

Description:
PRIOR PROVISIONAL APPLICATION  
       [0001]     The present application claims the benefit of U.S. Provisional Application Ser. No. 60/728,426, filed Oct. 20, 2006, which is hereby incorporated by reference in its entirety. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The current invention relates to an apparatus and method for separating and removing animal waste material from litter, and in particular, to a technique that automatically removes cat waste material from litter in an unenclosed litter box.  
       BACKGROUND OF THE INVENTION  
       [0003]     Many advances in technology related to automatic litter boxes have arisen to help improve the cleanliness of the litter box. One of the most significant advances is the use of what&#39;s called the “sifting method” of filtering litter. The sifting method has been employed by such devices as described in U.S. Pat. Nos. 4,846,104; 4,120,264; 5,507,252 and U.S. Pat. No. 5,662,066 (see also U.S. Pat. No. 6,463,881). The sifting method is significantly more effective than the so-called “raking method” (or “combing method”) as described in U.S. Pat. No. 5,048,065. The sifting method of cleaning litter has two major advantages over the raking method in that it is far more resistant to clogging, and generally does a much better job of cleaning the litter. Gravity is used to separate the litter from waste material instead of forcing a rake through the litter to remove solid waste material. The major flaw with the raking method is that a motor forces not only the rake through litter, but also the solid waste material though the litter as well. Although the rake can be made in such a way to travel relatively easily through litter, the unpredictable shapes and generally large surface area of solid waste makes it difficult to force waste clumps through such a dense and heavy material such as clay litter. The typical behavior of cats to bury their clumps makes this process even more difficult.  
         [0004]     There are often many undesirable effects with using such a raking method. One such effect is that clumps and other solid material can be wedged between the rack and the bottom of the litter pan, which can cause a smearing effect. The gradual build-up of such debris makes subsequent raking phases more and more difficult. Another such effect is that the mass of the litter itself helps to force litter clumps and other solid material in between the tines of the rake. In this scenario, gravity is actually hindering the filtering process. Because gravity is forcing the litter into the pan, the litter wants to stay where it is situated. As the rake and solid debris travel from one end of the litter pan to the other, the litter has to move out of the way of the debris, or be force to move in front of the debris itself and end up in the waste receptacle. The only way for the litter to get out of the way is to go above the debris, below the debris, or around the debris to either side. Gravity is always forcing the litter into the pan, and the litter that is forced to move out of the way of the debris is compressed against other litter within the litter pan. When the debris is close to the side of the litter pan, resistance is even greater. The options for which direction the litter can move are reduced, and further smearing can occur, and the increased force on the debris can further force the debris into the tines of the rake, clogging the rake. To compound the problem, it&#39;s common for cats to bury their waste into a corner, making a significant portion of the litter end up on one side of the litter pan. This makes it extremely difficult for the rake to filter the unevenly covered litter pan.  
         [0005]     Because of these problems, there is usually a narrow range at which the litter must be maintained. Too little litter, and the clumps will stick to the bottom of the litter pan. To high a level, and the force required to push the rake and the debris through the litter is too great for the device to handle. Aside from a clogged rake making the litter box ineffective, it also increases stress on the mechanical parts, motor, and power consumption. It is also extremely difficult to unclog the rake, as well as being an extremely undesirable task to take on. U.S. Pat. No. 6,851,386 tries to address this problem by introducing a rake that is less susceptible to clogging; however the raking method itself cannot change the force of gravity working against the debris or the mass of the clay. Although significantly less clogging is achieved by this new rake design, the effect is that instead of clogging, the rake actually breaks up the clumps and/or other solid material into smaller pieces, traveling through the rake instead of into the waste receptacle where it is intended to be communicated. This results in an incomplete cleaning process. Clogging can also be reduced by increasing the angle on the tines of the rake to reduce the negative impact gravity has on the filtering process; although this improves the process, it does so only to a certain degree. Although the raking method has numerous disadvantages, it has the significant advantage in that an open litter box design is easily achievable. The importance of this feature will be described later.  
         [0006]     The sifting method uses gravity to its advantage instead of to its disadvantage. Instead of moving relatively large masses of solid debris through dense clay litter, the sifting method uses gravity to make the litter move around the solid waste debris. The forces in effect are always relatively close to 1G, and no greater force than this is required to separate the solid material from the litter. The screen used to filter litter from solid waste material is therefore not subjected to the forces required by the raking method, and clogging is avoided. This method draws a parallel to the frequently demonstrated science experiment where a jar, a collection of small particles (e.g. sand), and a collection of larger particles (e.g. marbles) are provided. The sum volume of the small and large particles is such to approximate the volume of the jar. If the small particles are placed in the jar first, and then an attempt is made to place the larger particles in the jar, the effect of gravity on the small particles in the jar prevents them from moving out of the way to make room for the larger particles; however, by placing the larger objects in the jar first, and pouring the smaller particles in the jar second, the smaller particles will easily move around the larger objects, filling the jar with ease. This is another example of how gravity is used to help solve the problem, rather than hindering it from being solved. This principle is applied when the sifting method is employed, and provides a predictable, clog-free method of separating litter from solid waste material.  
         [0007]     Many products today employ the sifting method. One of the more advanced products is described in U.S. Pat. No. 6,463,881, where a globe-like structure is used to house filtered litter, a sifting mechanism, and to provide a certain amount of room for an animal, as well as a hole through which the animal can ingress/egress the globe. This product is far superior in filtering litter than a product that utilizes the raking method, but is an enclosed unit which as certain disadvantages. Being an enclosed litter box, this product does have the advantage of making it far more difficult for the cat to throw litter outside of the litter box; however there are also significant disadvantages as well. The first and most important of which is that many cats simply will not use enclosed litter boxes. Secondly, this product must have ports in the globe that open to let waste exit the globe and fall into the waste receptacle. These ports limit the size of the clumps that can fit through these the ports, preventing the use of the device for cats that create large clumps; this particularly true for cats with diabetes, as the clumps will not fit through the ports. Thirdly, it is relatively difficult to introduce fresh litter into the globe as well as clean the globe (which is recommended to be done periodically). Furthermore, there are weight restrictions for cats that must be within a 5-15 lbs. range. A cat less than 5 lbs. will not weigh enough to trigger the sensor, and cats over 15 lbs. will have trouble fitting into the globe.  
         [0008]     U.S. Pat. No. 5,167,204 attempts to use a rake-like structure, but through manual manipulation effectively employs a sifting mechanism. This has the significant advantage of using the sifting method while still providing a traditional open litter box that&#39;s attractive to the largest population of cats; however this mechanism has multiple disadvantages, the first of which is that the device would have to be very large in order to create a litter area large enough for a typical feline to use effectively. The second disadvantage is that the mechanism is not automated, and would be difficult to automate. The third disadvantage is that it is would be very difficult to level the litter without picking up the entire litter box and shaking it around.  
         [0009]     The raking method does have a significant advantage in that the process itself is conducive to the traditional open litter box design. Although it&#39;s possible to place an enclosure around such a litter box to help contain litter, an enclosure is not required in order to make the litter box operate. A litter box is only effective if the cat will use the device, and because many cats will simply not uses enclosed litter boxes, a perfectly designed enclosed system will not do the job if the cat does not elect to use it. For those cats that will not use an enclosed device, the alternative is that the cat will either use an unenclosed litter box if available, or an undesirable location if not available. Even cats that will use an enclosed litter box will often prefer an unenclosed litter box if given the choice. This makes it even more difficult to get the value out of a potentially expensive enclosed litter box device if a pet owner has multiple cats. Even if only one cat within a multi-cat household will not use an enclosed litter box, it is often the expectation of the pet owner to reap the benefits of the enclosed device with the cats that will use the enclosed device, while for the cat or cats that will not use the enclosed device, deal with the added labor involved in maintaining the unenclosed device for those stubborn cats only. However, because many cats that would otherwise use the enclosed device if that were their only option will often use the unenclosed device when given the choice, the effectiveness of the enclosed device is further reduced, as it gets used even less frequently than expected by the cat owner.  
         [0010]     The challenge is thus to create an automated litter box that has superior filtering capabilities by utilizing the sifting method, and yet has an open design to encourage use by as many household pets as possible. It is against this background and the need to solve these problems not addressed by prior art that the present invention was developed.  
       SUMMARY OF THE INVENTION  
       [0011]     Accordingly, it is an object of the present invention to provide an automatic litter box to employ a superior cleaning method that uses a screen and a temporary container, as well as a method for altering the relationship of the appropriate components relative to the vector force of gravity.  
         [0012]     It is another object of the present invention to provide an automatic litter box that is unenclosed to facilitate usage by all household pets.  
         [0013]     It is also an object of the present invention to provide an automatic litter box that significantly limits any unpleasant odors emanating from the litter box.  
         [0014]     It is yet another object of the present invention to provide an automatic litter box that is unenclosed to help facilitate cleaning and adding of litter.  
         [0015]     It is a further object of the present invention to provide an automatic litter box that does not significantly limit the size or weight of the pet.  
         [0016]     It is yet a further object of the present invention to provide an automatic litter box that can be used with pets, such as cats, that have diabetes.  
         [0017]     It is also an object of the present invention to provide an automatic litter box that can use traditional, inexpensive clumping litter.  
         [0018]     Another object of the present invention is to provide an automatic litter box that eliminates or significantly reduces mental stress of the pet owner.  
         [0019]     It is also an object of the present invention to provide an automatic litter box that more effectively seals off the waste receptacle to reduce odor and mold, and therefore allows the size of the waste receptacle to be increased, which will reduce the frequency required to empty the litter box.  
         [0020]     Additional objects, advantages, and novel features of this invention shall be set forth in the description that follows, and will also become apparent to those of reasonable skill in the art upon examination of the following specification. The objects and advantages of the invention may be realized and attained by means of the instrumentalities, combinations, and methods particularly pointed out in the appended claims.  
         [0021]     To achieve the foregoing and other objects and in accordance with the purpose of the present invention, as embodied and broadly described herein, an apparatus is disclosed for receiving and disposing of waste material from an animal, typically a cat. The apparatus includes a first unit assembly comprising an unenclosed litter compartment, a temporary receptacle, and a filtering screen. The unenclosed litter compartment allows an animal to ingress and egress the unenclosed litter compartment from multiple directions, and is also not covered from above. The temporary receptacle is provided to store filtered litter during the cleaning cycle. The unenclosed litter compartment and the temporary compartment are attached in such a way as to share at least one common surface continuation. This surface continuation may be described as a partial cylinder, although other continual shapes including but not limited to shapes such as partial sphere would also work. This common surface continuation (also described as the “common outer surface”) allows for a partial rotation of the unit assembly along that continual surface so as to affect the movement of litter and waste material out of the unenclosed litter compartment and into the temporary receptacle. A filtering screen is located between the unenclosed litter compartment and the temporary compartment. The screen covers the opening of the temporary compartment only allowing filtered litter to enter the temporary compartment. This screen may be pivotally mounted in order to allow filtered litter to more easily flow out of the temporary compartment and back into the unenclosed litter compartment after the filtering phase. A track may be disposed along the continual surface, and may follow the curved shape. This track may be attached to, or molded as, part of the continual surface. The track is designed to receive a sprocket that is turned by a motor.  
         [0022]     A support base is used to support and manipulate the first unit assembly in order to clean the litter box and dispose of waste into a waste receptacle. A waste receptacle may fit within and under the support base. The support base may also house electronics to activate and control the device. The support base may include a motor and a sprocket. The sprocket mates with the track of the first unit assembly. When the motor turns the sprocket, the first unit assembly is forced to rotate in the opposite direction of the sprocket rotation. This motor is triggered to perform a cleaning cycle through the use of a motion sensor. For example, a cat may break a beam of infrared light transmitted from an infrared emitter to an infrared detector. The controller senses the beam interruption, and begins a delay function after the beam transitions back from the interrupted state to the uninterrupted state. After a determinate amount of time (typically between 5 and 10 minutes), the physical cycle is triggered. The physical cycle may involve three partial rotations of the first unit assembly. The first partial rotation is a cleaning rotation whereby litter is communicated from the unenclosed litter compartment into the temporary receptacle. This partial rotation filters out solid waste material. Whereas litter may travel freely through the screen and into the temporary compartment, solid waste material is forced to bypass the temporary compartment, sliding over top of the screen and temporary compartment at the appropriate time during the first partial rotation. The solid waste material may then slide through a large hole within the support base, and into a waste receptacle.  
         [0023]     After the filtering phase, a litter-reintroduction phase may be performed whereby filtered litter is communicated out of the temporary compartment back into the unenclosed litter compartment. This is achieved by reversing the motor&#39;s rotational direction thereby reversing the rotation of the first unit assembly. This phase may over-rotate the First Unit Assembly in order to level the litter within the unenclosed litter compartment. The over-rotation may be employed to overcome the frictional resistance of the litter and the inner surface of the unenclosed litter compartment. The motor may then reverse direction again, and return the first unit assembly to the home position. While the First Unit Assembly is situated in the home position, substantial odor may be prevented from escaping the device by providing reasonable tolerances along the inside top edge of the Second Unit Assembly in relation to the proximity of the edges of the First Unit Assembly. The Second Unit Assembly may be constructed in such a way as to mate with the First Unit Assembly in order to substantially prevent odor from escaping from the waste receptacle. To further this goal, a flexible gasket material made of fur-like or other material may be used. This material may be flexible enough to help seal any gap between the First and Second Unit Assemblies, but also not produce substantial friction that would otherwise hinder the operation of the device. This gasket material can substantially reduce or eliminate odor emanating from the waste receptacle and decreasing the frequency required to empty the litter. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]     The accompanying drawings, which are incorporated in and form a part of the specification, illustrate the preferred embodiments of the present invention, and together with the descriptions serve to explain the principles of the invention, in which:  
         [0025]      FIG. 1A-1C  are side views of unit assemblies and their major components for one embodiment;  
         [0026]      FIGS. 2A-2C  are front views of the unit assemblies shown in  FIGS. 1A-1C ;  
         [0027]      FIG. 3  is a side view of an assembled device;  
         [0028]      FIG. 4  is a front view of an assembled device;  
         [0029]      FIGS. 5A-5K  illustrate a separation cycle of an embodiment device;  
         [0030]      FIGS. 6A through 6L  illustrate a reintroduction cycle of an embodiment device;  
         [0031]      FIGS. 7A and 7B  illustrate a return to home position cycle of an embodiment device;  
         [0032]      FIG. 8  is a perspective view of an embodiment First Unit Assembly with supports slats unobstructed by a filtering screen;  
         [0033]      FIG. 9  is a perspective view of an embodiment First Unit Assembly with supports slats an installed screen;  
         [0034]      FIG. 10  is a perspective view of a membrane;  
         [0035]      FIG. 11  is a perspective view of an embodiment First Unit Assembly illustrating attach points for one of the three membranes;  
         [0036]      FIG. 12  is a perspective view of an embodiment First Unit Assembly with drip caps and a lip; and  
         [0037]      FIG. 13  shows a controller. 
     
    
     COMPONENT IDENTIFICATION  
       [0038]      100  First Unit Assembly  
         [0039]      120  Unenclosed litter compartment  
         [0040]      122  Sidewalls  
         [0041]      124  Front, inside surface of sidewall  
         [0042]      150  Compartment to temporary hold filtered litter  
         [0043]      140  Screen to filter litter that is pivotally mounted  
         [0044]      130  Litter  
         [0045]      132  Animal waste material  
         [0046]      142  Screen attachment location where a flexible or non-flexible screen is pivotally attached, or a where a flexible screen is not pivotally attached  
         [0047]      110  Track that motor and sprocket uses to manipulate the First Unit Assembly  
         [0048]      114  Common outer surface of First Unit Assembly  
         [0049]      128  Lip  
         [0050]      129  Drip cap  
         [0051]      162  Position sensor trigger  1   
         [0052]      164  Position sensor trigger  2   
         [0053]      166  Position sensor trigger  3   
         [0054]      170  Slats  
         [0055]      180  Membrane  
         [0056]      182  Top portion of membrane  
         [0057]      184  Bottom portion of membrane  
         [0058]      200  Second Unit Assembly  
         [0059]      210  Wheels on which the First Unit Assembly rides  
         [0060]      250  Controller  
         [0061]      252  On/off button  
         [0062]      240  Motion detector  
         [0063]      242  Infrared transmitter  
         [0064]      244  Infrared detector  
         [0065]      230  Sidewalls  
         [0066]      220  Drive unit  
         [0067]      222  Sprocket  
         [0068]      224  Motor  
         [0069]      260  Position sensing unit  
         [0070]      262  Position sensor  1   
         [0071]      264  Position sensor  2   
         [0072]      266  Position sensor  3   
         [0073]      300  Waste Receptacle  
       DETAILED DESCRIPTION  
       [0074]     With reference to  FIGS. 1-4 , an embodiment of the instant invention  10  includes a First Unit Assembly  100 , a Second Unit Assembly  200  and a Waste Receptacle  300 . The Second Unit Assembly  200  provides a base that rests on a floor, counter, or other flat surface that is accessible by one or more pets, such as a cat or cats. The First Unit Assembly  100  rests on rollers  210  and a sprocket  222  of the Second Unit Assembly  200 , and is prevented from moving laterally by a track  110  on a common outer surface  114  of the First Unit Assembly  100  and sidewalls  230  of Second Unit Assembly  200 . A home position for the First Unit Assembly  100  is a position such that the top of the side walls  122  of the unenclosed litter compartment  120  are approximately parallel to the top of the sidewalls  230  of the Second Unit Assembly  200  and such that when litter  130  is placed in the unenclosed litter compartment  120 , the litter  130  will rest at level state, as depicted in  FIG. 3 . When the First Unit Assembly  100  is properly positioned on top of the Second Unit Assembly  200 , an infrared transmitter  242  and infrared detector  244  of a motion sensor  240  on the Second Unit Assembly  200  have a line of sight from one to the other that is unobstructed by the First Unit Assembly  100 . The Waste Receptacle  300  may be inserted from either the front or rear of the Second Unit Assembly  200  such that the waste receptacle  300  is directly under the Second Unit Assembly  200 , as shown in  FIGS. 3 and 4 . Litter  130  is placed in the unenclosed litter compartment  120 .  
         [0075]     1. Initialization  
         [0076]     The Second Unit Assembly also includes a controller  250 . Power is applied to the controller  250  by, for example, use of a  12 -volt power adapter. A component of the controller  250  is a switch or button  252  that allows the unit to be turned on or off. The unit will automatically begin a physical cycle when power is applied and the power switch or button  252  puts the unit into the “on” mode. This physical cycle is described in the following (see the section  3  below, “Physical Cycle”).  
         [0077]     2. Obstruction Detection and Delay  
         [0078]     After the unit  10  physically cycles once, the controller  250 , through use of the motion sensor  240 , having the infrared transmitter  242  and infrared detector  244 , detects the presence of a pet, such as a cat, by means of the pet&#39;s obstruction of the line of sight from the infrared transmitter  242  to the infrared detector  244 . This detection mechanism is a common technique utilized by those familiar with the art of motion detection through use of electronics. Once the pet leaves the unenclosed compartment  120 , line of sight between the infrared transmitter  242  and infrared detector  244  is reestablished, triggering a timer that is a component of the controller  250 . As known in the art, such timers are common components of device controllers, such as the controller  250 . The timer&#39;s purpose is to permit sufficient time for the litter to “clump,” and also to allow enough time for the pet to vacate the immediate area so as not to needlessly startle the pet when the unit begins to cycle. If at any time an obstruction is detected between the infrared transmitter  242  and infrared detector  244  while the timer is active, the timer process is aborted, and the timer process restarts only when the obstruction detected by the motion sensor  240  is removed from the unenclosed litter compartment  120 , reestablishing line of sight between the infrared transmitter  242  and infrared detector  244 . Once a predetermined amount of time has passed (for example, about  10  minutes) without any detected obstructions, the physical cycle begins.  
         [0079]     3. Physical Cycle  
         [0080]     The physical cycle is described in three phases: The first phase is the “separation” (i.e. filtering) phase, the second phase is the “litter reintroduction” phase, and the third phase is the “return to home position” phase. The first phase is illustrated by  FIGS. 5A through 5K .  FIG. 5A  identifies significant components of the First Unit Assembly  100  pertaining to the physical cycle. Furthermore, waste material  132  is identified in the  FIGS. 5A-5K , and is the object to be separated from the litter  130 .  
         [0081]     The physical cycle begins with the sprocket  222  turning through use of a motor  224  as controlled by the controller  250 . The sprocket  222  and motor  224  together provide a drive unit  220  that drives the physical movement of the First Unit Assembly  100 . As the sprocket  222  turns in a clockwise direction as viewed from  FIG. 1 , the First Unit Assembly  100  is rotated in a counter-clockwise direction due to the linkage of sprocket  222  of the Second Unit Assembly to the track  110  of the First Unit Assembly  100 . The First Unit Assembly  100  is partially rotated as shown in  FIGS. 5A through 5K ; that is, the First Unit Assembly  100  does not undergo a full 360° rotation. This partial rotation causes the combination of litter  130  and waste material  132  to move toward a screen  140 . The screen  140  only allows filtered litter  130  to move into temporary container  150 , forcing any waste solid  132  to pass by the temporary container  150  and into the waste receptacle  300 . The first phase is terminated when a position sensor trigger  162  is detected by first position sensor  262  of a position sensing unit  260 , as shown in  FIG. 2 . The result of the first phase is that waste solids  132  are removed from the litter  130 , by exiting the First Unit Assembly  100 , passing through the Second Unit Assembly  200 , and into the Waste Receptacle  300 .  
         [0082]     The second phase of the physical cycle begins when the first phase of the physical cycle ends. The drive unit  220  causes the motion of the First Assembly Unit  100  to reverse. The controller  250  controls the motor  224  to reverse the rotation of the sprocket  222  and begin turning counter-clockwise as viewed from  FIG. 1 , causing the First Unit Assembly  100  to rotate in a clockwise direction. The First Unit Assembly  100  is partially rotated, as shown in  FIGS. 6A through 6L . This causes the filtered litter  130  to be communicated out of the temporary container  150  by passing through and under the screen  140 , back into the unenclosed litter compartment  120  to its original position. The second phase ends when a second position sensor trigger  164  is detected by second position sensor  264  of position sensing unit  260 , as shown in  FIG. 2 . Note that the location of the second position sensor trigger  164  may be set to correspond to the approximate angle of repose of the litter  130 , so that at the end of the second cycle, the level of the litter  130  is approximately parallel with the sidewalls  122 .  
         [0083]     The third phase of the physical cycle begins when the second phase of the physical cycle ends. The drive unit  220  again reverses the direction of motion of the First Assembly Unit  100 . The controller  250  causes the motor  224  to reverse the direction of the sprocket  222  and begin turning clockwise as viewed from  FIG. 1 , causing the First Unit Assembly  100  to rotate in a counter-clockwise direction. The First Unit Assembly  100  partially rotates as shown in  FIGS. 7A and 7B . The third phase ends when the position sensor trigger  166  is detected by third position sensor  266  of position sensing unit  260 , as shown in  FIG. 2 . The result of the third phase puts the First Unit Assembly  100  back into its original home position. The physical cycle has now ended. The controller  250  again begins monitoring the motion detector  240  for an obstruction in the line of sight of the infrared transmitter  242  and infrared detector  244  in order to continue operation (see section 2, Obstruction Detection and Delay).  
         [0084]     The controller  250  that monitors detection of motion from the motion detector  240 , performs a delay, performs monitoring of the position sensing unit  260 , and performs motor  224  activation is a device, or combination of devices, familiar to those of reasonable skill in the art of building electronic devices.  
         [0085]     In the preferred embodiment, position sensor triggers  162 ,  164 ,  166  are permanent magnets, whereas position sensors  262 ,  264 ,  266  are hall effect sensors.  
         [0086]     In another embodiment reed switches may be used instead of hall effect sensors for position sensors  262 ,  264 ,  266 . The permanent magnets used in the preferred embodiment as position sensor triggers  162 ,  164 ,  166 ,may also be used in this embodiment.  
         [0087]     In another embodiment protrusions (or bumps) may be used instead of permanent magnets for position sensor triggers  162 ,  164 ,  166 , and lever switches or push buttons may be used instead of hall effect sensors as position sensors ( 262 ,  264 ,  266 ). This requires tight tolerances in construction as the bumps or other protrusions must be precisely located so as to mechanically trigger the lever switches or push buttons.  
         [0088]     In another embodiment, the position sensing unit  260  may comprise one single position sensor, used in conjunction with three triggers. In this embodiment, all three triggers are placed in-line with one another so that all three position sensor triggers can pass over the single position sensor. In this embodiment, a smarter controller  250  that better understands which phase is being preformed during the physical cycle is required. In this embodiment, the First Unit Assembly  100  must either be initially placed on top of the Second Unit Assembly  200  such that the single position sensor is located between position first sensor trigger  162  and third position sensor trigger  166 , or the controller  250  must be further developed to briefly ignore position third sensor trigger  166  during the first partial rotation of initialization. This is a cost-reducing embodiment, as the enhanced programming of the controller  250  is typically inexpensive or free, whereas the purchase and installation of the two otherwise unneeded position sensors would incur higher manufacturing costs.  
         [0089]     In another embodiment, an infrared emitter/detector pair is used instead of a single position sensor as described in the previous embodiment. The infrared emitter would be placed on one side of track  110 , and an infrared detector would be placed on the other side of the track  110  at the position where sensors  262 ,  264 ,  266  are located when viewed from  FIG. 1 . Permanent magnets would not be used in this embodiment; instead, holes would be drilled through both sidewalls of track  110  approximately at positions  162 ,  164 , and  166 , such that line-of-sight may be established through the track from the infrared emitter to the detector, but in such a way so as not to negatively effect the operation of the physical cycle. Furthermore, the position of these holes need not be precise and may be optimized to fall between the teeth of track  110 . In this embodiment, a more intelligent controller is also required as described in the previous embodiment; however infrared emitters/detectors are typically even more cost effective than a single hall effect sensor, and no permanent magnets would be required for position sensor triggers.  
         [0090]     In another embodiment, a step could be added to allow easier ingress/egress of an animal to/from the unenclosed litter compartment  120 .  
         [0091]     In another embodiment, the height of one or more of the sidewalls  122  of the First Unit Assembly  100  could be raised help contain litter  130 . A hole in the sidewalls  122  would have to be added if the way the sidewalls  122  were extended would obstruct the line-of-sight between the infrared/emitter detector pair  242 ,  244 . As long as an opening was preserved to allow ingress/egress of an animal, two sides, plus part of a third side could be raised. These extensions could be permanent in one embodiment, or optionally snap, screw, or otherwise fastened into place to extend the shallow sides  122  of the First Unit Assembly  100  after a pet has adjusted to the device. Sides could be added one at a time and the tolerance of the pet was observed to determine the practicality of the enhancement.  
         [0092]     In another embodiment, the step described in a previous embodiment could be used in conjunction with a pressure switch in lieu of the infrared emitter/detector pair  242 ,  244  to detect the passage of an animal. In this embodiment, the pressure switch would trigger the timer contained within the controller  250  upon ingress/egress of an animal. The delay (typically 10 minutes) would be long enough so as to not activate the physical cycle while the animal was in unenclosed litter compartment  120 , as an animal would be unlikely to want to remain in the litter box for that long, and would reset the timer again when the animal vacated the litter box, activating the physical cycle 10 minutes after leaving. This step would ideally cover the entire surface where an animal may ingress/egress the litter box. With raised sidewalls  122 , a small step may be used in front of the area where the animal may ingress or egress the litter compartment  120 . Without sidewalls  122 , the animal may ingress/egress the litter compartment from all three unenclosed sides of the litter box, and therefore a U-shaped step, and potentially multiple pressure switches, may be preferable for this embodiment. In this embodiment, only one of the multiple pressure switches would need to be actuated in order to trigger the timer in the controller.  
         [0093]     In another embodiment, the unit  10  may be manually operated. No motor  224  or controller  250  is required for this embodiment. Instead, a human manipulates the First Unit Assembly manually. This can be made easier by providing a drive unit in the form of one or more handles attached to the First Unit Assembly  100  in strategic locations so as not to hinder the operation of the device. One such location would be the front and top of the First Unit Assembly  100  as observed in the home position. When a handle is attached to the front edge of the first unit assembly  100 , the handle should ideally be angled upward in order that the leveling phase partial rotation can be fully realized. The handle may also-be high enough to allow manual operation while minimizing the stooping required to reach the handle. The brackets that attach the handle to the First Unit Assembly  100  may be attached in such a way as to allow the handle to pivot, allowing for easier operation and guaranteed clearance of the Second Unit Assembly  200 . Another such location could be on the top edge of the First Unit Assembly  100 . When attached to the top edge of the First Unit Assembly  100 , the handle ideally extends significantly beyond the top edge of the First Unit Assembly, and is pivotally mounted. The handle may extend significantly in order to allow passage of waste material  132  over the screen  140  and temporary compartment  150  and into the waste receptacle  300  without being intercepted by the handle or the hand of the person manually operating the device. Other locations for handles, knobs, or other such devices to be attached to the First Unit Assembly  100  could also be used.  
         [0094]     In another embodiment, support strips can be placed on one side of the screen  140  to prevent flexible screens  140  from deforming significantly when litter  130  is communicated away from the unenclosed litter compartment  120  and toward the temporary container  150  during the separation phase, as depicted in  FIGS. 5A through 5K . These support strips, depicted in  FIGS. 8 &amp; 9 , may be called slats  170 . Several slats  170  may be attached, as depicted in  FIG. 8 . The flexible or pivotally mounted screen  140  is mounted on a mount point  142  and rests against the slats  170 , as depicted in  FIG. 9 . The screen  140  may be either flexible or rigid, or some degree in between. A rigid screen  140  would need no support slats  170  in order to prevent the screen  140  from deforming during the separation phase. A flexible screen  140  might benefit from support slats  170  depending on the memory qualities of the material used in constructing the screen  140 . Materials that have poor memory qualities or insufficient stiffness to prevent significant deformity during the separation phase may require support slats  170  in order to ensure proper operation of the device. These support slats  170  do not significantly inhibit litter traversal during the separation phase or the litter reintroduction phase, but prevent the screen  140  from significantly deforming during the separation phase while not interfering with the flexible or pivotally mounted screen&#39;s  140  operation during the litter reintroduction phase. By pivotally mounting the screen  140  at the pivot points  142 , the litter may travel under the screen  140  instead of having to travel through the screen  140  during the reintroduction phase.  
         [0095]     In another embodiment, as shown in  FIGS. 10 and 11 , a flexible membrane  180  made of rubber, plastic, or other waterproof and flexible material may be added to the interior of the unenclosed litter compartment  120 . A membrane  180  may be attached in various ways to help dislodge litter clumps that might otherwise become stuck to the sides of the unenclosed litter compartment  120 .  FIG. 10  shows the membrane attachment locations along the top  182  and bottom  184  edges of the membrane  180 . The membrane  180  is mounted with a generous amount of slack from top to bottom mounting locations  182 ,  184 . The membrane  180  would facilitate dislodging of waste clumps during the separation phase (shown in FIGS  5 A through  5 K) of the physical cycle by allowing waste clumps to “peel away” from the membrane  180  instead of sticking to the rigid sides of the unenclosed litter compartment  120 . Membranes  180  may be attached to both sides  122  of the unenclosed litter compartment  120 , as well as the inside-front  124  of the unenclosed litter compartment  120 .  
         [0096]     In another embodiment, depicted in  FIG. 12 , a lip  128  on the top inside edges of the three open sides  122  of the unenclosed litter compartment  120  could be added to help contain litter  130 . The lip  128  may be attached along the accessible sides  122  of the unenclosed litter compartment  120 . When cats bury their waste, litter  130  will tend to pile against one or more sides  122  of the unenclosed litter compartment  120 , forming a ramp for subsequently flung litter  130  to fly out of the litter box  120 . A lip  128 , for example in the form of either a shelf edge or a partial cylinder, may be used to prevent substantial amounts of litter  130  from exiting the unenclosed litter compartment  120 . In the shelf edge configuration, the lip  128  would prevent litter  130  from exiting the litter box  120  by preventing the litter  130  from ascending beyond the height of the unenclosed litter box sides  122 . In the partial cylinder configuration, litter  130  would be redirected by the partial cylinder back into the unenclosed litter compartment  120 . Litter  130  would not be prevented from ascending above the top edge of the unenclosed litter compartment  120 , but the partial cylinder would direct the litter  130  back into the unenclosed litter compartment  120  laterally. Other shapes could also be used to redirect litter  130  without having to raise the sides  122  of the litter box  120 . This lip  128  would help direct litter  130  that would otherwise be flung out of the litter box  120  back into the litter box  120 .  
         [0097]     In another embodiment, a drip cap  129  can be used. A drip cap  129  may be attached along, one or more of the top edges of the unenclosed litter compartment  120 .  FIG. 12  shows a drip cap  129  attached along the three accessible sides  122  of the unenclosed litter compartment  120 . The purpose of the drip cap  129  is to force urine to drip towards the interior of the unenclosed litter compartment  120  instead of toward the sides  122 . This prevents litter clumps  132  from sticking to the sides  122  of the unenclosed litter compartment  122 . The drip cap  129  could be removable so as to make the unit easier to clean, although the drip cap  129  itself would facilitate the unit staying cleaner for a longer period of time. Although the drip cap  129  has the appearance of reducing the internal area of the unenclosed litter compartment  120 , the drip cap  129  itself can be urinated on, so the area the animal can use to deposit waste  132  is still effectively the same size as it would be without the drip cap  129 .  
         [0098]     In another embodiment, the rear panel of the Second Unit Assembly  200  is hinged at the top, and the Waste Receptacle  300  is inserted under the Second Unit Assembly  200  from the rear instead of the front as depicted in  FIGS. 3 and 4 . Therefore, the rear panel of the Second Unit Assembly  200  and the handle of the Waste Receptacle  300  are both located in the rear of the device. The hinge at the top allows for waste material  132  to accumulate and even mound slightly while still allowing the Waste Receptacle  300  to be removed. The hinged panel will pivot out of the way if mounded waste clumps  132  force it to do so as the Waste Receptacle  300  is slid out from under the Second Unit Assembly  200  from the rear of the device.  
         [0099]     In another embodiment, the front and rear panels of the Second Unit Assembly  200  may snap in place at the top so that if an animal or child were to obstruct the operation of the unit, the panel would snap out of place and prevent pinching the animal or child. In the previous embodiment, where the rear panel is hinged form the top, the fixed portion of the top-rear side serves a dual purpose of conforming to the First Unit Assembly&#39;s  100  rear surface and track to seal out odors, and to provide a fixed surface to which one or more hinges can be attached. This fixed rear edge could snap into place as well, and therefore snap out of place preventing pinching of an animal or child.  
         [0100]     The foregoing description is considered as illustrative only of the principles of the invention. Many modifications and variations are possible in light of the above teaching. Accordingly, all suitable modifications and equivalents may be resorted to falling within the scope of the invention as defined by the claims that follow.