Abstract:
A self-cleaning litter box for cats employs a comb drive to drive a comb through litter to remove waste from the litter. A sensor for detecting the presence of an obstruction is coupled to the comb drive and stops the comb drive upon detecting an obstruction. A manual mode selector switch and an actuating switch are provided to manually activate the cleaning of the litter box at a time deemed appropriate by the cat owner. A foot pedal unit may be provided for semi-automatic use. A removable tray for cat litter may be provided. The tray may be disposable. A pivotable ramp facilitates ingress to, and egress from, the litter box. The ramp may be carpeted. A tray receives the litter box and a hood encloses the litter box to provide privacy.

Description:
The present invention is directed to litter boxes and particularly to self-cleaning litter boxes for cats. 
     BACKGROUND 
     Cats are usually trained to use a litter box for elimination of both liquid and solid wastes. A cat litter box is normally made of plastic or like material so that a cat&#39;s urine will not leak through the box. Other cat litter boxes have been proposed, as in the construction described in U.S. Pat. No. 5,249,549 (Rockaitis), in which the litter box is made of a material that absorbs liquid but does not permit it to leach through to the exterior of the box. The litter used in boxes of this kind may be one of any number of particulate litter or other materials that absorb moisture from the waste of the cat. The material may also suppress odor from cat waste. Some forms of cat litter form clumps when wet. Usually, a cat will bury its solid waste in the litter material in the box. 
     Most cat owners take appropriate action to discard the litter from a cat litter box after an appreciable period of time, often several days. On the other hand, even before the litter has been thoroughly saturated with waste from the cat or cats that use it, a cat may be inclined to push some of the litter out of the box, particularly if the odor is strong. In any event, the person using a cat litter box may find the task of emptying the cat litter to be unpleasant. Thus, a number of devices have been proposed for cleaning cat litter boxes. Such devices are disclosed in U.S. Pat. No. 4,096,827 (Cotter), U.S. Pat. No. 4,117,804 (Moore et al.), U.S. Pat. No. 4,190,525 (Menzel), U.S. Pat. No. 4,325,325 (Larter), U.S. Pat. No. 4,325,822 (Miller), U.S. Pat. No. 5,048,465 (Carlisi), U.S. Pat. No. 5,226,388 (McDaniel), and U.S. Pat. No. 5,477,812 (Waters). 
     The self-cleaning cat litter box disclosed in the Carlisi patent utilizes a rake or comb that is normally maintained in a storage position at one end of the litter chamber. At predetermined intervals, the comb is moved through the litter, from the rake storage end of the chamber to the opposite end, which constitutes a discharge end for the chamber. At the discharge end of the chamber the rake moves up out of the litter and discharges any clumps collected by the comb into a disposal receptacle. Unfortunately, because cats are not consistent in their elimination habits, such periodic clearing may be too frequent, or not frequent enough. 
     The Waters patent describes a system for moving a comb or rake through the litter responsive to entry and exit of the cat from the litter box. In addition, Waters provides an improved disposal receptacle and alarms to report an insufficient litter supply and a full disposal receptacle. The entire disclosure of the Waters &#39;812 patent is incorporated herein by reference. 
     Despite the advances made by these prior art patents, there remains several deficiencies in self-cleaning litter boxes. First, if the cat is present in the litter box while the rake or comb is moving, the cat may be startled to move suddenly and spill the contents of the litter box or, the cat could be caught by the mechanism. Second, devices that require the passage of time or the activity of a cat to initiate the rake drive mechanism do not allow for use of the rake at other times. Third, easy access is needed to aid cats in entering and exiting the litter box. The open boxes allow litter to be spilled out and do not provide cover for cats that may desire privacy. 
     SUMMARY 
     The present invention alleviates to a great extent the deficiencies of the prior art by providing a litter box having a housing defining an upwardly open litter chamber for receiving cat litter, a comb disposed in the litter chamber, a carriage supporting the comb, and a comb drive for driving the comb between a storage position and a discharge position. The comb drive includes a reversible drive motor mounted on the carriage. A reverse sensor is coupled to the carriage. The reverse sensor is coupled to a first surface of the carriage and the sensor provides a shut-off signal to the comb drive when the sensor detects that the carriage has contacted a cat, or other obstruction, while moving between the storage position and the discharge position. According to one aspect of the invention, the reverse sensor includes a switch electronically coupled. to the drive motor for providing the shut-off signal to the comb drive in the closed position. In one embodiment of the invention, the reverse sensor is a leaf switch. 
     In another aspect of the invention, the litter box has a mode selector switch. The switch may have a manual operation selecting position and an automatic operation selecting position. In addition, a manual operation switch may be electrically connected to the mode selector switch. According to another aspect of the invention, the comb drive drives the comb between a storage position and a discharge position in response to actuation of the manual operation switch when the mode selector switch is in the manual operation selecting position. 
     In yet another embodiment of the invention, a rectangular tray has side walls and a bottom wall that cooperate to define a housing-receiving region. Hood supports are coupled to the rectangular tray. A hood is coupled to the supports. The hood includes an opening for a cat to enter or exit the litter box. According to another aspect of the invention, a housing access ramp is pivotally connected to the housing, preferably at the opening. 
     In still another embodiment of the invention, the litter chamber includes a removable litter tray for receiving the cat litter. 
     The present invention may also be provided with means for ensuring that the comb stops when it strikes a cat while moving between the storage and discharge positions. By stopping the comb, the situation in which a cat is pinned between the comb and a wall is prevented. 
     The invention provides a manual cleaning mode that allows the cat owner to initiate the waste removal upon the activation of a switch. This mechanism would allow the cat owner to clean the waste out of the litter box at a time deemed appropriate by the cat owner. 
     The invention also provides an enclosure for a self-cleaning litter box to provide privacy for the cat. The enclosure could also be used to prevent litter from being spilled out of the box. 
     Other features and advantages of the present invention will be readily apparent from the following description and drawings which illustrate preferred embodiments of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of an automated self-cleaning litter box for use by a cat, constructed in accordance with a preferred embodiment of the. invention, showing the litter box in a waiting condition with the comb at the storage position. The dress panels have been removed for clarity to expose the internal structure. 
     FIG. 2 is a perspective view of the litter box of FIG. 1 in an intermediate condition with the comb traversing the litter box between the storage position and the discharge position. 
     FIG. 3 is a perspective view of the litter box of FIG. 1 in a discharge condition with the comb in the discharge position. 
     FIG. 4 is a transverse sectional view taken along line  4 — 4  of FIG.  2  and includes the dress panels. 
     FIG. 5 is a side view, partially broken away, of another litter box constructed in accordance with the invention. 
     FIG. 6 is a plan view of the litter box of FIG.  5 . 
     FIG. 7 is an end view, as seen from the storage end, of the litter box of FIG.  5 . 
     FIG. 8 is a front view of a locking tab and a locking projection, according to a preferred embodiment of the present invention, for retaining a removable litter tray in the litter box of FIG.  5 . 
     FIG. 9 is a partially broken away side view of the locking tab of FIG. 8 engaging a locking notch formed on the locking projection. 
     FIG. 10 is a partially broken away side view of the locking tab of FIG. 8 illustrating the locking tab in a depressed position to disengage the locking tab from the locking notch. 
     FIG. 11 is a top view of a rotating tray lock for retaining the removable tray in the litter box of FIG.  5 . 
     FIG. 12 is a side view of the rotating tray lock of FIG.  11 . 
     FIG. 13 illustrates the rotating lock of FIG. 11 in an unlocking position. 
     FIG. 14 illustrates the rotating lock of FIG. 11 in a locking position. 
     FIG. 15 is a partial section view along line  15 — 15  of FIG. 13, through the litter box and removable tray of FIG. 5 illustrating a rotating tray lock in relation to the litter box and removable tray. 
     FIGS. 16-18 are partial perspective views illustrating the sequence of removing a removable litter tray from the litter box of FIG.  5 . 
     FIG. 19 illustrates a reverse sensing leaf switch, according to a preferred embodiment of the present invention, in an open-circuit configuration. 
     FIG. 20 illustrates the leaf switch of FIG. 19 in a closed-circuit configuration. 
     FIG. 21 is a block diagram of the drive and control for the litter box of FIG.  5 . 
     FIG. 22 is a side view of the self-cleaning litter box of FIG. 5, including a manual operation foot switch. 
     FIG. 23 is a flow chart for operation of the cat litter box of FIG.  5 . 
     FIG. 24 is a flow chart illustrating optional modes of operation for the controls of the automated self-cleaning cat litter box of FIG.  5 . 
     FIG. 25 is a perspective view illustrating a hood supporting structure, according to a preferred embodiment of the invention, including a tray and hood supports. 
     FIG. 26 illustrates the tray of FIG. 25 with a hood disposed over the hood supports. 
     FIG. 27 illustrates an end portion of a hood support of FIG. 25 engaging an opening formed in a sidewall of the tray; and 
     FIG. 28 illustrates a self-cleaning litter box disposed in the tray of FIG.  25 . 
     FIG. 29 is a sectional view of the waste receptacle of the Self-Cleaning Litter Box illustrated in FIG. 1 with a lid of the receptacle in a closed position. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIGS. 1-4 illustrate a self-cleaning litter box  20  that includes a comb  43  that rakes clumps of litter  71  into a waste receptacle  68 . The comb  43  moves from a storage position, shown in FIG. 1 to a discharge position, shown in FIG.  3 . As the comb  43  approaches the discharge position, the lid  69  of the waste receptacle  68  opens to allow clumps of litter  71  to enter the receptacle. After dumping the clumps of litter  71  into the receptacle  71 , the comb  43  automatically reverses direction to return to the storage position. A sensor  400 , shown schematically in FIGS. 1-4, detects the presence of a cat or other obstruction, and automatically stops the comb and reverses its direction of travel. 
     FIGS. 1-4 illustrate a litter box  20  having a pan-shaped housing  21 . The housing  21  has a near side wall  22 , a far side wall  23 , and a discharge end wall  24  joining the sidewalls  22 ,  23  at one end of the litter box  20 . The litter box  20  also has a comb storage end wall  25  connecting the sidewalls  22 ,  23  at the other end of the litter box  20 . The bottom of the litter box  20  is identified by reference numeral  26 . The fill level to which the box  20  is usually filled with cat litter is shown by litter level line  38  (dashed line). The litter level line  38  may be afforded by a continuous or interrupted ridge in the interior of the housing  21 . Thus, the litter box  20  has a discharge end  28  at one end and a comb storage end  29  at the opposite end. The sidewalls  22 ,  23 , end walls  24 ,  25  and bottom  26  to the box  20  are preferably formed in a molding operation that produces the complete housing  21 . 
     A comb shaft  41  extends across the litter box  20  between two side tracks  32 ,  33 . There are four hangers  42  journalled on and depending from the shaft  41 . Three of the hangers  42  appear in FIGS. 1-3. The fourth hanger  42  can be seen in FIG. 4. A comb or rake  43  is suspended from the hangers  42  and includes a plurality of tines  44 . In FIG. 1, which illustrates a waiting, or storage, condition, the comb  43  is located at the comb storage end  29  of the litter box  20 , and the tines  44  are elevated above the litter fill level  38 . In FIG. 2, which illustrates an intermediate condition, the comb  43  is traversing the litter box  20  from the storage end  29  to the discharge end  28 , and the lower ends of the tines  44  project down into the litter in the box  20 , close to the bottom  26  of the box  20 , also shown in FIG.  4 . In FIG. 3, the comb  43  is shown near the end of its raking stroke at the discharge end  28  of the litter box  20 . At the discharge end  28  of the litter box  20 , the tines  44  of the comb  43  again move upwardly out of the litter. 
     An elongated near side track or path member  32  extends along the top of the near side wall  22  of housing  21 . Track member  32  includes a multiplicity of equally spaced apertures  31 . Apertures  31  extend through an inclined portion  34  of rack  32  at the discharge end  28  of litter box  20 ; they also extend through a more steeply inclined portion  36  of rack  32  at the comb storage end  29  of the litter box  20 . This track construction is repeated on the opposite side of housing  21 . Thus, an elongated track member  33  projects horizontally from the vertical side wall  23 . Track member  33  includes a multiplicity of equally spaced apertures or perforations  39 . The pattern of apertures extends along an inclined portion  35  of the track member  33  at the discharge end  28  of litter box  20 . It also extends along a more steeply inclined portion  37  of the track  33  located at the comb storage end  29  of the litter box  20 . 
     A first main guide wheel  52  is affixed to the near end of shaft  41 . Guide wheel  52  includes a plurality of radially projecting guide pins or teeth  51  engageable in the apertures  31  of track member  32  and its extensions  34  and  36 . At the other end of shaft  41  there is a similar main guide wheel  53 . The radial projections  54  on guide wheel  53  are engageable in the apertures  39  of track member  33  and its extensions  35  and  37 . Guide wheels  52  and  53  cause the ends of shaft  41  to move along tracks  32  and  33 , based on rotation of shaft  41 , from the storage position of FIG.  1  through the intermediate position of FIG. 2 to the discharge position of FIG.  3  and back to the FIG. 1 storage position. 
     In addition to the main guide wheels  52 ,  53  referred to above, the drive and guidance system of litter box  20  includes two auxiliary guide wheels  64 ,  65 , located on the near and far sides of the litter box  20 , respectively, as seen in FIGS. 1-3. Auxiliary guide wheel  64  is mounted at the end of a lever  66  that projects from one of the hangers  42  used to suspend comb  43  from shaft  41 . Auxiliary guide wheel  64  rides along track  32  throughout the length of that track, including its upwardly inclined end sections  34  and  36 . Similarly, the auxiliary guide wheel  65  is mounted on a lever  67  and engages the other track member  33  and its extensions  35 ,  37  (FIG.  4 ). 
     FIG. 5 illustrates an alternative track  231 . In particular, the track  231  includes an upper surface  235  spaced apart from a lower surface  237  and a plurality of teeth  239  depending from the upper surface  235 . A guide wheel  253  for use with the track  231  includes a plurality of cogs  254  for engaging the teeth  239 . A secondary hub  241  extends outwardly toward the side walls from the wheel  253  and is sized to cooperate with the lower surface  237  to prevent the cogs  254  from disengaging from the teeth  239 . Advantageously, the use of teeth  239  depending from the upper surface  235  avoids the possibility of litter becoming lodged between the teeth  239  and blocking movement of the wheel  253 . 
     The improved self-cleaning cat litter box  20 , FIGS. 1-3, includes a comb drive that comprises a reversible electric motor  55  mounted on and connected in driving relationship to the shaft  41  that supports comb  43 ; the final gear  57  of the gear train that connects motor  55  to shaft  41  is the only gear that appears in the drawings. The motor  55  is energized by batteries contained in a battery case  56 . Motor  55  and the gear train represented by gear  57 , as well as battery case  56 , are supported by shaft  41 ; in conjunction with the shaft, they constitute the carriage  45  for the comb  43  in litter box  20 . A reversing switch  58  is mounted on and electrically connected to motor  55 . A lever  59  is mechanically connected to reversing switch  58 . Lever  59  has a limited pivotal movement, from the position shown in FIG. 1 to the position illustrated in FIG. 2. A first switch actuation pin  61  is located adjacent the comb storage end  29  of litter box  20 . A similar fixed switch actuation pin  62  is positioned at the other end, the discharge end  28 , of litter box  20 . 
     A waste receptacle  68  is positioned immediately adjacent to the discharge end  28  of the litter box  20 . In FIGS. 1 and 2, waste clumps  71  are indicated in the litter chamber; similar clumps  72  are shown, in FIGS. 1-3, as being already deposited in receptacle  68 . Receptacle  68  has a hinged lid  69  and a pair of indentations  63 ,  70  (FIG.  6 ). The indentations  63 ,  70  are formed in the bottom of the receptacle  68  and receive bosses  222 ,  223  (FIG.  29 ). The bosses  222 ,  223  retain the waste receptacle  68  in position within the litter box  20 . Waste receptacle  68  and its lid  69  are preferably formed of a biodegradable material. Moreover, receptacle  68  should be transparent; alternatively, lid  69  may be transparent or, of course, both may be transparent enough to permit the user to visually check the level of waste and litter in the receptacle  68 . Lid  69  is engaged by a pin  75  on a lid lift lever  73  that is pivotally secured to a vertical extension  27  of side wall  23 . The pivotal connection is indicated at  74 . There need be no comparable lid lift mechanism  73 - 75  at the near side of the machine,though one could be provided if motor  55  and battery case  56  were mounted closer to the center of the litter box. 
     Waste receptacle  68  may be formed of plastic or other suitable material. The lid  69  for receptacle  68  is hinged to the receptacle as indicated at  76 . A hinge of the so-called “piano” type may be used, but other hinge structures are acceptable. Lid  69  may also be formed of plastic. On the other hand, receptacle  68  and its lid  69  may be fabricated of other appropriate material. Preferably, receptacle  68  initially serves as a container for clean litter so that, once the receptacle  68  is ready to be discarded, it can simply be removed and a new receptacle  68  put in place after emptying clean litter from the new waste receptacle  68  into the chamber afforded by housing  21 . 
     A sensor may be used to determine whether or not the receptacle is full. In the embodiment of FIGS. 1-3, a sensor  243 , preferably a photodetector, is mounted on side wall  23  at a level indicative of a full receptacle. An appropriate light source  242  is mounted on side wall  22  opposite photodetector  243 . When the litter level rises in the receptacle to block the light from the source  242 , photodetector sounds an alarm, such as a buzzer, to alert the user. 
     Another sensor may be utilized to sense the exit of a cat from the litter chamber afforded by housing  21 . In the embodiment of FIGS. 1-3, there are two such sensors  82 ,  84 , both mounted on wall  23  above the litter fill line  38 . Devices  82  and  84  may comprise conventional photo detectors, each receiving a light beam from a source (not shown). FIG. 4 shows an appropriate light source  86  mounted on wall  22  above fill level  38 . Photodetector  82  (FIG. 4) is also located above fill level  38 . A single light source located centrally along the length of wall  22  can be used or there may be two such light sources  86 , one for each of the photo detectors  82 ,  84 . 
     As shown in FIGS. 5-7, a removable litter tray  300  is disposed in the litter box  20  adjacent the bottom  26 . The tray  300  includes a handle portion  306  and a tray portion  304 . The tray portion  304  is filled with litter to the fill line  38  as discussed above. The tray portion  304  includes a distal end  305  and a proximal end  307  and is designed to slide through an opening  301  of the storage end wall  25 . The side walls  22 ,  23  of the housing  21  may contain rails, detent projections or other mechanisms (not shown) to ensure the sliding engagement of the tray portion  304  in the litter box bottom  326 . The tray portion  304  is slid through the storage end wall  25  until the distal end  305  of the tray portion  304  comes into contact with the discharge end wall  24 . When the tray portion  304  comes into contact with the discharge end wall  24 , the handle portion  306  of the removable litter tray  300  extends through the storage end wall  25 . In preferred embodiments, the corners and edges of the housing  21  and the removable tray  300  are rounded to facilitate cleaning as illustrated, for example, in FIGS. 4 and 7. Preferably, the apparatus  200  has no nooks, crannies or other small spaces of the type that would permit litter or waste to slip out of or become lodged in the apparatus  200 . 
     Other features are also illustrated in FIGS. 5-6. In particular, an alternative lift mechanism  174  includes a lift plate  173 , connected to the litter box  20  by a hinge  176 , and a pair of end walls  175 ,  177  disposed orthogonally to the plane of the lift plate  173 . Each end wall  175 ,  177  includes a camming edge  179  operatively disposed to engage the carriage  45  as the carriage moves to the discharge position. Preferably, the lift plate  173  includes a plurality of apertures  181  for receiving complementary tabs  183  formed on the lid  69  of the receptacle  68 . The tabs  183  fit in the apertures  181  with a friction fit to connect the lid  69  to the lift plate  173 . Thus, as the carriage  45  approaches the discharge position, it engages the camming edges  179  and pivots the lift plate  173  about the hinge  176  to open the waste receptacle  68 . The friction fit of the tabs  183  in the lift plate  173  allows the lid  69  to be easily removed from the lift plate  173  to be disposed of with a full waste receptacle  68 . 
     As shown in FIGS. 5 and 6, the apparatus  200  also has parallel side walls  201  on opposite lateral sides. The side walls  201  may be formed of a suitable plastic material. The side walls  201  have top edges  202  extending from the back to the front of the apparatus  200 . The side walls  201  help prevent cat litter or other debris from being spilled out of the apparatus  200 . 
     As illustrated in FIGS. 8-10, the handle portion  306  includes a resilient locking tab  302  formed therein. A locking projection  320  extends downwardly from the outside surface  325  of the comb storage end wall  25  to a distal end  326 . The locking projection  320  includes a front wall  322  and a pair of sidewalls  324  extending from the edges of the front wall  322  to define a U-shaped channel. The distal end of the front wall  322  includes a semicircular opening  327  (FIG.  8 ), and the distal end of each sidewall  324  includes a notch  328 , (FIGS.  9 - 10 ). The notches  328  are disposed to engage the locking tab  302  when the tray portion  304  is completely slid into the housing  21 . 
     When the litter tray  300  is disposed in the litter box  20 , the locking tab  302  engages the notches  328  to retain the tray  300  in the litter box  20 . To remove the tray  300 , a user inserts a finger into the semicircular opening  327  and depresses the resilient locking tab  302 , causing the tab  302  to disengage from the notches  328 . Although a locking projection  320  and a locking tab  302  have been illustrated, it will be appreciated that other latching mechanisms can be used. The locking tab  302  is preferred, however, because it is easy to operate and is readily formed integrally with the removable tray during the molding process. 
     In addition to the locking tab  302 , the litter box  20  includes a pair of tray locks  330 , illustrated in FIGS. 11-15, disposed on the discharge end wall  24 . As shown in FIGS. 11-12, each tray lock  330  includes a locking disk  333  and a shaft  335  that projects from the bottom surface of the disk  333  and is offset from the center of the disk  333 . The shafts  335  include a groove  337  for receiving a circlip  338 . The shafts  335  are sized to extend through apertures  339  formed in the discharge end wall  224 , with the disks  333  cooperating with the circlip  330  to retain the tray locks  330  in position. Thus, tray locks  330  are rotatably connected to the discharge end wall  224 . The apertures  339  are located on the end wall  224  so that the offset portion of the disk  333  rotates between an unlocking position (FIG.  13 ), wherein the removable tray  304  is released for removal, and a locking position (FIG.  14 ). In the locking position, a portion of the disk  333  overlaps the distal end  305  of the removable tray to prevent removal, as illustrated in phantom in FIG.  15 . The tray locks  330  can be adapted to have grooves  341 . The grooves  341  would be used to allow a tool  334 , such as a screwdriver or a coin, to lock and unlock the tray locks  330 . Other indicia  343  may be added to indicate whether the tray locks  300  are in the locking or unlocking position. 
     As illustrated in FIG. 15, the removable tray  300  preferably includes a beveled edge  345  formed on the distal end  305 , and the discharge end wall  224  includes a beveled step  347  formed to be complementary to the beveled edge  345 . The beveled edge  345  and step  347  cooperate to provide a seam that resists litter intrusion. 
     To remove the litter tray  300 , as illustrated in FIGS. 16-18, a user inserts a tool  334  into the tray locks  330  to rotate the tray locks  330  in direction  332  (FIG. 16) to the unlocking position. Of course, different tray locks  330  can be used. For example, a sliding tray lock could be used. Once both tray locks  330  are in the unlocking position, the user may depress the locking tab  302  (FIG. 17) to disengage the tab  302  from the locking projection  320 . Once disengaged, the tray  300  may be removed from litter box  20  by pulling on the handle portion  306  in the direction  336  (FIG.  18 ). 
     In the preferred embodiment of the present invention, as shown schematically in FIGS. 1-3 and in detail in FIGS. 19-20, a reverse sensor  400  is coupled to a back side of the carriage  45  to avoid injury to a cat in the event that the carriage makes contact with the cat during movement toward the storage position. It will be appreciated that a forward sensor can be used to avoid injury to a cat if the carriage  45  contacts the cat during movement toward the discharge position. The reverse sensor  400  includes a reverse sensing bar  402 , an actuating bar  408 , and a leaf switch  410 . The leaf switch  410  is connected to the carriage  45  at a point adjacent the actuating bar  408 . The reverse sensing bar  402  held in a flexible relationship with the carriage  45  by first and second bar holders  404 ,  406  molded therein (FIG.  6 ). The bar holders  404 ,  406  contain springs (not shown) to provide this flexible relationship. 
     Referring to FIG. 19, the leaf switch  410  includes a base  420 , a flexible leaf switch arm  426 , a rigid leaf switch arm  422  and a leaf switch arm separator  424 . The separator  424  prevents the contacts  423 ,  425  from inadvertently making contact. The leaf switch arms  422 ,  426  have leaf switch contacts  423 ,  425 . The leaf switch arms  427 ,  429  may also include leaf switch contact protectors  427 ,  429 , respectively, to prevent damage to the contacts  423 ,  425 . 
     When the carriage  45  contacts a cat, or other obstruction, a force is applied to the reverse sensing bar  402 , and the force is transmitted to the flexible leaf switch arm  426  by the actuating bar  408 . The actuating bar  408  pushes the leaf switch arm  422  to bend the arm  422  around the leaf switch arm separator  424 , causing the leaf switch contact  425  to touch contact  423 . The leaf switch  410  is closed, and an electrical connection is maintained, while the contacts  423 ,  425  are in contact with each other. When the leaf switch  410  is closed, a signal is generated to stop and reverse the motor  55  (described below). 
     The leaf switch  410  is resiliently biased toward its open position (that is, the contacts  423 ,  425  are biased away from each other). The leaf switch  410  will be closed (as described above) when the sensing bar  402  contacts the end wall  25  and the contact  425  of the flexible leaf switch arm  426  is forced into contact with the contact  423  of the rigid leaf switch arm  422 . 
     Referring now to FIG. 21, motor  55  is energized from battery  56  through a pre-programmed micro-processor control  96 . Although not shown in FIG. 21, a conventional electrical power supply may alternatively be used to energize the motor  55 . Control  96  receives input signals from single space sensors  82 ,  84 . Additional inputs to control  96  may be supplied by a mode select switch  91 , a motor stall sensor  92 , a battery voltage sensor  93 , a home position sensor  94  for the comb  43 , a reverse sensor  400 , and a manual operation switch  370 . 
     The mode select switch  91  (FIG. 5) is a three position switch. The mode select switch  91  is switchable between an automatic operation selecting position, a manual operation selecting position and an off position. The mode select switch  91  allows a user to decide how the litter box  20  is to operate (manually, automatically, or not at all). No power is supplied to the litter box  20  when the mode select switch  91  is in the off position. The mode select switch  91  provides an automatic operation input and a manual operation input to the control  96 . In the off modes no input is generated because all components, including the control  96 , will not be functioning. 
     The motor stall sensor  92  determines whether the motor  55  is stalled. If the motor  55  is started by the control  96 , but becomes stalled, the motor stall sensor  92  will supply a motor stall input to the control  96 . 
     The battery voltage sensor  93  determines whether there is a low battery voltage condition. If there is a low battery voltage condition, the battery voltage sensor  93  supplies a low battery voltage condition input to the control  96 . The control  96  sends a signal to sound a buzzer  97  when the low voltage input is received. 
     The home position sensor  94  for the comb  43  determines whether the comb  43  has reached the “home” position. If the comb  43  has reached the “home” position, the home position sensor  94  supplies a “home” position input to the control  96 . In response to the home position input, the control  96  stops the motor  55 . 
     A manual operation foot switch  370  (FIG. 22) allows a user to initiate manual operation of the litter box  20  by closing the switch  370  if the mode selector switch  91  is in the manual position. When the switch  370  is closed, a manual operation switch activated input is sent to the control  96 . 
     Limit switches  95 ,  99  may be provided at the storage end  28  and at the discharge end  29  of the litter box  20 . One or more buzzers or other alarm devices  97  are included in the circuit so that the cat owner can be signaled when the litter box  20  is functional or when other conditions occur, such as an insufficient litter supply in the box  20  or a fill waste receptacle  68  or low battery voltage. 
     If desired, the apparatus  200  may be provided with a shut-off timer system (not illustrated). The shut-off timer system may be used to disable operation of the apparatus  200  for a predetermined period of time, for example, six hours. Thus, for example, the apparatus  200  may be disabled during the middle of the night, so that the apparatus  200  does not disturb resting persons or other pets. A push button over-ride system (not illustrated) may be provided to manually initiate a raking operation when the apparatus  200  is otherwise disabled by the shut-off timer system. 
     The motor stall sensor  92 , battery voltage sensor  93 , buzzer  97 , and leaf switch  410  of reverse sensor  400  may all be packaged in the same housing with the motor  55 . Such packaging would be particularly advantageous by eliminating the need for long wiring runs. 
     The mode selector switch  91 , home position sensor  94 , limit switches  95 , 99  and manual operation switch  370  can be incorporated in the litter box  20  in appropriate positions as desired. Home position sensor  94  may be coupled to or adjacent to the “home” position. For example, if the “home” position is determined to be the storage end  29 , then the sensor  94  should be located adjacent to the storage end wall  25 . Limit switch  95  can be positioned to be actuated by any part of the comb  43  or the carriage  45 . The limit switch  95  is disposed at the storage end  28  of litter box  20  and is activated when the comb  43  or carriage  45  reaches the storage end  28  of the litter box  20 . The limit switch  99  is disposed at the discharge end  29  of litter box  20  and is activated when the comb  43  or carriage  45  reaches the discharge end  29  of the litter box  20 . Manual operation switch  370  can be positioned adjacent the mode select switch  91 , the carriage  45  or any other desired location on the litter box  20 . 
     In operation, the comb  43  may initially be located at the comb storage end  29 . In this condition, the comb shaft  41  is elevated, the guide wheels  52 ,  53  having ridden up the extensions  36 ,  37  of tracks  32 ,  33 . The switch  58  and the lever  59  have engaged the pin  61 ; the motor  55  is shut off, but is set for forward movement. Removable tray  300  is filled with litter, approximately to level  38 . Photo detectors  82  and  84  receive light beams from sources  86  on the near wall  22  of the litter box (FIGS.  4  and  23 ). With no cat present in the litter box  20 , reception of the light beams by photo detectors  82  and  84  is unimpeded. All other mechanisms are in the positions shown in FIG.  1 . Lid  69  is closed over the receptacle  68 . The receptacle lid  69  is engaged by pin  75  at the end of the lever  73 , but remains closed because the lid opening lever  73  is inactive. 
     At this juncture, it may be assumed that a cat (not illustrated) enters the litter box  20  for the purpose of elimination of either liquid or solid waste. With some kinds of litter, the urine from the cat creates a clump in the litter with which the bottom portion of housing  21  is filled. For solid elimination, the clump is formed by the waste itself In either instance, the cat is likely to bury the waste or to cover it with other litter, especially with respect to solid waste. Thus, clumps  71  are produced by the cat, and those clumps are located at some level in the litter above the bottom of the removable tray  300  (FIG.  23 ). It is assumed that the box has previously been used and that previously deposited waste clumps  72  are already present in the waste receptacle  68 . 
     While the cat is present in the litter box  20 , the light beam to at least one of the photo detectors  82  and  84  is cut off. Usually, both light beams are blocked. However, this does not initiate a self-cleaning operation in the litter box  20 . Subsequently, when the cat leaves the litter box  20 , the light beam or beams again impinge upon the photo detectors. Accordingly, an output signal from one or both cat sensors is supplied to control  96  (FIG.  21 ). At this point, however, there still is no actuation of a self-cleaning operation in the box  20  by the comb  43 . The reason for the delay is that the cat might return to the litter box, deciding that its elimination activities have not been completed. In these circumstances, the light beams to one or both of the photo detectors  82 ,  84  are again cut off and the preset delay interval for actuation of a self-cleaning operation is not completed. 
     Ultimately, the cat leaves the litter box  20  for an interval long enough to exceed the preset time delay that is set into control  96 . That time interval is subject to substantial variation; a range of two to seven minutes is usually desirable. The self-cleaning operation carried out by the comb  43  should not be initiated while the cat is in the immediate vicinity because it is undesirable to cause the cat to have reason to be afraid of the litter box  20 . 
     In a preferred embodiment, the operation of the self-cleaning litter box  20  can be also be performed manually. Instead of waiting for the predetermined delay period, as previously described, cleaning of the litter box  20  may be initiated by the cat owner. Manual operation can be achieved by placing the mode select switch  91  (FIG. 5) into a manual operation selecting position. With the mode select switch  91  in this position, inputs from the photo detectors  82 ,  84  do not initiate the preset delay feature previously described. Instead, the control  96  looks for an input from the manual operation switch  370 . 
     FIG. 22 illustrates the use of a foot switch  372  as the manual operation switch  370 . The foot switch  372  is a normally open switch providing no input to the control  96  when open. The foot switch  372  is closed and thus activated when a cat owner steps on it. The closing of the foot switch  372  provides an input to the control  96  causing the comb  43  to rake the litter (described below). This may be desirable when the cat owner wants to remove the waste from the litter box  20  at a time he or she deems appropriate. 
     After the cat has left litter box  20  for a time exceeding the preset delay interval in control  96  (automatic operation) or after the manual operation switch  370  has been activated (in manual mode), motor  55  is energized from battery  56 , or a conventional power supply (not shown), through control  96 . As a consequence, gear  57  and shaft  41  are rotated in the direction of the arrow B in FIG.  1 . The initial movement of the comb carriage  45  (shaft  41 , motor  55 , and battery housing  56 ) is downwardly along track extensions  36  and  37 . In the course of this downward movement of comb  43 , its tines  44  are pushed downwardly into the litter in the bottom portion of housing  21 , well below fill line  38 . The bottoms of the tines  44 , when this movement is completed, are quite close to the bottom of the removable tray  300 , but preferably do not quite engage the bottom. 
     Motor  55  remains energized and shaft  41  continues to rotate in the direction of arrow B. As a consequence, comb  43  is driven across the litter chamber, from the storage end  29  to the discharge end  28 , as indicated in FIG. 2 by arrow A. Reference may also be made to FIG. 4, where the position of the comb and its tines  44  are illustrated. As the comb moves across the litter box  20 , in the direction of arrow A, the tines  44  engage any clumps  71  present in the litter, whether generated by the elimination of liquid or solid wastes by the cat. Comb  43  carries the clumps  71  toward the discharge position  28  at the far end of box  20 , that is, to the right hand end of the litter box  20  as seen in FIGS. 1 and 2. Comb  43  remains in a substantially erect position as shown in FIG.  2 . It is prevented from rotating in the direction of arrow B by the engagement of auxiliary guide wheels  64 ,  65  with tracks  32 ,  33  respectively. The forward motion of the comb  43  in the direction of arrow A is effected by rotation of shaft  41  in the direction of arrow B and the engagement of guide wheels  52  and  53  and their pins  51  and  54  in the apertures  31  and  39  of the two tracks  32  and  33  that define the comb path. 
     Ultimately, the comb  43  advances to a position where its main guide wheels  52  and  53  reach the upwardly inclined extension portions  34  and  35  of tracks  32  and  33 , respectively. Motor  55  is still energized; as a consequence, the carriage  45  moves up the ramps or track extensions  34  and  35  to the position shown in FIG.  3 . During this upward movement of comb  43 , lever  73  is engaged by the comb carriage  45  and is pivoted upwardly from the original position shown in FIGS. 1 and 2 to the elevated position shown in FIG.  3 . As a consequence, due to the engagement of pin  75  with a slot or like guide  77  in receptacle cover  69 , cover  69  is moved to the open position shown in FIG.  3 . When comb  43  reaches the discharge position shown in FIG. 3, the additional clumps  71  are discharged into receptacle  68  to join clumps  72  already present there. 
     When comb  43  reaches the position of FIG. 3, it actuates the limit switch  99 . The resulting output signal to control  96  (FIG. 21) reverses motor  55  and the motor  55  starts to rotate the shaft  41  in the direction of arrow C, FIG.  3 . Accordingly, the comb  43  is driven, by motor  55 , back to its storage position illustrated in FIG.  1 . In the process, the discharge lever  73  is disengaged and drops back down to its original position, so that the lid  69  on receptacle  68  again closes. The waste from the litter box  20  is now totally enclosed in waste receptacle  68 . 
     When comb  43  has finished its movement back to a point closely adjacent to the storage end wall  25 , its two main guide wheels  52  and  53  encounter the steeply inclined upward extensions  36 ,  37  of tracks  32 ,  33 . Motor  55  remains energized and pulls comb  43  and its shaft  41  up to the position shown in FIG.  1 . When the comb  43  reaches that position, switch  58  is actuated by pin  61  and sets motor  55  for subsequent operation in the forward direction. When comb  43  reaches the end of its travel, at the position shown in FIG. 1, the comb limit switch  95  (FIG. 21) is actuated and a signal is supplied to control  96  to shut off the motor. A “home” sensor  94  may be provided for the same purpose. Usually, it is desirable to have both a home sensor  94  and a limit switch  95  (see FIG. 21) to actuate the control  96  and make sure that the motor  55  is shut off with the comb  43  at the storage position  29  shown in FIG.  1 . 
     In a preferred embodiment, a reverse sensor  400  (FIGS.  6  and  19 - 20 ) is utilized to make sure that the motor  55  is stopped and reversed when the comb  43  strikes an object while returning to the storage position  29 . The reverse sensor  400  is normally open and does not provide an input to the control  96  while open. The reverse sensor  400  is closed when the reverse sensing bar  402  strikes an object forcing the actuating bar  408  to close the leaf switch  410 . When the reverse sensor  400  is closed, an input is sent to the control  96  indicating that the motor  55  should be stopped and reversed, and that the movement of the comb  43  should be stopped and reversed. 
     FIG. 23 is a flow chart illustrating a subroutine programmed into control  96  (FIG. 21) for a self-cleaning operation in the improved litter box  20 . The flow chart starts with a command to comb litter  101  supplied to the control  96 . As a consequence, a set direction and start command is supplied to the motor  55  in stage  102  of the subroutine. In the next stage  103 , if the motor  55  is stalled, that condition is sensed and an output command is received by the motor  55  (stage  105 ) to reverse the direction of the motor  55 . Ordinarily, however, the motor  55  will not be stalled and the next step (stage  104 ) is to determine whether the comb  43  is at its end of travel. If not, the subroutine returns to stage  103  and checks for a stalled motor  55 . If the comb  43  is located at the discharge end of its travel, an output signal is applied to reverse the motor  55  (step  105 ). 
     When the motor  55  has been reversed, the condition of the motor  55  is again checked to see if it is stalled. If so, there is an output signal to stop the motor  55  (step  108 ). Ordinarily, however, the motor  55  will not be stalled and an enabling signal is received (stage  107 ) to check and see whether the comb  43  is in its “home” position. When comb  43  reaches its “home” position, at storage end of litter box  20 ) there is an output signal sent to stop the motor  55  (stage  108 ) which directs the subroutine to return to the beginning of the subroutine (stage  109 ). If the comb  43  has not reached the “home” position, the subroutine proceeds to stage  107 A to determine if the reverse sensor  400  has been activated. If the reverse sensor  400  has not been activated, the subroutine returns to stage  106  and checks for a stalled motor  55 . If the reverse sensor  400  has been activated, there is an output signal (stage  107 A) to a stop motor (stage  108 ). The subroutine then returns to the beginning (stage  109 ). This completes the subroutine of FIG.  23 . 
     FIG. 24 illustrates a further subroutine that is also programmed into processor control  96  (FIG.  21 ). The subroutine starts with a power-on stage  111  that may be initiated by an appropriate switch (for example, the mode select switch  91 ). Alternatively, the subroutine may start with insertion of appropriate batteries into battery case  55  (FIGS. 1-3) or by plugging in a conventional power supply  20  (not shown). The next stage  112  in the subroutine is initialization of the control  96 . In the next subroutine stage  113 , the control  96  checks to determine whether the mode select switch  91  of FIG. 21 is set for manual mode. 
     If the manual operation mode is selected, the control  96  checks to determine if a manual operation switch  370  (FIG. 22) has been activated (stage  113 A). The manual operation switch  370  is normally open and provides a NO signal (stage  113 A) when open. The manual operation switch  370  is activated by the cat owner. When the manual operation switch  370  has been activated, a comb litter procedure is initiated (stage  114 ). If the manual operation switch  370  has not been activated, the subroutine returns to the mode check at stage  113 . 
     If the program is not set for manual mode, the subroutine checks for a low battery condition (stage  115 ). If a low battery voltage condition is ascertained, the subroutine checks to see if the alarm mode is set (stage  116 ) and, if the alarm mode is set, the subroutine actuates an alarm (stage  117 ) to produce a programmed output from buzzer  97  (FIG. 21) that alerts the user that a change of batteries is required. Outputs generated in stages  116  and  117  may be fed back to stage  113  in this subroutine in appropriate circumstances. If a conventional power supply is used to energize the motor  55 , the control  96  may be programmed to skip stages  115  to  117 . Ordinarily, however, when the voltages of the batteries are adequate, there is a NO output and the subroutine continues by checking for a full septic or waste receptacle  68  (stage  118 ). Ordinarily, the receptacle  68  will not be full. If the receptacle  68  is full, the subroutine returns to stage  113 . 
     In normal circumstances, with adequate room in the receptacle  68 , the subroutine checks to see if any septic is present (stage  119 ). If septic is present, the subroutine checks to determine if the comb  43  is in the “home” position (stage  121 ). If the comb  43  is in the home position, the subroutine checks for the presence of a cat in the litter box (stage  122 ). If the comb is not in the home position, or if the cat is not present in the litter box, the subroutine returns to the mode check (stage  113 ) and begins again. If the cat is present in the litter box, the subroutine waits for the delay time to expire (stage  123 ) and then executes a comb litter command (stage  124 ) and returns to the mode check (stage  113 ) and begins again. 
     Thus, the automated self-cleaning litter box  20  may be arranged so as not to frighten or disturb a cat; the self-cleaning movement of the comb  43  may not occur until there is a reasonable certainty that a cat using the litter box  20  has been gone for two to seven minutes, depending on the delay set into the control  96 , before the motor  55  is energized. Other sensors can be used instead of photo detectors  82  and  94 . For example, infra-red sensors receiving radiation from an appropriate infra-red source, or a strain gauge on pan bottom  26 , may serve the same purpose as the photo detectors of FIGS. 1-4. 
     The gear drive  57  that connects motor  55  to shaft  41  is not subject to fouling by the litter, which often includes powdery material that is likely to interfere with operation of other drive mechanisms such as a worm drive. Motor  55  should be sealed against dust and dirt, since it must operate in an adverse environment. Litter box  20  is simple and economical in construction, but should afford an extended operating life with little or no attention apart from periodic replacement of the litter and replacement of the batteries  56 . 
     In a preferred embodiment of the present invention, as shown in FIGS. 5 and 6, a durable ramp  350  is pivotally connected to the housing  21 . The ramp  350  includes carpeting  352  and first and second pivot pins  354 ,  356  molded to one end of the ramp  350 . The carpeting  352  is mounted upon a top side of the ramp  350 . The carpeting  352  is ribbed and made of a fabric that will trap litter and provide suitable paw-cleaning and scratching-post functions for a cat utilizing the ramp  350 . The ribbed carpet  352  traps litter. The carpet  352  may be easily removed for cleaning. 
     In order for the ramp  350  to be connected to the housing  21 , the two side walls  22 ,  23  may include first and second pivot holes  360 ,  362  at the discharge end  28  of the litter box  20 . The ramp  350  is attached to the housing  21  by placing the first pivot pin  354  and the second pivot pin  356  into pivot holes formed in the side walls  22 ,  23  of the litter box  20 . The carpeting  352  is facing up as depicted in FIG.  6  and will minimize litter tracking when the cat exits the litter box  20 . 
     Another feature of a preferred embodiment of the present invention, as shown in FIGS. 25-28, includes a rectangular tray  500  having first and second side walls  504 ,  508 , an end wall  506  connected between the side walls  504 ,  508 , and a bottom wall  502 . The first and second side walls  504 ,  508 , the end wall  506  and the bottom wall  502  cooperate to form a housing-receiving region  540 . The tray  500  may be thermal formed or molded and is designed such that the housing  21  may be placed within the housing-receiving region  540 . One aspect of the tray  500  is that it can be used as a catch-all if any litter or waste is kicked out of the self-cleaning litter box  20  by a cat. 
     Another aspect of the tray  500  is that it may be used to cooperate with a dome or hood  548  to define an enclosure  550  for the self-cleaning litter box  20 . The dome  548  may be used to provide privacy for the cat. The enclosure  550  includes a plurality of hood supports  530 . The hood supports  530 , may be metal or plastic strips. Each hood support  530  has a first end portion  532  and a second end portion  534 . To accommodate the hood supports  530 , the first and second side walls  504 ,  508  have a plurality side of wall openings  510 . The openings  510  are adapted to receive the hood support end portions  532 ,  534 . 
     The hood supports  530  are placed into the side wall openings  510  such that the end portions  532 ,  534  are retained therein by the resiliency of the hood supports  530  acting against the side walls  504 ,  508 . The hood  548  is placed over the hood supports  530  forming the enclosure  550 . The hood  548  has an opening  552  and may be made of cloth or any suitable material and may be connected to the hood supports  530  in any manner. For example, the hood supports  530  may be sewn into the hood  548 . Alternatively, the hood  548  may have ties that connect the hood  548  to the hood supports  530 . Alternatively, the hood  548  can drape over the supports  530  and attach to the sidewalls  504 ,  508 . 
     FIG. 29 illustrates the waste receptacle  68  and its lid  69  in the closed condition. There is a mass  271  of waste in receptacle  68 , but the receptacle is not yet full. Receptacle  68  is positioned in the litter box  20  for engagement with bosses  222  and  223 . The bosses  222  and  223  extend inwardly from the litter box side walls  22 ,  23 , respectively, to engage the indentations  63 ,  70  (FIG.  6 ). The walls of the waste receptacle  68  adjacent side walls  22 ,  23  are provided with aligned openings  226 ,  227 , respectively. Radiation from a source  242  on wall  22  impinges upon a detector  243  on wall  23  as long as the level of waste  271  in the receptacle  68  does not block the radiation. 
     While the invention has been described in detail in connection with preferred embodiments known at the time, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention.