Animal husbandry – Waste toilet or related device – Walled receptacle; e.g. – litter box – etc. – containing...
Reexamination Certificate
2000-12-07
2003-05-27
Price, Thomas (Department: 3643)
Animal husbandry
Waste toilet or related device
Walled receptacle; e.g., litter box, etc., containing...
Reexamination Certificate
active
06568348
ABSTRACT:
FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
BACKGROUND OF THE INVENTION
The present invention relates to a self-cleaning sanitary device for animals. The invention also relates to indoor and outdoor self-cleaning sanitary devices.
Many forms of sanitary devices have been developed to collect bodily waste from animals. The most common of these are litter boxes used by household pets, such as cats and dogs. Although litter boxes are generally accepted by animals, regular daily disposal of the solid waste is recommended. Lack of regular cleaning can produce odors and force the animals to navigate around, or unintentionally dig up, waste from previous days. This can encourage the animals to find less-disagreeable places to relieve themselves and weaken their “toilet training”. Similarly, releasing animals outdoors to relieve themselves can result in poor “toilet habits” that can become a source of aggravation and conflict with other users of the area, such as neighbors and passers-by. Clearly, a self-cleaning litter device is desirable to eliminate the disagreeable and often avoided task of manually cleaning litter.
The recent introduction and widespread availability of clumping litter has influenced the design of many self-cleaning litter devices. Clumping litter reacts with liquid waste (urine) to form solid clumps. The solid clumps can be collected in the same way as other solid waste (feces) to provide a cleaner litter area. Sufficient litter depth, however, is required to prevent the clumping litter from solidifying against, and bonding to, the bottom of the litter box.
Many self-cleaning litter devices are motorized and automated to operate unattended for extended periods. Solid waste is extracted from the litter and stored in a waste receptacle. A means is generally provided to reduce or prevent excessive odors from escaping the waste receptacle. The automated versions have short cleaning cycles (generally less than a few minutes) that are activated after a suitable time delay to allow the clumping litter to react. Short cleaning cycles however can produce fast, unexpected movements and motor noise that can easily scare the animals or increase their discomfort during use. The automated versions therefore use sensors and start/stop controls to detect if animals have used the devices and to avoid operating the cleaning cycles while animals are in the devices. Sensors and controls however increase the complexity and cost of the devices. A few of the more relevant self-cleaning litter designs are briefly described below.
Motorized self-cleaning litter devices using rectangular chambers (similar to the common litter box) are disclosed in, for example, U.S. Pat. No. 5,226,388, U.S. Pat. No. 5,477,812 and U.S. Pat. No. 5,544,620. Rake motion includes a forward stroke to extract solid waste from the litter; an upward stroke to lift the waste over the enclosing wall and dump it in a waste receptacle; and a backward stroke to smooth the litter and return the rake to its “parked” position. A disadvantage with these devices is litter buildup at the ends of the chamber due to the forward and backward strokes of the rake. This can interfere with proper rake operation and lead to reduced litter depth near the center of the chamber. Burying habits of the animals can further upset the litter distribution and can make extended periods of unattended operation problematic. In addition, waste deposited on the wrong side of the rake (e.g., during an interrupted cleaning cycle) is pushed to the rake's “parked” position during the backward stroke and must be manually removed.
Cylindrical self-cleaning litter devices using horizontally-positioned drums have been disclosed in, for example, U.S. Pat. No. 4,120,264, U.S. Pat. No. 5,048,464 and U.S. Pat. No. 5,509,379. Generally, these devices include a rake attached to the inner surface of the drum which sifts the litter during drum rotation. The cylindrical wall of the drum supports the litter and rises out of both sides of the litter area at an angle. Litter depth varies from a maximum near the center of the litter area to zero depth along the sides. Minimal litter depth along these sides can easily result in exposure of the cylindrical wall surface to liquid waste. This can cause clumping litter to adhere to the cylindrical wall surface and must be cleaned manually.
A self-cleaning litter device is described in U.S. Pat. No. 4,574,735 comprising a bowl-shaped, circular litter chamber. The device uses a stiff first rake, with horizontal tines extending in a curved or spiral shape from a spindle along the central axis of the chamber, to urge solid waste to the outer perimeter of the chamber during rake rotation. A flexible second rake then pushes the solid waste up a bordered ramp along the outer perimeter of the chamber into an opening that leads to a waste receptacle. Both rakes are driven by the spindle and quickly circle the chamber in 6 to 30 seconds. A disadvantage with this design however, is that the curvature of the stiff rake can also push solid waste against the border of the ramp. Solid waste can become trapped and smeared into the rake and along the border of the ramp which must be cleaned manually; or can break apart producing smaller pieces that may not be collected by the rakes. The side wall of the chamber can also become smeared with solid waste during contact to deflect the solid waste into a circular path. The means to remove solid waste from the chamber relies on contact with the floor of the ramp to deflect the flexible rake out of the litter. Over time, severe wear of the rake and the ramp can result due to the abrasive nature of most litters. In addition, the centrally-based drive system, while capable of meeting the demands of the rakes and accommodating the described means to remove solid waste from the chamber, inherently requires strong components and a strong support structure to transmit the forces needed at the outer ends of the cantilever-based rakes.
U.S. Pat. No. 5,931,119 discloses a self-cleaning litter device wherein a circular pan rotates past a rake during the cleaning cycle. The rake is normally vertical, outside the pan, and cantilevers into the pan to sift the litter. After sifting, the rake is rotated (to scoop the sifted waste) and cantilevered out of the litter pan. The solid waste eventually rolls down the rake (as it is cantilevered up) to fall into a waste receptacle. Drive mechanisms are required for both the pan and the rake. The means to cantilever and rotate the rake requires strong, accurate components and a strong support structure to sustain the forces produced during the sifting action and prevent the rake tines from scraping the bottom of the circular pan. In addition, the open waste receptacle cannot prevent the solid waste, now exposed to the air, from releasing odors back into the pan area and escaping the device. This requires frequent emptying of the waste receptacle and significantly reduces the period of unattended operation.
Many automated self-cleaning sanitary devices have unique and complicated approaches to reducing or preventing the escape of odors from the waste receptacle. U.S. Pat. No. 4,574,735 describes a rotating waste receptacle that mixes the waste with sanitizing and deodorizing chemicals. U.S. Pat. No. 5,477,812, U.S. Pat. No. 5,544,620, and U.S. Pat. No. 5,107,797 describe devices that combine a means to open and close a lid on the waste receptacle with the means to move the rake through the litter. U.S. Pat. No. 5,048,464 describes a rocking lid on a waste receptacle that tilts open by the weight of the solid waste. Because solid waste can be light in weight, the rocking lid design must be well balanced. In addition, the rocking lid design requires a gap around the perimeter of the lid to prevent jamming. The gap, however, can also allow odors to escape. Further, the rocking lid opens inward, into the waste receptacle, which reduces its maximum capacity.
Although a wide variety of designs exist for self-cleaning sanitary devices in general and self-
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