WASTE DISPOSAL SYSTEM

Abstract: A gate valve (10) is connected in a waste pipe system (16) between an inlet (12) and an outlet (14). A flat blade (24) is selectively movable between a closed position blocking the inlet from the outlet, and an open position allowing waste flow between the inlet and outlet. A pair of seals (30,32) are disposed in an abutting relationship aligned to receive the blade therebetween when in the closed position, and to seal the interior from the exterior of the pipe when the blade is in the open position. The seals are hollow and have one side (50) which collapses as the blade (24) moves to its closed position, thereby allowing them to partially rotate and roll against the blade surface, so limiting friction wear.

Description: This invention relates in general to waste disposal systems with gate valves, and, more particularly, to a system having a motorised gate valve that can be used as a flush valve in an aircraft waste disposal system, including those systems in which a pressure differential exists between the two sides of the valve. In recent years, efforts have been undertaken to replace the recirculating waste disposal systems found on vehicles with non-recirculating systems that utilise an on board supply of flushing liquid, usually potable water. For many years, the recirculating waste disposal systems have been utilised primarily to eliminate the need to carry extra liquid that would be needed for flushing. The recirculating waste disposal system started with a small pre-charge of flushing fluid and utilised any added liquid waste in the flushing process. As a result of some effort, waste disposal systems have been developed that require only minimal amounts of liquid in the flushing process. These systems permit use of an on-board potable water supply as a source of flushing fluid without imposing severe weight and/or storage penalties. Because the amount and volume of flushing fluid can be small, it is important to have a flush valve that will quickly open and close over a large orifice so that the waste matter will move out of the toilet unit and into the waste line rapidly. For those waste disposal systems that utilise a pressure differential between the environment of the toilet unit (normally at aircraft cabin pressure) and the exterior of the aircraft in flight, the flush valve must also provide a pressure seal to preserve the pressure differential and to avoid depressurization of the cabin when closed. Some prior art valves, as in US-A-4,199,828, have utilised a weighted flapper which opens when the weight of the waste matter and the pressure differential overcome the weight biasing the valve closed. Other valves have been designed with a diaphragm which occludes a bend in the waste line and acts as a seal, effectively separating the higher pressure toilet unit from the lower pressure waste tank. One such valve is shown in US-A-4,376,315. The diaphragm pinch valve, which is the essence of the disclosure of the latter patent, preferably utilises a major bend of goose neck shape or trap in the waste discharge lie. While in fact diaphragm pinch valves of this type have been constructed in a straight section of a waste discharge line, such valves are highly susceptible to damage (especially the flexible diaphragm member) from objects impinging on them as waste material is drawn through the valve. Further, in waste disposal systems utilising minimal amounts of flushing fluid, the use of a trap would hold waste products in proximity to the toilet unit of the system. In aircraft systems and in vacuum systems generally, it is preferable to have a direct waste line to the storage tank and it would be advantageous to have a substantially straight, gravity assisted line. The present invention overcomes the tendencies of this known type of pinch valves to be damaged by the internal flow of waste materials therethrough by having a relatively short, straight passage directly through the valve with no exposed seals or diaphragms. Accordingly, the passage of objects that would normally damage the known type of valve would have no effect on a valve made in accordance with the present invention. In order to provide a waste line that is suitable for low volume flush aircraft systems and one that could easily accommodate a vacuum-assisted flushing process, a flush valve is necessary that can maintain a pressure differential when closed and that can quickly open and close a wide aperture so that when the toilet unit of the system is flushed and the waste products and flushing fluid accumulate at the valve, a quickly opened and closed valve can let the pressure differential carry the waste products into the main waste line. Finally, it should be noted that most prior art valve seals used in gate valves are of the "O" ring or spring loaded type. None of these prior art seals have sufficient compliance to allow the seal to seal on itself and still not have so much static friction that the sliding gate cannot be withdrawn, without a large driving device, from between the seals with the valve in the closed position. Also, currently used prior art seals undergo severe wearing forces and must be replaced on a regular basis. GB 2 116 679-A relates to seals for gas valves. The sealing relies upon elastic plates which are bent into arcuate strips, held by a frame. This document discloses the features set out in the precharacterising portion of Claim 1. The present invention attempts to overcome these noted problems in the prior art seals used in waste system motorised gate valves by the use of a seal having a design permitting the seal, of rubber-like flexure, to mechanically rotate as the slide gate is moved into the valve closed position, inserted between the seals. As the slide gate is moves to its open position, that is, withdrawn from between the seals, the natural resilience of the elastomer in the seals along with the design of the seals, causes each seal to rotate back mechanically to its original position, each resiliently biased against the other, sealing the passing waste products from entry into the valve housing. This is necessary as the accumulation of waste products in the valve housing is unacceptable from a sanitary standpoint. Since the seals mechanically rotate in association with the slide gate, the seals experience little to no wearing forces and have a considerably longer life expectancy than prior art seals. According to a first aspect of the invention, a gate valve is characterised by the features set out in Claim 1. According to a second aspect, a waste disposal system is provided as set out in Claim 10. Thus, a motor driven, reversible gate valve may be provided between a toilet unit and a main waste line. The valve itself desirably has a blade that moves at right angles to the waste line and, when in a closed position, completely blocks the waste line. A reversible motor drives the valve between its open and closed positions. Limit switches can signal the motor to reverse directions. A seal of novel configuration is also disclosed which seals the interior of the valve body from the waste products passing through the valve when the blade is in the open position. Also, when in the closed position, the seals engage the blade surface, preventing any leakage either around the blade, or into the valve housing. The seals are mounted in a groove in the valve body, and include a design having a reverse curve (concave portion) in a side wall that permits the seal to partially collapse upon itself in a mechanical rotation to accommodate the width of the blade. In the event of a power failure or a motor problem, the valve mechanism can be manually actuated to either open or close the valve. Normally, however, an electrical motor will operate the valve blade, driving it in a first direction until a limit switch is engaged. At that point, the motor will stop until signalled to start again in the opposite direction, or, it can be immediately reversed until the other limit is reached and an entire cycle of closed, open and closed (a flush cycle) is completed. In operation in a vacuum assisted, low volume, aircraft waste disposal system, actuating a flush button or lever after using the toilet will cause a pre-measured quantity of flushing fluids to clean the contents of the bowl and carry the mixture to the gate valve. A slight delay can be provided between actuating the flush button and opening the valve so that the valve does not actuate until the flushing action of the flushing fluid is complete and the contents of the toilet unit are washed down to the area of the gate valve. After a delay suitable to assure that the entire contents of the toilet unit, including the flushing fluid, are out of the toilet unit and adjacent the gate valve, the valve motor is energised and the valve is opened beginning its cycle. Waste matter, mixed with the flushing fluid, is propelled toward the waste tank under the differential pressure that exists between the cabin and the exterior of the aircraft. In some embodiments the waste matter has the assistance of gravity, as well, to aid in the move toward a main waste collecting tank. After a pre-determined pause (which may be no pause at all), the valve motor is reversed and the gate valve closes, restoring the pressure differential and readying the toilet unit for re-use. Reversal of the valve motor may be automatically regulated by the use of limit switches as suggested above. Operation on the ground, in the absence of a pressure differential is still practical if there is a gravity assist available. Also, a fluid assist can be provided by using fluid jets to propel the wastes. The invention may be carried into practice in a number of ways, and one specific embodiment will now be described, by way of example, with reference to the drawings in which like reference numerals designate like parts throughout: Figure 1 is a plan view of a motorised gate valve embodying the invention; Figure 2 is a view taken along the line 2-2 of Figure 1 in the direction of the appended arrows; Figure 3a is an enlarged view of the area contained within the circular line 3a of Figure 2 prior to the blade engaging the seals as shown in Figures 3b and 3c described below; and Figures 3b and 3c illustrate the mechanical rotation of the seals of Figure 2 when the motorised gate valve of Figure 1 goes through an operational cycle. Figure 1 illustrates the general appearance of a motorised gate valve 10 constructed in accordance with an embodiment of the invention. Some detail of the waste disposal system associated with the motorised gate valve has been omitted from the drawing for ease of understanding the present invention. In a waste disposal system including a receptacle for receiving waste, a holding chamber for the waste and a waste pipe system communicating between the receptacle and the holding chamber through which waste can be transferred therebetween, the invention is illustrated in Figures 1 and 2 as being embodied in a motorised gate valve 10 that includes a hollow housing 11 with an inlet 12 and an outlet 14 connected to the waste pipe system 16. In a preferred embodiment for ease of maintenance and manufacture, the hollow housing 11 is made of two mating sections 18, 20, jointed by a plurality of nut and bolt combinations 22. A teardrop shaped blade 24 is pivotally connected at one end 26 to the interior of housing 11. The teardrop shaped blade 24 expands on an opposite end 28 to a diameter sufficiently large to engage a pair of seals 30, 32 (described below), and block, waste flow between the inlet 12 and the outlet 14. The blade 24 is selectively movable between a closed position blocking and sealing the inlet 12 from the outlet 14, and an open position allowing waste flow through the inlet 12 and the outlet 14. Both the open and closed positions of the blade 24 are shown in dotted cutline in Figure 1. An electric motor means 34 includes a reversible electric motor 36 operatively connected to the blade 24 through a gear means 38. The gear means 38 are a series of gears adapted to selectively move the blade 24 between the open and closed positions. In a preferred construction, a serrated gear can be formed in the end 26 of the blade 24 for pivotally connecting the blade 24 in the interior of the hollow housing 11. Thus, a reduction in parts can be accomplished by this construction. Sensing and control means 23 are operatively connected to the blade 24 and the electric motor means 34 for sensing the open or closed positions of the blade 24 and may cause reversal and shut-off of the electric motor means 34 based thereon. Preferably such sensing and control means include at least one limit switch 25 placed to be activated whenever the blade 24 reaches its extremes of pivoted travel, i.e., the open or closed positions. Additional limit switches can be disposed with regard to the blade 24 so that one would sense whenever the blade 24 was in the open position for automatically reversing the electric motor 36, thereby driving blade 24 back into its closed position. A second limit switch could be disposed to sense when the blade 24 had reached its closed position and shut-off the electric motor 36. Manually activated means 40 for selectively moving the blade 24 between the open and closed positions is provided by a cable or hard linkage system 42 that can be operated by a user. The manual system of opening and closing the blade 24 is a back-up safety system which is provided for the case of failure of the automatic electrical system described above. The seals 30 and 32 (mentioned above) are a pair of annular seals best illustrated in Figures 2 and 3a through 3c. These seals have an angled, hollow, D-shaped cross-section with a gap 44 between the ends 46 and 48 thereof and a reverse curve (concave portion) 50 in a side wall 52. It is the shape of the seals 30 and 32 that permits the gate valve of the present invention to operate with great efficiency and overcome prior art problems. Specifically, the sealing action between the blade 24 and the seals 30 and 32 does no depend wholly upon the elastomeric sealing properties of seals 30 and 32, but, to a great extent result from the mechanical rotation of the seal, allowing the seals to rotate in on themselves and out of the way of the blade 24 as the blade enters between the seals, as best illustrated in Figures 3a, 3b and 3c. The shape of seals 30 and 32 permits the seal to function over an extended time period without failure as the portions of the seals that contact with the blade 24 do so in a "rolling" and "wiping" fashion, thus virtually eliminating the wearing or abrasion of meeting parts against conventional "O" ring seals which are in compressive frictional engagement. Likewise, the seals 30 and 32 retain their flexibility and longevity without incorporating any metallic elements, which would tend to corrode in the environment of a waste disposal system. To clarify the mechanical rotation of the seals 30 and 32, reference is made to Figures 3a through 3c. Figure 3a shows the relationship of the blade 24 and the seals 30 and 32 prior to the blade 24 engaging the seals 30, 32. In this "pre-entry" position, the seals 30 and 32 abut one another along a side 54, forming a seal against the entry of undesirable waste material into the interior of the valve housing 11. Because the concave sections are partly collapsed, the elastic restoring force biases the seals into a sealing engagement. Figure 3b shows the blade 24 as it initially engages the seals 30 and 32, and the forces exerted on the seals to cause a mechanical rotation of the seals 30 an 32 in response to the lateral movement of the blade 24. As is illustrated in Figure 3c, the seals 30 and 32 fold along the side wall 52 in a mechanical rotation to produce a sealing effect with an angled surface 56 parallel to the blade 24 as indicated. Similarly, when the blade 24 is withdrawn from between the seals 30 and 32, Figure 3c, a reverse mechanical rotation of the seals occurs and the seals resume the shapes as seen in Figure 3a. In operation in association with a waste disposal system, the above described motorized gate control valve embodying the invention would be activated by a user actuating a flush button or lever after using the toilet unit of the system. The flush button or lever causes the electric motor 36 to begin to drive the blade member 24 of the valve 10 from its closed position to the open position after the flushing fluid is delivered to the toilet unit. Once the limit switches sensed that the blade member 24 was in the "open" position, they would cause the electric motor 36 to reverse and to drive the blade 24 into the "closed" position. Another limit switch would sense when the blade 24 had moved into the "closed" position and shut the motor 36 off. A slight delay can be programmed into the actuation system for the electric motor 36 so that any waste matter placed into the system would be given sufficient time to reach the closed valve prior to its beginning its operating cycle. Such a delay, not necessary in all cases, would insure that slow moving waste matter was not trapped on the wrong side of the gate valve. In operation, the blade member 24 forms a tight seal against the seals in the "closed" position to prevent leakage of waste matter into the interior of the hollow housing 11 and prohibits pressurized cabin air from exhausting to the outside. In the open position, the seals abut against one another in such a manner as to provide a fluid-tight seal against any waste matter from entering into the interior of the hollow housing 11. Thus, the interior of the hollow housing 11 and valve component parts contained therein are kept free of foreign matter that might cause maintenance problems were it to enter the interior of the hollow housing.

Claims: A gate valve (10) comprising a blade (24), selectively movable between a closed position, blocking a conduit (16), and an open position, the conduit having a pair of flexible hollow seals (30,32) between which the blade is sealingly received in its closed position and arranged mutually to co-operate when the blade is in its open position to seal the interior of the conduit from the exterior, characterised in that the seals have a concave or convex side (50) which is arranged to collapse as the blade is inserted between the seals, thereby causing the respective surfaces (56) of the seals in contact with the blade to undergo at least partial rolling movement against the blade as the blade is inserted. A gate valve as claimed in claim 1 in which each of the seals (30,32) has a gap (44) into the interior thereof along one side, the gap being arranged to close or partially close as the blade (24) is inserted between the seals. A gate valve as claimed in claim 1 or claim 2 in which the blade (24) is actuated by electric motor means (36), disposed outside the conduit (16) , the seals (30,32) sealing the interior of the conduit from the electric motor means. A gate valve as claimed in any one of the preceding claims in which the seals (30,32) are disposed in respect circumferential annular channels of the conduit (16). A gate valve as claimed in any one of the preceding claims in which the blade (24) is substantially planar and is mounted for pivotal movement in its own plane. A gate valve as claimed in claim 5 in which the blade (24) is arranged to pivot through an angle of less than 90 degrees between its open and closed positions. A gate valve as claimed in any one of the preceding claims in which manual actuating means (40) are provided for moving the blade (24) between its open and closed positions. A gate valve as claimed in any one of the preceding claims including automatic actuating means (34) arranged to move the blade (24) between its open and closed positions, and control means (23) arranged to sense either the open or the closed position of the blade and to switch off the actuating means in response to the said sensing. A gate valve as claimed in claim 8 in which the sensing is effected by a limit switch (25). A waste disposal system having a waste pipe (16) which is selectively blocked by a gate valve (10) as claimed in any one of the preceding claims.

Inventors: PEREZ, FREDERICK W.
Applicants: KAISER AEROSPACE & ELECTRONICS CORPORATION
Application year: 1987
Main classification: E03F1
IPC codes: B60R15, F16K3, E03D5, E03F1