Drain plug assembly for dishwasher, and the like
BACKGROUND OF THE INVENTION 
     This invention relates to drain plug assemblies for use in dishwashers, and the like. Typically, dishwasher systems provide a sequence of wash, rinse and drain cycles. The drain cycle releases the wash water from the dishwasher, and fresh water is then introduced into the dishwasher to begin the next sequence of cycles. 
     A drain plug assembly is employed to release the wash water from the dishwasher, and it is controlled by a solenoid which is actuated by a timer. The drain plug is simply lifted by the solenoid and then reseats by gravity following release of the used washwater. It is, of course, imperative that when the drain plug reseats, a positive shut off is obtained. 
     Dishwasher systems also employ chemical injection pumps and recirculation pumps to supply water and other components such as detergent, sanitizing chemicals and rinse additives to the machine. These pumps are also controlled by the timer to insure that the rinse additive, detergent and sanitizer solutions are supplied during their respective cycles in correct amounts along with the water. Since the amount of water and the other components must be present in the dishwasher in controlled quantities, the water level in the dishwasher must be accurately controlled. However, if the drain plug does not seat or reseat properly, water levels cannot be accurately maintained, and the sanitary washing capabilities of the system will be compromised. Hence, the amount of chemical solution, and the water level in the machine are critical to a sanitary wash. 
     Typical drain plug assemblies are disclosed in U.S. Pat. Nos. 1,963,685; 2,276,670; 2,764,385; 2,879,026; 3,703,189; 4,351,355; and; 4,437,487. 
     Many problems caused by drain plug assemblies in dishwashers are due to misalignment of the drain plug in the drain pipe of the dishwasher system. This results in uneven wear of the drain plug and necessitates a premature replacement. Also, reduced water levels will occur due to leakage, and, as indicated, this will lessen the effectiveness of the dishwasher. 
     THE INVENTION 
     According to the invention, there is provided a new and improved drain plug assembly for dishwashers, and the like. 
     The drain plug assembly comprises a hollow stem portion, and a ball plug valve disposed in sealing relation to a drain pipe of a dishwasher. The ball plug includes a seating portion disposed upwardly of the drain pipe and seated thereon, and an inwardly tapered portion extending within the drain pipe itself. A double O-ring seal comprising a seating seal and a guide ring seal are disposed around the lower portion of the plug. When the drain plug is stationary, the main sealing function is performed by the seating seal. When the assembly is raised or lowered, the guide ring seal maintains the assembly vertically aligned within the drain pipe. Consequently, there is little or no tendency for the assembly to tilt out of its sealing alignment with the drain pipe. This in turn reduces the amount of water and detergent solution which leaks out of the dishwasher. Also, the guide ring aids in the sealing function when the assembly is stationary. 
     If particles such as food, broken glass, etc., enter into the seat area of the assembly, they will be drained from the system, rather than becoming stuck and wearing away the seals, drain plug, or drain seat. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The single FIGURE is a cross sectional view in side elevation showing the drain plug assembly of this invention installed in a dishwashing system. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The drain plug assembly 10 of this invention is shown comprising a hollow stem element 11, and a lower ball plug element 12. The ball plug comprises a seating portion 13 and an inwardly tapered portion 14. Circumferential grooves 15 and 16 are defined on the seating and tapered portions 13, 14 respectively, each groove having a corresponding seating O-ring 17 and guide ring 18 mounted thereon. Typical materials of construction for the sealing and guide rings are HYPALON, VITON, and other plastics having resistance to highly corrosive detergent solutions. The stem portion and ball portion may be of stainless steel, PVC, etc. 
     The drain plug assembly is mounted within a connecting chamber comprising a dishwasher pan sump 20, drain sump 21, an inclined ball seat 22, drain pipe 23 defining an inner wall 23a, and a drain tee 24. The guide ring 18 contacts the inner wall 23a of the drain pipe 23 and forms a light, sliding fit therewith when the drain plug assembly 10 is raised or lowered. This enables the drain plug assembly to be maintained aligned in the drain pipe in a vertical orientation, and ensures proper seating and water levels. 
     The hollow stem element 11 of the drain plug assembly serves as an overflow drain, and this feature prevents flooding of the dishwasher. Also, use of the hollow stem enables a precise ratio of water to chemical solution to be maintained because it fixes the precise volume of water within the tank. When the appropriate amount and ratio of water to chemical solution is produced in the sumps 20 and 21, the solution mixture of water and chemical is pumped to the dishwasher in the appropriate timed sequence of wash and rinse cycles. 
     The upper end of the stem element 11 is attached by a chain 24 to a solenoid mechanism (not shown) which is actuated by a timer mechanism to control the rinse and wash cycles. Elevation of the drain ball assembly 10 by the chain 24 upon actuation of the solenoid permits wash solution from the dishmachine sump 20 and sump 21 to drain through the drain seat 22 and drain pipe 23 to sewer. 
     Use of the double O-ring design is critical to the seal of the drain plug because this simple feature allows easy replacement of the O-rings without replacing the complete drain plug assembly. 
     A leakage reduction of the wash and rinse solution of about 85% compared to prior art devices is obtained compared to prior art devices, using the drain plug assembly of this invention. This leakage reduction not only reduces costs for water and detergent solution, but also effects a much cleaner and more sanitary wash. In addition, there is less wear at the ball seat 22 and the O-rings 17 and 18 are easily replaced.