Cleaning and liquid contact with solids – Apparatus – With movably or flexibly mounted spray or jet applying...
Reexamination Certificate
2001-04-24
2002-08-27
Stinson, Frankie L. (Department: 1746)
Cleaning and liquid contact with solids
Apparatus
With movably or flexibly mounted spray or jet applying...
C134S201000, C134S199000, C239S242000, C239S244000, C239S264000
Reexamination Certificate
active
06439248
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the cleaning and disinfecting arts. It finds particular application in conjunction with the cleaning of animal cages and racks and also healthcare and scientific equipment, such as hospital beds, wheelchairs, utensils, carts and instrument containers, and will be described with particular reference thereto. It should be appreciated, however, that the invention is also applicable to the cleaning and disinfecting of other pieces of equipment, particularly those which have been in contact with biological wastes.
Items such as animal cages and associated racks and large pieces of healthcare and scientific equipment are generally cleaned at frequent intervals to remove biological waste, such as urine, feces, and uneaten food. Thorough cleaning aids in preventing the spread of disease and reduces the development of unpleasant odors. Washers have been developed to handle the large scale cleaning and disinfecting of animal such items. Typically, these are large enough for a load to be processed to be wheeled manually into the washer. Cleaning fluid is then sprayed through jets onto the load. The used fluid is collected in a pit or sump, below the washer. The fluid is either recycled or discarded, depending on the degree of contamination.
When large numbers of items are to be cleaned, the cycle time of the machine is an important factor. A washer for items such as cages is necessarily a large and invariably a costly investment, and it is thus desirable for a facility to clean all such items in a single washer. Typically, the jets which are used to spray cleaning fluid over the load operate at around 20 p.s.i. (1.4 bar). Stripping the often dried and adherent biological matter from the load with fluid at this pressure is time consuming and cleaning cycle times of 40 minutes or longer are common. In addition, low pressure washing uses large quantities of cleaning fluid to compensate for the low level of impingement of the sprays upon the process load.
The length and effectiveness of the cleaning system are also dependent on the arrangement of the jets within the washer. Cages and racks and scientific and healthcare equipment and racks are often large, with components which inhibit movement of the cleaning fluid, resulting in incomplete cleaning of the load. A number of systems have developed for directing the sprays of cleaning fluid so as to improve coverage of the load. In one system, a rotary spray arm is used. The pressure of the cleaning fluid causes the arm to rotate. Holes in the spray arm spray the fluid into the washer. The effectiveness of cleaning, however, is reduced because the sprays emitted tend to fight against each other, reducing the power of the sprays and varying their direction. Some of the energy of the spray is utilized in rotating the spray arm, reducing the water pressure efficiency of the spray. It is also difficult to ensure coverage of the entire load with a rotating spray arm. Further, the soil washed from the load tends to be pushed toward the center of the washer, collecting on parts of the load, rather than dripping off the load and into the sump.
In another cleaning system, a tube supplies cleaning-fluid to two spray bars or arms, movably mounted on either side of the washing chamber. The bars move simultaneously up the side of the washer, spraying fluid from nozzles as they travel. The sprays provide coverage of the entire washer, and increase cleaning efficiency through the effect of fluid dripping through the load. The system generally includes a complicated movement mechanism. A safety clutch is therefore provided to reduce the danger to workers in the event that the mechanism fails to operate properly. The sprays from the two spray bars tend to fight against each other. In a similar cleaning system, spray arms travel horizontally, rather than vertically. In addition to having some of the problems associated with the vertical cleaning system, the sprays tend to push the soil into the center of the load, resulting in less efficient cleaning.
There remains a need for a cleaning system with a reduced cycle time that strips the biological matter from the load and sanitizes the load more effectively.
Effective cleaning of the load is also achieved by maintaining the concentration of a selected detergent in the cleaning fluid. Because of the often high cost of the detergent, and the large quantities of cleaning fluid employed, it is desirable to maintain the detergent concentration close to the minimum level required to insure effective cleaning. Traditionally, the cleaning fluids are pumped in solution from storage tanks. Periodically, the fluid in the tank is replenished by the separate addition of detergent, in concentrated form, and water.
Measuring the actual concentration of the detergent in the tank is time consuming, therefore methods have developed which determine the concentration indirectly. Typically, one of two methods is used to estimate the concentration of detergent. In the first method, the addition of detergent to the tank from a detergent supply container is timed. The concentration of detergent is inferred from the operating time of a pump used to transfer the detergent. This provides a simple means of determining detergent concentration. However, if there is little or no detergent passing through the pump, which could occur, for example, if the pump is not working properly, then inaccurate measurements of detergent concentrations are obtained. Inadequate cleaning and sanitization of the process load results when the detergent concentration drops below a minimum level.
In the second method, the detergent concentration is inferred from a measure of the pH or conductivity of the cleaning solution. This correlates well with the detergent concentration in the fresh cleaning fluid. It is usual, however, to recycle a portion of the cleaning fluid from the washer into the tank for reuse. The recycled cleaning fluid contains soil from the load which influences the pH and conductivity of the cleaning fluid. Thus, the measure of pH or conductivity gives an inaccurate determination of the concentration of detergent in the tank, the inaccuracy becoming more pronounced at higher soil concentrations. There remains a need for a cleaning system that insures effective cleaning by providing a more accurate method of monitoring the rate of addition of detergent.
The cleaning fluid is generally retained in the sump. The cleaning fluid is pumped from the sump by a sump pump and circulated to the nozzles in the washing chamber. The fluid level in the sump must remain deep enough that the sump pump does not cavitate. Conventionally, cage and rack washers employ sumps of around 30-40 cm deep to supply the necessary depth of fluid for operation of a typical sump pump. To provide this depth, a large well is usually constructed through the floor beneath the washer, with suitable reinforcement for the washer. Constructing such a well within a concrete floor is frequently expensive and time consuming. In some floor structures, there is insufficient below ground depth available for the sump and the load is raised well above floor level to enter the washer. Ramps provide a means of raising the load, but as cages and hospital and scientific equipment are frequently heavy, it is difficult to push them up a ramp that is too steep. Shallow ramps make loading the washer easier but take up considerable space and are hazardous if wheeled carts are left unattended and accelerate down the slope.
Typically, a portion of the cleaning fluid is returned to the tanks for recycling after it has been used in the washer. Generally, sump pumps do not begin to operate until a sufficient head of fluid has collected in the sump. Thus, there is a delay between cycles while a portion of the used cleaning solution is discarded and replaced with fresh water and added detergent. In addition, because of the different soils encountered, cleaning systems typically include two or more cycles, each using a different cleaning fluid. Separ
Duchaine Mario
Emond Michel
Lemay Michel
Parent Ghislain
Rochette Daniel
Fay Sharpe Fagan Minnich & McKee LLP
Steris Corporation
Stinson Frankie L.
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