13-04-2016, 11:03 AM
design and fabrication of dishwasher pdf
Washing dishes is not the most rewarding task. Cooking can be creative, but cleaning up afterward seems like a waste of time and leaves the person washing complaining about "dishpan hands." The development of the dishwasher has helped relieve some of the monotony, as well as the grease and grime. It operates on a simple principle of washing dishes that have been placed on racks inside the machine with multiple jets of water. The modern dishwasher has features that cater to fine glassware or the toughest pots and pans; multiple cycles that clean, sanitize, and dry; and under-the-counter or stand-alone models for every size, use, and price range. It is far from perfect; tough foods may need personal attention before and after dishes and pans are cleaned in the dishwasher, and few owners of crystal glassware and fine china are willing to trust them to a machine. But the dishwasher, like other kitchen appliances invented and improved in the twentieth century, is a fixture in many kitchens of the twenty-first century.
The major obstacle to washing dishes has always been the availability of water. Early civilizations used limited numbers and types of dishes, utensils, and cookware and carried them to streams, ponds, or troughs of water for cleaning. The second choice was to carry the water to the dishes. Women carried water in buckets from communal water sources or from private pumps behind their homes or apartment buildings into the early twentieth century, when indoor plumbing finally brought water indoors, not only for bathing but for kitchen use as well.
The first dishwashers were patented in about 1850, but, like machines for washing clothes, they were large contraptions that used steam power and supplies of heated water to soak many dishes at a time. In some models, the dishes were held on cradles that rocked through the water; others had paddles that sloshed water around the dishes or circular racks that held the dishes and rotated to circulate them through the water. An assortment of propellers, plunging casings bearing the dishes, and plungers that drove water over the dishes were incorporated in other machines. In 1875, C. E. Hope-Vere created a machine that directed sprays of water toward racked dishes; the idea of the water jets was adopted by other inventors including A. W. Bodell, whose model was introduced in 1906. Another, the Blick machine, used a propeller that sprayed jets of water over racks filled with dishes. This basic idea is the one used today.
The first publicly displayed models were introduced in about 1915, but the dishwasher was not widely manufactured and sold to private families until about 1930. The dishwasher was not an immediate hit. The refrigerator was introduced at about the same time and swept America; but this is logical because food preservation is far more important than dishwashing. The machines were also too inefficient to completely eliminate hand work; to be fair, this was not entirely the fault of the dishwashers—soaps of the day were not suited to the task. By the 1950s, special dish-washing soaps that clean without sudsing and rinse away began to be developed especially for dishwashers, and the public began to demonstrate more interest. The automatic dishwasher is still not an absolute in every kitchen, but, by the 1970s when more women