Dishwasher history and its role in modern design Francesco Rosa, Edoardo Rovida, Serena Graziosi Department of Mechanical Engineering Politecnico di Milano Via La Masa, 1 Milano, 20156, Italy francesco.rosa@polimi.it Paolo Giudici, Claudio Guarnaschelli Mechanical Engineering students Politecnico di Milano Via La Masa, 1 Milano, 20156, Italy Dino Bongini Dishwasher Business Unit Indesit Company Via Aristide Merloni, 47 Fabriano, 60044, Italy dino.bongini@indesit.com Abstract— The fundamental steps in the development of electrical technologies have determined their strong diffusion in several applications that were previously hand operated and controlled. The household appliance industry is one of the sectors where this permeation had the major effects, fostering a continuous search for new design perspectives. Capturing such product evolution is fundamental in order to preserve knowledge coming from past experiences, which could act as a stimulus for new technical solutions or socio-economic analysis. Starting from the description of the dishwasher historical evolution, in this paper an approach to preserve such precious knowledge is presented: a functional representation of that knowledge is proposed end its role in modern design is discussed. Keywords- product evolution, functional basis, dishwasher electric motor. I. INTRODUCTION In the first decades of the XX century the electrical technologies begun to spread in many hand operated and controlled applications. That permeation opened new design perspectives, widening machine capabilities and reducing human efforts, as it has happened to several home appliances such as the dishwasher. Since from its first appearance in Western countries, the dishwasher has been seen as a welcome help and its importance has increased significantly in recent years influenced by new social trends that have made it an essential home appliance. Nowadays, under an engineering design perspective, a dishwasher can be considered as a complex system, since it integrates mechanical, electrotechnical and electronic features, whose interaction highly influences the cleaning performances of the product. That cleaning effect is the result of 3 physical actions such as: the mechanical impact of water on the load (e.g. pans, plates, cutlery, etc. placed on the two racks); the chemical action of the detergent; the thermal action of the water. While the mechanical effect depends on the rotation speed of the two spryer arms and then on the water pressure (since it strongly influences the rate of mechanical removal and the solubility of soil and detergent during the washing phase), the detergent component chemical reactions are activated by the water thermal energy, electrically heated up at a temperature that depends on the selected washing cycle (from 50-52°C in case of energy saving cycles, until 65°C for the intensive ones with an average consumption of 1,1÷1,2 kWh, even if there is a strong push to decrease such value). At the end of each washing cycle, a pump drains the water up. During the drying phase the water is heated up at about 65÷67°C; that cycle is then the most energy-intensive and for this reason manufacturers are now investing a lot of efforts to make this phase more energy saving. The hot water in turn heats dishes and their heat capacity enables the evaporation of the water film on them. Steam condensation occurs on the tub surfaces and the liquid is then collected and exhausted by the drain pump. A micro-filter and a central plastic wider-mesh filter continuously clean the water during the wash phase: dirty residues are separated and the hydraulic circuit is prevented from being clogged. An electronic system, or a timer, regulate the time duration of the cleaning process with the possibility, in selected models, to delay the start time of the cycle by 3, 6 or 9 hours. However, modern dishwasher design has come a long way from their original inception. The first systems for washing table furniture can be traced back up to 1850, when J. Houghton obtained a patent [1]. Anyhow, Mrs Josephine Cochrane is commonly acknowledged as the dishwasher inventor: in 1886 she obtained a patent about a manually operated machine capable to wash dishes; that machine worked by spraying soapy water onto dishes held securely within a rack [2]. The first electrical technology introduced in this family of machines was the electrical motor aimed to operate the pump used to circulate the water. Among the firsts, in 1917, Mrs Cochrane patented an electrically powered dishwasher. This invention began to be installed in homes in the 1920s. The diffusion of the dishwasher was limited to restaurants and hotels, mainly because of the high production costs and the unstable social and economical context, deeply influenced by the two World Wars. Thanks also to the new electrical power source, two main solutions were developed: in the first one, a sort of impeller was used to agitate the water so that it can reach and wash the dishes; in the second one, the water was directly sprayed on the dishes by means of rotating sprayer arms (that is the solution commonly adopted nowadays). After the Second World War, the more favourable context gave a great impulse to the spreading of household appliances. In the early 50s, the first completely automated dishwasher was realized. This new generation of dishwasher was able to complete autonomously the whole washing cycle, thanks to electro-mechanical sub-systems. Nevertheless, these first automatic dishwashers were not efficient enough to