Combination nozzle for Electrolux cleaner

This unit serves a dual purpose on a vacuum cleaner. Its parts are shown in Fig. 3.1, and it is assembled as follows. The bristles in their metal retaining ring pass over the annular section A. The protection ring goes inside the ring of bristles to locate an annular section. The ears  

The bristle holder, ears and protection ring are all injection-moulded items. Selection of suitable materials is dependent on a combination of production and service requirements. 

This is the largest moulding in the assembly, and its material selection is the most interesting. The part is made in semi-plasticized PVC (about 125% plasticizer). At room temperature it is quite rigid. At 60 C, however, it has rubbery properties, i.e. it can be stretched to allow location of other parts, and returns to its moulded shape when released. This allows the ears (pre-moulded) and bristles to be attached while the holder is still warm from the mould. When cool, the holder is rigid, and the brush and ears are firmly and permanently in position, with no possibility of separating later. 

It is difficult to think of another material which would perform in just this way. Other thermoplastics would not be sufficiently elastic, when softened, to return to shape after stretching to admit other parts. Vulcanized rubbers would not show the necessary thermoplastic behaviour. This material behaviour is explored in more detail in PST 1. 

This is made of very soft PVC (30% plasticizer), and its function is to prevent scratching of polished surfaces during cleaning. It fits snugly on to the annular part B and is then permanently fixed by ultrasonic welding to B . The selection of soft PVC for this part gives the required protection in service, and allows efficient welding of the two PVC components. PST 1 explains this material more fully. 

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