SPIRAL PITCH

The spiral pitch P (Figure 2.4) is the parameter affecting more the 'density' of the strip brush. Anyway the brush not always must be very dense. For example to remove deposits and easily discharge them, the pitch must be sufficiently large to avoid deposits to be held into the spiral.
Obviously the minimum value of P corresponds to B. The maximum value depends instead on the winding diameter D2: the larger D2 is the larger the maximum pitch can be.
We can define the following limits:

Apart from defining the density of the brush, the pitch can be used to solve mechanical problems of transport. In fact if P is sufficiently large to hold (entirely or partially) the parts to treat, the brush will function as a screw feeder, and to his rotation will be associated a transversal displacement of the material. So it is important, in this case, to specify if the winding must be right-hand or left-hand.
Finally we can have two spirals (one right-hand and one left-hand) converging to the middle of the brush. The effect is to convey the material to the middle or to the sides of the brush.
The screw feeder brush is particulary suitable when one must transport very soft material or solve noise problems.

DIMENSIONAL LIMITS

The strip brushes can hold a wide dimensional range.
In the linear strip brushes the base width B varies as indicated in Table 2.1 . The lenght has no limits, because are produced from coil with continuity. The total height H (Figure 2.4) is limited as indicated in Table 2.2.

-	SINGLE BAND							DOUBLE BAND
B	4	5	8	10	13	14	20	6	8
Hmax	100	150	200	200	400	400	400	200	350

TAB 2.2

 

With reference to the wound strip brushes (rollers), the limits are mostly related to the winding diameter D2 (Figure 2.4) . In fact there is always a minimum value for D2 below wich the strip brush cannot be wound. These limit values depend on the base B, and are indicated in Table 2.3 (base in galvanised iron). For bases in stainless steel one must increase by 50% the values of the table.
Concerning the maximum diameter of the brush D1 (Figure 2.4), generally it is not possible to exceed the value D1=1000 mm.

-	SINGLE BAND							DOUBLE BAND
B	4	5	8	10	13	14	20	6	8
D2min	12	15	20	25	80	80	160	30	50

TAB 2.3