Fig. 79.—“Closed” Type, Candy-Whittaker Sprinkler.
Automatic Revolving Distributors.—One of the first, if not the first, of the revolving distributors for percolating filters was the “Candy-Whittaker” sprinkler in its original form. This is supplied by the Patent Automatic Sewage Distributors, Ltd. It is now made in three different forms: the “Open” type, the “Enclosed” type, and the “Buoyant” distributor, as shown in [Figs. 78], [79], and [80]. The most prominent feature of these sprinklers is the mercury seal joint, for which it is claimed that it gives an absolutely watertight and frictionless joint, that it cannot freeze, and that no renewal of the mercury is required. It is stated that the use of the patent “check-ring” in combination with the mercury seal prevents any loss of the mercury, no matter what the head may be. Another feature is that the ball-bearings are moisture-proof, due to the special methods of construction. In addition to the above, the makers point to the special value of their compensating arms system, by means of which their distributors will work continuously with a very small volume of sewage and still be capable of dealing with any larger volume of sewage that may be required. The names of the “Open” and “Enclosed” types are self-explanatory, but the “Buoyant” type is specially designed to reduce the friction on the bearings. The revolving portion is supported by a float or buoy in the form of a cylindrical tank, which floats in a small chamber at the centre of the filter. The removal of all weight friction on this distributor reduces the power required to rotate it to the minimum.
Fig. 80.—“Buoyant” Type, Candy-Whittaker Sprinkler.
Another make of revolving distributor is well-known as the “Cresset.” This is manufactured by Messrs. Adams Hydraulics, Ltd., and is illustrated in [Fig. 81]. In this case the special feature is the joint between the revolving and fixed portions of the apparatus. It consists of a simple air-lock, formed by a cushion of air between two water columns. This is clearly seen in the illustration. It is obvious that this is an absolutely frictionless joint, so that there is no loss of head. It also has the effect of removing the strain to which the overhead ball-bearings are generally subject, so that the revolving body swings freely in the true vertical line from the cross head above. Another point is that no expense is involved, and very little trouble is incurred, in renewing this joint whenever it may be found necessary, but it has been maintained in perfect condition without requiring renewal for very long periods. Special means are provided for removing and replacing the ball-bearings in the cross-head without dismantling the distributor.
Another type of distributor manufactured by Messrs. Adams Hydraulics, Ltd., is their “Sypho-Jet,” as shown in [Fig. 82]. As its name implies, it is siphonic in action, and combines the functions of a sprinkler and intermitting valve in one apparatus. It may either be used in connection with a dosing tank or connected direct to the settling tank, from which it draws off a certain depth of water every time it fills to a certain height.