Patent GB-373717-A (GB)
Title: Improvements in filters
IPC: B01D29/00
Filed: 1931-04-02
Abstract: 373,717. Filters. ZWICKY, J., Beckyngton, Farnham Royal, HUNT, W. F., Gleneagles, Stoke Road, and TYLER, S. A., Grove House, Chalvey Grove, both in Slough, both in Buckinghamshire. April 2, 1931, No. 10066. [Class 46.] The flow of liquid through a filter or strainer is temporarily reversed for cleansing purposes by means of a piston sliding in a cylinder, means being provided for moving the piston against spring action to one end of a setting or non-cleaning stroke and there suddenly releasing it, so that the spring drives it through its cleaning stroke with a vigorous initial impulse, causing it to return filtered liquid through the straining member. The piston 6, Fig. 1, moves in a cylindrical extension 5 of the casing 1, the cylinder forming part of either the inflow or outflow chamber. It is shown as part of the inflow chamber, being separated from the rest by walls 8 making joint with the longitudinal ribs and end rings of the frame of the cylindrical filtering or straining member 2. The crown 7 of the piston is made separate from the skirt and acts as a valve which opens during the inoperative stroke of the piston. The skirt is moved by the crown 7 and a cross-bar 18 on the piston-rod 10. The piston is normally forced downward by a spring surrounding the piston-rod 10. It is lifted, through a push rod and lever 11, by a snail cam 12, which raises it gradually and then allows it to make a sudden movement downwards. To bring each part of the strainer in turn into cleaning position, it is rotatable by means of a handle 15, the cam 12 being rotatable with it and being so designed that the piston makes four cleaning strokes for each revolution of the strainer. Solid matter dislodged passes through the piston into a sump 16, towards which the incoming liquid is directed by a partition. In the construction shown in Fig. 3 the straining member 27 forms part of the piston sliding in the cylinder 29 and guided by a stem 34 sliding in a socket 35. The piston is depressed against the action of a spring 9 by an annular cam 12 acting through a lever 30 and turned by hand or driven continuously by the means that operates the pump forcing liquid through the strainer. A discharge cock 32 for the separated material may be opened mechanically through a rod 33. The liquid enters at 37, passes over an inwardly projecting part 38, scours the surface of the strainer, and passes through it and out through slots 39 in the cylinder 29 to an expanding annular channel 40 and the outlet 41. When the strainer rises it moves at such a speed that there is a relative backward flow through it, the normal flow through the apparatus not being positively arrested. In another construction the straining member forms the crown of the piston, and an apertured wall assists in distributing the liquid uniformly over it and provides a sheltered sump through the base of which solid material may be removed. According to the Provisional Specification the flow through a part of the filtering surface may be reversed by shielding that part from the pressure of the incoming fluid, so that the filtered fluid may return through the shielded part. Specifications 211,199 and 258,905, [both in Class 46, Filtering &c.], are referred to in the Provisional Specification.