US3403849A

US3403849A - Sludge centrifuge with intermittent discharge

Info

Publication number: US3403849A
Authority: US
Inventors: Henric Wilhelm
Original assignee: Alfa Laval AB
Current assignee: Alfa Laval AB
Priority date: 1965-12-15
Filing date: 1966-12-09
Publication date: 1968-10-01
Anticipated expiration: 1985-10-01

Description

1, 1968 H. w. THYLEFORS 3,

SLUDGE CENTRIFUGE WITH INTERMITTENT DISCHARGE Filed Dec. 2, 1966 2 Sheets-Sheet 1 B Y (47M fiy m M Oct. 1, 1968 H. w. THYLEFORS 3,403,349

SLUDGE CENTRIFUGE WITH INTERMITTENT DISCHARGE Filed Dec. 9, 1966 2 Sheets-Sheet 2 I N VE N TOR 7zenric WI/he/m Thyle/ors B Y 6a), x/me, 404%! 06 United States Patent 3,403,849 SLUDGE CENTRIFUGE WITH INTERMITTENT DISCHARGE Henric Wilhelm Thylefors, Stockholm, Sweden, assignor to Alta-Lave] AB, Tumba, Sweden, a Swedish corporation Filed Dec. 9, 1966, Ser. No. 600,641 Claims priority, application Sweden, Dec. 15, 1965, 1 30/65 6 Claims. (Cl. 233-20) ABSTRACT OF THE DISCLOSURE Separated sludge is discharged intermittently from the rotor of a sludge centrifuge byv movements of a first valve located in the rotor and operable hydraulically by opening and closing of a second valve for controlling the discharge of the hydraulic operating liquid; and the second valve, biased in the direction to close the first valve and thereby cut off the sludge discharge, is associated with electromagnetic means for actuating it in the opposite direction.

This invention relates to sludge centrifuges of the type in which intermittent discharge of separated sludge is efiected under control of a first valve operable hydraulically by a liquid which, on opening of a second valve, discrarges through an outlet of the rotor, the second valve being biased in the direction to close the first valve and thereby prevent discharge of sludge.

In prior centrifuges of this type, the movements of each of the two valves are controlled hydraulically. However, such control of the second valve does not make it possible to control exactly the period of time during which the valve for discharging sludge is kept open. According to the present invention, it is possible to attain more exact opening periods for the sludge discharge by providing electromagnetic means for opening the second valve.

Although it is possible to provide the valve-opening electromagnetic means on the centrifuge rotor itself and to operate such means from stationary devices, the second valve, according to a preferred embodiment of the invention, is arranged to be actuated by one or more stationary electromagnets preferably mounted on the centrifuge frame. In this way, the devices for the operation of the magnets are simplified.

According to a preferred embodiment of the invention, in which the second valve is formed by a body surrounding the rotation shaft of the centrifuge and located outside the rotor, the magnet or magnets surround the rotation shaft of the centrifuge. If only one magnet is used, it is made annular; and if a plurality of magnets are used, they are arranged in a uniform distribution around the shaft.

In order to prevent wearing between the centrifuge rotor and the magnet (or magnets) when the latter is stationary, an air space is provided between the magnet, usually its core, and the body of the second valve when it is in fully opened position.

The position of the sludge level in the centrifuge rotor can be sensed by known means. The sensing impulse thus otbained can be used to start an electrical timer which keeps the second valve open during a period of time determined empirically.

The invention is described more in detail below, reference being made to the accompanying drawings in which:

FIG. 1 is a vertical sectional view, partly in elevation, of the left-hand half of an embodiment of the new centrifuge, and

FIGS. 2 and 3 are schematic views of different embodiments of a timer for use with the centrifuge shown in FIG. 1.

3,403,849 Patented Oct. 1, 1968 ICC In FIG. 1, a centrifuge rotor 1 is driven by a vertical shaft 2. In the wall of the rotor are sludge discharge openings 3. These openings are closed by a piston valve 4 movable vertically in the rotor and operated by liquid supplied through a channel 5 in the shaft 2. The operating liquid flows from the channel 5 through holes 6 in the shaft and channels 7 in the rotor bottom into a space 8 between the rotor bottom and the piston valve 4. The rotor bottom has additional channels 9 which serve to discharge the operating liquid from the radially outermost portion of space 8. The outlet openings of the channels 9 are formed by tubular pads 10 of nylon or similar material and are noramlly closed by a vertically movable plate-like valve 11, which is biased in the closing direction by a coiled spring 12 concentrically surrounding the shaft 2.

A plurality of electromagnets 14 are mounted on the centrifuge frame 13 and are uniformly distributed around the shaft 2. In its fully opened position, the valve 11 abuts against a step 15 integral with the shaft 2, whereby an air space is provided between the underside of the valve and the upper ends of the cores 16 of the magnets 14. In this way, wearing between the rotating valve 11 and the stationary magnet cores 16 is avoided.

The winding or coil 17 of each electromagnet 14 is adapted to be energized by a timer. As shown in FIG. 2, the coils 17 of the several electromagnets are represented collectively at 17a and are energized from current source 18 (AC or DC) through a switch 20. The latter is closed and opened under control of a motor-driven cam 19.

As shown in FIG. 3, a source 21 of direct current is used in a circuit with a variable capacitor 22 which is connected in parallel to the windings 17a. A switch 23 is adjustable in two different positions, one of which is shown by a broken line and the other one by "a full line.

In operation, sludge-containing liquid to be separated is supplied to the centrifuge rotor 1 from above through a pipe (not shown). The valve 4 is kept closed by means of liquid which is supplied to the space 8 through the channel 5. After an empirical determination or an impulse from a sludge-level-sensing means, the cam disk 19 (FIG. 2) is started. As it rotates through one revolution, the cam 19 keeps the switch 20 closed for the period of time during which the valve 4 is to be kept open. When the switch 20 is closed, current passes through the coils of magents 14 so that the valve 11 is attracted by the magnets and takes its opened position. Thus, the operating liquid in the space 8 is thrown out and the valve is opened, whereby sludge accumulated in the centrifuge rotor is thrown out through the openings 3. At the step on the periphery of the came 19, the switch 20 opens and the magnets 14 release the valve 11, which is pressed back to closed position by the spring 12. The operating liquid from the channel 5 then refills the space 8, the valve 4 then being reclosed.

When the timer according to FIG. 3 is used, the switch 23 takes its broken line position prior to a sludge discharge, whereby capacitor 22 is charged by the source 21 of direct current. The capacity of the capacitor 22 is adjusted to a charge corresponding to the period of time during which the valve 4 is to be kept open. When sludge is to be discharged, the switch 23 is actuated to the position shown by the full line. The capacitor 22 is then discharged through the magnet windings 17, so that magnets 14 keep the valve 11 and consequently the valve 4 open for a period of time corresponding to the amount of the charge stored in the capacitor.

I claim:

1. In a sludge centrifuge having a centrifugal rotor, the combination of a first valve operable hydraulically to effect intermittent discharge of separated sludge from the rotor, the rotor having an outlet for discharging the liquid by which the first valve is operated hydraulically, a second valve for opening and closing said operating liquid outlet, means biasing said second valve in a direction to close said outlet and hold the first valve in a position to prevent discharge of sludge, and electromagnetic means for actuating the second valve in the opposite direction to open said outlet and thereby actuate the first valve to a position for discharging separated sludge.

2. The combination according to claim 1, in which the electromagnetic means are stationary.

3. The combination according to claim 1, comprising also a stationary frame supporting the rotor, the electromagnetic means being mounted on the frame.

4. The combination according to claim 1, comprising also a shaft on which the rotor is mounted for rotation, the second valve being located outside the rotor and surrounding the shaft, the electromagnetic means surrounding said shaft.

5. The combination according to claim 1, in which there is an air space between the electromagnetic means and the second valve when the latter is in its fully opened position.

6. The combination according to claim 1, comprising also a timer operatively connected to' the electromagnetic means for maintaining said second valve open for a predetermined period of time.

References Cited UNITED STATES PATENTS 3,134,932 5/1964 Ray 251-141 X 3,189,267 6/1965 Thylefors 233-20 3,193,194 7/1965 Steinacker 233 20 3,237,854 3/1966 Thylefors 233-20 3,255,958 6/1966 Simon 233-20 3,272,430 9/1966 Thylefors 233 20 ROBERT W. JENKINS, Primary Examiner.