FR2485383A1 - Linkage to raise and lower surface skimmer of decantation tank - is actuated by low pressure pneumatic jack pref. rubber bellows - Google Patents

Abstract

A power linkage for raising and lowering the skimming rake used to sweep surface scum from a rectangular or semicircular decantation tank. The tank is of the type in which the rake is mounted on a mobile chassis which bridges the tank and moves in one direction with the rake lowered to sweep the liq. surface and then back again with the rake raised to an inactive position. The rake is raised and lowered by a power linkage using an actuating jack. An air compressor serves an emulsion pump for shifting sludge from the bottom of the tank. The rake linkage actuating jack is now a pneumatic jack operated by low pressure air from the compressor serving the emulsion pump. The air pressure is pref. less than 0.4 bar and the pneumatic jack comprises a simple, deformable container made of resilient material, e.g. a corrugated, rubber bellows. Pref. as the mobile bridge chassis reaches each end of its travel, a pneumatic limit switch is triggered so that a pilot valve actuates the pneumatic jack. The skimmer is used to clean the top surface of liq. being treated in a sedimentation tank.

Description

 Skimming device for settling tank.

 The present invention relates to a skimming device for settling tanks used in the treatment of all types of water, in which the sludge which accumulates at the bottom of the tank is extracted by a system of emulsion pumps or "air-lifts" .

 In the rectangular or semicircular settling basins, scraping devices are used to extract and dispose of surface sludge (scum or floating) comprising a mobile chassis or an overhead crane which moves in alternative translation and is provided with a member taking a scraping position in one direction of its movement and an idle position in the other direction. In this idling position the scraper member is raised. The mobile chassis also comprises, in certain devices, a member for extracting bottom sludge by emulsion pump.

 The assembly of the motor mechanisms which ensure the translation of the overhead crane or of the mobile chassis and maneuver the scraping device to give it a scraping position or a raised position, requires a relatively heavy and expensive construction requiring cam and lever systems. delicate adjustment or complex electrical systems.

 It is also known to use hydraulic lifting devices for the scraping member, which for example comprise a pump supplying a pressurized agent and a dispensing device for causing this agent to act on the piston of an Xrin for controlling the the lifting device.

However, these devices have the drawbacks of using high pressure and of requiring storage capacity with pressure measuring means.

 The present invention relates to a skimming device which overcomes these drawbacks and allows the use of a low pre-existing pressure, with simple detection means.

 The device according to the invention, which is intended to be used in a settling tank comprising a device for extracting the bottom sludge by emulsion pump supplied with pressurized air, comprises at least one jack to ensure the lifting of the scraping member and is characterized in that the cylinder is a pneumatic cylinder at low pressure which is controlled by air on pressed ali # entant your emulsion pump.

 The emulsion pump for the extraction of bottom sludge is supplied from a source of air, with compressed air whose pressure is greater than the water pressure at the depth of introduction of the air into the settling tank, this depth generally being between 2 and 4 meters. This air source is used to control pneumatic cylinders.

 The supply pressure of the pneumatic cylinders is less than 0.4 bar. It is preferable to use cylinders constituted by deformable rubber capacities, the internal friction of which is low.

 The pneumatic valves and distributors connecting the cylinders to the air source are arranged on the scraping devices, the opening and closing of which are controlled by fixed cams.

The various characteristics and advantages of the invention will emerge from the description which follows, with reference to the accompanying drawings in which
Figure 1 shows schematically the device according to the invention.

 Figure 2 shows an arrangement of the invention in which two pneumatic cylinders raise and lower the surface scraper member.

 Figure 3 shows schematically the device according to the invention adapted to a semi-circular settling tank.

 The skimming device according to the invention shown schematically in Figure 1 is constituted by a scoop of foam 1 attached to the end of an arm 2; this is articulated around an axis 3 supported by a yoke 4 fixed to the scraper bridge 5. The scraper member, constituted by the arm and the scoop, is connected at its other end to a pneumatic cylinder 6 fixed to a yoke 7. This jack allows, by pushing, the lifting of the shovel 1. When the jack is put in the open air, the shovel 1 penetrates under the effect of its weight into the surface S of the settling tank, the arm 2 coming to bear on an adjustable stop 13.

 The jack 6 is constituted by an enclosure 8, made of corrugated rubber, closed at its ends by steel plates 9 which, tightened against the counter plates 10 by means of bolts, pinch the edge of the rubber enclosure. The enclosure is inflated and deflated by an opening 11 formed in one of the plates 9. The jack is fixed at its two ends by means of yokes and bolts 12, on the one hand to the yoke 7 d on the other hand on arm 2.

 The opening 11 of the jack is connected to a diaphragm distributor 14, with pneumatic control, which comprises a vent pipe 15 and is, moreover, connected by two valves 16 and 17 with mechanical control, to the booster pump 18 supplying the emulsion pump, not shown, intended for the extraction of sludge from the bottom of the settling tank. The distributor 14 and the valves 16 and 17 are carried by the traveling crane. The valves 16 and 17 are controlled by two cams 19 and 20 which are fixed.

When the scraper bridge 5 advances in direction A, the shovel 1 is lowered; the distributor 14 is arranged so that the pressure supplied by the booster 18 is not applied to the jack 6, this jack then being vented through the conduit 15.

 When the valve 16 reaches the cam 19, the pressure coming from the booster is applied to the left diaphragm of the distributor 14 and sent to the jack 6: the shovel 1 rises.

 An electrical system then stops the bridge and restarts it in direction B.

 When the valve 17 reaches the cam 20, the pressure is applied to the right diaphragm of the distributor 14; the jack 6 is vented through the conduit 15 of the distributor 17: the shovel 1 descends. The electrical system stops the bridge and restarts it in direction A.

 FIG. 2 shows an arrangement of the invention in which two pneumatic cylinders 6 and 6 'are used to raise or lower the shovel 1. In this case, when the cylinder 6 is pressurized, the cylinder 6' is vented and vice versa. The movement of the shovel can take place even when the masses are balanced around axis 3.

 The device according to the invention can be used in a semi-circular basin as shown in FIG. 3.

 The scraper bridge 5 is supported at one of its ends by a pivot with a vertical axis, consisting of a fixed part 21 and a movable part 22 whose rolling is ensured by balls 23. This end of the scraper bridge rests on the mobile part 22 by means of a hinge 24; the other end of the bridge rests, via a wheel, driven by a gear motor, on the outer edge of the settling tank. According to the invention, the control of the pneumatic actuator or cylinders allowing the scraper member to be raised is ensured in this case by fixing the cams 19 and 20 on the fixed part 21 of the pivot and by mounting the valves 16 and 17 on the movable part 22 of this pivot. The two mechanical parts 21 and 22 are free to rotate with respect to one another and precisely positioned for any other movement. The pivot being of small diameter, the assembly pivot, cams, distributor and valves for the control of the scraper member, forms a compact apparatus of easy adjustment, easy maintenance and precise operation. The electrical switches for starting, stopping and reversing the drive motor of the bridge drive, as well as their control cams are mounted on the fixed part 21 of the pivot.

It goes without saying that the present invention should not be considered as limited to the embodiment described and shown, but on the contrary covers all variants.

Claims (4)

 1. - Skimming device for a rectangular or semi-circular settling tank provided with means for extracting bottom sludge by emulsion pump supplied with pressurized air, comprising a movable frame (5) driven by a movement of va - and is provided with a surface scraping member (1) which takes up a position for scraping the floats in one direction and a raised position in the other direction and at least one jack (6) to ensure the lifting of the scraper member (1), characterized in that the cylinder  (6) is a low pressure pneumatic cylinder which is controlled by the compressed air supplying the emulsion pump.  2. - Device according to claim 1, characterized in that the supply pressure of the pneumatic cylinders or cylinders t6 or 6 ') is less than 0.4 bar.  3. - Device according to any one of the preceding claims, characterized in that the pneumatic cylinder or cylinders (6 or 6 ') are constituted by deformable capacities made of elastic material.  4. - Device according to any one of the preceding claims, characterized in that the control of the pneumatic cylinders (6 or 6 ') is ensured by means of a system comprising two pneumatic valves (16-17) with mechanical control fixed on the mobile chassis (5) supporting the surface scraping member (1), a pneumatic diaphragm distributor (14) pneumatically controlled by low pressure and two fixed cams (19-20) serving as stops, the assembly of the system alternately allowing the actuator (s) (6 and 6 ') to be placed under low pressure and vented to the atmosphere.