Abstract
In a centrifugal machine, collecting chambers, which are in a rotary bowl allocated to centrifugal separation of at least two phases, include a discharge port that can be opened or closed as desired by pistons, movement of which is controlled from outside by a reduced-friction system. Drawing volume is adjustable and proportional to volume of a transverse aperture in the pistons, the ports and the openings of the collecting chambers being offset. The machine enables pseudo-continuous drawing which makes it possible to maintain a continuous supply. The drawing volume, composition of the drawn product, and compactness thereof, in a case of a near-solid phase, are controlled.
Claims
1. A centrifugal machine comprising: a discharge system; a bowl rotating about an axis, the bowl being delimited by an outer wall enclosing a volume; the discharge system comprising: at least one collecting chamber occupying a portion of a volume of the bowl, at least one port in front of each collecting chamber through a wall of the bowl, a piston displaceable in a cell of the bowl wall between each port and the collecting chamber respectively, and a displacement device to displace the piston, the displacement device being non-rotatable; wherein each piston includes a solid section and a transverse aperture; and wherein the port is positioned offset in relation to the collecting chamber, and the transverse aperture is alternately aligned with the port and with the collecting chamber in radial directions relative to the axis through movement of the piston caused by the displacement device.
2. A centrifugal machine according to claim 1, wherein the displacement device comprises a ring coaxial with the bowl, whereby the piston is supported on the ring, and at least one actuator displaceable along the axis; the ring being connected either to the actuator or to the piston by a link using a bearing or a magnetic repulsion.
3. A centrifugal machine according to claim 2, wherein the piston is biased to the ring by a spring contained within the wall of the bowl.
4. A centrifugal machine according to claim 1, wherein the collecting chamber includes a section tapering towards the port.
5. A centrifugal machine according to claim 1, wherein the collecting chamber is recessed in the bowl wall.
6. A centrifugal machine according to claim 1, wherein the piston belongs to a module that is attached to the bowl and that further comprises a portion of the bowl wall.
Description
(1) The invention will presently be described with reference to the following figures:
(2) FIG. 1 shows the entire machine;
(3) FIG. 2, an alternative embodiment of the ring support device;
(4) FIG. 3, the device for the opening and closing of ports;
(5) FIG. 4, the pistons;
(6) FIG. 5, the discharge and collecting chambers;
(7) And FIG. 6, the discharge state.
(8) FIG. 1 schematically shows a rotating centrifugal machine equipped with the invention, comprising a rotary bowl 1 rotating about a vertical axis 30, and wherein the fluid, paste, slurry or substantially solid heavy phase, is centrifuged and driven downward by conventional means, such as conical plates widening towards the bottom centre of the bowl 1, and helical blades set within the bowl wall, and present among others in the aforementioned patent application. Collecting chambers 2 are arranged at the bottom of the bowl 1, each communicating with the exterior through a discharge port 3. A ring 4 is arranged below the bowl 1 and actuates the pistons 5 by means of rods 11. Each of the pistons 5 (shown in detail below) is associated with a collecting chamber 2 and several said chambers may be present, at equal height, around the bowl 1, although only a single such chamber is represented here. The ring 4 is rotationally driven with the bowl 1; it is secured to the bowl 1. Stationary actuators 17, fixed to the ground via a bearing 8 (a horizontal axis roller), around a system 7 for driving the bowl 1, transmit vertical movement to the ring 4, thereby enabling the movement of pistons 5. Alternatively, as shown in FIG. 2, but perhaps more preferably, the rod of each actuator 17 may be equipped with a permanent magnet 9, and the underside of the ring 4 with a layer of permanent magnets 10, so as to exert contactless and frictionless repulsion. Alternatively, the permanent magnets 9 may be arranged on a second ring not shown here, present below the ring 4 and secured to the actuators 17.
(9) FIG. 3 is a view showing the pistons 5, the ring 4 and the actuators 17 of the device in isolation. The pistons 5 have a body 12 supported by rods 11, secured to the ring 4, and an upper rod 13 surmounting the body 12, on which for example a spring 14 may be fitted, said spring downwardly pushing the piston 5 and thus maintaining its contact with the ring 4. As seen clearly in FIG. 4, the upper rod 13 also carries flat spots 15 to keep it at a set orientation (in case of translation of the piston 5, other embodiments of the piston and its movement being possible). The body 12 is crossed by a transverse aperture 16, while otherwise having a full section. It is also provided with four grooves 23, two on either side of the aperture 16, for receiving seals 22. Other sealing configurations are possible.
(10) Referring to FIG. 5, collecting chambers 2 are formed in the thickness of the wall 18 of the bowl 1. Their shape here is conical and outwardly convergent. They open into cylindrical cells 19 receiving the pistons 5 (only one piston 5 being shown). A rim 20 above the cells 19 is supported on the flat spots 15 and prevents rotation of the pistons 5, while simultaneously compressing the springs 14. Discharge ports 3 extend between the cells 19 and the exterior. The openings 21 of the collecting chamber 2 in the cells 19 are at a level below the discharge ports 3. Preferably, the system comprising the piston 5 and its surrounding, i.e. a portion of the wall 18, is removable and belongs to a module 24 attached to the rest of the bowl 1, optionally assembled thereto by screwing, wherein a seal 25 is arranged on the connection around the collecting chamber 2, so as to ensure sealability. This attached module allows for the replacement of the piston 5, for example if a new composition of the discharged phase, with different hydrodynamic properties so requires it.
(11) This device is provided with two main positions of the pistons 5: In the first of these, as shown in FIG. 5, the apertures 16 extend the openings 21 of the collecting chamber 2 and are thus likewise filled with the centrifuged heavy phase in the bowl 1, while the seals 22 present in the grooves 23 prevent said heavy phase from being introduced around the body 12 of the piston 5; the solid sections of the seals 22 obstruct the discharge ports 3; the pistons 5 are then supported on the lower rims 6 of the cells 19, and their support on the ring 4 (by means of the rods 11) is temporarily interrupted; In the other main position, as shown in FIG. 6, the ring 4 and the piston 5 are raised by the extension of the actuators 17 and the apertures 16 become extensions of the discharge ports 3: centrifugal forces expel their contents towards the exterior, where it is collected; the collecting chambers 2 are however blocked by the solid sections of the body 12. The reverse movements of the piston 5 thus alternately provide for the filling and discharge of the apertures 16, with precise dosage, equal to the volume of the apertures 16, of the amount of material removed; discharge is made possible by the powerful action of the centrifugal field that expels the solid. The apertures 16 thus form discharge chambers determining the discharge volume of material for every order.
(12) The ring 4 may be rotatably immobile, whereby the bearings 8 or the permanent magnets 9 are carried by the pistons 5 or, yet again, are arranged on a second ring parallel to the ring 4. Said bearings or permanent magnets may control the opening and closing of the ports 3 by displacing an intermediate part. They may also be rotationally displaced, rather than by translation. Despite its drawbacks, hydraulic rather than mechanical actuation would be possible. The aperture 16 may be formed by an end or by a lateral notch of the piston 5 or of the intermediate part, rather than forming a central bore. The invention may be applied to any rotating machine performing centrifugation: a cylindrical bowl having, horizontally screwed, etc., for dehydrating solids and/or clarifying fluids.
