US3630431A

US3630431A - Valve-discharge disc centrifuge

Info

Publication number: US3630431A
Application number: US18228A
Authority: US
Inventors: Yoshinori Oka; Ryuichi Takahashi
Original assignee: Mitsubishi Kakoki Kaisha Ltd
Current assignee: Mitsubishi Kakoki Kaisha Ltd
Priority date: 1969-06-18
Filing date: 1970-03-10
Publication date: 1971-12-28
Anticipated expiration: 1988-12-28
Also published as: DE2024726A1; GB1295526A

Abstract

The solids discharge openings in the radially outermost wall of a disc centrifuge bowl can be opened and closed by means of a valve ring axially moved by hydraulic pressure in annular chambers separated in a circumferential groove of said outermost wall by a collar on the valve ring. The chambers are about as far from the axis of rotation as the farthest portion of the bowl cavity, and the necessary valve operating force is therefore generated by centrifugal forces in very small chambers. Either one or both chambers are supplied with water to open and close the discharge openings, the radial widths of the chambers being different.

Description

United States Patent 2,862,659 12/1958 Nyrop VALVE-DISCHARGE DISC CENTRII'UGE 7 Claims, 1 Drawing Fig.

0.8. CI 233/20 A, 233/47 B041! 11/00 233/19 R,

19A, 16,20 R, 20 A, 1 D,47, 28

References Cited UNITED STATES PATENTS Primary Examiner- Patrick D. Lawson Assistant Examiner-George H. Krizmanich Attorney-Kelman and Berman ABSTRACT: The solids discharge openings in the radially outermost wall of a disc cenu'ifuge bowl can be opened and closed by means of a valve ring axially moved by hydraulic pressure in annular chambers separated in a circumferential groove of said outermost wall by a collar on the valve ring. The chambers are about as far from the axis of rotation as the farthest portion of the bowl cavity, and the necessary valve operating force is therefore generated by centrifugal forces in very small chambers. Either one or both chambers are supplied with water to open and close the discharge openings, the radial widths of the chambers being difi'erent.

Patented Dec. 28, 1971 INVENTOR.

BY. Maw aka/3 mm F) GENT VALVE-DISCHARGE DISC CENTRIFUGE This invention relates to valve-discharge disc centrifuges, and particularly to a hydraulic valve operating mechanism for such centrifuges.

The general type of centrifuge with the improvement of which this invention is concerned is well known, and a representative example is illustrated and described in Perry s Chemical Engineers Handbook (4th Edition, McGraw-l-lill Book Co., lnc., 1963, page -90 FlG. 19-141). The bowl of the centrifuge is rotated about an upright axis and has discharge openings for solids which communicate with the portion of the bowl cavity which is farthest from the axis of rotation. An annular valve member is axially moved by hydraulic pressure toward and away from a closing position in which the valve member blocks the discharge openings. The valve member may be mounted either on the inner face or on the outer face of the circumferential bowl wall.

The valve member forms a movable wall of two chambers which may be supplied with hydraulic fluid, normally water, and is moved by hydraulic pressure generated by centrifugal forces when the centrifuge bowl is rotated. The chambers in the known devices are located quite close to the axis of rotation and must therefore be made relatively large for generating a force adequate for moving the heavy valve member. Since the chambers have to be machined, at least in part, from the bowl wall, they substantially contribute to the cost of building the machine. They hold a relatively large amount of liquid, and the time required for filling and emptying them during opening and closing of the discharge openings is correspondingly long. The required amount of water in some instances is great enough so that the cost of the water constitutes a significant portion of the centrifuge operating expenses.

The primary object of the invention is the provision of a valve-discharge centrifuge free from the shortcomings of the known machines as set forth in the preceding paragraph.

With this object and others in view, as will hereinafter become apparent, the invention provides means on respective axial faces of the circumferential bowl wall and of the valve member which define two axially spaced chambers. One of the faces is formed with an annular groove about the axis of rotation. The groove is open in a radial direction and of a radial depth smaller than the axial width thereof. A collar on the other face occupies an axial intermediate portion of the groove and axially separates the two chambers, whereby the chambers axially expand and shrink during axial movement of the valve member. A liquid supply system alternatively keeps one or both of the chambers filled with liquid during rotation of the bowl.

Because the chambers are located not substantially nearer the axis of the rotation than the portion of the bowl cavity farthest from the axis which communicates with the solids discharge aperture in the circumferential bowl wall, the chambers can be made quite small. For the reasons outlined above, this fact results in a substantial reduction in the cost of building the centrifuge and in a saving in water or other liquid. Moreover, the solids discharge aperture can be closed and opened more quickly than in known comparable centrifuges having a hydraulic system of similar capacity.

Because of the high opening-and closing speed of the valve member, it is practical in the centrifuge of the invention to discharge only a portion of the accumulated solids, thereby making it unnecessary to interrupt the feeding of raw material to the centrifuge bowl during the solids discharge. The centrifuge is thus capable of truly continuous operation.

Other features, additional objects and many of the attendant advantages of this invention will readily become apparent from the following detailed description of a preferred embodiment when considered in connection with the appended drawing whose sole FIGURE shows a valve-discharge disc centrifuge of the invention in elevational section on its axis of rotation.

The upright drive shaft 13 of the machine coaxially carries a heavy-walled bowl 14. The bowl cavity 1 is upwardly bounded by a conical cover 14 attached to the bowl 14 by a threaded ring 34 which engages the approximately cylindrical outer wall of the bowl 14. Much of the cavity is occupied by a stack of conical sheet metal discs, only represented by its

retaining plates

2,3 for the sake of clarity, and conventional in itself. The material to be separated is fed to the cavity 1 from above through a coaxial tube 4 and substantially clear liquid is normally discharged through an opening in the topmost portion of the cover 14' in one or more fractions of different specific gravity.

The circumferential wall of the cavity 1 slopes obliquely from above and below in a radially outward direction to a row of slots 23 in the circumferential wall of the bowl l4 closely adjacent the lower rim of the ring 34. In the illustrated condition of the separator, the slots 23 are closed by a reduced upper edge portion 33 of an approximately cylindrical valve ring 15 engaging a valve seat 35 on the threaded ring 34. The inner surface of the ring 15 conformingly engages the outer, substantially cylindrical surface of the bowl [4 over more than percent of the axial height of the ring.

The outer face of the bowl 14 has a shallow annular groove 16 whose radial depth is but a small fraction of its axial height. An annular collar or shoulder 17 projects integrally from the valve ring 15 into the groove 16, occupies much of the groove, downwardly bounds an annular chamber 16' in the groove, and upwardly bounds a chamber 16', the radial face of the shoulder 17 in the chamber 16' being almost twice as wide as the corresponding face in the chamber 16". The chamber 16" is ofiset in its entirety from the radially outermost portion of the separator cavity in a radially outward direction, and only a very small portion of the chamber 16' is radially coextensive with the cavity, and both chambers are radially offset from the stack of discs between the

plates

2,3.

A downwardly open recess 20 in the bowl bottom about the shaft 13 is of stepped cylindrical shape. A small uppermost portion 22 of the recess is of reduced diameter- The lower end of the recess 20 is occupied by a hollow annular distributor 25, and an axially narrow portion 21 of the recess 20 contiguously above the distributor 25 is of greater diameter than the recess portion 22. A narrow conduit-18 having an orifice in a cylindrical wall of the recess portion 22 leads to the chamber 16', and a similar conduit 19 leads from an orifice in the cylindrical wall of the recess portion 21 to the chamber 16". A very narrow radial bore 24 in the valve ring 15 bleeds the chamber 16 to the ambient atmosphere in the illustrated valve position.

The distributor 25 is fixedly mounted on the drive shaft 13, and its bottom wall has an annular gap 25' near the shaft. lts top wall has an axial passage 29 whose upper orifice is axially aligned with the reduced recess portion 22 and another passage 30 leading into the recess portion 21 near the orifice of the duct 19.

A manifold ring 32 fixedly mounted on the nonillustrated supporting structure of the separator envelops the shaft 13. Nozzles 31 are mounted on the ring 32, extend into the interior of the distributor 25 through the annular gap 25' in the bottom wall of the distributor, and have respective orifices which are directed in'a radially outward direction against the inner, circumferential wall of the distributor. The nozzles 31 are connected to a water supply system by the ring 32 and a feed line 26 connected to the ring and provided with valves partly indicated by conventional symbols the source of water being indicated by an arrow 26. A pressure responsive valve 28 in the line 26 is provided with a bypass 27 and a manually operated valve 27 in the bypass.

The illustrated apparatus is operated as follows:

Prior to starting operation, the nonillustrated motor driving the shaft 13 is energized. When the bowl 14 reaches its operating speed, the nonillustrated main valve in the water feed line 26 is opened. The pressure-responsive valve 28, which is a conventional, adjustable, pressure-relief valve, permits the water to flow into the nozzles 31 and to be discharged into the distributor 25. The valve ring 15 is in the nonillustrated lower position in which the solids-discharging slots 23 are open, and the capacity of the chamber 16" is at a minimum maintained by cooperating, nonillustrated abutments on the collar 17 and the bowl 14.

The water discharged into the distributor 25 flows through the passage 30 into the recess portion 21, the conduit 19, and the chamber 16", and then is backed up in the distributor 25 to form a ring held by centrifugal forces against the outer axial wall of the distributor. Because of the great distance of the chamber 16" from the axis of rotation, the hydraulic pressure centrifugally generated in the chamber 16" is sufficient to lift the valve ring into the illustrated position in which it blocks the slots 23 although the chamber 16" is quite small in a radial direction.

When the inner surface of the water ring in the distributor 25 reaches the orifices of the nozzles 31 which are located approximately in a common cylindrical surface indicated in the drawing by a chain dotted line x-x, the pressure in the line 26 rises until the pressure differential across the valve 28 is insufficient to keep the valve open. No further water flows into the distributor 25 unless water is lost by leakage in an amount sufficient to draw the water away from the nozzle orifices. The centrifuge is then used in the usual manner to separate solids from liquid, and a cake of relatively dry solids builds up in the cavity 1 behind the slots 23.

When it is desired to discharge the accumulated solids, the bypass valve 27' is opened, and the thickness of the water ring in the distributor 25 is increased. When the inner wall of the cylinder reaches a position indicated by the chain-dotted line yy in the drawing, water can flow upwardly into the topmost portion 22 of the recess and reach the chamber 16 through the conduit 18. The flow section of the bleeder bore 24 is too small to decrease the centrifugally generated hydraulic pressure in the chamber 16' to a value significantly smaller than the pressure in the chamber 16 Since the annular piston face of the shoulder 17 in the chamber 16 is much greater than the corresponding face in the chamber the chamber 16' is expanded and water is discharged from the shrinking chamber 16" through the conduit 19. The valve ring 15 is lowered to open the slots 23 for discharge of solids.

When the valve 27' is closed, water bled from the bore 24 returns the inner liquid wall in the distributor 25 from the line y-y to the line xx. The loss of pressure in the chamber 16' causes the valve ring 15 to be returned to the illustrated closing position.

The amounts of water that need to be supplied or released for moving the valve ring between the opening and closing positions is very small because the chambers l6,l6" are as far from the axis of rotation as is possible, and because the distributor assembly including the nozzles 31 is located as closely to the axis of rotation as the shaft 13 permits. The annular cylindrical space defined between the lines xx and yy which basically determines the amount of water consumed in each cycle of operations is small because of its small overall diameter.

The valve 27 may be operated manually, by a timer,'by remote control, or automatically in response toaccumulation of a predetermined weight or volume of solids behind the slots 23 in the cavity 1 as is known in itself. The setting of the pres sure responsive valve 28 remains unchanged for a fixed rotary speed of the bowl, and may be adjusted to different bowl speeds or other changes in operating conditions to suit requirements.

While the illustrated embodiment of the invention is preferred at this time, numerous modifications may be made without departing from the spirit of this invention. The positions of the groove 16 and the shoulder 17 may be interchanged, for example, the groove being formed in the valve ring 15 and the shoulder 17 projecting from the circumferential wall of the bowl 14 into the groove to separate the chambers l6,l6".

Other changes and variations will readily suggest themselves to those skilled in the art on the basis of the instant teachings. It should be understood, therefore, that the foregoing disclosure relates only to a preferred embodiment of the invention,

and that it is intended to cover all changes and modifications of the example of the invention herein chosen for the purpose of the disclosure which do not constitute departures from the spirit and scope of the invention set forth in the appended claims.

What is claimed is:

1. In a centrifuge having a bowl defining a cavity therein; drive means for rotating said bowl about an axis, the bowl having a bottom wall transverse to said axis and a circumferential wall formed with a discharge aperture for solids communicating with a portion of said cavity farthest from said axis, a valve member of annular shape about said axis, said valve member and said circumferential wall having respective first and second axial faces sealingly engaging each other, hydraulic valve operating means for moving said valve member axially toward and away from an operating position in which said valve member blocks said discharge aperture, and means for discharging liquid from said bowl separately from said solids, the improvement in the valve operating means which comprises:

a. an annular collar. on said first axial face,

1. said second axial face being formed with an annular groove extending about said axis, said groove being open in a radial direction and being of a radial depth smaller than the axial width thereof,

2. said collar being received in said groove in sealing engagement with said second axial face and axially sealing two chambers in said groove from each other, said chambers axially expanding and shrinking during said I axial movement of the valve member,

3. said chambers being substantially as far from said axis as said portion of the cavity; and

b. liquid supply means for alternatively supplying one of said chambers or both chambers with liquid during rotation of said bowl,

1. said liquid supply means including means on said bottom wall defining a recess closely adjacent said axis,

2. two conduits connecting said recess to said chambers respectively and having respective orifices in said recess, one of said orifices being nearer said axis than the other orifice,

3. a source of liquid, and

4. valve means interposed between said source and said recess for keeping said recess sufficiently filled with said liquid during rotation of said bowl alternatively to reach one or both of said orifices.

2. In a centrifuge as set forth in claim I, the radial width of one of said chambers being greater than the radial width of the other chamber.

3. In a centrifuge as set forth in claim 1, said liquid supply means further including a hollow distributor member occupying a portion of said recess axially offset from said orifices and closely adjacent said axis, the portion of said distributor member nearest said axis being formed with a gap extending about said axis, a stationary nozzle extending through said gap into said distributor and having an orifice therein, said valve means communicating with said nozzle, said distributor member being formed with two passages connecting the hollow interior thereof with the portion of said recess communicating with the orifices of said conduit.

4. In a centrifuge as set forth in claim 3, one of said passages being nearer said axis than the other, said passages being adjacent respective orifices of said conduits.

5. In a centrifuge as set forth in claim 4, said valve means including a pressure responsive valve, said valve opening in response to a predetermined minimum pressure differential across the same, a bypass about said valve, and a shutoff valve in said bypass.

6. in a centrifuge as set forth in claim 1, said valve member being mounted on said circumferential wall outside said cavity.

7. In a centrifuge as set forth in claim 1, said second axial face being an outer face of said bowl, and said first face being an inner face of said annular valve member, said valve member being formed with a bleeder bore permanently open to the atmosphere and communicating with one of said chambers in the operating position of said valve member, said one chamber being connected by the associated one of said con- 5 duits to said one orifice.

Claims

1. In a centrifuge having a bowl defining a cavity therein; drive means for rotating said bowl about an axis, the bowl having a bottom wall transverse to said axis and a circumferential wall formed with a discharge aperture for solids communicating with a portion of said cavity farthest from said axis, a valve member of annular shape about said axis, said valve member and said circumferential wall having respective first and second axial faces sealingly engaging each other, hydraulic valve operating means for moving said valve member axially toward and away from an operating position in which said valve member blocks said discharge aperture, and means for discharging liquid from said bowl separately from said solids, the improvement in the valve operating means which comprises: a. an annular collar on said first axial face, 1. said second axial face being formed with an annular groove extending about said axis, said groove being open in a radial direction and being of a radial depth smaller than the axial width thereof, 2. said collar being received in said groove in sealing engagement with said second axial face and axially sealing two chambers in said groove from each other, said chambers axially expanding and shrinking during said axial movement of the valve member, 3. said chambers being substantially as far from said axis as said portion of the cavity; and b. liquid supply means for alternatively supplying one oF said chambers or both chambers with liquid during rotation of said bowl, 1. said liquid supply means including means on said bottom wall defining a recess closely adjacent said axis, 2. two conduits connecting said recess to said chambers respectively and having respective orifices in said recess, one of said orifices being nearer said axis than the other orifice, 3. a source of liquid, and 4. valve means interposed between said source and said recess for keeping said recess sufficiently filled with said liquid during rotation of said bowl alternatively to reach one or both of said orifices.

2. said collar being received in said groove in sealing engagement with said second axial face and axially sealing two chambers in said groove from each other, said chambers axially expanding and shrinking during said axial movement of the valve member,

2. In a centrifuge as set forth in claim 1, the radial width of one of said chambers being greater than the radial width of the other chamber.

3. a source of liquid, and

3. said chambers being substantially as far from said axis as said portion of the cavity; and b. liquid supply means for alternatively supplying one oF said chambers or both chambers with liquid during rotation of said bowl,

7. In a centrifuge as set forth in claim 1, said second axial face being an outer face of said bowl, and said first face being an inner face of said annular valve member, said valve member being formed with a bleeder bore permanently open to the atmosphere and communicating with one of said chambers in the operating position of said valve member, said one chamber being connected by the associated one of said conduits to said one orifice.