US2145541A - Inlet and outlet for closed centrifugal separators - Google Patents

Description

Jan. 3l, 1939. E. A. FoRsBERG 2,145,541

INLET AND OUTLET FOR CLOSED CENTRIFUGAL SEPARATORS 2 Sheets-Sheet 2 Filed- Jan. 26, 1935 wm/5.5.5'.- A Y @lL/@QM Yas Patented Jan. 3l, 1939 UNITED STATES PATENT OFFICE INLET AND OUTLET FOR CLOSED CENTRIF- UGAIi SEPARATORS Application January 26, 1935, Serlal'No. 3,558 In Sweden February 17, 1934 15 Claims.

tionary supply pipe. f

It is, however, difcult to provide tighteningv or sealing means that are reliable for this use, owing to the vibrations which cannot be wholly avoided and because of the usually high rotation speed. vThese diiculties are particularly great ifI the machine works at a comparatively high capacity. If a spindle of small diameter is used, a great pressure must be applied,` which'has an unfavorable influence on the durability of the tightening means; while if the diameter of the spindle is increased, the rperipherical speed also increases, causing the same'difliculty.

The present invention relates to a liquid sup ply device by means of which the above objections are overcome and which allows the supply of a great quantity of liquid without exposing the packings either to a dangerous pressure or to a perilous speed.

The invention is capable of being embodied in diierent specic constructions, several of which are shown in the drawings, inwhich- Fig. 1 is a vertical sectional view of the lower (infeed) end lof a' cylindrical bowl spindle, the xed supply pipe and associated parts, constituting one embodiment of my invention.

Fig. 2 is a vertical sectional view of a modication.

Fig. 3 is a vertical sectional view of another modication. o Fig. 4 is a vertical sectional view of still another modication, which comprises also a vertical sectional view of the upper (outfeed) end of a separator bowl, the xed discharge pipe and associated parts, andl a pipe connection between 45 the associated parts at the outlet and thoseat the inlet.

Fig. 5 is an elevation of a part of the wing wheel of Fig. 4.

Referring rst to the construction shown in Fig. 1: The bowl spindle I is hollow and is contracted toward its lower inlet end or neck 2. The

' end 2 is surrounded by a stationary chamber 3, making a tight joint with the end by means of a packing 4, which may be of dierent types but preferably consists of an elastic collar packing of the type commonly used at both the inlet and outlets of closedV centrifugals. The liquid is supplied through the stationary nozzle 5 which extends through the chamber 3 and into and through the interior of the end 2 and, in the 5 /specic construction shown, into the expanded section of the hollow spindle beyond (above in the construction shown) the end 2.`

By putting the liquid under suiiicient pressure a considerable quantity of liquid can be supplied per time unit through a nozzle of quite small dimensions, and as the dimensions of the end-piece 2 of course depend on those of the nozzle they can be kept lwithin suitable limits. The comparatively high pressure which may be required for the supply of the liquid is in usual manner changed into speed when theA nozzle is passed, which is again changed into pressure when the liquid flows out into thev wider portion of the spindle beyond the nozzle. The'change, however, is not so complete as to reach the original pressure, but reaches only the pressurewhich is necessary to circulate the liquid through the bowl. The difference corresponds vto a loss of eiect which is changed into heat. In practice this loss is generally not so great as to be of decisive importance, and on the other hand the advantage is attained that the pressure in chamber 3 is only as great as is necessary to force the liquid through the bowl, and consequently the packing 4 need not stand up to a very great load.

,In the embodiment shown in Fig. 1 the inner diameter of the nozzle 5 must be substantially smaller than that of the end-piece 2 owing to the necessary play and thickness of the material. 'As the force required to circulate the liquid varies inversely with the 4th and 5th 'potential of the nozzle (that is, for the rate of flow and the friction) it'isl evident that even a `comparatively small reduction of the diameter causes aconsiderable increase of the necessary pressure. n This is usually undesirable and while usually not a matter of great importance may in some cases be a serious objection.,

This objection is avoided. in the embodiment according to Fig. 2', in which the nozzle 50 does not extend past the 'end 2 but terminates a short way before (below in the ligure) the end. The interior diameter of the-nozzle 50 may be they same as, or somewhat smaller than, the interior 50 diameter of the end 2; or, in view of `the contracted form of the nozzle, may be even ya' Alittle'f'; -,greater than the inner diameter ofthe end 2.-' The liquid leaves the nozzle 50 in a free jet and, is thrown into the end 2.l The pressure in cham- 1g the bowl.

ber 3 may in this case be even lower than that required for passing the liquid through the bowl, the load on the packing l thereby being further reduced.

If the nozzle 5 has such dimensions that the whole pressure energy of the liquid is changed into velocity energy, it is possible tobring about a pressure in the clearance between the rotating shaft and the nozzle which is lower than the atmospheric pressure. This fact is particularly of importance in case it is desired to treatliquids for which it is diillcult to nd durable soft packings. This is the case with centrifuges which are used for the purification of transformer oil, the refining of lubricating oil and the like. In the treatment of materials of this kind it is not entirely satisfactory to use collar-shaped packings of rubber, which have proved to be suitable for the treatment of milk. With an energy converter of the type above described it is possible to allow a certain play between the pacln'ng and the spindle, as there is no danger of liquid leaking out through the packing owng to the partial vacuum. in the chamber'3, although air may of course leak in. If this is undesirable it is practicable to arrange a liquid container 'I'above or around the chamber 3, from which container liquid is sucked in through the play between the packing and the spindle into the chamber 3, the liquid preferably being the same as the liquid which is or was treated in the separator. In order to be sure in all circumstances that liquid is contained in the container arranged over or around the chamber 3, it is desirable to connect the chamber 'I with a chamber 8, containing a regulable supply of such liquid, the regulation being effected, for example, by means of a float III carried by a lever II which carries a valve I2 Acontrolling iniiow of liquid into the supply chamber 8 from a supply pipe 9. Wings `III maybe provided in the chamber I to preventwhirling of the liquid therein. According to the last described construction, as much liquid must be admitted into the chamber 3 as is sucked through the clearance between the supply pipe 5 or 5I!` and the rotating portion 2 of the spindle, which necessitates more or less complicated regulating devices, for instance, the float shown in Fig. 3. The supply of liquid'into chamber 3 may however be dispensed with, if the arrangement is modified as. disclosed F154.

The dimensions of the tube and the portion 2 of the spindle are so chosen in relation to the conditions of pressure within the centrifuge and the throughput of liquid as to generate an overpressure in the chamber 30 (corresponding to chamber 3 of Figs. l, 2` and 3) even if it be only slightly higher than the atmospheric pressure. A packing collar, such as I, closing the chamber 30 from the outer atmosphere is not provided. Instead, a ,wing-wheel I3 is fixed to the part 2. The wing-wheel almost fills the upper orifice of the chamber 30. Any liquid penetrating upwards past the wing-wheel is deflected by a screen I5 and is forced to low down on the wing-wheeL'by which it is brought into tl'ie chamber 3l. The wing-wheell is provided with a number of wings Il which catch the liquid and force it downwards and outwards. 'I'he wing-wheel thus acts as a sort of shield which prevents the liquid from flowing upwards from the chamber 3l.

The upper part of Fig. 4 shows a similar tightening device for an outlet positioned above 'I'he upper rim of the rotating verrounding the rotating tube, the said pocket com-- municating with the clearance between the ro-V tating vertical tube I6 and the fixed outlet pipe III bya slot I9 between the outer edge of the disc and the surrounding stationary housing. Over the disc there are provided i'n theiixed housing a number of wings 2| which prevent the liquid contained therein from rotating. In the pocket under the dise no stationary wings are provided, and therefore the liquid penetrating to this space is brought by the wings I8 into the rotation of the disc I1. With over-pressure in the outlet pipe the consequence is that'the liquid flows from the outside inwards in the pocket 2l to agiven level, the -position of which depends on the pressure in the outletpipe. It will be understood that quite important variations of the pressure in the outlet pipe can be counteracted by means of this arrangement.

Fig. 4 shows also a conduit 23 by which the pocket 2li under the rotating disc I1 communicates with the chamber 3l and/or the clearance between nozzle 50 and the lower end 2 of the hollow spindle. As much liquid is supplied through this conduit 23 as is required to compensate for the liquid which may be sucked in through the clearance between the end 2 of the 'spindle and the fixed tube 5D, in case there is atmospheric pressure in the chamber 3l. In the pocket 20 positioned under the rotating disc I 'I there is a pressure which-is much lower than the pressure in the xed discharge pipe I0, which extends from the clearance between the said pipe and the rotating tube I6 of the bowl. As will be seen vfrom the gure the fixed outlet pipe line 4l at its inlet has the shape of a diiusor having a great angle. 'I'he use of such a great angle is made possible by the fact that the column of liquid flowing upwards also rotates.

It will 4thus be seenthat considerable overpressure may be maintained at the inlet of the bowl without involving a pressure at the tightening device higher than atmospheric It thus becomes possible to use metal packings. by which a completely tight joint with the bowl spindle is not obtained, without entailing the disadvantage of heavy losses of liquid by leakage through the packings.

What I claim and desire to protect by Letters Patentis:

1. A centrifugal separator comprising a feed channel concentric and rotatable with a centrifugal bowl, said feed channel vhaving an inflow end of reduced diameter and being expanded beyond said end, a stationary feed pipe having a nozzle communicating with said inflow end between which and the nozzle is a small clearance, a stationary chamber adjacent the inow end of the feed channel, 'apacking between said chamber and the feed channel, a container from which liquid is sucked into said chamber between said packing and said feed channel, and means in said container to maintain a constant level of Vliquid therein.

2. A centrifugal separator comprising a feed -channel concentric and rotatable with a cenn-irugai bowl, said reed channel having n inm'w end of reduced diameter and being expanded beyond said end, a stationary feed pipe having a nozzle co with said' inflow end. there beingaclearancebetweensaidnnllle'andaidn inflow end, a stationary chamber adjacent said inflow end and communicating therewith through said clearance, an outflow channel concentric with and communicating with the/separator bowl, a, stationary discharge pipe into which said outlet channel discharges and between which and said outlet channel is a clearance, a stationary pocket adjacent and communicating with said clearance, and a `pipe connection between said pocket and chamber through which liquid is adapted to flow from said pocket into said chamber to compensate for liquid that may be sucked from the chamber through said clearance.

3. A centrifugal separator comprising a feed channel concentric and rotatable with a, centrifugal bowl, said feed channel having an inflow end of reduced diameter and being expanded beyond said end, a stationary feed pipe having a nozzle communicating with said inflow end, there beingV a clearance between said nozzle and said inflow end, a stationary chamber adjacent said inflow end and communicating therewith through said clearance, said, chamber having an opening communicating with the space outside it, an outflow channel concentric with and communicating with the separator bowl, aA stationary discharge pipe into which said outlet channel discharges and between which and said outlet channelfis a clearance, a stationary pocket adjacent and Icommunicating with said clearance, wings in said -eters of both being such, with reference to the pocket connecting with and rotating with said outlet channel, a pipe connection between said pocket and chamber through which liquid is adapted to flow from said pocket into said chamber to compensate for liquid that may be sucked from said chamber through said clearance, and an element in said chamber connected-and rotating with said feed channel and adapted to force liquid in said chamber away from said opening.

4. A centrifugal separator comprising a feed channel concentric and rotatable with a centrifugal bowl, said feed channel having an inflow end of reduced internal diameter and beyond said end being expanded in a taper having an included angle less than 60, a stationary feed pipe having a nozzle adapted to discharge liquid into said yfeed channel, said nozzle adjacent its outlet having an internal wall whose contour in the direction of flow is convex so as to have an internal taper with an angle gradually reducing in said direction and closely approaching parallelism with its center line at its discharge mouth and whose outlet end has a small clearance from the inlet edge of said inflow end, and a stationary chamber adjacent the inlet end of the feed channel and communicating through said clearance with the feed channel and nozzle, the diameter of the discharge extremity of the nozzle approximating that of the inflow end of the feed channel and the diamflow of liquid therethrough, that a pressure is maintained in said chamber below4 that of the atmosphere surrounding the separator.

5. A centrifugal separator in accordance with claim 4 and including also means to supply liquid to the stationary chamber to compensate for any liquid sucked therefrom into the stream of liquid being supplied to the separator.bowl.

- 6. A feeding device for a closed centrifugal machine, comprising in combination a stationary feed tube adapted to receive liquid under pressure, a nozzle at the exit end of said tube tapered `to approximately the delivery end of the nozzle adapted to convert pressure energy into vegradually increasing internal diameter adapted to convert velocity energy to pressure energy, and a closed chamber surrounding the junction of the tube with the spindle.

v'7. A feeding device for av closed centrifugal machine comprising in combination a stationary feed tube, a revolving hollow spindle in alignmerit with said tube and a closed chamber surrounding the juncture of said tube and spindle, the bore of the feed tube being gradually contracted in the direction of flow to approximately its delivery end and the bore of the spindle having an entrance endof a size so approximately that `of the outlet of the tube as to be adapted to smoothly receive and to be filled by a jet of liquid therefrom and being b eyond its entrance endgradually expanded in the direction of flow, whereby pressure energy is iirst converted into velocity energy and then velocity energy into pressure so' that the pressure at the junction is less than that at either the inlet or the outlet of the feeding device.

8. A cenrifugal separator comprising a stationary chamber, a bowl spindle concentric and rotatable with a centrifugal bowl and leading from said chamber to the bowl, said bowl spindle having anv inflow end portion of reduced but uniform internal diameter extending into said champortion of gradually increasing internal diameter affording a velocity energy to pressure energy converting expansion, and a stationary feed nozzle whose outlet end is of approximately the same size as the reduced inflow end of the spindle adapted to 4deliver liquid into the bowl spindle and between which and the reduced inflow end portion of the spindle is a small clearance.

9. A feeding device for a closed centrifugal machine, comprising a stationary chamber, a stationary feed nozzle entering the chamber, adapted to receive liquid under pressure and discharge it in a smooth stream, a bowl spindle leading from said chamber to a bowl, said bowl spindle having an inflow end portion of reduced but uniform internal diameter extending into said chamber and beyond said inflow end portion having a portion of gradually increasing internal diameter affordingV a velocity energy to pressure energy converting expansion, the outlet end of thefeed nozzle and the inlet end of the bowl spindle being of approximately the same size and having a small clearance between them and being in such relative positions that the stream of liquid from the nozzle will pass into the spindle.

10. A centrifugal separator comprising a feed y channel concentric and rotatable with a separator the atmosphere positioned around said feed chan- Ved to discharge liquid nel and commimicating therewith through said clearance, and an element in said chamber rotating with said feed channel and adapted to force liquid in said chamber away from said opening.

1l. A centrifugal separator comprising a feed channel concentric and rotatable with a separator bowl, said feed channel having an iniiow end of reduced internal diameter and being gradually expanded beyond said end, a stationary feed pipe having a nozzle with a wide angle internal A taper toward its entrance progressively changing to a narrow angle taper approaching a cylindrical form at its discharge end and adaptinto and completely fill said feed channel, there being a small clearance between said nozzle and the inflow end of the feed channel, a stationary chamber having an opening to the atmosphere positioned around said feed channel and communicating therewith through said clearance, an element in said chamber rotating with said feed channel and adapted to force liquid insaid chamber away from said opening, and a screen between said rotating element and said opening adapted to deflect any liquid which penetrates beyond said rotating element.

12. A centrifugal separator including `a. stationary chamber, a feed channel concentric and rotatable with a centrifugal bowl and leading fromrsaid chamber to the bowl, said feed channel having a comparatively short inflow end portion of reduced internal diameter and having, beyond its inflow end portion, a velocity energy to pressure energy converting expansion with an included angle less than.60, and a stationary feed pipe having a nozzle terminating within said chamber adjacent to and in line with the inflow end of said feed channel and whose terminus isfapproximately the same size as the inflowend of the feed channel, said feed pipe having a small internal diameter terminus and a pressure to velocity energy converting taper extending to said terminus.

13. A centrifugal separator including a feed channel concentric and rotatable with a centrifugal bowl and having its outlet communieating therewith, a stationary feed pipe having a diameter at its outlet approximating that of the entrance to the feedv channel and terminating adjacent to and axially in line with the inflow end of said feed channel anda closed chamber surrounding the ends of said channel and pipe, said feed pipe having a pressure energy to velocity energy converting section gradually reducing in diameter toward its terminus so as to approach parallelism with its center line adjacent said terminus and said feed channel having, beyond, but spaced from, its inflow end, a velocity energy to pressure energy converting internal lenlargement with an included angle less than 60 whereby the pressure in said chamber is substantially less than that at the entrance to said pipe or the outlet from said channel.

14. A centrifugal separator including a feed channel concentric and rotatable with a centrifugal bowl, a stationary feed pipe adapted to feed liquid into said channel, a stationary closed chamber surrounding the joint between said, channel and pipe, a packing between the wall of said chamber and said channel, said feed pipe having a gradual reduction in size toward its exit so as to approach parallelism with its center line adjacent said exit and at said exit of a size approximating that of the inlet end of the feed channel and adapted to 4convert pressure energy to velocity energy and said channel having, beyond, but spaced from, its inflow end a gradually expanding portion with an included angle less than 60 adapted to convert velocity energy toA pressure energy whereby the pressure in said chamber is substantially less than that required to force the desired quantity through the feed channel.

l5. A centrifugal separator comprising a reed channel concentric and rotatable with a centrifugal bowl and having an inflow end of reduced internal diameter and expanded beyond in a taper having an included angle less than 60, a stationary feed pipe having a nozzle adapted to discharge liquid into said feed channel and the inner wall of the delivery end portion of which is tapered successively concavely and convexly toward its outlet end so as to approach parallelism with its center line at about its extremity, the outlet edge of the nozzle having a small clearance, measured in the direction of flow, from the inlet yedge of the feed channel, the internal diameters Aof the discharge extremities of the nozzle and of the inflow extremity of the feed channel being approximately the same.

ERIK AUGUST FORSBERG.

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