Tubular centrifuge

BACKGROUND OF THE INVENTION ²⁵

Centrifuging devices have long been known in the prior art for separating ingredients or components in liquids which have different densities. Generally speaking, apparatus for separating materials of closely similar ₃θ densities comprise relatively massive machinery, often driven at very high rotational speeds. The equipment usually is designed with rotating centrifuging parts having relatively short radius. In order to accomplish the centrifugal separation of components which differ only ₃₅slightly in their specific gravities, where the machinery must be driven at extremely high rotational speeds, the mechanical parts must be carefully balanced and the whole apparatus made of rugged construction. The types of equipment just mentioned is adapted for heavy duty 40 service and for separation of relatively large amounts of material.

For separating relatively small quantities of materials, e.g. in liquids such as blood and other body fluids, or for separation of colloidal or chemical materials and the like in laboratory work, for example, there is a real need 45 for a small, simple and relatively inexpensive centrifuging apparatus. This is particularly true where the proportions of the slightly heavier (or lighter) materials to be separated from a liquid are relatively very small compared to the total volume of the liquid to be treated. 50 Where particles, globules or other components of such liquid are perceptibly higher in density, though much less in quantitative proportions than the main body of liquid, a simple inexpensive centrifuge is highly desirable.

SUMMARY OF THE INVENTION

According to the present invention, a looped length of tubing, preferably of substantial loop radius, which may or may not be part of a continuous liquid flow line, is θθ mounted appropriately and provided with suitable driving means so that it can be swung or rotated through a circular path at a suitable velocity. The radius of the path and the velocity are chosen to cause concentration of the denser particles or components in the outermost portion of the loop. The tubing may simply be filled once and have its ends blocked, prior to swinging, or it may comprise part of a continuous flow line so that the desired separation of components can be more or less continuous. The device thus may be made capable of collecting dense particles either from a small discrete quantity or continuously from a fluid which is constantly flowing through it. It is essential, of course, when a continuous stream is being treated, that the force acting on the dense particles, due to centrifugation, be not overcome by the force of •flow through the tube, which acts on the dense particles and tends to carry them through the system with the flowing liquid stream, even after they are separated.

The invention, therefore, is particularly suitable for centrifuging to remove small quantities of relatively easily separable materials. However, it may be designed for driving at high velocity for more difficult centrifuging operations. It is useful for treatment of small quantities or batches but can be used, with suitable precautions, for effecting relatively continuous separations at low feed ratio.

It is an object of the invention, therefore, to provide an improved centrifuge for accomplishing the types of separation just described. A particular object is to accomplish this with apparatus of relatively few parts and of very simple construction.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGURE 1 illustrates a simple embodiment of the invention wherein a centrifuging loop is formed of part of a continuous flexible tubing. Appropriate supporting means and drive mechanisms are included.

FIGURE 2 shows some relative dynamic relationship between the mounting means, the drive means and the loop of FIG. 1.

FIGURE 3 shows a modification wherein the loop is in the form of a rigid length, of pipe or tubing, having oppositely disposed end portions axially aligned substantially along the axis of the centrifuging path, the loop ends being connected by rotary seal joints with relatively fixed lengths of tubing. Appropriate drive means are included.

FIGURE 4 is a detail on a larger scale of a modified loop portion having a valve arrangement by means of which a centrifuged or separated material may be removed from the loop while the loop is still in motion.

FIGURE 5 illustrates another modification wherein the tube is simply filled and centrifuged for small batch operations, valve outlet mechanism being included here also.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIGURE 1, there is shown a length of hollow tubular material such as a plastic tubing capable of containing a liquid. This tube has an intermediate looped part 15 supported towards one end 11 in a stationary clamp or bearing device 13 which holds this part of the tubing relatively fixed and without rotation. The loop 15 is formed in the tube of the appropriate length for its centrifuging function. Opposite the stationary tube holding member 13 an eccentric rotatable tube holding device 17 is provided. It is arranged to be driven through a circular path, indicated at 25, FIG. 2, by an electric motor 19. Appropriate gearing 21, and driving connections of any suitable type 23 are provided and shown diagrammatically since their details are unimportant and their construction obvious to those skilled in the art. The arrangement is such that as the eccentric element 17 passes through its circular path 25 it swings the portion of the hose held in an opening 27 in the eccentric through the small circle indicated by the dotted line 25, FIGURE 2. By this means, the loop 15 is swung in a manner analogous to a child’s jump rope, passes through the path 29 which is of much larger radius than 27, and consequently the loop moves at much higher

3,498,533 linear velocity than that of the eccentric element 17. The motion is quite analogous to the motion imparted manually to a jump rope. The linear velocity of other outer part of the loop, 15, may be within any reasonable limits. It must of course be sufficient to cause the desired centrifuging and separation of the particular heavier or denser particles or components which are sought. These will concentrate at the outer portion of the loop as indicated at the area c in FIGURE 1.

Obviously, if the tube contains a flowing stream of material, instead of a small fixed batch, the stream itself will tend to sweep separated components, e.g. at c, FIG. 1, on through the line. However, if the flow rate is kept relatively quite low and the speed of centrifuge is relatively high, a concentration of heavier particles or components will be built up at c without being substantially swept on through the line.

As pointed out below, valve means may be provided, if desired, for removing separated materials from the outer part of the loop. A suitable catching shroud, not shown but of obvious type surrounding the loop, will be provided to collect the centrifuged material released through the valve.

Referring now to FIGURE 3, another arrangement is shown wherein the loop itself is in the form of a piece of rigid pipe or tubing, for example, a U-shaped pipe of stainless steel, copper, or other metal, having oppositely extending bearing end portions 33 and 35, respectively. These end portions are rotatably mounted in axial alignment along the axis or center line 37 of their rotation. Non-rotatable pipe sections 39 and 41 are provided with appropriate connecting end elements 43 and 45 to establish fluid tight connections respectively with the ends 33 and 35 of the revolvable loop 31. Rotary seals of conventional type, enclosed within conventional housing 47 and 49, respectively, may be packed with any conventional material in a manner appropriate to maintain the fluid tight relationship. Thus the loop 31 may be rotated with respect to the sealed joints whereas the connecting tubes sections 39 and 41 are stationary. With this arrangement, a liquid may be fed in from the left as indicated by arrow 51, passing through the loop 31 and out the other end, as indicated by arrow 53. As noted above, the flow rate must be relatively slow. A gear 55 is fixed to one of the end portions 33 or 35, e.g. the left end or side of the loop. The centrifuging portion 31 thus is driven by a gear 57 shown as mounted on the extended shaft 59 of a suitable electric driving motor 61. Obviously, the motor will be geared to drive the loop through its circular path at a suitable speed, depending on the radius of the loop, the centrifuging requirements, etc.

It has already been mentioned that outlet valve means may be needed for the separated material. Such a valve is not shown in FIGURES 1 and 3, but it is shown in outline in FIGURE 5 and in greater, detail in FIGURE 4. Any suitable outlet valve mechanism through which the centrifuged material may be removed, either continuously or intermittently, can be used. Such a valve, of course, is fixed to and must rotate with the loop. Therefore it should be capable of control, manual or automatic, from a point not in the path of the loop. As shown in FIGURE 4, this valve per se may comprise a body member 63, having an outlet 65, capable of being closed by a longitudinally shiftable slide valve element 67, under suitable control. A Bowden wire or equivalent device 69 is shown for the purpose but other controls may be used. The material centrifuged or separated from the main liquid is represented in FIGURE 4 by the area above the dotted line, indicated at 71. When this becomes sufficient in quantity to interfere with the flow of liquid through the tube, the centrifuge may be stopped at the bottom of its circular path, if desired, and the contents may be withdrawn from outlet 65 by opening valve 67. If it is desired to remove such material while the centrifuge is still in motion a surrounding and collecting shroud member of obvious type will be placed around the centrifuge to catch the material thrown therefrom by centrifugal force.

As pointed out above the flow rate of liquid through the centrifuge and the centrifugal force by which the removed material is concentrated must be properly coordinated if centrifuging is to take place from a flowing stream. With a low flow rate and a high centrifuging force the material to be removed may be built up to a modest supply before opening the valve 65. Alternatively, of course, the tube can simply be emptied continuously, or periodically at intervals. By shutting off the supply and disconnecting and draining the tube, e.g. in FIGURE 1 or FIGURE 5, the centrifuged material may be taken off in small increments, assuming that a concentration of the material to be collected has occurred within the outermost portion of the loop.

Referring to FIGURE 5, one arrangement is shown by which the tube is simply filled with a liquid and then its ends are sealed off. The tube 15 is looped much as in FIGURE 1 and supported on one end by a fixed member 13. At the other end a driving eccentric 17 operated by suitable gearing 81 from a motor 85 drives the tube in an orbital path, although the tube does not rotate with respect to its own axis. Suitable flow control or cut off means, such as C-clamps 87 and 89, are applied after the tube is filled from one end or the other or partly filled. Centrifuging now takes place, building up a concentration of the material to be removed near the point marked P at the bottom of FIGURE 5. A valve 91 is shown, which may be of the same general type as that shown in FIGURE 4. This valve is operable by moving to right or left a slidable collar 93, which is connected to the valve V by a suitable control such as a Bowden wire 95. The wire, of course, should be wrapped with or otherwise fastened to the tube so that it will not fly freely in space as the tube is rotated.

It will be understood, in the embodiment of FIGURE 5, that the material to be centrifuged may be concentrated and removed at the end of the operation by simply opening the valve after the centrifuge has come to a stop. On the other hand the accumulated separated material may be removed by opening the valve while the tube is still in rotation, provided that a suitable catching shroud and drain structure is arranged around the path of the centrifuge.

From the foregoing description it will be understood that the centrifuging tube or at least the loop portion may be either flexible and continuous and non-rotatable per se, or it may comprise a short revoluble loop section mounted in suitable bearings for rotation and with suitable liquid seals with respect to associated non-rotatable tubing connections.

As pointed out above the centrifuge can be operated continuously while flow is continuous, or it can be shut off or disconnected and reconnected at intervals for centrifuging a small batch of liquid contained within the looped tube. The centrifuged and separated material may be withdrawn continuously, by use of appropriate valve mechanism as will be described above, or it may simply be removed by occasional disconnecting and purging of the loop section without the use of valves. The arrangement can be varied as desired, depending on the particular requirements.

It will be obvious from the foregoing that a simple mechanism has been designed which can be constructed of very inexpensive materials if desired. The device is highly effective for its purposes. Its diameter, gyration radius, rate of rotation, etc., may be adjusted or designed as needed for the particular purpose. These and other modifications will suggest themselves to those skilled in the art.

While the invention has been particularly shown and

3,498,533 described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.