US 3228596 A
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K. G. REED Jan. 11, 1966 CENTRIFUGE 2 Sheets-Sheet 1 Filed Aug. 2, 1963 INVENTOR.
KARL G. EED
ATTORNEY Jan. 11, 1966 K. G. REED 3,228,596
CENTRIFUGE Filed Aug. 2, 1963 2 Sheets-Sheet 2 I F /g. 2
I 22 k 26 92 AW 94 90 28 30 68 INVENTOR.
Q KARL (3.:REED B ATTORNEY United States Patent 3,228,596 CENTRIFUGE Karl G. Reed, Wayne, Pa., assignor to Pennsalt Chemicals Corporation, a corporation of Pennsylvania Filed Aug. 2, 1963, Ser. No. 299,511 7 Claims. (Cl. 23324) This invention relates to continuous solids-discharge centrifuges. More specifically, this invention relates to such centrifuges disposed about a vertical axis and suspended from a single point, and to suitable suspensions therefor.
It is well known in the art that there is inevitably some imbalance in every centrifuge rotor. This imbalance may be caused in the manufacture by slight irregular distribution of weight in the centrifuge parts or non-alignment of the axes of the various parts. The imbalance may increase subsequently from improper reassembly in the field, from uneven wear, or from unbalanced loads. Any imbalance will, as the rotor spins, tend to cause vibration of the entire machine, and at critical speeds the imbalance often causes excessive, and at times dangerous, excursions of the rotor. The operating speed of a given machine, for this reason, is specified at other than a critical one and preferably well above the critical speed to make possible a higher degree of isolation. Even up at operating speed, however, vibrations due to imbalance invariably present the problems of how to avoid wear and how to avoid excessive transmission of vibration to adjacent structures.
For continuous solids-discharge centrifuge rotors disposed about a horizontal axis, vibrations have been dealt with by rigidly holding the shaft at either end of the centrifuge rotor. This is illustrated in the US. Patent 2,703; 676 which issued on March 8, 1955, on an application filed by Fred P. Gooch. In such an arrangement the two rigid bearings and the massive frame together are able to withstand and virtually arrest the vibratory forces involved.
More difficult problems are presented in the instance of the vertically disposed continuous solids-discharge centrifuge having a single-point suspension above the centrifuge bowl so that the bowl is disposed in pendulous fashion therebelow. Such machines, which have been found well adapted for pressure operations because of simpler sealing requirements, have posed unusually difiicult problems of wear and vibration. These problems have arisen because imbalance in such a system will tend to cause characteristicexcursions which are especially accented at critical speeds. The first type of excursion will be a gyration or lateral movement of the entire rotor and will be apt to cause bearing wear and severe vibrations which may be transmitted to the frame, to associated piping and equipment-possibly resulting in its ultimate damage and failure-and even to the building which the machine occupies. The second type of excursion will be a pendulum-like movement or pivoting of the rotor about its suspension. This type of excursion has the drawback that it may build up and result in destructive movements of the rotor. Additionally, in pressure machines, pressure changes tend to cause vertical move ment of the rotor. The second type of excursion and movements due to pressure change may cause misalignment of belts, disengagement of seals, etc.
It has been discovered practical to suspend such a vertical centrifuge from a bearing mounted to accommodate both lateral displacement and pivotal movement. An example of a prior art arrangement of this kind is shown in US. Patent 3,061,181 which issued October 30, 1962 on an application filed by Fred P. Gooch. In some such devices the benefits of freedom for lateral displacement Patented Jan. 11, 1966 were effectively achieved by mounting the spindle shaft housing on the casing with spring steel washers which damp pendulous movements and rubber mounts which permit lateral displacements and provide a force for restoring the rotor to the geometric axis of the machine. The present invention is regarded as an improvement on prior suspension systems for the reason, among others, that even better isolation is obtained.
An object of the present invention is to provide for a vertical centrifuge, suspension means which are relatively sof in the lateral direction with the consequent reduction in the level of the critical speed and improved isolation of vibratory movements of the rotor from the frame.
At the same time the invention has for an object to provide suspension means which are firm in controlling or damping pendulous or pivotal movement, eliminating the build up in the rotor of uncontrolled pendulous rhythmic movements which tend to increase in amplitude and which could literally result in the self-destruction of the machine. The means also damps vertical movement due to pressure changes inside the casing. By damping vertical movement due to these causes misalignment of drive belts or disengagement of seals is avoided.
The invention provides sealing means for permitting pressure operation of a centrifuge employing such suspension.
Other objects of the invention will become apparent to those skilled in the art on a study of the accompanying specification including the drawings comprising a part thereof, all of which describe a preferred form of appa ratus embodying the invention.
In the drawings FIGURE 1 is a broken side elevation partly in section of an apparatus embodying the invention. For simplicity some of the spacer assemblies are shown partially and in phantom; and
FIGURE 2 is an enlarged fragmentary elevation partly in section showing the spindle housing. For simplicity only two spacer assemblies are shown.
More specifically an apparatus embodying the invention is designated 10 and shown in FIGURE 1. It com prises a lower casing 12 which stands upright on its supporting structure to which it may be secured by annular base flange 14. Over the opening at the top of the lower casing 12 is secured the upper casing 16 which houses the centrifuge rotor. (To make possible larger presentation of areas involving the present invention, both the upper casing and the rotor have been broken in FIGURE 1.) Closing the upper end of the upper casing is the casing seal support 18. The casing seal support has uniformly spaced about its periphery at an equal radius openings which receive vibration mounts 20 (FIGURE 2).
Each vibration mount 20 comprises a spool-shaped element of rubber or other resilient material and is formed with outward flanges about its upper and lower ends. The flanges engage the casing seal support about the respective openings on the upper and lower faces thereof. The vibration mount is provided with an internal metal bushing 22 to assure that the internal diameter of the mount will receive the reduced lower end of a vibration mount spacer 24. Washers 26 are provided over the opposite end surfaces of the mount and are engaged by a shoulder on the spacer and a lock washer 28 at the lower end of the spacer, respectively. The spacer is clamped to the mount by a suitable nut 30.
The upper end of each spacer is similar reduced and receives a vibration mount 32. Each of the upper vibration mounts is spool-shaped and is formed with upper and lower outward flanges and receives a metal bushing insert 34. The mount is sandwiched between washers 36 and secured to the upper end of the spacer 24 by a lock washer 38 and nut 40. As shown the upper vibration mounts 32 engage respective openings in an outward flange about the spindle housing 42. The upper and lower ends of the hollow spindle casing receive the spindle bearing retainer 44 and the upper spindle seal housing 46 which together hold within the housing 42 sets of ball bearing assemblies 48, the upper one of which is preferably spaced above the lower by the race spacer 50. The spindle 52 is engaged by the inner race of the ball bearing assemblies which are held in relation to the spindle by the spindle shoulder 54 and the bearing nut 56.
To the upper end of the spindle is secured the drive pulley 58 which is mounted on the rear box housing 60. To the lower end of the spindle 52 is secured the centrifuge rotor 62 (FIGURE 1). The lateral movements of the lower end of the rotor are limited by the bumper ring 64 supported from the walls of the lower casing 12. Mechanism for driving the screw conveyor within the rotor includes a planetary gear train (not shown) within the gear box housing 60. As is conventional in such machines, the train includes ring gears formed in the wall of the gear box 60, an upper sun gear held stationary by the overload release mechanism 66 and the spline shaft 68 (FIGURE 2) disposed within the spindle by which power is transmitted from the gear train to the conveyor 70 within the rotor 62.
In operation, as with the device of the aforementioned Patent 3,061,181, feed mixtures is introduced through the feed tube 72 to the lower end of the conveyor 70 andfrom there outward into the rotor 62. Separated liquid discharges from the port 74 and leaves the upper casing 16 through a segregated leadoff (not shown). The solids discharge from the ports 76 and are collected below the lower casing 12.
To close off the interior of the casing 16 from the atmosphere, the spindle carries a mating ring 80 (FIG- URE 2), the opposite faces of which are engaged by opposed bellows seals 82- disposed between the seal holder 84 which is bolted to the seal housing 46', and an inward flange on the seal housing 46 itself.
Additionally to seal the unit the holder 46 carries on its under surfacea seal 86. Engaging the seal 86 is a sealing face 88 on the casing seal 90. The casing seal in turn is mounted on the casing seal support 18 and urged upward by spring 92. An annular seal 94 mounted on the casing seal 90 engages the inner face of casing seal support 18.
It will be understood from the above description and reference to the drawings that increased pressures may be maintained within the casing 16 by virtue of the seal 86, $8 which permits lateral movement of the spindle and the seals 82 which permit relatively rotary movement. By this means pressures up to 150 pounds per square inch and above have been satisfactorily maintained within the casing 12.
By virtue of the presented structure and other embodiments of the invention, excursions due to imbalance are accommodated by the lateral movement of the spindle housing. and the entire rotor as the spacers 24 pivot in their mounts. Further, the softness of the system in the lateral direction reduces the level of the critical speed so that the operating speed may be safely reduced correspondingly if necessary. The movement of the housing in the lateral direction may be on the order of of an inch, and once the movement is completed the resilience of the mount 32 and 20 exert a restoring effect urging the spindle back to' its axial position. Thus lateral vibratory movements which would otherwise be transmitted from the spindle housing 42 to the casing 12 and indeed the structure which the flange 14 engages are isolated by the suspension described. As may be readily imagined, such isolation not only reduces the wear on the parts of the centrifuge, but also minimizes the load on the bearings and contributes greatly to the life of the machine. At the same time the seal arrangement assues compartmenting of the casing from the atmosphere.
While the described suspension readily permits lateral excursions of the rotating elements, it holds them firmly in vertical position and firmly resists and dampens vertical movement or cocking due to the pivoting of the rotor about its suspension. By thus maintaining the housing in a relatively stable disposition with respect to the vertical, for instance in the range of 0.030 inch to 0.060 inch permissible movement, the danger of misalignment of the drive belt, disengagement of the seals, etc. is minimized. This is particularly important in the case of compact machines wherein to make the shaft as short as possible a very limited space can be made available for seals.
The selection of specific dimension of the spacers 24 and the mounts 20 and 32 may be easily developed by those skilled in the art and will depend on the characteristics of the rotating assembly involved. Suflice it to say, the combined effect of the spacers and mounts should permit lateral movement and effect a restoration of the rotor to the geometric axis of the machine. The present invention provides considerable flexibility in that the compliance or softness in the lateral direction can be varied either by changing the length of the spacers or by changing the hardness of the resilient mounts. At the same time the mounts should be relatively firm in the vertical direction to dampen pivoting movement of the rotor, etc.
The arrangement shown in the drawings embodies the invention and is illustrative. Variations are possible. For instance the gear box 60' which may be on the upper end of the machine to facilitate cooling may alternatively be below the point of suspension as in the Gooch Patent 3,061,181 and the machine would enjoy many of the benefits of the invention. Further basic types of machine may be different from that shownthe rotor wall may be perforate, for instanceand much of the benefit will obtain.
It is to be understood, therefore, that the above particular description is by way of illustration and not of limitation, and that changes, omissions, additions, substitutions and/ or other modifications may be made without departing from the spirit of the invention. Accordingly it is intended that the patent shall cover by suitable expression in the claims, the various features of patentable novelty that reside in the invention.
1. A centrifuge comprising a horizontally disposed support element, upstandingv rigid spacer elements pivotally mounted in said support element, the spacer elements being biased toward vertical disposition, a spindle housing pivotally mounted on the upper ends of the spacer ele ments, a spindle within the spindle housing rotatably mounted on an axis fixed with respect to the spindle housing, the spindle carrying a centrifuge rotor below the spindle housing.
2. A centrifuge as described in claim 1 wherein the spacer elements are resilientlymounted in the support element and the spindle housing is resiliently mounted on the upper ends of the spacer elements.
3. A. centrifuge as described in claim 2 wherein a drive pulley is secured to the upper end of the spindle above the spindle housing.
4. A centrifuge as described in claim 2 wherein the rotor contains a helical conveyor and the spindle carries above the housing a gear box by which the conveyor is driven by the spindle at a speed of rotation different from the speed of rotation of the rotor.
5. A centrifuge having a rotatable assembly comprising a vertical shaft, a gear box mounted on the upper end of the shaft, and centrifuge rotor means mounted on the lower end of the shaft, bearing means engaging the shaft intermediate the gear box and the rotor means, the bearing means having outwardly extending flange means with a plurality of openings therein, a stationary support surround-ing and spaced from the rotor means and formed with a plurality of openings spaced below and normally in alignment with the openings of the flange ean re pectively, aresilient spool yieldably fitted in each of said openings, the spools each having central bores and upper and lower ends overlapping the margins of the openings, respectively, rigid spacer elements connecting the bores in the spools in the support and in the flange means, respectively, each of the rigid spacer elements having enlarged means intermediate its ends, the upper and lower faces of which are greater in lateral dimension than the lateral dimension of the bores in the spools in the flange means and the support, respectively, the upper face of the enlarged means engaging the lower end of the spool in the flange means and the lower face of the enlarged means engaging the upper end of the spool in the support, the ends of the spacer elements extending through the bores of the respective spools, and the spools being sufficiently soft and the spools and the spacer elements having means dimensioned to permit the rotatable assembly movement in a lateral direction but substantially preclude movement in a vertical direction.
References Cited by the Examiner UNITED STATES PATENTS 309,826 12/1884 Dolph et a1 308146 3,061,181 10/1962 Gooch 233-7 3,151,074 9/1964 Gooch 233--24 M. CARY NELSON, Primary Examiner.
HENRY T. KLINKSIEK, Examiner.