US3333707A

US3333707A - Mounting arrangement for basket of centrifugal

Info

Publication number: US3333707A
Application number: US368615A
Authority: US
Inventors: Joseph B Bange; Thomas R Laven
Original assignee: Western States Machine Co
Current assignee: Western States Machine Co
Priority date: 1964-05-19
Filing date: 1964-05-19
Publication date: 1967-08-01
Anticipated expiration: 1984-08-01
Also published as: BE664108A; DE1482747A1; GB1101801A; FR1433630A; NL6506253A; DE1482747B2; DE1482747C3

Description

Aug. 1, 1967 J. B. BANGE ETAL 3,333,707

MOUNTING ARRANGEMENT FOR BASKET OF CENTRIFUGAL Filed May 19, 1964 3 Sheets-Sheet 1 Fig.1

WNW

INVENTORS JOSEPH B. BANGE BY THOMAS R-LAVEN ORNE y 1967 J. B. BANGE ETAL 3,333,707

MOUNTING ARRANGEMENT FOR BASKET OF CENTRIFUGAL Filed May 19, 1964 3 Sheets-Sheet 2 INVENTORS J O S E P H B B A N GE T H 0M AS R. L A V E N A 0R N E Y S Augl, 7 J. B. BANGE ETAL CENTRIFUGAL MOUNTING ARRANGEMENT FOR BASKET OF Filed May 19, 1964 3 Sheets-Sheet o Fig.3

INVENTORS JOSEPH B- BANGE THOMAS R- LAVEN 5o Fig.5 BY

W.a1w

A ORNEY United States Patent 3 333,707 MOUNTING ARRAN GEMENT FOR BASKET 0F CENTRIFUGAL Joseph B. Range and Thomas R. Laven, Hamilton, Ohio, assignors to The Western States Machine Company, Hamilton, Ohio, a corporation of Utah FiledMay 19, 1964, Ser. No. 368,615 10 Claims. (Cl. 210-365) This invention relates generally to a mounting arrangement for the basket of a centrifugal, particularly of the type in which the basket is rotated by a drive belt running around a pulley secured on the shaft of the basket,

An object of this invention is to provide a flexible mounting arrangement for the basket of a centrifugal of the described character which, in the event of an imbalance of the basket, permits the basket to oscillate or gyrate about the center of the pulley and thereby prevents undue stressing of the drive belt.

Another object is to provide a flexible mounting arrangement or suspension for the basket which permits adjustment of the stiffness, and hence the natural frequency, of the suspension.

A further object is to provide a flexible suspension which, when the basket is made to oscillate or gyrate by reason of an imbalance thereof, presents resistance to the imbalance force which increases with increasing displace ment of the basket from its neutral or normal position.

In accordance with an aspect of this invention, a centrifugal having its basket secured on a normally vertical shaft extending therebelow and carrying a pulley driven through a drive belt from a motor secured on a base structure, is provided with a flexible suspension for the basket comprising a bearing housing having the basket shaft journalled therein, and at least three mounting assemblies equally spaced apart around the bearing housing and eachincluding members rigidly joined to the bearing housing and to the base structure, respectively, one of the members of each mounting assembly having a portion lying substantially in a horizontal plane which contains the center of the pulley on the basket shaft and the other of the members of each mounting assembly having portions extending above and below said portion of the one member, each of the mounting assemblies further including elastomeric means interposed between the portions of the two members to yieldably resist relative vertical and horizontal movements of the latter, whereby the basket can gyrate about the center of the pulley on the basket shaft in response to an imbalance of the basket.

In a preferred embodiment of the invention, the portion of the one member of each mounting assembly lying substantially in a horizontal plane which contains the center of the pulley on the basket shaft is in the form of a lug having a vertical bore extending therethrough, and the other of the members includes a vertical spindle extending through the bore and having means thereon, for example, in the form of cup-like elements, defining annular recesses around the spindle opening toward the lug portion above and below the latter, and the elastomeric means are formed by an elastomeric sleeve interposed radially between the spindle and the bore of the lug portion and elastomeric discs substantially confined within the annular recesses and being engageable by the upper and lower surfaces on the lug portion.

In accordance with another feature of this invention, means are provided, for example, in the form of stepped washers, defining upper and lower surfaces on the lug portion which generally taper in the direction toward the adjacent annular recesses so that relative displacements of the lug portion and spindle in the axial direction of the latter tend to reduce the confined volume of the elastomeric disc resisting such displacement, and thus give rise to a restoring force that is increased in accordance with the magnitude of the displacement.

The mounting assemblies for a flexible suspension in accordance with this invention further preferably have means for adjusting the axial spacing between the cup like elements or other means defining the annular recesses extending around the spindle above and below the lug portion, and thereby make possible adjustment of the precompression of the elastomeric means of the mounting assembly for controlling the natural frequency of the suspension.

The above, and other objects, features and advantages of this invention, will be apparent in the following detailed description of an illustrative embodiment thereof which is to be read in connection with the accompanying drawings forming a part hereof, and wherein:

FIG. 1 is a side elevational view, partly broken away and in vertical section, of a centrifugal having a flexible mounting for its basket in accordance with this invention;

FIG. 2 is a detail horizontal sectional view taken along the line 22 on FIG. 1, but on an enlarged scale;

FIG. 3 is a detail vertical sectional View taken along the line 33 on FIG. 2;

FIG. 4 is a fragmentary sectional view corresponding to a portion of FIG. 3, but illustrating the adjustment of one of the mounting assemblies of the flexible suspension for varying the natural frequency of the latter; and

FIG. 5 is a view similar to that of FIG. 4, but illustrating the mounting assembly in a displaced condition.

Referring to the drawings in detail, and initially to FIG. 1 thereof, it will be seen that the invention is there shown applied to a continuous centrifugal which generally comprises a frusto-conical basket 11 mounted for rotation about a normally vertical axis within a housing 12. The basket 11 is underdriven, for example, by a motor 13 suitably supported on a rigid base structure 14 of the centrifugal and having a V-belt pulley 15 on its shaft which, by way of V-belts 16, drives a V-belt pulley 17 secured on the lower end of the basket shaft 18 which projects below the basket 11.

Since the present invention relates only to the flexible suspension 19 by which the basket 11 is rotatably mounted in housing 12, only a general description of the operation and arrangement of the centrifugal 10 will be given to promote understanding of the problems that are solved by the flexible suspension 19. Thus, it will be noted that, in the centrifugal 10, the mixture of liquids and solids to be centrifuged or separated is introduced by way of a supply pipe (not shown) extending from above into the basket 11 and discharging adjacent the bottom of the latte-r. By reason of the continuous feeding of the mixture to the basket and the continuous rotation of the latter, the mixture travels upwardly and outwardly along the inner surface of the frusto-conical side wall of the basket.-

The inner surface of the basket wall is formed by a perforated screen, and the basket wall has suitable drain openings extending therethrough. As the mixture travels upwardly along the wall of basket 11, the centrifugal action causes the liquid constituents thereof to travel outwardly through the wall of the basket for collection in an inner chamber 20 of the housing 12, while the solid constituents of the mixture are discharged radially outward over the top edge of the basket 11 and are collected in an outer chamber 21.

It will be apparent that, during the operation of the centrifugal, as briefly described above, there is the possibility of non-uniform distribution of the mixture within the basket 11 thereby leading to imbalance of the latter with respect to its axis of rotation. Such imbalance of the basket during its relative high speed rotation tends to cause gyration or oscillation of the basket. If such gyration or oscillation is rigidly resisted, as by providing the basket with an inflexible mount, then undesirable vibratory stresses are developed in the bearings rotatably supporting the basket shaft 18 to seriously impair the useful life of the bearings, and further the resulting vibrations are transmitted through the base structure 14 of the centrifugal to the building housing the same. On the other hand, if the basket 11 is provided with a flexible mount, and thus allowed to gyrate or oscillate when imbalance occurs during its rotation, care must be taken to avoid excessive stressing of the V-belts 16 between the pulley on the shaft of the fixedly mounted motor 13 and the pulley 17 on the shaft 18 of the gyrating basket.

7 In accordance with this invention, the suspension or mounting 19 for the basket 11 generally comprises a bearing housing 22 in which the basket shaft 18 is journalled, and at least three mounting assemblies 23 which are equally spaced apart around the housing 22 and which flexibly suspend the latter, and hence the basket 11, from a rigid, annular horizontal plate 24 extending around bearing housing 22 and forming part of the base structure 14 of the centrifugal.

In order to permit basket shaft 18 to be rotatably supported at locations above and below the center of gravity of basket 11, the basket is preferably provided with a downwardly open, hollow hub 25 (FIGS. 1 and 3) extending upwardly in the basket substantially above the bottom of the latter. Shaft 18 extends coaxially within hub 25 and has a flange 26 at its upper end secured, as by bolts 27, to the top of the hub. The bearing housing 22 extends upwardly between shaft 18 and hub 25 and contains bearings 28 and 29 (FIG. 3) which are vertically spaced apart and rotatably support basket shaft 18 at locations adjacent the upper end of the basket shaft and below the bottom of basket 11. Thus, the vertical location of the center of gravity of basket 11 is between bea-

rings

28 and 29 and, by reason of the relatively large vertical distance between such bearings, imbalance of the basket tending to cause gyration or oscillation thereof only produces moderate radial loads on the bearings.

In accordance with this invention, each of the mounting assemblies 23 generally includes two

members

30 and 31 which are rigidly joined to bearing housing 22 and to the annular plate 24 of base structure 14, respectively. As shown particularly on FIG. 3, each member 30 includes an arm 32 extending radially outward from the lower end of bearing housing 22 and being preferably integral with the latter. A boss 33 is formed at the outer end of each arm 32 and has a tapped bore 34 extending through the boss parallel to the axis of shaft 18. Each member 30 further includes an elongated spindle 35 having a threaded upper end portion 36 screwed into the tapped bore 34 and a hexagonal or other non-circular enlargement 37 at the bottom of the threaded portion 36 to receive a wrench or other tool by which the spindle 35 can be turned for tight engagement of the latter with the related radial arm 32.

The other member 31 is in the form of a bracket having a pad 38, at its top, secured by screws 39 to the underside of annular plate 24, and a lug portion 40 directed radially inward toward the axis of shaft 18 from the bottom of the member or bracket 31. The lug portion 40 lies and is centered in, and may be vertically symmetrical with respect to, the horizontal plane 41 (FIG. 3) which extends through the center of pulley 17 and also contains the longitudinal medial line of the V-belt 16. The lug portion 40 has a bore 42 extending vertically therethrough, that is, parallel to the axis of basket shaft 18, and formed with a diameter substantially greater than the diameter of spindle 35 so that the latter extends through bore 42 with a substantial radial clearance therebetween.

The member 30 of each mounting assembly 23 has means on the spindle 35 thereof defining

annular recesses

43 and 44 which open axially toward lug portion 40 above and below the latter. In the illustrated embodiment, the

annular recesses

43 and 44 are defined by upper and lower cup-

like elements

45 and 46, respectively. Element 45 has a central hole through which spindle 35 extends downwardly, and such element 45 is held tightly against the underside of hexagonal enlargement 37 by the upper end of a spacer tube 47 extending over spindle '35 and having a length shorter than that of the latter. Tube 47 is axially locked against element 45 by means of a nut 48 screwed 0n the lower threaded end portion 49 of spindle 35. The other or lower cup-like element 46 has a central hole dimensioned to receive the spacer tube 47, and element 46 is adjustably located along tube 47 by means of a nut 50 which is screwed on the lower threaded end portion 51 of spacer tube 47.

Each of the mounting assemblies 23 embodying this invention further includes a sleeve 52 of rubber or other elastomeric material extending around spacer tube 47 within bore 42 of lug portion 40, for yieldably resisting relative horizontal movements of the

members

30 and 31, and annular discs or

rings

53 and 54, also of rubber or other elastomeric material, filling the

recesses

43 and 44 defined by

elements

45 and 46, respectively, and being substantially confined in such recesses, for axial engagement with the upper and lower surfaces of lug portion 40, thereby to yieldably resist relative vertical movement of

members

30 and 31.

As shown particularly on FIGS. 3, 4 and 5, the lug portion 40 has means, for example, in the form of

stepped washers

55 and 56, at the top and bottom thereof defining surfaces 57 and 58 which generally taper in the direction toward the adjacent cup-

like elements

45 and 46, respectively, and which are engageable with the

elastomeric discs

53 and 54.

The above described flexible suspension 19 for basket 11 operates as follows:

When imbalance occurs in the rotated basket 11, the elastomeric sleeve 52 and

discs

53 and 54 of each mounting assembly 23 permit the member 30 of the latter, which is rigidly connected with the bearing housing 22, to move relative to the member 31 which is rigidly connected to the base structure 14, thereby cushioning the mounting for the basket and preventing the imposition of jarring loads on

bearings

28 and 29, and also preventing the transmission of undesirable vibrations to the base structure 14 and also to the building structure housing the centrifugal. Since the lug portions 40 of the several mounting assemblies 23 are centered in the horizontal plane 41 extending through the center of pulley 17, and the

elastomeric discs

53 and 54 equally resist downward and upward movements of each member 30 relative to the associated member 31, each mounting assembly may be considered as having a dynamic center lying in plane 41 so that the gyration or oscillation of basket 11 resulting from imbalance of the latter, and the resulting relative movements of

members

30 and 31 occur about the center of pulley 17, thereby avoiding excessive stressing of the V-belts 16 extending between pulley 17 and the pulley 15 on the shaft of drive motor 13.

It is further to be noted that the described flexible suspension 19 has a variable stiffness characteristic, that is, the restoring force tending to return the basket 11 to its normal vertical position increases in magnitude in accordance with the extent of the angular displacement of the basket from such normal position. When imbalance of basket 11 occurs during rotation of the latter, thereby causing gyration or oscillation of the basket about the center of pulley 17, the spindles 35 of the several mounting assemblies 23 are sequentially moved downwardly and upwardly relative to the lug portions 40 of the related mounting assemblies. The extent of such downward and upward movement of each spindle 35 relative to its lug portion 40 depends upon the angular displacement of the basket axis from the vertical during oscillation or gyration of the basket. By reason of the generally tapering form of the surfaces 57 and 58 provided at the top and bottom of each lug portion 40, the

elastomeric disc

53 or 54 which resists initial relative vertical movement of spindle 35 and lug portion 40 is not wholly confined within the

recess

43 or 44, but rather can bulge axially out of such recess through the gap between the surface 57 or 58 and the adjacent edge of the cup-

like element

45 or 46. However, as the relative vertical displacement of spindle 35 and lug portion 40 increases, the annular gap between the surface 57 or 58 and the edge or rim of the cup-

like element

45 or 46, respectively, is progressively decreased, thereby to further confine the elastomeric material within the

recess

43 or 44 as such material is compressed. The progressively increasing confinement of the elastomeric material within the

recess

43 or 44 increases the resistance to axial or vertical movement of spindle 35 relative to lug portion 40 is further accounted for by the fact that, in response to such relative vertical movement, the area of engagement of the surface 57 or 58 with the

elastomeric disc

53 or 54, respectively, is also progressively increased. In view of the foregoing, an increased imbalance force giving rise to an increased magnitude of oscillation or gyration of the basket 11 during rotation of the latter is resisted by increased restoring forces for maintaining the cushioned or flexible character of the suspension for the basket.

A comparison of FIGS. 3 and 4 will further show that turning of the nut 50 of each mounting assembly 23 makes it possible to axially displace cup-like element 46 along spacing tube 47, thereby to vary the axial spacing between

elements

45 and 46. When the axial distance between

elements

45 and 46 is reduced, the generally tapering surfaces 57 and 58 at the top and bottom of lug portion 40 enter recesses 43 and 44 and thereby increase the precornpression of

elastomeric discs

53 and 54. It will be apparent that such a change in the precompression of

elastomeric discs

53 and 54 alters the stiffness of the flexible suspension 19 and thereby changes the natural frequency of the flexible suspension. Accordingly, the flexible suspension 19 can have its natural frequency adjusted so as to be substantially different from the speeds at which the basket 11 is rotated during normal operation of the centrifugal 10, thereby to avoid the fortification or amplifying of the oscillation or gyration of the basket that would occur if imbalance occurred in the basket while the latter was rotated at the natural frequency of its flexible suspension.

It will be seen that the ends of the elastomeric sleeve 52 which yieldably resist relative horizontal movements of each spindle 35 and lug portion 40 are in contact with the related

elastomeric discs

53 and 54 so that a change in the precompression of the elastomeric discs, as described above, will also influence the precompression of sleeve 52 for varying the resistance of the latter to relative horizontal movements.

Although an illustrative embodiment of the invention has been described in detail above with reference to the accompanying drawings, it is to be understood that the invention is not limited to that precise embodiment, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention, except as defined in the appended claims.

What is claimed is:

1. In a centrifugal having a basket secured on a normally vertical shaft carrying a pulley driven through a drive belt from a motor secured to a side of said shaft in rigid relation to a rigid base structure; a flexible suspension for the basket comprising a bearing housing having the shaft journalled therein, and at least three mounting assemblies equally spaced apart around the axis of said shaft and each including two members rigidly joined to said housing and to said base structure, respectively, one

of said members of each mounting assembly including a lug portion having a vertical bore and being substantially centered in a plane which is substantially normal to said axis and contains the axial and radial center of the pulley on the basket shaft and the other of said members including a spindle extending through said bore and having means thereon defining shoulders equally above and below said lug portion in the normally vertical position of said shaft, each of said mounting assemblies further including elastomeric means interposed axially between said lug portion and said shoulders and radially between said spindle and lug portion to yieldably resist relative movements of the two members and to confine said relative movements to movements about said center of the pulley, whereby gyrations of the basket in response to an imbalance thereof occur about the center of the pulley on the basket shaft to minimize stressing of the drive belt.

2. In a centrifugal having a basket secured on a normally vertical shaft carrying a pulley driven through a drive belt from a motor secured to a side of the shaft in rigid relation to a rigid base structure; a flexible suspension for the basket comprising a bearing housing having the shaft journalled therein, and at least three mounting assemblies equally spaced apart around the axis of said shaft and each including two members rigidly joined to said housing and to said base structure, respectively, one of said members of each mounting assembly including a lug portion having a vertical bore and being substantially centered in a plane which is substantially normal to said axis of the shaft and contains the axial and radial center of the pulley on the basket shaft and the other of said members including a vertical spindle extending through said bore and cup-like elements on said spindle opening toward said lug portion above and below the latter and equally spaced from said lug portion in the normal vertical position of said shaft, each of said mounting assemblies further including an elastomeric sleeve interposed radially between said spindle and the bore of said lug portion and elastomeric discs contained in said cup-like elements to yieldably resist relative movements of said two members and to confine said relative movements to movements about said center of the pulley so that gyrations of the basket in response to an imbalance thereof occur about said center of the pulley for minimizing stressing of the drive belt, and means at the top and bottom of the lug portion defining surfaces with peripheral parts which generally taper in the directions toward the adjacent cup-like elements and cooperate with the edges of the latter to define annular gaps therebetween through which said elastomeric discs can bulge so that relative movement of one of the cup-like elements and the lug portion in the direction toward each other reduces the width of the gap through which said elastomeric disc in said one cup-like element can bulge and increases the area of contact of the elastomeric disc with said surface on the lug portion, thereby to increase the resistance of said elastomeric disc to further relative movement in said direction.

3. A centrifugal as in claim 2; further comprising means on said spindle for adjusting the axial spacing between said cup-like elements so that reduction of the axial distance between said cup-like elements serves to elTect pre-compression of said elastomeric discs and thereby control the natural frequency of the flexible suspension.

4. A flexible suspension for the basket of an underdrive centrifugal having a basket shaft journalled in a bearing housing; said suspension comprising at least three mounting assemblies equally spaced apart around the hearing housing and each including a rigidly supported bracket having a lug portion substantially centered in a plane perpendicular to the normal axis of the basket and formed with a bore parallel to said axis, a spindle mounted rigidly on the bearing housing and extending parallel to said axis through said bore of the related bracket,

means on said spindle defining annular recesses opening axially toward said lug portion at the opposite sides of the latter, elastomeric means interposed radially between said spindle and said bore of the lug portion and also substantially confined in said annular recesses by said lug portion to yieldably resist relative horizontal and vertical displacements of said bracket and spindle of each mounting assembly, whereby an imbalance of the basket causes the latter to gyrate about a center at the intersection of said axis and said plane, and means at the opposite sides of said lug portion defining surfaces to contact said elastomeric means and having peripheral parts that generally taper in the direction toward the adjacent recesses and cooperate with the edges of said recesses to define gaps therebetween through which said elastomeric means can bulge so that relative displacement of said bracket and spindle causes reduction of the width of one of said gaps through which said elastomeric means can bulge and simultaneously increases the area of contact of one of said surfaces with the elastomeric means resisting such displacement, thereby to increase the restoring force of the elastomeric means.

5. A flexible suspension as in claim 4; wherein said means defining the surfaces having generally tapering peripheral parts are constituted by stepped washers extending around said spindle between said lug portion and said means defining the annular recesses.

6. A flexible suspension as in claim 4; wherein said means defining the annular recesses includes a first cuplike element fixed on said spindle and opening toward one side of the lug portion, a second cup-like element slidable on said spindle and opening toward the other side of the lug portion, said spindle having a threaded portion extending beyond said second cup-like element, and a nut on said threaded portion adapted to be tightened against said second cup-like element for changing the axial distance between the latter and said first cup-like element, and thereby adjusting the natural frequency of the flexible suspension.

7. In a flexible suspension, the combination of two relatively movable members respectively having a lug portion with a bore extending therethrough and a spindle extending through said bore, means on said spindle defining annular recesses opening axially at the opposite sides of said lug portion, means at said opposite sides of the lug portion defining surfaces having peripheral parts that generally taper in the direction toward the adjacent recess and cooperate with the edges of said recesses to define gaps therebetween that vary in width upon relative displacements of said members in the direction of the axis of said spindle, and elastomeric means interposed radially between said spindle and said bore of the lug portion and also being substantially confined in said recesses by said surfaces so that relative displacements of said members in the direction of the axis of said spindle tend to cause bulging of said elastomeric means through the one of said gaps which is reduced in width while the area of contact of the adjacent one of said surfaces with said elastomeric means is increased, thereby to result in restoring forces that increase in accordance with the magnitude of said displacements.

8. In a flexible suspension, the combination as in claim 7; wherein said means defining the surfaces having tapered peripheral parts are constituted by stepped Washers at the opposite sides of the lug portion around said bore, and said elastomeric means include an elastomeric sleeve extending around said spindle within said bore and through said washers and elastomeric discs filling said annular recesses to engage said surfaces and the ends of said sleeve.

9. In a centrifugal having a basket secured on a normally vertical shaft carrying a pulley driven through a drive belt from a motor secured to a side of said shaft in rigid relation to a rigid base structure; a flexible suspension for the basket comprising a bearing housing having the shaft journalled therein, and at least three mounting assemblies equally spaced apart around the axis of said shaft, each of said mounting assemblies including two members rigidly joined to said housing and to said base structure, respectively, and being movable relative to each other upon gyrations of the basket in response to an imbalance of the basket, and means yieldably resisting relative movements of said two members and confining said relative movements to movements about a center which coincides with the axial and radial center of said pulley on the shaft, whereby gyrations of the basket cause minimal stressing of the drive belt.

10. In a centrifugal having a basket secured on a normally vertical shaft carrying a pulley driven through a drive belt from a motor secured to a side of said shaft in rigid relation to a rigid base structure; a flexible suspension for the basket comprising a bearing housing having the shaft journalled therein, and at least three mounting assemblies equally spaced apart around the axis of said shaft, each of said assemblies including two members rigidly joined to said housing and said base structure, respectively, for movements relative to each other upon gyrations of the basket in response to an imbalance of the basket, and elastomeric means interposed between said two members to yieldably resist said relative movements thereof, each of said assemblies having a dynamic center lying in a plane which is normal to said axis of the shaft and which contains the axial and radial center of said pulley so that said relative movements of said members are confined to movements about a center which coincides with said center of the pulley to minimize stressing of the drive belt by gyrations of the basket.

References Cited UNITED STATES PATENTS 1,815,170 7/1931 Summers 248-21 2,406,187 8/1946 Bayless 210-365 X 3,035,799 5/1962 Pierce 248-15 3,151,074 9/1964 Gooch 233-24 3,175,689 3/1965 Goodwin et al. 210365 3,207,627 9/1965 Dietzel et a1. 210--78 X REUBEN FRIEDMAN, Primary Examiner.

1. DE CESARE, Assistant Examiner.

Claims

1. IN A CENTRIFUGAL HAVING A BASKET SECURED ON A NORMALLY VERTICAL SHAFT CARRYING A PULLEY DRIVEN THROUGH A DRIVE BELT FROM A MOTOR SECURED TO A SIDE OF SAID SHAFT IN RIGID RELATION TO A RIGID BASE STRUCTURE; A FLEXIBLE SUSPENSION FOR THE BASKET COMPRISING A BEARING HOUSING HAVING THE SHAFT JOURNALLED THEREIN, AND AT LEAST THREE MOUNTING ASSEMBLIES EQUALLY SPACED APART AROUND THE AXIS OF SAID SHAFT AND EACH INCLUDING TWO MEMBERS RIGIDLY JOINED TO SAID HOUSING AND TO SAID BASE STRUTURE, RESPECTIVELY, ONE OF SAID MEMBERS OF EACH MOUNTING ASSEMBLY INCLUDING A LUG PORTION HAVING A VERTICAL BORE AND BEING SUBSTANTIALLY CENTERED IN A PLANE WHICH IS SUBSTANTIALLY NORMAL TO SAID AXIS AND CONTAINS THE AXIAL AND RADIAL CENTER OF THE PULLEY ON THE BASKET SHAFT AND THE OTHER OF SAID MEMBERS INCLUDING A SPINDLE EXTENDING THROUGH SAID BORE AND HAVING MEANS THEREON DEFINING SHOULDERS EQUALLY ABOVE AND BELOW SAID LUG PORTION IN THE NORMALLY VERTICAL POSITION OF SAID SHAFT, EACH OF SAID MOUNTING ASSEMBLIES FURTHER INCLUDING ELASTOMERIC MEANS INTERPOSED AXIALLY BETWEEN SAID LUG PORTION AND SAID SHOULDERS AND RADIALLY BETWEEN SAID SPINDLE AND LUG PORTION TO YIELDABLY RESIST RELATIVE MOVEMENTS OF THE TWO MEMBERS AND TO CONFINE SAID RELATIVE MOVEMENTS TO MOVEMENTS ABOUT SAID CENTER OF THE PULLEY, WHEREBY GYRATIONS OF THE BASKET IN RESPONSE TO AN IMBALANCE THEREOF OCCUR ABOUT THE CENTER OF THE PULLEY ON THE BASKET SHAFT TO MINIMIZE STRESSING OF THE DRIVE BELT.