US3332300A

US3332300A - Centrifugal equipment

Info

Publication number: US3332300A
Application number: US374094A
Authority: US
Inventors: Nyrop Per
Original assignee: Dorr Oliver Inc
Current assignee: Dorr Oliver Inc
Priority date: 1964-06-10
Filing date: 1964-06-10
Publication date: 1967-07-25
Anticipated expiration: 1984-07-25
Also published as: BE665190A; NL6507395A; DE1482710A1; FR1437832A

Description

July 25, 1967 P. NYROP 3,332,300

CENTRIFUGAL EQUiPMENT Filed June 10, 1964 5 Sheets-Sheet l INVENTOR. PER NYROP ATTORNEY.

July 25, 1967 I P. NYROP 3,332,300

CENTRIFUGAL EQUIPMENT Filed June 10, 1964 3 Sheets-Sheet 3 INVENTOR. PER NYROP ATTORNEY.

United States Patent 3,332,300 CENTRIFUGAL EQUIPMENT Per Nyrop, Norwalk, Conn., assignor to Don-Oliver Incorporated, Stamford, Conn. Filed June 10, 1964, Ser. No. 374,094 9 (Ilairns. (Cl. 74-675) This invention relates to drive arrangements in centrifugal equipment of the general type in which material being processed is subjected to centripetal force to separate it into component fractions. More specifically, the invention pertains to drive arrangements for centrifugal apparatus having an outer rotary member which confines and exerts centripetal force upon the process material and a coaxial, inner member rotating at a differential speed which conveys the material axially within the outer member.

Centrifugal equipment of the general type to which the present invention relates is shown by United States Patent 3,074,842 to Strong and United States Patent 2,863,560 to Linke et al. Further, as shown in the Linke et al. patent, it is known to effect the required differential speed between inner and outer rotary members by use of a cycloid drive arrangement in which the rotary members are respectively connected to rotate with the cycloid disc or discs and the cycloid cage. A cycloid drive is a well understood, albeit relatively complex, arrangement which is described in this specification only to the extent necessary to understand the present invention. Further description of the kinematics and operation of a cycloid drive may be obtained by exemplary reference to United States Patents 1,694,031 and 1,867,492 to Braren.

It is a characteristic of such cycloid drives that the cycloid disc or discs rotate in the same direction but faster than the cycloid cage or housing. Therefore, in the Linke et al. arrangement the inner rotary member or material conveyor which is connected to the cycloid cage rotates more slowly than the outer rotary member or cone which is connected to rotate with the cycloid disc.

It can readily be seen that the cycloid drive arrangement of Linke et al. can be adapted to drive rotary members of the type shown in the Strong patent, and this arrangement is conventional. In such an arrangement, a helically-vaned conveyor is connected to rotate with the cycloid discs and therefore rotates more rapidly than the outer cone which rotates with the cycloid cage through a connection at the drive-proximate end of the cone. Although this speed relationship is satisfactory and even preferable in many applications of such equipment, it is occasionally desirable when processing certain materials to have the conveyor or helix rotating more slowly. This condition is particularly preferable when maximum liquid removal from a material, for example a slurry of sugar crystals, is to be accomplished. This reversal of the differential speed relation of course necessitates a reversal of the pitch hand of the vanes of the conveyor.

Heretofore, the only cycloid-centrifuge structural arrangement known to accomplish this desired speed relation, the slower helix, was that shown in the Linke et al. patent. However, this arrangement of rotating members and their respective shafting involves several severe disadvantages. First, because the narrow upper end, that is, the drive-remote end, of the cone is suspended or connected to the inner shaft, feed apertures must be provided through this connection in order to permit material to enter. The constriction caused by such feed apertures, as compared to the completely open upper end of a bottomsupported cone, causes problems in getting adequate and reliable feed to the centrifugal device. Second, in many applications of centrifugal equipment, it is desirable to introduce a wash fluid at some intermediate point in the centrifugal processing of the material. In the type of centrifugal equipment exemplarily disclosed in this specification, a screening centrifuge, it is conventional to introduce wash fluid at the upper end of the helix for transmission to one or more axially-spaced outlet points in the helix. If the cone were top-suspended as in the Linke et al. patent, a very complex, expensive, troublesome, sealed arrangement would have to be provided to transmit the wash fluid through the upper end of the cone to get it to the upper end of the helix. Third, the most severe problem encountered with the top-suspended cone is the difliculty of preventing cone rocking or runout, that is, deviation from the central axis of the device. This problem is caused because the lower portions of the cone, which have the greatest radius and are therefore subjected to the greatest centrifugal forces, are farthest removed from the cone support, and because the secure attachment of the cone to the upper end of the inner shaft is more diflicult in view of the reduced bearing area inherently available than is the attachment of the cone at its lower end to the outer shaft.

It is also known in the prior art that with other drive arrangements, such as planetary gearing, it is possible to obtain concentric drive shafts wherein the inner shaft rotates more slowly than the outer. However, such drives are far less compact than the cycloid drive and are therefore disadvantageous as drives for centrifugal equipment. For example, comparing the drives necessary to transmit a torque of meter-kilograms at the operating speeds involved in one particular size of screening centrifuge, a cycloid drive having an axial length of 4 inches is required whereas a planetary drive having an axial length of about 6 /2 inches is required. Therefore, the cycloid drive is far more advantageous for use in the type of centrifugal apparatus to which the present invention relates.

Accordingly, it is a primary object of the present invention to overcome the problems and disadvantages inherent in prior art structures.

To accomplish this object, the present invention provides a unique cycloid drive arrangement in which the inner of two concentric output shafts rotates at a slower speed than the outer shaft. This arrangement of course permits the helix to be connected to the slower rotating inside shaft while a bottom-supported cone can be connected to the outside shaft. This unique speed relation between the concentric output shafts of a cycloid drive is accomplished by connecting the inside shaft to the cycloid cage and connecting the outside shaft to rotate with the cycloid discs. To accomplish this connection arrangement in the specific structure shown in the accompanying drawings, the outside shaft is provided with an enlarged portion which encompasses the cycloid cage and which is connected for rotation with the cycloid discs. A lower axial extension of this enlargement of the out side shaft forms an annular pulley shaft concentric with the conventional eccentric shaft of the cycloid drive. In this manner, the present invention provides an arrangement for a cycloid driven centrifugal apparatus having a bottom-supported cone whereby the helix may be driven more slowly than the cone.

Accordingly, other objects of the present invention are:

(1) The provision of improved centrifugal equipment in which a material-conveying, inner rotary member operates at slower speed than a drive-end-supported, outer rotary member.

(2) The provision of improved centrifuges incorporating a cycloid drive having two concentric output shafts wherein the inside shaft rotates at a slower speed.

(3) The provision of cycloid-driven screening centrifuges wherein the helix of the centrifuge is connected to the cycloid cage and wherein the conical screen support of the centrifuge is connected to rotate with the cycloid discs.

(4) The provision of screening centrifuges, which have bottom-supported, differentially-faster cones, which are more compact than those of the prior art.

(5) The provision of cycloid-driven screening centrifuges having bottom-supported, differentially-faster cones.

These and other objects of the present invention will become more fully apparent from the following description and appended claims when read in conjunction with the accompanying drawings in which:

FIGURE 1 is a schematic section of a screening centrifuge in which the cycloid drive arrangement of the present invention has been incorporated.

FIGURE 2 is a vertical section showing the structure of the rotor and of the drive and housing assembly of the centrifuge of FIGURE 1.

FIGURE 3 is a vertical section through the cycloid drive of FIGURE 1.

Referring to the drawings, a screening centrifuge is shown to illustrate an exemplary application of the present invention. However, it should be understood that the present invention is not limited in its application to the particular centrifugal apparatus disclosed.

Referring to FIGURE 1, screening centrifuge It) has an inlet opening 12 for feeding process material to a rotor 11 as indicated by arrows 14. The feed material passes to an annular conical space 16 in the rotor between a rapidly rotating perforated cone or screen support 18, which carries a conical screen (not shown) on its interior surface, and a rotating conveyor or helix 20. The rotation of cone 18 urges the process material against the screen. The screen retains one portion of the feed material, for example solids, while another portion of the feed material, for example a liquid, is centrifugally forced through the screen as indicated by arrows 22. The liquid is collected in one or

more chambers

24, 26, and 28 of a centrifuge housing 30. The liquid or effluent which passes through cone 18 is discharged from the

housing chambers

24, 26, and 28 through

respective effluent outlets

32, 34, and 36 as indicated by arrows 38. The material retained within cone 18 is conveyed axially downwardly by the action of helical vanes 40 on helix which rotates in the same direction as cone 18 but at a slightly lower speed as fully described hereinafter. The solids are finally discharged from rotor 11 through openings 42 as indicated by arrows 44 and are collected in a solids chamber 46 of housing to be finally discharged through housing opening 48 as indicated by arrow 50.

As shown generally in FIGURE 1, a drive and housing assembly 58 includes a fixed, double-cone-shaped, support housing 60 having

annular bearing assemblies

62 and 64. An annular outer shaft assembly 66 is mounted to rotate within

bearings

62 and 64 and is connected to the lower, wide end of cone 18. A concentric inner shaft assembly 68 connected to the upper end of helix 20 is mounted by

bearing assemblies

70 and 72 to rotate coaxially within outer shaft assembly 66.

The lower ends of

shaft assemblies

66 and 68 are separately connected to a cycloid drive which is completely described hereinafter. The cycloid drive is powered by a belt pulley 82 which is in turn driven by a belt or belts 84 (FIGURE 2) which extend from a power source such as a motor (not shown) into housing 30 (FIGURE 1) through a suitable belt opening 85.

Cycloid drive unit 80 further includes an eccentric shaft 86 which is suitably connected to housing 30. It is known to be desirable in some instances to incorporate a torque limiting device between the eccentric shaft and the housing and in other instances to rotate the eccentric shaft so as to vary the differential speed relation of the output shafts of the drive. However, these variations are not shown as they form no part of the present invention.

As shown in greater detail in. FIGURE 2, rotor 11 includes annular rings 91) and 92 suitably secured to the upper open end of cone 18 to form feed inlet opening 12. Cone 18 is formed by a conical member 94 which has a plurality of openings 96 therein for passage of effluent to the fluid chambers surrounding the cone. The cone is secured by screws 98 to a ring 108 containing the solids apertures 42. The ring is in turn secured by screws 102 to a cone hub 184, and the hub is non-rotatably connected to a hollow shaft 186 of outer shaft assembly 66 by any suitable means such as cap screws (not shown).

Still referring to FIGURE 2, helix 20 includes a lower conical portion 110 secured by a key 114 to rotate with a shaft 112 of inner shaft assembly 68. An upper conical portion 116 of the helix is connected to lower portion 110 by cap screws 118 and pins 120. In the particular embodiment illustrated, helix 20 of the screening centrifuge is provided with two series of

passages

122, 124 and 126, 128, 130, 132 to supply a wash fluid or fluids from concentric wash

fluid feed pipes

134 and 136 to the material being processed in the rotor.

Outer shaft assembly 66 further includes a bearing spacer 140 between

bearings

62 and 64, retaining assembly 146 for hearing 70, and a lock nut assembly 148 to retain bearings 62 as well as bearing spacer 140 and bearings 64 in place. Inner shaft assembly 68 is provided with an oil sealing arrangement 142 between cone hub 104 and inner shaft 112 and a lock nut assembly 144 to retain bearing 70 on shaft 112. Support housing 60 includes a seal assembly 150 to provide a seal between the stationary housing and the rotating hub 184. Housing 60 is further provided with a retainer 152 to maintain bearings 64 in position.

Referring to FIGURES 2 and 3, eccentric shaft 86 is suitably mounted 'by a connector (FIGURE 2) to housing 30 of the screening centrifuge. At the upper end of eccentric shaft 86, two

eccentric surfaces

162 and 164 are formed on eccentric 166 which is non-rotatably mounted on shaft 86 by key 168. Eccentric 166 is retained in position on the eccentric shaft by lock nut assembly 178. An oil seal assembly 172 is mounted on the extreme upper end of the eccentric shaft 86 to form a seal between the eccentric shaft and the inner surfaces 174 of the recessed lower end of inner shaft 112.

Referring now to the pulley driving arrangement for cycloid drive 80, pulley 82 is non-rotatably mounted by a key on an annular shaft 182 formed on a lower extension 184 of outer shaft assembly 66. Shaft 182 is mounted for rotation upon eccentric shaft 86 by bearings 184 (FIGURE 2) and 186 (FIGURE 3). Extension 184 of the outer shaft assembly is provided at its upper end with a retainer 187 for hearing 186, and further includes a generally disc-like portion 188 integral with shaft 182. Disc-like portion 188 has a plurality of cycloid disc pins 190 fixedly mounted therein. Upper and

lower cycloid discs

192 and 194 are mounted for rotation about

eccentric surfaces

162 and 164, respectively, by roller bearmgs 196. Each cycloid disc has a plurality of circular apertures 198 therethrough, the number of apertures in each disc being equal to the number of disc pins 190. Plus 190 are each equipped with a bushing 200 which has an outside diameter which is smaller than the inside diameter of the apertures 198 by twice the amount of crank throw of the eccentric surfaces. This clearance permits the cycloid discs and the lower unit 184 of the outer shaft assembly to rotate together about different axes at the same speed, that is, one for one.

At the toothed or cycled external peripheries 202 and 264 of

cycloid discs

192 and 194, respectively, the discs engage a plurality of cage pins 206 mounted in the cycloid cage 288. A retainer 210 to maintain the cycloid discs in position is secured to cycloid cage 288 by cap screws (not shown). Cage 208 is non-rotatably secured to a lower disc-like, integral portion 214 of inner shaft 112 as by cap screws 216.

Lower extension 184 of outer shaft assembly 66 is secured by cap screws 220 to a cup-like housing 222 which is formed integrally with outer shaft 106. Cup-like portion 222 is further provided with a cylindrical flange 224 spaced from the outer periphery thereof to cooperate with an upstanding cylindrical flange 226 (FIGURE 2) secured on housing 60 to form a seal to keep oil from the drive head from entering the pulley area.

In operation, pulley 82 is driven by belt 84 and directly rotates cycloid disc pins 190 as well as the outer shaft assembly 66 which is directly connected to cone 18. Revolution of disc pins 190 forces cycloid

discs

192 and 194 to rotate about the eccentric axes of

eccentrics

162 and 164. The engagement of the cycles on the external periphery of the cycloid discs with cage pins 206 forces ca-ge 208 to rotate at an angular velocity determined by the following equation:

Where W is the angular velocity of the eccentric; W2 is the angular velocity of the cycloid disc; W3 is the angular velocity of the cycloid cage; P is the number of teeth or cycles on the cycloid disc; and S is the number of teeth or pins on the cycloid cage. With the eccentric stationary (ti/ since P is necessarily less than S, W3 will be less than W2. Therefore, the cage 208 and inner shaft assembly 63 rotate at a lower speed (W3) than does the outer shaft assembly (W2).

Thus, the present invention accomplishes a slower differential rotation of the helix in a screening centrifuge without the necessity and the consequent disadvantages of suspending the cone from its upper end.

Although the eccentric has been described as being fixed or stationary, it should be noted that without substantial modification of the specific embodiment disclosed, it can be made to rotate so as to vary the differential speed relation between the helix and cone according to the above equation. Therefore, the term speed-controlled eccentric is sometimes used below to describe this type of eccentric. As specifically disclosed herein, the speed may be controlled to be zero.

Although the present invention has been described as applied in a screening centrifuge, it should be understood that the invention is not so limited. For example, drive units of the present invention can advantageously be utilized in a so-called centrifugal decanter of a type known in the art wherein the outer rotary member is substantially imperforate and has within it a helical conveyor.

As this invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, the present embodiment is illustrative and not restrictive. The scope of the invention is defined by the appended claims rather than by the description preceding them, and all changes which fall within the metes and bounds of the claims, or which are their functional as well as conjointly cooperative equivalents, are therefore intended to be embraced by those claims.

I claim:

1. In a centrifugal processing apparatus having an outer rotary member, a coaxial inner rotary member, and a coaxial, diiferential-speed cycloid drive unit at the discharge end of said rotary members having an eccentric, a cycloid disc mounted about said eccentric, a cycloid cage engaging the periphery of said disc, first means coaxial with said outer rotary member and connecting said outer rotary member at the discharge end thereof to said disc to rotate one for one therewith, and second means connecting said cycloid cage to said inner rotary member.

2. A combination as defined in claim 1 together with means for drivingly rotating said outer rotary member by an external source of power.

3. A combination as defined in claim 1 wherein said respective first and second connecting means are outer and inner coaxial shafts, respectively.

4. A cycloid-driven centrifugal apparatus having an outer rotary member, an inner rotary member, and a cycloid drive having an accentric, a cycloid disc rotatably mounted about said eccentric, and a cycloid cage en gaging the periphery of said disc, characterized by:

(a) means for driving said outer rotary member;

(b) means connecting said outer rotary member to said cycloid disc to rotate one for one therewith;

(c) and means connecting said cycloid cage to said inner rotary member to rotate said inner rotary member at a differentially slower speed than said outer rotary member.

5. In a centrifugal apparatus having an outer rotary member for exerting centrifugal force upon a material being processed and an inner rotary member for conveying material axially within the outer member, an improved cycloid drive located at one end of said rotary members and having a central axis coaxial with said inner and outer members for rotating them at differential speeds comprising:

(a) an eccentric;

(b) a cycloid disc mounted for rotation about said eccentric;

(c) rotary disc-engaged means connected to said cycloid disc to rotate one for one therewith;

(d) a cycloid cage mounted for rotation about the central axis of said drive unit and engaged with the periphery of said eccentrically mounted cycloid disc for differential rotation therewith;

(e) a first shaft means connecting said cycloid cage to said inner rotary member; and

(f) a second shaft means connecting said rotary discengaged means to the drive proximate end of said outer rotary member.

6. A combination as defined in claim 5 together with means for drivingly rotating said rotary disc-engaged means.

7. A combination as defined in claim 5 wherein said second shaft 'means is annular and encompasses said cycloid cage and said first shaft means.

8. In a centrifugal apparatus having an outer rotary member, a coaxial inner rotary member, and a coaxial diiferential speed cycloid drive at the discharge end of said rotary member, having an eccentric, a cycloid disc rotatably mounted on said eccentric, and a cycloid cage engaging the external periphery of said disc characterized by:

(a) a first set of concentric inner and outer shafts extending axially from one side of said drive;

(b) a second set of inner and outer concentric shafts extending axially from the other side of said drive;

(c) said inner shaft of said first set being fixedly connected to said accentric;

(d) means connecting said outer shaft of said first set with said cycloid disc to rotate one for one therewith;

(e) said inner shaft of said second set being fixedly connected to said cycloid cage and being adapted for connection at its drive-remote end to one rotor of the centrifugal apparatus;

(f) and said outer shaft of said second set being fixedly connected around said cycloid cage to said outer shaft of said first set and being adapted for connection at its drive-remote end to the other rotor of the centrifugal apparatus.

9. For use in a coaxial-dual-rotor centrifugal apparatus,

a cycloid drive having an eccentric, a cycloid disc rotatably mounted on said eccentric, and a cycloid cage engaging the external periphery of said disc characterized by:

(a) a first set of concentric inner and outer shafts extending axially from one side of said drive, said outer shaft being adapted to be driven by a powered means;

(c) said inner shaft of said first set being fixedly connected to said eccentric;

(d) means connecting said outer shaft of said first set with said cycloid disc to rotate one for one there- With;

References Cited UNITED STATES PATENTS Lindenburg 74-805 Cullen 74-801 Van Riel 210-374 Boerdijk 74-675 Linke et a1. 210-147 Hils et a1. 74-805 10 MARTIN P. SCHWADRON, Primary Examiner.

DAVID J. WILLIAMOWSKY, Examiner.

R. F. HESS, Assistant Examiner.

Claims

1. IN A CENTRIFUGAL PROCESSING APPPARATUS HAVING AN OUTER ROTARY MEMBER, A COAXIAL INNER ROTARY MEMBER, AND A COAXIAL, DIFFERENTIAL-SPEED CYCLOID DRIVE UNIT AT THE DISCHARGE END OF SAID ROTARY MEMBERS HAVING AN ECCENTRIC, A CYLOID DISC MOUNTED ABOUT SAID ECCENTRIC, A CYCLOID CAGE ENGAGING THE PERIPHERY OF SAID DISC, FIRST MEANS COAXIAL WITH SAID OUTER ROTARY MEMBER AND CONNECTING SAID OUTER ROTARY MEMBER AT THE DISCHARGE END THEREOF TO SAID DISC TO ROTATE ONE FOR ONE THEREWITH, AND SECOND MEANS CONNECTING SAID CYCLOID CAGE TO SAID INNER ROTARY MEMBER.