GB2097297A

GB2097297A - Rotor for use in centrifugal separators

Info

Publication number: GB2097297A
Application number: GB8211056A
Authority: GB
Original assignee: Hitachi Koki Co Ltd
Current assignee: Koki Holdings Co Ltd
Priority date: 1981-04-24
Filing date: 1982-04-16
Publication date: 1982-11-03
Also published as: DE3215138A1; GB2097297B; DE3215138C2; JPS57177359A

Abstract

A rotor for use in a centrifugal separator comprises a rotor shaft, a rotor body mounted on and extending around the rotor shaft, and a plurality of buckets mounted on the rotor body and angularly spaced at equidistant locations around the rotor shaft. The rotor body is made of a continuous fibrous composite material composed of continuous high- tensile fibers such as of glass, graphite, or boron impregnated with synthetic resin. The continuous high-tensile fibers extend between diametrically opposite pairs of the buckets across the rotor shaft, or between the rotor shaft and alternate buckets substantially in directions along which the rotor body is subjected to centrifugal forces. The rotor body includes a plurality of radial arms angularly spaced at equal intervals and supporting the buckets, respectively.

Description

SPECIFICATION Rotor for use in centrifugal separators The present invention relates to a rotor for use in a centrifugal separator.

Rotors for centrifugal separators serve to both hold thin-walled test tubes of plastics with samples contained therein and enable the supported test tubes to withstand pressures imposed by the samples while the latter are being subjected to centrifugal forces. Presently avilable rotors are made of alloys of aluminum or titanium and capable of withstanding centrifugal forces up to 580,000 G.

Rotor materials should have a large strengh as well as a small specific gravity, or a high specific tenacity. Titanium alloys have been found to be the best material for the rotors which meets the above requirement. Recent materials having higher specific tenacities than those of the titanium alloys include resins reinforced with high-tensile fibers such as glass fibers or graphite fibers. Such fiberreinforced resins, however, have not been put to use as rotors because they are difficult to be shaped to desired contour, lack uniformity in structure, and suffer from other difficulties.

The high-tensile fibers have an increased strength in their longitudinal direction, but are mechanically weak in the tranverse direction.

It is an object of the present invention to provide a rotor for centrifugal separators which can withstand greater centrifugal forces than conventional rotors could, is lightweight and less costly.

According to the present invention, a rotor for use in a centrifugal separator comprises a rotor body mounted on and extending around a rotor shaft, and a plurality of buckets mounted on the rotor body and angularly spaced at equidistant locations around the rotor shaft, the rotor body being made of a continuous fibrous composite material composed of continuous high-tensile fibers impregnated with synthetic resin and extending around the buckets and the rotor shaft substantially in directions along which the rotor body is subjected to centrifugal forces. The continuous high-tensile fibers may extend between diametrically opposite pairs of the buckets across the rotor shaft, or between the rotor shaft and alternate buckets. The rotor body includes a plurality of radial arms angularly spaced at equal intervals, the buckets being supported respectively on the radial arms.

Test tubes with samples contained therein are held respectively in the buckets which are supported on the fiber-reinforced rotor body at its radial arms against centrifugal forces imposed while the rotor is being rotated.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will now be described in detail with reference to the accompanying drawings, in which: Figure 1 is a vertical cross-sectional view of a rotor according to the present invention, Figure 2 is a plan view, partly cut away, of the rotor shown in Fig. 1, Figure 3 is a vertical cross-sectional view illustrative of a step of constructing the rotor of the present invention, Figure 4 is a schematic diagram showing a pattern in which high-tensile fibers are wound around buckets, Figure 5 is a perspective view of a bucket suitable for use in the rotor, and Figure 6 is a schematic diagram showing another pattern of winding high-tensile fibers.

DETAILED DESCRIPTION As shown in Fig. 1, a rotor R according to the present invention comprises a rotor shaft 1 having in its lower end a conical taper hole la which can be fitted over a spindle (not shown) of a centrifugal separator.The rotor shaft 1 is made of a material such as an alloy of aluminum or titanium capable of withstanding centrifugal forces to which the rotor is subjected. A bucket B is of a hollow cylindrical configuration having a chamber for receiving therein a test tube with a sample contained therein. The bucket B has a mechanical strength large enough to hold the test tube against centrifugal forces applied when the rotor R rotates. To this end, the rotor B is made of an alloy of titanium or a composite material composed of high-tensile fibers impregnated with synthetic resin.

A rotor body is mounted on and extends round the rotor shaft 1. The rotor body 2 is made of a continuous composite fibrous material composed of continuous high-tensile fibers such as of glass, graphite, or boron, and synthetic resin such as polyester or epoxy resin. The rotor body 2 includes a plurality of radial arms 2a angularly spaced at equal intervals and paired in diametrically opposite relation across the rotor shaft 1. A plurality of buckets B of the foregoing construction are supported respectively on the radial arms 2a of the rotor body 2. Thus, the buckets B as installed on the rotor body 2 are arranged in diametrically opposite pairs in symmetrical relation with respect to the rotor shaft 1. The buckets B extend at an angle to the axis of the rotor shaft 1. However, the buckets B may extend parallel to each other.

The rotor body 2 will be fabricated of the high-tensile fibers as follows: In Fig. 3, the rotor shaft 1 is fixed by a nut 6 in a central hole in a jig 3. Cores 4 are inserted respectively into the buckets B and secured to the jig 3 by nuts 7. The buckets B are affixed to the jig 3 by holder plates 5 which are fastened to the jig 3 by screws 8 in angularly equally spaced positions around the rotor shaft 1. The buckets B and the rotor shaft 1 are then successively fastened together by a continuous string of the high-strength fibers until the rotor body 2 is fabricated.

A pattern of winding such a continuous string around the buckets B and the rotor shaft 1 is shown in Fig. 4. Designated at B1 through B6 are buckets as fixed to the jig at angularly spaced locations. The high-tensile fiber string is fastened to a lower portion a of a winding shank 9 of the rotor shaft 1. Then, the string is wound around the bucket B1, brought to the diametrically opposite bucket B4 along the direction of the arrowhead b, past the rotor shaft 1, back to the bucket B1 along the direction of the arrowhead c. The string is wound alternately around the buckets B1, B4 several times to form a certain number of convolutions while the string is being kept under strong tension. Thereafter, the string is turned around the rotor shaft 1 toward the bucket B2 along the directions of the arrowheads d, e.The string is then coiled around the buckets B2, B5 along the directions of the arrowheads f, g for several convolutions. The string is directed along the directions of the arrowheads h, i toward the bucket B3 for being repeatedly wound around the buckets B3, B6. Subsequently, the string is brought back to the buckets B1, B4 to repeat the formation of convolutions. The string convolutions will be accumulated from the lower point a to an upper point w (Fig. 3) along the shank 9 at a rate dependent on the required mechanical strength of the rotor R. The later the outer diameter of the rotor R, the greater centrifugal forces the rotor R will undergo, and hence the larger the number of convolutions of the string around the buckets B.

Prior to winding around the buckets B, the high-tensile fibers that constitude the string are dipped in a container of synthetic resin such as polyester or epoxy resin until the fibers are impregnated with such synthetic resin. After a desired number of turns have been wound around the buckets B, the resultant assembly is heated and set, removed from the jig, whereupon the rotor R is completed. Since the dismetrically opposite buckets are interconnected by parallel fiber sections which are longitudinally highly resistant to centrifugal forces imposed while the rotor body 2 is rotating. Thus, the rotor body 2 is structured so as to utilize the mechanical strength of the fibers to a maximum degree.

Figure 5 shows the bucket B in detail. The bucket B has a flange 9 on one end thereof, and serrations such as parallel grooves 10 which serve to provide intimate contact with the rotor body 2 when the bucket B and the rotor body 2 are assembled together.

The rotor R shown in Fig. 2 has even buckets arranged in diametrically opposite pairs disposed across the rotor shaft. Where it is desired to form a rotor having odd buckets, high-tensile fibers impregnated with synthetic resin are wound around such buckets in a pattern as illustrated in Fig. 6. A string of such high-tensile fibers is first affixed to a lower portion a of a rotor shaft 1. The string is wound around a bucket B1 in the direction of the arrowhead b and directed back to the shaft 1. Then the string is coiled around an adjacent bucket B2 along the direction of the arrowhead c and brought back to the rotor shaft 1. The string is successively wound around succeeding buckets B3, B4, and B5 along the directions of fthe arrowheads d, e, and f, respectively. Such a winding pattern is followed a plurality of times until a desired shape of rotor body is produced. Thereafter, the synthetic resin impregnated in the hightensile fibers is set with heat applied.

Claims

1. A rotor for use in a centrifugal separator, comprising: a rotor shaft, a rotor body mounted on and extending around said rotor shaft; and a plurality of buckets mounted on said rotor body and angularly spaced at equidistant locations around said rotor shaft, said rotor body being made of a continuous fibrous composite material composed of synthetic resin and continuous high-tensile fibers extending around said buckets and said rotor shaft substantially in directions along which said rotor body is subjected to centrifugal forces.

2. A rotor according to claim 1, wherein said continuous high-tensile fibers extend between diametrically opposite pairs of said buckets across said rotor shaft.

3. A rotor according to claim 1, wherein said continuous high-tensile fibers extend between said rotor shaft and alternate buckets.

4. A rotor according to claim 1, wherein said rotor body includes a plurality of radial arms angularly spaced at equal intervals, said buckets being supported respectively on said radial arms.

5. A rotor according to any proceeding claim wherein said continuous high-tensile fibers are impregnated with synthetic resin.

6. A rotor for use in a centrifugal separator substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

7. A centrifugal separator including a rotor according to any preceding claim.