JPH06134344A - Rotor for centrifugal separator - Google Patents

Abstract

PURPOSE:To provide a mechanical accelerator preventive device as a safety device for preventing destruction when a rotor for an ultrahigh speed centrifugal separator is rotated at a speed above the permissible rotating speed. CONSTITUTION:This rotor consists of semi-cylindrical members 8 which has inside-diameter parts fitting to the outside diameter of the outer peripheral part of the rotor 1 and have through-holes penetrating from the outside-diameter part to the inside-diameter part as plural mechanical members in the outer peripheral part of the rotor, plural bolts which have contracted parts between the head parts and the threaded parts at the front ends and screw holes 6 which fit to the respective through-holes of the semi-cylindrical members. The semi- cylindrical members are directly screwed and fixed by means of the bolts to the outer peripheral part of the rotor for the centrifugal separator. The semi- cylindrical members and the head parts of the bolts disengage from the rotor when the bolts are broken. The rotor is brought into an unbalance state by this disengagement and is disengaged from a revolving shaft.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotor for an ultra-high speed centrifuge, and more particularly to a safety device which prevents damage to the rotor when the rotor is rotated beyond its allowable rotation speed.

[0002]

2. Description of the Related Art An ultra high speed centrifuge has a mass of 3 to 20 k.
Various rotors having a rotation speed of 20,000 to 100,000 rpm are prepared according to the application. The rotor is made of high strength aluminum alloy or titanium alloy material. Each of these rotors has a permissible rotational speed determined by the manufacturer,
In addition, the usable number of times of use life is also defined, and the user can safely use it by observing it. If the rotation speed exceeds these permissible rotation speeds, or if the rotation life is exceeded, the rotor will break and the centrifuge will be damaged. However, there is a possibility that a large amount of destructive energy may threaten the safety of the user. In addition, it is technically clear that as the ratio of the number of uses to the life of the number of uses increases, the breakage rotation speed when the rotor rotates beyond the allowable rotation speed decreases compared to that of a new rotor. is there.

In order to prevent this, in an ultra-high speed centrifuge, an electric or mechanical acceleration prevention device is often provided as a part of the centrifuge machine or the rotor, which allows the rotor to have its permissible rotation speed. You will be safely stopped when you cross. Such safety devices include electric acceleration preventing devices as described in JP-B-44-23889, JP-B-51-137160 and JP-B-59-5.
The mechanical acceleration prevention device described in No. 00009. In addition, as a measure for the number of times of use life, a usage record is made for the user every time the rotor is used,
It has been attempted to prevent the rotor from being destroyed by obliging to manage the number of times of use.

[0004]

However, there is a possibility that the electrical acceleration prevention device does not operate due to a failure of the electric circuit. As a result, the rotor may be rotated beyond the allowable number of rotations, leading to destruction. In that respect, the members are mechanically destroyed by centrifugal force as shown in Japanese Utility Model Publication No. 51-137160 and Japanese Utility Model Publication No. 59-500009.
The method of forcibly disengaging the rotor from the rotating shaft is excellent in accuracy. However, in this method, only one member is destroyed and activated, and there is difficulty in reliability of operation. For example, it is conceivable that the operating speed varies due to variations in material strength of working members and variations in processing accuracy, and the variations are expected to increase. Such variations are problematic for the purpose of safely stopping the rotor. In particular, in recent years, the performance of rotors has advanced, and the difference between the permissible rotation speed and the breaking rotation speed has become smaller, and a highly reliable product that reliably operates in this small range is required. Further, the mechanical members disclosed in Japanese Utility Model Publication No. 51-137160 and Japanese Utility Model Publication No. 59-500009 have the drawbacks that the shape is complicated and the processing is not easy. Also,
No measures are taken to reduce the breakdown rotation speed when the rotor rotates beyond the allowable rotation speed each time the rotor is used more times.

An object of the present invention is to provide a mechanical acceleration preventing device which is highly reliable, easy to manufacture and inexpensive to provide.

[0006]

In order to achieve the above object, a rotor for a centrifuge according to the present invention has a plurality of mechanical members on the outer peripheral portion of the rotor so that the rotor is rotated so as not to impair the rotational balance of the rotor. Installed symmetrically around the axis. The mechanical member includes a semi-cylindrical member having an inner diameter portion adapted to the outer diameter of the outer peripheral portion of the rotor and a stepped hole penetrating from the outer diameter portion to the inner diameter portion, and a screw portion at the head and the tip. A rotor for a centrifuge, which comprises a plurality of bolts having a constricted portion between them and a screw hole on the outer peripheral portion of the rotor that fits in each of the stepped holes of the semi-cylindrical member. It is achieved by directly screwing and fixing the outer peripheral portion of the. Further, in the relationship between the metal fatigue characteristics of the material of the bolt having the constriction between the head portion and the threaded portion of the tip and the metal fatigue characteristics of the material of the rotor body, a fatigue curve showing the relationship between load and fatigue life Is achieved by using a smaller material for the bolt.

[0007]

In the mechanical member constructed as described above,
The dimensions of each part of the semi-cylindrical member and the bolt are determined by the permissible rotational speed and size of the rotor to be mounted. In the mechanical member, centrifugal force is applied to the semi-cylindrical member and the bolt by the rotation of the rotor, resulting in a load that breaks the necked portion of the bolt, and by appropriately adjusting the dimensions of the necked portion of the bolt. The number of revolutions at which this breaks can be determined. When the bolt breaks, the semi-cylindrical member and the head of the bolt separate from the rotor. By this departure. The rotor becomes unbalanced and disengages from the rotating shaft. Further, by using the material of the bolt having the constriction between the head portion and the threaded portion of the tip as described above, the inclination of the fatigue curve showing the relationship between load and fatigue life is smaller than that of the material of the rotor body. The bolt can be destroyed before the rotor is repeatedly used many times.

[0008]

1 is a partial vertical cross-sectional view showing an embodiment of the present invention. In FIG. 1, a rotor 1 detachably attached to a rotary shaft 7 has a plurality of test tube storage holes 2, and an O-ring 4, a cover 3 and a handle for sealing the test tube storage hole portion 2 on the upper part. 5 is attached. On the outer peripheral surface of the lower part of the rotor, two semi-cylindrical members 8 having an inner diameter portion 10 matching the outer peripheral surface are symmetrically engaged with the central axis of the rotor and fixed by bolts 9. FIG. 2 is a top view of the semi-cylindrical member 8 and the bolt 9 according to the embodiment of the present invention. In the embodiment constructed as described above, when the rotor 1 rotates, a centrifugal force acts on the semi-cylindrical member 8 and the bolt 9 attached to the lower portion of the rotor, and a load outward is applied. The bolt 9 has a structure that opposes this centrifugal load. When the breaking load of the constricted part 14 of the semi-cylindrical member 8 and the bolt 9 that are symmetrically attached becomes equal to the centrifugal load. The necked portion 14 is broken, and the semi-cylindrical member 8 is separated from the rotor 1 outward. At this time, since the one semi-cylindrical member 8 and the bolt 9 are still attached to the rotor 1,
Reaches an unbalanced state and immediately disengages from the rotary shaft 7. Since the two semi-cylindrical members 8 engaged with each other and the bolt 9 are rarely broken at the same time, the above-described rotor 1 disengaging operation is surely performed. Also, the semi-cylindrical member 8 and the bolt 9
By engaging two of the two, the breakage probability is double that of the two members, and the reliability is increased. Therefore, it is naturally conceivable to increase the number of these safety element members (8, 9) to two or more, and the reliability can be further improved by increasing the number. Here, in order for the rotor 1 to break the constricted portion 14 of the bolt 9 at a predetermined rotational speed exceeding the permissible rotational speed, the mass of the semi-cylindrical member 8 and the position of the center of gravity in the radial direction, the rotational speed, the head of the bolt 9 are used. The centrifugal load calculated by the mass of the portion 12 and the position of the center of gravity in the radial direction may be equal to the breaking load obtained from the material strength of the bolt 9 and the dimension of the constricted portion 14, and the dimension of the constricted portion 14 may be changed. An arbitrary breaking speed can be obtained by changing the speed. Since the safety element member has a simple structure, it can be easily processed at low cost. FIG. 3 is a graph showing fatigue characteristics of the example of the present invention. In FIG. 3, the vertical axis represents the load, and the horizontal axis represents the number of metal fatigue fracture cycles. The solid line in the graph is the fatigue curve 15 of the rotor material, and the dotted line is the fatigue curve 16 of the bolt material.
Is represented. The slope of the fatigue curve 16 of the bolt material is shown to be smaller than that of the fatigue curve 15 of the rotor material.
If the rotor and bolt are designed to have the same breaking life at point B in the graph, the breaking load of the bolt will be lower than the breaking load of the rotor during use from point A to point B. . Applying this relationship to the above-mentioned actual usage conditions of the rotor, it can be understood that the bolt will break earlier if the rotor exceeds the allowable number of revolutions at any number of uses up to the service life of the rotor. See. As the actual material, when the rotor material is titanium alloy, the bolt material is smaller than the fatigue curve slope titanium alloy,
High strength aluminum alloy is suitable.

[0009]

According to the present invention, since a plurality of safety elements having a simple structure are provided below the rotor, the operation probability is improved, and it can be realized easily and at low cost. In addition, as a measure against the decrease in the breaking rotation speed when the rotor rotates more than the allowable rotation speed each time the rotor is used many times, the slope of the fatigue curve of the material of the bolt in the safety element is It can be solved by using a smaller one.

[Brief description of drawings]

FIG. 1 is a partial vertical sectional view showing an embodiment of the present invention.

FIG. 2 is a top view of a semi-cylindrical member and a bolt showing an embodiment of the present invention.

FIG. 3 is a graph showing fatigue characteristics of an example of the present invention.

[Explanation of symbols]

1 is a rotor, 2 is a test tube housing hole, 3 is a cover, 4 is an O-ring wall, 5 is a handle, 6 is a screw hole, 7 is a drive shaft, 8 is a semi-cylindrical member, 9 is a bolt, 10 is an inner diameter portion. , 11 is a through hole, 12 is a head, 13 is a threaded portion, 14 is a constricted portion, 15
Is a fatigue curve of the rotor material, and 16 is a fatigue curve of the bolt material.

Claims (2)

[Claims] 1. A centrifuge rotor having a structure which is detachably attached to a rotor rotation shaft and has a test tube housing hole for housing a large number of centrifuge test tubes. A semi-cylindrical member having an inner diameter portion that matches the outer diameter of the outer diameter portion and a hole that penetrates from the outer diameter portion to the inner diameter portion is arranged symmetrically with respect to the center axis of the rotor, and the head and the tip are arranged. A bolt having a constriction between the screw and the screw is engaged with the through hole of the semi-cylindrical member to directly screw the semi-cylindrical member into a screw hole provided in the outer peripheral portion of the centrifuge rotor. A rotor for a centrifuge, which is fixed by mixing. 2. A relationship between a load and a fatigue life in a relationship between a metal fatigue characteristic of a material of a bolt having a neck portion between a head portion and a screw portion of a tip and a metal fatigue characteristic of a material of a rotor body. The centrifuge rotor according to claim 1, wherein the material of said bolt has a smaller fatigue curve slope.