GB2146784A - Centrifuge including an out of balance detector - Google Patents

Abstract

The centrifuge comprises a fixibly electrically conducting rotor shaft (1), an electrically conducting annulus (8) surrounding, but spaced from a portion (7) of the shaft (1) and means for applying an electrical potential between the annulus (8) and the shaft (1). The detector is actuated by current flow caused by contact between the shaft (1) and the annulus (8). <IMAGE>

Description

SPECIFICATION Centrifuge including an out of balance detector This invention relates to a centrifuge including an out of balance detector.

Centrifuges are conventionally made with flexible rotor shafts so that when rotated they will take account of small imbalances in the sample or in the sample loading and will automatically centre themselves. However, if there is some gross imbalance in the loaded rotor, usually through incomplete or faulty loading, the rotor and the whole centrifuge will wobble. Such wobbling, if permitted to continue, would cause damage to both the materials being centrifuged and also the centrifuge itself. It is therefore necessary and conventional to detect any substantial out of balance and preferably for the detection mechanism to actuate a close down of the centrifuge.

We have now found an improved out of balance detector for a centrifuge.

According to the invention there is provided a centrifuge including an out of balance detector, the centrifuge comprising a flexible electrically conducting rotor shaft, an electrically conducting annulus surrounding, but spaced from, a portion of the shaft, means for applying an electrical potential between the annulus and the shaft, such that contact between the shaft and the annulus causes current to flow, the detector being actuable by the current flow.

The shaft may be of conventional construction and contains a mounted portion, e.g.

mounted in rotor shaft bearings. The electrical potential may be applied to or transmitted from the shaft through bearings or through brushes.

The detector may be, for example, an ammeter or an indicator light. The detector is preferably operable linked to actuate braking means on actuation of the detector.

The annulus is preferably mounted as far as is reasonably possible away from the mounted portion of the shaft, i.e. at a position where the flexing of the shaft is at a maximum when the rotor is out of balance. The annulus preferably surrounds an end portion, e.g. the rotor end portion, of the shaft. The annulus may be supported on a tube surrounding the rotor shaft, but the spacing between the shaft and the annulus should be less than between the tube and the shaft. The spacing between the annulus and the shaft should be sufficiently great to accommodate normal running of the centrifuge without electrical contact being made, but should not be so great that damaging out of balance running of the centrifuge can continue without the desired electrical connection being made.A satisfactory spacing will depend on the particular configuration of the shaft and annulus, but is preferably from 0.5 to 5mm, more preferably 1 to 3mm.

A preferred embodiment of the invention will now be illustrated with reference to the accompanying drawing, which is a side elevation, in partial section, of a centrifuge rotor shaft including an out of balance detector.

Referring to the figure, a flexible electrically conducting rotor shaft 1 is mounted in electrically conducting lower and upper rotor shaft bearings (2 and 3 respectively) in an electri cally conducting housing 4. The shaft 1 is driven by a drive pulley 5 attached by means of a screw 6 to the lower end of shaft 1. The upper end of the shaft 1 is provided with means for mounting a centrifuge rotor (not shown).

An electrically conducting annulus 8 mounted on an electrically conducting tube99 surrounds the upper end portion 7 of the shaft 1. The annulus 8 and tube 9 are spaced from the shaft 1 so that no contact is made between the shaft 1 and parts 8 and 9 when the rotor is running acceptably. The lower end of the tube 9 is mounted in a tubular insulating sleeve 10 which is supported by the housing 4. Electrical leads 11, 1 2 are provided for applying a potential between the annulus 8 and the shaft 1.

In operation, the shaft 1 is rotated by drive means coupled to the pulley 5. Provided that this rotation is acceptably in balance no contact is made between shaft 1 and annulus 8.

However, if the centrifuge is out of balance, shaft 1 will flex and touch against annulus 8 completing an electric circuit from the shaft 1, through the bearings 2 and 3, the housing 4 and lead 1 2 and annulus 8, tube 9 and iead 11. Flow of current in the circuit is detected by conventional circuitry, eg., an ammeter, and may be used to actuate drive disengagement means and/or braking means.

1. A centrifuge including an out of balance detector, the centrifuge comprising a flexible electrically conducting rotor shaft, an electrically conducting annulus surrounding, but spaced from a portion of the shaft, means for appiying an electrical potential between the annulus and the shaft, such that contact between the shaft and the annulus causes current to flow, the detector being actuable by the current flow.

2. A centrifuge according to Claim 1, wherein the detector is operably linked to actuate braking means on actuation of the detector.

3. A centrifuge according to Claim 1 or Claim 2, wherein the annulus surrounds an end portion of the shaft.

4. A centrifuge according to any one of the preceding claims, wherein the spacing between the shaft and annulus is from 0.5 to 5mm.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Centrifuge including an out of balance detector This invention relates to a centrifuge including an out of balance detector. Centrifuges are conventionally made with flexible rotor shafts so that when rotated they will take account of small imbalances in the sample or in the sample loading and will automatically centre themselves. However, if there is some gross imbalance in the loaded rotor, usually through incomplete or faulty loading, the rotor and the whole centrifuge will wobble. Such wobbling, if permitted to continue, would cause damage to both the materials being centrifuged and also the centrifuge itself. It is therefore necessary and conventional to detect any substantial out of balance and preferably for the detection mechanism to actuate a close down of the centrifuge. We have now found an improved out of balance detector for a centrifuge. According to the invention there is provided a centrifuge including an out of balance detector, the centrifuge comprising a flexible electrically conducting rotor shaft, an electrically conducting annulus surrounding, but spaced from, a portion of the shaft, means for applying an electrical potential between the annulus and the shaft, such that contact between the shaft and the annulus causes current to flow, the detector being actuable by the current flow. The shaft may be of conventional construction and contains a mounted portion, e.g. mounted in rotor shaft bearings. The electrical potential may be applied to or transmitted from the shaft through bearings or through brushes. The detector may be, for example, an ammeter or an indicator light. The detector is preferably operable linked to actuate braking means on actuation of the detector. The annulus is preferably mounted as far as is reasonably possible away from the mounted portion of the shaft, i.e. at a position where the flexing of the shaft is at a maximum when the rotor is out of balance. The annulus preferably surrounds an end portion, e.g. the rotor end portion, of the shaft. The annulus may be supported on a tube surrounding the rotor shaft, but the spacing between the shaft and the annulus should be less than between the tube and the shaft. The spacing between the annulus and the shaft should be sufficiently great to accommodate normal running of the centrifuge without electrical contact being made, but should not be so great that damaging out of balance running of the centrifuge can continue without the desired electrical connection being made.A satisfactory spacing will depend on the particular configuration of the shaft and annulus, but is preferably from 0.5 to 5mm, more preferably 1 to 3mm. A preferred embodiment of the invention will now be illustrated with reference to the accompanying drawing, which is a side elevation, in partial section, of a centrifuge rotor shaft including an out of balance detector. Referring to the figure, a flexible electrically conducting rotor shaft 1 is mounted in electrically conducting lower and upper rotor shaft bearings (2 and 3 respectively) in an electri cally conducting housing 4. The shaft 1 is driven by a drive pulley 5 attached by means of a screw 6 to the lower end of shaft 1. The upper end of the shaft 1 is provided with means for mounting a centrifuge rotor (not shown). An electrically conducting annulus 8 mounted on an electrically conducting tube99 surrounds the upper end portion 7 of the shaft 1. The annulus 8 and tube 9 are spaced from the shaft 1 so that no contact is made between the shaft 1 and parts 8 and 9 when the rotor is running acceptably. The lower end of the tube 9 is mounted in a tubular insulating sleeve 10 which is supported by the housing 4. Electrical leads 11, 1 2 are provided for applying a potential between the annulus 8 and the shaft 1. In operation, the shaft 1 is rotated by drive means coupled to the pulley 5. Provided that this rotation is acceptably in balance no contact is made between shaft 1 and annulus 8. However, if the centrifuge is out of balance, shaft 1 will flex and touch against annulus 8 completing an electric circuit from the shaft 1, through the bearings 2 and 3, the housing 4 and lead 1 2 and annulus 8, tube 9 and iead 11. Flow of current in the circuit is detected by conventional circuitry, eg., an ammeter, and may be used to actuate drive disengagement means and/or braking means. CLAIMS

1. A centrifuge including an out of balance detector, the centrifuge comprising a flexible electrically conducting rotor shaft, an electrically conducting annulus surrounding, but spaced from a portion of the shaft, means for appiying an electrical potential between the annulus and the shaft, such that contact between the shaft and the annulus causes current to flow, the detector being actuable by the current flow.

2. A centrifuge according to Claim 1, wherein the detector is operably linked to actuate braking means on actuation of the detector.

3. A centrifuge according to Claim 1 or Claim 2, wherein the annulus surrounds an end portion of the shaft.

4. A centrifuge according to any one of the preceding claims, wherein the spacing between the shaft and annulus is from 0.5 to 5mm.

5. A centrifuge including an out of balance detector substantially as herein described and with reference to the accompanying drawing.