GB1588373A

GB1588373A - Centrifuges

Info

Publication number: GB1588373A
Application number: GB7555/78A
Authority: GB
Original assignee: Heraeus Christ GmbH
Current assignee: Heraeus Sepatech GmbH
Priority date: 1977-02-24
Filing date: 1978-02-24
Publication date: 1981-04-23
Also published as: DE7705563U1

Description

(54) IMPROVEMENTS IN OR RELATING TO CENTRIFUGES (71) We, HERAEUS-CHRIST GmbH, a German body corporate of Gipsmuhlenweg 62, 3360 Osterode/Harz, Lauten, Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to centrifuges of the kind having interchangeable rotors.

A non-releasable, positive coupling has already been described in German Offenlegungsschrift 23 28 983, U.S. patent specification No: 3961745 also discloses a coupling between a rotor and drive shaft which operates on the same principle. With the known coupling it is still possible for relative movement to take place between the drive-transmitters and their companion members, although to a considerably lesser extent in the case of the subject of the German Offenlegungsschrift than in the case of the subject of the U.S. patent specification.

It is an object of the invention to provide a coupling affording positive torque transmission in which the rotor can be detachably connected for operating purposes to the drive shaft of a motor simply by placing it on the end of the shaft, in any desired position in the circumferential direction, and in which the transmission of power takes place without play.

Accordingly the invention consists in a centrifuge having a rotor which is detachably connected to the drive shaft of a motor by a two-part coupling, the drive shaft having a tapered portion, and wherein the coupling comprises a first part secured to the drive shaft and having at least one drive transmitting member therein for transmitting drive to said second part, and wherein said second part is housed within a recess in said rotor and has at least two pressure transmitting members therein which are biassed into engagement with the tapered portion of said drive shaft, and the coupling further including a member of resilient material interposed between said second part and a surface of the recess in which said second part is housed, said pressure members when the rotor is in position over the drive shaft being pressed by their cooperation with said tapered portions so as to transmit pressure radially to said recess surface via said member of resilient material.

The preferred manner of carrying out the invention has a variety of disadvantages.

The coupling is very simple to operate since it can be engaged merely by fitting the rotor onto the stub drive-shaft. There is no need for manipulation from the upper side of the rotor (as in the case of a clamping sleeve for example).

Since all relative movement is precluded, there is no slip and the whole of the torque to be transmitted is passed on even in the running-up phase.

In order that the invention may be more clearly understood, reference will now be made to the accompanying drawing which shows an axial section through one embodiment thereof by way of example.

Referring to the drawing there is shown the intermediate member of a coupling of a centrifuge according to the present invention. The coupling essentially comprises two parts, namely a part 1 secured to the drive shaft of the motor (not shown), and a part 2 which will be referred to below as the cagelike part. An end of the drive shaft which is thickened in compariton with the flexible part of the shaft, is marked 3, and engages in a corresponding central bore in the rotor 4 of the centrifuge. Parts 1 and 2 of the coupling are similarly accommodated in further central recesses in the rotor 4 whose diameters are greater than that of the end 3 of the drive shaft and which corresponds respectively to the outside diameters of the parts 1 and 2. Part 1 is permanently mounted on, e.g. shrunk onto, an end of the drive shaft adjacent the drive motor. .It contains drive-transmitting pins 8 which engage in part 2. Between parts 1 and 2, members such as cup springs 7 which are resilient in the longitudinal direction are arranged along a circular path around the drive shaft.

The drive-transmitting pins engage in corresponding bores in part 2.

At its erd vi < / most in the drawing, the art . . provided with a taper surface S. . r- .. miner 6, prefer- ably in layer form fizz cried or inset between part 2 and the surfaces of the recess in the rotor 4. This lir.=r may consist of rubber or another elastomer.

It is advantageous for the liner or inlay 6 to extend over the whole or almost the whole of the area of contact between part 2 and the recess surface in the rotor 4. The part of the liner 6 which lies radially beyond the circumference of part 2 is in contact with plungers 9 which are held in a horizontal position in the cage-like part 2 in such a way that their tapered heads 11 are pressed against a taper surface 12 formed on the drive shaft by coil springs 10 which surround them. The two taper surfaces 11 and 12 taper at the same angle. Taper surface 12 diverges in the direction of the drive motor.

The number of pressure plungers 9 is preferably even, but is at least two (only one being shown). The number of drive transmitting pins 8 is at least one and preferably two. troth must of course be distributed around the parts of the coupling circumferentially in such a way as not to interfere with one another. The taper heads 11 of the plungers 9 preferably lie opposite one another in the radial direction, although so that both a plunger 9 and a pin 8 can be shown in the same view the drawing does not show this arrangement. The heads 11 of the plungers 9 are contained in a recess 13 in part 2 of the coupling which is approximately cylindrical and whose centre axis coincides with the centre axis of the drive shaft. Part 2 rests against or is guided on the thickened end 3 of the drive shaft by the segment 14 of the shaft which extends above the recess 13.

The embodiment just described operates as follows:- The rotor is placed vertically onto the coupling from above with the end 3 of the drive shaft located axially within its central recesses and with the line 6 resting against part 2 of the coupling. Under its own weight the rotor 4 presses down on the cage-like part 2 via the taper surface 5, part 2 being vertically displaceable in relation to part 1.

At the time of the coupling the cup springs 7 are compressed and by means of the taper surfaces 11 and 12 the coupling forces are transmitted from the drive shaft radially via the plungers 9 to the rotor via the liner 6.

The wedge action of the taper surface 12 provides an effective increase in the pressure with which the plungers are forced into the rubber liner 6 by the weight of the rotor.

Thus, the torque from the drive motor is transmitted via the shaft, the part 1, the drive transmitting pins 8, the taper surfaces 11 and 12, the plungers 9 and the liner 6 to the rotor 4. The springs 10 on the plungers 9 are of a size such that the taper surfaces of the plungers are always pressed against the taper surface of the drive shaft.

To remove and uncouple the rotor, it is withdrawn upwards with reference to the drawings. When this is done the cage-like part 2 travels upwards with it until, when the cage-like part 2 is in its uppermost limiting position, the heads 11 of the plungers 9 are forced back by the springs 10 into the recesses 13.

As can be seen, the coupling according just described operates without the need for any additional manipulation of clamping or screw members and provides an easily operated detachable coupling for interchangeable centrifuge rotors.

WHAT WE CLAIM IS: 1. A centrifuge having a rotor which is detachably connected to the drive shaft of a motor by a two-part coupling, the drive shaft having a tapered portion, and wherein the coupling comprises a first part secured to the drive shaft and having at least one drive transmitting member therein for transmitting drive to said second part, and wherein said second part is housed within a recess in said rotor and has at least two pressure transmitting members therein which are biassed into engagement with the tapered portion of said drive shaft, and the coupling further including a member of resilient material interposed between said second part and a surface of the recess in which said second part is housed, said pressure members when the rotor is in position over the drive shaft being pressed by their cooperation with said tapered portion so as to transmit pressure radially to said recess surface via said member of resilient material.

2. A centrifuge as claimed in claim 1, wherein the pressure transmitting members are in the form of plungers whose ends adjacent the tapered portion of the drive shaft have a corresponding taper.

3. A centrifuge as claimed in claims 1 or 2, wherein the member of resilient material is applied to at least a radial region of the recess surface in the rotor which is in contact with said second part.

4. A centrifuge as claimed in any of the preceding claims, wherein said second part has a taper face whose centre axis coincides with the axis of rotation of the rotor.

5. A centrifuge as claimed in claim 5, wherein the said second part has a cylindrical recess which fits round the taper surface on the shaft.

6. A centrifuge as claimed in any of the preceding claims wherein members which are resilient in the axial direction are arranged between the two parts of the coupling.

7. A centrifuge as claimed in claim 6,

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. At its erd vi < / most in the drawing, the art . . provided with a taper surface S. . r- .. miner 6, prefer- ably in layer form fizz cried or inset between part 2 and the surfaces of the recess in the rotor 4. This lir.=r may consist of rubber or another elastomer. It is advantageous for the liner or inlay 6 to extend over the whole or almost the whole of the area of contact between part 2 and the recess surface in the rotor 4. The part of the liner 6 which lies radially beyond the circumference of part 2 is in contact with plungers 9 which are held in a horizontal position in the cage-like part 2 in such a way that their tapered heads 11 are pressed against a taper surface 12 formed on the drive shaft by coil springs 10 which surround them. The two taper surfaces 11 and 12 taper at the same angle. Taper surface 12 diverges in the direction of the drive motor. The number of pressure plungers 9 is preferably even, but is at least two (only one being shown). The number of drive transmitting pins 8 is at least one and preferably two. troth must of course be distributed around the parts of the coupling circumferentially in such a way as not to interfere with one another. The taper heads 11 of the plungers 9 preferably lie opposite one another in the radial direction, although so that both a plunger 9 and a pin 8 can be shown in the same view the drawing does not show this arrangement. The heads 11 of the plungers 9 are contained in a recess 13 in part 2 of the coupling which is approximately cylindrical and whose centre axis coincides with the centre axis of the drive shaft. Part 2 rests against or is guided on the thickened end 3 of the drive shaft by the segment 14 of the shaft which extends above the recess 13. The embodiment just described operates as follows:- The rotor is placed vertically onto the coupling from above with the end 3 of the drive shaft located axially within its central recesses and with the line 6 resting against part 2 of the coupling. Under its own weight the rotor 4 presses down on the cage-like part 2 via the taper surface 5, part 2 being vertically displaceable in relation to part 1. At the time of the coupling the cup springs 7 are compressed and by means of the taper surfaces 11 and 12 the coupling forces are transmitted from the drive shaft radially via the plungers 9 to the rotor via the liner 6. The wedge action of the taper surface 12 provides an effective increase in the pressure with which the plungers are forced into the rubber liner 6 by the weight of the rotor. Thus, the torque from the drive motor is transmitted via the shaft, the part 1, the drive transmitting pins 8, the taper surfaces 11 and 12, the plungers 9 and the liner 6 to the rotor 4. The springs 10 on the plungers 9 are of a size such that the taper surfaces of the plungers are always pressed against the taper surface of the drive shaft. To remove and uncouple the rotor, it is withdrawn upwards with reference to the drawings. When this is done the cage-like part 2 travels upwards with it until, when the cage-like part 2 is in its uppermost limiting position, the heads 11 of the plungers 9 are forced back by the springs 10 into the recesses 13. As can be seen, the coupling according just described operates without the need for any additional manipulation of clamping or screw members and provides an easily operated detachable coupling for interchangeable centrifuge rotors. WHAT WE CLAIM IS:

1. A centrifuge having a rotor which is detachably connected to the drive shaft of a motor by a two-part coupling, the drive shaft having a tapered portion, and wherein the coupling comprises a first part secured to the drive shaft and having at least one drive transmitting member therein for transmitting drive to said second part, and wherein said second part is housed within a recess in said rotor and has at least two pressure transmitting members therein which are biassed into engagement with the tapered portion of said drive shaft, and the coupling further including a member of resilient material interposed between said second part and a surface of the recess in which said second part is housed, said pressure members when the rotor is in position over the drive shaft being pressed by their cooperation with said tapered portion so as to transmit pressure radially to said recess surface via said member of resilient material.

7. A centrifuge as claimed in claim 6,

wherein the resilient members comprise cup springs which surround the drive shaft.

8. A centrifuge having a coupling substantially as hereinbefore described with reference to the accompanying drawing.