Laboratory centrifuge

A laboratory centrifuge for producing suspensions, sediments and the like, and for carrying out washing and similar processes, in which a motor-driven vertical shaft is arranged in a housing, said shaft carrying a shaft head on which magazines or such are pivotably mounted for receiving sample containers. The shaft head can be driven in either of two opposing directions and has two brackets arranged symmetrically to the axis of rotation the outwards extending arms of said brackets carrying an axle on which the magazines are pivotably mounted with axial play. The width of the magazines is slighter than the distance between the two bracket arms, and a locking device is present between the bracket arms and the magazines, becoming effective when the magazine abuts the respective bracket arm.

BACKGROUND OF THE INVENTION 
The present invention relates to a laboratory centrifuge for producing 
suspensions, sediments and the like, the carrying out of washing-and 
similar processes, in which a motor-driven vertical shaft is arranged in a 
housing, said shaft carrying a shaft head on which magazines or such are 
pivotably mounted for receiving sample containers. 
Laboratory centrifuges are already known which have the aforementioned 
structure. With some of these centrifuges it is known to lock the sample 
container-receiving magazines in a certain inclined position using magnets 
for example, so as to remove the liquid from the sample containers during 
the subsequent centrifugal action. The expense required for this is quite 
considerable. The magazines are furthermore only held in the desired 
position through the magnetic forces, which would lead to operational 
defect if the magnetic field failed. These defects would be extremely 
disturbing, especially with automatic running of the operation program. As 
long as the magazine container on the shaft head are mechanically lockable 
by hand, and interruption of the operating process will be necessary, and 
this prevents a fully automatic run of the process. 
SUMMARY OF THE INVENTION 
The invention is based on the task of improving a laboratory centrifuge of 
the type in question so that the magazines containing the sample 
containers automatically and securely take up the position desired during 
their fast or less fast rotation about the centrifugal axis in order to 
avoid operation defects caused through the magazines not taking up the 
intended position. 
It is also a task of the invention, to construct the members for obtaining 
this purpose in a manner that is as simple as possible and still is 
fail-safe. 
For solving this task, the invention suggests forming the laboratory 
centrifuge in question in such a way that the shaft head which can be 
driven in either of two opposite directions of rotation, has two brackets 
arranged symmetrically to the axis of rotation, facing each other. The 
outward extending arms carry an axle in the area of their outer ends, on 
or with which the magazines for the sample containers are pivotably 
mounted with axial play. The width of the magazine is slighter than the 
distance between both bracket arms, and there is a locking device between 
the bracket arms and the magazines, becoming effective when the magazine 
abuts the respective bracket arm. 
Further features of this improved laboratory centrifuge according to the 
invention are shown through the sub-claims and the following description 
of a particularly preferred embodiment of the invention which is 
schematically shown in the FIGS. 1 to 5 of the drawings and which is 
subsequently described in greater detail.

DESCRIPTION OF THE DRAWINGS 
In the housing 11 with latch-type cover 12 and control panel 13 arranged on 
the front side, the drive motor for the centrifuge is situated in the 
lower area and sets the shaft 14 with shaft head 15 in rotation. The shaft 
can be driven in counter clockwise or clockwise direction. Brackets 17 and 
18 are arranged on opposing sides on the shaft head 15, relative to the 
axis of rotation 16, with outwards extending arms 19a, 19b which carry the 
magazines 20 whose bores 21 take up the sample containers 22. The 
magazines 20 are mounted on the outer ends of the bracket arms 19a, 19b 
via the axle 23 which has both its ends hung in the slots 24 in the 
bracket arms 19a, 19b. The width of the magazines 20 is considerably 
slighter than the distance between the bracket arms 19a, 19b of the two 
brackets 17 and 18, so that when the magazines 20 abut the bracket arm 19a 
with their one lateral surface 25, there is a play S present between the 
opposing lateral surface 26 of the magazine and the neighboring bracket 
arm 19b. This play is greater than the height of the locking pin 27 which 
is situated on the inner side of the one bracket arm 19a, and which mates 
with a stop consisting of a pocket-drilled bore 28 when the surface 25 of 
the magazine 20 abuts the bracket arm 19a adjacent to said surface. The 
magazines 20 are able to slide backwards and forwards on their axle 23 in 
a generally circumferential direction relative to the axis of rotation, 
due to the play S between the two bracket arms 19a and 19b and the lateral 
surfaces of the magazines 20. Depending on the direction of rotation of 
the centrifuge shaft 14 or the shaft head 15, the magazines 20 either lie 
with their lateral surface 25 on the bracket arm 19a or, with the reversed 
direction of rotation, with their opposing lateral surface 26 on the 
bracket arm 19b due to inertial forces acting on these magazines when the 
shaft is accelerated in either direction. 
The axles 23 run in bearing bores in the magazines 20, which lie eccentric 
to the axis through the center of the magazines 20, so that the magazines 
20 have their lower end resting on the shaft head 15 in inoperative 
position (FIG. 4,5). 
For centrifuging, the centrifuge shaft 14 is driven in the one direction, 
i.e. counter clockwise ="L", whereupon the magazines 20 take up the 
position as shown in FIGS. 2 and 3. The magazines 20 then slide within the 
scope of the play S on their axle 23 against the bracket arms 19b, 
whereupon the stop bore 28 is released from the locking pin 27. Thus, with 
appropriate high rotational speed, the magazines 20 with their sample 
containers can swing their lower ends outwards to a centrifuge orientation 
so that substances suspended in the liquid can deposit on the bottom of 
the sample container. 
In order to subsequently remove the liquid situated in the sample 
containers from said containers while the substances deposited through the 
previous centrifugal action remain in the sample containers, the direction 
of rotation of the centrifuge shaft 14 is reversed after coming to a 
standstill. At the begining of this clockwise rotation =R, the magazines 
slide on their axle 23 against the bracket arms 19a, whereupon the locking 
pins 27 mate with the stop bores 28 and thus secure the magazines 20 in 
this inclined or slightly tilted decanting position caused by gravitation, 
as shown in FIGS. 4 and 5. In this position the magazines 20 as well as 
the sample containers 22 inserted in the magazines 20 have their top ends 
inclining outwards so that the liquid is flung out of the sample 
containers 22 at appropriately high rotational speed of the centrifuge 
shaft 14. Movement of a magazine along said axle may be described as 
generally circumferentially relative to the axis of rotation of said shaft 
and magazine, although said movement will obviously be in a straight line 
if said axle is straight. 
With such a construction of the centrifuge head and the sample 
container-receiving magazine applicable to said head, merely the reversing 
of the direction of rotation is required in order to be able to perform 
the operating steps "centrifuging" and "liquid spin-off" successively 
without additional steps or agents. Changing the direction of rotation of 
the drive motor or centrifuge shaft is sufficient alone, whereupon the 
necessary switch operations take place automatically and the blocking of 
the magazines loaded with sample containers in the required position is 
achieved. 
With the aforementioned embodiment, the axles 23 of the magazines are 
attached to the bracket arms 19a, 19b and the magazines can move on the 
axles 23. It is however also quite possible to firmly fix the magazines on 
the axles and to mount the axles in the bracket arms 19a, 19b with axial 
and rotational movement. 
Bearing surfaces are expediently arranged between the axles 23 and the 
magazines 20 or the bracket arms 19a, 19b, said bearing surfaces having a 
coefficient of friction as low as possible so that the magazines can slide 
or run smoothly in axial and radial direction, thus ensuring that the 
switch-over from one operation phase to the other will function perfectly. 
There are nozzles 31 present in the housing at predetermined points for the 
removal of liquids; with the present embodiment these are situated in the 
area of the rear wall of the housing 11 beneath the raised part of the 
cover 32. The liquid passes out through these nozzles upon actuation of 
the push switch 33 when the sample containers in the magazines are 
respectively situated beneath the nozzles 31. There is a control device 
situated beneath the control panel 13 on the front wall of the housing 11. 
This control device permits the running of predetermined operating 
programs without necessitating manual operation. The individual steps can 
of course also be controlled manually.