Distillation: apparatus – Apparatus – Types
Reexamination Certificate
2002-02-20
2004-05-25
Manoharan, Virginia (Department: 1764)
Distillation: apparatus
Apparatus
Types
C202S189000, C159S006100, C196S112000, C122S011000, C122S012000
Reexamination Certificate
active
06740206
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a rotary evaporator.
2. Description of the Prior Art
Rotary evaporators are known which are used to evaporate substances, particularly to evaporate solvents when pharmaceutical or chemical products are concentrated or distilled. With these known rotary evaporators, the liquid substances to be evaporated are placed into the hollow chamber of a rotatable rotating flask (evaporation vessel), usually in a heating bath. By rotating the flask, a thin liquid film is formed on the inside of the rotating flask and the substances, especially the solvent, then evaporate from this film. Some of the substance or solvent also evaporates directly from the surface of the liquid that is in the rotating flask. The vapor is conveyed from the rotating flask via a vapor line to a condenser, where it condenses out again. Generally speaking, a negative pressure or a vacuum is also generated in the rotating flask in order to raise the vapor pressure of the substances to be evaporated and to protect the product. In a passage area, the vapor line is joined to the rotating flask via a rotatable connection. The connection site is sealed off by of a rotary gasket.
German patent specification DE 1 224 062 discloses a rotary evaporator with a rotating flask that can be rotated around its axis of symmetry. The rotating flask is placed tightly on the standard tapered-ground joint of a glass adapter whose tapered part is inserted into the conical bore of a support ring having a worm gear crown. For purposes of driving the rotating flask, a screw attached to the drive shaft of a small electric motor equipped with a switch then engages the worm gear crown. The support ring can rotate in a ball bearing of a housing to which the motor as well as a condenser are affixed. The work flask can also pivot freely around a swiveling axis that runs perpendicular to its axis of symmetry. For this purpose, the housing has a bearing plate into whose bore a rigid, horizontal guide shaft of the apparatus stand has been inserted so as to rotate freely, as a result of which the rotating flask can move freely around the guide shaft or the swiveling axis in a radius until it is floating freely on the surface of a water bath.
The free movement around the swiveling axis or pendulum axis parallel to the axis of symmetry of the rotating flask theoretically makes it possible to concentrate any quantity of liquid in a large rotating flask of any desired size, whereby the flask size or the quantity of liquid to be concentrated in one operation is only limited by the size of the rotating flask that still allows comfortable use without requiring a special lifting and lowering mechanism. Therefore, with a rotary evaporator having such a pendulum system, the weight of the rotating flask, together with the substance to be evaporated that is in the flask, is held up in the water bath exclusively by the buoyancy of the rotating flask, as a result of which torques and forces acting upon the rotating flask holder are markedly reduced. A thumb screw on the bearing plate serves to hold the rotating flask in any desired slanted position (swiveling position), also independently of the water bath.
Together with the rotating flask affixed to the glass adapter, the latter—which can be rotated by means of the rotary drive—is sealed by a gasket with respect to another, non-rotating glass adapter connected to the housing. This stationary glass adapter is connected to the other parts of the rotary evaporator apparatus by means of a bellows made of pure polytetrafluoroethylene. The bellows serves to compensate for the relative movement between the pivoting unit consisting of the rotating flask, the drive means, the housing and both glass adapters as well as the stationary apparatus stand that does not swivel along with the unit. This swiveling axis runs through the bellows in the vicinity of its point of intersection between both diagonals. The bellows can be deformed during the swiveling motion around an initial position in which its center axis runs essentially vertical, that is to say, parallel to the force of gravity. The swiveling axis for the pendulum movement of the rotating flask and the axis of symmetry of the rotating flask, which is provided as the axis of rotation, intersect at a point of intersection and thus lie on the same plane in every swiveling position. Therefore, the bellows is positioned laterally offset parallel to the swiveling axis, relative to the rotational movement of the stationary glass adapter of the rotating flask.
In order to remove precipitate that forms in the glass adapters, according to German patent specification DE 1 224 062, a delivery and washing nozzle is installed on the side of the stationary glass adapter that faces away from the glass adapter that rotates, said nozzle serving to spray a rinsing fluid, which is fed via a two-way tap, against the inside walls of the glass adapters. Any precipitate that might be present in the glass adapters can.be removed in this manner and returned to the rotating flask, together with the liquid that is being newly introduced.
German application DE 35 22 607 A1 discloses another rotary evaporator having a pendulum system. With this rotary evaporator, the weight contained in the rotating flask or changes in this weight as the rotating flask enters the bath liquid are ascertained by weighing, and the result of the weighing is employed as the regulating or control parameter for the evaporation process. With this known rotary evaporator, the pendulum axis or swiveling axis is likewise arranged perpendicular to the axis of rotation; however, the pendulum axis does not run in the same plane as the axis of rotation but rather, as seen in the direction of gravity, the pendulum axis is arranged below the axis of rotation of the rotating flask. In the working position of the rotating flask, the axis of rotation creates an acute angle with respect to the vertical, in other words, with respect to gravity, so that the rotating flask is immersed into the liquid bath downwards at an angle. On the one hand, a drive part that drives the flask neck with the rotating flask around the axis of rotation is mounted in a swiveling bearing so as to swivel on a stand around the pendulum axis, and on the other hand, the drive part is damped against the swiveling motion by a shock absorber that is likewise attached to the stand. On the side of the drive part that lies opposite from the rotating flask, there is a vapor pipe that does not rotate around the axis of rotation, but that swivels around the pendulum axis. The product to be introduced into the evaporation process is fed in parallel to the axis of rotation at the free end of the vapor pipe. A branch leads essentially horizontally from the vapor pipe to a condenser, where the evaporated product condenses and runs down as distillate into a distillate receiving vessel. In order to compensate for the pendulum movement of the vapor pipe relative to the drive means and of the rotating flask relative to the stationary condenser, a compensating element is installed in the branch. The center axis of the compensating element, which matches the direction of flow of the vapor, runs essentially horizontal.
If, like in German patent specification DE 1 224 062 or with the rotary evaporator according to German application DE 35 22 607 A1, a bellows is employed as the compensating element, under unfavorable conditions, precipitates can form in the bellows which, due to the horizontal arrangement of the bellows, can accumulate in the lower folds and can no longer drain. Moreover, the compensating element in German application DE 35 22 607 A1 is located relatively far away from the pendulum axis, as a result of which the compensating element undergoes a relatively strong deformation, especially bending, stretching and/or compression, during the pendulum movement, which can give rise to malfunctions in actual practice under certain conditions.
Accordingly, an object of the present inven
Manoharan Virginia
Sidley Austin Brown & Wood LLP
LandOfFree
Rotary evaporator with a pendulum system with an offset fulcrum does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Rotary evaporator with a pendulum system with an offset fulcrum, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Rotary evaporator with a pendulum system with an offset fulcrum will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3224789