Vacuum pressure controller

Abstract

A vacuum pressure controller for vacuum distillation equipment is controlled to mix a dilution gas with the distillation vapors to control the vacuum pressure to which the distillation equipment is subjected.

Description

This application claims priority of U.S. provisional application 60/662,157 filed Mar. 16, 2005.

FIELD OF THE INVENTION

This invention relates to a vacuum pressure controller of the type that is used for rotary evaporators, vacuum ovens and stationary distillation equipment

BACKGROUND OF THE INVENTION

Vacuum pressure controllers are used in several chemical laboratory applications such as rotary evaporators, vacuum ovens and stationary distillation equipment. Of these, rotary evaporators are by far the predominant usage.

Vacuum pressure controllers maintain present vacuum pressure during these distillation processes at temperatures typically not exceeding 180° C. and for volumes up to about 30 liters of distilled liquid. The typical process setup consists of a distillation apparatus, a condenser with a liquid collector, a pressure controller and a vacuum pump. A rotary evaporator is disclosed, for example, in U.S. Pat. No. 6,709,025. Chemicals used during distillation require maintaining pressure in the range of several Torr to a few hundred Torr.

In these processes, the vacuum pump applies the vacuum to the system through a vacuum pressure controller. Prior controllers had different means of controlling the pressure. A pressure transducer was supplied to give a measurement of the pressure in the system and a controller controlled a valve to maintain the pressure set by the user. The valve, most typically an inline proportional or on-off valve, controlled the amount of vacuum applied to the distillation apparatus. Other systems would turn the vacuum pump on or off to control the amount of vacuum. These various methods sometimes shortened the pump life, required maintenance, or required time for the vacuum pump to recover from a low vacuum to a high vacuum.

SUMMARY OF THE INVENTION

The invention provides a vacuum pressure controller in which a dry gas, for example air, is bled into the vacuum stream in connection with maintaining the required vacuum pressure in the system. The gas bled into the vacuum stream dilutes the vapor, cools the mixture of vapor and gas admitted to the pump, prevents condensation in the vacuum pump. The result is a longer pump-life, longer maintenance intervals, a lower operation cost, and quicker recovery of the pump.

Using the invention, the diluted vapor is less chemically aggressive on the pump and other parts of the system. In addition, the lower operating temperature of the vapor diluted with the gas lowers the pump temperature, which increases its life. The vapor diluted with air also helps prevent internal condensation in the pump and by always permitting a flow through the pump, it lowers oil contamination in oil-sealed pumps. Since the pump can be run at or near its full speed all the time, the pump will recover quickly to its original vacuum pressure once the bleed valve is shut.

These and other features and advantages of the invention will be apparent from the detailed description and drawings.

The foregoing and other objects and advantages of the invention will appear in the detailed description which follows. In the description, reference is made to the accompanying drawings which illustrate preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a rotary evaporator system, including a vacuum pressure controller of the invention

FIG. 2 is an enlarged cross-sectional view of the valve illustrated in FIG. 1;

FIG. 3 is a perspective view of the valve;

FIG. 4 is a sectional view of an alternative embodiment of the rotary evaporator system wherein the vacuum pressure controller and pump are within the same housing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, the system 10 includes a rotary separator distillation apparatus 12, a vacuum pump 14 and a vacuum pressure controller 16 of the invention. The vacuum pressure controller 16 includes an air bleed valve 18 and a control unit 20. A first vacuum pressure line 22 connects the pump 14 to a manifold 24 of the unit 16 and a second vacuum pressure line 26 connects the manifold 24 to the rotary evaporator 12. A pressure transducer 28 is in communication with the manifold 24 to provide an electrical signal indicative of the vacuum pressure within manifold 24, which signal is input to control unit 20 by line 30. Control unit 20 includes dial 32 and pressure gauge 34 for a user to dial-in the level of vacuum that the user desires the system to produce. Line 36 connects the output of control unit 20 to the control input of valve 18 and control unit 20 controls valve 18, which may be a proportional valve or an on-off valve. Control unit 20 is similar to control units which have been used in prior vacuum pressure controllers that had in-line valves.

The valve 18 has an intake port 40 into which outside air flows when the valve 18 is opened by the control unit 20. Air entering the valve 18 through the port 40 flows through the valve 18 into the manifold 24 and there mixes with vapor entering inlet port 29 of the manifold 24 through the line 26. The mixture of air and vapor then flows through the manifold 24 and out the outlet port 31 of the manifold 24 through the conduit 22, into the pump 14, and after flowing through the pump 14 may be discharged by the pump 14 through the outlet of the pump 14.

FIG. 4 includes all of the components of FIG. 1. The difference between the two embodiments is that the components of the pump and the vacuum pressure controller are configured so as to be disposed within the same housing as the pump. Schematically, however, both rotary vacuum pressure systems operate in the same manner. For clarity those components which are depicted in FIG. 4 which correspond to a like component in FIG. 1 are given the same number as FIG. 1 except the reference numbers in FIG. 4 all have the suffix “a”. Thus, for example, 20a refers to the controller of FIG. 4 and 20 refers to the controller in FIG. 1.

A preferred embodiment of the invention has been described in considerable detail. Many modifications and variations to the preferred embodiment described will be apparent to a person of ordinary skill in the art. Therefore, the invention should not be limited to the embodiment described but should be defined by the claims which follow.

Claims

1. A vacuum pressure controller for a vacuum distillation comprising:

a manifold having an inlet port for receiving distillation vapor, an intake port for receiving a dilution gas, a chamber for mixing the distillation vapor and the dilution gas, and an outlet port through which the mixed distillation vapor and outlet gas are discharged from the manifold;

a valve controlling the admittance of dilution gas to the intake port of the manifold, the valve being responsive to a sensed pressure.

2. The system of claim 1 wherein a pressure transducer is in communication with the manifold.

3. The improvement of claim 2 wherein the sensed pressure that the valve is responsive to is the pressure sensed by the pressure transducer.

4. The system of claim 1 wherein the controller is disposed within a housing wherein the housing also houses at least part of a vacuum pump.