Device for Cooling and Silencing of Noise of a Compressor or Vacuum Pump

The present invention relates to a device for cooling and silencing of noise of a compressor or vacuum pump.

During operation of compressors or vacuum pumps, large quantities of heat are generated during compression and transport of the medium, and a compressor or vacuum pump must therefore be provided with an effective system for cooling of the compressor or pump and possibly also the medium after the same has been compressed.

During the operation of compressors or vacuum pumps, whether they are of the membrane, piston, or screw type, irritating noise is also involved, which in many cases constitutes a serious environment problem.

The object of the present invention is to provide an effective system for cooling of a compressor or vacuum pump, ssaid system at the same time providing superior silencing of the noise produced during operation of the compressor or vacuum pump.

The invention is furthermore intended to make possible for at least part of the large quantity of heat produced during operation of the compressor or vacuum pump to be used for the heating of premises or the like, e.g. the room in which the compressor or vacuum pump is installed.

Another aspect of the invention is to isolate the compressor or vacuum pump together with the cooling and silencing system from the surroundings in such a manner that the mechanical vibrations produced during operation only affect the surroundings on a small scale.

Finally, the invention is also intended to achieve a satisfactory cooling of the medium which passes through the compressor or vacuum pump and to deaden the irritating noise which spreads to the surroundings through this medium.

To accomplish the above-listed objects, both the compressor and the driving motor are of the kind which can be immersed and are arranged in a totally sealed container which encases a cooling and sound-absorbing liquid to such a level that the compressor or vacuum pump and driving motor are totally immersed in the liquid, the whole of the outer surface of the container is coated with sound-absorbing material, and at least one heat exchanger is arranged outside the container and the sound-absorbing material, said heat exchanger being in communication with the inside of the container in such a manner that the cooling and sound-absorbing liquid flows through the heat exchanger under the influence of the thermal circulation generated in the liquid.

The invention has a wide scope of use and can be employed generally with all kinds of compressors or vacuum pumps. Suitable fields of application are compressors and vacuum pumps used in connection with the dental and medical professions and also for industrial purposes. The above-mentioned examples, however, must not be regarded in a limited sense.

A suitable form of construction of the invention is described in the following, taking consideration to the attached schematical drawing which, in vertical section, shows a compressor or vacuum pump and device for the cooling and silencing of same.

The device shown in the drawing comprises a compressor 1 or vacuum pump (hereinafter, for the sake of simplicity, referred to as compressor only) which is coupled directly to and is driven by an electric motor 2. The compressor 1 can be of the membrane, piston or rotor type. The compressor 1 together with the motor 2 are housed in a totally sealed water-tight container 3 of such form that the walls and lid are situated at a distance from the compressor and driving motor. The container 3 encases a cooling liquid 4 of suitable composition to a level 5 situated slightly below the lid of the container, so that a space 6, to receive expansion of the cooling liquid 4, is formed between the level of the liquid 5 and the lid.

The sidewalls, bottom and lid of the container are coated with a suitable sound-absorbing material 7 and are covered by an outer housing 8 which lies close against the sound-absorbing material 7.

The compressor 1 and the driving motor 2 are thus completely surrounded by the cooling liquid 4 and the heat produced during operation is transferred to the cooling liquid. The thereby heated portion of the cooling liquid rises upwards towards the liquid level 5 and a thermal circulation is thereby produced in the liquid pool.

The device according to the invention also comprises a heat exchanger 9 which is provided outside the outer housing 8. One or more inlet tubes 10 to the heat exchanger 9 extend in a fluid-tight manner through the outer housing 8, the sound-absorbing material 7 and the sidewalls of the liquid container 3 and are in open communication with the inside of the container 3 somewhat below the level 5 of the cooling liquid 4. One or more outlet tubes 11 from the heat exchanger 9 are in a similar manner drawn to the inside of the liquid container 3 and open into same immediately above the bottom of the container. Through the thermal circulation produced in the cooling liquid 4, a portion of the heated cooling liquid flows through the entrance tubes 10, passes through the heat exchanger 9, and thereby transfers heat to the ambient air, and finally, in cooled condition, is returned to the liquid container 3 by means of the outlet tubes 11. The cooling liquid in the container 3 is thereby kept within a suitable degree of temperature for cooling of the compressor 1 and the driving motor 2, and overheating of the cooling liquid is prevented. At the same time a large proportion of the heat produced when the compressor is in operation is regained and can be utilized, for example, for heating of the ambient air. If considered suitable, the heat exchanger 9 can be arranged in a casing (not shown) which, under self-circulation, leads the air upwards along the heat exchanger 9 in counter-flow against the downward streaming cooling liquid. If necessary, several heat exchangers 9 can, of course, be connected to the liquid container 3.

The cooling liquid 4, which surrounds the compressor 1 and the driving motor 2, and also the liquid container 3 with the sound-absorbing material 7 and outer housing 8, is not only intended to afford an effective cooling of the compressor 1 and the driving motor 2, but also brings about a very effective silencing of the noise which arises during operation. Water can be used as cooling liquid, but if an improved deadening of sound is desired, a liquid having greater sound deadening power, e.g. glycol, could be used.

The compressor 1 and the driving motor 2 are assembled as a unit and rest upon the bottom of the liquid container 3 over vibration reducing elements 12. The bottom of the liquid container 3 rests in its turn upon the bottom of the outer housing 8 over further vibration reducing elements 14. The mechanical vibrations on the floor in which the device is installed, which arise in the compressor 1 and driving motor 2, are thereby prevented or their transfer reduced.

The medium which shall be compressed and/or transported is fed to the compressor 1 through a pipe 15 which extends in a water-tight manner through the outer housing 8, the sound-absorbing material 7 and the one sidewall of the liquid container 3 and in the whole of its length up to the compressor 1 is immersed in the cooling liquid 4. After compression, the medium is directed out from the compressor 1 through an outlet pipe 16 which is likewise totally immersed in the cooling liquid 4 and passes out through the sidewall of the liquid container 3, the sound-absorbing material 7 and the outer housing 8. In order to increase the cooling of the medium, it can at least be of advantage to extend the outlet pipe 16 in the cooling liquid 4 by means of coils. To prevent the irritating noise from spreading through the medium flowing to and from the compressor 1, it is suitable that silencers 17 be connected to both the pipes 15 and 16, said silencers being also totally immersed in the cooling liquid 4. These silencers 17 should preferably be of the absorption kind so that loss of pressure does not arise. An absorption type siliencer as disclosed in U.S. Pat. No. 2,840,180 may be used. A filter 18 can also be connected to the pipes 15 and 16, whereby the filter is situated outside the outer housing 8.

The compressor 1 is, in the known manner, provided with a pressure-reducing safety valve 20 and this valve is attached to a further pipe 19 which chiefly has the same extension as the pipes 15 and 16, and possibly also includes a silencer 17a.

A very effective cooling of the compressor 1 and the driving motor 2 through self-circulation during operation is thus achieved by the device according to the invention, whereby the heat taken up from the compressor and motor to a great extent is regained and used in a suitable manner. At the same time a very effective deadening of sound is obtained, the compressor being practically silent during operation. The working capacity of the compressor and driving motor is also improved.