Device for separating oil from the vent of an oil reservoir

Abstract: Device for separating oil from the vent of an oil reservoir, in particular from the sump (1) of an oil-free compressor, which device contains a filter (2) which is connected to the oil reservoir (1) via a vent line (3-4) and in which the oil is separated from the air, characterized in that it contains a line (3-4) for venting a suction pump (5 or 5A) for sucking in air from the oil reservoir (1) on the one hand, and in that it contains a connection (6) between the oil reservoir (1) and the environment on the other hand.

Description: The invention relates to an oil reservoir with vent system, comprising an oil-separating filter which is connected to the oil reservoir via a vent line and a suction pump installed within the vent line for sucking in oil laden air from the oil reservoir. The vent of an oil reservoir, in particular a sump vent of a compressor, is rich in oil aerosols, both dispersion aerosols and condensation aerosols. If the sump vent opens directly into the atmosphere, air with oil could be sucked into the compressor. The compressor and especially the cooling system can also be polluted by the oil. Hence the use of devices for separating oil from the sump vent. Such device must by all means avoid excess pressure in the sump, since excess pressure is very disadvantageous to the seals. With known devices of the above-mentioned type, the sump venting line opens directly into the filter. The pressure in the sump hereby depends on the contamination of the filter element, so that there is a risk of excess pressure in the sump. Such device is disclosed in US-A-3.246.639. A filter is connected via a vent line to a crank case forming an oil reservoir and a suction pump is installed in the vent line. A pressure drop occurs in the filter increasing with the degree of contamination of the filter. Said pressure drop may cause a relatively great pressure raise in the crank case. In another known device, the vent line is connected to a filter which is erected in a chamber in which is created an under-pressure. Oil can only be discharged from the chamber by switching off the device and by pumping out the oil by means of a pump. This device has a very complex construction due to the large number of components, and if any of the above-mentioned components fails, oil can be sucked out of the sump into the device. In other known devices, the filter is a ring-shaped, rotating filter which is mounted in a case and which is provided with blades, so that an air flow is created through the filter. Due to the centrifugal force, drops of oil which are formed in the filter are swung against the wall. The oil is collected at the bottom of the house, from where it can be fed back to the sump. In order to obtain enough centrifugal force, the filter must have a relatively large diameter, so that it takes up relatively much space. A rotating filter is relatively expensive and can easily become defective. Polluted air can escape between the rotating filter and the case. US-A-2.686.504 discloses an oil reservoir with two vent systems, each comprising a vent line provided with a moisture filter connected to the oil reservoir, a suction pump being installed within one of the vent lines, the other vent line forming a permanent fluid connection between the oil reservoir and the environment. The moisture filters aim to avoid contamination of the oil by moisture and a characteristic is that the moisture absorbing material or desiccant in both filters is continuously reactivated by heat of the exhaust. The moisture filters seem to decrease the oil consumption, what means that they also work at least partially as an oil filter. The invention aims to remedy the above mentioned disadvantages and to provide an oil reservoir with vent system which has a simple construction, which is reliable and which excludes any building up of pressure in the oil reservoir, also when one or more components of the device fail or wear out. This aim is reached according to the invention in an oil reservoir with vent system of the above kind whereby the oil reservoir is connected to the environment via a permanent fluid connection, in that the filter is mounted in a chamber which is provided with an air outlet and which is connected to the oil reservoir via a return line coinciding with at least part of the permanent fluid connection (6) which is a free connection. The oil which is separated in the filter is collected in the chamber and carried back to the oil reservoir via the return line, preferably as a result of the force of gravity. The device is practically dimensioned, so that a flow is sucked in via the vent line which is larger than the normal venting flow, i.e. the air flow which ends up in the oil reservoir via components of for example the compressor. Via the connection between the oil reservoir and the environment, an air flow flows to the oil reservoir which is equal to the difference between the flow which is sucked in via the vent line and the normal venting flow. The flow which is sucked from the oil reservoir by the suction pump and sent to the chamber and the size of the permanent free fluid connection of the oil reservoir with the environment, and particularly the size of the return line and the outlet of the chamber are preferably selected such that there is never created an excess or under-pressure in the oil reservoir which is disadvantageous to the working of the seals. According to an advantageous embodiment of the invention, the suction pump is an ejector to which is connected a compressed-air line, the vent line comprising a part between the underpressure part of the ejector and the oil reservoir and a part between the outlet of the ejector and the filter. The ejector does not contain any moving parts and thus is not subject to wear and tear. Preferably, a pressure regulator or a restriction device is hereby mounted in the compressed-air line. The compressed-air line is practically connected to a compressed-air network onto which a compressed-air source is connected. In order to better explain the characteristics of the invention, the following preferred embodiments of a device for separating oil from the air vent of an oil reservoir are described as an example only without being limitative in any way, with reference to the accompanying drawings, in which: figure 1 schematically represents a sump onto which is mounted a device according to the invention for separating oil from the air vent; figure 2 schematically shows a variant of the device for separating oil; figure 3 shows a practical embodiment of the variant according to figure 2. Figure 1 schematically represents the oil reservoir of a sump 1 of an oil-free compressor onto which is mounted a device for separating oil from the sump vent. This device mainly contains a filter 2, a sump venting line 3-4 between the sump 1 and said filter 2, and a suction pump 5 in the line 3-4 and a free and unobstructed permanent fluid connection 6 between the sump 1 and the environment. The part 4 of line 3-4 is connected to the inside of the standing ring-shaped filter 2 which is mounted vertically. The filter 2 consists of spongy material which collects oil in the shape of aerosol from the air, so that larger drops of oil are formed which drip off the filter 2. Under the filter 2 is provided a dish 7 to collect the oil. The filter 2 is erected in a chamber 9. The chamber 9 is provided with an outlet 10 to the environment. The bottom of the chamber 9 is connected to the sump 1 via a return line 8. This return line, together with the chamber 9 and the outlet 10, forms the above-mentioned connection 6. The working of the device is as follows. The suction pump 5 sucks in a flow Q1 of air polluted with oil via the part 3 of the line 3-4 from the sump 1. The dimensions of the device are selected such that this flow Q1 is larger than the normal sump venting flow QS, i.e. the flow which is brought via components of the compressor and especially via the sealings around the rotor shaft into the sump 1. The flow Q1 is directed via the part 4 of the line 3-4 through the filter 2. Via the connection 6, an air flow Q1-QS flows from the environment to the sump 1, so that the air content in this sump is constant once the balance is reached, and so that, as a consequence, also the pressure is constant. Polluted air can no longer flow from the sump 1 into the environment via the connection 6, since a flow Q1-QS constantly flows from the environment to the sump 1. The flow Q1, the size of the return line 8 and the size of the outlet 10 are preferably selected such that there is never created an excess pressure or underpressure in the sump 1 which is disadvantageous to the working of the sealings. Figure 2 schematically shows an advantageous variant of the device according to figure 3. The suction pump 5 consists of an ejector 5A on the inlet to which is connected a compressed-air line 11 and whose outlet opens into the filter 2 via the part 4 of the line 3-4 and whose underpressure part is connected to the sump 1 via the other part 3 of the line 3-4. The compressed-air line 11 is part of the compressed-air network which is fed with compressed air from the compressor or another compressed-air source. In this compressed-air line 11 is mounted a restriction device or a pressure regulator 12 upstream to the ejector 5A. The working of this variant is as follows. When the ejector 5A is fed with a flow QE of compressed air via the pressure regulator 12, a certain flow Q1 of air polluted with oil is sucked out of the sump 1 via the part 3 of the line 3-4. The dimensions of the device are selected such that this flow Q1 is larger than the normal sump venting flow QS. In the ejector 5A, this polluted air is mixed with the compressed air and the flow QE + Q1 of the mixture is directed via the part 4 of the line 3-4 through the filter 2. A part of the purified air, namely a flow which is equal to QE+QS can escape into the environment via the outlet 10. The drops of oil which are formed in the filter 2 drip off the filter and are carried back to the sump 1 via the return line 8 as a result of the force of gravity. Together with the oil, also a flow Q1-QS of purified air flows back to the sump 1 via the return line 8, so that the air content in this sump is constant once the balance is reached, and so that as a consequence the pressure is constant. The flow Q1 + QE which flows into the chamber, the size of the return line 8 and the size of the outlet 10 are preferably selected such that there is never created an excess pressure or underpressure in the sump 1 which is disadvantageous to the working of the sealings. As the compressed air for the ejector 5A comes from a compressor or another compressed-air source and is already filtered and dried, the filter 2 has a relatively long life. Figure 3 shows a practical embodiment of the variant according to figure 2. The return line 8, the chamber 9, the outlet 10 and an end portion of the part 3 of the line 3-4 are integrated in a component 13 in the shape of a small pot. The pressure regulator 12, the ejector 5A, the part 4 of the line 3-4 and the remainder of the part 3 are integrated in a second component 14 in the shape of a lid which is fixed to the component 13 by means of a bolt fastening 15. The whole is connected to the sump 1 of the gearcase by means of a flange attachment 16. The present invention is by no means limited to the embodiment described as an example and represented in the accompanying drawing; on the contrary, such a device for separating oil can be made according to all sorts of variants while still remaining within the scope of the invention as defined in the following claims.

Claims: Oil reservoir (1) with vent system, comprising an oil-separating filter (2) which is connected to the oil reservoir(1) via a vent line (3-4) and a suction pump (5,5a) installed within the vent line (3-4) for sucking in oil laden air from the oil reservoir (1), whereby the oil reservoir (1) is connected to the environment via a permanent fluid connection (6), characterised in that the filter (2) is mounted in a chamber (9) which is provided with an air outlet (10) and which is connected to the oil reservoir (1) via a return line (8) coinciding with at least a part of the permanent fluid connection (6) which is a free connection. Oil reservoir (1) according to claim 1, characterised in that the suction pump (5) is an ejector (5A) onto which is connected a compressed air line (11), the vent line (3-4) comprising a part (3) between the under-pressure part of the ejector (5A) and the oil reservoir (1) and a part (4) between the outlet of the ejector (5A) and the filter (2). Oil reservoir (1) with vent system, according to claim 2, characterised in that a pressure regulator or a restriction device (12) is mounted in the compressed-air line (11). Oil reservoir with vent system according to claims 2 and 3, characterised in that the return line (8), the chamber (9) with the outlet (10) and the end portion of the vent line (3-4) connected the oil reservoir (1) are integrated in a first component (13), whereas the pressure regulator (12), the ejector (5A) and the remainder of the vent line (3-4) are integrated in a second component (14) which is connected to the first component (13) by means of a connection (15). Oil reservoir with vent system according to any one of claims 2 to 4, characterised in that the compressed-air line (11) is connected to a compressed-air network of a compressed-air source.

Inventors: MAGITS HANS, MAGITS, HANS
Applicants: ATLAS COPCO AIRPOWER NV, ATLAS COPCO AIRPOWER N.V.
Application year: 1995
Main classification: F01M13
IPC codes: B01D46, F01M13, F04B39