Title of Invention	AN OIL-INJECTED COMPRESSOR FOR PRODUCTION OF COMPRESSED AIR
Abstract	The invention relates to an oil-injected compressor, in particular an oil-injected screw -type compressor, which comprises a motor-driven compressor unit (1) in order to produce compressed air and which co-operates with an oil circuit (5) for lubrication, which is arranged downstream from an oil, separating device (6) which is used to separate the oil from the compressed air. A self-resetting temperature switch (11), which is used to switch off the compressor unit (1) when the maximum temperature limit of the incoming compressed air is reached, is provided in the region of the inlet of the compressed air, which contains oil, in the oil separating device (6). At least one non-self-resetting additional temperature switch (12) is provided in the internal area of the oil separating device (6), which immediately switches off the compressor unit (1) following a fire or an explosion of the compressed air, which contains oil, and which is contained in the oil separating device (6).

Title of Invention

AN OIL-INJECTED COMPRESSOR FOR PRODUCTION OF COMPRESSED AIR

Abstract

The invention relates to an oil-injected compressor, in particular an oil-injected screw -type compressor, which comprises a motor-driven compressor unit (1) in order to produce compressed air and which co-operates with an oil circuit (5) for lubrication, which is arranged downstream from an oil, separating device (6) which is used to separate the oil from the compressed air. A self-resetting temperature switch (11), which is used to switch off the compressor unit (1) when the maximum temperature limit of the incoming compressed air is reached, is provided in the region of the inlet of the compressed air, which contains oil, in the oil separating device (6). At least one non-self-resetting additional temperature switch (12) is provided in the internal area of the oil separating device (6), which immediately switches off the compressor unit (1) following a fire or an explosion of the compressed air, which contains oil, and which is contained in the oil separating device (6).

Full Text	WO 2006/094781 PCT/EP2006/002121 Description Oil-injected compressor with a temperature switch The present invention relates to an oil-injected compressor, in particular an oil-injected screw-type compressor with a motor-powered compressor unit for production of compressed air, which interacts with an oil circuit for lubrication, which is followed by an oil separator device for separation of the oil from the compressed air, with a self-resetting temperature switch for switching off the compressor unit when the air/oil mixture flowing in reaches a maximum temperature limit being provided in the area of the inlet of the compressed air containing oil into the oil separator device. In addition to oil-injected screw-type compressors, the present invention is also used for other types of oil- injected compressors, for example, vane-cell compressors as well. In the case of compressors of the type that is of interest here, oil is injected by means of an oil circuit into the area of the moving compressor components, and on their bearing points, in order on the one hand to lubricate the roller bearings which are provided in this case and rotate at high speed, and in order on the other hand to prevent unacceptable heating in the area of the moving compressor components, as a result of friction. Furthermore, the oil is also used to seal the air side from other areas of the compressor. The use of oil- injected compressors such as these extends not only to stationary compressed-air supply installations, but also to mobile applications such as rail vehicle construction, or else to commercial vehicle construction where compressors are used to produce compressed air for the vehicle compressed-air supply system. WO 2006/094781 PCT/EP2006/002121 - 2 - Oil-injected compressors, such as oil-injected screw- type compressors, are known from the general prior art. An oil-injected screw-type compressor essentially comprises a compressor unit with at least one pair of compressor screws in the form of rollers, rotating in opposite directions to one another, and intermeshing with one another. This compressor screw arrangement is used to produce compressed air, in that air that is sucked in from the atmosphere from one side is converted by continuous compression to compressed air, which leaves the compressor unit via a spring-reset outlet valve. In this case, the compressor screw arrangement is driven via a drive shaft which is passed to the outside out of the compressor unit via a seal, by means of a motor which is flange-connected to it here, generally an electric motor. In order to lubricate, seal and cool the compressor unit, it is equipped with an oil circuit which, starting from an oil sump, supplies oil to the central area of the compressor screw arrangement as well as to roller bearings which are arranged in the area of the end face of the compressor screw arrangement. The oil which is injected here leaves this active area in the direction of an oil sump, which represents the reservoir for the oil circuit. The oil sump is generally located within an oil separator device which follows the oil circuit. The oil separator device is necessary in order to remove the oil from the compressed air again, so that compressed air which is free of oil is available on the output side. Conventionally, the oil separator device is formed essentially from an oil separator which operates in a manner known per se, on the force of gravity principle. The oil which is separated from the compressed air which contains oil and rises in the oil separator is gathered in the oil sump. The compressed air which is already partially free of oil and rises in the oil separator is then generally supplied to a WO 2006/094781 PCT/EP2006/002121 - 3 - cartridge-like fine separator and then leaves the oil separator device via a pressure-maintenance valve arranged on the output side. According to EN Standard 1012-1, it is not permissible for safe operation of an oil-injected compressor such as this for the oil temperature to exceed 120°C adjacent to the area in which the compressed air containing oil enters the oil separator device. A temperature switch is normally arranged in said area in order to comply with this Standard. The temperature switch switches on on reaching a temperature of 120°C and. stops the drive for the compressor unit, by switching off the motor. When the temperature falls into the range below 12 0°C again, the drive for the compressor unit is enabled again. US 5,118,2 60 discloses a temperature switch such as this for a screw-type compressor although, in this case, this is not in the form of an oil-injected screw- type compressor. The temperature switch is arranged at the outlet of the screw-type compressor within an outlet chamber. The compressed air which has been heated by the screw-type compressor flows past this. The temperature switch contains an electrical bimetallic element which interrupts the drive to the screw-type compressor when the temperature of the compressed air that has been produced reaches a specific maximum value. In addition to this temperature switch, which is arranged in the area of the compressed air flowing out of the compressor unit, a further temperature switch is located in the area of the electric motor that drives the screw-type compressor, and protects the entire unit against motor overheating. If a motor-powered compressor unit such as this is provided with oil injection, so that it is necessary to provide a downstream oil separator device in order to WO 2006/094781 PCT/EP2006/002121 - 4 - separate the oil from the compressed air, this results in the problem that internal fires or detonations can occur sporadically, despite the measure explained above to prevent overheating within the oil separator device. A singular event such as this normally occurs downstream from the temperature switch, as required in accordance with the Standard cited initially, within the oil separator device. So far, the reason for such an internal fire or detonation has not clearly been explained. In specialist circles it is assumed that this event is the consequence of electrostatic discharges within the oil separator device, producing electrical sparks. Lack of servicing and, in particular, lack of oil can also be considered as detonation causes. A fire or a detonation results in temperatures in the oil separator device and downstream from it which are many times higher than the specified temperature limit of 120°C. Since the temperature on the inlet side of the oil separator device, in particular because of the physical proximity of the oil sump, is matched only slowly to the hot temperature level, the required temperature switch in the area of the compressed air flowing in cannot react sufficiently quickly to the event of a fire or detonation within the oil separator device, or downstream from it. A fire or detonation can result in the components of the oil separator device, which are occasionally also produced from aluminum, burning through, while, furthermore, the bearing for the compressor screws can seize as a consequence of overheating or lack of lubrication, and in the case of the gray-iron and cast-steel housings normally used, this can even lead to explosive destruction of the compressor. Furthermore, combustion residues also enter the exhaust air. In summary, this singular event can result in hazards to personnel and damage to the compressor as well as consequential damage, which therefore cannot be prevented, or at least limited by the temperature switch required by the WO 2006/094781 PCT/EP2006/002121 - 5 - Standard. The object of the present invention is therefore to improve further an oil-injected compressor of the type mentioned initially so as to make it possible to cope with the negative effects of a fire or detonation within the oil separator device. On the basis of an oil-injected compressor according to the preamble of claim 1, the object is achieved in conjunction with the characterizing features of this claim. The subsequent, dependent claims specify advantageous developments of the invention. The invention includes the technical teaching that at least one non-self-resetting additional temperature switch is provided in the internal area of the oil separator device downstream from an oil-injected compressor, and switches the compressor unit off without delay in response to a fire or a detonation of the compressed air which is contained in the oil separator device and contains oil. For the purposes of the present invention, the expression internal area of the oil separator device should be understood as meaning the large-volume internal area which contains the oil/air mixture and, in particular, also the outlet area of the compressed air, from which oil has been separated, from the oil separator device as far as, at most, the inlet to a recooler which may be connected downstream in the outlet flow direction. The particular advantage of the solution according to the invention is that the specific positioning of the additional temperature switch ensures that the compressor is rendered inoperative without delay in the event of an internal fire or detonation. Specifically, in the case of compressed-air compressors, this suppresses the oxygen supply, immediately quenching the WO 2006/094781 PCT/EP2006/002121 - 6 - fire and avoiding consequential damage. Pressure relief is also normally initiated, assisted by the shut down process. In summary, the process of shutting down the compressor immediately, initiated according to the invention, extracts oxygen very quickly from the internal combustion process, quenching the fire. The additional temperature switch therefore renders the compressor inoperative quickly and permanently in the event of this event. This effectively prevents personnel injuries or total damage to the oil-injected compressor, as well as consequential damage. Since at least some of the components of the compressor will have already been damaged in this event, the compressor is rendered inoperative by the non-self-resetting additional temperature switch according to the invention until suitable maintenance personnel have carried out a repair and operation of the oil-injected compressor can resume after a new temperature switch has been fitted. The additional temperature switch should preferably be in the form of a fuse link, in order to ensure that the compressor is reliably reconnected only after said specialist repair. This is because a fuse link permanently interrupts the circuit bridged by the additional temperature switch and is reliably destroyed after initiation, thus precluding accidental reconnection of the compressor unit. Furthermore, temperature switches in the form of fuse links are quite simple components which can be obtained as mass- produced items. They also include particularly quick- reaction fuse links which are particularly suitable for the application according to the subject matter of the invention. In order to ensure that the additional temperature switch according to the invention is reliably initiated if the event occurs, it is preferably arranged in the WO 2006/094781 PCT/EP2006/002121 - 7 - outlet area of the internal area, as defined above, of the oil separator device, in which the flow speed of the compressed air flowing out of it is normally high. A particularly rapid temperature rise can therefore be observed in this area in the event of a fire or detonation, and can then be reliably detected by the additional temperature switch. One particularly suitable location for arrangement of the additional temperature switch is in the area between a pressure- maintenance valve, which is normally arranged on the outlet side of the oil separator device, and an upstream fine separator unit. It is also optimal to arrange the additional temperature switch, on the outlet side, in the compressed air flow in the area immediately following said pressure-maintenance valve. In a further measure which represents an improvement to the invention, extinguishants are additionally forced into the internal area of the oil separator device when the additional temperature switch trips, thus resulting in the oil-injected compressor being shut down by switching off the drive. Generally known fire-retardant substances, which extract oxygen by an appropriate chemical reaction from their surrounding area when heated, are suitable for use as extinguishants. These substances may be in the form of powder, foam and the like. According to another measure that represents an improvement to the invention, optical indication means can be provided, which signal the tripping of the additional temperature switch when the event occurs. The advantage of this measure is that the rare occurrence of a fire or a detonation within the oil separator device can be diagnosed without doubt by the maintenance personnel, thus allowing specific repair. The present invention is not intended solely for a WO 2006/094781 PCT/EP2006/002121 - 8 - single-stage, oil-injected compressor. It is accordingly possible for the compressor also to be in the form of a multistage compressor unit with each stage being followed by an oil separator device, in which case additional temperature switches according to the invention must then be provided adjacent to the oil separator device for each compressor stage. Further measures that represent improvements to the invention will be described in more detail in the following text, together with the description of one preferred exemplary embodiment of the invention, and with reference to the figures, in which: Figure 1 shows a longitudinal section through an oil- injected compressor with a downstream oil separator device, and Figure 2 shows a longitudinal section through an additional temperature switch for the oil separator device. As shown in Figure 1 an oil-injected screw-type compressor essentially comprises a compressor unit 1 which is driven by a motor 2. A compressor screw arrangement 3 which is mounted within the compressor unit by means of roller-bearing arrangements such that it can rotate, compresses air which is sucked in from the surrounding area by the rotary movement produced by the motor 2 and this air is supplied via an inlet channel 4. Oil for lubrication is injected from an oil circuit 5 in the axial central area of the compressor screw arrangement 3. Some of the oil which is required in this case for lubrication, cooling and sealing purposes is in this case introduced into the compressed air leaving the outlet side of the compressor screw arrangement 3. An oil separator device 6 follows the compressor unit 1, in order to separate the oil from WO 2006/094781 PCT/EP2006/002121 - 9 - the compressed air. The oil separator device 6 has an oil sump 7, in the area of which the compressed air which contains.oil and is produced by the compressor unit 1 flows into the oil separator device 6. This flow is passed firstly into the area of an initial oil separator 8. The initial oil separator 8 separates oil by the force resulting from the effect of gravity. The oil separated in this way enters the oil sump 7. After passing through the initial oil separator 8, the compressed air, from which some of the oil has already been removed, enters a fine separator 9. The fine separator 9 is in the form of a cartridge and filters the compressed air, which is partially free of oil, radially inwards via the outer radial wall area. From here the compressed air, which is now free of oil, is passed to an outlet 10 of the oil separator device 6 from where it is passed into the compressed-air system, which is not illustrated in any more detail. A self-resetting temperature switch 11 is arranged in the area of the inlet for the compressed air, which contains oil and is produced by the compressor unit 1, into the oil separator device itself. The temperature switch 11 switches the motor-powered compressor unit 1 off if a limit temperature of 120°C is exceeded. This is done by switching off the motor 2. This prevents the ingress of excessively hot compressed air containing oil into the oil separator device 6. When the temperature of the compressed air which contains oil and is flowing in falls below the stated temperature limit value, then operation of the compressor unit 1 is resumed. An additional temperature switch 12 is provided in addition to this safety device, which prevents overheating, in the internal area of the oil separator WO 2006/094781 PCT/EP2006/002121 - 10 - device 6. The additional temperature switch 12 identifies a temperature rise initiated as a consequence of a fire or a detonation within the Oil separator device 6 and then switches off the compressor unit 1 in order to prevent further consequential damage. For this purpose, and in contrast to the other temperature switch 11, the additional temperature switch is non-self-resetting in order to prevent operation from being resumed after the rare event mentioned. in this exemplary embodiment the additional temperature switch 12 is arranged in the compressed-air flow in the area between an outlet-side pressure-maintenance valve 13 and the upstream fine separator 9. This position of the additional temperature switch 12 is particularly suitable for the purpose according to the invention, since this is where the temperature rise occurs most rapidly as a result of the high flow speed of the compressed air flowing out and the proximity to the fine separator 9, with the additional temperature switch 12 in consequence reacting very quickly. As shown in Figure 2, the additional temperature switch 12 which is used for the exemplary embodiment described here comprises a pressuretight outer tube 14, at whose proximal end a screw union 15 is provided. The screw union 15 is used for screwing the temperature switch 12 into the housing of the oil separator device, which is not illustrated in any more detail here. A thermal fuse link 16 is accommodated at the distal end within the pressuretight tube 14 and opens when a maximum permissible limit temperature, which must be defined, is exceeded, thus interrupting the circuit formed via the two connecting lines 17. The interior of the pressuretight tube 14 is sealed with a filling compound 18. The non-self-resetting temperature switch 12 is located with its active area 19 within the compressed WO 2006/094781 PCT/EP2006/002121 - 11 - air flowing out of the oil separator device 6. The present invention is not restricted to the preferred exemplary embodiment described above. Modifications to it can also be covered by the scope of protection of the subsequent claims. For example, it is therefore also possible to use a different type of oil- injected compressor, such as a vane-cell compressor, provided this has a downstream oil separator device which, of course, does not need to be connected directly downstream from the compressor unit. Furthermore, the oil-injecting compressor unit may also be in the form of a multistage compressor unit with an oil separator device following each stage. In this case, it would be necessary to provide each oil separator device with an additional temperature switch according to the invention. WO 2006/094781 PCT/EP2006/002121 - 12 - List of reference symbols 1 Compressor unit 2 Motor 3 Compressor screw arrangement 4 Inlet channel 5 Oil circuit 6 Oil separator device 7 Oil sump 8 Initial oil separator 9 Fine separator 10 Outlet 11 Temperature switch 12 Additional temperature switch 13 Pressure-maintenance valve 14 Tube 15 Screw union 16 Fuse link 17 Connecting lines 18 Filling compound 19 Active area - 13 - File reference: PCT/EP2006/002121 Applicant: KNORR-BREMSE SYSTEME FUR SCHIENENFAHRZEUGE GMBH Our reference: 2922K PCT Kie/nu Date: December 14, 2006 New Claims 1-7 1. An oil-injected compressor, in particular an oil- injected screw-type compressor with a motor-powered compressor unit (1) for production of compressed air, which interacts with an oil circuit (5) for lubrication, which is followed by an oil separator device for separation of the oil from the compressed air, with a self-resetting temperature switch (11) for switching off the compressor unit (1) when the air/oil mixture flowing in reaches a maximum temperature limit being provided in the area of the inlet of the compressed air containing oil into the oil separator device (6), in which case, furthermore, at least one additional temperature switch (12) is provided in the internal area of the oil separator device (6) and switches the compressor unit (1) off without delay in the event of a fire or detonation of the compressed air which contains oil and is contained in the oil separator device (6), characterized in that the additional temperature switch (12) is non-self-resetting, and in that its tripping results in extinguishants being forced into the internal area of the oil separator device (6). 2. The oil-injected compressor as claimed in claim 1, characterized in that the additional temperature switch (12) is in the form of a fuse link,, in order to ensure that the compressor unit (1) is reconnected only after specialist repair (Figure 2). LK:hv - 14 - 3. The oil-injected compressor as claimed in claim 1, characterized in that the additional temperature switch (12) which is arranged in the internal area of the oil separator device (6) is fitted in the area in which the compressed air flowing out of it is at a high flow speed. 4. The oil-injected compressor as claimed in claim 3, characterized in that the additional temperature switch (12) is arranged in the compressed-air flow in the area between an outlet-side pressure-maintenance valve (13) and a fine separator (9) upstream of the oil separator device (6) . 5. The oil-injected compressor as claimed in claim 3, characterized in that the additional temperature switch (12) is arranged on the outlet side of the compressed- air flow in the area immediately after the pressure- maintenance valve (13). 6. The oil-injected compressor as claimed in one of the preceding claims, characterized in that optical indication means signal the tripping of the additional temperature switch (12), in order to provide information about the need to repair the oil separator device (6) as a consequence of the detonation. 7. The oil-injected compressor as claimed in one of the preceding claims, characterized in that the compressor unit is in the form of a multistage compressor unit with an oil separator device following each stage, with an additional temperature switch being provided on the oil separator device of each compressor stage. The invention relates to an oil-injected compressor, in particular an oil-injected screw -type compressor, which comprises a motor-driven compressor unit (1) in order to produce compressed air and which co-operates with an oil circuit (5) for lubrication, which is arranged downstream from an oil, separating device (6) which is used to separate the oil from the compressed air. A self-resetting temperature switch (11), which is used to switch off the compressor unit (1) when the maximum temperature limit of the incoming compressed air is reached, is provided in the region of the inlet of the compressed air, which contains oil, in the oil separating device (6). At least one non-self-resetting additional temperature switch (12) is provided in the internal area of the oil separating device (6), which immediately switches off the compressor unit (1) following a fire or an explosion of the compressed air, which contains oil, and which is contained in the oil separating device (6).

Full Text

WO 2006/094781 PCT/EP2006/002121
Description
Oil-injected compressor with a temperature switch
The present invention relates to an oil-injected
compressor, in particular an oil-injected screw-type
compressor with a motor-powered compressor unit for
production of compressed air, which interacts with an
oil circuit for lubrication, which is followed by an
oil separator device for separation of the oil from the
compressed air, with a self-resetting temperature
switch for switching off the compressor unit when the
air/oil mixture flowing in reaches a maximum
temperature limit being provided in the area of the
inlet of the compressed air containing oil into the oil
separator device.
In addition to oil-injected screw-type compressors, the
present invention is also used for other types of oil-
injected compressors, for example, vane-cell
compressors as well. In the case of compressors of the
type that is of interest here, oil is injected by means
of an oil circuit into the area of the moving
compressor components, and on their bearing points, in
order on the one hand to lubricate the roller bearings
which are provided in this case and rotate at high
speed, and in order on the other hand to prevent
unacceptable heating in the area of the moving
compressor components, as a result of friction.
Furthermore, the oil is also used to seal the air side
from other areas of the compressor. The use of oil-
injected compressors such as these extends not only to
stationary compressed-air supply installations, but
also to mobile applications such as rail vehicle
construction, or else to commercial vehicle
construction where compressors are used to produce
compressed air for the vehicle compressed-air supply
system.

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Oil-injected compressors, such as oil-injected screw-
type compressors, are known from the general prior art.
An oil-injected screw-type compressor essentially
comprises a compressor unit with at least one pair of
compressor screws in the form of rollers, rotating in
opposite directions to one another, and intermeshing
with one another. This compressor screw arrangement is
used to produce compressed air, in that air that is
sucked in from the atmosphere from one side is
converted by continuous compression to compressed air,
which leaves the compressor unit via a spring-reset
outlet valve. In this case, the compressor screw
arrangement is driven via a drive shaft which is passed
to the outside out of the compressor unit via a seal,
by means of a motor which is flange-connected to it
here, generally an electric motor. In order to
lubricate, seal and cool the compressor unit, it is
equipped with an oil circuit which, starting from an
oil sump, supplies oil to the central area of the
compressor screw arrangement as well as to roller
bearings which are arranged in the area of the end face
of the compressor screw arrangement. The oil which is
injected here leaves this active area in the direction
of an oil sump, which represents the reservoir for the
oil circuit. The oil sump is generally located within
an oil separator device which follows the oil circuit.
The oil separator device is necessary in order to
remove the oil from the compressed air again, so that
compressed air which is free of oil is available on the
output side. Conventionally, the oil separator device
is formed essentially from an oil separator which
operates in a manner known per se, on the force of
gravity principle. The oil which is separated from the
compressed air which contains oil and rises in the oil
separator is gathered in the oil sump. The compressed
air which is already partially free of oil and rises in
the oil separator is then generally supplied to a

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cartridge-like fine separator and then leaves the oil
separator device via a pressure-maintenance valve
arranged on the output side.
According to EN Standard 1012-1, it is not permissible
for safe operation of an oil-injected compressor such
as this for the oil temperature to exceed 120°C
adjacent to the area in which the compressed air
containing oil enters the oil separator device. A
temperature switch is normally arranged in said area in
order to comply with this Standard. The temperature
switch switches on on reaching a temperature of 120°C
and. stops the drive for the compressor unit, by
switching off the motor. When the temperature falls
into the range below 12 0°C again, the drive for the
compressor unit is enabled again.
US 5,118,2 60 discloses a temperature switch such as
this for a screw-type compressor although, in this
case, this is not in the form of an oil-injected screw-
type compressor. The temperature switch is arranged at
the outlet of the screw-type compressor within an
outlet chamber. The compressed air which has been
heated by the screw-type compressor flows past this.
The temperature switch contains an electrical
bimetallic element which interrupts the drive to the
screw-type compressor when the temperature of the
compressed air that has been produced reaches a
specific maximum value. In addition to this temperature
switch, which is arranged in the area of the compressed
air flowing out of the compressor unit, a further
temperature switch is located in the area of the
electric motor that drives the screw-type compressor,
and protects the entire unit against motor overheating.
If a motor-powered compressor unit such as this is
provided with oil injection, so that it is necessary to
provide a downstream oil separator device in order to

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separate the oil from the compressed air, this results
in the problem that internal fires or detonations can
occur sporadically, despite the measure explained above
to prevent overheating within the oil separator device.
A singular event such as this normally occurs
downstream from the temperature switch, as required in
accordance with the Standard cited initially, within
the oil separator device. So far, the reason for such
an internal fire or detonation has not clearly been
explained. In specialist circles it is assumed that
this event is the consequence of electrostatic
discharges within the oil separator device, producing
electrical sparks. Lack of servicing and, in
particular, lack of oil can also be considered as
detonation causes. A fire or a detonation results in
temperatures in the oil separator device and downstream
from it which are many times higher than the specified
temperature limit of 120°C. Since the temperature on
the inlet side of the oil separator device, in
particular because of the physical proximity of the oil
sump, is matched only slowly to the hot temperature
level, the required temperature switch in the area of
the compressed air flowing in cannot react sufficiently
quickly to the event of a fire or detonation within the
oil separator device, or downstream from it. A fire or
detonation can result in the components of the oil
separator device, which are occasionally also produced
from aluminum, burning through, while, furthermore, the
bearing for the compressor screws can seize as a
consequence of overheating or lack of lubrication, and
in the case of the gray-iron and cast-steel housings
normally used, this can even lead to explosive
destruction of the compressor. Furthermore, combustion
residues also enter the exhaust air. In summary, this
singular event can result in hazards to personnel and
damage to the compressor as well as consequential
damage, which therefore cannot be prevented, or at
least limited by the temperature switch required by the

WO 2006/094781 PCT/EP2006/002121
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Standard.
The object of the present invention is therefore to
improve further an oil-injected compressor of the type
mentioned initially so as to make it possible to cope
with the negative effects of a fire or detonation
within the oil separator device.
On the basis of an oil-injected compressor according to
the preamble of claim 1, the object is achieved in
conjunction with the characterizing features of this
claim. The subsequent, dependent claims specify
advantageous developments of the invention.
The invention includes the technical teaching that at
least one non-self-resetting additional temperature
switch is provided in the internal area of the oil
separator device downstream from an oil-injected
compressor, and switches the compressor unit off
without delay in response to a fire or a detonation of
the compressed air which is contained in the oil
separator device and contains oil. For the purposes of
the present invention, the expression internal area of
the oil separator device should be understood as
meaning the large-volume internal area which contains
the oil/air mixture and, in particular, also the outlet
area of the compressed air, from which oil has been
separated, from the oil separator device as far as, at
most, the inlet to a recooler which may be connected
downstream in the outlet flow direction.
The particular advantage of the solution according to
the invention is that the specific positioning of the
additional temperature switch ensures that the
compressor is rendered inoperative without delay in the
event of an internal fire or detonation. Specifically,
in the case of compressed-air compressors, this
suppresses the oxygen supply, immediately quenching the

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fire and avoiding consequential damage. Pressure relief
is also normally initiated, assisted by the shut down
process. In summary, the process of shutting down the
compressor immediately, initiated according to the
invention, extracts oxygen very quickly from the
internal combustion process, quenching the fire. The
additional temperature switch therefore renders the
compressor inoperative quickly and permanently in the
event of this event. This effectively prevents
personnel injuries or total damage to the oil-injected
compressor, as well as consequential damage. Since at
least some of the components of the compressor will
have already been damaged in this event, the compressor
is rendered inoperative by the non-self-resetting
additional temperature switch according to the
invention until suitable maintenance personnel have
carried out a repair and operation of the oil-injected
compressor can resume after a new temperature switch
has been fitted.
The additional temperature switch should preferably be
in the form of a fuse link, in order to ensure that the
compressor is reliably reconnected only after said
specialist repair. This is because a fuse link
permanently interrupts the circuit bridged by the
additional temperature switch and is reliably destroyed
after initiation, thus precluding accidental
reconnection of the compressor unit. Furthermore,
temperature switches in the form of fuse links are
quite simple components which can be obtained as mass-
produced items. They also include particularly quick-
reaction fuse links which are particularly suitable for
the application according to the subject matter of the
invention.
In order to ensure that the additional temperature
switch according to the invention is reliably initiated
if the event occurs, it is preferably arranged in the

WO 2006/094781 PCT/EP2006/002121
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outlet area of the internal area, as defined above, of
the oil separator device, in which the flow speed of
the compressed air flowing out of it is normally high.
A particularly rapid temperature rise can therefore be
observed in this area in the event of a fire or
detonation, and can then be reliably detected by the
additional temperature switch. One particularly
suitable location for arrangement of the additional
temperature switch is in the area between a pressure-
maintenance valve, which is normally arranged on the
outlet side of the oil separator device, and an
upstream fine separator unit. It is also optimal to
arrange the additional temperature switch, on the
outlet side, in the compressed air flow in the area
immediately following said pressure-maintenance valve.
In a further measure which represents an improvement to
the invention, extinguishants are additionally forced
into the internal area of the oil separator device when
the additional temperature switch trips, thus resulting
in the oil-injected compressor being shut down by
switching off the drive. Generally known fire-retardant
substances, which extract oxygen by an appropriate
chemical reaction from their surrounding area when
heated, are suitable for use as extinguishants. These
substances may be in the form of powder, foam and the
like.
According to another measure that represents an
improvement to the invention, optical indication means
can be provided, which signal the tripping of the
additional temperature switch when the event occurs.
The advantage of this measure is that the rare
occurrence of a fire or a detonation within the oil
separator device can be diagnosed without doubt by the
maintenance personnel, thus allowing specific repair.
The present invention is not intended solely for a

WO 2006/094781 PCT/EP2006/002121
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single-stage, oil-injected compressor. It is
accordingly possible for the compressor also to be in
the form of a multistage compressor unit with each
stage being followed by an oil separator device, in
which case additional temperature switches according to
the invention must then be provided adjacent to the oil
separator device for each compressor stage.
Further measures that represent improvements to the
invention will be described in more detail in the
following text, together with the description of one
preferred exemplary embodiment of the invention, and
with reference to the figures, in which:
Figure 1 shows a longitudinal section through an oil-
injected compressor with a downstream oil
separator device, and
Figure 2 shows a longitudinal section through an
additional temperature switch for the oil
separator device.
As shown in Figure 1 an oil-injected screw-type
compressor essentially comprises a compressor unit 1
which is driven by a motor 2. A compressor screw
arrangement 3 which is mounted within the compressor
unit by means of roller-bearing arrangements such that
it can rotate, compresses air which is sucked in from
the surrounding area by the rotary movement produced by
the motor 2 and this air is supplied via an inlet
channel 4. Oil for lubrication is injected from an oil
circuit 5 in the axial central area of the compressor
screw arrangement 3. Some of the oil which is required
in this case for lubrication, cooling and sealing
purposes is in this case introduced into the compressed
air leaving the outlet side of the compressor screw
arrangement 3. An oil separator device 6 follows the
compressor unit 1, in order to separate the oil from

WO 2006/094781 PCT/EP2006/002121
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the compressed air.
The oil separator device 6 has an oil sump 7, in the
area of which the compressed air which contains.oil and
is produced by the compressor unit 1 flows into the oil
separator device 6. This flow is passed firstly into
the area of an initial oil separator 8. The initial oil
separator 8 separates oil by the force resulting from
the effect of gravity. The oil separated in this way
enters the oil sump 7. After passing through the
initial oil separator 8, the compressed air, from which
some of the oil has already been removed, enters a fine
separator 9. The fine separator 9 is in the form of a
cartridge and filters the compressed air, which is
partially free of oil, radially inwards via the outer
radial wall area. From here the compressed air, which
is now free of oil, is passed to an outlet 10 of the
oil separator device 6 from where it is passed into the
compressed-air system, which is not illustrated in any
more detail.
A self-resetting temperature switch 11 is arranged in
the area of the inlet for the compressed air, which
contains oil and is produced by the compressor unit 1,
into the oil separator device itself. The temperature
switch 11 switches the motor-powered compressor unit 1
off if a limit temperature of 120°C is exceeded. This
is done by switching off the motor 2. This prevents the
ingress of excessively hot compressed air containing
oil into the oil separator device 6. When the
temperature of the compressed air which contains oil
and is flowing in falls below the stated temperature
limit value, then operation of the compressor unit 1 is
resumed.
An additional temperature switch 12 is provided in
addition to this safety device, which prevents
overheating, in the internal area of the oil separator

WO 2006/094781 PCT/EP2006/002121
- 10 -
device 6. The additional temperature switch 12
identifies a temperature rise initiated as a
consequence of a fire or a detonation within the Oil
separator device 6 and then switches off the compressor
unit 1 in order to prevent further consequential
damage. For this purpose, and in contrast to the other
temperature switch 11, the additional temperature
switch is non-self-resetting in order to prevent
operation from being resumed after the rare event
mentioned.
in this exemplary embodiment the additional temperature
switch 12 is arranged in the compressed-air flow in the
area between an outlet-side pressure-maintenance valve
13 and the upstream fine separator 9. This position of
the additional temperature switch 12 is particularly
suitable for the purpose according to the invention,
since this is where the temperature rise occurs most
rapidly as a result of the high flow speed of the
compressed air flowing out and the proximity to the
fine separator 9, with the additional temperature
switch 12 in consequence reacting very quickly.
As shown in Figure 2, the additional temperature switch
12 which is used for the exemplary embodiment described
here comprises a pressuretight outer tube 14, at whose
proximal end a screw union 15 is provided. The screw
union 15 is used for screwing the temperature switch 12
into the housing of the oil separator device, which is
not illustrated in any more detail here. A thermal fuse
link 16 is accommodated at the distal end within the
pressuretight tube 14 and opens when a maximum
permissible limit temperature, which must be defined,
is exceeded, thus interrupting the circuit formed via
the two connecting lines 17. The interior of the
pressuretight tube 14 is sealed with a filling compound
18. The non-self-resetting temperature switch 12 is
located with its active area 19 within the compressed

WO 2006/094781 PCT/EP2006/002121
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air flowing out of the oil separator device 6.
The present invention is not restricted to the
preferred exemplary embodiment described above.
Modifications to it can also be covered by the scope of
protection of the subsequent claims. For example, it is
therefore also possible to use a different type of oil-
injected compressor, such as a vane-cell compressor,
provided this has a downstream oil separator device
which, of course, does not need to be connected
directly downstream from the compressor unit.
Furthermore, the oil-injecting compressor unit may also
be in the form of a multistage compressor unit with an
oil separator device following each stage. In this
case, it would be necessary to provide each oil
separator device with an additional temperature switch
according to the invention.

WO 2006/094781 PCT/EP2006/002121
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List of reference symbols
1 Compressor unit
2 Motor
3 Compressor screw arrangement
4 Inlet channel
5 Oil circuit
6 Oil separator device
7 Oil sump
8 Initial oil separator
9 Fine separator
10 Outlet
11 Temperature switch
12 Additional temperature switch
13 Pressure-maintenance valve
14 Tube
15 Screw union
16 Fuse link
17 Connecting lines
18 Filling compound
19 Active area

- 13 -
File reference: PCT/EP2006/002121
Applicant: KNORR-BREMSE SYSTEME FUR
SCHIENENFAHRZEUGE GMBH
Our reference: 2922K PCT Kie/nu
Date: December 14, 2006
New Claims 1-7
1. An oil-injected compressor, in particular an oil-
injected screw-type compressor with a motor-powered
compressor unit (1) for production of compressed air,
which interacts with an oil circuit (5) for
lubrication, which is followed by an oil separator
device for separation of the oil from the compressed
air, with a self-resetting temperature switch (11) for
switching off the compressor unit (1) when the air/oil
mixture flowing in reaches a maximum temperature limit
being provided in the area of the inlet of the
compressed air containing oil into the oil separator
device (6), in which case, furthermore, at least one
additional temperature switch (12) is provided in the
internal area of the oil separator device (6) and
switches the compressor unit (1) off without delay in
the event of a fire or detonation of the compressed air
which contains oil and is contained in the oil
separator device (6),
characterized in that the additional temperature switch
(12) is non-self-resetting, and in that its tripping
results in extinguishants being forced into the
internal area of the oil separator device (6).
2. The oil-injected compressor as claimed in claim 1,
characterized in that the additional temperature switch
(12) is in the form of a fuse link,, in order to ensure
that the compressor unit (1) is reconnected only after
specialist repair (Figure 2).
LK:hv

- 14 -
3. The oil-injected compressor as claimed in claim 1,
characterized in that the additional temperature switch
(12) which is arranged in the internal area of the oil
separator device (6) is fitted in the area in which the
compressed air flowing out of it is at a high flow
speed.
4. The oil-injected compressor as claimed in claim 3,
characterized in that the additional temperature switch
(12) is arranged in the compressed-air flow in the area
between an outlet-side pressure-maintenance valve (13)
and a fine separator (9) upstream of the oil separator
device (6) .
5. The oil-injected compressor as claimed in claim 3,
characterized in that the additional temperature switch
(12) is arranged on the outlet side of the compressed-
air flow in the area immediately after the pressure-
maintenance valve (13).
6. The oil-injected compressor as claimed in one of
the preceding claims,
characterized in that optical indication means signal
the tripping of the additional temperature switch (12),
in order to provide information about the need to
repair the oil separator device (6) as a consequence of
the detonation.
7. The oil-injected compressor as claimed in one of
the preceding claims,
characterized in that the compressor unit is in the
form of a multistage compressor unit with an oil
separator device following each stage, with an
additional temperature switch being provided on the oil
separator device of each compressor stage.

The invention relates to an oil-injected compressor, in particular an oil-injected
screw -type compressor, which comprises a motor-driven compressor unit (1) in
order to produce compressed air and which co-operates with an oil circuit (5) for
lubrication, which is arranged downstream from an oil, separating device (6) which
is used to separate the oil from the compressed air. A self-resetting temperature
switch (11), which is used to switch off the compressor unit (1) when the maximum
temperature limit of the incoming compressed air is reached, is provided in the
region of the inlet of the compressed air, which contains oil, in the oil separating
device (6). At least one non-self-resetting additional temperature switch (12) is
provided in the internal area of the oil separating device (6), which immediately
switches off the compressor unit (1) following a fire or an explosion of the
compressed air, which contains oil, and which is contained in the oil separating
device (6).

Documents:

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Patent Number

271396

Indian Patent Application Number

3382/KOLNP/2007

PG Journal Number

09/2016

Publication Date

26-Feb-2016

Grant Date

18-Feb-2016

Date of Filing

11-Sep-2007

Name of Patentee

KNORR-BREMSE SYSTEME FUR SCHIENEN-FAHRZEUGE GMBH

Applicant Address

MOOSACHER STR. 80, 80809 MUNCHEN

Inventors:

#	Inventor's Name	Inventor's Address
1	SCHMID, MICHAEL	AM KELTIENHANG 27 85229 MARKT INDERSDORF
2	LIEBERT, KONRAD	TEXETSTR. 70 85737 ISMANING
3	ZIEGLGANSBERGER, NILS	KLEMENTINENSTR. 36 80805 MUNCHEN
4	HERING, KARL	BAHNHOFSTR. 53 83677 REICHERSBEUERN

PCT International Classification Number

F04C 29/00

PCT International Application Number

PCT/EP2006/002121

PCT International Filing date

2006-03-08

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	10 2005 010 690.0	2005-03-09	Germany