The present invention relates to a device for cont¬ rolling the supply of oil to a cooling and freezing plant which includes a freezing device with one or more evaporators connected to a device for cooling medium liquid and adapted to evaporate cooling medium liquid into cooling medium vapour, whereby the evaporator(s) is (are) connected to one or more freezing compressors via a suction collecting pipe and whereby the freezing compressor(s) is (are) adapted to compress the cooling medium vapour into compressed cooling medium gas, and which includes a cooling device with one or more coo¬ ling compressors which is (are) adapted, through a suction collecting pipe, to suck cooling medium eva¬ porated into gaseous shape into one or more evapora- tors, whereby an oil level regulator is provided to control the oil level in each cooling compressor, whereby the cooling medium preferably is of a type wherein oil is mixed with or float on top of cooling medium liquid. In devices of the abovementioned type it is de¬ sired to distribute oil to the various compressors in such a way that each compressor receives a prede¬ termined amount of oil. This is an essential require¬ ment since the compressors are damaged if they receive too little but also too much oil, but it might be difficult to attain especially when certain types of cooling medium are used.

The object of the present invention is to provide a device which better ensures that each compressor re- reives its predetermined amount of oil also if a coo¬ ling medium is used containing a relatively small amount of oil. This is arrived at according to the invention by means of the characterizing features of claim 1. The invention will be further described below with reference to the accompanying drawings, in which

fig. 1 with a principal sketch illustrates a so called one-step system with a device according to the invention; fig. 2 with a principal sketch illustrates a so called multi-step system with a device according to the invention; fig. 3 illustrates an intermediate cooling aggre¬ gate forming part of the multi-step system; and fig. 4 is a section along the line IV- 17 in fig. 3. The cooling and freezing plant 1 of fig. 1 is constructed according to a so called one-step system, while the cooling and freezing plant 2 of fig. 2 is built according to a so called multi-step system. In these cooling and freezing plants 1, 2, a cooling e- dium is utilized preferably of a type wherein oil is mixed with or floating on top of cooling medium liquid. As an exemple of such a cooling medium one can mention HCFC 22 (difluoro- onochloro-methane; CHF _^ Cl), which is substantially less polluting than previously uti- lized cooling media, but which is difficult to mix with oil in a proper manner, such that the compressors of the cooling and freezing plant 1, 2 receives pre¬ determined amounts of oil for impeccable operation. In the following we will describe a device which in one- -step as well as multi-step cooling and freezing plants 1 and 2 respectively, permits the use of the above- -mentioned cooling medium without causing any problem.

The one-step cooling and freezing plant 1 of fig. 1 includes a device 3 for cooling medium liquid. This device includes a conduit 4 for feeding the cooling medium liquid from a condensing device 5 in which comp¬ ressed cooling medium gas is condensed into cooling medium liquid into a tank 6 for cooling medium liquid. The liquid is brought from the tank 6 through a con- duit 7 into one or more evaporators 8, 9 and 10 forming part of a freezing device 11 in the cooling and free¬ zing plant 1.

In the evaporator(s) 8, 9 and 10, the cooling me-

dium liquid is evaporated into cooling medium vapour which is fed through a conduit 12 into a so called suction collecting pipe 13 or a corresponding device to which one or more freezing compressors 14-17 are connected. The freezing compressors 14-17 are adapted to suck cooling medium vapour into the suction collec¬ ting pipe 13, to compress said vapour and to discharge compressed vapour through a conduit 18. At each free¬ zing compressor 14-17 there is provided an oil level regulator 19 which is adapted to control the oil level in the respective freezing compressor 14-17 such that there always is a predetermined amount of oil therein. The contuit 7 feeding cooling medium liquid from the tank 6 is also connected to one or more evapora- tors 20, 21 and 22 forming part of a cooling device

23 in the cooling and freezing device 1. In the evapora¬ tor(s) 20, 21 and 22, cooling medium liquid is evapora¬ ted into cooling medium vapour, which is fed through a conduit 24 into a so called suction collecting pipe 25 or a corresponding device to which one or more coo¬ ling compressors 26-31 are connected. The cooling comp¬ ressors 26-31 are adapted to suck cooling medium va¬ pour from the suction collecting pipe 25, to compress said vapour and to discharge compressed vapour through a conduit 32. At each cooling compressor 26-31 there is provided an oil level regulator 33 which is adapted to control the oil level in the respective cooling compressor 26-31 such that there always is a predeter¬ mined amount of oil therein. The conduit 18 for compressed cooling medium va¬ pour leading from the freezing compressors 14-17 of the freezing device 11 and the conduit 32 for compressed cooling medium vapour leading from the cooling compres¬ sors 26-31 of the cooling device 23 are connected to a so called pressure collecting pipe 34 or a correspon¬ ding device common to the cooling and freezing devi¬ ces 23, 11.

From the pressure collecting pipe 34, the compres-

sed cooling medium vapour is fed through a conduit 35 into an oil separating device 36 wherein a portion of the oil is separated from the cooling medium vapour and collected. The cooling medium vapour is fed from the oil separating device 36 through a conduit 37 into the condensing device 5, wherein it is condensed and trans¬ formed into cooling medium liquid which is fed into the device 3 for cooling medium liquid.

In the cooling and freezing plant 1 there is also included an oil distributing device 38 which is adap¬ ted to feed oil from the oil separating device 36 to the oil level regulator 19, 33 of each compressor 14-17, 26-31 for continuous access of oil to said oil level regulators such that they can provide each compressor 14-17, 26-31 with such an amount of oil that predeter¬ mined oil level is restored if it should fall below a certain limit.

Since there is a higher pressure in the cooling device 23 than in the freezing device 11, it is essen- tial that the higher pressure in the cooling device 23 can not affect the oil in the oil distributing de- , vice 38 such that this distributes too much oil into the freezing device 11. In order to solve this problem, the oil distributing device 38 has been devided by means of a valve device 39 into one part 40 belonging to the freezing device 11 and another part 41 belonging to the cooling device 23. The valve device 39 is provi¬ ded to prevent transfer of the higher pressure in part 41 directly to part 40, and to ensure that the required amount of oil can flow from the oil separating device 36 through part 41 into part 40.

The valve device 39 preferably has a valve 42 which is adapted to normally close and when required open a connection 43 between parts 41 and 40. The valve 42 is provided to sense the oil level in an oil contai¬ ner 44 and to keep the connection 43 closed when the oil level in the oil container 44 exceeds a certain limit. If however, the oil level in the oil container 44

fall below a certain limit, the valve 42 is operated to open the connection 43 to discharge oil from part 41 into the oil container 44. When once again there is a predetermined oil level in the oil contai- ner 44, the valve 42 closes the connection 43.

Hereby, it is ensured that the amount of oil in the oil container 44 and thus, in part 40 is always sufficient without the high oil pressure in part 41 directly affecting the oil pressure in part 40. From the oil container 44, oil is fed into the oil level regulators 19 through a conduit 45 and in order to ensure that the pressure in the oil contai¬ ner 44 and in the suction collecting pipe 13 are the same, the interior of the oil container 44 is on top communicating with the interior of the suction collec¬ ting pipe 13 via a conduit 46.

Part 41 of the oil distributing device 38 coope¬ rates with the oil separating device 36 through a con¬ duit 47 which is adapted to feed oil from the oil sepa- rating device 36 into a collecting container 48 for oil. This collecting container 48 is through a con¬ duit 49 connected to the oil level regulators 33 of the cooling compressors 26-31 and also through a con¬ duit 50 to the connection 43 with part 40. In order to ensure that the pressure in the collecting contai¬ ner 48 and in the suction collecting pipe 25 are the same, the interior of said container 48 is on top, through a conduit 51, communicating with the interior of said pipe 25. For collecting suitable amounts of oil from the cooling medium vapour flowing from the evaporators 8, 9, 10 of the freezing device 11 through the conduit 12 into the suction collecting pipe 13 and portioning pre¬ determined amounts of oil into the suction collecting pipe 13, the conduit 12 opens into an oil collecting and portioning device 52. This device is provided to collect oil from the cooling medium vapour and portio¬ ning it into the suction collecting pipe 13 when the

oil level in the oil collecting and portioning device 52 has reached a certain limit.

The oil collecting and portioning device 52 pre¬ ferably includes an oil collecting container 53 which down below has an oil collecting member 54 formed by e.g. a lower end portion of the conduit 12. From the oil collecting container 53 above the oil collecting member 54 there is extending a conduit 55 for feeding cooling medium vapour into the suction collecting pipe 13 while oil proceeds downwards into the oil collec¬ ting member 54. Preferably, the oil collecting mem¬ ber 54 is down below connected to the suction collec¬ ting pipe 13 via an oil portioning conduit 56 which is dimensioned such that it successively leaks oil when the oil level in the oil collecting member 54 raises to a certain limit.

For collecting suitable amounts of oil from the cooling medium vapour flowing from the evaporators 20, 21 and 22 of the cooling device 23 via the con- duit 24 into the suction collecting pipe and portio¬ ning predetermined amounts of oil into the suction collecting pipe 25, the conduit 24 opens into an oil collecting and portioning device 57. This device is provided to collect oil from the cooling medium va- pour and portioning it into the suction collecting pipe 25 when the oil level in the oil collecting and portioning device 57 has reached a certain limit.

The oil collecting and portioning device 57 pre¬ ferably includes an oil collecting container 58 which down below has an oil collecting member 59 formed by e.g. a lower end portion of the conduit 24. From the oil collecting container 58 above the oil collecting member 59 there is extending a conduit 60 for feeding cooling medium vapour into the suction collecting pipe 25 while oil proceeds downwards into the oil collec¬ ting member 59. Preferably, the oil collecting mem¬ ber 59 is down below connected to the suction collec¬ ting pipe 25 via an oil portioning conduit 61 which

is dimensioned such that it successively leaks oil when the oil level in the oil collecting member 59 raises to a certain limit.

The cooling and freezing plant 2 illustrated in fig. 2 is designed as a multi-step system in the shape of a two-step system. The cooling and freezing plant 2 is, with the exception of the pressure collec¬ ting pipe 34 common to the cooling and freezing devi¬ ces 23, 11, identical to the cooling and freezing plant 1 of fig. 1 and therefore, the reference nume¬ rals for the cooling and freezing plant 1 have been substantially maintained in the cooling and freezing plant 2 of fig. 2.

Instead of feeding the compressed cooling medium vapour from the cooling and freezing compressors 26-31, 14-17 into the common pressure collecting pipe 34 and therefrom into the oil separating device 36, compressed cooling medium is fed from the freezing compressors 14-17 through an intermediate cooling aggregate 62 into the cooling compressors 26-31 and compressed coo¬ ling medium vapour therefrom into the oil separating device. Compressed cooling medium vapour from the free¬ zing compressors 14-17 is fed through a conduit 63 to the intermediate cooling aggregate 62 and thereto is also fed cooling medium liquid from the device 3 via a conduit 64. In the intermediate cooling aggregate 62, the compressed cooling medium vapour is cooled by the cooling medium liquid brought thereto and the cooled cooling medium is fed from the intermediate cooling aggregate 62 through a conduit 65, the conduit 24 and the suction collecting pipe 25 into the cooling comp¬ ressors 26-31 of the cooling device 23.

In order to separate oil from the received comp¬ ressed cooling medium vapour, the intermediate cooling aggregate has an oil separator 66 (see fig. 3). This is provided to separate oil from the cooling medium vapour by spraying the oil and cooling medium mixture received against surfaces, along which oil can flow

downwards and cooling medium leave upwards. The oil separator 66 preferably includes two horizontally or substantially horizontally extending tubes, namely an inner tube 67 extending preferably coaxially within an outer tube 68. The inner tube 67 is connected to the conduit 63 and thus, adapted to feed compressed coo¬ ling medium vapour. The outer tube 68 is connected to the conduit 64 for cooling medium liquid. The inner tube 67 is closed in its end portion and has apertures 69, 70 that are adapted to direct jets 71, 72 of oil and cooling medium mixture horizontally or substantially horizontally against the inner side 73 of the outer tube 68, whereby oil will flow downwards (arrows 74 and 75) while cooling medium will depart upwards (arrows 76 and 77). Hereby, oil 78 will flow along the bottom 79 of the outer tube 68 and cooling medium above said bottom. The oil will flow through the con¬ duit 65 to the conduit 24 and it will gather in the oil collecting and portioning device 57 as described above.

By means of the oil distributing device 38 describe above, it is ensured that all compressors during opera¬ tion of one-step as well as multi-step systems at each time receive sufficient amounts of oil, i.e. neither too small nor too large amounts of oil.

The invention is not limited to the embodiment described above and illustrated in the drawings, but may vary within the scope of the following claims. As an example of an alternative embodiment, the cooling medium can be of another type than described, the valve device 39 in the oil distributing device 38 may be of another type than shown, the oil collecting and portio¬ ning devices 52, 57 may be of another type than shown and the intermediate cooling aggregate 62 and/or the oil separator included therein may be of another type than described.

The freezing device 11 may have another suitable number of freezing compressors than four and another

suitable number of evaporators than three. The cooling device 23 may have another number of cooling compres¬ sors than six and another suitable number of evapora¬ tors than three.