Such couplings are utilised when e. g. refrigerating installations are to be filled with refrigerant, or when pressure and other operation parameters are to be measured at different places in the installation by means of suitable measuring apparatuses that therefore have to be connected to the installation.

When conventional couplings are connected to an installation in connection with performing one or several of the above operations, some of the fluid will inevitably leak out into the surroundings which thereby is polluted. If the fluid is a refrigerant, the operator risks being injured by liquid refrigerant.

US Patent No. 4,328,948 discloses a coupling consisting of a first and a second part that serve for joining a first and a second fluid line. There is a valve in the first part and a valve depressor in the second. The two parts are joined with a union nut whereby the valve depressor opens the valve. The fluid can now flow from one of the lines to the other. When the coupling is disassembled, the valve automatically closes the first line whereas the fluid flows out into the environment from the other. If the second line is supplied with fluid from a source containing fluid under pressure, e. g. a pressure cylinder, a separate valve can be provided for closing at this location. However, the fluid in the remaining

part of the second line will still flow out and pollute the surroundings and possibly injure people that are near by.

The thus known coupling is furthermore slow and difficult to operate, and it has a complicated and costly structure.

The object of the invention is to provide a coupling of the kind mentioned in the opening paragraph, that has simple and inexpensive structure, that is quick and easy to operate, and that is arranged in such a way that fluid does not leak out into the surroundings when the coupling is utilised.

The novel and unique features according to the invention, whereby this is achieved, is the fact that the coupling comprises a first threaded socket for being tightly screwed onto the threaded connection piece; a second valve placed in the first threaded socket, said valve having both a valve head abutting tightly against a valve seat in the first threaded socket in the closed position of the first valve, and a second valve spindle which at the same time is in a position near the first valve spindle; a second threaded socket for being tightly screwed onto the first threaded socket; and a valve depressor placed in the second threaded socket and arranged to open the second valve and via this valve the first valve when the second threaded socket is screwed onto the first one with a pre-fixed number of threads.

By means of this simple and inexpensive. structure, e. g. a manometer can quickly and easily be connected to e. g. a refrigerating installation without any of the refrigerant leaking out into the open during this.

In an especially simple and expedient embodiment, the first threaded socket can have a first opening section with an internal thread corresponding to the thread of the connection piece, a subsequent second opening section with a smaller diameter than the first one, and a subsequent third opening section with a smaller diameter than the second one whereby the transition face between the first and the second section are brought into close contact with the end face of the threaded connection piece when the first threaded socket is screwed onto the connection piece, whereas the transition face between the second and the third section forms the seat for the second valve.

In this case, the internal thread of the first threaded socket can be shaped on at least two dies that are displaceably placed in corresponding radial slits in the socket, and at the same time, a boss ring can be placed around the dies whereby at the interior periphery of the boss ring and the exterior periphery of the dies, there can be bosses that are shaped in such a way that the dies are displaced when the boss ring is turned.

When the dies are in an extreme position in their respective radial slits, the first threaded socket can quickly and easily be led in over the connection piece after which the thread of the dies can engage the thread of the connection piece by a little turn of the boss ring. By subsequently tightening the socket, the desired sealing between this and the socket is obtained. The sealing can be further ensured by placing a sealing ring between the two parts.

The first threaded socket can furthermore have a nipple with the second and the third opening section, and externally, the

nipple can have a first outer section with an external thread for assembly of the second threaded socket and a subsequent second smooth outer section for accommodating a sealing ring.

In this case, the second threaded socket can have a first opening section with an internal thread fitting the external thread on the nipple of the first threaded socket, a subsequent second smooth opening section for accommodating the above sealing ring on the smooth section of the nipple of the first threaded socket, and a subsequent third opening section with a smaller diameter than the second.

The second threaded socket can furthermore have a nipple for assembly of a hose which in use is connected to a connection of e. g. a manometer or a valve on a pressure cylinder.

The valve depressor can expediently have a disc placed close next to the transition face between the second and third opening section of the second threaded socket whereby passage openings are shaped in this disc within a centre area which mainly has a smaller diameter than the third opening section.

When the coupling is opened, an apparatus or a pressure cylinder connected via these openings can communicate with the installation.

The coupling is opened by screwing the second threaded socket a suitable number of threads in on the first threaded socket.

By screwing the second threaded socket in the opposite direction, the valve is closed, as the second valve will abut against its valve seat in the first threaded socket and at the same time let go of the connection with the first valve spindle whereby the first valve is closed also.

In this condition, the coupling can be removed from the installation without risk as the first valve prevents fluid from leaking out of the installation via the threaded connection piece, and the second valve prevents fluid from leaking out of the coupling and the devices connected to it.

The security against such fluid leakage is greatest when a sealing ring is placed between the second valve and its seat.

The invention will be explained in greater detail below, describing only exemplary embodiments with reference to the drawing, in which Fig. 1 is a diagram of an installation with two couplings according to the invention, Fig. 2 shows a coupling according to the invention taken along the line 11-11 in fig. 3, Fig. 3 is an axial sectional view of a coupling according to the invention in a first assembly stage, Fig. 4 shows the coupling in fig. 3 in a second assembly stage, Fig. 5 shows the coupling in fig. 3 in a third assembly stage, and Fig. 6 shows the coupling in fig. 3 in a fourth assembly stage.

The below detailed description of the invention is based on the example that the installation is the refrigerating

installation 1 shown schematically in fig. 1, comprising mainly a compressor 2, a condenser 3, and an evaporator 4. A first threaded connection piece 5 is connected to the low- pressure side of the installation and a second threaded connection piece 6 to the high-pressure side of the installation. Each threaded connection piece 5 and 6 are connected to a manometer 9 and 10 respectively via a coupling 7 according to the invention and a conduit or hose 8. On the low-pressure side, the pressure can e. g. be between 0 and 3 bar whereas it can be between 7 and 15 bar on the high- pressure side.

Fig. 2 shows the coupling seen from the end whereas figs. 3- 6 show the coupling seen in an axial sectional view, in four different phases during assembly on e. g. the first threaded connection piece 5.

A first valve 11 with a first valve spindle 12 is attached in the opening 13 of the connection piece. In the figures, the valve 11 is only shown schematically. The valve is of a kind known per se, and it will therefore not be described any further here. It is opened by depressing the valve spindle 12.

The coupling 7 mainly comprises a first threaded socket 14 for being tightly screwed on the treaded connection piece 5 and a second treaded socket 15 with the conduit 8.

The first threaded socket 14 has a first opening section 16 with an internal thread 17 fitting the external thread 18 of the connection piece 5, a subsequent second opening section 19 with a smaller diameter than the first 16, and a subsequent third opening section 20 with a smaller diameter than the second 19.

Between the first and the second opening section 16 and 19 is a transition face 21 with a packing 22 and between the second and the third section, a transition face 23 with a packing 24.

The first threaded socket 14 furthermore has a nipple 25 containing the second and third opening section 19 and 20. The nipple 25 has a first outer section 26 with an external thread 27 and a subsequent smooth second outer section 28.

The second threaded socket 15 has a first opening section 29 with an internal thread 30 fitting the external thread 27 of the nipple 25 of the first threaded socket 14, a subsequent smooth second opening section 31, and a subsequent third opening section 32 with a smaller diameter than the second 31.

The second threaded socket 15 furthermore has a nipple 33 for assembly of the conduit 8 which, in the case shown, is a hose attached to the nipple by means of a collar band 34.

In the second opening section 19 of the first threaded socket 14 is placed a second valve 35 with a valve head 36 and a second valve spindle 37. The transition face 23 with the packing 24 between the second and third opening section 19 and 20 create a valve seat 23,24 for the valve head 36.

In the second smooth opening section 31 of the second threaded socket 15 is placed a valve depressor 38 that consists of a disc 39 with a pin 40. The disc abuts against the transition face 41 between the second and third opening face 31 and 32 of the second threaded socket and is fixed in the socket by means of a lock ring 42. In the disc is shaped passage openings 43 that fluid-connect the second and third opening section 31 and 32. By means of a screw 44, the valve depressor 38 and the

second valve 35 are screwed together so that the valve head 36 of the second valve abuts against the pin 40 of the valve depressor. As it can be seen, this pin is extending under this through the third opening section 20 of the first threaded socket.

As shown in fig. 2, four radial slits 45 are formed at the first opening section 16 of the first threaded socket 14. A die 46 is displaceably placed in each of these slits. The internal thread 17 of the first threaded socket is shaped on the radially inmost end of these four dies 46.

Around the dies 46 is rotatably placed a boss ring 48 with a circumferential groove 49 in one of the sides. The groove is extending in waveform with eight wave sections 50 and 51 with alternately a little bigger and a little smaller radius than the preceding and succeeding section. At the outer end, each die 46 has a projection 52 with a pin 53 that engages with the groove 49. The boss ring 48 and thereby the dies 46 are held in place by means of a lock ring 47 (figs. 3-6).

In fig. 2, the pins 53 engage with a wave section 51 with a smaller diameter than the preceding and succeeding wave section 50. The dies are then in their inner position. By a little turn of the ring 48 one way or the other, the pins 53 glide up into a section 50 with a larger diameter whereby the dies are pulled out to their extreme position.

Fig. 3 symbolically shows the refrigerating installation 1 in fig. 1 with the first threaded connection piece 5 and the first valve 11 built in the connection piece. The connection piece is to be connected to the manometer 9 (not shown) via the hose 8 and by means of the coupling 7.

By means of its internal thread 30, the second threaded socket 15 of the coupling is screwed just so far onto the external thread 15 on the nipple 25 of the first threaded socket 14 that the second valve 35 with its valve head 36 abuts tightly against the valve seat 23,24 in the nipple 25.

An 0-ring 54 between the smooth second outer section 28 of the nipple 25 and the smooth second opening section 31 of the second threaded socket 15 creates together with the closed second valve 35 a sealing between the two threaded sockets 14 and 15. In the position shown, the coupling is thus closed completely tight. The O-ring can possibly lie in a groove (not shown) in the surface of one of the two sections 28 and 31 in order to thereby be able to position the 0-ring better.

In fig. 3, the boss ring 48 is furthermore turned into the position in which the pins 53 of the dies 46 are in the wave section 50 (fig. 2). The dies 46 are therefore in their extreme position in which the internal thread 17 of the first threaded socket 14 on the dies 46 freely can pass over the external thread 18 of the threaded connection piece 5.

As shown in fig. 4, it has therefore been possible to easily and quickly push the first opening section 16 of the threaded socket 14 with the internal thread 17 across the external thread 18 of the threaded connection piece 5 without thereby having to rotate the coupling. In fig. 4, the seat 21,22 of the first threaded socked 14 is now lying close to the threaded connection piece 5.

The transition face 21 with the packing 22 between the second and third opening section 16 and 19 of the first threaded

socket 14 creates a seat 16,19 for the end face 55 of the threaded connection piece 5.

When the boss ring 48 now is turned into the position in which the pins 53 of the dies 46 are in the wave section 51, the dies 46 are pushed into their inner position whereby their internal thread 17 are made to engage with the external thread 18 of the threaded connection piece 5.

By a little turn of the coupling 7, the seat 21,22 of the threaded socket 14 is then, as shown in fig. 5, made to tightly engage the end face 55 of the threaded connection piece 5 so that the coupling 7 is now tightly connected to the connection piece 5 and thereby the installation 1. As it can be seen, both the first valve 11 and the second valve 35 are still tightly closed but the valve spindle 37 of the second valve 35 is now near the valve spindle 12 of the first valve 11.

In fig. 6, the second threaded socket 15 is screwed a distance further onto the first threaded socket 14. Thereby, the valve depressor 38 with its pin 40 has lifted the second valve 35 free of its valve seat 23,24 and during this, the valve spindle 37 of the second valve 35 has at the same time pushed the valve spindle 12 of the first valve 11 in and thereby opened this valve 11.

Both valves 11 and 35 are now open whereby the refrigerating installation 1 via the open coupling 7 and the hose 8 is brought into open fluid-connection with the manometer 9 (fig.

1).

At disassembly of the coupling, the above operations take place in reverse order. Thereby, the situation in fig. 3 arises, in which the first valve 11 closes the installation 1 and the second valve 35 the coupling 7.

Refrigerant in the coupling 7, the hose 8 and the connected manometer can therefore not leak out and pollute the surroundings and injure people that are near by.

The invention is described above on the assumption that the refrigerating installation were to be connected to a manometer by means of the coupling according to the invention.

It goes without saying that the coupling can just as well be utilised for connecting any instrument or aggregate or for e. g. filling the refrigerating installation with refrigerant from a pressure cylinder.

The coupling according to the invention is as described above well suited for quickly, easily and nonpollutingly being coupled to a refrigerating installation. However within the scope of the invention, the coupling can be utilised for any installation, aggregate or container that contain a liquid and/or gas with the same advantage.