The object of such apparatuses is e. g. to measure the differential pressure in a certain point in the closed fluid cycle of a heating or cooling system, usually adjacent a balancing valve or a measuring valve. For this purpose conventional measuring nipples are provided with a slitted rubber body, through which, subsequent to an exposure, a measuring needle is inserted, which belongs to a measuring instrument, which indicates e. g. the pressure difference between two measuring points. The rubber body yields and closes respectively due to its elasticity.

Such measuring nipples often have only one sealing function against the environment as well as the fluid flow path, which allows a measuring signal output. Against the environment the nipples are sealing via a metallic contact between the connection end of the measuring nipple to said valve or the like and the housing of the valve. The sealing function, obtained in this way, is acceptable, provided the design and the handling is appropriate.

However, said rubber body has had weaknesses in practice. Its rubber mass looses its elasticity with time and at relatively high and low temperatures respectively and then a leakage can occur, particularly along the slit in the rubber body. I. a. for this reason it has often been considered necessary to provide such conventional measuring nipples with a sealing protective cap.

Also, already known constructions in this technical field have limitations as regards mounting capabilities and requirements as to space, which in certain cases might mean, that the measuring nipples should be mounted on the valve or the like by

means of chemical sealing means, which reluctantly are used in production due to their negative influence on the working environment.

US 4 565 211 relates to a branch nipple roughly of the type described in the introduction. This branch nipple, which belongs to a hydraulic circuit, has a pump tube connection, which temporarily can be blocked, a fluid path being opened between a fluid passage, shielded from the pump tube, and a connection device for connecting pressure measuring equipment. At said fluid passage there is no true valve but only switch means, which guide the fluid to said equipment, the pump pressure being avoided. There is only a true valve within the connection area for said connection device. Within the area with said switch means there are no sealing means, and consequently said fluid path probably will leak hydraulic fluid all the way up to said valve, also when it is closed. However, already in the initial phase of the connection of said equipment the connection device opens said valve simultaneously with the opening of the switch path. In this position the connection device is not firmly connected to the nipple without leakage problems, which means, that hydraulic fluid may leak out through the connection device, the pressure from the pump tube also increasing the risk of leakage, since said last-mentioned valve is designed in such a way, that it is opened up also at a small displacement, whereas said switch means in its turn are designed in such a way, that their displacement distance is relatively long and in said initial phase a hydraulic connection is established between said passage, the pump conduit and past said valve. Only in the absolute end phase of the switch means the pump tube is shielded from the fluid path to the valve, simultaneously with the tightening of the connection device. This tightening and the entire function of the connection device are connected to the valve as well as the switch means, and consequently none of these parts can be influenced without the other, which results in a large and obvious leakage risk, when the connection device is connected as well as when it is removed. For all these reasons such a construction if objectionable.

The object of the present invention is to as far as possible eliminate the above- mentioned drawbacks and develop a construction solution, which is simple, economic and reliable, as regards manufacturing, installation and operation. Also, it should be possible to provide already installed older valves and measuring flanges etc. with measuring nipples according to the present invention.

These objects are attained according to the invention by means of an apparatus of the type described in the introduction, which mainly is designed in the way set forth in the characterizing clause of claim 1.

Additional characterizing features and advantages of the invention are set forth in the following description, reference being made to the enclosed drawings, which show a preferred but not limiting embodiment of an apparatus according to the invention.

The drawings show in detail in : Fig. 1 a measuring nipple in a mainly diametrical cross-section, in an axial direction, which nipple forms a part of an apparatus according to the invention ; Fig. 2 a sectional view along section line 11-11 in Fig. 1 ; Fig. 3 a partially cut lateral view of a complete apparatus according to the invention before the application of a measuring tube to a measuring instrument; and Fig. 4 a magnified view, which corresponds to Fig. 3 but shows only the two measuring nipples after the application of the measuring tube to one of them.

In the drawings a complete apparatus 1 according to the invention is shown. This apparatus comprises as main components a point of measuring 2 in a fluid conduit 3, at least one measuring nipple 4 and a connection device 5 for the latter, which leads to a measuring instrument 6.

In Figs. 3 and 4 are shown as examples a point of measuring 2 adjacent a balancing valve 7, where the flow through fluid conduit 3 passes a seat 9, mounted in a valve housing 8, against which seat a valve cone 10 abuts, the position of which is designed

to be adjusted by means of a wheel 11 depending on a pressure drop value, which is determined by means of two measuring nipples, positioned on either side of said seat, one of which consequently being connected to inlet 12 of the valve and the other to outlet 13 of the valve. Measuring instrument 6 is connected via connection devices 5 to the nipples and the pressure difference is read.

Valve housing 8 is provided with sockets 14 and 15, each of them being designed to receive a nipple 4. The bottom areas of the sockets communicate via signal paths 16 and 17 with the inlet and the outlet respectively. The sockets are in their bottom areas provided with an internal thread 18 and 19 respectively and further outwards with an annular locking ring groove 20 and 21 respectively as well as with a bevel 22 and 23 respectively on the interior side of their free ends.

The measuring nipples are designed with a mainly rotation symmetrical cylindrical body 24 having a central, axial, through cavity 25 and a profiled exterior side, which includes, at its inlet end 26, a shorter external thread 28, suitably at a small distance from the respective free end side 27 and designed to gear with said internal thread 18 and 19 respectively. The free end side 27 is limited by an annular bevel 29, e. g. with a 45° angle, which is designed to be pressed against an annular sharp edge 30 and 31 respectively, formed by transverse and longitudinal annular surfaces, which encounter each other, at a socket bottom step 32.

Towards connection end 33 of the nipple, in order to connect a connection device 5, the nipple, which originates from inlet end 26, is in its turn surrounded by a groove 34, designed to receive an O-ring 35, a groove 36, designed to receive a lock pin 37, a safety flange 38, a polygonal flange, e. g. a hexagonal flange 39 and a special profiling 40, comprising e. g. a trapezoidal groove and a trapezoidal flange and designed to fasten said connection device.

Cavity 25 is divided into four sections, i. e. a long circular cylindrical guide hole 41, originating from connection end 33, designed to receive a piston 42, which projects from the connection end, a wider annular groove 43, connected to the hole and designed to receive an O-ring 44, a chamber 45 with a somewhat smaller diameter than the last-mentioned annular groove and a threaded bore 46, which is freely open at inlet end 26 and the diameter of which suitably is somewhat larger than the diameter of said chamber and is designed for a plug 47 to be screwed into it, in the end of which, which is accessible from end side 27, suitably a hexagonal opening or the like 48 is disposed, designed to receive a hexagon spanner, not shown. Guide hole 41 surrounds piston 42 with a cylindrical passage 49, through which fluid and pressure respectively is allowed to propagate from chamber 45 to the area outside connection end 33, when the conditions, described below, have been met.

Interior end 50 of piston 42 is, within the area with chamber 45, designed as a thick piston with an annular transition bevel to the pin-like main portion 51 with a somewhat smaller diameter. By means of this bevel the piston is designed to sealingly abut O-ring 44 using a compression spring 52, which is inserted between piston end 50 and interior end surface 53 of plug 47, e. g. by mounting a step portion 54 on the piston end to guarantee a safer mounting.

Chamber 45 is designed to communicate with the area at end surface 27 and consequently with one of signal paths 16 and 17 respectively, preferably via a radial cut 55 from the outside on an axial bypass 56 in the form of a tangential surface grinding, groove milling or the like, which at the one peripheral side of inlet end 26 penetrates its exterior thread and material in the entire axial extension of inlet end, but without at least appreciably interfering with bevel 29.

The apparatus according to the invention functions and is used in the following manner :

The measuring nipples are normally sealingly screwed into their sockets, bevel 29 abutting sharp edge 30 and 31 respectively and leveling out possible small irregularities in it, caused by deformation. Since plug 47 also functions as a sealing element, no fluid can pass from any of the signal paths to chamber 45. Connection end 33 of the measuring nipples may be protected by means of e. g. a hood, but this is not necessary. Since the chamber is empty or at least without pressure, a displacement of the piston against the force of the compression spring and consequently a temporary suspension of the sealing effect of the piston against O-ring 44 and groove 43 will be without consequences.

In this position, which is shown for the two nipples in Fig. 3 and for the nipple to the right in Fig. 4, a connection device 5, known per se, is applied, which is conducting via a measuring tube 57 to a measuring instrument 6, known per se, to one of the nipples. To the other nipple another connection device is also connected, which via another measuring tube also leads to the instrument, which is not shown in this figure. Connection device 5 surrounds with a sleeve-shafted portion 58 connection end 33 of the nipple, suitably all the way to polygonal flange 39. An O-ring 59 is then pressed against the outermost portion of special profiling 40, which O-ring is mounted in an interior annular groove 60 below an interior annular flange 61 in sleeve-shaped portion 58, which is screwed into a base portion 62 with a large diameter, which with an end portion 63, which has a smaller diameter, is inserted into a hooded nut 64, which surrounds a connection tube 65 from measuring tube 57 and clamps a shoulder 66 at its free end to end portion 63. On the outside of the free end of base portion 67 and sleeve-shaped portion 58 a lock housing 67 is slidably mounted in an axial direction, which by means of compression spring 68, which is supported by the end surface of the free end of base portion 62, is pressed away from the base portion and up to an abutment against a stop ring 70, which is inserted in an exterior groove 69 in sleeve-shaped portion 58. The sleeve-shaped portion receives lock balls 72 in wall holes 71, which are designed to, in a lock position, be pressed by lock housing 67 into the groove portion of special profiling 40, which is shown in

Fig. 4. A valve body 73 is then pressed against the force of a compression spring 74, which is supported by the bottom of base portion 62 and away from its seat 75 in sleeve-shaped portion 58 of piston 42, which in its turn is lifted away from its seat, i. e. O-ring 44. In this way fluid and pressure respectively can be propagated from the respective signal path through bypass 56, radial cut 55, chamber 45. passage 49, past radial openings 76 in valve body 73 and through connection tube 65 as well as tube 57 to measuring instrument 6. This can be done, only when the measuring nipple has been removed from edge 31, which is carried out by a screwing outwards, suitably until the lower wall of lock ring groove 36 hits the lock ring and presses it against groove 20 and 21 respectively in the corresponding socket. In this way an automatically sensible indication is obtained, when the opening position of the nipple in relation to the signal paths is attained.

In case the connection device 5 is to be removed, the measuring nipple will first be entirely screwed back into the corresponding socket, the bevel sealingly abutting sharp ring edge 31 and no fluid and pressure respectively being able to propagate from the respective signal path to the bypass, lock housing 67 then being drawn against the force of compression spring 68 against a step in base portion 62, in which position lock balls 72 can be pressed outwards in a radial direction and into an interior annular groove 77 in the end of the lock housing, which is turned away from the base portion, which is done by the removal of the entire connection device from the measuring nipple, compression spring 74, which is stronger than compression spring 52, first of all is allowed to expand and displace valve body 73 with a surrounding outer O-ring 78 to a sealing abutment against seat 75, designed as a truncated cone, in the sleeve-shaped portion 58, subsequent to which, when the removal of the connection device from the measuring nipple, also compression spring 52 again expands and displaces the piston to a sealing abutment against O-ring 44.

It is also important, that safety flange 38, when the nipple has been screwed into its position completely (see the right portion of Fig. 4), will shield socket opening

outwards in order to stop dirt from entering into grooves 20,21 and 36. It is shown in Fig. 4, that O-ring 35 is deformed elastically by the socket walls, when the nipple is inserted, and this will guarantee a satisfactory sealing outwards of the propagation path described above.

The apparatus according to the invention is characterized by new separate and combinational effects in comparison to already known connection devices. Thus, constantly physically, in a sensitive way influenced parts, such as slitted rubber bodies, have been completely eliminated. Also, the sealing is done in several safe steps instead of only one step, the sealing capability of the entire nipple/measuring point being dependent on this. The connection and the disconnection of the measuring instrument can be done with a sealing nipple and thus without the risk of unintentional leakage. Only when such a connection is completed, the nipple is opened without additional other means than those, which are used, when the nipple is to be mounted and removed respectively, i. e. an ordinary wrench or the like. The opening of the nipple is very simple, also when a high or low degree of opening is considered, since this is decided automatically by giving the service people the simple direction to screw the nipple out to a stop through lock ring 37. Such a stop means prevents also not authorized meshing with the apparatus. Also, the closing of the nipple is very simple and guaranteed to be efficient, since the screwing movement into the socket is automatically limited, not all of a sudden but with a soft braking but with a quickly increased resistance, which save all parts from damage.

Also, bypass 56 and radial cut 55 are very simple to manufacture through a quick and precise milling removal of nipple sections. Great accuracy in this regard is not important but nevertheless easy to attain. All sensitive rubber parts are carefully protected thanks to their design and their positions, a large life with retained quality and safety being guaranteed in a far-reaching way.

The present invention is mot limited to the embodiments described above and shown in the drawings but can be modified and supplemented in an arbitrary way within the

scope of the inventive idea and the following claims. Thus, it is of course possible to replace a bypass, designed in the nipple, or supplement the bypass with bypasses designed in the socket wall. At least to some extent the described rubber parts can be replaced by plastic parts. Pin-like portion 51 of the piston does not have to project beyond connection end 33. This portion can also end in the same plane as the end surface of the connection end or actually be somewhat recessed in order to be able to be pressed deeper into the nipple by valve body 73. Instead of a balancing valve or similar valve the apparatus can be mounted in arbitrary locations, e. g. adjacent a measuring flange or the like.