This invention relates to a sampling valve of the type comprising a valve body having an axial bore, a valve stem axially displaceable In the bore, and a stretchable hollow valve plug that is mounted on the front end of the valve stem and in its stretched posi¬ tion closes against a valve seat coaxial with the bore and extending from an annular channel communicating with a pair of hose connection branches of the valve body. Such a valve structure is disclosed in the published documents of Applicant's Danish Patent Application No. 2732/86. An important feature of this valve is that the valve plug is firmly bonded to the wall of the axial bore at least in its area adjacent the annular channel, for the purpose of preventing liquid from penetrating between the valve body and the plug. Such a risk is involved with a previously known sampling valve, cf. Danish Patent Specification No. 147,119, in which the plug is firmly bonded to the forward end portion of the stem and forms a plunger operating in the forward end of the bore.

In the latter case the plug may be withdrawn from the bore together with the valve stem, e.g. for renewal or for allowing the interior of the valve to be inspected, whereas in the former case such a withdrawal or removal of the plug from the bore is more compli¬ cated because its bonding to the bore wall must be broken. The plug may be thereby further damaged so that it cannot be used again. The sampling valve of the invention differs from the known structures by the feature that on the inner surface of the valve plug member a bead is provided which in the mounted position of the member projects into a circumferential groove formed in the valve stem

and having an axial length that is sufficient to permit the stretching of the valve plug from its open to its closed position.

Under normal operating conditions the groove of

5 the valve stem does not prevent the bead from moving axially backwards and forwards relative to the stem when the plug is stretched and allowed to retract, respectively. However, when it is desired to remove the

.plug for inspection or other purposes, the stem may

10. simply be withdrawn axially out of the bore, thereby causing the plug to be carried along after the bead has come into contact with the forward side wall of the groove. When the plug has got clear of the bore, it may easily be snapped free from the stem, if so

15 desired.

The invention will now be more fully described with reference to the drawing, in which

Fig. 1 is a side elevation and axial section of a preferred embodiment of the valve in its closed 20 position, and

Fig. 2 a similar view of the valve when open. In the illustrated embodiment the valve com¬ prises a body or casing 1 adapted to be firmly mounted in the wall 2 of a tank or pipe containing a 25 liquid from which samples shall be taken from time to time. A pair of hose connection branches 3 com¬ municate at their inner ends with an annular channel 4 adjacent a central valve seat 5.

A bore 6 in body 1 is co-axial with the 30 valve seat, and in this bore a valve stem is axially displaceable. The stem comprises a front or lower por¬ tion 7 and a back or upper portion 8 with a threaded connection 9 therebetween.

A stretchable hollow valve plug 10 fits into

35 the forward end of the bore 6 and rests with a collar

11 at its open end against a shoulder in the bore. The

plug 10 surrounds the forward end of the stem portion 7 which in Fig. 1 is urged to the left by a helical compression spring 12 so that the plug 10 is stretched longitudinally and with its forward end or bottom is held in close contact against the valve seat 5. In this position a small amount of liquid may be withdrawn from the tank or pipe by means of a hypo¬ dermic needle inserted through one of the branches and forced through the closed end of the plug 10. The upper portion 8 of the stem is associated with a manual control, not shown, which is detachably connected with the valve body by means of a union nut 13 and is operative to displace the stem 7, 8 back¬ wards against the force of the spring 12, so that the plug 10 is allowed to contract to the open position illustrated in Fig. 2.

On the inner side of the plug 10 an annular bead 14 is provided which projects into a circumfer¬ ential groove 15 in stem portion 7. The axial length of this groove is such that it offers sufficient clearance for the bead when the plug is stretched and allowed to contract as explained above.

When it is desired to inspect the interior of the valve or possibly exchange plug 10, nut 13 may be loosened and stem 7, 8 retracted rom the bore 6 whereby the plug 10 is carried along due to the con¬ tact between bead 14 and the forward side wall of groove 15.