DE3131943A1 - Gate valve with a threaded spindle which is axially fixed during operation - Google Patents

Abstract

In a gate valve (10) according to the invention, which has a back stop (66/88) which comes into effect when the threaded spindle (44), which is axially fixed during actuation, rises by a small amount, a system of gaps is provided to create play between the spindle nut (52) and the individual plates (38). This allows the use of a threaded spindle (44) of smaller diameter than one which has a sufficient cross-sectional area at the point at which it passes through the spindle gland (110) to allow the internal pressure in the gate valve cavity to be used to produce a sufficiently large force to overcome the frictional forces between the gate and the seating surfaces caused by the internal pressure, which counteract the movement of the threaded spindle, the threaded spindle (44) thus being able to move upwards as required. A further stop arrangement (180/182) for limiting the upward movement of the gate (36) is provided to define the position in which the full cross-section of the pipe is exposed. <IMAGE>

Description

Gate valve with axially firmer when actuated

Threaded spindle

The invention relates to a gate valve according to the preamble of claim 1 or claim 5, claim 6. In a known gate valve called "Graygate", as it is made by the Gray Tool Company,
Houston, Texas, USA. is currently sold, the pressure in the cavity of the valve body is built up when the gate valve is operated under pressure in the open position and then closed. If the slide is closed, this internal pressure is on the
Slide tongue segments, the segments against the
Seat surfaces are printed in the gate valve. The same pressure also loads the cross-sectional area of the threaded spindle. Therefore, the cross-sectional area that passes through the lead screw seal must be dimensioned so that the internal pressure applies sufficient upward force to overcome the frictional forces counteracting the screw movement, which are caused by the internal pressure between the valve tongue and the seat surfaces; this allows the threaded spindle to move upwards and at a rear

OFFICE 6370 OBERURSEL · · UNDENSTRASSE IO TEL. 06171/56849 TELEX 4186343 real d

OFFICE 8050 FREISING *
SCHNEGGSTRASSE 3-5
TEL. 08161/62091
TELEX 526347 pawa el

BRANCH OFFICE 8390 PASSAU LUDWIGSTRASSE 2 TEL. 0851/36616

/ ΙΟ *

present stop.

Boi a common safety shut-off device in the form of a Gate valve according to US-PS 37 89 875, is the threaded spindle diameter large enough to overcome the frictional forces, thereby ensuring that the lead screw can move at any time. From US-PS 41 49 558 and 42 45 661 further gate valves are known, which have basic designs similar to a gate valve according to the invention.

Tn a gate valve according to the invention, the one has a rear stop that comes into effect when the threaded spindle is axially fixed during actuation rises a small distance, there is a system of gaps between the lead screw nut and play to create play the slide tongue is provided. This ensures that a threaded spindle provided with a smaller diameter used; can be, as such, which has sufficient cross-sectional area at the point at which it passes through the threaded spindle seal in order to utilize the internal pressure in the gate valve cavity to to generate a sufficient force to counteract the pressure caused by the internal pressure between the slide tongue and to overcome frictional forces caused by the seat surfaces, which counteract the threaded spindle movement, so that the threaded spindle is intended to move upwards can move. Another stop arrangement to limit the upward movement of the slide tongue is provided, to determine the position that exposes the full cross-section of the pipeline.

Further details, features and advantages emerge from the following description of an embodiment ^OJ with reference to the drawing.

It shows

Fig. 1 is a vertical longitudinal section through an inventive Gate valve provided with the improved rear stop and the holding device according to the invention is. The gate valve tongue is

illustrated to the right of its center line in the lowered closed position and to the left of its center line in its raised open position,
10

FIG. 2 shows, in an enlarged illustration, the lower area from FIG. 1, and

3 shows a detail from FIG. 2 on the same scale, but in the raised position of the threaded pin

del.

In the following description are improved stops i nri ehtungon explained how it is in a shut-off gate valve can be provided in accordance with US-PS 42 45 661 a fusible part which allows the rear stop to become effective by melting out of a blocking position, as described in more detail below. The gate valve known from US-PS 42 45 661, which has a rear Has stop which is used when the threaded spindle is axially fixed during actuation and the bearing receiving cover closure are moved upwards so that, for. B. replaced the threaded spindle seal is also equipped with another device for actuating the rear stop, which becomes effective when the gate valve is exposed to heat of such intensity, that the functionality of the threaded spindle seal

3 ~> or other critical parts is in question. The further device works with the melting out of fusible material, the threaded spindle and its

Q 1 QA 3

Storage allows moving upwards relative to the slide cover. As can be seen without further ado, the blocking device can also be designed differently, for example in the form of a physically removable spacer part. Accordingly, the following description, which relates to the fusible part, is intended to can only be understood as an example of a wider range of possible solutions.

In Fig. 1 is a gate valve 10 with a housing 1? shown, which has a housing body 14. The housing body 14 has a longitudinal passage opening 16 which forms a flow channel. At the ends of the passage opening 16, the housing body IA has flanges with which the gate valve can be connected to form a shut-off device for the flow in the line.

A control chamber 20 is provided between the ends of the passage opening 16, which has a transverse channel which crosses the passage opening 16 and is open to the outside on a tubular projection 22 of the housing body IA. The projection 22 has a flat, end-face outer surface 24. 25th

The housing 12 also has a slide cover which rests flat on the outer surface 24 and with the housing body 14 z. B. is connected with screws 28. A sealing ring 30 is between the housing body 14 and the slide cover 26 inserted to seal the contact surface.

The slide cover 26 is annular or tubular

Element having a coaxially extending opening 32. 35

Tn of the control chamber 20 are seat surfaces 34 in the area of intersection with the passage opening 16 and one transverse to the

Passage opening 16 slidably movable slide tongue 36 intended. The slide tongue 36 consists of two individual plates 38 which can be spread apart and the gate valve contains a spreader 40 which presses the individual plates 38 against the seat surfaces 34 when the gate valve is closed, and which takes back the pressure force when opening the gate valve.

In FIGS. 1 and 2, the slide tongue 36 is raised in the open position on the left and lowered in the closed position shown on the right. When the gate valve 10 is open, the openings 42 are aligned through the respective individual plates 38 with the passage opening 16. When the gate valve 10 is closed, the restricted area of the respective individual plates 38 pressed against the respective seat surfaces 34.

A lead screw 44 is supported by a lead screw nut 52 is connected to the slide tongue 36 and extends out of the housing 12 through the opening 32 in the slide cover 26 out. Outside the housing 12, an actuating member 46 is connected to the threaded spindle 44. In the present Embodiment is the actuator a handwheel, by means of which by turning by hand in a Direction, the slide tongue 36 is raised and the gate valve 10 is opened and rotated in the other Direction the slide tongue 36 is lowered and the gate valve 10 can be closed. Other drives can can also be used.

The connection shown here between the slide tongue 36 and the threaded spindle 44 is in the US-PS 41 38 091 explained in more detail, to which reference is expressly made for further details. An open top, substantially cylindrical sleeve 48 is attached to the slide tongue 36. The sleeve 48 has a annular recess 50 extending perpendicular to the bushing axis in the vicinity of its upper one

'End up. A substantially semi-cylindrical design Half of the sleeve 48 is attached to the inner side of each individual plate 38 so that the halves to form the sleeve 4-8 face each other with their openings.

An internally threaded substantially tubular one Spindle nut 52 has a coaxial, annular projection 54 which, on its outside, lying between its axial ends, is attached. A hanging flange 56 with a coaxial ring axis is at the top End of the spindle nut 52 attached. The spindle nut 52 lies in the sleeve 48, the projection 54 in the Recess 50 protrudes and the annular flange 56 is arranged above the upper ends 58 of the individual plates 38. The annular flange 56 is surrounded radially by a torsion or spring plate 60, which at 62 on each of the individual platbons 38 of the slide tongue 36 is attached to the outer end of the sleeve 48. The radially inner surface the spring plate 60 and the radially outer surface of the annular flange 56 are through against each other a serration 64 set, the engagement of a relative rotational movement between the annular flange 56 and the Spring plate 60 prevents a low relative axial

* 5 movement allowed. Locking devices (not shown in more detail) can be provided to secure the annular flange 56 and the spring plate 60 in their position, and / or these elements can be designed in an integrated design or in one piece, with the notch connections

toothing 64 is omitted.

Further details of the threaded spindle 44 and the slide cover 26 are explained below in order to better understand the structure and mode of operation of the invention close.

The slide cover 26 has a substantially

IS

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connecting flange 66 extending in the radial direction and a tubular portion 67 extending coaxially upward therefrom. The opening 32 runs through both sections. At the point at which the opening 32 opens into the control chamber 20 is located a frustoconical ring seat 68 which is coaxial is arranged in the transition region of the opening 32 to an underside 70 of the flange 66.

In the axial direction a little bit above the ring seat 68, the substantially cylindrical one experiences Opening 3? eino orsto sudden Quorschni t.tsorwoi. torung, thereby forming a first upwardly facing shoulder 72. In the axial direction, further above, the experience Opening 32 a second sudden cross-sectional widening, whereby a second upwardly facing shoulder 74 within of the tubular portion 67 is formed.

An axial intermediate piece of the opening 32 in the tubular Section 67 of the slide cover 36 is provided with an internal thread at 76. Above the internal thread 76, the opening 32 has a circumferential groove 78 which is narrow in the radial direction and wide in the axial direction, which is delimited at "its upper side by an annular rib 80 pointing inward in the radial direction. Above A weather seal 82 is provided in opening 32 of annular rib 80.

The threaded spindle 44 has a ^{lower section 84 which is provided with an external thread ου} and which lies in the bushing 48 and - as explained in more detail above - is screwably connected to the slide tongue 36. In the axial direction, immediately above the point at which the threaded spindle 44 passes through the spindle nut 52

a collar 86 extending in the circumferential direction, which is arranged coaxially. An end face or shoulder 88 of the seen in the axial direction The collar 86 is frustoconical to match the seat 68

executed.

In normal use, as shown in FIGS is, the shoulder 88 remains spaced apart from the ring seat 68, and it remains between the two Surfaces in the V / o i illustrated in the drawing such a considerable gap.

Above the collar 86, the threaded spindle 44 has a long, cylindrical section 90 which runs in the axial direction and is not provided with a thread. In the axial direction above its opening out of the opening 32 in the slide cover 26, the threaded spindle 44 experiences a gradual reduction in its cross section, as a result of which a frustoconical area 92 is formed. Above this area 92, the threaded spindle 44 has an externally threaded shaft 94 which extends to its upper end. The area 92 stores the _em in a corresponding VJE i se frusto ff shaped manner executed hub ο β _to (j handwheel 4G. A snap ring 100 and a nut 102 are disposed on the shaft 94 to the hand wheel 46 to mount detachably mounted on the spindle 44 .

Inside the tubular section 67 of the slide cover 26, the cylindrical section 90 of the threaded spindle 44 is coaxial in the radial direction narrow shoulder 104, which is wide in the axial direction, on shoulders 106 and 108 that lie opposite one another.

A sealing insert 110 made from a stack of leather cuff elements is contained in the ring around the threaded spindle 44 and rests on the first shoulder 72. As illustrated in the drawing, the sealing insert 110 is after assembly by the injection of

Plastic material put into effect through a particularly nozzle-like injection opening 112.

A stuffing box 114 is in the ring around the threaded

■ si

'Spindle 44 arranged so that it is on the second Shoulder 74 rests and extends down so far that it supports the sealing insert 110.

A cover flap 116 is provided essentially in the form of an externally threaded tubular component and has an axially threaded intermediate portion 118 and an opening 120 therethrough on which a step-shaped cross-sectional constriction in an axially central region with the formation of a after has shoulder 122 pointing downwards. The part with the larger cross-section that leads to the shoulder 122, forms a space for receiving a bearing arrangement 124 for the threaded spindle 44. As clearly shown in the drawing, is a bearing bush 126, an annular disk 127 designed in accordance with a washer Fusible material, a ball bearing 128, a shaft ring 130, a ball bearing 138 and a snap ring 139 is provided.

After the sealing insert 110 and the gland 114 Are assembled, the bearing assembly 124 and the lid seal 30 are assembled and the lid cap 116 is unscrewed until the gland 114 is in the desired position Scope is compressed.

Below the threaded piece 118, the cover cap has a flat, circumferential recess 140. One Locking screw 142 is threaded through a 143 in ^ screwed the tubular part 67 of the slide cover 26, until it extends into the recess 140, which is located coaxially. This assembly prevents the locking screw 142 unscrewing the cover cap 116; in the practical version there are several locking screws 142 is provided on the circumference of the slide cover 26.

Above the threaded piece 118 the ceiling has a cap

an outer, concentric, narrow circumferential groove 144, the at least one lower, upwardly facing shoulder 146 owns.

c Kin retaining wire 148 for the top cap 116 is in the Screwed recess, which is formed by the opposing circumferential grooves 144 and 78. the The recess is longer in the axial direction than the thickness of the wire 148.

If the gate valve 10 is opened in everyday operation under normal conditions, the bearing arrangement prevents 124 an upward movement of the threaded spindle 44 in the slide cover 26. The slide tongue 36 becomes full

κ raised so that the openings 42 with the passage opening 16 of the housing 14 are aligned, a stop surface 180 is on the bottom of the sleeve 48 until it comes into contact with the lower end 182 of the lead screw 44 has been moved upwards, thereby under normal conditions a Lock against further lifting of the slide tongue 36 forms.

If, however, the gate valve 10 is open in use and is exposed to the pressure of the liquid in the Line system in which the gate valve 10 is installed, contained or transported can be a Leak occurs in the sealing insert 110. Under such conditions it may be necessary to remove the sealing insert 110 to be replaced while the gate valve 10 remains mounted in the line in the open position.

The invention makes such a repair possible through the following steps.

The locking screws 142 are unscrewed until they can be pulled out of the recess 140. Then the top cap 116 is unscrewed a few turns, which is limited by the retaining wire 148, the

clamped between the lower end face of the circumferential groove 78 and the upper end face 146 of the circumferential groove 144 is.

The lead screw 44, which is normally not moved upwards, can then be raised and tightened, whereby a metal-to-metal seal is formed between shoulder 88 and seat 68. While an effective seal remains intact, the retaining wire 48 snaps out, if the cover cap 116 is unscrewed, the bearing 124 becomes and the gland 114 is removed and if the sealing insert 110 is replaced, the gland 114 and the bearing 124 is reassembled, the cover cap 116 is is almost completely screwed on and the sealing insert 110 is activated through the injection opening 112. The sealing insert 110 is checked for leaks, while the retaining wire 148 reassembles the cover cap 116 tightened and the threaded spindle 44 rotated, which will loosen the metal seal formed at 88 and 68.

The heat-sensitive material of the ring washer 127 is a fusible, in particular metallic material, as it is, for. B. from US-PS 37 88 600, 37 71 540, 38 42 854 and 38 96 835 is known; the washer 127 is disposed axially between the upper bearing assembly 124 and the stuffing box 114. Does it come to a fire or the like, so probably the gasket insert

110 would be destroyed, dirt the ring disk 127, and

^ the molten residue flows out of the channels P, which are in communication with the receiving space for the annular disk 127 through the cover cap 116. Thereafter, the remainder of the bearing assembly 124 and lead screw 44 move upward until the stop is formed at 88 and 68 to prevent leakage. If the damage is not too great, the gate valve 10 can later be repaired by replacing the sealing insert 110 and the washer 127.

As illustrated in FIGS. 2 and 3 in detail, the annular recess 50 is in the individual plates 38 in the axial direction, for. B. in the vertical direction, longer than the axial thickness of the annular projection 54 on the spindle nut 52, namely by an amount which is designated in Fig. 2 below the projection 54 with A. This additional distance A in the axial direction is at least as large as and preferably slightly larger than the vertical distance C, which normally, as illustrated in FIG. 2, separates the stop sealing surfaces 88 and 68. Accordingly, when the threaded spindle 44 moves upward from its position shown in FIG. 2 to its position shown in FIG. Since a limited axial distance is provided for the annular projection 54 in the recess 50, the single-pole plates 38 do not have to be pulled up in order to enable the rear stop at 88 and 68. As a result, there is no need to pull the slide tongue sealing seats upwards relative to the ring seats 34. Accordingly, a fault-free stop is formed in any case even if the threaded spindle AA has a relatively small diameter at the point at which it extends through the sealing insert 110.

As the above description shows, the invention is not limited to the embodiment shown, but many modifications and changes are possible without departing from the scope of the invention.

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Claims (6)

Claims ί1 .) Gate valve with threaded spindle that is axially fixed when actuated, a) with a slide tongue in a sleu chamber is arranged, which crosses a flow channel in a valve housing, b) in which a threaded spindle] from a drive connection with the slide tongue extending outwards through a transverse channel, c) in which an annular seat surface is arranged on the slide housing inside the control chamber in this way is that it is the intersection area of the transverse channel with the control chamber surrounds the circumference, d) with an annular shoulder on the threaded spindle in such a position is provided, the axial distance to the annular seat surface during normal operation owns, e) in which a longitudinal passage opening in the valve housing forms a flow channel that forms the transverse channel or cuts the control chamber and is provided there with annular sealing parts, OFFICE 6370 OBERURSEL L1NDENSTRASSE 10 TEL. 06171/56849 TELEX 4186343 real d OFFICE 8050 FREISING '
SCHNEGGSTRASSE 3-5 TEL. 08161/62091 TELEX 526547 pawa d ZWF.IGHÜRO 83-30 PASSAU l.UDWIGSTKASSE 2 TEL. 0851/36616 ] whereby the slide tongue is plate-shaped with a blocking area and a passage area is provided, and wherein the slide tongue is provided in the transverse channel when rotated accordingly the threaded spindle is movable between a closed position and an open position, wherein in the closed position the blocking area closes off the flow channel and the slide zone in the blocking area seals against the annular sealing parts rests and in the open position the passage area with its opening through the slide tongue is axially aligned with the flow channel and f) in which bearings and seals are provided in the valve housing, which in normal operation the threaded spindle ] 5 store and seal in such a way that the threaded spindle is rotatable without a lifting movement, and which have at least one element which is out of its contact position is at least partially removable on the threaded spindle to give the threaded spindle an axially limited stroke movement corresponding to the axial distance between the annular seat and the one below it To enable ring shoulder on the threaded spindle, characterized in that the slide tongue (36) on the threaded spindle (44) with limited axial play in its Position is secured in such a way that in the closed position of the slide tongue (36) there is an axial backlash between the threaded spindle (44) and the slide tongue (36) of such a size occurs, which is at least the axially limited Movement play for lifting the threaded spindle (44) corresponds to when the bearing or sealing element is removed, so that the annular shoulder on the threaded spindle (44) in the closed position of the slide tongue (36) without requirement a sliding or pulling movement of the slide tongue (36) over the annular sealing parts in a rear Stop position on the annular seat of the valve housing can be raised. 2. Gate valve according to claim 1, characterized in that that an upwardly opening sleeve (48) is provided which has an upwardly pointing shoulder has that a part located at the lower end of the threaded spindle (44) is received in the sleeve (48) is, and that a downwardly facing shoulder of the threaded spindle (44) is provided within the sleeve (48) which is arranged such that it moves into the open position when the shut-off tongue (36) is lifted touches the upward-facing shoulder to create a positive stop against further lifting movement of the slide tongue (36) relative to the longitudinal passage opening (16) to create. 3. Gate valve according to claim 1 or 2, characterized in that that the bearing and sealing arrangement a) a first stepped cross-sectional widening in the transverse channel, which has a first upwardly facing shoulder (72) in the axial direction at a distance above the forms annular seat (34), b) a second sudden radial enlargement in the transverse canal, the second one pointing upwards Shoulder (74) in the axial direction at a distance above the first upward-facing shoulder (72) forms, c) a sealing ring (112), which the threaded spindle ^ (44) in the transverse canal, and that on the first shoulder (72) pointing upwards, d) an annular stuffing box (114) which surrounds the threaded spindle (44) in the transverse channel and which ^J rests on the second upward-facing shoulder (74) and has a tubular part that extends downward to the point of contact with the '' Sealing ring extends, e) an annular cover cap (116) which surrounds the threaded spindle, f) an area (118) provided with an external thread on the cover cap (116) and one with Internally threaded area on the housing in the transverse channel above the second upward "Ο pointing shoulder, this thread are interengaged to provide the gland (114) axially against the sealing ring (112) to press. g) a bearing arrangement (124) for the threaded spindle (44) between the threaded spindle (44) and the cover cap (116) is arranged in a secured position, ^ , whereby the sealing ring (112), even when the gate valve is open and installed, can be replaced by unscrewing the cover cap (116) and moving the threaded spindle (44) axially upwards until the annular shoulder (88 ) occurs on the threaded spindle (44) on the annular seat (68) in the valve housing (14) and seals this, the cover cap (116), the stuffing box (114) and the sealing ring (112) are removed from the transverse channel, a functional A replacement for the sealing ring (112) is installed, the gland (114) and the top cap (116) again be mounted and the cover cap (116) is screwed tight and the threaded spindle (44) is lowered again is attached to the annular shoulder (88) the lead screw from the annular seat (68) in to separate the valve body (14). 4. Gate valve according to claim 3, characterized in that • Net that the bearing and sealing arrangement is designed in such a way is that in the axial direction between the bearing assembly and the annular cover cap (116) Ring (127) made of fusible material is provided, which melts and leaks when the gate valve (10) is exposed to a sufficiently large amount of heat, such as a fire, to impair the functionality of the Sealing ring (112) would question, so that the bearing assembly (12Ί) in axial direction is shortened by an amount that the threaded spindle (44) a sufficiently large stroke movement allowed until the annular shoulder (88) on the threaded spindle meets the annular seat (68) in the valve body (14) touches and seals this. 5. Gate valve with axially firmer when actuated Lead screw that is rotated around the slide tongue relative to the flow channel located in the valve housing to raise or lower that a) a slide cover with a threaded spindle surrounding section, b) a bearing arrangement located in the tubular section which is installed between the threaded spindle and the slide cover to the threaded spindle to be rotatable, but normally 1 to avoid an axial movement relative to the valve cover, c) a first annular sealing surface on the lead screw and a second annular sealing surface on the valve cover, the two annular sealing surfaces are separated from one another at a distance during normal operation and thus do not form a surface seal, characterized in that d) the bearing arrangement (124) has as one of its components a component made of fusible material which the bearing arrangement (124) is extended in the axial direction, the component being made of fusible material is intended to melt and flow out if the gate valve (10) is at exceptional temperatures, such as B. a fire, is exposed, whereby an effective axial shortening of the bearing assembly (124) is effected, and thereby a limited axial movement of the threaded spindle (44) is allowed which is large enough to create a surface seal between the first and second annular Produce sealing surface as a rear stop for the gate valve, and e) the slide tongue (36) on the threaded spindle (44) with limited axial play in their position as 20 it is ensured that in the closed position of the slide tongue (36) an axial backlash between the threaded spindle (44) and the slide tongue (36) one such a size occurs, which is at least the axial limited play for lifting the thread-25 spindle (44) corresponds to the removal of the bearing or sealing arrangement, so that the annular shoulder (88) on the threaded spindle (44) in the closed position of the slide tongue (36) without the need for a sliding or Pulling movement of the slide tongue (36) with respect to the annular sealing parts in a rearward direction Stop position on the annular seat surface (68) of the valve housing (14) can be raised. 6. Gate valve with threaded spindle that is axially fixed during actuation, a) in which a slide tongue is located in a control chamber is ordered, which crosses a flow channel in a valve body, b) in which a threaded spindle is driven by a drive unit the connection with the slide tongue extends outwards through a transverse channel, c) in which an annular seat surface is arranged on the slide housing inside the control chamber in this way is that it surrounds the intersection area of the transverse channel with the control chamber circumferentially , d) in which an annular shoulder is provided on the threaded spindle in such a position that in normal operation has an axial distance from the annular seat surface, e) in which a longitudinal passage opening in the slide About housing forms a flow channel that intersects the transverse channel or the control chamber and there is provided with ring-shaped sealing parts, wherein the slider tongue is plate-shaped provided with a stop band and a pass band, and wherein the sliding tongue in the transverse channel with a corresponding rotation of the threaded spindle between a closed position and an open Stel system is movable, in the Schließstel- _Λ development of the blocking area closes the flow channel, and the slide tongue in the blocking area sealingly against the ring-shaped Sealing parts rests and in the open position the passage area with its opening through the slide tongue is axially aligned with the flow channel, and f) for the bearings and seals in the valve body are provided that in normal operation the thread store and seal the spindle in such a way that the threaded spindle can be rotated without lifting movement, and the have at least one element, which from its contact position on the threaded spindle at least is partially removable to the threaded spindle an axially limited stroke movement corresponding to the axial distance between the annular seat and the annular shoulder arranged below it on the threaded spindle to enable characterized in that an upwardly open Bushing (48) is provided in the gate valve, the has an upwardly facing shoulder that a part lying at the lower end of the threaded spindle in the Bushing (48) is received, and that a downwardly facing shoulder on the threaded spindle (44) within the sleeve (48) is provided and arranged such that it is the upwardly facing shoulder of the threaded spindle (44) touches during a stroke movement of the slide tongue (36) into the open position to one positive stop against a further stroke movement to form the threaded spindle (44) relative to the flow channel (16).