GB2164729A - Pinch valve - Google Patents

Abstract

A pinch valve has a housing (1) with a T-like arrangement of two holes (2 and 3), of which the first hole (2) runs through the housing (1) from a port in one side (4) to a port in the other (5). This hole is lined by an elastic collapsible pipe (6) which is able to be pinched by a plunger (16) mounted in the other hole. Between two end positions the plunger may be moved and set in a number of intermediate positions for different flow cross sections of the pipe by means of a setting device (54) which has detent elements (30). <IMAGE>

Description

SPECIFICATION A pinch valve The invention relates to pinch valves and more especially although not exclusively to a pinch valve having a housing with a first hole and a seond hole opening into the first hole in a T-like configuration, the first hole extending between two opposite sides of the housing and containing a flexible pipe which is able to be pinched, and the second hole contains a pinch plunger mounted therein so that it may slide between a first end position in which the pipe is released and a second position in which the pipe is pinched so that the bore thereof is completely obiturated.

Such a pinch valve may be used to shut off the flow of a fluid through a flexible pipe as rapidly as possible. Conventionally the second hole, in which the plunger slides, has a helical groove in the material defining its wall to receive a nosepiece on the plunger. The plunger has its outer end projecting out of the second hole and is connected here with a short angled operating lever. By turning the plunger using the lever through about 90 the plunger is screwed inwards owing to the cooperation of the nosepiece with the groove towards the pipe and pinches it so that it is completely shut off.In order to retain the plunger in either of the two end positions and to keep it from being shifted by the counter force of the elastic pipe, the two ends of the peripheral groove are set at a right angle to the axis of the second hole and it is then not possible for the plunger to move out of the one or the other end position of its own accord. There is no provision for intermediate settings of the plunger with the pipe in a partially pinched condition and such a setting would be very difficult to obtain, because of the counter force of the pipe on the plunger in any such intermediate position and such force will be transmitted to the nosepiece so that owing to its engagement with the walls of the groove a force component will result in the length direction of the plunger and the same will be turned.Accordingly it is very difficult or even impossible to reset the plunger into an intermediate position with the pipe partially pinched so as to get precisely the same flow cross section.

Therefore one object of the present invention is to remedy such disadvantages of the prior art.

A further object of the invention is to devise a pinch valve which makes possible variable flow rate control through the flexible pipe in the valve with the possibility of locking the plunger causing flow restriction in discrete positions between its two end positions.

A still further. aim of the invention is to make it possible for the pinch valve to be reset in given intermediate settings as frequently as possible, i. e. with reproducible adjustments of the valve plunger position.

In order to achieve these or other objects, in the invention a pinch valve comprises a housing with first and second holes therein placed in a T array with the second hole opening into the first hole between ends of the first hole in two opposite sides of the housing, a plunger slidably mounted in said second hole, a pipe of flexible material placed in said first hole, said plunger being able to be moved between a first end position in which it pinches the pipe and blocks it and a second position in which the pipe is released, a setting device connected with the plunger for setting the rate of flow through the pipe, and releasably engaging detent elements for establishing and releasably determining intermediate positions of such plunger between its said end positions.This makes it possible for the pinch valve to be utilized as a choke valve, whose different choke positions may be releasably set. This offers the advantage that any desired choking effect may be reproduced whenever needed and any position of the setting device is accurately tied to a given fluid choking effect.

If the setting device is provided with an indicating device as for example a scale and a pointer it will be substantially simpler to reproduce a setting of the pinch valve which has been previously used. If the setting device comprises interlocking detent elements able to move in relation to each other the result will be an extremely simple and straightforward structure of the device, while at the same time ensuring that there is no chance of the valve plunger wandering out of its set position. If the two detent elements are pressed together by spring force there will on the one hand be a secure locking of the two elements against each other while on the other hand however it will still be possible for the detent elements to be turned in relation to each other without excessive force.It is an advantage if one of the detent elements is stationary, as for instance by being anchored to the housing, while the other detent element is connected directly or indirectly with the plunger. If the moving detent element is provided with a setting lever, then setting will be facilitated. If the setting lever is adapted to swing about a pivot point and the moving detent element is able to participate in the same swinging or rocking motion, there is the advantage of a very simple possibility of coupling the setting lever with the detent element in a very simple manner. Additional coupling means such as levers will not be needed. A particularly simple way of mounting the stationary detent element on the housing is by way of screws, pins or the like.The pinch valve may be made highly compact if each detent elements are made like perforated disks or washers and are stacked coaxially on each other. Such a design is characterized by a very low wear rate. in this respect it is an advantage if the mating faces of the perforated disks are provided with mating teeth or serrations interlocking with each other so that the disks may not be unintentionally twisted in relation to each other with a loss of the setting made.In order to provide a very effective method preventing relative motion of one detent element in relation to the other while on the other hand making possible a twisting of the two elements in relation to each other with the expenditure of only a small amount of force, it is possible to have, a bearing pin running centrally and coaxially through the two detent elements and to bias the moving detent element towards the stationary detent element by means of a pressure spring mounted between the bearing pin and the moving detent element itself. In this respect assembly will be facilitated if the pressure spring is slipped coaxially onto the bearing pin and has its one end connected with the bearing pin by way of a fastener such as a circlip, a hollow spring pin or the like.

The cost of the pinch valve may be reduced if the bearing pin is formed by the plunger and if it projects from the second hole from the housing. In order to transmit the motion of the moving detent element to the plunger the two components may be positively locked together, as for example by a hollow spring pin or a cotter pin.

It is possible for the plunger to have a longitudinal cutout as for example a slot, aligned with the axial direction and extending in the radial direction, for the fastening element such as a hollow spring pin to run in. The breadth of the longitudinal cutout will in this respect be at least as large as the outer diameter of the fastening element, but is preferably somewhat larger than it. If now the plunger has a projection supporting it in a generally helical groove in the wall of the second hole of the housing so that turning of the plunger will be accompanied by an axial shifting thereof, then although the moving detent element is connected with the plunger all the time positively, there will be no hinderance of the axial motion of the plunger.

In accordance with a further useful development of the invention the housing has a slot adjacent to the second hole to run along the length thereof, such slot running radially through the housing as far as an outer face thereof radially in relation to the second hole.

The opening of the slot and the stationary detent element are in the same plane or in two planes that the parallel to each other.

This construction offers the advantage that a nosepiece on the plunger may run in the longitudinal cutout or slot so that axial displacement of the plunger at the same time causes a longitudinal displacement of the nosepiece.

This measure entails the further beneficial effect that the plunger does not have to be turned in order to change the choke setting and it is only necessary to apply a thrust in the axial direction of the plunger by way of the nosepiece extending through the longitudinal cutout or slot. This may be made possible by causing the nosepiece to extend beyond the outer face of the housing and to be plugged into a longitudinal slot in the setting lever to guide the motion of the nosepiece in the longitudinal direction of the setting lever.

Then any rocking of the lever about the bearing pin supporting the moving detent element causes a displacement of the plunger directly in the axial direction of the second hole.

If the moving detent element has a pointer mounted thereon to cooperate with a fixed scale, as for example one on the housing, there is then the advantage of being able to obtain a reading for the setting of the plunger whenever required.

As part of a further useful development of the pinch valve of the invention the plunger extends out of the second hole and has its end part fixed to the setting lever and extends roughly at a right angle in relation to the longitudinal axis of the plunger. Then rocking the setting lever about the longitudinal axis of the plunger will directly cause a rotation of the plunger itself in a very simple manner. In this connection a further useful effect is to be had if the moving detent element is mounted on the side of the setting lever facing towards the stationary detent element and is designed in the form of a latch. The end of the latch nearer the stationary detent element is preferably chamfered and snaps into the stationary detent element in an aligned manner.The stationary detent element is mounted coaxially to the longitudinally axis of the plunger, f. i. on the housing, in the form of a perforated disk or a crescent-like section thereof. The detent element may have teeth on its radially outer limit to mate with the chamfered latch end. In order to ensure engagement of the latch with the stationary detent element at any time the end of the latch remote from the stationary detent element is urged towards the setting lever by means of a spring and so presses the latch towards the stationary detent element. To release the locking engagement, the latch is best made with a release bar so that by the application of a force in the direction of the spring the latch may be moved clear of the stationary detent element and the locking action overriden. In order to be able to accurately check out the setting of the choke, the setting lever is made with an indicator hole in the overlap zone of the stationary detent element to cooperate with a scale on the stationary detent element.

In order to keep the latch from assuming skew position and then jamming it runs longitudinally in a guide sleeve on the setting lever.

Some working examples of the invention will now be described in detail on the basis of the accompanying drawings.

Figure 1 is a side elevation and partial section of an embodiment of the invention.

Figure 2 is a view of the embodiment in accordance with the section line A-A of Fig.

1.

Figure 3 is a view of a further form of pinch valve of the invention.

Figure 4 shows a further advantageous working example of the pinch valve of the invention.

Figure 5 is a view of the pinch valve of the invention following the section line B-B of Fig.

4.

Referring firstly to Figs. 1 and 2 the reader will be able to see a pinch valve with a housing 1, in which a first hole 2 has a second hole 3 opening into it in a T-like configuration.

The first hole 2 stretches from one side 4 to the other side 5 of the roughly cubic housing 1. The hole 2 accommodates an elastic collapsible pipe 6 or hose extending right through it. The pipe 6 projects past the sides 4 and 5 by a certain amount in order to present an opportunity of connection with further lengths of hose or pipes or the like. The outer face 7 of the flexible pipe 6 rests against the wall 8 of the hole 2 and is urged against it owing to its elastic properties.

As noted, the second hole 3 has its one end opening perpendicularly into the first hole 2, whereas the opposite end of the hole 3 is at the top side or face 9 of the housing 1, such side being perpendicular to the two other housing sides 4 and 5 that are generally parallel to each other. The port 10 of the hole 2 opening into the hole 3 is covered over by a section of the pipe 6. A generally cylindrical pressure shoe 11 is mounted in the hole 3 and may slide in the direction of its axis. At its end 12 adjacent the hole 2 this shoe is bluntly pointed. The shoe 11 has a radial nosepiece 13 projecting from its outer face and running in a longitudinal groove 14, which is made in the wall 15 of the hole 3. The shoe 11 is therefore so mounted in the hole 3 that it may run in the axial direction while being prevented from twisting about its own axis.

This shoe is part of a plunger 16, which in addition to the shoe has as its main part a cylindrical setting member 17. Like the shoe 11 the external diameter of the setting member 17 is also roughly equal to the diameter of the hole 3 but, with a slight clearance to allow motion in the hole. The setting member 17 is inserted in a downward direction into the hole 3 with its one end 18 foremost so that such end 18 engages the end 19 of the shoe remote from the end 12. This end 19 is in the form of an oblique sliding face 20 which extends at a certain angle to the longitudinal axis of the hole 3. The end 18 of the setting member 17 is made oblique at 21, 22 with the same angle as the sliding face 20.

There is a nosepiece 23 like a pin extending from the setting member 17 at a suitable point on its outer face. The nosepiece runs in a sloping or helical groove 24 in the wall of the hole 3 at 15. Any twisting of the setting member 17 about its longitudinal axis will cause the projection or nosepiece 23 to run along in the groove 24 so that the setting member will move towards or awa from the first hole 2 inside the housing 1. The sliding face of the member 17 will turn in relation to the sliding face 20 so that the shoe, which is kept from turning, will slide in the length direction of the second hole 3 towards the hole 2. Owing to the helical groove 24 and the oblique faces 20 and 22 the axial shift is produced in two stages.The crowned or bluntly pointed end 12 of the shoe 11 will then engage the pipe 6 and compress it so that the lumen of the pipe will be reduced where such pinching action takes place. Opposite the port 10 at 25 there is a ridge 26 of the housing in the first hole 2 so that the pipe 6 is somewhat dented at this position. In its second end position, in which the pipe 6 is completely closed, the shoe 11 is displaced so far towards and into the first hole 2 that the mutually opposite inner faces 27 and 28 of the pipe 6 are pressed together at the ridge 26.

The ridge 26 improves the sealing effect of the pinch valve.

The top end 29 of the setting member opposite to its sliding projects out of the second hole 3 above the top side 9 of the housing 1.

On the top side 9 there is a perforated disk or washer to act as a detent element 30 which is coaxial to the setting member 17.

This detent element 30 may be detachably fixed to the housing 1 or made integral therewith, or as in Fig. 1, it may be connected therewith by screws or locking pins or other fastening elements 31. In Fig. 2 the stationary detent element will be seen to be fixed by three fastening elements 31 spaced by about 1200 from each other. The inner diameter 32 of the washer-like detent element 30 is somewhat greater than the outer diameter 33 of the setting member 1 7 so that the setting member 17 may be moved in the central hole 34 of the detent element 30. The flat surface 35, facing away from the housing 1, of the detent element 30 is provided with teeth 36 running radially inwards from its outer edge to the inner diameter 32.On the surface 35 there is a second coaxial detent element 37 whose flat side 38 facing the housing 1 is provided with teeth 39 complementary to the teeth 36 and engaging them. The inner diameter 40 of the detent element 37 is the same as the inner diameter 32.

The detent element 37 has a fastener element 41, as f. i. a hollow spring pin, extending right through it diametrally and through a slot 42 in the setting member 17. The slot 42 extends in the axial direction of the setting member 17. The length of the slot 42 is equal to at least the maximum amount of adjustment of the setting member 17 and its breadth is slightly greater than the outer diameter of the fastener element 41.

The end 29 of the plunger 16 extends coaxially a certain distance past the detent element 37 and has a radial shoulder 43, for example in the form of a circlip. A pressure spring 44 is mounted on the setting member 17 and it is held between the shoulder 43 and the top side 45 of the detent element 37 facing away from the housing 1. In order to have a better engagement between the spring 44 and the top side 45 there is a washer 46.

On the outer edge 50 of the detent element 37 there is a radially extending setting lever 47 which is firmly locked to the detent element, as for example by welding or screws.

To improve handling and to avoid injury there is a setting handle 49 screwed on the end 48, remote from the detent element 37, of the setting lever 47. Such handle may for example be spherical. It is naturally possible for the setting lever 47 to be mounted at any other desired point on the detent element 37.

Furthermore a pointer 51 is mounted on the outer face 50 of the detent element 37 and is best fixedly connected thereto, as for example by screw means. The pointer 51 is directed radially away from the detent element 37 to cooperate with a scale 52, which is best arranged on the outer face 9 of the housing 1 and is coaxially placed in relation to the plunger 16. The length of the scale will be in accord with the maximum rotational displacement of the setting member.

The teeth 39 of the detent element 37 are pressed into engagement with the teeth 36 of the stationary detent element 30 by the force of the pressure spring 44. The detent element 37 is accordingly fixed so that may not be turned. By exerting a force on the setting lever 47 or the setting handle 49 in the circumferential direction of the detent element 37, the two sets of teeth 36 and 39 will 2be caused to ride over each other, i. e. the detent element 37 moves axially a small distance from the detent element 30. This axial displacement of the detent element 37 is opposed by the force of the spring 44, which is so designed that in the resting condition a secure locking action of the two interlocking sets of teeth 36 and 39 is ensured, while at the same time however being prepared to al iow a small axial motion of the detent element 37.The turning of the detent element 37 is for its part responsible for a twisting motion of the setting member 17 and the plunger 16 (via the fastening element 41) and owing to the cooperation of the nosepiece 23 and the groove 24 the plunger moves axially in the hole 2. Since the fastening element 41 runs in the longitudinal slot 42 free axial shifting of the plunger 16 is made possible as it turns about its axis.

A further embodiment of the pinch valve of the invention is to be seen in Fig. 3. The arrangement of the holes 2 and 3 remains the same as explained above, although the hole 3 is somewhat nearer to the side 4 of the housing than in Figs. 1 and 2. The plunger 16 is of single-piece construction since the shoe and the setting member are upited. Departing from the first embodiment, each detent element 30 and 37 has a separate bearing pin 53 passing through it coaxially, such pin being fixedly connected with the housing 1. The arrangement of each detent element 30 and 37 is as in the first embodiment of the invention, this being true of the scale 52 and the pointer 51 as well.However, departing from the first embodiment of the invention the setting device formed by the detent element 30 and the detent element 37 is not on the top side 9 of the housing 1 but on one of the side faces 55, whose plane is parallel to the length direction of the hole 3. The bearing pin 53 is placed perpendicularly in relation to the side face 55. A setting lever 47' is fixed to the detent element 37 so as to extend radially therefrom and between its ends it has a longitudinal slot 56 with a guiding function.

The hole 3 is connected by a slot 57 running in the longitudinal direction of the hole 3 and radially outwards towards the side face 55, to which it is perpendicular. A radial nosepiece 58 in the form of a pin runs outwards through this slot 57 so that the plunger 16 is kept from turning about its own axis in the hole 3. The nosepiece 58 projects past the side face 55 of the housing 1 and is received in the guide slot 56 of the setting lever 47. In order to prevent the setting lever 47' from being disconnected from the nosepiece 58 there is a circlip 59 on the nosepiece 58. The setting lever 47' is placed between the side face 55 and the circlip 59. It is best for the design to be such that the nosepiece 58 projects so far beyond the side face 55 that the setting lever 47' has a certain amount of freedom to move between the side face 55 and the circlip 59.

Owing to a spring as in Fig. 1 but not shown in Fig. 3, the detent element 37' is pressed against the stationary detent element, which is fixed in the housing 1. The sets of teeth of the two opposite surfaces or sides 35 and 38 engage with each other (see Fig.

1). If now the detent element 37 is is rocked by the lever 47' about the bearing pin 53, the result will be that the plunger 16 will be moved by way of the radial nosepiece 58 (joined to the setting lever 47') towards the pipe 6 or towards the face 9, dependent on the direction of motion of the setting lever.

The guide slot 56 causes a coupling between the translatory motion of the plunger 16 and the rotary motion of the detent element 37.

The manner of operation of the setting device 54 has been described in connection with Figs. 1 and 2.

A further embodiment or working example of the pinch valve of the present invention will be seen in Figs. 4 and 5. The arrangement of the plunger 16 and of the holes 2 and 3 in the housing 1 is the same as described in connection with Figs. 1 and 2. Unlike the embodiment of Fig. 1 the groove 24' is not inclined but aligned with a single plane radial in relation to the longitudinal axis of the hole 3.

The outcome of this is that any rotation of the setting member 17' does not cause a simultaneous axial shifting of the setting member. At its end 29' the setting member 17' is joined to a setting lever 47", which extends radially outwards from it and whose longitudinal axis is generally at a right angle to the longitudinal axis of the setting member 17'.

The setting lever 47" and the setting member 17' are fixedly joined together by a screw 60 and a pin 61. It would naturally be possible for the two parts to be joined together in some other way as for example by welding.

The setting lever 47" is plane parallel to the face 9 and between them there is a detent element 30', which is fixed to the housing 1.

The detent element 30' has the form of an arc of a circle centered on the longitudinal axis of the plunger. The end face 62 of the detent element 30' facing away from the plunger 16 has teeth running generally radially away from the plunger 16. A moving detent element 37' like a latch 64 is so mounted on the side 63 facing the housing 1 of the setting lever 47" so that the longitudinal axis of the latch 64 coincides with the longitudinal axis of the setting lever 47". The latch 64 runs in a guide sleeve 65 which is fixed to the setting lever 47' so that the latch 64 may shift in relation to the setting lever 47" in the direction of its length. The setting lever 47" and the latch 64 are so arranged that the longitudinal axis of the latch 64 is coplanar with the detent element 30'.The end of the latch 64 pointing towards the stationary detent element 30' is made oblique so that it exactly fits between the teeth 36' on the detent element 30'. The opposite end 67 of the latch 64 has a pin molded thereon plugged into and supporting a pressure spring 44'. One end of this spring 44' engages a shoulder 69 marking the end of the pin 61 and the beginning of the latch 64, while the other end of the spring engages a circlip or the like 43' on the setting lever 47".

Near the end 67 the latch 64 has a release pin 70 extending through it it. This pin 70 extends to the side both past the latch 64 and also past the setting lever 47". The force of the pressure spring 44' causes the end 66 of the latch 64 to be engaged with the teeth 36' on the detent element 30'. Because of the engagement of the end 66 and of the teeth 36' the plunger 16 is maintained in its position it which it is prevented from being turned. For changing the setting to another choke cross section it is simply necessary to press on the release pin 70 against the force of the spring 44'. As a result the end 66 and the teeth 36' are disengaged and it is possible to turn the plunger 16. Release of the release pin 70 will cause the teeth to be re-engaged.

The separate teeth 71 of the set of teeth 36' each have flanks 72 and 72' of differing length so that the two flanks of a tooth are at different angles The one tooth flank 72 is roughly radial in relation to the plunger 16, while the other tooth flank 72' is inclined to the flank 72 at an acute angle of for example 45" The end 66 of the latch 64 is so designed that it generally has the same form as the space between any two consecutive teeth.

The consequence of this is that on re-setting the setting lever 47' (as in Fig. 4) in a clockwise direction the latch 64 does not have to be operated separately, since the small slope of the tooth flank 72' causes automatic disengagement from the tooth. The placement of the plunger 16 and of the setting device 54 is in this case such that turning the setting lever in the clockwise direction increases the choking effect.

It is naturally possible for the teeth to be symmetrical in which case the individual tooth flanks would appear like isoceles triangles.

In the range of overlap between the stationary detent element 30' the setting lever has a viewing opening 73 making it possible to see the detent element 30'. There is a scale 52' on the detent element 30', produced for example by printing, to be seen through the opening 73.

Claims (36)

1. A pinch valve comprising a housing with first and second holes therein, the second hole opening into the first hole between ends of the first hole in two opposite sides of the housing, a plunger slidably located in said second hole, a pipe of flexible material located in said first hole, said plunger being movable between a first end position in which the plunger pinches and blocks the pipe, and a second position in which the pipe is released, a setting device connected with the plunger for setting the rate of flow through the pipe, and releasably engaging detent elements for establishing and releasably determining intermediate positions of said plunger between said end positions thereof.

2. A pinch valve as claimed in claim 1 wherein said setting device comprises display means for indicating individual plunger settings.

3. A pinch valve as claimed in claim 2 wherein said display means includes a scale and a pointer for co-operation therewith.

4. A pinch valve as claimed in any of claims 1 to 3, wherein said setting device comprises first and second relatively movable and relatively engageable detent elements of which the first element is stationary and attached to said housing and the second element is able to move with the plunger.

5. A pinch valve as claimed in claim 4, comprising spring means for urging said detent elements into engagement with each other.

6. A pinch valve as claimed in claim 4 or 5, comprising a setting lever attached to said second detent element.

7. A pinch valve as claimed in claim 6, wherein said setting lever is able to be rocked about a pivot point with a simultaneous and similar rocking motion of said second detent element.

8. A pinch valve as claimed in any of claims 4 to 7, comprising fastening members to hold said first detent element in place on said housing.

9. A pinch valve as claimed in any of claims 4 to 8, wherein said two detent elements are washer-like and coaxially stacked.

10. A pinch valve as claimed in claim 9, wherein said detent elements have faces engaging the respective other detent element, said faces having complementary engaging teeth thereon.

11. A pinch valve as claimed in any of claims 4 to 10, wherein said first detent element is placed between said housing and said second detent element.

12. A pinch valve as claimed in any of claims 4 to 11, comprising a bearing pin on which said detent elements are co-axially mounted.

13. A pinch valve as claimed in claim 12, comprising a pressure spring placed between said bearing pin and said second detent element, said spring pressing said second detent element onto the first detent element and causing engagement of the two detent elements.

14. A pinch valve as claimed in claim 13, wherein said pressure spring is co-axially arranged around said bearing pin and has one end resting on a projection on said pin.

15. A pinch valve as claimed in any of claims 12 to 14, wherein said bearing pin is formed by said plunger, same projecting out of said second hole.

16. A pinch valve as claimed in claim 15, wherein said plunger is positively joined to said second detent element.

17. A pinch valve as claimed in claim 16, comprising a securing element joining said plunger to said second detent element.

18. A pinch valve as claimed in claim 17, wherein said securing element fits into a slot extending axially in said plunger.

19. A pinch valve as claimed in claim 18, wherein the said slot has a breadth at least equal to the outer diameter of said securing element.

20. A pinch valve as claimed in any of claims 4 to 14, wherein said housing has a slot aligned with the second hole and extending radially from it as far as ohe outer face of said housing to a slot opening in first plane parallel to a second plane to which the plane of the stationary detent element is also parallel.

21. A pinch valve as claimed in claim 20, wherein said plunger running in said second hole has a radial projection slidingly extending through said slot.

22. A pinch valve as claimed in claim 21, comprising a setting lever with a slot therein for slidingly connecting it with said projection where same extends from a side of said housing.

23. A pinch valve as claimed in claim 22, wherein said lever is connected with said plunger and rocking of said second detent element in relation to the first detent element is transmitted by said lever to said plunger for axial motion thereof.

24. A pinch valve as claimed in any of claims 4 to 23, when dependent on claim 3, wherein the pointer is affixed to said second detent element and the scale for co-operation with said pointer is stationary.

25. A pinch valve as claimed in any of claims 1 to 8, wherein said plunger protrudes from said second hole and is attached to said setting lever at its end and the lever projects generally at a right angle in relation to a longitudinal axis of said plunger.

26. A pinch valve as claimed in claim 4, wherein said first detent element is in the form of at least a segment of a round disk with a concentric hole and is centered on a longitudinal axis of said plunger.

27. A pinch valve as claimed in claim 26, wherein said first detent element has a radially outer face with teeth or serrations thereon.

28. A pinch valve as claimed in claim 26 or 27, comprising a setting lever for shifting said plunger and wherein said second detent element is in the form of a latch on a side of said setting lever turned towards said housing.

29. A pinch valve as claimed in claim 28, wherein an end of said latch nearest said first detent element is oblique and adapted to engage teeth of said first detent element.

30. A pinch valve as claimed in claim 29, comprising a spring to urge said latch into engagement with said teeth on said first detent element, said spring engaging the end of said latch remote from said first detent element and said setting lever.

31. A pinch valve as claimed in any of claims 28 to 30, comprising a release pin on said latch to oppose the force of said spring.

32. A pinch valve as claimed in any of claims 28 to 31, wherein said first detent element has an overlap range wherein said setting lever has a viewing opening for co-operation with a scale on said first detent element.

33. A pinch valve as claimed in claim 32, comprising a sleeve on said setting lever for longitudinally guiding said latch.

34. A pinch valve substantially as hereinbefore described with reference to Figs. 1 and 2 of the accompanying drawings.

35. A pinch valve substantially as hereinbe fore described with reference to Fig. 3 of the accompanying drawings.

36. A pinch valve substantially as hereinbe fore described with reference to Figs. 4 and 5 of the accompanying drawings.