WO1988006690A1

WO1988006690A1 - Three-way valve with combined system for regulation and hydraulic balancing

Info

Publication number: WO1988006690A1
Application number: PCT/SE1988/000093
Authority: WO
Inventors: Rolf Strand; Hans Palmertz
Original assignee: Tour & Andersson Ab
Priority date: 1987-03-05
Filing date: 1988-03-02
Publication date: 1988-09-07
Also published as: SE8700924L; SE456689B; DK606888D0; FI88821C; AU1424388A; DK606888A; EP0418222A1; DK163598B; FI894172A0; DK163598C; FI88821B; SE8700924D0

Abstract

Three-way valve (1) including two co-axial through flow openings (12, 13) and a valve body (5) co-acting therewith, for optional distribution of the flow through these openings. The valve body comprises two mutually relatively axially movable valve body parts (6, 7), which can also be mutually relatively arrested. These parts are moved between different arresting positions by the valve body being urged by its stem against an abutment surface (the valve seat 14 or 15), at at least one through flow opening (12 or 13). A change in the relative axial positions of the valve body partts (6, 7) changes the total through flow capacity of the valve. The valve can thus achieve a variable constriction of the total flow.

Description

Three-way valve with combined system for regulation and hydraulic balancing

The present invention relates to a three-way valve of the kind more clearly apparent from the preamble to claim 1.

Three-way valves are used for variably combining two different incoming flows into a combined departing flow. They can also be used for variable division of an incoming flow into two separate departing flows. A three-way valve contains two co-axial valve openings co-acting with a common valve body having two seating surfaces or the like, which co-act with the valve openings. The distribution of the flow on the two-flow side tales place by moving the va l ve body between these openings. In these cases the flow proportions are also affected by the shape of the valve body, e.g. when it is provided with so-called flow contours, The flow characteristic of the three-way valve can thus be affected according to the prevailing need in this way, so that the characteristic does not necessarily vary rectal I nearly with the movement of the valve body.

In such a three-way valve of the prior art, the distribution of the flows passing through the valve tales place without the magnitude of the total flow being affected to any substantial degree. Such a valve must therefore be supplemented by further valve means for controlling the total flow. This is usually achieved by mounting a constricting valve on the side of the three-way valve having the single line or a supply line coming from the outside, e.g. a heating supply pipe. Such a constricting valve means extra costs and considerably more work for adjusting such as a central heating system, In such a system the three-way valve is usually operated automatically with the aid of an operating means remotely controlled from a regulating and control unit co-acting with different temperature transducers, e.g. transducers outdoors, for room temperature, and on delivery pipes. The regulation range of such a valve is limited, however, since the total flow cannot be affected. With incorrect adjustment of the associated constricting valve this can lead to a temperature which is too high or too low. The setting of the constriction valve can need further alteration for different seasons or when the installation is reconditioned etc.

Takeing into account the mentioned deficiencies in the already known three-way valves, the object of the present invention is to achieve a three-way valve, in which it is possible to provide regulation of the total flow through the valve while utilizing the valve body in the valve. A further object of the invention is to achieve a three-way valve, where such regulation can be provided with the aid of the ordinary operating means of the valve and in cooperation with its regulation and control unit.

For achieving these objects, a three-way valve of the kind mentioned above is characterized above all by the distinguishing features disclosed in the characterizing portion of claim 1.

Further advantageous distinguishing features of the invention are apparent from the subordinate claims and the following description of an embodiment of a three-way valve in accordance with the invention, where this embodiment is not to be regarded as restricting in any way, and with reference to the accompanying drawing, where; Figure 1 is a. section of a three-way valve in accordance with the invention, Figure 2 is a detail view of the valve body pertaining to the valve in Figure 1 and set for maxiumum flow through the valve, Figure 3 is the same as Figure 2 except that the valve body is set for the least possible flow through the valve, Figure 4 is a partially sectioned detail view of a first embodiment of a three-way valve in accordance with the invention, Figures 5, 6 are two views of a valve body in accordance with a second embodiment of the invention, Figures 7-9 illustrate two further embodiments of the invention, with and without so-called "split range" implementation, Figure 10 is a diagram illustrating how the flow characteristic of the valve varies with different settings of the valve body, and Figures 11, 12 are diagrams illustrating the relationsship between the movement of the valve stem and the distance between the parts of the valve body in a valve in accordance with the invention.

Figure 1 illustrates a three-way valve 1 in accordance with the invention, with a first valve duct 2 and two other valve ducts 3 and 4. In the illustrated example, the first valve duct is the outlet duct and the second valve ducts are inlet ducts. However, the flow direction can be opposite to what is shown. Between the first valve duct 2 and the second valve ducts 3 and 4 are intermediate walls 10 , 11 with two co-axial through flow openings 12, 13 having valve seats 14, 15. A valve body 5 comprising two parts 6 and 7 is arranged in the openings. These parts 6, 7 have seating surfaces 15, 16 co-acting with said valve seats 14, 15. The valve body 5 is movable between the two valve seats 14, 15 with the aid of a valve stem 8 and a not more closely illustrated conventional operating, means 9. The means 9 can be of optional type, e.g. a hand operated valve wheel. To enable full ut i l i zat i on of the advantages afforded by the invent ion , the operating means comprises a motor driven valve stem operating device which is controlled by such as the regulation and control system IS of a heating system via a control line 19. At least one of the intermediate walls 10, 11 has a threaded insert 20 to enable assembling the valve body between the openings IΞ, 13. The insert 20 is solely illustrated in Figure 4 and is not screwed into place until the valve body 5 has been assembled. The insert includes the valve seats 14 and 15. The valve stem is assembled, in a manner not more closely shown, in the valve housing 1 with the aid of such as a bush 22 and seals 24, as well as means for fixing or changing its axial position.

Both parts 6, 7 of the valve body 5 are mutually axially displaceable as is particularly shown in figures 2 and 3. The distance a between two points on the respective part 6,7 can be caused to vary between a least distance amax and a greatest distance amin. The least distance amax gives a maximum through flow capacity in both openings 12, 13 of the valve. Increasing the distance a gives increasing constriction of the through flow openings, and the greatest distance amin gives the least through flow capacity. Both parts 6, 7 are preferably movable between fixed setting positions, but can also be infinitely variably adjustable.

The through flow capacity through the respective opening IS, 13 depends on the position of the valve body 5, and also on the shape of the respective part 6, 7 of the body. This shape, the so-called flow contour, determines how the through flow area, is varied for axial movement of the valve body. For example, in figures 1-3 the upper valve body part 6 has an e l ip t ical or parabolic cross section. On the other hand, the lower body part 7 is cylindrical with a triangular recess 26. In the embodiment according to Figure 4, the upper body 6 and lower body 7 have cylindrical screening walls 28 and 29, respectively, with substantially parabolic or eliptical recesses 30. By suitable selection of flow contour, an optional variation of the flow capacity through the respective opening can be achieved in response to the position of the valve body. The total flow is then not necessarily constant but can vary in response to the position of the valve body and flow contour of the respective body part.

Figure 4 illustrates a detail in a three-way valve in accordance with the invention, in a first emobodiment of an axially adjustable valve body 6, 7. In the figure, the upper body part 6 comprises a cylindrical screening wall 28, a transverse wall 3S and a cylindrical wall 34 forming the middle portion of the valve body. The transverse wall has a passage 36 for the valve stem 8 and is also provided with a seal 38, e.g. an O ring, for sealing against the stem. The screening wall 28 has a sealing ring 40 intended for sealing engagement against the wall of the opening 12 in an insert 20. The wall 34 has arranged in an axial direction on its inner face a plurality of arresting recesses 42 of spherical segmental shape. In addition, the wall 34 has a sealing ring 44 intended for engagement against the cylindrical outside of the lower valve body part 7.

The lower valve body part 7 comprises a cylindrical screening wall 29, a transverse Wall 46 and a cylindrical wall portion 48. The transverse) wall has a through evacuating orifice 50 and a fastening hole 52 for the valve stem B. The part 7 and the valve stem 8 have transverse holes for a pin 54, which keeps them together. The screening wall 29 includes a groove for a sealing ring 56, this ring being intended for sealing engagement against the wall of the through flow opening 13. The wall 48 also has a radial hole 58 accomodating a spring 60 and a ball 6Ξ. The end of the spring away from the ball engages against a bottom plate 64, which is fixed in the hole 58 with the aid of threads or a press fit. Alternatively, the hole 58 can be a blind hole with a solid bottom. The cylindrical wall 48 can extend right up to the valve stem fixing hole 52, the transverse wall 46 then coinciding with the central wall 48. The hole 58 can then be straight through, with the spring 60 engaging against the valve stem 8, as illustrated in figures 7-9.

The three-way valve function is as follows. The valve body 5 is moved vertically by the valve stem 8 within the space .defined by the intermediate walls 10 and 11, With the aid of the arresting ball 62 and its accommodating arresting recesses 42 the upper valve body part 6 is caused synchronously to move with the valve stem in its movement. The movement of the valve body will then determine the flow distribution from, or to, the valve ducts 3 and 4. When the body part 6 has reached its upper boundary position 6 ', indicated in the figure with dashed lines, an abutment 66 in the upper end of the wall 34 is brought into engagement with an abutment surface 68 on the insert 20, alternatively on the intermediate wall 10. If the valve stem 8 is moved further upwards, the arresting ball 6S will be pressed out of its arresting recess and transferred to the one nearest above this recess. The arresting recesses are given the alphabetical denotations a-g.

In a corresponding way, for a downward movement of the valve stem 8 the upper body part 6 will be moved downwards, until it reaches a lower end position 6 ' ' indicated by dashed lines. The end surface 70 of the wall 34 will then be brought into engagement against an abutment surface 72 on the intermediate wall 11, or on an insert arranged in this wall. For a continued downward movement of the valve stem, the arresting ball 62 will be moved downwards one or more steps in a corresponding manner to a more downwardly positioned arresting recess 42. The downward movement of the body part 7 in relation to the body part 6 is restricted by a locking ring or circlip 74, arranged in a groove on the valve stem 8. The evacuation orifice 50 allows liquid to pass out from, and into, the space 76 defined by the transverse walls 32 and 46 when the body parts are mutually relatively displaced.

The total through flow area and capacity of the, valve are varied by this displacement of the parts 6 and 7 of the valve body 5. The through flow capacity is expressed as the kv value.

Figure 10 illustrates how the flow A through the valve duct 3 and the flow B through the valve, duct 4 vary in response to the position (stroke) of the body 5 and the mutually relative positions of its parts 6, 7. The instant position of the valve body is read off along the X axis and the through flow capacity kv through the openings 12, 13 along the Y axis. The flow through the upper opening 12 is shown by the curve A and the flow through the lower opening 13 is corresponded to by a plurality of curves Ba-Bg, which correspond to the different arresting positions of the body parts 6 and 7 in relation to each other. The instant flows A and B through the openings are obtained by going upwards from the position of the valve body on the X axis to the curve A and the applicable curve among the curves Ea-Bg (only a few are illustrated), the flows being read off on the Y axis. An example using dashed lines relating to the working range "d" is illustrated in the figure. The flows A and B can have different characteristics, and therefore the flow B is illustrated to the left in the figure for indicating scale graduation, which may possibly be different. The whole of the stroke range is thus available for all the curves Ba-Bg. The working ranges in question are denoted by double arrows a, d, g under the curves. If the valve body is moved to the right in the diagram, past the prevailing working range limit in the flow, the flow B will become zero or possibly a fixed minimum flow? while the flow A increases, simultaneously as the relative positions of the valve body parts 6, 7 are changed. In a following movement of the valve body to the left in the diagram the flow B is read off on the one of the curves Ba-Bg, which has its correspondence in the new arresting position. In the same way, on passing over the working range left boundary, there is an alteration of the relative position of the parts 6, 7 to a new arresting position with a new applicable working curve Ba-Bg with lower flows. When the valve body 5 is outside the working range in question, between it and an upper or lower end position 148 or 150, a liquid flow is obtained solely through one of the openings 13 or 12 according to the app l icab le curve Ba-Bg or the curve A.

The total flow AB consists of the sum of the instantly read-off flows on the curve A and the applicable curve Ba- Bg. This sum is usually substantially constant for each of the arresting positions of the valve body parts. A changed arresting position, i.e. an increased or decreased constriction, results in a substantial alteration of the total flow AB over the whole of the possible setting or working range for the valve body 5. The lower boundary value for the flow does not necessarily need to be zero, since the flow contour can be such that a certain minimum flow is always present. In such a case, no sealing ring 40 or 56 is used.

Figures 5 and 6 illustrate a second embodiment of a valve body 5 in accordance with the invention with an upper part 6 and a lower part 7 attached to a valve stem 8. The upper part 6 comprises a body 78 and a closure portion 30 with an annular flange 82 having a seating surface 16. There is a space 76 with a cylindrical outer wall between the body and the closure portion, this space being intended to accommodate the cylindrically shaped connection portion 84 of the lower valve body part 7. The body 78 has an arresting member 86 in the form of a spring, fastened in a conventional and optional way to the body 78. This member can also be formed in som other way, e.g. as a spring biassed detent member. The body 78 and the closure portion 80 are attached to the valve stem 8 with the aid of a threaded connection.

The lower valve body part 7 has essentially the form of a cylinder with an upper connection portion 84 and a lower closure part 88. This part also has an annular flange 90 With a seating surface 17. The closure part 88 has a seat or base 92, in the form of an externally threaded disk, for a return spring 94, The other end of the spring engages against the underside of the body 78. An evacuating orifice 96 is arranged in the base 92 for communication with an intermediate space 98 accommodating the spring 94. The closure part 88 can have an optional shape, suitable for obtaining the desired flow contour. It ca n also include recesses corresponding to the recesses 26 or 30. in which case the base can have the form of a ring, or arresting bosses projecting out from the closure part 88. The connection part 84 of the part 7 is provided with a glide sleeve 100, e.g. of plastics, which engages against the cylindrical outer wall of the space 76. The cylindrical inner wall of the connection portion engages against the similarly cylindrical body 78. A row of arresting projections 102 are arranged on the inner wall, and there are return and guide grooves in it for the arresting member 86, which is best seen in the detail view of Figure 6. In this figure there is seen a row of arresting projections 102, and to one side of the row a return and accommodating groove 104 for the arresting member 86. To one side of the groove 104 and partially open towards it there is a guide groove 106 for a guide means 108, e.g. a cylindrical projection. At both ends, the guide groove 106 has sloping deflection surfaces 110, 112, and at its lower end it has an open insertion groove 114 open to the space 98.

When the guide means presses against the respective deflecting surface 110, 112, there is achieved a relative rotational movement between the arresting member 86 arid the arresting projection 102. In this way, the arresting member can be brought into, and out from, engagement with the arresting projections. The guide means 108 will thus follow a path 116 arid the arresting means a corresponding path 118.

A change in the relative setting positions of both valve body parts 6, 7 is achieved in the following way. The valve body is moved downwards with the aid of the valve stem 8 until the seating surface 17 comes into engagement with the valve seat 15. A continued downward movement only moves the upper part 6, the arresting member 86 being displaced downwards past one or several arresting projections 102 to a new engagement position. When the valve stem is lifted, the arresting member 86 is arrested behind the arresting projection nearest above, and the valve parts maintain the obtained relative mutual position until the valve body is once again taken towards the valve seat 15 and a new adjustment takes place.

When the valve stem has taken the upper valve body part so far that the guide means 108 is brought into engagement against the deflecting surface 112, the guide means and the arresting member are deflected laterally. When the valve stem is now lifted, the arresting member can freely return through the return find accommodating groove 104 to an initial position 120 above the row of arresting projections. At the upper part of this return movement the guide means 108 and the arresting member 86 are deflected in the opposite direction by the deflecting surface 110.

The embodiment according to figures 7 and 8 substantially corresponds to the one in Figure 4. Instead of a cylindrical wall 28 and a cylindrical wall 34 of greater Diameter there is here a single cylindrical wall 124 having the same diameter throughout us length. In a groove in the wall 124 there is a circlip 126 which forms a shoulder 66. The circlip can be finally fitted by inserting a tool through the valve duct 2, and thus there is not required any threaded insert 20 in this embodiment. This embodiment further lacks an evacuation orifice 50 and sealing ring 44. Liquid passage to, and from, the space 76 takes place via a gap 128 between the cylindrical wall 124 and the valve body part 7, and particularly through the empty arresting recesses 42. There is preferably a plurality, e.g. 3 or 4 rows of such arresting recesses 42 with corresponding arresting means. With small valve openings it is very difficult to achieve an exactly predictable through flow capacity due to manufacturing tolerances and the like. The kv curve for a valve is therefore uncertain for openings of less than i/30 of the valve maximum opening. For a valve in accordance with the invention, this maximum opening is reduced to perhaps one third by the shortening of the stroke. The range with uncertain adjustment is unaltered and now constitutes 1/10 of the maximum flow. In so-called "split range" valves an auxiliary valve body is used to reduce the range of uncertain adjustment. Such an auxiliary valve body 130 is illustrated in Figure 9, and has a sealing ring 132 arranged at a central opening 134 with a valve seating 136 in the valve body part 6. The auxiliary valve body 130 is disposed on a tubular shaft 138 which surrounds the valve stem 8. The shaft has an outwardly directed flange 140, which is retained with a given clearance adjacent the valve bushing 142 by a member 144. The valve body is pressed downwards by a spring 146. Apart from the main flow within the opening 12 past the valve body part 6, a minimum flow passes the auxiliary valve body 130 via the opening 134 and further through the gap 128. Positional alteration takes place in this case by the valve body being pulled up until its auxiliary valve body closes, and further so that the flange 140 assumes a position 140', indicated by dashed lines, when it is in engagement against the bush 22. Further movement upwards of the valve body causes the arresting body 62 to assume a new arresting position 42 corresponding to a total larger through flow capacity. Alteration of the arresting position of the valve body parts 6, 7 in the opposite direction takes place in the same way as in Figure 4.

The implementation of both parts 6 and 7 of the valve body 5 kan be varied in many different ways within the scope of the invention. For example, in the embodiment according to Figure 5 the arresting member 86 may be arranged on the part 7 and the arresting projections on the part 6. The guide groove 106 and guide means 108 can also be optionally placed on one or other valve body part and do not need to connect up to arresting means and arresting projections. Furthermore, it is possible to arrange arresting means and arresting projections directed in the opposite direction as compared with Figure 5. In this case the valve stem 8 must pass through a passage in the part 6 and be fastened in the part 7. The return spring 94 is then disposed in the space 76 between the closure part 80 and the upper surface 122 on the connection portion 84. Here as well, the arresting member and arresting projections can be placed optionally on the respective parts 6 and 7.

The evacuation orifice 50 or 96 can be optionally arranged in the lower valve body part 7, or in the upper part 6. As illustrated in the figures, the evacuation orifice can be axially directed towards one of the valve ducts 3 or 4, but can also be radially directed towards the valve duct 2. It should be emphasized here that the return and accommodation groove 104 as well as the insertion groove 114 and guide groove 106 also serve as evacuation openings between the spaces 76 and 98.

The relative movements between the parts 6 and 7 in Figure 5 are illustrated in the diagram in Figure 11. The X axis here illustrates the stroke of the valve stem for relative displacement of both valve parts. As will be seen., the relative displacement only takes place in one direction and is followed by a jumping return to the initial position. If the valve stem is taken backwards and forwards after having reached the reversing position, without having reached the return position, when the guide means comes into engagement with the opposing upper deflecting surface, only the upper valve opening will be affected by such a. movement of the stem.

Figure 11 illustrates the relationship between the stroke of the stem movement and the distance a between two points on the parts 6 and 7 of the valve body 5. The greatest distance here is denoted by amin, since this distance corresponds to the least total through flow area of the three-way valve. In a corresponding way, the least distance Is denoted by amax,

Figure 12 is a corresponding diagram for a valve with a valve body essentially corresponding to the one in Figure 5, but where the arresting projection and arresting member are directed in the opposite direction. Changing the arresting position takes place there when the valve seating surface 16 comes against the upper valve seat 14.

In the embodiments with a valve body according to figures 4 and 7-9, the movement of the body parts takes place in steps in both directions. The distance a will thus accompany a stair-like curve in both directions without any sudden return. The movement in one direction takes place here by utilizing one abutment surface and in the other direction by utilizing the opposing abutment surface.

In these embodiments, the valve stem may be connected to the lower valve body part 7 from below, it then not having to pass through the upper part 6. In this case no passage 36 for the valve stem 8 is required. However, it is possible to allow an extension of the valve stem to pass through the part 6 to enable the arrangement of a circlip 74. The incoming valve duct on the stem side always comes from one side. To achieve a variation in the distance between the valve body parts 6 and 7 an abutment surface on the valve body is brought into engagement against an abutment surface on the valve housing. These surfaces can in principle have an optional shape, as valve seats and corresponding seating surfaces or abutments and abutment surfaces or some other implementation, e.g. projections or protruding abutments.

The arresting members and the arresting projections or recesses co-acting therewith can have optional conventional embodiment. For example, they can include an arresting body with at least partially spherical shape, which is actuated by or fastened to a spring. The arresting body can also have a triangular or other shape for co-acting with correspondingly formed arresting recesses or projections. The arresting member can also be a spring attached to one valve body part or it can be a sprung tongue integral with one valve body part.

A three-way valve in accordance with the invention can to advantage be used in a central treating system and be remotely operated with the aid of an operating means 9 from a control or regulating unit in an operating panel. In such a case the operating means must include sensing means for sensing alteration of the two parts of the valve body and for sending a signal to the control and regulating unit. This unit must namely have information as to the setting of the three-way valve, and which of the kv curves a-g in Figure 10 is the one to reckon with, for giving a correct instruction for setting the valve.

A valve in accordance with the invention can be provided with optional, closely spaced arresting positions to obtain the desired kv curves for the three-way valve in accordance with the invention. In an extreme case, the arresting means can have a friction surface which is pressed against a friction surface on the other valve body part. To obtain increased surity against sliding, the arresting means can, for example, include a permanent magnet, while the opposing arresting surface is manufactured from ferromagnetic material.

The placing and/or total absence of different seals or the like, 24, 33, 40, 44, 56, 100, 132 on one or other (the opposing) sealing surface is optional and does not affect the principle or function of the invention. Moreover, the flow contours can be optionally formed on the valve body parts, e.g. to include more than two V ports 26. The three-way valve in accordance with the invention is not restricted to co-acting with a motor driven operating means 19, and the latter can be of optional kind, e.g. the valve can he hand operated.

The invention is not restricted to the described embodiment examples, and can be varied in optional ways by the combination of distinguishing features and combinations of distinguishing features in the different embodiments and according to the following claims.

Claims

CLA I MS

1. Three-way valve (1) including a valve housing with a first valve duct (2) and two second valve ducts (3, 4), two co-axial openings (12, 13) connecting said first valve duct to said second valve ducts, and a valve body (5) arranged in said openings (12, 13), the valve body being movable in and/or between said openings (12, 13) with the aid of an externally, axially manoeuverab le valve stem (8), characterized in that the valve body (5) comprises two parts (6, 7), which are mutually relatively movable axially, and can be arrested in mutually relative positions, such that these parts can be caused to change their mutual relative positions with the aid of the valve stem (8) from the outside of the valve (1) and in that an alteration of said positions results in a change in the total through flow capacity (kv) of the valve.

2. Three-way valve as claimed in claim 1, characterized in that the parts (6, 7) of the valve body are mutually relatively movable between fixed arresting positions (a-g).

3. Three-way valve as claimed in claim 1 or 2, characterized in that the valve body is axially engageable, at least in one direction, against a valve seat (14 , 15) or an abutment surface (68, 72) on the valve housing, and/or that the valve body (5) is axially engageable with at least one valve seat (136) against a valve body (130) substantially stationary in the valve housing, such an engagement achieving an axial, relative displacement between both parts (6 and 7) of the valve body (5).

4. Three-way valve as claimed in any one of claims 1-3, characterized in that one part (6 or 7), of the valve body 5 ) has arrest ing means , e . g . recesses ( 42 ) or pro j ections (102) and in that the second part (7 or 6) has at least one arresting member, e.g. an arresting body (62) or an arresting spring (86), intended to engage in said arresting means.

5. Three-way valve as claimed in any one of the preceding claims, characterized in that said arresting member (62, 86) is axially movable between different arresting positions (a-e) of said arresting means (42, 102) in two directions and/or that the arresting member (62,86) and/or said recesses (42) or projections (102) have sloping abutment surfaces for enabling the arresting member to slide out of the respective arresting position when the valve body (5) is pressed against said valve seats (14, 15) or abutment surfaces (68,72) and/or said valve body (130), which is substantially stationary in the valve housing.

6. Three-way valve as claimed in any one of claims 1-4, characterized in that the arresting member (62,86) is movable between different arresting positions in coaction with said arresting means (42,102) in one direction and returnable in a path to one side of said arresting means (42,-102) and/or that the valve body (5) has a spring (94), which acts on the valve body parts (6, 7) in an axial direction.

7. Three-way valve as claimed in claim 6, characterized by a return groove (104) for the arresting member (62, 86) to one side of said arresting means (42, 102) and of means

(106-112) for lateral displacement of the arresting member (62, 86), said member being movable in a path (118) bypassing said arresting means (48, 102) and return groove (104).

8. Three-way valve as claimed in any one of the preceding claims, characterized in that the valve stem ( 8 ) passes through a passage (36) in one part (6) of the valve body (5) and is attached to the other part (7) of the valve body, and/or in that the valve stem has stop means ( a circlip 74) for restricting the mutual relative movement of the valve body parts (6, 7), and/or that the stem (8) passes through a valve body (130) having a tubular shan k (138), said valve body (130) together with the valve seat (136) of the valve body (5) being intended, when the valve body is close to its end position, to achieve an exact, controllable, small flow through an intermediate gap, an opening (134) in the valve body (6) and a gap (128) between the parts (6 and 7) of the valve body (5).

9. Three-way valve as claimed in at least one of claims 1-8, characterized in that the arresting member (62, 86) includes or comprises spring means (60 or 86) and/or in that the valve body (5) includes evacuation orifices (50, 96) and/or communication ducts (104, 106, 114) or a gap (128), with the aid of which the spaces (76, 98) communicate with each other and/or with the surroundings.

10. Three-way valve as claimed in one or more of the preceding claims, characterized in that the parts (6,7) of the valve body (5) are mutually, relatively displaceable with the aid of an operating means (9) arranged on the outside of the valve (1) and/or that the relative positions of the parts (6, 7) can be sensed by sensing means included in the operating means (9).