A FLUID FLOW CONTROL VALVE HAVING AN ADJUSTABLE CAPACITY VALUE

Abstract: A fluid flow control valve comprises a valve plug assembly (8) which is connected to a valve spindle (11) and which can be moved axially between a closure position in which it seats against a valve seat (2a) and a valve open position. The plug assembly comprises two main parts (9, 10), namely a hollow cylindrical body (9) and a plug slide (10) which is accommodated in the hollow cylindrical body (9). The cylindrical body (9) and the plug slide (10) have provided thereon, over an arcuate region which is smaller than the circumference thereof, port orifices (17, 18) which can be placed in different positions relative to one another, such as to vary the flow of fluid through the valve in a given valve-open position, and therewith also the capacity value of the valve. The plug slide (10) is connected to the spindle (11), by means of which the plug slide can be rotated to a selected one of, e.g. ten mutually different positions. The moveable part (10) of the plug assembly can be locked temporarily in relation to the fixed valve part (8) in the selected position of rotation, which is indicated on a scale (24).

Description: A fluid flow control valve having an adjustable capacity value. Field of invention The present invention relates to fluid-flow control valves of the kind set forth in the preamble to claim 1. The amount of water which a fluid-flow control valve can allow to pass through at a pressure difference of one (1) bar is called the "capacity value of the valve" and is designated k , and is sometimes referred to as the kvs-value. In the case of fluid-flow control valves, a distinction is often made between "single-seat" and "double-seat" valves. By "double-seat" is meant that the valve has two mutually parallel walls located between one and the same inlet and one and the same outlet, so as to equalize the forces generated by fluid pressure and acting on the valve plug. Although a three-way valve has two valve seats, it is usually referred to as a single-seat valve, since only one seat is located in each passageway bet¬ ween inlet and outlet. The present document describes primarily a single-seat 2-way valve, although it will be understood that the inventive principle can be applied with equal merit to a double-seat 2-way valve and to a 3-way valve. Background prior art A valve of the kind referred to in the introduction above is known to the art from SE-B-7314834-8 (Inreco AB). In the case of this known valve, a valve-plug part, which is moveable in relation to the valve spindle, is intended to form, together with a part fixedly mounted on the valve slide, a port of continuously variable area with retained axial displacement of the valve plug assembly, when the spindle is turned about its long axis. When configured as a 3-way valve, the slide has two slide parts which are delimited by sealing means and each of which is intended to coact with a moveable plug part and which, when the spindle is turned in one direc¬ tion, move apart so as to increase the valve through- flow area and, conversely, when the spindle is turned in the opposite direction, move together to reduce the valve through-flow area. This valve thus affords continuous variation of the through-flow area of the valve and therewith also of the capacity value of the valve. In many instances there is no need to be able to vary the valve capacity value continuously, since a valve which can be set to a number of distinct and mutually different valve settings which make possible indexed variation of the capacity value of the valve will often suffice. In cases such as these the valve components can be simplified from the aspect of manufacture, while still providing a fluid-flow control valve which can be adjusted to different settings with requisite accuracy to suit normal requirements. Examples of other known valves of this kind are found in publications DE-A-2 461697 (Bau ann), CH-A-581 284 (Klein, Schanzlin & Becker), DE-A-2 431 322 (Honeywell) and FR-A-2 450 984 (Automatic Switch Company) . All of these known valve constructions are relatively complicated, however, and will not permit the capacity value of the valve to be adjusted in the simple manner achieved by and desired with the present invention. Object of the invention An object of the invention is to provide a fluid-flow control valve of the aforesaid kind which is of simple manufacture and which when installed in a fluid circuit will allow the capacity value of the valve to be ad¬ justed from without, within wide limits, so as to obtain optimum valve characteristics in all circumstances. Another object of the invention is to provide a fluid- flow control valve which, in the case of certain embodi¬ ments thereof, will enable the capacity value of the valve to be varied continuously, by turning the valve spindle, but which in the case of the preferred embodi¬ ment will enable the capacity value to be adjusted in step-wise fashion, the valve components of this embodi¬ ment taking well defined positions in relation to one another. Summary of the invention. These and other objects are realized by the inventive fluid-flow control valve, the main characteristic fea¬ tures of which are set forth in the characterising clause of claim 1. Because one of the valve parts is arranged within and rotatable in relation to the other valve part, the valve can be set to the port area desired in each particular case, both readily and accurately, simply by turning the valve spindle, which is assumed to be connected to one of the valve parts, and therewith indirectly to the other of said valve parts. Furthermore, because the rotatable valve part can be temporarily fixated in relation to the other valve part in the selected valve setting, it is ensured that the accurate setting of the valve capacity value will be maintained until changed intentionally. Both of the aforesaid valve parts may be rotatable in relation to one another and the relative positional settings thereof adjusted, although it is preferred that one of said parts is connected to the valve spindle, which is rotatable, and that the other of said parts is held against rotation in the valve housing but is able to move axially therein. This enables the capacity value of the valve to be varied in the simplest possible manner, by rotation of the spindle, optionally in conjunction with axial dis¬ placement of the rotatable valve part in relation to the non-rotatable valve part. A preferred embodiment of the inventive valve is charac¬ terised in that one part of the valve plug assembly comprises a hollow cylindrical body having an outer peripheral sealing surface which faces the valve seat; in that the other part of the valve plug assembly comprises a slide which is accommodated in the cylin¬ drical body and the largest outer diameter of which cor¬ responds to the inner diameter of the cylindrical body; and in that each of the cylinder body and the slide present a plurality of port orifices along a given length of arc thereof, which is preferably less than half the circumference thereof, and are devoid of such orifices along a further length of arc thereof, which is preferably greater than half of said circumference. Such an arrangement provides a wide number of possible variations in the capacity value of the valve, since a large number of port orifices is to be found on those parts which present such orifices, these orifices optionally extending over almost half of the circum- ference of each of the valve parts concerned. By rotat¬ ing the one valve part in relation to the other, the valve can be brought to an operative state which coin¬ cides with any one of a large number of possible com¬ binations with respect to the mutual coaction between the port orifices of the two valve parts, thereby enab¬ ling the capacity value of the valve to be varied in an accurately defined manner within wide limits, in accor¬ dance with the invention. In practice, the two valve parts are preferably con¬ structed to coact so that the total flow past the valve plug assembly in a given valve-open position will corre¬ spond to the total axial flow through all of the port orifices in the cylindrical body plus the axial and radial flow through those port orifices in the slide part that are not covered by the imperforate part of the cylinder body. In this case, minimum flow past the valve plug assembly will occur when all of the port orifices in the slide part are covered by the imperforate part of the cylinder body, depending on the configuration of the orifices, i.e. there will be no radial flow. On the other hand, fluid will flow axially through the port orifices of the cylinder body, added to which is the possible flow of fluid along grooves or the like which extend axially along the imperforate part of the slide part, as descri¬ bed more in detail hereinafter, and which coincide with axial port orifices in the cylinder body, such that the port areas are added to one another. Maximum flow is obtained when the port orifices of the slide part coincide with the port orifices of the cylin¬ der body, wherewith, when the valve is fully open, the fluid will flow both axially and radially through the valve. The magnitude of this flow is determined mainly by the configuration of the port orifices, and the invention enables this configuration to be varied within wide limits, so that the desired valve characteristics can be obtained. Thus, the inventive fluid-flow control valve, in depen¬ dence on port orifice configuration and valve setting, can be set to any desired regulating characteristic, e.g. rectilinear, logarithmic, quadratic, or exponen¬ tially variable characteristic. In addition, the kvs- value of the valve can be changed readily in relation to the prevailing load on the valve. For instance, in the case of a valve which has a given, predetermined kvs- value, the flow therethrough can be doubled or halved, by simple adjustment to the valve setting. This is of particular benefit when the valve is used as a shunt valve in a central heating system in which it is desired to decrease the flow of medium during the summer months and in which the flow is doubled in the winter months, in order to improve heating economy. The inventive concept also enables the capacity value of a fluid-flow control valve to be adjusted simply and accurately, with the aid of a simple adjustment to the valve setting. As beforementioned, the resultant axial and radial flow through the ports is determined by the total, combined port area of the ports, and by efficiency. This variation in capacity value is afforded when that part of the valve slide which lacks port orifices, i.e. the imperforate part of said slide, is provided with axially extending grooves whose widths are adapted to the width dimension of the port orifices, therewith increasing the area which permits axial flow. It is preferred, in certain instances to provide the central parts of the cylindrical body and the plug slide with mutually engaging and mutually coacting coupling elements, e.g. teeth, balls, together with corresponding recesses or indents, and to arrange the valve slide in a manner such as to restrict axial movement of the slide, against the action of a spring, when setting the rota¬ tional positions of said valve components. When the valve is provided with coupling elements in the form of teeth, balls, and corresponding recesses, the valve may be constructed so that rotation of the spindle will cause the coupling elements to move out of engage¬ ment with one another, and so that renewed engagement of said elements is effected in a subsequent, accurately defined position. Alternatively, the valve may be constructed such that the aforesaid adjustments to the valve setting presup¬ pose axial displacement of the rotatable valve part, wherewith the spring means is effective in moving the spindle and the rotatable valve part back to their starting positions, upon reaching the desired valve setting. The cylindrical body of the valve plug assembly may have provided thereon an element which will enable said body to move axially along a guide means provided in the valve housing, therewith enabling the cylindrical body part of the valve plug assembly to move axially whilst being held against rotation. Furthermore, the central part of the valve slide may have an extension which protrudes through the central part of the cylindrical body and which has provided thereon a shoulder for receiving a part of square cross- section or some like part located on the spindle; and the spindle may be provided with an extension which is effective in urging the slide part against the cylin¬ drical body with aid of spring means. Alternatively, the central part of the cylindrical body may be through-passed by a part of the spindle which is connected to the plug slide of the valve, such as to allow the plug slide to rotate subsequent to being displaced against the action of spring means located on the outside of the valve plug. This axial displacement of the plug slide can be restricted, by providing stop means on the cylindrical body. This will normally presuppose axial displacement of the plug slide when adjusting the valve setting. When an inventive concept is applied in the costruction of a valve which is to be used as a 3-way valve, the valve will be provided with two mutually opposing valve plug assemblies of the aforesaid kind, each of said plug assemblies being intended to coact with its individual valve seat, such that when one seat is closed, the other is open. This enables each valve plug assembly to be brought individually to a desired setting. The invention will now be described in more detail with reference to exemplifying embodiments thereof illu¬ strated in the accompanying drawings. Brief description of the drawings. Figure la is a front view of part of an inventive fluid- flow control valve and shows the valve plug assembly in an axially displaced position. Figure lb shows part of Figure la in larger scale, namely part of the tooth segments on the two mutually coacting parts of the valve plug, these tooth segments enabling one valve part to be brought to a set position of adjustment in relation to the other. Figure 2 is a view corresponding to the view of Figure 1 and shows part of the lower part of the valve with the plug assembly in an open position. Figure 3 is a cross-sectional view taken on the line III-III in Figure 1, with the plug slide of the valve plug assembly located in a first position, in which radial flow through an open valve is prevented. Figure 4 is a view which corresponds to the view of Figure 2 and which shows an optional positionial setting of the plug slide of the valve plug assembly in which a given amount of flow is permitted radially through the valve. Figure 5 is a view corresponding to Figure 3 and illu¬ strating maximum radial flow through the valve. Figure 6a is cross-sectional view through a modified version of the valve plug assembly. Figure 6b shows a part of the Figure 6a embodiment in larger scale. Figure 7 is a cross-sectional view of a further embodi¬ ment according to the invention. Figure 8 is a front view of the embodiment shown in Figure 7. Finally, Figure 9 is a view from above of part of the fluid-flow control valve according to Figures 7 and 8. Description of preferred embodiments. The valve illustrated in Figure la and 2 is a 2-way valve. The valve includes a valve housing 1 and has a partition wall 2 located between an inlet chamber 3 and an outlet chamber 5, the inlet chamber having a screw- threaded inlet connector 4 and the outlet chamber having a screw-threaded outlet connector 6. Located between the two chambers 3, 5 is a valve seat 2a which is intended for coaction with a valve plug assembly, generally referenced 8. The plug assembly com- prises two main parts, namely a hollow cylindrical body 9 having an outer, peripheral sealing surface 9a which seats on the seat 2a, and a plug slide 10 which is accommodated in the cylindrical body 9 and which has port orifices provided therein. The valve plug assembly is connected to an axially moveable valve spindle 11, such as to enable the assembly to be moved axially between a valve closing position, illustrated in Figure 1, and a valve open position, illustrated in Figure 2. The spindle 11 carries a part 11a of square cross- section which extends axially between a block 14, provi¬ ded in the valve housing, and the plug slide 10. As will be described in more detail hereinafter, rotation of the spindle 11 will also result in rotation of the plug slide 10, therewith enabling the plug slide to be brought to various positional settings in relation to the cylindrical body 9 and consequently changing the capaity value of the valve. Extending axially in uniform spaced relationship along the cylindrical body 9 of the valve plug assembly 8, between the aforesaid sealing surface 9a and the end of the cylindrical body 9 is a number of port orifices 17, in the case of the illustrated embodiment nine in number, said port orifices being disposed around a length of arc which is smaller than half the circum¬ ference of said body, at a suitable pitch therearound. Those parts of the peripheral surface of said body 9 which define the port orifices 17 taper in a direction towards said end and can be said to form finger-like parts 9b on the cylindrical body 9. Thus, the area of the port orifices increases in a direction towards the end of the valve plug. The plug slide 10 also has provided therein port ori¬ fices, here referenced 18, which extend axially along and in uniform spaced relationship around a length of arc which is smaller than half of said circunference, the port orifices 18 also being nine in number and having the same pitch as the orifices 17 in the cylindrical part 9 of said valve plug. The outer dia¬ meter of the plug slide 10 coincides with the inner diameter of the cylindrical body 9 and the plug slide has formed therein grooves whose depths increase towards the outer end of the plug slide. This allows the port area to be adjusted to desired flow characteristics. As will be seen from Figure 1, those parts 10b of the plug slide which define the port orifices 18 also taper towards said end, i.e. have a finger-like configuration. The number of port orifices in the plug slide need not necessarily be the same as the number of port orifices in the cylindrical body, i.e. the pitch of the orifices may be the same or may vary between the two main com¬ ponents of the valve plug. This also applies to the configuration of the ports, which nay be the same or may vary between the said two main components. The plug slide 10 can be brought to accurately set positions of rotation in relation to the cylindrical body 9, by rotating the spindle 11, such that the de- sired number of orifices 18 in the plug slide of the valve plug assembly will coincide with desired number of orifices 17 in the cylindrical body 9. This accurate setting of the valve is made possible by the provision of teeth 9c on the hub part 9e of the cylindrical body 9, said teeth engaging with corres¬ ponding openings in the hub part lOe of the plug slide. In the case of the embodiment according to Figure lb, the configuration of the teeth 9c and openings 10c is such that rotation of the spindle will cause the teeth 11 to snap into and out of said openings subsequent to given axial displacement of the plug slide 10 connected to the spindle. This axial displacement of the plug slide takes place against the action of a plate spring 15. A scale 24 enables the prevailing setting of the valve to be read-off. In the case of the illustrated embodiment, the plug slide and the cylindrical body each have nine port orifices and the valve can thus be adjusted between ten different positions. When the valve is open to the extent illustrated in Figure 2, a given radial flow will be obtained in addi¬ tion to the axial flow which is always obtained through the port orifices 17 in the cylindrical body 9 when the valve is open, the magnitude of this radial flow depend¬ ing upon the number of orifices 18 in the plug slide which lie in register with the orifices 17 in the cylin¬ drical body of the valve plug assembly. Figures 3-5 illustrate three different positions to which the plug slide 10 of the valve plug assembly can be moved in relation to the cylindrical body 9. Figure 3 shows a position in which the valve is set to its minimum capacity value. In this case, the perforated region of the plug slide 10 of the valve plug assembly presenting the orifices 18 is turned to face away from the perforated region of the cylindrical body 9 pre¬ senting port orifices 17, wherewith no fluid will flow radially through the valve. However, fluid will flow axially through all nine of the port orifices in the cylindrical body 9. Thus, the through-flow area or volume represented by the port orifices is determined by the thickness of the peri- lϋ pheral surface of the hollow cylindrical body 9 and the cross-dimensions of said orifices. The area presented by the groove-like ports 20 provided in the periphery of the plug slide of the valve plug assembly is added to the area presented by the aforesaid port orifices. Figure 4 shows a positional setting of the valve in which fluid will flow radially through four of the orifices 17 present in the cylindrical body 9 of the plug 9, 10, these orifices coinciding with four orifices 18 in the plug slide 10. Fluid will also flow axially through the remaining five port orifices 17 in the plug slide 10 not covered by the cylindrical body 9 and also through a corresponding number of port-grooves 20. Four of the port-grooves are covered by the cylindrical body 9 in this setting of the valve, and consequently no fluid will flow axially along these grooves. Figure 5 shows a control valve setting in which fluid will flow radially through all nine of the port orifices 17, 18 which thus lie.in register with one another. Fluid will not flow axially along any of the groove- ports 20, however. The prevailing position of the plug slide of the valve at any one time is shown on a scale 24. In Figure 1, the scale is shown to indicate setting position 10, which corresponds to the valve setting illustrated in Figure 5. The aforesaid scale may be combined with a Table of the following kind, which tabulates the various positional settings of the plug slide in respect of different valve capacity values. Each of the port orifices is assumed to give an axial flow of magnitude A and a radial flow of 1__ magnitude B. Capacity value setting Setting position 1 Prev. port area = 9A on scale 24 2 8A + radial area R of ports 3 7A + 2R 4 6A + 3R 5 5A + 4R 6 4A + 5R 7 3A + 6R 8 2A + 7R 9 1A + 8R 10 9R Mutually meshing teeth on the central parts of the cylindrical body 9 and the plug slide 10 are referenced 9c and 10c respectively. The reference numeral 25 identifies two nipples by means of which the prevailing pressure drop across the valve can be measured, whereas the reference numeral 26 iden¬ tifies holes into which valve adjusting tools can be inserted for rotation of the valve spindle 11 and there¬ with positional adjustment of the plug slide 10 of the valve plug assembly. The reference numeral 27 identifies a guide means pro¬ vided in the valve housing for guiding an element 9d on the cylindrical body 9. Figures 6a and 6b illustrate an embodiment which differs from the earlier described embodiments, insomuch as the valve setting procedure presumes that the plug slide 10 of the plug assembly is displaced axially in relation to the cylindrical body 9. In the case of this embodiment, the teeth 10c' on the hub part 10e' of the plug slide 10 and the teeth 9c' on the hub part 9e' of the cylindrical body 9 and are configured so that they will not snap automatically into and out of one another when the spindle 11 is turned. The respective hub parts of the plug slide and the cylindrical body also have a slightly different form to the earlier described hub parts, so as to enable said axial displacement of the plug slide of the plug assembly. The extended end-part lib' of the spindle 11 is passed through the hub part 9e' of the cylindrical body 9, said hub part 9e' presenting a projection 9f which functions as a stop means for axial movement of the spindle. The extended spindle part lib' is joined with a dep¬ ending extension lOf' of the hub part 10e' of the plug slide 10. Axial displacement of the spindle 11 when setting the position of the plug slide 10 is effected against the action of a plate spring 15', which in the case of this embodiment is located above the cylindrical body 9. When the spindle 11 is displaced axially, the teeth 9c'and 10c' move out of engagement with one ano¬ ther, therewith enabling the valve to be adjusted to the valve setting desired. The plate spring 15' will ensure that the teeth remesh in the adjusted setting of the valve. 12 The valve illustrated in Figures 7-9 is especially suited for use in those cases where small amounts of fluid are to be controlled. The inlet and outlet chambers 3, 5 of the valve housing of this embodiment correspond to those of the earlier described embodiments. The same applies in general to the valve plug assembly 8, which also comprises in this case two main parts, i.e. a hollow cylidrical body 9 and a port-incorporating slide 10 which is connected to the spindle 11. In the case of this embodiment, the aforedescribed accurate positioning of the plug slide 10 relative to the cylindrical body 9 is not effected in the region of the two relatively moveable valve components, but in the cover 30 of the control valve, said cover having arranged therein a body 32 which is rotatable in an outer cover part 31 and which in turn surrounds and is rotatable with the spindle 11. The body 32 has a toothed part 32a which coacts with a ball 34 biassed by a spring 35, and a stop screw 36, part of which extends through the spring 35. When changing the mutual settings of the valve com¬ ponents 9, 10 the stop screw 36 is backed-off, whereupon - as with the earlier embodiments - a tool, not shown, can be inserted into one of the holes 26 for rotation of the body 32 and the spindle 11, until the desired set¬ ting is indicated on the scale 24. The screw is then re- tightened, so as to secure the valve setting. Similar elements, i.e. screw 36, spring 35 and ball 34, are provided on the opposite side of the valve, to enable the valve setting to be adjusted from the other side of the valve. Thus, the embodiment according to Figures 7-9 lacks the provision of for locking the two valve conponents 9, 10 located in the hub regions thereof. Instead, the spindle and therewith the valve part 10 are locked between fixed and moveable parts belonging to the valve cover. Consequently, it is not necessary for the plug slide 10 and the spindle 11 to move axially when adjusting the valve setting.

Claims: lϋ Claims 1. A fluid flow control valve having an adjustable capacity value and comprising a valve plug assembly (8) which is connected to a valve spindle (11) and which can be moved axially between a closure position in which it seats against a valve seat (2a) and a valve open posi¬ tion in which it is spaced from said seat, and which valve further comprises two parts (9, 10) which can be moved relatively to one another for the purpose of adjusting the valve through-flow area, by changing the combined area of ports (17, 18 and 20) provided on the mutually coacting valve parts, c h a r a c t e r i s e d i n t h a t one valve part (10) is at least partially accommodated in and rotatable relative to the other of said valve parts (9); and in that the desired total port area is obtained by temporarily locking the first-mentioned valve part in a predetermined position of rotation relative to the other valve part. 2. A valve according to claim 1, c h a r a c¬ t e r i s e d in that said one valve part (10) is connected to the spindle (11), which is rotatable, and in that the other valve part (9) is axially moveable but non-rotatable in the valve housing. 3. A valve according to claim 3, c h a r a c ¬ t e r i s e d in that the one part of the valve plug assembly (8) has the form of a hollow cylindrical body (9) having a peripheral sealing surface (9a) which faces towards a seat (2a); in that the other part of said plug assembly has the form of a slide (10) which is accommodated in the cylindrical body part (9) and the largest diameter of which corresponds to the inner diameter of the hollow cylindrical body; and in that the cylindrical body (9) and the plug slide (10) have a plurality of port orifices (17, 18) disposed along a peripheral portion thereof, said portion prefer¬ ably having an arcuate extension which is smaller than half the circumference of said plug assembly parts, whereas a further peripheral portion of said body (9) and said plug slide (10) lacks the presence of such orifices, said further portion preferably having an arcuate extension which is greater than half said circumference. 4. A valve according to claim 3, c h a r a c ¬ t e r i s e d in that when the valve is open, the total flow through the valve plug assembly (8) corresponds to the axial flow thrpough all port orifices (17) of the cylindrical body (9) plus the axial and the radial flow through those port orifices (18) of the plug slide (10) which are not covered by the imperforate part of the cylindrical body (9). 5. A valve according to claim 3 or claim 4, c h a r a c t e r i s e d in that the hub parts (9e, lOe; 9e' f 10e') of the cylindrical body (9) and the plug slide (10) present mutually meshing coupling elements, e.g. teeth (9c, 10c; 9c', 10c'), balls, and corres¬ ponding recesses or like openings; and in that the plug slide (10) can be moved axially to a limited extent when adjusting the rotational position of said plug parts, this limited movement being effected against the action of a spring (15; 15'). 6. A valve according to claim 3 or claim 4, c h a r a c t e r i s e d by means (32a, 34, 35, 36) located in the region of the valve cover and effective in temporarily locking the plug slide (10) relative to the cylindrical body (9). 7. A valve according to any one of the preceding claims, c h a r a c t e r i s e d in that port orifices (17, 18) of the cylinder body (9) and the plug slide (10) are defined by finger-like elements (9b, 10b) which project out from a central part (9e, lOe) and which optionally taper towards the end. 8. A valve according to any one of claims 3-7, c h a r a c t e r i s e d by means (9d) on the cylindr- ical body (9) intended for axial movement along a guide (27) provided in the valve housing. 9. A valve according to claim 8, c h a r a c ¬ t e r i s e d in that the central part (10e) of the plug slide (10) has provided thereon a projection which extends through the central part (9e) of the cylindrical body (9) and which is provided with a shoulder for coaction with a part (11a) of square cross-section on the spindlew (11) or some like part.

Inventors: AAKERBLOM AAKE, AAKERBLOM, AAKE
Applicants: INRECO AB
Application year: 1989
Main classification: F16K1
IPC codes: F16K1