Abstract:
Valve cartridge ( 10 ) includes a housing ( 32 ) having inlet member ( 54 ), outlet member ( 52 ) and screw thread ( 34 ). Cavity ( 36 ) extends axially through housing ( 32 ) within which is a piston ( 38 ) which moves axially against piston seal ( 44 ) to open and close tap ( 10 ). A flow chamber ( 40 ) is provided at the end of housing ( 32 ) and includes a first seal ( 42 ) for sealing against a valve seat ( 18 ) in the tap ( 10 ). Piston ( 38 ) can be moved axially by either a rotatable spindle ( 46 ) or, a solenoid ( 48 ) and push rod ( 50 ). Piston ( 38 ) is moved axially without any rotation. Coupling member ( 84 ) couples spindle ( 46 ) to piston ( 38 ) and rotates relative to the piston ( 38 ) and the spindle. When spindle ( 46 ) is turned a predetermined number of revolutions the coupling ( 84 ) causes piston ( 38 ) to abut piston seal ( 44 ), any further rotation of spindle ( 46 ) causes rotation of the coupling member ( 84 ) without effecting the axial position of piston ( 38 ). Ratchet members ( 92, 94 ), slip past housing splines ( 102 ) when the predetermined number of revolution or force is reached. This limits the sealing pressure of the piston ( 38 ) against the piston seal ( 44 ) irrespective of the number of turns made of spindle ( 46 ). Stops ( 64 ) limits maximum opening and prevents check valve ( 70 ) from being forced into sealing contact with inlet member ( 54 ).

Description:
FIELD OF THE INVENTION 
     The present invention relates to a valve cartridge for fitting into a valve and, in particular, but not exclusively, to a valve cartridge for fitting into a domestic tap. 
     BACKGROUND OF THE INVENTION 
     Domestic taps typically have an inlet which is adapted for coupling to a water pipe, a bulbous body in which is disposed a valve seat and valve cartridge, and an outlet in the form of a spout through which water can flow. The valve cartridge is provided with a stem having a handle located outside the body at one end and a washer located within the body at an opposite end for sealing against the valve seat. By turning on the handle, the stem is rotated about its longitudinal axis so as to axially move within the tap body. To close the tap, the handle is turned in a first direction so as to screw down the stem and push the washer against the valve seat. To open the tap, the handle is turned in the opposite direction and the washer is displaced upward by fluid pressure to allow water to flow through the valve seat and out the outlet. 
     The main cause of leakage in such taps is due to wear of the washer. This wear is usually caused by over-tightening of the handle and stem which leads to tearing, cutting or fracturing of the washer. Washers are normally loosely held within the bottom of the stem so that the two can rotate relative to each other. However, when the stem is over-tightened, the washer can also turn with the stem to accelerate wear against the valve seat. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a valve cartridge for insertion into a valve, such as a domestic tap, in which the above problems arising from overtightening can be substantially avoided. 
     According to one aspect of the present invention there is provided a valve cartridge for a valve having a fluid inlet, a fluid outlet, and a valve seat providing fluid communication between said fluid inlet and fluid outlet, said valve cartridge including: 
     a housing adapted for coupling to said valve, said housing provided with an axially extending first cavity; 
     a piston movable within said first cavity for controlling flow of fluid through said valve; 
     a flow chamber provided at one end of said housing and through which said piston can travel, said flow chamber having a first seal for sealing against said valve seat and a piston seal downstream of said first seal against which said piston can seal to prevent flow of fluid through said flow chamber, said flow chamber further including stop means for stopping said piston from moving axially therebeyond the stop means including a plurality of spaced apart lugs formed about the circumference at one end of said flow chamber so as to abut said one end of said housing, said lugs extending radially into said first cavity so as to stop said piston from moving therebeyond, the spaces between adjacent lugs forming openings through which fluid can flow when in transit from said inlet to said outlet, said piston and flow chamber juxtaposed relative to said valve so that the pressure of the fluid acts in a direction tending to force said piston against said piston seal; and, 
     an actuator for moving said piston axially without rotation between a closed position in which said piston abuts said piston seal with a predetermined pressure to prevent flow of fluid through said flow chamber, and a fully open position in which said piston is displaced from said piston seal and abuts said stop means to provide maximum fluid flow through said flow chamber; 
     whereby, when said housing is coupled to said valve, said first seal abuts said valve seat and said actuator can be operated to move said piston axially through said cavity between said closed position and said fully open position to control the flow of fluid from said inlet to said outlet. 
     Preferably said flow chamber is formed separately from said housing and is frictionally coupled to said one end of said housing. 
     Preferably said one end of said housing is formed with a circumferential rebate for receiving said lugs. 
     Preferably the outer diameter of said circumferential rebate is smaller than the outer diameter of said lugs so that a press-fit is formed between said circumferential rebate and said lugs to hold said flow chamber to said housing. 
     Preferably said flow chamber comprises a first part which includes said lugs and said piston seal, and a second part which includes said first seal, said first and second parts being press-fit together. 
     Preferably said first and second parts define a second cavity therebetween in which a non-return valve is housed for preventing flow of fluid through said flow chamber in the direction from said outlet to said inlet. 
     Preferably said actuator comprises a solenoid which is coupled to said piston. 
     Preferably the linear position of said solenoid within said housing can be varied to vary the position of the piston when in the fully opened position to progressively vary the flow of fluid through said valve. 
     In an alternate embodiment, said actuator comprises a spindle rotatably supported by said housing and extending through said first cavity said spindle coupled to said piston in a manner so that rotation for a predetermined number of revolutions of said spindle in a first sense causes relative axial movement between said piston and said spindle in a first direction whereupon the relative axial position of said spindle and piston remains unchanged in response to further rotation of said spindle in said first sense, and rotation for a predetermined number of revolutions of said spindle in an opposite sense causes relative axial movement between said piston and said spindle in an opposite direction whereupon the relative axial position of said spindle and said piston remains unchanged in response to further rotation of said spindle in said opposite sense. 
     This embodiment also includes, a coupling means for coupling said spindle to said piston with the piston coupled to said coupling means in a manner so as to allow relative rotation between said piston and said coupling means. 
     Preferably said valve cartridge further comprises detent means or ratchet mechanism acting between said coupling means and said housing to resist rotation of said coupling means during said predetermined number of revolutions of said spindle. 
     Preferably said detent means or ratchet mechanism includes a plurality of axially extending grooves formed on a circumferential surface of said first cavity and at least one protrusion coupled to said coupling means for receipt in one of said grooves. 
     Preferably said coupling means is provided with at least one extending finger on each of which one of said projections is formed. 
     Preferably said finger adapted to flex in the radial direction. 
     Preferably said coupling means is further provided with a screw thread for threadingly engaging said spindle. 
     Preferably said coupling means further includes a circumferential groove for engaging a lip which is formed on and extends partially about the circumference of said piston, thereby facilitating said relative rotation between said piston and said coupling means. 
     Preferably said coupling means is provided with a circumferential seal disposed between said finger and said groove. 
     According to another aspect of the present invention there is provided a valve cartridge for a valve having a fluid inlet, a fluid outlet, and a valve seat providing fluid communication between said fluid inlet and fluid outlet, said valve cartridge including: 
     a housing adapted for coupling to said valve, said housing provided with an axially extending first cavity; 
     a piston movable within said first cavity for controlling flow of fluid through said valve; 
     a flow chamber provided at one end of said housing and through which said piston can travel, said flow chamber having a first seal for sealing against said valve seat and a piston seal downstream of said first seal against which said piston can seal to prevent flow of fluid through said flow chamber, said flow chamber further including stop means for stopping said piston from moving axially therebeyond the stop means including a plurality of spaced apart lugs formed about the circumference at one end of said flow chamber so as to abut said one end of said housing, said lugs extending radially into said first cavity so as to stop said piston from moving therebeyond, the spaces between adjacent lugs forming openings through which fluid can flow when in transit from said inlet to said outlet, said piston and flow chamber juxtaposed relative to said valve so that the pressure of the fluid acts in a direction tending to force said piston against said piston seal; and, 
     a solenoid for moving said piston axially without rotation between a closed position in which said piston abuts said piston seal with a predetermined pressure to prevent flow of fluid through said flow chamber, and a fully open position in which said piston is displaced from said piston seal and abuts said stop means to provide maximum fluid flow through said flow chamber; 
     whereby, when said housing is coupled to said valve, said first seal abuts said valve seat and said actuator can be operated to move said piston axially through said cavity between said closed position and said fully open position to control the flow of fluid from said inlet to said outlet. 
     a housing adapted for coupling to said valve; 
     a spindle rotatably supported by said housing; 
     a piston coupled to said spindle in such a manner that rotation of said spindle about its longitudinal axis for a predetermined number of revolutions in a first sense and an opposite sense causes axial motion of the piston in a first direction and an opposite direction respectively between a sealing position and an opened position, and that the axial position of the piston remains unchanged upon further rotation in the same sense of said spindle beyond said predetermined number of revolutions; 
     a flow chamber associated with said housing and through which said piston can axially travel, said flow chamber provided with a first seal for sealing against said valve seat and a piston seal disposed downstream of said first seal against which said piston can form a seal when said piston is in said closed position to prevent fluid flow through said flow chamber, said flow chamber disposed so that when said housing is coupled to said valve, said first seal seals against said valve seat and said flow chamber can provide fluid communication between said fluid inlet and said fluid outlet; and, 
     a non-return valve disposed in said fluid chamber between said first seal and said piston seal to prevent fluid flow through said chamber in the direction from said outlet to said inlet; 
     whereby, in use, rotation of said spindle in said first sense causes said piston to move axially to said closed position in which is piston seals against said piston seal to close said valve with further rotation of said spindle in said first sense uneffecting the axial position of said piston, and rotation of said spindle in said opposite sense causes said piston to move axially away from said piston seal to progressively open said valve and allow fluid to flow from said inlet, through said flow chamber, and out said outlet, and where, the flow of fluid in the direction from said outlet to said inlet is prevented by said non-return valve. 
     According to another aspect of the present invention there is provided a valve cartridge for a valve having a fluid inlet, a fluid outlet and a valve seat providing fluid communication between said fluid inlet and fluid outlet, said valve cartridge comprising: 
     a housing adapted for coupling to said valve; 
     a spindle rotatably supported by said housing; coupling means retained within said housing and coupled at one end to said spindle in a manner so that rotation for a predetermined number of revolutions of said spindle in a first sense causes relative axial movement between said coupling means and said spindle in a first direction whereupon the relative axial position of said spindle and coupling means remain unchanged in response to further rotation of said spindle in said first sense, and rotation for a predetermined number of revolutions of said spindle in an opposite sense causes relative axial movement between said coupling means and said spindle in an opposite direction whereupon the relative axial positions of said spindle and coupling means remains unchanged in response to further rotation of said spindle in said opposite sense; 
     a piston coupled to an opposite end of said coupling means; 
     a flow chamber associated with said housing and through which said piston can axially travel said flow chamber provided with a first seal for sealing against said valve seat and a piston seal disposed downstream of said first seal against which said piston can form a seal to prevent fluid flow through said flow chamber, said flow chamber disposed so that when said 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings in which: 
     FIG. 1 is a longitudinal section view for a valve cartridge in accordance with a first embodiment of the invention; 
     FIG. 2 is an exploded and partial cut away perspective view of the valve cartridge shown in FIG. 1; 
     FIG. 3 is a longitudinal section view of a second embodiment of the valve cartridge; and, 
     FIG. 4 is a schematic representation of a valve in which embodiments of the valve cartridge can be used. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A valve  10  in the form of a domestic tap (FIG.  4 ), comprises a valve body  12  having an inlet  14  at one end and an outlet  16  at an opposite end. A valve seat  18  provides fluid communication between the inlet  14  and outlet  16 . Whether or not fluid flows through valve  10  is dependent upon the position of a washer  20  which can be moved into sealing engagement with the seat  18  by rotation of a spindle  22  and associated handle  24 . The washer  20  includes a stem  26  which is received within a blind hole formed in the spindle  22 . The spindle  22  is mounted within the body  12  in a manner so as to move axially up or down as it is turned anticlockwise or clockwise respectively. Thus, to close the valve  10  the spindle  22  is turned clockwise to push the washer  20  against the valve seat  18 . The downward pressure on the washer  20  can be increased by turning harder on the spindle  22 . The pressure applied may be sufficient so as to also cause the washer  20  to rotate with the spindle  22 . As discussed above, the application of excess pressure can damage the washer  20  to the extent that it no longer forms a seal with the seat  18  so that fluid can leak from the inlet  16  when it is otherwise intended that the valve  10  be closed. The spindle  22  is rotatably held within a crown  28  which is screwed to the body  12 . 
     Embodiments of the present valve cartridge  30  shown in FIGS. 1-3 were developed with a view to replacing the washer  20 , spindle  22 , and crown  28  of a conventional tap or valve  10 . However, these and other embodiments may be used in different types of valves and in different applications (eg. in valves in white goods or in parts washing machines). 
     In the embodiment shown in FIGS. 1 and 2, the valve cartridge  30  comprises a housing  32  which is adapted for coupling to a tap  10  by virtue of a screw thread  34  provided about an outer circumferential surface of an upper length of the housing  32 . An axially extending cavity  36  is formed centrally through the housing  32 . Disposed, at least partially, within the cavity  36  is a piston  38  which, as explained in greater detail below, can be moved axially to open and close a valve  10  in which the cartridge  30  is installed. A flow chamber  40  is provided at the end of the housing  32  which carries the thread  34 . The flow chamber  40  includes a first seal  42  for sealing against valve seat  18  of valve  10 . Also retained within the flow chamber  40  is a piston seal  44  against which the piston  38  can abut to prevent the flow of fluid (eg. water) through the flow chamber. When the piston  38  is moved from the seal  44 , water can flow through the chamber  40  and thus through the valve  10 . 
     The piston  38  is moved axially by an actuator, without rotation, between a closed position in which it abuts the seal  44  and a fully open position in which it is spaced by a maximum predetermined distance from the seal  44 . 
     In the embodiment shown in FIGS. 1 and 2, the actuator is in the form of a rotatable spindle  46 . In the embodiment shown in FIG. 3, the actuator is in the form of a solenoid  48  with push rod  50 . As will be explained in greater detail, both the spindle  46  and solenoid/push rod  50  act to move the piston  38  axially without any rotation and to close the piston  38  onto the seal  44  with a predetermined pressure. 
     In order to utilise the cartridge  30 , the housing  32  is threadingly coupled by thread  34  to the valve body  12 . The first seal  42  seals against the valve seat  18 . To control the flow of water through the tap  10  between the inlet  14  and outlet  16 , the piston  38  is axially moved within the housing  32  and flow chamber  40  between the closed position in which it abuts the piston seal  44  and a fully open position in which it is spaced by some maximum distance from the seal  44  to provide maximum water flow. 
     The present embodiments will now be looked at in somewhat greater detail. 
     The flow chamber  40  is made from two main parts  52  and  54  which are press-fit together. Part  54  which is at the distant end of the cartridge  30  is substantially cylindrical in form with an increased diameter portion  56  (refer FIG. 2) at the upstream end. The increased diameter portion  56  is provided with an annular recess  58  for seating the seal  42 . The first part  52  is also substantially cylindrical in form but is provided with a radially inwardly extending wall  60  at an end adjacent the housing  32 . A hole  62  coaxial with cavity  36  and through which the piston  38  extends is formed in the wall  60 . The piston seal  44  is seated on the interior surface of the wall  60 . Stop means in the form of spaced apart lugs  64  are formed about the circumference of the first part  52  on the side of wall  60  opposite the piston seal  44 . The lugs  64  extend radially inwardly into the cavity  36  so as to be able to abut base  66  of the piston  38 . 
     The second part  54  press-fits into the first part  52  to the extent that it bears against the piston seal  44 . When the first and second parts  52  and  54  are press-fit together, they define a cavity  68  in which is housed a non-return valve  70 . The non-return valve  70  is arranged so as to prevent the flow of water in the direction from the outlet  16  to inlet  14 . The components of the flow chamber  40  are dimensioned so that even when piston  38  is in the fully open position (ie. spaced from the seal  44  by a maximum displacement), it does not cause the non-return valve  70  to close the flow chamber  40 . 
     Piston  38  comprises a disc-like head  72  which tapers to a stem  74  on the side which abuts the piston seal  44 . The stem  74  is integrally formed with base  66 . The base  66  is disc like and is formed with a circumferential groove  76  which receives an O-ring  78 . An axially extending wall  80  is provided partially about the circumference of base  66  on a side opposite the stem  74 . An inwardly extending lip  82  is formed along the circumferential end of wall  80 . 
     Piston  38  is coupled to spindle  46  by coupling  84 . The coupling  84  includes a knob  86  at one end which can be received by the lip  82  so as to couple the piston  38  to the coupling  84  in a manner which allows relative rotation therebetween. A circumferential groove  88  is formed about the exterior surface of the coupling  84  for receiving O-ring  90  (shown in FIG.  1 ). A blind threaded hole  85  is cut axially in the coupling  84  for engaging thread  87  of spindle  46 . A number of spaced apart fingers  92  which extend in the axial direction are provided about the circumference of the coupling  84  at an end opposite the knob  86 . A projection  94  is formed at the tip of each finger on a side facing the circumferential wall of the cavity  36 . 
     Housing  32  is provided with an annular flange  96  adjacent the inboard end of thread  34 . The flange  96  forms a seat for O-ring  98 . When the cartridge  30  is screwed into valve  10 , the flange  96  presses the O-ring  98  onto the body  12  to form a fluid seal. A rebate  100  is formed in the housing  32  at an opposite end of the thread  34  for receiving the lugs  64 . The outer diameter of the rebate  100  is slightly smaller than the outer diameter of the lugs  64  so as to form a press-fit between the chamber  40  and housing  32 . 
     The circumferential surface of cavity  36  at an end opposite the rebate  100  is provided with a plurality of spaced apart axially extending grooves  102 . The grooves  102  together with fingers  92  and projections  94  form a detent means or system, or perhaps more accurately a ratchet mechanism, for resisting rotation of the coupling  84 , and thus the piston  38 , when the spindle  46  is turned clockwise or anticlockwise. 
     The spindle  46  is rotatably held and axially fixed within the housing  32  by a circlip or lock washer  104  which sits within a circumferential groove  106  formed about a part of the spindle  46  that lies outside of the body  32 . The remaining length of the spindle  46  outside of the body  32  is formed in a conventional manner and includes a knurled boss  108  and threaded rectangular section post  110  for receiving a conventional handle such as handle  24  shown in FIG. 4 
     When the cartridge  30  is fully assembled as shown in FIG. 2, the thread  87  of spindle  46  engages the thread in blind hole  85  of the coupling  84 , the knob  86  is received by the lip  82 , the head  72  of the piston  38  is disposed within cavity  68  and the flow chamber  40  is press-fit onto the body  32 . Housing  32  is coupled to the valve  10  by screw thread  34  and the first seal  42  seals against the valve seat  18 . Assume that the piston  38  is in the closed position so that head  72  abuts against piston seal  44 . In this configuration, the spindle  46  is screwed in the blind hole  85  of coupling  84  as far as possible. If one were to attempt to “further close” the valve  10  by turning spindle  64  in the clockwise direction, all that would happen is that the spindle  46  and coupling  84  will turn together within the housing  32  (the projections  94  ratcheting across grooves  102 ) with the piston  38  remaining stationary. The piston  38  remains stationary because the knob  86  simply turns inside the lip  82 . Therefore, no matter how much one continues to rotate the spindle  46  in the clockwise direction, the axial and rotational (angular) position of the piston  38  remains unchanged. Therefore, it is not possible for the piston  38  to apply any further pressure on the seal  46 , and there is no relative rotational movement between the piston head  72  and the seal  44 . 
     To open the valve  10  the spindle  46  can now be rotated in an anticlockwise direction. Because the spindle  46  is axially fixed to the housing  32 , this rotation forces the coupling  84  and thus piston  38  axially away from the spindle  46 . This lifts the piston head  72  from the seal  44  allowing water to flow through the flow chamber  40 , hole  62  and the spaces between the lugs  64 . Rotation of the coupling  84  prior to the piston  34  being moved to its fully opened position is resisted by, the projections  94  being located within respective ones of the grooves  102 . (If the coupling  84  were to rotate at this time with the spindle  46 , the piston would not move axially and there be stuck in one position). 
     The spindle  46  is prevented from disengaging from the coupling  84  by abutment of the lugs  64  with the base  66  of the piston  38 . This abutment also denotes the fully open position of the cartridge  30 . Any further rotation of the spindle  46  in the clockwise direction results in the coupling  84  turning with the spindle  46  with the knob  86  turning inside the lip  82 . At this point, the projections  94  are outside of the grooves  102  or alternately the fingers  92  can flex inwardly to ratchet grooves  102  thereby allowing the coupling  84  to turn. 
     In the second embodiment of the cartridge  130  shown in FIG. 3 like numbers are used to denote like features. The main difference between cartridge  30  shown in FIGS. 1 and 2 and cartridge  130  is that the spindle  46  is replaced by the solenoid  48  and push rod  50 . Further, as the push rod  50  only moves in an axial direction, the detent means composed of the fingers  92 , projections  94 , and grooves  102  is not required in this embodiment. The push rod  50  is connected with the coupling  84  in a fixed manner so that there is no relative movement either axial or rotational therebetween. 
     The end of housing  32 ′ opposite the flow chamber  40  is also of a slightly different configuration in order to allow connection to the solenoid  48 . This end is provided with a threaded boss  112  for receiving a mounting thread  114  of the solenoid  48 . A circumferential recess  116  is also formed about the free end of the boss  112  to receive solenoid housing  118 . Enclosed within housing  118  is the solenoid coil  120  and solenoid return spring  122 . The return spring  122  is bound between washer  124  located about an end of push rod  50  distant housing  32 ′ and a base plate  126  spaced from the washer  124  toward the housing  32 ′. Base plate  126  is seated on shoulder  128  formed on the inner circumferential surface of the housing  118 . Current carrying wires for energising the coils  120  pass through the housing  118 , but are not shown in this figure. 
     When the solenoid  48  is energised the push rod  50  moves linearly toward flow chamber  40  lifting the piston  38  from the seal  44 . This allows water to flow through the flow chamber  40  from inlet  14  to outlet  16 . When the solenoid  48  is de-energised the return spring  120  forces the push rod  50  to move linearly away from flow chamber  40  thereby pressing the piston  38  and particular piston head  72  against the seal  44 . This closes the flow chamber  40  preventing the flow of water from inlet  14  the outlet  16 . The pressure applied by the piston to the seal  44  is fixed by the return spring  122 . 
     As in cartridge  30 , it is not possible in cartridge  130  to apply any further or otherwise excessive force or pressure to the seal  44 . Additionally as the push rod  50  moves solely in the axial direction without any rotation, the piston  38  does not rotate. Even if for some reason while moving axially the push rod  50  were to rotate the coupling between the knob  86  and lip  82  would ensure that rotational motion is not imparted to the piston  38 . Indeed, as the rotation of push rod  50  is in practice exceedingly unlikely and even if it did occur it would be negligible the coupling  84 ′ could be completely dispensed with and the push rod  50  connected directly to the piston  38 . However, for the purposes of interchangeability and simplified manufacture, it is preferred that coupling  84 ′ be incorporated in cartridge  130 . 
     It will be further noted that when the solenoid  48  is energised the spacing of the piston head  72  from valve seat  44  is controlled by abutment of base  66  with the lugs  64 . 
     Now that embodiments of the valve cartridge have been described in detail it will be apparent to those skilled in the relevant arts that numerous modifications and variations may be made without departing from the basic inventive concepts. For example, in the cartridge  30  shown in FIGS. 1 and 2 the axial position of spindle  46  is fixed while the axial position of coupling  84  can vary in response to rotation of the spindle  46 . However, this can be reversed with the axial position of the spindle  46  being variable and the actual position of the coupling  84  being fixed. 
     Also, the knob  86  and lip  82  arrangement for providing rotational coupling between the piston  38  and coupling  84  can be replaced with any mechanical equivalent which achieves the same effect. It will be recalled that the spindle  46  cannot be screwed entirely out of the coupling  84  because of the abutment between lugs  64  and base  66  of the piston  38 . However, in an earlier working prototype maintaining a connection between the spindle  46  and coupling  84  was achieved by providing a circumferential flange about the spindle  46  adjacent thread  87  and forming diametrically opposed claws on the coupling  84  which can grip the flange. The claws were in the form of upstanding lugs which extend partially about the circumference of the coupling  84  and each provided with a lip on its inner surface which extends radially inwardly for sitting over the flange. The upstanding lugs are either made of flexible material or flexibly mounted on the coupling  84  so that they can be pushed apart by the flange when the spindle  46  is initially threaded into the coupling  84 . With this arrangement, when the spindle is rotated a pre-determined number of revolutions in the anti-clockwise direction, moving the piston  38  to the fully opened position, the flange about the spindle  46  abuts the lips on the upstanding lugs. Because the lugs are housed within the cavity  36  they are prevented from flexing radially outwardly in response to further anti-clockwise rotation of the spindle  46 . In this way the coupling  84  and spindle  46  are effectively locked together so that the coupling  84  now rotates with the spindle  46  in response to any further rotation in the anti-clockwise direction. 
     With cartridge  130  modifications can be made so as to allow the amount of separation between the piston head  72  and seal  44  to be varied. This provides a variable flow control of the solenoid operated valve cartridge  130 . This can be achieved either mechanically or electrically. 
     Embodiments of this invention can of course be used in valves for controlling flow of gases and other fluids. 
     The component parts of the valve cartridges  30  and  130  can be made of plastics materials and/or metals or metal alloys such as brass. 
     All such modifications and variations are deemed to be within the scope of the present invention, the nature of which is to be determined from the foregoing description and the appended claims.