FIELD OF THE INVENTION 
     A tank valve whose height above its point of attachment is adjustable. 
     BACKGROUND OF THE INVENTION 
     With the advent of low flow volume toilet tank installations, the available height for necessary tank valves has expanded greatly, from very short to very long heights. A single-height valve will no longer serve a wide range of installations. While it is an alternative, it is an expensive nuisance to provide valves for each desired height, or to provide parts made specifically for a given height. 
     Accordingly, efforts have been made to provide height adjustment means so that the height of valves can be adjusted to a number of different elevations. The problems to date have largely resided in the complexity of their height adjustment means. Devices such as collets and other threaded devices are known for the purpose. While these do provide the function, they do it with additional parts, and with parts that sometimes might loosen and let the valve slip and perhaps malfunction. 
     In addition, parts cost money. In a field such as toilet valves where pennies on the price can make the difference between getting an order or losing it, any device which functions as well or better at a lower cost can represent an important competitive advantage. 
     It is an object of this invention to provide a height adjustable valve which, except for the use of a two piece telescopic riser, does not require any part not otherwise required in a normal non-adjustable ballcock valve. 
     It is another object of this invention to provide structure for this purpose in which O-rings can be installed simply and without damage. 
     BRIEF DESCRIPTION OF THE INVENTION 
     A tank valve according to this invention includes a telescopic riser having an axis, an outer tube and an inner tube, which are axially slidable relative to one another. Both tubes have a central passage, and an upper end and a lower end. The inner tube has an outer wall which confronts the inner wall of the outer tube. 
     The outer wall of the inner tube has a continuous groove comprising lateral bar segments that are in planes normal to the central axis, and pass segments which are parallel to the axis. A tongue extends into the passage of the outer tube and engages in the groove. The bar segments and pass segments alternate so the relative axial position of the tubes (and thereby the height of the valve) can be adjusted by moving the tongue axially in the pass segments. The adjusted position will be set when the tongue is in a pass segment. The tubes are rotated relative to one another to enable the tongue to move from one pass segment to the next, and to trap the tongue in a bar segment. 
     The outer tube includes a guide which receives a stiffly flexible tank fill tube. The tank fill tube is fixed to a tube mount on the inner tube, which is bridged to the passage in the inner tube. The tube mount and guide are axially aligned when the tongue is at the mid-point of a pass segment, so the stiffness of the fill tube assists in resisting relative rotation of the inner and outer tubes. 
     According to preferred but optional features of this invention, a lead-in groove section is provided adjacent to the lower end of the inner tube which will permit the tongue to be inserted in the groove while leaving a ring groove exposed below the lower end of the outer tube but without a ring in it, then to receive an O-ring, and thereafter to draw the O-ring into the outer tube. After the application of the O-rings, a latch prevents future separation of the tubes. 
     In another embodiment, the tongue may be a separate part, and the lead-in section can be eliminated. 
    
    
     The above and other features of this invention will be fully understood from the following detailed description and the accompanying drawings, in which: 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view partly in cutaway cross-section of a valve according to the invention; 
     FIG. 2 is an exploded view of the valve of FIG. 1; 
     FIG. 3 is a cross-section taken at line  3 - 3  in FIG. 2; 
     FIG. 3A and 3B are fragmentary cross-sections showing two types of tongue. 
     FIG. 4 is a more detailed exploded view of the valve; and 
     FIG. 5 is an upper end view of the inner tube. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A tank valve  10  (sometimes herein called a “ballcock valve”) is shown attached to the bottom  11  of a water tank  12 , in which an agreed volume of water is to be maintained. The volume is sensed by its level  13 , this being a level-responsive valve. 
     Valve  10  includes a riser  15  which comprises an outer tube  16  and an inner tube  17 . A flange  18  around the outer tube backs up a conventional conical washer  19 . A thread  20  adjacent to the lower end  21  of the outer tube passes through a hole in the bottom of the tank to be engaged by a threaded nut  22  to hold the valve in place, attached to the bottom of the tank. 
     Valve  10  has a central axis  25  which when the valve is in use is usually vertical. The outer tube has an upper end  26  and an internal passage  27 . Passage  27  is defined by a circularly cylindrical inner wall  28 , extending from upper end  26  to lower end  21  of the outer tube. A tongue  30  (FIG. 3A) is integral with the outer tube. It projects into passage  27  for a purpose to be described. 
     A tube guide  31  is fixed to the outside of the outer tube. It extends axially along it. Its function is to receive and guide a stiffly flexible tank fill tube  32 . A notch  33  is formed in the flange  18  to pass tube  32  while the device is being assembled. The lower end of fill tube  32  will always be inside of the tank after it is installed. 
     Inner tube  17  has a central axial passage  35  and an outer wall  36  that is circularly cylindrical. Wall  36  extends from the upper end  37  to the lower end  38  of the inner tube. Its diameter is smaller than the diameter of inner wall  28  of the outer tube so the two tubes can be telescopically reciprocated relative to one another. 
     The riser further includes a bridge  40  into which passage  35  opens. Also, a tube mount  41  has a passage  42  in which the upper end of tank fill tube  32  is fixed. Tube  32  shifts in tube guide  31  when the tubes  16  and  17  are moved axially relative to one another. As will later be shown, when this valve is open to flow, water will flow from the riser, or more particularly from inner tube  17 , to passage  42  and tank refill tube  32 , into the tank to supply water to it. 
     A groove  50  (FIG. 4) has a path that extends along the length of the outer wall of the inner tube. Groove  50  primarily includes alternating laterally extending bar segments  51  and pass segments  52 . The bar segments extend laterally, and the pass segments extend axially. The function of this groove is to be engaged by the tongue to enable the height (length) of the assembled riser to be adjusted and retained. It will be seen that, because this tongue would project into any ring groove, it could thereby slice any O-ring already placed in the groove. This situation would be intolerable because the valve would leak. The alternative would be to install the tongue after assembly, but this would involve an additional part and assembly labor, both of which are undesirable situations. However, later installing of the tongue is within the scope of this invention, is shown in FIG.  3 B. 
     Reverting now to the lower end of the inner tube, it will be seen from FIG. 1 that when the inner and outer tubes are pressed together to form the shortest possible riser length, a portion  51  of the inner tube projects beyond the lower end  21  of the outer tube. An O-ring groove  52   a  (or grooves) is formed in this portion, and an O-ring  53  can be applied in this circumstance. Notice that at this time the tongue is far above the rings, very near to the bridge. In fact, to enable portion  51  to protrude even farther, an axial extension segment  55  of the groove, in the nature of a pass segment is provided. It is best aligned with a central portion of the segment. 
     Additionally, to enable the tongue to reach the groove when the riser is to be assembled, an axial lead-in segment  54  is provided starting at the lower end of the inner tube. This groove will cut across the ring grooves, but this will not affect the sealing properties of an O-ring seated in such a groove. Extension segment  55  and lead-in segment  54  are preferably axially aligned. 
     Evidently, should an effort be made to separate the inner and outer tubes after the O-ring is installed, the tongue would have to cut through the O-ring, which would destroy the integrity of the valve. Therefore means is provided to prevent their separation once the O-ring has been installed. 
     This is accomplished by providing a ratchet latch  60  in the lead-in groove. While a valve of this type is quite rigid, minor deflections still can be provided for. 
     Latch  60  has a ramp surface  61  and a latch surface  62 . The ramp surface will enable the tongue to pass over it when the tubes are assembled. A thirty degree ramp will cause the tongue to deform adjacent structure enough to let it pass over the rising ramp surface. However, the reverse is another situation. Then the effect is for the tongue simply to abut the latch surface, and the tubes cannot be separated. 
     The latch surface will be placed at an axial location where it will stop the separation movement near the intended available setting. The O-ring is applied after the inner and outer tubes are telescoped far enough that the tongue will not pass over it while the tubes are being put together. 
     As shown in FIG. 3B, a separate tongue  63  can be formed as part of a headed pin  64  passes through a hole through the wall of the outer tube. Then the O-ring can be installed first, and thereafter the tongue can be inserted. 
     The height of the valve is adjusted by rotating the tubes to align the tongue with a pass surface, moving the inner tube axially, and then rotating it along a bar segment to the next pass segment. When the desired height is reached, the tongue is left in a bar segment, so the tubes cannot be shifted. 
     Valve workings are contained in a cavity  70  between base  71  and cap  72 . Engagement means  73  (FIG. 5) such as are shown in Antunez U.S. Pat. No. 6,244,292, issued Jun. 12, 2001 releasably attaches the cap to the base. This patent is incorporated herein by reference in its entirety for its showing of such means. It will be noticed that a circular seat  75  surrounds the entrance of the inner tube&#39;s passage. A circular groove  76  on the outside of the seal communicates with the opening into the tube mount and the tank fill tube. 
     A differential pressure responsive valve operator  77  of the type shown in Antunez U.S. Pat. No. 6,244,292 controls the position of a flexible disc-like valve seal (not shown). This patent is incorporated herein by reference in its entirety for its showing of such an operation. When this seal sits on seat  75 , the valve is closed to flow. When the seal moves away from the seat, the valve is open to flow. This Antunez patent may be referred to for full disclosure of the workings and valve operation. 
     Control of the position of the seal and seat is accomplished by the well-known constructions designed in the above Antunez patents which are incorporated herein in its entity for its showing of valve structures by reference of this type. 
     The valve setting is basically determined by the position of a valve pin  80  connected to a first class lever  81  mounted to the cap. A float  82  is connected to linkage  83  attached to the other end of lever  81 . For convenience, this float can embrace the riser as shown. 
     Suffice it to say that when the water level is high enough, the valve pin will be lowered to a position where the differential pressure and differences in valve seal areas will combine to close the valve. When the water level falls, the reverse occurs and the valve opens. These are customary constructions which form no part of the invention and will not be further described. Persons skilled in the art will recognize them. 
     To summarize, when the valve is to be assembled, the inner tube, without an O-ring, will be inserted in the outer tube, all the way, manipulating them by rotating and passing them together as appropriate. When the inner tube projects far enough beyond the lower end of the outer tube, a ring or rings is applied. The fill tube will have been installed before or at this time. Notch  33  will enable it to be passed through the guide and into the tube mount. 
     If the construction of FIG. 3B is used, the O-ring can be installed first, and the pin and tongue inserted afterward. 
     Once this assembly is completed, the riser can be elongated as desired, but it can no longer be extended beyond the limit set by engagement of the tongue and latch surface. It can, however, be readily be adjusted to any height (length) between these extremes. 
     The foregoing embodiment is preferred, because the outer tube integrally includes the tongue, so there is not a secondary operation to install one. It is the advantage which gives rise to the lead-in segment of the groove in order that the O-ring can be brought into the outer tube without damage from the tongue. 
     When the tongue of  3 B is used, the lead-in segment and extension segment will not be needed, and the inner tube can be shorter, because the O-ring can be applied to it before it is inserted in the upper end of the outer tube. After than, the pin can be inserted and cemented in place, or otherwise permanently retained. This is another available advantage of the embodiment of FIG.  3 B. 
     This invention is not to be limited by the embodiments shown in the drawings and described in the description, which are given by way of example and not of limitation, but only in accordance with the scope of the appended claims.
A toilet tank valve having valve workings supported on a riser. The riser incorporates a serpentine ladder-like groove pattern engaged by a tooth, such that the height of the valve workings can be adjusted by a ladder-like relative movements of an inner and outer tube.