Abstract:
A novel non-scald mixing valve is provided of the type that utilizes a pressure-balancing piston to sense a change in the set flow conditions and automatically open or closes orifice to compensate for the change, the valve being characterized by the use of ceramic valving elements to provide both the valve shut-off function and the temperature-ratioing function. The ceramic valving elements fulfill the requirement that the positive shut-off function must be accomplished up-stream of the sensing pressure-balancing piston in order to avoid the use of check valves in the hot and cold water supplies.

Description:
This invention relates to improvements in non-scald mixing valves for shower and bath installations. 
     BACKGROUND OF THE INVENTION 
     Many variations on mixing valves for showers and baths have been developed and marketed. These include thermostatically controlled valves and pressure balanced valves. Typically a sensing-controlling element, such as a thermostatic expansion device or a pressure sensing-and-balancing piston senses a change in flow conditions and automatically opens or closes orifices to compensate for the change. To be effective the sensing-controlling element must “see” and act upon the incoming water flow upstream of any temperature setting element or mechanism. 
     Mixing valves of the type comprising a water pressure-sensing- and-balancing piston are exemplified by those disclosed in U.S. Pat. Nos. 2,308,127; 3,099,996; and 3,448,755. In such valves the hot and cold water sources are applied to opposite ends of the piston, and as pressure variations take place the piston is caused to move under the action of the pressure difference that occurs. The water flows through orifices controlled by the piston to another orifice pair that are set to proportion the hot/cold flow mix. 
     Since the sensing element, i.e., the water-pressure equalizing piston, must “see” and act upon the source water supply pressure, it must be connected directly across the hot and cold water supplies. Accordingly, if a leak occurs, hot water could be introduced into the cold water supply and vice-versa. To prevent that occurrence it is necessary to have a positive shut-off located up-stream of the sensing element. In mixing valves of the type described in the above-identified U.S. Patents, which type is more recently exemplified by the Temptrol® valves produced by Symmons Industries, Inc. of Braintree, Mass., this is accomplished by including two elastomeric “seats” that positively shut off the hot/cold supplies up-stream of the pressure balancing element. These seats are incorporated directly on the temperature setting, hot/cold ratioing element (the spindle assembly), obviating the need for separate check-valves as in many competing devices. 
     Also prior to the present invention it was recognized that use of ceramic members as valving elements in hot and cold water mixing valves offers several advantages, and a number of different water flow control products using ceramic components have been marketed. For example, kitchen and lavatory faucets using ceramic valving components have been developed and/or marketed by a number of companies, including Masco Corporation. See also U.S. Pat. No. 3,788,354, issued Jan. 29,1974 to Paul C. Symmons for Single Handle Water Mixing Valve. The use of ceramic valving elements in shower valves of the type having water pressure balancing piston elements is disclosed by U.S. Pat. No. 3,921,659 issued Nov. 25, 1975 to Charles J. Rudewick III for Modular Balanced Pressure Mixing Valve With Ceramic Valve Elements. Additionally Zurn Industries of Dallas, Tex. has marketed a shower valve using ceramic elements. However, to Applicant&#39;s knowledge, in the Zurn Company shower valve the ceramic elements are arranged so as to provide temperature-ratioing and shut-off control downstream of the pressure balancing element and, therefore, auxiliary check valves must be incorporated between the shower valve and the hot and cold water supplies to prevent backflow into the hot and cold water supply lines. 
     Non-scald shower and bath mixing valves using water pressure sensing-and-equalizing piston elements, notably valves having operating modes similar to those disclosed in said U.S. Pat. Nos. 2,308,127; 3,099,996; and 3,448,755, have achieved extensive commercial success because they have effectively eliminated the danger of accidental scalding resulting from a rapid change in water temperature as a consequence of a variation in water pressure, and also because their elastomeric seats positively shut off the hot and cold water supplies up-stream of the water pressure sensing and balancing means. 
     Nevertheless it has been recognized that there is a need to improve upon existing designs of non-scald mixing valves in a way that lowers manufacturing costs without any loss of non-scald protection and without requiring the use of check valves in the hot and cold water supply lines. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     The primary object of this invention is to provide a new and improved pressure-balancing non-scald mixing valve that offers the advantages of lower manufacturing costs, uses virtually indestructible ceramic valving elements, and avoids the need for check valves to prevent backflow into the hot and cold supply lines. 
     Another important object of this invention is to provide a new and improved pressure-balancing non-scald mixing valve that is characterized by the use of ceramic elements to provide both the shut-off function and the temperature-ratioing function. 
     A further object is to provide a new and improved non-scald mixing valve of the type having a water pressure-equalizing piston for automatically opening and closing orifices to compensate for changes in cold or hot water pressure, characterized by the use of ceramic elements as means for accomplishing the shut-off function and means for accomplishing the temperature-ratioing function, while allowing the piston to be connected directly across the hot and cold water supplies. 
     The foregoing and other objects hereinafter rendered obvious are accomplished by utilizing a sliding ceramic face valve pair to provide both the required shut-off function and the temperature-ratioing function, with one ceramic element constituting a stator and the other a slider. 
     More specifically the new and improved mixing valve design comprises a valve body having cold and hot water supply ports, at least one mixed water outlet port and an opening for accommodating a mixing chamber member and a spindle assembly that extends into the mixing chamber assembly. The mixing chamber member is hollow and defines a mixing chamber having cold water inlet and transfer ports and hot water inlet and transfer ports, with its cold and hot water inlet ports communicating with the cold and hot water supply ports. Disposed in the mixing chamber is a ceramic stator having hot and cold water inlet orifices that communicate with the mixing chamber&#39;s cold and hot water inlet ports and cold and hot water outlet orifices that communicate with the mixing chamber&#39;s cold and hot water transfer ports. The spindle assembly comprises (1) a balancing piston block disposed within and movable bidirectionally lengthwise of the mixing chamber member, and (2) and a ceramic slider engaged with and movable with the balancing piston block. The balancing piston block has an internal chamber and four side orifices that open into said internal chamber. The slider has a cold water inlet orifice, a cold water exit orifice, a hot water inlet orifice, and a hot water exit orifice aligned with first, second, third and fourth ones respectively of the four side orifices of the piston block. The spindle assembly also includes a pressure- balancing piston disposed within and slidable bidirectionally along the balancing piston block&#39;s internal chamber, the piston having a cold and hot water side inlet ports and cold and hot water end outlet ports. The cold and hot water outlet ports of said piston are in constant communication with the cold and hot water transfer ports of said mixing chamber, while the piston&#39;s cold and hot water inlet ports move through varying degrees of alignment with the cold and hot water inlet ports respectively of the mixing chamber as the piston moves back and forth. The degree that the cold and hot water inlet ports of the piston are aligned with the cold and hot water inlet ports respectively of the mixing chamber is a function of the pressures of the hot and cold water supplied to the mixing chamber&#39;s cold and hot water inlet ports. 
     The spindle assembly further includes an actuating member in the form of a lead screw that is coupled to the balancing piston block, an internally threaded stem surrounding and in screw thread connection with the lead screw, and stem-retaining means attached to said valve body for permitting rotational but not axial movement of said stem, whereby rotation of the stem will cause the lead screw and the balancing piston block to move axially according to the direction of rotation of said stem. Axial movement of the balancing piston block by rotation of the stem causes the cold and hot water inlet orifices and the cold and hot water exit orifices of the slider to move into and out of varying degrees of alignment with the hot and cold water inlet orifices and the cold and hot water outlet orifices of the stator, including a first “Off” piston block position whereby at least the cold and hot water inlet orifices of the slider are blocked by portions of the stator, a second “Full Cold” water flow piston block position whereby the cold and hot water inlet orifices of the slider are aligned with the cold and hot water inlet orifices of the stator and the cold water exit orifice of the slider is aligned with the cold water outlet orifice of the stator, but the hot water exit orifice of the slider is blocked by a portion of the stator, and a third “Full Hot” water flow piston block position in which the cold water exit orifice of the slider is blocked by a portion of the stator and the hot water exit port of the slider is aligned with the hot water outlet port of the stator. In the first position, no water can flow through the valve. In the second position only cold water can flow through the valve. In the third position only hot water can flow through the valve. When the piston block is positioned intermediate those second and third positions, both cold and hot water can flow through the faucet, with the proportions of hot cold water depending upon the degree of alignment of slider and stator orifices. 
     Other features and advantages of the invention are explicitly disclosed or rendered obvious by the following detailed description which is to be considered together with the accompanying drawings. 
    
    
     THE DRAWINGS 
     FIG. 1 is a perspective view in elevation of a mixing valve constituting a preferred embodiment of the invention. 
     FIG. 2 is a view similar to FIG. 1 but with the valve rotated 90° from the position shown in FIG. 1; 
     FIG. 3 is a plan view of the same valve; 
     FIG. 4 is a sectional view in elevation taken along line  4 — 4  of FIG. 3; 
     FIG. 5 is sectional view in elevation taken along line  5 — 5  of FIG. 4; 
     FIG. 6 is a longitudinal sectional view on an enlarged scale showing details of the assembly constituting, inter alia, the mixing chamber, spindle and the pressure balancing piston; 
     FIG. 7 is an end view of the assembly of FIG. 6; 
     FIG. 8 is a forward end view of the mixing chamber; 
     FIG. 9 is an axial sectional view of the valve cap; 
     FIG. 10 is a perspective view of the balancer porting block; 
     FIG. 11 is a plan view of the balancer porting block; 
     FIG. 12 is a bottom view of the balancer porting block; 
     FIG. 13 is a longitudinal sectional view of the balancer porting block 
     FIG. 14 is a back end view of the balancer portion block; 
     FIG. 15 is a front end view of the balancer porting block; 
     FIG. 16 is a side view in elevation of the seal plug for the balancer porting block; 
     FIG. 17 is a plan view of the outer end of the seal plug; 
     FIG. 18 is a side view of a spring retainer clip for the seal plug; 
     FIG. 19 is a perspective view of a sleeve that slidably contains the pressure balancing piston; 
     FIG. 20 is a cross-sectional view of the same sleeve; 
     FIG. 21 is a longitudinal sectional view of the pressure balancing piston; 
     FIGS. 22 is a side view of the ceramic slider; 
     FIG. 23 is a bottom view of the ceramic slider; 
     FIG. 24 is a bottom view of the ceramic stator; 
     FIG. 25 is an end view of the stator; 
     FIG. 26 is a side view in elevation of the lead screw; 
     FIG. 27 is a side view in elevation of the stem member; 
     FIG. 28 is a side view in elevation of a stem retainer; 
     FIGS. 29 and 30 are diagrams showing the relative positions of the ceramic slider and stator as the valve handle is turned to vary the flow from “Off” to “Full Hot”. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring first to FIGS. 1-5, the illustrated embodiment of the invention comprises a valve body  2  preferably, but not necessarily, made of brass and having cold and hot water inlet ports  4  and  6  respectively, a first outlet port  8  adapted for connection to a bathtub water inlet and a second outlet port  10  adapted for connection to a shower head. Additionally the valve body has a large threaded opening  12  to accommodate a valve cap  14  that serves to retain within the valve body the working components hereinafter described. 
     Referring specifically to FIGS. 4 and 5, the valve body has an internal passageway  16  that connects the two outlet ports  8  and  10 . Additionally the valve body has an internal bore  18  which is shaped and sized to accommodate a tubular element  20  that is designed to serve as a mixing chamber. Cold and hot water inlet ports  4  and  6  communicate with bore  18  via openings  4 A and  6 A respectively (see FIG.  5 ). Internal passageway  16  also communicates with bore  18  via cold and hot water outlet openings  16 A and  16 B respectively (see FIG.  4 ). 
     As seen best in FIGS. 6-8, mixing chamber element  20  is circular in cross-section and has a plurality of relatively circumferential ribs  22  that in turn have circumferential grooves in which are mounted resilient O-ring seals  24 . As seen in FIGS. 4 and 5, the rear (inner) end of mixing chamber element  20  is seated against an inner partition  40  that closes off the inner end of the valve body&#39;s internal bore  18 , and the O-rings  24  engage the inner cylindrical surface that defines bore  18  and thereby serve to prevent leakage of water between ribs  22 . Accordingly the ribs  22  cooperate with the cylindrical surface of the valve body that defines bore  18  to form four annual flow channels or chambers  26 A- 26 D. The two channels  26 B and  26 C are aligned with valve body cold and hot water inlet openings  4   a  and  6 A respectively and serve as inlet water flow chambers, while the other two channels  26 A and  26 D are aligned with the valve body cold and hot water outlet openings  16 A and  16   b  respectively and serve as outlet water flow chambers. Mixing chamber element  20  has four circumferentially elongated openings  28 A- 28 B in its side wall that communicate with flow channels  26 A- 26 D respectively. Openings  26 B and  26 C act as cold and hot water inlet ports respectively, and openings  26 A and  26 D act as cold and hot water transfer ports respectively. Hence cold and hot water can flow from valve body inlet openings  4 A and  6 A into the interior of mixing chamber member  20  via channels  26 B and  26 C and ports  28 B and  28 C respectively. Additionally water can flow from the interior of mixing chamber member  20  into passageway  16  via ports  28 A and  28 D, channels  26 A and  26 D and cold and hot water outlet openings  16 A and  16 B respectively. 
     The inside of mixing chamber element  20  is a constant diameter bore, except that it is enlarged by a longitudinally extending groove  30  (FIG. 8) and its opposite ends are tapered to facilitate insertion of components hereinafter described. Referring to FIGS. 7 and 8, the base of groove  30  is a flat surface  31 A, and at each of its longitudinal side edges that flat surface is joined to a narrow surface section  31 B that extends outwardly at an acute angle to it. Groove  30  serves to accommodate a ceramic stator  32  which is described later in greater detail. The forward (or outer) end surface of element  20 , i.e., the end surface nearest valve cap  14 , also is formed with two mutually aligned eccentric projections or ribs  34  that are sized to make a close fit in a pair of eccentric slots  36  formed in the inner end of valve cap  14 . 
     Disposed within bore  18  is a balancer porting block  46 . As seen best in FIGS. 10-15, the outer side of block  46  comprises a pair of flat oppositely disposed surfaces  48 A,  48 B, a third flat surface  50  that extends at a right angle to and joins surfaces  48 A,  48 B, and a curved fourth surface  52  that extends between and joins surfaces  48 A,  48 B. At the inner end of porting block  46  the surfaces  48 A,  48 B are terminated by slanted projections  56  that serve as anchor ledges for a spring clip  58  (see FIGS. 6,  7  and  18 ). Clip  58  has hook-shaped ends  60  that are shaped to firmly grasp projections  56 . 
     Porting block  46  has a cylindrical bore  62  that is formed with an open inner end but is closed off by a seal plug  66  (FIGS. 4-6,  16  and  17 ). Clip  58  serves to retain seal plug  66  in place in the inner end of bore  62 . The outer end of bore  62  is closed off by an end wall  68 . The latter is formed with a cavity  70  (FIG. 13) that connects with bore  62 . Bore  62  and cavity  70  are formed with mutually aligned side orifices or ports  72 A- 72 D (FIGS. 12,  13 ) that extend through the flat outer surface  50 . Preferably ports  72 A- 72 D are elongated transversely of the axis of the porting block, as illustrated in FIG.  12 . The flat surface  50  is interrupted by circular depressions  74 A- 74 D that surround ports  72 A- 72 D and serve as seats for O-rings seals  76  (FIG.  6 ). 
     Referring to FIGS. 6,  19  and  20 , disposed in bore  62  is a sleeve  80  that surrounds and serves as a guide for a pressure-balancing piston  82 . Sleeve  80  comprises three cylindrical annular sections  84  A-C. Section  84 B has cylindrical opposite end extensions  86  having a reduced outer diameter. However, the inner diameters of section  84 B, including its extensions  86 , is identical to that of sections  84 A and  84 C. Sections  84 A and  84 B are connected to one another by three parallel arms  88  that are spaced from another about the longitudinal axis of the sleeve so as to form three equally-spaced radial ports  90 A that communicate with the interior of annular sections  84 A and  84 B. Sections  84 B and  84 C are similarly connected by three additional arms  88  so as to form three additional equally spaced radial ports  90 B (FIG. 19) that communicate with the interior of annular sections  84 B and  84 C. Each of the sections  84 A-C is provided with a peripheral groove  94  to accommodate a seal in the form of a resilient O-ring  96  (FIG.  6 ). The O-rings  96  engage the internal surface that defines bore  62  and serve to prevent water from leaking out from between the sleeve and porting block  46 . Sleeve  80  is retained in bore  62  by action of plug  66  which also holds keeps it in engagement with end wall  68 . 
     Turning now to FIGS. 6 and 21, the balancing piston  82  comprises two hollow cylindrical end sections  100 A,  100 B, a solid center section  102 , and two hollow cylindrical connecting sections  104 A,  104 B that have a smaller diameter than sections  100 A and  100 B. The opposite end surfaces of sections  100 A,  100 B and  102  are all flat and extend at a right angle to the piston&#39;s longitudinal axis. The connecting sections  104 A and  1048 B are formed with a plurality of circumferentially spaced holes  106 A and  106 B respectively that serve as cold and hot water inlet ports respectively. Preferably but not necessarily, sections  104 A and  104 B each have four equally spaced inlet ports  106 A and  106 B as shown. The internal bores  108 A and  108 B of end sections  100 A and  1000 B serve as cold and hot water outlet ports respectively. The outside diameters of sections  100 A,  100   b  and  102  are identical and are sized to make a sliding fit in sleeve  80  that is close enough to prevent little or no water from passing between those sections and sleeve  80 , yet not so close as to prevent the piston from moving axially in the sleeve under a relatively small differential water pressure, e. 0.5 psi. The diameters of the internal bores  108 A,  108 B of sections  100 A and  100 B are identical, as are the areas of the internal surfaces  110 A and  110 B of section  102 . Consequently if the hot and cold water pressures applied to the piston via cold and hot water inlet ports  106 A and  106 B are equal, the piston will remain stationary in sleeve  80 . 
     Referring again to FIGS. 10-15, projecting from surface  50  of the porting block are four rectangular posts  112  , two adjacent each side surface  48 A and  48 B. Posts  112  serve to locate a ceramic slider  116  (FIGS. 6,  22  and  23 ) and cause it to move axially with the porting block. Slider  116  is a flat ceramic member that is generally rectangular but is formed with two rectangular slots  120  at each side which are sized to make a substantially close fit with posts  112 . Slider  116  also is formed with four ports or orifices  122 A- 122 D that are elongated transversely to the slider&#39;s longitudinal axis. These ports are spaced from one another by the same amount as the ports  72 A- 72 D of balancer porting block  46 . One face of slider  116  has two depressions  124  that are elongated in the direction of its longitudinal axis and surround ports  122 B and  122 C. 
     The slider is engaged with the porting block so that the depressions  124  face away from the porting block. When the slider is so disposed, its ports  122 A- 122 D are aligned with ports  72 A- 72 D of the porting block. In this connection it should be noted that seal plug  66  has a peripheral groove  125  (FIG. 16) that accommodates an O-ring seal  126  (FIG. 6) that makes a tight seal with the inner porting block surface that defines bore  62 , and also that it has a radially extending cavity  128  on its inner side that extends out to its periphery. The purpose of cavity  128  is to facilitate flow of water through porting block port  72 A. Accordingly plug  66  is oriented in the porting block so that its cavity  128  is aligned radially with port  72 A. 
     Turning now to FIGS. 24 and 25, the stator  32  is a flat rectangular member having opposite side surfaces  130  and  132 , with the stator being chamfered at the edges of side surface  132  so as to provide surfaces  140  that are slanted at the same angle as the surfaces  31 B of groove  30 . The stator makes a close fit in groove  30 , with its surface  132  lying flat against groove surface  31 A. The stator is provided with four orifices or port holes  142 A- 142 D that are spaced from one another exactly like ports  122 A- 122 D of slider  116 . These holes are all elongated transversely of the longitudinal axis of the stator. Additionally the surface  132  has four circular depressions  144 A- 144 D that surround ports  142 A- 42 D respectively. Seated in these depressions are O-ring seals  146  (FIG.  6 ). The stator is disposed so that the side with the depressions  144 A- 144 D faces the inner surface of the mixing chamber element  20 . The thickness of the O-ring seals  76  of the porting block and the O-ring seals  146  of stator  32  are sized so that the former are compressed between the porting block and the slider  116 , and the latter are compressed between the stator and the mixing chamber element  20 , with the result that the two sets of O-rings act as springs to keep the mutually confronting surfaces of the slider and stator fully and evenly engaged with one another at all times. In this connection it should be noted that, as shown in FIG. 4, the inner end of the stator lies tight against the inner partition  40  of the valve body when the valve is fully assembled, while its outer end is captivated by valve cap  14 . The mutually engaging faces of stator  32  and slider  116  are ground (lapped) flat to within 4 helium light bands so as to provide an intimate face seal whereby no water can pass between them while allowing the slider to move axially relative to the stator. 
     Referring now to FIGS. 6,  10 - 15  and  26 , the outer end of porting block  46  has two extensions  150  and  152  that extend parallel to the block&#39;s longitudinal axis. Extension  150  is positioned to be engaged by a stop screw  153  that is screwed into a threaded section  17  (FIG. 9) of an inclined bore  15  in valve cap  14 . when screw  153  is in the retracted position shown in FIG. 6, outward movement of the porting block is limited by engagement of extension  150  with valve cap  14 . However, when screw  153  is turned so as to intrude into mixing chamber element  20 , outward movement of the porting block is limited by engagement of extension  150  with screw  153 . 
     The second extension  152  has a circularly curved outer surface  154  that extends through an angle of about 300 degrees, and an inner surface that comprises a pair of mutually spaced flat side sections  156  and a circularly curved center section  158  which coact to form a channel  160 . However, the two side sections  156  are formed with like mutually confronting flat projections  162  that have square edges as shown and serve as retaining lugs for an elongate actuating member  166 . As shown in FIG. 26, actuating member  166  is a lead screw and comprises a cylindrical externally threaded lead screw section  168  and a porting block connecting section  170 . The latter also is cylindrical, except that intermediate its ends it has two diametrically opposed notches characterized by oppositely facing flat bottom surfaces  172  and flat side surfaces  174 . The porting block connecting section  170  interlocks with the second extension  152  of the porting block. The interlocking connection is made by inserting the connecting section  170  into the channel  160 , with the notched portion of the connecting section having its flat surfaces  172  disposed between and parallel to the projections  162  and end portion  176  of the connecting section  170  being captivated between projections  162  and the adjacent end face of end wall  68 . As a result the porting block and the actuating member  166  are releasably coupled together so that the porting block cannot rotate or move axially relative to the actuating member  166 . 
     Referring now to FIGS. 6,  9  and  27 , screwed on the actuating member  166  is a valve-operating stem  180 . The latter constitutes a hollow cylindrical body  182  that is internally threaded to mate with the external screw thread of actuating member  166 , plus an external flange  184  at its inner end. Valve cap  14  has a center bore  188  and actuating member  166  and stem  180  extend out though that center bore. As seen best in FIG. 9, center bore  188  has two counterbores that form annular shoulders  190  and  192 . Additionally the outer end of center bore  188  has an increased internal diameter so as to provide an inner surface  193  that has a screw thread for making a screw thread connection with a stem retainer member  196  (FIG. 9) that has an external screw thread at its inner end . It should be noted also that the outer surface of valve cap  14  has an enlarged diameter section  194  with a screw thread in its outer cylindrical surface to permit the cap to be screwed into the threaded valve body opening  12 . The outer end of the stem retainer has a smaller outside dimension and its exterior surface  198  has a hexagonal shape in cross-section to permit the retainer to be tightened or loosened by means of a wrench. The stem retainer is screwed into the valve cap far enough for its inner end surface to engage the outer internal shoulder  192  of the valve cap. When the stem retainer is in this position, the flange  184  of stem  180  is captivated between valve cap shoulder  190  and the inner end of the stem retainer, with the spacing between the inner end surface of the stem retainer and the shoulder  190  being set so that flange  184 , and hence stem  180 , is prevented from moving axially relative to the valve body while being free to rotate to cause actuator member  166  to move axially so as open or close the valve. 
     As seen in FIGS. 1 and 2, a handle  200  is affixed to the outer end of stem  180  for the purpose of turning it in one direction or the other to vary the cold and cold water mix. The handle has a threaded opening in which is screwed a set screw  202  (FIG. 1) that is used to secure the handle to the stem. As seen in FIG. 27, the stem has a depression  204  in its outer surface that is elongated lengthwise of the stem. This depression is sized to receive the inner end of set screw  202 , whereby to releasably lock the handle to the stem. The depression is elongated as shown so as to permit some adjustment of the axial position of the handle on the stem. 
     Operation of the valve is straightforward. Cold and hot water are introduced through ports  4  and  6  of the outer body  2  into the annular chambers  26 B and  26 C respectively formed by the body and mixing chamber member  20 . Then the cold and hot water flows through ports  28 B and  28 C into the orifices  142 B and  142 C of stator  32 , through ports  84 B and  84 C of slider  116  and ports  26 A and  26   b  of the porting block, ports  90 A and  90   b  of sleeve  80  and openings  106   a  and  106   b  of the piston into the cold and hot water chambers of piston  82 . The cold and hot water outlet flow paths are through piston ports  108 A and  108 B, the opposite ends of sleeve  80 , porting block ports  74 A and  74 D, slider orifices  122 A and  122 D, stator orifices  142 A,  142 D, mixing chamber member ports  28 A and  28 D and valve body outlet openings  16 A and  16 B to mixed water outlet ports  8  and  10 . 
     Referring to FIGS. 29 and 30, in the extreme “Off” position the ceramic pair  32  and  116  act to positively shut off cold and hot water flow. As the spindle-piston assembly carrying slider  116  is moved outwardly away from internal partition  40 , both the hot and cold water inlet ports are opened simultaneously, applying full line pressure to the both sides of the piston. In the “Full Cold.” position flow is constrained to flow only through the cold water side ceramic ports while the hot water side ceramic inlet port is still fully blocked. Further movement of the spindle-piston assembly in the same direction allows hot water to begin to flow into the valve via the stator and slider water inlet ports, producing a mixed water output from the valve. Movement of the spindle-piston assembly away from internal partition  40  causes the ceramic stator/slider pair to modulate the hot to cold mixing ratio, with the ratio of hot to cold water increasing with continued movement in the same direction. 
     As the spindle-piston assembly is moved to its furthest position, i.e., to the “Full Hot” position, the slider blocks the stator&#39;s cold water outlet port while the hot water outlet port is fully opened. 
     The invention offers a number of advantages. First of all, it provide a novel pressure-balancing non-scald mixing valve that improves on prior designs by employing ceramic elements to provide both the shut-off function and the temperature-ratioing function. A second advantage is that it comprises a spindle-balancing piston subassembly that can be easily removed from and inserted into the valve body. More specifically, the porting block, sleeve, shuttle and ceramic slider are contained within a cylindrical part, the “mixing chamber”, and that subassembly is removable and replaceable as a unit “cartridge” from the body of the valve. This enables the outer body to be plumbed up permanently, as in a shower stall, permitting the replacement of the inner subassembly alone. A further advantage is that the two ceramic elements are essentially flat plates that enable a relatively simple valving arrangement and offer the promise of lower costs coupled with long useful life. Still another advantage is that the valve components may be made from a variety of materials. It is preferred, but not essential that the outer body  2 , valve cap  14 , mixing chamber element  20 , and stem retainer  196  be made of brass, and actuating member  166  be made of stainless steel. However, a number of the internal parts may be plastic moldings, e.g., porting block  46 , plug  66 , and stem  180  may be made of a variety of plastic materials. Mixing chamber element  20  also could be made of a suitable plastic. 
     It should be noted that the valve may be modified in various ways without departing from the essence of the invention. For one thing, the invention is not restricted to valves of the type herein described and illustrated but may be used also in valves that do not incorporate pressure-balancing pistons. In this connection, it should be noted that the valve herein described and illustrated may be converted to a non-pressure-balancing mixing valve by (1) by removing piston  82  and its guiding sleeve  80  and (2) providing porting block  46  with an internal partition in bore  62  between the openings  72 B and  72 C so as to subdivide the interior of the porting block into two chambers, namely, a cold water chamber comprising outlet and inlet openings  72 A and  72 B respectively and a hot water chamber comprising inlet and outlet openings  72 C and  72 D respectively. In the mixing valve resulting from such a modification the two ceramic plates will function as previously described to provide full shutoff control and to vary the mixture of hot and cold water discharged from the outlet port(s) of the valve body. Also the valve body may be simplified by providing it with a single outlet port, thereby eliminating the need for the outlet passageway  16 . The sizes and number of certain of the ports or orifices also may be modified without changing the mode of operation of the invention. It should be noted also that the locations of the inlet and outlet orifices may be changed, e.g., the relative positions of the inlet and outlet orifices of the stator and slider may be reversed. A further obvious modification is to integrate porting block  46  and lead screw actuating member  166  by molding them together as a single component. This modification offers the advantage of reducing the number of parts and a possible lowering of manufacturing costs, while the two-piece arrangement shown in the drawings tend to permit greater mechanical tolerances and the ability to manufacture the porting block and the lead screw actuating member of different materials. Another possible modification is to adapt the valve for remote control. Such a modification would involve eliminating handle  200  and coupling stem  180  to a remotely controlled and reversible electromechanical driver device, e.g., a device comprising a reversible electric motor and a motion transmitting mechanism in the form of a gear train having an input gear driven by the motor and an output gear affixed to stem  180 , whereby operation of the motor will cause rotation of stem  180  in a direction determined by the direction of operation of the motor and the form of the gear train. 
     Still other modifications will be obvious to persons skilled in the art from the preceding detailed specification and the drawings.