Hot and cold water mixing device

In a hot and cold water mixing device, the slope in a medium-temperature range is gently, and the slopes in a low-temperature range and a high-temperature range are steep. When the target temperature of water mixture is set in the medium-temperature range, a combined biasing force of serially-arranged bias springs acts on a main shaft leftwards, a biasing force of a temperature-sensitive spring acts on the main shaft rightwards, and these biasing forces balance with each other so that the main shaft and valve elements are stopped. When a handle is turned to enter into the high-temperature range exceeding, e.g. 50.degree. C., a slide shaft biases the main shaft leftwards only with the second bias spring. When the handle is turned to enter into the low-temperature range, e.g. below 30.degree. C., the slide shaft biases the main shaft only with the first bias spring leftwards.

FIELD OF THE INVENTION
 The present invention relates to a hot and cold water mixing device, and
 more particularly to a hot and cold water mixing device of a thermostatic
 type in which a movable valve element is pressed from both sides by a bias
 spring and a temperature-sensitive spring made of shape memory material.
 In addition, the present invention relates to a control mechanism for hot
 and cold water mixing device which can control in such a manner that, in a
 low-temperature range where the spring constant of a temperature-sensitive
 spring made of a shape memory alloy is extremely reduced, a bias spring
 functions as a member for softening the operation force acting on a valve
 element for closing the valve after the valve element is seated and that
 the valve element is biased in a direction of closing a hot water port by
 a regulating member so that the hot water port can be forcedly closed for
 discharging only cold water.
 DESCRIPTION OF THE RELATED ART
 As a hot and cold water mixing device of thermostatic type, a device
 employing a temperature-sensitive spring made of a shape memory material
 such as a shape memory alloy is publicly known. As disclosed in Japanese
 patent application H06-147333, a hot and cold water mixing device of this
 type comprises a cylindrical valve body in which a cold water valve seat
 and a hot water valve seat are arranged, a valve element which can
 reciprocate in an axial direction of the valve body and is allowed to come
 in contact with the cold water valve seat and the hot water valve seat, a
 temperature-sensitive spring for biasing the valve element in a direction
 toward the hot water valve seat, a bias spring for biasing the valve
 element in a direction toward the cold water valve seat, and a temperature
 regulating handle for moving the bias spring.
 By selectively turning the temperature regulating handle, the bias spring
 is moved in forward and rearward axial directions so as to vary the force
 applied by the bias spring biasing the valve element, thereby changing the
 preset target temperature of water mixture.
 That is, the rearward movement of the bias spring reduces the force applied
 by the bias spring so that the valve element comes closer to the hot water
 valve seat and moves apart from the cold water valve seat, thereby
 lowering the preset target temperature. To the contrary, the forward
 movement of the bias spring increases the force applied by the bias spring
 so that the valve element moves apart from the hot water valve seat and
 comes closer to the cold water valve seat, thereby rising the preset
 target temperature. When the temperature of water mixture becomes
 different from the preset target temperature due to a variation in the
 temperature of supplied hot water and/or a fluctuation of the supply
 pressure of hot water in a state where water mixture of a preset target
 temperature is discharged, the temperature-sensitive spring expands or
 contracts to shift the valve element so that the temperature of water
 mixture is automatically recovered to a preset target temperature.
 In the conventional hot and cold water mixing device, the relation between
 the turning angle of the temperature regulating handle and the travel of
 the valve element is substantially straight and is represented by a broken
 line in FIG. 4. That is, for example, the travel of the valve element per
 a unit turning angle of the temperature regulating handle is substantially
 uniform in any of a low-temperature range below 30.degree. C., a
 medium-temperature range from 30.degree. C. to 50.degree. C., and a
 high-temperature range above 50.degree. C. The relation between the
 turning angle of the temperature regulating handle and the temperature of
 water mixture to be discharged is substantially straight in the overall
 range from the low-temperature range to the high-temperature range.
 In general, a faucet with a hot and cold water mixing device is desired to
 have a wider indication range for the medium-temperature range from
 30.degree. C. to 50.degree. C., as shown in FIG. 5a, allowing the fine
 control for water mixture in the medium-temperature range from 30.degree.
 C. to 50.degree. C., particularly, from 35.degree. C. to 45.degree. C. For
 this, the slope of a line (the slope of the line in FIG. 4) representing
 the relation between the turning angle of the temperature regulating
 handle and the temperature of water mixture in the medium-temperature
 range from 30.degree. C. to 50.degree. C. should be gentle. However, to
 make the slope simply entirely gentle, a signficantly large turning range
 of the temperature regulating handle is required for allowing the
 temperature control from the low-temperature range to the high-temperature
 range. In case of the temperature-regulating handle of a turning-type, the
 turning range of the handle (C-H: when the handle is at C, only cold water
 through a cold water supply pipe is discharged, while when the handle is
 at H, only hot water through a hot water supply pipe is discharged) should
 be 360.degree. or less (normally, 270.degree. or less). Accordingly,
 making the slope simply entirely gentle as mentioned above can not be
 employed actually (because the range C-H should be over 360.degree.). This
 is the reason why the conventional faucet has a small indication range for
 the medium-temperature range from 30.degree. C. to 50.degree. C., as shown
 in FIG. 5b.
 The present invention is made taking such a technical problem into
 consideration and a first object of the present invention is therefore to
 provide a hot and cold water mixing device in which the slope in the
 medium-temperature range is gentle and the slope in the low-temperature
 range and the high-temperature range is steep, so that a faucet with this
 hot and cold water mixing device has a wide indication range for the
 medium-temperature range.
 A control mechanism of the conventional hot and cold water mixing device
 will be described with reference to FIG. 20. A valve casing 801 has an
 inner cavity 802 passing through the center of the valve casing 801 for
 forming flow passages, and a hot water port 803 and a cold water port 804
 formed in a circumferential wall of the valve casing 801. A spool valve
 element 805 is fitted slidably in the axial direction of the valve casing
 801 for defining the flow rates of hot water and cold water by controlling
 the ratio of opening areas of the ports 803 and 804. The spool valve
 element 805 comprises a hot water valve element 805a and a cold water
 valve element 805b integrally connected and is biased by a
 temperature-sensitive spring 806 made of a shape memory alloy in a
 rightward direction and biased by a bias spring 807 in a leftward
 direction in this figure. The rightward and leftward directions are
 opposite to each other so that the spool valve element 805 is stopped at a
 position where the springs 806 and 807 balance with each other. One end of
 the bias spring 807 is supported by a plug member 808 so that the biasing
 forces of the springs 806 and 807 can be varied by moving the plug member
 808 in the axial direction. According to the varied biasing forces of the
 springs 806 and 807, the position of the spool valve element 805 is
 changed and the flowing rate between hot water and cold water are thus
 changed, thereby changing the temperature of water mixture.
 For instance, in a state that the spool valve element 805 is stopped at a
 preset position where the springs 806 and 807 balance, the supply pressure
 of hot water or cold water fluctuates so that the flowing ratio between
 hot water and cold water relative to the same opening area is varied,
 changing the temperature of obtained water mixture. The
 temperature-sensitive spring 806 senses such variation and works. That is,
 the temperature-sensitive spring 806 works as an automatically temperature
 regulating function by changing its biasing force corresponding to the
 temperature of obtained water mixture in such a manner as to move the
 spool valve element 805 in such a direction of correcting the temperature.
 Normally in a hot and cold water mixing device with an automatically
 temperature regulating function, when only cold water is discharged, the
 position of the spool valve element 805 in the axial direction should be
 controlled by the balance between the biasing forces of the
 temperature-sensitive spring 806 and the bias spring 807 such that the hot
 water valve element 805a of the spool valve element 805 is seated on a hot
 water valve seat.
 However, according to the control mechanism of the hot and cold water
 mixing device using the temperature-sensitive spring 806 made of a shape
 memory alloy, the spring constant of the temperature-sensitive spring 806
 decreases with decreasing temperature of water mixture and the force
 applied by the temperature-sensitive spring 806 is thus reduced.
 Accordingly, when operation for discharging only cold water is performed,
 the force biasing the spool valve element 805 may be too poor to
 completely close the hot water port 803, thus allowing the enter of hot
 water. Therefore, the hot and cold water mixing device using the
 temperature-sensitive spring 806 has a problem of not discharging
 completely only cold water.
 To solve this problem, the spring constant of the temperature-sensitive
 spring 806 is previously set relatively large. In this case, when
 operation for discharging only cold water is performed, the
 temperature-sensitive spring 806 can close the hot water port 803 against
 the biasing force of the bias spring 807. However, to previously set the
 spring constant of the temperature-sensitive spring 806 relatively large,
 the entire size of the hot and cold water mixing device must be large,
 also causing a problem of increasing the cost. There is an alternative
 measure that the spool valve element 805 is seated on the hot water valve
 seat directly by a member for adjusting the biasing force of the bias
 spring 807. However, the mechanical connection between the member and the
 spool valve element 805 brings another problem in the closing operation
 after the spool valve element 805 is seated on the hot water valve seat,
 that the operational force directly acts on the spool valve element 805 so
 that a force destroying the spool valve element 805 may be exerted on the
 spool valve element 805.
 Therefore, a second object of the present invention is to provide a control
 mechanism of a hot and cold water mixing device in which a hot water valve
 element is forcedly seated on a hot water valve seat by using a member
 varying the biasing force of a bias spring in a low-temperature range, the
 force acting on the valve element is buffered by the bias spring while
 allowing the valve element to be seated, and the bias spring further
 biases the valve element in a direction of closing a hot water port.
 SUMMARY OF THE INVENTION
 A hot and cold water mixing device according to first to eighteenth aspects
 accomplishes the aforementioned first object of this invention.
 A hot and cold water mixing device according to the first aspect comprises:
 a cylindrical valve body having a cold water valve seat and a hot water
 valve seat; a valve element which is slidable in the axial direction of
 said valve body and which can be seated on said cold water valve seat and
 said hot water valve seat; a temperature-sensitive spring for biasing said
 valve element in a direction toward said hot water valve seat; a bias
 spring for biasing said valve element in a direction toward said cold
 water valve seat; and a temperature setting member for moving said bias
 spring in the axial direction of said valve body. The mixing device
 further comprises a biasing force changing means for changing the biasing
 force of said bias spring so that the biasing force when said valve
 element is positioned in a range for discharging medium-temperature water
 mixture differs from the biasing force when said valve element is
 positioned in a range for discharging low-temperature water mixture or a
 range for discharging high-temperature water mixture.
 In this hot and cold water mixing device according to this invention, the
 biasing force of the bias springs can be changed so that the slope of a
 temperature line in the medium-temperature range becomes gentle.
 According to the second aspect of the present invention, a plurality of
 bias springs are provided as said bias spring, and said biasing force
 changing means controls such that the biasing force of only a part of said
 bias springs acts on said valve element when the valve element is
 positioned in the range for discharging low-temperature water mixture or
 the range for discharging high-temperature water mixture and that the
 biasing force of all of said bias springs serially acts on said valve
 element when the valve element is positioned in the range for discharging
 medium-temperature water mixture.
 In this hot and cold water mixing device, when the target temperature of
 water mixture is set in the low-temperature range or the high-temperature
 range, the biasing force of only a part of the bias springs acts on the
 valve element, while when the target temperature of water mixture is set
 in the medium-temperature range, the biasing force generated by the first
 and second bias springs which are serially connected acts on the valve
 element.
 As well known in the art, when, the combined spring constant of serially
 connected springs becomes a harmonic average of the spring constants of
 the respective springs so that the serially combined spring constant
 should be smaller than one of the respective spring constants. Therefore,
 according to the hot and cold water mixing device of the present invention
 according to the second aspect, the biasing force of the biasing springs
 when the target temperature is set in the medium-temperature range is
 small so that the slope indicating the travel of the valve element (i.e.
 the temperature of water mixture) relative to the turning angle of the
 temperature regulating handle is gentle, thus facilitating the fine
 control for setting the target temperature of water mixture.
 When the target temperature is set in the low-temperature range or the
 high-temperature range, the biasing force of the bias springs is larger
 and therefore the slope is steeper than that in case of the
 medium-temperature range. Therefore, a wider rotation range for the
 medium-temperature range can be obtained without increasing the entire
 rotation range of the temperature regulating handle.
 In an embodiment of the third aspect of the hot and cold water mixing
 device, according to the second aspect, said valve element is supported by
 a main shaft arranged coaxially with said valve body, said main shaft
 being slidable in the axial direction of said valve body; wherein said
 temperature setting member comprises: a rotational shaft arranged
 coaxially with said main shaft and having internal thread formed in the
 inner surface thereof, a cylindrical slide shaft arranged coaxially with
 said main shaft and having external thread to be engaged with said
 internal thread; a distal end collar and a proximal end collar formed on a
 distal end and a proximal end of said slide shaft, respectively, the
 distal end being apart from the valve element and the proximal end being
 near the valve element; a hook which is axially movably coupled to said
 slide shaft, and is prevented from moving in a direction toward the valve
 element when engaged with said proximal end collar; and a slide ring which
 is axially movably coupled to said main shaft and disposed between said
 hook and the valve element in such a manner as to be in contact with a
 collar-like stopper disposed on a middle portion in the longitudinal
 direction of said main shaft and to be in contact with said hook. The
 mixing device further comprises a first bias spring disposed between said
 slide ring and the valve element in the compressed state, and a second
 bias spring disposed between said hook and the distal end collar in the
 compressed state.
 As stated in the fourth aspect, this changing means may comprise: said main
 shaft extending from said valve element; a flange-like stopper disposed on
 the end of said main shaft; said collar-like stopper disposed on the
 middle portion of said main shaft; a stopper ring biased by said second
 bias spring in a direction to be pressed against the distal end collar of
 the slide shaft; and said slide ring biased by said first bias spring in a
 direction to be pressed against the hook, wherein when the valve element
 is positioned in a range for discharging medium-temperature water mixture,
 said flange-like stopper and the stopper ring are spaced apart from each
 other, said stopper ring is pressed against the distal end collar of the
 slide shaft by the second bias spring, said collar-like stopper and the
 slide ring are spaced apart from each other, and said slide ring is
 pressed against the hook by the first bias spring, and when the valve
 element is positioned in a range for discharging low-temperature water
 mixture, said flange-like stopper is engaged with said stopper ring and
 said hook is engaged with the proximal end collar so as to restrict the
 movement of the hook in a direction toward the valve body, whereby the
 biasing force of the second bias spring is applied to the valve element
 via the stopper ring and the main shaft in the same direction of the
 biasing force of said temperature-sensitive spring, and said collar-like
 stopper is engaged with the slide ring so that the biasing force of the
 first bias spring does not act on the valve element and the slide shaft.
 In another embodiment (fifth aspect) of the hot and cold water mixing
 device, according to the second aspect, the temperature setting member
 comprises: a rotational shaft arranged coaxially with said main shaft and
 having internal thread formed in the inner surface thereof; a cylindrical
 slide shaft arranged coaxially with said rotational shaft and having
 external thread to be engaged with said internal thread; and a clutch
 column arranged movably in the axial direction of said valve body, a first
 bias spring is disposed between said clutch column and the valve element
 in the compressed state, and a second bias spring is disposed between the
 clutch column and the slide shaft in the compressed state.
 In this case, it is preferable that the clutch column is engaged with the
 slide shaft so as to restrict the movement of the clutch column in the
 axial direction, or that the clutch column is engaged with the valve
 element so as to restrict the movement of the clutch column in the axial
 direction.
 According to the sixth aspect of the present invention, a plurality of bias
 springs is provided as said bias spring, and said biasing force changing
 means controls such that when the valve element is positioned in a range
 for discharging medium-temperature water mixture, the serially combined
 biasing force of the respective bias springs is applied to the valve
 element in a direction opposite to that of the biasing force of the
 temperature-sensitive spring, and when the valve element is positioned in
 a range for discharging low-temperature water mixture, the biasing force
 of a part of the bias springs is applied to the valve element in the same
 direction of the biasing force of the temperature-sensitive spring.
 In this hot and cold water mixing device, when the target temperature of
 water mixture is set in the medium-temperature range, all of the bias
 springs serially act on the valve element in the direction opposite to
 that of the biasing force of the temperature-sensitive spring. Since the
 biasing force of the serially combined bias springs should be smaller, the
 slope indicating the travel of the valve element (i.e. the temperature of
 water mixture) relative to the turning angle of the temperature regulating
 handle is gentle.
 When the target temperature of water mixture is set in the low-temperature
 range, a part of the bias springs biases the valve element in the same
 direction of the biasing force of the temperature-sensitive spring. In
 this case, the slope indicating the travel of the valve element (i.e. the
 temperature of water) relative to the turning angle of the temperature
 regulating handle is steep.
 In the seventh aspect of the hot and cold water mixing device, according to
 the sixth aspect, said temperature setting member comprises: a rotational
 shaft arranged rotatably about its axis and having internal thread formed
 in the inner surface thereof; a cylindrical slide shaft arranged coaxially
 with said rotational shaft and having external thread to be engaged with
 said internal thread; a clutch column arranged movably in the axial
 direction of said slide shaft; a first bias spring disposed between said
 clutch column and the valve element in the compressed state, and a second
 bias spring disposed between clutch column and the slide shaft in the
 compressed state.
 In the eighth aspect, an engaging member for engaging the slide shaft and
 the clutch column when the temperature is set at a low temperature by said
 temperature setting member is also provided, and this biasing force
 changing means comprises: a projecting shaft extending from said valve
 element toward the slide shaft; a stopper disposed on the end of said
 projecting shaft; and a washer biased by said second bias spring in a
 direction to be pressed against the slide shaft, wherein when the valve
 element is positioned in a range for discharging high-temperature water
 mixture or a range for discharging medium-temperature water mixture, said
 stopper and the washer are spaced apart from each other and said washer is
 pressed against the slide shaft by the second bias spring, and when the
 valve element is positioned in a range for discharging low-temperature
 water mixture, said stopper is engaged with said washer and said engaging
 member restricts the movement of the clutch column in a direction toward
 the valve body, whereby the biasing force of the second bias spring is
 applied to the valve element via the washer and the projecting shaft in
 the same direction of the biasing force of said temperature-sensitive
 spring. In this case, as stated in the ninth aspect, it is preferable that
 when the valve element is positioned in a range for discharging
 high-temperature water mixture, the clutch column comes in contact with
 the valve element or the slide shaft so as to restrict the movement of the
 clutch column in the axial direction.
 In addition, in the tenth aspect, this changing means may comprise: a
 projecting shaft extending from said valve element toward the slide shaft;
 a first stopper disposed on the end of said projecting shaft; a second
 stopper disposed on a middle portion of said projecting shaft; a first
 washer biased by said second bias spring in a direction to be pressed
 against the slide shaft; and a second washer biased by said first bias
 spring in a direction to be pressed against the clutch column, wherein
 when the valve element is positioned in a range for discharging
 medium-temperature water mixture, said first stopper and the first washer
 are spaced apart from each other and said first washer is pressed against
 the slide shaft by the second bias spring while the second stopper and the
 second washer are spaced apart form each other and the said second washer
 is pressed against the clutch column by the first bias spring, and when
 the valve element is positioned in a range for discharging low-temperature
 water mixture, said first stopper is engaged with said first washer and
 said engaging member restricts the movement of the clutch column in a
 direction toward the valve body, whereby the biasing force of the second
 bias spring is applied to the valve element via the first washer and the
 projecting shaft in the same direction of the biasing force of said
 temperature-sensitive spring, while said second stopper is engaged with
 said second washer whereby the biasing force of the first bias spring does
 not act on the valve element and the slide shaft.
 Further, in the eleventh aspect, this changing means may comprise: a
 projecting shaft extending from said slide shaft toward said valve
 element; a stopper disposed on the end of said projecting shaft; and a
 washer biased by said first bias spring in a direction to be pressed
 against the valve element, wherein when the valve element is positioned in
 a range for discharging high-temperature water mixture or a range for
 discharging medium-temperature water mixture, said stopper and the washer
 are spaced apart from each other and said washer is pressed against the
 valve element by the first bias spring, and when the valve element is
 positioned in a range for discharging low-temperature water mixture, said
 stopper is engaged with said washer and said engaging member restricts the
 movement of the clutch column in a direction apart from the valve body,
 whereby the biasing force of the first bias spring is applied to the valve
 element via the washer, the projecting shaft, and the clutch column in the
 same direction of the biasing force of said temperature-sensitive spring.
 In this case, as stated in twelfth aspect, it is preferable that when the
 valve element is positioned in a range for discharging high-temperature
 water mixture, the clutch column comes in contact with the valve element
 or the slide shaft so as to restrict the movement of the clutch column in
 the axial direction.
 In the thirteenth aspect, this changing means may comprise: a projecting
 shaft extending from said slide shaft toward said valve element; a first
 stopper disposed on the end of said projecting shaft; a second stopper
 disposed on a middle portion of said projecting shaft; a first washer
 biased by said first bias spring in a direction to be pressed against the
 valve element; and a second washer biased by said second bias spring in a
 direction to be pressed against the clutch column, wherein when the valve
 element is positioned in a range for discharging medium-temperature water
 mixture, said first stopper and the first washer are spaced apart from
 each other and said first washer is pressed against the valve element by
 the first bias spring, while said second stopper and the second washer are
 spaced apart from each other and said second washer is pressed against the
 clutch column by the second bias spring., and when the valve element is
 positioned in a range for discharging low-temperature water mixture, said
 first stopper is engaged with said first washer and said engaging member
 restricts the movement of the clutch column in a direction apart from the
 valve body, whereby the biasing force of the first bias spring is applied
 to the valve element via the first washer, the projecting shaft, and the
 clutch column in the same direction of the biasing force of said
 temperature-sensitive spring, while said second stopper is engaged with
 said second washer whereby the biasing force of the second bias spring
 does not act on the valve element and the slide shaft.
 In a hot and cold water mixing device according to the fourteenth aspect of
 the present invention, a plurality of bias springs is provided as said
 bias spring, and said biasing force changing means for changing the
 biasing force of the bias springs acting on said valve element controls
 such that when the valve element is positioned in a range for discharging
 high-temperature water mixture, the concurrent (total) biasing force of
 all of the bias springs is applied to the valve element in a direction
 opposite to that of the biasing force of the temperature-sensitive spring;
 when the valve element is positioned in a range for discharging
 medium-temperature water mixture, the biasing force of a part of the bias
 springs is applied to the valve element in a direction opposite to that of
 the biasing force of the temperature-sensitive spring; and when the valve
 element is positioned in a range for discharging low-temperature water
 mixture, the valve element is moved directly by said temperature setting
 member.
 In this hot and cold water mixing device, when the target temperature of
 water mixture is set in the high-temperature range, the concurrent biasing
 force of the plural bias springs acts on the valve element in the
 direction opposite to that of the biasing force of the
 temperature-sensitive spring so that the slope indicating the travel of
 the valve element (i.e. the temperature of water mixture) relative to the
 turning angle of the temperature regulating handle is steep.
 When the target temperature of water mixture is set in the
 medium-temperature range, only a part of the bias springs acts on the
 valve element in the direction opposite to that of the biasing force of
 the temperature-sensitive spring so that the slope indicating the travel
 of the valve element (i.e. the temperature of water mixture) relative to
 the turning angle of the temperature regulating handle is gentle.
 When the target temperature of water mixture is set in the low-temperature
 range, the valve element moves integrally with the temperature setting
 member, e.g. the slide shaft, so that the slope indicating the travel of
 the valve element (i.e. the temperature of water) relative to the turning
 angle of the temperature regulating handle is steep.
 In the hot and cold water mixing device of the fourteenth aspect, in the
 fifteenth aspect, said valve element is supported by a main shaft arranged
 coaxially with said valve body, said main shaft being slidable in the
 axial direction of said valve body; wherein said temperature setting
 member comprises: a rotational shaft arranged rotatably about its axis and
 having internal thread formed in the inner surface thereof; and a
 cylindrical slide shaft arranged coaxially with said rotational shaft and
 having external thread to be engaged with said internal thread, wherein
 said changing means comprises: a projecting shaft extending from said main
 shaft toward said slide shaft; a stopper disposed on the end of said
 projecting shaft; and a washer capable of coming in contact with said
 stopper, and wherein a first bias spring is disposed between said washer
 and the valve element and a second bias spring is disposed between said
 slide shaft and the valve element. When the valve element is positioned in
 a range for discharging high-temperature water mixture, said stopper and
 the washer are spaced apart from each other and the washer and the slide
 shaft are engaged with each other whereby the first bias spring is
 subjected to the reaction force by the slide shaft and thus biases the
 valve element, when the valve element is positioned in a range for
 discharging medium-temperature water mixture, the stopper is engaged with
 the washer wherein the application of the biasing force of the first bias
 spring to the valve element is cancelled, and when the valve element is
 positioned in a range for discharging low-temperature water mixture, the
 valve element and the slide shaft are engaged with each other so that the
 valve element and the slide shaft move integrally with each other.
 In a hot and cold water mixing device according to the sixteenth aspect of
 the present invention, a plurality of bias springs is provided as said
 bias spring, and said biasing force changing means for changing the
 biasing force of the bias springs acting on said valve element controls
 such that when the valve element is positioned in a range for discharging
 high-temperature water mixture, the concurrent (total) biasing force of
 all of the bias springs is applied to the valve element in a direction
 opposite to that of the biasing force of the temperature-sensitive spring;
 when the valve element is positioned in a range for discharging
 medium-temperature water mixture, the biasing force of a part of the bias
 springs is applied to the valve element in a direction opposite to that of
 the biasing force of the temperature-sensitive spring; and when the valve
 element is positioned in a range for discharging low-temperature water
 mixture, the biasing force of the other bias spring (springs) is applied
 to the valve element in the same direction of the biasing force of the
 temperature-sensitive spring.
 In this hot and cold water mixing device, when the target temperature of
 water mixture is set in the high-temperature range, the concurrent biasing
 force of the plural bias springs acts on the valve element in the
 direction opposite to that of the biasing force of the
 temperature-sensitive spring so that the slope indicating the travel of
 the valve element (i.e. the temperature of water mixture) relative to the
 turning angle of the temperature regulating handle is steep.
 When the target temperature of water mixture is set in the
 medium-temperature range, only a part of the bias springs acts on the
 valve element in the direction opposite to that of the biasing force of
 the temperature-sensitive spring so that the slope indicating the travel
 of the valve element (i.e. the temperature of water mixture) relative to
 the turning angle of the temperature regulating handle is more gentle than
 that in case of the high-temperature range.
 When the target temperature of water mixture is set in the low-temperature
 range, the other bias springs bias the valve element in the same direction
 of the biasing force of the temperature-sensitive spring. In this case
 also, the slope indicating the travel of the valve element (i.e. the
 temperature of water) relative to the turning angle of the temperature
 regulating handle is steep.
 In the hot and cold water mixing device of the sixteenth aspect, in the
 seventeenth aspect, said temperature setting member preferably comprises:
 a rotational shaft arranged rotatably about its axis and having internal
 thread formed in the inner surface thereof; and a cylindrical slide shaft
 arranged coaxially with said rotational shaft and having external thread
 to be engaged with said internal thread, and further comprising: a second
 bias spring being disposed between the slide shaft and the valve element;
 first and second collars disposed on said column and spaced apart from
 each other in the axial direction; a first washer and a second washer
 disposed to face said first collar and said second collar, respectively; a
 first bias spring disposed between said first washer and said second
 washer in the compressed state; a collar disposed on said slide shaft
 which is engaged with said first washer to press said first washer in the
 direction apart from the valve element when the slide shaft is moved in a
 direction apart from the valve element; and a step disposed on said slide
 shaft which is engaged with said second washer to press said second washer
 in the direction toward the valve element when the slide shaft is moved in
 a direction toward the valve element.
 A control mechanism of a hot and cold water mixing device according to the
 eighteenth aspect comprises: a main body having a hot water port and a
 cold water port formed in the circumferential surface thereof; a valve
 element disposed in an inner chamber of the main body; a
 temperature-sensitive spring and a bias spring for biasing the valve
 element; and a regulating member for controlling the position of the valve
 element by changing the biasing force of the bias spring, wherein the
 valve element is brought in contact directly or indirectly with one end of
 the bias spring and the regulating member is brought in contact directly
 or indirectly with the other end of the bias spring and the regulating
 member is controlled so as to change the flowing rates of hot water and
 cold water to obtain water mixture at a desired temperature, wherein the
 valve element is provided with a contact surface which can come in contact
 directly or indirectly with a regulating member contact surface of the
 bias spring, and the regulating member is provided with a contact surface
 which can come in contact directly or indirectly with a valve element
 contact surface of the bias spring, whereby the bias spring biases the
 valve element in a direction of closing the hot water port at least when
 the hot water port is closed.
 When the temperature of water mixture to be discharged is set in the
 low-temperature range, the spring constant of the temperature-sensitive
 spring may be too low to sufficiently cope with the supply pressure of hot
 water. However, in the hot and cold water mixing device according to the
 present invention, the valve element is directly or indirectly linked with
 the regulating member for varying the biasing force of the bias spring
 when the target temperature is set in such a range whereby the bias spring
 functions as a buffer for softening the operation force applied to the
 valve element after the valve element is seated and, in addition, the
 axial position of the valve element can be controlled via the regulating
 member. Further, the bias spring acts to bias the valve element in the
 closing direction.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
 [First Preferred Embodiment]
 FIG. 1 is a sectional view showing a hot and cold water mixing device
 according to the first preferred embodiment, FIG. 2 is a sectional view
 showing the hot and cold water mixing device shown in a state that
 high-temperature water is discharged, and FIG. 3 is a sectional view
 showing the hot and cold water mixing device in a state that
 low-temperature water is discharged. It should be noted that "left" and
 "right" in the following description correspond to "left" and "right" in
 FIGS. 1 through 3, respectively.
 A cylindrical valve body 10 has a cold water port 12 and a hot water port
 14 formed in a circumferential wall thereof and has a discharge port 16
 for water mixture at the left end thereof. The hot water port 14 is
 positioned more left than the cold water port 12. In the valve body 10, a
 convexity 20 is formed by inwardly swelling a portion of the inner surface
 of the body between the water ports 12 and 14. The right end surface of
 the convexity 20 functions as a cold water valve seat 22 and the left end
 surface functions as a hot water valve seat 24.
 A ling-like cold water valve element 32 is disposed to face the cold water
 valve seat 22 and a ring-like hot water valve element 34 is disposed to
 face the hot water valve seat 24 in such a manner that the valve elements
 32 and 34 are fitted to a cruciform portion 30a of a main shaft 30. The
 cross section of the cruciform portion 30a perpendicular to the axis of
 the main shaft 30 is formed in a cruciform shape.
 The main shaft 30 is arranged in such a manner as to be pressed rightwards
 by the temperature-sensitive spring 40 made of shape memory alloy and to
 be pressed leftwards by a first bias spring 42 and a second bias spring
 44. As a mechanism for moving the bias springs 42, 44 along the axial
 direction of the main shaft, a rotational shaft 50, a slide shaft 52, a
 hook 54, and a slide ring 56 are arranged surrounding the main shaft 30.
 A handle-mounting portion 50a at the right end of the rotational shaft 50
 is disposed to project rightwards from a shaft-through hole 60 of the
 valve body 10. A handle (not shown) is attached to this handle-mounting
 portion 50a. An E-ring 62 is fitted on a neck of the handle-mounting
 portion 50a, thereby preventing the movement of the rotational shaft 50 in
 the axial direction. Numeral 64 designates an O-ring.
 The left-end side of the rotational shaft 50 is formed in a cylindrical
 shape and is formed with an internal thread 50b. The right-end side of the
 cylindrical slide shaft 52 is formed with an external thread 52b which
 engages with the internal thread 50b whereby the rotation of the
 rotational shaft 50 moves the slide shaft 52 in the axial direction.
 The slide shaft 52 is formed with a collar (distal collar) 52a projecting
 inwardly at the right end of the slide shaft 52. A stopper ring 68 is
 engaged with the collar 52a. The stopper ring 68 is slidable in the axial
 direction along the inner surface of the slide shaft 52. An end of the
 second bias spring 44 is in contact with the stopper ring 68.
 The slide shaft 52 is formed with a collar (proximal collar) 52c projecting
 outwardly at the left end of the slide shaft 52. Pawls 54c at the right
 end of the hook 54 are engageable with the collar 52c. The hook 54
 comprises a disk portion 54a on the left side thereof which is arranged
 perpendicular to the axis of the main shaft 30 and a plurality of leg
 portions 54b extending from the outer periphery of the disk portion 54a in
 a rightward direction parallel to the axis of the main shaft 30. The pawls
 54c are formed by folding inwardly the ends of the leg portions 54b. The
 left end of the second bias spring 44 is in contact with the disk portion
 54a.
 The slide ring 56 is superposed on the disk portion 54a. The right end of
 the first bias spring 42 is in contact with the slide ring 56. The left
 end of the first bias spring 42 is in contact with a collar 32a convexly
 formed on an inner surface of the cold water valve element 32.
 The left-end portion of the cold water valve element 32 is slidably fitted
 onto the cruciform portion 30a of the main shaft 30. The light-end portion
 of the hot water valve element 34 is slidably fitted onto the cruciform
 portion 30a.
 Respectively fitted onto the cold water valve element 32 and the hot water
 valve element 34 are seal rings 72, 74 made of fluororesin having high
 sliding property. These seal rings 72, 74 water-sealingly and slidably
 abut on the inner surface of the valve body 10.
 The main shaft 30 has a flange 30b (a flange-like stopper) formed on the
 right end thereof which is sized to enter into the collar 52a and to be
 caught by the stopper ring 68. The main shaft 30 also has a collar 30c (a
 collar-like stopper) formed on a middle portion thereof which is sized to
 be caught by the slide ring 56.
 The operation of the hot and cold water mixing device structured as
 mentioned above will be described hereinafter.
 I. When the Target Temperature of Water Mixture is Set in the
 Medium-temperature Range From 30.degree. C. to 50.degree. C. (see FIG. 1)
 When the target temperature of water mixture is set at a temperature, for
 example, in the medium-temperature range from 30.degree. C. to 50.degree.
 C. as shown in FIG. 1, the combined biasing force of the serially-arranged
 bias springs 42, 44 (hereinafter, sometimes referred to as "serial biasing
 force of the bias springs 42, 44") is exerted leftwards to the main shaft
 30 via the cold water valve element 32, while a biasing force of the
 temperature-sensitive spring 40 is exerted rightwards to the main shaft
 30. The combined biasing force and the biasing force balance with each
 other and the main shaft 30 and the valve elements 32, 34 are thus
 stopped.
 In this state, when the actual temperature of water mixture becomes lower
 than the preset target temperature due to a variation in the supply
 temperature or the supply pressure of hot water, the temperature-sensitive
 spring 40 contracts so that the main shaft 30 is moved leftwards and a
 flow space for cold water between the cold water valve seat 22 and the
 cold water valve element 32 is reduced while a flow space for hot water
 between the hot water valve seat 24 and the hot water valve element 34 is
 increased, thereby returning (rising) the actual temperature of water
 mixture to the preset target temperature. To the contrary, when the actual
 temperature of water mixture becomes higher than the preset target
 temperature, the temperature-sensitive spring 40 expands so that the cold
 water valve element 32 and the hot water valve element 34 are moved
 rightwards together with the main shaft 30 so as to increase the flow
 space for cold water and reduce the flow space for hot water, thereby
 returning (lowering) the actual temperature of water mixture to the preset
 target temperature.
 When the handle is turned in the positive direction to increase the target
 temperature of water mixture to another temperature within the
 medium-temperature range, the slide shaft 52 is moved leftwards according
 to the rotation of the rotational shaft 50 in the positive direction so
 that the stopper ring 68 is also moved leftwards. As a result of this, the
 combined biasing force of the bias springs 42, 44 in the leftward
 direction is increased. Therefore, the bias springs 42, 44 shift the valve
 elements 32, 34 leftwards together with the main shaft 30 so as to
 increase the flow space for hot water and reduce the flow space for cold
 water, thereby increasing the temperature of water mixture. After the
 valve elements 32, 34 are shifted, the rightward biasing force of the
 temperature-sensitive spring 40 and the leftward biasing force of the bias
 springs 42, 44 balance with each other. When the actual temperature of
 water mixture deviates from the preset target temperature, the
 temperature-sensitive spring 40 expands or contracts, thereby returning
 the actual temperature of water mixture to the preset target temperature.
 When the handle is turned in the opposite direction to decrease the target
 temperature of water mixture to another temperature within the
 medium-temperature range, the slide shaft 52 is moved rightwards according
 to the rotation of the rotational shaft 50 in the opposite direction so
 that the stopper ring 68 is also moved rightwards. As a result of this,
 the leftward biasing force of the bias springs 42, 44 is decreased so that
 the valve elements 32, 34 are shifted rightwards together with the main
 shaft 30 so as to reduce the flow space for hot water and increase the
 flow space for cold water, thereby lowering the temperature of water
 mixture. After the valve elements 32, 34 are shifted, the rightward
 biasing force of the temperature-sensitive spring 40 and the leftward
 biasing force of the bias springs 42, 44 balance with each other. When the
 actual temperature of water mixture deviates from the preset target
 temperature, the temperature-sensitive spring 40 expands or contracts,
 thereby returning the actual temperature of water mixture to the preset
 target temperature.
 As mentioned above, when the target temperature of water mixture is set to
 any temperature in the medium-temperature range from 30.degree. C. to
 50.degree. C., both of the bias springs 42, 44 work. Assuming that the
 spring constants of the bias springs 42, 44 are k.sub.1, k.sub.2,
 respectively, the force pressing the main shaft 30 leftwards is the serial
 biasing force of the bias springs 42, 44 so that the spring constant of
 the serially combined bias springs is explained by 1/(1/k.sub.1 +/k.sub.2)
 which is smaller than either of k.sub.1, k.sub.2.
 Accordingly, when the preset target temperature is in the
 medium-temperature range, a ratio (a/A) between the travel (A) of the
 rotational shaft 50 and the slide shaft 52 and the travel (a) of the valve
 elements 32, 34 is relatively small. That is to say, the travel (a) of the
 valve elements 32, 34 per a unit angle of the rotational shaft 50 is
 relatively small. As a result, as shown by solid line in FIG. 4, the
 amount in change of the target temperature per the unit angle of the
 handle is small when the target temperature of water mixture is set in the
 medium-temperature range, that is, in the graph of FIG. 4, the slope of a
 temperature line in the medium-temperature range is gentle.
 II. When the Target Temperature of Water Mixture is Set in the
 High-temperature Range Exceeding 50.degree. C. (see FIG. 2)
 When the target temperature of water mixture is set at a temperature
 exceeding 50.degree. C., the slide shaft 52 is moved leftwards largely and
 the second bias spring 44 presses the slide ring 56 so that the slide ring
 56 comes in contact with the right end of the cold water valve element 32.
 Therefore, when the handle is turned to enter into the high temperature
 range exceeding 50.degree. C., the slide shaft 52 biases the main shaft 30
 via only the second bias spring 44 as shown in FIG. 2. The spring constant
 of the second bias spring 44 is k.sub.2 which is larger than the spring
 constant 1/(1/k.sub.1 +1/k.sub.2) in case of the medium-temperature range.
 Accordingly, the ratio (a/A) between the travel (A) of the slide shaft 52
 and the travel (a) of the valve elements 32, 34 is larger than that in
 case of the medium-temperature range. That is to say, the amount in change
 of the target temperature per the unit angle of the handle is larger than
 that in case of-the medium-temperature range. Therefore, in the graph of
 FIG. 4, the slope of the temperature line in the high-temperature range is
 steeper than that in the medium-temperature range. This means that the
 temperature of water mixture is significantly changed only by slightly
 turning the handle in the high-temperature range exceeding 50.degree. C.
 III. When the Target Temperature of Water Mixture is Set in the
 Low-temperature Range Below 30.degree. C. (see FIG. 3)
 When the target temperature of water mixture is set at a temperature below
 30.degree. C., the slide shaft 52 is moved rightwards largely and the
 collar 52c of the slide shaft 52 and the pawls 54c of the hook 54 are
 engaged with each other so that the hook 54 is moved rightwards together
 with the slide shaft 52. Then, the slide ring 56 comes in contact with the
 collar 30c so that the first bias spring 42 expands between the cold water
 valve element 32 and the slide ring 56 (the collar 30c). In this state,
 the biasing force of the first bias spring 42 does not act on the main
 shaft 30.
 Also in this case, as the target temperature is set significantly low (for
 example, the handle is turned to a position near "C"), the slide shaft 52
 is further moved rightwards so that the flange 30b on the right end of the
 main shaft 30 comes in contact with the stopper ring 68. In this state,
 the second bias spring 44 presses the main shaft 30 rightwards via the
 stopper ling 68 and the flange 30b so that the hot water valve element 34
 is pressed against the hot water valve seat 24 by the rightward biasing
 force of the temperature-sensitive spring 40.
 Therefore, when the handle is turned to enter into the low-temperature
 range below 30.degree. C., the leftward biasing force of the bias springs
 42, 44 does not act so that the hot water valve element 34 moves closer to
 the hot water valve seat 24 by the rightward biasing force of the
 temperature-sensitive spring 40. In addition when the target temperature
 is set to significantly low temperature, the biasing force of the second
 bias spring 44 acts on the main shaft 30 in the rightward direction
 whereby the hot water valve element 34 is pressed against the hot water
 valve seat 24 by the temperature-sensitive spring 40. Accordingly, the
 ratio (a/A) between the travel (A) of the rotational shaft 50 and the
 slide shaft 52 and the travel (a) of the valve elements 32, 34 is larger
 than that in case of the medium-temperature range. That is, the amount in
 change of the target temperature per the unit angle of the handle is
 larger than that in case of the medium-temperature range. Therefore, in
 the graph of FIG. 4, the slope of the temperature line in the
 low-temperature range is steeper than that in the medium-temperature
 range. That is to say, the temperature of water mixture is significantly
 changed only by slightly turning the handle in the low-temperature range
 below 30.degree. C.
 It should be noted that while the handle is turned into the low-temperature
 range below 30.degree. C., the stopper ring 68 may come in contact with
 the flange 30b before the slide ring 56 comes in contact with the collar
 30c.
 [Second Preferred Embodiment]
 The second preferred embodiment will be described with reference to FIG. 6.
 In this preferred embodiment, only one valve element 33 is adapted to
 regulate both a flow space for cold water and a flow space for hot water.
 In this preferred embodiment, contrary to the embodiment of FIGS. 1
 through 3, a cold water port 12 is positioned more left than a hot water
 port 14 so that a cold water valve seat 22 is also positioned more left
 than a hot water valve seat 24.
 The valve element 33 comprises a central shaft portion 33C arranged at the
 axis of a cylindrical valve body 10A, flanges 33A, 33B disposed on the
 left end and the right end of the central shaft portion 33C, a center
 flange 33D, a cylindrical portion 33E connected to a middle portion in the
 longitudinal direction of the central shaft portion 33C via the center
 flange 33D, a seal ring 73 which is disposed on the outer periphery of the
 cylindrical portion 33E and water-sealingly and slidably abuts on the
 inner surface of the body 10A, and through holes 33a, 33b, 33d formed in
 the flanges 33A, 33B, 33D, respectively.
 The right end of a temperature-sensitive spring 40 is in contact with the
 flange 33A. The left end of a first bias spring 42 is in contact with the
 flange 33B. Arranged between the valve element 33 and a slide shaft 52 is
 a clutch column 80.
 The clutch column 80 can reciprocate in the axial direction along the inner
 surface of the body 10A. The clutch column 80 has a collar 80a convexly
 formed on an inner surface of the clutch column 80. A first bias spring 42
 is disposed between the collar 80a and the flange 33B of the valve element
 33 in the compressed state.
 A second bias spring 44 is disposed between the collar 80a and a collar 52a
 of the slide shaft 52 in the compressed state. The clutch column 80 has a
 collar 80b convexly formed on an inner surface of the right-end portion of
 the clutch column 80. The collar 80b is engageable with a collar 52c
 formed on the left-end outer surface of the slide shaft 52.
 Other structures of the hot and cold water mixing device of FIG. 6 are the
 same as those of the hot and cold water mixing device of FIGS. 1 through 3
 and parts similar or corresponding to the parts of the hot and cold water
 mixing device of FIGS. 1 through 3 are marked by the same reference
 numerals.
 The operation of the hot and cold water mixing device structured as
 mentioned above with reference to FIG. 6 will be described hereinafter.
 I. When the Target Temperature of Water Mixture is Set in the
 Medium-temperature Range From 30.degree. C. to 50.degree. C.
 FIG. 6 shows the hot and cold water mixing device in a state that the
 target temperature of water mixture is set at a temperature, for example,
 in the medium-temperature range from 30.degree. C. to 50.degree. C. In
 this state, the combined biasing force of serially-arranged the bias
 springs 42, 44 is exerted leftwards to the valve element 33, while a
 biasing force of the temperature-sensitive spring 40 is exerted rightwards
 to the valve element 33. The combined biasing force and the biasing force
 balance with each other.
 In this state, when the actual temperature of water mixture becomes lower
 than the preset target temperature due to a variation in the supply
 temperature or the supply pressure of hot water, the temperature-sensitive
 spring 40 contracts so that the valve element 33 is moved leftwards and a
 flow space for cold water between the cold water valve seat 22 and the
 valve element 33 is reduced while a flow space for hot water between the
 hot water valve seat 24 and the valve element 33 is increased, thereby
 returning (rising) the actual temperature of water mixture to the preset
 target temperature. To the contrary, when the actual temperature of water
 mixture becomes higher than the preset target temperature, the
 temperature-sensitive spring 40 expands so that the valve element 33 is
 moved rightwards so as to increase the flow space for cold water and
 reduce the flow space for hot water, thereby returning (lowering) the
 actual temperature of water mixture to the preset target temperature.
 When the handle is turned in the positive direction to increase the target
 temperature of water mixture to another temperature within the
 medium-temperature range, the slide shaft 52 is moved leftwards according
 to the rotation of the rotational shaft 50 in the positive direction so
 that the clutch column 80 is also moved leftwards. As a result of this,
 the combined biasing force of the bias springs 42, 44 in the leftwards
 direction is increased. Therefore, the bias springs 42, 44 shift the valve
 element 33 leftwards so as to increase the flow space for hot water and
 reduce the flow space for cold water, thereby increasing the temperature
 of water mixture. After the valve element 33 is shifted, the rightward
 biasing force of the temperature-sensitive spring 40 and the leftward
 biasing force of the bias springs 42, 44 balance with each other. When the
 actual temperature of water mixture deviates from the preset target
 temperature, the temperature-sensitive spring 40 expands or contracts,
 thereby returning the actual temperature of water mixture to the preset
 target temperature.
 When the handle is turned in the opposite direction to decrease the target
 temperature of water mixture to another temperature within the
 medium-temperature range, the slide shaft 52 is moved lightwards according
 to the rotation of the rotational shaft 50 in the opposite direction so
 that the clutch column 80 is also moved rightwards. As a result of this,
 the leftward biasing force of the bias springs 42, 44 is decreased so that
 the valve element 33 is shifted rightwards so as to reduce the flow space
 for hot water and increase the flow space for cold water, thereby lowering
 the temperature of water mixture. After the valve element 33 is shifted,
 the rightward biasing force of the temperature-sensitive spring 40 and the
 leftward biasing force of the bias springs 42, 44 balance with each other.
 When the actual temperature of water mixture deviates from the preset
 target temperature, the temperature-sensitive spring 40 expands or
 contracts, thereby returning the actual temperature of water mixture to
 the preset target temperature.
 As mentioned above, when the target temperature of water mixture is set to
 any temperature in the medium-temperature range from 30.degree. C. to
 50.degree. C., both of the serially-arranged bias springs 42, 44 with the
 spring constant 1/(1/k.sub.1 +1/k.sub.2) work to press the valve element
 33. Therefore, just like the hot and cold water mixing device of FIGS. 1
 through 3, in the graph of FIG. 4, the slope of the temperature line in
 the medium-temperature range is gentle.
 II. When the Target Temperature of Water Mixture is Set in the
 High-temperature Range Exceeding 50.degree. C.
 When the target temperature of water mixture is set at a temperature
 exceeding 50.degree. C., the slide shaft 52 is moved leftwards largely.
 Accordingly,
 (1) the left end of the clutch column 80 comes in directly contact with the
 flange 33B;
 (2) the left end of the slide shaft 52 comes in contact with the collar 80a
 of the clutch column 80; or
 (3) a step 52s at the left end of an external thread 52b of the slide shaft
 52 comes in contact with the right end of the clutch column 80.
 Therefore, when the handle is turned to enter into the high temperature
 range exceeding 50.degree. C., the valve element 33 is moved by balance
 between the rightward biasing force of the temperature-sensitive spring 40
 and the leftward biasing force of either one of the bias springs 42, 44.
 The spring constant of the bias spring 42 or 44 is k.sub.1 or k.sub.2
 which is larger than the spring constant 1/(1/k.sub.1 +1/k.sub.2) of the
 combined bias springs applied in case of the medium-temperature range.
 Accordingly, the ratio (a/A) between the travel (A) of the slide shaft 52
 and the travel (a) of the valve element 33 is larger than that in case of
 the medium-temperature range. Thus, the amount in change of the target
 temperature per the unit angle of the handle is larger than that in case
 of the medium-temperature range. Therefore, in the graph of FIG. 4, the
 slope of the temperature line in the high-temperature range is steeper
 than that in the medium-temperature range.
 III. When the Target Temperature of Water Mixture is Set in the
 Low-temperature Range Below 30.degree. C.
 When the target temperature of water mixture is set at a temperature below
 30.degree. C., the slide shaft 52 is moved rightwards largely and the
 collar 52c of the slide shaft 52 and the collar 80b of the clutch column
 80 are engaged with each other so that the biasing force of the second
 bias spring 44 does not act on the valve element 33. In this case, the
 slide shaft 52 and the clutch column 80 are joined just like one rigid
 member. Therefore, when the handle is turned to enter into the
 low-temperature range below 30.degree. C., the clutch column 80 are moved
 integrally with the slide shaft 52.
 Accordingly, the ratio (a/A) between the travel (A) of the rotational shaft
 50 and the slide shaft 52 and the travel (a) of the valve element 33 is
 larger than that in case of the medium-temperature range. That is to say,
 the amount in change of the target temperature per the unit angle of the
 handle is larger than that in case of the medium-temperature range.
 Therefore, in the graph of FIG. 4, the slope of the temperature line in
 the low-temperature range is steeper than that in the medium-temperature
 range.
 [Third Preferred Embodiment]
 The third preferred embodiment (particularly claims 8 through 11) will be
 described with reference to FIG. 7.
 In this preferred embodiment, a valve element 133 further comprises a pair
 of flanges 331, 332 on the outer periphery of a flange 33B of the valve
 element 133. The flanges 331, 332 are arranged to be spaced apart from
 each other in the axial direction of the valve element 133. Other
 structures of the valve element 133 are the same as those of the
 aforementioned valve element 33 of FIG. 6.
 A clutch column 80A has a collar 80c convexly formed on an inner surface of
 a left-end portion of the clutch column 80A. The collar 80c is positioned
 between the flanges 331 and 332. The clutch column 80A is different from
 the clutch column 80 of FIG. 6 at a point that the collar 80b is not
 provided. A slide shaft 52 is different from the slide shaft 52 of FIG. 6
 at a point that the collar 52c is not provided.
 Other structures of the hot and cold water mixing device of FIG. 7 are the
 same as those of the hot and cold water mixing device of FIG. 6 and parts
 similar or corresponding to the parts of the hot and cold water mixing
 device of FIG. 6 are marked by the same reference numerals.
 I. In the hot and cold water mixing device of FIG. 7, when the target
 temperature of water mixture is set in the medium-temperature range from
 30.degree. C. to 50.degree. C., both of the serially-arranged bias springs
 42, 44 work so that a valve element 133 is pressed by a biasing force of
 the bias springs 42, 44 with a low spring constant. Accordingly, as shown
 in FIG. 4, the slope of the temperature line in the medium-temperature
 range is gentle.
 II. When the target temperature of water mixture is set at a temperature
 exceeding 50.degree. C., the slide shaft 52 is moved leftwards largely and
 the clutch column 80A is also moved leftwards so that the collar 80c is
 pressed against the left flange 331. In this case, the slide shaft 52 and
 the clutch column 80 are joined just like one member. Therefore, the valve
 element 133 is moved by balance between the rightward biasing force of the
 temperature-sensitive spring 40 and the leftward biasing force of the
 second bias spring 44.
 Since the spring constant of the second bias spring 44 is larger than the
 spring constant of the serially-combined bias springs 42, 44, the slope of
 the temperature line in the high-temperature range exceeding 50.degree. C.
 is steeper than that in the medium-temperature range as shown in FIG. 4.
 III. When the target temperature of water mixture is set at a temperature
 below 30.degree. C., the slide shaft 52 is moved rightwards largely and
 the collar 80c of the clutch column 80A comes in contact with the right
 flange 332 so that the valve element 133 and the clutch column 80A are
 joined just like one member. In this state, since the clutch column 80A
 and the valve element 133 are moved substantially integrally with the
 slide shaft 52, the slope of the temperature line in the low-temperature
 range below 30.degree. C. is steeper than that in the medium-temperature
 range as shown in FIG. 4.
 In the preferred embodiment of FIG. 7, when the target temperature is set
 at a temperature exceeding 50.degree. C., the slide shaft 52 may be
 pressed against the clutch column 80A in such a manner that the valve
 element 33 is moved by balance between the biasing force of the second
 bias spring 44 and the biasing force of the temperature-sensitive spring
 40.
 [Fourth Preferred Embodiment]
 A hot and cold water mixing device according to the fourth preferred
 embodiment will be described with reference to FIG. 8.
 This hot and cold water mixing device is similar to the hot and cold water
 mixing device of FIG. 6, but a projecting shaft 334 extending rightwards
 from the valve element 233 and having a flange (a stopper) 335 on the end
 of the projecting shaft 334 which can engage with a slide shaft 52 via a
 washer 85. The washer 85 is pressed against the left end surface of a
 collar 52a of the slide shaft 52 by a second bias spring 44.
 Other structures of the hot and cold water mixing device of FIG. 8 are the
 same as those of the hot and cold water mixing device of FIG. 6, but the
 slide shaft 52 has an extension extending in the leftward direction from
 the left end thereof.
 I. The operation of the hot and cold water mixing device of FIG. 8 when the
 target temperature of water mixture is set in the medium-temperature range
 is completely the same as the operation of the hot and cold water mixing
 device of FIG. 6. The valve element 233 is pressed leftwards by a biasing
 force of serially-combined bias springs 42, 44 with a low spring constant.
 In this state, the flange 335 is spaced apart from the washer 85 as shown
 in FIG. 8.
 II. When the target temperature of water mixture is set at a temperature
 below 30.degree. C., the slide shaft 52 is moved rightwards more than that
 of FIG. 8 so that collars 52c, 80b are engaged with each other and the
 clutch column 80 is thus drawn rightwards. The rightward movement of the
 slide shaft 52 brings the washer 85 in contact with the flange 335 so that
 the biasing force of the second bias spring 44 acts on the valve element
 233 via the projecting shaft 334 in the rightward direction. That is to
 say, the valve element 233 is strongly biased rightwards by a concurrent
 biasing force produced by the biasing force of the temperature-sensitive
 spring 40 and the second bias spring 44. On the other hand, the biasing
 force applied to the valve element 233 leftwards is only the biasing force
 of the first bias spring 42. The ratio (a/A) between the travel (A) of the
 slide shaft 52 and the travel (a) of the valve element 233 is larger than
 that in case of the medium-temperature range. That is to say, the slope of
 the temperature line in the low-temperature range is steeper than that in
 the medium-temperature range.
 It should be noted that during the handle is turn into the low-temperature
 range below 30.degree. C., the collars 80b, 52c may come in contact with
 each other before, to the contrary, after, or at the same time as the
 contact between the washer 85 and the flange 335.
 III. When the target temperature of water mixture is set at a temperature
 exceeding 50.degree. C., the slide shaft 52 is moved leftwards largely.
 Accordingly,
 (1) the left end of the clutch column 80 comes in contact with the flange
 33B;
 (2) the left end of the slide shaft 52 comes in contact with the collar 80a
 of the clutch column 80; or
 (3) a step 52s of the slide shaft 52 comes in contact with the right end of
 the clutch column 80.
 Therefore, the biasing force of either one of the bias springs 42, 44 is
 applied to the valve element 233 in the leftward direction. On the other
 hand, the biasing force applied to the valve element 233 in the rightward
 direction is only the biasing force of the temperature-sensitive spring
 40. That is to say, the slope of the temperature line in the
 high-temperature range is steeper than that in the medium-temperature
 range as shown in FIG. 4.
 [Fifth Preferred Embodiment]
 A hot and cold water mixing device according to the fifth preferred
 embodiment will be described with reference to FIG. 9.
 In this hot and cold water mixing device, just like the hot and cold water
 mixing device of FIG. 8, a projecting shaft 334 has a first flange 335 as
 a first stopper on the end of the projecting shaft 334 which can engage
 with a slide shaft 52 via a first washer 85 and the washer 85 is pressed
 against the left end surface of a collar 52a of a slide shaft 52 by a
 second bias spring 44. In FIG. 9, the projecting shaft 334 has a second
 flange 334F as a second stopper formed around an outer periphery thereof.
 In addition, a second washer 85A is disposed about the projecting shaft
 334. The second washer 85A is superposed on the left surface of a collar
 80a of a clutch column 80. The second flange 334F is sized to be allowed
 to freely pass through an inner hole of the collar 80a but not to pass
 through an inner hole of the second washer 85A. A first bias spring 42 is
 disposed between the second washer 85A and a flange 33B of the valve
 element 233 in the compressed state.
 Other structures of the hot and cold water mixing device of FIG. 9 are the
 same as those of the hot and cold water mixing device of FIG. 8.
 I. The operation of the hot and cold water mixing device of FIG. 9 when the
 target temperature of water mixture is set in the medium-temperature range
 is completely the same as the operation of the hot and cold water mixing
 device of FIG. 8. The valve element 233 is pressed leftwards by a small
 biasing force of the first bias spring 42 and the second bias springs 44
 which are serially combined to have a low spring constant. In this state,
 the flange 335 is spaced apart from the washer 85 as shown in FIG. 9 and
 the washer 85A is pressed against the collar 80a.
 II. As the target temperature of water mixture is set at a temperature
 below 30.degree. C., the slide shaft 52 is moved rightwards more than that
 of FIG. 9 so that collars 52c, 80b are engaged with each other and the
 clutch column 80 is thus drawn rightwards. The rightward movement of the
 slide shaft 52 brings the first washer 85 in contact with the first flange
 335 so that the biasing force of the second bias spring 44 acts on the
 valve element 233 via the projecting shaft 334 in the rightward direction.
 That is to say, the valve element 233 is strongly biased rightwards by a
 concurrent biasing force of the biasing force of the temperature-sensitive
 spring 40 and the biasing force of the second bias spring 44. In this
 case, the rightward movement of the clutch column 80 brings the second
 washer 85A in contact with the second flange 334F so that the first bias
 spring 42 is in the locked state between the flanges 33B and 334F and thus
 does not apply any biasing force to the valve element 233 in the axial
 directions. Accordingly, the ratio (a/A) between the travel (A) of the
 slide shaft 52 and the travel (a) of the valve element 233 is larger than
 that in case of the medium-temperature range. That is to say, the slope of
 the temperature line in the low-temperature range is steeper than that in
 the medium-temperature range as shown in FIG. 4.
 It should be noted that since the first bias spring 42 is in the locked
 state between the flanges 33B and 334F, the first bias spring 42 does not
 apply any biasing force to the slide shaft 52 too. (Applied to the slide
 shaft 52 is the biasing force of the second bias spring 44 only.)
 Therefore, a rotational shaft 50 is allowed to be smoothly rotated with a
 small torque.
 III. When the target temperature of water mixture is set at a temperature
 exceeding 50.degree. C., the slide shaft 52 is moved leftwards largely.
 The second flange 334F of the projecting shaft 334 comes in contact with
 the second washer 85A so that the first bias spring 42 is in the locked
 state between the flanges 334F and 33B and thus does not apply any biasing
 force to the valve element 233 in the axial directions. Applied to the
 valve element 233 in the leftward direction is the biasing force of the
 second bias spring 44 only. Applied to the valve element 233 in the
 rightward direction is the biasing force of the temperature-sensitive
 spring 40 only. Accordingly, the slope of the temperature line in the
 high-temperature range is steeper than that in the medium-temperature
 range as shown in FIG. 4.
 [Sixth Preferred Embodiment]
 A hot and cold water mixing device according to the sixth preferred
 embodiment will be described with reference to FIG. 10.
 This hot and cold water mixing device is similar to the hot and cold water
 mixing device of FIG. 7, but a projecting shaft 522 extending leftwards
 from the slide shaft 52 and having a flange (a stopper) 552 on the end of
 the projecting shaft 522 which can engage with a valve element 333 via a
 washer 87. The washer 87 is pressed against the right end surface of a
 flange 332 of the valve element 333 by a first bias spring 42. Other
 structures of the valve element 333 are the same as those of the valve
 element 133 of FIG. 7, except that the flange 33B is positioned more left
 than that of the valve element 133.
 Other structures of the hot and cold water mixing device of FIG. 10 are the
 same as those of the hot and cold water mixing device of FIG. 7.
 I. The operation of the hot and cold water mixing device of FIG. 10 when
 the target temperature of water mixture is set in the medium-temperature
 range is completely the same as the operation of the hot and cold water
 mixing device of FIG. 7. The valve element 333 is pressed leftwards by a
 first bias spring 42 and a second bias springs 44 in series. Since the
 spring constant of this serially combined springs is small, the slope of
 the temperature line in the medium-temperature range is gentle as shown in
 FIG. 4.
 II. As the target temperature of water mixture is set at a temperature
 below 30.degree. C., the slide shaft 52 is moved rightwards more than that
 of FIG. 10 so that the flange 552 comes in contact with the washer 87. A
 clutch column 80A is also moved rightwards so that a collar 80c thereof
 comes in contact with the right flange 332 of the valve element 333. In
 this state, the biasing force of the first bias spring 42 is applied to
 the valve element 333 via the clutch column 80A in the rightward
 direction. Applied to the valve element 333 are the total (concurrent)
 biasing force of a temperature-sensitive spring 40 and the first bias
 spring 42 in the rightward direction, and the biasing force of the second
 bias spring 44 in the leftward direction.
 When the target temperature is set in the low-temperature range, as
 mentioned above, the rightward biasing force of the first bias spring 42
 is added to the rightward biasing force of the temperature-sensitive
 spring 40. As a result, the biasing force applied to the valve element 333
 in the rightward direction becomes significantly large, so the ratio (a/A)
 between the travel (A) of the slide shaft 52 and the travel (a) of the
 valve element 333 is larger than that in case of the medium-temperature
 range. That is to say, the slope of the temperature line in the
 low-temperature range below 30.degree. C. is steeper than that in the
 medium-temperature range as shown in FIG. 4.
 III. When the target temperature of water mixture is set at a temperature
 exceeding 50.degree. C., the slide shaft 52 is moved leftwards largely.
 Accordingly,
 (1) the collar 80c of the clutch column 80A comes in contact with the left
 flange 331 of the valve element 333; or
 (2) the left end of the slide shaft 52 comes in contact with the collar 80a
 of the clutch column 80A.
 Therefore, the valve element 333 and the clutch column 80A, or the slide
 shaft 52 and the clutch column 80A are joined just like one member. In
 this state, the valve element 333 is biased by the temperature-sensitive
 spring 40 in the rightward direction, while the valve element is biased by
 one of the bias springs 42, 44 in the leftward direction.
 The spring constant of one of the bias springs 42, 44 is larger than the
 spring constant of the bias springs 42, 44 serially combined. Therefore,
 the slope of the temperature line in the high-temperature range exceeding
 50.degree. C. is steeper than that in the medium-temperature range as
 shown in FIG. 4.
 [Seventh Preferred Embodiment]
 A hot and cold water mixing device according to the seventh preferred
 embodiment will be described with reference to FIG. 11.
 In this hot and cold water mixing device, just like the hot and cold water
 mixing device of FIG. 10, a slide shaft 52 has a projecting shaft 522
 extending leftwards which has a first flange (a first stopper) 552 on the
 end of the projecting shaft 552 which can engage with a valve element 333
 via a first washer 87 and the washer 87 is pressed against the right end
 surface of a flange 332 of the valve element 333 by a first bias spring
 42.
 In this preferred embodiment of FIG. 11, the projecting shaft 522 has a
 second flange 522F as a second stopper. In addition, a second washer 87A
 is disposed about the projecting shaft 522. The second washer 87A is
 pressed against the right end surface of the collar 80a of the clutch
 column 80A by the second biasing spring 44 on the right side.
 It should be noted that the second flange 522F is positioned more left than
 the second washer 87A.
 The second flange 522F is sized to be allowed to freely pass through an
 inner hole of a collar 80a but not to pass through an inner hole of the
 second washer 87A.
 Other structures of the hot and cold water mixing device of FIG. 11 are the
 same as those of the hot and cold water mixing device of FIG. 10.
 I. The operation of the hot and cold water mixing device of FIG. 11 when
 the target temperature of water mixture is set in the medium-temperature
 range is completely the same as the operation of the hot and cold water
 mixing device of FIG. 10. The valve element 333 is biased leftwards by the
 first bias spring 42 and the second bias springs 44 in series. Since the
 spring constant of this serially combined biasing springs is small, the
 slope of the temperature line in the medium-temperature range is gentle as
 shown in FIG. 4.
 II. As the target temperature of water mixture is set at a temperature
 below 30.degree. C., the slide shaft 52 is moved rightwards more than that
 of FIG. 11 so that the second flange 552 comes in contact with the first
 washer 87. A clutch column 80A is also moved rightwards so that a collar
 80c thereof comes in contact with the right flange 332 of the valve
 element 333. In this state, the biasing force of the first bias spring 42
 is applied to the valve element 333 via the clutch column 80A in the
 rightward direction. Applied to the valve element 333 are the total
 (concurrent) biasing force of a temperature-sensitive spring 40 and the
 first bias spring 42 in the rightward direction.
 Further in this case, the projecting shaft 522 is moved rightwards together
 with the slide shaft 52 so that the second flange 522F comes in contact
 with the second washer 87A, thus moving rightwards the second washer 87A
 apart from the collar 80a. As a result, the second bias spring 44 becomes
 in the locked state between the flange 522F and the collar 52a and thus
 does not apply any biasing force to the valve element 333.
 When the target temperature is set in the low-temperature range, as
 mentioned above, the rightward biasing force of the first bias spring 42
 is added to the rightward biasing force of the temperature-sensitive
 spring 40. As a result, the biasing force applied to the valve element 333
 in the rightward direction becomes significantly large and the leftward
 biasing force of the second bias spring 44 is cancelled. Accordingly, the
 ratio (a/A) between the travel (A) of the slide shaft 52 and the travel
 (a) of the valve element 333 is larger than that in case of the
 medium-temperature range. That is to say, the slope of the temperature
 line in the low-temperature range below 30.degree. C. is steeper than that
 in the medium-temperature range as shown in FIG. 4.
 It should be noted that since the second bias spring 44 does not apply any
 biasing force to the slide shaft 52, a rotational shaft 50 is allowed to
 be smoothly rotated with a small torque.
 III. When the target temperature of water mixture is set at a temperature
 exceeding 50.degree. C., the slide shaft 52 is moved leftwards largely.
 Accordingly,
 (1) the collar 80c of the clutch column 80A comes in contact with the left
 flange 331 of the valve element 333; or
 (2) the left end of the slide shaft 52 comes in contact with the collar 80a
 of the clutch column 80A.
 Therefore, the valve element 333 and the clutch column 80A, or the slide
 shaft 52 and the clutch column 80A are joined just like one member. In
 this state, the valve element 333 is moved according to the balance
 between the biasing force of the temperature-sensitive spring 40 and the
 biasing force of one of the bias springs 42, 44.
 The spring constant of one of the bias springs 42, 44 is larger than the
 spring constant of the serially combined bias springs 42, 44. Therefore,
 the slope of the temperature line in the high-temperature range exceeding
 50.degree. C. is steeper than that in the medium-temperature range as
 shown in FIG. 4.
 [Eighth Preferred Embodiment]
 The eighth preferred embodiment will be described with reference to FIG.
 12. In a hot and cold water mixing device according to this preferred
 embodiment, bias springs are arranged in parallel. In this preferred
 embodiment, a first bias spring 401 is disposed between a cold water valve
 element 32 and a collar 52a of a slide shaft 52'. A main shaft 30' passing
 through the cold water valve element 32 has a right flange 30b which is
 sized to be allowed to pass through a hole 521 of the collar 52a. A washer
 89 is stopped by the flange 30b. A second bias spring 402 is disposed
 between the washer 89 and the cold water valve element 32. The washer 89
 is sized to be not allowed to pass through the hole 521 and is positioned
 on the left of the collar 52a as shown in FIG. 12 when water mixture at a
 temperature within the medium-temperature range is discharged. The cold
 water valve element 32 has a cylindrical hook 301 extending rightwards
 from the right end thereof and a pawl 302 as a stopping member formed on
 the end of the hook 301. The pawl 302 can be engaged with a collar 522
 convexly formed on an inner surface the slide shaft 52'.
 It should be noted that the hook 301 is formed in cylindrical shape and the
 pawl 302 is convexly formed in a collar-like shape on an outer surface of
 the hook 301 according to this preferred embodiment. The pawl 302 is
 positioned more right than the collar 522 as shown in FIG. 12.
 Other structures of this hot and cold water mixing device are the same as
 those of the hot and cold water mixing device of FIGS. 1 through 3 and
 parts similar or corresponding to the parts of the hot and cold water
 mixing device of FIGS. 1 through 3 are marked by the same reference
 numerals.
 The operation of the hot and cold water mixing device structured as
 mentioned above with reference to FIG. 12 will be described hereinafter.
 I. When the Target Temperature of Water Mixture is Set in the
 Medium-temperature Range From 30.degree. C. to 50.degree. C. (see FIG. 12)
 When the target temperature of water mixture is set at a temperature, for
 example, in the medium-temperature range from 30.degree. C. to 50.degree.
 C. as shown in FIG. 12, only the biasing force of the first bias spring
 401 is applied to the main shaft 30' via the cold water valve element 32
 in the leftward direction and the biasing force of the
 temperature-sensitive spring 40 is applied to the main shaft 30' via a hot
 water valve element 34 in the rightward direction. These biasing forces
 balance with each other. The biasing force of the second bias spring 402
 acts on the cold water valve element 32 and the main shaft 30' in the
 leftward and rightward directions but does not act on the valve elements
 32, 34 in the leftward and rightward directions not at all.
 In this state, when the actual temperature of water mixture becomes lower
 than the preset target temperature due to a variation in the supply
 temperature or the supply pressure of hot water, the temperature-sensitive
 spring 40 contracts so that the valve elements 32, 34 and the main shaft
 30' are moved leftwards and a flow space for cold water between a cold
 water valve seat 22 and the cold water valve element 32 is reduced while a
 flow space for hot water between a hot water valve seat 24 and the hot
 water valve element 34 is increased, thereby returning (rising) the actual
 temperature of water mixture to the preset target temperature. To the
 contrary, when the actual temperature of water mixture becomes higher than
 the preset target temperature, the temperature-sensitive spring 40 expands
 so that the cold water valve element 32 and the hot water valve element 34
 are moved rightwards together with the main shaft 30' so as to increase
 the flow space for cold water and reduce the flow space for hot water,
 thereby returning (lowering) the actual temperature of water mixture to
 the preset target temperature.
 When the handle is turned in the positive direction to increase the target
 temperature of water mixture to another temperature within the
 medium-temperature range, the slide shaft 52' is moved leftwards in such a
 range not to bring the collar 52a in contact with the washer 89.
 Accordingly, the biasing force of the first bias spring 401 in the
 leftward direction is increased so that the valve elements 32, 34 shift
 leftward together with the main shaft 30' so as to increase the flow space
 for hot water and to reduce the flow space for cold water, thereby
 increasing the temperature of water mixture. After the valve elements 32,
 34 are shifted, the rightward biasing force of the temperature-sensitive
 spring 40 and the leftward biasing force of the bias spring 401 balance
 with each other. When the actual temperature of water mixture deviates
 from the preset target temperature, the temperature-sensitive spring 40
 expands or contracts, thereby returning the actual temperature of water
 mixture to the preset target temperature.
 When the handle is turned in the opposite direction to decrease the target
 temperature of water mixture to another temperature within the
 medium-temperature range, the slide shaft 52' is moved rightwards in such
 a range not to bring the collar 522 in contact with the pawl 302 so that
 the valve elements 32, 34 shift rightward together with the main shaft 30'
 so as to reduce the flow space for hot water and increase the flow space
 for cold water, thereby lowering the temperature of water mixture. After
 the valve elements 32, 34 are shifted, the rightward biasing force of the
 temperature-sensitive spring 40 and the leftward biasing force of the bias
 spring 401 balance with each other. When the actual temperature of water
 mixture deviates from the preset target temperature, the
 temperature-sensitive spring 40 expands or contracts, thereby returning
 the actual temperature of water mixture to the preset target temperature.
 As mentioned above, when the target temperature of water mixture is set to
 any temperature in the medium-temperature range from 30.degree. C. to
 50.degree. C., only the bias springs 401 works. Assuming that the spring
 constants of the bias springs 401, 402 are k.sub.1, k.sub.2, respectively,
 the force pressing the main shaft 30 leftwards is k.sub.1 which is smaller
 than the concurrent biasing force of the bias springs 401, 402 explained
 by (k.sub.1 +k.sub.2).
 Accordingly, when the preset target temperature is in the
 medium-temperature range, a ratio (a/A) between the travel (A) of the
 slide shaft 52' and the travel (a) of the valve elements 32, 34 is
 relatively small. That is to say, the travel (a) of the valve elements 32,
 34 per a unit angle of the rotational shaft 50 is relatively small. As a
 result, as shown by solid line in FIG. 4, the amount in change of the
 target temperature per the unit angle of the handle is small when the
 target temperature of water mixture is set in the medium-temperature
 range, that is, in the graph of FIG. 4, the slope of a temperature line in
 the medium-temperature range is gentle.
 II. When the Target Temperature of Water Mixture is Set in the
 High-temperature Range Exceeding 50.degree. C.
 When the target temperature of water mixture is set at a temperature
 exceeding 50.degree. C., the slide shaft 52' is moved leftwards largely so
 that the collar 52a of the slide shaft 52' presses the washer 89 leftwards
 and the washer 89 is thus spaced apart from the flange 30b of the main
 shaft 30' leftwards. Therefore, when the handle is turned to enter into
 the high temperature range exceeding 50.degree. C., the slide shaft 52'
 biases the main shaft 30' by the concurrent biasing force of the bias
 springs 401, 402 leftwards. The spring constant of the bias springs 401,
 402 arranged in parallel is k.sub.1 +k.sub.2 which is larger than the
 spring constant k.sub.1 in case of the medium-temperature range.
 Accordingly, the ratio (a/A) between the travel (A) of the slide shaft 52'
 and the travel (a) of the valve elements 32, 34 is larger than that in
 case of the medium-temperature range. That is to say, the amount m change
 of the target temperature per the unit angle of the handle is larger than
 that in case of the medium-temperature range. Therefore, in the graph of
 FIG. 4, the slope of the temperature line in the high-temperature range is
 steeper than that in the medium-temperature range.
 III. When the Target Temperature of Water Mixture is Set in the
 Low-temperature Range Below 30.degree. C.
 When the target temperature of water mixture is set at a temperature below
 30.degree. C., the slide shaft 52' is moved rightwards largely and the
 collar 522 of the slide shaft 52' and the pawl 302 of the hook 301 are
 engaged with each other so that the biasing force of the bias spring 401
 does not act on the cold water valve element 32. In this case, the slide
 shaft 52' and the cold water valve element 32 are moved integrally with
 each other. Accordingly, the ratio (a/A) between the travel (A) of the
 rotational shaft 50 and the slide shaft 52' and the travel (a) of the
 valve elements 32, 34 is larger than that in case of the
 medium-temperature range. That is to say, the amount in change of the
 target temperature per the unit angle of the handle is larger than that in
 case of the medium-temperature range. Therefore, in the graph of FIG. 4,
 the slope of the temperature line in the low-temperature range is steeper
 than that in the medium-temperature range.
 It should be noted that when the slide shaft 52' is further moved
 rightwards by further turning the handle into the low-temperature range
 after the hot water valve element 34 comes in contact with the hot water
 valve seat 24, the cruciform portion 30a and the cold water valve element
 32 are spaced apart from each other.
 [Ninth Preferred Embodiment]
 The ninth preferred embodiment will be described with reference to FIG. 13.
 In this preferred embodiment, just like the embodiment of FIG. 6, one
 valve element 433 is adapted to regulate both of a flow space for cold
 water and a flow space for hot water.
 The valve element 433 comprises a column 335 extending rightward from a
 flange 33B thereof and first and second collars 336, 337 convexly formed
 on an outer surface of the column 335. The second collar 337 is positioned
 at the right end of the column 335. Disposed between the collars 336 and
 337 are first and second washers 91, 92. A first bias spring 42 is
 disposed between the washers 91 and 92 in the compressed state. The first
 washer 91 is sized to be caught by the a collar 526 described later.
 A slide shaft 520 has a cylindrical portion 525 extending leftwards and the
 collar 526 formed inwardly at the left end of the cylindrical portion 525.
 The collar 526 is positioned more left than the aforementioned first
 collar 336. The inner diameter of the collar 526 is larger than the outer
 diameter of the collar 336.
 The slide shaft 520 is formed with a step 527 to be positioned more right
 than the aforementioned collar 337. The slide shaft 520 is formed such
 that the inner diameter of a right portion from the step 527 is reduced.
 The second collar 337 has an outer diameter smaller than the
 reduced-diameter portion of the slide shaft 520 so that the second collar
 337 is never caught by the step 527. The washer 92 superposed on this
 collar 337 is sized to be caught by the step 527.
 A second bias spring 44 is disposed between the flange 33B of the valve
 element 433 and a collar 52a of the slide shaft 520.
 Other structures of the hot and cold water mixing device of FIG. 13 are the
 same as those of the hot and cold water mixing device of FIG. 6 and parts
 similar or corresponding to the parts of the hot and cold water mixing
 device of FIG. 6 are marked by the same reference numerals.
 The operation of the hot and cold water mixing device structured as
 mentioned above with reference to FIG. 13 will be described hereinafter.
 I. When the Target Temperature of Water Mixture is Set in the
 Medium-temperature Range From 30.degree. C. to 50.degree. C.
 FIG. 13 shows the hot and cold water mixing device in a state that the
 target temperature of water mixture is set at a temperature, for example,
 in the medium-temperature range from 30.degree. C. to 50.degree. C. In
 this state, only the biasing force of the second bias spring 44 is exerted
 leftwards to the valve element 433, while a biasing force of a
 temperature-sensitive spring 40 is exerted rightwards to the valve element
 433. These biasing forces balance with each other. Since the first bias
 spring 42 is disposed between the collars 336 and 337, the first bias
 spring 42 does not apply any biasing force to the valve element 433.
 In this state, when the actual temperature of water mixture becomes lower
 than the preset target temperature due to a variation in the supply
 temperature or the supply pressure of hot water, the temperature-sensitive
 spring 40 contracts so that the valve element 433 is moved leftwards and a
 flow space for cold water between a cold water valve seat 22 and the valve
 element 433 is reduced while a flow space for hot water between a hot
 water valve seat 24 and the valve element 433 is increased, thereby
 returning (rising) the actual temperature of water mixture to the preset
 target temperature. To the contrary, when the actual temperature of water
 mixture becomes higher than the preset target temperature, the
 temperature-sensitive spring 40 expands so that the valve element 433 are
 moved rightwards so as to increase the flow space for cold water and
 reduce the flow space for hot water, thereby returning (lowering) the
 actual temperature of water mixture to the preset target temperature.
 When the handle is turned in the positive direction to increase the target
 temperature of water mixture to another temperature within the
 medium-temperature range, the slide shaft 520 is moved leftwards within a
 range not to bring the step 527 in contact with the washer 92. As a result
 of this, the biasing force of the second bias spring 44 in the leftwards
 direction is increased. Therefore, the bias spring 44 shifts the valve
 element 433 leftwards so as to increase the flow space for hot water and
 reduce the flow space for cold water, thereby increasing the temperature
 of water mixture. After the valve element 433 is shifted, the rightward
 biasing force of the temperature-sensitive spring 40 and the leftward
 biasing force of the second bias spring 44 balance with each other. When
 the actual temperature of water mixture deviates from the preset target
 temperature, the temperature-sensitive spring 40 expands or contracts,
 thereby returning the actual temperature of water mixture to the preset
 target temperature.
 When the handle is turned in the opposite direction to decrease the target
 temperature of water mixture to another temperature within the
 medium-temperature range, the slide shaft 520 is moved rightwards within a
 range not to bring the collar 526 in contact with the washer 91. As a
 result of this, the valve element 433 is shifted rightwards together with
 the second bias spring 44 so as to reduce the flow space for hot water and
 increase the flow space for cold water, thereby lowering the temperature
 of water mixture. After the valve element 433 is shifted, the rightward
 biasing force of the temperature-sensitive spring 40 and the leftward
 biasing force of the second bias spring 44 balance with each other. When
 the actual temperature of water mixture deviates from the preset target
 temperature, the temperature-sensitive spring 40 expands or contracts,
 thereby returning the actual temperature of water mixture to the preset
 target temperature.
 As mentioned above, when the target temperature of water mixture is set to
 any temperature in the medium-temperature range from 30.degree. C. to
 50.degree. C., only the second bias spring 44 works to press the valve
 element 433 leftward by the biasing force of the second bias spring 44 of
 which spring constant is smaller than that of the parallel bias springs
 42, 44. Therefore, just like the hot and cold water mixing device of FIGS.
 1 through 3, in the graph of FIG. 4, the slope of a temperature line in
 the medium-temperature range is gentle.
 II. When the Target Temperature of Water Mixture is Set in the
 High-temperature Range Exceeding 50.degree. C.
 When the target temperature of water mixture is set at a temperature
 exceeding 50.degree. C., the slide shaft 520 is moved leftwards largely so
 that the step 527 comes in contact with the washer 92 and then moves the
 washer 92 leftwards. As a result of this, the bias springs 42, 44 work in
 parallel to press the valve element 433 leftwards. Accordingly, the ratio
 (a/A) between the travel (A) of the slide shaft 520 and the travel (a) of
 the valve element 433 is larger than that in case of the
 medium-temperature range. That is to say, the amount in change of the
 target temperature per the unit angle of the handle is larger than that in
 case of the medium-temperature range. Therefore, in the graph of FIG. 4,
 the slope of the temperature line in the high-temperature range is steeper
 than that in the medium-temperature range.
 III. When the Target Temperature of Water Mixture is Set in the
 Low-temperature Range Below 30.degree. C.
 When the target temperature of water mixture is set at a temperature below
 30.degree. C., the slide shaft 520 is moved rightwards largely so that the
 collar 526 comes in contact with the washer 91 and then moves the washer
 91 rightward. As a result of this, the concurrent (total) biasing force of
 the temperature-sensitive spring 40 and the first bias spring 42 is
 applied to the valve element 433 rightwards and the biasing force of the
 second bias spring 44 is applied to the valve element 433 leftwards.
 Therefore, the ratio (a/A) between the travel (A) of the rotational shaft
 50 and the slide shaft 520 and the travel (a) of the valve element 433
 when the handle is turned within the low-temperature range below
 30.degree. C. is larger than that in case of the medium-temperature range.
 That is to say, the amount in change of the target temperature per the
 unit angle of the handle is larger than that in case of the
 medium-temperature range. Therefore, in the graph of FIG. 4, the slope of
 the temperature line in the low-temperature range is steeper than that in
 the medium-temperature range.
 As described above, the hot and cold water mixing device according to the
 present invention can have a wider indication range for the
 medium-temperature range, thereby allowing the fine control for setting
 the target temperature of water mixture. In addition, according to the
 present invention, the temperature control from the low-temperature range
 to the high-temperature range can be obtained without increasing the
 entire range for the rotation of the temperature regulating handle.
 [Tenth Preferred Embodiment]
 A control mechanism of a hot and cold water mixing device 809 according to
 the tenth preferred embodiment will be described with reference to FIGS.
 14 through 18(B). As shown in FIG. 14, the hot and cold water mixing
 device 809 comprises a main casing 814 composed of two cylindrical members
 which are connected to each other by threads, and a valve casing 801
 fitted inside the main casing 814. A hot water valve element 811a is
 arranged in the valve casing 801 to face a hot water port 803 of the valve
 casing 801 in such a manner that the hot water valve element 811a is
 movable in the axial direction. A cold water valve element 811b is
 arranged in the valve casing 801 to face a cold water port 804 in such a
 manner that the cold water valve element 811a is movable in the axial
 direction. The hot water valve element 811b and the cold water valve
 element 811b are separate members and thus can independently move.
 The cold water valve element 811b has a cylindrical profile and is formed
 with upper and lower semicircle grooves 815 as shown in FIGS. 16A, 16B.
 Fitted in the grooves 815 are slide connecting members 813 as shown in
 FIGS. 18A, 18B. A cylindrical regulating member 812 has expanded portions
 816 formed on an outer surface of a front end portion thereof as shown in
 FIGS. 17A, 17B. The expanded portions 816 of the regulating member 812 are
 fitted to rear end portions of the slide connecting members 813. The
 regulating member 812 has convexities 817 for preventing the rotation
 thereof which are formed on opposite outer surfaces of the front end
 portion. The convexities 817 are fitted in rail grooves 818 formed in an
 inner surface of the valve casing 801 in parallel with the axial direction
 for preventing the rotation of the regulating member 812. The regulating
 member 812 has an external thread 819 formed on a rear end portion thereof
 which is engaged with an internal thread 821 formed on an inner surface of
 a cylindrical portion formed on the front end side of a handle shaft 820
 of the temperature regulating handle. Inside of the regulating member 812,
 one end of a bias spring 807 is fixed to a spring stopping member 822. The
 other end of the bias spring 807 is fixed to a portion inside the cold
 water valve element 811b.
 Therefore, as the temperature regulating handle is turned, the rotation of
 the handle is transmitted to the regulating member 812 through the
 internal thread 821 of the handle shaft 820. Since the regulating member
 812 is prevented from rotating by the fitting of the convexities 817 into
 the rail grooves 818 for preventing the rotation, however, the regulating
 member 812 moves in the axial direction. Accordingly, the biasing force of
 the bias spring 807 is varied, thus changing the open area of the cold
 water port 804.
 On the other hand, the hot water valve element 811a is a cylindrical member
 and is provided with a cruciform path dividing member 810 as shown in
 FIGS. 15A, 15B. The path dividing member 810 is disposed between the hot
 water port 803 and the cold water port 804 to divide a flow path into four
 paths in the circumferential direction. The path dividing member 810 has
 square members 823 disposed on central inner corners thereof,
 respectively. Each square member 823 has one surface 823a with length La
 as a short side of the member 823 and another surface 823b with length Lb
 as a long side of the member 823 wherein La&lt;Lb. Since the path (inner
 chamber 802) between the ports 803 and 804 inside the valve casing 801 is
 divided into four paths, hot water and cold water flow with eddies in the
 respective divisions as shown by arrows in FIG. 15B, thereby aiding in
 mixing hot water and cold water. That is, the occurrence of uneven
 temperature can be prevented.
 In addition, when the supply pressures of hot water and cold water are low,
 current forces of hot water and cold water flowing through the hot water
 port 803 and the cold water port 804 may be too poor to enter into the
 center. By the function of the square members 823, the flowing of cold
 water flowing through the water port 804 at the upstream side can be
 dispersed along lidge lines of the square members 823. In regions with
 strong flows of cold water, the direction of cold water flowing on the
 surface 823a and the direction of cold water flowing on the surface 823b
 are shifted at the terminal ends so that the water flowing on the surface
 823a flows inwardly so as to apply eddies in the directions shown by
 arrows to the entire flowing. The eddies involve hot water flowing through
 the water port 803 at the downstream side whereby hot water can enter into
 the center to accomplish enough mixing and agitation even when the supply
 pressure is poor. That is, the occurrence of uneven temperature can be
 prevented.
 The path dividing member 810 is integrally mounted to the inner surface of
 the hot water valve element 811a. The front end of an operating shaft 824
 is attached to the rear end of the path dividing member 810. A linkage
 ring 825 is fitted to an outer surface of a rear end portion of the
 operating shaft 824. The linkage ring 825 is adapted to be in contact with
 the rear end of the spring stopping member 822 when the temperature of hot
 and cold water mixture is in the low-temperature range. When the
 temperature is in other temperature ranges, the linkage ring 825 is spaced
 apart from the rear end of the spring stopping member 812 by the biasing
 force of a temperature-sensitive spring 806 and can freely move in the
 axial direction.
 The operation of the hot and cold water mixing device 809 structured as
 mentioned above will be described about two cases where the temperature of
 water mixture is set in the low-temperature range and where the
 temperature of water mixture is set in other than the low-temperature
 range. A description will now be made as regard to the case as a normal
 state where the temperature of water mixture is set in other than the
 low-temperature range. In this case, the hot water valve element 811a and
 the cold water valve element 811b are positioned to have predetermined
 open areas so that hot water and cold water flow at a predetermined ratio
 into an inner chamber 802 through the hot water port 803 and the cold
 water port 804, and are mixed to be mixture having a desired temperature
 to be discharged. In this case, the target temperature is set by operating
 or turning the temperature regulating handle shaft 820 to change the
 position of the regulating member 812 in the axial direction so as to vary
 the biasing force of the bias spring 807. Then, the biasing force of the
 bias spring 807 balances with the biasing force of the
 temperature-sensitive spring 806 so as to shift the hot water valve
 element 811a and the cold water valve element 811b in the axial direction,
 thereby varying the ratio between the open area of the hot water port 803
 and the open area of the cold water port 804. In this state, when the
 actual temperature of water mixture deviates from the preset target
 temperature due to a variation in the supply pressure or the like, the
 temperature-sensitive spring 806 senses this deviation and changes the
 spring constant to change the positions of the hot water valve element
 811a and the cold water valve element 811b in the axial direction.
 Accordingly the ratio between the opening area of the hot water port 803
 and the opening area of the cold water port 804 is varied. In this manner,
 the temperature of water mixture can be automatically controlled.
 When the temperature of water mixture to be discharged is set in the
 low-temperature range, the spring constant of the temperature-sensitive
 spring 806 made of a shape memory alloy is too low to sufficiently cope
 with the supply pressure of hot water. When it is desired to discharge
 only cold water, therefore, it is impossible to move the hot water valve
 element 811a in the axial direction to a position where the hot water port
 803 is completely closed. For this, in the hot and cold water mixing
 device 809 of this embodiment, the bias spring 807 is used as a buffer for
 softening the operation force after the valve element is seated and, at
 the same time, the regulating member 812 is operated to directly control
 the position of the hot water valve element 811a in the axial direction.
 That is, as the temperature-regulating handle shaft 820 is operated in the
 low-temperature range, the regulating member 812 is moved in the rightward
 direction in FIG. 14 so as to increase the opening area of the cold water
 port 804. Then, the right end of the spring stopping member 822 comes in
 contact with the linkage ring 825 of the operating shaft 824. After that,
 the operating shaft 824 is linked with the hot water valve element 811a to
 move the hot water valve element 811a in the rightward direction in FIG.
 14.
 Therefore, as the temperature regulating handle shaft 820 is turned within
 the low-temperature range, the axial position of the hot water valve
 element 811a can be directly controlled via the regulating member 812.
 This control can be continued until the hot water valve element 811a comes
 in contact with the valve seat of the hot water port 803 to shut off the
 flow of hot water so that only cold water is discharged. In addition, the
 biasing force of the bias spring 807 acts to soften the operation force
 after the hot water valve element 811a is seated on the valve seat of the
 hot water valve port 803, thereby preventing the hot water valve element
 811a from being broken. Further, when the operation for moving the
 regulating member 812 in the rightward direction in FIG. 14, i.e. the
 valve closing operation, is conducted after the hot water valve element
 811a is seated, the regulating member 812 is engaged with the slide
 connecting members 813 to move the cold water valve element 811a in the
 rightward direction in FIG. 14 to compress the bias spring 807, thereby
 also preventing the hot water valve element 811a from being broken by the
 valve closing operation after the valve element is seated. In addition,
 the biasing force of the bias spring 807 after the hot water valve element
 811a is seated is applied to the hot water valve element 811a in the
 closing direction. In brief, in this hot and cold water mixing device 809,
 when the target temperature is set in the low-temperature range, the bias
 spring 807 acts as a buffer for softening the operation force for closing
 the valve applied to the valve element and the axial position of the hot
 water valve element 811a is forcedly controlled via the regulating member
 812 to close the hot water port 803, thereby allowing only cold water to
 be discharged. After the hot water valve element 811a is seated, the bias
 spring 807 acts to bias the hot water valve element 811a in the closing
 direction.
 On the other hand, to discharge only hot water, the temperature regulating
 handle shaft 820 is turned in the opposite direction to largely move the
 regulating member 812 in the leftward direction in FIG. 14 so that the
 biasing force of the bias spring 807 is changed to bring the cold water
 valve element 811b in contact with the valve seat of the cold water port
 804.
 [Eleventh Preferred Embodiment]
 FIG. 19 is a longitudinal sectional view schematically showing a hot and
 cold water mixing device 826 according to the eleventh preferred
 embodiment. In this hot and cold water mixing device 826, a spool valve
 element 827, a regulating member 812, and a handle shaft 820 are arranged
 in an inner chamber 802 of a valve casing 801. The spool valve element 827
 has a large-diameter portion 827a and a small-diameter portion 827b. The
 front and rear ends of the large-diameter portion 827a function as a hot
 water valve portion 828 and a cold water valve portion 829, respectively.
 The valve casing 801 is provided with a hot water port 803 and a cold
 water port 804 which are formed in the circumferential surface of the
 valve casing 801. The positional relation between the hot water port 803
 and the cold water port 804 of the hot and cold water mixing device 826 is
 contrary to that of the hot and cold water mixing device 809 shown in FIG.
 14, that is, the hot water port 803 is positioned at the handle shaft 820
 side (at the right-hand side in FIG. 19). The small-diameter portion 827b
 of the spool valve element 827 has a concavity 830 formed in the inner
 surface thereof for mounting a bias spring 807.
 A front end portion of the regulating member 812 is inserted in the
 small-diameter portion 827b of the spool valve element 827 in such a
 manner the regulating member 812 can freely slide in the axial direction.
 The regulating member 812 has a concavity 831 formed in the outer
 circumferential surface of the inserted front end portion thereof for
 mounting the bias spring 807. The bias spring 807 is disposed between the
 concavity 831 of the regulating member 812 and the concavity 830 of the
 small-diameter portion 827b via rings 832 and 833 as spring seats which
 are disposed at the front and rear ends of the bias spring 807,
 respectively. The valve casing 801 has rail grooves 818 for preventing
 rotation formed in the inner surface thereof. The regulating member 812
 has convexities 834 formed in a middle portion thereof which are fitted in
 the rail grooves 818. The regulating member 812 has an external thread 819
 formed on an outer surface of a rear end portion thereof which is engaged
 with an internal thread 821 of the handle shaft 820.
 According to the hot and cold water mixing device 826 structured as
 mentioned above, when the temperature of water mixture to be discharged is
 set at a temperature in the normal operational state not in the
 low-temperature range, the spring-seat ring 832 for the bias spring 807 is
 caught by the front end of the concavity 830 of the spool valve element
 827 and is spaced apart from the front end of the concavity 831 of the
 regulating member 812 to form a free space therebetween. On the other
 hand, the spring-seat ring 833 at the rear end side is caught by the rear
 end of the concavity 831 of the regulating member 812 and is spaced apart
 from the rear end of the concavity 830 of the spool valve element 827 to
 form a free space therebetween.
 In this case, the hot water valve portion 828 and the cold water valve
 portion 829 of the spool valve element 827 are positioned to have
 predetermined open areas so that hot water and cold water flow at a
 predetermined ratio into the inner chamber 802 through the hot water port
 803 and the cold water port 804, and are mixed to be mixture having a
 desired temperature to be discharged. In this case, the target temperature
 is set by operating or turning the temperature regulating handle shaft 820
 to change the axial position of the regulating member 812 so as to vary
 the biasing force of the bias spring 807 within a range obtained by the
 free spaces of the spring-seat rings 832 and 833. Then, the biasing force
 of the bias spring 807 balances with the biasing force of a
 temperature-sensitive spring 806 so as to shift the hot water valve
 portion 828 and the cold water valve portion 829 in the axial direction,
 thereby varying the ratio between the open area of the hot water port 803
 and the open area of the cold water port 804. In this state, when the
 actual temperature of water mixture deviates from the preset target
 temperature due to a variation in the supply pressure or the like, the
 temperature-sensitive spring 806 senses this deviation and changes the
 spring constant to change the axial positions of the hot water valve
 portion 828 and the cold water valve portion 829. Accordingly the ratio
 between the opening area of the hot water port 803 and the opening area of
 the cold water port 804 is varied. In this manner, the temperature of
 water mixture can be automatically controlled.
 When the temperature of water mixture to be discharged is set in the
 low-temperature range, the spring constant of the temperature-sensitive
 spring 806 made of a shape memory alloy is too low to sufficiently cope
 with the supply pressure of hot water. When it is desired to discharge
 only cold water, therefore, it is impossible to move the hot water valve
 portion 828 in the axial direction (in the rightward direction in FIG. 19)
 to a position where the hot water port 803 is completely closed. For this,
 in the hot and cold water mixing device 826 of this embodiment, the bias
 spring 807 is used as a buffer for softening the operation force after the
 valve element is seated and, at the same time, the hot water valve portion
 828 is moved in the axial direction by the regulating member 812 so as to
 completely close the hot water port 803. That is, as the
 temperature-regulating handle shaft 820 is operated within the
 low-temperature range, the regulating member 812 is moved in the rightward
 direction in FIG. 19 so that the spring-seat ring 833 at the rear end side
 comes in contact with the rear end of the concavity 830 of the spool valve
 element 827 and is thus stopped. That is, as for the movement of the
 regulating member 812 in the rightward direction in FIG. 19, the
 regulating member 812 and the spool valve element 827 are mechanically
 linked via the bias spring 807.
 Therefore, the rightward movement of the regulating member 812 moves the
 spool valve element 827 via the bias spring 807 whereby the hot water
 valve portion 828 of the large-diameter portion 827a is softly seated on
 the valve seat of the hot water port 803 because the bias spring 807 also
 functions as a buffer for softening the operation force applied when the
 valve element is seat. That is, the hot water port 803 is forcedly closed.
 Thus, the cold water port 804 becomes in the fully opened state, to
 discharge only cold water. As the regulating member 812 is further
 operated in the valve closing direction after the hot water valve portion
 828 is seated, the spring-seat ring 832 is pulled by the front end of the
 concavity 831 of the regulating member 812 in the rightward direction in
 FIG. 19 so as to compress the bias spring 807, thereby preventing the hot
 water valve portion 828 from being broken. In addition, the biasing force
 of the bias spring 807 after the hot water valve portion 828 is seated is
 applied to the hot water valve portion 828 in the closing direction. As
 mentioned above, also in this embodiment, when the target temperature is
 set in the low-temperature range, the bias spring 807 functions as a
 buffer for softening the operation force for closing the valve applied to
 the valve element. In addition, the spool valve element 827 is forcedly
 moved by the regulating member 812 via the bias spring 807 to completely
 close the hot water port 803 by the hot water valve element 828. After the
 hot water valve portion 828 is seated, the bias spring 807 acts to bias
 the hot water valve portion 828 in the closing direction. The spring
 constant required for the temperature-sensitive spring 806 can be reduced,
 thereby reducing the entire size and restricting the increase in the
 manufacturing cost.
 By the way, the present invention is not limited to the aforementioned
 preferred embodiments, variable modifications may be made. For instance,
 the cold water valve element 811b and the regulating member 812 disposed
 in the inner cavity 802 of the valve casing may be integrally formed, or
 the regulating member 812 and the slide connecting member 813 may be
 integrally formed.
 As described above, a valve element is biased by a temperature-sensitive
 spring and a bias spring. The valve member is formed with a contact
 portion which can come in directly or indirectly contact with a
 regulating-member contact surface of the bias spring. The regulating
 member is provided with a contact portion which can come in directly or
 indirectly contact with a valve-element contact surface of the bias
 spring. Therefore, the valve element is directly or indirectly linked with
 the regulating member for varying the biasing force of the bias spring.
 When the target temperature is set in a low-temperature range, the bias
 spring functions as a buffer for softening the operation force applied to
 the valve element after the valve element is seated and, during this, the
 valve element can be moved in the axial direction via the regulating
 member. In this manner, a hot water port can be forcedly closed, thereby
 allowing only cold water to be discharged. After the valve element is
 seated, the bias spring acts to bias the valve element in the closing
 direction, thus enabling suitable operation for closing the valve element.
 Therefore, a temperature-sensitive spring with a reduce spring constant can
 be employed, thereby preventing the size of a faucet from being increased
 due to the increased size of the temperature-sensitive spring and thus
 restricting the increase in the manufacturing cost.