Abstract:
A thermoelement and a thermovalve incorporating the same, in which reliable operation is achieved with a simple internal structure, and there is no risk of contaminant jamming. The thermoelement includes a casing, a mounting portion, a shaft, a heat-sensitive medium, and a seal member for drawing the shaft into the casing when the heat-sensitive medium expands. The thermovalve includes a body including a valve body linked to a shaft of a thermoelement, and a seating part on/from which the valve body can be seated/separated.

Description:
TECHNICAL FIELD 
     The present invention relates to a thermoelement and a thermovalve incorporating a thermoelement, and more specifically, relates to a thermoelement and a thermovalve incorporating the thermoelement, in which a displacement means advances and retracts along with contractive and expansive actions of a thermosensitive medium. 
     BACKGROUND ART 
     Heretofore, a thermoelement for displacing a displacement means such as a shaft and a thermovalve in which the thermoelement is incorporated has been proposed, in which attention is focused on an expansive action of a thermosensitive fluid caused by a rise in the ambient temperature. 
     In Japanese Laid-Open Patent Publication No. 07-006675, an invention referred to as an “ampblock system wax type thermostat” is disclosed. According to the disclosure of Japanese Laid-Open Patent Publication No. 07-006675, a structure is revealed in which a wax  2 , which is enclosed in a temperature sensing part  1 , expands accompanying a rise in the ambient temperature, whereby a diaphragm  3  flexes and rises upwardly. As a result, solid particulate matter  18 , which is housed in an amp space  16 , rises and is displaced to thereby displace a piston  5 . 
     An invention referred to as a “thermo-actuator” is disclosed in Japanese Laid-Open Patent Publication No. 09-089153. According to such a “thermo-actuator,” a wax  11  fills a space between a rubber seal spool  5  and a thermosensitive cylinder  9 . In a state in which the thermosensitive cylinder  9  is cooled, the wax  11  shrinks upon solidification thereof, and since the area occupied by the wax  11  is reduced, a rubber seal straight pipe  3  is pressed under a spring load and is compressed in a bellows-like shape, whereby a rod  2  is pressed deeply into the rubber seal spool  5  to occupy an initial position. When the thermosensitive cylinder  9  reaches a predetermined temperature accompanying a rise in the ambient temperature, the wax  11  inside the thermosensitive cylinder  9  expands and the pressure thereof increases, so that as the seal spool  5  becomes flattened, the rod  2  is squeezed upwardly, and thus the bellows  3  rises and is restored to the form of a straight pipe. 
     An invention referred to as a “thermovalve” is disclosed in Japanese Laid-Open Patent Publication No. 2005-180461. According to this invention, a thermovalve  4  is inserted and arranged along an axial direction of a lubricating oil inlet  1 . When the lubricating oil that flows through the lubricating oil inlet  1  rises to a predetermined temperature, a thermally actuated member  6   a  inside a thermoelement  6  that makes up the thermovalve  4  expands, whereby a rod  6   b  is pushed out and presses down a valve plug  7 , and the lubricating oil is allowed to flow into an oil cooler from a lubricating oil outlet  2 . 
     SUMMARY OF INVENTION 
     Incidentally, the ampblock system wax type thermostat disclosed in Japanese Laid-Open Patent Publication No. 07-006675 is of a configuration in which a piston  5  is made to project from a piston retainer  10  by expansion of the wax  2 . Further, in the thermo-actuator of Japanese Laid-Open Patent Publication No. 09-089153 as well, when the temperature of the wax  11  that is accommodated inside the thermosensitive cylinder  9  rises to a predetermined temperature, the rod  2  is made to project out from the thermosensitive cylinder  9 . 
     Furthermore, the thermovalve of Japanese Laid-Open Patent Publication No. 2005-180461 is of a configuration in which, when the thermally actuated member  6   a  constituting the thermoelement  6  detects a predetermined temperature, the rod  6   b  becomes elongated and extends from the thermoelement  6 . 
     More specifically, in any of the inventions of Japanese Laid-Open Patent Publication No. 07-006675, Japanese Laid-Open Patent Publication No. 09-089153, and Japanese Laid-Open Patent Publication No. 2005-180461, by using the fact that the fluid is thermally expanded accompanying a rise in the ambient temperature, a rod or a shaft is made to project outwardly to thereby accomplish a desired function. 
     However, as is clear from the above actions, the aforementioned thermoelements are of a press-out type, and more specifically, of a type in which a rod or a shaft is pressed outwardly accompanying a rise in the ambient temperature. Consequently, by assembling this type of thermoelement on another apparatus, although it is possible to carry out a desired operation accompanying an advancing action of the rod or the shaft, on the other hand, there is a drawback in that the presence of the advanced rod or the like produces an adverse effect. 
     For example, when this type of thermoelement is assembled on a valve apparatus that faces toward a fluid passage, the structure in the interior of the valve apparatus becomes complex, and by the advancing operation of the rod, since the end of the rod projects into the fluid passage, an inconvenience occurs in that the pass-through area of the fluid that flows through the fluid passage is narrowed, and smooth flow of the fluid is impeded. 
     Furthermore, since the end of the rod or the like penetrates into the interior of the flowing fluid, biting-in of foreign matter takes place, whereas the valve structure has to be made more robust and it is inevitable that the size thereof is made larger in scale. Along therewith, a rise in manufacturing costs is unavoidable. 
     The present invention has been devised with the aim of overcoming the various drawbacks mentioned above, and has the object of providing a thermoelement and a thermovalve in which such a thermoelement is incorporated, in which a pulling operation is performed on a rod or a shaft that constitutes part of the thermoelement by expansion of a thermosensitive fluid having reached a predetermined temperature, whereby the internal structure of the thermoelement can be simplified and reduced in size while also enhancing durability. 
     The present invention includes a casing, a mount formed integrally with the casing and which is attached to an object, a shaft arranged displaceably in an interior of the casing with one end thereof being exposed to an exterior from the mount, a thermosensitive medium enclosed in the interior of the casing and which expands and contracts responsive to a change in ambient temperature surrounding the casing, and a seal member that pulls the shaft toward a side of the casing upon expansion of the thermosensitive medium. 
     According to the present invention, when the ambient temperature reaches the predetermined value, the thermosensitive medium expands, and the shaft is pulled or drawn in via the seal member toward the side of the casing. Consequently, a control for transporting workpieces or for interrupting the flow of a fluid can easily be performed. 
     Further, according to the present invention, the seal member preferably engages with another end of the shaft, and the shaft is pulled into the casing by flexure of the seal member in response to expansion of the thermosensitive medium. 
     Thus, with a simple configuration, an advancing and retracting operation of the shaft can be carried out assuredly. 
     Furthermore, according to the present invention, a tapered surface, which expands in diameter toward the other end, preferably is formed on a side of the other end of the shaft. Further, a portion of the seal member may be in contact with the tapered surface, such that upon expansion of the thermosensitive medium, the portion of the seal member preferably is pressed against the tapered surface of the shaft, whereby the shaft is displaced toward the other end side. 
     Thus, at the time that the thermosensitive medium undergoes expansion, the tapered surface, which is provided on the other end side of the shaft, can reliably cause the shaft to be displaced by the seal member. 
     The present invention further is characterized by a thermovalve, which is made up from a thermoelement and a valve main body in which the thermoelement is incorporated. In this case, the thermoelement includes a casing, a mount formed integrally with the casing and which is attached to an object, a shaft arranged displaceably in an interior of the casing with one end thereof being exposed to an exterior from the mount, a thermosensitive medium enclosed in the interior of the casing and which expands and contracts responsive to a change in ambient temperature surrounding the casing, and a seal member that pulls the shaft toward a side of the casing upon expansion of the thermosensitive medium. On the other hand, the valve main body includes a body formed with an inlet port into which a fluid is introduced and an outlet port through which the fluid is led out, a seat member disposed between the inlet port and the outlet port, and a valve plug that presses against and separates away from the seat member. One end of the shaft constituting the thermoelement is connected to the valve plug, such that upon expansion of the thermosensitive medium, the seal member pulls the shaft, whereby the valve plug is made to separate away from the seat member and allow communication between the inlet port and the outlet port. 
     When the thermosensitive fluid undergoes expansion, the shaft of the thermoelement is pulled inward, whereby the valve plug, which normally is closed, separates away from the seat member. Therefore, in a state in which no obstacle is present, i.e., in which the fluid passage area is not reduced, the fluid can pass freely between the inlet port and the outlet port, and biting-in of foreign matter does not occur. Consequently, without increasing the size of the valve itself, flow blockage of a required amount of the fluid can be carried out. 
     As a matter of course, the aforementioned thermovalve may be either a direct-acting type or a pilot type of thermovalve. 
     With the thermoelement according to the present invention, by the ambient temperature reaching the predetermined value, the thermosensitive medium expands and the shaft is pulled or drawn in toward the side of the casing. Consequently, a control for transporting workpieces or a flow-through control for a fluid can easily and reliably be carried out responsive to a change in temperature. 
     Further, with the thermovalve in which a thermoelement is incorporated according to the present invention, by expansion and contraction of the thermosensitive medium, advancing and retracting operations of the shaft of the thermoelement are performed, and along therewith, the valve plug opens and closes the fluid passage. In particular, since an operation to pull in the shaft is produced by expansion of the thermosensitive medium, the fluid can be made to flow without a decrease in area of the flow passage, and biting-in of foreign matter does not occur. Consequently, an effect is obtained in that, without increasing the size of the valve itself, flow blockage of a required amount of the fluid can be carried out. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1A  is a vertical cross-sectional view showing an extended state of a shaft of a thermoelement according to a first embodiment of the present invention; 
         FIG. 1B  is a vertical cross-sectional view showing a contracted state of the shaft; 
         FIG. 2A  is a vertical cross-sectional view showing an extended state of a shaft of a thermoelement according to a second embodiment of the present invention; 
         FIG. 2B  is a vertical cross-sectional view showing a contracted state of the shaft; 
         FIG. 3A  is a vertical cross-sectional view showing an extended state of a shaft of a thermoelement according to a third embodiment of the present invention; 
         FIG. 3B  is a vertical cross-sectional view showing a contracted state of the shaft; 
         FIG. 4A  is a vertical cross-sectional view showing an extended state of a shaft of a thermoelement according to a fourth embodiment of the present invention; 
         FIG. 4B  is a vertical cross-sectional view showing a contracted state of the shaft; 
         FIG. 5A  is a vertical cross-sectional view showing an extended state of a shaft of a thermoelement according to a fifth embodiment of the present invention; 
         FIG. 5B  is a vertical cross-sectional view showing a contracted state of the shaft; 
         FIG. 6  is a vertical cross-sectional view showing a first embodiment of a thermovalve in which a thermoelement according to the present invention is incorporated, and in which a valve plug thereof is in a closed state; 
         FIG. 7  is a vertical cross-sectional view showing a state in which the valve plug of the thermovalve shown in  FIG. 6  is opened; 
         FIG. 8  is a vertical cross-sectional view showing a second embodiment of a thermovalve in which a thermoelement according to the present invention is incorporated, and in which a valve plug thereof is in a closed state; and 
         FIG. 9  is a vertical cross-sectional view showing a state in which the valve plug of the thermovalve shown in  FIG. 8  is opened. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     A preferred embodiment in relation to a thermoelement according to the present invention, and a thermovalve in which the thermoelement is incorporated, will be described in detail below with reference to the accompanying drawings. 
     At first, various embodiments will be presented and described in detail in relation to basic structures of the thermoelement. 
       FIGS. 1A and 1B  show a first embodiment of the thermoelement according to the present invention. In the embodiments described below, the same reference numerals are used to designate elements having the same structure or that carry out similar functions, with English letters a-e being appended to such numerals for each of the respective embodiments. Accordingly, across all of the embodiments, structural elements thereof designated by the same reference numerals are assumed to carry out the same functions, and detailed description of such features will not be described anew. 
     In  FIGS. 1A and 1B , reference character  10   a  indicates a thermoelement according to the present invention. The thermoelement  10   a  includes a mount  12   a  made of metal and which is mounted on an object (not shown), and a casing  14   a  made of metal, a lower end of which is crimped and fastened to the mount  12   a , and which is rich in thermosensitivity. Male threads  16   a  are engraved around the mount  12   a , and a through hole  18   a  is formed in the mount  12   a  along the axis thereof. The through hole  18   a  expands in diameter on an upper end side, with an annular groove  20   a  being formed therein. As shown in the drawing, the upper end above the male threads  16   a  is expanded in diameter, thereby forming a flange  22   a . A guide member  24   a  for ensuring smooth operation of a later-described shaft is fitted into the annular groove  20   a.    
     The casing  14   a  is made up from a cylindrical body, and as illustrated, is thin-walled on the lower end thereof, which is fitted over and attached by crimping onto the flange  22   a  of the mount  12   a  from an outer side. An annular groove  28   a  is formed in the vicinity of the lower end of the casing  14   a , and another annular groove  30   a  is formed in the vicinity of the upper end of the casing  14   a . A further annular groove  32   a , which connects to the upper part of the annular groove  30   a  and is slightly larger in diameter than the annular groove  30   a , is provided in the casing  14   a.    
     As understood from  FIGS. 1A and 1B , a first seal member  40   a , in which a through hole is formed in the center thereof, is installed in the annular groove  28   a . A second seal member  42   a , in which a through hole is formed in the center thereof, is installed in the annular groove  30   a . The first seal member  40   a  and the second seal member  42   a  are made from a flexible material such as synthetic rubber or the like. A shaft  44   a  is inserted through the casing  14   a  in connection with the first seal member  40   a  and the second seal member  42   a . As shown in  FIGS. 1A and 1B , the lower end of the shaft  44   a  is inserted into the through hole  18   a , and the first seal member  40   a  is fitted into an annular groove  46   a  disposed under a central region of the shaft  44   a  using the through hole thereof. Further, the second seal member  42   a  is fitted into an annular groove  48   a  disposed on an upper end side of the shaft  44   a  using the through hole thereof. Furthermore, a metallic ring-shaped stopper  52   a  is fitted into an annular groove  50   a  provided on the shaft  44   a  at a location above the annular groove  48   a.    
     In  FIGS. 1A and 1B , reference character  54   a  indicates a flange that prevents the second seal member  42   a  and the stopper  52   a  from coming away from the shaft  44   a.    
     Next, a cap  60   a , which is made of metal, is fitted into the annular groove  32   a . As can be understood from  FIGS. 1A and 1B , the cap  60   a  contacts the outer circumferential surface of the stopper  52   a , while also pressing down on the upper surface of the second seal member  42   a  that is seated in the annular groove  30   a . The flange  54   a  is arranged inside the space formed by the cap  60   a  and the stopper  52   a . An upper end of the casing  14   a  is crimped inwardly in surrounding relation to a tapered surface  62   a , which is formed on an upper corner of the cap  60   a , to thereby firmly retain the cap  60   a.    
     In such a structure, prior to mounting the second seal member  42   a  in the annular groove  30   a , a fluid, for example a wax  70   a , which is made of a thermosensitive material and is capable of expanding and contracting due to a rise in the ambient temperature, fills or charges an annular or torus-shaped space that is formed by the casing  14   a  and the shaft  44   a . In particular, the wax  70   a  preferably is a thermosensitive material that exhibits thermal expansion abundantly upon heating. 
     The thermoelement  10   a  according to the first embodiment of the present invention is constructed basically as described above. Next, operations and effects of the thermoelement  10   a  will be described. 
     First, in  FIG. 1A , a condition is shown in which, under normal temperature, a distal end  72   a  of the shaft  44   a  is exposed to the exterior from the lower end of the through hole  18   a , and a central portion of the first seal member  40   a  is flexed downwardly. On the other hand, the second seal member  42   a  remains in a flat state. In such an initial state, a workpiece  74   a , which is transported from a non-illustrated conveyor in the direction of the arrow, abuts against the distal end  72   a . Thus, the distal end  72   a  of the shaft  44   a  prevents further movement of the workpiece  74   a.    
     When the ambient temperature rises above a predetermined value, the wax  70   a , which is made of a thermosensitive material, expands, and ultimately, the second seal member  42   a  is pressed upwardly by the wax  70   a . Along therewith, the shaft  44   a  with which the second seal member  42   a  is engaged rises upwardly along the guide member  24   a , so that ultimately, the flange  54   a  reaches the ceiling surface of the cap  60   a , and further upward movement thereof is inhibited. Accompanying the upward movement of the shaft  44   a , the first seal member  40   a  and the second seal member  42   a  are flexed upwardly as shown in  FIG. 1B . At this time, the distal end  72   a  of the shaft  44   a  naturally releases from engagement with the workpiece  74   a , and assuming that the conveying operation of the non-illustrated conveyor continues, the displacement operation of the workpiece  74   a  in the direction of the arrow is carried out. 
     Consequently, the male threads  16   a  of the mount  12   a  are engaged beforehand with the object, i.e., in screw grooves of a non-illustrated apparatus, whereby the thermoelement  10   a  is fixed thereon, and assuming that the thermoelement  10   a  is disposed in the vicinity of a non-illustrated conveyor, a control can be carried out with respect to advancing movements, stoppage, and restored movements of the workpiece  74   a  accompanying a change in temperature. For example, under ordinary temperature, the conveying operation of the workpiece  74   a  is prevented, whereas when the predetermined temperature is reached, an advancing movement of the workpiece  74   a  can be performed. Such an operation can be implemented by a so-called pulling operation to pull the shaft  44   a  that makes up the thermoelement  10   a  into the interior of the element. 
       FIGS. 2A and 2B  show a second embodiment of the thermoelement according to the present invention. 
     According to the second embodiment, a casing  14   b  that makes up a thermoelement  10   b  is constituted in the form of a bottomed cylinder made of metal. A mount  12   b  includes an annular projection  80   b  positioned along the axial direction, which is crimped onto a lower end of the casing  14   b . A guide member  24   b  is installed on an upper end of the mount  12   b , and the outer circumferential surface of the annular projection  80   b  of the mount  12   b  is formed in a tapered shape. A seal member  82   b  is disposed between the outer circumferential surface of the tapered portion of the annular projection  80   b  and the inner circumferential surface of the casing  14   b . A tapered surface  84   b  is formed on an upper portion of a shaft  44   b , and a flange  86   b  is formed at a position on the rear end of the tapered surface  84   b . The top surface of the flange  86   b  is disposed in facing relation to the upper bottomed surface of the casing  14   b . An expandable/contractible seal member  82   b  made of synthetic rubber or the like is installed in the interior of the casing  14   b , using the side wall of the casing  14   b  which is constructed in the foregoing manner, the tapered surface  84   b , the tapered surface of the annular projection  80   b , and the outer periphery of the guide member  24   b . A wax  70   b , which undergoes expansion at or above a predetermined temperature, is enclosed in an interior space that is formed as a result of folding the cylindrical seal member  82   b  in two overlapping layers. 
     The thermoelement  10   b  according to the second embodiment is constructed basically as described above. First, when the thermoelement  10   b  is assembled, the flange  86   b  side thereof is inserted into the casing  14   b , and next, the seal member  82   b  is inserted so that a substantially central portion thereof comes into contact with the bottom surface of the flange  86   b . Thereafter, the guide member  24   b  is inserted into a substantial center of the seal member  82   b . Then, the mount  12   b  is inserted into the casing  14   b , such that both ends of the seal member  82   b  become sandwiched between the tapered surface of the annular projection  80   b  and the annular circumferential wall of the casing  14   b , and are seated on an annular stepped part of the mount  12   b.    
     Lastly, the bottom part of the casing  14   b  is crimped with respect to the mount  12   b  to thereby complete fabrication of the thermoelement  10   b.    
     When the thermoelement  10   b , which is obtained in the foregoing manner, is put to use, at first, male threads  16   b  of the mount  12   b  are screw-inserted into a non-illustrated apparatus. As a result, similar to the first embodiment, a distal end  72   b  of the shaft  44   b  extends outwardly from the lower end of the mount  12   b . In such an outwardly extended state, a non-illustrated conveyor is energized and a workpiece  74   b  is displaced in the direction of the arrow. As a result, similar to the first embodiment, the workpiece  74   b  comes into abutment against the distal end  72   b , and further displacement of the workpiece  74   b  is prevented. When the ambient temperature changes, whereby the wax  70   b  reaches the predetermined temperature and is thermally expanded, the wax  70   b  imposes an applied pressure with respect to the seal member  82   b . Therefore, the inner wall surface of the seal member  82   b  presses on the tapered surface  84   b  of the shaft  44   b , and using the tapered surface  84   b , the shaft  44   b  is pressed upwardly. The flange  86   b  ultimately reaches the inner wall surface of the casing  14   b , whereby further upward displacement thereof is prevented. At this time, the lower end of the shaft  44   b  undergoes an upwardly rising retreating motion. Consequently, since movement of the workpiece  74   b , which was prevented by the distal end  72   b  of the shaft  44   b , is allowed again, the workpiece  74   b  can be moved to a next step by the non-illustrated conveyor. 
       FIGS. 3A and 3B  show a third embodiment of the thermoelement according to the present invention. 
     With the third embodiment, a casing  14   c , which is assembled together integrally with a mount  12   c , is made up from a ring-shaped body, including a large diameter portion  90   c , which is crimped onto and fixed to the mount  12   c  at a lower end of the casing  14   c , and a small diameter portion  92   c  on the upper end thereof. A shaft  44   c , which advances and retracts with respect to the mount  12   c , is a metal rod that includes a tapered surface  84   c  on the upper end thereof. 
     An annular groove  87   c  is disposed on the upper end of the mount  12   c . The lower end of a seal member  82   c  is seated on the top surface of the mount  12   c  between the large diameter portion  90   c  and the mount  12   c . The upper end of the seal member  82   c  is seated on a stepped part that makes up the small diameter portion  92   c  of the casing  14   c . A cap  60   c  is inserted into an upper open part of the small diameter portion  92   c , and a top part of the small diameter portion  92   c  is crimped, whereby the cap  60   c  is retained between the crimped top part and the upper end of the seal member  82   c . The middle portion of the seal member  82   c  is constructed to surround and contact the tapered surface  84   c  that is formed midway along the shaft  44   c . A thermosensitive wax  70   c  is enclosed as a fluid between the seal member  82   c  and a trunk portion  94   c  of the casing  14   c.    
     In  FIGS. 3A and 3B , reference character  24   c  indicates a guide member that is seated in the annular groove  87   c  provided in the mount  12   c.    
     As easily understood from  FIG. 3A , under ordinary temperature, a distal end  72   c  of the shaft  44   c  projects downward by a predetermined distance from the lower end of the mount  12   c . Accordingly, similar to the first embodiment and the second embodiment, a workpiece  74   c  can be stopped and positioned by the distal end  72   c.    
     On the other hand, when the ambient temperature rises and the wax  70   c  expands, the volume of the wax  70   c  displaces the shaft  44   c  through the seal member  82   c  toward the side of the cap  60   c . More specifically, since the expanded wax  70   c  presses the tapered surface  84   c  of the shaft  44   c  through the seal member  82   c , the shaft  44   c  rises to the position shown in  FIG. 3B , and the top of the shaft  44   c  arrives at the inner wall of the cap  60   c . As a result, since a retreating operation of the shaft  44   c  as a whole is carried out with respect to the casing  14   c , the workpiece  74   c  that engages with the distal end  72   c  of the shaft  44   c  can be displaced again to a next position by the non-illustrated conveyor. 
       FIGS. 4A and 4B  show a fourth embodiment of the thermoelement according to the present invention. 
     In the fourth embodiment, a shaft  44   d , which can be displaced along a through hole  18   d  disposed on the axis of a mount  12   d  constituting a thermoelement  10   d , is of the same diameter from the bottom end to the upper end thereof, and a flange  54   d  is disposed on the upper end thereof. A seal member  42   d  is disposed in contact with the flange  54   d . More specifically, the outer circumferential end of the seal member  42   d , which is sandwiched between a casing  14   d  and a cap  60   d  that is crimped and fixed to the casing  14   d , is of a disk shape. The outer circumferential end of the seal member  42   d  is retained by the cap  60   d  and the upper end of the casing  14   d , and the shaft  44   d  is inserted through a hole provided in the center of the seal member  42   d.    
     A partition wall  98   d  through which the shaft  44   d  is inserted is disposed at a midway location of the casing  14   d , and an annular groove  100   d  with an open upper end is disposed in the mount  12   d . A guide member  24   d  and a seal member  40   d  are stacked and arranged between the annular groove  100   d , the shaft  44   d , and the lower surface of the partition wall  98   d . In  FIGS. 4A and 4B , reference character  70   d  indicates a fluid, for example, a thermally expansive wax. 
     In the fourth embodiment, similar to the first through third embodiments, the wax  70   d  expands due to a rise in the ambient temperature, whereby the seal member  42   d  is pressed upwardly in  FIGS. 4A and 4B , and the shaft  44   d  undergoes movement until the top surface of the flange  54   d  comes into abutment against the inner wall of the cap  60   d . Such an abutting condition is shown in  FIG. 4B . According to the thermoelement  10   d  of the fourth embodiment, the same effects and advantages as those of the thermoelements  10   a  to  10   c  according to the first through third embodiments can be obtained. 
       FIGS. 5A and 5B  show a fifth embodiment of the thermoelement according to the present invention. 
     In the fifth embodiment, a mount  12   e  is accommodated in the interior of a bottomed cylindrical casing  14   e , and the casing  14   e  and the mount  12   e  are integrated together by crimping the lower end of the casing  14   e . A guide member  24   e  and a seal member  40   e  are stacked and arranged in the interior of the mount  12   e . A shaft  44   e  includes a tapered surface  84   e , and at a position where the tapered surface  84   e  terminates, as shown in  FIGS. 5A and 5B , annular projections  102   e ,  104   e  are separated mutually and formed integrally at upper and lower locations. A seal member  42   e  is accommodated between the annular projections  102   e ,  104   e . A wax  70   e  is enclosed in a chamber defined between the casing  14   e  and the shaft  44   e  including the tapered surface  84   e.    
     In such a structure, the wax  70   e  undergoes expansion when a predetermined temperature is reached due to a change in the ambient temperature. By the expanded volume thereof, the annular projection  102   e  serves as a pressure receiving surface, and since the tapered surface  84   e  is of a shape that expands in diameter upwardly, the shaft  44   e  is displaced upwardly in the drawing, and ultimately, the top surface of the annular projection  104   e  arrives at the inner wall surface of the casing  14   e . Consequently, in this way, since a distal end  72   e  of the shaft  44   e  undergoes a retracting operation, as shown in  FIG. 5B , is pulled into the interior of the casing  14   e , the same actions and effects as those of the first through fourth embodiments are carried out. 
     Next, thermovalves, in which thermoelements  10   a  to  10   e  constructed in the foregoing manner are incorporated, will be described in detail below with reference to  FIG. 6  and subsequent drawings. 
       FIGS. 6 and 7  show a direct-acting type two port thermovalve  200   a . The thermovalve  200   a  includes a body  202   a . On one end of the body  202   a , an inlet port  204   a  is formed through which a pressure fluid is introduced, and on the other end of the body  202   a , an outlet port  206   a  is formed. A seat member  208   a  is formed in an upstanding manner from the bottom of the body  202   a  in a direction substantially perpendicular to an axis extending between the inlet port  204   a  and the outlet port  206   a . As shown in  FIGS. 6 and 7 , using a top stepped part  209   a  of the body  202   a , a cylindrical cover  210   a  is erected on the body  202   a . A seal member  212   a  made up from an O-ring is interposed between the body  202   a  and the cover  210   a . As shown in  FIGS. 6 and 7 , through another seal member  214   a  made up from an O-ring, a bonnet  216   a  is fixed on an upper end of the cover  210   a.    
     The bonnet  216   a  includes a projection  218   a  that projects on a side of the body  202   a  at a central location in the axial direction thereof. A hole  220   a  is disposed at the bottom of the projection  218   a . A shaft  338   a , which constitutes part of a thermoelement  300   a , penetrates through the hole  220   a . The thermoelement  300   a  is constructed substantially the same or similar to the thermoelements  10   a  to  10   e  shown in the embodiments of  FIGS. 1A to 5B , and performs substantially the same or similar functions. In relation to the thermoelement  300   a , using an upper stepped part  222   a  of the projection  218   a , a seal member  224   a  is seated on an upper end where the hole  220   a  terminates. Screw grooves  226   a  are disposed on an inner circumferential surface of a hole that is provided along the axis of the bonnet  216   a . The thermoelement  300   a  is attached using the screw grooves  226   a.    
     More specifically, a mount  302   a  that makes up part of the thermoelement  300   a  is included, and screw grooves  304   a  are disposed on a portion of the outer circumferential wall of the mount  302   a . The screw grooves  304   a  are screw-engaged with the screw grooves  226   a  of the bonnet  216   a . A recess  303   a  is formed in the center of a lower end of the mount  302   a , and a stepped part  306   a  is provided on an upper end side thereof. 
     The stepped part  306   a  extends therearound in an annular shape and is formed with an outwardly projecting flange  308   a . A casing  310   a  is fixed by crimping a bottom portion thereof over the flange  308   a.    
     As understood from  FIGS. 6 and 7 , the casing  310   a  is cylindrical in shape, and a cap  320   a  is fitted on a top portion thereof. The cap  320   a  is positioned and fixed by crimping an upper end part of the casing  310   a  inwardly over the cap  320   a . The cap  320   a  includes an annular recess  322   a  that opens in an axial direction on the bottom of the cap  320   a , and the bottom of the cap  320   a  presses firmly on a seal member  324   a . A guide member  326   a  is fitted in the stepped part  306   a  of the mount  302   a , and a seal member  328   a  is fixed to an upper portion of the guide member  326   a , so as to press against an inside stepped part provided on the casing  310   a.    
     Accordingly, an annular space  330   a  is formed between the seal member  328   a  and the seal member  324   a , and a wax  500   a , for example, which undergoes expansion due to a rise in the ambient temperature, is enclosed in the interior of the annular space  330   a.    
     As understood from  FIGS. 6 and 7 , the shaft  338   a , which passes from below the cap  320   a  and through the hole  220   a  and is directed toward the seat member  208   a , extends so as to penetrate through the annular space  330   a  that encloses the wax  500   a . An annular groove  340   a  in which the seal member  224   a  is fitted, an annular groove  342   a  in which the seal member  328   a  is fitted, and an annular groove  344   a  in which the seal member  324   a  is fitted, are formed respectively along the shaft  338   a  while being separated mutually by predetermined distances. 
     A retaining member  350   a  is fixed to the lower end of the shaft  338   a . More specifically, the retaining member  350   a  includes a ring-shaped body  354   a , with which screw threads  352   a  provided on the lower end of the shaft  338   a  are screw-engaged. A valve plug  358   a  made of synthetic rubber or the like is sandwiched between the ring-shaped body  354   a  and the retaining member  350   a.    
     As will be described later, the valve plug  358   a  is displaceable and is capable of pressing against the top surface of the seat member  208   a . A disk  362   a , in which plural holes  360   a  are formed concentrically, is fixed to the retaining member  350   a . A coil spring  364   a  is disposed between the bonnet  216   a  and the disk  362   a  in surrounding relation to the projection  218   a , the shaft  338   a , and the retaining member  350   a . The coil spring  364   a  applies a pressing force to elastically press the disk  362   a  in a downward direction, and as a result, the valve plug  358   a , which is held in the retaining member  350   a , is pressed normally against the seat member  208   a.    
     The body  202   a , the seat member  208   a , and the valve plug  358   a  collectively constitute a valve main body  700   a.    
     The thermovalve  200   a  according to the present invention is constructed basically as described above. Next, operations and effects of the thermovalve  200   a  will be described. 
     Under ordinary temperature, for example, in the case that the surrounding ambient temperature is 25° C., the wax  500   a  enclosed in the annular space  330   a  does not yet undergo expansion. Consequently, only by the elastic force of the coil spring  364   a , the retaining member  350   a  is pressed downwardly in  FIGS. 6 and 7 , and the valve plug  358   a  is pressed against the seat member  208   a . Therefore, since the seat member  208   a  is in a stopped condition in cooperation with the valve plug  358   a , the fluid introduced from the inlet port  204   a  is not led out to the outlet port  206   a.    
     As the ambient temperature gradually rises and the wax  500   a  begins to expand, the expansive force thereof causes the seal member  324   a  to flex upwardly. As a result, the shaft  338   a  also rises, accompanied by the seal member  224   a , which is mounted on the annular groove  340   a , and the seal member  328   a , which is mounted on the annular groove  342   a , also being flexed in an upward direction. Such a feature implies that the valve plug  358   a  rises upwardly from the seat member  208   a  in opposition to the elastic force of the coil spring  364   a . As a result, the inlet port  204   a  and the outlet port  206   a  are placed in communication, and the fluid that was introduced from the inlet port  204   a  passes between the seat member  208   a  and the valve plug  358   a , and is led out to the outlet port  206   a.    
     On the other hand, by the ambient temperature returning to the normal temperature, the wax  500   a  undergoes contraction, whereupon the shaft  338   a  descends in the drawing, and in the thermovalve  200   a , the valve plug  358   a  becomes seated again on the seat member  208   a . As a result, communication between the inlet port  204   a  and the outlet port  206   a  is blocked. 
     The thermovalve  200   a  of the present embodiment focuses attention on the expanding and contracting function of the wax  500   a  responsive to changes in the ambient temperature, so that, in particular, the shaft  338   a  is displaced upwardly when a thermally expansive medium, preferably the wax  500   a , undergoes expansion accompanying a rise in the ambient temperature. More specifically, the shaft  338   a  is pulled inwardly toward the side of the thermoelement  300   a , and consequently, an opening operation can be performed without impeding progress in the flow of the fluid that flows from the inlet port  204   a  to the outlet port  206   a . Further, since an operation of pulling the shaft  338   a  inwardly is carried out, even if foreign matter intrudes into the fluid passage, biting-in of such foreign matter does not occur. 
       FIGS. 8 and 9  show another embodiment of the thermovalve according to the present invention. 
     With the thermovalve according to the second embodiment, several constituent elements thereof, which are the same as those of the thermovalve  200   a  according to the first embodiment, are designated using the same reference numerals, by appending trailing lower case English letters to the reference numerals as they are, and detailed description of such features is omitted. 
     A thermovalve  200   b  according to the second embodiment is a pilot type two-port thermovalve. The pilot type two-port thermovalve  200   b  includes a diaphragm  600   b  disposed between a cover  210   b  and a body  202   b . More specifically, the diaphragm  600   b  is sandwiched and gripped between the cover  210   b  and the body  202   b . A bulging portion  601   b  is formed substantially in the center on a lower surface of the diaphragm  600   b , and a hole  602   b  is provided therein between the bulging portion  601   b  and a circumferential edge portion of the diaphragm  600   b . A disk  604   b , a peripheral region of which is bent upwardly, is disposed concentrically with the diaphragm  600   b . A hole  606   b  provided in the disk  604   b  is of the same diameter as the hole  602   b  of the diaphragm  600   b  and communicates mutually therewith. The diaphragm  600   b  and the disk  604   b  are sandwiched and held together integrally at the axis thereof by a gripping member  610   b . More specifically, the gripping member  610   b  includes screw threads  612   b  on a lower end thereof, and by screw-engagement of a nut  614   b  onto the threads  612   b , the diaphragm  600   b  and the disk  604   b  are firmly clamped between the nut  614   b  and a main body  616   b  of the gripping member  610   b . An orifice  618   b  is provided in the form of a through hole that penetrates through the axis of the gripping member  610   b . The diameter of the orifice  618   b  is slightly greater in diameter than the holes  602   b ,  606   b . An upper distal end of the orifice  618   b  is capable of abutting against a valve plug  358   b , which is disposed on a lower portion in the center of a retaining member  350   b.    
     The retaining member  350   b  will now be described. As shown in  FIGS. 8 and 9 , the retaining member  350   b  is installed on a lower end of a shaft  338   b , which is formed with steps along the longitudinal direction thereof. The retaining member  350   b  includes stepped parts  650   b ,  652   b ,  654   b , and  656   b  having different diameters respectively along the axial direction. The valve plug  358   b  is installed centrally in the lower surface of the retaining member  350   b . The valve plug  358   b  is formed by an elastic body made of synthetic rubber. A coil spring  364   b  is interposed between a bonnet  216   b  and the largest diameter stepped part  650   b . By the elastic force of the coil spring  364   b , the valve plug  358   b  acts to close the upper end of the orifice  618   b  of the gripping member  610   b . The retaining member  350   b  and the disk  604   b , etc., are disposed in the interior of a chamber  630   b.    
     The body  202   b , a seat member  208   b , and the valve plug  358   b  collectively constitute a valve main body  700   b.    
     In  FIGS. 8 and 9 , reference character  300   b  indicates a thermoelement in which the valve main body  700   b  is incorporated, reference character  302   b  indicates a mount, and reference character  310   b  indicates a casing. 
     The thermovalve  200   b  according to the second embodiment of the present invention is constructed as described above. Next, operations and effects of the thermovalve  200   b  will be described. 
     Under ordinary temperature, for example, in the case that the ambient temperature is 25° C., a wax  500   b  does not undergo expansion. Consequently, the elastic force of the coil spring  364   b  presses the retaining member  350   b  downward, and the valve plug  358   b  closes the orifice  618   b  of the gripping member  610   b . As a result, a state is brought about in which flow of the fluid between an inlet port  204   b  and an outlet port  206   b  is blocked. More specifically, a condition is provided in which the bulging portion  601   b  of the diaphragm  600   b  is pressed against the seat member  208   b.    
     At this time, although the fluid from the inlet port  204   b  enters into the chamber  630   b  from the holes  602   b ,  606   b , since the chamber  630   b  is at the same pressure as the inlet port  204   b , the diaphragm  600   b  is not displaced. 
     Due to a rise in the ambient temperature, the wax  500   b  undergoes expansion. Consequently, a seal member  324   b  is flexed upwardly, and as a result, the shaft  338   b  rises, and ultimately, the retaining member  350   b  that is connected to the shaft  338   b  is raised upwardly. Thus, the valve plug  358   b  that closes the orifice  618   b  of the gripping member  610   b  separates away from the upper end of the orifice  618   b . By the aforementioned actions, communication is established mutually between the inlet port  204   b , the chamber  630   b , and the outlet port  206   b . As a result, the fluid that is introduced from the inlet port  204   a  passes through the holes  602   b ,  606   b , and further, from the orifice  618   b , the fluid arrives at the outlet port  206   b  and is led out to the exterior. During this time, since the opening diameter of the orifice  618   b  is of a larger diameter than the holes  602   b ,  606   b , the fluid can easily be led out to the outlet port  206   b.    
     If the ambient temperature decreases, the wax  500   b  undergoes contraction, whereupon the shaft  338   b  descends, and the valve plug  358   b  once again closes the orifice  618   b . As a result, the state of communication between the inlet port  204   b  and the outlet port  206   b  is blocked. 
     With the thermoelement according to the present invention, when the ambient temperature reaches a predetermined value, the wax expands and the shaft is pulled or drawn in toward the side of the casing. On the other hand, in the case that the ambient temperature is less than the predetermined temperature, the wax contracts and the shaft extends. Consequently, a control for transporting workpieces or a flow-through control for a fluid can be carried out accurately responsive to a change in temperature. Further, with the thermovalve according to the present invention, responsive to changes in the ambient temperature, advancing and retracting operations of the shaft that is connected to the thermoelement are performed, and opening and closing operations of the valve plug are carried out. In particular, when the ambient temperature becomes greater than or equal to the predetermined temperature, expansion of the wax causes the valve plug that faces toward the fluid passage to retract, and the fluid passage opens as large as possible. Accordingly, the fluid is allowed to flow sufficiently. Further, even if foreign matter infiltrates into the interior of the fluid passage, damage to the valve plug, etc., does not occur. Stated otherwise, an effect is obtained in that biting-in of such foreign matter can be prevented. 
     Although preferred embodiments of the present invention have been described above, the present invention is not limited to such embodiments, and various changes and modifications may be made to the embodiments without departing from the gist of the invention.