Abstract:
A closure cap which can screw onto the fixed neck of a cooling system expansion tank. The closure cap is provided with a screw cap and a threaded section in which a combination pressure-vacuum valve is mounted concentrically and in such a way that it can rotate in relation to the screw cap. The valve is provided with a sealing element which comes into tight contact with the fixed neck when the closure is screwed. To endure that the closure cap can be unscrewed only when the excess heat in the cooling system has been completely dissipated, it is proposed that the closure cap when screwed onto the fixed neck would be prevented from unscrewing means of a temperature-dependent control element.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a closure cap to be fixed in place, preferably by screwing, plugging and rotating, on, for example, a fixed connector of a motor vehicle radiator, a compensator reservoir for cooling or heating systems, or the like. 
     BACKGROUND OF THE INVENTION 
     Closure caps of this type are used, for example, in motor vehicle cooling systems, either directly as a radiator cap or as the closure of the compensator reservoir. The closure cap can either be screwed on by means of a screw thread, or it can be plugged on and turned by means of a bayonet element. In connection with motor vehicles there is a problem with respect to the closure caps, due to as a rule the pressure is high because the high temperature in the cooling system. Even if at the time of stopping the engine the temperature in the cooling system is not excessive, it is possible that after turning the engine off a temperature and therefore a pressure increase can take place because of a certain after-heating effect. If in such a case the closure cap is immediately removed, there is the acute danger of scalding for the respective user. This danger exists in particular also with screwable caps, since in the course of unscrewing the closure cap the user is not urged to slow the unscrewing process in the last phase, or better yet to interrupt it and mainly to wait until a pressure equalization with the ambient air has taken place. Although a ventilated connection between the cooling system and the exterior is opened in the course of unscrewing the closure cap, this cannot take place as rapidly as the user can possibly unscrew the closure cap. The same applies correspondingly when using a cap provided with a bayonet closure. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a closure cap of the type mentioned at the outset, which cannot be removed if the cooling system is still at an excess temperature, but only after the excess temperature has been completely reduced, and which nevertheless is constructed in a space saving manner. 
     This object is intended to be attained by means of a closure cap having an actuating element, a temperature-dependent control element in the form of a memory spring, a control bolt, and a return spring with a collar. The memory spring is disposed off-centered and seated in an axial recess in the cap or in the actuating element. The control bolt directly causes coupling or uncoupling of the cap and the actuating element, or the memory spring is centrally disposed and a horizontal connecting leg of a U-shaped coupling element rests above the actuating element on the end of the axial control bolt facing the cap. The memory spring is acted upon by a return spring, whose other end is supported on the interior surface of the cap so that lateral vertical connecting legs project from above in the direction toward the actuating element, and at normal temperatures engage axial recesses in the actuating element for achieving a connection which is fixed against relative rotation. 
     A closure cap is provided which cannot be removed if a critically high temperature still prevails in the cooling system (or in the heating system). By means of this it is prevented in every case that injuries because of high temperature and the overpressure resulting therefrom in the fixed connector can occur during opening of the closure cap. The temperature-dependent control element is here housed in a space-saving manner with the coupling element. 
     In accordance with an exemplary embodiment it is possible to provide the temperature-dependent element between the cap and the valve or the cap and the connector, so that locking, fixed against relative rotation, of the cap with respect to the fixed connector takes place. 
     However, a preferred embodiment of the present invention is realized by means of an actuating element maintained rotatable with respect to the cap and that at normal temperature a coupling, fixed against relative rotation can be achieved by means of the temperature-dependent control element. In this case it has been achieved that the cap turns idly with respect to the actuating element, so that removal of the closure cap from the fixed connector is impossible, even when using force. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further details of the present invention can be taken from the following description, in which the present invention will be described in detail and explained by means of the exemplary embodiment represented in the drawings. Shown are: 
     FIG. 1A, which is a longitudinal section, prepared at different levels on the left and right of the center line, through a closure cap screwed on a fixed connector of a reservoir and having a temperature-dependent unscrewing safety element in accordance with a first exemplary embodiment of the present invention, 
     FIG. 1B which is a top view in a partially broken representation, of a temperature-dependent control element employed as the unscrewing safety element in the closure cap in FIG. 1A, 
     FIGS. 2A and 2B, which show representations corresponding to FIGS. 1A and 1B of the closure cap and associated temperature-dependent control element, but in accordance with a second exemplary embodiment of the present invention,, 
     FIGS. 3A and 3B, which show representations corresponding to FIGS. 1A and 1B of the closure cap and associated temperature-dependent control element, but in accordance with a third exemplary embodiment of the present invention, 
     FIGS. 4 and 5, which are a representation respectively corresponding to FIG.,  1 A, but in accordance with a fourth and fifth exemplary embodiment of the present invention, 
     FIGS. 6 and 7, which are a representation respectively corresponding to FIG. 1A, but in accordance with a sixth and seventh exemplary embodiment of the present invention, 
     FIGS. 8 and 9, which are a representation respectively corresponding to FIG. 1A, but in accordance with an eighth and ninth exemplary embodiment of the present invention, 
     FIGS. 10 and 11, which are a representation respectively corresponding to FIG. 1A, but in accordance with a tenth and eleventh exemplary embodiment of the present invention, and 
     FIG. 12, which is a representation corresponding to FIG. 6, but in accordance with a twelfth exemplary embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The closure cap  10 ,  10 ′,  10 ″,  110 ,  110 ′,  210 ,  210 ′,  310 ,  310 ′  410  or  410 ′, represented in the drawings in twelve exemplary embodiments, which is screwed on the fixed connector  11  of a compensator reservoir, not further represented, of a motor vehicle cooling system, has a screw cap  14 ,  14 ′,  141 ″,  114 ,  114 ′,  214 ,  214 ′,  314 ,  314 ′,  414 ,  414 ′, an external thread element  21 ,  21 ′,  21 ″,  121 ,  121 ′,  221 ,  221 ′,  321 ,  321 ′,  421 ,  421 ′ and a valve  15 ,  15 ′,  15 ″,  115 ,  115 ′,  215 ,  215 ′,  315 ,  315 ′,  415 ,  415 ′. In these exemplary embodiments the connector  11  of the compensator reservoir has two concentric elements, namely an interior threaded element  13  on the outside and not shown in FIGS. 2A and 3A, which receives the external thread element  21 ,  21 ′,  21 ″,  121 ,  121 ′,  221 ,  221 ′,  321 ,  321 ′,  421 ,  421 ′ of the closure cap  10 ,  10 ′,  10 ″,  110 ,  110 ′,  210 ,  210 ′,  310 ,  310 ′,  410  or  410 ′ in a screwed manner, and a neck  16  located on the inside, which is engaged by the valve  15 ,  15 ′,  15 ″,  115 ,  115 ′,  215 ,  215 ′,  315 ,  315 ′,  415 ,  415 ′ of the closure cap  10 ,  10 ′,  10 ″,  110 ,  110 ′,  210 ,  210 ′,  310 ,  310 ′,  410  or  410 ′. It is understood that it is also possible to provide the closure cap  10 ,  10 ′,  10 ″,  110 ,  110 ′,  210 ,  210 ′,  310 ,  310 ′,  410  or  410 ′ with an inner thread and/or to embody it in such a way that it can be directly screwed on the fixed connector of a motor vehicle radiator. In connection with the closure cap  10 ,  10 ′,  10 ″,  110 ,  110 ′,  210 ,  210 ′,  310 ,  310 ′,  410  or  410 ′ in accordance with the present invention it is essential that it is provided with a temperature-dependent unscrewing safety element  20 ,  20 ′,  20 ″,  120 ,  120 ′,  220 ,  220 ′,  320 ,  320 ′,  420 ,  420 ′, which assures that the closure cap  10 ,  10 ′,  10 ″,  110 ,  110 ′,  210 ,  210 ′,  310 ,  310 ′,  410  or  410 ′ can only be removed or unscrewed from the respective fixed connector after the compensator reservoir or the motor vehicle radiator or the like has been lowered to the normal or ambient temperature. 
     In all exemplary embodiments the screw cap  14 ,  14 ′,  14 ″,  114 ,  114 ′,  214 ,  214 ′,  314 ,  314 ′,  414 ,  414 ′ of the closure cap  10 ,  10 ′,  10 ″,  110 ,  110 ′,  210 ,  210 ′,  310 ,  310 ′,  410  or  410 ′ is provided with a cover plate  22 , over which a gripping bar  23 , for example, extends diagonally. The screw cap  14 ,  14 ′,  14 ″,  114 ,  114 ′,  214 ,  214 ′,  314 ,  314 ′,  414 ,  414 ′ is hollow, while in the area of the gripping bar  23  the hollow chamber  24 , cylindrical per se, is extended by means of rectangular-shaped depressions  25 . 
     In the exemplary embodiments in accordance with FIGS. 1 to  9 , the screw cap  14 ,  14 ′,  14 ″,  114 ,  114 ′,  214 ,  214 ′,  314 ,  314 ′,  414 ,  414 ′ and the external thread element or connector  21 ,  21 ′,  21 ″,  121 ,  121 ′,  221 ,  221 ′,  321 ,  321 ′,  421 ,  421 ′ of the closure cap  10 ,  10 ′,  10 ″,  110 ,  110 ′,  210 ,  210 ′,  310 ,  310 ′,  410  or  410 ′ are separate components and are connected with each other in such a way that, although they cannot be moved axially, they are movable in the circumferential direction, and with the exemplary embodiments in accordance with FIGS. 10 and 11 they are respectively combined into a one-piece component. In the first case the connector threaded on the exterior is provided with an inward projecting annular collar  31 , which engages a holding ring  32  which is L-shaped in cross section and is discontinuous in the area of the depressions  25  and formed in one piece on the underside of the cover plate  22 . By means of this, the connector threaded on the exterior is maintained suspended on the underside of the screw cap. 
     Inside the screw cap  14 ,  14 ′,  14 ″,  114 ,  114 ′,  214 ,  214 ′,  314 ,  314 ′,  414 ,  414 ′ or the external thread element or connector  21 ,  21 ′,  21 ″,  121 ,  121 ′,  221 ,  221 ′,  321 ,  321 ′,  421 ,  421 ′ and concentrically with the latter, a valve housing  17  of the valve on the screw cap  14 ,  14 ′,  14 ″,  114 ,  114 ′,  214 ,  214 ′,  314 ,  314 ′,  414 ,  414 ′ is held rotatable in relation to the latter and essentially immovable in the axial direction. The relative rotatability between the valve housing  17  and the screw cap  14 ,  14 ′,  14 ″,  114 ,  114 ′,  214 ,  214 ′,  314 ,  314 ′,  414 ,  414 ′ is achieved in a manner similar to the relative rotatability between the screw cap and the connector threaded on the exterior. In a manner which will not be described in detail because it is known per se, the valve is embodied as a combined overpressure/underpressure valve which, in the state where the closure cap  10 ,  10 ′,  10 ″,  110 ,  110 ′,  210 ,  210 ′,  310 ,  310 ′,  410  or  410 ′ is screwed on the fixed connector  11 , opens in case of the appearance of too great an excess pressure or underpressure and thus protects the cooling system. At its front end  28 , the valve housing  17  is provided with an annular groove  26 , into which an O-ring  27  has been placed, which sealingly rests against the smooth inner surface  18  of the neck  16  of the compensator reservoir when the closure cap  10 ,  10 ′,  10 ″,  110 ,  110 ′,  210 ,  210 ′,  310 ,  310 ′,  410  or  410 ′ is entirely screwed on. 
     In the first exemplary embodiment in FIGS. 1A and 1B, a compression spring  36  is provided axially centered inside the hollow chamber  24  of the screw cap  14 , one end of which is supported on the raised part of the cover plate  22  in the area of the gripping bar  23 . A temperature-dependent control element in the form of an elongated narrow bimetal plate or strip  37  and an extended control plate  38 , which can be moved opposite the action of the compression spring  36  in the axial direction of the closure cap  10 , face the other end of the compression spring  36 . The bimetal plate  37  and the control plate  38  extend over a considerable portion of the length of the gripping bar  23 . In its center area the control plate  38  is embodied flat, and on its other outer end areas  41  (only one of which is visible in FIG.  1 A), it is provided with a crimping  42 , whose free end  43  can engage the annular collar  31  for a connection fixed against relative rotation. The bimetal strip  37  is disposed on the top of the control plate  38  facing the compression spring  36 . The center area  44  of the bimetal plate  37  lies between the other end of the compression spring  36  and the center area  39  of the control plate  38 . The bimetal strip  37  can be fixedly connected with the control plate  38  or rest only loosely on it. As can be taken from FIG. 1B, the center area  44  of the bimetal strip  37  which, the same as the control plate  38 , extends crosswise over the gripping bar  23  or the two depressions  25 , is provided with a rectangular-shaped recess  46  for a connection, fixed against relative rotation, with the screw cap  14 . The same applies in a similar way to the control plate  38  in a manner not shown. In a state of normal temperature (ambient temperature), the bimetal strip  37  is shaped in such a way that its outer free ends  45  are located in a plane above the center areas  39  or  44  of the control plate  38  or the bimetal strip  37 . The outer free ends  45  of the bimetal strip  37 , which therefore are concave, are held longitudinally movable in slits  47  of the screw cap  14 . 
     If the closure cap  10  in the state, where it is screwed on the connector  11  of the compensator reservoir  12 , as partially shown in FIG. 1A, is exposed to a preselected critical excess temperature in the connector  11  of the compensator reservoir, this excess temperature is transmitted to the temperature-dependent control element, i.e. the bimetal strip  37 , so that under the influence of this excess temperature it is deformed from its concave shape into a flat straight shape. This means that the center area  44  of the bimetal plate  37  moves against the force of the compression spring  36  and in this way relieves the control plate  38  of the pressure of the compression spring  36 . If the bimetal strip  37  and the control plate  38  are connected with each other in the center areas  39 ,  44 , the control plate  38  is lifted by the bimetal strip  37 . This means that the free ends  43  of the crimping  42  of the control plate  38  come free of the upper or toothed annular surfaces of the annular collar  31 . In other words, the external thread connector  21  and the screw cap  14  can be rotated with respect to each other, i.e. the external thread connector  21  is no longer moved along with the screw cap  14  when the latter turns; the screw cap  14  turns idly. 
     If the bimetal strip  37  and the control plate  38  are not connected with each other in the axial direction, the control plate  38  is only relieved of pressure when the bimetal strip  37  is deformed when an excess temperature occurs. In this case it is practical to provide the connection between the free ends  43  of the crimping  42  of the control plate  38  and the upper surface of the annular collar  31  of the external thread connector  21  by means of a toothed ratchet connection, so that upon pressure relief of the control plate  38  and rotation of the screw cap  14  it can slidingly move with its outer free ends over the surface of the annular collar  31  which is provided with teeth. 
     The second exemplary embodiment of the present invention represented in FIGS. 2A and 2B, differs from the exemplary embodiment represented in FIGS. 1A and 1B in the following manner: Although the compression spring  36  and the control plate  38  have the same shape as in the first exemplary embodiment, the compression spring  36  is supported with its other end directly on the control plate  38 . A circular bimetal plate  37 ′ (see FIG. 2B) is disposed on the underside of the control plate  38 . The central area  44 ′ of the bimetal plate  37 ′ rests against the underside of the control plate  38 , while the outer rim  51  of the bimetal plate  37 ′ is held in an annular groove  52  on the top of the valve housing  17 . 
     At ambient temperature, the bimetal plate  37 ′ is shaped and arranged in such a way, that under the pressure of the compression spring  36  the outer ends  41  of the control plate  38  can engage the top of the annular collar  31  of the external thread connector  21 ′ in a manner fixed against relative rotation. If an excess temperature occurs, the bimetal plate  37 ′ is deformed in such a way that its central area  44 ′ moves in an axial direction against the force of the compression spring  36  and in this way lifts the control plate  38 , so that its outer ends  41  come free of the annular collar  31 ′ of the external thread connector  21 ′. In this way the external thread connector  21 ′ cannot turn along with the rotation of the screw cap  14 ′. 
     No separate control element is provided in the third exemplary embodiment represented in FIGS. 3A and 3B, instead, the function of the control element  38  of the two previously described exemplary embodiments is taken over by the free ends  61  of a temperature-dependent control element, which is in the form of a bimetal plate  37 ″. The elongated bimetal plate  37 ″ has two arms  56  and  57 , which are connected in one piece with each other and which are provided with recesses  58 ,  59  near their connected area, by means of which they are held, fixed against relative rotation, in a respective shoulder  60  on the inside of the screw cap  14 ″. The free ends  61  of the bimetal plate  56 ,  57  are provided with teeth  63 , which can engage corresponding teeth  64  on the top of the annular collar  31  of the external thread connector  21 ″. 
     As can be taken from FIG. 3A, at normal temperature the two bimetal plate arms  56 ,  57  are formed in such a way, that they arch downward in relation to the central area, thus the bimetal plate  37 ″ can be embodied convex. If an excess temperature occurs in the connector  11  or the compensator reservoir, the bimetal plate  37 ″ is deformed into an approximately straight level, which means that the free ends  61  move pivotingly or deformingly upward. By means of this the teeth  63 ,  64  of the bimetal plate arms  56 ,  57  and the annular collar  31 ″ come free of each other. Therefore twisting of the external thread connector  21 ″ is no longer possible when the screw cap  14 ″ is turned; the screw cap  14 ″ turns idly. 
     In connection with the last mentioned third exemplary embodiment of the present invention it is also possible to make the bimetal plate  37 ″ in the form of a cross in the case where the screw cap  14 ″ is provided with a cross-shaped four-armed gripping bar in place of an elongated two-armed one. 
     In the fourth exemplary embodiment of the present invention represented in FIG. 4, the temperature-dependent unscrewing safety element  120  is formed by one or several temperature-dependent control elements in the form of one or several bimetal strips or plates  137 , which are disposed evenly distributed on the circumference of the screw cap  114 . The bimetal strip or plate  137  is clamped with both ends or its edge in a recess  148  on the inside of the screw cap  114 . The bimetal strip  137  or the bimetal plate is equipped in the center between the clamping receptacle(s)  149  with a control element embodied as a control cam  138 , which is oriented toward the external thread element  121 . The external thread element  121  has a number of axial bores  153  corresponding to the number of the bimetal strips or plates  137  or the number of control cams  138 , into which one or more of the control cams  138  can enter, so that an interlocking connection between the screw cap  114  and the external thread element  121  is generated. At normal temperature in the reservoir connector  11 , the bimetal strip or plate  137  is in the position represented in FIG. 4, in which a revolving connection between the screw cap  114  and the external thread element  121  has been made. In case of an excessively high temperature in the connector  11 , the bimetal strip or plate  137  is deflected into the position shown by dashed lines, in which the control cam  138  comes free of the axial bore  153  and therefore releases the interlocking connection. Now the screw cap  114  turns idly with respect to the external thread element  121 . 
     In the fifth exemplary embodiment of the present invention represented in FIG. 5, the closure cap  110 ′ has a temperature-dependent unscrewing safety element  120 ′ with a temperature-dependent control element in the form of a bimetal element  137 ′ on the inside of the screw cap  114 ′. The bimetal element  137 ′ is fastened approximately centered on the underside of the screw cap  114 ′ and has one or several arms  154 ′ evenly distributed over the circumference, whose free end cooperates with an axially extending control cam  138 ′. 
     With its front end  155 ′ facing the external thread element  121 ′, the control cam  138 ′ enters an axial bore  153 ′ of the screw cap  114 ′, while its rear end  156 ′, which engages an axial recess  158 ′ of the screw cap  114 ′, is supported on a return spring  159 ′. At normal temperature there is an interlocking connection, fixed against relative rotation, between the screw cap  114 ′ and the external thread element  121 ′ because the front end  155 ′ of the control cam  138 ′ engages the axial bore  153 ′ under the force of the return spring  159 ′. With an appropriately high temperature, the bimetal arm  154  of the bimetal element  137 ′ is deflected against the force of the return spring  159 ′, so that the front end  155 ′ of the control cam  138 ′ comes free of the bore  153 ′. The screw cap  114 ′ turns idly with respect to the external thread element  121 ′. 
     In the exemplary embodiments of the present invention represented in FIGS. 6 to  11 , the temperature-dependent control element of the temperature-dependent unscrewing safety element  220 ,  220 ′,  320 ,  320 ′,  420  or  420 ′ of the closure cap  210 ,  210 ′,  310 ,  310 ′,  410  or  410 ′ is constituted by a memory spring  237 ,  237 ′,  337 ,  337 ′,  437  or  437 ′. 
     In the sixth exemplary embodiment of the present invention represented in FIG. 6, a control bolt  238  is disposed in an axial recess  258  accessible from the interior of the screw cap  214 , wherein a return spring  259  is arranged around its back end  256 , and the memory spring  237  is arranged around its front end  255 . The return spring  259  is supported between the bottom of the axial recess  258  and a collar  257  while the memory spring  237  is supported between the collar  257  and its front abutment  254  Under normal temperature the front end  255  of the control bolt  238  is pressed by the force of the return spring  259  into an axial bore  253  in the external thread element  221 , so that an interlocking connection, which is fixed against relative rotation, is formed between the screw cap  214  and the external thread element  221 . At an appropriately high predetermined temperature the memory spring  237  expands and pushes the control bolt  238  against the force of the return spring  259  into the axial recess  258  in the screw cap  214 , so that the front end  255  of the control bolt  238  comes free of the axial bore  253  in the external thread element  221 . It is understood that such a temperature-dependent control element in the form of a memory spring  237  can also be provided at several locations which are evenly distributed over the circumference, in place of one location on the circumference of the closure cap  210 . See FIG.  12 . 
     In the seventh exemplary embodiment in accordance with the present invention represented in FIG. 7, the return spring  259 ′ and the memory spring  237 ′ are housed at different locations, namely in the screw cap  214 ′ and the external thread element  221 ′. While the return spring  259 ′ acts on a control bolt or cam  238 ′, the memory spring  237 ′ pushes on a counter-bolt  265 ′, whose front end  266 ′ in turn pushes against the front end  255 ′ of the control bolt  238 ′. Depending on the temperature prevailing in the connector  11 , either the front end  266 ′, of the counter-bolt  265 ′ or the front end  225 ′ of the control bolt  238 ′ are located in the axial bore  253 ′ of the external thread element  221 ′. In the case represented in FIG. 7, free-wheeling between the screw cap  214 ′ and the external thread element  221 ′ is provided at the predetermined unacceptably high temperature, since with its force caused by the high temperature the memory spring  237 ′ pushes the control bolt  238 ′ back against the force of the return spring  259 ′. The memory spring  237 ′ with the counter-bolt  265 ′ is maintained in a receiver housing  267 ′ disposed at the edge of the external thread element  221 ′. It is understood that here, too, instead of one temperature-dependent control element at a defined location of the circumference of the closure cap  210 , several such temperature-dependent control elements, distributed over the circumference, can be provided. 
     In the eight exemplary embodiment in accordance with the present invention of a closure cap  310  represented in FIG. 8, the temperature-dependent control element embodied as the memory spring  337  is disposed axially centered inside the valve  315 . A collar  357  of a connecting bolt  373  is axially movable in a cup-shaped element  371  of the valve  315  disposed above an interior valve seal  365 , wherein the connecting bolt  373  is acted upon by the memory spring  337  between its collar  357  and the bottom of the cup-shaped element  371  and projects through a lead-through  372  covering the cup-shaped element. The horizontal connecting leg of a control element  338  bent in a U-shape rests on the portion of the axial bolt  373  penetrating through the lead-through  372  and is acted upon by a return spring  359 , which on its other end is supported on the interior surface  24  of the screw cap  314 . With their finger-like ends  376 , lateral legs  375  of the control element  338 , projecting as far as the external thread element  321 , are located opposite an axial bore  353  in the external thread element  321 , and at normal temperature in the connector  11  enter it for a connection, fixed against relative rotation, between the screw cap  314  and the external thread element  321 . At the predetermined high temperature value the memory spring  337  expands against the force of the return spring  359 , so that the axial bolt  373  pushes the control element  338  against the force of the return spring  359  upward in the direction toward the inner surface  24  of the screw cap  314 , and in the course of this the finger-like ends  376  of the control element  338  come free of the axial bores  353 . Now the screw cap  314  turns idly with respect to the external thread element  321 . It is understood that the control element  338  can also have more than two lateral legs  375 , i.e. that it can be star- or cross-shaped, for example. 
     In the ninth exemplary embodiment in accordance with the present invention of a closure cap  310 ′ represented in FIG. 9, the memory spring  337 ′ is on the other side, viewed from the direction of the screw cap  314 ′, of the inner valve seal  365 ′. To this end the axial connecting bolt  373 ′ penetrates the seal  365 ′, so that the collar  357 ′ of the bolt  373 ′ is maintained axially movable inside the cup-shaped seal  365 ′. A shell-shaped sealing cuff  366 ′, on which the shell  366 ′ is indirectly supported, is provided facing away from the lead-through of the bolt  373 ′ through the seal  365 ′. The manner of operation of this ninth exemplary embodiment corresponds to that of the eighth exemplary embodiment. 
     In the tenth exemplary embodiment of the present invention of a closure cap  410  represented in FIG. 10, the temperature-dependent control element  437  of the temperature-dependent unscrewing safety element  420  has been placed into the connector  11  of the respective reservoir, by means of which it is achieved that at a predetermined high temperature value a blockage, i.e. a connection fixed against relative rotation, between the screw cap  414  and the connector  11  of the reservoir is achieved. Here, too, the temperature-dependent control element is formed by a memory spring  437  which, as in the exemplary embodiment of FIG. 6, together with a return spring  459  surrounds an inner or outer end  455 ,  456  of a control bolt  438 . The lower or inner spring in FIG. 10 is the memory spring  437 , one end of which is supported at the bottom of an axial recess  458  in the connector  11  and on the other end at a collar  457  of the control bolt  438 . On the other hand, one end of the reset or return spring  459  is supported on the collar  457  and the other end on an annular inset  460  of the axial recess  458 . The screw cap  414  has an axial blind bore or recess  453 , accessible from its interior, into which the tip of the front end  455  of the control bolt  438  can enter for a connection, fixed against relative rotation, and thus a blockage of the screw cap  414 . This occurs at high temperatures, in which the memory spring  437  is expanded against the force of the return spring  459  and in the process pushes the control bolt  438  into the axial blind bore  453 . It is also possible here to provide several control elements distributed over the circumference of the connector  11  in place of one temperature-dependent control element. 
     The eleventh exemplary embodiment of the present invention of a closure cap  410  represented in FIG. 11 essentially corresponds to the exemplary embodiment in FIG. 10, with the exception, that the memory spring  437 ′ and also the return spring  459 ′ have been displaced in the connector  11  further down or inward in the direction toward the water level of the respective reservoir. This only requires an extension of the control bolt  438 ′. 
     Thus, by means of the exemplary embodiments of the closure cap  10 ,  10 ′,  10 ″,  110 ,  110 ′,  210 ,  210 ′,  310 ,  310 ′,  410  or  410 ′, it is either achieved that the connector with the external thread can no longer be moved by the screw cap when a predetermined excessively high temperature occurs in the connector  11  or the compensator reservoir, since because of the deformation of the temperature-dependent control element, the control plate or the temperature-dependent control element itself are released from the connection, fixed against relative rotation, with the external thread connector of the closure cap, or achieves a lock, fixed against relative rotation, between the screw cap and the reservoir connector. At normal temperature the temperature-dependent control element returns into its initial position again, so that in the first case the connection, fixed against relative rotation, between the screw cap and the external thread connector is again made, and in the second case the lock is released. 
     In another exemplary embodiment of the present invention, not represented in the drawings, the temperature-dependent control element is not provided between the screw cap and the external thread connector, but between the screw cap and the valve housing. In this case the external thread connector is of one piece with the screw cap, and the valve housing is disposed inside the compensator reservoir connector  11 , fixed against relative rotation, but movable in the axial direction. In this case the function is as follows: At ambient temperature the valve housing is rotatable relative to the screw cap or the external thread connector, wherein during unscrewing of the closure cap the valve is taken along in the axial direction. However, if overpressure occurs while the closure cap is screwed on, the temperature-dependent control element cause a connection, fixed against relative rotation, or locking between the screw cap and the valve housing, which itself is held fixed against relative rotation in the connector  11 . The screw cap can therefore not be turned. 
     Although defined types of bimetal or memory springs have been represented and described above, it is understood that other shapes, such as flat, helical, straight forms or the like, are also possible for either the bimetal spring or also the memory spring. 
     The steps in accordance with the present invention can also be realized in connection with a closure cap which is connected in the manner of a bayonet closure with a connector. In this case the element described as a thread element is embodied as a plug-and-turn element, while the screw cap is embodied as a plug-and-turn cap. 
     It is understood that a closure cap of this type can be used not only with components of radiators or cooling systems, but also with components of heating systems.