Abstract:
A pressure cap for a fixed neck of an automobile radiator is provided with an outer cap component and with an inner cap component which has a flow connection between the inside and the outside of the tank and a valve arrangement for releasing and blocking the flow connection. The invention allows the bias of the pressure-relief valve body to be adjustable while the temperature inside the tank can be measured directly and the action of the pressure-relief/vacuum valve body remains constant, it is provided that the bias with which the pressure-relief valve body is pressed against the sealing seat can be adjusted by means of a thermal drive in the form of an expansion-material membrane capsule which has a temperature sensor that passes through the cap axis and extends into the tank&#39;s neck, and it is also provided that the vacuum valve body is arranged eccentrically in relation to the cap axis.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a pressure cap for fixed neck of a tank, in particular automobile radiators, provided with an outer cap component, an inner cap component and a valve arrangement. The inner cap component has a flow connection between the inside and the outside of the tank. The valve arrangement releases and blocks the flow connection. For this purpose, the valve arrangement has an axially movable pressure-relief valve body which is pressed against a sealing seat on the inner cap component with a bias controlled by the operating pressure in the tank. 
   BACKGROUND OF THE INVENTION 
   In a pressure cap known from DE 197 53 597 A1, the bias of the pressure-relief valve body can be controlled by the operating pressure and adjusted such that a piston-activated toggle or electric lifting magnet acts upon a pressure piece, and where a compression spring is provided between the pressure piece and the pressure-relief valve body. In the former case, the bias depends on the operating pressure of the automobile engine, and in the latter case, on an electric control or the ignition. 
   It has also been suggested before to control the bias of the pressure-relief valve body depending on the temperature inside the tank. For that purpose, the temperature-dependent control unit in the inner cap component is arranged in a space between the pressure-relief valve body and the outer cap component. This position of the temperature-dependent control element is disadvantageous for measuring and transmitting the temperature prevailing inside the tank because it is relatively far away from the inside of the tank and can therefore measure the temperature prevailing therein only with delay and with a considerable tolerance. 
   With the two above named types of pressure caps, the valve arrangement is provided with a vacuum valve body which is positioned concentric to and substantially within the pressure-relief valve body. 
   It is also known from DE 197 53 597 A1 to design the outer cap component with a locking element that can be incorporated in the neck, and a handling element which call be rotated in relation to the neck, whereby between both of these, an anti-rotation means is provided that can be engaged and disengaged. The anti-rotation means is embodied in a place eccentric to the longitudinal axis by a bolt which is loaded with a temperature-dependent bimetal or memory spring. In this case, too, the problem consists of the delayed and imprecise measuring of the temperature conditions inside the tank. 
   SUMMARY OF THE INVENTION 
   It is the object of the present invention to create a pressure cap of the type mentioned above for a fixed neck of a tank, in particular for automobile radiators, in which the bias of the pressure-relief valve body can be adjusted as the temperature inside the tank is measured directly and while the action of the pressure-relief/vacuum valve assembly remains constant. 
   This objective is achieved with a pressure cap of the type mentioned above for a fixed neck of a tank, in particular for automobile radiators, wherein the bias with which the pressure-relief valve body is pressed against the sealing seat is adjustable by means of a thermal drive in the form of an expansion-material membrane capsule which is provided with a temperature sensor which passes in the direction of the pressure cap axis and extends into the neck of the tank. The vacuum valve body of the valve arrangement is arranged eccentrically with respect to the pressure cap axis. 
   With the measures according to the invention it is achieved that the temperature-dependent drive element in the form of an expansion element can measure the temperature inside the tank directly and without delay. The temperature conditions inside the tank can be transmitted via the shortest and most direct route along the cap axis without having to accept the disadvantages caused by the effect of the pressure-relief valve body and in particular the effect of the vacuum valve body. 
   It is practical to provide the vacuum valve body at a distance from the pressure-relief valve body on the floor of the inner cap component. For this purpose the vacuum valve body is arranged on the underside of the inner cap component facing away from the pressure-relief valve body and releasably covers a vacuum channel in the floor of the inner cap component. 
   A simple holder is provided and the vacuum valve body is supported and arranged in a simple fashion on the floor of the inner cap component. For this purpose the floor of the inner cap component is covered by a further cap by which the vacuum valve body is supported, the vacuum valve body being axially movable against the effect of a compression spring, and the vacuum valve body being formed by an umbrella valve whose middle part is held in a fixed position between the floor of the inside cap component and a further cap and whose umbrella part covers the vacuum channel. 
   To create an anti-rotation means that reacts immediately and without delay, the outer cap component is provided with a locking element for the tank&#39;s neck, and with a handling element which can be rotated in relation to same, characterized in that the membrane capsule acts at one end upon the bias means of the pressure-relief valve body and at the other end upon an anti-rotation means between the handling element and the locking element. With this, it is achieved that the temperature measured immediately by the sensor and transmitted to the expansion element is used for the direct control of the anti-rotation means. 
   Advantageous embodiments of the anti-rotation means result from the anti-rotation means being on the side facing away from the membrane capsule and being loaded with a compression spring, by the anti-rotation means being formed by a check plate with vertical claws, whereby the check plate is axially movable in relation to the handling element but non-rotatable, and whereby the claws can be engaged in and disengaged from recesses in the locking element, by the membrane capsule being arranged between the check plate of the locking element and an axially movable guidance element between which and the pressure-relief valve body a compression spring is provided, and by the guidance element being surrounded by a temperature sensor in the form of a rod. 
   Advantageously, the temperature sensor is sealed against the pressure-relief valve body. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further details of the invention are described below, where the invention is described in with reference to the embodiments shown in the drawings, where: 
       FIG. 1  shows a schematic view of a lengthwise section of a pressure cap for an automobile radiator according to a first embodiment of the present invention; 
       FIG. 2  shows an interior view of the inner cap component without the pressure-relief valve body along line II—II of  FIG. 1 ; 
       FIG. 3  shows a view corresponding to  FIG. 1 , but only of the inner cap component, and the vacuum valve body according to a second embodiment of the present invention; and 
       FIG. 4  shows a view corresponding to  FIG. 1 , but only of the inner cap component, and the vacuum valve body according to a third embodiment of the present invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The pressure cap  10 ,  110  or  210  shown in the drawings by means of three embodiments is provided with a pressure-relief/vacuum valve assembly  11 ,  111 ,  211  which includes an pressure-relief valve body  12  that is the same in all embodiments, and a vacuum valve body  13 ,  113  and  213 , respectively. The opening pressure of pressure-relief valve body  12  can be adjusted in two stages with a thermal drive  14  that is the same in all embodiments, namely to an opening pressure that takes into consideration the automobile radiator overpressure at normal operation, and to an opening pressure that corresponds to the higher automobile radiator overpressure caused by the accumulated heat when the automobile engine is turned off. 
   According to the drawings, the outer cap component  16  of pressure cap  10 ,  110 ,  210 , which is the same in all embodiments, has a locking element  17  which in this case consists of a male threaded element for screwing and unscrewing the pressure cap to or from the opening of a neck (not shown) of an automobile radiator or other tank, and a handling element  18  which can be rotated against the locking element  17  and can be non-rotatably connected by means of an anti-rotation means  19  that is the same in all embodiments. It will be appreciated that the locking element  17  can also be designed as a bayonet connection instead of a male threaded element. 
   According to  FIG. 1 , the locking element  17  is provided with a diaphragm  21  (with an axial opening) from whose underside a male threaded sleeve  23  extends, and from whose upper side a connecting sleeve  24  extends axially, by whose radial flange  22  the locking element  17  is held rotatable at the handling element  18 , but axially suspended and immovable. On the outer edge, the handling element  18  extends under the flange  22  of connecting sleeve  24  of locking element  17  and is provided in the middle with circular guidance fingers  25  which extend axially inside and between which a compression spring  26  is provided which is supported at one end by the inside of handling element  18  and at the other end by a check plate  27  of anti-rotation means  19 . Check plate  27  is provided on an annular circumference with slots  28  in which the guidance fingers  27  of anti-rotation means  19  engage, such that check plate  27  of anti-rotation means  19  is anti-rotationally connected with handling element  18 . On its outer perimeter, the check plate  27  is provided with claws  29  bent axially downward, which engage in axial grooves  31  of diaphragm  21  of locking element  17  in their initial position according to  FIG. 1 , such that in this position, the anti-rotation means  19  is non-rotationally connected not only with handling element  18 , but also with locking element  17 , thus making it possible for the pressure cap  10  to be screwed to or unscrewed from the neck (not shown). As will be shown below, the anti-rotation means  19  is movable against the effect of compression spring  26  such that the claws  29  are disengaged from the grooves  31 , such that the anti-rotation between the anti-rotation means  19  and the locking element  17  is eliminated, which leads to the idling of handling element  18  on the locking element  17  and prevents the unscrewing of the pressure cap from the neck. 
   According to  FIG. 1 , suspended from the locking element  17  of outer cap component  16  is an inner cap component  15  holding the pressure-relief/vacuum valve assembly  11 , such that the inner cap component  15  is axially immovable against the outer cap component  16 , but rotatable in circumferential direction. The inner cap component  15  is provided with a valve pot  36  which is suspended from the locking element  17  and has radial flow-through openings  37 . The floor ( 38 ) of valve pot  36  is provided with a central opening  39  around which is provided an annular sealing surface  41  that is axially higher toward the inside. Bearing directly on this annular sealing surface  41  is the pressure-relief valve body  43 —with the radially outer sealing surface  42  of a sealing membrane  43 —under the effect of a compression spring  44  whose bias is adjustable. The pressure-relief valve body  12  is approximately hat-shaped, and the sealing membrane  43  is accommodated within its brim which is axially bent down toward the floor ( 38 ). At the other end, the compression spring  44  is supported by an axially movable pressure sleeve ( 46 ) which faces away from the pressure-relief valve body  12  and is supported by a fixed inner guidance sleeve  47  of inner cap component  15 . 
   The axial pressure sleeve  46  is acted upon via a freely supported pressure ring  48  by the thermal drive  14  which in the embodiments shown is designed as an expansion-material membrane capsule  50 . The membrane capsule  50  is arranged between the diaphragm  21  of locking element  17  and the check plate  27  of anti-rotation means  19 . An external ring flange  51  of membrane capsule  50  bears on a ring lug  52  of locking element  17 . The upper face of the central expandable section  53  of membrane capsule  50  lies on a central indentation of check plate  27 , and its underside lies on pressure ring  48 . The expansion-material membrane capsule  50  is connected in mid axis with a sensor rod  54  which passes through pressure-relief valve body  12  and is long enough to extend into the fixed neck of the tank or automobile radiator where it can directly measure the temperature prevailing therein. Sensor rod  54  has the effect of a capillary, is closed at its free end and connected inside the tank with membrane capsule  50 . Sensor rod  54  is filled with the same expansion material as membrane capsule  50 . Held as a seal between a ring shoulder  56  of sensor rod  54  and a fixed washer  57  is the radially inner sealing surface  58  of sealing membrane  43  of pressure-relief valve body  12 . In the upper section, sensor rod  54  serves as a guide for pressure sleeve  46  which surrounds it and for pressure ring  48 ′ in the lower section, which has a smaller diameter, sensor rod  54  passes through central opening  39  in valve pot floor  38  such that a concentric annular opening  39  remains. 
   According to the various embodiments, the vacuum valve body  13 ,  113 ,  213  is arranged eccentrically to the longitudinal axis of pressure cap  10 ,  110 ,  210 , on the underside of the floor  38  of valve pot  36  in a place where the annular section is surrounding the central opening  39 . 
   In the embodiment according to  FIG. 1 , the vacuum valve body  13  is formed as an umbrella valve  61  whose central main section  62  is plugged over a pin which protrudes from the underside of floor  38 . The radially outer annular sealing surface  65  of the circular umbrella rim  64  is biased against a sealing surface of the underside of floor  38 . As shown in  FIG. 2 , two connecting channels  67  and  68 , which lie opposite each other and pass through floor  38  of valve pot  36 , lead into space  66  between the main section  62  and the annular sealing surface  65 . Pulled over floor  38  of valve pot  36  is another cap  69  which is held by the inner cap component  15  and which is provided with an axial through-hole  71  around the corresponding section of sensor rod  54  and to whose inside floor the main section  62  of umbrella valve  61  is adjoining. 
   In case of a vacuum in the tank, umbrella rim  64  with its annular sealing surface  65  lifts off the sealing surface of valve pot floor  38 , such that a flow connection results through opening  71  and channels  67 ,  68  as well as the radial openings  37  toward the outside. 
   In the embodiment according to  FIG. 3 , the vacuum valve body  113  is formed by an axially movable body element  161  which is arranged in a stepped blind hole  174  of a cap  169  held at the inner cap component  115 . Through the effect of a compression spring  173  inside the stepped blind hole  174 , the raised annular sealing surface  175  of valve body element  161  is pressed against a corresponding sealing seat on the underside of floor  138  of valve pot  36 , where it acts as a seal. Within the annular sealing surface  175  of valve element  161 , at least one through-hole  176  is provided in floor  138  of valve pot  36 . In case of a vacuum inside the tank, the body element  161  of vacuum valve body  113  is lifted off the sealing seat on floor  138  against the effect of compression spring  173 . 
     FIG. 4  shows an embodiment of a vacuum valve body  213 , in which a ball element  261  is provided which is held within an axial recess  274  in the floor  238  of valve pot  36 . The ball element  261  is acted upon by a compression spring  273  such that it is pressed against a sealing seat around a through-channel  267  in the floor of recess  274 . On the other end, the undercut recess  274  is also provided with a through-hole  276  around which compression spring  273  is supported. Here, too, in case of a vacuum, the ball element  261  is lifted off the sealing seat against the effect of compression spring  273  to release recess  274 . 
   As  FIG. 1  shows, the thermal drive  14  in the form of membrane capsule  50  expands axially in the middle when the engine is running, which has the effect that due to the still excessive force of bias spring  44  of pressure-relief valve body  12 , the membrane capsule  50  expands upwards in the direction of Arrow B 2 , and the anti-rotation means  19  or check plate  27  lifts off so far that its claws  29  come free of the grooves  31  of locking element  17 . In that state, the anti-rotational connection between the locking element  17  and the handle element  18  is broken. When the engine is turned off, the temperature continues to rise due to accumulated heat in the tank and is transmitted via the sensor rod  54  to the membrane capsule  50 , with the effect that the membrane capsule  50  continues to expand in axial direction. Due to the fact that the membrane capsule  50  adjoins fingers  25  of handling element  18 , the membrane capsule  50  expands downward in the direction of Arrow B 1  against the effect of compression spring  44  and acts upon pressure ring  48  and the axial pressure sleeve  46 , such that the increased biasing force of compression spring  44  causes the opening pressure for the pressure-relief valve  12  to increase to a higher value such as 2.0 bar. In this state, the idling connection between handling element  18  and locking element  17  is maintained as well, since check plate  27  continues to remain in its uppermost position. Only after a complete cool-down is the initial position as shown in  FIG. 1  reached again.