Abstract:
The invention relates to a closing cap ( 10 ) for the fixed tubing of a motor vehicle radiator, comprising an inner part ( 14 ) with a flow connection means between the inside and the outside of the container, as well as a distributing mechanism for freeing and closing the flow connection means. A valve body ( 22 ) of the distributing mechanism ( 11 ), which can be reciprocated, is compressed under pre-stress towards the inside of the container against a sealing seat ( 21 ) at the inner part ( 14 ) of the cap, so that said valve body can be lifted from said sealing seat ( 21 ) when a threshold value of the pressure inside the container is exceeded. In order to produce a closing cap ( 10 ) which does not open in case of overpressure resulting from heat accumulation and which ensures that the container is protected in case of a continuing increase of pressure, in a simple and cost-effective way, the invention provides for in-use controlled adjustment of the pre-stress used for compressing the valve body ( 22 ) against the sealing seat ( 21 ).

Description:
FIELD OF THE INVENTION 
     The present invention relates to a pressure cap for a stationary filler neck of a tank, in particular a motor-vehicle radiator, according to the generic part of Claim  1 . 
     BACKGROUND OF THE INVENTION 
     In known pressure caps, for example for motor-vehicle radiators, the valve body of the valve arrangement is loaded in a constant manner in such a way that the flow connection between the inside and the outside of the radiator is opened when the pressure inside the radiator exceeds a certain threshold value. This then causes the air containing coolant to escape, Such simple pressure caps facilitate pressure equalization during operation of the motor vehicle when the pressure rises due to heating of the coolant in the radiator and when a critical pressure is exceeded. This is a safety aspect. However, in motor-vehicle radiators, overpressure due to accumulated heat also rises when the vehicle is not running, i.e. when the engine is turned off, and with the above named simple pressure caps, the valve arrangement is also opened completely, which poses the danger that a large amount of coolant escapes or evaporates, or that the radiator may even boil until empty, which means that coolant has to be replenished often. For that purpose, multi-stage pressure caps have been developed (DE 41 07 535 C1) which reduce the overpressure produced by accumulated heat differently than a considerably higher overpressure caused by malfunctioning. However, such a pressure cap is relatively expensive because it contains several contra-rotating valve-body parts and several sealing and counter-sealing surfaces. Furthermore, coolant is spilled in case of overpressure after the vehicle engine is turned off and the pressure is reduced. In that case, an absolute loss of water can be prevented only if an equalizing tank is provided to catch the liquid, or if an additional circulating pump is used which prevents the pressure from rising by circulating the coolant when the engine is turned off. However, this is expensive. 
     BRIEF SUMMARY OF THE INVENTION 
     It is therefore the objective of the present invention to create a pressure cap of the type mentioned above, which on the one hand simply and cost-effectively prevents the opening due to overpressure produced by accumulated heat, and which on the other hand ensures that the tank is protected when the pressure rises further. 
     This objective is reached with a pressure cap of the type mentioned above which has the characteristics named in the detailed description. 
     The measures according to the invention achieve that the pre-stress exerted on the valve body can be controlled in such a way, depending, for example, on the operation of the motor vehicle, that the pressure cap does not open in case of a defined rate of overpressure produced by accumulated heat. This prevents the escape of air mixed with coolant during that “operating phase”. Additional components such as equalizing tanks or circulating pumps are not required. Overpressure can be reached by cooling the vehicle&#39;s radiator during standstill. However, the pressure cap will open while the pressure rises above a certain safety threshold, to ensure that the cooling system is not damaged by bursting or leakages including the connector hoses. For example, the pre-stress means can be adjusted to two stages, i.e. to an opening pressure according to normal operation and a higher opening pressure which responds to pressure increase in case of accumulated heat. 
     The pre-stress means for the valve body can be controlled in various ways, according to the characteristics named in the detailed description. If the pre-stress means is controlled by negative pressure or overpressure, the set point can be picked up directly from the engine compartment of Otto engines or diesel engines. On the other hand, if an electrical signal is to be provided, it can be directly triggered, for example, when the ignition is on. 
     A preferred design for the pre-stress means of the valve body results from the characteristics named in the detailed description. 
     The power between the drive and the pressure piece [Druckstück] can be transmitted either directly or via a power transmission element, i.e. a type of transmission gear. Furthermore, it is possible to have a straight-line connection or a connection via an element reversing the drive direction. Preferred designs of the element reversing the drive direction are named in the detailed description. 
     The type and design of the drive can also vary, as is shown by the characteristics in the detailed description. 
     In a particularly advantageous way, the drive can be accommodated in the cover handle. A combination of the pressure cap and a safety device to prevent release at excess temperature is apparent from the detailed description. 
     Further details of the invention are described below, where the invention is described with reference to the embodiments shown in the drawings. The drawings show: 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 and 2 a diagrammatic longitudinal sectional view of the pressure cap for motor vehicle radiators according to a first embodiment of the present invention in a first and second active position, respectively, 
     FIGS. 3 and 4 a view corresponding to that in FIG. 1 and 2, but according to a second embodiment of the present invention and 
     FIGS. 5 and 6 a view corresponding to that in FIG. 1 and 2, but according to a third embodiment of the present invention; 
     FIGS. 7 and 8 a view corresponding to that in FIG. 1 and 2, but according to a fourth embodiment of the present invention and, 
     FIGS. 9 and 10 a top plan view, partly in a section according to arrow IX in FIG.  7  and according to line X—X in FIG. 9, respectively. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The pressure cap  10  or  10 ′ or  10 ″ or  10 ′″ shown in the drawings by means of three embodiments is provided with an overpressure valve arrangement  11  and is controlled in such a way that the opening pressure of the overpressure valve arrangement  11  can be adjusted to two steps by means of a drive  15 ,  15 ′,  15 ″ or  15 ′″, namely to an opening pressure taking into account the motor vehicle radiator overpressure at normal operation, and to an opening pressure which results from the development of accumulated heat when the vehicle engine is Turned off. 
     According to FIG. 1 and 2, the pressure cap  10  has an outer part  12  with a handle  13  and an outer threaded part  17  for screwing and unscrewing the pressure cap  10  to and from the opening of a motor vehicle radiator (not shown) or other tank, and an inner part  14  which can be inserted via an O-ring  16  as a seal into the filler neck of the motor vehicle radiator or other tank. The outer part  12  is connected to the inner part  14  either rigidly or lockably and rotatably, by an anti-rotation means (not shown here) that responds either to pressure or to temperature (FIG.  7  and  8 ). It goes without saying that the outer part  17  can also be provided with a bayonet connection. 
     The cylinder-shaped inner part  14  of pressure cap  10  is equipped with overpressure valve arrangement  11 . It has a bottom  18  and above the bottom a ring edge  19  extending inward, whose Top section is provided with a sealing seat  21  for a valve body  22  of overpressure valve arrangement  11 . The valve body  22  has a central hat-shaped part  23  on whose peripheral flange  24  rests a washer  26 . The hat-shaped part  23  is supported at the bottom  18  by a spring support  27 . The washer  26  is affected by a pressure spring  28  or overpressure valve spring which is supported at the other end in a sleeve  29  which is guided (moving up and down in axial direction) inside a guide cylinder  34  which has an axial stop  31  for sleeve  29 . The guide cylinder  31 , which also accommodates pressure spring  28 , is fastened to that end of inner part  14  that is facing away from the valve body  22 , and it ends a short distance before washer  26 . Thus, the guide cylinder  31  limits any possible opening movement of washer  26  or valve body  22 . Provided between bottom  18  and the inner part  14  are openings  32  leading into inner part  14  of the motor vehicle radiator or other tank. The inner part  14  also has openings  33  on the outer periphery and opposite guide cylinder  31  whose diameter is smaller; these openings  33  are in contact with the outside air. When the valve body  22  is lifted off the sealing seat  21 , a flow connection is established between the inside of the radiator or other tank and the outside air. 
     Movably accommodated in sleeve  29  is a pressure piece  36  whose other end extends into a chamber  39  between outer part  12  and inner part  14  where it has an articulated receptacle  37 . Provided opposite articulated receptacle  37  of pressure piece  36 , on the inside of handle  13 , is a stationary articulated receptacle  38 . The pan-like articulated receptacles  37  and  38  accommodate the cylindrical or spherical ends of a lever arm  42  or  43  or a toggle  41  which together with pressure piece  36  forms a reversal of movement or power. Connected to joint  44  of toggle  41  is a rod  45  of a piston  46  of drive  15  which is movable back and forth within a clutch cylinder  47  according to double arrow A. The piston rod  46  is provided with a centre joint  48  and surrounded by a control spring  49 , which is supported on one end by a collar  41  of piston rod  45  and on the end by the inner end of clutch cylinder  47 . The outside of clutch cylinder  47  is shaped like a sleeve in such a way that it can be connected to a hose (not shown) which represents the negative-pressure line and leads directly or indirectly to the engine compartment. 
     The control of the overpressure valve arrangement  11  of pressure cap  10  functions as follows: When the clutch cylinder  47  is latched into chamber  39  of handle  13  of pressure cap  10 , the control spring  49  is mechanically pre-stressed, so that the spring presses piston rod  45  inward, as shown in FIG. 2, and moves toggle  41  in the direction of arrow A 1 . When the two lever arms  42  and  43  of toggle  41  spread out at an angle, pressure piece  36  is moved in the direction of arrow B 1 , thus pre-stressing the overpressure valve spring  28 . In this manner, valve body  22  is provided with increased opening pressure. 
     Since negative pressure develops when the vehicle engine is started, piston  46  is pulled in the direction of arrow A 2 ., which causes piston rod  45  to pull back the toggle  41 , as shown in FIG.  1 . Thus, under the effect of the pressure spring  28 , the pressure piece  36  is moved upward in the direction of arrow B 2 , so that the pressure spring  28  is somewhat released. This results in a lower opening pressure for valve body  22 , which is normally set at about 1.4 bar. When the vehicle engine is turned off, there is no more negative pressure at piston  46 , which means that the control spring  49  can move toggle  41  back in the direction of arrow A 1 , namely to a stop which lies before dead centre. In that manner, the overpressure valve spring  28  is tight again, resulting in an opening pressure for valve body  22  (according to FIG. 2) that is increased to, for example, 2.0 bar. Now the valve body  22  can withstand the internal pressure of the radiator or other tank which results from the accumulated created when the engine is turned off. 
     When the clutch cylinder  47  is geared down to open pressure cap  10 , for example for replenishing coolant, control spring  49  is released all the way, so that the overpressure valve spring  28  switches by means of its own force as described above to the normal-mode opening pressure such as 1.4 bar. If after the pressure cap is screwed on again, the clutch cylinder  47  is inadvertently not connected to pressure cap  10 , the lower normal-mode opening pressure is automatically maintained, so that the motor vehicle can be operated as before. 
     According to other non-illustrated embodiments of the present invention, drive  15  can be formed, for example, by an appropriately charged membrane such as a domed membrane instead of the piston cylinder arrangement, and/or the pre-stress means can be controlled by overpressure through an appropriate change of the drive and the power-transmission element. 
     FIG. 3 and 4 show an embodiment of the present invention in which the piston cylinder arrangement (drive  15 ) controlled by negative pressure is replaced by an electrically controlled lifting magnet (drive  15 ′). The other components of pressure cap  10 ′ are identical to those of the embodiment according to FIG. 1 and 2, which means that corresponding reference numbers must be used. The tappet  56  of electrically controllable lifting magnet  55  is directly connected to joint  44  of toggle  41 . The function is as follows: The overpressure valve  11  has the basic setting of normal-mode opening pressure such as 1.4 bar. After the pressure cap  10 ′ provided with lifting magnet  55  has been screwed onto the vehicle radiator or other tank, contacts  57  of lifting magnet  55  are electrically connected to a control system such as the ignition. This electrical connection causes a lift movement of lifting magnet  55  in the direction of arrow A 1  and thus a movement of toggle  41  in that direction, whereby tappet  56  or joint  44  is led up to a stop beyond dead centre, as shown in FIG.  4 . This results in a higher opening pressure, such as 2.0 bar, for valve body  22  due to the tightened pressure spring  28 . 
     When the motor vehicle engine is started, lifting magnet  55  receives a control signal via a relay, which causes it to be pulled back, also pulling back toggle  41 . Overpressure valve spring  28  is released due to its inherent force, which means that valve body  22  has reached normal-mode opening pressure again. 
     When the vehicle engine is turned off, lifting magnet  55  received a control signal via the relay in question, so that the position according to FIG. 4 is reached again and the internal pressure of the tank, increased by accumulated heat, is intercepted. 
     If the electric connection is pulled off to open pressure cap  10 ′, lifting magnet  55  released toggle  41  due to its lifting movement in the direction of arrow A 2 , so that the overpressure valve spring assumes its position with the lower normal-mode opening pressure. This applies correspondingly if it is inadvertently forgotten to connect lifting magnet  55  electrically with the control relay when pressure cap  10 ′ is screwed on. 
     In the embodiments shown in FIG. 3 and 4, the electrically controlled lifting magnet  55  can be replaced by an electrical drive  15 ′ in the form of an electric motor whose threaded drive spindle is coupled in a drive-friendly manner with a parallel toothed rack or a coaxial threaded sleeve, which toothed rack or threaded sleeve is connected to joint  44  of toggle  41  at the end facing away from the drive spindle. 
     In the embodiments shown in FIG. 1 and 2 or  3  and  4 , drive  15  or  15 ′ is arranged in a position perpendicular to the extent of pressure spring  28 , and its circumference protrudes from handle  13  of pressure cap  10 . 
     In the embodiment of the present invention shown in FIG. 5 and 6, drive  15 ″ is arranged flush, i.e. axially aligned concentrically with pressure spring  28 , and it protrudes at the front of handle  13  of pressure cap  10 ″. Thus, in this embodiment, there is no toggle, which means that drive  15 ″ acts directly upon pressure piece  36 ″ and engages in same. In this embodiment, drive  15 ″ is a rotatable lifting magnet  55 ″ whose electrical contacts  57 ″ lead outside and whose threaded spindle  58  engages in the correspondingly formed pressure piece  36 ″. Otherwise, this embodiment works as described for the embodiment according to FIG. 3 and 4. 
     It goes without saying that a rotatable lifting magnet can also be used in the embodiment according to FIG. 3 and 4, and that a simple lifting magnet can also be used in the embodiment according to FIG. 5 and 6. 
     If in the embodiments according to FIG. 1 to  5  a toggle  41  is used as the power transmission element, it goes without saying that other power transmission elements such as eccentric cams, etc. can be used as well. 
     The fourth embodiment illustrated in FIG. 7 to  10  shows a pressure cap  10 ′″ with a design similar to that of pressure cap  10  according to FIG. 1 and 2. In this embodiment, handle  13 ′″ of the outer part  12 ′″ of pressure cap  10 ′″ is provided with a horizontal cylinder recess  47 ′″ which can be pressure-sealed at its open end by means of an easily removable coupling element  61  to which a hose  62  is connected. Inside cylinder recess  47 ′″ , a piston  46 ′″ moves back and forth in the direction of the double arrow A. Between coupling element  61  and the opposite end of piston  46 ′″ a control spring  49 ′″ is provided. The end  63  of piston  46 ′:, which faces away from coupling element  61 , runs through a hollow cylinder—provided by a blind hole drilled in—and via a coaxial cylindrical projection  64  at the other end of handle  13 ′″. Projection  64  is surrounded by a pressure spring  65  supported on one end by end  63  of piston  46 ′″ and on the other end inside handle  13 ′″. In a longitudinally central sector. a lever  42 ′″ is in a slot-shaped recess  66  of piston  46 ′″. End  67  of lever arm  42 ′″, which protrudes from piston  46 ′″ toward inner part  14 , is pivotably arranged in a recess  37 ′″ of pressure piece  36 ′″. As in the first embodiment, pressure piece  36 ′″ is supported by pressure sleeve  29  which in turn presses against valve body  22  via pressure spring  29 . The inner U-shaped end  68  of lever arm  42 ′″ surrounds a transverse stationary bearing pin  69  arranged close to the top section of the cylinder wall which faces away from pressure piece  36 ′″. It goes without saying that instead of the bearing pin, a bearing ball can be provided to support a corresponding cap of lever  42 ′″. Lever  42 ′″ creates a power-transmitting and direction-changing connection between piston  46 ′″ and pressure piece  36 ′″, so that (as shown in FIG. 7 and 8) when piston  46 ′″ moves as indicated by double arrow A, pressure piece  36 ′″ is moved in the direction of double arrow B, as in the embodiments described above. The function of this embodiment is the same as that of the embodiment shown in FIG. 1 and 2, i.e. the position shown in FIG. 7 results when negative pressure exists while the engine is running and also when coupling element  61  is removed from cylinder recess  47 ′″, while the position shown in FIG. 8 results if the engine was just turned off leading to excessive temperature or overpressure. 
     FIG. 9 and 10 show an embodiment of an easily releasable locking means for the coupling element  61  (provided with hose  62 ) on handle  13 ′″ or in cylinder recess  47 ′″. According to this, handle  13 ′″, as an extension of cylinder recess  47 ′″ has on the outside a protruding hook  71  across which a finger  72  on coupling element  61  catches and locks. Fastened to coupling element  61  is a wire spring  73 , the central section of which engages in a slot  75  of hook  71  when the spring is in a released state. By applying pressure to the free end  76  of wire spring  73 , it, or its central section  74 , can be moved out of slot  65  in hook  71 , so that the coupling element  61  can come free of handle  13 ′″ When coupling element  61  is plugged into cylinder recess  47 ′″, piston  46 ′″ is placed into the position shown in FIG. 8, but piston  46 ′″ is returned to the position shown in FIG. 7 when coupling element  61  is uncoupled from handle  13 ′″. 
     During this, control spring  49 ′″ remains at the corresponding end of piston  46 ′″. 
     FIG. 7 and 8 also show pressure cap  10 ′″ in combination with an anti-rotation means  80 , which responds to temperature, between outer part  12 ′″ and an engagement element  81  (provided with an outer threaded part  17 ), to which overpressure valve arrangement  11  is connected. Anti-rotation means  80  is provided with a coupling element in the form of a coupling pin  82  arranged inside engagement means  81  on a section of the circumference. Opposite the axially movable coupling pin  82 , a blind hole  84  is drilled axially into a wall  83  of handle  13 ′″. To provide the anti-rotational coupling of handle  13 ′″ and engagement element  81 , the corresponding end  90  of coupling pin  82  is inside blind hole  84 . In that position, pressure cap  10 ′″, can be removed from the radiator&#39;s filler neck. Coupling pin  82  can move up and down thanks to a bearing ring  88  held in engagement element  81  and is affected by a control arrangement that responds to temperature and which consists of a memory spring  86  and a back-pressure spring  87 . Memory spring  86  is supported at one end by the underside of this bearing ring  88  and at the other end by a shoulder  89  of coupling pin  82 . On the other hand, back-pressure spring  87  is supported on the opposite upper side of bearing ring  88  and engagement element  81 . If the memory spring expands at a temperature that is too high for the pressure cap to be removed, coupling pin  82  is moved downward until its end  90  comes out of blind hole  84 . This uncoupling allows handle  13 ″ to perform a hollow turn in relation to engagement element  81 . 
     Furthermore, such a pressure cap can also be used for equalizing tanks of cooling or heating systems, etc.