Patent Application
20050087532
The present invention relates to a lid for a tank of a fluid system such as a cooling water circuit of an automotive vehicle, the lid being preferably adapted to be screwed to a neck of the tank. The present invention is also applicable to lids of tanks of other fluid systems, such as cooling water circuits of a combined heat and power machine or another technical apparatus, wherein the fluid is heated to a high temperature, so that it may be dangerous to open a service or inspection lid of the tank.
When the lid of an expansion tank of an automotive vehicle is opened after the engine of the automotive vehicle has been running for some time and the cooling water has been heated thereby, persons might get seriously injured by hot coolant or coolant steam squirting out therefrom. To reduce this risk, it is known to lock the lid by means of a locking nose so that coolant steam can escape in a first opening position of the lid before the lid is fully opened. However, if the risk is not known, the lid may be rapidly opened to such an extent that scalds may occur after all.
It is the object of the present invention to further develop a lid for a tank of a fluid system of the above-considered type in such a manner that endangerment of persons by a hot coolant or coolant steam squirting out therefrom is reliably prevented.
According to the invention this object is achieved by the features of patent claim 1. Advantageous developments of the invention are characterized in the sub-claims.
According to the invention the lid is composed of two lid members that are captively secured to one another. The lid of the invention consists of an inner lid member which can be screwed to the neck of the tank and is preferably provided for this purpose on a substantially cylindrical inner wall with a thread that cooperates with a corresponding external thread of the neck of the tank, and of an outer lid member which covers the inner lid manner approximately in the form of a bell or mushroom and contains an upper lid wall and a circumferential wall which is integrally connected thereto and is gripped for rotating the lid. A coupling means is formed between the two lid members, the coupling means containing a medium that below a predetermined temperature or a predetermined temperature range is of such a consistency that the medium establishes a non-rotational connection between the outer lid member and the inner lid member while the medium above the predetermined temperature or predetermined temperature range assumes a consistency in the case of which the outer lid member is rotatable relative to the inner lid member. This means that the medium is so hard or firm or stiff at the temperatures at which the lid can be opened without any risk of fluid squirting out from the tank that the coupling means couples the two lid members together for joint rotation while from a predetermined temperature onwards the medium is so soft, flexible or even liquid that the inner lid member screwed onto the neck of the tank cannot be carried along when the outer lid member is rotated. A number of substances are suited as the medium, for instance a low-melting metal such as a bismuth alloy, wax or plastic materials having the above-mentioned properties.
It is ensured by the configuration of the lid according to the invention that the container of the fluid system cannot be opened when the fluid contained therein reaches or exceeds a predetermined temperature. When the fluid has cooled down, the coupling medium solidifies such that the outer lid member can carry along the inner lid member for joint rotation.
In further details of the present invention, the outer lid member and the inner lid member define an annular coupling chamber which is filled with the medium. It must here be ensured through suitable sealants that no medium can exit from the coupling chamber which is composed of wall sections rotatably arranged relative to one another. To this end internally lubricated O-rings, for instance, may be arranged that have a reduced friction coefficient and prevent the exit of the medium and the ingress of air into the coupling chamber, whereby in the case of a metallic medium its oxidation is prevented.
Furthermore, projections and/or recesses are formed on the inner lid member and the outer lid member in the area of the coupling chamber. Preferably, the wall sections of the inner lid member and the outer lid member which define the coupling chamber are provided with attachments or teeth that project into the coupling chamber. Said teeth are distributed preferably uniformly over the circumference and extend essentially over the whole height of the coupling chamber. The two rows of teeth should here be opposite to one another such that only a small space remains between the free ends of the teeth. The size of the projections or teeth, the size of the spaces, etc. must here be matched to the strength characteristics of the medium used.
Should it become necessary to open the lid of the invention despite excessively high temperatures inside the tank, for instance in a garage, the lid can be cooled suddenly, for instance by cold water, so that the medium hardens in the annular coupling such that the two lid members are coupled for joint rotation.
Further details of the invention will become apparent from the following description of a preferred embodiment and from the drawing, in which:
The expansion tank 1 designated with reference numeral 1 on the whole, of which only a small portion is shown, contains a tank neck 2 with an external thread 3 that is in engagement with an internal thread 4 of an inner lid member 5. Said inner lid member 5 is captively put together with a separate outer lid member 6 that covers the inner lid member 5 and surrounds it on the outside in the manner of a bell or mushroom. A closing section which is tapered downwards in steps and which is seated in the tank neck 2 and sealed relative thereto with three O-rings 9 is centrally formed on the upper wall 7 of the outer lid member 6. When the lid composed of the inner lid member 5 and the outer lid member 6 is rotated into the opening position, which will be still be described further below, the O-rings 9 which are seated in annular grooves 10 of the closing section 8 will be entrained upwards, where they lose their sealing effect on the larger diameter areas of the tank neck.
On its edge that is the upper one in the installed position, the inner lid member 5 has an annular wall portion 11 which engages into an annular groove 12 of the outer cover member 6. The inner cover member 5 is provided on its lower end portion with a horizontal wall section 13 which engages into an annular groove 14 of the outer lid member 6 and is gripped from below by a nose 15 of the outer lid member, the nose defining the annular groove 14 at the bottom, whereby the outer lid member 6 and the inner lid member 6 are captively held together.
An annular chamber 16 which is defined on the radial inside by a circumferential wall of the inner lid member 5 and on the outside by an inner wall of the outer lid member 6 is positioned between the inner lid member 5 and the outer lid member 6. Both walls have formed thereon teeth 17, 18 extending over the whole height of the coupling chamber 16, the teeth being evenly distributed over the circumference of the walls and being opposite to one another so that a relatively small distance remains between the teeth, the distance being correspondingly larger in the area of the indentations positioned between the teeth. The annular space 19 between the teeth and the intermediate indentations is filled with a medium that is so hard below a predetermined temperature or a predetermined temperature range of e.g. 80° C. to 85° C. that the medium establishes a non-rotational connection between the outer lid member 6 and the inner lid member 5 while it is so soft or liquid above said temperature that the outer lid member 6 is rotatable relative to the inner lid member 5.
This has the consequence that the two lid members form a non-rotational unit below the predetermined critical temperature so that whenever the outer lid member 6 is gripped and rotated on its circumferential surface 20, the inner lid member 5 is unscrewed from the tank neck 2. Within a higher temperature range the inner lid member will not rotate when the outer lid member 6 is rotated, so that any danger caused by exiting liquid or steam is prevented in an absolutely reliable way.
The coupling chamber 16 is sealed at the top and bottom by a respective O-ring which is internally lubricated so that it has a low coefficient of friction.
When despite high temperatures of the tank contents the lid is to be opened e.g. by a car mechanic in a garage, this can be done by rapidly cooling the lid with cold water that is poured over the lid, whereupon the medium in the coupling chamber will solidify right away.
| Number | Date | Country | Kind |
|---|---|---|---|
| 103 49 463.4 | Oct 2003 | DE | national |
