WO2001038184A1

WO2001038184A1 - Closing element for a fuel tank

Info

Publication number: WO2001038184A1
Application number: PCT/EP2000/010663
Authority: WO
Inventors: Mark Jesse; John-Peter Johannsen
Original assignee: Dolmar Gmbh
Priority date: 1999-11-24
Filing date: 2000-10-30
Publication date: 2001-05-31
Also published as: DE29920579U1

Abstract

The aim of the invention is to improve a closing element (100, 101) for a fuel tank, such that said element may be screwed tight to the fuel tank, without any danger of overtightening. Said closing element (100, 101) comprises a thread (14) and at least two tightening pressure surfaces (10, 20), arranged on, by, or in the head (13) of the closing element, upon which a force can be exercised by a tool, to generate the torque to drive the thread. The aim of the invention is achieved, in that overtightening is avoided, or reduced, by an appendix on the tool, whereby the normal to the surface (17) of the tightening pressure surfaces (10) comprises a component, opposed to the drive direction (18) of the thread (14).

Description

description

Closing element for a fuel tank

Technical field

The present invention relates to a closure element for a fuel tank, which has a thread and at least two screw-in pressure surfaces arranged on, on or in the head of the closure element, on which a force can be exerted with a tool to generate a torque driving the thread.

State of the art

Closure elements of the type mentioned are known, for example, in tools with a petrol engine and a petrol tank, in particular chain saws, brushcutters and the like. The closure element is screwed with its thread into a corresponding thread on the tank neck of the fuel tank in order to close the fuel tank against the escape of fuel or vapors. It is often advantageous that the closure element can be attached to the tank neck with a tool, for example if the latter is difficult to access. It may also be possible that a user cannot manually apply the required force with which the closure element has to be screwed tight, or that the closure element or the tank is dirty, so that one would like to avoid direct contact with the hands.

So that the closure element can be tightened with a tool, the head of the element is designed accordingly in order to offer points of attack for the tool. This happens in particular by

ßtSWiGUNGSKQPIE that at least two screw-in pressure surfaces are arranged on the head of the closure element, on each of which a force can be exerted with the tool. These at least two forces are then combined to form a torque that drives the thread in the screwing direction. The screw-in pressure surfaces mentioned can be made available through a slot, through bores, through elevations or the like on the head of the closure element. In known systems of this type, the closure element can then be screwed onto the neck of the fuel tank, for example with a combination key.

However, the problem arises that the user can effortlessly apply very high torques with the tool, which can cause the closure element to be over-rotated. The closure element is screwed into the socket of the fuel tank as far as it will go, and the torque acting beyond this then leads to damage to the closure element and / or the fuel tank. In order to avoid this, the user would have to be aware of the danger of overturning and additionally be able to precisely estimate the strength of the torque that is still permissible. However, this is usually not the case.

Presentation of the invention, task, solution, advantages

It was therefore an object of the present invention to improve a closure element of the type mentioned at the outset in such a way that it can be screwed onto the fuel tank without the risk of overturning, the addition of a tool for overturning being avoided or prevented.

This object is achieved by a closure element with the features of claim 1. Accordingly, the closure element for a fuel tank has a thread and at least two screw-in pressure surfaces arranged on, on or in the head of the closure element, on which a force for generating a torque which drives the thread can be exerted. The closure element is characterized in that the surface normal of the screw-in pressure surfaces has a component opposite to the direction of advance of the thread.

The surface normal of any surface is to be understood as a directed beam (arrow, vector) which is perpendicular to the surface and points away from the body on the surface of which the surface is formed. If friction forces are neglected, a tool can only exert forces on the screw-in pressure surfaces of the closure element which are directed perpendicular to the screw-in pressure surface. This force is therefore opposite in parallel to the surface normal of the screw-in pressure surface. Conversely, this means that the closing element exerts a counterforce on the tool via the screw-in pressure surfaces, which points in the direction of the surface normal of the screw-in pressure surfaces.

Since, according to the invention, the surface normals of the screw-in pressure surfaces have a component which is opposite to the direction of advance of the thread, it follows from this that the closure element exerts a counterforce via the screw-in pressure surfaces, which pushes the tool used for screwing back against the screw-in direction. Since the user of the tool primarily uses forces that are perpendicular to the thread axis and only to a lesser extent forces that are parallel to the thread axis (in the direction of advance of the thread), the force component explained above can be greater than that of the user in the axial direction Direction of the forces applied so that the tool slides off the screw-in pressure surface. This sliding occurs at the latest at the moment when the closure element is sufficiently screwed or at the stop, so that the "Normal" screwing in of the closure element can be carried out, but overtightening by slipping off the tool is prevented. It is advantageous that this type of overturn protection works regardless of whether the user is aware of the risk of overturning or not. The user can tighten the closure element "as tightly as possible", with no overtightening. It is also advantageous that this overturn protection is carried out by simple measures on the closure element, without requiring expensive changes to the tools.

According to claim 2, the screw-in pressure surfaces are preferably mirror-symmetrical with respect to the thread surfaces. A mirror-symmetrical design of the force-transmitting surfaces on the closure element with respect to the thread axis ensures that the forces transmitted by a tool are also symmetrical with respect to the thread axis. These forces therefore form a pair of forces that generate a torque around the thread axis without resulting in a total force. This means that the closure element is only rotated by the tool, but is not pressed in any direction in a translatory manner.

According to claim 3, the surface normal of the screw-in pressure surfaces with the thread axis preferably forms an angle of 15 ° to 85 °. At an angle of 15 ° the screw-in pressure surface is inclined by 75 ° with respect to the thread axis, at an angle of 85 ° it is correspondingly inclined 5 ° with respect to the thread axis. Conventional screw-in pressure surfaces, which generate no force component against the direction of advance of the thread, are parallel to the thread axis (angle of inclination 0 °), i.e. their surface normal is perpendicular (angle 90 °) to the thread axis. The greater the inclination of the screw-in pressure surface to the thread axis, the greater is the force component directed against the direction of advance of the thread, that is, the more sensitive is the over-tightening protection. About the inclination of the screw pressure area can be determined depending on the prevailing circumstances (requirements for the overturn protection, material properties of the locking element and tool etc.) the optimal start time of the overturn protection.

In an embodiment variant of the invention according to claim 4, there are elevations on the head of the closure element, in which at least one side surface is wholly or partly formed by a screw-in pressure surface. Elevations have the advantage that they are easily accessible for a tool. The screw-in pressure surfaces which are inclined according to the invention can also be retrofitted to conventional elevations on a closure element, or their inclination can be subsequently adapted to new requirements.

In another variant of the invention according to claim 5, the screw-in pressure surfaces are side surfaces of depressions embedded in the head of the closure element. Such depressions in the head of the closure element have the advantage that a smooth closure of the closure element is formed on the outside, that the force application surfaces are protected and that the force is introduced directly into the closure element, so that there is no risk of protruding parts breaking off.

Claim 6 relates to a further development of the last two design options of the invention, in which the surface normal of that side surface of the elevation (or of the depression) which lies opposite the screw-in pressure surface is perpendicular to the thread axis. This means that a tool acting on the side surface opposite the screw-in pressure surface cannot exert any force component in the direction of the thread axis, since the force that can be transmitted by such a tool (if the friction is neglected) is always in the direction of the surface normal. The side surfaces in question thus have an arrangement which from the State of the art for all side surfaces is known. If such surfaces lying parallel to the thread axis are used for the power transmission by means of a tool, no forces occur in the axial direction which could cause the tool to slip. Such slipping is also not desirable since, unlike when the closure element is screwed in, unscrewing is not required when unscrewing. Rather, it is advantageous if the tool can be used to exert a quasi arbitrarily large (opening) torque on the closure element.

Brief description of the drawings

In the following the invention is explained by way of example with the aid of the figures. Show it:

1 shows a perspective view of a closure element with elevations;

FIG. 2 shows a section along the line II-II according to FIG. 1;

3 shows a top view of a closure element with a slot-shaped depression 21.

Best way to carry out the invention

1 is a perspective partial top view of an inventive closure element 100 for a fuel tank. It can be seen that the closure element is composed of an external thread 14 and an adjoining head 13. The closure element 100 can be in one piece or in several parts. To close a fuel tank, the closure element 100 with the external thread 14 is screwed into a corresponding internal thread of a connector on the fuel tank in order to seal the connector in a sealing manner. Tools are generally used to screw in the closure element, which are in the illustrated embodiment engage the two elevations 11 on the head 13 of the closure element in order to generate a torque around the threaded axis 16 (FIG. 2).

In the case of known closure elements, the elevations 12 are essentially cuboid, so that for the tool used for rotation there are contact surfaces for the force transmission, which are parallel to the thread axis 16 or in other words perpendicular to the surface of the cover 13. With surfaces configured in this way, any desired torque can be practically exerted on the closure element 100 using a suitable tool, such as a combination key. When screwing in the closure element 100, however, this can be disadvantageous, since overtightening and thus damage to the closure element or the fuel tank can occur when the thread stop is reached. The user of the tool may find it difficult to estimate the maximum torque that may be expended or may not even know that he must pay attention to this.

In order to avoid this problem, in the closure element 100 according to the invention, the screw-in pressure surfaces 10, against which the tool rests during the screwing in of the closure element, are chamfered. The effect of this bevel is explained below with the aid of FIG. 2, which represents a schematic section through the closure element 100 shown in FIG. 1 along the line II-II.

The beveling gives the screw-in pressure surface 10 an orientation which is inclined to the thread axis 16. This can also be described using the so-called surface normal 17 of the screw-in pressure surface 10. The surface normal is a directed beam (arrow, vector), which begins in the surface and points away from it. The position of the surface normals 17 is indicated by an arrow in FIG. 2. The position of the screw-in pressure surface 10, which is inclined relative to the thread axis 16, can thus be described in that the surface normal 17 has a grain size. has component in the direction of the thread axis 16, this component pointing opposite to the screwing direction 18 of the thread.

A tool which rests on the screw-in pressure surface 10 can only transmit forces perpendicular to this surface when neglecting frictional forces. This means that the transferable forces are parallel to the surface normal 17 or that the counter forces exerted on the tool by the elevation 11 point in the direction of the surface normal 17. Due to the inclination of these surface normals 17 relative to the thread axis 16, the counterforce on the tool thus has an axial component which tends to cause the tool to slide off the screw-in pressure surface 10. This force can be easily compensated for by the user of the tool when the closure element is screwed in "normally". However, when the closure element 100 comes to a stop, the torque applied by the user increases, which is converted into a correspondingly increasing counterforce due to the inclination of the screw-in pressure surface 10. This also increases the axial component of the counterforce, so that the user can no longer prevent the tool from sliding off the surface 10. When the tool slides off the surface 10, however, the screwing-in process then ends automatically. Overtightening of the closure element 100 can no longer take place.

The elevation 11 has a second side surface 12 which is essentially opposite the screw-in pressure surface 10. A tool for transmitting a torque can also act on this second surface 12. However, the surface 12 is arranged in a conventional manner, that is to say that it lies parallel to the thread axis 16 and thus its surface normal 15 is perpendicular to the thread axis 16. A tool attached to this side surface 12 therefore does not experience any counterforce with an axial component. The tool therefore does not tend to slip. This is neither necessary nor desirable since the side surface 12 of the torque transmission when Screws the closure element 100 is used, in which no over-rotation can occur in principle.

3 shows an alternative embodiment of a closure element 101 in a top view. It can be seen that a slot-shaped depression 21 is embedded in the head 13 of the closure element, part of the side surfaces of this slot being designed as inclined screw-in pressure surfaces 20. These are identified by hatching in FIG. 3. The side surface pieces 19 lying opposite the inclined screw-in pressure surfaces are aligned in a conventional manner parallel to the thread axis. The closure element 101 behaves in the manner described in connection with FIGS. 1 and 2. When screwing in, a clockwise torque is exerted on the closure element 101 using a corresponding tool. The inclined surfaces 20 serve this purpose. If the closure element 101 comes to a stop, then the tool slides along the inclined surfaces 20 from the closure element 101 and the screwing-in process ends automatically. When unscrewing, on the other hand, a torque is transmitted counterclockwise over the surfaces 19, on which no axial force component arises which could lead to the tool sliding off.

Reference numerals:

100 closure element

101 closure element

10 screw-in pressure surface

11 survey

12 side surface

13 head

14 external threads

15 surface normals

16 thread axis

17 surface normals

18 direction of screwing

19 side panels

20 screw-in pressure surface

21 deepening

Claims

Expectations

1. closure element (100, 101) for a fuel tank, which a

Has thread (14) and at least two screw-in pressure surfaces (10, 20) arranged on, on or in the head (13) of the closure element, on which force can be exerted with a tool to generate a torque driving the thread, characterized in that that the surface normal (17) of the screw-in pressure surfaces (10) has a component opposite to the direction of advance (18) of the thread (14).

2. Closure element according to claim 1, characterized in that the screw-in pressure surfaces (10, 20) are mirror-symmetrical with respect to the thread axis (16).

3. Closure element according to one of claims 1 or 2, characterized in that the surface normal (17) of the screw-in pressure surfaces (10, 20) with the threaded axis (16) forms an angle (α) of 15 ° to 85 °.

4. Closure element according to one of claims 1 to 3, characterized in that the screw-in pressure surfaces (10) are side surfaces of elevations (11) arranged on the head (13) of the closure element (100).

5. Closure element according to one of claims 1 to 3, characterized in that the screw-in pressure surfaces (20) are side surfaces of recesses (21) embedded in the head (13) of the closure element (101).

6. Closure element according to one of claims 4 or 5, characterized in that the surface normal (15) of the side surface (12, 19) of the elevation (11) or the recess (21) opposite the screw-in pressure surface (10, 20) is perpendicular to the thread axis ( 16) is.