State of charge indicator for a battery

The invention relates to a charge status indicator for a equipped with a liquid electrolyte battery with a transparent viewing rod having an adjoining a cylindrical outer surface, formed by a conical reflecting surface tip a first end an observation area and a second end, and a the second end of the viewing rod attached, through which the electrolyte ball cage, in which at least one obliquely arranged to the longitudinal direction of the light rod ball guide channel for at least one ball with a defined specific gravity is formed, which extends over the height of the tip of the viewing rod and frontal and lower limits and a having provided with an interruption for the second end of the viewing rod upper boundary wall.

Such state of charge indicator is based on the fact that changes the specific gravity of the electrolyte in function of the state of charge. The specific gravity of the guided in the ball guide channel ball is, therefore, tuned to the specific gravity of the electrolyte, so that the ball is lighter than the electrolyte at a proper charge of the battery and therefore floats in the slanting channel. However, if the battery is discharged, the specific gravity of the electrolyte falls below the ball so that the ball in the ball guide channel drops down.

According to the <patcit id="pcit0001" dnum="DE2511426C2"><text>DE 25 11 426 C2</text></patcit> an oblique ball guide channel is provided, which ends at the tip of the viewing rod. Floats on the ball, because the battery is sufficiently charged, the ball at the end of the viewing rod is visible through the viewing surface at the first end. Through a colored design of the ball a color display (z. B. Green) can thus be realized for the correct charge state. The reflective surface at the second end of the viewing rod, a sufficient degree of filling of the battery with the electrolyte is also visible. Indeed, if the electrolyte level fallen so far that the tip of the viewing rod is no longer immersed in the electrolyte, the conical surfaces of the tip of the viewing rod form an interface with air, causing a total reflection occurs on the conical surfaces of the tip of the viewing rod, so that the tip as reflective face, so bright, appears. In contrast, if the electrolyte level is sufficiently high, the material of the viewing rod is chosen so that the refractive index of the viewing rod and electrolyte are approximately equal, so that no total reflection occurs. With the tip of the viewing rod thus an optical connection to the (dark) inside of the battery is made, so that a dark area appears on the viewing surface (without ball). Of course, a sphere is only visible if the electrolyte level is sufficiently high, because on the one hand the ball without electrolyte can not float on the other hand, the reflection surfaces cause at the tip of the viewing rod total reflection, not allowing so an observation in continuation of the light rod. Visible are thus three different states at the observation area, namely "light" for an insufficient electrolyte level, "dark" for an adequate level of electrolyte in the battery is discharged and "color ball" for an adequate electrolyte level and a sufficient battery charge.

A charge level indicator of the type mentioned is by <patcit id="pcit0002" dnum="EP1120641A2"><text>EP 1120641 A2</text></patcit> known. Therein, a ball guide channel is provided which is provided for the guidance of two balls with different specific weight. The ball guide channel has a length of about three ball diameters. The two balls have different colors which are different from the color of the ball cage. In the discharged state of the battery, both balls are at the lower end of the ball guide channel, whereby the upper ball at the tip of the viewing rod comes to rest. If sufficient electrolyte present, the color of the upper ball is attached to the observation area of ​​the viewing rod thus (for example, red) recognizable. This color indicates that the battery is discharged. In a medium load state, the upper (lighter) ball floats and disappears out of sight of the tip of the viewing rod to the upper end of the ball guide channel, while the lower ball not float, ie at the lower end of the ball guide channel out of sight of the viewing rod remains. With sufficient electrolyte level now the color of the housing (eg. Color) yellow to the viewing surface is visible. If the battery is in a good state of charge, floating on the lower ball and abuts against the upper, already aufgeschwommene ball, whereby it is positioned below the tip of the viewing rod. On the plot the color of the lower ball is (z. B. Green) as a signal for a good state of charge visible.

If the electrolyte level, however fallen, so he no longer has any contact with the level gauge, produced in the plot because of the total reflection at the conical reflecting surfaces of the tip of the viewing rod is a colorless, bright display, since the incident by the light bar light is totally reflected at the conical reflecting surface.

In such a state of charge indicator, the balls thus move at a contact line of the upper boundary wall of the ball guide channel, which may be with any cross-section, in particular circular or square, formed and must provide a defined lateral guidance of the balls. The upper boundary wall of the ball guide channel is interrupted by a recess into which protrudes the tip of the inspection rod. The pointed tip is thereby to lie about on the imaginary extension line of the upper boundary wall. The angle of the conical reflecting surfaces is considerably greater than the angle of inclination of the inclined ball guide channel. In operation of such a charge level indicator, it is possible that no clear display arise because the ball does not completely float in the desired manner, but get stuck in the ball guide channel. It may even happen that in the observation area, a partly red and partly green indicator can be seen. Generally, this can be remedied by knocking on the level gauge. Critically, however, when a degradation resulted from a hanging ball remained nil not detected and corrected by shaking or tapping.

The invention is therefore based on the object to make the display of a charge state indicator of the type mentioned störungsunanfälliger.

To achieve this object, a charge state indicator of the aforementioned type is inventively characterized in that the upper boundary wall adjoins continuously to the conical reflection surface at the transition to cylindrical surface.

The invention is based on the realization that a cause of the sticking of the ball is not to be found in the small by the small differences in specific gravity buoyancy forces, not overcome the example adhesion forces, but in the above the pointed tip of the viewing rod with primarily the upper boundary wall of the ball guide channel formed space, which is formed in particular by the different pitch angle of the ball guide channel on the one hand and the conical reflection surface of the viewing rod on the other hand. In practice, the linear guidance of the floating ball a stepped edge on which the ball can hang when floating. According to the invention, the upper boundary wall closes now adjustable to the conical reflection surface. For this purpose, the angle of the conical reflection surface is preferably exactly equal to the pitch angle of the ball guide channel, so that the upper boundary wall is aligned with the conical reflection surface. Of course, slight angular deviations of a few angular degrees (&lt;10 °) are harmless.

The connection of the upper limiting wall of the conical reflecting surface should be carried out with the smallest possible intermediate space, which in any case less than ¼ of the ball diameter, preferably less than 1.10 of the ball diameter, is. In practice can be realized a virtually gap-free connection.

The construction according to the invention is preferably carried out with the fact that the diameter of the cylindrical outer surface of the viewing rod is formed reduced in steps at the second end, so that the level gauge in the formed in the surface level on a corresponding annular shoulder of the ball cage is used and so the stepless transition of the conical reflecting surface is the upper boundary wall also possible. In contrast was provided in the known embodiments to adapt the annular shoulder of the ball cage to the slope of the conical reflecting surface, so as to allow the insertion of the defined inspection rod in the ball cage. This resulted in the need for much larger form the angle of the conical reflecting surface than the pitch angle of the ball guide channel.

It has also shown that it is expedient to form rounded the tip of the viewing rod and bordering on the level gauge edges of the upper boundary wall, since the balls preferably remain hanging on sharp edges and points.

The invention will be explained in more detail below with reference to an embodiment shown in the drawing. Show it<dl id="dl0001"><dt><b>figure 1a</b></dt><dd>a vertical section through a ball cage with an inserted tip of the viewing rod</dd><dt><b>figure 1b</b></dt><dd>a stepped horizontal section along the line AA in <figref idrefs="f0001">figure 1a</figref></dd></dl>

<figref idrefs="f0001">figure 1a</figref> can be one of an electrolyte permeable ball cage 1 recognize, which has a cylindrical seat 2 for a visual bar third The level gauge is provided at its lower end with a tapered, conical reflection surface 4, which ends in a pointed tip. 5 The view bar 3 has a circular cylindrical outer surface 6, which is provided to the conical reflection surface 4 toward a stage 7 with a reduced diameter. A correspondingly imposed guide 8 is provided in the ball cage. 1

The ball cage 1 has a ball guide channel 9, which forms with a longitudinal axis 10 of the viewing rod 3 forms an angle of approximately 45 ° and is delimited by front side walls 11 in its length. In the ball guide channel 9 is a first ball 12 and a second ball 13. The balls are preferably the same size and have different colors. The first ball 12 is preferably red, the second ball 13 formed preferably green.

The housing of the ball cage 1 is also preferably colored, especially yellow running. The first ball 12 has a lower specific weight than the second ball thirteenth With increasing density of the electrolyte thus the first ball 12 floats on initially, while the second ball 13 still remains in its lower rest position. Increases the density of the electrolyte loading further, floating on the second ball thirteenth

The length of the ball guide channel 9 is three diameters of the same size balls 12. 13

The upper boundary wall 14 has a recess 15 into which protrudes the end of the viewing rod 3rd The end of the viewing rod 3 is inserted into the recess 15 so that the conical reflection surface 6 merges continuously from the top 9 upwards in the upper boundary wall 14 of the ball guide channel. 9 As<figref idrefs="f0002">figure 1b</figref>, Which provides a view of the upper boundary wall 14 from below, illustrates the upper limitation wall 14 closes at the conical reflecting surface 4 on a guide line 16 with virtually no gap at.

In addition to the stepless and gap-free transition, preferably, the angle of the conical reflecting surface 4 is identical with the angle of inclination of the upper boundary wall 14 of the ball guide channel 9, so that conical reflecting surface 4 and upper boundary wall 14 of the guide line 16 is completely aligned with each other up to the top 5th

<figref idrefs="f0002">figure 1b</figref> leaves an edge 17 of the recess 15 seen. This edge 17 and the tip 5 can preferably be formed slightly rounded to 12, to avoid sharp edges on the guide line 16 of the balls. 13