Battery cap indicator

A battery cap indicator has a transparent cap which permits the viewer to read both electrolyte level and density simultaneously, the indicators also giving the viewer the ability to determine whether the readings are at the higher or lower end of an acceptable range. The float assemblies of the indicator are configured for minimum friction with the guiding structure of the indicator body.

BACKGROUND OF INVENTION 
This invention relates to battery caps and particularly to those which 
permit the condition of the electrolyte within the given cell to be 
determined without removal of the cap. 
Battery caps which permit viewing of some type of indicator in the battery 
cap have been well-known. Several of the designs which have been used are 
illustrated by the Sinclair patent, for example, U.S. Pat. No. 3,170,325, 
which has a cylindrical cap with a window. 
Another type of construction is shown by the Gosheff U.S. Pat. No. 
2,484,163 which discloses a transparent window for viewing the upper tip 
of a float. 
Another battery cap with an indicator is disclosed in the Sakamoto U.S. 
Pat. No. 3,895,964. This design has a floating ball which indicates the 
level or specific gravity of the electrolyte in the storage battery. 
A very common type of battery cap construction which has been used 
extensively is shown by the Melone U.S. Pat. No. 3,893,339. 
The above patents all show devices of the general type in which a battery 
indicator cap has a float with some type of indicator. However, the 
battery cap designs mentioned above have one or more disadvantages which 
the subject invention overcomes. 
SUMMARY OF INVENTION 
Accordingly, it is a principal object of this invention to provide a 
battery cap which is an improvement over previously existing 
indicator-type battery cap devices. 
Another object of this invention is to provide a battery cap which gives a 
dual simultaneous reading of both electrolyte level and density. 
A still further object of this invention is to provide a battery cap 
indicator which is more easily read than the devices of the past. 
A still further object of this invention is to provide a battery cap 
indicator in which the indicator elements give the observer an indication 
of electrolyte level and density over a desired range. 
A still further object of this invention is to provide a battery cap 
indicator in which the observer can readily see what the values are with 
respect to the higher and lower extremes of the range of acceptable 
values. 
Another object of this invention is to provide battery cap indicators with 
improved more freely-movable and relatively friction-free movement. 
A still further object of this invention is to provide an improved battery 
cap indicator in which the well and guide construction or the indicator 
floats have greater capability for better float guidance and movement. 
A still further object of this invention is to provide a battery indicator 
well for accommodating the floats in which the electrolyte is freely 
accessible to the interior and will readily permit flow therethrough while 
at the same time restricting electrolyte surges due to movement which 
would move the electrolyte up into the top portion of the battery cap. 
Another object of this invention is to provide a more economical and simple 
battery cap indicator construction. 
A further object of this invention is to provide a self-contained simple 
type of assembly which is readily molded and assembled. 
These and further features of this invention will be come apparent from the 
following description of the drawings.

DESCRIPTION OF THE INVENTION 
Referring to the drawings, a perspective half section of the battery cap 
assembly in position on the battery is shown in FIG. 1, and cross sections 
of this assembly are shown in FIGS. 6 through 8. The battery cap assembly 
generally indicated at 10 is mounted on the battery case top plate 12 and 
engages the circular upstanding flange 14 of each cell. The battery plates 
16 are shown below the battery cap assembly 10 which has its lower section 
immersed in the electrolyte fluid. The fluid level is approximately 
one-half inch below the surface of the battery casing top plate 12. 
The battery cap assembly 10 has an upper battery terminal top generally 
indicated at 20 which has an outwardly extending circular upper flange 22. 
It has a depending skirt 24 extending downwardly therefrom which extends 
over and engages the outer surface of the upstanding circular flange 14 of 
the battery case to hold the cap assembly in position. The inner circular 
section 26 lies between the circular outwardly extending flange 22 and the 
depending circular skirt 24, and receives the transparent removable top 
20. An interior resilient sponge filter 27 is located at the top inner 
surface of the top and covers the central vent hole 29. 
The other main subassembly is a lower depending generally cylindrical well 
30. The well 30 has a bottom piece 32 and a central longitudinally 
extending flat divider 34. Electrolyte entry slit openings 36 through the 
well extend from the bottom plate 32 of the well 30 upwardly to the lower 
surface of the top plate 12 of the battery to permit the electrolyte to 
move into and out of the well freely and yet to provide a restriction 
which controls excessive flow into the well. 
The center and longitudinally-extending divider 34 provides two 
semi-circular float containing sections as can be seen in FIG. 2. The 
electrolyte level float generally indicated at 40 has a lower float 
section 38 which is a solid semi-cylindrical section having longitudinal 
ribs 42 for engagement with the inside surfaces of the well. The ribs 
provide a low frictional area guide or runner to provide greater ease of 
movement of the float. An upper curved indicator section 44 is mounted on 
the float section and extends upwardly into the inside of the terminal 
cap-receiving top 28. The cap 28 is made of clear plastic so that the 
height of the indicator can be seen from the outside. The length of the 
indicator is chosen so that it will extend above lip 22 and inside of the 
top when the electrolyte level is within acceptable limits. 
The electrolyte density or hydrometer float generally indicated at 50 has a 
float section 48 which is semicircular in cross section as indicated in 
FIG. 5. The general outline and shape of this float is the same as that of 
the electrolyte level float 40. It has ribs 52 equivalent to the ribs 42 
of the electrolyte float which extend upwardly along its periphery. The 
indicator section 54 is curved and is a continuous extension of the 
circular surface of the float section and extends upwardly into the 
indicator cap 28. The length is chosen so that its top will be above the 
flange 22 of the battery cap assembly when the electrolyte density is at 
the bottom of the acceptable range. It will sink below this height as the 
electrolyte density becomes lower, and will rise to the top at the high 
valve for the range. The ribs 52 extend upwardly along the surface of the 
indicator to provide less frictional engagement with the inside of the 
well surface. This construction is the same as that shown for the float 40 
in the perspective view of FIG. 1. The material and weight of this float 
is selected for a density range of 0.81 to 0.95. 
FIG. 8 shows a half-sectional view of the battery cap assembly 20 in 
position. Note the fit of the flange 24 of the cap assembly down and over 
the upwardly extending circular flange 14 of the battery cell. It also 
should be noted that the downwardly depending well section 30 extends 
downwardly so that its bottom 32 just slightly clears the top of the 
battery plates 16. 
In FIG. 6, the condition of the electrolyte is shown with an acceptable 
electrolyte level and also an acceptable electrolyte density reading 
within the range. The tops of the indicators 44 and 54 are in a position 
above the circular lip 22 and can readily be seen through the transparent 
battery cap top 28. 
In FIG. 7, the electrolyte level 62 is low, and the electrolyte solution 
reading is a low one. Both floats 40 and 50 descend to the bottom of their 
respective semicircular well areas and rest on the bottom 32. Since the 
readings are below acceptable range, the top of the indicators are below 
the circular flange 22 and cannot be seen through the transparent top 28. 
In FIG. 8, the level of the electrolyte is at 64 and is acceptable and the 
indicator 40 shows above the flange 22, while the top of the indicator 54 
is below the circular lip 22, indicating low electrolyte density. 
With regard to the movement of the floats, it should be noted that they 
more readily slide up and down within the well, which is slightly tapered 
to eliminate binding. Note further that the ribs carried by the floats, as 
shown in FIG. 2, also act to eliminate binding. 
FIG. 9 shows another type of battery cap indicator in which the battery top 
66 has a flange 68 similar to the construction of the battery shown in the 
earlier figures. In this unit, generally indicated at 70, a large battery 
cap top 72 having a vent hole 73 has a simple circular configuration in 
which the lower end of the side wall fits over the flange 68. A closed 
circular housing 74 having a rectangular cross section fits within the 
circular flange 68 with its top having a lip which projects over the top 
of the flange 68. The housing has rectangular-shaped indicator-receiving 
slits 75 and 76 and vertically aligned slits 77 and 78 through the bottom 
surface of the housing. 
The electrolyte level float generally indicated at 80 has a solid 
floatation cylinder 82 and an integral vertically extending indicator 
element 84. 
The electrolyte density indicator float generally indicated at 90 has a 
solid cylindrical float element 92 and an integral vertical upstanding 
indicator element 94 of thin, substantially rectangular configuration. 
Both of the indicators have a length selected so that the indicators will 
be up at the top and in clear view to the observer when the condition of 
the electrolyte both in density (hydrometer) and level within the normal 
range. 
FIG. 10 is a perspective view of float 80. It will be noted that the end 
cross section indicator 84 is connected to the top of the surface. 
FIG. 11 discloses another modification of a battery type terminal cap in 
which construction similar to that of FIG. 9 for the upper section is 
disclosed and a single well configuration, generally indicated at 100, 
constitutes the bottom portion of the assembly. 
The transparent lower open end top 102 has a vent opening 103 with a filter 
absorbent member similar to that of FIGS. 1 and 9. The top is circular and 
is disposed over the circular upstanding flange 98 of the battery casing 
top cell wall 96, such that its lower depending skirt fits thereover in 
tight engagement. The well-piece has a circular top upstanding piece 104 
with a lip which sits firmly within and over the top edge of the 
upstanding flange 98. It has a top section 106 sealing the battery 
interior cap area from the interior of the battery case. An opening 107 of 
thin rectangular cross section is centrally located to accommodate the 
float indicator. The depending well section is cylindrical in shape and 
has four thin slits 109 to permit the electrolyte to pass into the 
interior of the well. The bottom 110 of the well is sealed and is 
positioned as with the assembly of FIG. 1 slightly above but close to the 
plates of the battery. 
In this instance, the float is a spherical solid member 120 with a thin 
rectangular section upstanding indicator piece 122. 
OPERATION 
Referring to FIGS. 1 to 8, the floats with their indicator will vary in 
height depending upon the density of the electrolyte and the level 
thereof. FIGS. 1 and 6 show the battery cap with both indicators in the 
optimum position when both density and liquid level are at a maximum. When 
the indicators fall, either the density of the electrolyte or the level is 
below optimum. The height of the window to the battery cap lip 22 gives 
the range for the battery electrolyte change in level or density. The 
height of the cap is selected so that the indicators will only appear when 
they are within the acceptable level range. The height of the cap can be 
figured at slightly more than half an inch. 
The floats of FIGS. 3 and 4 respectively are for electrolyte density and 
electrolyte level. The float is constructed in such a way that its density 
is approximately 0.913 so that it will sink if the density of the 
electrolyte falls below 1.240. 
With respect to the type material for the electrolyte float, polypropylene 
or similar type of plastic with a density of 0.921 or 0.91 may be 
selected. Any kind of material lighter than the electrolyte can be used. 
For balance, a ball of lead may be used at the bottom of the floats to 
provide better balance and weight so that the float will ride with the 
indicator in an upright position. 
The ratio of vertical piece volume, that is the indicator with respect to 
the float, is on the order of a ratio of 1 to 9 with a total value of 
1.250. 
With respect to the construction of the well, it should be noted that the 
well is tapered inwardly from top toward the bottom slightly. This 
construction permits more easy movement of the float and eliminates the 
possibility of the float sticking due to frictional engagement or cocking 
action. 
It should also be noted that each of the floats has ribs along the outer 
periphery thereof which also extend to the indicators, if the indicators 
are to be constructed in line with the outer periphery of the float. These 
ribs are for engagement with the surface of the well, such that they act 
as runners and reduce the friction-engaging surfaces. These ribs provide a 
very important aspect in this regard, since it is essential that the 
floats move freely. 
The slots in the wells are designed to provide a narrow passage for the 
electrolyte so that the level can actually be inspected while at the same 
time the narrow passage restricts flow such that there will note be 
overflow into the cap top. 
With respect to the indicators, they are preferably made of different 
colored material, such as red and blue, to distinguish the electrolyte 
level indicator from the electrolyte density indicator. 
It can be seen that with the provision of the simple construction 
heretofore described, it is possible to get both a hydrometer reading and 
a liquid level reading simultaneously which is continually observable. 
Removal of the cap for determination of level is unnecessary. Similarly, 
the need to use hydrometer reading instruments after removal of the cap to 
determine hydrometer reading is also unnecessary. 
Accordingly, it can be seen that in one simple structural embodiment of a 
battery cap assembly, a dual indicator function is accomplished. 
It is also apparent that with the construction of the well depth, its 
taper, and the rib construction of the floats, there is provided a 
relatively free-moving float for the well construction which eliminates 
the problem of float sticking. 
The unit is of simple construction so that it can be injection molded on a 
mass-produced basis, thereby providing for a nominally priced assembly. 
The dual function of two indicators is made possible by the central 
longitudinal piece 44 in the well, which provides for two semi-circular 
elevted cross-sectional float passages for the easy vertical movement of 
the floats within the simple dual section well construction of the 
assembly. 
A simple dual float battery cap terminal with a transparent indicator cap 
is shown in FIG. 9. This assembly dispenses with the use of a well and 
relies upon the vertically-spaced slots of the cap body to maintain the 
indicators in vertical aligned position. 
In FIG. 11, a battery cap assembly with a depending well is shown in which 
the central slot retaining configuration of 1 or 7 has sufficient 
clearance to allow slight play of the indicator and because of the 
clearance between the indicator 122 and the periphery of the rectangular 
slot. In this instance, the circular float 120 has clearance between the 
side walls of the indicator and does allow for some lateral movement. This 
configuration uses the deep well construction of FIGS. 1 to 8 with the 
thin vertical electrolyte passage slots. 
While this invention has been described, it will be understood that it is 
capable of further modification, uses and/or adaptations of the invention 
following in general the principle of the invention and including such 
departures from the present disclosure as come within known or customary 
practice in the art to which the invention pertains, and as may be applied 
to the essential features hereinbefore set forth, as fall within the scope 
of the invention or the limits of the appended claims.