Note: Descriptions are shown in the official language in which they were submitted.
10~;5~00
~ orol~D ~r ~ ~.NI~ION
It has long been recocJnized tllat lead-acid storage
batteries tend to emi.t hydrogen and oxygen while the battery
is.being charged and that thc gases so emitted must be vented
from the storage battery casing. Since storage batteries are
used in environments where sparks occur, the usual automobile
being a typical example, it is well known that venting of the
hydrogen and oxygen from the bat~ery causes a serious hazard
of explosion... Prior~art workers have sought to provide special
caps for the illing openings of the battery cells, for example,
with the caps so designed as to vent the explosive gases to the
atmosphere in a manner intended to minimize chances that an
explosion wou:Ld occur and also minimize chances that should an
external explosion occur, the explosion could propagate through
the vent cap into the interi.or of the cap and the battery.
Many such vent caps have been proposed, typically including
tortuous vent paths, relatively small vent apertures, and porous
vent bodies such as membranes, ceramic plugs or centered metal
plugs. In recent times, the use of porous vent plugs has
received considerable attention and such plugs have been
effective to prevent flame from propagating back through the
plug into the battery. Unfortunately, it has been found that
such devices have the disadvantage of establishing persistent
Bunsen burner-like flame, external to the plug, and that
'' ' ~
10~5400
persistcnce of the flamc gcnerates such a high temperature
as to e.g. melt the surrounding polymcric material in which
the plug is mounted, so that the plug is blown from its
mounting and explosion of the battcry results.
Though 1ame behavior has not been explained to
complete satis~action in terms of chemical kinetics and transport
properties of gas molecules, it is accepted that the flame
established by burning a combustible gas mixture of given
temperature, pressure and compositlon will not pass through an
oxifice smaller than a certain minimum size, commonly referred
to as the "flame quenching distance". Research on this subject
is reported in The Quenchinq of Laminar Oxvhydroqen Flames BY
Solid Surfaces, Raymond Friedman, Third Symposium on Combustion,
Flame and Explosion Phenomena, Williams and Wilkens Company,
Baltimore, Maryland, 1949, and Survey of HYdrogen Combustion
Properties, Isadore L. Drell et al, 1958, NAC~-TR-1383
The flame quenching distance stoichiometrlc mixture of
hydrogen and oxygen has been established as .0075 in. (.019 cm.)
under specific test conditions, and varying the relative
proportions of hydrogen and oxygen does not appear to change
the flame ~uenching distance dramatically. The flame quenching
distance appears to be relatively independent of the material
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of which the elemcnts defining the ori~ice are made.
Success of prior-art anti-explosion vent caps o~ the
type employing porous ceramic plugs and the like can be
explained by the fact that the capi.llary passages presented by
the porous plug are of a transverse dimension smaller than the
flame quenching distance.for a mixture of hydrogen and oxygen,
so that a flame cannot be propagated back through the plug
.into the battery. Failure o~ such devices, as a result of
the heat caused by a persistent external flame, appears to be
caused by the fact that, since the capillaries are immedlately
adjacent to each other and concentrated in a relatively small
area, the hydrogen-oxygen mixture is emitted from the capillaries
in a mode which is favorable to both ready ignition and persis-
tent burning.
OBJECTS OF THE INVENTION
A general object of the invention is to devise a cap
for storage battery openings which will be effective to prevent
both explosions and persistent external flames, and will also
trap electrolyte mist and prevent liquid electrolyte from
pumping through the cap when the battery is subjected to
vibration.
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Anothcr object is to provide such a cap which prcsents
at least one small vent orifice, sized and arranged to vcnt the
explosive ~ases from the battery without danger of persistent
external flame or explosion, with the arrangement being such
that the vent orifice or oriices are not subject to being
plugged.
~ further object is to provide such a cap which can
be manufactured at very low cost without use of expensive
materials or techniques.
SUMMARY OF THE INVENTION
The invention is based upon the discovery that, in
order to vent the explosive gases from a storage battery
without danger of a dangerously persistent flame or an explosion,
it is not enough simply to pass the gases through an orifice
or orifices dimensioned to provide the flame quenching distance
which has been established for a hydrogen-oxygen mixture.
Rather, it is also necessary to so provide the orifice or
orifices as to present at least a minimum effective cross-
sectional area and to direct the vented gases in a manner which
will disperse the vented gases into the atmosphere. In its
most advantageous forms, the invention provides a cap comprising
a hollow body dimensioned to close the storage battery opening,
. - ~4- .
10~5400
the hollow body having a transvcrse wall wi~h an opening
communicating between the interior of the cap and the interior
of the battcry, there being means at the outer end of the
hollow body defining at least one laterally directed vent
orifice or apcrture thro~l~h which the gases emitted by the
battery are constrained to flow, the at least one vent orifice
having a maximum dimension axially of the cap which is signi-
ficantly less than the flame quenching distance for a stoiehio-
metric mixture of hydrogcn and oxygen and a total effective
eross-sectional area of at least .001 sq. in. Best xesults
are achieved when the at least one vent orifice is in the form
of a plurality of slot-like openings spaced in a series extending
eireumferentially about the eap, so that the openi~gs are
directed radially with respeet to the central axis of the cap,
the maximum dimension of the slot-like openings in a direction
axially of the cap being in the range of .003-.005 ;n.
Alternatively, the eap can be formed with a continuous slot-
like opening which extends completely around the cap. Caps
aeeording to the invention are formed, as by injection molding,
from acid-resistant polymeric material, and comprise a generally
tubuler main body and a closure member secured to the outer
end of the main body, the main body and closure member cooperating
to define the laterally opening vent orifice or orifices.
--5--
10~5400
In order that the manner in which the foregoing and
othcr objects are achievcd according to the inven~ion can be
~nderstood in detail, particularly advantageous embodiments
thereof will be described with reference to the accompanying
drawings, which form a part of ~he original disclosure hereof,
and wherein:
Fic3. 1 is a vertical sectional view taken generally
on line 1-1, Fig. 2, of a vent cap for storage battery filling
openings according to one embodiment of the invention;
Fig. 2 is a top plan elevational view of the main body
of the cap of Fig. 1, viewed generally on line 2-2, Fig. 1;
Fig. 3 is an enlarged fragmentary perspective view of
a portion of the upper edge of the main body of Fig. 2;
Fig. 4 is an enlarged fragmentary view, partly in
vertical section and partly in elevation, taken generally on
line 4-4, Fig. l;
Fig. 5 is a bottom plan view of the closure member
employed in the vent cap of Fig. l;
Fig. 6 is a view, partly in vertical section and partly
in side elevation, of a ganged vent cap assembly for closing
three filling openings of a storage battery;
Fig. 7 is a top plan elevational view of the device
of Fig. 6;
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Figs. 8 and 9 arc vertical sectional views, similar
to Fig. 1, illustrating addi~ional embodiments of the invention
for closing a storage battery filling openlng:
Fig. 10 is an enlarged fragmentary vertical sectional
view illustrating the manner in which slot-lik~ lateral vent
apertures can be provided in accordance with another embodiment
of the invention;
Fig. 11 is a view similar to Fig. 10 illustrating
still another e~bodiment of the invention;
Fig. 12 is an axial sectional view of a vent cap
closing an opening of a "maintenance-free" storage battery,
taken generally on line 12-12, Fig. 12
Fig. 13 is an end elevational view of the main body
of the cap of Fig. 12, taken generally on line 13-13, Fig. 12;
and
Fig. 14 is an axial elevational view of a modified
form of the cap shown in Fig. 12.
.
DETAILED DESCRIPTION OF THE EMBODIMENT OF FIGS 1-5
Figs. 1-5 illustrate a vent cap, according to one
particularly advantageous embodiment of the invention, the cap
being constructed to close a single filling opening of a
conventional lead-acid storage battery (not shown). The cap
10fà~5400
comprises a main body 1 and a closurc member 2, bo~h members
1 and 2 being produced, advantageously by injection molding,
from a suitable polymeric material which has high resistance
to acid and good impact and tensile streng~hs.
. Main body 1 is generally cup-shaped and includes an
inner annular side wall portion 3 and an outer annular side
wall portion 4 which is of substantially larger diameter than
portion 3, portions 3 and 4 being joined by a generally
transverse annular shoulder portion 5. At its inner end, side
wall portion 3 is closed by a transverse wall 6 having a
centrally located circular opening 7. wall 6 is shallowly
frusto-coni.cal, slantlng away from closure member 2 and toward
the central axis of the cap. Formed integrally with wall 7
is an upstanding tubular portion 8 comprising a generally
cylindrical side wall 9 and a transverse end wall 1`0. Side
wall 9 is provided with a plurality of slots 11 which extend
from wall 7 t.hrough end wall 10 and communicate between the
interior of portion 8 and the annular space between that
portion and the wall portion 3 o main body 1. End wall 10
is provided with a centrally located circular opening 12.
Main body 1 also includes an integrally formed, axially
projecting annular partition 13 the inner surface 14 of which
.
1065400
forms an outcr e~tension o~ the inner surface of side wall
portion 3. The outcr sur~ace 15 of partition 13 is spaccd
significantly inwardly ~rom and is concentric with the generally
cylindrical inner surface portion 16 of outer side wall por~ion 4.
Partition 13 is provided wit-h a plurality of axially extending
slots 16 which extend from the frusto-conical surface 5a of
~shoulder portion 5 through the ou~er edge of the partition
and communicate between the space between the partition and
side wall portion 4, on the one hand, and the space enclosed
by the partition and side wall portion 3, on the other hand.
As best seen in Fig. 3, the inner surface of
side wall portion 4 includes, at the free end of the side wall
portion, frusto-conical surface portion 18 which tapers away
from closure member 2 and toward the axis of the cap, so that
the radial dimension of the circular outer edge of side wall
portion 4 is relatively small. This edge of side wall portion 4
is made up of a plurality of circumferentially spaced outwardly
projecting pedestal portions 19 and a plurality of flat
portions 20 each located between a different adjacent pair of
the pedestal poFtions 19. Elongated circumferentially of side
wall portion 4, pedestal portions 19 terminate in rounded ends
21 and have flat main surfaces 22, all of surfaces 22 lying in
`~ .
_g_
10~;5400
a common plane which i5 at right angles to thc central axis of
main body 1. At the centcr of each surface 22, before assembly
of the cap, is a very smal] outwardly directed conical projec-
tion 23. All of ~he flat surfaces 20 lie in a common plane
which is at right anglqs to the central axis of the main body
portion. The common plane occupied by flat surfaces 22 of the
pedestal portions is spaced from the common plane occupied by
surfaces 20 by a small distance a Fig. 4 which is significantly
less than .007 in. (.18 mm.) and is advantageously in the range
.003-.005 in. (.076-.13 mm.).
Outer wall portion 4 is provided with a plurality of
circumferentially spaced radial projections 24 which have flat
top surfaces 25 located in a common transverse plane spaced
significantly from the plane occupied by surface portions 20.
Projections 24 have rounded outer edges and curve inwardly and
toward the central axis of the cap to blend into the surface of
shoulder portion 5, as seen in Fig. 1. As will be ciear from
Figs. 2 and 3, projections 24 are equal in num~er to the raised
portions 19 of the outer edge of side wall portion 4 and each
projection 24 is centered on a different one of the portions 19,
the circumferential widths of projections 24 being approximately
equal to the circumferential length of edge portions 19.
--10--
1065400
. Comparinq Figs. 1 and 5, it will be seen that closure
member 2 comprises a body 26 having a flat lowcr surface 27
which is interrupt:ed only by an axially short, dependent .
circular skirt 28 having an outer diameter substantially equal
to the inner diameter of partition 13 so that the skirt 28 is
snugly embraced by the outer end portion of partition 13.
Body 26 is circular and its diameter is equal to the outer
diameter of wall portion 4.
For assembly, closure member 2 is put in place on main
body portion 1, with skirt 28 inserted within partition 13, and
with the peripheral portion of the bottom surface 27 of
member 2 engaging all of the conical projections 23, Fig. 3.
. Using a conventional ultrasonic welding device, the combination
. of member 2 and the adjacent portions of member 1 are vibrated
ultrasonically, with conical projections 23 acting as energy
directors, so that the polymeric material of projections 23
are brought to a state of fusion, clamping pressure being
applied conventionally by the ultrasonic welding device, and
member 2 thus being secured by fused polymeric material to
each pedestal portion 19 of the side wall portion 4, in the
fashion seen in Fig. 4.
10~5400
In the completed, cap upstanding tubular portion 8
coacts with side wall portion 3 and wall 6 of body 1 to define
a relatively large annular mist chamber indicated at ~, Fig. 1.
Similarly, partition 13 and side wall portion ~ of body 1
coact to define an annular mist chamber indicated at B, Fig. 1.
Mist chamber A is in communication with the interior of the
battery via slots 11, opening 12, `and opening 7. Mist chamber
B is in communication with mist chamber A via the slots 16.
With closure member 2 secured to body 1 as earlier
described, each surface portion 20, the corresponding adjacent
pair of rounded ends 21, and the adjacent peripheral portion
of surface 27 coact to define a thin slot S having the critical
height a, Fig. 4, which communicates between annular chamber B
and the atmosphere and which directs gases from the battery
radially outwardly from the cap. When the battery gases during
charging, the increased internal pressure of the battery will
cause the gases to flow into the cap via opening 7, thence
into chamber A via slots 11 and opening 12, thence via slots 16
into annular chamber ~, and finally out through the slots S.
So long as the dimension a of slots S is less than .007 in.
(.18 mm.), so as to be significantly smaller than the flame
quenching distance for a stoichiometric mixture of hydrogen
and oxygen the escaping gases will neither explode nor establish
,
-12-
.
1065400
a persistent flame, even though sparks be present in thc
immediate vicinity of the cap. In a typical, particularly
successful cap according to the invention, the exterior surface
of side wall portion ~ is right cylindrical, ~t.ere are sixteen
of the vent slots S, the height a is approxima~ely .004 in.,
the circumferential dimension of the slots, i.e., the
circumferen~ial distance between two adjacent pedestal portions
19, is .1 in., and the total transverse cross-sectional area
of all sixteen slots is thus approximatèly .0064 sq. in.
Since the hydrogen-oxygen mixture passing through
each slot S-during charging of the battery is discharged
radially outwardly in only a thin plananar fashion, the gas
mixture is quickly dispersed into the atmosphere so that the
concentration of hydrogen and oxygen is not sufficient to
allow a persistent flame to occur.
Acid mist, i.e., droplets of liquid acid entrained in
the escaping gas, will be mainly trapped in chamber A, readily
wetting the surfaces which define that chamber, and therefore
draining back to the battery via slots ll. Any acid mist
continu;ng through slots 16 will be trapped within chamber B
and will drain into chamber A, wetting the surfaces which
define chamber D and flowing over the upper surface of shoulder S
-13- l
1065400
and through slot 16, Considcring thc draining of liquid acid
trapped in chambers A and B, it will be noted that the down-
wardly and inwardly slantiny upper surfaces of bottom wall 6
and shoulder 5 continue as the in-lined end walls of slots
11 and 16, respective].y, to assure free drainage of the liquid
through the slots when the cap is in its normal upright
position.
~ Upstanding portion 8 is of substantial height, its
end wall 10 being in a plane adjacent of shoulder 5, so that
chamber A is not only of substantial volume but also of
substantial axial length. Accordingly, with the cap in its
upright position, an unusually large quantity of electrolyte
would have to be collected in chamber A before that quantity
would enter slots 16 of partition 13. Collection of such a
large quantity is precluded by the fact that the total area
of slots 11 is large, so that any trapped liquid acid drains
rapidly back through opening 7. It is also to be noted that
the slots 11 extend completely through top wall 10 and that
the top wall 10 is provided with a relatively large opening 12,
so that the combination of the upper portlons of slots 11 and
opening 12 will always provide space for free flow of gases
through the cap via slots 16 even though there might be a
slgnificant quantity of liquid acid in chamber ~. Under those
-14-
~0~5~00
cixcumstances, the outer chambcr B is effcctive as a mist trap,
and the free flow areas still remaining within the cap allow
gas flow in a relatively free and unimpeded fashion so that,
even if the gas flow tends to bc pulsating, as when the battery
is vibrated, it will not tend to pump the liq~id acid into
chamber B and thus into the area occupied by the slots S.
Provision of mist chambers ~ andB is particularly
advantageous because presence of liquid in the area occupied
by vent slots S would give rise to possible plugging of the
vent slots by the liquid, a problem which occurs with, e.g.,
prior-art caps employing porous vent plugs having small
capillaries.
It is also advantageous to guard against the possibility
of vent slots S becoming plugged by dirt, oil, grease or other
material from outside the battery. For this reason, the radial
projections 24 are provided to prevent the user's fingers from
contacting the periphery of closure member 2 and the external
surface of side wall portion 4 in the locations occupied by the
vent slots.
Another advantage of the structure shown in Figs. 1-5
is that, with the outer diameter of member 2 essentially e~ual
to the diameter of the outer surface of wall portion 4, the
~ -15-
10~;5~00
slots S in effect open through a cylindrical wall, therc being
no lateral o~erhang adjacent the vent slots. Presence of such
an overhang, as when the diameter o the closure member is
substan~ially greater than the diameter of wall portion ~,
tends to increase the possibility of occurrence of a persistent
flame at the mouth of the vent aperture.
With slot~ e vent apertures such as apertures S,
Fig. 4, the radial dimension of surfaces 20 should advantageously
not exceed about five times dimension a. Tllus, in a typical
cap according to Figs. 1-5, with the outèr diameter of wall
portion 4 equal to approximately 1 in. and distance a kept in
the range .003-.005 in., the radial dimension of surfaces 20
can be .05 in., and that small dimension is achieved by providing
the chamfer or frusto-conical surface 18. while the effec-
tiveness of the vent orifices in preventing persistent flames
and explosions depends to some degree on keeping the radial
dimension of surfaces 20 small, keeping this dimension small
is more important from the standpoint of avoiding stoppage of
the slot-like vent orifices by collection of liquid therein,
since the dimension a is so small that the vent ori~ices will
tend to act as capillaries if the radial dimension is too
large.
-16-
1065400
Members 1 and 2 can be formed of any suitable material
which is acid-resis~ant and possesses good impact and tensile
strengths, but it is particularly advantageous to employ a
polymeric material of such nature as to allow members 1 and 2
to be produced by injection molding. It is particularly
useful to employ a filled polypropylene of Group SE-O or
Group SE-l ~lame xetardant characteristics according to the
Underwriters Laboratories Burning Rating Code. Typical
materials having such characteristics are polypropylenes
containing both an organic halogen compound, such as
perchloropentacyclodecane, hexabromocyclodecane, tris(2,3-
dibromopropyl~ phosphate, and pentabromodiphenyl ether and a
smaller proportion of antimony trioxide.
THE EMBODIMENT OF FIGS. 6 AND 7
~ .
Figs. 6 and 7 illustrate a ganged assembly of three
vent caps according to the invention. The assembly includes
a main body 51 and a closure 52. Body 51 includes three
generally cup-shaped portions 51a, 51b, and 51c which are
mutually identical and each embody elements corresponding to
side wall portion 3, bottom wall 6, and upstanding portion 8
of the single cap embodiment hereinbefore described with
reference to Figs. 1-5. Portions 51a, 51b and 51c are joined
-17-
1065~00
integrally at their outer ends to a single wall structure 54
which, at one end, e~tends for 180 about the top of portion 51a,
at the other end extends for 1~0~ about the top of portion
of 51c and, as seen in Fig. 7, is otherwise in the form of
two straight upright walls. Between each adjacent pair of
portions 51a-51c, wall portion 5~ is joincd by a bottom wal]
portion 55, Fig. 6, which also joins the adjacent upper ends
of the respective portions 51a-51c.
W~ile the inner trap chambers, within portions 51a-51c,
as indicated at A', remain the same as trap chamber A, Fig. 1,
the partition 63, provided on member 51, is complementary in
plan shape to the outline of closure member 52. Accordingly,
the second trap chamber B' also follows the general outline
of the closure member, so that there is only one chamber B'.
Partition 63 is provided, throughout its length, with space
slots 67, so that the single chamber B' is in communication
with all of the chambers A' via slots 67. The upper edge of
wall portion 54 is formed in the same manner shown in Fig. 3,
so that the peripheral portion of the lower face of closure
member 52 cooperates with that edge to provide a plurality
of slot-like vent orifices S' in the same f`ashion hereinabove
described with reference to orifices S, Fig. 4. A plurality
-18-
-
~0~5400
Qf circumferentially spaced projections 74, int~gral with
wall 54, are provided to prevent contact between t}-e user's
fingers and slots S' and thus minimize chances that grease or
oil will be applied inadvertently.
Circular shoulders ~0, Fig. 6, are provided to space
wall portion 54 somewhat above the top of the battery casing
when the ganged assembly is in place with portions 51a-51c
each inserted in a different one of three filling openings
of the battery.
It will bè apparent that the ganged assembly shown in
Figs. 6 and 7 operates in the same fashion hereinbefore
described with reference to the embodiments of Figs. 1-5.
... . . . . .
THE EMBODIMENT OF FIG. 8
Though, when the vent orifices such as orifices S,
Figs. 1 and 4, are slot-like, the distance a must be signifi-
cantly less than the flame quenching distance for a stoichio-
metric mixture of hydrogen and oxygen, the circumferantial
dimension of the vent orifice is not limited and the cap can
comprise a single continuous oriice extending completely
therearound as seen in Fig. 8. Here, the structure is identical
to that shown in Figs. 1-5 except that the outer annular edge
of wall portion 4a presents a flat planar surface spaced away
from the peripheral portion of surface 27 of closure member 2
,.
--19--
1065400
by a distance significantly less than .007 in. and
advantayeously in the range .003-.005 in. Closure member 2
is secured to partition 13, as by ultrasonic welding. The
outer ed~e of wall portion 4a and ~le adjaccnt portion of
surface 27 combine to define the continuous annular vent
slot S".
THE EMBODIMENT OF FIG. 9
In this embodiment, portion 8a corresponding to
portion 8, Fig. 1, is made integral with closuxe member 2a,
as is partition 13a. Portion 8a is in the form of a cylindrical
tube which extends axially for the complete distance between
closure member 2a and the inner transverse annular wall 6a,
the free end of tube 8a simply engaging the surface of wall 6a.
Advantageously, the inner diameter of tube 8a is equal to the
diameter of openin~ 7a in wall 6a, so that the wall of opening
7a acts as an extension of the inner surface of tube 8a.
The annular end surface of tube 8a is made frusto-conical so
as to be in flush engagement with the frusto~conical surface
cf wall 7a.
Partition 13a is longer than the distance between
closure member 2a and shoulder S', and the outer diameter of
~0 ..
1065400
partition 13a is such that the free end portion of the partition
is telescopically embraced by tho inner surface of wall portion
3a, as shown.
Tube 8a is provided with a circumerentially spaced
series of slots lla with each slot extending for the full
lengtl~ of th~ tube. Similarly, partition 13a has a circum-
ferentiall~r spaced series of slots 17a with each slot extenaing
for tl~e full length of the partition. Thus, ` the first annular
mist trap, defined by tube 8a, wall portion 3a and a partition
13a, wall 6a, and a portion of closure member 2 communicates
with the interior of the storage battery via slots lla and
opening 7a when the cap is in place. The second annular mist
trap is external to tube 8a and communicates with the first
mist chamber via slots 17a
Slot-like vent orifices S are provided in the same
manner described with reference to Figs. 1-5.
THE E~5BODIMENT OF FIG. 10
.
Providing slot-like vent orifices in the manner
described with reference to Figs. 1-5 has the advantage of
assuring that the relatively close manufacturing tolerances
required to maintain distance a of the desired value can be
achieved without undue cost, and securing the closure member
-21-
.
1065400
to the main bod~ by ultrasonic welding is an important feature.
However, the need to minimize the radial dimension of surfaces 20,
Fig. 3, tends to reduce the area available for ultra-sonic
welding when the entire edge of side wall port on 4 is rcduced
by cham~erring at 18.
In the embo`diment of Fig. 10, pedestal portions l9a
have à radial dimension equal to the full thickness of wall
portion 4a, so that the radial width of pedestal portions l9a
can be, e.g., .06 in., giving a substantially larger ultra-
sonic welding area at each pedestal portion. In order to
~aintain the radial dimension of surfaces 20a small, the notch
between each adjacent pair of pedestal portions l9a is deepened
adjacent the inner diameter of the side wall portion. Tllus,
while inner surface 16a extends completely to the edge of the
side wall in the location of pedestal portions l9a, surface 16a
stops at an edge 16b in the location of each vent orifice, and
the edge 16b is spaced from the common plane of surfaces 22a
by a distance several times .007 in. Each edge 16b is defined
by the intersection between surface 16a and a surface 18a which
forms the bottom wall of the enlarged portion of the notch
between the pedestal portions. Thus, though the slot-like
vent orifices s"r, Fig. 10, are the same as in Figs 1, 3 and 4,
the size of the ultra-sonic welding area has been markedly
increased without requiring unduly expensive machining operations
when making the mold and without increasing the xadial width
of surfaces 20a.
-22-
10~5400
TRE EM13ODIME~.NT Ol~ FIG. 11
It is not esscntial that the pedestal portions provided
to define the vent orifices be on the main body of the cap.
As shown in Fig. 11, the outer annular edge of the main body
can be a continuous flat circularly extending surface, and
the pedestal poxti~ns l9b can be providcd as part of a peripheral
axially extending flange 81 on the closure member. Pedestal
portions l9b have been illustrated as hav;ng the same
configuration as pedestal portions l9a, Fig. 10, so that the
increased area for ultra-sonic welding is retained in this
embodiment without increasing the radial dimension of the
vent orifice.
THE EMBODIMENT OF FIGS. 12 A~D li
_
Figs. 12 and 13 illustrate a cap according to the
invention adapted for use in closing a vent opening of a
so-called "maintenance-free" automotive storage battery of the
type in which the battery casing has a horizontally extending
externally threaded vent (not shown).
In this embodiment, main body 85 is tubular and
cylindrical, one end being internally threaded at 86 to engage
the battery vent, the other end being internally chamferred
at 87 to provide a radially narrow annular edge on which
-23-
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pedestal portions 8~ are providcd as hereinbefore describ~d
with reference to Figs. 1-4, each adjacent pair of pedestal
portions 88 being separated by a flat surface ~9 corresponding
to surace 20, Fig. 3. ~ circular closure disc 90 is secured
to the flat aces of pedestal portions 88, the portion of the
flat inner face 91 of disc 90 combining with surfaces 89 and
pedestal portions 88 to define an annular series of slot-
like vent orifices Sl identical to the slots S, Fig. 4.
transverse wall 92, located intermediate the ends of body 85,
extends across the interior of the body and is provided with a
central opening 93. Wall 92, closure 90, and the portion of
the annula- side wall of body 85 therebetween, combine to define
a chamber which communicates with the interior of the battery
via opening 93 and with which the vent orifices Sl all
communicate. The outer surface of body 85 is formed with a
circumferentially spaced series of longitudinally extending,
outwardly projecting ribs 94 having ends 95 lying in a common
plane adjacent to the plane occupied by orifices Sl to keep
the user's fingers from directly engaging the mouths of the
vent orifices. ~he diameter of disc 90 is equal to the outer
diameter of the adjacent end of body 85, so that there is no
overhand adjacent the vent orifices. Body 85 and disc 90
are of thermoplastic polymeric material and disc 90 is secured
to pedestal portions 88 by fused polymeric material as a result
of ultra-sonic welding as hereinbefore described.
w2~
10f~5400
T~IE EMBODIMF,NT OF FIG. 14
The vent cap o~ this embodiment includes the same
structurc described with reference to Figs. 12 and 13 and
provid~s a second ann~lar series of slo~-like v~nt orifices S2
in addition to orifices Sl. Slots Sl o this embodiment are
completed by a ring 96 which has a flat end face 97 secured to
pedestal portions 88. The other end face 98 of the ring is
also flat. Closure member 99 has an axially projecting
peripheral flange 100 formed with pedestal portions 101 which
are secured to end face 98 of ring 96, pedestal portions 101
being separated by flat surfaces 102 so that the pedestal
portions, surfaces 102, and the corresponding portions of end
face 98 cooperate to define the oririces S2. Ring 96 is
chamferred at 103 adjacent end face 98 to decrease the effective
radial dimension of orifices S2. Closure member 99 is formed
with a plurality of circumferentially spaced radial projections
104 having end faces 105 which lie in a common transverse
plane spaced axially from the plane occupied by orifices S2.
Thus, ribs 94 and projections 104 cooperate to keep the user's
fingers from contacting both sets of vent orifices.
As will be apparent from Fig. 14, slots S2 are
staggered with respect to slots Sl, so that each slot S2 is
-25-
1065400
aligned with a different one of thc pedestal portions 88
rather than with one of the slots Sl. In thi.s manner, no
pair of slots Sl and S2 will dischar~e gases to the same area,
and a better dispersal o~ the gases into the atmosphere is
achieved. Similarly, projections ].04 are sta~gered relative to
rib~ 94.
