Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to the formation of lead-acid
battery plates.
The formation of lead-acid battery plates involves
immersing battery plate grids carrying the required lead-acid
battery paste in an aqueous solution of sulphuric acid and
then passing an electric current between the grids so as to
convert the paste on the grids to the active material of the
plates and subsequently charge the plates. In one known
method of performing this operation, the grids and the acids
are introduced into the battery box which is to define the
container of the finished battery and the box is sealed with
a battery lid, prior to the passage of the electric current.
This method is partlcularly suited to the production of drained,
charged batteries, that is batteries which are drained after
forming and then stored with their plates in a moist condition
until they are subsequently activated for service. However, this
known method suffers from the problem that gases are generated
during formation and these can result in the escape of acid,
ei.ther as an acid-laden mist or as acid bubbles, through the
filling and venting apertures in the lid. This problem is
especially pronounded if the forming operation is performed
at high temperatures or high current to decrease the formation
time. It is therefore an object of the present invention to
alleviate and/or minimise this problem.
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According to the present invention there is provided
a method of forming battery plates for a lead-acid battery com-
prising the steps of assembling at least one pack of battery
plate grids and separators into a battery box closed by a lid
having at least one filling and venting aperture, said at least
one pack including a plurality of grids carrying lead-acid
- battery paste required to produce positive battery plates alter- `.
nating with grids respectively carrying lead-acid battery paste ~ :
required to produce negative battery plates and with separators
.10 being interposed between adjacent pairs of grids, filling the : -
battery box with an aqueous solution of sulphuric acid, inserting
into said filling and venting aperture one end of a hollow body
which is formed at said one end with at least one opening con-
necting the interior of the battery box to the bore in the body,
and then passing an electric current through the grids so as to
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convert said paste to the active material of the paste and there-
: after charge the plates, gases generated by the passage of
electric cùrrent flowing through said opening and along the bore
in the body over baffle means provided in the body and escaping
through an aperture in a closure member at the other end of the
body~ acid entrained in said gases being removed by said baffles
means and returned to the battery box by way of said opening.~.
~ Preferably, said closure mem~er is in the form of a
separate lid closing said other end of the body.
Conveniently, said baffle means is defined at least in
part by a portion of said closure member extending into said
bore
Preferably, said body is formed at or adjacent said
one end with at least one longitudinally extending groove com-
municating with the bore in the body.
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Preferably, -the device includes a plurality of said
bodies which are each adapted at said one end for insertion into
a respective filling and venting aperture of a battery lid, and
which are joined together so that their longitudinal axes extend
substantially parallel, and a common removable lid closing the
other end of said bodies.
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Preferably, the current is passed at a temperature
of at least 150F and is performed in two stages separated by ,
a standing period of at least 30 minutes.
In the accompanying drawings;
Figures 1 and 2 are sectional views respectively
of part of a device according to one e~ample of the invention;
and
Figure 3 is a sectional view of the closure member
of the device of said one example,
Referring to the drawings, the device includes three
hollow, generally -tuhular bodies 11 joined by integral webs 12
so that the longitudinal axes of the bodies 11 are parallel.
Each body 11 tapers inwardly towards one end 13 and at its
opposite end 14 opens into an enlarged portion 15. The portions
15 together define a common, open trough 16 which is divided
by partition walls 17 extending between adjacent pairs
respectively of the portions 15. Formed in each partition
17 is a central groove 18 and a pair ofouter grooves 19
located at opposite sides res~ectively o~ the trough 16.
Adjacent the end 1.3, each body 11 is stepped inwardly
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I to define a tapered narrow portion 21 which at its free end is- ~ partially closed by an integral end wall 22. Formed in
each end wall 22 is a centrally disposed hole 23 which
communicates with the elonated bore 25 defined by t~e
1 5. respective tubular body 11. Moreover, formed in di~netrically
; I opposite regions of each portion 21 are respective grooves
24 which extend longitudinally from the respective end
~all 23 and also communicate with the as~sociated bore 25.
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As shown in Figuro 3, the device also includes a cover
! 10. 26 which~ in use, is detachably engaged with the trough 16
to define a common closure member for the bodies 11. The
J' ~ cover 26 includes an external wall 27 extending around an
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`.~ internal skirt 28 arranged so that, in use, the outer wall
of the trough 16 is received as a tight fit between the wall
15. 27 and skirt 28 to aid retention of the cover 26 on the t:rough
~l 16. Depending from the cover Z6 are three tubular projection~
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; ~ 29 each of which extends below the wall 27 and ls di~ided along
`, the majority of its length by a pair of di~netrioally o~posite
¦ grooves 31 (only one shown). When the cover 26 is engaged
!1 20. with the t~ough 16~ the projections 29 extend into respective
¦ portions 14 of the bodies 11 to define with the partition ~al.l
¢ . 17 baffle means for the gases which~ in use, pas.s through the
;~ bores 25. The cover 26 is also formed with a pair~of venting
apertures 32 located between the pairs respectively of
~l 25. acljacent projections 29.
The de~ice described above is intended to assist in the
~i, formation of oattery plates in sit~l; that is l~here the formatiGn
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occurs in the battery box which is to accom~lodate the fo~ed
battery plates. In such a method~ pasted battery plate grids
- are first assemblied into packs with separators being
interposed between the grids and with each pair of adjacent
5. grids carrying the paste required to prcduce a negati~re battery
plate and a positive battery plate respectively. ~he packs
are then positioned in the cell compartments defined within the
battery box and the required intercell connections are completed
through the partition walls dividing the box into the ce]l
10. compartments. The cell compartments are then filled with ~n
aqueous solution of sulphuric acid before or after which a
battery lid is welded to the open end of the box, the lid
being formed in conventional manner with fillin~ and venting
~- apertures communicating with th~ cell compartments respecti~ely~
15. The devic~ described is then engaged with the lid by
inserting each portion 21 into a respective filling and
venting aperture in the lid~ it bein~ appreciated that for a
I normal 8iX cell battery~ two such devices will b~ necessary.
i The tapsr on each portion 21 is arranged so that~ ~hen enga~ed
;;j 20. with the lidl only the free end of the portion 21 extends throug~h
,l' the resp~ctive filling and ~enting aperture into the associated
cell comp~rtment of the battery box. Thus each c~ll
compartment not only then commurlicates with a respective
~,~ bore 25 by way of the hole 23 and groove 24 in the associated
25. body 11, but also is vented to atmosphere by way o~ the groo~e
24.
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! lihen the or each device is engaged with the lid~
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, an electric current is passed between the grids in ther ' battery box so as to convert the pa~te onthe grids into
the required active mater.ia1 of the plates~and subsequently
chargethe plates. Pref~rably~ the passge of the electric
`5. current is performed in two stages separate by a period of
` ', standing of at least 30 minutes~ the first stage being
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terminated when the charge on the plates is at least 50%~
or more preferably at least goo,b of the required final value.
During passage of the electric current~ gases are
~o, evolved which cause the aci.d solution to bubble vigorously
especially if the forming temperature is allowed to rise
to~ards the upper end of the preferred forming temp0rature
¦ ¦ range of 150 F to 200 F. These gases are heavily laden
. with sulphuric acid~ but before being vented to atmosphere
~ through the apertures 32, must flow through the holes 23 and
; grooves 24~ along the bore3 25 and over the partition walls
17 and projections 29. Thus a large proportion of tho acid
is removed prior to the gasos venting to atmospllere,
particularly at the baffle means defined by the partltion walls
~, 20. 17 and projections 29, the acid thereby collected then
Ij, flowing down the tubes 11 baclc into the battery box.
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!~ Where the forming operat.;.on is performed at high
temperatures the bubbling of the acid solution can become
so severe as to cover the end walls 23 of the tubes ll~ b~t
25- in thi~ cas0 the bores 25 are still vented to atmopshere
!~ through the grooves 24 50 reducing the tendency for the acid
;3 to be drawn up the tubes 11~ If~ however, the bubbllng
incr0ases further 50 as to cover th0 entire length of the
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grooves 24, it will be seen that the length of the tubes 11
i5 sufficient to accommodate a relatively large amount of
acid r.ise before the acid overflows through the apertures 32.
Thus the device clescribed above enables battery plates
5. to be formed in situ at a relatively high temperature,
' that is between 150 - 200 F, without danger to the operating
¦ personnel and without excessive e~lectrolyte loss. Moreover~ the t
use of the device descr.ibed prevents particles of carbon
black~ which tend to be piel~ed up by the acid vapour from the
10. negative plates~ being deposited on the external walls of the
battery. In this way it is possible to avoid the detergent
washing step normally necessary with prior art forming
l teehniques to remove the carbon black deposits which would
otherwise give the battery an unsightly external appearance.
l 1g. In a modification of the dovice clescrlb~d above~ the
interior of eaeh body 11 is fl~l.ecl with ~n acid resistant
, fibrous packing, such as p.v.e. wool, which provide.s an
increased surface area within the bocly for contact with the
~3 aeid vapours f~nd henee improve the acid condensing properties
(¦ 20. of the device. As an alternat.ive, a similflr advantageous
;,j effect ean be achieved by provicl:ing a set of baffles in each
tubular body l1. In this ease, each set of baffles is
! eonveniently in the form of a plura1ity of semi-eircular pla1;es
spaeed along the length of an elongated carrier so thflt
25. adjacont plates extend perpendicular to, but in c;pposite
directions respective].y from a plain containing the longitudinal
j axis of the carrier and the diameter of each plate~ Each
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- carrier is conveniently arranged to locate in one of theprojections 29 formed on the underside of the cover 26 so that,
~, in use, the longitudinal axis of the carrier is co-extensive
' with the axis of the associated body 11. Moreover, the
5. diameters of baffle plates are preferably arranged to vary
. in accordance with the taper on their associated body 11 so
tha~ each plate engages the internal wall of the bo(~y and,
in u9e ~ the acid vapours are constrained by the plates to flow
I along a spiral path throùgh the body.
¦ 10. It is to be appreciated that the intercormected bodies 11
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and the cover 26 will normally be moulded in an acid resistant
thermoplastic materia].~ such as polypropylene,
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