A typical lead acid battery is susceptible to
premature failure if it experiences excessive side loads - not an unusual
situation to find itself under the bonnet of a car. The lead plates can
dislodge or buckle and end up touching each other causing internal shorting and
subsequent battery failure.
Johnson Controls in the US, a major leading battery
manufacturer saw a way to improve the life expectancy of their batteries. Their
approach was to lock the lead plates at the bottom of the battery by
effectively anchoring them in cured epoxy resin.
In order for the plate locking operation to be a
viable production process, Johnson Controls determined that each battery needed
a shot of around 15 - 20 cc's of mixed 2 part epoxy in the bottom of each of
the six cell chambers, and that this had to be achieved in no more than 15
seconds per battery. Furthermore, Johnson Controls needed the shot size to be
repeatable for each chamber within +/- 1%.
As a continuous production run was crucial, Johnson
Controls could not accept any downtime for material supply drum
Their initial thoughts were to assume that 6
independent metering systems were required, which would of made the whole
project prohibitively expensive. In addition, the system would need to be
flexible enough to allow adjustment to suit their full range of battery
What was the solution
Sealant Equipment & Engineering's (S.E.E.)
approach was to design a single continuous flow machine with sophisticated shot
controls to operate 6 individual dispense valves sequentially. Basically, one
valve at a time opened and closed until all 6 cells had been dispensed. This
would make the system considerably cheaper and the project financially
S.E.E. adapted the
SeeFlo® 582 fixed ratio meter / mix /
dispense machine to continuously meter the 2 part epoxy formulation accurately
without pulsation. The shot controls enabled a single metering system to supply
metered material to 6 mixing dispense valves in sequence. Each valve
incorporated a low cost disposable mixer nozzle removing the need for solvent
flushing, which are disposed of at the end of each day's production.
S.E.E. then designed and manufactured a suitable
fixture that would hold 6 valves above the battery casing and allow easy
adjustment of each valve to suit all battery sizes. A lifting mechanism was
also built in to raise the battery casing so that the mixer nozzles reached the
bottom of the casing. This was done to prevent epoxy getting on the side walls
of the casing which would affect the performance of the final product. Once
dispensing had been completed, the casing would be removed and the top cover
with lead plate assemblies attached would be lowered into the casing. The
bottom edge of the lead plates become immersed in the rapidly curing epoxy and
effectively anchoring them in place.
To ensure continuous dispensing without interruption,
a drum over drum, gravity-fed material supply system was used. This involved
mounting 2 off 45 gallon drums on their sides, one on to of the other on a
specially designed rack. The top drum was connected to the bottom drum via a
flexible hose. The bottom barrel served as a buffer stock of material and the
top drum was replaced as necessary. The outlet of the bottom drum was fed into
a stick pump to enable the material to be supplied to the
SeeFlo® 582 under pressure. This ensured that
the metering pumps never cavitated. The same material supply system was
utilised for the B component.
Once the system was installed at Johnson Controls, it
became evident that the casing raising & lowering feature was unnecessary
and the material leaving the dispense nozzle travelled vertically to the bottom
of the cell anyway. Without this feature, it became even easier to incorporate
the dispense station into a conveyorised system, thereby enabling even faster
automatic indexing of the battery casings and removing the need for an
Since the installation of the first system nearly 5
years ago, Johnson Controls have incorporated similar SeeFlo® 582 systems in 4 other plants
throughout the US and Mexico.
Recent developments include a 12 valve system capable
of dosing 2 battery casings at the same time.