US2220004A - Method of setting storage battery plates - Google Patents

Description

Oct. 29, 1940. E. w. SMITH ET AL 2,220,004

A METHOD OF SETTING STORAGE BATTERY PLATES Original Filed Nov. 3, 1932 F) 3 a l 5400 95 Patented Oct. 29, 1940 UNITED STATES PATENT OFFICE 2,220,004 METHOD OF SETTING STORAGE BATTERY PLATES Edward W. Smith and Clarence A. Hall, Philadelphia, Pa., assignors to The Electric Storage Battery Company, Philadelphia, Pa., a corporation oi. New J ersey 2 Claims.

The composition of the paste used for filling the grids of a storage .battery plate is usually such that certain chemical reactions take place after the paste has been applied to the grid which tend to harden the material. This hardening or setting process is somewhat analogous to that which occurs in cement after it has been mixed with water and should be carefully distinguished from the hardening due to drying or expelling of the moisture. In the case of a freshly pasted storage battery plate as'usually manufactured, if any considerable amount of true drying occurs by the expulsion or evaporation of the water before the true setting or hardening due to chemical reaction has taken place, the material will shrink and crack. If, however, the paste is allowed to set by chemical reaction before any substantial amount of drying takes place, the hardening effect of this setting will prevent subsequent shrinkage and cracking when the moisture is expelled. The apparatus disclosed by the applicants is designed to carry out this process of first setting without drying and subsequent dry- 8 ing in' a practical and commercial manner. The setting process, which is hastened by elevating the temperature, takes place in the first of the series of ovens where heat is applied in the presence of a highly humid or even saturated atmos phere in which there is no tendency for moisture to be driven out of the plates. The plates are retained in this oven until the setting has progressed sufficiently to prevent shrinkage and cracking when the subsequent drying takes place, and this subsequent drying is carried out inone or more ovens through which the plates are then passed. The apparatus disclosed by the applicants is especially designed to control the steps in this process and they co-operate to produce the flnal result.

One of the novel features of the disclosure is the introduction of means for spraying the plates with a setting and a hardening fluid as a further means for insuring that 'the' setting is suitably effected. This setting fluid as disclosed contains material in solution, such as sulphuric acid or ammonium sulphate, which reacts with the material of the paste to produce a hardening effect by chemical reaction.

In-drying storage battery plates subsequent to pasting, it is desirable to perform two distinct steps: (first) to heat the plates throughout to a relatively high' temperature short of the boiling point without the removal of a substantial portion of the moisture, using for this purpose a very humid atmosphere; and (second) to cause evaporation to take place by maintaining a high temperature in an unsaturated atmosphere. The process may be carried to the point of complete dryness, or it may be carried only so far as to set the paste sufficiently that when the plates are stacked upon one another their surfaces will not adhere.

The present invention includes apparatus for conveniently and economically carrying out the above drying or setting process, and is, especially adapted for usein connection with a plate lifter, forming the subject of Patent No. 2,006,844, filed by said Edward W. Smith for a machine for turning storage battery plates from horizontal to vertical position.

The present invention also includes the improvements in the process of drying storage battery plates which consists in applying liquid, in addition to the liquid contained in their paste, to the storage battery plates at some stage in the drying operation which includes the application of heat.

This application is a division of our joint copending application filed on or about the 3rd day of November, 1932, under Serial No. 641,037, now Patent No. 2,062,193.

In the following description, reference will be made to the accompanying drawing forming part hereof and in which:

Fig. 1 is a diagrammatic view illustrating, principally in vertical section, apparatus embodying features of the invention.

Fig. 2 is a transverse sectional view of the same.

modification.

Referring to Fig. 1, 2| and 24 indicate four conveyor chains having opposed projecting pins, suitable to engage storage battery plates F and hold the same in parallel side-by-side vertical plane arrangement, in the general mannerdescribed in the application above referred to. These con veyor chains pass through an oven-like enclosure divided into compartments l and 2 and finally through a short open ,run 3, roughly about as Fig. 3 is a view similar to Fig. 1 illustrating a long as one of the compartments. At the very column of plates.

titions of the oven compartments are provided heating means, and with a fan 6 and l for cirwith openings for the passage of the plates, such openings fitting the profile of the plates as closely as practicable, and having a short tunnel-like projection l0l li2. It will be noticed that, as there are. always one or more plates at a time in each of these short tunnel openings, the opening is continually closed so as to minimize intermixing of the atmosphere through the opening. Adjacent to the final'run of conveyor chains in the open air, at 3, there is placed a fan 88 arranged to blow a ,stream of air directly onto and through the advancing column of plates.

The operation of the apparatus is as follows: Plates coming directly from a pasting machine are unloaded therefrom, and delivered by means of the plate lifter l9 onto the four parallel conveyor chains 2! and 24, whence they are carried along in a side-by-side arrangement through the various compartments, and finally deposited on the rails 25.

The first compartment contains water in its lower part, so as to partly or entirely cover the steam coils, the water of course becoming heated thereby. The fan 6, by means of the pipes shown, delivers a current of humid air directly down upon this heated water, the air thereby becoming heated, and very strongly humidified or even saturated, Passing upward, this stream of air heats the column of plates through which it blows, without at the same time causing an appreciable drying, owing to its high humidity. After passing through the plates, the air is re-circulated.

In the second compartment, there is much less water at the bottom, so that part of the coil is directly exposed to the air. The air circulated by the blower 1 hence rises up through the compartment and through the column of plates at an elevated temperature and in a partly saturated condition, ready to absorb moisture from the plates, while maintaining them at an elevatedtemperature. g

Further control of the humidity in both ovens is provided by means of damper openings 8 and 9, which permit the discarding of a portion of the circulating atmosphere, to be replaced by fresh air drawn in through the tunnel openings Ill-l 2, or through other openings which may be supplied.

' In the final run of the conveyor 3, the plates are subjected to a mild draught of atmospheric air, which still further dries and at the same time cools them, so that by the time they reach the racks 25, they may be removed and piled on top of One another without danger of sticking together, even though not entirely dry.

As an example of a satisfactory set of conditions, we may give the following figures:

' 1st compt. temp. PIG-180 F. 90-100% humidity 2nd compt. temp, 150-170 F. 60% humidity such extent that it is no longer sticky, and hence the plates may be piled for storage, ready for final assembly.

It should be noted that this process of setting is very critical, and that careful control of the conditions is at all times necessary. The temperature and humidity in the compartments have to be varied to suit the thickness of plates, the composition of the paste, and even the atmospheric conditions; hence it is impossible to quote figures which will fit all cases, and these given merely happen to have been satisfactory for a particular kind of plates.

It also should be noted that, while we have shown an oven containing two compartments, it may be of advantage to use further sub-divisions so that the progressive changes of temperature and humidity may take place more gradually.

As a further refinement in this process, we refer to Fig. 3, which shows amodification by whihc the plates are passed through a cascade of a fluid which exercises a strong hardening or setting action upon lead oxide. The plates are first passed through the hot humid oven compartment l, where they are heated without substantial drying; next they are passed through a double cascade 20, which momentarily floods both plate surfaces; after which they pass on through further oven compartments, omitted from the figure, to avoid confusion, but substantially like that shown at 2 in Fig. 1. The "setting liquid of which dilute sulphuric acid and ammonium sulphate are examples, is stored in a tank 23; is delivered by means of a pump 24 into the troughs 20, flows through slots or holes 28 down over the plates; the surplus is collected in a trough 22 and thence returns by gravity to the tank 23. The tank 23 serves two main purposes: (first) it permits of adjustment of the strength of the solution, which constantly tends to become weaker; and (second) it furnishes means by heating coil 21, of regulating the temperature of the setting solution to conform to that of the plates.

In the drying or freshly pasted storage battery plates, unless care is exercised the paste has a tendency to shrink and to crack. The abovedescribed method of first heating in humid atmosphere and then drying in a partially saturated atmosphere makes it possible to accomplish adequate drying'without cracking; it is still a critical process, however, which needs very careful regulation} By the employment of the cascade; as above described, the limits within which successful setting and drying are accomplished are very much widened, and hence satisfactory results may be obtained without such extremely close control as is otherwise necessary. The drying may be carried to completion if desired; but

for ordinary purposes it is quite suiiicient to set the paste thoroughly, though without completely drying it.

The dousing of the plates thus described has been successfully practiced prior to the plates entering any of the heating compartments and also between the first and second compartments,

' so we do not wish to limit its use to the latter position, above described.

In the specification and claims, the word setting signifies a fixing of the particles of paste in such a manner that the tendency to crack with subsequent drying is very much reduced or eliminated.

We do not intend to be limited save as the scope of the prior art and of the attached claims may require.

We claim:

1. A process of setting and drying freshlypasted and unformed storage battery plates comto a saturated atmosphere at elevated tempera- 3 ture and at atmospheric pressure to retain the moisture while setting by heat, then flowing over the surfaces of said plates 2. liquid which causes the plates to set and harden, and then subjecting said plates to an unsaturated atmosphere at elevated temperature and at atmospheric pressure to remove the moisture only after setting has been effected.

. EDWARD W. SMITH.

CLARENCE A. HALL. 10

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