US2454053A - Process for the manufacture of storage batteries - Google Patents

Description

Nov. 16, 1948. c. D. GALLOWAY PROCESS FOR THE MANUFACTURE OF STORAGE BATTERIES Original Filed June 3,.1944

rm MA CYZIrZaEG j ?atenteol Nov. i16 1948 ssn PROCESS FOR THE MANUFACTURE OF STORAGE BATTERIES Charles D. Galloway, Wyndmoor, Pa., assignor to The Electric Storage Battery Company, a cor poraticn of New Jersey G Claims. i.

This invention relates to the manufacture of elements for storage batteries and, more especially, to the method of casting straps on the plate lugs of an assembled storage battery element and has for an object the provision of a method of p ying heat to the strap-metal while in the mold along a. localized area adjacent the tips of the lugs to efiect localized fusing of the strapmetal to the ends of the lugs without fusing of the strap-metal to the roots of the lugs.

Another object is to provide a new and improved method for casting the positive and negative connecting straps to the plates of a group of positive and negative plates with interposed separators completely assembled in their final relative positions, with localized welding of the end-portions of the lugs, and to accomplish this without danger of injury to the separators and without the possibility of so-called run-downs" of molten metal between the plates.

Another object of the invention is to provide improved methods for casting the connecting straps to the downwardly projecting plate lugs f the completely assembledelement in such a manner as to avoid crystallization and weakening of those ortions of the plate lugs which are relied upon for the mechanical support of the plates while providing for good and permanent electrical contact between the lugs and the strap.

Another object of the invention is to provide for carrying out the strap-casting operation in two steps whereof the first comprises pouring the molten metal into the strap mold around the plate lugs of the inverted element at a temperature sufilcient to fill the mold and the spaces between the lugs but insufficient to melt the metal of the lugs, while the second step comprises subjecting the under surface of the strap-casting as it rests in the mold together with the tips of the plate lugs to an elevated temperature for such brief period of time as will effect a welding of the lug to the strap for a short distance beneath said surface without melting or softening or otherwise impairing the molecular structure of the balance of the lug.

In carrying out the invention in one form thereof molten metal which is not hot enough to fuse the surfaces of the plate lugs is poured into the mold in quantity sufficient to form the strap. While the strap is still in the mold, heat is applied to a localized area of the mold adjacent the tips of the lugs to effect localized fusing or welding of the strap-metal to the end-portions of the lugs without fusing of the strap-metal to the roots of the lugs. The fused or welded areas are of high electrical conductivity and :provide low resistance paths for flow of current while the shrinkage of the metal about the roots of the lugs upon cooling provides Strong mechanical support of lug roots which have not been weakened by fusing or crystallization thereof.

The invention will be more clearly understood by referring to one embodiment thereof described below in connection with the accompanying drawing in which:

Fig. 1 is a plan view of a strap-casting mold embodying features of the invention; and

Fig. 2 is a sectional elevation on the line 2-2 of Fig. 1 showing also a portion of the inverted element.

In the drawing, l0 represents the mold block of any suitable material such as cast iron. It is provided with open top shallow mold cavities H and 12 of suitable shape and dimensions for casting the desired connecting straps, As shown in Fig, 2, the assembled element comprising positive plates 83, negative plates l4 and interposed separators |5, is located in an inverted position with the plate lugs l6 and I1 projecting downwardly into the corresponding mold cavities II and I2. The element may be held together by any suitable clamping device (not shown). The element is supported vertically on a slab l8 of heatinsulating and heat-resisting material whose upper surface is slightly above the upper surface of the mold proper. of the separators I5 rest on this slab and are thus prevented from coming into contact with the heated mold.

The mold cavities are provided with downwardly extending conical cavities l9 and 20 for integrally casting the terminal posts on the straps; Ejector pins 2? and 22 are shown at the base of the post'cavities I9 and 20 for removing the completed element with attached strap-castings from the mold. The ejector pins may be actuated by any suitable means not shown.

To provide for filling the mold, the gate cavities 23 and 24, located in gate blocks 25 and 26, are shown, through which the molten metal may be poured into the mold cavities proper. The gate blocks are here shown as detachable but may be integral with the mold block. After the castingshave solidified, the gates may be cut off either after the element and strap-castings have been removed from the mold or before removal. In the latter case, the gate blocks 25 and 26 will first be removed and the gates cut off in situ by any suitable means not shown.

Inserted through and closely fitting into suit- As shown in Fig. 2, the edges able openings in the floor of the mold cavities H and i2 are the super-heating inserts 21 and 28, respectively. Since these inserts are alike, the one shown at 21 will now be described. It comprises a block of steel or similar heat-conducting refractory metal whose upper rectangular face is fiushwith the floor of the mold cavity II and is longitudinally substantially coextensive with that cavity. In width, it corresponds with the horizontal length of the plate lugs I 6 and is located immediately below the row of these positive plate lugs. The vertical dimensions of the plate lugs I6 as here shown are such as to bring their ends close to but not actuallyin contact with the insert 21, leaving a narrqgv space 29 therebet-ween. Under some conditions, however, it may be satisfactory to bring these plate lugs into actual contact with the insert. Except for a short distance from its upper surface, the insert 21 is out of contact with the mold, there being interposed a Clearance space 30'to limit the transfer of heat from the insert to the mold. 'J. 'he insert 21 is provided with a downwardly extending projection 3| which is surrounded by a tubular water-cooled electrical conducting call 32 adapted to carry high-frequency alternating current for induc tively heating the insert 21 in the well-known manner. Standard apparatus for developing and applying suitable high-frequency current for in ductive heating is available on the market and it is not deemed necessary to illustrate or describe it here.

The insert 21 is provided with a duct 33 through which cooling-liquid may be circulated and suitably controlled as by the valve 34.

The operation of the apparatus above described is as follows:

The assembled element, comprising the desired number of positive and negative plates with interposed separators clamped together in their final relative positions, is inverted and supported on the mold as shown in Fig. 2, with the separators resting on the slab l8 and the plate lugs extending into the mold cavities ll and l2, with their ends above and close to or in contact with the upper surfaces of the inserts 21 and 28, re-

spectively. Molten metal, preferably lead-anti mony alloy, is then poured into the mold cavities II and I2 via the gates 23 and 24 until the cavities are filled to the upper level including the spaces between and beneath the plate lugs. lhe temperature of the molten metal is such that the plate lugs will not be melted or softened but will retain their shape or physical identity, as it has been found that such melting or softening produces crystallization and weakening of the lugs, causing them to break when subjected to stress or vibration in service.- The shrinkage of the molten metal on cooling and solidifying, which molten metal now around the plate lugs, as it rests in the mold, together with the tips of the plate lugs are in a brief period of time raised to an elevated temperature to effect a. welding or fusing of the lugs to the strap for only a short 'the lugs.

distance above the floor of the mold and without melting or fusing the roots or major portion of The heat necessary for the localized welding or fusing of the lugs is applied through the super-heating inserts 21 and 2B. In the illustrated form of the invention the shanks of the inserts are surrounded by high-frequency heating coils 32'. High-frequency current is passed through the heating coils 32 to heat inductively the inserts 21 and 28, the intensity and duration of the current and the resultant temperature and rate of application of heat by the inserts 21 and 28 to the metal being such as to melt the metal just above the upper surfaces of the inserts and melt the tips of the plate lugs. The intensity and duration of the current required to obtain the best results will vary with the dimensions of the strap-casting and the size and spacing of the plate lugs. With the volume of current available from standard apparatus for inductive heating applied to a standard type of storage battery element, a few seconds has been found adequate to give satisfactory results. As soon as the current is interrupted, cooling-water is circulated through the ducts in the inserts to prevent further heating effect and also hastens the cooling, solidification and final shrinkage of the strap around the lug --roots.

The length of the mold cavities II and I2 may be made sufficient to provide for the maximum width of element. For smaller elements, it is only necessary to block off the ends of the mold cavities. No other adjustment is necessary to provide for elements of various numbers or thickness of plates or various plate spacing.

It may be remarked that space is provided above the level of the molten metal in the mold and at the roots of the lugs for the access of air, which tends to keep the metal cool at the roots of the lugs and also to keep the adjacent portions of t e separators cool.

It will be noted that there is provided, in accordance with this invention, a group of storage battery plates assembled by their conducting lugs to a suitable connecting strap, wherein the plate lugs at their roots and over the major portion-of their length adjacent the plates are mechanically tightly gripped by the adjacent metal of the strap without being autogenously welded thereto, while the tips of the lugs are autogenously welded to the adjacent metal of the strap.

While one convenient form of apparatus for carrying out the process and producing the prodnot of this invention has been described, including inductively heated means for applying the superheating temperature locally to the tips of the plate lugs and the adjacent metal of the strap casting, it is not intended to limit the scope of the invention to this particular apparatus since other means may be employed forapplying localized superheating for the selective and localized fusing of the end-portions of the lugs to the adjacent metal of the strap.

This application is a division of my application Serial No. 538,564, filed June 3, 1944, and is-directed to and claims my improved process for assembling storage battery elements described in my original application. The described mold for the manufacture of storage batteries is not claimed -herein'since it is the subject-matter of and is claimed in my original application Serial No, 538,564; nor is the described product-claimed herein because it is the subject-matter of and is claimed in my divisional application Serial No. 568,797, filed December 19, 1944.

It will be obvious to those skilled in the art that modifications may be made in details of construction and procedure without departing from the spirit of the invention which is not limited in respect to such matters or otherwise than the appended claims may require.

1. claim:

1, in a process for casting straps on the plate lugs of an assembled storage battery element comprising positive and negative plates and interposed separators the steps of inverting the element and inserting the plate lugs into a suitable mold, surrounding the lugs with molten metal at a temperature insuflicient to melt or soften the lugs, and after the metal has cooled, while still in the mold applying heat locally to the tips of the lugs and the surrounding metal in the mold for a limited time suihcient to fuse them together only at said lug tips.

2, In a process for casting straps on the plate lugs of an assembled storage batte y element comprisin positive and negative plates with interposed separators the steps of inverting the element and inserting the plate lugs into a suitable mold, surrounding the lugs with molten metal at a temperature such that when the metal comes into contact with the lug-surfaces the metal is not hot enough to fuse such surfaces. and while the strap is still in the mold applying heat to a localized area of the mold adjacent the tips of the lugs to effect localized fusing of the strap-metal to the ends of the lugs without fusing of the strap metal to the roots of the lugs.

3. The method of producing on the lugs of storage battery plates a cast strap characterized by welded areas of high electrical conductivity at the tip-ends of the lugs which comprises inserting the lugs of the storage battery plates into a mold cavity with said lugs spaced from each other, surrounding the lugs with molten metal at a temperature such that when the metal comes into contact with the lug-surfaces the metal is not hot enough to fuse such surfaces, and while the strap is still in the mold applying heat to a localized area of the mold adjacent the tips of the lugs to effect localized fusing of the strap-metal to the 6 heat in a localized area of the mold adjacent the tips of the lugs to elevate the temperature thereof during such a brief period of time as will effect localized fusing of the strap-metal to the ends of the lugs without fusing of the strap-metal to the roots of the lugs, and shrinking the metal around the roots of the lugs by removing heat from the localized area of the mold and from the metal.

5. The method of producing on the lugs of storage battery plates a cast strap characterized by welded areas of high electrical conductivity at the tip-ends of the lugs which comprises inverting the plates and projecting the lugs thereof downwardly into a mold cavity with said lugs spaced from each other, pouring into the mold and about the lugs molten metal at a temperature such that when the metal comes into contact with the lugsurfaces the metal is not hot enough to fuse such surfaces and in quantity sumcient to form the strap, while the strap is still in the mold applying heat to a localized area of the mold adjacent the tips of the lugs at a rate and during a time intercal ends of the lugs without fusing of the strap-metal metal to the ends of the lugs without fusing of the strap-metal to the roots of the lugs and thereafter cooling said metal.

6. The method of producing on the lugs of storage battery plates a cast strap characterized by welded areas of high electrical conductivity at the tip-ends of the lugs and by shrinkage of the strap around the roots of the lugs which comprises inverting the plates and projecting thelugs thereof downwardly into a mold cavity with said lugs spaced from each other, pouring into the mold and about the lugs in quantity suflicient to form the strap molten metal at a temperature such that when the metal comes into contact with the lug-surfaces the metal is not hot enough to fuse such surfaces, while the strap is still in the mold inductively generating heat in a localized area of the mold adjacent the tips of the lugs at a rate and during a time interval which produces localized fusing of the strap-metal to the ends of the lugs without fusing of the strap-metal to the roots of the lugs. and shrinking the metal around the roots of the lugs by removing heat from said 10- ealized area of the mold and from the metal.

CHARLES D. GALLOWAY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED e'rii'rne PATENTS Barhoif June 23, 19 31

Images