A separator envelope for lead-accumulator electrode plates and a method for its production

Abstract: A separator envelope for accumulator electrode plates (2) has thickened edge portions (5) adjacent its side edges; the thickness of the portions (5) is greater than that (s) of the walls constituting the faces of the envelope, they extend from the bottom of the envelope to its mouth, and their widths are such as to cover the side edges of the plate when it is inserted in the separator.

Description: The present invention relates in general to lead accumulators for starting motor vehicles and, in particular, to the separator envelopes used to surround the plates constituting the negative electrodes and thus separate the positive and negative electrode plates. Such a separator envelope is generally formed by the folding of a sheet of microporous, absorbent material onto itself along a central fold line and the joining of its side edges. The object of the present invention is to prevent, or at least reduce, the incidence of short-circuiting between the positive and negative plates which may make the accumulator unusable. It has been found that such short-circuiting is frequently due to the perforation of the separator envelopes anc that such perforation occurs more frequently in the side edge regions of the separator which are in contact with the edges of the plate particularly when the plates have edges which are not chamfered or sides without rims. In view of the aforesaid object, the present invention provides a lead accumulator having the features defined in claim 1 and a method for producing a separator envelope for a lead accumulator-plate according to claim 4. In a first embodiment, each thickened edge portion is formed by a side portion of the sheet forming the separator which is folded onto itself for a width such that it covers the side edges of the respective plate. In another embodiment, the edges of the separator envelope have lateral beads perpendicular to the central fold line and thicker than the sheet, the beads forming the thickened edge portions when the sheet is folded to form the envelope. Further advantages and characteristics of the separator according to the invention will become clear from the detailed description which follows with reference to the appended drawings, in which: Figure 1 is a partially-sectioned plan view of a first embodiment of the separator envelope, with an electrode plate inserted therein, Figure 2 is a section taken on the line II-II of Figure 1, Figure 3 is a detailed view taken on the arrow III of Figure 1, on an enlarged scale, Figure 4 is a cross-section of a sheet for forming a variant of the separator envelope, and Figure 5 is a detail of Figure 4, on an enlarged scale. With reference to the drawings, a separator, indicated 1, has been folded to form an envelope in which an electrode plate 2 is inserted. The embodiment of Figures 1-3 uses a conventional separator available commercially and made from a microporous sheet, for example, of polyethylene with a wall thickness which is almost uniform except for ribs 3 which act as spacers between the electrodes in the envelope configuration. The sheet is folded onto itself along a central fold line which constitutes the bottom of the envelope. Each side portion 4 of the sheet is folded over inwardly or outwardly of the envelope along a fold line perpendicular to the central fold line and substantially parallel to the side edges of the sheet so that a folded-over region 5 with a thickness twice that s of the walls formed by the sheet is formed in each side edge region of the envelope. These thicker edge portions substantially reduce the risk of the perforation of the edge regions of the separator which are in contact with the edges of the plate, thus reducing the risk of short-circuiting. The side edges of the envelope are then joined together at 6. Figure 4 shows a separator 7 modified according to the principle of the invention in its extended configuration before it has been folded. Adjacent its edges, this separator has thickened edge portions or beads 8 which are about twice as thick as the walls of the separator. The widths of the beads 8 are such that, when the sheet is folded to form an envelope, they cover at least the side edges of the plate inserted in the envelope. In this embodiment, the envelope is also formed by the folding of the separator 7 onto itself along a central line, the beads 8 being superposed and joined together at their edges. Naturally, the principle of the invention remaining the same, the forms of embodiment and details of construction may be varied widely with respect to those described and illustrated by way of non-limiting example. Lead accumulators, particularly for starting motor-vehicle engines, including separator envelopes of the type specified above are intended to fall within the scope of the invention.

Claims: A lead accumulator for starting motor vehicles comprising a plurality of electrode plates (2) inserted in a separator envelope formed from a sheet of absorbent, microporous material folded onto itself along a central fold line and having, adjacent its side edges, thickened edge portions (5, 8) which are joined together and extend from the bottom of the envelope to its mouth, said thickened edge portions being integral with the envelope and having a thickness greater than that (s) of the walls constituting the faces of the envelope, characterised in that upon folding the sheet to form the envelope each thickened edge portion (5, 8) has a width such as to cover a strip-like end section of the side surface of the respective plate inserted in the envelope. A lead accumulator according to claim 1 comprising a separator in which the thickened edge portions (5) are about twice as thick as the walls formed by the sheet. A lead accumulator according to claims 1 or 2, wherein said thickened edge portion is formed by a side portion (4) of the sheet which is folded onto itself. A method of producing a separator envelope for lead-accumulator plates according to claims 1 to 3 by the folding of a sheet of absorbent material onto itself along a central line of the sheet and the joining of its side edges, characterised in that, before the joining, it includes the step of folding each side portion of the sheet onto itself along a fold line perpendicular to the central fold line of the sheet so as to form along the side edges of the envelope folded-over regions whose widths are such as to cover at least a strip-like section of the side surface of the plate when it is inserted in the separator.

Inventors: FOSSATI GIUSEPPE, LEMORINI LUCIANO, FOSSATI, GIUSEPPE, LEMORINI, LUCIANO, LEMORINI, LUCIANO, C/O INDUSTRIE MAGNETI
Applicants: IND ACCUMULATORI S P A SOC, SOCIETA'INDUSTRIALE ACCUMULATORI S.P.A.
Application year: 1991
Main classification: H01M2
IPC codes: H01M2