MXPA00008833A - Prismatic battery housing - Google Patents

Abstract

The invention features a prismatic battery (10) with an electrically conductive housing comprising an elongated, prismatic can (12) with an open end, and a housing cover (16) pressed into the open end of the can (12) and welded in place. The novel cover (16) has an outer flange (34) about its periphery, extending generally in the direction of extensions of the sides of the can, which elastically deflects as the cover is pressed into the can to provide good contact for welding. The cover has two raised bumps (36) forming internal pockets that are part of the internal volume of the cell. The bumps are also arranged to prevent rotation of the seal/vent assembly (18, 20, 22, 24, 26). One embodiment includes a plugged fill hole (46) in one of the bumps (36). Corresponding methods of manufacture are also disclosed.

Description

ACCOMMODATION FOR PRISMATIC BATTERY DESCRIPTION OF THE INVENTION This invention relates to batteries with prismatic housings, and their construction. The prismatic cells are prismatic instead of circular in their cross section. Examples of such prismatic cells include the rechargeable cells of nickel metal hydride Fß (NiMH) currently used in portable electronic equipment, such as cell phones, which have rectangular cross sections. The housings of such prismatic cells typically include a deep drawn (or longitudinally welded) can that is capped with a rigid, flat plate cover assembly having one or more electrical contacts. The cover is typically pressed down into the open prismatic end of the can until the top edge of the cover is slightly below the top edge of the can, and then welded in place (eg, by laser welding) to seal the cell. The accommodation materials REF .: 123144 include stainless steel or carbon steel, cold rolled, nickel plated (CRS). The precise tolerance of the can and the cover are required to provide intimate contact around the entire periphery of the cover for a good seal after welding. Ideally, the parts are of suitable dimensions line by line or for a slight adjustment of interference in order to avoid empty spaces along the weld joint. If the interference is excessive, the flat-plate-covered can is bulged / typically through the hole or holes punched through it for the contact / ventilation assemblies. If the cover flexes significantly, the seal in these holes is compromised. If there is an excessive local free space between the cover and the can, it will be difficult to obtain a hermetic laser welding, due in part to the lack of filler material used in the welding process. These problems can be faced by requiring extremely rigorous dimensional tolerances on the critical dimensions of the can and the cover, thereby increasing the cost of the components. Some current F6 designs employ total can tolerances of 0.05 mm (+/- 0.002 inches), for example, which can be difficult to achieve reliably and economically with deep drawing. The contact / vent assemblies are typically mounted in round holes punched through a flat plate cover, electrically insulated from and sealed to the cover with a polymeric seal. During manufacture and use, care must be taken to avoid rotation of the contact / ventilation assemblies within their mounting holes, which may cause internal shorting. Particularly with thin cells, such as the common F6 prismatic cells, care must be taken not to damage or distort the seal material in the contact / ventilation assembly during the welding process, due to the close proximity of the seal edge to the seal. the welding joint. By limiting the heat in the area near the seal, the distortion of the seal can be reduced and the rejection rate reduced due to leakage in the seal, but it can also result in a higher rejection ratio due to leakage in the joint. .

Many standard prismatic cell sizes, such as F6, require a specific height of their contacts relative to the edge of the open end of their cans. After the cover is welded in place, spacers are sometimes added between the cover and the outer contact to control this dimension. Ideally, the covers are accurately positioned as far out as possible to provide the greatest internal volume of cells for the active materials. The invention provides a prismatic housing cover construction that can effectively reduce the sensitivity of the sealing process to the dimensional tolerances of the cover / can, which can make possible the use of higher heat of welding without damage to the seal, and can provide, in some embodiments, additional internal cell volume and prevention of seal rotation through the use of raised cover portions. The invention characterizes a prismatic cell housing cover with an outer flange around its periphery, which generally extends in the direction of extension of the sides of the can. According to one aspect of the invention, a prismatic battery includes an electrically conductive housing having a prismatic can and a housing cover. The can has an open end defined between the opposing sides extending from the can, and the housing cover is located between and sealed against opposite sides at the open end of the can, such that the can and the cover enclose together one volume The cover has an outer flange around its periphery, with the flange generally extending in the direction of extension of the sides of the can, the sides of the flange and the can jointly defining a welded joint at the distal edge of the flange. Preferably, the cover has a raised portion that forms an internal pocket in hydraulic communication with the enclosed volume to provide the additional internal volume of the cell for active materials and / or electrolyte. The battery can be very thin for particular applications. For example, in presently preferred embodiments, the prismatic can has a minimum dimension between opposite sides at the open end, less than about 6.0 millimeters. In the illustrated modes, this dimension is approximately 5.0 millimeters. Various embodiments of the invention may contain one or more of the following characteristics. The cover is made of stamped metal. The cover is rectangular with rounded corners. The cover flange is tapered outwardly to provide pressure between the flange and the sides of the housing can. The raised portion has a filler hole through the cover, with a plug (eg, a metal ball) placed inside and sealing the filler hole. In some embodiments, the cover defines a hole therethrough, and the battery includes an external electrical contact coupled to the cover in the hole. A seal between the contact and the cover electrically insulates the contact from the cover. In some cases, the raised portion is accommodated to couple the seal to prevent rotation of the seal with respect to the cover. The cover has, in one embodiment, two raised portions of this type, the seal being located between and constrained against rotation by the two raised portions. Preferably, the height of the flange in the direction of extension of the sides of the can is at least three times the nominal thickness of the cover. According to yet another aspect, the invention provides a method for constructing a battery with a prismatic battery housing, electrically conductive. The method includes the steps of: (a) pressing a housing cover (having an appropriate flange, as described above) into the open end of an elongated, prismatic can to enclose a volume; and (b) welding the joint to seal the cover to the can. The welding step can be carried out, for example, by directing a laser beam in the joint in the direction of the extension of the sides of the can. Typically, the pressing step includes the elastically bending the sides of the can outwardly at the open end of the can. In some cases the raised portion has a filler hole (as described above), the method further includes, after welding, the steps of (c) adding electrolyte to the volume enclosed through the filler hole; and (d) plugging the filler hole to seal the enclosed volume. Prior to clogging, a high test pressure can be applied to the volume enclosed through the filler hole. Other features and advantages will be apparent from the following description of the embodiments of the invention, and from the claims. Figures 1 and 2 are cross-sectional, longitudinal, orthogonal views through a prismatic cell housing. Figure 3 is an enlarged view of the cover assembly of Figure 2. Figure 4 is a cross-sectional view of the cover, taken along line 4-4 of Figure 5. Figure 5 is a top view of the cover . Figure 6 is an enlarged view of the area 6 in Figure 2, without the insulator 32.

Figure 7 illustrates a second embodiment, with a filler hole plugged through an elevated portion of the cover. Figure 8 is a top view of the cover assembly shown in cross section in Figure 3. With reference to Figures 1 and 2, a prismatic cell 10 type F6 has a housing assembly that includes a nickel-plated CRS 12 can , deep sausage and cover assembly 14. The internal components of the ce.lda are not shown, but are typical of standard F6 cells, and include at least two electrodes. The cover assembly 14 includes a CRS cover 16 with stamped nickel plate, a plastic ventilation seal 18, a metal rivet 20, a washer 22, a vent plug 24 and a metal contact (tip) 26. During the Assembled, the cover 16 is pressed down on the open end 28 of the can 12 and welded around the entire length of its periphery along the joint 30 to seal the cover "to the can." An exterior insulator 32 of material heat shrinkable is placed on the housing after assembly.

With reference to Figures 3 and 4, the cover 16 has a nominal thickness tc of approximately 0.33 millimeters, and, since it is stamped at a total height Hc of 1.62 millimeters, it has a peripheral flange 34 extending to a wide side of the cover. The flange 34 has a shoulder height HL of approximately 1.3 millimeters. Also stamped on the cover are two raised protuberances 36, one on each side of the hole 38, which is punched through the cover at its center. The hole 38 can be punched through the blank of the cover from its outer side, before forming the flange and protuberances. By punching the hole from the outer side of the cover, a groove or ridge 40 is formed on its inner side and the outer surface 41 remains flat for sealing. The punching operation further provides a radius at the edge of the hole on the outer side of the cover, to assist with the insertion of the seal 18. The rivet 20 is inserted through the seal, the washer 22 is put in place, and The smaller inner flange of the rivet is formed to retain the rivet, seal and washer in place. The vent plug 24 and the tip 26 are put in place and the tip is welded in points to the larger outer flange of the rivet 20. As the seal 18 and the washer 22 are assembled, they electrically insulate the rivet and the tip of the rivet. the cover, since the cover is in electrical communication with the anode of the cell and the tip is in electrical communication with the cathode of the cell. The flange 34 is tapered with an outward direction at an angle? about 2.5 degrees, providing secure engagement with the internal surfaces of the housing can, as discussed below with respect to Figure 6. As shown in Figure 5, the sides 42 of the raised prob- erties 36 facing the orifice 38 of the assembly of the ventilation assembly, are arched, having a radius R of approximately 2.2 millimeters. These curved sides 42 restrict the oval vent assembly (the rivet 20 and anything in contact with it) from rotating in the hole 38 after the seal assembly and the tip to the cover, as shown in Figure 8. In addition to preventing seal rotation and ventilation, the protuberances 36 form cavities 44 (Figure 4) on the inner side of the cover, which provides an additional internal cell volume. The protrusions 36 and the flange 34 also increase the bending stiffness of the cover, which has finished total dimensions Wc and Lc of about 5.0 and 15.8 millimeters, respectively, slightly greater than the corresponding dimensions between the opposite sides of the can at its end. open. The four corners of deck 16 have an outside radius r, of approximately 0.75 millimeters to fit a similar internal radius at the corners of the can opening. With reference to Figure 6, the tapered shoulder 34 out of the cover 16 is elastically flexed in the inward direction as the cover is pressed into the open end of the can 12, while the sides of the can are flexed with direction outside. These bends or elastic bends provide a contact load between the can and the cover to ensure a tight fit in the joint 30, even with relatively high dimensional tolerances. For example, can 12 can be embossed with a side drag angle of 0.25 degrees and an opening tolerance greater than or equal to 0.1 millimeters (greater than or equal to 0.004 inches) in each dimension, while maintaining reliable pressure settings . Pressed in place, the cover contacts the inner surface of the can 12 along a length Xc of approximately 0.6 millimeters (preferably, approximately three times the thickness of the heavier wall of the two adjoining walls). After the cover is pressed into the can until the edge of the rim 34 is flush with the edge of the can 12 as shown, the cover and the can are welded together by a laser directed to the joint 30 in the direction of arrow A, producing a molten zone shown by broken line B and sealing the joint. The laser beam travels along the length of the junction 30 (either the cell or the laser can be physically moved) to complete the weld. Referring now to Figure 7, a second embodiment 14 'of the cover assembly has a cover 16' with a stuffing hole 46, plugged, in one of the raised protuberances 36. The fill hole is used for the pressure test and filling the cell with electrolyte after welding the cover assembly 14 'to the can, and is subsequently plugged with a 48-ball of stainless steel (e.g., about 1.6 millimeters in diameter) that is welded in place by laser or TIG welding.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (17)

CLAIMS Having described the invention as above, the content of the following claims is claimed as property:

1. A prismatic battery having an electrically conductive housing, characterized in that it comprises: a prismatic can having an open end defined between the opposite sides extending from the can; and a cover of the housing positioned between and sealed against the opposite sides at the open end of the can, and the can and the cover enclose a volume together, the cover has an outer flange around its periphery, the flange extends generally in the direction of extension of the sides of the can and defines with it a welded joint.

2. The prismatic battery 'according to claim 1, characterized in that the cover has a raised portion defining therein a bag in hydraulic communication with the enclosed volume.

3. The prismatic battery according to claim 1, characterized in that the prismatic can has a minimum dimension between the opposite sides at the open end, less than about 6.0 millimeters.

4. The prismatic battery, according to claim 1, characterized in that. the cover is made of stamped metal.

5. The prismatic battery according to claim 1, characterized in that the cover is rectangular with rounded corners.

6. The prismatic battery according to claim 2, wherein the cover defines a hole through it and the battery is further characterized in that it comprises: an external electrical contact coupled to the cover in the hole; and a seal placed between the contact and the cover to electrically isolate the contact from the cover.

7. The prismatic battery according to claim 6, characterized in that the raised portion is accommodated to engage the seal, to prevent rotation of the seal with respect to the cover.

8. The prismatic battery according to claim 7, characterized in that it comprises two raised portions, the seal is placed between and constricted against rotation by the two raised portions.

9. The prismatic battery according to claim 1, characterized in that the flange of the cover is tapered outwards to provide pressure between the flange and the sides of the housing can.

10. The prismatic battery according to claim 2, characterized in that the raised portion defines through this a filling orifice, the battery further comprises a plug placed inside and sealing the filling orifice.

11. The prismatic battery according to claim 10, characterized in that the cap comprises a metal ball.

12. The prismatic battery according to claim 1, characterized in that the height of the flange in the direction of the extension of the sides of the can is at least three times the nominal thickness of the cover.

13. A method for constructing a battery with a prismatic, electrically conductive battery housing, the method is characterized in that it comprises: pressing a housing cover at the open end of a prismatic can, elongated to enclose a volume, the open end being defined between the opposite sides that extend, from the can, the cover has an outer flange around its periphery, the flange extends generally in the direction of the extension of the sides of the can, and defines with it a joint, the cover it has a raised portion that defines in it a bag in hydraulic communication with the volume enclosed; and welding the joint to seal the cover to the can.

14. The method according to claim 13, characterized in that the welding step comprises directing a laser beam to the joint in the direction of the extension of the sides of the can.

15. The method according to claim 13, characterized in that the pressing step includes the elastically flexing the sides of the can with outward direction at the open end of the can.

16. The method according to claim 13, wherein the elevated portion defines through it a filling orifice, the method is further characterized by comprising, after welding: the addition of electrolyte to the volume enclosed through the filling hole; and plugging the filler hole to seal the enclosed volume.

17. The method according to claim 16, characterized in that it also comprises, before the tamponade, the application of a high test pressure to the volume enclosed through the filling orifice.