SEALED CASING FOR CONTAINING AN ELECTRIC ACCUMULATOR

Abstract: This sealed casing is provided for withstanding a certain pressure of an internal gas. It is formed by a wall (1) which has at least one closing area (10) formed by a plastic band (11) for connecting two edges of the wall (8 and 9). The closing area has an adhesive part (12A and 12B) where the band (11) is attached and a tightening area (13) where the band is simply stuck. Thus, under the influence of a large pressure, the plastic band shifts from its casing and creates an opening (15) to the exterior, so that excessive gas can escape.

Description: Sealed casing for containing an electric accumulator. The invention relates to a sealed casing provided for withstanding a certain pressure and intended to contain notably an electric accumulator, the casing being formed by at least one wall which has at least one closing area formed by a plastic band for connecting two edges of the wall. The invention also relates to a flat accumulator formed from such a casing. The invention finds highly significant applications, for example, for containing an accumulator of the lithium-ion or iead-acid type. United States Patent No. 5,326,652 describes such an accumulator and its casing. However, in that document, the problem of internal pressure of the accumulator is not mentioned. Indeed, the accumulators create pressures inside the envelopes formed by the casings containing them. This pressure may sometimes be so high that the envelope explodes, which is very dangerous, above all if the accumulator is of the type containing liϋhium. Therefore, valves may be provided which open when the variation of pressure exceeds a certain value that is incompatible with the solidity of this envelope. The present invention proposes a casing of the type defined in the opening paragraph, the casing having an effective and low cost valve which can be incoφorated notably in ultraflat casings. Therefore, such a casing is characterized in that the closing area comprises an adhesive part and a tightening part. Thus, thanks to the invention, when the pressure is too large, the tightening part which is not fixed to the edges of the wall may shift and leave an opening, so that the gas creating excessive pressure can escape. According to a first characteristic feature of the invention, the length of the tightening part is such that said tightening part comes loose from said edges under the influence of an excessive pressure, thus creating an opening to the exterior. If the elasticity of this tightening part is sufficient when the pressure becomes normal again, the part reassumes its natural position. The operation of the inside element is re-established. According to a second characteristic feature of the invention, at least one opening to the exterior of said plastic casing is provided at the level of said edges and the length of the tightening part is such that under the influence of excessive pressure the opening is brought into contact with die exterior of said casing after the band has shifted. These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. In the drawings: Fig. 1 shows in an exploded view a casing according to the invention, Fig. 2 shows an elevational view of the opening area, Fig. 3 shows the deformation of the band under the influence of pressure, Fig. 4 shows a variant of a preferred embodiment of a casing according to the invention, Fig. 5 shows the deformation of the band, Fig. 6 shows a second variant of an embodiment, Fig. 7 shows a third variant of an embodiment of the invention, Fig. 8 shows a fourth variant of an embodiment of the invention, and Fig. 9 shows a flat accumulator formed on the basis of a casing, all this in accordance with the invention. In Fig. 1 is shown a casing of cylindrical form. It is formed by a side wall 1 formed by a curved plate, so that it has a cylindrical form. A cap 3 blocks the upper part of the cylinder, whereas a base 5 blocks the lower part. This plate 1 has two edges 8 and 9 which, as a result of the plate being curved, come in each omer's proximity and overlap each other. For connecting these edges, a closing area 10 is provided in the part situated inside this overlap formed, in essence, by a silicon-based resin band 11. This area is to be such that when the cap 3 and the base 5 are put in place, the sealing of the casing thus formed is to be ensured. The casing is also to be able to withstand a certain internal pressure. According to the invention, this closing area 10 has an adhesive part 12A and 12B and a tightening part 13. In Fig. 1 , the tightening part 13 is situated between two adhesive parts 12A and 12B. This is shown in more detail in the cross-sectional view along C of Fig. 2. The adhesive part 12 is the part for which the plastic band 11 is solidly stuck on said edge 8 and 9, either by its natural adhesion, or by glue or also by ultrasound soldering. The tightening part is not stuck to the edges at all, or stuck only slightly. This may be realized by a teflon coating. This area 13 remains tightened, locked between the two edges 8 and 9. In Fig. 2 are shown in bold lines the places where the adhesion between the band and the edges exists. With respect to area 12A, the bold lines 15A and 16A show the adhesion between the band 11 and the edges 8 and 9, respectively. As regards the adhesive area 12B, the bold lines 15B and 16B show the adhesion between the band 11 and the edges 8 and 9, respectively. Fig. 3 shows the behavior of the closing area 10 when the internal pressure of the casing becomes excessive. Under the influence of this pressure, the tightening area no longer ensures that the band 11 is held in place. It is shifted to the exterior, so that an opening 15 is formed connecting the inside of the casing with the outside. The purpose of this is to reduce the pressure on the inside. Depending on the material of the band, this shift may be final or not. In the first case, the casing is thus to be replaced, and in the second case the band resumes its initial position due to its elasticity and the casing ensures its function. Fig. 4 shows the preferred embodiment of a casing according to the invention. It is formed by two plates 20 and 21 opposite each other and connected by the band 11 which is placed along the periphery of these two plates 20 and 21. The format of this casing recalls that of credit cards used by the public at large. As a matter of fact this casing is intended to contain lithium-ion or lead-acid battery elements and/or to be of a type described in United States Patent No. 5,326,652 mentioned above. The casing of Fig. 4 thus comprises in accordance with the invention a tightening area 13 which may be deformed under the influence of pressure and may let gas that causes this excessive overpressure escape by creating an opening 15 as shown in Fig. 5. Fig. 6 shows another embodiment of the invention. According to this other embodiment, at least one opening 35 is provided on the edge and one of the plates 20 or 21 or even in the two. Under normal pressure, this opening is masked by the band 11, or is located outside the envelope and does not let gas escape. This is shown in A in Fig. 6. The pressure becomes too high, under the influence of the pressure, the band is deformed at the level of area 13, and the opening 35 is unmasked letting the excessive gas escape. This is shown in B in Fig. 6. Fig. 7 shows another embodiment. In this Figure, the band is intersected by a sealed slot 45 or a gap at die level of the tightening area. The sealing is thus ensured as this is shown at A in Fig. 7. Under the influence of pressure, the part(s) situated on either side of the intersection of the tightening area is or are pushed outward, thus letting die suφlus gas escape, as is shown at B in Fig. 7. A last embodiment is shown in Fig. 8. The material which forms the casing is a deformable material, so that it is deformed in the case of oveφressure. At die level of the tightening area, as it is no longer maintained, an opening 35' is formed (see B in Fig. 8) and lets the gas escape. Fig. 9 shows in an exploded view an accumulator according to the invention. It is formed by a flat casing of me type shown in Fig. 3 and following and by an accumulator element 50 of the type described in cited Patent. The electrodes of this element are accessible via the plates 52 and 54 which are covered by me band 11 so as to ensure the sealing.

Claims: Claims: 1. A sealed casing provided for withstanding a certain pressure and intended to contain notably an electric accumulator, the casing being formed by at least one wall which has at least one closing area formed by a plastic band for connecting two edges of the wall, characterized in that the closing area comprises an adhesive part and a tightening part. 2. A sealed casing as claimed in claim 1, characterized in that the length of the tightening part is such that said tightening part overlaps said edges under me influence of a variation of pressure. 3. A sealed casing as claimed in claim 1, characterized in mat at least one opening to the exterior of said plastic band is provided at the level of said edges and in mat the lengm of the tightening part is such tiiat me opening is connected to me interior of said band under the influence of a variation of pressure. 4. A sealed casing as claimed in claim 1 , characterized in that the wall has a deformable area at the level of the tightening part and in that said deformable area deforms by forming an opening to the exterior under me influence of an a variation of pressure. 5. A sealed casing as claimed in claim 1, characterized in that the tightening part has a gap which opens under the influence of a variation of pressure. 6. An accumulator formed by at least one battery element and by a casing as claimed in one of the claims 1 to 5. 7. An accumulator as claimed in claim 6, characterized in mat said walls are formed by plates so that it appears in a flat form.

Inventors: VAN LERBERGHE STEVEN, VAN LERBERGHE, STEVEN
Applicants: LERBERGHE STEVEN VAN, PHILIPS ELECTRONICS NV, PHILIPS ELECTRONICS N.V., VAN LERBERGHE, STEVEN
Application year: 1997
Main classification: H01M2
IPC codes: H01M2, H01M10