Safety device for use in secondary battery

• US 5,766,793 A
• Filed: 10/08/1996
• Issued: 06/16/1998
• Est. Priority Date: 10/09/1995
• Status: Expired due to Fees

• Current Assignee: Wako Electronics Co., Ltd. (Toshiba Corporation)
• Original Assignee: Wako Electronics Co., Ltd. (Toshiba Corporation)
• Inventors: Hayashi, Toshiharu, Kameishi, Toshizou
• Primary Examiner(s): KALAFUT, STEPHEN J
• Application Number:
  US08/727,309
• Time in Patent Office: 616 Days
• Field of Search: 429/53, 429/56, 429/62
• US Class Current: 429/62
• CPC Class Codes: H01M 50/3425 in the form of rupturable membranes or weakened parts, e.g. pierced with the aid of a sharp member
• CPC Class Codes: H01M 50/574 Devices or arrangements for the interruption of current
• CPC Class Codes: H01M 50/581 in response to temperature
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A safety device for a battery which can prevent explosion of the battery due to overcharging or shortcircuiting. In the safety device, a current flows through generating unit, lead, terminal of a conductor case, PTC plate, annular terminal, contact to electrode lid. A disk spring, generally called a bimetal, is adapted to bend backward when it is heated to a predetermined temperature. If the generating unit heats up by producing gas due to overcharging or shortcircuiting, the disk spring is heated. When heated to a predetermined temperature, it will bend backward, while pushing up a moving piece, which in turn pushing up the contact, thus separating the contact from the annular terminal. The current-flow path in the battery is thus cut, so that the generating unit will not heat up any further.

Claims

1. A safety device for a battery having a battery case and a generating unit airtightly housed in the battery case, said safety device comprising:

a switch means adapted to be provided in a current-flow path of the battery; and

a thermally expansible member for gradually expanding in conjunction with a rise in temperature, wherein said thermally expansible member is disposed relative to said switch means such that, in response to a sufficient rise in temperature, said thermally expansible device will expand until said expansion effects a change over of said switch means.

2. The safety device for a battery as claimed in claim 1, further comprising a positive thermistor provided in the current-flow path in the battery.

3. The safety device for a battery as claimed in claim 1, further comprising a conductor case enclosing said thermally expansible member and said switch means, wherein said conductor case is formed with a hole through which the inside and outside of the battery case can communicate, and said hole is closed by a film adapted to rupture in response to a pressure in the battery case.

4. The safety device for a battery as claimed in claim 1, wherein said thermally expansible member is formed of a silicone rubber.

5. The safety device for a battery as claimed in claim 1, wherein said thermally expansible member is formed of a synthetic rubber.

6. The safety device for a battery as claimed in claim 1, wherein said thermally expansible device is formed of a synthetic resin.

7. A safety device for a battery having a battery case and a generating unit airtightly housed in the battery case, said safety device comprising:

a temperature-responsive deforming means in the form of a conductor, said temperature-responsive deforming means being adapted to deform when its temperature rises to a predetermined level; and

a switch means disposed adjacent to said temperature-responsive deforming means,

wherein said switch means is adapted to be provided in a current-flow path of the battery and said switch means changes over when said temperature-responsive deforming means deforms due to heat transferred from said switch means.

8. The safety device for a battery as claimed in claim 7, wherein said temperature-responsive deforming means is a bimetal comprising a plurality of laminated metal plates having different thermal expansion coefficients.

9. The safety device for a battery as claimed in claim 7, further comprising a positive thermistor for being provided in the current-flow path of the battery.

10. The safety device for a battery as claimed in claim 7, further comprising a conductor case enclosing said temperature responsive deforming means and said switch means, wherein said conductor case is formed with a hole through which the inside and outside of the battery case can communicate, and said hole is closed by a film adapted to rupture in response to a pressure in the battery case.