Method of heat sealing a battery

• US 5,197,994 A
• Filed: 11/26/1990
• Issued: 03/30/1993
• Est. Priority Date: 11/26/1990
• Status: Expired due to Fees

• Current Assignee: Daniell Battery Manufacturing Company Incorporated
• Original Assignee: Daniell Battery Manufacturing Company Incorporated
• Inventors: Brocksmith, Donald E.
• Primary Examiner(s): GROUP, KARL E
• Application Number:
  US07/618,073
• Time in Patent Office: 855 Days
• Field of Search: 429/175, 429/178, 429/185, 29/623.2, 156/499
• US Class Current: 29/623.2
• CPC Class Codes: B29C 65/20 with direct contact, e.g. using "mirror"
• CPC Class Codes: B29C 66/1142 Single butt to butt joints
• CPC Class Codes: B29C 66/341 Measures for intermixing the material of the joint interlayer
• CPC Class Codes: B29C 66/53461 joining substantially flat covers and/or substantially flat bottoms to open ends of container bodies
• CPC Class Codes: B29C 66/71 characterised by the composition of the plastics material of the parts to be joined welding bar compositions B29C65/125
• CPC Class Codes: B29C 66/8322 Joining or pressing tools reciprocating along one axis
• CPC Class Codes: B29C 66/9292 in explicit relation to another variable, e.g. pressure diagrams
• CPC Class Codes: B29K 2023/12 PP, i.e. polypropylene
• CPC Class Codes: B29L 2031/7146 Battery-cases
• CPC Class Codes: H01M 50/171 using adhesives or sealing agents
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y10T 29/4911 including sealing

Abstract

A heat sealed butt joint for plastic parts such as a battery formed by at least a two step force application. The adjacent portions of the butt joint of the battery cover and case are preheated to a near liquid state causing rollover on the sides of the joint. The first step force application is of a lighter amount and is held for a predetermined time which causes the heated rollover on the sides of the battery to solidify. The second step force is of a heavier amount and is held for a predetermined time which causes the molten polymers of the heated portions of the battery cover and case to mix and bond together while the solidified rollover from the first step acts as a dam to prevent further rollover during the second step. The formed sealed battery has improved bursting strength and the process can be used for joining various other butting plastic parts to improve the tensile strength of the bond between the parts.

Claims

1. A method for sealing a battery top cover, having a sealing surface, to a battery case, having a sealing surface, the top cover and the case having sides thereon, comprising the steps of:

(a) providing a battery top cover and case along with a battery heat sealing device having a heating platen for heating the sealing surfaces of the top cover and case;

(b) positioning the sealing surfaces of the top cover and the case against the heating platen with a force and heating the surfaces with the heating platen for a time to soften the surfaces to a near liquid state, the positioning of the sealing surfaces against the heating platen causing heated rollover of the softened surfaces on the sides of the top cover and the case;

(c) removing the heating platen from the sealing surfaces;

(d) bringing the heated sealing surfaces of the top cover and the case into contact with each other with at least a first contact force;

(e) holding the first contact force for a time to allow the heated rollover on the sides of the top cover and the case to solidify while the space between the sealing surfaces and the rollover remains molten;

(f) applying at least a second contact force for a time to the top cover and the case to mix and to physically bond the molten polymers from the sealing surfaces of the top cover and the case, with the solidified rollover preventing further rollover from forming on the sides of the top cover and the case during application of the second contact force; and

(g) releasing the contact forces from the top cover and the case thereby providing a sealed battery having increased bursting strength.

2. The method as defined in claim 1 wherein the sealing surfaces of the top cover and the case are heated to approximately 600 degrees Fahrenheit by the heating platen.

3. The method as defined in claim 1 wherein the first contact force is approximately 100 pounds of force applied across the sealing surfaces.

4. The method as defined in claim 3 wherein the first contact force is held for approximately three seconds.

5. The method as defined in claim 1 wherein the second contact force is approximately 1200 pounds of force applied across the sealing surfaces continuously from 100 pounds to 1200 pounds.

6. The method as defined in claim 6 wherein the second contact force is held for approximately 3 to 4 seconds.

7. A method for sealing adjacent butt joints of plastic components, the butt joints having sealing surfaces and sides, comprising the steps of:

(a) providing the adjacent butt joints and a heat sealing device for heating the sealing surfaces of the butt joints;

(b) positioning the sealing surfaces of the butt joints against the heat sealing device with a force and heating the surfaces for a time with the heat sealing device to soften the surfaces to a near liquid state, the positioning of the sealing surfaces against the heat sealing device causing heated rollover of the softened surfaces on the sides of the butt joints;

(c) removing the heating device from the sealing surfaces;

(d) bringing the heated sealing surfaces of the butt joints into contact with each other with at least a first contact force;

(e) holding the first contact force for a time to allow the heated rollover on the sides of the butt joint to solidify while the space between the sealing surfaces and the rollover remains molten;

(f) applying at least a second contact force for a time to the butt joints to mix and to physically bond the molten polymer of the sealing surfaces with the solidified rollover preventing further rollover from forming on the sides of the butt joints during application of the second contact force; and

(g) releasing the contact forces from the butt joints thereby providing a sealed butt joint having increased bursting strength.