Ultrasonic spot welding tip assembly and method for using the same

• US 4,647,325 A
• Filed: 03/21/1985
• Issued: 03/03/1987
• Est. Priority Date: 07/12/1984
• Status: Expired due to Term

• Current Assignee: Reynolds Consumer Products Incorporated
• Original Assignee: Presto Products Company
• Inventors: Bach, Gary
• Primary Examiner(s): WITYSHYN, MICHAEL G
• Application Number:
  US06/714,275
• Time in Patent Office: 712 Days
• Field of Search: 156/581, 156/73.1, 156/73.4, 156/290, 156/553, 156/580.1, 156/580.2, 156/157, 156/309.6, 156/380.8, 264/23, 425/174.2
• US Class Current: 156/73.1
• CPC Class Codes: B29C 65/08 using ultrasonic vibrations non-plastics element to plastics elements B29C65/645
• CPC Class Codes: B29C 66/0042 of the joining tool and the parts to be joined B29C66/0046 takes precedence; joining tool characterized by its composition B29C66/8122; joining tool characterized by its microstructure B29C66/8124
• CPC Class Codes: B29C 66/005 Detaching the article from the joining tool
• CPC Class Codes: B29C 66/1122 Single lap to lap joints, i.e. overlap joints B29C66/45, B29C66/472, B29C66/52272 take precedence
• CPC Class Codes: B29C 66/21 said joint lines being formed by a single dot or dash or by several dots or dashes, i.e. spot joining or spot welding
• CPC Class Codes: B29C 66/43 Joining a relatively small portion of the surface of said articles B29C66/45 takes precedence
• 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 66/73921 characterised by the materials of both parts being thermoplastics
• CPC Class Codes: B29C 66/81431 comprising a single cavity, e.g. a groove
• CPC Class Codes: B29C 66/81433 being toothed, i.e. comprising several teeth or pins comprising a single tooth B29C66/81429, or being patterned
• CPC Class Codes: B29C 66/8165 Carrier plates for mounting joining tool parts, e.g. for re-arranging the tool parts to make other forms
• CPC Class Codes: B29C 66/8167 Quick change joining tools or surfaces
• CPC Class Codes: B29C 66/81811 of the welding jaws
• CPC Class Codes: B29C 66/8322 Joining or pressing tools reciprocating along one axis
• CPC Class Codes: B29C 66/91421 of the joining tools
• CPC Class Codes: B29C 66/92653 said stops being adjustable
• CPC Class Codes: B29C 66/92655 by using several stops
• CPC Class Codes: B29C 66/9516 by controlling their vibration amplitude
• CPC Class Codes: B29K 2023/065 HDPE, i.e. high density polyethylene

Abstract

An ultrasonic welding tip assembly and associated method of use are described. The welding tips of the assembly may be conical with the cone height A and base width B having a ratio of A/B=1.2 or frusto-conical with a ratio of 0.76 in preferred embodiments. The welding tips are supported on anvils. In the welding process, the tips are only partially inserted into the material being welded so that the anvils remain spaced from the material. This space provides a reservoir into which molten material may flow away from the regions of the welding tips.

Claims

1. A method of spot welding a plurality of sheets of thermoplastic material together comprising the steps of:

(a) providing a plurality of welding tips adjacent to an obverse face of juxtaposed sheets of said thermoplastic material, each of said welding tips extending from an anvil and having a base attached to said anvil and an apex spaced from said anvil at a predetermined height above said anvil, said plurality of welding tips extending along a weld line to be formed in said juxtaposed sheets;

(b) inserting said welding tips into an obverse face of said juxtaposed sheets a sufficient distance so that each welding tip at least partially penetrates each sheet of material being welded, said distance being less than the height of said apex of said each welding tip above the anvil from which said each welding tip extends, to thereby provide a reservoir space between said anvil and the obverse face of said sheet material; and

(c) applying ultrasonic energy to said thermoplastic sheet material adjacent to said welding tips, said ultrasonic energy being applied by a welding horn extending along the entire length of said weld line and the ultrasonic energy applied adjacent to the distal ends of said weld line being slightly weaker than at intermediate positions along said line, the welding tips adjacent to the distal ends of said weld line having heights slightly greater than the heights of the welding tips intermediate the distal ends of said weld line.

2. A system for spot welding a plurality of sheets of thermoplastic material together comprising:

(a) a plurality of welding tips adjacent to an obverse face of juxtaposed sheets of said thermoplastic material, each of said welding tips extending from an anvil and having a base attached to said anvil and an apex spaced from said anvil at a predetermined height above said anvil, said plurality of welding tips extending along a weld line to be formed in said juxtaposed sheets;

(b) means for inserting said welding tips into an obverse face of said juxtaposed sheets a sufficient distance so that each welding tip at least partially penetrates each sheet of material being welded, said distance being less than the height of said apex of said each welding tip above the anvil from which said each welding tip extends, to thereby provide a reservoir space between said anvil and the obverse face of said sheet material; and

(c) means for applying ultrasonic energy to said thermoplastic sheet material adjacent to said welding tips, said ultrasonic energy being applied by a welding horn extending along the entire length of said weld line and the ultrasonic energy applied adjacent to the distal ends of said weld line being slightly weaker than at intermediate positions along said line, the welding tips adjacent to the distal ends of said weld lines having heights slightly greater than the heights of the welding tips intermediate the distal ends of said weld line.

3. The system of claim 2. wherein said means for inserting includes:

means for moving said welding horn against an opposite face of said juxtaposed sheets from said obverse face to thereby push said sheets onto said welding tips; and

stop means for stopping the movement of said welding horn when said welding tip penetrates into said sheets by said sufficient distance.

4. The system of claim 2 wherein the welding tips are selectively removable from the anvil from which they extend.

5. The system of claim 2 wherein the welding tips are cone-shaped, the base of each of said cone-shaped welding tips being supported on a major surface of the anvil from which it extends and having a maximum base dimension parallel to said major surface, the ratio of said predetermined height of said tip to said base dimension being approximately 1.2.

6. The system of claim 5 wherein the welding tips are right circular cones and wherein said base dimension is the base diameter thereof.

7. The system of claim 2 wherein the plurality of welding tips are staggered in two parallel rows along the welding line.

8. The system of claim 2 wherein the plurality of welding tips are clustered in groups.

9. The system of claim 2 wherein the welding tips are frustro-conical in shape, the base of each of said welding tips being supported by a major surface of the anvil from which it extends and having a maximum base dimension parallel to said major surface, the ratio of said predetermined height of said frustro-conical shaped tip to said base dimension being approximately 0.76.

10. The system of claim 9 wherein said frustro-conical shaped welding tip is a portion of a right circular cone, and said base dimension is the base diameter thereof.

11. The system of claim 9 wherein the frustro-conical welding tip is supported by a cylindrical projection, the diameter of said cylindrical projection being larger than said base dimension, thereby providing a shoulder around said base, whereby said shoulder acts as a stop against said obverse face.