Thermoplastic container end and method and apparatus for inertial spinwelding of thermoplastic container ends

• US 4,534,751 A
• Filed: 05/02/1983
• Issued: 08/13/1985
• Est. Priority Date: 08/05/1982
• Status: Expired due to Term

• Current Assignee: Packaging Resources Incorporated (Huhtamaki Oyj)
• Original Assignee: Cosden Technology, Inc.
• Inventors: Fortuna, Vincent, MacLaughlin, Donald
• Primary Examiner(s): Kimlin, Edward
• Assistant Examiner(s): Falasco, L.
• Application Number:
  US06/490,610
• Time in Patent Office: 834 Days
• Field of Search: 156/69, 156/73.9, 156/73.5, 156/294, 156/293, 156/303.1, 156/308.4, 228/112, 228/2, 228/DIG. 60, 229/5.5, 229/5.8, 229/5.6, 493/108, 493/390, 493/112, 493/388
• US Class Current: 493/108
• CPC Class Codes: B29C 65/0672 Spin welding
• CPC Class Codes: B29C 65/069 the welding tool cooperating with specially formed features of at least one of the parts to be joined, e.g. cooperating with holes or ribs of at least one of the parts to be joined
• CPC Class Codes: B29C 65/7885 Rotary turret joining machines, i.e. having several joining tools moving around an axis
• CPC Class Codes: B29C 66/12441 being a single wall
• CPC Class Codes: B29C 66/12463 being tapered
• CPC Class Codes: B29C 66/12469 being asymmetric
• CPC Class Codes: B29C 66/542 joining hollow covers or hollow bottoms to open ends of container bodies
• CPC Class Codes: B29C 66/63 Internally supporting the article during joining B29C66/49 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 66/72328 Paper
• CPC Class Codes: B29C 66/73921 characterised by the materials of both parts being thermoplastics
• CPC Class Codes: B29C 66/8226 Cam mechanisms; Wedges; Eccentric mechanisms
• CPC Class Codes: B29C 66/8322 Joining or pressing tools reciprocating along one axis
• CPC Class Codes: B29K 2023/065 HDPE, i.e. high density polyethylene
• CPC Class Codes: B65D 15/08 with end walls made of plastics material

Abstract

A thermoplastic end (110), particularly a bottom, for a container which has upstanding paperboard sidewalls (112) and which is inertially spinwelded onto the paperboard sidewall for bonding. The end portion (110) has an annular groove (148) for snugly receiving the sidewall (112) and a wall configuration (136, 138, 140, 142 and 144) which minimizes the forces exerted on the bond which would tend to dislodge the end portion. The wall configuration is generally in the form of an inverted U-shape with a portion of an upstanding wall of the U forming a side of the annular groove. The end portion has strengthening ribs (122) positioned generally within the region of U-shape and additional radial ribs imparting strength and rigidity to the container end. The paperboard sidewall may be internally lined with a layer of thermoplastic material or may be unlined. During spinwelding, a sidewall supporting mandrel having an expansible engaging portion is inserted into the sidewall and subsequently expanded to define a cylindrical surface of a diameter equal to that of the specified internal diameter of the sidewall. A teflon seating member at the end of the sidewall supporting mandrel establishes the depth to which the container end is inserted into the sidewall.

Claims

1. A method of making a container having a paperboard sidewall portion and a thermoplastic end portion spinweld bonded thereto, comprising the steps of:

providing a thermoplastic container end comprising

(a) a first portion for receiving one end of the container sidewall, said first portion comprising a first annular groove formed by a first wall member extending from the bottom of said groove and adapted to lie on the outer surface of the container sidewall and a second wall member relatively longer than said first wall member and extending from the bottom of said groove and being adapted to enter into the container and lie on the inner surface of the container sidewall; and

(b) a second portion, connected to said second wall member at a position remote from said first wall member and near the end of said second wall member adapted to enter into the container, said second portion including means for transferring to a direction normal to a spinwelded bond, any shear forces which arise due to axial forces on the container end which tend to shear said spinwelded bond, said shear force transmitting means comprising (i) an end-wall portion connected to and extending from said second wall member in a serpentine manner to form therewith a second annular groove of generally opposite orientation from said first annular groove and (ii) a plurality of circumferentially spaced radial ribs, extending between said second wall portion and said serpentine end-wall portion, said plurality of ribs being operable to transfer forces acting on said container end from shearing said spinwelded bond;

positioning said paperboard sidewall on a first mandrel having a vertical axis;

positioning said container end on a second mandrel, coaxial with said first mandrel;

rotating said second mandrel about said axis whereby said radial ribs on said end portion engage driving means on said second mandrel to rotate said end portion;

positioning an end of said paperboard sidewall into said first annular groove of said container end, whereby said shear force transmitting means supports said second wall member against lateral deflection and whereby the rotary inertia of said second mandrel generates frictional heat which spinweld bonds said container to said sidewall.

2. A method according to claim 1, further including the step of coating the paperboard sidewall with a coating of thermoplastic, synthetic resin material prior to positioning said sidewall on said first mandrel.

3. A method according to claim 1, wherein said second wall member is bevelled radially inwardly along a portion thereof, and said end-wall portion is connected to said second wall member at a radially inward location of said bevelled portion, whereby the bevelled portion facilitates said step of positioning an end of said sidewall into said first annular groove.