METHOD AND APPARATUS FOR HEATING STRIPE-LIKE AREAS ON CAN BODIES

• US 3,840,138 A
• Filed: 04/25/1973
• Issued: 10/08/1974
• Est. Priority Date: 04/25/1973
• Status: Expired due to Term

• Current Assignee: Glenn R. Mohr
• Original Assignee: Glenn R. Mohr
• Inventors: Mohr, Glenn R.
• Primary Examiner(s): Reynolds, Bruce A.
• Application Number:
  US05/354,350
• Time in Patent Office: 531 Days
• Field of Search: 219/8.5,10.41,10.43,10.53,10.57,9.5,10.71,10.79,10.49 117/93.2,93,21 118/641
• US Class Current: 219/635
• CPC Class Codes: B21D 51/2676 Cans or tins having longitudinal or helical seams
• CPC Class Codes: H05B 6/103 multiple metal pieces successively being moved close to the inductor

Abstract

This disclosure relates to the induction heating of stripe-like areas of can bodies under controlled conditions utilizing electrical energy on the order of 10 KHz and lower. The necessary heating is accomplished under very controlled conditions utilizing a plurality of separate coils.

Claims

1. A method of substantially uniformly heating a longitudinally moving member of a finite length along a longitudinally extending stripe-like area, said method comprising the steps of heating primarily along leading and trailing end portions thereof, and separately heating the member along the stripe-like area substantially between the end portions thereof.

2. The method of claim 1 wherein the heating of each of the end portions occurs separate and apart from one another.

3. The method of claim 2 wherein the heating of the members occurs sequentially starting at one end of the member.

4. The method of claim 1 wherein the heating pattern of each of the heated end portions is one wherein maximum heating occurs at the respective terminal end of the member and said heating reduces to minimum approaching zero spaced from the respective terminal end.

5. The method of claim 4 wherein the heating pattern effected by the separately heating of the member is one of substantially constant temperature for the major portion thereof and reducing to a minimum approaching zero adjacent the terminal ends of the member.

6. The method of claim 5 wherein areas of reduced heating by the several heating steps overlap and compensate to provide the substantially uniform heating.

7. The method of claim 1 wherein the member is a tubular member.

8. The method of claim 1 wherein the member is a can body.

9. The method of claim 1 wherein the member is a can body and a stripe of material to be processed is applied to the can body over the stripe-like area.

10. The method of claim 9 wherein the material of the stripe of material is a thermoplastic, and there is a like final heating of the can body to effect curing of the applied stripe of material.

11. The method of claim 10 wherein the thermoplastic material is applied as a powder and initial heating of the can body effects melting of the thermoplastic material and the final heating effects a cross linking of molecular chains of the thermoplastic material.

12. The method of claim 11 wherein the can body has a welded seam, the stripe-like area extends along the welded seam, and the stripe of material is applied to the can body while the stripe-like area remains heated from the welding and provides for said initial heating.

13. The method of claim 9 wherein the material of the stripe of material is a thermoplastic and is applied to the can body as a powder with the heating of the can body being sufficient to effect melting and curing of the thermoplastic material.

14. The method of claim 9 wherein the can body has a welded side seam, the stripe-like area is along the welded seam, the stripe of material is applied while the stripelike area remains heated, and the heating steps are subsequently performed.

15. The method of claim 14 wherein the material of the strip of material is a thermoplastic and is applied to the can body as a powder with the heating of the can body being sufficient to effect melting and curing of the thermoplastic material.

16. The method of claim 1 wherein the member is a can body and a stripe of material to be processed is applied to the can body over the stripe-like area both externally and internally.

17. The method of claim 16 wherein the heating steps are repeated and at least one of the stripes of material is applied to the can body intermediate heatings of the can body.

18. The method of claim 16 wherein the heating steps are repeated and there is a heating of the can body both prior to and subsequent to each application of a stripe of material.

19. The method of claim 18 wherein the material of the stripes of material is a thermoplastic, and there is a like final heating of the can body to effect curing of the applied stripes of material.

20. The method of claim 19 wherein the thermoplastic material is applied as a powder and initial heating of the can body effects melting of the thermoplastic material and the final heating effects a cross linking of molecular chains of the thermoplastic material.

21. The method of claim 20 wherein the can body has a welded seam, the stripe-like area extends along the welded seam, and a first of the stripes of material is applied to the can body while the stripe-like area remains heated from the welding and provides for said initial heating.

22. The method of claim 1 wherein the heating is effected by passing the member through separate fields of electrical energy.

23. The method of claim 22 wherein the electrical energy is low frequency electrical energy ranging from 3 to 10 KHz.

24. The method of claim 1 wherein the heating is effected by passing the member through separate fields of electrical energy produced by separate coils.

25. An apparatus for substantially uniformly heating a member of a finite length along a longitudinally extending stripe-like area comprising means for moving the member uniformly along a longitudinal path, and a series of heater means for separately heating the stripe-like area of a moving member, said series of heater means including first heater means for heating a member along the stripe-like area thereof to a desired temperature primarily along leading and trailing end portions thereOf, and second heater means for separately heating the member to the desired temperature entirely along the stripe-like area except for there being a minimal heating of the end portions thereof.

26. The apparatus of claim 25 wherein said first heater means include two separate heater means for separately heating the leading end portion and the trailing end portion.

27. The apparatus of claim 26 wherein said separate heater means are disposed on opposite sides of said second heater means along said path.

28. The apparatus of claim 26 wherein said separate heater means are of a different design from said second heater means.

29. The apparatus of claim 28 wherein said second heater means includes longitudinally elongated coils having longitudinal segments disposed parallel to said path in substantially centered relation thereto.

30. The apparatus of claim 29 wherein there are a plurality of said series of heater means and all of said second heater means are coupled in series.

31. The apparatus of claim 26 wherein each separate heater means includes a U-shaped core having two legs opposing said path and having an energizable winding on one leg only.

32. The apparatus of claim 31 wherein the cores of the two separate heater means are like oriented and the windings are on different respective legs.

33. The apparatus of claim 31 wherein the windings of the two separate heater means are coupled in series.

34. The apparatus of claim 31 wherein there are two of said series of heater means, and the first heater means of the two series of heater means are different to produce different heating results.

35. The apparatus of claim 34 wherein the windings of one of said first heater means are closer to said path than the windings of the other of said first heater means.

36. The apparatus of claim 34 wherein the windings of one of said first heater means are closer to said path than the windings of the other of said first heater means, and the number of windings of said one first heater means is less than the number of windings of said other first heater means.

37. The apparatus of claim 25 wherein the apparatus is particularly adapted for applying a side seam stripe to a can body and includes stripe material applying means, and said series of heater means are particularly adapted to process said stripe material.

38. The apparatus of claim 37 wherein said stripe material applying means is of the type for applying powdered material.

39. The apparatus of claim 37 wherein said series of heater means are operable to effect melting of applied stripe material.

40. The apparatus of claim 37 wherein said apparatus includes means for welding said side seam in advance of said series of heater means.

41. The apparatus of claim 40 wherein said stripe material applying means are disposed adjacent said welding means whereby a seam area of a can body is still at an elevated temperature when the stripe material is applied thereto.

42. The apparatus of claim 40 wherein said stripe material applying means are disposed in advance of said series of heater means.

43. The apparatus of claim 42 wherein there are a plurality of said series of heater means, and there is a second means for applying a second stripe forming material to a can body intermediate two of said series of heater means, one stripe material applying means being of the type for applying an internal stripe and the other stripe material applying means being of the type for applying an external stripe.

44. The apparatus of claim 25 wherein the moving means are particularly adapted for conveying can bodies of the type having a longitudinal seam, said apparatus including means for applying a meltable material to said side seam, and said series of heater means are operable to melt applied material along said seam.

45. The apparatus of claim 25 wherein each heater means is in the form of a ferrite filled coil.

46. The apparatus of claim 25 wherein each heater means is in the form of a coil energized by a low frequency current on the order of 3 to 10 KHz.

47. A method of curing on a can body a side stripe of thermoplastic material applied in powdered form comprising the steps of inductively heating the can body in the area of the side stripe to a temperature sufficient to effect melting of the thermoplastic material utilizing low frequency electrical energy, generally maintaining the temperature for a time sufficient to allow the melted material to flow and wet the underlying can body surface with there being a mixing of the powdered constituent thereof, and thereafter inductively heating the can body in the area of the side stripe to a temperature to effect cross linking of the thermoplastic material utilizing low frequency electrical energy.

48. The method of claim 47 wherein the frequency of the electrical energy is maintained substantially between 3 and 10 KHz.

49. The method of claim 48 wherein end portions of the can body in the area of the side stripe are heated separately from the remainder of the area.

50. The method of claim 47 wherein the can body is heated prior to the application of the stripe material.

51. The method of claim 50 wherein the can body has a side seam, the stripe material is applied over the side seam, and the can body is prior heated along the side seam during the formation thereof.