Differential pressure formed luggage with molded integrated frame

• US 5,894,007 A
• Filed: 03/14/1997
• Issued: 04/13/1999
• Est. Priority Date: 06/07/1995
• Status: Expired due to Fees

• Current Assignee: Samsonite Corporation
• Original Assignee: Samsonite Corporation
• Inventors: Bromley, Robert, Kapushion, Joseph, Younessian, Elliott
• Primary Examiner(s): Timm, Catherine
• Application Number:
  US08/818,023
• Time in Patent Office: 760 Days
• Field of Search: 264/522, 264/544, 264/549, 264/550, 264/553, 264/554, 264/318, 264/291, 264/292, 425/387.1, 425/388, 425/384, 190/121, 190/122
• US Class Current: 264/522
• CPC Class Codes: A45C 5/03 Suitcases
• CPC Class Codes: B29C 51/10 Forming by pressure difference, e.g. vacuum
• CPC Class Codes: B29C 51/34 for undercut articles
• CPC Class Codes: B29K 2023/12 PP, i.e. polypropylene
• CPC Class Codes: B29K 2055/02 ABS polymers, i.e. acrylonitrile-butadiene-styrene polymers
• CPC Class Codes: B29L 2031/7418 Suitcases

Abstract

The invention relates to hard sided luggage shells and other containers manufactured using vacuum forming or pressure forming of thermoplastics. A process for making shells and containers with integrally molded frames is disclosed, and products made by the method. A method of manufacturing differential pressure formed containers with framed openings, but without the need to attach a separate frame element to the molded shell. A process also is disclosed for reducing the undesirable stretching of shell material that occurs during differential pressure forming, particularly the thinning of corner portions of the shell or container. The process of the invention more efficiently utilizes the thermoplastic material by moving material from otherwise offal portions into the molded product. An improved method for severing the offal material from the final product is disclosed.

Claims

1. A process for molding a shell from a sheet of plastic material, the shell having a bottom and side portions extending from the bottom to a peripheral edge, the intersection of two side portions and the bottom generally defining a shell corner, the process comprising the steps of:

(a) heating the sheet of plastic material, the sheet having a central portion, a marginal portion, and a selvage portion;

(b) providing a mold means having a mold surface of a shape corresponding to the shell;

(c) providing a form space defined in part by the mold surface;

(d) providing at least one movable side draw form extending into the form space;

(e) positioning the central portion of the sheet in the mold means opposite the mold surface;

(f) providing a clamp remote from the mold surface;

(g) clamping the selvage portion of the sheet;

(h) disposing four rigid, upwardly extending, corner plugs within the form space;

(i) contacting the sheet with the four corner plugs and deliberately allowing the sheet to droop and sag by gravity between all four plugs to pre-stretch the central portion of the sheet;

(j) allowing the heated sheet to slide inwardly over the four corner plugs and into the form space prior to forcing the central portion against the mold surface;

(k) conforming the central portion of the sheet to the mold surface to form the bottom and the side portions of the shell;

(l) forcing the marginal portion of the sheet against the side draw form, thereby shaping the marginal portion to fashion a frame integrally formed with the central portion, said frame extending substantially continuously along at least one of the side portions of the shell, and said frame comprising a wall member and a flange, said forcing step comprising;

bending the marginal portion to form the wall member extending into the form space from the side portion of the shell; and

fashioning the flange so that said flange extends from the wall member to the selvage portion and is disposed at an angle with respect to the wall member and to the selvage portion;

(m) laterally retracting the side draw form to a retracted position substantially outside the form space;

(n) only after laterally retracting the side draw form, removing the shell from the mold surface; and

(o) severing the selvage portion of the sheet from the flange to free an edge of the flange whereby, after the step of severing, the peripheral edge is defined by the free edge of the flange.

2. The process of claim 1 wherein the step of heating the sheet of plastic material comprises heating a sheet of acrylonitrile-butadiene-styrene.

3. The process of claim 1 wherein the step of heating the sheet of plastic material comprises heating a sheet of polypropylene resin.

4. The process of claim 1 wherein the step of providing a mold means comprises providing a means for vacuum forming the sheet of plastic material against the mold surface.

5. The process of claim 1 wherein the step of conforming the the central portion of the sheet to the mold surface comprises supplying a pressure differential across the sheet to force the sheet against the mold surface.

6. The process of claim 5 wherein the step of supplying the pressure differential comprises:

(a) inducing a vacuum on one side of the sheet; and

(b) applying air pressure to the other side of the sheet.

7. The process of claim 5 wherein the step of supplying a pressure differential comprises providing a upper platen assembly movably disposed parallel and next to a lower platen assembly.

8. The process of claim 7 further comprising:

(a) stretching parts of the sheet prior to supplying the pressure differential; and

(b) retarding stretching of selected sections of the sheet which form the shell corners.

9. The process of claim 8 wherein the step of retarding stretching of sections of the sheet further comprises:

(a) disposing at least one corner plug between the upper platen assembly and the lower platen assembly plug to help shape at least one shell corner;

(b) cooling the corner plug; and

(c) placing the heated sheet in contact with the corner plug.

10. The process of claim 1 wherein the shell is a shell of a luggage case, and wherein the frame defines a hinged opening of the luggage case.

11. The process of claim 1 wherein the shell is a shell of a luggage case, and wherein the frame defines a hinged opening of the luggage case.

12. The process of claim 1 wherein the step of severing the selvage portion of the sheet is performed while the central portion of the sheet is conformed to the mold surface.

13. The process of claim 12 wherein the step of severing a selvage portion comprises:

(a) providing a movable plate proximate to the sheet;

(b) moving the plate toward a fixed block;

(c) pinching the sheet between the block and the movable plate; and

(d) separating the sheet from the mold surface after the sheet has been pinched.

14. A process for molding a luggage shell from a sheet of thermoplastic material, the luggage shell having a bottom, corner portions, and side portions extending from the bottom to a peripheral edge, comprising the steps of:

(a) heating a sheet of thermoplastic material, the sheet having a marginal portion at least partially surrounding a central portion and a selvage portion at least partially surrounding the marginal portion;

(b) partially surrounding a form space with a mold surface;

(c) placing at least one movable side draw form in an extended position protruding at least partially into the form space;

(d) providing a clamp remote from the mold surface;

(e) clamping the selvage portion of the sheet;

(f) disposing four rigid upwardly extending corner plugs in the form space;

(g) contacting the sheet with the four corner plugs and deliberately allowing the sheet to droop and sag by gravity between all four plugs to pre-stretch the central portion of the sheet;

(h) allowing the heated sheet to slide inwardly over the four corner plugs prior to forcing the central portion against the mold surface;

(i) forcing the central portion of the heated sheet against the mold surface;

(j) forcing the marginal portion of the heated sheet against the side draw form, while the side draw form is in the extended position, thereby shaping the marginal portion to define a frame, said frame comprising a wall member and a flange, along the peripheral edge, said step of forcing comprising;

bending the marginal portion to form the wall member extending at an angle from the side portions into the form space; and

fashioning said flange extending from the wall members and disposed at an angle with respect to the bottom; and

(k) translating parallel to the wall member the side draw form to a retracted position substantially outside the form space while the central portion is against the mold surface.

15. The process of claim 14 further comprising the steps of:

(a) severing the selvage portion of the sheet from the marginal portion; and

(b) separating the central portion of the sheet from the shell mold after severing the selvage portion.

16. The process of claim 15 wherein the step of severing the selvage portion further comprises:

(a) disposing a block means on one side of the sheet;

(b) providing a movable plate means on the other side of the sheet;

(c) moving the plate means toward the block means; and

(d) pinching the sheet between the plate means and the block means.

17. The process of claim 14 further comprising the step of substantially impeding the thinning of selected sections of the sheet corresponding to the corner portions of the shell.

18. The process of claim 17 wherein the step of substantially impeding the thinning of selected sections of the sheet comprises cooling the sections of the sheet prior to forcing the central portion of the heated sheet against the mold surface.

19. The process of claim 18 wherein the step of cooling the sections of the sheet comprises chilling said corner plugs.