Patent Publication Number: US-2023145792-A1

Title: Method For Producing A Suitcase, And Such A Suitcase

Description:
The invention relates to a method for producing a suitcase according to the preamble of claim  1 . 
     The invention further relates to a suitcase according to the preamble of claim  8 . 
     Suitcases, in particular hard-shell suitcases comprising at least one suitcase shell made of at least partially solid material but also suitcases having a suitcase shell made of a softer, frequently textile material are typically composed of several components, wherein a rough distinction is made between the suitcase shell and various attachments. Classically suitcases today are fitted with various attachments such as wheels, pull-out rods, side handles or other functional elements which are more heavily loaded during use. Usually these attachments consist of several components, in particular components which are attached in the suitcase shell and those which are attached outside the suitcase shell, which are connected to one another. 
     This fastening of the attachments to the suitcase shell is nowadays accomplished with screws or rivets. In this case, the suitcase shell is usually clamped between an interior and an exterior plastic part (together: conventional attachment) and the two plastic parts are connected by means of screws or rivets, wherein the screws are guided through holes in the suitcase shell. The exterior plastic part is, for example, the wheel housing. The interior plastic part, for example, a counterpiece to the exterior plastic part, is absolutely necessary for the strength of the conventional construction so that acting forces do not act directly on the edge of the opening in the suitcase shell and result in its rupture but the forces acting on the screw connection are thus better distributed over larger areas of the suitcase shell. The suitcase shell and/or the attachments in this case mostly consist of plastic but can also be made of metal such as aluminium, carbon and the like. An advantage with screws is that the items of luggage can thus be produced by relatively untrained staff and without special devices and machines. 
     During usage of the suitcase, there is the risk that it will be destroyed by incorrect or rough handling, wherein typically the connection between the wheels and the suitcase shell breaks since the greatest forces frequently act here. Fastening by means of screws (and to a lesser extent rivets) allows the replacement of defective attachments but only as long as the suitcase shell of the piece of luggage itself has not been destroyed. Unfortunately the suitcase shell also breaks very frequently for several reasons. For example, it is usual that the screws (made of metal) or rivets are stronger than the suitcase shell, with the result that the suitcase shell must absorb these forces at a small point. It is true that the inner part helps to distribute the forces from the screw somewhat further to the suitcase shell but ultimately the inner part can only somewhat cushion the forces, not distribute them completely to large areas of the suitcase shell. Also the suitcase shell is necessarily weakened by the holes for the screws at these points and in addition, the round hole for the screw produces a location of maximum stress, i.e. a point at which the pressure or tension acting due to external forces is concentrated as stress in the component. The hole in the suitcase shell or the large difference in the strength between screw and suitcase shell produces so to speak an “predetermined breaking point” in the suitcase shell and also in the attachment structure. If an attachment is held by four screws, for example, the entire acting load is then concentrated on those four screw points. The stress on the suitcase shell is also concentrated around those four openings which are absolutely necessary for the screws. 
     A further disadvantage of conventional screw or rivet connections is that these screws and the inner part in the interior of the suitcase would be visible and as a result covers and linings made of fabric which cover these inner parts and screws are necessary. This increases costs and weight of the suitcase. Also these lining materials typically do not abut closely against the suitcase shell with the result that the interior of the suitcase seems rather chaotic, creased, untidy and visually smaller compared to the smooth external appearance. 
     Another disadvantage of conventional screw or rivet connections is that these weigh a relatively large amount. Typically an interior plastic part is required and the screws made of heavy metal additionally increase the weight of the suitcase. 
     Finally, an incorrect handling when connected by untrained staff is possible since screws and rivets which are not fastened by precisely defined procedures usually have a high tolerance with regard to clamping force, angle, depth of the screw connection etc. Also the screw head can be destroyed when tightening which makes the future replacement of the attachments difficult. 
     Central for the various disadvantages of conventional attachments is therefore the necessary presence of inner elements which are heavy, expensive, unaesthetic and perturbing. 
     A suitcase has become known from IT MI20 101 347 A1 in which the suitcase shell and attachments are made of thermoplastic material. A frame can be attached to the suitcase shell by means of adhesive connections or weld connections. The type of fastening of the attachments such as handles or wheels, for example, is not described, wherein it is merely mentioned that the attachments should preferably be exchangeable. 
     DE 299 04 675 U1 describes a hard shell suitcase for a portable PC wherein the suitcase shells have damping protrusions made of an elastic material which can also function as standing feet and are preferably integrated in the suitcase shell. 
     EP 2 873 341 A1, US 2007/0290465 A1, US 2001/0043008 A1, US 2006/0207848 A1, US 2004/0163910 A1, US 2009/0166141 A1 or U.S. Pat. No. 6,279,706 B1 disclose some variants of attachments for suitcases which are all fastened by means of screws or rivets and have outer and inner elements. Other variants of the fastening of attachments in suitcase construction are not known hitherto. 
     U.S. Pat. No. 9,681,717 B2 discloses a foldable suitcase made of flexible material, i.e. without a suitcase shell made of substantially solid material and provides in the description the possible theoretical possibility of a welding, screw connection or riveting of inner part and outer part, i.e. no welding of attachments and suitcase shell but a welding of two components of a conventional attachment to one another. Here the flexible material is clamped between inner part and outer part and the inner part is provided in the form of a plate which is covered by inner lining. In this case, screws or rivets would possibly be replaced by welding without eliminating the specific disadvantages of conventional connection methods and without optimizing outer part and suitcase shell for the connection method since inner part, inner cover and therefore high weight and high costs still persist. The flexible suitcase shell of the suitcase must still have openings (and therefore weak points and predetermined breaking points) through which inner part and outer part can come in contact with one another in order to be welded. The conventional attachments are therefore completely retained here, only the possibility of different connection methods between inner and outer part is provided. The welding of inner and outer part via openings in the flexible fabric skin of the suitcase provides scarcely any advantages compared with screw connection, with the disadvantage that the welding is no longer releasable and therefore the outer part can no longer be replaced. 
     It is the object of the invention to provide a production method for a suitcase and such a suitcase which results in production of a suitcase which is as cost-effective as possible, rapid and as automated as possible with the lowest possible weight and high strength. The interior of the suitcase should be as undisturbed as possible and usable with maximum volume. Disadvantages of known methods and suitcases should be eliminated or at least reduced. 
     The object according to the invention is achieved in terms of method by the features of the characterizing part of claim  1  and by a suitcase according to the characterizing part of claim  8 . 
     The materially bonded connection of the attachments to the suitcase shell according to the invention provides considerable advantages. In this case, the attachments are connected directly to the suitcase shell without inner elements. The finished suitcase is therefore manufactured without screws and without an inner element. The materially bonded connection is typically made not at individual points but along lines or surface. Depending on the component, the connection site can be selected so that it is optimal for strength, appearance and the process. Since the connection distributes the forces not to individual points but along lines or entire surfaces, the connection between suitcase shell and attachment is substantially more uniform and stronger, therefore better suited to receive impacts and forces and distribute them more uniformly in the component. In order to be able to distribute the forces as effectively as possible and uniformly to the suitcase shell, the attachment is provided at least partially on the side facing the suitcase shell with a complementary surface corresponding to the surface of the suitcase shell at the provided position. “Complementary” is understood here as surfaces which nestle against one another after the connection process to produce the materially bonded connection at least on some areas. How much the two surfaces adapt to one another depends on the selected type of connection. In the case of adhesive connections, for example, the largest possible adhesive area with a roughened surface is required, therefore it is positive if the largest possible areas of attachment and suitcase shell are substantially and if also roughened, matched to one another. If the attachment is produced by means of overmoulding directly on the suitcase shell, a complete matching is obtained almost automatically. In the case of plastic welding on the other hand, only small areas of matching are required or desirable, in particular non-complementary protrusions on the attachment are feasible or desirable which however are fused during the connection process and whose fused mass then forms the connection along the complementary surface areas surrounding the protrusions. Depending on the process parameters and further considerations, the protrusions and accordingly the areas surrounding these should be dimensioned differently. Accordingly it is also feasible that after the connection process a cavity is present between the attachment and the suitcase shell, for example, in order to save weight or provide special functions. 
     The suitcase shell need not have any holes or other openings and is therefore substantially stronger for this reason. In addition to the better mechanical strength and better force distribution, a further advantage of the invention is the substantially reduced weight of the suitcase since there are no screws and inner elements. The production process can be fully or partly automated, as a result costs can be reduced and the process tolerance restricted. 
     Another advantage is that the suitcase shell seems completely smooth on the inside, uninterrupted and free from perturbations, therefore an inner lining is no longer required. This also reduces costs and weight and leads to a more pleasing interior of the suitcase. 
     The materially bonded connection by means of plastic welding, for example, ultrasound welding is particularly advantageous since relatively low investment costs must be expended for this. Both suitcase shell and also attachment can have a perfect appearance after the welding process. Other welding techniques such as vibration welding or laser welding can give similar results with a higher degree of automation but also reach higher investment costs. 
     The attachments must be suitably formed for the welding process. For this purpose elevations or protrusions are preferably provided on the surface to be welded, which for example are fused by rapid friction of the components and thus produce the materially bonded connection. 
     The attachments themselves can be produced, for example, by injection moulding, in which case metal elements and the like can be overmoulded in order to ensure particular functions. 
     An alternative form of materially bonded connection of attachments and suitcase shell can be accomplished by direct overmoulding of the attachments onto the suitcase shell. However, high investment costs are required for this. In this case, substantially the attachments are produced directly on the suitcase shell, whereby molten plastic is injected directly onto the suitcase shell, which is inserted in an injection mould, and then cured. 
     Another possible form of the materially bonded connection is adhesive bonding. Fundamentally attachments could also be materially bonded by adhesive bonding to the suitcase shell. However, adhesive bonding has various process-dependent disadvantages compared with welding or overmoulding. 
     In some cases it can also be feasible to combine different materially bonded connection methods on one suitcase or even on a single attachment. For example, an attachment could be welded at one point and adhesively bonded at a different point which is inaccessible for the welding device. 
     Even though the principles of the materially bonded connection, such as plastic welding or overmoulding, are known from other industries, these have not been applied hitherto in the suitcase industry. The reason for this lies in the specific circumstances and functions of the attachments and the manufacturing process of suitcases but also in the known methods themselves since suitcases are relatively large products which makes processing difficult in conventional machines. Attachments which are suitable for the method according to the invention must be completely new and developed without inner parts. The form and structure of the attachment changes fundamentally. The entire production process of suitcases must be completely changed for the new manufacturing method. 
     Attachments to which particular attention is paid during the manufacture of suitcases and which are more frequently mentioned in the prior art and which must transfer particularly high forces can be differentiated in particular into devices for the fastening of wheels (wheel housing and the like) and pull-out handles. Conventional wheel housings or holders for pull-out rods for suitcases are typically composed of several components (inner elements, outer elements, screws). In the case of wheel housings, the suitcase shell of the suitcase must be provided at least with holes for screws, but frequently a part of the wheel housing projects into the suitcase shell so that this must have large openings for inlet of this wheel housing into the interior of the suitcase. In the case of holders for pull-out rods, openings at least the size of the pull-out rods are required. 
     Usually the inner element and the outer element overlap the openings and holes in the suitcase shell with a small edge in order to compensate for possible tolerances; otherwise the attachments are held very compactly. The aims of this construction are rather compact dimensions and to minimize the negative effects of the screw and openings for the strength of the suitcase shell and the attachments. The wheel itself is fastened via bearings and axles to the wheel housing. These bearings and axles are partially overmoulded metal components. Since the force is only transferred via the screw points in any case, a special stress-minimizing harmony of suitcase shell and wheel housing is not necessary. Suitcase shell and attachment can only be in contact along a few points. The outer or inner element is typically fitted with screw domes in which the screws are fixed. These screw domes must have a certain height in order to allow the screw a sufficient hold. 
     In contrast to this, attachments which have been developed according to the invention are constructed and formed completely differently. The attachments can relay forces to the suitcase shell over their entire contact area. The attachments manage without an inner part. In order to be able to divert the highest torques and distribute the forces over the largest possible area of the suitcase shell, compact forms are rather disadvantageous, the attachments are therefore rather designed to be in contact with the suitcase shell over a large area. Both suitcase shell and also attachments ideally have rounded, stress-minimizing shapes and nestle against one another over a large area. Openings or holes in the suitcase shell are no longer necessary, the suitcase shell thus remains completely continuous and visually pleasing from inside and substantially stronger since points with stress peaks are avoided. The attachments no longer have devices for receiving screws (screw dome, screw holes and the like) but remain substantially extensively compact along the suitcase shell. 
     If the materially bonded connection is made by ultrasound welding or vibration welding, small protrusions to be fused can be provided as part of the moulding of the attachments but also on the suitcase shell. These protrusions to be fused can be configured relatively freely so that an optimal manufacturing or connection process is made possible. The position, shape and number can be optimized according to the vibration frequencies used and further process parameters. 
     The inner element is completely omitted in the method of manufacture and suitcase according to the invention. It is no longer necessary or helpful since the forces are transferred via the materially bonded connection directly from the attachment to the suitcase shell and no stress peaks are formed. Bearings and axles can be fabricated in one piece with the attachment and formed so that forces are diverted in a stress-minimizing manner. 
     The connection process of conventional attachments with the suitcase shell is nowadays accomplished by hand, wherein the outer element usually produced from plastic injection moulding is screwed onto the inner element by means of an electric screwdriver and the suitcase shell is clamped between these two parts. On the one hand, this only requires workers with little training and low cost machines, on the other hand the proportion of manual work is relatively high. Possible human errors cannot be excluded. The costs for the process depend on the costs of the human work force and increasing wages directly result in an increase in costs. 
     In contrast, the method of manufacture according to the invention can be fully automated or at least partly automated. The investment costs are therefore higher but the processes and tolerances can be monitored precisely, the cost per unit are comparatively lower and independent of wage costs. 
     A disadvantage of a fixed, non-detachable materially bonded connection of suitcase shell and attachment is that the attachments cannot be exchanged for possible repairs. In order to counteract this potential disadvantage, the attachments according to the invention can be formed so that they are designed to receive and for detachable fastening of further components which can then be exchanged. Compared with conventional designs, this variant has the advantage that the suitcase shell remains without openings and holes, thus the forces are substantially better transferred and the suitcase shell is stronger because no stress peaks can occur at holes. The interior of the suitcase also remains clean, the inner part is omitted and a fabric covering of screws and inner part is no longer required. In this variant the structure is overall stronger and the weight of the suitcase is lighter, the interior of the suitcase is more pleasing, nevertheless the detachable parts of the structure can be exchanged. 
    
    
     
       The invention will be explained further hereinafter with reference to preferred non-restrictive exemplary embodiments with reference to the drawings. In the drawings 
         FIG.  1    shows a schematic view of a suitcase with two suitcase shells with attachments arranged thereon; 
         FIGS.  2   a  and  2   b    show sectional views of the connection of a wheel housing as attachment to a suitcase shell of a suitcase according to the conventional method and the method according to the invention; 
         FIG.  3    shows a method of producing a suitcase according to the invention by means of ultrasound welding; 
         FIG.  4    shows a further method of producing a suitcase according to the invention by means of vibration welding; 
         FIG.  5    shows a method of producing a suitcase according to the invention by means of laser welding; 
         FIGS.  6  to  9    show various methods of producing a suitcase according to the invention by overmoulding an attachment; 
         FIG.  10    shows a conventional method of producing a suitcase by means of screws; 
         FIG.  11    shows a semi-automated method of producing a suitcase according to the invention by means of ultrasound welding; 
         FIGS.  12   a  and  12   b    show schematically a conventional connection of a wheel housing as attachment to a suitcase with a suitcase shell; 
         FIGS.  13   a  to  13   c    show various possible designs of the attachments according to the invention and/or suitcase shell of a suitcase; and 
         FIG.  14    shows a cutaway view of a section of a suitcase with attachment according to the invention and cover elements arranged thereon. 
     
    
    
       FIG.  1    shows a suitcase  1  consisting of two suitcase shells  1   a ,  1   b  with various attachments  31  arranged thereon and connected thereto, such as handle holders  2 , wheel housings  3 , a stopper  4  or a holding device  5  for a pull-out rod. 
       FIGS.  2   a  and  2   b    show in sectional views comparatively different constructions of attachments  31 , in this example, wheel housing  3 , wherein the connection is made in a conventional manner by means of screws ( FIG.  2   a   ) and in a manner according to the invention ( FIG.  2   b   ). 
       FIG.  2   a    shows an exemplary conventional attachment  31 . The exemplary conventional wheel housing  3  has an outer element  14   a  and an inner element  12  which clamp the suitcase shell  1   a ,  1   b  of the suitcase  1  provided with openings  19  between them by placing screws  11  from inside into the screw dome  15  of the outer element  14   a  of the attachment  31 . The outer element  14   a  and the inner element  12  each cover the openings  19  in the suitcase shell  1   a ,  1   b  by means of an overlap D. As a result of the necessary height of the screw dome  15 , the outer element  14   a  only lies on the suitcase shell  1   a ,  1   b  at a few points  20 . Located inside the suitcase  1  is a cover  13 , usually made of fabric, which visually covers the screws  11  and the inner element  12 . The vertical axle  16   a  for the wheels can be produced as an overmoulded metal part or in one piece with the outer element  14   a.    
       FIG.  2   b    on the other hand shows an attachment  31  according to the invention which nestles against the suitcase shell  1   a ,  1   b  along a comparatively large surface  10  and is attached there by the production method according to the invention. No inner element and no inner cover is provided or necessary. The exemplary wheel housing  3 ,  14   b  nestles harmoniously and without stress peaks against the suitcase shell  1   a ,  1   b  without interrupting this. The suitcase shell  1   a ,  1   b  is therefore designed without holes and need not be covered by a cover in its interior. In this variant the wheel housing  3  is designed in one piece and in this case already integrates the axle  16   b  for the wheel in a form which optimally absorbs forces and diverts them to the suitcase shell  1   a ,  1   b  over a large area. In this example there is a hollow region between suitcase shell and attachment. 
       FIG.  3    shows a method for producing a suitcase  1  according to the invention by ultrasound welding. In this case the attachment  31  is provided at the position provided for it on the suitcase shell  1   a ,  1   b . A sonotrode  24  of the ultrasound welding device vibrates the attachment  31  in the vertical direction and against a fixing element  23  or counterpiece at a frequency which is suitable for fusing the surface of the attachment  31  and/or the suitcase shell  1   a ,  1   b  and thereby produce a durable connection between suitcase shell  1   a ,  1   b  and attachment  31 . 
       FIG.  4    shows an alternative production method according to the invention as in  FIG.  3    but in this example the attachment  31  is not fused by vertical movements of the sonotrode  24  but by horizontal movements of the sonotrode  24  during vibration welding. 
       FIG.  5    shows an alternative production method according to the invention but in this example the attachment  31  and/or the suitcase shell  1   a ,  1   b  is fused by the action of a laser  29 . 
       FIGS.  6  to  8    show production methods according to the invention corresponding to  FIGS.  3  to  5    with the difference that the attachments  31  contain an overmoulded metal part  30  to improve functionality and/or the strength. 
       FIG.  9    shows a production method according to the invention, wherein the attachment  31  is produced directly on the suitcase shell  1   a ,  1   b  in the initially molten state. For this purpose the suitcase shell  1   a ,  1   b  is fixed in the interior at least in some places by means of a fixing element  26  and an overmoulding mould  25  is pressed from outside onto the suitcase shell  1   a ,  1   b . The molten plastic  27  is pressed through a channel  28  into a cavity in the overmoulding mould  25  and cools down and solidifies there. Then overmoulding mould  25  and fixing element  26  are removed. This process can be fully automated which however is associated with high investment costs. A disadvantage is furthermore that the attachments  31  are subject to various process-dependent restrictions in their design. 
       FIG.  10    shows a conventional production method wherein an outer element  14   a  and an inner element  12  of a wheel housing  3  are fixed by means of screws  11  which act in screw dome  15  on the suitcase shell  1   a ,  1   b  with openings  19  provided for this purpose. 
       FIG.  11    shows an exemplary semi-automated production method of a suitcase  1  according to the invention with the aid of a prepared holding device  23 . In this case, the attachments  31  are firstly inserted into the positions provided for the attachments  31  in the holding device  23 , then the suitcase shell  1   a ,  1   b  is inserted and fixed by means of fixing elements  24 . Now the attachments  31  are connected to the suitcase shell  1   a ,  1   b  by ultrasound welding by means of sonotrodes  24  and then the successfully connected combination of suitcase shell  1   a ,  1   b  and attachments  31  is removed from the holding device  23  for further processing. This method manages with relatively low investment costs. The individual production steps can be carried out by hand or by robot. 
       FIG.  12   a    shows the composition of a typical conventional attachment  31 , in this case a wheel housing  3 , in an exploded view. This shows the outer element  14   a  with screw domes  15 , two inner elements  12  and the wheel element  22  which, for example, is fixed by means of screws or rivets  23  on the outer element  14   a . As a result of the necessary height of the screw dome  15 , the outer element  14   a  only abuts against the suitcase shell  1   a ,  1   b  of the suitcase  1  at a few points  20 . 
       FIG.  12   b    shows a three-dimensional view of a typical broken suitcase shell  1   a ,  1   b  from practical experience, wherein forces on the outer element  14   a  were too great and the suitcase shell  1   a ,  1   b  has broken at an opening  19  for the screw or rivet  23  and the suitcase shell  1   a ,  1   b  has been destroyed. 
       FIGS.  13   a ,  13   b  and  13   c    show attachments  31  with small protrusions  6 ,  7  to be fused in detail. The protrusions  6 ,  7  are appropriately integrated in the attachments  31  according to the invention on the side facing the suitcase shell  1   a ,  1   b  or surface  10  or contact surface between attachment  31  and suitcase shell  1   a ,  1   b  and/or also on the suitcase shell  1   a ,  1   b  itself (not shown). As a result of friction or vibration processes according to  FIGS.  3  and  4   , these protrusions  6 ,  7  are heated and fuse, whereby a very firm and permanent connection of attachment  31  and suitcase shell  1   a ,  1   b  is made possible.  FIG.  13   a    shows a view of protrusions  6  in three-dimensional view,  FIG.  13   b    shows various exemplary paths of protrusions  7  on exemplary surfaces or contact surfaces of attachments  31  which can be selected depending on the action of force and component shape.  FIG.  13   c    shows a three-dimensional view of a one-piece attachment  31  according to the invention in the form of an exemplary wheel housing  3  with protrusions  6 ,  7  at many strategically suitable points which can be fused when connected by means of ultrasound welding and produce the materially bonded connection to the suitcase shell  1   a ,  1   b . The position, size and shape of the protrusions  6 ,  7  is selected so that this is optimal for the process and the selected devices and machines. 
       FIG.  14    shows a possible two-or multi-part embodiment of an attachment  31  or wheel housing  3  which nestles against the suitcase shell  1   a ,  1   b  of the piece of luggage  1  or suitcase  21  along the largest possible surface  10  and is attached there by the production method according to the invention. The suitcase shell  1   a ,  1   b  is designed without holes and need not be covered by a cover in its interior. In this variant, the attachment  31 , for example, the wheel housing  3  is designed to be two-part, wherein the attachment  31  is designed so that it is suitable for detachable fastening of the axle part  3 C. Various known mechanical methods are known for fixing the axle part  3 C, for example, a bayonet closure or various other locks and the like. In this variant, the vertical axis  16   c  for the wheel consists of metal which was overmoulded with plastic.