Abstract:
A jigsaw puzzle transporting system ( 10 ) having a bottom part ( 12 ), a base plate ( 16 ) and a lid ( 14, 14′, 14″ ) is provided. An at least substantially vertically projecting frame ( 26 ) is present on the bottom part ( 12 ) for peripherally surrounding the base plate ( 16 ). A shoulder ( 38 ) with a holding lace ( 40 ) fitting into the frame ( 26 ) projects from the lid. Side faces ( 42, 30 ), mutually facing in a closed position, of the shoulder ( 38 ) and of the frame ( 26 ) cooperate for releasably locking the shoulder ( 38, 38′, 38″ ) in the frame ( 26 ). The shoulder ( 38, 38′, 38″ ) in the closed position is positioned, relative to the base plate ( 16 ) received in the frame ( 26 ), such that a distance (S) between the holding face ( 40; 40′; 40″ ) and an upper surface ( 74 ), facing the latter, of the base plate ( 16 ) is less than a jigsaw puzzle piece height (S P ).

Description:
TECHNICAL FIELD 
       [0001]    The invention relates generally to a system for storing and transporting loose pieces arranged in a plane. In particular, the invention relates to a jigsaw puzzle transporting system for a partially or completely assembled jigsaw puzzle. 
       BACKGROUND 
       [0002]    Assembling jigsaw puzzle pieces is a popular pastime for people of widely varying ages, with degrees of difficulty matched accordingly. The degree of difficulty can be determined in particular by the number of jigsaw puzzle pieces. With an increasing number of jigsaw puzzle pieces, the probability of losing an individual jigsaw puzzle piece increases. The desired aim of completely assembling a jigsaw puzzle can thus become unattainable. To prevent loss of individual jigsaw puzzle pieces, the pieces are traditionally transported and stored in lockable boxes. 
         [0003]    As the number of jigsaw puzzle pieces increases, so does the space and time required for complete assembly of the jigsaw puzzle pieces. There is often no suitable assembly surface. For lack of time, the solving of the jigsaw puzzle is often interrupted prematurely. Moreover, jigsaw puzzle pieces arranged in conventional boxes may be mixed again due to vibrations during transport. 
         [0004]    For this reason, transport-safe storage systems for partially or completely assembled jigsaw puzzles have been developed. The document U.S. Pat. No. 3,504,915 describes a jigsaw puzzle box having a bottom part for doing the jigsaw puzzle on an integrated assembly surface, a drawer which can be pulled out under the assembly surface and is used to store individual jigsaw puzzle pieces, and a lid, the side faces of which completely encompass the outside of the bottom part, including the closed drawer, when the lid is closed. The laid-open application DE 10 2007 052 846 A1 describes a travel jigsaw puzzle container, in which an insert is received in a lower box half and has a plurality of compartments which can be closed by a base plate lying thereon. The base plate and any jigsaw puzzle pieces assembled thereon are secured by placing an upper box half thereover. On closing these transport-safe storage systems, large air volumes are displaced from the lid and flow past the assembled jigsaw puzzle pieces through narrow gaps at correspondingly high flow velocities, with the attendant risk of subjecting the jigsaw puzzle pieces to turbulence. 
         [0005]    It is the object of the present invention to provide an improved jigsaw puzzle storing and transporting system. 
       SUMMARY 
       [0006]    This object is achieved according to the invention by a jigsaw puzzle transporting system having the features of claim  1 . The jigsaw puzzle transporting system comprises a bottom part, a base plate and a lid. A substantially vertically projecting frame is present on the bottom part tax peripherally surrounding the base plate. A shoulder with a holding face fitting into the frame projects from the lid. Side faces, mutually facing-in a closed position, of the shoulder and of the frame cooperate for releasably locking the shoulder in the frame. The shoulder in the closed position is positioned, relative to the base plate received in the frame, such that a distance between the holding face and an upper surface, facing the holding face, of the base plate is less than a jigsaw puzzle piece height. 
         [0007]    Two functions can be achieved by the shoulder. Firstly, the shoulder fastened to the lid can cooperate with a corresponding side face of the frame fastened to the bottom pail. Thus, releasable locking between the lid and the bottom part can be achieved. The substantially vertically projecting frame on the bottom part can also be widened in a funnel shape for simplified releasable reception of the shoulder. Secondly, the holding face can contact any jigsaw puzzle piece lying on the base plate. A vanishing distance is also possible, so that in the closed position the holding face bears on the base plate without jigsaw puzzle pieces lying therebetween, but this is not imperative. 
         [0008]    Furthermore, the shoulder can have a deformation property, so that on (even small) deformation of the shoulder (in particular of the holding face), the holding face produces a corresponding surface pressure which can arise in the closed position owing to the height of a jigsaw puzzle piece lying on the base plate. As a result of the surface pressure of the holding face on jigsaw puzzle pieces lying on the base plate, force locking can be induced between the jigsaw puzzle pieces and the base plate. The force locking can maintain the jigsaw puzzle pieces in a desired position on the base plate. 
         [0009]    For precise positioning of the shoulder locked in the closed position, a side face of the shoulder can cooperate with an inner side face of the frame. The side face of the frame can project from the bottom part perpendicularly or in a conically widening manner. The side face of the shoulder can project from the lid perpendicularly or in a conically tapering manner (complementarily to the corresponding side faces of the frame. Corresponding latching elements (opposite in the closed position) on mutually facing side faces can be configured to engage with one another in the closed position. 
         [0010]    For all-round locking, the side face of the shoulder can completely peripherally surround the latter. The latching elements can be arranged all the way round (preferably at regular intervals) on the respectively mutually facing side faces of the shoulder and the frame. 
         [0011]    For storing individual jigsaw puzzle pieces, a plurality of indented compartments (preferably let into the bottom part) can be provided inside the frame. The base plate received in the frame (and bearing on the frame in the inside thereof) can close the indented compartments. 
         [0012]    For simpler release of the locked closed position, the lid can project in an edge region laterally beyond the shoulder of the lid. An edge thickness of the lid is then less in the edge region than a shoulder height. In the closed position, the edge region can be grasped from the side. The edge region can thus be used virtually as a grasping strip for manually releasing the locking. 
         [0013]    On closing and releasing the locking, air flowing between the shoulder and the frame can be conducted through a plurality of air conducting grooves in the holding face. In particular, the air can be discharged and supplied laterally in that the air conducting grooves are open towards the side lace of the shoulder. 
         [0014]    In order to prevent adhesion of jigsaw puzzle pieces lying on the base plate to the holding face on releasing the locked lid, the air conducting grooves can form a regular channel network on the entire holding face. In addition, it is thus possible, preferably by a rectangular cross-sectional profile of the air conducting grooves, to achieve a dimensional stabilisation of the shoulder and hence of the holding face. The latter enables a uniform distribution of the surface pressure of the holding face on jigsaw puzzle pieces lying at different places on the base plate. 
         [0015]    As an alternative to a rigid holding face, the holding face can be designed elastically deformably. In this case, the holding lace is preferably curved convexly (i.e. so as to bulge from the shoulder) in an open position. A curved convexly (i.e. so as to bulge from the shoulder) in the open position. A holding face pre-curved convexly in the open position can first come to bear on the base plate (or any jigsaw puzzle pieces lying thereon) at the centre of the surface. With increasing proximity to the closed position, the holding face can then bear on the base plate (or any jigsaw puzzle pieces lying thereon) up to the edge. A situation where jigsaw puzzle pieces lying close to an edge of the base plate cause reduction or elimination of the surface pressure towards the centre of the base plate can thus be precluded. 
         [0016]    The shoulder can be a thermoformed part made of plastic, a thin-walled injection-moulded part made of plastic or a cardboard pressed part. The elastic deformability can thus be achieved by a deformability of the wall of the shoulder. For this purpose, the shoulder is preferably thin-walled. Furthermore, the shoulder can be a hollow body. In the case of a pressure-tightly sealed hollow body, a compressibility of an enclosed gas can contribute to the elasticity of the shoulder. 
         [0017]    The lid can be prestressed (by a lid curvature in a longitudinal direction of the lid). The prestressing of the lid can curve the shoulder convexly in the open position. A more complex production of a (inherently) convex shoulder can then be dispensed with. 
         [0018]    The shoulder can also be an elastic, foamed moulded part. In the case of a prestressed lid, the shoulder can be (inherently) biplanar and be curved biconvexly by the lid stress only after fastening to the lid. A plane-convex moulded part can be fastened to a plane lid. The moulded part can be produced by foaming a negative shape of the shoulder or by cutting out the shape of the shoulder from a (cured) foam volume. 
         [0019]    The foamed moulded part can be air-permeable for an air circulating function (between the shoulder and jigsaw puzzle pieces lying on the base plate). For this purpose, a gas-percolating foam structure can be chosen. 
         [0020]    For removal of the base plate received in the frame, at least one recess can be provided on the frame, at which recess an edge piece of the base plate (bearing on the frame in the inside thereof) lies exposed and can be grasped. 
         [0021]    For one-handed transporting of the closed jigsaw puzzle transporting system, a first handle can be present on a first end region of the bottom part. For further securing of the closed position, a second handle can be present on a second edge region (opposite the first edge region in the closed position) of the lid. 
         [0022]    An edge side of the bottom part and an edge side of the lid can be formed in the manner of a hinge. The lid and the bottom part can then be pivotably movable between an open position and the closed position. This can facilitate reception of the shoulder in the frame. In principle, in the open position the lid can define a support for the base plate on the shoulder. The bottom part can provide a storage side for jigsaw puzzle pieces. With a permanent (pivotably movable) connection of the bottom part and the lid, a fixed playing arrangement can be provided in the open position. 
         [0023]    There can be provided on the edge side of the lid and on the edge side of the bottom part mutually parallel articulation axes. The two articulation axes can be spaced via a web element, arranged therebetween, in such a manner that a pivoting movement of the lid into the closed position tensions the web element. As a result of a tensile force transmitted via the articulation to the lid (and hence to the shoulder on the lid), additional force locking, acting in the sense of mutual bracing, between the facing surfaces in the closed position can be achieved. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    Further advantages and features of the invention will emerge from the exemplary embodiments described below with reference to schematic drawings, in which: 
           [0025]      FIG. 1  shows a perspective illustration of a first exemplary embodiment of the jigsaw puzzle transporting system in an open position; 
           [0026]      FIG. 2  shows a sectional view of the first exemplary embodiment of the jigsaw puzzle transporting system of  FIG. 1  in an intermediate position; 
           [0027]      FIG. 3  shows a sectional view of the first exemplary embodiment of the jigsaw puzzle transporting system of  FIG. 1  in a closed position; 
           [0028]      FIG. 4  shows qualitative profiles of deformation properties of the first and a second exemplary embodiment of the jigsaw puzzle transporting system; 
           [0029]      FIG. 5  shows a sectional view of the second exemplary embodiment of the jigsaw puzzle transporting system in the intermediate position; 
           [0030]      FIG. 6  shows a sectional view of the third exemplary embodiment of the jigsaw puzzle transporting system in the intermediate position; 
           [0031]      FIG. 7  shows a detail view of a grasping aid; 
           [0032]      FIG. 8  shows a plan view of a shoulder with latching elements; and 
           [0033]      FIG. 9  shows a detail view of a tension securing means. 
       
    
    
     DETAILED DESCRIPTION 
       [0034]      FIG. 1  shows a first exemplary embodiment of a jigsaw puzzle transporting system, designated generally by  10 , comprising a bottom part  12 , a lid  14  and a base plate  16 . In the exemplary embodiment shown, a common covering surface IS connects the bottom part  12  foldably to the lid  14  and is divided into a lower base  20  of the bottom part  12 , a hinge-like web  22  and an upper base  24  of the lid  14 . 
         [0035]    On the lower base  20 , a rectangular frame  26  projects perpendicularly to the lower base  20  with an edge face  28  parallel to the lower base  20  and an inner side face  30 , perpendicular to the lower base  20 , of the frame  26 . The frame  26  has, all the way round, a uniform height H from the lower base  20  which is a multiple of a base thickness D (which is the same for the lower base  20 , the web  22  and the upper base  24 ). A plurality of indented compartments  32  each with a compartment bottom  34  are arranged regularly inside the frame  26 . The frame  26  and the indented compartments  32  here form an integral thermoformed part. The indented compartments  32  terminate, with a compartment height F relative to the compartment bottoms  34 , at a bearing face  36  which is common to all the indented compartments  32  and parallel to the lower base  20 . The side face  30  of the frame  26  borders the bearing face  36  and is dimensioned such that the base plate  26  can be inserted into the frame  26  with a precise fit. The inserted base plate  16  bears on the bearing face  36  in a planar manner and closes the indented compartments  32 . The frame  26  projects, with its side face  30  up to the edge face  28 , by an internal height I beyond the bearing face  36 . The internal height I of the side face  30  of the frame  26  is greater than a base plate thickness G of the base plate  16 . 
         [0036]    On the upper base  24 , a shoulder  38  projects with a holding face  40  and a side face  42 , by a shoulder height A relative to a bearing region  44 , perpendicularly to the upper base  24 . The shoulder  38  and the hearing region  44  are produced here as an integral thermoformed part. The holding face  40  has a plurality of intersecting air conducting grooves  46 ,  48  as longitudinal indentations and transverse indentations, respectively. The air conducting grooves  46 ,  48  extend as far as the edge of the holding face  40  and lead into openings  50  in the side face  42 . In cross-section, the air conducting grooves  46 ,  48  have a U-profile. Within a manufacturing tolerance, the shape and size of the holding face  40  are of the same size or slightly smaller than the bearing face  36 . 
         [0037]    The lower base  20  is pivotably-movably connected via a first fold  52  to the web  22  and the latter is in turn pivotably-movably connected via a second fold  54  to the upper base  24 . The first fold  52  and the second fold  54  define two parallel pivot axes  56  and  58 , respectively. After insertion of the base plate  16  into the frame  26  in the direction of the arrow  60 , the lid  14  is pivoted by two superimposed pivoting movements  62  and  64  (see  FIG. 2 ) from an open position shown in  FIG. 1  over the bottom part  12 . At corresponding places of the side face  42  of the shoulder  38  and of the side face  30  of the frame  26 , a plurality of projecting ellipsoid sections  66  and indentations  68 , respectively, are arranged. On continued pivoting movement of the lid  14 , the ellipsoid sections slide over the side face  30  of the frame  26  and on reaching a closed position shown in  FIG. 3 , each one of the ellipsoid sections  66  projecting above the side face  42  engages in respectively one of the indentations  68 . Owing to an elasticity of shape of the ellipsoid sections  66  (and also a flexural elasticity of the side face  42  of the shoulder  38  and of the side face  30  of the frame  26 ), the shoulder  38  is fixed in the closed position at a defined height in the frame  26  by releasable positive locking. Penetration of the shoulder  38  into the frame  26  beyond the closed position is prevented by the bearing region  44  bearing against the edge face  28 . 
         [0038]    To assemble a jigsaw puzzle, the lid  14  is pivoted into the open position shown in  FIG. 1 . The first fold  52  and second fold  54  are non-restoring, i.e. in the open position they do not produce a restoring moment (in the direction of the closed position), so that the common to covering surface  18  of the lower base  20  and of the upper base  24  lies flat, completely un-folded, on a plane underlying surface (such as a table top). The base plate  16  is removed from the frame  26  by a movement shown by the direction of the arrow  60  in  FIG. 1  and placed on the shoulder  28 . The base surface  16  serves as a jigsaw puzzle surface, on which a jigsaw puzzle formed of jigsaw puzzle pieces  70  lying in the indented compartments  32  can he constructed. The jigsaw puzzle transporting system can thus be quickly laid out, for example, on a table or while travelling in a vehicle or an aircraft. An optimal assembly surface is always provided by the base surface  16  contained in the jigsaw puzzle transporting system  10 , so that it is possible to start the jigsaw puzzle immediately. 
         [0039]    A further advantage of the jigsaw puzzle transporting system  10  is the possibility of interrupting the jigsaw puzzle at any stage in a matter of seconds without a lot of clearing-up work. For this purpose, the base plate  16  with the jigsaw puzzle pieces  72  completely or partially assembled thereon is placed back into the mount, formed by the frame  26 , on the bottom part  12  in the direction of the arrow  60  shown in  FIG. 1 . Any jigsaw puzzle pieces  70  already pre-sorted for continuation of the jigsaw puzzle remain separated from one another in the indented compartments  32 . Through the pivoting movement of the lid  14  into the closed position shown in  FIG. 3 , the shoulder  38  occupies its fixed position in the frame  26 . In the closed position, there is a gap with a gap height S=I−G−A between the holding face  40 , dimensionally stabilised as a result of the air conducting grooves  46 ,  48 , and a facing upper side  74  of the inserted base plate  16 . The gap height S is chosen to be slightly less than a thickness S P  of the jigsaw puzzle pieces  72 , in dependence on an elasticity (corresponding to a slight deformation) of the shoulder  40 . Here, S is chosen to be between 0.80 S P  and 0.95 S P , preferably S=0.9 S P . According to a deformation characteristic  76 , shown in  FIG. 4 , of the shoulder ( 38 ) (at the holding face  40 ), a surface pressure P acts on the jigsaw puzzle piece  72  lying between the base plate  16  and the holding face  40  owing to the holding face  40  bearing on the jigsaw puzzle piece  72  since S&lt;S P . The (normal force of the) surface pressure results in force or frictional locking between each jigsaw puzzle piece  72  and the base plate  16 . The partially or completely assembled jigsaw puzzle pieces  72  on the base plate  16  thus retain their position even if the jigsaw puzzle transporting system  10  is turned vertically so that the base plate  16  is parallel to the force of gravity. In this way, the jigsaw puzzle is fixed in the state that has been reached and is stored in a space-saving manner in a matter of seconds and without a lot of clearing-up work. 
         [0040]    A lower handle  78  and an upper handle  80  are fastened, laterally in the centre, to the lower base  20  and the upper base  24 , respectively, on a side opposite the web  22  in each ease. The handles  78 ,  80  form elastic loops parallel to the lower base  20  and upper base  24 , respectively, and project laterally beyond the lower base  20  and upper base  24 , respectively. When carrying the jigsaw puzzle transporting system  10  folded up in the closed position shown in  FIG. 3 , both handles  78  and  80  can be grasped by one hand, with the result that an additional closing force presses together the bottom part  12  and the top part  14  at the side opposite the web  22  and additionally counteracts undesired unfolding of the jigsaw puzzle transporting system  10 . 
         [0041]    As can best be seen in  FIG. 3 , the lower base  20  and the upper base  24  have respectively a flat lower edge region  82  with a width B U  and a flat upper edge region  84  with a width B D  at the side opposite the web  22 . The upper edge width B D  (between the side face  42  of the shoulder  38  and an edge  86  of the upper base  24 ) is greater than a width B K  of the edge face  28 , so that the upper edge region  84  projects laterally beyond the frame  26  in the closed position shown in  FIG. 3 . The edge width B U  of the lower edge region  82  is chosen to correspond to the projection of the upper edge region  84 . The lower edge region  82  and the upper edge region  84  Corm, at the side opposite the web  22  in the closed position, two grasping strips for manually opening the jigsaw puzzle transporting system  10  (in the closed position shown in  FIG. 3 ). For this purpose, one hand each grasps respectively one of the edge regions  82  and  84  in order to apply a force sufficient to overcome the positive locking between the engaged ellipsoid sections  66  and indentations  68 . 
         [0042]    The flat and mostly light jigsaw puzzle pieces  72  present to an air flow a relatively large contact surface compared with their light weight. Besides the dimensional stabilisation of the holding face  40 , the air conducting grooves  46 ,  48  have the advantageous effect of inhibiting turbulence formation on the closing and opening (shown in  FIG. 2 ) of the lid  14  due to the pivoting movements  62  and  64 . An air flow which forms on the closing of the lid  14  due to the holding face  40  coming closer to the upper surface  74  of the base plate  16  is conducted by the air conducting grooves  46 ,  48  to the free openings  50  at the side faces  42  of the shoulder  38 . The air conducting grooves  46 ,  48  let into the shoulder  38  thus make it possible to prevent an air flow on the base plate  16  which lifts off the jigsaw puzzle pieces  72  lying loosely on the upper surface  74 . 
         [0043]    Furthermore, on the opening of the lid  14 , the air conducting grooves  46 ,  48  create an air supply for quick pressure equalisation in the space between the holding face  40  and the jigsaw puzzle pieces  72 . Adhesion, caused by negative-pressure formation, of the jigsaw puzzle pieces  72  lying loosely on the upper surface  74  to the holding face  40  lifting off during opening can thus be prevented. In particular, as a result of a substantially smooth upper surface  74  of the base plate  16 , it is possible to achieve the effect that on the opening of the lid  14  greater adhesion acts between the base plate  16  and the loose jigsaw puzzle pieces  72  than between the holding face  40  and the jigsaw puzzle pieces  72 . The jigsaw puzzle transporting system  10  can thus be quickly opened and closed without subjecting the jigsaw puzzle pieces  72  to turbulence. 
         [0044]    The depth of the air conducting grooves depends on the flow volume. The air conducting grooves running at the surface may also be designed as discernible contours, for example in the form of a jigsaw puzzle structure, or as characters. Alternatively, instead of surface air conducting grooves, air conducting channels may be provided (concealed) behind the holding face  40  in the shoulder  38 , the channels being fluidically connected to the holding face  40  via blind bores. 
         [0045]    The jigsaw puzzle transporting system  10  is produced from adhesively bonded or (ultrasonically) welded plastic parts. In an alternative embodiment, the material used is cardboard or a combination of cardboard and plastic. A transparent plastic film (not shown) is stretched over the covering surface  18 . A printed paper sheet with a size corresponding to the covering surface  18  can be inserted between the plastic film and the covering surface  18  for varying the design of the covering surface  18 . Alternatively, the covering surface  18  is permanently designed with printed decorations, pictures or logos. 
         [0046]      FIGS. 5 and 6  show respectively a second and third exemplary embodiment of the jigsaw puzzle transporting system  10 , which differs from the first exemplary embodiment shown in  FIGS. 1 to 3  only in the design of the lid  14 . The second exemplary embodiment shown in  FIG. 5  has a lid  14 ′ with a double layer  24 ′ comprising the upper base  24 , integrally connected to the web  22  via the first fold  52 , and an additional curved layer  88 . A curvature, shown in  FIG. 5 , of the double layer  24 ′ can be produced by a surface connection of the upper base  24  and the curved layer  88  in the curved state of the layers  24 ,  88 . For this purpose, a substantially full-surface adhesive bond of the upper base  24  and the curved layer  88  is pressed in a correspondingly curved pressing mould until the bond has cured. Since in each case one surface element of a length L W  (perpendicular to the pivot axis  58 ) of the curved layer  88  is adhesively bonded to a somewhat shorter surface element of length L B  of the upper base  24 , the desired curvature of the double layer  24 ′ results. The curvature of the double layer  24 ′ is transmitted to the elastic shoulder  38 ′ fastened to the double layer  24 ′ and leads to a convex curvature of the holding face  40 ′. As a result of this pre-bending of the lid  14 ′ in the open position, a pressure on the base plate  16  distributed uniformly (laterally) over the holding face  40 ′ in the closed position is achieved. In particular, a partial lifting-off of the holding face  40 ′ from the base plate  16  (or the assembled jigsaw puzzle pieces  72 ) in the closed position is prevented. 
         [0047]      FIG. 6  shows a third exemplary embodiment of the jigsaw puzzle transporting system  10  with a lid  14 ″. The lid  14 ″ comprises a plane upper base  24  and a plane-convex shoulder  38 ″, one side, connected to the upper base, of the shoulder  38 ″ being plane and the holding face  40 ″ being convex. The shoulder  38 ″ is a plastic thermoformed part with an elastic holding face  40 ″. 
         [0048]    In a variant, the shoulder  38 ″ is a plane-convex moulded part made of elastic foam (in the cured state). The foam imparts the elasticity to the holding face  40 ″. Furthermore, the holding face  40 ″ has a structure comprising many small surface Openings, owing to the porosity of the foam in the shoulder  38 ″. The foam material thus achieves a comparable air circulating function to that described in the first exemplary embodiment with reference to  FIGS. 1 to 3 . 
         [0049]    A (generally location-dependent) deformation characteristic  90  of the elastic holding face  40 ″ is shown (for a randomly chosen point in the holding face  40 ″) in  FIG. 4 . A shallower gradient of the deformation characteristic  90  compared with the deformation characteristic  76  corresponds to the greater hardness of the dimensionally stabilised holding face  40  at a comparably chosen surface pressure P (point of intersection of both deformation characteristics). 
         [0050]      FIGS. 7 to 9  show further detail designs which can each be combined with each of the above-described exemplary embodiments of the jigsaw puzzle transporting system  10 .  FIG. 7  shows an enlarged detail view of the frame  26  with the base plate  16  inserted in the frame  26 . A circular-segment recess  92  acting as a grasping aid is provided on the edge face  28  of the frame  26 . An edge piece  94  of the base plate  16  lies exposed in the circular-segment recess  92 . The exposed edge piece  94  can be removed from the frame  26  by a finger in the direction shown by arrow  96 . In a preferred embodiment, a single circular-segment recess  92  is provided laterally in the centre on one of the short sides of the frame  26  shown in  FIG. 1 . On removal, the exposed edge piece  94  is lined above the edge face  28 , with the result that the base plate  16  is inclined by a small angle corresponding to the longer side of the base plate  16 . Through the small inclination, slipping of jigsaw puzzle pieces  72  lying loosely on the base plate  16  can be avoided. Alternatively, a respective circular-segment recess  92  can be arranged laterally in the centre on each opposite side. It is also possible for two respective circular-segment recess  92  to be provided on both longer sides of the frame  26 . The latter embodiment makes it possible to remove the base plate  16  stably from the frame  26  with two pairs of fingers. 
         [0051]      FIG. 8  shows a plan view of the shoulder  38  with the holding face  40  and the side face  42  (parallel to the viewing direction). A multiplicity of ellipsoid sections  66  project at regular intervals L E  all the way round on the side face  42  of the shoulder  38 . As a result of the multiplicity of ellipsoid sections  66  which in the closed position each engage with a corresponding indentation  68  on the side lace  30  of the frame  26 , the closed position is also secured against considerably vibrations during transport. Owing to the pivoting movement of the lid  14 , on opening not all of the ellipsoid sections  66  and indentations  68  are disengaged at the same time. This prevents a sudden jerk on opening, which would displace the jigsaw puzzle pieces  72  lying on the base plate  16 . 
         [0052]      FIG. 9  shows a detail view of the web  22  pivotably-movably connecting the bottom part  12  and the lid  14 . A length L S  of the web  22  between the first fold  52  and the second fold  54  is dimensioned somewhat shorter in relation to the shoulder height H, so that on pivoting  64  into the closed position a tensile force Z is transmitted by the upper base  24  via the second fold  54  to the web  22 . The tensile stress Z of the upper base  24  is maintained in the closed to position by a reaction Z′ of the web  22  and produces an additional contact pressure of the facing side faces  30  and  42 . The contact pressure produces additional force locking between the engaged latching elements  66  and  68 .