Abstract:
A puzzle consists of six or more elongated pieces. Each piece has a polygonal cross-section and a cavity whose dimensions are determined by the polygonal cross-section. The pieces can be arranged in two opposing groups of three or more pieces each, arranged substantially in parallel, and such that the cavity in each piece is filled by portions of other pieces as the groups are advanced toward each other. The pieces can be assembled and disassembled only in such a way that each piece is moved relative to others in a different direction to interlock the pieces in an assembled configuration, and no individual piece can be disengaged from the assembled configuration without disengaging all of the pieces.

Description:
BACKGROUND OF THE INVENTION 
     I. Field of the Invention 
     The present invention relates generally to the interconnection of solid objects, and, more particularly, to three-dimensional geometric and mechanical puzzles. Specifically, one embodiment of the present invention provides a mechanical puzzle consisting of six or more elongated pieces having a polygonal cross-section and a method of assembly characterized by movement of the pieces being assembled in different directions simultaneously. 
     II. Description of the Prior Art 
     Means and methods of connecting solid objects have contributed to the advancement of the building industry for many generations. Log cabins using slotted logs as building members are well known. Mortise-and-tenon joints are commonplace in wooden furniture construction. 
     Also, three-dimensional geometric and mechanical puzzles have been used as a source of entertainment and mental challenge for many years. Such puzzles may appeal both to the intellect and the aesthetic sense of the solver. They typically consist of a plurality of pieces which when properly manipulated will interlock in an assembly to form one or more predetermined geometric shapes. See, for example, U.S. Pat. No. 3,721,448. 
     The number of techniques for connecting the pieces of a mechanical puzzle appears to be limited, and, consequently, the discovery of a new configuration attracts interest from solvers and collectors. The interest arises from practical considerations such as stability as well as difficulty in assembly and disassembly, and also aesthetic considerations such as symmetry. 
     One type of mechanical puzzle is known as a “coordinate-motion” puzzle. See, Coffin, Stewart T.,  The Puzzling World of Polyhedral Dissections , Oxford University Press: New York, 1990, Chap. 12. Such puzzles cannot be assembled sequentially, but rather at some stage of assembly they require the simultaneous manipulation of three or more pieces or groups of pieces. Certain puzzles of this type have been constructed in which all pieces must move simultaneously, inwardly during assembly and outwardly during disassembly. No known puzzle of this type has been developed in which identical pieces must move simultaneously in different directions, some inwardly and others outwardly, during both assembly and disassembly. 
     Additionally, no known coordinate-motion puzzle has been designed in the configuration of three or more pieces interlocked with three or more other pieces such that the total thickness of the assembled configuration is that of the span of a single piece. Such a shape would enhance the stability of the puzzle and simplify packing and shipping. 
     Moreover, known coordinate-motion puzzle configurations are not typically scaleable. Arrangements of the elongated pieces in which the interlocking mechanism is used at both ends or at several places along their length would allow the connection of large arrays of pieces to form complex structures. 
     SUMMARY OF THE INVENTION 
     The present invention provides a puzzle consisting of six or more pieces that are preferably identical except for nonessential decoration, length, or embellishment. The pieces typically have the shape of elongated bars of solid material with a polygonal cross-section, and each piece is provided with a cavity that enables pieces to interlock and grip each other. The cavity in each piece is dimensioned so as to permit three or more other pieces to fit parallel to each other within the cavity and at a substantially right angle to each piece in whose cavity the parallel pieces are disposed. 
     The puzzle in accordance with the present invention is assembled by dividing the pieces into two groups of at least three each, consisting of two or more outer pieces and at least one middle piece, and, for each group, placing the three or more pieces in each group together so that two or more outer pieces are parallel with the middle piece between them such that the cavities of all of the pieces in the group are oriented in the same direction. The two groups are then advanced toward each other, with the cavities of the pieces of the respective groups facing toward each other, until the outer pieces of the two groups are moved into contact with the floors of the cavities of the outer pieces of one group substantially perpendicular and disposed in close contact with the floors of the cavities of the outer pieces of the other group. The middle piece of each group is placed so that the points along one edge span the floors of the cavities of the outer pieces of the opposing group and reach beyond their edges, and then the outer pieces of each group are slid apart while the middle pieces are simultaneously slid toward the opposing group. When the middle pieces of the two groups meet, assembly is complete. In the assembled condition, the puzzle is stable. 
     The puzzle is disassembled by reversing the assembly procedure. Specifically, the puzzle is disassembled by pulling the middle piece of each group as far apart from each other as possible while simultaneously squeezing the outer pieces in each group toward each other, combining pulling and squeezing until all of the pieces separate. 
     In accordance with various embodiments of the puzzle in accordance with the present invention, the pieces can have various polygonal cross-sections. In one embodiment, for example, the pieces have a square cross-section. In another embodiment, the pieces have a hexagonal cross-section. Other cross-sections such as a pentagonal cross-section are also contemplated. 
     Furthermore, the puzzle of the present invention can consist of six or more pieces. In one embodiment, for example, the puzzle comprises an equal number of pieces in each opposing group of pieces. In another embodiment, the number of pieces in one group can differ from the number of pieces in the other group. 
     Also, the pieces can be identical, or the pieces can have different diagonal cross-sectional shapes or widths. For example, in a modified embodiment of the puzzle in which the pieces have a square cross-section, one or both of the two pieces comprising the middle piece of each group during assembly may have an arbitrary configuration on the portion of the piece which faces away from the opposing pieces when the puzzle is assembled. Examples of the precise relative dimensions of the pieces and cavities are shown in the accompanying drawings and described below. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other features and the concomitant advantages of the puzzle in accordance with the present invention will be better understood and appreciated by those persons skilled in the art after a consideration of the accompanying drawings in conjunction with the detailed description of the preferred embodiments that follows. In the drawings: 
     FIG. 1 is a perspective view of one embodiment of an assembled puzzle in accordance with the present invention; 
     FIG. 2 is a perspective view of one of the pieces of the puzzle shown in FIG. 1; 
     FIG. 3 is an end view of the puzzle piece shown in FIG. 2 along line  3 — 3  which appears in FIG. 2; 
     FIG. 4 is a side view of the puzzle piece shown in FIG. 2; 
     FIG. 5 is a top plan view of the puzzle piece shown in FIG. 2; 
     FIG. 6 is a perspective view of the puzzle shown in FIG. 1 as assembly is commenced; 
     FIG. 7 is a perspective view of the puzzle shown in FIG. 1 while the puzzle is being assembled; 
     FIG. 8 is a perspective view of another embodiment of an assembled puzzle in accordance with the present invention; 
     FIG. 9 is a perspective view of the puzzle shown in FIG. 8 as assembly is commenced; 
     FIG. 10 is a perspective view of the puzzle shown in FIG. 8 while the puzzle is being assembled; 
     FIG. 11 is a perspective view of a further embodiment of an assembled puzzle in accordance with the present invention; 
     FIG. 12 is a perspective view of yet another embodiment of an assembled puzzle in accordance with the present invention; 
     FIG. 13 is a perspective view of still another embodiment of an assembled puzzle in accordance with the present invention; and 
     FIG. 14 is a perspective view of another embodiment of an assembled puzzle in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     One embodiment of the puzzle in accordance with the present invention, generally indicated by the numeral  10 , is shown in FIG. 1 in assembled condition. The puzzle  10  comprises a plurality of pieces  12 . For example, as shown in FIG. 1, the puzzle  10  consists of at least six pieces  12 . Each piece  12  of the puzzle  10  is elongated and has a polygonal cross-sectional shape. For example, as shown in FIG. 1, each piece  12  has a square cross-section. As will be described in more detail later, the number of pieces can be greater than six, for example, seven, and the cross-sectional shape can be hexagonal, pentagonal, etc. 
     The pieces  12  are preferably constructed of a rigid material such as wood, metal, or bakelite or other hard plastic, of sufficient length to accommodate the cavities described below. The surfaces of the pieces  12  must be smooth enough to permit assembly or disassembly without damage. 
     FIG. 2 is a perspective view of one of the pieces  12  of the puzzle  10  shown in FIG.  1 . FIG. 3 is an end view of the piece  12  along the line  3 — 3  shown in FIG.  2 . As shown in FIG. 3, the piece  12  has a square cross-section. In the case of the square cross-section, each side of the square has a dimension s. The length of a diagonal d of the square cross-sectional piece  12  is therefore approximately 1.414×s. 
     As shown in FIGS. 2,  4 , and  5 , each piece  12  comprises a cavity  14  having a floor  16  and two end walls  18 . Preferably, the floor  16  and end walls  18  are substantially flat and smooth to provide an even surface when contacted by another piece  12  to provide a bearing or contact surface during assembly and to assure proper fit when the pieces are in the assembled condition. The cavity  14  extends from one end of the piece  12 , which intersects one end wall  18 , to another end, which intersects the other end wall  18 . In the case in which each piece  12  has a square cross-section, the interior angles of the end walls  18  of the cavity  14  with respect to the floor  16  of the cavity are each 45°, as shown in FIG.  4 . 
     As shown in FIG. 5, the floor  16  of the cavity  14  spans the diagonal width of the piece  12 . The dimensions of the cavity  14  are such that an opening  20  along one edge of the piece  12  is at least 2.0×d, and the floor  16  of the cavity is rectangular having a width with a dimension d and a length at least 3.0×d. With these dimensions for the cavity  14 , the floors  16  of two other pieces  12  can pass side-by-side through the opening  20  along the one edge of another piece, and the cavities of three pieces can be disposed within the cavity of any one piece or the cavities of as many as three side-by-side pieces. The length of each piece  12  must be greater than the length of the cavity  14 . 
     The puzzle  10 , whose assembled condition is shown in FIG. 1, is assembled as follows. First, the six pieces  12  comprising the puzzle  10  are grouped into two sets of three pieces, as shown in FIG.  6 . Each group consists of two outer pieces  12 A and  12 B and one middle piece  12 C. For each group, the three pieces  12 A,  12 B, and  12 C are placed together so that the two outer pieces  12 A and  12 B are side-by-side and edge-to-edge with the middle piece  12 C between them such that the cavities  14  of all of the pieces in the group are oriented in the same direction. The two groups of pieces  12  are then advanced toward each other, with the cavities  14  of the pieces of the respective groups facing toward each other, until the outer pieces of the two groups are moved into contact with the floors  16  of the cavities of the two outer pieces  12 A and  12 B of one group oriented substantially perpendicular and disposed in close contact with the floors of the cavities of the two outer pieces of the other group. Also, the middle piece  12 C of each group is placed so that the points along the edge on either side of the opening  20  of the cavity  14  span the floors  16  of the cavities of the outer pieces  12 A and  12 B of the opposing group and reach beyond the edges of the outer pieces of that opposing group. 
     Then, as shown in FIG. 7, the side-by-side outer pieces  12 A and  12 B of each group are slid apart, while the middle pieces  12 C are simultaneously slid toward the opposing group. Considered in more detail, the pieces  12  are slid in the directions of the arrows  22 A,  22 B,  22 C,  22 D,  22 E, and  22 F simultaneously. No two pieces move in the same direction. The movement of all pieces  12  is substantially rectilinear. When the floors  16  of the cavities  14  of the middle pieces  12 C of the two groups meet, assembly is complete. In the assembled condition, the puzzle  10  is held by friction in a stable state. 
     Another embodiment of the puzzle in accordance with the present invention, indicated by the numeral  10 ′, is shown in FIG. 8 in assembled condition. As shown in FIG. 8, the puzzle  10 ′ consists of six pieces  12 ′, each of which has a hexagonal cross-section. In the case of the pieces  12 ′ having a hexagonal cross-section, each side of the hexagon has dimension h. The length of the diagonal d′ is 2.0×h. Each piece  12 ′ has a cavity  14 ′ with a floor  16 ′ and two end walls  18 ′. The cavity  14 ′ extends from one end wall  18 ′ to the opposite end wall in such a way that the interior angles of the end walls of the cavity  14 ′ with respect to the floor  16 ′ of the cavity are each 60°. The floor  16 ′ of the cavity  14 ′ spans the diagonal width of the piece  12 ′. The dimensions of the cavity  14 ′ are such that the length of the opening  20 ′ along one edge is at least 2.5×d′, and the floor  16 ′ of the cavity is rectangular having a width d′ by a length of at least 3.0×d′. The length of each piece  12 ′ must be greater than the length of the cavity  14 ′. 
     The puzzle  10 ′, whose assembled condition is shown in FIG. 8, is assembled as follows. First, the six pieces  12 ′ comprising the puzzle  10 ′ are grouped into two sets of three pieces, as shown in FIG.  9 . Each group consists of two outer pieces  12 A′ and  12 B′ and one middle piece  12 C′. For each group, the three pieces are placed together so that the two outer pieces  12 A′ and  12 B′ are separated by a distance h with the middle piece  12 C′ between them such that the cavities  14 ′ of all of the pieces in the group are oriented in the same direction. The two groups of pieces  12 ′ are then advanced toward each other, with the cavities  14 ′ of the pieces of the respective groups facing toward each other, until the outer pieces of the two groups are moved into contact with the floors  16 ′ of the cavities of the two outer pieces  12 A′ and  12 B ′ of one group oriented perpendicular and disposed in close contact with the floors of the cavities of the two outer pieces of the other group. Also, the middle piece  12 C′ of each group is placed so that the points along the edge on either side of the opening  20 ′ of the cavity  14 ′ span the floors  16 ′ of the cavities of the outer pieces  12 A′ and  12 B′ of the opposing group and reach beyond the edges of the outer pieces of that opposing group. 
     Then, as shown in FIG. 10, the outer pieces  12 A′ and  12 B′ of each group are slid apart, while the middle pieces  12 C′ are simultaneously slid toward the opposing group. Considered in more detail, the pieces  12 ′ are slid in the directions of the arrows  22 A′,  22 B′,  22 C′,  22 D′,  22 E′, and  22 F′ simultaneously. No two pieces move in the same direction. The movement of all pieces  12 ′ is substantially rectilinear. When the floors  16 ′ of the cavities  14 ′ of the middle pieces  12 C′ of the two groups meet, assembly is complete. In the assembled condition, the puzzle  10 ′ is held by friction in a stable state. 
     FIG. 11 shows another embodiment of the puzzle in accordance with the present invention, indicated by the numeral  10 ″, which is similar to the puzzle  10 ′ shown in FIG. 8, except that the cross-section of each piece  12 ″ is a pentagon, rather than a hexagon. The pieces  12 ″ shown in FIG. 11 can be formed by extending two of the faces of a hexagonal piece shown in FIG. 8 until they meet to form an edge. In contrast to the hexagonal pieces  12 ′ shown in FIG. 8, the pieces  12 ″ shown in FIG. 11 do not have a symmetrical cross-section. However, the pieces  12 ″ are otherwise constructed and assembled as described in connection with the embodiment described in connection with FIGS. 8-10. 
     FIG. 12 shows an embodiment of the puzzle in accordance with the present invention, indicated by the numeral  10 ′″, that is similar to the puzzle  10  shown in FIG. 1, but consists of seven pieces, including four pieces  12 ′″ 0  and three pieces  12 ″″, as compared to the six pieces  12  which comprise the puzzle  10 . On the one hand, the pieces  12 ′″ have the same configuration as the pieces  12 . On the other hand, the pieces  12 ″″ each have a cavity  14 ″″, the dimensions of which are such that the opening  20 ″″ along one edge of the piece  12 ″″ is at least 3.0×d″″ and the floor  16 ″″ of the cavity is rectangular having a width with a dimension d″″ and a length at least 4.0×d″″. The pieces  12 ″″ and  12 ″″ are assembled in a manner similar to that described in connection with the embodiment described in connection with FIGS. 1-7. 
     FIG. 13 shows an embodiment of the puzzle in accordance with the present invention, indicated by the numeral  10 ″″, comprising two pieces  12 ′, such as shown in FIG. 8, and four pieces  12 ″, such as shown in FIG.  11 . The puzzle  10 ″″ is assembled in the same manner as the puzzle shown in FIG.  11 . 
     FIG. 14 shows an embodiment of the puzzle in accordance with the present invention, indicated by the numeral  10 ′″″, that is similar to the puzzle  10 ′″ shown in FIG. 12, but consists of six pieces instead of the seven pieces shown in FIG.  12 . The puzzle  10 ′″″ includes two pieces  12 ′″ and three pieces″″ identical to the correspondingly numbered pieces shown in FIG.  12 . Additionally, the puzzle  10 ′″″ comprises a sixth piece  12 ′″″ which is equivalent to the two middle pieces  12 ′″ shown in FIG. 12 combined. On the one hand, the pieces  12 ′″ and  12 ″″ have the same dimensions as the correspondingly numbered pieces shown in FIG.  12 . On the other hand, the piece  12 ′″″ has a cavity  14 ″″, the dimensions of which are such that the opening  20 ″″ along one edge of the piece  12 ′″″ is at least 2.0×d″″ and the floor  16 ″″ of the cavity is rectangular having a width with a dimension 2.0×d″″ and a length at least 3.0×d″″. The pieces  12 ′″,  12 ″″, and  12 ′″″ are assembled in a manner similar to that described in connection with the embodiment described in connection with FIGS. 1-7. 
     While various embodiments of a mechanical puzzle assembly are described above, the principles of the present invention also apply to puzzles in which the configuration of the puzzle pieces is modified. For example, in a modified embodiment of the puzzle shown in FIGS. 1-7 in which the pieces have a square cross-section, one or both of the two pieces  12  comprising the middle pieces of each group during assembly, that is, the pieces  12 C, may have an arbitrary configuration on the portion of the piece which faces away from the opposing pieces when the puzzle is assembled, such as a relieved portion  12 CA or an extended portion  12 CB, respectively, as shown in dotted lines in FIG.  7 . Also, the present invention generally teaches fastening together parallel groups of elongated pieces of solid material, of a class of polygonal cross-sections, without the use of extraneous materials. The present invention utilizes precisely sized cavities in the pieces to join with similar cavities in other pieces of the same or similar material to form a solid, stable connection without the use of nails, screws, glue, or other fastening devices. Therefore, although the present invention has been described in connection with three-dimensional mechanical puzzles, it will be readily apparent to persons skilled in the art that other articles of manufacture can be constructed in accordance with the present invention, including frames for pictures or windows; enclosures for cables, rods, and other elongated materials; religious icons; etc. These and other changes and modifications and applications of the present invention to construction of various articles of manufacture can be made without departing from the scope of the invention as defined by the appended claims.